United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/9-80-047
December 1980
Research and Development
Proceedings
7th
United States/J
Conference on
Sewage Treatment
Technology
1980
May 19-21, 1980
Tokyo, Japan
••mi..«
-------
EPA-600/9-80-047
December 1980
PROCEEDINGS
SEVENTH UNITED STATES/JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
MAY 19-21, 1980
TOKYO, JAPAN
OFFICE OF INTERNATIONAL ACTIVITIES
OFFICE OF WATER AND WASTE MANAGEMENT
WASHINGTON, D.C. 20460
OFFICE OF RESEARCH AND DEVELOPMENT
WASHINGTON, D.C. 20460
CINCINNATI, OHIO 45268
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
CINCINNATI, OHIO 45268
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DISCLAIMER
These Proceedings have been reviewed by the
U.S. Environmental Protection Agency and approved for
publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
11
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FOREWORD
Environmental improvement is a worldwide need. Maintaining
clean water supplies and managing municipal and industrial wastes is
a vital element of a quality environment.
The participants in the United States-Japan cooperative project
on sewage treatment technology have completed their seventh conference.
These conferences, held at 18-month intervals, give the scientists and
engineers of the cooperating agencies an opportunity to study and compare
the latest practices and developments in the United States and Japan.
These Proceedings of the Seventh. Conference comprise a useful body of
knowledge on sewage treatment, which will be available not only to
Japan and the United States but also to all nations of the world who
desire it.
inistrator
Washington, D.C.
111
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CONTENTS
FOREWORD iii
JAPANESE DELEGATION vi
UNITED STATES DELEGATION vii
JOINT COMMUNIQUE 1
JAPANESE PAPERS 5
UNITED STATES PAPERS 365
TECHNICAL SEMINAR PAPERS (U.S.) ?19
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JAPANESE DELEGATION
SATORU TOHYAMA
Head of Japanese Delegation
Director, Department of Sewerage
and Sewage Purification
Ministry of Construction
DR. MAMORU KASHIWAYA
Head, Research and Technology
Development Division
Japan Sewage Works Agency
TSUTOMU TAMAKI
Head, Sewage Works Division
Department of Sewerage
and Sewage Purification
Ministry of Construction
KAZUO OHMIYA
Senior Researcher
Research and Technology
Development Division
Japan Sewage Works Agency
SHIGETAKA KOZEN
Head, Planning Division
Department of Sewerage
and Sewage Purification
Ministry of Construction
TETSUICHI NONAKA
Senior Technical Advisor
Sewage Works Bureau
Tokyo Metropolitan Government
MUNETO KIUIBAYASHI
Head, Water Quality Control
Division, Public Works Research
Institute
Ministry of Construction
SHIGEKI MIYAKOSHI
Head, Construction Division
Sewage Works Bureau
City of Yokohama
DR. KEN MURAKAMI
Chief, Water Quality Section
Water Quality Control Division
Public Works Research Institute
Ministry of Construction
TAKASHI YONEDA
Director, Sewage Works Bureau
City of Kyoto
DR. TOSHIKI OHSHIO
Head, Water Pollution Control
Division, Water Quality Bureau
Environment Agency
DR. TAKESHI KUBO
CO-CHAIRMAN OF THE CONFERENCE
PRESIDENT
JAPAN SEWAGE WORKS AGENCY
VI
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UNITED STATES DELEGATION
JOHN J. CONVERT
General Chairman of Conference and Team Leader
Director, Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
DR. JOSEPH B. FARRELL
Chief, Ultimate Disposal Section
Treatment Process Development Branch
Wastewater Research Division
Municipal Environmental Research Laboratory
UiS. Environmental Protection Agency
Cincinnati, Ohio 45268
JOHN M. SMITH
Chief, Urban Systems Management Section
Systems & Engineering Evaluation Branch
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
HERBERT R. PAHREN
Physical Science Administrator
Field Studies Division
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
WALTER E. GARRISON
Chief Engineer and General Manager
County Sanitation Districts
of Los Angeles County
1955 Workman Mill Road
P.O. Box 4998
Whittier, California 90607
HOWARD L. RHODES
Deputy Director, Water & Special Programs
Florida Department of Environmental
Regulation
Twin Towers Office Building
2600 Blair Stone Road
Tallahassee, Florida 32301
vii
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H-
H-
UNITED STATES AND JAPAN DELEGATES TO THE SEVENTH CONFERENCE, TOKYO, JAPAN
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MR. SATORU TOHYAMA, HEAD OF THE JAPANESE DELEGATION EXTENDS WELCOME TO MR. JOHN J. CONVERY,
TEAM LEADER, UNITED STATES DELEGATION AT OPENING OF SEVENTH CONFERENCE, TOKYO, JAPAN
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DELEGATES ON FIELD VISIT
DELEGATES VISIT "WITHIN-VESSEL" COMPOSTING FACILITY
MINAMI-TAMA S.T.P. (TOKYO)
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JOINT COMMUNIQUE
SEVENTH UNITED STATES/JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
MAY 21, 1980
1. The Seventh United States/Japan Conference on Sewage Treatment
Technology was held in Tokyo from May 19 to 21, 1980.
2. The United States Delegation headed by Mr. John J. Convery,
Director, Wastewater Research Division, Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency (USEPA),
Cincinnati, Ohio, was composed of three representatives from the USEPA,
one representative from the State of Florida, and one representative
from a local authority (Los Angeles County).
3. Mr. Satoru Tohyama, Director, Department of Sewerage and Sewage
Purification, Ministry of Construction, was Head of the Japanese
Delegation, which consisted of five National Government representatives,
three Japan Sewage Works Agency representatives, and three local govern-
ment officials (Tokyo, Kyoto, Yokohama).
4. The chairmanship for the Conference was shared jointly by Mr.
John J. Convery and Dr. Takeshi Kubo, President of the Japan Sewage
Works Agency.
5. During the Conference, papers relating to joint research projects
on sludge treatment/disposal and instrumentation, and automated control
of municipal sludge treatment facilities were presented by both sides.
A Progress Report on U.S./Japan Joint Research Projects (Japanese side)
was presented. Data and findings on the joint research projects were
useful to the development of improved control technology practices for
each country. A decision was made to expand the scope of the joint
research projects conducted by the two countries to include energy
conservation, operation and maintenance practices, and small flow
treatment systems.
6. Principal topics of the Conference were current water pollution
control programs in each country including innovative and alternative
technology, regional approaches, toxic wastes, health effects, combined
sewer technology and reuse of wastewater. The discussions which followed
each presentation were mutually productive and useful to both countries.
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7. In addition to the Conference, the technical seminar organized
by the Japan Sewage Works Association is planned, and about 200 active
members of the Japan Sewage Works Association are registered to attend
the seminar. During the seminar, presentations will be made by each
U.S. delegate to be followed by floor discussions.
8. Field visits in Kyoto, Himeji, Tokyo, Yokohama, and Tsukuba areas
are planned to inspect wastewater treatment facilities in these areas.
9. Recent engineers exchanges between the two countries included a
two-week visit in 1979 to Japan by Mr. James C. Gratteau, County
Sanitation Districts of Los Angeles County, California, and a six-
month long visit in 1979 to the United States by Dr. T. Mori, Japan
Sewage Works Agency. Mr. S. Kyosai, Public Works Research Institute,
Ministry of Construction, is spending 12 months in the United States.
Both sides agreed to continue the engineers exchange programs.
10. A new initiative was agreed to, which will include the exchange
of summaries of important research reports and design guidelines on
new technologies.
11. It was proposed by the United States side that the Eighth
Conference shall be held in the United States about October 1981.
12. A Proceedings of the Conference will be printed in English and
Japanese.
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JAPANESE PAPERS
BASIC POLICIES FOR SEWAGE WORKS IN JAPAN 5
Satoru Tohyama, Director, Department of Sewerage
and Sewage Purification, Ministry of Construction
CURRENT ISSUES IN WATER POLLUTION CONTROL ADMINISTRATION IN JAPAN.. 3?
Toshiki Oshio, Environment Agency, Government of Japan
REGIONAL WASTEWATER TREATMENT PLANNING IN TOKYO BAY AREA 57
Tsutomu Tamaki, Head, Sewage Works Division, Department of
Sewerage and Sewage Purification, Ministry of Construction
AUTOMATED CONTROL OF SLUDGE TREATMENT SYSTEMS 89
Mamoru Kashiwaya, Kinichiro Azuma and Akio Kuwayama,
Research and Technology Development Division,
Japan Sewage Works Agency
ENGINEERING EVALUATION OF MUNICIPAL SLUDGE INCINERATORS 121
Kazuo Ohmiya and Sadaharu Takahashi, Research and Technology
Division, Japan Sewage Works Agency
PUBLICLY OWNED TREATMENT WORKS PRETREATMENT CONTROL PRACTICE
IN TOKYO 16?
Tetsuichi Nonaka, Senior Technical Advisor,
Sewage Works Bureau, Tokyo Metropolitan Government
DEODORIZATION IN SEWAGE TREATMENT PLANTS OF YOKOHAMA 199
Shigeki Miyakoshi, Head, Construction Division,
Sewage Works Bureau, City of Yokohama
AUTOMATIC WATER QUALITY ANALYZERS FOR SEWERAGE SYSTEMS 2^3
Ken Murakami, Public Works Research Institute,
Ministry of Construction
CURRENT STATUS OF COMBINED SEWER PROBLEMS AND THEIR CONTROL
MEASURES IN JAPAN 263
Muneto Kuribayashi, Director, Water Quality Control Division and
Eiichi Nakamura, Research Engineer, Sewage Works Section, Public
Works Research Institute, Ministry of Construction
WATER QUALITY IMPROVEMENT IN YODO RIVER AND SEWAGE WORKS IN KYOTO.. 311
Takashi Yoneda, Director, Sewage Works Bureau, City of Kyoto
PRACTICAL APPLICATIONS FOR REUSE OF WASTEWATER 331
Takeshi Kubo, Vice President, Japan Sewage Works Agency
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Seventh US/Japan Conference
on
Sewage Treatment Technology
BASIC POLICIES FOR SEWAGE WORKS IN JAPAN
May 19, 1980
Tokyo, Japan
Satoru Tohyama
Director,
Department of Sewerage and Sewage Purification,
Ministry of Construction
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BASIC POLICIES FOR SEWAGE WORKS IN JAPAN
1. Present Situation of Sewerage Installations in Japan ..... 9
2. Role of Sewerage and Its Diversification ................. 12
3. Conservation of Water Quality as Water Resources ..... .... 13
4. Promoting Effective Utilization of Resources ...... . ...... 1-6
5. New Developments in Sewerage Administrative and
Financial Policies ..................................... . . 18
5.1 Sewerage Improvement If
5.1.1 Targets for Improvement ]_g
(a) Basic Policies 18
(b) Long-term Arrangement Targets 20
(c) Immediate Arrangement Targets 21
5.1.2 Method of Sewerage Improvement and Arrangement .... 22
(a) Effective Promotion of Sewerage Arrangement .. 22
(b) Promotion of Tertiary Treatment .............. 23
(c) Promotion of Sewerage Arrangement as
Flood Control Measures 25
(d) Harmony with Community 26
(e) Promotion of Energy and Resource Conservation 27
5.1.3 Securing Financial Resources for
Sewerage Arrangement 28
5.2 Maintenance and Management of Sewerage 29
5.2.1 Methods of Maintenance and Management 29
(a) Wide-scale Disposal of Sewage Sludge 29
(b) Strengthening of Control over Pre-treatment 31
Facilities
(c) Promotion of Effective Use of Resources 32
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(1) Effective Utilization of
Sewage Sludge
(2) Reutilization of Effluent from
Sewerage ............................. 33
(d) Arrangement of Executing System
5.2.2 Securing Financial Sources for Maintenance
and Management ................................. 35
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Thus, it may be said that sewerage installations in this
country are presently in the "developing stage". It cannot be
denied that this has occurred because the importance of sewerage
service has not been fully recognized by the people and because
Japan has been backwardness in urban development. Urbanization
has begun without providing sewerage services.
However, people's requests for sewerage systems have greatly
increased in recent years and, in response to this, the government
has also expanded its sewage works recently.
Real sewerage layout in this country began after the enactment
of the Sewerage Law in 1953 and the First 5-year Sewerage Arrange-
ment Plan in 1963. A 5-year Sewerage Arrangement Plan, which is
the basic plan for sewerage improvement, has been executed 4 times
from 1963 to the present. The project scale has tripled at each
time of the plan revision. Economic plans have been made several
times up to now, and the position of sewerage investment within
public investment has rapidly improved. That is, the share of
sewerage investment was only 3.3% in the Medium Term Economic Plan
from FY 1958 to FY 1968, but it reached 7.1% in the Economic Flan for
the Second Half of the 1970's, which means that share of sewerage
investment doubled during this period and the amount of investment
increased about 12 times. In addition, according to New Economic
and Social Seven-Year Plan, established in August last year, public
investment amounting to 240 trillion yen (prices as of 1978) was
planned for the 7 years from FY 1979 to FY 1985.
A sum of 18.2 trillion yen was appropriated for sewerage
services. Its share of total investment was 7.58%, a further
increase.
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BASIC POLICIES FOR SEWAGE WORKS IN JAPAN
1. PRESENT SITUATION OF SEWERAGE INSTALLATIONS IN JAPAN
In recent years although priority in investment has been
placed on the projected upgrading of social overhead capital to
improve the quality of people's lives, the present status of dif-
fusion of sewage coverage in Japan is not necessarily satisfactory.
With respect to the rate of diffusion of sewage coverage at
the end of fiscal year 1973, population in the areas where sewerage
services were available was only 27% of the whole population in
this country. This means that two-thirds of the population was
not receiving sewerage services..
On the other hand, the diffusion of water supply systems has
already reached 90% in this country and, thus, there is a large
gap oetween the diffusion of sewerage and water supply systems.
With respect to the situation of diffusion in urban areas,
the mean rate of diffusion in the ten largest cities at the end
of fiscal year 1978 was 56%, while that of other areas was only
15%, indicating a presence of unbalanced sewerage diffusion that
varies depending upon the urban scale and locality.
(Refer to Fig. 1)
(10,000 persons)
12,000-
10,000
8,000
6,000
4,000
2,000
Fig. 1
Total population
10,733
11,004
9,718
9,905
11,323 11,529
26.7
3,072
7.9
2,716
2,253
1,283
30
20
10
1964 65 66 67 68 69 70 71 72 73 74 75 76 77 78
(Fiscal year)
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Table-1 Amount of Social Overhead Capital Investment
under Economic Plans and 5-year Plans for Sewerage Arrangement
(Uniti 100 million yen)
^v. Economic plans
Public \.
works ^x^
Roads
Housing
Sewerage
Urban parks
Water supply
Total
Gross
5-year Sewerage
arrangement plan
Period of project
Amount of investment
New Economic
and Social
Seven-Year Plan
{•79 -V. '85)
Amount of
investment
460,000
135,000
182,000
45,000
142,000
964,000
2,400,000
Share
19.2
5.6
7.6
1.9
5.9
40.2
100
Economic Plan for
tne Second Half
of the 1970 's
(•76 -v. '80)
Amount of
investment
195,000
65,000
71,000
15,400
55,000
401,400
1,000,000
Share
19.5
6.5
7.1
1.5
5.5
40.1
100
4th
•76 t 'HO
(Contingency)
71,000+4,000=75,000
Basic Economic
and Social Plan
(•73 •>• '77)
Aggount of
investment
190,000
60,800
56 , 500
13,000
47,000
367 , 300
900,000
Share
21.1
6.8
6.3
1.4
5.2
40.8
10O
New Economic and
Social Develop-
ment Plan
(•71 •>• '75)
Amount of
investment
117,000
39,000
23,000
4,300
29,000
212,300
550,000
Share
21.3
7.1
4.2
0.8
5.3
38.6
100
3rd
'71 ^ '75
(Contingency)
25,000+1,000=26,000
Economic and Social
Development Plan
(•67 ^ '71)
Amount of
investment
61,500
17,100
9,300
2,070
16 , 100
106,070
275,000
Share
22.4
6.2
3.4
0.7
5.9
3B.6
100
2nd
•67 -v. '71
(Contingency)
9,OOO+300=9,30O
Medium Term
Economic Plan
(•64 t '68)
Amount of
investment
41,000
11,200
5,792
805
9,000
67,797
178,000
Share
23.0
6.3
3.3
0.4
5.1
38.1
100
1st
•63 ^ '67
4,400
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With respect to the forth 5-year Plan for Sewerage Arrange-
ment which is currently being carried out, the period of this plan
is from FY 1976 to FY1980 and a total amount of 7.5 trillion yen
was appropriated for construction. Works amounting to 1.7816
trillion yen are being carried out in FY 1980 as the last year of
this plan. As a consequence, the completion rate of the 5-year
plan will 98.4% and sewerage diffusion to population served will
finally become 30%.
On the other hand, with respect to the status of the construc-
tion of sewerage works, local public bodies are very aggressive in
carrying out these projects because more people now recognize the
importance of sewerage facilities. At the end of FY 1978, public
sewerage construction work was being carried out in 616 cities
and towns, 19% of the total number (3,255) of cities and towns
in this country. Treatment was started in 291 cities and towns,
9% of the total. (Refer to Table-2)
Table-2 Completion Stage of Public Sewerages
(As of March 31, 1979)
Population
class
Total number of
cities & towns
Number of cities
S towns under-
taking projects
Number of cities
& towns in
which treatment
has begun
Less than
lOOxio3
3,082
448
(15%)
143
(5%)
100X10 3
to
30QX103
126
119
(94%)
101
(80%)
300X103
to
lxlOS
39
39
(100%)
37
(95%)
More than
ixio6
10
10
(100%)
10
(100%)
Total
3,257
616
291
With respect to River Basin sewerage, operation was already
started at 24 out of 66 places. It may be said that the "con-
struction-maintenance-management age'1, where both construction and
management will be performed together, has just begun in this
country.
11
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2. ROLE OF SEWERAGE AND ITS DIVERSIFICATION
The role of sewerage treatment has expanded as times change.
When modern sewerage treatment was first introduced, its main
purpose was to improve the living environment by immediately
removing sewage and to prevent floods by removing storm water,
today sewer treatment is performed by sewerage facilities so that
it now has become an indispensable service for preventing water
pollution in public water areas. In addition, as a result of
improvements in the standard of living and modes of life of people
in recent years, they now are more concerned with bettering the
quality of life. Thus, people now think that not only those who
live in urban areas but also those living in fanning areas natural-
ly have the right to enjoy sewerage services.
Also, special attention must be paid to the fact that sewer-
age systems are more frequently being built as part of the
national land policies of the government. The Third Comprehensive
National Development Plan established in November, 1977 had adopted
an "Integrated Residence Policy" as a basic planning approach in
its national land policies for the future. This scheme is intended
to form an all-round environment for human occupancy where the
natural, human and production environments would be harmonized to
gether. In order to realize a population arrangement reflecting
this policy (Table-3) and particularly to promote stable living
conditions for the young generation in local areas, it is required
to preferentially carry out sewerage arrangement, an important
factor for the formation of an all-round living environment in
rural districts.
12
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Table-3 Population Frames for Integrated Residence by
the Third Comprehensive National Development Plan
District'v"\_
Tokyo
Metropolitan
Zone + Osaka
Zone
Others
Total
Actual population
(unit in 10,000)
1975
4,270
(3,520)
6,920
(2,860)
11,190
(6,380)
1985
4,850
(4,260)
7,780
(3,880)
12,630
(8,140)
2000
5,380
(5,080)
8,860
(5,100)
14,240
(10,180)
Increase in population
(unit in 10,000)
1975VL985
580
(740)
860
(1,020)
1,440
(1,760)
1975^2000
1,110
(1,560)
1,940
(2,240)
3,050
(3,800)
Note: DID (Densely Inhabited District) population frame is
shown in ( ).
3. CONSERVATION OF WATER QUALITY AS WATER RESOURCES
In general, water pollution is being managed better as a
result of a strengthening of control in the quality of effluent
and sewerage arrangements in recent years. Particularly, sewerage
treatment is performing a very important role in improving the
water quality of urban rivers. For instance, water quality is
improving very quickly as sewerage improvement work progresses
in the basins of rivers running through large cities, such as the
Sumida River in Tokyo, and through major regional cities such as
the City of Sendai and the City of Okayama. For example, sweetfish
and bull trout, which usually live in mountain streams, now can be
caught in the Hirose River which runs through the City of Sendai.
Also, in the City of Sapporo where the winter Olympics were once
held, salmon now come up the rivers which run through this city.
In the Sumida River of Tokyo, a traditional boat race between
Waseda University and Keio University and fireworks festivals
were discontinued for many years because of pollution. They are
now reinstituted and are again summer attractions in Tokyo. All
of this clearly indicates the positive effects of the sewerage
treatment improvements.
13
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With respect to all public water areas, only 0.07% of all
water areas contain materials harmful to human health, such as
cadmium, that do not conform to the environmental quality standards
of FY 1978. The number of water areas having harmful materials
not conforming to this standard is decreasing each year.
On the other hand, in view of the degree of achievement in
environmental water quality standards for "living environment
items", 21.2% of rivers, 35.6% of lakes and 17.5% of sea areas do
not conform to the values of environmental quality standards in
FY 1978. These circumstances are undesirable. Particularly in
wide, closed-type water bodies such as Tokyo Bay, Ise Bay, and
the Inland Sea are, a rich nutriment of water has occurred as a
result of the accumulation of nutritious salts such as phosphorus
which are contained in residential and industrial waste water due
to a poor exchange of water. Organic material such as plant-type
plankton has increased, which cause red tides each year and
damages to culture-type fisheries. (Refer to Fig. 2 and Table-4)
Fig. 2 Degrees of Achievement of Environmental Water
Quality Standards in Wide, Closed-type Water Bodies
100
90
30
70
60
50
40
30
20
10
n
.
. Sato Inland
Sea area
National
^^ ^ ToJcyo Bay
" F""^
.
0
.
^^
^~
—
Ise Bay
^~
—
Remarks:
1.
2.
3.
This is the rate of achievement related to COD value.
Rate of achievement is derived by
No. of water areas where env.
quality stds. are achieved
.No. of water areas where env.
quality stds. are met
100(%)
"National" means water areas other than Tokyo Bay,
Ise Bay and the Inland Sea.
(Source: Environment White Paper, FY 1978)
14
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Table-4 Number of Confirmed Occurrences of Red Tide
\Water area
1971
1972
Tokyo Bay
3
Ise Bay
55
47
Seto Inland Sea
108
140
1973 56 | 161
1 I ;
1974
3 36
1975 3 ' 22
1
1976
1977
1978
7
13
22
33
35
31
113
224
148
125
74
Source: "Present situation of Ocean
Pollution" surveyed by Maritime
Safety Agency
Therefore, for the water areas stated above, a total mass
effluent control system that aims to reduce the total quantity of
pollution was introduced in June last year in addition to che
conventional concentration control. This aims to reduce the
present total quantity of pollution by approximately 10% by 1984,
the target year. Sewerage treatment is considered to be an im-
portant measure governing the success of this total mass effluent
control system. Quantitative and qualitative upgrading of sewerage
treatment is urgently sought for.
In addition, some water areas now require the use of tertiary
treatment to improve the rate of nitrogen and phosphorus removal
in order to prevent excessive nutriment and to further improve
the quality of water normally subjected to secondary treatment
for removing BOD, SS, etc.
15
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"Present Situation of Execution of Tertiary Treatment Work"
Place:
[River basin Sewerage]
Tama River catchment
sewerage: Minamitama
Treatment Plant
Kasumigaura Jonan
catchment sewerage:
Tone Purification
Center
Teganuma catchment
sewerage: Teganuma
Sewage Treatment
Plant
Start of
Executing Start of treatment Method of
body: work(FY): (FY): treatment:
Metro.
Tokyo
Ibaraki
Pref.
Chiba
Pref.
FY 1974 FY 1975
FY 1973 FY 1978
FY 1978
Concentrated
settling +
quick filter-
ing (partly
including
absorption
by activated
carbon)
Concentrated
settling +
quick
filtering
FY 1981 Quick
(planned) filtering
[Public Sewerage]
Ochiai Treatment Metro. FY 1976
Plant Tokyo
Hirano Treatment Osaka FY 1976
Plant City
Tamatsu Treatment Kobe FY 1980
Plant City (planned)
Concentrated
settling +
quick
filtering
Quick
filtering
Concentrated
settling +
quick
filtering
4. PROMOTING EFFECTIVE UTILIZATION OF RESOURCES
According to "the Water Resources Development Plan and Water
Utilization toward 1990" (Ministry of Construction) announced in
November, 1978, an insufficient supply of water in the future is
forecasted. For instance, a shortage of 6.91X108 rnVyear in the
Winami-Kanto District, of 3.01*103 m3/year in the Keihanshin
16
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District, of 2.22X1Q8 mVyear in the Northern Kyushu District, and
of IS.Qxio8 m3/year in total for ten other districts throughout
the nation is forecast, so that securing new water resources has
now become a big problem that must be solved.
As a matter of fact, a serious water shortage occurred in
the City of Fukuoka in the northern district of Kyushu during the
summer two years ago, thus revealing the weakness of large cities
to water shortages. In addition to the City of Fukuoka, there
are many other districts and cities where serious water shortages
similar to the one in the City of Fukuoka could occur at any time;
some of these areas are the South Kanto, and the cities of Sendai,
Nagoya, Kyoto and Kobe.
In order to cope with such circumstances, the reutilization
of treated water from sewerage has been more frequently reviewed
or reexamined in recent years as part of the effective utilization
measures for water resources.
At present, about 6Qxlo8 m3 of treated water is discharged
from sewerages each year. But only 3*loa mVyear is being used
as cooling water and cleaning water at final sewage treatment
plants, and about 1X109 mVyear is being used as industrial water
and landscape water outside of the treatment plants. The remaining
water is directly discharged to public water areas at present.
In parallel with progress in sewage works in future, it is expected
that treated water from the sewarages will continuously increase
in quantity (98>
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to 2.4X106 mVyear (70% water content), but only about 10% of
this amount was effectively used for recovery by green farm lands,
and about 80% was disposed in land and sea reclamation areas and
a remaining 10% returned to the ocean. It is expected that the
amount of sewage sludge generated will increase further as sewage
works progress in future (11.7xlOs m3 in FY 1985 with 70% water
content). However, securing lands that can be reclaimed in this
country is getting extremely difficult, and sewage sludge can be
disposed of in such reclamation lands in the nation only for the
next 10 years in view of the present situation of reclamation
land acquisition. Some cities have enough land for only the next
year or less for sludge disposal.
nation only for the next 10 years in view of the present situation
of reclamation land acquisition. Some cities have enough land for
only the next year or less for sludge disposal.
In improving the sewerages for the future, disposal of the
sewage sludge itself is an important problem and it seems necessary
to promote the treatment and disposal of sewage sludge in wider
areas but, at the same time, it is considered necessary to ag-
gressively carry out the effective utilization of sewage sludge
such as recovery for green fanning lands with special attention
to the usefulness of sludge as one of the resources.
5. NEW DEVELOPMENTS IN SEWERAGE ADMINISTRATIVE AND
FINANCIAL POLICIES
5.1 Sewerage Improvement
5.1.1 Targets for Improvement
(a) Basic Policies
It is apparent that sewerages must be so improved that they
may be able to appropriately resopond to many social needs, and
the consensus of the majority in this country is that top priority
in the execution of sewage works should be given to the improvement
of the rate of diffusion of sewerages for the time being in order
to quickly cope with the considerable slowness in sewerage ar-
rangement.
18
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Also, it is very clear that local public organs that are in
the stage of maintenance and operation as a result of progress
made in the sewage works, must properly maintain and operate the
sewerages in order to effectively provide for the functions of
sewerages.
Under the present circumstances in which the Japanese economy
is shifting toward long-term stable growth in response to the
changes in the domestic and foreign environment, such as severer
restrictions on use of energy and resources, integrated policies
such as the expansion of measures against pollution sources for
preventing water pollution, must be appropriately carried out
in order to adequately and totally promote the formation of a
better living environment. Special precautions must also be taken
for the following points when improving sewerages as basic in-
frastructure for the environment:
(1) To steadily improve the rate of diffusion of sewerage treat-
ment, sewerage improvement in live with local needs is to be
promoted; for example, sewage treatment methods and maintenance
and operation measures are to be selected by fully considering
the actual local situation. If necessary, quality improvement is
to be undertaken. For example, the upgrading of existing facili-
ties, and promotion of tertiary treatment for preventing excessive
nutrition are to be made.
(2) To maintain the function and stable service of sewerages,
proper administraton and operation are to followed. For example,
the proper management of sewage facilities, proper treatment and
disposal of sewage sludge, and the strengthening of control and
monitoring of inferior wastewater will be necessary.
(3) To promote the sound development of sewage works, adequate
allocation principles for the burden to local public organs and
users with respect to construction, maintenance and operation of
sewage facilities are to be established, and a financial base for
the sewage works is to be strengthened.
19
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(b) Long-term Arrangement Targets
The following targets for long-term sewerage arrangement are
to be established toward the year 2000:
(1) Improving the rate of diffusion of sewerages:
By the year 2000, sewerages are to be fully arranged in urban
areas not only for large cities but also for local cities and,
in addition, sewerage arrangement required for improving living
environment of rural districts and for conserving the water
quality of lakes and swamps as good natural environments is to be
carried out, thus raising the ratio between total population and
sewerage-served population to those of developed countries in
Europe and the Americas.
(2) Technically improving sewage treatment:
To achieve environmental quality standards for water and to
prevent excessive nutrition in wide closed-type water bodies,
measures to reduce pollutants at pollution sources are to be
strengthened. At the same time, with respect to sewage works,
tertiary treatment for removing organic matter and nutritious
salts such as phosphorus is to be realized where it is required.
(3) Upgrading existing facilities:
To maintain the functions of publci sewerages, old defective
facilities are to be remodeled and combined sewerages are to be
upgraded depending upon the local conditions. Also for improving
safety in urban areas, measures against floods are to be
strengthened by raising the probability year related to the storm
water removal plan in close coordination with flood control
measures to be taken as part of river projects.
(4) Performing wide-scale treatment and disposal of sewage sludge:
To perform the proper treatment and disposal of sewage sludge,
wide-scale treatment and disposal of sewage sludge is to be carried
out in response to local conditions. Effective use of the sludge
as, for example, organic fertilizer or as soil improvement
20
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materials is to be promoted by returning it to the natural
cycle.
(5) Effecting recycled utilization of treated water from sewerage:
Treated water from sewerage is to be reconsidered as past
of water resources and aggressively utilized. Particularly for
areas where a short supply of water is expected, projects for
reutilizing the treated water from sewerage are to be carried
out.
(c) Immediate Arrangement Targets
In order to achieve the targets of the long-term arrangement of
sewerage, the target of sewerage arrangement urgently needed is
to raise the ratio of sewerage-served population to total popula-
tion to 55% by 1985, based upon the fundamental concept of the
7-year New Economic Society Plan. The following points are to be
empnasized during execution:
(1) Sewerage arrangement in local cities where the diffusion of
sewer systems is presently slow is to be accelerated to jromote
the Integrated Residence Policy.
(2) Sewerage arrangement required for preventing floods in urban
areas and for assuring higher safety in urban life is to be ac-
celerated.
(3) Sewerage arrangement required to obtain the early fulfillment
of the Public hazard prevention plan and of environmental quality
standards for water established by the government and to respond
to the total mass effluent control system in wide, closed-type
water bodies is to be accelerated.
(4) To prevent excessive nutrition in wide, closed-type water bodies
and lakes, tertiary treatment is to be accelerated in the water
areas where great damage occurs due to red tides.
(5) Sewerages required for conserving the quality of water in
tourist resorts and lakes with excellent natural scenery and
sewerages for rural districts are to be encouraged.
21
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(6) Wide-scale treatment and disposal of sewage sludge is to be
accelerated. Effective utilization of sewage sludge and treated
water from sewerages is to be accelerated.
5.1.2 Method of Sewerage Improvement and Arrangement
(a) Effective Promotion of Sewerage Arrangement
It has now been recognized that sewerages are required not
only in large cities but also in small and intermediate local
cities, and rural districts. Therefore, priority areas for pro-
moting sewerage arrangement for the future have been shifted
from large cities to local cities. Thus, sewerage projects will
become more active in local cities and farming, forestry and
fishing villages from now on. However, financial and technical
powers in these local areas are generally smaller than those of
large cities, so that it is considered to be more effective to
promote wide-scale unified sewerage arrangement with centralized
treatment plants provided for local cities and farming villages
within the jurisdictions of at least two local government bodies,
in view of investment efficiency, management efficiency, the
administrating system for construction, maintenance and operation,
and the overall effects on water quality conservation.
As methods for wide-scale sewerage arrangement, there are
two methods; one of them is called the "wide-scale public sewerage
method", in which public sewerage covering two or more cities,
towns and/or villages is provided for and administered by a co-
operative; the other method is called the "river basin sewerage
method" in which planning and arrangement is made for each unit
basin in two or more cities, towns and/or villages by the pre-
fectural government as an administrator. It is required to fully
utilize these methods in the future in order to promote the ef-
fective sewerage arrangement in local urban areas.
In addition, the population estimated for design purposes
for these local areas is normally smaller than that of intermediate-
22
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scale cities, so that costs for constructing, maintaining and
operating treatment plants per capita are higher, and also poorer
efficiency in pipe installation will result since villages are
scattered in these local areas.
When making sewerage arrangements for these small cities or
villages, it is not necessarily rational to use conventional
systems and treating methods from the viewpoint of promoting
energy and resource conservation and of performing effective
management and operation. Therefore, while promoting research and
development work for energy saving techniques, it will be required
to make efforts for the decentralization of treatment plants
depending upon the degree of population concentration, for the
positive adoption of easily maintainable, operable treatment
facilities, for the adoption of economical treatment methods,
for the simplification of treatment facilities, for the execution
of cleaning and inspection of facilities, and for the execution
of collection and monitoring" of sewage sludge, whereby developing
new forms of sewerage arrangement particularly suited to actual
local conditions, instead of relying upon sewerage systems that
have been developed mainly in large cities.
(b) Promotion of Tertiary Treatment
Through analysis on the amount of COD load by source in three
water areas subjected to the total mass effluent control system
and on the amount of generated phosphorus load in Seto Inland Sea,
it was found that there is a large amount of generated load from
domestic sewage in all cases. Thus, arrangement of sewerage has
become more important for reducing the amount of generated load
due to such domestic sewage.
Since COD and even phosphorus can be removed to a certain
degree by secondary treatment, top priority must be given to the
arrangement of sewerage in order to conserve water quality and to
prevent excessive nutrition in water bodies subjected to total
mass effluent control and lakes functioning as water resources,
in view of the present situation of sewerage arrangement, which
is progressing too slowly.
23
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However, for preventing water pollution in these water
bodies, it is of course required to strengthen overall measures
against generating sources, such as the reduction of the amount
of polluted load at the source, reduction of phosphorus in
synthetic detergents and restricting their use, and the proper
execution of culture-type fishery businesses. For conserving the
quality of water in public water bodies, control of the genera-
tion of the polluted load is needed, instead of expecting too
much sewerage, thus taking total conservation measures.
Based .upon the above considerations, it may become necessary
to organically introduce the tertiary treatment for water bodies
where urgent measures are needed because of the considerable
pollution and frequent occurrence of damage caused by red tide..
Though large construction costs will be needed for carrying
out tertiary treatment, it must be understood that its benefit
area is huge and not limited to that area served by sewarage.
Conservation of the water environment as a national land resource
is demanded from both the national and historical viewpoints, so
that subsidies from the national government for tertiary treatment
should be naturally different from that for the system up to
secondary treatment.
Also, high costs will be paid for maintaining and operating
the tertiary treatment facilities, but rules of allocation for
the burdens have not been clearly defined as yet.
For solving this problem, it will be required to establish
the proper allocation of burdens to be borne by the national
government, prefectural government, city, town or village authority,
and users depending upon local characteristics, in consideration
of the range of each tertiary treatment plant and its purposes.
such as the prevention of excessive nutrition in wide, closed-type
water bodies, and the fulfillment of environmental quality stand-
ards for water in wide water conservation areas such as lakes.
For example, with respect to the total development project of
Lake Biwa, which is important as a precious drinking water source
24
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for the Kinki District, the allocation of burdens was determined
after making an adjustment among the local public organs concerned.
Beneficiary prefectures in downstream areas bear part of the ex-
penses for the water resource development project. For tertiary
treatment at lakes required for the conservation of wide-range
water resources, the question of downstream areas bearing appropri-
ate portions of the burden according to the benefits they receive
may be worthy of examination.
(c) Promotion of Sewerage Arrangement as Flood Control Measures
Traditionally in Japan, inundation control is one of the
important purposes of sewerage arrangement. Many cities in this
country have frequent rains and located in slough areas. In ad-
dition, mountains are steep and storm water tends to run off very
quickly.
In the 1960's, many large-scale housing land development
projects were conducted in the outskirts of many cities in order
to accept the population movement to large cities such as Tokyo
and Osaka. Rapid development in these urban areas reduced paddy
fields, green areas and vacant lots, further increased the storm
water run-off coefficient as a result of the construction of
buildings and the paving of roads, and immediately increased storm
water run-off that was previously balanced, quickly increasing the
possible danger of inundation in urban areas.
It is difficult to increase the widths of downstream rivers
in response to increasing storm water run-off caused by the sudden
development in upstream and middle-stream basins. Therefore, for
these areas, execution of total flood control measures, including
the arrangement of river facilities, control of storm water run-
off by construction of regulating pondages and retention ponds,
and the encouragement of safe land utilization will become necessary
Particularly for preventing flooding, all facilities related to
storm water removal, including not only rivers but also storm
water channels/ must be provided in-accordance with plans while
maintaining the conformity of the overall facilities and the
balance with each other.
25
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(d) Harmony with Community
Construction of sewage treatment plants is frequently opposed
by community residents because of their bad image with residents,
the possible occurrence of odor and air pollution. This problem
of opposition by residents frequently has occurred in this country
because treatment plants have been constructed adjacent to re-
sidential areas or villages.
For this reason, local public bodies have tried to fully
consider the possible impact to the nearby environment prior to
the construction of sewage treatment plants, and have carried out
environmental protection measures such as providing covers for
treatment facilities, the installation of odor prevention facilities
and air pollution prevention facilities, and planting within treat-
ment plant sites in order to obtain the understanding and coopera-
tion of community residents. The forceful execution of such
environmental planning is also indispensable in the future.
Particularly in view of the formation of a pleasant environment
in the surrounding area, measures for such surrounding areas must
be positively carried out; for example, sewage treatment plants
should be constructed as part of parks associated with other urban
park projects.
Especially for the treatment plants for river basin sewerage,
answering people's opposition is more difficult than that of public
sewage treatment plants since the former gives treatment not only
for sewage from the local city or village, but also for sewage
coming from other cities or villages.
Therefore, for an organic and integrated execution of environ-
mental arrangement in the area near sewage treatment plants for
the river basin sewerage, effective measures for the community must
be taken very cautiously by the prefectural government as adminis-
trator for the river basin sewerage, in close collaboration with the
relevant city, town or village as a beneficiary body.
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(e) Promotion of Energy and Resource Conservation
Japan, where no oil is produced, takes the current world oil
situation extremely seriously, and the government is trying to
save energy and natural resources as much as possible in every
field and propose that the whole economy of this country should
shift toward energy and resource conservation systems.
Conventionally, the arrangement of sewerage in this country
was mainly promoted in large cities, and efficient execution of
the works was possible by adopting high-energy consumption type
sewerage systems, such as activated sludge systems, but the sewage
works came to a turning point in the severe world energy supply
situation currently in progress.
In consideration of the diversified roles imposed on the
sewerage and the high public function it offers, the sewerage
treatment must perform energy and resource conservation and solve
its own problems. Thus, from now on, it is very important to
develop new technology for energy and resource conservation and to
apply aggressively the results of researcn to actual sewerage.
Actually, for existing sewerage, it will be required to
apply the energy-saving type operating and controlling method to
such existing facilities and to encourage the switch to energy-
.saving type facilities. For new installations, it will be required
to adopt the most effective energy-saving systems that are con-
ceivable at present.
It is expected that sewerages will be widely adopted and
constructed from now in small cities and rural districts, but ef-
ficiency of pipeline arrangement will become'poor since the
population is small in these areas. Construction cost for sewage
treatment plant per capita will be relatively high when these
villages are scattered.
For promoting the sewerage arrangement in such areas, it is
indispensable to adopt energy-saving type systems suited to the
particular conditions of such areas.
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5.1.3 Securing Financial Resources for Sewerage Arrangement
Current funding methods for sewerage arrangement slightly
vary depending upon the types of sewerage system, but the funding.
methods for main public sewage works and river basin sewerages
are as indicated in Fig. 3, that is, funds are provided in the
form of national subsidies, local bonds, ordinary city burdens,
prefectural burdens and beneficiary burdens.
(1) Public sewerage
Pipe, conduit, etc.
Fig. 3
Sewage treatment plant
Subject of
subsidy
Single ,
6
10
\
3.4
10
o.e)
10 J
. National
•expenditure
Issue of
bond
Issue of
bond
• — ~_ —• —
2.83
10
Subject of
subsidy
National
expenditure
Single
_6
10
! 3.4
Issue of 10
bond
^Issue of
bind
/ft
10
Urban planning tax, beneficiary
burdens, city burdens, etc.
(2) River basin sewerage
Pipe, conduit, etc.
Subject of
subsidy(90%;
Single
/
2
1
\
!_
4
\
]~-,(
" . ' •
National
expenditure
Issue of
bond
- —
s
(1U
\,
^\,
r
.9
10
1
i
-Issue of
bond
Sewage treatment plant
. Subject of
subsidy (95»7~"'~\ Singie
(
3
4
\
\
3 '
16 ,
J- (
National
expenditure i
3 '
':..-\
. - • . • /
Issue of —
bond / 4 x _
Prefectural burdens, etc.
_
12
28
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For the last several years, financial resources for each
sewage work has steadily expanded, and particularly national sub-
sidies and local bonds have grown considerably. It may be said
that sewage works have been expanded mainly because of the expan-
sion of these subsidies and bonds.
On the other hand, under present circumstances where the
national economy of Jpaan is forced to shift to stable growth, it
can be easily forecasted that both national and local governments
will have more tight and inflexible situations financially. This
situation must be fully taken into account in carrying out the
sewage construction.
Particularly for small and intermediate local cities where
sewerage arrangement is specially needed, it will be required to
create a new system for securing financial resources which is
different from the ptesent one in consideration of their current
financial conditions, in order to aggressively promote sewerage
arrangement for the future.
5.2 Maintenance and Management of Sewerage
5.2.1 Method of Maintenance and Management
The final objective of sewage construction is not to construct
the facilities but to properly operate and control them.
In consideration of the highly public character of the system,
each sewerage administrator is required to make every effort for
the optimum maintenance and operation of facilities.
By reviewing the problems associated with sewerage maintenance
and oepration in this country, the following items are considered
to be the most important problems that are to be solved from now.
(a) Wide-scale Disposal of Sewage Sludge
It is expected that the amount of sewage sludge from sewage
treatment plants will increase considerably as sewage works progress
in the future, but work will be finally completed only after sewage
sludge is properly treated and disposed. For stably treating and
29
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disposing the sludge, its effective use has to be positively
promoted and reclamation land for the disposal of sludge must be
aggressively secured.
On the other hand, securing disposal and reclamation lands
has become very difficult as a result of progress in urbanization.
In addition, under current circumstances, where incineration cannot
be easily performed because of the increasing demand for energy
conservation, it can be said that the disposal of sewage sludge is
now creating very serious problems.
For stably disposing the large amount of sludge expected in
the future, it will be more effective to make wide-scale plan,
for treating and disposing sewage sludge for a wider district,
not limited to the relevant prefecture, city, town, or village
and to treat and dispose of the sewage sludge by each sewerage
administrator in conformity to this plan.
Particularly in large urban zones such as Tokyo and Osaka
where sewerage arrangement must be quickly promoted in response
to the total quantity control in the future and tertiary treatment
has to be primarily conducted as required, the generation of a
huge amount of sludge is forecasted. But securing sludge disposal
land is now very difficult, which makes disposal within the city
area almost impossible for cities located in these large urban
zones.
Thus, in large urban zones where securing sludge disposal
lands as a prerequisite for sewerage arrangement is very difficult,
it is very hard to use conventional methods in which the individual
sewerage administrator can dispose of it independently. As a
result, there is a tendency for a prefectural or national govern-
ment body to act as an executing organ for arranging fundamental
conditions for the sludge treatment and disposal, based upon the
wide-scale approach through coordination not limited to the single
prefecture, city, town or village.
30
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(b) Strengthening of Control over Pre-treatment Facilities
To achieve the purpose of sewerage arrangement and to
effectively perform sewerage arrangement, the sewerage law will
impose "compulsory use" that is unusual for public property laws,
so that the sewerage must accept as a rule all domestic and
industrial wastewater, regardless of its origins.
When accepting the industrial wastewater, it is requested
that a factory generating sewage harmful to functions of sewage
facilities and materials that cannot be removed in sewerage, must
perform pretreatment for such sewage within the factory in advance
to reduce such harmful matters below the minimum standard level.
Thus, such a factory is legally obligated to install pre-treatment
facilities.
Particularly for harmful materials such as heavy metals,
quality standard similar to that of sewage discharged to ordinary
public water bodies has been determined. Thus, it is said that
an important water quality conservation policy comparable to that
of pollution control in public water bodies is being effected
through the sewerages.
With respect to the sewerage law, provisions for control of
water quality were prepared in 1976, in which, to cope with harmful
sewage, a new direct penalty system, advance check system and
correction order system were introduced in addition to the con-
ventional system for compulsory installation of pre-treatment
facilities.
The number of factories and work places where the installation
of pre-treatment facilities is obligated within sewerage treatment
zones was about 20,000 at the end of 1979, and more than 15,000
factories installed such required facilities. This is considered
to be an improvement since the rate of installation of such facili-
ties at the end of 1979 is about 85% compared to 63% at the end
of 1975.
However, there are still about 3,000 factories that have not
installed such pre-treatment facilities.
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Most factories which have not installed the required
facilities are small establishments, and more than 70% of them
indicated that they could not install such facilities because of
funding problems and the difficulty of finding proper land for
the facilities.
For the purpose of ensuring the pre-treatment activities by
such small estbalishments, it is required to positively promote
joint-pretreatment through the preparation of industrial zones
for small firms, measures for ensuring long-term low-interest loans
for the pre-treatment facilities, and offering necessary guidance
and technical assistances by sewerage administrators, as part of
the policies for the small business.
At the same time, the public sewerage sector should strengthen
its monitoring and patrol system including the arrangement of
monitoring instruments and the securing of monitoring personnel,
while maintaining tight coordination with environmental administr-
ation .
(c) Promotion of Effective Use of Resources
While maintaining the optimum maintenance and control for the
sewerage, the problems to be coped with in the future will be the
promotion of the effective utilization of products made from the
sewerage, that is, treated water and sewage sludge.
Effective utilization of these resources will also, in con-
sequence, solve problems in sewerage maintenance and operation, and
this is considered to be an extremely effective measure, immediately
responding to the limited resource age in this country.
(1) Effective Utilization of Sewage Sludge
As already stated before, it is important to consider that
sewage sludge is to be effectively utilized as a resource as much
as possible instead of merely disposing of it, for the purpose of
stabilizing sludge disposal. At present, only 10% of total sludge
is effectively being used, mainly as fertilizer or soil improvement
material by returning it to agricultural lands and green areas.
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It is important to promote this use for agricultural lands
and green areas also in the future. For this purpose, it is
indispensable to make the sludge easier to handle by users and
to obtain the trust of users. For this purpose, a system related
to sludge quality control and sludge distribution must be es-
tablished.
While promoting £he use of sewage sludge in agricultural
lands and green areas, research and development work for utilizing
the sewage sludge as raw material for construction materials such
as concrete aggregates, bricks and concrete blocks and for re-
covering valuable materials such as phosphorous and aluminum from
the sewage sludge, must be aggressively carried out.
(2) Reutilization of Effluent from Sewerage
Water resource development in this country has been conducted
so extensively that it seems to be very difficult to secure new
water resources. Particularly in large cities, the water supply-
demand relationship is extremely unstable as a result of the
excessive concentration of population and industries.
In order to protect sound social activities in these areas
in the future, reutilization of effluent from sew:rage must be
considered in addition to more rational use of water by saving and
other means.
Reutilization of effluent from sewerage is considered as water
for miscellaneous urban use such as water for toilets and cleaning
water, for industrial water, for agricultural water, and for
gardening.
In Japan, effluent from sewerage is already being used on a
small scale but, except for a few examples, the real application
of effluent has not yet been started.
Reutilization of effluent from sewerage will be considerably
increased in the future and, for its actual application, it will
become neqessary to clearly define the position of effluent as a
.water resource and to establish an overall plan for water demand
and supply. In addition, various surveys establishing water quality
33
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standards and facility standard suited to each application must
be quickly made to promote the efficient reutilization of the
effluent.
(d) Arrangement of Executing System
Sewerage facilities must be properly operated at all time
and their usefulness will be realized only when they are properly
maintained and controlled. Discontinuity in services after the
commencement of treatment by these facilities is not permitted.
Therefore, the arrangement of a complete system is indispensable
during planning and operation for these facilities. Thus, provi-
sions of Article 12 of the sewerage law require that engineers
engaging in planning, designing, supervising, maintaining and
operating the sewerage plants are to have predetermined qualifica-
tions. However, at present, qualified engineers are not necessarily
sufficient in ordinary cities and become insufficient as the size
of the city gets smaller.
For steadily promoting sewage construction in small and
intermediate cities in the future, it is urgently required to
secure engineers who engage in construction work. At the same
time, securing maintenance and operating engineers is also urgently
needed in order to perform maintenance and operation work appro-
priately, such as control of effluent, treatment and disposal of
sludge, and monitoring of inferior sewage in response to the
commencement of sewerage treatment. For this purpose, it is
required not only to secure personnel and provide organization in
relation to the sewage works, but also to improve the capabilities
of each engineer through effective training. In arranging the
executing system under circumstances, where demand for simplified
administrative organization is increasing, it is required to
strengthen cooperation with other departments such as those in the
environmental sector, to cooperate with adjacent regional public
bodies, and to promote mutual cooperation in joint-pre-treatment
and technical assistance with such bodies.
34
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In consideration of the role of sewerage in water quality
conservation in public water bodies, basic work such as water
quality monitoring should be directly controlled by the sewerage
administrator. Work such as simple labor should be contracted to
outside private firms in order to effectively achieve the work
load within the limited administrative syst
5.2.2 Securing Financial Sources for Maintenance and Management
Conventionally, maintenance and operating costs for the
sewerage treatment were provided by the "private burden for sewer1'
and "public burden for storm water" and, as a rule, the portion
related to sewage was borne ^y users of sewerage in the Eorm of
a sewerage service charge. The portion related to storm water was
borne by the city since the latter was related to a natural phe-
nomenon and thus charging cicizens was not considered practical.
The number of cities, towns and villages tnat begin the
joint-use of sewerage will continuously increase in the future,
and securing financial sources for proper maintenance and operation
will become indispensable for effectively achieving the role of
sewerage treatment.
In order to secure financial sources for the maintenance and
operation of the sewerage plants, the public role related to
sewerage services must be taken into account, and it will be re-
quired to establish a rule by which proper burdens will be imposed
to users, in addition to enlarging financial measures for the
burden to be borne by public bodies.
Users of sewerage services can be known and clearly determined
but, on the other hand, they are also obligated to pay the appro-
priate social cost as originators of water pollution, so that it
is considered that the principle of the "private burden for sewer"
and "public burden for storm water" should be also be applied in
the future in securing financial sources for service maintenance
and operation.
35
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Seventh US/Japan Conference
on
Sewage Treatment Technology
CURRENT ISSUES IN WATER POLLUTION
CONTROL ADMINISTRATION
IN JAPAN
May 19, 1980
Tokyo, Japan
Toshiki Oshio
Environment Agency
Government of Japan
37
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1. CURRENT STATE OF POLLUTION IN JAPANESE WATERS
Although still very fair from a satisfactory state, an overall improvement
of water quality may be noted in Japanese waters in recent years. Let me
start by examining the pollutants for which environmental water quality
standards have been established under the provisions of the Basic Law for
Environmental Pollution Control. As regards toxic or harmful substances
relating to protection of human health such as cadmium, mercury and PCBs,
the ratio of samples exceeding the respective standards to the total number of
samples taken has continued to decline over the years. (See Table 1.)
Table 1. Ratio of Samples Exceeding Water Quality Standards
Relating to Protection of Human Health To The Total
Number of Samples Taken
Substances
Cadmium
Cyanide
Organic P
Lead
Cromium (VI)
Arsenic
Total Mercury
Alkylmercury
PCBs
Water Quality
Standards
0.01 ppm
N.D.
N.D.
0.1 ppm
0.05 ppm
0.05 ppm
0.0005 ppm*
N.D.
N.D.
1970
(%)
2.8
1.5
0.2
2.7
0.8
1.0
1.0
0
-
1975
(%)
0.31
0.02
0
0.32
0.02
0.24
0**
0
0.38
1978
(%)
0.15
0.01
0
0.05
0.01
0.15
0**
0
0.02
(* Annual averages; ** In number of sampling sites)
Among a number of substances and items for which there exist water
quality standards relating to the preservation of our living environment, taking
BOD levels in rivers for example (See Table 2), a general trend toward
improvement may again be noted here. The non-compliance rate, however, is
high among small rivers and streams flowing through large urban districts.
The rate of achievement of environmental standards in 1978 was: 61% for
water bodies belonging to Category AA, 71% for Category A, 52% for
38
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Category B, 42% for Category C, 48% for Category D, and 40% for Category
E, with an overall achievement rate of 60%.
Table 2. Ratio of Samples Exceeding Water Quality
Standard for BOD in Rivers
Water Quality
Categories
AA
A
B
C
D
E
Water Quality
Standard
for BOD
1 ppm
2 "
3 "
5 "
8 "
10 "
1971
36.7
30.9
35.6
39.9
52.8
70.2
1975
31.4
24.4
27.4
42.6
37.8
49.7
1978
28.1
23.6
31.9
45.0
30.6
46.2
(Number of
Water Bodies)
(275)
(980)
(498)
(225)
( 80)
(139)
Taking for another example the number of coliform groups, one would
get a non-compliance rate of 79% for all water bodies in Category AA (the
standard is less than 50 MPN/100 ml), 70% for Category A (ditto, less than
1,000 MPN/100 ml), and 56% for Category B (ditto, less than 5,000 MPN/
100 ml). No improvement can be seen in this respect.
Turning next to COD levels in coastal waters, a general trend for
improvement may again be recognized, but the rate of achievement in 1978
was: 59% of water bodies in Category A, 79% in Category B, 99% in
Category C, with an overall achievement rate of 75%. The rate was particular-
ly low in the "enclosed" or "semi-enclosed" bodies of water. (See Table 3)
39
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Table 3. Ratio of Samples Exceeding Water Quality Standard
for COD in Coastal Waters to the Total Number of
Samples Taken
Water Quality
Categories
A
B
C
Water Quality
Standard
for COD
2 ppm
3 "
8 "
1971
38.5
30.5
15.2
1975
19.6
18.3
7.4
1978
17.6
17.1
6.1
(Number of
Water Bodies)
(215)
(190)
(117)
Looking at COD levels in lakes and reservoirs, here again one may note
an overall trend for improvement, but the actual rate of achievement of water
quality standard is extremely low, as illustrated by the achievement rates of
29% of water bodies in Cagetory AA, 47% in Category A, only 14% in
Category B, with an overall average rate of 38%. (See Table 4)
Table 4. Rate of Achievement of the COD
Standard for Lakes and Reservoirs
Water Quality
Categories
AA
A
B
C
Water Quality
Standard
for COD
1 ppm
2 "
5 ••
8 "
1971
13.9
79.4
91.8
-
1975
62.0
69.4
84.6
40.7
1978
66.9
63.3
73.0
41.7
(Number of
Water Bodies)
(21)
(57)
(14)
( 1)
40
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2. WATER POLLUTION IN SEMI-ENCLOSED COASTAL WATERS AND
AN AREAWIDE POLLUTION LOAD CONTROL SYSTEM
In the three metropolitan regions of Tokyo Bay, Ise Bay and Seto
Inland Sea lives 53% of the total population of Japan, and 65% of manufac-
tured goods are produced by these regions. As naturally to be expected, a
large amount of pollutants is discharged into these so-called "enclosed" water
areas. The flushing rate, or turnover of water with the outer fringes of the
ocean, is very small, and organic substances are easily retained and accumulate
in these water bodies. Due to the great influx of nutrients, moreover, the
process of eutrophication is in rapid progress. As a result, the water pollution
problem for these waters is getting worse and more complex every year.
In order to cope with this worsening progress of water pollution, the
84th session of the National Diet in 1978 enacted a Special Measures Law for
Seto Inland Sea Environmental Preservation and amendments to the Water
Pollution Control Law, both of which went into effect in June, 1979. With
the objective of achieving and maintaining environmental water quality standards,
the new Law and the amendments of 1978 introduced a system of measures
aimed at an "areawide control of water pollution load", which sought to cut
down on the amount of total pollutant loadings into the three water areas in
an effective and integrated manner, from all sources including domestic house-
holds and hydraulic load of rivers in upstream inland areas.
Targeted reduction in COD load, according to the type of sources and
to each prefecture, goals for raising the percentage of sewered population, basic
guidelines on setting new effluent control standares, etc. were to be specified in
a comprehensive PoEutant Reduction Plan. The Plan was approved by the
Prime Minister in March, 1980, which set a deadline of 1984 for reducing the
COD loadings to the levels shown in Table 5.
41
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Table 5. General Features of Tokyo Bay, Ise Bay and Seto
Inland Sea regions and the Goals for Reduction
of COD Load
Surface Area of Water Body
(km2)
Volume of Water
(X100 million m3)
Population (1976) (XI, 000)
Manufactured Goods (1976)
(trillion yen)
COD Loadings in 1984
(target) (tons/day)
Domestic Sources
Industrial Sources
Others
Tokyo Bay
1,400
540
22,200
32.2
660
386
180
94
Ise Bay
2,300
460
9,090
18.4
426
179
208
39
Seto Inland
Sea
23,000
7,330
28,130
44.5
1,283
517
666
100
In this connection it is important to note that expanding sewerage
networks is an essential requirement for the achievement of these goals, as
indicated by the still very low rate of sewered population in these regions: in
1977, it was 38% in the Tokyo Bay region, 27% in the Ise Bay region, and
31% in the Seto Inland Sea region.
Along with reduction of COD loadings, inflow of nutrients must be
controlled so as to reduce production of organic material by phyto-planktons
utilizing those nutrients. In 1977, for example, 24% (680,000 tons) of all
fishery products in Japanese coastal waters was raised in the Seto Inland Sea.
The number of "red tides" observed in the Sea, which was 48 in 1967, jumped
from 79 in 1970 to 320 in 1975 and 165 in 1978. The red tides along with
them brought heavy damages to fishery production in the Seto Inland Sea, and
became an important issue to be urgently tackled with.
42
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In the face of this event, measures were taken under the Provisional
Law for Seto Inland Sea Environmental Preservation to reduce by 1976 the
COD loadings from industrial sources by more than one half of 1972 levels.
Thus, the average COD concentration in the whole Sea area in 1977 was
brought to 1.7 ppm, while its transparency (Secci depth) was 5.8 meters, Total
N 0.28 ppm, Total P 0.029 ppm. The overall rate of achievement of water
quality standards was 75% (40% for Category A, 80% for Category B, and 98%
for Category C). Compared with national averages, the achievement rate of
water bodies in Category A, which make up a major part of the Inland Sea, is
very low.
Furthermore, daily inflow of phosphorous into the Seto Inland Sea
reaches as high as 81 tons per day. (34 tons from domestic sources, 33 tons
from inductrial sources, and 14 tons form other sources).
In order to raise the water quality of the Seto Inland Sea, the Special
Measures Law for Seto Inland Sea Environmental Preservation provides for
measures to reduce the input of nutrients into the Sea area. On the basis of
this Law, Director-General of the Environment Agency in July, 1979 directed
the governors of relevant prefectures to draw up plans, including specific
measures, to reduce or maintain the present level of P loadings into the Sea by
1984, depending on the prevailing state of pollution by the nutrient. Further
studies will be conducted regarding possibilities for reduction of P concentrations
in Tokyo and Ise Bays.
3. EUTROPHICATION OF LAKES AND RESERVOIRS
Of the 93 lakes and reservoirs for which water quality data are available,
54 show a pH of 8.5 or above, and a DO of more than 10 ppm. In these
lakes, pH rises as C02 is taken up by the multiplying population of algae, and
DO increases to the extent it becomes super-saturated. Many of the lakes and
reservoirs have thus become enriched with nutrients. Lake Suwa, for example,
had a nitrogen concentration of 0.26 ppm and phosphorous concentration
43
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of 0.02 ppm in 1931, whereas the corresponding figures rose to 3.51 ppm and
2.47 ppm respectively in 1978.
Table 6. COD Levels in The Major Lakes of Japan
Name of Lake
Tega-numa
Mikata-goko
L. Kitagata
L. Suwa
Kasumiga-ura
Hachiro-gata
L. Biwa
Water Quality
Category
B
B
B
A
A
A
AA
Maximum
Concentrations
Observed
49 ppm
72 "
16 »
164 -
112 "
26 "
7.5 "
Daily Means
at Standard
Sampling Sites
(75% Values)
28 ppm
22 „
15 „
15 n
14 "
14 »
5.7 «
75%V/
W.Q.S. Values
5.6
4.4
3.0
5.0
4.7
4.7
5.7
It should also be noted that Japanese lakes, many of which are still in
an oligotrophic state and have long been associated with one of the greatest
transparencies in the world, are rapidly deteriorating in terms of their clarity/
transparency. Secci depth of Lake Shikotsu, for example, decreased from 25
meters in 1925 to 18.7 meters in 1978, while in Lake Towada it was reduced
from 20.5 meters in 1930 to a mere 9.8 meters in 1978. The phenomenon of
lake eutrophication is not restricted to natural lakes, either. It now extends to
many of the man-made reservoirs constructed for drinking water purposes. Of
a total of 155 revervoirs surveyed in 1979, 55 is reported to have suffered
cases of fungus-like odor and taste in the water. In other cases, filters were
clogged by mass populations of algae and filtering efficiency lowered.
44
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4. A CASE STUDY OF LAKE BIWA AND EFFORTS TO CONTROL ITS
EUTROPHICATION
Lake Biwa is unique among Japan's more than 500 freshwater lakes.
It is by far the largest of them all, with a surface area of 673 km2, maximum
depth of 103.6 meters, and 27.5 billion tons of water stored. Yet it is
situated entirely within a single prefecture of Shiga, a relatively less developed
region of this highly industrialized nation. The Lake supplies a large volume of
water (4,000 to 6,000 million tons annually) to the metropolitan region of
Osaka and Kyoto with over 13 million population as their sole source of
industrial, irrigation and drinking water.
Topographically, the Lake is divided into two distinctive parts, the small
southern end called the South Lake and by far the larger one the North Lake.
As far as the North Lake is concerned, water quality indices of transparency,
pH, SS, BOD, COD, Total N and Total P remained more or less constant over
the years. See Figure 1. In recent years, however, and particularly since
1977, the "red tides" which had heretofore been restricted to the South Lake
alone spread to the North Lake, which may by all accounts be called
"oligotrophic" in the present state. Figure 2 marks specific areas and extent
of red tide observation during May - June 1979.
45
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Figure 1. Water Quality in Lake Biwa
5.8
5.4
(annual mean of daily averages
at 48 monitoring stations)
5.S (Norch Lakej>5 V 5.7
(South Lake) ^
L9 l£ 1.6 U 1-9 L8 L8
(a)
Transparency
1966 67 68 69 70 71 72 73 74 75 76 77 73 79
(E341X42) (43) (44) (45) (46) (47) (48) (49) (50) (SI) (52) (£3) (SO
( PH )
as -)
S.O
1.5
7.0
6.5
(dc$!)
7.9 *L7.9
(North Lake)
(South Lake)
(b)
PH
1966 67 68 69 70 71 72 73 74 75 76
78 79
'- )
2,0
1.5 -
1.0 -
as -
1.75
(South Lake)
1-52 1.53,---., 1.45 1-51 1.44 US 1.47 1.53
'- ' " '
(North Lake]
(c)
BOD
0-59
i i 1 i 1 1 1 1 1 1 1 1 1 1—
1966 67 63 69 70 71 72 73 74 75 76 77 78 79
(South Lake)
46
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1 0 -
8 -
5
4 -
2 -
(South Lake)
8JJ
8.4
6.0
(e)
SS
(North Lake)
——>
2.1
1966 67 58 59 70 71 72 73 74 75 76 77 73 79
as -
(South Lake) g.53
0.4 •
0.3 -
0.2 -
ai -
0 34 •'"'
(f)
(North Lake^_^g_29a2T"7>I7~~(123 T— N
*^"^ n *?T *^i n *y? u. ^4
0.19
1966 67 63 69 70 71 72 73 74 75 76 77 73 79
3 5 -
3 0
2 5 •
2 0 •
1 5 •
1 0
5 -I
35
31 (South Lake)
27 .-' \ 27
25-'
v 23 .—.:r._3'
(North Lake)
(s)
T-P
,o .0
1966 67 63 69 70 71 72 73 74 75 76 77 73 79
(Source: Environment Agency and
the Shiga Prefectural Government)
47
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Fig. 2. Algal Blooms Sighted on Lake Biwa (1979)
6/8
Okinoshima Is.
S?
5/22
48
major cities
rivers
red tides
observed
dates of
observation
-------
Clearly, phosphorus is not the sole cause of eutrophication, but
recognizing that it is a key element in our efforts to prevent further deteriora-
tion of the nation's waters, the Government of Japan, though not backed up
by any law, has in the past "guided" the detergent manufacturers to reduce
the phosphate content in their products. The industry responded with a
"voluntary restraint" in the use of phosphates, usually in the form of sodium
tripoly-phosphate or NasP3O,0, as a "builder" in detergents. Thus, the
phosphate limit in detergents, which was as high as 20% by weight (in P:OS
equivalent) before, was reduced to 15% beginning in January 1975, to 12% as
from January 1976, and further down to 10% in January 1979. Owing to the
"administrative guidance" of the Ministry of Trade and Industry and to the
detergent industry's own "voluntary restrictions", the P2O5 content in powdered
detergents for household use has continued to decline over the years, although
total production of phosphate-detergents gradually recovered from an all-time
low of 409,000 tons in 1975 (peak production of 624,000 tons in 1974).
See Table 7
According to an estimade made by the prefectural government, 48% of
phosphorus loadings into Lake Biwa is generated by domestic sources (general
households), of which 38%, or 18.2% of the total input, is caused by phos-
phates contained in detergents for household use. See Talbe 8, The
percentage of sewered population is extremely low, a mere 5% in Shiga
Prefecture.
49
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Table 7. Annual Production in Japan of Detergents and Soap
(Unit: 1,000 tons)
A. Synthetic detergents
1 . for household use
a. powder
b. liquid
( 1 ) for laundry
(2) for dish-washing
(3) for other household uses
2. for industrial use
B. Soap
1 . for laundry
a. powder
b. solid
2. for bath use
3. for industrial use
1975
592
409
183
269
122
21
11
75
15
1976
679
450
229
301
147
23
11
96
17
1977
719
474
245
328
151
25
12
98
16
1978
823
532
291
45
192
54
365
156
27
11
104
15
Source: Statistical Yearbook of Chemical Industries)
50
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Table 8. Phosphorus Loadings into Major Lakes of Japan by Source
Sources
Domestic
Factories
Animal feedlots
Agriculture
Forestry and others
(Total)
Lake Biwa
(1975)
(kg/day) (%)
1,117 48.0
682 29.3
325 13.9
205 8.8
2,329 100.0
Lake Kasumigaura
(1973)
(kg/day) (%)
409 31.0
349 27.0
330 25.0
218 17.0
- -
1,306 100.0
Lake Suwa
(1973)
(kg/day) (%)
184 48.0
42 11.0
20 5.0
80 21.0
55 15.0
381 100.0
(Breakdown of domestic sources
for Lake Biwa only)
Night soil 18.7% of total
Detergents 18.2%
Direct drainage
into the Lake
and rivers
11.1%
48.0%
(Source: for Lake Biwa Shiga Prefectural Government
for Lake Kasumigaura and Lake Suwa Environment Agency)
51
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On October 16th, 1979 when its legislature unanimously passed a bill
entitled the "Prefectural Ordinance for the Control of Eutrophication of Lake
Biwa", Shiga Prefecture became the first in Japan to not only totally ban the
sale and use of phosphate-containing detergents but also regulate nitrogen and
phosphorus levels in effluents from industrial plants and public sewage treatment
facilities. The Ordinance, which was promulgated the next day to take effect
within one year (presently scheduled to go into effect as of July 1, 1980),
prohibits any act of selling, displaying for sale or supplying household
detergents containing phosphates and strictly forbids any person to use them
or present them to others as a gift. The Ordinance further empowers the
prefectural government to establish effluent discharge standards (maximum
permissible levels) for nitrogen and phosphorus discharged from factories and
other industrial facilities, sewage treatment plants and private septic tanks above
a certain size.
By taking this bold step forward, the government and people of Shiga
demonstrated their will and determination to protect, even at their own
expense, the nation's single largest source of clean water from the threat of
eutrophication, and thus set an important precedent for the other prefectures.
The Ordinance at the same time authorized the prefectural government to
regulate factory effluents in terms of phosphorus and nitrogen concentrations.
Specific values for the effluent standards are to be set and promulgated in a
separate regulation pursuant to the provisions of the new Ordinance.
It would be the basic objective of the new effluent regulations to bring
down the level of phosphorus concentration in the lake water by 1985 to that
at least of the period 1965-70, and to maintain, or at least not to deteriorate
from, the nitrogen level existing in 1975. In more concrete terms, the targeted
levels of water quality for nitrogen and phosphorus are shown in Table 9,
which also provides a comparison between the present state and the future
expected state with and without enforcement of the proposed new regulations
in terms of nifrogen and phosphorus concentrations as well as in absolute
amounts of inputs of the two nutrients into Lake Biwa. An estimated 111
factories or about 20% of all existing industrial plants and facilities will be
required to install additional or new pollution control equipment in order to
52
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meet the stiff regulatory standards.
In addition, the new Ordinance instructs the governor of Shiga to take
appropriate measures to reduce nutrient inputs into the Lake as a whole,
including provision of technical advice and guidance to the farmers, dairy farms,
forestry operators and households on proper management techniques and
practices. In other words, it is the aim of the Ordinance to enable the
prefectural government to take a comprehensive approach in combatting
man-caused eutrophication of Lake Biwa, from point as well as non-point sourc
sources. The Ordinance taken together with proposed new regulations,
therefore, may be regarded as a form of "area-wide total pollution load control
system" adopted by and applicable to a single Prefecture of Shiga.
53
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Table 9. Water Quality Targets for Lake Biwa in Relation
to Proposed Eutrophication Control Measures
Water
Quality
North
Lake
South
Lake
Total Loading at
Sources
Framework for
estimation
(Assumptions)
1975
Nitrogen
0.28 mg/1
0.33
2 1,4 54 kg/day
Phosphorus
0.010 mg/1
0.015
2,329 kg/day
Population: 985,621
Production: 1,526.5
billion yen
1985 without control
Nitrogen
0.31 mg/1
0.40
28,656 kg/day
Phosphorus
0.017 mg/1
0.023
3,539 kg/day
1985 targets with control
Nitrogen
0.25 mg/1
(estimates)
0.25-26
0.30
(estimates)
0.32-33
Phosphorus
0.010 mg/1
0.009-11
0.015
0.012-14
2 1 ,982 kg/day 1 ,876 kg/day
(rate of reduction)
23 % 47 %
Population: 1,230,000
Production: 3,267.5 billion yen
(at 1975 prices)
(Source: Shiga Prefectural Government based on a simulation model)
-------
5. INTEGRATED APPROACH TO EUTROPHICATION CONTROL
In order to facilitate adoption and implementation of comprehensive
measures to control eutrophication, Environment Agency decided to establish a
set of "water quality objectives" for phosphorous and nitrogen, and in
December 1979 convened a group of experts to consider and recommend
appropriate levels of water quality regarding nitrogen and phosphorous with a
view to controlling, and wherever possible preventing, the progress of
eutrophication in the nation's various enclosed or semi-enclosed waters. The
group is expected to finalize its recommendations by the summer of 1980 as
far as the water quality objective for phosphorous levels in lakes and
reservoirs is concerned. The objectives for P concentrations in other areas and
those for nitrogen are expected to take much longer to materialize.
In March 1980 the Environment Agency also announced its plans for
developing an integrated approach to eutrophication control, which included,
among other things, an appeal to all government ministries and agencies to
refrain from using phosphate-containing detergents at their organizations and
affiliated institutions, including public schools and government-run hospitals and
clinics. Notable among other measures to be taken were: accelerated
deployment of sewerage networks, ensuring appropriate maintenance of
individual household septic tanks, management of farming practices, mitigation
and recycling use of wastes from dairy industry, further research into methods
of control of non-point sources, development of technology for advanced waste
water treatment, etc.
55
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Seventh US/Japan Conference
on
Sewage Treatment Technology
REGIONAL WASTEWATER TREATMENT PLANNING
IN TOKYO BAY AREA
May 19, 1980
Tokyo, Japan
Tsutomu Tamaki
Head,
Sewage Works Division,
Department of Sewerage and Sewage Purification,
Ministry of Construction
57
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Regional Wastewater Treatment Planning in Tokyo Bay Area
Contents
1. Outline of the Area 5,<
1.1 Natural Conditions • 59
1.2 Social Conditions 61
2. Water Quality &
2.1 Present Condition of Water Quality &.-
2.2 Influent Pollution Load 67
2. 3 Water Quality Simulation Models ?2
3. Environmental Standards and Measures for their Achievement 76
3.1 Environmental Standards and Current Water Quality 76
3.2 Allowable Load ^
4. Present Status and Problems of Sewerage Development and
Sewage Sludge Treatment and Disposal in Tokyo Bay Area .... 79
. Outline of Regional Sewerage Plan ................ ......... S3
5.1 Advanced Wastewater Treatment (AWT) Plan .. .......... ... 83
5.2 Sludge Treatment and Disposal Plan ..................... 83
•
5.3 Outline of Regional Sewage Sludge Treatment and
Disposal Plan .......................................... gc
5 . 4 Effects of Regional Sewage Plan ..... ................... 86
5 . 5 Future Problems ........................................ 38
58
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REGIONAL WASTEWATER TREATMENT PLANNING IN TOKYO BAY AREA
1. OUTLINE OF THE AREA
1.1 Natural Conditions
Tokyo Bay is located nearly in the middle of Japan. It is
surrounded by the Miura Peninsula to the west and the Boso
Peninsula to the east. It is linked to the Pacific Ocean by the
Uraga Strait. The term Tokyo Bay designates the inlet area to
the north of the Kannon and Futtsu capes. It extends about 80km
from the north to south end. Its maximum east-west width is 30km,
with an average of about 16km. The surface area is 1,400 km ,
with a volume of about 54 km . To the north of the Honmoku and
Futtsu capes, the sea bed is composed of estuarive deposits, with a
shallow water depth of less than 40 m and a relatively monotonous
bottom configuration. A 1^2 m shallow intertidal zone extends
for about 1^2 km from the shore line. Water depth increases
gradually toward the offing. Between the Kannon and Futtsu capes,
the bay narrows to about 6 km. At this line, the bottom configura-
tion differs greatly from that in the inner part of the bay.
Water depth also increases to over 50 m, producing a large sub-
marine valley starting at a water depth of 100 m at a point about
2 km off Kurihama in the Uraga Strait. This valley curves point
at the bottom of Sagami Bay with a water depth of 1,000 m.
The basin area of Tokyo Bay is about 7,700 km2. The basin
has a rectangular form long in the NW-SE direction across the
bay, but the greater part of the basin area strectches to the NW
(Fig. 1.1). The basin area is about 5.5 times the bay surface
area.
Nine major rivers flow into Tokyo Bay. These are cited in
Table 1-1. The precipitation over the basin is about 1,500 mm a
year. The Basin area is situated in the monsoon region so that
there is much rainfall in summer but little in winter. The annual
peak rainfall occurs before the typhoon season (September to
October), followed by the rainy season. River flow varies in
59
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Fig. 1.1 Tokyo Bay Basin Map
Gunca
Prefecture
Tochigi
Prefecture
60
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accordance with the rainfall pattern. Large rivers flowing into
Tokyo Bay are heavily utilized for urban water systems. Their
water is controlled in a complicated manner, which includes dam
operations, introduction of water from other water systems to
the north and west and water conveyance between rivers. Thus,
because of such artificial controls, river flow into the bay
considerably differs from the resulting from natural conditions.
Table 1-1 Major Rivers Flow into Tokyo Bay
Edo River
Naka River
Ara River
Sumida River
Tama River
Tsurumi River
Koito River
Obitsu River
Yoro River
Basin area
(km2 )
183
915
2,267
593
1,184
238
146
273
247
Inflow into
the Bay, 1975
(10s mVyear)
3,087
1,145
821
2,042
568
636
137
252
218
Water quality (BODs)
1977 mean
3.3
6.4
2.9
5.2
7.3
4.4
4.0
3.7
1.7
Environmental
standard
B(3)
C(5)
B(3)
D(8)
C(5)
D(8)
C(5)
B(3)
B(3)
Numerical figures according to Comprehensive Basin-Wide Sewarage
System Study in Tokyo Bay Area.
1.2 Social Conditions
Tokyo Bay basin belongs to the South-Kanto district. Ad-
ministratively, it includes the Tokyo Metropolis, the greater
part of Saitama Prefecture and parts of Kanagawa and Chiba
Prefectures. These form the Metropolitan area with the capital
Tokyo at its center. It is the center in all aspects of the
administration, economy and culture of Japan.
To represent the national status of the Tokyo Metropolis,
which is a particularly important administrative entity in this
district, the statistics can be given:
61
-------
1% of agriculture;
10% of population, dwelling houses and social capital;
20% of productive, cultural and consumptive activities;
40% of financial activities; and
60% of the highest executives, accumulation of large
enterprises and concentration of intellectuals.
The population and industrial shipment of those parts of
the said district which are included in the Tokyo Bay basin in
terms of their proportion to those of the whole country in 1975
are given as shown in Table 1-2-1. It will be seen that within
the basin, which is only 2% of the whole national land area 20%
of the population and 22% of the industrial production of the
whole country are conentrated. In Japan, which has the highest
density of population and where productive activities are carried
out at the highest density in the world, the Tokyo Bay basin is
an area which has them accumulated to the highest extent.
Table 1-2-1 Population and Industrial Shipments of the
One Metropolis and Three Prefectures of the
Tokyo Bay Basin (1975)
\vltern
Prefecture\
Tokyo
Kanagawa
Saitama
Chiba
Total
Whole
Country
Area
(km2)
Adminis-
trative
section
2,145
2,391
3,799
5,115
(3.6%)
13,450
Within
basin
1,724
508
3,369
1,910
(2.0%)
7,511
377,535
Population
(1,000 persons)
Adminis-
trative
section
11,669
6,398
4,821
4,149
(24.2%)
27,037
Within
basin
11,554
3,435
4,551
2,548
(19.7%)
22,088
111,934
Industrial
Shipments
(¥100,000,000)
Adminis-
trative
section
114,866
120,329
52,006
55,840
(26.9%)
343,041
Within
basin
114,688
72,487
47,037
46,129
(22.0%)
280,341
1,274,329
Population of administrative sections by National Census;
Industrial shipments by Industrial Statistics; and figures
within basin by Comprehensive Basin-Wide Sewerage System Study
in Tokyo Bay Area.
62
-------
Under the Third Comprehensive National Development Plan,
plans have been made to distribute the population and industrial
activities to the local districts so that the weight of the Tokyo
Bay basin area to the whole country will relatively decrease in
the future. Yet, the population and industrial activities in the
Tokyo Bay basin will continue to remain at a high level
(Table 1-2-2).
Table 1-2-2 Changes in the Population in the One
Metropolis and Three Prefectures
Prefecture
Saitama
Chiba
Tokyo
Kanagawa
Total
1960
. Urban
Total
area
[ 2,431 ; 896
2,306 663
1 9,684
i 3,443
17,364
8,908
2,411
12,878
1965
Total
3,015
2,702
10,369
4,431 !
21,017
Urban
area
1,320
1,053
10,099
3,175
15,647
1970
Total
3,367
3 , 366
11,408
5,472 i
24,113
Urban
area
2,126
1,706
10,376
4,290
13,998
1975
Total
4,821 ;
4,149
! 11,674 !
i i
! 6,398 i
1 27,042
i
Urban
area
3,113
2,394
11,279
5 ,401
22,187
Within the Tokyo Bay basin there are a total of 171 muni-
cipalites: 23 special wards, 25 cities, 5 towns and 1 village in
Tokyo; 4 cities including-2 specially designated cities in
Kanagawa; 39 cities, 35 towns and 16 villages in Saitama; and
17 cities, 10 towns and 1 village in Chiba.
Looking over the locations of these cities, many of the cities
located along the bay have an industrial character. Large scale
plants such as steel and chemical industry are located along the
bay. Further, the bay is surrounded by leading trade ports such
as Yokohama Port (annual cargo handling of 116,990,000 tons),
Tokyo Port (58,540,000 tons) and Chiba Port (124,820,000 tons).
The cargo handling of these three ports accounted for 11% of
the whole country. The inland cities are characterized in
eccentric circles about the urban center of Tokyo. The urban
center of Tokyo is a central area of business, and the resident
63
-------
population is lower than that of its periphery. Some sub-centers
are located in the periphery. These center and subcenters are
closely connected with one another by means of road and railroad
networks. Further out from the sub-centers are located the
cities of the so-called "bedroom towns", surrounding the central
area. These cities include some new residential towns with
populations at the level of about 300,000. The outer periphery
of these residential cities extends as far as 50 km from the
urban center along railroads running out from the center. The
area within the radius of 50 km is rapidly becoming urbanized,
and the urabn area is expanding, linking the cities. Beyond the
50 km zone, independent cities are located here and there, but
the weight of the population, etc. is very low, if taken against
the basin as a whole.
Among the cities within the Tokyo Bay area those performing
sewage treatment as of 1978 are 40 in total (with the 23 wards of
Tokyo taken as one city), and the number of sewage treatment plants
is 58. The population covered by these treatment plants is
9,000,000 or about 40% of the population in the basin area. The
total quantity of sewage treated is 7,136,000 m3/day. The treat-
ment facilities now operating are largely of a combined type, but
those to be constructed hereafter are, for the greater part, of
separate systems. The urban area is spreading to connect the
cities with one another, and this trend will continue or intensify.
Thus, for sewage disposal to meet the requirements of such a
situation, regional sewage systems are being constructed or planned.
In some of the cities in the basin where no sewage treatment is
provided, construction of sewage systems is in progress. In almost
all of the cities, construction plans are being formulated.
2. WATER QUALITY
2.1 Present Condition of Water Quality
In the Tokyo Bay area artificial pollution is produced in
large quantities because of the accumulation of a high density of
64
-------
population and productive activities in the basin on one hand,
and from physical factors such as the poor exchange of sea water
with the open sea on the other. Thanks to measures taken from
the first half of 1970's to control water pollution, the pollution
has been reduced in these years. Yet, Tokyo Bay is still highly
polluted. From 1971 water analysis has been made periodically
in Tokyo Bay. Measurements are made at least once a month at
48 points in the bay. Measured COD nan, which shows the extent
of organic pollution, is changing remarkably from season to
season. That is, at any point in the bay, the 'COD mn concentra-
tion is low in winter and high in summer. At some locations, it
is not rare that the peak value in summer is several times the
normal value. This is produced because Tokyo Bay is a water
area of considerable eutrophication, so that algae production of
phytoplankton constitutes a considerable part of the organic
pollution. Thus, seasonal changes are caused by such internal
production. This is verified from the vertical distribution of
the COD mn concentration. In surface water, the COD mn con-
centration is very high in summer/ while in the bottom layers,
the seasonal change in COD mn concentration is negligible. In
summer, sea water in the bay stratifies, and the water temperature
in the surface layer becomes high. This induces the propagation
of phytoplankton. This is also the cause of seasonal changes
in COD mn values. Seasonal changes in the COD mn concentration
at selected points in the bay is shown in Fig. 2.1.
As stated above, the COD mn concentration in Tokyo Bay has
a certain pattern related to seasonal change. In horizontal
distribution, it has some of these characteristics. For example,
the horizontal COD distribution is not constant throughout the
year but changes more or less from season to season. Seasonal
wind in the bay may be the cause of such change. In the horizontal
distribution, the COD mn concentration is, of course, very high
near the influx of large pollution loads. In the case of Tokyo
Bay, large rivers are concentrated in the northwestern part of
65
-------
Fig. 2.1 Seasonal Change of COD mn Concentration
(Mean Value of Surface and Bottom Layers)
th)
COD
(mg/U
'75
124
10-
1 3 5 79 11 135 79111 35 79111 3 (ronth)
246 8 1012 12468 1012 2468 10 12 2
•75 - '76 '77 '78
COD H l\ C 15
2 4 6 8 10 12 2 4 6 8 10 12 2 46 8 10 12 2
66
-------
the bay. The pollution load is concentrated these. Thus, as
a whole, a high concentration area of COD mn appears in the
northwestern part of the bay, and the concentration tends to
decrease toward the east coast and bay entrance to the south.
The influence of seasonal winds appears to be strong, particularly
in the surface layer. The southerly wind in summer_ acts to
prevent the high concentration area in the north from spreading
into the bay. while the northerly wind in winter acts conversely
to accelerate the diffusion. Distributions of COD tun concentra-
tion in February and May 1975 are illustrated in Figs. 2.2 and
2.3, respectively.
2.2 Influent Pollution Load
For the simulation of water pollution in Tokyo Bay and the
examination of policy measures for reducing the load and meeting
environmental standards, a forecast of the pollution load occurring
in the basin and that flowing into Tokyo Bay was made.
Pollution loads from artificial sources, such as domestic
sewage, industrial wastewater and livestock wastewater, were
calculated by multiplying the population, industrial shipment and
quantity of poultry by the respective unit values. The generated
load is treated at sewage treatment plants, night-soil disposal
plants or treatment facilities provided by factories to meet the
effluent standards before it is discharged into a river, etc.
The discharged COD mn load into the basin is about 700 tons/day
or 35% of the total generated (about 2,000 tons/day).
The loads discharged into the basin flow into Tokyo Bay via
rivers or other water channels. The routes differ. In the case
of Chichibu City, located at the western part of the basin, the
load flows a distance of nearly 150 km. On the other hand,
sewage treatment plants located along the bay coast discharge the
load directly into Tokyo Bay. Such routes of flow into the bay
were charted properly, and the influx to Tokyo Bay was calculated
according to the method described below. For the load flowing
67
-------
Fig. 2.2 Distribution of COD mn Concentration in February 1975
(Mean Value of Surface and Bottom Layers)
68
-------
Fig. 2.3 Distribution of COD mn Concentration in May 1975
(Mean Value of Surface and Bottom Layers)
69
-------
into Tokyo Bay via a rivers, the lowermost point of the river at
which both flux and COD mn concentration were obvious (such
points were termed 'the fair flow terminals' was plotted. The
transit load at the point was obtained by multiplying the flux
by the COD mn concentration. For the river basin above the fair
flow terminal and the area of direct flow into the bay, the influx
into the river and that into the bay were calculated from the
discharged loads according to a specific formula. This formula
was derived from the measurement data of six areas, with the
population density and water volume density of the respective
basins taken as parameters. For the inflow load to the fair flow
terminal of the river, influx to the bay was calculated by measure-
ments of the COD mn concentration in the river channel. When sea
water was mixed, dilution by sea water was taken into consideration
in the value of measurement of the CJZ. ion concentration. Further,
in the rivers, the COD mn concentration was measured at various
points at a frequency of at least once a month so that the influx
to the bay was calculated by month. The annual mean values of
the influx load and influx water volume (fresh water) to Tokyo
Bay in 1975 are given in Table 2-2 and Fig. 2.4. The influx load
to the bay is about 440 tons/day or nearly 63% of the approximately
700 tons/day total load discharged in the basin.
70
-------
Fig. 2.4 Distribution Chart of COD Load Flowing
into the Bay
50 40 30 20 10 1
NO. Nomenclature
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
CB-2
CB-3
CE-4
CB-5
CB-6
TB-1
TB-2
TB-3
TB-4
TB-5
KB-1
KB- 2
KB-3
KB-4
Koito River
Obitsu River
YSrO River
Edo River
Naka River
Ara River
Sumida River
Tama River
Tsurumi River
71
-------
Table-2-2 Influx Water Volume and Load into Tokyo Bay
Units: Water Volume, 1,000 m3/day, and
Load, COD mn t/day
Block
Koito River
1975 Mean
Water
Volume
374
Obitsu Rvier 691
Y5ro River 597
Edo River 8,458
Naka River 3,138
Ara River
Sumida River
Tama River
Tsurumi River
River Total
2,248
5,595
1,557
1,879
24,537
Load
0.66
1.42
0.70
46.00
41.72
29.92
82.90
10.68
19.86
233.86
Block
CB-2
CB-3
CB-4
CB-5
CB-6
TB-1
TB-2
TB-3
TB-4
TB-5
KB-1
KB-2
KB-3
KB-4
Direct dis-
ch arge to
the Bay
Total
Total
1975 Mean
Water
Volume
468
533
514
983
628
26
641
983
1,575
54
1,768
674
778
204
9,829
34,366
Load
4.13
6.14
4.20
12.64
11.61
1.44
22.47
22.18
40.29
2.74
41.44
19.91
14.38
3.29
206.86
440.72
2.3 Water Quality Simulation Models
Analysis of water pollution in Tokyo Bay by computer was
started in or about 1970. Some models are now available in the res-
pective fields. There are two water quality simulation models in
use. One is a tidal current simulation model for the reproduction
of tidal phenomena in the bay with the water level variation at
the bay entrance, inflow to the bay, etc. given. The other is a
water quality simulation model reproducing the distribution of
COD mn concentrations in the bay from the inflow, advection,
72
-------
diffusion decrease, etc. of the load in use with the results of
tidal calculations. The models used this time are outlined below.
Tidal Current Simulation Model
o Two dimensional, one layer; Tokyo Bay sectioned in 2 km-meshes.
o Partial differential equations of the equations of continuity
and motion are substituted by differential equations, and
numerical solutions are obtained under given initial and
boundary conditions.
o The result is expressed as a value of integration of the tidal
current in one day, or the so-called residual flow.
Water Quality Simulation Model
o Two dimensional, one layer; The regions of calculation and
mesh are the same as those of the tidal current calculation
model. In the vertical direction, water quality is assumed to
be uniform.
o Change in water pollution quantity in the respective meshes is
resolved by numerical analysis according to the so-called
equation of diffusion, under which the change is due to advec-
tion, diffusion, inflow of the load and decreases owing to
self-purification.
o For tidal currents, the results of the calculations from the
tidal current calculation model, or the residual flow, is used.
Accordingly, the result is given as daily mean water quality.
The results of reproduction of the average residual flow in
the bay in May according to the tidal current calculation model and
of the COD mn concentration (except COD mn by algae production) in
the bay, according to the water quality calculation model, are
shown in Figs. 2.5 and 2.6, respectively. The results of reproduc-
tion of both tidal current and COD mn concentration are considered
to be good, upon reference to the results of observation so far
obtained.
73
-------
Fig. 2.5 Tidal Current Calculation Result,
Residual Flow, May 1975
74
-------
Fig. 2.6 Water Quality (COD) Calculation Result, May 1975
Value of
measurement
SS0.5.
Value of
calculation
I = 0.002C2
(Case la)
75
-------
3. ENVIRONMENTAL STANDARDS AND MEASURES FOR THEIR ACHIEVEMENT
3.1 Environmental Standards and Current Water Quality
Tokyo Bay is divided into 18 water areas, and for each water
area, an environmental water quality standard is stipulated. Taking the
environmental standards in terms of COD mn concentration, the bay is
classified into 3 categories of A(less than 2mg/£), B(less than 3 mg/£) ,
and Cdess than 8 mg/£). To check whether or not the environmental
standard is observed, a total of 48 environmental data points are
provided in the bay, according to the water area classification,
and at each point, measurement of the water quality is made at a
frequency of at least once a month. Specifications of the environ-
mental standard and locations of the environmental data points
are shwon in Fig. 3.1. Whether or not the environmental standard
is achieved is determined by the 75% value of annual measurement
of the water quality (or the value corresponding to 1/4 of the
whole counted from higher concentration). As of 1975, the environ-
mental standard was achieved at 21 points, or 44% of all environ-
mental data points. However, they are, for the most part, points
belonging to Class C along the coast. In Class A and B water
areas constituting the greater part of the bay, the environmental
standard is rarely achieved.
3.2 Allowable Load
In view of the environmental standards being rarely achieved
in Classes A and B against the COD mn influx load of 440 tons/day
of 1975, the extent the influx load to the bay should be suppressed
in order to achieve the environmental standards of Tokyo Bay as
a whole was determined.
Organic pollution of Tokyo Bay is caused by two factors:
pollution due to influent organic pollutants and that due to algae
production by phytoplankton. In principle, these two are considered
to be independent phenomena. The highest frequency of the COD mn
concentration corresponding to the 75% value as a whole of the bay
76
-------
Fig. 3.1 Water Quality Environmental Data Points and
Class Specifications in Tokyo Bay
Legend
Environmental Data Points
A Tokyo (8 Points)
• Kanagawa(20 Points)
• Chiba (20 Points)
77
-------
is May. When this period is taken, the influent load accounted
for 47% of the COD ran of the bay in May 1975 and internal pro-
duction accounted for the remaining 53%. From the distribution
of COD mn concentration in the bay, it was presumed that algae
production would be of higher weight toward the central part of
the bay which had a relatively lower concentration of COD mn.
In such a situation, it would be imperative in achieving
the environmental standard, to reduce the influent load and, at
the same time, suppress algae production.
The mechanism of internal production is not yet known,
although efforts are being made to clarify it. The numerical
simulation model is not yet complete. Thus, in obtaining the
allowable influx load, calculation was made with some stages set
for the level of internal production.
From the calculation results, it was found that in order
to achieve environmental standards, the influx load had to be
less than about 220 tons/day and that algae production had to be
suppressed to a level of less than about 1/4 of that in May 1975.
The allowable quantity of about 220 tons/day corresponds to about
one half of the inflow of 440 tons/day in 1975. When the storm
water overflow from the existing combined sewer systems in the
basin, to which control measures are difficult to apply, or natural
pollution due to storm water is considered, considerable efforts
would be required for reducing the current inflow by more than
one half. When the increasing quantity of water to be treated in
the future is taken into consideration, treatment facilities in
the basin must have the discharge water quality improved to about
COD mn 5-10 mg/5, after 20 years.
On the other hand, in order to suppress algae production to
that of about 1/4 of the present, if the factors governing the
rate of algae production are taken to be nutrient salts of nitrogen
and phosphor, it is estimated that a greater part of this genera-
tion will have to be reduced by the discharge control at the
artificial sources of generation.
78
-------
4. PRESENT STATUS AND PROBLEMS OF SEWERAGE DEVELOPMENT AND
SEWAGE SLUDGE TREATMENT AND DISPOSAL IN TOKYO BAY AREA
Development of sewerage systems in Tokyo Bay area is in
progress mainly around the large cities, and in the 23 wards.
The development is complete for 70% of the whole area. In the
peripheral areas, 2 or 3 cities have almost completed the develop-
ment. However, in Chiba and Saitama, where population is increasing
rapidly, development is slow. Thus, total coverage by sewerage
systems in the area as a whole is about 40 percent.
Construction of sewerage systems is being urged for various
sites in the area, and in Tokyo, Yokohama, Kawasaki and Chiba
cities and Tokyo, Saitama and Chiba Prefectures, construction of
regional sewerage systems designed for smaller cities in the area
is in progress.
The cost of construction of the sewerage systems in the area
around Tokyo Bay is about ¥480,000,000,000 (or about $2,000,000,000)
in fiscal 1979.
In regard to drainage systems, in those areas of Tokyo,
Kawasaki and Yokohama where sewerage was planned and construction
was executed from an early time because of the importance of the
area for the respective cities or as a measure for preventing
storm water flooding, the combined system is extensively employed.
But, in the areas where construction has started recently, separate
systems are generally employed.
Table 4-1 shows the major sewage treatment plants now in
operation or under construction.
At present, the largest plant is the Morigasaki Wastewater
Treatment Plant, Tokyo, located near the former Tokyo International
Airport.
Treatment is conducted largely under the activated sludge
process, and the sludge is subjected to dewatering directly or
after anaerobic digestion. It is then disposed of, partly after
incineration or by land reclamation.
79
-------
Table 4-1 Major Sewage Plants in Operation or under
Construction (Tokyo Bay)
Planned treatment capacity, 200,000 m3/day or more.
Starting Date
Jane of. Plant Type and Project Entity Qf Op.r>tlon,
!
i
[Saitama Prefecture]
AraKawa Left Side Basin, Regional Sewerage Sal tana 19*72
Soutr. Prefecture
Arakawa Left Side Basin , . "
Nort-T
Arakawa Rignt Side Basin ' "
Nakagawa ( " "
IC~.ii>a Prefecture!
Inbanuma Basin . Regional Sewerage i Chiba 1974
i Prefecture |
Edogawa. Left Side Basin ' " " 1
[Tokyo Hetropolia]
Snli>aura j Municipal Sewerage; Tokyo 1931
; i Metropolis
Mikawa]lma 1 " 1922
Kosuge ' " " 1977
Sunanechi " "1 1*30
Odai • - 1962
Sningaahi " : " 1974
denial ! - 1964
Mongesaki * . 1966
'
Kltatama No. 1 Regional Sewerage " 1973
Tanagawa Upstream n j " 1976
Minaoutama | " ' " 1971
AraXawa Rignt Side '
Tokyo :
[Kanagawa Prefecture] >
Yokohama '
Kohoku ' City 1 1972
Midori | " • 1977
Kanagawa " [ - 1973
Nanbu " ! - 1955
Kanazawa " " 1979
Ineiaki " Kawasaki 1961
; City
Raw - - i 1973
Todoroki " " I
1 i 1 1
Current
Capacity
1,000
mVday
210
-
154
•
1,130
700
150
680
3SS
705
4SO
1,280
136
75
53
"
88
74
191
234
69
300
122
-
Planned
Capacity
1,000
m'/day
: 1.383
602
1,280
2,040
1,344
1,524
303
1,590
950
450
1,220
420
1.350
450
1,810
450
64*
473
693
439
443
517
234
325
357
245
360
R* marks
6 Cities.
5 Cities, 1 town.
10 Cities, 3 towns.
9 Cities, 6 towns.
7 Cities, 5 towns, 2 villages.
6 Cities, 1 town.
o Cities.
5 Cities, 2 towns.
5 Cities.
10 Cities.
•1 Treatment systems all u»e tne activated aluoge process.
80
-------
In order to achieve the environmental standards in Tokyo
Bay, advanced wastewater treatment (AWT) will be required in
almost all the treatment plants in the future. However, extension
of the sewerage systems is of primary importance, so that construc-
tion presently is limited to secondary treatment facilities. But,
hereafter, construction of AWT facilities must be expedited.
Most treatment plants can only afford enough land for secondary
treatment. Thus, securing enough land for wastewater treatment
and constructing facilities including those for AWT are problems
to be resolved later.
On the other hand, as the sewerage project progresses and
treatment becomes intensive, it is believed that there will be
increasing quantities of sewage as well as sludge. The result of
a survey of the quantities of sewage and sludge at present and
in the future is shown in Table 4-2. As seen, in 1995, the popula-
tion served by sewage treatment will expand about 3.1 times,
effluent about 3.8 times and sludge in terms of dewatered cake
about 5.9 times the 1978 values. At present, disposition of
sewage sludge in the Metropolitan area is such that land and sea
surface reclamation accounts for about 99% of the final disposition.
Figure 4.1 shows the generated sewage sludge in the Metropolitan
area by year and by form (shown as dewatered cake).
If we assume that sludge is generated as a matter of course
from the activities for the maintenance of life and the living of
man, who is a member of the natural world, it is considered to be
a principle for disposition of the sludge to place the sludge in
the cycle of material circulation. Particularly, in the inland
area, it is thought desirable to review the value of sewage sludge
as a resource and replace it in the biological cycle as soon as
practicable, in a reasonable form, with soil as a medium to return
it to the green and farm land. Studies on the application of
sludge for construction materials such as aggregate, reduction to
ocean, etc. must also be carried out positively. In this way,
sludge disposal should, as a rule, take a form of infinite disposal.
81
-------
Table 4-2 Sewage Treatment in 1978 and 1985 in the Tokyo Bay Area
~~~ ______^^ Year
Items —- ~ — ^_____
1) Area served (ha)
2) Population served
(1,000 persons)
3) Population density
( 2)/l) 1,000) (persons /ha)
4) Quantity of effluent
(1,000 m3/day)
5) Sludge quantity generated
(1,000 mVday in terms
of cake)
6) Number of treatment plants
7) Population served per
plant (1,000 persons)
8) Quantity of effluent per
plant (1,000 m3/day)
9) Sludge quantity per plant
(1,000 m3/day)
1978
78,820
9,003
114
7,136
1,340
58
155
123
21
1995
299,400
27,550
92
27,422
7,970
75
367
366
109
1995/1978
3.8
3.1
0.8
3.8
5.9
1.3
2.4
3.0
5.2
Fig. 4.1 Generation of Sludge by Type and by Year
(in* Terms of Dewatered Cake)
(1,000 ton/year)
9,000
8,000
7,000
6,000
'78 '80 '85 '90 '95(year)
(Note) Moisture content of dewatered cake = 75%.
82
-------
But, in the large city regions such as the Metropolitan area
where the urban area is expanding continously and the population
is overcrowded, for almost all cities it is difficult to secure
land for treatment plants to dispose of sludge independently.
For the adequate disposition of the growing amounts of sludge
generated hereafter, it is very difficult to complete the disposi-
tion of the sludge within the administrative area of one local
government. It is, therefore, required for local governments
concerned to plan an area-wide sewerage project conforming to
their individual requirements and thus promote the project.
5. OUTLINE OF REGIONAL SEWERAGE PLAN
5.1 Advanced Wastewater Treatment Plan
In planning an AWT system for Tokyo Bay, it should be kept
in mind that some local governments have their own individual AWT
plans. Others do not. In the case that a plan permitting ef-
ficient and effective development is developed for the latter,
a regional block is conceivable for the AWT.
Thus, it was arranged that the reigonal blocks would be
established as shown in Fig. 5.1. It was decided that (1) those
treatment plants which could from the economic as well as technical
points of view individually perform AWT should be excluded and
(2) consideration should be given to recycle the effluent from
AWT, and that for the others, individual treatment would be con-
sidered. Under this plan, it is estimated that against the flow
of effluent from AWT of 27,420,000 m3/day in 1995, the corresponding
quantity of effluent treated by regional AWT plants would be
5,780,000 m3/day for the Tokyo Bay coast block and Ara River System
midstream block. The required land area would be about 130 hectares.
5.2 Sludge Treatment and Disposal Plan
Along with progress in sewerage development on one hand, and
the requirements for AWT in the achievement of environmental
83
-------
Fig. 5-1 Quantities of Effluent from AWT by Block
Plants for
inclusion in
regional
treatment.
84
-------
standards on the other, the quantity of sewage sludge will in-
crease in the future. For treatment and disposal of such sludge,
it is very difficult to secure land, not only for sewage treatment
plants, but also for the disposal of the sludge. The reasons for
this are given below.
(1) In the Metropolitan area, land is heavily used, so that it is
in fact impossible to secure adequate land.
(2) It is very difficult to obtain the consent and cooperation
of inhabitants who live near land designed for disposal.
(3) The disposal land must be sought in the future at more remote
sites, and this involves a number of problems such as trans-
portation costs, transportation systems, etc.
For the foregoing reasons, disposal must be directed toward
seaside reclamation, etc. However, adequate sites for this are
limited. It is, therefore, necessary for local governments to
cooperate with one another over a wide area and use the available
space for disposition effectively, and thus ensure stable disposal
of sludge over a long period in the Metropolitan area as a whole.
5.3 Outline of Regional Sewage Sludge Treatment and Disposal Plan
Tables 5-1 and 5-2 show the scale of the regional age sludge
treatment and disposal bases determiend from the future plans of
the respective local governments and forecasts of the quantity of
sludge generated. These plans include the sludge transportation
system, relay stations, sludge treatment facilities (thickener,
digestion tank, dewatering equipment and incinerator), landing
equipment, return flow treatment equipment, power generation
equipment, etc. A schematic diagram of the foregoing is shown in
Fig. 5.2.
85
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Table 5-1 Scale of Regional Sludge Treatment Facilities
Raw sludge
Dewatered cake
Ash
Scale of Treatment
Facilities m3/day
66,540
(DS 998 t/day)
1,910
1,370
Land Required for
Facilities ha
Approx. 50 ha
Table 5-2 Scale of Regional Sludge Disposal Land
Sea side reclamation
Sludge quantity for reclamation
600 ha
87 mil./m3
5.4 Effects of Regional Sewage Plan
When sewage treatment/disposal is taken up as a regional
project in a large city area, the following advantages may be cited.
(1) An efficient social investment is effected.
By executing a regional project, social investment becomes
more efficient than if the project is executed separately by the
local governments concerned. Further, the additional value of
creating a new space in a large city area is substantially great.
(2) Adequate maintenance is made.
By extending the project over a wide range, the maintenance
cost is reduced. For the maintenance and operation of AWT, excel-
lent engineers can be obtained. This strengthens the maintenance
and operation system.
Further, sludge disposition is made systematically under
careful management by the regional sludge treatment/disposal
projects.
86
-------
oo
Fig. 5-2 Schematic Diagram of Regional Sewage Sludge Treatment and Disposal Plan
Sludge DJ sjxisdl Equipment
crp^.-"-
Dewateiing Incjnet a tot
f'aci 1 i ties
iat ion
I Sludge llandl ing Equipment
Exhaust tJas Treatment
Receiving Biological
Tank Treatment
Return Flow Treatment Equipment
(Supernatant Treatment) Sand
a r"^
ristip fe
Activated j"
Filter Carbon Ab-
sorption Tower
&.
Disinfec-
tion Tank
at ]
~han Power Genera-
t ion Eguipment
Power Generation
Equipment
-------
(3) Reclaimed land is usable for AWT along the bay coasts.
Considering the very difficult condition for securing of
the land for AWT, some treatment plants along the Tokyo Bay coast
must use seaside reclamation for land for AWT. The reclaimed
land is usable as land for AWT of the secondary treatment effluent
gathered from such plants.
(4) The existing sludge treatment land is usable as land for AWT.
Under the very difficult conditions for securing the land
for AWT, there are some treatment plants which are capable of
coping with AWT if sludge treatment land is converted, with the
sewage sludge treatment and disposal, resorted to the "regional
system.
(5) Recovery of the energy from sludge provides an economic
return to society.
By recovering the energy from decomposition gas, etc. gene-
rated from a large amount of sewage sludge effectively, the energy
consumed in the plant can be provided and the excessive energy
can be returned to society through power generation, etc.
Simultaneously, the quantity of sludge to be disposed of may be
reduced.
5.5 Future Problems
Carrying out the plan in the future requires a full examination
of the following problems.
(1) Execution of environmental assessment.
(2) Technical development of the processes of energy and resource
saving.
(3) Examination of the plan for recycling the effluent from AWT.
(4) Long ranging forecasting of sewage sludge treatment and
disposal.
(5) Examination of measures for controlling sludge at the source.
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
AUTOMATED CONTROL
OF
SLUDGE TREAMENT SYSTEMS
May 20, 1980
Tokyo, Japan
Mamoru Kashiwaya
Kinichiro Azuma
Akio Kuwayama
Research and Technology Development Division,
Japan Sewage Works Agency
89
-------
AUTOMATED CONTROL OF SLUDGE TREATMENT SYSTEMS
CONTENTS
Page
1 . Introduction ................. • ...... • ....................... '1
2. Basic Flow Diagram of the Sludge Treatment System . .......... 93
3. Current Techniques of Operation and Control for 96
Sludge Treatment Processes ..................................
3 . i Sludge Gravity Thickening .................................. 96
3 . 2 Sludge Digestion ......................................... . . 97
3 . 3 Digested Sludge Elutriation ..................... . .......... 99
3 . 4 Chemical Conditioning . ......... . .................... . ...... 99
3 . 5 Sludge Dewatering ..... . ........... . ...... . .............. ... 101
3 . 6 Sludge Incineration ... ..................................... 102
3 . 7 Heat Treatment ........................................... . . 104
4. Current Monitoring and Control Techniques for
Sludge Treatment Systems ................................... . 106
4.1 Type I [[[ 106
4'2 ^Pe n [[[ 106
4 . 3 Type HI ...............................................
5. Future Progress in the Operation and Control of
Sludge Treatment Processes ........... ...... .................
5 . 1 Sludge Thickening ............ . ............................. 108
5 . 2 Sludge Digestion ........................................... 108
5.3 Digested Sludge Elutriation ................................ 109
5 . 4 Chemical Conditioning ...................................... 109
5 . 5 Sludge Dewatering .......................................... 109
5 . 6 Sludge Incineration ........................................ 109
6. Future Progress in the Monitoring and Control of
Sludge Treatment Systems .................................... 116
6 . 1 Type IV [[[ 116
-------
INTRODUCTION
At present, various measuring instruments and control equipment are used
in the operation and maintenance of sewage treatment plants, reflecting
the remarkable development of electronic engineering in recent years.
At several plants, operation and maintenance are carried out with digit-
al computers.
In sludge treatment systems, which constitute a major part of sewage
treatment plants, an increasing number of measuring instruments and
control equipment is being applied.
These instruments and equipment are used in a manner to ensure stable
operation of each sludge treatment system and to ensure high-quality
effluent whatever the quantitive and qualitive fluctuations of sewage
inflow to the plant. Thus, measuring instruments and control equipment
are employed in each stage of the sludge treatment process, including
the receiving of raw sludge from the sewage treatment system, the reduc-
tion of sludge volume, the stabilization of organic matter, and possible
final disposal of the sludge.
Given that sludge from the sewage treatment system varies widely in both
quality and quantity; for the prupose of receiving, reducing, stabilizing
and disposing of the sludge, automated control of the sludge treatment
system must be such that:
i) the maximum functioning of each stage can be obtained,
ii) the operation as the entire system can be optimized, and
iii) each constituent process can be functionally coordinated with the
others.
The target performance of the automated control is as follows:
iv) improved sludge treatment efficiency of each process and at the
same time of the system as a whole,
v) prevention of a temporary drop in sludge treatment capacity due to
a partial failure of treatment facilities; namely, the prevention
of stagnant accumulation of sludge in the sewage treatment system
that may lead to deterioration of effluent quality,
91
-------
vi) reduction of operation and maintenance costs of the sewage treat-
ment plant, and
vii) improvement of working conditions for operators and workers engaged
in sludge treatment.
92
-------
2. BASIC FLOW DIAGRAM OF THE SLUDGE TREATMENT SYSTEM
Fig. 2.1 shows the sludge treatment systems of sewage treatment plants
in Japan, classified by design sewage flow capacity.
Most sludge treatment systems in Japan are conbinations of either
thickening-dewatering-incineration processes or thickening-anaerobic
digestion-dewatering processes. In a limited number of small sewage
treatment plants, the aerobic digestion process is employed instead of
the anaerobic digestion process. Some large sludge treatment systems
use a combination of thickening-heat treatment-dewatering-incineration
processes.
In view of the present status and future prospects of sludge treatment
systems, a sludge treatment system in which the processes shown in Fig.
2.2 are combined has been studied.
Sludge treatment systems consist of some or all of the processes A, B,
C and D in Fig. 2.2. Processes A and B each have alternatives.
Process A-(2) is a process of recent development. It uses either a
centrifugal or flotation method for the mechanical thickening of excess
sludge from the activated sludge process. Up until now, however,- proper
control methods for the mechanical thickening have not been reported.
In the alternative process to the process B, aerobic digestion is not
employed, partly because its use is limited to small sewage treatment
plants and partly because energy costs in Japan seem to make the
development of aerobic digestion unlikely.
Each process shown in Fig. 2.2 has a sludge pump well or a storage
tank. If each process is to be operated and controlled in an orderly
way without being influenced by quantitative flucturations, and also
to facilitate maintenance, periodic inspection and so on, it is desirable
to install a storage tank of large capacity. Neverthless, no definite
design concept has been established for determining the capacity of
storage tanks.
93
-------
Fig. 2.1 Classification of Sludge Treatment Systems
120.
no -
100 -
90
(I>
0 70
£ 60
rf
w
50
40
30 -
20
10
Sewage
Flow
](
F
E
C-2
C-l
B-2
B-l
A-2
A-l
3,000
m3/d
CC
C-4
B-3
<
C-3
C-2
B-2
-2
A-l
10,00
i> 50.
C-4
D-l
C-l
A-l:
A- 2:
B-l:
B-2:
B-3:
C-l:
C-2:
C-3:
C-4:
D-l:
D-2:
E :
F :
r=n
C-3
C-2
C-l
A- 2
A-l
F
D-2
C-4
Bo
— £
D-2
C-3
C-2
A-2
A-l
Thicken ing-Dewat
Thick en ing-Dewat
Thickening-Aerob
Thickening-Aerob
Thickening-Aerob
Thickening- Anaer
Thickening-Anaer
Thickening -Anaer
Thickening-Anaer
Thickening- Heat
Thickening-Heat
Thickening only
Air Drying only
CA
**
^^ ^ ^ —
C-3
C-2
A-2
A-l
D-l
3,000 100,000 a 300,000
100,000 «v.
300,000
in /d
Dewatering-Incineration
Aerobic Digestion
Aerobic Digestion-Dewatering
Aerobic Digestion-Air Drying
Anaerobic Digestion
Anaerobic Digestion-Dewatering
Anaerobic Digestion-Dewatering-Incineration
Anaerobic Digestion-Air Drying
Heat Treatment
Heat Treatment-Incineration
m3/d
-------
Fig. 2.2 Considered Flow Diagram of Sludge Treatment
Processes
A - 1
Pump well or
storage tank
Gravity
thickening
Thickened
sludge
A - 2
storage tank for
excess sludge
Gravitv
thickening
Pump well or
storage tank for
excess sludge
Mechanical
thickening
Thickened
primary sludge
Thickened
excess sludge
Thickened
sludge
3 -
Pump well or
storage tank for
thickened sludge
heating
1
Anaerobic
digestion
ligested gas
Elutriated
sludge
Digested
sludge
3 -
Pump well or
storage tank for
thickened sludge
Pretreatment
of thickened
sludge
Heat
treatment
Heat treated
sludge
Pump well or
storage tank for
thickened, digest-
ed, elutriated or
heat treated
sludge
Chemical feed
1
Dewatered
sludge
Chemical
conditioning
Dewatering
fuel and air
Dewatered
sludge
Sludge hopper for
dewatered sludge
s
upply
I
Incineration
-^^^»»
axhaust gas
treatment
Ash
95
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3• CURRENT TECHNIQUES OF OPERATION AND CONTROL FOR SLUDGE TREATMENT
PROCESSES
Sludge treatment systems usually employ a sequence control system for
interlocked operation of a number of instruments and equipment incorpo-
rated in its processes. Closed control loops are often used to regulate
chemical feed for sludge dewatering, etc.
Process operation and control techniques now in wide use are described
below.
3.1 Sludge Gravity Thickening
3.1.1 Inflow control
The sludge from the primary sedimentation tank is sent to the sludge
thickener through a storage tank. In some sewage treatment plants,
the drawing of sludge from the primary sedimantation tank is sub-
jected to an ON/OFF control signal from a solid concentration meter
monitoring the sludge drawing pipe, Excess sludge from the final
settling tank continuously or intermittently returned at a fixed
rate from the return-sludge storage tank to the primary sedimenta-
tion tank, or pumped directly to the sludge thickener.
In sewage treatment plants of relatively large size, if the sewage
flow is almost the same as the design flow, the sludge is fed to the
thickener continuously or intermittently because its sludge produc-
tion amount is so great. In small sewage treatment plants, or even
in large treatment plants where sewage flow is comparatively low,
sludge is intermittently fed to the thickener according to a time
schedule coordinated with the drawing of thickened sludge.
3.1.2 Thickened sludge control
There are four methods of drawing thickened sludge.
(1) ON/OFF control of the thickened sludge drawing pump by timer.
(2) ON/OFF control of the thickened sludge drawing pump by timer
and preset counter to draw a fixed amount of sludge daily.
Operation of the thickened sludge drawing pump is interlocked
with the liquid level in the sludge digestion tank or sludge
-------
storage tank to which it is connected.
(3) Sludge drawing control by sludge concentration.
The operation of the sludge drawing pump is started by a timer
and stopped by an under-concentration signal from a solid con-
centration meter monitoring the sludge drawing pipe.
(4) Thickened sludge drawing control by the volume of solids.
In this method, thickened sludge drawing pump is started and
stopped by signals from a solid concentration meter and preset
counter so that the quantity of solids per drawing operation is
limited to a preset value.
In comparatively large sewage treatment plants, when the sewage in-
flow is almost the same as the design, flow, sludge drawing is carri-
ed out semi-continuously by method (1).
In small plants or in large plants that are treating a lower sewage
flow than the design flow, sludge drawing is performed intermittent-
ly by method (2). There are few, if any, plants that employ methods
(3) and (4). In most plants, solid concentration meters are used
simply for indication and alarm purposes.
3.1.3 Sludge collector control
The sludge collector is run at a fixed speed, and is manually start-
ed and stopped.
3.2 Sludge Digestion
3.2.1 Sludge feed, drawing and transfer controls
Sludge feeding, sludge drawing and supernatant drawing are controll-
ed only by a fixed delivery control process using a preset counter.
No other control processes are currently employed. Sludge feed
control is interlocked with the thickened sludge drawing pump for
the sludge thickener.
Transportation of sludge to the secondary digestion tank by gravity-
feed, and the drawing of digested sludge is controlled by the level
in the digested sludge storage tank or by a timer.
97
-------
The supernatant from the secondary digestion tank is gravity-drawn.
Seed sludge is transferred by the seed sludge transfer pump which is
operated intermittently by a timer or manually. A level alarm is
installed to protect the sludge digestion tank from a nagative
pressure.
3.2.2 Agitator control
The sludge in the sludge digestion tank is mixed by gas agitation or
by a mechanical agitation device. Gas agitation is generally used,
however. Agitation is carried out either continuously or intermit-
tently by a timer. Even intermittent agitation is carried out
interlocked with the sludge feed pump or boiler when thickened sludge
is being fed or the boiler is being operated.
In the secondary digestion tanks, in which scum is produced, agita-
tion is carried out intermittently to break up the scum. There are
two types of agitating diffusers for sludge mixing and scum breaking
in secondary digestion tanks, and gas distribution control is also
used for this purpose.
3.2.3 Temperature control
There are two ways of heating in sludge digestion tanks; one in
which heat exchangers are used, and the other in which steam is
blown in directly. In the former type, the sludge temperature is
controlled by regulating the flow rate and temperature of the hot
water. In the latter type, the temperature control is carried out
by regulating the steam flow. Namely, the temperature of the sludge
digestion tank is controlled to a set value in a feedback control
process in which the hot water circulating pump or steam control
value is subject to ON/OFF control.
Boilers must comply with the "Boiler and Pressure Vessel Safety
Codes". Start-up must be carried out attended by an operator even
if a remote control system is employed. The boiler is started and
stopped based on sludge digestion tank temperature indication and
alarm signals.
-------
3.3 Digested Sludge Elutriation
3.3.1 wash water control
The wash water is fed in a fixed ratio to digested sludge volume.
At present, however, strict ratio control is not performed, but in-
stead a wash water valve or wash water pump is simply ON/OFF con-
trolled in interlock with the digested sludge feed valve.
3.3.2 Elutriated sludge drawing control
The drawing of elutriated sludge is controlled by ON/OFF control
signals to a sludge pump based on a sludge storage tank level signal
or a timer signal.
3.4 Chemical Conditioning
Chemical conditioning facilities vary widely depending on what type of
dewatering device is used and whether a lime and ferric chloride
combination or polymer is used.
3.4.1 Chemical dissolving control
(1) Slaked lime
Slaked lime stored in a hopper or a silo is passed to a dis-
solving tank by a flow conveyor. It is then adjusted to milk
of lime at 15% to 20% concentration. The dissolving is carried
out continuously or in a batch process.
In the batch process, a contant lime feeder and a diluting
water control valve are intermittently operated by a dissolving
tank level signal and a timer signal in order to feed lime and
water in a fixed ratio, mix and agitate them.
Chengeover from one dissolving tank to another is carried out
automatically.
In the continuous process, lime and diluting water are supplied
continuously in a fixed ratio. The agitator in the tank is
automatically operated with a tank level signal.
The hopper sliding device, air blower, dust collecting fan, bag
filter and other auxiliaries are operated in interlock with the
constant feeder.
99
-------
(2) Ferric chloride
Commercial ferric chloride has a concentration of about 38%.
It is stored in a storage tank, and gravity-fed or transger
pumped into a. dissolving tank where it is diluted to about one
quarter of its original concentration. Feeding is controlled
by a dissolving tank level signal.
(3) Polymer
polymer is commerically available as a liquid or powder. The
liquid polymer is about 10% in concentration and is stored in
the storage tank. The polymer is diluted to about 1% in a mixer
halfway to the dissolving tank. It is further diluted to
between 0.3 and 0.5% in the dissolving tank.
Polymer powder is handled just the same way as slaked lime.
3.4.2 Chemical feed control
Chemical feed control is conducted either in a batch process or in
a continuous process.
In the batch process, the running time of chemical feed pumps or
chemical feed valves and of sludge feed pumps is controlled by timer
signals and level signals in order to regulate the chemical feed
ratios to preset values. In the continuous process, control valves
or fixed delivery pumps are used to control the chemical feeds.
Chemical feed control by control valves is carried out just as for
ordinary valves. Chemical feed control by fixed delivery pumps is
carried out by stroke control and/or speed control. Chemical feed
rates can be calculated from the stroke and speed of the fixed
delivery pump, but usually is measured with a magnetic flowmeter.
Chemical feed control is classified into two types; constant propor-
tional ratio control in which a chemical is fed at a fixed ratio to
the sludge flow, and mass constant proportional ratio control in
which sludge flow and solid concentration are factors.
At present, constant proportional ratio control is most widely used.
In either case, the optimum chemical feed rate for dewatering sludge
is determined after a leaf test or examination of moisture content
of the dewatered cake produced from the dewatering device.
100
-------
3.4.3 Sludge feed control
If the sludge inflow is continuous, the chemical feed is carried out
by constant ratio control. Thus, sludge feed should preferably be
fixed. If a mixing tank is small, the level in the mixing tank will
vary over a wide range, requiring the sludge feed pump to be started
and stopped frequently. For this reason, the level in the mixing
tank is regulated at a constant value by speed control of the sludge
feed pump.
For this, control is carried out using the level in the mixing tank
in the primary control loop as a control variable. The manipulating
input of the sludge feed pump in the secondary loop is given by cas-
cade control. This method is also applicable to the sludge-feed
joint-mixing tank for a number of filter presses operated in parallel
3.5 Sludge Dewatering
3.5 1 Vacuum filter
If vacuum filters are to maintain their rated performance at all
times, it is necessary to always keep the sludge level in the vat at
a constant value. The opening of the sludge feed valve in the
sludge feed pipe from the mixing tank may be controlled automatically
to keep the sludge level within the permissible range. With this
method, however, the sludge feed pipe is likely to become clogged
with solids. At present, sludge feed valves are operated simply by
ON/OFF control in order to maintain sludge levels in vat.
Meandering of the filter cloth is detected by a sensing switch,
which actuates an air cylinder to correct the meandering. If the
air cylinder fails to correct the meandering, a safety switch func-
tions to automatically shut down the rotation of the vacuum filter.
Auxiliaries are operated in interlock with ON/OFF control of the
vacuum pump.
3.5.2 Filter press
Filter presses are operated to a batch process in which the steps
are:
pressure feeding sludge, compression of sludge, (air blowing),
101
-------
opening of frames, (filter cloth runing), filter cloth washing, and
closing of frames. Operation is essentially of the sequence timer
control type.
If the sludge feed pressure exceeds a preset value, the relif valve
functions to shut down the sludge feed. The cycle time is set after
examination of the moisture content of dewatered cake and filtering
rate of chemical conditioned sludge.
3.5.3 Centrifuge
The speed of the sludge feed pump to the centrifuge is controlled to
maintain the sludge feed rate at a constant value, and the concen-
tration of solids is measured for mass calculations. Polymer feed
is controlled to a constant ratio according to the results of mass
calculations.
The sludge feed rate and chemical feed rate are determined according
to solid recovery rate which is estimated from the state of the
filtrate.
3.5 4 Belt press type dewatering device
The sludge feed rate is to be kept constant just as for centrifug-
ing. The type and feed rate of polymer are determined by the results
of preliminary tests. And, the sludge feed rate, filter cloth
tension, and filter cloth transfer speed are determined according to
the thickness and moisture content of sludge cake obtained in actual
operation. The meandering of the filter cloth is corrected with a
band meandering adjustment meter.
3.6 Sludge Incineration
There are various types of incinerators including a multi-hearth furnace,
fluidized bed furnace and rotary kiln. Furnaces of the same type
vary in flow scheme, instrumentation and equipment, from manufacturer
to manufacturer.
Control is divided into dewatered cake receiving and feed, fuel supply,
combustion air supply and exhaust gas treatment subprocesses.
102
-------
3.6.1 Dewatered cake receiving and feed
If the dewatering device and incinerator are to be operated concur-
rently, a sludge cake hopper is only necessary while the incinerator
is out of services. On the other hand, if the dewatering device is
run for 8 hours, while the incinerator is operated for 24 hours a
day, a cake storage hopper is required.
To control the reciving of sludge cake at the feed hopper, a signal
from a weigher or level switch in the cake hopper is used to start
and stop the feed conveyor. Changeover to the storage hopper of the
dewatered cake is carried out by means of a reversible feed conveyor.
So that dewatered cake can be fed to meet the rated capacity of
the incinerator, the weigher at one end of the feed conveyor issues
a signal to control the speed of the constant feeder and the feed
conveyor. This method has the drawback that if the moisture content
of dewatered cake is high, it is impossible to feed the required
amount of dewatered cake.
3.6.2 Fuel supply
To transfer heavy oil from an underground fuel tank to a service
tank, the delivery rate of the fuel transfer pump is controlled by
the levels in the respective tanks. Fuel is supplied from the ser-
vice tank to the burner by a service pump, which is cascade control-
led based on the furnace temperature.
3.6.3 Combusion air supply
Starting and stopping of the incinerator are under sequence control.
For starting-up and stopping, the burners are controlled according
to heating and cooling programs. In some cases, a holding program
is used to the incinerator temperature from an arbitrary value to a
specified holding value.
The combustion air supply is under ratio control with respect to the
heavy-oil feed rate. For the multi-hearth furnace and other furnaces,
the air-to-fuel ratio is set. mechanically, and both air and fuel
valves are controlled from a single station.
In some furnaces, a damper is used to control the furnace tempera-
103
-------
ture. In some cases, the secondary air supply is controlled by a
damper so as to keep the oxygen concentration in the exhaust gas
at a fixed level.
The pressure in the multi-hearth furnace is kept negative by a blower.
The negative pressure is kept constant by damper control.
3.6.4 Exhaust gas treatment
The exhaust gas is scrubbed through acid and/or alkaline solution.
When the pH value of the scrubbing solution shifts outside a set
span, a feed valve opens to make up the solution with a concentrated
liquid. The scrubbed wastewater is neutralized as the same way.
Electric dust precipitators, blowers, etc. are under sequence
control.
3.7 Heat Treatment
3.7.1 Pretreatment facility
A drum screen, grit removal cyclone, etc. are provided as pretreat-
ment facilities for the heat treatment process. These devices are
program controlled in coordination with the operation of the
thickened-sludge drawing pump.
3.7.2 Reaction facility
Raw sludge run out of a disintegrator is passed by a high-pressure
sludge pump to a reactor via a heat exchanger. Water is passed
through the reactor until the inside of'reactor attains a specified
temperature. When the inside of reactor has reached a specified
temperature, sludge is changed in instead of water. The disintegrator
and high-pressure sludge pump are operated for conditional control.
The reactor is controlled so that the liquid level, temperature and
pressure are held at their set values.
The heat-treated sludge is discharged from the reactor by a sludge
discharge valve which is opened and closed intermittently by reactor
liquid level and timer signals. So that the sludge is maintained at
the reaction temperature, the exhaust gas vent valve is controlled
with the opening of the steam feed valve at a preset steam feed rate.
104
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The gas is vented intermittently by a timer. The flow rate is con-
trolled by making use of an orifice flowmeter. The pressure of
steam supplied from the boiler is controlled to a fixed value by a
pressure regulator.
105
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4. CURRENT MONITORING AND CONTROL TECHNIQUES FOR SLUDGE TREATMENT
SYSTEMS
The monitoring and controlling of sludge treatment systems have been
undertaken as part of the overall monitoring and control of entire
sewage treatment plants.
This chapter discusses the monitoring and control of entire sewage
treatment plants, not just matters concerned with sludge treatment
systems. Monitoring and control systems have been changing from the
hitherto hardware-related technology, as represented by analog
controllers and relay boards, to highly flexible software-intensive
technology relying on microcomputers and programmable sequences. Signal
transmission systems have also been changing from direct transmission
types using a network of cables to multiplex transmission types which
require fewer cables.
The monitoring and control systems now in use in sewage treatment plants
in Japan of three types as follows.
4.1 Type I
In the simplest type, monitoring and control is done with analog meas-
uring instruments installed at the side of each treatment unit or on
the control board in the sludge treatment building. The controllers
are manually adjusted by an operator. The operator reads the analog
measuring instruments and writes out a daily report.
4.2 Type It
This system is just the same as in Type I, but a computer is installed
alongside and independent of the treatment facilities.
Data read by the operator from the analog measuring instruments on the
control board is input to the computer. The information from the com-
puter is indicated on a display panel, and at the same time is printed
out as part of a daily report. The operator observes the display panel
and the printed-out results makes a judgement, and manually adjusts the
controller.
106
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4 . 3 Type ITT
The monitoring and control methods are just as for Type I, except that
the information from the measuring instruments located at each treat-
ment device or facility is fed on-line to the computer. The informa-
tion processed through the computer is indicated on a display panel and
at the same time printed out as a daily report. The main memory of the
computer is usually 16 '^ 32 KW.
The operator evaluates the data on the display and printed-out results,
and manually adjusts the controllers.
107
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5. FUTURE PROGRESS IN THE OPERATION AND CONTROL OF SLUDGE TREATMENT
PROCESSES
In the future, various instruments with higher reliability and greater
durability will be developed, and the dynamic characteristics of sludge
and its treatment processes will be understood more clearly. It will,
then, be possible to introduce a computer-aided optimum process control
system. Examples of operation and control systems for various treatment
processes which will be a reality in the future and described below.
5.1 Sludge Thickening
(1) For the gravity thickener, the sludge drawing pump will be
started and stopped on a signal from a sludge surface layer detec-
tor. At present, this method is being tried on an experimental
basis.
(2) For the centrifugal thickener, the viscosity of thickened sludge
will be measured to produce a signal for control of the differen-
tial speed of the outer and inner drums of the centrifuge to
control the thickened sludge concentration to a fixed value. (See
Fig. 5.1)
(3) For the floatation thickener, the turbidity of the supernatant
will be measured to produce a signal to control the sludge feed
rate.
5.2 Sludge Digestion
The concentration and pH of the thickened sludge to be fed into the
sludge digesting tank will be measured, and alkaline chemical feed,
sludge feed rate and seeding sludge recirculation rate will be under
feedback control, proportional feedback control and/or feed-forward
control.
This method is now being tested experimentally. Also, by measuring pH,
temperature, and chemical composition and the amount of digested gas,
the alkaline feed rate, seed sludge recirculation rate and heating tem-
perature, etc. will be integrally controlled. (See Fig. 5.2)
108
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5.3 Digested Sludge Elutriation
The alkalinity of the anaerobic digested sludge will be measured for
ratio control of the wash-water feed rate. (See Fig. 5.3)
5.4 Chemical Conditioning
Measuring the moisture content of dewatered cake, turbidity of filtrate,
pH of conditioned sludge, etc., the chemical feed will be under feed-
back control. A method in which pH of chemical conditioned sludge is
controlled to a fixed value by measuring the pH of the filtrate dis-
charged from the vacuum filter is now being tried on an experimental
basis. (See Fig. 5.4)
5.5 Sludge Dewatering
(1) For the vacuum filter, the drum speed and agitator speed will be
put under feedback control by measuring the moisture content of
dewatered cake and cake thickness.
(2) For the filter press, the volume of iltrate will be measured for
controlling the moisture content of dewatered cake to a fixed
value. (See Fig. 5.5)
(3) For the centrifuge, sludge concentration and filtrate turbidity
will be measured for controlling the sludge feed rate. If it
becomes possible to measure the moisture content of dewatered cake
quickly, it will become practical to control the differential
speed between the outer and inner drums of the centrifuge.
(4) For the belt-press dewatering device, the control of filter cloth
transfer speed may be practical if it becomes possible to measure
the moisture content of dewatered cake quickly.
5.6 Sludge Incineration
The feed rate of sludge to the incinerator will be put under cascade
control by measuring the furnace gas temperature. (See Fig. 5.6)
By measuring NOx and SOx in the exhaust gas, the operation of exhaust
gas treatment equipments will also be controlled.
109
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Fig. 5.1 Automated Control of Cetrifugal Thickener
Flow- Concent-
meter ration
Meter
Centrifugal
Thickener
Measurement
of Viscosity
Visco-meter
for
Thickened Sludge
B: Back-drive
M: Motor
Filtrate
Measurement
of Suspended
Solids
110
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Anaerobic
Gas
Fig. 5.2 Automated Control of Digestion Tank by Using the Means of
Measurements of Temperature, pH and Anaerobic Gas Composition
Sludgt
Foed
to
dewatering
device
Digestion
Tank
Primary Digestion Tank
Secondary
Digestion
Tank
Alkali
Agent
-------
Fig. 5.3 Primary Elutriated Sludge - Washing Water
Ratio Control by Using the Means of
Measurement of Total Alkalinity in Digested
Sludge
Controller
Servomotor
Converter
Electric
Drive Valve
Operation
Circuit
Primary
Elutriated 11 ' 11
Sludge 1| |r~~~""
Flow
Meter
Converter
Valve Prosition
Indicator
Flow
Meter
Washing
Water
Supply
To Secondary
Elutriation Tank
112
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Fig. 5.4 Constant pH Control of Coagulant Dosing Sludge Fed
for Vacuum Filter
Thickened,
Digested or
Elutriated
Sludge
RS
Coagulant
Dose
Acid Dose
Flowmeter
Sludge
Cpngulant
Mixing Table.
Vacuum
Filter
Filtrate
PH
113
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Fig. 5.5 Automated Constant Moisture Content Control
for Filter Press
Solid
Contents
set for
Feed
Sludge
Computation
of Objective
feed sludge
Volume
Computation
of Objective
Filtrate
Volume
Objective
Moisture
Content of
Dewatered
Cake
Feed Sludge stop
Sequence
Controller
Flow Meter for
Feed Sludge
Filter Press
Flow Meter for
Filtrate
114
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Fig. 5.6 Dewatered Cake Control by Using the Means of Inner
Gas Temperature Measurement for Multi-hearth Incinerator
Sludge Feed
Conveyer
Measurement of
furnace Gas
Temperature
M: Motor Drive
PS:
Programme
Setting
Multi-heath
Incinerator
115
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6. FUTURE PROGRESS IN THE MONITORING AND CONTROL OF SLUDGE TREATMENT
SYSTEMS
Full development of measuring instruments and control equipment for the
operation and control of all the processes will make it possible to com-
puterize the automatic control of sludge treatment systems without
difficulty. Control systems Types IV to VI below have already been tried
experimentally in several sewage treatment plants in Japan.
6.1 Type VI
This type of control system conbines computer-aided automatic control
with the Type HI system described in Section 4.3 above. The controllers
are set by computer outputs. Supervisory control is carried out at
CRTs terminals at a central control station. The main memory capacity
of the computers use is about 32 ^ 64 KW. Usually, an auxiliary memory
is required to main memory.
6.2 Type V
A computer is used for direct process control in place of the conven-
tional analog controllers. Other functions are similar to those of
Type IV.
6.3 Type VI
To use a wider range of computer functions, the controlled system is
configured in several levels depending on the size and purpose of the
component subsystems. Each subsystem is controlled by a separate
computer with suitable capacity and functions to form a comprehensive
control system.
Each process is under Direct Digital Computer control using a micro-
computer, and the master computer is assigned a Set Point Control level
function (including a data logging function). The memory capacity of
the micro-computer is about 16 KW, and that of the master computer is
about 32 ^ 64 KW. Usually, an auxiliary memory is required.
116
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7. DISCUSSION
Sludge treatment systems must always respond to fluctuations in the
quantity and quality of the sludge produced in the sewage treatment
system.
The sludge treatment system is a complex of various processes, and has
several problems that must be solved for the purpose of ensuring stabi-
lized performance of each process and of the system as a whole or a year
long basis.
The treatment faciliteies or devices available for each sludge handing
process have" merits and demerits, and should be selected based on an
in-depth study. In the planning stages of a sewage treatment plant,
engineers are often unsure whether the treatment facilities or devices
will be optimum or not for the sludge to be treated.
The treatment facilities or devices for these processes have been under-
going rapid technological innovations, which offers the risk of increas-
ing investment in the selection of facilities or devices and formulation
of sludge treatment systems from the long-range standpoint.
The sludge treatment systems require a large number of automatic measur-
ing instruments for automation of each process or for the system as a
whole.
Many quantitative measuring instruments which monitor sludge flow, level
ect. have already been proved to work well through operation and mainte-
nance in sewage treatment plants. On the other hand, such instruments
as are used for measuring parameters like sludge concentration are still
to be improved as they leave much to be desired in stability and relia-
bility.
The measuring instruments for sludge treatment systems are always
installed in severe environmental conditions than those for sewage
treatment systems, and there are many problems awaiting solution in the
operation and maintenance and also in the durability of the instruments
The operation and maintenance of automatic controlled sludge treatment
systems needs well-trained operators, who must have a full understanding
of the system configuration, the operating conditions of measuring
117
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instruments and control equipment, and also must always respond correctly
and quickly to emergency situation.
At present, however, there are few, if any, such operators, and training
provisions are not adequate. Yet, the automated control of sludge
treatment systems will probably bring many benefits, as already discus
It is therefore to be hoped that measuring instruments and control
equipment are gradually upgraded.
The basic concepts at present for the sutomated control of sludge treat-
ment system are as follows.
(1) Sludge treatment systems should be designed so that each process
can be operated sutomatically. The treatment facilities and auxil-
iaries which are to be installed in batteries or trains should be
designed to permit independent automatic control.
The engineering should be such that systems can continue service
even if a few processes or treatment facilities becom faulty.
(2) Large-scale sludge treatment systems usually rely on a large number
of treatment facilities and auxiliaries in a process.
Thus, it is necessary to duplicate these facilities and auxiliaries
for alternate use.
(3) Sludge trea-tment systems should preferably be a combination of
conventional site monitoring and control systems installed close to
treatment facilities, and a centralized supervisory control system
operated from a central control room station.
It is also desirable that data be collected at the central control
station for future improvement of facilities or devices and to improve
operation and maintenance activities.
(4) In large-scale sludge treatment systems, the data to be monitored
controlled, measured and recorded becomes voluminous, and the
analytical methods of collecting data in an efficient way should be
studied in advance.
For sludge treatment systems of medium size or larger, data collec-
tion and recording should be carried out automatically.
For smaller sludge treatment systems, data collection and recording
118
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should be undertaken by operators, and analog or digital measuring
instruments for data collection and recording should be installed
wherever required.
(5) The present state-of-the-art measuring instruments leave much to be
desired in adaptability, response and reproducibility.
So far as these instruments are concerned, the controllers associ-
ated with them should be designed to allow manual operation based
on personnel judgement of actual treatment results. However, ample
space should be allocated to accommodate future facilities for the
automatic control which will become possible.
119
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Seventh US/Japan Conference
on
Sewage Treatment Technology
ENGINEERING EVALUATION
OF MUNICIPAL SLUDGE INCINERATORS
May 20, 1980
Tokyo, Japan
Kazuo Ohmiya
Sadaharu Takahashi
Research and Technology Development Division,
Japan Sewage Works Agency
121
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CONTENTS
1 . Introduction ............................................. 123
2 . Multi-Hearth Furnace ..................................... 124
3 . Fluidized Bed Furnace .................................... 127
129
4 . Rotary Kiln .............................................. 7
5. Comparison of Three Types of Incinerators from
an Engineering Point of View .............................
6. Economic Comparison of Dewatering - Incinerating
facilities .... ............. ...... ..... ....... ..... ....... 132
6 . 1 Preconditions ...... ..... ....... .... ............ .„.,,. 132
6. 2 Comparison of Utility Costs ...... ... ................ 134
6.3 Comparison of Installation Costs and Occupancy Areas
6.4 Summary of the Economic Comparison of Dewatering and
Incineration .... ........... ........ ............... . . 139
ANNEX-1 Calorific Value and Chemical Composition of
Dewatered Cakes ... .. .......................
ANNEX-2 Exhaust Gas Treatment Equipments .................... 142
122
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1. INTRODUCTION
Incineration of sewage sludge was started in 1965 in Japan.
Installation of incinerators as of March 1978 is indicated in Table
1.1. As can be seen, 70 percent of the incinerators installed in
the past are multi-hearth furnaces. Recently, however, the fluidiz-
ed bed furnace and other new types have come to be employed.
However, with increasing installation of incinerators at sewage
treatment plants in municipalities, some difficult problems have
occurred. One particularly serious problems is air pollution from
exhaust gas. Increasing operation and maintenance costs due to the
sharp rise in prices of fuel is also a problem. Installation and
operation of exhaust gas treatment facilities upon the demand of
Pollution Control Departments of Prefectural Governments or inhabi-
tants in the vicinity of sewage treatment plants are making the
cost of incineration of sewage sludge much higher.
Many municipalities are finding it difficult to locate landfill
sites for sewage sludge and have to reduce the volume of sludge as
much as possible before dumping the sludge. In fact, some munici-
palities consider it unavoidable to incinerate the sludge, in spite
of energy costs or environmental problems this right cause for the
future.
In drafting this report, data was collected from detailed
surveys of the operation of 3 multi-hearth incinerators, 2 fluidized
bed incinerators and 2 rotary kilns. Data was also collected by
questioning many engineers from Sewage Works Departments of munici-
palities who had experience in the design, operation and maintenance
of incinerators. Based on this data, engineering and economic evalu-
ations of these three types of incinerators were made.
These detailed surveys were conducted starting from the de-
watered cake being fed into the incinerator and burnt until it was
reduced to ash, dust, vapor and exhaust gas (including the discharge
from the exhaust gas treatment).
During the survey period, the respective incinerators were so
operated that there would be as little variation as practicable in
123
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the volume and characteristics of the feed cakes and heavy oil.
For the survey items, those that would permit a thorough
understanding of the material and heat balances during incineration
were chosen. The survey items thus include the volume and charac-
teristics of feed cakes (moisture content; contents of volatile
solids, carbon, hydrogen, nitrogen, sulfur, chlorides and oxygen;
and upper and lower calorific values), the volume of air feed and
its characteristics (temperature and humidity), the auxiliary fuel
feed and its temperature, furnace temperature and exhaust gas
volumes and temperatures at the furnace and heat exchanger outlets.
The outlines of the survey result are shown in Table 1.2. For the
rotary kilns, city gas of a low calorific value of 4,460 K cal/N-m3
was used as an auxiliary fuel so that the feed of the auxiliary fuel
is given after conversion to that of heavy oil in table 1.2. The
overall air supply rate is expressed by the ratio of the air supplied
and penetrated to the incinerator over the theoretical air required
for combustion of the cakes and heavy oil.
Heat recovery^from the exhaust gas from the incinerator is not
made in the case of the multi-hearth incinerators because of low
exhaust gas temperature. But in the case of the fluidized bed
furnaces, 2^3 heat exchanger units were arranged in series for heat
recovery between 880^900°C and 390'M40°C. In the case of the rotary
kilns, one unit had some heat recovery made, but the other had no
heat recovery made at all.
2. MULTI-HEARTH FURNACE
The volume and characteristics of dewatered cakes fed to the
multi-hearth furnace are subject to variation, although to a slight
degree, in accordance with the conditions of sludge treatment, such
as concentration and dewatering. But for such slight variation,
stable operation is insured as the dry and burning zones in the
furnace move up and down gently and automatically.
However, when dewatered cakes adapted for self-burning with a
higher calorific value are fed into the furnace, they are burnt in
124
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the dry zone. For preventing such burning in the dry zone, it is
necessary to introduce a large amount of air into the furnace and
reduce the furnace temperature. Further, by the introduction of
such a large amount of air, it is possible to prevent damage of the
furnace wall, rotary arm and rotary cheese due to high temperature.
As a rule, the multi-hearth furnace is operated continuously.
When operation is intermittent, burning of auxiliary fuel is re-
quired to preventing temperature change in the refractories of the
furnace and for maintaining the furnace temperature.
According to measurement results, the dust contained in the
exhaust gas at the outlet of the furnace is not much, about 1^2 g
per N.m of exhaust gas. However, the odor in the exhaust gas at
the furnace outlet was found to be very high, about 2,000^8,700.
Fig. 2.1 illustrates a furnace of nominal capacity of 300
tons-wet base/day, and Fig. 2.2 and Table 2.1 show the results of
trial calculations of the material balance and heat balance.
In designing a multi-hearth furnace, the points to be noted
are given below.
1) Feed of the dewatered cakes to the furnace should be made at a
constant rate and continuously.
2) Moisture content of the dewatered cakes is preferably 60^80%.
3) When the moisture content of dewatered cakes is less than 55%,
air should be fed in the dry zone of the furnace so that the
furnace temperature does not rise abnormally.
4} Dewatered cake loading to the overall furnace area is adequate
at 30MO kg-wet base/m2-hr.
5) The temperature in the burning zone is preferably 700^00°C
to prevent the increase of combustibles contained in the ash
and in consideration of the heat resistance of the furnace wall
materials.
6) The temperature of the exhaust gas at the furnace outlet is
preferably 250^300°C.
7) The overall air supply rate to the furnace was actually 2.8^2.9.
But, to prevent the increase of combustibles in the ash and to
reduce the volume of exhaust gas, it is preferably 1.4^2.0.
125
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8) For preventing the formation of clinker and protecting the
rotary arm and cheese in the furnace, the auxiliary fuel burner
should be of such a structure that the flame is not introduced
into the furnace directly.
9) The concentration of dust emitted out of the chimney is reduced
to less than 0.05 g/N.m3, if an electric dust precipitator or
an efficient water-scrubber is installed.
10) The concentration of SOx in the exhaust gas is reduced to less
than 50 ppm, if water and/or chemical - absorption scrubbers
are installed.
11) The concentration of NOx in the exhaust gas at the furnace
outlet is 30^120 ppm upon conversion with the oxygen concent-
ration in air taken as 12%.
12) Noise abatement measures should be taken, if required. For
example, noise generating machines such as induction fans,
blowers, compressors, etc., can be installed in a sound absorb-
ing chamber.
In operation and maintenance of the multi-hearth furnace, other
points to be noted are as follows.
13) Operation of the furnace is made by maintaining the moisture
content and feed of the dewatered cakes at a constant rate
within the design capacity, controlling both the temperature
of the dry zone adjacent to the burning zone automatically and
the oxygen content in the exhaust gas at the furnace outlet
adequately.
14) In the high temperature sub-zone in the furnace are contained
mechanical rotary devices such as the mixing arm and cheese
and several stages of extended furnace beds. In addition to
the furnace wall, these are also subject to damage due to
high temperature. Therefore, the furnace should be inspected
periodically at least once a year (for such inspection, about
15 days is required).
15) The annual operating rate of the furnace is 85^89%, including
the time necessary for periodical inspection.
126
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3. FLUIDIZED BED FURNACE
The volume and/or characteristics of the dewatered cakes fed
to a furnace may vary more or less with time, depending on the de-
watering condition. However, because of the large heat storing
capacity of silica sand kept in the fluidized bed furnace, the
furnace is insured against instable operation.
The fluidized bed furnace is characterized in that when it is
operated intermittently, for example, if it is operated in the day-
time only, it has a far smaller decrease in the inner temperature
of the furnace, compared to the other type furnaces during the night
time because of the great heat storage of silica sand. Thus, while
the operation is discontinued, it is not required to keep the inner
temperature of the furnace high with an auxiliary burner to protect
the furnace wall. Further, in resuming operations, it does not
take much time before the dewatered cakes are burnt steadily.
From measurement results, it was found that because of a high
exhaust gas temperature of about 800°C at the furnace outlet, the
odor concentration of the exhaust gas was relatively low at 300^
1700. But, the heat taken out by the exhaust gas is so much that
installation of a heat exchanger is required. By such heat exchanger,
the combustion air is heated to about 450°C before it is supplied
to the furnace.
Fig. 3.1 shows an incinerator of a nominal capacity of 50
tons-wet base/day, and in Fig. 3.2 and Table 3.1 are shown the
results of trial calculations of the material balance and heat
balance of the incinerator, respectively.
In designing a fluidized bed furnace, the points to be noted
are given below.
1) Feed of the dewatered cakes to the furnace should be made
constantly and continuously.
2) According to the measurement result, the dewatered cake feed
loading per unit area of the furnace was 200 kg/m2-hr with
cake having a moisture content of 80% and an ignition loss of
50% per dry solid, or 270 kg/m2-hr with cake of a moisture
127
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content of 65% and an ignition loss of 40% per dry solid.
Further, the average velocity of the combustion wet gas in the
furnace was about 0.8 m per second although it varied with the
particle size and density of the fluidizing media.
3) The intake of dewatered cake to the furnace should be provided
in the fluidizing layer or at a higher level of the furnace.
One inlet is enough for furnaces of a nominal capacity of 50
tons-wet base/day or less.
4) The quiescent height of silica sand forming the fluidizing
layer is generally 1^1.5 m. About 1.5 times of the quiescent
height is the height for fluidizing.
5) The free board level of the furnace must be about 3 times the
fluidizing height of the silica sand in order to form an
adequate fluidizing layer.
6) The proportion of radiant heat from the furnace wall to the
input heat is about 5^10%.
7) The overall air supply rate of the furnace was measured as
1.4^1.6. But, to prevention increase of combustibles in the
ash and to decrease the volume of exhaust gas, it is preferable
to set an overall air supply rate at about 1.3 or less.
8) Combustion residues are all taken out of the furnace top so
that preliminary dust precipitation equipment, such as a
cyclone dust collector, is required immediately behind the
furnace outlet.
9) The concentration of dust emitted from the chimney may be re-
duced to less than 0.05 g/N-m3, if an electric precipitator or
an efficient water-scrubber is installed.
10) The SOx concentration in the exhaust gas is reduced to less
than 50 ppm when water and/or chemical - absortion scrubbers
are installed.
11) The NOx concentration in the exhaust gas at the furnace outlet
is 90M60 ppm upon conversion with an oxygen concentration
taken as 12%.
12) Noise abatement measures should be taken, if required. For
example, noise generating machines such as induction fans,
128
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blowers, compressors, etc., can be installed in a sound ab-
sorbing chamber.
In the operation and maintenance of the fluidized bed furnace,
other points to be noted are as follows.
13) Operation of the furnace is made by maintaining the moisture
content and feed of the dewatered cake at a constant rate
within the design capacity, and adequately controlling the
temperature of the fluidizing layer and free board zone,
furnace pressure and oxygen concentration at the furnace
outlet.
14) Quantitative loss of the silica sand or fluidizing medium was,
according to the measurement results, about 20 kg per ton of
the dry solid of the dewatered cake fed. Supply of the silica
sand depends on measuring the variation in pressure loss of
the supplying air.
15) The furnace should be inspected periodically, at least once a
year (about 7 days being required for such periodical inspection)
16) The annual operation rate of the furnace was 92%, including
the time taken for periodical inspection.
4. ROTARY KILN
The rotary kiln is suited for stable operation as the dry and
burning zones move forward or rearward automatically, according to
fluctuations in the volume and characteristics of the dewatered
cake fed to the kiln.
The rotary kiln is operated continuously as a rule, but when
it is operated intermittently, burning of auxiliary fuel is required
to prevent temperature change in the refractories of the furnace
and for maintaining the furnace temperature.
For the rotary kiln, it is necessary to install an emergency
combustion column drive in order to cope with any sudden electric
power outage. This drive is intended to prevent deformation of the
combustion column by discharging the cake remaining in the kiln.
129
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With respect to the two rotary kilns shown in Fig. 4.1, the
results of trial calculations on their material and heat balances
are shown in Fig. 4.2 and Tables 4.1 and 4.2, respectively.
In designing a rotary kiln, points to be noted are given below.
1) Feed of the dewatered cakes to the kiln should be made con-
stantly and continuously.
2) The heat capacity coefficient in the dry zone of the kiln is
about 200 K cal/m3-hr-°C with a combustion column diameter of
1.6 m.
3) The flow capacity of combustion wet gas per unit cross-sectional
area of the combustion column is about 3,300 kg/m2-hr.
4) The exhaust gas temperature at the outlet of the combustion
column is preferably set at about 300°C.
5) The radiant calorific value of the column should be less than
15% of the input heat.
6) According to the measurement results, the overall air supply
rate to the kiln was 2.4^3.2. Depending on the structural
characteristics, the air penetrating tends to become greater.
It is desirable to reduce the air penetrating through the
rubbing part of the combustion column so far as practicable
so that an overall air supply rate of 1.4^2.2 is provided.
7) The concentration of dust emitted out of the chimney may be
reduced to less than 0.05 g/N-m2, if an electric precipitator
or an effective water-scrubber is installed.
8) The SOx concentration in the exhaust gas may be reduced to
less than 50 ppm, if water and/or chemical - absorption scrubbers
are installed.
9) The NOx concentration in the exhaust gas at the combustion
column outlet is 70^100 ppm upon conversion with an oxygen
concentration set at 12%.
10) Noise abatement measures should be taken, if required. For
example, noise generating machines such as induction fans,
blowers, compressors, etc. can be installed in a sound absorp-
tive chamber.
130
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In operation and maintenance of the rotary kiln, other points
to be noted are as follows.
11) Operation of the kiln should be made by maintaining the mois-
ture content and feed of dewatered cakes at a constant rate
within the design capacity and, at the same time, controlling
the exhaust gas temperature and oxygen concentration at the
combustion column outlet.
12) There are no mechanical rotary parts present in the combustion
column, but the column itself rotates. Therefore, periodical
inspection should be carefully carried out for missing refrac-
tories in the combustion column, wear on the rollers supporting
the combustion column and adjustment of the rubbing part be-
tween the rotary combustion column and the fixed hood (about
7 days being required for the inspection).
13) The annual operation rate of the kiln was 80%, including the
time required for periodical inspection.
5. COMPARISON OF THREE TYPES OF INCINERATORS FROM AN ENGINEERING
POINT OF VIEW
Upon the results of these detailed surveys, the three types of
incinerators were compared with one another from the engineering
point of view. The results are as follows.
1) The multi-hearth furnace has the furnace bed fixed, and agita-
tion and transportation of the cake in the furnace are made as
the rake rotates. The rotary kiln has the cake in the kiln
agitated and transported by rotating the combustion column
itself. Accordingly, both furnaces are simple to operate.
On the other hand, the fluidized bed furnace involves
consumption of the silica sand due to its fluidizing and crack-
ing so that technical skill is required during operation to
maintain the fluidizing layer in optimum condition to burn the
cake continuously.
2) Incinerators with design capacities of more than 100 tons-wet
base/day per unit were limited to the multi-hearth furnace.
131
-------
3) When operation is intermittent, the multi-hearth furnace and
rotary kiln require burning of auxiliary fuel to maintain the
temperature during suspension periods. In this respect, the
fluidized bed furnace is better in that it can be started
without auxiliary heating.
4) As regards the odor of exhaust gas at the furnace outlet, the
fluidized bed furnace has the least.
5) The fluidized bed furnace allows operation with a lower over-
all air supply rate than the other furnaces.
6) For the fluidized bed furnace, it is necessary to install a
cyclone dust collector to separate combustion residue or ash
from exhaust gas.
7) With respect to the SOx concentration in the exhaust gas at
the furnace outlet, these three furnaces are nearly the same.
8) For the NOx concentration in the exhaust gas at the furnace
outlet, the three furnaces are nearly the same. The NOx con-
centration calculated with an oxygen concentration taken as
12% is lower than 250 ppm.
6. ECONOMIC COMPARISON OF DEWATERING - INCINERATING FACILITIES
6.1 Preconditions
With the sewage sludge generated from a sewage treatment
facility having a design capacity of 50,000 m3/day to 200,000 mVday
dewatered by a vacuum filter, filter press or centrifuge, and the
dewatered cake burnt in use of multi-hearth furnace, fluidized bed
furnace or rotary kiln, the respective combinations at the facili-
ties were compared with one another with respect to the utility
cost, installation cost and occupancy area.
Calculations were based on data obtained from detailed surveys
and other approved methods.
A. Sewage flow
50,000 m3/day, 125,000 m3/day and 200,000 m3/day, respectively.
132
-------
B. Sludge production and its characteristics
1) Dry solid generated in sewage
11.5 tons/day, 23.75 tons/day and 46.0 tons/day for the fore-
going sewage flows respectively.
2) Moisture content of thickened sludge
96%.
3) Composition of dry solids in sludge
Volatile solids, 60%; ash, 40%.
4) Lower calorific value of volatile solids (According to ANNEX-1)
5,400 K cal/kg-VS.
5) Composition of volatile solids (According to ANNEX-1)
With vacuum filter and filter press: (Cioo Hjao NU OM )jS; and
with centrifuge: (Cioo HIM NU 0^3) 587.
C. Operation of dewatering devices
1) Operation hours
6 days per week, 6 hours per day.
2) Kinds of coagulants and dosing rate
With vacuum filter and filter press: lime 35% and ferric
chloride 7% for dry solids (by weight); and
with centrifuge: Polymer 1% for dry solids (by weight).
3) Dewatering rate
Vacuum filter: 15 kg-dry base per hour per mz of filter area
Filter press: 5 kg-dry base per hour per m2 of filter area
4) Moisture content of dewatered cake
With vacuum filter: 77%.
With filter press: 65%.
With centrifuge: 80%.
5) Scale of dewatering devices used in calculations
Vacuum filter: 20 m2, 30 m2, 40 m2 and 50 m2, respectively.
of filter area
50 m2, 75 m2, ]
of filter area
5m3, 10 r
per hour.
Filter press: 50 m2, 75 m2, 100 m2 and 125 m2, respectively,
filter area
Centrifuge: 5m3, 10 m3, 15 m3 and 20 m3,. respectively,
133
-------
D. Operation of incinerators
1) Operating hours
7 days per week 24 hours per day
2) Auxiliary fuel
A-type heavy oil (lower calorific value, 10,280 K cal/kg,- and
specific gravity, 0.89).
Composition: C, 85.5%; H, 12.6%; 0, 0.5%; N, 0.5%; and S, 0.9%
3) Ambient conditions
Temperature, 20°C; absolute humidity, 0.01 kg-H2O/kg-air; and
specific gravity, 1,293 kg/N-m3.
4) Dewatered cake feed temperature: 20°C
5) Cooling water temperature: 20°C
6) Exhaust gas temperature at furnace outlet
With multi-hearth furnace: 250°C
With fluidized bed furnace: 800°C
With rotary kiln: 500°C
7) Ash discharge temperature
With multi-hearth furnace: 250°C
With fluidized bed furnace: 800°C
With rotary kiln: 250°C
8) Overall air supply rate
With multi-hearth furnace: 2.9
With fluidized bed furnace: 1.6
With rotary kiln: 2.6
9) Furnace heat loss
15% for each of the three types of furnace.
10) Supply of silica sand in the case of fluidized bed furnace
20 kg per ton of dry cake.
11) Scale of incinerators used in calculation
With multi-hearth furnace: 30 tons, 40 tons, 50 tons and
100 tons per day, respectively.
With fluidized bed furnace: 30 tons, 40 tons, 50 tons and
100 tons per day, respectively.
With rotary kiln: 30 tons, 40 tons, 50 tons and
100 tons per day, respectively.
134
-------
E. Flow diagram of exhaust gas treatment equipment (Reference ANNEX-2)
With multi-hearth furnace:
(250°C)
r- Spray scrubber »• Chemical-absorption scrubber
(40°C) „. ,
: ». Discharge.
With fluidized bed furnace:
(800°C) (250°C)
* Heat exchangers * Dry cyclone dust collector
Bentury scrubber »• Chemical-absorption scrubber
(40°C) _. ,
y Discharge.
With rotary kiln:
(500°C) „ ^ , (250°C), _ t ,.
» Heat exchanger * Bentury scrubber :—»
(40°C)
Chemical-absorption scrubber ». Discharge.
F. Unit costs of materials
Auxiliary fuel (A-type heavy oil) , ¥35/5,; Electric power,
¥10, KWH; Slaked lime, ¥30Ag; Ferric chloride, ¥25/kg in 38%
solution; Polymer, ¥l,400/kg; Sodium hydroxide, ¥56/kg; Industrial
water, ¥15/m ,- and Silica sand, ¥25/kg-
G. Occupancy area
It was assumed that both the dewatering equipment and incinera-
tor would be arranged horizontally.
6.2 Comparison of Utility Costs
6.2.1 Calculations of the utility of dewatering devices
To obtain the utility of dewatering devices, the following
estimate was made.
1) The dosed quantity of coagulant corresponding to the dry solid
of the sludge generated in each case was calculated.
2) The supplied quantity of industrial water used in dewatering was
calculated for cleaning the filter cloth, dissolving the coagu-
lant, water sealing of the vacuum pump, etc.
135
-------
3) Electric power consumption was calculated for the vacuum pump,
oil-pressure pump, sludge press pump centrifuge, etc. For
continuous operation machines, power was estimated as 0.8 of
the value obtainable by multiplying the motor output by the
hours of operation of dewatering devices. For machines of
intermittent operation, it was taken as 0.4 of the value ob-
tained by multiplying the motor output by the hours of operation
of the dewatering devices. Table 6.1 shows the primary units
of the utilities for dewatering devices.
6.2.2 Calculation of the heavy oil consumption for dewatered cake
burning
In order to obtain the heavy oil consumption for dewatered
cake burning, the following estimate was made.
1) The input heat to the furnace was calculated as the sum of the
calorific value of dewatered cakes and that of heavy oil.
2) The potential heat of dewatered cake was calculated from the
volume and moisture content of the cake fed, the dosed quantity
of coagulants and lower calorific value of the dewatered cake.
The lower calorific value of dewatered cakes is 5370 K cal/kg-VS,
as shown in ANNEX-1.
3) The potential heat of heavy oil was calculated from the quan-
tity of heavy oil required per hour and its lower calorific
value.
4} The output heat from the furnace was calculated as the sum of
the heat which the moisture in the dewatered cakes removes as
exhaust gas, heat taken out upon discharge of ash, heat taken
out as exhaust gas upon combustion of volatile materials and
heavy oil, and heat loss from the furnace wall, etc.
5) Heavy oil consumption was calculated by expressing the input
and output heats as calorific volumes per hour, and assuming
that these were equal.
The amount of heavy oil consumed for combustion of dewatered
cake by type of furnace and by moisture content of dewatered cake
is shown in Fig. 6.1.
136
-------
It will be seen from Fig. 6.1 that heavy oil consumption per
unit weight of cake increases sharply with an increasing moisture
content in dewatered cakes or a decreasing lower calorific value
of dewatered cake. It will also be seen that when the same de-
watered cake is burnt, the fluidized bed furnace consumes the
largest amount of heavy oil. This is because the temperature of
exhaust gas from the fluidized bed furnace is as high as 800°C and
the potential heat of the combustion gas of volatile solid and
heavy oil is remarkably high.
Plotting the results of the detailed surveys shown in Table
6.1 into Fig. 6.1, it can be seen that heavy oil consumption is
approximately the same, except for the fluidized bed furnace G.
This fluidized bed furnace G has an exhaust gas temperature of
880°C at the furnace outlet, or a greater rate of the potential
heat of combustion gas being removed, thus producing a greater
consumption of heavy oil than that of calculation shown in Fig. 6.1.
In the case of the multi-hearth furnace shown in Fig. 6.1
where the moisture content is 65% and the lower calorific value is
2750 K cal per kg, of dry cake, the dewatered cake is suited for
self-burning.
6.2.3 Calculation of utilities, other than heavy oil required for
combustion
In order to obtain values for the utilities, except heavy oil,
required for combustion, the following estimation was made.
1) The amount of sodium hydroxide consumed was calculated from the
weight of SO2 in dewatered cake and the' quantity of sulfur
contained in heavy oil.
2) The amount of industrial water consumed in the scrubber was
provided with reference to the result of detailed surveys.
3) Electric power consumption was calculated as stated in paragraph
6.2.1 with all of the motors of conveyor, induction fan, fluidiz-
ing blower, etc. classified into those used continuously and
those used intermittently.
137
-------
6.2.4 Utility cost for dewatering
The utility cost was calculated by multiplying the primary
units shown in Table 6.1 by the unit costs. It is highest with the
vacuum filter and lowest with the centrifuge, but there is not much
different between devices, the vacuum filter being only 7% and the
filter press by only 4% higher than the centrifuge.
The proportion of the cost of dosed coagulant in the utility
cost is 90^93% in the dewatering devices.
6.2.5 Utility costs for incinerating
Estimates of the utility costs for incineration are shown in
Table 6.2.
The utility cost required for burning the same dewatered cake
is lowest with the multi-hearth furnace and highest with the fluidiz-
ed bed furnace.
6.2.6 Utility costs for dewatering and incinerating
In the utility costs of the combination of dewatering devices
and incinerator shown in Table 6.2, the combination of filter press
and multi-hearth furnace is the cheapest. In this case, the de-
watered cake is self-burning and heavy oil is not required. Where
the filter press is used, the utility costs are generally low. On
the other hand, the highest utility cost results from the combina-
tion of vacuum filter and fluidized bed furnace, the utility cost
being 5.5 times that of the combination of filter press and multi-
hearth furnace.
Fig. 6.2 illustrates the utility cost required for dewatering
and incineration per unit of sludge solid for each of the sewage
flows of 50,000 mVday, 125,000 rnVday and 200,000 m3/day, respectively
In each case of sludge production of the sewage flows, the
combination of filter press and multi-hearth furnace is the cheapest.
In this case, however, the dewatered cake is self-burning and it
may become difficult to control the furnace. On the other hand, the
highest utility cost is the combination of vacuum filter or centri-
fuge and fluidized bed furnace.
138
-------
However, the multi-hearth furnace and rotary kiln may require
after-burning of exhaust gas to reduce foul odors, depending on the
location of the installation. Such after-burning of exhaust gas is
not required in the fluidized bed furnace. Accordingly, depending
on the installation site, the combination of filter press and
fluidized bed furnace may have the cheapest utility cost.
6.3 Comparison of Installation Costs and Occupancy Areas
Indexes of the installation costs of the combinations of the
3 types of dewatering devices and incinerators are shown in Fig.
6.3. The proportions of dewatering devices and incinerators in the
installation cost are shown in Table 6.2.
In Fig. 6.3, the installation cost was highest when the filter
press was used for dewatering, regardless of the type of the in-
cinerator. This is because the installation cost of the filter
press is about 3 times higher than those of the dewatering devices.
The areas of occupancy of the combinations of the 3 types of
dewatering devices and incinerators are shown in Fig. 6.4. Further,
in Table 6.4 are shown the areas of occupancy of the dewatering
devices and incinerators respectively.
The area of occupancy of the combination of dewatering devices
and incinerators was smallest when the fluidized bed furnace was
employed, regardless of the type of dewatering device.
6.4 Summary of the Economic Comparison of Dewatering and Incinera-
tion
1) In the comparison of the utilitiy costs for vacuum filter,
filter press and centrifuge, the centrifuge is the cheapest.
With the filter press and vacuum filter, the utility costs were
higher by 4% and 7% over the centrifuge, erspectively.
2) The utility cost for incineration is cheapest with the multi-
hearth furnace and most expensive with the fluidized bed furnace.
3) According to calculation results with exhaust gas treatment made
by a scrubber and a chemical absorption scrubber, the fluidized bed
furnace was highest in the consumption of heavy oil. However,
139
-------
if after-burning of the exhaust gas is undertaken, in the case
of multi-hearth furnace or rotary kiln, the foregoing relation-
ship will be reversed.
4) The utility cost of the combination of dewatering devices and
incinerators is cheaper when the filter press is employed as
a dewatering device. Particularly, in the case of the combina-
tion of filter press and multi-hearth furnace, the utility cost
is cheapest. On the other hand, the combination giving the
highest utility cost is that of vacuum filter and fluidized bed
furnace. The cost is as high as 5.5 times that of the combina-
tion of filter press and multi-hearth furnace.
5) The installation cost according to the combination of dewatering
devices and incinerators is highest when the filter press is
employed as a dewatering device regardless of the type of in-
cinerator.
6) The area of occupancy of the combination of dewatering devices
and incinerators is smaller when the fluidized bed furnace is
employed, regardless of the type of dewatering device.
140
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ANNEX- 1 CALORIFIC VALUE AND CHEMICAL COMPOSITION OF DEWATEKED CAKES
Dewatered cakes collected from 20 sewage treatment plants were
subjected to chemical analysis. The results are shown in Table A.I.
The contents of carbon, hydrogen and nitrogen per unit weight
of the volatile solid did not differ significantly from cake to
cake. But, it has been found that the content of combustible
sulfur differs greatly from cake to cake. This is, with the dewater-
ed cakes having polymer or no coagulant, combustible sulfur accounts
for about 90% of the content of total sulfur, but in the case of the
dewatered cakes having both lime and ferric chloride, it is only
3^10%. In the latter case, it is supposed that a greater part of
sulfur contained in the dewatered cake will remain in the ash upon
burning.
If it is assumed upon the result of elementary analysis that
the volatile solid gasifying at burning entirely consists of oxygen,
except the foregoing four elements, the following molecular composi-
tion is conceivable.
• Volatile solid contained in dewatered cake having both lime and
ferric chloride.
NU 01,3)73 .............................. ---- .. (A.I)
0 Volatile solid contained in dewatered cake having polymer or no
coagulant .
= (Cioo Hia NII 0^3)53 7 ...... ... ........................... (A. 2)
Then, assuming that upon complete combustion of such volatile
solids, carbon would be converted to CO2, hydrogen to H2O, sulfur
to SO 2 and nitrogen to NO for 2% by weight, the remaining being
emitted as nitrogen gas, calculations were made on the theoretical
quantities of air and combustion gas. The results are as shown in
Table A. 2.
Next, the higher calorific value of measurement (Qh) is given
as a function of the ratio of the weight of volatile solids to the
weight of dry cake (V) , as shown in Fig. A.I.
141
-------
That is,
Qh = 58V (A. 3)
Regardless of the kind of dewatered cake, the higher calorific
value per kg, of volatile solid is 5,800 K cal.
The lower calorific value per kg, of volatile solid is given,
from formulas (A.I), (A.2) and (A. 3) as 5,370 K cal.
ANNEX-2 EXHAUST GAS TREATMENT EQUIPMENTS
With the multi-hearth furnace and rotary kiln, the dust con-
centrations at the furnace outlet were 1^2 g/N-m3 and 2^10 g/N-m3
respectively. With the fluidized bed furnace, however, combustion
residues are discharged entirely out of the furnace top. The com-
bustion residues are precipitated by a cyclone dust collector, and
the dust concentration at the furnace outlet is 30^80 g/N-m3.
Use of the cyclone dust collector is a suitable method of dust
precipitation if the particles are of a size of lOy or greater and
in high concentration. With the combustion residue of a fluidized
bed furnace, the cyclon dust collector has a precipitating efficien-
cy of 80^0%.
For the spray scrubber, a counter contact flow system of ex-
haust gas and water is employed. Where the dust concentration was
0.5^2.0 g/N-m3 and the water-to-exhaust gas ratio was 8 £/m3, the
dust precipitating efficiency was 85%.
For the bentury scrubber, a parallel contact flow system of
exhaust gas and water is employed. Where the dust concentration
was 3MO g/N-m3 and the water-to-exhaust gas- ratio was 24 £/m3, the
dust precipitating efficiency was 98^9%.
The wet electric dust precipitator is designed for precipita-
tion of dust particles of a size less than ly. With the dust con-
centration at 0.1 g/N-m3, it provided a dust precipitating efficiency
of 85^9%.
Table A.3 shows the survey data of exhaust gas treatment equip-
ment for multi-hearth furnace. The exhaust gas from the furnace
142
-------
outlet is scrubbed with water at the spray scrubber, then with
sodium hypolorite and sodium hydroxide solutions at the chemical-
absorption scrubber.
Offensive odor substances removed the water washing include
the following:
Ammonia, acetaldehyde, trimethylamine and hydrogen sulfide.
Offensive odor substances removed by alkali scrubbing include
the following:
Methyl mercaptan, hydrogen sulfide and methyl sulfide.
Offensive odor substances removed by acid scrubbing include
the following:
Ammonia and trimethylamine.
Offensive odor substances removed by scrubbing with sodium
hypochlorite solution include the following:
Methyl mercaptan, hydrogen sulfide and methyl sulfide.
Accordingly, as the exhaust gas at the furnace outlet is scrub-
bed with water, alkali, acid and sodium hypochlorite, the dust
concentration, SOx and hydrogen chloride are reduced, while methyl
mercaptan, hydrogen sulfide, methyl sulfide, trimethylamine and
acetaldehyde are also removed, so that the odor concentrations
emitted into atmospheric air range between 500 and 1500.
143
-------
Table 1.1 Incinerator Installations in Japan
(March 1978)
Types of Furnace
Multi-hearth furnace
Fluidized bed furnace
Rotary kiln
Stoker furnace
Others
Number
68
10
3
6
5
Design Capacity
(ton -wet base/day)
5 ^ 300
8 -v. 50
24 ^ 36
5 ^ 43
-
Cake Moisture
Content (%)
55 'V- 80
65 -x, 85
60 ^ 80
47 ^ 55
-
144
-------
Table 1.2 Results of Detailed Survey
V
1
2
3
4
5
6
7
8
9
10
11
12
13
14
a;::==^I^~~~ _______^^ Type of Furnace
^ ^^^ Name of SewageX
-\T~~~~— -—_ Treatment Plant
Tt<=>ms — .. ^~- —
^^--\^^ Unit \^
Design capacity
Cake feed
Cake moisture content (wet base)
Dry cake lower calorific value
Fuel consumption of heavy oil
Air supply
Exhaust gas temperature at
furnace outlet
Exhaust gas temperature after
heat exchange
Wet volume of exhaust gas
Dry volume of exhaust gas
Ash discharge
Combustion temperature
Overall air supply rate
Furnace wall and other
unidentifiable heat
loss/Input heat
tons-
wet base/day
kg/hr
%
K Cal/kg.
dry-base
«./hr
Nm3/hr
°C
°C
Nm3/hr
Nm3/hr
kg/hr
°C
-
%
Multi-heart Furnace
S
300
12,550
78.5
2,690
498
32,100
270
-
46,000
31,000
1,100
850
2.8
16
A
40
1,530
82.5
2,500
113
5,230
280
-
7,050
4,980
122
750
2.9
18
N
50
1,843
68.7
2,430
49
4,420
340
-
6,220
3,940
300
826
2.2
22
Fluidized Bed
Furnace
y
40
1,425
81.2
3,560
95.5
2,330
-
442
3,470
2,300
75
874
1.2
29
G
50
1,725
80.5
2,000
175
3,360
880
390
5,300
3,230
168
900
1.4
9
Rotary Kiln
KN
24
1,055
61.2
1,980
*36.2
3,280
500
376
4,330
3,070
161
**800
2.4
24
KO
36
1,438
78.4
3,280
*71.1
6,060
500
-
7,790
5,940
96
**900
3.2
15
.fc.
(Jl
* Assumed fuel consumption converted from city gas based on lower calorific value.
** Assumed combustion temperature estimated from the formula of heat conduction upon measurement of
the surface temperature.
-------
Table 2.1 Heat Balance of Multi-hearth Furnace
(300 tons-wet base/day)
20°C base
Input Heat
K cal/hr
(1) Combustion heat of
dewatered cake
7.252xl06
(2) Combustion heat of
A-type havy oil
3.504xl06
10.756xlOS
%
67.4
32.6
100.0
Output Heat
K cal/hr
(1) Exhaust gas potential
heat
3.844xl06
(2) Cake moisture evapo-
ration latent heat
5.773xl06
(3) Ash potential heat
0.009X106
(4) Radiant conduction
and other heat loss
1.130xl06
%
35.7
53.7
0.1
10.5
100.0
146
-------
Fig. 2.1 Flow Diagram of Multi-hearth Furnace
(300 tons-wet-base/day)
I Hot air
I furnace
_r
Hulti-
heartli
f UtlliCO
Treated
effluent
Acid
dbborptio
sctubbcr
CooI Ing
towur 1
alisotft ion
scrubber
J
(Dfdin)
_-.!_
"1
~i r
1
Cool mg 1 g
tower 2 I
Electric 1 _^^
t^cec 1^.1 td- |V£/ *"
tor 1 F«»n
Ueating
furnace foe
[ireventing
white snoke
Ueroaenej
.- j r^i
• l
-------
Fig. 2.2 Material Balance of Multi-hearth Furnace
(300 tons-wet base/day)
oo
Dewatered cake: 12,550 kg/hr
273°C
["Moisture contents: 9,852 kg/hr~|
|_Dry solids contents: 2,698 kg/hrj
A-type heavy oil: 347 kg/hr-
Air supply: 41,093 kg/hr j
(32^113 NmVhr)
-*-Exhaust gas: 52,898 kg/hr
Dust: 68 kg/hr
"Exhaust gas:. 46,000 NmVhr
Moisture: 15,000 Nm3/hr
Carbon Dioxide: 1,736 Nm3/hr (5.6%)
.Oxygen: 4,402 Nm3/nr (14.2%)
55°C
->-Ash: 1,092 kg/hr
-------
Table 3.1 Heat Balance of Fluidized Bed Furnace
(50 tons-wet base/day)
(Furnaqe and to Heat Exchanger Outlets)
Input Heat
K cal/hr
(1) Combustion heat of
dewatered cake
6.72X105
(2) Combustion heat of
A- type heavy oil
14.84xl05
21.56X105
%
31.2
68.8
100.0
Output Heat
K cal/hr
(1) Exhaust gas potential
heat
5.91xl05
(2) Cake moisture evapo-
ration latent heat
8.13xl05
(3) Ash and dust potential
heat
0.14xlOs
'(4) Discharge heat for
white smoke prevention
3.05xl05
(5) Radiant conduction
and other heat loss
4.33xl05
21.56xlOs
%
27.4
37.7
0.7
14.1
20.1
100.0
149
-------
Fig. 3.1 Flow Diagram of Fluidized Bed Furnace
(50 tons-wet base/day)
(Dewatared
cake)
—3
(Heavy
oil) _,=
•o
0)
N
H
•O
H
rH Q
J p
CM XI 4-»
Primary and
secondary
heat ex-
changers
(Ash and dust)
(Water
(Drain) supply)
Jet
collector
Exhaust
gas fan
T Point of measurement
-------
Fig. 3.2 Material Balance of Fluidized Bed Furnace
(50 tons-wet base/day)
358°C
Dewatered cake: 1,725 kg/hr
A-type heavy oil: 147 kg/hr
Air supply: 4,299 kg/hr
( 3,357 NmVhr)
39 kg/hr]
36 kg/hrj
ir J *"
\
Fluidized
bed
furnace
Exhaust gas: 6,003 kg/hr
Dust and ash: 168 kg/hr
Exhaust gas:
Moisture:
Carbon Dioxide:
_Oxygen:
5,300 Nm /hr
2,067 Nm3/hr
378 Nm3/hr (11.7%)
187 Nm3/hr (5.8%)J
-------
Table 4.1 Heat Balance of Rotary Kiln (24 tons-wet base/day)
Input heat
(1) Combustion heat of
dewatered cake
(2) Combustion heat of
city gas
(3) Heat air acquired at
air preheater
Total
xlO3 K cal/hr
810
327
(72)
1,137
%
71.2
28.8
(6.3)
100.0
Output heat
(1) Potential heat of,
theoretical wet base
exhaust gas
(2) Potential heat of
excessive air
(3) Potential heat of
penetrating air
(4) Potential heat of
evaporation of cake
moisture
(5) Latent heat of evapora-
tion of cake moisture
(6) Potential heat of ash
(7) Radiant heat of kiln
(8) Unidentifiable heat
(9) Heat exhaust gas emitted
at air preheater
Total
xlOJ K cal/hr
196
117
103
101
386
15
167
52
(72)
1,137
%
17.2
10.3
9.1
8.9
33.9
1.3
14.7
4.6
(6.3)
100.0
(Jl
(Note) Parenthesized data represent heat circulation.
-------
Fig. 4.1 Flow Diagram of Rotary Kiln
(24 tons-wet base/day)
Ln
OJ
Hot water
"
(Dewatered cake) T ^(Air> 1
. 1 M *• '
* Jj HoL wat
(City gas) f No. J ^ « .^ heat e>
^^ Rotary kiln ^-2 changei
1 *—, ' H M
» /- 1
(ASh> INO 2
(Water) |
(No. 3
T
er Cyclone
~ £ dust
separator
^jDust)
(Water)
T "
Electirc i I c
•* precipi* - J "^ N
*. -,..,-... C.Q/ *J OJ
Cacor E ^ 0 3
0« p P 0
f-. 4.) t) *-)
§ ^ 1
• |]«-*^DF
0 ^
m ^i
3 «
1
>-,
V
H
«* 6
-T
I (Drain)
Mote: Nos. 2 '• 3 Rotary kilns are of the same
type as No. ) Rotary kiln under measurement.
Point of measurement
-------
Fig. 4.2 Material Balance of Rotary Kiln
(24 tons-wet base/day)
Ln
A Air supply: 1,678 kg/hr
Dewatared cake; 1,055 kg/hr
A Air supply: 2,559 kg/hr
City gas: 58 kg/hr
Ash: 161 kg/hr
Rotary kiln
Exhaust gas: 5,189 kg/hr
(Including dust: 42 kg/hr)
(Note) A: Estimated calculation
-------
Table 6.1 Primary Units of Utilities for Dewatering and Incineration During Steady Burning"
(per ton of dry solid)
\r^^-\ Items
Inone- \Dewater^\ Noisture
ra tors \ in9 contents
\ Devices \ ^
Multi-hearth
furnace
Fluidized
bed furnace
Hotary kiln
Vacuura
filter
Filter
press
Centrifuge
vacuum
filter
Filter
press
Centrifuge
Vacuum
filter
Filter
press
centri fuije
77*
65%
uo%
77%
65%
80%
77»
65»
80%
Fuel
A-ty,»
heavy oil
t/ton.
dry solid
210
0
130
480
120
34O>-350
140
ao
25O
Kerosene*
t/ton-
dry sol id
340
2BO>-290
290
-
-
-
310
240
29O
Electric power
For de-
watering
KWH/ton-
dry solid
80
60-^0
140
80
bo^ao
140
UO
60"^)0
140
For
burning
KWK/ton •
diy solid
J1OM10
240%36O
25OH8O
430^600
2HO-V.JBO
34O>-540
]40-'^)bO
26O->-300
340-1-1 to
, Total
KWII/ton-
dry solid
390->490
300-^440
390>-520
510->-680
330->46O
47O>*80
4 2O >• 540
320 HbO
480^00
Chemcals
Line
kg/ton-
dry solid
350
3bO
-
350
350
-
150
350
-
Ferric
chlor ide
kg/ton-
dry sol id
180
1BO
-
180
180
-
I BO
18O
-
Polymer
kcj/ton-
dry bolid
-
-
10
-
-
10
-
-
10
soda
kg/ ton-
dry solid
20
10
50
30
20
SO'-^O
30
20
50
watering
taVton-
dry solid
40
10
5-^10
40
10
S--IO
40
10
5-»10
Mater
For inci-
nerat ion
m'/ton.
dry sol id
140'>-15O
90
1 20>.130
lbOv.170
90->-100
140->.150
180-^.190
140-V150
160 '-ISO
Total
mVton.
dry solid
1 BOM 90
100
130->-140
200^2 10
llO-x-120
140-1-150
22O>-230
160
170MBO
Mi seel -
laneou-.
Silicj
sand
kg/ ton •
dry sol I ii
-
-
-
30
30
20
-
-
-
on
Ln
• Stiwago flow is within tttu range of SO, Ooa^OU.OOO »J/day.
• * Kerosene is for dired bunting and deodor 121119.
-------
Table 6.2 Utility Cost Required for Steady Burning
(Japanese Yen per ton of dry solid)
(February 1979)
(Yen)
N. ^--^^^ Items
NDewater^-^
Incinera- x. • ^~~~-^
\ ing . ^-^_
tors \^ Devices ^~~~~^.^
Multi-hearth
furnace
Fluidized
bed furnace
Rotary kiln
Vacuum filter
Filter press
Centrifuge
Vacuum filter
Filter press
Centrifuge
Vacuum filter
Filter press
Centrifuge
Fuel
A- type
heavy oil
7,525
0
4.375
16,975
4,200
12,075
12,075
2,975
8,925
Electric
power
-
3,600
3,000
3,150
5,150
3,250
4,400
4,000
3,150
4,000
Chemical
Caustic
soda
1,120
560
2,800
1,680
1,120
3,080
1,680
1,120
2,800
Water
Industrial
water
2,175
1,350
1,875
2,475
1,425
2,175
2,775
2,175
2,550
Miscel-
laneous
Silica
sand
-
-
-
750
750
500
-
-
-
Total
14,400
4,900
12,200
27,000
10,700
22,200
20,500
9,400
18,300
Ul
01
-------
Table 6.3 Proportions for Dewatering Equipment
and Incinerators in Equioment Costs
~"~"~~-— ZI^~~ • Sewage flow
IncineratorsX Equipments ^^^^^
Multi-hearth
furnace
Fluidized bed
furnace
Rotary kiln
Vacuum filter
Incinerator
Total
Filter press
Incinerator
Total
Centrifuge
Incinerator
Total
Vacuum filter
Incinerator
Total
Filter press
Incinerator
Total
Centrifuge
Incinerator
Total
Vacuum filter
Incinerator
Total
Filter press
Incinerator
Total
Centrifuge
Incinerator
Total
50,000
m3/day
27%
73%
100%
54%
46%
100%
30%
70%
100%
26%
74%
100%
52%
43%
100%
29%
71%
100%
30%
70%
100%
57%
43%
100%
33%
67%
100%
125,000 200,000
m /day i mVday
32% 32%
68% 63%
100% 100%
62% 67%
38% i 33%
100% 100%
35% ! 34%
65% 66%
100%
100%
34% 33%
66% 67%
100% 100%
61% 69%
39%
31%
100% 100%
35%
65%
100%
37%
63%
100%
65%
35%
100%
39%
61%
100%
35%
65%
100%
36%
64%
100%
71%
29%
100%
38%
62%
100%
157
-------
Table 6.4 Approximate Occupancy Areas of Dewatering Equipment and Incinerators
(Unit: m )
\^~~-—_^De water ing Devices
^v ^^"~~-- -~_an d Incinera-
\v ~-~~^^_^ tors
Incine- ^v v
rators \. Sewage f low\
Multi-hearth
furnace
Fluidized
bed furnace
Rotary kiln
50,000 m3
125,000 m3
200,000 m3
50,000 m3
125,000 m3
200,000 m3
50,000 m3
125,000 m3
200,000 in3
Vacuum
filter
650
1,520
2,170
650
1,520
2,170
650
1,520
2,170
Incine-
rator
3,190
4,600
6.900
1,920
2,630
3,940
3,190
4,600
6.900
Total
3,840
6,120
9,070
2,570
4,150
6,110
3,840
6,120
9,070
Filter
press
920
1,540
2,630
920
1,540
2.630
920
1,540
2,630
Incine-
rator
2,880
4,600
4,600
1,800
2.630
2,630
2,880
4,600
4,600
Total
3.800
6,140
7,230
2,720
4,170
5,260
3,800
6,140
7,230
Centrifuge
580
1,010
1, 340
580
1,010
1,340
580
1,010
1,340
Incine-
rator
2,880
5,040
6,900
1,800
3,070
3,940
2,880
5,040
6,900
Total
3,460
6,050
8,240
2.380
4,080
5,280
3,460
6,050
8,240
oo
-------
Fig. 6.1 A-type Heavy Oil Consumption versus Dewatered
Cake Calorific Value and Moisture Content
Cfl
«J
.a
-H •
— c
0 0
01 JJ
a
£
05
C
$
>.
700
500
300
200
100
70
50
30
20
10
*
Note
R77
M80
M77
F65
R65
1500 2000 2500 3000
Dry cake lower calorific value (Kcal/kg-dry cake)
1 M: Multi-hearth furnace
F: Fluidized bed furnace
R: Rotary kiln
Note 2 Numerical figures show the moisture contents (%) of feed cake
159
-------
Fig. 6.2 Utility Cost Required for Dewatering and Incineration during Steady Burning
(Japanese Yen per ton of dry solid)
Sewage flow at 50,000 mVday
With multi-hearth furnace
Vacuum filter 31,700
Filter press 22,000
Centrifuge
28,200
With fluidized bed furnace
Vacuum filter
m.
44,300
Centrifuge
38,700
Sewage flow at 125,000 mVday
With multi-hearth furnace
Vacuum filter 31,600
Filter press 22,000
Centrifuge
28,300
With fluidized bed furnace
Vacuum filter
43,900
Filter press
28,000
Centrifuge
(February 1979)
Sewage flow at 200,000 m3/day
Kith multi-hearth furnace
Vacuum filter 30,500
Filter press 20,500
I I
Centrifuge 26,800
With fluidized bed furnace
Vacuum filter
Filter press 26,000
42, 500
Centrifuge
36,600
With Rotary Kiln
Vacuum filter
37,700
Filter press 25,300
Centrifuge
34,600
With Rotary Kiln
Vacuum filter
37,600
Filter press 26,400
Cen tr i f uge
34,900
With Rotary Kiln
Vacuum filter
36,300
Filter press 24,400
Centrifuge
33,100
0 10,000 20,000 30,000 40,000 50,000 0 10,000 20,000 30,000 4O,000 50,000 0 10,000 20,000 30,000 40,000 50 000
»• * »•
Yen/ton-DS
Yen/ton-DS
Yen/ton-DS
Incineration f ~=^ Dewatering
-------
(Ti
Fig. 6.3 Approximate Cost Indexes of the Dewaterinq and Incineration Facilities
(February 1979)
Multi-hearth furnace
1>
10
15
20
Sewage flow (- lo'V/day)
Fluidized bed furnace
!- I 2
20
Sewage flow (^ 10sm'/day)
Rotary kiln
10
15
20
Sewage flow (* lo'*mj/day)
-------
Fiy. 6.4 Approximate Occupancy Areas for Dewateriny
Incineration Facilities
KJ
0)
id
o
c
fd
Q<
D
U
u
o
8,000
Il6,000
4,OOC
2,000
Multi-hearth
furnace and
Rotary kiln
Fluidi zed
bed furnace
Mu] Li-hearth furnace
Kluidiiii'd bed furnace
Rotary kiln
Vacuum filter
Filter press
centri fuye
Sewage flow. (' 10'mJ/day)
-------
Table A.I Characteristics of Raw Sludge Cake
Sawage
Treatment
Plants
FG
GA
MS
,1H
BT
UN
US
El
SF
MI
3Yc
SYk
BH
DM
El
3B
BK
RK
SF
KM
MS
US
DO
AO
Chemicals
Ferric
Chloride
Lime
Ferric
Chloride
Lime
••
"
•
-
••
-
••
Polymer
••
<•
Ferric
Chloride
Per-oxide
Heat
treatment
-
Dewa ter ing
Devices
Vacuum
filter
••
»
••
••
Filter
Press
-
-
"
••
Centrifuge
-
-
••
Belt Press
Vacuum
filter
Filter
press
-
tlo. of
Analysis
3
1
2
2
2
3
1
1
3
1
2
4
1
1
1
1
11
4
1
1
1
1
1
L
VS3/DS
(*)
53.0
46.9
49.5
46.7
47.4
40.1
33.2
39.2
38.1
38.3
66.4
49.9
68.1
84.7
61.5
73.2
78.1
63,7
53.7
51.2
44.6
42.7
51.7
47.0
Calorific
Values
3,163
2,680
2,980
2,790
2,360
2. 340
1,960
2,190
2,110
2,310
3,390
2,980
4,030
4,690
3,420
4,440
4,430
4,030
2,550
2,950
2,750
2.56Q
2,960
2.630
r
26.4
27.1
27.6
26.3
27.5
23.4
16.7
23.2
21.5
21.8
36.5
27.6
37.5
41.9
32.3
39.5
40. 5
37.8
23.1
27.4
24.5
24.0
28.8
24.8
H
5.4
4.0
4.3
3.9
4.1
4.1
3.6
3.9
3.3
4.2
4.8
4.2
5.5
6.8
4.9
5.6
5.7
5.3
3.8
3.5
3.3
3.0
3.1
2.9
N
4.3
3.7
3.7
3.1
3.1
3.0
2.1
3.3
3.3
2.8
5.7
2.6
3.9
5.7
3.9
5.7
2.9
2.3
4.0
3.2
2.7
2.8
3.0
3.3
S
0.62
0.90
0.91
1.0
1.3
1.7
0.73
0.93
2.2
1.2
1.0
1.6
1.0
1.1
1.0
2.8
0.70
1.1
2.7
Sulfur
Combusti-
ble
0.1
0.1
0.1
0.0
0.7
0.0
-
1.5
-
0.9
1 .4
-
0.2
1.3
0.3
1.0
0.8
0.6
0.6
163
-------
Table A.2 Theoretical Air and Combustion Gas Volume per Unit Dewatered Cake Volatile Solid (kg)
^=
Kinds of \.
Dewatered Cake^\Ga
Lime added cake
Polymer added cake
and cake with no
chemicals
- I terns
^^^-- -^
s Compos itiorT~^-^!^'t
N;> (Air)
CO?
H20
SO 2
NO
N2 (Volatile solid)
Total
N2 (Air)
C02
H^O
SO 2
NO
N2 (Volatile solid)
Total
Theoretical Combustion Gas Volume
Wet Base (Go)
Nm3/kg-vs
4.21
1.01
0.905
0.0015
0.0022
0.0543
6.18
4.19
0.99
0.90
0.014
0.0022
0.053
6.15
Dry Base (Go1)
Nm3Ag-VS
4.21
1.01
0
0.0015
0.0022
0.0543
5.27
4.19
0.99
0
0.014
0.0022
0.053
5.25
% or ppm
-
19.1 %
0
280 ppm
420 ppm
-
100 %
-
18.8 %
0
2,600 ppm
410 ppm
-
100 %
Theoretical
Air Volume
(Lo)
Nm3/kg-VS
5.93
5.90
-------
Table A.3 Performances of Exhaust Gas Treatment Equipments
in a Multi-hearth Incinerator
^=5^-^^ Point of
^"\^-\^^ Measurement
Items of ^\. ^"~^\^^^
Measurement ^\^ ri^t^-.
Exhaust gas
temperature
Exhaust gas volume
(wet)
Exhaust gas volume
(dry)
Moisture content
Dust
CO 2
°2
CO
SOx
NOx
HCJ,
CJ,2
Ammonia
Trimethylamine
Hydrogen sulfide
Methyl sulfide
Methyl mercaptan
Dimethyl disulfide
Acetaldehyde
Styrene monomer
Odor Concentration
°C
Nm3/H
II
%
g/Nm3
%
11
11
ppm
11
li
il
It
11
n
il
il
ti
it
11
it
Furnace
Outlet
232
11,350
8,680
23.5
0.545
6.7
12.1
0.0
55.3
99.4
120.07
1.46
131.54
0.297
1.300
0.143
0.473
0.0005
<1.0
<0.001
6,900
Spray
Scrubber
Outlet
28
9,540
9,170
3.9
0.138
6.2
13.0
0.0
11.1
85.1
24.84
1.46
10.80
0.123
0.436
0.052
0.242
0.0004
<1.0
<0.001
Chemical-
Absorp-
tion
Scrubber
Outlet
30
9,960
9,535
4.3
0.070
6.0
13.5
0.0
9.8
81.0
11.65
6.11
Q.15
0.067
0.396
0.034
0.182
0.0002
<1.0
<0.001
1,400
Chimney
Outlet
68
12,495
11,910
4.7
0.034
4.2
15.3
0.0
4.3
71.8
10.34
2.24
3.83
0,028
0.235
0.017
0.114
0.0001
<1.0
<0.001
165
-------
0
tn
•o
IT
.*
i-i
fl
O
fl
U
OJ
3
'I
y
•H
U-l
ITJ
O
0)
Fig. A.I Volatile Solid Ratio VS. Upper Calorific Values
in Various Dewatered Cake and Slurry
5,000
4,000
3,000
2,000
30
A Lime and Ferric
^ chloride-added cake
0 Polymer-added cake
x Cake with no
chemicals and slurry
/ E
40
Oh = 58 VS
50
60
70
80
90
Volatile solid ratio (VS/DS) [%]
166
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
PUBLICLY OWNED TREATMENT WORKS
PRETREATMENT CONTROL PRACTICE
IN TOKYO
May 20, 1980
Tokyo, Japan
Tetsuichi Nonaka
Senior Technical Advisor,
Sewage Works Bureau,
Tokyo Metropolitan Government
167
-------
PUBLICLY OWNED TREATMENT WORKS
PRETREATMENT CONTROL PRACTICE IN TOKYO
1. INTRODUCTION . 170
1.1 Scale of Sewer System in the Inner City of Tokyo 1?0
1.2 Example of Interference with the Wastewater Treatment Plant caused
by Industrial Wastewater
1.2.1 Copper 1?0
1.2.2 Cyanides 1?1
1.2.3 Oils. ^71
1.2.4 Synthetic detergent 171
2. STATUS OF INDUSTRY EFFLUENT LIMITATIONS 173
2.1 Method of Control 173
2.1.1 Regulation by penalties 173
2.1.2 Regulation by an obligation for installation of pretreatment facility 173
2.2 Specified Industry Subject to Guidance and Average Wastewater
Quality Classified by Industry-by-industry 175
2.3 Situation of Pretreatment Facility Installed 175
2.4 Surveillance and Guidance Program for Industrial Wastewater -'"
-in/
2.4.1 Structure of execution ±f°
2.4.2 Status of surveillance 177
2.4.3 Steps for regulation of industrial wastewater 177
2.4.4 System for nomination of person responsible for wastewater quality control . 178
3. FINDING AND GUIDANCE TO THE INDUSTRY NOT INSTALLED
THE PRETREATMENT FACILITY 180
4. LOAN SYSTEM 180
5. MAINTENANCE OF THE PRETREATMENT FACILITY lp,2
6. RECENT TREND OF THE PRETREATMENT INSTALLATION 183
6.1 General Trend 183
6.1.1 Treatment process . . . . 183
6.1.2 Utilization of recoveries 183
6.1.3 Treatment of copper and zinc .. 183
6.1.4 Prepackaged unit treatment 183
6.1.5 Dewatering of sludge . .. . .. 183
6.2 Features of Treatment Classified by Industry-by-industry 185
6.2.1 Foods processing industry . . 185
6.2.2 Textile industry ... . 185
6.2.3 Metal products manufacturing 185
6.2.4 Machinery manufacturing (1 ) —(with metal-plating process) .. .... 186
6.2.5 Machinery manufacturing (2) - (without metal-plating process) . 186
0.2.6 Regular metal-plating industry . ... 186
6 2.7 Plate making and printing 1™
6.2.8 Chemical industry . . . 136
0.2.9 Ceramics industry . . . . ... 186
0.2.10 Others . . . 186
168
-------
6.3 Example of a Joint Treatment of Wastewater Discharged from Collective
Minor-sized Factories 187
6.3.1 Structure of facility 188
6.3.2 Joint treatment facility of wastewater 188
6.3.3 Recycling for reuse of industrial wastewater 1-90
6.4 Example of a Joint Treatment of Highly-concentrate Cyanide Wastewater 190
6.4.1 Objective items for treatment 190
6.4.2 Treatment method 3-90
6.4.3 Status of treatment 193
[Reference Materials]
1. Letter Requesting for Investigation on Wastewater
2. Inquiry Sheet for Industrial Wastewater
3. Ledger of Factory Subject to Guidance
169
-------
1. INTRODUCTION
1.1 Scale of Sewer System in the Inner City of Tokyo
A sewer system is presently serving approximately 70% of the inner city of Tokyo that com-
prises of 23 Wards, but when viewed regionally, the 'spread in the eastern area of Arakawa River is
somehow backward.
Overall scheme is planned to divide the inner city of Tokyo into 10 regional wastewater treat-
ment districts depending on its topographical features in order to equalize the quantitative loads
mutually. When the scheme is complete, the district's common sewer system can provide for about
10.36 million people and will have a capacity of treating 9.79 million cubic meters per day. The
eight wastewater treatment plants are presently operating and their treatment capabilities are
5,453,000m3 /day now.
A densely industrial area, when viewed from the geographical distribution of factories, is
located in both sides of Shingashi River, nearby area of Mikawashima Wastewater Treatment Plant,
Suna-machi, Yotsugi, both sides of Meguro River and the area along Tama River. In these areas,
the industries consist mostly of minor-sized factories such as textiles, metal-plating, plate making
for printing, metal products manufacturing, etc. Food processing, iron and steel manufacturing,
and chemicals manufacturing in the area are comparatively large-sized industries, but, in terms of
number of factory, these comprise of less than 10% of the categorized industry.
The categorized or specific industry represents factory and establishment that are within the
bounds of possibility of discharging wastewater limited by the Sewerage Law or Sewerage Ordi-
nance of Tokyo Metropolitan Government into a Publicly Owned Treatment Works (POTW) sys-
tem. The industry of this category is discharging, on average, about 390,000 m3 /day of total
volume received by all regional wastewater treatment plants in Tokyo.
1.2 Example of Interference with the Wastewater Treatment Plant caused by Industrial Wastewater
Some of interferences with the sewage treatment plant caused by industrial wastewater in the
past are presented as follows.
1.2.1 Copper (experienced at Mikawashima Plant in 1973}
a. Influent and influence on the plant
Sudden deterioration of the secondary effluent quality was involved, resulting in lowering a
40 cm of transparency down to I 0 cm. An exceptional inflow of copper was found when the survey
of the effluent quality variation with time was conducted for cause-finding. The inflow of waste-
water containing concentrations of higher than 1 mg/£ extended over four hours at intervals of 30
to 60 minutes intermittently. The maximum concentrations of copper in stream were 2.1 mg/C.
It was assumed that the degradation of the effluent quality was caused by lowered effect of the
activated sludge process due to the presence of copper.
Investigation on the trunk sewer was made to search after a point of discharger. The search
was reached upto a lateral sewer, however, an industry discharged such wastewater was not identi-
fied.
b. Measures
The activation of the activated sludge process was restored by seeding continuously normal
active sludge introduced from another source into an aeration tank.
Henceforth, the regulation for discharge of copper and zinc was also imposed on a factory that
discharges wastewater of less than 50 m3/day, since the amendment to the Regulations for Sewerage
Ordinance Enforcement of Tokyo Metropolitan Government was enacted in February, 1976.
170
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1.2.2 Cyanides (experienced at Mikawashima Plant in 1974)
j. Influent and influence on the plant
In the early morning, a colloidal precipitation in the effluent was identified. The effluent
quality was examined and 0.5 mg/£ of cyanides was detected in the effluent. Considering of timing
of discovery, it was assumed that cyanides in higher concentrations inflowed during night time.
The colloidal precipitation was caused by the residues of fine particles, resulting from a partial
destruction of activated sludge.
b. Measures
Investigation on the trunk sewer was conducted immediately after such finding, however, a
source of discharge was not identified since a sudden inflow of cyanides passed through in a short
period.
Alteration to the operation mode was not made, but the effluent quality returned to a normal
on the following day.
1.2.3 Oils (seen at Shibaura Plant in 1973)
a. Influent and influence on the plant
In the treatment plant that received wastewater mixed with wastes from slaughterhouse, a
lot of forth of dark-yellowish scums were formed in the aeration tank and final sedimentation
tank. The scums were formed of froth that was derived from surfactant, oil droplet and activated
sludge floe. Oil contents in the scums were about 6% as dry weight.
b. Measures
Oil fence was installed at the inlet of final sedimentation tank. This prevented the scums from
flowing over the weir and residual scums were collected for disposal.
The slaughterhouse modified the discharge line of wastewater and a plain oil separator was
changed to the flotation tank employing dispersed air. In addition, the plant for activated sludge
process was improved.
1.2.4 Synthetic detergent (seen at Mikawashima and Ochiai Plants in 1974)
a. Influent and influence on the plant
Inflow of ABS, that is a chief ingredient of synthetic detergent for domestic use, generated
froth in the aeration tank on such occasion that a temperature was low, decomposition ability of
activated sludge was degraded, or MLSS concentrations were lowered. The froth.was also found at
an outfall. This was due to the residue of ABS in the effluent. The froth was scattered around by
windage, which sometimes interfered with inhabitants living in the immediate neighborhood.
Residual concentrations of ABS (sodium alkyl benzene sulfonate) in the effluent from the waste-
water treatment plant are shown in Table 1.1.
Table 1.1 Concentration of sodium alkyl benzene sulfonate (ABS)
(Average of 1974)
Sewage Treatment Plant
Mikawashima (Asakusa District)
Mikawashima (Ogu District)
Mikawashima (Aizome District)
Ochiai
Influent
(mg/2)
4.4
5.1
4.8
5.6
Treated water
(mg/C)
0.9
0.9
0.6
0.8
171
-------
h Measures
The steps to increase MLSS concentrations and decrease amount of supplying air were em-
ployed in the aeration tank as the measures. As another measures for prevention of froth growth,
antifoaming agent such as silicon was fed into a defoaming tank and the polystyrene form plates
\vere installed to allow absorption of the froth.
The products of synthetic detergent was turned to a soft-type in 1974. This allowed a biode-
^rability of the synthetic detergent of more than 85%, thus resulting in a remarkable reduction of
froth forming.
172
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2. STATUS OF INDUSTRY EFFLUENT LIMITATIONS
The effluent limitations set forth in the Sewerage Law and Sewerage Ordinance of Tokyo
Metropolitan Government are applicable to those industries or factories that are located in the
regional wastewater treatment districts and discharge wastewater into the public sewer.
2.1 Method of Control
The control or regulating can be broadly classified into two categories.
2.1.1 Regulation by penalties
The specified industry that is categorized under the statutory regulation is prohibited to
discharge wastewater quality in excess of the effluent limitations described in Table 2.1. Any
industry that violates any ordinance or regulation shall be prosecuted and, in some cases, punished
directly. In the discretion of the General Manager of Publicly Owned Treatment Works system, an
order for facility improvement or order for suspension of discharging wastewater can be issued
without dispute to those in violation or those who possibly violate the regulation.
2.1.2 Regulation by an obligation for installation of pretreatment facility
The regulation imposes an obligation to install the pretreatment facility to the dischargers of
wastewater in excess of the effluent limitations stated in Table 2.1. The order for facility improve-
ment or suspension of discharge can be published to those in violation of the regulation.
173
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Table 2.1 Pretreatment standards for industrial users of POTW
Categories
Dischargers to Publicly Owned Treatment Works system where
terminal treatment plant is installed.
Industry not installed specified facility
Organic phosphorus
Lead
I/////// ///////.
mMm
W///. 1 W///A
Chromium (VI)
0.5
0.5
Arsenic
0.5
0.5
Total mercury (*)
w/*** wM™^m
0.005
0.005
Alkyl mercury
PCB
not detectable/!
Wfr^M/A
//not detectable /
WT^W/.
not detectable
0.003
not detectable
0.003
(Note) 1. Unit, except for pH, is expressed in rng/8.
2. Value in bracket ( ) related to BOD, SS, pH and Temperature is applicable to manufacturers and gas
suppliers.
3. Pretreatment standards expressed in solid lined square \HHllb are directly related to the penalties by
regulations. Among these limitations, the standards of copper, zinc, phenol, iron, maganese, fluorine
related to the industries installed specific facilities have been applicable to the factories constructed
after April 2, 1972.
4. Indication in plain square [ | relates to the obligation of pretreatment facility installation.
(*) Total mercury represents mercury, alkylmercury and other mercury compounds.
174
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2.2 Specified Industry Subject to Guidance and Average Wastewater Quality Classified by Industry-
by-industry
The public sewer users that possibly discharge wastewater in excess of the effluent limitations
set forth by Law or Ordinance are specified as industry or establishment required for guidance.
The subject industry is divided into 21 categories. Table 2.2 illustrates an average wastewater
quality discharged from major type of industries.
Table 2.2 Average effluent qualities for industry-by-industry categories
(mg/C)
""\^
Foods
Textile Mills
Pulp & paper
Iron & steel
Metals
Machinery-1
Machinery-2
Electroplating
Printing
Chemicals
Leather
tanning & finishing
Ceramics
Wastes disposal
Others
Chromium
-
0.008
0.01
0.02
0.31
0.44
0.10
4.40
0.77
0.06
12.4
0.13
-
0.0008
Copper
-
-
-
0.34
2.48
0.41
2.26
9.37
2.51
0.06
-
0.007
-
0.003
Zinc
-
0.06
0.17
2.61
4.22
0.42
0.83
13.4
7.02
2.99
-
0.17
0.002
0.12
Cadmium
-
-
-
-
0.001
0.0007
-
0.0008
0.0009
0.0004
-
0.11
-
0.00008
Lead
-
0.05
0.05
0.003
0.27
0.03
0.009
0.06
0.05
0.17
-
0.13
-
0.06
Arsenic
-
-
-
-
-
-
-
-
-
-
-
-
-
0.000004
Total
mercury
-
-
-
-
0.000005
0.00009
0.0002
-
-
0.00002
-
-
-
0.000002
SS
31
96
121
15
18
7
4
18
1
17
270
32
-
-
2.3 Situation of Pretreatment Facility Installed
As seen in Table 2.3, the ratio of the pretreatment installed is reaching a higher percentage
year by year. Recent status of the pretreatment facility installation of industry-by-industry cate-
gories is shown in Table 2.4.
Table 2.3 Status of the pretreatment installation
Fiscal year
Specific industrial
categories
No. of installation
completed in the year
Cumulative No. of
installation completed
Installation ratio (%)
1975
2,789
439
1,940
69
1976
3,043
419
2,359
78
1977
3,946
857
3,216
82
1978
4,269
455
3,671
86
1979
(as of end of
December)
4,634
227
3,898
"«7,
175
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2.4 Surveillance and Guidance Program for Industrial Wastewater
2.4.1 Structure of execution
The surveillance for the industrial wastewater and guidance for the pretreatment facility
installation and maintenance are executed by the organization as shown in Table 2.5.
Table 2.5 Organization chart for implementation of surveillance and guidance program
related to industrial wastewaters
(Head Office)
(Division)
Operation Maintenance
Improvement
Advisor to the
Director
/'Guidance on\
V Wastewaters/'
(Management Office)
(Section)
Private Drainage
I
Assistant Advisor
to the Director
( Guidance on \
V Water Quality/1
(Subsection)
Guidance of
Water Quality
Technical Guidance
Water Quality
Examination (1)
Water Quality
Examination (2)
(Personnel)
(7)
(4)
(10)
(10)
(Note) Dotted line denotes the staff.
Management
Water Quality
Control
Total
/ 8-subsection\
V80 personnel^
113
176
-------
Overall operation is shared at the head office. The subsection in charge of guidance on waste-
water quality has an assignment to give a guidance to the installation and operation of the pretreat-
ment facility, and to give a guidance and control of the implementation of the regulation related to
the industrial wastewater quality. The subsection in charge of technical guidance deals with an
investigation and guidance in the technology related to the pretreatment of the industrial waste-
water. The subsection of water quality examination conducts the examination and test of waste-
water quality discharged from industry.
Direct surveillance and guidance to the factory are conducted by the subsection of water
quality control at the Management Office. In other words, the assignment of the office includes an
examination of wastewater quality, an acceptance of application, a guidance to the pretreatment
facility installation and maintenance, and regulating industrial wastewater quality.
2.4.2 Status of surveillance
Frequency of surveillance conducted was, on average, 1.4 times per one factory as seen in
Table 2.6. This may not be sufficient. However, a priority of on-the-spot inspection was given to
the factories that discharge harmful pollutants such as heavy metals, the factories that discharge
wastewater of more than 100 m3/day, and the factories discharge the regulated substances such as
acidic wastes, copper and zinc. The 50 factories received on-the-spot inspection of more than five
times a year. The cases of violation pointed out by the surveillance program are shown in Table 2.7.
Table 2.6 Annual number of on-the-spot inspection per one industry
(FY1979)
Factory subject to surveillance
4,269
Aggregated number of on-the-spot inspection
5,931
Average
1.4
Table 2.7 Status of violation
Fiscal year
1976
1977
1978
1979
(as of December)
No. of case for surveillance
3987
6025
6198
5162
No. of case in violation
1716
2283
2050
1451
Ratio of violation (%)
43
38
33
28
No. of violation cited above includes cases of minor violation.
2.4.3 Steps for regulation of industrial wastewater
The factory in violation will receive a phase-by-phase administrative guidance and an adminis-
trative punishment. The phase-by-phase guidance consists of oral notice, written notice, warning,
hearing and order for improvement including order for suspension of wastewater discharge. The
state of violation is shown in Table 2.8.
177
-------
Table 2.8 Trend of control under regulations
Fiscal Year
1976
1977
1978
1979 (As of December)
Notice
1368
1921
1354
1150
Warning
348
404
368
257
Hearing
31
21
g
13
Order for
improvement
26
13
35
14
2.4.4 System for nomination of person responsible for wastewater quality control
In connection with the surveillance program for wastewater, the system for nomination of the
person responsible for wastewater quality control was established in April 1978 under the Sewerage
Ordinance of Tokyo Metropolitan Government. The purpose of such promulgation is to clarify
where the responsibility lies in the inner side of the factories or industries and to effectuate a
maintenance and control of the pretreatment facility including the treatment facility for sewage
discharged from the specific facilities.
The job description of the person responsible for wastewater quality control is:
a. proper management of how-to-use facility which produces sewage, the volume of sewage and
wastewater quality;
b. maintenance and control of the pretreatment facility, record of operation log, and taking other
necessary measures;
c. measurement and record of wastewater quantity and quality to be discharged to the public
sewer;
d. data related to the sludge produced at the pretreatment facility; and
e. measures in case of the facility failure and emergency.
The qualification of the person responsible for wastewater quality control shall be the person
who holds the qualification for a supervisor of pollution control under the Law concerning Consoli-
dation of Organization for Pollution Control at Specified Factory, or the person who is qualified for
a supervisor of pollution control under the Ordinance for Pollution Control of Tokyo Metropolitan
Government, and the person who completed lessons at a short course held by the General Manager
who is managing the sewerage system of Tokyo.
The industry categories requiring for guidance must select the person responsible for waste-
water quality control and must be filed with the Sewage Works Bureau of Tokyo. Number of the
person responsible for wastewater quality control is shown in Table 2.9.
Table 2.9 No. of the person responsible for wastewater quality control
1979
(as of end of March)
1979
(as of end of December)
Specific factories
4,269
4,634
No. of the person selected
2,833
3,469
Ratio of selection (%)
66.4
74.9
178
-------
An independent management at each industry is gradually strengthened by an establishment of
*ht' iystem f°r places tne person responsible for wastewater quality control, thus resulting in the
•tendency of reducing number of cases in violation.
179
-------
3. FINDING AND GUIDANCE TO THE INDUSTRY NOT INSTALLED THE PRETREAT-
MENT FACILITY
The percentage of the pretreatment facility installed is on increase year by year. Total number
of industry categories subject to guidance is 4,629, out of which the number of industry that has
not installed the pretreatment facility is 497 as of the end of March, 1979.
Table 3.1 Contrary trend to the pretreatment installation
^^-\^Classification
R eason - — — _____^^
Financial difficulty
Difficulty in spacing
Planning to move
Planning to install
Subject to surveillance
Total
Minor-scale industry
109
28
10
61
83
291
Small- and medium-
scale industry
155
5
1
6
24
191
Large-scale industry
1
2
0
13
54
70
Total
265
35
11
30
161
552
Most of them are minor- or small- and medium-sized industries. For reference, a breakdown of
the reason for those who have not installed the pretreatment facility is presented in Table 3.1,
which is the result of the investigation made at the end of 1977. It is presumed such a tendency
has been continuing without a significant change.
Viewing from enterprise-size wise, the industry referred to above comprises 53% of minor-
sized industry operated with not more than 20 employees, 34% of small- and medium-sized industry
operated with not more than 100 employees and paid-in capital of not more than 10 million yen,
and 13% of large-sized industry. The ratio of minor-sized industry is more than a half. "Planning"
described in Table 3.1 includes the industry that have already contracted with manufacturer to
install the pretreatment.
Though the industry has an intention of installing the pretreatment, those who still have no
prospect of installation by the reasons of "financial difficulties" or "difficulty in securing land"
will comprise 64% of substantial industry that has not installed the pretreatment (472 factories
excluding those in the stage of planning). The number of minor-sized industry comprises a half of
the whole.
"Subject to surveillance" represents the industry required for continuous surveillance to guide
the installation of the pretreatment facility. This classification comprises 34% of the substantial
industry that has not installed the pretreatment. Tokyo Metropolitan Government will strongly
promote the guidance for installation of the pretreatment in a manner of giving a full explanation
regarding the treatment process, the financing aids (loan system) and others, basing on the results
obtained from the study of the industry categories, the enterprise-size wise and the reasons for not
having installed the pretreatment yet.
4. LOAN SYSTEM
Those industries intending to install new pretreatment, or to enlarge or modify the existing
plant, or improve the production process can utilize the financial aids such as loan system of govern-
mental agencies. The outline and the status of loan utilization are shown in Table 4.1.
180
-------
Table 4.1 Financing mediation program for pretreatment installation and its status of utilization
Bodies for mediation
Pollution Control Bureau,
Tokyo Metropolitan Gov-
ernment
Pollution Control Bureau,
Tokyo Metropolitan Gov-
ernment
Labor and Economic Bu-
reau, Tokyo Metropolitan
Government
Specified Ward of Tokyo
Metropolitan Government
(-1)
Environmental Pollution
Control Service Corpora-
tion
Smaller Enterprise Fi-
nance Corporation
Peoples' Finance Corpora-
tion
Environmental Sanitation
Finance Corporation
Name of financing
aid system
Finance mediation system
for pollution control fund
of Tokyo Metropolitan
Government
Loan system of pollution
control fund of Tokyo
Metropolitan Government
Fund loan system for
equipment modernization
of small- and medium-
scale industry
Loan system for pollution
control fund
Loan system for pollution
control facilities
Loan system for industrial
pollution control
Loan system for pollution
control
Loan system for treatment
facility of polluted water
Terms and conditions
Limit of loan (Yen)
20 million
7 million
12 million
3 million
Within 80% of construction
cost for small- and medium-
scale industry and within
50% for large-scale industry
210 million
25 million
22 million
(additional 15 million yen
is allowable)
Annual interest
2% for industry with 10
employees or less
4% for industry with 1 1
employees or over
2% for industry with 10
employees or less
4% for industry with 1 1
employees or over
No interest
2%
6.5 %
7.35%
First 3 years: 7.15%
Remaining: 7.65%
First 3 years: 7.15%
Remaining: 7.65%
First 3 years: 7.15%
Remaining: 7.65%
Term of
redemption
Within
7 years
Within
8 years
Within
12 years
Within
5 years
Within
10 years
Within
10 years
Within
10 years
Within
10 years
TOTAL
Fiscal year of
1977
No. of
case
74
0
0
81
0
0
27
0
182
Amount
(Yen)
(million)
501.27
0
0
212.50
0
0
101.90
0
815.67
Fiscal year of
1978
No. of
case
21
0
0
63
1
4
12
0
101
Amount
(Yen)
(million)
139.60
0
0
179.50
100.00
41.50
49.58
0
510.18
Fiscal year of
1979 (.2)
No. of
case
6
1
0
34
1
7
9
0
58
Amount
(Yen)
(million)
38.18
1.50
0
98.76
80.00
151.01
28.15
0
397.60
00
(Note) (• 1) denotes the system being employed in Bunkyo Ward and presented as an example
(»2) represents the status as of end of December 1979
-------
5. MAINTENANCE OF THE PRETREATMENT FACILITY
Even in the industries that have already installed the pretreatment may sometimes violate the
effluent standards if the facility is not maintained or controlled properly. As a cause of violation, it
can be broadly classified into two categories. One is that a problem lies in the pretreatment itself,
and another is that a problem lies in the operation and maintenance of the pretreatment facility.
As seen in the statics shown in Table 5.1, the latter comprises about a half. Improper control
of instrumentations and improper chemical groupings of wastewater are seen remarkably. The
Sewage Works Bureau of Tokyo Metropolitan Government imposed, as stated earlier, an obligation
on the industrial categories to select the person responsible for wastewater quality control with the
aims to have him control and maintain properly the pretreatment facility.
Table 5.1 Classification of causes for violation
Cause for violation
Constructional defect of pretreatment facility
Improper capability of pretreatment facility
Improper control of raw water including chemical groupings of effluent
Improper control of consumable materials such as water treatment chemicals
Improper control of measuring instruments for facility
Improper operation of pretreatment facility
Discharging wastewater without treatment
Ratio (%)
12
10
13
12
27
19
7
182
-------
6. RECENT TREND OF THE PRETREATMENT INSTALLATION
5.1 General Trend
6.1.1 Treatment process
The industry discharging wastewater of less than 1 m3 /day employs a batch treatment and a
Continuous treatment is practised for wastewater of not less than 1 m3 /day. If the control method
is divided into automatic and manual control mode, the continuous treatment employs automatic
control while the batch treatment employs automatic and manual control which can be split fifty-
fifty.
6.1.2 Utilization of recoveries
The industry develops a tendency to reclaim for reuse of wastewater by recovering partially
or wholly. The collection methods employed are ion exchange process, electrodialysis and evapora-
tion process. Another process is to polish up the treated wastewater by using filter after treatment
of pressurized flotation or chemical precipitation. Among the processes, the evaporation is em-
ployed for the treatment of rinsing water of chromium plating and the chromium (VI) recovered by
condensation is returned to the plating bath for reuse. Reclaimed water by the ion exchange
process is collected, but the resin regeneration wastewater is discharged into the sewer after treated
chemically.
The electrodialysis is used for recovery of copper, chromium, etc., but the operation is carried
out at the most effective electrolytic concentrations. The residual concentrations are still high so
that the wastewater is required to be treated chemically prior to discharging.
6.1.3 Treatment of copper and zinc
The regulation for copper and zinc was also imposed on the industry discharging wastewater
of less than 50m3/day in May, 1975. The treatment of zinc was a matter of concern, but it was
proved that the zinc was eliminated by a hydroxide coagulation. Example of flow diagram is shown
in Figure 6.1.
When copper and zinc group wastewaters contain cyanides and chromium (VI), the wastewater
is divided into each group, but, if not, the wastewater is treated by the chemical precipitation
process in the group of acid-alkali. Example of flow diagram for batch treatment and for con-
tinuous treatment are shown in Figures 6.2 and 6.3, respectively.
6.1.4 Prepackaged unit treatment
Most of unit type treatment made of steel and PVC are in prepackaged unit that is fully
equipped with necessary treatment process. The prepackaged unit requiring only water and elec-
trical connections on-site operation tends to be employed at an experimental facility or a research
laboratory where the volume of wastewater is less than 0.5 m3/day and many substances are re-
quired to be treated. Metal industry and machinery manufacturing with an operation of plating
process are also in tendency of employing such a prepackaged unit type treatment.
6.1.5 Dewatering of sludge
Most of industries that produce the sludge as a result of wastewater treatment tend to install
the dewatering device. This is to aim at reducing volume to be disposed of finally. Small-sized filter
press and bag filter press are employed mostly at the industry which produces less volume of sludge.
Centrifuge, vacuum dehydrator, belt press and filter are employed in other area.
183
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Fig. 6.1 Flow diagram for treatment of pH, SS, Cu, Zn at N Metals
Capacity: 9m3 /day
Acid -alkali waste
1.5m3/h (max.)
n
IF
v v v v
ABC
r
Cylindrical
sand-filter
No. 1 storage tank | pH control tank
2.7m3 0.6m"
T
T r
1
Sedimentation No. 2 storage tank Neutralization tank Discharge tank
tank 0.4m3 0.5m3 0.5m3
5 m'
Material of tank: concrete, iron, PVC
Filter press I
Fig. 6.2 Flow diagram for treatment of pH, CN, Cr6f, T-Cr, Zn at T metal-plating
Process: batch (manual operation)
Capacity: 0.6 m3/day
Material of tank: Iron, PVC
Cyanide
0.3m3/d
Treatment tank Ikon)
of cyanide
0.7m3
Treatment tank (PVC)
of chrome
0.7m3
\
_x
\
/
I
I
I
I
JM
— tb \-4
Filter tank
(Iron-made)
1m3
n
i
Neutralization tank Catch-basin
(iron-made) 20B
0.5m3
184
-------
Fig. 6.3 Flow diagram for treatment of zinc wastewater containing
cyanide and chromium (VI) at S Metal-plating
Substances to be treated: pH, Cr6+, T-Cr, Zn at S plating
Process: Automatic and continuous operation
Capacity: 12m3/day
3hrome
ISrrr/h
Storage tank
(PVC-made)
1m3
Acid-alkali
1 mVh
IF
Storage tank
IPVC-made)
2m3
AT-type sedimentation tank
i
A'
«•
I1
d
^ •
I
1
Discharge
Reduction pH control Retention tank Neutralization tank
tank tank 0.4m3 1 m"
0.4m3 1 m3
Sludge tank
r\
Bag filter-press
6.2 Features of Treatment Classified by Industry-by-lndustry
6.2.1 Foods processing industry
The items of wastewater to be treated are pH, BOD, SS and animal/vegetable oils. Generally,
volume of wastewater for treatment is large.
The treatment process by activated sludge, rotating biological contactor, contact aerator,
trickling filter, coagulation and sedimentation and pressurized flotation axe employed. Filter press
and belt press are used for dewatering of sludge.
6.2.2 Textile industry
Most of wastewaters in the process are dyeing wastes and the item to be treated is pH. Since
a large volume of wastewater are discharged, the continuous and automatic control system are
employed. Besides neutralization, reduction, chemical precipitation and dewatering plant are
equipped with where chromic acid is used in the process.
6.2.3 Metal products manufacturing
The items to be treated are pH, copper, zinc and SS. In any event, pH is always controlled.
In some cases, the sedimentation process is employed additionally.
185
-------
6.2.4 Machinery manufacturing (1)-(with metal-plating process)
Wastewater treatment is required as same level as the regular metal-plating industry, since
the metal-plating is included in the manufacturing process. The objective items for treatment are
pH, SS, Cr6+, total Cr, CM, Cu, Zn, Fe, etc.
6.2.5 Machinery manufacturing (2)-{without metal-plating process)
Though the metal-plating process is not included, the factory, where chrome treatment is'
employed, is required to equip with the reduction treatment since it discharges Cr6*.
6.2.6 Regular metal-plating industry
This type of industry discharges less wastewater, compared with other industry categories.
Mostly a batch treatment is employed. The treatment facility such as the reduction process and
oxidation is generally used, but, in some cases, ion exchange resin and chromic acid are recovered
by evaporation to condensate.
6.2.7 Plate making and printing
Most of factories are required to treat pH only. If the plate making process includes the
development of PS plate (aluminum-made), the neutralization by injecting carbonic acid gas is re-
quired in many cases since the alkali wastewater is discharged. Where etching process of copper
and zinc plate is employed, the wastewater is neutralized by addition of caustic soda for further
sedimentation.
6.2.8 Chemical industry
Wastewater quality discharged from industrial factories is varied, so the treatment process is
not standardized. In general, the raw materials are recovered to the most possible level. In the most
cases, the objective item for treatment is pH only.
6.2.9 Ceramics industry
When the zinc is discharged in the process of glass product manufacturing, the wastewater
is treated by a hydroxide coagulation. Fluorine is precipitated in a form of CaF^ by a lime co-
agulation.
6.2.10 Others
a. School, institute, establishment for chemical analysis, laboratories
Establishment in this category is featured that it discharges a small amount of wastewater but
contains various harmful substances. In most cases, a prepackaged unit type wastewater treatment
process for laboratory is used. Operation mode of the unit is a batch treatment by manual or semi-
automatic control. Among heavy metals, Hg and Cd are treated checmically and a chelate resin or
activated carbon adsorption is installed to prevent a leakage of Hg and Cd.
b. Hotel and lodging
Wastewater contains wastes from a cuisine, thus resulting in a large amount of oil contents.
Flotation process is employed in the prior or main stage, and then a rotating biological contactor,
activated sludge process and coagulation process are employed for removing BOD and SS in the
later stage. An example of flow diagram which combines the pressurized flotation and rotating
biological contactor for the treatment of wastewater discharged from O Hotel is presented in Figure
6.4.
186
-------
Fig. 6.4 Flow diagram for treatment of cuisine wastewater at 0 Hotel
Substance to be treated: BOD, SS, Oil
Process: Pressurized flotation and rotating biological contactor
Capacity: 516m3/day
Tank: Concrete-made
Screen Measuring tank Pressurized flotation tank Rotating biological contactor
N.C.S. 0.5m3 41.2m3 3,500m3
0-Lh
i>
Discharge tank
9m3
{Sedimentation tank
51.6m3
Oil storage tank
7m3
Sludge tank
15m3
6.3 Example of a Joint Treatment of Wastewater Discharged from Collective Minor-Sized Factories
In general, the minor-sized factories are located in the mixed area of housing and factories.
Nearby inhabitants have voiced their desire that the government would buckle down to the problem
of pollution control. However, those factories are facing with a certain difficulty in installing the
effective pretreatment facility due to smaller land space of the factory and financial difficulties.
Also, since those factories employ only limited number of employees, a difficulty in placing the
persons who maintain and control the wastewater treatment plant on full-time duty has been in-
volved. In such circumstances, the factories in this category are apt to pay less attention to proper
treatment. In order to resolve such a bottleneck, it will be essential for the government to promote
actively the enforcement of a policy. The measures to be taken are to induce a relocation of the
factory located in the mixed area of housing and industry, to have them accelerate the improvement
of production process aiming at pollution prevention, and at the same time, to have them install
a joint treatment facility for wastewater.
Jyonan Denka Kyodo Kumiai (Jyonan Galvanization Cooperative Association) promoted to
collectivize metal-plating factories and to install a joint treatment facility of wastewater (Metal-
plating Center). The scheme was planned on the grounds mentioned previously and brought into
existance as a series of "promotions of pollution abatement of electroplating industry and for joint
treatment" Metal-plating Center was organized and the wastewater treatment was completed in
March 1975 and put on stream in September 1975. Further information is given in the following
chapter.
187
-------
6.3.1 Structure of facility
"Metal-plating Center", comprizing of collective 10 factories, has a land space of 4,600m2
and its building floorage of 2,300m2, out of which 150m2 is allotted for a joint wastewater treat-
ment facility, exhaust gas scrubber and analysis room. Business status is classified into 7 copper-
plating, 3 zinc-plating, 7 chrome-plating, 7 nickel-plating, 1 tin-plating and 3 silver-plating.
6.3.2 Joint treatment facility of wastewater
Overall wastewater discharged from individual factory amounts to about 170m3 /day. In-
dependent treatment facility for individual group of wastewater is installed, and segregation of
wastewater depending on group and separated treatment are well managed.
Group of wastewater is divided into 10 groupings, that is, zinc cyanide, copper cyanide, acid-
alkali iron, acid-alkali copper, nickel, copper pyrophosphate, chromate, chrome plating, highly-
concentrate acid-alkali iron and highly-concentrate acid-alkali copper. Fundamental treatment
processes employed are an oxidation by sodium hypochlorite for cyanides, the reduction by sodium
bisulfite for chromium (VI) and coagulation for heavy metals. The treatment of highly-concentrate
cyanide wastewater has been entrusted to Jyonan Treatment Center (refer to Chapter 6.4—Example
of a joint treatment of highly-concentrate cyanide wastewater). The flow diagram of the treatment
is shown in Table 6.5.
Sludges of nickel, chrome, copper and zinc group are dewatered by a filter press, and then
sent to the refineries for the purpose of cyclic use of raw materials. The dewatered sludge trans-
ported annually and content concentrations of effective ingredients are shown in Table 6.1.
Table 6.1 Volume of dewatered sludge and concentration
of effective consituent content
Type of dewatered sludge
Chromium group
Copper group
Zinc group
Iron group
Weight transported annually
(ton/year)
44
24
15
62
Effective constituent content
(%)
22
31
25
5
(Note) Volume of discharge is expressed in wet weight.
188
-------
Fig. 6.5 Flow diagram of a joint-treatment in metal-plating center
Symbol:
Flow of wastewater
Treatmenl system
Plating
facility Waste groupings
^ Flow of supernatant liquid
^> Flow of slurry
--^> Flow of cake
' ^ Flow of filtrate
r-1
OO
City water
170 5 mj /d)
r "
1
u_
(36m3/d)
ppor cycim o asa (24m'/d)
-i 3. Copper acid base
(50m1 /d)
_. 4. Highly concentrate
copper acid base (Twice/year)
^ 5. Copper pyrophosphate
Dase (2m3/d>
^ 6 Iron arid bfHfl _ ...
(71mVd)
(40.5rn3/d)
_:,. 7 Highly rnnrnnlrate
iron, acid and alkali (Twice/year)
base
(8m5 /d)
Ion (20m3
-> 0. Cluomebdie > exchanger (A
(81.6mJ/dl
Ion 1
-J»10. Sodium bichromate base— > exchanger '
i
i
Oxidation- ,, ., „
decomposition ^
Oxidaiion-
decomposition
> • > water-t =J> Z|nc s|udge i
, . i.it , in9 t
l.ll.l. r !
1
1
"nl '
. ^ pH adiustmenl to V 1
!' form hydroxide ^ || i
1
^ pH adjustment ^ „ 1
' by lime . tf UB 1
l_ SK water- - i
" -^'ing "> Copper sludge. 1
•v'., .. , ' ' ' ' '
-I " — n U
~7 n ' De- ""i^
\ ^ Neutralization to \ ' ,...,,„, 1
/dl
U water- |
I1 i i"n^>|ng i=J> Nickel sludge t
1
P U' m° water
— * ^ina --^Chrome sludge
1 1 ri^ rf, S /H t
• Neutralization
M1
(170.5 m3/d)
-------
6.3.3 Recycling for reuse of industrial wastewater
a. Ion exchange
Wastewater of chromate and chrome plating is treated individually by an ion exchanger, and
most of treated water is reused for rinsing water. The wastewater of ion exchange resin regenera-
tion is treated separately at the joint treatment facility.
b. Treated water of joint treatment facility of wastewater
About 20% of the treated water (40m3 /day) is sent to the factory, and reused as roughing
wash water in the pretreatment process of plating.
6.4 Example of a Joint Treatment of Highly-Concentrate Cyanide Wastewater
Wastewater of cyanide group generated at an electroplating can be broadly classified into the
wastewater containing cyanide concentrations of 50—200 mg/£ that is discharged normally and
continuously, and the wastewater containing highly-concentrate cyanide of 15,000—45,000 mg/£.
It is a matter of course to treat the normally discharging wastewater individually at the factory that
produces such wastewater.
However, since the highly-concentrate wastewater contains high concentrations of free cyanide
and complex cyanide, a higher level of treatment technology and a higher cost for treatment are
required. Collective treatment will be more acceptable economically or technically.
In the collaboration with Tokyo Metropolitan Government, Tokyo Metal-plating Pollution
Control Corporative Association (formed by membership of 1,100 companies) built a joint treat-
ment facility named as Jyonan Treatment Center, which has a land space of 1,300m2 and waste-
water treatment capacity of 200 kiloliters/month.
In June 1972, the Center began to collect the highly-concentrate cyanide wastewater from the
metal-plating factories in Tokyo area and is now functioning to transport the treated sludges, after
an intermediate treatment, for reclamation.
6.4.1 Objective items for treatment
The wastewater containing highly-concentrate cyanide of electrolytic degreased liquid, exhaust
neutralization liquid of plating bath, nickel-stripping liquid is the objective items for treatment.
6.4.2 Treatment method
»
The treatment method of a highly-concentrate cyanide wastewater employed in the Jyonan
Treatment Center is, so called, a steam dryer and high temperature incineration. This method is to
evaporate the wastewater to form dried solids, which receive heat treatment at the metal refinery
where the cyanide is decomposed and heavy metals are recovered as an effective ingredient.
Outline of the steam dryer and high temperature incinerator is shown in Figure 6.6 and the
flow diagram of Jyonan Treatment Center is illustrated in Figure 6.7, respectively.
a. The wastewater collected from the metal-plating industry by three trucks is maintained in a
state of alkaline, and stored temporarily in the wastewater receiving tank which is served also
for precipitation tank as well. The volume of wastewater collected is ranging from 140 to 210
kiloliters per month. The wastewater is kept gently in the tank for about 48 hours, and
separated into supernatant and settled sludge while allowing settlement of solids.
b. The supernatant is condensated under a reduced pressure in the condensation tank, and
reformed to the flake state by drying on the surface of drum dryer. The dried solids in form
of flake of 30-35 tons per month are produced and sent to the metal refinery in container.
190
-------
^ The dried solids are fed into a high temperature furnace of the refinery and incinerated at
about l,200°C for two hours to decompose cyanide as well as to recover zinc and copper in
the incineration stage. Waste gas, cleaning waste and residual suspended solids are turned to
non-pollutant substances.
j Cooled condensation discharged from the condensation tank and drum dryer contains ammonia
which is produced in a reaction of [NaCN + 2^0^ HCOONa + NH3 ]. Therefore, the cooled
condensation is sent to an ammonia stripper where the ammonia stripping is achieved.
e. Ammonia-free wastewater discharged from the ammonia stripper contains a small amount of
cyanides and heavy metals. The wastewater will be treated by alkali treatment to remove
cyanides and then by sedimentation to eliminate heavy metals. The settled hydroxide is sent
to the metal refinery together with the dried solids after dewatering.
f. The treated water is discharged into the sewer after adjusting pH.
Fig. 6.6 Outline of steam dryer and high-temperature incinerator
Source
Highly-concentrate
cyanide waste
Collection by
truck
Receiving
Conce
by stea
Low-ten-
dried
Dried
Transp
byt
r—
High-ten
treat
Metal r
Wast
ntration
m dryer
If ^
perature
solids
solids
ortation
ruck
1 1
iperature
ment
ecovery
e gas
/-
\
Steam
Co<
conde
Amr
strif
Cy
decorr
Heavy
sepai
Treatei
sling
nsation
nonia
iping
anide .
position AmrT
Inciner
metals toxjc i(
ation redi
Waste
i water incj(1
\ \
Discharoe nie/-
lonia
ation for
igredient
jction
gas of
erator
1
I I
191
-------
Fig. 6.7 Flow diagram of treatment plant at Jyonan Treatment Center
Steam
l-D
K)
Ejecter
flow of liquid
flow of vapor
Cyanide
decomposi-
tion tank
Cooling
~ water
Condensate
storage
Dried slag container
Precipitator Supernatant
storage tank
- To metal refinery
-------
6.4.3 Status of treatment
Analytical value of ingredients of each process at the Jyonan Treatment Center is presented in
Table 6.2.
Table 6.2 Chemical composition of each process at Jyonan Treatment Center
^^^-\^J>ampie
\^JJnit
Total cyanide
Cadmium
Copper
Zinc
Total Fe
Total chromium
Nickel
Highly concentrate
wastewater
mg/fi
21,000
50
5,500
3,500
400
50
1,400
Effluent to sewerage
mg/2
0.7
0.02
1.1
0.5
1.1
0.08
0.2
Dried solids
%
15
0.4
6
5
0.8
0.05
0.9
193
-------
[Reference Materials]
1. Letter requesting for investigation on wastewater
2. Inquiry sheet for industrial wastewater
3. Ledger of factory subject to guidance
194
-------
1.
Letter requesting for investigation on wastewater
To:
From: Sewage Works Bureau
Tokyo Metropolitan Government
Subject: Request for investigation on industrial wastewater
Recently, an increasing concern on water pollution has been recognized, and an enforcement
of legislation concerning Water Pollution Control Law and Sewerage Law has been strengthen-
ed gradually.
Now, the Sewage Works Bureau of Tokyo Metropolitan Government has decided to conduct a
study of wastewaters discharged from industries.
You are therefore requested that you may necessarily return the enclosed "Investigation sheet
on industrial wastewater" to the address indicated at the bottom of this letter not later than
(day) (month) (year). Filling-in the blanks may be referred to the specimen attached.
Filled-in form will be returned to:
Any doubt or inquiry may be made to the address above.
Manager of Administration Office
(Note) Production process chart and floor plan are also attached.
195
-------
2. Inquiry sheet for industrial wastewater
SECRET
Inquiry sheet for industrial wastewater
Date
Name of
factory
Representative
Person in charge
Tel:
Address
Type of
business
Capital V
Area of factory m2
Employee
Working hour from to
Holidays
Major products and amount of production (per month)
Wastes required for treatment
group
group
group
group
Wastes not requir-
ed for treatment
m3/d
m3/d
m3/d
m3/d
m3/d
Amount of raw materials and
chemicals used (per month)
Water source and volume for use
City water
Industrial water
Well water
River water
Others
Total
m3/d
m3/d
m3/d
m3/d
m3/d
m3/d
Fluctuation
with time of
wastewater
Continuously
Intermittently
Remarks
(Note) Production process chart and floor plan are attached.
196
-------
3. Ledger of factory subject to guidance
Ledger of factory subject to guidance (face)
Filed on (datel
Name of
factory
Address
Tel
Representative
Person re-
sponsible
for water
quality
control
Status!
Name
Category No.
Receiving wastewater
[reatm8n, plant
Record of guidance
Date
Capital
When
plant
was on
stream
(date)
Area of
factory
Major products and a-
mount of production
Employee
Working
hour
Holidays
from
Required for treatment
group
group
group
group
group
group
Not required
for treatment
m/d
Water source and vol-
ume for use
City water
Industrial
water
Well water
River water
Others
Total
m/d
Major raw materials,
chemicals and
amount consumed
m /dj Discharge to POTW
Objective item of water
quality
Application for use
Report on water
quality improvement
Type of specified facility
(No.. Name)
Application for
Pretreatment facility
Application for speci-
fied facility
Completion of
Pretreatment. etc.
Application for respon-
sible person for water
quality control
Pretreatment facility
{installed or not)
Warning
Warning
Warning
Warning
Warning
Hearing
Order
Remerks
Ledger of factory subject to guidance (back)
Production process chart (F low diagram)
Raw
water
Checkups
of
treated
effluent
at a time
of com-
pletion
Sampling
(date)
Place of
sampling
Items of water quality and measurement
Floor plan of factory
Histry of maior guidance
'Motel
tem-by-item punches are provided along margin space to aggregate.
197
-------
Seventh US/JAP AN Conference
on
Sewage Treatment Technology
DEODORIZATION IN SEWAGE
TREATMENT PLANTS OF
YOKOHAMA
MAY 1980
TOKYO JAPAN
SHIGEKI MIYAKOSHI
HEAD, CONSTRUCTION DIVITION
SEWAGE WORKS BUREAU
CITY OF YOKOHAMA
199
-------
J
Content
Foreword •
1. Current State of Deodorization Equipments 202
1.1 Basic Considerations Concerning Odor Control 202
1.1.1 Outline of Legal Regulations Governing Oder 202
1.1.2 Odor Measurement Methods 206
1.1.3 Odor at Sewerage Facilities 20"
1.2 History of the Installation of Deodorization Equipment 209
1.3 Actual Results of Operation
1.3.1 Measured Values of Odor
1.3.2 Operation and Maintenance Costs of Deodorization
Equipment 234
1A Problems of Existing Deodorization Equipment 214
2. Deodorization Experiments in the Grit Chamber 220
2.1 Purpose .............. ... 220
2.2 Plan 220
2.2.1 Location of Experiment and its Deodorization Method 220
2.2.2 Target Values of Deodorization 221
2.2.3 Outline pf Experiment Equipment 221
2.2.4 Sampling 225
2.3 Profile of Odor 226
2.3.1 State of Sewage Treatment at the Experiment Locations 226
2.3.2 State of Odor Generation at the Grit Chambers „ . . . . 226
2.4 Effects of Deodorization 229
2.4.1 Removal of Odor Unit . ... 229
2.4.2 Removal of Offensive Odor Substances 232
2.5 Summary 238
2.5.1 Original Odor ............ 238
2.5.2 Effect of Deodorization . 238
2.5.3 Operation Controlability 239
2.6 Future Problems 239
Afterword • • • • • 241
200
-------
Foreword
Improper operation or inadequate equipment at a sewage treatment plant or a
pumping station will cause offensive odor. This may lead to complaints from people
living in nearby houses.
In recent years, it has therefore become important to control offensive odor
when a new treatment facility is constructed.
Odor control is a difficult matter, because sensing the odor is different by indi-
vidual, and even if a small amount of it is sensed, and there is a fact that many
unknown points are still left about the offensive odor substances.
This paper intends to introduce the current state of odor, and its control in
Yokohama.
201
-------
1. Current State of Deodorization Equipments
1.1 Basic Considerations Concerning Odor Control
1.1.1 Outline of Legal Regulations Governing Odor
In Japan, various laws and ordinances have been enacted for the regulation of
environmental pollution with the Basic Law for Environmental Pollution Control as
the base. Table 1 shows the laws and ordinances regarding offensive odor.
According to the national law and ordinance eight kinds of offensive odor sub-
stances are designated at present (Table 2). Their regulation standards are shown in
Table 3. These values have been established by the "Six Grades Odor Intensity
Method" (Table 4), taking a 2.5 odor grade index as the lower limit and 3.5 as the
upper limit.
On the other hand, the actual regulation standards of each local government are
determined by the prefectual governor by taking local or special social conditions
into account. However, in the large cities designated by Cabinet Ordinance, these
standards are to be determined by the mayor. The regulation standards in
Yokohama are determined as shown in Table 5. Through a consolidation of these
laws and ordinances, the responsibilities of the odor generating source have been
clarified and the application of administration treatment made easier.
However, there is a problem as to whether all kinds of offensive odors which
exist as combined offensive odor can be controlled by regulating only eight kinds of
substances out of dozens of offensive odor substances. Naturally, there are limita-
tions in regulating such substances or an individual basis.
For this reason, it is better considered to detect offensive odor compositely by
human sense rather than to regulate individual offensive odor substance for the
definite evaluation of the damage caused by offensive odor and the more effective
removal.
The measuring method of test by human sense will be described later. Tokyo
metropolis has partially revised the Environmental Pollution Control Ordinance and
its Operational Regulation in 1977, and is regulating odor unit (Table 6) based upon
the "triangle bag test".
202
-------
Table 1 System of Laws Regarding Offensive Odor
1
Basic Law for
Environmental
Pollution Control
(Law No. 132, 1967)
Offensive Odor
Control Law
(Law No. 91, 1971)
(From Article 2
and Article 18 of
the Law)
Operational Ordinance
-| of Offensive Odor
Control Law
(Cabinet Order No. 207,
1972)
(From Article 4 and
Article 6 of the Law)
Operational Regula-
tion of Offensive
Odor Control Law
(Ordinance of the Prime
Minister's Office No. 39,
1972)
Article 2 Definition of Offensive Odor
Article 9 Environmental Standard
Article 10 Emission Control, etc.
On the whole, these are general descriptions and the details are covered
by the separate Operational Ordinance or Regulations in a more concrete
form.
Article 2 Definition of Offensive Odor Substances
(To be established by Cabinet Ordinance.)
Article 3 Designation of Regulation Area
(To be established by Prefectural Governor.)
Article 4 Regulation Standards
(To be established upon the Regulations of Boundary Line of
Site and Stack Outlet established by prefectural governors
based upon the Order of Prime Minister's Office.)
Article 6 Public Notice of Designation of Regulated Area
Article 18 Delegation of Administration
Administration within the authority of the prefectural gover-
nors authorized under this Law may be delegated to the
mayors of municipalities in accordance with the provisions
of the Cabinet Order
Article 1 Prescribes 8 substances as offensive odor substances
— Refer to Table 2.
Article 2 Delegation of Administration
Clause 2 Administration within the authority of the prefectural gover-
nors authorized under the Offensive Odor Control Law may
be delegated to the mayors of the designated city about the
designation of regulated area and the establishment of regula-
tion standards and so on.
Article 1 Provides the range of regulation standards for each substance
in the boundary line of site. Refer to Table 3.
Article 2 Provides the establishment of regulation standard for each
substance at the stack outlet.
Article 3 Provides that the measuring methods is decided by the Chief
of Environment Agency.
O
2
o
>•
(From Article 2 Clause 2 of the
Operational Ordinance of Offensive
Odor Control Law)
Detailed Operational Regulation
of Offensive Odor Control Law
(City Regulation No. 90, 1973)
(From Article 2 Clause 2 of the
Operational Ordinance of Offensive
Odor Control Law.)
Regulated Area and Regulation
Standard and so on based upon
the Offensive Odor Control Law
(City Notice No. 3, 1978)
Provides the administration delegated to the mayor based
upon the law.
Regulated area (Applied to the urbanized area determined
by the Construction Plan of Yokohama International
Port City.)
Regulation Standard
(1) Value of Regulation Standard in the boundary line of
site is given in the separate table. Refer to Table
5.
(2) Regulation Standard at the stack outlet to conform
with Article 2 of the Operational Regulation of
Offensive Odor Control Law.
203
-------
Table 2 8 Substances Regulated by the Operational Ordinance of Offensive Odor
Control Law
Substance
Regulated Year
Ammonia
Trimethyl amine
Hydrogen sulfide
Methyl mercaptan
Methyl sulfide
Dimethyl disulfide
Acetaldehyde
Styrene
1972 by Cabinet Order No. 207
Ditto
Ditto
Ditto
Ditto
1976 by Cabinet Order No. 242
Ditto
Ditto
Table 3 Regulation Standard Values of the Operational Regulation of Offensive
Odor Control Law
(ppm)
Substance ^^^^
Ammonia
Trimethyl amine
Hydrogen sulfide
Methyl mercaptan
Methyl sulfide
Dimethyl disulfide
Acetaldehyde
Styrene
Odor grade index
Detective
Threshold
Value
0.1
0.0001
0.0005
0.0001
0.0001
0.0003
0.002
0.03
1
0.3
0.0004
0.002
0.0003
0.0005
0.001
0.006
0.08
1.5
Recogni-
tion
Threshold
Value
0.6
0.001
0.006
0.0007
0.002
0.003
0.01
0.2
2
Regulation Standard
Values (At boundary
line of site)
1 2 5
0.005 0.02 0.07
0.02 0.06 0.2
0.002 0.004 0.01
0.01 0.04 0.2
0.009 0.03 0.1
0.05 0.1 0.5
0.4 0.8 2
2.5 3 3.5
10
0.2
0.7
0.03
0.8
0.3
1
4
4
40
3
8
0.2
20
3
10
20
5
(References)
The relationship between the grade index and the each substance is shown as follows:
y "Odor grade index
x •Concentration (ppm)
Ammonia
Trimethyl amine
Hydrogen sulfide
Methyl mercaptan
Methyl sulfide
Dimethyl disulfide
Acetaldhyde
Styrene
y - 1.6744 log x +2.3838
y - 0.9007 log x + 4.5588
y - 0.9502 log x + 4.1379
y - 1.2525 log x + 5.9895
y - 0.7843 log x + 4.0634
y - 1.0 log x + 4.523
y - 1.053 log x + 3.948
y - 1.4356 log x+3.105
204
-------
Table 4 Six Grades Odor Intensity Method
Odor grade index
Description
No odor
Barely detectable odor (Detective threshold)
Light odor perceptible of its kind (Recognition threshold)
Definite odor
Strong odor
Overpowering odor
Table 5 Regulation Standard Values at Boundary
Line of Site in Yokohama City
(ppm)
Substance
Ammonia
Trimethyl amine
Hydrogen sulfide
Methyl mercaptan
Methyl sulfide
Dimethyl disulfide
Acetaldehyde
Styrene
Concentration
1.0
0.005
0.02
0.002
0.01
0.009
0.05
0.4
Table 6 Regulation Standard Values of Odor Unit in Tokyo Metropolis
" — Location
District - — — _______^
Industrial specialized district.
Industrial district.
Semi-industrial district Commercial district
Neighborhood commercial district.
District other than above.
At stack outlet
1000
500
300
At boundary line of site
20
15
10
Note:
1.
The odor unit is defined as the air dilution multiple when the air with offensive odor is diluted
into the odorless air, and it can be determined by the triangle bag test.
When determing the value, the odor unit at the stack outlet must be taken as the averaged value
during an operation period, and the odor unit at the boundary line of site must be taken from
the instantaneous value at its peak.
This regulation must satisfy both values at the stack outlet and the boundary line of site.
205
-------
1.1.2 Odor Measurement Methods
The odor measurement methods currently used are as follows:
a. Measurement of odor substance concentration by chemical analysis.
b. Sensory test judged by smell.
In Japan, the Offensive Odor Control Law currently designates the use of the
chemical analysis method falling under category (a). However in some of the local
governments, the sensory test falling under category (b) is used.
Kinds of main odor measurement method are described as follows:
a. Chemical analysis methods
(D Gas chromato- _
graphic method
r-FID
Flame lonization
'•Detector ^
- Hydrocarbons (Styrene)
•- Aldehydes (Acetaldehyde)
Amines (Trimethylamine)
LFPD
Flame Photometoric,
Detector
Sulfur compounds
.Hydro
^sulfide
,-Methyl
Hydrogen, .Methyl ,
' ^mercaptan'
)
.Dimethyl^
disulifde
vsulfide
(2) Absorptiometric method — Ammonia
(3) Gas chromatograph mass spectrometory (GC-MS)
{Coulometric analysis
^ u u-
Gas chromatographic
method
b. Sensory test methods
-------
In the investigations and experiments which are noted in this paper, an ab-
sorptiometric method was used for ammonia, and a gas chromatograph method for
such substances as sulfur compounds, trimethylamine, acetaldehyde, and styrene.
On the other hand, a triangle bag test was used for the sensory test.
The triangle bag test is carried out as follows:
Six panels composed of personnel who will actually carry out the test are pre-
selected. They will have passed the screening test to eliminate those with an ab-
normal sense of smell. The air in the odor bag (capacity of 3 liters) is replaced two
or three times with air deodorized by activated carbon and finally, completely
filled. The sample gas (gas with offensive odor) is then injected through a syringe to
obtain the designated dilution multiple.
Two other bags (odor bags) are also fully filled with the air deodorized by
activated carbon and passed to the panels, together with the first bag filled with the
gas to be tested. The members of the panel smell these through the nose cone and
record the number of the bag which they judge to be giving off an offensive smell.
If the answer of the panel is accurate, the dilution multiple (initially approximately
three) is increased in a stepwise fashion and the test is closed at the step where
the panel's answer becomes inaccurate or impossible. The dilution multiple at
that point is recorded.
In this way, the dilution multiple at which the used odorless air brings the
offensive odor of the sample to its threshold value (minimum odor unit perceptible
by the sense of smell) is taken as the odor unit for that panel. The averaged value of
the odor unit obtained from four panels, excluding two panels which show the maxi-
mum and minimum values is taken as the odor unit in that particular case.
Calculation method of odor
X' = log ai + log a?
where
X' = Threshold value
a, = Maximum dilution multiple value at which the panel's answer
is accurate
a7 = Dilution multiple value at which the panel's answer becomes
inaccurate or impossible
Y = 10X
Y = Odor unit
X,' + X,' + X3' + X4 '
x =_
(Averaged value of X' for four panels excluding the maximum
and minimum values)
207
-------
1.1.3 Odor at Sewerage Facilities
Regarding the actual condition of odor unit at sewage treatment plants and
pumping stations, one may consult an investigation report1' which indicates that the
odor unit is 100 ~ 1,000 in grit chambers when screening, 100 ~ 10,000 in primary
sedimentation tanks, 30 - 200 at a height 30 cm above the liquid level in aeration
tanks, and 200 ~ 1,000 at a height 30 cm above the liquid level in sludge thickening
tanks.
In other instances, the occurrence of odor pollution is assumed to be as shown
in Table 7 by using O.E.R. (Odor Emission Rate) i.e. the product of emitted gas
volume and odor unit.-^ According to this table, it can be assumed that in sewerage
facilities a small scale odor pollution occur-or will occur-at the value of O.E.R.
105 ~ 10*.
1) "Investigation Report on Odor and Deodorization" Data No. 1257
Laboratory of Civil Engineering, Ministry of Construction
2) "Basic Problems of Deodorization in the Sewerage Work"
Yoshihiro Shigeta
Journal of Sewerage, Monthly
Vol. 2, No. 81979
Table 7 Occurrence Condition of Offensive Odor and OER
Odor Emission Rate
(Total OER)
[Nm3/min]
10* or below
10s -'
io7-'
10* -'"
10"-"
Occurrence Condition
of Odor Pollution
Will not occur except in
special case.
Small scale pollution
occurs at present or is a
possibility.
Small or medium scale
pollution occurs.
Large scale pollution
occurs.
Maximum source for
occurrence of pollution
and actual example is
a few.
Typical Examples of tadustry
Bakery
Brewery
Paint manufacturer or painting
plant
Printing ot ink plant
Leather plant
FRP plant
Bait or fertilizer plant
Sewage treatment plant
Foundry
Night soil treatment plant
Swinery or poultry
Petroleum chemical plant
KP plant
Cellophane plant
Slaughterhouse
Rayon plant
Large scale KP plant without
pollution control
Remarks
Maximum reaching dis-
tance of odor is 1 to
2 km and complaints
arise mostly in the range
of 500m. It is assumed
that complaints will not
arise beyond 1 km.
Maximum reaching dis-
tance of odor is 2 to
4 km and complaints for
offensive odor arise
within 1 km range.
Maximum reaching dis-
tance of odor is within
10 km and complaints for
offensive odor arise within
the range of 2 to 3 km.
Maximum reaching dis-
tance of odor extends to
some tens of kilometers,
and the range of damage
is 4 to 6 km.
Note: This table was compiled from the data produced in the past ten years regarding total OER and pollution
through offensive odor by Japan Environmental Sanitation Center.
208
-------
1.2 History of the Installation of Deodorization Equipment
The first deodorization equipment in Yokohama was installed to control the
high concentration odor which was generated by the discharge of night soil from the
night soil carrier when it was mixed with raw sludge and treated by digestion. This
equipment included an ozone deodorizer and deodorization equipment utilizing the
catalytic combustion method.
The deodorization equipment was also required for the high concentration
odor generated from the wet air oxidation plant (W.A.O.).
Since then, with the installation of covers for grit chambers and sludge thicken-
ing tanks, installation of deodorization equipments as well as ventilation equipments
has been mainly proceeded to improve working circumstances.
With the construction of sludge heat dryers and sludge incinerators, it has
become necessary to control offensive odor generated from these facilities.
On the other hand, it has become increasingly necessary to consider the
immediate environment when constructing pumping stations in dense residential
areas where there are tall buildings or where the pumping station is a combined
facility with buildings such as public halls and libraries.
In Yokohama, deodorization equipment has been adopted which is appropriate
to the working circumstances and immediate environment.
However, continuous and thorough reviews are necessary on odor control since
various kinds of odor exist in the sewage treatment plants and pumping stations.
The history of the installation of deodorization equipments in Yokohama is
shown in Table 8, and Fig. 1 a ~ m show their flows.
209
-------
Table 8 History of Installation of Oeodorization
Installation Date
May, 1962
Dec. 1967
Feb. 1971
Apr. 1971
Apr. 1972
Mar. 1975
Oct. 1976
Dec. 1977
Apr. 1978
June, 1978
Sep., 1978
Oct, 1978
July, 1979
Aug. 1979
Name of Treatment Plant or
Pumping Station
Chubu S.T.P.
Nambu S.T.P.
Hokubu 1st S.T.P.
Hokubu 1st S.T.P.
Chubu S.T.P.
Nambu S.T.P.
Midori S.T.P.
Hokubu 1st S.T.P.
Kohoku S.T.P.
Kanazawa S.T.P.
Kanagawa S.T.P.
Hodogaya P.S.
Totsuka P.S.
Hokubu 1st S.T.P.
Origin of odor
Night soil discharge
room
Night soil discharge
room
Wet air oxidation
plant (Gas-liquid
separator and
solid-liquid
separator
Wst air oxidation
plant, (oxidized
slurry pumping
room.)
Grit chamber
Sludge heat dryer
Grit chamber
Sludge thickening
tank and others
Sludge storage
tank and others
Sludge incinerator
Sludge storage
tank and others
Grit chamber
Grit chamber
Wet air oxidation
plant
Deodorization Method
(Ozone l+[Water]
[Catalytic combustion]
[Catalytic combustion]
[Carbon 1
[Ozone ]+[Water]
[Direct combustion]
[Water]
(Carbon!
(Water)
(Direct combustion]
[Water]
[Carbon]
(Water]+
(Ozone ]+( Catalyst]
[Direct combustion]
or [Catalytic combustion]
[Water] : Water scrubbing method
[Ozone] : Ozonization method
[Carbonj Activated carbon method
[Catalyst] Catalytic ozonization method
210
-------
Equipment in Yokohama
Reason for Installation
Remarks
Due to high concentration offensive odor generated
when discharging night soil from carrier to receiving
tank.
Same as above and also to utilize digestion gas
effectively
Due to high concentration offensive odor generated
from WAO equipment (Exhaust gas)
Odor unit of oxidized slurry is comparatively low.
Grit chamber was covered.
To utilize digestion gas effectively and due to high
odor unit of exhaust gas. •
To lower odor unit by some degree beside to
improve ventilation.
To make operation and maintenance easier although
original odor unit is at medium grade.
To lower odor unit by some degres.
Due to high odor unit of exhaust gas
To lower odor unit by some degree.
As residence area is very close although odor unit
is low.
As the facility is in the same building of public hall
and the installation area is narrow.
As catalyst in the installed deodonzation furnace
lost its activation in a short time.
See Fig. 1, a
Basic Law For Environmental Pollution Control
was established in August, 1967 and offensive
odor was defined as pollution.
See Fig. 1, b
See Fig. 1. c
Offensive Odor Control Law was established in
June 1971 and five substances were regulated.
See Fig. 1, d
Operational Ordinance of Offensive Odor Control
Law and Operational Regulation of the Law were
established in May 1972.
See Fig. 1, e
See Fig, 1, f
See Fig. 1, g
See Fig, 1, h
Regulated District and Regulation Standard were
established by. Yokohama City Notice No. 3 in
May 1978.
See Fig. 1, i
See Fig. l,j
See Fig. 1, k
See Fig. 1, 2& m.
211
-------
Fig. 1 Flow Sheets of Installed
Fig. 1 Flow Sheets of Installed Oeodorizaoon Equipment
a. Nambu S. T. P. - Night soil discharge room
Digestion- gas
Tentative storage Supernatant Combustion Stack
tank liquid tank furnace
Sludge pumping Sludge storage
well tank
Legend
Pump
Fan
Gas flow 30 m' min
Reaction temp. 400 'C
Catalyst Platinum
Contact time 0.13 sec
b. Hokubu 1st S. T. P. - Oxidized slurry pumping room
Oxidized slurry
pumping room
Activated carbon
column
Gas flow 50 m' min
Carbon volume 390 kg
L. V. 0.39 m/sec
Contact time 0.42 sec
c. Chubu S. T. P. - Grit chamber
Air supply duct Exhaust duct
Ch generator
(Cross section of
grit chamber)
Grit chamber
Gas flow 870 m' mm
L, G 1.3 i. m'
Water scrubber 1.3 m. sec
(L. V.)
Oi feeding rate 104 g Hr
Contact time 2.0 sec
d. Nambu S. T. P. - Sludge heat dryer
Digestion gas
—ffl
Heat exchanger
Stack Gas flow 160 m' min
_. . Combustion temp. 700 'C
— Digestion gas ^tention time 0.5 sec
Heat dryer
Cyclone
Combustion furnace
e. Midori S. T. P.-Grit chamber
Exhaust Supply
Water scrubber
Grit chamber
Gas now 1365 m' min
L,G 0.62 £ ,'m'
Water scrubber [ 4 m/sec
(L. V. )
Detention time 4.4 sec
f. Hokubu 1st S. T. P. - Sludge thickening tank
Sludge distributing tank
Activated carbon column
Sludge thickening tank
Gas flow 14.5 m' mm
Carbon volume 312 kg
L. V. 0.2 m sec
Contact time 3.0 sec
212
-------
Deodorization Equipment
g. Kohoku S. T. P. - Sludge thickening tank and others
Gas flow
L G
160 m1 mm
1.88 t m'
Dewatered cake
hopper room
Water scrubber 0.97 m sec
(L. V )
Stack Contact time 1.5 sec
discharge Supernatant „
tank liquid tank iludSe
Water scrubbber
Elutriated
Chemical
tank
sludge tank mixing tank
h. Kanazawa S. T. P. Sludge incinerator
Sludge Scrubber Electrostatic £S Heat exchager. Stack
incinerator Prec.pitator Combustion furnace
Gas flow 280 m' min
Combustion temp. 650-800 'C
Detention time 0.5 sec
Kanagawa S. T. P. -Sludge storage tank and others
Sludge storage Carbide Chemical
tank storage mixing tank
tank
Water scrubber
Gas flow 15 m' mm
I G 1.65 t. m'
Water scrubber 1 7 m-sec
(L. V )
Contact time 0.72 sec
Hodogaya P S. -Grit chamber
Motor room
Pumping room
Stack Activated
carbon
column
Gas flow 2700 m' mm
Carbon volume 25000 kg
L. V. 0.435 m-sec
Contact time 1.38 sec
Gnt chambar
k. Totsuka P. S. - Grit chamber
Stack
<3 Reaction Catalyzer
Water scrubber chamber
Gnt chamber
Gas flow 2100 m1 mm
L, G 1.1 e m'
L V I '• 0 m sec (water)
< 0. 42 m sec (catalyst)
a feeding rate 500 g/hr
Detention time I 3. 1 sec (water)
'2. 6 sec (reaction)
Contact time „ ,3 ^ (cauly3t|
Hokubu 1st S. P T -Wet air oxidation /Catalytic combustion'
V method
n
From W. A. 0.
IFfe
Stack p^eat exct,anger Combustion Catalyzer
furnace
Gas flow 42 m' mjn
Combustion temp. 409 -Q
Calayst Platinum
Contact time 0 144 sec
m. Hokubu 1st S. T P. -Wet air oxidation
n
From W A. 0.
, ^^ combustion \
\ method /
Stack Heat exchanger
Combustion
furnace
Gas flow 42 m' mm
Combustion temp 800 'C
Detention time 0 3 sec
213
-------
1.3 Actual Results of Operation
1.3.1 Measured Value of Odor
Table 9 shows the odor values measured during the operation of deodorization
equipments in Yokohama.
Table 10 shows the converted value of the each offensive odor substance into
the corresponding odor grade index.
The maximum value is shown in bold type letters.
The major component of measured substances was hydrogen sulfide in the
sewage treatment system, and methyl mercaptan in the sludge treatment system.
Fig. 2 shows the odor unit based upon the sensory test and the maximum odor
grade index. According to this figure, the odor grade index and the odor unit show a
high correlation.
Fig. 3 shows the result of deodorization effect indicated by the odor unit. It
shows that exclusive treatment by water scrubbing does not give a good effect.
1.3.2 Operation and Maintenance Costs of Deodorization Equipment
The routine operation of deodorization equipment requires little manpower.
The exchange work of activated carbon or various catalysts differ with the type of
equipment, and although they are of the same type, the expenses incurred will
differ according to the scale of the equipment used.
The comparison of direct operation and maintenance costs (power cost, water
cost, and articles of consumption) for each type, excluding labor costs and capital
costs are shown in Table 11.
In the activated carbon method, the life of activated carbon is assumed to be
six months, but its actual life may be longer than that because of the lower odor
unit when compared with the designed value. It may be that the operation and
maintenance costs fall to the same level as those for the ozonization method.
The operation cost of equipment which use fuel, such as the direct combustion
method or the catalystic combusion method, is higher than that for other methods.
The operation and maintenance cost for the equipment of catalystic combusion
method with the same capacity is 50% less than that for the direct combustion
method. When digestion gas is used as fuel i.e. Nambu Sewage Treatment Plant, the
cost will largely decrease even with the direct combustion method.
1.4 Problems of Existing Deodorization Equipment
Problems on each treatment methods of existing deodorization equipments are
as following.
a. Water scrubbing method
In the case as the Midori Sewage Treatment Plant where the odor unit of origi-
nal odor is low, offensive odor substances contained in scrubbing water may be
stripped to cause the odor unit or the amount of offensive odor substances to
be increased.
Even in the case of a sludge storage tank where the odor unit of original gas is
considerably high, as in the Kanagawa Sewage Treatment Plant, the removal
rate of offensive odor was only around 50%.
Such being the case, the deodorization effect cannot be expected through use
214
-------
Table 9 Actual Results of Operation of Deodorization Equipments
S I f
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'UOOOOl OOO01
-------
Table 10 Odor Grade Index of Each Offensive Odor substance
S.T.P. and Sampled Location
Chubu S.T.P.
Grit Chamber
Midori S.T.P.
Grit Chamber
Totsuka P.S.
Gnt Chamber
Hodojaya P.S.
Gnt Chamber
Hokubu 1st S.T.P.
Sludge Thickening
Tank
Kohoku S.t.P
Slutijr StoragB
Tint
Kanagawa S.T.P.
Sludge Storage
Tank
Kanazawa S.T.P.
Sludge
Inanerator
Before Deodorizauon
After Deodonzation
Before Deodorizatioa
After Deodorization
Before Oeodonzation
After Deodonzation
Before Deodonzation
After Deodonzation
Before Deodorization
After Deodorizaooit
Before Deodonzation
After Deodonzation
Before Dsodorization
After Deodonzation
Before Deodonzation
After Deodonzation
Odor Grade Index of Each Offensive Odor Substance
Hydrogen
Sulfide
2.5
•::;.&«;;
2.3
2.0
2.7
1.6
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1.3
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1.9
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1.2
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Methyl
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1.7
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1.7
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Dimethyl
Disulfide
1.3
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1.3
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1.6
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1.3
-------
K
x
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D O 0
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ll> 25 50 |x u' 25X10- 50X10 |x|u' 25X|0' 50x|0' |X|U'
Deodociza Origin S T P
tion meihod of odor Or P S
lOiune) Wil chdinljct Chubu
' |Walci| S T I'
IWdicrl (,nl chamber Midori
S T P
ICarbnul dm chamber tlodutjaya
C S
ICaibuu) Slud^t lluck Hukubu lil
LhinK lank S T P
IWale.l bludnc Kananawa
ilorane unk S T P
.Ljulyln , Wrf a" "X1 Mokubu U
Linin,,,,.,,,1 ^<"'" P'»"' S '!' I'
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U-Beiul
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j
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a
•^^
5x |U 5.0x |0 III' 3?
:
—
!
i^m
III' ID' 1
g. 3 Removal of Odor Unit of Each
Deodorization Equipment
Odor Unit
-------
Table 11 Operation and Maintenance Costs in Previously Installed Deodorization
Equipment
Deodorization
Method
[Water]
(Water] + [Ozone] +
[Catalyst]
(Carbon)
[Catalytic combustion]
[Direct combustion)
ditto
ditto
Origin odor
Grit chamber
ditto
ditto
Wet air oxidation plant
ditto
Sludge incinerator
Sludge heat dryer
Deodorizing Capacity
(m3/rnin)
1,365
2,100
2,700
42
42
280
160
Operation and Maintenance
Cost (¥/l,OOOmJ)
6.2
20.9
23.1
993
2,033
1,073
74.8(1,296)
Notes:
1. Labor cost and capital cost (depreciation, interest) are not included in the operation and maintenance cost.
2. It is assumed that power cost is ¥11/KWH, water cost is ¥200/mJ, and city gas cost is ¥110/m3
3. Activated carbon and catalyst are included as articles of consumption and their life times are assumed as designed
values.
Activated carbon 6 months
Platinum catalyst 2 years
Oxidized cobalt 2 years
4. In the operation and maintenance cost of Nambu sewage treatment plant, figures shown in parentheses are the
converted values into city gas.
of [water] when the odor unit is low. Even in the case of a high odor unit,
there is a limitation on the deodorization for this equipment.
In the deodorization by [water], when service water is circulated, offensive
odor substances dissolved in water will be stripped of gas and liquid at their
saturation points. Water must therefore be exchanged periodically. When
secondary treated water is used, it should be used once for all.
By using [water] as a single method, the deodorization effect cannot be
expected. It must therefore be considered as a pre-treatment method to be used
together with another method.
b. Ozonization method
When the offensive odor in a grit chamber is deodorized by using [ozone] +
[water], such major offensive odor substances as hydrogen sulfide and methyl
mercaptan can be removed. However, the odor unit after deodorization does
not decrease as expected, due to the presence of residual ozone. In cases it even
becomes higher.
Ozone threshold value was about 0.005 ppm and, after deodorization, ozone
concentration value was-about 1.00 ppm.
In order to remove offensive odor substnaces when [ozone] is used, the feeding
rate of ozone must be heightened. On the other hand, by making the ozone
density higher, activated carbon must be used to remove it, since the odor unit
becomes higher due to the residual ozone.
c. Catelytic ozonization method
By using [water] + [ozone] + [catalyst] for deodorization, the effect is diffi-
cult to judge because measurement is limited to one occasion and the odor unit
of the original gas is as low as 130. However, the odor unit after deodorization
218
-------
is below 10 and the offensive odor substances are removed sufficiently.
In this type of deodorization equipment, it is important to remove mist after
water scrubbing to protect the catalyzer and to control the flow to equalize the
load on the catalyzer.
d. Activated carbon method
In the deodorization of offensive odor in the grit chamber by using [carbon],
although the odor unit of original gas is low, the removal rate reaches over 90%
and the offensive odor of sulfide compounds is sufficiently removed. The
activated carbon is still not broken after 10 months.
As the result of deodorization of offensive odor from a sludge thickening tank,
the removal rate reaches over 90%, although the odor unit varies from 4,000 to
55,000, and the removal rate of hydrogen sulfide and methyl mercaptan also
surpasses 90%. There is a tendency for methyl sulfide, dimethyl disulfide, and
ammonia increases after deodorization. It is therefor considered that there is
a limit to the effect by using activated carbon.
Pre-treatment will be necessary for offensive odor of high concentration and
for other substances that cannot be removed off their offensive odor by
[carbon].
e. Catalytic combustion method
In the case of the wet air oxidation plant, the original gas of odor unit as high
as 520,000 is decreased to 200 or so after deodorization by using the catalytic
combustion method.
As the deodorization temperature is lower than [direct combustion], consump-
tion of fuel gas is lower to make the operation and maintenance cost cheaper.
However, [catalytic combustion] requires a stopping period of the deodoriza-
tion equipment to exchange the catalyst, and in facilities generating original gas
of high odor unit continuously, spare devices will be required.
f. Direct combustion method
By using this method, the average removal rate of original gas (odor unit close
to 10,000) is approximately 80%. Offensive odor substances are almost all
removed showing a removal rate of 80 ~ 98%.
However, it is considered that odor unit after the deodorization is not so low as
expected because NO2 increases after deodorization. The threshold value of
NOj is said to be about 0.03 ppm, and when NQ2 reaches to about 100 ppm,
the odor unit will be around 3,000.
The same thing can be said about the deodorization of exhaust gas from the
sludge heat dryer. However, the measurement of sulfide compounds is difficult
due to the effect of SOx. The concentration of holmaldehyde tends to increase
more than that of original gas.
As for the exhaust gas of W.A.O., the odor unit close to 1,000,000 in the
original gas decreases to about 200 after deodorization. However the operation
and maintenance costs are higher when compared with other equipment.
As the [direct combustion] characteristically generates NOx and it has a
notable effect on the odor unit, it is considered that countermeasures against
NOx will become important in future.
219
-------
2. Deodorization Experiments in the Grit Chamber
2.1 Purpose
Offensive odor generated from sewage treatment plants or pumping stations
differs in its odor unit and composed substances according to the kind of facility,
operation method, and scale. There have been cases where deodorization equipments
previously installed did not give good results because of inadequate attention to
design or precise onsite requirements.
The city of Yokohama decided to grapple with countermeasure against offen-
sive odor in order to select the best deodorization method. Experiments were first
carried out on the grit chambers.
The major reasons were as follows:
a. There are many pumping stations.
b. They have great influence on the surrounding areas as they are located on the
urbanized area, and covering the grit chamber, ventilation, deodorization have
become necessary.
c. A removal method for offensive odor with a large gas flow and low odor unit
such as that found in grit chambers, has not yet been established.
2.2 Plan
2.2.1 Location of Experiment and its Deodorization Method
The three grit chambers at Chubu Sewage Treatment Plant, Isogo Pumping
Station, and Totsuka 2nd Sewage Treatment Plant were selected for the experiment.
The criteria for selection were as follows:
a- The grit chamber is covered.
b. The actual flow is close to the design flow.
The following three methods were selected for the experiment.
a. [Chemical] + [Carbon]
([Chemical]: Chemical scrubbing method)
b. [Water] + [Ozone] + [Carbon]
c. [Imp. carbon] + [Carbon]
([Imp. carbon]: Acid or alkaline impregnated activated carbon)
The reason is described below and various deodorization methods are shown in
Fig. 4. The grit chambers selected for this experiment showed a low odor unit
because the odor was diluted by using forced ventilation methods.
It is widely known that the activated carbon method is most useful against low
odor unit. However, activated carbon is expensive and usually requires pre-treatment
to prolong its life by decreasing the constant load on it. Furtheremore, effective
deodorization is expected only by applying pre-treatment when low odor unit is
generated from the grit chamber, which is subject to a large odor variation with
time.
These experiments were carried out by the city in co-operation with three
manufacturers of deodorization equipment. Each manufacturer carried out the
experiment by installing all three types of equipment at one of the three locations.
The purpose of the experiments was to compare each method, and was not to com-
pare the quality of the equipment of each manufacture for a specified deodorization
method.
220
-------
2.2.2 Target Values of Deodorization
The target values of the experiment were determined as 30 or below for the
odor unit and 2 or below for the odor grade index at the stack outlet.
The reason why the target value for the odor grade index was determined as 1
is due to the necessity of confirming the deodorization effect to meet the recogni-
tion threshold value, because in Yokohama it may be necessary to install the
sewerage facilities in densely populated areas.
According to an investigation on odor for the deodorization equipment already
installed, the odor unit corresponding to 2 in the odor grade index was about 40
(Fig. 2).
On the other hand, judging from Table 7, "Occurrence Condition of Offensive
Odor and O.E.R.", it is considered that odor pollution will not occur if the value is
below 1 x 10s. The exhaust gas flow in Chubu Sewage Treatment Plant, Isogo Pum-
ing Station, and Totsuka 2nd Sewage Treatment Plant were 1600, 4000, 1700
Mm3 /min. respectively. Taking these gas flows into account, the odor unit should be
set around 30 in order to make the value of O.E.R. below 1 x 10s.
Taking the above into account, the target value of 30 was taken for the odor
unit, which is the designated dilution multiple of the triangle bag test.
2.2.3 Outline of Experiment Equipment
Fig. 5 through Fig. 7 show the flow sheets of each deodorization method,
Table 12 is explanation of each method and Table 13 through Table 15 show the
specifications of major equipment.
Fig. 4 Classification of deodorization methods
Adsorption method I [Activated carbon method
Acid or alkaline impregnated
activated carbon method
Acid or alkaline
scrubbing method
Chlorination method
Ozonization method
—I Masking method
Combustion method
Direct combustion method
Catalytic combustion method
Soil bed method, etc.
221
-------
Fig. 5 Flow Sheets of Deodorization
Method at Chubu S. T. P.
Fig. 6 Flow Sheets of Deodorization Fig. 7 Flow sheets of Deodorization
Metho at Isogo P. S. Method at Totsuka 2nd S. T. P.
>c
pll OKI'
t
__|_(Aciivair<
ctrb«4i tot
-Dll.BriiM.lor "*"«>
|l'arb«*i| i |imp.
•citvaird 4
I Ax id in*>ft
(V) hi>«
(Q) m ,
@ OKI'
a |CHcluk»l| i |CnUtn|
i >-
X
X
Aftalinr ftl
Acllvalfd c
cukMta
b |W.m| i |lliunt| i
Wau-i »ruM»r
nd «i»ix
X
:.||IM|I catbiml
Aclrvulcd c^rdiia cu
II..,.
-------
Table 12 Outline of Deodorization Methods
(Chemical)
+
(Carbon |
| Water |
+
(Ozone)
•f
(Carbon)
(Imp. carbon)
+
(Carbon)
Chubu S.T.P.
Isogo P.S.
Totsuka 2nd S.T.P.
Chemical scrubbing
o Consists of two towers of alkaline scrubbing
and water scrubbing.
o In alkaline scrubbing, NaOH and NaCIO are
used to remove acid odor substances and
chroline odor is removed by water scrubbing.
o Consists of two lowers of acid scrubbing and
alkaline scrubbing.
o In acid scrubbing H, SO, is used to remove
alkaline odor substances. In basic scrubbing
the same method as Cliubu S.T.P. is used.
o Consists of two lowers of acid scrubbing and
alkaline scrubbing.
o In acid scrubbing, same method as Isogo P.S.
is used. Only NaOH is used in alkaline scrubbing.
Activated carbon
o By using pelletized coconut activated carbon.
neutral odor substances are adsorbed.
o By using crashed coconut activated carbon,
neutral odor substances are adsorbed.
o Same as Chubu S.T.P.
Water scrubbing + ozonization
o Consists of water scrubbing tower and ozone
reaction tower.
° 1 ppm of ozone is fed before gas enters into
each tower of water scrubbing and ozone
reaction.
o An orifice plate is placed in the ozone reaction
lower to mix gas and ozone.
o Consists of only one lower which combines
water scrubbing and ozone reaction.
0 0.5 ppm of ozone is fed at the time of water
scrubbing.
0 Negative pressure by ejector is used to feed
ozone.
Activated carbon
o Pelletized coconut activated carbon is used
for adsorbing neutral odor substances and
activated carbon lo remove the residual
ozone are used.
o Crashed coconut activated carbon is used
to adsorb neutral odor substances and to
remove the residual ozone.
o Consists of water scrubbing tower and ozone
reaction tower.
o 3.9 ppm of ozone is fed into water scrubbing
lower.
o Volume of water scrubbing is such as to bring
humidity lo the stale where the ozone reaction
properly proceeds.
Catalyst
o Catalyst is used to promote the reaction of
offensive odor substances with ozone and to
remove the residual ozone.
First stage
o Activated carbon (pelletized coconut) is used
lo adsorb neutral offensive Oder substances.
o Alkaline activated carbon (pellelized coconut)
lo adsorb acid offensive odor substances is used.
o Alkaline impregnated (pelletized coconut)
activated carbon to adsorb acid offensive odor
substances is used.
Second stage
o Acid impregnated activated carbon (pellelized
coconut) is used to adsorb alkaline offensive
odor substances.
o Same as left.
o Same as left.
Third stage
o Halogen impregnated activated carbon (pelletized
coconut) is used to adsorb methyl sulfide and
dimethyl disulfide.
o Crached activated carbon is used lo adsorb
neutral offensive odor substances.
o Pelletized activated carbon is used to adsorb
neutral offensive odor substances.
to
to
-------
Table 13 Specifications of [Chemical] + [Carbon]
~~ • Location
Operation • __^
Specifications " -__
Acid
scrubbing
tower
Alkaline
scrubbing
tower
Activated
carbon
column
Gas flow (m3/min)
Acid circulation (C/min)
PH
Contact time (sec)
Linear velocity (LV) (m/sec)
Liquid by gas ratio (L/G)(2/m3 )
H, SO4 (g/Hr)
Alkali circulation (2/min)
PH
Contact time (sec)
Linear velocity (LV) (m/sec)
Liquid by gas ratio (L/G)(8/m3 )
NaOH (g/Hr)
NaCIO (g/Hr)
Gas flow (m3/min)
Linear velocity (LV) (m/sec)
Contact time (sec)
Chubu S.T.P.
4.4
(Water) 2.2
-
0.8
1.5
0.5
-
13.2
10.0
1.0
1.5
3.0
6.56
2.78
0.9
0.3
1.0
Isogo P.S.
5.0
13.0
3.0
1.4
1.18
2.6
0.66
13
8.5
1.4
1.18
2.6
3.38
0.24
5
0.25
1.2
Totsuka
2nd S.T.P.
15.0
50.0
4.0
1.0
1.0
3.3
9.0
50.0
11.0
1.0
1.0
3.3
150.28
-
15
0.4
1.4
Table 14 Specifications of [Water] + [Ozone] + [Carbon]
_____^^ Location
Operation — •
Specifications " ' — - —
Water
scrubbing
tower
Ozone
reaction
tower
Activated
carbon
column
Gas flow (m'/min)
Water (Z/min)
Contact time (sec)
Linear velocity (LV) (m/sec)
Liquid by gas ratio (L/G)(e/mJ)
Ozone feeding rate (ppm)
Linear velocity (LV) (m/sec)
Contact time (sec)
Gas flow (m3/min)
Linear velocity (LV) (m/sec)
Contact time (sec)
Chubu S.T.P.
3.2
1.6
1.1
1.1
0.5
2.0
1.1
2.8
0.9
0.3
(Carbon) 0.65
(Ozone) 0.5
Isogo P.S.
5.0
9.7
0.8
1.18
1.94
0.5
-
-
5.0
0.25
1.2
Totsuka
2nd S.T.P.
5.0
0 ~ 0.018
1.2
0.9
0 ~ 0.0036
3.9
0.42
4.76
5.0
0.42
0.2
Table 15 Specifications of [Imp. carbon] + [Carbon]
-^^^ Location
Operation ^^~~~-~-^^^
Specifications ^~~~~---^^
Gas flow (m3/min)
Linear velocity (LV) (m/sec)
Contact
time
First stage
Second stage
Third stage
Chubu S.T.P.
0.9
0.3
0.67
0.67
0.67
Isogo P.S.
5.0
0.25
1.0
1.0
1.0
Totsuka
2nd S.T.P.
1.67
0.4
1.1
1.1
1.1
224
-------
2.2.4 Sampling
a. Sampling points from where samples were collected were as shown in Fig.
8 in corresponding to deodorization for the grit chamber in operation.
b. Samplings were made while grit dredging was being carried out, and when the
offensive odor unit of original gas was assumed to be high. The sampling day
was selected as the day following two days of continuing dry weathers.
c. Frequence of sampling was determined as shown below. One of the objects of
the experiment was to investigate the breaking down condition of activated
carbon. Therefore after three months, the measurement was performed twice a
month since the life of activated carbon was assumed to be six months.
Date
Sampling
frequency
1979
Jul.
1
Aug.
1
Sep.
1
Oct.
2
Nov.
2
Dec.
2
Fig. 8 Sampling Points
chubu SIP j— J [Alkali]
?*
J ,„.
L-J [Carbonl
sogo P S.
r— > [Ac«J|
(S2)
rj [Witrr] 1- 1
©
< [Ozont] 1
r?
c
©
H(AlkaU] 1— •
<&
.... , j.p T |
ULU.L Ul I J I
J [Alkaline]
[ [carbon J
Totajka 2 rd S- T P.
?.
I fAlkahne I
"Imp. c arbon J
©
, fAcui 1 T ,
[imp. carbon J
<®
f
H[Otone) U
^
, fAcid 1 J
[imp. carbon "]
1
[Alkali] • Alkaline scrubbing method. [Acid] Acid scrubbing method.
[Alkaline carbon]- Alkaline activated carbon method.
[Acid imp. carbon)* Acid impregnated activated carbon method.
[Alkaline imp. carbon): Alkaline impregnated activated carbon method.
(Halogen imp. carbon): Halogen impregnated activated carbon method
Sampling points of offensive odor are 5. to S-
Sampling point of Si to obtain original odor gas.
Sampling points of S. S. and S. to obtain pre-treatment gas.
Sampling points of S> S> and S> to obtain gas at stack outlet.
©
_J [Carbon (-.1 >
©
J [Carbon J *•
(?)
urid Halogen ^-j^^
up. mp.
arbon, carbon J
[Carbon] j — ' »
'(So)
[Carbon) |— C .
©
(Carbon] | — I •
|
©
[Carbon] - • -L. •
-^"^
^
CatalystI i—
•S
[Carbon) — J — »
225
-------
2.3 Profile of Odor
2.3.1 State of Sewage Treatment at the Experiment Locations
The state of sewage handling at the treatment plants or pumping station which
were selected as experiment locations is shown in Table 16. Combined sewerage
systems have been adopted at all of these facilities and the major source is domestic
sewage.
In the Chubu Sewage Treatment Plant and Totsuka 2nd Sewage Treatment
Plant, the effluent from sludge treatment returns into the grit chambers.
Table 16 State of Sewage Treatment at the Experiment Locations
^^^
State of treatment
Location
^^
Design dry weather flow (mj /day)
Actual dry weather flow (m J /day)
Sludge treatment
Return waste from sludge
treatment system
Ventilation
Method
Frequency
(Times/hour)
Chubu S.T.P.
64,800
75,900
Digested sludge
dewatering
Yes
(2.9?9
Forced supply
and forced
exhaust
3.2- 10.8
Isogo P.S.
234,000
232,000
None
None
Natural supply
and forced
exhaust
12.8
Totsuka
2nd S.T.P.
49,300
37,300
Raw sludge
dewatering
Yes
(3.0%)
Forced supply
and forced
exhaust
7.6
2.3.2. State of Odor Generation at the Girt Chambers
Table 17 shows the variation range of original odor in the grit chambers. Fig. 9
shows the odor units and Table 18 shows the variation of odor grade index for each
substance.
Fig.
1000 •
800-
600-
400-
i
- 200
3
100
80
60.
9 Odor Unit of Original Gas at Grit
Chamber (at Exhaust Duct)
o—o Chubu S. T. P.
o—o Isogo P S.
x > Totsuka 2 nd S. T. P.
Aug. Sep. Oct.
(Date)
—I—
Nov.
226
-------
The average odor units at the exhaust duct of the grit chamber of each experi-
mental location were 450, 110, and 240 respectively. As the frequence of ventilation
cycles for each experimental location was 3.2, 12.8, and 7.6 times an hour, the
values of 1440, 1408, and 1824, which are obtained by multiplying these figures by
each odor unit, are assumed as the odor unit at odor source. The odor unit at the
conveyor trough of the grit dredger was 1320 (550 - 2310).
The major substances were hydrogen sulfide and methyl mercaptan as sulfur
compounds, though each element varies greatly. Methyl sulfide was also generated in
rather large quantities.
Methyl mercaptan had been detected at the Chubu Sewage Treatment Plant
until September i.e., since the start of the experiment, but it was not detected after
October. Trimethyl amine was also detected.
At the Isogo Pumping Station acetaldehyde was also detected.
Table 17 shows the values during the operation of the grit dredger, but Table
19 shows the values of odor for each substance while the grit dredger was out of use
at the Totsuka 2nd Sewage Treatment Plant. By operating the grit dredger, it can be
seen that the odor concentration varies ten times for hydrogen sulfide and around
twice for methyl mercaptan and other substances.
Table 17 State of Odor Generation at the Grit Chamber
___— """"
Odor unit
Hydrogen
sulfide
Methyl
mercaptan
Methyl
sulfide
Dimethyl
diniUide
Ammonia
Trimethyl
mine
Acetaldehyde
Styrene
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor (nde index
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor grade index
Concentration (ppm)
Odor grade index
Chubu S.T.P.
Range
230 - 730
0.008 - 0.44
2.2-3.8
N.D. -0.011
<1 - 3.5
N.D. - 0.0036
<1 - 2.1
N.D. - 0.0019
<1 - 1.8
0.11 -0.3
<1 - 1.5
0.001 -0.11
1.9 - 3.7
N.D.
<2
N.D.
<1
Average
430
0.11
2*
0.0033
2.0
0.0012
1.6
0.0008
1.3
0.19
1.2
0.023
2.6
tsogo P.S.
Range
13 -310
0.0004 - 0.3
1.0 -3.8
N.D. - 0.0073
<1 -34
N.D. - 0.004
<1 - 22
N.D. - 0.0016
<1 - 1.7
0.1 -1.9.
<1 -2.9
N.D. - 0.0001
<1 - 1.0
N.D. - 0.2
<2-3J
N.D. -0.031
<1 - 1.0
Average
110
0.073
2.5
0.0028
2.4
0.0021
1.8
0.0005
1.2
0.73
2.0
<0.0001
<1
0.064
2J
0.011
<1
Touuka 2nd S.T.P.
Range
68 -430
0.038 - 0.41
2.8-3.8 j
0.0004 - 0.023
1.7 -33
0.0012 - 0.0096
1.8- 2.5
0.0002 - 0.0023
<1 - 1.9
0.03 -0.14
<1 - 1.0
Average
210
0.18
3-3
0.0058
23
0.0034
2.0
0.001
1.4
0.095
<1
N.D. -0.0004 | 0.00013
<1 - 1.5 1.2
N.D.
<2
N.D.
<1
227
-------
Table 18 Odor Grade Index of Each Substance at the Grit Chamber
Substancex.
Chubu S.T.P.
i July
i 16
Hydrogen - -2,
sulfide ; **
Methyl ' -i,
mercaptan
Au»
•Wf
.»»
Methyl . , . , fe
sulfide v 7 ,„
Dimethyl
disulfide
Ammonia
Sep.
3.*
a»;
Oct.
15
Z2
Oct
23
,«•
Nov.
13
..*r-
<1 <1 <1
1.6 1.9 1.6 <1
1.0 , 1.3 ' 1.7
<1 " 1.2
Trimethyl E**«£
amine •-,'* *v
Acetaldehyde
Styrene
<2
<'
?'t»l
-
-
<'
|i?
-
-
Isogo P.S.
July
19
1.0
<1
<1
A^g.
-±»i,
;-**,
'.'23?)
Sep.
20
?-
OcL
16
;^2i*
Oct.
29
» 2t24
• 3UT 1.6
i'aLti'j 1.7 21*'
1.8 I 1.0 <1 <1 1-5 1.7 <1 <1
1.5 j <1
IB
<2
-
1.9
-
1 -4 t" -Jtg^
1.9
g*?.
1.5 :
<2
1.0
*?t7v
<'
<2
<»
Totsuka 2nd S.T.P.
Nov. ; July ! Aug. Sep.
8 ! 17 ' 10 7
;<*«•,
:-**.
!>$3V .v'38»"'
2;9 £3<1'
^!,v'\ i
1.7
! Oct. Oct.
12 ' 25
!.)«»
}'*»
1.7 1.8 1.8 2.0 !. £W<
.•XT
'',*?'
s?*
Nov.
9
.»-
>
1.8
1.0 : <1 1.1 1.0 | 1.4 i 1.9 1.8
2.0 <1 <1 i 1.0
<>
•V}',''5; ;;.'
<•
1.5 1.2
<•
<» <1 <1
<1 <1 1.4
<2 <2 <2 <2
<1 <,
<•
<»
<2
<«
<^
<«
Table 19 State of Odor generation at Totsuka 2nd S.T.P. when Grit Dredger is
not operated
^-^^
Hydrogen sulfide
Methyl maicaptan
Methyl sulfide
Dimethyl disulfide
Ammonia
Substance concentration (ppm)
Range
0.0014-0.038
0.0021 ~ 0.0037
0.0006 ~ 0.0043
N.D. -0.0023
0.01 -0.09
Average
0.015
0.0027
0.002
0.00077
0.04
Odor grade index
Range
1.4 - 2.8
2.6-2.9
1.5 -2.2
<1 - 1.9
<1
Average
2.1
2.7
1.8
1.3
<1
228
-------
Fig. 10 Removal of Odor Unit
at Chubu S. T. P
1000-
500-
f = yx>-
•2 =
100-1
2A Effects of Deodorization
2.4.1 Removal of Odor Unit
a. Chubu Sewage Treatment Plant
The removal of odor unit at the Chubu
Sewage Treatment Plant is shown in Fig.
10.
Target value
x x-
July.
"1
- 500-j
I 300-1
1 i 100-
July.
1000-
_ 500-
4 300
|
£ 1 100-
li *>-
|-30-|
:j
10-
Aug.
12300)
Sep. OCL Nov.
Targat value
\
Aug. Sep. OCL N'ov
\ Target value
The results show that the odor unit
at the stack outlet by each of method,
[Chemical] + [Carbon], [Water] +
[Ozone] + [Carbon], or [Imp. carbon]
+ [Carbon], was below 30 of the target
value, and the removing rate was more
than 90% in each case. It can therefore
be said that the removal is stable when
using any of these methods.
The removal of odor unit in the pre-
treatment of [Chemical] + [Carbon]
and [Imp. carbon] + [Carbon] showed
similar tendency. By using the former
method in the pre-treatment, four cases
out of six showed odor unit of below 30.
In the latter case, five cases out of six
showed values below the target values.
In the pre-treatment [Water] + [Ozone]
+ [Carbon], the odor unit showed values
either equal to or exceeding the original
odor. This is because of the effect of
residual ozone in the gas as sampling
point was performed immediately after
ozone feeding point.
July.
Aug.
Sep.
Oct.
Nov.
Odor unit of original gas and removing raw of odor unit
30
50 100 300 500 1000
Odor unit of original gas IP
Curve of target removing race
RO,..,.!;^ 100
1: Odor unit of original gas
O: Target odor unit
Ro: Target removing rate
[Chemical] - [Carbon]
' [Water] - [Ozone] - [Carbon]
[Carbon] - [Imp. cardon]
229
-------
Fig. 11 Removal of Odor Unit
at Isogo P. S.
1000-
_ 500-
J 300-
ii. 30
0 Original odor gas
• Pre-treatment outlet
x Stack outlet
Target value
ju-
10-
*2^"--~ \
-------
Fig. 12 Removal of Odor Unit
at Totsuka 2nd S. T. P.
1000-
500'
ir
73 1001
Original odor gas
Pre-treatment outlet
Stack outlet
(Cheniica
50-
3D-
10-
*-~^ / Target value
-„ /
~--»~- ^
*— ,__j< x x x x
July.
Aug.
Sep.
Oct.
_ 1000.
•! 500-
1 = 300
T 5
I 3 100'
50-
10-
X
\
x.^
\ /
y' Target val
, ^
c. Totsuka 2nd Sewage Treatment Plant
Fig. 12 shows the removal of odor unit at
the Totsuka 2nd Sewage Treatment
Plant.
(D iBy using any of three methods, similar
results for the removal of odor unit
were obtained at the stack outlet and
almost satisfied the target value. How-
ever, the first measurement (July 7)
by using [Water] + [Ozone] + [Cata-
lyst] did not satisfy the target value, due
to initial troubles.
(2) When comparing the deodorization
effect in the pre-treatment by using the
three methods, an odor unit of around
10 was shown in the pre-treatment of
[Imp. carbon] + [Carbon]. The result in
the pre-treatment of [Chemical] +
[Carbon] showed the tendency to be
intermediately effective when compared
to the other two methods.
July.
Aug.
Sep.
Oct
Nov.
1000
I =
tl;
500-
300
30
10-
July.
Aug.
Sep.
Oct.
Nov.
Odor unit of original gas and mmoving rat* of odor unit
1%)
100
_ 90-
= 80
C
' 70
I 60
"3
a 50-
30-
20-
10
0
[Imp.
ncal] T [Carbon)
,ter) +• [Ozone] i-(Catalya]
cardon] -r [Carbon]
30 50 100 300 500 1000
Odor unit of original ffas iD
231
-------
2.4.2 Removal of Offensive Odor Substances
a. Chubu Sewage Treatment Plant
Fig. 13 shows the removal of offensive odor substances at the Chubu Sewage
Treatment Plant.
Table 20 shows the removal of offensive odor substances and the value of odor
grade index. Hydrogen sulfide was almost removed in the pre-treatment in case
[Chemical] + [Carbon] or [Carbon] + [Imp. Carbon] was used. In case of
[Water] + [Ozone] f [Carbon], after treatment was necessary to reach the
total removing rate of 99% obtained by other method.
Table 20 Removal of Offensive Odor Substances and Odor Grade
Index at Chubu S.T.P- (Average value)
Hydrogen
sulfide
Methyl
tnercapttji
Methyl
nilfide
Dimethyl
dhulfide
Ammonia
Trimethyl
amine
Concentration
(pptnl
Original
odor
0.11
Odor grade index
Removing rale of
concentration (%)
Concentration
(ppml
Odor trade index
Removing rate of
concentration (%)
0.0033
2.0
Concentration j ^
Odor grade index 1.6
Removing rate of
concentration (%) i
fp°,J!nT'It'ion ! o-0008
Odor grade index : 1.3
Removing rate of
concentration^)
Concentration
(ppra)
Odor grade index
Removing rate of
concentration^)
Concentration
(ppm)
Odor grade index
Removing rate of
concentration (%)
0.19
1.2
0.025
IsS^HS
IChemicalMCarbonl
Pre-
treatment
0.0014
After-
treament
0.0011
1.4 i 1.3
98.7
0.0003
1.3
90.9
0.00087
1.5
27.5
Total
21.4 99
0.0003
1.3
0.00053
1.4
39.1
N.D. N.O.
<1
100
0.17
1.2
10.5
0.011
ims
56
90.9
55.8
<1 . j
0.15
1.1
11.8
0.0015
1.5
86.4
100
21.1
94
l*tt«HO«»»i-nCarbon |
Pre-
treatment
0.0089
2.0
91.9
0.00047
1.5
85.8
0.0015
1.7
-
After-
treatment
0.0019
1.5
78.7
Total
98.3
0.00018
1.1
61.7
94.5
0.00077
1.5
(Carbon l+IImp. carbon)
Pre-
treatment
0.0013
1.4
98.8
0.00018
1.2
94.5
0.0013
1.6
48.7 35.8
a ooo 13 0.00009 :
<1 <1
83.8
0.12
1.0
36.8
29.2 88.5
0.14
1.0
-
0.013 0.00097
1-7
48
92.5
26.4
96.1
0.00009
<1
89. 2
0.20
1.2
0.011
1.7
56
After-
treatment
0.0011
1.3
15.4
0.00007
Total
99
<1
62.8
98
0.00049
1.3
62.3
N.D.
59.2
<1
100 100
0.18
1.2
10
0.00018
1.2
98.4
S.I
99.3
It was possible to remove methyl mercaptan to a level of more than 90%. By
using [Chemical] + [Carbon], about 90% can be removed in the pre-treatment,
but it is not so effectively removed in the after-treatment.
As for the removal of methyl sulfide, the effect of pre-treatment was not
enough by using [Water] + [Ozone] + [Carbon] or [Carbon] + [Imp. carbon],
and the removing rate using [Chemical] + [Carbon] was below 30%. The total
removing rate was about 50% by using [Carbon] + [Imp. carbon] or the
[Chemical] + [Carbon] and was below that value by using [Water] + [Ozone]
+ [ Carbon].
In the case of dimethyl disulfide, since its original odor unit is low, the odor
was removed 100% by using either [Chemical] + [Carbon] or the [Carbon] +
[Imp. carbon]. The effect of [Water] + [Ozone] + [Carbon] was inferior to
these methods. However, by using [Chemical] + [Carbon], the odor was
removed 100% only in the pre-treatment.
232
-------
Fig. 13 Removal of Substances at Chubu S. T. P.
-^Carton]
ABBJ. S«PL Ctt. Nov.
NtaW
Aae. SOL Oct. No*
At* See. OH. No*
. \ A / J-
eri - [Otcwej •*• {Carbon)
Aug. ^co. On. N.
AUB. SCO- OH. NOT.
Au*. ^o. Oct. N««
233
.Carbon j -«- 'Imo- carboni
»t i \ i
i
*
\ / •/ \ I
^//
-------
As for ammonia, the removal was low by using any of these methods. This is
because its original odor is so low and close to the detective threshold value.
The removing rate of trimethyl amine was above 90% by using any of the
methods, but after-treatment was necessary as the removing rate in the pre-
treatment was below 60%.
b. Isogo Pumping Station
Fig. 14 shows the removal of offensive odor substances at the Isogo Pumping
Station. The removal of substances and the value of odor grade index are
shown in Table 21.
Although hydrogen sulfide was removed by some 98%, when [Water] +
[Ozone] + [Carbon] was used, as in the case of the Chubu Sewage Treatment
Plant, after-treatment was necessary as the removing rate in the pre-treatment
was 70%.
The total removing rate of methyl mercaptan was as high as 98 to 100%.
Table 21 Removal of Offensive Odor Substances and Odor Grade
Index at Isogo P.S. (Average Value)
Hydrogen
uiiflde
Methyl
mercaptan
Methyl
iulflde
Dimethyl
diuiUU*
Ammonia
Trimethyl
imioe
Concentration
(ppm)
Odor grade index
Removing nte of
concentration (%)
Concentration
(ppm)
Odor grade index
Removing rate of
concentration (%)
Concentration
(ppnil
Odor grade index
Removing nte of
concentration (%)
Concentration
(ppm)
Odor grade index
Removing rale of
concentration (%)
Concentration
(ppm)
Odor grade index
Removing rate of
concentration (%)
Concentration
(ppm)
Odor pade index
Removing rate of
concentration (%)
Original
odor
0.073
iPlaSlS
0.0028
IChomicilMCaibonl
Pre-
treatment
0.002
1.5
97.3
0.00032
1.4
0.0021
1.8
0.0005
1.2
0.75
10
-------
i§. 14 Removal of Substances at Isogo P. S.
(Carbon)
Aug. Seo- Oct So*.
Aue Sw- Oct. Nov.
.._Suck
(Waterl^-iOronel-t
Aug. Sep. On Nov
Au«. Sep. Oci No-
ALJR. Sep. Oct N<
1200
10DB
Au«. Sep Oct Nov
'Carbon ]-(Imo. carbon]
1200
1000
MO
235
-------
Definite results for ammonia were not obtained (Fig. 14) because the variation
of measured values of both original gases and treatment gases was so wide.
c. Totsuka 2nd Sewage Treatment Plant
Fig. 15 shows the removal of offensive odor substances at the Totsuka 2nd
Sewage Treatment Plant. The removal of substances and the value of odor
grade index are shown in Table 22.
The removal of hydrogen sulfide showed a similar tendency to that at the
Chubu Sewage Treatment Plant, and Isogo Pumping Station. Particularly the
removal in the after-treatment was high.
Table 22 Removal of Offensive Odor Substances and Odor Grade Index at Totsuka
2nd S.T.P. (Average Value)
Hydrogen
sulfide
Methyl
mercaptan
Methyl
sulflde
Dimethyl
disulfide
Ammonia
Trimethyt
amine
Original
odor
Concentration j « . fl
(pprn) : °-18
Odor grade index If ;«||RS nnni
(ppm) i °-°°l
Odor grade index : 1.4'
Removing rate of :
concentration (%)
Concentration
(ppm)
Odor grade index
Removing rate of
concentration (%)
Concentration
(ppm)
Odor grade index
Removing rate of
concentration (%)
0.095
<1
0.00015
1.2
I Chemical |+| Carbon |
Pre-
treatment
0.011
1.8
93.9
0.0043
25.9
0.0031
2.0
8.8
0.0011
1.4
0.012
<1
87.4
After-
treatment
0.00028
L.2
Total
97.5 99.8
N.D.
|W»t.rMOio«.| tfCarbonl 1
Pre-
treatment
0.064
fe&JTjiS
64.4
0.0041
-------
Fig. 15 Removal of Substances at Totsuka 2nd S. T. P.
-*• [Carteo]
[Witer] * [Drone] -*• [C*rbooi
Aw. 39. Oa. No*.
I
{Carbon ]~[lmg. carbon}
Aa«- Sep. Get. No*
237
-------
As for methyl suifide and dimethyl disulfide, the total removing rate was not so
good by using [Chemical] + [Carbon] or [Water] + [Ozone] + [Catalyst],
since the results were about 40% in the former case and about 60% in the latter.
By using [Imp. carbon] + [Carbon] however, the removing rate of more than
90% was obtained. The concentration of ammonia and trimethyl amine were
below the detective threshold values even in the original odor.
25 Summary
The observations from the deodorization experiments at the grit chambers are
as follows:
2.5.1 Original Odor
a. The original odor at the grit chamber largely varies with the operation of
mechanical equipments.
b. The generated odor unit was assumed to be around 1500.
c. Major substances of odor generated from the grit chamber were hydrogen
suifide and methyl mercaptan as sulfur compounds.
d. In some cases, the odor grade indices of methyl suifide and trimethyl amine
were above 2 at the exhaust ducts of the grit chambers but the odor grade
indices of ammonia, dimethyl disulfide, acetaldehyde, and styrene were below
2.
2.5.2 Effect of Deodorization
a. The values of odor unit were below 30, which was the target value of the
experiment, and sometimes showed a value below 10, which was the limit
value of measurement by using any particular method ([Chemical] + [Carbon],
[Water] + [Ozone] + [Carbon], or [Imp. carbon] + [Carbon]). Results seem-
ed to be good.
b. By using [Chemical] + [Carbon] or [Imp. carbon] + [Carbon], there were
some cases in which the target odor unit of 30 was obtained only by the pre-
treatment of deodorization. However, by using [Water] + [Ozone] + [Carbon],
some cases were observed when the odor unit reached a higher level than the
original odor due to the residual ozone after the pre-treatment.
c. Removal of each offensive odor substance was generally as follows:
(J) Hydrogen suifide
A removing rate higher than 98% was obtained by using any of the three
methods ([Chemical] + [Carbon], [Water] + [Ozone] + [Carbon], and
[Imp. carbon] + [Carbon]). By using either [Chemical] + [Carbon] or
[Imp. carbon] + [Carbon], 94 to 100% was removed in the pre-treatment,
but the removal was inferior to [Water] + [Ozone] + [Carbon] as the rate
was 65 - 92%, and therefore after-treatment was necessary:
(D Methyl mercaptan
A removing rate of more than 90% was obtained by using any of the three
methods. In some cases, the removing rate was below 30% in the pre-treat-
ment, but nevertheless, a rate of more than 80% was obtained.
238
-------
(D Methyl sulfide
The removing rate of methyl sulfide fluctuated between 36% and 95%
because its original concentration was close to the recognition threshold
value. The effect was unstable because neither the pre-treatment nor the
after-treatment shows any marked effect.
® Dimethyl disulfide
Although the original odor concentration was close to the detective thresh-
old value, the removing rate by using [Imp. carbon] + [Carbon], was more
than 80% in the pre-treatment and 94 to 100% in the after-treatment for the
original concentration. On the other hand, in the cases of [Chemical] +
[Carbon] and [Water] + [Ozone] + [Carbon], the removing rate showed
unstable values, i.e. between 38 to 100%.
(D Ammonia
Even "by using any of these three methods, a good removal cannot be expect-
ed for ammonia since the removing rate was very low both in the pre- and
after-treatments.
® Trimethyl amine
The removing rate of trimethyl amine was about 50% in the pre-treatment
and 94 to 99% in the after-treatment for the original concentration at the
Chubu Sewage Treatment Plant.
d. Characteristics of deodorization effect
(D Good deodorization effect was obtained for hydrogen suifide and methyl
mercaptan which are the major substances comprising offensive odor. The
effect of pre-treatment was best in [Imp. carbon] + [Carbon] followed by
the [Chemical] + [Carbon] and [Water] + [Ozone] + [Carbon] ranked last.
(2) By using sodium hypo-chrolite in [Chemical] + [Carbon], the removing rate
in the pre-treatment was much improved.
2.5.3 Operation Controlability
An automatic control is possible in each deodorization method. However, in
[Chemical] + [Carbon] and [Water] + [Ozone] + [Carbon], operation procedure
becomes complicated when compared with [Imp. carbon] + [Carbon] because
more auxiliary equipment is required.
The control of equipment when the contents of offensive odor substances vary
greatly, as in case of [Chemical] + [Carbon], a constant deodorization effect can be
obtained by adjusting the operation of the chemical pump.
It is difficult to control the ozone feeding rate in the case of [Water] +
[Ozone] + [Carbon]. No control is necessary for [Imp. carbon] + [Carbon].
2.6 Future Problems
a. Enclosure of offensive odor source
In order to carry out effectively and economically the countermeasures against
offensive odor, it is necessary to enclose and cover the location from which the
offensive odor is generated and to collect securely a small amount of high odor
unit gas. To achieve this, it is preferable to contain the main part of the grit
239
-------
dredger below the landing work platform and only treat the deodorization for
the exhaust from the limited portion of the lower part.
Machines which do not protrude so much above the landing work platform,
such as the grit dredger of bucket conveyor type, are preferable. However, in
the grit chamber of the combined sewerage system, the usual fixed bucket
conveyor type cannot be used because a large amount of grit enters in stormy
weather. The city is developing and constructing a new type of equipment in
which the sprochet wheel at the bottom can be raised or lowered (See Fig. 16).
Fig. 16 Types of Grit Dredger
Bucket Conv«v«r Typ« Grit Omdgor (ImprovxJ Typel
By using this equipment, when the lower part of the landing work platform is
deodorized, the space volume will be decreased to about one fifth, such as at
the Chubu Sewage Treatment Plant. A decrease in the capacity of deodoriza-
tion equipment can thus be obtained.
b. Operation type with cost effectiveness
The odor unit of grit chamber is different according to the operating conditions
i.e. whether the grit dredger is operating or not. In some cases when the grit
dredger is not operating, no deodorization is necessary because the odor unit is
at a low level. It is necessary to consider the operation method by which good
cost performance is obtained for deodorization equipment since the stopping
time is longer than the operating time.
c. Substances to be deodorized
The offensive odor generated from the grit chamber can be decreased by
removing the offensive odor prescribed by law. However, in order to promote
the deodorization more effectively, it is necessary to investigate the characteris-
tic odor from sewage and establish countermeasures.
d. Odor unit of exhaust
The target value of odor unit at the stack outlet was set at 30 in this experi-
ment so as the exhaust to be odorless at the boundary line of site, but it is
necessary to review to what extent the odor unit at the stack outlet is allowed
in order to meet with future environmental circumstances.
e. Odor control for the grit chamber of sanitary sewerage system
In this experiment, the grit chamber of combined sewerage system was used,
but in future it will be necessary to investigate the actual operating conditions
in a sanitary sewerage grit chamber and establish practical countermeasure for
it.
240
-------
Afterword
The city decided to investigate the actual state of existing deodorization equip-
ment in the sewage treatment plants and pumping stations, and to establish counter-
measures for offensive odor. In this connection, deodorization experiments for low
odor unit gas were first carried out at the grit chambers which had been installed at
many locations. Some observations on the results have been described above.
In Yokohama, it has been considered necessary to place covers at the primary
sedimentation tanks and also in some places where the surroundings warrant the
placing of covers at aeration tanks. Continuing systematic reviews and development
are considered necessary for offensive odor control and deodorization.
Finally, I would like express my sincere appreciation for the kind cooperation
of Messrs. Y. Hattori, Senior Technical Advisor, M. Noguchi, S. Kaminaga,
S. Kobayashi, S. Ushiyama, T. Kawabata, T. Yamada, H. Ishii, S. Yoshimi, and
other personnel concerned.
241
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
AUTOMATIC WATER QUALITY ANALYZERS
FOR
SEWERAGE SYSTEMS
May 20, 1980
Tokyo,Japan
Ken Murakami
Public Works Research Institute
Ministry of Construction
243
-------
AUTOMATIC WATER QUALITY ANALYZERS FOR SEWERAGE SYSTEMS
CONTENTS
1. Introduction 24.5
2. Overview of the Use of Automatic Water Quality Analyzers
in Japan 246
3. Automatic Analyzers for Monitoring Organic Loading
in Treated Water 248
4. Automatic Analyzers for Hazardous Substances 254
5. Conclusion 261
244
-------
1. Introduction
Automatic water quality analyzers are finding increasing use in
sewerage systems, particularly at sewage treatment plants of large
cities.
The strong interest by engineers in the quality control of inductrial
waste water discharged into public sewerage systems and in the process
control of sewage treatment plants has led to the utilization of
automatic analyzers. The energy crisis has drown the attention of
process engineers to automatic control in search of means of energy-
saving. Moreover, the amendment of the Water Pollution Control Act
in 1979 obliges all sewage treatment plants in areas to which the
loading regulation system is applicable to carry out automatic measure-
ment and recording of the concentrations of organic substances in
treated water.
In these circumstances, the development and actual use of automatic
water quality analyzers will be even further promoted.
This paper gives an overview of the use of automatic water quality
•
analyzers in sewerage systems in Japan, the outlook of automatic analy-
zers for organic loading monitoring under the loading regulation
system, and the current state of development of automatic monitoring
equipment for hazardous substances.
2. Overview of the Use of Automatic Water Quality Analyzers in Japan
697 sewerage authorities throughout Japan were surveyed by questionnaire
to grasp the current' state of use of automatic water quality analyzers.
Some of these authorities have no sewage treatment plants, and as few as
113 (16.2%) responded. On a population served basis, however, the ratio
of respondents to the total was about 80%.
Fig. 1 summarizes the results of the questionnaire survey.
Automatic water quality analyzers in use number 19 types in all.
Fig. l(a) gives the number of units of each analyzer in use.
The most popular instrument is the DO meter with 373 units is use,
245
-------
followed by pH meters, sludge density meters, MLSS meters, thermo-
meters, turbidimeters, sludge level guages, conductivity meters,
residual chlorine meter, and so forth.
Fig. l(b) shows analyzers classified by the location of measurement.
DO meters, pH meters, sludge density meters, MLSS meters, and so forth,
which lead the list of analyzers, are used chiefly for measuring
water quality in treatment processes. These instruments are employed
mostly for monitoring water quality. However.- DO meters, MLSS meters,
residual chlorine meters and sludge density meters, etc., are also
used in some cases for automatic control of treatment processes.
Application in automatic control is expected to increase in the future.
Many respondents reported that the majority of analyzers in use were
satisfactory as far as operation of the instruments was concerned.
It is rather surprising, however, that the performances of many
conductivity meters and OKP meters, which are expected to have less
problems, were reported to be unsatisfactory.
This may be because the meaning of these parameters is not clear,
resulting in poor maintenance of the instruments. Other instru-
ments with which "unsatisfactory in operation" accounted for a
considerable proportion of the total included COD meters, TOC
meters, SV meters, and pH meters.
The parameters for which many respondents considered the accuracy to
be unsatisfactory included ORP, conductivity, TOC, COD, pH, ammonia-
cal nitrogen, and MLSS.
It is noteworthy that those instruments which were reportedly poor
in operation were generally viewed as having poor accuracy. Dis-
satisfaction with accuracy was generally stronger than with operation.
246
-------
to
4^
-J
Fig. 1 Current state of Automatic Analyzers for Sewerage Systems
K) •''> ("•
Accuracy ur.it Ion (t) ru.|K>uu (t)
I'ldou of
Mouaiirumuiit (»)
Sludge Lovcl
I I Satisfactory I "1 Salt sf actory I j Miinltorlnij [ ] Raw Scwa
[;.;:;. | Fair
l^^J arttiafactory
Automatic
Control
I Mil-
! eat. isfactory
Not Evaluated
f|".iryV'l Treatment
^•''''•- J Trecosuoti
^^^^ SecoitJary
(lnkn<.»wn
(a)
N\nnlitjl u f
-------
3. Automatic Analyzers for Monitoring Organic Loading in Treated Water
The Water Pollution Control Act was amended in June 1979 to add a
loading regulation system to the effluent standards then in force
(concentration regulation) in an attempt to further restrict the load-
ings of pollutants descharged into public bodies of water.
Currently, the Seto Inland Sea, Ise Bay and Tokyo Bay are designated
as specified water bodies to which this loading regulation system is
applicable. The loading to be controlled is the COD loading, which
is stipulated as a manually analyzed COD measured in accordance with
the acid permanganate method as specified in Japanese Industrial
Standard K-0102-1974, "Testing Method of Industrial Waste Water."
Under the loading regulation system, polluters, including sewage
treatment plants, are required to limit their effluent loadings to
within respective assigned values and at the same time to measure and
record them.
Sources whose daily discharge is in excess of 400 m3 are obliged to
install a continuous flowmeter and an automatic analyzer for organic
substances that will provide data with a significant correlation to
manually analyzed COD values. The analyzers recommended for this
include the COD analyzer, VU photometer, TOC analyzer and TOD analyzer.
Installation of automatic monitoring instruments is mandatory by
June 1981 for every sewage treatment in specified areas.
In order to obtain information for selecting analyzers, problems
with the operation and maintenance of instruments now in use and the
correlation between automatic analysis and manual COD analysis were
investigated in detail.
As of December 1979, 15 COD analyzers were in use at 14 sewerage
systems. Of these, 13 units were installed for monitoring effluent
COD at sewage treatment plants. The other two were installed at pump
stations to monitor raw sewage flowing into sewage treatment plants.
The oldest instrument had been in use 5 years and 4 months, and the
newest 1 month; the average age being about 2 years. In most cases,
the cleaning and calibration of the instruments was carried out weekly.
248
-------
Table 1 lists results for the ratio of the period during which the
instruments were actually operated to the total intended period of
operation (time ratio of operation). Periods during which the
instruments were stopped for regular maintenance or because of power
failure are included in the period of actual operation. As shown in
the table, the time ratio of operation very high. About half of
instruments were actually operated for more than 90% of the intended
period. It should be noted however that instruments handling raw
sewage showed a poor time ratio of operation of 50% or lower. The
time ratio of operation was higher when the instruments were maintained
by their manufacturers than by employees of the authorities, suggest-
ing that maintenance of these instruments requires relatively high
skill.
Troubles reported in sampling systems were clogging of pumps and
sampling tubes by suspended solids, or development of slime. Analy-
zers suffered from clogging of the potassium permanganate titrator,
short life of the reference electrode, clogging of drain pipe by
deposition of silver chloride, and corrosion of parts. These facts
show that the instruments themselves need to be greatly improved.
The correlation coefficients with manufally analyzed COD were as given
in Table 2 and show a similar tender to the time ratios of opera-
tion. It is quite logical to consider that well-maintained instru-
ments produce data that closely conform with manually analyzed COD
data. The two instruments which handled raw sewage showed low
correlation coefficients; maintenance alone may not be responsible,
but account should be taken of the fact that dilution of samples
cannot be varied in automatic analyzers.
As of December 1979, 9 sewage treatment plants were using 10 TOC
analyzers for continuous monitoring of TOC. The oldest instrument
had been in operation 6 years and 9 months, and the newest 2 months;
the average being about 2 years. Of these, 7 units were used for
monitoring effluent TOC, and the other 3 for automatic TOC measurement
of raw sewage or primary settled sewage.
Some instruments had already been disqualified from automatic con-
tinuous measurement, and only five installations could offer data on
the time ratio of operation. (Table 3)
249
-------
Table 1 Ratio of the Period in which COD Analyzers were
Actually Operated to the Whole Period
Sample
Raw Sewage
Secondary
Effluent
Maintenance
by:
Sewerage
Authority
Sewerage
Authority
Manufacturer
Ratio of Actually Operated Period (%}
more than
90
70 ^ 90
Number of COD
2
5
3
1
50 ^ 70
Analyzers
Less than
50
2
2
Table 2 Correlation Coefficient between COD Data by
Manual Analysis and Automatic Analyzer
Sample
Raw Sewage
Secondary
Effluent
Maintenance
by:
Sewerage
Authority
Sewerage
Authority
Manufacture r
Correlation Coefficient
more than
0.9
0 . 7-K) . 9
0 . 5-MD . 7
Less than
0.5
Number of COD Analyzers
2
3
2
2
2
2
250
-------
Table 3 Ratio of the Period in which TOC Analyzers were
Actually Operated to the Whole Period
Sample
Raw Sewage
Secondary
Effluent
Ratio of Actually Operated Period (%)
more than
90
70 ^ 90
50 'V, 70
less than
50
Number of TOC Analyzers
1
2
2
1
1
251
-------
Except for one case, all these instruments were maintained by em-
ployees of. the sewerage authorities. Half of the instruments were
washed once a day, and many users reported that necessity of
freaquent maintenance was one of the demerits of TOC analyzers.
Troubles reported with TOC analyzers include clogging of the sampling
tube, the furnace corrosion, entrainment of moisture into the in-
frared analyzer, and large fluctuations in the flow of carrier gas.
In principle, clogging and corrosion problems are difficult to
overcome.
There was only a single case in which a TOD analyzer was employed for
automatic measurement; it had been used for 3 years and 6 months for
measurement of raw sewage with a high time ratio of operation of 85%.
The instrument was maintained daily, which is a considerable amount of
work.
Recently, the UV photometer has been attracting the attention of those
concerned because of its simple maintenance.. At present, there are
4 sewage treatment plants where UV photometers are employed for
monitoring organic substances in ..effluent. The oldest instrument
is 9 months old, and the newest is 1 month old. In almost all cases,
the time ratios of operation were nearly 100%. Troubles reported
include contamination of the flow cell due to insufficient automatic
cleaning, drift in measurements due to changes in ambient temperature,
and scattering of measurements due to large changes in turbidity.
Although the UV photometers used have the function to concurrently
measure the absorption of visible light (the spectral sensitivity
differs with manufacturers) in order to compensate the effect of
turbidity; there may be such instruments that need improvement in
correction mechanism.
It is well known that there usually a good correlation between UV
absorbance and COD, but it is also known that the degree of correla-
tion varies with the sewage and sometimes varies considerably with
time even at the same treatment plant. The eligibility of the UV
photometer as practical and effective instrument for monitoring COD
loading will depend largely on the stability of the correlation.
The UV photometer is essentially an instrument to measure dissolved
252
-------
organic matter. It is not suitable for use where suspended solids
variation is large.
Apart from the survey referred to above, the Sewerage Bureau of the
Osaka Municipal Government carried out a comparative field test of
COD analyzers of five manufacturers and UV photometers of three
manufacturers using secondary effluents for about two months to
examine the performance of these instruments as automatic monitoring
instruments under the COD loading control program. During the test,
the instruments were maintained by their respective manufacturers once
a week. To investigate the correlation with manually analyzed COD,
24 hour-round-the-clock surveys were carried out three times in
addition to regular sampling and analysis at fixed time every day
throughout the test period.
Most of the instruments operated satisfactory. The lowest time ratio
of operation of the COD analyzers was 86% and the highest was 100%.
The time ratios of operation of the UV photometers were generally
higher than those of the COD analyzers. The lowest time ratio of
operation of the UV photometers was 96%.
Troubles experienced with the COD analyzers during the test period
were blocking of the potassium permanganate titrator and clogging
of the drain pipe of the reactor vessel with deposited silver chloride.
UV absorption measurements in some cases were impaired by base line
drifts which may have been attributable to insufficient automatic
cleaning of flow cells. The correlation coefficients determined
from each round-the-clock survey were all above 0.8, but for all
the data during the test period, the overall correlation coefficients
were lower. COD analyzers and UV photometers are considered to be
better instruments than TOC or TOD analyzers as automatic monitor-
ing equipment required by the COD loading control system. However,
performances of some models of these instruments are not necessarily
satisfactory. Therefore, a standard specification for these instru-
ments is to be prepared in the near future.
253
-------
4. Automatic analyzers for hazardous substances
Although the necessity for automatic monitoring of hazardous sub-
stances is very high, actual application is far from wide spread due to
the lack of suitable automatic analyzers and for other reasons.
At present, except for indirect monitoring by the measurement of pH,
electrical conductivity, and so forth, there is only one case of
automatic monitoring of cyanide in raw sewage.
Concerned over the situation, the Ministry of Construction has
commissioned the Association of Electrical Engineers to develop auto-
matic analysis and monitoring instruments for hazardous substances.
The Association of Electrical Engineers has organized a committee of
users and manufacturers to evaluate and modify existing instruments
and to develop new devices through laboratory and field tests with
the assistance of manufacturers. Up to now, total cyanide, chromium,
cadmium, copper, lead and mercury have been studied. The development
of instruments for total cyanide has been completed, and their standard
specifications prepared. For chromium, cadmium and copper, one-year
field tests using prototype models have just been completed, and stand-
ard specifications for these instruments are being prepared. Surveys
on lead and mercury analyzers are still in the first stages.
Except for the mercury analyzer, all the instruments investigated by
the Committee use automated colorimetry or an ion selective electrode
system. Atomic absorption spectrophotometry, high-frequency plasma
spectrography, X-ray fluorometry, and other highly sophisticated
methods may be utilized, but their applications have not yet been
studied since this would require a change in'the concept of automatic
analyzers for on-site use. The work being done by the committee is
summarized below. A description of cyanide analyzers is omitted here
because they were described at the fifth and the sixth conferences.
Total chromium analyzers
Total chromium analyzers using the diphenylcarbazide method are now
available from several manufacturers. Their applicability to the
automatic monitoring of chromium in raw sewage has been tested, and
it was found that they would fail where the concentration of reducing
254
-------
substances was high or changeable over a wide range. Laboratory tests
were then conducted to look for possible improvements. It was found
that preliminary oxidation of samples by aeration under acid conditions
before adding potassium permanganate was effective in reducing and
stabilizing the consumption of potassium permanganate.
The use of Sodium hypobromide, or other oxidizing agents, which can
easily remove excessively dosed chemicals were studied, but their
application to automatic analyzers was throught difficult because of
corrosion, reagent stability, and so on.
An improved model, a batch type device with a preoxidation stage and an
automatic background compensating function was manufactured. This
was tested for six months at a treatment plant handling mainly metal
finishing wastewater and for another six months at a municipal sewage
treatment plant.
Clogging of the drain pipe from the heating vessel, crystallization of
diphenylcarbazide in the pipe during winter, and other mechanical
troubles were encountered at the initial test. The device has been
running fairly well since these troubles were overcome. Data from
manual analysis and the data from the automatic analyzer are compared
in Fig. 2.
Although the degree of agreement is not so good, the bulk of data fall
within an error range of +_ 20%. Calibration was not carried out
throughout the most part of the test period to examine full-scale
drift.
The accuracy may have been improved if the calibration had been carried
out frequently, that is, once a week or so.
At present, based on the test results, efforts are being made to pre-
pare standard specifications for total chromium analyzers.
For automatic analysis of hexa-valent chromium, there are several
instruments available on the market, which also use the diphenyl-
carbazide method. Their application to raw sewage is problematic from
the viewpoint of reliability because the automatic background correc-
tion range is often exceeded by sample blanks and because the presence
of reducing substances of high concentrations greatly interferes with
255
-------
Fig. 2 Comparison of Analytical Values of Cr by
Automatic Analyzer and Manual Analysis
NJ
01
0)
N
n)
£
o
•rH
U
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
o Colorimetry
• Atomic Absorption (Direct)
x Atomic Absorption
(Solvent Extraction)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Cr by Manual Analysis
-------
the diphenylcarbazide method.
For this reason, an analyzer based on UV absorption has been studied.
This method, however, has problems. At around 365 nm where UV absorp-
tion by hexa-valent chromium has its peak, interference from iron is
considerable. At a longer wavelength, for instance 436 nm, the iron
interference decreases, but the absorption sensitivity is lowered, and
at the same time absorption by organic substances becomes relatively
significant. It was found through laboratory and field tests that
these problems were difficult to overcome.
Therefore, UV absorption is judged impractical.
Cadmium analyzers
There is no colorimetric method suitable for automatic measurement of
cadmium. Therefore, the development of an automatic analyzer using an
ion selective electrode has been proceeded with. So far, there have
been two new developments in iron selective electrodes. One is a
ceramic electrode whose surfaces can always be maintained in good
condition by means of a rotor turned by a magnetic stirrer. This
electrode minimizes drift during continuous long-term operation.
Another is the development of a new reference electrode that responds
to organic substances just as the cadmium ion selective electrode
does with its potential not being affected by cadmium.
An automatic analyzer using these electrodes was made and tested.
Its operation is as follows. A measured sample is acidified to become
1.2N hydrochloric acid solution, and then heated to dissolve cadmium
in the solids, and filtered through a coarse media filter. As masking
agents for ions of iron, copper and lead, salicylic acid and thiourea
are added to the filtrate, then the fittrate is passed through an
anion exchange resin column to adsorb cadmium. Cadmium is desorbed
with distilled water, and the eluate is adjusted to a proper ionic
strength and measuredments made with ion selective electrodes. Two
anion exchange columns are provided, which are used alternately to
minimize contamination.
Field tests were carried out for six months at each of two municipal
sewage treatment plants. At first, troubles were caused by deterio-
ration of tubes and tube fittings by hydrochloric acid. After the tube
257
-------
materials were improved, the analyzer operated in good order. Fig. 3
compares data from manual analysis and from the automatic analyzer.
As shown, cadmium could measured to an accuracy of +0.1 pCd even when
the concentration was as low as about 0.002 mg/£.
At present, standard specifications for automatic measuring equipment
based on this system are being prepared.
Copper analyzer
The colorimetric analysis of copper (cuprous ion) based on the bathocu-
proine method is less affected by interferences and is suitable for
automation. A batch type measuring instrument with an automatic sample
blank compensating function was subjected to field tests.
Initially, a pre-treatment section was used consisting of: (1) acid
addition and heating to dissolve copper contained in solids; (2) filt-
ration through a coarse media filter; (3) pH adjustment; and (4)
addition of ascorbic acid to reduce the cupric ions.
The field tests revealed that the measurements by the automatic
analyzer always gave smaller values than manual analysis. The cause
of this was attributed to the facts that when the concentration of
sulfides in the sample was high, the copper dissolved by the added acid
formed copper sulfides again, when the pH was adjusted before color
development. For this reason, the instrument was modified to add
potassium permanganate to oxidize the sulfides before filtration.
As a result of the modification, it became necessary to add ascorbic
acid prior to filtration to prevent such troubles as clogging of the
filter and copper adsorption due to the formation of manganese dioxide.
At present, standard specifications are being prepared for copper
analyzers using this modified system.
Lead analyzers and mercury analyzers
Laboratory tests are under way to develop lead and mercury analyzers.
Field tests will be started in FY1980.
For the automatic measurement of lead, an improved ion selective
electrode has already been developed just as in the case of cadmium,
258
-------
=•*
~x
&
M
OJ
Fig. 3 Comparison of Analytical Values of Cd
by Automatic Analyzer and Manual Analysys
O'.l
NJ
Ln
o
-P
o
+J
O.01
X)
•a
o
0.01 o.l
Cd by Manual Analysis (mg/fc)
-------
and an automatic analyzer using it is under study.
Like cadmium, lead forms a negatively charge chloride ion complex, and
can therefore be separated in an anion exchanger. It is expected that
a system similar to the cadmium analyzer will be applicable to the
analysis of lead.
As regards mercury, two manufacturers have already put on sale automatic
inorganic mercury analyzers which use flameless .atomic absorption
spectrophotometry. At present, these instruments are being laboratory
tested to develop a pretreatment system allowing total mercury analysis.
260
-------
5. Conclusion
Automatic water quality measurement in the field of sewerage has two
applications; one for the control of treatment processes, and the other
for monitoring qualities of inflow sewage and effluent.
Automatic analyzers and sensors for the control of treatment processes,
particularly the activated sludge are at the stage of practical use,
except those for measuring organic loadings.
DO meters, pH meters, MLSS meters, and, sludge density meters, for
example, are widely used. They will be used increasingly in keeping
with the development and spread of automatic treatment processes con-
trol.
As regards automatic analyzers for monitoring influent sewage, very
few kinds of analyzers, such as pH meters, are currently in use.
Automatic analyzers for monitoring toxic substances in raw sewage
are being developed, and those for cyanide, total chromium, cadmium
and copper have now become available. But they must be still further
improved as they are costly and require fairly heavy maintenance.
As regards the automatic monitoring of effluent, COD analyzers and UV
photometers will find increased use since the amendment of the Water
Pollution Control Act makes it mandatory for the sewerage authorities
in specified areas to carry out automatic measurement of COD loading
in effluent.
261
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
CURRENT STATUS OF COMBINED SEWER PROBLEMS
AND
THEIR CONTROL MEASURES IN JAPAN
May 21, 1980
Tokyo, Japan
Muneto Kuribayashi
Director, Water Quality Control Division
Public Works Research Institute
Ministry of Construction
Eiichi Nakamura
Research Engineer, Sewage Works Section
Public Works Research Institute
Ministry of Construction
263
-------
CONTENTS
PAGE
1. Introduction 265
2. The score of combined sewer problems 267
2.1 General 26?
2.2 Characteristics of combined sewage 271
2.3 Mathematical models 281
3. Measures taken against combined sewer problems 291
3.1 Improvement of intercepting systems 291
3.2 Storage 294
3.3 Experimental measures 304
4. Conclusions 309
264
-------
1. Introduction
Combined sewer systems in which sanitary sewage and stormwater are
collected and disposed of through a common sewer have lower construction
costs than separate sewer systems. They are widely employed in Japan
because, in addition to being inexpensive, they are easy to install
along the narrow roads in urban areas. Another advantage of combined
sewer systems is their simplicity in that the collection and disposal
of sewage and inundation control can be achieved by a single network
of sewers.
The history of sewerage, starting with primitive drains and developing
to modern urban drainage systems terminating in treatment plants, has
seen the spontaneous growth of combined sewer systems. In old cities
in Europe and North America, and in Tokyo and Osaka in Japan, where
sewerage has a long history, combined sewer systems are prevalent.
In combined sewer systems, however, when it rains, part of the sewage
is sometimes directly discharged into receiving waters without
treatment. In response to public demand for a higher-quality water
environment, it has recently been recognized that control of combined
sewer overflows is of increasing importance.
When the inflow to a sewage treatment plant is increased by stormwater,
part of the sewage is discharged after only sedimentation and
disinfection. Some experts warn that this kind of primary effluent
is a source of water pollution that cannot be reglected.
In Japan, with the exception of the metropolises, most local cities
lag far behind in terms of the coverage of sewerage. National
policies for sewage works have yet to place major emphasis on the
extension of sewers and new installation and expansion of sewage
treatment plants.
There are few, if any, cities that can afford to study the problems
inherent in the combined sewer system, and provide measures against
them.
Unlike sewage treatment plants which are local in scale, the sewer
system is larger in size running under roads in complicated meshes.
265
-------
Therefore, the improvement of sewer system involves many problems both
technically and financially. And, this has delayed the solution of
combined sewer problems.
A recent survey has warned that not only the overflows from the
combined sewer, but stormwater runoff from highly developed areas is
fairly contaminated. The problem here lies not only in pollution due
to combined sewer overflows, but shows a more complex spectrum involved
in all discharge from urban drainage systems and their relations with
the quality of receiving waters.
This paper deals with combined sewer problems that have been brought
to the fore in Japan, and the measures that have been, and will be,
taken.
266
-------
2. The score of combined sewer problems
2.1 General
As of the end of fiscal 1979, municipalities with public sewage works
numbered 579 in Japan. Most of them constructed their sewage works
in the past 10 years or so. Municipalities which are experiencing
serious combined sewer problems are in the minority. Water pollution
problems in Japan today are still largely accounted for by dry weather
sanitary sewage in the districts without sewerage.
Combined sewer problems of sewage collection and disposal have been
subject to wide and careful attention by sanitary experts.
Combined sewer problems are, for instance, always on the top of the
list of topics to be discussed at meetings of the Workshop on Sanitary
Works, a sanitary engineer forum. These discussions may be summarized
into the following three points.
(1) There are cas^s of dry weather overflows from diversion chambers
where the volume of sewage generated per area has been increased
by the increase in per capita water consumption, by increase in
population in areas with sewers, or by urban renewal.
(2) Where wet weather effluent from sewage treatment plants, diversion
chambers and pump stations is a major pollutant source for
receiving waters, the quality of receiving waters can no longer
be improved substantially as long as existing sewerage systems
remain unchanged.
(3) The separation of sewers involves both technical and financial
difficulties.
Where the stormwater runoff itself is contaminated, the separation
of sewers does not offer any viable solution to the problem.
Although these discussions have not yet been revolved, almost every
city has come to employ a separate sewer system for its new instal-
lations based on the situation in Europe and United States and of the
role played by sewerage in the conservation of the quality of receiving
waters.
267
-------
This is not because they regard the separate sewer system as the
solution to wet weather problems, but because the separate sewer
system is considered to be more economical than the combined sewer
system where the existing drainage channels can be turned to good
account in the drainage of stormwater.
In this case, water pollution by dry weather sewage can be solved more
rapidly by the separate system than by the combined sewer system.
According to a survey conducted in fiscal 1973, about 2,080 km2 area
(27% of the sewerage projected area of 7,732 km2) had sewer con-
struction completed, which included 1,546 km2 of combined sewer areas
and 540 km^ of separate sewer areas. At the time when the survey was
conducted, 76% of the area with sewers was accounted for by combined
sewer systems, but by the end of the sewerage construction project,
that percentage will be reduced to 36% (see Fig. la).
Of the population projected of 70.3 million to be served by sewerage,
about 38 million, or 54%, had already been covered with sewers, and
69% of this percentage live in areas with combined sewer systems. In
the final stage of the project, the population with combined sewer
systems will be 53% of the projected population (see Fig. Ib),
exceeding the population covered by the separate sewer systems.
Notwithstanding on-going projects to promote separate sewer systems,
the problems of combined sewer systems will remain undiminished.
The overflows from the combined sewer system are under the control of
uniform effluent standards pursuant to the Water Pollution Control Act
which governs general discharges. (Table 1)
Some municipalities have regulations that impose tighter control over
effluents than the Government-set uniform effluent standards.
The improvement of combined sewer systems to meet such tightened
standards is not only unrealistic, but is also unlikely to improve
the water quality of the receiving waters. .
At present, the Japan Sewage Works Association has an in-house
committee to study how and to what extent the combined sewer system
should be improved.
268
-------
Fig. la Sewerage Projected Area
Fig. Ib Sewerage Projected Population
TOTAL
POPULATION
269
-------
Table 1. Dili form Effluent Standards
(1) Items for the protection of the human health
Item
Standard
value
Cyanide
Maximum
1 ppm
Alkyl mercury
Not detected
Organic
phosphorous
Maximum
1 ppm
Cadmium
Maximum
0.1 ppm
Lead
Maximum
1 ppm
Chromium
(hexavalent)
Maximum
0.5 ppm
Arsenic
Maximum
0.5 ppm
Total Mercury
Not detected
(2) Items for the conservation of the living environment (General Items)
Item
Standard
value
PH
Rivers &
lakes
5.8-8.6
Sea
5-9
BOD
Dally average
120 ppm
Maximum
160 ppm
COD (Mn)
Dally average
120 ppm
Maximum
160 ppm
S3
Dally average
150 ppm
Maximum
200 ppm
No. of collform
groups
Dally average
3,000 per cm3
NJ
^J
O
Remarks: 1. The above effluent standards Is to be applied to (water emitted from) plants or factories with
the normal daily discharge of more than 50 cubic meters.
2. The COD standards are not to be applied to water discharged directly into rivers from plants or
factories, and the BOD standards are not to be applied to water discharged directly to lakes or
sea from plants or factories.
3. The pll standards are not to be applied to (water discharged from) the sulphur mining industry
(including the mining of iron sulfide ores co-existing with sulphur).
(3) Items for the conservation of the living environment (Special items)
Item
Standard
value
Oil
(substances of extract
N-hexane)
Petroleum &
related oils
Maximum
5 ppm
grease
Maximum
30 ppm
Phenols
Maximum
5 ppm
Copper
Maximum
3 ppm
Zinc
Maximum
5 ppm
Iron
(soluable)
Maximum
10 ppm
Manganese
Maximum
10 ppm
Chromium
Maximum
2 ppm
Flourine
Maximum
15 ppm
Remarks: 1. The above effluent standards are to be applied to (water emitted from) plants or factories with
the normal daily discharge of more than 50 cubic meters.
2. Tlie Iron (soluable) standards are not to be applied to (water emitted from) the sulphur mining
industry (Including the mining of iron sulfide ores coexisting with sulphur).
-------
!.2 Characteristics of combined sewage
How much pollutant load is discharged from the combined sewerage
during wet weather? What ratio does it contribute to the total load
as against secondary effluents from sewage treatment plants? These
are the first questions to be asked in clearing up the problems of
combined sewer systems. In line with these questions, 16 experimental
districts were assigned throughout Japan, as shown in Fig. 2, for the
purpose of investigating the quantity and quality of dry-weather and
wet-weather combined sewage. A survey was conducted for 3 years from
fiscal 1975 to fiscal 1977. Of the 16 experimental districts, 4 had
separate sewer systems, for which the quantity and quality of storm-
water runoff was examined.
The characteristics of each experimental district are summarized in
Tables 2a and 2b.
It is often said that urbanization has inflicted serious effects on
the hydrological cycle in areas in which urbanization has taken place.
The problem of urban drainage systems in wet-weather conditions may
be regarded as one problem of the hydrological cycle in urbanized
areas.
Fig. 3 shows the relationship between the peak dry-weather flow and
population density in the drainage area. Urban renewal, or an
acromegalic state, as represented by the mushrooming of high-rise
buildings replacing low-rise houses is often seen in built-up areas.
This counts a snapback in daytime population, increasing the dry
weather peak flow.
In Japan, side weirs are widely used as a diversion facility, and
the dry-weather overflow is in many cases caused not by the malfunction
of diversion facilities, but as a result of increase in peak dry-
weather flow that exceeds the capacity of interceptors.
Figs. 4a, 4b and 4c show the relationships between total railfall
and total stormwater runoff in three areas having different ratios
of impervious area to total area. In the figures, the slopes of the
solid lines are set eaual to the ratio of imoervious area. Rainfall
271
-------
Fig. 2 Map of The Experimental Districts
(Kitakyushu),
(Fukuoka)
HONSHU/ (Yokohama)
E
(Kawasaki)
(Hiroshima)/ J
0
P
272
-------
Table 2. & Character 1m leu of Ki[,e i l»«ril/il iiluirlclM (Combined Scuer Syeten)
d I a t r I c: t
-J
u
(a av 1 1 y
f ltl"U
la uv 1 1 y
1 low
1- uia|iJiig
Puai[iliig
( < i a v 1 t y
1 l<,u
'It uw 1 ty
flow
IJt aluag.e
area
(lu«)
41. 11
542
269.5
'J5.n
i'l.Wi
6H.1/
•jy.5
I4B.49
Ai.50
21i.lA
'W.6
I/. 61
Popult
Uay t lue
6,655
165,019
5H.690
12.298
3.579
18.26B
1 2 , 800
i?.iao
41.200
27.0OO
3.971
9.700
(day)
I/, 000
(nlElit)
It lull
Reu Ideil L
4,016
I55.0'9l
61,167
9.001
4.270
8.15H
1.7BO
25.2BO
604
11.727
1.861
1.09B
Sever
d lan^elKC
( — )
lOfrv.
900
6000x4125
4000x1600
1650x1650
25flrv.
1200
210"-
1950*1950
250-*-
It 50
250-^
1000*1910
100-'-
2000*1150
2SO".
2200x2200
200-1-
1200x1680
2}Qr>-
1160x1060
Max.
f low rule
la dry-
uc-utlu-t
(•^/S)
O-O1)?
2.11
1.57
0.10
0.052
0.282
0.189
0.80'J
0.1H5
0.261
0.028
0.247
Larul uu
-------
Table 2.b Characteristics of Experimental Districs (Separate Sewer System)
Drain-
age
district
H
N
0
P
Drain-
age
system
Gravity
flow
Gravity
flow
Gravity
flow
Gravity
flow
Drain-
age
area
(ha)
17.17
26.75
13.69
106.4
Population
Day-
time
9,300
2,420
1,499
Resi-
dent
2,695
3,227
988
24,568
Sewer
diameter
(mm)
1200x
1030^.
30x70
2500x
1800
SOOx
400
6500x
2100
Land use
Residen-
tial
(ha) (Z)
8.55 49.8
26.75 100
6.72 49.1
Com-
mercial
(ha) (Z)
8.02 46.7
0 0
6.97 50.9
In-
dustrial
(ha) (Z)
0.60 3.5
0 0
0 0
Read
area
(ha) (Z)
5.72 33.3
4.99 18.7
1.69 12.3
7.0 6.6
Imper-
vious
area
(ha) (Z)
12.10 70.5
12.14 45.4
7.30 53.3
85.0 79.9
Fig. 3 Population Density Vs. Peak Dwf Rate
Population density (capita/ha)
274
-------
is held back by infiltration, depression storage, interception, and
so on.
As regards urban areas, rainfall is considered to be mostly held
back in pervious areas where infiltration and depression storage are
prevalent. The following formula is applicable to urban areas.
Total runoff
- Ratio of impervious area
Total rainfall
This formula shows that an increase in the ratio of impervious area
tends to increase the total stormwater runoff and hence to increase
the wet-weather overflow. Thus, urbanization exacerbates this problem.
Tables 3 and 4 summarize water quality data obtained from the experi-
mental districts with both combined and separate sewer systems.
To put it simply in terms of average water quality, the overflows
from the combined sewer system can be blamed for its failure to
meet effluent standards only in suspended solids. The storm runoff
from districts with separate sewer systems is not better in terms of
suspended solids than the wet-weather overflows from combined sewer
systems. Raw sewage, wet-weather combined sewage and storm runoff,
are qualitatively compared in Fig. 5.
The flow of raw sewage, stormwater and their loads (8005) in a typical
combined sewer system in Japan are schematically represented in Fig. 6.
The existing combined sewer system reduces a generated BOD loading
of 4,890 kg/ha/yr ( = 4,700 kg/ha/yr + 190 kg/ha/yr) to 1,440
kg/ha/yr; namely, the overall system has a BOD removal efficiency
of about 70%.
Table 5 shows the mean values of the concentrations of heavy metals.
The heavy metal concentrations in stormwater runoff differ greatly
from district to district. In district M, instantaneous concentrations
were observed to be 1.80 mg/£ for zinc, 1.93 mg/J, for copper and
0.74 mg/J, for lead, showing that stormwater runoff is not so
innocuous. In residential areas, the stormwater runoff has
comparatively low BOD, COD and heavy metals concentrations, but depend-
ing on localities high concentrations of ABS and n-hexane extracts.
275
-------
Fig. 4a
50
D district (A =3 5.1 ha,
Ratio of impervious area = 0.458)
40
a
o
30
20
10
10 20 30 40 50 60
Total rainfall (mm)
70
Fig. 4b
60
50
« 40
o
30
20
10
.0
B district (A =542 ha, Ratio of impervious
area = 0. 532)
o
o
10 20 30 40 50 60 70 80 90
Total rainfell (mm)
276
-------
Fig. 4c
70 r
60
.50
40
F district (A =68. 4 ha,
Ratio of Impervious area = 0. 780)
10 20 30 40 50 60 70
Total rainfall (mm)
80 90
300r
200
100
20
10
0
200
100
Fig. 5 Typical Quality of Raw Sewage, Combined
Sewage and Storm Runoff
SS(mgA)
KN(mgA)
Eg Raw Sewage
O Storm Runoff
200
TP(mg/i) ir.a Coliform G. (N/mi)
10°
Combined Sewage
277
-------
Table 3. Dry Vs. Wet Weather Quality of Combined Sewage
A
B
C
D
E
F
G
H
I
J
K
L
Dry Weather Quality
(mg/i)
BODs
21*560
138
23*151
103
12*229
127
35*281
110
16*374
123
39*180
131
8*205
127
66*691
303
11*180
95
14*203
108
6*414
111
21*297
144
COD(Mn)
6*158
42
/
10*136
53
24*191
49
15*293
116
12*67
52
9*63
55
35*359
211
16*76
40
17*148
65
8*129
35
14*150
53
SS
14*163
70
12*157
83
12*205
88
19*258
76
8*844
151
26*184
74
13*125
89
22*194
119
19*202
84
12*187
80
7*328
67
18*540
113
Wet Weather Quality
(mg/i)
BODs
10*465
83
11*613
82
7*347
76
13*182
59
13*503
46
7*247
39
34*288
81
52*522
194
3*260
68
10*314
59
26*840
109
10*1791
114
COD (Ma)
18*146
49
/
9*304
55
24*126
31
9*268
51
4*46
22
21*153
50
19*265
137
6*81
43
13*167
44
13*280
55
8*198
59
SS
44*604
197
55*716
160
10*1250
134
49*240
117
4*1090
249
8*565
80
52*550
224
14*668
192
13*368
148
25*294
101
21*2130
324
20*2850
202
Number of
Rainfalls
9
11
9
10
13
12
10
9
10
10
9
10
*upper:range of quality, lower:weighed mean quality
278
-------
Table 4. Quality of Storm Water Runoff
M
N
0
P
Quality (mg/i)
BOD
1.7^980
40.9
1.2^88.6
10.5
3.1-W0.4
28.8
3 . 1XL4 . 3
9.3
COD(Mn)
2.9M.90
27.2
5.1V2.8
24.2
0.4M.3.8
4.9
SS
9.4^2561
267.3
3.2^490
309.9
8.3^279
107.8
18.0^476
149 = 9
TP
0.05^2.96
0.45
0.003^1.44
0.24
0.06^1.67
0.24
KN
1.40^71.50
19.28
0.61^5.73
2.70
(TN)
O.OM-1.2
0.63
Number of
EUinfalls
10
10
4
7
*upper:range of quality, lower:weighed mean quality
Table 5. Concentration of Heavy Metals
(mg/1)
Zn
Raw Sewage
Wee Weather
Combined
Sewage
Stona Water
Runoff
0.020
^2.230
(0.475)
(0.415)
(0.390)
. Cu
0.013
•UD.8AA
(0.041)
(0.080)
(0.087)
Pb
0.000
1-0.040
(0.005)
(0.050)
(0.093)
Cd
0.000
V1.002
(0.000)
(0.001)
(0.001)
Hi
0.000
^-0.002
(0.000)
(0.012)
(0.004)
Cr
0.000
M3.001
(0.000)
(0.013)
(0.000)
( ): axexage concentration, figures of wet weather
combined sewage are the average of 12 districts, figures of
stora water runoff are the average of 2 districts
279
-------
Fig. 6 Typical Combined Sewerage in Japan
3780mm/yr
L „
4700ko/ha/yr
SECR
OVERFLOW
upper:sewage
volume in nrri/yrf
lower:BOD load
in kg/ha/yr
960mm/yr
190kg/ha/yr
59Qn/yr
BY-PASS ING 40rnm/yr
30kg/ha/yrs]
170kg/ha/yr
jSTOnm/yr
770ko/ha/yr
280
-------
2.3 Mathematical models
As one way of attacking combined sewer problems, simulations by mathe-
matical models are used with which we can assess the effect of presumed
solution on the combined sewer system.
The Public Works Research Institute of Ministry of Construction has
developed three mathematical models of different levels to handle
several situations.
The loading rate of wet-weather combined sewage is closely related
to flow rate. (Figs. 7a, 7b)
In the case of SS loading, the correlation with flow rate is
particularly significant.
For BOD, COD and SS, the following formulas have been established.
L = Cl-(Q - Qc) (for BOD, COD) ... (1)
L = C2-Q(Q - Qc) (for SS) ... (2)
Where, L is the loading rate (g/sec.); Q is the flow rate (m3/sec.),-
Qc is the critical flow rate, (mVsec.); and C is a constant.
Qc is not the critical shear stress in a strict sense; in Figs. 6,
7a, 7b it is found that its value approaches Qc (which is larger
than zero) asymptotically.
Thus, it is logical to use the critical flow rate Qc in Formulas
(1) and (2) .
According to formulas (1) and (2), the loading rate is a single-valued
function of flow rate; but actually, it is not so simple. The flow
rate versus loadings is shown in Figs 8a, 8b, 8c, 9a, 9b and 9c, in
which plots are numbered in the order of sampling.
It is found that BOD and SS load plots form a clockwise loop. It
is reasoned that this looping is caused because wet weather loading
is dependent at once on the flow rate and residual loads and also
because the residual loads will lower toward the end of a rainfall
period.
281
-------
Fig. 7a Relation Between Flow Rate and BOD Loading
4000
B district
as as i
4 6 8 10
Flow rate Q (m3/sec)
20
40
282
-------
Fig. 7b Relation Between Flow Rate and COD Loading
20000
: 1977
A : 1976
D : 1975
T : 1974
a : 1973
40 60 80
Flow rate Q (xn«Vsec)
283
-------
SS BOD
(mg/1)
13
400-
300-
200
100
130
11
2001(-
9
8
7
6
•1005
4
3
Q(raVs)
Fig. 8a
flow rate (nvVsec)
BOD (mg/i)
— SS (mg/i)
V
12 14 16 18 20 22 0
10
12 14
16
18
time
Fig. 8c
Fig. 8b
2000
4000
2000
as i
4 6 8 10 20
Q (m3/3)
0.60.81
2 4 6 8 10
Q (m-Vs)
284
-------
SS BOD
(mgAKmg/i)
400
300-
100.
Q(mVs)
10020-
IS
Fig. 9a
BOD (mg/l)
SS (mg/l)
flow rate (ra'/s)
2330 0 100 200 300 400 500 600
time
Fig. 9b Fi9- 9c
10000
700
6000
'4000
2000
1000
600
400
200
100
,]
'/**•
J
/I
Oil
/ o*
V OJ7
i\
0/1
/
f
JflC
s}
/
<=k3
f
"/
*
/-
/-on
K
3
y>
5 10 15 20 30
Q(ra3/s)
285
6 S 10 20 30
Q(m-Vg)
-------
BOD and COD loadings are largely influenced by the residual loads,
while the effect of residual loads on SS loading is smaller.
Taking into account the effect of residual loads, the equations of
motion for loading rate are as follows:
L = Ci-P2(Q - Qc) (for BOD and COD) ... (3)
L = C2-P-Q(Cj - Qc) (for suspended solids) ... (4)
Where, P is the residual load (g) on the sewer bottom.
Fig. 10 compares loads for wet-weather combined sewerage and loads
for dry-weather combined sewerage, both being observed for about
eight consecutive days.
The hatched sections denote wet weather periods.
Generally speaking, wet-weather loadings are higher than dry-weather
loadings, but dry-weather loadings just after the rain are lower
than ordinary dry-weather loadings. This is because just after a
rainfall, part of the load in raw sewage is trapped or precipitates
in the bottom of the sewer.
During wet weather when the velocity is high, these accumulated loads
are carried away increasing wet-weather loadings above dry-weather
loadings.
For BOD, COD and SS, positive loads are defined as the sum of wet-
weather loadings which exceed dry-weather loadings. Negative loads
are defined as the sum of loading differences between dry-weather
loadings just after rain and the ordinary dry-weather loadings.
Positive loads and negative loads are compared below.
BOD: Positive + = Negative -
COD: Positive + > Negative -
SS : Positive + » Negative -
In the case of BOD, positive loads are equal to sewage loads deposited
in the sewer during dry weather.
286
-------
Fig. 10 Relation Between Positive Loads and
Negative Loads
g/s
150
100
50
BOD
L.02
y
+1.84
+.57
DWF=9LO (g/s)
: Xi
£+ =4.49 ton
Z& =4.94 ton
+.44
g/s
ICO
50
COD
+3.15
- +.31
+.57
A
DWF=60.8(g/s)
-1.62
-0.40
1+ = 4.41 ton
Z- = 3. 03 ton
-1.01
g/s
150
100
50-
+4.36
,(307)
S3
+1.00
71
+1.55
X
+26.14
f
DWF=65.0(g/s)
+13.07 +1 02
Z+ = 47.14 ton
1- = 3.93 ton
X^04/ /
i/f, X. ,Xi
-0.88
JUL/5 JUL/6 JUL/7 JUL/8 JUL/9 JULAO JULAl JULA2
287
-------
In the case of COD and SS, positive loads are larger than negative
loads. That is, part of the positive loads is contributed by inflow
loads from roads surfaces, roofs and sediments in catch basins,
together with stormwater.
Accordingly, the equations of motion for COD and SS can be rewritten
as follows to take account of external loadings.
L = C1'P2(Q - Qc) + (1/3.6)'ki'S-r (for COD) ... (5)
L = C2-P-Q(Q - Qc) + (1/3.6)-k2-S-r (for SS) ... (6)
Where, k is a constant; S is the amount of residual loads on road
surfaces, in gutters, catchment basins, etc.; and r is the rainfall
intensity (mm/hr.).
The formulas for projecting BOD, COD and SS loading rates are
summarized in Table 6, together with continuity equations.
If a stormwater runoff model (e.g., modified RRL method) is combined
with the above loads forecasting formulas, we can evaluate wet weather
loads when rainfall data are given. Figs, lla, lib and lie demonstrate
that the observed values and the calculated values are in good
agreement.
288
-------
Table 6. Equations of motion and continuity for predicting
wet weather combined sewer loadings
BOD L =• Ci-P2- (Q - Qc)
j p
— = dwf loading - L
COD L = C2-P2. (Q - Qc) + y^-k.-S-r
- dwf loading - C2-P2.(Q - Qc)
SS_ L - C3.P-Q.(Q - Qc) + -jk2.S-r
|| - dwf loading - C3-P-Q.(Q - Qc)
If ' a> ~ 376ka's-r
L » loading rate (g/sec)
C - coefficient
P » residual load in the sewer line(g)
Q - flow rate (mVsec)
Qc =• critical flow rate (mVsec)
k » coefficient (I/mm)
S - residual load on road surface, roof-top, cat'ch basin, gutter,
and so on (kg)
r » rainfall intensity (mm/hr)
a - loading supply rate (g/sec)
k(COD) - 0.10 (rough surface street)
-- 0.15 (smooth surface street) (I/mm)
k(SS) - 0.20 (rough surface street)
-- 0.30 (smooth surface street) (I/mm)
a (COD) - 1.0 (inactive area)
-- 5.0 (active area) (kg/ha/day)
a(SS) - 10 (inactive area)
-- 50 (active area) (kg/ha/day)
289
-------
06S
observed c
(6/5)
6.96
15.67
6.21
6.64
5.57
12.67
6.30
14.73
14.98
38.69
14.06
13.76
15.66
40.99
38.80
63.63
52.84
101.92
90.27
110.36
62.57
60.30
29.61
35.24
16.61
14.10
7.18
alcu-
l«t«d t
f (• /« t
fU/d) "
14.25
12.79
7.01
2. 26
3.66
12.64
10.65
16.77
20.37
19.99
19.33
21.26
26.41
32.50
32.57
32. «4
36.71
50.14
60.83
61,36
56.99
54.53
41.53
30.47
23.49
17.52
14.50
S
o'c --•!-•
CO
0
CO
CO
0
oc
oc
0 C
C 0
0 C
0 C
0 C
C 0
oc
C 0
C 0
c
c
c
CO
c
0 C
C 0
0 C
oc
0 C
**
o
o
*a
n *•
S 10
oo •>
« i" c
• *-*•• H*
S2 » cr
3£ C
• • o •
OjfT 9
• •
b
D
6
0
0
obMrvcd
(0/SI
18.144
21.900
12.032
10.700
9.216
10.961
11.392
13.104
16.401
27.170
30.940
24.600
16.200
17.520
11.746
10.425
13.360
13.832
16.531
16.627
12.922
17.459
18.467
19.062
27.161
32.032
24.414
17.610
13.632
8.517
8.056
6.664
10.961
13.832
11.680
10.472
calcu-
*f»fc
23.840
16.524
13.639
10.402
6.742
11.449
13.642
22.217
26.6*2
31.204
29.131
23.624
20.589
15.534
13.700
14.964
19.449
21.866
26.730
26.697
21.967
26.039
41.716
46.502
44.396
43.920
35.589
29.669
21.561
15.772
13.653
13.642
12.259
14.126
13.50S
10.355
S
"
0 C
CO
oc
0
0 "J
0... H-
gin
oc gr
0 C B
o e oo SH-
o c ss I M
o It rtt
0 S ° 2
oc 3£ r
co £5 "
oc a»
oc &
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
0 C
e
0
oc
0
obMrvad
ealeu-
(6/5)
6.60
7.64
13.90
11.63
9.70
6.72
21.30
61.20
131.82
169.05
142.98
65.52
49.54
34.12
21.84
19.46
22.42
10.19
9.09
9.54
6.33
6.35
4.77
4.59
4.23
3.50
6.13
4.66
3.17
3.57
(S/I)
1 U/d J
2.30
3.57
3.51)
3.99
4.50
3.91
16.94
66.02
144.69
106.19
164.79
134.41
90.59
71.86
40.21
31.45
24.59
15.69
10.40
6.45
7.08
5.43
4.23
3.93
3.59
3.56
3.56
2.53
1.18
2.22 1
ico • ' '
1C 0
1C 0
1C 0
1 CO
1C 0
CO
C 0
o
0 C
0 C
0 C
0 C
0
oc
oc
0
0
0
0
CO
CO
0
CO
CO
0
0
1 ' *
0 c
Of
w
0 • C
c
•fl
^--
US
n .
g
. ^
00 5 H*
is E
» H* m
si s.
< f o
• % g
&»» B
a
^
-------
3. Measures taken against combined sewer problems
3.1 Improvement of intercepting systems
The improvement of intercepting systems is one of the commonest
approaches to the solution of combined sewer overflow problems.
Usually, interceptors are improved in two ways; in one, the height of
the overflow weir is increased; in the other, the interceptor is
increased in diameter or bypass interceptors are constructed. In
Japan, inceptor capacity is usually designed to be about three times
the dry-weather peak flow.
But, some places have experienced dry-weather overflow problems when
stormwater to be intercepted lowered because of increases in sewage
flow. To attack this kind of problem with symptomatic remedies, the
improvement of intercepting system has a quick effect.
While this can reduce overflows, it allows the primary effluent to
increase. Accordingly, the effect of the intercepter on the entire
combined sewer system in reducing pollutant loadings is small.
Figs. 12a and 12b shown an example of wet-weather primary effluent.
In the sewage treatment plant 0, sludge is treated at a separate
plant, and there is no return of supernatant from the sludge treatment
plant. On the other hand, treatment plant S receives supernatant
from the sludge treatment facility into grit chambers. As a result,
the quality of the primary settling tank influent is higher than that
of raw sewage, and the quality of primary effluent is higher than
that of raw sewage which enters the plant during rainfall. In cases
like treatment plant S, effluent loads will be increased all the more
by increasing intercepting capacity.
In the case of treatment plant 0, the wet-weather primary treatment
efficiency (1 - PffiMluenfqSSy7) » —lly 30% for BOD,
30% for COD and 40% for SS. If the intercepting system is improved
and the primary treatment efficiency left unchanged, there will be
little reduction of effluent loads from the entire combined sewer
system.
Figs. 13a and 13b show a case of increased intercepting capacity in
291
-------
Fig. 12b
300
200
Q
o
100
Fig. 12a
14 15 10 17 18 19 20 21
600
600
400
I
Q
3
300
200
100
\io
14 IS 16 17 IB 19 20 21
Time
18
ISH
u|
uC
12
II
-------
which year-round wet-weather effluent flows and loadings are given
with respect to the primary treatment facility, the secondary treatment
facility and the overall combined sewer system.
Depending on the conditions of receiving waters, the reduction of
overflow loads from diversion chambers in the upper reaches of a
river may lead to an improvement in water quality. Usually, however,
the improvement of intercepting systems alone cannot lead to improve-
ment of the combined sewer system as a whole unless the primary
treatment efficiency or wet-weather treatment system is concurrently
improved.
Fig. 13 (a) Effluent volume during wet weather vs.
interceptor capacity
-p
^s^
£
0)
£
1
"e
3
«s
n
d o£
2 i^
^— < '
•g
«
S
>ol
w
&uu-
400
300
200
100
0
~~- ^_
Total loads
primary
\ *
\ *^**P
V°'"'
VM—MMMM*
loads
_-- — °
x^x secondary loads
<* *>^ ' "
overflow loads
i i i
"*~ •
1234 (mm/hr)
Interceptor capacity
293
-------
3.2 Storage
Storage is a truly effective measure in coping with the problems of
combined sewer systems.
There are two main storage methods; on-site storage in which storm-
water runoff is pooled before being run into the sewerage, and off-site
storage in which stormwater runoff is accepted into the sewerage and
then pooled in a storage basin connected to the sewerage system.
On-site storage
Porous pavements are beneficial not only to pedestrians, but to
stormwater control. As regards the clogging of porous pavement,
the Construction Department of the Tokyo Metropolitan Government
conducted a survey as shown in Fig. 14.
According to the survey, it is found that the permeability is likely
to become around 5 to 10 ml/15 sec., which corresponds to an
infiltration Capacity of 20 to 40 mm/hr. Even if a pavement loses its
permeability, as when it has been loaded with foreign objects, it
still seems to offer good infiltration.
Some municipalities require measures for stormwater control as a
link in flood control in housing or industrial development.
Fig. 15 is a runoff regulatory basin installed in the lower reaches
of a newly developed area.
During fine weather, the runoff regulatory basin is turned into
tennis courts.
In some housing complexes, the open spaces between buildings are
depressed below the surrounding areas and the inlets of catchment
basins are reduced with orifices to control the runoff. (Fig. 16)
Off-site storage
Off-site storage can be mainly classified into in-line storage and
off-line storage. In any method, the stored sewage is released to the
treatment plant for secondary treatment when the sewage flow has been
reduced after rainfall.
294
-------
Fig. 14 Time Relevant Permeability
Porous Pavement Media
of
Permeability (ml/15 sec)
H» tO CO rfx 01 01
O O O O O O
O O 0 O O O
c
V
\\
\N
\
^
, S
k
\
, — <
N
>• r
\
\
k\
''4
t=—^
o Yu
• Ha
o Ka
r-^
rakucho
tagaya
namachi
b^d
i»
74/ 75/ 76/ 77/
Feb Dec Jan Mar Nov Dec Mar Sep Mar
295
-------
Fig. 15 Runoff Regulatory Basin
by T. Yamaguchi, Practices of Detention Storage in Japan,
Public Works Research Institute NO.1174
Fig. 16 Orifice of Catch Basin Inlet
by T.Yamaguchi
-------
For in-line storage, the size of the upper-reach sewer is made larger
than that of the lower-reach one in order to control runoff with an
orifice. Ichinomiya City uses this method to reduce overflow and at
the same time to overcome the chronic problem of inundation in the
upper reaches for want of the capacity of the lower sewer system.
In Nagoya, the sewers in the middle reach are oversized to provide
storage capacity for inundation control. After construction of this
storage system, the inundation which the city had experienced about
three times a year has not repeated.
Fig. 17 shows the Tennoji-Benten Trunk Sewer under construction by
the Osaka-Municipal Government. The water level of the river that
so far has drained the wet-weather overflows from the combined sewer
system is now above the outfalls because of urban development in the
upper basin and subsidence in the area, and this trunk sewer is
planned to accommodate wet-weather overflows.
A pump station downstream of the trunk sewer will drain overflows
into the Yodo, one of the largest rivers in Japan, in the case of
heavy rainfall.
For normal rainfalls, overflows will be stored in the trunk sewer.
The maximum diameter of the sewer pipe is 6 m, and the aggregate
length is about 14 km with a storage capacity of about 88,000 m^,
corresponding to a rainfall of 6.6 mm in covered areas.
Off-line storage is classified into two; one method in which a storage
basin is provided around the diversion chamber in the middle part of
the sewer system or near the pump station, and another method in
which a storage basin is installed at the treatment plant with an
oversized intercepter sewer.
The former is better in that it can reduce overflows of the combined
sewer system and its loads.
Fig. 18 shows a plan of the detention storage basins installed by the
Yokohama Municipal Government near Hodogaya Pump Station.
They total 18, each being 6 m in depth, 2 m in width and 35 m in
length. Their total storage capacity is 22,680 m3. equivalent to
297
-------
6.4 mm of rainfall. The wet-weather sewage detained in these basins
is sent to the treatment plant for secondary treatment when the sewage
flow has fallen. By the installation of these basins, the associated
combined sewer system has been improved in BOD effluent loadings and
is equivalent to a separate sewer system. This improved combined
sewer system has been proved to discharge loads 10% less than would be
expected from conversion into a separate sewer system.
In a separate sewer system, if the effluent loads due to stormwater
runoff were to be reduced, there would be difficulties in the use of
existing treatment facilities as stormwater and sanitary sewage have
g^uite different characteristics. It would be almost imperative to
install a new treatment plant for processing stormwater runoff. In
the case of a combined sewer system, however, wet weather sewage is
trained to give characteristics that permit the use of existing
facilities. Yokohama's improved combined sewer system has far higher
in load removal efficiency than any other separate sewer system without
stormwater control facilities.
The combination of storage and treatment goes a long way toward the
reduction of pollutant loads and at the same time serves to some
degree as a flood control function for receiving waters.
Table 7 summarizes the construction costs for basins,
Overflow sedimentation basin
The overflow sedimentation basin functions just the same as the
storage facility unless it is topped up. The difference between a
storage basin and an overflow sedimentation basin is in whether the
basin in question is to accommodate combined sewer overflow or to
discharge it directly into the receiving waters after the basin is
topped up. (Fig. 19)
If the storage capacity of the basin is sufficient, there would be
no quality problem if combined sewer overflow were to be discharged
directly into receiving waters when the basin were nearly full. On
the other hand, if the basin's capacity were insufficient, the basin
could well be used for sedimentation purposes in expectation of
load removal.
298
-------
Fig. 20 shows a plan of the overflow sedimentation basins installed
at the Nakanoshima Pump Station in Osaka. At present, two basins have
been completed.
Figs. 21a, 21b, 21c and 21d show SS removal by these basins. While
the basins can clip the peak concentrations of influent, their
sedimentary removal rate is not so high. Pollutant removal by the
storage of first flush is high, however.
Table 7 Construction Cost of Detention Storage
City
YOKOHAMA
OSAKA
M
NAGOYA
ICHINOMIYA
"
II
YAMATO-
KORIYAMA
Type
off-sewer
in-sewer
off-sewer
(sed. basin)
in-sewer
in-sewer
in-sewer
off-sewer
off-sewer
Main Purpose
poll, control
flood control
poll, control
flood control
flood control
flood control
poll, control
poll, control
Storage
Capacity
( M3 )
23,000
51,700
630
2,000
2,450
1,100
4,500
17,000
Cost
( yen/M3 )
338,500
173,000
38,600
26,500
13,600
39,000
16,000
299
-------
Fig. 17 Tennoji-Benten Trunk Sewer under way
by Osaka Municipal Government
300
-------
Fig. 18 Detention Storage in Yokohama City
/( \\ II
grit
chamber
Fig. 19 System flows of Detention Storage
and Sedimentation Basin
directly
discharged
interceptor
directly
discharged
301
-------
Fig. 20 Sedimentation Basin in Osaka City
Sanitary sewage
efQuent baaln
Storm sewage
effluent baa La
Fig. 21a
Fig. 21b
10 U
KTt. UtaT. 10
302
14 in
(Tim*)
-------
Fig. 21c
la 11
I»T» r-ti. n
Fig. 21d
IS M
ITImr)
303
-------
3.3 Experimental measures
Swirl regulator/concentrator
Treatment facilities designed solely for combined sewer overflows
are extremely disadvantageous from the economic viewpoint. The swirl
regulator, however, costs less to construct and needs little or no
expenses for maintenance, and is effective as a measure against
combined sewer problems.
The Public Works Research Institute of the Ministry of Construction
and the Bureau of Sewerage of the Tokyo Metropolitan Government have
been experimenting with prototype swirl regulators of 0.9 m and 1.2m
in diameter in order to assess their pollutant removal efficiency.
Table 8 shows test results achieved by the Tokyo Metropolitan Govern-
ment's Sewerage Bureau on artificial turbidity.
Fig. 22 shows a forecast of removal rate of a 12 m 0 swirl regulator,
obtained by applying Froude's law to Table 8.
The prototype swirl regulator has the drawback that it needs a height
difference between the influent sewer and overflow sewer. For this
reason, the two organizations are studying the improvement of swirl
regulators.
Sewer flushing
It is well known that the flushing effect of stormwater conveys bottom
loads off the sewer to cause the so-called first flush of low quality.
A sediment loads survey was conducted in 300 manholes within the B
district. Of them, 44 disclosed deposits filling more than a quarter
of the invert. (See Fig. 23)
The BOD load in the sewer way estimated by gravimetric analysis and
qualitative analysis of several typical deposits to be about 1.0 to
1.5 ton/km2.
More than 70% of the aggregate sewer length was accounted for by
pipes of 500 mm or less in diameter where deposits were formed.
Therefore, if sediment in pipes of 500 mm or less can be forced into
304
-------
pipes of larger size, not only the problem of first flush, but a sub-
stantial part of the combined sewer problems can be solved.
Water was discharged into an upstream manhole and was sampled from a
downstream manhole. (See Fig. 24)
Analysis results for the sampled water are shown in Fig. 25. The
pouring rate was 3 I/sec., and the pouring duration was 30 min. To
determine the initial loads deposited inside the pipe, water was
discharged for 30 min. at a rate of 8 £/sec. after the 3 I/sec, test.
It was found that about 50% of the initial BOD load (326 g/73.8 m
of sewer) could be washed away in 15 min. by water discharge at
3 Vsec.
Catch basin
A catch basin is usually constructed to have a sand arresting pit
more than 15 cm deep at its bottom. (See Fig. 26)
Debris and sand carried in from road surfaces should be trapped in
this pit. According to a survey conducted by the Public Works
Research Institute of the Ministry of Construction, about 15% of
catch basins were found to be totally filled up; those catch basins
where the sediment height exceeded 10 cm accounted for more than a
quarter of the total. (See Fig. 27) In view of this, the regular
cleaning of catch basins is one solution to overflow problems.
Other experimental projects include road cleaning, which was started
in 1979, no definite results are available yet.
305
-------
Fig. 22 Removal Efficiency of Swirl Regulator
Concentration
100
90
§ 80
070
60-
Grit
Settleable
suspendid
solids
5 10 15x103
Inflow rate (m3/h)
Fig. 24 Experiment of Sever Flushing
80 m
Regulatory tar
, )Pj*T=
n nun
ik
^
6300
T T^Si
27.80m
779 -
1
($300
I 7%0
46.00m
No.l
\ ///ni mm
„, •
I
($350
I 7%o
No. 2
•9*7— •
306
-------
Fig. 23 Deposits in The Sewer
307
-------
Fig. 25 Quality Variation During
Sever Flushing
1000
500
-100
>
3 50
a
o
a
Q"
o
« 10
CD
a
00
e]
el
O
Vl
03
0)
.a
o
bfl
a
o
0>
o BOD
A SOD (Mn) (mg/i)
1 I
0 5 10 15 20 25 30
Time (min.)
20--
10-
Fig. 26 Catch Basin
Fig. 27
J L
J 1 L
10 20 (cm)
Height of deposits in catch basin
308
-------
Table 8- Rciuov.il K( f i i -I em- v Of Swirl (l)«1.2m)
LO
O
U3
ZeolUe
•
Powder
carbon
Anthlaslte
»
•
I tal Ian
nlllec
Rice hull
Barnyard
grass
Styrol
"
•
"
Specific
grav ft (ty
2.13
2.13
1.50
1.41
1.41
1.41
1.23
1.09
1.06
1.05
1.05
1.05
1.05
Diameter
otra
0 . fr>.2 . 4
0.5^1 .4
0 . 5-M) . 6
2.0
1.0
0.5
1.5M.7
2"° 3.5
7.5
1 . 8^2 . 0
3.0
2.0
1.2
0.7
MolaLun e
conLeut
X
J.7
3.7
18.9
0. 7
0. /
0.7
6.5
8.9
9.0
0.1
0.1
0.1
0.1
I'D 8.1/l,r
99.6
98.3
90.3
'1-
99.9
97.3
97.5
92.9
97.9
92.0
86.7
72.9
-------
4. Conclusions
Combined sewer problems in Japan and their countermeasures have been
discussed.
To tackle combined sewer problems, we should firstly consider how to
make the most of existing facilities. The combination of storage and
treatment facilities will be appropriate.
Secondly, we should decide the extent that the effluent loads should
be reduced.
For this, it is necessary to establish a model forecasting the quantity
and quality of combined sewer overflows, as well as a model for evaluat-
ing the quality of receiving waters.
At present, it is not clean what impact combined sewer overflows have
on the quality of receiving waters.
This is particularly the case with the relationships between overflow
loads and the dry-weather quality of receiving waters, which are an
important theme awaiting our study efforts.
Every engineer accepts that the simpler a mathematical model is, the
better it is. Any drainage area has limits to the geographical and
hydrological data that can be collected specific to it.
Thus, the use of black box type models as introduced in this paper is
worth trying.
While the separate sewer system has been improved little, it will incur
no overflow problem for the time being except for in some water
characteristics.
As regards storm runoff from highly congested areas, separate sewer
systems will not be sufficient, and additional measures should be
provided. In Japan, there are many infiltrated sanitary sewers, and
surveys on inflow/infiltration control are being carried out.
310
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
WATER QUALITY IMPROVEMENT IN YODO RIVER
AND SEWAGE WORKS IN KYOTO
I.1
J
May 21, 1980
Tokyo, Japan
TAKASHI YONEDA
Director,
Sewage Works Bureau,
City of Kyoto
311
-4
(J
ui
CQ
I
-------
WATER QUALITY IMPROVEMENT IN YODO RIVER
AND SEWAGE WORKS IN KYOTO
1. Preface 313
2. Outline of Yodo River 313
2.1 Characteristics of Catchment Area 313
2.2 Water Utilization 315
2.3 Outline of Water Quality 31?
2.4 Control by Laws 319
3. Sewage Works Project in Kyoto City 321
3.1 Project Outline 321
3.2 Improvement of Water Quality in Yodo River 323
4. Conclusion 329
312
-------
1. PREFACE
The Yodo River running through the five prefectures of Osaka, Kyoto, Shiga,
Nara and Mie has a catchment area of 7,280 km2 including Osaka and Kyoto cities
and other growing satellite cities. With a total population of 9,700,000 in the catch-
ment area, the Yodo River is the foundation for social, economic, cultural and
industrial activities in western Japan.
Among the Japanese rivers having large flow fluctuations, the Yodo River is
comparatively flow-stabilized river since Lake Biwa is located in the upper stream
of the river. The catchment area of the Yodo River has prospered since olden days,
depending much upon the stabilized water resources. Today, the Yodo River brings
blessings of nature to the area as water resources for water supply, industrial and
agricultural uses.
The Yodo River, which has such an important role in the Kinki regional sphere,
has been facing some problems because of pollution of water quality, outbreak of
red water in Lake Biwa, offensive smells for waterworks, increase of ammonia
nitrogen in the lower basin of the river; all affected by an increase of pollutant loads
brought by the rapid development of industry and the concentration of population
in its catchment area.
The City of Kyoto, situated in the midstream basin of the Yoro River, is a great
city of 1,460,000. All wastewaters from the city and its neighboring area are dis-
charged into the Yodo River, but on the other hand, the Hanshin (Osaka-Kobe) area
in the lower stream basin of the river is taking water on recycling process system.
As a result, the water pollution of the Yodo River has been emerging as
problem from an early stage. In 1958, the Council for Yodo River Water Pollution
Control was inaugurated by 21 organizations including the central government
and related local governments and water using bodies, and river supervisor, user and
discharger have been exerting efforts to prevent pollution of the Yodo River water.
In order to carry out the improvement of water quality in the Yodo River,
the construction of sewage works in the catchment area of the river is the most
effective way. Especially, the sewage works in Kyoto City is most importance, so
Kyoto City has positively expanded sewerage systems as one of the important poli-
cies of the city.
With the extension and construction of the sewage works and strengthening
of control over wastewaters from factories in Kyoto City showing good effects,
water pollution in the Yodo River has been gradually reduced since the peak year
of 1969 and the river has been restored to the present environmental standards.
Here is a report about the process for improvement.
2. OUTLINE OF YODO RIVER
2.1 CHARACTERISTICS OF CATCHMENT AREA
The catchment area of the Yodo River is divided into the five portions of
the Uji River, the Katsura River, the Kizu River, Lake Biwa in the upper stream
basin of the Uji River and the main stream of the Yodo River after joining the
three rivers. (See Fig. 1 and Table 1).
The hydrogeographic characteristics of the sub-catchment areas contribute
to a good water balance for the entire basin of the Yodo River and are providing
313
-------
Fig. 1 Map of Yodo River Catchment
Hyogo
Pref.
Dam >
— Catchment Border
- Prafectural Border
ID
Km
314
-------
Table 1 Catchments of Yodo River System
Name
Lake Biwa
Uji Raver
Kizu River
Katsura River
Main Stream
of Yodo River
Total
Catchment
Area
KmJ
3,848
506
1,596
1,100
231
7.281
Length
Km
—
53.9
189.2
114.3
35.8
393.2
Fig. 2 Monthly Flow of
Yodo River System
Runoff
Rainy Typhoon
Season Season
200
mm
50 .
- Lake Biwa
— -— Kizu River
• - - - Katsura River
Der
Mar
June
Sept.
Dec.
sufficient water resources to the Yodo River: Namely, runoff of rain water in
the three basins of the Yodo River is recording much quantity in the Lake Biwa
basin for snowmelting period of March and April, the Katsura River basin for
the rainy season of June and July and the Kizu River basin during the typhoon
season of August and September, respectively (See Fig. 2).
Accordingly, these basins with their respective climatic features contribute
to the stabilization of flow of the Yodo River by mutually covering their different
points. Particularly, outflow from the Lake Biwa basin which occupies about half
of the Yodo River basin has much advantage in river improvement and water utili-
zation through the natural adjustment of Lake Biwa with its 680 km2 in surface
area and 27,500 million m3 in Lake water capacity.
The Yodo River catchment basin also comprises of several basins geographical-
ly close to each other. At the time of flooding, a narrow portion of the respective
basin makes a natural adjustment to attenuate peak flow and waters used for water
supply, agriculture and industry in the upper and middle stream basin, are also
recycled for use in the lower river basin.
Besides the above-mentioned natural advantages, flow control is being carried
out at the dams of Takayama, Shorenji, Muro-o and 'Amagase and Seta River weir.
As a result, the flow at Hirakata of the Yodo River is showing stabilization. High
water and ordinary water volume are not much as compared with the important
rivers in this country (See Fig. 3), but the volume of low water and drought water
levels are big next to the Shinano River which runs in Nagano Prefecture.
The flow of various branch rivers of the Yodo River are shown in Table 2,
but as compared in this table, catchment area in Lake Biwa occupies 53% of the
Ycdo River catchment basin, but contribution ratio to Hirakata flow is about
70%, showing the important role of Lake Biwa.
2.2 WATER UTILIZATION
The monthly flow of the Yodo River at Hirakata is comparatively stable
through four seasons with 147.4 m3/sec. - 467.2 m3/'sec. as shown in Fig. 4.
315
-------
Table 2 Discharge of Branch Rivers of Yodo River System
Name of
River
Ujt
Katsura
Kizu
Yodo
Name of
Station
Yodo
Katsura
Yawata
Hiiakata
Discharge mj/sec.
Maximum
1,980
1,744
2,519
5,228
High
Water
203
28
46
282
Ordinary
Water
138
17
29
197
Low
Water
103
11
21
148
Draughty
Water
79
5
13
105
Minimum
51
0
5
66
Annual
Average
186
27
51
264
1969-1978
Fig. 3 Discharges of Main Rivers
in Japan
mm/day
Fig, 4 Monthly Discharge of
Yodo River (Hirakata)
m'/sec
500
400
300
200
100
0
Average
264.2
Jan. Mar.
June
Sept. Dec.
1969-1978
High
Water
Ordinary
Water
Lorn Draughty
Water Water
As a result, the ratio of water utilization is high, and of about 10 billion m3 in
annual volume of flow of the Yodo River, about 11% is used as water supply for
general households, 4% as industrial water and 5% as agricultural water, or about
20% in water utilization ratio.
If maintenance water is included, the utilization ratio becomes about 45%.
Thus, water in the Yodo River is being used very effectively as compared with
10% of the average utilization ratio elsewhere in this country. Since water demand
is expected to further increase in parallel with economic development in the Kinki
regional sphere, the ratio of dependence upon the Yodo River will become even
higher.
As the total population and the water supplied population in the Yodo River
basin are shown in Fig. 5, concentration of population was seen in the lower basin
for 10 years in the upper period and in the middle basin and its vicinities for the
same years in the latter period.
Water taken from the Yodo River as water resources is being supplied to almost
all parts of Osaka Prefecture and some parts of Hyogo Prefecture while the water
utilization population in these lowest basins is about 11 million. The water intake
volume is shown in Fig. 6. As demand for water in the future is estimated as shown
in Fig. 7, highly effective use of water resources is required along with the develop-
ment of water resources.
316
-------
.Unit:
M million
14
12
10
I 6
a.
Fig. 5 Population Change in Yodo River
Catchment
Fig. 7 Prediction of Water Demand
for Hanshin Area
Im'/sec)
150
100
50-
Middle Catchment
Hyogo
Pref.
„ Osaka
Pref.
1975
1980
1985
1955
1960 1965
1970
1975
Fig. 6 Intake in Downstream of Yodo River (Maximum Intake) 1971
>
3 S
f 5
"5
&
1 2
^ a
Total
Total
Osaka Pref.
Hyogo Pref.
Total
Osaka Pref.
Hyogo Pref.
=m
=i
i
fy
J
I
j
20
40
60
80m3/sec.
2.3 OUTLINE OF WATER QUALITY
The pollution of the water quality in the Yodo River has increased at a quick
tempo since 1955 but the trend for improvement or stoppage of pollution is seen
after 1969, which recorded the worst water pollution level. The outline of water
quality according to rivers is described as follows: (See Fig. 8 and 9).
As to the Katsura River, it is hard to see change of water quality since around
1971 at Togetsu Bridge in the upper stream basin of the river because the river
water at the bridge shows little artificial pollution with BOD (biochemical oxygen
demand) making around 1 mg/£. Miyamae Bridge which receives almost all waste-
waters from Kyoto City marked BOD 23.4 mg/2 in 1969, the highest figure on
record, but the BOD is dropped to 10 mg/8 since 1975.
As to the Uji River, water quality in its upper basin is close to that of Lake
317
-------
mg/S
24
22
20
18
16
8 14
0 12
0 10
8
6
4
2
Fig. 8 BOD Trend of Yodo River System
Yodo River
(Hirakata Bridge)
Kattura River
(Miyamaa Bridge)
Uii River (Goko Bridge)
Kizu River (Goko Bridge)
1965
1970
1975
1978
Fig. 9 Location of Sampling Point
Osaka Bay
318
-------
Biwa, showing little change of BOD 1.5 mg/fi after 1975. Goko Bridge which
receives some of the discharged waters of Kyoto City is also recording little change
of BOD 2.4 mg/fi since 1975 after a high value of BOD 3.9 mg/fi in 1969.
As to the Kizu River, the water was clean with BOD marking less than 1 mg/fi
before 1970 but the BOD gradually become higher in concert with the development
in its basin, but is marking little change of BOD 1.6 mg/C after 1973.
Water quality in the main stream of the Yodo River at Hirakata, involving the
three biggest confluent rivers, is affected not only by wastewaters from Hirakata
City areas on the left bank, but also by water qualities of the three branch rivers.
The right bank of the river, affected by the Katsura River, is polluted remarkably
by BOD 6.0 ~ 6.8 mg/fi from 1959 to 1973, showing a higher value than the BOD
4.5 ~ 5.5 mg/fi of the left bank but the difference of BOD concentration is becom-
ing less in accordance with improvement of water quality in the Katsura River.
As a result, the average BOD at Hirakata of the Yodo River was gradually im-
proved from 6.2 mg/fi in 1969 as the highest figure to 3.2 mg/fi in 1975. The present
condition of the water quality in these rivers is shown in Table 3.
Table 3 Water Qualities of Yodo River System
1978
Name of
River
Katsura
Uji
Kizu
Yodo
Name of
Station
Togetsu
Bridge
Miyamae
Bridge
Goko Bridge
Goko Bridge
Htra-
Kata
Left
Center
Right
mg/8
DO
10.6
7.0
9.2
10.4
8.8
8.3
8.2
mg/8
BOD
1.1
9.4
2.3
1.4
4.2
4.3
4.5
mg/8
COD
2.2
13.7
3.3
2.2
6.1
6.3
6.7
ftig/8
SS
2.1
26.5
10.2
29.1
18.1
16.7
15.6
No. of
Coliform
Groups
17.0x10*
3.0x10'
2.9x10'
7.3xlOJ
12.4x10"
7.4xl04
15.5x10*
mg/8
NH.-N
0.10
3.73
-
-
0.89
0.87
1.08
2.4 CONTROL BY LAWS
After the enforcement of the Basic Law for Environmental Pollution Control
in 1967, the environmental standard for the Yodo 'River was established in Sep-
tember, 1970 (See Fig. 10). The Water Pollution Control Law was also enforced in
1970. As a result, control for wastewaters from the specified plants throughout the
country and enforcement of punishment against violators of the laws were codified.
The control for wastewaters from the specified facilities is handled by the Water
Pollution Control Law and other prefectural ordinances but effluent from the
sewage treatment plants are further regulated by the Sewerage Law. The effluent
standards of sewage treatment plants in Kyoto City are shown in Table 4.
As the Seto Inland Sea Environmental Preservation Special Law and the Water
Pollution Control Law were revised in 1978, the control on total load of COD
(Chemical Oxygen Demand) discharged to the Seto Inland Sea. Ise Bay and Tokyo
Bay, which are extensive closed water area, was adopted. Since Kyoto Prefecture
319
-------
Fig. 10 Environmental Standard of BOD for Yodo Rivar System (mg/e)
had to accept application of the new control as a prefecture in the upper portion of
the Seto Inland Sea, the total load of COD to be discharged from treatment plants
in Kyoto City is also controlled. In the Seto Inland Sea, guidance will be given to the
reduction of phosphorus and its compounds as a preventive measure against eutro-
phication.
The Kyoto Prefectural Government which has worked out a pollution preven-
tive plan for the Yodo River Basin in 1972 according to the Basic Law for Environ-
mental Pollution Control is now taking various countermeasures to achieve an
environmental standard of water quality with the extension and construction of
sewage works as a mam pillar of these countermeasures. The extension and construc-
tion of sewage works are also required as a step of the total load control system
for reducing pollutant substances from livelihoods. Thus, great attention is being
paid to the sewerage systems in Kyoto City because the urgent extension and con-
struction of the sewage works is eagerly desired.
320
-------
Table 4 Effluent Standards of Treatment Plant
Items
PH
BOD (mg/2)
SS (rag/ 5)
Cliform Groups (per me)
Cadmium (mg/2)
Cyanide (mg/2)
Serous^*'
Lead (mg/2)
sr <«*«>
Arsenic (mg/2)
SSU <-«">
^cU ^V
Standard Value
5.8-8.6
Daily Ave. 20 or Less
Daily Ave. 70 or Less
Daily Ave. 3,000 or Less
0.05 or Less
0.5 or Less
0.5 or Less
0.5 or Less
0.25 or Less
0.25 or Less
0.005 or Less
ND
Items
PCB
N-Hexane
Extracts
Phenol
Copper
Zinc
(mg/2)
Mineral
Oil (mg/2)
Animal and
Vegetable
Fats (mg/tt)
(mg/2)
(mg/2)
I me/1 2)
Iron (Soluble) (mg/2)
Manganese
(Soluble)
Chrome
Fluorine
Nickel
Boron
(mg/2)
(mg/2)
(mg/2)
(mg/2)
(mg/2)
Standard Value
0.003 or Less
5 or Less
30 or Less
1 or Less
3 or Less
5 or Less
I
10 or Less
10 or Less
2 or Less
15 or Less
2 or Less
1 or Less
3. SEWAGE WORKS PROJECT IN KYOTO CITY
3.1 PROJECT OUTLINE
The sewage works project in Kyoto City was begun in 1930 as an emergency
unemployment countermeasure project. The city has been carrying out the project
as one of the city planning projects since 1934. As the first treatment plant in
Kyoto City, Kisshoin treatment plant (with treatment capacity of 7,800 m3/day by
activated sludge process) begun operation in 1934, followed by the operation of the
Toba treatment plant (with treatment capacity of 78,000 m3/day by activated
sludge process) in 1939. The construction work of sewerage systems was suspended
due to the Second World War in 1943, but the extension and construction of the
sewage works had so far been made in an area of 1,342 ha in addition to the above-
mentioned two treatment plants.
The project was resumed in 1949 and in 1956 the Long Range Plan for Con-
struction of Sewage Works in Kyoto City was worked out to fully accelerate the
project. On the other hand, the central government worked out its five-year plan
starting in 1963 with the purpose of carrying out the extension and construction
of sewage works. Its investment was rapidly expanded in one plan after another.
The Kyoto City Office is also accelerating a project based on its plan to meet
the five-year plan of the central government. Kyoto City is positively faking the
steps for the extension and construction of the sewage works as one of the im-
portant policies for an international sightseeing city and also for the security of
water resources in the lower stream basin of the Yodo River to prevent the pollu-
tion of river water quality. The extension and construction of sewage works are
shown in Table 5.
The sewage works project is now under way according to the fourth five-year
plan for the fiscal years 1976-80 for the construction of sewage works by the
central government. The five-year plan of Kyoto City called for the expenditure
of ¥142 billion for the sewage works projects with the design to see that the treat-
321
-------
ment area is extended by 2,283 ha to 7,080 ha; treatment capacity is increased
by 242,000 m3/day to 1,005,000 m3/day and the ratio of served population against
total population is set from 47% to 61% (Table 6). The construction project is
shown in Table 7.
Total designed sewer area of Kyoto City which is equal to the proposed future
urbanized area (16,221 ha) is divided into six treatment districts as shown in Table 8
and Fig. 11. By 1990, all of the present urbanized area is scheduled to be served by
sewerage systems.
Table 5 S«wage Works States - April 1979
Tabl®6 Summary of Five-Year Plan
(FY 1976-1980)
Total City Area
Urbanized Area
Total City Population
Service Area
Percentage to Urbanized
Area
Service Population
Percentage to
Total Population
Sewer Length
Treatment Capacity
Toba Plant
Kisshoin Plant
Fushimi Plant
61,061 ha
14,887 ha
1,458,019 Persons
5,857 ha
39.3 %
758,110 Persons
52.0 %
1,534,518 m
957,500 m3/day
750,000 m3/day
125,000 rn3/day
82,500 m3/day
Total Cost
For Old Urban Area
For New Urban Area
Project Target
(At End of 1980)
Service Area
Percentage to
Urbanized Area
Service Population
Percentage to
Total Population
Sewer Length
Treatment Capacity
¥142 Bil.
¥130 BO.
etc. ¥ 12 Bil.
7,080 ha
48 %
918,000 Persons
61 %
2,012 Km
1,005,000 m3/day
Tabto 7 Sswaga Works of Kyoto City
^==::~~— -^__^ Year
Item ' _____
Cost
Total Cost (VIMiL)
Sewer (¥1 Mil.)
Plant (VIMiL)
Service
Area
(ha)
Increase
in Year
Total at
End of Year
Sewer Length (Km)
Service Population
Treatment
Capacity
(1,000m3 /day)
Increase
in Year
Total at
End of Year
1971
7405
3,240
4,265
187
3,767
997.5
616,060
72.5
600.4
1972
8,275
4,745
3,530
217
3,984
1,066.8
651,650
117.5
717.9
1973
13,900
7,715
6,185
392
4,376
1,131.3
681,690
-
717.9
1974
16,047
11,874
4,173
221
4.S97
1,199.1
688,140
-
717.9
-"" ' 3rd 5-Year Program
1975
24,918
14,812
10,106
200
4,797
1,267.4
693,700
45
762.9
.1976
23,659
14.962
8.697
254
5,051
1,331.4
700,260
45
807.9
1977
26,187
20,960
5,227
356
5,407
1,428.9
726,830
59.6
867.5
1978
33,683
25,326
8.357
450
5,857
1,534.5
758,110
90
957.5
1979
40,000
32,920
7,080
788
6,645
1,758.2
808,400
47.5
1,005
4th 5-Year Program
322
-------
Table 8 Overall Program
Name of Sewer
District
Toba
Kisshoin
Fushimi
Yamashina
Katsura
Mukarjima
Total
Sewer
Service Area
8.160ta
587
2,171
1,984
2,300
519
16,221
Type of Collec-
tion System
Combined,
Separate
Combined
Combined,
Separate
Separate
Separate
Separate
Plant
Treatment Capacity
mj/day
1,225,000
165,000
238,000
Type of Treat-
ment Process
Activated Sludge
Process
••
163,000
-
-
1.791,000
-
-
Remarks
Oxygen Aeration
Process for
80,000 m3/day
Sewerage System for
Right Bank Catchment
of Katsura River
Sewerage System for
Left Bank Catchment
of Uji River
Note: Sewerage System for Right-Bank Catchment of Katsura River
Planned Area - A part of Kyoto City, Muko City, Nagaokakyo City, Oyamazaki Town; 5,088 ha
Rakusai Purification Center; 427,000 m3/day. Partially operated on Oct. 18, 1979
Sewerage System for Left-Bank Catchment of Uji River - Plan under way.
3.2 IMPROVEMENT OF WATER QUALITY IN YODO RIVER
When pollution load flowing into the main stream of the Yodo River in 1970
was compared to other rivers, the Katsura River marked 60%, the Uji River 36% and
the Kizu River about 4%. The ratio for each prefecture recorded at Hirakata point
in the main stream of the Yodo River is shown in Fig. 12, Kyoto City occupies its
great weight in water quality pollution in. the Yodo Paver with about 55% in all
basins and about 69% in midstream basin.
In Kyoto City, an increase of wastewaters from industrial factories and general
households with the rapid industrial development (See Fig. 13) and increase of
population and promotion of livelihood standards (See Fig. 14) have brought an
increase of pollutant substances, causing pollution problems in the rivers due to the
delay in extension and construction of sewage works. On the other hand, treatment
plants faced a lack of treatment capacity with the increasing inflow of sewage and
treatment efficiency was lowered due to the increased wastewaters from factories,
markedly worsening effluent quality for a time.
There are many dyeing plants in Kyoto City (with about 24% in industrial
shipment and about 55% in the total number of factories), greatly affecting influent
quality at the treatment plants. The overload of water volume and water quality
due to the discharge of nightsoil into the sewer caused insufficient treatment.
Since instant effect on improvement of water quality of the river can be
obtained by expanding treatment capacities at first, Kyoto City has decided to
exert its efforts particularly for the construction of treatment facilities. About
49.3% of the total project cost was Invested for construction of treatment plants
to increase the treatment capacities from fiscal 1966 to 1972.
-------
Fig. 11 Sewer District of Kyoto City
Kisshoin Plant
324
-------
Fig. 12 Breakdown of Pollutant Load Discharged into Yodo River by Prefecture
At Hirakata Point in 1970
Whole Catchment
Middle Catchment
(¥100
Billion)
15
4
!
«
10
5
Fig. 13 Yearly Change of Industrial
Products Shipped
1960
1965
1970
1975
Fig. 14 Population & Water
Consumption
per Capita
,1,000 ,
Persons
1955 1960 1965 1970 1975
(liter per
capita)
500
400
300
200
100
Kyoto City started the discharge of nightsoil into the sewer from around 1950.
In order to solve the adverse effect caused by the discharge of nightsoil, the city
office built digestion tanks (capacity-415 ki/day) in the Toba Treatment Plant
compound in 1966 and installed storage facilities in 1968 at two nightsoil discharge
depots in the city to discharge nightsoil uniformly into the sewer during the night
period of low inflow load to the treatment plant.
On the other hand, Toba Treatment Plant extended its facilities to meet the
increasing quantity of inflow sewage and maintain the water quality, resulting in
the gradual improvement of effluent quality and upgrading the water quality to the
level that is a little better than effluent standards since 1972.
325
-------
The treatment capacity, inflow sewage quantity, discharged nightsoil quantity
and effluent quality at the Toba Treatment Plant are shown in Fig. 15 and the
present condition of influent and effluent qualities at the various treatment plants
is shown in Table 9.
As the process for the construction of treatment plants was shown in Fig. 16,
the Toba Treatment Plant has been carrying out its extension work since 1959,
currently reaching 750,000 m3/day treatment capacity.
The Kisshoin Treatment Plant completed the A-line facilities with treatment
capacity of 85,000 m3/day in 1967 and also built B-line facilities with treatment
capacity of 40,000 m3/day in 1977 after dismantling the old facilities, raising the
total treatment capacity of 125,000 m3/day. The B-line facilities use the oxygen
aeration process judged to be most suitable as a result of comparative tests for
various kind of treatment methods. There are many factories in the sewer district,
especially causing difficulty of treatment due to high concentration of inflowing
sewage affected by dyeing effluents.
The Fushimi Treatment Plant has completed facilities with a treatment capa-
city of 27,500 m3/day and started the operation in 1972. The present treatment
capacity is 82,500 m3/day.
Fig. 15 Relationship between Effluent BOO and Treatment
Capacity at Toba Plant
(1,000
700
500
300
100
m'/Day) /' \ (m
f \ —
\ •-•"' \ ^
\ Treatment Capacity I -
*»^ _—-— ^"*" ' Maximum Daily Influent
S \ ^
' "~ \ Flow
f^ \
/ \
' \^
s
- x
%
s
v--—. ~
Effluent BOD "-^ ^.' _
j/e)
100
80
60 Q
o
03
1
40 uj
20
0
2,000
•3 I 1.000
„ = ?
c ° a
2 - •=
14.8
"
Tin
fl
•"
•
1970
1975
1978
326
-------
Table 9 Characteristics of Influent and Effluent At Each Plant (mg/2)
Toba Plant
Influent
Effluent— Nishi Takase River
Effluent— Katsura River
Kisshoin Plant
Influent— A-Line
Influent-B-Line
Effluent
Fushimi Plant
Influent
Effluent
BOD
223.6
11.4
11.4
137.5
212.5
13.8
151.9
12.1
SS
152
13
7
99
NH4-N
13.30
9.67
9.67
8.92
161 18.27
8
99
8
9.59
5.49
1.20
T-P
3.52
2.09
1.26
2.94
3.14
1.17
2.98
1.07
Anion
Surfactant
5.4
0.3
0.3
7.1
5.3
0.7
3.5
0.3
(1,000m3/Day)
1,000 |
300
600
400
200
Fig, 16 Breakdown of Treatment Capacity by Plant
Total
£ P
.if
^ u,
i I JB.j.1 JB-i
1965
1970
11 mA 11 mrA i
1975
1979
327
-------
In addition to three plants, the new Ishida Treatment Plant is now under way.
The plant is expected to start operation with a treatment capacity of 20,000 m3/day
by the end of 1980. If the plant starts its operation, all the treatment plants in
Kyoto will be operated.
As mentioned, the extension and improvement of the Toba Treatment Plant,
which treats most of the sewage in Kyoto City, has contributed to the improve-
ment of the sewage works through the improvement of treatment and extension
of sewer district. As a result, pollutant substances, discharged from the city, have
remarkably decreased. The water quality in the Katsura River was 23.4 mg/£ in the
highest BOD, but it became 8 to 10 mg/£ recently. The water quality of the Yodo
River was 6.8 mg/£ at its worst but recently became 3 mg/£, almost reaching the
environmental standard (See Fig. 17).
The water quality of the Yodo River aggravated in 1973, 1977 and 1978 but
this was due to the fact that these years were water shortage years, aggravating
flow conditions in various rivers. When the average annual discharge in these years
is compared with those of the last 10 years, 1973 was about 77% and 1977 was
about 74% while 1978 decreased to about 55%.
The BOD load surveyed at Hirakata in the main stream of the Yodo River
was 54.7 t/day on annual average in 1977 and 52.3 t/day in 1978, remaining little
change. The effect of water quality improvement in the Yodo River by the exten-
Fig. 17 Relationship between River Water
it/day)
110
100
90
e
—
S 80
1
I70
oc
-
?
• -o
(0
2
<8
(ha)
.6,000
1 60
0
§ 50
CD
40
30
•4,000
•2,000
•
*
V
1
t
1
t
1
t
tJ
1
t '
1 •
--../ /
/BOO
/
,-*
-
^
^
-
*>
/
f •
/ i .*" '''BOO Load Removed
i y
', y
\ /'
\ f
\ '
'•/
|
/'.
/ '. BOD of Katsura River Served Area
1
V-*"*\ ,''"' '•
% J r«5\
of Yodo River _
'
***.
^
\
K.
l*^"
/
/
"
\
\
x
,
f..-
„
-
>N
-
•
,
•
-
25
20 -
Q
O
m
j
1
15 0
2
-------
sion and construction of the sewage works in Kyoto City reflects the survey for
biological water quality pollution. Fig. 18 shows pollution of water quality accord-
ing to the index for judgment of biological water quality at 10 years intervals since
1955.
According to this, water pollution in the Yodo River turned to worse during
the decade from 1955 to 1965, but the water quality in 1975 is believed to have
dropped to that in 1955 due to remarkable reduction of pollutant substances
discharged from the Katsura River, Shin Takase River and canal as a result of the
extension and construction of sewage works in Kyoto City.
4. CONCLUSION
The Yodo River flows through six prefectures as the most important water
resource in the Kinki regional sphere and its water utilization population is about
Fig. 18 Biological Water Quality Pollution Maps
km
50
40
30
20
10
0
1955
Uji River
1965
Uji River
197S
Uji River
Yamashina
River
Canal
Shin Takase
River
Mouth
HE
Uji
Tidal
Area
River
Mouth
Tidal
Area
River
Mouth
Hirakata
Polysaprobe
Zone
a-Matotaprobe
Zone
(J—Masosaprobe
Zone
OHgosaprobe
Zone
329
-------
14 million. But since Kyoto City is situated in the midstream in the Yodo River
basin, it faced water quality problems from an early period as important issues for
water utilization for the downstream basin and the reduction of pollutant substances
from Kyoto City became an urgent issue.
The water quality pollution in the Yodo River was improved to the extent
that the environmental standard relating to human health on noxious substances
such as cadmium and mercury was maintained due to strict control over water
quality in wastewaters discharged from factories, plus the construction of the
sewage works in Kyoto City and the environmental standards relating to living
environment such as BOD etc. were also almost achieved.
A new problem, however, is the trend to increase ammonia nitrogen in the
river. Ammonia nitrogen often reaches a considerably high concentration at the time
of low flow or at low water temperature in the river.
The destination of discharge in the Yodo River is the Seto Inland Sea which
is extensive closed water bodies but red tides often occur, damaging the fishing
industry and living circumstances. In respond to such a situation, the sewage works
are required to study employment of advanced treatment as the occasion demands,
in addition to upgrading treatment efficiency.
In order to carry out the improvement of water quality in the Yodo River,
the reduced amount of pollutant substances from the cities is needed. Since the
ratio of served population to the total city population is 52% at the present, Kyoto
City is considering the extension of the area for the construction of the sewage
works by a secondary treatment process for the time being. The present secondary
treatment showed effective for the improvement of water quality in the Yodo
River by removing organic matters such as BOD as well as 20 ~ 40% of the nitrogen
and 30 ~ 50% of the phosphorus.
However, since the advanced treatment processes are considered necessary
in the future, research and study are now being conducted for the advanced treat-
ment technologies. In Kyoto Prefecture, the sewerage systems in the right bank
basin of the Katsura River started operation from October, 1979 and the extension
of the sewerage systems is under way in Kyoto, Muko and Nagaokakyo cities and
Oyamazaki Town.
The sewerage project of the left bank basin of the Kizu River is also making
progress and the survey to complete the sewerage plan .for the left bank basin of
the Uji River is under way. Since the sewerage systems have been planned for most
all areas of Kyoto Prefecture along the Yodo River Basin, extensive construction
of the sewage works is expected soon.
At the present, water quality in the Yodo River remains on the same level,
so the construction of the sewage works on a larger scale is needed to further carry
out the improvement of water quality in the river, to achieve and maintain the
environmental standards in the future. The construction of the sewage works in
Kyoto City and other cities in the Yodo River Basin remains an urgent problem.
330
-------
Seventh US/JAPAN Conference
on
Sewage Treatment Technology
PRACTICAL APPLICATIONS FOR REUSE OF WASTEWATER
May 21, 1980
Tokyo, Japan
Takeshi Kubo
Vice President,
Japan Sewage Works Agency
331
-------
PRACTICAL APPLICATIONS FOR REUSE OF WASTE WATER
1. An Outline of Water Resources in Japan ..... ............. . 333
2 . Water Utilization and Future Demand ...................... 330
3. Future Demand and Supply Program for Water Resources ..... 3^
4. Strengthening the Water Quality Management Program
in the Basin .......................................... ...
Reuse
6.2 Problems to Be Examined and Studied in Direct Reuse
of Municipal Wastewater Effluents ...........
5 . Conservation of Water ............................ . ....... 351
6 . Reuse of Municipal Wastewater Effluents ........ ... ....... 358
6.1 Present Status of Municipal Wastewater Effluents
.358
1. Water Quality Standard for Direct Reuse ......... 360
2. The Economics of Direct Reuse of Municipal
Wastewater Effluents ___ .... ..................... 360
3. Energy Consumption in the Direct Reuse of
Municipal Wastewater Effluents ....... .......... . 361
4 . Water Rights .................................... 36!
5 . Psychological Problems Resulting from the Direct
Reuse of Municipal Wastewater Effluents ......... 362
332
-------
1. AN OUTLINE OF WATER RESOURCES IN JAPAN
Japan is a long and narrow island country in which 70% of the
land is mountainous and each river basin drainage area is relative-
ly small. For exanple, the longest river in Japan, the Tone River
is only 322 km in length. Most rivers flow rapidly from the moun-
tains to the sea. Rain water comes down and runs swiftly into the
sea. This process takes only a few days, and consequently the
water quality of rivers in Japan has been maintained quite well.
Historically, the Japanese people have enjoyed the nation's natural
beauty, describing it with phrases such as "purple mountains and
clean waters."
Under these circumstances the numbers of times water is reused
in the course of its flow downstream in the river basin is quite
small in comparison with water reuse in continental rivers.
Statistics calculated from data gathered for 18 years from
1956 to 1973 at 1,260 rainfall gauging stations located throughout
the country shows that average annual rainfall in .a normal year is
1,788 mm. It is 1,480 mm and 2,131 mm for dry and wet year respec-
tively. The total amount of annual rainfall over the nation's total
area of 377,484 km2 for normal, dry and wet years are 674.9 bil.m3,
558.7 bil.m3 and 804.4 bil.m3, respectively. If we subtract the
amount of evaporation loss from these figures we can calculate the
absolute maximum water resources available as shown in Table-1.
The annual loss of water due to evaporation is known to remain
at almost the same level every year, but it is also known that the
evaporation loss in mountain areas and in the flat areas differ.
The National Land Agency divides the availability of water re-
sources into the following three classes.
Class 1 Amount of rainfall in mountainous regions where water can
be stored in impounding reservoirs and maintained in good
quality for use downstream.
Class 2 Amount of rainfall in flat inland regions where water can
be used for agricultural irrigation and other purposes.
This water is less useful than that found in mountainous
regions.
333
-------
Class 3 Amount of rainfall in narrow coastal regions. This water
may possess the least utility.
Out of nation's total land area, the proportion of mountainous,
flat inland and coastal regions are respectively 70%, 18% and 12%.
The maximum available water resources in Japan can be divided into
three classes, as shown in Table-2. Judging from this data it can
be said that a fairly large amount of water (around 70%) is highly
available. We, however, must consider the regional distribution
of water, because the amount of maximum available water differs
from region to region.
When we look at the regional distribution of annual rainfall
(available), it varies greatly by region, as shown in Table-3 and
Fig. 1. Evaporation loss also varies by region according to
whether it is mountainous or flat, as shown in Table-4.
The major seasons with substantial rainfall in Japan differ
from region to region. Usually they are early summer (called the
Baiu season) and early autumn (called the typhoon season). But in
Hokkaido, Tohoku and Hokuriku on the Japan Sea coast, winter brings
heavy snowfalls. Actually there is no Baiu season .in Hokkaido
region. In the Tokyo area, 20% of the annual rainfall comes during
the typhoon season, with another 20% falling during Baiu season.
Both midsummer and winter are relatively dry. This means that rain-
fall is concentrated in short wet seasons. There is no constant
rainfall during the year. This makes it difficult to utilize water
resources effectively.
The maximum water resources available in each region can be
calculated by using data on the annual rainfall (available) and
evaporation loss, as shown in Table 3 and 4.
From the view point of water usage, the maximum water resources
available per capita can also be calculated. Particularly data in
a dry year may be useful. This is shown in Table-5.
334
-------
Table-1 Water Resources in Japan
Dry Year
Normal Year
Wet Year
Annual Rainfall
(mm)
1,480
1,788
2,131
Total Amount
of Rainfall
(bil.m3)
558.7
674.9
804.4
Maximum Available
Water Resources
(bil.m3)
333.3
449.4
579.1
UJ
Ul
Note: 1. Calculated from data gathered at 1,260 rainfall gauging stations throughout the country
during the 18 years from 1956 to 1973
2. Dry year: The year when the second lowest rainfall was registered during the 18-year period.
3. Normal year.- The 18 year average
4. Wet year: The year when the second highest rainfall was registered during the 18-year period.
Table-2 Availability Classification of Water Resources in Japan
Dry Year
Normal Year
Wet Year
Class 1
(bil.m3) (%)
236.9 71.1
310.8 69.2
394.4 68.1
Class 2
(bil.m3) (%)
58.1 17.4
81.9 18.2
107.6 10.6
Class 3
(bil.m3) (%)
38.3 11.5
56.7 12.6
77.0 13.3
Maximum Available
Water Resources . „
(bil.m3) (%)
333.3 100.0
449.4 100.0
579.1 100.0
-------
Table-3 Annual Rainfall (available) by Region in Japan
Region
Hokkaido
Tohoku (The Pacific Side)
Tohoku (The Japan Sea Side)
Kanto
Hokuriku
Tokai
Kinki
Chugoku
Shikoku
Kyushu
Okinawa
Whole Country
Annual Rainfall (available) (mm)
Dry Year
590
1,153
639
748
1,633
1,379
959
868
1,021
924
267
883
Normal Year
764
1,439
898
1,023
2,026
1,780
1,283
1,192
1,439
1,406
1,127
1,191
Wet Year
956
1,724
1,148
1,305
2,429
2,214
1,624
1,607
2,043
2,000
1,791
1,534
Table-4 Evaporation Loss by Region
Region
Hokkaido
Tohoku (The Pacific Side)
Tohoku (The Japan Sea Side)
Kanto
Hokuriku
Tokai
Kinki
Chugoku
Shikoku
Kyushu
Okinawa
Loss in Mountainous
Regions
(mm/year)
400
400
600
450
650
450
600
600
650
700
-
Loss in Flat
Regions
(mm/year)
560
560
840
630
910
630
840
840
910
980
980
336
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Fig. 1. Map of Japan by Region
Hokkaido
Kinki
Shikoku
Kan to
Chubu
Okinawa
337
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Table-5 Maximum Available rtater Resources per capita by Region
Region
Hokkaido
Tohoku (The Pacific Side)
Tohoku (The Japan Sea Side)
Kan to
Hokuriku
Tokai
Kinki
Chugoku
Shikoku
Kyushu
Okinawa
Whole Country
Population
(1,000)
5,184
6,176
5,216
32,776
2,776
11,778
17,402
6,997
3,904
12,071
945
104,665
Maximum Available
Water Resources
(bil.m3)
Dry Year
49.3
49.5
23.4
37.6
20.6
40.3
26.2
27.7
19.2
38.9
0.6
333.3
Normal Year
63.8
61.8
32.9
51.5
25.7
52.1
35.0
37.9
27.0
59.2
2.5
449.4
Wet Year
79.9
74.0
42.0
65.7
30.7
64.8
44.3
51.2
38.4
84.1
4.0
579.1
Maximum Available
Water Resources
(mVcapita)
Dry Year
9,510
8,015
4,486
1,167
7,421
3,422
1,506
3,959
4,918
3,223
635
3,185
Normal Year
12,307
10,008
6,308
1,549
9,258
4,424
2,011
5,431
6,918
4,904
2,645
4,294
Wet Year
15,413
11,982
8,052
2,039
11,059
5,502
2,546
7,317
9,836
6,967
4,233
5,533
CO
U)
00
-------
The maximum water resources available in a dry year for the
Kanto region (including the Tokyo Metropolitan area) is the lowest
in Japan, registering 1,167 m3/capita/year. The value of maximum
available water resources is a theoretical one. In reality, prac-
tical available water resources have been mainly limited by the
economic base.
Actually, water consumption in 1975 was estimated at about 90
billion cub. m. This corresponds to 27% of the maximum water re-
sources of 333.3 billion cub. m. available in a dry year.
When we consider that riverflow is reduced to less than one-
third the annual average maximum available water resources during
dry seasons, it can be said that this figure appears to be rather
a high value.
2. WATER UTILIZATION AND FUTURE DEMAND
In the utilization of water in Japan, the agricultural sector
has historically received.top priority and special concessions.
Because the staple food of the Japanese people has been rice and
paddy fields have been developed gradually throughout the country
since 200 B.C., particularly during the farming season sufficient
irrigation water has been demanded by farmers. But most agricultural
water has long been used in accordance with traditional practices
and, therefore, agricultural water consumption has not been fully
analyzed, as compared with other water uses.
The agricultural land in the suburbs of large cities has been
considerably reduced in the past twenty years because of the rapid
urbanization of these areas. Demand for-agricultural water usage
has been decreasing rapidly in these areas. But the demand for
municipal and industrial water has increased quickly in the same
period thanks to urbanization and industrialization.
339
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Urbanization has been swift. Structural change in industries
has occurred and at the same time population has commenced to move
from agricultural villages to cities. It is anticipated that this
trend will continue. As shown in Table-6, the population of urban
areas was 43.7% of the total population of Japan in 1960. This
figure increased to 48.1% in 1965 and 53.5% in 1970. National Land
Agency estimates that this figure will increase to 71.5% by the
year 2000.
According to this estimate by the National Land Agency, the
Ministry of Construction announced a survey of "Present and Future
Demand for Water". As shown in Table-7, this estimates water demand
by region. In 1975, 87.6 billion cub. m. of water was used
in Japan. Out of this figure, 12.3 billion cub. m. of water was
used for municipal purposes (14% of the total water used); 18.3
billion cub. m. was for industrial use (20.9%); and 57.0 billion
cub. m. was for agricultural use (65% of the total).
The estimate of future water demand in Japan by 1985 is 114.5
billion cub. m. Out of this figure, 18.7% is for municipal use,
25.6% is for industrial use and 55.7% is for agricultural use.
Municipal water demand has been stimulated by the rise in the
standard of living, urban population growth and larger city size.
This has led to an increase in per capita consumption, as shown in
Table-8. Municipal water demand is expected to continue growing
in the future. Water demand for industrial uses has increased
since 1960 as top priority was placed on heavy industry.
Most heavy industries have been located in coastal areas.
They have tried to draw their water from groundwater sources. From
around 1950 the utilization of groundwater for industrial purposes
increased sharply. But exessive drawing of groundwater, parti-
cularly for industrial purposes, has caused the following problems?
(1) The groundwater table in coastal industrial areas was lowered
and the groundwater itself was invaded by salt water flows.
(2) Land subsidence occurred on a large scale due to the exessive
drawing of groundwater.
340
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Table-6 Increase of Urban Population
1960
1965
1970
1975
1985
1990
2000
Total Population
(thousands)
93,419
98,275
104,665
110,940
123,749
128,272
136,899
Urban Population
(thousands)
40,830
47,261
55,997
63,823
79,942
86,327
97,883
Urban Population
Total Population
(%)
43.7
48.1
53.5
57.0
64.6
67.3
71.5
Growth Rate of
Total Population
(%)
1965/1960 1.02
1970/1965 1.27
1975/1970 1.35
1985/1975 1.01
1990/1985 0.72
2000/1990 0.65
Growth Rate of
Urban Population
(%)
1965/1960 2.97
1970/1965 3.45
1975/1970 2.65
1985/1975 2.28
1990/1985 1.55
2000/1990 1.26
-------
Table-7 Present and Future Demand for Water Resources in Japan
(billion cub. m./year)
Region
Hokkaido
Tohoku
Kan to
Hokuriku
Tokai
Kinki
Chugoku
Shikoku
Kyushu
Okinawa
Whole Country
Demand of Water Resources by Region
1975
Municipal
0.41 7
1.01 5
4.34 25
0.30 7
1.52 16
2.44 25
0.75 10
0.37 10
1.10 11
0.11 46
12.35 14
Industrial
1.23 21
1.88 10
3.39 19
1.09 23
3.72 40
2.66 27
1.77 23
0.99 26
1.52 16
0.03 12
18.28 21
Agricul-
tural
4.3 72
15.8 85
10.0 56
3.3 70
4.1 44
4.7 48
5.1 67
2.4 64
7.2 73
0.1 42
57.0 65
Total
5.94 100
18.69 100
17.73 100
4.69 100
9.34 100
9.80 100
7.62 100
3.76 100
9.82 100
0.24 100
87.63 100
1985
Municipal
0.91 11
1.97 8
7.50 31
0.75 10
2.55 19
3.71 29
1.34 14
0.67 14
2.05 16
0.19 46
21.46 19
Industrial
2.20 27
3.64 16
5.07 21
1.48 27
5.95 45
3.63 29
2.93 31
1.44 30
2.88 22
0.06 15
29.28 26
Agricul-
tural
4.98 62
17.53 76
11.49 48
3.51 63
4.75 36
5.29 42
5.24 55
2.73 56
8.10 62
0.16 39
63.78 55
Total
8.09 100
23.14 100
24.06 100
5.56 100
13.25 100
12.63 100
9.51 100
4.84 100
13.03 100
0.41 100
114.52 100
CO
-------
Table-8 Per Capita Water Supply by Population Size
Population
(1,000 person)
Over 1,000
500 '^ 1,000
250 ^ 500
100 ^ 250
50 ^ 100
10 ^ 50
5 ^ 10
Under 5
Per Capita Water Supply
2/capita/d
448
371
370
350
337
304
272
197
Note: Data are for 1974
Under these circumstances the Government took steps to control
groundwater by prohibiting the new construction of deep wells and
the expansion of existing deep well in specified areas. They pro-
moted the construction of public industrial water supply system.
Water was supplied to industries in these specified areas at a
comparatively cheap price. This was in compensation for the pro-
hibition on groundwater usage. The cost of water for industries
using public industrial water supply systems has been maintained
at a low level by financial assistance from both central and local
governments. Accordingly, these public industrial water supply
systems expanded in recent years.
But recently it has been becoming increasingly difficult to
secure new water rights for obtaining water from rivers, and more
effective utilization and conservation have been developed at
factories through the promotion of recycling. Reclaimed water from
municipal effluents also has been used.
The water demand for agricultural uses is still increasing
because the agricultural water supply and drainage network for paddy
fields has expanded to facilitate the introduction of large, agri-
cultural machinery. But requirements for agricultural water
throughout country have changed recently, as. shown in Table-7-
343
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3. FUTURE DEMAND AND SUPPLY PROGRAM FOR WATER RESOURCES
The Ministry of Construction constructed a survey of "Supply
Programs for Water Resources" in accordance with water demand by
region, as shown in Table-9.
Most regional supply programs were based on constructing dams
upstream in river basins. In recent years, it has become increas-
ingly difficult to develop these plans, and dam construction has
been delayed due to a decrease in appropriate dam sites and strong
opposition against dam construction arising from local inhabitants.
Consequently, water shortage areas, such as the large metropolitan
areas of Tokyo, Kyoto, Osaka, Kobe and Northern Kyushu, have been
forced to depend on unstable sources like the river basins of the
Tone, Yodo and Chikugo rivers.
In order to cope with this situation, further efforts to
encourage the public to conserve water, as well as the development
of dam construction and water recycling are expected.
Recently there has been a growing recognition in Japan of the
fact that water resources are limited just like oil and other
mineral resources and it is very important to learn how to use the
limited water resources and develop the technology for the recycl-
ing and reuse of wastewater. In this sense, we have to pay atten-
tion to the fact that effluents from municipal wastewater treatment
plants will increase in accordance with the development of sewage
collection systems. The construction of sewerage systems has been
progressing smoothly. Of course, it will take time to develop
further sewerage systems throughout the country, but it can be
clearly understood that when 40%, 70% and 90% pf the population are
provided with sewerage systems, we shall have another 3.62, 11.83
and 193.2 billion cubic meters per year respectively from sewage
effluents, as shown in Table-10. When we expect serious shortages
of water, particularly in the dry season, we shall have to evaluate
the value of municipal wastewater effluents and also recognize again
the increasing importance in municipal wastewater quality control.
344
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Table-9 Estimate of Water Demand and Supply in 1985 by Region
(billion cub. m/year)
Region
Hokkaido
Tohoku
Kanto Northern Kanto
Southern Kanto
Hokuriku
Tokai
Kinki Kyoto, Osaka, Kobe Area
Others
Chugoku Japan Sea Si'de
Seto Inland Sea Side
Shikoku
Kyushu Northern Kyushu
Others
Okinawa
Whole Country
Additional Demand
1.91
4.14
3.57
5.20
1.07
4.43
1.97
1.53
0.33
1.32
0.52
1.02
1.90
0.20
29.11
Possible Supply
2.27
4.46
3.80
4.51
1.24
4.70
1.66
2.02
0.38
1.55
0.71
0.80
2.15
0.21
30.46
Balance
0.36
0.32
0.23
A0.69
0.17
0.27
A0.31
0.49
0.05
0.23
0.19
A0.22
0.25
0.01
1.35
-------
Table-10 Estimate of Municipal Effluents by Region in Accordance
with the Development of Sewerage Systems
(billion cub. m/year)
Region
Hokkaido
Tohoku
Kanto Northern Kanto
Southern Kanto
Hokuriku
Tokai
Kinki Kyoto, Osaka, Kobe Area
Others
Chugoku Japan sea Side
Seto Inland Sea Side
Shikoku
Kyushu Northern Kyushu
Others
Okinawa
Whole Country
Population Sewered/National Population (%)
28
0.28
0.26
0.22
2.22
0.11
0.73
1.61
0.05
0.02
0.21
0.09
0.22
0.11
0.03
6.17
40
0.47
0.41
0.35
3.65
0.15
1.03
2.27
0.19
0.06
0.36
0.15
0.43
0.19
0.08
9.79
70
0.79
1.38
0.91
6.10
0.39
1.91
3.36
0.39
0.15
0.71
0.41
0.78
0.60
0.12
18.00
90
1.26
2.51
1.71
7.40
0.72
2.86
4.01
0.71
0.26
1.14
0.64
1.15
0.96
0.16
25.49
OJ
*»
CTi
-------
Table- I'l
Name of City
Hitachi
Takasaki
Kawaguchi
Funabashi
Mohara
Otsu
Ashiya
Kakogawa
Takasago
; Kurume
^
J lizaka
Tokyo
Tokyo
Tokyo
Tokyo
Tokyo
Kawasaki
Nagoya
Nagoya
Osaka
Kitakynshu
Kitakyushu
Fukuoka
Present Status of Direct Reuse of
Name of Plant
Ikenogawa
Jyonan
Ryoke
Nishiura
KawanakaJ ima
Otsu
Ashiya
Ogami
Takasago
Tsufuku
lizaka
Morigasaki
Sunamachi
Shibaura
Shibaura
MikawaJ ima
Iriezaki
Meijo
Sennen
Nakahama
Hiagari
Kogasaki
Tobu
Additional Treatment
Rapid Sand Filter
Microstrainer
Microstrainer
Microstrainer
Microstrainer
Microstrainer
Rapid Sand Filter
Rapid Sand Filter
Coagulation & Rapid
Microstrainer
Coagulation & Rapid
Rapid Sand Filter
Coagulation, Rapid
Wastewater Effluei
Process Cub.m/d
30
1800
770
5900
1000
500
100
1200
300
2600
550
980
Sand Filter 3600
UlO
Ib5
70310
15^17
20
Sand Filter33000
3500
5l»6l|
15700
Sand Filter lUOO
Purpose
Flush toilet
Dilution for Night Soil Treatment Plant
Washing water for Night Soil Treatment Plant
Dilution for Night Soil Treatment Plant
Pilot Plant of AWT
Spray Irrigation
Washing water for Night Soil Treatment Plant
Industrial water use
Dilution water for Night Soil Treatment Plant
ii
Coolig & Washing of Solids Incineration Plant
Industrial water
Washing Cars
Washing
Industrial water
Industrial water, cooling
Pipe cleaning
Industrial water, cooling, washing
Landscape Irrigation
Washing of Solids Incineration Plant
Industrial water
Industrial water
-------
4. STRENGTHENING THE WATER QUALITY MANAGEMENT PROGRAM IN THE BASIN
Surface water development in the major river basins in Japan has
been intense and additional dam sites for new development which are
economical and physically feasible have been harder to find. Parti-
cularly during the dry summer when increased demand makes water
levels harder to maintain in rivers, attention is now shifting to
the low flow itself. Emphasis has been on controlling municipal
and industrial pollution as the major causes of poor water quality
during the summer low flows, but the quantity and quality relation-
ship of surface water is not always adequately accounted for in
present water resources plans.
The situation on this matter in Japan is as follows:
According to the institutional structure in Japan, water policy
is administered by the National Land Agency. Water quantity is
planned by the Ministry of Construction and several other Ministries
are responsible for specified water utilization programs on agricul-
tural water (the Ministry of Agriculture and Forestry), drinking
water (the Ministry of Health and Welfare) and industrial water
(the Ministry of International Trade and Industry).
Water quality is under jurisdiction of the Environmental Agency
which is strongly oriented toward quality and sometimes is weak in
dealing with quantity issues. Water quantity issues are more or
less interrelated with water quality problems. Both quantity and
quality in most rivers in urban areas are influenced by human
activities and water quality may be at its poorest during the dry
summer when streamflow is low and temperature is high.
Water supply and wastewater treatment projects are separately
planned, financed and constructed at all levels, usually by dif-
ferent agencies. In a river basin indirect reuse through discharge
of an effluent to a river and withdrawal downstream is a common
practice and we should reemphasize the importance of interaction
among wastewater management alternatives and area-wide water
supplies.
348
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From the viewpoint of water resources, the integrated planning
and management of the quantity/quality of surface water should be
organized. Coordinated management approaches between corresponding
agencies for quantity/quality should be primarily considered, but
as a result of intense surface water resource development and
programs coordinated management approaches are generally hampered
by many different agencies at the government level, each having its
own different objectives for managing the same water resources.
Each agency may often overlook key interrelationships which may
result in mutual benefits.
The Comprehensive Basin Sewerage Plan of Sewerage Act 2-2 is
intended to be a comprehensive study of all point pollution sources,
leading to the development of a cost-effective plan to control
these pollution sources in order to attain environmental water
quality standards.
This study is to be coordinated between the Ministry of Con-
struction and the Environmental Agency. The provisions of the
Comprehensive Basin Sewerage Plan are; Sewerage Act Article 2-2
"Comprehensive Basin Sewerage Plan."
If rivers and other public bodies of water or coastal areas,
to which the ''environmental water quality standard" is applied to
maintain a sound living environment in relation to water pollution
as provided for Paragraph 1, Article 9 of the Basic Law for Environ-
mental Pollution Control (P.L. 132 of 1967), satisfy the require-
ments as specified by the Cabinet Order, each prefecture shall
present "a comprehensive basin sewerage plan" to the respective
public bodies of water or coastal areas for the purpose of bringing
the environmental conditions of the subject area in line with the
"environmental water quality standard."
In the "comprehensive basin sewerage plan," each of the follow-
ing items shall be specified clearly as stipulated by the Ordinance
of the Ministry of Construction:
1. Basic policy on the improvement of sewerage
2. Matters related to the area where the effluent should be dis-
charged and disposed of through a sewerage system
349
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3. Matters related to the location, structure and functions of
the basic facilities of sewerage systems in the area mentioned
in the preceding paragraph.
4. Matters related to the sequence of execution of actual sewerage
improvement works in the area specified by item 2.
The "comprehensive basin sewerage plan" shall be determined in
consideration of each of the following matters;
1. Topography, precipitation of the specified area, flow of the
river water and other natural conditions.
2. Prospective land use in the specified area.
3. Prospective water use in the subject water area for public use.
4. Prospective amount and quality of wastewater in the subject
area.
5. Location where the wastewater is discharged.
6. Cost-effective analysis related to improvement of the sewerage
systems.
In planning a "comprehensive basin sewerage plan" under the
provisions of paragraph 1, the prefectural governments shall listen
in advance to the opinions of prefectural and municipal officials
concerned and shall obtain approval from the Minister of Construc-
tion as specified by the Ordinance of the Ministry of Construction.
The Minister of Construction shall consult with the Administra-
tor of the Environmental Agency prior to giving the foregoing
approval.
In the event that a revision has been made on the environmental
water quality standard as provided for in paragraph 1, resulting in
changes of matters specified under each item of paragraph 3, and
other necessitating changes to be made in the "comprehensive basin
sewerage plan," the prefectural authorities shall make the necessary
changes on the "comprehensive basin sewerage plan" without delay.
In this case, provisions from paragraph 2 to the preceding paragraph
will be applied.
In the "comprehensive basin sewerage plan" coordination to
various plans on water problems is absolutely necessary.
350
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Consideration should be paid to expanding the scope of the
"Comprehensive Basin Sewerage Study" by requiring this study to
contain program areas which address:
1. Coordination of land use controls for nonpoint pollution sources
2. Water conservation (moderation of water demand) coordination
3. Recycling and reuse plan coordination
4. Agricultural irrigation water use plan coordination
5. Integrated quantity/quality program coordination
6. Low flow control plan and wastewater treatment plan coordination
7. Water supply and wastewater treatment plan coordination
8. Hazardous wastes disposal plan coordination
In these cases it is extremely important that hazardous wastes
such as organic poisons and heavy metals be prevented from entering
rivers and public sewers/ because these materials might easily pass
through conventional municipal wastewater treatment plants, and
hazardous wastes would impair the environmental water quality
standards. In any case, the "comprehensive basin sewerage plan"
should help to act as a go-between for water quality and quantity
plans.
5. CONSERVATION OF WATER
The term water conservation has been used so far to refer to
supply rather than demand control, but it also means reducing the
per capita demand on the municipal water supply. During the period
from May 20, 1978 to March 24, 1979 Fukuoka City in Northern Kyushu
experienced a ten month restriction in its water supply due to very
severe drought. It was the worst drought in ninety years in Nor-
thern Kyushu. In light of the severe drought during this period,
water conservation is very much on Fukuoka citizen's mind. Since
the drought the inflow to the municipal wastewater treatment plants
in Fukuoka City has been reduced as a result of a conservation
movement by Fukuoka citizens and the development of a line of water
saving fixtures. Conservation in the sense of demand control has
been receiving increased recognition as a desirable alternative in
351
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solving water shortage problems.
Over the long term, conservation by Fukuoka City could reduce
or delay the need to expand its water supply or wastewater treat-
ment facilities. If the City of Fukuoka wants to obtain additional
water rights to get more water, a large amount of funds would be
needed to expand existing facilities. Thus, water conservation is
an attractive policy for controlling water demand.
For the short term, however, in the absence of a phased program,
as a result of conservation throughout Fukuoka City the Fukuoka
Water Supply Department might have to raise rates to meet its finan-
cial obligations. Actually it is claimed by the Fukuoka Water
Supply Department that annual revenue would decrease due to a water
sales decrease and, consequently, water rate increases would out-
weigh savings from reduced water use. This is because public
water supply systems in Japan, as well as the Water Supply Depart-
ment of Fukuoka City, rely most frequently on the use of bonds to
finance not only operating expenses but also capital costs by
revenue from water sales. But we have to make another evaluation
from a different angle of energy savings on municipal conservation.
There is another way to promote conservation which may be
indicated in the case of City of Osaka. This case shows that when
considering the conservation of water, an increasing and progres-
sive sewer user charge system might be quite effective. In the
pricing structure for water use and wastewater there is a trend
toward either a fixed rate per cubic m. or an increasing and pro-
gressive rate per cubic m. in accordance with increasing demand.
A pricing structure carefully developed and applied to the different
classes of water use could be a fair and effective incentive for
reducing excessive water use or wastewater. Of course, a pricing
structure such as a rate system alone is not an adequate mechanism
to conserve water. It may be that public education can help to form
a concensus in conservation or be one of the incentives for encourag-
ing more effective conservation and selecting those who should
conserve.
352
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In the case of the City of Osaka, the increasing and progres-
sive sewer user charge system as shown in Table-11 was employed,
and also the sewer user charge system according to strength shown
in Table-12. As a result of application of these sewer user charge
systems, the water usage pattern in the City of Osaka has changed
significantly as shown in Table-13. The pollution load in terms
of BOD or COD and SS from industrial dischargers into public sewers
also has been dramatically reduced as shown in Fig. 2 and Fig. 3.
It is clear from Table-13 that yearly flow from monthly dischargers
of 10,001 cubic m. into public sewers have decreased year by year,
but flow from dischargers less than 50 cubic m. per month, that is
per average domestic sewage/family, have gradually increased year
by year. From Fig. 2, it can be said that the higher BOD loading
dischargers have been trying to reduce their BOD loads more effec-
tively in order to pay less in sewer user charges. This may be one
of the economic incentives for water conservation.
Table-11 The Change of Sewer User Charge System
by Quantity in City of Osaka
User Discharge
(Cubic m. per month)
Basic Rate up to 8 cub. m.
Basic Rate up to 10 cub. m.
Increasing Rate
10 ^ 20 cub. m. (per cub. m. )
-21 ^ 30
31 -v 50
51 -v 100
Over 101
101 ^ 200
201 ^ 500
501 ^ 1,000
Over 1,001
1,001 ^ 5,000
Over 5,001
1972
(yen)
50
70
10
15
16
17
18
18
18
18
-
18
18
1974
(yen)
50
70
10
15
16
17
-
20
25
30
-
40
40
1979
(yen)
-
100
20
27
30
35
-
40
50
60
-
80
90
353
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Table-12 The Change of Sewer User Charge System by Strength (BOD or COD, SS)
- Surcharge for Industrial Users - in City of Osaka
(Unit: yen per cub. m.)
Strength (mg/&)
201 ^ 300
301 ^ 450
451 '^ 600
601 ^ 850
851 % 1,100
1,101 ^ 1,350
1,351 ^ 1,600
1,601 ^ 1,850
1,851 '^ 2,100
2,101 ^ 2,350
2,351 % 2,600
1973
BOD (COD)
2
6
6
13
13
23
23
33
33
42
42
SS
2
7
7
16
16
27
27
38
38
49
49
1974
BOD (COD)
4
13
13
28
28
50
50
72
72
91
91
SS
5
16
16
36
36
61
61
86
86
110
110
1977
BOD (COD)
8
18
30
46
66
86
106
126
146
166
186
SS
9
21
35
55
79
103
127
152
176
200
225
UJ
U1
-------
Table-13 Change of Sewage Discharge due to Increasing Sewer User Charge System
in City of Osaka
User Discharge
(cub. m. per month)
0 ^ 50
51 ^ 1,000
1,001 ^ 10,000
Over 10,001
Total
Sewage Discharge cubic meter per annum
1973
cub. m.
187,986
124,725
74,308
135,612
522,631
%
36.0
23.9
14.2
25.9
100.0
1974
cub . m.
196,506
113,828
67,008
120,177
497,519
%
39.5
22.9
13.5
24.1
100.0
1975
cub. m.
209,478
118,511
69,905
109,493
507,387
%
41.3
23.3
13.8
21.6
100.0
1976
cub. m.
216,270
113,847
67,521
98,121
495,759
%
43.6
23.0
13.6
19.8
100.0
1977
cub. m.
223,403
115,600
67,725
85,192
491,920
%
45.4
23.5
13.8
17.3
100.0
OJ
Ln
Ln
-------
Fig. 2 The Impace of Sewer User Surcharge System
by Strenth, BOD or COD in the City of Osaka
Year
1973
20JA300
mg/£
(4,591.25)
30r-600
mg/l
(5,962.05)
1974
1975
1976
1977
(Unit: ton/year)
24,831.30
2,101^2,600 ing/2,
(1,786)
1,601^2,100 mg/£.
(555)
1,101^1,600 mg/i-
(558.9)
601^1,100 mg/Jl
(11,378.10)
19,294.25
(1,354.05)
(305.25)
(1,135.05)
(3,040.45)
14,465.15
(537.30)
(140.60)
(401.85)
(2,564.45)
14,016.10
(646.65)
(495.80)
(759.05)
(2,476.05)
12,544.20
(836.28)
(717.61)
(585.40)
(1,969.35)
356
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Fig. 3 The Impact of Sewer User Surcharge System
by Strength, SS, in the City of Osaka
Year
1973
60rVL,lOO mg/i
(760.75)
(Unit: ton/year)
13,028.30
2,101^2,600 mg/2.
(937.65)
_ 1,101^1,600 mg/2,
(294.3)
201^300
mg/£
(2,507.25)
301^600 mg/i
(4,905)
1,601^2,100 mg/1
(3,683.35)
1974
(2,469.25)
1975
(1,704.50:
(1,935)
1976
1977
(4,292.10)
(2,803.10)
(2,127.50)
4,187.45
(51.7)
(239.7)
(171.45)
(85.1)
5,156.70
(404.60)
(218.70)
(70.30)
(35.25)
(135.75)
3,563.47
(383.78)
(254.43)
(1.73)
(17.33)
(103)
8,038.35
(418.50)
(973.35)
(1,Q52.30)
(997.65)
357
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6. REUSE OF MUNICIPAL WASTEWATER EFFLUENTS
6.1 Present Status of Municipal Wastewater Effluents Reuse
Total municipal wastewater discharge in Japan amounted to 6.17
billion cubic meters per day in 1978 and will eventually amount to
25.5 billion cubic meters per day. This will become a dependable
and stable source of relatively high-quality water. In comparison,
approximately 0.73 million cubic meters per day of municipal waste-
water effluents are directly reused in 201 projects for various
purposes by municipal wastewater treatment plants. Purposes include
washing, cooling, pump sealing, defoaming etc. through treatment
processes at the sites. About 0.16 million cubic meters per day
are directly used in 22 projects, mostly for agricultural and land-
scape irrigation and for industrial cooling purposes primarily in
the water-scarce areas shown in Table-14.
These figures show that direct reuse of municipal wastewater
effluents at this moment is a very small portion of the total muni-
cipal wastewater discharge in Japan. Each of the examples in
Table-14 is a classic example of municipal wastewater effluent reuse.
These reuse projects have been conducted as pioneering work. Thus,
their main significance might be as a precedent for future reuse
projects.
Direct reuse of municipal wastewater effluents should be care-
fully considered. This involves a pipeline or similar conduit,
frequently including pumping from the plant to the user. Direct
reuse is limited to specific locations and requires site analysis
of technical, economic alternatives according to the local condi-
tions and the importance of allowing local conditions to determine
the system most suited for each situation. Direct reuse of munici-
pal wastewater effluents appears to offer additional potential to
ease the competition for water through its application to such
nonpotable users as agricultural and landscape irrigation and in-
dustrial uses. A huge amount of water has been applied to paddy
fields in Japan, as mentioned above, and some experiments in the
direct reuse of municipal wastewater effluents for agricultural
358
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irrigation to .paddy fields have been going on in several sites pay-
ing particular attention to nitrogen content in the effluents.
Water reuse for agricultural irrigation would be reasonably attrac-
tive and economical in some parts of Japan.
In promoting the reuse of municipal wastewater effluents,
viruses and new toxic chemicals require additional research even
before they can be indirectly reused in municipal wastewater ef-
fluents. Direct reuse of municipal wastewater effluents for the
drinking water supply cannot be considered at this moment in Japan.
Further research and experimentation are absolutely requried to
provide additional assurance on the safety and health effects.
But direct reuse of municipal wastewater effluents can provide a
mechanism for obtaining drinking water supplies from other uses by
exchanging and substituting treated reclaimed municipal effluents.
This means that the exchange of water rights among different water
right owners through a mechanism of reuse systems would be expected,
Reuse means here use of municipal wastewater effluents for
some nonpotable purposes. Such reuse is already widespread for
indirect reuse, wherein municipal wastewater discharged to a river
by one user is withdrawn downstream by another. Thus, downstream
water-users such as water supply, agricultural and industrial users
are quite often involved in the water usage cycle in a river basin
and wastewater may be put through several cycles of indirect reuse
in the river basin. The Water Supply Department of Kyoto City has
been drawing water for drinking purposes from Lake Biwa, located in
the Yodo River Basin. After usage, Kyoto's wastewater effluents
have been discharged downstream in the same Yodp River. The major
water source of the Tokyo Metropolitan Water Supply Department has
been taken from the Tone River. Almost all local municipalities in
Gunma Prefecture are located upstream on the Tone River. Their
wastewater has been discharged directly into Tone River and with-
drawn downstream for drinking purposes in the Tokyo Metropolitan
area. Indirect reuse of municipal wastewater effluents through
discharge of an effluent to a river and withdrawal downstream, is
359
-------
recognized*to be so important that the complexities of reuse also
need to be recognized and evaluated.
6.2 Problems to Be Examined and Studied in Direct Resue of Munici-
pal Wastewater Effluents
1. Water Quality Standard for Direct Reuse
There is no water quality standards for direct reuse of muni-
cipal wastewater effluents in Japan. There is still significant
potential uncertainty relating to the health effect associated with
some types of direct reuse of municipal wastewater effluents.
Examples include the irrigation of food crops, contamination of
groundwater sources used for drinking water and recreation, and the
degree of treatment needed to avoid health risks. Advanced waste
treatment and disinfection may be desirable for these purposes, but
it appears that at least secondary treatment and disinfection may
be required for direct reuse of municipal wastewater effluents for
these purposes. This is mainly due to economic considerations.
2. The Economics of Direct Reuse of Municipal Wastewater Effluents
The economics of direct reuse of municipal wastewater effluents
is a major factor which will limit the extent of its implementation.
Foremost is cost of reuse in relation to the cost of other sources
of supplies and alternatives to additional supply, as well as the
cost and high energy use of the technology itself in the case of
advanced waste treatment. Both capital and operational expenditures
for direct reuse of municipal wastewater effluents tend to be high.
Transportation and storage of reclaimed effluents are usually
required. Pipelines often containe pumping systems wihich may
increase transportation costs. The economics associated with
advanced waste treatment processes include the high cost of con-
struction and operation, large requirements for energy and chemicals,
and the increased amount of sludge produced in advanced waste treat-
ment processes which require disposal.
If we consider the competition from alternative sources,
existing municipal water supplies and public industrial water
360
-------
supplies in Japan can often be provided at less expense than would
be required for direct reuse of municipal wastewater effluents.
This is because existing municipal water supplies and public
industrial water supplies usually come from relatively open sources
which were developed at pre-inflation prices many years ago.
Public industrial water supplies are financed by a grant and loan
system in compensation for the prohibition of groundwater pumping
as mentioned above.
One of the problems for direct reuse of municipal wastewater
effluents is the primary market for municipal wastewater effluents.
Reuse for agricultural irrigation, which may be quite attractive,
is often found among users least willing to pay for water. Some-
times such water is free for historical reasons. when a reuse
project is analyzed, its desirability is strongly affected by the
magnitude and source of financial assistance, such as grants and
loans from federal government. Thus water economy problems should
be reconsidered more carefully.
3. Energy Consumption in the Direct Reuse of Municipal Wastewater
Effluents
The potential need for treatment and transportation may make
municipal wastewater effluent reuse projects relatively energy
consumptive. Energy implications must be evaluated and technologi-
cal developments to save energy are also needed in this field.
Energy problems in Japan will become more severe in the future.
4. Water Rights
The right to use water has certain attributes of the property
right. Water rights for river water should be obtained by permis-
sion of each corresponding river authority. This is determined by
River Law, but many water rights concerned with existing agricul-
tural irrigation are sometimes uncertain and historically prescrip-
tive. Reuse is possible if it allows increased riverflow and/or
reduced discharges and hence reduced river flow but improved river
water quality. Reuse, therefore, can provide a mechanism for
adjusting water rights among various water right owners by exchang-
361
-------
ing or substituting treated reclaimed effluents. This mechanism
will be explored in more detail in the future.
5. Psychological Problems Resulting from the Direct Reuse of
Municipal Wastewater Effluents
There are many examples which involve the psychological in-
ability to accept the direct reuse of municipal wastewater effluents
due to lack of scientific consensus on the degree of treatment need-
ed to protect against risks to health.
Public educations and the acceptance of municipal wastewater
effluents in relation to reuse are sometimes emotional and volatile
issues, but the importance of these psychological problems must not
be neglected and public education on the scientific aspects of
water reuse may be necessary to overcome them.
362
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UNITED STATES PAPERS
MUNICIPAL TREATMENT REQUIREMENTS AND PRACTICES TO MAINTAIN
WATER QUALITY IN THE TAMPA AND ESCAKBIA BAY AREAS
Howard L. Rhodes, Division of Environmental Programs,
Florida Department of Environmental Regulation, Tallahassee
INSTRUMENTATION AND AUTOMATION CONTROL OF MUNICIPAL SLUDGE
TREATMENT FACILITIES ......... .
Irwin J. Kugelraan, Municipal Environmental Research
Laboratory, ORD, T:S3PA, Robert C. Polta, Ph.D., and
Don Stulc, Metropolitan Waste Control Commission, and
George A. Mathes, EMA, Inc., St. Paul, Minnesota
IMPACT OF INNOVATIVE AND ALTERNA TIVE TECHNOLOGY IN THE UNITED
STATES IN THE 1980's ........................................... 515
John M. Smith and Jeremiah J. McCarthy, Municipal Environmental
Research Laboratory, ORD, USEPA and Henry L. Longest II,
Office of Water Programs, ORD, USEPA
PARALLEL EVALUATION OF BELT FILTER PRESSES AND LOW SPEED
SCROLL CENTRIFUGES ............................................. 579
Walter E. Garrison and Robert W. Horvath, Los Angeles
County Sanitation Districts, Whittier, California
THERMAL CONVERSION OF SLUDGE IN A MULTIPLE HEARTH FURNACE,
USING A SUB-STIOCHIOMETRIC SUPPLY OF OXYGEN .................... 60?
Joseph B. Farrell, Municipal Environmental Research
Laboratory, ORD, USEPA
OCCURRENCE AND REMOVAL OF TOXICS IN MUNICIPAL WASTEWATER
TREATMENT FACILITIES ........................................... 633
John J. Convery, Jesse M. Cohen and Dolloff F. Bishop,
Municipal Environmental Research Laboratory, ORD, USEPA
HEALTH EFFECTS RESEARCH ASSOCIATED WITH MUNICIPAL WASTEWATER
TREATMENT AND SLUDGE DISPOSAL ............... A .................. 70?
Herbert R. Pahren, Health Effects Research Laboratory,
ORD, USEPA
363
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MUNICIPAL TREATMENT REQUIREMENTS AND PRACTICES TO MAINTAIN
WATER QUALITY IN THE TAMPA AND ESCAMBIA BAY AREAS
by
Howard L. Rhodes
Division of Environmental Programs
Florida Department of Environmental Regulation
2600 Blair Stone Road
Tallahassee, Florida 32301
OFFICE OF RESEARCH AND DEVELOPMENT
WASTEWATER RESEARCH DIVISION
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
365
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ABSTRACT
This paper was written with the objective of showing the
relationship of regulation of sewage works to the maintenance
or improvement of water quality in the receiving body of water.
Two Florida estuaries were examined in this report, Tampa and
Escambia Bays.
Reviews of past data and regulatory schemes that led to
upgrading sewage treatment works were made for comparison pur-
poses with the state of the environment today.
These reviews led the author to conclude that as important
as sewage discharges are to water quality in estuaries, problems
were caused by other activities of man that had as much, if not
more, impact on water quality- These activities included indus-
trial discharges, dredge and fill operations, and non-point
source discharges. Each appears to have a synergistic effect
on water quality in estuaries. Thus, each will have to be
addressed to solve the water quality problems of the past.
Based on data today, Escambia Bay is very slowly recovering
from pollution of the 1960's. Tampa Bay is also showing marginal
signs of improvement. Regulatory action in the municipal, indus-
trial, drege and fill and non-point source sectors have together
begun to positively impact water quality in these systems.
366
-------
ACKNOWLEDGMENTS
This paper could not have been compiled without the
computer assistance of Scott Schomer and Joe Hand. Landon
Ross provided assistance in gathering biological data and
evaluating it. Troy Mullis compiled information on municipal
sewage treatment plants and Ms. Diane Hunt researched the
historical background. Particular thanks is given to Ms. Pat
Kennedy for typing drafts, putting together the final document
and insuring that details of the paper meshed.
Special thanks is given to Howard Curren of the Tampa
Sewer Department; Vincent Patton, Public Works Director, City
of St. Petersburg; William Johnson, Chief Operator, Hillsborough
County River Oaks Plant; Quentin L. Hamptom, Consulting Engineer
for the Cities of Largo and Belleaire; and, William H. Palm,
Consulting Engineer for Palmetto.
367
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SECTION 1
INTRODUCTION
In the mid 1960's, the State of Florida encountered numer-
ous instances of environmental problems including fish kills,
eutrophication, accelerating growth of water weeds, turbidity,
bacterial increases and loss of aquatic habitat. In response
to the increased environmental awareness by the public of the
State, the Florida Legislature created the Florida Air and Water
Pollution Control Commission.
This Commission saw the solution to the pollution problem
as being the control and containment of point source discharges
both municipal and industrial. This strategy was followed for
the two years the Commission was in existence. The successor
agency was the Department of Pollution Control in 1969. This
agency existed until a reorganization occurred in 1975 combining
it into the Florida Department of Environmental Regulation
(FDER) .
These agencies were mandated by the State Legislature to
require secondary treatment of sewage and industrial waste by
January 1, 1973. This was defined by an administrative rule to
be 90 percent removal of pollutants in 1969. The defacto policy
of the Commission and the Departments was to bring about the
treatment of wastewater as expeditiously as possible. Imple-
mentation of this policy did not in fact allow for a cause-
effect relationship to be established between discharges and
water quality. Monitoring that would have shown the impact of
this policy was not implemented. Raw or primary discharges were
to be cleaned up as a matter of public policy as soon as
possible. Later, in 1972, federal law and policies reinforced
this policy and little cause/effect was demonstrated nor
improvements monitored.
For industry, this policy led to voluntary compliance with
administrative orders, consent orders and court orders. Most
of the industry was very compliant and worked to achieve the
secondary standards in 1972 and 1973. By the end of 1975, most
industries had attempted to comply with the secondary standard.
Municipal compliance was another issue, however. The U.S.
Congress was debating the Water Pollution Control Act during
1971-1972 until its final enactment in October 1972. Provisions
were being made to provide for construction grants for municipal
368
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facilities somewhere in the range of 50 and 80 percent of con-
struction cost. A figure of 75 percent was finally selected.
For a three year period, there was a virtual standstill in new
construction that would solve municipal point source problems
because municipalities waited for federal grant dollars. In
retrospect, it could be reasonably argued that more would have
been accomplished if no grants had been available. This issue
is debatable though and it might be true that without the grants
less would have been achieved because every regulatory decision
would have been more closely scrutinized. At any rate, using
this grant program, nearly all 1980 Florida dischargers will be
capable of providing secondary treatment or better.
Sewage treatment was subjected to special requirements in
two areas of the State. Two separate areas of the State had
special water quality problems and special events happened that
pushed these two areas of the State toward treatment above sec-
ondary into advanced treatment for surface water dischargers.
Responding to constituency desires, numerous water quality
problems and a common belief that secondary treatment was inad-
equate in the Tampa Bay system and other bays of west-central
Florida, two State Legislators decided to file a regional bill
to require a minimum treatment for municipal waste of the highest
order, i.e. Advanced Waste Treatment (AWT). AWT was later de-
fined by administrative regulation to be effluent standards of:
Biochemical Oxygen Demand (BOD) - 5 mg/1
Suspended Solids (SS) - 5 mg/1
Total Nitrogen (TN) - 3 mg/1
Total Phosphorus (TP) - 1 mg/1
This regional bill defined a specific geographic area. This
geographic area's population was thus required to pay more for
sewage treatment than other people in the State.
This bill's passage was not so much that water quality was
bad, since that fact was well recognized, but another ramifica-
tion. The bill's passage was caused by the environmental polit-
ical atmosphere of the times, by a strong crusade of environ-
mental organizations in the Tampa Bay area and by pleas from a
local Girl Scout group. This Girl Scout organization did not
want secondarily treated sewage discharging into the ocean pass-
ing 3-8 kilometers from the camp. Emotionalism and the spirit
of the times made a bill of this nature hard to oppose. Thus,
with the passage of a single bill, AWT was required for all bays
in west-central Florida.
Water quality studies done before this law were only mar-
ginally considered in its adoption. Water quality problems
existed before, during and after the law's passage. Cause-
369
-------
effect relationships were speculated on but they did not form
the basis of the statute.
In retrospect, there is doubt that water quality would ever
have improved if a cause-effect relationship had to first be
proven. The fast growing area would most likely have only fur-
ther damaged the water quality with secondary treatment. The
estuary systems are far too complex to solve with simple answers.
Even today the exact cause of some of the water quality problems
are not fully understood. As proven in the United States for a
period of forty years, water quality standards alone did not
control pollution. Regulatory practices in the United States
were targeted in the 1940's, 50's and 60's to cause-effect water
quality solutions. They did not work. It took a uniform tech-
nology standard to clean up many waterways. This does not imply
though that water quality studies cannot be used to refine the
degree of treatment or the pollutants removed but these studies
are not exact sciences and the legal profession can create nu-
merous roadblocks to effective regulation in such an atmosphere.
The other special requirement came about as a result of
massive fish kills in Escambia Bay in 1969-1971. The Governor
of Florida in August 1969 demonstrated to the citizens that he
was doing something about the problem by calling on the Federal
Water Quality Administration to convene a Federal-State Enforce-
ment Conference. The purpose of such a conference was for state
and federal enforcement officials to ascertain the,cause of the
fish kills as best they could and recommend corrective actions.
The recommendations were for all industries and the municipality
to provide very high levels of treatment prior to discharge into
the Escambia Bay. Also, further dredging was prohibited and a
physical obstruction (an abandoned railroad tressel) was recom-
mended to be removed.
The industries complied with the subsequent consent orders,
the tressel was removed and the dredging stopped; however, the
municipality was caught up in an array of problems, including
passage of the 1972 Water Quality Law. At first the City of
Pensacola was to provide this same high level of treatment to
its Northeast Sewage Treatment Plant (STP), as was required by
the industries. Later, the City proposed connecting to the
Pensacola Main Street Plant. On March 2, 1973, the U.S. Envi-
ronmental Protection Agency (EPA) wrote a letter containing the
following excerpt to the area regional planning council.
"2. Determining the impact of waste
discharges — specifically that of the
Pensacola Main St. Plant—was addressed
by the Technical Advisory Committee.
The professionals listed in the minutes
of those meetings acknowledged the
limitations of mass balance calculations
370
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such as the ones performed by both
project consultants and EPA. Based
on available data and their judgment,
it was agreed that changing water
quality had degraded biological and
aquatic productivity in the Bay system
and there was sufficient evidence of
a sensitivity to nutrients. A
simplified dissolved oxygen analysis
therefore was concluded to be incapable
of providing the full range of consid-
erations relevant to water quality
enhancement in Pensacola Bay. It
was recognized that expansion of
a 9 MGD [3.4X104 m3/day] facility
to 18 MGD [6.8X1Q4 m3/day] while
maintaining 90 percent BOD5 removal
would ultimately double wasteloads
to the Bay. Clearly, neither
maintenance nor enhancement could
result from an overall increase in
wasteloads. Within the context of
enhancement and non-degradation,
the TAG concluded that no additional
wasteloads should be discharged from
the Pensacola Main St. Plant. Any
expansion, therefore, would require
higher degrees of treatment commen-
surate to the load constraints of
the present discharge."
Several water quality studies were made before and after these
decisions. An exhaustive three year study was made by EPA
shortly after the above letter was written and it did not show
any significant new findings. There continued to be support for
the decision not to increase the mass loadings to the Bay. Thus,
the future expansion had to be a higher degree of treatment than
secondary. The City of Pensacola then proposed AWT of BOD-5 ppm,
SS-5 ppm, TN-3 ppm and TP-1 ppm. This proposal was accepted by
the regulatory agencies and a 7.56X104 m3 day AWT Plant ultimately
constructed. Cooperation between the City and the regulatory
agencies was good until seven years later when the City pro-
tested the level of treatment. To this day, the issue is not
fully resolved to everyone's satisfaction.
Thus, with both of these special requirements came manda-
tory decisions to provide AWT for municipal dischargers into
the Escambia and Tampa Bay systems. The Tampa Bay system has
had extensive modelling in subsequent years, but it still does
not tell what cause-effect relationships exist. Modelling of
the Escambia Bay system has not been done and there are ques-
tions whether it can be economically done with the present state
371
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of the art techniques. Conclusions regarding the effectiveness
of these arbitrary pollution methods will be explored later. In
the following pages a comparison is made between past conditions,
what has happened and what is the present status of municipal
treatment and water quality in Escambia and Tampa Bays.
372
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SECTION 2
ESCAMBIA BAY
PHYSICAL CHARACTERISTICS AND HISTORY
The Escambia Bay system is comprised of three bays, Escambia
Bay, Pensacola Bay and East Bay. These Bays are influenced by
the Gulf of Mexico and Santa Rosa Sound. Escambia Bay is the
system most impacted by pollution problems. This area's average
temperature is 20 °C and receives an annual rainfall of 152 centi-
meters per year. The surrounding topography ranges from gentle
sea level slopes to heights of 33 meters above sea level.
Escambia Bay ranges in depth from .3-7 meters, averaging
2.5 meters at mean low water. The surface area of the Bay is
10,000 hectares with a 33 meter wide navigation channel trav-
ersing the Bay north to south at a depth of ten feet. The
maximum freshwater flow of the Escambia River is 2.09x10^
and the minimum is 1.61x10^- m^
Tidal effects consist of one high tide and one low tide
daily with a tidal range of .5 meters. 18.8 percent of the Bay
volume is potentially exchanged every tidal cycle due only to
tidal effects. The displacement time for freshwater to replace
the full volume of the Bay is 18 days and 3.2 days depending on
flow. Assuming complete mixing, 5.3 days would be required to
completely flush the Bay volume by tidal exchange alone. Physi-
cal displacement time at low river flow is 92 days, at mean
annual discharge 18 days and high river discharge 1.6 days.
The northeast section of the Bay has poor tidal exchange
and the discharge of the Escambia River discharging to the south
east hinders total exchange of the saline water flowing north-
ward in the upper Bay. Thus, a short-circuiting effect occurs
in the northeast section of the Bay where the industrial dis-
charges occur. (See the following four graphs for current
patterns at high and low flows: Figures 1, 2, 3, 4.)
Over the years, Escambia Bay has suffered an estimated 80
percent decrease in fishing value since 1952. The Bay suffered
20 fish kills in 1969, 75 fish kills in 1970, approximately 70
fish kills in 1971 and a massive oyster kill in 1971. (See
Table 1 for relative size of fish kills.) It was shown that
disease caused the kills; however, there is reason to believe
that the oysters had been stressed by pollution, dredging and
373
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ESCAMBIA BAY CURRENT PATTERNS
FLOODING TIDE
JUNE, 1970
Red Bluff
Northeast S.T.P.
Bohemia
Surface Currents
Bottom Currents
Figure 1. Escambia Bay Current Patterns - Flooding Tide - June, 1970
374
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Monsanto
ESCAMBIA BAY CURRENT PATTERNS
EBBINGTIDE
JUNE, 1970
Floridatown
Air Products
American Cyanamid
Bohemia
Surface Currents
Bottom Currents
Figure 2. Escambia Bay Current Patterns - Ebbing Tide - June, 1970
375
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ESCAMBIA BAY CURRENT PATTERNS
FLOODING TIDE
SEPTEMBER 1969
Figure 3. Escambia Bay Current Patterns - Flooding Tide - September, 1969
376
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ESCAMBIA BAY CURRENT PATTERNS
EBBING TIDE
SEPTEMBER, 1969
Red Bluff
Northeast S.T.P.
Bohemia
Surface Currents
-^ Bottom Currents
Figure 4. Escambia Bay Current Patterns - Ebbing Tide - September, 1969
377
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TABLE 1.
FISH KILLS - MULAT/MULATTO BAYOU
Date
June 21,1970
June 29, 1970
July 1, 1970
July 5, 1970
July 7, 1970
July 12, 1970
July 13, 1970
July 27, 1970
August 25, 1970
September 28, 1970
Octobers, 1970
August 12, 1971
August 22, 1971
September 12, 1971
September 15, 1971
Estimated Number
Killed
250,000
750,000
2,000
Over 1 Million
Over 10 Million
10,000
2,500
One Million
500-700
One Million
200,000
Over 1 Million
Over 2 Million
Over 1 Million
OverS Million
378
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Polychlorinated Biphenol (PCB) contamination and were most sus-
ceptible to disease. In 1971, virtually every organism taken
from the water had PCB residues. Sediments even today contain
PCB residue. Marine grasses were reduced by roughly 70 percent,
apparently by pollution, dredging and filling and shoreline
alterations. Shrimp production decreased during the period.
A fish camp operator stated in 1970 that he bought $500
worth of live shrimp for use as bait for speckled trout, red
fish and flounder per year. Five to seven years previously he
was purchasing $10,000 worth of shrimp per year. His boat
rental records show similar declines.
The Federal-State Enforcement Conference occurred in late
1969 with several conclusions, the most important of which were:
(1) point source discharges were to remove 94 percent of the
carbonaceous material, 94 percent of the nitrogenous material
and 90 percent of the phosphorus, and virtually all settleable
solids: (2) no further dredging in the Bay until a plan was
established to handle dredged material on upland disposal sites;
and (3) the abandoned railroad tressel was to be removed.
The relative contribution of industry and the Northeast STP
for each constituent is shown in Figures 5, 6 and 7. As can be
seen, BOD was more a function of industry and was relatively
small for sewage. However, with regard to phosphorus and Total
Kjeldahl Nitrogen (TKN), the sewage treatment plant made major
contributions. Table 2 shows the final loads allowable under
the Enforcement Conference recommendation.
These recommendations were based primarily on levels of
carbonaceous, phosphorus and nitrogen that appeared to cause
problems in similar waters or in experimental work. Thus,
levels of unstabilized carbon of 0.26 mg/1, nitrate nitrogen
of 0.03 mg/1 and 0.01 mg/1 were set as targets based on unpol-
luted waters to bring pollution in Escambia Bay under control.
Industry, under consent orders with the State of Florida,
began to clean up their discharges. Some regulatory action has
continued but initial efforts were satisfying.
The Northeast STP had similar pollutant removal require-
ments as those recommended for industry. The City has chosen to
combine sewage plants and provide AWT. Likewise, the City
decided to help clean up interior tributaries flowing through
the City to the Bay because of tributary pollution problems
caused by package plants within the City. These smaller STP
flows were transmitted to the main plant via interceptor trunk
lines, thus moving all sewage discharges to a single point.
Federal grant dollars were used to centralize the discharges and
to build the AWT Plant. This single AWT Main Street Plant is
379
-------
Container Corp. of America
44,530 P.E.
ALABAMA
"FLORIDA
SCALE
6.45 Square Centimeters = 25,000 P.E.
American Cyanamid Co. rW
26,710 P.E. -N-
FIVE DAY B.O.D. WASTE SOURCES
ESCAMBIABAY
Figure 5. Five Day B.O.D. Waste Sources — Escambia Bay
380
-------
BREWTON
Container Corp. of America
20,300 P.E.
ALABAMA
FLORIDA
SCALE
6.45 Square Centimeters = 50,000 P. E.
Northeast S.T.P.
69,040 P.E.
American Cyanamid Co.
170,440 P.E.
-N-
/TOTAL KJELDAHL NITROGEN WASTE SOURCES
ESCAMBIA BAY
Figure 6. Total Kjeldahl Nitrogen Waste Sources - Escambia Bay
381
-------
BREWTON
Container Corp. of America
18,300 P.E.
ALAJ3A MA ESCAM m A
FLORIDA ESCAMBIA co
SCALE
6.45 Square Centimeters = 20,000 P.E.
CO
SANTA ROSA CO
Air Products
30,040 P.E.
-N-
^American Cyanamld Co.
370 P.E.
/' TOTAL PHOSPHORUS WASTE SOURCES
ESCAMBIA BAY
Figure 7. Total Phosphorus Waste Sources - Escambia Bay
382
-------
GO
oo
TABLE
SOURCE
American
Cyanamid
Container
Corp.
Escambia
Chemical
Monsanto
Northeast
STP
TOTAL
BOD =
TOC =
TKN =
2. ALLOWABLE WASTE DISCHARGE LOADING FOR MAJOR SOURCES OF POLLUTION
CARBONACEOUS
5- Day
BOD TOC
425 500
2230* 3120*
17 12
605 282
137 39
3414 3953
biochemical oxygen demand
total organic nitrogen
total Kjeldahl nitrogen
NITROGENOUS PHOSPHORUS
TKN NH3-N N02NO3-N Total Ortho
249 32 42 -
30 12-17 8
197 137 143 35 35
102 66 80 46 29
101 84 - 23 12
679 331 265 121 84
NH3-N = ammonia nitrogen
N02, N03-N = nitrite-nitrate nitrogen
* The contribution to Escambia Bay from this effluent will be 450 pounds per day of five-day BOD and 625
pounds per day of TOC.
-------
now nearing operational status. Figure 8 shows the location of
the unconsolidated facilities.
The AWT Plant in Pensacola, Florida is a physical-chemical
treatment process. The plant receives industrial waste and is
designed to treat both domestic and industrial waste. It should
become operational within the next eight months.
CHEMICAL WATER QUALITY
Substantial water quality data was acquired in 1969. This
1969 data shows the state of water quality during the fish kills.
TKN was at maximum concentrations in the northeast section of the
Bay in the vicinity of the industrial outfalls. The surface
value in this area was 1.9 mg/1, approximately three to four
times more than in other areas of the Bay system. Nitrate Nitro-
gen was at a maximum in the northeast section where its concen-
tration was ten times greater than in other areas of the Bay at
a surface mean concentration of 1.16 mg/1.
Phosphate concentrations were highest in the northeast sec-
tion with a mean concentration of 0.292 mg/1. The second highest
concentration of 0.112 mg/1 was observed just north of the North-
east STP.
Dissolved Oxygen (DO) in the Bay is dependent on several
variables. The four major factors which may directly affect DO
in Escambia Bay are: (1) stabilization of soluble or suspended
oxygen demanding materials; (2) stabilization of bottom sediments
containing high organic content; (3) photosynthesis and respi-
ration by algae; and (4) reaeration.
Surface concentrations of DO were all measured above 5.0 mg/1
in the upper Bay. In the lower Bay, samples were above 7 mg/1.
There were wide swings in surface DO caused by algal photo-
synthesis. Wide swings in surface DO of up to 6.8 mg/1 in a day
were measured and indicates a highly enriched environment. Sedi-
ment demand on the DO of the water column causes a lower DO of
roughly 4.0 mg/1. Conditions in the Bay unfavorable for fish are
created due to the shallow nature of the Bay in the northeast
section, the warm water temperatures, the algal respiration and
the sediment demand.
The algal concentrations in Escambia Bay are shown in Figure
9- This may indicate that Mulatto Bay, a tributary to Escambia
Bay and a focal point of several fish kills, acted as a trap for
nutrients either because of the abandoned railroad tressel or
dredging in the Bayou. The bottom of the Bayou is muck due to
dredging where previously it was a grass bed. Reasons for high
algal concentrations likely are the result of a highly complex
physical and chemical synergism in and adjacent to the water
column„
384
-------
ro
00
T3
cu
(0
*
OJ
00
Ul
CD
n>
3
I
to
o
-------
TOTAL LIVE ALGAE
ESCAMBIA BAY
9/23-25/69
Figure 9. Total Live Algae - Escambia Bay - 1969
386
-------
The chemical water quality of the Escambia River and
Escambia Bay over the last eight years gives few clues to lead
one to believe that the water quality has been enhanced since
1969-1971. (See Figures 10, 11, 12.)
BIOLOGICAL WATER QUALITY
While not trying to give a totally accurate representation
of the biological system, most of the studies in the period
1969-1974 pointed to problems. Fundamentally, it seems many
of the problems are attributed to the disappearance of grass
beds as a primary indicator of a major change in the overall
ecosystem structure. Figure 13 shows the gradual progression
of loss in the grass beds in Escambia Bay from 1949-1974. This
long-term insidious alteration and resulting ecosystem disap-
pearance is perhaps the major cause of loss of biological pro-
ductivity. Likely causes include: (1) increased turbidity and
siltation; (2) excessive shoaling and shifting of bottom sub-
strate due to dredging activities; (3) simultaneously enhanced
deposition of oxygen demanding organic sediments; and (4) the
introduction of nutrients to the system resulting in a micro-
phyte system instead of a macrophyte system. This results in
grass bottom organisms being replaced by organisms adapted to
the sludge bottom ecosystem. Oysters, shrimp, some fish and
smaller organisms may be casualties of this change.
Data gathered by the Florida Department of Environmental
Regulation (FDER) do not show dramatic trends when macro-
invertebrates samples are measured versus time. (See Figures
14-20.) These figures may be interpreted in the following way:
Biotic Index
0-10 organic pollution
10 - 20 potential problems
•^"20 absence of organic pollution
Diversity Index
<• 1 poor biological community
1 - 3 fair to good biological community
-»- 3 stable and diverse biological
community
This lack of a dramatic trend may be the result of having
insufficient data or it may show the lack of comparative data
during highly polluted stages. Two other alternatives are less
reassuring. Since the first two attribute the problem to data
acquisition, these latter two point to other problems. The
third alternative suggests a requirement for a very long time
to lapse before the system again becomes fully healthy and the
fourth would indicate that once destroyed, a marine estuary
387
-------
33023001 UPPER ESCRMBIfl RIVER
« 2
72.00 Vt.QO 76.00 78.00 80.00
YEflRS
a o
S ui-
70.00 72.00 Tt.OO 76.00 78.00
YEfiRS
Figure 10. Water Quality - 8 Parameters - 1970-1979
388
-------
33020009 L0UER ESCRMBIR RIVER
rv
co
01
70.00 72.00
7t.OO 76.00
YERRS
78.00 80.00
d
^
CD
70.00 72.00
76.00 78.00 80.00
YERRS
Figure 11. Water Quality - 8 Parameters - 1970-1979
389
-------
3302QC11 ESCnMBIfl BflY
m o
S -
1
"o
g.
IS
a
70.00 72.00 7t.OO 76.00 78.00 80 00
YERRS
70.00 72.00 7t.OO 76.CO
YEflRS
78.00 80.00
Figure 12. Water Quality - 8 Parameters - 1970-1979
390
-------
1-51 1-58 10-61 10-65 11-74
ESCAMBIA BAY GRASSBEDS
1949-1974
1-49
Figure 13. Escambia Bay Grassbeds - 1949-1974
391
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 33.02.0001
BODY OF WATER: ESCAMBIA RIVER
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
U>
&
NJ
«
1
a
6-1
5-
4-
2-
1 -
*
I \
73
74
75
76 77
Quarters and Years
78
79
^60
-50
-40
CD
I
-30 2.
I
-20
- 10
ill i i i i i i i i i i i i r \ \ \
FlWSPS FlWSPS FlWSPS FlWSPS FlWSPS FlWSPS FIW
80
Figure 14. Macroinvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 33.02.0009
BODY OF WATER: ESCAMBIA RIVER
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
6-1
I-60
OJ
«3
CO
1=5-
5-
3 -
2-
1 —
-50
-40
-30 2.
I
-20
-10
I I I \ \ \ I I I I I T I I I I I I I I I T
F I W SP S F I
FlW SP S FlW SP S FlW SP S FlW SP S F I W SP S
73 74 75 76 77 78
Quarters and Years
W SP S
79
W
80
Figure 15. Macrolnvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 33.02.0019
BODY OF WATER: ESCAMBIA RIVER
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
6 -
5 -
4 -
1 3-
0)
>
b
2 -
1 —
r *O
"••-l^
\
F W SP S F VJ S
73 74
.*•-....
/ ' 'I--
•
1
PS F W SP S
75 76
••••••«.!
^T
1 i
F 1 W
*
»
•
*
*. T
-•
1
1 1
SP S F
77
—I
1 1 1 1 1 1 1 1
WSPS FlWSPS FIW
78 79 80
-30
-25
-20
(D
O
-15 |
X
-10
- 5
Quarters and Years
Figure 16. Macroinvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.:
BODY OF WATER:
33.02.0C11
ESCAMBIA BAY
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
OJ
i-D
Ul
6~1
5 -
4-
IT?
I 3-
01
>
Q
2-
1 4- ,'H
r\ I xx^x\L-i P \j T T I T
\I 'l I J^i- T ' I 1 I T~ n
1 ^ 1-— 1 I*'*' li^^t> 1 -*• i
1 I i ^ T ^^i i\ 1
Y ^
r-30
-25
-20
CO
0
-15 2!
!D
X
-10
- 5
III III III III III 1 1 1 1
F W SP S F W SP S F W 'SP S FWSPS FWSPS FWSPS F 1 W
73 74 75 76 77 78 79 80
Quarters and Years
Figure 17. Macrofnvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.. 33.03.0C30
BODY OF WATER: EAST BAY
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX t= FLORIDA I
U>
U3
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.:
33.02.0023
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA I
6-1
5-
4 -
ig
I 3
S 3~
3 «.-
1 -
,
---""" /
T --"" * '
\"
\ V
\ *-*-*"*•
\ -,-.--
P"
-30
-25
-20
CD
O
-15 "
a
a
%
-10
- 5
iii i i i i i i i i i i i i i i i i i i i i
F WSP S F WSP S FIWSP S FlwSP S F 1 W SP S FlWSP S Flw
73 74 75 76 77 78 79 80
Quarters and Years
Figure 19. Macroinvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 33.03.00J4
BODY OF WATER: SANTA ROSA SOUND
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
; INDEX (= FL
6-1
5 -
4 -
ig
>•
| 3-
V
(_o £
vo O
00 2 -
1 -
{,
A* T
\ _L_ T
\ / i i H
N
iii i i i i i i i i i i i i i i i iii
FWSPS FWSPS FlWSPS FlWSPS FlWSPS FWSPS FW
73 74 75 76 77 78 79 80
-30
-25
-20
CD
O
-
-15 2.
Q.
-------
would require several lifetimes for recovery.
Fortunately, the first two alternatives seem to be the more
likely ones. After the big fish kills in 1969-1971 and the re-
sulting clean up by the industries, fish kills have been minimal
and the fish population has increased. Since the early part of
the 1970's, some grass beds have begun to re-emerge. Fish,
shrimp and oysters have begun to repopulate the cleaner fringes
of the Bay showing that the clean up was effective.
SEDIMENT
Alluded to earlier, sediment is a real problem in the Bay
system. Unconsolidated sediments range in depth from .6 meters
or less to 2 meters. Approximately one-third of the Bay is
covered with greater than 2 meters of sediment. (See Figure 21.)
Comparison of Escambia Bay sediments with those of an adjacent
bay, show the sediment is rich in carbonaceous, phosphorus and
nitrogenous material with relative proportions as follows:
Escambia Bay East Bay
C 45.4 54
N 5 .75
P 1 1
Thus, as the ecological system sees these nutrients, nitrogen is
6.75 times larger in Escambia Bay than East Bay in the same
system.
Some studies performed by the Federal Water Quality Admin-
istration in 1970 reveal concentration patterns of these nutrients
in the sediments. Figures 22, 23, 24 show the concentration
patterns for each nutrient. This sediment load could continue to
have detrimental effects for many years after the point sources
are cleaned up.
Griffin (1972) stated that the bay system is practically
isolated from the Gulf of Mexico even though there is a physical
connection and the Bay is tidally influenced. This determination
was based on findings that showed the clay, mortimorillonite,
found in Pensacola Bay in abundance was not found in the sediment
shelf of the Gulf. Other bay systems did show a commonality of
depositions in the Gulf and in the Bay. He did find that the
clay migrated into Escambia Bay. This shows that man's activity
within Pensacola Bay influences Escambia Bay more than one would
have guessed. It thus appears that essentially all of the fine
grained inorganic detritus going into the Escambia-Pensacola Bay
system will be deposited within that system. Thus, the bay sys-
tem may not flush as well as might be suggested by the tidal
influence or freshwater introduction. Dredging and sewage dis-
charges in Pensacola Bay thus have an impact on Escambia Bay.
399
-------
Monsanto
ESCAMBIA BAY SEDIMENT
DEPTH
JUNE,1970
.6 Meters or Less
1.7 Meters or Less
Greater than 1.75
Figure 21. Escambia Bay Sediment Depth - June, 1970
400
-------
Monsanto
TOTAL PHOSPHORUS AREAL DISTRIBUTION
UPPER ESCAMBIA BAY SEDIMENT
Total Phosphorus Area of Upper Bay Affected
<0.01
<0.02
<0.03
>0.03
Floridatown
Air Products
American Cyanamid
17
39
65
35
ESCAMBIA BAY SEDIMENT
TOTAL PHOSPHORUS DISTRIBUTION
JUNE, 1970
Note: Percent total phosphorus, dry weight basis
Figure 22. Escambia Bay Sediment, Total Phosphorus Distribution — June, 1970
401
-------
• Monsanto
TOTAL OXYGEN DEMAND AREAL DISTRIBUTION
UPPER ESCAMBIA BAY SEDIMENT
Total Oxygen Demand Area of Upper Bay Affected
g/kg %
<25 10
<50 27
<75 48
<100 70
>100 30
Floridatown
Air Products
American Cyanamld
~/
/
UNITS: g of Oxygen per day kg of sediment
ESCAMBIA BAY SEDIMENT
TOTAL OXYGEN DEMAND DISTRIBUTION
JUNE, 1970
Figure 23. Escambia Bay Sediment, Total Oxygen Demand Distribution — June, 1970
402
-------
TOTAL ORGANIC NITROGEN AREAL DISTRIBUTION
UPPER ESCAMBIA BAY SEDIMENT
Total Organic Nitrogen Area of Upper Bay Affected
<0.05
<0.10
<0.15
<0.20
>0.20
11
31
56
60
40
ESCAMBIA BAY SEDIMENT
TOTAL ORGANIC NITROGEN DISTRIBUTION
JUNE, 1970
UNITS: Percent total organic nitrogen, dry weight basis.
Figure 24. Escambia Bay Sediment, Total Organic Nitrogen Distribution — June, 1970
403
-------
This may be one of the most important discoveries relating to
estuary systems in the Gulf of Mexico, i.e. tidal flushing is
not as effective in removing pollutants as would appear looking
at the physical parameters.
CONCLUSIONS
Municipal sewage treatment requirements are stringent for
this bay system even though it has not been modelled. Attempts
at modelling to show cause-effect relationships have not been
successful; however, it is most likely the lack of sophistication.
It has been suggested that the system acts like a lake part of
the year. This is supported by the observance of a partial
stratification each year. The Bay is also affected by the amount
of rainfall, tides, temperature and wind effects. Due to all the
variables, it is quite possible that the bay system cannot be
reasonably modelled for predictive purposes.
With this lack of modelling and cause-effect relationships,
questions continue to arise regarding the wisdom of the Enforce-
ment Conference orders. However, the result speaks clearly in
that fish kills today are practically non-existent. Oysters are
again growing and shrimp catches are increasing. There continues
to be water quality studies. It is certain these studies will
continue for a number of years in order to determine the best
level of municipal treatment required. Chemical and biological
water quality parameters show deficiencies in trying to determine
improvement trends. Again, our sophistication in sampling and
interpreting results may be the biggest cause for not being able
to clearly show trends.
With existing uncertainties, regulatory agencies will in all
likelihood allow modifications to the treatment levels if addi-
tional water quality data demonstrates inappropriate treatment
levels. This is true especially in light of increasing costs of
operating an AWT Plant. In effect, the public interest test of
benefits versus cost is quite likely to determine statutory and
administrative requirements in the future. Since the facility
is built, inflation no longer impacts construction costs and the
major concern is that of operation and maintenance. There is
little doubt that this Bay must be protected in the future as
population pressures cause more point and non-point source
pollution.
If thorough studies of cause-effect relationship had been
required, very little would have been accomplished to this day.
Other water systems are much more clearly understood and cause-
effect relationships are more easily demonstrated. Yet, the
eutrophication and physical processes are so complex in some
waters that mandatory directives may be the only way to save
those waters before they are totally destroyed. Estuaries are
extremely sensitive and fragile systems.
404
-------
Recognizing the difficulties of predicting and showing
cause-effect relationships, this bay system clearly was in a
horrible state in 1970. Today the situation is dramatically
different. No shrimp were found in quantity in the system until
the spring of 1976. In the summer of 1977, profitable catches
of shrimp were reported in Escambia Bay as far north as the
interstate bridge. Speckled trout were also being caught in
good numbers. Oyster beds and grass beds are being re-estab-
lished. Larvel oysters and small oysters are being found in
large quantities in the Bay since the total kill in 1971 and
partial kill in 1974-1975. Grasses, mostly ulgrass (Vallisneria
Americana) , are spreading along the river mouth and northwest
shoreline of Escambia Bay and other parts of the bay system less
affected by earlier pollution.
In conclusion, it must be stated that had the regulatory
agencies done nothing, the improved conditions might exist
today- This seems highly unlikely; however, there is no way
to prove otherwise. Since no pre-monitoring can be compared
with post-monitoring, cause-effect relationships are hard to
establish. It is clear that problems existed in the Bay before
regulatory action and that those problems have been mitigated
after the regulatory action. This suggests a direct relation-
ship between the problem and the subsequent action. As late
as 1975, the U.S. EPA still recommended that the sewage dis-
charges to the Escambia-Pensacola Bay system be limited and
AWT was still recommended for the Pensacola Main Street Plant.
The FDER has continued to support this recommendation due to
the poor circulation and continuing problems in some of the
bayous tributary to Escambia Bay and Pensacola Bay.
405
-------
SECTION 3
TAMPA BAY
PHYSICAL CHARACTERISTICS AND HISTORY
Tampa Bay lies on the west-central coast of Florida and is
composed of several sub-bays, all of which jointly constitute
Tampa Bay. Area rainfall averages about 122 centimeters per year,
50 percent of which occur in the summer months of June to Septem-
ber. However, as in the Escambia Bay area, hurricanes can have
drastic impacts on the amount of rain the area experiences, some-
times to levels of 25-50 centimeters in a few days time. The
topography is extremely flat with elevations exceeding no more
than 6-8 meters at the highest points. (See Figure 25.) Depths
in the bay system range up to 10 meters except in the Tampa ship
channel which is today being deepened to 14 meters. The tide's
diurnal range is 1 meter.
The Tampa Bay system has been recognized as having a pollu-
tion problem since the early 1960's. In 1965, state and local
governments studied the problem of odors caused by decaying algae
in the western part of Hillsborough Bay. Housekeeping was gener-
ally recommended, i.e. removal of the algae. This in retrospect
was a stop gap measure and little was done by state, local or
federal officials until the late 1960's when a federal study
(June 1967) known as the "Hagan Report" was conducted (Hagan
1969). During the late 1960's, local government called on state
and federal authorities to help solve the pollution problems in
the Bay. This study identified the problems occurring in the bay
system and proposed solutions. Now roughly ten years later, a
number of these recommendations have been completed, one of which
was the construction of an AWT Plant for the City of Tampa. The
results have not been fully evaluated, but there are some im-
provements. Dramatic results were envisioned when regulatory
orders for treatment were first issued. These have not occurred.
Perhaps the bay system has not had ample time to recover and only
time will tell if the corrections really worked. Bay sediments,
dredge and fill activities and stormwater runoff may also have
more impact on the Bay than early regulatory activities en-
visioned.
Within Tampa Bay, the currents have been studied extensively
by Dr. Bernard Ross, Professor at the University of South Florida.
He has modelled the entire Bay and it is fairly well known, based
on the model, what happens to a distinct particle released to the
406
-------
Figure 25. Topography of the Tampa Bay Land Area
407
-------
Bay. Dissolved substances have also been modelled to show the
impact of dilution from tidal mixing and rainfall. (These cur-
rents behave as•shown in Figure 26.)
This model is very important in trying to assess the impact
that wasteload allocations will have on the bay system for regu-
latory purposes. In developing the model, 1254 neutrally buoyant
particles were spaced one-half mile apart, released and studied
for location every ten minutes for thirty days. The accompanying
figure shows the location of these particles after thirty days.
(See Figure 27.) Many escaped the bay system but significant
numbers remained. Most of the particles accumulated at a spot
on the Gulf side of the peninsula, in the main ship channel, in
upper Old Tampa Bay and in Hillsborough Bay.
Dissolved substances were studied using non-reactive tracer
substances. The study lasted until a seed concentration of 10
mg/1 was reduced to 1 mg/1 in each area of the Bay. This was
done by looking at these concentrations through monthly cycles
of tides. Based on this phase of the study, it took approxi-
mately 180 days to have a 70 percent reduction in the non-reactive
substance in the water column of Tampa Bay. Ross calculates that
25.8 percent of the tidal quantity of water is permanently re-
moved from Tampa Bay by mixing with the Gulf of Mexico. He
claims that as the tide leaves Tampa Bay, it carries dissolved
material. When the water exits Tampa Bay, it mixes with Gulf
water. When the new tide comes into Tampa Bay, it returns much
of the same dissolved substance. Indeed, the model shows that
74.2 percent of the dissolved substance returns from the Gulf.
As is true in most bay systems in Florida, freshwater has
a significant effect on the predominantly saltwater ecosystems.
Sources of freshwater in Hillsborough Bay are predominantly the
three rivers: Hillsborough, Alafia and Palm Rivers. They act
on the bay system as if they were point source discharges. In
the case of the Alafia River, it is both a source of freshwater
and a major source of phosphate pollution. During its flow, it
acquires phosphate from natural sources and phosphate mine dis-
charges. The drainage basin for these rivers is the source of
most of the United States' phosphate fertilizers. Thus, the
addition of phosphates to Tampa Bay is not unexpected.
In_the early days of Tampa and St. Petersburg, fish life,
water birds, grass beds and shoreline vegetation were much more
abundant than they are today. In 1837, John Lee Williams,
writing in "The Territory of Florida", wrote that
"Extensive schools of fish are
so thick as to almost impede
the boat in shoal waters. Sea
fowl are also exceedingly nu-
merous. The beautiful flamingos
408
-------
TAMPA BAY
NET VELOCITIES AT EACH POINT
FOR 1 TIDAL CYCLE
Figure 26. Net Current Velocities - Tampa Bay
409
-------
TAMPA BAY
LOCATIONS OF PARTICLES AFTER 30 DAYS
INITIAL UNIFORM DISTRIBUTION
Figure 27. Location of 30 Day Particles — Tampa Bay
410
-------
in particular appear in long
files."
While it is difficult to quantify statements such as the above,
conclusions can be drawn that before human population pressures
were present in the area, Tampa Bay was flush with numerous
species of fish, fowl and plants. Today, fishing has decreased
and fowls and plant life are not as plentiful. Brown pelicans
almost disappeared from the area in the late 1960's. Later, the
cause for this became known. Pesticides built up in the birds,
causing the eggshells to become exceedingly thin and to crack and
consequently causing a low hatch rate, depleting the species.
After bans on the use of certain pesticides, this species began
to populate the area again, albeit somewhat slowly.
Pollution followed man into the Bay areas. Some problems
were noted at infrequent intervals in the 1920's. As the area
rapidly expanded in the 1950's and 1960's, the problems became
intensified. As related to water quality, these problems were
manifested as bad odors from the water, high turbidity, high
coliforms, low dissolved oxygen and algal growth. The cause of
these problems cannot be totally attributed to municipal sewage
even though it has a significant part in causing the problems.
Industrial discharges, non-point source runoff, residential and
urban development and dredging and filling are other causes which
had to be corrected in conjunction with treatment of domestic
sewage. These all seemed to act in a synergistic manner in
causing the above problems and all had to be attacked so solve
water quality problems.
The cause of odors starting in the 1920's was found to be
the red algae Gracilaria and was found and identified by the
Hagan investigative team in 1967. The cause was attributed to
an unbalanced ecosystem which had too much carbon, nitrogen and
phosphorus materials in the water column. The same was true of
the sediment. With this imbalance, the algae grew exceedingly
well in the saltwater. Not being tolerant to freshwater which
periodically diluted the saltwater, the algae died and the resul-
tant odors were repugnant. This algae generally grew in less
than six feet of water. The littoral zone of parts of Tampa Bay
received reduced light penetration due in part to increased algae
from an overenriched water column, turbidity from dredging and
natural color. This reduced light penetration resulted in de-
struction of saltwater marshes and grasses. The dredging and
filling in the 1960's also destroyed much shoreline vegetation.
Thus, the problems exacerbated each other and solving one problem
did not solve the water quality problem.
Dredging and filling sections of the Bay and shoreline seem
to be the most insidious long-term water quality problem in
Florida's pollution control efforts. Port development, shore-
line alteration and causeways for highways are examples of such
411
-------
dredge and fill operations. Non-point sources followed by domes-
tic and industrial waste discharges appear to be the next worst
causes of pollution affecting water quality. The most easily
solved problems were point source ones. The point source abate-
ment strategy in Florida was followed two years later with an
abatement strategy for dredge and fill operations. Almost nine
years after implementation of the above abatement strategies,
the regulatory agencies are still seeking the best control
stormwater runoff abatement strategy.
Point sources were identified on numerous occasions over
the years as being the cause of pollution. This reinforced the
point source abatement strategy. Hillsborough Bay was in the
worst condition of the bays composing the Tampa Bay system and
the volume of point source discharges into that Bay gave credence
to the point source strategy. The following tables show the
relative contributions of industries and domestic sewage dis-
charges to Hillsborough Bay. (See Figures 28, 29, 30 for BOD,
Ammonia and Kjeldahl nitrogen and phosphorus contributions.)
During the 1970"s, major reductions were made on phosphorus
loadings coming from industrial plants. No water quality studies
preceded these abatement efforts and the efforts were based solely
on technology-based standards. The effectiveness of this action
on industrial plants can be seen by looking at several figures
for phosphorus water quality data in the Tampa Bay system moni-
tored during the 1970's. (See Figures 31, 32, 33, 34, 35.)
Thus, it is known that industries were the major contributors of
high phosphorus levels in the system and that the reduction of
phosphorus in the water column was caused by the treatment of
the industry's wastewater.
SEWAGE TREATMENT
Confronted with a State law that required advanced sewage
treatment without regard to water quality, many of the cities
became inventive in order to avoid the expensive capital and
operations cost of these requirements. In several instances,
cities in the area chose other less expensive means of treatment
and effluent disposal or chose to try technology not widely
tried. (Figure 36 depicts the location of major municipal sewage
plants in the Tampa Bay area.)
Each municipality chose a somewhat different method of
addressing the requirements. The following seven cases illus-
trate the direction each city chose, the design flow of the new
facilities, the method of effluent disposal and, in some cases,
the schematic of the plant's design. These different approaches
were encouraged by a regulatory attitude in Florida that required
governments to meet standards without telling them how to do it.
It should also be noted that the regulatory scheme is highly
decentralized in Florida to the district and county level
412
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TSTP - TAMPA SEWAGE TREATMENT PLANT
MSTP - MacDILL SEWAGE TREATMENT PLANT
AR — ALAFIA RIVER
HR — HILLSBOROUGH RIVER
PR — PALM RIVER (SIX MILE CREEK)
MacDILL AIR FORCE BASE
^ 5 DAY BOD
\_) ULTIMATE BOD
KILOGRAMS/DAY
0
2,500
5,000
MAJOR WASTE SOURCES
BIOCHEMICAL OXYGEN DEMAND
Figure 28. Major Waste Sources — Biochemical Oxygen Demand
413
-------
TSTP - TAMPA SEWAGE TREATMENT PLANT
MSTP - MacDILL SEWAGE TREATMENT PLANT
AR — ALAF1A RIVER
HR — HILLSBOROUGH RIVER
PR — PALM RIVER (SIX MILE CREEK)
USPP - U.S. PHOSPHORIC PRODUCTS CO.
NCC— NITRAM CHEMICAL CO.
MacDILL AIR FORCE BASE
^ AMMONIA
O TOTAL KJELDAHL NITROGEN
KILOGRAMS/DAY
0
MAJOR WASTE SOURCES .
AMMONIA AND KJELDAHL NITROGEI\T
Figure 29. Major Waste Sources — Ammonia and Kjeldahl Nitrogen
414
-------
TSTP -
MSTP -
AR —
HR —
PR —
USPP -
NCC —
TAMPA SEWAGE TREATMENT PLANT
MacDILL SEWAGE TREATMENT PLANT
ALAFIA RIVER
HILLSBOROUGH RIVER
PALM RIVER (SIX MILE CREEK)
U.S. PHOSPHORIC PRODUCTS CO.
NITRAM CHEMICAL CO.
MacDILL AIR FORCE BASE
MAJOR WASTE SOURCES
TOTAL PHOSPHATE
Figure 30. Major Waste Sources — Total Phosphate
415
-------
24020008 RLRFIR RIVE
N0RTH PR0NG
CD
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70.00
71 .00
—i
72.00
73.00 74.00 75.00
YERRS
76.00
77.00
78.00
79 .00
80 .00
Figure 31. Phosphorus Levels
-------
24020003 flLRFIfl RIVER KRIN SLCTI0N
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70.00 71.00 72.00 73.00 74.00 75.00
YEflRS
76 .00
77.00
78 .00
79.00
80.00
Figure 32. Phosphorus Levels
-------
2H01019Q MIDDLE TflMPfl BflY
o
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70.00
71 .00
72.00
73.00
74.00
75.00
YEflRS
76.00
77 .00
78.00
79.00
80.00
Figure 33. Phosphorus Levels
-------
24040093
L 0 T n M P n B fl Y
o
CD
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cn
en
(SI
X
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70.00 71.00 72.00 73.00 7H.OO 75.00
YEflRS
76.00
77.00
78.00
79.00
80.00
Figure 34. Phosphorus Levels
-------
4010230 M0UTH 0F TflMPfl BHY
a
CO
70.00
71 .00
72.00
73.00
74 .00
75 .00
YEflRS
76.00
77.00
78.00
79.00
80.00
Figure 35. Phosphorus Levels
-------
TAMPA HOOKERS
P.OI NT
CLEARWATi.e.R, ., .
•
J.:- BELLEAIR..-;
J'-U.S. PHOSPHOBl
•I:/".'SOUTH CROSS BAYOU ''J°&?>f;
Figure 36. Major Municipal Dischargers - Tampa Bay - 1970
421
-------
providing maximum citizen input to decisions affecting a local
government.
The legislation calling for AWT came about as a result of
numerous local perceptions. One of these perceptions was that
secondary treatment requirements in 1972 were inadequate and
legislation was passed requiring AWT in the Tampa Bay area. The
geographical area was rather limited during the early stages of
the legislative process but was defined to cover much of west-
central Florida by the time it became law. Perhaps the lobbying
group that had the most influence on its passage was a local
district of Girl Scouts that was very concerned about their
recreational camp being too close to a proposed sewage treatment
plant.
The following are examples of how municipalities have
changed the method of disposal or have met the statutory require-
ments for AWT.
St. Petersburg STP
The City has four plants that in 1970 discharged to the
Tampa Bay system and adjacent coastal waters. The combined de-
sign flow of the plants in the 1980's will be approximately
2.26X10^ m-Vday. Today all but one plant discharges to land on
the peninsula. This remaining plant will join the other three
in land application upon completion of construction. Land
application has been accomplished by two methods, deep well
injection and spray irrigation. Deep wells are used during
wet periods and spray irrigation during dry periods on parks,
golf courses, lawns and other green spaces. Deep wells are
275-400 meters deep.
Since the public is very likely to come in contact with the
spray, it has been treated to be virtually virus free. This is
accomplished by secondary treatment, coagulation, filtration and
chlorination. The City spent $400,000 to have a well known vi-
rologist, who opposed the spray system, test for viricidal
efficiency before starting the irrigation systems. After demon-
strating the efficiency of this system in removing viruses, this
virologist is now one of the leading advocates of this system.
An added benefit is the water and nutrients are reused in a
water short area. Treasure Island, an independent city, opted
to tie into the St. Petersburg system.
This is truly a case of federal, state and local cooperation
in making the construction grants program work. Today the con-
straints at the federal level would prevent such a system from
coming to fruition.
422
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South Cross Bayou and McKay Creek STP
These two facilities are owned by Pinellas County and the
County has opted to remove their surface discharges to deep well
injections. These deep wells are 275-400 meters deep with no
significant overlying freshwater aquifers. These systems ulti-
mately will displace saltwater far out into the Gulf of Mexico.
The total design flow in the 1980's is 1.26X105 m3/day.
Belleair STP
This municipality is composed of wealthy individuals and
they wanted to retain their own system and discharge their ef-
fluent to the Gulf of Mexico. Their system was thus required to
have AWT with a design flow of 1.89X10-* m3/day. This system is
an aeration system for both carboneous and nitrogenous components.
Largo STP
This City had a very innovative engineer who designed an AWT
Plant for the cost of a normal secondary system. It was designed
for 3.4X104 m^/day but has never used chemicals in the AWT system.
The effluent was filtered, however. Instead it discharged to a
series of ponds around a golf course. The water from the ponds
was sprayed on the golf course and no discharges occurred except
during very rainy periods when the discharge is allowed to drain
through a swampy mangrove marsh before entering the Bay system.
Today, the City has contracted with a private company to convert
part of the existing system to AWT using existing structures.
This new experimental process does not use energy expensive
chemicals. This is a demonstration project between private
industry and a local government costing the local government
only a margin of the cost of a regular project. (See Figure 37
for schematic of the retrofitted plant.)
Clearwater STP
This City has been caught and squeezed between changing
planning requirements and regulatory inconsistencies. At pre-
sent, one plant is nitrifing and discharging to a stream, one
plant was supposed to go to a deep well system that did not work,
one plant discharges to a spray irrigation site with a high
groundwater table and one plant discharges to Tampa Bay. All
systems are waiting for the completion of an Environmental Impact
Statement by the U.S. EPA. The sum total of design flows for
these facilities is 6.42X104 m^/day.
Hillsborough N.W. STP
This is a county owned plant that has been forbidden to
expand because of water quality constraints. It has a design
capacity of 1.7X104 m3/day and provides a high quality AWT
423
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BASIN LAYOUT - LORGO A/O RETROFIT
SECONDARY
CLARIFIER
WASTE SLUDGE
1
PASS
NOT USED
PASS
NOT USED
STAGE
oxir
STAGE
OX 1C
STAGE
OXIC
STAGE
OXIC
i SLUDGE — \X"™>
RECYCLE TO 1 AND DR^
BASIN y
r^
11
10
8
STAGE 2
ANAEROBIC
STAGE 3
AMAPRHRIP
STAGE 4
ANAEROBIC
STAGE 5
ANAEROBIC
STAGE 6
ANAEROBIC
STAGE 7
ANAEROBIC
STAGE 1
NOT USED
PRIMARY
CLARIFIER
DEGRITTED
INFLUENT
Figure 37. Flow Schematic of City of Largo Sewage Treatment Plant
424
-------
effluent that meets the restrictive AWT standards. (See Figure
38 for schematic of the plant.)
Tampa
This City perhaps has the largest AWT Plant in the United
States. It has a design flow of 2.26X105 m3/day and is highly
complex. In the past, this discharge has been attributed to be
the cause of many of the water quality problems in Hillsborough
Bay- There is little question that it is a contributor, the
extent of its contribution is unknown. The plant is today
achieving effluent AWT limitations that meet the very strict
standards set ten years ago. (See Figure 39 for the schematic
of the plant.)
Palmetto
In contrast with most other cities in the State of Florida,
this City decided receipt of federal dollars did not justify the
commensurate "red tape" (excessive requirements and paperwork).
The City built an innovative sewage treatment plant, solely with
their own money, that would meet the State's requirements. This
plant's processes are generally known as the "Bardenpho Process"
and is not chemically nor overly energy intensive.
These are some of the major municipal facilities that en-
circle Tampa Bay. Their reaction to the requirements of AWT
mandated by statute and defined by regulation are informative.
To this day, the Tampa Bay system still has some water quality
problems. There are some indications of recovery though only
time will tell if this statutory mandate expedited the clean up.
CHEMICAL AND BIOLOGICAL WATER QUALITY
Many low values of DO have been recorded during the summer
months for several years. BOD levels have remained fairly low
even though large quantities were discharged into Hillsborough
Bay. During periods of high odor intensity in 1967, however, the
DO was never less than 5.1 mg/1. Therefore, it was concluded
that the odor problem was not a direct function of' soluble and
suspended organic material depleting DO through anaerobic de-
composition.
During the intensive studies of 1968, the chlorophyll a mean
concentration was determined to be 35 mg/1 indicating a highly
tropic level with a large plant biomass caused by an excess of
nutrients. Figure 40 shows the levels of chlorophyll a found in
the bay system in 1978. Data for 1979 reveal that the chlorophyll
a_ still reaches 35-40 mg/1, although the mean in the worst
polluted areas is decreasing.
425
-------
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Contact
-------
O
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en
H
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OXYGEN
GENERATION
AND STORAGE
PUMPING
STATION
INTERMEDIATE
PUMPING STATION
JUNCTION CHAMBER
SCREEN
AND GRIT
BUILDING
ADMINISTRATION
AND O AND M
J r-j 1 BUILDING
GRIT
CHAMBER
OXYGEN REACTORS
PRIMARY
SEDIMENTATION
TANKS
MAIN
PUMPING
STATION
DIGESTION
TANKS
FINAL SEDIMENTATION TANKS
SLUDGE
TREATMENT
BUILDING
CHEMICAL STORAGE
AEROBIC
DIGESTION
TANKS
POST AERATION
AND CHLORINE
CONTACT
FILTER
BUILDING
n
j
BEDS
SLUDGE /
LOW THICKENING /S
fURE TANKS
]
1^
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I
i
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FILTE
OUTFALL
SIMPLIFIED SITE PLAN, TAMPA
PROPOSED
EXISTING
-------
Hillsborough Co.
CHLOROPHYLL A
(UG/L)
1978
Figure 40. Chlorophyll A ug/l - 1978
428
-------
Limiting nutrient algal assay studies conducted in 1975 by
FDER revealed that in all cases the nitrogen spiked sample waters
produced algal growth greater than either the control or phos-
phorus spiked samples. These results indicate that at all sta-
tions and dates sampled, nitrogen was the nutrient limiting
phytoplankton growth. (See Figures 41, 42 for results of these
tests as well as sample location.)
The City of Tampa in 1979 requested a variance from FDER
seeking to discontinue phosphorus removal. Based on the algal
assay studies and previous industrial phosphorus removal, FDER
granted the request. This saved the City considerable money and
there was evidence that water quality was not being enhanced by
this requirement. Nitrogen, however, is still required to be
removed.
It was mentioned earlier in this paper that phosphorus
levels in the water column had decreased over the last ten years.
In most cases, the level has dropped two to ten fold over this
time frame. Figure 43 shows that most of the phosphorus problem
in the Bay is caused by the Alafia River. When the loading in
this river decreased, the level in the Bay decreased.
Historical data shows the Tampa Sewage Plant to be a major
cause of ammonia and coliform pollution. Figure 44 clearly shows
the ammonia levels in Hillsborough Bay were caused by the Tampa
Sewage Treatment Plant. Fecal coliform bacteria in Hillsborough
Bay may not be solely derived from the Tampa Sewage Plant but
isopletes done in 1968 show a large number are caused by this
plant. (See Figure 45.)
Extensive monitoring in Tampa Bay has been conducted since
1972 by both Hillsborough County and FDER. Figure 46 depicts the
location of 54 weekly and/or monthly sampling locations in the
Bay conducted by Hillsborough County. Numerous parameters are
analyzed. Hillsborough County 1978 data confirm that significant
coliform reductions occurred after the Tampa Plant went into
operation. (See Figure 47.) FDER data for 1979 show significant
reductions in TKN and fecal coliform. (See Figures 48, 49 for
comparison of Recent (R) versus Historical (H) pollutant levels
in both arms of Tampa Bay.
Gracilaria, the red algae in Hillsborough Bay, is present
because of the excess nutrients. Its excessive volume is killed
off in the presence of freshwater thus causing a bad odor problem.
It is hoped that reductions in the nitrogen and phosphorus will
eventually clean up this problem in the Tampa Bay system.
Biological data collected by FDER over the last seven to
eight years for macroinvertebrates show some improvements as
shown in Figures 50, 51, 52, 53. Hillsborough Bay in particular
appears to be showing some improvement. A comprehensive
429
-------
3
-a
103
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II I I
I I I I
I I I I
TAMPA BAY ALGAL ASSAYS
SEPTEMBER - OCTOBER 1975
Control
Nitrogen
Phosphorus
D
H
STATION
-------
Figure 42. Location of Algal Assay Sampling Stations
431
-------
PHOSPHATE CONCENTRATION mg/l as P
SURFACE SAMPLES
MEAN FOR PERIOD OF STUDY
MacDILL AIR FORCE BASE
MacDILLSTP
US PHOSPHORIC
PRODUCTS CO.
PHOSPHATE CONCENTRATION
Figure 43. Phosphate Concentrations - Hillsborough Bay - 1969
432
-------
AMMONIA
mg/l as N
SURFACE SAMPLES
MEAN FOR PERIOD OF STUDY
MacDILL AIR FORCE BASE
US PHOSPHORIC
PRODUCTS CO.
AMMONIA CONCENTRATION
Figure 44. Ammonia Concentrations - Hillsborough Bay - 1969
433
-------
FECAL COLIFORM
Figure 45. Fecal Coliform — Hillsborough Bay — 1969
434
-------
WATER QUALITY
SAMPLING STATION
TAMPA BAY
Figure 46. Sampling Stations in Tampa Bay - 1972-1980
435
-------
ST. PETERSBURG
Hmsborough Co.
Manatee
FECAL COLIFORM
BACTERIA
(MF, CONFIRMED)
1978
Figure 47. Fecal Coliform - Hillsborough Bay - 1978
436
-------
ERST TflMPfl BflY
M8/L
D.0.
MB/L
S
SU
PH
SU
o
Ul
CD -1
(O
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S
- Ul
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-------
WEST TRMPfl BRY
MB/L
D.0.
P-
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Figure 49. Water Quality Trends
438
-------
MACROINVERTEBRATE PARAMETERS VS TIME
u>
NATURAL SUBSTRATE DIVERSITY
6-,
5-
4-
'S
&•
« 3-
S
5
2 -
1 —
o\su i *_T VVMI cn.
F 1 W SP S F
73 74
\JL.LJ IrtlVIrrt DMI
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75
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W SP S F I W SP S F
76 77
1 T
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L'-*''* \ /
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1 1 1 1 1 1 1
W SP S F 1 W SP S F
78 79
W
80
-30
-25
-20
g
-15 }
a.
-10
- 5
Quarters and Years
Figure 50. Macrolnvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 24.03.0207
BODY OF WATER: HILLSBOROUGH BAY
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
6-
5 -
4 -
1?
f 3-
1
Q
2-
1 —
i.
,\ ^ /Xj
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V \ t \ A
^"-*> ^ A x ' \ /
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III I I 1 I I I I I 1 I I I 1 1 I I 1 I I I
FWSPS FWSPS FlWSPS FlwSPS FlwSPS FIWSPS FIW
-30
-25
-20
-15
-10
- 5
73 74 75 76 77 78 79 80
Quarters and Years
Figure 51. Macroinvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.: 24.01.0190
BODY OF WATER: TAMPA BAY
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
6-i
r-30
Diversity (d)
5 -
4 -
3 -
2-
A
-25
-20
(D
O
-15 °
-10
- 5
III I I I I I I I I I I I I I I I I 1 I I
FlWSPS FlWSPS FlWSPS FlWSPS FlWSPS FlWSPS F I W
73 74 75 76 77 78 79 80
Quarters and Years
Figure 52. Macrolnvertebrate parameters vs time.
-------
MACROINVERTEBRATE PARAMETERS VS TIME
STATION NO.. 24.01.0230
BODY OF WATER: BISHOP'S HARBOR
NATURAL SUBSTRATE DIVERSITY
ARTIFICIAL SUBSTRATE DIVERSITY
BIOTIC INDEX (= FLORIDA INDEX)
to
6-]
5 -
4 —
lg
£ o
« j —
1
2-
1 -
A
/ \ *^'*^ / ^\~~ — "41— -^^^
lr \ -^*'X'\T/1"T
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-30
-25
-20
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-15 *
I
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i i I |^ i II r i i i f iiiir
FlWSPS FIWSPS FlWSPS FlwSPS FlWSPS FIWSPS FlW
73
74
75
76 77
Quarters and Years
78
79
80
Figure 53. Macroinvertebrate parameters vs time.
-------
biological study is presently underway to see what impact the
AWT Plant is going to have on Hillsborough Bay. Unfortunately,
several more months are required to gather and evaluate this
date.
SEDIMENT
The sediments of Tampa Bay are laden with high levels of
phosphorus (1-3 percent by weight) and nitrogen (.1--5 percent
by weight). These have been deposited in the bay system for many
years. They have tended to be deposited along the ship channel
and in the gyres caused by the currents in the Bay. These areas
have heavy depositions, though sediment is present to some degree
throughout the Bay. Without new depositions, it is reasonable
to expect that these deposits could begin to stabilize. Unfor-
tunately, the AWT Plant in Tampa was becoming operational and
other municipal dischargers were upgrading or removing the dis-
charges, a major ship channel-deepening project (Tampa Bay Ship
Channel) was and still is underway. It is suspected that this
project has today masked many of the beneficial effects of the
upgrades on municipal sewage treatment works. This is believed
to be caused by leaching of nutrients, especially nitrogen, from
the muck in the sediments in the ship channel. Water quality
data clearly show some increases in suspended solids in the last
two to four years that coincide with the only significant dredg-
ing in the bay system (ship channel dredging). (This can be
seen in Figures 54, 55, 56, 57, 58 for water quality in the
Tampa Bay system.)
CONCLUSIONS
The effect of the special law has most probably been unduly
expensive to citizens for the cost of sewage treatment in some
areas covered by the law. There is most likely little justifi-
cation for it based on water quality needs in those areas. In
contrast, the law appears to have been beneficial to water
quality in the upper reaches of Tampa Bay and the Pinellas County
Peninsula. In all likelihood, water quality cause-effect rela-
tionships could not have been determined. It seems clear that
an effort applied to demonstrating this cause-effect relation-
ship did not do so in a fully satisfactory manner. The variables
are clearly easier to predict in the Tampa Bay system than the
Escambia Bay system and yet it is still a challenging task.
Water quality has improved after advanced waste treatment at
the City of Tampa Sewage Treatment Plant. Whether this high
degree of treatment is enough is yet to be determined.
Another aspect of this law is reuse of water. The area
covered by the law is a water-short area. While the law did not
have reuse in mind when it was passed, it is having the effect of
promoting reuse. This causes significant reductions in water use
and thus, an important resource is not wasted. Strange as it may
443
-------
24020003 RLRFIR RIVER MRIN SECTI0N
- =
g
o. ^
oi 8-
in
8
u>
= 8
g „,-
70.00 72.00 Tt.OO 76.00 78.00 60.00
YEflRS
70.00 72.00 7H.DO 76.00 78.00 80.00
YERRS
Figure 54. Water Quality - 8 Parameters - 1972-1979
444
-------
2^020207 HILLSB0R0UGH BRY
Q -
Z
JU.A-/A l\-
^ o
a
si
CD
70.00 72.00 7t.OO 76.00 78.00 80.00
YEflRS
70.OO 72.00 Tt.OO 76.00 78.00 80.00
YEflRS
Figure 55. Water Quality - 8 Parameters - 1972-1979
445
-------
2^040093 0LD TflMPfl BflY
ro
s _.
70.00 72.00 7H.OO 76.00 76.00 80.00
YEflRS
a 9
co ""
70.00 72.00 7H.OO 76.00
YEflRS
78.00 80.00
Figure 56. Water Quality - 8 Parameters - 1972-1979
446
-------
2H010190 MIDDLE TflMPfl BflY
A^v^
0)
en
s
a
a
^
CO
70.00 72.00 7t.OO 76.00 78.00 80.00
YERRS
70.00 72.00
7H.OO 75.00 78.00 80.00
YERRS
Figure 57. Water Quality - 8 Parameters - 1972-1979
447
-------
2^010230 M0UTH 0F TRMPR BRY
CO 8
s -•
in 3
tn
70.00 72.00 Tt.OO 76.00 78.00 80.00
YEflRS
70.00 73.00 7H.OO 76.00 78.00 90.00
YEFIRS
Figure 58. Water Quality - 8 Parameters - 1972-1979
448
-------
seem, this law is causing implementation of a goal of the federal
statute passed a year or so after the State law. The federal
statute addresses the reuse of wastewater and this geographical
area is reusing wastewater to save freshwater and avoid the cost
of AWT.
If the nitrogen in the system does not become fixed after
the ship channel dredging stops and the Tampa treatment plant
continues to remove nitrogen, then, the three most probable
causes of high nitrogen level in the water will be the Alafia
River, leaching from sediments and urban stormwater runoff. The
regulatory agencies will also have to reconsider the abatement
strategy since a solution will most likely not become readily
apparent and a manner of equity will become involved.
A massive study is being undertaken now by the City of Tampa
funded in part by a National Urban Runoff Program Grant to deter-
mine the significance of urban stormwater and what can be done
about it, if anything.
Further studies of the Alafia River to find the causes of
relatively high nitrate levels will be done by FDER.
449
-------
BIBLIOGRAPHY
1. Circulation and Benthic Characterization Studies Escambia
Bay, Florida. U.S. Environmental Protection Agency, South-
east Water Laboratory, Technical Services Program, Athens,
Georgia, 1971. 32 pp.
2. Johnson, Bruce. Escarosa: A Preliminary Study of Coastal
Zone Management Problems and Opportunities in Escambia and
Santa Rosa Counties, Florida. Florida Coastal Coordinating
Council, 1971. 30 pp.
3. Rinkel, Murice D. and James I. Jones. Escarosa I. An
Oceanographic Survey of the Florida Territorial Sea of
Escambia and Santa Rosa Counties. State University System
of Institute of Oceanography in Cooperation with the
Florida Coastal Coordinating Council, 1973. 365 pp.
4. Hopkins, Thomas S. Marine Ecology in Escarosa. University
of West Florida, Coastal Coordinating Council, 1973. 100 pp.
5. Effects of Pollution on Water Quality, Escambia River and
Bay, Alabama and Florida. U.S. -Department of the Interior,
Federal Water Pollution Control Administration, Southeast
Water Laboratory, Technical Services Program, Athens,
Georgia, 1980. 63 pp.
6. Griffin, G.M. Sources and Dispersal of Clay Minerals in the
Escarosa Area of Northwest Florida as Related to the Move-
ment of Particulate Pollutants. A Report to the Coastal
Coordinating Council and the State University System
Institute of Oceanography, 1972.
7. Olinger, Lawrence W. Environmental and Recovery Studies of
Escambia Bay and the Pensacola Bay System, Florida. U.S.
Environmental Protection Agency, Region IV, Surveillance
and Analysis Division, 1975. 322 pp.
8. Livingston, Robert^J. The Effects of Dredging and Eutro-
phication on Mulat-Mulatto Bayou (Escambia Bay, Pensacola,
Florida). Report for the Florida Department of Transporta-
tion, 1972. 40 pp.
9. West Florida 208 Study. West Florida Regional Planning
Council, 1979.
450
-------
10. Flood and Associates, Inc. Project Plan for Water Quality
Management, Pensacola Urban Area. Prepared for Pensacola,
Florida City Council, 1973. 227 pp.
11. Atlantis Scientific. Environmental Impact Assessment, Water
Quality Analysis, Escambia River and Bay. National
Commission on Water Quality, 1976. 269 pp.
12. Conference Proceedings: In the Matter of Pollution of the
Interstate Waters of the Escambia River Basin (Alabama-
Florida) and the Intrastate Portions of the Escambia
Basin within the State of Florida. First and Second
Session, August 1969 and February 1971.
13. Schomer, Scott. Florida Department of Environmental
Regulation, Unpublished Report and Data.
14. Hagan, John. Problems and Management of Water Quality in
Hillsborough Bay, Florida. Hillsborough Bay Technical
Assistance Project Technical Programs, Southeast Region
Federal Water Pollution Control Administration, Tampa,
Florida, 1969. 83 pp.
15. Wilkins, Richard G. Environmental Quality 1976, 1978,
1979 Hillsborough County, Florida, Annual Reports.
Hillsborough County Environmental Protection Commission.
16. Florida Department of Environmental Regulation. Unpublished
Chemical and Biological Water Quality Data, 1970-1980.
17. Lewis, Roy R. and William D. Courser. McKay Bay: Past,
Present and Future. A Joint Report by Save Our Bay, Inc.
and the Tampa Audubon Society, 1972. 57 pp.
451
-------
INSTRUMENTATION AND AUTOMATION CONTROL
OF
MUNICIPAL SLUDGE TREATMENT FACILITIES
Irwin 0. Kugelman, Sc.D.
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Robert C. Polta, Ph.D., and Don Stulc
Metropolitan Waste Control Commission
St. Paul, Minnesota 55101
George A. Mathes
EMA, Inc.
St. Paul, Minnesota 55101
INTRODUCTION
Dewatering and ultimate disposal of sludge resulting from primary and
secondary treatment is a major problem in the United States. Costs range
from 30% to 50% of the total treatment expense depending on the plant size
and the technology applied. One potential method of reducing costs in this
area is the application of instrumentation and automation to process control
of dewatering and ultimate disposal. Unfortunately only minimal application
of instrumentation and automation has been made in this area. Thus the U.S.
EPA entered into a joint program with the Minneapolis-St. Paul Metropolitan
Waste Control Commission (MWCC) to investigate, develop, and demonstrate
process control and automation of dewatering and incineration of domestic
sewage sludge.
Based on frequency of use in the U.S. and availablility of full-scale
parallel lines of equipment at MWCC, the decision reached was to concentrate
on the following four processes: gravity thickening, chemical conditioning,
vacuum filtration, and multiple-hearth incineration. The data on automation
of a gravity thickener was presented at the last U.S.-Japan Conference in
October 1978 (1). The full details of the study are in an EPA report (2).
This paper will deal with the studies conducted on the other three unit
operations.
The studies here involve determination based on literature sources,
laboratory tests and field tests of control strategies for each unit operation
453
-------
including an evaluation of the instrumentation and automation necessary to
implement the control strategy. As the studies were conducted on full-scale
equipment side by side with identical manually controlled equipment the cost
effectiveness of the automation could be determined. Additionally the three
unit operations are connected in series and were evaluated as an overall
treatment line rather than individual units. That is, a control strategy
was developed for economic optimization of the overall sludge handling line
rather than optimization of each unit separately.
Unfortunately all of the studies have not been completed at this time.
Therefore this paper will deal with the progress made to date on each phase
of the project.
FACILITY DESCRIPTION
A. General
The Metropolitan Waste Control Commission (MWCC), which was formed in
1970, currently operates 16 wastewater treatment plants in the Minneapolis-
St. Paul metropolitan area. Average flows at the facilities fall in the
range of approximately 0.2 to 200 mgd. All of the work described in the
following sections was conducted at the Seneca Wastewater Treatment Plant
which is located on the Minnesota River in the City of Eagan, Minnesota.
This facility serves a number of suburban communities south of Minneapolis.
The Seneca Facility was placed in operation in July 1972 with an
average design capacity of 24 mgd. During 1979 the flow averaged
approximately 13.5 mgd. Based on MWCC records approximately 5% of the
influent flow is from industrial sources. The treatment scheme consists of
screening, grit removal, primary sedimentation, complete mix activated
sludge, final sedimentation, and chlorination prior to discharge to the
receiving stream.
B. Liquid Train
The liquid treatment portion of the plant is divided into two parallel
treatment trains each with a nominal capacity of 12 mgd. The following
paragraphs describe one of the parallel treatment trains; however,
considerable flexibility does exist and the flows can cross over between
trains at several points as illustrated in Figure 1.
The raw wastewater is screened to remove large debris which might
interfere with mechanical equipment downstream. Grit is removed in an
aerated grit chamber with a detention time of approximately 15 minutes.
Subsequent to grit removal the wastewater flows by gravity to the
primary sedimentation basin. This basin is square and has a side wall depth
of 12 feet. The surface overflow rate at design flow is 512 gpd/sq. ft. The
basin is equipped with a center inlet and sludge plows for central sludge
withdrawal. Surface skimming equipment is provided for removal of scum.
454
-------
FLOW DIAGRAM-LIQUIDS PROCESSING
H
MECHANICAL
SCREEN AND
GRINDER
GR|T TO HUMP
SLUDGE RETURN
AERATION
BASIN
AERATION
BASIN
M
THI
"ii'i:
'':;':;
DESIGN FLOW - 2-1 MGD
RAW WASTEWATER
GRIT RtMOVAL
1-6 cf/mg/day
PRIMARY TREATMENT
nNA,
EFFLUENT
BOD 2,160 lb/day
SS 2,660 Ib/day
FIGURE 1. SENACA TREATMENT PLANT
-------
The primary effluent is distributed by gravity to two mechanically
aerated basins each with a volume of approximately 730,000 gal. Total
aeration time at design flow, excluding sludge recycle, is approximately 3
hours. The dissolved oxygen concentration in the basin is adjusted by
controlling the aerator submergence with adjustable weirs. The mixed liquor
discharges to two square final sedimentation basins with side wall depths of
15 feet. The surface overflow rate at design flow is 490 gpd/sq. ft. These
basins utilize center inlets and skimming equipment similar to the primary
basins; however, the sludge collector is of the "vacuum cleaner" type. Both
variable and fixed speed pumps are used to return and waste sludge as
required. Excess sludge is wasted to floatation thickeners.
The plant effluent is disinfected with chlorine prior to discharge to
the receiving stream. The chlorine contact chamber provides a nominal
retention time of 22 minutes at design flow prior to discharge through
approximately 0.5 mile of 84 inch diameter outfall sewer.
The discharge permit granted by the state of Minnesota requires that
the Seneca plant meet the following effluent requirements:
Suspended Solids
BOD
Fecal Coliform
30 mg/1
25 mg/1
200/100 ml
During 1979 the average effluent concentrations were:
Suspended Solids
BOD
Fecal Coliform
20
16
17 (average of monthly
geometric means)
C.
Sludge Train
1. General
The solids processing operations are housed in the Seneca solids
processing building and include floatation thickening of waste activated
sludge, vacuum filtration and incineration. All of the primary and waste
activated sludges generated in the Seneca liquid treatment trains are
processed along with sludges hauled to Seneca from other Mw"CC facilities.
During 1979 approximately 38 million gallons of liquid sludge was processed
including approximatley 10 million gallons which was hauled to the plant.
The schematic diagram presented in Figure 2 describes the sludge
dewatering trains. Each of the two parallel treatment trains consist of
chemical conditioning facilities, one vacuum filter and one incinerator. The
two trains can be cross connected just upstream of the incinerators. The ash
from each incinerator is slurried and transported to a lagoon for gravity
dewatering and storage.
456
-------
To Stack
FeCI3
40%
H,0
CaO
90%
To Incinerator
CO O
a, O.
-O1 O
3 01
-Air'
_u
Fe
r
>
CI3 10%
i
T
y
I
•^
'/
Cone
Tanh
H20 To Stack
4-
£i—»-Ash Pond
FIGURE 2. SLUDGE PROCESSING AND ULTIMATE DISPOSAL FLOW SHEET
-------
The vacuum system is common to both the form and drying zones of the
filter. Under normal operating conditions a vacuum of 20 to 25 inches Hg can
be maintained in the form zone; however, if cracks develop in the drying zone,
the form vacuum drops substantially.
The cake discharges from the filter media by gravity and falls onto a
horizontal conveyor belt which in turn discharges to an inclined conveyor
which is used to load the incinerator.
5. Incineration
The filter cake is discharged from the inclined conveyor to a screw
conveyor which subsequently discharges to the 23 ft. diameter seven hearth
incinerator through a hinged drop gate. The incinerator has a rated capacity
of 7 ton/hr. at 22% solids. Burners are located on hearths no. 3, 5, and 6
to provide the energy to maintain combustion temperatures. The burners can
be fueled with natural gas or fuel oil.
The cake and ash are moved from hearth to hearth by a series of rakes
or plows attached to rabble arms which rotate around a central shaft. The
rotational speed of the rabble arm drive can be adjusted in the range of 0 to
2 RPM.
Ash is discharged from the bottom hearth into a slurry tank. The ash
slurry is then pumped to an ash pond for intermediate storage. Ash balls
which consist of volatile sludge solids covered and insulated by char are
removed on a bar screen just above the slurry tank. Combustion air is
supplied from several sources. Air is metered into the furnace at each
burner to ensure complete combustion of the fuel. The induced draft fan
maintains a slight negative pressure in the furnace; thus air will be pulled
into the furnace at all openings. An atmospheric air damper is located on
hearth seven to provide combustion and cooling air. Significant quantities
of air may also enter at the ash slurry chute as well as port holes that are
left open. The rabble arm shaft cooling air can be returned to the furnace
or discharged directly to the stack.
The hot gases, soot and fly ash discharged from the furnace are ducted
at a wet plate impingement type scrubber and subsequently discharged to the
stack.
OPERATING CONSIDERATIONS FOR SLUDGE TRAIN
A. General
Prior to 1970 most of the small treatment facilities in the
metropolitan area disposed of their sludges on land. As the metropolitan
area expanded and environmental legislation turned more restrictive it became
increasingly difficult to obtain land, and permits, for disposal of the
increasing volumes of sludge. Although MWCC is aggressively pursuing a land
disposal program (approximately 20,000 tons hauled to farms in 1979)
incineration and land disposal of ash will be the major sludge disposal scheme
in the forseeable future.
458
-------
2. Storage
The primary sludge and air floatation thickened waste activated sludge
along with the hauled sludges are discharged to two holding tanks. The tanks
are 40 feet deep and have a combined capacity of approximately 615,000 gal.
The contents of the tanks may be mixed by introducing air near the bottom on
a timed or manual basis. The mixing air is vented to the incinerators to
prevent odor problems.
Sludge can be withdrawn from the tanks at seven points along the side
wall between 0 and 35 feet above the tank floor. In addition supernatant
removal is provided with the supernatant returned to the primary influent.
The sludge is removed from the storage tanks using positive displacement
pumps of the progressing cavity type and transported to the conditioning tank
through approximately 150 feet of 6 inch dia. pipe.
3. Chemical Conditioning
Ferric chloride and lime are used to condition the sludge prior to
dewatering. Ferric chloride is delivered to the facility in solution form at
a nominal concentration of 40% FeCl3. The concentrated solution is diluted to
approximately 10% FeCl3 in a 2000 gal day tank. Air operated diaphram pumps
are used to transport the diluted FeCl3 solution to the point of addition to
the sludge. Prior to the initiation of this study the FeCl3 was added to the
sludge at the base of.the conditioning tank. The point of addition was
changed to allow for some additional mixing prior to lime addition. The
current addition point is approximately 25 feet downstream of the sludge pump
and approximately 125 feet upstream of the conditioning tank.
Lime is delivered to Seneca by railcar and stored in a large silo. The
delivered material is approximately 90% CaO by weight. The CaO is converted
to Ca(OH)2 using standard slaking apparatus. The Ca(OH)2 slurry is maintained
at approximately 10% CaO by weight and is transported to day tanks by gravity.
Positive displacement pumps, of the progressive cavity type, are used to
transport the lime slurry to the conditioning tank.
The conditioning tank has a volume of approximately 200 gal. and is
equipped with a variable speed mixer. The mixing impeller consists of 3
vertical, triangular shaped blades and rotates in the range of 25 to 84 RPM.
The conditioned sludge discharges from the tank over a weir approximately 16
in. long and flows down an inclined pan to the filter vat.
4. Vacuum Filtration
A conventional rotary drum filter, manufactured by Dorr-Oliver, is used
to dewater the conditioned sludge. The drum is 12 ft. in diameter and has a
total area of 528 sq. ft. The drum is covered with polyethylene media and can
be rotated in the range of 9 to 30 RPH.
The filter vat is equipped with a variable speed, paddle type agitator
which can be operated in the range of 5.7 to 13 cycles per min.
459
-------
The Seneca liquid trains are currently operated at approximately 50% of
design capacity; however, because sludge is hauled from several other treat-
ment facilities, the sludge processing trains are operated at their practical
capacity. In these circumstances the goal for the sludge processing trains
is "process the maximum quantity of sludge".
B. Sludge Processing Limitations
1. Chemical Conditioning
Each of the two sludge processing trains at Seneca consists of three
processes in series - chemical conditioning, vacuum filtration and
incineration. Depending on circumstances, any one of the three processes can
be the rate limiting step.
Prior to the initiation of this project the filter operator had no
quantitative criteria on which to judge the effectiveness of chemical
conditioning. If the cake discharged from the filter cloth and a reasonable
cake production rate was maintained the sludge was judged to be adequately
conditioned. If problems were encountered, cake discharge or production rate,
changes were made in the ferric chloride and/or lime dose. Each operator's
response was based largely on his previous experience. In terms of meeting
the plants performance goal the natural tendency was to overdose.
Because sludges from several plants were/are being processed at Seneca,
problems were encountered even when the chemical rates were extremely high. As
the physical and chemical characteristics of the raw sludge change the
dewatering characteristics of the conditioned sludge may change significantly
even when overdosed.
Rapid changes prevent both the filtration and incineration processes
from maintaining steady state conditions. The operators have observed that
old sludges are much more difficult to condition than fresh sludges; however,
if an inventory in the sludge holding tank is maintained at a minimum, the
impact of batch discharges from other plants on sludge properties is increased.
Because of the nature of the material used for conditioning, the
chemical feed pumps fail periodically. The impurities in the lime accelerate
the wear of both the stator and rotor of the progressive cavity pumps; and,
impurities in the ferric chloride prevent the check valve from sealing
properly allowing back flow. When the sludge is overdosed significantly it is
difficult to recognize the gradual deterioration of pump performance and acute
failures are more likely to occur. When one of the pumps fails, the operator
most likely will not become aware of this fact until the cake does not discharge
from the cloth and pump speed adjustments do not alleviate the problem. Such
failures require a full shut down of the filter and incinerator until another
pump is put into service, the filter vat and conditioning tank are purged of
the poorly conditioned sludge, and the filter cloth is cleaned.
As the subsequent chapters will point out in detail many of the problems
related to chemical conditioning can be ameliorated by monitoring the physical
and chemical characteristics of the raw and conditioned sludges.
460
-------
2. Vacuum Filtration
Prior to the initiation of this study the vat level was not automatically
controlled on either of the filters. The operator thus had four options to
change the cake yield: (1) change drum speed, (2) change vacuum, (3) change
sludge pumping rate and (4) change chemical conditioning. As a practical
matter the vacuum is held at max-imum value at all times. If the sludge is
overdosed moderate changes in chemical feed rates do not affect a significant
change in dewatering characteristics. The four options were thus reduced to
changes in the drum speed and/or pumping rate. Change in drum speed generally
required a change in sludge pumping rate. After several revolutions the vat
level reaches a new equilibrium. Small step changes are required to ensure
that the vat does not overflow or go so low as to expose the form zone on the
filter. Because of the lack of simple automated control and the uncertain
nature of the manual control scheme available,it is unlikely the operating
goal was attained a significant portion of the time.
Because of the variable nature of the raw sludge, the conditioning
process and filter operation itself, it is extremely difficult for an operator
to maintain a steady output of cake with uniform burning characteristics.
The data presented in Figure 3 were collected during a 24 hour period in
1975. The solids content of the cake varied from 14% to 25.5% and the
volatile solids content fell in the approximate range of 53% to 68%. For a
six hour period the sludge was returned to the plant headworks because a cake
which would discharge from the filter cloth could not be formed. During a
similar sampling period in 1976 the solids content varied in the range of
approximately 20% to 28% and the filter yield varied by a factor of three.
Experience with the sludges processed at Seneca indicates that the phi
of the conditioned sludge must be raised to approximately 12.0 to obtain
adequate dewatering characteristics. At this high pH there is a definite
tendency to deposit lime on all surfaces including the filter cloth and
vacuum system. When the sludge is overdosed it is reasonable to believe that
this plating tendency increases thus causing increased downtime for acid
cleaning.
3. Incineration
Because there is no cake storage capacity at Seneca, the incinerator in
each train must burn the cake as produced. This must be accomplished within
the constraints of meeting air pollution standards and maintaining hearth
temperatures below 2000°F to protect the furnace structure. In addition, it
is required that good volatile destruction be obtained and the formation of
ash balls be minimized.
Because of the variable nature of the filter output it is extremely
difficult to maintain steady burning conditions in the incinerator. The
situation is further complicated by the fact that the analog temperature
control system, designed to control the burners, does not function properly
because of interaction between the hearths. In addition, the excess oxygen
461
-------
NJ
ID
•H
r-1
O
&~-S
I
d>
cti
u
28
26
24
20
18
16
12
10
16 1? 20 22 24
n 2 4 6 8 10 12
Time - Hours
rH 4
FIGURE 3. VARIABILITY OF CAKE DISCHARGE FROM VACUUM FILTER UNDER MANUAL CONTROL
-------
level is not measured and therefore cannot be easily controlled.
In the existing system the operators have few tools available to them
to attain the operating goal and must make judgements based on past
experience and process understanding. It is thus not surprising to find that
the performance of the entire sludge processing train can and does vary from
shift to shift.
C.
Cost
The total operating cost for sludge dewatering and incineration at
Seneca is the sum of the costs for chemicals, energy, and labor. In the
following paragraphs an attempt is made to characterize portions of these
cost categories for the Seneca solids processing trains for the year 1979.
All costs are in terms of January 1980 dollars.
Based on Seneca operating records for 1979 approximately 38 million
gallons of sludge with an average solids content of 5% was dewatered to yield
approximatley 88 million pounds of cake with an average solids content of
21%. The quantities and costs for conditioning chemicals were as follows:
1979 Cost
Matl.
FeCl3
CaO
Total
Ib.
1,362,000
3,358,850
4,720,850
Avg. Dose-%
8.5
21
29.5
Total-$
95,340
96,660
192,000
$/Ton Sludge-Sol
11.95
12.11
24.06
ids
Natural gas is supplied to the Seneca facility on an interruptable
basis. As the system wide demand for gas increases during the cold weather
months the gas supply is terminated and an alternate fuel (oil) must be used
in the incinerators. During 1979 incinerator fuel quantities and costs were
as follows:
Fuel
Natural Gas
Oil
Quantity
117,188 mcf
149,020 gal
1979 Cost
Tota1-$ $/Ton Sludge-Sol ids"
140,625 17.62
119,214 14.94
Total
259,839
32.56
463
-------
A total of five positions are involved in the operation of the solids
building as follows:
Annual Cost
Position % Time (all shifts and fringe benefits)
Building Operator (foreman) 90 $93,000
Filter Operator 100 $102,000
Incinerator Operator 100 $102,000
Laborer 100 $91,000
Laborer 50 $45,000
Total - $433,000
Based on 1979 records the labor cost per ton of sludge solids processed is
approximately $54.26.
Only those costs that are easily estimated and allocated to the solids
processing trains were presented above. The two remaining cost items that
will be significant are electricity and maintenance (contract and by MWCC
tradesmen). At the present time no attempt has been made to estimate these
costs.
For those cost categories considered the dewatering and incineration
cost per ton of sludge solids totals approximately $110.90. It does appear
that this unit cost can be reduced by improved process control. The elimina-
tion or reduction of chemical overdose and underdose should result in a net
reduction of chemicals and provide a more uniformly conditioned sludge for
filtration. By manipulating the filter variables, submergence, drum speed,
and vacuum, the filter cake yield can be adjusted to meet operating goals and
produce a more uniform output. Uniform loading of the incinerator will
significantly reduce the temperature excursions and should reduce fuel
consumption. It is also anticipated that the total weight of sludge solids
processed can be increased by maintaining steady operation. If a significant
change can be obtained the unit cost for labor may be reduced; however, there
will most likely be a labor cost associated with improved process control in
terms of process control hardware maintenance.
464
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CHEMICAL CONDITIONING
A. Preliminary Studies
Chemical conditioning is used to alter the dewatering characteristics
of sludges. In order to achieve control over this operation it is necessary
to estimate or directly measure the dewatering characteristics of the sludge
as a function of chemical addition. The two most commonly used methods of
estimating sludge dewaterability on a filter are capillary suction time (CST)
and specific resistance (SR). The CST method developed by Baskerville and
Gale (3) involves the time measurement of water withdrawn by gravity from a
sludge sample placed in a metal cylinder. The rate of water movement is
measured by the time required for the water to move through a standard
distance on a section of chromatography paper. CST measurements have been
related to the chemical dose applied to sludge, to the resulting pH (4), and
to characterize the filterability of conditioned sludge exposed to shear
forces (5). The SR method of determining sludge filterability developed by
Coackley (6) involves filtration of a conditioned sludge sample through a
given filter medium under a known vacuum. The volume of filtrate as a
function of time is used to calculate the SR. This parameter has been
related to chemical dose, pH and CST (4), (7), and vacuum filter performance
(8).
Ideally as the sludge dewatering characteristic changes an on-line
measurement would send a signal which could be used to vary the chemical dose
so as to achieve the desired dewatering characteristics. Unfortunately
neither CST or SR are directly measurable on-line. However, it was felt that
a correlation was possible between other parameters which could be measured
on-line and CST or SR or both.
In order to develop these correlations previous records of the
performance of the vacuum filter, chemical dosing, and pH measurements were
made. These indicated some fair correlations between CST and these other
parameters. The literature indicated that in addition shear stress (9) and
Oxidation Reduction Potential (ORP) (10) should also be considered.
An extensive series of bench scale tests were conducted from November
1978 thru February 1979 in which samples of raw sludge were conditioned with
ferric chloride and lime and measurements of pH, ORP, suspended solids, shear
stress, CST, and SR were made. Table I gives the parameters measured. Table
1A in the appendix presents the data collected in this phase of the study.
The data analyses was conducted with the Statistical Package For the Social
Sciences software at the University of Minnesota Computer Center. These data
yielded the following correlation equation for the SR of the sludge after
ferric and lime conditioning. The correlation coefficient (R) was 0.85.
SRL = -5.9 + 0.76 CSTL - 1.52 SSL + 0.165 T 60 - 0.098 T 30 n)
+0.003 ORPL - 0.055 T 12 + 0.83 PHL - 0.03 TL
The^regression analyses indicated that essentially all of the useful information
is incorporated into the model after the addition of the third term T 60.
465
-------
TABLE 1. PARAMETERS MEASURED IN DEVELOPMENT OF
SLUDGE DEWATERABILITY CORRELATIONS
Symbol Definition
SSR Suspended solids concentration in raw sludge, % solids
PHR pH of raw sludge
PHF pH of ferric chloride conditioned sludge
PHL pH of lime conditioned sludge
ORPR ORP of raw sludge, mv
ORPF ORP of ferric chloride conditioned sludge, mv
ORPL ORP of lime conditioned sludge, mv
T 12 Shear stress of lime conditioned sludge, 12 RPM,
dyne/sq. cm.
f 30 Shear stress of lime conditioned sludge, 30 RPM,
dyne/sq. cm.
T 60 Shear stress of lime conditioned sludge, 60 RPM,
dyne/sq. cm.
CSTR CST of raw sludge
CSTF CST of ferric chloride conditioned sludge
CSTL CST of lime conditioned sludge ,.,
SRL Specific resistance of lime conditioned sludge X 10 m/kg
SSL Suspended solids concentration in lime conditioned sludge,
% solids
TL Temperature of lime conditioned sludge, °C
PF Ferric chloride feed % by weight dry sludge solids
PL Lime feed % by weight of dry sludge solids
466
-------
A simpler equation using the important parameters of equation 1 is
given in equation 2. The latter equation has an R of 0.82.
SRL = 5.4 + 3.94 (CSTL/SSL) + 0.56 T 60 (2)
Unfortunately all the parameters in equations (1) and (2) are not easy to
monitor on-line. For example CST cannot be monitored on-line and it is not
feasible to measure shear stress at more than one value of speed of rotation
of a viscometer. The best equation using parameters which can readily be
measured on-line is equation 3 below with R=0.69.
SRL = 17.2 - 1.06 SSL + 3.41 PHF - 3.86 PHR + 0.006 PHF (3)
+ 0.1 TL- 0.45 PHL - 0.016 T 30
This preliminary analysis indicated the potential feasibility of
constructing a workable sludge conditioning model from on-line data.
B. On-line Data Collection and Instrumentation
In order to verify or modify the correlations given above, sensors were
installed in the actual chemical conditioning system to collect data on-line.
First the experiences with the instrumentation are discussed below.
1. Suspended Solids
A Biospherics Models 52-H solids analyzer had been installed in June,
1977 to moniter raw sludge solids input to the vacuum filter. Calibration
data collected during 1978 showed a correlation of 0.93 between the analyzer
readings and laboratory analysis. The unit failed in January, 1979 and was
replaced by another Model 52-H analyzer in February, 1979. Calibration data
for the second analyzer also averaged 0.93 with a range of 0.87 to 0.96.
These analysers have shown excellent performance.
2. pH Analyzers
Sampling systems were initially installed to transfer both raw and
ferric chloride conditioned sludge to open vessels where immersion type pH
assemblies were used to monitor pH. An automatic clean water flushing was
installed to prevent plugging on the suction side of the sampling pumps. The
suction line was kept clear; but, the suction port of the sample pumps
plugged repeatedly and the sampling system was abandoned.
Insertion type pH probes were procured and installed to monitor both
the raw and ferric chloride conditioned sludge. Some problems have been
encountered with debris on the ferric sludge electrode and the seals between
the electrode and probe housing have failed on several occasions. The
subsequent leakage to the transmitter enclosure caused problems. The data
collected in 1978 yield correlation coefficients of 0.89 and 0.94 for the raw
467
-------
ferric chloride sludge monitors, respectively. The correlation coefficients
are based on comparisons of the readings of the monitors and a reference
instrument.
Additional data collected over a 6 month span in 1979-80 for the raw pH
probe showed that the instrument calibration was adjusted approximately once
every 2 weeks. In 45 checks against pH buffer the average difference in the
pH reading from the buffer standard was 0.06 pH unit. The pH probe
monitoring ferric chloride sludge was recalibrated approximately once per
week. In 57 checks against buffer standards the average difference in the pH
reading from the buffer standards was 0.16 pH unit.
The pH of the lime conditioned sludge was monitored with an immersion
type assembly inserted into the conditioning tank. Scaling of the probe and
rag accumulation presented a maintenance problem. In order to maintain an
acceptable response the probe had to be cleaned at least once per day. The
insertion of the probe along the wall of the tank was found to create a
"dead" spot in the mixing which resulted in slow response times. Better
response has been achieved by mounting the probe directly into the stream
existing the conditioning tank. In 1978, calibration data for the lime
sludge pH probe yielded a correlation coefficient of 0.97 between instrument
readings and reference values in the pH range of 12.0 to 12.4. In 1979-80
Calibration data collected over a 6 month time span showed that the
instrument calibration was adjusted an average of once per week. In 46
checks against buffer standards the average difference in the pH reading from
the buffers was 0.15 pH unit.
3. Oxidation Reduction
ORP insertion type probes were mounted in the sludge piping to monitor
the ORP in the raw and ferric chloride conditioned sludge. Calibration of
the probe monitoring the raw sludge was difficult because continued drifting
in potential was observed when standard millivolt solutions were used to
calibrate the instrument in the -100 to -500 millivolt range. The stability
problem was partially resolved by using freshly prepared calibration
solutions. Forty-eight to 72 hours were required for electrode equilibration
following cleaning or calibration.
The ORP probe monitoring the ferric chloride sludge was calibrated in
the -200 to +200 millivolt range using stable redox standards. Ferric
coating of the electrode was frequently encountered necessitating daily
checking and/or cleaning.
4. Viscosity
Based on the relationships obtained between sludge fiIterability and
laboratory viscosity measurements, an on-line viscometer (Brookfield Model
VTPV, 0-500 centipoise) was installed in the sludge conditioning tank in
January, 1980. The instrument was installed with a 48 inch baffle tube
housing a motorized spindle suspended at the bottom of the tube. An outlet
port in the tube allowed conditioned sludge to exit through the side of the
tube allowing a continuous flow to pass the spindle. The bottom of the baffle
468
-------
tube was screened to prevent debris from entering the chamber. Initial on-
line tests were conducted comparing the instrument output to CST measure-
ments taken on the conditioned sludge exiting the conditioning tank. Despite
repeated testing, the instrument output could not be correlated to the CST
measurements. The viscometer was removed from the conditioning tank in order
to conduct static tests in quiescent samples.
Based on the instrument output in the static tests, it appears that the
viscometer is not sufficiently sensitive to changes in CST to provide useful
on-line conditioning information. This must be investigated further because
viscosity terms appear not only in CST correlations but in SRL correlations
equations 1, 2 and 3.
5. On-Line Data and Analysis
During the period September-December 1979 a total of 65 data sets were
collected with the on-line instrumentation discussed above. These data are
presented in Table 2A in the appendix. Measurements of viscosity were at 30
rpm and were conducted off line, as were measurements of CST and SR.
Preliminary analyses of the data did not include viscosity data. In addition
it was decided to use a split model with CST correlated against parameters
measured after ferric chloride addition and SR correlated against parameter
measurements after lime conditioning.
Two equations presented below have been elucidated for CST by multiple
correlation.
CST 1 = 21.7-10.2(PHD)+7.6(PHF)+1.8(SSR)-0.083(ORPD)+0.064(ORPF) (4)
CST 2 - 60.1-1.16(PHD)-3.9(PF)-0.153(ORPD)+1.9(SSR)+10.3(PHF)
+0.067(ORPF) (5)
In these equations PHD = PHR-PHF, ORPD - ORPR-ORPF|
R = 0.62 for equation (4)
R - 0.85 for equation (5)
Figure 4 presents a plot of these two equations against some recent (February
1980) data. Equation (4) CST 1 fits the data better in the early part of the
run while equation (5) CST 2 fits better during the latter part. Data
collection will be continued to improve this correlation.
Equations 6 and 7 below were developed from the on-line data.
SR 6 = 21.1-0.22(PL)-0.3(PF)-1.06(SSR)+.003(ORPD) (6)
+ 0.79(PHD)-0.61PHL
SR 7 - 32.4-0.29PF-1.04SSR-1.79(PHL) (7)
where ORPD and PHD are the same as in equation (4) and (5).
469
-------
40
CST TIME
(SEC)
30
20
10
11:00 12:00 13:00 14:00
TIME (2-12-80)
15:00
16:00
ST1
.Measured CST
FIGURE 4. COMPARISON BETWEEN CST PREDICTED BY CORRELATION EQUATIONS
FROM ON-LINE SENSOR DATA AND LABORATORY MEASUREMENT
-------
Equation 6 has the better correlation coefficient R=0.8 than equation 7
R=0.67. The former equation contains more terms and a greater number which
occur in the CST correlation equations 4 and 5. Data collection will
continue to improve these equations. It is hoped that viscosity measurements
can be included as these should improve the equations developed. In addition
some consideration is being given to the use of a non-linear equation format
to fit the data. Finally SR values directly generated by the full scale
filter operation rather than by laboratory tests will be available for the
final correlation.
C. Design of Chemical Conditioning Control Systems
1. Control Loop Decoupling
The conditioning control problem is to design a control strategy that
controls the ferric chloride addition and the lime addition by adjusting pump
speeds so that the. sludge is conditioned properly. Tests conducted early in
the project indicated that for optimal conditioning the two chemicals should
be added at different locations in the process flow. This would avoid the
ferric and lime interacting with each other instead of the sludge. These
tests resulted in changing the ferric chloride addition point from just below
the mix tank to just after the magnetic flow meter in the sludge feed line.
With this change the ferric chloride had about 2 minutes ( 100 feet of pipe)
to condition the sludge prior to reaching the lime addition point. A second
result of this separation was that the control strategy was decoupled and
made serial; first ferric, then lime, with a two minute time difference.
Hence, the conditioning control strategy was broken into two control loops
for design.
Design of the conditioning control systems was conducted prior to and
coincident with the development of the chemical conditioning models presented
previously. In the discussion below some of the activities in conjunction
with control based on simpler models (i.e. mass flow proportional) than those
which were developed is discussed. It was this early work which partially
indicated that more sophisticated conditioning models would be required if
the system was to be optimized.
2. Ferric Chloride Control
The first ferric chloride control strategy was a simple feed forward
mass flow pacing control. A ratio was entered and the ferric chloride
metering pump speed was adjusted in proportion to the pounds of solids
entering the process. This strategy functioned as designed but resulted in
periodic over and under dosing whenever sludge type or quality changed.
Because of the variability of sludge quality, it became very difficult to
determine the correct dose ratio at any given time without extensive lab
analysis.
In order to minimize the effects of sludge variability on the control,
a feed back type of control was designed. The most significant measurable
feedback variable as determined by lab conditioning tests was pH. The
requirement that the variable be measurable by on-line instrumentation heavily
471
-------
influenced this selection. The first implementations of control using a pH
loop were unsuccessful due to instrument/sensor problems. The pH sensor
depended on a sample system that proved to be unreliable. However, the
experiments did indicate that the pH control approach would work. The
sampling system was removed and in-line probes were installed to measure both
pH and ORP of the ferric conditioned sludge.
Testing was conducted to determine the process dynamics for a pH
control loop. Parallel tests were conducted simultaneously on ORP as a
second feed back variable. The ferric tests show that both the pH probe and
the ORP probe measure a change when the ferric pump speed is changed. The pH
signal was observed to contain much more noise than the ORP signal. The
frequency of the pH noise appears to correspond to the stroke rate of the
ferric pump, which indicates that mixing is not complete in the sludge line.
The ferric conditioner may be remaining in pockets in the sludge line at
regular intervals thereby causing the signal "noise." The ORP signal is
relatively smooth.
The ferric tests Table 2 indicate that the time before response
(deadtime) of the pH and ORP are about the same. However, the process
storage time (time to reach 63% of final value) for the pH signal is much
shorter than the ORP. Since the pH signal would require a filter (which
introduces a delay), the pH and ORP signals are relatively equivalent,
dynamically, in their advantages and disadvantages for use as feedback in the
control.
The analyses of the FeCI_3 testing provides the prerequisite data to
construct a dynamic model for pH of the process. A block diagram of this
model is shown in Figure 5. The model is expressed in Laplace transform
notation for control system convenience. The model indicates that a change
of 1 gpm in pump speed multiplied by the process gain of -0.89 would result
in a pH change of -0.89 after a sufficient time was elapsed. The deadtime
and lag times appear as coefficients of the Laplace variable S. Using this
dynamic process model the theoretical gains for the PID three mode controller
were calculated.
Even with a closed loop pH control running, it became apparent from
data on the feed sludge, that there was again no simple pH setpoint that the
control loop could use. Thus, the feed back approach; even though variations
in pumping and in ferric chloride concentrations were now eliminated,
required additional parameters to make the loop functional and responsive to
real sludge conditioning needs.
As indicated previously the best indicator of how well the sludge had
been conditioned after ferric chloride addition was determined to be either a
(SR) analysis or a (CST) measurement. However, neither of these parameters
were measureable with instrumentation for use in a control system. Both,
however, were parameters that could be setpointed with a specific value with
a reasonable degree of confidence. A control strategy that could control the
CST of the ferric conditioned sludge so that the CST stayed within a relatively
small deadband around a stated setpoint should in principle compensate for
normal changes in sludge quality. CST was chosen over SR because it was a
472
-------
TABLE 2.
PROCESS DYNAMICS Fed3 CONDITIONING
Date Time
9-19 11:30
9-19 13:50
9-19 14:27
9-21 15:14
Chart pump change
(GPM)
A 2.6
B 2.4
C 2.7
D 2.7
Averages
K
process gain
-1
-0
-0
-1
-0
.00
.74
.80
.03
.89
eH
TD
dead time
(min)
1
1
1
1
1
.5
.8
.0
.3
.3
TPS
K
storage time
(mi n )
2
2
2
1
2
.0
.3
.2
.8
.1
-1.
-0.
-0.
-1.
-0.
10
72
70
29
95
ORP
TD
(min)
1.4
1.2
1.4
1.3
1.3
TPS
(min)
3.2
3.4
4.7
3.6
3.7
-------
Process
Noise
FECL3
(0-6 gpm)
Pump Speed Control
-0.89e
-1.33S
0.75S + 1
Process Value
2-6 PHU
0.95e
-1.33S
2.4S + 1
ORP
-200 to +200 MV
FIGURE 5, DYNAMIC MODEL FOR FeC13 EFFECT ON pH AND ORP OF SLUDGE
-------
much simpler measurement to make and correlated very well with specific
resistance when 50!ids were taken into account.
The previous sections have discussed in detail the development of a
model that relates measureable process parameters to the ferric conditioned
sludge CST. The use of this model in the control strategy design is shown in
Figure 6. The pH feedback loop is retained because of its advantages of 1)
providing corrective action on errors, 2) eliminating pump metering
fluctuations, 3) eliminating ferric chloride concentration fluctuations, and
4) minimizing the dependence on process sensors.
The model receives inputs from the process sensors and calculates a
predicted conditioned sludge CST value. This prediction is then compared to
the desired CST setpoint. If they are different an adjustment is calculated
for the pH controller's setpoint which ultimately will change the CST to its
desired value. To avoid coupling problems the control part of the CST model
is designed to be recalculated very infrequently relative to the pH
controller, thereby appearing to be constant to the controller. The control
strategy flow chart is shown in Figure 7.
3. Lime Control
The development of the lime control strategy paralleled the ferric
control very closely. First a mass flow proportional control was designed,
followed by a pH feed back control which led to a modeling effort. In this
case the SR of the lime conditioned sludge was chosen because it can be
related to filter yield by a procedure described in the next section. The
control strategy for lime is shown in Figure 8. Either equation 6 or 7 or
some variant will be used as the SR model.
Dynamic testing of the lime pH response was conducted to determine the
process model and the 3-mode controller tuning constants. The lime tests
show that the pH after lime addition is very high and relatively insensitive.
Large changes in lime pump speed were necessary to obtain relatively small
changes in pH. In some of the tests lime dose was so high at the beginning
of the test that virtually no change was observed in the pH.
The dynamic model based on this testing can be expressed in Laplace
Transform Notation as:
CaO
(0.15 gpm)
0.44 e
-3.15S
4.2 S + 1
pH
(9-13 pH)
Therefore a change of 1 gpm will result in a pH change of 0.44 after a
sufficient time period and provided the pH is not already near the saturation
point.
475
-------
CST setpoint
I
Feed \ " * CST Model
Sludge ^pH >CST = f(8S)pH
yOR£._> orp,orpf,pH
1
1
^ sp
P3
Contro.
r
1
/ FECL3 \ |
\ Daytank ) v'
^x_ Ferric
^s. Pump
Flow SSolids pH ORP
Sludge 1
Feed >-" ' ' ' __
"" ^PHF ~) FECL3
S, Conditioned
'x ^ORPF) Sludge -~~^~.
t y MIX
I TANK
Feedback pHF \
ter
ORPF
/
process
sensors
a
7
FECL3 conditioned
sludge
FIGURE 6. FERRIC CHLORIDE DOSE CONTROL
-------
Yes
Calculation
Get Sensor
Values & Calc
CST Model
Recalculate
the pH
setpoint
Apply limits
Ti'mpr
Reset delay
timer
calculate
PID algorith
output new
numn sneed
FIGURE 7. CST CONTROL STRATEGY FLOW CHART
477
-------
TABLE 3. PROCESS DYNAMICS LIME CONDITIONING
Date
9/14
9/21
9/21
9/26
10/2
Time
1130
1451
1558
1704
1604
Pump
Change
gpm
2.05
3.2
14%
9%
2%
K TD
(min)
-
.33 3.0
.54 3.3
-
_ _
TPS
(min)
-
9.3
5.4
-
_
Averages .44 3.15 7.35
478
-------
feed forward
feed back
parameters
Specific Resistance Model
FECL3 CST
Setpoint
I
to CST
setpoint
on Figure 7-11
Lime pH
Setpoin
sp
intnixe
Lime
SLurry
Day
Tank
PH
controllei
1
I
I
\l/
i r ^
M
£_f_e.ec
•s,
S
Ibac.K
I mi XPT
Mix
tank
FECL3
Conditioned N-
Sludge
Lime
Pump
to Vacuum
Filter Basin
FIGURE 8. LIME DOSE CONTROL
-------
DEVELOPMENT OF VACUUM FILTER CONTROL
A. Preliminary Work
Preliminary work on the vacuum filter included literature studies,
field observation and lab test data to identify possible filter control
strategies and the instrumentation necessary to implement the strategies.
Manual operation of the filter relies very heavily on visual observation and
experience for proper operation. Based on these investigations the
instruments shown in Figure 9 were selected to study the automation and
optimization of control on the vacuum filter. As will be seen this selection
was based on the vacuum filter control strategy model given in C below.
B. Instrumentation
For each of the instruments involved specifications were prepared to
ensure proper operation in the harsh environment anticipated. Below a brief
description of the instruments is given and their relative success.
1. Raw Sludge Flow
Sludge flow to the filter is measured using a Fisher-Porter magnetic
flowmeter. This meter is part of the existing plant instrumentation
installed when the plant was built in 1968. This meter provided a reliable
metering of the raw sludge with little upkeep required.
2. Vat Level
Measurement of sludge level in the filter vat was added as part of the
automation project. Manual operation of the filter relies on periodic visual
inspections of the level. Satisfactory instrument accuracy was achieved with
both sonic and capacitance type level sensors. The Endress Mauser sonic
transmitter was utilized for the control strategies. The use of a stilling
well and digital filtering of the signal were required to minimize the effect
of wave action caused by the vat agitation. Frequent flushing of the
stilling well was required to avoid sludge buildup and maintain instrument
accuracy.
3. Drum Speed and Agitator Speed
Both the filter drum drive and the vat agitator drive were originally
equipped with hand crank speed controllers without feed back ability. Both
variable drive units were modified for remote control by adding reversing
motor actuators; tachometers were installed to provide feedback. These
modifications provide the interfacing necessary for control with a computer
based control system.
4. Vacuum Pressure
Form vacuum and dry vacuum measurements were originally made using
local gauges. Control was implemented through manual valves. Rosemount
differential pressure transmitters were installed on both the form and dry
480
-------
00
Agitator
Speed
Form
Pressure
Cake
Thickness
DRUM
r
/ fi/// *///////////1 / /
Valve
Dry Positio
Press
Conveyor
Moisture
Weight
FIGURE 9. INSTRUMENTATION OF VACUUM FILTER
-------
vacuum lines for remote monitoring. A motor actuated center line valve was
installed on the form vacuum replacing the existing manual valve. The
automatic valve can be controlled locally or through the computer remotely.
5. Cake Thickness
A Wesmar sonic type transmitter was installed to measure the thickness
of the cake formed on filter drum. The sensor is calibrated to read 0-1" of
cake. The modified instrument range created difficulties but yielded
satisfactory results. The signal required heavy filtering to smooth the
process noise created by the variation in cake surface and the slightly
eccentric filter drum. The drum is out of round by approximately 0.2 inches.
Zero drift is somewhat of a problem and requires frequent checking.
6. Cake Weight
Filter output is measured by a BIF conveyor scale. The filter was
originally equipped with a scale which was replaced during the automation
study. Irregularities in cake placement along the belt require the
instrument output to be heavily filtered. Zero shift has been a continuous
problem with the instrument, most of which can be attributed to water on the
belt or buildup of sludge cake on the conveyor system.
7- Cake Moisture
On-line measurement of filter cake moisture content is an important
feedback measurement indicating vacuum filter performance. Because of the
importance of the measurement for automation and the lack of tested
instruments for on-line cake moisture analysis, a testing program was
undertaken. Several instruments, from different manufacturers were tested
that utilized infrared reflectance and microwave reflectance techniques.
The performance of the instruments was affected by the uneven loading
of cake on the conveyor belt, varying distances between sensor and material
on the belt, sludge surface characteristics, and in some cases sensitivity to
the residual conditioning chemicals in the cake. The tests indicated that
the moisture analyzers did track together, even though variations in sludge
cake orientation, etc., made correlations to actual moisture look very poor.
Tests of analyzers in the lab measuring mixed samples correlated much better
to actual moisture than when the units were mounted on the conveyor. Based
on this fact a sampling system was devised to deliver a more homogenous
sample to the analyzers. The sampler consisted of a pump that ground up the
cake and delivered it to a small conveyor where moisture was measured. The
results of this test were mixed, and compounded by the problems of sampling
the cake. The testing program results indicate that the instruments tested to
date are not suitable for the application of measuring cake moisture on a
vacuum filter discharge conveyor.
C. Modeling
The vacuum filter model which will be used is based on the yield equation
given below. This equation is derived from mass balance considerations (1).
482
-------
(8)
L = Filter Yield Dry Solids/Unit Area/Unit Time
P = Vacuum Level in Form Zone
w = Dry Cake Solids per Unit of Filtrate
x = Ratio of Form Time to Cycle Time
u = Viscosity of Filtrate
t = Time of 1 Filter Cycle
SR = Specific Resistance
It can be seen that the parameters in this equation with the exception
of SR are physica-1 constants of nature (u), physical operating parameters of
the filter ( P, x, t) or output goals ( L, w). Thus if the correlations
which are being established in this study between SR and on-line parameters
(pH, ORP, etc.) are satisfactory, feed forward control of vacuum filter
operation will be achieved. As indicated previously tests are confirming to
sharpen the correlation equation for SR. Especially important is to use data
from full scale operation of the filter to determine values of SR for the
correlation. Figure 10 presents some data collected in 1978 with SR values
determined in the laboratory and SR values calculated from the vacuum filter.
These data indicate fair correlation between SR values generated in the
laboratory and SR values calculated from filter performance, and reinforce
the need to establish the final correlation using full scale filter generated
SR values.
D. Proposed Control System Design
Control of the vacuum filter may be broken down into four control
loops, corresponding to the four parameters which may be varied. They are
vat level, drum speed, pressure and agitation speed. All but the agitator
speed are included as parameters in the yield equation above and their
relationship to production may be determined using the yield model. A
description of each of the proposed control loops is described below.
1. Vat Level
This control loop (Figure 11) controls the speed of the raw sludge pump
to maintain the vat at a set level. The algorithm is a cascade control loop.
The internal loop is a flow control loop which receives the sludge flow
signal as feedback and outputs a speed adjustment signal to the pump motor.
The outside cascade loop provides the flow setpoint to the flow controller
based on vat level.
The level setpoint to the outside loop can be operator input or
controlled by an algorithm which modulates the level setpoint based on a
manually entered cake moisture content value.
483
-------
12
O
4-1
cd
t-i
o
rO
cd
01
o
c
cd
4-1
W
•H
W
0)
u
•H
M-l
•H
O
246
Specific Resistance
8 JO
(Filter Data)
12
FIGURE 10. COMPARISON OF LABORATORY & VACUUM
FILTER GENERATED VALUES OF SPECIFIC
RESISTANCE ON THE SAME SLUDGE
484
-------
00
t_n
Se
Com]:
t point 1
FLOW
CONTROL
mter
Feedback
1 Q £3 t- T-»/~»
Moisture ,
reedback
^1-
k. P . • ,
f T
•- LliVfcL, *~ CUNT
CONTROL Operator
ALGORITHM input
h
EL
ROL
i
{DIGITAL
FILTER
1 '
1
1
—
i
1
1
Filter Vat
FIGURE 11. FILTER VAT LEVEL (DRUM SUBMERGENCE) CONTROL
-------
This control strategy has been tested and implemented successfully
using operator setpoints for vat level. Further testing and refinements are
necessary before fully automatic control can be attempted. Operating
experience shows that the maximum production of dry cake solids occurs with a
very low vat level.
2. Drum Speed (Figure 12)
This control loop is a simple speed control loop. The speed controller
receives feedback from the drum tachometer and outputs speed adjustment
signals to the drum drive motor. Setpoint to the speed-controller can be
input by the operator or modulated by a production control algorithm (Filter
Yield).
Early observations have shown the production response of the vacuum
filter qualitatively consistent with the yield model. According to the model
dry production should increase proportional to the square root of drum speed.
This relationship has not been tested and fully verified as of yet.
The speed control loop has been tested and implemented using operator
input speed setpoints. Finalization of a speed setpoint algorithm is pending
further testing and evaluation.
3. Pressure Control
This control loop is a conventional pressure control loop. The pressure
controller would receive feedback from the form vacuum pressure sensor and
output control adjustments to the form pressure control valve. A setpoint
for the pressure would come from either operator input values or a pressure
control algorithm based on the yield equation. Normal operating practice
has been to leave the pressure valve full open, using maximum pressure.
Optimization of form pressure and design of a control algorithm is question-
able at this time.
4. Agitator Control
This control loop is a speed control loop in the same manner as the
drum speed control. The effect of the vat agitator on filter yield is not
addressed in the yield model. However operating observations have shown that
increased agitator speed will result in a thinner, dryer cake. Further
testing of this effect is planned to determine the importance of the vat
agitator and how it should be controlled.
The experiences described above with respect to the response of the
vacuum filter to changes in control parameters were not performed with
control of the dose of ferric chloride and lime by the SR correlations. Thus
they can not give quantitative confirmation of the model. During the next
few months the vacuum filter performance will be tested with tight control of
SR, in order to obtain quantitative confirmation.
486
-------
Moisture
Chemical
Flows^
MODEL
ALGORITHM
t t
1 |
1
i !
i i
Computer | |
1 1
I 1
1 1
Incinerator
Operator
i
1 t
| |
I 1
1
|
I Feedback *
1
Input
' Setpoint
SPEED
CONTROL
,
1
Setpoint
ill 4
1 i
L ,
L _ n
i
|
1
1
AT) Weight
FIGURE 12. VACUUM FILTER CONTROL
-------
DEVELOPMENT OF INCINERATION CONTROL
A. Initial Considerations
Unlike the situation for vacuum filter control some degree of automation
was available for the multi-hearth incinerator. This control system consisted
of panel mounted PID controllers for:
a) temperature control on each of the burning
hearths (#3, #5, & #6)
b) pressure control in the furnace
c) differential pressure across the scrubber
The pressure controllers which are used to adjust air flow into the
incinerator have generally functioned well and are generally kept in the
automatic mode. The temperature control loops have not functioned well and
are thus usually set in the manual mode. Unfortunately the operator has no
feed forward or feedback strategy to follow, rather the goal is to burn all
the sludge coming to the incinerator. Thus hearth temperatures fluctuate
significantly and excessive fuel use results.
To aid in determing the optimum control system, some consideration was
given to the interactions which occur in the incinerator. A preliminary
model of the incinerator was developed and testing was planned based upon the
model. Sludge flow changes are considered the basic cause for variations in
the hearth temperatures. It seemed consistent that a change in sludge feed
rate would affect all the hearths with hearth #3 being most strongly effected
and hearths #5 and #6 affected to a lesser degree. Similarly, it was
expected that fuel flow changes would only affect the hearth on which the
change was actually taking place, and the hearths above it. This interpretation
of incinerator operation led to the model shown in Figure 13 which is
presented in Laplace Transform Notation. Testing was then planned to determine
the process parameters and the accuracy of the model. This is described
below under Dynamic Testing.
B. Instrumentation
1. Existing Instrumentation
Since the incinerator is equipped with automatic controllers for
temperature and pressure, much of the instrumentation was already installed
and operating. This required that attention be given to signal types and
ways to interface these instruments to the computer system. This, in
general, was not a serious problem. All signals that were 4/20 mA or 10/50
mA were directly connected to the system multiplexer. The remaining types
were interfaced using standard plug-in signal converters to provide a
representative 4-20 mA signal.
A weight signal is provided on-line, but was found to be quite noisy.
Filtering was added to make this a useful parameter.
488
-------
CO
Feed
Rate
FIIP!
Flow
Hearth #3
FUP!
Flow
Hearth #5
Fuel
Flow
Hearth #6
C-
S
*
H
}
1
"
I
"if
|_
*
+\
J*
|
^,1
V * I
•
R
^
A
R
A =
R
R -
>
c
vd
Ths +
_H<
V
Tgs +
y
c
1
1
A
+,r
y
A
^i +
Moar-fh i3
neartn ffo
^ ^ Temperature
i f
Hearth #5
J ^ Temper 3 ture
/
N Hearth #6
J Temperature
* Anticipated Interaction
FIGURE 13. INITIAL INCINERATOR MODEL
-------
Damper positions are taken from the existing panel mounted indicators;
the voltage across these indicators is converted to 4-20 mA by a signal
converter.
The existing bolometer measures wet opacity and records the information
on a circular chart recorder. The pen servo mechanism was returned to the
vendor for addition of an interface which would output 1-5 VDC, this in turn
will be converted to 4-20 mA.
The existing furnace pressure and scrubber differential pressure were
10-50 mA signals. In these cases, the multiplexer input channel was simply
wired into the existing loop.
2. Added Instrumentation
In order to determine the relative efficiency of the computer control
system as compared to the local automatic control system, the auxiliary fuel
into the incinerator has to be metered. Turbine meters were installed in the
main natural gas line feed to each incinerator. Each meter is equipped with
a pulse head which generates a series of pulses proportional to the rate of
gas being used. This in turn is converted to 4-20 mA. At present, these
meters are not working properly and have been returned to the factory for
repair. A similar arrangement was used for measurement of the fuel oil flow.
These have not been tested at this time.
The exit gas flow will be measured in an attempt to calculate an energy
balance for the incinerator. The original intent was to install an insertion
turbine meter in the duct downstream from the breach of the incinerator.
However, there was not enough straight run duct to assure a reasonably
accurate measurement. Therefore, the meter was installed upstream of the ID
fan damper. The flow now measured is the total air flow drawn by the ID fan
which includes the ambient air from the scrubber.
Additional Type K thermocouples were installed in existing thermowells
to provide temperature measurement at various points in the air ducts and on
each hearth.
An important parameter is the oxygen in the exit gas from the incinerator,
The higher this value the larger the excess air entering the furnace and the
greater the fuel use (excess air serves to cool the furnace). A Hays
Republic monitor which employs sampling of the gas and transport of the
sample to the monitor located outside the incinerator was used for 2 months.
Continual difficulty with plugging of the sampling system resulted in
abandonment. A in-situ monitor (Dynatron) was installed in the exhaust duct
upstream of the scrubber. It was in place for 1 month prior to use and was
found defective. After repair it functioned for 2 weeks and again failed.
Failure was due to cracking of its ceramic cartridge; possibly due to
exposure to a zero oxygen atmosphere when the furnace was overloaded. It is
being repaired and will be installed again as this type has functioned well
in other incinerators. A manual device was used to collect the data discussed
here.
490
-------
The rabble arm speed is to be measured by a proximity switch which will
detect the presence of a rabble arm drive gear tooth. This will result in a
pulse train proportional to the speed of the rabble arm. As in the fuel flow
measurement, the pulse train will be converted to a 4-20 mA signal for input
to the multiplexer.
C. Dynamic Testing
1. Temperature Characteristics
a) Objective
In developing temperature control systems for the incinerator, a
model of the temperature dynamics is necessary to determine the
type and degree of interaction between the various hearth
temperatures, as well as the relative speed with which process
changes can occur. It is toward this end that testing of each
hearth temperature dynamics was conducted.
b) Test Setup
Although computer control is intended to be implemented on
Seneca Incinerator #1, testing of temperature dynamics was
performed on Incinerator #2. Incinerator #1 was unavailable
at the time the test was scheduled to be performed. Since
the hearth construction of each is identical, it is felt that
the test results are representative of each incinerator. All
temperature controllers were placed in manual mode.
A thermocouple from each of hearth's #3, #5, and #6 was directly
connected to a 3-pen strip chart recorder. Temperature
changes were then observed on each hearth in response to
various burner combustion air valve position changes. Since
the burner valve positions were not connected to a strip chart
recorder, the position change was simply noted on the temperature
chart recording at the time of occurance. The response curve
resulting from a burner valve position step change was then
used to calculate the respective process gain, time constant,
and deadtime.
Also tested was the hearth temperature response to variation
in the shaft cooling air damper position. When the shaft
cooling air damper position is 0%, all of the shaft cooling
air is directed to the exhaust stack. Increasing the position
to 100% increases the amount of air flow to hearth 7 of the
incinerator.
c) Observations
The calculated process parameters resulting from the step-change
tests of the burner combustion air valves are presented in
Table 4. The deadtime values are the result of a second series of
491
-------
TABLE 4. ESTIMATED MODEL PARAMETERS FOR INCINERATOR
Test
No.
3
15
K3
1.4
1.2
T3
4.0
3.6
D3
0.4
0.4
Comments
Hearth #5 is not fired.
Test
No.
5
6
16
K5
0.8
0.9
2.4
K56
1.9
2.1
6.1
D5
0.2
0.2
0.2
T5
4.0
4.0
4.0
Comments
Hearth #6 is not fired.
Hearth #6 is not fired.
Test
No.
7
11
12
18
K6
1.3
0
0
0.5
T6
6.0
_
_
2.0
D6
2.5
__
_
0.8
K65
1.9
0.8
1.0
0.7
T65
6.0
6.0
4.5
3.0
D65
1.0
1.0
0.5
0.7
Comments
Startup of hearth
#6 from 0-50%
Test Conditions
Furnace #2 10/13/79
Feed Rate = 4.2 tons/hour
Rabble Speed =2.1 rpm
Legend
K = Gain
D = Dead Time
T = Storage Time
Laplace Transform
Ke
,-DS
TS + 1
492
-------
tests which were performed to more accurately determine the process
deadtime. These values are used in Laplace Transform format to
describe the system dynamics.
During the testing, it was observed that the process gain varied
considerably and cannot be considered a constant value in the
process model. Figure 14 is a plot of the calculated process gain
as a function of burner combustion air damper position. The
process control system will have to accomodate this non-linear
gain function.
The observed temperature response indicated that, as anticipated,
fuel changes to hearth #3 had no effect on hearth's #5 and #6, and
hearth #5 and #6 did no appear to have a major affect on hearth
#3. It is thought that a change in temperature on hearth #3, as a
result of burner firing on #5 and/or #6, probably does occur after
a sufficient length of time, but this effect can be neglected for
control purposes. Apparently, hearth #4 serves to isolate hearth
#3 from the lower burning hearths. The testing did indicate a
strong interaction between hearths #5 and #6. This intersect is
accentuated by the relative location of the respective thermocouple
which is discussed in more detail in another section.
During testing, the sludge feed rate was observed to fluctuate
significantly on occasion. The effect of this on the various
hearth temperatures can be seen in Figure 15. In this particular
instance increases in fuel and air flow to hearth #3 was clearly
unable to handle the step-change of sludge load. This resulted in
dramatic temperature change on hearth #3.
Hearth temperature changes were observed to occur only for position
changes of the shaft cooling air damper in the 20% to 50% range.
d) Problem Areas
The test results indicate that there is considerable interaction
between hearths #5 and #6. It appears that this is due in part to
the location of the hearth #5 and #6 thermocouples and the
incinerator design. As can be seen in Figure 16, thermocouple #6
is located directly below a drop-hole in hearth #5. This allows
radiation from hearth #5 to heat the thermocouple in hearth #6.
Consequently, when the hearth #5 burners are increased, both
hearth #5 and #6 temperature signals are increased. In a similar
fashion, the thermocouple in hearth #5 is located such that it
responds to heat from hearth #6 which is convected up through the
drop-holes. The heat is then trapped beneath hearth #4 and warms
the hearth #5 thermocouple. In order to reduce the interaction
between hearth #5 and #6, a plate is being considered that would
cover the drop-hole above the hearth #6 thermocouple.
As stated earlier, the hearth process gain was found to be variable
and dependent upon the position of the respective hearth burner
493
-------
c
•H
CO
C
CO
CO
QJ
u
o
!-J
PH
0 10 20 30 40 50 60 70 80
Hearth Air Damper Position, %
90
100
FIGURE 14. PROCESS GAIN OF HEARTH TEMPERATURE RESPONSE
TO HEARTH COMBUSTION AIR DAMPER POSITION
494
-------
1800,
PV - TEMPERATURE HEARTH #3
1700
1600
PV
1500
1400
100'
804
MV J
•604
40'
20 4
PV - Process Variable, °F
MV - Manipulated Variable, %
SW - Sludge Weight, tons/hr
Controller #3 in Auto
Hearth #6 - off
FURNACE #1
October 31, 1979
MV -
1300
/ •<- Combustion Air Damoer P^vsition
PV - Temperature, Hearth //5
SW - Sludge Weight
lill
SW
1:00
i i
1:30
2:00 2:30
Time, PM
3: On
3:30
4-00
FIGURE 15. EFFECT OF STEP CHANGE IN SLUDGE FEED ON HEARTH TEMPERATURES
-------
Central
Shaft
I Hearth
Furnace
Wall
B3
B5
T3
T6
FIGURE 16. THERMOCOUPLE POSITION IN INCINERATOR
496
-------
combustion air damper (Figure 14). This will be compensated by
the process control system.
2. Air Flow Characteristics
a) Objective
As with the temperature control system, developments of a control
system for air flow will be based upon a model of the air flow
dynamics. To determine those dynamics, it is necessary to obtain
the relationship between scrubber differential pressure,
incinerator pressure, ID fan damper position and scrubber ambient
air damper position.
The dynamics of the percent oxygen in the exit gas as it relates
to the shaft cooling air damper position, furnace atmospheric air
damper position, and the furnace pressure were also tested. Percent
oxygen is of considerable importance as it has a significant
impact on the amount of fuel consumed by the furnace.
b) Test Set-up
All air flow tests were done on incinerator #1 which is the
incinerator to be controlled. For determination of factors
affecting oxygen in the incinerator exit gas, the following
parameters were monitored on a 3-pen recorder; hearth #1
temperature, sludge feed weight and percent oxygen.. The furnace
pressure, and the hearth #3, and hearth #5 temperature controllers
were maintained in automatic mode. The oxygen analyzer available
at the time of testing was a portable unit not intended for
continuous measurement. However, the unit can operate continuously
for a period of 5 minutes, which was sufficient to measure the
exit gas oxygen content resulting from a process change.
To determine the relationship between furnace pressure and
scrubber differential pressure, these and the ID fan damper
position were recorded on the 3-pen recorder. Step changes of
position were then made to the ID fan damper and ambient air
damper. The furnace pressure and scrubber differential pressure
controllers were in manual mode.
c) Observations
With regard to oxygen content in the exit gas, no change was
observed as a result of changes in the atmospheric air damper
position. This is due to the relatively small air flow controlled
by this damper compared to the total air flow through the
incinerator from uncontrolled sources.
As can be seen from Figure 17, changes in the shaft cooling air
damper position had no effect on 02 level at positions below 20%
and above 50%. Between 20% and 50%, a total change of 1.5% oxygen
497
-------
SHAFT COOLING AIR DAMPER POSITION,
20
40
60
80
100
13
12
Cooling An
4
Furnace Pi
essure
11
10
-.1 -.2 -.3 -.4
Furnace Pressure, Inches Water
FIGURE 17. EFFECT OF FURNACE PRESSURE & SHAFT
COOLING AIR DAMPER POSITION ON
OXYGEN FURNACE GAS
-.5
498
-------
was observed.
The strongest influence on percent oxygen was produced by changes
in the incinerator draft pressure. This is because the furnace
pressure determines the amount of air that enters from the
uncontrolled source.
With regard to the relationship involving furnace pressure and
scrubber differential pressure, it was found that changes in ID
fan damper positions produced rapid changes in both the furnace
pressure and scrubber pressure. Conversely, the scrubber ambient
air damper had only a minimal effect on the scrubber differential
pressure and a slightly greater effect on the furnace pressure.
d) Problem Areas
To enhance the controllability of the excess oxygen and thus
reduce excess fuel consumption, reduction of the various air leaks
into the furnace is necessary. The major uncontrolled sources are
the vacuum filter vent line, the ash slurry tank, the ash ball
chute, and the sludge flapper valve on the top of the furnace.
Only the vacuum filter vent line is truly uncontrollable. The
remaining three items may be modified to reduce the air which
passes through, and suggestions have been made to plant management
to effect these changes.
The weak response to changes in the scrubber ambient air damper
may be attributed to plugging of the ambient air duct. This is
being investigated and may result in re-testing of this parameter
should the duct be plugged.
D. Process Model
1. Temperature Model
a) Physical Characteristics
The general physical layout of the incinerator is shown in
Figure 18. There are three basic zones within the furnace. The
top zone (hearths #1 and #2) is for drying of the sludge. This is
followed by the burning zone (hearths #3, #4, and #5) in which
combustion of the sludge takes place. The last zone is that of
final combustion and cooling prior to discharge to the ash hopper.
The major disturbance variable to the incinerator temperature is
the sludge feed.
Sludge feed to the incinerator is measured by weight scale on the
inclined conveyor. As mentioned earlier, the weight signal is
very noisy. There is also a long time delay between a change in
sludge weight and the observed effect on temperature. The noisy
signal and the time delay results in a significant potential for
inaccuracy in any feed forward control. This eliminates the use
499
-------
From
Burner
Combustion
Air Fan
FIGURE 18. SCHEMATIC OF INCINERATOR
500
-------
of weight as a control parameter. However it will be needed for
efficiency calculations and it is anticipated that some signal
filtering will make it useful for that purpose. In addition it
will be used to prevent gross overload of the incinerator as was
illustrated in Figure 15. Observations indicate rabble arm speed
changes appear to have a very slow effect on the incinerator
temperature. However, variation of rabble arm speed affects the
sludge resident time on each hearth and, as such, may play a part
in optimization of the incinerator.
In developing the temperature control model, both the sludge feed
rate and the rabble arm speed were not incorporated. In both
instances it is felt that hearth combustion control, using natural
gas or fuel etc., will react quickly to sludge loading changes and
will not require the use of these variables, unless an overload of
wet sludge occurs.
b) Dynamic Characteristics
A summary of the test results in the multivariable Laplace Transfer
model shown in Figure 19. As can be seen from the structure of
the mathematical model, there is considerable interaction-between
hearths #5 and #6. It appears that this is due to the location of
the hearth #5 and #6 thermocouples and the incinerator design. It
is anticipated that when the drop-hole over thermocouple #6 is
physically blocked, the model may then be simplified because the
interaction between hearth #5 combustion to the hearth #6 thermo-
couple will be negligible. This eliminates one interaction and
simplifies the control strategy. As stated earlier, the process
gain was found to change considerably during the testing and must
be treated as a function of combustion air damper position. Thus
it is shown as a variable K rather than a constant in Figure 19.
2. Air Flow Model
a) Physical Characteristics
The flow path of gas through the incinerator is shown in Figure 20.
There are three sources of air into the incinerator that can be
manipulated by valves. They are burner combustion air, rabble arm
shaft cooling air and atmosphere air. The major uncontrolled
sources are the vacuum filter vent line, the ash slurry tank, the
ash ball chute, and the sludge flapper valve on the top of the
furnace.
The ID fan pulls the flue gases out of the furnace and through the
scrubber. The flow of gas depends upon five variables. They are,
the ID fan damper position, the burner combustion air valve
position, the cooling air valve position, the atmospheric air
valve position and the ambient air valve position. A change in
any one variable will effect the gas flow, resulting in a change
in pressure and oxygen. However, the burner combustion air valve
501
-------
Hearth #3
Combustion Valve (%)"
v -°-4s
Ke
3.8S + 1
Temp. #3 (°F)
Hearth
Combustion ValVe (%)
Hearth #6j
Combustion Valve
Ke
-0.2S
4.OS + 1
Ke
-0.8S
4.90S + 1
Ke
-1.65S
4.OS + 1
Temp. #5 (°F)
+ 1 >•
K
4. OS + 1
*
Temp. /'6 (°F)
Note
Time constants and dead times are in minutes
FIGURE 19. DYNAMIC TEMPERATURE MODEL OF INCINERATOR
502
-------
Cooling Air
to Stack
To Stack
Sludge Flapper Valve Opening
Cooling Air
to Furnacd- '^
Atmospheric
Air
4
Furnace
r-Sj
(O_
<-^l <
Burner Combustion
Air
< Other Uncontrolled
Air Sources
Ash Ball Chute Opening
Ash Slurry Tank Opening
Cooling
Air Fan
FIGURE 20. FLOW PATH OF GAS THROUGH INCINERATOR
Ambient
Air
503
-------
is not an independent manipulated variable because it is committed
to the control of hearth temperature. In addition, transient
tests revealed that the atmospheric air valve position had a
negligible effect on gas flow. The three remaining manipulated
variables are the inputs to the process control model. The
outputs of the model are the furnace pressure, the scrubber
differential pressure and the oxygen in the flue gas.
b). Dynamic Characteristic
The time response of the pressure variables is very fast, within a
few seconds, while the time response of the oxygen measurement is
considerably slower. The structure of a multivariable Laplace
transformer model is shown in Figure 21. Some additional testing
with the in situ oxygen analyzer is needed when it becomes available
in order to completely measure the model parameters.
The model shows the highly interacting characteristics of the gas
dynamics in the incinerator and scrubber. This interacting aspect
must be addressed in the design of the control system. So far,
the testing has revealed an unexpectedly low process gain relating
the ambient air valve to the scrubber differential pressure. It
appears that this may be due to plugging of the ambient air duct.
This process gain will be remeasured after this duct has been
cleaned. The testing also revealed high values of oxygen in the
flue gas. This is due to air leaking through the sludge flapper
valve, the ash slurry tank opening and the ash ball chute opening.
This creates a significant excess air problem. If the furnace is
to operate at lower values of oxygen and save fuel, then the air
leaks must be sealed.
E. Proposed Control
1. Temperature Control
The proposed control system for hearth #3 and hearths #5 and #6 is
shown in Figures 22 and 23, respectively. As can be seen, the value non-
linearity will be accounted for with a software module which will modify the
PID output based upon the relative position of the combusion air damper. The
combustion air damper used for control will be whichever position signal is
higher. The two burners on each hearth will be controlled in parallel.
Figure 23 outlines hearth #5 and #6 burner control as it is anticipated
to exist after the patch of the hearth #5 drop-hole. It is felt that the
lead/lag module shown will be sufficient to account for whatever interaction
remains between hearth #5 and #6.
2. Air Flow Control
The control system for Air Flow has not been completed yet because as
indicated above necessary modeling parameters are not yet available.
504
-------
Cooling
Air Damper
Ambient
Air
Damper
ID Fan
Damper (%)
-0.04e
-5s
0.38e
-4s
-0.43e
-s
0.14e
-3s
F.x c ps s Air
Scrubber
Diff. Pressure
(% of full scale)
Furnace
Pressure
I of full scale)
Note
Dead time is in seconds
* dynamic model yet to be determined
FIGURE 21. DYNAMIC AIR FLOW MODEL FOR INCINERATOR
505
-------
Isetpoint I
Combustion
Air
Valve
Linearizer
Function
Hearth
Temp
To Burner #2
FIGURE 22. CONTROL SYSTEM HEARTH #3
506
-------
Burner
No. 1
*T To Burner
#1
HEARTH #6
Burner #2
FIGURE 23. CONTROL SYSTEM HEARTHS #5 & #6
507
-------
SUMMARY
To date control strategies, and instrumentation packages to automate
operation based on these control strategies, have been developed for the
three individual unit operations of chemical conditioning, vacuum filtration
and multiple hearth incineration. The strategy for chemical conditioning
provides for predictive control of the sludge dewaterability by manipulating
the chemical dose. The strategy for vacuum filtration provides for feed
forward control of filter yield and/or moisture content of the filtered
sludge. Manipulation of filter speed, depth of submergence, perhaps vacuum
level, and perhaps vat agitation will be used to effect control. For the
incinerator control of the furnace temperature profile will be accomplished
by manipulation of fuel feed to the various hearths and control of the flow
of air into the furnace.
It should be appreciated that the control strategies devised were not
always the most desireable. For example, if direct on-line measure of sludge
dewaterability was available it could be used as a feed back parameter for
chemical conditioning rather than the correlation equation used. If an on-
line measurement of cake mositure were available it could be used as a feed
back parameter for control of vacuum filtration; as a complement to the feed
forward strategy developed here. Finally if an on-line sludge calorimeter
were available it could be used as a feed forward parameter to control the
incinerator.
The control strategies which have been developed and which will be
implemented at this site can be used to optimize the performance of each unit
operation. Indeed one of the scheduled activities in this research program
is a side-by-side demonstration of automated vs. manual operation and control
of the sludge handling operations. However, it must be realized that these
operations are not isolated but rather interactive. Examples of interaction
include:
1) Specific Resistance (SR) is a link between chemical
conditioning and vacuum filter operation. The chemical
conditioning dose is altered to produce a desireable SR
value is established by the desired production rate or
moisture content of the vacuum filter discharge. SR of
course is not the only parameter which is available to
affect vacuum filter performance. Speed of rotation,
depth of submergence, etc., can also be used to affect
output; but SR is a prime factor and an interactive one
as well.
508
-------
2) Cake production and moisture content are links between
the incinerator and the vacuum filter. Production of
excessive quantities of wet cake will overload the
incinerator, while production of excessive quantities
of dry cake may result in excessive temperature build-up
and incinerator damage. Production of a cake with
thermal characteristics that continually vary is also
not good as it can lead to incinerator damage through
thermal shock.
It is clear than that optimization of each individual operation will
not yield optimum system performance. Rather optimization will require that
the interactions noted above be taken into consideration in an overall
optimization model. At the present time such a model is being formulated. It
will be programmed into the process control computer system which was
installed at this site. This computer system has a two fold purpose. It has
been used as a data gathering and modeling unit during the time the individual
control strategies were under development, and will conduct the automated
process control of the treatment line. An interesting feature of this system
is the ability to take data as generated and use it to continually update
process models. Thus even after the system goes on-line the process models
will be automatically updated.
With respect to system optimization the computer based model will use
existing input and output goals, process models, and cost information to
operate the system on the most economical basis. For example, the program
will decide at any instant whether in order to meet temperature goals in the
incineration step it is most economical to alter chemical dose, change speed
of operation of the vacuum filter, or use more fuel. It would be impossible
for a human operator to make such decisions many times a day; because of all
the variables involved. Another type of problem the optimization model will
address is how to handle maintenance scheduling, temporary changes in system
loading or a partial breakdown of equipment. For example, scheduled
maintenance and downtime could be handled by running production prior to
shutdown at such a rate that ample sludge storage space was available for the
time the system was out of service. Eventually both sludge handling lines
will be automated which will provide the computer with the ability to shift
loading from one line to another.
509
-------
REFERENCES
1. Kugelman, I.J., "Progress in Instrumentation and Automation",
Proceedings of the Sixth U.S.-Japan Conference on Sewage Treatment
Technology, EPA-600/9-79-039 (October 1978).
2. Polta, R.C., Stulc, D.A., "Automatic Sludge Blanket Control in an
Operating Gravity Thickener", Environmental Protection Technology
Research Report, EPA-600/2-79-159, (November 1979).
3. Baskerville, R.C., Gale R.S., "A Simple Automated Instrument for
Determining the Filterability of Sewage Sludges", Journal of Water
Pollution Control G.B., 67 233-241 (1968).
4. Stulc, D., Christensen, G., "Chemical Reactions Affecting Filterability
in Iron-Line Sludge Conditioning", M.S. Thesis, University of Minnesota
(March 1977).
5. Dick, R.L., "Sludge Treatment" Chapter 12 in Physicochemical Processes
for Water Quality Control, W.J. Weber, Wiley - Interscience, New York,
(1962).
6. Coackley, P.C., "Laboratory Scale Filtration Experiments and Their
Application to Sewage Sludge Dewatering" in Biological Treatment
of Sewage and Industrial Wastes, McCabe, J. and Eckenfelder, W.W.,
ed. Vol. 2 Reinhold Corp., New York (1958).
7. Gale, R.S., "Research in Filtration of Sewage Sludges", Filtration &
Separation, 9, No. 4, 431-436 (July-August 1972).
8. Gale, R.S., "Some Aspects of the Mechanical Dewatering of Sewage
Sludges", Filtration & Separation, J5, No. 2, 133-143 (March-April 1968)
9. Annual Report, U.S. EPA Grant S803602 to MWCC of Minneapolis-St. Paul,
(1979).
10. Tenney, N.W., et. al., "Chemical Conditioning of Biological Sludges
for Vacuum Filtration", Journal of the Water Pollution Control
Federation, <42, R1-R20 (1970).
11. Rich, L.G., Unit Operations of Sanitary Engineering, John Wiley & Sons,
Inc. New York (1961).
510
-------
TABLE 1A. SLUDGE CONDITIONING DATA SUMMARY
Nov. 1978-Feb. 1979
Pi
CO
CO
4.8
4.8
3.5
3.5
3.8
3.8
-0
-0
5.0
-0
6.0
-0
5.1
-0
-0
5.5
-0
4.7
5.8
4.8
5.1
5.4
Pi
PS
PM
6.05
-0
6.30
6.30
6.30
6.25
-0
-0
5.75
-0
6.05
-0
5.95
-0
-0
6.15
-0
5.90
6.20
6.00
5.90
6.00
P"M
w
PM
5.70
-0
5.25
5.55
5.65
5.80
5.85
5.80
5.70
-0
5.70
5.60
5.80
5.70
-0
6.00
5.40
5.65
6.25
5.65
5.80
5.75
i-j
ns
PM
11.90
12.20
12.30
12.10
12.30
12.35
12.40
12.35
12.30
12.20
12.30
12.30
12.30
12.30
12.25
12.35
12.35
12.40
12.35
12.25
12.30
12.35
Pi
PM
Pi
0
-160.
0
-125.
-125.
-160.
-150.
0
0
-160.
0
-130.
0
-120.
0
0
-155.
0
-125.
-150.
-130.
-110.
-140.
PM
PM
Pi
0
-20.
-0
25.
-25.
-20.
-35.
-65.
-60.
-110.
-0
-90.
-105.
-90.
-70.
-0
-140.
-35.
-65.
-155.
-80.
-85.
-125.
nJ
PM
Pi
O
-325.
-340.
-370.
-350.
-425.
-430.
-415.
-430.
-450.
-425.
-415.
-425
-420.
-440.
-460.
-400.
-415.
-395.
-410.
-450.
-440.
-420.
CN
rH
H
6.8
5.7
4.1
4.3
3.7
9.2
5.7
4.4
8.3
13.2
14.0
21.3
12.5
10.3
10.1
4.8
7.0
7.8
6.3
8.7
12.7
4.7
0
ro
H
11.0
9.2
7.0
7.9
5.7
10.1
8.1
7.5
10.8
17.8
18.1
23.5
15.0
13.5
14.9
7.3
10.0
11.4
10.4
14.0
11.3
8.0
o
^D
H
19.6
13.7
12.2
12.5
8.7
15.3
14.1
11.7
15.3
26.2
23.4
26.8
23.3
18.9
23.2
11.3
15.8
16.7
17.1
16.9
18.4
11.7
pi
H
CO
CJ
343.
-0
380.
338.
471.
500.
-0
-0
564.
-0
451.
-0
492.
-0
-0
499.
-0
440.
317.
325.
452.
607.
PM
H
CO
U
45.5
-0
25.6
29.8
45.3
66.0
76.8
73.9
137.0
-0
199.0
93.0
191.0
134.0
-0
433.0
47.2
119.0
122.0
101.0
1.21.0
275.0
nj
H
CO
u
12.1
9.7
8.4
8.9
10.4
9.3
11.3
11.4
13.4
17.2
13.2
11.7
12.5
12.6
13.3
12.8
13.4
11.6
14.8
12.0
13.3
12.4
HJ
pi
CO
18.0
5.6
2.9
5.5
3.3
3.3
4.8
4.7
4.5
10.0
4.0
3.6
2.9
4.1
5.2
1.5
4.3
5.1
7.7
2.1
5.6
3.0
HJ
co
CO
4.5
4.4
4.3
3.6
4.6
4.6
4.9
4.5
6.3
5.4
6.2
6.1
6.4
5.8
5.3
7.1
5.2
5.4
5.4
5.6
5.3
5.4
HJ
H
22.0
24.5
25.0
24.0
22.5
25.5
-0
-0
24.0
24.0
-0
24.0
24.0
-0
-0
25.0
~0
21.5
25.0
22.0
21.0
21.0
(continued)
-------
TABLE 1A. (continued)
frf
CO
00
-0
3.9
4.2
4.3
4.5
5.1
-0
6.8
4.6
4.9
5.3
4.8
4.3
4.2
4.7
4.6
P<
ffi
PH
-0
6.10
6.25
6.30
6.20
6.50
-0
6.55
6.15
6.25
6.30
6.55
6.05
6.00
6.05
6.20
&
PM
-0
5.50
5.75
5.00
5.75
2.70
-0
6.00
5.30
5.90
6.00
6.30
5.90
5.80
5.90
5.95
hj
w
PM
12.20
12.30
12.30
12.30
12.45
7.50
11.65
11.95'
11.50
12.05
11.55
12.35
12.20
12.20
12.30
12.30
rt
PM
ft
o
0
-105.
-150.
-140.
-145.
-190.
0
-180.
-150.
-135.
-165.
-160.
-115.
-135.
-175.
-185.
PM
PM
Pd
O
-100.
-100.
0
-85.
445.
-0
-120.
95.
-100.
-135.
-120.
-110.
-95.
-175.
-160.
i-j
PM
P4
O
-370.
-438.
-440.
-514.
-472.
-250.
-430.
-460.
-105.
-245.
-376.
-367.
-435.
-370.
-449.
-500.
CNl
i-l
H
6.0
8.7
15.0
8.8
11.3
8.0
-0
8.8
13.5
24.4
23.4
10.5
6.3
3.7
9.1
10.9
o
o
H
15.0
16.3
23.0
19.4
20.6
23.6
22.6
31.3
24.9
29.6
50.7
22.3
15.2
12.8
17.9
22.0
&
H
CO
u
337.
440.
522.
314.
655.
-0
656.
342.
370.
346.
267.
667.
650.
324.
237.
PM
H
CO
o
30.6
65.7
27.3
50.2
51.2
-0
102.0
30.8
111.0
88.4
72.2
190.0
155.0
156.0
115.0
ij
H
CO
0
14.7
10.5
10.7
8.9
11.6
14.0
11.6
9.2
8.5
8.5
9.1
10.2
9.9
10.8
7.6
8.4
£
CO
10.0
2.5
3.4
2.1
3.0
14.0
2.0
2.7
3.0
2.6
2.8
2.8
4.2
-0
2.7
2.4
nj
CO
CO
4.7
4.4
4.9
5.8
5.8
5.9
5.2
5.7
5.0
5.4
6.1
5.6
5.1
5.0
5.9
6.1
i-J
H
19.5
23.0
20.0
23.0
25.0
23.0
23.0
20.5
18.0
20.0
23.3
23.0
18.5
20.0
12.5
24.0
* - 0 means no value except for ORPR where 0 means no value
-------
TABLE 2A. SUMMARY OF ON-LINE CONDITIONING DATA
Sept.-Dec. 1979
ui
NUM
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
PF
12.0
8.5
15.0
14.5
15.0
15.5
16.0
11.5
16.0
13.5
11.5
10.0
10.5
10.0
22.0
15.0
18.0
18.0
11.0
15.5
17.0
14.5
12.0
18.5
16.0
15.5
10.0
10.0
6.3
7.9
7.7
13.1
10.7
PL
56
56
72
34
21
14
26
28
47
50
39
43
38
29
41
30
24
21
20
56
53
46
45
27
22
17
21
19
18
15
19
26
13
DAY
910
910
910
910
914
914
914
914
919
919
919
919
919
919
921
921
921
921
921
925
925
925
925
926
926
926
1002
1002
1004
1005
1005
1010
1010
SSR
4.2
4.2
4.0
4.2
3.5
3.4
3.7
3.6
3.9
3.8
3.8
3.8
3.9
3.9
3.8
3.7
3.8
3.8
4.0
3.7
3.9
3.8
3.9
3.8
3.8
3.8
3.8
3.7
4.2
4.2
4.3
4.7
4.6
PHR
5.70
5.70
5.70
5.70
5.90
5.90
5.85
5.85
5.95
6.00
6.00
6.00
5.95
5.95
5.80
5.80
5.80
5.80
5.75
5.90
5.90
5.90
5.90
5.85
5.85
5.85
5.90
5.90
6.10
6.00
5.95
6.05
6.05
PHF
4.80
5.10
4.70
4.75
4.70
4.80
4.70
5.50
4.85
5.35
5.45
5.70
5.30
5.45
4.20
5.05
4.75
4.70
5.00
5.30
5.10
5.20
5.35
4.80
5.30
5.40
5.40
5.45
5.90
5.55
5.60
5.40
5.60
PHL
12.20
12.20
12.15
12.15
11.55
9.80
12.15
12.25
12.30
12.30
12.35
12.35
12.35
12.35
12.15
12.30
12.15
11.90
12.00
12.45
12.40
12.50
12.50
12.20
12.20
11.95
12.20
12.10
12.30
11.85
12.25,
12.25
12.20
ORPR
-340
-340
-338
-338
-312
-315
-315
-342
-420
-420
-420
-420
-420
-420
-338
-338
-338
-338
-338
-310
-310
-308
-310
-310
-315
-321
-345
-345
-335
-340
-340
-348
-348
ORPF
70
5
70
75
150
155
185
75
50
45
35
10
50
25
195
70
100
110
75
30
55
-12
-30
80
40
30
-125
-115
-60
-65
-80
-45
-40
vise
6.7
6.3
5.7
6.9
5.7
12.4
6.3
7.6
6.1
5.7
6.1
6.7
6.2
7.0
6.9
6.3
6.7
6.0
6.8
7.0
7.9
8.0
8.4
4.7
6.8
6.8
9.1
9.1
8.1
11.4
10.8
6.9
9.5
CSTF
19.7
30.2
19.1
19.5
13.3
15.8
14.9
17.8
14.3
15.6
15.4
18.3
16.6
14.5
14.9
16.4
14.9
15.3
16.5
16.5
15.9
18.3
23.7
17.1
19.4
21.9
26.4
33.3
56.0
55.1
58.5
20.6
34.1
SRL
1.35
3.25
1.30
1.85
3.20
25.90
1.65
2,05
1.15
1.35
1.50
1.65
1.50
1.95
0.85
1.45
1.30
2.35
2.45
1.45
1.50
2.30
2.10
1.65
1.95
3.05
2.80
3.50
5.60
11.90
5.70
1.50
2.85
' continued'
-------
TABLE 2A. (continued)
NUM
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
PF
8.3
13.0
12.0
14.0
11.5
11.5
8.5
8.3
7.8
7.5
17.0
15.0
13.5
11.5
12.0
10.5
17.4
13.7
11.7
8.4
7.6
6.6
11.3
9.8
8.9
8.5
8.6
8.3
6.7
8.1
9.2
7.7
PL
13
23
27
26
24
22
27
21
18
16
50
18
36
34
22
14
20
23
23
16
16
20
21
21
16
14
17
39
11
21
26
21
DAY
1010
1016
1022
1022
1022
1022
1024
1024
1024
1024
1026
1026
1029
1029
1029
1029
1204
1205
1205
1205
1206
1206
1207
1207
1207
1207
1207
1212
1212
1212
1213
1213
SSR
4.6
4.9
4.1
4.0
4.2
4.2
3.7
3.8
3.7
3.8
3.2
3.2
4.0
4.0
4.0
4.1
3.8
5.4
5.4
6.4
4.4
4.4
4.2
4.2
3.8
3.8
3.8
3.3
3.8
3.7
3.7
3.7
PHR
6.05
6.10
6.75
6.70
6.65
6.65
5.80
5.85
5.80
5.80
6.30
6.25
6.20
6.15
6.10
6.10
5.60
6.20
6.20
6.00
5.75
5.75
5.70
5.80
5.60
5.65
5.60
5.90
5.80
5.90
5.50
5.50
PHF
5.75
5.15
5.40
5.30
5.40
5.45
5.45
5.40
5.55
5.60
5.10
5.15
5.05
5.35
5.40
5.60
4.50
6.05
6.05
5.90
5.60
5.60
5.70
5.60
5.55
5.65
5.60
5.65
5.65
5.30
4.80
4.90
PHL
12.15
12.20
12.25
12.20
12.10
12.00
12.25
12.25
12.25
12.10
12.35
12.10
12.20
12.20
12.15
12.10
12.20
12.20
12.25
11.90
11.80
12.40
12.10
12.30
12.25
11.50
12.30
12.40
12.05
12.15
12.10
12.10
ORPR
-350
-355
-370
-370
-370
-370
-350
-345
-348
-349
-360
-351
-355
-352
-342
-345
-340
-345
-345
-345
-325
-325
-340
-340
-340
-340
-340
-305
-305
-305
-295
-295
ORPF
-60
-5
-180
-140
-110
-100
25
-5
-30
-45
-5
5
-20
-50
-65
-100
-100
-118
-125
-105
-85
-92
-158
-160
-165
-152
-150
-55
-55
-35
92
50
vise
10.0
6.2
9.9
7.1
7.2
9.1
7.6
7.7
9.9
9.3
5.7
6.3
8.3
8.5
7.3
7.9
8.5
32.0
19.5
39.0
8.3
7.5
9.2
17.5
6.2
8.4
8.8
11.0
10.0
13.8
10.9
12.6
CSTF
52.1
25.5
32.1
28.1
31.4
31.3
34.0
34.8
38.9
44.9
20.1
23.4
26.0
27.5
30.4
40.0
28.3
36.9
39.1
48.5
64.2
63.4
51.7
54.1
25.1
40.7
51.7
21.3
28.2
34.4
30.4
36.1
SRL
6.00
1.30
2.05
1.75
1.75
2.70
2.50
2.75
4.05
6.80
1.35
3.95
1.85
2.50
2.75
3.30
2.35
1.25
1.65
1.50
4.50
2.60
1.35
2.05
2.65
5.40
3.90
2.60
5.60
4.10
2.25
4.10
-------
IMPACT OF INNOVATIVE AND ALTERNATIVE TECHNOLOGY
IN THE UNITED STATES IN THE 1980'S
John M. Smith and Jeremiah J. McCarthy
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Henry L. Longest II
Office of Water Program Operations
U.S. Environmental Protection Agency
Washington, D.C. 20460
I. INTRODUCTION
Recent History of Wastewater Pollution Control in the United States
The design and construction of municipal wastewater treatment facilities
in the United States in the 1970s have been significantly impacted by federal
laws since 1956 when the Federal Water Pollution Control Act (PL 84-660) was
passed. The role of the federal government during this time has been to
establish national policies and goals for abatement of pollution and protec-
tion of health and the environment and to provide federal support for the
construction of necessary treatment works.
The Congress of the United States recognizes and protects the rights of
the fifty states as being primarily responsible for controlling water pol-
lution within their boundaries. Between 1956 and 1972, 13,764 municipal
treatment plants were constructed with federal assistance totaling 5.2 bil-
lion dollars which represented an average of 37% of the total cost of con-
struction.
In 1972 the Federal Water Pollution Control Act Amendments were passed
(PL 92-500). This act reaffirmed and expanded the goals of earlier federal
legislation and set specific targets to achieve by July 1, 1983 water that
is clean enough for swimming, recreational use, protection and propagation
of fish, shellfish, and wildlife; and by 1985 to eliminate all discharges
of pollutants in the Nation's waters. Two major provisions of this act were
to establish a uniform national minimum effluent standard of secondary treat-
ment and to authorize an increase in the federal share of construction to 75%
of the total project cost. The total amount of funds authorized from 1972 thru
1980 by the Federal Water Pollution Control Act Amendments (PL 92-500 and
PL 95-217) was 33.98 billion dollars (1).
515
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This increase in federal support of municipal construction and the pro-
mulgation of a uniform national minimum effluent standard has resulted in
accelerated construction of secondary treatment facilities. The following
table illustrates the increases in population served and total number of
secondary and tertiary municipal treatment plants constructed in the United
States from 1968 to 1979.
TABLE 1
INCREASE IN POPULATION AND NUMBER OF MUNICIPAL TREATMENT PLANTS
"CONSTRUCTED IN THE UNITED STATES FROM 1968 TO 1979 (2)(3)(4T
Type of 1968 1979
Treatment Pop. Served x 106 No. Facilities Pop. Served x 10° No. Facilities
Secondary
Tertiary
81
3(a)
9,333
10
110
5
13,108
1,207
(a) Population Estimated
Current Treatment Practice
The design of municipal treatment plants in the United States during the
1960s and early 1970s has followed traditional engineering practices. Planning
emphasis has been placed on regional water quality and stream basin analyses
necessary to establish levels of point source and non-point source controls
that are adequate to protect federally established national water quality
goals under PL 92-500. All streams in the United States are classified by
the states as to intended use and quality. There are 6,493 total stream seg-
ments with 3,299 being classified as water quality limited and 3,194 classified
as effluent limited (5). The national minimum secondary effluent standard
applies to the effluent limited segments and higher levels of treatment are
required by the water quality limited stream segments. For the water quality
limited stream segments, waste load allocation studies were undertaken to
establish point source effluent limits thus providing a specific design goal
for the planning, engineering, and design of wastewater treatment plants. Pro-
cess selection in the past has largely been based on a cost effectiveness
analysis for meeting a particular effluent goal rather than a cost benefit
analysis that considers stream impacts. Recently, decisions to construct
advanced waste treatment facilities are considering the costs and benefits
of improved water quality.
Design practice in the United States for municipal treatment plants from
the early 1950s to the early 1970s has been strongly influenced by the state
governments because of their responsibility for the review and approval of
facility plans and specifications. All but a few of the 50 states have adopted
specific design criteria for sizing and selection of components and equipment
used in the commonly employed biological treatment processes of activated
sludge, trickling filter, and stabilization ponds. The recommended standards
516
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for sewage works established by the Great Lakes-Upper Mississippi River Board
of State Sanitary Engineers in 1947, now referred to as the Ten State Stan-
dards, has been the dominant influence in municipal wastewater treatment plant
design practice during this time period.
Standard design requirements such as those included in the Ten State
Standards are being increasingly viewed by present-day designers as overly
conservative and not widely applicable to the more sophisticated designs. A
recent study by USEPA of 29 non-structural factors affecting the construction
cost of municipal treatment plants indicated that the use of overly conserv-
ative standard design requirements was the most important single cost factor
for meeting a specific effluent design goal. Elimination of standard design
requirements was estimated to reduce total construction cost by 10-20% (6).
Recognizing the increased per-user cost of wastewater treatment, the USEPA,
first with enactment of PL 92-500 and again with the 1977 amendments (PL 95-217),
has placed strong emphasis on both the consideration of a wide range of treat-
ment alternatives for a given treatment plant and a rigorous cost effectiveness
analysis to determine the lowest cost design. This has been vitally important
in view of the increasing number of technologies that have become available
for treatment of municipal wastewaters in the 1970s.
A draft Innovative and Alternative Technology Assessment Manual pub-
lished in October of 1979 by EPA-OWPO and ORD summarized the cost, appli-
cability, and energy utilization of 117 separate technologies currently being
used for municipal wastewater treatment (7).
New National Goals
Because of the large, sparsely populated land areas of the United States
compared to Japan and the increased cost of centralized treatment and disposal
by conventional technologies, recent federal legislation including both the
FWPCA of 1972 and the 1977 amendments to this law have strongly encouraged
the consideration of technologies such as land application that reclaim and
recycle wastewater and wastewater constituents, conserve energy, reduce overall
cost and reduce the migration of pollutants. Technology-related goals, policies,
and key regulations and guidelines of each law are summarized in Table 2.
The basis for an increased federal role in identifying and encouraging
specific methods of treatment and technologies is clearly evident from the
specific changes in the language of the legislation between the FWPCA of 1972
and the 1977 amendments as summarized in Table 2. The overall thrust of the
new law is to more clearly identify technological goals and to offer specific
incentives for their use. The incentives to encourage Innovative and Alter-
native (I/A) Technologies are an increase in federal construction grants from
75% to 85% using special set-aside funds of 2% in fiscal years 1979 and 1980
and 3% in fiscal year 1981 that can only be used to increase the federal grant
share of the capital cost at I/A facilities. This increase underscores the
intent of Congress to increase the use of Innovative and Alternative Tech-
nology to over 25% of all construction grants awarded in fiscal year 1981.
This act has effectively set the stage for dramatically changing the practice
of sanitary engineering design in the United States over the next ten years.
517
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TABLE 2
THE FEDERAL WATER POLLUTION CONTROL ACT OF 1972 AND THE 1977 AMENDMENTS
THE FEDERAL WA1ER POLLUTION CONTROL ACT OF 1972
Ui
H
00
GOALS AND POLICIES
Goals:
. Eliminate the discharge of pollutants by July 1, 1985
. Achieve interim goal which provides for the protection and
propagation of fish, shellfish, and wildlife and provides
for recreation in and on the water by July 1, 1983 (fishable,
swimmable goal)
Policies:
. Eliminate the discharge of toxic pollutants
. Provide federal assistance for construction of publicly owned
treatment works
. Development and implementation of areawide planning to control
point source and non-point source wastes
. Conduct research and demonstration studies to develop technology
• Promote efficiency in government management and implementation
of program
MORE IMPORTANT REGULATIONS, REQUIREMENTS, AND GUIDELINES
. Requires basin with planning for point source and non-point
source wastes
• Requires best practicable waste treatment technology
. Requires technology that:
(a) considers advanced waste treatment
(b) reclaims and recycles water
(c) confines disposal of pollutants
(d) recycles pollutants
(e) encourages revenue producing facilities
(f) combines open space and recreational considerations
. Requires infiltration/inflow studies
. Provides 75% grants for publicly owned treatment works
. Requires user charge and industrial cost recovery
. Established national minimum treatment level of secondary
treatment
POLICIES, IMPLEMENTING REGULATIONS, AND GUIDELINES ADDED BY THE 1977 AMENDMENTS TO THE
ABOVE 1972 ACT (THE 1977 AMENDMENTS ARE ALSO KNOUN AS THE CLEAN WATER ACT OF 1977 (PL 95-217)
Goals:
• None
Policies:
. Authority of each state to allocate quantities of water
within its jurisdiction shall not be superceded or
abrogated by this Act
• Federal agencies shall cooperate with state and local
agencies to develop comprehensive solution to prevent,
reduce, and eliminate pollution
MORE IMPORTANT REGULATIONS. REQUIREMENTS, AND GUIDELINES
• Requires consideration of innovative and alternative tech-
nologies for all facility plans initiated after Sept. 30, 1978
4 Increases federal support from 755! to 85% for innovative and
alternative technologies
. Provides guarantee for replacement of innovative and alter-
native technology plant components that fail to meet design
or performance standards
. Identifies individual technologies to be encouraged such as
land application
. Provides a 15% cost preference in the cost effectiveness
analysis for innovative and alternative technologies
. Extends federal eligibility to privately owned treatment
facilities and alternative wastewater collection systems
. Allocates 4% of federal construction grant funds for con-
struction of treatment facilities in small communities
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The new national goals place strong emphasis on the use of natural systems
and improved biological processes that conserve energy and reduce costs and
recycle wastewater and wastewater nutrients for beneficial uses.
II. INNOVATIVE AND ALTERNATIVE TECHNOLOGY
Following enactment of the 1977 amendments, the USEPA moved forward
swiftly in developing the regulations and guidelines necessary to achieve
the goals of the act while still maintaining the momentum of the Construc-
tion Grants Program. Table 3 summarizes the ten sections of the law and
eight separate regulations that pertain to innovative and alternative tech-
nology.
The legislation and regulations noted above formed the basis of the
Innovative and Alternative Technology Program now in operation as part of
the USEPA's Construction Grants Program. An assessment manual (7), pro-
mulgated by USEPA as a part of the 35.908 Innovative and Alternative Tech-
nology regulation, defines I/A Technology and forms the basis for classifi-
cation and screening of all municipal treatment technologies as conventional
concepts of treatment, Alternative Technology, or Innovative Technology.
» Innovative Technology is defined as processes and techniques
that are developed methods which have not been fully proven
under the circumstances of their contemplated use and which
represent a significant advancement over the state of the art
in terms of meeting the national goals.
. Alternative Technology is defined as wastewater treatment
processes and techniques that are proven methods which pro-
vide for the reclaiming and reuse of water, productively
recycle wastewater constituents, or otherwise eliminate
the discharge of pollutants or recover energy.
Conventional concepts of treatment are generally defined
as biological or physical chemical processes with direct
point source discharge to surface waters.
The regulations further distinguished Innovative and Alternative Tech-
nology by specifically identifying the Alternative Technologies and by
establishing six criteria for qualifying any technology as Innovative. The
general classification scheme is shown in Figure 1.
Any technology in the Alternative category as defined by the regulations
can qualify as Innovative by meeting any one of the six qualifying criteria
shown. Any technology that has not been identified as Alternative falls into
the category of conventional concepts of treatment and can qualify as inno-
vative by meeting either the cost or energy criteria. These criteria are de-
scribed as follows:
519
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TABLE 3
SUMMARY OF INNOVATIVE AND ALTERNATIVE TECHNOLOGY LEGISLATION AND REGULATIONS
LEGISLATION PL 95-217, DECEMBER 27, 1977
REGULATION 40 CFR 35, SEPTEMBER 27, 1978
to
Section
201(d) - Encourages the design and construction of revenue
producing facilities
201(g)5 - Requires all applicants to study innovative and
alternative technology
201(i) - Encourages energy conservation in the design of
all publicly owned treatment works
201(e) - Encourages the reduction of total energy require-
ments in the design of publicly owned treatment
facilities
201(j) - Provides for 15% cost preference in the cost
effectiveness analysis for all innovative and
alternative technology
202(a)2 - Increases federal grant from 75% to 85%
202(a)4 - Limits grant eligibility to publicly owned
treatment wor1
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01
N)
ALTERNATIVE TECHNOLOGY
Specifically Identified forms of treatment and unit
processes
Effluent Treatment
- land treatment
- aquifer recharge
- aquaculture
- silviculture
- direct reuse
Inon potable)
- horticulture
- revegetation of
disturbed land
- containment ponds
- treatment and storage
prior to land
application
- preapplication treat-
ment
- land application
- composting prior to
land application
- drying prior to
land application
Energy Recovery
- co-disposal of
sludge and refuse
- anaerobic digestion
with >90% methane
recovery
- self-sustaining
incineration
Individual and On-
Site Systems
- oil-site treatment
- septage treatment
- alternative col-
lection systems
for small com-
munlties
QUALIFYING CRITERIA
Improved Applications
of Alternative Technology
(Any 6 Criteria)
Conventional
Concepts
CONVENTIONAL CONCEPTS OF CENTRALIZED TREATMENT
Generally defined biological or physical chemical
processes with direct point source discharges to
surface waters
Improved operational
reliability
Improved toxics
management
Increased environ-
mental benefit
Improved joint treat-
ment potential
Must Meet
Cost or Energy
15% LCC reduction
201 net primary
energy reduction
FIGURE I
GENERALIZED CLASSIFICATION OF INNOVATIVE AND ALTERNATIVE TECHNOLOGY
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1. The life cycle cost of the eligible portions of the treatment
works excluding conventional sewer lines is at least 15% less
than that for the most cost effective alternative which does
not incorporate innovative wastewater treatment processes and
techniques (i.e., is no more than 85% of the life cycle of the
most cost effective non-innovative alternative).
2. The net primary energy requirements for the operation and
maintenance of the eligible portions of the treatment works
excluding conventional sewer lines are at least 20% less than
the net energy requirements of the least net energy alternative
which does not incorporate innovative wastewater treatment pro-
cesses and techniques (i.e., the net energy requirements are
no more than 80% of those for the least net energy non-Innovative
alternative must be one of the alternatives selected for analysis
under Section 5 of Appendix A.
In the above life cycle cost comparisons, the following apply:
. The non-innovative alternative must be clearly identified.
. The cost effectiveness of the non-innovative alternative will be
judged against the best available state of the art cost information.
. The basis of the comparison is the lowest present worth cost with
the cost effectiveness analysis for each system being conducted
in accordance with USEPA prescribed Cost Effectiveness Analysis
Guidelines.
. Aggregation of component cost savings is permitted providing all
applicable provisions of the Cost Effectiveness Analysis Guidelines
are met.
• The cost comparison between the proposed innovative and non-innovative
alternatives must be made on a completed treatment works basis
(grant eligible portions excluding conventional sewer lines) even
though the proposed potentially-innovative portion is a sub-system
or component.
• In the comparative analysis, both systems must provide equivalent
levels of pollutant control.Equivalency of the following factors
must be considered.
- Design minimum effluent quality standards
- System reliability with respect to effluent quality
and residual disposal
- Residual treatment and disposal
- Level of toxic material control
- Environmental benefit
522
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The energy analysis compares the net primary energy utilization of the
proposed innovative alternative with that of the least net primary energy
utilization non-innovative alternative. In this analysis, the required 20%
net primary energy savings must be made on the total treatment works basis
(eligible portions excluding conventional sewer lines) including treatment
and disposal of all residuals except where an upgrading or expansion of an
existing treatment works is encountered. In this case, only the treatment
works associated with the increased capacity and/or level of treatment shall
be considered for inclusion in the energy analysis. All increases in energy
use in other portions of the plant must be accounted for in the above net 20%
energy savings calculation. The energy audits for the potentially innovative
and non-innovative alternative technologies must be made on an equivalent
basis. The following general requirements and conditions should be con-
sidered.
1. The boundaries and boundary conditions of system or system
components receiving energy audits must be fully described
including all flow streams entering or leaving the treat-
ment works.
2. A materials balance for all significant influent and effluent
streams including flow, mass, temperature, etc., must be
included in the analysis.
3. Differences in hydraulic profile required of different
treatment systems must be accounted for in the energy
analysis.
4. The system's energy balance must include the treatment and
disposal (including transportation) of all residuals.
5. In determining the energy consumed to dewater sludge, the
energy balance point is the sludge stream entering the
dewatering process or the thickening process when thickening
is required. All energy balances required to document energy
recovery will be based on annual values. The sludge mass to
be used in the analysis is the average annual sludge mass
projected over the project planning period.
6. For processes where the energy utilization is a function of
influent flow, the energy analysis must consider the increase
in plant flow over the project planning period as permitted
by the USEPA Cost Effectiveness Analysis Guidelines.
7. The net primary energy reduction of 20% does not distinguish
the form or location of the energy savings. The savings
should be computed at the boundary of the proposed treatment
works in BTU or KwH/year. The conversion efficiency of
fossil fueled electrical power generation and distribution
to the plant site may be taken as 32.5%. A heat to electrical
power conversion of 10,500 BTU/KwH may be used in this calcu-
lation.
523
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8. Energy saving credits may be granted for lower grade fuel
substitutions.
9. Net primary energy is the net energy consumed for the com-
plete treatment of wastewater, including the transportation
and ultimate disposal of all residuals.
In addition to meeting cost and energy criteria, innovative technology
must have some element of increased risk and associated benefit. Traditional
engineering practice has always dictated a very low element of risk for the
construction of full scale public works projects supported by federal expen-
ditures. In passing PL 95-217, Congress clearly intended that a higher degree
of risk be permitted for innovative technology. The permitted degree of risk
should be compared to the potential for significant state-of-the-art advance-
ment. High risk, high potential state of the art advancement projects may be
judged acceptable for funding where high risk, low potential state of the art
advancement projects may be deemed unacceptable. The concept of risk vs.
stage of technology advancement used in this program is shown in Figure 2.
oo
>-H
o:
Q
WINDOW OF ACCEPTABLE RISK
FOR INNOVATIVE TECHNOLOGY
TECHNOLOGY
NOT
FULLY
DEVELOPED
PROVEN
TECHNOLOGY
STAGE OF TECHNOLOGY DEVELOPMENT
FIGURE 2
WINDOW OF ACCEPTABLE RISK
Technologies to the left of the window of acceptable risk in Figure 2
are considered not fully developed and are too risky compared to benefits for
full-scale construction. Technologies to the right of the window of risk are
considered proven and should not benefit from the increased innovative tech-
nology funding provisions. The innovative program is designed to encourage
designers to develop technologies that are within the window of acceptable
risk. This calls for a conscious decision on the part of the designers to
524
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depart from traditional practice and propose higher than normal risk designs
that have increased potential for achieving cost, energy, or other benefits.
This is a key element in this new national program.
From a procedural point of view, all facility plans for the construc-
tion of municipal treatment plants proposed by consulting engineers are
evaluated by the state and EPA regional offices in a three-step process
shown in Figure 3.
The first step is the determination if the proposed technology involves
increased risk (Point A). The second step is the determination if the tech-
nology meets the innovative qualifying criteria (Point B). The third and
final step is the determination if the proposed technology is the most cost
effective system to meet the effluent quality goals. In this last step, all
I/A Technologies are given a 15% advantage or preference in the required
cost effectiveness analysis.
I/A Technologies passing the three step qualifying process are awarded
an 85% federal grant instead of the normal 75% grant. These projects also
qualify for a replacement grant if the higher risk technology fails to meet
design or performance standards within the first two years of operation.
A critical element of the entire I/A Program is the method by which the
states receive and distribute the increased grant funds. Each state is allo-
cated a portion of the federal construction grant budget each year according
to assessment of need. Two percent of this allotment for fiscal years 1979
and 1980 and three percent for fiscal year 1981 is set aside to be used only
to increase the 75% federal share to 85%. A minimum of one half of one per-
cent must be spent on Innovative rather than Alternative Technology. A
strong incentive for the states to encourage the expenditure of their set
aside funds is the provision that if they are not spent, the states cannot
participate in any reallotment of the 75% funds remaining at the end of a
given fiscal year.
III. RESPONSE TO AND SUCCESS OF THE PROGRAM DURING THE FIRST ONE AND ONE-HALF
YEARS
The USEPA Construction Grants Innovative and Alternative Technology Pro-
gram has been in operation for approximately 1 1/2 years. Initial national
management efforts during the first year emphasized information dissemination
and training of design engineers as well as state and federal review authorities,
A comprehensive Innovative and Alternative Technology Assessment Manual was
prepared during the first year and distributed to over 6,500 engineers (7).
This manual summarizes the federal legislation and regulations, provides
detailed procedural guidance for identifying and judging I/A Technologies,
and summarizes the cost, energy, and performance of 117 state-of-the-art
technologies used as the baseline of conventional technology. Additionally,
over 30 separate technical training seminars were held to acquaint over 2,600
designers with the I/A Program requirements.
525
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Ln
to
CTi
Fully Proven Meet Innovative Classification an)
In Circumstances Criteria Cost-Effective Funding Decision
ALTERNATIVE TECHNOLOGY
Specifically identified forms of treatment and unit
processes
Effluent Treatment Energy Recovery
- land treatment - co-disposal of
- aquifer recharge sludge and refuse
- aquaculture - anaerobic digestion
- silviculture with >90% methane
- direct reuse recovery
(non potable) - self-sustaining
- horticulture incineration
- revegetatton of
disturbed land Individual and On-
- containment ponds Site Systems
- treatment and storage
prior to land - on-site treatment
application - septage treatment
- preapplication treat- - alternative col-
ment lection systems
for small com-
Sludge muni ties
- land app) ication
- composting prior to
land application
- drying prior to
land application
CONVENTIONAL CONCEPTS OF CENTRALIZED TREATMENT
processes with direct point source discharges to
surface waters
YES
NO
YES
/
NO
1 115% cost pre-
YES I,, feretice for
N0 VL publicly owned
>A YES 1 - "5* cost pre-
1 NO | publicly owned
VES ^D
NO YU
YES A r no cost
NO I preference
1 YES I 115% COSt Pre~
not funded
- 85% Innovative
- not funded
not funded
— 75% conventional
- 85% innovative
NO | publicly owned if
| energy criteria
1 VES Ajj | Is wet not funded
NO |
not funded
FIGURE 3
INNOVATIVE AND ALTERNATIVE TECHNOLOGY DECISION METHODOLOGY
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Response to the program from the design engineers has been mixed. They
have approached the concept of innovative municipal designs with cautious
optimism. Part of their reluctance is due to additional planning and engineering
effort required for developing I/A Technology projects. The new evaluation pro-
cedures force all designers to learn a new set of design requirements and pro-
cedures which increase their non-billable costs while they have little assurance
of recovering the added investment because of the interim nature of the presently
authorized three-year program.
Other factors contributing to a slower-than-expected start of this
program was the concern that the entire planning, design, and construction
process may be slowed down to the point where increased costs due to infla-
tion would outweigh the advantages of the I/A Technologies. Another concern
on the part of designers is that during the last year of the three-year program,
additional efforts to plan and design I/A projects would be wasted because the
authorization to increase federal grants for construction would expire. Typ-
ically in the United States, facility planning (Step 1) and detailed designs
(Step 2) costs average 7% of the total capital cost for municipal treatment
plants. The normal time for planning and detailed design including state and
federal approval range from 1 1/2 to 3 years depending on size and complexity
of the facility and the level of public participation in resolving identified
local environmental issues.
Notwithstanding the above concerns on the part of design engineers and
the inherent time lags in implementing a new national program, results during
the first 1 1/2 years have been very encouraging. Two hundred seventy-three
facility plans have been received that include Innovative and Alternative
Technology. Of these, 235 are for one or more of the 19 identified Alter-
native Technologies and 38 are for Innovative Technologies. The Innovative
Technology facility plans are equally divided between proposed life cycle
cost and energy saving designs.
The state governments' participation in the program has generally been
supportive but all states have not yet established administrative procedures
to fully implement the program because many were awaiting further clarifica-
tion of procedure and policy direction from USEPA regional offices.
Because of the wide diversity of population density, geographical, and
climatic features between the states, their ability to effectively benefit
from the I/A Technologies differ markedly. The identified Alternative Tech-
nologies such as land application, aquaculture, silviculture, and other
natural system technologies are more widely used in the midwestern and
southwestern agricultural states with large, sparsely populated, poten-
tially productive land areas. Improved centralized biological treatment
plants, thermal sludge reduction procedures, and energy recovery and con-
servation systems are more widely used in the more populated eastern sea-
board and Great Lakes areas. On-site technologies and the more cost effective
alternative collection systems are used in all small communities (less than
3,500 persons) scattered throughout the U.S.
527
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One of the immediately evident impacts of the I/A Program, even at this
early stage, is a much closer link between the practicing engineers and the
research community. Within USEPA, the Office of Research and Development and
the Office of Water Program Operations are jointly participating in the pro-
gram in an intensive and increasingly successful effort to develop and dis-
seminate information on emerging Innovative and Alternative treatment approaches,
Requests for information and assistance on new technological approaches have
increased sharply during the past year. Another measure of increased interest
in Innovative Technology is an increasing number of proposals for research
demonstration and development grants from research communities and private
industry.
A review of the I/A facility plans submitted thus far in the program
indicates a wide range of technologies being considered by designers through-
out the country. A partial listing of I/A projects representing different
technologies, along with projected cost and energy savings, is shown in
Table 4. These projects illustrate some of the newer technologies being
proposed for municipal treatment in the U.S. Some have not yet been approved
by the respective states or by the USEPA regional offices.
IV. SELECTED INNOVATIVE AND ALTERNATIVE TECHNOLOGIES
Summarized below are several examples, conceptual designs, treatment
technologies, or techniques which demonstrate the broad scope and intent of
the federal Innovative and Alternative Technology Program. They include
both specific case histories and more general technology summaries. All
are concerned with promoting national pollution abatement goals through
increased emphasis on cost savings, energy conservation, improved appli-
cation, or any combination of these. These examples were selected because
they illustrate a wide range of technological and conceptual approaches
proposed throughout the U.S. for solving local water quality problems.
Some of the examples were found to meet the specific cost and energy cri-
teria for Innovative Technology while others qualify as Alternative Tech-
nology.
In particular, there are nine summaries: Aquaculture and overland flow
(part of land treatment) are discussed in general because they are promising
Alternative Technologies which are expressly mentioned in the law as being
desirable alternatives to conventional wastewater treatment.. Unlike the
proven slow rate and rapid infiltration land application systems, detailed
design criteria for these systems are not as well developed. Thus, while
potential benefits are great, these technologies still exhibit some risk.
The combined sludge/solid waste disposal and energy recovery plant at Memphis,
Tennessee is an example where an Alternative Technology also qualified as an
Innovative Technology because of significant energy savings. The joint
municipal and industrial waste facility proposed for Dodge City, Kansas is
a good example of a conceptual design for a joint industrial municipal treat-
ment facility which generates revenue, achieves maximum energy recovery, and
recycles nutrients. Other elements of these projects include Alternative Tech-
nologies of aquaculture and land application. A combined aerobic/anaerobic
528
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TABLE 4
COST AND ENERGY SAVINGS OF SELECTED INNOVATIVE OR ALTERNATIVE PROJECTS
Project Name
or Location
Description of Technology
Innovative (I) or
Alternative (A) Projected Savings
Designation Cost or Energy
Comments
Dodge City, Kansas
Livingston, Montana
Joint anaerobic digestion of feed lot,
packing house and municipal sludge
lagoon, aquaculture treatment with
sale of methane and fertilizer
Windmill powered air activated
sludge plant by using 5 40 Kw
solar wind energy conversion sys-
tem in small windmill form
I & A
Energy 25? Comprehensive conceptual design
Cost 10% for joint treatment with excel-
lent reuse, recycle, and energy
recovery features
May be co-funded by EPA and DOE
Energy>20% power to be fed to network and
treatment plant to draw power
from same network
Kalamazoo, Michigan
Powdered activated carbon in single
stage activated sludge with wet
oxidation regeneration of carbon to
treat highly industrialized muni-
cipal wastewater
Cost 16«
Large municipal plant 50 mgd
Montgomery, Alabama
Recovery of methane from anaerobic
digesters, cleaning, compressing,
and use to fuel sanitary department
vehicles
N/A
First use of methane to
fuel vehicles by municipal
government under Construction
Grants Program
Hardinsburg, Kentucky
Efficient use of large available
hydraulic head at site to assist
rotation of rotating biological
contactors
Energy 36% Plant design also incorporates
other energy saving and re-
covery design features
Fountain Run,
Kentucky
Hybrid system design for serving
sparsely populated area. Includes
on-site treatment by septic tank
soil absorption, collection by
small diameter gravity sewers and
collection by pressure sewers and
conventional sewers
N/A
One of the first examples of
hybrid design and comprehensive
planning using alternative col-
lection and treatment tech-
nologies in the U.S. under the
new Innovative and Alternative
Technology Program
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TABLE 4 (Continued)
Craig-New Castle,
Virginia
Pressure sewer collection of septic
tank effluent, solar pond heated
anaerobic lagoon followed by
facultative pond and fish aqua-
culture pond
N/A
Final design may differ from
original proposal
Nassau County, New York
Short detention time fluidized
bed biological treatment to meet
secondary treatment standards
Cost 15% This design does not meet the
required cost or energy savings
Energy ?_Q% for innovative technology but
has high potential and very wide
applicability in the U.S.
HilIsborough,
New Hampshire
Secondary treatment plant emphasizing
rotating biological contactors.
Plant is unique because of the total
integrated energy saving design
features that include solar anaer-
obic digester heating, energy
efficient building design, heat
recovery from the effluent and
heated covered rotating biological
contactors.
Conceptually innovative design
Energy 20% to maximize total energy savings
thru the use of all feasible
energy recovery concepts in an
area of high energy costs.
U)
O
Composting of municipal primary
Portland, Maine and secondary sludge and use for
soil amendment on municipally
owned 1 and
N/A
None
York County,
Pennsylvania
Aerated lagoon followed by land
irrigation to meet secondary
treatment standards
. N/A
One of the more commonly used
methods of land application in
sparsely populated areas with
suitable soils
Oxidation ditch (circular channel)
Atmore, Alabama method of activated sludge treat-
ment with unique draft-tube aerator
Aeration method uses U-tube prin-
ciple for more efficient aeration
using two prime movers that also
have advantage of decoupling dis-
solved oxygen control and channel
velocity
A very reliable and energy
Energy 20?i efficient method of secondary
treatment for small (0-10 MGD)
plants. These systems also
exhibit high potential for
single stage nitrlfication-
denltrification
Lorraine, Kansas
Three cell total containment
lagoon
N/A
One of the more common forms
of treatment for small com-
munities 1n Midwest. Treatment
is by evaporation and slow
percolation
N/A—The cost and energy saving criteria are not applicable to alternative technology
-------
sludge digestion process proposed for Lackawanna, New York is a case history
where formal evaluation of the cost and energy savings of the process qualified
it as Innovative Technology. In another example, USEPA research to improve
activated sludge aeration efficiency is summarized. A deep well biological
treatment process for Ithaca, New York is representative of a new biological
treatment approach which exhibits potential cost and energy savings. Finally,
two examples of technologies showing promising Innovative characteristics
which have been developed with partial USEPA research assistance are given.
These are the vertical well chemical reactor system and fluidized bed bio-
logical treatment. The fluidized bed biological reactor was formally submitted
and was recommended for approval as Innovative Technology. The vertical well
chemical reactor system is at an early stage of development, but exhibits strong
potential for cost and energy savings for sludge and higher strength wastes.
Vertical Well Chemical Reactor (8)(9)
Description
A vertical well chemical reactor (VWCR) system utilizes the fact that
all organic substances can be oxidized in a liquid state if sufficient air
(oxygen), temperature, and pressure requirements are met. Organic combustible
elements are principally carbon and hydrogen and, in some cases, sulfur (when
in sufficient quantities). Ideal combustion reactions for carbon and hydrogen
including heat liberated are:
C + 02-*-C02 + 9.1 KwH/kg C (14,100 BTU/lb C)
2H2 + 02 —*• 2H20 + 39.4 KwH/kg H2 (61,100 BTU/lb H2)
In general, for most waste materials the range of heat released per
pound of air required has been found to be from 0.35-0.41 KwH (1,200 to
1,400 BTU).
The objective of the VWCR system is to release this heat from the sewage
or sludge and completely destroy all volatile elements while minimizing com-
bustion imperfections and heat losses. Excess air quantities (above stoi-
chiometric requirements) are required in varying amounts to take into con-
sideration differences between ideal and actual conditions.
The principal feature of the VWCR system is its use of an extended
vertical U-tube for achieving reaction pressures, temperatures, and reten-
tion time. The tubes can be suspended from the top of a conventinoal cased
well and may extend to depths over 1,524 m (5,000 feet). The waste fluid
and air are injected into a tube at the earth's surface. As the waste stream
and air flow down the tube, they undergo natural pressurization due to the
hydrostatic head above. Thus, water pumps and air compressors need only be
nominally sized to overcome surface friction and gravity losses and do not
need to develop the high pressures actually experienced at the bottom of the
U-tube.
531
-------
Two concentric tubes form the U-tube which is made of 300 Series stain-
less steel. The smaller downcomer tube is surrounded by hot treated waste
from the larger concentric upcomer tube. Figure 4 is a schematic of the
top view.
WELL CASING
UPCOMER
(EFFLUENT)'
HEAT EXCHANGE Hf I ( nil = AIR LINE
FLUID
INSULATION
/ ^<^s£gx^ \
DOWNCOMER'
(INFLUENT) IRON CASING
FIGURE 4
VERTICAL HELL CHEMICAL REACTOR SCHEMATIC, TOP VIEW
Heat exchange is very efficient and as influent waste approaches the
bottom of the tube system, temperature and pressure become sufficiently
high to support maximum oxidation. Pressures of over 1,500 psi and tem-
peratures exceeding 600°F may be reached. Tube lengths and diameters are
appropriately sized to allow adequate retention time (normally about 1/2 to
one hour) in the oxidation/combustion zone. The well size estimated as
necessary to treat sludge from a "typical" domestic wastewater treatment
plant are as follows: a 55.9 cm (22 inch) diameter well for sludge from
a .14 x 106 m3/day (37 mgd) biological wastewater treatment plant; a 35.6 cm
(14 inch) diameter well for sludge from a .075 x 106 m3/day (20 mgd) plant;
and 15.2 cm (6 inch) well for .019 x 106 m3/day (5 mgd) and below.
Oxidized waste finally flows up the tube system and is gradually cooled
as heat is transferred to the downflowing fluid. Pressure also decreases
due to decreasing hydrostatic head as the fluid ascends. Thus, the pres-
surization and depressurization of the fluid waste and recouperative heat
exchange are accomplished in a nearly reversible thermodynamic process.
Excess heat is continually removed from the reaction zone by means of a
heat exchange jacket and high pressure cooling water or other fluid. The
high pressure, high temperature fluid is available for use at the ground
surface as a high quality energy source.
The USEPA is currently sponsoring research on a pilot scale system
designed to investigate the feasibility and cost of treating raw domestic
sewage sludge by the VWCR oxidation process. It is felt the cost and energy
savings gained by eliminating the expensive high pressure equipment used by
conventional surface wet oxidation processes could be significant. The raw
532
-------
sludge being used has an input COD in the neighborhood of 3,000 mg/1. The
research is being conducted at a pilot wastewater treatment plant in Denver,
Colorado using a stainless steel reactor having a 5.1 cm (2 inch) diameter.
Depth of the reactor into the ground is 457 m (1,500 feet). Approximately
22,740 1 (6,000 gallons) of sludge will be processed daily. Oxidation
efficiency as percent COD removal will be documented. Operational param-
eters and sludge dewatering characteristics will be measured as well as
will selected analyses for nitrogen, phosphorus, organic, and heavy metal
compounds. The study is scheduled to be completed in November, 1980.
One example where the VWCR process is being considered as an Innovative
unit process for treating a high strength municipal/industrial wastewater is
at Montrose, Colorado where a new wastewater treatment plant is scheduled to
begin construction in late 1980. Influent wastewater average flow is pro-
jected to be 13,230 m^/day (3.75 mgd) and is composed of industrial (candy
factory) and municipal wastes. Expected COD should range between 650-700 mg/1
with a high sugar content which makes it desirable for wet oxidation. Pre-
liminary calculations based on laboratory test results require 2 VWCR 1,524 m
(5,000 feet) deep operating at temperatures up to 338°C (640°F). Preliminary
layout and sizing for the Montrose VWCR treatment plant is diagrammed in
Figure 5. Detailed analyses and final design considerations or options are,
at this writing, still being developed for the Montrose facility.
Ideal conditions for the VWCR process, as with other wet oxidation pro-
cesses, are when the exothermic reactions of its oxidized organic wastes
provide adequate energy as heat to keep combustion self-sustaining and indeed
to provide additional energy for other plant requirements. Most effective
oxidation occurs between 260-302°C (500-575°F). In general, the waste (as
sludge or wastewater) must be primarily organic in make-up and have a minimum
COD of approximately 400 mg/1 before exothermic reactions occur.
Efficient, recuperative heat exchange between the downflowing influent
and rising effluent is also desired if the process is to be cost effective.
In general, a A T of 1.5°C or less will be the VWCR design criteria. Once
the surrounding earth equilibrates to reaction temperatures, it acts as an
excellent insulator or heat envelope so that reliable, high efficiency trans-
fer can reasonably be expected in the long term.
The VWCR U-tube uses 300 Series stainless steel for corrosion-resistant
linings. More exotic metals could be required for specific waste streams.
It has no moving parts and, therefore, incurs small operation and maintenance
costs. A conservative design estimate for tube life is 15 years.
Actual cost and energy data are, of course, very waste and site specific.
The heat value of the waste will vary and this greatly affects oxidation per-
formance. The objective of VWCR operation is, as indicated earlier, to main-
tain its desired temperature for a long enough period of time so that all
organic substances can be sufficiently oxidized to meet effluent requirements.
(Pressure is fixed by reactor depth.) When exothermic conditions exist, as
is expected most of the time, cooling water maintains the desired temperature
range within the reaction zone and carries excess heat back to the surface for
533
-------
01
U)
*>.
LIQUID FEED
50 PSIG
COMMINUTORS
RAW
HASTEWATER
GRIT
CHAMBER
~
——^F3 '
>
VWCR COMPONENTS
AIR COMPRESSORS #1 50 HP
(2 EACH) #2 25 HP
WATER PUMPS
(2 EACH)
OTHER
VWCR HP
LIQUID FEED
HEAT EXCHANGE
FLOTATION TANK AND
SOLIDS THICKENER
NOMINAL HEAD
HP ACFM PSIG
36.5 174 42.6
15.9 27.4 74.5
HP GPM PSIG
51. 1300 50
0.8 7.9 100
#1 #2
COMPRESSORS
H-X
COOLING WATER
VWCR
HP
7.5
TO HEAD OF PLANT
TO DISPOSAL
SOLIDS THICKENER
EFFLUENT
FLOAT OUT
FIGURE 5
PRELIMINARY MONTROSE VWCR TREATMENT SYSTEM LAYOUT
-------
other potential uses. When additional heat is needed such as for start-up
or when the heating value of the waste drops below critical levels, it is
supplied as steam by a pre-heat boiler.
The Montrose VWCR schematic demonstrates how these considerations are
approached and illustrates the use of the heat exchanger and pre-heat boiler.
Note also the use of the flow equalization tank preceeding the VWCR system
which serves to dampen both hydraulic and organic slug loading. Similarly,
the 12 acre-foot polishing pond also serves as an effluent damper and mixer,
allowing final C02 to come out of solution and the pH to equilibrate with
other organic acids formed (such as carbonic and acetic) which are among
the final oxidation products. The Montrose VWCR system is being designed
with 100% redundancy. One reason for its conservative design is because it
is the first for a relatively large flow (13,230 m3/day) and it is desired
to insure continuous operation should some component require maintenance or
modification. The dual configuration will also allow flow-splitting studies
and long-term operation and maintenance data to be developed.
Laboratory and pilot scale data have given information about the degree
of treatment which can reasonably be expected. COD removal should be between
80% to 90% or more. Effluent is, of course, disinfected and the solids, as
an inert ash, are easily dewatered. It has been estimated that the volume
of dewatered solids remaining after oxidation should be typically 0.11 m3
(4 ft3) per 3,780 m3 (million gallons) of wastewater.
Table 5 shows the results of desk-top design calculations for treating
domestic wastewater sludge from two sizes of wastewater treatment plants.
Design assumptions are conservative and are indicated in the table. Cost
and energy data are for the VWCR system proper (i.e., U-tube plus associated
pumps and compressors, flotation tank, and solids thickener) and include
well drilling costs.
TABLE 5
ESTIMATED VWCR SYSTEM COST AND ENERGY USE FOR TREATING SLUDGE AT
TWO MUNICIPAL WASTEWATER TREATMENT PLANTS
Nominal Plant Size
18.9x103 m3/day (5M6D) 75.6x103 m3/day (20MGD)
Capital costs, million dollars, $10 2.5 5.0
Raw energy available, kw 556.4(1.9xlO^BTU/hr) 2196.2(7.5xlO^BTU/hr)
Energy consumed, kw 87.8(0.3xlO°BTU/hr) 263.5(0.9xl06BTU/hr)
Operation, man years 3.5 3.5
Total pump power, kw 93.2 (125 hp) 261.0 (350 hp)
Reactor outer diameter, cm 15.2 (6 in) 35.6 (14 in)
*Assumptions: 0.24 kg COO/m3 (2000 Ibs COD/MG)
3.87 kwh/kg COD (6000 BTU/lb COD) heating value
75 percent recoverable heat, 1219.2 m (4000 ft) reactor depth
includes U-tube system, flotation tank, solids thickener
535
-------
Innovative or Alternative Technology Characteristics
Although the thermodynamic principles involved in wet oxidation are well
established, the VWCR system is a unique engineering application of these
principles which has potential for significant energy recovery and cost
savings compared to conventional unit processes which it might replace. Its
desirable characteristics include three main areas. First, heat losses are
minimized once surrounding earth is at equilibrium promoting efficient heat
transfer and energy savings. This includes the potential for selling the
energy (heat from the hot water) gained from the exothermic reactions.
Secondly, its configuration promotes land conservation. It is estimated
that the lana required for a VWCR system (U-tube, pumps, compressors) to
treat sludge from a 151,200 m3/day (40 mgd) plant is approximately 2,023 m3
(one-half acre). (Conversely, it should be noted that well drilling costs,
if necessary, can be expensive.) Finally, the concept itself is extremely
efficient because it takes advantage of natural hydrostatic head to create
the pressures desired.
The use of natural forces to attain a desired result means potentially
more reliable operation as well as cost savings compared to the expensive
high pressure equipment normally used. Cost savings are also potentially
available as a result of the natural advantages of the wet oxidation pro-
cess. These include its ability to oxidize strong waste liquors and sludges
without pretreatment, and the inert, easily dewatered sludge it produces.
While the VWCR system has significant potential, formal data acquisition
has only recently begun at pilot scale (July 1979) and the process has yet to
be operated full scale. Thus, the technology is not fully developed and there
is some r~!sk involved. High temperatures and pressures promote accelerated
corrosion or deposition when conditions and water constituents are at the
right levels. There is some possibility of plugging the U-tube reactor.
Start-up and shut down procedures, operation and maintenance protocols,
mechanical and thermodynamic problems in large-scale operations still have
to be addressed. These represent an engineering challenge to a technology
which can potentially meet national environmental goals of increased energy
recovery and improved cost effectiveness.
Improved Aeration Efficiency and Reliability (10)(11)
Description
The Innovative and Alternative Technology Program administered by the
USEPA tangibly rewards promising technologies intended for full-scale treat-
ment which have a reasonable chance of effecting significant cost or energy
savings, resource conservation or reuse, or public benefits. It would be
foolish, however, to expect these technologies to emerge from a vacuum, and
no such pretense is made. USEPA wastewater research efforts are oriented
towards enhancing development and management of wastewater treatment tech-
nologies or techniques which have a high potential for significant beneficial
impact on wastewater treatment objectives. Attention is not limited to
536
-------
treatment facilities alone. It includes scrutiny of the approaches and bases
for developing, selecting, and optimizing the unit processes or unit operations
used.
One example is USEPA recognition of the need for an oxygen transfer stan-
dard method of measurement in municipal wastewater. There are two common
complaints about oxygen transfer equipment. These are: (1) difficulty in
correlating manufacturers' claims with field test data; and (2) difficulty
in projecting oxygen transfer efficiencies from clean to wastewater systems.
As a result, discrepancies between anticipated and actual field conditions
often necessitate substantial field modifications to the aeration equipment
furnished.
Table 6 illustrates clean water oxygen transfer efficiencies for several
generic aeration devices under standard conditions. Noting the uncertainties
created when trying to translate clean water oxygen transfer efficiencies to
field conditions, R.C. Brenner wrote, "It is quite evident that if the claimed
oxygen transfer capabilities of fine bubble aeration systems in particular
can be substantiated (for municipal wastewaters) via repeated testing using
valid standardized test and evaluation methodology and if the maintenance
requirements of these devices are not exorbitant, substantial savings in
power are possible in contrast to the traditional, widely used coarse bubble
options" (11). As a result of this recognition, USEPA has undertaken research
in three related areas.
From August 1977 to February 1979, the Los Angeles County Sanitation
Districts (LACSD) supported in part by USEPA, conducted a series of clean
water oxygen transfer tests designed to obtain data under closely controlled
conditions comparing various generic types of submerged air aeration equip-
ment. Six types of devices were selected which represented typical methods
of dispersing various sizes of bubbles:
Fine Bubbles Medium Bubbles Coarse Bubbles
Jet Aerators Static Aerators Fixed Orifice
Dome Diffusers Variable Orifice
Tube Diffusers
All devices were compared using the same test tank and identical test
procedures throughout. The test tank was 6.1 m x 6.1 m x 7.6 m (20 ft x
20 ft x 25 ft) maximum variable depth. Clean water dissolved oxygen uptake
was carried to equilibrium using water chemically deoxygenated with sodium
sulfite and a cobalt chloride catalyst. Three runs at four different depths
(3.0, 4.6, 6.1 and 7.6 m) were made. Each run had a different input power
level (varying from .01-.04 Kw/m3) delivered to the water. Diffuser con-
figurations were selected by aerator manufacturers who were allowed different
configurations for different depths but had to maintain a constant config-
uration over the series of tests at any given depth. The configuration or
geometric pattern selected was one intended to be economically feasible at
full scale and over the range of input powers evaluated.
537
-------
TABLE 6
COMPARATIVE CLEAN WATER OXYGEN TRANSFER INFORMATION FOR
AIR AERATION SYSTEMS UNDER STANDARD CONDITIONS (a)
Type of Aeration Device
Mechanical Aerator
Low speed surface
High speed surface
Turbine sparger (b)
Fine Bubble Aerators (c)
Fine Bubble Diffuser
(a) Total floor coverage
(b) Side wall mounted
Jet Aerator (b)
Coarse Bubble Diffuser (c)
Static aerator
Coarse bubble dual aeration
Coarse bubble single side
aeration
Range of
Clean Water 0,
Transfer (%)
-------
of the LACSD field study are finalized, a year-long study of data and ex-
periences from energy-efficient air aeration activated sludge treatment plants
in other countries has been commissioned by USEPA. Europe, and especially
Britain, has had considerable experience with fine bubble diffusers in its
activated sludge plants. Assessment and review of operating experiences
and data from 13 European treatment plants is intended to fill the data
gap while more extensive data are being generated in the United States.
The study, which is nearing completion, will analyze and summarize timely
and useful operating data from full-scale plants having a 4-8 year data base
using fine bubble diffusers. The final report is expected to be available
by October 1980.
As indicated previously, the clean water testing by the LACSD was done
using the non-steady state reaeration method. Considerable effort was made
to keep constant all external variables so that differences in aerator per-
formance could be attributed with confidence to inherent limitations and not
outside influences. Generally speaking, the fine bubble aeration systems
showed a significant improvement over coarse bubble spargers. Aerator trans-
fer efficiencies and energy consumption under the varying conditions described
earlier were measured and documented to include information such as that
illustrated in Table 6. The final report on this effort has not been com-
pleted at this writing, but is expected to be published shortly and will
contain detailed data about the various aerator performances.
Completion of field tests on porous dome diffusers, porous tube dif-
fusers, and jet aeration systems at LACSD's Whittier Narrows Wastewater
Treatment Plant is ex pected by early 1982. Data gathered over a two-year
period is intended to supply needed information for at least three areas
which lack an adequate data base for good cost and energy estimations.
First, long-term operational and maintenance problems of fine bubble aera-
tion devices such as air filtering requirements, external diffuser clogging,
and diffuser breakage will be documented and analyzed. Secondly, oxygen
transfer efficiencies in respiring full-scale activated sludge systems sub-
ject to real-world influences will be closely and comprehensively measured
over time. Finally, the potential for developing an efficient, high-rate
activated sludge process (i.e., short detention times, high organic loadings)
with fine bubble aeration systems will be explored. The high volumetric
organic loadings utilized by high-solids, high-rate systems can be sustained
only by efficient oxygen transfer such as provided by use of pure oxygen
aeration or hopefully by fine air bubble production. Decreased bioreactor
volume and energy savings would be the by-products of a successful study.
The LACSD effort will also include extensive measurements to determine
alpha and beta factors under field conditions. These factors, particularly
alpha, significantly affect aeration equipment field design. Alpha is the
ratio of the overall oxygen transfer rate coefficient in wastewater to that
in clean "tap" water. Alpha is known to vary considerably for different
wastewaters, tank geometries, and bubble sizes. Beta is the ratio of the
wastewater system dissolved oxygen saturation concentration to that in clean
water. These tests will be conducted in the same mixed liquor tanks as the
performance evaluations, affording the unusual opportunity to measure alpha
and beta factors on a plant rather than laboratory scale.
539
-------
The survey and evaluation of existing energy efficient air aeration
devices in other countries is intended to provide timely maintenance infor-
mation and operating data which will beneficially impact use of fine bubble
aeration equipment in existing and future activated sludge plants. The survey
will define and summarize international professional trade literature with
respect to aerator availabilities and process and maintenance performance.
It will document and assess records from actual operating plants with a
good data base and sufficient history ( >4 years) to provide a reliable
indication of actual aerator processes and maintenance performance. Finally,
it will address wherever possible points of controversy concerning the
efficiency of various aerator types where good quality data can be developed
on specific points. The resulting report should provide USEPA and the indus-
try with an early and definitive report about fine bubble aerator performance
in operating, full-scale activated sludge systems.
Innovative or Alternative Characteristics
The underlying concept of the Innovative and Alternative Guidelines is
to provide incentive for widespread adoption of municipal wastewater treat-
ment technologies or techniques which represent advancement in the current
state of the art with respect to meeting the national environmental goals
set out by Congress. Energy efficiency and cost effectiveness are two of
these goals met by improved oxygen transfer. In particular, the long-term
benefits obtainable from more efficient aeration devices have been summarized
by Brenner and represent a case-in-point which demonstrates desirable Inno-
vative characteristics: confidence in the efficiency and field performance
of fine bubble wastewater aeration devices should result in more efficient
high-rate activated sludge systems with a concomitant savings in energy
over design techniques to avoid unintended undersizing of oxygen transfer
equipment.
Deep Well Biological Reactor (12)(13)
Description
A deep well biological reactor (DWBR) is basically a vertical activated
sludge reactor which has the potential to reduce land area required for
treatment, life cycle costs, and energy requirements. Treatment of raw
wastewater occurs at elevated pressures with turbulent mixing promoting
efficient oxygen dissolution and intimate biota/substrate contact. Figure 6
illustrates schematically the DWBR configuration.
Influent raw wastewater and sludge recycle are fed to the head tank
located directly above the DWBR, where it combines with return sludge. The
DWBR is divided into an upflow section (called the riser) and a downflow
section (called the downcomer). The primary purpose of the head tank is
to allow spent air to disengage from the mixed liquor exiting the riser,
prior to re-entry into the downcomer.
540
-------
INLET
COMPRESSOR
RISER AIR
OOWNCOMER AIR
\
SLUDGE RECYCLE
A
OUTLET
DOWNCOMER
-RISER
SHAFT CASING
FIGURE 6
DWBR HYDRAULICS
is
circulation of the mixed liquor in the shaft
pump principle using compressed air injected into the
the
induced by a
riser
air supply is
The initial
simple air lift
side of the shaft. Once shaft circulation is established,
gradually transferred to the downflowing side.
Since the veolicity of the rising bubbles injected into the downcomer is
4-7 times less than the liquid velocity in the downcomer, these bubbles are
carried downward to the bottom of the shaft. In many designs, a large por-
tion of the bubbles will be completely dissolved before they reach the bottom
of the shaft.
541
-------
The driving force causing circulation is created by the net difference in
total bubble volume (voidage) between the riser section and in the downcomer
section. Above the air injection point, there is no voidage. Therefore, the
liquid in the downcomer has a lower average voidage and its greater weight
forces the flow down the shaft. As the liquid travels up the riser, pressure
decreases and bubbles of nitrogen, carbon dioxide, and residual oxygen are
formed and then released to the atmosphere in the head tank. Treated effluent
then overflows to the solids separation system.
The USEPA is supporting a municipal demonstration project at Ithaca,
New York. It utilizes a second generation DWBR configuration and began
operation in October 1979. In this configuration, approximately 2/3 of
the compressed air is fed to the riser leg, 1/3 to the downcomer leg. The
technique greatly increases voidage in the upper section of the riser making
it virtually impossible for hydraulic reversal to occur. Further, virgin
air is introduced along with influent wastewater, optimally matching oxygen
demand with oxygen availability. Mixed liquor for subsequent clarification
is withdrawn below the point of air/wastewater introduction to prevent un-
treated wastewater from short circuiting to the shaft discharge line.
Ithaca will be investigating solids separation of DWBR effluent using
two modes. In the sedimentation mode, vacuum degassing to remove additional
effervescence preceeds conventional gravity settling. MLSS in the reactor
are usually restricted to 5,000 mg/1 due to the settling characteristics of
the mixed liquor solids in the sedimentation tank. Recycle sludge thickens
to roughly 10,000 mg/1 resulting in a recycle flow rate of approximately
100% of influent flow.
The flotation mode takes advantage of the natural tendency of the mixed
liquor leaving the riser to float. MLSS concentrations as high as 10,000 mg/1
can be maintained in the reactor without impairing flotation solids separation
efficiency. A smaller DWBR volume can therefore be utilized while retaining
F/M levels in the design range of 0.75-1.0. Solids in the float can vary
from 6-8% eliminating the need for further thickening and allowing a small
float recycle flow rate of about 20%. Flotation aids may be necessary, how-
ever, offsetting savings in bioreactor size and sludge disposal costs.
Schematics of the DWBR in both sedimentation and flotation modes are illus-
trated in Figures 7 and 8.
The Ithaca municipal demonstration plant DWBR is 136 m (446 feet) deep
and has a main steel casing of 43.82 cm (17.25 inches) ID grouted to the
geological formation with cement. The primary downcomer is 29.85 cm
(11.75 inches) OD. Compressed air is added to both the downcomer (approx-
imately 0.566 standard m3/min) and the riser (approximately .934 standard
m-Vmin) using a 14.9 kw (20 hp) compressor. The DWBR acts as a plug flow
bioreactor. Biological growth and substrate utilization proceeds in accordance
with the Michaelis-Menten relationship. Operation is based on an average BOD
influent of 150 mg/1. The combination of high intensity mixing in the shaft
(Reynolds Numbers > 100,000) and elevated pressures (to 8 atm) would produce
oxygen utilization efficiencies in excess of 90% with an influent BOD of
500 mg/1 or more. However, with the relatively weak Ithaca influent,
circulation air requirements govern and oxygen utilization is only expected
542
-------
COMPRESSOR
[RAW INFLUENT^."
U>
HEAD
TANK
DOWNCOMER
SURGE
TANK
VACUUM
DEGASSER
JLL
ID
RETURN SLUDGE
[
SEDIMENTATION TANK
CL
TJ
p FLUENT
SCUM
ZJWASTE SLUDGED
FIGURE 7
DWBR SEDIMENTATION MODE
-------
Ul
FOAM
OXIDATION
TANK
y^-v
COMPRESSOR
SECONDARY
DOWNCOMER
INTERMITTENT WASTE
BOTTOM SLUDGE
FIGURE 8
DWBR FLOTATION MODE
-------
to reach 40-45%. Biological sludge production for the Ithaca plant is ex-
pected to be equal to or less than 0.6 kg biological solids/kg BOD removed
at F/M loadings of 0.75-1.0. Operational parameters to produce secondary
treated effluent (BOD/SS as 30/30 mg/1) are summarized in Table 7. Effective
operation of the plant will depend on controlling MLVSS within a predetermined
F/M range over time.
TABLE 7
DWBR OPERATING PARAMETERS
Operational Mode
Parar-eter
DWBR
Average Influent Flow,
MLSS,
SRT,
F/M1,
Volumetric Loading ,
m /day
NGD
mg/1
days
day"1
kg BOD /day/m3 ,
Shaft Detention Time*
Recycle Flow Rate,
Solids Separation Unit
Overflow Rate,
d
Mass Loading ,
Return Sludge TSS,
Waste activated
Sludge3,
Ib BOD /day/1000 ft*
minutes, nominal
minutes, actual
bottom sol ids
recycle, percent
float solids
recycle, percent
m /day/m
GPD/ft^
kg TSS/day/m2-
Ib TSS/day/ft^
percent
kg TSS/kg BOD
removed
kg TSS/day
Ib TSS/day
F let at-i on
757
0.2
10,000
5.7
0.74
5.54
346
39
24
40
20
20.1
494
321
66
(bottom solids)
2-3
(float solids)
6-8
0.6
54
120
Sedimentaticn
379
0.1
,000
5.7
0.74
2.77
173
78
39
100'
10.1
247
103
21
1-2
0.6
60
1. F/M ratio expressed as influent BOD in kg/day and MLVSS under aeration
in !
-------
Innovative or Alternative Technology Characteristics
The Ithaca municipal demonstration plant project is intended to investigate
the feasibility of DWBR technology and gather potential scale-up data for
building a full-scale plant to treat its wastes. Average flow at Ithaca is
approximately 37,800 rrH/day (10 mgd) with peak flow expected at 93,366 rrH/day
(24.7 mgd). In a full-scale DWBR facility at Ithaca, high grade waste heat
would be available from its two proposed 112 kw (150 hp) compressors (224 kw
total) and could be used to heat an enclosed process facility. Heat recovered
from the compressor oil lubricant at 65.5-71.0°C (150°-160°F) cooled to
48.9°C (120°F) yields 164 kw (560,000 BTU/hr).
Additional savings will occur if, as may be the case for Ithaca, chemical
flotation aides can be eliminated. Highly concentrated waste sludge, space
economy, and lack of moving parts in the subsurface shaft all contribute to
potentially lower costs. Pilot plant efforts at Ithaca are directed towards
establishing what actual net cost and energy savings can be expected as well
as providing definitive scale-up data. Items which will be addressed include:
1. The desirability of operating in the flotation or gravity mode.
2. The effect of flow and organic loading variations.
3. The exact quantity of chemicals, if any, required to aid flotation.
4. The effect of chemical addition to primary effluent for phosphorus
removal.
5. The exact quantities of sludge produced by the system.
6. Full scale power requirements.
7. Full scale equipment configuration: the cost and feasibility to
operate a single shaft with two flotation tanks compared to two
shafts with one flotation tank.
Joint Municipal and Industrial Waste Treatment (14)(15)
Description
In order to meet National Pollution Discharge Elimination Permit con-
ditions, Dodge City, Kansas, a midwestern city discharging wastewater to the
Arkansas River, considered several treatment alternatives to upgrade and
expand its existing treatment facilities. Significant in their evaluations
was the fact that its wastewater contained a large quantity of high strength
meat packing wastes (3,400 of 15,700 m3/day). The alternatives evaluated
included trickling filter followed by rotating biological contactor (RBC)
treatment, and different combinations of land application and joint waste-
water treatment. This last alternative was possible because a privately-owned
biogas conversion plant utilizing and processing manure from cattle feed
546
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lots was interested in treating some or all of the Dodge City's wastewater.
The private plant produced methane and fertilizer for resale from its biogas
conversion facilities. The city could share in methane gas revenue. Fur-
thermore, the private plant routed its solids dewatering centrate to aqua-
culture basins whose effluent could be used for crop irrigation. The alter-
natives considered are summarized in Table 8.
TABLE 8
TOTAL NET PRESENT WORTH COMPARISON OF
ALTERNATIVES AS SHOWN IN THE DODGE CITY FACILITY PLAN
Treatment Net Total
Alternatives Considered Present Worth*
C Trickling filter plus RBC $6,329,800
treatment and discharge
E Complete treatment by 6,927,700
privately-owned plant;
wastewater to crop irrigation
F Wastewater treatment and dis- 5,689,00
charge with sludge and meat
packing flow to privately-
owned plant
G Land application of entire 8,953,100
flow on city-owned site (7,279,270)
H Seasonal land application 7,518,100
(7,279,270)
*1978 dollars
( ) 115 percent of 56,329,800
Comments
Most cost effective non-
innovative alternative
Not including irrigation
revenue of $62,200/year
Proposed as innovative in
application
Are alternative technology
and qualify for 15% cost
effectiveness preference
Are alternative technology
and qualify for 15% cost
effectiveness preference
The facility plan describing the alternatives in detail was submitted to
USEPA in accordance with the new national I/A provisions. A preliminary cost
analysis made to determine if joint treatment could qualify as Innovative
Technology identified alternative F (Table 8) as the lowest cost Innovative
Technology with baseline non-innovative technology being alternative C.
Note that Alternative Technologies E and H (land application) did not meet
115% cost criteria over alternative C and thus were eliminated from further
consideration. Alternative F also did not meet life cycle cost criteria to
qualify it as Innovative Technology. However, closer inspection (detailed
below) suggested it could qualify under net primary energy criteria.
Alternative F falls under the classification of conventional concepts of
treatment and must meet either a 15% life cycle cost reduction or a 20% energy
547
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reduction over Us nearest non-innovative competitor in order to be clas-
sified Innovative Technology. As noted previously, a preliminary analysis
did not indicate 15% cost savings (although cost savings were close enough
so that final cost re-evaluations prior to the final design may save 15% or
more). A net primary energy analysis did show energy savings above 20%. A
summary of the energy analysis is summarized in Table 9. Alternative F was
subsequently recommended for additional I/A funding, however it was not
adopted because of local environmental factors. It is included here to
demonstrate the excellence of the concept.
TABLE 9
NET PRIMARY ENERGY ANALYSIS FOR ALTERNATIVES C AND F
FOR THE DODGE CITY FACILITY PLAN
Net Primary
, Energy
Alternative C @ Q=15687 m /day (4.15 MGD) _ kwh/year
Raw wastewater pumping 252,849
Head works 77,010
Primary clarifier and sludge pump 14,632
Flow equalization basin 11,295
Recycle and equalization pumping station 508,266
RBC units 550,365
Effluent reaeration basin 20,279
Solids disposal 45,340
Subtotal 1,480,306
Net digester energy produced (-520,000)
Net primary energy 960,306
Alternative F @ 0=12285 m3/day (3.25 MGD)
Raw wastewater pumping 197,195
Plant head works 77,010
Building heat 14,375
Re-equip existing primary clarifier 11,551
Flow equalization basin 8,727
Recycle equalization pump station 397,885
RBC units 341,411
Effluent reaeration 15,915
Hy Plains and sludge pump station 156,587
Standby effluent pumping 7,187
Standby power 5,647
Electrical control center 7,187
1,240,677
Net equivalent exported energy (-520,000)
Net primary energy 720,677
Percent Net Primary Energy Savings- ^960'306 j77) X 10° 24.9%
548
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Innovative or Alternative Technology Characteristics
In addition to the cost and energy savings estimated above, the fol-
lowing considerations contributed to the overall Innovative Technology
assessment of Dodge City's wastewater facility plan:
1. The unique, mutually beneficial arrangement between a
municipality and private industry for the purpose of
wastewater treatment.
2. Maximum recycle and reuse of the industrial wastewater
and domestic wastewater sludge for fertilizer, energy
production, and irrigation.
3. The use of a revenue-generating complex.
There were also some risks recognized as associated with the Innovative
Technology approach proposed:
1. Operation of the plant is dependent upon the privately-owned
conversion plants continued financial and technical stability.
2. Use of the solids dewatering centrate as feed to the aqua-
culture system is not proven technology. Some pretreatment,
such as dilution, will have to be explored.
In spite of these risks, it was felt that the costs, energy conservation,
and public benefits were significant enough that the project could be con-
sidered Innovative in its approach and qualify for additional federal funding.
Fluidized Bed Biological Treatment (16)(17)
Description
Nassau County, New York is presently designing additional secondary waste-
waster treatment facilities to upgrade and expand their existing Bay Park
Wastewater Treatment Plant from .23 to .265 x 106 m3/day (60 to 70 mgd).
Expansion facilities will utilize fluidized bed biological treatment (FBBT).
This design is another example of an improved biological treatment process
submitted to USEPA for increased grant funding under the new National I/A
Program. It was recommended for funding.
The FBBT process consists of a columnar bioreactor partially filled with
fine grained media such as carbon or sand having an effective size approximately
0.6 mm and a uniformity coefficient of 1.4. Primary effluent is passed up
through the bottom with enough velocity ( > .01 m/sec) to expand or "fluidize"
the media. The media acts as a support surface upon which a firmly attached
biomass eventually grows and thrives. Fluidizing the media effectively in-
creases pore volume because the particles are not in contact. Flow through
the fluidized bed is laminar even though all particles are suspended and kept
549
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in motion. As a result, intimate contact of the entire surface area is
assured giving greater opportunity for the biomass to effectively consume
wastewater contaminants. Oxygen is provided by a 61 m (200 feet) deep oxygen
fed U-tube reactor. Reactor effluent at the Bay Park plant passes through a
conventional secondary clarifier before discharge. A diagram of the fluidized
bed reactor using a U-tube aerator is shown in Figure 9.
PRIMARY \
INFLUENT
,— OXYGEN
RECYCLE
SAND SEP-
ARATION
PUMP
FINAL CLARIFIER
(OPTIONAL)*
WASTE BIOLOGICAL
SOLIDS
U-TUBE
ALTERNATIVE SOLIDS SEPARATION DEVICES ARE UNDER CONSIDERATION. EXISTING
FINAL CLARIFIERS ARE PROPOSED TO BE USED AT BAY PARK WASTEWATER TREATMENT
PLANT.
FIGURE 9
FBBT REACTOR SCHEMATIC
Advantages of the trickling filter and the activated sludge processes
are utilized in the FBBT process. As in trickling filters, the reactor
requires no recirculation to maintain high concentrations of biomass. Fur-
thermore, pilot reactors have resulted in MLVSS > 14,000 mg/1 compared to
typical conventional activated sludge MLVSS concentrations of 1,500 mg/1.
As a result, treatment time and bioreactor volume are reduced. Pilot
plant evaluations using wastewater from the Bay Park Wastewater Treatment
Plant have indicated that with a recycle ratio of 1.5, satisfactory sec-
ondary treatment of its primary sewage is possible in as little as 15
minutes pilot reactor empty bed detention time compared to the several
550
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hours required for conventional activated sludge treatment. Recycling is
necessary because dissolved oxygen content is limiting. It has not been
possible to add sufficient oxygen to the wastewater in a single pass to
support the biological oxidation that occurs in the high MLVSS reactor.
Expanded bed height and particle size control (biological slime thickness)
is maintained by automatic ultrasonic controllers that operate a proprietary
sand-separation pump which keeps sludge height between set limits. Separated
sand is returned to the bed and sludge floe continues to final clarification.
Another system option is to withdraw waste solids from internal sand separation
tubes thus eliminating the necessity of a secondary clarifier. The sludge
removed has a 1-3% solids concentration and is approximately 0.1-0.3% by
volume of the forward flow. The relatively high sludge solids concentration
and low sludge flow reduce sludge handling costs considerably.
Considerable effort has been made investigating methods and techniques
to dissolve large amounts of oxygen in Bay Park wastewater since FTTB
feasibility studies began in the latter part of 1974. Early studies deter-
mined that pre-dissolved oxygen in the wastewater was desired over direct
injection because of the undesirable turbulence and effervescence created
in the fluidized bed reactor by the latter operation. Different methods
of oxygen dissolution were explored. These included an aeration cone device
which was designed to provide long contact time between the oxygen gas and
water, and a pressure swing oxygenating device which incorporated wastewater
transfer pumps in its pressure loop eliminating the need for them to work
against a pressure head. The most successful method to date has been an
oxygen-fed U-tube used to add dissolved oxygen to the incoming wastewater
before entering the reactor. The technique forces the liquid and dissolved
gas down the U-tube. Natural hydrostatic head increases the pressure as the
mixture travels downward. An increase in dissolved gas deficit and thus
an increase in gas transfer results. The U-tube configuration used, unlike
that the name suggests, has two concentric tubes where the gas/liquid mixture
is pumped down the middle smaller one and the dissolved gas mixture flows up
the larger. Design criteria and preliminary FBBT and U-tube specifications
are summarized in Table 10.
TABLE 10
PRELIMINARY DESIGN CRITERIA AND REACTOR SIZING FOR THE 10 MGD
EXPANSION OF THE BAY PARK UASTEUATER TREATMENT PLANT
Average Design Conditions Reactor Characteristics
Influent flow 37800 m3/day Reactor size (LxWxD) 7.6x4.3x9.1 m
(10 MGD) (25x14x30 ft)
Influent BOD 157 mg/1 Number of reactors 4
Maximum BOD 235 mg/1 U-tube size: concentric tubes of
Effluent BOD 20 mg/1 nominal diameter 0.6 m.down leg
MLVSS = 15,000 mg/1 xO.9 m up leg x61.0 m deep
F/M 0.65 dayl (2ftx3ftx200ft deep)
Flux 9.3xlO-3 m/sec (15 gpm/ft2) Number of U-tubes 4
Recycle ratio 3 Expected sludge production
02 to U-tube = 5490 kg/day 0.67x!06kg/day (1.48xl06lb/day)
(12103 Ibs/day) Expected energy consumption =
(fluidized bed and U-tube only)
4300 kwh/day
Effective sand size 0.8 mm
551
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The FBBT operation is expected to meet secondary discharge permit stan-
dards (BOD/SS concentrations averaging 30/30 mg/1) more cost effectively and
energy efficiently than conventional activated sludge plants. These advan-
tages are due principally to its inherent design which utilizes desirable
characteristics from both trickling filter and activated sludge processes
and allows higher loadings; its low volume of sludge production; and the
potential elimination of secondary clarification requirements. These advan-
tages can result in fewer and smaller treatment units performing the same
degree of treatment. Preliminary indications are that overall operation
and maintenance costs will remain approximately the same as activated sludge.
Innovative or Alternative Technology Characteristics
In the case of the Bay Park Wastewater Treatment Plant, expected life
cycle treatment cost savings and net primary energy savings did not meet
strict Innovative Technology guidelines. The construction grant eligible
portion of this project excluding non-alternative sewers resulted in an
estimated cost savings of 2.6% and net energy savings of 8.6% over a con-
ventional activated sludge baseline comparison. These savings are less
than the 15% and 20% cost/energy guidelines stated in the regulations.
There are some risks associated with the technology also and these were
considered. In particular, more information is needed about the performance
of the proprietary sand separation device and the oxygen-fed U-tube for exter-
nal oxygen dissolution. These two components are considered critical to the
overall performance of the system.
Notwithstanding the judgement that the proposed fluidized bed technology
does not in the strictest sense meet I/A cost and energy criteria or that
more operational data is needed about some of its components, it is felt
the process offers substantial potential for energy and, to a lesser extent,
cost savings. Pilot studies now underway will likely reduce the risk of
FBBT to acceptable levels within the next six months to a year. It is further
felt that the public benefit from the projected advancement in the state of
the art outweighs the added risk of full-scale use. The promise of FBBT as
a viable alternative to other biological treatment operations remains high.
Land Treatment of Wastewater (18)(19)
Description
Land treatment is the controlled application of liquid wastes onto the
land surface by spray or surface spreading to achieve a designed degree of
wastewater renovation through natural physical, chemical, and biological
processes within the soil matrix.
Land treatment systems are designed to meet one or more of the following
objectives: wastewater treatment as a final or intermediate process to meet
regulatory limitations; wastewater disposal (zero discharge); water conservation;
crop or forest growth enhancement; or landscape irrigation.
552
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There are enough technical similarities among the various modes of land
treatment to group them into three broad categories:
1. Slow Rate Systems involve the surface spreading or spray
irrigation of up to 10.2 cm (4 inches) of wastewater per
week onto vegetated tracts of land possessing moderately
permeable soils, with the flow path being soil infiltration
and percolation to groundwater. The slow rate process
(also called crop irrigation) couples wastewater management
with recycling of nutrients in crop production. These
systems usually offer the highest degree of reliability
and potential longevity.
2. Rapid Infiltration Systems constitute the percolation of
large volumes of wastewater, commonly at rates measured
in feet per week, through very highly permeable soils.
Also known as infiltration/percolation, rapid infil-
tration emphasizes water reclamation rather than direct
nutrient recycling.
3. Overland Flow Systems embody the controlled application
of liquid wastes onto the upper portion of densely vegetated,
gentle, uniform slopes possessing clay soils of very low
permeability. Treatment is effected as the liquid flows
slowly and evenly downslope over the soil biomat surface
towards a collection system. Unlike the other land treat-
ment systems, the product water from overland flow is
almost always discharged directly to surface waters.
An interagency work group co-chaired by the USEPA and the U.S. Army
Corps of Engineers prepared the Process Design Manual for Land Treatment
of Municipal Wastewaters which was published in October 1977.The manual
is now established as the basic resource for those who conceive, plan, and
design land treatment systems in the United States. The basic unit opera-
tions and unit processes are discussed in detail and the design concepts
and criteria are presented. The manual gives design examples and includes
case study descriptions of operational systems.
When designing land treatment systems, it is important to recognize
that no single design value or even one set of values can be realistically
applied to all locations which have variable climate, geology, and treatment
needs. For this reason, USEPA guidelines are varied to suit a number of
possible situations and include ranges of values whenever possible. Tables
11 and 12 summarize the range of criteria for important design factors.
Land treatment is capable of achieving treatment levels comparable to
the advanced wastewater treatment technologies. It achieves these levels of
treatment with a comparatively low energy demand for most designs because
recovery and beneficial reuse of wastewater nutrients through crop produc-
tion are usually an integral part of the process. When designing land treat-
ment systems, the health effects of wastewater contaminants in the air, on
the crop, and in the groundwater must be addressed as well as soil composition
553
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TABLE 11
COMPARISON OF DESIGN FEATURES FOR LAND TREATMENT PROCESSES
Feature
Application techniques
Annual application
rate, m (ft)
Field area required,
106 m2 (acres)fb>
Typical weekly appli-
cation rate, cm (in)
Minimum preapplication Primary
treatment provided
in United States
Slow Rate
Sprinkler, or
surface* '
0.6 to 6.1
(2 to 20)
0.23 to 2.27
(56 to 560)
1.3 to 10.2
(0.5 to 4)
Primary , ,
sedimentation
Principal Processes
Rapid Infiltration
Usually surface
6.1 to 170.7
(20 to 560)
0.01 to 0.23
(2 to 56)
10.2 to 304.8
(4 to 120)
Primary
sedimentation
Overland Flow
Sprinkler or
surface
3.0 to 21.3
(10 to 70)
0.06 to 0.45
(16 to 110)
6.35 to 15.2(c)
(2.5 to 6) , ..
15.2 to 40. 6V '
(6 to 16)
Screening and
grit removal
Disposition of
applied wastewater
Need for vegetation
Evapotranspiration
and percolation
Required
Mainly
percolation
Optional
Surface runoff and
evapotranspiration
with some
percolation
Required
(a) Includes ridge-and-furrow and border strip.
(b) Field area in acres not including buffer area, roads, or ditches for
1 Mgal/d (43.8 L/sec) flow.
(c) Range for application of screened wastewater.
(d) Range for application of lagoon and secondary effluent.
(e) Depends on the use of the effluent and the type of crop.
554
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TABLE 12
COMPARISON OF SITE CHARACTERISTICS FOR LAND TREATMENT PROCESSES
Characteristics
Slope
Soil permeability
Depth to
groundwater
Climatic
Slow Rate
Principal Processes
Less than 20% on culti-
vated land; less than
40% on noncultivated
land
Moderately slow to
moderately rapid
2 to 3 ft (minimum)
(0.61 to 0.91 m)
Storage often needed
for cold weather and
precipitation
Rapid Infiltration
Not critical; excessive
slopes require much
earthwork
Rapid (sands, loamy
sands)
10 ft (lesser depths
are acceptable where
underdrainage is
provided)
None (possibly modify
operation in cold
weather)
Overland Flow
Finish slopes
2 to 8%
Slow (clays,
silts, and
soiIs with
impermeable
barriers)
Not critical
Storage often
needed for
cold weather
and land area requirements.
Innovative or Alternative Technology Characteristics
The Federal Water Pollution Control Act Amendments of 1972 mandated a
comprehensive federal-state-local government program to reduce, prevent, and
eliminate water pollution. Its intent was to redirect waste management towards
recycling, reclamation, and confined disposal of wastes. The Clean Water Act
of 1977 re-emphasized this intent by providing additional financial incentives
for cost effective innovative and alternative approaches to waste management.
It specifically included land treatment as an Alternative or Innovative Tech-
nology and required that such technologies be considered when evaluating
alternative wastewater treatment operations to be partially funded by federal
construction grants.
USEPA policy and guidance specific to land treatment has included two
major actions. The design manual discussed earlier provided a major source
of technical information and guidance in land treatment facility planning.
A major EPA policy statement issued October 1977 promised vigorous support
of land treatment and a critical assessment of reasons given for rejecting
land treatment or requirement for high levels of preapplication treatment.
These actions, in addition to the financial incentives for innovative and
alternative technologies provided by the Clean Water Act, are intended to
encourage major progress towards achieving the recycling, reclamation, and
reuse intent of the 1972 and 1977 Acts on control of water pollution.
555
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Municipal Wastewater Aquaculture (7)(20)
Description
Aquaculture is the production of aquatic organisms under controlled
conditions. Aquatic flora and fauna are included for both marine and fresh-
water systems. Historically, aquaculture has been practiced for centuries
for the production of food, fiber, and fertilizer. The application of waste
materials to produce aquaculture systems for their fertilizer value is a
more recent practice in some parts of the world. Only during the past ten
years however has the use of designed aquaculture systems for treatment and
management of municipal wastewaters been given serious consideration.
Aquaculture is most often considered for nutrient removal and polishing
treated effluents. Studies investigating wastewater treatment using these
natural systems have focused on three principal areas:
1. The culture of water hyacinths (Eichhornia crassipes) for
treatment of municipal wastewater has progressed more
rapidly than those utilizing other plants. A native of
South America, water hyacinths are found naturally in
waterways, bayous, and other backwaters of the U.S.
Insects and disease have little effect on water hyacinths
and they thrive in raw and partially treated wastewater.
Wastewater treatment is accomplished by passing it
through a hyacinth-covered basin. Batch treatment
and flow through systems with single or multiple cells
are used. The plants remove nutrients, BOD, suspended
solids, and heavy metals.
2. Natural wetlands such as marshes, bogs, swamps, both
marine and freshwater, have inadvertently served man
as natural waste treatment systems for centuries. A
wide diversity of plant species allows wetland vege-
tation to survive added stresses of concentrated waste-
water effluents. Constructed artificial wetlands can be
designed to meet specific project conditions while pro-
viding new wetland areas that improve wildlife habitats.
Wastewater treatment in natural or artificial wetland
systems is generally accomplished by sprinkling or flood
irrigating the wastewater into the wetland area, or by
passing the wastewater through a system of ponds, channels,
or basins where aquatic vegetation is actively growing.
Managed wetlands have been shown to reliably provide pH
neutralization and some reduction of nutrients, heavy
metals, organics, BOD, COD, SS, fecal coliforms and
pathogenic bacteria.
3. Three approaches have been explored for the culture of
fish utilizing municipal wastewater. These are fish stocking
directly into sewage lagoons; addition of sewage effluent to
556
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fish ponds; and conversion of sewage into lower food chain
organisms such as algae and micro-invertebrates before dis-
charging into food ponds. The most popular fish investigated
have been from the carp family. A very real problem with the
production of fish exposed to wastewater is ultimate use of
the fish. The risks associated with human consumption of
these fish are not quantified with any degree of confidence,
and other uses such as fertilizer or feed material may not
be cost effective.
Design criteria is very site specific. Like land treatment, no single
design value or even one set of values can realistically be applied to all
locations which have variable climate, geology, and treatment needs. Climate
is a major limitation since effective treatment is linked to the active
growth phase of the emergent vegetation. Ranges of design and performance
data reported for aquaculture systems using water hyacinths or artificial
wetlands receiving secondary effluent or higher quality wastewater are sum-
marized in Table 13.
TABLE 13
RANGES OF DESIGN AND PERFORMANCE DATA
FOR SOME AQUACULTURE SYSTEMS (7]*~
Design Ranges Performance Ranges
Detention Time 4-15 days BOO Reduction:
Land Requirements., COD Reduction:
2.1-16.1 rrr-day nr (2-15 acres/MGD) TSS Reduction:
Depth 0.6-1.5 m (2-5 feet) N Reduction:
P Reduction:
Heavy Metals:
35-95%
43-37%
29-87%
40-94%
0-94%
highly variable
*Aquatic plants receiving secondary or better wastewater quality.
Subject to temperature constraints, municipal wastewater aquaculture
appears reliable from a mechanical and process standpoint. It has the poten-
tial for development as an economical, simple, and effective alternative
for municipal wastewater treatment and management. It can yield a product
of economic value (such as fertilizer) and there are indications that some
systems can be energy producers by conversion of a crop such as water hyacinths,
to a fuel. Information available at this time is not adequate to consider it
fully developed technology for design of operational aquaculture systems
treating municipal wastewater inputs. More data acquisition and evaluation
is needed from different aquaculture systems to obtain reliable design cri-
teria. Proceedings from a USEPA seminar entitled, "Aquaculture Systems for
Wastewater Treatment," held at the University of California at Davis, Sep-
tember 11-12, 1979, are soon (at this writing) to be published and should
provide additional information about aquaculture system performance.
557
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Innovative or Alternative Characteristics
Aquaculture is specifically mentioned, along with agriculture and silvi-
culture, in the Federal Water Pollution Control Act Amendments of 1972 as an
alternate wastewater treatment method for use in meeting national water quality
goals. The Clean Water Act of 1977 further encourages the consideration of
Alternative Technologies such as aquaculture by providing additional con-
struction cost assistance when they can be shown to be reasonably cost
effective compared to more conventional methods of treatment. Aquaculture
is a natural, potentially revenue-producing alternative to conventional
wastewater treatment methods and can contribute to environmental enhancement
as well as remove water contaminants.
Combined Sludge/Solid Waste Disposal and Energy Recovery System (21)(22)
Description
The disposal/energy recovery system presently under design by the City
of Memphis, Tennessee will convert sorted and shredded solid waste (referred
to as Refuse Derived Fuel--RDF), industrial liquids, and municipal sludge
to steam at a sludge/waste energy conversion center (SWEC) using multi-hearth
incineration furnaces. Revenue is gained from the steam sold to private
industry (95%). Additional revenue is made selling ferrous metals separated
at the RDF facility (5%). Reject solid waste materials go to a Tennessee
approved landfill.
RDF is used in lieu of fuel oil in the multi-hearth furnaces to incinerate
dewatered sludge from the North and South (Maxson) Wastewater Treatment Plants.
Coal/RDF waterfall incinerators are provided for back-up and peak demand periods
to insure steam production levels.
Sludge comes from the nominal 302,400 m3/day (80 mgd) South and 510,300 m3/day
(135 mgd) North wastewater treatment plants. Influent to these plants is high
in organic matter (BOD *400 mg/1). Sludge treatment facilities will be up-
graded at both locations to provide a sludge cake of sufficient quality for
incineration. The industrial liquid waste contributes only 37.9 m3/day
(10,000 gpd) to the SWEC. Sludge/solid waste process flow is outlined in
Figure 10.
Design of the multi-hearth furnace had two major governing criteria.
The first was that proper temperature and excess air requirements be met
in the afterburner to insure burn out of the hydrocarbons so that air pol-
lution standards would be met. Secondly, it was designed to perform satis-
factorily, i.e., overcome control problems, in view of the fact that the
quality (composition heating value) of its two major fuels, RDF and sludge,
would vary.
In the design, values of selected characteristics of the sludge and RDF
were determined as reasonable. Sludge quantities to be incinerated were
expected to be 907,185 kg/day (1,000 tons per day). RDF quantities to do
this were then estimated and it was determined there would be enough RDF
558
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I. NORTH SEWAGE TREATMENT PLANT
Industrial
Liquid
Waste
Industrial Liquid
Waste Processing
Facility
ILW
Sludge
Sludge
Oewatering
Facility
Sludge Cake
II. SOUTH SEWAGE TREATMENT PLANT
Sludge
Sludge
Oewatering
Facility
Sludge Cake
Multi-Hearth
Sludge/Waste Energy
Conversion Center
T
RDF
Steam
Refuse Derived Fuel
Manufacturing
Facility
Solid
Waste
FIGURE 10
COMBINED SLUDGE/SOLID UASTE DISPOSAL AND ENERGY RECOVERY FACILITIES
produced to incinerate the sludge. Basic design criteria and assumptions for
the multi-hearth designs were as follows:
Multi-Hearth Afterburner Requirements:
816°C (1500°F) @ 100% excess air (or equivalent)
Sludge Characteristics:
Quantity to be Incinerated:
Composition:
Gross Heating Value:
Sludge Volatile Analysis "1
Combustion Product Analysis]
RDF Characteristics:
907,185 kg/day (1,000 TPD)
80% Water, 11% Volatiles, 9% Ash
0.71 KwH/kg (1,100 BTU/lb)
Air Pollution Considerations
20% Water, 70% Volatiles, 10% Ash
4.52 KwH/kg (7,000 BTU/lb)
Air Pollution Considerations
Composition:
Gross Heating Value:
RDF Volatile Analysis "I
Comubstion Product Analysis)
Final design of the system required a 1:1 ratio of sludge to RDF by
weight for adequate incineration. As noted previously, it was recognized
that fuel quality would vary (via percent moisture and, therefore, heating
value). The multi-hearth furnace was designed to operate within a range of
559
-------
conditions requiring more or less quantities of fuel to maintain afterburner
temperature requirements. Mil Hi -hearth furnace recommended modes of operation
are summarized in the table below.
TABLE 14
COMBINED FUEL FURNACE RECOMMENDED MODES OF OPERATION
Operational Mode
Fuel
Wet Sludge
RDF
Optimum Values
(Case A)
A1/A3
0.91xl06kg/day
(1000 TPD)
@0.710 kwh/kg
(1100 BTU/lb)
(80% H20)
0.67/0.61 kg/day
(740/674 TPD)
@4.518 kwh/kg
(7000 BTU/lb)
(20% H20)
Design Basis
(Case A)
A2
0.91xl06kg/day
(1000 TPD)
(30.710 kwh/kg
(1100 BTU/lb)
(80% H20)
0.91xl06kg/day
(1000 TPD)
@4.518 kwh/kg
(7000 BTU/lb)
(20% H20)
Sub-Optimum Values
(Case B)
B1/B3
0.91xl06kg/day
(1000 TPD)
@0.568 kwh/kg
(880 BTU/lb)
(34% H20)
1.16/1.04kg/day
(1278/1150)
03.550 kwh/kg
(5500 BTU/lb)
(30% H20)
Innovative or Alternative Technology Characteristics
The desirability of the multi-hearth furnace was based on the difference
between the cost of auxiliary fuel (RDF) and the revenue generated from the
live steam. This was done by considering the sludge/RDF weight mixture,
appropriate heat values, excess air, and incineration requirements. A heat
balance or combustion calculation exercise was done for each operational
mode and total steam generation made. Cost of the RDF fuel supplied was
subtracted from the value of the steam. A "net gain" (or loss) was found.
The net gains for the operating conditions defined previously are:
A!
5,359
Net Gain ($/Day)
A2 A3
7,076 4,168
6,227
4,654
Some brief notes about these figures: Coal was examined as an alter-
nate for RDF but not explored further because it had less steam-producing
value and less net gain or revenue was produced. The cost of RDF fuel was
taken as $0.50/106 BTU produced. Steam value was estimated at $2.00/1,000 Ib
sold.
560
-------
The expected net gain or net energy output exceeded by over 20% that
energy which would have been required by a single purpose sludge-only pro-
ject and, therefore, the co-disposal project was considered Innovative.
Because the project involves co-disposal of solid and liquid wastes,
only the portion which involves sludge disposal is considered eligible for
federal construction grant funds. The eligible portion was found by con-
sidering what fraction of the entire project a sludge-only disposal project
would be then increasing it by the 15% incentive which interim USEPA policy
allows for Alternative or Innovative projects.
Grant Eligible _ ^ ,,- (Present Worth of Single Purpose Sludge-Only Project)
Fraction ' (Present Worth of Multiple Purpose Project Minus
Present Worth of Energy Required by Sludge Treat-
ment and Disposal Facilities)
Cost of the co-disposal project was multiplied by this fraction and
funded as Innovative Technology at 85%. Since approval of this project,
USEPA policy has changed regarding eligible portions of co-disposal pro-
jects. The eligibilities must be determined on a case-by-case basis using
present policy.
Combined Aerobic/Anaerobic Sludge Digestion Process (23)(24)
Description
The City of Lackawanna, New York is proposing to replace existing
anaerobic sludge digestion facilities at their 17,010 m^/day (4.5 mgd)
oxygen activated sludge wastewater treatment plant by a combined aerobic/
anaerobic digestion process. The combined digestion process (CDP) receives
heat necessary for anaerobic digestion under mesophilic or thermophilic
conditions from a preceding oxygen-fed aerobic digestion step which oxidizes
part of the volatile suspended solids (VSS). The VSS destroyed during
aerobic digestion include unionized volatile acids and total volatile solids
which, if in high enough concentrations, can cause upsets in anaerobic
digesters.
Figure 11 is a schematic of the CDP process and a conventional activated
sludge process for comparison. Sludge from primary clarifiers and thickened
waste activated sludge from a pure oxygen secondary process is to be treated.
An alum sludge will also be present. The combined sludges will be first
treated in an aerobic tank with a retention time of 1.2 days which generates
enough heat for either mesophilic or thermophilic anaerobic digestion in a
second step. In the aerobic digester, pure oxygen will be used to minimize
heat losses through the vent gas. The vent gas, which will contain unused
oxygen, will be recycled in the secondary treatment process. Additional
oxygen-generating capacity will be required as the amount of additional oxygen
required in Step 1 of the sludge digestion process exceeds the spare capacity
of the secondary treatment oxygen-generating units. Dissolved oxygen in the
aerobic digester is estimated to be 2 mg/1. Enough heat will be generated by
the process to maintain a 54°C (129°F) temperature.
561
-------
EXCESS 02 TO A.S.
EXOTHERMIC HEAT
SLUDGE GAS
COMPLETE
MIX
ANAEROBIC
DIGESTER
(FIXED COVER)
> GAS UTILIZATION
SUPERNATANT
SLUDGE RECYCLE
V TO SLUDGE
DEWATERING
COMBINED SLUDGE DIGESTION
ACTIVATED
SLUDGE
THICKENER
>-SUPERNATA
IT
SLUDGE
PRIMARY
WET WELL
SLUDGE
4
SLUDGE GAS
COMPLETE
MIX
ANAEROBIC
DIGESTER
(FLOATING
COVER)
y.
I
SUPERNATANT
SEPARATION
ANAEROBIC
DIGESTER
(FLOATING
COVER)
4
/
r
....... W. rJIPrf?NATANT
>" TO SLUOGE DEWATERING
CONVENTIONAL SLUDGE DIGESTION
GAS HEAT RECYCLE
FIGURE 11
COMBINED AND CONVENTIONAL TWO STAGE ANAEROBIC DIGESTION
The Step 2 anaerobic digestion will take place in the two existing
15.2 m (50 feet) diameter tanks which will be remodeled. Within one tank
will be installed a new 9.1 m (30 feet) diameter fixed cover anaerobic
digester with gas mixing. The temperature is estimated to be 50°C (122°F).
Digested sludge from the first stage anaerobic tank will be fed to a second
tank to be used for supernatant separation and additional gas collection.
Digested sludge from the anaerobic second stage can be recycled to the first
stage to insure sufficiently high SRT. A floating cover is to be provided.
The gas spaces between the two anaerobic tanks will be interconnected. Total
retention time in the anaerobic digesters is eight days. Sludge will be
dewatered by centrifugation with existing drying beds as standby. Supernatant
and centrate will be treated to remove phosphorus. Sludge disposal is proposed
to be by contract. The contractor will dispose of the sludge in a landfill.
562
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In the dual digestion process, auxiliary heating of the anaerobic digester
is unnecessary because of exothermic first-stage oxidation due to closed tank
use of pure 02. This allows utilization of digester gas energy for other
than anaerobic digester heating purposes. Out of 161,310 m3 of digester gas
expected every year, 107,540 m^ can be used for in-plant heating and 53,770 m^
will be left for power generation. The actual power demand to be satisfied
is 51 kw. The comfort heating boiler and generating equipment will be arranged
so that heating will take first priority and power generation will take surplus
only.
The combined aerobic/anaerobic digestion seeks to incorporate advantages
of each type of digestion and minimize their drawbacks. Aerobic digestion is
inherently a more stable and quicker oxidation process, but it consumes more
energy. Anaerobic digestion, although a slow process and susceptible to
upset, has a low energy requirement and produces methane. Using the pro-
cesses in sequence allows the aerobic reactor (oxygen fed) to provide adequate
heat for anaerobic digestion, which in turn frees the methane produced for
other energy uses. Table 15 summarizes the design parameters for the
Lackawanna CSD process.
TABLE 15
PRELIMINARY DESIGN DATA FOR LACKAWANNA SLUDGE DIGESTION
Raw Sludge
Primary:
Secondary:
Combined:
Flow:
Solids Content:
VSS/TSS:
Temperature:
Operating Conditions
Aerobic Digester:
Retention Time:
Dimensions:
Temperature:
Oxygen Consumption:
Oxygen Utilization:
D.O.:
Heat Value of VSS
Destroyed in Step 1:
Anaerobic Digester:
Retention Time:
Dimensions:
Temperature:
VSS Destruction:
Digester Gas
Destroyed in
Anaerobic Stage:
1361 kg/day (3,000 Ibs/day)
1179 kg/day (2,600 Ibs/day inclusive of 800 Ibs/day
alum sludge)
2540 kg/day (5,600 Ibs/day)
60.5 m3/day (16,000 gpd)
4.2% TSS
0.63
Minimum 6°C (43°F)
1.2 days
3.6mx8.2nSWD+0.6FB (11ftx27ftSUD+2ftFB)
54°C (129°F)
1.8 kg/kg VSS destroyed in Step 1
55 percent
2 mg/1
16,000 BTU/lb
8 days
9.1mx7.6SUD+0.91mFB (30ftx25ftSUD+3ftFB)
50°C+ (122°F)
43 percent
0.81 kg/m3 VSS (13CF/lbVSS)
563
-------
Innovative or Alternative Technology Characteristics
Utilization of aerobic followed by anaerobic sludge digestion allows
potentially more reliable and stable sludge treatment operation. As indi-
cated previously, aerobic digestion is less subject to upset because aerobic
bacteria are faster growing. Aerobic digestion converts a highly biodegradable
fraction of the sludge to simpler cell matter and heat, in effect providing
a more uniform, easier to digest feed to the more sensitive anaerobic pro-
cess. Furthermore, because no nitrification occurs in the aerobic digester
(the temperature is too high), ammonium bicarbonate is formed which has a
high buffering capacity against low pH upsets. The overall result is a more
rapid and extensive solubilization of the substrate.
A unique aspect of the CSD process is the possibility to pasteurize the
sludge because of the relatively high temperatures (> 52°C) and detention
times encountered in thermophilic aerobic digestion. If properly stabilized
and excessive heavy metals are not present, the sludge can be disposed on
land.
The CSD at Lackawanna is energy efficient. All of the methane gas
generated by the anaerobic digester is recovered and productively utilized.
Thus, by definition, the digestion qualifies as Alternative Technology.
Unlike conventional digestion, heat required for digestion is supplied from
the preceeding aerobic digester, freeing the heat generated as methane gas
for other purposes. The amount of oxygen needed for aerobic digestion (to
proceed exothermically) exceeds the extra capacity of the pressure swing
absorption (PSA) oxygen-generating facilities at Lackawanna used for the
secondary, pure oxygen activated sludge treatment. Additional capacity has
to be provided, but the energy required for the additional requirements are
more than offset by the energy contained in the methane gas.
An energy balance around the digestion process indicated that conven-
tional two-stage anaerobic digestion would yield from 1.08 to 1.62 x 10^ KwH
per year. Digester heating requirements are estimated at 1.35 x 106 KwH/year
and power requirements are estimated at .06 x 10^ KwH/year. Therefore, the
net annual energy yield is -0.33 to 0.21 x 106 KwH/year. During the cold
months, supplemental heating would be required.
The CSD process is estimated to yield about 0.16 x 106 m3/year digester
gas or 1.00 x 106 KwH/year. Mechanical energy for additional oxygen generation
and mixing are estimated to be 0.42 x 106 KwH/year. The net energy yield
is, therefore, 0.58 x 106 KwH/year as compared with -0.33 to 0.21 x 106
KwH/year for conventional anaerobic digestion.
Since this is a newly-developed process, there is some risk that the
benefits claimed will not be realized at full scale. Results are available
from bench scale testing (14 1 reactors) and pilot scale testing (to 1,516 1
reactors) at Tonawanda, New York. There is an on-going demonstration pro-
ject at Hagerstown, Maryland. Because it has successfully progressed beyond
the bench scale and small pilot plant stage and has been adequately tested
in a successful field demonstration project, it does meet USEPA requirements
for developed technology. Preliminary cost data also indicate that the CSD
564
-------
process is cost effective compared to conventional anaerobic digestion for
use at the Lackawanna Wastewater Treatment Plant.
In summary, the CSD process has adequately demonstrated the potential
for increased operational stability, additional environmental benefits, and
possible cost and/or energy savings over conventional anaerobic digestion.
For these reasons it is considered an Innovative Technology.
V. PROJECTED IMPACT AND BENEFITS OF THE INNOVATIVE AND ALTERNATIVE TECHNOLOGY
PROGRAM (25j
The foregoing discussion has centered on the recent history of design
practice and construction of publicly owned treatment plants in the United
States including the Innovative and Alternative Technology Program initiated
to implement the new goals of the Clean Water Act of 1977. Although it is
still very early in the program to draw definitive conclusions, it is clear
that this program is already beginning to impact design practice. The more
immediately obvious effects are an increase in cost effectiveness analysis
efforts, inclusion of a comprehensive energy study as a part of facility
planning, the consideration of a much broader number of alternatives and,
finally, consideration of higher risk/higher benefit technologies.
Both Congress and the USEPA are vitally interested in measuring the
progress of the program at the earliest possible stage in order to formulate
recommendations for extending authorizing legislation and revision or fine
tuning of implementing regulations.
In an effort to estimate the overall effectiveness of the Innovative and
Alternative Technology Program, USEPA's Office of Research and Development
completed an analysis of program impacts in February of 1980. This analysis
was based on experience gained through the first 1 1/2 years of the initial
three-year program. The principal data bases used in the analysis were all
the Innovative and Alternative Technology project facility plans submitted
to USEPA; historical USEPA Construction Grant records, the 1978 National
Municipal Technology Needs Survey, consultation with state and federal review
authorities; and the experience of the Office of Research and Development
regarding the applicability of emerging new technologies. The analysis was
further based on the assumption that the Innovative and Alternative tech-
nology set-aside funds for fiscal years 1979, 1980, and 1981 for both Inno-
vative and Alternative Technologies would be obligated and that current
regulations and qualifying criteria, as described in the Innovative and
Alternative Technology Assessment Manual (7) would be followed. The analysis
considered the impacts for three time periods: the initial three-year period--
fiscal years 1979, 1980, and 1981; a one-year extension for fiscal year 1982;
and a four-year extension for fiscal years 1983 through 1986.
For fiscal years 1979, 1980, and 1981, 17% of construction grant pro-
jects are estimated to qualify as Innovative Technologies. For fiscal years
1979 and 1980, 25.5% of the projects are estimated to qualify for Alternative
Technologies. This will increase to 42.5% in fiscal year 1981. Collectively,
42.5% of the construction grant projects are estimated to qualify for Innovative
565
-------
and Alternative Technologies for fiscal years 1979 and 1980, and 59.5% for
fiscal year 1981.
In fiscal year 1979, an expenditure of $21 million of Innovative set-aside
funds, which is equivalent to $716 million of construction grant funds, is
estimated to save $133 million due to adoption of Innovative Technology. This
is equivalent to a return of 632% for each Innovative set-aside dollar spent,
or a saving of 18% based on the total construction grant dollars expended.
An expenditure of $63 million of fiscal year 1979 Alternative set-aside funds,
which is equivalent to $1.07 billion of construction grant funds, is estimated
to save a total of $365 million due to the use of Alternative Technology. This
is equivalent to a return of 579% for each Alternative set-aside dollar spent
or a saving of 34% based on construction grant dollars expended. In summary,
a total of $84 million spent as Innovative and Alternative set-aside funds,
which is equivalent to $1.786 billion of construction grant funds, will result
in $498 million or 28% total construction grant savings. Savings resulting
from the Innovative and Alternative Technology Program for fiscal years 1980
and 1981 have also been estimated and shown in Table 16.
TABLE 16
SUMMARY OF PROJECTED COST SAVINGS FROM THE NATIONAL
INNOVATIVE AND ALTERNATIVE TECHNOLOGY PROGRAM
Fiscal
Year
79
80
81
82
I/A Set-Aside
(SMillion)
I A I+A
21 63 84
17 51 68
17 85 102
22.5 112.5 135
Innovative
Saving
($ Million)
133
106
106
142
$ Saved
$ Set-Aside Spent
6.32
6.32
6.32
6.32
Alternative
Saving
($ Million)
365
295
492
652
$ Saved
$ Set-Aside
5.79
5.79
5.79
5.79
Spent
The total construction grant appropriations, annual set-aside funds,
projected number of Innovative and Alternative projects, percentage of each
project identified as Innovative or Alternative Technology, and the dollar
savings resulting from each is summarized in Table 17.
In terms of dollars saved per dollar expended, the Innovative and Alter-
native portions of the program are about equal, with the former slightly
more effective than the latter. In the Innovative Technologies, the 15%
life cycle cost criteria is about ten times more effective in savings than
the 20% energy saving criteria. In the Alternative Technologies, savings
from sludge handling and associated energy conservation and recovery systems
are insignificant due to their low projected activity volume and low savings
margin. About two-thirds of the savings in the Alternative Technologies are
566
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TABLE 17
NATIONAL IMPACTS OF THE INNOVATIVE AND ALTERNATIVE TECHNOLOGY PROGRAM ON
THE CONSTRUCTION GRANTS PROGRAM
. Innovative
Total''' and Total
Appropriation Alternative Ho. of
Grant For Step 3 I Set Aside Grant
Fiscal Appropriation Projects (t Million) Projects
Tear ($ Billion) ; ($ Billion)
79 4.2 3.91
80 3.4
81 3.4
Tort Ion of
Total
l»o. of'3' Ho. of'*' No. of
Dollar »a1a« Dollar »alue
of portion of (fi', of
Dollar
Portion of (n>i of
Innovative (r<> Projects
8?
Ln
4.5
lion) I
1 21
6 17
6 17
8 22.5
A
63
51
fl5
112.5
Step 3
1,005
812
Projec
184
148
812 148
1,074 197
Innovative Alternative l+h Projects I Identified As,
Projects Projects ($ HUHon) Innovative!*) (
275 459 716 17
223 371 576 17
371 519 576 17
492 689 766 17
Alternative Projects |
Projects (identified As
<9>
I » A
Projects
Identified As
I * A
U)
ion)__ 'Alternative!*) (t Million)
1,070
867
1,443
1.914
25.5
25.5
42.5
42.5
1,7B6
t,443
7,019
2,6(10
42.5
42.5
59.5
59.5
NOTES: (1) Based on Step 3/(Step 1 + Step 2 + Step 3) = 93% Also see Exhibit 1
(2)
(3)
(4)
Based on an average project federal share of $3.89 million. For FY 79, $3.91 billion/$3.89 million = Ij005 A1so see Exhibit I
Based on 1/2? set-aside for innovative projects. For FY 79, $21 million x 8.5 x 4/$3.89 million = 184 Also see Exhibit II
Based on i'1/2* set-aside for 1979 and 1980, and 2 1/2% set-aside for 1981 and 1982 for alternative projects. For FY
$63 million x 8.5 x 2/$3.89 million = 275. For FY 81, $85 million x 8.5 x 2/S3.89 million = 371 Also see Exhibit II
(5) For FY 79, 184 x $3.89 million = $716 million
(6) For FY 79, $716 million/$4.2 billion = 17*
~" 275 x $3.89 million = $1,070 million
79,
(7)
(8)
For FY
For FY
79,
79, $1,070 million/$4.2 billion = 25.5*
(9) For FY 79, $716 million + $1,070 million = $1,786 million
(10) For FY 79, $1,786 m1llion/$4.2 billion = 42.5*
-------
TABLE 17 (Continued)
EXHIBIT I
Calculations of Average Project Cost and Average Project Federal Share:
From OWPO Fact Sheet, as of October 31, 1979, grants awarded for Step 3 are
21.6 billion for 5,554 grants.
21,600,000,000/5,554
per project
$3,889,089/grant or about $3.89 million federal share
3.89/0.75 $5.19 million project cost per project
Assume the above costs are based on second quarter of 1977 money as being
jsed in MCD-37.
From MCD-37, $5.19 million project cost is equivalent to a construction cost of
S4.23 million ($5.19 mil lion/1.2264=$4.23 million), which is for a secondary
treatment, new construction with a flow rate of 2.3 mgd. Use 2.5 mgd as the
average plant size.
Step 3 grants/(Step 1 + Step 2 + Step 3)
For FY79, Appropriation for Step 3
Total number of grant projects
$21.6 billion/$23.2 billion
93%
= $4.2 billion x 0.93
$3.91 billion
$3.91 billion/$3.89 million
1,005
EXHIBIT II
Calculations of Innovative and Alternative Projects, Number of Projects and Federal
Share
Assume ratio of innovative (I) projects to alternative (A) projects is 1:3 for FY79
and 80, and 1:5 for FY81 and 82 based on quarterly report of 40 I to 216 A. 25% of
all I projects qualify for 85% funding, and 50% of all A projects qualify for 85%
funding. (Exhibit X).
For FY 79:
Number of Innovative Projects
Number of Alternative Projects
Innovative Projects Federal Share
Alternative Projects Federal Share
$21 million/($3.89 million x 0.25/8.5)
184
$63 million/($3.89 million x 0.5/8.5)
275
184 x $3.89 million
$716 million
275 x $3.89 million
$1,070 million
568
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from land application and other natural systems because of their high activity
and savings. The lower projected volume on-site and alternative collection
systems contribute about one-third of the total Alternative Technology savings
due to their high margins on saving which is close to twice that of land
application and other natural systems.
If the Innovative and Alternative Technology Program is extended to
fiscal year 1982 with 3% total Innovative and Alternative set-aside and a
minimum of 1/2% set-aside for Innovative Technologies from a total construc-
tion grant appropriation of $4.5 billion, a total of $142 million is estimated
to be saved by expending $22.5 million of Innovative set-aside which is equiv-
alent to $766 million of construction grants. Savings of $652 million are
projected from an Alternative set-aside of $112.5 million or construction
grants of $1.914 billion. A total savings of $794 million are projected
for a total Innovative and Alternative set-aside of $135 million for con-
struction grants totaling $2.68 billion. These projected savings for
fiscal year 1982 are also shown in Table 16.
The Innovative and Alternative Technology Program has the further
potential to achieve significant cost and energy savings from projects
to be funded in fiscal years 1982 through 1986. An estimate of this impact
was developed by conducting a comprehensive review of technologies which
could potentially save cost or energy or meet other goals of the Clean Water
Act of 1977. A list of these technologies was compiled under seven general
categories as follows: biological, chemical or physical, land application,
other natural systems, sludge handling and energy recovery, energy conser-
vation and recovery, on-site and alternative collection systems. The status
of development and potential application of each technology, including
applicable size ranges, treatment levels, waste streams, and geographical
areas, is shown-in Table 18.
Column one of Table 18 lists each of the seven general categories of
technologies described previously in Table 17. Column two indicates the
potential number of facilities to be funded during the four-year period
which could potentially realize cost and/or energy saving benefits. These
figures are estimated based upon the calculation that 3,290 construction
projects would be funded according to the following analysis. Assuming
that $4 billion/year will be appropriated for fiscal years 1983, 1984, 1985,
1986; $16 billion will be available for funding purposes. Out of this total,
7% would typically be used for planning and design projects according to
records of the grants program from its inception. It is assumed that 13%
will be collectively used for projects which would not be direclty influenced
by the Innovative and Alternative Technology Program. These would include
such projects as infiltration/inflow and sewer replacement and rehabilitation.
Therefore, 80% of the $16 billion, or $12.8 billion, remains as the amount
which could be influenced directly. Using the historical average Step 3
construction cost of $3.89 million, 3,290 construction projects could poten-
tially realize cost and/or energy savings. In column two, out of the 3,290
projects, 1,500 would include biological treatment technologies which could
potentially save costs or energy. In a similar manner, 400 would include
chemical or physical technologies, 1,000 would include land treatment tech-
nologies and natural systems, 1,000 would include sludge treatment and
569
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TABLE 18
CALCULATIONS OF POTENTIAL COST AND ENERGY SAVINGS OF THE
INNOVATIVE AND ALTERNATIVE TECHNOLOGY PROGRAM FOR PROJECTS TO BE FUNDED IN FISCAL YEARS 1982 THRU 1986
-5-
-2- -3-
PnloutUl Average -4-
-i- Ho. of Size of Calculated
Calculated
Energy Use
of the Average -6- -7-
-8-
-9-
Calculated Calculated
Total LCC Total
Category Projects Baseline LCC of the Baseline Range Range Savings Energy Savings
of I/A Influenced by Conventional Average Baseline Conv. Facility of LCC of Energy if) Kw hr/yr x lO"**
en Technology I/A Pronram Facility (nwjd) Conv. Faclllly(SH) Kw hr/yr x JO"3 Savings (X) Savings (I) (2x4 x 6) (2x5x7)
0 Biological 1.500 2.5 0.65
Chew teal or 400 2.5 0.65
Physical
Land Application 000 1.0 3.5
Other Natural 200 1.0 3.5
Systems
Sludge 1.000 2.5 8.65
lUndllmi and
Energy llccovc-ry
Other Energy 1.500 2.5 0.65
Conservation
and Recovery
Oil-Site and 1.000 0.35 1.2
Alternative
Collect Ion
Systems
1.125 20 - 30 20 - 30
1.125 5-15 5-15
500 30 - 40 10 - 20
500 30 - 40 50 - 70
1.125 10 - 20 30 - 40
1.125 10 - 20 20 - 30
231 20 - 30 10 - 20
TOTALS
2.6 -3.09
0.17-0.52
0.84-1.12
0.21-0.20
O.BC-1.73
1.30-2.60
0.24-0.36
6.22-10.5
3.30-5.06
0.23-0.60
o. 4n-o.no
0.50-0.70
3.30-4.50
3.30-5.06
0.23-0.46
11.5-17.26
-------
associated sludge energy recovery technologies, 1,500 would include other
energy saving technologies. These estimates are based upon the distribution
of existing facilities, historical patterns of use for each type of tech-
nology as experienced in the Construction Grants Program and ORD experience
in the Innovative and Alternative Technology Program thus far, as well as
stated goals of USEPA involving, for example, the number of projects which
should include land treatment and natural systems. The total number of pro-
jects in all categories is larger than 3,290 because all of the categories
are not mutually exclusive.
Column three indicates the average size of a project for each category
of technology which would realize cost or energy saving benefits. The
9,450 m^/day (2.5 mgd) figure is the average size of projects historically
funded by USEPA. The sizes for the other categories are smaller due to
the nature of the technologies involved typically being limited to smaller
communities.
Columns four and five present the calculated life cycle cost and energy
use for a conventional facility not using Innovative or Alternative tech-
nologies. These values serve as a baseline for estimation of cost and
energy savings. Life cycle costs used here are those present worth costs
of construction and operation and maintenance costs and are calculated based
on $5.19 million construction costs for a 9,450 m^/day (2.5 mgd) facility.
Approximately 60% of total life cycle costs are estimated as construction
costs. Therefore, the life cycle cost for a 9,450 m3/day (2.5 mgd) facility
is $8.65 million. The life cycle cost for other size facilities was cal-
culated using the same unit cost per mgd. For this analysis, at this size
range spread, scale factors were ignored. Energy use for a conventional
treatment facility was calculated using 450,000 KwH/year/mgd for a 9,450 m-^/day
(2.5 mgd) facility, and 500,000 KwH/year/mgd for a 3,780 rrH/day (1.0 mgd)
facility. For a 1,323 m^/day (0.35 mgd) on-site and alternative collection
system 660,000 KwH/year/mgd was used and includes an allowance for energy
used for conventional collection as well as treatment. The energy figures
used for treatment represent total energy requirements for a typical con-
ventional activated sludge plant and do not include the net energy recovered
from anaerobic digestion.
Columns six and seven indicate the ranges of estimated percent of life
cycle cost and energy savings of innovative and alternative technologies used
in lieu of conventional technologies. The percent savings are given based
on total life cycle costs and total energy use in the conventional baseline
facility. They are not based on unit process savings. The estimates of
savings are based upon research and development experience, fundamental
process considerations, and experience in the Innovative and Alternative
Technology Program to date. Columns eight and nine present calculated
total potential life cycle cost and energy savings for each category of
technology listed.
The total present worth (capital cost plus operation and maintenance
cost) dollar savings which could be potentially realized from the four-year
program range from $6.22 to $10.5 billion. Of this, $3.73 to $6.3 billion
would be for construction savings; and $2.49 to $4.2 billion would be for
571
-------
operation and maintenance savings. The construction dollar savings amount
to 22% to 37% of construction dollars. User charges would be reduced due
to lower operation and maintenance costs and lower local share requirements.
According to the 1978 Needs Survey, $35.6 billion is required to meet
the Year 2000 needs in categories which could be directly affected by the
Innovative and Alternative Technology Program. Of this, from 22% to 37%
could potentially be saved amounting to $7.3-13 billion over the long term.
Potential energy savings for projects funded during fiscal years 1983
through 1986 range from 11.5 to 17.3 x 108 KwH/year which is 9% to 13% of
the 1977 energy requirements for municipal wastewater treatment in the
United States.
In addition to the immediate cost and energy impacts previously des-
cribed, the benefits derived from continuation of the Innovative and Alter-
native Technology Program for an additional four-year period beyond fiscal
year 1982 are estimated to far outweigh the additional investment. Initial
program benefits are derived from: (a) demonstrating the immediate effects
of a slightly higher risk as a part of design practice; (b) removal of the
more obvious disincentives to innovative designs; (c) injection of arbitrary
increased cost and energy saving goals to encourage improved design; and
(d) strong encouragement of the increased use of certain natural treatment
systems. Because of the inherent 6-8 year lag time in our planning, design,
and construction process, and also because of the traditional conservative
nature of consulting engineers and state review authorities and their reluc-
tance to change, the initial three-year program will serve primarily to develop
momentum in the program. Consultants and equipment manufacturers have approached
the initial three-year program cautiously, questioning the benefits of learning
and competing under a new set of standards and guidelines with no guarantee of
further federal commitments. Because of the legislative requirements and
intensive national training program, many medium and larger size consulting
firms and equipment manufacturers are now equipped to aggressively pursue
improved Innovative and Alternative designs (approximately 1,500 consultants
have attended a series of two-day intensive Innovative and Alternative Tech-
nology seminars). Continuation of the program will maximize the investment
made to develop this capability.
The Innovative Technologies proposed during the first 1 1/2 years of
the three-year program were those already developed to some extent by pri-
vate and public sector basic research efforts. Program continuation for an
additional four years beyond 1982 is estimated to stimulate basic and develop-
mental research needed for second generation innovative and alternative tech-
nologies. This potential is especially high in regard to improved natural
systems.
The ultimate objective of the program is to persuade municipal decision
makers, consulting engineers, and the general public that innovative and alter-
native technology performs better and is less costly than conventional approaches,
without a continued need for a federal fiscal incentive program. It is antici-
pated that this wall be accomplished by establishing as standard practice
572
-------
reduction of over-conservativlsm In design, greater consideration of natural
systems, and improved cost and energy analyses.
Present experience suggests that continuation of the Innovative and
Alternative Technology Program will offer the following benefits:
• Provide for improved resource recovery and beneficial use
of wastewater constituents.
. Firmly establish as standard practice a reduction in over-
conservative designs, a new emphasis on improved cost
analysis and energy considerations, and greater consideration
of alternative technologies in the design of POTWs.
• Create an incentive for improved basic research in both
public and private sectors due to confidence in continuation
of a market for improved technology.
. Create confidence in the consulting engineering profession
and state review authorities in higher risk, higher benefit,
less conservative designs.
• Increase the consideration and appropriate use of natural
systems.
. Substantially increase private sector research in more
reliable cost and energy efficient equipment.
• Reduce secondary energy utilization for production of
chemicals and energy intensive materials of construction.
. Reduce long-term operation and maintenance costs to the
community, especially future energy needs.
• Provide incentive for engineering curriculum improvements
including emphasis toward natural systems and alternative
technologies.
573
-------
ABBREVIATIONS AND ACRONYMS
A
atm
BOD
BTU
C
QC
CDF
cm
COD
CWA
D
DOS
$
DWBR
°F
FB
FBBT
F/M
- Alternative Technology
- atmospheres
- 5-day biochemical oxygen
demand
- British Thermal Units
- Carbon
- degrees Celsius
- combined digestion process
- centimeter
- chemical oxygen demand
- Clean Water Act
- depth
- dual digestion sludge
process
- U.S. dollars
- deep well biological
reactor
- degrees Fahrenheit
- free board
- fluidized bed biological
treatment
- food to microorganism
ratio
ft
FWPCA -
gpm -
H2 -
H20
hp
hp-hr -
I
I/A -
ID
in
kg
kw
KwH
L
1
LACSD -
Ib
LCC -
ft
Federal Water Pollution Control
Act
gallons per minute
Hydrogen
water
horsepower
horsepower-hour
Innovative Technology
Innovative and Alternative
Technology
inner diameter
inch
kilogram
kilowatt
kilowatt hour
length
liter
Los Angeles County Sanitation
Districts
pound
life cycle costs
574
-------
ABBREVIATIONS AND ACRONYMS (Continued)
m
MCD
mgd
mg/1
MLSS
mm
no.
02
OD
ORD
%
PL
Pop.
POTW
PSA
RBC
RDF
sec
SS
- meter
- USEPA Municipal Construc-
tion Division
- million gallons per day
- mi 1 1 igram per 1 iter
- mixed liquor suspended
solids
- millimeter
- number
- Oxygen
- outer diameter
- USEPA Office of Research
and Development
- percent
- Public Law
- population
- publicly owned treatment
works
- pressure swing absorption
rotating biological
contactor
- refuse derived fuel
- seconds
- suspended solids
SRT
SWD
SWEC
TPD
TSS
U.S.
USEPA
VSS
VWCR
W
sludge retention time
- side wall depth
- Sludge/Waste Energy
Conversion Center
- tons per day
- total suspended solids
- United States
- United States Environmental
Protection Agency
- volatile suspended solids
- Vertical Well Chemical
Reactor
- width
575
-------
REFERENCES
1. USEPA, Clean Water Fact Sheet, November 1979, Office of Water Program
Operations, Waterside Mall, 401 "M" Street, SW, Washington, D.C. 20460
2. USEPA, Municipal Waste Facilities Inventory, February 14, 1979, Office
of Water Program Operations, Waterside Mall, 401 "M" Street, SW,
Washington, D.C. 20460
3. Smith, J.M., Upgrading Existing Wastewater Treatment Plants, USEPA
Technology Transfer Design Seminar, Atlanta, Georgia, May 8-10, 1973
4. Metcalf and Eddy, Inc., Wastewater Engineering Treatment, Disposal and
Reuse, Second Edition, McGraw-Hill Book Company, 1979
5. USEPA, Interim Report on the Impact of Public Law 92-500 on Municipal
Pollution Control Technology, Municipal Environmental Research Laboratory,
Cincinnati, Ohio 45268, EPA-600/2-76-018, January 1976
6. USEPA, Novel Methods and Materials of Construction, Municipal Environ-
mental Research Laboratory, Cincinnati, Ohio43268, EPA-600/2-79-079
7. USEPA, Innovative and Alternative Technology Assessment Manual Draft,
Office of Water Program Operations, Washington, D.C.20460, MCD 53,
EPA-430/9-78-009
8. Various correspondence and monthly reports, Municipal Sludge Disposal
by Vertical Tube Reactor Process, USEPA Contract No. 68-03-2812,
Cincinnati, Ohio, July 1979-February 1980
9. Personal communication with Russ Herman, Director of Waste Management
Projects, Vertical Tube Reactor Corporation, Englewood, Colorado,
March 1980
10. Brenner, R.C., Personal communication, USEPA, Cincinnati, Ohio
February-March 1980
11. Brenner, R.C., Philosophy of and Perspectives on Air Oxygen Transfer
Standards - the EPA View, Proceedings of the ASCE/EPA Workshop Toward
an Oxygen Transfer Standard, Pacific Grove, California, April 11-14, 1978
12. Various correspondence and monthly reports, Deep Shaft Demonstration
Grant 5806801, USEPA, Cincinnati, Ohio, October 1979-January 1980
576
-------
13. Eco-Research Ltd., Visitors Brochure for Ithaca Deep Shaft Pilot
Demonstration Plant, Ithaca, New York, February 1980
14. Smith, J.M., Review of Wastewater Facilities Plan for Dodge City, Kansas
EPA Memorandum, Cincinnati, Ohio, December 20, 1978
15. Black and Veatch Consulting Engineers, Wastewater Facilities Plan for
Dodge City, Kansas, Addendum No. 2, October 31, 1978
16. Smith, J.M., I/A Project Review and Recommendations for 10 mgd Expansion
of Bay Park Wastewater Treatment Plant, Nassau County, New York, EPA
Memorandum, Cincinnati, Ohio, September 6, 1979
17. Ecolotrol, Inc., Proposed Fluidized Bed Design for Bay Park 10 mgd
Plant Expansion, Bethpage, New York, July 21, 1978
18. Thomas, R.E., and Reed, S.C., EPA Policy on Land Treatment and the Clean
Hater Act of 1977, Seminar on Land Treatment of Municipal Wastewater
Effluents, Cincinnati, Ohio, June 1979
19. Jewell, W.J., and Seabrook, B.L., A History of Land Application as a
Treatment Alternative, Washington, D.C.,20460, EPA-430/9-79-012,
April 1979
20. Duffer, W.R., and Moyer, J.E., Municipal Wastewater Aquaculture,
Ada, Oklahoma, EPA-600/2-78-110, June 1978
21. Leonard S. Wegmari Co., Inc., Alternative Analyses for Treatment and
Sludge Handling Systems, Atlanta, Georgia, August 26, 1977
22. USEPA Region IV, Environmental Review of Nonconnah Creek Basin 201
Wastewater Facility Plant, Atlanta, Georgia, February 1979
23. Smith, J.M., Review of the City of Lackawanna, Erie County, New York
Proposed Innovative Project No. C-36-852, EPA Memorandum, Cincinnati,
Ohio, January 17, 1980
24. Nussbaumer and Clark, Inc., Addendums No. 2 and No. 3 to the Wastewater
Facilities Report for the Lackawanna Sewage Treatment Plant, Lackawanna,
New York, February-April1979
25. USEPA I/A Technical Support Group, Impacts of National Innovative and
Alternative Technology Program and Justification for Extension to
Fiscal Year 82 (Draft), Cincinnati, Ohio, February 12, 1980
577
-------
PARALLEL EVALUATION OF
BELT FILTER PRESSES AND
LOW SPEED SCROLL CENTRIFUGES
By
Walter E. Garrison
and
Robert W. Horvath
Los Angeles County Sanitation Districts
Whittier, California
Presented at
SEVENTH UNITED STATES AND JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
May 18 - June 1, 1980
Tokyo, Japan
579
-------
ACKNOWLEDGMENTS
Partial funding of this work was provided by the State of California and the
United States Environmental Protection Agency. The field investigations were
conducted by Thomas J. LeBrun, David Bachtel, and Richard Trubiano, research
engineers for the Los Angeles County Sanitation Districts.
580
-------
I. INTRODUCTION
For almost a decade the Sanitation Districts of Los Angeles County have con-
ducted sludge dewatering research in response to increasingly stringent
standards regulating effluent and sludge discharge to the ocean from the
Joint Water Pollution Control Plant in Carson, California. Most recently,
the sludge dewatering studies culminated with the side-by-side testing of
full scale low speed scroll centrifuges and belt filter presses. A brief
summary of the earlier pilot studies and the results of the full scale
testing are presented in this paper.
A. EXISTING FACILITIES
The Joint Water Pollution Control Plant (JWPCP) currently provides advanced
primary treatment for 15 m^/s (350 mgd) of domestic and industrial waste-
water. The plant treats approximately 75 percent of the flow in the entire
Sanitation Districts system, which serves a population of four million.
Other treatment plants in the system return their sludge to sewers which
terminate at the JWPCP, so it serves as a central solids processing facility
for the whole system.
Sludge and floatables from the primary settling tanks are anaerobically di-
gested for approximately fifteen days and dewatered by centrifuges. Basket
centrifuges are provided in sufficient capacity to dewater approximately one-
half of the sludge flow. With polymer conditioning at 2 g/kg (4 Ib/ton),
these machines are capable of recovering over 90 percent of feed suspended
solids and producing a cake with 22 percent total solids. The remainder of
the sludge flow is dewatered by high speed, countercurrent flow scroll cen-
trifuges, which are able to recover only one-third of the feed solids.
B. PURPOSE OF THE TESTS
In the 1970's, both federal and California discharge standards were enacted
which required an increased level of treatment at the JWPCP, including a ban
against the discharge of sludge into the Pacific Ocean. Construction is now
in progress which will provide 8.8 m^/s (200 mgd) of secondary treatment,
using the high purity oxygen activated sludge process. Dewatering studies
were conducted to select equipment needed for two reasons:
1. A large amount of waste activated sludge will be produced when secondary
treatment commences.
581
-------
2. Digested primary sludge production exceeds the capacity of the existing
basket centrifuges, and the existing high speed scroll centrifuges can-
not provide acceptable solids recovery for the remainder of the sludge.
II. PILOT STUDIES
Initially, a great variety of schemes were studied for the processing of
waste activated sludge (WAS). These included thickening by gravity, dis-
solved air flotation, and centrifugation; aerobic digestion, and anaerobic
digestion at both mesophilic and thermophilic temperatures; and heat treat-
ment, as well as wet oxidation at low or intermediate pressure. WAS pro-
cessed by the above methods and anaerobically digested primary sludge were
dewatered by means of vacuum filter, plate and frame filter press, belt
filter press, scroll centrifuge and basket centrifuge. Details of these
tests have been described elsewhere.(1»2)
As a result of the pilot studies, it was decided that WAS would be thickened
by dissolved air flotation, and anaerobically digested. A final decision
was not made on the dewatering equipment at this time. A qualitative charac-
terization of the dewatering performance achieved on anaerobically digested
sludge is presented in Table 1. Vacuum filtration of digested waste acti-
vated sludge (DWAS) met with little success, requiring very high doses of
inorganic chemicals for conditioning, and exhibiting very poor discharge of
sludge from the media. Pressure filtration, although producing excellent
cakes and solids recovery, also required prohibitively high dosages of
conditioning chemicals. Basket centrifugation of 100 percent DWAS met with
little success; however, if substantial amounts of digested primary sludge
(DPS) were blended with the DWAS, acceptable performance could be achieved.
The Districts' experience with full scale operation of basket centrifuges on
DPS has shown this device to require the least amount of polymer condition-
ing to achieve good recovery, while also producing an acceptably dry cake.
The scoll centrifuge and the belt filter press were considered to demon-
strate the best overall performance for both DPS and blends of DWAS plus
DPS. Dewatering of 100 percent DWAS, and handling of the cake thus produced,
were generally found to be less than satisfactory. These two devices were
then subjected to full scale, long term testing to further evaluate opera-
tion and maintenance characteristics, as well as the conventional dewatering
parameters such as cake solids, recovery, and chemical requirements.
III. DESCRIPTION OF FULL SCALE EXPERIMENTS
A. EQUIPMENT DESCRIPTIONS
Four pieces of equipment were selected which appeared to represent the best
technology available at the conclusion of the pilot experiments in early
1978. Of the four machines selected, three were the largest size marketed
by the respective manufacturers for this application.
582
-------
TABLE 1. Dewatering Characteristics Determined by Pilot Studies
Device
Vacuum Filter
Pressure Filter
Basket Centrifuge
Scroll Centrifuge
Belt Filter Press
SI udge
Type
DWAS
DWAS
DWAS
DPS
DWAS
DPS
DWAS
DPS
Cake
Dryness
F
E
P
G
G
G-E
G
G-E
Chemical*
Requirements
P
F-P
G
E
G
G
G
G
Solids
Recovery
F
E
F
G
G
G-E
F-G
G
DWAS = Waste activated sludge, anaerobically digested
DPS = Primary sludge, anaerobically digested
E = Excellent G = Good F = Fair (moderate)
P = Poor
* Lime and ferric chloride used to condition sludge for vacuum
and pressure filters. Polymer used for centrifuges and belt
filter presses.
583
-------
The four devices included:*
1. A 2.2 meter Winkle belt filter press (Ashbrook-Simon-Hartley Co.)
2. A 2.0 meter Magnum belt filter press (Parkson Corp.)
3. An 80 cm (32 inch) diameter Kruger 280 MC low speed scroll centrifuge
(Ingersoll-Rand Corp.).
4. A 91 cm (36 inch) diameter Bird HB5900 low speed scroll centrifuge
(Bird Machine Co.)
The two belt filter presses varied substantially in their design as shown in
Figures 1 and 2. The notable features of the Winkle press include a very
large gravity drainage zone, followed by a vertical V-shaped section which
provides hydrostatic pressure to aid in dewatering and distributes the sludge
evenly across the belt width; the Winkle press also employs in-line polymer
mixing and flocculation rather than a separate flocculation vessel. The
Magnum press design includes an inclined gravity drainage zone with relatively
greater liquid depth, fabric belts operated at reduced tension to permit a
less massive frame, and a third belt made of rubber strips to provide high
pressure dewatering.
The two scroll centrifuges were more similar in design. Both were of the
type commonly designated as "low speed," developing centrifugal force of about
one thousand times gravity or less. Both could be classified as the concur-
rent flow type, with the sludge cake being conveyed in the same direction as
the flow of influent sludge. The Kruger centrifuge is different in its use
of a second scroll designed to introduce the flow to the liquid pool with
less turbulence. The Kruger devotes proportionately more length to the
beach or drainage area and less to the settling zone in comparison to the
Bird, as can be seen in Figures 3 and 4.
It is especially notable that during the course of the testing, one of the
centrifuges was eventually modified by the addition of an automatically
controlled, variable speed backdrive. The backdrive of a centrifuge is the
mechanism which controls the speed of the scroll conveyor relative to the
bowl. This speed differential directly affects the amount of solids that
are held in the bowl during operation. By automatically controlling the
scroll differential in proportion to the amount of torque developed on the
scroll shaft, close control of the solids retention in the bowl could be
achieved, similar to the way a sludge blanket might be controlled in a
sedimentation tank. The importance of this development is explained later
in this paper.
Use of trade names is not intended as an endorsement of the products,
but serves as a reference for design features which cannot be described
within the scope of this paper.
584
-------
DRAINAGE ZONE
oo
IN-LINE
STATIC
MIXER
SIDE BAFFLE WITH RUBBER SEALS ALONG BOTTOM
ROW OF V SHAPED PLOWS
TO TURN SLUDGE
LOWER BELT
WASHWATER
UNIT
BELT
TENSION ING II
UNIT
BELT TRACKING
ADJUSTABLE ROLLER
VERTICAL
DEWATERING
ZONE
SHEAR ZONE
S"
25 cml 125 cm
PRESSURE
ZONE
CAKE DISCHARGE
VIA SCRAPER BLADES
HIGH PRESSURE ROLLER
f)
HIGH PRESSURE
HYDRAULIC SYS
WASHWATER
UNIT
FEED SLUDGE
BELT LENGTH:
UPPER BELT'- 15.5m (51 ft.)
LOWER BELT 20.1m (66 ft.)
OVERALL DIMENSIONS^
HEIGHT: 3.1m (10 ft.)
LENGTH^ 5.4m (17.7 ft.)
WIDTH-' 3.2m (10.5 ft.)
WEIGHT:
10,900 kg (12 tons)
BELT
TRACKING
ADJUSTABLE
ROLLER
Figure I. Schematic of the Winkle Press Model 3V.
-------
CAKE DISCHARGE
SCRAPER BLADES
CO
UPPER^BELT
BELT
TENSIONING
ROLLER
SIDE BAFFLE WITH
RUBBER SEALS-
ALONG BOTTOM
UPPER
WASHWATER
UNIT
SLUDGE PLOWS 8
DISTRIBUTORS
INCLINED DRAINAGE ZONE
PRESSURE ZONE
BELT TRACKING
ADJUSTABLE ROLLER
I I cm
WASHWATER
UNIT
BELT
TENSIONIWG-
ROLLER
FEED SLUDGE
8 POLYMER
FROM
FLOCCULATION
TANK
BELT LENGTH; UPPER - !0m (32.8 ft) OVERALL DIMENSIONS: HEIGHT- 2.3m (7.5ft.) WEIGHT' 6820kq (7.5 tons)
LOWER-I4.lm (46.5 ft.) LENGTH-4.5m (14.8ft.)
WIDTH-2.7m (8.7ft.)
Figure 2. Schematic of the Magnum Press MP 80.
-------
SCROLL
FEED SCROLL
POLYMER
SLUDGE CAKE OUTLET
CENTRATE
r 280MC Centrifuge.
SCRCL
SLUDGE CAKE OUTLET
CENTRATE
HB5900 Centrifuge.
SLUDGE 8
587
-------
B. EXPERIMENTAL VARIABLES
Throughout the testing of the four devices, cake dryness and suspended solids
recovery were the dependent variables measured, while sludge feed rate and
polymer dosage were controlled as independent variables. The feed sludge
used for most tests was DPS with a suspended solids concentration of 2.5 to
3.0 percent. Various blends of DPS and DWAS were also tested to the extent
that DWAS was available; suspended solids concentrations of the blends were
in the range of 2 to 3 percent.
Each machine was provided with certain adjustable features. For the belt
filter presses, these are typically belt speed, belt tension, washwater
flow, and the optional use of high pressure zone mechanisms in the last
stage of pressing. Several different belt weaves were also tested. For the
centrifuges, bowl speed, pool depth, and scroll differential can be adjusted,
though with greater difficulty than associated with the belt press adjust-
ments. After the automatic backdrive was added to the centrifuge, scroll
torque became an important new variable. These machine parameters were
systematically varied to determine their effects and optimize performance.
C. METHOD OF EVALUATION
The ultimate objective of the test program was to select a system which would
result in the lowest total cost to dewater and dispose or reuse the sludge
generated at JWPCP. Therefore, while the test program was being conducted,
the results were continually subjected to an economic analysis that reflected
the total system cost for sludge processing. This provided the means to
evaluate the relative importance of cake dryness, polymer dosage, and hydrau-
lic capacity, thus providing direction for the conduct of further tests.
Total cost included the following items: amortized capital; polymer use;
power consumption; operating labor; maintenance labor and materials; and cake
disposal. Cake disposal at JWPCP will be by three separate means: landfilling
with refuse; windrow composting for reuse as a soil conditioner; and
Carver-Greenfield dehydration plus thermal processing for energy recovery.
For the typical system analysis, cake disposal was found to account for about
one-half of the total cost, polymer about one-fourth, capital about one-
eighth, and power, operation and maintenance about one-eighth. It is clear
that these circumstances resulted in a great emphasis on obtaining a dry cake
to reduce disposal cost, and to a slightly lesser extent, minimizing polymer
use. Flow capacity per machine and direct power consumption for dewatering
were found to influence total costs to a much smaller degree. This was most
clearly demonstrated by the fact that the scroll centrifuges were ultimately
determined to achieve optimum performance at feed rates of approximately half
of what might normally be expected from machines of the size tested. In
addition to the factors of cost, all machines were subject to the requirement
that suspended solids recovery be at least 90 percent, so that the liquid
sidestream could be handled without excessive degradation of the JWPCP
effluent.
588
-------
IV. RESULTS AND DISCUSSION
A. BELT FILTER PRESS PERFORMANCE
Belt filter presses can be operated to achieve a wide variety of results, by
varying such parameters as belt speed, belt tension, polymer dosage, and
auxiliary high pressure zone features. A series of experiments were per-
formed in which these parameters were systematically varied to determine the
effects on cake dryness and suspended solids recovery. These experiments
clearly indicated that a number of tradeoffs can be made among the factors
that affect system cost and performance.
1. Variation of Belt Speed and Polymer Dosage
Belt speed directly affects cake solids and suspended solids recovery, and
indirectly affects the required polymer dosage. A series of tests were con-
ducted with screened digested primary sludge at a feed rate of 32 m /h (140
gpm) and different polymer dosages. Figure 5 shows that by lowering the belt
speed, 1-3 percent drier cakes can be produced. Reducing the belt speed
causes the sludge level to build up in the gravity drainage zone. Minimum
belt speed is limited by the ability of the side baffle seals to contain the
sludge within the gravity drainage zone; failure occurs when the sludge runs
off the belts and is lost to the filtrate trays. Increasing the polymer
dosage has a dual effect on cake solids. At any given belt speed, more water
is released from the sludge because of the improved flocculation. In addi-
tion, belt speed can be lowered before failure occurs in the gravity drainage
zone, further increasing cake dryness.
Figure 6 shows the effects of belt speed on solids recovery. In a belt
press, solids are lost in two ways. They may either pass through the belt
and appear in the filtrate, or they may adhere to the belt and be removed by
the washwater. The results at moderate and high polymer dosages are typical
for a sludge that is adequately flocculated. Increasing the belt speed
exposes a given amount of sludge to more belt area. Since each square meter
of belt traps a relatively uniform amount of solids after scraping, the high
belt speed causes a greater amount of sludge to be lost in the washwater.
Similarly, when using the high pressure zone features which apply external
pressure on the belts, drier cake solids can be achieved, but additional
solids will be squeezed into the belts and lost in the washwater. In con-
trast, at the minimum polymer dosage, significant amounts of unflocculated
solids passed through the belt with the filtrate when belt speed was lowered,
overshadowing the normal advantage achieved by lower belt speed.
A further effect that was observed during the testing related to hydraulic
capacity. Stable operation could be maintained at higher feed rates to the
belt filter press by increasing the belt speed. However, other parameters
can suffer from the increased belt speed, as described above.
In summary, lower belt speed can be used to maximize cake dryness and re-
covery in many cases. If it is desired to use the bare minimum of polymer or
maximize hydraulic throughput, higher belt speeds may be required. Cake
589
-------
LOW POLYMER DOSE 3.8g/kg (7.5 Ibs/ton)
J3 27
* 26
CO
o
I] 25
O
CO
UJ 24
8 23
FAILURE
BELT SPEED
TOO SLOW
H
WITH HIGH
RESSURE ZONE
2345
BELT SPEED, m/min.
MODERATE POLYMER DOSE 4.9g/kg (9.7 Ibs/ton)
CO
28
27
Q
j 26
O
CO
u 25
O 24
FAILURE
'BELT SPEED
TOO SLOW
WITH HIGH
RESSURE ZONE
2345
BELT SPEED, m/mia
CO
31
30
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28
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HIGH POLYMER DOSE 7.5g/kg (I5lbs/ton)
.FAILURE .
BELT SPDJ
I^n
WITH HIGH
PRESSURE ZONE
2345
BELT SPEED, m/min.
Figure 5. Effect of belt speed on cake solids using
screened primary digested sludge.
590
-------
100
LOW POLYMER DOSE 3.8g/kg (7.5 Ibs/ton)
85 *
£«
HI
8 85
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ft:
CO
o
IJ 75
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CO
WITH HIGH
PRESSURE ZONE
2345
BELT SPEED, m/min.
6
DS RECOVERY ,%
MODERATE POLYMER DOSE 4.9g/kg (9.7Ibs/ton)
_
O
O
95 -
90
85
O 80
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WITH HIGH^
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2345
BELT SPEED, m/min.
OLIDS RECOVERY, %
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D Ol O Ol O
HIGH POLYMER DOSE 7.5g/kg
i i i i
WITH HIGH ^S
PRESSURE ZONE
i i i i
(15 Ibs/ton)
i i
^^
i i
CO 0
2345
BELT SPEED, m/min.
Figure 6. Effect of belt speed on solids recoveries
using screened primary digested sludge.
591
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dryness can be improved by increasing polymer dosage above the minimum re-
quired for stable operation, and this effect can be maximized by simultane-
ously lowering the belt speed.
2. Variation of Belt Tension
Experiments were conducted to determine the effects of belt tension on cake
solids and recovery. Screened DPS was run at feed rates of 25 - 39 rrr/h
(110 - 170 gpm) and polymer dosages of 3.5 - 5.0 g/kg (7 - 10 Ib/ton). The
results are depicted in Figure 7. Tests were made with and without the
high pressure zone, which in this case uses two opposing rollers to cause a
"wringer" effect.
Three trends are clear:
1. Higher belt tension produces drier cake. A fourfold increase in
tension resulted in cake solids roughly three percent higher, equivalent
to a ten percent reduction in dewatered cake volume.
2. Higher belt tension causes a loss in solids recovery on the order of
2-5 percent, primarily because solids were pressed into the belt and
removed with the washwater.
3. High pressure zone features further increased cake solids by 1 - 2
percent, but caused additional solids to be lost in the range of
1-5 percent.
When blends of DPS and DWAS were dewatered, similar trends were noted, but
as the percentage of DWAS in the blend increased, the effects became less
significant. This is because the biological sludge does not have the struc-
ture to withstand much pressure, and as belt tension is increased, the sludge
will eventually squeeze out from the edges of the belt. For sludge blends
consisting primarily of DWAS, belt tension must be kept low, and high pres-
sure zone features are not likely to be of any use.
3. Belt Weave
Several different belt weaves were tested during the course of the study. A
very fine mesh belt tested on DPS was found to blind quickly, so that inade-
quate drainage occurred in the gravity zone. A very coarse weave belt neces-
sitated the use of higher polymer dosage to achieve adequate recovery in com-
parison to the standard belt. Two belts were tested on blends of DWAS and
DPS, and, unexpectedly, the coarser weave demonstrated better performance.
It was concluded that any evaluation of belt filter press performance should
include a trial of several belt types to match the proper belt to the in-
dividual sludge characteristics.
592
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WITHOUT HIGH PRESSURE ZONE
WITH HIGH PRESSURE ZONE
U)
31
30
CO 29
h-
55 28
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27
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25
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FLOW DOSE
m3/hr g/kg
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-• 32 3.5
-• 32 4.0
• 39 5.1 A
0 10 20 30 40
BELT TENSION, kgf/cm2
31
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25
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10 20 30 40 50 0
BELT TENSION, kg f/cm2
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100
95
90
85
50
80<
10 20 30 40
BELT TENSION, kg f/cm2
10 20 30 40
BELT TENSION, kg f /cm2
Figure 7. Effects of belt tension on Winkle Press performance
using primary digested sludge
50
50
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B. LOW SPEED SCROLL CENTRIFUGE PERFORMANCE
When testing started on the centrifuges, both were of a conventional design.
However, early in the program, one of the machines was modified by the addi-
tion of a variable speed backdrive and automatic controls to vary the scroll
speed as a function of torque developed on the scroll; the scroll of this
machine was also changed at the same time to a design believed to be more
suitable for dewatering DWAS. The results with both fixed and variable
scroll speeds are described below.
1. Fixed Scroll Speed
One centrifuge was run through a series of tests with DPS in which bowl speed
was varied from 900 to 1200 rpm, pool depth was varied from 19.2 to 19.7 cm,
and feed rate from 23 to 68 m-Vh (100 - 300 gpm). Cake solids and suspended
solids recovery were analyzed as a function of polymer dosage. The most suc-
cessful results were obtained at maximum bowl speed and pool depth, and some
of the results are shown in Figures 8 and 9. The recovery curve showed a
clearly-defined break at about 2.5 - 3.0 g/kg (5-6 Ib/ton) of polymer. Be-
low this dosage, flocculation was insufficient and recovery dropped rapidly.
Above this, recovery was consistently high. This held true until the flow
rate was raised to 57 m^/h (250 gpm), at which point the machine appeared to
be overloaded, and nearly twice as much polymer was required to achieve
acceptable recovery. At the lower flow rates, once the sludge was sufficient-
ly flocculated, there was little to be gained by addition of more polymer.
Cake solids fluctuated in the range of 21 - 23 percent regardless of feed
flow or polymer dosage. The optimum results on DPS for this machine were
thus found to be a feed rate of 45 m^/h (200 gpm), and a polymer dosage of
3 g/kg (6 Ib/ton), producing a cake with 22 percent total solids and recovery
of 96 percent.
Similar data trends were demonstated by the second centrifuge that was
tested. However, by comparison, it had a higher hydraulic capacity, a
slightly lower polymer requirement, and produced cakes that were several
percent lower in total solids. At the conclusion of the fixed scroll speed
centrifuge tests, it appeared doubtful that these devices would be competi-
tive with the belt filter presses.
2. Variable Scroll Speed
When the first centrifuge was modified by the addition of an automatically
controlled backdrive, a dramatic change in performance was observed. Results
of the tests on DPS are included in Figures 8 and 9. Polymer requirement to
achieve excellent recovery changed only slightly. Hydraulic capacity of the
machine dropped to about two-thirds of the former optimum flow rate. Most
significantly, total solids of the cake increased by about four percent.
This is equivalent to a fifteen percent reduction in the volume of dewatered
sludge produced. This change in performance brought the centrifuge into
direct competition with the results achievable with the belt filter press.
The automatic backdrive also made a marked improvement in the stability of
the centrifuge's performance, as will be discusseed in a later portion of
this paper.
594
-------
100
95
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75
70
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DIGESTED PRIMARY SLUDGE
BOWL SPEED 1200 rpm
POOL DEPTH 19.7 cm
FIXED SCROLL SPEED 6 rpm
A 23 m3/h
• 34 nn3/h
• 45 m3/h
* 57 m3/h
- VARIABLE SCROLL SPEED
• 30 m3/h
12345
POLYMER DOSE, g/kg
Figure 8. Low Speed Scroll Centrifuge
Recovery vs. Polymer Dosage.
7
595
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29
28
27
26
to 25
9
8 24
g 23
c£ 22
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17
16
15
14
DIGESTED PRIMARY SLUDGE
BOWL SPEED 1200 rpm
POOL DEPTH 19.7cm
FIXED SCROLL SPEED 6 rpm
A 23 m3/h
• 34 m3/h
* 45 m3/h
— VARIABLE SCROLL SPEED
• 30 m3/h
2345
POLYMER DOSE, g/kg
Figure 9. Low Speed Scroll Centrifuge -
Cake Solids vs. Polymer Dosage.
596
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Automatic control of the scroll differential in proportion to scroll torque
also provides an additional means to optimize performance in accordance with
the user's needs. When the automatic controller is set to maintain a higher
scroll torque, the centrifuge builds up an increased inventory of solids
within the pool volume. The increased retention of solids in the bowl results
in a drier cake, but less pool volume is available for clarification. To
compensate for this, additional polymer must be added to improve flocculation
and maintain solids recovery. In an experiment with DPS designed to test
this phenomenon, it was found that cake solids increased in a linear fashion
from 26 percent to over 29 percent as scroll torque was increased; over the
same torque range, polymer dosage had to be increased by approximately 1.2
g/kg (2.4 Ib/ton) in order to maintain adequate recovery. This demonstrated
that the setting of scroll torque could be used as a means to trade off cake
dryness versus polymer requirement.
C. PERFORMANCE COMPARISON
Most of the testing to establish the operating characteristics of each
machine was done using DPS as described earlier. A number of tests were also
run using blends of DWAS and DPS containing from 25 percent to 70 percent
DWAS on a dry solids basis. A summary of the optimum results from all of the
tests are shown as a function of sludge composition in Figure 10. As shown
earlier, a variety of results can be achieved with each device. The values
selected for this figure were influenced by the cost analysis which estab-
lished the relative importance of cake dryness, polymer dosage and flow
capacity. Repeatability of the data was also considered, and greater weight
was placed on data taken during simultaneous tests, in which the effects of
variation in sludge quality were mitigated. All of the results shown for the
centrifuge were achieved with the unit employing the automatically controlled
backdrive. The optimum belt filter press results were also achieved with
only one of the units tested.
What is most striking about the results shown in this figure is not the dif-
ferences, but the similarities of performance. When total system costs to
operate the two types of devices were compared, the differences did not
appear to be significant when compared to the variability of the data used to
establish costs. This ability of the centrifuge to match the performance of
the belt filter press was not found to be the case until the introduction of
the automatic backdrive.
The results for blended sludge containing more than 50 percent DWAS are
rather questionable. All of the machines exhibited considerable difficulty
in maintaining stable performance on sludges containing a high percentage of
DWAS, requiring high polymer dosages and achieving recovery below the minimum
acceptable (90 percent). On the belt filter presses, it was difficult to
contain this sludge within the belts. This was somewhat unexpected, because
pilot testing of the belt filter presses had shown acceptable performance on
a blend containing 70 percent DWAS.
Smaller presses (0.5 to 1.0 m belt width) from both manufacturers supplying
the large scale units had been tested during the pilot studies. Although the
597
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30
9 25
8
u 20
8 15
2 10.0
o
o:
7.5
5.0-
O
u
cr
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2.5
35
30
25
20
15
100
1 /
•BFP
LSSC
UJ
O
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90
85
% DIG. PRIMARY 100
% DIG. WAS 0
I I
I 7
BFP
LSSC
50
50
SLUDGE COMPOSITION
0
100
Figure 10. Summary of de water ing performance for Belt Filter Press
vs. Low Speed Scroll Centrifuge.
598
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term pilot study is used, these units were both normal production size units
that were almost identical to the larger units with the exception of belt
width. The larger units had difficulty matching the performance of the
smaller units for all types of sludge tested, especially in terms of cake
dryness. A possible explanation is that the smaller units could more effec-
tively tension the belt, and contain the sludge within the belts in a manner
that was difficult to reproduce in the larger units. There is some inherent
limitation in the belt width that may be used. Wider belts should be woven of
larger fibers to withstand distortion and maintain uniform high tension; how-
ever, the fiber size is also governed by the required filtration properties
of the belt. Belt filter press manufacturers for the most part are using the
same type of belt fabric on all size machines, and this may result in rela-
tively poorer performance on the larger units.
Although a number of different scroll centrifuges were also tested in the
pilot studies, these tests could not be matched up with the large scale
studies to provide information on the effects of scale-up.
There are some other differences in performance that are not evident from the
results shown thus far. The single highest value for cake solids achieved by
the belt press on DPS was 33 percent, whereas with the centrifuge, the
highest value was just under 30 percent. These values are representative of
only a few test runs, and are not likely to be achievable on a long term
basis. The very dry cakes were also produced at the expense of high polymer
dosage, particularly in the case of the belt filter press. However, there
does appear to be some evidence that, taken to the extremes, the belt press
can produce a slightly drier cake.
The reaction of the machines at minimum polymer dosage is also quite dif-
ferent. Under normal operation, there is a certain amount of variation in
the sludge flow rate, and even more so in the suspended solids concentration
of the sludge, that cannot be avoided. When a minimum polymer dosage is
chosen for the average conditions, there are likely to be periods when the
sludge is under-conditioned. When under-conditioning occurs on the belt
filter press, the sludge will drain poorly in the gravity zone, and the
sludge depth will increase until the seals cannot prevent it from flowing off
of the edges of the belt. Similarly, a poorly conditioned sludge can squeeze
out from between the belts in the pressure zones. These conditions result in
a drastic loss in solids recovery, and some decline in the dryness of the
cake. Under similar conditions, the centrifuge does not fall into a failure
mode, but suffers a more gradual loss in recovery as the solids level builds
up in the pool. The machine equipped with the automatic backdrive was also
found to automatically compensate for such variations, and maintain the dry-
ness of the cake. It is for these reasons that Figure 10 shows that the
belt filter press requires a polymer dosage about 0.5 g/kg (1 Ib/ton) higher.
The additional polymer is necessary to achieve stable performance on the belt
filter press because intermittent under-conditioning causes a much more
severe loss of recovery (from sludge spillage) than occurs with the centri-
fuge.
Although both types of devices were able to achieve recovery well above that
required for the JWPCP, there was some difference that might be significant
599
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in other situations. It was found that the centrifuge could be adjusted
to achieve in excess of 98 percent recovery on digested primary sludge with
a moderate increase in polymer dosage. Under similar conditions, the belt
filter press appeared to be limited to a maximum of about 96 percent re-
covery, which by comparison would leave twice the amount of solids remaining
in the liquid sidestream. The practical limitation on the belt filter press
is that, after solids are scraped from the belt, there will always be a small
amount pressed into the belt weave which will be removed with the washwater.
The centrifuge does not have a parallel limiting factor.
The factor of flow capacity is frequently the most controversial, because of
the role it plays when equipment is acquired by a competitive bid process.
Note that the belt filter press represented in Figure 10 was shown to have an
optimum capacity of 34 m3/s (150 gpm) on DPS, while the centrifuge capacity
was selected to be only 28 m3/s (125 gpm). Of these two devices, the centri-
fuge has a first cost roughly 50 percent higher. However, it is notable
that this centrifuge (before addition of the automatic backdrive) was oper-
ated successfully at flows as high as 68 m3/s (300 gpm). It might also be
considered that the second belt filter press tested was found to have an
optimum capacity of only 22 m3/s (100 gpm), although both presses were of
similar belt width. The wide variation in capacity for seemingly comparable
machines points out that the capacity for a particular machine can only be
established by field testing, with all of the other operating conditions
clearly specified. It must be recognized that the cost to manufacturers
will be determined only by the number of-machines he must supply, but that
this may be only a small part of the total cost to the user for the life of
the project. It is recommended that bidding situations should be avoided
which give a large advantage to the manufacturer who can supply the least
number of machines.
V. OPERATION AND MAINTENANCE EXPERIENCE
A. TOTAL OPERATING TIME
The various factors that were found to affect operation and maintenance are
the subject of this portion of the paper. During the test program, one of
the belt filter presses was operated for a total of 1600 hours. The second
belt filter press was operated only 350 hours, because of belt failures
which will be described below.
The centrifuge equipped with the automatic backdrive was acquired on a long
term lease after normal testing concluded, and was then placed into regular
service on digested primary sludge. By February, 1980, more than 3500 hours
had been logged on the machine. The second centrifuge was operated for a
substantially shorter time because it was not placed into regular service.
B. EASE OF OPERATION
1. Belt Filter Press
The belt filter press provides an advantage to the operator because all parts
600
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of the process can be readily seen and understood, and the results of opera-
tional changes are quickly apparent. It was found that the belt filter press
could be started and placed into stable operation within a few minutes. A
minimally acceptable operation can be maintained by an operator of relatively
low skills. However, the efficiency of operation can be greatly affected by
the choice of belt speed and belt tension, use of high pressure features,
control of polymer injection and mixing, adjustment of washwater, and a
number of other variables which are peculiar to each machine. The use of
these features to their maximum advantage can be easily ignored if the
operator is not interested in achieving the most economical operation.
The sensitivity of the belt filter press to changes in sludge conditioning
was touched upon earlier. When the belt filter press is operated near the
minimum polymer dosage, periods of under-conditioning are likely to occur if
there are variations in the flow, suspended solids concentration, or sludge
quality (such as the percentage of WAS in combined sludges). Under-condi-
tioning usually results in a drastic loss of solids recovery, because sludge
spillage occurs from the sides of the machine. Although many manufacturers
provide some kind of sensing device to maintain certain performance indica-
tors, they are of questionable efficacy because sludge loss can occur almost
anywhere in the machine. It is recommended that users of belt presses pro-
vide a large volume of holding capacity (e.g., one day storage) to dampen
fluctuations in sludge quality and allow feed flow to be carefully con-
trolled. Continuous monitoring of flow and feed suspended solids concentra-
tion with automatic compensation for polymer dosage may also be effective.
If variations in the sludge feed cannot be closely controlled, intentional
overdosing with conditioning chemicals may be the only answer.
2. Centrifuge
Operation of the centrifuge by the unskilled operator is made slightly more
difficult because he cannot see what is taking place inside the machine, and
must use a certain amount of deductive logic to understand what happens when
he makes a process change. Also, a condition such as poor centrate quality
is more easily overlooked, since the process is fully contained; by compari-
son, the signs of poor performance on the belt filter press are readily
visible.
On most centrifuges, changes in the bowl speed, scroll differential or pool
depth require some disassembly of the machine, and so are less likely to be
attempted than the type of adjustments that are applicable to the belt press.
As a result, the centrifuge requires a more extensive program of pretesting
to select the correct machine settings before it is placed into normal
service.
The use of the automatically controlled backdrive greatly simplifies the
operation of the centrifuge, particularly the maintenance of stable perfor-
mance. The programming of the automatic controller makes startup very easy,
by allowing the centrifuge to build up the correct inventory of solids and
then adjusting the scroll speed to discharge them at the appropriate rate.
The use of scroll torque to control scroll speed is very successful in com-
pensating for variations in feed flow and suspended solids concentration.
601
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During the testing program, feed flow jumped to as high as twice the normal
flow rate for short periods. When this happened, the centrifuge suffered a
temporary loss in recovery, but maintained excellent cake dryness. The
automatic backdrive provides a means for maintaining stable operation which
does not yet appear to be available for the belt filter press. Since the
process is fully enclosed, the problem of sludge spillage is not a factor,
as it is with the belt filter press. Where variation in sludge quality can
cause considerable variation in polymer requirement, such as in the dewater-
ing of combined primary and waste activated sludges, it is still recommended
that storage be provided ahead of dewatering to equalize the fluctuations in
sludge quality.
C. MAINTENANCE OF WEARING PARTS
1. Belt Filter Press
The belt filter press has a large number of moving parts, including bearings,
rollers, and hydraulic pistons for belt tracking. Nevertheless, most parts
are small enough and easily accessible, so that even most small facilities
would have no difficulty in maintaining these parts. Specification of long
life parts with effective seals to prevent water intrusion would be expected
to keep replacement costs to an acceptable level.
The major concern with this type of device is the matter of belt life. Al-
though it was found that a set of belts could be easily replaced in a matter
of hours, the cost for a set of belts for a two meter machine is likely to be
$3,000 - $5,000, and the Districts' experience indicates that the life is
likely to be only about three to six months in continuous service.
During the course of the testing of the press that was operated 1,600 hours,
three belt sections failed, amounting to one full set of belts. One belt was
torn immediately after startup, apparently due to an improperly adjusted
scraper blade. The other two occurred near the end of the testing. The belt
manufacturer stated that these failures were due to a weaving problem that
caused reduced strength and that had since been corrected; however, by this
time, a number of frayed areas had appeared, indicating that the material was
reaching the end of its life under any circumstances.
The second press, which was operated only 350 hours, also damaged three sets
of belts. This machine exhibited difficulty in obtaining a uniform distri-
bution of sludge on the belts at the end of the gravity drainage zone. This
poor distribution apparently allowed the belts to wrinkle as they passed
through the rollers, and the fabric was weakened at these points and eventu-
ally torn. The poor distribution of sludge was believed to be caused by
improper cleaning of the lower belt by the washwater system. Although a
number of different belt types and spray systems were tried, this problem was
never solved.
Scraper blades on the first machine were found to be worn out after 1,400
hours. Sharp, well adjusted scraper blades are critical to the maintenance
of acceptable recovery. The blades must be adjusted to ride closely on the
belt, but if too tight, can catch any irregularity in the belt and tear it.
602
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The cost and time to replace scraper blades is considered to be minor. How-
ever, the condition and adjustment of the blades is a critical feature that
should be checked frequently.
2. Centrifuge
The moving parts of the centrifuge are relatively fewer and larger. Handling
of the large, rotating assemblies would be of most concern at small plants.
In a large plant it is practical to provide suitable overhead or mobile
cranes to handle these assemblies, and it is also likely that sufficiently
skilled workers would be available for on-site maintenance. At small plants,
some factory maintenance of the rotating assemblies may be required.
The Districts have operated high-speed, countercurrent flow scroll centri-
fuges for over a decade, providing a greater base of experience to evaluate
this type of device. In that time, it has been found that wear of the scroll
tips is the only item of major concern. Bearing failures have been almost
nonexistent. Scroll tips have been hard-faced with new weld material
approximately every 2,000 hours when used in continuous service on DPS. All
repair has been performed on-site. A test of a scroll with ceramic tipped
flights is also now in progress. To date, this has exhibited a life of at
least eight times that for conventional hard-facing. Since the new centri-
fuges operate with a scroll differential an order of magnitude lower than
the old centrifuges, a further increase in life is expected. Overall, scroll
maintenance is expected to be an easily manageable problem, particularly for
a facility the size of the JWPCP.
The automatic backdrive equipment includes high pressure hydraulic systems,
and conventional electronic controllers for closed-loop control. Neither
have exhibited any particular maintenance problems, although they do create
the requirement for some degree of skilled maintenance.
D. NOISE AND VIBRATION
Noise and vibration are of little concern for a belt filter press installa-
tion. Noise from a scroll centrifuge is quite noticeable, but not so high
as to require ear protection for workers. Vibration is also noticeable.
This caused a small problem, because the automatic controller was mounted on
the same platform as the centrifuge, causing some electrical connections to
loosen up. Since this was a temporary installation, no provision had been
made to shield the controller from vibration. In a permanent installation,
it is recommended that sensitive electronic controls be isolated from vibra-
tion. Structural components and fasteners should be designed to resist
vibration. The rotating assemblies of the centrifuge may require a periodic
rebalancing, especially after rebuilding of scroll tips, to avoid excessive
bearing wear.
E. REQUIREMENT FOR PRE-SCREENING
Belt filter presses were tested with both screened and unscreened PDS.
Screening was provided by a rotating cylindrical strainer with 0.25 cm (0.1")
603
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slots. When operated on unscreened sludge, fibrous materials were found to
quickly build up on scraper blades and in the washwater unit enclosure.
Larger objects were also found in the sludge which appeared capable of punc-
turing the belts. Prescreening of the sludge is thus considered an important
adjunct for a belt filter press facility. Operation of the scroll centrifuge
on unscreened sludge has not presented any problems.
F. CLEANUP
Operation of a belt filter press can be rather messy, particularly when
failure due to under-conditioning causes sludge to run out from the sides of
the machine. One of the presses also had a constant problem of filtrate and
washwater spilling from the sides of the machine, even during stable opera-
tion, and a fine mist escaping from the spray wash unit. Scraper units and
filtrate trays are sites where solids build up. It is recommended that a
belt press installation be designed with daily washdown by hosing in mind.
Good drainage and safe walking areas are thus important.
Since the centrifuge is a fully enclosed machine, cleanliness is much less of
a problem. Problems are confined to conveyor areas, which should be designed
for frequent washdown for both centrifuges and belt filter presses.
G. ODOR EMISSION
The belt filter press generally has large free surface areas where the sludge
is exposed to the atmosphere, particularly in the gravity drainage zone. A
considerable amount of odors can be emitted, especially if the sludge is in-
adequately digested. Also, a large amount of steam can be released if the
sludge is still hot from anaerobic digestion. If the presses are located
within a building, large vent hoods over each press would be recommended, and
the ventilation system should be designed for good drainage of condensation.
The centrifuge is an enclosed machine, so odor emission is less of a problem.
A vent is necessary because of the windage from the rotating assembly, and
the duct work from this vent should also be designed for drainage of conden-
sate.
H. AUXILIARY WATER REQUIREMENTS
The belt filter presses require an auxiliary supply of water for washing the
belts. The flow rate required was found to be roughly 50 to 100 percent of
the flow rate of sludge to the machine, and the pressure is typically 7
kgf/cm (100 psi) or more. Since the cost of the water is relatively minor,
the auxiliary water is only a problem if some kind of treatment must be
provided for the liquid sidestream.
The centrifuge requires only a small amount of auxiliary water for cooling.
I. ENERGY REQUIREMENTS
The major power requirement for the belt press derives from the pumping of
washwater. Overall, the low speed scroll centrifuge requires about three
604
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times as much power when operated at the capacities indicated in this paper.
In spite of this higher demand, the power costs were minor when compared to
the other costs of dewatering and disposal.
VI. CONCLUSIONS
1. The belt filter press and the low speed scroll centrifuge with the auto-
matically controlled backdrive can achieve equivalent performance on di-
gested primary sludge, and blended sludge containing as much as 50 per-
cent by weight of digested waste activated sludge. For both machines,
dewatering of combined sludge containing a high percentage of DWAS re-
sulted in low recovery, high polymer requirement, and a dewatered cake
that was difficult to handle.
2. The addition of the automatically controlled, variable speed backdrive
to the centrifuge resulted in a great improvement in cake dryness at
the expense of hydraulic capacity. This change placed the centrifuge
in direct competition with the belt filter press.
3. Both the belt filter press and the low speed scroll centrifuge can
achieve a wide variety of results on any given sludge, depending on the
selection of feed rate and polymer dosage, and the adjustments of
various mechanical features. This was found to be especially true on
the belt press, which allows for easy adjustment of several mechanical
variables. The automatically controlled backdrive provides a similar
flexibility for the centrifuge.
4. Both types of device were relatively easy to start up and operate. Belt
filter press operation is easier to understand for the novice because
all parts of the process are clearly visible. The belt filter press was
more subject to instability and drastic failure characterized by sludge
spillage when under-conditioning of sludge occurred. The automatic
backdrive contributed significantly to the stability of performance
achieved by the centrifuge.
5. The major concern for maintenance of the belt filter press is belt life.
Belts would be expected to last three to six months in continuous
service, and cost $3,000 to $5,000 per set for a two meter machine. For
the centrifuge, scroll tip replacement is the major maintenance item.
Ceramic hardfacing would be expected to last several years in continuous
service. Replacement costs are comparable to the costs for one set of
belts on the belt filter press. If the replacement could not be per-
formed onsite, additional costs would be incurred for transportation to
the factory. The centrifuge's large, rotating assemblies may be more
difficult to maintain at a smaller facility than the type of components
that make up a belt filter press.
6. Belt filter press operation can be relatively messy, and emit signifi-
cant amounts of odor and moisture. Scroll centrifuge operation is sub-
ject to moderate noise and vibration.
605
-------
REFERENCES
1. Summary Report - Waste Activated Sludge Processing Studies for the Joint
Water Pollution Control Plant. Los Angeles County Sanitation Districts,
Whittier, CA, January 1979.
2. LeBrun, Tom and Rick Trubiano, Memorandum-Summary of Belt Filter Press
Performance. Los Angeles County Sanitation Districts, Whittier, CA.,
April 27, 1978.
606
-------
THERMAL CONVERSION OF SLUDGE IN A MULTIPLE HEARTH FURNACE,
USING A SUB-STIOCHIOMETRIC SUPPLY OF OXYGEN
Joseph B. Farrell
Wastewater Research Division
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268 USA
INTRODUCTION
In June 1975, the Interstate Sanitation Commission (ISC) released a
report (1) by an engineering firm, Camp, Dresser, and McKee (COM), which
evaluated the alternatives for sludge disposal for the New York Metropolitan
Area if ocean disposal were no longer permitted. The engineering firm con-
cluded that the most cost-effective alternative was incineration in multiple
hearth furnaces with disposal of sludge ash to landfill. In the New York
Metropolitan Area, the suggestion that all sludge be incinerated would be
unpalatable. Public experience with municipal solid waste incinerators and
with incinerators from multi-dwelling housing units has been bad in this
area, and an adverse reaction from the public sectors would likely develop
even though sludge incineration would be much more likely to be free of
nuisance than solid waste incineration. At least in part to avoid this
potential obstacle (in this writer's opinion), the authors of the report
suggested that "pyrolysis" could be used to process the sludge. The "pyrolysis1
could be conducted in a multiple hearth furnace. The technology was not yet
developed and could conceivably fail. In that case, the multiple hearth
furnaces could be used to incinerate the sludge. In a second more detailed
report (2), the authors proposed a "pyrolysis" process that followed closely
the method suggested by Majima, et al. (3), in which sludge was predried
before it entered a multiple hearth furnace for the pyrolysis step.
Shortly after the COM report (1) to the ISC became available, this
writer was reviewing plans for sludge disposal at the Blue Plains wastewater
treatment plant in Washington, D.C. One of the disposal options seriously
being considered at this time was incineration. Local codes required that
the incinerator off-gases be passed through an afterburner and the design
engineers proposed an exit temperature of 870 °C. Combustion of a high
grade fuel—oil or gas--would be required in the afterburner. Fuel costs
would be excessive and a valuable national resource would be consumed. The
writer realized that the "pyrolysis" mode of operation of a multiple hearth
furnace (MHF) would produce a burnable gas at the top of the furnace. After-
burning very likely could be achieved without the need for high quality
fuel. As a consequence, a project to investigate "pyrolysis" in a MHF was
included in the Municipal Environmental Research Laboratory (MERL) research
-------
The MERL Laboratory contacted the Interstate Sanitation Commission
(ISC) and found them eager to pursue an evaluation. The ISC interests were
slightly different- from MERL's. They were interested in the potential of
"pyrolysis" for reducing the emissions of toxic materials to the environment.
The investigation was planned to meet both objectives. The facilities to be
used were the pilot plant of Nichols Engineering Company at Belle Meade,
N.J. Sludges from the New York Metropolitan Area were to be tested. Experi-
mental work was carried out in two phases, one completed in 1977, and the
second in 1979. Final reports on the entire study were received in late
1979.
The processes for "pyrolyzing" sludge envisioned and actually carried
out do not fit the conventional sense of the term pyrolysis. This has
caused a degree of controversy in the United States over calling the pro-
posed processes "pyrolysis." Ordinarily, pyrolysis means decomposition in
the absence of oxygen. There are numerous pyrolytic processes: thermal
cracking of petroleum, destructive distillation of wood, pyrolysis of coal,
pyrolysis of solid waste (using indirect heat transfer). The process con-
figurations proposed for sludge introduce air or oxygen into the reaction
vessel. The gaseous products of pyrolytic decomposition of sludge are
partially combusted within the reactor to supply heat, and in some operating
modes the sludge solids are eventually exposed to an oxygen-rich atmosphere.
Uncombusted gaseous products are generally completely combusted in an after-
burner. Overall results superficially resemble incineration. In fairness,
it should be said that the specific process conditions may produce a solid
residue as well as particulate and gaseous pollutant streams much different
from those produced by incineration.
Objectors to the term "pyrolysis" evidently suspect that a new name has
been invented for an old process—that "pyrolysis" is essentially incinera-
tion with the same old pollutional potential but with a new name that carries
with it the implication that there is no release of gaseous pollutants. On
the other hand, alternative names such as starved-air combustion or partial
combustion do not convey the idea that the processes offer better control of
the reaction at the solid-gas interface than conventional combustion. As a
compromise this presentation refers to the "pyrolysis" processes for sludge
as thermal conversion with sub-stoichiometric oxygen supply (TC-SSOS).
Publications by Japanese authors (3) indicated that sludge could be
decomposed in a multiple hearth furnace (MHF) under conditions that did not
expose the sludge to strongly oxidizing conditions, and that produced a
combustible fuel gas at the top of the furnace. Because the sludge is not
thoroughly combusted, it does not release all of its heating value; con-
sequently, some strategem must be used to allow autothermal operation.
These authors predried the sludge to about 70 percent solids. In our
approach, it was decided to achieve the same goal by dewatering the sludge
to a high degree by means of filter presses or diaphragm filter presses.
Some supplemental fuel might be required in the MHF, but the large amount of
fuel required for the afterburner would be eliminated.
The primary objectives of the experiments carried out by Nichols Engi-
neering for the ISC were as follows:
608
-------
1. Demonstrate that by controlling the air supply, a MHF can be
operated to discharge a combustible gas at the top hearth and an
inert residue from the bottom hearth. The combustible gas should
have sufficient heat of combustion to burn completely in an after-
burner, reducing unburned hydrocarbon to acceptable levels. (This
operating procedure is referred to as thermal conversion, sub-
stoichiometric oxygen supply: TC-SSOS).
2. Investigate the air pollutional discharges and solid residues
produced by TC-SSOS and compare them to operation of the MHF in
the incineration mode.
As the following presentation indicates, the objectives were incom-
pletely realized. Additionally, review and assessment of the air pollution
data have not yet been completed. Nevertheless, much knowledge has been
gained. New ways to process sludge in a MHF have been discovered that may
possibly lead to useful solid products from sludge.
EXPERIMENTAL APPARATUS
A schematic diagram of the experimental apparatus is presented in
Figure 1. Also shown on this diagram are the various sampling points. The
preparation of the filter cake was carried out in advance of the furnace
runs. During a four-day period preceding a series of furnace runs, sludge
was delivered from the sewage treatment plants to the Belle Meade pilot
plant by tank truck, dewatered, and stored in 200 liter drums.
MHF - the TC-SSOS runs were carried out in a 0.91 m diameter six hearth
MHF, which is illustrated in Figure 2. Sludge cake is metered by a feed
conveyor and enters the top hearth (Hearth 1) through a rotary star valve.
The sludge cake is rabbled inward towards the center drophole, through which
it falls to Hearth 2. Here the sludge cake is rabbled outward, where it
falls through the drophole to Hearth 3, and so on down through the furnace.
Final product exits from Hearth 6 into a sealed drum.
Each hearth is equipped with a gas burner and metered gas and air
supply. Steam can be injected on each hearth. There is an exhaust line
containing a damper (valve) from each hearth. These lines are joined in a
common manifold leading to the afterburner. The afterburner is'a refractory-
lined chamber, 2 m^ in volume, equipped with a gas-air burner and an auxiliary
air supply. Actual hearth area in the furnace is about 3.1 m2. Gas tempera-
ture can be measured on all hearths, and bed temperature can be measured on
Hearths 3, 4, and 5. The temperature is also measured, in the approximate
center of the afterburner. Gases from the afterburner are drawn through a
scrubber where they are cleaned and cooled, and discharged to the atmosphere.
Filter Press - Preliminary determinations of dewatering rates were
conducted with a small filter press with 0.3 x 0.3 meter plates. Sludge
cake for the furnace runs was produced on a 1.2 x 1.2 m filter press. For
609
-------
CTi
h-1
o
FILTER
PRESS
WATER
1 Sludge sampling
2 Feed sampling
3 Filtrate sampling
4 Hourly furnace residue sampling
5 Analyses for SOX, NOX, and hydrocarbons
6 Particulate sampling
7 Scrubber water sampling
8 Influent water sample
FIGURE1 ILLUSTRATION OF MATERIAL FLOW WITH
SAMPLING POINTS INDICATED
-------
1 Gas-air inlets, flows are metered
2 Low pressure air blower
3 Rotating rabble arm, 2 or 4 per hearth (only
rabble arm on first hearth is shown)
4 Ash hopper
5 Charge fed by belt feeder
6 Rotary valve
FIGURE2 FLOW SHEET OF BELLE MEADE MHF
611
-------
the first of the four experimental campaigns, the plates were of convention-
al design; for all later campaigns, the plates were equipped with diaphragms
that permitted squeezing of the cake to produce a higher solids content.
Cake thickness was 3.2 cm for the first campaign and about 2.7 cm for later
campaigns. Maximum pressures applied were 689 k Pa (100 psi) in Campaigns
II and III and 827 k Pa for Campaign IV.
The cakes stored in the drums for the furnace runs were in large frag-
ments and could give trouble in the small MHF by plugging dropholes or by
burning incompletely—incomplete burning was experienced in some of the
Campaign I runs. For Campaign II, a rotating blade cake breaker was used to
reduce the size of the cake. For Campaigns III and IV, a cake breaker com-
prised of two motor-driven rollers was used to crush the cake and blend
sludge batches of different moisture contents.
ANALYTICAL PROCEDURES
A great variety of analytical measurements were made. For measurements
of typical wastewater parameters such as BOD, procedures outlined in Standard
Methods (4) were used.
Sludges and particulate samples were analyzed for metals. Methods used
were atomic absorption, X-ray fluorescence, and inductively coupled argon
plasma (ICAP). Samples were dissolved by digestion in aqua regia in most
cases. Samples subjected to high temperatures, in some cases, were also put
in solution by digestion with HF.
Ultimate and proximate analyses of the sludges and residues were con-
ducted using standard ASTM procedures (5). Carbon, hydrogen, nitrogen,
sulfur, and ash are determined directly and oxygen is determined by differ-
ence. Heat of combustion is determined, using a Parr bomb and sodium peroxide
The "proximate analyses for fuels" was used as a control procedure and
was run hourly on sludge feed and residue. Proximate analyses determine
volatiles (VOL), fixed carbon (FC), and ash. To determine volatiles, the
solids are dried at 105 °C and then heated in the absence of air for 7-1/2
minutes at 949 °C. The percent volatiles in the loss in weight relative to
the weight of the dried sample. To determine fixed carbon, the devolatilized
sample is burned to ash at 949 °C. The net loss in weight is the fixed
carbon. This determination also yields the percent ash. It is important to
note that the volatiles determined by proximate analyses does not correspond
to the volatile solids determination carried out by sanitary engineers. The
sum of VOL and FC is essentially the same as the sanitary engineer's volatile
solids. Reference made to volatiles (VOL) in this presentation refers to
the volatiles of the proximate analysis for fuels and never to the sanitary
engineer's volatile solids determination.
Particulate discharges were measured using standard EPA methods. All
measurements were made on unabated discharges, that is, upstream from the
particle removal devices. Total particulate catches were measured by the
612
-------
EPA-5 method (6) and the SASS train (7). The SASS train not only gives
total particulate but fractionates the particulates into size ranges. Experi-
ments were also made with the Anderson sampler, which also fractionates the
particulates.
Detailed consideration of these devices is not warranted here because
discussion of air pollution results is not considered in this presentation.
It is necessary to note that for both the EPA-5 and the SASS train, the
sampled gases are withdrawn isokinetically, and are brought to an oven main-
tained at a temperature above the dewpoint of the gas (121 °C). The final
filter, which is a glass fiber filter, reportedly removes particles down to
0.1 micrometer in size.
Analyses were also conducted for NOX and S02- No further discussion is
warranted here because results have not been reported in this presentation.
EXPERIMENTAL RESULTS
Filter Press Experiments
Preliminary experiments with the 0.3 x 0.3 m filter press were con-
ducted to determine whether the sludges proposed for TC-SSOS could be
dewatered at reasonable rates to sufficiently high solids contents. Results
of unoptimized tests carried out at 689 k Pa (100 psi) differential pressure,
using polymers and lime and ferric chloride as conditioning agents, are
presented in Table 1. Solids contents above 26 percent (conditioning-agent
free basis) were obtained in all cases. Of eight sludges, all but one could
be dewatered either with polymers or with ferric chloride and lime. Better
results were expected with fresher sludge, optimized dose of conditioning
agent, and the use of a diaphragm filter press. Consequently, the thermal
conversion tests were scheduled to proceed.
Prior to a series of thermal conversion tests, a large batch of de-
watered sludge cake must be produced. Liquid sludge, delivered by tank
truck is fed together with polymer solution or aqueous ferric chloride into
a pug mill, where the two streams are mixed. The mixture is pumped to a
holding tank which is kept well-mixed by an air lance. For ferric chloride-
lime conditioning, the lime (Ca(OH)2) is added to the holding tank. The
sludge is delivered to the filter press by a diaphragm pump. Pumping is
stopped when pressure reaches 480-550 k Pa (70-80 psi). Compressed air is
applied to the diaphragms (689 k Pa) and the cake is squeezed for 5-15
minutes. Sludge cake is stored in drums 1 to 4 days before use.
Results obtained during the first three experimental campaigns are pre-
sented below:
613
-------
TABLE 1
Preliminary Dewatering Experiments with Sludges
from the New York Metropolitan Area
Sludge
Source
Coney Island, NYC Digested
26th Ward, NYC
26th Ward, NYC
Cedar Creek
Raw
Digested
Raw
Conditioning Agent
Dose (WT %)
Lime and
Ferric
Polymer Chloride
.72
0.20
0.65
0.35
35
34.5
32
20
Percent Solids
in Cake
Conditioning
Agent-Free
Actual Basis
39.9
44.9*
26.8
26.7*
25.1
40.8
22.5
31.9
39.9
37.6
26.8
21.3
25.
34,
22.5
28.1
If amount of inert additive (such as a conditioning agent) is not too
large, its addition will not affect thermal performance of a sludge in a
MHF provided solids content on an additive-free basis is unchanged.
Chemically conditioned sludges indicated by the asterisk will have poorer
thermal performance than the corresponding polymer-conditioned sludge
because additive-free solids content is lower.
614
-------
SLUDGE CAMPAIGN % SOLIDS
Coney Island Digested I 31.9
Coney Island Raw II A 41.4
II B 42.2
Rahway Raw III 31.5
Jersey City Primary IV 51.0
These results were obtained with polymer conditioning. In Campaign II B, a
considerable amount of sludge was conditioned with lime and ferric chloride.
Poor results were being obtained with polymer, so lime and ferric chloride
were used instead. The sludge could then be filtered but solids content was
not improved.
Solids contents for these campaigns were lower than anticipated. Part
of the reason for the poorer results was the concentration of the operating
staff on producing sludge cake at a high rate, unfortunately at the expense
of cake solids content. Consequently, the solids contents were lower than
anticipated. In Campaign IV, with Jersey City polymer-conditioned primary
sludge, higher pressures were used (up to 827 k Pa - 120 psig) and the
squeezing period was extended to about 47 minutes. Sludge cake averaged
51.0 percent solids.
These results point up an important consideration. It is important to
have a properly designed dewatering system with adequate capacity if thermal
conversion processes are to be economically attractive. Diaphragm filter
presses can produce sludge cake at higher than design rates if cycle times
are shortened, but lower cake solids will result.
Operating Modes and Campaign Descriptions
In the course of the investigation, four thermal conversion modes were
used, one with greater than stoichiometric oxygen supply (TC-GSOS) and three
with sub-stoichiometric oxygen supply (TC-SSOS). The presentation will be
made simpler if these modes are explained in advance. The modes are:
TC-GSOS: Incineration (INC)
TC-SSOS: Low temperature char (LTC)
: High temperature char (HTC)
: Carbon burned ash (CBA)
INC: Incineration is the normal operating mode for sludge disposal in
an MHF. Air in substantial excess is introduced on the lower
hearths and is still in excess in the exhaust gas leaving the MHF.
Sludge drie's on the upper hearths, volatile combustible gases are
released and burn in the overhead space in the middle hearths, and
the fixed carbon is burned out of the solids as they proceed to
615
-------
the lower hearths. Normally there is a substantial countercurrent
effect. Ash is cooled by incoming air and exiting gases are cooled
as they evaporate moisture from the sludge. Cooling of the exiting
gas is desirable because there is excess air present. Combustion
could take place on the upper hearths if the gas were hot and
could continue out of the furnace into the duct work. Unfortunate-
ly, volatile hydrocarbons released into the cool exiting gas do
not combust, and excessive hydrocarbon levels can result.
LTC, HTC: Both of these operating modes produce char. LTC utilizes
a lower average temperature in the furnace so the char contains
more VOL and FC. An arbitrarily selected maximum temperature is
650 °C. HTC utilizes temperatures up to 870 °C. For both methods,
it is important not to have high oxygen concentrations near the
solid phase, because this could cause combustion at the surface of
the solids. Low oxygen concentrations should prevail on all
hearths, The difference between the LTC and HTC mode is indistinct
--there is actually a continuum of conditions with the proportion
of VOL and FC relative to inerts in the ash depending on the tem-
perature level. Because there is a deficiency of oxygen for com-
bustion, the gases leaving the furnace will contain unburned
gaseous substances.
CBA: Like LTC and HTC, this mode uses a sub-stoichiometric amount of
air; that is, less oxygen is added than is needed to completely
burn the sludge. However, on the lower hearths, a local excess of
oxygen is used in order to burn out the residual VOL and FC in the
ash. In the upper hearths, the gas streams will contain combustible
gases such as CO, possibly H2, and low molecular weight hydro-
carbons.
A general description of the experimental campaigns, their objectives
and findings follows. Table 2, which will be used in discussions later on,
lists the significant runs in the various campaigns.
CAMPAIGN I: Coney Island digested sludge was polymer conditioned and
filter pressed. Average solids content was 32-35%. No cake breaker
was used. Cake frequently came through furnace in unburned lumps;
consequently, a cake breaker was used in all later campaigns. This
campaign was primarily a learning operation. For example, in Table 2,
four of the runs in Campaign I used less then 10 percent of the
theoretical air needed for combustion. Excessive quantities of natural
gas were used during these runs for heating the MHF.
CAMPAIGN II (A and B): Coney Island digested sludge was polymer condi-
tioned and dewatered with the diaphragm press to about 42% solids. The
II A portion of this campaign was conducted in a winter weather emer-
gency and natural gas could not be used. The furnace was preheated by
burning wood in it. Fortunately, the sludge cake was high in solids
and autogeneous operation was achieved. The furnace run summary sheet
for Run II A 3 is shown in Figure 3. Inlet air flow to each hearth was
modulated to keep as nearly uniform temperature as possible on the
616
-------
TABLE 2
Summary of Pertinent Runs Made in Campaigns I, II, and III
Run
Campaign No.
I
II A
II B
III
8
9,
31
1R1
2.1
2.2
2'
3
7
8
1
Run
Duration
(HR)
6
5
5.75
5
6
7
Net Air
Flow to
Furnace
(SCFM)
107
(-6)
8
(-10)
127
128
101
69.4
111.9
94.9
225.8
91.2
116.2
5.5
12.3
4
2.5
5
5
2
4.75
70.7
72.5
106.3
166.1
217.0
146.7
117.5
116.9
Theoretical VC and
Air Needed Vol. in
to Combust Residue
Sludge (%) (%)
111.7
-6
8.4
7.3
-10.4
133.0
134.0
105.0
45.4:
73.3:
62.1-
170.8,
69.0:
87.9'
58.5
60.0
88.0
137.5
179
121
97
3
23.5
28.0
24
4
12
0
15
96.8
2.4
19.1
38.4
20.3
2.2
35.0
23.9
31.0
19.6
7.1
4.5
5.5
9.7
9.4
13.6
T av/
654
514
705
783
644
687
538
648
679
639
602
684
666
684
Operating
Modes
HTC
LTC
HTC
INC
LTC,S-D4
HTC
LTC,S-Dj
HTC,S-D-
CBA
INC
INC
INC,LowO,
CBA '
CBA
1 - Runs that were 5 hours or longer and had no significant process upset.
2 - Steam injection
3 - Data for these runs were plotted in Figure 6
4 - S-D means split draft.
5 - T av. is the average of the six hearth temperatures.
617
-------
Furnace run summary sheet, Campaign II5 Part A
Steady state 3 Date 2-3 & 4, 1977
Stack gas :
Afterburner & hearth
flows (SCFM):
Fuel Air
0
13.6
10
18.5 + 1.5
40.7 + .7
20.7 + 1.3
Remarks
ar LLI
*v
s
1510
Oi""1
b
s
*^
X"
*v
V
1 /
V
f^
f
s
U
I
V
325
250
1400
1450
1400
129
^
DSCFM
7oCO
Grains/DSCF
Feed analysis/flow:
Total 250 Ib/hr.
Water 156.20 Ib/hr.
Solids 93.80 Ib/hr.
Ash 16.49 Ib/hr.
Vol. 64.93 Ib/hr.
F.C. 12.38 Ib/hr.
E.V. 9039 BTU/#(dry)
,— Steam
0 Ib/hr.
Product analysis/flow
Total 17.42 Ib/hr.
Ash 13.88 Ib/hr.
Vol. .623 Ib/hr.
F.C. 2.913 Ib/hr.
H.V. 3795 BTU/i'/(dry)
Pyrolys is
Andersens taken at 22:37 & 01:48
FIGURE 3: SUMMARY FOR RUN II A3
618
-------
central hearths. Note that the gases leaving the furnace increase in
temperature 485 °F (270 °C) when air is added to the afterburner.
In the B portion of Campaign II, the "split-draft" technique was
utilized. Instead of withdrawing all of the exhaust gases from the top
hearth, the damper in the line connecting Hearth 6 (the lowest hearth)
to the manifold leading to the afterburner was partially opened.
Splitting the "draft" between the top and bottom hearths leads some of
the combustion gases downward. Because there is an inflow of gases low
in oxygen into the lower hearths, introduction of air at the lower
hearths is less likely to cause combustion at the solid surface in
these hearths. Additionally, if the gases contain incompletely burned
gases, heat can be generated in the lower hearths by addition of air.
Unfortunately, it was not possible to measure the amount of the gases
drawn from the top and bottom hearth. Judging from the position of the
dampers, the flow from the top hearth was about 3 to 4 times the flow
from the bottom hearth in split draft operation.
CAMPAIGN III: Feed was Rahway, N. J., raw sludge, polymer conditioned
and dewatered on the diaphragm press. Average solids content was 31.5%.
This run was largely devoted to developing comparative LTC, HTC, and
INC conditions for air pollution studies. Split drafting was used in
the LTC and HTC runs. A few CBA runs were made. Figure 4 shows a run
summary sheet for Run III.3. Relatively high flow of air to the lower
hearths burned the VOL and FC out of the residue. Note the substantial
temperature increase from the top hearth to the afterburner. The small
amount of natural gas (1.2 SCFM) added at the afterburner does not add
significantly to the temperature increase. It generates about 1270
kJ/min, which just slightly overcompensates for the afterburner heat
losses, which are estimated to be 875 kJ/min at 1600 °F (871 °C).
CAMPAIGN IV: Feed was Jersey City, N. J., raw sludge, polymer con-
ditioned and dewatered on the diaphragm press. Solids content averaged
51.0%. This campaign took place about a year after the other campaigns.
Its purpose was to obtain definitive information on air pollutional
discharges and the effect of the various operating modes on these
discharges.
Residence Time in the MHF
During the course of a run in Campaign I, a batch of sludge cake which
had been conditioned with ferric chloride and lime was introduced into the
MHF with no attempt to blend it beforehand with the preceding polymer-
conditioned batch. This provided an excellent opportunity to determine the
residence time in the MHF by determining iron and calcium content of the
exiting ash. Rabble arm speed during this run (Run 1.12) was 0.17 RPM.
Results of the experiment obtained with calcium are presented in Figure
5. The ordinate shows the relative departure that still exists between C
and its ultimate value Cp. Results were quite similar for iron but the
experimental points more scattered. Residence time of 1.57 hours, assuming
plug flow, was calculated on the basis of an average depth of 1.5 inches on
619
-------
Furnace run summary sheet, Campaign III
Steady state 3 Date 6/23/77
Time 3-7:00
Afterburner & hearth
flows (SCFM) :
Fuel Air
1.2+.3
126
0
0
0.88+.11 18+.5
1+.
0
0
38+.5
1605
°F
+32
v/
1196+26
1759+22
1759+26
1235+48
884+49
688+56
Stack gas :
70C02
DSCFM
7o0
Grains /DSCF
Feed analysis /flow :
Total 245
Water 164.64
Solids 80.36
Ash 18.88
Vol. 54.08
F.C. 7.47
H.V- 10,109
Ib/hr.
Ib/hr.
Ib/hr.
Ib/hr.
Ib/hr.
Ib/hr.
BTU/#(dry)
. — Steam
0 Ib/hr
1. 7 RPM
Product analysis/flow
Total 20.7 Ib/hr.
Ash 19'.23 Ib/hr.
Vol. 1.34 Ib/hr.
F.C. 0.13 Ib/hr.
H.V. 573 BTU/#(drv)
Remarks :
Reducing
atmosphere in the devolatilizing hearths and excess oxygen in
the carbon burning hearths.
FIGURE 4: SUMMARY FOR RUN III 3
620
-------
u
CF = NEW FEED COMPOSITION
CQ = ORIGINAL UNIFORM COMPOSITION
C = COMPOSITION AT MHF OUTLET
plug flow
completely mixed
0 0.5 1.0 1.5 2.0 2.5 3.0
TIME FROM FEED COMPOSITION CHANGE (HR)
FIGURES EFFECT OF A STEP CHANGE IN FEED COMPOSITION
ON OUTLET CONCENTRATION
-------
the available hearth area and an average ash density of 0.32 g/cm3. Passage
of the sludge ash through the unit was much faster than the plug flow resi-
dence time would indicate. More rapid passage was expected than predicted
by the plug flow model because there is always a "dead bed" residue on the
hearths of a MHF that does not move and slowly mixes with the surface
materials. Passage, however, is even faster than is indicated by rabble arm
speed (6 min per revolution or 0.6 hour for six hearths). Consideration of
the geometry of the MHF, particularly the location of dropholes on the
alternating "in" and "out" hearths, indicate that shortcircuiting of sludge
or ash to lower hearths could occur. This would account for the rapid
appearance of the tracer in the exiting stream.
Residue analyses from INC runs indicated that VOL and FC residues were
greater than expected. The rapid passage from inlet to outlet of some
solids is probably the cause of the high values. This effect would doubt-
lessly be lower with larger diameter furnaces, and burnout would be better.
The experiment serves as a reminder that scale-up to full scale equipment
must be done judiciously.
Solid Products Produced
As noted earlier, the furnaces can be run in four modes, LTC, HTC, CBA,
and INC. The CBA and INC modes produce essentially the same product, a
thoroughly burned-out incinerator ash. The HTC mode produces a char with
very little volatile material whereas the LTC mode contains more fixed
carbon and substantially more volatile material.
A comparison of the feed sludge with products is shown in Table 3 for
two operating modes. As Table 2 shows, in the runs corresponding to these
char samples, oxygen supply was substantially below the stoichiometric
requirement for combustion of the sludge. The temperature shown in Table 3
is the average of the six hearth temperatures. The lower average tempera-
ture produces a material higher in both volatiles and fixed carbon than the
high temperature runs. Despite significant differences in volatiles and
fixed carbon, the chars have similar heats of combustion on an ash-free
basis. The LTC chars have heats of combustion on a total mass basis that
are as high as RDF and some poor quality coals.
Both the LTC and HTC chars are free-flowing mixtures of powder and
granules. Bulk densities are low—substantially lower than for incinerator
ash. A char was removed from the MHF and burned to a low VOL and FC content.
Samples were removed periodically during the experiment and unsettled density
as well as VOL and FC were measured. The following equation expresses the
relationship obtained between density and the sum of VOL and FC:
p = 3.2 x 10-4X2 - 0.02X + 0.575
where X = sum of FC and VOL
P = density (g/cm3)
622
-------
TABLE 3
Comparison of Char Produced in LTC and
HTC Operating Modes with Feed Sludge
Material Characteristics
Run
Material
Source
%Ash
%Vol
%FC
Heat of Average
Combustion Temperature^
(kcal/kg) (°C)
Actual
II A2
II A3
III 1
III 2
Feed
Residue
Feed
Residue
Feed
Residue
Feed
Residue
16.
61.
17.
79.
24.
69.
25.
80.
8
6
6
7
3
0
1
4
71.
9.
69.
3.
66.
11.
65.
3.
6
1
2
6
7
7
9
5
11.
29.
13.
16.
9.
19.
9.
16.
6
3
2
7
0
3
0
1
5205
3048
5021
1618
5806
2313
5659
1542
Ash-Free
6256 514
7939
6094 705
7972
7672 538
7461
7555 648
7867
Operating
Mode
LTC
HTC
LTC
HTC
1 - Average of the six hearth temperatures
623
-------
Typical densities (calculated from this equation) are:
Product % FC + VOL (g/cm3)
LTC char 25 0.28
HTC char 12.5 0.32
incinerator ash 2 0.55
The properties of the chars, such as adsorbent power or degree of water
solubility have not yet been investigated.
Correlation of Char Content versus Furnace Conditions
For a given sludge, under conditions that the bed of solids in the
hearth is not exposed to a high oxygen concentration, the rate of loss of
VOL and FC would be expected to primarily depend on the temperature-time
relationship as the solids pass through the furnace. When the bed is not
incandescent from combustion on its surface, the temperature of the solids
is probably reasonably well represented by the temperature of the surround-
ing refractories, since the heat received by surfaces at these temperature
levels is primarily by radiation. The only temperature measurements avail-
able are readings of thermocouples in the gas phase above the hearth, which
are exposed to convection and radiation. These readings would be inter-
mediate between gas and surface temperatures and can be used as an approxi-
mation to the surface temperature.
Figure 6 shows the percent FC and VOL in the residues that have passed
through the furnace plotted against the average of the six hearth tempera-
tures. The runs selected for this figure are indicated in Table 2. Only
LTC and HTC runs where less than 90 percent of the theoretical air was used
are included. The correlation is reasonably good when it is considered that
the temperature profiles were not uniform from run to run and conditions
were not held constant very long. Correlation of FC and VOL content against
the sum of the fourth power of the absolute temperatures on each hearth
(£. - T]4 + T2^ ... + T5^) was attempted because at elevated temperatures
heat transfer rate should be proportional to the fourth power of the absolute
temperature. However, no correlation was achieved. Evidently, the tempera-
ture level experienced by the char thus is more important than the average
rate of radiative heat transfer on the hearths.
Material and Heat Balances
Several serious problems were encountered in the investigation in
attemptingto close heat and material balances. Leaks were present in the
system. There was some outleakage from the furnace and some inleakage at
the afterburner. Gas analyses at the furnace exits and the afterburner exit
proved unsuccessful, due to difficulties that occurred in transporting the
samples offsite to the gas chromatograph. Calculations of mass and energy
flows were made from inputs and reasonable assumptions for gas composition.
624
-------
I
CO
UJ
_J
5
O
>
Q
Z
<
Z
O
QQ
O
G
UJ
X
u.
40-
30-
20-
10H
0
O
A
O CAMPAIGN H
CAMPAIGN ED
O
O
500 550 600 650 700
AVERAGE OF HEARTH TEMPERATURES
750
FIGURES EFFECT OF TEMPERATURE ON FIXED CARBON AND
VOLATJLES CONTENT OF ASH UNDER REDUCING
CONDITIONS
-------
Combustion in the Afterburner
There are twa important questions about afterburner performance-does
the gas have a sufficiently high heat of combustion to ignite and burn at an
adequately high rate, and are the hydrocarbon gases reduced in concentration
to meet air pollution requirements?
Because gas analyses are not available for the gases exiting from the
furnace, the heat of combustion cannot be determined with a high degree of
confidence. However, afterburner temperature and the top hearth temperature
are known. Consequently, when split-draft is not being used and natural gas
usage at the afterburner is small, it is possible to determine whether the
discharge gases are igniting and whether there is enough fuel value to cause
a substantial temperature increase. Four runs for which these conditions
apply are shown below:
Run Operating Top Hearth Afterburner
Mode (°C) (°C) T(°C)
II A 1 HTC 399 927 528
II A 2 LTC 304 810 506
II A 3 HTC 552 821 279
III 3 CBA 647 874 127
In Run III 3, an amount of natural gas was used that approximately offset
the heat loss from the afterburner.
The above data indicate that the offgases do ignite and produce tempera-
tures high enough for practicable recovery and very likely high enough to
completely oxidize all unburned hydrocarbons. Unfortunately, the after-
burner is substantially oversized. Gases exit from the afterburner at an
actual rate on the order of 0.4 m3 per second (dry gas basis), giving a
residence time of 5.0 seconds. Commercial scale afterburners have shorter
residence times (but probably better mixing). It is likely that the proof
of the operability of the afterburner will have to await more carefully
scaled tests.
The second question posed above must also await further tests. Experi-
ments using the oversized afterburner at the Nichols pilot plant would not
produce conclusive evidence of performance of afterburners with more prac-
tical residence times.
626
-------
Losses of Metals
As noted earlier, difficulty was experienced in closing the material
and energy balances because gas analyses were lacking. The material balance
problem is simple for substances that remain in the solid phase, particularly
the metals. Since feed and residue rates were measured, a material balance
is possible for all runs for which particulate samples are available.
When results for Campaign I, II, and III were analyzed, material bal-
ances around the MHF and the afterburner showed that losses of lead and
cadmium were occurring for the higher temperature runs. Principally to
obtain more reliable data and also to determine whether certain operating
modes gave lower losses, Campaign IV was run.
A complete analysis of the results of Campaign IV has not been made, so
the present discussion must necessarily be superficial. However, the results
support the findings of the first three campaigns—the volatile metals, par-
ticularly lead and cadmium, show poor material balances for the high tempera-
ture processes. Output is always lower than input.
Figure 7 shows the results obtained for INC, LTC, and HTC modes. Con-
sider the HTC mode for cadmium. The data show that the sum of the cadmium
in the residue and in the unabated particulates amounts to only half of the
total cadmium. The remainder is not accounted for. The amount of cadmium
in the unabated particulates is of concern, but air pollution control equip-
ment will capture most of this. The amount not accounted for is of serious
concern. If our data are correct, this material has escaped capture by a
filter designed to remove particles down to 0.1 micrometer in size. Our
pollution control equipment may not remove and recover very much of the "not
accounted for" fraction. It should be noted that Takeda and Hiraoka (8)
have observed similar metal losses in pyrolysis or combustion of sewage
sludge.
DISCUSSION AND CONCLUSIONS
The New Operating Modes and Products
The experiments conducted have demonstrated the feasibility of operating
a multiple hearth furnace in the CBA, LTC, and HTC modes, to produce a burn-
able gas at the top of a multiple hearth furnace. The system presents sub-
stantial advantage when afterburning is needed. Heat recovery is feasible
and no additional fuel is needed for afterburning. Information was not
collected on production rates for these new modes of operation. However,
Nichols1 staff suggest that LTC has the highest rate, and HTC is next. INC
has a rate slightly higher than CBA.
The new products, LTC and HTC char, have interesting potential. They
could possibly serve as adsorbents for wastewater treatment. LTC char has a
heat of combustion, equivalent to some low quality coals, and could serve as
a fuel. The LTC char should also contain most of the heavy metals which
conceivably could be removed or recovered from it.
627
-------
NJ
00
100%
INC LTC HTC
100%-
INC LTC HTC
Not
accounted
for
Particulates
50%-
Residue
CADMIUM
LEAD
FIGURE 7 MATERIAL BALANCE FOR CADMIUM AND LEAD
FOR INC, LTC, AND HTC MODES, CAMPAIGN 4
-------
Losses of Metals
Previous studies by the EPA's Municipal Environmental Research Labora-
tory (9) have indicated significant amounts of lead and cadmium in the par-
ticulates from sludge incinerators that escape collection. Nevertheless,
the quantities are not sufficient to seriously threaten environmental
quality. If unaccounted for quantities are included, this may no longer be
true. It is imperative that a program be commenced soon to determine the
true extent of losses (after particulate abatement) from sludge incineration
facilities.
DEVELOPMENTS AND PLANS
A most significant development is the construction of a TC-SSOS facility
at Arlington, Virginia. The unit which is outlined schematically in Figure
8 has been designed by Alexander Potter Associates with the assistance of
Nichols Engineering and Research Corporation. The unit is not equipped for
split-draft, but is designed to operate in the CBA mode. Heat recovery with
a waste heat boiler and power generation by means of a steam turbine is
planned.
EPA's research plans will concentrate on evaluation of facilities such
as the Arlington plant, and on the problem of metal losses during the
various thermal conversion modes.
ACKNOWLEDGEMENT
The work was an integrated effort of the Interstate Sanitation Commission,
Nichols Research and Engineering Corporation, and the U. S. EPA. Thanks are
extended to Dr. Alan Mytelka of the ISC, Mr. Charles Von Dreusche of Nichols,
Mr. Walter Lobo, consultant to Nichols, and Mr. Howard Wall, EPA project
officer, for their leadership of this joint effort.
629
-------
SLUDGE
CAKE
ASH
DISCHARGE
AIR
SUPPLY
AUXILIARY
AIR
1 Sludge cake storage hopper
2 Eight-hearth MHF
3 Afterburner
4 Waste heat boiler
5 Venturi Scrubber
6 Tray Scrubber
7 Fuel and combustion air to hearths and to
afterburner
FIGURES SAC UNIT UNDER CONSTRUCTION AT
ARLINGTON, VIRGINIA - CBA MODE
(SAC - STARVED AIR COMBUSTION)
630
-------
LITERATURE CITED
1. Camp, Dresser, and McKee, and Alexander Potter Associates, Phase I
Report of Technical Alternatives to Ocean Disposal of Sludges in the New
York City-New Jersey Metropolitan Area, June 1975. Prepared for the
Interstate Sanitation Commission.
2. Camp, Dresser, and McKee, Phase II Report of Technical Investigation
of Alternatives for New York-New Jersey Metropolitan Area: Sewage Sludge
Disposal Management Program, June 1974. Prepared for the Interstate
Sanitation Commission.
3. Majima, T., Kasakura, T., Naruse, M., and Hiraoka, M., "Studies of
Pyrolysis of Sewage Sludge." To be published.
4. Standard Methods for Examination of Water and Wastewater, American Public
Health Association, Washington, D. C. (1975).
5. ASTM-D129, American Society for Testing Materials, Easton, Maryland.
6. U. S. EPA, in Fed. Register 3^ (247), Dec. 23, 19971, pp. 24888-24890.
7. Harris, D. B., Kuyhendal, W. B., Johnson, L. D., "Development of a Source
Assessment Sampling System." U. S. EPA, Industrial Environmental Re-
search Laboratory, Research Triangle Park, N. C. 27711.
8. Takeda, N., and Hiraoka, M., "Combined Process of Pyrolysis and Combus-
tion for Sludge Disposal." Envir. Sci. Technol., 10_, 1147-1150
(Nov. 1976).
9. Wall, H., and Parrel 1, J. B., "Particulate Emissions from Municipal
Wastewater Sludge Incinerators." Proceedings, Semi-Annual Tech. Conf.
of Mid-Atlantic Section of Air Polln. Contr. Assn., Newark, N. J.,
April 27, 1979.
631
-------
OCCURRENCE AND REMOVAL OF TOXICS
IN MUNICIPAL WASTEWATER TREATMENT FACILITIES'*
John J. Convery, Jesse M. Cohen, Dolloff F. Bishop**
INTRODUCTION
Some 20 years ago there was a growing concern by the predecessor
organizations of the U.S. Environmental Protection Agency that synthetic
organics (and certain naturally prevalent compounds) were contaminating the
environment - air, water and soil. Thus it was that investigations on
controlling these compounds have historically been an integral part of the
research program. Still, some excellent research was accomplished; for
example, water sources and drinking water were shown to contain substantial
amounts of organic matter as measured, in a gross way, by the carbon chloro-
form extract (CCE) and by the carbon alcohol extract (CAE). By tedious
wet- chemical methods, specific organics were identified using such tech-
niques as carbon adsorption for concentrating the organics, infra-red and
UV spectroscopy for compound identification and gas chromatography when
that instrument became available.
Such crude (in retrospect) techniques produced results slowly, but the
information gained in this way was sufficient to confirm the widespread pre-
valence of synthetic organics in the environment and to arouse concern about
their effects. Confirmation of these early data proceeded rapidly when
analytical methodology and instrumentation was developed to cope with the
problem of qualitatively and quantitatively determining the vast array of
organic and inorganic compounds that are produced, discarded and environ-
mentally dispersed by our modern society. Chemical sales in the United
States in 1978 involved some 70,000 different substances, and in recent years,
almost 1,000 new chemicals have been introduced into commercial production
annually.
By a series of legislative acts, the Congress of the United States
charged EPA and other agencies with the responsibility of safeguarding the
public as well as the environment, from the hazards of toxic chemicals.
The objective of this paper is to review, briefly, the legislative mandates,
the impact that these acts have on a segment of the environment, - the muni-
cipal wastewater treatment plant - and finally a description of the research
which responds to the problem of toxic compounds in municipal wa-stewaters.
* Paper for presentation at the Seventh Joint United States/Japan Conference
in Tokyo, Japan - May 1980.
**Director, Wastewater Research Division, Municipal Environmental Research
Laboratory, USEPA; Chief, Physical-Chemical Treatment Section, WRD;
Chief, Technology Development Support Branch, WRD.
633
-------
REGULATORY FRAMEWORK FOR URBAN TOXICS MANAGEMENT
The need for data on the occurrence and removal of toxics in municipal
wastewater treatment facilities is derived from the informational require-
ments of environmental legislation, the consent decree agreement (1) and
the implementation requirements of federal, state and local regulatory
agencies. The primary sources of toxics, their routes of transport in an
urban^environment and applicable environmental laws to control toxics are
shown schematically in Fig. 1. Summaries of the important laws for toxics
management are presented in Appendices A and B. Toxics control management
requires a systematic approach of limiting environmental exposures through
the application of discharge restrictions on important sources which are
consistent with control technology capabilities, economic considerations,
environmental management objectives as well as environmental quality criteria.
An essential element in EPA's urban toxic control strategy is the use
of industrial pretreatment regulations. The intentions of the Agency in
applying these regulations are to protect the operational stability of the
municipal wastewater treatment facilities, limit the pass-through of
toxics to the receiving waters and, conceptually important, to maintain
the quality of municipal sludges at levels suitable for environmentally
safe disposal, including reclamation and reuse, if possible.
The pretreatment regulations establish the means for applying and
enforcing technology-based standards for 21 major industrial categories
(including 294 sub-categories) to control some 65 classes of potentially
toxic industrial pollutants (defined as 129 specific compounds). Separate
regulations are being developed and promulgated for each industrial cate-
gory which will define national standards based on a determination of the
"best available control technology which is economically achievable" (BATEA).
The regulated industries and toxics (priority pollutants) to be controlled
are listed in Tables 1 and 2, respectively. Candidate BATEA technologies
are being evaluated in terms of their toxics removal capabilities. Oper-
ationally, monitoring of the BATEA pretreatment facilities will not in-
clude specific analyses of all or even of many of the priority pollutants
because of costs and analytical service availability considerations.
Treatment facility performance will be monitored using more traditional
parameters which will document the level of operational stability, and, it
is hoped, will indicate or infer a level of control of the priority pollutants
Pretreatment programs will be required for publicly owned treatment
systems with a total design flow greater than five million gallons per day
which receive industrial wastes which are subject to pretreatment regu-
lations. EPA estimates that approximately 568 sewage authorities will be
requiring pretreatment from about 40,000 industrial sources.
Primary responsibility for implementing the pretreatment program resides
either with the local authorities with back-up by EPA or with the 32 states
634
-------
CTi
RCRA
HazardousWaste
OSHA-Toxics Control in The Work Place
CAA-National Emission Standards
For Hazardous Air Pollution
RCRA
Crop Uses
and Land Application
,,CWA
Pretraatment
Ijof Industrial
1 (Sources
Areawidej
Planning
\ ^ To control
M Runoff
Product and Use \Sources
Approval
FIFRA TSCA
Municipal Wastewater
Treatment Facilities
/
Legend
RCRA-Resource Conservation and Recovery Act
of 1976 (PL 94 - 580)
CWA -Clean Water Act of 1972 (PL 92-500) and 1977
(PL 95 - 217)
CAA - Clean Air Acts of 1970 (PL 91 - 604) and 1977
(PL 95-95)
FIFRA- Federal Insecticide, Fungicide and Rodenticide
Act of 1972 (PL 92 - 516)
TSCA -Toxics Substance Control of 1976 (PL 94-469)
OSHA -Occupational Safety and Health Act
CWA
NPDES Permits
Water Quality Standards
Figure 1. Toxics Transport In An Urban Environment And Applicable Environmental Legislation
-------
having NPDES (National Pollution Discharge Elimination System) permit
authority. Local authorities will be allowed to relax the national pre-
treatment standards for industrial discharges based on documented capa-
bility of the local publicly owned facilities to remove toxics. Two
additional provisions are necessary for approval of local removal credits.
The practice may not preclude sludge reclamation and reuse opportunities
nor limit the use of innovative and alternative technology. Approximately
360 authorities are expected to apply for removal credits.
EPA will help fund development of local pretreatment programs through
construction grants and areawide planning grants but will not fund the
studies necessary to document local removal credits.
TABLE 1. CONSENT DECREE INDUSTRIES
Timber Products Processing
Auto, Other Laundries
Organic Chemical Manufacturing
Iron & Steel Manufacturing
Petroleum Refining
Inorganic Chemicals Manufacturing
Textile Mills
Leather Tanning, Finishing
Non-Ferrous Metals Manufacturing
Paving, Roofing Materials
Paint, Ink Formulation; Printing
Soap, Detergent Manufacturing
Steam Electric Power Plants
Plastic, Synthetic Materials, Mfg.
Pulp, Paperboard Mills; Converted
Paper Products
Rubber Processing
Miscellaneous Chemicals
Machinery, Mechanical Products Mfg.
Electroplating
Ore Mining, Dressing
Coal Mining
EFFECTS OF PRETREATMENT PROGRAMS
It is too soon to judge the eventual impact of industrial pretreatment
BATEA regulations on the concentration of priority pollutants in municipal
wastewaters and sludges. There are, however, limited case histories of the
impact of municipal sewer ordinances on the concentration of heavy metals
on municipal treatment facilities. The City of Grand Rapids, Michigan,
passed a municipal ordinance in January 1969, which limited industrial efflu-
ent metals concentrations for cadmium, copper and nickel to 1.5 mg/1; zinc
to 6.0 mg/1 and total chromium to 2 mg/1. Within seven years the total metal
concentration in the influent wastewater dropped 87% from 12-13 mg/1 to 2 mg/1
Effluent levels decreased 92% from 9-10 mg/1 to 1 mg/1. Metal concentra-
tions in the sludge were reduced 58-66%.
The most significant effect of reduction of influent metals concentration
is the consequent reduced content of the metals in sludge. This effect is
illustrated in Table 3 where metals content of sludge (dry basis) before
and after pretreatment programs are shown for the cities of Buffalo, New
York; Grand Rapids, Michigan; and Muncie, Indiana.(2) The data for Los
Angeles, California, are shown for changes in influent concentration of
metals resulting from industrial pretreatment programs. (3)
636
-------
TABLE 2 PRIORITY POLLUTANTS
Compound Name
1. *acenaphthene
2. *acrolein
3. *acrylonitrile
4. *benzene
5. *benzidine
6. *carbon tetrachloride (tetrachloromethane)
^Chlorinated benzenes (other than dichlorobenzenos)
7. chlorobenzene
8. 1,2,4-trichlorobenzene
9. hexachlorobenzene
^Chlorinated ethanes (including 1,2-dichloroethane, 1,1,1-trichloro-
ethane and hexachloroethane)
10. 1,2-dichloroethane
11. 1,1,1-trichloroethane
12. hexachloroethane
13. 1,1-dichloroethane
14. 1,1,2-trichloroethane
15. 1,1,2,2-tetrachloroethane
16. chloroethene
*Chloroa1kyl ethers (chloromethyl, chloroethyl and mixed ethers)
17. bis(chloromethyl) ether
18. bis(2-chloroethyl) ether
19. 2-chloroethyl vinyl ether (mixed)
*Chlorinated naphthalene
20. 2-chloronaphthalene
*Chlorinated phenols (other than those listed elsewhere; includes
trichlorophenols and chlorinated cresols)
21. 2,4,6-trichlorophenol
22. parachlorometa cresol
*Specific compounds and chemical classes as listed in the consent decree.
637
-------
TABLE 2 (Contd.)
23. *chloroform (trichloromethane)
24. *2-chlorophenol
*Dich1orobenzenes
25. 1,2-dichlorobenzene
26. 1,3-dichlorobenzene
27. 1,4-dichlorobenzene
*Dich1orobenzidine
28. 3,3-dichlorobenzidine
*Dichloroethylenes (1,1-dichloroethylene and 1,2-dichloroethylene)
29. 1,1-dichloroethylene
30. 1,2-trans-dichloroethylene
31. *2,4-dichlorophenol
*Dichloropropane and dichloropropene
32. 1,2-dichloropropane
33. 1,3-dichloropropylene (1,3-dichloropropene)
34. *2,4-dimethylphenol
*Di'rn'troto1 uene
35. 2,4-dinitrotoluene
36. 2,6-dinitrotoluene
37. *1,2-diphenylhydrazine
38. *ethylbenzene
39. *fluoranthene
*Ha1oethers (other than those listed elsewhere)
40. 4-chlorophenyl phenyl ether
41. 4-bromophenyl phenyl ether
42. bis(2-chloroisopropyl) ether
43. bis(2-chloroethoxy) methane
*Halomethanes (other than those listed elsewhere)
44. methylene chloride (dichloromethane)
45. methyl chloride (chloromethane)
46. methyl bromide (bromomethane)
47. bromoform (tribromomethane)
48. dichlorobromomethane
633
-------
TABLE 2 (Contd.)
49. trichlorofluoromethane
50. dichlorodifluoromethane
51. chlorodibromomethane
52. *hexachlorobutadiene
53. *hexachlorocyclopentadiane
54. *isophorone
55. *naphthalene
56. *nitrobenzene
*Nitropheno1s (including 2,4-dinitrophenol and dinitrocresol)
57. 2-nitrophenol
58. 4-nitrophenol
59. *2,4-dinitrophenol
60. 4,6-dinitro-o-cresol
*Nitrosamines
61. N-nitrosodimethylamine
62. N-nitrosodiphenylamine
63. N-nitrosodi-n-propylamine
64. *pentachlorophenol
65. *phenol
*Phtha1ate esters
66. bis(2-ethylhexyl) phthalate
67. butyl benzyl phthalate
68. di-n-butyl phthalate
69. di-n-octyl phthalate
70. diethyl phthalate
71. dimethyl phthalate
*Polynuc1ear aromatic hydrocarbons
72. benzo(a)anthracene (1,2-benzanthracene)
73. benzo(a)pyrene (3,4-benzopyrene)
74. 3,4-benzofTuoranthene
75. benzo(k)fluoranthane (11,12-benzofluoranthene)
76. chrysene
77. acenaphthylene
639
-------
TABLE 2 (Contd.)
78. anthracene
79. benzo(ghi)perylene (1,12-benzoperylene)
80, fluorene
81. phenanthrene
82. dibenzo(a,h)anthracene (1,2,5,6-dibenzanthracene)
83. indeno (1,2,3-cd)pyrene (2,3-o-phenylenepyrene)
84. pyrene
85. *tetrachloroethylene
86. *toluene
87. *trichloroethylene
88. *vinyl chloride (chloroethylene)
Pesticides and Metabolites
89. *aldrin
90. *dieldrin
91. *chlordane (technical mixture and metabolites)
*DDT and metabolites
92. 4,4-DDT
93. 4,4-DDE (p,p'-DDE)
94. 4,4-DDD (p.p'-TDE)
*endosu!fan and metabolites
95. a-endosulfan-alpha
96. b-endosulfan-beta
97. endosulfan sulfate
*endrin and metabolites
98. endrin
99. endrin aldehyde
*_heptach1or and metabolites
100. heptachlor
101. heptachlor epoxide
*hexach1orocyclohexane (all isomers)
102. a-BHC-alpha
103. b-BHC-beta
104. r-BHC (lindane)Gamma
640
-------
TABLE 2 (Contd.)
105. g-BHC-Delta
*po1ych1orinated biphenyls (PCB's)
106. PCB-1242 (Arochlor 1242)
107. PCB-1254 (Arochlor 1254)
108. PCB-1221 (Arochlor 1221)
109. PCB-1232 (Arochlor 1232)
110. PCB-1248 (Arochlor 1248)
111. PCB-1260 (Arochlor 1260)
112. PCB-1016 (Arochlor 1016)
113. *Toxaphene
114. *Antimony
115. *Arsenic
116. *Asbestos
117. *Beryllium
118. *Cadmium
119. *Chromium
120. *Copper
121. *Cyanide
122. *lead
123. *Mercury
124. *Nickel
125. *Selenium
126. *Silver
127. *Thallium
641
-------
TABLE 2 (Contd.)
128. *Zinc
129. **2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
*Specific compounds and chemical classes as listed in the consent decree.
**This compound was specifically listed in the consent decree. Because of
the extreme toxicity (TCDD), we are recommending that laboratories not
acquire analytical standard for this compound.
642
-------
TABLE 3. EFFECT OF PRETREATMENT PROGRAMS ON METAL CONTENT OF
SLUDGE AND WASTEWATER
Metal
Cadmi urn
Chromium
Copper
Lead
Nickel
Zinc
Sludge mg/kg Dry Solids Basis Wastewater mg/1
Pretreat.
Time
Before
After
Before
After
Before
After
Before
After
Before
After
Before
After
uffalo(a)
100
50
2540
1040
1570
330
1800
605
315
115
2275
364
Grand Rapids
11000
2700
3000
2500
3000
1700
7000
5700
Muncie
23
9.5
2000
675
1750
700
8500
1000
8500*
150
5800
2700
0.037
0.019
0.70
0.43
0.45
0.30
0.40
0.34
0.31
0.21
1.55
1.17
(a) Projected Values
(b) Change in Influent Concentration from January 1975 - January 1977
* Annual report, 1974 and 1975, from Muncie Sanitary District, reports
a value of 430 mg/kg instead of the 8500 reported in the Federal
Register (2).
643
-------
ENVIRONMENTAL QUALITY CONSIDERATIONS
Water Quality Criteria
As part of the consent decree agreement EPA is required to promulgate
water quality criteria for 65 specified toxic pollutants. Proposed water
quality criteria for the 65 priority pollutants are shown in Table 4. (4)
These criteria, when issued in their final form after public comment, may
serve as the basis for enforceable standards under the administrative rule-
making procedures by either the states or EPA as provided for under Sections
302, 303, or 307(a) of the Clean Water Act. Publication of the criteria per
se has no regulatory impact.
Recent Congressional testimony (5) before the House Committee on Public
Works and Transportation identified 13 states which have general toxic sub-
stance standards based on some fraction of the acute lethal levels as
determined by aquatic toxicity tests (i.e., 1/10 of the 96 hour TLm). Four-
teen states have included limitations on specific toxic pollutants such as
arsenic or cyanide in their water quality standards. A summary of the types
of state water quality standards is shown in Table 5. The human health
effects water quality criteria relate primarily to exposures through drinking
water and for consumption of contaminated aquatic life. Where multiple
criteria levels were defined for incremental cancer risk levels to man of 10~7
to 10~5, the value shown in Table 4 is the most conservative value (higher
concentration). These criteria are not to be confused with finished (treated)
drinking water standards which are established under the Safe Drinking Water
Act. The finished or treated drinking water standards are established on the
basis of human health effects criteria plus consideration of control technology
capabilities and economics.
Land Disposal Criteria
An interim final* regulation containing the minimum criteria to provide
guidelines for the disposal and utilization of wastewater treatment plant
sludge was published in September 1979. As proposed, any owner or operator
of a publicly owned treatment works must comply with these criteria when
disposing of sludge on the land. The essential elements of the proposed
criteria are summarized in Appendix C entitled "Criteria for Sludge Applica-
tion to Land." The criteria are structured to define unacceptable impacts,
i.e., those that present a "reasonable probability" of adverse effects on
health or the environment. The criteria do not apply to domestic sewage,
treated domestic sewage or hazardous wastes. They do apply to solid wastes,
which include municipal sludge and septage. The priority pollutants were not
specifically included in the criteria to protect groundwater from sludge
disposal facilities. Rather, the maximum contaminant levels (MCL) specified
in the National Interim Primary Drinking Water Regulations are applicable with
the exception of turbidity and man-made radionuclides.
*Interim final means a regulation which is final and enforceable but the
Agency is still seeking public comment.
644
-------
TABLE 4. PROPOSED WATER QUALITY CRITERIA FOR PRIORITY POLLUTANTS
Compound
1. *Acenaphthene
2. *Acrolein
3. *Acrylon1tri1e
4. *Benzene
5. *Benz1dine
6. *Carbon tetrachloride
(tetrachloromethane)
Freshwater Aquatic Life
24-Hr.AvgCelling
yig/1 pg/1
Saltwater Aguatlc Life
24-Hr Avg. Ceiling
110
1.2
130
3,100
620
240
2.7
300
7,000
1,400
7.5
0.88
130
920
2,000
17
2.0
290
2,'000
4,600
*Chlor1nated benzenes
(other than dichlorobenzenes)
7. Chlorobenzene
8. 1,2,4-Trichlorobenzene
9. Hexachlorobenzene
*Ch1oririated ethanes
(including 1,2-dichloroethane,
1,1,1-trichloroethane and
hexachloroethane)
10. l,2-D1chloroethane
11. 1,1,1-Trlchloroethane
12. Hexachloroethane
13. 1,1-Oichloroethane
14. 1,1,2-Trichloroet.hflnp
15. 1,1,2,2-Tetrachloroethane
16. Chloroethene
*Ch]oralkyl ethers
(chloromethyl, chloroethyl and
mixed ethers)
17. Bis(chloromethyl) ether
18. Bis(2-chloroethyl) ether
19. 2-Chloroethyl vinyl ether (mixed)
Human
Health
Effects
MC
2.6
7.0
5.9
2.7
1.8
O.OZxIO-3
0.42
*Specific compounds and chemical classes as listed in the consent decree.
-------
TABLE 4 (Contd.)
Freshwater Aquatic Life
Coroi
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
24-Hr. Avg
pound pg/1
*Chlorinated naphthalene 29
2-Chloronaphthalene
*Chlorinated phenols
(other than those listed
elsewhere; includes tri-
chlorophenols and chlorinated
cresols)
2,4,6-THchlorophenol 52
- Tetrachlorophenol
Parachlorometa cresol
*Chloroform (trichloromethane) 500
*2-Chlorophenol 60
*Dichlorobenzenes
(total all isomers)
1,2-Dichlorobenzene 44
1,3-Dichlorobenzene 310
1,4-Dichlorobenzene 190
*0ichlorobenzidine
3,3-Dichlorobenzidine
*pichlorpethy1enes
( 1 , 1-Oichloroethylene and
1,2-Dichloroethylene)
1,1-Oichloroethylene 530
1,2-Trans-dichloroethylene 620
Ceiling
UgTl
67
150
1200
180
99
700
440
-
1200
1400
Saltwater Aquatic Life
24-Hr.Avg. Ceiling
ng/1
Celling
wg/l
2.8
620
15
22
15
6.4
1400
34
49
34
1700
3900
Human
Health
Effects
.08-3.93
31. *2,4-Oichlorophenol
0.4
110
100
263
2.1
0.3
230
0.1
1.3
0.5
a Depends on form (octo-tri]
-------
TABLE 4 (Contd.)
Freshwater Aquatic Life
?4-Hr.Avg.
Compound jjg_/T
*Dichloropropane and
dichloropropene
32. 1,2-Dichloropropane 920
33. 1 ,3-Oichloropropylene
( 1,3-Dichloropropene) 18
34. *2,4-Dimethylphenol 38
*Dinitrotoluene
35. 2,4-Oinitrotoluene 620
36. 2,6-Dinitrotoluene
37. *1 ,2-Diphenylhydrazine 17
38. *Ethylbenzene
39. *Fluoranthene 250
*Haloethers (other than those
listed elsewhere)
40. 4-Chlorophenyl ether
41. 4-Bromophenyl phenyl ether 6.2
42. Bis(2-chloroisopropyl) ether
43. Bis(2-chloroethoxy) methane
*Halomethanes (other than
those listed elsewhere)
44. Methylene chloride
(Dichloromethane) 4,000
45. Methyl chloride
(Chlorornethane) 7,000
46. Methyl bromide
(Bromome thane) 140
47. Bromoform (Tribromomethane) 840
48. Dichlorobromomethane
49. Trichlorof luoromethane
50. Dichlorodif luoromethane
51. Chlorodibromomethane
CeiTing
HZ!
2,100
250
86
1,400
38
-
560
14
9,000
16,000
320
1,900
-
-
Human
Saltwater Aquatic Life Health
24-Hr. Avg. Ceiling Effects
ug/1 gg/1 yg/l
400 930 203
5.5 14 0.63
-
0.740
0.4
1,100
0.30 0.69 200xlQ-J
-
11.5
1,900 4,400 2
3,700 8,400 2
170 380 2
180 420 2
32,000
3,000
-------
TABLE 4 (Contd.)
CD
Compound
52. *Hexachlorobutadiene
53. *Hexach1orocyc1opentadiene
54. *Isophorone
55. *Naphthalene
56. *N1trobenzene
*N1tropheno1s (Including
2,4-dinitrophenol and
dinitrocresol)
2-Nitrophenol
4-Nitrophenol
*2,4-D1nitropheno1
4,6-Dinitro-o-cresol
57.
58.
59.
60.
61.
62.
63.
*N1trosamines
N-nitrosodlmethylamine
N-nitrosodiphenylamine
N-nitrosodi-n-propylamine
N-nitrosodiethylamine
N-nitroso-di-n-butylamine
N-nitrosopyrolidine
64. *Pentach1orophenol
65. *Phenol
*Phthalate esters
66. Bis(2-ethylhexyl) phthalate
67. Butyl benzyl phthalate
68. Oi-n-butyl phthalate
69. Di-n-octyl phthalate
70. Diethyl phthalate
71. Dimethyl phthalate
Freshwater Aquatic Life
74^ffr.Avg.Ceiling
7.0
4,700
1,100
6,200
550
180
130
0.39
2,100
480
2,700
240
79
57
6.2
600
14
3,400
Saltwater Aquatic Life
24-Hr.Avg.Ceiling
vg/1
Ceiling
"Ti/r
97
53
53
37
220
120
120
84
3.7
8.5
Human
Health
Fffects
0.77
1.0
460
143xlO-3
30
68.6
12.8
0.026
0.0092
0.013
0.11
140
3,400
10,000
5,000
60,000
160,000
-------
TABLE 4 (Contd.)
Compound
*Po1ynuc1ear aromatic hydrocarbons
72. Benzo(a)anthracene
(1,2-benzanthracene)
73. Benzo(a)pyrene (3,4-benzopyrene)
74. 3,4-Benzofluoranthene
75. Benzo(k)fluoranthane
(11,12-benzofluoranthene)
76. Chrysene
77. Acenaphthylene
78. Anthracene
79. Benzo(gh1Jperylene
(1,12-benzoperylene)
80. Fluorene
81. Phenanthrene
82. D1benzo(a,h)anthracene
(1,2,5,6-dibenzanthracene)
83. Indeno (1,2,3-cd)pyrene
(2,3-o-phenylenepyrene)
84. Pyrene
85. *Tetrachloroethylene 310
86. *Toluene 2,300
87. *Tr1chloroethylene 1,500
88. *V1nyl chloride (chloroethylene) -
Pesticides and ntetabolltes
89. *Aldr1n
90. *D1eldrin
91. *Chlordane (technical
mixture and metabolites) 0.024
*DDT and metabolites
92. 4,4-DDT
93. 4,4-DDE (p,p'-DDE)
94. 4,4-DDD (p,p'-TOE)
Freshwater Aquatic Life
73-Hr.Avg.Celling
wjZL
Saltwater Aquatic Life
?fr-Hr.Avg.Ceiling
700
5,200
3,400
79
100
180
230
0.36
9.1x10-3
0.18
Human
Health
Effects
2.0
17,400
21
517
4.6x10-5
4.4xlO-8
1.2x10-3
0.98x10
-3
-------
TABLE 4 (Contd.)
Cn
o
Compound
*Endosu1fan and metabolites
95. a-Endosulfan-Alpha
96. b-Endosulfan-Beta
97. Endosulfan sulfate
*Endrin and metabolites
98. Endrin
99. Endrin aldehyde
*Heptach1or and metabolites
100. Heptachlor
101. Heptachlor epoxide
*Hexach1orocyclohexane
(all isomers)
102. a-BHC-Alpha
103. b-BHC-Beta
104. r-BHC (lindane)-Gamma
105. g-BHC-Delta
*Pglych1orinated blphenyls
(PCB1s)
106. PCB-1242 (Arochlor 1242)
107. PCB-1254 (Arochlor 1254)
108. PCB-1221 (Arochlor 1221)
109. PCB-1232 (Arochlor 1232'
110. PCB-1248 (Arochlor 1248
111. PCB-1260 (Arochlor 1260
112. PCB-1016 (Arochlor 1016)
113. *Toxaphene
114. *Antimony
115. *Arsenic
116. *Asbestos
Freshwater Aquatic Life
74-Hr.Avg.Celling
yg/1 tig/1
0.042
0.0020
0.0015
0.0015
.007
120
57
Saltwater Aquatic Life
24-Hr.Avg.Ceiling
yg/1ug/1
0.49
0.10
0.45
0.0047
0.0036
0.031
0.05
6.2
0.24
.20
0.47
1,000
130
0.19
29
.12
67
Human
Health
Effects
100
2.3xlO-4
16xlO-3
28x10-3
54x10-3
21xlO'3
2.6x10-4
4.7x10-4
145
0.02 .
soo.ooo''
.JCO.uuu tioers/Hter tor ID--" target risk level
-------
TABLE 4 (Contd.)
LH
Freshwater Aquatic
24-Hr. Avg.
Compound
117.
118.
119.
120.
121.
122.
123.
124.
125.
126.
127.
128.
*Beryllium
*Cadmium
*Chromium
*Copper
*Cyanide
*lead
*Mercury
*Nickel
*Selenium
*Silver
*Thal lium
*Zinc
ng/1
e(1.24 ln(hard)-6
e(0.87 ln(hard)-4
e(0.65 ln(hard)-l
1.4
e(1.5 ln(hard)-3.
e(1.02 ln(hard)-l
9.7
0.009
_
e(0.67 ln(hard)+0
Cei
Life
ling
Saltwater Aquatic Life
73-Hr. Avg.
pg/l
.65)
.38)
.03)
37)
.02)
.67)
e
e
e
e
e
e
(!
(0
(1
(0
(0
.24
.30
.88
38
.47
22
1.9
_
.64
ln(hard)-l
ln(hard)-3
.46)
.92)
ln(hard)-1.03)
ln(hard)-l.
ln(hard)+4
ln(hard)+2
39)
.19)
.46)
ug/1
1.0
0.79
_
_
_
4.4
0.26
_
-
Cei ling
yg/1
16
18
_
_
-
10
0.58
_
-
Human
Health
iffects_
ug/ 1
0.087
10
50
1,000
200
50
133
10
10
4
5,000
129.**2,3,7,8-Tetrachlorodibenzo-
p-dioxin (TCDD) -
*Specific compounds and chemical classes as listed in the consent decree
**This compound was specifically listed in the consent decree. Because of
the extreme toxicity (TCDD), we are recommending that laboratories not
acquire analytical standard for this compound.
4.55xlO-7
-------
TABLE 5. STATE WATER QUALITY STANDARDS
Specific Water
Quality Standard
£v:
TD
40
Effluent
Limits
o
•V-J
S
c:
o
Al abama
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Idaho
111 i no is
Indi ana
Iowa
Kansas
Kentucky
Louisiana
Maine
Mary! and
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
12/77
5/76
9/75
2/79
7/78
11/77
4/75
3/79
6/78
6/73
5/79
5/78
3/79
8/78
7/75
10/77
8/77
7/78
2/79
12/73
10/73
7/77
4/75
9/74
10/77
2/78
4/77
1/78
4/77
1 / ' '
9/78
12/78
i t_ / / LJ
Mil
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X X
X X
X
X
X
X
X
X
X
X
X
XXX
X X
XXX
X X
X
X X
X
X X
X
X
X
X
X
X
X
X X
X
X
X (3)
X
X X
X X
X
X
X
X
X
X
(2)
X
(2)
X
(2)
652
-------
TABLE 5 (Contd.)
Specific Water
Quality Standard
c>
CD .^
0
Effluent
Limits
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
<+- ^
o
CD T-,'
2/78
3/79
4/76
10/76
12/77
4/77
1/79
12/77
2/76
10/78
3/78
11/74
12/77
4/78
6/78
3/79
Co •"-
c
o
0 f
X X
X X
X
X X
X
X
X X
X
X
X X
X
X
X
X
X X
X
CD v~ """
"O O i_ iv
.5 .? ° •£
•*° ^ -o 5^
i/} CD -, m
CD Q-cX _J
Q_ Co c
X X
X
X
X X
X
X X
X X
-Q / \
^- / ^
•^3 / O
A- / CQ
X
X
X
X
X
X
X X
X
X
X
X
VJ
-(-J
IV CD
•^ 0}
C: ti
0 -V
§ -^
(2)
X
(2)
X
(2)
X
Source: BNA - Environmental Reporter, "State Water Laws" updated
as of October 1, 1979
1. Identified are any effluent limits contained in
regulations that are more stringent than
Secondary Criteria
2. Specific Waste Load Allocation Provisions
3. BOD Water Quality Standards
653
-------
Hinesly (6) reported on the heavy metal content in runoff and drainage
waters from sludge-treated field lysimeter plots. The studies indicated that
log normal distributions best characterized the population of metal concen-
trations with geometric mean concentrations being the most useful for assess-
ing results. The sludge loading rates and heavy metal loading rates were
significantly higher than currently recommended loading criteria. The re-
sults, shown in Table 6, indicate that copper concentrations increased the
most with time and cumulative loading. Cadmium concentrations exceeded the
criteria in the 1972-73 period but were largely due to high background levels
for the control.
Air Quality Criteria
Specific air quality limits, based on the Occupational Safety and Health
Administration (OSHA) air quality standards, have not been promulgated for
the practice of sludge disposal to the land. The OSHA standards for 22 of
the more volatile priority pollutants are listed in Table 7. (7) These
standards are presented in this paper only as a point of reference with
which to compare volatile priority pollutant emissions around a municipal
treatment facility which may affect the work environment of treatment plant
operators. Field measurement of air concentrations over an aerated grit
chamber and aeration basin for these volatile priority pollutants are also
shown in Table 7.
These data, which are very limited, suggest that air quality above
wastewater treatment plant unit operations will generally not be a problem.
Forced ventilation of waste treatment facilities will further reduce ambient
concentrations. The only potential problem suggested by these data is the
concentration of 1,1,2-trichloroethane over the aeration basin.
ANALYTICAL METHODS
For analysis, the priority organics are divided into purgeable and
extractable classes. The extractable class is further subdivided into
acid, base neutral compounds and into a selected neutral subclass of
pesticides and PCB's. The Agency has developed methodology (8) for the
measurement of these priority toxic organics based on GC/MS technology.
Succinctly, the methodology separates the purgeable priority organics from
the environmental sample by purging with inert gas and trapping of the
organics on a Tenax and silica gel trap. The organics are then desorbed,
identified and quantitated with packed column GC/MS analysis. The method-
ology separates the extractable organics by extracting with methylene
chloride, first at pH 11 and then at pH 2, and then identifies and quanti-
tates the organics in the base neutral and acid extracts by packed column
GC/MS analysis.
The basic methodology for purgeable and extractable organics has been
extensively applied to four raw municipal wastewaters (9). The initial
application of the basic methodology on municipal raw wastewater missed
four of the purgeable organics; chloromethane, dichlorodifluoromethane,
vinyl chloride and bromomethane. With substitution of charcoal for the
654
-------
TABLE 6. HEAVY METAL CONTENT IN DRAINAGE FROM SLUDGE APPLIED TO FIELD LYSIMETERS
Ln
Lysimeter Loading
Drainage Water
(Control)
Drainage Water
(Sludge Amended)
Year
1969
1970
1971
1972
1973
1974
1969
1970
1971
1972
1973
1974
Annual Sludge
Appl ication Rate
mT/ha
19.33
36.15
104.69
32.19
58.75
70.73
16.37
52.78
57.83
44.38
61.08
Terminated
Zn
Kg/ha
122
312
464
135
224
350
158
427
265
192
248
-
Cu
(dry
27
69
114
22
38
114
36
101
69
33
41
Cd
weight)
5.2
22.2
24.0
5.8
6.7
21.7
7.9
22.6
13.2
7.8
6.8
Zn
mg/l
0.019
0.016
0.016
0.021
0.015
0.016
Cu
(geo mean
0.007 0
0.009 0
0.012 0
0.004 0
0.008 0
0.012 0
Cd
1
.003
.009
.004
.003
.011
.004
Zn
mg/l
0.037
0.038
0.033
0.021
0.018
0.015
Cu
(geo
0.016
0.026
0.029
0.007
0.011
0.013
Cd
mearf)
0.006
0.013
0.008
0.004
0.010
0.005
-------
TABLE 7. ANALYSIS FOR PRIORITY POLLUTANTS IN AIR STREAM FROM GRIT CHAMBER
AND AERATION BASIN AT SOUTH BURLINGTON, NC MUNICIPAL TREATMENT PLANT
Priority Pollutants
OSHA STDSd Priority Pollutants - ng/1
(ng/1) Grit Chamber Aeration Basin
Methyl bromide 80,000
Dichloromethane 1,736,000
1,1-Dichloroethylene
Acrylonitrile
1,2-Trans-dichloroethylene 790,000
Chloroform 240,OOO11
1,2-Dichloroethane
1,1,1-Trichloroethane 1,900,000
Carbon tetrachloride 62,900
Bromodichloromethane
1,2-Dichloropropane 350,000
Benzene 32,000
Trichloroethylene 537,000
Bromoform 5,000
Tetrachloroethylene 678,000
1,1,2,2-Tetrachloroethane 34,000
Toluene 753,000
Ethyl benzene 434,000
Chlorobenzene 345,000,
1,2-Dichlorobenzene 300,000
1,3-Dichlorobenzene
1,1,2-Trichloroethane 54,600
ND
114 + 7
1.5 +_ 2.0
ND
188
21,963 + 8,316
448 + 72
4,468 + 668
ND
260 + 34
41,850 + 4,950
93 + 5
16,095 +_ 1,705
ND
54,000 +_ 9,000
ND
31,835 + 2,665
3,275 + 275
38
ND
88,500
ND
ND
117 + 1
ND
ND
75 +_ 7
3,472 + 205
320 + 23
487 +_ 35
ND
52 +_ 12
35,850 + 2,350
126 + 24
2,931 + 277
ND
19,300
570
262
190
19
2,700
41,910
a 8-hour time weighted average unless otherwise noted (standards based
on T=25°C, P=760 mm Hg)
b
maximum
never to be exceeded
656
-------
silica gel in the Tenax trap and purging at 49°C, the modified approach
identified all of'the purgeable priority organics and exhibited the best
overall recoveries (^90%) for the analysis of priority organics in muni-
cipal wastewaters.
The basic methodology (8) does not measure all of the extractable
priority pollutants well. N-nitrosodimethylamine does not chromatograph
effectively under the conditions of the method and is sufficiently volatile
as an extractable organic to result in poor analyses. Hexachlorocyclo-
pentadiene, while successfully determined (10) in some laboratories has
been missed by others (9).
The neutral compound, 2-chloroethyl vinyl ether, also was not de-
tected (9) by the basic methodology. Thermal decomposition of 1,2-di-
phenylhydrazine to azobenzene and N-nitrosodiphenylamine to diphenylamine
has also been observed (11). Co-eluting pairs of anthracene-phenanthrene,
benzo(a)anthracene-chrysene, and benzo(b)fluoranthene-benzo(k)fluoranthane
on the specified packed GC column are not resolved by mass spectroscopy
and, therefore, not distinguishable by the methodology. When desired,
the use of capillary GC columns (SP-2100 on 30 m wall-coated capillary) in
place of the packed column (12) can eliminate the co-elution problem for
the three co-elution pairs.
Finally, the bases (benzidines) have been difficult to chromatograph
at low concentrations. An alternative HPLC method (13)(14) specifically
for benzidines has significantly lowered detection limits. Verification
of the benzidines for legal purposes may, however, require a GC/MS pro-
cedure.
The detection limits for the organics depend on the sample matrix.
Agency estimates on detection limits in wastewaters for the basic method-
ology are typically 10 ug/1 for most of the purgeable and base/neutral
priority organics. Agency estimates for most of the acid (phenols)
organics in wastewaters are typically 25 ug/1.
Kleopfer, et al., (10), recently completed a statistical evaluation
of EPA's basic methodology using data from seven laboratories on both
industrial and municipal wastewaters. The statistics (Table 8) indicate
an overall average recovery of about 90% of the purgeables and about 80%
of the acids (phenols) from both distilled water and wastewater analyses.
Significant wastewater matrix effects did not occur for either the purge-
ables or the acids. Indeed, compared to recoveries in distilled water,
the overall average recoveries in the wastewater analyses increased slight-
ly for purgeables and decreased slightly for acids. In the purgeable and
acid analyses Kleopfer found that the recoveries for specific organics
decreased significantly (purgeables, at the 99% confidence level; acids,
at the 95% level) as the volatility of the organics increased.
For base/neutrals, pesticides and PCB's, the study revealed signifi-
cantly lower average recoveries in the wastewater analyses (68% for base/
neutrals, 59% for pesticides and PCB's) compared to those in distilled
657
-------
water (84% for base/neutrals and 78% for pesticides and PCB's). The lower
recovery in the wastewater analysis was attributed to increased reactivity
of these classes of priority organics. When Kleopfer separated the base/
neutral class into more chemically reactive and less chemically reactive
groups, the statistical analyses confirmed the greater variability and
poorer recoveries in the more reactive grouping.
TABLE 8. RECOVERIES OF PRIORITY POLLUTANTS
Recoveries (percent)
Method Standard* Sample Spike
**
Priority Pollutant Fraction
Volatile (purgeables)
Acids (phenols)
Base/Neutrals
Pesticides and PCB's
P ±
90 t
84 +
84 t
78 +
c^**
Sp
13
13
25
11
P
92
76
68
59
± Sp***
t 15
t 19
t 21
+ 11
* Method standard refers to recoveries by standard addition to
distil led water.
•kit
Sample spike refers to recoveries by standard addition to sample.
***
P t Sp are weighted averages of the data points and are in
units of percent recovery t one standard deviation (Sp).
The quality control data (10) specified in the methodology (8) re-
vealed the quality control limits (* 3 a) for percent recoveries on
individual organics often ranged from zero to several hundred percent.
This broad range for some of the organics indicates that either the basic
methodology or the analytical performance of the laboratories could be
improved. Nevertheless, as an analytical tool for such a wide variety of
organics, the methodology with proper quality control is generally satis-
factory for the screening analysis of the organics.
Municipal sludges contain sufficient interferences such that the
Agency's basic methodology is not successful. The complex samples and those
samples where low detection limits (^1 ug/1) are desired require alternative
approaches or additional separation and clean-up procedures. To improve
analyses of purgeable organics in sludge samples and to lower their detec-
tion limits in all samples, DeWalle and Chian (15) have modified the purge
and trap method (Table 9) to include an on-column cryotrap after the Tenax
column and ahead of a capillary GC column. The cryotrap, cooled by liquid
nitrogen, captures the organics during desorption from the Tenax column.
658
-------
TABLE 9. ANALYSIS OF PURGEABLE ORGANICS BY CRYOTRAP
CAPILLARY GC/MS
5 ml sample
Purging with
Adsorption on Tenax Trap
Desorption at 180°C with back flushing
On column Cryotrapping of desorbed organics with liquid nitrogen
Release of organics and capillary GC/MS analysis
(30 m SE-54 WCOT column)
External standard method for quantisation
659
-------
The cryotrap is then rapidly warmed to focus and release the organics into
the capillary GC. The improved resolution of the capillary column along
with the cryotrap is claimed to reduce detection limits of the purge and
trap method. Possible future improvements in the purge and trap method
to reduce the sludge matrix effects include the use of salts (Na2$04
"salting out") or warming of the sample above ambient temperature to
improve the purgeability of the organics.
The large amount of extractable organics in complex samples such as
sludges, requires special extraction techniques (16) and separation and
clean-up procedures before GC/MS analysis. The principal classes of
organic interferences (15)(16) extracted from raw municipal wastewater and
sludge samples are:
. L i p i d s
• Fatty acids
. Saturated hydrocarbons.
In the complex samples, the large amounts of extractable interferences
overwhelm both the GC and the mass spectrometer. In order to permit
analysis these interferences must, therefore, be reduced in the extract
fractions before injection into the GC/MS system.
Three principal conventional approaches are available for this
reduction:
. Acid base separation
. Molecular size separation by gel permeation
chromatography
• Polarity separation (silica gel chromatography, etc.)
The acid/base separation is the fundamental separation approach
behind the Agency's basic methodology (8). In this methodology, base/
neutral extraction followed by acid extraction divides the total amount of
interferences between acid and base extracts, separates the.base/neutrals
from the acids and thus reduces the degree of interference in each fraction
injected in the GC/MS detector. Acid/base separation, however, may be
applied at many points in a separation scheme to remove or separate acid
compounds from neutrals or bases in a complex extract.
Molecular size separation is especially effective in removing the
lipids and high molecular weight fatty acids and hydrocarbons from the
extract. These materials apparently thermally decompose in the GC system
and create very complex GC chromatograms. Large amounts of these materials
will also reduce GC column life.
Separation due
used to separate the
priority organics.
to polarity with silica gel (16) or florisil (15) is
saturated hydrocarbons from the aromatic or polar
A cesium silicate approach (15), has also been
660
-------
employed to separate the acids (phenols) from the base/neutrals priority
organics and from neutral interferences.
The separation or "clean-up" approaches can be assembled in various
combinations to reduce the interferences from extracted municipal sludges.
A method has been developed by DeWalle and Chian (15) for the analysis of
the extractable priority organics in complex samples. The methodology
Table 10, uses an acid/neutral extraction followed by a base extraction;
gel permeation chromatography (GPC) of the acid/neutral extract into two
fractions and a discard which contains the large interferences; florisil
chromatography of one GPC fraction for separation of the saturated hydro-
carbons from those priority neutrals in the fraction; and cesium silicate
for separation of the acids (phenols) from the priority neutrals in the
second GPC fraction. The phenol fraction from the silicate separation may
be derivatized with diazomethane before GC/MS analysis or analyzed by
fused silica capillary column GC without derivatization. The method pro-
duces three neutral fractions which may be combined into a single extract
before GC/MS analysis or analyzed separately. The method uses capillary
GC/MS techniques for the final analysis. The pesticides and PCB's are
analyzed in the neutral fraction. Alternative extraction techniques under
evaluation include homogenization-centrifugation, liquid/ liquid extraction
and extractive steam distillation.
The Municipal Environmental Research Laboratory uses the DeWalle and
Chian procedures for measuring the purgeable and extractable organics in
both wastewater and sludge samples in the survey of 25 cities. The data
indicate detection limits for the priority organics of about 1 ug/1 for the
extractables and <1 pg/1 for the purgeables in wastewater samples. The
data also suggest detection limits of 5-10 pg/1 for the organics in
sludge samples. The method is not fully satisfactory for all of the
priority organics in all the highly variable sludge matrices. Losses of
individual organics occur either through reaction with the matrix or
losses in the separation processes. At the present time, insufficient data
have been assembled to provide statistical analysis of the recoveries of
the priority organics by the method.
OCCURRENCE IN WASTEWATER
Shortly after the establishment of the list of priority pollutants as
the chemicals of most concern to EPA, it became obvious that a data base
of occurrence and removal in municipal wastewater treatment plants was
urgently required. Toward that goal three major surveys were undertaken;
one conducted by the Cincinnati Laboratories, consisting of a survey of 25
cities and another more extensive survey of 40 cities is being carried by
the Washington Headquarters Office of Water Planning and Standards and,
finally, an additional study is underway in which six cities have been
selected for an intensive study of the sources of priority pollutants. The
study also includes the monitoring of the treatment plant. None of these
survey studies has been completed, thus, the information available at this
time is incomplete and firm conclusions cannot be made. Additionally,
other survey studies for selected metals on the priority pollutant list
are concurrently being conducted by intensive sampling at single plants
661
-------
TABLE 10. ANALYSIS OF EXTRACTABLE ORGANICS WITH CLEAN-UP AND CAPILLARY GC/MS
Sample
Extraction at pH 2 with CH2C12
Drying and concentration
Addition of pentane
GPC on Biobead S-X2
Extraction at pH 12 with
Drying and concentration
GC/MS analysis
(30 m capillary GC-SE54)
Internal standard quantification
cr,
CTi
NJ
I
Discard
(lipids)
Concentration and
exchange into
pentane
I
Florisil separation
Discard
(hydrocarbons)
50% pentane/
ether extract
Solvent Exchange
and concentration
I
Cesium silicate
separation
extract
Ether
extract
Concen- Concentration
tration
GC/MS analysis of neutrals
30 m capillary GC-SE54
Internal standard quantification
Methanol p
henol extract
Partition to CH?C1?
I
Concentration
I
GC/MS Analysis
Internal standard
quantification
-------
in order to establish data on removals of metals by unit treatment processes
All literature, both published and that available in government, state and
local records, is being searched for information on the occurrence and
removal of priority pollutants. Thus far, much of this information is
concerned with metals.
At the completion of all of these studies, and others, a fairly clear
picture will emerge on the extent of the problem of priority pollutants in
wastewater. These surveys will constitute the data base which will improve
planning and environmental regulation.
Selection and Sampling of Survey Cities
'Considering that there are some 20.6 thousand municipal treatment
systems in the United States, it was important that the small number of
cities that would be sampled (25 + 40 = 65 cities) would constitute a
reasonably representative sampling of the country. Several criteria were
established, including, size of flow, geographic' location, proportion of
industrial waste discharged to the plant including differing types of
industrial discharges, type of treatment including primary, activated
sludge, trickling filter, physical-chemical processes and degree of treat-
ment quality being achieved. The final selection of the cities to be
sampled is depicted in Fig. 2 showing the geographic locations and names
of the cities. The plant locations of both the 40- and 25-city surveys
are shown.
In the 25 city plant survey a single 24-hour composite sample is
being taken from influent, primary effluent and final effluent. A grab
sample is taken from the digester. Where chlorination of final effluent
is practiced, a sample is taken both before and after chlorination.
Fifteen of the cities will be resampled. The 40 city survey is designed
similarly except each plant will be sampled for one week.
Data collection on the six city survey will concentrate on the waste-
water collection system, as well as the municipal plant with the objective
of determining the sources of the pollutants; i.e., the amounts and kinds
of compounds contributed by industrial, commercial and domestic sources.
Since the samples were to be 24-hr composites, there was some concern
about the losses from the sample of the more volatile components that are
commonly present in wastewater; for example, chloroform or trichloro-
ethylene which are known to have half-lifes in open vessels of only 20-30
minutes. To circumvent these anticipated losses a special sampler was
developed at our laboratory (17). The sampler concept is simply a closed
increasing-volume container obtained by using the principle of a piston
schematically illustrated in Fig. 3 . A further modification was develop-
ed on the 25 city survey and incorporated into a novel sampler system.
In operation, four or more samplers are located at various sampling points
at the plant. Sampling times are radio-transmitted to each sampler and
controlled by a mini-computer which determines the sampling sequence based
on time of flow through the plant.
663
-------
(Ti
(Ti
coloradoTprlnga
• - 25 CITY SURVEY
O - 10 city survey
icflt
a
Oklahoma city
APPI.ETON ,
2'jaoK
-
3t.l9ul3
muncle D3pl
Indianapolis g "
hlooiolngton a U Cincinnati
Virginia
O beach
S3hevllle
0
CHATTANOOGA
^FATETTCTILLE
spartaftburg J
ontfvie
Figure 2. Locations of Cities Being Surveyed for Priority Pollutants
-------
FROM SYSTEM -*--
SAMPLING POINT"
A
c
SAMPLE
TIMER
B
TO OTHER SAMPLERS
rtr/
f ^
SAMPLE
CHAMBER
/ TEFLON
FLOAT
*
STIRRING
/BAR
D
^X-AIR
MAGNETIC
MIXER
TO TO SAMPLE
WASTE VIAL
VALVE
TYPE
FUNCTION
A
B
C
2-WAY
SOLENOID
3-WAY
SOLENOID
MANUAL
TOGGLE
MANUAL
NEEDLE
DIRECT SAMPLE
TO VALVE B
DIRECT SAMPLE
TO CHAMBER
TRANSFER COMPOSITE
SAMPLE TO VIAL
& DRAIN REMAINDER
CONTROL MIXER
SPEED
FIGURE 3. AUTOMATIC COMPOSITE SAMPLER FOR VOLATILE HALOGENATED ORGANICS
665
-------
Survey Results
The 25 city survey is being conducted by the combined efforts of the
University of Washington and Georgia Institute of Technology. A major
portion of the study to date has been spent on developing the analytical
procedures appropriate for the analyses of such difficult-to-analyze samples
as raw wastewater and particularly sludges. The analytical implications
have been discussed previously in this paper. At this time, twenty-five
plants have been sampled but the results from only three are available,
and even these data are incomplete.(15)
The Renton treatment plant in Seattle, Washington, serves a population
of 198,000 and has an average dry weather flow of 136,000 m3/day (36 mgd),
5% of which is contributed by industrial discharges. There are 37 permits
for industrial waste discharge to the plant. The plant is a conventional
activated sludge system with an aerated grit chamber and with effluent
disinfection by chlorine and S02 dechlorination. Sludge is not treated at
this plant but is pumped to another plant for treatment and disposal. The
plant is well operated and produces a good effluent; average influent BOD
of 273 mg/1 is reduced to 12.5 mg/1 and suspended solids from 351 mg/1 to
12.5 mg/1. In addition to the conventional parameters, samples were
analyzed only for the priority pollutants. Thus, other synthetic organic
compounds may be and almost certainly were, also present - only the priority
pollutants were identified and quantified. Since the tapes from the G.C-
Mass Spectrometer are available as well as the individual solvent extracts,
it is possible, at the conclusion of this phase of the study, to reanalyze
the samples for compounds other than those on the priority pollutant list.
The Oakland, California, plant serves a population of 575,000 with
a dry weather flow of 235,000 m3/day (62 mgd) of which 15% is contributed-
by industrial discharges. The plant is an activated sludge system but
varies from the previous plant in that the system includes prechlorination
(for odor control but also providing the potential for forming chloro-
organic compounds), aerated grit chamber (with the potential for loss of
volatile organics), pure oxygen activated sludge aeration and final effluent
chlorination and dechlorination. Influent BOD and suspended solids of
330 mg/1 and 470 mg/1 are reduced to 8 mg/1 and 21 mg/1, respectively.
Primary and secondary sludges are anaerobically digested, vacuum filtered
and disposed to sanitary landfill. This plant differs, therefore, from
the Renton plant in that the main flow contains sludge return flows.
The third plant sampled was the Clayton treatment plant in Atlanta,
Georgia. The plant treats a flow from a population of 367,000 with a dry
weather flow of 246,000 m^/day (65 mgd). Percent industrial contribution is
not available at this time but some indication is the 122 permits issued
for industrial wastes discharge. The system consists of grit removal,
primary sedimentation and pure oxygen activated sludge aeration. Chlori-
nation is added for disinfection. Primary and secondary sludges are
combined and anaerobically digested, dewatered by centrifugation and
incinerated. The raw wastewater, in contrast to the previous two plants,
666
-------
is relatively weak with a BOD and suspended solids content of 122 mg/1
and 141 mg/1 which are reduced to 31 mg/1 and 40 mg/1, respectively.
The data on all of the plants, for all of the priority pollutants
and sampling points are summarized in Table 11. The sludge analyses varied
with the plant. For the Seattle plant, untreated and combined primary
and secondary sludge was sampled. For the Oakland and Atlanta plants the
sample was taken after anaerobic digestion. Furthermore, the data for
sludge are reported as micrograms per liter of liquid sludge. These data
will subsequently be recalculated on the basis of dry solids, but this
information is not now available. If one assumes that the solids concen-
tration of the sludge was on the order of 3-4%, then the sludge values
(on a dry weight basis, ug/kg) would be higher by a factor of 33-25.
The analyses, to date, covering the first three plants found 87
priority pollutants of the 127 compounds on the list (asbestos and dioxin
were not analyzed). Not unexpectedly, there is a wide variation among
plants for compounds identified and in concentrations found. Similarly,
removals for specific compounds, varied from zero to almost 100%. Not-
withstanding these variations some tentative observations can be made.
Of the 87 compounds found, 24 organics and 13 metals were found in all
of the plants. Chlorination for disinfection generally increased the
concentration of certain compounds. While most compounds were detected
at increased concentrations in the sludge, the phthalate esters and the
polynuclear compounds tended to accumulate in the sludge to much greater
concentrations. These trends will become more apparent and conclusive
as the data from the remaining plants become available.
An attempt was made to identify those compounds in the plant effluents
(after chlorination) which were equal to or exceeded the concentration
for which criteria have been proposed for freshwater or marine aquatic
life or for human health effects (Table 4). In essence, this list points
out the compounds which may require some special attention. This information
is presented in Table 12 in which the maximum concentration of the compound
found in any of the effluents (after chlorination) from the plant survey
is shown in the first column. Column two lists the aquatic (freshwater
or saltwater) criterion which is equal to or exceeded by the effluent con-
centration. Generally, the 24-hour average value was selected. The ratio
of effluent concentration to the aquatic life criterion, shown in column
three, provides an indication of the amount of dilution required to reduce
the effluent concentration to the criterion concentration. This calculation
was repeated for human health effects criteria, where this applied for
the particular compound, and are shown in columns four and five. Column
six shows the range of percent removals obtained at the three treatment
plants. Thus, a presumption can be made that whenever removal of a com-
pound exceeds %95% at the treatment plant and the effluent concentration
still exceeds some criteria, then this compound may require special attention
667
-------
TABLE 11. QCCURENCE AND REMOVAL OF PRIORITY POLLUTANTS AT THREE TREATMENT PLANTS
No.
1
4
6
7
8
10
11
13
•14
16
18
Compound
Acenaphthene
Benzene
Tetrachloromethane
Chlorobenzene
1 ,2,4-Trichlorobenzene
1 ,2-Dichloroethane
1 ,1 ,1-Trichloroethane
1 ,1-Dichloroethane
1 ,1 ,2-Trichloroethane
Chloroethane
Bis(2-chloroethyl )ether
Plnt^
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Infl.
Sew.
Sec.
Effl.
Sec.
Effl. ,,,
Cnlor. Sludge1'
% (c\.
Rem.^'Tox.
a' Concentration, /jg/1
0,1
0.3
0.9
8.8
10.5
7.7+
0.6
177.3
0.6
1.5
0.5
8.4+
9.1
88.4
1791 +
1.7
6.7+
0.9
0.1
0.12
0.05
3.0
0.6
0.2
0.3
0.1
0.5
2.0
1.3
11.2
26.9
36.1
0.4
1.6
0.6
2.5
0.01
0.1
2.9
0.04 21.5
8.9 5.2
12.4
1.1
0.1
0.5 22.8
13.5
0.3
1.7
6.0
1.1 +++
32.6 12.1
36.3
30.8 +++
1.8
1.9 2.3
-H-+
1.8 +++
0.01
94
66 x
92++
99.9
85
65
0
85++
0
70
98++
6
92++
92
668
-------
TABLE 11 (Contd.;
No.
21
23
25
26
29
30
31
32
34
36
37
Compound
2,4,6-Trichlorophenol
Trichloromethane
(chloroform)
1 ,2-Dichlorobenzene
1 ,3-Dichlorobenzene
1 ,1-Dichloroethylene
1 ,2-Trans-dichloro-
ethylene
Oichlorophenol
1 ,2-Dichloropropane
2,4-Dimethylphenol
2,6-Oin1trotoluene
1 ,2-Diphenylhydrazine
Sec.
Infl. Sec. Effl. ,h.
Sew. Effl. Chlor. Sludge10 J
Rem.(cVox.
Pint'3' Concentration, >ug/l
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
14.3
4.2 4.0 7.5 4.5
37.5 19.1 34.2 0.5
17.1+ 0.4 0.6 +++
4.8 3.0 3.9
1.8 1.3 0.2 15.8
43.9 1.2 10.1 312
0.7
0.2 0.4 5.5
3.1 0.4 1.3 17.0
0.5 3.9
1.8 1.1
43.2+ 1.2 0.6 +++
0.3 0.2 1.6
0 . 9+ +++
9.4
1.2
58.2
42.6
2.6
0.02
0.1
5 x
49 x
98++
38
28
97 x
0
86 x
x
97+ +
0.01
3.6
669
-------
TABLE 11 (Contd.;
No.
38
39
42
43
44
47
48
49
50
55
56
Compound
Ethyl benzene
Fluoranthene
Bis(2-chloroisopropyl )
ether
Bis(2-chloroethoxy)
methane
Methylene chloride
(dichloromethane)
Bromoform
Dichlorobromomethane
Trichlorof 1 uorome thane
Dichlorodifluoromethane
Naphthalene
Nitrobenzene
Pint'
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Infl.
Sew.
Sec.
Sec. Effl. ,, > % . ,
Effl. Chlor. Sludge10' Rem}c;Tox.
a' Concentration, xjg/1
0.18
148.3
0.2
3.1
0.6
0.16
0.31
293
9.0
647 +
1.5
0.7+
1.5
34
59+
9.2+
1.3
6.8
10.9
0.3
0.1
0.17 1.2 1.5
0.3 0.8 161
1.3
42.3
0.05 0.1 27.2
0.06
0.3 0.2
0.3 0.1
0.02
304 327
4.6 7.3 0.2
182 141 +++
1.3 7.6
0.9
+++
+++
3.5
+++
0.2 11
76
4.1 0.4 319
0.01
6
99.8
17 x
62
0 x
49 x
72++ x
90++
85
62
90
670
-------
TABLE 11 (Contd.l
No.
57
60
61
62
63
64
66
67
68
69
70
Compound
2-Nitrophenol
4,6-Dinitro-o-cresol
(4,6-Dinitro-2-methyl-
phenol )
N-nitrosodimethylamine
N-ni trosodiphenyl amine
N-nitrosodi-n-propyl-
amine
Pentachlorophenol
8is(2-ethylhexyl )
phthalate
Bjjtyl benzyl phthalate
Di-n-butyl phthalate
Di-n-octyl phthalate
Diethyl phthalate
Pint
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Infl.
Sew.
Sec.
Sec. Effl.
Effl. Chlor.
%
Sludge(b' Rem!
^a' Concentration, .ug/1
0.2
1.3
0.5
6.7
30
1.3
275
50
6.7
126
IS
5.6
11
13
11
6.6
9.S
1.4
5.3
0.4
0.2
0.06 0.3
0.1
0.1
12 15
13
0.9 13
3.4
11
0.4
1.6 3.7
l.S 5.4
6 4.9
5 l.S
0.2
0.1
0.3 0.2
1.4
7.7
0.1
123
60
40
7400
3800
20
3100
120
l.S
200
120
240
6.0
S3
99
31
78
91
68
45
62
98
79
;Tox.
671
-------
TABLE 11 (Contd.;
No.
71
72
73
74
75
76
77
78
80
81
84
Compound
Dimethyl phthalate
Benzo(a)anthracene
( 1 ,2-Benzoanthracene)
Benzo(a)pyrene
3,4-Benzofluoranthene
Benzo(k)f luoranthene
Chrysene
Acenaphthylene
Anthracene
Fluorene
Phenanthrene
Pyrene
Pint1
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Sec.
Infl. Sec. Effl.
Sew. Effl. Chlor.
'a)
1 ' Concentration, u
0.7
0.4 0.1
0.1 0.1
0.1
0.1
0.1
0.4
6.1
0.7
0.1
0.2 0.04
0.05
0.07
0.2
0.6
1.7 0.1
0.4 0.4
1 ;2
3.2 0.3 0.3
0.2
0.8
0.1 0.2
Qt
Sludge(b) Rem.(c)Tox.
g/i
4.2
0.8
4.8
8.4
15
8.0
14'
14
23
20 80
9.6
5.8
51 94
0
27
100 91
25
40
672
-------
TABLE 11 (Contd.)
No
85
86
90
91
91
91
92
93
94
(P
95
96
Compound
Tetrachloroethylene
Toluene
(Methyl benzene)
Dieldrin
Y-Chlordane
;j-Chlordane
Chlordene
4,4'-DDT
4,4'-DDE
4,4'-DOD
,p'-TDE)
a-Endosulfan-Alpha
b-Endosulfan-Beta
Plnt^
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Infl.
Sew.
Sec.
Effl.
Sec.
Effl.
Chlor.
Sludge(b)
Rem.
Tox,
Concentration, >ug/l
6.4
49
560+
0.8
112
70+
0.02
0.05
0.21
0.5
0.3
0.2
0.4
0.1
1.1
0.5
0.2
0.2
0.3
0.17
0.1
0.28
0.23
20
10
5.
8.
1.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
3
4
0
7
05
20
2
2
1
3
1
1
2
4
05
2
14
01
24
25
4.
11
1.
1.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
4
0
5
1
04
1
8
6
1
1
5
2
2
0.04
0.
0.
0.
01
14
1
0.
04
38
++
36
•+
126
++
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
•+
02
06
7
7
2
5
5
1
6
3
2
04
4
2
4
05
0
80
99++
0
99
99++
5
50
33'
50
0
91
37
17
91
86
39
X
X
X
X
X
X
X
X
X
673
-------
TABLE 11 (Contd.)
No.
97
98
100
101
102
103
104
Compound
Endosulfan sulfate
Endrin
Heptachlor
Heptachlor epoxide
a-BHC-Alpha
b-BHC-Beta
T -BHC-Gamma
(lindane)
105
114
115
117
g-BHC-Delta
A-BHC
Antimony
Arsenic
Beryl lium
Pint'
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
Infl.
Sew.
Sec.
Effl.
Sec.
Effl.
Chlor.
Sludge(b)
* (c)
Remr'Tox,
4' Concentration, jug/1
0.2
37
0.15
5
0.13
0.58
0.23
0.41
0.14
4
3.8
<1
12
14
60
0.2
< 1
4
0.08
0.40
0.13
0.16
0.15
0.9
4.5
2.5
<1
4.4
11.3
30
0.2
< 1
5.1
4.
0.
0.
0.
0.
0.
0.
0.
0.
9.
0.
4
< 1
<1
4.
11
8
2
4
01
08
36
44
14
16
9
87
5
.3
30
0.
< 1
2.
1
9
1.3
0.26
0.16
0.32
0.12
0.13
40
120
<1
400
1400
5000
3.4
14
23
47
92
61
0
0
34
63
19
50
0
x
0
x
X
X
X
X
X
X
X
X
674
-------
TABLE 11 (Contd.)
No. Compound
118 Cadmium
119 Chromium
120 Coppec
121 Cyanide
122 Lead
123 Mercury
124 Nickel
125 Selenium
126 Silver
127 Thallium
128 Zinc
Plnt(a)
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
C
R
0
c
R
0
C
R
0
C
R
0
C
R
0
C
Infl
Sew.
. Sec.
Effl.
Sec.
Effl.
Chlor.
Concentration,' u
22
34
1.1
170
390
56
100
140
21
29
126
28
12
96
117
11
17
9.6
105
640
560
1
<]
3.8
17.3
9.3
9.6
<1
*1
125
1600
1700
23
<1
<1
35
41
16
1
140
31
8
65
7
14
13
47
2
13
0.7
80
290
1400
1
<1
3.8
1
2.1
7.1
<1
"1
50
150
500
14
«- 1
< 1
30
66
15
1
70
31
0
77
4
6
25
22
1
10
1.6
70
150
865
1.8
<1
7
1
<1
7.1
<1
<1
25
200
300
S1udge(b)
9/1
400
3000
770
2200
1900
23,000
2100
15,000
2500
120
20,000
190
4000
13,000
85
270
480
9500
35,000
99,000
9
85
<1
213
250
400
<1
-------
TABLE 12. COMPOUNDS FOUND IN EFFLUENTS THAT EXCEED SOME ENVIRONMENTAL CRITERION
Compound
Benzene
Chloroform
1 ,2-Dichlorobenzene
1 ,1-Dichloroethylene
Fluoranthene
Methylene chloride
N-Nitrosodimethylamine
Tetrachloroethylene
Chlordane (tech)
Endrin
Heptachlor
Arsenic
Beryl 1 ium
Cadmium
Copper
Cyanide
Nickel
Selenium
Silver
1
Max Cone
In Effluent
yg/l
8.9
34
10
3.9
0.1
327(c)
0.4
25
0.8
0.4
0.01
30
2.9
14
70
77
865
7
7.1
2
Aquatic
Criteria
yg/l
15
0.3
0.009
0.002
0.0015
29
0.79
1.4
4.4
0.009
3
Ratio(a)
2.3
3
89
200
7
1
89
55
1.6
789
4
Human Health
Effects
yg/l
15
2.1
1.3
2.0
0.026
2.0
0.001
0.00023
0.02
0.087
10
133
10
5
Ratio(a)
0.6
16
3
16
15
13
800
44
1500
33
1.4
6.5
0.7
6
Ranged
% Removal
66-92
5-98
97
17
49-72
-
0-99
5-50
-
-
19-63
-
>97
0-99
48-75
0-55
-
26-94
-------
TABLE 12 (Contd.)
Compound
Chromium
Acenaphthene
1 ,2-dichloroethane
1 ,1 ,2-trichloroethane
naphthalene
Dieldrin
4,4-DDT
a-BHC-alpha
g-BHC-beta
y-BHC-gamma
6-BHC-delta
1 2
Max Cone Aquatic
In Effluent Criteria
yg/1 yg/1
66(Total)
2.9
6.0
1.8
0.4
0.1
0.5
0.13
0.44
0.16
0.9
3 4
Human Health
Effects
RatioU) yg/1
50
20x10-3
7
2.7
143xlO-3
4.4X10'8
0.98xlO"3
16xlO-3
28xlO"3
54xlO-3
21x10-3
5
Ratio(a)
0.8
145
0.9
0.7
2.8
230x1 O4
510
8
16
3
43
6
Range^)
% Removal
71-89
94
0-85
-
62-85
-
91
-
-
0-61
-
(a) Ratio of effluent concentration to aquatic or health criterion
(b) Range of percent removal in three city treatment plants
(c) High values may be due to contamination from analytical extraction solvent
-------
REMOVABILITY - TREATABILITY
The municipal wastewater treatment plant physically occupies a central
position in the scheme to control hazardous and toxic substances in liquid
wastes. Industrial discharges (even after pretreatment) and commercial
and household wastes generally enter a municipal treatment plant for treat-
ment. How well the receiving stream (and ambient air surrounding the treat-
ment plant) is protected against contamination by synthetic organic and
metal compounds depends on the effectiveness of wastewater treatment pro-
cesses for removal of these substances. There is, therefore, the unavoid-
able need to assess the effectiveness of conventional and unconventional
wastewater processes to reduce influent concentrations to levels accept-
able for discharge to surface waters.
While the terms "removability" and "treatability" have commonly been
used interchangeably, there is a justifiable reason (for research purposes)
to make a distinction between the two terms. It is useful to consider
that treatability is a property or characteristic of the molecule, in much
the same way as solubility or vapor pressure. Treatability of a compound
is determined by specified procedures under controlled conditions and thus
compounds can be compared or ranked relative to other compounds. The
position in a ranking of compounds can provide some insights on the behavior
in a certain treatment process. For example, a compound which adsorbs on
carbon by batch isotherm testing, at 300 mg/g of carbon is more likely to
be removed from solution than a compound that is adsorbed at 10 mg/g.
Such treatability research is necessary in order to provide the data base
to formulate more vigorous modeling of how compounds in general behave in
a treatment process.
It is recognized that the treatability of a compound, much like its
solubility, will change when conditions change; such as mixture with other
compounds, aqueous composition, pH, etc.
Removability is a more general term which simply describes the change
(or no change) in concentration of a compound between entering a process
and leaving a process. Several treatability mechanisms may, and usually
do, operate in a process to achieve a change in concentration. A good
example is the activated sludge process. A change in concentration of a
compound between influent and effluent can occur via several treatment
mechanisms including: stripping, biodegradation, adsorption, precipitation,
hydrolysis, etc. Thus, removability will be highly characteristic of the
conditions of the process at some time and place.
Research on the 114 organic compounds on the priority pollutant list
was planned to occur in phases. The first phase consists of a series of
"screening" tests for all of the compounds for all of the three processes
being considered (biodegradation, carbon adsorption, air stripping).
Most of this phase has been completed. The preliminary results will be
discussed in this paper. The second phase will consist of dynamic
678
-------
rather than static or batch tests and will include more complex solutions
of mixtures of compounds and wastewaters rather than distilled water test
solutions. This phase has not yet been started. The third phase will
consist of "removability" tests in which treatment systems rather than
individual unit processes will be evaluated for removal of mixtures of
organic compounds in wastewater. Some preliminary research has been
completed in this phase and additional work is being conducted at pilot
plant scale at our new Test and Evaluation facility located in Cincinnati,
Ohio.
Biodegradability
Perhaps the single most important process for control of toxic organic
compounds is biological decomposition. Thus, the biodegradability of a
compound is an essential element of information. It is also important, in
the test for biodegradability, to isolate insofar as it is possible, other
mechanisms of removal that occur in operating biological plants, such as
adsorption on sludge and stripping from solution. The screening test
selected to meet these criteria, is the simple static flask procedure in
which the compound is dissolved (or emulsified) into BOD dilution water
(described in Standard Methods) supplemented with 5 mg/1 of yeast extract.
This medium supplies sufficient nutrients for active biological growth but
will not produce excess solids.
The test compound (usually at concentrations of 5 and 10 mg/1) and
nutrient solution contained in 250 ml flasks, either cotton stoppered or
glass stoppered for the volatile compounds, were inoculated with 10 ml of
settled domestic sewage. The flasks were incubated in the dark in a con-
stant temperature room at 25°C for seven days. The flasks were shaken
daily to ensure homogeneous distribution of the culture. At the end of
the first incubation period, part of the contents of the flask was used to
analyze for residual test compound, and another portion was used as inocu-
lum for a fresh flask. Three weekly subcultures were prepared resulting
in a total elapsed time of 28 days for each test. The usual analytical
procedure consisted of solvent extraction, solvent volume reduction and
completion of the analysis by gas chromatography.
At this time, the experimental work on the screening test for biode-
gradability is nearing completion, and is continuing, but preliminary data
are available for most of the priority pollutant compounds. (18) Some
typical results are shown in Table 13 where the data for a single class
of compounds, the halogenated ethers, are shown. Bis(chloromethyl )ether,
the remaining ether compound in the priority pollutant list, is the most
active carcinogenic ether, and will be determined at a later date under
special safety precautions.
Several types of reactions to biodegradation can be deduced from the
screening test. Both bis-(2-chloroethyl)ether and bis-(2-chloroisopropyl)
ether are readily degradable and 2-(chloroethyl vinyl)ether is degradable
after a short acclimation period. The remaining three ether compounds are
not degradable with bis(2-chloroethoxy)methane being completely resistant
to degradation within the 28-day acclimation period.
679
-------
TABLE 13. BIODEGRADABILITY OF HALOGENATED ETHERS BY STATIC FLASK TEST
Test Compound(a)
Percent Degradation of Compound in 7 Days
FirstSecondThird
Perfor- Original Sub- Sub- Sub-
mance Culture Culture Culture Culture
Bis-(2-Chloroethyl) ether D 100 100 100 100
2-Chloroethyl vinyl ether D 76 75 100 100
4-Chlorodiphenyl ether N 0 32 36 1
4-Bromodiphenyl ether N 0 19 36 0
Bix-(2-Chloroethoxy) methane N 0 0 0 0
Bis-(2-Chloroisopropyl) ether D 85 100 100 100
(a) Test concentration - 5 mg/1
D Degradable
N Not significantly degradable
Some 90 compounds of the 114 organic compounds on the priority pollutant
list have been completed or are in various stages of completion. Of these,
23 compounds, or 29% of the total tested, listed in Table 14, have been
found to be either non-degradable within the 28 days of three successive
subcultures or have shown less than 50% reduction in concentration indicating
that microbial adaptation to the compound was slow. It should be clearly
understood that the screening test has limitations, and it would be dangerous
to extrapolate these data to continuous flow biological systems which contain
high concentrations of active biological solids and where longer times are
available for microbial acclimation to the compound. Nevertheless, it can
generally be assumed that those compounds that are readily degraded in the
screening test are likely to be degraded in continuous flow biological sys-
tems. The screening test also serves the purpose of identifying those com-
pounds which, while they were not degradable in this test, will require the
second level of testing by operating bench-scale continuous flow activated
sludge systems. This approach is planned for the compounds that show little
or no degradation in the screening test. Also shown on Table 14, column 2,
are the carbon adsorption capacities of these compounds calculated at an
initial concentration of 100 ug/1. The adsorption process is discussed in
the next section.
Activated Carbon Adsorption
One process that is increasingly being considered to control synthetic
organic compounds, especially for those compounds which are refractory
to biological degradation, is activated carbon adsorption. Unfortunately,
carbon is selective in its ability to adsorb compounds. The capacity,
in terms of milligrams of compound adsorbed per gram of carbon, varies
over 2 to 3 orders of magnitude and certain classes of compounds are
not adsorbed at all. As another tool to evaluate the treatability of a
compound it is necessary to determine its adsorption on activated carbon.
680
-------
TABLE 14. NON-DEGRADABLE COMPOUNDS AND CARBON ADSORPTION CAPACITIES
Percent reduction Carbon adsorption
Compound after 3rd sub-culture capacity^) (mg/g)
4,6-Dinitro-o-cresol 52 76
1,2-Dichlorobenzene 35 47
1,4-Dichlorobenzene 16 41
1,2,4-Trichlorobenzene 24 78
Hexachlorobenzene 5 450
1,2-Benzanthracene 0
Chrysene 59
4-Chlorodiphenyl ether 1.0 61
4-Bromodiphenyl ether 0 30
Bis(2-chloroethoxy)methane 0 2.6
Polychlorinated biphenyls - PCB
1016 48
1221 48
1232 120
1242 66
1248 0
1254 0
1260 0
N-nitroso-di-N-propylamine 28^ 16
Bromoform 59 ^ 5.7
Dichlorobromomethane 55^a) 1.9
1,1,2-Trichloroethane 38(a) 1.4
1,1,1,2-Tetrachloroethane 27 ^ 4.5
1,2-Dichloroethane 41(a) 0.5
^a' Data only for the results from first sub-culture = 14 days
W Adsorption capacity for 100 yg/1 initial concentration at neutral pH
681
-------
As of this date, adsorption isotherms have been obtained in almost all of
the priority pollutants. (19) A report on this work is in preparation.
This report will contain the activated carbon capacities at several initial
concentrations of compound, the constant, K, and slope 1/n, of the powdered
or granular carbon to reduce differing initial concentrations of compound
to specified residual concentrations.
The most commonly used technique to determine adsorbabil ity of compounds
on carbon, or any other sorbent, is to determine an adsorption isotherm,
which measures the extent to which an organic chemical partitions itself
between the solid and solution phases of an aqueous solution of the compound.
Experimentally, the test is conducted by contacting various amounts of carbon
with a solution of the compound with a known initial concentration. After
a period of contact, during which time the suspension is stirred, the
carbon is separated from the suspension and the clear solution is analyzed
for residual compound.
In our laboratory, a granular carbon from a single major manufacturer
was pulverized until all of it passed a 200 mesh screen. Special care was
taken to assure that the initial concentration of compound did not exceed
its solubility. Solutions were prepared in distilled water in most cases.
Special precautions were also taken for compounds that are volatile by
using containers that were completely filled by the solution and were
tightly capped during the contact period. For those compounds that are
ionizable, the isotherm was determined at three pH's; 3.0, 7.0 and 9.0 by
adjusting the solution pH with acid or base. After two hours of contact-
ing time at room temperature, the carbon was separated by filtration through
various types of filters. Residual compound was determined by a variety of
analytical methods including TOC, U-V spectroscopy and gas chromatography
by either the purge and trap technique or by solvent extraction, solvent
volume reduction and G.C. detection.
The adsorption data were plotted according to the Freundlich equation.
While this equation is empirical it is nonetheless widely used and has been
found to describe adequately the adsorption process in dilute solution.
The Freundlich equation has the form:
* =
The data were plotted according to the logarithmic form of the equation
which has the form:
log = log K + 1/n log Cf
where:
X = (C0-Cf) V = initial concentration of solution in mg/1 minus
final concentration in solution at equilibrium
multiplied by solution volume, V, in liters.
M - weight in grams of adsorbent (carbon).
682
-------
Cf = final concentration of solute in mg/1 at equilibrium
K = intercept at Cf - 1 (log Cf = 0)
1/n - slope of the line
For the dilute solutions in this study, this equation yields a straight
line with a slope of 1/n and the intercept equal to the value of K when
Cf = 1 (log Cf = 0). The intercept K, is an indicator of adsorption capac-
ity, expressed as milligrams of compound per gram of carbon. The slope,
1/n, indicates the intensity of adsorption. Linear least squares regression
analysis was used to locate the line which also permitted the calculation
of the correlation coefficient, r.
Whether a compound adsorbs on carbon and at what capacity depends on
a multitude of parameters of both the carbon particle as well as the char-
acteristics of the organic molecule. Much research remains to be done to
understand the mechanisms which determine the adsorption characteristics
of a compound. Active research, in this laboratory and others, is provid-
ing some answers. It is entirely likely that with sufficient basic infor-
mation it will be possible to predict the adsorption behavior of any un-
tested compound based simply on a knowledge of molecular characteristics.
This line of research is being pursued in this laboratory with the ultimate
objective of being able to predict the carbon adsorption behavior of the
vast numbers of untested compounds and the continuing outpouring of newly
developed organic compounds. Actual testing of these thousands of compounds
is impractical, if not impossible, and a capability to predict is essential.
An example of the influence of pH and differing substitutions on the
phenol molecule is shown in Table 15. The carbon capacity, X/M,is shown
for phenols and substituted phenols at three pH's at an initial concen-
tration of 10 mg/1 for each compound. Two observations can be made. For
an acidic ionizable compound such as phenol, adsorption capacity is maximum
at acidic pH's and this behavior holds true regardless of the substitutions
made to the original phenol molecule. A second observation is that, at
neutral pH, the adsorption of phenol increases from 80 mg/g to 160 mg/g
when two nitro groups are added to the molecule. Uhen a 9-carbon alkyl
group is added (nonyl), the capacity jumps to 595 mg/g. Addition of five
chlorine atoms, as in pentachlorophenol, confers high adsorbability.
A further example of the effect of substitution on an aromatic compound
is shown in Table 16. The carbon adsorption capacities, in mg/g, are
shown for the compounds all at an initial concentration of 1 mg/1. The
data show an increase in adsorption capacity as differing functional groups
are added to a benzene parent molecule. It is clear that the changes in
adsorption cannot be attributed to some simple explanation, such as molecu-
lar weight, since ethyl benzene and styrene side chains differ only slightly
in molecular weight and in the presence of a C = C in the styrene substitu-
tion. The data suggest that, in addition to changes in atoms and simple
groupings such as nitro- or hydroxo-, the adsorbability is also affected
by molecular structural differences.
683
-------
TABLE 15. ADSORPTION OF PHENOL AND SUBSTITUTED PHENOLS
Compound
Phenol
2,4-Dinitro-
phenol
Nonylpheno'
Pentachloro-
phenol
pH
3
7
9
3
7
9
3
7
9
3
7
9
X/M, mg/gx"'
85
80
70
405
160
75
570
595
275
635
385
260
' K
12
13
22
168
18
41
55
254
148
260
145
100
1/n
0.86
0.77
0.49
0.38
0.95
0.25
1.03
0.37
0.27
0.40
0.42
0.41
r
0.92
0.91
0.94
0.99
0.94
0.87
0.97
0.98
0.98
0.98
0.98
0.98
(a) Measured at 10 mg/1 initial concentration.
684
-------
TABLE 16. ADSORPTION CAPACITIES FOR BENZENE AND SUBSTITUTED BENZENES
Compound
Structure
Adsorption
Capacity*(mg/g)
Benzene
1.0
Phenol
-OH
21
Ethylbenzene
H H
(/ \VC-C-H
HH
53
Nitrobenzene
2
68
Chlorobenzene
93
Styrene
H H
120
l-Chloro-2-nitrobenzene
CI
130
Measured at 1 mg/1 initial concentration.
685
-------
A final example is shown in Table 17 where adsorption capacities are
shown for uracil and substituted uracils. While not a priority pollutant,
the compound is a common component in sewage. Two observations can be
made from the data. One, that adsorption capacity changes as the parent
compound is halogenated and, further, that the kind of halogen atom -
chlorine, bromine or fluorine - exerts its own characteristic influence on
adsorption. Another point that should be made, although not apparent from
the data shown, is that uracil is an innocuous metabolic byproduct in
urine, but when halogenated, as does occur during disinfection, the com-
pound becomes increasingly toxic. Fluorouracil is considered to be a
mutagenic compound.
These examples demonstrate that adsorption capacity of a parent mole-
cule changes as differing atoms are added and as differing structural
changes are made to side chains. The problem is that, at this point,
there is no immediately apparent reason why these changes occur.
In the previous examples, the compounds were tested individually
where the compound adsorbed on the carbon free of any extraneous competi-
tion or interference. Realistically, compounds rarely occur alone in
solution and competition with other compounds will almost always occur.
The effects of these interactions are illustrated by Table 18, where
adsorption capacity data are shown for six closely related halogenated
methanes and ethane. These compounds are common artifacts of disinfection
of water with chlorine. When the compounds were determined individually
in a mineralized distilled water, the compounds can be arranged in order
of increasing adsorption capacities. In this example, capacities are
expressed as micrograms per gram of carbon at an initial concentration
of 100 micrograms per liter. There is an order of magnitude difference
between the least and most adsorbable compounds. When these same compounds
are now dissolved together in a volume of mineralized distilled water at
the same initial concentration of 100 ug/1 for each compound and the
adsorption for each individual is determined, the order of adsorption
remains unchanged. Put another way, each compound in the mixture behaves
as an individual compound. The only effect observed is that the capacities
are reduced by approximately one-half. This indicates that there is compe-
tition among the compounds for adsorption sites, but since the ranking is
preserved, each compound exerts its own degree of adsorption. And, finally,
the last column shows the results of the mixture of compounds in clarified
secondary treated wastewater. With the competition from the organics in
the wastewater, the adsorption of the individual compounds is further re-
duced. But - with one exception - the order of adsorption capacity is
preserved. The single exception may be due to the analytical difficulties
of determining parts-per-billion of highly volatile compounds.
Continuing research in this area will provide the data base from which
general conclusions can be made, thus providing the capability to predict
the adsorption characteristics of any unknown compound. For prediction,
the technique of structure-activity analysis is a promising approach.
686
-------
TABLE 17. ADSORPTION OF URACIL AND SUBSTITUTED URACILS
H
i
N
/ N
H-C C=0
11 I ^
C N -H ~
* ^^ ^
^ -^^
H' C
11
O
Compound X/M,mg/g
Uracil 55
5-Fluorouracil 65
5-Methyluracil 90
5-Chlorouracil 100
5-Bromouracil 130
/
^ H-C
-^ H
xc>
/
H
K 1/n
9.3 0.76
2.0 1.52
27 0.51
25 0.60
49 0.43
N
' ^
C-OH
I
N
sc*
|
OH
r
0.84
0.88
0.91
0.97
0.98
10 mg/1
pH = 7.0
X/M Decreased at higher pH values.
687
-------
TABLE 18. ADSORPTION DATA FOR HALOHYDROCARBONS
Clarif. Sec.
Miner. Water Miner. Water Effluent
Compound Alone Mixture Mixture
Dichloroethane 1070(a) 440 520
Chloroform 1580 930 365
Bromodichloromethane 3370 2560 875
Carbon tetrachloride 4660
Dibromochloromethane 7520 4540 885
Tribromomethane 28700 10800 1530
y
(a) — values in yg/g at Co = 100 yg/1
VOLATILITY
Even a casual inspection of the organics on the list of priority pollu-
tants will show that many of the low molecular weight chlorinated hydrocarbons
are volatile compounds. It follows from this that loss of these compounds
from solution can be an important route of removal from the aqueous flow, but
this also indicates that the potential exists for contamination of the air
around a wastewater treatment plant. Treatment plants offer ample opportunity
for volatilization from processes such as the flows in the collection system,
aerated grit chambers, settlers and most especially from aeration basins where
the driving force for desorption from solution is provided by the air or
oxygen aeration. Thus, it is not surprising that volatilization from water
bodies to the atmosphere is generally recognized as a significant pathway for
transfer of organics from one environmental medium to another.
The volatilization process from an aqueous solution is generally accepted
as consisting of diffusion of the solute from the bulk of the water to the
interface, followed by transfer across the interface and finally diffusion
from the interface to the bulk of the air phase.
There have been many attempts in the literature to develop mathematical
models which would predict the rate of volatilization of a compound from
aqueous solution. Most models incorporate such parameters as Henry's Law
constant, gas and liquid phase mass transfer coefficients and, more recently,
models have incorporated coefficients which account for other parameters that
affect the volatilization such as adsorption on solids and rate of biodegra-
dation.
An important coefficient in virtually all of the models is the Henry's
Law constant. This constant is an expression of the distribution of a
volatile solute at equilibrium between the liquid and the vapor phases.
For compounds with low solubility, Henry's Law constant can be calculated
from the aqueous solubility of the compound and the vapor pressure of the
pure compound, both at the temperature of the system. Unfortunately for
688
-------
many of the compounds of environmental interest, Henry's Law constant is
not available, and furthermore, the information needed for calculating the
constant - solubility and vapor pressure - are either nonexistent or
erroneous.
The laboratory of the Wastewater Research Division in Cincinnati, Ohio,
undertook the task of experimentally determining Henry's Law constant. (20)
The procedure chosen for this work was described by Mackay, et al. (21)
In brief, the procedure consists of stripping with nitrogen at a controlled
rate of flow a solution of the test compound in a water-jacketed column
maintained at a constant temperature of 25°C. The solution was sampled at
timed intervals and the decrease of concentration due to the stripping was
recorded. Various analytical methods were used depending on the compound
being tested and included such procedures as U-V spectroscopy, purge and
trap gas chromatography and solvent extraction, solvent volume reduction
and gas chromatography using electron capture detection.
The test apparatus is shown in Fig. 4. Cylinder nitrogen flows through
a flow control ratameter and then through a gas absorption bottle to saturate
the gas with water, and is then delivered to the test solution through a
glass frit which produces fine bubbles of gas. The solution is temperature
controlled by circulating constant temperature water through a jacket around
the solution. The sampling tube inlet is located approximately at the mid-
depth of the solution. The solution was generally sampled and analyzed at
timed intervals until the remaining concentration approached the limits of
analytical detection. The curve is then determined by least squares regres-
sion analysis.
An example of the experimental results is shown in Fig. 5 for ethyl-
benzene where concentration shown as In absorbance at 260 nm is plotted vs.
time in minutes. Henry's Law constant was calculated by the following
equation:
H = - slope x VRT =
G
H = Henry's Law constant, m3atm mol~^
slope = Change in solution concentration/minute
V = Volume of test solution, m3 = 9.925 x 10~4 m3
R - Gas constant, jj^Jf ' 8.2 x 10-5
T = Temperature in degrees K = 298 °K
G = Gas flow in m3/min - 1.0 x 10~4 m3/min
Henry's Law constant for ethylbenzene calculated from the experimental
data is
6.40 x ID'3 m3 atm moH
689
-------
Bubble Flow Meter
: Exhaust/Hood
Sample 1
Valve 3"
-10 psi
Sample
Volume
(1 Liter)
X-//Frit
Metering
Pump
20ml/min
\ i
&
Constant
Temperature
Bath
(298 K)
Flow Control
(0—300 cc/min)
Water
Saturation
Figure 4. Apparatus For Experimental Determination of Henry's Law Constant
-------
•2.0f-
CTi
-6.0
20 40 60 80
Time - Minutes
Figure 5. Determination of Henry's Law Constant For Ethylbenzene
100
-------
When the necessary information on aqueous solubility and vapor pressure
are available, Henry's Law constant can be calculated by the following
equation:
H (calculated) = 16.04 x MU x VP x R x T =
O A I
where:
MW = Molecular weight, g/mol = 106.16 g/mol
VP = Vapor pressure, mm = 9.5 mm
R = Gas constant, "»3 atrn = 8.2 x 1CT5 m3 atm
mol UK mol UK
S = Solubility, mg/1 = 206 mg/1
T = Temperature, °K = 298 °K
In this example the calculated value is 6.44 x 10~3 m3 atm.mol"^ which
corresponds very well to the experimentally determined value. Thus, when-
ever accurate values for solubility and vapor pressure are available the
calculated Henry's Law constant will be essentially equivalent to the
experimentally determined value.
The results of the experimental work are shown in Table 19. The com-
pounds represent essentially all of the compounds on the priority pollutants
list that have appreciable potential for volatility. An interesting obser-
vation is that certain compounds with very low vapor pressures, as for
example the pesticides, have substantial volatility from aqueous solution
because of the concurrent extremely low aqueous solubility. The column
labeled "calculated" in the Table 19 illustrates the difficulty and in-
accuracy in calculating the constant. The basic information is either
lacking, inaccurate or involves the problem of vapor pressure extrapolation
for solids.
In summary, this work points out the incentives for using experiment-
ally determined values for Henry's Law constant rather than the inaccurate
calculated values. Additionally, many compounds are volatile that would
not be judged to be if based on vapor pressure alone.
Removability
It was recognized, early in the research program that while treatability
studies of pure compounds in distilled water were useful and provided needed
information quickly, other studies which involved mixtures of compounds in
wastewater solutions were equally important. Thus, concurrent with the pure
compound research, pilot plant studies were undertaken to investigate the
capabilities of selected treatment systems to remove mixtures of toxic com-
pounds. The first phase of the study has been completed and is reported on
below.(22) The research is being continued to include additional compounds
and other treatment processes.
692
-------
TABLE 19. HENRY'S LAW CONSTANTS
Priority
Pollutant
Number
Compound
Experimental Calculated
m-3 atm mol~^ x 10~3
1 Acenaphthene
4 Benzene
6 Carbon tetrachloride
7 Chlorobenzene
8 1 ,2,4-Trichlorobenzene
9 Hexachlorobenzene
10 1,2-Dichloroethane
11 1,1,1-Trichloroethane
12 Hexachloroethane
13 1 ,1-Dichloroethane
23 Chloroform
25 1,2-Dichlorobenzene
26 1 ,3-Dichlorobenzene
27 1 ,4-Dichlorobenzene
29 1,1-Dichloroethylene
30 1,2-Trans-dichloroethylene
32 1 ,2-Dichloropropane
33 1 ,3-Dichloroproylene
38 Ethyl benzene
44 Methylene Chloride
47 Bromoforin
48 Bromodichloromethane
43 Trichlorofluoromethane
51 Dibromochloromethane
56 Nitrobenzene
60 4,6-Dinitro-o-cresol
65 Phenol
77 Acenaphthylene
80 Fluorene
85 Tetrachloroethylene
86 Toluene
87 Trichloroethylene
89 Aldrin
90 Dieldrin
91 Chlordane
100 Heptachlor
101 Heptachlor epoxide
107 Arochlor 1254
113 Toxaphene
Experimental
m-3 atm mol ~ '
0.241
5.55
29.30
3.93
1.42
1.70
1 .10
4.08
9.85
5.45
3.39
1.94
2.63
2.72
14.90
5.32
2.82
3.55
6.44
3.19
0.532
2.12
58.30
0.783
0.0238
0.0014
0.0013
0.114
0.117
28.70
5.92
11.70
0.496
0.0584
0.0479
1.48
0.0316
8.37
4.89
Calcu la ted
x 10"3
sol id
5.49
30.00
3.71
2.31
sol id
1.34
4,92
no data
5.53
3.23
2.00
2.97
sol id
15.10
4.05
2.31
1.35
6.44
2.84
0.595
no data
136.00
no data
0.0230
no data
sol id
sol id
sol id
28.50
6.44
11.70
solid
sol id
sol id
sol id
no data
sol id
no data
693
-------
In the pilot plant study, two treatment systems were operated - a
physical-chemical system consisting of alum clarification and granular media
filtration followed by granular activated carbon, the other was a convention-
al activated sludge system consisting of a primary settler, an aeration tank
and a final settler. Raw wastewater was obtained from a large interceptor
sewer serving a residential and commercial area of Cincinnati, Ohio. The
feedwater to the pilot plants was spiked to contain approximately 150 jug/1
of five selected organic compounds from the priority pollutant list - carbon
tetrachloride, trichloroethylene, ethylbenzene, nitrobenzene and dimethyl
phthalate. Samples were collected by automatic samplers (using the specially
developed sampler for volatile compounds) and composited over three and four
days. The volatile compounds were analyzed by a purge and trap method com-
bined with gas chromatography while the non-volatiles were extracted with
methylene chloride, solvent volume reduced and the analysis completed with
gas chromatography with a flame ionization detector.
In addition to the five organics, four metals were spiked into the feed-
water and removals monitored throughout the system. The metals included
copper, lead, cadmium and mercury. In the case of both the organics as well
as the metals, the initial concentration entering the treatment system was
the sum of the spike and the background content of the raw wastewater.
Table 20 shows the removals obtained by alum clarification and dual media
filtration. The first three compounds are volatile and one would expect the
observed 40-60% loss during clarification. Some of the loss, however, was
due to incorporation into the sludge.
TABLE 20. AVERAGE REMOVAL OF TOXICS BY
ALUM CLARIFICATION AND FILTRATION
Compound
Carbon tetrachloride
Trichloroethylene
Ethylbenzene
Nitrobenzene
Dimethyl phthalate
Copper
Cadmium
Lead
Mercury
Raw
ug/1
0
0.1
1.1
38
7.3
Raw-Spiked
ug/1
138
169
155
170
178
285
137
232
19
Filtered
ug/1
68
102
61
109
153
36
6
28
1.1
Removal
51
40
61
36
14
87
96
88
94
Sludge
mg/kg
19
60
124
311
Not unexpectedly, good removals, ranging from 87-94%, were obtained for
the metals. No sludge analyses are available at this time but it can be
assumed that the amounts of metal removed are undoubtedly in the sludge.
694
-------
The effluent from the alum clarification served as the feed to two
granular activated carbon contactors, the first of which had an empty bed
contact time of five minutes; the second provided ten minutes contact for
a total of fifteen minutes. The purpose of the relatively short contact
time in the first column was to obtain information on breakthrough within
a reasonable time for all of the compounds tested. The breakthrough curves
are shown in Fig. 6. The flow rate to the columns was 4.0 1/min (1.1 gpm).
Almost total breakthrough was observed for carbon tetrachloride and trichloro-
ethylene, which is consistent with the low carbon capacities determined by
the isotherm treatability studies. Breakthrough was being approached for
dimethyl phthalate and nitrobenzene while ethylbenzene had achieved a break-
through of only 40% at the end of 1600 hours of operation. The breakthroughs
cannot be rigorously explained by the isotherm data since the influent con-
centrations of the compounds reflected the varying removals by the prior alum
clarification, and therefore, the feed concentrations varied from 67 ^ig/1 to
156/ug/l for the compounds.
The data for the pilot activated sludge system are shown in Table 21.
The feedwater was from the same source as that for the physical-chemical
system. Removals for all of the organics were 98% or greater, resulting
in small residual concentrations in the effluent. The mechanisms of removal
are not readily evident from the data. It is clear, however, that carbon
tetrachloride and trichloroethylene were probably removed from the system
mainly by stripping, and that the remaining compounds were partially de-
graded and in part accumulated in the sludge. Removal of the metals ranged
from 70-78% and while no sludge analyses are available, the metals removed
from the bulk flow are almost certainly associated with the sludge.
TABLE 21. AVERAGE REMOVAL OF TOXICS BY ACTIVATED SLUDGE SYSTEM
Primary Final Removal Primary
Influent Eff1. Eff1. Sludge
Compound ug/1 ug/1 ug/1 % mg/kg
Carbon tetrachloride 130 119 0.8 99+ 0.21
Trichloroethylene 182 164 2.3 99 4.7
Ethylbenzene 193 156 2.1 99 78
Nitrobenzene 173 167 3.1 98 158
Dimethyl phthalate 206 204 3.8 98 74
Copper 349 174 106 70
Cadmium 171 72 38 78
Lead 271 109 69 75
Mercury 20 7.4 6. 71
695
-------
O
O
-v.
O
O)
c
(0
E
a)
cc
c
O
'•+J
ro
-n
c
a)
o
c
o
O
la
c
o
4J
o
ra
L-
u.
1.00
0.00
0.60
0.40
0.20
0
CONTACT TIME = 5 MINUTES
0
400 000 1200
Time on Stream (HR)
1600
BREAKTHROUGH OF ORGANICS FROM 1.2m CARBON BED
FIGURE 6
-------
SUMMARY
An attempt has been made in this paper to collect into one place infor-
mation from many sources - legislative, regulatory, technical and investi-
gative - in order to present a coherent view of the problems of toxic sub-
stances. The emphasis has been on those factors which most affect the
municipal wastewater treatment plant.
Starting in the early 1970's, the U. S. Congress, through a series of
legislative acts and amendments, has sought to control and regulate pollution
in the environment. The Environmental Protection Agency is but one of
several agencies which have been mandated a responsibility in the specific
area of toxic substances. With the issue of the Consent Decree in 1976,
and the designation of 129 specific compounds, research on the control,
fate in the environment and health aspects of these and other toxic compounds
began in earnest.
Much research is currently underway to respond to these needs. Survey
and research data, however, are only now becoming available. Thus, this
paper had had to rely on preliminary results - mostly unpublished - which
are too sparse to form firm conclusions. Nevertheless, some tentative
trends can be observed, which may or may not be supported when all of the
data become available.
Thus it can be seen, from Table 3, that pretreatment of industrial
wastewaters for removal of metals significantly reduced the concentration
of "etals in the raw wastewater to a municipal plant. This effect is most
evident in the reduction of metals in the sludges.
Very early in the research, it became evident that analytical methods
for the priority pollutants would have to be developed that were capable
of qualitative and quantitative detection of these compounds at the parts-
per-billion level in all types of wastewaters and sludges. This has been
done, but it is clear that much more analytical methodology research will
still be required.
With analytical procedures available, it was possible to start surveys
of municipal plants - 65 cities in two separate surveys - to assess the
situation in the field on the occurrence and concentration of priority
pollutants entering and leaving municipal treatment plants, including the
sludges. Based on the results of only three cities, it appears that most
of the priority pollutants - 87 out of 129 - were detected in the influent
but generally at low concentrations - <10 ug/1. The treatment plants -
activated sludge - were capable of achieving substantial reductions in
concentrations for most of these compounds. Removals were apparently
achieved by a combination of processes including stripping, biodegradation
and by sorption into the sludge. Nevertheless, some thirty compounds.
697
-------
were detected in effluent samples which were at or near the concentrations
proposed for stream water quality criteria. While it can be expected
that dilution in the surface waters will provide some margin for safety,
these compounds may require some attention if other cities encounter
higher influent concentrations. Studies of the emission of volatile
priority pollutants from aerated grit chambers and aeration basins showed
that, even at the liquid/air interface only one compound, trichloroethane,
came close to reaching maximum permissible average air concentrations
that have been established by OSHA. Clearly, much more data are needed
before it can be concluded that emissions of priority pollutants from
treatment systems either are or are not a problem.
In the short term, survey studies and research on removal of toxic
organics by treatment systems will provide the answers to the immediate
needs of the regulatory agencies. For the longer term, research on
treatability of organic compounds is essential. It is from this type of
research that the mechanisms of treatment - volatility, biodegradation,
sorption, etc. - will be understood sufficiently in order to predict the
behavior of organic compounds other than the limited list represented by
the priority pollutants. Much research will be required on treatability
to obtain the necessary biological-physical-chemical information in
order to acquire the ability to predict the behavior of untested compounds.
698
-------
REFERENCES
1. Natural Resources Defense Council (NRDC) et al . , vs Train, 8 ERC
2120 (1976).
2. Federal Register, 44, No. 175, Sept. 7, 1979, Rules and Regulations.
3. "Process Design Manual for Sludge Treatment and Disposal,"
EPA 625/1-79-011, Center for Environmental Research Information,
Technology Transfer, Cincinnati, Ohio 45268, Sept. 1979.
4. Federal Register, 44, 15926, March 15, 1979.
Federal Register, 44, 43660, July 25, 1979.
Federal Register, 44, 56628, October 1, 1979.
5. Mauzy, M. P., "Statement for the Record of Subcommittee on Oversight
and Reviews, Committee on Public Works and Transportation, U. S.
House of Representatives," Nov. 28, 1979.
6. Hinesly, T. D., and Jones, R. L., "Heavy Metal Contents in Runoff
and Drainage Waters from Sludge-Treated Field Lysimeter Plots,"
Proceedings National Conference on Disposal of Residues on Land,
EPA, Office of Research and Development, St. Louis, Missouri,
September 13-15, 1976.
7. U. S. Department of Labor, Occupational Safety and Health Administra-
tion, 2206 "General Industry," November 7, 1978.
8.
Federal Register, _44, 233, December 3, 1979, "Guidelines Establishing
Test Procedures for Analysis of Pollutants, Proposed Regulation,"
pp. 69526-69558.
9. Levins, P. L., et al., "Source of Toxic Pollutants in Influents to
Sewage Treatment Plants," USEPA draft report, Office of Water
Planning and Standards, Washington, D. C., November 1979.
10. Kleopfer, R. D. , Dias, J. R., and Fairless, B. J., "Priority Pollutant
Methodology Quality Assurance Review," USEPA Region VII Laboratory,
Kansas City, Kansas 66115.
11. "Seminar on Analytical Methods for Priority Pollutants," Proceedings
USEPA, Denver, Colorado, November 1977.
12. Pressley, T. A., Municipal Environmental Research Laboratory,
USEPA, Cincinnati, Ohio, Private Communication.
699
-------
13. "Development and Application of Test Procedures for Specific Organic
Toxic Substances in Wastewater Category 7-Benzidines." Report for
EPA Contract 68-03-2624 (in preparation).
14. Federal Register, 44, 233, December 3, 1979, "Guidelines Establishing
Test Procedures for Analysis of Pollutants, Proposed Regulations,"
pp. 6948-6949.
15. DeWalle, F., and Chi an, E., "Presence of Priority Organics in Sewage
and Their Removal in Sewage Treatment Plants." First Annual Report,
July 1, 1989-May 31, 1979, Grant 806102, USEPA, Municipal Environ-
mental Research Laboratory, Cincinnati, Ohio 45268.
16. Warner, J. S., et al., "Analytical Procedures for Determining Organic
Priority Pollutants in Municipal Sludge," EPA-600/2-80-030, Municipal
Environmental Research Laboratory, USEPA, Cincinnati, Ohio 45268
(in press).
17. Westrick, J. J., and Cummins, M. D., "Collection of Automatic Composite
Samples Without Atmospheric Exposure," Jour. Water Poll.Control Fed.,
5±, 2948 (December 1979).
18. Tabak, H. H., "Biodegradability Studies with Priority Pollutants."
In-house laboratory progress reports, USEPA, Municipal Environmental
Research Laboratory, Wastewater Research Division, Cincinnati, Ohio,
July 1979-January 1980.
19. Dobbs, R. A., "Activated Carbon Adsorption Isotherms for Priority
Pollutants." In-house laboratory progress reports, USEPA, Municipal
Environmental Research Laboratory, Wastewater Research Division,
Cincinnati, Ohio, July 1979-January 1980.
20. Warner, H. P., "Determination of Henry's Law Constant for Selected
Priority Pollutants." In-house laboratory reports, USEPA, Municipal
Environmental Research Laboratory, Wastewater Research Division,
Cincinnati, Ohio, July 1979-January 1980.
21. Mackay, D., Shiu, Wy, and Sutherland, R. P., "Determination of
Air-Water Henry's Law Constants for Hydrophobic Pollutants,
Environ. Sci & Tech., 13, 333 (March 1979).
22. Westrick, J. J., "Pilot Plant Studies on Removal of Selected Priority
Pollutants." In-house pilot plant data, USEPA, Municipal Environmental
Research Laboratory, Wastewater Research Division, Cincinnati, Ohio.
23. Federal Register, 44, 53438, September 13, 1979, Sludge Criteria
Reference.
700
-------
APPENDIX A
Federal Laws and Agencies Affecting Toxic Substances Control —'
Responsible
Year Enacted Agency Sources Covered
Toxic Substances Control Act 1976 EPA Requires premarket evaluation of all new
chemicals (other than food additives, drugs,
pesticides , alcohol , tobacco); allows EPA
to regulate existing chemical nazards not
covered by other laws related to toxic
substances
Clean Air Act 1970, amended EPA Hazardous air pollutants
1977
Federal Water Pollution Control 1972, amended EPA Toxic water pollutants
Act 1977
Safe Drinki'ng Water Act 1974, amended EPA Drinking water contaminants
1977
Federal Insecticide, Fungicide, 1945, amended EPA Pesticides
and Rodenticide Act 1972, 1975,
197S
Act of July 22, 1954 (codified as 1954, anended EPA Tolerances for pesticide residues in food
§346(a) of the Food, Drug and 1972
Cosmetic Act
Resource Conservation and Recovery 1976 EPA Hazardous wastes
Act
Marine Protection, Research and 1972 EPA Ocean dumping
Sanctuaries Act
Food, 3rug and Cosmetic Act 1933 FDA Basic coverage of food, drugs and cosmetics
Food additives amendment 1953 F3A Food additives
Color additive amendments 1960 FDA Color additives
New drug amendments 1962 fOA Crugs
New animal drug amendments 1963 FDA Anima 1 drugs and feed addi ti ves
Med:cal device amendments 1976 FDA Medical devices
Wholesome Meat Act 1967 USDA Food, feed and color additives and pesti-
Wholesome Poultry Products Act 1963 cioe residues in raeat and poultry
Occupational Safety and Health Act 1970 OSHA Workplace toxic chemica's
Federal Hazardous Substances Act 1966 CPSC "Toxic" household products (equivalent to
consumer products)
Consumer Product Safety Act 1972 CPSC Dangerous consumer products
Poison Prevention Packaging Act 1970 CPSC Packing of dangerous chi1dren's products
Lead Based Paint Poison 1973, amended CPSC Use of lead paint in federally assisted
Prevention Act 1976 housing
Hazardous Mdterials Iransportion 1970 DOT (Matei— Transportation of toxic subs tanees
Act ia f s Trans* generally
p o r ta t i o n
Bureau)
Federal Railroad Safety Act
Ports and Waterways Safety Act
Dangerous Cargo Act
1970
1972
1952
DOT (Fed-
eral Rail-
road Admin)
DOT [Coast
Guard)
Rai 1 road safety
Shipment of toxic materials by water
CPSC = Consumers Proouct Safety Commission
DOT U.b Department of Transportat on
EPA - U.S. Environmenta1 Protection Aqency
FCA Federal Drug AdJiil nistration
OShA - Cccjpational Safety and Health Administration
LJSDA = U.S. Department of Agriculture
- F-'ora "En vi ronmertj! Qual'ty," tne Ninth Annual Report of the Council on Enviror\nental Quality,
December 1973.
701
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APPENDIX B
KEY ENVIRONMENTAL LEGISLATION RELATED TO TOXICS MANAGEMENT
AND MUNICIPAL WASTEWATER TREATMENT FACILITIES
Clean Water Act of 1977
(TL 95-2171
201(g)
204(b)
208
301(h)
302(a)
303
304(a)
304(g)
307(a)
307(b)
307(b)(c)
402(a)
403
405(d)
405(e)
Clean Air Act of 1977
(PL 95-95)
112
provides for uniform, enforceable national
standards for clean water, a national
permit program for point-source discharges;
federal funds for construction of sewage
treatment systems, and state and area-
wide planning and management programs to
address nonpoint-source discharges.
construction grants
user charges
management plans
relaxed effluent limits for municipal
facilities
water quality based effluent limits
water quality standards
publish and periodically update water
quality criteria
pretreatment guidelines
toxic pollutant list & effluent limitations
industrial variances
pretreatment standards
NPDES permits
ocean dumping
issuance of guidelines for the disposal
and utilization of sludge
requires conformance by POTW's to guidelines
provide for the protection and enhancement
of air quality through regulation of pol-
lutant emissions and establishment of air
quality standards
national emission standards for hazardous
air pollutants (asbestos, beryllium,
mercury, vinyl chloride, benzene, are
currently regulated)
702
-------
Appendix B (continued)
122
Resource Conservation and
Recovery Act of 1976
(PL 94-580)
1008(a)(3)
3001
3005
4004(a)
4005(b)
4005(c)
Toxics Substances Contro'
Act of 1976(PL 94-469)
Safe Water Drinking Act of 1974
Sec. 1412(a)
Federal Insecticide, Fungicide
and Rodenticide Act of 1972
{PL 92-516)
Sec. 3
Sec. 6
- certain unregulated pollutants such as
cadmium, arsenic, polycyclic organic
matter (soot), radioactive releases
- requires a regulatory system for the
treatment, storage, and disposal of
hazardous wastes
- defining open dumping criteria
- identifying hazardous municipal sludges
and solid waste
- permits for municipal facilities treat
ineu storing or disposing of hazardous
sludge on-site
- disposal facility criteria to dis-
tinguish sanitary landfills from
open dumps
- inventory of open dumps
- prohibition of open dumping
- gives EPA broad discretionary author-
ity to control hazardous chemical
substances (excludes pesticides).
Provides for direct control of new
and existing chemicals, requires
premarket screening of new chemicals,
and provides for authority to require
testing of a chemical's toxicity.
If an unreasonable risk is posed by
a chemical the EPA can prohibit or
limit its manufacture, processing,
distribution, use and disposal.
- Interim Primary Standards
9 inorganics, 6 pesticides, 3 categor-
ies of radioactive substances.
- helps to control the entry of pesticides
into the water environment.
All pesticides must be registered
with and classified by EPA for
general or restricted use.
- Cancellation applied usually to a
specific set of uses or inadequacy
of a label.
703
-------
APPENDIX C
CRITERIA FOR SLUDGE APPLICATION TO LAND
(23)
Cadmium Criteria for Food Chain Crop Uses
1. Cd < 2 mg/kg - no special provision
Cd > 2 mg/kg - pH 6.5 @ time of application
2. Annual application rate of cadmium - tobacco, leafy vegetables,
root crops for human
consumption 0.5 kg/ha
3. Annual application rate of cadmium - all other crops -
2.0 kg/ha to June 30, 1984
1.25 kg/ha to Dec. 31, 1986
0.5 kg/ha to Jan. 1, 1987
4. Cumulative application rate for cadmium
Max. Cumulative Application rate (kg/ha)
Soil pH < 6.5 Soil pH > 6.5
Soil cation exch.
cap. meq/IOOg
5
5-15
5
5-15
* These application rates apply only if soil pH is maintained at pH 6.5
for food-chain crops or for animal feed where pH 6.5 is 'adjusted at time
of application or planting, whichever occurs later and pH is maintained
and a distribution plan for animal feed is prepared and notification of
future land owners of the presence of high cadmium and the prohibition of
food-chain crops.
5
5
5
5*
10*
20*
5
10
20
Polychlorinated Biphenyls (PCB) Criteria
For animal feed uses including pasture crops for animals for milk
production
PCB Content (dry weight)
<10 mg/kg
>10 mg/kg
no special requirements
sludge incorporation into soil or surface
application and crop/milk monitoring for
FDA criteria which are, 0.2 mg/kg act.vol.
weight for animal feed crops, and 1.5 mg/kg
(fat basis) for mi Ik.
704
-------
Disease Control Criteria
Sludge applied or incorporated
into the soi1
Septage Disposal
Where sludge or septage is
applied to land where crops
for direct human consumption
are grown within 18 months
of application
Alternative 1
must be treated prior to application
by a process to significantly reduce
pathogens such as anaerobic or aero-
bic digestion, air drying, compost-
ing, lime stabilization or other
similar technique
and
12 months of controlled public access
One month prohibition of grazing
animals whose products are consumed
by humans.
Alternative 2
burial or trenching
Alternative 1
must be treated prior to application
by a process to significantly reduce
pathogens such as anaerobic or aero-
bic digestion, air drying, compost-
ing, lime stabilization or other
simi1ar technique
Alternative 2
site control provisions of 12 months
of controlled access and one month
prohibition of grazing animals whose
products are consumed by humans.
Alternative 3
burial or trenching
Process which Significantly Reduces
Pathogens (PSRP), in addition,
processes to further reduce patho-
gens such as beta ray irradiation,
gamma ray irradiation, pasturiza-
tion or other equivalent methods or
processes such as high temperature
composting, heat drying, heat treat-
ment or thermophilic aerobic diges-
tion with site control provisions if
there is direct contact of sludge
and edible portion of the crop.
705
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GROUNDWATER PROTECTION CRITERIA
Maximum Contaminant Level (MCL)
for Inorganic Chemicals
Arsenic
Barium
Cadmium
Chromi urn
Lead
Mercury
Nitrate (N)
Selenium
Si 1ver
Fluoride (function of temperature)
MCL for Organic Chemicals1
Chlorinated Hydrocarbons
Total Trihalomethanes
Endrin
Lindane
Methoxychlor
Toxaphene
Chlorophenoxys
2,4-D (2,4-dichlorophenoxy-acetic acid)
2,4,5-T Silvex (2,4,5-trichlorophenoxy-
proprionic acid)
Level (mg/1)
0.05
1.0
0.010
0.05
0.05
0.002
10.0
0.01
0.05
1.4-2.4
Level (mg/1)
0.10
0.0002
0.004
0.1
0.005
Level (mg/1)
0.1
0.01
These are the currently regulated organic chemicals. The Agency is
considering the establishment of MCL's for the following additional
organic chemicals in the yg/1 to mg/1 range:
Trichloroethylene
Tetrachloroethylene
Carbon tetrachloride
1,2-Dichloroethane
1,1,1-Trichloroethane
1,1,2-Trichloroethane
.cis-1,2-Dichloroethylene
706
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HEALTH EFFECTS RESEARCH ASSOCIATED WITH
MUNICIPAL WASTEWATER TREATMENT AND SLUDGE DISPOSAL
Herbert R. Pahren
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
INTRODUCTION
Many wastewater treatment plants are constructed in urban areas close to
residential areas. These systems generally contain aeration basins or
trickling filters where there is an opportunity for small droplets of wastewater
to be emitted. These droplets could contain a bacterium or virus and evaporate
very rapidly to yield droplet nuclei in the size range of 1 to 20 microns in
diameter, known as aerosols.
A number of persons have investigated the types of organisms emitted and
the density in relation to distance from the treatment plant. Probably the best
overview of the subject was written by Hickey and Reist (1,2). These
microorganisms travel passively with the wind and their density decreases with
time and distance as a result of atmospheric dispersion, die-off (loss of
viability), and deposition (removal from the air) (3). The potential for plant
workers and nearby residents to inhale viable organisms certainly exists.
However, there has never been a systematic investigation to confirm or negate
the existence of a health hazard from these viable wastewater aerosols.
With this background, the Health Effects Research Laboratory of the U.S.
Environmental Protection Agency arranged for several studies to gather infor-
mation on health effects associated with aerosols from uncovered wastewater
treatment plants. These studies were conducted by personnel from universities
or research institutions.
EPIDEMIOLOGY STUDIES
Two types of epidemiological studies were carried out. The first type
involved the analysis of existing public health data to determine if there was
any relationship between the operation of a wastewater treatment plant and
disease patterns. These retrospective studies could be carried out quickly
because the basic data already existed and just needed to be analyzed
statistically. The second type of investigation consisted of prospective
seroepidemiological studies, involving blood samples for antibody testing for
various microbiological agents, as well as clinical samples, such as throat
cultures or stool samples.
707
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Retrospective Studies
The first investigation utilized data available from a community health
study which was carried out over a seven-year period at Tecumseh, Michigan (4).
Illness in the community was related to distance from the activated sludge plant
in Tecumseh. Dwelling units around a nonemitting location upwind from the
treatment plant were used as a control group. Results showed that both
respiratory and gastrointestinal illnesses were greater than expected for
persons living within 600 meters of the sewage treatment plant. However, the
data suggest the higher rates are related to higher densities of lower
socioeconomic families with crowded living conditions rather than to the
treatment plant (5).
In a second retrospective study (6), illness rates of students at an
elementary school, located adjacent to a new advanced wastewater treatment
plant, were measured by analyzing recorded absenteeism at this school before and
after start-up of the new plant. Attendance at eight nearby schools was used for
control rates. There were two sources of aerosols at the treatment plant, the
aeration basin of the secondary treatment process and an aerated surge basin
used to equalize the flow into the secondary process. Aerosol exposure
locations for the children could take place at two locations, the playground
area which was within 50 meters of the aerated surge basin, and the 'classroom
area located 400 meters from the aeration basin. On warm days the classroom
windows were open.
A daily exposure index was computed for each location-aerosol source
combination, based on the four wind direction observations for the day recorded
at a nearby airport. If an observation was within the range of downwind
directions for the location-source combination, it was given a value of 1.0.
Wind direction observations within 30 degrees of this range were considered to
represent occasional exposure and given a value of 0.5. The four observation
values for the day were then summed to yield the daily exposure index for that
location-source combination. Thus, a daily exposure index of 4.0 would indicate
steady exposure from the aerosol source throughout the school day, while a daily
exposure index of 0.0 would indicate no exposure.
The frequency distribution of the daily exposure index over the 355 school
days, over a two year period following operation of the treatment plant, are
presented in Table 1. A review of the data indicates that the student exposure
was relatively infrequent.
Densities of microorganisms were measured in the aerosols at 30 and 100
meters downwind from the aeration basins and projected to the distance at the
school. Based on breathing rates, a child would inhale a maximum of 3.5 fecal
streptococci and 9 mycobacteria during a day when the wind blew steadily toward
the school.
Detailed examination of school attendance patterns for the two year period
prior to the operation of the sewage treatment plant and the two year period
following operation revealed no difference for the school next to the treatment
plant. Similar comparisons of attendance at this school with the eight other
nearby schools showed no differences. Although school attendance is not the
most accurate indicator of illness, the data provide no evidence of an adverse
health response from the treatment plant.
708
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TABLE 1. FREQUENCY DISTRIBUTION OF DAILY EXPOSURE
INDEX OF STUDENT EXPOSURE
Number (N) and Percent (%) of School Days
Exposure Location:
Aerosol Source:
Classroom Area
Aeration Basin
N
7
/o
Surge Basin
N %
Playground Area
Aeration Basin
N %
Surge Basin
N %
Daily Exposure Index
0
0
1
1
2
2
3
3
4
.0
.5
.0
.5
.0
.5
.0
.5
.0
196
48
35
22
21
13
10
4
6
55
14
10
6
6
4
3
1
2
191
53
31
27
26
13
9
2
3
54
15
9
8
7
4
3
1
1
155
58
45
23
23
18
17
8
8
44
16
13
6
6
5
5
2
2
137
52
44
26
34
21
14
10
17
39
15
12
7
10
6
4
3
5
Prospective Studies
The first seroepidemiological study was carried out around a new 64,000
cubic meter per day activated sludge plant in the State of Illinois (7). Persons
were evaluated for one year prior to start-up of the treatment plant and one year
after operation.
The epidemiological studies were divided into two parts. One part
consisted of having over 4200 persons who lived between 0.4 and 5.0 kilometers
from the plant answer questions in a questionnaire regarding their illnesses and
health status. Detailed statistical analyses were then conducted to determine
if results could be related in any way to the operation of the plant. Another
part of the study included taking clinical specimens from 282 persons near the
plant. Table 2 presents the type of tests made on the human subjects.
TABLE 2. CLINICAL TESTS OF PARTICIPANTS
Blood - metals, antibodies
Urine - metals
Hair - metals
Throat swabs - bacteria, virus
Feces samples - bacteria, virus, metals,
helminths, protozoa
709
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Environmental measurements near the treatment plant indicated that it was
a source of indicator bacteria, coliphage, specific pathogenic bacteria,
enteroviruses, and mercury in the aerosols emanating from the aeration basins.
However, the levels of microbiological or chemical agents of the air, soil, and
water samples in the neighboring residential areas were not distinguishable
from the background levels.
Based on questionnaire results alone, the responses showed a slight
increase in gastrointestinal symptoms after operation of the plant for persons
living the nearest distance. Streptococci isolations in the throat swabs also
increased. In contrast, tests for 31 viral antibodies and attempted isolations
of many pathogenic bacteria, parasites, and viruses yielded no evidence of an
adverse health effect from the wastewater treatment plant. On balance, the
overall conclusion was that the plant did not present a health hazard for nearby
residents.
Another seroepidemiological study was conducted near a one million cubic
meter per day sewage treatment plant in Chicago, Illinois (8). The surface area
of sewage exposed to the atmosphere in aeration basins and settling tanks is
55,000 square meters. The plant has been in operation since 1929.
Study design was somewhat similar to that described above. A health
questionnaire survey was made of 2,378 persons over an eight month period.
Stool and throat specimens were collected from children under age 12 for
bacteria and virus isolates. A total of 318 persons gave paired blood samples,
at the beginning and end of the eight month period, which were tested for
antibody to three types of polioviruses, five types of coxsackie B viruses, and
four types of echoviruses. Antibody titers in the respective sera obtained at
the beginning of the study were used to determine the rates of previous
infections by these specific viruses and the number of persons susceptible to
each of these agents. The air near the treatment plant was sampled for certain
gases, metals and viable particles which could be emitted by the plant.
Table 3 shows that the plant was a source of total viable particles and
total coliforms. The coliforms were at background levels at 800 meters downwind
while total viable particles were still above background at 800 and 1600 meters.
Table 4 relates the number of persons whose paired blood samples showed an
increase in antibody level for any of the five coxsackieviruses and four
echoviruses tested, compared to the average household exposure to total viable
particles for these persons. Negative seroconversion data are also presented.
The differences observed were not sufficient to suggest the seroconversions
were related to high exposure to microbial aerosols, as indicated by total
viable particle counts. In fact, persons who seroconverted to echoviruses were,
on the average, exposed to lower counts.
Overall conclusions from this investigation were that the sewage treatment
plant was a source of airborne total aerobic bacteria-containing particles and
total coliform bacteria as measured in the community. The concentration
profiles of trace metals, particulates, nitrates, sulfates, sulfur dioxide,
nitrogen dioxide, hydrogen sulfide, and chlorine in the community indicated
that the plant was not a source of these constituents. Relationships were not
710
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TABLE 3. AVERAGE DENSITIES OF MICROBIAL AEROSOLS
Distance
0.8 km
upwind
On-plant
downwind
0.8 km
downwind
1.6 km
downwind
Total
coliforms
number /m^
1.2 (26)*
6.9 (26)
1.2 (25)
1.0 (24)
Total
viable
particles
number /m-*
143 (62)
376 (68)
198 (68)
218 (60)
* Number of samples shown in parentheses.
TABLE 4. SEROCONVERSIONS COMPARED TO EXPOSURE
Average total viable
particle exposure,
Virus Type number/m^
Coxsackieviruses Bl to 5
Seroconversion (46)* 175
No seroconversion (272) 160
Echoviruses 3, 6, 9, 12
Seroconversion (25) 145
No seroconversion (292) 163
* Number of persons in category.
711
-------
found by regression analyses between total viable particles exposure indices
and :
(a) self-reported acute illness rates,
(b) pathogenic bacteria isolation rates,
(c) prevalence rates of antibody to certain enteroviruses, and
(d) virus antibody titers.
In an effort to check persons with the highest exposure to wastewater
aerosols, and with the best probability of showing a response, studies were made
of wastewater workers. It is recognized that such exposure could be due to
direct contact with sewage or handling equipment contaminated by sewage as well
as exposure by means of the aerosol route. There have been a few efforts in the
past to evaluate the health of sewage treatment plant workers, but most of these
studies were of limited scope (9-17).
A prospective seroepidemiological study was carried out in three metro-
politan areas: Cincinnati, Ohio; Chicago, Illinois; and Memphis, Tennessee
(18). The primary study group consisted of about 100 newly employed activated
sludge plant workers at the three cities. In addition, in Cincinnati two other
groups of about 50 persons each were evaluated, sewer maintenance workers and
persons who had worked at a primary sewage treatment plant prior to the
activated sludge plant work. As additional control groups, water treatment
plant workers were selected in Chicago, utility workers in Memphis, and highway
maintenance workers in Cincinnati.
Detailed madical tests were conducted on both exposed workers and con-
trols. Factors considered included liver function, immunoglobulin levels,
illness rates, blood chemistries, urinalysis, parasitic, bacterial, and viral
infections, and antibody to several bacteria and numerous viruses. A serologic
survey for viral antibodies of the families of study participants was also
conducted to check on the possibility of transmission of infectious agents from
the job to the home, and consisted of 87 families of wastewater workers and 41
control families.
The only difference in illness rates among worker groups which was
statistically significant was the difference in gastrointestinal illness
between inexperienced workers and other groups. Results between experienced
workers and controls were not significantly different. This is shown in Table
5. These gastrointestinal illnesses were mild and generally appeared within the
first several months of employment. There was no relationship between the
occurrence of illness and rise of antibody titer for any of the numerous agents
checked.
The study failed to demonstrate any differences among groups for immuno-
globulin levels or liver function tests. There was no evidence of any increase
in hepatitis, as reflected by the liver tests, in workers exposed to wastewater.
Stool examinations showed no evidence of increased parasitic infection in the
wastewater exposed workers. Isolations of Salmonella and Shigella in rectal
swabs were not significantly different between the exposed and non-exposed
groups, nor were blood antibody to Salmonella, Leptospira and Legionella
pneumophila different. Interestingly, 34.4 percent of the workers exposed to
712
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TABLE 5. CLINICAL ILLNESS IN WASTEWATER WORKER GROUPS
Illness per 100 Worker-months of Exposure
Gastro-
Worker Group Respiratory intestinal
Combined
Respiratory
and Gastro-
intestinal Other
Total
Inexperienced
Experienced
Treatment Plant
Sewer Maintenance
Control
6.5
8.0
5.5
4.9
3.6
2.4
1.3
1.5
1.7
0.9
0.5
1.0
3.8
3.6
4.0
3.3
15.6
14.9
11.3
10.7
sewage and 35.4 percent of the controls had antibody to Legionella pneumophila.
The possibility of an increase in viral infections in wastewater workers was
also investigated by means of cultures of throat and rectal swabs and extensive
serologic surveys. A major concern in this study was the occurrence of
enterovirus infections because of the frequency that enteroviruses can be
recovered from sewage. Neither the serologic tests for antibody nor culture
results demonstrated a significant increase of viral infections in the
wastewater exposed workers. In the study of families, there were no differences
between results of the two groups of families.
AEROSOL ASSESSMENT
The comprehensive investigations described leave little doubt that working
at or living near a wastewater treatment plant does not present a microbio-
logical hazard to the people. However, it should always be kept in mind that
sewage contains potentially pathogenic agents and workers at sewage treatment
plants should always maintain good personal hygiene and sanitation practices.
Washing hands with soap and water prior to eating and changing from work clothes
to street clothes at the end of the work day are two examples of good practice.
When sewage treatment takes place within a totally enclosed building, the
treatment plant workers are potentially exposed to higher concentrations of
infectious agents, allergens or irritants than in an outdoor setting. Although
one study of employee health in enclosed sewage treatment facilities in
Manitoba, Canada did not demonstrate unequivocally a relationship between
pathogens in the work environment and employee illnesses, short-term absen-
teeism due to sinusitis seemed to be related to the work environment (19).
Adequate ventilation and a monitoring program for airborne contaminants and
employee health should be encouragedin this situation.
713
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One may wonder why, when people have been exposed to microorganisms from
the wastewater treatment processes, they did not generally become infected or
ill. A combination of several reasons may be offered.
1. The densities of specific pathogens in the aerosols were low, and were
reduced rapidly with time and distance from the source.
2. With a respiration rate of approximately one cubic meter per hour, a person
would ordinarily inhale very few organisms unless constantly exposed for
many hours.
3. The exposure levels were below the minimum infective dose.
4. Microorganisms in wastewater are primarily enteric organisms whereas the
route of exposure was respiratory. The proper surface receptor sites for
the organisms may not have been available.
5. Nonspecific immunity, which responds quickly to foreign substances, was
capable of handling the few microorganisms inhaled. In this situation
phagocytic ce"lls, called macrophages and polymorphonuclear leukocytes,
tend to engulf the particles from the external environment and subse-
quently digest them. These actions undoubtedly took place prior to
initiation of the specific humoral and cell-mediated immunity response
whereby specific antibody and T-cells are formed.
6. Exposed persons were probably in good health and better able to combat
infection than would sickly persons.
7. Infectious agents other than those checked may have caused an undetected
infection.
MUNICIPAL SLUDGE RESEARCH PROGRAM
In addition to research on wastewater treatment, the Health Effects
Research Laboratory has undertaken a research program on potential health
problems encountered when municipal sewage sludge is applied to land for
agricultural purposes. Several of our studies are conducted jointly with the
Municipal Environmental Research Laboratory. The objective is to provide a
scientific basis for determining the extent to which the U.S. Environmental
Protection Agency should regulate agricultural uses of municipal sewage sludge.
It is my intent to briefly outline the types of projects being carried out this
year.
Cadmium
Of the various trace metals that may be contained in municipal sludge,
cadmium is the metal of most concern. The studies may be put into four groups:
background information, fundamental studies, high risk populations, and assess-
ments .
Tables 6, 7 and 8 list the types of studies underway in the first three
groups. Assessments are carried out by U.S. EPA staff and attempt to bring all
the information together in a manner which allows a judgment to be made on
maximum permissible levels in sludge.
714
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TABLE 6. BACKGROUND TASKS ON CADMIUM
1. Cadmium and beta2-microglobulin levels in urine of the
United States population.
2. Cadmium and other metals in soils and food crops of the
United States.
3. Cadmium intake as measured by stool samples.
4. Passage of metals, organics and pathogens through the
sludge-soil-plant-animal pathway.
TABLE 7. FUNDAMENTAL STUDIES WITH CADMIUM
1. Mechanism of intestinal cadmium absorption in rats.
2. Availability of cadmium to rats from crops grown on cadmium
enriched soils.
3. Role of aging processes on chronic effects in the rat
kidney from cadmium.
TABLE 8. STUDIES OF HIGH RISK GROUPS
1. Assessment of cadmium exposure and risk in an American
vegetarian population.
2. Cadmium intake and health effects in a population with a
high oyster consumption.
3. Ingestion and absorption of heavy metals in undernourished
populations.
715
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Microbiological
Since municipal sludge contains many bacteria, viruses, and parasites,
there is interest by the U.S. EPA of potential microbiological hazards
associated with the use of the sludge on agricultural lands. Table 9 summarizes
several health related studies being conducted. With a valid data base, the
Agency may issue regulations for the proper handling of sludge when it is
planned to utilize its nutrient value for agricultural lands.
TABLE 9. MICROBIOLOGICAL PROJECTS RELATED TO SLUDGE
1. Health risks associated with composting sludge.
2. Microbial aerosols generated with spraying liquid digested
sludge by tank truck.
3. Epidemiological study of farm families that utilize muni-
cipal sludge.
4. Assessment of health risks from microorganisms in sludge
applied to land.
5. Survival of Ascaris eggs in sludge applied to soils.
6. Survey of sludges for parasitic contamination.
REFERENCES
1. Mickey, J.L.S. and Reist, P.C. Health Significance of Airborne Micro-
organisms from Wastewater Treatment Processes. Part I: Summary of
Investigations. J. Water Pollution Control Fed., 47:2741-2757 (1975).
2. Hickey, J.L.S. and Reist, P.C. Health Significance of Airborne Micro-
organisms from Wastewater Treatment Processes. Part II: Health Signifi-
cance and Alternatives for Action. J. Water Pollution Control Fed.,
47:2758-2773 (1975).
3. Kenline, P.A. and Scarpino, P.V. Bacterial Air Pollution from Sewage
Treatment Plants. Amer. Industrial Hygiene Asso. J., 33:346-352 (1972).
4. Monto, A.S., Napier, J.A., and Metzner, H.L. The Tecumseh Study of
Respiratory Illness. I. Plan of Study and Observations on Syndromes of
Acute Respiratory Disease. Amer. J. Epidemiology, 94:269-279 (1971).
5. Fannin, K.F., Cochran, K.W., Ross, H., and Monto, A.S. Health Effects of
a Wastewater Treatment System. EPA-600/1-78-062. U.S. Environmental
Protection Agency, Cincinnati, Ohio (1978).
716
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6. Johnson, D.E., Camann, D.E., Harding, H.J., and Sorber, C.A. Environ-
mental Monitoring of a Wastewater Treatment Plant. EPA-600/1-79-027.
U.S. Environmental Protection Agency, Cincinnati, Ohio (1979).
7. Johnson, D.E., Camann, D.E., Register, J.W., Prevost, R.J., Tillery, J.B.,
Thomas, R.E., Taylor, J.M., and Hosenfeld, J.M. Health Implications of
Sewage Treatment Facilities. EPA-600/1-78-032. U.S. Environmental
Protection Agency, Cincinnati, Ohio (1978).
8. Carnow, B., Northrop, R., Wadden, R., Rosenberg, S., Holden, J., Nea1, A.,
Sheaff, L., Scheff, P., and Meyer, S. Health Effects of Aerosols Emitted
from an Activated Sludge Plant. EPA-600/1-79-019. U.S. Environmental
Protection Agency, Cincinnati, Ohio (1979).
9. Dixon, F.R., and McCabe, L.J. Health Aspects of Wastewater Treatment. J.
Water Pollution Control Fed., 36:984-989 (1964)
10. Sample, A.B. Occupational Aspects of Weil's Disease. J. Royal Inst. Pub.
Health Hyg., 15:303 (1952).
11. Randall, C.W., and Ledbetter, J.O. Bacterial Air Pollution from Activated
Sludge Units. Amer. Industrial Hygiene Asso. J., 27:506-519 (1966).
12. Ledbetter, J.O., Hauck, L.M., and Reynolds, R. Health Hazards from
Wastewater Treatment Practices. Environmental Letters, 4:225-232 (1973).
13. Dean, R.B. Assessment of Disease Rates Among Sewer Workers in Copenhagen,
Denmark. EPA-600/1-78-007, U.S. Environmental Protection Agency, Cin-
cinnati, Ohio (1978).
14. Dowling, H.F. Airborne Infection - The Past and the Future. Bacteriol.
Reviews, 30:485 (1966).
15. Rylander, R. , Andersson, K., Belin, L., Berglund, G., Bergstrom, R. ,
Hanson, L., Lundholm, M., and Mattsby, I. Studies on Humans Exposed to
Airborne Sewage Sludge. Schweiz. Med. Wschr 107:182 (1977)
16. Clark, C.S., Cleary, E.J , Schiff, G.M., Linnemann, C.C., Phair, J.P., and
Briggs, T.M. Disease Risks of Occupational Exposure to Sewage. J.
Environ. Engineering Div , ASCE, 12:375-388 (1976)
17. Anders, W. The Berlin Sewer Workers. Zeitschrift for Hygiene. 1:341-371
(1954).
18. Clark, C.S., VanMeer, G.L., Linnemann, C.C., Bjornson, A.B., Gartside,
P.S., Schiff, G.M., Trimble, S.E., Alexander, D., and Cleary, E.J Health
Effects of Occupational Exposure to Wastewater In: Wastewater Aerosols
and Disease. H.R. Pahren and W. Jakubowski (Eds.), U.S. Environmental
Protection Agency, Cincinnati, Ohio (1980)
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19. Sekla, L. , Gemmill, D. , Manfreda, J., Lysyk, M. , Stackiw, W. , Kay, C.,
Hopper, C., Van Buckenhout, L., and Eibisch, G. Sewage Treatment Plant
Workers and Their Environment: A Health Study. In: Wastewater Aerosols
and Disease. H.R. Pahren and W. Jakubowski (Eds.), U.S. Environmental
Protection Agency, Cincinnati, Ohio (1980).
718
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UNITED STATES PAPERS PRESENTED AT TECHNICAL SEMINAR
THURSDAY, MAY 22, 1980
SECTION 301(h) OF THE CLEAN WATER ACT OF 1977 - A MID-COURSE
CORRECTION IN MARINE POLLUTION CLEAN-UP 721
Henry L. Longest, II, Office of Water Program Operations,
ORD, USEPA
IMPROVED OPERATION AND MAINTENANCE OPPORTUNITIES AT MUNICIPAL
TREATMENT FACILITIES 731
John M. Smith, Francis L. Evans III and Jon H. Bender,
Municipal Environmental Research Laboratory, ORD, USEPA
STATUS OF DEEP SHAFT WASTEWATER TREATMENT TECHNOLOGY IN NORTH
AMERICA 777
Richard C. Brenner and John J. Convery, Municipal
Environmental Research Laboratory, ORD, USEPA
CURRENT DESIGN AND OPERATING EXPERIENCE WITH ANAEROBIC SLUDGE
DIGESTION 825
Walter E. Garrison, Carl A. Nagel and R. Steven Easley,
Los Angeles County Sanitation Districts, Whittier, California
SLUDGE COMPOSTING: PROCESSES AND FUTURE DIRECTIONS 863
Atal E. Eralp and Joseph B. Farrell, Municipal
Environmental Research Laboratory, ORD, USEPA
719
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SECTION 301(h) OF THE CLEAN WATER ACT OF 1977
A MID-COURSE CORRECTION IN MARINE POLLUTION CLEAN-UP
by
HENRY L. LONGEST, II*
and
JOSEPH F. SCHIVE*
*Mr. Longest is the Deputy Assistant Administrator for the
U.S. Environmental Protection Agency, Office of Water Program
Operations
*Mr. Schive is an Attorney with the U.S. Environmental Protection
Agency in the Office of Water Program Operations
721
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Section 301 (h) of the Clean Water Act of 1977 is, perhaps, the
most important provision of this Act. It is important not only to the
United States, but to Japan and to all nations that utilize the resources
of our oceans. Briefly, Section 301 (h) provides for the modification
of secondary treatment requirements for publicly owned treatment works
(POTWs) which discharge into marine waters, if they can demonstrate,
to the satisfaction of the Administrator of EPA, compliance with eight
statutory criteria established by Congress. Before I get into detail
about Section 301 (h), let me give you a few facts to point out the
importance of this provision to Japan and some historical background
on U.S. water pollution control legislation to put Section 301(h) into
perspective.
Japan which is about the size of the State of California has a
coastline of 18,425 miles, well over half the length of that of the
United States. This fact, together with excellent oceanographic fishing
conditions has contributed to make Japan one of the world's leading
fishing nations. A recent annual report of the Food and Agriculture
Organization of the United Nations showed that Japan ranked first in
fishing production and in 1977 Japan's total fish catch was 10.76
million tons. V dependence on the sea, Japan has become increasingly
concerned about the pollution of ocean waters. In the last 35 years,
as Japan has emerged as an industrial power, it has experienced the
same problems as other industrialized nations - increased pollution
from large industrial complexes and from concentrated population
centers both of which are primarily located in coastal areas. In a
report by the Japanese Ministry of Foreign Affairs, it was reported
that Japan has a total of 12 petrochemical complexes in operation -
all located along coastlines. 2/ At the same time, the rapid growth
and concentration of population in urban centers in coastal areas has
added to the environmental stress on coastal waters, particularly
those of bays and inland seas.
I point out these facts simply to show how similar the problems
are that our countries are facing, and to stress the fact that what we
do with respect to the oceans could have profound effects on all of
us. Senator Edmund Muskie, the Chairman of the U.S. Senate Subcommittee
on Environmental Pollution, made this point quite clearly when he
said:
Our planet is beset with a cancer which threatens
our very existence and which will not respond to
the kind of treatment that has long been prescribed
in the past. The cancer of water pollution was
engendered by our abuse of our lakes, streams,
rivers, and oceans; it has thrived on our
half-hearted attempts to control it; and like
any other disease, it can kill us. !/
With these strong words, Senator Muskie introduced one of the
most important and controversial pieces of environmental legislation
722
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in the United States and, perhaps, the world. The Federal Water
Pollution Control Act Amendments of 1972 (Public Law 92-500) commonly
referred to as the Clean Water Act, was born in an environment of
controversy which has surrounded it throughout its existence. Vetoed
by President Nixon on the grounds that it carried "an unconscionable
price tag", the legislation came close to not being enacted into law.
However, a unified Congress felt strongly enough about the threats of
continued and worsening water pollution, to override the President's
veto by an overwhelming margin. This action by Congress did not end the
controversy.
Another controversial aspect of this legislation was that it
contained a major change in the enforcement mechanism of the Federal
water pollution control program - a shift of emphasis from water
quality standards to technology-based effluent limitations. Both of
these controversial aspects of the 1972 legislation are intimately
related to Section 301(h) of the Clean Water Act of 1977. This Act,
like the 1972 Act, also amended the Federal Water Pollution Control
Act.
Prior to 1972, U.S. water pollution control laws established
clean-up requirements for dischargers based on their impact on receiving
water quality. Water quality standards were to be set as the control
mechanism. 4/ Under this approach, individual States were to designate
the uses of water to be protected, the kinds and amounts of pollutants
to be permitted, the degree of pollution abatement to be required, and
the time in which such abatement should be achieved.
It quickly became apparent that there were a number of problems
inherent in this approach to clean-up. Difficulties were encountered
in establishing reliable and enforceable effluent limitations on the
basis of a given stream quality. This resulted from the imprecision
of models for water quality and the effects of effluents in most
waters. Also, the fact that water quality standards relied on the
assimilative capacity of receiving waters was viewed as a problem.
Thus, the Federal Water Pollution Control Act Amendments of 1972 (the
1972 Act) introduced a completely different approach to water pollution
control - minimum nationwide requirements based on the capabilities of
treatment technology. Under this approach, similar dischargers were
required to clean up to the same extent, regardless of their impacts
on the receiving waters. In addition to these nationwide requirements,
the 1972 Act introduced a nationwide permit system called the National
Pollutant Discharge Elimination System (NPDES), and authorized a major
funding commitment by the Federal government for construction of
municipal treatment works. The permit system provided an effective
method for enforcement of effluent limitations and other conditions
which were contained in the permits. The Administrator of EPA was
given the authority to enforce those limitations and conditions under
Section 309 of the Act. The virtues of this approach were clear. It
made detection of violations and subsequent enforcement easier, and it
was equitable.
723
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The 1972 Act established effluent limitations for "point sources"
which was defined under the Act, and it distinguished "publicly owned
treatment works" (POTWs) from other point sources. For POTWs, the
1972 Act established two clean-up milestones. First, every POTW had
to achieve effluent limitations based on "secondary treatment" by not
later than July 1, 1977, and, by not later than July 1, 1983, effluent
limitations based on the "best practicable waste treatment technology."
EPA, subsequently, defined secondary treatment in terms of four pollutant
parameters - biochemical oxygen demand (BOD), suspended solids, pH and
fecal coliform - and established national uniform minimum effluent
limitations for these pollutants to be attained by all POTWs by the
1977 deadline, (fecal coliform limitations were deleted from the
definition in 1976).
With this background, I should explain the relationship between
the two controversial aspects of the 1972 Act, to which I referred
earlier, and POTWs. First, the "unconscionable price tag" of the 1972
Act was made up primarily of 18 billion dollars that was to be used
for federal funding of up to seventy-five percent of the costs of
construction of municipal waste treatment plants, i.e., POTWs. Secondly,
the uniform secondary treatment requirements, almost immediately
became the subject of attack by a number of West Coast municipalities
which argued to both Congress and EPA that secondary treatment was not
necessary to protect the marine environment or to assure the attainment
and maintenance of water quality in deep ocean waters. Thus, the
controversy continued. On the one hand, the President, concerned
about the high costs of clean-up, impounded a substantial portion of
the money allocated for the job, while, on the other hand, debate
raged over the merits of secondary treatment for certain POTWs discharging
into marine waters.
The municipalities which argued against secondary treatment
contended that it traditionally had been defined in terms of pollutant
parameters and levels of pollutant reduction which are important for
fresh water ecology, where the discharge of oxygen-demanding wastes
and sedimentation of suspended solids results in distinct environmental
degradation, but that such pollutants have little significance for
deep ocean waters where wastes are rapidly aerated and dispersed by
strong currents and tidal actions. Some POTWs located in West Coast
estuaries which exhibit a high degree of flushing also argued that
secondary treatment provided no significant environmental benefit
because discharges were rapidly oxygenated, dispersed, and carried
into the open ocean. On this basis, these municipalities maintained
that they should be exempted from the 1972 Act's secondary treatment
requirement, and the associated capital, maintenance and operating
costs.
In response to this debate over secondary treatment, EPA, in
1974, formed the Task Force on Secondary Treatment of Municipal Ocean
Discharges. This task force was asked to examine the need for secondary
treatment of wastewater discharged to the ocean from POTWs and to make
724
-------
recommendations on whether to propose to Congress any exceptions to
the secondary treatment standards. Additionally, the National Commission
on Water Quality which had been established under the 1972 Act to
study and report to Congress on all aspects of achieving or not achieving
the 1983 effluent limitations and goals established in Section 301(b)(2)
of the Act, made recommendations concerning marine outfalls in its
Reports to Congress in March, 1976. The recommendations of the two
groups differed.
The EPA Task Force concluded that any amendments to the 1972 Act
should maintain the concept of technology based effluent limitations,
because not enough was known about the effect of pollutants on the
ocean environment to permit the establishment of effective guidelines
or protocols for a case-by-case approach to establishing effluent
limitations. V It recommended that in some cases the July, 1977
deadline should be extended so that further study could be done on
new, undeveloped technologies which might prove better suited to
marine pollution control than secondary treatment. 6/
The National Commission on Water Quality staff also noted the
lack of information that existed on the impacts of pollution on marine
ecology. U However, the Commission, in its report, recommended that:
Congress authorize waiving, deferral or modification
of the 1977 requirements on a category-by-category
basis for near-shore ocean discharges of publicly
owned treatment works... where the Administrator
determines that the adverse environmental impacts
of such action will be minimal or nonexistent... 8/
Despite this recommendation there was substantial reservation about
wholesale revision of either the 1977 treatment requirements or the
concept of uniform technology based standards. Nevertheless, as a
result of the testimony of the West Coast municipalities before Congress,
the Congress included Section 301(h) in the Clean Water Act of 1977.
As I mentioned earlier, Section 301(h) provides that the Administrator
of EPA, upon application by a POTW and with the concurrence of the
State, may issue a NPDES permit which modifies EPA's effluent limitations
for BOD, suspended solids and pH, where the applicant discharges into
certain ocean and estuarine waters and demonstrates to the satisfaction
of the Administrator, by showing compliance with eight statutory
criteria set forth in Sections 301(h)(l) through 301(h)(8), that the
modification will not result in any increase in the discharge of toxic
pollutants or otherwise impair the integrity of receiving waters. The
permits containing these modified requirements are to be issued for a
fixed term not to exceed five years. Decisions on reissuance or
termination of the permits will have to be made at the time of expiration.
At this point, the obvious questions are what are these statutory
criteria and what does Section 301(h) do to the technology-based
effluent limitations scheme established by the 1972 Act. To answer
725
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the latter question, it is necessary to consider the history of the
1977 amendments. In introducing the Conference Report on the 1977
amendments, Senator Muskie noted that, Congress, in the 1972 Act,
established as an objective the restoration of the chemical, physical,
and biological integrity of the Nation's waters, and a national goal
of the elimination of the discharge of pollutants. £/ He hastened to
add that, with the 1977 Act, those objectives and goals remained the
same.
There was a general consensus that the 1972 Act was working, that
the Nation's waters were being cleaned up. The 1977 Act was not
intended to make widespread changes to the national water pollution
clean-up effort. Rather, it was viewed as an effort at "fine tuning"
the clean-up program and as a "mid-course" correction to be made in
light of lessons learned and experience gained after 5 years of effort.
Thus, Section 301(h) was viewed as a part of that fine tuning and the
eight statutory criteria that it set forth were intended to assure
continued progress in protecting and improving the Nation's marine
waters, while, at the same time, providing flexibility to direct
limited resources to priority water pollution problems.
To answer the first question, the eight statutory criteria which
an applicant must meet are the following:
First, there must be an applicable water quality standard specific
to the pollutant for which the modification is requested. The degree
of effluent reduction necessary to meet this standard must be provided
as a minimum.
Second, the modified requirements must not interfere with the
attainment or maintenance of that water quality which assures protection
of public water supplies and maintenance and propagation of a balanced
indigenous population of shellfish, fish and wildlife, and must allow
recreational activities in and on the water.
Third, the applicant must have established, to the extent practicable,
a system for monitoring the impact of such discharge on a representative
sample of aquatic biota.
Fourth, the modified requirements must not result in any additional
requirements on any other point or nonpoint source.
Fifth, all applicable pretreatment requirements for sources
introducing waste into such treatment works must be enforced.
Sixth, the applicant, to the extent practicable, must have established
a schedule of activities designed to eliminate the entrance of toxic
pollutants from nonindustrial sources into such treatment works.
Seventh, there must not be any new or substantially increased
discharges from the point source of the pollutant to which the
726
-------
modification applies above that volume of discharge specified in the
permit.
The last criterion is that any Title II Construction Grant funds
available to the owner of the treatment works must be used to achieve
the degree of effluent reduction required by Section 201(b) and (g)(2)(A)
or to carry out the requirements of Section 301(h). The two sections
of the Act referred to in this last criterion call for the application
of the best practicable waste treatment technology over the life of
the POTW. These criteria placed a substantial burden on POTWs seeking
modifications under Section 301(h). This was Congress' way of showing
that they were seriously committed to the objectives and goals of the
Act.
EPA promulgated regulations implementing Section 301(h) in June, 1979
Again, this was not an easy task, nor was it accomplished without
controversy. I should point out that EPA, like all Federal agencies,
is required by law to provide public notice and opportunity for comment
to the general public on all rule-making by the Agency. Additionally,
EPA, as a matter of policy, encourages public participation above and
beyond the requirements of law. Thus, to assure adequate public
participation the Agency held a public meeting to obtain comments on
how the statutory criteria should be implemented, and then, after
proposed regulations were published, public hearings were held to
receive comments on them. In addition, many written comments on the
regulations were submitted.
As you can imagine, there were many diverse opinions on how
Section 301(h) should be implemented. Rather than dwell on these
differences, I shall simply point out a few of the major areas of
dispute.
Perhaps the most controversial aspect of the regulations was the
agency's interpretation of the term "existing discharge" which appears
in Section 301(h) and the limitation which that interpretation placed
on eligibility for a modification. The Agency originally interpreted
this to mean that Section 301(h) modifications could only be obtained
for those discharges which existed on the date of enactment of Section
301(h), i.e., December 27, 1977, and that modifications could not be
based on any changes to those discharges - such as relocation of
outfalls, improvements to outfalls or treatment works - even if they
had been planned for some time or were currently under construction.
Needless to say, many commenters claimed that this interpretation
contravened Congress' intent. In response to the public comments, the
Agency reexamined the legislative history and concluded that, indeed,
Congress did intend to allow modifications to be based on improvements.
A second controversial issue was the amount of data gathering and
the uniform reporting requirements, particularly with respect to
small, remote communities which discharged primarily domestic waste
having little or no toxic materials. In response, EPA developed a
727
-------
separate policy for Native Alaskan Villages and indicated it would use
its discretion in scheduling secondary treatment for these villages
and communities in Puerto Rico and the U.S. territorial possessions in
the Caribbean and the Pacific, where industrial toxic wastes were not
a factor. At the same time, the Agency pointed out that it had no
authority to categorically exempt communities based on the size or
volume of their discharge, but that given the nature of their discharges,
the monitoring and reporting requirements should be substantially
reduced for them.
Finally, the difficulty of predicting the impacts of future
outfalls or treatment system improvements was much commented upon.
This was raised in the context of whether it was possible to make
predictive judgments as to whether future construction would enable an
applicant to meet the stringent water quality, physical, chemical and
biological criteria set forth in the regulations, and would enable
applicants to show that their discharges would assure the protection
and propagation of a balanced, indigenous population of shellfish,
fish and wildlife. The determination of what constitutes a balanced,
indigenous population is, in itself, very difficult. In response to
the comments on this issue, the Agency advised applicants of the
difficulty of this task and of the lack of established methodologies
for making such predictions, but concluded that applicants would not
be excluded from applying for modifications simply because their
applications required predictive judgments.
When the final regulations were published they included a deadline
for submission of applications which gave POTWs ninety-days to submit
their applications. This deadline occurred on September 13, 1979,
and, while it also is a subject of dispute, seventy final applications
were submitted as of that date. Due to the relatively recent deadline
for submission of applications, the final results on the impacts of
Section 301 (h) are not yet determined. The Agency is currently
reviewing the applications that have been submitted, but it is too
early to predict which or how many applicants will qualify for modi-
fications. Decisions, however, will be made over the course of the
next two years. For those applicants receiving modifications, there
will be, as I mentioned earlier, monitoring requirements to assure
that their modified discharges are meeting the requirements of Section
301(h).
It will take some time for monitoring and assessing the data
received in this program before the final chapter of the debate over
secondary treatment and ocean discharges can be written. Only then
will we have enough information to assess reliability of programs such
as industrial pretreatment programs, toxic control programs, and non-
industrial source control programs, which are the substance of Section
301(h).
Our final objective in this effort is to ascertain a level of
treatment for ocean discharges which will enable us to achieve the
728
-------
goals and objectives of the Clean Water Act. This may require one
level of treatment for POTWs which discharge domestic waste and another
level of treatment for POTWs which have industrial waste and toxic
materials in their effluent. Once these levels of treatment are
ascertained, it may be necessary to revise the Clean Water Act to
enable the Administrator of EPA to define ocean discharge requirements
or to allow permanent modification of secondary treatment requirements.
As you can see, there still remains much to be done and this will
take time. EPA expects that during this period, through continued
research efforts by EPA and other U.S. Agencies, and by their counterpart
organizations in other countries, such as Japan, and international
organizations, we shall come to understand much more about the effects
of what we discharge into the oceans. Hopefully, through the continued
exchange of ideas, research and technology, we shall be able to
eliminate any detrimental effects.
729
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REFERENCES
]_/ Facts and Figures of Japan, Foreign Press Center (1980).
2/ The Japan of Today, Ministry of Foreign Affairs (1978).
3/ Senate Consideration of the Report of the Conference Committee,
October 4, 1972, reprinted in a A Legislative History of the
Water Pollution Control Act Amendments of 1972 (January 1973).
1 Legislative History, at 161.
4_/ Report of the Committee on Public Works, United States Senate,
S. Rep. No. 92-414, 92rd Cong., 1st Sess. 8 (1971), 2 Legislative
History, at 1426.
5/ Secondary Treatment of Municipal Ocean Discharges, United States
Environmental Protection Agency, Task Force Report, at 15.
6/ Id, at 2.
7J The National Commission on Water Quality Staff Report, at IV-76, 77
8/ The National Commission on Water Quality, Report to the Congress
(1976), at 17.
9/ U.S. Senate Debate on the Conference Report, December 15, 1977, 3
Legislative History, at 425.
730
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Improved Operation and Maintenance Opportunities
~~~at Municipal Treatment Facilities
John M. Smith*
Francis L. Evans III**
Jon H. Bender***
I. INTRODUCTION
A vital component of the U.S. strategy to meet the National Water
Quality Goals of the Federal Water Pollution Control Act of 1972 (PL 92-
500) and the 1977 Amendments (PL 95-217) is to substantially improve the
performance of publicly owned municipal treatment works through the inte-
gration of state and federally-issued permits, federal enforcement actions,
and the federal Construction Grants Program (1).
Today there are over 20,000 publicly owned municipal treatment plants
in the United States with another 1,000-1,200 new plants being constructed
each year. The Federal Water Pollution Control Act of 1972 (PL 92-500)
and the 1977 Amendments (PL95-217) established a national municipal effluent
standard of secondary treatment for these facilities unless water quality
standards require higher levels of treatment.
Although federal and state governments subsidize from 75-98% of the
capital costs of publicly owned municipal treatment facilities, the local
government bears the responsibility for operation of these plants in
accordance with effluent permit requirements established by the National
Pollutant Discharge Elimination System (NPDES) mandated by the Federal
Water Pollution Control Act (FWPCA) of 1972. The FWPCA of 1972 further
provides that municipal facilities failing to meet permit conditions are
subject to a range of enforcement actions including fines, administrative
orders, and judicial actions for extreme violations. Conformance with
permit requirements is based on a self-reporting process for all municipal
facilities with supplemental compliance monitoring by state and USEPA
Regional personnel.
**
***
John M. Smith is Chief of the Urban Systems Management Section, Systems
& Engineering Evaluation Branch, Wastewater Research Division, Municipal
Environmental Research Laboratory, Cincinnati, Ohio 45268
Francis L. Evans III is Program Manager for Municipal Energy Conservation
Jon H. Bender is Program Manager for Plant Operation and Design, within
the USMS, SEEB, WRD, MERL, Cincinnati, Ohio
731
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Several national studies since 1975, including legislatively mandated
clean water reports to Congress in 1975 and 1976, and a U.S. Government
General Accounting Office (GAO) study conducted in 1977 conclusively
demonstrated that publicly owned municipal treatment facilities were not
meeting permit requirements (2)(3)(4). The GAO study indicated that 40%
of all treatment facilities failed to meet design BOD removals and 49%
failed to achieve SS design removal efficiencies. The study further
documented that only 25% of all trickling filters were in compliance with
federal secondary treatment standards for BOD and SS removal. As of 1977,
only 50% of all publicly owned municipal treatment plants were in compliance
with federally mandated National Pollutant Discharge Elimination System
standards.
II. THE NATIONAL SURVEY SUMMARY
Recognizing the significance of the non-compliance problem and the
ineffectiveness of the current federal enforcement programs, the USEPA's
Office of Research and Development undertook a comprehensive national
study of publicly owned municipal treatment plants in 1975 to identify and
quantify the specific causes of inadequate performance and to formulate
recommendations for improvement. Corollary objectives of the study were
to identify future research needs and to demonstrate methods of improved
performance. Treatment facilities were selected for study based on sequential
screening and selection procedures. USEPA regional offices and state
regulatory agencies assisted in initial selection of plants by compiling a
list of potential study sites. Plants not meeting one or more of the
following general screening criteria were eliminated from the selection
process.
1. The plant must incorporate some variation of suspended growth,
fixed film, or aerated lagoon biological treatment.
2. The plant should not be severely hydraulically or organically
overloaded, nor have obvious identifiable structural or component
deficiencies.
3. The plants should range in size up to 38,000 m3/d (lOmgd) and
all major units should be operating.
4. No enforcement action should be underway or pending against the
municipality or authority involved.
Site visits were made to a total of 287 facilities to collect more
detailed data than the original screening information in order to select
those plants at which more comprehensive evaluations would be conducted.
The number of site visits, preliminary evaluations, and states included in
the survey is shown in Figure 1. These initial site visits required one-
half to one full day at each facility to evaluate such things as process
configuration; influent and effluent wastewater characteristics; condition
of equipment; and discharge permit criteria. Also, the plant superintendent
and operating personnel were questioned regarding problems they saw as
732
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interfering with plant operations.
O/ indicates No. of site visits per state
/O - indicates No. of preliminary evaluations per state
Totals 287 site visits
103 preliminary evaluations
18 states
Figure 1. States Including Number of Site Visits and Number
of Preliminary Evaluation in USEPA National Survey (5)(6)
In addition to the data collected from the initial 287 site visits,
103 facilities were selected for further comprehensive evaluations. The
purpose of the comprehensive evaluations were to examine in detail the
system and unit process performance and to evaluate existing operation,
maintenance, and administrative practices. Each plant evaluation involved
a team of professional engineers and experienced plant operating personnel
and required three to five days of onsite field work. In all, 70 potential
problem areas were investigated at each facility.
733
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In order to quantify and report the deficiencies and problems at
plant sites, both individually and collectively, a plant evaluation
summary was developed, consisting of a weighing scale and a ranking
table. The scale was devised to rank the 70 different factors that could
limit plant performance. For each factor identified at a facility, the
extent to which it adversely impacted plant performance was quantified
according to the weighing scale points as defined in Table 1. The factors
affecting plant performance were then ranked in decreasing order of severity
as shown in Table 2.
Table 1
Weighing Scale Used to Quantify Adverse Impact
Ueighing Effect of Specific Factor on
Scale Plant Performance
0 No significant effect on plant performance
1 Minor effect on plant performance
2 Minimum indirect effect on plant performance
on continuous basis or major direct effect on
plant performance on a periodic basis
3 Major effect on plant performance
Based on the results of the comprehensive surveys, the 10 highest ranking
causes of poor plant performance result from inadequate plant operation
and plant design deficiencies. The highest-ranking factor (#1) was in-
adequate operator application of concepts and testing to process control.
This coupled with the fourth-ranked factor, inadequate understanding of
wastewater treatment, indicates that for various reasons operators were
not applying the proper concepts of operation to process control. These
reasons are attributable to inadequate or incorrect sampling and testing
procedures for process control (Factor #2), improper technical guidance
(Factor #5), ineffective O&M manual instruction (Factor #9), and signi-
ficant design deficiencies (Factors #3, 6, 7, 8, and 10), all of which
prevent an operator from controlling and "tuning" his treatment system to
varying influent hydraulic and pollutant loading characteristics. The 10
leading causes of inadequate performance are described below.
734
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Table 2.
1 *^1*J
Factor
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
SO
S!
62
63
64
65
66
67
68
69
70
Area
Operation
Operation
Design
Operation
Operation
Design
Design
Design
Operation
Design
Design
Design
Operation
Design
Operation
Design
Administration
Design
Administration
Design
Administration
Maintenance
Design
Design
Operation
Maintenance
Design
Design
Maintenance
Maintenance
Administration
Administration
Administration
Maintenance
Design
Administration
Administration
Design
Maintenance
Design
Operation
Design
Administration
Design
Maintenance
Operation
Administration
Design
Design
Maintenance
Maintenance
Design
Operation
Design
Design
Design
Operation
Operation
Maintenance
Design
Administration
Design
Administration
Operation
Design
Design
Design
Design
Administration
Design
Limiting Factor
Description
Operator Application of Concepts & Testing
to Process Control
Process Control Testing
infiltration/ Inflow
Sewage Treatment Understanding
Technical Guidance
Sludge Wasting & Return Capability
Secondary Process Controllability
Secondary Process Flexibility
O&M Manual Inadequacy!')
Aerator
Sludge Treatment)')
Industrial Loading
Staff Training
Secondary Clarifier
Performance Monitoring
Ultimate Sludge Disposal
Plant Administration. Familiarity with Needs
Disinfection!'!
Plant Staff - Number
Plant Hydraulic Loading
Plant Staff • Plant Coverage
Spare Parts Inventory
Laboratory Space & Equipment
Return Process Stream
Equipment Malfunction
Lack of Preventive Maintenance Program
Alternative Power Source
Organic Loading
General Housekeeping
Maintenance Scheduling & Recording
Administration Policies
Plant Staff Productivity
Insufficient Funding
Manpower
Preliminary Unit Design(')
Staff Motivation
Working Conditions
Alarm Systems
Critical Pans Procurement
Flow Proportioning to Units
Staff Aptitude
Inoperability Due to Weather
Staff Supervision
Primary Units!*}
Equipment Age
O&M Manual • Use By Operators!')
Salary
Lack of Standby Units for Key Equipment
Lack of Unit By-Pass
Technical Guidance - Emergencies
Availability of Preventive Maintenance Ref
Flow Backup
Staff - Level of Education
Toxic Loading
Submerged Weirs
Plant Location
Staff Level of Certification
Staff • Insufficient Time on Job
Staff Expertise - Emergencies
Seasonal Variation Loading
Unnecessary Expenditures
Process Automation for Control
Personnel Turnover
Shift Staff Adequacy
Unit Accessibility
Process Accessibility for Sampling
Process Automation for Monitoring
Equipment Accessibility for Maintenance
Bond Indebtedness
AWT Units!')
No
Factor was
ranked #1
24
0
9
9
7
9
3
3
0
6
3
4
0
3
0
1
2
1
2
0
0
0
0
1
2
1
0
7
0
0
2
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
o
o
0
0
o
o
0
of Times
Factor was
noted
89
67
56
50
47
43
55
37
40
27
36
27
31
26
31
30
21
20
22
18
26
23
30
18
17
20
24
13
17
19
15
17
16
14
20
19
18
19
14
12
13
12
13
9
14
12
12
9
12
10
10
7
9
8
6
6
8
7
9
7
7
6
4
3
3
4
2
2
o
0
'Not included m every plant evaluated
735
-------
1. Operator Application of Concepts and Testing to
Process Control—This factor was ranked as the
most severe deficiency and leading cause of poor
performance at 23 facilities and was a high-ranked
factor at a total of 89 out of the 103 plants evaluated.
It occurs when a trained operator in a satisfactorily
designed plant permits less than optimum
performance. This factor was ranked when incorrect
control adjustment or incorrect control test interpre-
tation occurred, or when the use of existing inade-
quate design features continued when seemingly
obvious operations alternatives or minor plant modi-
fications could have been implemented to improve
performance. The lack of testing and control were not
necessarily the result of inadequate training or
comprehension in these areas, but simply the lack of
or inability to apply learned techniques.
2. Process Control Testing Procedures—Inadequate
process control testing involves the absence or
wrong type of sampling or testing for process
monitoring and operational control. This deficiency
leads to making inappropriate decisions. Standard
unit process tests such as mixed liquor suspended
solids, mixed liquor dissolved oxygen, mixed liquor
settleable solids, and return sludge suspended solids
for activated sludge processes were seldom or never
conducted Also, important operating parameters
such as sludge volume index, F.M ratio and mean cell
retention time in suspended growth systems or
recirculation rates in trickling filter plants were
usually not determined. This factor adversely
impacted performance at 67 of the 103 plants
evaluated.
3 Infiltration/Inflow—The results of this widespread
problem are manifested by severe fluctuations in
flow rates, periods of severe hydraulic overloading,
and dilution of the influent wastewater so that both
suspended and fixed biological systems are loaded to
less than optimal values. The extreme result is the
"washout" of suspended growth systems as a result
of the loss of solids from the final clarification stage
during high flow periods. This factor was ranked first
at 56 of the 103 plants evaluated.
4 Inadequate Understanding of Wasteweter
Treatment—This factor is distinguished from Factor
#1 in that it is defined as a deficiency in the level of
knowledge that individual staffs at various
facilities exhibit concerning wastewater treatment
fundamentals. On occasion, an operator's primary
concern is simply to keep the equipment functional
rather than to learn how the equipment relates to the
processes and their control This factor adversely
affected performance at 50 plants and was the
leading cause of poor performance at nine facilities.
5. Technical Guidance—Improper technical guidance
includes misinformation from authoritative sources
including design engineers, state and federal regula-
tory agency personnel, equipment suppliers,
operator training staff and other plant operators. At
any one plant, improper technical guidance was
observed to come from more than one source. This
factor was ranked as the most severe deficiency at
seven plants, and was an adverse factor at 47
facilities.
6. Sludge Wasting Capability—This factor was ranked
as the leading cause of poor performance at nine
facilities and was a factor at 43 plants studied. This
factor includes inadequate sludge handling facilities
and the inability to measure and control the volume of
waste sludge. Either one or both of these conditions
was noted as having a major impact on performance
at several plants.
7. Process Controllability—The lack of controllability
was evident in the inability to adequately measure
and control flow streams such as return sludge flow
and trickling filter recirculation rates. While
measurement and control of return activated sludge
flow were the most frequent reasons for rating this
factor, process controllability was not a major cause
of poor performance. It prevented an operator from
"tuning" his treatment system to the varying
demands which were placed on it by hydraulic and
organic loading fluctuations. This factor occurred at
55 plants and was the leading factor at three
facilities.
8. Procei* Flexibility—Lack of flexibility refers to the
unavailability of valves, piping and other appurten-
ances required to operate in various modes or to
include or exclude existing processes as necessary to
optimize performance. Poor flexibility precludes the
ability to operate an activated sludge plant in the
contact stabilization, step loading or conventional
modes and the ability to bypass polishing ponds or
other downstream processes to discharge high qual-
ity secondary clarifier effluent. Either the lack of, or
inadequate, process flexibility was noted as the lead-
ing cause of poor performance at three plants and
was a factor at 37 facilities.
9. Ineffective O&M Manual Instruction—This situa-
tion, existing at 40 plants, was judged serious
although the adverse effect was moderate. The poor
quality of most plants' O&M manuals undoubtedly
has contributed to operators' general lack of under-
standing of the importance of process control and the
inability to practice it, but a competent staff could use
other available information sources.
10. Aerator Design—Deficiencies in aerator design were
the major cause of poor performance at six facilities
and were less significant factors at an additional 21
plants. Deficiencies were noted in the type, size,
shape, capacity, and location of the unit and were of
such a nature as to hinder adequate treatment of the
waste flow and loading and stable operation.
736
-------
For each factor shown in Table 2, the area of design, operation,
maintenance, or administration is identified. Also shown is the number of
times that a factor was ranked Number 1; i.e., the number of times the
factor was the leading cause of poor performance, and also the number of
plants at which the factor had a "minor" or more serious adverse impact on
plant performance. In some cases, plant evaluations did not include every
factor being evaluated for potential adverse impact. These factors are
marked in the table by an asterisk. However, all factors were noted as
having an adverse impact either when the factor was present and a deficiency
or an adverse effect was observed or when the factor was not present and
an adverse effect resulted from its absence. As noted on the table,
operational problems and design deficiencies comprise the top 16 leading
causes of poor plant performance.
In addition to the summary information shown here, each of the 103
plant evaluations conducted over a 3 1/2 year period resulted in a report
60 to 100 pages in length, describing in detail the interrelationships of
the administrative, operational, design, or maintenance factors affecting
performance. The report also documented all operating costs associated
with each facility and outlined a specific correction program to optimize
performance without major capital improvements. This information is
included in EPA's Office of Research and Development national operations
and maintenance computerized data base to be discussed later.
Other major conclusions from the National Survey as they affect the
potential for improved operations and maintenance of municipal treatment
plants are listed below.
1. Lack of aggressive federal enforcement against municipal dischargers
has failed to provide needed local government incentive for con-
sistently meeting effluent permit requirements.
2. Fixed film facilities were more often affected by deficient
design practices, while suspended growth facilities were more
affected by operational problems (5).
3. Total plant staff size, total plant staff cost, specific plant
staff size, specific plant staff cost and plant staff salary did
not significantly correlate with good or poor plant performance.
4. In nearly all facilities surveyed, adequate manpower was provided
for proper plant operations and maintenance. Plant maintenance
was satisfactory, but plant operations was unsatisfactory even
though a greater proportion of the operator's time was spent con-
ducting "operations" tasks.
5. Current operator practices for the smallest facilities surveyed,
0-380 m-Vd (0-O.lmgd), were poor. For larger facilities sur-
veyed, 3800-38,000 nwd (1.0-10.0 mgd ), operator practices were
only fair. (These conclusions based on 30 plants)(5).
737
-------
6 For all of the facilities studied, operation and maintenance
costs varied from $0.25/m3 ($0.93/1000 gal) for 380 m-Vd (0.1
mgd) facilities to $0.03/m3 ($0.10/1000 gal) for 76,000 m-Vd (20
mgd) facilities.
7. In a sub-set of 30 plants studied, significant differences in O&M
costs between suspended growth and fixed film facilities were
noted as shown below.
Plant Size
m3/d
(mgd)
0.0-380 380-3,800 3,800-38,000
Type Plant (0.0-0.1) (0.1-1.0) (1.0-10-0)
Suspended Growth
O&M Cost $/m3 0.25 0.12 0.06
(S/1000 gal) (0.93) (0.45) (0.21)
Fixed Film
O&M Cost $/m3 -- 0.09 0.03
($/1000 gal) ( -- ) (0.35) (0.10)
8. Although maintenance factors were cited in some instances as con-
tributory to inadequate performance, they were not a significant
or dominating factor in most of the plants studied.
9. O&M manuals were noted to be of marginal value during the study.
10. On-site training including "trouble-shooting techniques" to
increase operators' understanding of process control was strongly
recommended as an effective remedial solution.
11. Plant staffing and staff salaries, although less than that recom-
mended by USEPA staffing guidelines in some instances, were not
considered major factors.
12. For 30 of the plants studied, average operation staff salary
ranged from $10,501/year for a 0.0 to 380 m3/d (0.0 to 0.1 mgd)
facility size range to $13,107/year for a 3,800 to 38,000 m3/d
(1.0 to 10.0 mgd) size range. Total salaries for these 30 plants
ranged from 17.2% to 66.3% of total plant operating costs with an
average of 46%.
III. A NEU APPROACH FOR IMPROVING PERFORMANCE
In a critical evaluation of the data from the above National survey,
it was noted that at each treatment facility a combination of factors
limiting performance was always observed and that a single cause of poor
performance at any one facility was never observed. Because there is an
interrelationship between performance limiting factors and corrective
738
-------
programs, and because most existing correction programs focus on single
problems only, a new approach which addresses all problems at a single
facility was developed as more effective in improving existing plant
performance. This approach is called a Composite Correction Program
(CCP). The purpose of the CCP is to eliminate all the performance
limiting factors at a plant through the implementation of the correction
recommendations that are made as a part of the comprehensive evaluation.
The general approach is to improve the process control decision
making capability of the plant superintendent and the operators and to
eliminate administrative, maintenance, and operations factors which were
preventing optimum performance of the treatment system. In a few cases,
minor plant modifications were recommended that could be made either by
the plant staff or a local contractor.
Among the services provided during the on-site technical assistance
were the establishment of process control monitoring and testing programs,
operator training to improve the application of concepts and testing to
process control, adjustment of plant staffing and rescheduling of staff
activities, minor modification of a clarifier, and modification of plant
operations to optimize and maintain the performance of the biological
units.
The CCP was successfully demonstrated at several facilities. When
the program was implemented at the Havre, Montana Wastewater Treatment
Plant, a significant improvement in plant effluent quality resulted and
permit standards could be met consistently. At the Havre plant, the
effluent quality for six months prior to implementation of the CCP averaged
31 mg/L for BOD and 30 mg/L for TSS. Both BOD and TSS concentrations
averaged less than 10 mg/L for an eight-month period following initiation
of the CCP and development of desired activated sludge characteristics.
During that period of time, the plant's BOD loading increased by 27%, yet
BOD discharged to the receiving stream decreased by 68%..
At other facilities where the CCP technical assistance approach was
used, improved performance resulted from changes in plant operations or
minor changes in plant design features. The improvement in effluent quality
that was achieved at 12 of the plants evaluated is shown in Table 3.
The significance and impact of a CCP approach to optimizing plant
performance are indicated by improved effluent quality at the demonstration
facilities and by the potential improvements which could be realized if
such a program were implemented at all the facilities at which comprehensive
evaluations were performed.
Of the 103 facilities evaluated, only 37 plants (36%) were meeting
their respective NPDES standards consistently. However, if as a result of
the evaluations, the recommendations were implemented, it was estimated
that an additional 51 treatment plants could consistently meet NPDES standards,
and 88 plants (86%) would achieve optimal levels of performance beyond
which further improvement in effluent quality would not be possible without
upgrading the existing facilities.
739
-------
Table 3. Plant Performance Improvement Thru Implementing CCP
ACTUAL
FLOW
FACILITY (MGO)
022 45
(0.012)
EFFLUENT QUALITY
TSS (mg/L)
BEFOREAFTER
35 10 60 10
029
048
050
053
060
061
5,190
(1.37)
1,300
(0.34)
640
(0.17)
420
(0.11)
1,900
(0.49)
640
(0.17)
31 9.7 30
68 10 116
45 10 80
32 10 50
10
10
10
10
45 35 37
27
37 10 42
10
PLANT TYPE - COMMENTS
Activated sludge, extended aeration, with
polishing pond. The return sludge flow rate
was excessively high, causing solids loss over
the clarifier weir. The R/Q ratio was re-
duced from about 1000% to about 100%, and
excessive solids loss was eliminated. A
pond bypass should be installed to discharge
good final clarifier effluent to the re-
ceiving stream.
Activated sludge, conventional, without pri-
mary clarifier. Changes in return and waste
sludge control procedure were implemented
and a plant deficiency was corrected.
Activated sludge, conventional, without pri-
mary clarifier. Insufficient sludge wasting
and sludge bulking. Increased wasting con-
trolled sludge bulking. An I/I problem
should be corrected.
Activated sludge, extended aeration, without
primary clarifiers. Insufficient sludge wasting
was corrected. Increased wasting controlled
sludge bulking. Operations testing and
process controls were implemented.
Activated sludge, extended aeration, without
primary clarifiers. Insufficient sludge
wasting was corrected. Decreased return,
controlled scum withdrawal, and increased
wasting, was well as implementation of
operations testing and process controls were
completed.
Two-stage trickling- filter with primary
(second-stage is an activated bio-filter
system). A valve leaking mixed liquor to
the chlorine contact basin influent was
found. Plant effluent is still marginal
because of design limitations in aeration
capacity.
Activated sludge, contact-stabilization,
without primary clarifier. Inadequate sludge
wasting and return control provided. Return
flow rate not controlled. Operations testing
and process control were implemented and good
effluent quality maintained. A piping modi-
fication should be completed to operate con-
ventionally.
740
-------
Table 3. (Continued)
ACTUAL
F.LOW
m3/d
FACILITY (MGPj_
065 490
(0.13)
EFFLUENT QUALITY
BOOs (mg/L) TSS (ma/ 1)
BEFORE AFTER BEFORE AFTER
72 21 143 8
082
310
(0.083)
50
20
75
30
085
086
097
3,200
(0.84)
1,800
(0.48)
3,200
(0.84)
50
10
108
10
75
23
10
150
34
15
PLANT TYPE - COMMENTS
Activated sludge, contact stabilization
without primary clarlfiers. Solids loss
occurred due to inadequate sludge mass and
return sludge control. Minor modifications
were made to the return sludge and wasting
mechanism and to the chlorine contact tank.
Activated sludge, contact stabilization and
parallel trickling filter. Flow splitting
to the two plants was not optimized.
Solids loss from the contact stabilization
plant occurred repeatedly due to inadequate
process control. The digester was used as
part of the reaeration basin. Sludge beds
must be subsidized with wethaul of sludge
for ultimate disposal.
Activated sluge, oxidation ditch without
primary clarifiers and with sludge lagoons.
Excessive solids loss due to inadequate
process control understanding. Mass con-
trol and process control testing were
improved. Ultimate sludge disposal capability
must be expanded.
Activated sludge, extended aeration without
primary clarifiers and with sludge lagoons.
No wasting was practiced. Existing sludge
lagoons have inadequate capacity. A
sludge truck for land application of sludge
was purchased.
Activated sludge contact stabilization with-
out primary clarifiers, with aerobic
digester and roller press sludge de-
watering. The approach to process control
was misdirected and was leading towards
poor performance. Process control under-
standing was increased and impending
problems were avoided. I/I problems an-
ticipated in isolated cases.
Because of the demonstrated success of the CCP developed in this
survey, the USEPA's Office of Enforcement has adopted the procedure for
widespread use as a part of its national enforcement strategy for publicly
owned municipal treatment facilities.
To assist in this effort, USEPA's Office of Research and Development
has expanded and refined the plant evaluation and CCP procedure into a
protocol that is applicable to a wide range of plant sizes and types and
contains the necessary cost estimating guidelines, evaluation checklists,
and other necessary information to be used by consulting engineers
throughout the country for improving plant performance.
741
-------
Recent statements from Eckardt C. Beck, Assistant Administrator for
USEPA's Water and Waste Management Program, and Jeffrey G. Miller, Acting
Director for USEPA's Enforcement Division, excerpted from an October 10,
1979 policy address at the Water Pollution Control Federation annual
meeting in Houston, Texas indicate EPA's increasing concern for improving
the operation and maintenance of the Nation's municipal treatment facilities
as well as the use of previously-mentioned protocols. The text of this
statement is shown below.
Sawaga Treatment
EPA LAUNCHING NEW DRIVE
AGAINST IMPROPER PLANT OPERATION
HOUSTON, Tex. — (By an Environment Reporter Staff
Correspondent) — Prooer operation and maintenance of
municipal sewage treatment systems is now a top concern at
the Environmental Protection Agency, and two key agency
officials here said treatment system management will be
emphasized in EPA's water and enforcement programs.
Eckardt C. Beck, Assistant Administrator-designate for
EPA's Water and Waste Management programs, October 10
told 3 meeting of the Water Pollution Control Federation im-
proper municipal treatment system operation and
maintenance is "one of the major reasons" why almost 60
percent of the municipalities nationaUy failed to meet the
1977 Clean Water Act deadline for compliance with secon-
dary treatment standards.
Beck said "O&M" now stands for "Operation and
Management" in the municipal sector. Management, he add-
ed, "means more than polishing the knobs and pipes."
Beck told WPCF conference attendees the benefits of
EPA's construction grant program — plant expansion and im-
proved treatment processes — wilj be negated without
proper plant management. In some instances management
alone vrill result in a plant complying with secondary treat-
ment requirements. "If you can achieve compliance without
major new construction — do it," he said.
Us« of Contractor* Urg«d
Beck said in some instances the key to proper plant
management may be for a municipality to contract with a
private firm for plant operation and maintenance.
"I am a firm believer that the solutions to our environmen-
tal problems demand an involvement of the private sector,"
Beck said. He also announced EPA is now usin£ demonstra-
tion grants "to act as a catalyst to attract more private
firms into the business of upgrading plant services."
Jeffrey G. Miller, acting director for EPA's enforcement
division, told the WPCF conference attendees the "tremen-
dous disparity" between municipal and industrial com-
pliance with Water Act requirements has led to a "shift of
emphasis from industrial to municipal" dischargers.
Miller said improper municipal treatment plant operation
is a major reason why so many systems failed to meet the
Water Act's 1977 secondary treatment deadline, and he
promised increases in the number of enforcement actions.
Miller said municipalities do not "feel in a position of
risk" and therefore have little incentive to operate treat-
ment systems efficiently. "It's plain we have to change that
attitude," he said, and he urged listeners to look for a
"trend" as treatment plant supervisors are sued, and court
appointed experts take over management of municipal
systems.
"The message must get out" that cities are at risk. Miller
said. He predicted EPA and Justice will bring about 50 to 60
cases against municipalities that fail to properly operate
their treatment systems.
Miller said that in many of the cases Section 311 of the
Water Act will be used to require "immediate clean-up" of
municipal discharges. He also said EPA is developing a
diagnostic protocol that can tell plant operators why their
system is not meeting discharge standards.
Miller said the test procedure will cost about $15.000 and
may in the future be lied to National Pollutant Discharge
Elimination System permit issuance or resolution of en-
forcement actions.
In addition to the national interest in adopting the plant evaluation-
CCP approach, the State of Colorado was recently awarded an EPA research
cooperative agreement to demonstrate the cost effectiveness of the approach
for 20 municipal treatment plants as a part of the state's enforcement
activities. Another state in EPA's Region 5 is also planning a state wide
demonstration of the CCP.
It is estimated that over 70% of the non-complying plants in the U.S.
can be brought into compliance with NPDES permits using this approach at
a plant cost of $10,000 to $25,000 (1977 dollars) per plant depending on
plant size and complexity (5)(6).
IV. IMPACT OF NATIONAL SURVEY IN DIRECTING ORD RESEARCH INCLUDING RECENT
RESULTS~
In addition to providing an in-depth understanding of the four major
categories of problems affecting the performance of municipal treatment plants
742
-------
and the development of the CCP, the National Survey results have been the
major influence in directing USEPA Office of Research and Development programs
in plant operation and design in fiscal years 78 through 83.
This program, operated on a national basis under the authority of
Title I of the Federal Water Pollution Control Act, has the following goals:
. Reduce the construction and operating cost of municipal collection and
treatment systems
. Improve municipal treatment plant performance and reliability
. Reduce energy consumption
• Provide baseline cost and performance data to support operating program
management and administration and regulatory activities
Support Agency enforcement activities
sh
The research program is divided into four specific areas to accompli
the above goals. The specific areas of research, research projects, and
National Survey problem areas addressed are shown in Table 4.
While it is not possible to discuss each of USEPA's current research
projects, recent research activity and Agency emphasis in the areas of:
(a) identifying specific design deficiencies; (b) development of design
guidelines; (c) improving plant reliability, and (d) improving plant oper-
ations and management will be discussed in the following sections.
Identification and Proposed Methods for Reducing Design Deficiencies in
Municipal Treatment Plants
Design deficiencies in municipal treatment plants is a very broad
classification of problems that were found to be present in varying degrees
in nearly every plant studied in the National Survey. Because of the
severity and widespread distribution of design deficiencies, a separate
research program was undertaken in 1978 by EPA's Office of Research and
Development to identify and analyze the problems and to develop a design
deficiency matrix and correction manual to be used by consulting engineers
during the planning and design of new facilities, and for state and EPA
authorities for their use in reviewing and approving plans and specifications
for the construction of federally funded facilities (7).
The manual has also been designed for use in correcting design
deficiencies at existing municipal plants. The manual describes design
deficiencies that can increase plant operation and maintenance requirements,
annual operating costs, energy requirements, and can contribute to perfor-
mance and reliability problems, poor safety practices, and/or decrease the
flexibility of plant process control. The manual is intended to provide
design engineers with guidance that will make their designs more operable
and maintainable at less cost as well as more flexible in providing adequate
performance during times of changing influent characteristics. The manual
is divided into three main sections.
743
-------
Table 4. USEPA Current Plant Operation and Design Research Program (1980)
RESEARCH PROGRAM
DESIGN AND ENGINEERING AND COST-EFFECTIVENESS ANALYSIS
Develop a Decision Optimization Methodology for Residuals Management
Mgm't Information System for Toxics-C/E of Pretreatment; NPDES Impact
Energy Assessment Procedures Manual
O&M Practices of Land Treatment Processes
Impact of Recycle and Return Flows on Plant Performance
Low Cost Correction of Design Deficiencies
Impact of Peak Hows on Conventional Process Performance
RBC's Performance, Operation & Design
Computerized Data Base-O&M Cost, Design & Performance
Integrated Community Utility Systems
Operation and Performance of Fine Bubble Aerators
Improving the Basis for Design
* Design Information Series
* Analysis of O&M Costs of Conventional Collection Systems
Dev. & Implement a Cost Analysis System for WW Collection Systems
Demonstrate O&M Cost Reduction in WW Collection & Treatment Systems
IMPROVEMENT IN SYSTEMS RELIABILITY
* Identify & Quantify Factors Affecting Reliability; incl. Toxics
* Mechanical Reliability of Conventional Components of Plants
* Improving Clarifier Performance thru Improved Hydraulics
Demonstrate Improved Clarifier Performance
Develop Methodology & Guidelines for Systems Reliability Analysis
Evaluate Private Sector Expertise to Conduct CCPs
Survey & Performance Analysis of POTW Contract Operation
Methodology for Evaluating Alternative Water Quality Management
Analysis of Methods for Evaluating Established Stnds. & Monitoring
Requirements for Water Quality Monitoring
Evaluate Feasibility & Demonstrate Fail -Safe Treatment Processes
IMPROVEMENT IN PLANT DESIGN AND OPERATION
* Areawide Demonstration of CCP
Areawide Demonstration of CCP - 2nd Site
Develop & Evaluate Effectiveness of On-Site Training Programs
Optimize Opertion of a Group of Small WWTPs
Evaluate & Demonstrate Centralized Management of O&M Activities
Computer Program Development for Centralized Management
Computer Program Dev.-C/E of Alternative Systems in Urban Areas
Protocol for Comprehensive Plant Evaluation
Improving O&M and Design of Land Application Systems
Engineering Eval.and Analysis-Extramural Support for In-House Studies
AUTOMATION AND INSTRUMENTATION
tvai. intelligent Computer to Monitor & Control Operations of WWTP
Feasibility Study for Establishing an Instrument Certification Lab
Dev. Specs & Testing Protocol for On-Line Measuring Inst. & Auto.
Dev. Organ. Design & Management Plan for Inst. Cert. Lab.
Support of Instrument Certification Lab
Evaluate Application of Computer Technology to Control of WWTPS
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NATIONAL SURVEY PROBLEM AREAS
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* Major emphasis on these programs in fiscal years 1979, 1980 and 1981
A Administration
D - Design
0 Operation
M Maintenance
744
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. Design Deficiencies Matrix
. Design Consideration Modules for New POTWs
. Design Deficiency Correction Modules for Existing POTWs
Design Deficiencies Matrix
Design deficiencies commonly found in POTWs are categorized in a
matrix format. The 14 categories used and the number of deficiencies
addressed in each category are listed below.
Number Category No. of Deficiencies
1.0 General Plant Design 884
2.0 Preliminary Treatment 226
3.0 Primary Treatment 82
4.0 Air Activated Sludge 392
5.0 Oxygen Activated Sludge 18
6.0 Trickling Filter 110
7.0 Disinfection 76
8.0 Anaerobic Digestion 134
9.0 . Aerobic Digestion 62
10.0 Sludge Dewatering 318
11.0 Lagoons 162
12.0 Land Application 574
13.0 Sludge Disposal 66
14.0 Sludge Reduction 156
Within each of the above categories the deficiencies are further
grouped according to type and then numerically referenced to unit operations
and components specific to the category. The deficiency groups used
include:
• Layout, arrangement, and placement of components in design of
plant
• Hydraulic design considerations
• Mechanical design considerations
. Electrical/instrumentation design considerations
• Safety considerations
. Environmental considerations
Design Consideration Modules for New POTWs
The design deficiencies listed in the matrix are discussed in "Design
Consideration Modules," in terms of items that should be reviewed by the
engineer during design of a new or expansion of an existing wastewater
treatment plant. Features of the module format are as follows:
745
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. The report section, deficiency matrix category, and applicable unit
operation or component are indicated in the upper left-hand corner.
This information allows the reader to cross-reference the deficiency
matrix with the design consideration modules.
. A treatment plant block flow diagram is presented in the upper right-
hand corner. The deficiency category represented by the module is
shaded to allow the reader to visually identify the portion of the
plant discussed.
. The design deficiencies, including reference number and description,
listed in the matrix are presented in a column on the left side of
the page and the associated design consideration discussed in a
column opposite the deficiency.
. The module page number also identifies the deficiency category dis-
cussed. The first, second, and third digit of the page number rep-
resent the deficiency category, unit operation/component, and actual
page sequence, respectively.
Design Deficiency Correction Modules for Existing POTWs
Suggested methods to correct the design deficiencies presented in the
matrix, when already present at an existing wastewater treatment facility,
are described in "Design Deficiency Correction Modules." The format of these
modules is the same as the "Design Consideration Modules." In addition,
where applicable, the correction procedure includes required relevant
information such as methods, materials, cost, and a sketch.
The manual is used by locating the design deficiencies in the matrix
organized by category and deficiency group, then by referring to the
appropriate design consideration modules for new plants, or to the design
deficiency correction module for existing plants.
The manual includes 3,260 identified deficiencies with correction
modules and design consideration modules for each. The manual will be
published by USEPA in mid-1980 and distributed to all consulting engineers
and state and federal review authorities.
It is anticipated that the use of this document will have a significant
impact in reducing the occurrence of design deficiencies in new plant
construction. Its impact in correcting deficiencies in existing plants
will depend on increased incentives for improved operation through more
aggressive state and EPA enforcement activities.
Development of Design Guidelines
Because of USEPA's role as a regulatory agency, it has been concerned
with the establishment of standards for, and regulation of pollutant
discharges to the environment rather than being actively involved in
specifying, controlling, or significantly impacting the design of
746
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facilities for meeting necessary levels of control. Design practice,
and changes in design practice, have been left to professional societies
such as the American Society of Professional Engineers, the Water Pollution
Control Federation, the Ten State Standards Committee, Consulting Engineers
Council, and the Boards of Health of the various states, and other scientific
and professional groups.
This role has changed somewhat in recent years for municipal treatment
plants due to the large increase in federal funding of these facilities,
the overall increase in both capital and operating costs, and the recognition
of the impact of deficient designs and inappropriate design criteria on
these costs.
In an attempt to improve current design practice without being
prescriptive, EPA's Office of Water Program Operations and Office of
Research and Development have initiated a new series of design information
and guideline documents (DIGS) to be prepared by EPA in concert with
leading consultants and experts in the field. These information and
guideline documents will be based on the latest results from EPA sponsored
and other full scale research studies, full scale performance data and
other state-of-the-art technical information and will provide in a condensed
format, a synopsis of both the methods and scientific basis for the
rational design of municipal treatment works unit processes, systems,
and system components. Improved guidance and design information will be
disseminated for both conventional and-newer technologies through the
publication of four to six documents per year for the next five
years. The documents will undergo an intensive two-step peer review
process to insure the highest possible technical quality before final
publication. The overall development of the information and guideline
documents is under the direction of an executive committee including
membership from EPA, ASCE, and WPCF. The first five documents, to be
finished in 1981, are for the subjects of: (a) hydraulic peaking; (b) ro-
tating biological contactor design; (c) land application; (d) effects of
sidestreams on biological treatment plants; and (e) aeration devices.
Improving the Reliability of Municipal Treatment Facilities
USEPA research activities for improving the reliability of municipal
wastewater treatment plants were initiated in January 1978, and are
scheduled for completion in 1981.
The program evolved because: (a) current USEPA reliability guidelines
for municipal treatment plants were outdated; (b) the complexity of new
secondary treatment facilities had sharply increased; (c) a much greater
choice of mechanical components and unit process variations was being
incorporated into new designs; and (d) USEPA has become increasingly
concerned about the effect of toxic materials on biological processes
and the ability of these processes to remove these materials.
747
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The approach chosen to investigate overall plant reliability was to
classify the nearly 120 separate unit processes or operations currently
used for treatment into the three categories of: (1) biological
treatment, (2) physical and chemical processes, and (3) mechanical
components. The next step was to investigate each of these classifications
in detail to form the necessary data base for conducting a systems reliability
analysis. The ultimate goal is to describe the least costly system
design configuration for achieving a given effluent quality reliability.
Biological Stability/Reliability
Research studies to define the stability and reliability of both
activated sludge and trickling filter plants were conducted for USEPA's
Office of Research and Development by the University of California at
Davis, California. The results of these studies as described in draft
final reports and a paper submitted for publication in the WPCF Journal
are summarized below (8)(9)(10).
Effluent Standards
Before discussing stability and reliability relationships for
biological treatment plants, it is necessary to review the effluent
standards for secondary treatment that form the design criteria for 64%
of the new facilities that will be constructed in the U.S. between now
and the year 2000 (11). The effluent limitations for secondary
treatment defined by USEPA under PL 92-500 are as follows:
"The arithmetic means of the secondary treatment effluent BOD and
SS concentrations shall not exceed 30 mg/L in a period of 30
consecutive days, nor shall exceed 45 mg/L in a period of
7 consecutive days. In addition, the arithmetic means of the
concentrations of BOD and SS remaining in the effluent over any
30-day period shall not exceed 15 percent of the arithmetic mean of
the values in the influent (85 percent removal)."
It is important to note that this standard is based on an
arithmetic mean for BOD and SS concentrations and that the standards do
not recognize the natural variability of biological plant performance,
nor do they readily permit the use of probabilistic design methodologies.
Study Approach
The study approach was to analyze statistically the performance of
43 activated sludge plants and 11 trickling filter plants to examine the
variability of effluent quality and to examine the effects of influent
characteristics, operational factors, design criteria, and reactor
configurations on plant stability and reliability. Initial correlation
and regression analysis for the group of activated sludge plants showed
that consistent relationships between effluent concentrations, influent
loading, biological and operational variables did not exist for the
748
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group. Better correlation was found possible for single plants, particularly
for plants not performing properly (8).
The analysis of plant effluent variability for BOD and SS for both
the activated sludge and trickling filter plants clearly defined the
distribution of effluent values and led to the formulation and verification
of a potentially powerful probabilistic design model for both processes.
Only the study results pertaining to activated sludge will be summarized
in this paper.
Conclusions of Stability/Reliability Analysis
The following conclusions were reached based on a detailed study of
43 activated sludge plants ranging from 2,300 to 791,000 m3/d (0.6 to
209 mgd) (8).
Performance
1. Effluent concentrations of BOD and SS varied significantly
among the plants in this study. Mean effluent BOD values
ranged from 1.9 to 85.6 mg/L with a group average of 15.8 mg/L.
Mean values for effluent SS ranged from 2.5 to 80.1 mg/L with a
group average of 19.4 mg/L. On the average, the effluent SS
concentration and its variation is greater than the corresponding
effluent BOD values.
2. Solids separation facilities are presently a limiting factor in
the performance of activated sludge treatment systems.
3. Effluent concentration distributions are not symmetrical and
generally are skewed farther to the right than to the left of
the most frequent value.
4. A lognormal distribution was found to fit consistently the
observed effluent BOD and SS data best.
Reliabi1ity
5. A probabilistic approach to process design provides a theoretical
basis for the analysis of process reliability.
6. The Coefficient of Reliability (COR), defined on a probability
basis, can be used to relate mean constituent values to selected
discharge standards.
749
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7. A reliability model has been developed that can be used for
both the estimation of the mean value in design of a process or
for the prediction of effluent quality in a plant under operation.
Stability
8. "Standard deviation" is the most appropriate measure of stability.
9. Plants having a standard deviation of less than 10 mg/L for
both effluent BOD and SS may be considered as "stable" statistically;
plants with a standard deviation of greater than 10 mg/L may be
considered "unstable".
10. The mean effluent BOD for stable plants is usually less than 17
mg/L, the mean effluent SS values is less than 15 mg/L.
Effluent BOD and SS concentrations in stable plants rarely
exceed 60 mg/L.
11. Unstable plants have annual mean effluent BOD and SS values
greater than 16 mg/L and 10 mg/L, respectively. The maximum
daily BOD and SS concentrations of these plants are usually
much greater than stable plants and exceed 90 mg/L and 130
mg/L, respectively.
12. Process upsets occur more often due to high values of SS as
opposed to high values of BOD in the final effluent.
13. There is no relationship between the size of plant and stability.
14. Various activated sludge processes ranked in terms of decreasing
stability and reliability are as follows: (1) step-feed and
step aeration; (2) conventional; (3) complete-mix, and (4) contact-
stabilization.
Variability
15. Generally, no single variable can be used to characterize the
variability of effluent BOD and SS in all plants. Coefficients
of correlation between effluent concentration and other variables
are insignificant and vary in both magnitude and sign.
16. No significant time-related trends or cycles were found for
activated sludge effluent data.
17. The effect of the lag period between influent and effluent
variables is insignificant.
18. The combination of all available variables (input, environmental,
and operational) can only be used to explain between 13% and
61% of the effluent BOD and between 5% and 52% of the effluent
SS fluctuations (depending on the plant). The remaining variations
(due to inherent or human factors) could not be explained in
the study.
750
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19. Variables controlling plant performance vary from plant to
plant. In most cases, one or two variables can be used to
explain more than 90% of the total variability that was
accountable.
20. Among all variables, wastewater temperature was the most significant
in accounting for effluent variations. Other variables found
to be significant (minimum significance of 5%) depending on the
plant include time, flow, SVI, influent BOD, MCRT, MLSS, and
influent SS.
21. In many plants, the mean cell residence time (MCRT) was not
properly used for plant operation. Only a few plants were
operated in such a way that the MCRT was a useful operating
parameter.
Model Formulation
The reliability model developed during the study relates the mean
constituent value m/ (i.e., the design value), to a standard, Xs (as set
by USEPA), that must be achieved on a probability basis. The model will
be summarized here. The reader is referred to the original work for
details of the development (8)(9)(10)(12).
For log normal distribution of effluent BOD and SS values from
activated sludge plants, the following expression can be derived for the
Coefficient of Reliability (COR) (8).
r
COR = ™* = (Vx + 1)1/2 exp J -Zi.^tLn (V/ + I)]1/2 \ (1
Xs I J
where mx ' = mean constituent value (design value)
Xs = a fixed standard
Vx = coefficient of variation
~L\-<& - a number with the property that P(Z^ T-\-&) = 1 -°^
where Z is a normally distributed variable with mean
zero and variance P one. The value of Z]__,^ may be
obtained from standard normal variate tables.
Ln = natural logarithm
Design Procedures
The above equation can be used to design a wastewater treatment
process to meet an effluent quality equal to Xs a stated l-cx. percent
of the time when the coefficient of variation Vx for the particular
process is known. Analysis of effluent quality from the 43 activated
sludge facilities in this study resulted in the Coefficients of Variation
shown in Table 5.
751
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Table 5. Statistics of the Annual Effluent BOD & SS Concentration
Data for Different Process Types (8).
Process type
Conventional
Complete-mix
Step- Feed/ Aeration
Contact Stabilization
Extended Aeration
Kraus
Aerated Lagoon
All Plants
Conventional
Complete-Mix
Step- Feed/ Aeration
Con tact- Stabilization
Ex tended- Aeration
Kraus
Aerated Lagoon
All Plants
No. of
plants
Mean
X
S
X
Standard
deviation
X
5
X
Coef.
of
variation
X
S
X
BOD
18
5
13
1
1
1
1
13
12.80
16.82
10.81
38.38
11.11
21.02
30.35
15.76
6.85
6.67
7.68
32.08
—
—
—
13.13
9.51
13.21
8.28
28.17
5.31
9.85
11.61
11.28
7.99
6.51
7.56
20.92
—
—
—
10.19
0.69
0.77
0.68
Q.76.
0.37
0.11
0.38
0.70
0.25
0.13
0.25
0.11
—
—
—
0.23
SS
18
5
13
1
1
1
1
13
11.92
19.88
16.23
10.88
8.82
21.12
58.79
19.10
10.53
11.19
16.65
26.75
—
—
—
17.03
16.02
19.65
16.83
37.66
5.28
9.26
18.71
18.35
18.61
16.92
23.89
26.18
—
—
—
20.60
0.86
1.00
0.83
0.90
0.60
0.38
0.32
0.81
0.38
0.51
0.31
0.11
—
—
0.37
After selection of Xs and 1 o< , the COR for the process is cal-
culated according to Equation (1) and then the mean constituent value
(mx) necessary to meet the Xs standard is computed. The mean constituent
value is then used for kinetic modeling and other process design con-
siderations. A most significant advantage of using this approach is
being able to describe the coefficient of variations of different biological
processes, and by using the (COR) to design to meet probabilistic rather
than deterministic effluent standards.
During this model development, the stability of the activated sludge
process was studied. Examination of the descriptive statistics for the
43 facilities resulted in the conclusion that plants having a standard
deviation of less than 10 mg/L for both effluent BOD and SS were considered
stable. The mean constituent value (mx) for this case would be equal to
the standard deviation divided by the process coefficient of variation.
A related finding of this study as it applies to the relationship
between activated sludge plant design and effluent standard setting is
that deterministic standards should be based on the geometric mean rather
than the arithmetic mean for parameters that are lognormally distributed.
752
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Justification of this approach is predicated on the concept that the
distribution parameters (mean and standard deviations) are simply related
to the distribution function and more accurately describe the central
tendency of the data. Geometric mean data lends itself very well to
analysis of multiple time periods such as 7 and 30 day averages since the
mean and standard deviation of geometric mean values for any time period
are easily calculated.
Physical Process Reliability
As noted from the above study, physical process reliability is an
integral part of activated sludge plant design and has a significant
influence on the coefficient of variation. In particular, the variability
of SS is noted to be greater than the variability of BOD for activated
sludge plants and solids separation facilities (final clarifiers) were
noted to limit the performance of activated sludge plants. Because of
the large potential for improved secondary clarifiers to increase overall
activated sludge treatment efficiency, EPA's Plant Operation and Design
Research Program has initiated several studies examining the hydraulic
performance of secondary clarifiers as the first in a series of studies
of the reliability and performance of physical and chemical processes.
One of the major differences in the design of secondary clarifiers
and other process design decisions that affect overall plant performance
is that the geometry of both rectangular and circular clarifiers are
prescribed, to a large extent, by the standard designs of equipment
manufacturers. Most secondary clarifiers are sized based on gross hydraulic
loading in terms of average and peak overflow rates and little consideration
is given to differences in settleability of mixed liquor as it affects
the shape and size of stilling basin design, flow distribution within
the clarifier, development of surface area of the clarifier, or the
effects of sludge blanket height and rates of sludge withdrawal.
The initial physical process reliability study was conducted by
Crosby, Young, and Associates under contract to USEPA (13). This project
included the study of eight full-scale clarifiers where performance
problems were thought to exist. The overall approach was to monitor
clarifier baseline performance, conduct dye tracer studies to identify
hydraulic characteristics, modify clarifier inlet baffling or stilling
basin design, and to document the changes in performance due to the
modifications. The location and physical characteristics of the clarifiers
studied are shown in Table 6. Both rectangular and circular final clarifiers
from both air and oxygen activated sludge plants were included in this
study.
753
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Table 6. Clarifler Locations and Physical Characteristics
Location
Albuquerque, NM
Dallas, TX - Ten
Mile Creel;
Regional Haste
Treatment Plant
Holly H111, FL
Morganton, NC
Oakland, CA -
East Bay Municipal
Utility District
Main Plant
Process Hater
Orange County, FL
Sand Lake Waste-
water Treatment
Plant
Stamford, CT
Process Design
Type (nP/d x 10^)
Air Activated 148.00
Sludge
A1r Activated 25.50
Sludge
Mechanical 4.54
Activated Sludge
Pure Oj 30.30
Activated Sludge
Pure 0? 636.00
Activated Sludge
Air Activated 3.78
Sludge
Air Activated 114.00
Sludge
Mechanical 75.70
Activated Sludge
Design Surface Sludge
Clarifler Dimensions Depth Overfloj Rate Renoval
Type (m) (m) (mW/d) Mechanism
CFPO 41
CFPO 32
R 20
4.9
CFPO 24
PFPO 43
CFPO 14
R 63
23
CFPO 40
(dlam) 4.0 27.8
(diam) 3.7 32.1
(L) 2.7 23.5
(W)
(diam) 4.9 32.6
(dlam) 4.3 26.5
(diam) 3.0 25.6
(L) 4.0 19.7
M
(dlam) 4.0 30.6
. — . — .
Siphon
Siphon
Chain I
Flight
Siphon
Siphon
Siphon
Traveling
Bridge
Siphon
Siphon
CFPO - center feed, peripheral overflow
PFPO - peripheral feed, peripheral overflow
R - rectangular
The analytical approach to evaluate each clarifier was to continuously
inject Rhodamine dye into a clarifier inlet stream and to monitor the
dye concentrations at 25 predetermined points in the clarifier at 30-
minute intervals for a period of 1 1/2 to 2 hours. Suspended solids
were also measured at the 25 sampling points to permit correlation with
dye concentrations. Dye dispersion and solids wave tests were also
conducted to indicate directional preferences in the clarifier and to
determine the effect of sludge removal mechanisms on clarifier hydraulics.
Typical flow patterns for one such test are shown in Figure 2.
Figure 2.
Typical Results of Flow Pattern Test Showing Dye
Concentrations in a Longitudinal Section of Clarifier
After 15 Minutes of Continuous Dye Release
(Note: Vertical Scale Exaggerated)
754
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The contours of equal dye and suspended solids concentrations plotted
on a scaled section of the clarifier graphically illustrate the flow
patterns that exist. Principle findings of this phase of the study are
summarized below.
Inlet and Outlet Design:
1. For circular clarifiers, the typical solid skirt baffles induce
a back eddy region that prevents good vertical distribution of
incoming mixed 1iquor.
2. Effluent weir leveling is critical to good horizontal
of flow. Weir level variations of +_ 3.0 mm (0.12 in
result in flow direction preference of + 20%.
di stribution
) can
3. Effluent weir placement at
is not optimum. This resu
patterns are directed radia
clarifier above the sludge
at the peripheral wall. The
weir is located is then the
and, therefore, the region
phenomenon is clearly shown
Figure 3.
the periphery of circular clarifiers
ts from the fact that typical flow
ly outward along the bottom of the
blanket and then turn strongly upward
peripheral wall where the effluent
location of greatest upward flow
of highest solids levels. This
in the radial cross-section of
Figure 3.
Distribution
Stamford
of TSS in a Radial Cross-Section of
s
arifier #'
The Effects of Localized
Upflow are Apparent
(Note: Vertical Scale Exaggerated)
our
755
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Note the high total suspended solids ranging from 78 to 97 mg/L in
the immediate vicinity of the effluent weir. It is also obvious that a
large center portion of the clarifier surface is not effectively used
even though average overflow for the entire surface area is the common
design standard for final clarifiers in the U.S.
Effect of Sludge Withdrawal:
For circular clarifiers, settling performance is adversely affected
by high rotational speeds of sludge removal mechanisms. In one
clarifier, an increase in effluent suspended solids from 25 to 75
mg/L was noted at the effluent weir after passage of the sludge
collection mechanism. Excellent correlation was found between
these solid waves and sludge collector movement. The solid wave
was found to follow the sludge collector by about 90°. At Morganton,
North Carolina, reducing the sludge collector speed by 56% reduced
total effluent suspended solids from 36.6 to 25.5 mg/L.
Subordinate Flow Influences:
In addition to the above, four additional factors (wind, temperature,
seiche, and speed of hydraulic response) were studied. These results
are summarized below.
1. Maximum changes in inlet and outlet temperature was 0.06°C and
was determined to have no significant influence on clarifier
performance.
2. The effect of wind speeds was evaluated for rectangular clarifiers
varying between 2-4 meters (7-14 ft) deep by 10-50 meters (33-
164 ft) long. The wind speeds necessary to cause a water surface
elevation difference of 2 mm (0.08 in.) was 113 km/h (70 mph)
for a 10 meter (33 ft) basin, 37 km/h (23 mph) for a 30 meter
(98 ft) basin, and 23 km/h (14 mph) for a 50 meter (164 ft)
long basin. For typical V-notch weirs, a 3 mm (0.12 in.) water
surface elevation difference would cause a 20% difference in
flow. The conclusions drawn from this analysis is that wind
speed, although not readily observable, can exert a significant
influence on clarifier performance by creating a directional
imbalance.
3. Surface seiche periods for rectangular clarifiers were calculated
to range from 3.2 seconds for a 4 meter (13 ft) deep by 10
meter (33 ft) long clarifier to 25.0 seconds for a 2 meter (7
ft) deep by 50 meter (164 ft) long clarifier. Final clarifiers
were noted to have two free surfaces, the visible water surface
and the sludge blanket surface. The oscillation period for
sludge blankets was judged to be double the time period shown
for the visible surface oscillation. Because of the wide variations
in tank size and geometry, frequency and amplitude of clarifier
seiches, quantitative determination of their overall effect on
756
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clarifier performance could not be made.
4. Hydraulic response speed for clarifiers was found to follow the
small amplitude wave speed. For a 3.0 meter (10 ft) deep clarifier,
the wave speed was calculated to be 5.5 meters/second (18 fps).
A rapid change in influent flow rate will be reflected at the
effluent weir in a matter of seconds for most clarifier sizes,
thus indicating the importance of reducing influent pumping
peaks.
Solids Transport Model:
• By considering horizontal flows in clarifiers to be turbulent,
and by using some simplifying assumptions including uniform
eddy viscosity and particle settling velocity, a diffusion
model was formulated to describe solids transport within the
clarifier resulting from amplitude variations in plant flow.
The model proposed is shown below.
(2)
= solids transport relative to that expected at
steady flow
T = total period of measured values
u = spatial average instantaneous forward velocity at
same cross-section (mid-radius of circular clarifier'
v = time average of u values
In one demonstration at Holly Hill, Florida, the installation of
new reaction baffles and a 3.8 m^ (1,000 gal) storage upstream of the
final clarifier reduced effluent suspended solids from 20.7 to 15.5 mg/L
in one case and from 17.2 to 11.5 mg/L in another. The limited data
collected indicated hydraulic turbulence is created rapidly by influent
hydraulic peaks, but die-off time is much longer, on the order of basin
detention time, thus significantly increasing the time of additional
solids transport.
Because of the encouraging initial results, a major follow-on study
is planned to further develop and verify the solids transport model. It
is anticipated that the results of this investigation of final clarifier
performance, along with the follow-on studies, will lead to improved
design procedures used by consulting engineers as well as improved standard
designs by major equipment suppliers. The demonstrated success in
modifying existing clarifiers to improve suspended solids removal
during this study at Morganton, North Carolina and Holly Hill, Florida
757
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have proven to be very cost effective compared to alternative upgrading
methods. The overall study has also indicated the importance of weir
leveling, minimizing plant influent pumping peaks, even flow distribution
between parallel clarifiers, and maintenance of appropriate rotational
speeds of sludge collectors.
Mechanical Components Reliability
Another major effort in EPA's Plant Operation and Design Research
Program is development of a new data base on the reliability of major
mechanical components. Preliminary results of a study conducted by
Southwest Research Institute is summarized below (14).
The primary objective of this project is to quantify the in-
service reliability of a broad classification of generic types of
critical mechanical components found in conventional secondary wastewater
treatment plants. The reliability statistics investigated include
mean time between failure (MTBF), mean time to repair (MTTR), and
availability as a percent of scheduled operating time. Conventional
secondary wastewater treatment processes included in the study are
air activated sludge, oxygen activated sludge, trickling filter, and
rotating biological contactor treatment systems. The investigative
approach taken in this study was to:
1. Select the broad classifications/generic types of critical
mechanical components which, upon failure, would have significant
adverse impact on effluent quality
2. Identify a representative number of treatment plants within
the United States which have good maintenance records for
the generic types of equipment of interest
3. Visit selected plants to collect data and statistically
analyze and evaluate the results.
The broad classification of equipment selected for this first
phase study effort includes:
1. Pumps 6. Valves
2. Power transmissions 7. Controls
3. Motors 8. Pressure vessels
4. Compressors 9. Conveyors
5. Diffusers
758
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The above classification of equipment was based on a criticality
analysis of the processes to be included in the study. The analysis
included components of the four secondary treatment processes previously
listed.
Treatment plants were then contacted to determine the availability
of the data included. Nine plants having the records necessary were
visited and the available data were collected. The data was then keypunched
and the reliability statistics calculated by computer-aided analysis.
Mean time between failure (MTBF) data for power transmissions and
motors are presented in Tables 7 through 13. These data were obtained
from the computer printout.
Table 7. Mean Time Between Failures (MTBF) by Application
Broad Classification Power Transmission
_App1ication
Raw Uastewater Pumnino
Intermediate Uastewater Punpino
Clarifier. Circular Center Drivc-
Clarifier, Souare/Rectannular
Center Drive
Return Activated Sludoe
Oxygen Generation/Storage
Dissolved Air Production
Rotating Biological Contactors
Mechanical Aerators
Total
(1)
No. of
Units
6
7
65
35
27
5
6
56
42
(2)
Ho. of
Failures
10
0
240
17
0
0
2
0
12
(3)
Oneratinci llrs
(xlO6)
0.20060
0.13077
3.86276
3.85670
0.48780
0.06309
0.47090
1.2550
0.7762
(4)
Overajl
(6)
(5) I") (7)
. - , Min. MTBF Max. MTBF Overall90%CL
J_xJ_0°_)_|[rs_ 1*10^1 Hrs (xlO6) Mrs (xlCTj
0.01884
0.18861
0.016045
0.080438
0.70370
09389
17630
8670
249
311
11.10382
0.06136
0.03562
0.007841
0.026890
0.009929
0.5919
0.1678
0.09101
0.003816 2.5120
0.34950 0.3764
0.04735
0.016045
0.06091
1.8670
0.01303
0.05679
0.013885
0.067602
0.21180
0.02740
0.08847
0.54490
0.04365
0.03317
759
-------
Table 8. Mean Time Between Failures (MTBF) by Size Range
Broad Classification - Power Transmission
Size
(Horsepower)
0-1
1-5
6-25
26-100
101-500
Over 500
(1)
No. of
Units
76
19
61
36
45
12
(2)
No. of
Failures
243
43
1
12
10
2
(3)
Operating Hrs
(xlO6)
6.18386
0.4806
2.3100
0.7426
0.83474
0.55206
(4)
Overall MTBF
(xlO6) Hrs
0.02537
0.01101
1.37640
0.05862
0.07838
0.20645
Min. MTBF
(xlO6) Hrs
0.009929
0.009816
0.63160
0.03476
0.007841
0.02689
(6)
Max. MT6F
(xlO6 Hrs
2.5120
0.01785
1.8670
0.06091
0.3764
0.1763
(7)
Overall 90%
(xlO6)
O CD O O O O
.0234087
.009119
.59387
.0417P
.054204
.10373
CL
Total
249
311
11.10386
0.03562
0.01101
1.3764
0.03317
Table 9. Mean Time Between Failures (MTBF) by Generic Group
Broad Classification - Power Transmission
Generic Group
Concentric Reducer
Parallel Shaft
Right-angle Shaft
Vertical Shaft
Variable Speed Orive Hydraulic
Variable Speed Drive Others
Gear Box
Chain Drive
Belt Drive
(1)
No. of
Units
18
73
51
51
13
4
32
4
3
(?)
No. of
Failures
2
2
180
44
0
8
65
5
5
U)
Operating Hrs.
(xlOS)
0.32806
1.9017
3.5208
1.4049
0.2349
0.08603
3.0108
0.1012
0.5160
(4)
Overall MTBF
(xlO6) Hrs
0.12268
0.71091
0.019479
0.031394
0.3495
0.009839
0.04578
0.1785
0.09132
(5)
M in. MTBF
(xlO6) Hrs
0.02814
0.09389
0.009929
0.01925
0.007841
0.009816
(6)
Max. MTBF
(xlO6) Hrs
0.3764
1.8670
2.5120
0.06091
0.02689
0.6313
(7)
Overall 90? CL
(xlO5)
0.06164
0.35881
0.01650
0.022783
0.1020
0.00662
0.03932
0.01910
0.05578
Total
249
311
11 .10439
0.03562
0.009839
0.71091
0.03317
760
-------
Table 10. Mean Time Between Failures (MTBF) by Application
Broad Classification - Motors
Generic Group - Multiphase
Application
Raw Wastewater Pumping
Intermediate Uastewater Pumping
Screen ing/Conimunition
Clarifier, Circular Center Drive
Clarifier, Square/Rectangular
Peripheral
Return Activated Sludge Handling
Recirculation Pumping
Oxygen Generation/Storage
Dissolved Air Production
Dissolved Air/O? Application
Rotating Biological Contactor
Mechanical Aerators
Secondary Sludge Pumping
Total
(1)
No. of
Units
25
14
3
62
28
27
14
5
11
2
56
24
14
(2)
No. of
Failures
26
2
0
20
0
48
6
0
22
2
56
0
1
(3)
Operating Mrs.
(xlO6)
0.5997
1.0500
1.2160
2.5530
3.1224
1.0227
0.3541
0.0564
0.5255
0.0361
1.2550
0.4510
0.2529
(4)
Overall MTCF
(xlO6) Mrs
0.02249
0.3931
1.8100
0.1236
4.4935
0.02102
0.0531
0.08392
0.02319
0.01353
0.02215
0.6711
0.1513
(5)
Min. MTBF
(xlO6) Mrs
0.00983
0.0422
0.5650
_
0.01858
0
_
0.0216
(6)
Max. MTBF
(xlO6) Hrs
0.02795
1.3340
2.5120
_
0.02282
0
_
0.3226
(7)
Overall 907. CL
(xlO6)
0.01772
0.1973
0.5283
0.09442
1.3560
0.01759
0.03362
0.02449
0.01792
0.006789
0.01876
0.1959
0.0650
285
183
12.4948
0.0680
0.02102
4.4935
0.0620
Table 11. Mean Time Between Failures (MTBF) by Size
Broad Classification - Motors
Generic Group - Multiphase
(i)
Size Ho. of
(Horsepower) Units
0-1
1-5
6-25
26-100
101-500
Over 500
Total
70
15
64
60
52
24
285
(2)
No. of
Failures
20
0
56
59
18
30
183
(3) (4) (5) (6)
Operating Hrs. Overall MTBF Min. MTBF Max. MTBF
(xlO6) (xlO6) Hrs (xlO6) Hrs (xlO6) Hrs
4.2410
0.3794
3.5260
2.702
0.9590
0.6870
12.4947
0.2147
0.5646
0.0621
0.0460
0.0540
0.0231
0.0680
0.1236
0.0222
0.0210
0.0135
0.00983
0.0231
2.512
1.810
1.334
0.3226
0.09831
0.5646
(7)
Overall 90% CL
(xlO6)
0.1349
0.1648
0.0527
0.0347
0.0332
0.0157
0.0299
761
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Table 12. Mean Time Between Failures (MTBF) by Size
Broad Classification - Motors
Generic Group - Variable Speed AC
(1) (2) (3) (4) (5) (6) (7)
Size No. of No. of Operating Mrs. Overall MTBF Min. MTBF Max. MTBF Overall 90% CL
(Horsepower) Units Failures (xlO6) (xlO6) Mrs ixlO^Hrs. (xlO6) Hrs (xlO6)
101-500
Over 500
Total
15
2
17
0
2
2
0.27)00
0.03614
0.30714
0.40330
0.01351
0.11482
0.01081
0.01351
0.01081
0.4033
0.11770
0.00682
0.05795
Table 13. Mean Time Between Failures (MTBF) by Application
Broad Classification - Motors
Generic Group - Variable Speed AC
Application
Intermediate Wastewater Pumping
Return Activated Sludge Handling
Total
(4) (5) (6) . (7)
No. of Ho. of Operating Hrs. Overall MTBF Min. MTBF Max. MTBF Overall 90% CL
Units Failure 6 (xlp6) (xlp6) (x1Q6) (xlO6)
(1)
to.
Unvts
1
16
17
(2)
o. o
Failures
(3)
ting
(xlO6
0.01807
0.28907
0.30714
0.0181
0.1729
0.11482
0.01081
0.01081
0.4033
0.1729
0.00465
0.07432
0.05800
762
-------
Tables 7 through 13 present MTBF values by application, size range,
and generic group for the broad classifications of power transmission and
motors. The MTBF values are shown in column four/and columns one through
three indicate the quantity of data utilized to calculate the MTBF values.
Columns five and six show the minimum and maximum MTBF values calculated
for the given application, size range, and generic group. These values
define the dispersion across the application, size range, or generic group.
The last column lists the 90% confidence level MTBF value. There is a 90%
chance that the true MTBF value is at least equal to the value shown in the
last column. Other statistics have been calculated but are not included in
these tables. These include mean time to repair, availability, corrective
and preventative maintenance hours/unit/year.
The component MTBF values developed during this study have been com-
pared with other reliability data sources. They appear to be in the same
order of magnitude. This would indicate that they are reasonable estimates
of the true MTBF.
These data will provide valuable information to design engineers and
plant operations personnel. Of greater significance, however, is that the
performance of generic equipment now can be predicted for a given application,
size range, and unit operation. Proper equipment selection for a given
application can also be enhanced. Operations personnel can benefit in that
preventative maintenance efforts can be more efficiently managed.
Systems Reliability Analysis
The four year goal of USEPA reliability research program is to integrate
the findings of the previously described research efforts in biological
process stability/reliability and physical process and mechanical component
reliability into a comprehensive reliability design methodology. The design
methodology will permit trade-off analysis of total treatment works costs
vs. various levels of effluent or unit process reliability. Results will
be used to establish new reliability guidelines to indicate desired equipment
redundancy and to identify critical spare part inventories for treatment
plants. Development of the reliability model will begin in 1981, and is
scheduled for completion in late 1982.
It is expected that use of the systems approach to reliability analysis
will reduce conservative design features of certain municipal treatment
plant components that are not critical in consistently meeting effluent
discharge standards.
Plant Operation and Management
Both local governments who bear the cost of municipal treatment plant
operations in the U.S. and state and USEPA who share the responsibility for
enforcement of effluent standards are concerned with the rising labor and
energy costs of municipal plant operation and management.
USEPA programs, in the past, have addressed the cost of operation as a
part of the cost effectiveness analysis required in the Construction Grants
Program, but have not aggressively dealt with improving plant operation and
763
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management until passage of the Clean Water Act of 1977. Operations and
management concerns have become more acute recently because of the increasing
labor and energy costs, increased federal enforcement activities, and the
trends toward decentralized treatment by an increasing number of smaller
facilities. The Office of Research and Development has undertaken a number
of studies designed to improve the management and lower the cost of operation
at municipal treatment facilities. These efforts include: (1) development
of a national computerized operation, maintenance, and management data base
to collect, store, and analyze O&M costs of municipal treatment facilities
throughout the U.S.; (2) development of a circuit rider operation and main-
tenance cost model (CROM); and (3) the increased use of instrumentation and
automation to optimize plant operation and control. Each of these recent
activities is briefly described below.
Computerized Operation, Maintenance, and Management Data Base
The computerized data base was established to provide a centralized
source of biological wastewater treatment data related to design, cost,
operation, and performance of municipal treatment facilities and to allow
the extraction of data in an efficient reporting format which permits data
manipulation without major programming involvement. When fully functional,
the system will represent one of the most detailed and comprehensive sources
of engineering and performance data that will be capable of supplying the
information necessary for analyses and decision making and will facilitiate
the capability of the research program to respond to federal, state, and
local agency requests for information and assistance.
In order to optimize computer data storage utilization and the process
of information extraction, the Wastewater Treatment Processes Information Sys-
tem, as the computerized data base is formally termed, was designed and
cTeve loped in four subsystems.
1. Data Management Subsystem
All data are entered through the Data Management Subsystem. It
permits data to be added to and changed within the data Master
File and to be checked for proper value limits and coding. Several
functions are included to optimize use of storage space and to
allow maximum efficiency in data retrieval.
2. Data Extract Subsystem
The Data Extract Subsystem consists of COBOL programs to extract
the desired data from the master file. The individual data
elements extracted are stored in an Extract File. The outputs
from this subsystem are used by the report generation and
statistical analysis subsystems.
3. General Reporting Subsystem
An easily programmable Mark IV report generator comprises this
subsystem. Through Mark IV, a programming language that requires
a low level of programming effort, a variety of reports can be
generated using the data elements in the Extract File. Data
presented through the subsystem may be organized in detailed or
summarized format using some calculations.
764
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4.
Analysis Subsystem
Statistical ^
This subsystem performs statistical analyses not capable on Mark
IV and includes plotting capabilities on a drum plotter.
in
The relationships of these subsystems are shown on the system flow chart
Figure 4.
Inputs to Computerized Data Base
Data inputs to the computerized data base originate in various forms
from rough operating logs to centralized computerized data systems. The
data are of varying levels of quality ranging from precise research data to
self monitoring data generated by municipalities. To identify the quality
level, one of three quality factor notations is assigned to each data element
when it is entered into the Master File.
Figure 4. System Flow Chart for "Wastewater Treatment Processes
Information System"
765
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The data Include design parameters, state/county and permit information,
operation costs, current physical conditions, physical plant details, cause
and effect and operational factors data, sludge handling and disposal data,
and relevant performance information.
The following general data sources have been identified and input to
the system during the first year of operation:
1. Summary research reports containing more than 120,000 data elements
summarized from other reports, plant operation and performance
log sheets, unpublished research data, etc. The reports include
performance, monitoring data collected at various time intervals
such as hourly, daily, monthly, and/or annually; operational
data, O&M cost data, poor plant performance cause and effect
data, etc.
2. Research reports on individual plants containing 15,000 general
and parameter data elements with a major emphasis on overall
plant performance. Operation and performance of individual unit
processes may be addressed but usually not in depth.
3. Research reports on 75 facilities with comprehensive data on
individual unit processes. These may include a complete evaluation
of only one unit such as an aerator, clarifier, etc., or they may
include several units. These data elements number about 25,000.
4. Research reports on single parameters such as phosphorus where
data is collected on several unit processes both before and after
using various biological and chemical means of removing phosphorus.
This data will normally be collected for several monitoring points
at various time intervals.
5. EPA regional permit and compliance reports on individual plant
performance and regional surveillance and analysis reports.
6. EPA Needs Survey which represents 130,000 general and parameter
data elements from 10,000 municipal facilities. These data are
currently being entered into the data base.
7. EPA Form 7500-5 which includes a range of general and parameter
data of low detail on the operation and maintenance of individual
wastewater treatment plants.
8. National Survey results for all site visits and preliminary evalu-
ations containing general and parameter data in great detail.
Output Reports
From the data in computerized storage, a large variety of information
can be extracted, coordinated, and analyzed in a wide variety of calculations,
plots, and reports. Typical programs that have been developed are summarized
below.
766
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1. Search the entered data bases and present summary information and
statistical calculations of summary information for the various
biological treatment plants or a unit process modification as a
function of detailed design, operational, loading or performance
factors, size, age, location, or performance.
2. Provide a complete breakdown of all influent and effluent con-
stituents and their concentrations for all plants or particular
types of plants.
3. Identify all monitoring points and the concentration of each
parameter for these points at various time intervals (if given
any one time value, the computer shall be required to calculate
other time values).
4. Calculate percent removals for all plants or particular types of
plants at various flow ranges, temperatures, time of the year, or
influent concentrations.
5. Present unit O&M costs as a function of plant size, location,
staffing, temperature, etc., for all biological plants and/or
modifications thereof.
6. Present overall plant and unit performance as a function of plant
size, location, hydraulic and organic loading, staffing, plant
operation, temperature, or design factors.
7. Present cause and effect of poor plant performance as a function
of plant size, location, hydraulic and organic loading, staffing,
plant operation, temperature, design factors, or available funds.
This data base contains detailed O&M cost and performance information
from over 300 facilities and less detailed information on 10,000 facilities
is now being entered into the program. The data base is expected to grow
by inclusion of detailed cost and performance information for 300-500 new
facilities per year. The program is being used by both research scientists
within EPA's research organization and by state and federal operating pro-
gram personnel.
Centralized Management of Small Satellite Facilities
In further efforts to study methods to improve overall performance at
current operating cost, or to lower overall costs while maintaining acceptable
effluent quality the concept of centralized management of satellite treatment
facilities is being investigated. On-going studies have included examination
of several modes of operation including independent operation of each plant,
circuit rider operation, telemetry operation, plant consolidation, as well
as various mixes of the above operational modes.
767
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A Circuit Rider Operation and Maintenance Model (CROM) has been developed
by EPA researchers based on the detailed O&M data from 14 small treatment
facilities in Houston, Texas with flows ranging from 6 to 3,800 m3/d
(0.0016 to 1.0 mgd). Mathematical cost functions were developed as a function
of actual plant flow. Separate costs for materials and labor are calculated
for operation, maintenance, administration, and circuit riding. The cost
for operation includes plant operation, sludge removal, and laboratory
recordkeeping. Maintenance costs include maintenance and repair. Administration
costs include supervision and management fees. Circuit rider costs include
labor and vehicle costs associated with transportation.
Use of the model includes varying any of the above input cost functions
to determine the effect on overall system costs. Future development and
expansion of the model will permit optimization of the various management
modes previously mentioned. Tables 14 and 15 list the input variables and
output parameters of the program. In a comparison of the estimated cost of
operation and management for 14 plants in Houston, the CROM predicted a
circuit rider management mode cost of $234,641 per year compared to an
actual cost of $243,737 per year. Refinements to the cost curves used in
the model are expected to improve the accuracy substantially.
Future simulation studies are planned in conjunction with management
modes that include use of remote sensing and telemetry from satellite
facilities to central control stations.
Another EPA sponsored study is currently underway in Cuyahoga County,
Ohio, to provide data on the cost and effectiveness of centralized management
of a system of small (package) treatment plants using low cost instrumentation,
electronics, and telecommunications equipment. The objectives are to evaluate
O&M management alternatives and to evaluate the application of micro-electronic
technology in reducing costs and optimizing the operation and maintenance
of package plants. The study is providing considerable data on the costs
and benefits of purchasing, installing, operating, and maintaining monitors
on wastewater treatment systems equipment.
The demonstration site is a 760 m-Vd (0.2 mgd) activated sludge package
plant operated by the Cuyahoga County Sanitary Engineering Department. The
monitoring equipment, including both field proven sensors and safety-security
sensors, is oriented toward a basic low-cost monitoring concept capable of
providing an alarm at a central site in order to detect impending plant
upset or mechanical breakdown. The system is to be optimized for centralized
management of small satellite plants that use circuit rider operators. The
monitoring system installed is shown in Table 16. It includes sensors and
alarms for monitoring equipment status, process operation, and security and
safety.
The heart of the monitoring system is the Programmable Logic Controller
(PLC) that serves as the interface between the sensors and the telephone
alarm transmitting system. The PLC scans through the 25 equipment, process,
and security sensors and responds to an alarm status according to a pre-set
program of relay-type logic. In alarm status, a telephone call is initiated
768
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Table 14. Input Variables to CROM
NCASE number of data cases to be executed by the program
NP number of plants in the circuit rider system
NDATA number of input data sets to be run for the circuit
rider system
ID alpha-numeric identification for the circuit rider
system
NAME plant name
Q actual plant flow, mgd
ODHR hourly labor rate for operations labor, S/hour
MDHR hourly labor rate for maintenance labor, S/hour
ADHP. .hourly labor rate for supervisory labor, S/hour
CRDKR hourly labor rate for circuit riding labor, S/hour
PCT indirect labor costs, percentage
WPI current wholesale price index for industrial commodities
(U.S. Oeparment of Commerce)
HPH average travel speed of circuit rider vehicles,
miles/hour
CHILE cost per mile of circuit rider operation, S/mile
CIR number of circuits or sub-circuits in the system
NSTOP number of stops on a circuit
MILES total length of a circuit, miles
DAYS frequency of a circuit, days/week
WEEKS duration of a circuit, weeks/year
HS(J) identification numbers of plants on a circuit
Table 15. Output Parameters from CROM
N
PLANT
Q
MYR
OMAT
OLAB
WHAT
MLAB
AMAT
ALAS
CRMAT
CRLAB
TCOST
plant identification number
plant name
actual plant flow, mgd
circuit rider miles of travel charaed to a plant,
miles/year
annual cost of operations material, S/year
annual labor cost of operations, S/year
annual cost of maintenance materials, S/year
annual labor cost of maintenance, S/year
annual cost of administration material, S/year
annual cost of supervision labor, S/year
annual cost of circuit rider material, S/year
annual labor cost of circuit rider labor, S/year
annual total cost of plant, S/year
769
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Table 16. Small Plant Monitoring System
^UNCTION
ES
ES
ES
ES
ES
ES
ES
ES
ES
ES
ES
PO
PO
ES,S/S
S/S
,
PO
SENSOR
Liquid Level
Power
Demand
Thermocouple
Air Pressure
Thermocouple
Power Demand
Level
Detectors
Thermocouple
Power
Demand
Thermocouple
Power
Demand
Dissolved
Oxygen
Residual
Chlorine
Chlorine Gas
Smoke/Fire
Turbidimeter
LOCATION
Lift Station
Wet Well
Lift Station
Pumps
Lift Station
Pumps
Blowers
Blower
Bearings
Blowers
Clarif iers
Return Sludge
Pumps
Return Sludge
Pumps
Sludge Scraoer
Drive
Sludge Scraper
Drive
Aeration
Tanks
Chi or i ne
Contact Tank
Equipment
Bui Idinq
Equipment
Bui Iding
Effluent
ALARM
Low Level
High Level
On-Off
High Temp.
Low Pressure
High Temp.
On-Off
High Sludge
Level
High Bearing
Temperature
On-Off
High Torque
On-Off
Low DO
High DO
High Level
High Level
On-Off
High Level
PROTECTION AGAINST
Loss of Pump Prime
Flooding
Power Outage
Loss of Lubrication
Leak in Air Headers
Loss of Lubrication
Power Outage
Washout of Sludge
Loss of Lubrication
Power Outage
Motor Overload
Power Outage
Shock Load Demand
Excessive Aeration
Excessive Usage
Gas Cylinder Leak
Fi re
Process Upset
ES Equipment Status
PO Process Operation
S/S Safety/Security
770
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to reach the circuit rider operator and a pilot light is set for the alarm
and recorded on the PLC readout unit. The telephone calling electronics
includes a pre-established hierarchy of telephone numbers that repeats in
sequence until an electronic acknowledgement signal, actuated by the call
receiver, is received by the unit.
The equipment is in place and, although rigorous data generation has
not yet begun, some interesting observations have been noted.
1. When chlorine cylinders are changed, an alarm and/or warning
condition exists in the cylinder storage area.
2. The chlorine feed unit malfunctioned, requiring a service call by
the manufacturer.
3. The bearing temperatures on the blowers ranged from 43°C (110°F)
to 49°C (120°F), well within the manufacturer's suggested maximum
operating temperature for the lubricant of 71°C (160°F).
4. One of the three final clarifiers is most heavily loaded, consistently
showing the highest sludge blanket level and sludge particle
washout, particularly during morning peak flows.
5. The plant has only limited flexibility for blower operation in
that at least two of the four blowers are required to run the air
lift sludge pumps; and in winter, three blowers must often be run
to prevent icing in the aerators.
6. A snow plow was stolen from the grounds.
REMAINING PROBLEMS AND FUTURE O&M INITIATIVES
From a national perspective, the record of compliance for municipal
treatment plants in the U.S. must be improved to meet the goals of the
Clean Water Act of 1977. EPA's Plant Operation and Design research program,
as well as research conducted elsewhere, has provided a solid technological
basis for improved municipal compliance. Inherent problems in achieving
significant plant performance improvements on a nationwide basis continue
to be more institutional and attitudinal than technological. The split in
responsibility between the designer and operator, together with the lack of
professional concern on the part of the designer for successful plant opera-
tion over the life of the facility, is the fundamental reason for poor
plant performance.
USEPA's efforts, which have been construction oriented, have lacked a
directed and effective O&M objective during the Construction Grants Step I,
II, and III processes. The scope and emphasis of a new strategy must include
the encouragement and support of the development and implementation of
rational design standards for conventional and alternative technologies;
the development of public and private expertise to plan, design, and review
O&M requirements for plant performance optimization; and the development of
771
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programs to assure optimum plant operation followed by decisive actions,
including enforcement, to assure implementation of the programs.
State and local agencies have not recognized nor accepted their respon-
sibilities for the correction of operational problems for assuring continuing
efficient plant operations. These agencies have not sought the assistance
of private sector expertise capable of providing operations technical assistance
nor have these agencies trained their own personnel in that area. Enforcement
activities have not provided the incentives to encourage the development of
private sector expertise in operational technical assistance.
The failure of both the public and private sectors of the pollution
control community to recognize their responsibilities and to be held accountable
for their decisions and actions significantly contribute to the continuing
problem.
The engineering design community and equipment manufacturers and suppliers
play key roles in the pollution control effort. Yet in providing their
services they are not held responsible for the decisions they make in the
design of facilities, for the reliability and operability of the facilities
and equipment they furnish, nor for the information they disseminate to
plant administrative and operations personnel. As a result, the local
community is put in the untenable position of spending a lot of money for a
treatment plant that may be poorly designed or is incapable of being operated
properly. There will be no improvement in the situation until consultants
and equipment suppliers are held responsible for their products, the decision
they make, and the actions they take.
The designer's responsibility must be extended to include a guarantee
of plant performance. The concept that successful plant operation is a
professional activity and responsibility must be encouraged.
Improved system design of conventional technology and cost effective
design of innovative and alternative processes must be encouraged. Deficiencies
in treatment plant design have been identified as one of the primary causes
of poor plant performance. Deficiencies are noted not only in the design
of individual unit processes but also on the relationship of units within a
system that hinders the reliability and stability of the system and prevents
the system from performing optimally. The design community has relied upon
existing and often irrational design criteria, ignoring comprehensive analysis
and performance and operational experience of existing municipal treatment
plants.
Existing programs to train operators and provide them the required
information to properly monitor, control, and operate their plants are
ineffective. Operators have not been able to transfer their classroom
instruction to practical on-site problem solving; they do not use much of
the guidance and instructional materials provided by federal programs because
they do not understand them, and they are provided with often-conflicting
information from a variety of sources that are not held accountable for the
instruction provided. There is a lack of programs that can improve plant
772
-------
operator on-the-job effectiveness including on-site training and site specific
instructional material for process operation and control.
Evaluations of facility plans and design do not adequately consider
the instrumentation and automation alternatives to process monitoring and
control nor the cost and performance advantages of centralized management
of POTWs where feasible as an alternative to construction of regional facilities.
There are no requirements for planners and engineers to evaluate alternative
strategies to achieve improvements in reliability, energy conservation,
operating cost, and efficiency for individual plants or groups of plants.
There is a need for a two-prong approach to insure optimum plant per-
formance through improved operation. First, existing plants being upgraded
must undergo a comprehensive O&M review through an improved construction
grant review process. Comprehensive plant evaluations should be required
for all plants requesting federal grant funding. For plants not needing
construction but not in compliance, mandatory O&M reviews should be required
as the first step in enforcement actions. Despite existing measures to
assist communities to plan for and implement sound O&M programs, there is
widespread failure on the part of the community to fulfill its responsibility.
The USEPA must provide, through rigorous enforcement actions, the incentive
for communities to bear the prime responsibility for fulfilling their obligations,
773
-------
REFERENCES
1. USEPA, National Municipal Policy and Strategy for Construction Grants,
NPDES Permits and Enforcement Under the Clean Water Act, Office of
Water Program Operations, Washington, D.C.20460, October 1979
2. USEPA, Clean Hater Report to Congress, Washington, D.C., 1974
3. USEPA Clean Water Report to Congress, Washington, D.C., 1975-1976
4. Comptroller General of the United States, Continuing Need for
Operation and Maintenance of Municipal Waste Treatment Plants,
Report to Congress, Washington, D.C., CED-77-46, April 1977
5. Hegg, B.A., Rakness, K.L., and Schultz, J.R., Evaluation of Operation
and Maintenance Factors Limiting Municipal Wastewater Treatment Plant
Performance, EPA 600/2-79-034, June 1979
6. Gray, A.C., Paul, P.E., Roberts, H.D., Evaluation of Operation and
Maintenance Factors Limiting Biological Wastewater Treatment Plant
Performance, EPA 600/2-79-078, July 1979
7. Ball, R. 0., Manual for Identification and Correction of Typical
Design Deficiencies at Municipal Wastewater Treatment Facilities,
EPA Contract No. 68-03-2775, December 1979
8. Niku, S., Schroeder, E.D., Tchobanoglous, G., and Samaniego, F.J.,
Performance of Biological Wastewater Treatment Plants Reliability,
Stability, and Viability, Civil Engineering Department, University
of California, Davis, California 95616, EPA -Grant No. R-805097-01,
June 1979
9. Hough, R., Niku, S., Schroeder, E.D., Tchobanoglous, G., Performance
of Biological Wastewater Treatment Plants Reliability, Stability, and
Variability of Trickling Filters, Civil Engineering Department,
University of California, Davis, California 95616, EPA Grant
No. R-805097-01, June 1979
10. Niku, S., Schroeder, E.D., and Samaniego, F.J., Performance of Activated
Sludge Processes and Reliability Based Design, University of California,
Davis, California, EPA Grant No. R-805097-01
11. USEPA, Cost Estimates for Construction of Publicly Owned Wastewater
Treatment Facilities, Office of Wacer Program Operations, Washington,
D.C.
774
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REFERENCES (Continued)
12.
13.
14.
15.
Benjamin, J.R., and Cornell, A.,
for Civil Engineers, McGraw-Hill
Probability, Statistics, and Decision
Book Company, 1970
Crosby, R.M., and Bender, J.H., Hydraulic Considerations that Affect
Secondary Clarifier Performance, EPA Technology Transfer, Center
for Environmental Research Information, Cincinnati, Ohio 45268,
March 1980
Shultz, D.W., Evaluation
of Conventiona
and Documentation of Mechanical Reliability
Plant Components, Phase I Draft Report,EPA Contract
No. 68-03-2712, November 1978
Cuyahoga County Centralized Management and Instrumentation, Monitoring
and Process Control Study, EPA Grant No. R-806333010, September 18,
1978
775
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STATUS OF DEEP SHAFT WASTEWATER
TREATMENT TECHNOLOGY IN NORTH AMERICA
Richard C. Brenner and John J. Convery
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268 USA
INTRODUCTION
Municipal pollution control technology is entering a period of rapid
change as a consequence of the Clean Water Act Amendments of 1977 (Public Law
95-217) (1) related to innovative and alternative technology. For qualifying
technology, these Amendments provide an increased level of Federal funding of
up to 85 percent of the capital costs and, if necessary, 100 percent of the
replacement costs as a warranty provision. These economic and risk assump-
tion incentives by the Federal government are intended to encourage increased
consideration of lower cost and more energy efficient municipal wastewater
treatment facilities and accelerate the rate at which such technologies are
developed and put into practice. A technology can qualify as innovative if
it offers, compared to the most cost effective conventional technology, the
potential to reduce life cycle costs by 15 percent or reduce net primary
energy requirements by 20 percent. These cost and energy effectiveness com-
parisons must be made on a site specific basis. Therefore, no technology,
per se, can be deemed innovative. Specific technologies have been deemed
alternative. A complete description of the criteria and methodology of
establishing whether a technology is innovative or alternative in a specific
application is included in the Innovative and Alternative Technology Assessment
Manual (2).
One of the emerging technologies that will be evaluated against innova-
tive criteria in the next few years is the Deep Shaft Process developed by
Imperial Chemical Industries Ltd. (ICI) in the United Kingdom and Europe and
refined and marketed in North America by its Canadian affiliate C-I-L Inc.
The process is marketed in Japan by ICI Japan.
Based on published information, this technology provides several potential
process improvements, compared to conventional activated sludge technology,
which may result in savings in treatment costs, energy requirements, and
space requirements. These potential economies are attributed to substan-
tially higher organic loading capacity, reduced detention time, more efficient
oxygen and power utilization through improved contacting, and reduced sludge
production and processing requirements.
777
-------
The purpose of this paper is to briefly review the development of Deep
Shaft technology, report on the initial results of a U.S. Environmental Pro-
tection Agency (EPA) demonstration evaluation project at Ithaca, New York,
and report on the status of the technology in North America.
HISTORICAL DEVELOPMENT
BACKGROUND
The ICI Deep Shaft Process originated from basic aerobic fermentation
technology developed by the Agricultural Division of ICI for the production
of single cell protein from methanol (2,3). This fermentation technology
utilizes a pressure cycle contactor in which air for biological oxidation
also provides the driving force for liquid circulation. Reportedly (4), the
fermenter is capable of achieving an oxygen transfer intensity of 10 kg 02/m3/
hr (0.62 Ib/ft3/hr) at a power economy of 1.5 kg 02/kWh (2.5 Ib/hp-hr). Oxygen
transfer efficiency at this intensity is over 50 percent. A schematic of the
ICI single cell protein fermenter and a description of British and Japanese
developmental efforts can be found in Reference 5.
Municipal wastewaters and even high strength industrial wastewaters do
not require such a high oxygen transfer intensity as that required for single
cell protein production because of lower concentrations of microorganisms and
substrate, less biodegradable substrate, and slower microorganism growth
rates in waste treatment applications. For these reasons, the fermenter
configuration was changed for waste treatment applications to provide much
longer bubble contact time by increasing the length of the reactor in the
form of a deep shaft to achieve higher oxygen transfer efficiency and power
economy. Another significant difference between wastewater treatment appli-
cations and fermenter applications is the cell mass management objective to
one of minimization rather than maximization.
PROCESS DESCRIPTION
A simplified schematic of the basic Deep Shaft reactor is shown in Figure 1.
Raw wastewater, after normal screening and degritting, is continuously dis-
charged into the downcomer together with the return sludge. Compressed air
is piped into both the downcomer and the riser to provide the oxygen required
for treatment as well as the driving mechanism to maintain circulation velocities
of 1-1.5 m/sec (3-5 ft/sec). The depth of the shaft is set so almost all of
the bubbles are dissolved at the bottom.
From the downcomer, aerated liquid passes into the riser section and
flows upward. As the hydrostatic pressure decreases, bubbles form removing
carbon dioxide, nitrogen, and unused oxygen from the liquid. A slightly
expanded section at the top of the shaft (head tank) serves as a gas dis-
engagement zone. Some of the mixed liquor overflows the head tank to a solids
separation process and the remainder of the mixed liquor is recirculated to
the downcomer. The details of the reactor design and mode of operation vary
depending on the choice of sedimentation or flotation for the final solids
separation function. These details are provided in subsequent portions of the
paper.
778
-------
INLET
AIR
SLUDGE RECYCLE
OUTLET
DOWNCOMER
RISER
SHAFT
CASING
FIGURE 1. ICI SHAFT CONFIGURATION AND HYDRAULICS
779
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FIRST PILOT FACILITY AT BILLINGHAM, ENGLAND
In mid-1974, evaluation of the ICI pilot facility was started at the
Billingham sewage works in Great Britain. A total of 363 m3/day (96,000 gpd)
of wastewater was treated in a Deep Shaft reactor 39 cm (15.25 in.) in inside
diameter (ID) and 130 m (426 ft) deep. The solids separation sequence in-
cluded natural flotation, mechanical degassing, and sedimentation. Flotation
was chosen to make use of the fine bubbles already present in the rising
liquid and to permit rapid return of sludge. Flotation also provides a thick-
ened float for subsequent dewatering. Degassing was provided to eliminate
the interference residual air bubbles would have on sedimantation.
The pilot unit, when evaluated on a domestic waste with influent 6005
and suspended solids concentrations of 195 and 210 mg/1, respectively, pro-
duced an effluent 6005 of 28 mg/1 and an effluent suspended solids of 36 mg/1
at a 1.3-hr nominal shaft detention time. The mixed liquor volatile suspended
solids (MLVSS) content was 3100 mg/1, and the F/M loading was 1.1 kg BOD5/day/
kg MLVSS. The effluent suspended solids concentration ranged from 18 to 55
mg/1 (6).
In September 1975, the solids separation sequence of the pilot plant
facility was modified to improve effluent quality and simplify operations.
This amounted to elimination of the natural flotation tank and the use of a
vacuum degasser prior to the sedimentation tank. The pilot plant at Billing-
ham is approximately represented in Figure 2. Figure 2 is actually a sche-
matic of the ICI Deep Shaft Process in the gravity clarification mode as it
is being evaluated at Ithaca.
The pilot unit at Billingham was evaluated in the gravity clarification
mode at constant and variable flows for almost a year (7). Constant flow
results showed average effluent values for 8005 of 15 mg/1 (range, 6-35) and
suspended solids of 18 mg/1 (7-39) at an F/M loading of 0.8 kg BODs/day/kg
MLVSS, a nominal shaft detention time of 70 minutes, and mixed liquor suspend-
ed solids (MLSS) of 4400 mg/1 (2000-6000). Variable flow results indicated
average effluent values for 6005 of 22 mg/1 (9-50) and suspended solids of
26 mg/1 (5-62) at approximately comparable operating conditions.
Sludge production was carefully monitored at Billingham under constant
flow conditions and with an average F/M loading of 1.26 kg BOD5/day/kg MLVSS.
A yield of 0.5 kg sludge/kg BOD5 converted was suggested as a reasonable
level to anticipate with typical raw wastewater characteristics and under
diurnal flow operation (7).
DEVELOPMENT IN NORTH AMERICA
In 1975, ICI extended process licenses to C-I-L Inc. in North America
and ICI Japan in Japan.
Eco-Research Ltd., a wholly-owned subsidiary of C-I-L Inc., is responsible
for Deep Shaft development in North America. Eco established a pilot plant
in Paris, Ontario, Canada, to optimize the ICI Deep Shaft flowsheet incorporating
flotation rather than sedimentation as the means of suspended solids separation.
780
-------
COMPRESSOR
RAW INFLUENT
HEAD
TANK
DEEP
SHAFT
SURGE
TANK
VACUUM
DEGASSER
..CI
DOWNCOMER
RETURN SLUDGE
'RISER
SEDIMENTATION TANK
CT
SCUM
WASTE SLUDGE
FIGURE 2. SCHEMATIC OF DEEP SHAFT SYSTEM USING GRAVITY CLARIFICATION
-------
Deep Shaft with gravity clarification was thought to be uneconomical in North
America. Deep Shaft aeration followed by flotation clarification offered the
potential to reduce the bioreactor volume and to make multiple use of compressed
air for biological treatment, circulation of mixed liquor through the shaft,
and flotation separation. Flotation allowed the bioreactor to be operated at
MLVSS concentrations in excess of 10,000 mg/1 without impacting suspended solids
separation using flotation. Flotation clarification yields a solids float con-
centration of 5-10 percent, which reduces return sludge volume and eliminates
the need for additional thickening prior to dewatering.
Results of the pilot plant studies at Paris on 454 m3/day (120,000 gpd)
of a combined domestic-industrial wastewater were reported by Sandford (7).
Influent average values for 6005 and suspended solids were 141 and 217 mg/1
(75-726), respectively. Ten mg/1 of liquid ferric chloride is added to the
raw wastewater at Paris for phosphorus removal. The shaft at Paris has an ID
of 39 cm (15.25 in.) and a depth of, 155 m (508 ft), providing a nominal deten-
tion time of 55 minutes. With an average MLSS of 6000 mg/1 (3000-16,000), the
F/M loading averaged 1.0 kg BODs/day/kg MLVSS (0.4-2.0). The flotation area
provided was 13.9 m^ (150 ft^). Because of the high surfactant load of 30 mg/1
average and 150 mg/1 peak from the industrial wastes, 10 mg/1 of polymer was
required to stabilize flotation clarification.
Effluent quality for the period of March-June 1977 averaged 24 mg/1 (7-96)
for BOD5, 15 mg/1 (1-56) for soluble BODs, and 29 mg/1 (10-121) for suspended
solids. Weekend operating results with a lower (30 percent COD) industrial
load were better with effluent 6005 values of 13 mg/1 (5-33) and suspended
solids values of 18 mg/1 (10-32).
Short-term operating results (1 month) at a flow of 681 m^/day (180,000 gpd)
and a nominal shaft detention time of 35 minutes produced effluent quality
values of 23 mg/1 for 6005 and 28 mg/1 for suspended solids. For a 2-week
period, the textile mill and associated surfactant contribution was eliminated.
Under these conditions, stable operation was achieved with a polymer dose of
3 mg/1.
Operating problems at Paris during June 1977 included power failures (8 hr)
and blockage in the surge tank feed system (16 hr). Development efforts through
the late 1970's were directed at eliminating the need for chemical flotation
aids and improving operational stability of flotation clarification.
IMPORTATION TO THE UNITED STATES
From 1975 to 1978, EPA scientists were aware of the Deep Shaft pilot
studies taking place at Billingham and Paris. Numerous meetings and consul-
tations took place with representatives of ICI, C-I-L Inc., and Eco-Research
Ltd. The primary topics of these meetings concerned the optimum time, place,
and mechanisms for defining the potential applicability of Deep Shaft technol-
ogy to United States (U.S.) municipal wastewater treatment practices. It was
mutually agreed that the process would have restricted market potential in the
States without an EPA sponsored evaluation project. Because of the desire of
the several firms to protect their collective and respective patent positions,
it was further agreed that no research and development (R&D) project using public
782
-------
funds should be initiated in the U.S. until such time as the technology was
developed to the point where it could justifiably be demonstrated at a meaning-
ful engineering scale.
After preliminary discussions with several municipalities, the City of
Ithaca, New York, was selected as an acceptable site for conducting a compre-
hensive evaluation. Effective September 21, 1978, an EPA demonstration grant
(No. S806801) was awarded to Ithaca to construct and operate a 757-m3/day
(0.2-mgd) Deep Shaft pilot demonstration plant on the grounds of its existing
wastewater treatment plant. The grant project is discussed in detail in a
subsequent section of this report.
RECENT TECHNOLOGICAL DEVELOPMENTS
BACKGROUND
Eco-Research Ltd. has conducted a continuing program of Deep Shaft
research and development since its parent firm, C-I-L Inc., acquired the
North American license to the technology in 1975. As indicated in the pre-
vious section, Eco's early efforts were devoted to evaluating the feasibility
of mating a Deep Shaft bioreactor with flotation clarification for liquid/solids
separation. The resulting flowsheet is referred to as Eco I.
Eco I utilizes the basic shaft configuration developed by ICI. In this
configuration, influent wastewater and return sludge are added to the head
tank surmounted on the shaft. Mixed liquor is drawn off from the side of the
head tank for subsequent clarification.
Once the feasibility of employing flotation for independent mainstream
clarification became evident, Eco turned its attention to modifying the design
and operation of the shaft to enhance its biological profile and improve its
compatibility with the revised mode of solids separation. Examination of
Figure 1 reveals that the upper section of the shaft downcomer is not aerated,
except for residual dissolved oxygen (DO) carrying over from the riser. The
combined mixture of influent wastewater and return sludge introduced at the
top of the downcomer in the ICI and Eco I configurations does not contact
virgin DO until it reaches the downcomer air injection point at approximately
the 40 percent depth level of the shaft. Consequently, as much as 15-20
percent of the total shaft circulation route may be anoxic, depending on
waste strength. It is apparent that the upper section of the downcomer leg is
not the most effective section of the shaft for satisfying the high initial
oxygen demand of the substrate.
A feature of the ICI and Eco I shaft operating modes that is counterpro-
ductive to efficient flotation is the withdrawal of mixed liquor at the surface.
As mixed liquor travels up the riser leg, it degases. By the time it reaches
the head tank, much of the carbon dioxide, nitrogen, and unused oxygen, which
were dissolved in the lower section of the shaft, has been stripped from
solution. The dissolved gas driving force for inducing flotation clarification
of mixed liquor solids is thereby considerably reduced.
783
-------
SHAFT MODIFICATIONS - ECO II
The above described characteristics of ICI and Eco I shaft geometry and
operation led to the development of a revised shaft configuration (Eco II)
with influent injection and mixed liquor takeoff both accomplished at depth.
As illustrated in Figure 3, Eco II utilizes a multi-channel design concept
featuring one primary downcomer (D]), one primary riser (R-|), one secondary
downcomer (02), and three secondary risers (one designated R2 and two desig-
nated D2R-]). The secondary downcomer and secondary risers are restricted
to the upper 35-50 percent of the shaft. The primary downcomer and primary
riser run the full depth of the shaft. In the lower section of the shaft,
the primary riser occupies the full annulus between the primary downcomer and
the outer casing. In the upper section in the area of the secondary downcomer
and secondary risers, the primary riser consists of two channels occupying
only a portion of the annulus.
Influent wastewater and return sludge are introduced to the shaft through
the D2 secondary downcomer. The D2 downcomer is turned up at its lowest
point, forcing the influent-return sludge mixture back up the two short D2Ri
secondary risers and on into the two upper R] primary riser channels. The
injection level where the D2Ri sections discharge into the upper primary
riser channels is normally selected to fall within the range of one-third to
one-half the shaft depth.
Compressed air is injected into the upturned D2R"| risers near the bottom.
Influent wastewater and microorganisms are thereby contacted with makeup air
at a point of high oxygen solubility. The two upper channels of the primary
riser now become the zones of initial high oxygen uptake, replacing the less
efficient upper downcomer section which serves this role in the ICI and Eco I
shaft designs.
Air injection into the D2R~| secondary risers serves two purposes. First,
it aspirates the influent wastewater-return sludge mixture into the shaft at
depth using the air-lift principle. Second, it provides the motive force
(along with primary downcomer air) for circulating mixed liquor around the
shaft's main primary downcomer-primary riser loop at a rate about eight times
greater than the influent wastewater flow rate. Thus, influent wastewater is
diluted on entering the shaft at an approximate ratio of 8:1. The resulting
fluid velocities and detention times per pass are on the order of 1-1.5 m/sec
(3-5 ft/sec) and 4-6 minutes, respectively.
The second major design change in the Eco II shaft is the relocation of
the mixed liquor withdrawal point from the head tank to the R2 secondary
riser. R2 runs within the R] primary riser from the withdrawal point to the
surface. The entrance to R2 is located slightly below the point at which
influent wastewater and return sludge are injected into R] . This arrangement
precludes the possibility of short-circuiting untreated wastewater directly
to the shaft effluent line. The two principal advantages of the revised
method of transporting liquid from the shaft are: (1) the transfer of mixed
liquor to the flotation tank with a higher dissolved gas content and (2) the
provision of maximum single-pass treatment time following the initial contact
of incoming substrate, biomass, and injected air.
784
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HEAD TANK
SEDIMENTATION MODE
INFLUENT INLET
DIRECT TO D,
FLOTATION MODE
INFLUENT TO D2
OUTLET FROM
Rj TO SWIRL TANK
FIGURE 3. ECO II SHAFT CONFIGURATION AND HYDRAULICS
785
-------
Typical Eco I and Eco II gas voidage diagrams are presented in Figure 4
for a 133-m (435-ft) deep shaft with an assumed air injection depth in both
legs of 53 m (175 ft). Gas voidage is defined as the volume of undissolved
gas per unit volume of liquid. The shape of the voidage diagrams is directly
related to the amount and distribution of air injected. In the Eco I design,
approximately two-thirds of the total air supply is added to the downcomer
and one-third to the riser. Conversely, the Eco II design adds only one-
third to one-half of the total air supply to the primary downcomer and one-
half to two-thirds to the primary riser through the D2R] sections. More air
is needed proportionally in the riser of an Eco II shaft due to the afore-
mentioned introduction of wastewater and return sludge in the upper section
of this leg. Another distinction is that total air requirements to sustain
circulation at desired velocities are about 20 percent less for Eco II than
Eco I. The smaller Eco II air requirements are due primarily to the more
efficient air lift achieved by riser side air injection into the D2R] sections
rather than the larger R] leg and to a lesser degree to the higher velocities
created by the channel configuration in the upper half of the shaft.
During shaft startup in either the Eco I or Eco II modes, air is initially
fed to the riser leg only. The riser air displaces a portion of the liquid
in the upper riser section. This produces a gas/liquid dispersion in the
upper section of the riser with less net density than the liquid in the down-
comer leg. The pressure differential thus created tends to push up on the
liquid in the riser, causing the shaft contents to begin to circulate. The
liquid pushed out the top of the riser into the head tank loses virtually all
its gas bubbles by disengagement and venting before proceeding back down the
downcomer, accounting for the absence of gas voidage in the upper section of
the downcomer (Figure 4). Once stable circulation is achieved, the large
difference in voidage betweeen the riser and downcomer sections is no longer
needed and a portion of the air feed is transferred to the lower section of
the downcomer. Only a small pressure differential is required to maintain
circulation once it is established.
The shift in air injection toward the downcomer leg once circulation is
established is greater in the Eco I than in the Eco II operating mode. The
retention of a higher percentage gas voidage in the upper riser section of an
Eco II shaft results in improved hydraulic stability and essentially elimin-
ates the potential for hydraulic reversal to occur.
The claims made for the new Eco II bioreactor can be summarized as follows:
1. Anoxic zones within the shaft are eliminated.
2. Substrate removal kinetics and the shaft's overall biological profile
are enhanced owing to the better matching of oxygen demand with oxy-
gen availability.
3. Single-pass plug flow treatment time in a high-intensity aerobic
environment is maximized.
4. Total air requirements are decreased and organic loading capacity is
increased by 15-20 percent each.
786
-------
Head Tank Liquid Level
Downcomer Air
Injection
Depth (175 ft)
Notes:
1. Eco I Air Injection
a = 2 c
2. Eco II Air Injection
d = 1.4 b
3. b = c
4. b + d = 0.8 (a + c)
5. 1 ft = 0.305 m
Riser Air
Injection
Depth
(175 ft)
Eco I Mode
Eco II Mode
Downcomer Gas Voidage -*
^ Riser Gas Voidage
FIGURE 4. TYPICAL ECO I AND ECO II GAS VOIDAGE DIAGRAMS
787
-------
5. Dissolved gas drive for suspended solids separation by flotation is
optimized.
6. The overall improvement effected in flotation performance by Item 5
above reduces or eliminates the need for the addition of polymers or
other flotation aids to achieve a high degree of suspended solids
removal in the final effluent.
7. Hydraulic stability of the circulating mixed liquor is improved.
ECO II SYSTEM DESCRIPTION
The complete Eco II system, shown schematically in Figure 5, is comprised
of more than a bioreactor and a flotation clarifier. Auxiliary tanks and
piping networks are an integral part of system design. Figure 5 is repre-
sentative of the Deep Shaft flotation mode demonstration facility recently
installed at Ithaca. For simplicity, the shaft has been depicted as a single
tube with a divider wall forming the primary downcomer and primary riser legs.
The D2 secondary downcomer and the R2 secondary riser are shown, but the short
D2R] secondary riser sections have been omitted for clarity purposes. The
operational scheme of an Eco II system is described below, as taken primarily
from the Ithaca Operating and Maintenance Manual (8).
In contrast to an Eco I head tank, which is enclosed but supplied with a
direct vent to the atmosphere, an Eco II head tank is enclosed and operates
at a supra atmospheric pressure of 2000-5600 kgf/m^ (3-8 psig). Oxygen dis-
solution in the head tank is thereby minimized, allowing higher concentrations
of DO to be carried over to the downcomer than would remain in equilibrium
with the atmosphere. Disengaged bubbles exit the head tank as off gas to the
foam oxidation tank. The foam oxidation tank is vented.
Eco has determined that foam can be more efficiently stabilized in a
separate sidestream tank. The deleterious effects of foam on microbial acti-
vity are thus minimized in the shaft, permitting the utilization of a somewhat
smaller bioreactor volume and a higher F/M loading. Eco's operational experi-
ences to date indicate that little foam is generated in the shaft with typical
municipal wastewaters. Sidestream foam oxidation appears to be more pertinent
to naturally foaming wastes found in the discharges from breweries, dairy pro-
ducts processing, and textile manufacturing (9).
Partially treated or collapsed foam is displaced to the holding tank and
eventually back into the shaft. Raw influent and floated return sludge also
enter the shaft from the holding tank after first being contacted and mixed
in a trough that runs along and slightly below the flotation tank beach.
Bottom return sludge is recycled to the holding tank in a separate line. The
mixture of influent wastewater, float return sludge, bottom return sludge,
and collapsed foam is air lifted into the shaft via the secondary downcomer
(02) and secondary risers (D2Ri), as illustrated previously in Figure 3.
The swirl tank briefly intercepts mixed liquor as it is transported to
the flotation tank. The residence time of 10-15 seconds provided by the
swirl tank (at average flow) is long enough to strip out large bubbles that
788
-------
00
FOAM
OXIDATION
TANK
EFFLUENT"^
SECONDARY
DOWNCOMER
INTERMITTENT WASTE
BOTTOM SLUDGE
FIGURE 5. SCHEMATIC OF DEEP SHAFT SYSTEM USING FLOATATION CLARIFICATION
-------
would disrupt flotation, but not so long to promote effervesence of dissolved
gases and/or small bubbles.
The pressure required to force the mixed liquor out through the R2 sec-
ondary riser is provided by the difference between the liquid levels in the
head tank and the swirl tank (distance A in Figure 5). This head differential
offsets the friction losses in the R2 section. Therefore, as the liquid
level in the head tank increases, the output of R2 increases. In order to
limit the height requirements of the head tank, it is pressurized as previously
indicated to between 2500 and 5600 kgf/m2 (3 and 8 psig). This is equivalent
to increasing the liquid level in the head tank. The exact pressure in the
head tank is governed by the liquid level in the foam oxidation tank (distance
B in Figure 5). The height of liquid above the bottom of the air outlet pipe
in the foam oxidation tank is proportional to the pressure in the head tank.
If polymer or other chemicals are required to aid in flotation separation,
they are introduced to the mixed liquor in the pipe directly beneath the
swirl tank feeding the flotation tank. Variable rate skimmers are provided
to collect the floated solids and draw them toward and onto the beach. Some
fraction of the mixed liquor solids (mainly the inerts) will not be amenable
to flotation and will sink instead. These solids are collected by bottom
scrapers and a screw conveyor for direct gravity return to the holding tank,
as shown in Figure 5, or alternately for pumped return to the influent trough
fronting the beach.
Wasting of floated solids is accomplished through an orifice in the
beach. An automatic timed valve in the waste sludge line can be used to con-
trol the float solids wasting rate. Bottom solids wasting is controlled in a
similar manner.
FLOTATION DESIGN AND OPERATIONAL IMPROVEMENTS - ECO III
Based on experimental work at their Paris, Ontario pilot facility, Eco
claims to have advanced the state-of-the-art of flotation clarification,
particularly as applied to Deep Shaft technology. The advancements made are
reportedly in the areas of eliminating sophisticated (but operationally
troublesome) instrumentation and controls, improving performance reliability
during periods of large hydraulic fluctuations through the system, and en-
hancing hydraulic and mass loading capacities. Eco has not disclosed the
details of the Eco III design improvements to EPA at the time of this writing.
Eco will publish these details at a future date.
The first Deep Shaft system that will include the Eco III concept is
currently under construciton for the City of Portage la Prairie, Manitoba,
Canada (9). This plant is designed to treat an average flow of 14,300 m3/day
(3.75 mgd) with wet weather capacity to 37,800 m3/day (10 mgd). The Ithaca
demonstration unit may eventually be equipped with an Eco III flotation tank.
In effect, future Eco III Deep Shaft plants will really consist of a third-
generation bioreactor and a second-generation flotation tank. For convenience,
this flowsheet will be referred to simply as Eco III in the remainder of the
paper.
790
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THE ITHACA DEMONSTRATION PROJECT
SITE SELECTION
The City of Ithaca is located in the state of New York at the south end
of Cayuga Lake approximately 80 km (50 mi) southwest of Syracuse, New York.
The climate in this northern United States region ranges from severe freezing
in the winter to high temperatures in the summer. Ithaca is the home of
Cornell University, which contributes substantially to the City's waste load.
Ithaca's existing wastewater treatment plant provides primary clarifi-
cation and secondary treatment using the trickling filter process for a popu-
lation equivalent of 40,000. The primary treatment section of the plant
dates back to 1938, and the trickling filter units were completed in 1961.
These facilities have an average design flow rate of 15,100 m-Vday (4 mgd)
with peak flow capacity to 60,600 m^/day (16 mgd). Currently, the average
dry weather flow is approaching 26,500 m^/day (7 mgd). Peak flows in excess
of 60,600 m3/day (16 mgd) occur occasionally throughout the year.
The City's treatment plant is obviously overloaded and needs to be expand'
ed and upgraded to provide satisfactory secondary treatment in line with Fed-
eral and State effluent regulations. The plant property borders greenbelt
park areas that have been developed along the Cayuga Lake shoreline. The
presence of a major university and the tourist and recreational appeal of the
lake have produced an environmentally active and aware local constituency.
The Ithaca citizenry is consequently opposed to any treatment plant expansion
proposal that would encroach on the adjacent parkland.
The above dilemma faced by Ithaca was a paramount incentive in the City's
decision to seek an EPA grant to evaluate and demonstrate the Deep Shaft Pro-
cess. City officials are anxious to identify potential new wastewater treat-
ment alternatives that minimize land utilization.
In addition to the assured continuing interest and cooperation on the
part of the City due to the above situation, EPA selected Ithaca as the site
of the first municipal assessment of Deep Shaft technology in the United
States for the following reasons:
1. The City's consulting firm is currently preparing a Facilities Plan,
which is the first step in the approval process for an EPA treatment
plant construction grant. The Deep Shaft evaluation can be completed
in time to consider the process for the Ithaca plant expansion prior
to final design selection. Plant design represents Step 2 in the
U.S. Construction Grants Program sequence.
2. The existing wastewater flow is sufficiently large to permit a side-
stream demonstration study without disrupting main plant operations.
3. A diversity of influent waste streams including raw wastewater, pri-
mary effluent, trickling filter effluent, and anaerobic digester
supernatant are available for feed to the Deep Shaft pilot unit.
791
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4. The Ithaca wastewater treatment plant is staffed with well-qualified
operating and supervisory personnel. The City also has an excellent
relationship with the engineering firm that will oversee the conduct
of the project and evaluate the process data and cost effectiveness.
It is believed the above factors will all contribute to the successful
completion of a comprehensive pilot demonstration project. The results and
engineering assessments to be derived therefrom should have nationwide impact
in defining the future applicability of Deep Shaft technology to the waste-
water treatment problems of the United States.
DEMONSTRATION SYSTEM DESCRIPTION AND DESIGN
The Ithaca pilot demonstration system was flexibly designed to permit
operation in two different modes. These two modes are flotation clarification
utilizing an Eco II flowsheet (Figure 5) and gravity clarification preceded
by vacuum degassing utilizing the original ICI flowsheet (Figure 2). The
shaft has been constructed to operate with secondary downcomer and riser
sections (Eco II) or without them (ICI). A single liquid/solids separation
tank has been provided to serve as both a flotation clarifier and a gravity
clarifier.
The steel shaft casing has an inside diameter of 44 cm (17.25 in.), a
depth of 136 m (446), and is grouted to the geological formation with cement
(10). The inner concentric primary downcomer has an outside diameter of 30
cm (11.75 in.) and a depth of 133 m (436 ft). The annulus formed between the
outer casing and the inner primary downcomer constitutes the primary riser.
Excluding the head tank, the volume of Ithaca's shaft is 20.5 m^ (5418 gal).
The secondary downcomer (02) begins about 3 m (10 ft) below the base of
the head tank and runs within the primary riser (R]) to a depth of 61 m (200
ft). The short D2R] secondary riser sections, which are connected to the D£
downcomer, discharge influent wastewater and return sludge into the R] pri-
mary riser about 9 m (30 ft) up from the bottom of the D;? section. The
opening to the secondary riser mixed liquor withdrawal pipe (R2) is also
positioned at the 61-m (200-ft) level within the primary riser. Air is
injected at two locations: 55 and 60 m (180 and 196 ft) down from the base
of the head tank in the primary downcomer (D-|) and secondary risers (D2R"|),
respectively (8). Referral to Figure 3 will assist the reader in comprehend-
ing Ithaca pilot shaft internal geometry.
The dimensions of the liquid/solids separation unit are 3.4-m (11.25-ft)
wide x 11.0-m (36-ft) long x 4.0-m (13-ft) SWD (9). The surface area equals
37.6 m2 (405 ft2). This tank is equipped with both top and bottom variable
speed scrapers to collect floated solids (or scum during sedimentation oper-
ation) and settled solids, respectively. By opening and closing a few valves,
the tank is readily converted from the flotation mode to the gravity clari-
fication mode and vice versa.
The vacuum degasser shown preceding the sedimentation tank in Figure 2
consists of 16.5-m (54-ft) high tower with an inner concentric pipe (10).
792
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Mixed liquor from the surge tank flows up the annulus under a vacuum of
approximately 10~6 atmospheres. Effluent from the degassing tower is piped
directly into the sedimentation tank (10).
The vacuum degasser and surge tank are employed only when the pilot
system is operated in the gravity clarification mode. Since it would be
counterproductive to maximize the gas content of the mixed liquor leaving the
shaft in the gravity clarification mode, the secondary downcomer and riser
sections are not utilized and the head tank is not pressurized. In addition,
the foam oxidation, swirl, and holding tanks and the influent trough used in
the flotation clarification mode are idle during gravity clarification oper-
ations. Influent wastewater combined with underflow return sludge enters the
head tank directly. Mixed liquor destined for gravity clarification is dis-
placed from the head box into the top of the surge tank.
Air is supplied to the shaft from a 15-kW (20-hp) compressor. Startup
operations (discussed later on) have determined that a constant air supply
rate of 25 I/sec (53 scfm) is required for maintenance of desired circulation
velocities in the Eco II shaft configuration (flotation clarification mode).
This air supply rate is equivalent to an oxygen supply rate of 650 kg/day
(1434 Ib/day). The above air supply is distributed 15.6 I/sec (33 scfm) to
the riser side via the D2R] secondary risers and 9.4 I/sec (20 scfm) to the
D] primary downcomer. At this air supply rate, the compressor operates at a
line draw of roughly 11 wire kW (15 wire hp). Air supply requirements and
distribution for the ICI or Eco I shaft configuration (gravity clarification
mode) have not yet been defined. However, it is estimated total air supply
requirements will be 15-20 percent greater with approximately two-thirds
delivered to the downcomer and one-third to the riser.
The relationship of the Deep Shaft pilot demonstration plant to the
Ithaca main plant treatment facilities is illustrated schematically in
Figure 6. A sidestream of raw wastewater is normally diverted to the Deep
Shaft pilot unit after screening and grit removal. A line was also recently
installed allowing a sidestream of primary effluent to be fed directly to the
demonstration system, when desired. No piping has been provided to introduce
trickling filter effluent to the Deep Shaft plant at this time. An evaluation
using trickling filter effluent as feed would be on interest only in the
event nitrification became a requirement. Digester supernatant can enter the
Deep Shaft facilities via its recycle to the main plant headworks. Treated
effluent and waste sludge from the demonstration plant are pumped to the
influent end of the main plant primary clarifiers to preclude any discharge
of pilot effluent streams to the receiving water. To facilitate winter
operation and protect the solids separation unit during flotation operations,
a prefabricated 15-m x 12-m (50-ft x 40-ft) metal building has been provided
to house the entire Deep Shaft demonstration facility.
Ithaca's Deep Shaft demonstration plant was designed to have a nominal
capacity in the flotation clarification mode (Eco II flowsheet) of 757 m3/day
(200,000 gpd) at an influent BOD concentration of 150 mg/1. Hydraulically,
the system can handle 1325 m3/day (350,000 gpd). Due to solids loading con-
straints and corresponding lower attainable MLSS concentrations, nominal
design capacity in the gravity clarification mode (ICI flowsheet) is only 379
m3/day (100,000 gpd). Diurnal flow variation capability is available for
793
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INFLUENT
-J
SCREENING
GRINDING
GRIT REMOVAL
DIGESTER
SUPERNATANT
COMBINED PRIMARY
AND WASTE
SLUDGE '
PRIMARY EFFLUENT
RAW
WASTEWATER
SLUDGE FILTRATE
_DEWATERED SLUDGE
TO LAND DISPOSAL
DEEP SHAFT
PILOT DEMONSTRATION
PLANT
DEEP SHAFT
EFFLUENT
AND WASTE
SLUDGE
FIGURE 6. FLOW DIAGRAM OF ITHACA'S EXISTING WASTEWATER TREATMENT PLANT
-------
programmed stressing. A complete listing of design criteria for the two
operating modes is summarized in Table 1.
PROJECT OBJECTIVES
Eco-Research Ltd. would have preferred to limit the Ithaca Deep Shaft
evaluation to flotation clarification only. EPA's position, however, was
that the original ICI gravity clarification flowsheet, which is still marketed
in the U.K., Europe, and Japan, should be included in the study to add perspec-
tive. A compromise was effected wherein both operating modes could be assess-
ed, but by designing flexibility into the system, dual units were avoided.
With this brief introduction, project objectives are given below (12).
1. To
To evaluate the efficiency and reliability of the Deep Shaft Process
in treating a typical municipal wastewater under varied operating
conditions.
2. To provide guidance to U.S. engineers on the applicability of the
Deep Shaft Process to U.S. municipal treatment practices and to
define critical design and operating parameters.
3. To compare solids separation performance and associated shaft oper-
ating characteristics in both the flotation and gravity clarification
modes.
4. To develop capital and operating cost estimates to apply Deep Shaft
technology to a wide range of municipal projects.
5. To define flotation chemical aid requirements, if any.
6. To compare Deep Shaft operation and performance (including sludge
production and energy consumption) to traditionally accepted oper-
ating and performance values of conventional activated sludge systems,
both air and oxygen.
7. To evaluate process performance with and without alum addition for
phosphorus removal.
8. To compare process performance on raw wastewater feed vs. primary
effluent feed.
9. To determine whether typical U.S. municipal treatment plant personnel
can be trained to effectively, routinely, and independently operate
a Deep Shaft Process.
SYSTEM STARTUP SUMMARY
The startup program was commenced on October 8, 1979, and continued
until November 12, 1979, under Eco personnel. The demonstration plant was
then turned over to the City who operated it through November 30, 1979, at
which time the system was shut down for flotation tank modifications and
belated installation of the primary effluent feed line. Following the
795
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TABLE 1. DESIGN CRITERIA FOR ITHACA DEEP
SHAFT DEMONSTRATION SYSTEM
Parameter
Bioreactor
Nominal design flow, m /day
mgd
MLSS, mg/1
SRTa, days
F/M loadingb, kg BOD5/day/kg MLVSS
Volumetric organic loading '
kg BOD./day/mS
Ib BOD^/day/lOOO ftJ
Detention time , minutes
nominal (Q)
actual (Q + R)
Solids Separation Unit
Surface overflow rate,
m^/day/m2
gpd/ft2
Mass loading6, kg TSS/day/m29
Ib TSS/day/ftz
Return sludge flow rate, % of Q
float recycle
bottom recycle
Return sludge concentration, % TSS
float sol ids
bottom solids (intermittent)
Waste activated sludge ,
kg TSS/kg BOD. removed
kg VSS/kg BOD^ removed
kg TSS/ day b
Ib TSS/day
Flotation
Clarification
Mode
757
0.2
10,000
2.1
0.74
5.54
346
39
24
20.1
494
321
66
20
40
7-10
3-4
0.75
0.45
77
170
Gravity
Clarification
Mode
379
0.1
5000
2.1
0.74
2.77
173
78
39
10.1
247
103
21
N.A.
100
N.A.
1-2
0.75
0.45
39
85
(continued on next page)
796
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TABLE 1. (continued)
a Defined as kg MLSS in bioreactor/(kg TSS lost in waste activated sludge and
final effluent/day).
b F/M loading assumes an influent 6005 concentration of 150 mg/1 and a mixed
liquor volatile content of 75 percent.
c Volumetric organic loading estimated assuming influent 6005 of 150 mg/1,
a mixed liquor volatile content of 75 percent, a nominal shaft diameter
of 0.44 m (17.25 in.), and a shaft depth of 136 m (446 ft).
dActual detention time based on sludge recycle rates of 100 percent in the
gravity clarification mode and 20 percent and 40 percent, respectively, for
float solids and bottom solids in the flotation clarification mode.
e Mass loadings based on total sludge return rates of 60 and 100 percent and
MLSS concentrations of 10,000 and 5000 mg/1, respectively, in the flotation
and gravity clarification modes.
fActivated sludge wasted per unit of BOD5 removed based on an influent 6005
of 150 mg/1 and an effluent BODs of 15 mg/1.
departure of the Eco process startup engineer, it soon became evident that
the City operators still lacked sufficient judgment to maintain the proper
wasting balance between float solids and bottom solids. Deteriorating per-
formance was soon evident in increasing effluent suspended solids. The
modifications prescribed by Eco to correct the problems were to provide
separate control over flotation tank internal fluid recirculation and sinking
sludge return rate.
The 53 days (36 Eco, 17 City) of operation documented in Eco's startup
report (11) were comprised of 3 days at 70 percent of design flow, 46 days at
the flotation mode design flow of 757 m3/day (200,000 gpd), 2 days at 150
percent of design flow, and 2 days at reduced flow to repair equipment. Oper-
ating results for the 36 days Eco was in charge of the startup program are
summarized below (11):
1. Effluent total 6005 averaged 15 mg/1 vs. 135 mg/1 entering for a
removal of 89 percent. Total 6005 results are plotted in Figure 7.
The EPA 30 mg/1 minimum acceptable effluent 6005 limitation is shown
for reference. Effluent soluble BOD5 averaged 6 mg/1 during the
same period.
2. Suspended solids removal averaged 91 percent with 30 mg/1 in the
effluent against 334 mg/1 in the influent, which exactly meets EPA's
minimum acceptable suspended solids limitation. These results were
achieved, with the exception of 3 trial days, without the use of a
polymeric flocculation aid. Suspended solids data are presented
graphically in Figure 8. As indicated, effluent suspended solids did
797
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500 1
400 —
300 —
CD
2
Q
O
CQ
_l
<
H
o
200 —
100-
INFLUENT
EFFLUENT
30 MG/L MINIMUM EFFLUENT STANDARD
i i i i [ i i I i i r T i in r i r i T i i i i T \ \ \ \ \ i i i i i
9 10 11 12 13 14 15 16 17 18 19 20 21 22 2324 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12
OCTOBER
1979
NOVEMBER
FIGURE 7. ITHACA DEEP SHAFT BOD5 DATA DURING STARTUP
798
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800—I
600 —
(5
U)
o
O ann —
400
Q
HI
Q
Z
LU
Q.
w
D
200 —
T
INFLUENT
EFFLUENT
Y-3U M
"• *~ *~-
30 MG/L MINIMUM EFFLUENT STANDARD
r ii i i i i i i i i i i i i i \v\ \\ i \i \\\ r\\ n rrn
9 10 11 12 13 14 15 16 17 18 1920 21 2223242526 27 2829 30 31 1 2 3 4 5 6 7 8 9 10 11 12
OCTOBER
1979
NOVEMBER
FIGURE 8. ITHACA DEEP SHAFT SUSPENDED SOLIDS DATA DURING STARTUP
799
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exceed 30 mg/1 on occasion.
3. An average effluent total COD concentration of 66 mg/1 was achieved.
Based on an average influent total COD of 485 mg/1, removal was 86
percent for the period.
4. Effluent soluble COD mirrored the acclimatization of the Deep Shaft
biomass, dropping from an initial level of 100-110 mg/1 to 50-60 mg/1
after 2-1/2 weeks to 20-30 mg/1 after 3-1/2 weeks. Influent total
COD values are plotted against effluent soluble COD values in Figure 9,
5. Suspended solids in the float blanket (top return) generally ranged
from 8-8.5 percent; underflow solids (bottom return) ranged from
2.5-3.5 percent.
6. Due partially to anaerobic digester supernatant solids returned to
the main plant headworks, the reactor biomass developed rapidly
reaching an operating MLSS concentration of 10,000 mg/1 within 2 days.
By the second day, effluent specifications of 30 mg/1 6005 and 30 mg/1
suspended solids were being produced at 70 percent of design flow
(530 m3/day = 140,000 gpd).
7. Except for rotifers, a diversified microfauna was observed micro-
scopically within 6 days of startup. (Note: Rotifers, which are
typically present in mature conventional activated sludges, have
never been detected in Deep Shaft municipal wastewater cultures.)
The aforementioned recycle of digester supernatant to the headworks of
the Ithaca plant caused problems for operating personnel during startup. The
anaerobic digester's mechanical agitator is currently non-operational. To
provide needed stirring in the digester, overflow digester liquor is continu-
ously pumped to a large holding tank and back to the digester (see Figure -6).
Twice a week (usually Sunday and Thursday nights), the pump is turned off,
solids are allowed to settle in the holding tank, and supernatant is diverted
from the tank to the plant's grit chamber. These digester supernatant "dumps"
last 5-6 hr, and despite the preceding settling period in the holding tank
contribute high slug loadings of organics and suspended solids to the Ithaca
raw wastewater.
The demonstration plant raw wastewater sidestream takeoff is located near
the exit from the grit chamber. Consequently, shaft bioreactor influent
received the effect of the "dumps" virtually undampened. Influent total COD
and suspended solids concentrations increased 10-20 fold during the 5- to
6-hr "dump" periods. The solids were highly mineralized (50 percent +_ vola-
tile fraction) and, therefore, did not increase influent total BODs by the
same proportion. This shock condition made it impossible to hold system
biomass inventory at prescribed levels, often increasing MLSS to 15,000 mg/1
and above. The digester supernatant was also observed to have a temporary
inhibitory impact on mixed liquor respiration rates.
The biweekly digester supernatant "dump" policy produced the following
effects on Deep Shaft performance. Effluent suspended solids increased from
800
-------
(3
5
1500 —.
1400 —
1300 —
1200 —
1100 —
1000 —
900 —
800 —
Q
O 700 —
CJ
600 —
500 —
400 —
300 —
200 —
INFLUENT (TOTAL COD)
100 —
EFFLUENT (SOLUBLE COD)
I I I I I I I ! I I I I I I I I I I I I I I I I
9 10 11 12 13 14 15 16 17 18 19 20 21 2223242526 27 28 29 30 31 1
I I I
234
I T
56
I I I I I
8 9 10 11 12
OCTOBER
1979
NOVEMBER
FIGURE 9. ITHACA DEEP SHAFT COD DATA DURING STARTUP
801
-------
a typical background level of 30 mg/1 +_ to peaks of 40-80 mg/1. Effluent
total COD exhibited corresponding increases, peaking at concentrations ranging
from 100-200 mg/1. Recovery to steady-state effluent quality generally occurred
within 12 hr of the initiation of the shock loadings. Recovery time could be
minimized by careful operation and anticipation of the "dumps."
Float quality was also impaired by the shock loadings, thinning out from
a normal thickness of about 60 cm (24 in.) to 15 cm (6 in.) or less. A 3-mg/l
dose of cationic polymer (Stockhausen "Praestol" 423K) was beneficial in
helping to maintain desirable float characteristics during the "dumps," but
at the expense of increased effluent suspended solids, probably due in Eco's
opinion to rendering more floes neutrally buoyant (11). The float blanket
also typically recovered to "pre-dump" stability within 12 hr.
The difficulties that could be anticipated over a long-term evaluation
period from the digester supernatant slugs became more evident when the
demonstration plant was turned over to the City. For the 17 days from Novem-
ber 13 through November 30, 1979, with City operators in control, effluent
quality deteriorated on the average to 27 mg/1 total 8005 (69 percent removal),
106 mg/1 suspended solids (70 percent removal), and 151 mg/1 total COD (65
percent removal). Effluent deterioration was attributed to the lack of oper-
ator experience in adjusting process sludge wasting requirements, particularly
in response to the supernatant discharges.
The primary effluent feed line was initially thought of as an optional
wastewater source to be utilized only during planned experimental phases.
Following the startup experiences, a joint decision was made to switch the
shaft influent source from degritted raw wastewater to primary effluent during
the 5-6 hr that future supernatant "dumps" occur. By taking advantage of the
solids removal capacity of the main plant primary clarifiers, shaft influent
pollutant levels should not increase so dramatically and rapidly. Although
the pilot system exhibited excellent recovery capability^ it was felt that
coping with frequent supernatant discharges would dilute the major emphases
of the project and disrupt the accurate recording and analysis of critical
data such as excess sludge production and flotation tank response to routine
variations in loading. In the impending Ithaca plant expansion, the City's
engineering design firm will in all likelihood modify the existing sludge
handling scheme and smooth out internal recycle flows or treat them separately.
Installation of the primary effluent feed line and the aforementioned
flotation tank modifications proceeded from December 1, 1979, to February 6,
1980. The demonstration plant was then restarted under Eco supervision. The
Deep Shaft system is scheduled to be turned over to the City again by April 1,
1980. Operating and supervisory roles within the Ithaca plant staff in rela-
tion to the pilot plant have been more clearly defined since the initial
startup. This should lead to improved process understanding and operational
judgment. One of the more important measuring sticks of process practicality,
however, will be the degree of ease or difficulty City personnel experience
in establishing routine operating and maintenance schedules and consistent
performance. Their progress will be closely monitored in the coming months
as they attempt to carry out the evaluation program described in the following
802
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subsection under the overall engineering control of the City's consultant,
who is also relatively inexperienced regarding Deep Shaft technology, and
with minimal dependence on Eco.
EXPERIMENTAL DESIGN
Evaluation Program
Once the Ithaca staff has achieved a stable operating regime, a 64-week
evaluation program will be undertaken. The program tentatively consists of
42 weeks of phased evaluations in the flotation clarification mode (Eco II
flowsheet, Figure 5) and 22 weeks in the gravity clarification mode (ICI
flowsheet, Figure 2). Future incorporation of Eco III concepts in the Ithaca
flotation tank could alter or expand the evaluation schedule. The evaluation
program, outlined in Table 2, is designed to address the objectives listed
earlier in this section, principally those related to process performance,
operational stability, operating criteria, and process costs.
Analytical Program
The large analytical load to be generated by the aforegoing evaluation
program will be shared between Ithaca's treatment plant laboratory and a
commercial laboratory (12). The City will conduct total and volatile sus-
pended solids analyses; in-plant DO, pH, and wastewater temperature determin-
ations; and 1-liter sludge settling tests. The analyses to be assigned to
the commercial laboratory consist of total and soluble 6005, total and soluble
COD, the nitrogen series, total phosphorus, fecal coliforms, oil and grease,
chlorides, alkalinity, and heavy metals. In addition, Ithaca operators will
be responsible for monitoring flow rates (including waste activated sludge),
power consumption, and mechanical components as well as performing regular
visual checks.
The streams to be sampled include system influent, system effluent,
mixed liquor, float recycle and waste, and bottom recycle and waste. Major
contaminants of interest (6005, COD, suspended solids) as well as DO, pH,
temperature, and sludge settling will be assayed 5 days per week. Nutrients
will only be analyzed once per week, except for special sampling periods when
they will be determined 5 days per week. Heavy metals, chlorides, alkalinity,
oil and grease, and fecal coliforms will be run periodically. During certain
designated test periods, effluent soluble BOD5 frequency will be increased to
trace process response to rapidly changing organic load patterns.
Project Costs and Staffing
There are four parties to the Ithaca demonstration grant project: the
EPA Office of Research and Development as the grantor, the City of Ithaca as
the grantee, Eco-Research Ltd. as proprietary process subcontractor to the
City, and the consulting firm of Sterns and Wheler (S&W), Cazenovia, New
York, as engineering subcontractor to the City. The Principal Investigator
for the project is an employee of S&W. The responsibilities of S&W include
supervising demonstration plant operations and data collection, evaluating
Deep Shaft process performance and costs, convening meetings to discuss
803
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TABLE 2. TENTATIVE ITHACA EVALUATION PROGRAM
Phase No. of Weeks
Flotation mode
1. Constant flow - raw wastewater feed 6
2. Diurnal flow with periodic wet weather 12
peaking corresponding to plant wet
weather flow - raw wastewater feed
3. Combined organic and hydraulic overloads 8
by increasing flow incrementally at normal
strength maintaining a 1.5/1.0 diurnal
peaking factor - raw wastewater feed
4. Primary effluent feed - diurnal flow 8
5. Alum addition on primary effluent 4
feed -, diurnal flow
6. Alum addition on raw wastewater 4
feed - diurnal flow
Subtotal 42
Gravity mode
1. Constant flow - raw wastewater feed 6
2. Diurnal flow - same as Step 2 above 12
3. Combined organic and hydraulic 4
overloads - same as Step 3 above
Subtotal
Grand Total 64
progress and alter direction (if required), and preparing progress reports
and a final report for publication. Eco's responsibilities to date have
consisted of turnkey procurement, construction, and commissioning of the
demonstration plant and training Ithaca and S&W personnel. They will also
provide process expertise and advice, as needed, throughout the project.
Eco's contractual responsibility to the City has been primarily tied to
the front end of the project. At the point the pilot system is turned over
to the City around April 1, 1980, responsibility for the remainder of the
project will shift to S&W. EPA considers this separation of vested interests
and independent, unbiased engineering assessment essential to the prosecution
of a credible R&D project.
804
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The estimated total project cost is $787,000. Of this amount, EPA is
contributing $500,000. EPA also maintains liaison with project personnel and
participates in technical and budget decisions through its assigned Project
Officer. Eco, in addition to process design costs, which are not included in
the project budget, has contributed $250,000 toward the construction cost of
the pilot demonstration plant. The construction cost was $491,000, or roughly
62 percent of the estimated total project cost. The installation history of
the Deep Shaft pilot plant will be drawn upon extensively in developing an
estimated capital cost for a proposed expanded 37,800-m3 (10-mgd) facility
for Ithaca. Ithaca is providing approximately $37,000 to the R&D project in
the form of operating and laboratory personnel time and services.
Visitors' Program
Consulting engineers, municipal personnel, government officials, industry
representatives, and the public, both domestic and foreign, are encouraged to
visit the Ithaca Deep Shaft demonstration plant. Visitation programs have
been scheduled for-2-3 consecutive days during the middle of each month, at
which time Eco, City, and/or S&W representatives will conduct guided tours
through the facility. Visits to the plant can be confirmed by contacting Eco
at telephone number (416)226-7430 or writing to Ithaca Visitors' Program,
c/o Eco-Research Ltd., P.O. Box 200, Station A, Willowdale, Ontario,'Canada,
M2N 5S8 (10).
ENGINEERING AND ECONOMIC CONSIDERATIONS
DESIGN AND OPERATING CRITERIA
General Comments
The Deep Shaft Process departs substantially from conventional activated
sludge alternatives in appearance, design criteria, and operational mode. To
list the most obvious:
1. It utilizes a vertical rather than a horizontal bioreactor.
2. Its mixed liquor solids tend to float instead of settle.
3. It does not require diffusion equipment or mixers to dissolve oxygen.
4. The microorganisms in its biomass are subjected to wide swings in
hydrostatic pressure rather than uniform hydrostatic pressure.
5. It operates as an ultra high-rate suspended growth process with low
nominal detention times and highly concentrated biomass.
6. It produces internal oxygen uptake rates up to 8-10 times higher
than traditionally accepted values.
7. It reportedly converts some organics directly to carbon dioxide and
water, resulting in less excess sludge production than occurs at
comparable F/M loadings with surface systems.
805
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8. It produces a 3-8 times more concentrated waste sludge than achieved
conventionally.
9. Its minimum air supply requirement to sustain mixing, i.e., shaft
circulation at desired velocities, is substantially larger per unit
volume than to maintain solids suspension in horizontal bioreactors.
The above deviations from conventional activated sludge practice present
difficulties in comparing Deep Shaft with other suspended growth process
alternatives using time-honored sanitary engineering analysis techniques.
This is particularly true of substrate utilization kinetics, oxygen transfer,
power requirements, and excess sludge production. Equitable process design
comparison is further hampered in that the preferred feed for Deep Shaft
systems in most cases is raw wastewater, while conventional activated sludge
systems with the exception of extended aeration are normally mated with pri-
mary clarification.
The Ithaca demonstration project as well as several full-scale plants
soon to begin operation in Canada are expected to substantially broaden the
data base of the Deep Shaft flotation clarification mode. In the interim,
the historical and ongoing experiences derived from Eco's pilot facility at
Paris, Ontario, continue to serve as the major source of design and operating
criteria for the Deep Shaft Process.
Process Comparisons
Suggested design and operating criteria for treating typical municipal
wastewater are given in Table 3 for several activated sludge options. The
processes compared include the Deep Shaft flotation mode without primary
clarification, conventional air activated sludge with and without primary
clarification, oxygen activated sludge with and without primary clarification,
and extended aeration (no primary clarification).
Typical municipal wastewater was defined for this exercise as having total
6005 and suspended solids concentrations of 200 mg/1 each. Primary clarifi-
cation removals of 35 percent for total BOD5 and 65 percent for suspended
solids were assumed. Sufficiently conservative design values were selected
to produce an anticipated average secondary effluent quality of 20 mg/1 each
of total 8005 and suspended solids. Extended aeration operated at the condi-
tions shown would also be expected to produce a nitrified effluent.
Table 3 represents an attempt to develop a preliminary process basis for
evaluating Deep Shaft against competing alternative technologies. Recommended
design values for the air, oxygen, and extended aeration options can be found
throughout the literature (13, 14, 15, 16, 17, 18, among others). The ranges
shown for these three processes reflect the approximate consensus of the litera-
ture, where possible, tempered in some cases with judgment and best estimates.
Eco generated reports and correspondence (7, 9, 10, 11, 12, 19, 20) were relied
on for the most part in defining parameter ranges for Deep Shaft. In drawing
conclusions from Table 3, the reader is cautioned that the design and operating
criteria presented for Deep Shaft are much more tentative at this time than for
the historical technologies.
806
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00
o
TABLE 3. COMPARATIVE DESIGN AND OPERATING CRITERIA OF SELECTED ACTIVATED
SLUDGE PROCESSES FOR TREATING TYPICAL MUNICIPAL WASTEWATER
Parameter
Bioreactor
Nominal detention time, hr
MLSS, mg/1
% volatile
F/M loading, kg BODg/day/kg MLVSS
Volumetric organic loading,
kg BODc/day/m3 ,
Ib BODg/day/1000 ftJ
Sludge retention time3, days
Solids Separation Unit
Surface overflow rate:
3 2
average, m /dayXm
gpd/ft^
K T 0
peak , m /day/m
gpd/ft2
Deep Shaft
Flotation
Mode Without
Primary
Clarification
0.5-0.75
7000-12,000
0.6-0.7
0.75-1.25
5.6-8.0
350-500
2-4
20-29
500-700
41-49
1000-1200
Air Activated Sludge
Without
Primary
Clarification
6-8
2000-3000
0.65-0.75
0.3-0.5
0.5-0.8
30-50
3-6
20-29
500-700
41-49
1000-1200
With
Primary
Clarification
5-7
1500-2500
0.7-0.8
0.25-0.45
0.4-0.65
25-40
4-8
20-29
500-700
41-49
1000-1200
Oxygen Activated Sludge
Without
Primary
Clarification
1.5-2.5
4000-6000
0.65-0.75
0.55-0.8
2.2-3.2
135-200
1-2
13-26
450-650
37-45
900-1100
With
Primary
Clarification
1.25-1.75
3500-5000
0.7-0.8
0.5-0.75
2.0-2.8
125-175
2-3
20-29
500-700
41-49
1000-1200
Extended
Aeration
(No Primary
Clarification)
18-36
3000-6000
0.55-0.65
0.05-0.15
0.16-0.32
10-20
20-30
12-16
300-400
33-41
800-1000
(continued on next page)
-------
TABLE 3. (continued)
CO
o
CO
Parameter
2
Mass loading, kg TSS/day/m
Ib TSS/day/ft^
Solids Separation Unit (cont. )
Return sludge flow rate, % of Q
Return sludge concentration, % TSS
Air, Oxygen, and Power Requirements
Air supply rate, m /kg BODs removed
std. ft3/lb BODg removed
Oxygen utilized, kg/kg BODg removed
Oxygen transfer efficiency in
wastewater, % (On utilized /O, supplied)
Oxygen transfer rate in wastewater,
kg 02/wire kUh
Ib Oj/wire hp-hr
Aeration system power requirement,
wire kWh/1000 m3
wire hp-hr/mil gal
Deep Shaft
Flotation
Mode Without
Primary
Clarification
293-439
60-90
15-25, float
30-50, bottom
7-10, float
3-4, bottom
6-25c
100-400°
2.0-2.4
40-90C
0.9-2.7C
1.5-4.5C
80-289
500-1800
Air Activated Sludge Oxytjen Activated Sludge
Without With Without With
Primary Primary Primary Primary
Clarification Clarification Clarification Clarification
73-122 49-98 146-195 122-171
15-25 10-20 30-40 25-35
25-45 25-50 30-60 30-70
0.8-1.2 0.6-1.0 1.2-2.0 1.0-1.5
50-94d .
800-1 500a
0.9-1.3 1.0-1.4
8-1 5d 90-95
0.9-1.5d 1.2-1.5e
1.5-2.5d 2.0-2.5e
112-177 64-112 121-145 72-88
700-1100 400-700 750-900 450-550
Extended
Aeration
(No Primary
Clarification)
73-122
15-25
75-150
0.75-1.0
187-250f
3000-4000'
1.8-2.2f
8-15d
0.9-1.5d
1.5-2.5d
193-321
1200-2000
(continued on next page)
-------
TABLE 3. (continued)
00
o
Parameter
Sludge Production
Primary sludge TSS^, g/m
Ib/mil gal
Waste activated sludge:
VSS, g/m3
Ib/mil gal
kg/kg BODg removed
TSS, g/m3
Ib/mil gal
kg/kg BODg removed
Total plant raw + waste sludge TSS,
g/m3
Ib/mil gal
Final effluent solids :
VSS, g/m3
Ib/mil gal
TSS, g/m3
Ib/mil gal
Deep Shaft
Flotation
Mode Without
Primary
Clarification
-
72-90
600-750
0.4-0.5
108-138
900-1150
0.6-0.75
108-138
900-1150
13
110
20
170
Air Activated Sludge
Without
Primary
Clarification
-
96-132
800-1100
0.55-0.75
138-186
1150-1550
0.75-1.05
138-186
1150-1550
14
120
20
170
With
Primary
Clarification
132
1100
54-78
450-650
0.5-0.7
72-102
600-850
0.65-0.95
204-234
1700-1950
16
130
20
170
Oxygen Activated Sludge
Without
Primary
Clarification
-
96-120
800-1000
0.55-0.65
138-168
1150-1400
0.75-0.95
138-168
1150-1400
14
120
20
170
With
Primary
Clarification
132
1100
54-66
450-550
0.5-0.6
72-90
600-750
0.65-0.8
204-222
1700-1850
16
130
20
170
Extended
Aeration
(No Primary
Clarification)
-
36-60
300-500
0.2-0.35
60-96
500-800
0.35-0.55
60-96
500-800
12
100
20
170
(continued on next page)
-------
TABLE 3. (continued)
CO
M
o
Parameter
Sludge Production (cont.)
Total sludge production (waste +
effluent) in secondary system:
VSS, g/m3
Ib/mil gal
kg/kg BODc removed
TSS, g/m3
Ib/mil gal
kg/kg BODc removed
Deep Shaft
Flotation
Mode Without
Primary
Clarification
85-103
710-860
0.45-0.55
128-158
1070-1320
0.7-0.9
Air Activated Sludge
Without
Primary
Clarification
110-146
920-1220
0.6-0.8
158-206
1320-1720
0.9-1.15
With
Primary
Clarification
70-94
580-780
0.65-0.85
92-122
770-1020
0.85-1.1
Oxygen Activated Sludge
Without
Primary
Clarification
110-134
920-1120
0.6-0.75
158-188
1320-1570
0.9-1.05
With
Primary
Clarification
70-82
580-680
0.65-0.75
92-110
770-920
0.85-1.0
Extended
Aeration
(No Primary
Clarification)
48-60
400-600
0.25-0.4
80-116
670-970
0.45-0.65
a Defined as kg HLSS in bioreactor/(kg TSS lost in waste activated sludge and final effluent/day).
Dry weather peak.
c Depends on shaft diameter and degree of air tuning in shaft (Eco II vs. Eco III).
Lower values representative of coarse bubble diffusers; higher values representative of fine bubble diffusers.
e Lower values apply to systems employing pressure swing adsorption (PSA) oxygen generation; higher values apply
to systems employing cryogenic oxygen generation.
Includes oxygen requirements to sustain nitrification.
9 Calculated on the basis of 65 percent removal of an assumed raw wastewater concentration of 200 mg/1.
Assumes a final effluent TSS of 20 mg and final effluent solids volatility in accordance with assumed mixed
liquor volatility of respective processes.
-------
Projected operating conditions of Deep Shaft that vary markedly from the
other activated sludge processes shown include its low bioreactor detention
time and inversely high MLSS levels and organic load capacities and the high
mass loading capabilities and return sludge concentrations of its solids sepa-
ration unit. Oxygen activated sludge, which is itself considered a high-rate
suspended growth process, requires about three times as much bioreactor volume
for equivalent treatment based on Table 3 estimates.
Deep Shaft's uniquely high return sludge solids levels and mass loading
characteristics are due, of course, to the first-of-kind substitution of
flotation for sedimentation in achieving mainstream liquid/solids clarifica-
tion. Flotation is the process element that Eco believes is essential to
making Deep Shaft economically viable in North America. In addition to
approximately doubling the attainable MLSS concentration (and by inference
halving required bioreactor volume), flotation operation produces a floated
solids concentration sufficiently high as to require no subsequent thickening
during waste sludge handling. The potential for eliminating waste sludge
thickening altogether will ultimately be decided by the degree of bottom solids
wasting required. The thinner bottom solids in large enough quantities could
dilute thicker float waste sludge to the point that some form of supplemental
thickening would be needed.
The basic parameters governing bioreactor and flotation unit sizing and
performance have been fairly well established at Paris and other pilot study
locations (7). Further, the results of Ithaca's initial startup period tended
to confirm bioreactor and flotation clarifier sizing criteria. The factors
relative to Deep Shaft operation that still remain very much in a state of
flux involve air/oxygen/power requirements and sludge production. These facets
of the Deep Shaft Process are discussed in the following two subsections.
Air and Power Requirements
The data in Table 3 indicate a predicted wide variance for the above Deep
Shaft parameters, much more so than for the comparative processes. This wide
variance is due largely to shaft diameter and corresponding energy loss attri-
butable to friction. The relationship of organic loading to oxygen transfer
based on Eco kinetic models (9) is shown in Figure 10 for the 44-cm (17.25-in.)
ID Ithaca pilot shaft. For this particular shaft, projected air requirements
for hydraulic circulation are considerably larger than for biological metabolism
The net result of this disparity is relatively low apparent oxygen transfer
efficiencies (OTE's) of 38-53 percent in the F/M region (0.75-1.25 kg BODs/
day/kg MLVSS) of interest for municipal wastewater. Actually, most of the
oxygen supplied is dissolved at the bottom of the shaft. However, since
biological oxygen demand isn't sufficient to use it all, some of the DO effer-
vesces and is eventually lost from the system.
To illustrate the interdependence of shaft diameter and power requirements,
consider that the Ithaca pilot shaft (Eco II design) needs an air supply rate
of 22 I/sec (53 scfm), equivalent to 650 kg 02/day (1434 Ib/day), to sustain
desired circulation velocities. This is accomplished with a line (or wire)
power draw of 11.2 kW (15 hp). Assuming a motor efficiency of 90 percent
and an air compressor efficiency of 85 percent, the power delivered to the
811
-------
16—1
12 —
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Z
HI
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SHAFT CIRCULATION AIR REQUIREMENT = 1434 Ib O2/day
NOTES:
1. OXYGEN TRANSFER RATE = 4.14 Ib 02/wire hp-hr
AT 100% OXYGEN TRANSFER EFFICIENCY
2. 1 Ib = 0.454 kg
3. 1 lb/day/1000 ft3 = 0.016 kg/day/m3
4. 1 Ib/hp-hr = 0.608 kg/kWh
5. 1 mgd = 3785 m3/day
6. 1 gal = 3.785 I
ASSUMPTIONS:
1. SHAFT VOLUME = 5400 gal
2. MLVSS = 7500 mg/l
3. INFLUENT FLOW = 0.2 mgd
I
T
T
T
100
— 90
— 80
— 70
-60
-50
— 40
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z
111
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150 300 450 600
AVERAGE INFLUENT TOTAL BOD5 (mg/l)
750
1
0
1
0
1 1
0.75 1.5
F/M LOADING (kg
1 1
350 700
1
2.25
BOD5/day/kg
I
1050
I I
3.0 3.:
MLVSS)
I I
1400 17E
VOLUMETRIC LOADING (Ib BOD5/day/1000 ft3)
FIGURE 10. OXYGEN TRANSFER ORGANIC LOADING
RELATIONSHIPS FOR ITHACA DEEP SHAFT PILOT SYSTEM
812
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water in the shaft is approximately 8.6 kW (11.5 hp). Given a shaft volume
of 20.5 m3 (724 ft3), the mixing power requirement for the Ithaca pilot shaft
is about 0.42 kW delivered to the water/m3 (16 hp/1000 ft3).
By contrast, a 112-kW (150-hp) compressor will be used to supply air for
the two 137-cm (54-in.) diameter x 137-m (450-ft) deep shafts at Portage la
Prairie up to influent flows of 227,000 m3/day (6 mgd) (20). Assuming that
the line draw proves to be the full 112 kW (150 hp) and using the same motor
and compressor efficiencies as Ithaca, the mixing power requirement for this
design is only about 0.21 kW delivered to the water/m3 shaft volume (8 hp/
1000 ft3), or half of the Ithaca pilot shaft requirement. Anticipated appar-
ent OTE at Portage la Prairie is much higher than 38-53 percent. The Portage
la Prairie system is being constructed using an Eco III design approach.
Eco III, in addition to modifying flotation tank operating procedures, employs
a concept Eco calls "air tuning," which is claimed to result in lower net air
requirements.
Similarly, a possible Eco I Deep Shaft design proposed in April 1979 (21)
for Ithaca's eventual 37,800-m3 (10-mgd) expansion can be shown to have a pro-
jected mixing power requirement of 0.33 kW delivered to the water/m3 shaft
volume (12.5 hp/1000 ft3). This calculation is based on the proposed use of
a 225-kW (302-hp) compressor to supply air to two 152-cm (60-in.) diameter x
187-m (615-ft) deep shafts. Eco now believes that by applying Eco III design
concepts, compressor size for a full-scale Ithaca plant could be reduced to
134-149 kW (180-200 hp). If substantiated, proposed mixing power delivered
to the water would decrease to around the 0.21-kW/m3 (8-hp/1000 ft3) figure
projected for Portage la Prairie.
The above discussion emphasizes that minimum mixing power requirements
for Deep Shaft can be expected to vary by 100 percent, depending on shaft size
and system design. Conversely, the power requirement to adequately mix bio-
mass solids in conventional horizontal tanks has been fairly well established
at about 0.013 kW delivered to the water/m3 tank volume (0.5 hp/1000 ft3),
irrespective of tank geometry. Adjusting tank volume to obtain equivalent
treatment with an air activated sludge system, say 6-hr detention time for
air activated sludge vs. 40 minutes for Deep Shaft, increases conventional
tank mixing requirements to 55-60 percent of that for Deep Shaft.
Another factor that must be considered in defining power requirements is
biological oxygen demand, whereas air requirements for mixing would be suffi-
cient to satisfy Deep Shaft oxygen demand with most municipal wastewaters,
this is not the case in many conventional activated sludge designs. For
example, coarse bubble air diffuser systems can consume 0.039 kW delivered to
the water/m3 (1.5 hp/1000 ft3) or more to satisfy oxygen demand. Fine bubble
air diffusers and oxygen activated sludge transfer equipment more nearly match
biological power with mixing power requirements.
The preceding discussion suggests that careful engineering analysis will
be essential to equitable comparison of aeration power requirements for Deep
Shaft with conventional technology. On the basis of the limited and somewhat
speculative information now available, Table 3 indicates that Deep Shaft
aeration system power requirements can range anywhere from decided economic
813
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attractiveness to being just barely competitive with extended aeration.
Oxygen Utilization and Sludge Production
A claimed Deep Shaft operating characteristic that defies accepted biolo-
gical process behavior concerns excess sludge production. Total biological
sludge production for the Deep Shaft Process is estimated in Table 3 at
0.45-0.55 kg VSS/kg total BODs removed. Corresponding estimates for conven-
tional air and oxygen activated sludge processes are 0.6-0.85 and 0.6-0.75 kg
VSS/kg total BODs removed, respectively. The issue is not that Deep Shaft
estimated sludge production is less than that of conventional suspended growth
options, but that such claims should be made in view of the exceedingly high
F/M loadings that are imposed on the process.
Traditionally, biological kinetic theory has held that in the absence of
oxygen deficiency a direct relationship exists between F/M loading and sludge
production. Such a relationship explains, for instance, the low sludge yield
of extended aeration units. The equal to slightly less predicted yield of
oxygen activated sludge vs. air activated sludge in Table 3 despite the
former's much higher (approximately double) typical F/M loading has been
variously attributed to improved oxygen penetration of microfloc (22) and/or
the large amount of sludge inventory routinely maintained in some oxygen
final clarifiers (23). With the latter hypothesis, oxygen activated sludge
F/M loadings based only on aerator sludge inventory are represented as arti-
facts. The smaller actual F/M loadings, calculated taking total system sludge
inventory into account, reportedly fall into line with prevailing sludge pro-
duction theory.
Reported Deep Shaft sludge yield does not agree with the above traditional
relationship. The anticipated yield at an F/M loading of 1.26 kg BOD5/day/kg
MLVSS with conventional processes would be expected to approach 1 kg VSS/kg
6005 removed and to exceed 1 kg TSS/kg BODs removed, rather than the 0.5 kg/kg
6005 removed yield (7) suggested on the basis of the Billingham study.
Eco's explanation for the observed low sludge yield both at Billingham
and Paris is that it "hypothetically results from extremely high oxygen
uptake rates (200-250 mg 02/g VSS/hr) occurring in the vicinity of the D2R]
influent wastewater injection point, which stimulates direct conversion of
organic carbon to carbon dioxide and water and bypasses the customary cell
synthesis process" (20). Figure 10 suggests that something unusual is happen-
ing in the shaft in terms of unit oxygen utilization (consumption) that may
relate to sludge yield. The Eco kinetic models on which Figure 10 is based
predict that in the F/M range of 0.75-1.25 kg BODs/day/kg MLVSS, oxygen utili-
zation varies from 2.4-2.0 kg/kg BODs removed, assuming a total BODs removal
of 90 percent. This is roughly twice the utilization rate normally encountered
in biological systems that are not nitrifying.
High oxygen utilization rates would seem to be tied to the claimed high
oxygen uptake or respiration rates. If in fact these rates of oxygen utili-
zation can be substantiated, the plausibility of reported low sludge yields
would be strengthened, either through auto-oxidation of cell mass or through
some other unexplained metabolic pathway.
814
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COST CONSIDERATIONS
Factors Affecting Costs
The Deep Shaft Process is characterized by a number of potential cost
savings attributes, site specific cost features, and currently indeterminate
economic considerations that taken together preclude comprehensive cost analy-
sis for generalized comparisons at this time.
Biological reactor detention times in the order of 40 minutes are one-
ninth to one-thirty sixth of the typical required reactor volumes of conven-
tional air and extended aeration plants. Shaft placement costs can, however,
be thirty times more expensive per unit volume than a surface system (7).
Land area required for Deep Shaft plants can be as little as 25 to 35
percent of land area required for conventional plants. In addition to land
cost savings, this characteristic of reduced size suggests applicability for
plant expansion plans in areas of limited land availability or wherever
housing the plant facilities is an important consideration.
For municipal applications, aeration requirements will generally be
established by hydraulic circulation requirements rather than organic load
considerations. The power requirement to achieve minimum acceptable hydraulic
circulation rates of 1-1.5 m/sec (3-5 ft/sec) is a function of the friction
loss in the shaft, which is a function of shaft diameter.
Shaft diameter, ranging from 0.5 to 10 m (1.5 to 33 ft), together with a
depth determination, ranging from 100 to 200 (325 to 650 ft), establishes the
reactor volume and detention time for a given flow and circulation rate.
Shaft diameter also determines the shaft placement technology. Sandford et
al. (7) provided useful insight on shaft placement technology. Shafts with a
diameter of less than 3.7 m (12 ft) are usually drilled. Shafts larger than
5.5 m (18 ft) are usually mined. Shaft placement technology is well estab-
lished using conventional oil and water well drilling technology with over
2,500,000 oil wells being placed in the past 25 years. All shafts are encased
for their full length with either steel or concrete and grouted to the sub-
surface geology using sulfate resistant cement. Sandford further reports,
"Shaft placement technology is also sufficiently developed to allow, with
confidence, the installation of shafts in earthquake and slide areas."
The use of flotation clarification further contributes to reduced land
requirements through potential elimination of post-clarification thickening,
reduced recycle volumetric requirements, and higher mass loading capabilities
for the clarification process.
Cost factors which are indeterminate at this time include: (1) the
amount of polymer, if any, that is necessary to achieve effluent quality
objectives and stable flotation performance and (2) the amount of waste
sludge produced per unit of 6005 removed.
815
-------
Dunlop (24) provides a useful overview of the characteristics of the
sludge produced by the Deep Shaft Process. A summary of his findings are
shown in Table 4.
TABLE 4. CHARACTERISTICS OF DEEP SHAFT SLUDGE
Parameter
Deep Shaft Sludge
Conventional
Activated Sludge
Adenosine triphosphate content, /jg/ml 0.8062
Sludge specific activity, 32 - 46
mg 02/g MLSS/hr
Ks determination 50
(Michaelis-Menten plot), mg/1
Floe size, microns 30 - 100
Protozoal population No change
Capillary suction time, sec 50 - 100
Specific resistance to filtration^ 1.44
1014 in./kg
Compressibility 0.85
0.9908 Billingham
0.5368 Durham
15 - 58
20 - 50
30 - 1800
200 - 400
(digested primary)
8.54
(0.5 to 2 normal)
0.78
These results indicate that there is no major difference in the charac-
teristics of Deep Shaft sludge compared to conventional sludges. The six-
fold decrease in specific resistance measured experimentally was statistically
significant, but the Deep Shaft value is within the range of reported values
for conventional sludges. The capillary suction time of 50-100 sec suggests
a good dewatering sludge.
It is interesting to note that the specific activity reported by Dunlop
for Deep Shaft sludge is 4-5 times lower than the 200-250 mg 02/g VSS/hr
oxygen uptake rates claimed by Eco. The discrepancy is believed to be due
to differing environmental conditions. Eco's values apply to sludge exposed
to the high oxygen transfer intensity existing within an operating shaft.
Dunlop's data were developed by laboratory methodology on sludge withdrawn
from a shaft. Eco's position is that ordinary microbes respond favorably to
high aeration intensity and exhibit oxygen uptake rates in the shaft that
cannot be duplicated in standard laboratory tests (20).
816
-------
Cost Estimates
Thompson (19) published cost estimates for Deep Shaft and extended
aeration for the City of Portage la Prairie, Manitoba, in March 1979. These
costs are compared in Table 5 for capital and in Table 6 for operation and
maintenance (O&M). The plant is designed to treat a dry weather flow of
14,300 m3/day (3.75 mgd)(peak wet weather flow of 37,800 m3/day = 10 mgd) with
a combined domestic/industrial organic load of 5440 kg BOD5/day (12,000 Ib/day)
TABLE 5. CITY OF PORTAGE LA PRAIRIE CAPITAL COST COMPARISON
Extended Aeration Using
Unit Process Deep Shaft Jet Aerators
Aeration - $430,000
Final clarification $103,000 830,600
Head works 904,600 980,600
(screening, degritting)
Outside services 165,000 276,100
(roads, piping)
Eco (fixed price including 1,750,000
shaft, compressors, piping,
flotation tank, mechanical
equipment, and instrumentation)
Engineering 201,000 272,000
Total $3,123,600 $2,789,300
The consultant recommended Deep Shaft on the basis of lower operating
costs, the offer by Eco-Research Ltd. of a firm price for construction costs,
the significantly lower electrical requirements (a rapidly increasing cost
component), the ability to easily house the facility, and the improved dis-
posal characteristics of the flotation sludge.
In September 1977, Sandford (7) reported the capital costs of Deep Shaft
facilities treating 2270 m3/day (0.6 mgd) and 90,800 m3/day (24 mgd) of domes-
tic wastes and 13,600 m3/day (3.6 mgd) of combined domestic/industrial wastes
as being $0.5 million, $6.5 million, and $2.0 million, respectively. These
cost estimates included installation of the shaft and solids separation sys-
tem, all compression equipment, process control equipment, piping, and civil,
electrical, mechanical, and painting work required. They did not include pre-
liminary treatment (screening, degritting, headworks, etc.), post-treatment
(disinfection, sludge dewatering), or any buildings.
817
-------
TABLE 6. CITY OF PORTAGE LA PRAIRIE OPERATION
AND MAINTENANCE COST COMPARISON
Extended Aeration Using
Unit Process
Electricity
Chemicals
Sludge hauling
Salaries
Maintenance
Fuel
Subtotal O&M
Amortization, 20 yr @10%
TOTAL ANNUAL COST
Deep Shaft
$28,486
62,850
48,667
40,000
52,000
6,500
238,503
366,899
$605,402
Jet Aerators
$56,971
30,000
60,833
40,000
52,000
6,500
246,304
330,215
$576,519
Preliminary cost estimates were prepared in a 1979 facilities planning
exercise comparing 13 alternative treatment systems for a proposed 37,800-m-V
day (10-mgd) plant expansion at Ithaca, New York (25). The estimates indi-
cated that Deep Shaft was competitive, both on the basis of capital and O&M
costs, with the two or three most cost-effective conventional alternatives.
The estimators acknowledged that several important cost factors could not be
confidently assessed for the Deep Shaft Process at that time. Cost sensitive
features of Deep Shaft that will ultimately determine its full-scale economic
attractiveness for Ithaca include: (1) the degree to which the process must
or should be housed and the required quality of that housing and associated
utility services, (2) the quantity of flotation aid chemicals required, if
any, (3) excess sludge production, (4) full-scale power requirements, (5) the
feasibility of eliminating sludge thickening equipment, (6) geologic condi-
tions and associated drilling costs, (7) the degree of permissable and/or
realistically achievable design flexibility to reduce shaft and flotation unit
redundancy, and (8) the level of operating sophistication and attention re-
quired.
CURRENT STATUS OF DEEP SHAFT IMPLEMENTATION
NORTH AMERICAN IMPLEMENTATION
Eco's market activities in North America to date have been primarily rele-
gated to Canada. As indicated in Table 7, three full-scale Deep Shaft plants are
818
-------
TABLE 7. DEEP SHAFT PLANTS IN NORTH AMERICA
00
Location
Virden, Manitoba,
Canada
Portage la Prairie,
Manitoba, Canada
Molson Breweries Ltd.,
Barrie, Ontario,
Canada
Ithaca, New York,
U.S.A.
Paris, Ontario,
Canada
Molson Breweries Ltd.,
Barrie, Ontario,
Canada
Anheuser-Busch Inc.,
Wil 1 iamsburq, Virginia,
U.S.A.
Agropur Dairy Ltd. ,
Notre-Dame-de-bon-
Conseil, Quebec, Canada
Type of
Plant
Full scale,
Eco I design
Full scale,
Eco III design
Full scale.
Eco II design
Demonstration,
Eco II design
Experimental ,
Eco III as of
April 1980
Pilot,
Eco II design
U-tube pilot,
Eco I design
U-tube pilot,
Eco I design
Type of
Wastewater
Municipal
Municipal/
food processing
wastes
Brewery
wastes
Municipal
Municipal/
textile
wastes
Brewery
wastes
Brewery
wastes
Dairy
wastes
Influent
BOD5, mg/1
200
400
2400
100-175
150-200
1000-6000
1500-2000
1000
Status as
, Design Flow of March
my day mgd 1980
2400 0.63 Operating
(startup)
14,200 3.75 Under
construction
2180 0.58 Operating
(startup)
757 0.20 Operating
(startup)
454 1.20 Operating
(study completed)
* * Study completed
* * Study completed
* * Study completed
* Denotes the use of variable loadings to determine organic stress-performance relationships.
-------
presently either being started up or constructed in Canada (9). The other
five locations listed in Table 7 encompass various size development studies
ranging from small U-tube pilot plants to the 757 m^/day (0.2-mgd) demon-
stration facility at Ithaca (9).
Deep Shaft technology is applicable to a variety of wastewater treatment
situations. Because of its high oxygen intensity and transfer characteristics
as well as its fixed air supply requirements for fluid circulation, Deep Shaft
will probably find its greatest cost effectiveness in treating high strength
industrial wastes. Eco's initial industrial contacts have been with two
breweries and one dairy. The full-scale Molson brewery waste treatment facili-
ty is an outgrowth of an earlier pilot study at the same site.
The cost attractiveness of Deep Shaft for municipal treatment should be
enhanced as the fraction of industrial contribution increases, provided the
type of wastes being discharged into the municipal sewer system do not inter-
fere with flotation efficiency. Portage la Prairie (plant scheduled for
startup in November 1980) is an example of a city with a relatively strong
combined municipal/industrial wastewater that should be well suited to Deep
Shaft treatment.
IMPLEMENTATION OUTSIDE NORTH AMERICA
Implementation of the Deep Shaft Process outside North America has
involved the United Kingdom, Europe, and Japan, as summarized in Table 8 (9).
The U.K. and European plants represent the realization of Deep Shaft marketing
efforts by the parent company, ICI, Billingham, England. The two pilot studies
in Japan, one completed and one still in progress, were initiated through the
offices of ICI Japan.
In contrast to the North American Deep Shaft pilot and full-scale instal-
lations, all of which are of Eco design and utilize flotation clarification,
the U.K., European, and Japanese facilities employ the ICI flowsheet, i.e.,
gravity clarification preceeded by vacuum degassing. The emphasis on industrial
clients is noticeably higher in the U.K. and Europe than in North America.
Eco's decision to substitute flotation clarification for gravity clarification
was based partly on: (1) their perceived larger'potential municipal market in
North America and (2) the accompanying need to reduce shaft volume and associ-
ated costs to enhance Deep Shaft's competitive position in treating the high
volume-low strength municipal wastewaters typically found in Canada and the
United States.
A related technology that should be briefly mentioned is the U-Tube
Aeration System marketed in Japan by Kubota Ltd. While similar to the Deep
Shaft Process in that it utilizes a vertical, drilled-shaft bioreactor,
Kubota's system employs liquid pumping rather than compressed air injection
to provide the motive force for circulating mixed liquor.
820
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TABLE 8. DEEP SHAFT PLANTS OUTSIDE NORTH AMERICA
00
K)
Location
Emslandstarke Co. ,
Eml ichheim,
West Germany
Anglian Water Authority,
Marsh Farm,
Thurrock, U.K
Kimberly Clark Co.,
Prudhoe, U.K
ICI Agricultural Division,
Pruteen, U.K.
Leer, West Germany
Billingham, U.K.
Holdenhurst, U.K.
Undisclosed, Japan
Toyonaka, Japan
ICI Petrochemical
Division, Wilton, U.K.
ICI Petrochemical
Division, Wilton, U.K.
Type of
Plant
Full scale,
ICI design
Full scale,
ICI design
Full scale,
ICI design
Full scale,
ICI design
Full scale,
ICI design
Experimental ,
ICI design
Pilot, ICI
design
Pilot, ICI
design
Pilot, ICI
design
Pilot, ICI
design
Pilot, ICI
design
Type Of Influent 3Design Flow
Wastewater BODg, mg/1 m /day mgd
Potato 2000 1050 0.28
processing
wastes
Cornstarch (50%+), 1060 6650 1.76
municipal (20%), (max.)
misc. industrial (30%)
De-inking mill 1000 21,600 5.71
wastes
Single cell protein - 1575 0.42
production wastes
Mixed municipal/ 400 32,500 8.58
dairy/industrial
Municipal 200 363 0.096
Municipal _ * *
Chemical wastes 3000 * *
(organic chlorides)
Municipal 200-600 2400 0.63
Chemical wastes 4500 * *
(terephthalic acid
manufacturing)
Chemical wastes 2400 * *
(phenol and phenol ics)
Status as
of March
1980
Operating
Operating
Operating
Periodic
operation
Under
construction
Study
completed
Operating
Operating
Study
completed
Study completed;
full-scale plant
planned
Operating
* Denotes the use of variable loadings to determine organic stress-performance relationships.
-------
SUMMARY
This paper has presented: (1) a review of the United Kingdom origins of
the Deep Shaft Process, (2) a synopsis of the development program undertaken
in Canada by Eco-Research Ltd. to refine the technology for marketing in
North America, (3) a description of EPA's R&D efforts currently underway to
ascertain the applicability and cost effectiveness of the process for use in
the United States, and (4) an overview of the critical design and operating
features requiring further evaluation that will ultimately determine Deep
Shaft's role in the wastewater treatment field.
The development of the Deep Shaft Process has been rapid. Eight full-
scale treatment plants are either in operation or under construction in Canada,
West Germany, and the United Kingdom. At least five different process designs
or configurations (ICI, Eco I, Eco II, Eco III, and Kubota) have evolved in
the brief 6-year period since the first pilot facility was started at Billing-
ham, England, in 1974.
Penetration of the U.S. municipal market will depend in large measure on
the outcome of the Ithaca, New York demonstration project, as well as the
economic and risk assumption incentives of the innovative and alternative
funding provisions of the Clean Water Act Amendments of 1977 (1). At this
point in time, Deep Shaft is considered to represent a novel and potentially
innovative alternative to conventional suspended growth biological treatment.
Additional operating and performance data must be generated before comprehen-
sive engineering comparisons and an assessment of the process' innovative
status can be made. The Ithaca project is expected to contribute significantly
to a fuller understanding and characterization of both the flotation and
gravity clarification modes of liquid/solids separation and their effect on
cost and energy utilization estimates.
822
-------
REFERENCES
1. U.S. Environmental Protection Agency, Draft, "Innovative and Alternative
Technology Assessment Manual." Washington, D.C., EPA-430/9-78-009 1978.
2. Gibson, M. R., Maslen, F. P., Roesler, F. C., and Smith, S. R. L.,
British Patent Number 1353008.
3. MacLennan, D. G., Ousby, J. C., Owen, T. R., and Steer, D. C., British
Patent Number 1370892.
4. Ousby, J. C., Walker, J., and Jones, R.. T., "Treatment of Domestic Sew-
age Using the ICI Deep Shaft Process." ICI publication, Billingham,
England, undated.
5. Rosenzweig, M., and Ushio, S., "Protein from Methanol." Chemical Engi-
neering, pp. 62-63, January 7, 1974.
6. Bolton, D. H., and Ousby, J. C., "The ICI Deep Shaft Effluent Treatment
Process and Its Potential for Large Sewage Works." Presented at IAWPR
Workshop on Design-Operation Interactions at Large Wastewater Treatment
Plants, Vienna, Austria, September 8-12, 1975.
7. Sanford, D. S., and Chisholm, K. A., "The Treatment of Municipal Waste-
water Using the ICI Deep Shaft Process." Presented at 29th Annual
Western Canada Water and Sewage Treatment Conference, Edmonton, Alberta,
Canada, September 28-30, 1977.
8. Eco-Research Ltd., "Operating and Maintenance Manual for Ithaca Deep
Shaft Demonstration Plant." Willowdale, Ontario, Canada, October 1979.
9. Letter communication from D. S. Sandford, Eco-Research Ltd., to R. C.
Brenner, U.S. Environmental Protection Agency, Cincinnati, Ohio, Febru-
ary 20, 1980.
10. Eco-Research Ltd., "Visitors' Brochure for Ithaca Deep Shaft Demonstration
Plant." Willowdale, Ontario, Canada, February 1980.
11. Gallo, P., and Sheppard, J. D., Eco-Research Ltd., "Report on the Com-
missioning of the Deep Shaft Demonstration Plant, Ithaca, New York."
Willowdale, Ontario, Canada, January 1980.
12. City of Ithaca, New York, Board of Public Works, Grant Application to
U.S. Environmental Protection Agency, Office of Research and Development,
Washington, D.C., "Evaluation of Deep Shaft Biological Wastewater Treat-
ment Process." April 6, 1978.
823
-------
13. U.S. Environmental Protection Agency, Office of Technology Transfer,
"Process Design Manual for Upgrading Existing Wastewater Treatment Plants.'
Washington, D.C., October 1974.
14. U.S. Environmental Protection Agency, Environmental Research Information
Center, Technology Transfer, "Process Design Manual - Wastewater Treat-
ment Facilities for Sewered Small Communities." Cincinnati, Ohio,
October 1977.
15. Metcalf & Eddy, Inc., "Wastewater Engineering: Treatment, Disposal,
Reuse." Second Edition, McGraw-Hill Book Co., 1979.
16. Nash, N., Pressman, W. B., and Krasnoff, P. S., "Oxygen Aeration at
Newtown Creek." U.S. Environmental Protection Agency Report No. EPA-
600/2-79-013, Cincinnati, Ohio, June 1979.
17. Pearlman, S. R., and Fullerton, D. G., "Full-Scale Demonstration of Open
Tank Oxygen Activated Sludge Treatment." U.S. Environmental Protection
Agency Report No. EPA-600/2-79-012, Cincinnati, Ohio, May 1979.
18. Brenner, R. C., "Status of Oxygen-Activated Sludge Wastewater Treatment."
U.S. Environmental Protection Agency, Environmental Research Information
Center, Technology Transfer, Cincinnati, Ohio, October 1977.
19. Thompson, G. E., "Selection of Deep Shaft Technology for the City of
Portage la Prairie, Manitoba." Presented at Workshop 79 on New Develop-
ments in Wastewater Treatment, University of Toronto, March 7-8, 1979.
20. Telephone communication from G. E. Thompson, Eco-Research Ltd., to R. C.
Brenner, U.S. Environmental Protection Agency, Cincinnati, Ohio, March 3,
1980.
21 Letter communication from M. L. LeBlanc, Eco-Research Ltd., to R. Fedatoff,
Stearns and Wheler, Cazenovia, New York, April 25, 1979.
22. Stamberg, J. B., Bishop, D. F., and Hais, A. B., "Activated Sludge Treat-
ment Systems with Oxygen." U.S. Environmental Protection Agency Report
No. EPA-600/2-73-073, Washington, D.C., September 1973.
23. Austin, S., Yunt, F., and Wuerdeman, D., "Parallel Evaluation of Air and
Oxygen Activated Sludge." Draft report submitted to U.S. Environmental
Protection Agency by Los Angeles County Sanitation Districts, Contract
No. 14-12-150, Cincinnati, Ohio, December 1979.
24. Dunlop, E. H., "Characteristics of Sludge Produced by the Deep Shaft
Process." ICI publication, Billingham, England, undated.
25. Letter communication form D. E. Schwinn, Stearns and Wheler, Cazenovia,
New York, to R. C. Brenner, U.S. Environmental Protection Agency,
Cincinnati, Ohio, January 14, 1980.
DISCLAIMER
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the U.S. Environmental Protection
Agency.
y 824
-------
CURRENT DESIGN AND OPERATING EXPERIENCE WITH
ANAEROBIC SLUDGE DIGESTION
By
Walter E. Garrison
Carl A. Nagel
and
R. Steven Easley
Los Angeles County Sanitation Districts
Whittier, California
Presented at
SEVENTH UNITED STATES AND JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
May 18 - June 1, 1980
Tokyo, Japan
825
-------
ACKNOWLEDGEMENTS
Partial funding for the design and construction of the circular digesters
discussed in this paper was provided by the State of California and the
United States Environmental Protection Agency.
826
-------
I. INTRODUCTION
For the past five decades, the Sanitation Districts of Los Angeles County
have successfully designed and operated anaerobic sludge digestion systems.
The Districts' experience until recently has been primarily limited
to the digestion of primary sludge. In July 1975, the California Regional
Water Quality Control Board, in accordance with revised federal waste dis-
charge requirements, mandated the staged installation of secondary treatment
at the Joint Water Pollution Control Plant (JWPCP) in Carson, California.
The Districts are currently constructing 8.8 m3/s (200 mgd) of high purity
oxygen activated sludge treatment facilities at JWPCP. Based on extensive
field pilot plant research studiesO), a sludge processing scheme that in-
cludes anaerobic sludge digestion was chosen by the Districts to treat the
waste activated sludge (WAS) from the oxygen activated sludge units. This
paper discusses the following:
• The basic advantages of anaerobic sludge digestion to the Districts.
• The design parameters and important construction features of the di-
gesters presently under construction.
• The current operating principles and process control procedures for the
digestion systems at JWPCP.
A. EXISTING FACILITIES
The Joint Water Pollution Control Plant currently provides advanced primary
treatment for 15 m3/s (350 mgd) of domestic and industrial wastewater. A
site layout for the major treatment works discussed in this paper is shown in
Figure 1. The plant treats approximately 75 percent of the flow in the en-
tire Sanitation Districts' system, which serves a population of four million.
The effluent from the plant is discharged to the Pacific Ocean through deep
ocean outfalls 3.2 km (two miles) off the coast. Five other treatment plants
in the system return their sludge to sewers which terminate at JWPCP, so the
plant serves as a central solids processing facility for the whole system.
The following is a brief summary of the flow diagram for JWPCP as shown in
Figure 2. After passing through the inlet works and grit chambers, the
wastewater flows through fifty-two primary settling tanks. The settled
sludge and concentrated floatables from the primary tanks are pumped to di-
gesters for anaerobic biological treatment. JWPCP has two digestion systems,
one comprised of rectangular digesters and one of circular, which are shown
in Figure 1. The digesters have a combined capacity of 249,000 m3 (8.78
827
-------
million cu ft) and presently treat a primary sludge flow that averages
9500 m3 (2.5 million gallons) each day, as shown in Figure 17. After di-
gestion the sludge is dewatered by centrifuges and the wet cake is either
air-dried and composted on open fields or truck hauled to a landfill for
disposal. The composted solids are sold to a local fertilizer company for
use as a soil conditioner and fertilizer base.
B. SECONDARY TREATMENT FACILITIES
Construction is in progress for the secondary treatment facilities, Stages I
and II, which are shown in Figure 1. Presently the contracts awarded for
both secondary treatment facilities and waste activated sludge processing
facilities total almost 100 million dollars. Of this total, over 21.5
million dollars in construction contracts have been awarded recently for
facilities for flotation thickening and anaerobic digestion of the waste
activated sludge. Low speed scroll centrifuges have been selected for de-
watering the digested waste activated sludge and design of the facility has
begun.
II. ADVANTAGES OF ANAEROBIC DIGESTION
The basic advantages of anaerobic sludge digeston to the Districts are listed
and briefly discussed thereafter.
• Energy Recovery
« Sludge Storage and Equalization
a Reduced Odor Potential
® Reduced Health Risk
The anaerobic digestion systems at JWPCP presently produce 160,000 m^
(5.65 million cu ft) per day of digester gas of which' 50 percent is currently
utilized in the plant. Digester gas is used by reciprocating engines to
pump primary effluent to the ocean and in the future to secondary treatment,
and to generate approximately 50 percent of the electrical power used at
JWPCP. Digester gas is also used by boilers for digester heating. Presently
the remaining 50 percent of the gas is sold to a refinery adjacent to JWPCP.
The existing power plant is being replaced by a combined cycle total energy
plant (under design) which will increase the utilization of the digester gas
from the present 50 percent to 100 percent, as shown in Figure 3' '. Of
equal importance, the overall thermal efficiency obtained from the gas will
increase from approximately 23 percent at the present time to greater than
60 percent. This increase in thermal efficiency is achieved by using more
efficient prime movers and by recovering the waste heat for digester heating,
and miscellaneous building heating and cooling. This efficient and complete
utilization of the digester gas will provide almost 80 percent of the total
828
-------
energy requirements for the entire JWPCP after completion of the present
8.8 m3/s (200 mgd) secondary treatment expansion.
Since a minimum hydraulic detention time must be provided for the anaerobic
biological process, sludge is stored in the digestion tanks for a consider-
able number of days. This storage provides equalization of both sludge
characteristics and sludge flow. The benefits of equalization on downstream
sludge processes, such as dewatering, are significant in terms of economic
savings, reduced operational control requirements and increased performance.
Additional sludge storage capacity in excess of design is available in
the digesters at JWPCP by temporary use of gas space. Figure 13 shows that
a 1.2 m (4 ft) gas space exists between the sludge level in the tank and the
roof. Up to 0.6 m (2 ft) of this gas space can be used for temporary
sludge storage during unscheduled downtime of the sludge dewatering facility
and will provide up to 16,000 m3 (565,000 cu ft) of additional capacity.
Without this large reserve capacity, excessive storage of sludge in the
primary settling tanks would become necessary with resulting deterioration in
primary effluent quality and operational problems with sludge pumping from
the primary tanks.
The reduced odor potential from digested sludge has allowed the Sanitation
Districts to air-dry and compost approximately one-third of its dewatered
sludge on open fields at JWPCP. The operation is presently limited to the
site shown in Figure 2 because of space available and a need for further
improvements in odor reduction and odor control during the composting
operation.
The temporary storage of dewatered digested sludge is needed to eliminate the
need for around the clock hauling to the landfill and to provide wet weather
storage for the composting operations. In conjunction with a minimal chemi-
cal scrubbing system, odor release has not been a problem from digested
sludge stored in large silos at the sludge dewatering facility.
Compared with the handling of raw primary sludge, digested sludge provides a
reduced health risk to the public and especially to employees since the
anaerobic digestion process reduces pathogen levels'^).
III. DESIGN PARAMETERS AND CONSTRUCTION FEATURES
A. MASTER PLAN FOR CIRCULAR DIGESTERS
In the late 1960s, an expansion of the anaerobic digestion system at JWPCP
was planned to handle the increased sludge flow from additional primary sedi
mentation tanks and from planned future plant expansions.
The circular digestion system was chosen to be identical in process, opera-
tion and control to the rectangular digestion system which operates at high
organic loading rates. A simplified process flow schematic of the circular
829
-------
digestion system is shown in Figure 4 and consists of digestion tanks com-
pletely mixed by gas recirculation, uniformly heated by direct steam injec-
tion, and uniformly loaded by an automated sludge feed system. The sizing
and design criteria for the digestion tanks and individual systems are sum-
marized in Table 1 and discussed below.
The resulting master plan for the circular digestion system is shown in
Figure 5 and consists of circular digestion tanks and sludge pump stations
interconnected by pipe galleries, and a centralized control building which
also houses the boilers used for digester heating.
The first six of the circular digesters are in operation and presently digest
primary sludge. The remaining six digesters, which complete the master plan,
are under construction and will provide an additional 85,000 m3 (3 million
cu ft) of digester capacity to treat an average thickened waste activated
sludge flow from secondary treatment of approximately 0.044 rrr/s (1 mgd).
B. DIGESTER SIZING
The design geometry, size, and number of digestion tanks were selected after
an evaluation of the process requirements, economics, and site limitations.
The design selected provided the maximum total digester volume within a
limited area at minimum cost.
An average hydraulic detention time of 15 days was selected for the first six
circular digesters. This detention time is considered conservative design
for primary sludge digestion at JWPCP, since successful operation at deten-
tion times as low as 10 days has been achieved at high organic loading
rates. Successful operation is defined as the operation of the digesters
with a consistent volatile solids destruction of 50 percent or greater. The
volatile solids loading rate chosen per unit volume of design capacity was
2.4 kg/m3/day (0.15 Ib/cu ft/day), based on a 5 percent raw primary sludge
solids concentration with 70 percent volatility. This was again conservative
design because rectangular digesters at JWPCP have been successfully operated
at loading rates up to 6.4 kg/m3/day (0.40 Ib/cu ft/day). For waste acti-
vated sludge digestion, the design detention time and solids loading rate
are listed in Table 1.
Deep tanks were selected to minimize scum formation. By minimizing the tank
surface area through which the digester gas is released, the maximum surface
turbulence is developed while scum formation is minimized.
A circular design geometry was chosen with each digester having a volume of
approximately 14,160 m3 (500,000 cu ft), an inside diameter of 38 m (125 ft),
a side water depth of 11 m (36 ft) and a maximum water depth of 15 m (50 ft).
The circular tanks selected by the Districts' design staff were the largest
diameter and the deepest tanks which had previously been constructed as
digesters in the United States. Twelve of the tanks conveniently fit the
site available and were selected for the master plan as shown in Figure 4.
830
-------
C. MIXING SYSTEM
Continuous and complete mixing is of prime importance in successful anaerobic
digester operation at high organic loading rates. It performs several dis-
tinct functions, including:
• Providing intimate sludge-organism contact.
• Insuring uniform temperature distribution.
• Assuring by-product and buffering distribution.
t Minimizing scum formation.
• Minimizing bottom deposits.
• Preventing stratification.
Mixing can be accomplished in digesters either mechanically, hydraulically or
by gas recirculation. Mechanical mixers are usually propeller-type of either
upflow or downflow design and may be reversible. Hydraulic mixing is accom-
plished by external pumps which take suction from various lower elevations or
locations and discharge at various points at or above the liquid surface.
Gas mixing is used by the Districts and has become the most commonly used
type of mixing in the United States. Various systems are used to compress
the digester gas and inject it at some depth below the liquid surface.
Mixing may be continuous or intermittent, with continuous mixing practiced by
the Sanitation Districts. Intermittent mixing is acceptable only when di-
gesters are heavily loaded and the resulting gas production is sufficient
to keep the tank adequately mixed. Even in this case, other factors such as
erratic loading can trigger a partial upset which might have been avoided
with continuous mixing.
The circular digesters at JWPCP are mixed by gas recirculation through in-
ternal draft tubes, as shown in Figure 13. Each gas mixer in the circular
digesters consists of a 1.2 m (4 ft) diameter steel draft tube with gas
diffusion heads at a submergence of 3.7 m (12 ft), and a surface baffle plate
to provide for energy recovery. The gas mixers for the circular tanks are
similar in design but larger than the gas mixers used in the rectangular
digesters at JWPCP.
Prior to design of the circular digesters, a visual model study was con-
ducted at the California Institute of Technology to investigate different
multicellular configurations of gas mixer units. Because it was not possible
to accurately model gas recirculation rates and establish power requirements
in this laboratory investigation, two different mixing unit configurations
were incorporated into the digester design for full scale evaluation. Tank
No. 1 was constructed with 9 gas mixer units while Tank Nos. 2, 3, and 4 were
each constructed with 5 gas mixer units with provisions for four additional
mixer units. Three gas compressors were installed on Tank Nos. 1-4 to allow
831
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for varying the total gas recirculation rate between 1.1 and 3.8 m3/s (2400
to 8100 cfm).
During 1973 and 1974 the Districts conducted a full scale field investigation
on Tank Nos. 1-4 to compare the two mixing designs and to determine the
effect on mixing efficiency of gas recirculation rate and number of gas mixer
units. The study included the following:
• Measurement of active digester volume and the time required to achieve
complete mixing of the digester contents using a fluoride salt tracer.
0 [Measurement of the depth of bottom deposits in the digesters with re-
spect to time.
• Monitoring of gas production and close control of digester loading
rates.
Based on the results of this study, it was concluded that 1) the future cir-
cular digesters should each be designed with a total of 5 gas mixer units and
2) all existing and future circular digesters should be operated at a gas re-
circulation rate of 1.4 m3/s (2900 cfm)H)- Figures 6, 7, and 8 show the
recommended mixing system design for the circular digesters.
Probably the most significant observation of this study was that gas recir-
culation rates in excess of 3,4 m3/s (7300 cfm) did not prevent the buildup
of bottom deposits. The study also determined that the mixing system
design recommended for the circular digesters provides an individual cell
turnover time of about 24 minutes and a complete tank turnover time of 2 to 3
hours.
D. HEATING SYSTEM
The purpose of the heating system is to raise the temperature of the sludge
to a range which provides the optimum environment for the organisms.
Digesters are commonly operated in either the mesophilic range (30°C to 38°C)
or the thermophilic range (45°C to 57°C). Either range produces satisfac-
tory digestion, however difficulties in maintaining the higher temperatures
and some reported problems of poor solids-liquid separation have resulted in
the more common use of the mesophilic range. Provision of heat to maintain
the proper temperature may be accomplished by external or internal heat
exchangers or by direct steam injection.
The digesters at JWPCP are presently heated by direct steam injection which
is injected in the draft tube of the mixer units, as shown in Figure 6. Low
pressure steam from the boilers is piped to each mixer unit where it is
measured and then discharged through a separate submerged steam injection
line in the middle of the draft tube. Because the gas mixing system is
efficient, uniform heating is normally achieved by adding steam through only
one or two gas mixer units, usually the units closest to the sludge feed
points.
832
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In the future, waste heat from the previously mentioned combined cycle total
energy plant will be used to heat all the digesters at JWPCP. Digesters will
either continue to be heated by direct steam injection, using steam produced
from waste heat boilers; or by external spiral-type sludge heat exchangers,
using low level condenser waste heat from a steam turbine.
E. FEED SYSTEM
Continuous or frequent incremental feeding is vital to satisfactory opera-
tion. Feeding is accomplished at JWPCP by adding sludge to each digester
several times each day. This is not so important from the standpoint of
possible intermittent over or under feeding, as it is to equalize variations
in sludge concentration, sludge characteristics, and industrial solids. If
each digester is fed only once each day, the sludge fed to any one tank may
differ greatly from that fed to another tank. Thus by incremental feeding,
these variations are equalized.
Maximum solids concentration is essential for good digester operation. Pro-
viding as thick a feed sludge as possible provides for maximum detention
time, lowers heating requirements, and prevents dilution of buffering capa-
city and the excessive loss of seed organisms. The concentration of solids
in the sludge feed directly affects the digester detention time and loading
relationship. For a given digester volume, the only way to increase either
detention time or loading rate without decreasing the other, is to increase
the solids concentration in the feed sludge.
Sludge thickening may be accomplished either in the settling tanks or in
separate thickening facilities. Sludge blanket control, density meters and
timer controlled positive displacement pumps have been used successfully to
thicken the sludge in settling tanks. Separate sludge thickening facili-
ties typically use flotation processes, centrifuges, or vacuum filters. If
both primary and secondary sludges are involved, a combination of these
thickening devices may be necessary.
A uniform sludge solids concentration is needed at JWPCP throughout the day
to allow the digesters to be fed on a volumetric basis, thus permitting easy
measurement and control. For the raw primary sludge this is achieved by in-
termittent sludge pumping, which is automatically controlled by nuclear
density gauges in conjunction with timers. A single large capacity centri-
fugal pump withdraws sludge in sequence from four to six primary tanks, as
shown in Figure 9. Timer controls initiate the pumping process, while a
density controller terminates the pumping process and provides a continuous
monitoring of the solids concentration.
The waste activated sludge (WAS) from the secondary treatment facilites at
JWPCP will be thickened to a minimum 3.5 percent by dissolved air flotation
prior to digester feeding, as shown in Figure 2. Polymer addition to the
flotation process will insure that a uniform and concentrated waste activated
sludge is fed to the digesters.
The uniform control of raw primary sludge concentration at JWPCP has allowed
digester loading to be successfully controlled by volumetric means using
833
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automatic incremental feed control systems. The two independent sludge feed
control systems for the circular digesters are shown schematically in Figure
10. Each digester can receive primary sludge or thickened waste activated
sludge (TWAS) in combination or separately, and is normally fed each sludge
in 10 equal increments each day. The volume of sludge fed to each digester
per feeding is manually set on individual incremental feed counters. Dif-
ferent digester loadings are achieved by different settings of these incre-
mental feed counters.
The following is a brief description of the sequential feeding operation for
the circular digesters, as shown in Figure 10. Both raw primary sludge and
TWAS are pumped through separate piping systems and discharged into the top
of each digester, as shown in Figure 11. The digester feed pumps start
and stop automatically, based on sludge levels in their respective wetwells,
and pump at constant flow rates. When a digester has been fed the volume of
sludge set on its incremental feed counter, the feed valve to the next
digester in the sequence is automatically opened and the preceding feed
valve is automatically closed. In the same manner as described above, the
individual control system for both sludges will feed each digester the amount
indicated on its incremental feed counter. After completion of each cycle
through the digesters, the control system switches back to the beginning of
its sequence and repeats the cycle beginning with the first digester. The
feed control systems for both the rectangular and circular digesters feed
all the sludge in preset proportions to all the digesters in service.
With good uniform control of solids concentration, incremental feeding, volu-
metric measurement, and good sampling to determine average solids concentra-
tion; the sludge loading of individual digesters at JWPCP is controlled at
desired rates from day to day.
F. STRUCTURAL DESIGN FEATURES
The major structural design features for the circular digesters at JWPCP are
described below.
1. Roofs. Digester roofs are the fixed type with flat slab reinforced con-
crete construction. Each roof is supported by an exterior wall at its
perimeter and by interior reinforced concrete columns, as shown in Figures 12
and 13. The roof is designed to support gas compressor equipment and piping,
and sits on a continuous neoprene pad at the wall to allow for movement of
the wal 1.
Since the roof is gas tight, it is protected against structural damage by gas
seals which are designed to vent the digester gas in the tank to the atmos-
phere if the gas system pressure rises too high. Each digester has four gas
seals which are essentially U-tubes filled with water and are located as
shown in Figure 16.
2. Walls. The circular tank walls, shown in Figure 13, are prestressed con-
crete, vertically post-tensioned, and horizontally wrapped on the outside
834
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face with prestressing strands covered with gunite. The walls are supported
on neoprene bearing pads to allow for movement during post-tensioning and
filling of the tank.
The digestion tank design drawings for all twelve digesters also incorporated
a reinforced concrete wall design as an alternate to the prestressed wall de-
sign. Although never constructed, this alternate design insured competitive
bidding for the tank wall construction, a major cost item, and resulted in
economical construction of the digestion tanks.
3. Bottoms. Tank bottoms in the circular digesters are constructed of rein-
forced concrete and are of two different designs. Tank Nos. 1-6 have conical
shaped bottoms, which the Districts' operation staff has found difficult to
clean. As a result, the bottom design was changed to a hopper configuration
for the six tanks under construction. The hopper bottom design is shown in
Figure 12 and its design features are discussed below.
G. CLEANOUT SYSTEM
Over a period of time, scum and grit accumulate in digesters and reduce
the volume available for active digestion. Without removal of these items,
the active volume is eventually reduced to the point where overloading
occurs. Scum consists of a floating mat of sludge, grease, rags, plastic,
and other materials. Slowing the rate of accumulation is achieved primarily
by adequate mixing.
A portion of the grit which passes through the plant's grit removal facili-
ties accumulates in the digesters, constantly decreasing the active volume.
This in turn places an increasing stress on the digestion process. Maximum
efficiency of the grit removal facilities must be achieved to minimize the
grit load entering the digesters. Although the draft tube design is superior
to other types of mixers in maintaining sand suspension^), most grit enter-
ing a digester will be deposited on the bottom and cannot be resuspended.
The frequency of cleaning varies depending upon the rate of accumulation of
scum and grit which is in turn dependent on the efficiency of the grit re-
moval process, the sludge loading rate, mixing efficiency, and the quality
of solids received. Generally, cleaning must be done at intervals of three
to eight years. One way to determine the need for cleaning is to probe the
tank with rods or other devices through sample wells to determine the extent
of the scum and grit accumulations. Comparing the usable digester volume
with the volume required for the desired loading rate will also indicate the
need for cleaning. Occasionally digesters require cleaning because draft
tubes become clogged or partially clogged with rags and debris.
The digester tank bottom for Tank Nos. 7-12 is shown in Figure 12 and con-
sists of four hoppers which are designed to facilitate cleaning. Operational
experience in cleaning existing rectangular digesters with a variety of
hopper designs led to the configuration shown and the following design
features:
835
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• Horizontal walkways are provided around the perimeter of the hoppers,
allowing a safe and convenient work location for District personnel
during cleanout operations.
t Cleanout and recirculation piping are installed in cleanout galleries
under each digester, as shown schematically in Figure 14. The gallery
provides complete access to all cleanout piping, which is subject to
clogging during cleanout operations.
• High and low pressure primary effluent pipe connections are provided
inside the digesters for washdown and dilution water purposes.
• Large openings, 2.44 m (8 ft) in diameter, are provided in the tank
tops for personnel access to the tanks during cleaning, as shown in
Figure 16. Access to the bottom is normally provided by either a
specially designed ladder with safety cage, which is lowered by crane
through the large access openings and secured to the walkway, or by a
special type of moving platform which is air motor driven allowing
personnel to enter the digesters safely and easily.
During tank cleanout, grit and other material are pumped from the hoppers by
the cleanout pump through the drain piping shown in Figure 14. High pres-
sure primary effluent is used to breakup the top scum layer as shown in
Figure 15, while low pressure primary effluent is added to dilute the de-
posits to approximately 6 percent solids for pumping to the digester clean-
ings facility. High pressure primary effluent is also used to backflush the
hopper drain lines when clogging occurs.
The cleanout pumps are connected by a force main to a central digester clean-
ings facility shown in Figure 1. This facility is shown schematically in
Figure 15 and includes the following three stages:
• Stage 1 consists of self-cleaning, non-clogging sidehill screens called
Hydrasieves. Larger solids in the flow stream are removed by the
screens and conveyed to trucks for landfill disposal.
• Stage 2 utilizes cyclone separators with dewatering screws, which
together are called Hydrogritters, to remove the grit from the flow
stream. The grit removed is also conveyed to trucks for landfill
disposal.
• Stage 3 utilizes dissolved air flotation with polymer addition to re-
move the remaining floatable and settleable material and a substantial
portion of the suspended solids. Final effluent from the flotation
system contains 200-300 mg/1 of solids and is discharged to the inlet
works head of JWPCP.
H. SAFETY FEATURES
As previously discussed, anaerobic digesters produce combustible methane gas
which is explosive and contains hydrogen sulfide. Therefore, the following
836
-------
safety features have been incorporated into the design of the circular
digestion system at JWPCP:
• Electric motors and lighting fixtures on the tank tops are explosion
proof design.
• Explosion proof portable blowers are used to ventilate the digestion
tanks during cleanout and provide 23.6 m3/s (50,000 cfm) of fresh air.
• Pipe galleries shown in Figure 5 are continuously ventilated by a large
positive ventilation system which is alarmed on failure.
I. MISCELLANEOUS DESIGN FEATURES
The following design features are in addition to those already discussed.
• The gas system at JWPCP consists of flow meters and condensate traps
at each digester, a looped piping system around the plant, two waste
gas burner stations, and metering of digester gas at all usage points.
The waste gas burners are only needed when normal gas usage is inter-
rupted .
• Each tank is equipped with nine sample wells as shown in Figure 16. A
sample well consists of a seal pipe that extends below the sludge sur-
face to prevent escape of digester gas when samples are withdrawn. A
hookup to the compressed digester gas is provided to allow flushing the
sample well before drawing a sludge sample.
• Each tank is equipped with four temperature wells and temperature
sensing units, as shown in Figure 16. Centralized temperature indica-
tion is provided for all digestion tanks in the control building shown
in Figure 5.
• Districts' field studies have shown that foaming in digesters receiving
waste activated sludge should be minimal, providing that good mixing,
uniform temperature and uniform feeding are maintained. However, tem-
porary foaming may occur during startup of the digesters with waste
activated sludge and during other periods of non-uniform operation.
Should foaming occur, the level in the digesters can be lowered from
the normal level of 1.2 m (4 ft) below the roof to a lower level of
2.4 m (8 ft) below the roof, as shown in Figure 13. This lower level
will allow normal operation of the digestion system to continue during
periods of temporary foaming while protecting against foam entering the
gas system or gas recirculation compressors.
837
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IV. DIGESTER CONTROL AND OPERATING EXPERIENCE
A. PROCESS CONTROLS
1. Temperature Control. The methane producing bacteria are particularly
sensitive to changes in temperature. Rapid fluctuations in temperature can
cause an imbalance between the acid and methane producing bacteria resulting
in a digester upset. For mesophilic operation, the optimum temperature range
is 30°C to 38°C (85°F to 100°F) with temperatures being maintained at about
35°C (95°F) in most installations. Satisfactory operation is possible
anywhere within the range, but to allow time for the organisms to become
acclimated, temperature changes greater than 0.5°C (1°F) per day should be
avoided.
To achieve adequate control, digester temperatures should be monitored daily.
Controls can be automatic, semi-automatic or manual. Where heating is done
by external heat exchangers, a slight change in the setpoint is all that is
needed to produce a minor temperature change. Manual control of direct steam
injection is used at JWPCP. Operator experience is required to adjust the
steam flow rate properly to produce the desired temperature change.
2. Mixing Control. The degree of control is dependent on the type of mixing
device used. For mechanical mixers, control is limited to the number of
hours operated per day and whether the upflow or downflow mode is used.
Where gas mixing devices are utilized, the number of units in operation can
be varied, as can the number of hours operated per day and the amount of
gas injected per draft tube or injection point.
In addition to visual observation, which indicates only surface conditions,
there are several methods to determine if mixing is adequate. One of the
best methods is by measuring the temperature at various depths and at several
locations in the tank. Any variation greater than 1 or 2°C (2 or 4°F) is
indicative of poor mixing and possible future operational problems.
A similar analysis of mixing conditions can be made by taking samples at
various locations and depths thoughout the tank and analyzing the samples for
total solids or other components. This method is more time consuming, but it
provides information on scum and grit deposits while the temperature profile
does not.
A third method utilizes radioisotope or salt tracers to determine detention
and mixing times. This is a relatively simple method but it can lead to false
conclusions unless the volume of scum and grit deposits are known with some
degree of accuracy.
3- Loading Control. For medium to large installations automated feed sys-
tems are normally provided. However, to insure satisfactory performance, a
program of sampling, meter calibration and equipment maintenance is neces-
sary. This program must involve all components of the system including the
solids thickening facilities, incremental feed system and all measuring
838
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and recording instruments. Failure to quickly observe and correct malfunc-
tions can result in digester upsets. Frequent calculations must also be made
to insure operation within the proper control ranges.
B. ANALYTICAL CONTROLS
Figures 17 and 18 graphically display the results of analytical tests per-
formed to determine the conditions and efficiency of the digestion systems at
JWPCP. Value and use of each type of test is described briefly below.
1. pH. Daily determinations of pH are considered normal practice in di-
gester operation. Due to the normal buffering capacity, the pH changes quite
slowly and thus it is not an indicator of digester operation to be relied on
by itself.
2. Alkalinity. This test measures the relative buffering capacity of the
system. It too is a relatively insensitive indicator, even when used in
conjunction with pH measurements.
3. Volatile Acids. The volatile acids content of the digesting sludge is
probably the most universally used indicator of digester condition. Proper
operating levels of the volatile acids will depend on sludge feed character-
istics, detention time and other operational variables. There are a variety
of methods used for determining the volatile acid content. Each method has
its own range to be used as a guideline for successful operation. All fall
within the range of 50-150 mg/1 with an upper limit for any system of
approximately 800 mg/1.
4. Volatile Acid-Alkalinity Relationship. The ratio of volatile acids to
alkalinity and particularly the rate of change in this relationship is an
excellent means of determining the digester environment. Each plant will
have its own characteristic ratio for proper operation. Generally the ratio
will be less than 0.1 and any increase above 0.3 to 0.4 indicates severe
stress and the need to take immediate corrective action. As the ratio
approaches 0.8, there is a depression in pH indicating the digester is then
in serious trouble. Remedial action at this time may be too late to stop a
major decline in digester efficiency.
5. Gas Production. Digester gas usually has a composition of 35-40 percent
carbon dioxide and 60-65 percent methane with trace amounts of hydrogen sul-
fide and other gases. The heat value may range from 18,600 - 26,000 kJ/m3
(500-700 BTU/cu ft) depending on the type of waste treated and degree of
digestion accomplished.
Both the quantity and quality of the digester gas are indicators of digester
conditions. Any sharp drop in gas production , as measured by individual gas
meters, is cause for alarm and indicative of potential problems. Under nor-
mal conditions the gas produced will have a fairly uniform composition of
methane and carbon dioxide. Any deviation from this norm, such as an in-
crease in the carbon dioxide content, is a warning of impending trouble and
indicates the need for investigation.
839
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Calculations should be performed routinely to determine the amount of gas
produced per unit of volatile matter destroyed. Expected production ranges
from 750 I/kg (12 cu ft/lb) to 1,125 I/kg (18 cu ft/lb), depending on the
sludge characteristics and operational conditions.
Fats and greases yield the highest gas production, carbohydrates fall in the
middle, and proteins produce the least quantity of gas. A long range decline
in gas production per unit of volatile matter destroyed generally indicates a
change in sludge characteristics.
6. Volatile Solids Destruction. Volatile solids destructin is a measure of
the amount of organic matter converted to the end products of water and gas.
It is not a tool for daily use in determining digester efficiency, but rather
for determining loadings and long-term efficiency. The percent reduction of
volatile matter is dependent on the sludge characteristics, detention time,
and digester operation. For primary sludges, a volatile solids reduction of
50-60 percent should be attainable. Due to the fact that secondary sludges
are more resistant to digestion, somewhat lower volatile destruction results,
as shown in Table 1.
C. PHYSICAL CONTROLS
1. Loadings. For any large system, the analytical tests chosen for control
of digester operation should be performed at least five days each week. When
the results of the tests are available, the conditions of each digester
should be assessed and the loadings for the next day should be determined.
For any digester that shows even minimal signs of stress, the loading must be
reduced slightly. Conversely, for digesters which show normal or healthy
conditions, the loadings may be gradually increased. If sufficient capacity
exists, the loadings can be adjusted from digester to digester on a daily
basis while maintaining good digestion efficiency at very high loading rates.
2. Toxic Wastes. Frequently toxicity is blamed for digester upsets, but
only rarely is it found to be the causative agent, particularly in large
treatment plants. Heavy metals are usually the prime suspect. However,
normal digester operation produces sufficient hydrogen sulfide which forms
insoluble compounds with the heavy metals making them unavailable to the
organisms. As long as hydrogen sulfide is present in the digester gas, heavy
metal toxicity should not be suspected. Strong organic bactericides, pesti-
cides and fungicides can be present in high enough concentrations to cause
toxicity. Cases of this type are normally associated only with small systems
with a large contribution from industries producing these types of chemicals.
Strong oxidants, such as nitrates and chromates, are considered to be toxi-
cants; but due to the sept'icity of digesting sludge, they must be present in
very high concentrations to cause trouble. Ammonium, potassium, sodium,
magnesium, and calcium ions also can be toxic if chemical agents are used for
pH control, particularly if ammonia or sodium componds are used. Care should
be taken to exclude high concentrations of known toxicants from the collec-
tion system by adequate source control.
840
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V. COSTS
A. CONSTRUCTION
Construction of Digestion Tanks 7-12, which complete the master plan as out-
lined previously, began in September 1979 and will be completed in three
years. These tanks are being constructed at a cost of $17,500,000, which
corresponds to $210 per m3 ($5.80 per cu ft) of digester capacity.
B. OPERATION AND MAINTENANCE
Table 2 presents operation and maintenance costs for digester operation at
JWPCP during 1979. Included is their relationship to total plant costs, as
well as unit costs per cubic meter (million gallons) of flow and cost per
metric ton (ton) of dry solids digested. Also shown is the amount of gas
production and its relative value compared to an equivalent amount of
natural gas at current prices. It is readily apparent from Table 2 that the
value of the gas produced is over 2.8 times the operation and maintenance
costs associated with its production.
VI. SUMMARY
1. The efficient and complete utilization of the digester gas at JWPCP will
provide almost 80 percent of the total energy requirements for the entire
plant after completion of the secondary treatment expansion.
2. The Sanitation Districts have achieved dependable operation and maximum
methane gas production from anaerobic sludge digestion by providing com-
plete mixing, uniform mesophilic temperatures, and uniform sludge feed-
ing. The design and construction of anaerobic digesters which can be
operated at high organic loading rates minimizes digester volume while
allowing a constant supply of digester gas to be produced for energy
recovery.
3. The Sanitation Districts' circular digestion system at JWPCP has proven
to be an economical design based on construction cost, land utili-
zation, operating costs, and operational flexibility.
841
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REFERENCES
1. Task I and II Reports - Waste Activated Sludge Processing Studies for
the Joint Water Pollution Control Plant. Los Angeles County Sanitation
Districts, Whittier, CA, June 1976 and October 1976, respectively.
2. Adams, G.M., Eppich, J.D., Garrison, W.E., Gratteau, J.C., "Total Energy
Concept at the Joint Water Pollution Control Plant." presented at the
51st Annual Conference of the Water Pollution Control Federation,
October 1978.
3. "Criteria for Classification of Solid Waste Disposal Facilities and
Practices; Final, Interim Final, and Proposed Regulations." Federal
Register, Vol. 44, No. 179, p. 53438, September 13, 1979.
4. Easley, R.S., Summary Report - Digester Mixing Evaluation at the Joint
Water Pollution Control Plant. Los Angeles County Sanitation Districts,
Whittier, CA, April 10, 1975.
5. Lament, A.W.G., "Air Agitation of Pachuca Tanks." The Canadian Journal
of Chemical Engineering, p. 153, August 1960.
842
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TABLE I . Design Criteria for Los Angeles County Sanitation Districts Circular
Digestion System at JWPCP.
Digestion Tanks
Tank Configuration
Number of Tanks
Diameter per Tank
Volume per Tank
Side Water Depth
Maximum Water Depth
Circular
12
38 m (125 ft)
14,200 m3 (500,000 cu ft)
llm (36 ft)
15.2 m (50 ft)
Data for Digestion of 100% Waste Activated Sludge
Detention Times (6 tanks in service)
At Average Sludge Flow
At Maximum Sludge Flow
Volatile Solids Loading 8 Average Flow
Volatile Solids Destruction
21 days
14 days
1.3 kg/m3/d (0.08 Ib/cu ft/d)
30%
Data for Digestion of 100% Primary Sludge
or Combined Digestion
Detention Times
At Average Sludge Flow
At Maximum Sludge Flow
Volatile Solids Loading
At Average Sludge Flow
Volatile Solids Destruction
15 days
10 days
2.4 'kg/raVd (0.15 Ib/cu ft/d)
50%
Digester Mixing System
Method
Number of Gas Mixers per Tank
.Type of Gas Compressors
Number of Gas Compressors per Tank
Capacity per Gas Compressor
Discharge Pressure per Gas Compressor
Number of Gas Compressors Operated (maximum)
Gas Recirculation w/Internal
Draft Tubes
5
Rotary Positive
Displacement
2
1.4 m3/s (2900 cfm)
52 kN/m3 (7.5 psig)
1
Digester Heating System
Method
Number of Boilers
Number of Boilers Operated (maximum)
Rating of Boiler (each)
Capacity of Boiler (each)
Boiler Fuel
Digester Temperature
Direct Steam Injection
3
2
370 kW (500 hp)
7800 kg/h (17,500 Ib/hr)
Digester Gas
35°C (95°F)
Digester Feeding System
Method
Number of Incremental Feedings per Day
Control System
Incremental Volumetric Feeding
10
Automatic Incremental
Feed Counters and
Valve Sequence Controls
Digester Cleanout System
Number of Cleanout Pump Stations
Type of Pumps
Number of Pumps for Two Tanks
Capacity per Pump
Horizontal Centrifugal
w/V-belt Drives
1
0.095 m3/s (1500 gpm)
843
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00
TABLE 2. Summary of 1979 Operation & Maintenance Costs for Anaerobic Digestion
at JWPCP.
Jan-June July-Dec
Total Digester Costs - $ 692,480 719,755
% of Total Plant Costs 13.50 14.00
Cost $103/m3 ($/MG) of Flow 2.75 (10.40) 2.85 (10.70)
Metric Tons (Tons) - dry wt. 88,300 (97,300) 91,800 (101,200)
Cost $/Metric Ton ($/Ton) - dry wt. 7.85 (7.10) 7.85 (7.10)
Gas Produced - 106 m3 (106 cu ft) 31 (1,080) 29 (1,029)
106 kJ (106 BTU) Produced 736,000 (698,000) 711,000 (674,000)
Natural Gas Value Equivalent
@ $2.85/106 kJ
($3/106 BTU) - $ 2,098,000 2,026,000
-------
a a
CO
*>
ui
rVWWW^
'-WvSAAT
f
J
A- PRIMARY SETTLING TANKS
B- DIGESTERS
C- SLUDGE DEWATERING
D- COMPOSTING SITE
E- SECONDARY TREATMENT
F- AIR FLOTATION
G- NEW TOTAL ENERGY PLANT
H- DIGESTER CLEANING FACILITY
FIGURE I . Site layout of Joint Water Pollution Control Plant
-------
POLYMER
CO
>£>
CTi
PRIMARY
SETTLING
TANKS
INLET
WORKS
GRIT
CHAMBERS
SECONDARY
TREATMENT
PRIMARY
SLUDGE
AIR
FLOTATION
TOTAL
ENERGY
PLANT
DIGESTER GAS
SLUDGE
DE-WATERING
DIGESTERS
GAS
ENGINE
DRIVEN
PUMPS
OCEAN
OCEAN
WASTE
ACTIVATED
SLUDGE
LANDFILL
COMPOST
AND
RECYCLE
FIGURE 2. Flow diagram of Joint Water Pollution Control Plant (1983).
-------
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(50)
0-
-I 3.2
(-45)
DIGESTER
GAS
EDISON
(4500KW)
ENERGY
USE
PUMPING
ON SITE
POWER
GENERATION
(I3500KW)
&HEAT
RECOVERY
EDISON
(4500KW)
FIGURE 3. 1983 JWPCP Energy Balance.
847
-------
CO
*>
CO
FROM AIR
FLOTATION
THICKENED WASTE
ACTIVATED SLUDGE
s-
RECIRCULATED
r- DIGESTER GAS
FROM PRIMARY
SETTLING
RAW PRIMARY
SLUDGE
TO OTHER
DIGESTERS
STEAM FROM
BOILER HOUSE
FROM OTHER
DIGESTERS
TO GAS SYSTEM
TO SLUDGE .^
DEWATERIN*
TO SLUDGE -
DEWATERING
FIGURE 4. Flow schematic of Circular Digestion System at JWPCP.
-------
CLEANOUT PUMP STATION
CO
GALLERY
FIGURE 5. Master Plan
Circular Digestion System
at JWPCP.
CONTROL BUILDING
DIGESTED PRIMARY
SLUDGE PUMP STATION
DIGESTION TANK
RAW PRIMARY SLUDGE
PUMP STATION —
DIGESTED WASTE ACTIVATED
SLUDGE PUMP STATION
-------
DIGESTER GAS
TO SYSTEM PIPING
GAS COMPRESSOR
COMPRESSED
DIGESTER GAS
PLAN
FIGURE 6. Digestion tank top at JWPCP
showing gas mixers and piping.
850
-------
APPROXIMATE
MIXING CELL
BOUNDARY
GAS MIXER
SLUDGE
FEED
POINT
SLUDGE
RUNOFF
PLAN
FIGURE 7. Digestion tank top at JWPCP showing mixing cell
configuration
851
-------
00
Ln
K)
SECTION
(SEE FIGURE 7)
FIGURE 8. Draft tube flow circulation pattern at JWPCP
-------
FROM OTHER
oo
01
PRIMARY
INFLUENT
)DENSITY
K GAUGE
DENSITY SIGNAL
SLUDGE PUMP
START &
PUMPING UNIT
TIMERS & DENSITY
CONTROLLER
T£> I AK I &
STOP SIGNAL
i
I
OPEN-CLOSE
SIGNAL
PRIMARY
EFFLUENT
SLUDGE BLANKET
PRIMARY SETTLING TANKS
_TAN.K DRAW
OFF VALVE
FIGURE 9. Schematic of a raw sludge pumping unit at JWPCP
-------
00
Ul
FROM WET WELL
DIGESTION TANK
INCREMENTAL FEED
COUNTERS AND
SEQUENCE CONTROLS
FLOW SIGNAL
FEED VALVE
FLOW METER
RAW PRIMARY SLUDGE
OR WASTE ACTIVATED
SLUDGE PUMP STATION
TO TANKS 4-12
OPEN-CLOSE
SIGNAL
TO TANK -#" I
TO TANK #2.
jXf-—^- TO TANK
FIGURE I 0. Schematic of the circular digestion tank feed control system at JWPCP
-------
RAW PRIMARY
SLUDGE FEED
POINT
THICKENED WASTE
ACTIVATED SLUDGE
FEED POINT
DIGESTED
SLUDGE RUNOFF
PIPING
FIGURE I I. Digestion tank top at JWPCP showing
sludge feed and runoff piping
855
-------
WALKWAY
PIPE GALLERY
BELOW WALKWAY
COLUMN
WALKWAYS
HOPPER
SLOPES
PLAN SECTION
DRAFT TUBE
STAiRS
FIGURE 12. Digestion tank hopper bottom at JWPCP
856
-------
CO
Ui
GAS SPACE
NORMAL LEVEL
LOW LEVEL
GRADE
HOPPER
DIGESTED SLUDGE
RUNOFF PIPING
'- PIPE GALLERY
SECTION B-B
(SEE FIGURE I I)
FIGURE I 3. Digestion tank cross section at JWPCP
-------
PRIMARY EFFLUENT (
CLEANOUT PUMP
WALKWAY
PLAN
DIGESTER DEPOSITS
JO DIGESTER
CLEANINGS
FACILITY
PIPE GALLERY
PRIMARY EFFLUENT
DILUTION WATER
SECTION C-C
FIGURE I 4. Circular digestion tank hopper and cleanout
gallery piping at JWPCP
858
-------
FLOAT TO SLUDGE
DEWATERING FACILITY
00
un
PRIMARY
EFFLUENT
HYDRASIEVE
CLEANOUT
PUMP
SURGE &,
MIXING TANK
EFFLUENT
TO PRIMARY-
SETTLING
SETTLED SLUDGE
TO SLUDGE
DEWATERING FACILITY
FIGURE 15. Flow schematic of Digester Cleanings Facility at JWPCP
-------
GAS MIXER
r MANHOLE
GAS SEAL
SAMPLE WELL
TEMPERATUR
WELL
ACCESS
OPENING
PLAN
FIGURE I 6» Digestion tank top at JWPCP showing access
openings and penetrations
860
-------
130
1400
MOO
800
10
FIGURE 17. JWPCP Digestion Parameters.
861
-------
4.6
w
E
0>
1.6
8.0
X
0_
7.0
300
ZOO
100
1979
JUL. AUG. SEP. OCT. NOV. DEC.
LOADING
A A A
A A JL. A
DIGESTING SLUDGE
VOLATILE ACIDS
DIGESTER GAS
ALKALINITY
40
CM
O
35 O
30
4000
3000 O)
E
2000
FIGURE 18. JWPCP Digestion Parameter, continued.
862
-------
SLUDGE COMPOSTING: PROCESSES AND FUTURE DIRECTIONS
Atal E. Eralp and Joseph B. Parrel 1
Wastewater Research Division
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268 USA
INTRODUCTION
Composting is the biological oxidation of organic substrates in an
aerobic environment (1). The dominant organisms are molds and thermophilic
bacteria. Because living organisms grow on the organic substrate, it must
contain the nitrogen, phosphorus, and potassium essential for growth as well
as certain trace elements. The process is remarkably insensitive to operat-
ing conditions, and can take place in static piles that are only occasionally
or never overturned for aeration as well as in frequently mixed windrows. A
characteristic of composting is the generation of temperatures higher than
ambient. Temperatures commonly reach thermophilic conditions (50-70 °C).
This creates a substantial advantage for composting when treating sanitary
wastes, because these temperatures destroy pathogens.
Composting of agricultural and animal wastes to produce a humus-like
product is a process that has been utilized by man from antiquity (2). As
anyone who has composted garden wastes is aware, the process transforms a
bulky nuisance into a reduced mass of a valuable soil conditioner. As con-
cern for environmentally and aesthetically acceptable disposal has developed
in the world community, interest has grown in applying this desirable process
to waste disposal. Composting primarily directed at converting sewage sludge
into a useful or easily disposed product was unknown in the United States
about fifteen years ago. Since then, development of sludge composting has
been rapid. Already several full-scale operations are underway and many more
are in the design stage. The process is probably receiving more attention
and serious consideration than any other treatment or conversion process de-
veloped in recent years.
The objective of this presentation is to review the state of the art of
sludge composting in the United States, consider the impact of developments
in Europe, and describe EPA's continuing activities to develop the technology.
Composting of Sludge and Solid Waste
In the period from about 1960 to 1970, there was strong interest in com-
posting of solid waste in the United States and in Europe (3). The process
863
-------
was combined with resource recovery of metals and glass from the solid waste.
Sewage sludge, raw or digested, was added when available to provide nutrients.
Virtually all of these enterprises in the United States have ceased operation.
Their failure is attributed to the lack of a market for the product. The ex-
perience in Europe has been similar.
The failure of these processes has provided guidance for the development
of composting processes for sludge. Solid waste is plentiful. Its abundance
is one of the reasons why composting of solid waste has been unsuccessful.
The large quantities of compost produced quickly saturate local markets and
the price of the product falls.
Another problem has been the poor quality of the composts from solid
waste. They have contained materials (glass, plastic, colored thread) that
are inert and identifiable. These substances remain after biodegradable por-
tions disappear and are aesthetically undesirable. In our development ef-
forts, we have not encouraged work with substances other than sludge that
would degrade the value fo the product.
Another competitive handicap for solid waste has been the relatively low
cost of alternative means of disposal. The composts had to sell for a good
price to offset the cost of composting. Unlike solid waste, processes to
convert sludge to innocuous forms, to use it, or dispose of it are all expen-
sive. Thus, reasonable costs can be borne for sludge composting without the
need to recover most of the processing costs by sale of the product.
Windrow Composting of Sludge
The traditional method of composting of agricultural products and solid
waste has been to pile the material to be composted into long rows (commonly
called windrows), roughly triangular in cross-section. This procedure has
been followed in windrow composting of sludge (4).
Oxygen for the composting process reaches the interior of the windrow by
natural circulation of air through the mass as well as by periodic mixing.
For circulation to occur and to maintain aerobic conditions, the pile must be
porous and of the proper moisture content. Sludge cake must be pre-mixed
with previously made compost, leaves, sawdust, or the like to achieve a
moisture content of about 60 percent. Besides accomplishing air exchange,
mixing also makes certain that all material in the pile is in the interior
at one time or another where high temperature will destroy pathogens. In the
first few days after the windrow is formed, mixing will likely be required
more often then later on; and about 5 to 20 "turnings" are needed during the
3 to 4 week composting period. Mixing is usually accomplished with a mobile
unit specially designed for mixing and turning compost. The windrows are
from 3-7 feet high by 7-15 feet at the base. There is no blanket of pre-
viously composted sludge either underneath or covering the windrow.
An outstandingly successful windrow composting operation has been car-
ried out by the Los Angeles County Sanitation Districts (5). At their
Figeroa Street plant, 100 dry tons per day of digested sludge is composted,
using previously made compost as a moisture-absorbing and bulking agent.
864
-------
Part of the reason for their success is the warm dry Los Angeles climate and
the use of a relatively high solids sludge cake. Windrow composting may per-
form better in more inclement parts of the United States if the operation is
protected from rain and if a moisture absorbing agent is used, preferably one
that also composts and adds its energy to the system.
The Beltsville Aerated-Pile Method
The aerated-pile method for composting sludge was developed by staff of
the U. S. Department of Agriculture's Science Education Administration at
Beltsville (USDA-SEA), in a cooperative effort supported by the U. S. EPA.
This method has been described in numerous publications (6,7) and will not
be described in great detail here.
In this process, air is drawn through a deep pile comprised of carefully
premixed sludge and a bulking agent (such as wood chips) by means of blowers
and air pipes placed underneath the pile in a porous base such as wood chips.
The pile is constructed of carefully premixed sludge and bulking agent. It
is then covered with a blanket of unscreened previously composted material,
and is not mixed again unless the mixture for some reason did not adequately
compost. This configuration is diagrammed in Figure 1. An extended aerated
static-pile configuration is recommended for large installations. Essen-
tially, adjacent individual piles are built onto one another. This extended
configuration reduces the need for cover material by as much as 50 percent
and the need for composting pad space by 50 percent. Details of the method
are presented elsewhere (7).
A blanket of unscreened composted sludge is used to insulate the piles
so that all the parts of the composting sludge will obtain a temperature of
55 °C in the coldest zone for a minimum of 2 days. The compost blanket also
screens out malodorous volatile compounds that may be released from the pile.
Total height of static piles should not exceed 12 feet including the base
material qf the blanket.
A pile of screened composted sludge is needed to adsorb the odor that
comes from the blower that draws air through the pile. Approximately one
cubic yard of screened composted sludge is needed for every 4 dry tons of
sludge in the static pile. This odor adsorbing pile will cause too much
back pressure and will not adequately remove odors if the moisture content is
in excess of approximately 50 percent.
Presently the most successful sewage sludge composting operations are
both simple and flexible in design and operation and are based on the static-
aerated pile and windrow techniques. In Table 1, locations where composting
is successfully practiced in the U.S.A. are listed together with selected
characteristics of operations.
865
-------
SCREENED
COMPOST
WOODCHIPS
AND SLUDGE
PERFORATED
PIPE
WATER TRAP
FOR CONDENSATES
FILTER PILE
SCREENED COMPOST
"
,t
2H
fr - ~ -- -
Ll
^ A« Mrrnrn
I---L--,—
.....J!
• • .- - fc
/\
^
i
>0iior Fflt«r
Blow«r
PLAN VIEW
CROSS SECTION A-A
I -JH/2 f» |
[- 2H *»|
CROSS
SECTION
B-B
Figure 1. Beltsville Forced-Aeration System
866
-------
TABLE 1. SELECTED CHARACTERISTICS OF SEWAGE SLUDGES AT STUDIED COMPOSTING FACILITIES
oo
Location
Static Aerated Pile
Washington, DC
Beltsville, MD
Blue Plains
Camden, NJ
Bangor, ME
Durham, NH
Windsor, Ontario
Windrow
Los Angeles, CA
Upper Occoguan, VA
Composting
Mode(a)
E
E
E
S1udge(b) Dewatering Mode
A
Raw
P+S+CP
P+S+CP
P
P
P
P
Anaerobically
Digested
P
AWT
vacuum filter
vacuum filter
belt press
vacuum filter
coil filter (CF)
centrifuge + CF
vacuum filter
solid bowl/
basket centrifuges
filter press
(a) E - Extended static aerated pile
A - Aerated windrow
(b) P - Primary
S - Secondary
CP - Chemical precipitation of phosphate
AWT - P+S+CP+ ion exhange + filtration + C adsorption
(c) %VS - Percent of total solids present that are volatile
Solids
Content
23
40
75
40
Sludge
Composition
Lime Fed 3
0
35
17-24
17-24
24-28
22-28
20
20-25
55
55
77
60
_
50
25
25
0
1
10
7
8
8
0
0
5
8
0
5
-------
Guidance for Unconflned Sludge Composting Processes
Because of the importance the deep-pile and windrow composting systems
are assuming in the United States, it is worthwhile to present some guidance
based on experience gained thus far with these rapidly developing processes.
The U. S. EPA's Office of Water Program Operations is preparing a technical
bulletin on sewage sludge composting. This bulletin will provide guidance to
Regional EPA Administrators, local authorities, and consulting engineers in
designing and operating municipal sludge composting systems.
It is recognized that as more experience is gained the guidance will be
revised. Nevertheless it usefully summarizes experience gained so far in the
U.S.A. Some of the highlights from the draft bulletin are presented below.
For pathogen control it is recommended that the temperature of the com-
posting sewage sludge should be at 55 degrees C or above for a minimum of 2
days to minimize pathogens. If in a windrow, the windrows should reach 55
degrees or above in the interior each time after 5 turnings during 15 of the
21-30 day composting period. (This suggestion is subject to change—the
number of days at 55° may be reduced.)
Experience has shown that composting by the static pile or windrow tech-
niques takes a minimum of 21 days to become adequately stabilized, for
achievement of reasonably lowered moisture levels, and for pathogen reduction.
The windrow operation may take a little longer time period than the static
pile system. Furthermore, both composting operations may take a little
longer during both wet and cold periods. One month storage of composted
sludge for curing and additional pathogen reduction has generally been neces-
sary after windrow composting and is desirable after static pile composting.
There are other conditions which are also of importance in achieving
good composting. These are:
1. Cleanliness (minimizes malodor, dust, spread of Aspergillus
fumigatus spores).
2. Proper blending with bulking agent to achieve moisture contents
of 40 to 65 percent to permit uniform penetration of air.
3. Proper aeration.
4. Avoidance of opening composting piles during unfavorable
meteorological conditions such as temperature inversion
and very calm air. For example, this often occurs during
summer in parts of the northeastern United States.
5. Keen sensitivity to the concerns of neighbors (screening
with trees and shrubbery; planting of flowers and grass;
and avoidance of noise, dust, and malodor).
6. Treatment with lime of particularly septic sludges or
septages prior to exposure on the pad for mixing.
868
-------
7. Back-up capability for temporary sludge disposal, such as
by landfilling or trenching, when composting is not possi-
ble due to breakdown, bad weather, etc.
8. A several day sludge storage capacity before composting to
avoid a necessity of operation on the wettest of days.
9. Enclose the screening operation to minimize dust.
10. Hard surface pad for active composting, preferably of
concrete.
European Within-Vessel Composting Processes
Composting is an aerobic biological process and, as such, depends on pH,
moisture, oxygen, and major and minor nutrients. All of these factors are
needed to be optimized for optimum composting process. The composting opera-
tions in U.S.A. are being conducted mainly in the open air, and there is
obviously no control over temperature, humidity, and precipitation. It has
been claimed that by composting within an enclosed vessel the above param-
eters can be better controlled and the time period can be reduced from 21
days to one week or even shorter. Additionally, effective odor control,
minimum labor, and low maintenance are among the advantages claimed for
within-vessel composting.
A few years ago, reports were received that within-vessel sludge com-
posting processes were receiving rapid acceptance in Europe. At this time,
one manufacturer (BAV) initiated sales efforts in the United States. To
evaluate these and other claims a review study of the status of European
practices on sewage sludge composting was conducted by Battelle Laboratories
under a contract with the U. S. Environmental Protection Agency (8). One of
the objectives of this study was to identify the existing composting prac-
tices in Europe and compile information on operating modes, effectiveness,
reliability, and costs.
Since the technology is relatively new and is evolving rapidly, a
variety of sources, in addition to the literature, were used to obtain the
necessary information. Discussions were held with composting process in-
ventors, license holders, plant manufacturers, and plant operators. Repre-
sentatives from Ministries on Environmental Affairs from France, Germany,
Italy, The Netherlands, United Kingdom, Sweden, and Switzerland were also
interviewed to obtain their evaluations and leads to new data on sewage
sludge composting. In addition, site visits by Battelle-Geneva, Battelle-
Frankfurt, and Battelle-Columbus scientists to selected operating plants were
made.
Of the seven European countries surveyed for sewage sludge composting
practice, West Germany is the center of activity with more than 30 commercial
within-vessel plants. Sweden follows with 20 which are either in operation
or in the planning and design stage; Switzerland has nine plants of which
eight are the Dano rotating drum process; France has five; the United Kingdom
has one; Italy and The Netherlands have none. These are plants which use
869
-------
sewage sludge as the predominant waste component. If municipal solid waste
(MSW) intensive systems are also included, these numbers are much higher.
In Table 2, the major European composting processes were presented
according to the process type.
TABLE 2. EUROPEAN SEWAGE SLUDGE COMPOSTING PROCESSES
Category
Process
Number of
Operating Plants
Within Vessel(a)
BAV 19
Carel Fouche Languepin 1
Roediger/Fermenttechnik 1
Schnorr Valve Cell 2
Societe General D'assainissement
et de Distribution (SGDA) 1
Triga 2
Weiss 3
Windrow
Rotating Drum(a)
Pressed Brick
Fermentation Cells
BIO-Manure
Hazemag
PLM
Buhler
Dano
HKS
Brikol lare
Prat
2
•"
9
2
2
1
[a) These processes usually include a final windrow cure.
In the following paragraphs, six European "within-vessel" processes are
briefly described. The information includes the unit sizes, operating his-
tory, and the plant locations.
Process - The Carel Fouche Languepin (CFL) Corn-
building composting plants since 1965. Fermentation takes
comprising five levels. A vertical set of
unit (or digester). Two blowers per
inject or draw air from each of the five cells fitted with air
ducts. The top cell is charged with the freshly pulverized MSW.
added to the MSW before feeding. The fermentation mass passes
the digester in five steps, and communication between cells
gratings. The residence time in the digester is
Carel Fouche Languepin
pany has been
place in cells arranged in blocks
five cells represents one fermentation
digester can
distribution
Sludge can be
vertically down
is achieved by tilting floor
870
-------
approximately a week. The only CFL plant which processes MSW and sludge is
the Montbeliard plant which has been in operation since mid-1977. The daily
capacity is 150 t/d or MSW and 5 t/d of sludge with a water content of 80 to
85 percent.
Development of a new digester--CFL is just beginning a research program
aimed at the development of a new digester for the fermentation of sludge.
This research is sponsored by the French Environmental Ministry. The pilot
digester will process 1 m-Vd of sludge mixed with carbon sources and/or
minerals and/or polystyrene spheres. The aim of this research is to obtain a
product similar to a peat because the French importation of peat is expen-
sive.
BAV Process - Biologische Abfallverwertungsges, mbH & Company (BAV) has
constructed at least 19 plants in West Germany within the past several years
and has at least five additional plants being designed or under construction.
Most BAV reactors are designed for capacities equivalent to populations of
30,000. However, BAV systems have been designed to service communities of
10,000 and to service cities of 110,000.
The BAV process has evolved from the general method that was patented by
F. Kneer (German patent No. 2253009, June 19, 1975). Essentially, the
process consists of aerating a mixture of dewatered primary sewage sludge,
sawdust, and cured compost in an open-top, cylindrical vessel. The dewatered
sludge, sawdust, and cured compost mixture slowly descends, by gravity,
through the vessel's length in about 12 days. The descending mixture is
aerated by compressed air which' is distributed at the base of the vessel.
The composting rate can be controlled, within limits, by the aeration rate.
A diagram of the reactor vessel and its components is presented in Figure 2.
A conveying screw is used to remove product at the base of vessel
mechanism. This screw rotates around the vessel's radius and brings the
compost product towards a center exit port. The product, after within-vessel
composting is placed in windrows for a curing period.
SGAD Process - In 1975 the "Societe Generale D'assainissement et de
Distribution" (SGAD) built a plant in Salon de Provence under a BAV license
to process sewage sludge and municipal solid wastes. Initial problems with
the extraction screw conveyor led to key modifications and a proprietary
design. No other plants have been built in recent years.
Salon de Provence plant - SGAD operates this plant which processes the
municipal solid wastes and the sludge for a population equivalent of 60,000.
The MSW is ground and screened. The larger fraction is fermented. The
latter fraction is mixed with sludge having a water content of 94 percent.
This mixture is then fed into two reactors of 600 m3. There is a buffer
storage between the mixer and the reactors. The temperatures at different
locations and the C02 content of the exhaust gases are recorded. The resi-
dence time in the reactor is about 15 days. The mixture is then removed and
sent to the curing piles. The curing is carried out in 2 m high piles
approximately 10 weeks without turning.
871
-------
Raw Material Distribution Rake
Raw Material Feed Port
(15-20) Temperature Probes
6
Aerator
(11-13) Gas Sensors for
02 + C02
1 Insulated
Container
•Temperature Recorder
Oxygen Cylinder
Finish Product Exit Port
Figure 2. BAV Composting Vessel
872
-------
Schnorr Valve-Gel 1 Process - There are two operating plants in West
Germany based upon the Schnorr Valve-Cell Process, one at Denkendorf and the
other at Rastatt. A third plant is under construction at Gaggenau. The
manufacturer is Fa. Dambach Industrieaniagen GmbH.
The fermenting towers used in the valve-cell process shown in Figure 3
are 10 m long, 4 m wide, and 15 m high and consist of 10 tiers, one above the
other. The floor of each tier consists of perforated valves which can be
opened and closed hydraulically. The fermentation mixture is fresh sludge
with a solid content of 22-25 percent plus ground-up bark with a diameter of
5-10 mm and is fed into the top tier. When the valves are opened, the
material falls onto the floor below.
At the start of the process, the towers are initially filled with an
equal mixture of dewatered sludge and ground-up bark. After the process is
established, a portion of finished compost is recycled back into the system
by mixing it with fresh sludge and bark in a 2:2:1 proportion. Thus, the
quantity of ground bark required for the process is reduced. The mixer, a
scrape conveyor track, is located below the sludge and recycle compost con-
tainers. The product (feedstock) from the mixer passes through a set of
rubber rollers before being conveyed to the top of the tower. The purpose of
running the feedstock through the rubber rollers is to further loosen the
material, by breaking any lumps which may have formed. This tends to keep
the feedstock fluffy, which thereby increases the opportunity for aerobic
composting.
Every third day, the content of the tower is let down one tier at a time
by opening the floor valves so that a residence time of 30 days results.
Every second tier is aerated from the front and the alternate tiers from the
back. Directing the air in this way ensures that it flows through the fer-
mentation material. The fermentation mixture is spread out in layers of 1 m
deep in each tier, and as it drops from tier to tier, further mixing and
loosening occurs. Temperatures of 70 °C and above are reached during a two-
week fermentation period; thus, the sewage sludge is made completely hygienic.
The temperature is utilized to control air flow to the process. Temperature
probes are attached at three places in the fermentation towers.
Roediger/Fermenttechnik Process - This process was developed by Profes-
sor Baader (Institute for Agricultural Technique, Brunswick) for animal
wastes and has been adapted for sewage sludge (Figure 4). Fa. Wilhelm
Roediger Industriehafen has constructed only one demonstration plant which is
located at Mittleres Wutachtal, West Germany.
Previously dewatered sludge is combined with dried returns in a double-
shaft mixer to obtain a mixture with approximately 50 percent water content.
The mixture is fed into the reactor by a vertical conveyor. Aeration in the
fermentation reactor is achieved by having floor grating. At certain inter-
vals during the fermentation process, the grating is set in motion and the
material falls through a catch funnel into a screw conveyor fixed below it.
The material is then fed back into the reactor via the vertical conveyor.
Air is blown through the grating at such a high rate that excess oxygen is
873
-------
1 biocell reactor
2 distributor
3 conveyor
^ sludge container
5 returns container
6 coagulant container
7 discharge conveyor
8 dump conveyor
9 sawdust conveyor
10 pumps
11 sawdust bunker
Figure 3. Schnorr Biocell System
874
-------
Sludge metering punp
00
•^J
ui
{sludge dematerlng J
Sludge
Dry
material
storage
Dryer
laterial (broken)
Breaker
Process flow sheet of the FERMENTECHNIK Syetem
FERMENTECHNIK
for Environmental Protection
EURAMCA INC.
Figure 4. Roediger and Fermentechnik Method
-------
supplied. The fermentation process reaches a disinfection temperature of
approximately 72-74 °C within 24-36 hours. The circulation process mentioned
above ensures that all material passes through this high-temperature zone
several times during the fermentation period. The material is then formed
into pellets and dried.
Triga Process - The reactor is a concrete tower divided into four com-
partments and is called a "Hygienisator." Figure 5 is a diagram of the Triga
composting reactor. The sludge refuse mixture is fed in at the top of the
tower. A concrete wall is used to provide thermal insulation and to assure
that design temperature is achieved quickly. The residence time varies from
4 to 10 days according to the composition of the mixture. Air is pulled out
of the top of the tower to produce an air flow from the bottom to the top of
the tower. The air-flow rate is controlled by the temperature in the bed.
At the start of the process, the air flow is regulated so that the tempera-
ture in the bed remains at 70-80 °C. A screw extractor at the bottom is used
to remove the product. The screw is externally mounted to permit better
access. The fermentation mass is recycled to avoid compaction at the bottom
of the tower. After the digestion, the product is cured to achieve addi-
tional stabilization. Since this process draws air through the reactor,
control of potential odor problem is much simpler, at the discharge of the
blower. At the beginning of 1978, two sludge-only plants were in operation
in France, although plants based on MSW have been in operation for about 10
years.
Summary Comments on the European Processes - The review of European
processes and a detailed examination of one of them revealed some interesting
information. It is without question that the processes work. They produce a
compost product which should find better acceptance than solid waste compost.
Municipalities are adopting the processes. They all appear to be expensive,
and a detailed analysis of one process showed total annual costs (including
amortization) to be several times the cost of the Beltsville Aerated Pile
method. Technical problems exist. For example, conditions are unlikely to
be uniform across the cross-section of the within-vessel reactors. Systems
that mix the mixture or recirculate it are more likely to produce a uniform
product. The processes generally show little economy of scale, so costs per
ton do not decrease much as plant scale increases. Nevertheless, it is
evident that within-vessel processes for sludge composting are successful and
worthy of consideration by municipalities in the United States.
Within-Vessel Systems in U.S.A.
Several solid waste-sludge composting systems have been available in the
United States for many years, but no systems were available specifically de-
signed for sludge. Recently some United States manufacturers have adapted
their processes to sludge composting, and some European manufacturers are
attempting to penetrate the U. S. market.
Metro-Waste - The Metro Waste composting system, which is marketed by
Resource Conversion Systems, Inc., is fundamentally a forced aeration static
pile system housed in an elongated rectangular container (Figures 6 and 7).
The loading, mixing, and unloading of sludge and bulking agent are
876
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1-2-12 belt conveyors
3 feed port
4 water spraying nozzles
5 temperature probe
6 aerator
7 screw extractor
8 axis
9 trolley
10 rolling path
11 finish product exit port
12 finish product conveyor
Figure 5. Triga Composting Reactor
877
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f—Building Line
New Material
' i BIO-nKACTORS / / TrenBTer Cnr -«-
—=9. rj / / —
U /'/ r
U Tripper // AR! -Loader -^j
1
' 1
jltl Stage
itrtx Mixer
Storape/Sh1pplng
Figure 6. Metro-Waste Bioreactor
878
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OD
^J
VD
Figure 7. Loading and Unloading of Metro-Waste Bioreactor
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accomplished mechanically by a conveyor system and an "agiloader" (9). This
system was originally developed in 1964 for municipal solid waste at Largo,
Florida, and later used for mixture of sewage sludge and solid waste. How-
ever, because of the lack of a market for composted solid waste, this and
two other operations were abandoned. Presently, Resource Conversion
Systems, Inc., is actively promoting this system for sludge application.
Paygro System - The Paygro system was originally based on a metro-waste
system. Modifications were made and the improvements were patented by Paygro,
Inc. Since 1972, bark and cow manure were composted and marketed as potting
soil. Composting facilities, which occupy about 40,000 square feet of en-
closed reactors, are located at South Charleston, Ohio. During the last
year, Paygro, through their manufacturing agent, the Henry P. Thomson Company,
have been experimenting with municipal sludge. Based on the preliminary
results, they expect to construct full-scale facilities for a municipality
during the next year.
Fermentechnick-Euramca - This European-developed system is being active-
ly promoted by Euramca, Inc., of Addison, Illinois. The system was described
above under European systems. Euramco, Inc., has a portable 5 m^ test unit
which can be used for preliminary studies. The unit was experimented on at
Los Angeles and other places but as yet has not been adopted for full-scale
operation.
BAV System - For a period, the BAV system was actively marketed in the
U. S. and Canada. There seems to be little marketing effort now. BAV appears
to be directing its efforts to a new approach based on passage of the mixture
to be composted through a horizontal reactor.
Future Activities Concerning Sewage Sludge Composting
The several activities planned or in progress by EPA's Municipal Environ-
mental Research Laboratory (MERL) are listed below.
1. Within-Vessel Composting. MERL is continuing evaluating European
systems under a contract with Camp, Dresser, and McKee, a Boston consulting
firm. They will be concentrating mainly on existing BAV tnoreactors in
Germany and a recently introduced tunnel reactor by BAV.
2. Metro-Waste and Paygro Systems. Paygro System is the only within-
vessel composting system (now composting mainly cow manure) operating on a
large scale that seems adaptable to a compost feed mainly comprised of
sewage sludge. For the summer of 1980, it is planned to evaluate the system
using sewage sludge from Columbus, Ohio.
3. Indices for Composting. To determine the progress of composting,
parameters conventionally used to indicate degree of sewage treatment or
sludge stabilization are normally used. These parameters are biological
oxygen demand (BOD), chemical oxygen demand (COD), caloric content of sludge,
volatile solids content, carbon to nitrogen ratio, etc. Although they suc-
cessfully indicate, for example, the progress of anaerobic digestion, their
suitability for composting has not been documented. Through cooperative
880
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agreements with municipalities or universities, investigations will be con-
ducted to identify the most significant parameters, so that the extent of
composting can be evaluated, and the performance of various composting
systems can be compared.
4. Optimize Static-Pile Composting. A project is now underway aimed
at evaluation and development of temperature control strategies to maximize
organic matter degradation in aerated static-pile composting. This is
directed by Drs. Melvin Finstein and John Cirello of Rutgers University. The
main objective of this proposal is to demonstrate that the composting
process can be hastened by using temperature control as a primary process
control parameter. Benefits expected from the successful completion of this
demonstration are: a) more rapid stabilization, thereby decreasing space
and facility requirements; b) insuring a well-stabilized end-product; and c)
minimizing the amount of process residue needing final disposition.
The above objectives will be accomplished by evaluating various tem-
perature control strategies while being mindful of the interrelationships
among temperature, moisture, and aeration. The field experiments will be
performed at the Camden, New Jersey, treatment plant site, using compost
piles specifically operated for this research.
5. Utilization of Compost. An extremely important subject, which is
outside the scope of this presentation, is the utilization of compost. The
composition of compost from sludge reflects the composition of the sludge
from which it is derived. Compost made from a sludge containing some toxic
metals must be used with caution, or possibly should not be made at all. An
interagency agreement is continuing with the USDA-SEA to investigate the
uptake of metals in crops grown on soil amended with compost made from
sludge.
6. Evaluation of New Technology. It is expected that Innovative and
Alternative Technology Program being conducted by EPA's Construction Grants
Division will result in construction of plants using new approaches to com-
posting, including within-vessel systems. MERL plans to grant funds to
municipalities to document the performance of these systems and publish
evaluations. At this time, no grants have been made but at least one appli-
cation is expected within a year.
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REFERENCES
1. Golueke, C. G., "Composting." Rodale Press, Emmaus, Pennsylvania (1972).
2. Goldstein, J., "Sensible Sludge." Rodale Press, Emmaus, Pennsylvania
(1977).
3. Wiles, C. C., "Composting of Refuse." In "Composting of Municipal
Residues and Sludges," Information Transfer, Inc., Rockville, Maryland,
p. 20 (1977).
4. Willson, G. B., and Walker, J. M., "Composting Sewage Sludge, How?"
Compost Science, p. 30, September-October (1973).
5. Horvath, R. N., "Operating and Design Criteria for Windrow Composting of
Sludge." In "Design of Municipal Sludge Compost Facilities," Information
Transfer, Inc., Rockville, Maryland, p. 88 (1978).
6. Epstein, E., et al., "A Forced Aeration System for Composting Wastewater
Sludge." Jour. Water Poll. Control Fed., 48, No. 4, 688, (April 1976).
7. Willson, G. B., et al., "Manual for Composting Sewage Sludge by the
Beltsville Aerated-Pile Method." A manual prepared by the U. S. Depart-
ment of Agriculture, Beltsville, Maryland. In press.
8. Battelle Columbus Laboratories, "Evaluation of Within-Vessel Sewage
Sludge Composting Systems in Europe." EPA No. 600/2-79-088 (1980).
9. Brown, V., Personal Communication (1980).
10. DeKemp, F., Personal Communication (1980).
882
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/9-80-047
3. RECIPIENT'S ACCESSION'NO.
4.TITLE AND SUBTITLE
PROCEEDINGS: SEVENTH UNITED STATES/JAPAN CONFERENCE
ON SEWAGE TREATMENT TECHNOLOGY
5. REPORT DATE
Decefnber 1980
6. PERFORMING ORGANIZATION CODE
7". AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
10. PROGRAM ELEMENT NO.
Cinti. OH
Washington,, DC
11. CONTRACT/GRANT NO.
12.SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory-Gin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Proceedings - May 19-21. 1980
14. SPONSORING AGENCY CODE
EPA/600/14
15.SUPPLEMENTARY NOTES Conference sponsored by Office of Int' 1 Activities, Office of Water
\ Waste Management (Wash,DC 20460); £ Office of Research £ Development (Wash,DC 20460).
rhis volume prepared § published by Office of Research § Development, Cinti. OH 45268.
16. ABSTRACT
As part of joint interests in environmental matters between the United States
and Japan, a Conference on Sewage Treatment Technology is held at intervals of about
18 month. This pbulication contains papers from the Japanese group and from the
American side that were presented at the Seventh Conference held in Tokyo, Japan.
Subject matter covered included innovative & alternative technology, regional
approaches, toxic wastes, health effects, combined sewer technology and reuse
of wastewater.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Tnnovative & alternative technology
regional approaches
toxic wastes
health effects
combined sewer technology
reuse of wastewater
b.IDENTIFIERS/OPEN ENDEDTERMS
c. COSATI Field/Group
Water pollution control
13B
3. DISTRIBUTION STATEMENT
To Public
19. SECURITY CLASS (This Report)
Unclassified
21. M£L OF PAGES
893
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
883
irU.S. GOVERNMENT PRINTING OFFICE: 1981—757-064/0239
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