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EPA/600/9-85/014
May 1985
PROCEEDINGS
NINTH UNITED STATES/JAPAN CONFERENCE ON
SEWAGE TREATMENT TECHNOLOGY
U
September 19-21, 1983
Tokyo, Japan
VJ
\J
OFFICE OF INTERNATIONAL ACTIVITIES
OFFICE OF WATER
WASHINGTON, D.C. 20460
CINCINNATI, OHIO 45268
OFFICE OF RESEARCH AND DEVELOPMENT
WASHINGTON, D.C. 20460
CINCINNATI, OHIO 45268
U S Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floof
Chicago, It 60604-3590
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
CINCINNATI, OHIO 45268
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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FOREWORD
The maintenance of clean water supplies and the
management of municipal and industrial'wastes are vital
elements in the protection of the environment.
The participants in the United.States-Japan cooperative
project on sewage treatment technology have completed their
Ninth 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 develop-
ments in the United States and Japan. These Proceedings of the
Ninth 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.
William D. Ruckelshaus
Administrator
Washington, D.C.
ill
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CONTENTS
t
Foreword ill
List of Japanese Delegates and Presentation Topics vi
List of United States Delegates and Conference Presentations viii
List of United States Delegates and Technical Seminar Presentations. . . ix
Joint Communique 1
Japanese Papers 3
United States Papers 429
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LIST OF JAPANESE DELEGATES AND PRESENTATION TOPICS
Delegates
Presentation Topics
Tsutomu Tamaki
Team Leader-Director
Department of Sewerage and Sewage
Purification
City Bureau, Ministry of Construction
Hiroshi Kurokawa
Head, Planning Division
Department of Sewerage and Sewage
Purification
City Bureau, Ministry of Construction
Itaru Nakamoto
Head, Sewage Works Division
Department of Sewerage and Sewage
Purification
City Bureau, Ministry of Construction
Keiichi Fukui
Head, Water Quality Control Division
Public Works Research Institute
Ministry of Construction
Dr. Ken Murakami
Chief, Water Quality Section
Water Quality Control Division
Public Works Research Institute
Ministry of Construction
Shunsoku Kyosai
Chief, Ultimate Disposal Section
Water Quality Control Division
Public Works Research Institute
Ministry of Construction
Daisaku Sugito
Head, Water Pollution Control Division
Water Quality Bureau
Environment Agency
Current Topics on Sewage Works in
Japan
Construction Technology Assessment
System and Develooment of Mechanical
Aerators for the Oxidation Ditch
Process
Current Status of Development in
Automatic Water Quality Monitoring
Equipment for Wastewater Treatment
Upgrading of Anaerobic Digestion
Process
Recent Developments in Japanese
Water Quality Management Policy
(Continued)
VI
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LIST OF JAPANESE DELEGATES AND PRESENTATION TOPICS (Continued)
Delegates
Presentation Topics
Muneto Kuribayashi
Head, Division of Research and
Technology Development
Japan Sewage Works Agency
Dr. Kazuhiro Tanaka
Chief, Section of Research and
Technology Development
Division of Research and Technology
Development
Japan Sewage Works Agency
Dr. Nagaharu Okuno
Head, Section of Engineering
Research and Development
Sewage Works Bureau
Tokyo Metropolitan Government
Hiroshi Ouchi
Senior Technical Advisor
Construction Division
Sewage Works Bureau
Yokohama City Office
Kazunari Matsunaga
Director, Construction Division
Sewage Works Bureau
Osaka City Office
Hiroo Nakagawa
Deputy Director, Sewage Works Bureau
Kobe City Office
Survey of Infiltration/Inflow in
Sewer Systems
Nitrogen and Phosphorus Biological
Removal Systems Research
Manufacturing Artificial Light Weight
Aggregates from Sewage Sludge
Study on Fluidized Bed Incineration
with a Drying System
Secondary Sewage Treatment Using
Contact Aeration Process
Pilot Plant Study on Treatment of
Supernatant from Thermal Sludge
Treatment Process
VII
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LIST OF UNITED STATES DELEGATES AND CONFERENCE PRESENTATIONS
Delegates
Presentation Topics
John J. Convery - Delegation Leader
Director
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Henry L. Longest
Director
Office of Water Program Operations
U.S. Environmental Protection Agency
Washington, D.C. 20460
Paul N. Guthrie
Director, Office of
Intergovernmental Programs
Department of Natural Resources
Madison, Wisconsin 53707
Cecil Lue King
Director
Research and Development
Metropolitan Sanitary District
Chicago, Illinois 60611
Paul F. Gilbert
Plant Engineer
Metropolitan District Commission
Hartford, Connecticut 06101
Gary R. Lubin
Environmental Engineer
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Removal and Partitioning of Vola-
tile Organic Priority Pollutants
in Wastewater Treatment
History of the Federal Construc-
tion Grants Program
Clean Water in Wisconsin
Energy Recovery, Reuse and
Conservation at Metro Chicago
Coarse Bubble to Fine Bubble
Aeration Retrofit
Energy Use at Municipal Waste-
water Treatment Plants - Over-
view and Case Studies
Addresses are correct as of September 21, 1983.
viii
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LIST OF UNITED STATES DELEGATES AND TECHNICAL SEMINAR PRESENTATIONS
(Continued)
Delegates
John J. Convery - Delegation Leader
Director
Wastewater Research Division
Municipal Environmental Research
Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Henry L. Longest
Director
Office of Water Program Operations
U.S. Environmental Protection Agency
Washington, D.C. 20460
Paul N. Guthrie
Director
Office of Intergovernmental Programs
Department of Natural Resources
Madison, Wisconsin 53707
Cecil Lue-Hing
Director
Research and Development
Metropolitan Sanitary District
Chicago, Illinois 60611
Paul F. Gilbert
Plant Engineer
Metropolitan District Commission
Hartford, Connecticut 06101
Gary R. Lubin
Environmental Engineer
Wastewater Research Division
Municipal Environmental Research
Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
I
Presentation Topics
rogress in Sequencing Batch Reactor
Technology
History of the Federal Construction
Grants Program
Clean Water in Wisconsin
Sludge Management Plans and Practices
at the Metropolitan Sanitary District
of Greater Chicago
Sludge Incinerator Fuel Reduction
Program
The Biological Aerated Filter -
Progress of Development in the
United States
Addresses are correct as of September 21, 1983
ix
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JOHN J. CONVERY, HEAD OF THE. U.S. DELEGATION
BEING GREETED UPON ARRIVAL CHUO WASTEWATER TREATMENT PLANT
AIGAWA REGIONAL SEWERAGE SYSTEM - OSAKA
VISIT OF U.S. DELEGATION TO A SLUDGE SMELTER
CHUO WASTEWATER TREATMENT PLANT - OSAKA
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BRIEFING OF U.S. DELGATION AT SMELTING FURNACES
CHUO WASTEWATER TREATMENT PLANT - OSAKA
A WORKING SESSION AT SITE VISIT TO THE
WASTEWATER TREATMENT PLANT - OSAKA
XI
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SITE VISIT TO PORT ISLAND NORTH PARK - KOBE
TOUR OF A CONTACT AERATION FACILITY
SUZURANDAI WASTEWATER TREATMENT PLANT - KOBE
xii
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JOINT COMMUNIQUE
Ninth United States/Japan Conference on
Sewage Treatment Technology
Wednesday, September 21, 1983, Tokyo, Japan
1. The ninth United States/Japan Conference on Sewage Treatment Technology
was held in Tokyo from September 19 to 21, 1983.
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
Wisconsin, and two representatives from local authorities (Metropolitan Sani-
tary District of Greater Chicago and Metropolitan District Commission of
Hartford).
3. Mr. T. Tamaki, Director, Department of Sewerage and Sewage Purification,
Ministry of Construction, was Head of the Japanese Delegation, which consisted
of seven National Government representatives (six from the Ministry of Con-
struction and one from the Environment Agency), two Japan Sewage Works Agency
representatives, and four local government officials (Tokyo, Yokohama, Osaka,
and Kobe) .
4. The Chairmanship for the Conference was shared jointly by Mr. John
Convery and Mr. T. Tamaki. Dr. T. Kubo, President of the Japan Sewage Works
Agency, attended as a special advisor and accepted the delegations from both
sides. Dr. Kubo served as the Japanese Chairman for the First through Eighth
Conferences.
5. During the Conference, both sides presented papers relating to joint re-
search projects on biological removal of specific contaminants, municipal sludge
disposal, instrumentation and automation, energy conservation, operation and
maintenance practices, and small flow treatment.
6. Principal topics of the Conference were (1) institutional structures and pol-
icies on sewerage and water pollution control and (2) technological developments
on energy conservation, toxic wastes, contact aeration, sludge treatment, manu-
facturing construction materials from sludge, infiltration problems in sewer
systems, etc. The discussions following each presentation were mutually produc-
tive and useful to both countries.
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7. The Conference was followed by the Technical Seminar, which was organized
by the Japan Sewage Works Association. Some 300 active members of the Japan
Sewage Works Association attended the Seminar, which involved presentations
by the U.S. Conference delegates and floor discussions.
8. An inspection visit was made to a metropolitan Tokyo facility producing
light-weight aggregates from sludge. Also planned for the U.S. Delegation
were field visits to wastewater treatment facilities in Fukuchiyama City, Nara
Prefecture, Osaka Prefecture, Osaka City, and Kobe City, and an inspection tour
of the Public Works Research Institute (Ministry of Construction) and the Na-
tional Institute for Environmental Studies (Environment Agency) in Tsukuba
Science City.
9. Recent exchanges of engineers between the two countries include a 3-week
visit to Japan by Dr. James A. Heidman, Municipal Environmental Research
Laboratory, USEPA, in 1982. Mr. A. Oshima, Japan Sewage Works Agency, plans
a year's stay in the United States beginning in October 1983. The United States
intends to send two engineers to Japan during the next 2 years. Both countries
agreed to continue the engineer exchange programs.
10. A decision was made to continue exchanging summaries of important research
reports and design guidelines on new technologies.
11. The United States proposed that the Tenth Conference be held in the United
States about October 1985.
12. A proceedings of the Conference will be printed in English and Japanese.
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JAPANESE PAPERS
CURRENT TOPICS ON SEWAGE WORKS IN JAPAN 5
Tsutomu Tamaki, Director, Department of Sewerage and Sewage
Purification, City Bureau, Ministry of Construction
RECENT DEVELOPMENTS IN JAPANESE WATER QUALITY MANAGEMENT POLICY. ... 43
Daisaku Sugito, Director, Water Quality Management
Division, Water Quality Bureau, Environment Agency,
Government of Japan
UPGRADING OF ANAEROBIC DIGESTION PROCESS 61
Shunsoku Kyosai, Chief, and Yoshio Ohshima, Senior Researcher,
Ultimate Disposal Section, Water Quality Control Division,
Public Works Research Institute, Ministry of Construction
PILOT PLANT STUDY ON TREATMENT OF SUPERNATANT FROM THERMAL SLUDGE
TREATMENT PROCESS 107
Hiroo Nakagawa, Deputy Director, Sewage Works Bureau, Kobe
City Office
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM 159
Hiroshi Ouchi, Senior Technical Advisor, Sewage Works Bureau,
the City of Yokohama
MANUFACTURING ARTIFICIAL LIGHT WEIGHT AGGREGATES FROM SEWAGE SLUDGE. . 195
Nagaharu Okuno, Head, and Akitoshi Yamada, Senior Researcher,
Section of Engineering Research and Development, Department
of Sewage Works, Tokyo Metropolitan Government
SECONDARY SEWAGE TREATMENT USING CONTACT AERATION PROCESS 227
Kazunari Matsunaga, Director of Construction Division, Sewage
Works Bureau, Osaka City Office
CONSTRUCTION TECHNOLOGY ASSESSMENT SYSTEM AND DEVELOPMENT OF
MECHANICAL AERATORS FOR THE OXIDATION DITCH PROCESS 267
Itaru Nakamoto, Head, Public Sewage Division, Sewerage and Sewage
Purification Department, City Bureau, Ministry of Construction
CURRENT STATUS OF DEVELOPMENTS IN AUTOMATIC WATER QUALITY MONITORING
EQUIPMENT FOR WASTEWATER TREATMENT 295
Ken Murakami, Water Quality Section, Public Works Research
Institute, Ministry of Construction
(Continued)
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JAPANESE PAPERS (Continued)
NITROGEN AND PHOSPHORUS BIOLOGICAL REMOVAL SYSTEMS RESEARCH 331
Kazuhiro Tanaka, Section Chief, Research and Technology
Development Division, Japan Sewage Works Agency
SURVEY OF INFILTRATION/INFLOW IN SEWER SYSTEMS 375
Muneto Kuribayashi, Director, and Hiromi Ito, Deputy Director,
Research and Technology Development Division, Japan Sewage
Works Agency
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Ninth US/Japan Conference
on
Sewage Treatment Technology
CURRENT TOPICS
ON
SEWAGE WORKS IN JAPAN
September 19-21, 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Tsutomu Tamaki
Director
Department of Sewerage & Sewage Purification
City Bureau
Ministry of Construction
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TABLE OF CONTENTS
1. INTRODUCTION
2. THE PROGRESS OF FIFTH FIVE-YEAR PROGRAM FOR
SEWERAGE CONSTRUCTION ............................................ 8
3. SEWAGE PROJECTS FOR WATER QUALITY CONSERVATION IN LAKES AND
OTHER SEMIENCLOSED WATER AREAS ................................... 13
4 . SMALL-SCALE SEWERAGE SYSTEMS ..................................... 19
5 . MODEL PROJECTS FOR SEWERAGE CONSTRUCTION ......................... 24
5.1 IMPRESSIVE SEWERAGE PROJECT AND GOOD-IDEA SEWERAGE PROJECT ---- 24
5 . 2 IN-SEWER TREATMENT MODEL PROJECTS ............................. 27
6. TREATMENT, DISPOSAL AND EFFECTIVE UTILIZATION OF SEWAGE SLUDGE ... 28
6.1 THE STATUS QUO OF SEWAGE SLUDGE TREATMENT AND DISPOSAL ........ 28
6.2 TRANSITION OF TREATMENT AND DISPOSAL OF SEWAGE SLUDGE ......... 30
6 . 3 SLUDGE UTILIZATION ---- . ....................................... 31
6.4 FUTURE STRATEGIES AND TACTICS FOR SLUDGE DISPOSAL ............. 33
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1. INTRODUCTION
"The socio-economic environment of Japan has changed drastically.
Japan now is facing severely limiting constraints on energy and
resources, financial difficulties, and other various national and
international problems, and at the same time is being urged to play a
more active international role as a developed and advanced country. The
Japanese government is determined to do its best for the benefits of the
world while solving domestic problems through administrative reform. For
the purpose of drastic reform and streamlining of its administration, the
Japanese government is also determined to organize a responsible body
consisting of the greatest minds of the country."
This is the Japanese government's expressed commitment which led to
the adoption at an extraordinary session of the Diet held in the fall of
1980 of a law concerning the establishment of an ad hoc administrative
reform commission.
According to the law, the 2nd Ad Hoc Commission on Administrative
Reform was started on March 16, 1981. On July 10, about four months
after its inauguration, the commission submitted to then Prime Minister
Zenko Suzuki its first proposal for administrative reform. The proposal
provided guidelines for the government agencies to prepare their budgets
for the fiscal year 1982. Specifically, the proposal directed the
government to formulate its 1982 budget without increasing taxes or the
amount of special government bond issues.
As a result, spending on public projects was cut below the level of
the previous year. The fiscal 1980 budget for public works had already
remained on the same level as that for the preceding year. For the four
years from that time up to the present, investments on public projects
have been pegged. The Ad Hoc Commission on Administrative Reform touched
upon the matter of the sewage projects in its report titled "Concerning
the Consolidation of Government Subsidies and Other Matters" prepared by
its Third Technical Committee. The report recommended that the
government should review the criteria for granting subsidies for public
works, including sewerage construction, establish a system of determining
the subvention ratios, scrutinize public works projects rigorously,
tighten eligibility requirements, and rationalize subvention services.
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It was also proposed that the beneficiaries-will-pay principle
should be more rigorously applied to the construction and operation of
sewage projects, industry-related public facilities and various other
public works with due consideration given to equity. In fact, we cannot
speak of present-day sewage works in Japan without speaking of Japanese
government policies or public opinion in favor of administrative reform.
The following shows the problems now confronting Japan's sewage works
under financial difficulties, and the measures taken by public
enterprises engaged in sewage treatment against various problems,
together with relevant remarks.
2. THE PROGRESS OF FIFTH FIVE-YEAR PROGRAM FOR SEWERAGE CONSTRUCTION
Mr. Tokuji Annaka reported on the antecedents and particulars of the
Fifth Five-Year Program for Sewerage Construction at the eighth US/Japan
Conference. As shown in Tables 1 and 2, the Fifth Five-Year Program is
based on the New Seven-Year Socio-economic Plan, and is designed to
increase the ratio of the sewer-served pupulation from 30% at the end of
fiscal 1980 to 44% by the end of fiscal 1985. The total investment
planned for the program is ¥11,800,000 million (inclusive of adjustment
program expenses of ¥590,000 million). As it turned out, the economic
situation had so deteriorated that the New Seven-Year Socio-economic Plan
had to be reviewed while the Fifth Five-Year Program for Sewerage
Construction was being formulated. In any event, the Fifth Five-Year
Program for Sewerage Construction was decided upon by the cabinet in
November 1981.
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Table 1 Five-year program for sewerage construction
(Unit: million yen)
Classification
Public sewerage
with government grant
by local municipalities
Regional sewerages
with government grant
by local municipalities
Urban storm water conduit
Specified public sewerages for
industries
with government grant
by local municipalities
Specified public sewerages for
conservation of the environment
with government grant
by local municipalities
Adjustment program expenses
Contingency allowances
Total
Total expenses for projects with
government grants
Total expenses for projects by local
municipalities
New program
(1981 - 1985)
8,391,000
5,161,500
3,229,500
2,230,000
2,073,900
156,100
460,000
27,000
18,100
8,900
102,000
76,500
25,500
590,000
-
11,800,000
7,790,000
3,420,000
Preceding
program
(1976 - 1980)
5,455,000
3,276,400
2,178,600
1,250,000
1,162,500
87,500
270,000
61,000
44,600
16,400
64,000
48,000
16,000
-
400,000
7,500,000
4,801,500
2,298,500
Table 2 Forecast of sewer service by the five-year program for
sewerage construction
Item
4
Total population (x 10 )
4
Sewer-served population (x 10 )
Coverage (%)
End of fiscal 1980
11,706
3,454
30
End of fiscal
12,286
5,390
44
1985
Note: including projects by local governments
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Table 3 shows the progress of the Fifth Five-Year Program for
Sewerage Construction. Every public undertaking is subject to tight
no-growth ceiling budgeting, not excepting the area of sewerage
construction. The budget for every sewerage construction project has
been cut every year; although more than half the period of the Fifth
Five-Year Program for Sewerage Construction has passed, the amount of
investments made so far is far less than half the planned value.
In order to complete the Fifth Five-Year Program for Sewerage
Construction, it will be necessary to secure funds equal to 55% of the
total planned costs in the remaining two years and to increase working
capital at an annual growth rate of more than 60% from 1984 ahead.
But an improvement in the public financial situation within the next
few years is a remote possibility (Fig. 1), and the Fifth Five-Year
Program for Sewerage Construction appears to have no chance of being
fulfilled.
Table 3 Progress of five-year program for sewerage
construction (Total expenses)
(Unit: million yen)
Classification
Planned
five-year
amount
fiscal
Amount
invested
1981
Pro-
gress
ratio
/»\
fiscal
Amount
invested
1982
Cumu-
la-
tive
pro-
gress
fiscal
Budget
1983
Cumu-
la-
tive
pro-
gress
ratio
ratio
Public sewerage
Regional sewerage
Urban storm water
conduit
Specified public
sewerage for
industries
Specified public
sewerage for
conservation of
environment
Total
Adjustment
program expenses
8,391,000 1,460,900 17.4 1,393,721 34.0 1,183,892 48.1
2,230,000
460,000
27,000
102,000
294,739 13.2 248,302 24.4
65,047 14.1 55,417 26.2
3,152 11.7
11,096 10.9
2,634 21.4
9,653 20.3
235,618 34.9
49,629 37.0
2,542 30.8
9,351 29.5
11,210,000 1,834,934 16.4 1,709,727 31.6 1,481,032 44.8
590,000
Grand total
11,800,000
Note: The amounts invested in and before fiscal 1982 include the
comprehensive national land development adjustment program
expenses, etc.
10
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50
40
30
20
10
National budget
Cumulative total of deficit-covering
national bonds issued
(original budget base)
Expenditures for
sewerage construction I
18,349
18,052,
Total expenditure
for sewage works
Note' The data through fiscal 5,307
1981 refer to actual values,
including incentives, etc.
The data for fiscal 1982
denote the original budget.
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77
79 80 81 82
-i 19,000
- 18,000
• 17,000
772
- 16,000
- 15,000
• 14,000
- 13,000
. 12,000
- 11,000
- 10,000
- 9,000
- 8,000
- 7,000
• 6,000
. 5,000
. 4,000
- 3,000
- 2,000
1,000
x 10 yen
Fig. 1 Japan's financial status, and the flow of expenditures for
sewerage construction
11
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Under these bleak financial circumstances, the municipalities are
feeling hardships as regards how to attain their objectives in sewage
works within a limited budget. The following is a list of major policies
proposed for fiscal 1983 sewerage construction projects.
(1) To promote the sewage projects in line with the Regional
Environmental Pollution Control Program and The Area-wide Pollutant
Load Abatement Plan.
(2) To promote the sewerage construction for the purpose of promoting
regional housing development. (To construct efficient sewerages to
meet the sizes and characteristics of local cities.)
(3) To promote the construction of sewers in developed areas for the
purpose of preventing inundation and improving urban amenities.
(4) To promote the construction of sewer systems in advance of new urban
development, and to promote the construction of sewer systems for
developed areas in connection with further large-scale housing
development.
(5) To promote the construction of sewerages in rural communities for
the purpose of protecting the water environment.
(6) To promote advanced wastewater treatment in order to achieve and
maintain environmental water quality standards and to prevent the
eutrophication of landlocked waters; to start model urban storm
water conduit projects for the treatment of domestic effluents by
"in-sewer treatment projects"; and to promote the improvement of
combined sewers.
(7) To promote the agricultural utilization of sewage sludge and
electric power generation with sludge digester gas for the purpose
of saving energy and resources.
(8) To continue model projects for the purpose of turning treated
wastewater to good use.
(9) To conduct investigations for the promotion of wide-area treatment
and disposal of sewage sludge in the Tokyo metropolitan area, Kinki
area, etc.
12
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3. SEWAGE PROJECTS FOR THE WATER QUALITY CONSERVATION IN LAKES AND OTHER
SEMIENCLOSED WATER AREAS
Public water supplies in Japan are generally improving in quality in
recent years, though there still remain many waters where the quality is
far from acceptable. Especially as regards landlocked waters such as
inland seas, semienclosed bays, lakes and reservoirs, eutrophication with
nutrient salts such as nitrogen and phosphorus and the resultant
proliferation of algae are exacerbating the water quality if the basins
have large pollutant sources. Lake Biwa, Lake Kasumigaura, Lake Suwa,
Tokyo Bay, Ise Bay, and the Seto Inland Sea are among the most notorious
landlocked waters in Japan. mhe pollution in these waters due to
eutrophication is almost past remedy. Unless proper government measures
are taken, their value as water sources or tourist resources will soon be
lost.
In order to fight this problem, the Seto Inland Sea Conservation Law
was passed in June 1978, and the Water Pollution Control Law was amended
to introduce the so-called total load control concerning COD in the
basins draining into Tokyo Bay, Ise Bay and the Seto Inland Sea. Along
with this, sewerage construction in these basins was given top priority;
in fiscal 1981, for example, about ¥521,300 million or about 34.4% of the
total national budget for sewage projects (¥1,513,800 million) was
invested into the Public sewerage systems, Regional sewerage systems,
Specified public sewerage systems for industries, and Specified public
sewerage systems for conservation of the environment in the 13
prefectures surrounding the Seto Inland Sea.
To prevent eutrophication, however, not only COD, but also nutrient
salts such as nitrogen and phosphorus must be stopped from entering into
the waters. In March 1980, the Environment Agency made public its basic
policy for eutrophication prevention. Since then, studies have been made
to set limits on nitrogen and phosphorus discharges into lakes and
reservoirs. In December 1982, Environmental water quality standards
concerning nitrogen and phosphorus in lakes and reservoirs were announced
as shown in Table 4, and the studies on effluent standards commenced.
13
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Table 4 Environmental water quality standards concerning nitrogen and
phosphorus in lakes and reservoirs
Item
Type
I
II
III
IV
Water uses
Natural environment protection, and types II
through V
Tap water Classes 1, 2, 3 (excluding special
uses)
Pisciculture Class 1
Bathing and types III through V
Tap water Class 3 (special uses) and types
IV and V
Pisciculture Class 2 and type V
Standard
Total
nitrogen
less than
0.1 rag/lit.
less than
0.2 mg/lit.
less than
0.4 mg/lit.
less than
values
Total
phosphorus
less than
0.005 mg/lit.
less than
0.01 mg/lit.
less than
0.03 mg/lit.
less than
Pisciculture Class 3
Industrial water
Irrigation water
Environmental protection
0.6 mg/lit.
less than
1 mg/lit.
0.05 mg/lit.
less than
0.1 mg/lit.
Measuring methods
As per speci- As per speci-
fied in fied in
Table 7a Table 8a
Remarks: 1. The standard values refer to annual average values.
2. As regards the irrigation water, the standard values for
total phosphorus do not apply.
Notes: 1. Natural environmental protection: Environmental protection
in resort areas etc.
2. Tap water Class 1: Water requiring simple purification as
by filtration.
Tap water Class 2: Water requiring ordinary purification as
by settling and filtration.
Tap water Class 3: Water requiring advanced treatment
including pretreatment. "Special" means special
purification operations capable of removing odors.
3. Pisciculture Class 1: For aquatic life such as salmon and
fresh river trout, etc. and for aquatic life coming under
the category of Pisciculture Classes 2 and 3.
Pisciculture Class 2: For aquatic life such as pond smelts,
etc. and for aquatic life coming under Pisciculture Class 3.
Pisciculture Class 3: For aquatics life like carp, gibel,
etc.
4. Environmental protection: Water not arousing discomfort in
daily life (including promenading along shoreline etc.).
(Tables 7a and 8a are omitted here)
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It goes without saying that sewerage is a viable measure against
water pollution in landlocked waters. While the conventional secondary
treatment plants are designed primarily for the removal of BOD, they can
also remove 20 to 40% of the nitrogen and phosphorus which are the major
culprits of eutrophication. In Japan, the sewer coverage is quite low,
and it is planned to push forward the construction of secondary treatment
plants for various landlocked waters for some time now. In some waters
which are desperately plagued with eutrophication, it will be necessary
to install advanced treatment systems capable of removing nitrogen and
phosphorus as well as BOD and SS. In fact, advanced treatment facilities
are already in use at the Konan Purification Center of the Lake Biwa
Regional Sewerage System and the Kohoku Purification Center of the
Kasumigaura Regional Sewerage System as shown in Fig. 2.
As regards Lake Biwa, the construction of advanced treatment
facilities for the removal of nitrogen and phosphorus has been under way
at the Kosei Purification Center since fiscal 1982.
Konan Purification Center, Lake Biwa Regional Sewerage System
Nitrified liquor recycled biological nitrification-denitrification process
Primary settling tank
Denitnfication tank
Nitrification tank
Secondary settling
tank
Rapid sand
filtration tank
Chlonnation tank
Kohoku Purification Center, Kasumigaura Regional Sewerage System
Alum
Conventional
activated
sludge process
Primary settling tank
Aeration tank
Secondary sPtthng
tank
Rapid sand
filtration tank
Fig. 2 Sewage treatment process flow employed for the Konan Purification
Center, Lake Biwa Regional Sewerage System, and the Kohoku
Purification Center, Kasumigaura Regional Sewerage System
15
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The demand for advanced treatment for the control of water pollution
due to eutrophication will grow in future, but the implementation of
advanced treatment technologies entails the following problems.
(1) A system for quantitative evaluation of the effects of advanced
treatment on the water quality improvement has not completely be
established. Specifically, it is difficult to work out an optimum
advanced treatment plan for a given water quality target.
(2) Sewer service is recognized as a minimum national requirement to
which every citizen is entitled for healthy and comfortable living.
In view of this, there are opinions arguing that increasing the
sewer coverage be given top priority. There are controversies over
whether the budgets be appropriated for the construction of advanced
treatment plants in specific areas or for extension of sewer
services to unsewered areas under the current situation of financial
difficulties. A general rule for the logical distribution of
budgets for sewerage construction has not been established yet.
(3) If the costs for maintenance and operation of advanced treatment
plants are to be counterbalanced by billing the users, such users
will be put at a disadvantage compared with those in other areas.
If only those living in lower basins can enjoy the benefits of water
quality improvement in the form of, say, water resources, by
advanced treatment in the upper basin, this will give rise to a
serious problem of who should bear the cost for water quality
improvement.
As regards (1), the Basic Study Commission on the Construction of
Sewerage for Eutrophication Prevention has been making studies for the
formulation of a basic plan for eutrophication preventive sewerage
systems since fiscal 1980.
So far, sewerage systems for the prevention of water pollution due
to BOD, COD and SS have been designed and engineered within the framework
of the Comprehensive Basin-wide Planning of Sewerage System. But the
basic plan for eutrophication preventive sewerage systems aims at
including nitrogen and phosphorus as pollutants to be controlled together
with BOD, COD, and SS.
16
-------
Fig. 3 shows a presumed procedure for formulating a basic plan for
an eutrophication preventive sewerage system. Compared with the analysis
of BOD, COD, and SS, pollution analysis relating to eutrophication has
differences or difficulties on the following points.
(1) It is said that compared with BOD, COD and SS, much of nitrogen and
phosphorus loads is generated by farmland, forests and other
non-point sources rather than by point sources.
However, the best methods of estimating the generated loads of
nitrogen and phosphorus from non-point sources have not necessarily
been established.
(2) Although nitrogen and phosphorus are considered less susceptible to
dissipation during transportation from sources to the receiving
waters compared with BOD, COD, and SS, not all of them yet reach the
landlocked waters because part of nitrogen will be lost by
denitrification or other processes, while phosphorus is accumulated
in the soil of the basin by adsorption, etc. The load run-off
ratio, which means the ratio of the pollutant load carried off into
the landlocked waters to the total pullutant load generated in the
basin, is hard to estimate logically so far as nitrogen and
phosphorus are concerned.
(3) Nitrogen and phosphorus running into the landlocked waters
invigorate the growth of algae, increasing the primary productivity
in a given body of water only to invite organic pollution. But
little is known about the quantitative relationship between the
influent loads of nitrogen and phosphorus and the level of organic
pollution. Among the currently available methods are statistical
methods including the critical nutrient loading model proposed by
Vollenweider, and the dynamic ecosystem model first tried by Di
Toro, et al. The models to be applied should naturally be selected
depending on the data available and the nature of the water quality
information to be forecast, but the criteria for such selection
still remain in nebulous.
17
-------
Fact-finding surveys for
population, industrial
activities, natural
conditions, etc
Basic data for pollution
analysis annual discharges,
water quality characteri-
stics, low flow, runoff
discharge, etc
Water supply-demand
plan, water resources
development plan, annual
low flow
Assumption of future frame-
work (population, industry,
etc }, future specific unit
of discharge, etc
Sev
verage coverage
Other measures
Limitations on location
Location of sewenge
facilities
Pnonties for construction
projects
Cost-account ing of
projects
Cost-to-benefit ratio
analysis
Preparation of final plan
Fig. 3 Survey flowchart for master planning of sewerage construction
18
-------
The Basic Study Commission on the Construction of Sewerage for
Eutrophication Prevention has been making progress with the study of all
these problems based on scientific data, and is expected to formulate a
manual for the Comprehensive Basin-wide Planning of Sewerage System to
fight off eutrophication problems.
As regards (2) and (3), it will be necessary to work out measures
that will be accepted to all. At present, the utility of sewerages is
being studied from the various angles including the axiology of water
quality conservation, for the purpose of formulating logical guidelines.
4. SMALL-SCALE SEWERAGE SYSTEMS
The sewer-served population in Japan was about 32% of the total
population at the end of fiscal 1982. But there are great regional
differences in sewer service between the local municipalities. The sewer
service in towns and villages is quite low compared with the cities. For
example, the sewer-served population in the 11 cities designated by the
Cabinet order, including Tokyo and Osaka is 73%, while that in the other
municipalities is a mere 20%.
Table 5 shows the frequency distribution of municipalities with
public sewerage in relation to population size. The rate of
municipalities with sewerage is 100% in the cities with a population of
more than 300,000, 53.4% in the cities with a population of 30,000 to
50,000 and 4.8% in the cities with a population of up to 10,000.
In the past sewer service in comparatively small rural communities
with a small population has remained quite low. The factors explaining
this are as follows.
(1) Such local communities could not afford to invest in sewerages
because they lacked the ways and means.
(2) The government promoted the construction of sewerages with emphasis
on the increase of sewer service, and was only ready to invest in
cost-efficient highly populated areas.
(3) Sewerage systems were designed and engineered for use for
metropolises, and sewerage technology for small cities was not well
developed.
19
-------
In recent years, however, people in rural communities all over the
country are beginning to voice their strong desire for the construction
of sewerages, which possibly will fit in with the movements of the
regional domiciliation scheme (a plan in which the country is divided
into several regions for domiciliation, and living infrastructural
facilities are developed to meet regional characteristics for the purpose
of encouraging people to live in these regions in order to use the
national land in a balanced way without overpopulation or depopulation
problems) extolled in the Third Comprehensive National Development Plan.
Since the mid-1970s, the so-called U-turn phenomenon (in which the
youths after graduation from universities in large cities go back home
and find jobs in their birthplaces) has become conspicuous. In addition,
urbanites who prefer country life are increasing in number. Living
standards in the country side have also improved. All these have
combined to increase the demand for flush toilets. As lifestyles in the
rural communities have changed, domestic wastewater and effluents from
septic tanks are beginning to pollute the public waters in the country.
While septic tank-type flush toilets have become increasingly
popular in the country in the last few years to the extent that their
population coverage surpasses the sewer-served population, there are many
cases in which the septic tanks are maintained and managed poorly.
The quality of the discharges from the septic tanks is poor under
the effluent standard of as high a BOD value as 90 mg/lit. The pollution
of public waters is seriously concerned, accordingly.
In view of this, the Ministry of Construction started a specific
public sewerage system for conservation of the environment in fiscal
1975. It is classified by purposes into natural environment protection
sewerage and rural community sewerage.
20
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Table 5 Number of municipalities having sewerage as classified by
population size
Public sewerages
Population
size
1 million
plus
500,000 to
1 million
300,000 to
N, 500,000
j__i
100,000 to
300,000
50,000 to
100,000
30,000 to
50,000
10,000 to
30,000
up to
10,000
Total
Total n umbei
of munici-
palities
10
9
36
136
213
251
1,089
1,510
3,256
Number of
municipali-
ties going
on sewage
projects
10
9
36
128
173
133
196
42
727
Specified public sewer-
age for conservation of
Total
Ratio
the environment
Number of
municipali-
ties with
sewerage
services
10
9
35
116
97
50
54
11
382
Number of
municipali-
ties going
on sewage
projects
0
0
3
3
8
8
25
32
79
Number of
municipali-
ties with
sewerage
services
0
0
2
4
3
2
2
6
19
Number of
municipali-
ties going
on sewage
projects
10
9
36
128
174
134
216
72
779
Number of
municipali-
ties with
sewerage
services
10
9
35
116
97
50
55
15
387
Ongoing
projects
100
100
100
92.8
81.7
53.4
19.8
4.8
23.9
Sewerages
in commi-
ssion
100
100
97.2
84.1
45.5
19.9
5.1
1.0
11.9
Notes: 1. Population data from the Oct. 1, 1980 national census.
2. Some municipalities are counted for both public sewerages and specified public
sewerages for conservation of the environment, and the footings are adjusted by
subtracting those which are counted twice.
-------
Natural environment protection sewerage is designed for tourist
resorts, such as Lake Akan and Lake Ashinoko, where much celebrated water
quality is beginning to be degraded with the prosperity of tourism. Some
lakes have lost their transparency, and some others have been so vitiated
even to send off offensive odors. In fiscal 1982, natural environment
protection sewerage was constructed at 35 places to improve local water
environments.
Rural community sewerages are designed to protect the public waters
due to domestic wastewater from farming communities, fishing communities,
etc., where the demand for flush toilets has been increasing in keeping
with the urbanization of lifestyles. In fiscal 1982, rural community
sewerages were constructed at 49 places.
So far, sewerage systems have progressed in the urban areas, and
their design and engineering know-how reflect urban conditions which are
quite different from those in rural communities. The size of a sewerage
system for a rural community is generally small, and existing sanitary
engineering know-how cannot always be applied to it directly. For
example, the road density, traffic volume, underground structures,
conditions for the acquisition of right-of-ways, and influent loads and
their changes in the rural communities differ greatly from those in urban
areas. The planning and construction of sewerages change from community
to community depending on location, environmental conditions, and the
nature of the communities, even when the population size is almost the
same.
The Ministry of Construction has been studying the methods of
planning and designing small sewerage systems since fiscal 1981, for the
purpose of effective planning and construction of sewerages for rural
communities. The achievements so far were compiled in the Small-scale
Sewerage Planning Guidelines (draft) published last March.
This draft specifies what should be taken into account in working
out a basic plant for a small-scale sewerage system for a community size
of 2 households to 5,000 people. Compared with the conventional
guidelines for sewerage system planning, the draft has the following
features:
22
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(1) The area for which a small-scale sewerage system is to be
constructed usually is rural, and the population there is unlikely
to grow fast. Thus, the planned target year is basically set at the
present time.
(2) In a conventional sewerage system, the minimum size of a sanitary
sewer is set at 200 mm in inside diameter. In a small-scale
sewerage system, this size will not produce enough tractive force.
For this reason, the service sanitary sewer pipe is set at 100 mm in
principle.
(3) As regards sewage treatment, not only the conventional activated
sludge process which has been used most widely for the conventional
medium-size and large-size treatment plants, but also the sequential
batch reactor process, semi-batch oxidation ditch process, oxidation
ditch process, aerated lagoon process, extended aeration process,
high-rate aeration process, rotating bio-disc contactor process,
contact aeration process, trickling filter process, single-stage
nitrification-denitrification process, metal-salt coagulation
process, filtration process, and other various physico-chemical
processes are taken up, and their selection criteria are stated in
consideration of local conditions.
(4) There is a great possiblity that farms and green lots abound around
small-scale sewage plants for the easy disposal of sludge. In view
of this and from the viewpoint of energy economy and sludge
recycling, it is planned to promote the use of sludge for
agricultural purposes. Specifically, the draft shows several
standard sludge processing flows applicable to small-scale sewage
treatment plants for these purposes.
As logical design techniques and design and engineering parameters
have been established by the Small-scale Sewerage Planning Guidelines
(draft), the Ministry of Construction is now planning to start
small-scale sewerage model projects from the coming fiscal year. In
these projects, the Ministry of Construction will select as models
projects in which such Specified public sewerage systems for the
conservation of the environment or small-scale Public sewerage systems
that are designed with efficient processes. The Ministry of Construction
will extend technical and financial assistance to such projects.
23
-------
5. MODEL PROJECTS FOR SEWERAGE CONSTRUCTION
As shown in Fig. 1, the sewage works in Japan have fallen prey to
the influence of austerity budgeting programs for two consecutive years.
In spite of financial retrenchment, the municipalities are called upon to
step their efforts to promote the construction of such sewerage systems
as are viable both economically and technically.
The Ministry of Construction set afloat the "impressive sewerage
project" and "good-idea sewerage project" in fiscal 1982 and the
"in-sewer treatment project" in fiscal 1983.
5.1 IMPRESSIVE SEWERAGE PROJECT AND GOOD-IDEA SEWERAGE PROJECT
These projects were designed to obtain a deep understanding and the
strong support of the general public concerning sewage projects.
Specifically, sewage projects which have an appealing effect on the local
inhabitants or public opinion or which have been designed with new
technologies or the people's ideas are taken up as models for
demonstration of effects. Special budgetary credit is given to these
projects.
In fiscal 1982, 20 model projects got started with a total ¥3,000
million. They included the "Save-the-King-Crab Sewerage Project (Okayama
City, Okayama)," "Sewerage Project for Protection of Yanagawa Riverside -
the Hometown of Poet Hakushu (Mitsuhashi and Yanagawa Official
Cooperation, Fukuoka)," "Metropolis Inundation Protection Operations
Bypass Sewerage Project (Utsunomiya, Tochigi)," "Batch-type Sewage
Treatment Project for Promotion of Sewage Treatment Technology (Maizuru,
Kyoto)," and "Farewell-to-Boots Operations Project (Hamamatsu, Shizuoka).'
In fiscal 1983, it is planned to evaluate creative projects worked
out by local municipalities according to the following criteria and
target of selected projects as coming under the impressive sewerage or
the good-idea sewerage category.
24
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(1) Impressive sewerage projects
A project which is effective in accelerating the construction of
sewerage and is appealing to the minds of the local inhabitants or
the general public.
- Eligibility requirements -
1. Having a quick-fix effect.
2. To be located for the protection of well-known waters.
3. A project which will encourage a citizens' movement for the
construction of sewerages.
(2) Good-idea sewerage project
A project based on innovative technologies for the reduction of
costs for construction, operation, and maintenance of sewerages.
- Eligibility requirements -
1. To reduce construction costs.
2. To reduce installation space.
3. To save maintenance and management expenses through the
reduction of needs for resources, energy and labor.
4. To improve treatment efficiency.
5. To appeal to the local populace from the viewpoint of
environmental protection.
In fiscal 1983, 12 impressive sewerage projects and 7 good-idea
sewerage projects were newly listed. Some of them are as outlined in
Table 6,
25
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Table 6 Examples of impressive sewerage systems and good-idea
sewerage systems newly selected for fiscal 1983
Impressive sewerage
(1) Clean Otaru Canal
Operations for
Protection of What
It was in the
Pioneering Age
(Otaru City,
Hokkaido)
To protect the
traditional water-
scape of the canals
from domestic waste-
water by quick
buildup of sewerage
systems.
(2) Sewerage for Conser-
vation of Traditio-
nal Beauty of
Yodo Castle (Kyoto
City, Kyoto)
To install well-
equipped sewerage
systems for the pur-
pose of recouping the
water quality in the
moats and canals
around the remains of
the Yodo Castle which
are endangered by
domestic effluents.
(3) Agricultural Waste-
water Reclamation
Operations (Yamate
Village, Okayama)
Yamate Village is
destitute of water
resources such as
rivers and is
always feeling a
water shortage
because annual
rainfalls are
short. The
project is to
recover wastewater
treatment plant
effluent for
irrigation and
industrial
purposes.
Good-idea sewerage
(1) All-Participatory
Wealth-from-Waste
Purification Center
(Tazawako Town, Akita)
To reduce sewage
plant construction
costs and to promote
the recycling of
refuse by using waste
plastics as biological
contact filter
materials in the
biological contact
oxidation process.
(2) Energy-efficient
Sludge Treatment
Plants working on
Waste Heat of Refuse
Incinerator (Zushi
City, Kanagawa)
A sludge drying plant
is annexed to a
municipal refuse
incineration plant.
Waste heat available
from the incineration
plant is used to dry
sludge cake to reduce
sludge volume,
stabilize sludge
quality, and at the
same time to save on
fuel, operation, and
maintenance costs.
(3) Air-economized
Sewage Treatment
Process (aerobic/
anaerobic
biological filtra-
tion process)
(Takane Town,
Yamanashi)
A treatment process
designed for a
small-scale
sewerage system
which economizes
on air injection
by making use of
anaerobic microbes
for treatment.
26
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5.2 IN-SEWER TREATMENT MODEL PROJECTS
The urban storm water conduit is one of the urban facilities used
for draining stormwater quickly out of the urban area. In those areas
where sewage plants are not installed, a storm water conduit is likely to
be used for collecting and draining not only stormwater but also domestic
wastewater. What is carried by the storm water conduit includes slop and
other domestic washings (excluding raw sewage), effluents from septic
tanks and industrial effluents, causing the receiving public waters to be
polluted.
As a matter of course, this problem should be solved by new
construction and amplification or improvement of sewerage. However, in
those areas which cannot wait, it is necessary to take a jury-rigging
measure like a utility purification device installed in a sewer.
In view of this, the Ministry of Construction decides on an in-sewer
treatment model project for the storm water conduit under its care.
In an in-sewer treatment system, contact materials such as net,
ropes and pebbles, which offer a good habitat for microbes are installed
in the storm water conduit for treatment of wastewater through biological
oxidation. As shown in Fig. 4, in-sewer treatment systems are in general
classified into two types:
In fiscal 1983, in-sewer treatment model projects will be started at
several places in the Kasumigaura Basin and the Lake Biwa Basin.
(A) In-line system
Urban storm water conduit
Grit chamber and screen
Contact oxidation tank
Settling tank
Fig. 4 A schematic view of in-sewer treatment system
27
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(B) Bypass system
Weir
Urban storm water conduit
Intake
Grit chamber and screen
Contact oxidation tank
Return
Settling tank
Fig. 4 A schematic view of in-sewer treatment system (Cont'd)
6. TREATMENT, DISPOSAL AND EFFECTIVE UTILIZATION OF SEWAGE SLUDGE
At present, the sewage treatment plants in Japan are treating about
6,700 million m of wastewater a year, turning out large volumes of
sludge. Infact, the sludge poses many problems to every municipality,
and efforts are being made to find a way out for proper treatment and
disposal of sewage sludge.
6.1 THE STATUS QUO OF SEWAGE SLUDGE TREATMENT AND DISPOSAL
Table 7 shows the outlets of sewage sludge during the period from
November 1981 to October 1982. The total volume of sludge disposed is
about 2,390,000 m , of which about 78% was dumped in the form of
dewatered sludge cake, about 12% in the form of incinerated ash, about 8%
in the form of digested sludge, and about 3% in the form of dry sludge.
It should be noted that the volume shown refers to the sludge when
carried out of plants. Sludge which is turned into compost for
agricultural use is counted as dry sludge.
28
-------
Sludge which is dumped at landfills leads the rest, accounting for
some 47% of the total. This is followed by land reclamation with about
30%, utilization with about 15% and others with about 8%. The 8% portion
mainly includes disposal in the ocean. The land reclamation is widely
practiced by large municipalities where sludge production is
prohibitively voluminous. Of the total sludge cake producted in Japan,
some 49% undergoes incineration; in the cities designated by the Cabinet
order, the incineration average ratio is about 57%, and in other ordinary
cities, the average ratio is about 35%, suggesting that every large city
is making efforts to extend the service life of fast-dwindling disposal
sites by reducing the quantity of sludge.
Table 7 Disposal of sewage sludge
(Nov. 1, 1981 - Oct. 31, 1982)
(unit: x 103 m3)
•\^ Disposal
^^\ method _ ,,;.,, Land M*.-n «.,•„„
„, , ^\ Landfill •• . • Utilization
Sludge \^ uauu reclamation
condition ^^\
Dewatered sludge
Incinerated ash
Dried sludge
Digested sludge
Total
(%)
871
140
6
7
1,024
(43)
726
102
0
0
828
(35)
260
35
54
0
349
(15)
Others
13
0
0
173
186
(8)
Total
(%)
1,870
(78)
277
(12)
60
(3)
180
(8)
2,387
(100)
29
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6.2 TRANSITION OF TREATMENT AND DISPOSAL OF SEWAGE SLUDGE
Fig. 5 shows the annual transition of sewage sludge treatment and
disposal. It is found that the sludge production has been rising year
after year. On a sludge cake basis, the sludge volume rose from about
.3
3,640,000 m in 1981 to about 3,840,000 m in 1982, but the volume of
disposed sludge has been running almost constant at about 2,400,000 m'
for the past five years, owing to efforts made to increase the
incineration rate and to improve the dewatering efficiency for the
reduction of sludge volume. The increase of the incineration rate is
demonstrated in Fig. 5 which shows a steady increase in the volume of
incinerated ash disposal. A look into the transition of disposal methods
over long periods shows that the volume of sludge recovered for useful
purposes has been rising. This upward trend reflects the promotion of
sludge utilization for farmland and green areas.
Disposed volume by type of sludge
260
240
220
200
180
160
140
120
100
80
60
40
20
0
191
242
240
239
. Digested sludge
Dried sludge
Incinerated ash
~— Dewatered sludge
74
78
81
82 Fiscal year
Fig. 5 Annual transition of sewage sludge disposal
30
-------
Disposed volume by uses
240 239
- Others
- Utilization
— Land reclamation
81
82 Fiscal year
Fig. 5 Annual transition of sewage sludge disposal (Cont'd)
6.3 SLUDGE UTILIZATION
The recovery of sludge for use is shown in Table 8, and its annual
transition, in Fig. 6. In fiscal 1982, the recovered volume dropped from
the fiscal 1981 level. This is because the recovery of digested sludge
decreased.
Instead, sludge was recovered in forms with lower water content; on
a sludge cake basis, the recovery rate of sludge has been increasing
steadily.
Table 8 Utilization of sewage sludge
•^~~^_sii
Uses
Farmland
and green
lots
adge condition
^^
by municipal
government
by fertilizer
companies,
etc.
Subtotal
Construction materials
Total
De-
watered
sludge
205
55
260
0
260
Inciner-
ated ash
1
9
10
25
35
Dried
sludge
5
0
5
0
5
(x
Compost
49
0
49
0
49
103 m3)
Digested
sludge
0
0
0
0
0
Total
260
64
324
25
349
31
-------
Thickened and digested sludge
Composted sludge
Dried sludge
Incinerated ash
Dewatered sludge
82 Fiscal year
Fig. 6 Annual transition of sewage sludge utilization
The greater part of the sludge recovered is used for soil
conditioning or fertilizing croplands and green lots. For these
agricultural purposes, sludge cake is most widely used. Some sludge cake
is delivered to fertilizer manufacturers, who process it into useful
forms like compost or dry sludge. In recent years, those municipalities
which have entered the composting business are growing in number.
The volume of sludge which is turned into construction materials
remains low, accounting for a mere 1% of the total. In Sapporo, sludge
ash is used as a fill for land leveling and banking. In Tokyo, sludge
ash is used for a roadbed aggregate. All these processes are being
conducted experimentally.
32
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6.4 FUTURE STRATEGIES AND TACTICS FOR SLUDGE DISPOSAL
Whether sludge will be treated and disposed of without trouble in
future is a matter of critical importance governing the future of the
entire sewage project field. Although sludge is a threat to our future
well-being, it can also be a rich vein of resources. Sludge is, so to
speak, a modern version of the ugly duckling.
The following are the strategies and tactics on hand to solve sewage
sludge problems:
Strategy I: Reduction of sludge volume
The most widely accepted method of reducing the volume of sludge is
incineration. But incineration processes consumes a great deal of energy
and call for labor for operation and maintenance. In some areas, it is
hard to procure sites for incinerators. To provide against these
problems, the following tactics are being considered:
Tactic 1: Wide-area joint-use incineration plants
These are intermural incineration plants for joint use by a number of
municipalities for high-efficiency continuous operation. Where there are
a number of sewage treatment plants operated by a single municipality, as
in a large city, it is practical to haul dewatered sludge cake from
sewage treatment plants to an incineration plant for intensive
incineration.
Tactic 2: Combustion with refuse
Combustion of sludge and refuse together is advantageous in two ways:
first, the refuse produces the heat required for the incineration of
sludge, and second, it is possible to moderate the incineration
temperature when burning refuse of high calorific value. In Japan, the
disposal of city refuse is under the jurisdiction of the Ministry of
Health and Welfare. Studies are now being pushed forward to formulate a
system for distributing the costs, duties, and responsibilities between
the Ministry of Construction and the Ministry of Health and Welfare for
the construction, operation, and maintenance of sludge/refuse
incinerators. In Japan, there is only one sludge/refuse incineration
plant in Kanazawa.
33
-------
Tactic 3: Development of technology for self-sustainable combustion
Usually, the lower calorific value of dewatered sludge cake is positive.
It is theoretically possible to sustain the combustion of dewatered
sludge cake if an ideal incinerator of a high thermal efficiency is
used. In support of this process, there are two self-sustained
combustion incinerators, one each at Takaoka City and Nagoya City. If
the technology for self-sustainable combustion of sewage sludge is well
established and popularized, auxiliary fuel, which now is consumed at 50
to 70 lit. of heavy oil per ton of sludge cake, can be dispensed with,
and at the same time, excess energy will be available for more productive
purposes.
Strategy II: Promotion of sludge recycling for farmland and green lots
The use of sludge for farming and similar purposes is slow to progress,
because the heavy metals and coagulants contained in it are much
dreaded. A market has yet to be developed for it. The social consensus
on the utilization of sludge for farming purposes is far from firm.
Tactic 1: Establishment of application standards
It is necessary to formulate standards for the utilization of sludge for
agricultural purposes based on surveys of the fertilizing effect of
sludge and the effects of heavy metals, etc. The Ministry of
Construction and the Japan Sewage Works Agency have been studying this
problem for more than 10 years. Recently the Ministry of Construction
and the Japan Sewage Works Agency have jointly compiled the Guidelines
for Application of Sewage Sludge Compost to Farmland (draft). According
to the draft guidelines, the following limitations are imposed.
(a) Feedstocks should be limited to sludge cake available from domestic
wastewater only from the viewpoint of safety.
(b) Composting should be carried out at temperatures above 60°C for
hygiene.
(c) The compost should be subjected to aerobic fermentation and 1 to 3
months of open yard storage and turnover for sufficient
post-fermentation.
34
-------
(d) The compost should be enriched with potassium and other chemical
fertilizers to offer a well-balanced fertilizer formula.
Continued efforts are being made in this respect to establish a
standard for agricultural applications of sewage sludge in the long run.
Tactic 2: Development of distribution channels for sludge-turned
compost
So far the sewage bureaus of the manicipal governments usually have
distributed sludge-turned compost almost free of charge, only to dumpen
the entrepreneurship of those who are willing to commercialize the
sludge-turned compost. To avoid this farce, studies will be made to go
hand in hand with these entrepreneurs for promoting sludge-turned compost
on the existing fertilizer distribution channels.
In the future, measures will be studied for enlisting the existing
fertilizer channeling routes for marketing sludge-turned compost.
Strategy III: Utilization of sludge for construction materials
The recycling of sewage sludge for construction purposes is considered
most ideal and promising not only for safety but also from the viewpoint
of market potential. At present, the government, local municipalities,
and businesses are making progress with respective projects for the
development of sludge ash calcining and smelting technologies, finding
the sludge ash outlets as artificial lightweight aggregates, tiles, and
bricks.
Tactic 1: Development and improvement of technologies for costs
reduction
By making use of the energy recovered from sludge (Strategy IV), the cost
can be reduced. It is expected that the lightweight aggregates will be
produced at a lower cost than the conventional lightweight aggregates.
However, the demand for gravel aggregates is higher, and it is urged
to develop technologies for the reduction of costs for the productions of
gravel aggregates through sludge smelting.
35
-------
Tactic 2: Study and evaluation of quality
At present, the study and evaluation of sludge-turned construction
materials is carried out by sanitary engineers. But sludge-turned
construction materials should undergo study and evaluation by users such
as concrete engineers, road construction engineers, and soil mechanics
engineers. The Ministry of Construction has been playing up the
ministry-wide surveys for the utilization of sludge-turned construction
materials according to the Comprehensive Project for Technological
Development for Recovery of Wastes for Civil Engineering and
Construction, which was started in fiscal 1981. At present, the Ministry
of Construction is conducting experiments and studies on the physical
properties of sludge-turned gravel aggregates, cost analysis of smelting
operations, and construction and civil engineering applications.
Tractic 3: Demonstration of sewage projects using sludge turned
construction materials
If the sum of the cost for the ordinary treatment and disposal of sewage
sludge and the cost for the ordinary construction materials is larger
than the cost for sludge-truned construction materials, it will require
administrative guidance in order for sludge-turned construction materials
such as artificial lightweight aggregates be used for the construction of
sewage projects. It is therefore planned to raise substantive results in
the construction of sewage projects to establish a strong toehold for the
promotion of sludge-turned construction materials.
Tactic 4: Streamlined management of sludge-turned construction
materials production department
For the purpose of opening up a market for sludge-turned construction
materials and improving the management efficiency of the sludge-turned
construction materials production department, it will be necessary to
provide measures such as the establishment of a streamlined organization,
the introduction of private funds, etc.
36
-------
Strategy IV: Recovery of energy from sludge
As regards the recovery of energy from sludge, digester gas-fired
electric power generation is most popular. In addition, the various
other ways of recovering energy from sludge are under study. The
recovery of energy from sludge is important as it supports other
strategies in terms of energy.
Tactic 1: Promotion of digester gas-fired electric power generation
In Japan, power generation systems working on anaerobic digester gas are
still at an elementary stage. The digester gas-fired power generation
plants now in commission or under construction number only seven
throughout Japan. Their capacities range from 130 kW to 500 kW to share
15% to 40% of the electric power required by respective sewage treatment
plants.
The Ministry of Construction is hastening the preparation of a
design manual for digester gas-fired power generation plants. It is
expected that the manual will be published within this fiscal year.
Tactic 2: Development of other methods for recovery of energy
At present, the harnessing of excess heat available from self-sustained
incineration process, briquetting of organic materials from sludge, etc.,
are being contemplated. There are some municipalities conducting pilot
plant studies for new energy recovery technologies.
Strategy V: Planning of wide-area sewage sludge treatment and disposal
system
At the eighth US/Japan Conference on Wastewater Treatment Technology, Dr.
Kubo, head of the Japanese Delegation, announced a scheme for wide-area
treatment and disposal of sewage sludge in the catchment area of Tokyo
Bay, giving a warning that an integrated system of sewage sludge
treatment and disposal be established in good time as it is becoming
increasingly difficult to find sites for sewage treatment and sludge
disposal.
37
-------
But in June 1981, the Law of Environmental Centers for Waste
Reclamation was passed. Since then, the circumstances surrounding sewage
sludge treatment and disposal have changed slightly. This law specifies
a principal organization which should undertake the development of a
large-scale reclamation site for wastes turned out in megalopolises.
Naturally, the wastes to be handled by such an organization include
sewage sludge. This means that sewage projects need not always make an
effort for the procurement of dump sites. However, the disposal amounts
and the costs of disposal are dependent on the location of dump sites,
the amounts of other wastes, and disposal methods, etc. "t this time,
however, there are many unsettled factors as to the specifics of sludge
disposal.
In 1982, the Osaka Bay Environmental Center for Waste Reclamation
was chartered according to the Law of Environmental Centers for Waste
Reclamation, and the sewerage operators in the greater Osaka Bay area are
being urged to establish a proper system for sewage sludge disposal. In
view of this, the Ministry of Construction is studying a total system for
sewage sludge treatment and disposal. The study is concerned more with
the integration of tactics or methodology than with independent tactics.
The study flow is as shown in Fig. 7. Fig. 8 shows an example of a case
study concerning the sludge transportation system proposed for the
greater Osaka Bay area.
According to this example, it is proposed that a raw sewage
collecting pipeline network interconnecting treatment plants located
within 20 to 30 km from the joint dump site be provided for purpose of
economy.
38
-------
Basic survey of
wide-area planning
of sewerages for
landlocked water
(fiscal 1980)
Opinion survey
concerning sludge
treatment and
disposal
—
Analysis of
data obtained
by opinion
surveys
Study for the siting of
wide-area joint dump
sites in view of sludge
collection and
transportation
Coordination with the
local municipalities
concerned
Study of the economic
feasibility of wide-area
jojnt incineration
Economic analysis of
sewage sludge collection
and transportation
systems
Study on joint
incineration
Determination of wide-
area joint disposal
quantities of sewage
sludge and the served araas
Demand-supply survey
for utilization of sewage
sludge
Study on project
Study on the construction
of wide-area joint
incineration plants
Study on th* collection
and transportation system
Master plan for wide-area
sewage sludge treatment
and disposal
Survey of the benefits
of sludge utilization
Survey of energy-efficient
measures for processing
sewage sludge
Study on the deployment
of sludge-processing
facilities
Long-term plan for sludge
treatment and disposal
Surveys in fiscal 1980
and earlier
Fiscal 1981 surveys
Surveys in fiscal 1982 and subsequently
Fig. 7 Survey flow for the planning of wide-area sewage sludge
treatment and disposal systems
-------
Plants from which dewatered
or incinerated sludge is trucked
Plants from which raw sludge is
transported by pipeline
Joint treatment and
disposal plants
Wakayama Prefecture
Fig. 8 A case study on a sludge transportation system for the Greater
Osaka Bay Joint Sludge Treatment and Disposal System
7. CONCLUSIONS
Some of the current topics concerning sewage projects in Japan have
been discussed. As stated in Chap. 1, the current socio-economic
conditions in Japan are not always in favor of sewage works. Under these
conditions, the sewage works operators are being called upon to tackle
various problems highly crucial to the future of the disposal of Japan's
ever-increasing domestic and industrial wastes.
40
-------
The first priority is to find a cost-effective way to dispose of
wastes within a limited budget. Investment should therefore be made
selectively for maximum effects and quick returns. Specifically, we are
asked to rack our brains for the selection of projects, control of
capital investment, employment of economic processes, etc. In the
future, we will be required to extend sewer services to small cities and
rural communities. In these areas, the scale of sewerages will be small,
and the investment efficiency will be low, as well. For this reason,
sewerage systems will have to be changed to best meet local
characteristics for the purpose of maximizing investment effects. The
Small-scale Sewerage Planning Guidelines (draft) referred to in Chap. 4
has been formulated with these future needs in mind.
Secondly, the importance of sewerage systems must be emphasized to
the people to get a strong support from the general public for the
promotion of sewage projects. To this end, it will be necessary to pick
model projects appealing to local inhabitants or the general public and
to develop such techniques as are instrumental to playing up
quantitatively and with cogency what sewerage brings about for the common
good. The model projects touched upon in Chap. 5 have been implemented
as part of this public enlightenment program.
Thirdly, financial policies for sewerage systems should be studied.
The existing financial system should be reviewed to identify the
problems, and the opinions of the public, government authorities, and
academic and industrial circles should be polled in pursuit of an
effective, rewarding, and truly workable financial system. In view of
this, the Fifth Sewege Works Financial Policy Study Committee is
addressing itself to study the future of sewage works financial policies.
41
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
RECENT DEVELOPMENTS IN
JAPANESE WATER QUALITY
MANAGEMENT POLICY
Sept. 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Daisaku Sugito
Director,
Water Quality Management Div.
Water Quality Bureau
Environment Agency
Government of Japan
-------
1. CURRENT STATE OF POLLUTION IN JAPANESE WATERS
The situation regarding water pollution in Japan has on the whole im-
proved in the last few years, although there still remain many water bodies
which stand far from "desirable" levels prescribed by the environmental water
quality standards. According to the results of the nationwide water quality
monitoring conducted in 1981, 0.05% of the samples analyzed contained cadmium
or other toxic substances in concentrations exceeding the water quality
standards related to the protection of human health. This figure represents
a remarkable drop from 1.4% in 1970 and shows that the situation has continued
to improve over the years. It is particularly noteworthy that in no places
total mercury was found to exceed the standard, nor was there any single
sample containing alkyl mercury or organic phosphorus. (Table 1-1)
Table 1-1. Ratio of Samples Exceeding Environmental Water Quality
Standards in Terms of Toxic Substances (1981)
Item
Cadmium
Cyanide
Organic phosphorus
Lead
Chromium (VI)
Arsenic
Alkyl mercury
PCB
Total*
Number of
samples (A)
29,231
24,410
9,022
29,339
25,082
26,749
7,933
4,126
155,892
Number of samples
exceeding environ-
mental water quality
standards (B)
34
2
0
8
0
30
0
0
74
Ratio (%)
(B)/(A)
0.12
0.01
0.00
0.03
0.00
0.11
0.00
0.00
0.05
Total mercury
1981
Number of
samples
31,023
Number of
samples
exceeding
0.0005 mg/«,
29
Number of places
where readings
exceed environmental
quality standards
0
* Excepting total mercury
44
-------
Regarding BOD, COD, and other indices related to the preservation of the
living environment, Tables 1-2 and 1-3 illustrate that of the total of 2,935
water areas (2,279 rivers, 103 lakes and reservoirs, and 553 sea areas) which
had been classified by 1979, 1,938 water areas (1,443 rivers, 44 lakes and
reservoirs, and 451 sea areas) accounting for 66.0% (68.7% for the previous
year) have been found to meet the standard for BOD or COD, both typical
indicators of water quality. Thus, on the whole, 34.0% of the total water
areas have not attained the standards (Table 1-2).
It is true that among the water bodies surveyed there were some which
had not yet reached their "target dates" for the attainment of the water
quality standards, but even if they were excluded, many water bodies which
had been classified up to 1976, with target periods falling under either "a"
(immediately) or "b" (as early as possible within five years), only 70.8%
have been found to meet the standards. This indicates that there is need for
further strengthened efforts for water pollution control in the coming years.
(Table 1-3)
Table 1-2. How Environmental Water Quality Standards are
Met in Terms of BOD or COD
Water areas
classified
Total water areas
Water areas
classified at the
end of 1976
Water areas
classified for
1977
Number of
water areas
(A)
2,935
2,634
["a" or "b"
2,296 ]
123
["a" or "b"
116 ]
Number of water
areas meeting
environmental
quality standards
(B)
1,938
1,722
["a" or "b"
1,625 ]
98
["a" or "b"
97 ]
Ratio %
(B) / (A)
66.0
65.4
["a" or
70.8
79.7
["a" or
83.6
"b"
]
"b"
]
Note: "a" and "b" refer to the target periods within which the
environmental water quality standards are to be attained
as follows:
a: immediately, b: as early as possible within five years.
45
-------
The achievement rates for environmental standards in different water
bodies are — rivers: 63.3% (previous year 67.2%), lakes and reservoirs: 42.7%
(41.6%), and seas: 81.6% (79.8%). The achievement rates for small and medium-
size rivers, lakes and reservoirs within major city areas, inland bays and
inland seas, and other inland waterways remain unsatisfactory, and this fact
has become one of the main characteristics of the pollution of public waters
in recent years.
Table 1-3. How Environmental Water Quality Standards are Met
in Terms of BOD or COD — By Type of Water Area
Category
of water
areas
AA
A
B
C
D
E
Total
Target
period
a
b
c
a
b
c
a
b
c
a
b
c
a
b
c
a
b
c
a
b
c
Total
Rivers (BOD)
Number
of
water
areas
(A)
266
16
5
773
198
55
238
199
68
77
95
67
14
33
32
12
31
100
1,380
572
327
2,279
Number of
attaining
environmental
quality
standards (B)
184
7
0
609
118
12
172
100
16
59
44
13
12
19
16
9
19
34
1,045
307
91
1,443
Ratio
(B)/(A)
(%)
1981
64
44
0
79
60
22
72
50
24
77
46
19
86
58
50
75
61
34
76
54
28
63.3
1980
75
50
0
83
61
22
79
53
33
76
49
22
93
66
47
82
56
36
81
56
31
67.2
Lakes and reservoirs (COD)
Number
of
water
areas
(A)
15
3
4
37
22
7
7
3
4
1
-
-
60
28
IS
103
Number of
water areas
attaining
environmental
quality
standards (B)
4
0
1
26
11
1
1
0
0
0
-
-
31
11
2
44
Ratio
(B)/(A)
(%)
1981
27
0
25
70
50
14
14
0
0
0
-
-
52
39
13
42.7
1980
40
0
25
65
48
14
14
0
0
0
-
-
51
38
13
41.6
Sea areas (COD)
Number
of
water
areas
(A)
189
40
7
133
59
7
81
34
3
403
133
17
553
Number of
attaining
environmental
quality
standards {B)
134
20
J
125
50
4
81
34
2
340
104
7
451
Ratio
(B)/(A)
(%)
1981
71
50
14
94
85
57
100
100
67
84
78
41
81.6
1980
74
40
14
89
76
71
100
97
67
84
70
47
79.8
-------
2. WATER QUALITY IN ENCLOSED WATER AREAS
Enclosed water areas such as inland seas, inner bays, lakes and reser-
voirs are prone to suffer from a large influx of pollutants, particularly
organic ones from various sources. The pollutants in turn tend to accumulate
in these enclosed water bodies. Thus, they attain environmental quality
standards to a lesser extent than other water areas and show progressive
eutrophication or gradual degradation of water quality resulting from an
influx of substances containing nitrogen and phosphorus as well as from an
excessive algae and other aquatic plants.
Such enclosed water areas attained environmental water quality standards
to the following extent in 1981: Tokyo Bay, Ise Bay and the Seto Inland Sea
achieved 61%, 59% and 81% respectively, which are lower than the 84% for
other sea areas, while lakes and reservoirs achieved only 42.7%. (Tables 2-1,
2-2, 2-3)
As for the number of red tides observed in 1981, 5 were in Tokyo Bay,
20 in Ise Bay and 55 in Seto Inland Sea, while fresh water red tides (in Lake
Biwa, etc.) and 'aoko' (water-bloom caused by green algae) (in Kasumigaura,
Lake Suwa, etc.) were seen in lakes and reservoirs.
Table 2-1. Trends in Water Pollution: Rate of achievement
Environmental Water Quality Standards Relating
to the Living Environment (BOD or COD)
^~~— — — -___
Rivers
Lakes and reservoirs
Coastal water areas
Tokyo Bay
Ise Bay
Seto Inland sea
Others
Total
'74
51.3
41.9
70.7
44
47
67
77
54.9
'75
57.1
38.6
72.4
44
53
69
77
59.6
'76
57.6
40.7
76.4
67
47
72
81
60.6
'77
58.5
35.2
76.9
61
47
73
81
61.2
'78
59.5
37.5
75.3
61
53
75
77
61.7
• 79
65.0
41.8
78.2
61
53
76
82
66.7
'80
67.2
41.6
79.8
61
53
72
85
68.7
'81
63.3
42.7
81.6
61
59
81
84
66.0
47
-------
Notes: 1. Rivers: BOD lakes and reservoirs, and coastal water
areas: COD
2. The achievement rate (%) :
No. of water areas complying
with environmental quality standards
No. of water areas to which environmental
quality standards are applied
-x 100 (%)
Table 2-2. Water Quality
of Major Coastal Water Areas (COD)
Unit: mg/K.
Tokyo
Bay
TQP
X OC
Bay
Seto
Inland
Sea
Area
Chiba Port
Tokyo Port
Yokohama Port
Nagoya Port
Kinuura Port
Yokkaichi Port
Osaka Port
Mizushima Port
Iwakuni Port
Tokuyama Port
Mishima-
Kawanoe Port
Catego-
ries of
water
quality
standards
C
C
C
C
C
B
C
C
B
B
B
Stand-
ard
value
8
8
8
8
8
3
8
8
3
3
3
'70
2.2
3.8
*3.4
6.5
*2.4
3.9
4.8
2.7
3.0
*2.3
2.9
'76
2.6
3.4
1.8
3.6
2.5
2.7
4.4
2.0
2.6
2.8
2.3
'77
2.9
3.4
2.4
3.8
2.7
2.8
3.5
2.1
2.7
2.4
2.0
'78
3.9
3.3
3.1
3.9
3.0
3.1
4.4
2.0
2.0
2.4
2.1
'79
4.2
3.1
3.1
3.5
3.2
4.3
4.7
2.6
2.5
3.2
2.5
•80
3.7
3.1
3.2
3.4
2.8
3.3
3.8
2.4
1.8
2.5
2.5
'81
3.9
3.8
3.5
3.3
2.8
3.4
4.9
2.2
2.1
2.8
1.8
Notes: 1. Figures in annual average
2. *1971 data
48
-------
Table 2-3. Water Quality of Major Lakes (COD)
Unit: mg/Jl
Lake
Lake Akan
Lake Towada
Lake Shinji
Kasumigaura
Lake Biwa
(North)
Lake Biwa
(South)
Lake Suwa
Teganuma
Categories
of water
quality
standards
AA
AA
A
A
AA
AA
A
B
Standard
value
1
1
3
3
1
1
3
5
'70
2.6
0.6
3.5
3.8
—
—
3.4
11
'76
2.7
0.8
3.4
6.2
1.6
2.7
6.8
17
'77
2.6
0.9
3.6
7.1
1.8
3.0
9.1
18
'78
2.3
0.9
4.0
9.1
2.3
3.6
11
22
'79
2.8
0.9
4.0
11.8
2.3
3.5
6.3
26
'80
2.5
0.8
4.3
9.2
2.2
3.0
6.2
23
'81
2.9
0.8
4.0
7.9
2.2
3.1
5.1
22
Note: Annual average.
49
-------
3. MEASURES FOR EUTROPHICATION CONTROL
Eutrophication basically denotes the phenomenon of lakes and reservoirs
being gradually enriched by nutrients such as nitrogen, phosphorus, etc. sup-
plied from streams running into them. In recent years, lakes and reservoirs,
in addition to inland seas and bays have begun to suffer from increasing
levels of nutrients allowing algae and other aquatic life to propagate. This
is resulting in progressive degradation of water quality, presenting problems
of water quality management.
The degradation of water quality by eutrophication has given rise to
various problems: losses in the beauty of lakes and reservoirs due to decreases
in their transparency or changes in their colour, troubles in filtration of
water purifying plants and offensive odor or bad taste of drinking water, in
fish species and so on. Also, sea areas have long been troubled, by the red
tides in fisheries.
In order to enable local governments as well as other organizations
concerned to take measures for controlling the progress of eutrophication in
lakes and reservoirs, the Environment Agency established, on December 25,
1982, environmental water quality standards for nitrogen and phosphorus, based
on the recommendation of the Central Council for Environmental Pollution
Control. A summary of the recommendation of the Council follows.
50
-------
Table 3-1. Environmental Water Quality Standards on Nitrogen and
Phosphorus in Lakes and Reservoirs
Category
I
II
III
IV
V
Purpose of water use
Conservation of natural environment, and
uses listed in II-V
Water supply classes 1 , 2 and 3
(excluding special types) ;
Fishery type 1, bathing; and uses listed
in III-V
Water supply class 3 (special types) , and
uses listed in IV-V
Fishery type 2, and uses listed in V
Fishery type 3; industrial water; agri-
cultural water; conservation of the
living environment
Standard values
Total
Nitrogen
0.1 mg/£
or less
0.2 mg/ Si
or less
0.4 mg/£
or less
0.6 mg/£
or less
1 mg/£ •
or less
Total
Phosphorus
0.005 mg/Jl
or less
0.01 mg/£
or less
0.03 mg/£
or less
0.05 mg/£
or less
0.1 mg/£
or less
Notes: 1. The standards are measured in terms of annual averages.
2. The standards for total phosphorus are not applicable to
agricultural water uses.
3.1 Basic Views
3.1.1 Problems in various water uses arise when a body of water becomes
eutrophic as a result of increased inflow and concentration of nitrogen and
phosphorus. Diminished transparency of water impairs the scenic value of the
water body. Eutrophication also gives tap water a foul smell and taste or
filtration problems at water purification plants and causes fish and shellfish
to die.
3.1.2 These problems result mainly from excessive growth of planktons, or
"algal blooms."
3.1.3 The growth of algae and other plants is basically controlled by the
levels of nitrogen and phosphorus present in the water.
51
-------
On the basis of the elemental views cited above, environmental standards
for nitrogen and phosphorus in lakes and reservoirs should be established in
order to prevent nitrogen and phosphorus in lake water from causing excessive
algal growth and thus maintain the desirable state of the living environment.
3.2 Water Uses and Environmental Conditions
3.2.1 Nature Conservation
The eutrophication-caused multiplication of algae reduces the trans-
parency of water and turns the color of water green or brown. This results
in a deteriorated scenery and other adverse effects on the natural environ-
ment.
With a view towards maintaining the quality of water in the lakes and
reservoirs (such as Lakes Mashu and Shikotsu in Hokkaido), which ensures
sufficient transparency nitrogen (meaning total nitrogen) should be held
below 0.1 rag/a and phosphorus (meaning total phosphorus) below 0.005 mg/£.
3.2.2 Drinking Water
Among the problems in water supply, which are caused by eutrophication,
are smelling or foul taste of water and problems in water purification opera-
tions, such as clogging in the filtration system, which results from multi-
plied algae.
Since the patterns of the problems vary, different approaches were taken
in the deliberation of the Council so as to take into account such specific
patterns corresponding to the categories of water use as well as to respective
water treatment processes adopted.
(a) Category 1 Drinking Water Supply
In the case of the category 1 drinking water supply (which requires
simple purification processes such as filtration), smelling substances and
others are decomposed and removed in the course of low speed filtering. While
this seems to prevent the problem of smelling or foul taste of water, the
filtering basin sometimes gets clogged because of multiplied algae. When this
happens, the basin's filtering capacity sharply diminishes.
52
-------
Considering the quality of water in those water-supplying lakes and
reservoirs which have faced with filtering problems (such as the southern
part of Lake Biwa, the Murayama Reservoir, and Lake Nojiri), and that of other
trouble-free lakes, nitrogen should be kept below 0.2 mg/£ and phosphorus
below 0.01 mg/£ in setting the standard values for the category 1 water supply.
(b) Category 2 and 3 Drinking Water Supply
The category 2 drinking water supply involves sedimentation, filtering,
and other normal purification processes. The category 3 drinking water
supply involves more sophisticated purification processes, which include
preparatory treatment.
Various kinds of purification trouble arise in their cases. The presence
of multiplied algae in water sometimes requires an increase in the amount of
drugs consumed in the coagulation and sedimentation pond and shortens the
life time of the rapid-filtering basin.
Considering the water quality in water-supplying lakes and reservoirs
which have experienced these problems (such as Lakes Kasumigaura and Sagami
and the Hatake Reservoir) and that of other trouble-free lakes, nitrogen
should be held below 0.4 mg/£ and phosphorus below 0.03 mg/£ if the normal
functions of water purification facilities are to be maintained.
Since the removal of smelling substances is difficult through the normal
purification processes, their presence sometimes causes foul odor or taste
bad in tapped water. Problems of smelling or foul taste of drinking water
have recently arisen in various parts of the country. Considering the situa-
tions of such problems, as reviewed by a Countermeasures Panel of Japan Water
Supply Association and other bodies, and the quality of water in trouble-free
water-supplying lakes and reservoirs, nitrogen should be kept below 0.2 mg/fc
and phosphorus below 0.01 mg/£ so as to prevent smelling or foul taste of
tap water, such as mold odor.
In the case of some of the category 3 where removal of smelling sub-
stances is ensured through normal purification operations, nitrogen should be
held below 0.4 mg/£ and phosphorus below 0.03 mg/£.
53
-------
3.2.3 Bathing
A representative inland water body used as a bathing resort is Lake Biwa
(northern section). Although this section is generally in a satisfactory
condition, some of the bathing shores are not. Considering the good quality
of water in the same section in the mid-1960s, nitrogen should be held below
0.2 mg/£ and phosphorus below 0.01 mg/£ in setting the standard values for
bathing areas.
3.2.4 Fisheries
Trout and other species of the salmon family and "ayu" (sweetfish)
flourish in lakes and reservoirs with low levels of nitrogen and phosphorus.
"Wakasagi" (smelt) live in water bodies with medium levels of nitrogen and
phosphorus. Species with strong resistance against pollution, such as carp
and "funa" (crucian carp) dominate where concentrations of these substances
are high.
Accordingly, the above groups of species were used as representative
species in the deliberations on environmental quality standards to protect
fishery resources. The underlying concept was to set the standards at levels
low enough for each species to live and permit natural reproduction and
growth.
(a) Category 1 (species of the salmon family and "ayu")
Species of the salmon family, such as "hime masu" (Oncorhynchus nerka)
and "ayu" live where there is clean water bodies such as Lakes Chuzenji and
Biwa.
The principal species in Lake Chuzenji is changing from "hime masu" to
"wakasagi" as eutrophication is deteriorating the quality of water. The
quality of water in the northern section of Lake Biwa remains generally fit
for "ayu".
In view of these facts, nitrogen should be held below 0.2 mg/£ and
phosphorus below 0.01 mg/£ when the standard values for category 1 are set.
(b) Category 2 ("wakasagi"-type species)
Among the bodies of water with high "wakasagi" output are Lakes Suwa and
54
-------
Hachiro. But production in Lake Hachiro has been falling in the recent years
as the quality of water is no longer fit for "wakasagi." Production in Lake
Suwa has been leveling off. But existing levels have been maintained by the
release of fries. If conditions for natural reproduction and growth are to
be secured, improvement in the quality of water is warranted.
Considering these points, nitrogen should be kept below 0.6 mg/£ and
phosphorus below 0.05 mg/& when the standard values for category 2 are set.
(c) Category 3 (carp and "funa")
The proportion of carp and "funa" in fishery resources is tending to
increase both in percentage terms and quantitatively in keeping with the rise
in nitrogen and phosphorus concentrations. But problems arise when nitrogen
exceeds 1 mg/£ and phosphorus 0.1 mg/£.
Lake Kojima and two marshes — Teganuma and Inbanuma — have these sub-
stances in excess of these levels. Over the years, production in these bodies
of water has been leveling off or falling. In Teganuma and Inbanuma there
have been such problems as smelling fish flesh and dead fish.
In view of these facts, nitrogen should be held below 1 mg/£ and phos-
phorus below 0.1 mg/£ when the standard values for category 3 are set.
3.2.5 Water for Agricultural Use
Paddy rice plants are apt to overgrow during their principal growth
period (about 40 days after seedlings are transplanted in paddies from their
beds) and thus become liable to disease when there is too much nitrogen,
particularly ammonia nitrogen, in water for agricultural use. The presence of
excessive nitrogen in the stage of ear differentiation causes plants to grow
too long between the lower joints. When plants fall down or end up being
immature as a result, the yield suffers.
Considering these points, nitrogen should be held below 1 mg/H in setting
the standard values for irrigation water.
3.2.6 Industrial Water
The multiplication of algae, which results from eutrophication, makes
water turbid, and this gives rise to problems in the use of industrial water.
55
-------
The levels of nitrogen and phosphorus in the major lakes and reservoirs from
which water is drawn for industrial purposes, such as Lakes Kasumigaura and
Biwa, are generally below 1 mg/£ and 0.1 mg/£ respectively. No problems will
arise when they are at these levels.
In view of this, the standard values for industrial water should be set
below 1 mg/& for nitrogen and below 0.1 mg/Jl for phosphorus.
3.2.7 Environmental Conservation
The progress of eutrophication leads to the abnormal multiplication of
algae and causes tall water grasses to flourish. The offensive odor, given
off by them when they are decomposed, causes people discomfort. Among the
bodies of water in this condition are Inbanuma and Lake Kojima.
Considering the quality of water in these lakes and reservoirs, the
standard values for the conservation of the environment should be set below
1 mg/£ for nitrogen and below 0.1 mq/l for phosphorus.
3.3 Effluent Standards for Nitrogen and Phosphorus
In an effort to attain the environmental water quality standards, the
Water Pollution Control Law lays down the national effluent standards for
specified facilities which discharge wastewater into public water areas. For
water areas where the application of the uniform national effluent standards
is judged insufficient to attain the environmental water quality standards,
the Law provides that stricter effluent standards may be set by an ordinance
of the prefecture having jurisdiction over that perticular water body.
At present, the possibility and scientific basis for establishing efflu-
ent standards for nitrogen and phosphorus are being discussed deliberately by
the Central Council for Environmental Pollution Control.
56
-------
4. A NEW LEGISLATION FOR LAKE WATER PROTECTION
On May 13, 1983, after more than two years of arduous inter-departmental
negotiation within the government, a draft bill for the preservation of water
quality in lakes and reservoirs was decided.upon by the Cabinet and was pre-
sented on the same day to the Diet (Japanese National Parliament). The
Government-proposed bill was then sent to the Environment Committee of the
House of Representatives (Lower House), but, due to shortage of time before
its closure, the bill was not debated upon to any extent during the current
session. The Committee instead allowed the Director-General of the Environ-
ment Agency to give a brief introductory statement before it, and decided
to "continue its delicerations" (e.e. postpone its decision) until the next
session of the Diet.
In light of the fact that the Environment Committee itself and the
Special Committee on Environmental Pollution and Traffic Safety of the House
of Councillors (Upper House) had in the previous year both passed almost
idential resolutions calling for the Government's strengthened efforts to
protect the natural environment as well as water quality of lakes and reser-
voirs around Japan and for the promotion of a new legislation toward that
end, the Government-proposed bill is likely to meet little opposition in both
Houses, and, if all goes well, is expected to become a law during the next
extraordinary session of the Diet to be opened in the fall of this year.
An outline of the proposed legislation follows:
Under the provisions of the proposed bill,
(1) The Government shall provide basic policy guidelines for the pro-
tection of lakes and reservoirs.
(2) The prefectural governors shall draw up environmental protection
plans regarding lakes and reservoirs which are threatened with degradation
of its water quality and considered to require comprehensive and systematic
measures of protection to overcome the problem. The national and municipal
authorities should carry out the plans accordingly.
57
-------
(3) Various measures for water quality protection, such as establishment
of sewerage, should be taken steadily according to the characteristics of
lakes and reservoirs under a long-term and comprehensive plan so that the
measures as a whole will achieve the desired results. Such plans should
include the strengthening of effluent control on factories and other business
premises, permit for the establishment of specified facilities, prevention
of pollution caused by small-scale livestock feedlots, fish culture grounds,
domestic waste water, agricultural drainage, etc., and introduction of area-
wide total pollutant load control system.
(4) The State shall give maximum possible financial aid to municipali-
ties, while both the State and municipalities should strive to provide factory
operators and others with necessary assistance regarding financing and taxa-
tion.
58
-------
< Outline of the Proposed Legislation >
Basic Guidelines on Lakes and
Reservoirs Water Quality Management
Prime Minister
(with Cabinet decision)
views of the municipalities concerned
I
proposal for designation by the
Prefectural Governor
Designation of a lake & Designated Area
rviews of prefectural
governors concerned
•Prime Minister
(with Cabinet decision)
or
Designation of lakes to come under Area-
wide Total Pollutant Load Control System
• Cabinet Order
Lake Water Quality Management Program
• policy directions
• promotion of public works for
sewerage & sewage treatment, waste
disposal, aeration, dredging of
sediments, etc.
• effluent control & other regulations
Special regulations to reduce pollution
load on the lakes and reservoirs
• to be drawn up every 5
years by the Prefectural
Governor
views of the municipali-
ties and other bodies
concerned
• consent of the Prime
Minister (with agreement
of the Council on En-
vironmental Pollution
Control)
1) Pollutant load control standard to be
applied to Specified Facilities within
Designated Area (Prefectural Governor
to set the standard)
2) Application of regulations under Water
Pollution Control Law to facilities
other than the Specified Facilities
3) Performance (structure & management)
standard to be established by the
Prefectural Governor and applied to
Designated Facilities (e.g. livestock
feedlot, fish culture)
59
-------
4) Introduction of Areawide Total Pollutant
Load Control System to the lakes desig-
nated by Cabinet Order
Implementation of public works to preserve
lake water quality
Other
measures
• administrative guidance, advice, recommendation to domestic and
other sources of pollution
• preservation of the lakeside natural environment
• financial assistance and aid-in-grant to prefectures and munici-
palities, cooperation between governmental organizations concerned,
etc.
60
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
UPGRADING
OF
ANAEROBIC DIGESTION PROCESS
September 19-21,1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Shunsoku Kyosai
Chief
Ultimate Disposal Section
Water Quality Control Division
Public Works Research Institute
Ministry of Construction
Yoshio Ohshima
Senior Researcher
Ultimate Disposal Section
Water Quality Control Division
Public Works Research Institute
Ministry of Construction
61
-------
TABLE OF CONTENTS
Page
1. INTRODUCTION 63
2. PRESENT STATUS OF ANAEROBIC DIGESTION IN JAPAN 64
3. GAS YIELDS OF PRIMARY SLUDGE AND EXCESS SLUDGE 72
3.1 TEST METHOD 72
3.2 RESULTS 74
4. EFFECTS OF HIGH-CONCENTRATED FEED SLUDGE ON GAS YIELD 79
4.1 TEST METHOD 79
4.2 RESULTS 80
5. INCREASE OF GAS YIELD BY THE THERMAL CONDITIONING
OF FEED SLUDGE 84
5.1 THERMAL CONDITIONING PROCESS 84
5.2 120°C THERMAL CONDITIONING OF EXCESS SLUDGE 85
5.2.1 Test Method 85
5.2.2 Results 86
5.3 BATCH DIGESTION TESTS ON SLUDGE SUBJECTED TO THERMAL
CONDITIONING AT VARIOUS TEMPERATURES 88
5.3.1 Test Method S9
5.3.2 Results 39
5.4 CONTINUOUS DIGESTION TEST OF SLUDGE WITH THERMAL CONDITIONING
TEMPERATURE AS A PARAMETER 98
5.4.1 Test Method 98
5.4.2 Results 99
6 SUMMARY 103
62
-------
1. INTRODUCTION
Japan is the second largest oil-consuming country in the free world,
and its energy sources are almost entirely dependent on imports.
Securing a stable source of energy supply, promoting energy-saving
measures, and at the same time developing the alternatives to oil to
minimize the dependency on oil are of critical importance to Japan.
Fully realizing the significance of the matter, we investigated a way of
saving energy in the wastewater treatment plants which are now
increasingly growing in number and also of utilizing potential energy
resources available there.
As of 1980, there were some 480 wastewater treatment plants in
Japan, and their total annual energy consumption was something like
2,000 million kWh in electric power and about 460,000 kl in heavy oil.
As the number of wastewater treatment plants will continue to grow in the
future, their energy consumption will increase in proportion.
In the wastewater treatment plant, the anaerobic digestion process
is operated mainly for the purpose of reducing the volume of sludge
produced and at the same time stabilizing its quality. It gives off
digester gas, including methane, with a heat value of 5,000 to 6,000 kcal
per Nm . So far the digester gas has been used in Japan only for
heating the digestion tank. If we could increase the output of digester
gas, the anaerobic digestion process would be turned into a useful energy
source.
This paper is primarily concerned with the following.
(1) Present status of anaerobic digestion in Japan
(2) Gas yields of primary sludge and excess sludge
(3) Effects of high-concentrated feed sludge on gas yield
(4) Increase of gas yield by the thermal conditioning of feed sludge
63
-------
2. PRESENT STATUS OF ANAEROBIC DIGESTION IN JAPAN
As touched upon earlier, there were some 480 wastewater treatment
plants in Japan as of 1980, of which about 180 were equipped with
digestion tanks. As shown in Table 1, 156 out of these 180 wastewater
treatment plants were operated on a system involving a thickening
process, anaerobic digestion process, and dewatering process and disposal
process.
The sludge treated in this way amounted to about 240,000 tons a year
in terms of solids of thickened sludge, or about 26% of about
930,000 tons produced by all the systems. Of the 180 wastewater
treatment plants, 17 were operated on a thickening-anaerobic
digestion-dewatering-incineration system, accounting for about 24% of the
total amount of sludge generated. All told, about a half of the sludge
was treated by the digestion process.
From Table 1, it can also be said that:
(1) incinerated ash (56%) and dewatered sludge (43%) accounts for nearly
99% of the total quantity of sludge disposed of and that
(2) the incinerated ash is largely classified into two sludge treatment
systems - one consisting of thickening, dewatering and incineration
and the other consisting of thickening, anaerobic digestion,
dewatering and incineration. The plants operating on these two
systems were 55 and 17 respectively, turning out sludge at
290,000 tons/yr. and 220,000 tons/yr. In most large-scale
wastewater treatment plants, incineration was preceded by an
anaerobic digestion process.
The majority of those wastewater treatment plants with an anaerobic
digestion tank were operated as follows.
• Two-stage digestion with 30 days of solids retention,
• mesophitic digestion at a temperature of 30 C to 37 C,
• steam injection heating,
• agitation by gas mixing
64
-------
Table 1 Applied sludge treatment processes
Form of
disposed
sludge
Liquid
Dewatered
Dried
Composted
Sludge treatment processes
Withdrawal
Thickening
Thickening-Anaerobic Digestion
Thickening-Aerobic Digestion
TOTAL
Thickening-Dewatering
Thickening-Anaerobic Digestion-Dewatering
Thickening-Aerobic Digestion-Dewatering
Thickening-Wet Oxidation-Dewatering
Thickening-Thermal Conditioning-Dewater ing
TOTAL
Thickening-Drying
Thickening-Anaerobic Digestion-Drying
Thickening-Aerobic Digestion-Drying
Thicken ing-Dewatet ing-Dry ing
Thickening-Anaerobic Digest ion-Dewater ing-Dry ing
TOTAL
Thickening-Dewater ing-Composting
Thickening-Anaerobic Digestion-Dewatering-Compostinc
TOTAL
Number
Having
the
processes
5(0)
19(16)
3(2)
11(8)
38(26)
116(12)
156(7)
17(1)
1(0)
6(0)
296(20)
6(0)
1(0)
1(0)
2(0)
7(1)
17(1)
1(0)
3(0)
4(0)
Of WTPs
Disposed
by the
processes
5
3
1
3
12(3)
104
163
17
1
6
291(65)
5
1
1
2
6
15(3)
1
3
4(1)
Treated solids based
on thickened sludge
xl,000 tons/year %
-
3.88
1.82
0.02
5.72
138.07
243.46
2.31
9.16
7.43
400.43
0.00
-
0.03
1.88
4.86
6.77
0.37
2.08
2.45
0
0.41
0.19
0.0
0.61
14.77
26.04
0.24
0.98
0.79
42.84
0.0
0
0.0
0.20
0.51
0.72
0.03
0.22
0.26
-------
Table 1 Applied sludge treatment processesl (Cont'd)
Form of
disposed
sludge
Incinerated
Ash
Sludge treatment processes
Thickening-Dewater ing- Incineration
Thickening-Anaerobic Digestion-Dewater ing-Incineration
Thickening-Aerobic Digestion-Dewater ing-Incineration
Thickening-Thermal Condi tioning-Dewater ing- Incineration
TOTAL
TOTAL
WTPs having sludge treatment facilities and transporting sludge
to other WTPs.
Unknown and
TOTAL
no sludge production
Number
Having
the
processes
55(0)
17(0)
0(0)
4(0)
76(0)
431(47)
40
6
477
of WTPs
Disposed
by the
processes
82
34
8
4
128(100)
450(100)
—
27
477
Treated solids based
on thickened sludge
xl,000 tons/year %
286.72
221.33
0.68
10.58
519.31
934.68
934.68
30.
23.
0.
1.
55.
100
100
67
67
07
13
56
-------
As shown in Fig. 1, about 50% of the wastewater treatment plants
were operating at a gas yield (gas production/feed sludge volume) not
exceeding 5:6, reportedly lower than similar treatment plants in the west.
ZD
IX
f! 20
(0
a
c
1 15
03
0)
4
9
4
C>
5
20
5
^
6
23
6
^
7
9
7
^
8
19
8
10
12
10
?
11
8
11
<>
12
5
12
?
13
3
13
-------
(3) Difference in secondary treatment
In Japan, the aeration time for secondary treatment is
generally longer than that in Europe and the U.S.A. Namely, the
sludge itself has already been reducing the gas production when it
enters the digestion tank.
(4) Difference in sidestreams from sludge treatment processes to water
treatment process
The flow of the sidestreams and SS loadings in them are said to
be larger than in Europe and the U.S.A. As the sludge that has
little potential to generate gas is circulated, the apparent gas
yield is reduced.
While the four factors are conceivably responsible for the low gas
yield, we cannot be categorical about which is the principal cause. Now
we shall discuss the effects of sidestreams.
Fig. 2 is a histogram showing the frequency distribution
relationship between the supernatant ratio (supernatant of digested
liquor/feed sludge volume) and the number of digestion tanks as of 1980.
20
10
EL
Supernatant
ratio
Number of
WTPs
100
2
100
90
16
90
80
17
80
70
25
70
60
28
60
50
20
50
^
40
18
40
3d
14
30
^
20
11
20
10
6
10
0
5
Fig. 2 Frequency distribution of supernatant ratios
68
-------
It is found from this figure that more than a half of the national
total of the digestion tanks were operated at a supernatant ratio of 60%
or higher. The SS concentration in the supernatant is extremely high,
and is one of the causes of the reduction of gas yield as discussed in
item (4) above.
The next point for consideration is the concentration of digestion
tank feed sludge and draw-off sludge.
Figs. 3 and 4 show the frequency distribution of the concentrations
of digestion tank feed sludge and draw-off sludge; the concentrations of
feed sludge or thickened sludge were less than 2% in about 30% of the
wastewater treatment plants in Japan and less than 3% in 70% of the
wastewater treatment plants.
50
40
30
I 20
10
Solids con-
centration
Number ot
WTPs
9
26
1
2
47
2
i
3
74
3
?
4
59
?
5
14
5
6
2
6
7
Fig. 3 Frequency distribution of feed sludge concentrations
69
-------
50
40
F ou
§
'o
° 20
to
rr
10
n.
Solids con-
centration
Number of
WTPs
0
^
1
16
1
^
2
29
2
<>
3
41
3
6
10
6
C3
7
6
7
<•
8
3
8
^
9
2
9
^
10
Fig. 4 Frequency distribution of draw-off sludge concentrations
In Japan, the concentrations of the thickened sludge are generally
low. This may be attributed to the decomposition of sludge in the
thickener due to high mean temperatures and also to the reduction of
solids-liquid separation performance due to decomposition. From Figs. 3
and 4, it is found that the concentration of solids in the sludge
increases after passing through the digestion tank.
Fig. 5 shows the mass balance in the digestion tank in terms of
draw-off solids ratio (solids in draw-off sludge/solids in feed sludge).
20
£ 15
S.
\-
° 10
I
3
z
n
Draw-off
solids ratio
Number of
WTPs
100
3
100
^
90
27
90
^
80
9
80
50
23
50
-------
Those wastewater treatments which showed a draw-off solids ratio of
more than 90% account for about 15%. In these plants, 90% of the solids
in the feed sludge was sent as digested sludge to the succeeding
processes, including dewatering process, and the remaining 10% was turned
into digestion gas or returned in the form of supernatant.
As shown in Fig. 6, the unit capacity of digestion tank varies over
a wide range from several hundred cubic meters to 5,000 cubic meters.
70
60
50
•6
S 40
ro
tr
30
20
10
n
Digestion
tank capacity
(m3)
Number of
WTPs
0
f
500
34
500
c>
1,000
36
1,000
?
1,500
68
1,500
f
2,000
46
2,000
f
2,500
55
2,500
f
3,000
3,000
^
3,500
48 48
3,500
e>
4,000
29
4,000
^
4,500
36
4.500
f
5,000
15
5,000
^
5,500
18
5,500 | 6,000
^
6,000
11
^
6.500
5
6.500
f
7,000
2
7,000
t>
7,500
7,500
<>
8,000
6
8,000 8.500 9,000 9,50C|10,000
-------
3. GAS YIELD OF PRIMARY SLUDGE AND EXCESS SLUDGE
This chapter is primarily concerned with the gas production by
anaerobic digestion of primary sludge, excess sludge and mixed sludge and
the causes of the differences in gas yields. To investigate these,
laboratory tests were conducted as reported here.
3.1 TEST METHOD
Using an arrangement shown in Fig. 7, we conducted a test for 8
weeks at a digestion temperature of 30°C with the solids retention time
set at 30 days.
Fig. 7 Digestion test arrangement
During the test period, sludge was fed and drawn off once a day.
The sludge used for the test is classified into six types as shown in
Table 2.
72
-------
Table 2 Characteristics of feed sludge
Sludge
1- Primary
1-Excess
2-Primary
2-Excess
sludge
sludge
sludge
sludge
3-Mlxed sludge
3-Excess
sludge
TS
mg/i
40,100
37,100
38,400
42,600
37,900
41,000
VS
mg/d
(84.6)
33,900
(85.0)
31,500
(61.8)
23,700
(69.2)
29,500
(67.6)
25,600
(77.9)
31,900
T-C
mg/£
(42.1)
16,890
(48.2)
17,870
(31.0)
13,060
(33.4)
14,220
(36.8)
13,950
(41.7)
17,080
T1— N T~P
mg/2, mg/£,
(4
1,
(9
3,
(5
2,
(6
2,
(4
1,
(8
3,
.2)
690
.8)
640
.2)
000
.7)
850
.7)
770
.6)
520
(0.
304
(1.
519
(1.
440
(1.
465
(1.
449
(1.
619
8) 10.0
4) 4.9
1) 6.5
1) 5.0
2) 7.9
5) 4.9
Heat value WTPs from which sludge
cal/g
4,310
4,900
3,580
3,660
3,730
4,370
was sampled
Separated sewer system
Conventional activated sludge
No sludge treatment facility
Separated but partially
combined sewer system
Conventional activated sludge
Thickening-De water ing
Combined sewer system
Conventional activated sludge
26,000 m3/D
process
88,000 m3/D
process
90,000 m7/D
process
Thickening-Anaerobic Digestion-Dewatering
Note: Values in parentheses are percentages to TS.
-------
From three wastewater treatment plants, primary sludge and excess
sludge were sampled. At No. 3 wastewater treatment plant, mixed sludge
was sampled instead of primary sludge. The sampled sludge was pulverized
and screened to remove large blocks. Then, it was adjusted to a solids
concentration of about 4% for test.
Before test, 7 lit. of the digested sludge was charged into each
test tank as seed sludge, and 1 lit. of the test sludge was injected in
about 2 weeks for acclimation of the seed sludge.
3.2 RESULTS
During the 8-week test period, the weekly production of total gas
volume and methane gas volume per gram of organics (VS) in the feed
sludge was measured as shown in Figs. 8 and 9. The gas production was
almost constant over the entire test period.
(B/gvs)
( 0.7
0.6
c
g
? 0.5
•o
o
Q.
I 0.4
0.3
0.2
0.1
1-Primary sludge
A
2-Excess
sludge
Weeks
Fig. 8 Gas production per gram of feed VS
74
-------
(B/gvs)
9
a
0.5
0.4
0.3
0.2
0.1
1 -Primary sludge
3-Mixed 1-Excess sludge
sludge O-—
2-Primary
sludgeD^
.3-Excess
2-Excess
sludge
Fig. 9 Methane gas production per gram of feed VS
Table 3 compares the six types of sludge with respect to the mean
value of gas production in the latter half (4 weeks) of the test period.
Table 3 Gas production
1-Primary sludge
1-Excess sludge
2-Primary sludge
2- Excess sludge
3-Mixed sludge
3-Excess sludge
Gas yield
(&/g .vs)
0.688
0.478
0.349
0.274
0.393
0.385
Methane yield
(£/g .VS)
0.389
0.306
0.238
0.179
0.243
0.238
Methane ratio, %
56.5
64.0
68.2
65.3
61.8
61.8
Fig. 10 shows the relationship between the gas production per gram
of VS and the organics ratio (VS/TS).
75
-------
(e/gvs)
0.7
0.6
0.5
33
o>
'
O 0.4
0.3
0.2
O 1-Primary sludge
1-Excess sludge
O 3-Mixed
sludge
O 3-Excess sludge
2-Pnmary
sludge
° 2-Excess sludge
60
70
80
90 (VS/TS) (%)
Fig. 10 Content of organics in sludge, and gas yield
Tables 2 and 3 and Fig. 10 show the following.
(1) For each specific wastewater treatment, the gas yield per gram of VS
is greater in the primary sludge than in the excess sludge, and the
gas production in the mixed sludge comes in between.
(2) For either excess sludge or primary sludge the greater the organics
ratio, the larger the gas production per gram of VS.
(3) In the separated sewer wastewater treatment plant where there are no
sidestreams from the sludge treatment process, the organics ratio in
the sludge is higher than in other plants.
(4) The methane gas ratio in the produced gas is less influenced by the
type of sludge, and is in the range of 55 to 70%, or about 60% on
the average.
76
-------
In order to investigate why the primary sludge produces more gas
than the excess sludge, the composition of organics was analyzed.
l&bles 4 and 5 show the analysis of carbohydrates, fats, and
proteins in the feed sludge and digested sludge tested.
liable 4 An analysis of organics in feed sludge
Feed sludge
1- Primary
1-Excess
2- Primary
2-Excess
sludge
sludge
sludge
sludge
3-Mixed sludge
3-Excess
sludge
TS
mg/£
40
37
38
42
37
41
,100
,100
,400
,600
,900
,000
VS Total
% carbohydrate,
84.
85.
61.
69.
67.
77.
6
0
8
2
6
9
49.
13.
6.
6.
19.
9.
2
2
9
0
5
0
Total
% fat, %
7.
26.
12.
12.
8.
20.
0
9
2
1
1
3
Total
protein, %
11.
27.
26.
26.
26.
27.
9
6
3
3
3
5
Table 5 An analysis of organics in digested sludge
Feed sludge
1- Primary sludge
1-Excess sludge
2-Primary sludge
2-Excess sludge
3-Mixed sludge
3-Excess sludge
TS
mg/£
19,100
22,000
32,500
23,200
27,700
27,000
VS Total
% carbohydrate,
59.1
68.8
51.3
54.7
53.7
64.7
7.6
6.8
7.0
7.5
7.9
6.9
Total
% fat, %
9.8
14.4
8.3
7.3
8.3
12.4
Total
protein, %
20.0
31.9
21.3
24.4
20.0
28.1
These three components account for 70 to 80% of the total organics
in the sludge. As regards the feed sludge, the primary sludge shows a
high content of carbohydrates, whereas the excess sludge a high content
of fats and proteins.
77
-------
The component ratios of the organics in the feed sludge are compared
with those in the digested sludge below. In the digested sludge, the
content of carbohydrates falls to a specific level irrespective of the
content of feed sludge. The residual quantity of fats in the digested
sludge has some correlation with the content of fats in the feed sludge.
The reduction of proteins is not so high as compared with the two
components referred to above.
From the above, it is inferred that carbohydrates and proteins in
the feed sludge govern the gas production, and that the carbohydrates are
particularly influential.
Fig. 11 shows the correlation between the total carbohydrate ratio
and fat ratio and the gas production per unit quantity of feed VS.
(e/gvs)
-o
01
8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
•
0
*
• Primary sludge
0
O Excess sludge
X Mixed sludge
0 10 20 30 40 50 60
Total carbohydrate and total fat
in feed sludge (%)
Fig. 11
As is clear from Fig. 11, the correlation is highly significant, and
has little to do with the types of sludge. One can therefore conclude
that the primary sludge produces more gas than the excess sludge because
of the higher content of carbohydrates and fats contained in the former.
78
-------
4. EFFECTS OF HIGH-CONCENTRATED FEED SLUDGE ON GAS YIELD
As discussed in Chapter 2, the concentration of feed sludge to the
digestion tank is generally lower in Japan than in Europe and the U.S.A.
In Japan, the capacity of the digestion tank is determined according to
the following formula.
V
where V is the capacity of digestion tank, 0, is the feed sludge
volume, Q7 is the draw-off sludge volume, and T is the solids retention
time (usually 30 days) .
Namely, the lower the concentration of feed sludge, the greater
becomes the capacity of the digestion tank required. The increase in the
capacity of digestion tank leads to the increase in energy required for
heating the digestion tank. In order to minimize the energy demand, it
is imperative to increase the feed sludge concentration. In view of
this, the wastewater treatment plants in Japan are beginning to employ
the flotation thickening process or centrifugal thickening process. The
adoption of mechanical thickening processes in Japan is intended not only
for the reduction of heating energy requirements, but also for the
improvement of thickening process and the reduction of overall cost for
the processes following it. The main interests of this chapter are the
effects of an increase in the feed sludge concentration on the
performance of the existing digestion tanks and on the gas production.
4.1 TEST METHOD
For the test, the same arrangement (Fig. 7) as explained in
Chapter 3 was used. The number of test tanks was six. They were paired
off, and the digestion temperature was set at 30 C for one pair, 33 C
for another pair, and 36 C for the remaining pair. The sludge adjusted
at a concentration of 4% and 6% was digested for a solids retention time
of 40 days, 30 days, 20 days and 15 days. For each solids retention
time, the test was conducted for 4 weeks. That is to say the test was
conducted for an total period of 16 weeks.
79
-------
During the test period, the sludge was fed and drawn off once a
day. The sludge used for the test was the mixed sludge sampled at a
wastewater treatment plant, pulverized, screened, and adjusted to 4% and
6% in concentration by a centrifugal thickener. Table 6 shows an
analysis of the sludge tested.
Table 6 An analysis of feed sludge
TS VS T-C T-N T-P VS/TS
mg/£ mg/& mg/£ mg/£
4% feed 41,280 32,130 17,050 1,960 372 77.8 8.7
sludge
6% feed 60,840 47,440 25,310 2,860 483 78.0 8.8
sludge
For the test, each of the six test tanks was filled with 8 lit. of
the same sludge, and was left to stand for 2 weeks at a specified
digestion temperature. Then, the test tanks were run on a one daily feed
and discharge basis with respective solids retention times.
4 . 2 RESULTS
Figs. 12 and 13 show the weekly gas production and weekly average
methane ratio per unit quantity of feed organics over a total test period
of 16 weeks.
80
-------
0.7.
d, °-6
Of
I °-5
(0
u 0.4-
0.3
0.2
0.1
Organic loading
0.8g/d./lit.
1.5g/d./ht.
2.0 g/d./lit.
S 60.
ro
0)
c
CD
£ 50
u
10 11 12
13 14 15
Weeks
16
30 °C
33'C
36-C
10 11 12
13 14 15
Weeks -
16
Fig. 12 4% sludge-gas yield and methane ratio
81
-------
u
0.6
a> 0.5
0.4-
0.3
0.2
0.1
- 70
o
S 60
I 50
Organic loading,
1.5g/d./lit
2.4g/d./lit.
3.0g/d./lit.
10 11
12
13 14 15
Weeks
16
10 11 12 13
14 15_
Weeks
Fig. 13 6% sludge-gas yield and methane ratio
In the 40-day solids retention time in the first 4 weeks, methane
bacteria in the sludge would have proliferated. The gas yield increased
week after week during the period. The increase in gas production shows
a significant difference depending on the digestion temperature. The
time required for the gas production to level off was 2 weeks at a
digestion temperature of 36°C, 3 weeks at 33°C and 4 weeks at 30 C.
It was found that the 6% sludge took a somewhat longer time for
stabilized gas production than the 4% sludge.
In the 5th week, the loading was increased a step for a 30-day
solids retention. The test tanks showed almost the same gas production;
the gas yield was held at a level of about 0.55 lit./gVS.
Pigs. 14 and 15 show the gas yield vs. solids retention time
relationship for the 4% and 6% sludge.
82
-------
r
5 0-6
>
en
3 0.5
fO
0.3-
0.2
0.1-
O 30'C
A 33 'C
D 36 °C
Total gas
Methane ga
30 20
Solids retention time, days
15
Fig. 14 4% sludge-gas yield
0.7.
0.6
f 0.5 ^
•v
0>
> 0.4 -
Ifl
to
0.3
0.2
0.1
0
O 30-C
A 33°C —
D 36 "C
Total gas
•—— Methane gas
30 20
Solids retention time, days
15
Fig. 15 6% sludge-gas yield
Plotted are the mean values of the data obtained in the latter 2
weeks in each solids retention period.
From these figures, the following are found.
(1) No noticeable change in gas yield with change in digestion
temperature and solids retention time.
83
-------
(2) No significant difference in gas yield between 4% and 6% sludge; the
gas production remained at 0.55 lit./gVS on the average.
(3) Likewise, the methane gas yield was held almost constant at
0.33 lit./gVS.
From the above, it is concluded that the sludge with a high
concentration of about 6% can be processed successfully under usual
digestion conditions.
5. INCREASE OF GAS YIELD BY THE THERMAL CONDITIONING OF FEED SLUDGE
As discussed in Chapter 2, the gas yield in the wastewater treatment
plants in Japan is low. For the sake of energy utility, it is desirable
to develop an economical method of improving the gas yield.
A method of sludge pretreatment, called thermal conditioning, is
already being studied. It is recognized that thermal conditioned sewage
sludge increases gas production in the digestion tank. It has been
reported that the effect of thermal conditioning on the improvement of
gas yield is considerable particularly in the case of excess sludge.
This chapter is concerned with the thermal conditioning process
investigated in relation to the following.
(1) Effects of thermal conditioning on the excess sludge in Japan.
(2) Optimal temperature for thermal conditioning of excess sludge.
(3) The effects of thermal conditioning on the primary sludge.
(4) Solids-liquid separation performance and dewaterability of thermally
conditioned digested sludge.
(5) Quality of supernatant separated from the thermally conditioned
digested sludge.
5.1 THERMAL CONDITIONING PROCESS
Usually, the thermal conditioning of sludge is carried out for 30 to
120 min. at a temperature of 180 to 210°C in an anoxic, pressurized
state, for the purpose of altering colloidal or gel substances in the
sludge in order to produce a sludge with a high thickenability and a high
dewaterability.
-------
The operating principles of the thermal conditioning process are
argued as follows. The sewage sludge forms hydrophilic colloid
consisting of organics such as proteins, carbohydrates and fibrous
residues and inorganics. The colloidal particles are encapsulated with
hydrated layers. When the sludge is heated, water molecules are
invigorated, increasing the collision and combination of sludge
particles. The hydrated layers are broken up, and coagulation takes
place (thermal coagulation phenomenon). The colloidal gel structure is
destroyed at heat, and the water contained in it is separated (bleeding
phenomenon). In addition, the organics in the sludge are subjected to
hydrolysis at heat, and are dissolved (liquefaction of sludge). These
phenomena are considered to take place not in stages, but concurrently
during the thermal conditioning. As a result, the sewage sludge is
turned into one which is high in settlability and dewaterability. The
degree to which the sewage sludge is reformed is governed by the time and
temperature of reaction. While the thermal conditioning improves
settlability and dewaterability, it degrades the concentration, color and
odor of the supernatant produced by the liquefaction of the sludge.
This chapter deals with an experiment in which the thermal
conditioning process was used to precede the digestion process.
5.2 120°C THERMAL CONDITIONING OF EXCESS SLUDGE
The test was designed to investigate whether the thermal
conditioning would improve the gas yield of excess sludge in Japan.
5.2.1 Test Method
For the test, two digesters with an effective capacity of 20 lit.
were used. The excess sludge pretreated in an autoclave for 30 min. at
120 C was put into one digester, and the control sludge was put into
another digester. These two digesters were run in parallel in order to
compare respective gas outputs. The digestion was conducted over a
period of 8 weeks at a temperature of 35°C with the solids retention
time set at 30 days.
85
-------
The sludge used was taken from the return sludge pit of a wastewater
treatment plant, and was thickened to about 2.5% in TS concentration.
The wastewater treatment plant from which the sludge was sampled was
designated for the treating of domestic wastewater only, and the sample
was considered to be the highly stabilized excess sludge.
Table 7 shows an analysis of the excess sludge used for test. Prior
to the test, seed sludge was acclimated with the test sludge for 2 weeks.
Table 7 An analysis of feed sludge
Sludge
TS
mg/£
VTS
mg/£
T-C
mg/Jl
T-N
rag/A
T-P
mg/£
VTS/TS
%
C/N
Control
25,000 17,800 9,750 1,560 350 71.2 6.3
(428)
120 C thermally 26,100 18,500 (2,110) 1,700 370 70.9
conditioned
( ): Supernatant
5.2.2 Results
Fig. 16 shows the weekly gas production over the 8-week period.
Fig. 17 shows the weekly average methane ratio.
30
-20
o
13
O
a- 10
-------
Methane ratio (B) —
S-J OC
o c
— C~
<•>-, o
123456
Control sludge
120°C thermally
conditioned sludge
g-^j— o
7 8
Weeks •"
Fig. 17 Weekly average methane ratio
As shown, the gas production from the 120 C thermally conditioned
sludge was higher than from the control sludge. In the latter 4 weeks,
the gas production from the thermally conditioned sludge was 58% more
than that from the control sludge. The gas yield was 0.19 lit./gVS for
the control sludge and 0.29 lit./gVS for the thermally conditioned
sludge, showing that the latter was up 53% from the former. Table 8
shows an analysis of the final draw-off digested sludge.
Table 8 An analysis of digested sludge
Sludge
TS VTS T-C
mg/Si mg/H mg/£
T-N T-P VTS/TS
mg/£
C/N
Control 21,100 13,500 7,470 1,510 360 64.0 4.9
(606)
120°C thermally 19,600 11,700 (1,110) 1,660 380 59.7
conditioned
( ): Supernatant
The organics in the thermally conditioned sludge were reduced more
than 58% than those in the control sludge, substantiating the gas
production increase by the thermal conditioning.
87
-------
It has thus been corroborated that the thermal conditioning process
is quite effective for the improvement of gas yield from the excess
sludge in Japan, and that the liquifaction of sludge by thermal
conditioning has a close relationship with the increase in gas
production. In the next section, discussions are made about the optimum
temperature that maximizes the gas yield and the effects of thermal
conditioning on the primary sludge.
5.3 BATCH DIGESTION TESTS ON SLUDGE SUBJECTED TO THERMAL CONDITIONING AT
VARIOUS TEMPERATURES
The tests conducted were the same as in the foregoing, except that
the thermal conditioning temperatures were changed. The tests were
carried out with respect to three cases to compare the gas yields. The
conditions for each case were as follows.
(1) Case I
Batch digestion test using thermally conditioned excess sludge
and control sludge. Heating conditions: 70°C, 87°C and 120 C
(2) Case II
Batch digestion test using thermally conditioned excess sludge
and control sludge. Heating conditions: 120°C, 150°C and 180 C
(3) Case III
Batch digestion test using thermally conditioned primary sludge
and control sludge. Heating conditions: 120°C, 150°C and 200°C
88
-------
5.3.1 Test Method
For all cases I, II and III, the digestion was carried out in the
batch process. For each case, four digesters with an effective capacity
of 10 lit. were used. The digestion temperature was set at 35°C.
Prior to the test, 6 lit. of seed sludge and 4 lit. of test sludge were
loaded into each digester.
5.3.2 Results
Here, the findings are discussed case by case, and then summarized.
(a) Case I
Fig. 18 shows the cumulative total of gas production with time
over a test period of 56 days.
50
40
s 30
3
§
S 20
10
D 120"C thermally conditioned
A 87 °C thermally conditioned
O 70 °C thermally conditioned
— Control
14
28
42
56 70
Days elapsed
Fig. 18 Case I: Cumulative gas production
89
-------
The total volume of digestion gas produced from the control
sludge was about 24 lit. TO produce the same amount of digestion
gas, the 70°C thermally conditioned sludge took 44 days, the
87°C sludge took 30 days, and the 120°C sludge took 20 days. It
is found that for an ordinary solids retention time of about 30
days, the thermal conditioning has a significant bearing on the
improvement of gas yield. For up to 120 C, the higher the thermal
conditioning temperature is, the greater the amount of gas
production results.
Table 9 shows an analysis of the test sludge, and Table 10 an
analysis of the digested sludge.
Table 9 An analysis of feed excess sludge (Case I)
TS VTS T-C T-N T-P VTS/TS
S1Udge mg/£ mg/£ mg/£ mg/g, mg/£ %
Control 26,500 20,400 11,100 1,860 380 77.0 6.0
(420)
70°C thermally 27,200 20,800 (2,110) 2,250 420 76.5
conditioned
87°C thermally 25,500 19,500 (2,500) 1,770 390 76.5
conditioned
120°C thermally 26,900 20,600 (2,900) 1,790 390 76.6
conditioned
( ): Supernatant
90
-------
Table 10 An analysis of digested sludge (Case I)
Sludge TS VTS T-C T-N T'P VTS/TS C/N
mg/£ mg/£ mg/£ mg/£ mg/£ %
Control 18,300 11,800 7,560 1,860 361 64.5 4.1
(1,440)
70°C thermally 18,200 11,700 (1,450) 1,850 368 64.3
conditioned
87°C thermally 17,600 11,100 (1,520) 1,810 361 63.1
conditioned
120°C thermally 17,200 10,800 (1,540) 1,820 365 62.8
conditioned
( ): Supernatant
The control sludge and thermally conditioned sludges were
compared in terms of the amount of residual organics in the digested
sludge. So far as the temperatures used for thermal conditioning
are concerned, the higher the temperature, the smaller the residual
amount of organics, explaining why the gas production was increased
at high thermal conditioning temperatures.
(b) Case II
Fig. 19 shows the cumulative total volume of the gas produced
with time.
91
-------
50
40
I30
I 20
10
a 180'C thermally conditioned
A 150'C thermally conditioned
° 120 °C thermally conditioned
— Control
14
28
42
56 70
Days elapsed
Fig. 19 Case II: Cumulative gas production
The total volume of gas produced over a solids retention time
of 56 days was up 36% for the 120°C thermally conditioned sludge,
up 52% for the 150°C sludge and up 54% for the 180°C sludge as
against 26 lit. marked by the control sludge. In the 180 C
sludge, gas production rate was retarded for the first 10 days.
With regard to total gas volume it is inferred that the best thermal
conditioning temperature is somewhere between 150 C and 180 C.
Table 11 shows an analysis of the test sludge, and Table 12 an
analysis of the digested sludge.
92
-------
Table 11 An analysis of feed excess sludge (Case II)
_, , TS VTS T-C T-N T-P VTS/TS
9 mg/H mg/Si mg/£ mg/£ mg/£ %
Control24,20019,10010,3001,93043478.95.3
(380)
120°C thermally 25,000 19,900 (2,660) 2,060 436 79.6
conditioned
150°C thermally 24,400 19,100 (4,510) 1,970 429 79.3
conditioned
180°C thermally 24,500 18,800 (5,870) 2,040 420 76.7
conditioned
( ): Supernatant
Table 12 An analysis of digested sludge (Case II)
„, , TS VTS T-C T-N T-P VTS/TS
9 mg/£, mg/Si mg/£ mg/£ mg/£ %
Control17,50011,7006,9301,92038966.93.6
(1,230)
120°C thermally 15,800 9,940 (1,500) 1,920 408 62.9
conditioned
150°C thermally 15,700 9,900 (1,550) 1,920 401 63.1
conditioned
180°C thermally 15,500 9,640 (1,830) 1,930 401 62.2
conditioned
( ): Supernatant
93
-------
Referring to Table 11 and Table 12, it is found from the change
in total carbon in the supernatant that the liquefaction of
thermally conditioned sludge progressed, and that the total carbon
in the supernatant of the thermally conditioned sludge reduced
greatly compared with the control sludge. It is considered that the
high BOD component in the supernatant resulting from thermal
conditioning got reduced sufficiently by the anaerobic digestion
process.
Table 13 shows an analysis of organics in the supernatant of
the test sludge.
Table 13 An analysis of organics in supernatant (mg/lit.)
Case II
Sludge Carbohydrate Fat Protein
Control 57.9 32.1 240
120°C thermally 231 179 2,670
conditioned
150°C thermally 447 186 5,080
conditioned
180°C thermally 546 273 6,630
conditioned
Table 14 An analysis of organics in digested sludge (mg/lit.)
Case II
Sludge Carbohydrate Fat Protein
Control 992 1,060 4,660
120°C thermally 787 1,400 3,590
conditioned
150°C thermally 741 1,030 3,360
conditioned
180°C thermally 650 1,200 3,470
conditioned
94
-------
The higher the thermal conditioning temperature the more the
liquefaction of organics in the sludge was promoted, and this was
particularly the case with proteins. Table 14 shows an analysis of
the organics in the digested sludge. A marked difference between
the control sludge and thermally conditioned sludge suggests that
the proteins in the thermally conditioned sludge may have been
subjected to violent gasification.
(c) Case III
Fig. 20 is a cumulative graph of the volume of gas generated
from the primary sludge.
70
60
| 50
u
•§
S. 40
I 30
2
3
d 20
10
p 200 °C thermally conditioned sludge
A 150°C thermally conditioned sludge
O 120°C thermally conditioned sludge
— Control sludge
14
28
42
58
70 84
Days elapsed
98
Fig. 20 Case III: Cumulative gas production
The 120 C sludge made a quick start in giving off gas, while
the 200 C sludge was far slower. The cumulative total of gas
volume after 12 weeks of operation was 65.0 lit. for the control
sludge, 66.1 lit. for the 120°C sludge, 64.0 lit. for the 150°C
and 56.2 lit. for the 200 C sludge. The following conclusions are
reached accordingly.
95
-------
(1) The gas production is impeded by heating up to 200 C.
(2) The thermal conditioning has little or no effect on the
improvement of gas yield for the primary sludge.
Tables 15 and 16 shows the concentrations of the organics in
the test sludge and digested sludge.
Table 15 An analysis of organics in feed sludge (mg/lit.)
Case III
Sludge
Control
120°C thermally
conditioned
150°C thermally
conditioned
200°C thermally
conditioned
Carbohydrate
6,159
(170)
7,051
(510)
6,324
(1,128)
4,877
(354)
Fat
3,812
(250)
3,896
(130)
4,248
(314)
5,598
(1,462)
Protein
9,629
(1,064)
9,142
(1,410)
8,702
(4,849)
8,218
(6,676)
( ): Supernatant
Table 16 An analysis of organics in digested sludge (mg/lit.)
CASE III
Sludge
Control
120°C thermally
conditioned
150°C thermally
conditioned
200°C thermally
conditioned
Carbohydrate
1,121
(217)
1,060
(221)
995
(202)
962
(237)
Fat
892
(336)
732
(322)
876
(326)
1,516
(796)
Protein
4,169
(1,242)
4,528
(1,159)
4,493
(1,377)
4,216
(1,836)
( ): Supernatant
96
-------
(d) A summary of Cases I, II and III
The finding of Cases I, II and III are summarized as follows.
(1) Although the excess sludge increases gas production by thermal
conditioning, the primary sludge does not.
(2) The thermal conditioning temperature at which the gas
production from excess sludge is maximized lies in the range of
150°C to 180°C.
(3) The high BOD load in the supernatant due to thermal
conditioning poses no problem because it is disposed of during
the digestion process.
(4) The total carbon liquefaction ratio (decomposition ratio) is
shown in Fig. 21 with respect to excess sludge and primary
sludge. As shown/ the primary sludge shows a much smaller
ratio.
100
• Excess sludge
X Primary sludge
a*
g"
n
c
o
I 50
V
3
_l ' i ' 1 L-
70 80 90 100 110 120 130 140 150 160 170 180 190 200
Thermal conditioning temperature, °C
Fig. 21 Sludge liquefaction and thermal conditioning temperature
97
-------
(5) The thermal conditioning is effective for the excess sludge,
but not for the primary sludge. This is due primarily to the
ratio of carbohydrates + fats to the total organics. As shown
in Fig. 11 in Chapter 2, carbohydrates and fats are easy to
gasify, and the primary sludge containing large quantities of
these substances generates large volumes of digested gas. The
thermal conditioning of the primary sludge to produce
gasifiable and dissolvable proteins has an immaterial effect on
the increase of gas production. On the contrary, the excess
sludge usually has a small ratio of carbohydrates + fats to the
total organics, and thus the effects of the dissolved proteins
are relatively significant to increase in gas production
through thermal conditioning. In addition to this, noteworthy
is the fact cited under item (4) above.
5.4 CONTINUOUS DIGESTION TEST OF SLUDGE WITH THERMAL CONDITIONING TEMPERATURE
AS A PARAMETER
At the beginning of Chapter 5, the study subjects (1) through (5)
were listed. Items (1) through (3) and (5) have already been discussed,
and here we will discuss item (4) concerning the solids-liquid separation
and dewaterability of thermally conditioned sludge.
5.4.1 Test Method
The test arrangement used was almost the same as referred to in the
foregoing. The test sludge used was excess sludge. The excess sludge
sample was thickened by a centrifuge to a concentration of 2.5%.
The test was conducted concurrently for the control sludge, 120 C
sludge, 150°C sludge and 180°C sludge.
The digestion was carried out at a temperature of 35°C for 8 weeks
for the 20-day solids retention and for 4 weeks for the 10-day solids
retention.
98
-------
5.4.2 Results
Table 17 compares the test sludges and control sludge with respect
to gas production and composition.
Table 17 Gas yield and gas analysis
Feed
sludge
CONTROL
120°C
150°C
180°C
_, . Gas analysis
Sludge 1
retention CH CQ
time 4 2 Others
20-day
10-day
20-day
10-day
20-day
10-day
20-day
10-day
71.3
70.3
70.3
70.8
68.6
68.5
68.8
68.3
27.4
27.6
28.8
28.9
30.6
31.2
30.1
31.1
1.3
2.1
1.7
0.5
0.8
0.3
1.3
0.3
Gas
yield
(H/l*
feed
sludge)
2
1
5
1
8
5
6
5
.87
.68
.58
.81
.58
.21
.85
.25
Methane
yield
(«/*•
feed
sludge)
2
1
3
3
4
3
4
3
.05
.18
.95
.25
.51
.57
.70
.59
Gas
yield
(Vg.vs)
0
0
0
0
0
0
0
0
.16
.10
.30
.28
.36
.32
.38
.34
Methane
yield
(£/g.VS)
0.11
0.07
0.21
0.20
0.25
0.22
0.28
0.23
Fig. 22 shows the time-dependent changes of gas production. All
these confirm the effectiveness of thermal conditioning.
1 23456 7 8 9 10 11 12
Fig. 22 Gas production change
99
-------
For both the control and thermally conditioned sludges, the gas
production per lit. of feed sludge or gram of feed VS is slightly larger
by the 20-day solids retention than by the 10-day solids retention.
Fig. 23 shows the settlability of sludge measured by making use of a
1 lit. measuring cylinder.
Control 12CTC 130°C 140^
Thermally conditioned feed sludge (24 hrs. later)
20-day solids retention digested sludge (24 hrs. later)
Fig. 23 Settlability of thermally conditioned sludge and digested sludge
The samples of the digested sludge were taken in the final week of
the 20-day solids retention digestion test. The control sludge, the
120°C thermally conditioned sludge and their digested sludge hardly
settled. The settlability of the 150°C thermally conditioned sludge
varied over a wide range from a supernatantless state to a heavy
thickening of about 50% in volume. On the other hand, the digested
sludge always separated into sediment and supernatant, producing a
supernatant of 30 to 50 vol.% in 24 hrs.
100
-------
The 180°C digested sludge was thickened to 40% in an hour, and was
reduced to about 20% in volume in 24 hrs. along a slow-decreasing curve.
To sum up, it can be said that the settlability and thickenability of the
thermally conditioned sludge are more or less inherited by the
anaerobically digested sludge.
The 150°C and 180 C thermally conditioned sludge and their
digested sludge were compared by a filter leaf test. For the test, the
sludge was thickened for 8 hrs. and cleared of supernatant. The digested
sludge used was sampled from what was subjected to a 10-day solids
retention digestion. At first, we presumed that the comparison would be
made without chemical conditioning. But even the 180°C thermally
conditioned sludge showed a extremely poor dewaterability, and
necessitated the injection of ferric chloride by 10% and slaked lime by
25% per unit weight of solids in order to attain a filtration velocity of
about 10 kg/m h. On the other hand, the 150°C sludge called for
twice as much chemical injection to attain the same filtration velocity.
The thermally conditioned sludge and its digested sludge showed no
substantial difference in dewaterability, though the digested sludge was
a little inferior. On the other hand, the comparison between the
thermally conditioned digested sludge and the control digested sludge
showed that the former gave a better dewaterability than the latter.
All these are summarized as follows.
• Digestion of thermally conditioned sludge does not improve
dewaterability.
• Thermally conditioned sludge is better in dewaterability than the
sludge without thermal conditioning.
Regarding the odor of digested sludge, the measurements are shown in
Table 18.
101
-------
•Cable 18 Sludge odors
Q,or Hydrogen Methyl
Slud^e concentration s^f^e, mercaptan,
ppm ppm
Feed, control
Feed, thermally
conditioned at 120°C
Feed, thermally
conditioned at 150 C
Feed, thermally
conditioned at 180 C
Digested, control
Digested, thermally
conditioned at 120°C
Digested, thermally
conditioned at 150°C
Digested, thermally
conditioned at 180°C
4,100 0.58
73,000 0.25
230,000 0.20
1,300,000 0.02
1,700 0.33
550 ND
980 ND
980 ND
0.11
2.91
2.84
0.09
0.25
0.04
0.06
0.04
Acet-
aldehyde, Remarks
ppm
0.14
7.83
2.24
12.4
0.12
0.10
0.08
0.13
Odor
intensity 5
Odor
intensity 5
Odor
intensity 5
Odor
intensity 5
Odor
intensity 3-4
Odor
intensity 4
Odor
intensity 4-5
Odor
intensity 4
Nitrogen gas was blown into 200 ml of sample sludge at a rate of
10 lit./hr., and the odors of entrained gases were measured. The
measurements show that the odors of the sludge can be reduced drastically
by digestion. In support of this, the irritating odor peculiar to
aldehyde resulting from thermal conditioning was lowered in the digested
sludge.
The colorimetric results of supernatant are shown in Table 19.
102
-------
Table 19 Color of supernatant
Origin of supernatant Chromaticity
Feed sludge, control 16
Feed sludge, 120°C 130
thermally conditioned
Feed sludge, 150°C 200
thermally conditioned
Feed sludge, 180°C 600
thermally conditioned
Digested sludge, control 50
Digested sludge, 120°C 130
thermally conditioned
Digested sludge, 150°C
thermally conditioned
Digested sludge, 180°C
thermally conditioned
Digested sludge, 150°C 260
Digested sludge, 180°C 700
It is found that the colors produced by thermal conditioning cannot
be removed by anaerobic digestion.
6. SUMMARY
The discussions in the foregoing chapters are summarized as follows.
(1) In Japan, as of 1980, there were some 480 wastewater treatment
plants of which about 180 were equipped with a digestion process.
Of the 180 wastewater treatment plants, 156 were operated on a
system consisting of thickening, anaerobic digestion, dewatering and
disposal processes, and 17 were operated on a system consisting of
thickening, anaerobic digestion, incineration and disposal
processes. The wastewater treatment plants operating on the former
system accounted for 26% of the national total of sludge generated,
and those on the latter system accounted for 24%, on the basis of
solids in thickened sludge.
103
-------
(2) In Japan, the digestion tank typically is operated on the following
conditions.
• Solids retention time, 30 days
• Mesophitic digestion (30 C to 3
• Heating by steam injection
(3) About 50% of the wastewater treatment plants with digestion tank
show a gas yield not exceeding to 5 or 6 £/£«feed sludge.
(4) Those wastewater treatment plants where more than 50% of digestion
tank influent was returned to the water treatment process in the
form of supernatant accounted for about two thirds of the total of
wastewater treatment plants with digestion process.
(5) If the organics content is fixed, the primary sludge gives off more
digestion gas per unit quantity of feed VS than the excess sludge.
(6) The probable cause of the phenomenon stated in (5) above is that the
primary sludge contains more carbohydrates and fats in the total
organics than the excess sludge.
(7) The ratio of methane to the total volume of digestion gas is about
60% on the average.
(8) Highly thickened sludge with a concentration of about 6% can be
digested satisfactorily under usual digestion conditions.
(9) The effects of thermal conditioning are significant on the excess
sludge, but are little on the primary sludge.
(10) By thermal conditioning, the excess sludge has its organics more
liquefied than the primary sludge.
(11) The carbohydrates and fats are considered susceptible to
gasification even under usual digestion conditions.
(12) Thermal conditioning works very effectively on the excess sludge
because it steps up the gasification potential of the excess sludge
from an essentially low to quite a high level.
(13) The optimum thermal conditioning temperature for excess sludge is
within the range of 150°C to 180°C. The high level of dissolve
BOD which is unavoidably developed by thermal conditioning can be
reduced to a satisfactory low level in the digestion process.
(14) The high thickenability imparted by thermal conditioning to the
sludge is retained even after digestion.
104
-------
(15) The dewaterability of sludge digested after thermal conditioning is
a little higher than that of control sludge which is not subjected
to thermal conditioning.
(16) Odors of the thermally conditioned sludge are reduced by digestion.
(17) Hie colors caused by thermal conditioning cannot be removed by
digestion.
105
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
PILOT PLANT STUDY ON TREATMENT OF SUPERNATANT
FROM THERMAL SLUDGE TREATMENT PROCESS
September 19-21, 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Hiroo Nakagawa
Deputy Director
Sewage Works Bureau
Kobe City Office
107
-------
PILOT PLANT STUDY ON TREATMENT OF SUPERNATANT
FROM THERMAL SLUDGE TREATMENT PROCESS
1. INTRODUCTION 110
2. GENERAL DESCRIPTION Ill
2.1 Outline of Small-Scale Pilot Plant for Thermal Treatment Ill
and Melting System Sludge Treatment
2.2 Specifications of Each Equipment 113
2.2.1 Centrifugally Sludge Thickening Equipment
2.2.2 Air-Injection Low-Temperature Thermal Treatment
Equipment
2.2.3 Sludge Dewatering Equipment
2.2.4 Sludge Steam-Dryer
2.2.5 Sludge Melting Furnace
2.3 Properties of Supernate from Thermal Sludge Treatment 116
2.3.1 Changes in Properties of Sludge by Thermal Treatment
2.3.2 Water Quality of Raw Wastewater for the Experiment
2.4 Target of Treated Water Quality 118
2.5 Description of Plant for Treatment of Supernate 118
from Thermal Treatment
3. MODIFIED MIXED LIQUOR RECIRCULATION ACTIVATED 121
SLUDGE PROCESS BY AIR BLOWING
3.1 Experimental Procedure 121
3.2 Experimental Results 123
3.2.1 Characteristic of Raw Wastewater for The Experiment
3.2.2 BOD Removal
3.2.3 CODMn Removal
3.2.4 Nitrogen Removal
3.2.5 Nitrification Rate
3.2.6 Nitrification Reaction in Anaerobic Tank
3.2.7 Denitrification Reaction
3.2.8 Supplied Air Volume and Dissolved Oxygen Concentration
108
-------
3.2.9 Alkalinity B alance
3.2.10 Phosphorus Removal
4. MODIFIED MIXED-LIQUOR RECIRCULATION ACTIVATED 141
SLUDGE PROCESS BY PURE OXYGEN BLOWING
5. FIXED MEDIUM TYPE NITRIFICATION-DENITRIFICATION 141
PROCESS
6. COAGULATIVE PRECIPITATION 144
7. HIGH-RATE SAND FILTRATION 145
8. ACTIVATED CARBON ADSORPTION 146
9. COST FOR TREATMENT 147
9.1 Flow Sheet of Plant for Treatment of Supernate 147
from Thermal Sludge Treatment
9.2 Construction Cost and Operation Cost 148
10. CONCLUSION -1-51
109
-------
1. INTRODUCTION
There has been an annual increase in volume of sludge discharged from a
sewage treatment process with the diffusion of a sewage system. The present situa-
tion is such that major cities, in particular, are burdened with increased cost required
for sludge treatment and securing of the site for ultimate disposal.
Recently, a high rise in energy price and a sense of insecurity for energy supply
have required review of sludge treatment. Thus, the selection of a proper treatment
process allowing reduction of volume for ultimate disposal and biochemical stabili-
zation of sludge economically has become an important theme.
Kobe city has conducted investigations to study a new method for sludge treat-
ment using a small-scale sludge treatment plant combining the following processes,
established in the West Sewage Treatment Plant in fiscal 1979. This method consists
of mechanical concentration of sludge, followed by air-injection low-temperature
sludge thermal treatment to improve the dewaterability of raw sludge, which is
subjected to pressure filtration without dosing to produce dehydrated cake, which is
then converted, using a steam dryer, into low-moisture dryed cake to be fed to a
heavy oil burning type furnace so that organic matter in the cake is burned and, at
the same time, ash or inorganic matter is melted to be slagged.
Sludge -
Centrifugal
Thickening
Equipment
Air- Injection
Low-Temper-
ature Sludge
Thermal
Treatment
System
Filter Press
Indirect
Heating
Type
Steam
Dryer
Heavy Oil
Burning
Type
Furnace
Kobe city entrusted the technological assessment on the sludge treatment per-
formed using this small-scale plant to Japan Sewage Works Agency, which investi-
gated this sludge treatment system in relation to treatment performance, operation
ease, and economical advantage, and reported the results. This investigation, how-
ever, left behind the subject of treatment of supernate produced from thermal
sludge treatment process of this system. Supernate from the thermal sludge treat-
ment is brown in color with high concentrations of organic matter and nutrient salt.
Therefore, Kobe city constructed a pilot plant for treatment of supernatant
liquid from thermal sludge treatment in the West Sewage Treatment Plant in fiscal
1981 to undertake investigations on system for treatment of supernate and system
for maintenance and management, and entrusted analysis of the results and report
preparation to Japan Sewage Works Agency. Very great pollutional potential of
supernate from the thermal sludge treatment requires studies on treatment perform-
ance and economical advantage to be completely performed with consideration
given to the effluent standard for public water area.
110
-------
During the process of operation of, and investigation and experiment on this
pilot plant, the staff from Kobe municipal Sewage Works Bureau and Japan Sewage
Works Agency cooperated with each other through full consultation and much
discussion so that the investigation and experiment would be successful with signifi-
cant results obtained.
2. GENERAL DESCRIPTION
2.1 Outline of Small-Scale Pilot Plant for Thermal Treatment and Melting System
Sludge Treatment
A plant for thermal treatment and melting treatment, built in the Kobe munic-
ipal West Sewage Treatment Plant, is a small-scale one having a capacity of treating
approximately 6m3 /day of sludge with a solid content of 2%. This plant is com-
posed of a centrifugally sludge thickening equipment, air-injection low-temperature
thermal treatment equipment, dewatering equipment, steam drying equipment, and
melting equipment. Its flow sheet is given in Fig.-l.
Photo, Thermal Treatment Equipment
111
-------
Decomposed gas
. 1 Raw sludge Centrifugal
storage tank thickner ~"
Thermally treated Thermally treated
sludge thickner sludge tank
Raw s.udge sludge thickner Supernatant ^^ " " j » No-2 heat
carrying pump feed pump ^rrw.n pump* + * -» *(p)- • • •' " • e.x?nange
Thermally treated
sludge pump
Cooling water Hot water I
circulation pump i
Boiler wate
feed pump
P
Filter cloth washing water
for the cooling
zone of furnace
heat bo'**" water
boiler feed pump
Hot water mediurr
Figure-1 Flow Sheet of Small-Scale Pilot Plant for Thermal Treatment and Melting System Sludge Treatment
-------
Photo; Centrifugally Sludge Thickening Equipment
In this system, mixed raw sludge is first concentrated to about 4% by means
of a centrifugal thickening equipment to be fed to a thermal treatment equipment,
in which the resultant concentrated sludge is subjected to low-temperature thermal
treatment for 30—90 minutes at the reaction temperature of 155—165°C, pressure
of 7-9kg/cm2, and air injection of 10-15Nm3/m3 of sludge. The thermal-treated
sludge is concentrated to about 8% in a gravitational thickener before being de-
watered by a filter press at the filtration rate of about 6kg—DS/m2 -hr to obtain
dehydrated cake with the water content of 40-50%. This cake is further reduced
in water content to the extent of 20% by a steam dryer, and then fed to a heavy oil
burning type melting furnace, in which combustibles are burned with ash discharged
as slag. Thermally decomposed gas, discharged from a low-temperature thermal
treatment reactor and then cooled to about 85° C using a cooling apparatus, and
exhaust gas (about 85° C) from the steam dryer are cooled in a scrubber before
being fed to a secondary combustion room of the melting furnace. Exhaust gas
from the secondary combustion room is allowed to pass through a waste heat
boiler, and scavenged before being released into the atmosphere. In addition,
malodorous gases present in a sludge treatment building is deodorized by using
sodium hypochlorite, sodium thiosulphate, etc. to be discharged into the air.
2.2 Specifications of Each Equipment
2.2.1 Centrifugally Sludge Thickening Equipment
Basket Type, Interior Volume: l.lm3, Centrifugal Effect: 200-500G, Treat-
ment Capacity: 10m3/H.
This equipment, developed to concentrate sludge difficultly subjected to
gravity concentration, feeds sludge to a revolving cylindrical vessel, and, through
skimming, withdraws concentrated sludge collected in the circumferential area by
giving centrifugal force horizontally with feed and withdrawal of sludge performed
at intermittent operation. The time required for one cycle is about 1—2 hours when
the raw sludge SS is 0.3—0.5%, and about 20—30 minites when it exceeds 1%.
113
-------
2.2.2 Air-Injection Low-Temperature Thermal Treatment Equipment
Reactor Type: Perforated-Plate Gas-Liquid Contactor
Reactor Volume: 2.4m3
Capacity: Reaction Temperature; 165°C, Reaction Pressure; 7.5kg/cm2,
Air Injection; 15m3/m3 of sludge, Treatment Capacity; 2.3m3/H
The air-injection low-temperature thermal treatment equipment is mainly com-
posed of a primary heat exchanger, reactor, secondary exchanger, thermally treated
sludge thickening tank.
Sludge, concentrated to 4—5% in a sludge thickening tank, is heated to about
120°C in a primary heat exchanger, and is then pressure-fed to a reactor.
The heat exchanger, which is of double cylinder type, supplies heat water
medium, subjected to heat recovery in the secondary heat exchanger, to the external
cylinder to heat untreated sludge passing through the internal cylinder. The reactor
interior is heated, using steam generated by a boiler to reach temperature (165°C),
at which sludge is thermally treated. In addition, the inside is kept in oxidizing
atmosphere by injecting air from the lower part of the reactor to improve the
dewaterability of sludge, and, at the same time, allow partial oxidative decomposi-
tion of odorous components generated from sludge. Thermally treated sludge,
which has completed reaction, is subjected to heat exchange, and cooled to be fed
from a sludge drain valve to the thermally treated sludge thickening tank, in which
the sludge is concentrated for about 8 hours, and the supernate is discharged to the
outside of the system as an supernatant liquid from the thermal sludge treatment.
2.2.3 Sludge Dewatering Equipment
Type: Horizontal Plate Filter Press
No. of Filtration Rooms: 10
Filtration Area: 25m2
Capacity' Filtration Rate; 6kg DS/m2-H(cake moisture; 50%)
The dewatering equipment, a filter cloth travelling type filter press, allows
thermally-treated and concentrated sludge with moisture of 92% to be converted
into cake with moisture of below 50%. Sludge is fed by means of a feed pump
at filtration pressure of 3-5kg/cm2, and the resultant cake is then squeezed by
expanding a diaphragm using water with a high pressure of about 15kg/cm2 for
dewatering. The cycle time is about 20 minutes.
2.2.4 Sludge Steam-Dryer
Type: Dual Paddle-Screw Type Steam Dryer
Capacity: Treatment Capacity; 70kgDS/H(cake moistre; 50% to 20%)
Heat Transfer Area: 8.47m2
The dryer, a indirect heating type steam dryer, feeds pressure steam, obtained
by heat recovery from a melting furnace, to the inside of paddles, and, using this as
a heat source, dries cake in contact with the paddle metal face.
114
-------
2.2.5 Sludge Melting Furnace
Type: Vertical Double Cylinder and Heavy Oil Burning type
Melting Furnace
Capacity: Cake Treating Capacity; 90kg/H (moisture; 20%)
This heavy oil burning type sludge melting furnace melts dried cake for its
stabilization and reduction, and encloses hazardous heavy metals, contained in
sludge, in the crystal structure of an inorganic component to make such a safety slag
as allowing no elution.
The furnace consists of furnace outer cylinder and inner cylinder, which are
concentric with each other. A main combustion burner has been installed at the
upper center of the inner cylinder, while, at the bottom center of the outer cylinder,
a small-diameter outlet has been mounted, below which a secondary combustion
room with auxiliary burners on the side is located, which is furnished with a slag
watertank in its bottom. Dried cake with the moisture content of 20% is charged
from a feed port into a ring-shape space in the furnace. The furnace outer cylinder
revolves at a slow speed so that, as the charge of the dehydrated cake into the ring-
shape space advances, the cake is fed from the lower end of the outer cylinder
toward the outlet, forming a reverse conical side wall. The space formed by the side
wall of dehydrated cake and the ceiling of the inner cylinder, which is referred to as
a flame chamber, is maintained at temperatures as high as 1,300—1,400°C. Com-
bustibles are burned into waste gas, while ash is discharged as melt slag into the
outside of the furnace. (Fig.-2)
Mam burner
Dried cake
Inner cylinder
Outer cylinder
Odor gas
injection hole
Outer cylinder
roller
Figure-2 Cross Section of the Melting Furnace
115
-------
2.3 Properties of Supernate from Thermal Sludge Treatment
2.3.1 Changes in Properties of Sludge by Thermal Treatment
Table-1 gives the properties of sludge fed to the thermal treatment and melting
plant. According to the table, the raw sludge fed to the centrifugal thickener is
sludge with a high content of organic components, showing 1.6—2.3% for TS
concentration, 1.5-2.0% for SS concentration, and 80-90% for the content of
organic matter. Table-2 indicates the properties of concentrated sludge obtained by
subjecting the raw sludge to centrifugal concentration, properties of thermally treated
sludge produced by the subsequent air-injection low-temperature thermal treatment
of the concentrated sludge, and properties of supernatent liquid resulting from
gravity concentration of the thermally treated sludge, followed by solid-liquid
separation.
Table-1 Characteristics of Mixed Raw Sludge in West Wastewater Treatment Plant
Items
Temperature °C
pH
TSmg/ 1
SSmg/ I
VSS%
The first research (summer)
Aug. 22-31, 1979
Sample
size n
37
//
tt
ft
tt
Max.
325
58
20,500
19,200
872
Min.
290
51
14,000
13,000
801
Average
X
305
-
16,300
15,100
833
The 3rd research (winter)
Jan. 17-Feb. 9, 1980
Sample
size n
38
"
tt
"
ft
Max.
135
665
41,700
37,000
924
Min.
80
600
16,800
13,700
809
Average
X
11.6
-
22,800
20,700
881
Table-2 Results of Thermal Sludge Treatment Experiment
Aug. 22-31, 1979
Items
PH
TS
VTS
SS
vss
BOD
S-BOD
CODcr
S-CODcr
CODMn
S-CODMn
TOC
S-TOC
-
mg/£
%
mg/fc
%
mg/£
mg/2
mg/£
mg/2
mg/2
mg/£
mg/£
mg/ 1
Concentrated sludge
Sample
size
10
"
//
„
tt
4
//
Average
-
50,500
776
43,900
815
20,900
5,260
70,200
6,150
1 1,400
782
18,900
it
2,390
Thermally treated
sludge
Sample
size
10
"
It
ft
//
4
//
//
tt
It
ft
//
ft
Average
-
39,200
799
28,000
78.8
15,700
7,720
67,300
15,200
10,200
4,200
25,300
6,290
Supernate from
thermal treatment
process
Sample
size
10
tt
-
ft
-
tt
-
"
-
ft
-
//
-
Average
-
12,700
-
949
-
7,690
-
15,900
-
4,730
-
6,290
-
S; soluble, BOD: 5-days BOD
116
-------
Table-2 (Continued)
Jan. 17-Feb.9,1980
Items
PH
TS
VTS
SS
VSS
BOD
S-BOD
CODcr
S-CODcr
CODMn
S-CODMn
TOC
S-TOC
T-Nmg/
P04-Pmg/
-
mg/2,
%
mg/£
%
mg/fc
mg/£
mg/£
mg/£
mg/x.
mg/£
mg/2,
mgl I
mg/£
mg/J.
Concentrated sludge
Sample
size
10
//
//
/t
/t
4
//
//
//
//
//
//
//
//
//
Average
-
48,000
838
41,500
862
31,500
6,820
62,400
9,030
10,900
1,300
18,600
3,700
2,140
525
Thermally treated
sludge
Sample
size
10
//
//
/f
//
4
//
//
//
//
ft
tf
//
tt
//
Average
-
33,900
81 7
26,000
837
21,200
7,610
52,700
12,700
9,810
4,060
16,400
5,300
1,700
442
Supernate from
thermal treatment
process
Sample
size
10
//
-
//
-
//
-
//
-
//
-
4
-
4
//
Average
-
10,900
984
7,740
13,100
3,840
5,600
1,060
158
2.3.2 Water Quality of Raw Wastewater for the Experiment
Among supernatent liquid discharged from this sludge treatment system,
supernate from thermal sludge treatment, filtrate from press filter, filter media
washing water, condensed water from thermal treatment reactor decomposed gas,
decomposed-gas scrubber water, and steam dryer waste gas scrubber water were
decided to be treated. Scrubber water for waste gas from melting furnace air pre-
heater was decided not to be treated regarding it as wastewater possible to be
discharged in terms of water quality. The water quality of mixture of these waste-
water was confirmed to be almost similar to that of doubly diluted supernate
from thermal sludge treatment. Thus, in the pilot plant study on treatment of
supernatant liquid, the supernate from thermal sludge treatment was diluted with
tap water so that its water quality might approach to that of mixed wastewater to
be used as raw wastewater for the experiment. Table-3 gives the water quality of
this raw wastewater. With regard to each water quality-related item of BOD, COD,
Kj-N, and T-P, the percentage of soluble portion was 70-90%.
117
-------
Table-3 Characteristic Qualities of Raw Wastewater
for the Experiment
Items
pH
BOD
CODMn
CODcr
SS
T-N
Kj-N
NHa-N
NOn-N
T-P
Color
M-alkalinity
(mg/£)
(mg/£)
(mg/£)
(mg/£)
(mg/£)
(mg/JL)
(mg/£)
(mg/£)
(mg/£)
(degree)
(mg/£)
Average
6.00
3,154
2,080
5,959
663
641
623
180
17.8
83.3
1,656
276
Standard
deviation
0.72
907
428
1,222
298
138
132
72
6.6
33.6
268
191
NOn; NCh + NCb
2.4 Target of Treated Water Quality
Kobe city, in which treated water is discharged into Seto Inland Sea, when tak-
ing into consideration the control by immutable weight of CODMn based on the Law
on Special Measures for Seto Inland Sea Environmental Protection (fiscal 1979), and
further the administrative guidance on regulation of phosphorus to be expected in
future, requires the target of treated water quality to far exceed the technical
standard for effluent specified in the government ordinance of The Sewerage Law.
Therefore, the target of treated water quality was established making reference to
the effluent standard for nitrogen and phosphorus based on the Lake Biwa Eutrofi-
cation Control Ordinance, and experimental results and literature so far obtained.
The target of treated water quality thus established is below 5mg/L for BOD,
below 30mg/L for COD, below 5mg/L for SS, below lOmg/L for total nitrogen, and
below 5mg/L for total phosphorus.
2.5 Description of Plant for Treatment of Supernate from Thermal Treatment
The combination of biological, chemical, and physical treatment processes is
required to eliminate each pollutant from raw wastewater colored with high con-
centrations of pollutant. First, to remove BOD, COD, and nitrogen, a two-stage
biological treatment, in which nitrified liquor recycled biological nitrification-
denitrification process by suspended microbe using activated sludge is employed,
followed by nitrification and denitrification of low-concentration nitrogen by
adhering microbial film sticking to filling-up media, was performed. After the
biological treatment, a physico-chemical treatment combining coagulative precipi-
tation, high-rate filtration, and activated carbon adsorption was carried out. Fig.-3
provides a flow sheet of the pilot plant.
118
-------
Water supplying
•(A) For each tank
Supernatant--
aupernatam--—^
from thermal I
sludge treatment J
Storage tank
Balancing tank
1
(
1
5
^
fl
f
Mixed -de
(air bio
Anaerob
tank
3
u!
composin
wing sySt
c Aer
c=
:=U
9t«
•m)
Ob!
nk
: tank
NaOH
I
i
i
= c=
ij.u
To flash mixing tank
Final settling Submerged Demtrification Reaeration tank
tank b,oox«Jat,on tank
tank
To flash
mixing tani-
Submerged Demtnftcation Reaerat.on tank
biooxidation tanl(
tank
-NaOH
•- Coagulant
~~ Organic polymei
From reaeration tank
Coagulant
precipitator
Pump pit Activated carbon adsorption
Figure-3 Treatment of Supernate from Thermal Sludge Treatment
- Pilot Plant Flow Sheet -
-------
Photo; Treatment of Supernate from Thermal Sludge Treatment
- Pilot Plant -
A mixed-decomposing tank, given in this figure, means treatment vessels for
performing nitrified liquor recycled nitrification-denitrification treatment by
suspended microbe, which are divided into the front-stage anaerobic tanks and rear-
stage aerobic tanks. The mixed-decomposing tank is composed of an air blowing
system and a pure oxygen blowing system so that both may be compared with each
other. Wastewater treated by both treatment methods is further treated in a
submerged biooxidation tank and a denitrification tank by air blowing. Coagulative
precipitation, sand filtration, and activated carbon treatment are provided to further
treat wastewater treated in the previous process in such a manner as loading waste-
water treated either by the air blowing method or oxygen blowing method..
120
-------
3. MODIFIED MIXED LIQUOR RECIRCULATION ACTIVATED SLUDGE
PROCESS BY AIR BLOWING
3-1 Experimental Procedure
A mixed-decompsing tank treats sludge using biological nitrification-denitrifi-
cation reaction based on a nitrified liquor recycling system. Fig.-4 gives its flow
sheet, while Table 4 the specifications of experimental equipment.
Nitrified liquor
recycling pump
Raw wastewater
Balancing
tank
-^
n
te—i
^H
©
r^,
°s°°s
Anaerobic tank
_L __,__! 1
Aerobic tank j Blower
L£
x_x Final settling tank
Q Return sludge
pomp
Figure-4 Flow-Diagram of Mixed-Decomposing Tank
Table-4 Specification of Experimental Apparatus
^~~~~— - — _^^ Items
Facility ^^^~-~~-^^^
Balancing tank
Mixed-decomposing
tank
Anaerobic
tank
Aerobic
tank
Final settling tank
Instrument
1st stage
2nd stage
1st stage
2nd stage
3rd stage
4th stage
Sth stage
6th stage
total
Tank capacity
(m3)
8.0
1.6
1.4(0.7)
1.4(0.7)
2.2(1.1)
2.2(1.1)
2.2(1.1)
2.2(1.1)
9.6
2.8
(1.4)
8.8
(4.4)
1.2
Size
!,600Wx3,100Lx2,000H
600Wx 1,100L(550)
x 2,200H x 2 tanks
800Wx 1,100L(S50)
x 2,500H x 4 tanks
800^x2,400H
Specification
Mechanical agitation with
propeller(0.4KW x 2 units)
Diffuser (pore size 25Qm,
void 40%)
Diffuser (pore size 25Qu,
void 40%)
Rectangular clarifier
(center-drive, 0.2KW)
(with picket fence)
(1) Air flowmeter Rotor meter
(2) pH meter Glass cell type indicating controller
(3) DO meter Diaphragm galvanometer (Fixed type)
Portable meter, Type EIL 1520 (Field measuring type)
Remark) The numbers indicated in parenthesis for the items, volume and dimension
apply to Run 4 and the following Runs.
121
-------
The nitrified liquor recycling rate and return sludge volume were, respectively,
200% and 100% in relation to the inflow volume with the total recycling rate of
300%. The volume ratio of anaerobic tank to aerobic tank was 1:3. The anaerobic
tank (denitrification tank) has been equally divided in volume by a partition plate
into two tanks with the total volume of 2.8m (2 x 1.4m). The aerobic tank (nitrifi-
cation tank) has also been equally divided in volume by partition plate with a 10cm
x 10cm "opening" into four tanks with the total volume of 8.8m (4 x 2.2m). With
the design inflow volume (Q) of 2.4m3/day for the mixed-decomposing tank, in this
experiment, an attempt was made to increase the inflow load varying it from 0.5Q
to 2.5Q in sequence. Fig.-5 indicates water temperature and load condition for each
Run.
The biological reaction is greatly affected by temperature. The temperature
control was performed only in the final Run 6 at water temperature of 22—23° C.
No temperature control was carried out in the other Runs.
m3/day
Number Run No
Q Designed inflow
volume (24m3/dayl
2.5Q
2Q
15Q
1Q
0.5Q
20 25
Temperature in tank (°C)
30
35
Figure-5 Inflow Volume and Temperature in Mixed-Decomposing Tank of Each Run
122
-------
In Table-5 experimental conditions used in each Run are indicated. In Run 4
and the following Runs, the capacity of the mixed-decomposing tank was halved
due to surface loading and solid loading become too much in a final settling tank.
Also in this case, partition plate was newly added to make an attempt at
maintaining the flow condition in the tank the same.
To the aerobic tank, in which alkali is consumed with the reaction of nitrifi-
cation, caustic soda (0.8% solution) was added as alkali source to compensate for
its consumption.
In Run 3 and the following Runs, a pH meter was used to control pH in the
fianl chamber of the aerobic tank at 6.5-7.0. Run 1 and Run 2 show cases, in
which pH control was not performed, and Run 2 was subjected to no alkali supply.
These Runs were carried out to know the feasibility of treatment of supernate from
thermal sludge treatment with no addition of alkali, because the solution sometimes
contains alkali to a considerable extent.
In the denitrification tank (anaerobic tank), in which air stirring was performed,
MLSS was so high at 5,500-8,500 that its inside became anaerobic atmosphere
with DO of ave. 0.13ppm and ORP of ave. 200mv. For each Run, two weeks were
taken as an acclimatizing period due to the modification of conditions, and experi-
mental data was obtained by four-week steady operation after the acclimatizing
period. Excess sludge, by measuring the interfacial level of the final settling tank
once a day, was withdrawn by timer operation so that the level might be in the
range of about 15—20cm below the water level. The excess sludge volume was
determined from measurements of withdrawn and stored excess sludge volume in pit
and sludge concentration.
3.2 Experimental Results
Tables 5, 6, and 7 show the operating conditions and experimental results
relating to the modified mixied liquor recirculation activated sludge process. The
water temperature of raw wastewater was 13°-40°C, while the water temperature
of the tank interior was in the range of 13°-35°C. The treated wastewater
volume was in the range of 1.28m3/day-5.94m3/day (the treated wastewater
volume for Run 4 and the following Runs, in which the tank capacity was halved,
is compared with that for Run 1 — Run 3 by doubling the actual inflow volume).
The detention time was in the range of 1.95 days — 8.9 days in relation to the
inflow volume.
123
-------
Table-5 Results of Modified Mixed Liquor Recirculation Activated Sludge
Process by Air Blowing (1)
Items
Run No
-_
Period
Temperature of raw wastewater ("C)
Temperature in tank (°C)
Treated volume (m3/day)
Recycled nitnfied liquor volume (m3/day)
Return sludge (m3/day)
Total liquid volume (m3/day)
Recycling ratio
Tank volum
(m3)
Detention ti
(hr)
(day)
me
Anaerobic tank
Aerobic tank
Total
Final settling tank
Anaerobic tank
Aerobic t
nk
Total
Settling time (hr)
Air volume
(m3/hr)
Air volume
(m3/day)
MLDO
(mg/l)
A
w
ra
(
ir-
tio
3air/0)
Air-tank volume
ratio
(m3/m3/hr)
Anaerobic
tank
Aerobic
tank
1st stage
2nd stage
3rd stage
4th stage
5th stage
6th stage
Anaerobic tank
Aerobic tank
Total
Anaerobic tank
Aerobic tank
Total
Air volume per BOD removed
Air-m3/kg-BOD
MLSS(mg/H)
MLVSS (%)
SRT
(day)
Total volume
Mixed-decomposing tank
Aerobic tank
1
4/15-
5/15
202
f!65~\
V254 )
197
/162--N
\ 250 )
1 28
1 63
(125*)
1
(86
1
30
402
211*
28
88
11
6
2
51 7
(22 )
1625
(68)
2142
( 89)
127
51
53
98
81
68
51
262
715
977
017
029
13
24
22
20
204
559
763
39
34
73
282
5,769
787
36
33
25
2
6/2-
6/29
323
1 380 J
276
^23 I-A
'• 30 0 I
243
479
(197*)
243
(998*)
965
297*
28
88
11
1
6
2
276
(1 2)
869
(36)
1 145
(48)
59
41
40
190
157
152
154
194
1,586
1,780
006
009
26
19
33
51
80
653
733
29
75
104
235
5,526
81 2
42
38
29
3
7/23-
8/24
36 1
/342-N
V 395 1
330
<-295~\
350 1
355
681
(192*)
396
(1116*)
1432
304*
28
88
11 6
1 2
190
(08)
547
(25)
787
(33)
40
50
50
215
212
210
215
240
2.045
2,285
006
009
165
239
329
411
68
576
644
36
97
133
203
6330
849
23
21
16
4
9/7-
10/5
274
(245-A
1 310 )
269
(250~\
» 293 /
240
480
(200 *)
243
(101 1*)
963
302*
1
4
44
58
1
2
140
(06)
440
(1 8)
580
(24)
60
60
281
288
144
1366
1510
021
326
451
60
569
629
43
129
172
245
6,792
883
18
15
12
5-
10/22-
10/29
223
(200~\
V 245 >
21 2
/190-\
V227 /
297
60
(202*)
298
(1003*)
11.95
302*
1 4
44
58
1
2
113
(05)
356
(1 5)
469
(135)
48
804
194
201
192
948
l.MO
Oil
418
552
65
319
384
57
90
147
135
6,915
903
11
9
7
5-
2
11/2-
11/5
21 0
/210-\
V 210 /
196
' 202 /
238
48
(202*)
236
(990*)
954
301*
1 4
44
58
1
2
14 1
(06)
444
(19)
585
(24)
6 1
726
174
186
174
864
1,039
006
410
595
73
363
436
3 1
82
11
2
157
7,234
900
10
8
6
5-
3
11/9-
11/19
166
(130~\
\ 195 1
146
/125~\
\ 170 /
1 78
36
(202*)
1 79
(1005*)
7 17
305*
i
4
44
58
2
189
(08)
593
(25)
782
(33)
8 1
640
131
135
154
638
792
016
511
675
86
359
445
46
6 1
106
153
8,167
902
23
19
14
6-
1
11/24-
11/26
264
/263-N
V 265 1
265
(24 5- N
V 285 1
1 39
30
(216*)
162
( 1 165*)
601
333*
14
44
58
1
2
243
(1 0)
764
(32)
1007
(42)
96
548
117
114
132
554
586
009
398
507
95
399
494
39
53
92
179
8,426
883
26
21
16
6-2
1 1/27-
12/10
235
(185-A
V 27 1 /
224
(193-^
V 245 )
1 77
361
(204*)
181
(102.2*)
7
9
303*
14
44
58
12
189
(08)
597
(25)
786
(33)
80
628
117
116
151
559
710
010
386
482
85
316
401
45
53
98
152
6,332
866
21
18
13
6-3
12/14-
12/25
232
(190-A
V 26.8 1
234
( 250>
209
4 19
(200*)
209
(1001*)
837
300*
14
44
58
1
2
16 1
(07)
505
(21)
666
(28)
69
638
122
126
153
595
748
005
213
361
73
285
358
46
56
114
87
7j044
858
15
13
10
124
-------
Table-6 Results of Modified Mixed Liquor Recirculation Activated Sludge
Process by Air Blowing (2)
h^ — _J^N°
Surface loading (m3/m2/day)
Solid loading SSkg/m'/day
SV30
SVI
RSS
(Tola!)
T-N-SS loading (kg/kg/day)
(Total)
T-N-capacity loading (kg/m3/day)
(Total)
KJ.N.SS loading (kg/kg/day)
(Total)
Kj-N.capac,ty loading W""/d,y)
(Total)
K,N-SS loading
(Aerobic tank)
K,N,apac, ,
NOn-N-SS loading , (kg/kg/day)
(Anaerobic tank)
vt/-. kt j (kg/m /day)
NOn-N-capacity loading , . . . ,
r ' " (Anaerobic tank)
BOD removal rate (%) Total
CODMn removal rate (%)
T-N removal rate (%)
Kj-N removal rate (%)
NH4-N removal rate(%)
T-N removal rate (%) Anaerobic tank
Kj-N removal rate (%)
NOn-N removal rate (%)
T-N removal rate (%) Aerobic tank
Kj-N removal rate (%)
Effluent , NOn-N/T-N (%)
NH4-N removal rate (%)
1
48
27
855
150
11,720
209
1675
055
332
0058
0335
0034
0 195
0013
0072
0012
0068
0016
0090
0021
0 116
98 1
785
71 8
875
861
512
61 0
222
228
56 9
235
2
97
53
759
139
10020
196
0816
025
140
0 128
0706
0077
0424
0025
0 130
0023
0 126
0030
0 166
0.037
0200
98 7
768
77 2
885
93 2
50 7
39 3
90 5
35 9
51 1
68 2
3
150
94
748
119
12,085
360
1015
032
256
0 158
0991
0 103
0644
0028
0 180
0028
0 174
0036
0230
Of.51
0320
98 9
81 5
78 2
91 1
93 7
48 1
40 0
71 2
/,
52 3
60 2
77 3
4
97
65
779
115
12.660
261
1084
042
125
0 161
1 088
0 124
0836
0036
0243
0035
0237
0046
0312
0080
0538
99 1
84 1
76 3
93 0
96 4
36 2
10 1
94 0
13 2
743
71 2
91 9
5 I
119
82
903
131
11,620
451
1524
053
304
0215
1 488
0 169
1 165
0049
0338
0048
0239
0063
0434
0038
0260
98 2
823
62 1
66 6
A
21 0
152
81 4
10 3
21 2
14 0
144
5 2
95
68
960
133
12,250
526
2215
078
418
0 165
1 192
0 136
0979
0036
0 259
0.035
0252
0046
0 333
0041
0298
979
836
61 0
687
/\
205
107
872
. 96
277
215
218
5 3
71
58
955
118
13,590
261
1469
049
227
0 1 14
0921
0093
0747
0025
0208
0025
0202
0033
0267
0 145
0 115
988
827
55 1
576
A
102
88
686
128
18 1
79
67
6- 1
60
50
900
107
13,245
228
1649
058
580
0081
0678
0054
0456
0014
0 116
0013
0 112
0018
0 148
0038
0329
99 3
877
744
943
984
577
148
964
^
68.5
782
953
6- 2
72
45
954
153
10,990
208
1 175
040
305
0 144
0900
0 110
0685
0030
0 187
0030
0 195
0039
0257
0052
0339
984
859
814
94 1
987
567
515
71 1
^
582
692
95 1
6-3
84
59
969
137
11.470
334
1607
038
161
0217
1 526
0 128
0888
0043
0300
0 041
0290
0054
0382
0060
0437
989
843
802
903
89 1
564
458
94 1
^
440
527
649
A, minus value
125
-------
Table-7 Results of Modified Mixed Liquor Recirculation Activated Sludge
Process by Air Blowing (3)
— — — _
Items
pH
M-alkalimty
mg/l
mg/2
CODcr
SS
mg/£
T-N
mg/£
Kj.N
mg/i
NCh-N
NO3-N
mg/t
T-P
mg/H
Color degre
-_________^ Run No
taw wastewater
Anaerobic tank outlet
Aerobic tank outlet
taw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Dosing
:ma] tank effluent
taw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
?aw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
vlixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tani outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic lank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Effluent, NOn-N/T-N(%)
Raw wastewater
Anaerobic tank inlet
Anaerobic tank outlet
Mixed-D tank effluent
Removal rate (%)
Raw wastewater
Effluent
Plan
4,200
,087
50
988
2,200
925
500
773
350
50
857
650
343
240
63
605
177
34
944
45
166
206
858
200
168
158
21
1
67
67
55
469
163
74
162
18
3,070
1,042
89
58(10)
98 1
1,775
831
-
382
785
5,954
2 555
975
944
84 1
699
365
151
207
704
642
334
163
181
718
625
259
101
78
875
201
83
36
28
86 1
16
79
62
103
569
80
69
64
20
2
6 1
74
55
352
98
295
0
14
3,356
880
126
42(4)
987
2,011
856
583
467
768
6,483
2,422
1,068
844
870
726
288
209
142
804
618
261
129
141
772
602
203
123
69
885
237
72
52
16
932
16
58
55
72
51 1
87
78
-
73
16
1,610
1 010
3
58
73
67
224
101
283
140
60
3,240
923
114
36(2)
989
2,100
814
493
388
815
5.819
1 957
938
670
885
544
247
214
148
728
587
241
125
128
782
570
178
107
51
91 1
159
46
42
10
937
18
63
18
77
60 2
53
40
35
34
1 550
990
4
66
76
67
319
135
549
212
74
2,633
675
219
24(3)
99 1
2,015
743
571
321
84 1
5,652
1,849
1,263
581
897
671
232
253
85
87 3
587
251
160
139
763
571
172
155
40
930
149
41
65
53
964
16
78
50
99
71 2
59
48
1
44
25
1,620
1,050
5 1
56
76
76
124
398
653
0
489
2,910
761
331
51(15)
982
2.278
869
643
403
823
6,652
2,273
1,480
813
878
552
177
88
52
906
660
353
279
250
62 1
643
322
273
215
666
132
149
181
155
A
17
31
57
35
140
117
75
-
61
48
1.800
1,190
5-2
5 1
75
74
27
254
604
0
330
2,910
792
284
62(12)
979
2.390
890
604
391
836
6,400
2.146
1.393
728
886
615
218
176
86
860
631
343
273
246
61 0
616
299
267
193
687
122
130
170
133
A
15
44
56
53
215
97
70
-
61
37
1.600
1.280
5 3
5 1
76
78
74
555
807
0
716
3,009
780
293
37(10)
988
2,437
922
638
421
827
6.412
2,166
1.448
750
883
705
221
154
60
91 5
677
398
349
304
55 1
661
375
342
280
576
153
205
238
221
A
17
23
7 1
24
79
114
72
-
58
49
1.720
1.490
6- 1
5 1
75
66
37
60
476
70
67
2,841
671
62
19(3)
993
1,913
622
322
235
877
4,386
1,387
590
388
91 2
313
101
41
30
904
484
206
87
124
744
471
129
84
27
943
123
30
41
2
984
13
77
28
97
782
67
54
-
50
25
1,640
960
6- 2
52
74
69
85
110
403
144
110
2.930
74
87
47(10)
984
2.222
783
387
313
859
4,911
1,615
746
516
895
452
163
94
67
852
645
250
108
120
814
629
184
89
37
94 1
151
385
35
2
987
16
67
19
83
692
115
72
-
57
50
1.740
1,200
6-3
57
77
70
241
294
746
231
311
4,235
1.091
367
46(9)
989
2.467
906
648
387
843
6.645
2.734
1.431
645
903
1,035
291
98
43
958
835
333
145
165
802
804
260
141
78
90.3
230
76
71
25
89 1
31
73
43
87
527
144
116
-
106
26
1.910
1.400
( ) soluole , A, minus value
126
-------
3.2.1 Characteristic of Raw Wastewater for The Experiment
BOD and CODMn of raw wastewater used for the experiment is considerably
high in comparison with those for ordinary sewage. The BOD-to-CODMn ratio is
about 1.4 from Fig.-6. Ordinary municipal sewage contains night-soil and domestic
miscellaneous wastewater, the former of which contains a large amount of organic
acid, thus being difficult to be measured as CODMn. Organism-derived high molecu-
lar organic matter, such as starch contained in domestic miscellaneous wastewater is
also lower in CODMn than in BOD. Accordingly, for sewage, which mainly consists
of night-soil and domestic miscellaneous wastewater, BOD/CODMn is larger than 1.
Ordinary sewage has the BOD/CODMn of about 1.8, which, after biological treat-
ment allowing removal of biologically decomposable matter, decreases to about 1.0.
In light of the fact that raw wastewater used in the experiment is 1.4 in BOD/
CODMn, this raw wastewater is considered to be slightly difficult to be subjected to
biological treatment as compared with common municipal sewage.
5,000
4,000
3 3,000
Q
O
2.000
1,000
BOD=1.4CODMn
I
1,000
2,000
3,000
CODMn (mg/2)
Figure-6 Relation between BOD and CODMn of Raw Wastewater
With regard to CODMn and CODcr, the relationship; CODcr = 2.3CODMn +
1,300 was obtained. Of total BOD, SS (suspended solid) - BOD is small, while
S-BOD (soluble-BOD) much at almost 80%. With ordinary sewage, S-BOD holds
50%. This suggests that BOD is satisfactorily available as organic carbon source to
heterotrophic denitrifying organisms.
T-N of raw wastewater for treatment is 640mg/L, about 20 times that of
ordinary sewage, which is about 30mg/L. Kj-N occupies 97% of T-N in treatment raw
wastewater, and 99% for ordinary sewage, showing that both little contain NO2 -N
and NOs -N forms. Org-N accounts for about 70% of T-N with about 450mg/L,
while NH4 N about 30% of T-N. Alubuminoid-nitrogen accounts for 45% of Org-N
with about 200mg, indicating that organic nitrogen in other forms than alubuminoid
form is relatively much contained. The BOD/T-N ratio for raw wastewater is about
4.4, while 3.7-4.4 for primary tank effluent of ordinary municipal sewage on the
average.
127
-------
3.2.2 BOD Removal
BOD-SS load was 0.058-0.217kgBOD/kgSS-day, and BOD hydraulic loading
0.335-1.488kgBOD/m3 day, when MLSS was 5,500-8,400mg/L. This treatment*
condition allowed reduction in BOD from 2,600-4,200mg/L for inflow wastewater
to 19-62mg/L for treated wastewater, giving the removal percentage of 98-99%.
The soluble-BOD was 2-15mg/L. Fig.-7 shows the relationship between T-BOD
and S-BOD for treated wastewater.
S-BOD = 0.233 (T-BOD) - 2.08
Fig.-8 gives the relationship between BOD-SS loading and BOD removal level
per unit SS.
20
15
10
D
O
m
t/i
(S-BOD) = 0.233(T-BOD)-2 08
O f*un 1
• " 2
© " 3
© " 4
0 " 5
d " 6
50
100
T-BOD (mg/H)
150
200
Figure-7 Relation between T-BOD and S-BOD
(effluents from mixed-decomposing tank)
128
-------
0.30 r
0.20
o
w
Q
o
CO
0.10
Removal rate 100%
Effluent temperature (
• below 15
© 15-20
-------
1,000 -
Anaerobic tank
Anaerobic lank
outlet
laerobrc tank inlet)
Aerobic tank
outlet
1,000 -
Figure-9 Variation of BOD in Mixed-Decomposing Tank
Anaerobic tank, the 1st stage inlet
Anaerobic tank, the 1st stage outlet
Anaerobic tank, the 2nd stage outlet
Aerobic tank, the 1st stage outlet
/Aerobic tank, the 2nd stage outlet
/ Aerobic tank, the 3rd staoe outlet
/ / J
"•—A ' / / stage outlet
Aerobic tank, the 4th
30 40 50
Detention time (hr|
80
Figure-10 Variation of BOD and CODMn in Mixed-Decomposing Tank
130
-------
3.2.3 CODMn Removal
The CODMn concentration of raw wastewater was about 2,100mg/L, about
80% of which is accounted for by soluble-CODMn. This is characteristic of super-
nate from thermal sludge treatment.
Operation was undertaken with CODMn-SS loading of 0.03-0.17kgCODMn/
kgSS-day and CODMn hydraulic loading of 0.2-1.2kgCODMn/m3-day. The COD
decreased from 1,700—2,500mg/L for inflow wastewater to 240—470mg/L with the
removal percentage of 75—88%.
As described above, BOD is removed in a mixed-decomposing tank to such a
high extent taht BOD of treated wastewater is 19—62mg/L, but, because CODMn
contains hard-biodegradable substances, CODMn remains at about 300-400mg/L,
even when BOD is most removed.
Between CODMn and BOD of treated wastewater, the following relation was
obtained.
CODMn = 1.551BOD + 309
CODMn removal efficiency is closely related to color degree removal. The ave.
color degree is 1,687 for inflow wastewater, and 1,173 for treated wastewater, while
the percentage of color degree removal was 30.5%. (Color degree measuring method:
Platinum-Cobalt method).
3.2.4 Nitrogen Removal
In terms of ave. values for each Run, the ave. water temperature of tank interior
was 15°C-33°C (20°C-33°C, when excluding Run 5), Kj-N loading 0.012-0.048
(0.012-0.041, when excluding Run 5) kg-Kj-N/kgMLSS-day, and Kj-N hydraulic
loading 0.07-0.29 (0.07-0.29, when excluding Run 5)kg-Kj-N/m3-day. As a result
of this treatment, T-N removal percentage was 55-81% (72—81%, when excluding
Run 5), and NH4-N removal percentage 0-99% (86-99%, when excluding Run 5),
when the detention time was 2.0—8.9 days (2.4—8.9 days, when excluding Run 5) in
relation to the inflow wastewater volume, and the recycling rate 3.0 except for that
of Run 1. Among the above, Run 5 was extremely low in nitrogen removal per-
centage because of reduced water temperature combined with increased nitrogen
loading. Fig.-l 1 shows the relationship between T-N-SS loading and T-N removal
level per unit SS.
131
-------
0.06
0.05
0.04
0.03
0.02
0.01
Effluent temperature (°C)
• below 15
® 15-20
-------
BOD/TKN
• This experiment
1 ) O Japan Sewage Works
Agency (Toda)
100
50
.c
in
_j
S
Z
-
OJ
2
|
J 0.5
z
0 1
2) A Marlborough
O 2) X Plue Plains
3} © Kyoto, Toba
O 4) O Right Bank of Sagami
O River in Kanagawa
D Q Prefecture
5} v Left Bank of Arakawa
A O— River
7
0 00 x »63 -
_A 0 0» 0 •
00 $ »51 *62 «3
L_ 0 X 5'2 •
2
_
5-3 •
• 6-1
— 1
1 1 1 1 1
10 15 20 25 30
Temperature (°C)
44
32
30
30
48
1 8
3.6
Figure-12 Relation between Temperature and Nitrification Rate
1) Construction Ministry, Shiga Pref., Japan Sewage Works Agency,
"Development and Investigation on Advanced Sewage Treatment
Technology" (1980)
2) US, EPA, "Process Design Manual for Nitrogen Control" (1975)
3) Sakai, Sumiyama, "Collection of Lectures Presented at the 17th
Sanitary Engineering (Research) Meeting" (1981)
4) Kanagawa Pref., "Report on Experiment and Research Related
to Advanced Sewage Treatment" (March, 1979)
5) Shiga Pref., Japan Sewage Works Agency, "Engineering Research
relating to Management for Operation of Nitrified Liquor Re-
cycled Denitrification Process" (1981)
133
-------
Influent
Effluent
222
250
528
197 275
21 201 (^3
NH4-N
Run 3 NOn-N Org-N
Influent
Effluent
259
19.3
175
548
26.9
74 18.5 £22.9;
NH4-N
Run 4 NOn-N
Org-N
Influent
Effluent
31.2
16.4
52.4
\
26.0
35.8
1.9 293
68
68
70
NH4-IS,
Run 5 1 NOn-N Org-N
Influent
Effluent
424
514
Influent
Effluent
523
58 7
1.8 4.5
489
260
1671
NH4-N
Run 5-2 NOn N Org-N
I 1
Influent
Effluent
18 110
NH4-N
Run 5-3 NOn-N Org-N
118
128
/
38 1 49. 1 I
\ A
281 HJII
93
415
25.8
92
NH4-N
Run 6-1 NOn-N Org-N
Effluent
374
48 1
20 1 20 8
aim
18 336
NH4-N
Run 6-2 NOn-N Org-N
200
Influent
Effluent
263
149
14 4
588
79 184
Effluent
21 226
102
Note 1 Numbers given in the figure indicate the percentage (%) of each nitrogen concentration in relation to T-N at the
inflow point.
2 The concentration at the inflow point was calculated from the quantity of and each nitrogen concentration in
inflow wastewater, recycling water, and return sludge.
3 111| [[I indicates nitrogen removed by sludge withdrawal
4 | j indicates nitrogen biologically denitrified, the left side part of which shows nitrogen denitrified from
NOn-N at the inflow point, while the right part shows denitrified nitrogen nitrified in the anaerobic
tank with the values given in
Figure-13 Fractional Variation of Nitrogen of Different Forms at the Influent and Effluent Points of Anaerobic Tank
(air blowing system)
-------
Fig.-12 is the relationship between nitrification rate and temperature in a mixed-
decomposing tank compared with other investigation results obtained from other
municipal sewage. The nitrification rate for Runs 1, 2, 3 and 6-1 was low in com-
parison with that for the other experimental examples, while Runs 4, 5, and 6-2
provided the values close to those given in the other reports. Regarding the former
Runs, in which Kj-N load was low, and detention time was long, calculation as zero
order reaction led to apparently low values. On the other hand, with the latter
Runs, high Kj-N load and short detention time allowed the nitrification rate not to
become low.
3.2.6 Nitrification Reaction in Anaerobic Tank
Fig.-13 shows changes in level of nitrogen by form in the anaerobic tank. The
concentration of each nitrogen at the entrance of the anaerobic tank was determined
by calculation from each nitrogen concentration in the recycling liquor return
portion and raw wastewater. Together with this, the figure also indicates nitrogen
removal by sludge withdrawal. The percentage of nitrogen contained in sludge was,
when expressed in Kj-N/MLSS, 9.52% on the average, and 11.08% when expressed
in Kj-N/MLVSS. The percentage of T-N removal by sludge withdrawal was about
20%.
Fig.-13 shows a marked decrease in Kj-N for Runs 1, 2, 3 and 6-2. In the other
Runs, little change was observed in Kj-N, taking into account the intake of nitrogen
by sludge.
The decrease in Kj-N for the Runs mentioned above was estimated to be
attributable to nitrification reaction in the anaerobic tank.
On the other hand, consideration of nitrification reaction in the anaerobic tank
allowed alkalinity balance to approach to the theoretically calculated value.
The nitrification reaction in the anaerobic tank, in which air stirring was per-
formed to prevent sludge putrefaction, thus permitting DO concentration in the
tank to be maintained at 0.1-0.5mg/L, is considered to possibly occur.
3.2.7 Denitrification Reaction
Fig.-14 shows the relationship between BOD removal level and denitrification
level in the anaerobic tank. The regression formula is expressed by the following
equation.
BOD Removal (mg/L) = 4.4 x denitrified nitrogen quantities (mg/L) + 270
135
-------
1,500 -
1,000
Q
O
m
500
Y = 4 376X + 273.9
Run 1
" 2
" 3
" 4
" 5-1
" 5-2
" 5-3
" 6
I
Theoretical value BOD/N = 2.86
I
0 100 200
Denitrified quantity (mg/£ )
Figure-14 Relation between BOD Removed and Denitrified Quantity
Usually, BOD equivalent to two—three times as much as denitrified nitrogen
quantities is used, but, according to the above equation, about 50% more was used.
This is considered to be attributed to a small percentage of T-BOD used as hydrogen
donor. In addition, as the reason for this, a decrease in BOD concentration, which is
removed in other than denitrification reaction with about 300mg/L, with the
removal of suspended solid mainly in the anaerobic tank, and a decrease in BOD by
biological decomposition in an anaerobic tank are considered. In particular, this can
also be inferred from the fact that the detention time for the aerobic tank, in which
air stirring was performed, was long with 10—50 hours.
With denitrification reaction in each Run taken as zero order reaction, the de-
nitrification rate in the anaerobic tank was calculated to determine its relation to
water temperature, which is given in Fig.-15. The figure shows that the denitrifica-
tion rate rises with an increase in water temperature.
The denitrification rate, which is 30-90mgN/gMLSS when excluding that for
Run 5, is apparently low due to the long detention time for the anaerobic tank.
136
-------
100!
90
80
70
60
50
40
30
20
S 10
6-2
O
52
Number, Run No
O
53
10
15
20
30
Temperature (°C)'
Figure-15 Relation between Temperature and Denitrification Rate in
Mixed-Decomposing Tank (air blowing system)
3.2.8 Supplied Air Volume and Dissolved Oxygen Concentration
Table-8 gives supplied air volume, air-wastewater ratio, air-tank volume ratio,
and DO concentration in each Run.
Air was blown into the anaerobic tank at the air-wastewater ratio (blowing air
volume / inflow volume) of about 90 to prevent the putrefaction of mixed liquor
in the tank with the average DO of 0.2mg/L in the second tank of the anaerobic
tank. On the other hand, air was blown into the aerobic tank at the air-wastewater
ratio of about 440 with the average DO of 4mg/L in the final stage tank. Initially,
in Run 1, supplied air volume was varied with 10m3/hr, 8m3/hr, 7m3/hr, and
5m3 /hr for each tank of the aerobic tank so that DO of about 2mg/L might be
attained for each tank of the aerobic tank.
In a final settling tank, however, DO concentration dropped with the occur-
rence of dentrification, which caused SS to be floated with the result that SS of
supernate from the final settling tank was 200mg/L.
Accordingly, in Run 2 and the following Runs, DO was decided to be increased
in the final stage tank of the aerobic tank. Air was supplied to each tank of the
aerobic tank at almost the same level. As a result, DO was 3mg/L—6mg/L in the
final stage tank of the aerobic tank, which presumably caused denitrification to
difficultly occur in the final settling tank, allowing the outflow SS to be reduced
to 50-100mg/L.
The air-wastewater ratio of the total mixed-decomposing tank is about 530,
which is very high as compared with that of the conventional activated sludge
process. In addition, the air-tank volume ratio [blowing air volume (m3 /hr) / tank
volume (m3)], G/V value, is considerably high with 3—5 for the anaerobic tank and
5—13 for the aerobic tank, in comparison with 0.4-0.7 for the conventional acti-
vated sludge process.
137
-------
The reasons why air was supplied in such a large volume may be high BOD and
N concentration, which result in a large amount of oxygen used for BOD removal
and denitrification reaction, MLSS concentration as high as 6,OOOmg/L, and tank
water depth as shallow as 2.5m compared with the water depth for the conventional
aeration tank.
Table-8 Air Volume, DO and ORP in Mixed-Decomposing Tank
\ Items
Run\
No \
1
2
3
4
5 - 1
5 - 2
5-3
6 - 1
6-2
6-3
Average
Raw wastewatet
m3/day
1 28
2 43
3 55
2 40
2 97
2 38
1 78
1 39
1 77
2 09
-
ORP
(mV)
-
-244
-228
-262
-228
- 98
-135
-230
-178
-201
-200
Anaerobic tank
Air
mj/hr
109
8 1
100
60
8 0
7 26
640
5 48
628
6 38
-
Air-waste-
water ratio
m3/m3
204
80
68
60
65
73
86
95
85
73
89
Air-tank
volume ratio
(G/V)
m3/m3/hr
3 89
2 89
3 57
4 29
5 71
3 05
4 57
3 9!
4 49
4 56
4 09
ORP
(mV)
-311
-252
-216
-300
-220
-320
-265
- 98
-208
-213
DO
(mg/O
0 23
0 09
0 07
0 29
0 1 1
0 06
0 16
0 09
0 10
0 05
0 13
Aerobic tank
Air
m3/hr
298
66 1
85 2
56 9
39 5
360
266
23 1
23 3
24 8
-
Air-waste-
water ratio
m3/m3
559
653
576
569
319
363
359
399
316
285
440
Air-tank
volume ratK
(G/V)
m3/m3/hr
3 39
751
968
1293
897
818
6 05
525
5 30
5 64
7 29
ORP
(mV)
-
- 3
-132
DO
(mg/l)
1 99
3 24
286
-86 389
-175
- 80
-125
-100
- 20
- 73
- 88
4 85
5 03
593
4 53
4 34
2 87
395
Total, mixed-
decomposing tank
Air-waste
water ratio
m3/m3
763
733
644
629
384
436
445
494
401
358
529
Air-tank
volume
ratio
(G/V)
m3/m3/hi
7 28
1040
13 25
17 22
14 68
11 23
1062
9 16
9 79
11 4
11 38
200,-
100 -
oc
O
-100
-200
y = 30 1x - 236 (r = 0.74)
Anaero 1st
-400 L_
A Anaerobic tank the 1st stage
A " 2nd "
O Aerobic tank the 1st stage
2nd "
3rd "
4th "
(Average values have been used)
Figure-16 Relation between ORP and DO in Mixed Decomposing Tank
(air blowing system)
138
-------
Fig.-16 shows the relationship between oxidation ruduction potential and dis-
solved oxigen in the anaerobic tank and aerobic tank.
As shown in the figure, correlation exists between both of them. The figure,
which has given using average values, shows that the interior of the mixed-decom-
posing tank, including the aerobic tank, in which a good amount of dissolved oxygen
is present, is in the anaerobic atmosphere.
The broken line in the figure indicates the time, when the loading became high
and, at the same time, no denitrification proceeded with reduced ORP of the whole
tank. The alternate long and short dash line indicates the case, in which the applica-
tion of a heater allowed nitrification to satisfactorily progress with increased ORP.
3.2.9 Alkalinity Balance
Alkalinity balance in the anaerobic tank and aerobic tank was determined. As
a calculating expression, the following equation was used, assuming that each form-
wise nitrogen varies in concentration in each tank.
(Alk)out - (Alk)in = A(Org-N) x 3.57 - A(Kj-N) x 7.14 + A(T-N) x 3.57 - (Alk)b
where (Alk)in
(Alk)out
(Alk)b
(Org-N)
(Kj-N)
(T-N)
inflow wastewater alkalinity
effluent alkalinity
added alkalinity
inflow wastewater (Org-N) - effluent (Org-N)
inflow wastewater (Kj-N) - effluent (Kj-N)
inflow wastewater (T-N) - effluent (T-N)
Fig.-17 and Fig.-18 show the relationship between theoretical alkalinity values and
measured alkalinity values, using this equation.
Calculated value
X
/
Theoretical line
500 Measured value
O Run 1
--1,000
Figure-17 Alkalinity Balance in Anaerobic Tank (air blowing system)
139
-------
Calculated value O Run 1
600
500
400
300
9 200
309
100
a
0
-100
-200
• " 2
® " 3
Theoretical line 9 @ " 4
/ © • a
~ / • ®
P. © / 0w @
_ tv 9 ®v
D Sq($ *
o / ®
- X0* 9
< i 0 , , , , i ,
200 400 600 800 1,000 1,200 1,400
- Measured value (mg/ i as CaCOs )
-
Figure-18 Alkalinity Balance in Aerobic Tank (air blowing system)
With regard to the anaerobic tank, the theoretical alkalinity values and meas-
ured alkalinity values are in considerable agreement with each other, while the
aerobic tank provided great variations in measured alkalinity values, showing a
tendency of alkalinity being larger in measured values, that is to say, a tendency of
alkalinity having been supplied to the aerobic tank. This is estimated to be attri-
buted to 500— l,200mg/L of volatile organic acid contained in inflow raw waste-
water, which volatilized mainly in the aerobic tank, thus resulting in relatively
increased alkalinity.
Stoichiometrically volatilization of Img of acetic acid equals an increase of
0.833mg in CaCOa. Accordingly, volatilization of the total amount of organic acid
mentioned above as acetic acid leads to an increase of 400— l,OOOmg/L in alkalinity.
pH in the aerobic tank lower than in the anaerobic tank, which makes it difficult
to catch hold of organic acid to the aerobic tank, the detention time for the aerobic
tank about three times that for the anaerobic tank, and the blowing air volume for
the former about five times that for the latter suggest volatilization of organic acid
in the aerobic tank.
3.2.10 Phosphorus Removal
The T-P removal percentage was about 14%-50%.
In the present experiment, no biological dephosphorization was particularly
observed in Runs 1 - 4. The relationship between T-P removal percentage and
nitrogen removal percentage in each Run, however, shows that Run 5, in which little
nitrification proceeded, provided a higher T-P removal percentage than the other
Runs. Progressed nitrification reaction is said to result in increased concentrations
of NCh-N and NCh-N contained in recycling liquor, which causes the anaerobic tank
not to attain complete anaerobic condition with restricted release of phosphorus,
thus leading to difficultly proceeding biological dephosphorization.
140
-------
4. MODIFIED MIXED-LIQUOR RECIRCULATION ACTIVATED SLUDGE
PROCESS BY PURE OXYGEN BLOWING
With a covered pure oxygen activated sludge system adopted in the aerobic
tank, experiment on a modified recycling method was conducted. A pilot plant was
operated with the nitrified liquor recycling rate of 100% and return sludge rate of
200%. In the anaerobic tank, aeration was performed for stirring with MLDO of
0.1 -0.3mg/L. In the aerobic tank, biological oxidation was carried out at supplied
oxygen volume of 2-4m3Ch/m3 of raw wastewater with MLDO of 7-13mg/L.
With respect to removal of BOD and CODMn this process gave good results as
in the case of the modified mixed liquor recirculation process by air blowing.
Regarding removal of nitrogen, however, good results were not obtained.
Therefore, in the latter part of the experiment, the final stage tank of the
aerobic tank was changed from a closed-type to an open-type with air blowing
performed in the final stage tank. This resulted in progress of nitrification, which
allowed the percentage of nitrogen removal to be improved.
5. FIXED MEDIUM TYPE NITRIFICATION-DENITRIFICATION PROCESS
Wastewater treated by the modified mixed liquor recirculation process by air
blowing was fed to a submerged biooxidation tank for fixed medium bed nitrifi-
cation. The filling-up media had the specific surface of 100m2/m3, supplied air
volume was 40-80 times as much as filling-up media volume, and DO concentration
in the tank was maintained at 2-6mg/L. However, good removal of BOD and T-N
in a mixed-decomposing tank resulted in poor propagation of adhering microbe,
causing little nitrification reaction to proceed.
The nitrification percentage for Run 6 was relatively high with 27.2% on the
average (water temperature; 10°C). This is 54% in terms of values at 20°C. The
coefficient of temperature used here, whose value is 0 = 1.11, was determined from
the nitrification rate in a mixed-decompsing tank. In Run 6, when Kj-N loading
was 0.13kg/m3/day, the nitrification percentage of 80%, which can be expected with
a large adhering microbe level, was obtained as one experimental value.
In the modified mixed liquor recirculation process, experiment on Run 2, in
which pH control was not performed, was carried out by dosing alkali agents.
The alkalinity balance in the tank was almost in agreement with the theoretical
alkalinity value.
In the mixed-decomposing tank and submerged biooxidation tank, BOD, which
can be used as microbial mutrient by denitrifying bacteria was most removed. Thus
to the denitrification tank, methanol was added.
When a value [ratio of methanol to (NOz-N)+(NOs-N)] is 3 or more, no effect
of carbon source on denitrification percentage was observed, while, with a value of 2
or less, a decrease in denitrification percentage was observed. With NO2-N + NOs-N
loading in the range of 0.05—0.18kg/m3-day, the denitrification percentage is about
70—95%. Also in this case, in which no information was provided on adhering
microbe level, no quantitative analysis was conducted. Table-9 and Table-10 give
the results on fixed medium type nitrification-denitrification process for air-blowing
mixed-decomposing tank effluent.
141
-------
Table-9 Treatment Efficiency of Submerged Biooxidation Tank
(treated; effluents from mixed-decomposing tank by air blowing)
(Table indicates average value of experimental data of each Run)
~"^-\^^ Run No.
Items ---~_^^
Inflow volume m3/day
Temperature °C
Detention time hr
pH in
out
Alkalinity in
[NaOH dosing]
mg/d out
BOD in
mg/ i out
Ave. removal rate (%)
CODMn in
mg/ 1 out
Ave. removal rate (%)
CODcr in
mg/ 1 out
Ave. removal rate (%]
SS in
mg/ i out
Ave. removal rate (%]
T-N in
mg/ 1 out
Ave. removal rate (%]
Kj-N in
mg/ i out
Ave. removal rate (%]
NH4-N in
mg/ i out
Ave. removal rate (%]
Org-N in
mg/ i out
Ave. removal rate (%'
NOn-N in
mg/ £ out
Ef fluent ;NOn-N/T-N(%>
T-P in
mg/J> out
Ave. removal rate (%)
1
1.07
17.9
61
5.48
5.49
18
0
12
58(10)
45
19
382
359
6.0
944
697
26.2
207
200
3.3
181
177
2.2
78
76
A
28
33
A
50
43
14
103
101
57.1
64
60
6.2
2
2.26
25.2
28
5.51
6.64
14
28
76
42
28
333
467
406
13
844
776
8.1
142
64
54.9
141
134
49
3
3.29
30.7
19
6.67
7.09
60
0
98
36
9
75.0
388
328
15.4
670
536
20
148
38
74.3
128
114
10.9
69 51
67 45
1.4 11.6
16 10
18 12
A A
53
49
7.5
72
67
50.0
73
69
5.4
40
33
175
77
69
60.1
35
34
2.8
4
220
24.5
28
6.69
6.65
74
0
60
24
3
87.5
21
70
15.8
81
78
17.7
85
16
81.8
139
126
9.3
40
29
26.2
5.3
1.6
69.8
34.7
274
21.0
99
77
61 1
44
44
0
5-1
2.50
17.8
25
7.57
7.50
489
0
415
51
25
509
403
364
96
813
675
170
52
10
80.7
250
221
11.6
215
187
13.1
155
134
13.5
60
53
11.7
35
34
15.4
61
60
1.6
5-2
2.02
17.0
31
7.43
7.25
30
0
14
62
14
774
391
347
11.2
728
607
166
86
20
76.7
246
224
8.9
193
162
15.1
133
110
17.3
60
52
13.3
53
62
27.7
61
53
13.1
5-3
1.61
129
39
7.80
7.61
716
0
443
37
24
351
421
394
6.4
750
656
12.5
60
15
75.0
304
281
7.5
280
223
20.5
221
174
21.3
59
49
11.9
24
58
20.6
58
60
A
6-1
1.27
13.9
49
6.60
5.26
67
0
5
19(3)
33
A
35
49
A
88
07
A
30
13
56.6
124
168
A
27
48
A
2
27
A
25
21
16
97
120
71.4
50
60
A
6-2
1.57
10.0
39
6.86
6.91
18
0
84
49
12
74.4
313
254
18.8
516
406
21.3
67
23
65.6
120
115
4.1
37
30
27.2
2
1
50
36
29
19.4
83
85
73.9
57
50
12.2
6-3
1.77
14.6
35
6.99
7.16
311
0
251
46
22
52.1
387
363
6.2
645
591
8.4
43
50
A
165
157
4.8
78
65
28.7
25
15
40
53
50
5.7
87
92
58.6
106
112
A
BOD, (, ) soluble BOD, A ; minus value
* The removal percentage givwi in the table indicates the average value of removal percentage in relation to
the individual experimental results.
142
-------
Table-10 Treatment Efficiency of Denitrification TanK
(treated; submerged biooxidation tank effluent)
(Table indicates average value of experimental data of each Run)
~~~~~— —^ Run No.
Items ^~~~~"----^^
Inflow volume trf/day
Temperature °C
Detention time hr
DO mg/£
Methanol added mg/i
1
1.07
18.0
49
0.24
465
Methanol/NOn-N ratio(%) 4.5
pH in
out
M-Alkalinity in
mg/ i out
BOD in
mg/ a out
Ave. removal rate (%)
CODMn in
mg/St out
Ave. removal rate (%)
SS in
mg/£ out
Ave. removal rate (%)
T-N in
mg/ 1 out
Ave. removal rate (%)
Kj-N in
mg/2 out
Ave. removal rate (%)
NH4-N in
mg/i out
Ave. removal rate (%)
NOn-N in
mg/£ out
Ave. removal rate (%)
T-P in
mg/ i out
Ave. removal rate (%)
5.49
7.49
12
284
45
93
A
359
357
0.56
200
212
A
177
92
48.0
76
79
A
33
26
21.2
101
13
87.1
60
53
11.7
2
2.26
25.1
22
0.12
319
4.9
6.64
7.22
76
272
28
52
A
406
409
A
64
91
A
134
76
43.3
67
67
0
18
15
16.7
67
9
86.6
69
65
5.8
3
3.29
31.2
15
0.08
282
4.1
7.09
7.48
98
307
9
14
A
328
290
11.6
38
27
28.9
114
62
45.6
45
51
A
12
14
A
69
12
82.3
34
31
8.8
4
2.20
24.5
23
0.27
468
4.8
6.65
7.26
60
323
3
5
A
270
250
7.4
16
8
50
126
59
53.2
29
36
A
1.6
1.5
6.3
97
23
76.3
44
43
2.3
5-1
2.50
18.0
20
0.20
153
4.5
7.60
7.49
415
505
25
25
0
364
347
4.7
10
16
A
221
179
19.0
187
172
8.0
134
125
6.7
34
7.3
78.5
60
62
A
5-2
2.02
16.8
25
0.09
260
4.1
7.25
7.50
214
382
14
15
A
347
288
17.0
20
16
20
224
191
14.7
162
168
A
110
120
A
62
23
62.9
53
53
0
5-3
1.61
13.0
31
0.18
224
3.7
7.61
7.60
443
528
24
22
8.3
394
366
7.1
15
19
A
281
236
16.0
223
213
4.5
174
165
5.2
58
23
60.3
60
58
3.3
6-1
1.27
13.5
40
0.10
365
3.1
5.26
7.28
5
313
33
134
A
249
324
A
13
11
15.4
168
123
26.8
48
88
A
27
52
A
120
35
70.8
60
55
8.3
6-2
1.59
10.5
31
0.14
360
4.4
6.91
7.08
84
191
12
87
A
254
285
A
23
13
43.5
115
83
27.8
30
32
A
1
3
A
85
51
,40
50
49
2.0
6-3
1.77
11.3
28
0.12
303
3.4
7.16
7.35
251
390
22
94
A
363
381
A
50
36
28
157
92
41.4
65
56
13.8
15
6
60
92
36
60.9
112
117
A
A ; minus value
* The removal percentage given in the table indicates the average value of removal percentage in relation
to the individual experimental results.
143
-------
A re-aeration tank is located behind a submerged biooxidation tank. In the re-
aeration tank, the percentage of BOD removal was 35% on the average. Also in
Kj-N, NH4-N, NOn-N, and T-P other than this, little change was observed between
before and after treatment.
6. COAGULATIVE PRECIPITATION
Table-11 shows the efficiency of treatment by coagulative precipitation. In
the physico-chemical treatment experiment following coagulative precipitation,
alterations were not made in inflow wastewater volume, but in conditions, such as
chemicals addition percentage. For Run 5, no experiment was performed on coagu-
lative precipitation. For Run 3, wastewater treated by a pure oxygen blowing
process was used.
As coagulant, combination of 200mg/L of aluminium sulphate and 0.5mg/L of
anionic polymer, and combination of 500mg/L of ferric chloride and 0.5mg/L of
anionic polymer were used with good results obtained.
That is, these cases both provided good removal percentage in relation to
CODMn, T-P, and color degree. The average CODMn removal percentage was 38%,
average T-P removal percentage 93%, and average color degree removal percentage
5 5%. A proportional relation was shown between color degree removal percentage
and CODcr removal percentage.
Table-11 Results of Coagulative Precipitation Experiment
(Table indicates average value of experimental data of each Run)
\ ^^^^ Items
Run\ ^^^^
1
2
3
6
Raw waste
pH
8 02
Effluent '801
Removed quantity _
Removal rate (%) -
Raw waste 736
Effluent 636
Removed quantity
Removal rate (%)
Raw waste 7 g 7
Effluent 716
Removed quantity
Removal rate (%) _
Raw waste 759
Effluent 7 18
Removed quantity _
Removal rate (%)
Raw waste
Effluent
-
743
6 79
Removed quantity
Removal rate (%)
_
-
M-alkalimty
mg/j.
326
195
131
402
276
48
228
826
1,118
530
588
526
327
93
234
71 6
319
99
220
690
BOD
mg/J
32
11
21
65 6
24
6
18
75 0
22
12
10
455
13
0 4
09
692
42
24
18
429
CODMn
mg/e
337
237
100
29 7
386
224
162
42 0
392
262
130
33 2
246
130
116
47 2
308
211
97
31 5
CODcr
mg/2
802
546
256
31 9
659
416
243
369
676
480
196
290
427
201
226
529
514
302
212
41 2
SS
mg/ £
72
142
-70
-
56
24
32
57 1
17
16
1
5 9
6
9
-3
-
20
13
7
350
Kj-N
mg/J
76
57
19
25 0
66
45
21
31 8
275
246
29
10 5
35
16
19
54 3
41
35
6
14 6
NH4-N
mg/J
25
22
3
120
18
17
1
5 6
240
218
22
92
2
1
1
500
8
7
1
12 5
NOj-N
NOa-N
mg/e
4
4
0
0
6
4
2
33 3
4
6
-2
-
24
18
6
25 0
31
27
4
129
T-P
mg/i
58
13
45
77 6
61
2
59
96 7
18
0 9
17
94 4
41
1
40
97 6
73
3
70
95 9
Color
degree
_
_
-
1,061
420
641
604
1.083
747
336
31 0
Coagulant
dosing
AI;O3
200mg/t
Polymer
OSmg/ft
AhOs
200mg/i
Polymer
OSmg/J
FeCIs
SOOmgli
Polymer
0 Smg/t
979
FeCls
294 500mg/£
685 Polvmer
70 0
OSmg/H
1 126
481 FeC'3
300mg/l
645
57 3
foiymer
OSmg/ i
144
-------
7. HIGH-RATE SAND FILTRATION
Using downflow and pressure type high-rate filtration, operation was per-
formed with the condition of LV = 188m/day. As the treatment efficiency, the
average SS removal percentage was 30%. With regard to the other items, little
treatment efficiency was observed.
Table-12 gives the experimental results on high-rate sand filtration.
Table-12 Results of High-Rate Sand-Filter Experiment
(Table indicates average value of experimental data of each Run)
\~"""~^^^^ Items
Run\ ^~^\
1
2
3
4
5
6
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Alkalinity
(mg/d)
195
203
(-4)
48
47
0
530
492
7
93
92
0
452
454
0
99
98
0
BOD
(mg/O
11 4
108
5
62
64
0
11 7
10 9
7
04
06
0
15 6
154
0
23 5
20,3
14
CODMn
(mg/it)
237
274
(-16)
224
218
3
263
258
2
130
129
0
341
339
0
211
206
2
CODcr
(mg/*)
546
546
0
416
401
4
480
459
4
201
204
0
620
599
3
302
291
4
SS
(mg/il)
142
100
30
237
125
47
16
11
31
93
68
27
18
11
39
13
22
(-70)
Kj-N
(mg/Jl)
57
60
(-5)
45
44
0
246
243
1
16
16
0
175
177
0
35
36
0
NH4-N
(mg/H)
22
23
0
17
17
0
218
213
2
14
14
0
126
126
0
7
7
0
N°J>N
N03 N
(mg/J.)
42
4 1
0
37
33
10
56
44
21
178
187
(-5)
14
11
21
27
26
0
T-P
(nig/*)
127
92
28
20
1 7
15
09
08
0
12
06
50
56
57
0
3
3
0
Color
(degree)
-
-
-
420
416
0
747
763
0
294
290
0
1,161
1.161
0
481
482
0
145
-------
8. ACTIVATED CARBON ADSORPTION
Experiment was conducted using a downflow and pressure type granular acti-
vated carbon adsorption tower pilot plant. The adsorption tower, composed of 3
towers with effective length of 1.68m, was operated in a merry-go-round style with
a contact time of 100 minutes and LVof 72m/day. The average CODMn removal
percentage for the treated wastewater was 81% (range: 72—92%). The adsorption in
the first tower, when the CODMn of wastewater in the third tower was below
30mg/L, was 160-200g/kgAC with the water-AC ratio of about 550, which made
the life of activated carbon before replacement about 30 days. An activated carbon
adsorption process with coagulative precipitation omitted, which allows only three
days as the life of activated carbon before replacement, was confirmed to permit no
practical application.
Table 13 and Fig.-19 give the experimental results on activated carbon adsorp-
tion treatment.
Table-13 Efficiency of Activated Carbon Treatment
(Table indicates average value of experimental data of each Run)
\^~~ — ^^ Items
Run\^ — -^^
1
2
3
4
5
6
Designed
value
Raw waste
Effluent
Removal tate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Raw waste
Effluent
Removal rate(%)
Alkalinity
(mg/Jt)
203
219
( -8 )
47
98
(-109)
492
484
2
92
129
( -40 )
454
475
( -5 )
98
129
(-32 )
-
-
-
BOD
(mg/Z)
108
4 1
62
6 4
4 1
36
109
68
38
06
05
17
154
162
(-5)
20 3
8 6
58
15
5
67
CODMn
(mg/«)
274
49
82
218
40
82
258
42
84
129
10
92
339
95
72
206
53
74
200
30
85
CODcr
(mg«)
546
100
82
401
69
83
459
67
85
204
23
89
599
152
75
291
80
73
-
-
-
ss
(mg/«)
100
12
88
125
55
56
11
10
9
68
2 1
69
1 1
10
9
22
6
73
10
5
50
Kj-N
(nig/ JO
60
29
52
44
20
55
243
201
17
16
2
88
177
135
24
36
14
61
78
9
88
NH4-N
(mg/e)
23
21
9
17
16
0
213
195
8
14
11
21
126
122
3
7
7
0
3
3
-
NOi
NOa>N
(mg/Z)
4 1
23
44
3 3
1 4
58
44
1 6
64
18 7
162
13
11
86
22
26
26
0
1
1
-
T-P
(mg/H)
9 2
3 1
66
1 7
1 2
29
0 8
0 6
25
06
02
67
57
32
44
3
2
34
5
5
-
Color
(degree)
-
-
-
416
11
97
763
112
85 '
290
6
98
1.161
123
89
482
34
93
-
-
-
Alb-N
(mg/«)
21 8
4 4
798
15 1
27
82 1
160
26
838
84
0 6
929
23 1
70
697
14 4
2 1
86 1
75
6
92
100
S 80
S
i 60
ra
I 4°
20
0
r
_
-
-
n
_
r-i
n
n
n
-
Alkalinity BOD CODMn CODcr
SS
Kl-N
NH4-N NOn-N
T-P
Color
Figure-19 Removal Rate of Respective Water Quality Items in Activated
Carbon Adsorption Process
146
-------
9. COST FOR TREATMENT
9.1 Flow Sheet of Plant for Treatment of Supernate from Thermal Sludge Treat-
ment
In calculating the treatment cost, the same process as used in the experimental
plant was intended to be adopted as a treatment method. In the experiment, how-
ever, the removal efficiency in a fixed medium type nitrification-denitrification
process fell short of the planned value due to shortage of adhering microbe level, etc.
Therefore, studies were undertaken on the following three cases.
1 st Case Adoption of the same process as used in the experimental plant
- Assumption that the Kj-N removal percentage in the submerged biooxi-
dation tank (fixed medium bed) is 54%
- Assumption that the T-N removal percentage in the denitrification tank
(fixed medium bed) is 78%
2nd Case Adoption of the same process as used in the experimental plant
- Assumption that the Kj-N removal percentage in the submerged biooxi-
dation tank (fixed medium bed) is 80%
- Assumption that the T-N removal percentage in the denitrification tank
(fixed medium bed) is 89%
3rd Case No fixed medium type nitrification-denitrification to be performed.
Fig.-20 gives a flow sheet used for design calculation, while Table-14 provides
estimated treatment efficiency for each case.
Flow equalization tank
Recycling liquor
Mixed decomposing
tank L
Return sludge
Final settling tank
< Methanol >
< NaOH >
< Coaglant >
FeCh
Polymer
' (p)- — •*• Excess sludge
(for sludge treatment)
Submerged biooxidation tank
Denitrification tank
Reaeration tank I (Case 3
I m -— - - '
Flash mixing tank
Flocculation tank
Coagulative precipitation tank
High rate filtration tank
Case 1, 2
— —— Case 3
(excluding submerged
biooxidation, denitrification and
reaeration process)
Activated carbon
adsorption towers
Figure-20 Flow Sheet of Treatment Plant of Supernate from Thermal Sludge
Treatment Process
147
-------
Table-14 Expected Treatment Efficiency
\^
Items ^^^^
BOD meJi
CODMn mg/j,
SS mg/l
T-N mg/i
Kj-N mg/ 1
NH4-N mg/Jl
NOn-N mg/ {,
T-P mg/ 8,
ROU/
wastewater
3.200
2,200
640
640
628
182
12
110
Cas
Effluent
5
30
5
17
10
7
7
5
e 1
Removal
rate (%)
998
986
99.2
97.3
984
962
-
955
Cas
Effluent
5
30
5
10
4
3
6
5
e 2
Removal
rate (%)
998
986
992
983
994
984
-
955
Cas
Effluent
10
30
5
120
22
16
98
5
e3
Removal
rate (%)
997
98.6
992
81 3
965
91.3
-
955
9.2 Construction Cost and Operation Cost
Table-15 shows calculations on construction cost and operation cost in relation
to the above three cases. The construction cost for this pilot plant, when roughly
calculated with its scale enlarged to l,0003m/day, is 1,500-1,800 million yen, or
1.5—1.8 million yen per m3 of treated wastewater. Omission of fixed medium type
nitrification-denitrification equipment, which provided poor treatment efficiency,
makes the construction cost 1,200 million yen.
Of the operation management cost, the maintenance management cost (mainly
power charges and chemicals expenses) is 400-500 yen/m3. The summation of
depreciation expense and maintenance management cost is 600—650 yen/m3.
A little less than 50% of this was accounted for by facilities for the modified mixed
liquor recirculation activated sludge process, 20% by fixed medium type nitrifi-
cation-denitrification equipment, and the remaining 30% by facilities for physico-
chemical treatment.
148
-------
Table-15 Construction Costs, Depreciation
Charges of the Treatment Facility
Treatment Process
Expenses, Chemicals Expenses and Power
for Supernate from Thermal Sludge
Process
Suspended sludge
type recyclation
process
Fixed medium
bed type
nitrification and
denitrification
process
Coagulative
precipitation
High-rate sand
filtration
Activated carbon
adsorption
Common cost
Total
Cost
Construction costs (million yen)
Depreciation expenses (yen/m3)
Chemicals expense , / j\
+ Power charge (.yen/m ;
Sub- total (yen/m3)
Construction costs (million yen)
Depreciationexpenses (yen/m3)
Chemicals expense (vfn/m^\
+ Power charge (.yen/m )
Sub-total (yen/m3)
Construction costs (million yen)
Depreciationexpenses (yen/m3)
Chemicals expense (ven/m3 1
+ Power charze (.yen/m ;
Sub-total (yen/m3)
Construction costs (million yen)
Depreciation expenses (yen/m3)
Chemicals expense , _/_3\
+ Power charge (yen/m )
Sub-total (yen/m3)
Construction costs (million yen)
Depreciationexpenses (yen/m3)
Chemicals expense (ven/m3'>
+ Power charge (.yen/m )
Sub-total (yen/m3)
Construction costs (million yen)
Depreciationexpenses (yen/m3)
Chemicals expense (Ven/m3"!
+ Power charge (.yen/m )
Sub-total (yen/m3)
Construction costs (million yen)
Depreciationexpenses (yen/m3)
Chemicals expense f ven/m3 1
+ Power charge tyen/m )
Sum Total (yen/m3)
Case 1
704
89 2
210 0
299 2
707
87 0
453
132.3
67
10 5
380
48.5
58
9 7
1 7
1 1.4
201
34 9
116 2
1511
80
7.3
0
7.3
1,817
238.6
41 1.2
649.8
Case 2
673
864
210.0
2964
449
55.6
495
105.1
67
105
38 0
48.5
58
9 7
1 7
1 1.4
201
34.9
1 1 6.2
151.1
80
7 3
0
7.3
1,528
204.4
4 15.4
619.8
CaseS
703
89 9
201.2
300 1
-
-
-
-
67
10.5
380
48 5
58
9 7
1 7
1 1 4
261
45.9
249 5
2954
80
7 3
0
7.3
1, 169
163.3
499.4
662.7
Fig.-21 shows the percentage, at which each unit process holds the construction
cost, depreciation expense and operation cost (power charges and chemicals ex-
penses), power charges, and chemicals expenses in relation to Case 1.
149
-------
Construction cost
Highrate filtration (3.2%) -
Coagulative precipitation (3.7%)
Common cost (4.4%)
\
Suspended medium system (38.7%)"
Fixed medium bed system (38.9%) •
Activated carbon
adsorption (11.1%)
Depreciation expense and operation cost
Suspended medium system (46%)
Highrate filtration (1.8%) Common cost (1 1%)
'Fixed medium bed
system (20.4%) ' .
Activ
adsorption (23 3%)-
Power charge
\
Coagulative precipitation (7.5%)
Activated carbon adsorption (0 9%) -
Highrate filtration (1 0%).
Coagulative precipitation (0.5%) -
Suspended medium system (91 3%)
Chemicals expense
Fixed medium bed system (6.5%)
Suspended medium
system (22.0%)^O
\
Fixed medium bed system (14 3%) Coagulative precipitation (15.6%)
Figure-21 Percentage of Cost Accounted for by Each Unit Process
Table-16 gives estimates on operation cost relating to thermal treatment and
melting equipment for reference.
The total waste liquid volume, when sludge with 100 ton-DS/day is subjected
to low-temperature thermal treatment, is 3,880m3 /day.
Estimation was performed with a treatment scale taken as 20 ton-DS/day.
150
-------
Table-16 Operating Costs of Thermal Treatment and Melting Process
(yen/ton)
^^~~~^^_ Cost
Process ^^~~~"~-^__^^
Pretreatment (liquid cyclon)
Centrifugal concentration
Low temperature thermal
treatment
Dewatering (press filter)
Drying
Melting
Deodoration
Common
Total
Power
charge
108
4,675
4,447
2,199
1,048
2,873
1,584
118
17,052
Heavy oil
-
-
-
-
-
13,289
-
-
13,289
Water for
industrial
use
-
-
-
-
-
608
224
-
832
Chemicals
expense
-
-
-
-
-
49,952
644
-
50,596
Total
108
4,675
4,447
2,199
1,048
66,722
2,452
118
81,769
Note) Assuming that treated water is used for filter media washing water and seal water, only
electric charges have been added up.
10. CONCLUSION
It was confirmed that supernate from thermal sludge treatment, when doubly
diluted and individually treated by a series of unit procesees, modified mixed liquor
recirculation activated sludge process, fixed medium type nitrification-denitrifica-
tion process, coagulative precipitation process, high-rate sand filtration process, and
activated carbon adsorption, can be discharged directly into the sea. The actual
design, however, is considered to require further studies on recycling rate for mixed
liquor recirculation process, volume of nitrification tank, and other problems.
The present report was compiled from "Technological Assessment on Experi-
mental Plant for Treatment of Supernatant from Thermal Sludge Treatment in Kobe
City, March 1982, J.S.W.A." I wish to thank Dr. Kazuhiro Tanaka, Chief of Research
and Technology Development Section of Japan Sewage Works Agency for his kind
instruction in this compilation.
I also wish to express our appreciation to Mr. KazuoOmiya*! and Mr. Isao
Kinoshitaf 2 who took direct charge of this assessment.
*1 Water Quality Control Division, Environmental Preservation Bureau,
Tokyo Metropolitan Government
*2 Tokyo Branch, Japan Sewage Works Agency
151
-------
OPERATION PERFORMANCE OF SLUDGE TREATMENT PILOT PLANT
WITH THERMAL TREATMENT AND MELTING SYSTEM
(ABSTRACT)
(1) Centrifugal Thickening Equipment
a) The centrifugal thickening machine is retentive of sludge for 5 to 10 minutes.
Concentrated sludge of given concentration can be obtained by properly com-
bining centrifugal effect, and sludge supply time and sludge amount supplied
per one cycle as shown in Fig.-l and Table-1.
b) Electric energy required for operating inspected machine was 1.3Kwh to
2.5Kwh per cubic meter for raw sludge (Concentration of SS was 2%) and
ISOKwh per ton for concentrated sludge solid.
c) It is economical to increase SS amount wasted during the unit time by raising
concentration of SS contained in supplied sludge as high as possible with
gravitational thickening.
6 •
i 5 •
Centrifugal effect 400G
Sludge supply speed 10m3 /hr
D
/
P
90 3
80
15 20 25
Sludge supply time per one cycle (mm )
Figure-1 Sludge Supply Time vs Concentration of Concentrated Sludge
152
-------
Table-1 Result of Concentration Test
Operational conditions
Centrifugal
effect
(G)
200
300
400
500
400
Sludge supply
speed
Objectives
m3/hr
5
10
15
10
5
10
15
5
10
IS
10
10
10
Results
mfhr
46
8.4
11.8
7.9
4.4
8.1
127
4.7
8.2
131
82
8.2
86
Sludge
supply
time
mm/cycle
60
40
30
25
50
25
20
40
25
20
15
20
25
Supplied sludge (in)
Supplied
sludge
amount
m3 /cycle
4.62
5.62
5.90
330
3.69
338
423
3.15
3.43
435
205
2.73
357
Concen-
tration
ofSS
%
1.70
1.70
200
1.67
2.08
2.11
2.07
2.12
1.69
169
1.86
2.20
2.2 G
Solid
amount
kg/cycle
78.9
95.2
118.0
549
76.8
76.0
87.7
668
57.8
73.1
38.3
60.1
80.6
Concentrated sludge (out)
Concentra-
ted sludge
amount
m3 /cycle
1.156
1.176
1049
1.113
1.005
0.996
1005
1.081
1.113
1.107
1.083
1.086
1.092
Concen-
tration
ofSS
%
56600
67600
81000
51900
73100
57500
64900
52300
55400
66700
26400
48800
58000
Solid
amount
kg/cycle
65.5
79.7
850
576
73.5
57.3
65.3
565
617
73.9
28.3
53.0
636
SS
recovery
%
88.2
764
25.5
81 9
86.0
81.7
595
923
798
693
933
888
86 H
Supernatant (out)
Supernatant
amount
m3/ cycle
3460
4440
4850
2190
269(1
2610
3230
2070
2310
3210
0970
1 640
•J470
Concen-
tration
ofSS
%
0.275
0502
1 59
0418
0399
0549
101
0262
0441
0635
035
0.411
0172
Solid
amount
kg/ cycle
96
222
77 I
•12
106
14 4
326
5.5
101
203
34
6.7
11.6
-------
(2) Equipment for Thermal Treatment
a) Steam increased volumes of thermal-treated sludge by 11%. TS contained in
sludge decreased by 15 to 20% by thermal treatment. It was estimated that
about 30% of SS, about 40% of nitrogen and almost none of phosphorus
contained in raw sludge dissolved. (Refer to Table-2 of original) (Table-2,Fig.-2)
b) The decomposition rate of SS was in inverse proportion to the concentration of
SS. This means that treatment at high sludge concentration reduces BOD and
COD load contained in supernate. The concentration of supplied for thermal
treatment must be 5 to 6%. (Fig.-3, Fig.-4)
c) When sludge was treated at 165°C for 60 minutes, Kerosene of 13 to 15 liters
per inputted sludge of one cubic meter was consumed to generate steam
supplied for the reactor.
d) It was hard to dehydrate sludge when it was treated at 155°C, so reaction
temperature must be kept 165°C for satisfactory dehydration.
365 M4
Thermal treated
SS
59 6
S3
W™%
,--'182 ,-''
|^O 22-2
(
Reduced portion of TS
Table-2 Dissolution rates of Phosphorus
and Nitrogen
j^^^^RunNo
Photphonis(^)
Nilrogen (*)
1
0
389
2
73
459
3
0
36.8
4
0
374
I Figures shown above are the ones when TS contained in concentrated sludge
is regarded as 100
2 DS = TS - SS
,Sol phosphorusin . .Sol phosphorus
Jiisolimon rales 'thermal treated iludgc1 " (m raw i\udgf I
>lpho»phUIUS - (AllphojphorusLn, -Sol phosphorus.
'supplied sludge > ~
Figure-4 Autoclave Test Results
Concentration of SS in sludge
supplied for thermal treatment
Figure-3 Concentration of SS in Supplied
Sludge - SS Dissolution Rate
154
-------
(3) Dewatering Equipment
Supplied sludge was easy to be dewatered, and the proportion of gross SS to all
the SS contained in the sludge was very large. Therefore, dewatered cake with
low moisture (30 to 45%) could be obtained by the use of Filter press., when
filtration rate was 6 to 10kg/m2 -hr. (Table-3)
(4) Equipment for Melting Furnace
It was favorable for melting treatment that a small quantity of moisture and
a large quantity of organic components was contained in supplied cake and
melting point of ash content of the cake was low.
a) The amount of kerosene consumed in melting furnace was about 170 liters per
inputted solid of one ton under the condition that DS of 20% moisture and
4,OOOKcal/kg low calorific power was inputted with rated load.
b) The amount of kerosene consumed in melting furnace depends on inputted
amount of dried cake, moisture contained in sludge, and combustion calory.
(Fig.-5 to Fig.-8)
Amount of treated solid Moisture in cake
kg ds/hr) (%)
74 3 22 7
700 370
92 5 14 6
567 193
50 6 25 6
82
23 5
Figure-5 Heat Balance in Melting Furnace
0 40 50 60 70
Amount of treated solid (kg ds/hr)
Figure-6 Amount of Treated Sludge
vs Amount of Consumed
Fuel
155
-------
Table-3 Thermal-treated Sludge Dewatering Test by the Use of Filter Press
Dew
-CT'$0nC
Sludge
supply
tune
(mm)
5
10
IS
s
10
15
5
10
IS
ate ring
itions
Compres
sion tune
(min)
is
10
s
IS
10
s
IS
10
9
Remark
Sludge
amount
(m3 /cycled
0)
0931
2167
2297
0938
2070
2200
1008
1650
2008
Thermal-treated concentrated sludge
SS
(mg/lO
12,
47.400
54.800
SI.600
80.000
73.700
69.700
78.000
63.200
65.200
SS
amount
(kg/cycle)
<3MEx<2x 10
44461
112752
118525
75040
152559
153340
83304
104280
130791
Gross
SS
(rng/d )
32.400
44.100
-
53.900
47.400
27.200
43.500
36.500
36.100
Vol. Solid
Gross SS
(%)
866
889
-
871
870
<")8
91 0
91 2
900
Gross
SS/SS
(%)
684
805
-
674
643
390
SS8
578
554
Sludge supply pressure 8kg/cm2 ,
Squeezing pressure 15kg/cm2
(Both fixed)
Dehydrated cake
Produced
amount
(kg/cycle)
-
-
-
982
764
878
1.120
899
1.040
SS amount
(kg/cycle)
xio
-
-
-
1 156
1 294
1 940
1404
1 483
1873
Filtration
rate
(kg/m2hr)
468
951
1043
487
881
1020
564
836
978
SS
recovery
(%)
8*"5fa>x 10°
-
-
-
978
986
982
977
983
982
-------
J 'GC-
3
iCC 20C 300 400 500
Amount of fuel consumed perfludge of one Ion (x103kcal/hl
50C 1 000 1 500
Sludge load in combustion chamber (xlo'kcal/m3 hrl
Figure-8 Combustion Calory of Sludge vs
Amount of Consumed Fuel
0 10 20 30 40
Rate o( moisture contained in cake inputted into furnace (%)
Figure-7 Moisture in Sludge vs
Consumed Fuel
c) Auxiliary fuel for drying was not required because heat recovery was per-
formed from gas exhausted by melting furnace by the use of waste heat boiler.
Steam recovered by waste heat boiler was used for drying and heating for heat
treatment, which could reduce amount of kerosene consumed during thermal
treatment by 30%. It is expected that further efficient heat recovery will lead
to more economical running. (Fig.-9)
d) Slag, whose bulk specific gravity and true specific gravity are 1.2 to 1.3 and 2.6
to 2.7, respectively, can be used for reclamation. There are few possibility that
the slag scatters. (Table-4, Table-5)
Table-4 Characteristics of Melting Slag
Table-5 Result of Dissolution Test
\iondm
* |D,»I
-
-
-
1.400
20
70
086
1 29
261
263
40
70
066
133
259
266
20
90
005
133
263
270
20
50
005
1 17
256
271
1...,,,
1 nil
Cd
CN
0. Melting flag
Cn, Zn, Fe %
"""" mg/kg
3.3
<0.1
<1
110
<2
2.4
1.7
<0 01
2 4
n
0 04
0 22
1 39
180
82
74
<0.4
0.3
<1
4.1
<2
1.7
0 013
<0 01
<0 1
6 4
0.15
0 11
6 83
820
630
260
Supemalanl
liumilan
mg/e
<0 02
<0.01
<0 01
<0 2
<.0 02
<0.005
<0 000 5
<0 000 5
<0 000 5
<0 1
<0.02
0 04
0 27
0 11
<~0 02
0 37
157
-------
Radiation (564)
No.2 Heat exchanger
Ln
00
Unit X 10'Kcll /hr.
Radiation (including blow)
1 29 (31*1
Latent heat generated by
evaporation of moisture contained
071
Dried cake 0 44
Steam enthalpy 1 29
V\
Dehydra"°" jj Dehydrated cake
Slag os
Cooling water 13
Latent heat due
to evaporation
* Figures shown in ( ) indicate the amount of consumed kerosene
except for unknown loss
Melting Duct radiation
furnace 0.2 A'r P'eheate
Waste heat boiler
Figure-9 Heat Balance in Total Test through All the Process
-------
Ninth US-Japan Conference
on
Sewage Treatment Technology
Study on Fluidized Bed Incineration
with a Drying System
September 19-21, 1983
Tokyo
ihe work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Hiroshi OUCHI
Senior Technical Advisor
Sewage Works Bureau
The City of Yokohama
159
-------
Contents
Foreword
1. Preliminary Experimental Results 164
2. Pilot Plant Study 165
2.1. Outline I65
2.1.1. Equipment 165
2.1.2. Dryer testing 165
2.1.3. Incinerator testing -*-65
2.1.4. Waste-heat boiler testing !67
2.1.5. Integrated operation testing 167
2.2. Results 167
2.2.1. Characteristics of dewatered cake 167
2.2.2. Dryer 161
a. Water content reduction 167
b. Performance 171
c. Dried cake 172
d. Dryer material 172
2.2.3. Incinerator 172
a. Maximal water content for self-sustaining combustion 172
b. Combustion 172
2.2.4. Waste-heat boiler 176
a. Performance 176
b. Corrosion 177
2.2.5. Integrated operation 177
a. Heat input and output -*-' '
b. Fuel consumption 177
c. Exhaust gas, drain and furnace ash 177
2.3. Discussion 183
2.3.1. Energy efficiency 183
2.3.2. Controlling the water content of dried cake I84
a. Disk speed ^84
b. Steam pressure level 184
c. Drying time 184
2.3.3. Material i84
a. Dryer 184
b. Waste-heat boiler 184
3. Introduction of a Full-Scale Plant 185
System planning 185
Incinerating capacity 185
3.1.2. System outline 186
3.1.3. Heat flow and supplementary fuel consumption 187
3.2. Estimated costs 193
3.2.1. Construction costs 193
3.2.2. Operating costs 193
Summary and Acknowledgements 194
160
-------
Foreword
This report presents the results of experiments with a pilot incineration plant comprising a
fluidized-bed incinerator and a dryer, and describes a working facility built in accordance with
those experimental results. Processing the dewatered cake in a dryer before feeding it into the
incinerator reduces the amount of exhaust gas, thus lowering fuel consumption and increasing
incineration capacity.
By way of introduction, though, a few words are in order on the evolving incineration
needs of the City of Yokohama. As of March 1983, about half of the population of the city was
served by sewer lines. Aiming to extend sewer service to everyone in Yokohama by the year 2000,
the Sewage Works Bureau is currently laying sewer at the rate of 1,000 m per day, as well as
building new sewage treatment plants and expanding existing plants. All of the city's plants are
set up for secondary treatment, using the activated sludge process, and broadening sewer service
is rapidly increasing the amounts of sludge turned out by these plants (Fig. 1).
Yokohama's high population density of 67 persons/hectare and the ongoing
residentialization of surrounding areas make it virtually impossible to secure new fill sites for
disposing of sludge in the city. Sludge should ideally be returned to the natural cycle of decay and
renewal, and Yokohama did in fact begin supplying a certain amount of dehydrated cake as
fertilizer for green zones and farms in 1977. However, given the impossibility of substantially
boosting demand for fertilizer in very-urban Yokohama, the city has decided to incinerate all
sludge for the time being, to reduce its volume and thereby extend the useful life of fill sites.
The limited availability of land does not allow for building incinerators at all of the
treatment plants, so Yokohama is having to construct central incinerators, each of which is to
take dewatered cake from a number of treatment plants. Moreover, these treatment plants,
which have been constructed over a span of some twenty years, turn out differing sorts of
dewatered cake by a variety of processes, not all of which were originally intended to facilitate
incineration.
Incinerators for Yokohama must therefore be both large and capable of operating reliably
on a diet of various kinds of dewatered cake. Air-quality safeguards are also absolutely essential,
as is deodorization of exhaust gas. Incinerators are furthermore expected to minimize fuel
consumption.
From the standpoint of fuel consumption, self-sustaining combustion would of course be
the ideal mode of sludge incineration. Unfortunately, thoroughly reworking the entire treatment
process at each of Yokohama's historically diverse sewage plants so as to permit this would
require huge investment, and would not be economical. The city therefore opted to build new
incineration facilities to handle the sludge output of existing sewage treatment plants, and to
study means for minimizing fuel consumption by these facilities.
Incinerators can be broadly divided into multiple-hearth furnaces and fluidized bed
furnaces, with two characteristic patterns of heat consumption (Fig. 2). Multiple-hearth furnaces
feature reliable operation and have been used extensively in large-scale facilities, but they are
heavy consumers of fuel. This is because the huge amount of air required for combustion
translates into a proportionally large volume of exhaust gas, and also because fuel must be used
in deodorization.
On the other hand, fluidized bed furnaces require neither a large amount of air for
combustion nor deodorization of their exhaust gas, and therefore consume relatively little fuel.
Fluidized bed furnaces have yet to see service in many large-scale facilities, but recent progress in
micro-computerization and other ancillary technology promises to ensure reliable operation.
161
-------
a c
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Foreword
Drying and incineration are performed as a single process in conventional multiple-hearth
furnaces and fluidized bed furnaces, and so the water content vaporized out of the dewatered
cake is all heated to the temperature of the incinerator exhaust gas.
In order to avoid having to heat the full water content of the cake in the fluidized bed
furnace, systems have been devised in which the dewatered cake is dried in a separate process
prior to incineration. Drying the cake beforehand at low temperature (about 100° C) to bring the
water content down to the point where the cake will burn by itself reduces the amount of
supplementary fuel needed when the cake is then incinerated. And less vapor from the cake and
less exhaust from fuel combustion translate into greater incinerating capacity.
Since no such separate-drying system had previously been employed in a full-scale plant,
the Sewage Works Bureau of the City of Yokohama installed a pilot system at its Kanazawa
Sewage Treatment Plant and conducted testing from June 1980 to May 1982 to confirm system
performance and operability.
163
-------
1. PRELIMINARY EXPERIMENTAL RESULTS
Before the pilot system study got underway, preliminary experiments were done to
determine the optimum type of dryer. Calculations indicated that drying by indirect heat would
offer better fuel economy and less exhaust gas than drying by direct-heat, so dryers of the former
kind were used for the preliminary experiments.
Since different sewage treatment plants turn out cake of differing water content, calorific
value, and physical composition, the primary object of the preliminary experiments was to select
the dryer featuring the most consistently reliable operation with all kinds of cake. Experiments to
this end were carried out with steam-tube dryers, high-speed paddle-mixing dryers, and a low-
speed disk-mixing dryer (Table I). The low-speed disk-mixing dryer performed best in terms of
the above-mentioned selection criterion, and was therefore chosen for the pilot plant testing.
(Details of the preliminary experiments are described in Chapter 3, "Experiments on Separately
Dried Sludge Incineration," of the report, New Aspects of Sludge Incineration in Yokohama,
submitted at the Eighth US-Japan Conference on Sewage Treatment Technology.)
Table 1. Summary of preliminary experiments
Dryer
Steam
tube
heating
type
High
speed
paddle
mixing
type
Low*
speed disk-
mixing
type
Feed
process
Direct feed
Feed-
back
process
Direct
teed
Vlixer
Grinder
mixer
Paddle
angle
0°C
Paddle
angle
30° C
Direct feed
Sticking
Unable to
operate
No
No
No
No
No
Stability
-
Poor
Dried cake grains
gradually expand
Good
Poor
Cake sticking at inlet
causes over-drying at
outlet (25% or less)
Poor
Operation is stabilized
with a narrow range at
300 tpm rotating speed
and 150 kg/hteed rate
Good
Operation
-
Poor
Many accessories
are required
Poor
Many accessories
are required
Poor
Motor load some-
times fluctuates to
point of overload
Good
Poor when feed
rate is varied
Good
Controllability of dried
cake water content
-
Although controllable by
changing the dried material
feed back ratio, it is hard
to operate practically
Although controllable by
changing the dried material
feed back ratio it is hard
to operate practically
-
-
Correlation cannot be
obtained (at 20-40rpm
rotating speed and 2-7
kg/crrrG steam pressure)
Evaporation
rate
kg H; O/nr h
-
-
4-6
-
14-17
20-30
164
-------
2. PILOT PLANT STUDY
2.1. OUTLINE
The pilot plant consisted of the low-speed disk-mixing dryer selected in the preliminary
experiments and a fluidized bed furnace. Its sludge capacity was 10 t/day.
2.1.1. Equipment
A flowchart and specifications for the pilot plant equipment appear in Fig. 3.
Dewatered cake from the hopper is metered into the dryer by a weight sensitive conveyor.
After drying, the cake is then fed into the furnace. Exhaust gas from the dryer is purged of
moisture in a cooling condenser and then recycled for use as carrier gas for steam generated in
the dryer and as fluidizing airflow for the furnace.
Ash is separated out of exhaust gas from the furnace in the cyclone, after which the gas is
fed into the waste-heat boiler. There it is dehumidified and desulfurized in an absorptive cooling
tower and then released into the atmosphere.
Steam from the waste-heat boiler and supplementary boiler is stored in a steam header for
use as the heat source for drying. The waste-heat boiler was initially equipped with an auxiliary
burner, but when it proved too difficult to adjust the pressure inside the furnace the auxiliary
burner was abandoned in favor of a separate, supplementary boiler.
2.1.2 Dryer testing
The following experiments were carried out to investigate the performance of different
methods of dryer operation:
a. Water content reduction
It was assumed that dryer disk r.p.m., steam pressure, drying time, and dryer exhaust
treatment would affect the water content of the dewatered cake. Optimum values for these
variables were therefore sought and dryer controllability investigated.
b. Energy efficiency
In order to quantify the energy efficiency of respective methods, the rate of water content
vaporization per unit of dryer heating surface was investigated in conjunction with electrical
consumption.
c. Dried cake
The effects of different percentages of dried cake water content on the handling and other
properties of the cake were studied.
d. Dryer material
Test pieces of SUS304 and SUS316 were mounted at the dryer casing inlet and outlet.
Corrosion of these pieces was checked by penetrative flaw detection and by microscope.
2.1.3. Incinerator testing
a. The maximum water content for self-sustaining combustion by dried cake in the furnace
was determined.
b. Differences in combustion characteristics and heat distribution inside the furnace between
when dried cake is incinerated alone and when dewatered sludge (not yet dried in the dryer)
and dewatered cake are incinerated together were investigated.
165
-------
Secondary effluent
Steam (Max 10 kg/cm2G)
A A, A. V
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No
Unit
Model
Main dimensions
Volume
1
Cake hopper
Cubical type
2,350mm(W)x3,000
mm(L) x 2.150(H)
mm(H) 12m'
2
Dryer
Low-speed disk-
mixing type
Heating surface
area 10m'
10t/day
3
Condenser
3-stage spraying
direct cooling type
760mm(dia) x
6,OOOmm(H)
12m'/min at
100°C
4
Incinerator
Fluidized bed
furnace
1,1 00/1, 600mm
(dia)x9,200mm(H)
Dewatered cake
10t/day
5
Fluidizing air blower
Multiple stage
turbo-blower
125mm(dia)
lOm'/minx
3,500mmAq
6
Cyclone
Refractory
castable
lining
980mm (dia ) x
4,300mm(H)
40m'/min at
800° C
7
Waste-heat boiler
Water tube type
Heating surface
area 29rrf
194 kg/h x
10 kg/crrrG
8
Induced draft fan
Plate type
250/200mm(dia)
30m'/min x
450mmAq
9
Scrubber
Upper part
Spray type
Lower part
Packed tower
750mm(dia) x
15,OOOmm(H)
20mVmm
at 250° C
10
Boiler
Single pass
type
Heating surface
area 5 8m:
350kg/ hx
10 kg/crrrG
Z
O
C/)
m
2
Fij». 3 Flowchart and equipment specifications
-------
Pilot Plant Study
2.1.4. Waste-heat boiler testing
a. Waste-heat boiler performance was investigated in terms of heat efficiency, coefficient of
overall heat transfer, and amount of steam generation.
b. Test pieces of SUS304, SUS310S, SUS316, and STPG38 (calorized) were mounted in
the boiler water pipe and furnace outlet duct to gauge the effects of sulfur oxides, HC1, and
other corrosive gases thought to occur in the furnace exhaust gas. Test piece corrosion was
checked, as before, by penetrative flaw detection and by microscope.
2.1.5. Integrated operation testing
The integrated operation of the dryer, furnace, and waste-heat boiler was tested in relation
to the following items:
a. Total heat input and output
b. Fuel consumption
Fuel consumption was compared between the conventional and separate-drying systems
for each type of sludge.
c. Composition of exhaust gas, drain and furnace ash
2.2 RESULTS
2.2.1 Characteristics of dewatered cake
Six types of dewatered cake, from four sewage treatment plants, were used in the pilot
plant testing (Table 2). It can be seen from Table 2 that water content, VTS, net calorific value,
and other characteristics of the dewatered cake vary greatly with the type of dewatering machine,
the coagulant used, and whether or not an anaerobic digestion process is used.
2.2.2. Dryer
a. Water content reduction
Experiments revealed the following as factors affecting the water content of dried cake:
i. Dryer disk r.p.m. (Fig. 4)
As is clear from Fig. 4, varying the speed of disk rotation has no effect on the water content
of the dried cake up to 15 r.p.m., but begins to increase the water content at higher speeds. At 10
r.p.m., however, the cake turns together with the disk shaft, and since it is not churned it does not
heat evenly. Accordingly, 15 r.p.m. would seem to be the optimum speed for disk rotation.
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60-
50-
40-
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20
30
40 rpm
(max)
Fig. 4 Dryer disk r.p.m. and water content of dried cake
167
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
Table 2. Dewatered cake characteristics
Sewage treatment plant
Treatment
Dewatering machine
Coagulent
Sludge type abbreviation
Water content (%)
VTS (%)
Net calonfic value (kcal/kgDS)
Chubu STP (C)
Thickening and
anaerobic digestion
Belt filter (BF)
Ca(OH)2 and Fe:CI,
C-d-BF
78
(77-79)
41
(39-43)
2,000
(1,900-2,200)
Totsuka II STP (T)
Thickening (r)
Pressure filter (PF)
Ca(OH): and Fe:Cl,
T-r-PF
67
(61-71)
44
(40-45)
2,200
(1,800-2,500)
Thickening (r)
Centrifuge (CF)
Polymer
T-r-CF
80
(77-82)
73
(68-78)
3,700
(3300-4,100)
Sewage treatment plant
Treatment
Dewatering machine
Coagulent
Sludge type abbreviation
Water content (%)
VTS (%)
Net calorific value (kcal/kgDS)
Kanagawa STP (K)
Thickening (r)
Centrifuge (CF)
Polymer
K-r-CF
77
(74-80)
57
(53-64)
3,200
(3,000-3,500)
Nambu STP (N)
Thickening (r)
Centrifuge (CF)
Polymer
N-r-CF
78
(75-80)
66
(60-73)
3,800
(3,500-4,000)
Thickening and
anaerobic digestion(d)
Centrifuge (CF)
Polymer
N-d-CF
74
(70-77)
47
(43-53)
2,600
(2,400-2,900)
Note Figures indicate average values, the overall ranges being given in parentheses
ii. Steam pressure
The temperature of the steam rises in proportion to its pressure, thus increasing the
amount of heat transferred to the sludge and lowering the water content of the dried cake. But
cake will bake onto the heating surfaces if they are too hot, and this will diminish the amount of
heat transferred and raise the water content of the dried cake.
Varying the steam pressure between 5 and 9 kg/cm2G produced no change in the water
content of the dried cake (Fig. 5). However, a thin film of cake sometimes baked onto the dryer
shaft and disk when cake having a raw protein content of more than 25 percent was dried at a
steam pressure of 8 kg/cm2G. It was therefore concluded that a steam pressure of 5 kg/cm G
would be best, since this will ensure reliable operation even with dewatered cake that is high in
raw protein content.
in
Drying time
Increasing the drying time increases the amount of heat transferred to the sludge and
thereby lowers the water content of the dried cake. Drying time is varied by adjusting the angle of
the dryer and the height of the outlet weirs.
168
-------
Pilot Plant Studv
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70-
60-
50-
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10-
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0 2
(100°C) (135°C)
6
(164°C)
10
(175°C) (183°C)
Steam pressure (kg/cmJG)
Fig. 5 Steam pressure and water content of dried cake
Dryer angle
The dryer itself must be set at an angle to make the cake flow. Too slight an angle will not
produce any flow at all, while an excessive angle will move the cake through the dryer too fast for
proper drying. The experiments conducted in regard to dryer angle are summarized below:
O/100 angle: Dewatered cake having a water content of less than 75 percent did not
flow at all, collecting instead at the dryer inlet.
0.75/100: All types of dewatered cake flowed smoothly, regardless of water
content.
1 /100 or greater: Dewatered cake containing more than 80 percent water liquefied when
heated and flowed out along the bottom of the casting too fast for
proper drying.
Height of outlet weirs
Increasing the height of the outlet weirs (Fig. 6) increases the holding capacity of the dryer,
thus lengthening the drying time. Accordingly, the water content of the dried cake decreases as
weir height increases (Fig. 7).
iv. Amount and treatment of exhaust gas from dryer
A proper amount of carrier gas must be used in dryer operation to carry away steam
generated from the cake. Insufficient carrier gas will unnecessarily limit vaporization, while too
much will increase the volume of dryer exhaust gas to the point of complicating treatment work.
Nonetheless, experiments revealed that larger volumes of exhaust gas were accompanied by
lower water content in the dried cake (Fig. 8).
Experiments also indicated that the water content of the dried cake was 3-5 percent higher
when all of the exhaust gas was recycled than when it was all released into the atmosphere (Table
3). This is because carrier gas that has cooled somewhat in the course of recycling allows some of
the steam from the cake to condense back out onto the cake.
169
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
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70-
60-
50-
40-
30-
Fig. 6 Dryer weirs
-T-r-CF
-N-d-CF
Disk diameter
200 300 400 500
Weir height (mm)
Fig. 7 Weir height and water content of dried cake
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Fig. 8 Amount of exhaust gas and water content of dried cake
170
-------
Pilot Plant Study
Table 3. Exhaust gas treatment and water content of dried cake
Amount of
exhaust gas (Nm'/H)
Temperature of
recycled carrier
gas at inlet (°C)
Water content of
dried cake (%WB)
All released
into atmosphere
170-180
-
55
All recycled
170-180
30
58
170-180
40
62
Note Experiments were conducted using N-r-CF raw cake fed at the rate of 420 kg/h
b. Performance
i. Dewatered cake type and water vaporization rate
The formula below was used to obtain the rate of water vaporization per unit of heating
surface:
R —
F x {[W/(100-W)] - [W'/(100-W')]i IQO-W
A " 100
where R is the rate of vaporization (kg/m2h),
F is the sludge feed rate (kg/h),
W is the water content of dewatered cake (%),
W is the water content of dried cake (%), and
A is the heating surface area.
The rate of vaporization thus vanes according to the type of dewatered cake and the water
content to which the cake is dried. Table 4 shows the relationship between dried cake water
content and vaporization rate for different sludge feed rates. The vaporization rate averaged 16
kg/ m2h when cake was dried to a water content of 45-53 percent, and 20 kg/m'h when the water
content of the cake was brought down to 51-62%.
Table 4. Dewatered cake type and water vaporization speed
Cake volume
Cake type
C-d-BF
T-r-PF
T-r-CF
K-r-CF
N-r-CF
N-d-CF
280-330 kg/h
Water content
oj dried cake (%)
45-52
-
46-53
45-53
48-53
45-52
Vaporization
speed (kg/rrrh)
17
(15-18)
-
16
(15-19)
16
(15-16)
17
(16-20)
16
(15-17)
380-440 kg/h
Water content
of dried cake (%)
55-61
55-63
55-62
55-62
56-63
55-59
Vaporization
speed (kg/nrh)
19
(18-20)
17
(15-18
21
(20-22)
9
(17-22)
20
(17-24)
20
(18-23)
Note Figures represent average values, the overall ranges being given in parentheses
171
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
ii. Dewatered sludge type and electrical consumption
Different types of dewatered sludge require different levels of power to churn and therefore
impose differing loads on the dryer's disk shaft drive motor (Table 5). PF cake, being
comparatively dry and stiff, requires a particularly large amount of electric power consumption.
Table 5. Electric power consumption
Dewatered
cake type
C-d^BF
T-r-PF
T-r-CF
K-r-CF
N-r-CF
N-d-CF
Power consumption
4-5
5-6
4 ~ 5
4-5
3-4
4-5
c. Dried cake
Comparison of dried cake and dewatered sludge composition revealed little difference in
physical make-up other than water content (Table 6). As for the form of the dried cake at
different levels of water content, it was found that dried cake consisting of at least 60 percent
water becomes a very sticky, amorphous mass. At a water content of around 55 percent, the cake
forms into lumps averaging 80 mm in diameter and ranging as large as 200 mm diameter. At a
water content of no more than 50 percent, CF cake forms into lumps as large as 100 mm in
diameter, while BF cake granulizes into pieces no larger than 50 mm in diameter.
d. Dryer material
Test pieces of SUS304 that were mounted on the dryer casing evidenced corrosive pitting
over their entire surface area. Similarly mounted test pieces of SUS316 suffered corrosion only at
welded points, where minor corroded depressions occurred.
2.2.3. Incinerator
a. Maximal water content for self-sustaining combustion
Fig. 9 represents the correlation between the percentage of water content of dried cake
fed into the fluidized bed furnace and the amount of kerosene that had to be burned as
supplementary fuel. It can be seen that cake with a water content of 52-60 percent required no
more than 7 liters of kerosene per ton of cake to sustain combustion. This may therefore be
regarded as essentially the upper range of water content for nearly self-sustaining combustion.
b. Combustion
When dewatered cake was incinerated alone, vigorous combustion occured immediately
above the layer of sand (Fig. 10). The temperature inside the furnace was highest at mid-
freeboard, with heat discharge from the furnace walls keeping the temperature down at points
higher. When dried cake having a water content of 54 percent was incinerated alone, combustion
began inside the sand layer, showing mounting intensity up to just above the sand. The
temperature inside the furnace was highest at lower freeboard.
172
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STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
Incinerating dried cake having a water content of 46-53 percent together with dewatered
sludge having a water content of 77-81 percent resulted in stable combustion extending from the
sand up through the lower freeboard. The two types of cake were fed into the furnace by separate
conveyors and no special effort was made to mix them together.
When dried cake having a water content of 5 percent was incinerated alone, intense
combustion occurred inside the sand layer. The temperature exceeded 1,000° C in the upper part
of the sand layer and it was impossible to maintain stable furnace operation.
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Fig. 9 Water content of dried cake and kerosene consumption
174
-------
Cake
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60° C 250° C
Temperature
Fig. 10 Furnace combustion
Furnace temperature distribution: Mixed
(dried/dewatered) cake
Ol 1 1
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led/dewa
ake, 68%
ried/dewc
ake, 69%
ned/dew
ake, 64%
\
tered \\
water) \\
itered J,
water) \]
atered '
water)
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500°C 600°C 700°C 800°C 900°C
300°C 450°C
320° C
Temperature
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
2.2.4. Waste-heat boiler
a. Performance
The temperature differential measured between the exhaust gas inlet and outlet in actual
operation of the waste-heat boiler was quite a bit smaller than anticipated at the design stage, as
was the amount of steam generated (Table 7). This is because, for one thing, heat loss from the
ducts was greater than expected and the temperature of the exhaust gas at the inlet to the waste-
heat boiler therefore that much lower. For another thing, blowing the water pipes in the boiler
clear of accumulated soot only once every 5-6 hours diminished the efficiency of heat transfer.
Soot accumulation in the pilot-system boiler allowed the outlet temperature of the exhaust
gas to rise at the rate of about 10° C/ h. This temperature dropped some 50° C each time the water
pipes were blown clear of soot (Fig. 11).
Meanwhile, incorporation of an auxiliary burner lowered boiler efficiency by increasing its
overall size and thereby permitting more heat loss through radiation.
Table 7. Waste-heat boiler performance
Exhaust gas volume
Dry gas (Nm'/h)
Water content (Nm'/h)
Temperature
Inlet temperature (°C)
Outlet temperature (°C)
Efficiency (%)
Coefficient of overall
heat transfer (kcal/nvh°C)
Steam generation (kg/h)
Design conditions
400
230
800
250
95
24
190 at 10 kg/cnvG max
Actual performance
700
200
635
290
86
21
150 at 9 kg/crrrG normal
o
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o
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Soot blowing
Soot blowing
300-
200-
100-
12345
Time (h)
Fig. 11 Soot blowing and waste-heat boiler outlet temperature
176
-------
Pilot Plant Study
b. Corrosion
Test pieces of SUS mounted in the waste-heat boiler showed no abnormality, but those of
STPG38 corroded over their entire surface. Calorization proved ineffective in preventing
corrosion. Water pipes (STPG38) in the test system also suffered corrosion, this being
particularly severe at the boiler outlet.
2.2.5. Integrated operation
For integrated operation, an auxiliary boiler was operated in addition to the waste-heat
boiler in order to supply enough steam to the dryer to ensure self-sustaining combustion of the
cake in the furnace. For the sake of comparison, experimenters also carried out incineration by
the conventional method (i.e., burning dewatered cake alone in the fluidized bed furnace without
running it first through the dryer). While the system using separate-drying and incineration was
able to process 10 tons of dewatered sludge per day, the system in which dewatered sludge was
fed directly into the furnace could handle only 4.1 tons per day.
a. Heat input and output
Table 8 presents a detailed accounting of heat input and output. Fig. 12 groups component
inputs/outputs by category to graphically illustrate the heat balance, while Fig. 13 is a heat
flowchart. It will be noted in Table 8 that radiation from the furnace accounted for only 17
percent of total heat output in the system employing separate-drying and incineration, but
represented 32 percent of the total in the conventional system. Also significant is the relatively
large, 9.5 percent share for steam drain residual heat in the overall heat output of the separate-
drying system.
b. Fuel consumption
Table 9 gives the fuel consumption rates for the two systems with different types of cake.
These rates relate to fuel burned by the auxiliary boiler in the case of the separate-drying system
and, in the case of the conventional system, to supplementary fuel burned in the furnace. The
separate-drying system consumed around 60 percent as much kerosene per ton of dewatered
cake as the conventional system, regardless of cake type.
c. Exhaust gas, drain and furnace ash
The findings of analysis of exhaust gas and wastewater can be found in Fig. 14. Exhaust gas
ultimately released into the atmosphere from the furnace after reduction processing showed an
odor index of 920 (as determined through triangle testing). There were substantial amounts of
sulfur oxides and HC1 in the exhaust gas from the dryer, and even still in that from the condenser,
so water-scrubbing will not always be sufficient in itself to absorb all the acidic gases out of the
dryer exhaust.
177
-------
Table 8. Heat input and output
oo
Dewatered cake
Heat output
per ton of
dewatered cake
Notes
Separate-drying
100 t/day
Heat in
Cake calorification
Kerosene calorification
Heating effect of fluidizmg
air blower
Total
Heat out
Exhaust gas from dryer
Exhaust gas from
waste-heat boiler
Exhaust gas from
auxiliary boiler
Heat radiation from
dryer
Heat radiation from
waste-heat boiler
Heat radiation from
auxiliary boiler
Heat radiation from
ducts
Heat radition from
steam lines
Residual heat in
steam dram
Cooling of dried cake
Residual heat in
furnace ash
Total
290,000 kcal/h
232,000
5,000
527,000
155,000 kcal/h
109,000
27,000
12,000
10,000
14,000
39,000
15000
50,000
5,000
3,000
527,000
(55 0%)
( 440)
( 1 0)
(1000)
(29 4%)
( 207)
( 51)
( 23)
( 19)
( 27)
( 74)
( 28)
( 95)
( 09)
( 06)
(1000)
61,265,000 kcal/t
T-r-CF dewatered cake 80 3%
water, 71 1% VTS, 3,520
Conventional
4 1 t/day
Heat In
Cake calorification 117,000 kcal/h
Kerosene calorification 158,000
Total 275,000
Heat out
Exhaust gas from preheater 136,000 kcal/h
Exhaust gas from
furnace 88,000
Heat radiation from
preheater 12,000
Heat radiation from
ducts 18,000
Heat radiation from
preheated air lines 20,000
Residual heat in
furnace ash 1,000
Total 275,000
( 425%)
( 575)
(1000)
( 494%)
( 320)
( 44)
( 65)
( 73)
( 04)
(1000)
1,610,000 kcal/t
kcal/kgDS net calorific value, 52 6% max
water content (dried) for self-sustaining combustion
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-------
Pilot Plant Study
Separate-drying system
[10 t (dewatered cake)/day]
T-r-CF dewatered cake 80 3% water,
71 1% VTS
3,520 kcal/kgDS net calorific value
100%
Other 1%
Heat radiation from
ducts 10 2%
Steam drain 9 5%
Other 1 5%
Conventional system
[41 t (dewaterea cake)/day]
Kerosene 57 5%
100%
Heat radiation from
ducts, etc 14 2%
Fig. 12 Heat input and output
179
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
Separate-drying system
[10 I (dewatered cake)/day]
Steam 17 2%
Heat radiation from auxiliary boiler 4 8%
Heat radiation from
steam lines 5 2%
100 0%
77 9%
Dewatered cake^
100% (0418 t/h, j
290,000 kcal/h)
Kerosene 800% 276 l/h (232,000 kcal/h)
Heat radiation from
furnace 30 3%
Exhaust gas
from auxiliary boiler
93%
Steam dram
1 7 2%
Heat radiation
from dryer
4 1 %
Cooling of
dried cak
1 7%
Dryer
~\
j
Heat radiation from
ducts 13 5%
Exhaust gas
Furnace ash
1 0%
Dried cake 101 4%
_J
Heat radiation
Warmed air from waste-heat
from fluidizmg boiler
air blower 3 50/0
1 7%
Exhaust gas
53 5%
Heat radiation from
furnace 75 2%
T-r-CF dewatered cake 80 3% water,
71 1%VTS
3,520 kcal/koDS net calorific value
Exhaust gas 37 6%
Conventional system
[4 1 t (dewatered cake)/day]
Exhaust gas
Furnace ash
09%
Furnace
(323,000 kcal/h)
276 1 %
Dewatered cake
1000% (0169 t/h,
117,000 kcal/h) }
100 0%
Preheated air 41,0%
K Heat radiation from
~r ducts 15 4%
Heat radiation from
preheater 10 3%
Kerosene 135 1 % Heat radiation
(188 l/h, 158,000 kcal/h) from preheated Exhaust gas
airlines 171% 1162%
Fig. 13 Heat flow
180
-------
Table 9. Incineration metho'd and fuel consumption
co
Dewatered cake
N-r-CF
Water 80%
VTS 68%
Net calorific value 3,800 kcal/kg-DS
T-r-CH
Water 80%
VTS 71%
Net calorific value 3,500 kcal/kg-DS
K-r-CF
Water 77%
VTS 55%
Net calorific value 3,200 kcal/kg-DS
N-d-CF
Water 74%
VTS 45%
Net calorific value 2,400 kcal/kg-DS
C-d-BF
Water 78%
VTS 38%
Net calorific value 2,000 kcal/kg-DS
T-r-PF
Water 68%
VTS 40%
Net calorific value 2,400 kcal/kg-DS
Separate-drying
Dewatered
cake
(t/day)
10
10
95
11 5
15
10
Kerosene
consumption
l/h
23
28
24
30
51
19
l/t A
56
66
62
635
83
46
Conventional
Dewatered
cake
(t/day)
45
4
4
45
4
5
Kerosene
consumption
l/h
17
19
18
19
24
15
l/t B
91
111
103
107
143
735
AX 100
B
[%]
62
59
60
59
58
63
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05
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-------
oo
ho
1. Dryer exhaust gas
Dust (g/Nm1) 004
SOx (ppm) 11
Hcl (ppm) 130
Cl: (ppm) 0 1
Ammonia (ppm) 44
Trimethyl amine
(ppm) 1
Hydrogen sulfide
(ppm) 9
Methyl sulfide
(ppm) 1
Methyl disulfide
(ppm) 07
Methyl mercaptan
(ppm) 5
Odor index 1 100 x 10'
2. Condenser exhaust gas
Dust (g/Nm' 002
SOx (ppm) 5
HCI (ppm) 61
Ob (ppm) 0 1
Ammonia (ppm) 0 8
Trimethyl amine
(ppm) 0 9
Hydrogen sulfide
(ppm) 05
Methyl sulfide
(ppm) 09
Methyl disulfide
(ppm) 08
Methyl mercaptan
(ppm) 4
Odor index 230 x 10'
3. Condenser wastewater
pH 72
SS (ppm) 21
BOD (ppm) 160
COD (ppm) 28
4. Furnace exhaust gas
Specific gravity 1 4-1 7
(air)
Dust (g/Nm' 39
CO (ppm) 2,000
SOx (ppm) 520
NOx (ppm) 20
HCI (ppm) 530
5. Cyclone exhaust gas
Dust (g/Nm') 6
Sample T-r-CF
6. Furnace ash
Water (%) 0 5
Ignition loss (%) 1 0
Elemental analysis
C (%) 0 6
H (%) ND
N (%) ND
Cl (%) 0012
Combustible
sulfur (%) ND
Noncombustible
sulfur (%) 1 2
Cr6*
Content (ppm) ND
Effluent (ppm) ND
7. Waste-heat boiler
exhaust gas
Dust (g/Nm') 3
8. Scrubber exhaust gas
Dust (g/Nm') 007
CO (ppm) 2,000
SOx (ppm) 05
NOx (ppm) 14
HCI (ppm) 10
Cb (ppm) o 1
Odor index 920
9. Scrubber
pH 61
SS (ppm) 260
BOD (ppm) 8
COD (ppm) 20
Phenol (ppm) ND
PCB (ppm) ND
Secondary effluent
Kerosene Service water
Sodium hydrate
Steam (10 kg/cm:G max
Dewatered
cake
hopper
Dryer
Condenser Incinerator Auxiliary boiler Waste-heat Induced
boiler draft fan
Fig. 14 Analysis of gas, drain and furnace ash
Scrubber
Drain
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-------
Pilot Plant Study
2.3. DISCUSSION
2.3.1. Energy efficiency
The separate-drying system consumed less fuel in experiments than the conventional
system. However, steam from the waste-heat boiler proved to be insufficient in itself to heat the
dryer enough to bring the water content of the sludge cake down to the point where self-
sustaining combustion could be obtained. A kerosene-burning auxiliary boiler therefore had to
be installed to provide additional steam, and this limited the energy savings over the
conventional system to 40 percent. Factors presumed to be responsible for this are as follows:
— The surface area of the furnace, boilers, pipe and ducts used in the pilot system was large in
proportion to the capacity of the system, resulting in an unnecessarily large amount of heat
loss through radiation (2.2.5).
— The waste-heat boiler was inefficient (2.2.4).
— A larger than anticipated share of total heat output was lost as steam drain residual heat
(2.2.5)
The Table 9 values for sludge cake net calorification and fuel consumption are represented
graphically in Fig. 15. As is clear from the graph, the pilot system required no fuel to process
dewatered cake offering net calorification of 870 kcal/ kg. It is because the sewage treatment
facilities now in operation in Yokohama cannot turn out sludge of this quality that the auxiliary
boiler had to be installed. However, a larger-scale system will lose a smaller percentage of its total
heat output through radiation, thus greatly lowering the level of net calorification required of
sludge cake for processing without supplementary fuel (3.1.3). Moreover, eliminating the
auxiliary burner chamber and implementing continuously-operating automatic mechanisms for
soot blowing and ash removal will improve the efficiency of the waste-heat boiler. Recycling
steam drain as feedwater for the boiler will also help, this not having been done in pilot system
testing (3.1.2).
100-
0 200 400 600 800 1,000
Net calorific value of dewatered cake (kcal/kg)
Fig. 15 Net calorific value of dewatered cake and fuel consumption
183
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
2.3.2. Controlling the water content of dried cake
Controlling the water content of cake fed into the furnace is a key to maintaining stable,
self-sustaining combustion. Disk speed, steam pressure and drying time were regarded as
potential means to this end.
a. Disk speed
The disk speed must be neither too fast nor too slow for good mixing (2.2.2). Given the
possibility of different disk diameters, optimum disk speed should perhaps be considered in
terms of circumference speed rather than r.p.m. Thus the 20-30 r.p.m. at which good mixing was
obtained in preliminary testing with 250 mm diameter disks translates into a circumference speed
of 0.26-0.39 m/ s, while the 15 r.p.m. that yielded good mixing in pilot-system operation with 500
mm-diameter disks works out to a circumference speed of 0.39 m/s. A circumference speed of
0.3-0.4 m/s would therefore seem to produce the best mixing, regardless of r.p.m.
b. Steam pressure level
Varying the steam pressure brought about virtually no change in the water content of the
dried cake (2.2.2).
c. Drying time
Experiments confirmed that adjusting the drying time by changing the height of the outlet
weirs allows a certain degree of control over the water content of the dried cake (2.2.2). It was
found in batch-operation testing, for instance, that cake can be dried to a water content of less
than 20 percent if a long enough drying time is used. In any case, handling requirements dictate
that the water content of dried cake be brought down at least as low as 50 percent or so, even if
this happens to be lower than the maximum water content for self-sustaining combustion. Stable
combustion was achieved by burning dried cake of this 50 percent water content together with
dewatered cake, the feed-rate of the latter being varied to control the overall water content
(2.2.3).
2.3.3. Material
a. Dryer
HC1 in the dryer exhaust gas caused pitting on SUS304. Corrosive pitting also occurred on
welded portions of SUS316 test pieces, but the parent metal was unaffected. For the dryer, then,
it would appear necessary to use good-welding, low-carbon steel of at least the quality of
SUS316L.
b. Waste-heat boiler
Corrosion was found all over STPG38 test pieces and the water pipes of the waste-heat
boiler used in the pilot system. This was due to the action of sulfur oxides and HC1 in water that
condensed out of the furnace exhaust gas on account of both frequent starting and stopping and
failure to keep the apparatus sufficiently clear of ash and soot. It is felt that STPG38 will be an
adequate material for a working boiler, since a full-scale plant will feature uninterrupted
operation and automatic and continuous removal of soot and ash.
184
-------
3. INTRODUCTION OF A FULL-SCALE PLANT
3.1. SYSTEM PLANNING
3.1.1. Incinerating capacity
Yokohama's sewage works plan calls fora total of eleven sewage treatment plants, of which
nine were operating as of March 1983. Central incinerators for burning sludge generated by the
different treatment plants are being constructed at the Kanazawa and Hokubu No. 2 coastal
plant sites. Treatment plants will ultimately be connected to these two incinerators by sludge
lines, with sludge cake to be transported by truck until the pipelines are completed.
The Kanazawa facility is to process sludge cake from the six treatment plants in southern
Yokohama, meaning that the separate-drying incineration system used will need to have an
incinerating capacity of 150 tons per day. On the basis of findings of the previous investigation,
water content of 80 percent, VTS of 65 percent, and net calorification of 3,300 kcal/kgDS were
assumed for purposes of basic calculations. These values would result in a maximum water
content of about 65 percent for self-sustaining combustion by cake fed into the furnace.
However, pilot system testing showed that dried cake containing as much as 65 percent water
would cause problems by sticking to the conveying apparatus. It was therefore decided to dry
some of the dewatered cake from treatment plants to 50 percent and then mix this with the rest of
the (undried) cake to bring the overall water content of cake fed into the furnace to 65 percent.
Thus 107.2 tons of the 150 tons of dewatered cake processed daily would be run through the
dryer before incineration, and 42.8 tons fed directly into the furnace (Fig. 16).
4,465 kg/h (1072 t/day)
Solids 893 kg/h
Metering
feeder
Dryer
Dewatered cake
Water content 80%
VTS- 65%
Net calorific value 3,300kcal/kgDS
Water vaporized by the dryer
2,679 kg/h
1,786 kg/h (42 9 t/day)
Solids 893 kg/h
Water 893 kg/h
Metering
feeder
1,785 kg/h (428 t/day)
Solids 357 kg/h
Water 1,428 kg/h
3,571 kg/h (85 7 t/day)
Solids 1,250 kg/h
Water 2,321 kg/h
Furnace
Fig. 16 Feed rates to dryer and furnace
185
-------
STUDY ON FLIIIDIZED BED INCINERATION WITH A DRYING SYSTEM
3.1.2. System outline
Table 10 presents basic design criteria for the separate-drying system, Table 11
specifications for main units, Fig. 17 a system flowchart, and Fig. 18 a layout diagram. The
flowchart is explained below:
Dewatered cake from the various treatment plants is dumped into the cake pit (1), from
which a crane (2) loads it into the incinerator feeder (3) and cake hopper (4). As already
described, about two-thirds of the daily volume of 150 tons of dewatered cake is loaded into the
cake hopper for metering into the dryer (5). The dryer heats the cake indirectly at a steam
pressure of 5 kg/cm2G to bring the water content down to 50 percent. The remaining dewatered
cake is metered out of the feeder (3) at the rate of about 50 t/day.
Dried and non-dried cake are metered onto the same conveyor for transport into the
furnace (6), where they are incinerated together. Since the composite water content of the cake is
low enough to permit self-sustaining combustion, no supplementary fuel (LNG in the case of
non-self-sustaining combustion) need be used in the furnace. Exhaust gas at a temperature of
around 800° C is directed from the furnace to the cyclone (7), which separates dust out of the gas.
When the system is operated conventionally, exhaust gas that has been purged of dust in the
cyclone (7) passes through an air preheater (8) en route to the cooler (9). In the case of operation
as a separate-drying system, gas from the cyclone passes next through the waste-heat boiler (14)
and then goes to the cooler (9). After passing through the cooler the exhaust gas is directed
through an electrostatic dust precipitator (10) and absorptive cooling tower (11). An induced
draft fan (21) drives the gas to the stack (12), where it is mixed with air to prevent dense smoking
and then released into the atmosphere.
Table 10. Design criteria
Incinerating
capacity
Dewatered cake
Furnace
&
!
Coagulent
Water content (%)
VTS (%)
Net calorific
value (kcal/kgDS)
Exhaust gas
temperature at
furnace outlet (°C)
Excess air ratio
Furnace ash
VTS (%)
Fuel
Water vaporization
(kg/h)
Water content
of dried cake (%)
150 t/day
Inorganic
55 ~ 80
25 ~ 55
1,100 ~ 2,600
Polymer
70 - 80
35- 80
1,600 ~ 3,700
750 ~ 850
Approx 1 3
Less than 3
LNG (9,900 kcal/Nm')
Approx 3,200
Approx 50
186
-------
Introduction of a Full-Scale Plant
Steam generated by the waste-heat boiler (14) is supplied as a heat source to the dryer (5).
Steam drain from the dryer is recovered at 4 kg/cm'G (151° C) into a drain tank (13) to be reused
as feed water for the waste-heat boiler and auxiliary boiler (15).
A condenser (17) removes moisture from dryer exhaust gas. A blower (22) then drives some
of the gas into the furnace (6) to oxidize combustion, but circulates most back into the dryer for
reuse as carrier gas for carrying off, as steam, water vaporized out of the sludge cake.
Furnace ash discharged from the cyclone (7), waste-heat boiler (14), air preheater (8),
cooler (9), and electrostatic dust precipitator (10) is carried by a conveyor (18) to an ash hopper
(19). Ash collected there is moistened with water and then carried away in trucks.
Table 11. Specifications of min units
Unit
Incineration equipment
Furnace
Hot air generator
for system start-up
Cyclone
Air preheater
Fluidizing air
blower
Electrostatic
precipitator
Absorptive cooling
tower
Induced draft fan
Drying equipment
Dryer
Condenser
Waste-heat boiler
Auxiliary boiler
Specifications
Fluidized bed furnace, 5,500 mm (dia) x 12,270 mm (h),
100 t/day capacity (150 t/day as separate-
drying system)
220 x 104 kcal/h, 700° C max
420 Nm'/min , 85% dust-separating efficiency,
1,430 mm (dia) x 5,190 mm (h)
Countercurrent, vertical multi-cylinder type,
354 6 nv heating surface
Multi-stage turbo blower, 150 Nm'/mm x
3,600 mmH20 x 150 kW
Dry horizontal flow type, 14,000 Nm'/h, 190-340°C,
dust concentration less than 002 g/Nm'DG at outlet
3-stage spray type (sodium hydrate and water) 2,100
mm (dia) x 14,500 mm (h), 14,000 Nm'/h, 40° C at outlet
Radial type, 250 NmVmm x 900 mmH;0 x 75 kW
Indirect heating, low-speed^ mixing type, 100 nv
heating surface, 10 kg/crrrmax steam pressure, 37 kW
3-stage spry type (sodium hydrate and water), 1,250
mm (dia) x 10,000 mm (h), 50 Nm'/min , 30° C at outlet
Natural circulation, pipe type, 3 5 t/h
vaporization at 10 kg/cnvG, 294 m2 heating surface
Furnace flue type, 1 t/h vaporization at 10 kg/crrrG,
24 7 rrr heating surface
Quantity
1
1
2
2
1
1
1
1
2
2
1
1
3.1.3. Heat flow and supplementary fuel consumption
Fig. 19 shows the flow of heat input and output as calculated for the system on the basis of
the pilot system study and basic calculations for the full-scale plant. Since heat loss via furnace
radiation is directly proportional to the square root of the incinerating capacity, this loss as a
percentage of heat input to the furnace will be much smaller with the full-scale plant (7 percent)
than with the pilot system (30 percent). And relatively less radiative heat loss means that self-
sustaining combustion can be obtained with a given type and condition of sludge cake at a higher
water content (Fig. 20). Thus the maximum water content for self-sustaining combustion rises to
65 percent with a system capacity of 150 t/day.
187
-------
©
00
00
No
1
2
3
4
5
6
Unit
Cake pit
Crane
Incinerator feeder
Cake hopper
Dryers
Furnace
Quantity
1 (5)
1 (dual)
1
1
2
1
No
7
8
9
10
11
12
Unit
Cyclones
Air preheaters
Cooler
Electrostatic precipitator
Absorptive cooling
tower
Stack
Quantity
2
2
1
1
1
1
No
13
14
15
16
17
18
Unit
Steam drain tank
Waste-heat boiler
Auxiliary boiler
Steam heater
Condensers
Ash conveyors
Quantity
1
1
1
1
2
3
No
19
20
21
22
•
Unit
Ash hoppers
Fluidizmg air blower
Induced draft blower
Condenser exhaust blowers
Quantity
2
1
1
2
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70
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Fig. 17 Flowchart
-------
Sodium hydrate
00
I
Fig. IS System layout (w/reference numbers from Fig. 17)
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
Separate-drying system
Steam 43 2%
Radiation from
Radiation from auxiliary boiler 0 2%
Radiation from
furnace 7 1 %
LNG 17 4%
Radiation from
ducts 3 5%
Dryer
n from
40%
i
Cooling of
dried cake
09%
Exhaust gas 94 6%
Furnace ash
1 6%
Exhaust air
48 3%
Radiation from
waste-heat boiler
Warmed air 2 4%
1 6%
Sample
Water content 80%
VTS' 65%
Net calorific value 3,300 kcal/kgDS
Exhaust gas
4 5 5%
Radiation from
furnace 10 6%
100%
Furnace
T202 5%
_J
Conventional system
Exhaust gas
1 90 2%
Furnace ash
1 7%
185 1 %
Pnheater
Preheated air 475%
r~
LNG 55% Radiation from
preheated air line Exhaust gas
82% 127%
Fig. 19 Heat flow
Radiation from
ducts 5 1 %
_N Radiation from
-l/preheater 24%
190
-------
Introduction of a Full-Scale Plant
Heat flow comparison between the pilot system (Fig. 13)and the full-scale plant (Fig. 19)
reveals that specific heat consumption with the latter will be only about 1 / 5 that seen with the
former. The primary reasons for this are to be found not only in the relative reduction of
radiative heat loss from the furnace and ducts achieved through larger scale, but also in more
efficient operation by the waste-heat boiler and in recovery of steam drain from the dryer at 4
kg/cm2G for recycling as boiler feed water.
Moreover, just as with the pilot system, it should be possible to reduce specific fuel
consumption by about a third with the working facility by employing the more heat-efficient,
separate-drying system.
Fuel consumption with the full-scale plant, however, will of course vary according to the
net calorific value of the dewatered cake (Fig. 21). As can be seen from Fig. 21, incineration with
the separate-drying system requires 30-40 Nm3 less fuel (LNG) per ton of sludge cake than
conventional incineration, in which all of the dewatered cake is fed directly into the furnace.
Points A and A' in the graph indicate fuel consumption with dewatered cake having a net
calorific value of 300 kcal/ kg. Whereas a conventional system consumes some 30 Nm1 of LNG to
incinerate a ton of sludge in this case, a separate-drying system requires no fuel at all. The
relationship between water content and the net calorific value of solids is shown in Fig. 22 for
dewatered cake of this calorific value.
_
E
o
o
0)
-------
STUDY ON FLUIDIZED BED INCINERATION WITH A DRYING SYSTEM
Conventional system
Separate-drying system
60
50
c
o
Q.
E
Z3
tfl
C
o
o
40
30
20
10
0
-100 0 100 200 300 400 500
Net calorific value of dewatered cake (kcal/kg)
Fig. 21 Net calorific value of dewatered cake and fuel consumption
90-
80-
70-
8
s
"ro
50-
40-
30-
1000
4000
2000 3000
Net calorific value of dry solids (kcal/kg)
Fig. 22 Net calorific value of dry solids and water content
(dewatered sludge having a net calorific value of 300 kcal/kg)
192
-------
Introduction of a Full-Scale Plant
3.2. ESTIMATED COSTS
3.2.1. Construction costs
Table 12 gives current construction costs by capacity for separate-drying incineration
systems. These totals include equipment, piping, electrical instrumentation, engineering, and
installation costs, but exclude the cost of buildings and land. Manufacturer estimates were used
to compute equipment costs, with the other costs then being calculated as percentages of these. It
is plain from the table that specific construction cost declines as incinerating capacity increases,
the inference being that a 150 t/day facility could be built for only three-times the cost of a plant
having a fifth (30 t/ day) that capacity.
Table 12. Incinerating capacity and construction cost
(unit ¥ million)
Construction cost
Specific
construction cost
(¥ million/t capacity)
30 t/day
973
(43)
32
(139)
50 t/day
1,391
(62)
27
(117)
80 t/day
1,932
(86)
24
(104)
100 t/day
2,259
(100)
23
(100)
150 t/day
2,999
(133)
20
(87)
Note Figures in parentheses are percentages of the corresponding costs with a 100 t/day facility
3.2.2. Operating costs
Table 13 lists specific LNG consumption and specific electrical consumption for separate-
drying incineration systems of different capacities. Fuel consumption was calculated on the basis
of test results, electrical consumption in terms of the rated power requirements of principal
equipment in continuous operation. The table suggests that, while specific electrical
consumption will not change very dramatically with incinerating capacity, merits of scale will
indeed manifest significantly in the case of specific LNG consumption.
Table 13. Incinerating capacity and specific consumption of LNG and electricity
Incinerating
capacity
LNG (Nm'/l)
Electrical
capacity (kWh/t)
30 t/day
34
68
50 t/ day
23
59
80 t/day
17
57
100 t/day
14
54
150 t/day
11
48
Notes
1 Dewatered cake
Water content 80%, VTS 65%, net calorific value 3,300 kcal/kgDS
2 LNG
Net calorific value 9,900 kcal/Nm1
193
-------
SUMMARY AND ACKNOWLEDGEMENTS
As described in this paper, the City of Yokohama conducted a pilot system study to
determine how effectively an incineration facility comprising a fluidized bed furnace and
separate-dryer would be able to incinerate the various types of dewatered cake generated by the
city's eleven sewage treatment plants. This study confirmed the energy efficiency and reliability
of such a system. In fact, study findings suggest that a full-scale facility of 150 t/day capacity
could incinerate sludge without using any supplementary fuel for combustion.
The author wishes to acknowledge the untiring effort by all the staff who worked so
hard in carrying out the testing, and to express his appreciation for valuable assistance provided
in preparing this report by Mr. Eiichi Oiwa, of the Electrical and Mechanical Designing
Division, and Messrs. Yoshiyuki Nakamura and Hitoshi Kobayashi, of the Planning Division.
-------
9th US/Japan Conference
on
Sewage Treatment Technology
MANUFACTURING
ARTIFICIAL LIGHT WEIGHT AGGREGATES
FROM
SEWAGE SLUDGE
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Nagaharu Okuno, Dr. Eng.
Head
Akitoshi Yamada,
Senior Researcher
Section of Engineering Research and Development
Department of Sewage Works
Tokyo Metropolitan Government
195
-------
TABLE OF CONTENTS
Page
1. SLUDGE DISPOSAL AND ITS COST IN TOKYO 197
2. FROM COARSE TO FINE AGGREGATE 199
3. DEVELOPMENT OF ARTIFICIAL LIGHTWEIGHT FINE AGGREGATE PRODUCTION
PROCESS 20°
3.1 Characteristics of Sludge Ash 20°
3.2 Binder for Pelletizing 203
3.3 Pelletizing and Drying 205
3.4 Kiln 208
4. PHYSICAL PROPERTIES OF ARTIFICIAL LIGHTWEIGHT AGGREGATE
(ALWA) 211
5. DEMONSTRATION PLANT 215
6. COST
218
196
-------
1.
SLUDGE DISPOSAL AND ITS COST IN TOKYO
In the past, sewage sludge could easily be disposed of by simple
incineration. Sewage ash was used for coastal reclamation and was
beneficial for soil conditioning. This is now nothing more than a
legend. Problem of hexa valence chromium contamination began. Because
it was feared that the leachate of the hexa valence chromium-loaded
sludge ash might possibly contaminate the environment, it was decided
that the disposal of sludge ash from all Tokyo Metropolitan urban area
should be done at the dump site located beyond the central breakwater of
Tokyo Bay. This landfill was planned to fill up to 32 meters above sea
level and, sludge ash cannot be disposed of directly, because landfill
must possess a required level of bearing strength.
For this reason, sludge ash, sludge cake and cement are mixed and
formed into tough blocks before disposal at the site. Figure 1 shows a
flowchart of present sludge handling and disposal.
Total sewage
(received by 9 plants)
1,323x106 m3
(349,537 MG)
Liquid sludge
(27,702,410 tons)
7,318 MG
Sludge cake
(1,037,823 tons)
2,288 x106 IDS
Sludge cake
(436,990 tons)
936 x 106 Ibs
Portland cement
(40,339 tons)
88 x 106 Ibs
f Blended \—
Ash
(41,062 tons)
90 x 106 Ibs
Land Reclamation Site
(Tokyo Bay)
Fig. 1 Flowchart of sludge handling and disposal
197
-------
Table 1 Statistics of sludge handling in Tokyo's sewage plant
Name of
Sewage Plant
Shibaura
Sunamachi
Mikawashima
Odai
Ochiai
Morigasaki
Shinkashi
Kosuge
Kasai
Total
Influent rate (m3)
annual
272,509,390
176,572,350
231,054,270
110,806,870
181,776,030
370,607,760
133,337,700
45,879,510
12,169,330
daily
746,600
483,760
633,030
303,580
498,020
1,015,360
365,310
125,700
63,050
annual daily
1,534,713,210 4,204,690
Liquid Sludge (m3)
annual
2,494,390
3,991,070
daily
6,830
10,930
Pumped to
Sunamachi Plant
9,255,940
Pumped to
Odai Plant
6,995,800
4,463,660
378,480
123,070
25,360
19,170
12,230
1,040
1,130
annual daily
27,702,410 75,900
Sludge cake (t)
annual
150,691
316,571
-
207,427
-
281,221
67,680
11,120
3,113
daily
413
867
-
568
-
770
185
30
29
annual daily
1,037,823 2,843
Incinerated cake (t)
annual
-
316,520
-
201,693
-
72,465
10,274
-
-
daily
_
867
-
553
-
199
28
-
-
annual daily
600,952 1,646
For these reasons, the net operating cost of ash disposal after
incineration has risen to approximately ¥6,500 per ton of solid
(1.2$/lb). Naturally, this motivated us to find uses for the sludge and
produce somethings from the sludge ash.
The first trial to this purpose was to produce lightweight coarse
aggregate (LWCA) .
198
-------
Photo 1 Light weight coarse aggregates made of sludge ash
LWCA made of sludge ash is shown in Photo 1. It has a grain size of
1 to 1.5 cm and a specific gravity of 1.3, and its quality compares well
with that of other natural coarse aggregates.
2. FROM COARSE TO FINE AGGREGATE
The lightweight coarse aggregates available on the market are
usually made of shale. The main ingredients of shale are silica and
aluminum, shale also contains a small amount of volatile materials.
When fragments or pellets of shale are heated to 1000 to 1200°C, the
silica becomes fused, and at the same time, the volatile materials become
gas. Thus, the grains of shale are puffed out. When they are cooled,
they become a hard, yet lightweight aggregate because they are porous
cores covered with finetextured adamant shells.
As reported at the 8th conference, we developed a process of
converting a mixture of 70% shale and 30% sludge ash into a lightweight
coarse aggregate with quality equal to what is available on the market.
Although it is good news to find the way of turning sludge ash into
being a profitable operation, it leaves much to be desired as is
enumerated below.
199
-------
(1) Sludge ash accounts for only 30% of the lightweight coarse
aggregate, and this percentage must be improved for total disposal
of sludge ash.
(2) Sludge-converted lightweight coarse aggregate has no advantages to
the aggregate now available on the market, and thus stands no
comparative advantage to compete with it.
(3) Lightweight coarse aggregate is used only for construction purposes,
and supply exceeds demand.
To overcome these problems, we modified the goals for sludge ash
technology development project as follows:
(1) To develop products consisting mainly of sludge ash.
(2) To develop products which can compete with similar existing products.
(3) To develop products which have a wide market.
3. DEVELOPMENT OF ARTIFICIAL LIGHTWEIGHT FINE AGGREGATE PRODUCTION PROCESS
3.1 Characteristics of Sludge Ash
Table 2 shows a chemical analysis of shale and sludge ash.
200
-------
Table 2 Composition of sludge ash and shale
\
Si°2
A12°3
Pe203
FeO
P2°5
CaO
MgO
Na2O
K20
so3
c
co2
Cl
Total
Ign. Loss
Ash
Ave.
39.55
16.41
11.75
2.09
10.10
8.36
2.46
1.84
1.36
0.84
0.67
0.13
0.05
95.60
2.67
Var.
4.90
1.35
0.73
0.48
2.43
1.76
0.11
0.51
0.27
0.22
0.12
0.07
0.05
1.05
0.96
Shale
Ave.
64.30
16.34
1.34
3.23
-
1.20
1.23
1.94
2.55
0.65
0.66
1.75
-
95.19
7.34
Shale is the principal ingredient of the lightweight aggregate now
available on the market. We sampled and analyzed the sludge ash
discharged from the Shinkashi Sewage Plant operated by the Tokyo
Metropolitan Government. The results are as summarized in Table 2. It
was found that the ratios of the main ingredients, such as SiO ,
A12O_ and FeJD., varied greatly among samples. This forced us to
develop an artificial lightweight fine aggregate production process that
allows a large variance in the principal ingredients.
Figure 2 is a triangular chart showing the chemical composition of
shale and sludge ash.
201
-------
Optimal condition for
light weight aggregates
Shale
\/W\ Ash (Polymer)
Ash (lime)
0 10 20 30 40 50 60 70 80 90 100
Flux (%) ^
(FeaOs, FeO, CaO, MgO, Na2O, K20)
Fig. 2 Composition of ash and shale
When compared with shale, sludge ash contains less SiO but more
Fe2O3 and CaO. Generally, the higher the content of CaO, the higher
the melting point of the feedstock. The higher the melting point, the
lower the viscosity of the fused feedstock; namely, the substance cannot
contain gases within it, reducing the structural strength of the
resultant fine aggregate. It would be assumed, therefore, that sludge
ash would produce aggregate of poor quality. To clarify this point, we
conducted a thermal analysis, with the findings summarized in Table 3.
202
-------
Table 3 Thirmal characteristics of sludge ash
Sample
No.
1
2
3
4
5
6
7
8
9
10
Ave.
Var.
Previous
incin-
eration
temp.
(°C)
873 - 930
898 - 950
840 - 953
836 - 914
779 - 856
863 - 922
872 - 948
887 - 948
860 - 937
810 - 912
-
-
Softening
temp, at
106.7
poise
(°C)
966
982
1000
993
980
982
958
960
964
984
976.9
13.5
Melting
temp, at
103.8
poise
(°C)
1110
1155
1134
1146
1090
1142
1112
1113
1105
1100
1120.7
20.8
Gas generation
range
(°C)
873 - 966
898 - 982
840 - 1000
836 - 993
779 - 980
863 - 982
872 - 958
887 - 960
860 - 960
810 - 984
-
-
volume
(%)
0.29
0.23
0.26
0.32
0.50
0.32
0.33
0.23
0.34
0.61
0.34
0.12
Calcination
range
(+°C)
8
11
9
10
8
8
9
8
9
8
8.8
0.98
Optimum temp.
(°C)
1056
1086
1080
1081
1048
1078
1051
1046
1051
1055
1063.2
15.1
As Table 3 clearly shows, the difference between the softening point
and melting point of the sludge ash is no more than 50 degrees
centigrade, and the temperature difference where the softening of sludge
ash surface and the foaming inside occurs is as only 10 degrees
centigrade. Obviously, this demands that we develop a kiln that can
control the calcining temperature quite accurately. It seems probable
that the ash produced by incinerating sludge cake at high temperatures
releases little gas during calcination causing the lightweight fine
aggregate quality to be poor. Thus it may be important to maintain the
sludge cake incineration temperature as low as possible.
3.2 Binder for Pelletizing
The sludge ash is pelletized, dried, then calcined into fine
aggregate.
203
-------
First, the particles of sludge ash are mixed with glue (binder) into
paste, and then made into pellets by a pelletizer. The binder is
required to hold the pellets in shape and at the same time to vesicate
the pellets with heat. The quality of the product is determined by the
quality of binder used. We tested waste alcohol, sludge slurry and
sludge cake as binders.
Table 4 Effect of glue on dried pellet strength
Glue
(Binding
material)
Waste alcohol
Liquid sludge
Sludge cake
% of glue
added
0
10
20
30
30
45
Moisture
content
in raw
pellet (%)
25.6
24.7
22.9
20.7
30.0
28.2
Compressive
strength of
dried pellet
(lOmmirf) (kg)
1.3
2.8
8.7
16.3
1.4
9.1
Table 4 shows the effect of binders on pellet strength. When water
or sludge slurry was used as a binder, the compressive strength of the
pellets remained as low as 1.3 to 1.4 kg. On the other hand, sludge cake
improved the pellet strength to as high a value as 9.1 kg. However,
blending sludge cake and sludge ash uniformly is not easy. The final
results showed that waste alcohol worked best. Figure 3 shows the
relationship between the proportion of alcohol and pellet strength.
— 15
.c
c
0>
0)
a
o
a
10
Sludge cake
Liquid sludge
0 10 20 30
Alcohol (%)
Fig. 3 Strength of dried pellet vs % of waste-alcohol added
204
-------
When the proportion of waste alcohol added was 20% or more, the
compressive strength of pellets could be increased above the practical
value of 2.5 kg. Figure 4 shows the specific gravities of fine
aggregates produced by calcining the pellets with various binders.
Specific
gravity
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
Waste
alcohol
10%
" 20%
" 30%
1020
1100
1040 1060 1080
Temperature (°C)
Fig. 4 Specific gravity of calcined pellet vs calcining temperature
As shown, the pellets made with 20% waste alcohol as a binder have
the lowest specific gravity. It was later than a 20% mix proportion of
alcohol was much liable to decrease the undersize during calcination thus
improving the yield. However, a 10% mix proportion of alcohol can be
sufficient enough to decrease the undersize.
3.3 Pelletizing and Drying
Based on the findings of the basic studies discussed above, a
mini-plant was constructed to continuously produce lightweight fine
aggregate from sludge ash. Its flow sheet is shown in Figure 5.
205
-------
Glue
(Binder)
Waste-alcohol
Sludge ash
Crasher (Crash)
Paddle mixer
(Blending)
Pan-pelletizer
Band dryer (drying)
Fluidized bed kiln
Products
Classification of pellet size
Artificial lightweight aggregates (ALWA)
Fig. 5 Flow sheet of pilot plants
First, a vibration mill pulverizes sludge ash. The pulverized
sludge ash is then passed through a 200-mesh screen, and the undersize is
then is mixed with waste alcohol and water in a paddle mixer (Photo 2)
into paste. The paste is then converted into pellets of 0.6 to 3.0 mm in
diameter through a pan type pelletizer (Photo 3). The pellets are dried
by a band dryer and calcined in a kiln (Photo 4).
206
-------
Photo 2 Paddle mixer
Photo 3 Pan-type pelletizer
207
-------
Photo 4 Band dryer
3.4 Kiln
The kiln which calcines the dry pellets into lightweight fine
aggregate is required to fulfill the following requirements:
(1) To heat the pellets quickly to promote foaming.
(2) To fluidize the pellets to prevent cohesion of pellets.
(3) TO keep high thermal efficiency to control temperature accurately.
To achieve these requirements, we developed a kiln as illustrated in
Figure 6, and called it a 3-stage fluidized kiln. Photo 5 shows the
cross section of this kiln in operation.
208
-------
Traditionally, a rotary kiln was used for this purpose. One of the
disadvantages of the rotary kiln is cohesion between raw materials during
calcination. The performance is entirely dependant on whether ALWA can
be efficiently produced from sole sewage ash in the kiln. A 3-stage
fluidized kiln proved to be the most effective. The developed kiln
consisted of three cylindrical chambers. Each chamber had a different
diameter and was interconnected to the other via a tapered neck. From
the top to the bottom of the chambers, the diameters were 22, 18, and 15
centimeters (the cross-sectional area ratio of the three chambers was
2.5/1.5/1).
Raw materials, pellets, were fed into the top chamber and air, mixed
with natural gas, was put into the bottom chamber. The bottom chamber
was for calcination, the middle and top chambers were for drying.
With the given air flow rate supplied into the bottom chamber, a
certain amount of pellets held in each chamber was set automatically
because of the balance between gravity and floating force affect the
pellets. As air enters each chamber through the necked port, the pellets
are moved vigorously. When raw materials are fed into the top chamber of
the kiln, the same amount of calcinated pellets come out from the bottom
outlet. Complete mixing of the pellets is performed within each chamber,
and a plug flow is seen in each chamber. Thus, a continuous operation is
performed.
209
-------
Pellet
—— Exhaust gas
Burner
Heated gas
Burner
End product
Fig. 6 Fluid!zed kiln
Photo 5 Cross
section of fluidized kiln
210
-------
4. PHYSICAL PROPERTIES OF ARTIFICIAL LIGHTWEIGHT AGGREGATE (ALWA)
Photo 6 shows the appearance of various grain sizes of ALWA produced
by the process discussed above. Compared with the products now available
on the market, our ALWA exhibits a higher degree of sphericalness.
Table 5 shows the physical properties of the ALWA produced compared
to conventional products.
Photo 6 Outlooking of different size of ALWA
Table 5 Physical characteristics of lightweight aggregates
Size
0.6 - 1.2 mm
1.2 - 1. 7 mm
1.7 - 2.5 mm
2.5 - 3.5 mm
Mixture
Moisture
absorbance
{24HR, %)
8.4
(15.4)
9.0
(11.9)
8.5
(13.2)
9.2
(ll.D
8.8
(12.9)
Specific
gravity
1.57
(1.64)
1.47
(1.66)
1.35
(1.61)
1.21
(1.60)
1.40
(1.63)
Weight/vol ume
ratio
0.944
(0.954)
0.875
(0.938)
0.812
(0.921)
0.716
(0.902)
0.868
(0.977)
Compressive
strength (kg)
1.7
(1.8)
4.1
(4.7)
4.8
(7.9)
5.3
(9.7)
( ): existing conventional LWA
211
-------
It was found that our ALWA has a lower specific gravity and slightly
less conpressive strength. Table 6 shows the compressive strength of
cement mortar mixed with ALWA.
Table 6 Compressive strength of cement mortar mixed with ALWA
Test piece
including:
New-ALWA
Conventional LWA
Sand
Compressive strength
(kg/ cm2)
7 days
244
282
307
28 days
418
457
478
Its test showed a compressive strength of 244 kg/cm after eight
2
days and 418 kg/cm after 28 days.
Unlike other conventional products, the ALWA is producible in any
grain size from 0.3 to 5 mm in diameter. The ALWA can be used as a
filler for plastic board, the base material for tennis courts or as
artificial soil for flower pots. In addition, it may be used as material
for concrete blocks, heat-insulating panels and other secondary cement
products.
Photos 7 through 11 demonstrate some applications of ALWA.
212
-------
o
CO
hd
H
i
•8
R
0
H-
M
(D
-------
Photo 9 Thermal insulating siding
Photo 10 Wall panel
214
-------
Photo 11 Artificial soil
5. DEMONSTRATION PLANT
A demonstration plant is designed using the findings of the basic
studies and it is installed in the Odai sewage plant. Figure 7 shows
flow sheet of the demonstration plant. It has an hourly production
capacity of 500 kg probably the smallest practical output. Since July
1983, the plant has been in operation. Both technical and economical
feasibility of manufacturing ALWA will be fully evaluated through
operational data observed at the demonstration plant. Photos 12 to 22
show the unit processes of the demonstration plant.
215
-------
Pelletizer and Dryer
Kiln
Sludge ash © [)=!
Storage
Fig. 7 Flow sheet of LWA manufacturing plant (capacity: 1)
216
-------
Local Water Supply
Feeding pump
No 3 bucket
elevator
Fig. 7 (Continued) Flow sheet of LWA manufacturing plant (capacity:!)
217
-------
6. COST
Now the running data of the demonstration plant are accumulated.
Later the precise costs for the operation of large scale commercial
plants can be demonstrated. At present, only rough cost estimation is
available. This is shown on Table 7. In the table, the operational
costs include depreciation, interest expense, repair cost, labor cost,
fuel cost, and electric charges. In a small plant with a daily output
capacity is 12 tons (26,460 Ibs.), the production cost is ¥38,590/ton
(7.3
-------
Table 7 Initial and running cost estimation of AIA manufacturing plant
Daily
capacity (tons)
dbs)
Const, cost (*)
(?)
Running cost
(*/ton)
($/lb)
12
26,460
598,200,000
2,492,500
38,590
7.3
24
52,920
598,200,000
2,492,500
25,200
4.8
72
158,760
1,156,470,000
4,819,000
18,450
3.5
120
264,600 Ib
1,570,960,000
6,546,000
16,760
3.2
Notes
1. 1 US$ = 240 Japanese Yen
2. Running cost includes: labour, repair, amortization, interest, fuel,
and electricity
3. Cost of disposing ash: ¥6,500/ton, 1.2$/lb
4. Retail price of existing light weight aggregater: 3.2$/lb
5. Number of operator: 10
6. Period of amortization: 7 years
7. Interest: 7.5 % per year
8. Working day: 300 day/year
9. Net production rate: 80%
Artificial
lightweight
aggregates
Direct use
Indirect use
(mixed with
other materials)
De-odour ant
Back fill material
Foundation material
Artificial soil
Flower pot
Infiltrate pavement
Concrete block, or tile
Thermal insulating panel
Others
Fig. 8 Potential use of ALWA
219
-------
Photo 12 Outlooking of plants
Photo 13 Storage of ash
220
-------
Photo 14 Paddle mixer
Photo 15 Pelletizer
221
-------
u
•O
•O
I
V4
0)
V4
•a
0)
•o
-H
(A
C
o
4-1
O
CNI
CM
CM
-------
photo 18 Kiln
Photo 19 Storage of ALWA
223
-------
Photo 20 Scrubber and EP
Photo 21 Feeding inlets for ash and binder material
224
-------
Photo 22 Control panel
225
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
SECONDARY SEWAGE TREATMENT
USING CONTACT AERATION PROCESS
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
September 20, 1983
Tokyo,Japan
Kazunari Matsunaga
Director of Construction Division
Sewage Works Bureau
Osaka City Office
227
-------
EXPERIMENT OF SECONDARY SEWAGE TREATMENT USING
CONTACT AERATION PROCESS
1. Introduction 229
2. Contact Aeration Equipment 230
2.1 Features and Operating Principle of Equipment 230
2.2 Full-scale Experimental Equipment 232
3. Results of Operation 236
3.1 Results of Normal Operation 236
3.2 Effect of Load Fluctuation 241
3.3 Maintenance and Control 250
4. Quantity and Quality of Sludge Produced 251
5. Solid-liquid Separation with Fine Screen 253
5.1 Principle and Description of Fine Screen 255
5.2 Selection of Screen 25S
5.3 Hydraulic Loading on Screen 260
5.4 Protection against Clogging of Screen 26°
5.5 Comparison of Quality between Screen-passed Effluent
and Final Settled Effluent 264
6. Summary 266
228
-------
1. INTRODUCTION
The activated sludge process is highly appreciated at present
as a superior method for sewage treatment. However, it has been
pointed out that this process has problems in that it requires
special techniques for control and maintenance, gives rise to a
large quantity of sludge, requires much energy for aeration, and
so on. Recently, various wastewater treatment technologies using
biofilm have been studied and, based on such studies, a number of
treatment processes have been proposed. The major processes are
the rotating biological contactor (RBC) process and the contact
aeration process in the municipal wastewater treatment. The RBC
process is said to take less time to treat sewage, as compared
with the activated sludge process, but space saving cannot be ex-
pected since the reaction tank is shallow, offering virtually no
difference from the activated sludge process.
As a process worthy of study, especially for large cities
under space constraint due to high population density, such as in
Osaka, the contact aeration process was chosen out of many biolog-
ical filters, and conducted experiments to evaluate it.
The contact aeration process can be roughly classified into
two types: one is to install packing media in the downstream por-
tion of the spiral or circulating flow; the other is to effect
multi-line aeration (in which diffusers are spaced uniformly across
the entire tank bottom) and to install packing media where bubbles
come up. The honeycomb tube contact aeration process — belonging
to the former type was once investigated for effects on ter-
tiary treatment.
This study revealed that tertiary treatment, although per-
formed at a far lower BOD concentration than secondary treatment,
often caused clogging of packing media. This clogging necessi-
tated stoppage of operation several times a month to clean the
media with air and water.
229
-------
In the latter aeration type, equipment for conducting multi-
line aeration from below the packing media, consisting of synthe-
tic resin nets, has already been developed for treatment of indus-
trial wastewater. This equipment was considered worthy of further
study as viable secondary sewage treatment equipment, on the basis
of the results of the tertiary treatment experiment conducted by
the municipality. Therefore, after the small-scale pilot experi-
ment, another experiment was carried out on this equipment using
an actual sewage treatment facility.
The results of this experiment showed that the process could
be applied to secondary treatment as an alternative to the acti-
vated sludge process. This paper presents the results of these
experiments.
This paper also includes some considerations with regard to
the possibility of using a fine screen for solid-liquid separation
so as to minimize plant site area requirements.
2. CONTACT AERATION EQUIPMENT
2.1 FEATURES AND OPERATING PRINCIPLE OF EQUIPMENT
Fig. 1 shows a conceptual drawing of the contact aeration
equipment used in these experiments.
In the aeration tank, plastic net media are arranged in
parallel with the flow. The perforated diffuser pipes installed
across the flow below the packing media are used for multi-line
aeration with the objectives of supplying dissolved oxygen to the
sewage and agitating it. Organic substances contained in the
sewage are removed by the activity of the microorganisms adhering
to the packing media. The microorganisms accumulated on the media
surface are detached while the sewage is agitated by means of
aeration, and undergo solid-liquid separation in the final set-
tling tank.
230
-------
Fig. 1 Conceptual Drawing of Contact Aeration Equipment
231
-------
The major trouble with the contact aeration process is the
clogging of the packing media. In this equipment, the clogging
trouble is eliminated by using net media and renewing accumulated
microorganisms through increased agitation intensity by means of
aeration from below the packing media.
The increase in agitation intensity is also expected to pro-
mote substrate removal by microorganisms accumulated on the
packing media.
2.2 FULL-SCALE EXPERIMENTAL EQUIPMENT
The full-scale experiment was carried out, using a facility
consisting of aeration tanks and a final settling tank, at the
Suminoe Sewage Treatment Plant in Osaka City. The aeration tank
had been designed for spiral-flow step aeration using diffuser
plates. The Suminoe Sewage Treatment Plant has a treatment capac-
ity of 220,000m3/day. Since only about 5% of the influent at this
treatment plant is industrial wastewater, this plant has the
higher percentage of domestic wastewater among the 12 treatment
plants in the city.
The layout of the experimental equipment is shown in Fig. 2.
Out of the four aeration tanks constitutirg the experimental
system, the latter two tanks were used for installation of packing
media. The contact aeration tank process is preceded by the pri-
mary sedimentation and followed by the final settling where solid-
liquid separation was carried out.
Photo 1 shows the experimental equipment under operation.
Table 1 shows the specifications of the equipment.
The contact aeration tank was composed of net media, their
supports and the aeration device. The packing media consisting
of polyethylene nets of 13mm meshes were reinforced with stainless
steel binding frames and fixed to the supports at predetermined
intervals. The nets were arranged 40 ~ 100mm apart in parallel
with the flow. (Photo 2)
232
-------
Final settling tank
Aeration tank
Primary settl-
ing tank
u
D
D
D
D
n
1
1 — 1
u
n
u
n
u
n
. ,
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u
n
u
n
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u
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II
n
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HZI
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izzi
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Area for
experiment
Machinery room
OO
CO
Final settling tank 159.8
Aeration tank Primary settling tank
31.4
Final settling tank contact aeration tank
Second First
tank tank
15
Primary settling tank
(Unit: m)
Fig. 2 Layout of Experimental Equipment
-------
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Photo 1 General Views of Contact Aeration Tanks
234
-------
Table 1 Specifications of Experimental
Contact Aeration Equipment
Effective capacity of aeration tank:
Packing media capacity :
Packing media Material :
Shape :
Mesh :
Installation intervals
Inlet :
Middle :
Rear :
Diffuser device
Pipes with
perforation
Water surface area of final settl-
ing tank
860m3
500m3
Polyeth-
ylene
Net
13mm
100mm
60mm
40mm
(02mm; 40
^ 60mm
pitch)
370m2
Photo 2 Packing Media under Construction
235
-------
The volume occupied by the installed packing media was approx-
imately 60% of the total effective volume (860m3) of the tank.
The aeration device consisted of steel risers and stainless
steel diffuser pipes. The diffuser was of the coarse bubble aera-
tion type, with 2mm perforations.
For control of air supply, four flow meters were installed.
Air supply was designed to be large in the inlet region under high
BOD load and taper off toward the outlet. The flow rate of the
effluent was measured with a weir-type flow meter installed at the
effluent channel in the final settling tank.
3. RESULTS OF OPERATION
3.1 RESULTS OF NORMAL OPERATION
In order to study whether this process is applicable to sec-
ondary sewage treatment as an alternative to the activated sludge
process, experiments were continued under similar operating condi-
tions throughout a year, with a 4 •>. 5-hour aeration time and an
air-water ratio of 5 ~ 6. Fig. 3 shows the average operating con-
ditions for individual months. During the experimental period,
the overflow rate in the final settling tank was small 10 ~ 15m^/
m^'day. As for hourly fluctuation of influent sewage, the ratio
of maximum to minimum flow was 1.5 ~ 2, or within 50% of the daily
average flow rate.
Water quality was measured for a composite sample taken 3
times during the daytime twice a week. The monthly average water
quality is shown in Table 2. The values concerning water tempera-
ture, BOD and SS are converted into graphic forms in Fig. 4. Dur-
ing the period of measurement, the concentration of dissolved
oxygen at the outlet of the aeration tank was 2 ~ 4mg/£.
236
-------
4-1
C
03
01
6,000
4,000
o
•H
0)
!
4-1 E
,
•H 03
P Cr •
0) c^
E -H E
D -0 \
rH OJ 01
00^
^ p_^j , .
0) fl
P X 3 \
p a om
0) 03 rH g
to P MH ~-
20
10
0
'78
9 10 11 12 1 2
• 79
Fig. 3 Operating Conditions (Monthly Average)
237
-------
Table 2 Monthly Results of Normal Operation
Values in
Water tem-
perature
PH
Transparency
SS
T-BOD5
S-BODs
T-CODun
s-coDMn
S-TOD
S-TC
NH3-N
Influent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Removal
Influent
Effluent
Removal
Influent
Effluent
Removal
Influent
Etf luent
Remo va 1
Influent
Effluent
Remova 1
Influent
Effluent
Remova 1
Influent
Effluent
Unit
°C
—
cm
cm
rag/*
mg/Jl
a*}/t
ag/t
%
mg/£
mq/i
%
mg/Jl
mg/8.
%
mq/i
rag/i
%
mg/fc
mg/Jl
*
mg/H
mq/i
%
mq/i.
mg/Jl
May
1978
20.8
(1.1)
7.31
(0.19)
7.43
(0.11)
6.0
(1.4)
34
(11)
86.0
(14.0)
12.0
(1.0)
72.0
(9.9)
8.8
(2.1)
87.8
37.6
(9.0)
5.4
(2.1)
85.6
63.9
(11.5)
19.4
(1.6)
69.6
36.0
(7.9)
16.2
(2.4)
55.0
226
(28)
106
(20)
53.1
85
(8)
54
(8)
36.5
18.8
(2.2)
19.6
(1.8)
Jun.
23.4
(1.3)
7.26
(0.18)
7.29
(0.11)
6.5
(1.1)
35
(8)
53.8
(6.4)
8.7
(0.4)
61.2
(11.7)
9.8
(0.8)
84.0
37.1
(8.5)
7.0
(0.6)
81.1
43.9
(4.0)
17.6
(1.9)
59.9
33.1
(4.0)
15.9
(1.6)
52.7
161
(51)
84
(27)
47.8
67
(17)
47
(11)
30.0
19.4
(4.1)
17.7
(4.3)
Jul.
27.3
(1.1)
7.22
(0.12)
7.29
(0.04)
7.0
(1.3)
44
(7)
53.7
(13.5)
7.6
(1.9)
56.7
(6.8)
8.1
(2.2)
84.3
35.7
(7.1)
5.4
(0.7)
84.9
38.5
(3.6)
16.4
(2.4)
57.4
30.2
(3.1)
15.4
(2.1)
49.0
148
(21)
75
(11)
49.3
68
(9)
45
(5)
33.8
15.5
(6.3)
14.4
(2.2)
Aug.
28.6
(0.3)
7.08
(0.17)
7.24
(0.09)
7.6
(1.6)
> 50
(9)
60.2
(13.6)
8.4
(2.0)
50.8
(7.6)
9.8
(1.4)
80.7
33.8
(7.3)
6.4
(2.0)
81.1
44.8
(5.1)
18.9
(3.9)
57.8
33.7
(3.3)
17.0
(2.4)
49.6
158
(23)
72
(10)
54.4
68
(10)
43
(6)
36.8
15.1
(6.3)
12.4
(4-. 4)
Sep.
26.3
(1.1)
7.03
(0.21)
7.05
(0.22)
6.3
(0.8)
45
(9)
70.9
(16.9)
10.0
(3.4)
58.8
(10.6)
9.2
(1.6)
84.4
37.0
(3.4)
6.7
(0.8)
81.9
48.5
(2.2)
19.8
(1.1)
59.2
33.8
(2.0)
17.8
(1.1)
47.3
166
(25)
71
(15)
57.2
71
(8)
41
(7)
42.3
17.0
(2.2)
15.1
(3.1)
Oct.
21.0
(1.4)
7.12
(0.20)
7.12
(0.23)
6.5
(1.3)
31
(12)
71.9
(18.8)
13.1
(4.9)
67.1
(6.5)
10.4
(1.5)
84.5
46.4
(5.2)
7.5
(0.7)
83.8
50.7
(3.4)
18.8
(1.6)
62.9
40.5
(2.6)
17.3
(1.2)
57.3
160
(34)
68
(14)
57.5
74
(7)
44
(7)
40.5
16.9
(3.0)
15.6
(3.2)
parentheses indicate standard deviation.
Nov.
17.9
(1.4)
7.18
(0.30)
7.25
(0.21)
7.8
(4.3)
40
(13)
93.7
(43.2)
11.8
(5.9)
74.2
(19.6)
8.7
(1.4)
88.3
53.5
(18.7)
5.8
(1.5)
89.2
53.2
(7.7)
17.9
(1-8)
66.4
44.1
(11.1)
17.0
(1.9)
61.5
178
(36)
69
(14)
61.2
75
(10)
42
(7)
44.0
18.7
(4.0)
17.1
(5.9)
Dec.
15.6
(0.6)
7.24
(0.25)
7.22
(0.13)
7.3
(1.9)
42
(10)
78.5
(23.6)
9.4
(3.6)
80.0
(1.8)
9.5
(3.9)
88.1
55.6
(2.4)
6.3
(2.9)
88.7
57.5
(2.5)
19.1
(2.3)
66.8
47.3
(2.7)
17.8
(4.5)
62.4
178
(24)
81
(13)
45.5
75
(8)
47
(7)
37.3
15.1
(0.9)
15.9
(4.8)
Jan .
1979
12.7
(0.9)
7.44
(0.10)
7.40
(0.08)
9.9
(1.8)
46
(9)
49.8
(17.4)
7.8
(2.9)
73.0
(9.9)
9.7
(0.5)
86.7
57.5
(9.7)
6.6
(0.6)
88.5
51.5
(7.3)
17.5
(2.1)
66.0
41.8
(5.7)
15.9
(2.6)
62.0
185
(31)
80
(11)
56.8
79
(10)
52
(6)
34.2
19.9
(4.4)
20.8
(3.6)
Feb.
12.9
(1.0)
7.44
(0.10)
7.33
(0.08)
5.5
(1.6)
38
(6.6)
114
(36)
12.8
(5.6)
84.1
(10.0)
11.4
(1.0)
86.4
52.5
(7.2)
7.0
(2.0)
86.7
55.9
(8.8)
17.0
(3.2)
69.6
42.5
(5.2)
14.7
(2.5)
65.4
183
(22)
86
(18)
47.0
73
(8)
51
(8)
30.1
19.6
(4.3)
17.4
(5.3)
Mar.
13.0
(0.4)
7.36
(0.13)
7.33
(0.07)
6.5
(2.1)
40
(6.9)
78.8
(34.4)
9.4
(2.4)
82.4
(8.2)
11.2
(0.7)
86.4
50.0
(2.8)
8.0
(1.5)
84.0
60.3
(5.1)
19.5
(0.9)
67.7
47.2
(3.9)
16.7
(1.4)
64.6
193
(19)
87
(17)
54.9
75
(5)
49
(5)
34.7
19.7
(2.6)
17.6
(1.5)
238
-------
u
3
-P
0)
-P
a)
4J
rd
S
Q
O
PQ
in
w
30
25
20
15
10
80
60
40
20
120
100
80
60
40
20
(1) Water temperature
10 11 12 1
-A
--A
456
(3) SS
9 10 11 12 1 2
4
'78
7 8
10 11 12 1
'79
2 3
• Influent sewage
A Treated effluent
• Influent sewage
o Influent sewage
(Soluble)
A Treated effluent
A Treated effluent
(Soluble)
Fig. 4 Monthly Change in Quality of Influent and Effluent
239
-------
The quality of effluent was stable, with both BOD and SS
being at approximately 10mg/J2.. These values were not signifi-
cantly different from the values for effluent treated by the acti-
vated sludge process during the same period under lighter BOD
volumetric loading. However, according to visual observation, the
effluent treated with this process was less transparent than that
treated with the activated sludge process, appearing slightly
opaque.
Despite a water temperature difference of approximately 15°C
between summer and winter, no significant difference was observed
in the quality of the effluent. It is thought that the equipment
had surplus capacity, since operation was carried out with rela-
tively low BOD volumetric loading.
Virtually no nitrification occurred throughout the experimen-
tal period. This is probably because the quantity of air
supplied for aeration was not enough to initiate a nitrification
reaction in the latter half of the tank where nitrification may
advance, since a large quantity of air was supplied at the inlet
of the aeration tank to remove organic substrates such as BOD,
while the air quantity was limited on the outlet side.
An understanding of the quantity of microorganisms adhering
to the packing media is essential for this biological treatment
process. Nevertheless, no easy method of quantification was
found.
In this experiment, test pieces were placed at 6 locations
inside the tanks and the quantity of microorganisms in one entire
tank was estimated based on the amount of microorganisms attached
to the 6 test pieces.
The test pieces used were the same packing media as installed
in the tank, measuring 220cm x 45cm. The test pieces were taken
out of the tank in summer and winter to determine the quantity
of microorganisms in the tank as a whole, based on the dry weight
240
-------
of the biofilm separated from the test pieces. The quantity of
microorganisms per tank capacity was approximately 2,500mg/£ in
summer and approximately 3,200mg/£ in winter. These values are
similar to the MLSS concentration for the activated sludge proc-
ess.
3.2 EFFECT OF LOAD FLUCTUATION
A sewage treatment plant must achieve stable and high efflu-
ent quality. For that, BOD loading should be kept constant at all
times. In the actual plants, however, hourly load fluctuation is
unavoidable.
Generally speaking, sewage treatment using biological filters
is superior to the activated sludge process in coping with load
fluctuation. Hence, an attempt was made to compare the effect of
load fluctuation between the two processes.
The experiment on the activated sludge process was carried
out in an existing facility next to the one used in the experimen-
tation on the contact aeration process. The facility was made
operable independently, with the addition of a sludge return
device.
The experiment on load fluctuation was carried out by artifi-
cially causing the flow to fluctuate according to a pattern with a
peak during the daytime, as shown in Fig. 5. In this experiment,
the daily average flow was kept constant and operation targets
were set at three stages, with the ratios of hourly peak flow to
daily average flow at 1, 2 and 2.5.
At each ratio, operation was continued for 1 ~ 2 weeks, and
in the latter half of the experiment, fluctuation was measured
every two hours for a 24-hour period. Runs were made twice a year
— in autumn and winter. The results of the runs are shown in
Tables 3 and 4, for the contact aeration process and the activated
sludge process, respectively.
241
-------
9 n .
1.5 .
1.0 •
0.5
1 —
Daily average
influent f 1 nw [
• Min. hour-
ly influ-
ent flow
0
9:
11
Max. hourly in-
fluent flow
1 t
1 ,
1 1
:00 16:00 9:00
00 10:00
11
i
i
i i
:00 16:00
10:00
Max. hourly influent flow _ .
Fig. 5 Load Fluctuation Pattern (When avf>r*nt> influent flow ~2'0)
average influent flow
-------
The typical examples of hourly change in BOD volumetric load-
ing and BOD concentration of the effluent under different operat-
ing conditions are given in Figs. 6 through 9.
As an actual facility was employed for this measurement, it
was impossible to apply exactly the same BOD loading and aeration
time to every experiment. Therefore, most data were gathered for
an aeration time of about 6.5 hours. The target aeration time of
6.5 hours is the same as the design value for the activated sludge
process now employed in Osaka City.
Tables 3 and 4 show that the daily average BOD can be kept
below 20mg/& for both contact aeration process and activated
sludge process, if the fluctuation is within 2.4 ~ 2.5 times the
daily average influent flow rate.
As long as the flow fluctuation is small, both processes pro-
duce effluent with little fluctuation over time, as shown in Figs.
6 and 8. However, if the hourly fluctuation becomes large, the
BOD of the effluent temporarily exceeds 20mg/£, even if the daily
average BOD is below 20mg/&. The reason: in the contact aeration
process, soluble BOD remains, and in the activated sludge process,
SS flows out of the final settling tank despite the fact that sol-
uble BOD is stabilized at a low value.
Judging from the fact that soluble BOD shows a stabler, lower
value in the activated sludge process than in the contact aera-
tion process, the former process is superior to the latter in its
capacity to remove substrate in the aeration tank when BOD load
fluctuatin occurs due to flow fluctuation.
With regard to solid-liquid separation, comparison between
the activated sludge process and the contact aeration process is
practically impossible, since overflow rates in the final settling
tanks are different.
243
-------
Table 3 Treatment Performance of Contact Aeration Process (Fluctuation with Time)
Period
Autumn
(Oct.i
Nov.)
Winter
(Jan.i
Mar.)
Qmax
Qave
1.20
2.04
2.50
3.00
1.30
2.01
2.80
2.20
Average
Water Tem-
perature
21.8
23.0
21.2
20.5
11.8
11.2
12.3
12.7
Daily BOD
Loading
(kg/m3 -day)
0.19 10.43
(0.32)
0.27 10.79
(0.40)
0.12 10.99
(0.34)
0.08 10.95
(0.31)
0.35 10.45
(0.39)
0.26 10.75
(0.36)
0.191 1.00
(0.39)
0.24 10.99
(0.44)
Aeration
Time
(hr)
5.7318.60
(6.8)
3.03 i 8.87
(6.1)
2.551 12.30
(6.4)
2.53 i 28.70
(7.8)
5.21 16.88
(6.1)
3.201 9.25
(6.6)
2.4H 12.60
(6.2)
2.441 10.10
(5.4)
Settling
Tank Over-
flow Rate
(m3/m2-day)
6.6 i 9.7
(8.1)
4.91 18.8
(9.2)
3.5i 22.3
(8.9)
1.31 22.3
(7.4)
7.4 i 11.6
(8.9)
5.01 18.1
(9.0)
4.H 25.2
(9.0)
5.5i 22.8
(10.3)
Treated Effluent (mg/2)
T-BOD
7.5110.2
(8.7)
10.51 17.1
(13.1)
11.2125.9
(16. 4-)
9.6 i 15.5
(12.6)
8.81 13.6
(12.2)
8.5i 27.2
(16.2)
14.51 35.2
(21.4)
9.3i 27.7
(15.5)
S-BOD
6.4 19.2
(7.7)
7.81 12.1
(10.1)
6.81 22.3
(12.0)
5.419.8
(7.6)
7.3i9.9
(8.4)
6.5^23.5
(14.1)
11.0i24.7
(13.9)
6.2i 18.9
(9.3)
SS
2.818.0
(5.9)
6.0i 15.0
(8.8)
6.0i 17.3
(10.8)
7.2i 13.2
(9.2)
11.3% 19.0
(15.7)
3.4i 19.6
(10.2)
13.01,20.0
(15.1)
10.0% 32.7
(17.8)
Remarks
Constant air supply
tl
Proportional air
supply
Constant air supply
Proportional air
supply
Notes: 1. Values in parentheses indicate the average of all data.
2. Air volume was 5 times the daily average flow of influent sewage under each experimental condition.
-------
Table 4 Treament Performance of Standard Activated Sludge Process
(Fluctuation with Time)
Period
Autumn
(Oct.^
Nov.)
Winter
(Jan.^
Feb.)
Qmax
Qave
1.12
2.41
2.54
1.06
2.10
2.43
Average
Water Tem-
perature
(°C)
25.1
22.3
21.5
12.7
12.8
12.7
Daily BOD
Loading
(kg/m3 'day)
0.19^0.29
(0.24)
0.14 ^0.98
(0.34)
0.10 ^0.75
(0.25)
0.28^0.42
(0.32)
0.21^0.64
(0.33)
0.18^0.92
(0.37)
Aeration
Time
(hr)
6.08^ 7.00
(6.84)
2.60^ 11.73
(6.28)
2.60^ 13.53
(6.61)
6.15^ 7.25
(6.55)
3.25^9.95
(6.55)
2.60^11.15
(6.32)
MLSS
(mg/Jl)
1,600^ 2,130
(1,905)
1,270^ 1,610
(1,505)
1,060^ 2,190
(1,500)
1,700^ 1,910
(1,835)
1,150^ 1,890
(1,418)
1,830^1,950
(1,890)
Settling
Tank Over-
flow Rate
(mVm -day)
18.7^ 21.6
(19.2)
11.2^50.5
(20.9)
9.7^50.5
(19.9)
18.1^21.3
(20.1)
13.2^40.4
(20.1)
11. 8"^ 50.5
(20.8)
Treated Effluent (mg/£)
T-BOD
3.6^6.2
(4.9)
5.1^41.6
(18.8)
17.0^ 37.7
(27.7)
7.6^ 11.5
(9.3)
5.3^ 14.3
(9.2)
4.0^ 32.9
(11.6)
S-BOD
1.1^2.6
(1.9)
1.4^ 7.0
(3.4)
1.9^6.0
(3.5)
1.2^5.2
(3.5)
1.4^6.5
(3.7)
1.1^6.7
(3.3)
SS
1.0^ 9.4
(5.3)
7.3^25.5
(14.8)
15.8^ 57.1
(31.5)
6.4^ 17.2
(8.8)
4.8^ 11.0
(7.0)
3.8^ 58.0
(12.6)
Remarks
Constant air supply
M
Proportional air
supply
Constant air supply
,,
„
ho
-p-
Ln
Notes: 1. Values in parentheses indicate the average of all data.
2. Air volume was 5 times the daily average flow of influent sewage under each experimental condition.
-------
c ^0.60
• Influent BOD
oInfluent soluble BOD
A Effluent BOD
A Effluent soluble BOD
20 22 24
Time (hour)
Max. hourly flow/daily average flow=1.20
(Water temperature: 21.8°C)
Fig. 6 Change with Little Load Fluctuation
(Contact Aeration Process)
246
-------
1.00
tn
C
-a 0 . 80
p tj. 0.60
O X
pq ~-
0.40
0.20
0
110
100
90
80
70
60
D
§
50
40
30
20
10
0
• Influent BOD
o Influent soluble BOD
A Effluent BOD
A Effluent soluble BOD
10 12 14 16 18
20 22 24
Time (hour)
Max. hourly flow/daily average flow=2.50
(Water temperature: 21.0°C)
Fig. 7 Change with Load Fluctuation (Contact Aeration Process)
247
-------
3 -3 0.60
o <*>
Q (7
O ^
ffl —
tJi
e
Q
o
m
0.40 •
0.20 -
100
90
80
70
60
50
40
30
20
10
• Influent BOD
o Influent soluble BOD
A Effluent BOD
A Effluent soluble BOD
10 12 14 16 18 20 22 24 2 4 6
Time (hour)
Max. hourly flow/daily average flow=1.12
(Water remperature: 24.8°C)
Fig. 8 Change with Little Load Fluctuation
(Activated Sludge Process)
248
-------
1.00
c *
"•O •§ 0.80
(0 •
O ">
Q ^ 0.60
o ^
CQ ~
0.40
0.20
0
120
110
100
90
80
5 70
\
-H 60
Q
O
CQ
50
40
30
20
10
^ \
/ \
' *.
• Influent BOD
° Influent soluble BOD
A Effluent BOD
A Effluent soluble BOD
10 12 14 16 18 20 22 24 2 4 6
Time (hour)
Max. hourly flow/daily average flow=2.43
(Water temperature: 12.6°C)
Fig. 9 Change with Load Fluctuation
(Activated Sludge Process)
249
-------
Table 3 shows the results of an experiment in which the quan-
tity of air supply for aeration was changed in proportion to
influent flow fluctuation. When air supply was made proportional
to flow rate, the effluent quality tended to improve, as compared
with effluent from equipment operated with a constant air supply.
This is probably because the rate of substrate removal by
microorganisms is increased by the reduction in thickness of the
liquid film on the surface of the biofilm, when the quantity of
air supplied is increased during the daytime as the equipment
receives a large quantity of influent with high BOD load, thereby
increasing the agitation intensity on the surface of the packing
media.
3.3 MAINTENANCE AND CONTROL
Since the present process requires no sludge return, the
quantity of air supply is the sole operating factor. In addition,
no particular care need be taken as to sludge blanket depth in the
final settling tank, due to low SS concentration of influent flow-
ing into the tank. Therefore, this process is believed to be
easier to maintain and control than the activated sludge process.
Another advantage with regard to maintenance and control is that
this process is free of the bulking which is typical of the acti-
vated sludge process.
The reduction of operating factors means, on the other hand,
that once the equipment is built, it is not capable of responding
to changes in circumstances through operations. This is why more
than enough research must be carried out and appropriate con-
siderations introduced at the design stage.
Particularly, the air flow rate, the sole operating factor in
this process, must be determined so as to permit uniform formation
of air bubbles over the entire bottom area.
250
-------
4. QUANTITY AND QUALITY OF SLUDGE PRODUCED
In the actual treatment plant, it is generally difficult to
measure the quantity of sludge from the activated sludge process,
since the quantity of sludge existing in the treatment system is
by far larger than that of the sludge produced.
In the contact aeration process, on the other hand, the quan-
tity of withdrawn sludge in the final settling tank equals the
quantity of produced sludge, since no sludge is returned. There-
fore, it is relatively easy to determine it.
From the process flow rate and the SS concentrations of the
contact aeration tank influent and effluent and the secondary set-
tled effluent, the SS balance was calculated to determine the
quantity of sludge produced. Meanwhile, for reference, the con-
centration of the sludge withdrawn from the final settling tank
was measured on a composite sample taken 7 times during the
daytime and, based on this value and the quantity of withdrawn
sludge, the sludge production was determined.
The ratio of produced sludge to the quantity of SS removed in
the secondary treatment by the contact aeration process was approx-
imately 60 ~ 80% when the equipment was operated normally under
similar conditions throughout a year. The percentage was higher
in winter and lower in summer. In the activated sludge process
over the same period at the Suminoe Treatment Plant as a whole,
the annual average excess sludge was nearly equal to the quantity
of removed SS. The annual average BOD volumetric loading of the
activated sludge process was about 0.3kg/m3'day, slightly lower
than that of the contact aeration process. Thus, it can be con-
cluded that the contact aeration process produced less sludge than
the activated sludge process.
In Osaka City, sludge treatment generally consists of gravity
thickening and subsequent anaerobic digestion. A gravity thicken-
ing experiment using a 1-liter cylinder and an anaerobic digestion
251
-------
experiment using 2-liter batch equipment were conducted on the
sludge from the contact aeration process and the activated sludge
process. The results are shown in Tables 5 and 6.
Table 5 shows that there is no significant difference in grav-
ity thickening between the sludges from the contact aeration proc-
ess and the activated sludge process.
Based on Table 6, which describes the results of the anaero-
bic digestion experiment on both sludges, it can be concluded that
the contact aeration sludge was better treated than activated
sludge in terms of organic substance reduction ratio, volume of
gas generated per unit weight of volatile solids decomposed and
volume of gas generated per unit of volatile solids added, etc.
It is therefore assumed that sludge from the contact aeration
process can be treated in the same way as activated sludge, in so
far as gravity thickening and anaerobic digestion are concerned.
Table 5 Thickening Characteristics
Activated Sludge
Initial Con-
centration
(mg/£)
3,570
8,446
16,000
Concentration
after 24 Hours
(mg/£)
17,000
24,841
25,806
Ratio of
Concen-
tration
4.8
2.9
1.6
Contact Aeration Sludge
Initial Con-
centration
(mg/Jl)
3,654
3,658
12,500
Concentration
after 24 Hours
(mg/£)
31,774
22,863
26,600
Ratio of
Concen-
tration
8.7
6.3
2.1
252
-------
5. SOLID-LIQUID SEPARATION WITH FINE SCREEN
From the viewpoint of effective utilization of land, Osaka
City has conducted solid-liquid separation in the activated sludge
process, using 3-story settling tanks at three of twelve treat-
ment plants.
We researched the solid-liquid separation method for the con-
tact aeration process likely to reduce area of the treatment
plant.
The experiment was based on the assumption that solid-liquid
separation of effluent from the contact aeration tank can be
achieved using a fine screen, since the effluent contains slightly
lower SS than effluent from the primary settling tank and most of
the suspended solids are large and strong floes detached from the
packing media.
253
-------
Table 6 Results of Experimental Anaerobic Sludge Digestion
Sludge Mixing
Ratio
Sample : Seed
sludge
1:0.3
Sample : Seed
sludge
1 : 0.3
Sample : Primary
sedimentation :
Seed sludge
1:1:1
Measuring Item
Initial VSS concentration
VSS reduction
Gas generation per unit
weight of volatile solids
decomposed
Gas generation per unit
weight of volatile solids
added
Initial VSS concentration
VSS reduction
Gas generation per unit
weight of volatile solids
decomposed
Gas generation per unit
weight of volatile solids
added
Initial VSS concentration
VSS reduction
Gas generation per unit
weight of volatile solids
decomposed
Gas generation per unit
weight of volatile solids
added
Unit
mg/£
%
£/g
£/g
mg/&
%
i/g
i/g
mg/£
%
£/g
i/g
Activated
Sludge
11,890
27.3
0.97
0.265
8,370
44.5
0.73
0.325
13,630
29.9
1.33
0.400
Contact
Aeration
Sludge
11,720
32.0
1.18
0.378
8,690
46.2
0.85
0.393
13,720
35.4
1.34
0.47A
Notes: 1. In the reaction tank with a capacity of 2£, sludge was di-
gested by the batch method at a constant temperature of 35°C.
2. The organic substance content of sample sludge was 58^63%
for activated sludge and 56^62% for contact aeration sludge.
254
-------
5.1 PRINCIPLE AND DESCRIPTION OF FINE SCREEN
The fine screen used in the experiment is illustrated in Fig.
10. It is a solid-liquid separation device- in which a number of
wedge-shaped wires, triangular in cross-section, are arranged in
parallel at fixed intervals. This screen was erected at an in-
clination of approximately 60° from the horizontal plane. When
sewage was made to flow down onto the screen, water passed the
screen through the slits between the wedge-shaped wires, during
which process the sewage was treated. Meanwhile, separated sludge
slid down the screen with natural gravity, to produce separated
sludge. (Photo 3)
In order to pre-
vent clogging, a ro-
tating brush was in-
stalled on the back
surface of the screen
so that it could be
cleaned from the rear.
The brush, made of
synthetic resin,
moved reciprocally
beneath the screen,
while rotating, to
clean the entire back
surface of the screen.
The operating
ratio of the brush
was set at 25% (7-
second operation and
21-second stoppage)
for the 33cm-wide
screen used in the Photo 3 The Fine Screen Used
experiment. in the Experiment
255
-------
In the experiment, influent was fed from the outlet of the
contact aeration tank down to the screen by means of a siphon so
as not to break the floe, as illustrated in Fig. 11. For the
experiment, 33cm-wide 60cm-long screens were mainly used.
c
o
•rH
4-J
U
QJ
U
c
Ql
QJ
M
U
00
0)
a
«
x:
U)
i
QJ
Cn
TD
0)
3
M-l
O
U
•P
QJ
QJ
O
0)
Q
QJ
QJ
QJ
q
•H
Cm
en
256
-------
N5
Ln
Flow indicator
Air-
Inf luenf
Flow indicator
Pump
LI I Pg
Contact aeration tank
1st tank 2nd tank
Drafted
sludge
•-Effluent
Final settling tank
Screen
Screen-passed effluent
Fig. 11 Flow Sheet of Fine Screen Experiment
-------
5.2 SELECTION OF SCREEN
This screen was originally developed for the purpose of
thickening sludge. In order to maximize concentration of
separated sludge, the slits between wedge-shaped wires in the
lower part of the screen were made wider than those in the upper
part.
From Fig. 12, which shows the relationship between slit size
and quality of screen-passed effluent, it was concluded that the
sludge thickening screen with a wider slit in the lower half was
not a suitable alternative to the final settling tank and that it
was necessary to use screen with a 30p slit size — the minimum
size available at present — over its entire surface.
40
-------
As a means of improving the quality of screen-passed
effluent, isolation of effluent passing the lowest portion of the
screen was effective, since such effluent was by far lower in
quality than that passing the upper portion of the screen.
The most effective ratio of the quantity of separated
effluent to the quantity of sewage made to flow down the screen
was 5%, as shown in Fig. 13. Effluent thus separated should be
taken out together with the separated sludge, or returned to water
treatment facilities.
^D
E
effluent
to
o
I 15
w
w
rd
a
1
5
0)
0 10
0)
0
w
w
5
1 1 1 1
•^
f V . .
< . ' '• •
w ^^^
- -
Screen (30jj)
1 1 1 I
5 10 15 20
Ratio of separated water (%)
Fig. 13 Ratio of Separated Water vs.
SS of Screen-passed Effluent
25
259
-------
5.3 HYDRAULIC LOADING ON THE SCREEN
Unless the hydraulic loading on the screen is increased,
plant site area cannot be reduced. Therefore, an increase in the
hydraulic loading on the screen was emphasized even at the expense
of reduced concentratoin on separated sludge.
According to the estimate by the municipality, solid-liquid
separation using the screen can be achieved in an area about 20%
of the existing single-story final settling tank, if sewage is
treated at a rate of 30m3/hr per meter of screen width. This
means that the plant site area requirement is even smaller than
that for a 3-story settling tank.
Fig. 14 shows the relationship between the hydraulic loading
on the screen and effluent SS. As the loading increased, the ef-
fluent quality tended to deteriorate. Yet, the degree of deterio-
ration was very low: Effluent SS was approximately 20mg/Jl when
the hydraulic loading on the screen was 36m^/m'hr.
The relationship between the concentration of separated
sludge and the loading is shown in Fig. 15. As the flow in-
creased, the quantity of separated sludge increased, while its
concentration declined. The ratio of the quantity of sludge to
the flow was approximately 1.3%, when the rate of treatment was
o
36m /m'hr. If it is necessary to raise concentration of sludge,
sludge once separated with the screen can be further concentrated
with the use of another screen.
5.4 PROTECTION AGAINST CLOGGING OF SCREEN
The screen used in the experiment was prevented from clogging
by cleaning it with a rotating brush fitted on the back surface of
the screen. However, when the screen was operated continuously,
the quantity of separated sludge flowing down on the screen sur-
face tended to increase. This was probably due to the generation
and growth of biological slime on the surface of the screen.
260
-------
Since such slime could not be removed perfectly by cleaning from
the back using the rotating brush alone, the surface of the screen
was also cleaned by means of high-pressure spray. The specifica-
tions of the spray are shown in Table 7. Fig. 16 shows the re-
lationship between the percentage of separated sludge quantity and
the number of days elasped using operation frequency of the spray
as parameter.
The term "percentage of separated sludge quantity" means in
this context the ratio of separated sludge quantity to the quan-
tity of influent to the screen. Fig. 16 indicates the remarkable
effectiveness of the high-pressure spray.
261
-------
Quantity of separated sludge (inVm-hr)
SS of screen-passed effluent (mq/?,)
K3
(^
fo
M
BJ
3
a
cn
fD
•a
BJ
rt
a
cn
c
a
O
O
o
ro
3
rt
^
0)
rt
H-
O
3
*<
a
tr>
O
B)
a
3
03
o
3
CO
o
^
ro
ro
3
<
w
0
Hi
cn
ft!
Qi
^
Q) i—i
C NJ
h-'
H-
O
CL
H-
3
O
w
n
H<
ro
ro
3
3
3"
o
Ln
o
o
o
o
o
o
U)
o
o
o
o
o
o
3
Hi
fD
3
en
Ul
CO
Ln
Ln
O
O
O
fO
c
B)
rt
H-
rt
Concentration of separated sludge (mg/£)
O
Hi
cn
o
H
fD
ft
3
I
>D
B>
W
w
ra
HI
HI
EH
a
H-
O
a
H-
3
3)
O
n>
ro
3
NJ
O
LO
o
cn
o
o
IT
-------
Table 7 High-pressure Spray Cleaning Device
Quantity of water used
Spraying pressure
Unit cleaning time
10£/min.
20kg/cm2
Average 3 min .
(Max. 5 min.)
6 8 10 12
Days elapsed
16
18 20
£ None
O Cleaned every two days
O Cleaned every day
Q Cleaned twice a day
Fig. 16 Effect of High-pressure Cleaning of Fine Screen
263
-------
5.5 COMPARISON OF QUALITY BETWEEN SCREEN-PASSED EFFLUENT ANd
FINAL SETTLED EFFLUENT
Figs. 17 and 18 show a comparison between effluent passing
the screen having uniform 30p slits, with a percentage of sepa-
rated sludge quantity of 5% and hydraulic loading of 30 ~ 36m3/
m'hr, and effluent from the final settling tank. At the time of
this experiment, the final settling tank was operated with an
overflow rate of 5 ~ 26m /m2'day, under relatively light load.
The values concerning the screen-passed effluent were
obtained by analyzing a composite sample taken 3 times during the
daytime, while the values concerning effluent from the final
settling tank were obtained by analyzing a sample subjected to
mixing for 24 hrs.
On the average, the screen-passed effluent showed BOD higher
by approximately 2mg/& and SS higher by approximately 4mg/& than
effluent from the final settling tank.
The screen treatment experiment was conducted in the last
year of the 4-year period of operation of the contact aeration
equipment. In the latter half of the year especially, loss of
aeration uniformity in the contact aeration tank was observed
visually, and as a consequence the quality of effluent from the
final settling tank deteriorated.
The investigation conducted at the time of removal of the
equipment upon completion of the experiment revealed that some of
the steel risers used for aeration were corroded, with some holes
formed on their surfaces. This seems to have caused an insuf-
ficient supply of air to the diffuser pipes, promoting clogging
and, as a result, lessening the quality of effluent immediately
before the end of the experiment.
264
-------
ro
CT>
Ln
p-
X!
O
O
•3
CD
hi
H-
01
o
M
Hi
Ml
I—'
C
tD
ft
SS of screen-passed effluent (mg/£)
BOD of screen-passed efTfluent (mg/J.)
to
to
0
Ml
ro
Hj
Ml
I— '
O
3
Oi
rt
M-
H
3
X"
K)
O
O
i
hj
H-
cn
0
M
Hi
Mi
CO
O
D
D
H-
h-'
^
(B
Hi
[D
-------
6. SUMMARY
To sum up the findings of these experiments on the contact
aeration process using net packing media, employing the full-scale
equipment.
(T) The contact aeration process in which multi-line aera-
tion is carried out from below the net packing media can be used
for secondary sewage treatment as an alternative to the activated
sludge process.
(|) As advantages of the contact aeration process, easy main-
tenance and control and reduced production of sludge are noted.
A disadvantage is the poorer appearance of the screen-passed
effluent, as compared with the effluent treated by the activated
(T) The capacity of the contact aeration process to remove
soluble BOD is more vulnerable to load fluctuation than that of
the activated sludge process. The treatment efficiency of the
contact aeration process tends to increase if the quantity of air
supply is made proportional to the flow rate of influent and if
the air supply is increased when BOD load is high.
(4) The sludge from contact aeration process is not signifi-
cantly different from the activated sludge, with regard to gravity
thickening and anaerobic digestion.
(s) If solid-liquid separation of the contact aeration proc-
ess is achieved with the use of a fine screen instead of the final
settling tank, the plant site area can be reduced, though the
quality of effluent is diminished, compared with effluent obtained
when a final settling tank is employed.
266
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
CONSTRUCTION TECHNOLOGY ASSESSMENT SYSTEM AND
DEVELOPMENT OF MECHANICAL AERATORS
FOR THE OXIDATION DITCH PROCESS
September 19 ~ 21, 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Itaru Nakamoto
Head of Public Sewage Division
Sewerage and Sewage Purification Department, City Bureau
Ministry of Construction
267
-------
CONTENTS
Page
1. PREFACE 269
2. CONSTRUCTION TECHNOLOGY ASSESSMENT SYSTEM 271
3. THEMES OF THE SYSTEM RELATED TO SEWERAGE 272
4. ASSESSMENT OF MECHANICAL AERATORS FOR OXIDATION DITCH
PROCESS 277
(1) Reasons for the Selection of the Theme 277
(2) Conventional Oxidation Ditch and Aerators 280
(3) Determination of Goals of Development 283
(4) Results of Assessment 285
(5) Discussions on Oxidation Ditch Process 292
268
-------
1. PREFACE
Ministry of Construction is currently carrying out research
and development of various kinds of basic construction techniques
in order to improve social capital and promote smoothly and effec-
tively various policies required to meet the needs in construction
administration which have become quite diversified and sophistica-
ted in recent years.
The studies concerning sewerage are being performed under the
budgets available, mainly sewerage survey costs and administrative
department costs. Themes of study are varied; some themes are
related to basic study but others are immediately applicable to
actual work, and the rest are related to the study of future direc-
tions in the administration of sewerage works.
The Water Quality Control Department of Public Works Research
Institute, an affiliated organization to Ministry of Construction,
and Research and Technology Development Division, Japan Sewage
Works Agency is doing most of the research and development, but the
Ministry of Construction is also carrying out research and develop-
ment generally on themes required for carrying out sewerage projects.
On the other hand, themes of research and development by the
private sector as well as by the government on construction tech-
niques are extremely progressive and highly sophisticated, and it
has become vitally important to carry out the research and devel-
opment with close collaboration between the government and private
sector in order to improve construction technology as a whole.
Ministry of Construction established in 1977 the basic policy
for research and development "5-year Plan for Research and Develop-
ment of Construction Technology (FY 1977 to 1981)" as follows.
(T) In carrying out comprehensive research and development projects
as well as overall research and development, it is required to
establish clear research goals and programs and to organize the
research and development organizations in such a manner that the
purposes can be achieved within a predetermined period of time
269
-------
with close cooperation among government, private sector and
academic circles.
(2) New research and development methods such as joint study be-
tween the government and the private sector are to be devel-
oped in order to aggressively promote research and develop-
ment on construction technology and enable the private sector
to utilize the results.
As one of systems for more aggressively promoting the research
and development of construction technology by the private sector
in accordance with the policy stated above, the construction tech-
nology assessment system was established in FY 1978.
This system will properly assess the function and performance
of the research and development results of construction technology
conducted by the private sector and will publicize them in order to
promote aggressive utilization of new techniques and to further ac-
celerate the research and development in the private sector.
This system has been adopted because it become necessary to
properly assess and to organize the diffusion of the new techniques
in order to quickly introduce them to construction sites since
people tend to be conservative in introducing new techniques because
public costs are used as financial resources in the area of public
construction projects, estimation of economic effects due to intro-
duction of new techniques is not easy, and failures associated with
introduction of new techniques are not easily permitted.
270
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2. CONSTRUCTION TECHNOLOGY ASSESSMENT SYSTEM
Actual policies to be carried out under the construction tech-
nology assessment system are prescribed in "Construction Technology
Assessment Rules (Issue No.976 by Ministry of Construction on May
24, 1978)" which is outlined in Fig. 1.
That is, the Minister of Construction will announce the tech-
nical subjects to be assessed in Official Gazette thus inviting
private firms to submit their proposals. Then, the achievements of
research and development submitted by applicants (enterprises and
corporations) will be thoroughly assessed, and assessment papers
will be issued based upon the results of the assessment and public-
ly announced.
In this assessment, preliminary technical assessment will be
performed by Technology Center for National Land Development and
then, based upon the results, the new techniques will be carefully
assessed by the assessment committee organized by the Ministry of
Construction.
(consignment organ | || Ministry of Construction!
Establishment of construc-
tion technology assessment
rules
Determine
research
be assess
tion of themes of
ed
•
He
res
aring of
earch plan
DisCUSSlO
assessmen
committee
{Consignment of t
Preliminary I 1 Con51gnlnent ot 1
assessment 6. tfists t others
| Preliminary assessment
report
n by Examinatic
t of assess-
* ment item.
t
1
Discussion of result
pre liminary assessme
Review by assessment
committee
papers
Private sector!
1 H^if,es 1
L^^
B Publicly inviting researchers
(Official Gazette)
Submission of achievements of
research (already developed)
App 1 1 cat ion s
(not yet developed)
Research and
Notifying items required for ' f '
assessment applications * Completion of
Assessment [ research and
applications " dcveiopmenr
s of
nt
L papers
Announcement of
ment * Note: Notified to
Regional Construction
Bureaus, prefectural
governments and other
public bodies concerned.
Fig. 1 Flow of Construction Technology Assessment System
271
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3. THEMES OF THE SYSTEM RELATED TO SEWERAGE
Since the start of the construction technology assessment
system in 1978, approximately 3 to 5 themes related to construction
are assessed every year.
Themes of research related to sewerage for which researchers
were already invited are "development of microwave furnace for
sewer sludge to melt" and "development of large-diameter egg-shaped
hard vinyl chloride pipe with high rigidity" for FY 1978, "develop-
ment of ultra-deep aeration system for sewer treatment" for FY 1979,
"development of energy-saving type aerator by diffuesed air" for FY
1980, "development of mechanical aerator for oxidation ditch process"
for FY 1981 and "development of sewage solid-liquid separation method
by screen process" for FY 1982 (refer to Table 1).
Themes being publicly announced now consist of four themes re-
lated to water treatment, one theme related to sludge treatment, and
one theme related to sewer pipe. In recent two years, themes tend
to be related to the small-scale-sewerage system because new public
sewerage projects tend to be small in Japan. That is, as shown by
Fig. 2, most municipalities with populations greater than 50,000
have already started sewerage projects but the municipalities with
populations of less than 50,000 have delayed in starting the projects
and in particular most municipalities with populations of less than
10,000 have not yet started sewerage construction projects. There-
fore, in order to achieve a target value of 90% for the population
coverage rate of sewerage by the beginning of 21st century, it is
necessary to make more efforts to improve sewerage even for these
small municipalities. Since small municipalities have different
financial abilities and organizing powers from those of large muni-
cipalities, approaches differing from conventional sewerage processes
will be required. That is, it is not easy to find skilled workers
for maintaining and controlling the sewage treatment plant in a
small city and, thus, the maintenance and control must be simple, and
since population density of a small city is low, a pipe and pumping
272
-------
station system for small-scale-sewerage must be newly developed.
Thus, development of techniques related to small-scale-sewerage will
increasing important.
273
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Table 1 Themes of Construction Technology Assessment by Ministry of Construction
Fiscal Year of
Invitation
Subjects
Objects of
Development
Goals of
Development
Applicants
1978
Development of microwave furnace for
sewer sludge to melt
To develop microwave melting furnace
capable using microwaves to melt and
solidify sewer sludge, turning it into
chemically stable glassy material with-
out however generating harmful exhaust
gas but permitting, the melted and sol-
idified substances to be used as con-
struction materials.
1) Maximum treating capacity of furnace
of about 5 tons/day.
2) Exhaust gas generated from the proc-
ess, being capable of meeting the
requirements set forth in Air Pollu-
tion Prevention Law (Law No. 97 in
1968) .
3) Melted and solidified glassy materi-
als being capable of meeting the
Order of Prime Minister's Office
(Order No. 5 in 1973) determining
the criteria for industrial wastes.
4) Melted and solidified glassy sub-
stances being capable of providing
the strength required for aggregates.
5) Comparatively low costs of manufac-
turing, operating and maintaining
the melting furnace.
1 firm
1978
Development of large-diameter egg-shaped
hard vinyl chloride pipe with high rigi-
dity
To develop hard vinyl chloride pipe
having an egg-shaped section with excel-
lent hydraulic properties, large dia-
meter, sufficient strength and endurance.
1) Strength determined by the flat test
(in accordance with test method
established by Standard K-l of Japan
Sewage Works Association) being capa-
ble of meeting the strength of class
1 centrifugal reinforced concrete pipe
(external pressure strength against
cracking load of JIS A 5303) .
2) Nominal diameter of about 500 mm.
3) Endurance almost equal to or higher
than that of class 1 centrifugal
reinforced concrete pipe.
2 firms
1979
Development of ultra-deep aeration system
for sewer treatment
To develop activated sludge process using
ultra-deep aeration tank requiring only a
small area.
1) Required processing capacity greater
than 1,000 m3/day.
2) Process providing values of biochemical
oxygen demand (BOD) and suspended solids
(SS) of final effluent capable of meet-
ing the technical requirements set forth
in Para. 1 of Article 6 of the Enforce-
ment Ordinance of Sewerage Law (Cabinet
Order No. 147 in 1959) .
3) Simple operation.
4) Low maintenance and management costs.
5) Simple environmental measures.
2 firms
-------
Table 1 Themes of Construction Technology Assessment by Ministry of Construction (Cont'd)
Fiscal year of
Invitation
Subjects
Objects of
Deve lopment
Goals of
Development
Applicants
1980
Development of energy-saving type
aerator by diffused air.
To develop energy-saving type aerator
to be used for diffused air type acti-
vated sludge process at the sewage
treatment plant.
1) Power consumption is to be reduced
by more than 20% compared to con-
ventional air diffusing equipment.
2) For ordinary sewage, the aerator
is to be able to provide the values
of biochemical oxygen demand (BOD)
and suspended solids (SS) of final
effluent meeting the technical
requirements set forth in Para. 1
of Article 6 of the Enforcement
Ordinance of Sewerage Law.
3) Connection to existing aeration
tank is to be easily made.
4) Simple operation.
5 firms
1981
Development of mechanical aerator for
oxidation ditch process
To develop efficient mechanical aerator
using oxidation ditch process as one of
sewage treatment methods.
1) Required current speed is to be
obtained.
2) Oxygen is to be efficiently supplied.
3) Sufficient mixing and agitating
ability.
4) Easy equipment maintenance and ope-
ration.
5) Simple environmental measures.
8 firms
1982
Development of sewage solid-liquid separa-
tion method by screen process
To develop solid-liquid separation process
using screens for economicaly separation
of sewage solids from liquids, convention-
ally performed with settling basin.
1) Quality of treated water almost equal
to that of settling basin is to be
obtained.
2) Easy maintenance and operation.
3) Sufficient endurance.
4) Economical.
ho
-vl
Ul
-------
Number of
munici-
palities
1000 -
500 -
1089
1510
247
251
Example :
Cities of
Chitose,
Tendo ,
Izumo
213
109
Example:
Cities of
Akita,
Nara,
Kofu,
Tsuchiura,
Kamakura-
138
Population Population
thousands below 10
Example:
Cities of
Hakodate,
Utsunomiya,
Kurashiki
Niigata,
Yokosuka,
Nagasaki
35
36
36
Total number of
municipalities
Number of municipalities
carrying but the sewage
projects
Number of municipalities
with sewerage already in
service
Example:
Cities of
Hiroshima,
Okayama,
Kagoshima,
Sakai,
Sendai
Example:
Metropolitan
Tokyo,
Cities of
Yokohama,
Osaka,
Kyoto
9 9
10 10 10
10 to 30 30 to 50 50 to 100 100 to 300 300 to 500 500 to 1,000 over 1,000 x 103
Fig. 2 Number of Municipalities Carrying Out the Sewerage Projects by Population Rank (end of FY 1982)
-------
4. DEVELOPMENT OF MECHANICAL AERATOR FOR OXIDATION DITCH PROCESS
Ministry of Construction invited firms interested in develop-
ing a "mechanical aerator for oxidation ditch process" as a theme
for construction technology assessment on July 1, 1981. In response
to this invitation, eight firms submitted applications, preliminary
assessment was performed by the Technology Center for National Land
Developments in 1982, subsequent assessment was performed by the
Technology Assessment Committee in Ministry of Construction in March
1983, and it was recognized that all eight firms satisfied the deve-
lopment goals.
(1) Reasons for the Selection of the Theme
When constructing sewage treatment plants in small cities,
unlike conventional plants built for large and medium cities, the
following items must be taken into account:
(T) Because of the small scale, no benefits due to a large scale
can be expected for construction, maintenance and administra-
tion costs, and these costs tend to become high.
(2) Since it is difficult to obtain professional maintenance
engineers, complicated and sophisticated equipment are not
appropriate.
(3) It is required to respond to considerable fluctuations of
influent water which is peculiar to small-scale sewage treat-
ment plants.
It becomes difficult to cope with the situations described
above by using the conventional activated sludge process which is
widely being used for large and medium municipalities. (Refer to
Table 2.) On the other hand, compared to highly dense large cities,
large sites for sewage treatment plants relative to unit amount of
water can be more easily obtained in small cities. The oxidation
ditch process is worthy of note since it can use this advantage in
order to cope with the difficult situations stated above.
277
-------
Table 2 Numbers of Sewage Treatment Plants by Treatment Process
(At the end of FY 1980)
oo
\ Process of
\ treatment
DesignX
capacityX
( 10 'mJ'dayK
Less
than 5
5 -v 10
10 ^ 50
50 ^ 100
100 ^ 500
^^ 500
than
Total
Low
class
Sedimen-
tation
process
2
2
1
5
Medium class
High
rate
trickling
filter
process
4
3
7
1
1
16
Aero-
accele-
rator
2
14
3
2
21
High class
Conven-
tional
activat-
ed sludge
process
31
35
97
55
72
6
296
Stepped
aeration
process
5
5
14
24
31
7
86
Extended
aeration
process
16
1
17
Contact
stabili-
zation
process
3
3
Pure
oxygen
aeration
process
3
3
Oxida-
tion
ditch
4
4
Rotary
bio-
logical
contact-
er
process
3
2
1
6
Total
73
45
135
84
107
13
457
Notes: 1. If more than two treatment methods are used in one plant, the method with the larger capacity is
indicated in this table.
2. Detail of 457 treatment plants in total: Public sewerage; 423 treatment plants
River basin sewerage; 27 " "
Specified public sewerage; 2 " "
Public sewerage to preserve the 5 " "
national environment;
-------
According to the oxidation ditch method, a relatively shallow
elliptic water channel is installed, high-concentration activated
sludge is mixed with sanitary sewage by a mechanical aerator, and
then the mixture is circulated and treated by aeration for a long
time.
Features of this method are:
(T) Since ditch capacity is large and retention period is long,
amount of MLSS in ditch is large and thus stability is high
against a large load fluctuation. Also, even though the
amount of return sludge is made constant, the amount of MLSS
fluctuates little in response to the change in sludge concen-
tration, so that maintenance can be performed easily.
(2) Since primary sedimentation basin can be omitted, the portions
requiring maintenance work can be reduced and the total labor
required can be reduced.
(3) Since a mechanical aerator is used for ditch aeration, the
equipment is simple and can be easily repaired.
(4) Since sludge age is long, 15 to 30 days, sludge is subjected
to a sort of aerobic digestion and, thus, the sludge can be
treated easily.
Because of the features listed above, the theme of "develop-
ment of efficient mechanical aerator for oxidation ditch process"
was selected in order to promote efficient sewerage construction
in small municipalities as key point of future sewerage construc-
tion.
279
-------
(2) Conventional Oxidation Ditch and Aerator
Conventional oxidation ditch has a track-shaped endless water
channel aboXit 1 m deep and treats sanitary sewage by circulating
and aerating the sanitary sewage by rotors. As shown in Fig. 3, the
treating process has no primary sedimentation basin and consists of
ditch and final sedimentation basin, but the final sedimentation
basin is not installed when performing batch treatment.
Rotor
Ditch
Influent
sewage —
Return
sludge
Final
sedimentation
basin
•Treated
water
Fig. 3 Flowchart of Oxidation Ditch
This conventional method is designed for MLSS of 3,000 - 5,000
mg/£, hydraulic retention time of 24 - 48 hours, BOD-SS load of 0.03
- 0.05 kg/SS kg.day, and a sludge return ratio of 50 to 150%.
Kessner brush rotors were used many years ago but recently flit
steel bar rotors, steel angle rotors and cage type rotors are widely
being used. Generally flat steel bar rotors have been used for the
public sewerage in this country. The flat steel bar rotor is made
of steel vanes, each about IS to 30 cm long attached in parallel to
the periphery of a rotating shaft with a diameter greater than 0.5
m, which is rotated at a speed of 60 to 120 revolutions per minute.
One or more rotors are normally installed facing the direction of
flow of each ditch.
280
-------
At present, there are seven sewage treatment plants using
oxidation ditches in Japan and their specifications are as listed
below.
281
-------
Table 3 Sewage Treatment Plants Based on Oxidation Ditch Process
Name of
municipalities
Nikko
Toyohashi
Tomakomai
Ohgata , Akita
Pref.
Ohmihachiman
Terai , Ishikawa
Pref.
Hikami, Hyogo
Pref.
Plant name
Yumoto Plant
Takane Plant
Yufutsu Plant
Ohgata plant
Okinoshima
Purification
Center
Public Sewerage
Eastern
Purification
Center
Nishinaka Plant
Design population
(persons)
6,840
1,650
7,200
4,000
1,010
3 , 600 for
overall ,
1,800 for
1st step
5,100
Design capacity
(m'/day)
3,250
650
4,300
1,536
420 for
overall ,
210 for
1st step
1,800 for
overall,
900 for
1st step
3,860
Quality of
influent water
(mg/!,)
BOD: 94
SS: 113
BOD: 200
SS: 200
BOD: 200
SS: 250
BOD: 150
SS: 200
BOD: 235
SS: 210
COD: 120
T-N : 40
T-P: 4
BOD: 220
SS: 200
BOD: 210
SS : 160
Quality of
treated water
(mg/Z)
BOD: 20
SS: 30
BOD: 20
SS: 60
BOD: 20
SS: 50
BOD: 20
SS: 40
BOD: 20
SS: 20
COD: 20
T-N : 20
T-P: 0.5
BOD: 18
SS: 50
BOD: 20
SS: 40
Sludge treatment
(disposal)
Thickening •*
mechanical
dewatering
Solar drying -*•
land
application
Thickening -*•
vacuum carryer
-*• to Nishi-machi
treatment plant
Thickening •*•
mechanical
dewatering
-»• disposal
Solar drying •*
land applica-
tion
Thickening •*•
storage
-»• (vacuum carryer)
•» scheduled to
dispose outside
of plant
Thickening -»•
solar drying
->• land applica-
tion
Remarks
Residential and
sightseeing
waste water
Residential and
livestock waste
water
Residential
waste water
Residential
waste water
Residential waste
water started in
July 1982 , second-
ary treatment -f
sand filtering
Underground struc-
tures, aboveground
park facilities ,
residential waste
water
Residential waste
water ,
started in Apri 1
1983
00
ro
-------
(3) Determination of Goals of Development
Oxidation ditch has a long retention time (3 to 4 times) in
aeration tank and a high concentration of MLSS (2 to 3 times) com-
pared to the conventional activated sludge process, so that a larger
amount of oxygen is needed for the treatment.
Amount of oxygen consumed is given by the following formula:
s n x
N=a Io§oQ + b io§o v ©
where, N
S
r|
Q
X
s
Amount of oxygen consumed (kg-02/day)
Concentration of influent BOD (mg/Jl) (200 mg/£)
BOD removal factor (0.9)
3
Amount of influent water (m /day)
Concentration of MLSS (mg/£)
V Capacity of aeration tank (m3)
Amount of oxygen required per 1 kg of BOD removal
(0.5 kg-02/kg-BOD)
b : Amount of oxygen required per 1 kg of MLSS daily
(0.1 kg-Oa/kg-BOD)
Design parameters for conventional activated sludge process
and oxidation ditch process are given below.
(a) Design parameters for conventional activated sludge
process:
BOD-SS load: 0.4 kg/SS kg-day
MLSS concentration: 1500 mg/£
(b) Design parameters for oxidation ditch process:
BOD-SS load: 0.05 kg/SS kg'day
MLSS concentration: 4000 mg/£
For (a) : V = — Q
^"""^ J
For (b) : V = Q
Therefore, from equation (T) , the amount of oxygen consumed
is given by
Standard activated sludge process: — = 0.14 kg-02/day • m3
Oxidation ditch process: JL = Q>4g kg_02/day . m3
283
-------
Therefore, in the oxidation ditch process, the amount of oxygen
supplied is 3.5 times greater than that needed in the convention-
al activated sludge process. Thus more energy is required.
Therefore, the greatest problem in the oxidation ditch proc-
ess is to develop an aerator having a high oxygen supply effi-
ciency .
The following five items were thus established as goals of
development:
(l) To secure the current speed required.
(5) To supply oxygen efficiently.
(3) To provide a sufficient mixing and agitating capacity.
(4) To assure easy maintenance and control of equipment.
(5) To assure measures that can be easily implemented for
the surrounding environment.
Among the five goals of development listed above, efficiency
of oxygen supply of item (2) is the most important. For the cur-
rent speed of item (I), a minimum current speed of 10 cm/sec was
established from the results of survey conducted by Public Works
Research Institute, Ministry of Construction. For the oxygen
supply efficiency of item (2), 1.8 kg-Oa/kwh minimum was estab-
lished since the efficiency must be greater than that of conven-
tional aerator. For the mixing and agitating capacity of item (3),
the distribution of both MLSS and DO was checked and it was
determined that the standard deviation for MLSS should be less
than 10% from the mean value within the same section. DO distri-
bution was used only for reference.
In performing the assessment, the following items were con-
sidered as prerequisites for the sanitary sewage and sewage treat-
ment facilities being considered:
(T) Sanitary sewage is to be ordinary sewage, such as resi-
dential waste water and business waste water (from
offices, hospitals and places of business), that can be
biologically decomposed.
284
-------
(2) Sewage treatment facilities other than those being con-
sidered in the assessment are required to have the pre-
determined functions provided, as a rule, in accordance
with "Design manual for Sewerage Facilities (JSWA)".
(3) Equipment used for the aerator are required to have been
manufactured under proper quality control.
(4) Results of Assessment
Equipment considered for assessment were 8 products manufac-
tured by 8 companies: IHI Superrotor by Ishikawajima Harima Heavy
Industries Co., Aqubarotor by Kawasaki Heavy Industries Co., Kubota
KR-2 type rotor by Kubota Steel Co., Mammothrotor by Kurita Indus-
tries Co., Orrotor by Organo Co., Sigmarotor by Shinko Pfaudler Co.,
Carousel Aerator by Sumitomo Heavy Industries Co., and Draft Tube
Aerator by Ataka Industries Co.
Four of them, IHI Superrotor, Aqubarotor, Kubota KR-2 Rotor,
and Mammothrotor, are of horizontal shaft type, while three of
them, Orrotor, Sigmarotor and Carousel Aerator are of vertical
shaft type. The remaining rotor of Draft Tube Aerator will mix
and agitate activated sludge and create a current speed by means
of an rotor placed at the upstream side of draft tube and also
supply oxygen from blower.
All of these aerators were recognized to satisfy the above
mentioned goals of development.
Detailed results of assessment for these aerators are shown
in separate reports, however, the outline of the assessment for
the eight aerators is shown in Table 4 and Table 5.
285
-------
Table 4 Comparison Table for Results of Assessment of Mechanical Aerator for
Oxidation Ditch
N3
CO
\ Aerator name
Assessed \
item \
1 Rotor type
2 Principle
Summary of
_ aeration
perform-
ance
(refer to
drawings)
4 Influence
upon envi-
ronment
(1) Noise
Splash
(2} water-
drops
(3) Vlbra"
t3) tion,
odor
S Endurance
IHI Superrotor
Horizontal rotor
Mechanical aeration equipment
developed for the oxidation
ditch has a horizontal rotor
which is rotated in the straight
section of ditch in order to
supply oxygen, mix and agitate
activated sludge and cause it
to flow.
When MLSS concentration is about
2,500 to 3,500 mg/£ and speed of
aerator is 60 rpm, the power
density is 8.7 W/m3, mixing and
agitating conditions in oxida-
tion ditch are good, and a cur-
rent speed required for circu-
lation can be obtained. In the
range where the efficiency is
the highest, the oxygen supply
efficiency is about 2.3 kg-02/
kwh, and thus this equipment is
recognized to be efficient for
the oxidation method.
Noise sources are driving sec-
tion such as motor reduction
gear and aerator which genera-
tes splashing sounds. Noise
can be considerably reduced with
soundproof cover for driving
section and with splash-proof
cover. By taking these meas-
ures depending upon the envi-
ronmental conditions , most
problems can be solved.
This problem can be solved by
with splash-proof cover.
There will be no special prob-
lem.
It is reported that there has
been no endurance problem since
this equipment should operate
for ten years.
Aqubarotor
Same as the left
Same as the left.
When MLSS concentration is in
the range of about a 3 ,300 to
4 , 400 mg/A , power density is
^4,1 W/m3, mixing and agitating
conditions within the oxidation
ditch are good and current
speed required for circulation
can be obtained. In the range
where the efficiency is high-
est, the oxygen supply effici-
ency is about0 2. 2 kg-02A«h
and, thus, jtnis equipment is
considered to be efficient for
mechanical aeration to be used
with the oxidation ditch method.
Same as the left.
Same as ihe left.
According to the results of
operation of experimental fa-
cilities for the period of ^ 9
months in the past, there has
been no endurance problem.
However, long-term endurance
has not yet been confirmed.
Kubota KR-2 Rotor
Same as the left.
Same as the left.
a; 1,800 ^3,000 mg/H
b; 10.7 W/m3
c; 2.3 Kg-O2/kwh
Same as the left.
Same as the left.
d; 17 months
Mammoth rotor
Same as the left.
Same as the left.
a; 3,500 ^5,200 mg/£
b; 8.1 W/m3
c; 2.4 kg-Oa/kwh
Same as the left.
S ame as the left.
d; 9 months
Continued
-------
Table 4 (Continued) Comparison Table for Results of Assessment of Mechanical
Aerator for Oxidation Ditch
I-O
oo
\Aerator name
Assessed \
item \
1 Rotor type
2 Principle
Summary of
aeration
perform-
ance
(refer to
drawings)
4 Influence
upon envi-
ronment
(1) Noise
Splash
(2) °*
v ; water-
drops
Vibra-
U) tion,
odor
5 Endurance
Orrotor
1
Mechanical aeration equipment
developed for oxidation ditch
has a vertical shaft type rotor
which is rotated at a corner in
the ditch in order to supply
oxygen, to mix and agitate ac-
tivated sludge and to causes it
to flow.
a; 3,922^ 4,082 mg/£
b; 7.6 W/m3
c; 2.2 kg-02Awh
Same as the left.
Same as the left.
Same as the left.
d ; 11 months
Sigmarotor
Same as the lef t .
Same as the left.
a; 3,020^3,120 mg/£
b; 5.1 W/m3
c; 2.4 Kg-02/kwh
Same as the left.
Same as the left.
Same as the left.
d; 12 months
Carousel Aerator
Same as the left.
Same as the left.
a; 4,190^4,690 mg/£
b; 4.9 W/m3
c; 2,8 Kg-02/kwh
Same as the left.
Same as the left.
Same as the left.
d; 1 year & 4 months
Draft Tube Aerator
Draft tube
Mechanical aeration equipment
developed Tor oxidation ditch
method mixes and agitates the
activated sludge and creates
a current by the rotor at the
upstream side of draft tube
connected from the upstream
side to downstream side of a
partition while oxygen is
being supplied by a blower.
a; 3,590^4,450 mg/£
b; 5.0 W/m3
c; 2.2 kg-02/kwn
Noise sources are driving
section such as motor reduc-
tion gear and the blower and
tube outlet which generate
air noise . However , noise
from the driving section and
blower can be considerably
reduced by covering them with
sound-proof covers. Noise
problems can be solved by tak-
ing these measures depending
upon environmental conditions.
There will be no special prob-
lems.
Same as the left.
d ; 1 year & 6 months
-------
Table 5 Overview of Aeration Performance (relations among oxygen supply efficiency,
mean and minimum current speed, MLSS distribution and power density)
(1/4)
ho
00
00
Oxygen supply
efficiency
(kg-02/kwh)
Current speed
(cm/sec.)
0
40
30
20
10
0
20
MLSS distribu-
tion (Standard
deviation/ 1
mean) (%)
IHI Superrotor
Section shape of ditch:
2.0 m (width) x2.5 m (water depth)
60 rpm
71 rpm
48 rpm
Section
III
Mean current speed
Minimum current speed
60 rpm 71 rpm
71 rpm
O Section II
A Section III
Section VI
5 10 15 20
Power density (W/m3)
25
Oxygen supply
efficiency
2
(kg-02/kwh)
0
40
30
Current speed
(cm/sec.)
10
0
20
MLSS distribu-
tion (standard
deviation/
mean) (%)
Aqubarotor
Section shape of ditch:
2.0 m (width) x2.5 m (water depth)
Section III
52 rpm
78 rpm
52 rpm
Mean cur-
rent speed
Minimum
current
speed
O Section
A Section
I
II
D Section III
^Section IV
5 10 15 20
Power density (W/m3)
25
-------
Table 5 Overview of Aeration Performance
(2/4)
Kubota KR-2 Rotor
Mammothrotor
NJ
00
vo
Oxygen supply
efficiency
(kg-02/kwh)
Current speed
(cm/sec.)
MLSS distribu-
tion (Standard
deviation/mean)
Section shape of ditch:
4.4 m (width) xi m (water depth)
0
40
20
10
0
20
Section IV
— Mean current speed
.-—Minimum current speed
10
15
20
Section shape of ditch:
2.5m (width) x 2.5 m (water depth)
Oxygen supply
efficiency
(kg-02/kwh)
0
40
Current speed 30
(cm/sec.)
20
10
MLSS distribu-
tion (Standard
deviation/mean)
O 72 rpm
A 48 rpm
Section IV
Mean current speed
Minimum current speed
O 72 rpm
A 48 rpm
O
A
D
O
Section
IV
V
VII
Power density (W/m
10 20 30 40
Power density (W/m3)
50
-------
Table 5 Overview of Aeration Performance
(3/4)
NJ
VD
O
Orrotor
Section shape of ditch:
3.0 m (width) xl.5 m (water depth)
Sigmarotor
Section shape of ditch:
2.4 m (width) X2.0 m (water depth)
j
Oxygen supply
efficiency
(kg-02/kwh)
1
0
40
30
Current speed
(cm/sec. )
20
10
0
20
MLSS distri-
bution (Stan
dard 1Q
deviation/
mean) (%)
0
jf
Section V
— — ^ — — — Minimum current sr>(?i?cl
.
__- O
P >*~ n w
/ ~°
- r-*~
I'
A
v
\ O Section I
\ A Section II
\ D Section III
<^\ O Section IV
/^ii " Section V
. "W II i/ *
j
Oxygen supply
efficiency 2
(kg-02/kwh)
1
0
40
30
(cm/sec. )
20
10
0
20
MLSS distribu-
tion (Standard
deviation/ IQ
mean) (%)
0
~~-^
-
Section v
/.
o Section II
A Section IV
D Section V
O Section VI
-Hfc-J * 6—.
10
15
20
25
10
15
20
25
Power density (W/m3)
Power density (W/m )
-------
Table 5 Overview of Aeration Performance
(4/4)
Carousel Aerator
Section shape of ditch:
Draft Tube Aerator
Section shape of ditch:
6.0 m (width) xi.i m (water depth)
3
2
Oxygen supply
efficiency
(shaft power)
(kg02/kwh) i
0
40
Current speed
3D
(cm/sec.)
20
10
0
20
MLSS distribu-
tion (Standard 10
deviation/mean )
0
j . u in vwiuuii/ " x. / in iwdtei: ueptii; J
&v>
Section IV
—^— Mean current speed
— — Minimum current speec
r_-— 1>-
X'0
-------
(5) Discussions on Oxidation Ditch Process
The technology of the aerators was assessed, lead to many dis-
cussions were of the oxidation ditch itself.
At first, the problem of load fluctuation was discussed. Load
fluctuation is great in small sewage treatment plant and, even
though the ability of the ditch method to withstand the fluctuation
is high, it is still limited. If the amount of influent water in-
creases, the surface overflow rates at final sedimentation basin
increases, the size of floe becomes small after aeration for a long
time, and settling of sludge in the ditch becomes increasingly dif-
ficult.
Because of this, a method of changing the water level in the
ditch can be considered, with which the direct influence of fluctu-
ation in water volume upon the final sedimentation basin can be
prevented. This can be easily performed by connecting the ditch to
the final sedimentation basin with a pipeline instead of the open
channel conventionally used. Another advantage of this method is
that, if water volume increases, the submerged depth of aerator
blade increases, resulting in an increased amount of oxygen supply.
If water volume decreases, the opposite phenomenon will occur.
The idea of this method was proposed by a manufacturer who used a
vertical shaft type aerator, and this idea is considered to be
very interesting since it is also able to provide a stable quality
of treated water.
Secondly, the problem of treatment flow was discussed. Oxi-
dation ditch method was originally invented by Dr. Pasveer of
Holland. Pasveer's ditch consists of a simple batch-operated ditch.
However, treatment of continuously influent sewage by the batch
method alone was difficult to perform by the control techniques at
that time and, thus, the flow has changed to the present type of
flow having an independent final sedimentation basin as the size
of sewerage has increased.
However, sludge in the ditch does not easily settle, MLSS
concentration is high, and a small surface overflow rates of 10
to 15 m3/m2-day is requested for the final sedimentation basin,
292
-------
thereby increasing the construction cost. On the other hand, in
the case of batch method, a large area of ditch itself can be uti-
lized as sedimentation ditch, which is advantageous in view of
both the construction cost and treatment performance. At present,
control devices such as automatic valves and level switches are
widely being used and, thus, the usefulness of batch type Pasveer's
ditch should be revalued.
Thirdly, the problem of ditch water depth was discussed. Con-
ventionally, water depth of about 1 m was prescribed in view of
current speed and low construction cost. Therefore, a large site
was needed and installation was possible only when the land was
inexpensive. However, unlike the past when work was mainly per-
formed by manual labor, most work is now performed mainly by machi-
nery so that deep excavation is now possible by the same machine
and at the same price. Also, it is now possible to efficiently
impart a current speed by improving the aeration equipment. During
technology assessment, it was found that a required current speed
can be obtained from an economical ditch with a depth of 2.5 m, so
that now it seems to be possible to build and use inexpensive
ditches.
293
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
CURRENT STATUS OF DEVELOPMENTS
IN
AUTOMATIC WATER QUALITY
MONITORING EQUIPMENT
FOR
WASTEWATER TREATMENT
September 19-21,1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Ken Murakami
Water Quality Section
Public Works Research Institute
Ministry of Construction
295
-------
TABLE OF CONTENTS
Page
1. INTRODUCTION 297
2. PERFORMANCE EVALUATION OF WATER QUALITY ANALYZERS FOR TREATMENT
PROCESS CONTROL 297
2.1 PERFORMANCE EVALUATION OF pH METERS 298
2.2 PERFORMANCE EVALUATION OF DO METERS 309
3. AUTOMATIC SAMPLER FOR WATER QUALITY MONITORING 324
4. AFTERWORD 33°
296
-------
1. INTRODUCTION
Automation of the measurement of water quality is important for the
sewerage because it concerns the control of treatment processes and the
monitoring of raw sewage and treated effluent. In view of this, both
users and manufacturers are endeavoring to develop instrumentation
technologies. Fully aware of the needs for the improvement of water
quality measurement, the Ministry of Construction is conducting a
contract research program, covering evaluation of the performance of
automatic water quality analyzers for treatment process control,
development of automatic sampler for water quality monitoring,
development of automatic instruments for measuring total phosphorus and
total nitrogen, and automation of analyzers for laboratory use. This
paper deals with the performance evaluation of the automatic water
quality analyzers and the development of automatic sampler for which
there has been some progress.
2. PERFORMANCE EVALUATION OF WATER QUALITY ANALYZERS FOR TREATMENT
PROCESS CONTROL
In recent years, more and more sewage treatment plants have come to
use automatic water quality analyzers for water quality monitoring and
automatic control of treatment processes. Almost all new plants use semi
or fully automatic water quality analyzers. The effectiveness of these
instruments in the operation of sewage treatment plant is largely
dependent on the measuring accuracy, mechanical reliability, and
maintainability. Particularly in the case of automatic control of
treatment processes, the reliability of the automatic control is
dependent on the reliability of the sensors used.
297
-------
In generalr the performance analysis of automatic water quality
analyzers is conducted in two stages: (1) evaluation of basic performance
using clean water, and (2) evaluation of practical performance under
actual service conditions. In many cases, the performance stated on the
manufacturer's catalog refers to the basic performance (1). The
inspection standard of the manufactures association and the Japanese
Industrial Standards guarantee the basic performance. But, regarding the
practical performance (2), it is rarely the case that users can obtain
substantial information from manufacturers because manufacturers usually
do not have suitable sites for carrying out field tests. Some
information is available from users. Such information, however, is based
on an individual instrument, and is not made public in many cases.
Concerned about this situation, the Department of Sewerage and
Sewage Purification, Ministry of Construction, started a field survey for
evaluation of performance and reliability of automatic water quality
analyzers which were commonly used in sewage treatment plants. The
survey has been carried out as contract research with the Association of
Electrical Engineering. The Association organized a committee consisting
of members representing both manufacturers and users to conduct the
survey. The committee began with the pH meter, and conducted field tests
over a period of 8 months in cooperation with four manufacturers. Then,
the field tests on DO meters were begun in cooperation with eight
manufacturers, and will be completed shortly.
2.1 PERFORMANCE EVALUATION OF pH METERS
1) Test methodology
The evaluation.of an instrument may change depending on the
test methodology. After a series of heated discussions concerning
methodology, the committee decided upon the following method for the
purpose of examining the maintenance frequency to ensure correct
measurement and the mechanical reliability of the instruments.
(1) Each participant manufacturer to offer two identical pH meters,
one for operation without maintenance (unattended electrode)
and one for operation with maintenance including calibration at
specified interval (attended electrode).
298
-------
(2) Test at two sites, one representing bad water condition (such
as grit chamber) and one representing fair water condition
(such as aeration tank).
(3) Design and installation method of the test instrument to be
left to the discretion of each participant manufacturer;
provision of an automatic cleaning device also to be decided by
manufacturer.
(4) The installation of each instrument to be by its manufacturer,
but maintenance to be the responsibility of the Association of
Electrical Engineer.
(5) All the electrodes furnished by the manufacturers to be
operated in so far as possible under the same water quality
conditions.
(6) One series of tests to last 2 months with regard for the limit
of unattended operation; two series of identical tests to be
performed at both grit chamber and aeration tank.
(7) Weekly or fortnightly measurement of pH by a meter for
laboratory use on the occasion of instrument maintenance, which
is considered a good approximation of the true value.
(8) Checkup of both attended and unattended electrodes with a known
pH solution for responsiveness after every series of tests.
(9) Every manufacturer to inspect and adjust the electrodes after
each series of tests; the same electrodes to be used over the
entire test period unless damaged.
2) pH meters tested and their installation
The pH meters furnished by the four participant manufacturers
were all fitted with an automatic cleaning device. Their
installation schemes are as shown in Figs. 1 to 4. Electrode
holders at the grit chamber, were quite lengthy, because the depth
from ground level to the water surface would reach to about 7 m.
299
-------
The pH meters furnished by manufacturers A and B used
disposable cartridges for the sensing elements, while those
furnished by manufacturers C and D employed a combination electrode
of a glass electrode, reference electrode and a thermistor. The
automatic cleaning device was of the water jet type for A's test
instrument, of the ultrasonic type for B's, of the continuous air
bubble type for C's and of the ultrasonic/intermittent air jet
combination type for D's.
3) Results
The tests started on September 10, 1981. In the first two
series of tests conducted at the grit chamber, the recorders and
other parts were frequently out of order. The period during which
measurement was obtained compared to total test period was 91%, 58%,
88% and 89% for A, B, C and D, respectively. The failures were
mostly attributed to the recorders, though some of the pH meters
stopped intermittently. The failures of the pH meters themselves
included electrode damage due to floating materials, deterioration
of electric insulation between the glass electrode and reference
electrode, the slackening of internal solution makeup pipe,
disconnection of cleaning water pipe, etc.
As the return flow with high pH from the sludge treatment
process is drained just upstream of the grit chamber, the
measurements were affected by this return flow. Therefore, pH
readings differed depending on the location of the meters, making it
difficult to compare the readings directly. The water level in the
grit chamber changed for more than expected, hampering normal
measurement when the water level dropped so much as to expose the
electrodes above water.
300
-------
CO
A
KCI /
Reservoir
Tank
I!
pH Electrode
Water Jet Nozzle
Rope
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Supporting Post
Fig. 1 Conceptional diagram of installation, model A pH meter
301
-------
pH Transducer
T Gallery
pH Electrode
US Transmitter
Fig. 2 Conceptional diagram of installation, model B pH meter
Hook
Electrode Hanging Rope
Being Wound Up
Pipes
Frame Rope Holding Pipe
Holder
Guard Pipe
Fig. 3 Conceptional diagram of installation, model C pH meter
302
-------
US Generator
*
Tf
I"
o
r^
ro"
(l_
i
CO
/
- -
- -
Holder (nt
>.pH E
_x- - -
_ _ _ _
_ _ - - _
- - - -
Electrode
Fig. 4 Conceptional diagram of installation, model D pH meter
During the test period, there was noticed a considerable period
during which the response of the unattended electrodes seemed to be
lost as compared with the attended ones. One of the assumed causes
was that foreign objects encrusted the entire surface of the
unattended electrode and in consequence checked the water exchange
between main stream and electrode surface. The degree to which the
electrodes were covered with foreign objects varied widely from
model to model, and the difference in the structural design of
electrodes, holders and cleaning device, etc. was considered a major
factor, though the location was also a factor because the electrodes
in the upper reaches would catch foreign objects more easily than
those in the lower reaches.
On the other hand, all the tested models experienced the same
problems considered mainly attributable to poor response of attended
electrodes. It was found that these troubles were developed by the
clogging of the reference electrode junction with greasy matter.
303
-------
The electrodes were wiped with soft paper at the time of maintenance
which resulted in accelerating the cloggings. This is a matter of
maintenance procedure, and every manufacturer should improve the
maintenance manual with due consideration given to the quality of
water to be measured.
At the grit chamber, the maintenance cycle was governed by the
need for removal of bulky waste from the electrode surface. Some
electrodes were covered entirely within a week. If this problem
could be improved, then the measurement accuracy would be in a range
of pH ±0.2 to 0.3 (about 0.5 at the worst) without maintenance for
about a month, though the maintenance cycle may vary from model to
model.
The tests at the aeration tank started on January 20, 1982.
For this test, manufacturers removed or turned off the automatic
cleaning devices. Just as in the case of grit chamber tests, two,
series of 2 months tests were conducted. As the attended and
unattended pH meters showed no significant difference in
measurements even after the first two months, the calibration of the
unattended electrodes was done only with those which the
manufacturers considered necessary. The maintenance cycle for the
attended electrodes for the second series was set at once every two
weeks.
The period during which record of measurement was obtained
compared to the total test period was 98%, 74%, 84% and 100% for A,
B, C and D, respectively. Most of the failures were attributed to
the failure of the recorders. Only a single failure was noticed of
a pH meter when its reference electrode internal solution makeup
pipe came off. Fig. 5 shows part of the recording taken after about
the first two months of tests. The first series ended on March 25
and the unattended electrodes were serviced. After cleaning, the
unattended electrodes were used to measure a standard solution at pH
6.92; the readings with A, B, C and D electrodes were 6.96, 7.15,
7.16 and 6.92, respectively. For a standard solution of pH 4.00,
they showed respectively 4.00, 3.90, 4.05 and 3.93. Thus, A's
unattended electrode was remitted from calibration, and the
unattended electrodes furnished by B, C and D were calibrated.
304
-------
o
Ln
(MHHHMHHHMHt IHWWIHtlHIHIIH
IIIMIIIIIIIIIIIIIIItlltllimillllHIIMII
22
23
24 25
March, 1982
26
27
28
29
30
31
. Without With
* * Mainte- o Mainte-
nance
nance
Fig. 5 Comparison of pH readings (Last portion of the 1st series and
first portion of the 2nd series tests in an aeration tank)
-------
In Fig. 5, it is shown that B's unattended electrodes produced
a considerable error at the end of the first series. The solids
lodged between the electrode surface and ultrasonic cleaning device
were considered responsible for the trouble. Though not shown in
the figure, C's attended and unattended electrodes sometimes created
a differential of about 0.4 pH in measurements. This may have been
caused by the accumulation and subsequent dropping-off of slime on
the electrode surface. The measurement errors were not always
limited to the unattended electrodes, but were found with the
attended electrodes as well. As in the case of grit chamber tests,
the fouling of the reference electrode junction may have been the
cause of the measurement errors by the attended electrodes.
A record of measurements taken about 1 week after the start of
the second series (about 80 days after the start of the first
series) is shown in Fig. 6, and a record of measurements taken about
2 months after the start of the second series (about 4 months after
the start of the first series) is given in Fig. 7. According to
Fig. 6, it is found that C's unattended electrode began to record a
measurement error about 10 days after the start of the second
series. About 2 months after the start of the second series, C's
recorder got out of order and, therefore, record was not obtained.
Errors went up and down cyclically just as in the case of the first
series. As regards B's unattended electrode, similar fluctuations
though with much less magnitude were noticed.
As is evident from Fig. 7, the measuring was of fairly good
standard. Judging from the May 15 data showing pH changes, the
unattended electrodes showed good response characteristics.
After tests, a standard pH solution was measured with the
unattended electrodes for the purpose of checking their response
time. A's and B's electrodes showed a response time of 2 to 3 min.,
while C's and D's were about 10 min. The difference between the pH
value of the standard solution and the measured pH value was within
0.2 by A's and D's and in the range of 0.2 - 0.6 by B's and C's.
306
-------
LO
O
April, 1982
Fig. 6 Comparison of pH readings (First portion of
the 2nd series test in an aeration tank)
f Without
* * Mainte-
nance
With
B Mainte- '
nance
-------
OJ
O
00
6 : itIIIIIIIIIHIHIHIIII HHIIHIIHIHIIHIIII IHIIIIIIIIIIIIIIHIIH IIIIIIIIIIIIHIIIIIIIH Illllllllllllllllllllll IIIIIIIIIHIIIIIHIIIII IIIIIIHIIHIIIIIIIIIII MMIHIIIIIIMIMHIII IHIHIIIIIIIIIHIIIIII HH
6 : iiMiiiiiiiiiiiiiitmt mmHmtmmmH mmiiiiiiiiniHiiii iiiiiiiiiimiiiimw mwHmwwww IIIIIMIHIIIIIIIIIIIH iiiiiiiiiniiiinwm H«HH«Hiiiiiiimiii|niiiiiii
11 12 13 14 15 16 17 18 19
PH
•? =
/ :
R =
Model C
11
12
13
14
15
16
17
18
19
20
6
11
19
20
Without With
« Mainte- B Mainte- '
nance nance
Fig. 7 Comparison of pH readings (Last portion of
the 2nd series test in an aeration tank)
-------
4) Summary
So long as the electrode surface can be prevented from becoming
encrusted with foreign matter, the pH measurement of influent at the
grit chamber will be accomplished with an accuracy of ±0.2 to ±0.3
(±0.5 max.) if the pH meter is maintained about once a month. All
the models need much improvement from the viewpoint of structural
design. The electrode holder and automatic cleaning device should
be designed not to become easily tangled with large floating
substances. At the grit chamber, the flow velocity is comparatively
high, and the distance is great between the ground level and the
water level. Accordingly, the electrode holder becomes awkwardly
large, making the maintenance work very difficult. Cleaning the
electrode surfaces with a soft material like tissue paper or gauze
is liable to clog up the reference electrode junction. Cleaning
with a detergent or acid solution is a better method.
With regard to the aeration tank measurement, maintaining an
accuracy level of ±0.2 in pH value required a maintenance cycle of
about once a month for some models and once every two to three
months for other models. This difference would have been caused by
the electrode installation method rather than by the performance of
the electrode itself. Most of the electrodes could be cleaned
satisfactorily with soft materials like tissue paper, but for some
models particularly when their reference electrode junctions were
made of ceramices this method was inadequate as in the case of
measurement at the grit chamber.
2.2 PERFORMANCE EVALUATION OF DO METERS
1) Test methodology
Basically the same methodology as with the pH meter was used
with the exception of the following points with regard for DO meter
characteristics.
(1) At the sewage treatment plant, the DO meter is used mostly in
the aeration tank. Therefore, the test site was limited to the
aeration tank only.
309
-------
(2) One series of tests was set at 4 months as it was considered
that the instruments would serve for a considerably long period
without maintenance at the aeration tank. The total test
period was set at 8 months to repeat the same tests by two
series.
In the pH meter tests, there was a considerable period
during which the recordings were unavailable because of
recorder failures. For this reason, each manufacturer was
asked to use a recorder which was unlikely to fail.
2) DO meters tested, and their installation
Eight manufacturers participated in the DO meter test program.
Of these eight, two manufacturers used electrodes of the same make,
and another two manufacturers used electrodes of another make. The
remaining four manufacturers used electrodes of their own.
Therefore, six types of electrodes were used in all. E's and F's
electrodes were of the galvanic type without membrane, and the other
manufacturers used the galvanic electrodes with membrane. The DO
meters were installed at the tail end of the aeration tank at an
interval of about 3 m, so that the DO meters could be tested at a
place with large DO fluctuation. Figs. 8 through 13 show the
installation schemes. Model E and F DO meters employed the
electrodes of the same make, and G and H DO meters also used
identical electrodes. For this reason, the installation schemes for
E and H are not shown.
A's electrode was installed in a protection tube, permitting
removal for maintenance by pulling up on the electrode cable. Other
manufacturers' used an electrode integrated rigidly with its
holder. The size and weight of the electrode holders vary
considerably for different manufacturers. This factor affected the
ease of maintenance also greatly.
The electrodes of A, C and D were not fitted with an automatic
cleaning device. B's electrode used a continuous air bubble
cleaning device, and E's and F's used a continuous filing for
cleaning. G's and H's employed an automatic intermittent water-jet
cleaning device.
310
-------
PVC Guard Pipe
DO Electrode
Fig. 8 Conceptional diagram of installation, model A DO meter
311
-------
• Holder Support
V
.0 '
0.
DO Electrode and
Cleaning Device
Fig. 9 Conceptional diagram of installation, model B DO meter
312
-------
Holder
Holder Support -
250/
V
. Metal Fitting
Fig. 10 Conceptional diagram of installation, model C DO meter
313
-------
Handrail
Holder Support
Holder
DO Electrode
Fig. 11 Conceptional diagram of installation, model D DO meter
314
-------
0133
PVC<
SUS'
TEF'
1
^*
XJ-
'l
s*
.
CO
5
i
•o
o
I
1070
- *— -
8
(N
1. ~
042 c
3 S
*~
a
o
SO]
0
n ^
a
V
Q
3
Fig. 12 Conceptional diagram of model F DO meter
315
-------
Cleaning
Controller
Transducer
Hook
Fittings
Holder
DO Electrode
Fig. 13 Conceptional diagram of installation, model H DO meter
3) Results
The first series of tests started on October 25, 1982, and
ended on March 2, 1983. The second series is now in progress. In
the first series, almost every DO meter could furnish data for the
entire period as the recorder failure was minimal.
Figs. 14 through 18 show examples of DO recordings taken 4
weeks, 8 weeks, 10 weeks and 17 weeks after the first series began.
In these figures, the solid lines show the measurements by the
attended electrodes, and the dotted lines by the unattended
electrodes. In the 4th week, a slight difference in measurement
between the attended and unattended electrodes of A, D, E and F were
seen. Of them, the measurement errors of A, E and F were found
ascribable to the attended electrodes. The errors with A's attended
electrode was due to the fact that the calibration was made before
the temperature of the electrode internal solution was balanced with
that of the standard solution.
316
-------
As the ambient temperature fell, the temperature difference
between the aeration tank water and the standard solution reached 15
degrees centigrade or more, and the trouble occurred probably
because the volume of internal solution in A's electrode was
relatively large. The troubles with E's and F's electrodes were
found to be invited because the ionic strength of standard solution
used at the time of calibration was below a specified value. F's
attended electrode disclosed erratic measurements on and off in the
4th week, and thereafter. Later the trouble was identified as
attributable to the exposure of the electrode due to a drop in water
level. D's measurement error was caused by the degradation in
sensitivity of the unattended electrode as its membrane surface
began to be contaminated.
Entering the 8th week, the measurement by D's unattended
electrode fell further as shown in Fig. 15. Also, H's unattended
electrode showed a slight decline in measurement. The measurements
by the unattended electrodes of A, B and C tended to fall slightly
in a higher range of DO.
According to the recordings for the 10th week appearing in
Fig. 16, it is found that the measurements by the unattended
electrodes of D, H, etc. fell markedly. As there was little point
in continuing tests with these electrodes, it was decided that the
manufacturers could maintain the unattended electrodes if they
wanted to, and could restart the test. On January 11, D and H
conducted the servicing of unattended electrodes, and on January 18,
A and B conducted servicing. After washing of the membrane
surfaces, these electrodes showed little or no drift in both zero
and span; the drift was about 1% for most electrodes and 5% at the
worst. It was therefore concluded that the degradation in
measurements must have been due to the fouling of membrane
surfaces. C, E, F and G chose to continue the four-month continuous
tests as originally planned without servicing the unattended
electrodes.
According to Fig. 17 showing the measurements in the 14th week,
the electrodes showed satisfactory values on the whole, though there
was some difference in measurement between the attended and the
unattended. The differences of E's and F's electrodes were fairly
significant.
317
-------
OB 1 • » / 1 )
Model A
26 27 28 29
00 t•a / 1 J
23 24 (2§) 26 27 28 29
DO 1 » o / 1 )
26 27 28 29
Model D
23 24
00 (no/1)
26 27 28 29
23 24 (2S) 2
27 2B 29
DO (»»/!)
27 28 29
26 27 28 29
With Maintenance
Without Maintenance
Fig. 14 Comparison of DO readings (4th week)
318
-------
OB t•g/ 1 )
Model A
25 24 25 26 27
..DO (••/!) Model H
2'
0^
>***V
2 I
/•* —
**&*s
25 24 25
December, 1982
/
A i
rjf*Vr
26
"•X.^,^
-^M
—L
27
Without
intenance
Maintenance
Fig. 15 Comparison of DO readings (8th week)
319
-------
1 0
8
6
4
2
0
08 ( m,I 1 )
Model A
^^
VA.
\
—4 V
yj ^
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L-r^\.
x«
-£»v^
Y
j/A*»-'"^"-«
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x/
04 (§J) 06
D 8 ( »p/l )
07
Model B
08 09
1 0
06 07 08 09 10
Model D
i o-
":
b-
4'
2'
^W«'~."V
"'N.
^^
r X
V.
/\
/ v
•A7
X-N^
f X
x_
lr
/~~S-S.
/
/
ts*1*^1
LJ-'^S-l
\^
XA
08 t
Model E
*~«b~_
^Vi
Jjfi^-
V
V
/\
/ V
^J v
/*^L
V
/*S5**«^,
/
•.-/^W*****
04
06 07 08 09
04 $S) 06 07
D 8 1 • » / 1 ) Model H
OB 09
1 0
^•v
r-'*V
V
/\
/ V
J v
jf~\
s* \
ni— iifl
/
B^Vv
>^
1 0
06 07 08 09
1 0
With Maintenance
Without Maintenance
Fig. 16 Comparison of DO readings (10th week)
320
-------
i u-
8"
6"
4"
A
U'
1 U
B"
6"
2"
U
1 0'
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DO t • B /
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DO t mo /
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03
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,-x
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03
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xa
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03
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03
/\
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Model A
04
Model B
AL
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Model C
Au
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Model D
/"\—i
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04
Model E
_
r\—^
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Model F
xV
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04
Model G
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05
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rf^-v
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f\_f.
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05
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05
//^^v^
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y*^-^
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r^"^ fl
l^j 'ter
06
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j^y1^ ^^"
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06
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_(^~\
r «\ ,
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~\Z&
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— ~ rA_
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01
03 04 05 08 07
February, 1983
With Maintenance
- Without Maintenance
Fig. 17 Comparison of DO readings (14th week)
321
-------
1 0
DC I . » / 1 1
Model A
22
28
i 0-
8'
B'
4'
J'
<^*^5x
«a#s
° 22
DO (•»/
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8'
b-
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ffP***^
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f \;
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1 0'
8'
8'
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17 ^\A
° 22 £s)
DO ( BO /I >
1 0'
B1
6'
4:
'i'
^^^
•/V">*;^v
"^ ^?P
[/£"•"••••
>JV
' » ^
nDO (••/!)
1 0-
B-
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i'
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8'
*:
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^/^•^
HA- »
22 ' (5J)
DO (••/!)
xVx
•J^ ~*^$L
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y^~ "^\ft
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24
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24
\^/>
25
Model 0
•~ — v
\s-
25
Model E
/*"> I ^-
rtjf/^y^-H.
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u
24
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24
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, / \-
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24
^^^
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25
Model F
X*"- -\
Vy
25
Model G
V
V
2 5
Model H
^^-^\
" ^\
^
ff'^^is^
r ^S(f
26
-X^-~^
r "S^
26
f ^~^&
26
26
_ _
/• "^r
26
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27
,s~~*~ ~~*
27
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27
_r/=N«^»
27
jt+>^^*£
27
_^n^w
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><*
28
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28
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28
ff^f/\
/^-•-tt^i
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28
-_,
v^ 'LV
V^
28
*Z~~?3>.
Hr*
24 25 26 27 28
February, 1983 With Maintenance
............. without Maintenance
Fig. 18 Comparison of DO readings (17th week)
322
-------
There were two probable causes: a reduction of flow through the
measuring cell of the unattended electrode due to the clogging of
flow passage, and a failure to calibrate the attended electrode
accurately in winter when the saturation DO concentration exceeded
the full scale of the instruments (12 mg/£).
Entering the 17th week, some models began to show a large
measurement error as shown in Fig. 18. But C's and D's unattended
electrodes which ran on for four months without any care proved
their excellent performance.
The repairs and adjustments made during the test period
included the following. The membraneless galvanic electrodes
furnished by E and F showed wide variances in measurement in the
early stages of the test period. To solve this problem, a condenser
with larger capacity was put into the electrical circuit to increase
the integral time constant. But this detracted from their response,
taking much time for calibration work. One time each A's and H's
attended electrodes experienced a bubble trapped to inner side of
the membrane. The membrane or electrode were replaced.
Automatic cleaning devices were found to be effective. G and H
used identical electrodes, and their automatic cleaning devices were
also the same type, using a water jet system. But, H's unattended
electrode deteriorated faster than G's. Probably this was due to
delicate differences in design such as cleaning intervals, water jet
pressure, and clearance between the nozzle and membrane. In other
words, the automatic cleaning is effective so far as it is carried
out properly. C tested electrodes without automatic cleaning
device, but they also installed an electrode with an automatic
intermittent air jet cleaning device at the same place as the test
electrode for the purpose of investigating the effects of automatic
cleaning. The electrode with the cleaning device was operated for
four months without servicing, but its measurements showed quite a
good agreement with those obtained by the attended electrodes even
after four months of tests.
323
-------
4) Summary
The frequency of maintenance required for continuous
measurement of DO in the aeration tank at an accuracy of ±0.2 to
±0.3 mg/£ will be about once a month at the shortest and once every
two to three months at the longest. Most of measurement error was
attributed to the fouling of electrode membrane. This can be
eliminated by washing the membrane surfaces.
The absolute value of error is high when DO is high, and low
when DO is low. It is found that the contamination of electrode
membrane surfaces little affects the response of the electrode. The
ease of maintenance differs considerably with models. Those models
which are difficult to maintain are likely to be operated without
good maintenance when actually used. The manufacturers are required
to expend more effort for improving the maintenability.
3. AUTOMATIC SAMPLER FOR WATER QUALITY MONITORING
It is of great importance not only for proper treatment of sewage
but also from the viewpoint of sludge disposal to monitor whether the
concentrations of hazardous substances in industrial effluents discharged
into public sewer system are below the limits specified in the
pretreatment standards. At present, the harmful substances contained in
the industrial effluents are usually sampled and analyzed manually. An
automatic sampler that detects abnormalities in water quality and takes
samples automatically would be an useful tool to establish a more
effective monitoring system. In view of this, efforts have so far been
made to develop an automatic sampler which can be installed at a sewage
treatment plant, pump station or within the manhole of a public sewer and
which is equipped with a pH meter that responds to abnormal pH values and
signals the sampler to take samples automatically. The antecedents of
the development of this sampler have been reported at the preceding
conference.
This kind of automatic sampler, however, cannot identify the sources
of pollutants. It is therefore strongly urged to develop an automatic
sampler that is small enough to be installed within a connection manhole
between public and private sewers.
324
-------
At present, the development of this sampler has been promoted by the
Association of Electrical Engineering at the request of the Ministry of
Construction. Three different prototypes are under field tests for
improvement. The following is an overview of the current development
status.
1) Specifications
The major performance characteristics required of the automatic
sampler are as listed below.
(1) To be small enough to be installed within the connection
manhole (standard size: 300 mm in diameter and 600 to 650 mm in
depth).
(2) To be made of corrosion-resistant materials; and to accommodate
electrical components into a totally sealed enclosure.
(3) To be able to sample more than 100 m£ at a time, and to be able
to sample more than 4 times in succession.
(4) To sample water when the pH value of the water has run in
excess of a preset range, when the water level in the manhole
has exceeded a preset value, or when the above two conditions
have concurred, or to sample water at predetermined intervals.
(5) To be capable of recording or memorizing the times sampled and
pH values.
(6) To be powered with a battery with a capacity to run the sampler
for at least a week within the connection manhole.
(7) To permit free adjustment of waiting time from the installation
in the connection manhole to the start of operation and of the
standby time between two successive sampling operations.
(8) To weigh less than 30 kg in gross weight or preferably less
than 25 kg.
325
-------
2) Prototypes and field tests
According to the specifications above, three different
prototypes were produced. They are being improved through field
tests. Shown on Photo 1 is A's prototype which uses a
bellows-shaped sampling bottle as illustrated in Fig. 19 instead of
a pump. The sampling bottle is set contracted in advance. When a
sampling signal is given when an abnormal pH value is detected, the
sampling bottle expands to take a sample by suction. There are four
sampling bottles in all, each with a sampling capacity of about
120 mjfc. For the purpose of protecting the pH electrode, a trough
with a semicircular cross section contoured to fit the invert is
provided at the bottom. The weirs on both sides of the trough hold
water in the trough even when there is no flow in the manhole. This
automatic sampler is equipped with an 1C memory capable of
memorizing about 1,000 pH data, and can be used as an automatic pH
monitor. What can be memorized is pH values measured every hour on
the hour and pH values measured at an interval of 1 min. after
sampling.
326
-------
Ratchet Solenoid
Sampling
Tube
Bellows Shaped
Sampling Bottle
Bottle Clutch
Fig. 19 Sampling mechanism
Prototype B is as shown on Photo 2. It uses a vacuum pump to
take samples into a glass sampling bottle. The prototype has six
sampling bottles in all/ each having a capacity of 600 m£. The
bottom is provided with a trough having the same shape and function
as A's.
Prototype C is shown on Photos 3 and 4. The sampling is
carried out by making use of a vacuum pump just as with Prototype
B. It has six sampling bottles with a capacity of about 200 m£
each. This prototype is not equipped with a trough, instead a
slitted cylinder is used to accommodate the pH electrode and
sampling tube as shown on Photo 4. At present, field tests are
under way using these automatic samplers, and efforts are being made
to improve their performance with emphasis on the mounting methods
of pH electrode and sampling tube head. It is expected that they
will be refined enough to withstand practical usage.
327
-------
Photo 1
Photo 2
328
-------
Photo 3
Photo 4
329
-------
4. AFTERWORD
As regards the automatic water quality analyzers for treatment
process control, the performance evaluation of pH meters and DO meters
has been nearly completed, and the maintenance frequencies necessary for
required accuracy and the modes in which the errors appear have been
clarified. The series of field tests conducted would have been usefull
and rewarding to all the participating manufacturers in various ways ar
they could learn what the actual installation environment is. The
automatic sampler for water quality monitoring would go a long way towa> d
improving the monitoring systems for industrial effluents. Some sewerac
authorities have already started a study to apply this kind of automatic
sampler for reinforcing their water quality monitoring systems.
To close this paper, the author would like to express profound
gratitude to the engineers of the sewage treatment plants and
manufacturers for their unlimited assistance and cooperation extended
during the survey.
330
-------
Ninth US/Japan Conference
on
Sewage Treatment Technology
NITROGEN AND PHOSPHORUS
BIOLOGICAL REMOVAL SYSTEMS RESEARCH
September 19 -21, 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Kazuhiro Tanaka
Section Chief
Research and Technology Development Division
Japan Sewage Works Agency
331
-------
CONTENTS
Page
1. INTRODUCTION 333
2. OUTLINE OF SURVEY BY PUBLIC WORKS RESEARCH INSTITUTE .. 336
2.1 Improvement of Nitrification and
Denitrification Process 336
2.2 Survey concerning the Simultaneous Removal of
Nitrogen and Phosphorus through Addition of
Coagulant to Single-Sludge Recycling System 342
3. SURVEY BY JAPAN SEWAGE WORKS AGENCY 346
3.1 Experimental Facility and Operating Method 346
3.2 Operational Results 351
3.2.1 Phosphorus Removal 354
3.2.2 Nitrogen Removal 367
3.3 Results of Flow Rate Fluctuation Survey 370
3.4 Sludge Production 370
3.5 Others 373
3.5.1 BOD, COD and SS Removal 373
3.5.2 Sludge Characteristics 373
3.6 Summary 373
ACKNOWLEDGEMENT 373
BIBLIOGRAPHY 374
332
-------
1.
INTRODUCTION
The phenomenon of eutrophication in Japanese closed waters has
been in progress for a long time, but it is only since about 1979
that definite countermeasures have begun to be taken. Specifically,
it was in 1979 that the Environmental Agency first indicated its
guidance policy concerning phosphorus reduction in the Seto Inland
Sea. Furthermore, prefectural ordinance effluent standards for
nitrogen and phosphorus were set for Lake Biwa and Kasumigaura, as
shown in Table 1, and definite control of nitrogen and phosphorus
was commenced accordingly.
Table 1 Nitrogen and Phosphorus Effluent Standards
at Lakes Biwa and Kasumigaura
(mg/Jl)
01
-------
In December, 1982, the Environmental Agency announced environ-
mental standards for nitrogen and phosphorus in lakes and marshes,
and the work of setting effluent standards for nitrogen and phos-
phorus is now being handled by the Central Council for the Control
of Environmental Pollution.
Eutrophication control has thus become nationwide and techno-
logical steps to remove nitrogen and phosphorus are now required
for sewage systems, too.
The research for advanced wastewater treatment in Japan com-
menced around 1971 when the Public Works Research Institute of the
Ministry of Construction established a 250 m3/day pilot plant at
the Shitamachi Sewage Treatment Plant in Yokosuka City and commenc-
ed research into the removal by chemical coagulation of phosphorus
from secondary effluent. Later, surveys and research were also con-
ducted by the Japan Sewage Works Agency, Sapporo City, Tokyo Metro-
polis, Yokohama City, Yokosuka City, Osaka City, Kobe City and
Fukuoka City etc. as developments towards advanced wastewater treat-
ment technology.
Surveys and research concerned mainly with the physicochemi-
cal treatment and their results were brought to the Tertiary Treat-
ment Cooperative Conference (later renamed the Advanced Treatment
Conference) established by the Ministry of Construction in 1971,
and the collection and exchange of information were actively
carried out at this conference.
With the continuing oil crisis of the first four years of the
1970s as a juncture, the reduction of necessary materials and
energy consumption began to be required of sewage treatment. Under
these circumstances, the emphasis in advanced wastewater treatment
technology development shifted from the physicochemical process to
the biological process for nitrogen and phosphorus removal.
Since 1978 the Public Works Research Institute has been study-
ing the removal of nitrogen by single-sludge nitrification/denitri-
fication process and also the simultaneous removal of nitrogen and
phosphorus by the addition of alum at the pilot plant established
at the Toba Sewage Treatment Plant in Kyoto City. Furthermore, it
334
-------
.ias been conducting demonstrative studies into biological nitrifi-
cation and denitrification at a 1,500 m3/day sewage treatment plant
since 1981, in cooperation with Hamamatsu city.
In 1980, the Japan Sewage Works Agency began demonstrative
studies into nitrogen removal by the single-sludge nitrification/
denitrification process at the Arakawa Wastewater Treatment Plant
in Saitama Prefecture and research concerning the removal of nitro-
gen and phosphorus by the anaerobic and aerobic systems is continu-
ing.
Local public entities are also deeply interested in the remov-
al of nutrient salts by biological systems, and related surveys
and reserach are being conducted by Ibaraki Prefecture, Nagano
Prefecture, Tokyo Metropolis, Kawasaki City, Yokosuka City and
Fukuoka City, etc. Research and development relative to the bio-
logical removal of nitrogen and phosphorus is also being actively
conducted by private research organizations.
In the 20th annual meeting of the Japan Sewage Works Associa-
tion held in Nagoya City in May 1983 , as many as 30 research
reports were made concerning the biological removal of nitrogen
and/or phosphorus and there was heated debate on the subject. A
wide range of studies was reported on, including not only the re-
moval of nitrogen and/or phosphorus by anaerobic and aerobic acti-
vated sludge processes but also the combined use of these with the
physicochemical process and the application of the anaerobic and
aerobic methods to the oxidation ditch and rotating biological
contactor processes.
As seen above, the development of advanced treatment techno-
logy concerning nutrient salts is being advanced with the view to
expand the function of the conventional biological process and to
improve the secondary treatment facilities for the future setting
of effluent standards for lakes and marshes.
This article deals with the surveys and research conducted by
the Public Works Research Institute and the Japan Sewage Works
Agency concerning the biological removal of nitrogen and phosphorus.
335
-------
2. OUTLINE OF SURVEY BY PUBLIC WORKS RESEARCH INSTITUTE
(2)
2.1 Improvement of Nitrification and Denitrification Process
In cooperation with Hamamatsu City, the Public Works Research
Institute has been improving existing biological nitrification/
denitrification facilities in order to bring about system simplifi-
cation and treatment cost reduction.
The Hitomigaoka Purification Center in Hamamatsu City is a
small sewage treatment plant with a designed daily average flow of
about 1,500 m /day. Since its discharge goes into Shonai Bay, the
targeted quality of effluent discharge is extremely severe, as
indicated in Table 2. Originally, this sewage treatment plant was
designed as an extended aeration process but advanced treatment
facilities comprising a nitrification tank, a denitrification tank,
coagulation and flocculation tanks, a rapid sand filter and an
activated carbon column were put into operation in June 1981 as
an addition to the existing secondary treatment facility in order
to meet these stringent targets. The flow diagram of this process
is given in Fig. 1 (a). In this flow, nitrogen is removed by
nitrification/denitrification (addition of methanol) after second-
ary treatment; there is no clarifier between the nitrification tank
and the denitrification tank and a two-sludge system is at work
there. The final effluent fully satisfied the target values shown
in Table 2 thanks to the addition of the advanced treatment facili-
ties. However, there were such problems as a complicated process
configuration and the high operational cost of power and chemicals.
Meanwhile, the secondary treatment facility is, as already state,
designed as an extended aeration process, and, moreover, the volume
of sewage that actually flowed in represented only 50^60% of the
designed value and thus the secondary treatment facility could be
diverted to other uses. So, the operation of the two-sludge nitri-
fication/denitrification system was stopped and operation was shifted
to a single-sludge recycling nitrification/denitrification system
336
-------
(a)
1
1
ox 'ox
1
ST(I)
NT
DNT
Dischar
(b)
BR
i i '
i i i
AN| OX,AN|OX
ST(I)
PT
DIT
UF
Discharge
(c) •
OX | AN | AN |OX
1 1 i
ST(I)
PT
DIT
UF
Discharge
(d)
BR
' 1 1
OX[AN [AN [ ox
UF
Discharge
BR : Biological Reaction Tank, AN: Anoxic, OX: Oxic, DNT: Denitrification Tank
DIT: chlorination Tank, ST(I): Sedimentation Tank (I), ST(II): Sedimentation Tank (II)
UF : Upflow Filter, NT: Nitrification Tank, PT: Coagulation/Filocculation Tank, CA: Carbon Column
Fig. 1 Flow Diagram of Hitomigaoka Purification Center
-------
(recycling system) and single-sludge non-recycling nitrification/
denitrification system (non-recycling system), using the existing
aeration tank. It was found from the operation results in flow (a)
that an activated carbon column was not especially necessary to
achieve the targeted effluent quality.
Operation was thus carried out according to the flows shown
in (b), (c) and (d) of Fig. 1. In Flow (b), the first and the
third of the four cells into which the aeration tank was divided
were anoxic cells while the second and the fourth were aerobic
cells. Nitrified liquid was recycled from the second cell to the
first cell.
In Flow (c), the first and fourth cells were aerobic cells
while the second and third cells were anoxic cells and denitrifi-
cation was effected by endogenous respiration.
In Flow (d), the coagulation/flocculation tanks and the
chlorination tank were eliminated from Flow (c).
The survey took place from September 1981 to June 1982.
Table 3 shows the conditions of operation and Table 4 shows the
summary of operational data.
Table 2 Target Effluent Quality for Hitomigaoka
Purification Center
BOD 5 mg/£
COD 10 mg/£
SS 3 mg/£
T-N 5 mg-N/£
T-P 1 mg-P/£
338
-------
Table 3 Operational Conditions
^ ^^^low^
From
Operating period
To
Volume of influent (Q-m3/day)
L reaction tank
ogica
O
m
Return sludge ratio (r.%)
Recycling ratio (R.%)
£ Per cell
•ri Total
•S Cell 1, 2
| «£« «">•«
Q
Total
Ratio of Air Flow to
Influent Flow
MLSS (mg/Jl)
MLVSS (mg/i)
MLVSS/MLSS
SV (%)
SVI
SRT (day)
SAT (day)
Return sludge concentration
(mg/S,)
Volume of excess sludge
(mVday)
Amount of Al addition (mg-Al/H)
Amount of chlorine addition
(mg-Cl/d)
Amount of methanol addition
(mg/£)
(a)
Sep S, 1981
Oct 4,1981
907
66
0
8.6
17.2*
0*
5.2
10.4*
16.7
2,800
1,670
0.60
21
75
14.7
14.7
8,880
10.9
2.7
2.5
36
(b)-I
Oct S, 1981
Feb. 2. 1982
735
100
200
10.6
42.6
2.7
5.3
16.0
11.1
3,480
2,410
0.69
56
162
58.8
29.4
6,550
9.2
3.0
1.5
0
(b)-II
Feb 3, 1982
Feb. 22, 1982
644
110
220
12.1
48.6
2.8
5.8
17.2
10.3
1,740
1,310
0.75
23
131
57.2
28.6
3,350
7.6
3.4
1.7
0
(b)-III
Feb 23, 1982
Api. 9, 1982
707
85
200
11.1
44.2
2.9
6.0
17.8
9.4
3,500
2,620
0.75
83
228
78.2
39.1
6,320
7.1
3.1
1.6
0
(c)
Api 10, 1982
May 10, 1982
808
74
0
9.7
38.7
5.6
5.6
22.4
10.8
3,390
2,550
0.75
90
265
41.3
20.7
7,830
11.4
2.9
2.1
0
(d)
May 11, 1982
Jun. 16, 1982
829
72
0
9.4
37.7
5.5
5.5
22.0
11.8
3,440
2,510
0.73
93
270
31.0
15.5
9,840
13.6
0
0
0
Cells 1 and 2 were not used.
339
-------
Table 4 Summary of Operational Data
Flow
(a)
(b)
I
II
III
(c)
(d)
Treatment stage
Influent
Secondary
effluent
Dem tri fled
effluent
Effluent of
coagulation/
tank
Filtrate
Effluent of
carbon column
Influent
Biologically
treated
effluent
Effluent of
coagulation/
f locculation
tank
Filtrate
Influent
Biologically
treated
effluent
Effluent of
coagulation/
flocculation
tank
Filtrate
Influent
Biologically
treated
effluent
Effluent of
coagulation/
flocculation
tank
Filtrate
Influent
Biologically
treated
effluent
Effluent of
coagulation/
flocculation
tank
Filtrate
Influent
Biologically
treated
effluent
Filtrated
Water
temperature
25.2
25.5
26.0
25.7
25.7
25.3
16.9
16.8
16.9
16.9
10.5
11.0
11.0
11.0
13.5
14.0
14.0
13.5
17.7
IB. 2
18.0
18.2
22.0
21 9
22.1
pH
7.1
6.7
7.0
6.9
7.2
7.4
7.3
6.9
6.7
7.0
7.6
6.5
6.1
6.5
7.3
6.6
6.6
6.9
7.1
6.8
6.8
7.0
7.2
6.7
7.0
SS
105.0
30.0
11.0
19.0
3.0
2.0
143.0
23.0
10.5
5.0
84.0
22.0
4.5
1.5
130.0
19.0
5.4
1.4
200.0
22.0
9.0
4.0
109.0
13.0
1 0
BOD
84.3
13.2
3.4
2.2
1.1
0.6
150.0
13.0
4.0
1.8
150.0
4.6
2.1
1.0
200.0
15.0
4.2
1.5
25O.O
11.0
1.6
1.8
180.0
6.2
1.9
DBOD
5.1
1.3
1.3
1.1
0.4
55.0
1.9
1.4
0.7
34.0
1.5
1.2
0.4
89.0
2.3
0.8
0.4
51.0
3.7
100.0
1.7
1.5
COD
40.8
15.7
8 4
5.9
3.8
1.8
62.2
11.0
6.2
4.5
68.0
13.0
6.6
4.9
67.0
11.0
5.6
4.4
62 0
7.8
5.4
4.1
51.0
6.8
4.1
DCOD
4.8
4.5
3.7
3.5
1.7
31.0
5.3
4.0
3.9
44.0
6.8
4.6
4 .2
40.0
6.2
4 8
3.8
30.0
6.4
31.0
3.2
3 7
Alka-
linity
51
143
52
190
43
140
57
130
52
44
43
140
52
52
T-N
16.7
13 9
2.9
2.8
2.2
2.9
29.5
8.3
7.9
8.2
41.0
16.0
15.0
14.0
32.0
5.4
4.6
4.5
30.0
3.5
3.1
2.9
33.0
4.8
4 0
NH4-N
12.3
2.8
ND
ND
ND
ND
20.0
0.7
0.6
0.7
25.0
0.6
0.6
0.6
23.0
0.6
0.7
0.6
21.0
0.1
0.2
0.2
20.0
0.1
0.3
NOX-N
0.7
9 4
2.0
1.9
1.3
2.3
0.5
5.4
5.3
6.2
1.8
13.0
13.0
13.0
0.5
2.8
3.3
3.4
0.2
2.5
2.2
1.8
0.2
2.9
2.5
T-P
4 6
2.5
3 1
1.5
0.6
0 3
4.6
2.5
0.9
0.6
8.7
3.4
0.3
0.3
4.1
3.0
O.7
0.3
3.7
1.8
0.8
0.5
5.2
1.7
1.2
PO*-P
2.1
1.4
1 0
0.3
0.3
0.3
1.9
1.5
0.3
0.2
3.0
2.0
0.1
0.2
2.1
1.7
0.1
0.2
2.3
1.3
0.4
0.4
3.2
1.3
1.2
340
-------
The following conclusions were derived from these survey
results:
(1) Biological nitrification/denitrification process was improved
from a two-sludge system (Flow (a)) to a single-sludge recycl-
ing system (Flow (b)) to a single-sludge non-recycling system
(Flows (c) and (d)) and the T-N target quality could be
achieved by any of these systems. It is therefore desirable
that the single-sludge non-recycling system which costs the
least to operate, be adopted.
(2) Biological dephosphorization occurred in the biological reac-
tion tank by the single-sludge non-recycling system and T-P
in filtrate of biologically treated effluent decreased to a
level only slightly above the target value of final effluent
quality. It is therefore considered that the T-P target
quality can even be achieved by omitting the coagulation/
flocculation tanks, as in Flow (d), by the addition of a small
quantity of alum to the end of the biological reaction tank
or to the sand filter.
(3) If chlorine for disinfection is injected into the sand filter
influent, SS leaks into the filtrate. To achieve the target
quality value of SS = 3 mg/&, it is advisable to omit chlorine
disinfection. Even in this case, the number of coliform
groups in the filtrate decreases to less than 3,000 per milli-
liter.
(4) The target quality values of BOD = 5 mg/H and COD = 10 mg/£
could be achieved- by any of the treatment flows.
(5) From the above, the present optimum treatment flow at the
Hitomigaoka Purification Center is the formula adding a small
quantity of alum to Flow (d). The treatment cost (power cost
+ chemical cost) by this flow is 49% and 75%, respectively,
compared with Flow (a) and Flow (b).
-------
2.2 Survey Concerning the Simultaneous Removal of Nitrogen and
Phosphorus through Addition of Coagulant to Single-Sludge
Recycling System(3)
A survey designed to simultaneously remove nitrogen and phos-
phorus by adding a coagulant to the single-sludge recycling system
is being conducted at the Toba Sewage Treatment Plant in Kyoto
City, using a 300 m3/day pilot plant. The flow diagram of the
pilot plant is shown in Fig. 2. This survey concerns the phospho-
rus removal effect by the addition of alum to the recycling system,
its impact on the removal of nitrogen and the properties of sludge.
Table 5 and Table 6 shows the conditions of operation and the
summary of operational data. The following has so far been re-
vealed by this survey:
(1) SS in effluent is high in inverse proportion to the concentra-
tion of the added alum and the T-P and COD also increase ac-
cordingly.
(2) SS in effluent from this system is more filterable than that
from conventional activated sludge process.
(3) With the addition of alum, an alkalinity equivalent to 5.5
times the concentration of aluminum is required.
(4) If the concentration of aluminum added is less than 4 mg/&,
it does not affect the nitrification and denitrification re-
actions .
(5) If the concentration of aluminum added is within the range of
2^6 mg/£, the biota do not seem to be adversely affected.
(6) With the addition of alum, there is a sludge corresponding to
about 5.6 times the concentration of the aluminum added.
(7) The concentration of gravitationally thickened sludge is
2 % 3%.
(8) Aluminum does not appear to inhibit anaerobic digestion.
(9) Sludge from this system is somewhat inferior in dehydration
capacity to that from the conventional activated sludge process.
342
-------
Aeration Tank
Final Clarifier
Sand Filter
Primary
Effluent
Chemical
Addition
Ano-
xic
Aero-
bic
Aero-
bic
Aero-
bic
Recycling Liquor
Return Sludge
Thickener
Excess
Sludge
Filtrate
-*- Supernatant
Concentrated Sludge
Fig. 2 Flow Diagram of Kyoto Pilot Plant
-------
Table 5 Operational Conditions of Pilot Plant
— — _______c:ase
Aeration Tank
Influent Flow (m3/d)
Detention Time (hr)
Anoxic
Aerobic
Sludge Return Ratio (%)
Recycling Ratio (%)
Ratio of Air Flow to
Influent Flow
Excess Sludge Ratio (%)
MLSS (mg/£)
BOD-SS Loading
(kgAg-day)
SRT (day)
Temperature (°C)
Alum Dosage (mgAl/£)
Final Clarifier
Detention Time (hr)
Overflow Rate
(m3/m2/day)
Sand Filter
Filteration Rate (m/day)
I
300(S)
8
2
6
50
100
8.6
0.50
2218
0.073
10.3
25.1
0
4
15
180
II
300 (S)
8
2
6
50
100
6.2
0.40
1960
0.084
9.1
25.9
2
4
15
180
III
300 (S)
8
2
6
50
100
6.8
0.45
2914
0.064
13.2
25.7
4
4
15
180
IV
300(S)
8
2
6
50
100
8.4
0.86
3354
0.071
11.7
21.0
6
4
15
180
V
300 (V)
8
2
6
50
100
9.6
1.01
2434
0.109
8.8
17.3
4
4
15
140
(S): Steady Flow
(V): Varied Flow
344
-------
Table 6 Summary of Operational Data
to
-p-
^^•^^ Case
Items^^^
BOD
ATU-BOD
COD^
CODMn-D
SS
K-N
K-N-D
NH4-N
NOT-N
T-P
T-P-D
Alkalinity
I
Inf.
52.5
52.3
29.7
60.1
17.34
12.7
2.57
118.2
Eff.
9.3
5.5
19.4
9.4
39.6
3.05
1.09
0.0
5.6
2.49
1.95
47.7
II
Inf.
54.6
41.2
23.3
57.4
14.9
11.2
2.07
104.2
Eff.
10.4
6.3
22.1
5.8
55.5
2.82
0.62
0.2
6.4
1.43
0.20
28.8
III
Inf.
57.5
45.2
27.6
55.8
17.68
14.5
2.67
122.8
Eff.
8.2
4.6
17.6
6.9
33.3
2.47
1.09
0.6
4.4
1.45
0.16
42.2
IV
Inf.
81.0
54.9
29.9
55.7
24.20
13.7
3.11
133.3
Eff.
7.5
4.7
12.2
8.3
15.0
2.30
1.47
1.7
5.1
0.52
0.03
24.4
V
Inf.
87.7
62.9
39.3
62.4
24.81
16.8
3.00
132.4
Eff.
13.7
5.1
17.0
9.6
19.2
3.46
2.10
1.0
5.2
0.67
0.16
34.3
Inf: Primary Effluent, Eff.: Bio-Treated Effluent
-------
3. SURVEY BY JAPAN SEWAGE WORKS AGENCY
The Japan Sewage Works Agency, jointly with Shiga Prefecture
and Saitama Prefecture, conducted a demonstrative study concerning
the removal of nitrogen by the single-sludge recycling system in
1980 ^ 1982^ ', using one train of the Arakawa Wastewater Treatment
Plant, and is still studying the single-sludge recycling system
for simultaneous removal of nitrogen and phosphorus.
3.1 Experimental Facility and Operating Method
One train of the Arakawa Treatment Plant (conventional acti-
vated sludge process) was used for this survey. This train can be
operated completely independently of the others including the
return sludge system. The dimensions of the train used for the
study are shown in Table 7. This facility was remodeled according
to the flow indicated in Fig. 3. Main items for remodeling are
as follows:
(1) The air diffuser was dismantled from the first cell of the
aeration tank and two agitators (11 KW each) were installed
instead.
(2) The air diffuser was dismantled from the second cell of the
aeration tank and two aeration agitators (7.5 KW each) were
installed instead. These agitate, but can also be used as
an aerating unit by connecting a blastpipe.
(3) An submersible pump was installed at the fourth cell of the
aeration tank so that nitrified liquor could be recycled to
the second cell.
346
-------
Table 7 Dimensions of Demonstration Train
Primary
Clarifier
Aeration
Tank
Final
Clarifier
Width
(m)
4.3
9.0
4.3
Length
(m)
50.0
85.0
56.0
Effective
water
depth (m)
4.0
5.0
4.45
Number of
Tanks
2
1
2
Capacity
(m3)
1,720
3,825
2,143
Remarks
Divided
into four
equal cells
Primary
clarifier
Anaerobic Anoxic or
cell
Recycling of
nitrified liquor
aerobic
cell
Aerc Die
' cells
Agitator
Return sludge
Final
:larifier
Final
'effluent
Excess sludge
Fig. 3 Flow Diagram of Experimental Train
347
-------
The demonstration train was operated under two different con-
ditions: Operation Modes I and II. The flow of each mode is shown
in Fig. 4. In Mode I, operation designed solely for the biological
removal of phosphorus was carried out, using the first cell as an
anaerobic tank, the second and subsequent cells as aerobic tanks,
while in Mode II, the first cell was used as an anaerobic tank, the
second cell as an anoxic tank (denitrification cell), and the third
and subsequent cells were operated as aerobic tanks, with nitrified
liquor recycled from the bottom end of the fourth cell to the second
cell, and with the biological removal of nitrogen being carried out
in addition to the removal of phosphorus.
The major operating conditions in Modes I and II are shown in
Table 8.
The influent was constantly supplied and the return sludge
ratio was also constant.
348
-------
Primary
i
Anaerobic
Aerobic
Aerobic
Aerobic
Final
clarifier
\ /
Final
effluent
Return sludge ^p
(a) Operation Mode I
Primary
clarifier
Recycling of
nitrified liquor
Anaerobic
Anoxic
Aerobic
Aerobic
Final
clarifier
Final
effluent
Return sludge
(b) Operation Mode II
Fig. 4 Operation Mode
349
-------
Table 8 Operation Conditions
OJ
Ul
o
~^\^
Volume of influent
(m3/day)
Volume of return
sludge (m3/day)
Volume of recycled
liquor (m /day)
Aeration tank
detention time (hr)
MLSS (mg/£)
MLRSS (mg/£)
SRT (day)
SAT (day)
BOD-SS load
(kgAg-day)
Period
Operation Mode I
Run-1
14,340
3,480
-
6.4
2,040
14,090
12.1
9.1
0.16
Jun . 7 ^
Jun . 28 ,fe2
Run- 2
16,580
4,230
-
5.5
2,330
16,370
11.7
8.8
0.20
Jun. 29^
Jul.14,'82
Run- 3
9,620
2,450
-
9.5
1,940
14,800
12.3
9.2
0.10
Jul . 15 ^
Jul . 30 ,'82
Run- 7
10,850
2,740
-
8.5
2,620
19,330
13.7
10.3
0.13
Jan. 24^
Feb. 9, '83
Operation Mode II
Run- 4
7,110
2,430
5,700
12.9
1,950
12,720
33.1
16.5
0.06
Aug. 27 ^
Oct. 25, '82
Run- 5
8,590
3,210
5,700
10.7
3,740
19,680
63.9
31.9
0.04
Nov . 8 ^
Nov. 24, '82
Run-6
5,980
2,810
5,700
15.4
4,050
20,480
30.8
15.4
0.04
Nov. 25^
Jan. 19, '83
(Notes) 1. Each figure is a mean.
2. The aeration tank detention time is based on the volume of influent.
3. SAT is SRT for sludge in the nitrification cells.
-------
3.2 Operational Results
Summary of operational data for each run (1, 2, 3, 7) in
Operation Mode I is shown in Table 9 and for each run (4, 5, 6) in
Operation Mode II is shown in Table 10. Of these runs, Run 4 saw
heavy typhoon rain in early August and mid-September and the con-
centration of influent was lower than ordinary due to the influx
of stormwater and this condition continued for a considerable
period after the rain.
351
-------
Table 9 Summary of Operation (Mode I)
Water
temperature (°C)
PH
T-P
Soluble T-P
Soluble O-P
T-N
Soluble T-N
NHit-N
BOD
COD
ss
M-alkalinity
P/MLSS (%)
Run-1
21.6
(20.5 o, 22.1)
7.1
(7.0 o 7.3 )
3.43
(1.75 o, 4.8 )
1.84
(1.00 o 2.83)
1.57
(0.83 o, 2.58)
21.6
(14.5 % 26.8)
-
15.0
(10.0 o, 17.2)
87.2
(52.9 0,112.7)
37.9
(22.8 0, 54.3)
71.4
(40 o 120 )
127.2
(101.9 0144.0)
7.0
(6.5 o 7.5)
0.44
(0.14 o 0.74)
0.36
(0.08 o 0.84)
0.30
(0.05 "" 0.70)
13.2
(9.9 0,16.1 )
-
5.5
(3.7 o 8.0 )
6.0
(4.1 o 7.5 )
8.3
(5.8 Oil. 5 )
4.5
(1.8 0,11.4 )
72.2
(58.4 089.7)
Run- 2
22.1
(21.2 o, 23.3)
7.2 7.3
(7.1 o 7.3 ) (7.2 o 7.6 )
4.78
(2.28 0-10.26)
2.33
(1.18 o, 4.35)
2.05
(0.72 o 4.25)
29.1
(17.9 "V. 43.4)
-
13.9
(10.7 0 16.7)
106.4
(72.2 0,161.9)
52.8
(33.1 0,113.6)
109.3
(30 0 260 )
138.7
(115.2 0,154.2)
0.41
(0.14 o, 0.85)
0.33
(0.08 o. 0.80)
0.23
(0.02 0, 0.76)
14.6
(12.8 ^ 16.6)
-
10.9
( 5.4 o, 13.0)
5.3
( 4.3 0 7.3)
8.8
( 5.2 0 10.6)
3.1
( 1.5 o 4.6)
124.7
0.02.5 0147.5)
Run- 3
22.8
(21.8 0, 23.2)
7.2
(7.1 o, 7.3 )
3.30
(1.58 0. 4.13)
2.04
(1.00 ^ 2.73)
1.71
(0.74 o 2.57)
19.5
(17.9 o 20.7)
-
9.6
( 4.1 0 12.8)
73.9
(67.0 0, 79.1)
40.7
(25.6 0 53.5)
62
(24 0 130 )
131.0
(91.0 0,146.0)
7.1
(6.8 -v 7.4 )
0.80
(0.17 0, 1.24)
0.72
(0.11 % 1.12)
0.63
(0.05 o, 1.06)
11.3
(10.2 ^ 12.2)
-
1.4
( 1.0 0, 2.2)
4.2
( 2.1 o, 5.7)
8.0
( 6.9 o, 9.2)
2.0
( 0.7 o, 3.7)
65.9
(48.7 o, 95.3)
4.09 3.91 3.98
(3.69 0 4.49) (3.60 o, 4.25) (2.75 o, 5.08)
Run- 7
14.4
(14.0 0 14.9)
7.3 7.2
(7.1 0,7.4) (7.2 o, 7.3)
4.16 0.80
(3.32 o 5.07) (0.61 o 1.18)
2.42 0.39
(2.05 ^ 2.83) (0.39 ^ 1.02)
2.13 0.46 -
(1.78 o 2.43) (0.27 o, 1.0 )
31.8 20.7
(30.5 o, 34.6) (19.1 o, 22.6)
24.8 19.6
(23.2 o, 26.5) (18.3 o, 21.0)
20.8 17.4
(19.8 o 22.3) (14.2 o, 20.3)
115.9 6.7
ttOO.5 0,131.4) ( 5.8 o 7.5)
56.6 14.2
(54.2 o, 59.5) (13.2 o, 15.2)
83.0 9.2
(48 o, 114 ) ( 4.6 o 13.8)
150.5 145.3
0.45.50,156.1) 033.50,152.5)
3.82
(3.65 0. 4.10)
Ln
ho
(mg/d)
(Notes) 1. 24-hour composite samples were used for analysis.
2. Left: Primary effluent. Right: Final effluent. Top: Means value. Bottom: Range.
3. P/MLSS is by a sample at the bottom end of the aerobic cell.
-------
Table 10 Summary of Operation (Mode II)
Water
temperature ( °C )
PH
T-P
Soluble T-P
Soluble O-P
T-N
Soluble T-N
NHj-N
BOD
COD
SS
M-alkalinity
P/MLSS (%)
Run- 4
22.4
(18.6 -V 25.1)
7.1
(6.8 -\, 7.3 )
2.16
(1.11 -\, 4.93)
0.99
(0.44 ^ 1.79)
0.79
(0.33 % 1.59)
16.5
(8.0 ^ 22.9)
12.4
(6.3 -x. 16.7)
9.9
(3.0 % 14.6)
60.1
(27.6 ^112.4)
30.2
(18.8 ^ 46.2)
55.2
(20 -\, 144 )
123.2
(58.1 ^146.8)
7.1
(7.0 % 7.5 )
0.52
(0.09 % 1.13)
0.44
(0.05 ^ 1.02)
0.37
(0.01 0, 0.95)
8.3
(4.8 ^ 10.7)
8.0
(4.7 -V 10.4)
0.2
(0.0 % 2.0)
2.7
(1.4 ^ 10.3)
7.0
(5.4 ^ 12.1)
3.5
(0.5 ^ 19.1)
66.4
(57.2 ^ 75.8)
3.52
(2.88 ^ 4.75)
Run- 5
19.2
(19.0 ^ 19.5)
7.3
(7.2 % 7.5 )
2.57
(1.85 % 3.67)
1.12
(0.63 % 1.71)
0.94
(0.45 ^ 1.41)
22.1
(16.1 ^ 29.7)
17.6
(12.7 ^ 23.2)
14.3
(9.6 ^ 19.6)
70.7
(53.0 'v 95.4)
35.8
(29.1 % 42.9)
59.7
(36 'V 72 )
145.7
0.28.7^157.3)
7.3
(7.1 -V 7.5 )
0.19
(0.14 ^ 0.23)
0.11
(0.09 ^ 0.14)
0.05
(0.03 ^ 0.07)
10.6
(7.7 ^ 13.6)
10.3
(7.5 -V 13.5)
5.6
(0.0 ^ 10.1)
4.5
(1.1 ^ 6.6)
8.4
(5.4 ^ 16.2)
3.0
(0.3 % 4.4)
100.9
(62.0 -^121.0)
3.62
(3.42 T- 3.77)
Run- 6
16.2
(14.3 % 17.8)
7.2
(6.9 ^ 7.4 )
4.35
(2.50 % 6.71)
2.41
(1.21 ^ 3.84)
2.13
(0.82 ^ 3.66)
28.1
(17.2 'V 34.8)
21.1
(12.1 -V 24.7)
17.7
( 9.5 -v. 20.9)
99.5
(45.4 0,130.0)
45.3
(36.4 T- 58.6)
74.1
(42 ^ 150 )
146.6
tt04.. S'v 158.1)
7.1
(7.0 'v, 7.4 )
0.28
(0.21 -v 0.53)
0.18
(0.13 % 0.34)
0.11
(0.05 ^ 0.24)
11.8
(7.8 ^ 17.1)
11.4
(7.4 -V 15.2)
5.0
(0.0 % 8.2)
4.0
(1.6 % 6.4)
7.7
(5.9 ^ 8.7)
3.7
(0.1 % 13.0)
92.7
(71.5 ^ 110.0)
4.04
(3.60 ^ 4.70)
(Notes) 1. 24-hour composite samples were used for analysis.
2. Left: Primary effluent. Right: Final effluent. Top: Means value.
3. P/MLSS is by a sample at the bottom end of the aerobic cell.
(mg/JO
Bottom: Range.
-------
3.2.1 Phosphorus Removal
Figs.-5 and 6 are cumulative frequency curves prepared for
the data of the entire period on the respective T-P concentration
of the primary and final clarifier effluents. From the figure,
the T-P concentration of primary effluent is 3.38 mg/£ on the
average. The mean value of the final effluent is 0.47 mg/£ and
the T-P concentration for the accumulative frequency of 90% is
0.94 mg/£.
Run No. = 1234567
Acummulated Freq. of T-P IN
Mean = 3.379
St. Deviation = 1.568
Total Number = 85
1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12
T-P concentration of primary effluent (mg/&)
Fig. 5 Cumulative Frequency of Primary
Effluent T-P Concentration
354
-------
100
o
Run No. = 1234567
Acummulated Freq. of T-P OUT
Mean = 0.474
St. Deviation = 0.307
Total Number = 85
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
T-P concentration of final effluent (mg/H)
2.0
Fig. 6 Cumulative Frequency of Final
Effluent T-P Concentration
355
-------
This indicates that during the period of this survey, the
final effluent T-P concentration was less than 1 mg/& in 90% of
all the measured data.
The cumulative frequency at the effluent T-P concentration
of 0.5 mg/£ is 61%, and it is expected that this value will be
exceeded in a considerable number of cases if the target value of
effluent T-P concentration is set at 0.5 mg/£.
However, it must be noted that the operation was carried out
under varied conditions with the object of studying how different
operation control factors affect the removal of phosphorus and,
after slight remodeling, an existing secondary treatment facility
was used in the experiment. Therefore, operation by this system
was not necessarily made under the optimum conditions.
(1) Phosphorus Release in Anaerobic Tank and T-P Removal Efficiency
Fig. 7 shows the relation between the soluble ortho-phosphate
concentration (to be abbreviated hereafter as S-O-P) in a anaerobic
cell and the T-P removal efficiency of the system. On the whole,
T-P removal efficiencies are in a higher range if the concentration
of phosphate in the anaerobic cell is higher. It can also be seen
that when it rains, phosphate concentration in the anaerobic cell
is low and the T-P removal efficiency is also often low. The T-P
removal efficiency is sometimes more than 90%, even in times of
rain, but this is due to the fact that the concentration of the
influent itself is low as the result of influx of rainwater.
Fig. 8 shows an example of measurement of S-O-P concentrations
at different points of the system in both fine and rainy weather.
There was heavy typhoon rain on September 12 and the concentration
of influent continued to be very low for the measurement of
September 27. As indicated by this figure, no release of phosphate
occurred in the anaerobic cell after heavy rainfall, and therefore,
no phenomenon of biological luxury uptake was observed either.
However, the effluent T-P concentration itself in rainy weather is
not greatly different to that for fine weather because the T-P
concentration of the influent is low.
356
-------
The fact that no phosphate release takes place during heavy
rain is considered to be attributable not only to the increase of
NOT-N (NOJ-N + NOI-N) and the rise of DO in influent but also to
the decrease of BOD in the influent with the influx of rainwater.
100
-------
10
S-O-P
Sep. 27
(after rain)
Sep. 10
(fine weather)
T-P
Primary Anaerobic Anoxic Aerobic Aerobic Final Primary Final
effluent cell cell cell cell efflu- efflu- efflu-
ent ent ent
Fig. 8 Example of Measurement of S-O-P Concentrations at
Different Points of the System
Fig. 9 shows the relation between the amount of denitrifica-
tion and the S-O-P concentration in anaerobic cells particularly
with respect to Run 4 where the effect of rain was great. It can
be seen from this figure that if the quantity of NOT-N coming into
an anaerobic cell increases, so increasing the amount of denitrifi-
cation in the cell, then phosphate release is suppressed. Fig. 10
shows the relation between ORP and the S-O-P concentration in an
anaerobic cell. If the ORP is positive, there is no phosphate
release. If the ORP value is negative, then the S-O-P concentra-
tion in the tank is large in inverse proportion to the ORP value.
It is therefore important to keep the ORP in the anaerobic cell
negative and small to ensure the satisfactory removal of phosphate.
358
-------
10
Run-4
o
+J
c
01
o
0
o
CM
I
I
5 io
Amount of Denitrification (N-kg/day)
Fig. 9 Relation between Quantity of Denitrification
and S-O-P Concentration in Anaerobic Cell
c
o
0)
c
0
o
o
15
10
Run-4,5
100
-100
-200
-300
-400
ORP (mV)
Fig. 10 Relation between ORP and S-O-P
Concentration in Anaerobic Cell
359
-------
(2) BOD Concentration in Influent and the Removal of Phosphorus
Fig. 11 shows the relation between the concentration of BOD
at the head of an anaerobic cell and the S-O-P concentration in
this cell.
Phosphorus release, which is a prerequisite to the biological
removal of phosphorus, is satisfactory in direct proportion to the
concentration of BOD at the head of the anaerobic cell.
The tendency for the T-P removal efficiency of the system to
increase with the increase of BOD in the influent could be seen
but this was not clear. Furthermore, nothing was found concerning
the minimum BOD concentration necessary to stabilize the T-P re-
moval efficiency.
20
15
o?
IT
di
o
w
10
O
A A
D
d
D D
D
D
Legend
• Run-1
O Run-2
• Run-3
D Run-4
A Run-5
A Run-6
tt Run-7
50
100
150
BOD (mg/£)
Fig. 11 Relation between Influent BOD
and S-O-P in Anaerobic Cell
360
-------
(3) Phosphorus Release and Uptake Rate
Phosphorus.Release Rate
In calculating the phosphorus release rate, it was presumed
from the results of the laboratory experiment in 1981(5) that the
release rate of ortho-phosphate could be expressed by the follow-
ing equation:
f£ = Kr-X (1)
dt
Where,
C : S-O-P concentration (mg/£)
Kr: S-O-P release rate constant (mg/gMLSS-hr)
X : MLSS concentration (g/£)
Fig. 12 shows the relation between Kr and water temperature.
In the laboratory experiment(5)f using sludge which was not accli-
matized to anaerobic/aerobic operation, Kr was dependent on the
water temperature but this was not clear in this full-scale survey.
The above-mentioned 1981 laboratory survey also showed that
Kr increased in proportion to the BOD concentration. The relation
between the BOD concentration at the head of the anaerobic cell
and Kr is shown in Fig. 13 for full-scale data.
Fig. 13 indicates that Kr generally tends to increase if BOD
is high. Kr can be expressed as the following equation:
Kr (mg/gMLSS.hr) = 0.0236 x BOD (mg/£) - 0.0036 (2)
361
-------
4.0
3.0
2.0
1.0
0 •• °
A A
M
O Q
D
CO
CO
Dl
0.1
A A
0.05
Legend
- • Run-1
O Run-2
• Run-3
D Run-4
A Run-5
A Run-6
tt Run-7
0.01
12
15 20
Water Temperature (°C)
25
Fig. 12 Relation between Kr and Water Temperature
362
-------
4.0
3.5
3.0
•£ 2.5
JS
w
Cn
6 2.0
1.5
1.0
0.5
Legend
Run-I
Run-2
Run-3
Run-4
Run-5
Run-6
Run-7
50
100
BOD (mg/£)
Fig. 13 Relation between Kr and BOD
363
-------
Phosphorus Uptake Rate
It was presumed from the results of the 1981 survey^) that
the phosphate uptake rate could be expressed as:
f£ = -Ku-X-C (3)
dt
Where,
Ku: S-O-P uptake rate constant (1/gMILSS-hr)
Fig. 14 shows the semi-logarithm plot of Ku to water temper-
ature. Ku is distributed mainly within the range of 0.2 ^ 0.6 with
approximately 0.35 as the center.
(4) Re-release of Phosphate in the Final Clarifier
When sedimented and deposited in the clarifier, sludge final-
ly becomes completely anaerobic after endogeneous denitrification
and may re-release phosphate that it absorbed for once.
The concentration of S-O-P in the supernatant of the returned
sludge was far greater than that at the bottom end of the aerobic
cell - except for Run 4. Fig. 15 shows the relation between S-COD
and S-O-P in the supernatant of the return sludge and the amount
of phosphate re-release in the final clarifier. As can be seen
from this figure, S-O-P in the supernatant of the return sludge
is high in proportion to its S-COD. In the case of Run 4, the
quantity of residual organic matter (BOD) in the return sludge was
small because of the dilution of the influent with rainfall and
the longer detention in the aeration tank. Therefore, the quantity
of re-released phosphate was smallest.
By contrast, in Run 7 the quantity of residual organic matter
in the return sludge was large because of the increased inflow
during the period of low water temperature. Thus, the quantity of
re-released phosphorus was large.
Fig. 16 shows the relation between the quantity of re-released
phosphate and the sludge surface level in the final clarifier.
The mean sludge level did not differ much between Rund 5^7 but
phosphorus re-release was largest in Run 7.
It is considered from the above that in order to prevent the
364
-------
re-release of phosphate in the final clarifier, it is important to
not only appropriately control the sludge surface level in the
clarifier but also to remove organic matter thoroughly in advance.
1.0
0.5
x:
w
\
0.1
0.05
0.01
00 O
Legend
• Run-1
O Run-2
• Run-3
D Run-4
A Run-5
A Run-6
-$ Run-7
12
15 20
Water temperature (°C)
25
Fig. 14 Relation between Ku and Water Temperature
365
-------
15
• 6
• 1
• 3
•5
Re turn
Mv-
• 4
i .... i ..... i .
10 15 20
Return sludge S-COD (mg/£)
25
(Note) The mean value for each run.
The figure shows Run number.
Fig. 15 Relation between Return Sludge S-COD
and S-O-P Concentration and S-O-P
Release in Final Clarifier
366
-------
3 0.5
s5
£ 0.4
(0
0)
0.2
? 0>1
w
• 7
1.24
• 5
0 0.5 1.0 1.5 2.0 2.5
Sludge surface level (m)
(Note) The mean value for each run.
Fig. 16 Relation between Sludge surface Level
in Final Clarifier and S-O-P Release
3.2.2 Nitrogen Removal
During the period of Operation Mode II (Runs 4^6), not only
phosphorus removal but also the removal of nitrogen by the recycl-
ing formula were carried out. According to the mean values in
Table 10, the respective T-N removal efficiency was 49.7%, 52.0%
and 58.0% for Run 4, Run 5 and Run 6. Since this survey stressed
the removal of phosphorus, the operation for the removal of
nitrogen was not necessarily under optinum conditions. To achieve
high nitrogen removal, influent Kj-N should as a principle, be
nitrified as much as possible but during the period of Operation
Mode II, Kj-N remained in the final effluent.
(1) Nitrification Rate
The nitrification rate in the aerobic cells was calculated
by the following equation:
367
-------
CN2 -
- DTN-X ....................................
Where ,
KN : Nitrification rate constant (mg/gMLSS-hr)
CNi : NOip-N concentration at bottom end of
denitrifi cation cell (mg/&)
CN2 : NOT-N concentration at outlet of Nitrification
cell (mg/£)
DNT: Real detention time
X : MLSS concentration (g/£)
In this calculation, it was assumed that nitrification fol-
lows the zero-order reaction and that the nitrification cell was
a plug flow reactor. Only data with at least 0.5 mg/£ of HNi,+-N
remaining at the nitrification cell outlet were used.
The relationship between KN and water temperature is expres-
sed as follows :
KN = 0.0985 x e0.1156T (mg/gMLSS-hr) .............. (5)
Taking Run 6 as an example, the nitrification rate from
equation (5) is 2.60 mg/hr for the mean water temperature of
16.2°C, and the mean MLSS concentration of 4,050 mg/&.
Therefore, the aerobic tank detention time necessary to completely
nitrify the influent Kj-N concentration of 27.6 mg/£ was 10.6 hr,
whereas the actual aerobic tank detention time was 7.7 hr, indi-
cating that the nitrification time was insufficient.
(2) NOT-N Balance
An NOip-N balance in the system was prepared for Runs 4^6.
A typical example is shown in Fig. 17. In this figure, "+" means
the increase of NOx-N through nitrification and A means its de-
crease through denitrification. The figure shows that denitrifi-
cation occurs in both the denitrification cell and the final
clarifier. Thus, the NOT~N in the return sludge was mostly deni-
trified in the final clarifier and very little returned to the
anaerobic cell. The results of the survey of single-sludge re-
cycling nitrification/denitrification system conducted in 1980 ^
368
-------
1981 ' revealed that hardly any NOp-N into the
anaerobic cell.
After heavy rain, the denitrification capacity of the final
clarifier declined and the concentration of NOT-N in the return
sludge increased. This, along with the increase of NO^-N in the
influent itself, suppressed the release of phosphorus in the an-
aerobic cell. It will thus be necessary to consider the increase
of NOT-N in the anaerobic cell not only by influent, but also that
by return sludge in order to cope with the effect of rain.
Qr
1.18
•
0.88
2.06
1.28
A0.78
46.91
48.19
2.48
A45.71
88.4
+85.92
Qr
127.63
-1-39.23
(August 25)
Q = 7,140
Q = 2,668 m3/day
Q = 5,700 m3/day
Fig. 17 NOrp-N Balance During Run 4
369
-------
3.3 Results of Flow Rate Fluctuation Survey
In the last part of Run 4, the effect of flow fluctuation upon
phosphorus removal was surveyed. Fig. 18 shows an inflow fluctua-
tion pattern and the S-O-P change with time. The removal of S-O-P
was always satisfactory regardless of flow fluctuation, even though
the S-O-P concentration in the anaerobic cell changed considerably
with fluctuations in flow.
The change of S-O-P in the denitrification cell was almost
similar to that of the anaerobic cell.
The S-O-P concentration in the first aerobic cell was slightly
affected by flow fluctuation but the S-O-P concentration in the
second aerobic cell showed no change at all, presumably because the
capacity of the aerobic cells was sufficient and the fluctuation
of phosphorus concentration in the anoxic cell was absorbed in the
aerobic cells.
3.4 Sludge Production
Table 11 shows the excess sludge production. Excess sludge
production per BOD removed was much the same regardless of opera-
tion mode, water temperature, etc. and its mean value throughout
all data was 0.569 kgAg- In the survey conducted in 1980 ^ 1981
on single-sludge recycling nitrification/denitrification system,
using the same facility^4), excess sludge production was 0.297
kg/kg in the period of low water temperature and 0.335 kg/kg in
that of high water temperature. Thus, the value obtained in this
survey was considerably larger.
370
-------
o
I
en
500
400
Primary effluent
Anaerobic cell
Anoxic cell
First aerobic cell
Second aerobic cell
Final effluent
Volume of influent
100
0
U-l
C
•H
o
0)
O
(Time)
Fig. 18 Effect of Flow Fluctuation
-------
Table 11 Excess Sludge Production
Period
June 11
^
June 30
August 25
'V.
September 6
November 22
•X.
December 22
Average
Run
1,2
4
5,6
-
Water temper-
ature (°C)
21.5
24.6
17.4
-
MLSS
(mg/fc)
2,090
2,330
4,160
-
(A) BOD
removed
(kg/day)
1,065.2
474.3
531.9
684.1
(B) SS
removed
(kg/day)
856.5
464.5
460.6
582.9
(C) Excess
sludge
produced
(kg/day)
608.5
283.5
293.5
389.4
«"«
0.571
0.598
0.552
0.569
,C,/(B,
0.710
0.610
0.637
0.668
(C)
(A) + (B)
0.317
0.302
0.296
0.307
-J
N3
-------
3.5 Others
3.5.1 BOD, COD and SS Removal
As indicated in Tables 9 and 10, the removal of BOD, COD and
SS was satisfactory and stable throughout the entire period of the
survey.
The transparency of the final effluent was 70 ^ 100 cm on the
average, with the exception of Run 7. In this run, the SS concen-
tration in the final effluent was somewhat higher than that in
other runs and its transparency remained at an average of 33 cm.
3.5.2 Sludge Characteristics
During the period of this survey, SV30 was at 15 ^ 40 and SVI
was within the range of 70 ^ 100. As far as can be determined by
these indices, the settling characteristics of sludge did not dif-
fer greatly when compared to the conventional activated sludge at
the other trains of the plant.
3.6 Summary
The following has determined so far from the demonstration
operation of biological phosphorus and nitrogen removal system:
(1) A final effluent T-P concentration of less than 1 mg/£ can be
obtained by an anaerobic/aerobic system.
(2) Nitrate nitrogen suppresses phosphorus release in the anaero-
bic cell and the phosphorus removal efficiency drops.
(3) ORP is useful as a control index of anaerobic cell.
(4) Phosphorus release and uptake rates were not so affected by
the water temperature. Phosphorus release is affected by the
influent BOD.
ACKNOWLEDGEMENT
The author would like to express his thanks and appreciation to
the Public Works Research Institute of the Ministry of Construction,
373
-------
Shiga Prefecture, Saitama Prefecture, and to Messrs. Kazuo Takeishi,
Takao Murakami and Atsushi Miyairi who were directly connected with
this research.
BIBLIOGRAPHY
1. Proceedings of the 20th Annual Meeting of the Japan Sewage
Works Association, 1983
2. S. Kyozai and Y. Harada: "Advanced Wastewater Treatment at
Hitomigaoka Purification Center, Hamamatsu City", Journal of
Japan Sewage Works Association, Vol. 20, No. 224, 1983
3. T. Shimizu, K. Kobori and H. Suzuki: "Simultaneous Removal
of Nitrogen and Phosphorus by Nitrification and Denitrifica-
tion Process with Addition of Alum", Journal of the Japan
Sewage Works Association, (to be published)
4. T. Murakami et al: "Study of Nitrified Liquor Recycled
Biological Nitrification-Denitrification Process", Proceed-
ings of the Japan-German Workshop on Wastewater and Sludge
Treatment, 1982
5. K. Tanaka and T. Murakami: "Research on Biological Nitrogen
and Phosphorus Removal System", Research Bulletin of Japan
Sewage Works Agency, 1982
374
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Ninth US/Japan Conference
on
Sewage Treatment Technology
SURVEY OF INFILTRATION/INFLOW
IN SEWER SYSTEMS
September 19-21, 1983
Tokyo, Japan
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Muneto Kuribayashi
Director
Hiromi Ito
Dupty Director
Research and Technology Development Division
Japan Sewage Works Agency
375
-------
CONTENTS
Page
1. PREFACE „ „...„ 377
2. PROCEDURES FOR INFILTRATION/INFLOW SURVEY 0 378
2.1 Outline of the Surveyed Areas „. „ 378
2.2 Fluctuation Analysis of Daily Sewage Flow „.... 383
2.3 Fluctuation Analysis of Hourly Influent ....... 386
3. ESTIMATION OF INFILTRATION/INFLOW „ „ „ 391
301 Estimation of Stormwater Inflow 391
3.2 Estimation of Groundwater Infiltration 396
4. MEASUREMENT OF INFILTRATION/INFLOW 398
4.1 Hydraulics of Groundwater Infiltration ..„ 398
402 Measuring Methods for I/I Flow ... „ 403
4.3 Infiltration Flow from Each Sewer Facility ... 406
4.4 Presumption of Inpouring Points of Groundwater . 410
5o TECHNIQUES FOR I/I REDUCTION IN SEWERS „ 413
5.1 Watertightness of Branch Pipe Connections „.... 413
5.2 Watertightness of Joints in House Sewers 416
5o3 On-site Watertightness Tests „ 417
5.4 Infiltration/Inflow and its Reduction Techniques 421
REFERENCES . „ 0 „ 426
BIBLIOGRAPHY .„ 428
376
-------
1. PREFACE
As a result of the spread of sewage works and the increase of
drainage areas, the amount of influent to sewage treatment plants
has increased in recent years. In the sewer treatment plants
where the influent is likely to exceed the design flow, the re-
examination of the design value becomes necessary. The presence
of influent sewage exceeding the design flow has become obvious
in recent years.
Influent sewage other than sanitary sewage is called "In-
filtration/Inflow (I/I)" and is considered to be generally rela-
ted to rainfall and groundwater. It is only very recently that
Infiltration/Inflow has begun to be studied quantitatively.
Between fiscal years 1978 to 1981 and after reference from
the Ministry of Construction, JSWA surveyed the Infiltration/
Inflow to sewerage and possible measures for its prevention.
This report has been prepared after examination of the inpouring
mechanism of I/I based on the above survey and also proposes
some improved design and maintenance procedures.
377
-------
2. PROCEDURES FOR INFILTRATION/INFLOW SURVEY
Since it is usually possible for I/I to inpour through all
portions of sewer in a drainage area, it is not possible to di-
rectly take out the I/I in the influent sewage. Ideally, the
amount of infiltration may be determined by stopping all sanitary
sewage within the drainage area, but sanitary sewage through a
sewer line in service can in general be stopped only partially.
If, however, it can be stopped like this, then the amount of
infiltration can be estimated by measuring directly the influent
in that portion. The estimation accuracy of the sanitary flows
will be directly reflected upon the accuracy of the amount of
infiltration, so that the accurate grasping of the sanitary flows
become extremely important.
Described in this chapter, are the outline of the I/I survey
performed for the test areas as well as the statistical estima-
tion of sanitary sewage.
2.1 Outline of the Surveyed Areas
The I/I to sewer system was surveyed for test areas preselec-
ted. Most analyses stated up to Chapter 4 were based on the data
obtained from this survey. Outline of these areas as well as ob-
servations will be described in this Section.
Drainage subsections A and B of Y-city satisfying the follow-
ing conditions were selected as the survey areas:
(T) The drainage area is to be small so as to make the de-
tailed survey possible.
(5) The majority of the survey area is to be composed of
residential districts.
(D The anticipated amount of groundwater infiltration is to
differ between the two subsections.
(4) The survey area is to be served with separate sewers.
378
-------
Y-city is located on diluvial plateau and alluvium formed
by a river running through the central part of the plateau. The
surface of the diluvial plateau is covered with a loam layer 3
to 5 m thick, beneath which are alternating fine sand and clay layers.
The alluvium is covered with a humus soil layer about 3 m thick,
with soft clay layer underneath.
Subsections A and B in the survey area are closely located
as shown in Fig. 2.1. Most of subsection B is located on the
diluvial plateau, but one-third of subsection A is on the alluvium
and the remaining two-thirds is on a land gently sloping from
the alluvium to the diluvial plateau and having a difference of
about 7 m in elevation.
Outline of the sewer lines embedded in both the drainage
subsections is shown in Table 2.1 and Fig. 2.1. Also shown in
this figure are the sewer lines located below the average ground-
water level.
Table 2.1 Outline of Sewer Facilities
Name of drainage subsection
Area of district (ha)
Pipe diameter (mm)
Total length of sewers (m)
Number of spans
Earth covering (m)
Mean level of ^
sewer bottom
Number of house sewers
Number of manholes
A
8.8
250
2,041
65
1.CK2.9
220
66
(1,008)
( 32)
( 1.85)
( 7.75)
( 127)
( 33)
B
14.8
250
2,927 (
80 (
0.9^3.5 ( 3.
(10.
266 (
81 (
98)
3)
22)
46)
1)
4)
Values shown in ( ) concern with sewers below groundwater level.
379
-------
5^"^ Drainage
11 subsection \\'
A
Sewer system below
groundwater level
• Groundwater observation well
Fig. 2.1 Plan of district
380
-------
In order to grasp the real quantity of the I/I, it becomes
necessary to observe the sewage flow at the lowest point of
drainage subsection, mean groundwater level and rainfall depth
within the area. The groundwater level was regularly observed
once a day by using the existing 12 wells in the area, and addi-
tionally at one bore hole where its level was recorded automati-
cally. The amount of rainfall was automatically recorded at
three places in that and adjacent areas, and then it was hourly
averaged and commonly used for both the drainage subsections.
The purpose of these observations was to obtain mean values
of I/I instead of the detailed distribution of I/I throughout
the whole survey area. Therefore, the mean daily groundwater
level obtained from the observation was used as analysis data
for each subsection.
Fig. 2.2 shows the daily changes in sewage flow, ground-
water level and amount of rainfall for a survey period of about
3 months in subsection A. For subsection B, various misconnec-
tions to sanitary inlets were investigated, as these are one of
causes of stormwater inflow.
381
-------
1400
1200
Fig. 2.2 Fluctuations in daily influent and explanatory factor
(drainage subsection A)
382
-------
2.2 Fluctuation Analysis of Daily Sewage Flow
Sewage flow to a sewage treatment plant or a pumping station
is normally measured in hour units. For both of the drainage sub-
sections in the survey area, the hourly sewage flow was measured
at the end of each subsection. In this Section, the factors af-
fecting daily sewage flow fluctuation obtained from the hourly
sewage flow will be determined. If these factors are quantitative-
ly determined, then the daily sewage flow can be estimated.
Where there seems to be no change such as an additions to
the sewer line in the drainage subsection, the factors of fluctu-
ation in daily sewage flow can be abstracted by the statistical
handling. Domestic sewage flow will indicate certain tendencies.
That is, it is known that the amount of domestic water used varies
by season and a day of the week (weekly fluctuation), and the
amount of laundry water varies with rainy and fine days.
Generally, the factors of fluctuation affecting the daily
sewage flow are as follows:
(l) Season;
(2) Day of the week;
(5) Amount of rainfall; and
(4) Groundwater level.
In addition to the above, other factors such as geological condi-
tions and kinds and states of sewers may exist but these cannot
be easily handled statistically if a particular area is preselected
as the survey area. Therefore, only the four factors listed above
will be considered hereinafter.
Of these four factors of fluctuation, the seasonal fluctuation
factor and weekly fluctuation factor are qualitative variates while
the amount of rainfall and groundwater level are quantitative variates.
The statistical analysis method for explaining the daily sewage flow
as a dependent variate by such two kinds of fluctuation factors has not
been generally established. However, since the quantitative variates can
383
-------
be easily transformed to qualitative variates, quantification
analysis was used by handling all of four factors as qualitative
variates. Quantification regression analysis is one of multi-
variate analyses and its concept is shown in the references at
the last part of this report.
Four qualitative items were classified into categories in
accordance with the following criterions:
(I) Seasonal fluctuation:
Two weeks were considered as an unit, and the period
of observation was divided into 6 categories.
(2) Weekly fluctuation:
Days of the week from Sunday to Saturday were used as
variates. Therefore, the variates were divided into
7 categories.
(5) Amount of rainfall:
Daily rainfall is an quantitative statistic but was divided
into 6 categories within the range obtained during the
observation period. Also, fine days (days without any
rainfall) became one category.
(4) Groundwater level:
As for rainfall, the ranges of groundwater level were
classified into a total of 6 categories, thereby each
groundwater level being divided into one of categories.
The ranges of these variates differ between drainage
subsections A and B but the number of categories was
the same.
Results of application of the quantification analysis are
indicated in Fig. 2.3.
384
-------
Factor
Category
No.
NO. Of
samp-
les
Estimated A: Mean value: 345.5 m /day —O
addend B. Mean value; 475.5 m3/day --•
Period (every 2 weeks!
in May,
in June
4th.week in May
5th.week
1st.week
2nd.& 3rd.weeks in June
4th.week
1st.week
2nd.& 3rd
4th.week
in June,
in July
.weeks in July
in July
A B
6 6
14 14
12 12
14 14
4 12
6 12
-50
100
150
Day of the week
Sun., holiday
Mon.
Tues.
Wed.
Thur.
Fri.
Sat.
7 9
8 10
9 10
9 10
8 11
7 10
8 10
Daily rainfall
Fine day
( 0) ^ 5 mm
( 5)^10 mm
(10)^20 mm
(20)^30 mm
(30)^ mm
31 40
10 14
3
9
1
2
Groundwater level
(B)
-.8^ -.6
-. 6 ^ -. 4
-.4^ -.2
-.2 ^ 0
0^.2
10
20
18
12
3
7
(A)
.2^.3
.3^.4
.4^.5
.5^.6
.6^ .7
.7% .8
7
14
12
15
7
1
-50
50
100
150
Total numbers of samples
56 70
Fig. 2.3 Estimation of daily influent by quantification analysis
385
-------
The estimated value of the influent for a particular day is ob-
tained by adding the mean value to the sum of regression coeffi-
cients corresponding to categories for four factors. The cor-
relation coefficient between estimated values and observed values
is 0.95 for subsection A and 0.87 for subsection B, so that the
application of the quantification analysis is considered to be
appropriate.
According to Fig. 2.3, an obvious correlation is recognized
between the groundwater level and the regression coefficient (esti-
mated addend) in subsection A. Since this groundwater level is based
on the average level of the sewer base in the subsection, the presence of
positive correlation can be considered when the groundwater level
is over the bottom level. Also, the same correlation will be
obtained in subsection B when the groundwater level rises.
With respect to the daily rainfall, a correlation the same
as that of the groundwater level can be expected but a fluctua-
tion appears to some extent. This seems to be caused by the fact
that the number of days of heavy rainfall is small and that there
is no clear difference in the amount of water supply when the
daily rainfall is less than 10 mm.
The regression coefficients due to the factor of day of the
week are almost the same between both subsections, which means
that this factor must te considered as one of fluctuation factors.
Seasonal fluctuation has been generally known but it is not pos-
sible to grasp the tendency of seasonal fluctuation within such
a short observation period of as 3 months.
2.3 Fluctuation Analysis of Hourly Influent
It is generally known that the fluctuation in hourly sewage
flows in 24 hours a day has a particular pattern for each day of the
week. In addition, calculating the amount of I/I, accurate esti-
mated values of hourly flow becomes necessary. Therefore, the
estimated hourly flow in the drainage subsection was calculated
by the method described below.
386
-------
That is, it was first confirmed by factor analysis that each
day of a week has the particular pattern of daily fluctuation.
Then, mean water flow in every hour of each day of the week was
determined as a proportion to the daily sewage flow and it was
confirmed that the daily fluctuation pattern actually varies.
Finally, the estimated hourly flow was obtained by multiplying
the daily sewage flow estimated in the previous section by the
estimated proportion in every hour.
In the factor analysis, the 24 values for the hourly influ-
ent per day were expressed as proportions to the daily water flow,
and a set of these values was used as a sample. Samples corre-
sponding to 52 days were used for each of drainage subsections A
and B in the analysis. Consequently, the contribution of the
first factor was 85% and about 92% up to the third factor for
both subsections, and the outline of fluctuation pattern of each
day of the week can be explained using up to the third factor.
Since scores of the first factor of each sample were in the
range between 0.8 and 1.0, the fluctuation pattern cannot be clas-
sified. Each day was then classified based on the scores of sec-
ond and third factors. Scores of two factors are shown in Fig.
2.4 for subsections A, and in Fig. 2.5 for subsection B.
387
-------
Sundays, holidays
-'__.
! a
Saturdays
A±*L
Legend
a Sundays, holidays
O Saturdays
"t" Weekdays
-.6 -.5 -.4 -.3 -.2 -.1 0 .1 .2 .3 .4 .5 .6
Fig. 2.4 Results of factor analysis of daily fluctuation
in influent (drainage subsection A)
Q Sundays, holidays
O Saturdays
-f- weekdays
-.6 -.5 -.4 -.3 -.2 -.1 0 .1 .2 .3 .4 . S .6
Fig. 2.5 Results of factor analysis of daily fluctuation
in influent (drainage subsection B)
388
-------
According to these figures, the daily fluctuation patterns
can be classified into two major groups of the Sunday and holiday
group and the weekday group. Within the weekday group, there is
a Saturday group slightly separate from the weekdays so that it
is possible to distinguish the Saturday group from the remaining
weekdays. Since there is no great difference in the daily fluc-
tuation pattern between the remaining weekdays, it is more appro-
priate to classify the daily fluctuation patterns into three
groups; the Sunday and holiday group, the Saturday group and the
weekday group.
The average daily fluctuation pattern of each group for both
of the drainage subsections is indicated in Figs. 2.6 and 2.7.
If the fluctuation pattern of the weekday group is used as a ref-
erence, then the fluctuation of the Sunday and holiday group has
a delay of 1 to 2 hours from 7:00 AM to 4:00 PM, and the fluctua-
tion of Saturday group has an increase of about 1.5% in daily
sewage flow from 12:00 AM to 4:00 PM. Also, the Saturday group
sometimes indicates a local maximum at about 2:00 PM. The daily
fluctuation patterns also have other features but these will not
be explained here.
According to the analysis stated above, hourly sewage flow/
daily sewage flow ratio will sometimes vary more than 5% between
groups depending upon the time, so that it seems to be necessary
to at least take account of the weekly fluctuation when estimat-
ing each hourly flow.
389
-------
12
24
Fig.
2.6 Daily fluctuation patterns of influent
(drainage subsection A)
12
£ 10
3 6 -
12
Pime
24
Fig.
2.7 Daily fluctuation patterns of influent
(drainage subsection B)
390
-------
3. ESTIMATION OF INFILTRATION/INFLOW
3.1 Estimation of Stormwater Inflow
The infiltration/inflow can be mainly divided into two kinds;
the I/I due to stormwater and the I/I due to groundwater. The amount
of stormwater inflow is, as same as ordinary runoff phenomena,con-
sidered to appear in the influent after a certain time of the
rainfall. On the other hand, the groundwater infiltration general-
ly fluctuates in response to the groundwater level and thus its
influctuation is considered to be smaller than that of stormwater
inflow. Therefore, the amount of stormwater inflow contained in the
influent can be obtained by subtracting the mean sanitary flow during
rainy days from the measured sewage flow.
Though mean sanitary flow during rainy days should be esti-
mated for the condition of no rainfall, it usually cannot be cal-
culated. Then, it is normally estimated on the base of the
mean sewage flow for the fine days. The amount of stomwater
inflow was estimated by the following sequence in this analysis:
(T) To estimate the daily sewage flow by taking account of the
seasonal and weekly fluctuations.
(2) To assume that there will be no daily fluctuation in the
amount of groundwater infiltration and that a constant
flow will inpour every hour in the day.
(3) To calculate the hourly sanitary flow by the procedures
described in the previous chapter.
(4) To assume particular hours during which the influent will be
influenced of rainfall. Then, for the hourly influent in
hours other than these, to change the amount of ground-
water infiltration in such a manner that the sum of
squares of difference between the hourly flows derived
as sum of steps (5) and (3) listed above will become a
minimum value. Sewage flow for every hour when the sum of
squares of difference becomes a minimum is the mean hourly
sewage flow.
391
-------
(5) Amount of stormwater inflow is determined by the sum of
the difference between the measured sewage flows and
the estimated sanitary flows within the assumed hours.
The results obtained are indicated in the form of a relation
betwen amount of stormwater inflow and amount of single rainfall
in Figs. 3.1 and 3.2. In this case, the amount of single rain-
fall is the amount of rainfall in a continuous period of time
when the hourly rainfall depth becomes higher than 0.5 mm. In
calculating the amount of stormwater inflow the duration of rain-
fall and one hour after rainfall were used.
392
-------
O
>
120
100 -
80 -
60 -
40 _
20 -
Line Q shows regression line.
Line (2) shows water volume corresponding to
misconnected roofs.
Fig. 3.1
10 20
Single rainfall depth (mm)
30
Relation between rainfall and stormwater
inflow (drainage subsection A)
120
100 -
10 20 30
Single rainfall depth (mm)
Fig. 3.2 Relation between rainfall and storrawater
inflow (drainage subsection B)
393
-------
For the drainage subsection B, misconnections of stormwater
catchments to sanitary sewer inlets were investigated, which are
considered to be one of causes of stormwater inflow. The results
of this investigation are shown in Table 3.1. According to this
table, the total roof area related to the misconnections in sub-
section B is to 2,173 m2 which is about 7% of the total roof area
in the same subsection. The roof area related to the misconnec-
tions in subsection A was estimated to be 2,517 m2 based on the
measured value of the subsection B.
Table 3.1 Survey on misconnected roofs
Name of drainage subsection
Number of houses surveyed
Number of houses with
sanitary sewage inlets
Residential area
Roof area
Open space
Number of connections with
roof drains
to stormwater catchments
to sanitary sewage inlets *
to lawns
Area of misconnected roofs *
B
325
253
71,897 m2
32,720 (45.5%)
39,177 (54.5%)
1,339
190
110
1,039
2,173 m2
A
293
(2,517) m2
Fig. 3.2 shows the amount of stormwater inflow indicated by
straight line (T) derived as the difference between the influent
and the mean sanitary flow, and the flow corresponding to the
misconnections indicated by straight line (2) . According to
this figure, if the amount of rainfall is small, most of the
394
-------
storntwater inflow is directly caused by the inflow of rainwater
from roofs related to the misconnections. However, if the amount
of rainfall is large, the amount of inflowing rainwater will exceed
the value corresponding to the roof area. Major inflow passage
of stormwater inflow will start from roofs to stomwater drainage
facilities and to sanitary sewage inlets, but other passages can
be also considered when the amount of rainfall increases. The
other passages are listed below:
(l) There are certain inflows to sanitary sewage inlets other
than those resulting from the misconnections.
(|) While rainwater on lands such as gardens other than house
lots is permeating underground', it flows into the sewers
through their defective portions. If the amount of rain-
fall is large, the groundwater level may rise within a
short period of time.
(3) Rainwater on roads flows to manholes.
Among these passages listed above, it was confirmed by mea-
surement that the inflow through manholes is very small, but the
inpouring passage @ from the sanitary sewage inlets was not
confirmed.
The inflow of rainwater to sewers in the middle of permeation
into the ground is considered to be proportional to the total area
of the openings in the defective portions of sewers but the amount
of this inflow may not be large. The other possible cause is the
rise in groundwater level and this will temporarily occur when
there is a large amount of rainwater. However, though the hourly
fluctuation in groundwater level was measured in this survey,
the results could not be fully utilized ifi the analysis so a
detailed survey on this fluctuation will be necessary in future.
The abovementioned is also the case with subsection A indi-
cated in Fig. 3.10
395
-------
3.2 Estimation of Groundwater Infiltration
The actual estimation of groundwater infiltration will be
explained in the next chapter. This section presents the simpli-
fied estimation appliable only to subsections A and B. The resi-
dential area accounts for the major part of subsections A and B,
and there are only few factories and offices that discharge waste
water during the night. Then, the minimum value of influent at
night after 24 hours without rain, is considered to be caused by
only the groundwater.
Therefore, the minimum hourly influent for a fine day was
determined as the amount of groundwater infiltration. In the sub-
section A, the obtained relation between the amount of ground-
water infiltration and the groundwater level is shown in Fig. 3.3.
In subsection B, the relation with the groundwater level was not
obtained since the groundwater level was often lower than the
sewer bottom.
•O 1,200
\
"E 1,100
c 1,000
o *~
4J
(0
M-l
C
0)
4-1
rt
•a
o
4J
c
8
900
800
700
600
500
400
300
200
100
0
Sewer
' Bottom
Sewer
top
0.1
0.2
0.3
0.4
0.5 0.6 0.7 0.
Groundwater level (from sewer bottom) (m)
Fig. 3.3 Groundwater level and groundwater infiltration on
fine days (drainage subsection A)
396
-------
According to Fig. 3.3 the rate of increase of infiltration
is small for the range where the groundwater level is from the
top of main sewer to the central portion of house connections (a
height of about 60 cm from the sewer bottom). At the top of
house connections or at heights close to the sanitary sewer cat-
chment (a height of more than 70 cm from the sewer bottom), the
amount of infiltration is large and the increase rate is also
large. The amount of infiltration when the groundwater level was
near the main sewer was not measured. Generally, groundwater
infiltration is considered to be not present when the ground-
water level is under the height of the sewer bottom. There-
fore, in this case, it is considered that fluctuation of the
distribution of groundwater levels in the area was great and a
considerable amount of I/I inpoured through sewers in some
areas even though the mean groundwater level was below the mean
height of sewer bottom.
397
-------
4. MEASUREMENT OF INFILTRATION/INFLOW
4.1 Hydraulics of Groundwater Infiltration
In studying the hydraulics of groundwater infiltration into
sewers, the location of infiltration (the defective portions of
sewers), must be clarified. However, it is generally difficult
to survey the location of defective portions (openings) and their
area and the geological conditions in surrounding areas. Hence,
in this kind of survey, the hydraulics of groundwater infiltra-
tion is assumed in advance and then the correctness of this as-
sumption is comprehensively verified. This method was also used
in this survey.
If a model as shown in Fig. 4.1 is considered as the rela-
tive positional relation between the embedded sewer and ground-
water , then the amount of influent (pumped discharge) Q is given
by the following formula:
Q = 4krQ (H-h0) (1)
where, H : original groundwater level
h : water level in well
o
r : radius of well
o
k : coefficient of infiltration
Eq. (1) is applicable only to shallow wells with their bot-
toms not reaching to an impermeable layer and is related to only
the permeation through the bottom while the wall of the well
consists of impermeable materials. Also, this equation seems to
express the steady state when the amount of influent is con-
siderably large and the surrounding groundwater level beicomes
equal to the water level in well.
398
-------
Fig. 4.1 Hydraulics of shallow well
When groundwater infiltration into the sewers is almost neg-
lected in comparison to the groundwater supply, the fluctuation
in groundwater level resulting from I/I seems to be very small.
In this case, the hydraulics of I/I is considered to be similar
to that of the orifice.
When the water level in a tank is H, the quantity of runoff
Q is given by Eq. (2) for the orifice.
Q = Ca/2gH (2)
where, C : coefficient of discharge
a : sectional area of orifice
When the I/I from only one defective portion in a sewer is
considered, then Eq. (2) can be applied as it is. Therefore, for
calculating the I/I in the whole drainage area by Eq. (2) the
following assumptions were prepared and then the phenomenon at
points was extended to the phenomenon in the whole area:
(T) Groundwater level will not fluctuate as a result of
the I/I flow.
(2) The relative height between groundwater level and sewer
will be maintained constant within the drainage subsec-
tion.
(3) Sections of defective portions in a sewer will be con-
tinuously distributed above the sewer bottom in average.
399
-------
Based on the above assumptions, the groundwater infiltra-
tion model within the drainage area is considered to have the
average section of sewer system as shown in Fig. 4.2.
Sanitary
sewage
inlet -
House
sewer
Branch pipe
Main
sewer
///&>/
.»
c=z
r
r
r
r
r
r
\*rvr
1 ^y
1 ~ Groundwater
1 level
1 Vertical
HZJ distribution o
1 opening sectio
To other main sewer
Fig. 4.2 Sewer model
The relation between infiltration flow and groundwater level
can be obtained by assuming the vertical distribution of section-
al areas of openings at defective sewer (inlets of I/I). From
several examples of vertical distribution of sectional areas of open-
ings the relation between groundwater level and infiltration flow
was estimated as shown in Table 4.1. This estimation will be
explained below.
400
-------
Table 4.1 Distribution of Opening Widths and Calculating
Formulas of Infiltration
No.
1
2
3
4
5
Distribution
pattern of
opening
widths
t
hi
o
t
hi
d
o
•" w
V.
r
\_
^ w
Total
sectiona]
area of
openings
A
A
A
A
A
Opening width
distribution
formula
W(h)
A
hi
hi2 t
3A 2
hi3
2A (h - t)
A
d
Ca] culating formula of
infiltration
Q(h)
3/2
(hj>h > o)
. 8 5/2
(hji h > o)
(hji h i o)
^ ,3,
v 1 v^ i
(hj^ h i o)
1 / 3, ,
r • r\ / Vi \ /V» \ 2 ( x^ /2 1
*-"" / *~ 9 1 " ' ( ~r~ 1 I ~~~ 1 \ -L "™" \ J. — ) f
i- (hi^ h>d)
/ / h \ 2
( d -> o, hj> h > o)
401
-------
When the groundwater height from the sewer bottom is h,
then the flow rate from an opening at a height t will be given
by Fq. (3),
dQ(t) = C.W(t)/2g(h- t)dt (3)
where, C : coefficient of discharge
W(t) : width of opening at height t
dQ(t): flow rate from a sectional area W(t)dt
at height t.
Therefore, total flow Q(h) is given by Eq. (4).
Q(h) =/ C-W(t)/2g(h-t)dt (4)
When the total area of an opening from height t=o to t=hi takes
a constant value (A), the vertical distribution of opening widths
W(t) will be given and the infiltration flow can be determined
as function of groundwater level h from Eq. (4).
Shown in Fig. 4.3 are the relations between the infiltra-
tion flow Q and groundwater level h, which corresponds to the
distribution of opening sections stated in Table 4.1. In the
actual measurement of the amount of infiltration, the relation
similar to the distributions (2) and (3) of opening sections is
often obtained for many cases.
402
-------
Nos. shown correspond to those shown in Table 4.1.
1.0
0.2 0.4 0.6 0.
Groundwater level h (x
1.0
Fig. 4.3 Infiltration volume due to opening width
distribution pattern
4.2 Measuring Methods for I/I Flow
Amount of groundwater infiltration may be estimated by com-
prehensively analyzing the discharge at the end of sewer line or,
partially, by measuring the difference in discharge between the
downstream end and upstream (inpouring) end of the sewer concerned.
The former was already explained. In the latter case, the amount
of infiltration is small compared to the influent and thus is
within the measuring error of discharge, so that it may not be
403
-------
obtained without solving this problem. Therefore, sewage flow is
temporarily stopped and only discharge corresponding to the I/I
is measured.
Three methods have been developed for measuring the I/I flow,
pumping method, water-filling method and compressed air supply
method. The pumping method will measure the discharge at the
downstream end after stopping all I/I sources of sewage. In this
measurement, the I/I stored upstream of the weir at an end is
pumped up and its volume is measured. In this case, the relation
between groundwater level and infiltration flow, is obtained by
performing measurement at lee.st two of different groundwater
levels.
In the water-filling method, the quantity of leakage from
a sewer filled up with fresh water after stopping sewage flows
is obtained by measuring the water level in a manhole.
Water level in manhole can be adjusted to the desired level above
the groundwater level in surrounding areas, so that the relation
between infiltration flow and groundwater level may be easily
obtained.
In the compressed air supply method, low-pressure air (0.1
to 0.5 kg/m2) is used instead of water and then the amount of
air leakage is measured.
In these measuring methods for infiltration flow, the mea-
sured values obtained must be corrected in order to allow the
proper estimation of the amount of infiltration. In the case of
the compressed air supply method, the conversion of an amount of
air to an amount of water and the clarification of air leakage
mechanism are necessary, and also the correlation of this method
with other methods is not clec^r. Therefore, the compressed air
supply method is not suited to the estimation of the amount of
infiltration. It seems to be appropriate to use this method for
detecting large defective portions in sewers.
404
-------
The same sewer was measured with both the pumping method
and the water-filling method and then the correlation of the
measured values was examined. Fig. 4.4 indicates the comparison
between these measured values. According to this figure, the
values obtained from the water-filling method are about 10 times
those obtained from the pumping method, and the correlation
between them appears to be very excellent.
Since the groundwater level is not considered in Fig. 4.4,
the difference between the phenomena of I/I and water leakage
cannot be clearly determined. Values about 10 times greater
are likely to occur as long as the sectional areas of the
openings at the defective portions of house sewers and inlets
are as large as the case of the vertical distribution patterns
(2) and(3) shown in Table 4.1.
4-1
01
0)
CP
c
a'
.p
nj
>
ft
en
n)
o
0.1
0.01
o
/o
o
m
O
«
-------
4.3 Infiltration Flow from Each Sewer Facility
In several cities, the amount of infiltration in existing
sewer facilities was measured by the pumping and water-filling
methods described in the previous section. Sewer facilities
were divided into two groups depending upon the kinds of sewer
materials, and the results of measurement of infiltration will
be explained hereafter. However, in this section, only the
measurement by the water filling method will be explained for
more easy determination of the difference in amount of infiltra-
tion between different kinds of sewer facilities.
(1) Infiltration from manholes and main sewers
Amounts of infiltration from the main pipe between adja-
cent manholes and from a manhole at the upstream end of the
main sewer were estimated by measuring the quantity of leakage
with the water filling method. Two kinds of quantities were
measured at each point. That is, the quantity of leakage from
manholes and main pipe and also the quantity of leakage from
only manholes were measured separately and the difference bet-
ween these two quantities was calculated as the quantity of
leakage from the main pipe. These measuring procedures were
applied by moving the water stopping packer.
Results of measurement are shown in Fig. 4.5 in which
quantities of leakage from manholes and main pipe are plotted
on both axes. According to this figure, the quantity of leakage
from the main pipe is 25&/min (0.78£/min/m) as maximum and
about 8.l£/min (0.28£/rain/m) in average. Also, the quantity of
leakage from manholes is 3.23£/min as maximum and 1.0l£/min in
average.
406
-------
10
G
cn
0.1
Hume pipe
Hume pipe
Hume pipe
Hume pipe
(with water-
expansive
rubber)
1 10
Leakage volume from main sewers (1/min)
100
Fig. 4.5 Leakage volume from main sewers and manholes
Measured sewers was chiefly made of three kinds of materials;
Hume concrete pipe, vitrified clay pipe and polyvinyl chloride
(PVC) pipe. Among these kinds of pipes, Hume concrete pipes
indicated a slightly larger quantity of leakage but the dif-
ference in the quantity of leakage between kinds of pipe materials
was not generally significant. However, the quantity of leakage
from main pipes and manholes was small when the main pipe had
leak-proof connections such as Hume pipes connected with water-
expansive rubber.
407
-------
(2) Infiltration from house sewers and sanitary sewage inlets
The amount of infiltration from house sewers and sanitary
inlets can be estimated by a series of measurement based on the
water-filling method. That is, the quantity of leakage from the
house sewers alone can be obtained by subtracting the quantity
of leakage from the inlets alone from that from a set of house
sewers and inlets. Water stopping packers are attached to the
lowest point of house sewer for the former and to the highest
point for the latter in order to measure the fluctuation in water
level in the inlets.
Results of measurements performed for 4 areas are shown in
Fig. 4.6. This measurement was performed for clay pipe and
PVC pipe used for house sewers and for Hume pipe or clay pipe
and PVC pipe used for the main sewer.
30
20
(U
e
3
i-H
O
>
0)
Cn
IB
nj
01
10
1
' 1 ' 1
Legend Lateral sewers; main sewers
• Clay pipe; clay pipe
O Clay pipe; Hume pipe
•
H
»
B,
1 *
^ • 1
• PVC pipe; PVC pipe
Q PVC pipe; FRP pipe
D PVC pipe; Hume pipe
T m + an/2
A m - On/2
I . .
t
0 10 20
Leakage volume from house sewers (£/min)
30
Fig. 4.6 Leakage volume from house sewers and inlets
408
-------
According to Fig. 4.6, the quantity of leakage from the
house sewers is small when the same kind of material is used
for both the main sewer pipe and house sewers and is large when
the different kinds of materials are used. This means that
connections between the main sewer and house sewers are defect-
ive at the branches, or the connecting conditions of branch
pipes are greatly affecting tine connections with house sewers
or the joints of house sewers.
On the other hand, the quantity of leakage from the inlets
remains almost the same independent of the kind of material of
house sewer.
(3) Mean amount of infiltration at each facility
Based on the quantities of leakage from manholes, main
sewers, house sewers and .sanitary inlets obtained by the measure-
ments stated above, the quantities of leakage from standard
combinations of these facilities were obtained and indicated
in Table 4.2.
Table 4.2 Infiltration volume at each part of sewer
system
Name of
facility
Main sewers
Manholes
House sewers
Inlets
Sample
number
3,573m
125 sites
82
82
Total
leakage
volume
SL/min
1,198.35
127.12
470.8
618.4
Unit quantity
of leakage
0.335 Jl/min/m
1.017 5,/min/
site
5.74
7 . 54
Standard
quantity
10m
0.35 sites
1.46 sites
1.46 sites
Estimated
infiltra-
tion
volume
S-/min
3.35
0.36
8.38
11.01
23.1
Per-
cent-
age
(%)
14.5
1.5
36.3
47.7
100.0
Note.- Standard quantity means the quantity of each facility
per 10 m of main sewer and is the mean value in the
test district concerned.
409
-------
Table 4.2 shows the average values based on the water-
filling method, and the actual amount of infiltration can be
estimated after making corrections with groundwater level.
However, the amount of groundwater infiltration usually becomes
large when the groundwater level is high. Therefore, the fact
that about 80% of the total amount of infiltration is inflow
from house sewers and inlets will remain almost the same even
after making corrections.
4.4 Presumption of Inpouring Points of Groundwater
Change in the amount of infiltration in response to the
different inpouring points of groundwater was determined as the
amount of infiltration for each sewer facility in the previous
sections. However, in this section, the amount of infiltration
will be determined in the form of a relation with the ground-
water level, and then the method of assuming the groundwater
inpouring points (in the form of height from the bottom of main
sewer) will be explained.
If the vertical distributions of opening section in sewer
facility are considered to be (T) , (2) and(3) of Table 4.1 and
if the groundwater level (h) is given by the height from the
sewer bottom, then the amount of infiltration is given as a
function of the groundwater level. This function was general-
ized from the calculating formula shown in the same table.
Q(h) = a-hn (5)
where, a : constant.
In Eq. (5), the distribution of opening section is expres-
sed as n-th power of h. Therefore, this power value will be
considered as an index for expressing the distribution of open-
ing section and will be called "I/I distribution index".
410
-------
If the amount of infiltration is measured twice when the
groundwater levels are different at certain sewer facilities, and
the distribution index n can be obtained from Eq. (6).
n = Iog(q2/qi)/log(h2/hi) (6)
where, q. = Q(h^), i = 1, 2.
Index, n should here be considered to correspond to the mean height
of hi and h2-
The I/I distribution indexes were calculated for several sets
of two measurements at the same point with different groundwater
levels which were selected of the infiltration measurements by the
water-filling method described in the previous section, and then
the results were indicated in Fig. 4.7. According to this figure,
the distribution index n takes a value close to 2 when the ground-
water level is lower than 1m, and a value close to the broken
line in the same figure when the level is higher than 1m. This
will explain, as indicated in the previous section, that the
inpouring rate of I/I varies with the kind of sewer facility and that
the inflow rate becomes large as the location of the sewer
facility becomes closer to the ground surface.
Some house sewers had no defective portions and the distri-
bution index n in these cases was small. Also in Fig. 4.7, some
indexes n were close to 1.
This kind of I/I distribution index may be also averaged for
a particular drainage area and, if this index is built in an I/I
inpouring model, then the total amount of infiltration within the
drainage area may be given as a function of the groundwater level.
411
-------
10
X
0)
T3
o
4J
3
o
e
H
01234
Groundwater level from sewer bottom (m)
Fig. 4.7 Relation between groundwater level and
I/I/distribution index
412
-------
5. TECHNIQUES FOR I/I REDUCTION IN SEWERS
The I/I flow such as groundwater to the sewers can be pre-
vented either by technical or administrative measures. The ad-
ministrative measures are performed according to the conditions
of I/I and the technical eliminating measures and will therefore
not be reviewed in this report„
The technical preventive measures must be taken in each
stage of planning, construction, maintenance and management of
the sewer facilities. In this chapter, the watertightness of
sever facilities which was examined by the test already performed,
and the I/I eliminating techniques which was suggested from the
examination of watertightness will be explained.
5.1 Watertightness of Branch Pipe Connections
Watertightness of the connections between main pipes and
branch pipes was investigated for the purpose of I/I reduction.
The investigation was for the most of connecting methods cur-
rently used and developed. In the experiment were used the
sewer models, having the main sewer made of Hume concrete pipe
and the branch sewer made of two typical kinds of clay pipe and
polyvinyl chloride pipe. These pipes were connected together
in the same manner as on construction sites, and then the water
pressure-resisting strength and tension-resisting strength re-
quired for maintaining the watertightness at the connections of
branch pipes were measured.
Branch pipe ^ Measurement of
displacement
Cc
Water stop-
ing plate
n
\
nection ( \
\ \ ^
1 Water stc
/
NA. JL
^ ^
Main sewer
ping plate
Water pressure
pump
Water stoping plate
Fig. 5.1 Watertightness testing apparatus
413
-------
The water pressure-resisting strength was measured in the
form of the water pressure at the time when water leaks begin
due to pressure at an assembly model of a main pipe and branch
pipes filled up with water as shown in Fig. 5.1. Strengths
obtained are shown in Fig. 5.2 by comparing the clay pipe with
the PVC pipe. Also, the tension-resisting strength was obtained
as the load needed for pulling out the branch pipe, and the load
at a time of rupture was used as the tensile strength. Strengths
obtained are shown in Fig. 5.2 and Fig. 5.3.
In Figs,, 502 and 5.3, connecting methods used are indicated
by symbols. These symbols are listed below.
M : Mortar caulking method
MU : Caulking method using mixture of mortar and
urethane resin paste
E : Epoxy resin caulking method (Ei, £2)
U : Urethane resin caulking method
UG : Urethane resin injecting method
C : Compression joint method (only for clay pipe)
According to Fig. 5.2, the motar caulking method convention-
ally used provides a low strength for clay pipe and PVC pipe while
the caulking method and injecting method using polymer adhesives
such as epoxy resin and urethane resin provide a high strength.
Caulking method using adhesives made of mortar mixed with urethane
resin paste provides a strength higher than that of mortar method
for the clay pipes and almost equal to that of mortar method for
PVC pipes0
The compression joint method used only for clay pipe is able
to provide a water pressure-resisting strength equivalent to
that of resin type caulking method when the displacement of branch
pipe is forcibly restricted.
414
-------
Note: Broken line indicates the occurrence of
leakage at places other than connecting
portions.
Limit water pressure at clay pipe connection
(kq/cm2)
Fig. 5.2 Limit internal water pressure at
branch pipe connection
Limit load at clay pipe connection
(tons)
Fig. 5.3 Tensile limit load in branch
pipe connection
415
-------
5.2 Watertightness of Joints in House Sewers
Water-tightness of house sewers is concerned with the con-
necting conditions at joint and connections those of the inlets
and the main pipe. At the pipe joints, local failure or connec-
tion gap occurs due to differential settlement in surrounding
ground, accumulation of repeated load on roads or impact due to
earthquake, thereby decreasing the watertightness. Considerable
decrease in watertightness occurs also particularly when back-
filled earth is insufficiently rolled and compacted. Consequently,
the watertightness of house sewer was considered to be mainly related
the displacement and then the test was performed as explained
below.
When a displacement is given to a main pipe or house sewer,
wstertightness at the connections will decrease. A testing
apparatus shown in Fig. 5.4 applied to simulate the embedding
conditions on the site was used, and the displacement required to
leak the pressured water from pipe was measured. In this case,
the pipe to which.a pressure of 1.0 kg/cm2 was applied prior to
the measurement was filled up with water.
Results of the tests conducted for three different kinds
of connecting methods are expressed as function of the displace-
ment at loading point at the time of occurrence of water leak
and are indicated in Fig. 5.5. On the basis of Fig. 5.5, the
watertightness of each joint is considered to have the features
as explained below.
When mortar joints were pressured with 1.0 kg/cm applied
to the inside of pipe, water leaked out and, even without pres-
sure being applied, joints were broken after a displacement of
1.2 mm. Therefore, its watertightness is considered to be
broken even by a slight movement of ground.
Ordinary compression joints are able to maintain their water-
tightness up to a displacement of 4 to 7 cm. In the case of the
improved type of deep socket or socket with spacer, watertight-
ness can be maintained up to a displacements of 15 cm.
Rubber ring socket joints are able to maintain watertight-
ness up to a displacement of 12 to 17 cm. However, this value
416
-------
of displacement includes the deformation of PVC pipe as house sewer
so that these joints themselves are able to withstand displace-
ments almost equal to that of compression joints. Flexible
joints or expansion joints as improved types of the rubber ring
socket joint will hardly contribute to the improvement of water-
tightness and are used only for the simplification of piping
work.
5.3 On-site Watertightness Tests
In order to confirm the characteristics of connecting methods
for branch pipe and house sewer explained in the previous sections,
the Watertightness of the pipes actually laid on site was tested.
On-site Watertightness tests were performed by measuring the
quantity of leakage based on the water filling method for both
the house sewers and branch pipes.
Combinations of branch connections and house sewer joints
are shown in Table 5.1. Quantity of leakage at each connection
is indicated in Fig0 506.
Table 5.1 Combinations of Connections and Joints
in On-site Watertightness Test
Main sewer
Hume pipe
Hume pipe
Hume pipe
Hume pipe
Branch pipe
connection
Mortar
Mortar &
urethane
Urethane
Epoxy
Mortar
Mortar &
urethane
Urethane
Epoxy
Compression
joint
Branch pipe
Hume pipe
PVC pipe
Clay pipe
Clay pipe
Joints for
house sewers
Rubber ring
socket
Rubber ring
socket
Mortar
Mortar &
urethane
Urethane
Epoxy
Compression
joint
House sewers
PVC pipe
PVC pipe
Clay pipe
Clay pipe
417
-------
Water pressure
pump
x) fp)
Inlet
Displacement
(T) to (6) show joint and connection Nos.
Fig. 5.4 Displacement testing apparatus
20
3
0
•c 15
c
O
•O
IS
O
4-1
•H
s
4J
i
a
w
•rH
10
Rubber ring
socket joint
Compression
joint
Caulking
connection
0 5 10 15 20
Limit displacement with loading on main sewer (cm)
Fig. 5.5 Limit displacement at lateral
sewer joint
A18
-------
20
(U
a 10
•rn
a
from branch
Ul
0)
H ")
> I
0)
nl
-------
Fig. 5.6 shows the quantities of leakage from house sewer
and branch pipe plotted on both axes, from which the combinations
of connecting and jointing methods can be classified into four
groups relative to the watertightness as listed below.,
(T) A combination of caulking methods used for both the
joints of house sewer and connections of branch pipes
(clay pipe).
(2) PVC rubber ring sockets used for house sewers and mortar
type adhesive used for connecting branch pipes.
(D Compression joints are used for clay pipes.
(4) Branch pipe connections by polymer adhesives and PVC
rubber ring socket joints.
Characteristics of watertightness of the above combination of
joints and connections will be described below.
(I) Connections by compression joints are appropriate when
using clay pipes for branch pipes and house sewers.
Particularly, when using the caulking method for house
sewers accompanied with cumulative displacement, it
becomes necessary to install pipes in such a manner that
surrounding ground will not move after installation.
(2) Connection method using rubber ring socket joints and
polymer adhesives is suited to the PVC pipes. When the
caulking method is applied with bonding agents such as
mortar or mixtures of mortar and urethane resin, the
watertightness obtained will greatly fluctuate.
(3) Among the various kinds of connecting and jointing meth-
ods, only a few methods will be able to provide complete
watertightness. Realistic standard of watertightness
should be about 1 £/min of quantity of leakage (for water-
filling method).
420
-------
5.4 Infiltration/Inflow and its Reduction Techniques
In FY .1979, the proportion of Infiltration/Inflow to the in-
fluent was surveyed by a simple method in 26 drainage districts
throughout the country. Results of this survey are outlined in
Table 5.2. Fig. 5.7 shows the relation between the daily influent
per ha. of drainage area and the proportions of sanitary flow,
groundwater infiltration, and stormwater inflow.
J.UU
d?
- 60
:o influent
*»
O
Proportion 1
NJ
5 O
U
D
D
rP
Q *mri Average proportion
* . ° °Dw
m O a Sanitary flow
* % 60.2
D D
D
*0 * Groundwater
tf infiltration
• - • 37.0
0 • .'•*
• «.
i. O • Stormwater
OsA Of\ inflow
O ^^Xk PPi-fW O -, o
— u ooo> oC8» o — — 2-8
10 20 50 ' io'o 20"0
Daily influent per 1 ha of drainage area (m3/day/ha)
Small symbols show the proportions based on supplied
water volume.
Fig. 5.7 Proportion of infiltration to influent
421
-------
Table 5.2 Proportion of Infiltration to Influent
Name of
drainage
district
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
w
X
Y
Z
Average
Area of
drainage
(ha)
1,646
846
702
337
483
446
511
270
302
279
230
131
170
223
115
171
151
147
129
142
113
110
59
21
15
9
Drainage
population
(xio3)
184.1
97.1
40.2
19.8
62.0
44.7
15.8
9.4
30.6
11.3
28.3
7.3
12.5
9.8
17.4
7.0
13.0
21.1
18.0
13.9
15.3
66.9
10.2
4.2
0.9
0.8
Length of
sewer line
(km)
412.1
227.4
172.2
171.3
101.9
95.0
70.0
60.8
59.9
58.3
57.3
47.3
45.7
41.1
40.7
40.3
35.6
33.4
29.9
27.0
24.4
22.1
12.8
4.9
.3.6
1.9
Annual
influent
(xio'm3/
year)
24,467
8,319
3,046
3,010
8,079
5,277
885
1,730
4,660
2,531
2,777
1,126
1,027
843
4,732
4,484
943
2,137
1,780
1,127
1,783
895
1,164
597
80
72
Proportion to influent
Sewage flow
(%)
40.1
(67.5)
76.2
41.7
(97.9)
71.4
(98.2)
22.2
57.1
(25.5)
53.7
79.4
(84.2)
25.5
(62.6)
(74.8)
68.5
66.0
68.6
63.3
68.8
76.5
(96.3)
(53.6)
92.7
50.8
60.2
Groun-^water
infiltration
(%)
58.6
(30.6)
20.7
56.5
(0)
27.2
(0)
74.7
41.4
(73.1)
42.9
18.7
(10.5)
64.4
(33.7)
(19.7)
27.0
31.6
29.0
35.0
30.0
21.5
(0)
(45.2)
5.5
44.9
37.0
Stormwater
inflow
(%)
1.3
(1.9)
3.1
1.8
(2.1)
1.4
(1.8)
3.1
1.5
(1.4)
3.4
1.9
(5.3)
10.1
(3.7)
(5.5)
4.5
2.4
2.4
1.7
1.2
2.0
(3.7)
(1.2)
1.8
4.3
2.8
Remarks
Combined
system
Notes: 1. Values shown in ( ) are based on supplied water volume.
2. Average was obtained by eliminating values based on note 1.
422
-------
According to Fig. 5.7, the proportion of annual stormwater
inflow to the influent is about 3% and the proportion of ground-
water infiltration to the influent is about 37%. Though there is
no obvious relation between these emounts of infiltration and
influent per unit area, it will be known that the range of fluctua-
tion in the proportion of groundwater infiltration decreases as
the influent per unit area becomes larger. This probably means
that Infiltration/Inflow will flow in sewer systems under a steady
state as the sewage flow approaches a certain limit along with
population increase within a drainage area,,
However, the proportion of groundwater infiltration generally
shows no clear correlation with the drainage area, drainage popu-
lation and length of pipeline. Therefore, it will be more appro-
priate to consider that the amount of infiltration increases as
the number of defective portions in sewer systems becomes larger
and that defects in sewer systems occur at random.
The simplified method used in this survey is different from
that described in Chapter 2. That is, the amount of stormwater
inflow is calculated on the assumption that the hourly fluctuation
in daily mean sewage flow is constant through the year. Also, the
hourly minimum sewage flow per day is calculated on the assumption
that it equal to used as the amount of groundwater infiltration.
Accordingly, if a more detailed survey is performed, the estimated
proportion of annual groundwater infiltration to the influent is
likely to become somewhat smaller.
Infiltration of groundwater into sewer systems is taken into
account in the sewer line planning, and about 10 to 20% of daily
maximum sanitary flow is used as amount of groundwater. On the
other hand, according to the survey of actual conditions, the
proportion of groundwater infiltration to the sanitary flow is
about 50% as annual average. In this averaged value is included
that of the drainage district where the present sanitary flow
does not reach the design value. Hence, it becomes necessary to
multiply the value obtained by a ratio between the present daily
423
-------
mean sanitary flow and corresponding design value. At present,
since the daily sanitary flow does not reach the design value
in most sewage treatment plants, the amount of groundwater infilt-
ration is considered to be less than the expected amount as long
as the conversion stated above is performed.
This amount of groundwater infiltration will increase as long
as the conventional method of sewer piping work is performed.
Also, if the amount of infiltration increases, the flowing capacity
of sewer system may become insufficient, quality of treated water
may worsen, or the treatment and maintenance costs may increase due
to overloading of sewage treatment plants. These undesirable con-
ditions may also create serious technical administrative and finan-
cial problemso
From the results of tests obtained up to now, the following
techniques can be .considered for the prevention or reduction of
infiltration/inflow:
(1) Improvement of ground around sewer system.
(2) Improvement of durability and strength of materials of
sewer pipes.
(3) Improvement of watertightness of connections and joints
of sewer pipes.
(3) Improvement of expansibility of joints of house sewers.
(5) Prevention of misconnections to sanitary sewage inlets.
Though these prevention techniques are known, previous targets
of improvement were not quantitative and the degree of influence
upon the reduction of infiltration was not clear. As a result of
the present survey, the inflow mechanism of the Infiltration/Inflow
and the general relation between the kinds of sewers and the amount of
the infiltration have been found, so that proper goals of research
and development of the prevention techniques can now be more easily
determined. Important improvement techniques will be briefly ex-
plained below.
424
-------
Though the improvement of ground around sewer systems was
generally considered for the back-filled earth, low permeability
as well a? high bearing capacity are needed in areas where the
groundwater level is high.
Currently, Hume concrete pipes, clay pipes and polyvinyl
chloride pipes are mainly used for sewers with small and medium
diameters. Strength of these materials is mainly discussed from
a different viewpoint such as workability and economy but the
•
present strength seems to be sufficient for the prevention of.
Infiltration/Inflow.
The mortar caulking method used for connecting sewer pipes
should not be used when the displacement of sewer system or its
surrounding ground is likely to occur. A caulking connection
method using polymer adhesives currently developed can provide
effective watertightness for the PVC pipes.
Clay pipes themselves cannot respond properly to displace-
ment and thus joints of house sewers should have an expandable
structure so as to allow the whole sewer system to properly
respond to displacement. The compression joint method currently
developed enables both the watertightness and proper response to
the displacement to be obtained.
In addition, the amount of infiltration can be reduced also
by the administrative guidance but this has not been explained
here.
425
-------
REFERENCES Quantification Regression Analysis (Hayashi's Model)
The purpose of quantification analysis is to explain a certain
dependent variate Y (external criterion) by using explanatory
factors having r-kinds of qualitative characteristics which are
considered to be affecting the fluctuation of dependent variate.
The basic formula required for calculation will be described below.
Qualitative explanatory factors will be respectively classi-
fied into the categories of PI, Pa, ... pr kinds, and the reaction
of sample with each category will be expressed by a dummy variable.
If a sample V is considered, the dummy variable can be defined by
Eq. (1).
1 : when sample v reacts with j category
of i factor.
...(1)
0 : when sample v does not react with j
category of i factor.
Each sample V must react with one of categories in a certain
factor. Therefore, such a relation may be represented by Eq. (2).
]>2 X(l) = 1 i = 1,2,... , r factor (2)
V = 1,2,..., n sample
It is assumed that the following linear relation will occur
between dependent variate Y and dummy variable:
R(2) (2) R(2M2)
+ PI X !v> + + P X
P2 P2V
o(r) (r) R(r) (r)
1V Pr XPrv
ev ; V = 1, 2, .. ,., n (3)
426
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where, ev is a disturbance term or a random variable.
Then, Eg.(3) is expressed as follows in matrix notation:
Y =X3 + e (4)
Then, the following basic assumption is made for e :
E(e)= 0 (expected value of ey is 0) (5)
E(ee') = eln (variance of ey is constant e,
covariance is 0) (6)
Xis a set of fixed numbers (7)
r
Rank of X = P - (r - 1) < n, p = XlPi <8>
i=l
If the estimate vector of g to be determined is expressed by
]3, then the following formula will hold:.
Y=X8 + | (9)
The "Method of least squares" should be applied to Eq. (9)
^
and 3 should be determined in such a manner that sum of residual
/\
squares ,e'e will become the smallest. Then, this § is the coe-
fficient related to each category. If ev =0 is applied in Eq. (3),
then the dependent variable Yv is obtained as a linear sum of
the explanatory factors.
427
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BIBLIOGRAPHY
1. "Guideline for Infiltration/Inflow Reduction in Sewer Systems",
March 1983, Department of Sewerage and Sewage Purification
Construction.
2. Ishihara and Koroma, et al. "Applied Hydraulics (Part I)",
P.204, 1973, Maruzen.
3. Eiichi Suzuki "Environmental Statistics", 1975, Environmental
Information Science Center.
4. Haruhiko Iguchi "Multivariate Analysis and Computer Programs",
1972, Nikkan-Kogyo.
5. "Handbook of Sewer System Evaluation and Rehabilitation", Dec.
1975, Technical Report, U0S. EPA 430/9-75-021.
6. Mather, P.M, "Computational Methods of Multivariate Analysis
in Physical Geography", 1976, John Wiley & Sons.
428
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UNITED STATES PAPERS
THE PAST IS PROLOGUE: LOOKING BACK, LOOKING AHEAD AT THE UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY'S CONSTRUCTION GRANTS PROGRAM 431
Henry L. Longest II, Office of Water Program Operations,
U.S. Environmental Protection Agency, Washington, D.C.
COARSE BUBBLE TO FINE BUBBLE AERATION RETROFIT 483
Paul F. Gilbert and James H. Chase, Hartford Water Pollution
Control Plant, the Metropolitan District Commission,
Hartford, Connecticut
CLEAN WATER IN WISCONSIN 505
Paul N. Guthrie, Jr., Wisconsin Department of Natural Resources,
Madison, Wisconsin
REMOVAL AND PARTITIONING OF VOLATILE ORGANIC PRIORITY POLLUTANTS
IN WASTEWATER TREATMENT 559
Albert C. Petrasek, Jr., Barry M. Austern, and Timothy W.
Neiheisel, U.S. Environmental Protection Agency, Cincinnati, Ohio
ENERGY USE AT MUNICIPAL WASTEWATER TREATMENT PLANTS: OVERVIEW AND
CASE STUDIES 593
Gary R. Lubin, Wastewater Research Division, Municipal
Environmental Research Laboratory, U.S. Environmental
Protection Agency, Cincinnati, Ohio
ENERGY RECOVERY, REUSE, AND CONSERVATION AT METRO CHICAGO 629
Cecil Lue-Hing, Hugh McMillan, Raymond R. Rimkus, and Forrest C.
Neil, the Metropolitan Sanitary District of Greater Chicago,
Chicago, Illinois
PROGRESS IN SEQUENCING BATCH REACTOR TECHNOLOGY 663
E.F. Barth, B.N. Jackson, and J.J. Convery, Wastewater Research
Division, Municipal Environmental Research Laboratory, U.S.
Environmental Protection Agency, Cincinnati, Ohio
THE BIOLOGICAL AERATED FILTER - PROGRESS OF DEVELOPMENT IN THE U.S. . 683
Gary R. Lubin, Wastewater Research Division, Municipal
Environmental Research Laboratory, U.S. Environmental Protection
Agency, Cincinnati, Ohio
SLUDGE MANAGEMENT PLANS AND PRACTICES AT THE METROPOLITAN SANITARY
DISTRICT OF GREATER CHICAGO 719
Cecil Lue-Hing, Hugh McMillan, Forrest C. Neil, and Raymond R.
Rimkus, the Metropolitan Sanitary District of Greater Chicago,
Chicago, Illinois
429
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UNITED STATES PAPERS (Continued)
SLUDGE INCINERATOR FUEL REDUCTION PROGRAM 753
Paul F. Gilbert, Hartford Water Pollution Control Plant, Hartford
Metropolitan District Commission, Hartford, Connecticut, and
Eugene W. Waltz, Energy Engineering and Research Division,
Indianapolis Center for Advanced Research, Indianapolis, Indiana
430
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THE PAST IS PROLOGUE:
LOOKING BACK, LOOKING AHEAD
AT THE UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY'S
CONSTRUCTION GRANTS PROGRAM
by
Henry L. Longest II
Director, Office of Water Program Operations
Environmental Protection Agency
401 M Street SW
Washington, D.C. 20460
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
431
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THE PAST IS PROLOGUE:
LOOKING BACK: LOOKING AHEAD
At the United States
ENVIRONMENTAL PROTECTION AGENCY'S
CONSTRUCTION GRANTS PROGRAM
Contents
Subject
Abstract
INTRODUCTION
HISTORICAL BACKGROUND
Before 1948
Federal Water Pollution Control Act of 1948
Water Pollution Control Act Extension of 1952
Federal Water Pollution Control Act of 1956
Federal Water Pollution Control Act Amendments of 1961
Water Quality Act of 1965
Clean Water Restoration Act of 1966
Environmental Action and EPA
Water Quality Improvement Act of 1970
1970 Permits Program
FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
Goals
NPDES Permit Program
Treatment Levels
Construction Grants Program
Problems
Funding
Federal/State Role
Permits
Water Quality Standards
Secondary Treatment Controversial
Compliance
CLEAN WATER ACT OF 1977
State Delegation
Extended Deadlines
Rural States
Innovative and Alternative Technology
Waivers for Ocean-Discharging Communities
432
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Clean Water Act of 1977 (Continued)
Funding
Progress
Problems
Advanced Treatment
FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1980
MUNICIPAL WASTEWATER CONSTRUCTION GRANTS AMENDMENTS OF 1981
Funding
Extended Deadlines
Immediate Changes
Changes October 1, 1984
CONSTRUCTION GRANTS; THE PRESENT
Program Priorities
Regulatory Reform and Guidance
State Delegation
Overview
Water Quality
Advanced Treatment
Project Completions
Compliance
Industrial
Municipal
New Factors
Secondary Treatment Redefined
Waivers for Ocean-Discharging Communities
Municipal Compliance Policy
Financial Capability
Financial Capability Policy
I/A and Appropriate Technology
Financing Publicly Owned Treatment Works
States: Restructure Programs
CONSTRUCTION GRANTS; THE FUTURE
Funding
New Federalism
Infrastructure
Privatization
Self-Sustaining Public Utilities
New Directions
Management
Facility Planning and Design
Secondary Treatment
Innovative and Alternative Technology
Small Communities and Appropriate Technologies
Advanced Treatment
433
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New Directions (Continued)
Ocean-Discharge Waivers: 301(h)
Pretreatment of Industrial Wastes
Legislative Background
1972 Clean Water Act
1976 Consent Decree and the 1977 Clean Water Act
Implementation of Clean Water Act Pretreatment Requirements
EPA's Pretreatment Program
General Pretreatment Regulations
Pretreatment Standards
Removal Credits
EPA Studies and Pretreatment
National Effluent Standards for Direct Dischargers
Sludge
Sludge as a Resource
Land Application of Sludge
Sludge Quality and Land Application
Marketing Sludge Products
Sludge and the Future
THE PAST IS PROLOGUE
Progress
Water Cleanup
Foundation for Future
Reforms in Place
EPA-State Commitment
ATTACHMENTS
A. Evolution of the Construction Grants Program
B. NRDC Consent Agreement/1977 Clean Water Act
List of Toxic Pollutants
C. Effluent Guidelines: Proposed and Final Rules
D. Control of Industrial Wastewater Discharges in the U.S.
BIBLIOGRAPHY
434
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ABSTRACT
The Federal Water Pollution Control Act of 1972 created the
multibillion-dollar construction grants program as part of a massive
Federal assault on the country's widespread water degradation caused by
decades of unchecked municipal and industrial water pollution. The
program would attack municipal pollution by helping communities pay for
construction of municipal wastewater treatment facilities. Industries
were to build treatment facilities with their own resources.
The 1972 legislation's premise was that no one has the right to
pollute. It aimed to achieve fishable and swimmable waters by 1983 where
possible and a total elimination of all pollutant discharges into
navigable waters by 1985. Its stated goal was no less than "... to
restore and maintain the chemical, physical, and biological integrity of
the Nation's waters."
To achieve its goals, the Act set a minimum national effluent
standard for all municipalities and industries that discharged into
navigable waters and demanded a technology known as secondary treatment
or its equivalent to meet the standard. Where State water quality
standards were higher than the minimum national standard, dischargers had
to meet the more stringent State standards. To enforce the national and
State standards, the Act called for a national permit program that
required all who discharged significant amounts of wastewater into
navigable waters to get a Federal permit. The Act set strict enforcement
procedures that called for heavy fines or possible imprisonment for
willful or repeated violators.
To help municipalities meet the new requirements, the 1972 Act
authorized $18 billion for the construction grants program to help pay
for treatment facilities. The Federal Government paid 75 percent of the
project's cost and the community, usually with State help, paid the other
25 percent. Total appropriations for the program through October 1984
amount to over $40 billion.
This paper traces the evolution of Federal water pollution control
from the turn of the century to the landmark 1972 legislation and the
construction grants program. It describes the growth of the program, its
redirection toward the States with the 1977 amendments, and the further
acceleration of this direction with the 1981 amendments. The paper re-
counts the successes and the problems of the construction grants program
and looks at its probable future direction as the Federal role phases into
one of overview and the States assume management of their own programs.
435
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THE PAST IS PROLOGUE:
LOOKING BACK, LOOKING AHEAD
AT THE UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY'S
CONSTRUCTION GRANTS PROGRAM
Henry L. Longest II
Director, Office of Water Program Operations
Environmental Protection Agency
401 M Street SW
Washington, D.C. 20460
INTRODUCTION
Inscribed near the portico of the National Archives building, the
repository of my country's historic documents in Washington, D.C., are the
words, "The Past Is Prologue." Those words seem almost personally tailored
to my subject today—the evolution of the water pollution control programs
in the United States.
A little over 10 years ago, the United States Environmental Protection
Agency (EPA) submitted its first annual report to Congress on the 1972
Clean Water Act. That Act was the most far-reaching water pollution
control legislation in United States history. Its official title was the
Federal Water Pollution Control Act Amendments of 1972. It aimed to
eliminate all pollutant discharges into navigable waters by 1985 and to
make waters fishable and swimmable by 1983. Its stated goal was no less
than "... to restore and maintain the chemical, physical, and biological
integrity of the Nation's waters." EPA's report to Congress was dated May
31, 1973, just 7 months after the Act went into effect on October 18, 1972.
Today I would like to give you an overview of my country's efforts to
clean up its waters, before and since the landmark 1972 legislation. I
shall especially focus on the construction grants program, which I
administer.
The 1972 legislation created the multibillion-dollar construction
grants program to help States and municipalities finance construction of
wastewater treatment facilities. The program would be the most visible
part of the massive Federal and State assault on the country's widespread
436
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water degradation, the result of centuries of unchecked industrial and
municipal pollution.
My review will highlight four areas in the program's evolution: the
changing Federal-State role; the technology vs. the instream-water-quality
approach emphasized by various legislation; enforcement provisions; and
financing.
That we are all here at this conference sharing information on our
successes as well as our problems in water pollution control testifies to
the continuing dedication to environmental protection, not just in my
country and Japan, but in all countries represented here today.
HISTORICAL BACKGROUND
In the United States, this present widespread public support for
environmental legislation was slow in coming. All but six Congresses since
1897 considered Federal participation in water pollution abatement. More
than 100 bills were introduced in the Congress, but none passed.
BEFORE 1948
The first specific Federal water pollution control legislation was the
Rivers and Harbors Appropriations Act of 1899, often called the Refuse Act.
This legislation's goal was not basically to control pollution but to
prevent obstructions to navigation by prohibiting dumping of solids into
navigable waters without a permit from the U.S. Army Corps of Engineers.
Later, the 1912 Public Health Service Act authorized investigation of water
pollution related to diseases. The 1924 Oil Pollution Act attempted to
control oil discharges in coastal waters to protect aquatic life, harbors
and docks, and recreation facilities. There were attempts in 1936, 1938,
and 1940 to pass comprehensive national legislation to protect water
quality but each failed.
FEDERAL WATER POLLUTION CONTROL ACT OF 1948
It was not until 1948 that the first comprehensive national
legislation aimed specifically at controlling industrial and municipal
water pollution was enacted. This was the Federal Water Pollution Control
Act of 1948 (P.L. 80-845).
The Act authorized $22.5 million for each of 5 years from 1948 to 1953
for 2 percent loans to States, municipalities, and interstate agencies to
build wastewater treatment works that would control pollutant discharges
into interstate waters and tributaries. Loans could be $250,000 or
one-third the cost of construction, whichever was less. The Act also
authorized Federal grants of $5 million over the same 5 years to be awarded
to States and municipalities to help plan and design wastewater treatment
facilities. In addition, $5 million, at $1 million each year, was
authorized for grants to States to study ways to prevent pollution from
industrial wastes.
437
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While the 1948 Act provided the first comprehensive Federal, State,
and local cooperative approach to water pollution, it was more important in
concept than in effect. It resulted in only a trickle of money to study
industrial pollution and to help plan and design treatment works.
The Act recognized and preserved the primary rights and responsibi-
lities of the States to control water pollution. There were no Federally
required goals and no effective enforcement. The Federal Government could
sue violators only with the consent of the State in which the violation
occurred.
In prophetic words the Senate report of July 8, 1947, warned that "...
failure to accomplish adequate progress through cooperative efforts of
Federal and State agencies will undoubtedly call for much stronger and more
direct Federal enforcement measures at some subsequent session of
Congress."
WATER POLLUTION CONTROL ACT EXTENSION OF 1952
In 1952 Congress extended the Act for 3 years, from 1954 through 1956,
with P.L. 82-579. But, again, the Act had little real national impact.
FEDERAL WATER POLLUTION CONTROL ACT OF 1956
The first major legislation to reflect a significant Federal financial
commitment to a national pollution control program came 4 years later, with
the Federal Water Pollution Control Act of 1956 (P.L. 84-660). This Act is
often referred to as the "Old Law."
The 1956 legislation called for increased cooperation between the
Federal Government and the States to develop a broader national effort
against water pollution and permitted Federal participation in a wide range
of activities. They included Federal-State cooperation in developing
programs, increased technical assistance to States, and broadened research.
The law authorized a 10-year grant program at $50 million a year from
1956 to 1966 to help communities finance construction of wastewater
treatment facilities. Grants were limited to 30 percent of the total
project cost with a maximum of $250,000. This dollar ceiling, in effect,
limited grants to small projects.
Federal intervention in enforcement was still limited to cases
involving interstate waters, and enforcement still involved joint Federal
and State efforts.
As pressures of population and economic growth upon the country's
natural resources continued to multiply, it was obvious that authorized
Federal funding fell far short of needs.
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FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1961
These pressures and the public's rising interest in pollution control
were reflected in the 1961 amendments to the Federal Water Pollution
Control Act (P.L. 87-88). This Act increased authorizations and the
Federal grant share and strengthened Federal enforcement for interstate
waters.
Federal grants remained at 30 percent of the project's cost but
Federal support could now be as high as $600,000. Where communities joined
to build one project, Federal grants could go as high as $2.4 million.
Authorizations increased from $80 million for fiscal year 1962 to $90
million for fiscal 1963 and $100 million a year each for fiscal years 1964
to 1967.
The law extended Federal enforcement authority to coastal waters and
navigable intrastate waters under certain restricted conditions but still
required State permission before Federal enforcement. In an important
extension of Federal authority, the law permitted Federal suits against
polluters of interstate waters without the State's permission.
WATER QUALITY ACT OF 1965
Water quality became a predominant value with the second major
amendment to the Water Pollution Control Act, the Water Quality Act of 1965
(P.L. 89-234).
The 1965 Act directed that States develop water quality standards for
interstate navigable waters. A water quality standard is a legal
expression of the amount of pollutants allowed in a particular water body.
The standards are based on water quality criteria that provide a level of
water quality needed for a range of designated uses. The Federal
government develops the water quality criteria which States include in
their standards. The States decide the water body's designated use. The
State standards were subject to Federal approval. The Act created the
Federal Water Pollution Control Administration to administer the national
program.
The Act increased annual authorizations for constructing wastewater
treatment works to $150 million for fiscal years 1966 and 1967. It also
provided grants for research and development in better ways to control
overflow from storm sewers and combined storm-sanitary sewers.
Enforcement continued to be difficult. The Act continued the basic
instream water-quality approach to pollution control. Federal enforcement
applied only to interstate waters and the burden of proof rested with the
enforcing agency. An enforcement action had to prove the waste discharge
reduced the quality of receiving waters below the established instream
water quality standards or that the discharge endangered health and
welfare. The statute also directed that the courts consider the cost of
cleanup. These and other limitations led to a widespread perception that
more stringent standards and enforcement procedures were needed.
439
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CLEAN WATER RESTORATION ACT OF 1966
A year later Congress authorized a massive expansion in the Federal
financial commitment to the construction of wastewater treatment facilities
with the Clean Water Restoration Act of 1966 (P.L. 89-753). The
legislation authorized a Federal expenditure of $3.5 billion over a 4-year
period from fiscal years 1967 to 1971. The Federal share increased from 30
percent to a maximum of 55 percent. While this represented an increased
Federal commitment, the actual funds appropriated by Congress for fiscal
years 1967 to 1971 were little more than half the authorized amounts.
ENVIRONMENTAL ACTION AND EPA
The slow pace of water cleanup led to mounting public frustration and
contrasted sharply with technological breakthroughs in other areas.
In 1969, two seemingly unrelated events captured national attention.
On June 22, the Cuyahoga River in the State of Ohio caught fire. Less than
a month later, on July 20, Neil Armstrong walked on the moon.
The country's mood then was that man's reach no longer exceeded his
grasp. Technology had stretched his arm to the moon. So technology could
certainly clean up the environment here on Earth, given the will and the
money. And money was no problem in 1969. The national budget showed a
$3.3 billion surplus.
Environmental concerns were everywhere in 1969 and they were rapidly
translated into action in the following years. Congress passed the
National Environmental Policy Act of 1969 (NEPA) requiring assessment of
environmental impacts before major Federal actions were initiated. The
growing power of the environmental movement came into sharp focus on April
20, 1970, with Earth Day, a nationally organized outpouring of ecological
fervor across the country. On July 9 President Nixon created the
Environmental Protection Agency by sending to Congress Reorganization Plan
Number 3. The Plan transferred 15 government units with their functions
and legal authority to the new agency effective December 2, 1970. The
Agency saw its first administrator, William D. Ruckelshaus, confirmed by
Congress the next day.
WATER QUALITY IMPROVEMENT ACT OF 1970
The 1970 Water Quality Improvement Act (P.L. 91-224), passed in April
of that year, repealed the 1924 Oil Pollution Act and added strong oil
control provisions to the Federal Water Pollution Control Act. The 1970
Act also added significant innovations to the basic law, such as providing
for demonstration projects for Great Lakes cleanup and manpower training
programs to increase the number of water pollution control personnel. But
Congress and the Administration saw that the public wanted a still stronger
and more visible Federal commitment to clean up the Nation's waters.
440
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1970 PERMITS PROGRAM
To get started on immediate cleanup, the newborn EPA and the U.S. Army
Corps of Engineers launched a national permit program December 23, 1970,
claiming authority under the 1899 Refuse Act. The new program required all
industries that discharged into navigable waters to get Federal permits.
Unlike the Federal Water Pollution Control Act, which used the water
quality standards-enforcement approach to pollution control, the Refuse Act
Permit Program used an effluent limitation approach. This meant
restricting pollutants at the point of effluent discharge. The Refuse Act
also applied to intrastate as well as interstate navigable waters. Though
a year later an Ohio Federal judge struck down the permit program, EPA
staff continued to check and verify information on the 23,000 permit
applications received. They hoped to keep the program going until new
legislation could be passed.
Meantime, extensive hearings convinced Congress that the then current
legislative approach was not working. The consensus was that the country
needed a law with strong teeth and that the teeth should be a permit
program and national technology-based standards and effluent controls.
FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
The result was the Federal Water Pollution Control Act Amendments of
1972 (P.L. 92-500), a sweeping rewrite of all existing water pollution
control legislation. The Act's premise was that enforceable national
technology based effluent controls were needed in addition to the previous
emphasis on achieving instream water quality. It set ambitious new goals
and authorized massive Federal funding to achieve them.
Goals
The complex 89-page law, enacted October 18 over Presidential veto,
required minimum technology based effluent standards for industrial and
municipal wastes. These were described as "best practicable technology"
for industrial wastes and secondary treatment as the equivalent for
municipal wastes. All dischargers were to achieve these levels of
treatment by July 1, 1977, to meet the Act's goals: fishable, swimmable
waters by 1983, where achievable, and a total elimination of pollutant
discharges into navigable waters by 1985.
NPDES Permit Program
The Act extended Federal enforcement powers to intrastate as well as
interstate waters and called for a National Pollutant Discharge Eliminaton
System (NPDES) permit program to force dischargers to meet the national
goals. The NPDES permit program incorporated many features of the Refuse
Act permit program. Concentrating first on the most significant sources of
pollution, EPA established a policy that by December 31, 1974, permits
would be awarded to each of the approximately 5,000 most significant
industrial and municipal facilities that discharged directly into navigable
441
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waters. Each permit set specific limits on the amount and kind of each
pollutant discharged and established an enforceable schedule for
compliance. Both civil and criminal penalties were provided. Violators
could be fined up to $25,000 a day and imprisoned up to a year with
increased penalties for repeated violations.
Treatment Levels
In addition to the 1977 treatment requirements, direct industrial
dischargers were to have in place "best available technology" (BAT) by July
1983, where economically achievable. EPA was ordered to publish a list of
toxic pollutants and effluent standards for these pollutants 6 months after
it published the list. Industry was to comply with effluent standards for
65 toxic pollutants within a year after EPA published the standards.
Industries that discharged to publicly owned treatment works (POTWs) were
to install systems to pretreat waste that could harm the POTW or pass
through to pollute receiving waters and sludges.
For municipalities, EPA defined secondary treatment as 85 percent
removal of biochemical oxygen demand (BOD) and suspended solids or 30
milligrams per liter for BOD and 30 milligrams per liter for suspended
solids. In addition, pH was limited at 6.0 to 9.0 and fecal coliform at
200 per 100 milliliters. This definition meant treatment facilities funded
since the 1956 "Old Law" and not designed for secondary treatment would
need to be upgraded.
Although the new law shifted emphasis to enforcement through
technology based effluent standards, it also retained requirements for
achieving instream water quality based on State water quality standards.
Where needed to meet water quality standards, industrial and municipal
dischargers were required to apply more stringent effluent controls.
The Act demanded a radical turnaround in the way industry, States, and
municipalities dealt with water pollution. Congress felt that industries
could raise money to accomplish cleanup on their own but that muncipalities
could not.
Construction Grants Program
To help communities meet the stringent new treatment requirements, the
Act created the construction grants program to help municipalities finance
construction of needed wastewater treatment facilities.
The Act made available a staggering $18 billion to fund the program
for 3 years from fiscal years 1973 through 1975: $5 billion for 1973; $6
billion for 1974; and $7 billion for 1975.
The money was to be used for 75 percent Federal grants to help
municipalities pay for new treatment facilities or upgrade facilities
already operating. The municipality, usually with State help, would pay
442
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the other 25 percent. The grants were awarded in three different steps:
Step 1 for facility planning; step 2 for design; and step 3 for actual
construction.
Almost every component of a wastewater treatment system qualified for
funding under the definition of "treatment works." Besides the treatment
plant itself, it included major sewer rehabilitation, storm sewers,
interceptor and collector sewers, control of infiltration/inflow and
combined sewer overflow, and purchase of land for land treatment systems.
The grant money was allocated to States according to an allotment
formula specified by Congress. Allocations depended on the State's total
needs as compared to national needs. To determine what these needs were,
Congress directed that EPA submit a needs survey to Congress every 2 years.
Each State had to develop a priority system and draw up a priority list
that set the order for project funding. EPA had to approve the priority
system and review the list.
The Act also provided the first direct Federal funding for State waste
treatment management planning on an areawide basis and authorized major
research and development to develop new technology to eliminate pollutant
discharges into navigable waters and contiguous zones and oceans. To
supply the technical expertise the new treatment facilities would need, the
Act provided funds to help States build manpower training centers and to
develop training programs and materials through State and academic
institutions.
Problems
Funding—
The $18 billion made available over 3 years for the construction
grants program in 1972 was thought to be enough to solve the major water
pollution problems as they were then defined. But problems surfaced
immediately.
President Nixon impounded $9 billion of the available funds as soon as
the Act passed because he felt the funds were excessive and could not be
effectively spent. Funding in the ensuing years remained unstable and
unpredictable. Actual funding for fiscal year 1973 was $2 billion; for
1974, $3 billion; and for 1975, $4 billion. The impounded $9 billion was
released in 1976 on a ruling of the United States Supreme Court.
Federal/State Role—
Initially the new program incurred resentment in some State and local
governments who felt that their authority decreased as their workload
increased. Besides dealing with a complex new law and regulations and a
complicated new grants process, States were assigned numerous new tasks.
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While the law provided grant funds to assist States financially with
their new duties, these and other problems strained the resources of EPA
and State and local governments.
Permits—
Though EPA had 23,000 industrial permits almost ready to issue as a
result of its 1970 permit program, these were only part of the 60,000
permits that needed to be issued to municipal, industrial, and other
dischargers. The law encouraged EPA to delegate permitting and enforcement
authority to States that could handle the task. But all States, delegated
or not, had to review and certify each permit for consistency with their
water quality standards.
Water Quality Standards—
In addition, States had to revise their water quality standards to
meet the more stringent requirements of the 1972 Act. The 1965 Act
required that States develop water quality standards for interstate waters.
The 1972 Act required that these standards be revised and that Federal
enforcement authority apply to intrastate as well as interstate waters.
More stringent water quality standards and effluent requirements also
often imposed financial hardships on communities who were required to build
costly central treatment systems which they determined they could not
afford to operate and maintain, much less build.
Secondary Treatment Controversial—
The uniform secondary treatment requirements drew immediate criticism
from many dischargers who felt the standard was too rigidly defined. The
stringent effluent requirements came under attack by several West Coast
communities who argued that secondary treatment was unnecessary for
effluent discharged into deep ocean waters where wastes rapidly aerate and
disperse and where many fresh-water micro-organisms cannot survive. These
communities pressured Congress and EPA to grant waivers from secondary
treatment to qualifying ocean-discharging communities.
EPA amended the secondary treatment definition in 1976 and 1977. It
deleted the fecal coliform limitation, clarified the pH requirement, and
relaxed the suspended solids requirement for ponds that treated less than 2
million gallons of wastewater a day. This left secondary treatment defined
as 30 milligrams per liter for biochemical oxygen demand (BOD) and 30
milligrams per liter for suspended solids (SS) or 85 percent removal of BOD
and SS on a monthly average.
Compliance—
As the 1977 secondary treatment deadline approached, it became obvious
it would not be met. Needs estimated in 1973 at $60.7 billion by 1976
totaled $96 billion. These needs included total system capital costs and
allowed for future population growth of approximately 20 years. A
444
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factor contributing to higher costs was that some States set stringent
water quality standards which meant higher and more expensive levels of
treatment than secondary. Another problem was that EPA failed to publish
the required list of toxic pollutants or effluent standards to control them
due to a lack of sound scientific information on toxics and limited EPA
resources.
Industry outpaced municipalities in meeting the July 1, 1977, best
practical technology (BPT) deadline. By that time 81 percent of the most
significant industrial dischargers issued permits by the end of 1974 had
BPT in place but only 30 percent of municipalities had achieved secondary
treatment. Two major factors accounted for this difference in compliance.
First, municipalities were not required to be in compliance if they were on
schedule to achieve secondary treatment and had received an EPA
construction grant or were on the State's priority system to receive a
grant. Second, most of the Agency's permitting and compliance efforts were
devoted to industrial dischargers.
CLEAN WATER ACT OF 1977
Congress saw the need for midcourse corrections and responded with the
1977 amendments to the Clean Water Act (P.L. 95-217) of December 27, 1977.
The 1977 amendments significantly changed the direction of the
construction grants program. They encouraged delegation of the program to
the States and authorized delegated States to use construction grants funds
to manage their programs. They also provided financial relief for small
communities; encouraged innovative and alternative technologies and
conservation, recycling, and reuse of wastewater constituents; directed
that communities choose the most cost effective system to solve their
wastewater problems; and extended the secondary treatment compliance
deadline.
State Delegation
The 1977 amendments authorized States to take over major portions of
the construction grants program through delegation agreements. Delegated
States could use 2 percent or a minimum of $400,000 of their annual
construction grant allotment to manage their programs. But not all
activities could be delegated. EPA still retained statutory authority to
make grant awards, resolve audits and appeals, make judgments on National
Environmental Policy Act requirements, and, by order of Congress, review
high-cost advanced treatment projects.
Extended Deadlines
The Act extended the July 1, 1977, secondary treatment deadline to
July 1, 1983, for most noncomplying communities and extended the best
practicable technology (BPT) deadline to April 1, 1979, for industrial
dischargers. The 1983 best available technology (BAT) requirements for
industry were expanded to include toxic pollutants.
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Rural States
To help alleviate adverse economic impacts on small communities, the
1977 amendments directed that rural States set aside 4 percent of their
allotments for alternative systems in communities of 3,500 or less and
allowed these projects to get 85 percent Federal grants. An alternative
technology is one that has proven its worth in actual use. These systems
include septic tanks and upgraded variations for individual residences or
clusters of residences, pressure and vacuum sewers, small-diameter gravity
sewers, and many others.
Innovative and Alternative Technology
To force new technology and reduce costs, all States had to set aside
a percentage of their annual allotments for innovative or alternative (I/A)
technologies. Set-aside percentages were 2 percent in fiscal years 1979
and 1980 and 3 percent in fiscal year 1981. An innovative technology is
defined as one that has not yet proven its worth in the anticipated use.
I/A portions of projects received 85 percent Federal grants. Provision was
also made to reimburse communities for failed innovative approaches.
Waivers for Ocean-discharging Communities
Congress also allowed EPA to grant waivers from secondary treatment
requirements to qualifying communities that discharged to the ocean and
that applied for waivers by September 13, 1979.
Funding
Congress authorized a total of $25.5 billion for the construction
grants program for fiscal years 1978 through 1982. Actual appropriations
for fiscal year 1977 through fiscal year 1979, however, were $10.1 billion.
Progress
The construction grants program made impressive progress despite the
massive effort it took to get the giant program into operation with such
uneven funding. By 1980 the program had matured to a high degree of
operational stability. The Federal and State governments had grown
accustomed to working together. States understood the program's
complexities and many were on their way to full delegation. A national
pool of trained State personnel had been created. EPA enhanced State
personnel resources by drawing upon the expertise of the Army Corps of
Engineers through an agreement in 1978. Because of the Corps' expert
knowledge of construction practices and cost control, it was brought into
the program to help States and EPA manage construction projects and to help
prevent waste, fraud, and mismanagement. As municipal and industrial
treatment facilities began to operate around the country, observable water
quality benefits appeared. Rivers and lakes that once spawned masses of
algae and dead fish now began to support fishing and recreation activities.
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Problems
At the same time, however, recurring problems plagued the grants
program. Ten years after the 1972 Act and with over $30 billion actually
committed to specific projects, the Act's goals were still unmet. Annual
Federal funding levels remained unpredictable. Increased costs consumed
construction dollars as projects plodded through the three-step grant
process. Some projects that took 2 years to 3 years to complete under the
1956 "Old Law" now dragged on for 7 years to 9 years. Through the years
money was stretched too thin as funding eligibilities expanded and project
completion dates were extended for lack of funds or to allow construction
of other projects. As populations exceeded or fell short of planning
projections, some plants were either overloaded or underused.
There was also a growing perception that the high levels of Federal funding
and inadequate enforcement fostered pubic indifference to construction
costs and to effective plant operations and maintenance.
It became evident, too, that secondary treatment was still too rigidly
defined and for certain projects not worth the marginal improvement in
water quality it produced.
Advanced treatment—
An added problem was that some States set unattainable uses for
certain water body segments that then demanded stringent water quality
standards. This meant effluent discharged into these segments needed more
advanced and more costly treatment than secondary. This occasionally led
to construction of expensive advanced treatment projects whose effluent had
little overall impact on receiving water quality but a severe impact on the
financial resources of the community supporting the project. Concern over
advanced treatment costs led Congress in 1979 to require that the EPA
administrator personally review every proposed advanced treatment project
that exceeded the costs for secondary treatment by $1 million or more.
Congress raised this figure to $3 million for fiscal year 1980 because the
reviews strained EPA headquarters personnel resources and caused project
delays that increased project cost. Though advanced treatment reviews
revealed that many proposed projects were badly needed, some were not.
FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1980
Congress had made limited changes in the law with P.L. 96-483 enacted
October 21, 1980. This legislation allowed a State governor to reduce new
Federal grants to 55 percent or less uniformly across the State. It also
extended expiring funding for the I/A program, then just beginning to
produce results.
But the new Administration in 1981 felt the program was too complex
and too costly in view of national budget demands. It also felt the States
needed more flexibility and authority to decide how they would meet the
Act's requirements.
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MUNICIPAL WASTEWATER CONSTRUCTION GRANT AMENDMENTS OF 1981
The Administration in 1981 submitted legislation that restructured the
program. Congress enacted most of the Administration's proposals in the
"Municipal Wastewater Treatment Construction Grant Amendments of 1981"
(P.L. 97-117).
The 1981 amendments further redirect the program toward the States,
reduce Federal funding, and more strongly emphasize water quality through
targeting of funds to current treatment needs and to projects that impact
the country's highest-priority water bodies.
Funding
The amendments reduce potential Federal funding to $36 billion, a 60
percent reduction over the previous $90 billion projected, through
limitations on grant eligibility. They authorized $2.4 billion for fiscal
year 1982 and similar amounts through 1985.
Extended Deadlines
The Act extends several important deadlines. The July 1, 1983,
deadline for municipal secondary treatment is extended to July 1, 1988, for
most municipalities. The deadline for ocean-discharging communities to
request waivers from secondary treatment requirements was extended from
September 13, 1979, to December 29, 1982.
Immediate Changes
The amendments call for immediate as well as future changes in the
program. Several changes took effect December 29, 1981, when the law went
into effect. The law:
—Eliminates new grants for facility planning and design. These are
now locally financed and the architect/engineer guides the grantee. EPA
makes an allowance, rather than reimbursement, for these costs when a
project gets a grant for construction. The State can reserve up to 10
percent of its allotment for advance allowances to small communities who
cannot finance these costs. This allowance is later added as a percentage
of the construction grant.
—Redefines secondary treatment to include trickling filters,
oxidation ponds, and lagoons as the equivalent of secondary where water
quality is not adversely affected.
—Extends the I/A program. The mandatory 3 percent I/A set-aside is
increased to 4 percent of the State allotment and can go as high as 7 1/2
percent at a State's discretion. I/A projects get grants 20 percent higher
than those for conventional systems but cannot exceed 85 percent of the
project's cost.
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—Retains the 1977 requirement that rural States set aside
4 percent of their allotment for alternative projects in communities of
3,500 or less or sparsely populated areas of larger communities.
Changes October 1, 1984;
To allow an orderly transition, most of the other major changes take
effect October 1, 1984, when:
—The Federal grant share drops from 75 percent to a maximum of 55
percent for new construction funded after October 1, 1984. However, phased
or segmented projects, those where the total project is not constructed or
funded as one total package, that got 75 percent grants before Oct. 1, 1984,
will get 75 percent grants for later phases or segments of the same
facility if Federal funds are available.
—There will be little or no funding of reserve capacity for future
growth.
—Eligible categories for Federal funding are restricted to treatment,
new interceptors, and infiltration/inflow correction. The State can use up
to 20 percent of its allotment to fund otherwise ineligible categories such
as new collectors or treatment of high-priority combined sewer overflow
discharges.
CONSTRUCTION GRANTS: THE PRESENT
PROGRAM PRIORITIES
The Administration undertook several initiatives to achieve new
program priorities. These priorities emphasize regulatory reform,
accelerated delegation of the program to the States, increased orientation
toward water quality improvement, municipal compliance, and assurance of
local financial management capability.
REGULATORY REFORM AND GUIDANCE
Regulatory reform translating the 1981 amendments into action is well
underway. Final construction grant regulations and discretionary guidance
along with new regulations on State delegation and redefined secondary
treatment will be published when the new Administrator approves them.
However, we had interim regulations in effect May 12, 1982, 5 months after
the legislation passed. Also underway is guidance to ensure effective
local financial management capability; wastewater utility management; user
charges; project operation, maintenance, and performance; and Federal
program management.
STATE DELEGATION
Our first priority is accelerated delegation of the program to the
States. States are assuming project management functions as the EPA role
phases into program overview and monitoring. Delegated States now provide
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over 60 percent of program staffing; in the next 18 months State staffing
will represent about 70 percent of the total. By that time, too, more than
half the States will manage everything that can be delegated. Forty-seven
States have accepted delegation and we expect all States to be delegated by
the end of 1985.
Overview
To help States oversee and manage the program, in April of this year
we issued a brief but comprehensive guidance booklet that describes the
regulatory, policy, and management requirements States must address as they
assume major management of the construction grants program. The booklet
reviews State and Federal roles and responsibilities under a delegated
program and sets forth basic principles for delegation and overview. Our
primary objective is to turn over all possible project administration to
the States. Certain projects, however, continue to need Federal
involvement. These include projects that have interstate impacts; require
environmental impact statements; involve Federal court cases, enforcement
investigations, or allegations of waste, fraud, or mismanagement of Federal
funds; are affected by ocean-discharge waivers; require advanced treatment;
or are subject to special eligibility considerations or Congressional
inquiry. The guidance discusses the management information EPA needs to
assess progress toward national program goals, manage the national program
in a fiscally responsible manner, and respond to national information
reporting requests for budget and legislative requirements.
WATER QUALITY
States are redirecting their programs toward an increased emphasis on
needs in priority water bodies. They are identifying these waters to
concentrate resources where pollution has impaired a desired and attainable
water use. They must also review and, if necessary, revise their
construction grant priority systems and priority lists. The 1981
amendments require that States review and, if necessary, revise all water
quality standards by December 29, 1984. Federal dollars will be targeted
to priority water bodies and to construction projects that can most improve
water quality or alleviate public health threats. An important new
analytical tool for States and EPA will be a new computer system EPA is
developing that will link State water quality data with information in the
EPA Needs Survey data base and several other Federal data bases.
Advanced Treatment
Headquarters has reviewed 80 proposed advanced treatment projects
since 1979 and has saved communities $825 million in projects with capital
costs of $1.67 billion. We estimate operation and maintenance savings at
another $20 million a year. Of projects reviewed since 1979, 52 percent
needed changes. In 1982 Headquarters made changes in all projects it
reviewed. We plan to review over 25 advanced treatment projects in fiscal
year 1983.
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PROJECT COMPLETIONS
An urgent concern is to complete projects under construction and to
minimize funding of newly phased or segmented projects. About 2,770
treatment facilities funded since 1972 are completed. Another 2,844 are
under construction and are 90 percent completed. A related objective is to
accelerate completion of all administrative requirements on completed
projects to eliminate backlogs that developed over the years.
COMPLIANCE
The almost 64,000 permits issued since 1972 are the driving force for
compliance. These were issued to 15,600 municipal and 48,300 industrial
dischargers. Because most of these permits are expiring or have already
expired, major efforts are now underway to reissue permits that reflect new
requirements.
Industrial
Industries have outpaced municipalities in meeting their permits.
Eighty-one percent of the major industrial dischargers met their 1977
deadlines for best practicable technology (BPT) and this increased to 85
percent in 1982. Ninety-six percent have treatment in place or are on
schedule to install the necessary equipment.
Municipal
We have witnessed a dramatic improvement in municipal compliance since
1977, when only 30 percent of municipal facilities were achieving secondary
treatment. Now 77 percent of all publicly owned treatment works (POTWs)
nationwide are meeting their effluent limits or are on schedule to do so.
Plants built since 1972 perform better than older plants. In 1982, 82
percent of all major POTWs, those that discharge more than 1 million
gallons a day, and 87 percent of major plants funded since 1972 were in
compliance.
Small plants that discharge less than 1 million gallons a day account
for the majority of compliance problems. We expect improved performance
over the next 2 years in these plants, largely as a result of State efforts
to provide onsite, over-the-shoulder training to small-plant operators and
to help small communities assure adequate, updated user charge and
financial management systems. States have developed a substantial training
capability with Federal help. Through the years we have progressed from
training operators to training instructors to developing extensive
curricula and training materials. We have helped fund construction of over
25 State training centers. We believe State and local governments must
prepare to accept responsibility to maintain their own training programs to
help ensure permit compliance.
An added factor that will improve compliance is that the 1981
amendments and our regulations insist that the project comply with its
permit within 1 year of startup. To assure this and to focus
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responsibility for compliance, the engineering contractor must stay with
the project during the first year of operation. At the end of the year the
grantee certifies to the EPA regional administrator that the project can
and does comply with its permit. Where compliance has not been achieved, a
remedial action program will be developed with the State and grantee.
New Factors
Secondary Treatment Redefined—
The 1981 amendments redefined secondary treatment to include trickling
filters, oxidation ponds, and lagoons as the equivalent of secondary
treatment where water quality is not adversely affected. This redefinition
could help 2,000 small trickling filter systems.
Waivers for Ocean-Discharging Communities—
The 1977 amendments created section 301(h) of the Clean Water Act
primarily in response to pressure from ocean-discharging West Coast
communities who argued that secondary treatment was unnecessary for
effluent discharged into deep ocean waters where wastes rapidly aerate and
disperse. Section 301(h) allows EPA to modify permit effluent limitations
for BOD, suspended solids, and pH where the applicant discharges into
certain ocean and estuarine waters. This does not waive requirements for
pretreatment of industrial waste or for a monitoring program to determine
the discharge's impacts on the marine environment. The applicant must
demonstrate that the modification will not increase toxic discharge or
impair the integrity of the receiving waters. Each waiver application must
be evaluated individually. Communities were to apply for waivers by
September 13, 1979.
The 1981 amendments provided additional time for communities to seek
waivers. By the new deadline of December 29, 1982, EPA had received
applications from 207 municipal dischargers. EPA has made decisions on 55
of these applications. One decision, a denial for a system in the State of
Washington, is final. Of the 54 tentative decisions, we have denied 34 and
approved 20. Most of those approved were from West Coast dischargers and
most proposed at least primary treatment. All will be required to control
toxics by pretreatment and nonpoint source control programs and to monitor
compliance with section 301(h) ocean-discharge requirements. Applicants
who were denied waivers generally discharged to enclosed embayments rather
than to deep ocean water or waters with sufficient tidal action to
dissipate the effluent. Responsibility for granting or denying waivers has
been delegated to the EPA regional administrators.
Municipal Compliance Policy
The 1972 Clean Water Act said municipalities had to have secondary
treatment by July 1977. The 1977 amendments extended that deadline to 1983
for those who requested an extension and, for these, the 1981 amendments
again extended the deadline to 1988.
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We will soon have ready what we think is a reasonable municipal
compliance and enforcement policy to meet these deadlines. It is premised
on the Clean Water Act's original assumption that no one has the right to
pollute.
Our draft policy states that EPA and the States will set effluent
limits and enforceable compliance schedules no later than July 1985 for all
POTWs not already in compliance. The schedules will require that POTWs be
in compliance by July 1988 wherever possible. The policy will ensure that
POTWs already completed, especially those that used Federal funds, achieve
compliance and remain in compliance. States must develop compliance
strategies by March 1984.
FINANCIAL CAPABILITY
Many performance and compliance problems stem directly from poor
financial management of projects and the community's myopic look into its
future responsibilities at the time it received a grant.
Under the restructured construction grants program, localities assume
far greater responsibility to finance and manage their own projects. The
community that applies for a grant must prove the proposed project is
anchored in a sound financial footing and that the system selected will
solve the community's pollution problems in the most cost-effective way.
The program's new emphasis on financial responsibility is so crucial
that the 1981 amendments and our new regulations say a community cannot get
a grant unless it demonstrates it has the financial capability to build the
proposed project and to operate and maintain it after it is built. For
instance, a grant applicant must submit a user charge system that produces
enough revenue for effective operation and maintenance. The grantee also
has to demonstrate that it has the legal, institutional and management
capability to build, operate and maintain the plant.
Financial Capability Policy
These requirements are described in a new policy that clearly outlines
State and community responsibilities and helps a community demonstrate its
financial capability. It encourages the community to draw up a
comprehensive profile of its ability to pay for the proposed facility. The
applicant has to answer questions on the project's scope, the local
government's roles and responsibilities, the project's capital cost and
annual costs per household, the community's ability to afford the project,
and how it plans to finance the project.
The grant applicant must certify it has analyzed the project's costs
and financial impacts on the community and that the community has the
financial capability to build and operate the facility. States should work
with grant applicants to review the applicant's financial capability and
the financial feasibility of the project.
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The financial capability policy's purpose is to get local governments
to take an early and realistic look at their ability to finance and operate
their proposed treatment works. This is a critical step in preparing them
to take on a larger share of the project's capital cost as Federal funding
phases down.
I/A and Appropriate Technology
Closely linked to good financial planning is selecting the appropriate
technology. Grant applicants must show they have chosen the most
cost-effective system. For small, unsewered communities this is usually an
alternative system.
The 1977 Clean Water Act amendments created the innovative and
alternative (I/A) and rural funding programs that help finance these I/A
systems. These programs are proving their worth. We have awarded $200
million in Federal grants to help finance over 1,000 projects that have
saved communities over $900 million. About 860 of these projects are
alternative systems and 200 are innovative. It is too soon to evaluate the
success rate for innovative systems because to date only 11 of these
projects are operating. But of over 175 alternative projects in operation,
those proving most successful are land treatment of wastewater, land
spreading of sludge, containment ponds, small-diameter gravity sewers, and
pressure sewers. Many of these Federally funded I/A projects have won
national awards for engineering excellence.
We have already issued many publications and are preparing several
more to inform State and local governments about I/A and other appropriate
technologies. One of our publications has been translated into Japanese by
the DoJo Joka Senta Company located in Tokyo. The publication is a foldout
that describes 21 alternative systems in plain language. The systems
illustrated include septic tanks; mound systems; pressure, vacuum, and
small-diameter gravity sewers, and others. Our other publications include
a 400-page onsite system design manual, a foldout on overland flow, and a
foldout that compares costs of various technologies. More detailed cost
comparisons will be avilable in a booklet we will publish in September.
Also available then will be six new foldouts, each of which will describe
an I/A system. The systems are sequencing batch reactors, counter current
aeration, biological aerated filter, aquaculture, wetlands, and
intrachannel clarification. Also under consideration are brochures on 90
percent methane recovery, land application of sludge, alternative
collection systems for small communities, biological phosphorus removal,
vacuum-assisted sludge drying beds, rapid infiltration, composting for
small wastewater treatment plants, and intermittent discharge systems.
These technologies will increasingly help small communities solve
their water pollution problems at reasonable costs.
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FINANCING PUBLICLY OWNED TREATMENT WORKS
States: Restructure Programs
To make the best use of the limited Federal funds available, we
encourage States to restructure their construction grants programs. They
can reduce the Federal grant share uniformly throughout the State to spread
Federal funds to the greatest number of projects of all sizes and strive to
ensure that projects are completed. To accomplish this, communities who
apply for new grants must state that they will complete the projects with
or without Federal funds. The 1980 Clean Water Act amendments allow States
to reduce Federal grant shares right now and some States are already doing
this. It should be done in a way that minimizes the financial impact,
especially on small, low-income communities.
CONSTRUCTION GRANTS: THE FUTURE
FUNDING
Congress has authorized $44.3 billion since 1972 to fund the
construction grants program but total appropriations through fiscal year
1984 are $40.4 billion. The Administration asked for and received about
$2.4 billion for fiscal years 1982, 1983, and 1984. The current law
authorizes funding through fiscal year 1985. We do not know at this point
precisely what direction future funding will take.
New Federalism
One direction may be the one President Reagan sent to Congress
February 24, 1983. Under the Administration's proposal, construction
grants is one of several Federal grant programs that would be returned to
the States. It would be funded at $2.4 billion a year for 5 years, from
fiscal year 1984 through fiscal year 1988. The States could take over the
program if they wished during any one of the 5 years. They would have to
use the construction grants portion of the funds entirely for construction
grants the first year but could divert 20 percent of the funds for other
purposes the second year, 40 percent the third year, 60 percent the fourth
year, and 80 percent the fifth year. All grant programs returned to the
States would be financed by Federal excise taxes on alcohol, cigarettes,
and telephones.
Infrastructure
Other legislation has been introduced in the Congress to fund
wastewater treatment facilities through State or Federal infrastructure
banks. Infrastructure is the current term in the United States for public
works, the permanent physical structures that form the underlying
foundation of a society's basic services. Infrastructure includes, among
other things, roads, bridges, wastewater treatment and drinking water
facilities. The legislation would fund wastewater facilities' capital
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costs with grants or loans from infrastructure banks. The banks' capital
would be replenished by various means, including loan payback or revenues
from user charges.
Privatization
In some areas of the United States, the private sector is
experimenting with financing wastewater facilities and either leasing them
back to the municipality or running the facilities for profit. The
investment tax credit provision of the 1981 tax law would allow a firm
operating a leased facility to make a profit.
SejLf—sustaining Public Utilities
However capital costs are financed, we encourage local governments to
operate their facilities as self-sustaining public utilities that generate
enough revenue for proper operation and maintenance. This approach
strengthens the community's incentive to protect its investment. It also
educates the user into an awareness of the true costs of wastewater
treatment. The out-of-sight, out-of-mind syndrome that has hidden the
treatment plant on the edge of town has applied to its costs as well. The
public expects sewage treatment to be cheap. In fact, cheaper than monthly
charges for pay television. This unrealistic perception puts local
government officials who must provide the service in a difficult position.
The user must come to realize that wastewater treatment and protection of
public health deserves, and may require, a substantial financial commitment
in the town's and the citizen's budgets.
NEW DIRECTIONS
Ten years of experience in directing and working with the massive
construction grants program have given EPA, the States, and localities some
insights into the potential successes or problems that can occur as
certain concepts or systems are actually put into practice. I'd like to
share some of our findings with you since they may benefit wastewater
programs in other countries as well as those in the United States.
Management
It has become clear that many local governments do not plan or manage
their projects carefully. This seems to relate to the high level of
Federal and State funding. The 75 percent Federal grant share coupled with
10 percent to 15 percent State funding demands little local capital
investment. This creates local indifference to the real cost of the
facility. Reduced Federal grants provided by the 1980 and 1981 amendments
should spur communities on to more careful evaluation of alternatives and
of future growth when they plan their project and to sound management
practices once the facility is built.
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Facility Planning and Design
Local indifference to project planning and cost was also reinforced by
the 75 percent Federal grants for facility planning and design. Many
communities failed to weigh the real need for their project or its impact
on the community until the project was ready for construction. Now
facility planning and design are locally financed. This attracts community
attention at the planning stage and increases the sense of local
responsibility. The 1981 Clean Water Act amendments authorize an allowance
that pays a percentage rather than the full cost of planning and design and
the allowance is authorized only when a project gets a grant for
construction. This prevents Federal funding of planning and design for
projects that may never be built.
Secondary Treatment
EPA's rigid definition of secondary treatment proved to be unrealistic
and unnecessarily costly for many communities adequately served by
technologies other than activated sludge which was used as the base for the
definition. The definition before the 1981 Amendments stood at 30
milligrams per liter for biochemical oxygen demand (BOD) and 30 milligrams
per liter for suspended solids (SS) or 85 percent removal of BOD and SS on
a monthly average. The definition precluded use of such proven
technologies as trickling filters, oxidation ditches, and lagoons unless
they were upgraded with an additional treatment process to reach the
secondary standard. The definition also drove the use of sophisticated
technologies that many communities could not afford to operate and
maintain, much less build. The 1981 Amendments redefined secondary to
include trickling filters, oxidation ditches, and lagoons where water
quality is not adversely affected. This redefinition will especially help
small communities of less than 10,000 people which are usually well served
by these and other less costly systems.
Innovative and Alternative Technology
We are heartened by the success of the innovative and alternative
(I/A) and rural funding programs created by the 1977 Clean Water Act
amendments. Systems funded under these programs have already saved
communities over $900 million in building and operating costs and many have
won national awards for engineering excellence. Over 175 of the 860
Federally funded alternative projects are now operating. Those proving
most successful are land treatment of wastewater, containment ponds,
small-diameter gravity sewers, pressure sewers, and land spreading of
sludge. Alternative systems are usually the most cost-effective systems
for small communities who often have cost and operational problems with
conventional activated sludge technology and central sewering. It is still
too early to judge the success rate for innovative systems because to date
only 11 of the 200 systems funded are completed and operating.
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Small Communities and Appropriate Technologies
Most communities of less than 10,000 people probably should not even
consider conventional activated sludge systems but should rely instead on
I/A or other appropriate technologies. The redefinition of secondary
treatment in the 1981 Amendments will help small communities by allowing
lagoons, trickling filters, and oxidation ditches to be considered the
equivalent of secondary treatment where water quality is not adversely
affected. These systems are among those generally considered more
appropriate for small communities than activated sludge.
We've found that communities with less than 1,000 people simply cannot
afford activated sludge treatment with central sewers regardless of Federal
funding. For communities of 3,500 or less or sparsely populated areas of
large communities, alternative systems are usually the most cost-effective
choice. Systems such as land treatment, containment ponds, small-diameter
gravity sewers, pressure sewers, septic systems and upgraded variations of
them cost less to build, operate, and maintain; have lower user costs; use
less energy; create less sludge; and are simpler to operate than
conventional central systems.
Use of these systems could have prevented some small communities from
building activated sludge treatment facilities they could not afford. This
overbuilding sprang from various causes; among them, excessive population
projections, overly stringent State water quality standards and resultant
stringent effluent limitations, and the rigid definition of secondary
treatment. It's true that small communities should provide adequate
capacity for reasonable future growth. But they must project their needs
with care. Under-used facilities are costly to operate and maintain and
may not last to the end of their design life. We expect the 1981
Amendments and our program reforms to help curb overbuilding of treatment
systems. Among other changes, the restriction on funding of reserve
capacity for future growth and our financial capability policy will
encourage communities to select the most appropriate technology that will
solve their wastewater problems at a reasonable cost.
Advanced Treatment
EPA Headquarters review of 80 advanced treatment (AT) projects since
1979 has justified congressional concern that some AT projects might be
built that were not necessary. The reviews revealed that AT elements of
some proposed projects could be eliminated. Between 1979 and 1982 the
reviews saved an estimated $825 million in capital costs and another $20
million a year in operation and maintenance costs. The Agency had
pressured the States in the early 1970s to move rapidly toward "fishable,
swimmable" waters wherever attainable. The result was increasingly
stringent State water quality standards that drove many communities to
advanced treatment. The congressional appropriations committees in 1979
became concerned that AT facilities would be built that did not provide a
corresponding improvement in water quality or public health for the
additional dollars needed. The comittees required the EPA Administrator to
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personally approve each proposed AT project that exceeded the costs for
secondary treatment by $1 million or more. Congress raised this figure to
$3 million for fiscal year 1980 because of the drain on EPA personnel
resources. The reviews have prevented several unnecessary proposed AT
projects from going forward to construction.
Ocean-Discharge Waivers: 301(h)
I am concerned that this section of the Clean Water Act granting
waivers from secondary treatment to qualifying communities that discharge
to the ocean may be a step backward in the water cleanup effort. These
waivers are the first departure from the minimum technology based
wastewater treatment standard. Industry will still need to pretreat its
waste to remove hazardous and toxic pollutants before discharging to the
POTW and the POTW will need to monitor the impact of its discharge.
Moreover, the prohibition against discharge of sludge still applies. But
we know that secondary treatment removes substantial amounts of toxic
metals and toxic organics and without secondary treatment we really don't
know how the waivers will impact the marine environment. It's clear we'll
have to keep close watch on the effects of these waivers.
Pretreatment of Industrial Wastes
The Administration and Congress are working to resolve one of the most
complex issues still confronting the goal of clean water. This is
pretreatment of industrial waste. This year's congressional hearings on
reauthorization of the Clean Water Act have focused on pretreatment as a
priority item. Our legislative proposals and those of other interested
parties are still before the Congress. Though EPA realizes some
fine-tuning of its approach to pretreatment may be needed, it believes
pretreatment remains a necessary part of our nation's effort to achieve
clean water.
Pretreatment is a largely unfulfilled Clean Water Act requirement that
certain industries who discharge wastewater to publicly owned treatment
works (POTWs) pretreat their wastewater to remove specified amounts of
toxic and other pollutants before discharging the waste to POTWs.
Pretreatment protects the environment and POTWs from damage that can occur
when hazardous or toxic waste enters a public wastewater system not
designed to treat these wastes. Pretreatment specifically aims to prevent
damage to the treatment system itself or interference with its operation,
contamination of municipal sludge that inhibits its reuse or disposal, or
passthrough of pollutants to receiving waters.
Controversy has surrounded pretreatment and EPA's attempts to
implement it since the requirement was first stated in the 1972 Clean Water
Act. The 1972 provision and the 1977 amendments of it have, over the
years, drawn fire from industry, POTWs, and public interest groups alike.
Pretreatment exemplifies the Herculean task EPA faces when it tries to
develop equitable national pollutant controls based on national standards
that, in turn, are based on scientific information and technology that are
sophisticated, complex, and often controversial.
459
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Legislative Background—
1972 Clean Water Act
The 1972 Clean Water Act prohibited discharge of toxic pollutants in
toxic amounts into navigable waters. The Act directed that EPA first
identify toxic pollutants and then issue two types of national standards to
control them. For industries that discharged directly to waterways, EPA
was to issue a national uniform effluent standard for each pollutant that
applied to all classes of industries. For industries that discharged to
POTWs rather than directly to waterways, EPA was to issue national uniform
pretreatment standards. The pretreatment standards were to prevent
discharge of any pollutant that interfered with, passed through, or was
otherwise incompatible with the POTW. But lack of the necessary personnel
and of sound scientific and technological information prevented EPA from
identifying the toxic pollutants or from issuing the standards to control
them.
1976 Consent Decree and the 1977 Clean Water Act
Delay in issuing the effluent standards and the pretreatment standards
prompted several environmental groups to sue EPA. This resulted in a 1976
Federal court order that come to be known as the "toxics consent decree."
The consent decree ordered that EPA develop national effluent standards for
65 "priority" toxic pollutants which EPA later subdivided into 129 toxic
substances. The standards were to be incorporated in the permits of direct
industrial dischargers in 21 classes of industries. The decree also
ordered that EPA issue regulations setting minimum pretreatment standards
to control priority and certain other pollutants discharged to POTWs by
industries and other sources of nondomestic waste.
The 1977 Clean Water Act incorporated the terms of the consent decree
as the basic national approach to control of toxic and certain other
pollutants in the industrial wastestream. The Act defined three classes of
pollutants and demanded technology based standards to control them. The
classes are conventional, toxic, and nonconventional. Conventional
pollutants mean those traditionally controlled by wastewater treatment
systems. These include BOD, suspended solids, oil and grease, pH, and
fecal coliform. Toxics include those identified in the 1976 consent decree
and in the Act. Nonconventional pollutants include those not otherwise
designated, such as phosphorus, nitrogen, and ammonia.
Implementation of Clean Water Act Pretreatment Requirements—
EPA's Pretreatment Program
The underlying concept of the EPA pretreatment program is that the
municipalities must assume the prime responsibility for enforcing the
national program. The framework for the national program consists of the
general pretreatment regulations and the national pretreatment standards,
both of which aim to control priority and certain other pollutants.
460
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General Pretreatment Regulations. The general pretreatment
regulations require States and municipalities to develop local pretreatment
programs that enforce national pretreatment standards. The regulations
detail the components of a pretreatment program and identify the
responsibilities of EPA, State and local governments, and industry. The
regulations were issued June 26, 1978, were amended January 28, 1981, and
are in force as of March 13, 1981.
The regulations state that any POTW with a design flow of more than
5 million gallons a day must have established a pretreatment program by
July 1, 1983. POTWs with flows of less than 5 million gallons a day are
also required to establish a pretreatment program if nondomestic waste the
POTW treats causes upsets, sludge contamination, violations of NPDES
permits, or is discharged to the POTW by a significant industrial user
subject to national pretreatment standards.
EPA estimates that 1,700 of the nation's POTWs must develop local
pretreatment programs. EPA and authorized States have approved 200 local
pretreatment programs and expect this number to grow to 400 by the end of
the year. They expect to approve 900 more in 1984 and the remainder by the
end of 1985. So far, 15 States have pretreatment programs approved by EPA.
A recently formed task force of EPA and State officials expects to have a
strategy for POTW compliance with pretreatment requirements ready by the
end of this year.
Pretreatment Standards.— The general pretreatment regulations
establish two types of pretreatment standards to control pollutant
discharges into POTWs: prohibitive discharge standards and national
categorical pretreatment standards.
Prohibitive discharge standards apply to all industrial and commercial
establishments connected to POTWs. Prohibitive standards protect the
POTW's plant and operations by prohibiting discharge of pollutants that
create a fire or explosion hazard in the sewers or treatment works; are
corrosive, with a pH lower than 5.0; obstruct flow in the sewer system or
interfere with operation; upset the treatment processes to cause a
violation of the POTW's permit; or increase the temperature of wastewater
entering the treatment plant to above 104 F. The prohibitive standards are
expressed in general terms in one comprehensive regulation. The POTWs
issue the specific prohibitive standards for their users.
National categorical pretreatment standards apply to discharges from
23 classes of industries thought to be the most significant sources of
toxic pollutants discharged to POTWs. The 23 classes of industries cover a
total of 15,000 individual industrial facilities. The categorical
pretreatment standards protect both the environment and the POTW and are
issued by EPA. They apply to industries that discharge to POTWs (indirect
dischargers) and correspond to the national uniform effluent standards that
apply to industries that discharge directly to waterways (direct
dischargers). Both standards contain numerical limitations for toxic
pollutants commonly discharged by a particular industry and are published
461
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together as one regulation governing that industry. Altogether EPA will
issue national categorical pretreatment standards for 23 classes of
industries and national effluent standards for 28 classes of industries.
The numbers are different because five classes of industries do not
discharge to POTWs and so do not require pretreatment standards. To date,
EPA has issued national categorical pretreatment standards for 11 classes
of industries and has proposed standards for 7 others. The remaining
standards are to be issued by July 1, 1984.
A major concern of the Administration's 1983 legislative proposals is
that there may be certain cases where full implementation of national
categorical pretreatment standards is not necessary. The Administration is
grappling with the problem of how to provide relief where it is justified
yet maintain the program's momentum and protection.
Removal Credits
The 1977 Act recognized that secondary treatment actually removes
substantial amounts of priority pollutants. To reflect this removal, the
law modified the 1972 pretreatment requirement by empowering POTWs to grant
their industrial users "removal credits." Removal credits are
modifications of the national categorical pretreatment standards. They
reflect the amount of toxic and certain other pollutants removed by the
POTW. To grant removal credits, a POTW must have a pretreatment program in
place and must be meeting secondary treatment or be on schedule to do so.
Removal credits must not jeopardize the quality of the POTWs sludge or the
quality of receiving waters.
POTWs, industries, and public interest groups have, from various
perspectives, attacked the concept of removal credits and its
implementation by EPA. Much of the criticism centers on the concept's
complexity. Other criticism focuses on the lengthy testing and
administrative procedures POTWs must perform to demonstrate removal of
priority pollutants. Some industries complain that denial of removal
credits results in "treatment for treatment's sake."
We are trying to streamline the process for granting removal credits
and have proposed revisions to the general pretreatment regulations to
accomplish this. We expect to issue the final revisions on removal credits
in early 1984.
EPA Studies and Pretreatment—
Two EPA studies need special mention in discussing pretreatment. One
began in 1978 and the second in 1981. The results of the first, commonly
referred to as the "40-city Study," were used in arriving at recommended
national removal credits that POTWs could use as a base for their own
programs. The study results, published as a final report in September
1982, indicated that well-operated secondary treatment plants remove
substanial amounts of heavy metals and some toxic organics. Half of the
462
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secondary treatment plants reduced priority pollutant metals by 70 percent,
volatile priority pollutants by 82 percent, and base neutral priority
pollutants by 65 percent.
The second study analyzed pollutant loads contributed by industrial
customers at 2,000 POTWs. The study included all POTWs that discharged
more than 5 million gallons a day and some smaller plants with a history of
operational problems or with significant industrial contributors of toxics.
Among the report's findings were that there has been substantial control of
metals by industrial pretreatment—a 65 percent reduction from raw
discharge levels; but less control of toxic organics—a 37 percent
reduction from raw discharge levels. The study also indicated that
pretreatment would, on the average, reduce heavy metals and toxic organics
in municipal sludges by 52 percent and 67 percent, respectively.
National Effluent Standards for Direct Dischargers—
After initial delays, EPA is making major progress in developing and
issuing the national uniform effluent standards for direct industrial
dischargers called for by the 1976 toxics consent decree. These national
effluent standards correspond to the national categorical pretreatment
standards for indirect dischargers. EPA was unable to issue effluent
standards on schedule for the original 21 classes of industries identified
by the 1976 consent decree that were thought to be the most significant
sources of toxic pollutants. By regrouping, the 21 classes of industries
were expanded to 34 by a March 9, 1979, modified consent decree and, later,
to 28 by an August 25, 1982, court order. To date, EPA has issued 14 final
effluent standards and proposed 10 others. By October 1983 EPA will have
issued 21 final effluent standards and by October 1984 will have issued all
28 currently required.
The Administration's proposals to amend the Clean Water Act in 1983
would extend the deadlines for industries to comply with national effluent
standards for priority pollutants from July 1, 1984, to July I, 1988. This
would allow industries a reasonable time to build the needed treatment
facilities after the standards are issued.
Sludge
Those of you who deal with environmental problems on a daily basis
will appreciate a sentence by the great English educator and writer Matthew
Arnold, who said of a friend, "He saw life steadily and saw it whole."
That is how we constantly strive to look at the environment—to see it
whole—as we increasingly discover that all environmental problems are
interrelated. The solution to a problem in one area can become part of the
problem in another.
A classic example is the challenge to POTWs of what to do with the
nearly 7 million dry tons of sewage sludge produced each year by 150
million Americans and some 87,000 industries that discharge waste to more
than 15,000 municipal sewage treatment works. The volume of this
463
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product of central treatment will grow markedly as more and more treatment
facilities begin to operate. One estimate is that by 1990 United States
POTWs will produce 16 million tons of dry sewage sludge every year, nearly
three times the volume produced each year in the 1970s. From 30 percent to
50 percent of a conventional treatment plant's capital costs go for the
sludge management system and we estimate that POTWs spend more than $500
million a year in operating and maintenance costs for sludge disposal and
reuse. Clearly, sludge portends a major waste management problem for the
years ahead if we do not work to find an integrated solution right now.
We are working toward that solution by drawing on the collective
wisdom of an EPA sludge task force organized in July 1982 to produce an
integrated sludge management policy. To assure a broad-based policy, the
task force solicits views and information from States, localities,
universities, other Federal agencies, and public interest groups. The goal
is a balanced policy that weighs environmental risks as well as the
benefits and costs of various sludge management options. The group is
working toward a comprehensive sludge management guideline under section
405 of the Clean Water Act. The task force expects to have the guideline
ready this year.
We still have to deal with the fragmented regulatory approach that now
regulates sewage sludge under potentially conflicting provisions of at
least seven major laws that deal with discrete environmental concerns.
Besides the Clean Water Act, these statutes include the Resource
Conservation and Recovery Act of 1976, the Toxic Substances Control Act of
1976, the Marine Protection Research and Sanctuaries Act of 1977, the Clean
Air Act, the Safe Drinking Water Act, and the National Environmental Policy
Act of 1969.
Sludge as a Resource—
The emerging sludge policy reflects the Agency's view that sludge is a
valuable resource that should be used and recycled to capture its nutrient
and organic components.
The idea that sludge is an asset to be used rather than a problem to
be disposed of takes on added weight now that traditional methods of sludge
disposal are becoming environmentally, politically, or economically
unacceptable. Incineration is expensive and uses high amounts of energy.
Landfills draw public protests, the more so now amid the mounting public
clamor over toxic waste. Ocean dumping has largely phased out since the
mid-1970s, mostly for environmental reasons, though a limited number of
coastal cities are still permitted to use this method if authorized by a
Federal court order. Lagoons and storage basins still provide a cheap and
convenient way to treat sludge but odor problems and possible groundwater
contamination usually arouse public opposition from nearby residents. All
of these restrictions have kindled new interest in an old concept—land
application of sludge.
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Land Application of Sludge—
Land application of sludge is one of the most cost-effective ways to
reuse or dispose of sludge. Recent estimates are that 40 percent of all
sludge produced in the United States is applied to the land. This compares
with 25 percent in 1976. When properly applied, the sludge serves as a
fertilizer supplement and soil conditioner that can be used in agriculture,
forestry, land reclamation, and other land management activities. A U.S.
Department of Agriculture study indicated that sludge can supplant 1
percent of all nitrogen and 4 percent of all phosphorus now supplied in the
United States by chemical fertilizers.
We are beginning to see land application projects come into operation
that were funded under the innovative and technology provisions of the 1977
Clean Water Act and the 1981 Amendments. Twenty-two of the 150 facilities
funded under the I/A program are now operating. Many other land
application projects that were not Federally funded have been successfully
operating throughout the country for years, most on private land.
Spreading sludge on cropland or other farmland is the most common
method of land application in the United States. This technique has been
used for decades, especially in the midwestern part of the country. Only
in recent years, however, have the necessary research and monitoring
studies been undertaken to develop sound guidelines for this use. It
requires careful management and application practices and is regulated or
otherwise controlled by EPA, the State, and the locality. Most
municipalities supply sludge to farmers at little or no cost so there is a
decided cost advantage in reduced fertilizer costs. Several areas of the
country apply sewage to surface-mined or other drastically disturbed land
as an aid to reclamation. The cities of Chicago and Philadelphia transport
sludge over 200 miles to surface-mined land reclamation projects. Sludge
application to forest land is another option for sludge reuse and disposal
but not widely used in the United States because data about the impact of
heavy metals on the forest ecosystem is limited. An interesting note is
that studies are underway to evaluate the use of sewage sludge in
stabilizing certain ash-covered forest production areas near the famous
Mount St. Helens volcano in the State of Washington.
Sludge Quality and Land Application
Despite its advantage and widespread use, land application is not
problem free. Some pathogenic bacteria, viruses, and parasites survive
most sludge processes. To minimize the potential from public exposure to
pathogens, EPA has established special criteria to use in processing sludge
before it is applied to cropland. This sludge must undergo a process that
reduces the pathogen levels. Some of these processes are aerobic and
anaerobic digestion, air-drying, heat-drying, irradiation, composting, and
lime stabilization.
465
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Toxic pollutants and heavy metals remain a constraint to greater use
of sludge in agriculture. Scientic knowledge about these substances has
evolved rapidly, but there is still disagreement about what levels are
acceptable for sludges applied to agricultural land. Recent U.S.
Department of Agriculture research suggests that a good sludge that might
be used safely by the general public can be defined. We need more research
to verify this. Among other things it is an important concept in setting
national pretreatment standards for industrial waste. It is clear that
EPA's industrial pretreatment policy must be tied directly to sludge
quality since pretreatment enhances the sludge as a resource and will
simplify control and regulatory oversight procedures. One study indicates
that pretreatment would reduce heavy metals in POTW sludge by 52 percent
and toxic organics by 67 percent. Projections are that pretreatment
coupled with additional removal of heavy metals and toxic organics by
secondary treatment at the POTW should result in a cleaner sludge than is
produced by secondary treatment alone.
Marketing Sludge Products—
There is a growing interest in the United States in marketing sludge
products as an organic fertilizer or soil conditioner for use by commercial
nurseries, gardeners, golf courses, and similar users. The process
attracting the most attention is composting, which stabilizes the sludge
through microbial decomposition. The "aerated pile" method developed by
the U.S. Department of Agriculture is one the most successful processes
because it can be used to compost both small and large quantities of either
digested or undigested sludges in a relatively short time. The process
involves mixing the sludge with a bulking agent, such as wood chips, to
increase aeration. The mixture is then placed in carefully constructed
piles for several weeks during which stabilization and curing take place.
Composting reduces the levels of persistent organic compounds and
pathogens. It is considered an alternative technology under the Clean
Water Act and is eligible for up to 85 percent Federal construction grants
for land, equipment, and related construction costs.
The marketing of sludge products is the only disposition of sludge not
now regulated by EPA but we expect this to be a prominent part of the
comprehensive sludge regulation or guideline that the EPA sludge task force
will develop.
Sludge and the Future—
The greatest challenge for the future is how to capture the resource
potential of this valuable byproduct. We have learned a great deal about
the safe use of sludge in the last 10 years. Through cooperative efforts
of EPA, the U.S. Department of Agriculture, the U.S. Food and Drug
Administration, land-grant universities and others, we have identified
contaminants of regulatory concern and have issued regulations and
guidelines for agricultural use of sludge. But we are really just
beginning to see the sludge issue "steadily and to see it whole," to use
Matthew Arnold's fine words. I am confident, however, that with a
466
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comprehensive sludge policy and continuing research and other cooperative
ventures by Federal and State agencies and universities,we will make the
same kind of progress with sludge that we have seen in wastewater treatment
and other environmental programs.
THE PAST IS PROLOGUE
PROGRESS
We have come a long way since the "Old Law" of 1956 and the "New Law"
of 1972, now simply referred to as the Clean Water Act. Besides this Act,
we have seen at least 13 other major environmental laws passed and we have
seen considerable progress in meeting the goals of these laws. And, of
special importance for this discussion, we have seen the construction
grants program mature.
Water Cleanup
We still lack detailed monitoring data that would give us a long-term
comparative analysis on water cleanup. We especially lack biological data.
But States all across the country report dramatic evidences of cleanup at
specific sites. Perhaps the most heartening is Lake Erie, one of the
United States' five great lakes. In the 1950s some analysts pronounced
Lake Erie a dying lake and predicted it could take up to 500 years for the
lake to return to life, if, indeed, it was possible at all. Massive algal
blooms covered the lake with slimy green mats. The algae deprived the
bottom water of 65 percent of its oxygen in the summer months. By 1979,
thanks to municipal and industrial pollution controls, only 6 percent of
the bottom water lacked oxygen. Clean-water game fish now survive in the
lake, and the beaches, closed for more than a decade, have reopened.
In another area of the country, we have the Neches River tidal area in
Texas. In the 1960s, oil refinery and chemical plant wastes colored the
river water black. A 65 percent reduction of dissolved oxygen was measured
at one location. The fish, mainly large-mouth bass, stayed above the city
of Beaumont, avoiding the 25-mile stretch between Beaumont and the tidal
area at the mouth of Sabine Lake. Between 1970 and 1975, EPA awarded $10.5
million in grants to build secondary treatment plants and ancillary
treatment facilities along the Neches River. Industry built facilities to
provide clarification and aeration systems to neutralize high or low pH
levels and separation devices to remove oil from the water surface. By
1976 EPA had issued NPDES permits to all major industrial and municipal
dischargers along the river. Shrimp moved up the Neches in numbers large
enough to plug up industrial intakes, and commercial crabbers worked these
waters for profit. In 1976, a tarpon was caught in Sabine Lake, the first
in over 30 years.
Equally dramatic success stories are the Connecticut River, where the
first salmon was caught in over a hundred years; and the St. Johns River in
Jacksonville, Florida, where a massive water and sewer construction program
467
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in 7 years transformed what Jacksonville's mayor called an "open sewer" to
a river that now supports swimming and water sports. We have more than 70
examples of such cleanups in waters from Hawaii to Maine and from Alaska to
Texas. And we expect to see more of these stories as the thousands of
plants now under construction begin to operate.
FOUNDATION FOR FUTURE
It seems clear that, regardless of how wastewater treatment facilities
are financed, the day of large Federal categorical grants is phasing out.
The major responsibility to finance these projects will gradually shift to
local governments which will operate and maintain the treatment works as
self-sustaining public utilities. States and localities will need to
establish monitoring programs to ensure continued water quality
improvement.
Reforms in Place
As States and localities take over more and more responsibility for
meeting water quality goals, they will find they have a good foundation on
which to build their own programs. They will find that the 1981 amendments
to the Clean Water Act, the simpler and shorter construction grants
regulations and guidance, and major management reforms will ease the
transition as they assume major program functions. They will find that the
municipal waste treatment program has come into better balance as a more
cost-effective program.
EPA-State Commitment
EPA and the States face a great challenge in the years ahead but I
believe we can look for continued progress as the States exercise their
full prerogatives under the 1981 legislation. We have a strong but
realistic Clean Water Act with deadlines, permits that demand compliance,
and other enforceable requirements. EPA is fully committed to work with
the States to carry out its mandate for clean water under this important
legislation. The Nation's goal of cleaning up its waters has not changed.
The way it will be done HAS.
THE END
468
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Att. A
EVOLUTION OF THE CONSTRUCTION GRANTS PROGRAM
AS 5/83
STATE PRIMACY•
FEDERAL/STATE
ENFORCEMENT.
LIMITED TO
SMALLER
PROJECTS-
DOLLAR LIMIT.
FWPC ACT OF
1948 (P.L. 80-845
NO FUNDS APPROPRIATED.
FWPC ACT OF
1956
P.L 84-660
("OLD LAW")
30% GRANTS.
5250,000 CEILING.
S50MILLION/YR.
FEDERAL/STATE
WO STANDARDS.
WATER QUALITY
ACT OF 1965
P.L. 89-234
SAME FUNDING LIMITS AS
PJ.. 84-660.
STATE ALLOTMENTS
RELATED TO
POPULATION.
CLEAN WATER
RESTORATION ACT OF
1966
P.L 89-753
NEPAOF
1969
P.L. 90-190
WATER QUALITY IMPROVEMENT
ACT OF 1970
P.L 91-224
40%-55% GRANTS.
NO CEILING.
S203 MILLION-'68.
S1.000 MILLION-'71.
52,000 MILLION • '72.
STATE BY STATE
ALLOTMENTS BY
"NEEDS1.'
ZERO DISCHARGE OF
POLLUTANTS BY 1985.
FISH/SWIM BY 1983.
BPWTT BY 1983.
SECONDARY TREATMENT
BY 1977.
PRIORITY LISTS.
UC/ICR.
BPWTT., ETC.
89 PAGES OF LAW.
(TITLE II = 11 P.).
REDUCE PAPERWORK.
FWPC ACT AMEND.
OF 1972
P.L 92-500
("NEW LAW")
COMPREHENSIVE FEDERAL/STATE
WQ PROG RAM.
BASIN PLANNING
STATE PLANNING
AREA PLANNING
NPDES
EFFLUENT STDS.
CONSTRUCTION GRANTS.
STATE DELEGATION.
I/A.
BUY AMERICAN.
STEP 2+3.
COST EFFECTIVE.
ENERGY.
MARINE WAIVERS FOR
SECONDARY.
CLEAN WATER ACT OF 1977
P.L. 95-217
DECEMBER 27,1977.
DEC. 29, '81:
NO FED $ STEP U2
BUT ALLOWANCES.
ADVANCES TO SMALL
COMMUNITIES.
SECONDARY BY '88.
REDEFINE SECONDARY.
MARINE WAIVERS BY
'82.
I/A 4-7Js«
CWA AMENDMENT
P.L. 96-483
OCTOBER 21,1980
MUNICIPAL WW CG AMDTS
OF 1981
P.L. 97-117
DEC! 29, 1981
*AUTHORIZED
GREAT LAKES DEMONSTRATION.
FEDERAL ACTIVITIES.
MANPOWER TRAINING.
75% GRANTS.
NO CEILING.
S18 BILLION: '73 -'75.
FUNDS IMPOUNDED.
FUNDS RELEASED.
"CONTRACT AUTHORITY"
STEP 1, STEP 2. STEP 3.
REIMBURSEMENT-SZ7B.
OBLIGATION DEADLINES.
"SUFFICIENT FUNDS"TO
SOLVE THE PROBLEM(AS
THEN DEFINED).
75% GRANTS.
NO CEILING.
85% - I/A.
100% - REPLACEMENT (I/A).
S1.0 BILLION-'77*
S4.5 BILLION-78*
S20.0 BILLION-79-82*
ICE.
GOVERNOR MAY REDUCE
FEDERAL SHARE.
CMAG = 2% OF AUTHORIZATION.
OCT. 1, '84:
55% MAX. GRANT; I/A 20%>.
NO FED $ RESERVE CAPACITY.
ELIG: TREATMENT, NEW IN-
TERCEPTORS, I/I CORR.
INELIG. CATEGORIES UP TO
20% OF STATE ALLOTMENT.
$2.4B FY 'Bl^'85. *
469
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Attachment B: NR[)C CONSENT AGREEMENT
and
CLEAN WATER ACT OF 1977
TOXIC POLLUTANTS
Acenaphthene*
Acrolein*
Acrylonitrile*
Benzene*
Benzidine*
Carbon tetrachloride (tetrachloromethane)*
Chlorinated benzenes (other than dichlorobenzenes)*
chlorobenzene
1,2,4-trichlorobenzene
hexachlorobenzene
Chlorinated ethanes (including 1,2-dichloroethane, 1,1,1-trichloroethane
and hexachloroethane)*
1,2-dichloroethane
1,1,1-trichloroethane
hexachloroethane
1,1-dichloroethane
1,1,2-trichloroethane
1,1,2,2-tetrachloroethane
chloroethane
Chloroalkyd ethers (chloromethyl, chloroethyl, and mixed ethers)*
bis(chloromethyl)ether
bis(2-chloroethyl)ether
2-chloroethyl vinyl ether (mixed)
Chlorinated naphthalene*
2-chloronaphthalene
Chlorinated phenols (other than those listed elsewhere; includes trichloro-
phenols and chlorinated cresols)*
2,4,6-trichloroph eno1
parachlorometa cresol
Chloroform (trichloromethane)*
* Specific compounds and chemical classses as listed in the NRDC Consent
Agreement and Committee Print 95-30, Data Relating to H.R. 3199 (Clean Water
Act of 1977), Committee on Public Works and Transportation, 95th Congress,
1st Session, GPO, 1977
470
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2-chlorophenol*
Dichlorobenzenes*
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
Dichlorobenzidine*
3,3'-dichlorobenzidine
Dichloroethylenes*
1,1-dichloroethylene
1,2-dichloroethylene
2,4-dichlorophenol*
Dichloropropane and dichloropropene*
1,2-dichloropropane
1,3-dichloropropene
2,4-dimethylphenol*
Dinitrotoluene*
2,4-dinitrotoluene
2,6-dinitrotoluene
1,2-diphenylhydrazine*
Ethylbenzene*
Fluoranthene*
Haloethers (other than those listed elsewhere)*
4-chlorophenyl phenyl ether
4-bromophenyl phenyl ether
bis(2-chloroisopropyl)ether
bis(2-chloroethoxy)methane
Halomethanes (other than those listed elsewhere)*
methylene chloride (dichloromethane)
methyl chloride (chloromethane)
methyl bromide (bromomethane)
bromoform (tribromomethane)
dichlorobromomethane**
trichlorofluoromethane**
dichlorodifluoromethane
chlorodibromomethane
Hexachlorobutadiene*
Ibid
Deleted from list by EPA. These toxic chemicals have no significant
potential for exposure to water.
471
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Hexachlorocyclopentadiene*
*
Isophorene
*
Naphthalene
*
Nitrobenzene
*
Nitrophenols (including 2,3-dinitrophenol and dinitrocresol)
2-nitrophenol
4-nitrophenol
2,4-dinitrophenol
4,6-dinitro-o-cresol
Nitrosamines*
N-nitrosodimethylamine
N-nitrosodiphenylamine
N-nitrosodi-n-propylamine
Pentachlorophenol*
Phenol*
Phthalate esters*
bis(2-ethylhexyl)phthalate
butyl benzyl phthalate
di-n-butyl phthalate
di-n-octyl phthalate
diethyl phthalate
dimethyl phthalate
Polynuclear aromatic hydrocarbons*
benzo(a)anthracene (1,2-benzanthracene)
benzo(a)pyrene (3,4-benzopyrene)
3,4-benzofluoranthene
benzo(a)fluoranthene (11,12-benzofluoranthene)
chrysene
acenaphthylene
anthracene
benzo(ghi)perylene (1,12-benzoperylene)
fluorene
phenanthrene
dibenzo(a,h)anthracene (1,2,5,6-dibenzanthracene)
ideno(1,2,3-cd)pyrene (2,3-o-phenylenepyrene)
*
Tetrachloroethylene
*
Toluene
*
Trichloroethylene
* Specific compounds and chemical classes as listed in the NRDC Consent
Agreement and Committee Print 95-30, Data Relating to H.R. 3199 (Clean
Water Act of 1977), Committee on Public Works and Transportation,
95th Congress, 1st Session, GPO, 1977
472
-------
Vinyl chloride (chloroethylene)*
Pesticides and metabolites*
aldrin
dieldrin
chlordane (technical mixture and metabolites)
DDT and metabolites*
4,4'-DDT
4,4'-DDE(p,p'-DDX)
4,4'-DDD(p,p'-TDE)
Endosulfan and metabolites*
ct-endosulfan-Alpha
B-endosulfan-Beta
endosulfan sulfate
Endrin and metabolites*
endrin
endrin aldehyde
Heptachlor and metabolites*
heptachlor
heptachlor epoxide
Hexachlorocyclohexane (all isomers)*
a-BHC-Alpha
6-BHC-Beta
y-BHC(lindane)-Gamma
6-BHC-Delta
Polychlorinated biphenyls (PCB's)*
PCB-1242 (Arochlor 1242)
PCB-1254 (Arochlor 1254)
PCB-1221 (Arochlor 1221)
PCB-1232 (Arochlor 1232)
PCB-1248 (Arochlor 1248)
PCB-1260 (Arochlor 1260)
PCB-1016 (Arochlor 1016)
Toxaphene*
Antimony (Total)*
Arsenic (Total)*
Asbestos (Fibrous)*
Ibid
473
-------
Beryllium (Total)*
Cadmium (Total)*
Chromium (Total)*
Copper (Total)*
Cyanide (Total)*
Lead (Total)*
Mercury (Total)*
Nickel (Total)*
Selenium (Total)*
Silver (Total)*
Thallium (Total)*
Zinc (Total)*
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)'
* Ibid
474
-------
Attachment C: EFFLUENT GUIDELINES DIVISION
FEDERAL REGISTER CITATIONS FOR PROPOSED AND FINAL RULES
7/25/83
Industry
Coal Mining
Coil Coating
Phase I
Phase II (Canmaking). . ..
Electrical/Electronic Components
Phase I
Phase II
Foundries (Metal Molding and Casting)
Inorganic Chemicals
Phase I
Phase II
Leather Tanning 4 Finishing
Nonferrous Metals
Phase I
Phase II
40 Cfft PART
467
461
434
465
465
468
469
469
413
464
415
415
420
425
433
& 413
421
421
TVPE RULE
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promul gat ion
Proposal
Promul gation
Proposal
Promul gation
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposed
Admendment
Proposal
Promulgation
Proposal
Promul gation
Proposal
Promulgation
Proposal
Promul gation
Proposal
Promul gation
Proposal
Promul gation
Proposal
Promul gation
Proposal
Promulgation
SIGNATURE*
ll/ 5/82
[09/83]
10/29/82
[01/84]
12/30/82
9/30/82
12/30/80
ll/ 5/82
1/31/83
(10/83)
10/29/82
(07/83)
8/11/82
3/31/83
2/28/83
(11/83)
1/24/78
8/ 9/79
8/11/82
10/29/82
[06/84]
7/10/80
6/16/82
(09/83)
(06/84)
12/24/80
5/18/82
6/13/79
ll/ 7/82
8/11/82
11 5/83
1/31/83
(01/84)
[02/84]
[11/84]
FEDERAL REGIsTEft
47 FR 52626
47 FR 51052
46 FR 3136
47 FR 45382
46 FR 2934
47 FR 54232
48 FR 6268
47 FR 51278
47 FR 37048
48 FR 15382
48 FR 10012
43 FR 6560
44 FR 52590
47 FR 38462
47 FR 51512
45 FR 49450
47 FR 28260
46 FR 1858
47 FR 23258
44 FR 38746
47 FR 52848
47 FR 38462
48 FR 32462
48 FR 7032
...
CITATION
11/22/82
11/10/82
01/13/81
10/13/82
01/12/81
12/ 1/82
02/10/83
11/12/82
08/24/82
04/08/83
03/09/83
02/14/78
09/07/79
08/31/82
11/15/82
07/24/80
06/29/82
01/07/81
05/27/82
07/02/79
11/23/82
08/31/82
07/15/83
02/17/83
—
* Administrator s signature; ( ) is the projected schedule approved by the Court on August 25, 1982 and
October 26, 1981; [ ] is the revised schedule, pending approval by the Court, that has been requested by EPA
(R. Hanmer Affidavit, June 21, 1983).
475
-------
EFFLUENT GUIDELINES DIVISION
FEDERAL REGISTER CITATIONS FOR PROPOSED AND FINAL RULES
7/25/83
Industry
0 Nonferrous Metals Forming
0 Ore Mining
0 Organic Chemicals and Plastics S ....
Synthetic Fibers
0 Pesticides
0 Petroleum Refining
0 Plastics Molding & Forming
0 Pulp & Paper
0 Textile Mills
0 Timber
46 CFR PART TVPE RULE
471
440
414
& 416
455
419
439
463
466
430
& 431
423
410
429
Proposal
Promul gation
Proposal
Promulgation
Proposal
Promul gation
Proposal
Proposal -
(Analytical
Methods)
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
Proposal -
(PCB's)
Proposal
Promulgation
Proposal
Promulgation
Proposal
Promulgation
SIGNATURE*
[01/84]
[10/84]
5/25/82
11/05/82
2/28/82
(03/84)
11/05/82
1/31/83
(12/83)
11/27/79
9/30/82
11/07/82
(09/83)
[01/84]
[10/84]
1/19/81
ll/ 5/82
12/11/80
10/29/82
10/29/82
10/ 3/80
ll/ 7/82
10/16/79
8/27/82
10/16/79
I/ 7/81
FEDERAL REGISTER CITATION
47 FR 25682
47 FR 54598
48 FR 11828
47 FR 53994
48 FR 6250
44 FR 75926
47 FR 46434
47 FR 53584
46 FR 8860
47 FR 53172
46 FR 1430
47 FR 52006
47 FR 52066
45 FR 68328
47 FR 52290
44 FR 62204
47 FR 38810
44 FR 62810
46 FR 8260
06/14/82
12/ 3/82
03/21/83
11/30/82
02/10/83
12/21/79
10/18/82
11/26/82
01/27/81
11/24/82
01/06/81
11/18/82
11/18/82
10/14/80
11/19/82
10/29/79
09/02/82
10/31/79
01/26/81
* Administrator's signature; ( ) is the projected schedule approved by the Court on August 25, 1982 and
October 26, 1984; [ ] is the revised schedule, pending approval by the Court, that has been requested by EPA
(R. Hanmer Affidavit, June 21, 1983).
476
-------
Attachment D:
CONTROL OF INDUSTRIAL WASTEWATER DISCHARGES
IN THE UNITED STATES*
CLEAN WATER ACT
PL92-500 t PU5-217.
SECTIONS 301. 30< 306. 307 C 308
I
EFFLUENT LIMITATIONS GUIDELINES
MO STANDARDS FOR INDLSTRLU.
OlSOtAflGES
TEDMLOeY-BASEO REGULATIONS
FOR EACH 'SUBCATEGOHY WITHIN
Ml INDUSTRY DEVELOPED BT
EPA EFFLUENT GUIDELINES DIVISION
BPT Beat ProctictDle Control
Trcrmology Curentlv Available
BCT Be'* Convention!) Pol-
lutint Control Technology
£eono«icillr Acnicvwle
NSPS N*« Source Perforwtct
St»no*ro«
1
'
| INLUHtUI UlbCHAHGtRS J
^ PSF^ Pr«tr«it»«f>t StonttcrM
For EiKtlng Sources
^ P5NS Prctrcitsent St*nowas
For Net Sourcet
IMPLEMENTATION
AND ENFORCEMENT
IfGUSTfllM. PEIMIT
R€CUL*TIONS
KMICIPU. PEWIT
WO GEICRM. PRETREATICNT
DIRECT DISCHARGE PERMIT APPLICATION
SUBMITTED BY INOUSTRT
POTM' PVJBLICALLY OHNEO TREAT1CMT
IOWS POTV SIGNS PRETflEATICNT ABCE-
>«in KITH IWUSTRT C APPLIES FOB
MMICIPAL DISOUAGC PEHMH
APPROVED STATE AND
EPA REGIONAL MATER
ENFORCEMENT OFFICES
WATER QUALITY
CONSIDERATIONS
NPOES PERMIT
CISUUKCf EL1«II
INDUSTRIAL NPOES PERMIT \J*
NATIONAL POLUTJUIT I I
IKAIION STSTE> \\
MUNICIPAL NPOES
* James D. Gallup, USEPA
477
-------
BIBLIOGRAPHY
"Activities of the Grants Assistance Program;" USEPA, Office of
Administration; Wash. D.C.; May 1983.
"Administrator's Management Accountability System: Second Quarter FY 1983
Report;" USEPA, Office of Management Systems and Evaluations; Wash. D.C.;
Mar. 31, 1983.
Bastion, Robert K.; "EPA Comprehensive Review of Municipal Sludge
Management Alternatives;" USEPA, Office of Water Program Operations;
Wash. D.C.; for Proceedings of National Conference and Exhibition on
Municipal and Industrial Sludge Utilization and Disposal; Atlantic City,
N.J.; Apr. 6-8, 1983.
"Clean Water Act with Amendments;" Water Pollution Control Federation;
Wash. B.C.; 1982.
"Clean Water: Report to Congress - 1973;" USEPA; Wash. D.C.; May 1973.
U.S. Government Printing Office: 727-849/763; 1973.
"Clean Water: Report to Congress - 1974;" USEPA; Wash. D.C.; June 1974.
"Clean Water: Report to Congress - 1975-1976;" USEPA; Wash. B.C.; 1977.
Consent Decree; Civil Action No. 2153-73; U.S. District Court for the
District of Columbia; Natural Resources Defense Council, et. al, vs. Train;
June 1976.
"Construction Grants Delegation and Overview Guidance;" Final Draft;
USEPA, Office of Water Program Operations; Wash. D.C.; April 1983.
Costle, Douglas M.; Administrator, USEPA; Statement before the Oversight
and Review Subcommittee, Public Works and Transportation Committee; U.S.
House of Representatives; Nov. 1, 1979.
"Department of Housing and Urban Development, and Certain Independent
Agencies Appropriations; Hearings before a Subcommittee of the Committee
on Appropriations on H.R. 6956;" Committee on Appropriations; U.S. Senate;
97th Congress, 2d Session; 1983.
"Determining National Removal Credits for Selected Pollutants for Publicly
Owned Treatment Works;" USEPA, Office of Water Regulations and Standards,
Office of Analysis and Evaluation; EPA 440/2 82-008; September 1982.
478
-------
Eidsness, Frederic A., Jr.; Assistant Administrator for Water, USEPA;
Remarks before the Water Pollution Control Federation; Wash. D.C.;
Apr. 19, 1983.
Eidsness, Frederic A., Jr.; Assistant Administrator for Water, USEPA;
Statement before the Water Resources Subcommittee, Public Works and
Transportation Committee; U.S. House of Representatives; Feb. 23, 1983.
"Fate of Priority Pollutants in Publicly Owned Treatment Works: 30-Day
Study;" USEPA, Effluent Guidelines Division; EPA 440/1-82/303; Wash. D.C.;
July 1982.
"Fate of Priority Pollutants in Publicly Owned Treatment Works: Final
Report;11 vol. 1; USEPA, Effluent Guidelines Division; EPA 440/1-82/303;
Wash. D.C.; September 1982.
"Federal Guidelines: State and Local Pretreatment Programs;" vol. 1;
USEPA Office of Water Program Operations; Wash. D.C.; MCD-43; January 1977,
"Federal Water Pollution Control Act, as amended through December 1981;"
(33 U.S.C. 466 et seq.); Environment and Public Works Committee;
U.S. Senate; 97th Congress, 2d Session; Serial No. 97-8; U.S. Govt.
Printing Office; Wash. D.C.; February 1982.
"Gallup, James D.; "The Effluent Guidelines Development Process in the
United States;" USEPA, Office of Water Enforcement, Permits Branch;
Wash. D.C.; 10th Australian Water and Wastewater Association Convention;
Sydney, Australia; Apr. 15, 1983.
"Guide to the Clean Water Act Amendments;" USEPA, Office of Public
Awareness; OPA 129/8; Wash. D.C.; November 1978.
"Guide to Regulations and Guidance for the Utilization and Disposal of
Municipal Sludge;" USEPA, Office of Water Program Operations; Wash. D.C.;
MCD-72, 430/9-80-015; September 1980.
"Health Effects of Land Treatment - Is It Really Safe?" USEPA, Region 5;
Chicago, 111.; March 1980.
Hernandez, John W., Jr.; USEPA; Statement before the Water Resources
Subcommittee, Public Works and Transportation Committee; U.S. House of
Representatives; July 21, 1981.
Hernandez, John W., Jr.; USEPA; Statement before the Water Resources
Subcommittee, Public Works and Transportation Committee; U.S. House of
Representatives; Feb. 24, 1982.
Hernandez, John W., Jr.; USEPA; Testimony before Environmental Pollution
Subcommittee, Environment and Public Works Committee; U.S. Senate;
June 8, 1981.
479
-------
Hernandez, John W., Jr.; USEPA; Testimony before Environmental Pollution
Subcommittee, Environment and Public Works Committee; U.S. Senate;
July 21, 1982.
Hernandez, John W., Jr.; "Water's Role in Rebuilding America's
Infrastructure;" Presentation before Water Resources Congress;
Mar. 10, 1983.
"Innovative and Alternative Technologies for Wastewater Treatment;" USEPA,
Office of Water Program Operations and Office of Research and Development;
Wash. B.C.; October 1982.
"Land Application of Municipal Sewage Sludge for the Production of Fruits
and Vegetables: A Statement of Federal Policy and Guidance;" USEPA, U.S.
Food and Drug Admin., and U.S. Dept. of Agriculture; Wash. D.C.; 1981.
"Legislative History of the Water Pollution Control Act Amendments of
1972;" vols. 1 and 2; 93d Congress, 1st Session; Serial No. 93-1;
Jan. 1973; U.S. Govt. Printing Office; Wash. D.C.
"Legislative History of the Water Pollution Control Act Amendments of
1977;" vols. 3 and 4; 95th Congress, 2d Session; Serial No. 95-14; Oct.
1978; U.S. Govt. Printing Office; Wash. D.C.
"Less Costly Wastewater Treatment For Your Town;" USEPA; Office of Water
Program Operations; March 1983.
Longest, Henry L. II, and Joseph F. Schive; "Section 301(h) of the Clean
Water Act of 1977: A Midcourse Correction in Marine Pollution Cleanup;"
USEPA, Office of Water Program Operations; Wash. D.C.; 7th United
States/Japan Conference on Sewage Treatment Technology; May 19-30, 1980.
"Message of the President Transmitting Reorganization Plan No. 3;"
July 9, 1970; Weekly Compilation of Presidential Documents, vol. 6,
No. 28; July 15, 1970.
"Municipal Pretreatment Program Guidance Package;" USEPA, Office of Water
Program Operations; Wash. D.C.; Sept. 23, 1980.
"Municipal Wastewater Treatment Construction Grants Amendments of 1981"
(P.L. 97-117); 97th Congress; Dec. 29, 1981.
"National Environmental Policy Act of 1969, As Amended" (P.L. 91-190);
Jan. 1, 1970.
"New Jersey Infrastructure Bank;" Background Paper; State of New Jersey;
September 1982.
Parr, James; "Improving Soils with Organic Wastes;" U.S. Department of
Agriculture, Agricultural Research Service; Biological Waste Management
and Organic Resources Lab; Beltsville, Md.; 1978.
480
-------
President's Proposed Legislation on New Federalism; Executive Office of
the President, Office of Management and Budget; Wash. D.C.; Feb. 25, 1983.
Quarles, John; "Cleaning Up America;" Houghton Mifflin Co.; Boston; 1976.
"Review of the Municipal Wastewater Treatment Works Program;" USEPA,
Construction Grants Review Group; Wash. B.C.; Nov. 30, 1974.
Rodgers, William H., Jr.; "Environmental Law;" West Publishing Co.;
St. Paul, Minn.; 1977.
Rosenbaum, Walter A.; "The Politics of Environmental Concern;" Praeger
Publishers; New York, N.Y.; 1973.
Ruckelshaus, William D.; Administrator, USEPA; Statement before Environment
and Public Works Committee; U.S. Senate; May 4, 1983.
Ruckelshaus, William D.; Administrator, USEPA; Testimony and Administration
Proposals on Clean Water Act Reauthorization before Environmental Pollution
Subcommittee, Environment and Public Works Committee; U.S. Senate;
June 14, 1983.
"Sludge and the Land: the Role of Soil and Water Conservation Districts in
Land Application of Sewerage Sludge;" Prepared by the National Association
of Conservation Districts for USEPA, Office of Water Program Operations;
Wash. D.C.; 430/9-82-007; September 1982.
"Sludge Recycling for Agriculture Use;" USEPA, Office of Water Program
Operations; Wash. D.C.; 430/9-82-008; October 1982.
"Small Wastewater Systems: Alternative Systems for Small Communities and
Rural Areas;" USEPA, Office of Water Program Operations; FRD-10;
January 1980.
"Solutions for Financing Infrastructure;" Engineering News Record;
March 1983.
Southworth, Robert M.; "Industrial Categorical Pretreatment Standards;"
USEPA, Office of Water, Effluent Guidelines Div. Paper presented before
Association of Metropolitan Sewerage Agencies Seminars on Industrial-
Municipal Pretreatment Program Implementation; Anaheim, Calif.;
June 19, 1980.
"USEPA General Pretreatment Regulations for Existing and New Sources;"
Federal Register; vol. 46, No. 18; Jan. 28, 1981.
"USEPA Pretreatment Regulations;" Federal Register, vol. 43, No. 123;
June 26, 1978.
"USEPA Legal Compilation: Statutes and Legislative History, Executive
Orders, Regulations, Guidelines and Reports;" January 1973.
481
-------
"USEPA Legal Compilation: Statutes and Legislative History, Executive
Orders, Regulations, Guidelines and Reports;" Supplement II, vols. 1 and
2; January 1974.
"USEPA Organic Chemicals and Plastics and Synthetic Fibers Category
Effluent Limitations Guidelines, Pretreatment Standards, and New Source
Performance Standards;" Federal Register; vol. 48, No. 55; Mar. 21, 1983.
"U.S. House of Representatives Report No. 92-911; Committee on Public
Works; Mar. 11, 1972;" A Legislative History of the Water Pollution Control
Act Amendments of 1972; vol. 1; Jan. 1973; U.S. Government Printing Office;
Wash. D.C.
"U.S. Senate Report No. 92-414; Committee on Public Works; Oct. 28, 1971;"
A Legislative History of the Water Pollution Control Act Amendments of
1972; vol. 2; January 1973; U.S. Government Printing Office; Wash. D.C.
482
-------
COARSE BUBBLE TO FINE BUBBLE AERATION RETROFIT
by
Paul F. Gilbert and James H. Chase
Hartford Water Pollution Control Plant
The Metropolitan District Commission
Hartford, Connecticut
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
483
-------
COARSE BUBBLE TO FINE BUBBLE AERATION RETROFIT
by: Paul F. Gilbert, Plant Engineer
Hartford Water Pollution Control Plant
The Metropolitan District Commission
Hartford, Connecticut
James H. Chase, Chief Chemist
Hartford Water Pollution Control Plant
The Metropolitan District Commission
Hartford, Connecticut
ABSTRACT
A fine bubble diffuser system retrofit at the Metropolitan District
Commission - Hartford Water Pollution Control Plant, shows promise of a
two and one-half year payback on an investment of $600,000. The 45 million
gallon per day activated sludge process was designed with a coarse bubble
diffuser system operating at 7% oxygen transfer efficiency. The system
has been replaced with fine bubble ceramic dome diffusers at 277, oxygen
transfer efficiency.
The reseach phase of the retrofit program included; investigation
of high efficiency oxygen transfer systems, pilot testing of the most promis-
ing technology, and examination of the interfacing of existing and new equip-
ment. Design recommendations were concurrently prepared by MDC staff, con-
sultant and equipment manufacturers.
The retrofit construction began in mid 1982 and completed in November.
The transitional phase to fine bubble operation and the following five month
period presented numerous operating problems which were systematically cor-
rected, resulting in significant savings.
The savings realized from a baseline period of operations were a 227,
overall reduction in total plant power consumption and a 547, decrease in
the 3,000 horsepower blower power consumption. The projected cost savings
for 1983 is $200,000.
484
-------
INTRODUCTION
From plant start-up in 1972, the coarse bubble diffusser system supply-
ing air to the activated sludge process at the Hartford Water Pollution Con-.
trol Plant has been an energy intensive operation. This situation has re-
sulted primarily from the fact that one 3,000 horse power blower, rated at
66,000 standard cubic foot per minute, (SCFM) has not provided sufficient
air for the 60 MGD activated sludge process. While there has been the cap-
ability of placing a second blower on line which would provide the required
amount of air, the electrical cost associated with operating two units
simultaneously has been prohibitive.
More specifically, the annual electrical consumption at the plant was
slowly increasing between 1973 and 1979 (see Figure 1). Between 1979 and
1982 a large decrease in energy use was realized through the upgrading of
the sludge handling operation to belt filter presses and a new incinerator
operating mode. Despite this reduction in electrical energy consumption,
annual electrical costs continued to increase through 1982. With forecasts
of continued electrical rate increases and with continued high air consump-
tion in the activated sludge process, the staff of the Hartford Water Pollu-
tion Control Plant embarked on a technology investigation to reduce the air
consumption by upgrading the efficiency of the system.
Preliminary investigations quickly indicated that the coarse bubble
diffuser system was providing a very low transfer efficiency. Newa"ir diffu-
sion processes were considered and pilot testing begun. In conjunction with
the equipment manufacturers and the consultant, a fine bubble system was
chosen which would enhance the oxygen transfer, reduce air consumption, de-
crease electrical requirements, eliminate the use of the 2nd blower and,
finally, maintain control of our operating budget.
After selecting the most efficient fine bubble system, plans and speci-
fications were prepared for bidding purposes. The Contract was awarded to
the Norton Company the successful bidder. The new system was installed in
mid 1982 and placed in full operation in November.
Since full implementation the overall savings in air consumption, energy
and cost have been most impressive, (as indicated in Figure No. 1). The
projected electrical savings for 1983 for example, is approximately $200,000
with a payback period of 2-1/2 years.
485
-------
p
Si 25
UJIDO
075
H
Z
_l
a.
050
025
26
§24
|22
z
z
*20
<
I-
e
16
TOTAL PLANT ELECTRICAL
USAGE
PROJECTED
ELECTRICAL COSTS
SAVINGS '200,000.
TOTAL PLANT ELECTRICAL
COSTS
FINE BUBBLE
OIFFUSER RETROFIT
PROJECTED
ELECTRICAL
ENERGY REDUCTION
1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983
YEAR
FIGURE I ANNUAL PLANT ELECTRICAL CONSUMPTION a COSTS
BACKGROUND
The Hartford Water Pollution Control Plant (HWPCP), designed in 1968
and completed in 1971, treats waste water from six greater Hartford area
towns with an average daily flow of 45 million gallons daily (MGD). The
plant handles preliminary, primary and secondary activated sludge treatment.
The activated sludge and sludges from three additional water pollution con-
trol plants are pumped to dissolved air floatation thickeners and subsequently
blended with primary sludge. This homogenous mix is then pumped to belt
filter presses, after which it is incinerated in two of our three multiple
hearth incinerators.
ACTIVATED SLUDGE PROCESS
The activated sludge process is designed for 60 MGD with a current
average flow of 45 MGD. The flow from primary treatment is pumped to second-
ary then split into six aeration tanks. Each tank is 194 ft. long, 80 ft. wide
and 15-1/2 ft. deep. The tanks are divided into 4 passes each to permit step-
feed. Return sludge is fed into the head end of pass No. 1. Primary sewage is
normally split among passes No. 1-2-3- and 4. (see Figure 2).
486
-------
MAIN INFLUENT CHANNELS
INFLUENT
EFFLUENT
FIGURE 2 SECONDARY TREATMENT SYSTEM
487
-------
Having the flexibility of a Step Feed configuration is highly beneficial.
When the MLSS (mixed liquor suspended solids) is high, the step configuration
that is set tends toward a contact mode of operation to relieve the solids
loading rate on the final clarifiers. With the MLSS at a desirable range,
a more conventional mode is used to shift solids from the aeration tanks to
increase clarifer loadings and improve the density of waste sludge to thick-
ening.
Due to Biochemical Oxygen Demand (BOD) and hydraulic loadings, only four
out of the six aeration tanks have been operational. The mixed liquor from
the aeration basins flows to six circular 125 ft. diameter clarifiers. The
overflow from the clarifers is chlorinated between May and September and
discharged to the Connecticut River.
The sludge from the final clarifiers is returned to a common wet well, at
which point 957, is returned to the aeration system, at a rate equal to 25?0 of- plant
flow the balance is wasted to the dissolved air floatation thickening system.
Due to a prior inefficient sludge dewatering operation, which pre-
vented sludge from being wasted in the correct amount, the MLSS and MCRT
(mean cell residence time) were far above design. As a result, foam in
large amounts was always present on the surface of the aeration tanks, to the
point where the foam would infiltrate into the Y-walls. This caused handling
problems in the galleries below.
Large quantities of scum were also always present on the clarifiers,
creating serious problems in the winter months. The formation of "scumburgs"
would trip the collection equipment, necessitating the use of a crane with
a clamshell to remove the frozen scum from the clarifiers.
Due to the belt filter press retrofit of the last three ye^ars, it has
been possible to more efficiently process the sludge, thereby remicing MLSS,
MCRT, and sludge inventories. This has benefitted the process tremendously
and also helped to solve foam and scum problems.
AIR SUPPLY
The air for the aeration system, as mentioned earlier, is continuously
supplied by one of three Brown-Boveri Rotary Vane Blowers. Each unit is
rated at 3,000 HP with a maximum output of 66,000 SCFM at 7.5 psi.
The initial air diffusion equipment, installed in 1972, was a Chicago
Deflecto Diffuser, a coarse bubble device with large 3/8 in. diameter orifices
on the periphery of the diffuser. This diffuser's oxygen transfer rate
when tested was found to be 77«; however, with energy being so inexpensive,
emphasis was placed on a uncomplicated system that required little maintenance.
The spiral roll created by the design required only 252 diffusers per pass
and also kept the tank floor free of equipment, facilitating cleaning when
necessary. Air filtration was provided by a series of oil cleaned screens.
488
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From the beginning, the one compressor always operated at full capacity;
yet it never fulfilled the DO (dissolved oxygen) requirements in the aeration
system, particularly in the first pass and during the summer months. Faced
with both the expensive possibility of placing the second compressor on line
and steady electrical rate increase, the Hartford Water Pollution Control
Plant staff began its research and investigation into a more efficient
system in early 1978.
RESEARCH AND INVESTIGATION
The objective of the research phase of the project was to determine and
select the most efficient, cost effective and compatible air diffusion equip-
ment available. In order to carry out this task, research and investigation
were divided into the following categories:
"Available Technology Investigation
"Pilot Testing
"Potential Air Usage with New Technology
"Main Blower-Turndown Evaluation
"Electrical Power Monitoring
"Piping System Investigation
"Air Filtration Requirements
"Instrumentation System Requirements
„, -**--*--.-" . ,- ^vcr * • ->*—
"Systems Evaluation
\»
\ v
"Final Report and Recommendations
AVAILABLE TECHNOLOGY INVESTIGATION
Manufacturers, suppliers, consultants, and end users were contacted
in order to gather as much information on the various types of available
diffusion equipment. Realizing at the onset of our research that mechanical
aerators and jet aerators would not be compatible with our system, we pro-
ceeded to investigate ceramic and plastic tubes, static mixers, ceramic dome
diffusers, etc. Preliminary investigations pointed to the ceramic dome as
being an efficient system; it was, therefore, chosen for testing.
489
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PILOT TESTING
Our first test was basic in that it consisted of mounting a single
ceramic dome on the bottom of a large container and connecting it to an
air supply. Observations of the bubble size, formation, patterns, etc. were
made and compared to the performance of a coarse bubble diffuser. The com-
parison looked promising enough to proceed.
The second test consisted of evaluating the performance of two side by
side 55 gallon drums outfitted with an air supply, air flow gauges, and a
portable dissolved oxygen (DO) meter. This investigation compared "head on"
the coarse bubble diffuser against the fine bubble dome. With the drums
filled with activated sludge, and air flows held constant, the fine bubble
diffuser dome set-up would rapidly develop and maintain at least double the
DO level of the coarse bubble diffuser. Conversely, if air flows were ad-
justed to maintain the same DO in each drum, the dome diffuser required one
half as much air as the coarse bubble diffuser.
The original test stand compared one dome against one coarse bubbler.
This was not realistic from a design standpoint because one dome required
a higher operating pressure than is required by one coarse bubble diffuser.
A third test was conducted with the use of a 300 gallon activated
sludge pilot plant, in which could be mounted up to 4 domes and one coarse
bubble diffuser, piped independently. The tank was set up as an aeration
tank with a continuous flow-through of activated sludge from one of our
operating plant aeration tanks.
The tests though essentially a repetition of the barrel studies, were
run at the more realistic fine bubble dome to coarse bubble diffuser ratios
of 2:1 and 4:1. The two to one ratio turned out to be a lower ratio than
necessary; however, sufficiently realistic data was generated by the 4:1
arrangement to estimate the savings of air usage in a full plant scale up.
Each diffuser system in the tank was run alternately over short periods of
time in order to maintain a steady DO.
The amount of air required by each diffuser system to maintain the
steady DO was recorded. Several runs were made and savings in air usage
ranged from 50-607o
One unfortunate characteristic of the fine bubble system was thte
increase in foam experienced in the 300 gallon pilot tank. Since the
new dewatering operation with Belt Filter Presses would allow the maintenance
of lower MCRT's (by increased wasting) it was felt that this problem could
be minimized.
490
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POTENTIAL AIR USAGE WITH NEW TECHNOLOGY
The pilot tests indicated that there would be a 50 to 6070 total air
reduction. The design data indicated that approximately 8,000 SCFM was
required to maintain the solids in suspension in the influent channels, with
14,000 SCFM necessary for aeration. The total anticipated air usage ranged
from 18,000 to 22,000 SCFM. With the main compressor normally operating at
66,000 SCFM, the next concern was the turndown capability of the main com-
pressor.
MAIN BLOWER - TURNDOWN EVALUATION
With assistance from an engineer from Brown Boveri (blower manufacturer),
the capability of the rotary vane 3,000 HP blower was reviewed. Its surge
point, efficiency and power consumption were studied and a procedure was
then devised to reduce the output of the blower while maintaining a fixed
discharge pressure.
From the initial 66,000 SCFM the blower discharge was slowly reduced to
10,000 SCFM. The unit never reached its surge point and performed well
throughout the range, with a minimal loss in operating efficiency.
ELECTRICAL POWER MONITORING
Early in the project, it was realized that it would be necessary to
determine the energy usage of the blowers. Therefore, the installation of
a watt meter and the plotting of daily kilwatt-hour readings and total air
usage was begun. This base line data was necessary to determine what portion
of the entire plant's electrical power consumption could be attributable
to the blower, in order to accurately calculate potential savings.
PIPING SYSTEM INVESTIGATION
The existing air piping system in the Hartford Water Pollution Control
Plant is constructed of spiral welded steel and wrought iron pipe. Some
corrosion, rusting, and scaling of these types of pipes usually occur after
a few years of service; they do not, however, normally cause operating prob-
lems in coarse bubble aeration systems. In order to be certain that the
existing air pipes were rust free and capable of being used for fine bubble
diffusers, it was necessary to field inspect.
To perform the inspection, the main blower was shut down so that en-
trance to the piping could be gained through an access manhole on the 5 ft.
diameter discharge air main. The piping was examined from the compressor
down to the 2 ft. diameter branch lines. Since none of us was slim enough
to get through the 12 in. lines, a few fittings were removed to permit
inspection. This was also done for the 6 in. drop headers. The suction
lines from the air filters to the compressor were also closely inspected.
491
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The results of the inspections revealed the following:
°The bituminous epoxy coating in the air mains and suction
lines were in excellent condition, and would be suitable
for the fine bubble system.
°The coating in the 12 in.lines in tank Nos. 1-2-3-4 was found
in good condition. The coating in the similar lines in
tank No. 5 & 6 was damaged with resulting rusting and
scaling. This situation was caused by the fact that these
tanks had not been in use and would remain empty for the
near future.
°The 6 in. drop headers were rusted and would require re-
placement for use with the fine bubble system.
AIR FILTRATION INVESTIGATION
The fine bubble ceramic domes and tubes would require removal of 95
percent of all particles in the inlet air down to particles 0.3 microns
in size. The existing automatic oil bath filters were capable of removing
only about 25 to 30 percent of the particles and, therefore, were not useable
.with the fine bubble system. Several alternative systems were evaluated
including American Air Filters' Biocell and Electro-pak filters.
The Biocell filters which would be installed inside the existing inlet
plenum, would require a structural frame. There was sufficient spa'ce in the
inlet plenum to permit the modifications. The Electro-pak, is an electro-
static precipitator, because of its expense and large size, was not deemed
practical for the installation.
INSTRUMENTATION SYSTEM REQUIREMENTS
The air control system was designed with flow control and flow indicators
to each pass of every aeration tank. A DO probe senses the amount of dis-
solved oxygen in the pass, the signal is fed to an analyzer, then to an
electronic controller where the DO is manually set. The Output signal from
the controller modulates a 12 in. motor operated butterfly valve which controls
the amount of air to match the set-point DO.
As each pass is modulated, the main venturi senses the change in pres-
sure and flow in the entire system. A pressure controller modulates the vane
in the compressor to maintain a constant system pressure.
With low air flows anticipated due to the retrofit to the fine bubble
system, the range efficiency of the instrumentation system and the effects
of low air flows on the DO probes were potential problems. The equipment
manufacturers were contacted and given the projected operating parameters.
They recommended that the existing range tubes in each flow transmitter be
492
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replaced with new range tubes so that the transmitters would be sensitive to
future operation with the reduced air flows. Recalibration of the trans-
mitters would be necessary. In addition, the air flow totalizer gears and
the air flow indicator scales for each flow controller would also require
replacement.
The DO probe manufacturer indicated that, despite the change from a
spiral roll to vertical uplift diffusion and smaller bubbles, the existing
probes would function satisfactorily.
As a follow-up to the study conducted by the Metropolitan District,
Metcalf & Eddy Consulting Engineers, the original designers of the plant,
(M & E) were retained to evaluate the existing coarse bubble diffuser system
as well as the proposed installation of the fine bubble ceramic dome and
tubes diffuser systems. The M & E evaluation would include investigating
the oxygen transfer efficiences of these systems, present and projected air
requirements and power usage of the three systems, present and future waste-
water flows and load projections and the system's relative cost effectiveness
over a planning period of 20 years (1982 - 2001).
Based on the cost-effectiveness study,some of the major conclusions
were:
1. For the future operating conditions expected at the Hartford
Water Pollution Control Plant, clean water oxygen transfer
efficiences for the existing, coarse bubble would be 77=; the
proposed fine bubble tube efficiencies would be 15% and^the
efficiencies for the fine bubble ceramic domes would be 297».
2. Minimum air requiWRfieirts for the fine bubble domes would be
dictated by the air needed for mixing to keep the MLS-&- in
suspension.
3. Peak air demand for proposed fine bubble domes could be
supplied by one existing blower throughout the planning period.
4. Peak air demands for the existing coarse bubble system, as well
as for the proposed fine bubble tubes, would require simultaneous
operation of two blowers during warm summer months.
5. Even with increased submergence and increased headlosses with
fine bubble domes and tubes, the total system head on the
compressors would be well within the capacity of the existing
blowers.
6. Blower surging would not be expected to occur for the expected
air demand with the proposed fine bubble systems.
7. The capital as well as operating costs of the fine bubble domes
would be smaller than those for the fine bubble tubes.
493
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8. Due to higher initial capital expenditures and higher opera-
tional costs of the fine bubble tubes (resulting from low
oxygen transfer efficiencies), the fine bubble domes would
have a distinct cost advantage over the tubes.
FINAL RECOMMENDATIONS
On the basis of testing, inspections, research, analysis and evaluations
of the Hartford Water Pollution Control Plant operations, and analyses and
evaluations of proposed fine bubble diffuser systems and their related cost
effectiveness, it was recommended that the MDC:
1 Initiate design to prepare plans and specifications to retrofit
four of the six aeration tanks to fine bubble ceramic domes.
2. Modify the existing valves and rate controllers on air lines
to each individual pass of each tank and replace the associated
range tubes in the transmitters. Change the air flow rate
indicator scales.
3. Install bio-cell air filters in all three inlet plenums of
the three compressors.
DESIGN CONSIDERATIONS
The layout and design of the fine bubble dome diffuser system was such
that a maximum portion of the existing air piping was utilized. Likewise,
the submerged air distribution piping feeding air to the ceramic diffusers
was designed to facilitate an easy and economical installation. When fully
operational and treating a similar strength and volume of wastewater as the
previous coarse bubble diffuser system, the system would require only ap-
proximately 5070 of the required coarse bubble horsepower.
Contract specifications required that, as a minimum average, 7,550 Ibs.
0«/day had to be transferred to the wastewater, while 14,000 Ibs. day was
needed to accommodate the maximum average loading. O'ther wastewater para-
meters, such as alpha .75, beta = .95, DO = 2.0 mg/1 and Tw=15° C, were
also specified as well as the airflow distrubtion per pass for each of the
four passes per tank. The total air supply to each aeration tank was
specified to be distributed uniformly in each pass, according to the follow-
ing proportions in conjunction with the minimum diffusers:
PASS PERCENT DISTRIBUTION MINIMUM DIFFUSERS/TANK
#1 35% 1,085
#2 25% 775
#3 25% 775
#4 15% 465
Total Per Tank 100% 3,100
494
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The required minimum number of domes were 12,400 for the total system
of four tanks.
The selected fine bubble diffuser system had to have guaranteed oxygen
transfer efficiencies of 287=, 267. and 237., at diffuser flow rates of .5, 1.0
and 2.0 scfm/dome, respectively. The minimum air flow criteria of 0.5 scfm/
dome was established to prevent water side fouling. Furthermore, a mixing
requirement of 0.12 scfm/ft^ of tank bottom was established along with a
minimum dome spacing of 2 feet on center. The mixing requirement had to main-
tain solids in suspension and prevent solids accumulation on the tank floor.
The most efficient dome layout would require uniform air flows through
each dome, while satisfying the natural variation in air demand along the
length of a step feed aeration tank. Locations with high demand would need
proportionately more domes than locations with low demand. Therefore, the
dome distribution pattern for tanks one and two was based on oxygen uptake
studies.
The studies were conducted by District staff at sixteen locations along
the four passes of one tank. These studies indicated the need for a tapered
distribution pattern. The first design pattern was based on this tapered
distribution and other previously indicated design constraints.
Possible alterations of the step feed configuration was another design
consideration. Additional base plates were available in most passes for
future modifications of dome patterns and each of the seven grids in a pass
was to have a throttling valve for fine tuning.
The first two operational tanks were to be field tested and additional
modifications would be designed into tanks three and four as needed.
DO measurements were taken in tanks one and two as they came on line with
the fine bubble system. Operational changes since the initial design stage
had caused a shift in the demand pattern. The DO profiles indicated that
more domes were necessary at the influent end of the passes.
Redistribution of the domes was easily accomplished in tanks three and
four by use of the spare base plates available in the original design.
SYSTEM HARDWARE
The air distribution piping as installed has the built-in capability
for expansion to accommodate additional diffuser domes since extra (507.)
dome baseplates were initially fabricated to the plastic piping. Diffuser
locations not in use. were made inoperative by simply plugging off the air
release holes. The plastic air distribution piping network was easily assem-
bled using 4 in. UPVC (unplasticized polyvinyl chloride) pipe and 4 in. (UPVC)
expansion tees. The system is installed one foot off the tank floor thus
providing a 14.5 ft. vertical clearance to the water surface. Pipes and
fittings are supported and anchored to the concrete floor using a Norton
designed adjustable stainless steel pipe support assembly.
495
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Ceramic Diffuser Made From
Crystalline Fused Alumina
Orifice Bolt with
13/64" Control-
Orifice
Base Plate
V'UPVC Pipe
316 SS SUPPORT
304 SS WEDGE ANCHOR
FIGURE 3 TYPICAL DOME DIFFUSERS & PIPING
-------
Two 1/4 in. diameter stainless steel anchor bolts secure the pipe to the
floor while a stainless steel band holds the 4" UPVC to the pipe support.
Air is delivered to each of the seven air distribution grids per pass by a
single vertical 4 in. stainless steel pipe which drops directly into a 4 in. UPVC
tee. Air emerges from the piping network up through a plastic bolt having
a specified orifice size (13/64 in. dia.). This orifice bolt also serves as a
means of attaching the porous ceramic dome diffuser to its plastic base-
plate. Neoprene sealing gaskets are placed under the head of the orifice
bolt and between the dome edge and the UPVC baseplate (see Figure 3). Ideally,
only fine bubbles on the order of 2mm will be emitted from the pores of
ceramic diffusers. In fact, the many small oxygen bearing bubbles that are
released into the wastewater comprise the main reason for a very high system
oxygen transfer efficiency. The Hartford aeration system, with its numerous
diffuser domes, provides highly efficient oxygen transfer and mixing.
Each of the independent UPVC air distribution grids contains a simple
moisture blowout assembly which removes any residual moisture after the start
of airflow to the system.
INSPECTION & TESTING
During all phases of construction, MDC personnel continously inspected
the performance of the independent contractor. It was most important that
the system be installed exactly as designed, to assure an efficient operating
system.
As each piping network was installed, alignment and elevations were
verified. The ceramic domes were thoroughly inspected prior to installa-
tion and further checked in place for proper gasketing and bolt torque.
"" 0>
Upon completion of each tank, clean water was metered to 3-in
the piping for a system leakage test. With corrections made, the water level
was slowly increased to full depth while observing the air distribution
patterns. The tank was then stabilized and placed into operation.
OPERATIONAL RESULTS
As shown in Fig. 4, baseline data prior to the fine bubble retrofit
spans the period of mid-May-to August 1982. Air usage averaged 64 MCFD
(Mil, Cu. ft./day) and Power usage average 31,000 KWH/day during this period.
497
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BLOWER KWH CONSUMED
I PER DAY
CHANNEL
AIR REDUCTION
MAY J'JN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR
1982
FIGURE 4 DAILY BLOWER AIR USAG a ELECTRICAL CONSUMPTION
During this same period MLSS averaged between 2500-4000 rag/L; the blower
discharge pressure ranged between 7.5-7.7 psi. The air control was on auto-
matic, with air valves controlled by signals from DO probes in each pass
which maintained an averaged of 1 ppm DO.
When the first fine bubble aeration tank was placed on line on August 9,
the air usage immediately dropped to 54 MCFD; power usage dropped into the
28,000 KWH/day range.
The second fine bubble aeration tank went on line September 2; during
this time, MLSS concertrations had been rising, and a small initial drop in
air usage was followed by an intentional increase over the previous base line
value. As the MLSS rose into the 5000 MG/L range, increased air requirements
began to exaggerate the different pressure requirements of the coarse and fine
bubble systems which were on line concurrently with the same automatic con-
trol system. The resulting anaerobic conditions in much of the fine bubble
system caused a bulking condition with subsequent loss of solids in the
498
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effluent. The air supply to the entire system was increased until a solution
to the distribution problems could be found. During this time sludge was
vigorously processed to return MLSS to a 2500 MG/L design range and to ensure
that excess DO was established throughout the system. After this operational
control problem, the air usage was decreased to seek an economoical operating
condition.
On October 28, the installation of the entire project was completed and
the fine bubble operation established in all aeration tanks. When fully on-
line, air usage dropped to 36 MCFD and the power fell to the 22,000 KWH/day
range. This range was maintained until year's end while working on the auto-
matic air controls.
During the first week of 1983, a brief increase in MLSS caused air dis-
tribution problems with a consequent large increase in KWH/day. It became
apparent that the automatic air control in its present state would not allow
further reductions in KWH. The very act of controlling the system caused
the blower to work under a greater load than was necessary to delivery an
adequate air supply. Some passes were also being locked out by the automatic
equipment which increased the risk of water side fouling on the fine bubble
diffusers.
In mid-January the system was placed in the manual mode of operation,
with DO probes being used for monitoring purposes only. In the automatic
mode the discharge pressures on the compressor varied between 7.1 and 7.4 psi.
After the switch to the manual air control operation, the blower's discharge
pressure was adjusted to 6.8 and all air control valves were locked fully
open. Air usage dropped slightly but power consumption fell by over 1070;
further experiments with the blower vane position control resulted in another
107o reduction in power.
In mid-April, influent channel air consumption was carefully reduced by
one-half. The resulting surplus in air to the aeration tanks allowed further
air reductions to 22 MIL cu. ft./day and power reduction to 15,000 KWH/day.
Foam problems have always existed and were experienced during the entire
baseline period of operation; then became worse as the fine bubble tanks came
on line.
In mid-January, after a short period of time at an MCRT of 3-5 days, foam
problems disappeared completely. The only hint of a reoccurrence of the foam
resulted from an increase in MCRT above the 3-5 day range.
Placing the fine bubble system on line on an incremental basis caused
numerous operational problems, as just described. However, the activated
sludge process has been stabilized and is performing exceptionally well.
499
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SAVINGS
The following figures serve to demonstrate the electrical savings and
annual cost savings due to the retrofit program.
-10
CD
u-30
-------
Figure 6. Daily Plant Electrical Consumption & Percent Reduction
o
I- 6
I-
z
o
(E
UJ
0.18
20-
22
55
54
o
O
O
53
51
50
z
2 49
I-
Q.
3 48
47
f- _, 45
<
H 44
2 43
42
41
40
PLANT TOTAL CONSUMPTION OF
ELECTRICAL ENERGY PER DAY
DAILY PERCENT DECREASE
IN TOTAL ENERGY CONSUMPTION
MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR
1982 1983
FIGURE 6 DAILY PLANT ELECTRICAL CONSUMPTION a
PERCENT REDUCTION
During the baseline period (May-July) the total plant electrical con-
sumption was 54,000 KWH/day. This total includes power for Preliminary
treatment, Primary Treatment, Effluent Pumping, Secondary Treatment and Sludge
Processing. The retrofit program has reduced the total plant electrical con-
sumption to 42,000 KWH/day, a 22% overall decreases.
501
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1.25
to
oc
o
Q
1.00
0.75
o
_!
_J
2
i
en
H-
tn
o
o
_i
<
E
i-
o
UJ
LJ
< 0.50
Z
Z
<
PLANT
BLOWER EL
TOTAL ELEbTRICAL COSTS
ECTRICAL C JSTS
TOTAL
ANNUAL
.SAVINGS
'300,000
ANNUAL
SAVINGS IN
BLOWER
OPERATING
.COSTS
r 200,000
1979
1980
1981
YEAR
1982
1983
FIGURE 7 ANNUAL PLANTS BLOWER ELECTRICAL COST
Figure 7. Annual Plant & Blower Electrical Costs
This figure demonstrates the continuous rising trend in electrical costs
over the past few years, up to 1983. The broken line indicates the con-
tinued increase in costs for the plant and blower coarse bubble had con-
tinued. The solid line represents the projected electrical costs with the fine
bubble aeration system. Based on the above, the project electric
costs for the blower will b£ reduced by $200,000 - and result in a like savings
in the anticipated plant costs. At this continued rate, the payback period
will be 2-1/2 years.
502
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CONCLUSIONS
The Metropolitan District's fine bubble retrofit program represents the
coordinated efforts of the MDC's management and staff, and our consulting
engineers, manufacturers and contractor. As you have seen, the investment
has been very beneficial, on a cost benefit basis, and the upgrading of our
system has improved the efficiency of our operation.
The entire undertaking has been a learning process. Placing the system
on line and making the transition to fine bubble aeration reminded us of the
initial phases of start-up when the Hartford plant was initially placed in
operation in the early 1970's.
As we continue to fine tune the new system, we are planning the follow-
ing associated projects:
"Computer Feasibility - the Norton Co., has been retained to investigate
the application of a computer to monitor the status of all
16 DO probes, acquire operating data, and eventually apply
the computer to system control.
°Grid Adjustment - Plans are being made to empty tanks 1 and 2 to
readjust the grid pattern to match tanks 3 and 4. This will
also give us the opportunity to inspect the system.
"Manometers Installation - Manometers will be installed on all
16 flow venturies to permit the operators to personally check
the accuracy of the instrumentation. Operation at air flows
close to water side fouling limits requires an accurate mode
of operation.
"Retrofit Investigation at Satellite Plants - With two satellite
plants operating with coarse bubble aeration systems, the
acquired knowledge will be utilized to investigate the
potential retrofits to fine bubble at these plants.
The work described in this paper was not funded by the U.S. Environ-
mental Protection Agency, and therefore, the contents do not necessarily
reflect the views of the Agency and no official endorsement should be
inferred.
7/20/33
503
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CLEAN WATER IN WISCONSIN
by
Paul N. Guthrie, Jr.
Wisconsin Department of Natural Resources
Madison, Wisconsin 53707
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19 - 21, 1983
Tokyo, Japan
505
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CLEAN WATER IN WISCONSIN
Paul N. Guthrie, Jr.*
Wisconsin Department of Natural Resources
The adoption of the United States Constitution, coming after the failing
years under tne Articles of Confederation created an opportunity for states
to act in unison and for the United States Congress to act nationally
witnout inhibition caused by a single state's political desire.
Over the nearly 200 years since the creation of the Constitution, the
national government has evolved into a strong, centralized power. Yet,
ironically, the decentralized administration of many national laws allows
individual states, along with their local subdivisions and citizens
(rightfully clothed witn a democratic cynicism of central authority) to
engender a vast diversity in implementation of national programs.
Thus, in each section of the United States, local background and history
coupled with state law and political nativity act together to fulfill the
national interest. Regionalism is a reality in the administration of
national environmental objectives, and in the pursuit of clean water in
Wisconsin.
Water Resources and Wisconsin
In order to understand the evolution and significance of water resource
protection in Wisconsin, it is helpful to understand the resource itself.
Water is plentiful in the state. It occurs in several distinctly different
conditions, each with a characteristic vulnerability to use and to
pollution. The three major types of surface water bodies in Wisconsin are:
Acreage
1. Major rivers and tributary streams 176,358
2. Inland lakes 970,869
3. The Wisconsin Great Lakes 6.439.700
^586,927
Major River Basins
Tne largest river in the state is the Mississippi which forms part of
Wisconsin's western border. The Wisconsin River is the major Mississippi
Author's Note: The writer of this paper wishes to acknowleuge the
many persons within the Wisconsin Department of Natural Resources whose
work has been summarized in this paper and to give a special note of thanks
to Mary Ann Heidemann and Daniel Moran for their personal assistance and
counsel.
506
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tributary within tne state, flowing as a spine through central Wisconsin.
Two-thirds of the state's surface run-off drains into the Mississippi
system. The remaining orie-tnird drains into the Great Lakes, principally
through the Fox River. (See maps 1 and 2)
Historically, the Fox and Wisconsin rivers have been tne state's most
important waterways. Near Portage, Wisconsin, these rivers lay less than a
mile apart, making a water linkage possible between the Mississippi and the
Great Lakes. Early exploration and settlement of the state was keyed to
the exploration of the Fox-Wisconsin transportation routes. These two
rivers continue to host large portions of the water and industrial
development within Wisconsin, most notably the pulp and paper industry.
Small feeder streams in the upper watersheds of the state are far more
likely to be affected by agricultural use and rural development than by
industry. Rich soils in the southern portion of Wisconsin and proximity to
major mid-western markets have combined to make Wisconsin tne nation's
number one dairy products supplier. Control of agricultural run-off is a
concomitant water quality problem in the small and intermittent streams of
rural Wisconsin.
Inland Lakes
Wisconsin boasts one of the greatest concentrations of lakes in the
world—more than 14,927 at last count. These lakes are largely the result
of glaciation. They formed in shallow depressions of the ground or as
"kettle Lakes" in glacial outwash, marking the melting spot of large,
buried blocks of ice.
While northern Wisconsin's soils are too thin, rocky and wet for most
agricultural crops, the northern Wisconsin's "lake country" did support a
aense coniferous forest. Early in tne state's history, tnis forest was
exploited for the region's burgeoning lumber industry. By the beginning of
tne 20th century, only a cut-over wasteland remained. Conservation and
reforestation efforts in the beginning in tne early 1900's are responsible
for tne resurgence of nortnern Wisconsin as a prime recreation and tourism
area.
The Wisconsin Great Lakes
The Great Lakes system comprises tne largest supply of fresh water in the
world. With Lake Superior on its northern border, and Lake Michigan to the
east, the State of Wisconsin has a special interest in the quality of the
waters, and the effect that quality has on limiting resource use.
Tne Great Lakes were first exploited as transportation linkages. Green
Bay, the largest bay of Lake Michigan, was locus for the earliest trading
posts anu settlements in the state. Explorers landed near the present City
of Green Bay, in 1634, less than twenty years after the initial arrival of
the pilgrims on the eastern seaboard. This early interest was based on the
soon fulfilled hopes of finding a water route from the Lakes to the
Mississippi River.
507
-------
MAP 1
WISCONSIN
508
-------
MAP 2
n....««P i^ ' ^
CIS
509
-------
Later, the Great Lakes provided cneap freight routes to ship grains and
ores from the Upper Midwest to markets and manufacturing centers in
Michigan, Illinois, Ohio and Pennsylvania and New York. Along with
industrial development came significant water quality deterioration.
Quality Control for a Diverse Resource
The diverse pollution problems endemic to Wisconsin's inland lakes, stream
systems and to the Great Lakes require a diverse set of pollution control
measures. The administrative challenge, then, is to structure state law
and agency program development to fit the unique needs of Wisconsin's
resource base. A fortunate blend of national and state legal tradition has
allowed Wisconsin to tailor a uniquely successful approach to managing the
state's water resource problems.
The Public Trust
For many centuries there has existed in some western cultures, a tneory and
practice for the protection and control of navigable waters and of the
seashores. This "public trust" doctrine has identifiable origins in early
Roman law, and was perpetuated into English practice via the Magna Charta
(1215).1 The trust doctrine established a principle of the sovereign's
limited and protective ownership2 of the tidelands and the beds of
navigable waters.3
Similarly, the public rights in water and navigation were recognized in the
provisions of the Ordinance of the United States Congress in 1787, which
said in part:
P. Nanda and William K. Ris, Jr. "The Public Trust Doctrine: A
Viable Approach to International Environmental Protection". Ecology Law
Quarterly 5(ly76):2yl; University of California, Berkley.
2"The beas of all navigable rivers where the tide flows and reflows,
and of all estuaries or arms of the sea, is by all vested in the Crown.
But this ownership of the Crown is for the benefit of the subject, and
cannot be used in any matter so as to derogate from, or interfere with^the
right of navigation, which belongs by law to the subjects of the realm".
Gann v. Free Fishers of Whitstable, 11 Eng. Rep. 1305 (H.L. 1865) as quoted
in Nanda and Ris, "The Public Trust Doctrine ..." page 298.
3See also: Victor J. Yanneconne, et al., Environmental Rights and
Remedies, Vol. 1, (Rochester, New York: the Lawyers Cooperative Publishing
Company, 1972) chapter 2.3, 16.
510
-------
"...tiie navigable waters leading into the Mississippi and St. Lawrence,
and the carrying places Detween the same, shall be common highways and
forever free, as well as to the inhabitants of the said territory as to
the citizens of tne United States and those of any other states that
may be admitted to the confederacy without any tax imposed or duty
thereof."4
Since the earliest of times, Wisconsin's well-being has been linked to it's
waters. The earliest European explorers followed tne rivers, the lakes,
the bays, and the portages which had Deen used for centuries by native
inhabitants. Along these travel corridors people settled and economic
activity developed. River junctions and portages were natural meeting
points and modern settlements grew where these early places of commerce
were situated. Tnese realities of settlement, coupled with tne provisions
of the Northwest Ordinance, were passed along into the organic law of the
Territory of Wisconsin.5 Public rights in navigable waters were finally
locked into the fabric of modern Wisconsin with their adoption into the
State's constitution, upon entry into the union in 1848.6
To understand the pursuit of clean water in 19b3, one must understand these
historical linkages. For Wisconsin, water is the state's most important
legacy and in it's pursuit of pollution abatement, not only is the state
fulfilling the need for the protection of the public health of it's
citizens, out is also carrying out it's responsibilities under wnat has
become known as the public trust doctrine. Through a long history of
judicial decisions unique to Wisconsin, state courts have widened the scope
of the public trust, moving from a more narrow interpretation of the
doctrine as a restriction on physical obstruction, taxation or impost to a
^1 U.S. Stats., bl, article 4. An Ordinance for the Government of
the Territory of the United States North West of the River Ohio, July 13,
1787.
5U.S. Stats., Chapter LIV, Sec. 12, April 20, 1836.
Constitution of the State of Wisconsin, Article IX, Section I 11848).
511
-------
view encompassing tne public's right for recreation, fishing and hunting,
and to the prevention of pollution.?
The public trust legacy in Wisconsin has not made the road to effectively
managed pollution abatement an easy progression. But it is one factor,
that coupled with 20th century concerns for the public health and the
recent increase in public environmental awareness, tnat has helped to
solidify public support for aggressive pollution abatement efforts.
Public Health
Second in importance to the broadened judicial backing provided by the
puolic trust doctrine has been the slow, often eradicate but steady
increase in the public perception of public health.
For example, Earl Murphy in his study cites tne fact tnat while the use of
chemicals for breaking up and disinfecting sewage was known since 1802, it
was not until 1844 in Manchester, England where primary treatment using
cnemical precipitants, filtration, settling and agitation was employed, and
in the United States in the year 1939, only 50% of the population had sewer
connections, and of this 50% only one-half (e.g., 25%) had sewage treatment
of any kind before discharge to water bodies.8
In Wisconsin, understanding was equally slow, consider the following:
?"The wisdom of the policy wm'ch in the organic laws of our state
steadfastly and carefully preserved to the people, the full and free use of
public waters, cannot be questioned. Nor should it be limited or curtailed
by narrow constructions. It should be interpreted in the broad and
beneficial spirit that could rise to it in order that the people may fully
enjoy the intended benefits. Navigable waters are public waters and as
such should endure to the benefit of the public. Tney should be free to
all commerce, for travel, for recreation and also for hunting and
fishing..." Dana Shooting Club v. Hustings, Ibb Wis. 2bl, 271. "We are the
trustee of navigable waters within our borders, for the benefit not only of
the people of our state, but tne benefit oT the people of the whole United
States." In Re Crawford. L&D District, 182 Wisconsin 409. "This case
causes us to reexamine the concept of public benefit in contrast to public
harm and the scope of an owner's right to use of his property We start
with the premise that lakes and rivers in their natural state are
unpolluted and the pollution which now exists is man-made. The State of
Wisconsin under the Trust Doctrine has the duty to eradicate the present
pollution and to prevent future pollution in it's navigable waters." Just
v. Marinette County, 56 Wis. 2nd 7.
SEarl Finbar Murphy, Water Purity. A Study in Legal Control Natural
Resources (Madison: University of Wisconsin Press, 1961) PP 38-39.
512
-------
[1893]: "The result is that in every city in this country are founa the
most superficial and temporary expedients in nearly all sanitary work, and
every year the problems become more intricate and difficult a solution, for
the evils multiply as the population in each city increases."^
LI950]: "I lived here 70 years arid a little sewage never harmed anyone."10
Generally in Wisconsin, early efforts at public health protection and
pollution abatement were ones of forcing municipalities and private
entities to spend monies for tne protection of their citizens ana their
customers. For the most part early statutes succeeded that had an economic
ratner tnan a public healtn or safety basis. Throughout history, cost anu
private economics have retarded competent pollution abatement and
appropriate infrastructure developmentJl However, by the end of the
19th century changes were beginning.
The 19th century in tne United States was a century of local responsibility
with limited communications, and while legislation might be theoretically
sound, it often left issues totally to local administration, and thus,
vulnerable to local manipulation. In this century and especially in
Wisconsin, with the advent of progressive state government, an overall
"statewide" constituency evolved. And with this broaden constituency came
a less parochial view of public health and public protection.
Public Opinion
The third and critical ingredient in the increased statutory and financial
support of pollution abatement has come as a result of a major shift in
public opinion. In the last 15 years public interest and support for
environmental protection has grown substantially. In Wisconsin, tnis
degree of public acceptance has been large. For example, in a 1978
poll12 produced by tne Wisconsin Center for Public Policy, a
yMurphy, Water Purity p. 42; quoting W.O.B. Lingade, Second Secretary
of the Wisconsin State Board of Health in 1893.
lOMurphy, Water Purity, p. 43; Quoting the MiiwauKee Journal of
10/29/50.
11 IBID; Especially chapter 2. See also: The Natural Resources of
Wisconsin, An Inventory of the Natural Resources Committee of State
Agencies (Madison, 1956).
Wisconsin Center for Public Policy, "The People on Wisconsin"
(Madison, copyrighted 1978).
513
-------
carefully selected cross section of adult Wisconsin residents indicated
that environmental problems were second!3 only to taxes as the state's
"biggest problem".
In a 1981 survey, it was reported that "tne Wisconsin adult population is
very interested in nature and the environment. Eighty-one percent of all
persons interviewed were very interested in at least one nature topic.
Eighty-seven percent were very interested in at least one environmental
quality/management topics".14
Recently, these Wisconsin findings are being paralleled in national
surveys. In a 1982 survey conducted by the Lou Harris organization, 74% of
those polled felt curbing water pollution was a very important factor in
improving the quality of American life. Sixty percent wanted the Federal
Clean Water Act made stricter and 70% indicated a willingness to pay $100
or more in new taxes and costs to achieve clean water.15
In an April 1983 survey for the New York Times/CBS News, b8% of those
surveyed agreed with the following:
"Protecting the environment is so important that requirements and
standards cannot be too high and continuing environmental improvement
must be made regardless of cost".16
The Development of Environmental Management Structures and Institutions
Environmental management in Wisconsin has emerged from several historical
roots. Notable, because of both their diversity and their commonality.
13Also, a similar finding is found in: "Public Survey, July 1978,
WDNR Office of Policy and Analysis" conducted by the University of
Wisconsin Survey Research Lab.See also, a 1976 survey, Wisconsin Center
for Public Policy Studies, "A Survey of the Attitudes of Wisconsin Citizens
Towards Public Policy and Their Media. August 197b, Hart Research
Associates, Inc."
^Environmental Resources Unit, University of Wisconsin,
Environmental Education Needs and Interest of Wisconsin Adults (Madison,
1961) p.61.
15Lou Harris and Associates, Inc., "A Survey of American Attiiuae
Towards Water Pollution", prepared for the Natural Resources Council of
America, December 1982.
New York Times, April 17, 1983.
514
-------
Conservation
Many current state environmental activities are derived from what can De
described as traditional resource conservation functions. In 1867,
Wisconsin's first forestry commission was created and a Board of Fisn
Commissioners was established in 1874. Fish and game wardens were
appointed in 1885 and 1887, ana a state Department of Forestry was created
in 1897. A State Park Board began in 1907.
In 1915, a full time, three person Conservation Commission was estaolisned
which pulled together into one administrative organization, fisheries,
forestry, parks, and fish and game management and enforcement. From 1915
until 1967 through various legislative structurings, the "Conservation
Department" carried out its activities.17
Public Health18
In 187b, out of tne growing health problems of the era, there was formed
the State Board of Health. As apart of its activities, it began to test
the waters of the state for pollution and to recommend methods of water
purification and sewage treatment. After 29 years, in 1905, tne Board was
given official powers to require water and sewer systems in cities and
villages. In 1911, legislation was passed, assigning power to regulate
sewerage facilities and to enforce the laws witn regard to tne protection
of water supplies. Sanitary engineering as an activity of the Board was
funded in 1919 as part of the state's first water pollution act.19
Water Regulation
In 1874, Wisconsin created the Board of Railroad Commissioners, later
titled the Public Service Commission (the chief state public utility
regulation organization). In 1915, this organization was assigned
responsibility for the administration of Wisconsin's laws regulating lakes
and streams.20 Prior to this time, the Legislature, by statute, directly
managed the waters of the state.
17John Bubolz, "A History of Wisconsin Water Pollution Central
Agencies and Factors to Consider in Their Reorganization"; River Basin
Planning Seminar Unpublished Paper, May 1966.
Wisconsin Legislative Reference Bureau, 1981-1982 Blue Book, (Madison,
Dept. of Administration) 1981, p. 468.
18Murphy Water Purity, Cn. 4.
19Wis. Stats. 1919, ch. 447.
20Regulatory jurisdiction over lake levels, rates of stream flow,
dams, dock lines and alterations of navigable waters.
515
-------
Over tiie years, (the Conservation Commission because of its role as
protector of the resource, and the State Board of Health because of it's
concern tor disease prevention), ooth agencies became involved in water
pollution prevention. And each agency came to its perceived role from a
di fferent perspecti ve.21
Coordination
In 1927, the Committee on Water Pollution22 was established to try and
coordinate the activities of the several agencies vis a vis water
pollution. The Committee was composed of representatives of the State
Board of Healtn, the Conservation Commission and the Railroad Commission.
Members of the Committee were presumed to represent their agency's point of
view in the establishment of a unified state water pollution policy. The
Committee was also assigned certain powers2-* in it's own right, even though
it used the State Board of Health, Bureau of Sanitary Engineering as its
administrative staff.24
In addition to these principal historical actors in water management,
others, notably the Office of the Attorney General, the Natural Resources
Committee of State Agencies, the State Soil and Water Conservation
Committee, the State Laboratory of Hygiene and the State Geologist have
also played roles.2^
21Murphy, Water Purity p. 8b; The health agency wanted to stuay
causes, and make inquiries into trie ways of controlling pollution and
economic conditions. The Conservation Commission uelievea that pollution
was illegal and that the dischargers should be made to stop.
22Wis. Stats., 1927 en. 264.
23These included administration ana enforcement of all laws relating
to pollution of surface waters; the authority to study and investigate
surface water pollution; and tne authority to discover economical and
practical means of pollution control. In later years, the Committee would
also be assigned the ability direct experimental facilities, to treat
aquatic nuisances and to enter into interstate agreements.
24Sources on the Committee include: Donald h. Carmichael, "Forty
Years of Water Pollution Control in Wisconsin: A Case Study"; 67 Wisconsin
Law Review 350 pp. 353-357.
Bubolz, "A History of Wisconsin Water Pollution Control".
Murphy, Water Purity, p. 85.
2i)Harold H. Ellis, et al. Water Use Law and Administration in
Wisconsin, (Madison: Univ. of Wisconsin Extension, 1970), page 19o.
516
-------
Tne Department of Resource Development
In August, 19t>62t>, a new water resources act abolished the Committee on
Water Pollution ana transferred it's functions into a newly created
Division of Water Resources, the Department of Resource Development. This
act also transferred most of the water functions of the State Board of
Healtli to the same division. One year Jater, water regulatory powers of
the old Railroad Commission, (in 1967 called the Public Service Commission)
were consolidated witnin the Department of Resource Development.
The Department of Natural Resources (WDNR)
In 1967, as a part of a total functional reorganization of the executive
branch of Wisconsin state government, the consolidation of water management
was completed with the creation of the Department of Natural Resources.
Tnis new Department finally merged the water activities of the Department
of Resource Development (formerly State Board of Health, Public Service
Commission) ana the Conservation Department into one administrative
agency2? tnus, tieing together closely related traditional conservation
activities, historical state water regulations functions with newly
emerging, environmental regulation and public health protection. The
Department of Natural Resources is currently the ayency charged with
management of Wisconsin's environment. The Department is responsible for
implementing the laws that protect and improve Wisconsin's air, land,
water, wildlife, fish and forests. The WDNR is also assigned
responsibility under numerous federal laws that delegate management ana
enforcement tasks to the state.
WDNR: Organization and Structure
In 1983 the Department of Natural Resources is governed t>y a seven member
board of private citizens appointed by the Governor, with the advise and
consent of tne State Senate. This policy board appoints it's Secretary who
serves as the Chief Executive Officer of the Department.
Major staff organizational units of the Department include four aivisions:
Environmental Standards, Resource Management, Enforcement and Management
Services. Six field districts provide line operational capacity for the
numerous program functions. In addition to the specified staff functions
noted above, the Office of the Secretary has specialized units in Legal
Services, Intergovernmental Programs and Management and Budget.28
26Wis. Stats. 1966, ch 614.
2?Wis. Stats. 1967, ch. 75.
28See Attachment A. and MAP 3
517
-------
DNR FIELD DISTRICTS and AREAS
MAP 3
— DISTRICT BOUNDARIES
•••• AREA BOUNDARIES
D DISTRICT OFFICES
• AREA OFFICES
! NORTHWEST
•SXlfl
SOUTHEAST
MII«nukM
518
-------
WDNR: 1/ileiter Functions:
Within tne current Department of Natural Resources several units are
responsible for water-related activities. Functions, historically
associated with water quantity and navigation are housed within the
Division of Enforcement's Bureau of Water Regulation and Zoning. This
Bureau also has responsibility under current law relative to floodplain and
shoreland zoning.
Traditional conservation functions (including fisneriesj are operated
within the Resource Management Division.
Grants administration activities for wastewater facilities construction are
housed in the Bureau of Water Grants, Office of Intergovernmental
Programs. Technical engineering support for construction projects is
supplied by the Bureau of Waste Water Management, Division of Environmental
Standards.
The remaining elements of water activities are housed within the Division
of Environmental Standards, with its Bureau of Wastewater Management,
Bureau of Water Resources Management and Office of Operations and
Maintenance, Bureau of Water Supply (drinking water) and Bureau of Solid
Waste Management (groundwater, etc.).^9
In a more program oriented approach, water activities to tne Department can
be defined in terms of point source, nonpoint, stream water quality, lake
water quality, and groundwater management. Attached are tables and figures
that more thoroughly demonstrate WDNR cross organization water
activities.30
Wisconsin Water Quality Standards3^
Wisconsin's water quality management program supervised by the Department
of Natural Resources is designed to improve and protect the state's
waters. This task involves many activities from monitoring wastewater
treatment plants to seeking to curb farm runoff. While Wisconsin has had
water quality standards for many decades, earlier requirements were based
on protection of public health or navigability. Today, water
characteristics or indicators which are more directly related to pollution
are monitored, analyzed and governed.
29See Attachment B.
3°See Tables 1, 2, 3, 4, 5 and Figures 1 and 2. Source: Wisconsin
Dept. of Natural Resources "Development Document for a Post - 1983 Water
Quality Management Strategy" - (Madison: May 1982).
31 Wisconsin Department of Natural Resources, Water Quality
Management: Putting the Pieces Together (Madison, 1980)
519
-------
Grant
Disbursements Staff
i«\n
125-
-
OF DOLLARS
8
MILLIONS
^4
o
-3
-2
'
-1
Figure 1. Water Quality Management
expenditures by pollution source 1982.
520
-------
Grant
Disbursements Staff
70 -
•
60 •
50 •
5 40-
_j
^
0
u.
o
MILLIONS
8
2O
IO
n
STAFF & GRANTS
EPA
grants
State
giants
EPA
grants
State
grants
State
grants
LEGEND
STREAKS LAKES GROUND
WATER
EPA & STATE
n
STAFF ONLY
WOE
WOP
MWW
ENF
NPS
BWG
PftF
IWW
FM
WRZ
ADM
woe ^-WOP
.^^u nn»
nw
ILR
FM «"
wnz
ws
. , "'" • '", ENF
AW MM
0 A W O> •**
MILLIONS OF DOLLARS
- 1
STREAMS LAKES GROUND
WATER
Figure 2. Water Quality Management
expenditures by resource base 1982.
521
-------
Abbreviations Used 1n Figures 1 and 2
ADM - Administration, training, professional development, etc.
BWG - Bureau of Water Grants
ENF - Environmental Inforcement
FM - Bureau of fish Management
1LR - Inland lake Renewal
IWW • Industrial Wastewater Section
MWW • Municipal Wastewater Section
NFS - Nonpolnt Source Section
P&F - fretreatment and Fees Section
SW » Bureau of Solid Waste Management
WQE - Water Quality Evaluation Section
WQP - Water Quality Planning Section
WRZ - Bureau of Water Regulation and Zoning
WS - Bureau of Water Supply
522
-------
TABLE 1. CURRENT LEVEL OF EFFORT FOR POINT SOURCE MANAGEMENT (FY 1982)
Unit or Program
Staffing
Grant $ Disbursements
Staff Years $ Expenditure
Water Quality Evaluation
Water Quality Planning
Municipal Wastewater
Industrial Wastewater
Water Grants
Pretreatment and Fees
Administration
Enforcement
F1sh Management
EPA Municipal Grants
State Municipal Grants
22.9
22.4
57.8
21.5
30.1
11.4
31.4
5.8
5.9
€18,300
605.610
1.560,870
580,500
813.240
307.800
848.880
155,790
100.300
State Septic System Grants
Subtotal s
20$. 2
$5.591.290
46.000.000
75.500.000
2,000,000
$123,500.000
TOTAL EXPENDITURES 4129,091,290
(staff and grant
disbursements)
523
-------
TABLE 2. CURRENT LEVEL OF EFFORT FOR NONPOINT SOURCE MANAGEMENT (FY 1982)
Unit or Program
Staffing
Grant $ Disbursements
Staff Years $ Expenditure
Water Quality Evaluation
Water Quality Planning
Nonpoint Source
Inland Lake Renewal
Administration
Subtotals
13.6
9.6
11.1
6.5
9.7
50.5
366,930
260,280
299.430
174.150
261,900
$1.362,690
2.811,900
1,150,000
$3,961.000
TOTAL EXPENDITURES
(Staff and Grant
disbursements)
$5,324,590
524
-------
TABLE 3. CURRENT LEVEL OF EFFORT FOR STREAM WATER QUALITY MANAGEMENT (FY 1982)
Unit or Program
Staffing
Grant $ Disbursements
Staff Years $ Expenditure
Water Quality Evaluation
Hater Quality f Tanning
Municipal Vlastewater
Industrial Uastewater
Konpolnt Source
Water Grants
Pretreatment and Fees
Enforcement
fish Management
Water Reg and Zoning
Administration
EPA Municipal Grants
State Municipal Grants
Subtotal s
25.2
25.7
48.8
16.5
9.2
24.1
*.l
3.4
15.8
27.0
31.3
235.1
$ 679.590
£93.900
1.316,250
445.770
249.210
651 .240
21 9,240
90.990
268.600
729,000
845,100
46,118.890
2.342.500
19.380.000
46,035,468
$67.757,967
TOTAL EXPENDITURES $73.946.857
(staff and grant
disbursements)
525
-------
TABLE 4. CURRENT LEVEL OF EFFORT FOR LAKE WATER QUALITY MANAGEMENT (FY 1982)
Unit or Program
Staffing
Staff Years
Water Quality Evaluation 11.0
Water Quality Planning 5.7
Municipal Wastewater 4.2
Industrial Wastewater 1.0
Nonpoint Source
Water Grants
Pretreatment and Fees
Inland Lake Renewal
F1sh Management
Water Reg and Zoning
Administration
EPA Municipal Grants
State Municipal Grants
Subtotals
(3.5)
(4.0)
(1.0)
2.0
6.
1.
6.
21.
23.
7.
89.
0
0
5
4
0
4
2
<5.
(1.
(4.
(5.
(2.
(26.
0)
0)
7)
0)
0)
2)
$ Expenditure
296.190
153,090
112,320
27,000
53
162
27
174
363
621
199
,190
,000
.000
,150
,800
,000
.800
$2,189.540
Grant $ Disbursements
{94.500)
(108,000)
(27.000)
(135,
(27.
(79,
(135,
(54,
000)
000)
900)
000)
000)
(660,400)
468,500
2,300,000
25,620,000 (25,620.000)
24,915,000 (24,915.000)
$53,303,500(50,535.000)
TOTAL EXPENDITURES $55,493,040 (51,195,400)
(staff and grant
disbursements)
* lumbers in .parenthesis are staff years, staff expenditures. *nd grants for
Great Lakes management activities only,.
526
-------
TABLE 5. CURRENT LEVEL OF EFFORT FOR GROUNDWATER QUALITY MANAGEMENT (Fy 1982)
Unit or Program
Staffing Grant S Disbursement*:
Staff Years $ Expenditure
Water Quality Planning
Municipal Wastewater
Industrial Wastewater
Pretreatroent and Fees
Solid Waste
Water Supply
Enforcement
Administration
State Municipal Grants*
State Septic System Grants
Solid Waste Planning Grants
Subtotals
TOTAL EXPENDITURES
(staff and grant
disbursements)
1.1
4.4
4.0
2.3
47.5
7.0
2.0
2.5
70.8
30,780
118,260
107.730
61 ,560
1 ,282,500
189,000
54,000
67,500
$1,911,330
$8,960,862
4.549,532
2,000,000
500,000
$7.049,532
* This entry is for land disposal system grants.
527
-------
Following the lead of the Clean Water Act of 1972:, the state's policy has
been a goal of fishable, swimmable waters, wherever possible. Deciding
where it is possiole to achieve this goal is a challenge involving the
examination of natural conditions of a particular waterway, absent
man-induced pollutants.
For those waterways deemed to be able to achieve flshaole and swimmable and
for other uses, standards are established, which place limits on water
quality indicators for each class and use of water. Table 6 shows current
basic standards.
These standards and classifications give us the definition of clean for
each waterway and thus we have assigned for each stream a minimum quality
definition. Once these are assigned then actions to identify ana to
appropriately correct sources of pollution can be begun.
Limiting what and how municipalities and industries discharge to the
state's waters, is the soul of Wisconsin's water quality management
program. Determining to what degree a discharger must treat its wastewater
is a function of two things: (1) Minimum standards of the Federal Clean
Water Act and State Statute and (2) The water quality standards appropriate
for each stream. The Federal Clean Water Act mandates basic treatment
requirements for industries and municipalities. Wisconsin has also
established for municipalities effluent limits based upon the
classification of the receiving waters (see Table 7).
For waters where basic treatment levels are not sufficient to meet water
quality standards, special attention is given to each with a process
wasteload allocation. In such an analysis the total assimilative pollutant
level for stream is determined and dischargers are trien allocated a
prorated discharge amount. The most complicated allocation of this nature
is found on the Fox and the Wisconsin rivers.
Operating under federal delegation and state law, these standards of
discharge are managed through the Wisconsin Pollution Discharge Elimination
System (WPDES). Under this permit system, all discharges must have a
permit with a stated requirements prior to discharge. All must comply witn
these levels. Under Wisconsin and federal law, failure to comply is
subject to severe penalty including civil and criminal actions. The impact
of this management system can best be seen by a profile of water quality in
Wisconsin, historic and current.
Water Quality in Wisconsin: Historical
To someone arriving on the scene today it is difficult to fully describe
the degree of water degradation that Wisconsin suffered as a result or its
long struggle to organize and manage its resources. In its first 135 years
of statehood, Wisconsin has destroyed its waters and forests and then
reclaimed them. And as the institutional organization of management
agencies finally became coordinated, about at the same point in time, water
quality management began to have notable impact on the waters of the state.
528
-------
WISCONSIN'S WATER QUALITY STANDARDS
TABLE 6
All waters of the state must not have objec-
tionable shore or bottom deposits, floating or
submerged debris, oil, unsightly color, odor,
or toxic chemicals.
In addition there are these more precise
standards for varying uses and classifications
ol waterways.
t
'/
ft
!f
// it I
//
V *>
//
/
•* ^
More _ j
Sl'ingenl
1
1
1
L.
aio
»*
Waterways
•iso capable
ol supporting
trout renr
also capable
o< supponing
trout :
Waterways
•iso used ts
Public wster
supply
iftaie'»ay&
capable o'
balanced
a no
recreation
—
i-^
1
•
L.
f
-•
L.
Continuous
non-continuous
streams
Conimuous
non-continuous
suaams
1 Continuous
Slieanis
L»kfi I
nonages
non- continuous
streams
Lakes t
- e 6-9
JtO
- • 69
JO
. S 69
"so"
- S 69
^0
- •> 69
SO
. 5 *»
SO
0
t
~W
3
»«
i,
69
3
69
v 6
00?
.02
OJ
too
»so
MO
0'*
* Ci
Lets
Stringem
••
L.
Iniermcdxie
Not ccpabie
txlanoO
•quit ic litf
Mcrgintl
Not c*p»Nt
ol (upponing
•ny lith HI*
^«
i
r
i
.j
non-contmuout
Stl«Tlt
DJltuMd
surface.
diluent
channels.
wellandt.
continuous.
non-continuous
stnwms
"755" -7-
6-9 -
* Based on site specific analysis
** Criteria providing for the protection and propagation of fish, shellfish, and wildlife and for recreation In
and on the waters.
529
-------
Table 7
MUNICIPAL WASTEWATER TREATMENT EFFLUENT STANDARDS
These are the established effluent limits for discharges to
Wisconsin waterways. Limits on other pollutants may also be
set If doing so Is necessary for ensuring that waters meet
water quality standards.
/
i<
/
//
*
*
Base Standards
For discharges
to waterways
that must meet
for these cate
Cones ol water
quality stand
eras (see
Water Quality
Standards chart)
f
1
|
L.
Fishabie
and
Swimmabie
Intermediate
1.
Marginal
•
h
. ..
Continuous.
noncontmuous
streams
_
noncontmuous
Diffused surface.
effluent channels.
wetlands.
streams
t V ° to
/////
<6 b
-------
While water can truly be described as Wisconsin's most precious resource,
it has been regularly exploited with utter disregard for the impact on
water quality. Tnis degradation has been as a result of four primary
sources: point source discharges from industries and municipalities; the
cutting over and transportation of timber; poor soil protection and animal
waste practices in agricultural communities; and the impacts of growing
urbanization on natural water courses and drainage.
The early history of Wisconsin is marked with events of public outrage of
water conditions results leading to new laws, agencies and procedures to
eradicate damaging practice, but as likely as not, tne public outcries were
focused as easily manifested symbols of problems rather than fundamental
causes. Before the 1920's data compatible with the current diagnostic
measurements were rare. Early public concerns on water pollution evolved
around odor, unsitelyness, disease transmission, navigation barriers, and
trie survival of species of popular sport fishes.
As a method of introduction to current water quality in Wisconsin and as a
frame or reference to the cnanges tnat have occurred in tne last few years,
early data is most striking. For simplicity sake, the state's two most
utilized rivers (the Fox and Wisconsin River) provide ample documentation
of change.
Fox River 192632
"Tne Lower Fox River in past years has been used rather extensively as
a source of recreation. Boating, swimming, and fishing constitute the
main pleasures the river affords, but largely as a result of increased
stream pollution of an objectionable character, the recreational value
has been lost. At times ... the river is often unsightly and
ill-smelling the sewage pollution constitutes a continual menace of
water born disease....33
32The Fox River (Wisconsin) rises near Portage, Wisconsin, passes
through several lakes into Lake Winnebago, then flows northeasterly to the
Green Bay of Lake Michigan. Tne Lower Fox (from Neenah-Menasha to Green
Bay) constitutes one of the principal industrial centers in the state with
14 dams in the 31 miles from Lake Winnebago to Green Bay. In 1926, 34 pulp
and paper mills producing 1,034 tons daily were utilizing the stream for
discharge. In addition, six small cities with population of approximately
90,000 persons were also discharging to the river. In 1982, in this same
reach of stream approximately 5,700 tons of daily production was
recorded. Figure 4 shows major discharges to the Lower Fox.
33Wisconsin State Board of Health Stream Pollution in Wisconsin, a
Joint Report of the Conservation Commission and State Board of Health of
Wisconsin concerning activities in the control of stream pollution from
July 1, 1925 to December 31. 1926, Madison 1927.
531
-------
"0
H-
-------
Figure 4
LOWER FOX RIVER DISCHARGERS
LAKE WINNEBAGO TO DEPERE
Wriflhtstown STP
Foremost-Appleton Division
Riverside Paper Co
APPLETON
Butte des Morts Utility Di
Menatha S. D.
East and West
Kimberly Clark.
Lake view Division1
George Whiting Paper
Bergstrom Pa
NEENAI
Heart of the Valley STP
Hammermill-Thilmany Djyj
Appleton Paper Combined Locks Division
Mid Tec Paper Co
eton STP
ENASHA1
Consolidated Paper-Apple ton
Wia Tltau*
ah-Menasha STP
Kimberlv Dark,
Neenah and Badger
Globe Divisions
LAKE WINNEBAGO
10 miln
533
-------
Lower Fox River, July 8-9, 192634
Location
Lake Winnebago Outlet
Appleton (above dam)
Rapids Croche (above dam)
Little Rapids (above dam)
DePere (above dam)
Green Bay (Main Street)
July
Temp.
26
27
29
29
28
8
DO
(PPM)
5.7
3.7
2.1
2.4
2.0
July
Temp.
25
27
25
24
25
25
y
DO
(PPM)
6.4
5.4
3.o
2.3
2.0
1.9
As a result of these preliminary investigations more detailed studies were
carried out. Figure 3 show data for the summer of 1926 in graphic form.
Twenty-nine years later in 1955 comparable location data shows worse
conditions below Lake Winnebago than previously recoraea.
LOWER FOX RIVER, 195535
June
Location
Lake Winnebago Outlet
(Neenah channel )
Menasha Channel
(Neenah channel )
Appleton (above dam)
DePere (above dam)
Green Bay
(C°)'
ly.2
20.5
21.9
22.0
20.5
DO
(PPM)
8.68
10.74
6.9
1.21
.64
July
Temp.
(C°)
26.5
27.1
30.0
28.2
2o.3
DO
(PPM)
10.81
11.41
6.98
1.47
.52
Ten years later (1965) data for Green Bay showed little change, but by 1967-68
change was beginning.
34State Board of Health, Stream Pollution, p. 14<+. Location shown are
edited to relate closely with later data.
•^committee on Water Pollution, tne Sulphite Pulp Manufacturers'
Research League; Evaluation of Stream Loading and Purification Capacity;
Cooperative State-Industries Studies in the Lower Fox River in 1956, (Madison,
1957).
534
-------
LOWER FOX RIVER AT GREEN BAY 1965-6836
Year
Survey Dates
Early
Temp. DO
C" (PPM)
Mid
Temp . DO
C" (PPM)
Later
Temp . DO
C" (PPM)
1965 (to/7, 6/29 8/24) 21 6.0 24 3.6 23 .9
1966 (5/31, 6/29, 8/31) 17.5 4.3 26.5 1.7 23 .1
1967 (6/1, 6/*3, 7/26) 18.5 4.6 21 5.2 bl 7.2
1968 (6/25, 7/16, 8/20) 22 2.7 27 5.2 25 4.7
Data for 1974-1981 indicates still further improvement on the Lower Fox.
These changing conditions are especially notable because during the 50 year
period profiled a five fold increase in paper production occurred along this
stretch of the river. In addition, as environmental management continued,
between 1^73-81 8005 loadings have dropped from 208,296 pounus a day to
39,947 pounds a day along the stream.
Location
THE LOWER FOX RIVER SUMMER 197437
June
Temp. DO
July
Temp. DO
August
Temp. DO
Lake Winnebago Outlet 18
Appleton
DePere
Green Bay 20
(PPM) (IT)(PPM) fir)(PPM)
8.5
7.6
7.1
7.9
22
24
6.6
7.2
'7.5
6.7
24
9.b
6.4
7.7
8.8
3&Wisconsin Department of Natural Resources, Surface Water Quality
Monitoring Data, 1965-68, (Madison).
37Data is for June 24, July 25, August 21, 1974. Appleton and DePere
data is estimated from continuous data plots: Department of Natural
Resources, State of Wisconsin Surface Water Quality Monitoring Data,
1973-1976 (Madison); Automatic Water Quality Monitoring ot the Fox and
Wisconsin Rivers in 1972-1981 (Madison 1982).
535
-------
LOWER FOX RIVER SUMMER 198138
June July August
Year Temp. DO Temp. DO Temp. DO
(CUV (PPM) (Cu) (PPM) (Cu) TPPM)
Lake Winnebago Outlet 20.9 6.9 23.1 7.9 22.2 7.9
Appleton 21 6.0 22.9 4.5 22 6.7
Rapid Croche (Plot Est) - 6.8 - 7.b - 7.8
DePere 22 6.8 23 10.2 24 8.5
Green Bay (Plot Est) - 7.0 - 5.2 - b.2
The Upper Wisconsin 1926 to 198139
The Upper Wisconsin River from Rhinelander to Petenwell flowaye is one of the
hardest working rivers in the world with 29 major industrial and municipal
dischargers (Figure 5). In a July Iy26 stream survey results showed
conditions ranging from good D.O. levels at Rhinelander (above the first
discnarger) to 0 D.O. conditions below Wausau and a repeated condition of .5
DO below Nekoosa.
In 1955, studies indicated little change in the conditions of 30 years earlier
with 0 D.O. situations immediately oelow Rothschild and again in Nekoosa. A
summary of Wisconsin River sampling data is shown in TaDle 8 for the years
19^6 to 19bl which like Fox River data reflects a major shift in river
conditions, beginning in tne late lyoO's.
In addition to the regular monitoring data available for the Upper Wisconsin,
beginning in 1973 and continuing each year until 1980, a series of synoptic
38(a) IBID; WDNR Automatic Water Quality Monitoring, (b) Wisconsin
Department of Natural Resources; State Surface Water Quality Monitoring
Data, 1981 (Madison, Iy83)
Wisconsin River rises at Lac Vieux Desert, and flows south and
westward to the Mississippi at Prairie du Chien, a distance of almost 400
miles. The part of the Wisconsin that is most impacted by pollution occurs
between Rhinelander and Nekoosa, a distance of 150 miles. During its
passage of this reach, the river crosses 20 dams and receives the
discharges of many industrial concerns and municipalities. In terms of the
pulp and paper industry, 18 discharged to the river in I92b.
536
-------
St. Regis Paper Co.—
RhinelanderSTP-
Tomahawk Power & Pulp
Tomahawk STP
Owens of Illinois
RHINELANOER
Merrill STP -
Ward Paper Co.
TOMAHAWK
Figure 5
APPROXIMATE LOCATION OF
MUNICIPAL AND MAJOR INDUSTRIAL
WASTE DISCHARGES
TO THE UPPER WISCONSIN RIVER
MERRILL
BrokawSTP-
Wausau Paper
Wausau STP
Weyerhauser
American Can.—Rothschild-
Rothschild STP
Mosinee STP
Mosinee Paper
Big EauPleine
Consolidated-Stevens Point
Stevens Point STP-
Consolidated-Wis. R."
NEPCO-Whiting-Plover"
Whiting STP
BROKAW
WAUSAU
Lake Wausau
MOSINEE
DuBay
Biron STP
WISCONSIN RAPIDS
Petenwell
STEVENS POINT
PLOVER
—Consolidated—Biron
—Consolidated—Kraft
-Consolidated—Wis. Rapids
~Wis. Rapids STP
•NEPCO-Port Edwards
Port Edwards STP
'NEPCO-Nekoosa
'Nekoosa STP
} common
outfall
. common
outfall
10
miUs
Water Quality Limited Segments on
the Wisconsin River
Castle Rock
537
-------
T/IBLE e
Wisconsin River - Dissolved Oxygen (ppm)
1926-1981
Loca'1
f Ions
Year/Mo nth/Day Khlnelander Hat Rapids Merrl II Wausau Ureen Bay BTron Nekoosa Petenxell
C* DO C' DO C' DO C° DO C° DO C" DO C* DO C° DO
1926- July (15-22) 20 7.8 22 7.2 23
1-0 26 1.6 26 .1 26
2.5
1955-August (10-18) 23.3 6.6 23.8 5.3 26.3 .5 282 .57
1965-June (17, 8) 2|.
July (13, 27) 24
August (8, 24) 23
1966-June (8, 13) 24
Oi July "2) 27
u> August (28, 22) 24
00
1967- June (8, 13) 19
July (12) 22
August (18, 22) 21
1968-June (18, 25) 19.
July (29, 23) 22.
August (20, 27) 24.
1974-June (6, 24) 19 8.2 19 4.3 19
July (25) 23 6.7 23 3.1 2?
August (23) 22 7.0 23 4.5 22
1981-June (17,23, 18 7.8 17 6,3 16 8.8 16
24,25)
July (16,22 20.5 7.8 21 5.3 19.5 6.7 20
12,13)
August (3,13,2) 20.5 8.0 22 6.5 21 8.3 21
5 4.3 |B
2.4 21
2.1 23
2-6 |8
I.I 2 24
1.7 22
5.7 ,9
3.7 21
5.8 21
5 6.2 21
5 5.4 24
5 4.6 22
5.5 3.8 6.2
5.3 (Plot 2.6 (Plot 4.8 (Plot
(8/23) 8.2 Est. ) 3.4 Est.) 5.6 Est. )
8.5 18 8.0 17 8.5 20 8.4 20
7.4 22 8.1 22 8.4 23 8.9 25
8.3 23.5 8.8 22
7.8
5.9
8.4
6- 1
6.4
5.4
6.8
5.4
6.0
7. t
6. 7
6.6
6.4
3.0
5.2
7.2
12.5
5.5
2798P
-------
surveys^ were carried out on the entire upper river from kninelander (mile
post 340.4)to Petenwell Dam(mile post 171.9).
Tnese surveys provide some of the most detailed information ever collected on
the river. And while it is not practical in this paper to detail all the
dissolved oxygen data, a few unsophisticated highlights are symptomatic of the
changes occurring in the River.
WISCONSIN RIVER SURVEYS 197,5-80
DISSOLVED OXYGEN VALUES
Total Values Values Lowest Highest
Survey Dates Samples Below 3(ppm) Above 7(ppm) Value(ppm) Value(pprn)
% %
July 9-18, 1973 625 128 20.5% 59 9.4% .2 8.6
Aug 6-17, 1975 338 91 26.9% 19 3.3% .0 9.6
June 27-29, 1978 578 7 1.2 115 20% 1.7 9.0
July 15-17
Aug 18-19, 1980 332 3 1.1% 199 59.9% 1.8 11.0
As was the case with the Fox River during this period, paper and pulp
production increased to 6U51.4 average tons daily ana BODt, discharged
dropped. (From 462,817 daily average Ibs in 1973 to 28,314 daily average Ibs
in 1981.) Thus with water management has come increased and improved water
quality and economic expansion.
Water Quality in Wisconsin: Current
A good profile of current water quality is gained by reviewing ambient water
quality data, contained in the National Water Quality Information System
40Tne general procedure for synoptic surveys was to have one or more
river crews begin at Rhinelander and over the course of several days
progress to Petenwell Dam taking field measurements and obtaining water
quality samples. Field measurements were made every .1 to one mile
depending in river characteristics. For example, dissolved oxygen
measurements were typically made above dams and below dams (1/10 mile or
less) while stretches of river with consistent hydraulic cnaracteristies
were measured only every mile. Readings were also taken at a variety of
depths and at several points across tne River. Source: Wisconsin
Department of Natural Resources, "Water Quality Modeling of the Upper
Wisconsin River for Wasteload Allocation Development (Water Quality Data),
Madison, 1982.
539
-------
(Storet).4! General indicators of water quality sampled in the ambient
monitoring network -- nutrients, biochemical oxygen demand, and suspended
solids -- are presented in the following comparison. Tne mean of the data
collected for each parameter was determined for two two-year periods, water
years 1980-81 and calendar years 1977-78. Selection of these two distinct
periods of time provides a "gap" and allows comparison of ambient quality over
time.
Tnis profiles again in parameters beyond dissolved oxygen the major changes
occurring in Wisconsin streams^
Organic nitrogen
One uf tne limiting factors of plant growth is nitrogen. Organic nitrogen is
the form that is tied up in organic compounds by plants and animals. It is
also significant in that it eventually decomposes into ammonia wnich can oe
toxic to aquatic life. Monthly ambient monitoring indicates that 27 percent
of the stations show a decrease in organic nitrogen levels over the past three
years. The greatest reductions in tne parameter occur in the Lake Michigan
tributaries. Some monitoring stations, sucn as Oconto and the Upper Fox River
at Berlin and Neenan-Menasha, indicate a drop of 25-50 percent in organic
nitrogen. Other stations show a lesser drop in organic nitrogen.
Neillsville, on the Black River, shows a major reduction in organic nitrogen
levels. There is no conclusive reason for the reduction, although owner 200
manure storage facilities have been established in the area since 1977. In
most other parts of the state, organic nitrogen levels in rivers remain fairly
constant. The majority of the state monitoring stations indicate values of 1
milligram per liter (mg/1) or less. The proolem area of the lower Rock River
is still apparent; nonpoint source loading compounded by municipal discharge
may be tne primary reasons.
41 This federal information STO-RAGE and RET-RIEVAL system is used for
the compilation, of data from fixed station monitoring sites and provides a
"snap shot" look at tne chemical condition of state's waters over time.
Wisconsin first established a network of monthly water quality monitoring
stations in 1961. A new revised monitoring network, was establisned in
1977 (Table 9). Accumulated stream flow records were a major site
selection criterion. Stations selected were located in water use areas or
particular land use areas representing a broad spectrum of sites, from
paired stations around problem areas to clean water streams. Stations on
the Fox and Wisconsin Rivers provides a broad, inclusive data base.
data presented here is from: Wisconsin Department of Natural
Resources - Wisconsin Water Quality: 1982 Report to Congress (Madison,
1982).
540
-------
WISCONSIN'S MONTHLY MONITORING PROGRAM
TABLE 9
Station In
Figure Station Location
I. Black River (Galesvllle)
2. Black River (Nail Isvl He)
3. Bols Brule River (Brule)
4. Chlppewa River (Eau Claire)
5. Chlppewa River (tblcombe)
6. Flambeau River (Park Falls)
7. Flambeau River (Plxley)
8. Fox (Illinois) River (Waukesha)
9. *Fox River (Appleton)
10. Fox River (Berlin)
II . *Fox River (Oe Pere)
12. *Fox River (Neenah-Menasha)
13. Kewaunee River (Kewaunee)
U. Klckapoo River (Steuben)
15. Klnnlcklnnlc River (Milwaukee)
16. Lake Superior (Ashland)
17. Mississippi River (Alma)
IB. Mississippi River (Hastings)
19. Mississippi River (Lake Pepln)
20. Mississippi River (Lynxvllle)
21. Mississippi River (Red Wing)
22. Montreal River (Saxon)
23. NemadJ I River (Superior)
24. Namekagon River (Riverside)
25. Oconto River (Glllett)
26. Oconto River (Oconto)
27. Pensaukee River (Pensaukee)
28. Peshtlgo River (Peshtlgo)
29. Rock River (Afton)
30. Rock River (Indlanford)
31 . Root River (Racine)
32. Sheboygan River (Sheboygan)
33. Twin River-east (Two Rivers)
34. Twin River-west (Shoto)
35. "Wisconsin River (Blron)
36. * Wisconsin River (Du Bay Dam)
37. Wisconsin River (Hat Rapids)
38. Wisconsin River (Merrill)
39. "Wisconsin River (Nekcosa)
40. "Wisconsin River (Petenwel I)
41. Wisconsin River (Rhlnelander)
42. "Wisconsin River (Wausau)
43. Wisconsin River (Wise. Dells)
44. Wolf River (New London)
* denotes continuous monitoring station
541
-------
-------
Ammonia
To a small extent, ammonia is naturally present in surface waters as a waste
product of fish and as a breakdown product of organic nitrogen compounds. But
additional amounts from wastewater may raise inriver concentrations to a point
of toxicity to aquatic life.
High ambient values indicated by tne 1977-/8 statewide monitoring have dropped
markedly. The Oconto River at Oconto and the Root River show the most
dramatic reduction in ammonia concentration, eacn over 75 percent. Also,
Afton, downstream from municipal sources on the Rock River, shows a
significant decrease in ammonia.
Reduction trends are also apparent on the Wisconsin and Mississippi Rivers
where stations average at least a 25 percent reduction. Overall, more than 40
percent of the monitoring stations snow decreases in ammonia concentrations
over the past three years.
Total phospnorus and dissolved phosphorus
Phosphorus, in addition to nitrogen, is a primary limiting factor in plant
growtn. Excessive concentrations in surface waters may cause algal blooms and
weed growth. Phosphorus occurs in surface waters in a variety of forms.
Total phosphorus measures trie sum of ortnophospnate, an organic phosphate
applied to agricultural land and carried to surface waters in runoff; organic
pnosphorus, a form tied up in biological processes; and condensed pnospnates,
such as detergent phosphates which eventually change into orthophosphate in
surface waters. Dissolved phosphorus or orthopnosphate is phosphorus in the
form most readily available to plants.
Statewide, there has been a downward trend in mean total phosphorus
concentrations. Approximately one-half of the monitoring sites show
decreasing concentrations, while the remaining stations show relatively no
change. Along the Mississippi and Fox Rivers, stations average a decrease of
over 25 percent and tne Rock River stations each snow about a one-tnird
reduction in total phosphorus. Tne majority of the Great Lakes tributaries
also show reductions in mean total phosphorus levels. LaKe Superior stations
all show negligible amounts, below 0.05 mg/1. Lake Michigan tributary
monitoring indicates higner levels but the degree of reduction from the
1977-78 mean concentration averages 20 percent at most of the stations. Total
phosphorus levels are still relatively high in the very southern, most
populous part of the state; the Fox (Illinois) and the Root Rivers' sites
monitor no appreciable change since 1977. Throughout most of the state,
though, mean total phosphorus levels at the problem sites have been
significantly reduced.
The existing statewide pattern of mean dissolved phospnorus "levels is similar
to that of total phosphorus — relatively high concentrations in the southern
and south central regions and low levels around the rest of the state.
Previous problem areas are still apparent, but at a greatly reduced level.
543
-------
Since 1977-78, the trend of dissolved phosphorus levels nas been downward at
over half of the monitoring stations; the remainder have been relatively
static conditions.
Overall, each of the major rivers shows a drop in dissolved phosphorus
concentrations. Many of the Lake Michigan tributaries average at least a *5
percent reduction, and concentrations at the ROCK River stations are down by
more than one-third. Mississippi River monitoring stations do not show any
pattern in changing dissolved phosphorus levels. A significant decrease has
been recorded at Neillsville on the Black River. The other major state river
system, the Wisconsin River, also shows many lowered mean values, all less
tnan 0.04 mg/1.
Biochemical oxygen demand
Biochemical oxygen demand is a measure of the amount of oxygen used by
microorganisms as they break down organic matter in the river. The BOD values
used in this analysis are based on the standard b-day analysis anu inuicate
water quality degradation caused by point sources.
Seventy-four percent of the stations snow a decrease in BOO concentrations.
The succession of seven stations on the Wisconsin kiver indicates that inriver
concentrations have been reduced by about one-third over the past three
years. The Fox River stations have also shown a marked reduction in the
amount of BOD (about one-third). A major cutback in organic waste discharge
by cities and paper mills along these rivers has been a primary factor in the
resulting improvement.
Two paper mill discharges which caused major problems in the 1970s (on the
Flambeau and Oconto Rivers) show a trend of major improvement. Since a
reduction in mill discharge wastes, downstream concentrations are reduced more
than 50 percent. Measurement of BOD on the Mississippi River at Hastings,
monitoring the water quality impacts trie Minneapolis, Minnesota Twin Cities
uroan area upstream, also shows a reduction. Biochemical oxygen demand is not
monitored at stations where organic loadings cannot be attributed to a
specific point source.
Suspended solids
Suspended solids, a primary cause of iririver turoidity and siltation may also
exert an oxygen demand if the mean concentration is high. The problem can be
naturally occurring, or compounded by poor agricultural practices and
wastewater discharge from industries and municipalities.
In general, high concentrations of suspended solids are found in the
peripheral rivers of the state, and lower amounts in the central area. The
majority of trie monitoring sites show low to medium concentrations, under 20
mg/1.
Over the past four years, about one-third of the stations nave shown a
decrease in suspended solids levels. Considerable decreases were noted at
sites with a high degree of soil erosion -- the Kickapoo and Nemadji Rivera.
544
-------
In each case, monitoring shows inriver concentrations down by over
one-third. Other trends are variable though substantial. The Kinnickinnic
and Kewaunee stations each indicate over a 50 percent drop in soli as levels
while the Root and Peshtigo Rivers show increases of 23 percent and more.
Fifty percent of the stations statewide snow no appreciable change in the
magnitude of the suspended solids mean.
Water Quality Management - Facility Status
The history of both municipal and industrial wastewater facility construction
in Wisconsin has been a slow one with very modest progress in the early days.
In 1873, Milwaukee was the first place in Wisconsin to have a public water
system. Legislation for public sewers was passed in 1869 and in 1889 sewerage
plans were required of cities in Wisconsin. In 1925, tnere were only 60
municipal wastewater plants of any character in Wisconsin. There were less
industrial ones. By 1940, 213 treatment facilities were in operation and in
1947, 47 more had been added.43 Beginning in the 1950's municipal facility
construction was largely stimulated by grant programs from either the federal
or state government and industrial construction was carried out under penalty
of law.
Industrial
Shortly after tne passage of P.L. 92-500, in 197k: witn its statutory deadlines
industrial discharges because the leaders in the clean-up of Wisconsin's
waters.
As the data noted for trie Lower Fox and Upper Wisconsin rivers suggests, the
massive loading reductions from principal dischargers has contributed greatly
to the rebound of usable water. During tne spring of 1983 90-9b% of all 1,034
industrial permittees in the state were meeting their permit requirements.
Obviously, process and groupings of processes vary according to treatment
needs and stream requirements. Yet a compilation of current processes shows
tne broad range of industrial permittee process usage. Table 10 is a summary
compilation of processes by permitted water use type.
Municipalities
Wisconsin's municipalities because of their generally less organized
character, slower decision making processes and historical reliance on outside
grants initially lagged far behind in carrying out the requirements of the
1972 Federal Act.
43|viurpnyj Water Purity, pp. 60, 86,
545
-------
TABLE 10
Wisconsin Industrial Dischargers
Water Treatment Processes
1983
Process
Waste water
Absorption Pond
Activated Sludge Cont STB
" " Conventional
" " Ext. Aeration
" " Two Stage
" " Pure Oxygen
Aerated Lagoon
Aerobic Digestion
Anaerobic Digestion
Belt Press
Chemical Addition
Chemical Conversion
Chlorine
Coagu 1 at 1 on-F 1 uctuat Ion
Dech lorl nation
D 1 s 1 nf ect ion-Ge nera 1
Dralnf leld
Dissolved Air Plot
F| Iters General
Gravity Thicken
Ion Exchange
Land Disposal General
Land Spread Ing
Nltrlf Icatlon
Oil and Grease Removal
pH Control
Pressure F I Iters
Primary Gravel Sediment
Pr 1 m/Pre 1
RBCs
Reverse Osmosis
Ridge and Furrow
Screen Ing
So 1 Ids Removal
Sol Ids Treatment
Spray Irrigation
Stabll Izatlon Pond
Trlckl Irg Filters
Tube/Plate Set).
Ultra Filtration
94
1
4
6
1
28
2
6
1
3
3
9
6
1
1
21
II
1
1
9
75
1
44
12
1
158
20
1
2
79
21
2
1
38
10
3
1
1
Contact
Cool Ing Water
31
7
3
6
1
8
2
2
3
3
3
14
1
20
2
6
1
1
23
9
18
2
18
2
3
15
II
1
4
37
19
1
Non-Contact
Cool Ing Water
With
Additives
5
3
1
1
2
1
2
5
6
8
3
1
2
3
2
5
1
10
8
1
1
1
1
18
9
2
3
Without
Additives
4
1
1
1
1
1
1
3
7
7
2
1
2
5
1
2
1
4
1
1
1
1
1
1
5
4
4
Domestic
Wastewater Other
1
1
1
1
1
2
2
3
1
1
3
2
2
3
6
1
3
1
3
1
1
4
2
2
1
1
2
1
2
1
1
1
1
-------
Process
Waste water
Contact
Cool ing Water
with
Additives
NO n~ Contact
Cool Ing Water
Without
Add Itives
Domestic
Wa stewater
Other
Secondary Biological
Secondary Clarification
Mult I Media Filter
Oxidation Ditch
No Treatment
Packed Towers
Floccul Basin
Wet Oxidation
Vacuum F| Iters
2
299
9
2
I
13
I
16
I
2
I
I
I
3
12
3
6
I
-------
This latter factor, analysis suggests, was the largest (disincentive to
compliance, and until the advent of the Wisconsin Fund-in 1978, Wisconsin
municipalities were not succeeding in seeking compliance.
Federal Program
Between 1955 and 1966, 2*5 federal grant offers were made, totalling
$51,904,183. Between 1966 and 1972, 89 projects (construction cost of
$181,834,174.00) were funded at the 50% level or less anu 166 projects
(construction cost of $101,875,000.00) received the maximum grant share of
55.4%.44 Since 1972 federal grants totalling $581,017,970.00 nave been
awarded to Wisconsin communities by the U.S. Environmental Protection
Agency.40
State Funding
Trie first Wisconsin State water pollution abatement grant program was
originated in August, 1966.46
In January of 1970, $144 million was allocated for a ten year period to assist
municipal water pollution control facility development. An additional
$13,085,000 was added in 1977. Over 600 grants were funded during this
program.
In 1977 as earlier efforts ended tne US-EPA federal program became mired in
its own web of administrative ineptitude and congressional inaction, The
Wisconsin legislature began to grapple with the reality of how to achieve
compliance with the Federal Act within the time limits prescribed by law. In
this introspection, certain conclusions were evident:
1. The lack of timely and consistent federal grant allocations destroyed the
ability to expeditiously plan ana build needed projects.
2. A shortage of planned and designed projects ready for construction caused
unnecessary construction delays when money was made available.
3. Given the needs and rapidly accelerating inflation, the federal grants
alone were not sufficient to carry out the federal law.
4. A single system of reviews, irrespective of funding source and
requirements, for all municipal wastewater projects, was essential to
prompt project planning and completion.
44"Status of State Wastewater Grant Program," Unpublished Paper,
Wisconsin Department of Natural Resources, July 18, 1975.
4^"step 1--393 grants totalling $116,929,578,00; Step 2—199 grants,
$27,702,615.00; Step 3--163 grants, $436,385,777.00 (as of 1-3-83;.
46Section 144.21, Wis. Stats.
548
-------
5. To promote expeditious community action, a single priority system,
equitably designed, evenly administered and essentially stable was
necessary to provide local governments with a sense of progress.
6. Uniform statewide enforcement of Clean Water Act violations would need to
be maintained to encourage timely completion of projects.
The Wisconsin Fund4?
From tnese conclusions, the Wisconsin Legislature establisneu the Wisconsin
Fund to make possible a coordinated statewide program of construction. The
fund was tne glue to hold the program together; to provide adequate resources
in a timely manner; to make planning and design adhere to a time schedule by
having monies available on time; to consolidate review staffs from both the
federal and the state programs with the assistance of delegation under the
Cleveland-Wright Amendment's and to coordinate planning and design with
consistent and applicable priority setting.
The Wisconsin Fund's philosophical premise was simple: triat because of the
vicissitudes of the federal program, with its stops and starts, changing rules
anu laws, funding cuts and rescissions, etc., no soundly conceived long-term
project scheduling could be achieved and as a result, costs were
uncontrollaole.
As a grant program, the statute is simple. It provides for a system of grants
to municipal government's similar in nature to the federal grant program, and
while some differences in eligible costs were enacted45^ basic project
concepts were maintained. Conditions such as trie adoption of user fee systems
and Operation and Maintenance plans were required and the federal priority
system was adopted. Grant shares of 60% for step 3 and 75% for steps 1 and 2
grants were adopted. Since May, 1978, 248 step 3 grants have been awarded
4?144.24 Wis. Stats: The complete Wisconsin Fund program as proposed
by the Governor and enacted by the Legislature included several elements
including nonpoint source abatement grants, solid waste siting and planning
monies, septic tank system rehabilitation and point source grants. For the
purposes of this paper only the point source program is referred to by the
term Wisconsin Fund.
48Section 205(g)(2), Federal Clean Water Act
49For example: 10 years of treatment plant reserve capacity, 1985
capacities for interceptors and collector systems eligibility only in
previously unsewered communities.
549
-------
totalling $265,603,369.50 In audition, another $147,168,270 has been
committed for 1983 construction.
As a result primarily of the Wisconsin Fund, by the end of the 1983-84 budget
year it is expected that 90% of Wisconsin's 5b7 municipal facilities will
comply with required discharge limits or be under construction.
Currently, a detailed inventory is underway as to processes in use in
Wisconsin facilities.51 Preliminary information snows, for example, that of
the 5b7 facilities, 234 (42%) utilize Activated Sludge processes, 220 (36%)
utilize ponds and lagoons and 123 (22%) use trickling filters or RBc
processes. In terms of processes utilized, with approximately 60% of all
permittees surveyed, Table 11 lists the results to date.
Current Municipal Construction Needs
Under the Federal Water Pollution Control Act, municipal treatment plants are
required to achieve certain water quality oojectives. Estimates of total
expenditures necessary to reach these levels have been difficult to develop,
and in the early uays of the Act, they were very bad. However, over time a
basic system of biennial cost estimation developed by the U.S. EPA has begun
to serve as a good data source for decision makers.
This system, while hampered on the national analysis level of political
decisions changing the need definitions to fit particular national government
budgetary purposes, has served Wisconsin well because of the state's decision
to complete the 1976 survey on a 100% on-site survey basis.
Each subsequent survey has been designed as a correction from mat base,
modified to reflect changing conditions, court decisions ana final cost
estimates. In 1977, it was estimated that $2.3 billion in 1976 dollar costs
would be necessary to meet pollution abatement standards between 19/7 and
1990. It was also estimated that these costs would grow by $324 million
during the same 13 years because of increased treatment need ana capacity
generated by population growth. Current estimates, based on 1982 data show
for the first time an impact from the Wisconsin Fund expenditure and a real
lessening of need.
50Projects totalling $6,634,829 for step 2, and 14 projects or
$550,047 have also been awarded. These lesser amounts reflect the tactical
decision to fund most step 1's arid step 2's out of federal monies. Thus,
$419,856,515 of State Funds have been committed since 1978.
51 Final data is expected to be available by August 1983 anu will be
supplied as a supplement and attachment for this section.
550
-------
TABLE 11
Wisconsin Municipal
Wastewater Processes
1983-
PARTIAL DATA (60% of Permittees)
Percentage
No. of Times Total Processes
TREATMENT PROCESS Utilized Utilized
Secondary Biological
Activated Sludge-Conventional
Activated Sludge-Contact Stabilization
Activated Sludge-Extended Aeration
Oxidation Ditch
Trickling Filters
Packed Towers
RBC's
Aerate Lagoon
Stabilization Lagoon
Septic Tanks
Activated Sludge-General
Post Aeration
Polishing Pond
Holding Pond
Nitrification
Sand filters
Chemical Addition
De Chi ori nation
Filters-General
Multi -Media Filters
Land Disposal -General
Absorption Pond
Spray Irrigation
Ridge and Furrow
Chlorine
Ultra Violet
10
20
8
6
53
2
16
44
50
2
70
20
23
11
7
17
31
2
b
1
3
27
2
2
182
5
1.6
3>2
1.3
1.0
8.6
.3
2.b
7.1
8.1
.3
11.3
3.2
3.7
1.8
1.1
2.8
5.0
.3
.8
.1
.b
4.4
.3
.3
29.4
.8
2798P
551
-------
Analysis: Current Municipal Construction Needs (Table 12)52
In viewing future pollution abatement needs in Wisconsin, it is necessary to
review current estimates. And to fully interpret the fiscal situation for
Wisconsin communities, it is necessary to separate "needs" into two
categories: the Milwaukee Metropolitan area project and the balance of the
state.
As taole 1* indicates, by the end of 1983 construction year, outstate
Wisconsin will have approximately $62:3,910,000 in unconstructed backlog
projects. Of this amount $188,288,000 were identified as "needed" new
collector systems; elements that are not generally necessary for immediate
compliance with the Clean Water Act.53 jne data further identifies some
need for combined sewer work ($125,829,000) and a significant amount of new
interceptor activity. Much of this latter category would be in conjunction
with new treatment facilities under construction or planneu.
For the Milwaukee area, the situation is more pressing than in the balance of
state. As of December 31, 1981, unmet Milwaukee project needs are estimated
at $1,037,437,000. At the end of 1983 it is further estimated that
$1,086,299,000 will remain.
In terms of trie types of construction, Milwaukee represents the classic larger
city. Treatment facilities in need of major work consist of 43% of the total
cost. Major sewer rehabilitation (5%) is less extensive than one might
expect, but new interceptors (31%) largely to accommodate already existing and
overflowing volumes and to interconnect the two treatment facilities, is a
major cost. And lastly, correction of ancient and overflowing combined
sewer/storm water systems of the older city is estimated at 18%
Overall in fiscal and management terms Wisconsin's most serious challenge will
be in the Milwaukee area.
The Milwaukee Program
In order to achieve compliance in Milwaukee the following elements are
necessary:
for this paper is derived from: US EPA, Office of Water
Programs Operations, 1982 Needs Survey, Cost Estimates for Construction of
Publicly-owned Waste Treatment Facilities, December 31, 1982. As corrected
for interpretation errors, costs and needs are shown as of December 31,
1981.
^Except in a few unique cases where severe pollution from an
unsewered area is flowing directly into a body of water
552
-------
Table 12
Wisconsin Municipal Needs - 1982: (OOO's)
Project Category Milwaukee Balance or State
Backlog Year 2000 Backlog Year 2000
Secondary Treatment 5b4,883 5b4,b83 220,000 331,000
Advanced Secondary 86,000 143,000
Advanced treatment
Inflow/Infiltration 120 120 32,000 32,000
Major Sewer Rehabilitation 71,265 71,265 7,735 8,735
New Collectors 21,712 21,712 188,288 2bb,2b8
New Interceptors 406,262 406,262 125,829 213,738
Combined Sewer Overflow 243,195 243,195 I2b.ti29 125,029
TOTALS (OOO's) $1,307,437 1,307,437 799,590 1,120,590 2,107,027
2,4/18,027
Wisconsin Municipal Needs* - 1982
Adjusted
Milwaukee Balance ot State
12/31/81 Backlog "needs" 1,307,437 799,590
1982 Construction - 78,138 - 73,b80
1982-83 Fundings - 143.000 - 102.000
Net Balance FY 1984 Backlog 1,08b,299 623.910
* To reflect 1982, 1983 construction activity for treatment plants
Milwaukee costs are court ordered expenditures
553
-------
- Rehabilitate sewer lines to reduce clear water inflow and infiltration
- Construct relief sewers to abate overflow including 17 miles of large
diameter storage/tunnels.
- Rehabilitate and expand Jones Island Wastewater Treatment Plant
- Rehabilitate and expand the Southshore Wastewater Treatment Plant
- Improve waste solids handling
- Improve and expend interceptors to all areas of the district and to
eliminate some small inefficient local treatment facilities.
- Construction of storage facilities and interceptors to eliminate bypassing
in local systems
The estimated total cost or the Milwaukee program is $2.1 billion. (1983
dollars):
ELEMENTS ESTIMATED COSTS
- Jones Island $478,824,000
- Southshore $266,800,000
- Interceptors ana relief sewers $760,049,000
- Sewer rehabilitation $791,011,000
- Off site solids management $3b,412,000
- Combined sewage overflow $478,83,000
- Hydraulic and controls $18,890,000
TOTALS $2,107,878,000
By and large by the middle of this decade outstate communities will nave
completed their new construction. In Milwaukee design and construction must
continue for 13-lb years.
Management ana Structure
Management for Wastewater projects in communities otner than Milwaukee has
traditionally been very simple. Each community (or group of communities where
joint facilities are planned) hires a private consulting engineering firm to
plan and ultimately design adequate treatment facilities. Tne municipality
then submits its plans and designs to the Department of Natural Resources
(WDNR) for review and approval. If grant funds are Deing requested, this
process may be tailored to the special needs of a particular grant program.
In all cases, facilities are designed to meet enforceable permit limits under
the Federal Clean Water Act and comparaole Wisconsin State Statutes.
Generally, the Department of Natural Resources through its field offices and
its Division of Environmental Standards provides technical assistance and
advice to municipalities throughout tne process. In tne case of failing older
facilities, the Department may do existing plant analyses, to aid in
determining the causes of old plant failure.
In local communities the oversignt of planning and design consultant varies,
from almost no technical oversight to detail project management. Generally,
in smaller communities, facility planning and construction is totally
entrusted to the consulting engineering who manages the project. Municipal
554
-------
oversight is essential fiscal and political - providing tne funds when
necessary.
In larger communities where public works departments or sewerage
commissions/districts exist — more give and take occurs and the planning and
design firm is essentially adjunct staff.
In Wisconsin at present, there are at least nine or more distinct types of
statutorily approved municipal units of government providing sewer
services.5** Each of these type units operate somewhat differently and each
type has a unique organic enabling statute.
And, while each and every one of these operating systems are appropriately
permitted and regulated for pollutant discharge, the lack of consistency ana
structure does cause problems. This is most especially true in terms of
management and fiscal capacity.
As treatment facilities and systems are constructed and become more
sophisticated ana more costly to build, operate and maintain, many of these
districts will oecome hard pressed to function effectively ana efficiently.
In practical terms, a legally organized district is viewed in today's
managerial and fiscal world as reDuttally presumed to have the capacity to
carry out its chartered activities. In many instances, the elimination of
this presumption will only occur at the point of crisis or nonperformance.
To some, such a risk of large scale public capital investments with inadequate
operating entities is concerning, but when coupled with the oovious
environmental risk associated with nonperformance, it is critical.
In Wisconsin, the structure of managing agencies needs serious attention.
Sucn a concern is further highlighted by the increased need to install
adequate operation ana maintenance practices in recently completed the
facilities. Fundamental to this effort is the need to establish local
community wastewater treatment as an "important" public responsibility. No
longer is it possible for the small community to staff its treatment
facilities with the unused time of more traaitional employees sucn as street
workers, snowplow operators or park employees. Modern facilities, require
persons with training to manage the facilities and to regulate operations.
54These include: joint sewer districts (pursuant to Section 144.07,
Wis. Stats.); metropolitan sewerage districts (Section 66.02); city and
village governments (Section 62.18); town sanitary districts (Section
66.072 and 60.30); town utility districts (Section 66.027); county utility
districts (Section 5y.083); intergovernmental contract districts (Section
66.30); and the Milwaukee metropolitan district (Chapter 282, Laws of 1981
555
-------
Conclusion
Since October IB, 197i: it has been the policy of the United States to seek to
"restore and maintain the . . . integrity" of the nation's waters and at tne
same time to "recognize, preserve, and protect the primary responsibilities
and rights of states to prevent, reduce and eliminate pollution . . ."^
The management challenge of both pursuing pollution elimination and protecting
the rights of the fifty states has been one of great difficulty and it has
resulted in various results from state to state.
In Wisconsin, the pursuit of Clean Water has reached a higher than typical
degree of success because of several unique circumstances. Tne current
accomplishments in water quality improvement have been the result of
advantageous historical circumstance, the coming together of administering
agencies into a single management unit, the implementation of comprehensive
management approaches, tne enforcement of new and invigorated federal and
state laws and the investment of billions of dollars by local and state
government and private industries in new treatment facilities.
Wisconsin is, at present, within sight of achieving many of the treatment
requirements of the Clean Water Act.
To finally achieve the ultimate goals of the Act and to eliminate the
discharge of all pollutants will require much more than traditional point
source treatment.
To tnis end, in tne next decade, Wisconsin will see increased efforts at
taming agricultural arid urban run-off problems, eliminating toxic hazards .both
air and water.encouraging nonpoint pollutant problem solving and building an
understanding with all citizens of the impacts of run-off in the fundamental
water quality of tne State.
55Public Law 92-500 Section 101
"THE WORK DESCRIBED IN THIS PAPER WAS NOT FUNDED BY THE U.S. ENVIRONMENTAL
PROTECTION AGENCY. THE CONTENTS DO NOT NECESSARILY REFLECT THE VIEWS OF
THE AGENCY AND NO OFFICIAL ENDORSEMENT SHOULD BE INFERRED.
556
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ATTACHMENT A
Ln
tn
ate of Wisconsin
PARTMENT OF
TURAL RESOURCES
Office of Planning
and Analysis
****
Bureau of Finance
Bureau of Management
and Budget
Bureau of
Legal Services
i —
1
OFFICE
OF THE
SECRETARY
Deputy Secretary
Executive Assistant
1 1
DIVISION OF
ENVIRONMENTAL
STANDARDS
****
Bureau of
Air Management
....
Bureau of
Solid Waste
Management
• ••**
Bureau of
Wastewater
Management
Bureau of
Water Resources
Management
....
Bureau of
Water Supply
....
Technical Services
....
Office of
Wastewater Operation
and Maintenance
DIVISION OF
ENFORCEMENT
****
Bureau of
Law Enforcement
....
Bureau of
Water Regulation
and Zoning
Office of
Environmental
Enforcement
....
Bureau of
Environmental
Impact
I —
Office of
Intergovernmental
Programs
****
Bureau of
Aid Programs
Bureau of
Water Grants
1 1
FIELD
DISTRICTS
*•***
Southern
_.
_.
Southeast
--
-.
Lake Michigan
West Central
_.
...
North Central
_.
...
Northwest
DIVISION OF
RESOURCE MANAGEMENT
**•**
Bureau of
Engineering
....
Bureau of
Fish Management
....
Bureau of
Wildlife Management
....
Bureau of
Forestry
Bureau of
Parks and Recreation
....
Bureau of
Real Estate
....
Bureau of Research
....
Office of Lands
....
Bureau of
Endangered Resources
DIVISION OF
MANAGEMENT
SERVICES
****
Bureau of
Information
and Education
....
Bureau of
Information
Management
....
Bureau of
Program Services
Bureau of
Personnel
....
Office of
Employee
Development
....
Affirmative
Action
Office
-------
Ui
Ln
00
Wisconsin Department pf Natural Resources
DIVISION OF ENVIRONMENTAL STAMiAkOS - ORGANIZATIONAL CHART
Air, Water, Wastewater, Solid Wastes and Water Resources Management Programs
ATTACHMENT B
Office of Operation
i Maintenance
T. Kroehn. Dir.
Div. of Environmental
Standards
L. Wlble. Administrator
L. Lueschow. Asst. Admin.
Technical Services
Section
(Vacancy). Chief
Operation I Maintenance
of Treatment Works
Wastewater * Water Trtmt.
Operator Certification
and Training
Jur. of Water Supply
R. Krill, Dir.
Public Water Supply
Section
R. Baumelster. Chief
IPrivate Water Supply
I Section
l(Vacancy). Chief
Trtmt. Plant i Water
Main Approvals
Safe Drinking Water Act
Bacti, Radioactivity,
Org., Pesticides I
Metal Contain.
Well Code
High Cap. Well Approvals
Hell Driller & Pump
Inst. Licensing
School i Trtmt. PH.
Wells
Chem. Trtmt. 4 Addns.
Groundwater Emergencies
Heat Pump/Inject. Well
Considerations
5/17/83
Bur. of WastewaterMgmt.
C. Blabaum. D1r.
Municipal Mastewater
Section
C. Burney, Chief
Industrial Hastewater
Section
H. Witt. Chief
Pretrmt. I Fees
Section
S. Klelnert. Chief
Wastewater Permits
Wastewater Compliance Nonit.
WW Trtmt. i Sewer Plan Reviews
Review SEMORE Reports
NR 101 Discharge Fee Prog.
IW Pretrtmt. for POTW Dlsch.
Enf. Decisions I Referrals
State & CWA Discharge Req.
Sludge Management
Infiltration/Inflow Analysis
Oper. and Malnt. Manual Rev.
Sewer Ext. Ban Considerations
Special Assignments
F. H. Schraufnagel
C. W. Threinen
ANC i Pest Control
Div. Budget
Div. Work Plans
DNR Lab Coord.
Acid Rain
D1v. Data Coord.
Quality Assurance
Bur. of Solid Wastes
Mgmt.. P. Dldier. Dir.
Residuals Mgmt. & Land
Disposal Section
R. Schuff. Chief
Hazardous Waste Mgmt.
Section
W. Rock, Acting
Systems Management
Section
R. Fischer. Chief
Mine Reclamation
Section
G. Relnke, Chief
Revw. Solid, Haz. & Hng. Waste Fac.
Feaslb. Studies, Constr., Oper.,
Closure & Long-term Care Plans
Adm. Fed. RCRA and Related Super-
fund 4 St. Haz. Wste. Prog.,
Incl. Spills. PCBs 1 Wste. Oil
Mgmt. Progs.
Issue Licenses for Solid, Haz.,
6 Mng. Wste. Facil. & Sept. Tank
Wste. Hlrs.
Computer 1 Manual Data Mgmt. for
Prog. Lie., Approv., Monit.,
Reporting i Enf. Activities
Adm. State's SW Areawide Ping.
Grants Program
Coord. SW. UE, Trng. and Public
Participation Activities
Reg. Explor., Prospect, and
Metallic Mining Activities
Bur. of Water Res.
Mqmt.. B. Baker. Acting
Water Quality Evil. Sec.
J. HcKersie. Chief
Water Quality Plan. Sec.
J. Cain. Chief
Nonpoint Source Sec.
J. tonrad. Chief
Inland Lake Renewal Sec.
0. Williams. Acting
Groundwater Coordination
Sec.. K. Kessier. Coord.
Bur. of Air Management
D. Theller. Dir.
Engineering t Surveil-
lance Section
D. Packard. Chief
Air Monitoring Section
J. Chazln. Chief
Air Impact Analysis t
Planning Section
P. Koziar. Acting
WQ Standards
Ambient WQ Monitoring
Wis. & Fox Auto. Monit.
WQ Modelng. & Wasteload
Allocation
Biennial WQ Rpt. to Congress
WQ Certifications
Power Plant Intake & Dlsch.
Requirements
Fish Bioaccumul. & Tox.
Public Participation
Liaison to Deslg. Agencies
WQ Areawide Planning
Sewer Service Area Del In.
Nonpoint Source Prog. Incl.
Priority Wtrshds. 1 Local
Projects
Lake Classification
Inland Lake Renewal
Support to Local Lake Districts
Coord. Groundwater Planning,
Policy & Standards
Permits and New Source
Rev.
Emission Inventories
Stack Test, i Vehicle
Insp.
NR 101 Emission Fees
Env. (Air) Impact Review
Com pi lance Plans
Air Quality Monitoring
Episode Watch t Alerts
Exceedence Analysis I
Tracking
Implementation Plans
Non-attainment Area
Plans
Regional Transp. Plans
-------
REMOVAL AND PARTITIONING OF VOLATILE
ORGANIC PRIORITY POLLUTANTS IN
WASTEWATER TREATMENT
by
Albert C. Petrasek, Jr., Barry M. Austern,
and Timothy W. Neiheisel
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
559
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REMOVAL AND PARTITIONING OF VOLATILE, ORGANIC
PRIORITY POLLUTANTS IN WASTEWATER TREATMENT
by: Albert C. Petrasek, Jr., Ph.D., P.E.a
Barry M. Austern, Ph.D.b
Timothy W. Neiheiselc
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
ABSTRACT
A pilot-scale study was conducted to evaluate the removal and parti-
tioning of 16 volatile, organic priority pollutants in conventional waste
water treatment processes. The apparatus used consisted of two, parallel,
2.2 1/s treatment sequences of primary clarifiers, aeration basins, and
secondary clarifiers. The aeration basins were covered to permit quantita-
tion of stripping losses. One treatment sequence was used as a control, to
provide data at ambient concentrations; the other system was continuously
spiked with a methanol solution containing the compounds investigated.
Substantial removals of all compounds were observed, with nine com-
pounds having removals >99 percent; 1,1,2-trichloroethane had the lowest
removal, 80 percent.
Desorption from the primary clarifier accounted for approximately 24
percent of the losses but was observed to be functionally dependent on the
Henry's Law constants of the compounds studied. Stripping from the aeration
basin was a major removal mechanism. The stripping losses observed in the
study were compared with losses predicted by a clean water stripping model.
The observed losses were lower than the predicted losses, and the difference
was attributed to sorption to the biomass.
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved
for presentation and publication.
a Chief, MERL Pilot Projects, Test and Evaluation Facility
b Research Chemist, U.S. EPA, MERL
c Research Biologist, ERC-Duluth, Newtown Fish Toxicology Station,
Cincinnati, Ohio
560
-------
INTRODUCTION
Controlling the discharge of toxic materials to the environment is
essential for the protection of our natural resources. The technological
advances of the last 70 years have made possible the manufacture of a wide
variety of synthetic materials for various end uses. Some of these materials
exhibit mutagenic, teratogenic, or carcinogenic characteristics, and a
significant number of the xenobiotic chemicals persist in the environment
for protracted periods.
The U.S. EPA has principal responsibility for limiting the entry of
toxic materials to the environment, and during the past several years, the
Agency has conducted a number of investigations concerning alternate control
strategies and technologies. One area of concern is the ability of the
municipal wastewater treatment plant to protect receiving waters from the
intrusion of toxic materials.
The Agency's Municipal Environmental Research Laboratory (MERL) has
been conducting both extramural and in-house research to evaluate the
removability and partitioning of toxic materials in publicly owned treatment
works (POTW's). This paper presents the results of a pilot-plant study
conducted at the Agency's Test and Evaluation Facility (T&E) in Cincinnati,
Ohio to evaluate the removal and partitioning of volatile organic priority
pollutants in POTW's. Similar research concerning the semivolatile organic
priority pollutants and the metals has been reported previously (1,2).
561
-------
EXPERIMENTAL PROTOCOL
PILOT PLANT OPERATIONS
The principal objective of this project was to quantitate the removals
of the volatile, organic priority pollutants that could be expected in a
conventional POTW. Other objectives were to develop additional data rela-
tive to the partitioning and stripping of the materials in conventional
wastewater treatment processes.
The treatment sequence selected as being most representative of a
typical POTW was primary clarification followed by conventional, plug-flow,
activated sludge. Two, parallel, 2.2 1/s (35 gpm) pilot plants were used
for this study and are shown in a simplified schematic diagram in Figure 1.
The degritted and comminuted raw wastewater was pumped from the Cincinnati
Mill Creek Wastewater Treatment Plant to a head tank at the T&E Facility.
To avoid plugging of process piping, gross solids were removed by a 1.27 mm
static screen at the project site. The wastewater was then pumped to the
influent splitter box. Nominal operating conditions for the pilot-scale
treatment sequences are presented in Table 1.
The primary clarifiers were 2.95 m in diameter and had a side water
depth (SWD) of 3.6 m. At 2.2 1/s, the overflow rate was 28 m3/m2 • day.
The aeration basins were 5.4 m long, 3 m wide, and had a SWD of 3.6 m,
which resulted in a theoretical residence time of 7.5 hrs at a flow of 2.2
1/s. Conventional Sanitare® coarse bubble diffusers were used for the
study, and the nominal air flow was 57 1/s. The secondary clarifiers were
3.6 m in diameter and had a SWD of 3.6 m. At 2.2 1/s the overflow rate was
18.4 m3/m2 • d.
Every four hours the operations staff monitored the influent and return
activated sludge (RAS) flows and the level of the spike stock solution,
which was fed into the influent of the experimental system with a metering
pump. Furthermore, grab samples were collected for monitoring mixed liquor
(ML) and RAS oxygen uptake rates (OUR's), ML and RAS centrifuge volumes, ML
settled sludge volume, pH, turbidity, and alkalinity.
Routine analyses for total suspended solids (TSS), the nitrogen series,
total phosphorus, and chemical oxygen demand (COD) were performed on 24-hr
composite samples.
ORGANICS SAMPLING AND ANALYSIS
The compounds that were studied are shown in Figure 2, and are given
in Table 2, along with some of the more important physical/chemical proper-
ties for the compounds. The spike solution, containing the 16 compounds
that were studied, was prepared weekly; methanol was used as the solvent.
A one-liter, stoppered, graduated cylinder was used as the spike solution
reservoir, and pumping rates were monitored by recording the volume in the
reservoir every four hours.
562
-------
CONTROL TRAIN
AERATION BASIN
WASTE ACTIVATED
SLUDOE
EXPERIMENTAL TRAIN
AERATKM BASM
SECONDARY
CLARFER
WASTE ACTIVATED
• SECONDARY EFFLUENT
SECONDARY EFFLUENT
Figure 1. Simplified process schematic diagram of volatile priority
pollutant pilot plant.
563
-------
TABLE 1. NOMINAL OPERATING CONDITIONS FOR THE
A AND B SYSTEMS USED ON THE VOLATILE
PRIORITY POLLUTANT PROJECT
I. Design Flow, Qd = 35 gpm
= 50,400 gpd
II. Primary Clarifiers -
Diameter = 9'-8"
Weir Diameter = 9'-l"
SWD = 12'-0"
Surface Area = 73.4 ft2
Surface Overflow Rate = 687 gpd/ft2
III. Aeration Basins -
L:W:D = 17'-7":10'-0":12'-O1
Surface Area = 175.8 ft2
Volume = 2,110 ft3
= 15,780 gal.
Residence Time (Qd) =7.5 hrs.
IV. Secondary Clarifiers -
Diameter = 11'-11"
SWD = 12'-0"
Surface Area = 111.5 ft2
Surface Overflow Rate = 452 gpd/ft2
564
-------
DICHLOROMETHANE
Cl
I
Cl —C-H
I
H
1,1-DICHLOROETHENE
Cl H
\ /
CHLOROFORM
Cl
I
Cl - C - H
I
Cl
CARBON TETRACHLORIDE
C!
I
CI-C-CI
I
Cl
1,2-DICHLOROPROPANE
H Cl H
I I I
CI-C-C-C-H
i i t
H H H
TRICHLOROETHYLENE
Cl Cl
Cl
\
H
1,1,2-TRICHLOROETHANE
Cl Cl
I I
CI-C-C-H
i
H
i
H
DIBROMOCHLOROMETHANE
Br
CI-C-Br
i
H
BENZENE
O
1,1,1 -TRICHLOROETHANE
Cl H
i i
CI-C -C-H
i i
Cl H
BROMODICHLOROMETHANE
Br
Cl -C-CI
I
H
CHLOROBENZENE
Cl
o
TETRACHLOROETHYLENE
Cl Cl
Cl
TOLUENE
\
Cl
1,1,2,2-TETRACHLOROETHANE
Cl Cl
I I
H-C-C-H
i i
Cl Cl
VOLATILE PRIORITY POLLUTANTS STUDIED
ETHYLBENZENE
CH3CH2
i
O
Figure 2. Volatile priority pollutants studied.
-------
TABLE 2. COMPOUNDS STUDIED AND SELECTED PHYSICAL/CHEMICAL PROPERTIES
Compound
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 ,2-Dichloropropane
Trichloroethylene
1 , 1 ,2-Trichloroethane
Dibromochloromethane
Benzene
1,1, 1-Trichloroethane
Bromodichloromethane
Chlorobenzene
Tetrachloroethylene
1,1,2, 2-Tetrachloroethane
Toluene
Ethylbenzene
Henry ' s
Hc
(g a m~3/
g » m~3)
0.13
0.62
0.16
1.26
0.12
0.49
0.03
0.03
0.23
0.20
0.09
0.16
1.19
0.16
0.25
0.27
Law Constant
H
(M3 o atm/
mol. x 10~3)
3.19
15.0
3.93
30.2
2.82
11.7
0.74
0.78
5.55
4.92
2.12
3.93
28.7
0.38
5.93
6.44
KOW
(Octanol/
Water
Partition
Coeff.)
18
30
93
437
190
195
148
123
135
148
76
691
758
363
490
1412
566
-------
In order to circumvent the problems associated with the compositing of
samples containing volatile organic compounds, grab samples were used for
these analyses. The samples were collected in 40-ml glass vials with
Teflon®-sealed screw caps.
The off-gases from the aeration basins were sampled with Tenax traps.
All gas samples were collected in duplicate, at a flow rate of 100 cc/min
for 10 min. The one-liter sample volume was determined from breakthrough
studies conducted on the Tenax traps.
The compounds were analyzed by EPA Method 624 (3). The GC column was
1% SP-1000 on Carbopack B, 180 cm by 2 mm ID, which was programmed at 8°
C/min after a 2-min hold at 50° C.
Samples were added to the column using the Bellar-Lichtenberg purge
and trap technique with a Tekmar LSC-1 apparatus. A 5-ml sample was purged
for 11 minutes with 40 ml/min of helium onto a Tenax/silica gel trap. The
trap was desorbed onto the column, which was at room temperature, by heating
the trap to 180° C and backflushing with the GC carrier gas for three
minutes. The column was then heated to 50° C, beginning the previously-
described program. The mass spectrometer was turned on and data acquisition
initiated.
Between runs the trap was baked at 225° C with a helium flow.
The mass spectrometer was a Finnigan 3300 which scanned from 35-400
amu every three seconds. The instrument was tuned to meet the £-Bromo-
fluorobenzene (BFB) criteria. This compound was also used as the internal
standard in each run.
567
-------
RESULTS
CONVENTIONAL PARAMETERS
During this 12-month study, the average mixed liquor suspended solids
(MLSS) concentrations for the control and experimental systems were 2,400
and 2,900 mg/1, respectively. The average sludge retention time (SRT) for
the control system was 5.3 days, and for the experimental system was 5.9
days. The mean ML-OUR was 36 mg/l»h for the control and 40 mg/loh for the
experimental process; other operational parameters are presented in Table 3.
Table 4 summarizes the performance of both treatment sequences with
respect to the conventional water quality parameters. Data are presented
only for the control system primary clarifier. After two months of almost
identical, parallel operation, the other primary effluent sample was deleted
to reduce laboratory workload.
TSS and COD removals were good for both systems, averaging 93 and 86
percent, respectively. At the relatively high SRT's, substantial nitrifica-
tion occurred during much of the project, as the nitrogen series data
indicate. The effluent TSS concentrations and turbidity values for both
systems indicate that good treatment was obtained during the study.
VOLATILE ORGANIC COMPOUNDS
During this study, a total of 20 sets of samples were collected for
volatile organics analysis. The mean concentrations observed in the control
treatment sequence are presented in Table 5, along with percent removal
data for the primary clarifier and the entire treatment sequence.
The influent data represent ambient concentrations in the raw wastewa-
ter after static screening, and a "less than" indicates that at least one
sample analysis was below detection limits. Toluene and chlorobenzene were
both present in relatively high concentrations, 160 and 102 pg/1, respec-
tively. Additionally, methylene chloride, 1,1-dichloroethene, chloroform,
1,1,1-trichloroethane, ethylbenzene, tetrachloroethylene, and tetrachloro-
ethane were all present at concentrations greater than 10 yg/l.
The removal data for the primary clarifier vary considerably from
compound to compound, but in general, substantial removals were observed,
with an average of 36 percent for all compounds. However, the concentrations
observed in the primary sludge were quite low, which indicates that
partitioning to the primary sludge was not a significant removal mechanism.
Very low concentrations were observed for all compounds in the RAS and
the activated sludge effluent. The removals observed in the control
treatment sequence were very good for most of the compounds studied.
However, in several instances the influent concentrations were too low to
properly assess removability. The influent to the experimental system was
spiked with the compounds being studied to improve the quantitation of
removability, and Table 6 presents the mean concentrations observed in the
568
-------
TABLE 3. SUMMARY OF PROCESS OPERATION DURING
THE VOLATILE PRIORITY POLLUTANT STUDY
Parameter
Influent Flow - 1/s (gpm)
RAS Flow - 1/s (gpm)
WAS Flow - 1/d (gpd)
Primary Sludge Flow - 1/d (gpd)
Air Flow - 1/s (scfm)
MLSS - mg/1
RAS - mg/1
ML Cent. Vol. - percent
RAS Cent. Vol. - percent
ML - OUR - mg/l»h
RAS - OUR - mg/l«h
Normalized ML - OUR - hr"1
Normalized RAS - OUR - hr~l
SVI - ml /gin
SRT - days
System
Control
2.33 (37.0)
0.62 (9.8)
1980 (523)
1889 (499)
56.6 (120)
2,439
10,987
3.1
15.5
35.8
101.6
0.015
0.009
122
5.3
Experimental
2.11 (33.5)
0.64 (10.2)
1998 (528)
2290 (605)
56.6 (120)
2,886
11,889
3.7
14.9
40.4
88.2
0.014
0.007
153
5.9
569
-------
TABLE 4. SUMMARY OF PROCESS PERFORMANCE DURING THE VOLATILE PRIORITY POLLUTANT STUDY
Parameter
TSS
COD
Total-P
TKN
Organic-N
NH3-N
N02-N
N03-N
Total-N
Alkalinity (as CaC03)
Turbidity (NTU)
Influent
(mg/1)
416
573
9.3
42.4
16.6
25.8
0.1
0.18
42.7
-
-
Primary
Effluent
(mg/1)
202
329
6.3
36.2
11.1
25.1
0.1
0.3
36.6
251
199
Primary
Clarifier
Removal
(percent)
51
43
32
15
33
3
-
-
14
Activated Sludge
Effluent
Control Experimental
(mg/1) (mg/1)
28
88
3.2
11.9
3.9
8.0
1.1
13.1
26.1
91
11
30
77
3.1
11.4
3.7
7.7
0.65
15.1
27.2
90
10
Total Plant
Removal
Control
(percent)
93
85
66
72
76
69
-
-
39
-
-
Experimental
(percent)
93
87
67
73
78
70
-
-
36
-
-
-------
TABLE 5. MEAN CONCENTRATIONS OBSERVED IN THE CONTROL TREATMENT SEQUENCE
Compound
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 ,2-Dichloropropane
Trichloroethylene
1,1, 2-Trichloroethane
Dibromochlorome thane
Benzene
1,1, 1-Trichloroethane
Bromodichlorome thane
Chlorobenzene
Tetrachloroethylene
and
Tetrachloroe thane
Toluene
Ethylbenzene
Influent
(ug/D
<30.6
<10.7
10.8
<6.2
<0.2
<4.2
<2.9
<0.6
<2.7
<65.0
<0.2
102
<24.0
160
<24.5
Primary
Effluent
(Mg/D
<22.3
<3.7
7.2
<3.3
<0.3
<2.9
<0.5
<0.3
<2.7
34.2
<0.2
87.3
<2.8
114
7.3
Removal
by
Primary
Clarif ier
(percent)
27
65
33
47
-
31
83
50
-
48
-
14
88
29
70
Activated
Sludge
Effluent
(Ug/D
<2.5
<0.2
<0.4
<0.2
<0.2
<0.2
<0.6
<0.2
<0.3
<0.9
<0.2
<0.5
<0.2
7.3
<0.2
Removal
by Return
Treatment Activated
Sequence Sludge
(percent) (ug/1)
>92 <1.4
>98 bdl
>96 <3.4
>97 bdl
<1.2
>95 bdl
>79 <6.5
>67 <1.3
>89 <1.5
>99 <1.5
bdl
>99 <1.6
>99 <3.0
95
>99 bdl
Primary
Sludge
<40.4
bdl
<7.5
<1.5
<3.6
<23.3
<3.2
bdl
<9.0
<37.2
bdl
648
164
654
283
bdl = below detection limit
-------
TABLE 6. MEAN CONCENTRATIONS OBSERVED IN THE EXPERIMENTAL TREATMENT SEQUENCE
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 ,2-Dichloropropane
Trichloroethylene
1 , 1 ,2-Trichloroethane
Dibromochlorome thane
Benzene
1,1, 1-Trichloroethane
Bromodichlorome thane
Chlorobenzene
Tetrachloroethylene
and
Tetrachloroe thane
Toluene
Ethylbenzene
Influent
(Mg/1)
118
79
137
60
309
107
133
58
73
132
89
197
252
255
82
Primary
Effluent
(Mg/D
89
34
143
32
295
68
155
49
61
96
64
163
263
198
69
Primary
Sludge
(ug/D
<143
<40
<208
<14
<461
389
<219
<10
121
<220
<25
953
2033
974
766
Activated
Sludge
RAS Effluent
(Ug/l) (pg/1)
<21 <4.0
<1 <0.2
<7 3.6
<1 <0.2
<1 <6.0
<1 <1.5
31 28.0
<2 <7.0
<1 <0.2
<1 <0.3
<1 <0.2
<5 <1.3
25 16.0
<2 <0.6
<1 <0.2
Aeration
Basin
Off-gas
(ng/1)
-
425
838
322
1628
609
663
1291
225
1022
1155
149
1227
672
243
Removal
by
Primary
Clarif ier
(percent )
25
57
0
47
5
36
0
16
16
27
28
17
0
22
16
. -
Removal
by
Treatment
Sequence
>97
>99
>97
>99
>98
>99
80
>88
>99
>99
>99
>99
94
>99
>99
-------
experimental system during this investigation. Due to the ubiquitousness
of methylene chloride in the organics laboratory, the concentrations of
that compound found in the aeration basin off-gas were considered unreliable
and they are not reported.
The data for the primary clarifiers indicate that substantial decreases
in concentration occurred for most compounds, the average decrease being 24
percent. However, the concentrations observed in the primary sludges were
low, which indicates that partitioning to the sludge was not the principal
removal mechanism. Losses due to volatilization at the clarifier surface,
the weir plate, and in the effluent channel appear to be the major points
at which the volatile compounds leave the primary clarifiers.
With the exception of 1,1,2-trichloroethane and dibromochloromethane,
very good removals were observed in the spiked process. The average removal
for all compounds was greater than 96 percent; 60 percent of the compounds
were present in the effluent at a concentration less than 2.5 ug/1, and 45
percent were found at concentrations less than 1.0 ug/1.
TOXICITY REDUCTION
During this investigation, static acute toxicity tests were conducted
using fathead minnows (Pimephales promelas), an invertebrate (Daphnia
magna), and a bacteria toxicity assay (Microtox® by Beckman Instruments,
Inc.). The procedures used followed the guidelines of Peltier (4) and have
been reported in detail by Neiheisel (5). The data presented in Table 7
summarize the results obtained when all three organisms were being used for
the studies, and represent six sets of toxicity tests. The values reported
are the percent of sample in the test container necessary to cause the
desired organism response.
For all three sample locations, the samples from the spiked, experimen-
tal system were no more toxic than these from the control system. Addition-
ally, for all three organisms there was no significant difference in the
toxicity of the influent and primary effluent samples. The LC50 values for
the minnows and the Daphnia magna ranged from 30 to 40 percent and for the
Microtox® from 8 to 10 percent. The secondary effluent samples were not
acutely toxic to the organisms used.
573
-------
TABLE 7. SUMMARY OF ACUTE TOXICITY DATA
Sample
Influent
Primary
Effluent
Secondary
Effluent
Cont.
Expt.
Cont.
Expt.
Cont.
Expt.
Fathead Minnow
96-hr LC50 in %a
32.1
31.9
36.3
32.4
MOO
MOO
Daphnia magna
48-hr LC50 in %a
33.8
31.0
39.8
35.6
MOO
MOO
Microtox®
15-min EC50 in %a
9.7
7.8
9.6
8.6
MOO
MOO
a percent of sample in dilution
574
-------
DISCUSSION
The data presented in Table 8 summarize the distribution of the volatile
compounds in the experimental treatment sequence. The primary sludge did
not contain appreciable amounts of most of the compounds. Some partitioning
to the solids is evident, especially for chlorobenzene, ethylbenzene,
toluene, tetrachloroethylene, and tetrachloroethane.
Several investigators have suggested that the octanol-water partition
coefficient, Kow, is a useful tool for estimating the sorption of organic
compounds to particulate material (6,7,8). Figure 3 is a plot of primary
sludge concentration factors (Fs) versus the Kow's. The sludge concentra-
tion factors, for each compound studied, were computed by dividing the
concentrations in the primary sludge (ug/1) by the influent concentrations
(yg/1). The correlation between Fs and Kow is reasonably good.
The major losses of the volatile organic compounds during primary
clarification are due to desorption. Thibodeaux (9) has discussed desorp-
tion from basins and rivers, and has presented desorption data for 11
compounds from aerated basins. Liss and Slater (10) presented a model of
gas exchange at the air-sea interface, based on the two-film theory. They
calculated overall mass transfer coefficients (KL) ranging from 10.6 to 20
cm • h~ , with the liquid phase transfer coefficients (k^) ranging from 10.7
to 20 cm 9 h and the gas phase transfer coefficients (k ) varying from
1,030 to 1,900 cm » h~l. Mackay and Leinonen (11) extendea previous work
on desorption of low solubility compounds (12) to include the liquid film
resistances reported by Liss and Slater (10). Calculated parameters for 14
compounds were reported, with K^'s ranging from 1.5 x 10 m o hr for
Lindane to 0.144 m « h~l for benzene.
Dilling, et al. (13) conducted a study of the evaporation rates of
five chlorinated compounds. The studies were conducted in deionized water
with initial concentrations of 1.0 mg/1. In subsequent work, Dilling (14)
presented evaporation rate data for 27 chlorohydrocarbons. The experiments
were conducted in 250-ml stirred beakers (200 rpm). The observed rates
were generally first order, and the experimental data agreed reasonably
well with rates calculated by using the methods of Liss and Slater (10) and
Mackay and Leinonen (11).
Thibodeaux (9) has presented models for desorption from both plug-flow
and completely-mixed basins. The fraction desorbed from a plug-flow basin
can be calculated by:
Fp = 1 - e(-KLav T) (1)
where Fp is the fraction desorbed from the basin, KL is the overall liquid
phase mass transfer coefficient (L • t ), a is the interfacial area per
unit volume (L~l), and T is the mean residence time (t).
575
-------
TABLE 8. SUMMARY OF MASS BALANCES ON THE EXPERIMENTAL SYSTEM
Compound
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 , 2-Dichloropropane
Trichloroethylene
1,1, 2-Trichloroethane
Dibromochloromethane
Benzene
1,1, 1-Trichloroethane
Bromodichloromethane
Chlorobenzene
Tetrachloroethylene
and
Tetrachloroethane
Toluene
Ethylbenzene
Primary3
Sludge
1.4
<0.7
2.0
<0.3
<2.0
4.7
2.1
<0.2
2.3
2.1
<0.4
<6.6
10.7
5.1
12.3
Percent of Each Compound Found
at Indicated Sample Location
Activated13 Wasteb Aerationb
Sludge Activated Basin
Effluent Sludge Off-gas
<0.5 <0.3
<0.1 <0.1 72
<0.2 <0.1 34
<0.1 <0.1 59
<0.2 <0.1 32
<0.3 <0.1 41
<1.8 0.4 25
<1.4 <0.1 >100
<0.1 <0.1 15
<0.1 <0.1 62
<0.1 <0.1 >100
<0.1 <0.1 5
0.6 0.2 27
<0.1 <0.1 20
<0.3 <0.1 21
a based on influent concentrations
b based on primary effluent concentrations
576
-------
O
12
10
8 -
O
a
LU
O
Q
ID
_J
CO
2 -
cc.
Q_
0
YI0.0065X + O.61
RS0.85
10
100
1000
10000
K
ow
Figure 3. Primary sludge concentration factors, primary sludge concentration
divided by influent concentration, versus KQW for compounds studied.
-------
Other investigators (15,16,17) have shown that the gas and liquid
phase mass transfer coefficients can be related to KL by:
!_ = 1 1 (2)
KL ki kg Hc
where k^ and kg are the liquid and gas film mass transfer coefficients (L
« t"1), respectively, and HC is the Henry's law constant (m • 1^/m » 1^).
Henry's law constants, HC, are dimensionless (g • m~^/g » m~^) parti-
tioning ratios which are related to the more frequently-encountered data in
the literature by:
H = Hc RT (3)
where H is the Henry's law constant (atm o m^ » mol"1 e K"1); R is the
universal gas constant, R = 8.206 X 10~"5 (atm » m^ • mol"1 » K"1); and T is
the absolute temperature (°K).
As shown by Equation 2, the overall transfer coefficient, KL, is a
function of the Hc for any given compound. Therefore, the amount desorbed
from a primary clarifier will be functionally dependent on the Hc of the
particular compound. Figure 4 is a plot of the fraction of each compound
desorbed, F, versus the Hc for each compound. The data exhibit considerable
scatter; however, the general trend is apparent.
The fraction of each compound desorbed was computed from the data in
Table 6, and Equation 1 was used to compute KT 's for each compound. In
order to determine values for k-, and k , K-r was plotted versus H
(Equation 2). The intercept then gives k^~* (k, = 37.9 cm » h"*), and the
slope is k ~1 (kg = 1400 cm • h"1).
&
Liss (17) has defined the total resistance to mass transfer, Rt , as
and the individual liquid and gas phase resistances (r-, and r ) as k,
and (Hk „) , respectively. Therefore, Equation 2 may be rewritten as:
c „
Rt = rl + rg
For those compounds with Hc's of about 0.024, the resistances in both
the gas and liquid phases are approximately equal. For compounds with
Henry's constants greater than 0.03, the liquid film resistance will control
mass transfer, since r^ will be much greater than rg.
The values obtained for k^ and kg, and the Henry's constants, were
used to compute overall mass transfer coefficients, KL'S, for each compound.
The KL'S are presented in Table 9, along with overall mass transfer
coefficients reported by other investigators. With the exception of this
study, all of the values in Table 9 are based on either tap water or
distilled water as the matrix.
The KL'S determined for compounds with low Hc's are in good agreement
with the other data. However, many of the other KL'S are two to three
578
-------
30
25 -
20
o
15 -
10
5 -
0
YS0.34X - 0.30
RS0.73
0 10 20 30 40 50 60
FRACTION DESORBED, F - %
Figure 4. Influence of HC on desorption from the primary clarifier
of the experimental system.
579
-------
TABLE 9. COMPARISON OF REPORTED VALUES OF THE OVERALL MASS TRANSFER COEFFICIENT, KL, FOR DESORPTION
Mackay and
Compound Leinonen (11)
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 , 2-Dichloropropane
Trichloroethylene
00
° 1,1, 2-Trichloroethane
Dibromochlorome thane
Benzene 14.4
1,1, 1-Trichloroethane
Bromodichlorome thane
Chlorobenzene
Tetrachloroe thy lene
Tetrachloroe thane
Toluene 13.3
Ethylbenzene
Reported Values Of KL (cm • h *)
Liss and Kyosai, This
Dilling (14) Slater (10) et al. (20) Study
13.1 31.4
13.4 17 36.3
11.4 32.4
10.6 10.7 37.1
30.9
11.3 11 35.9
13 19.9
17 19.9
33.9
11.4 15 33.4
15 29.1
32.4
10.2 37.1
6.7 13 32.4
10 34.2
7 34.4
-------
times the previously-reported values. Many factors may effect desorption,
so the differences are not surprising. The presence of other compounds,
electrolytes, oils and greases, and sorbents in the wastewater will result
in non-ideal behavior. Furthermore, the hydrodynamics of the various
experimental systems have not been well-defined. The energy input to any
system will influence the film renewal rate and, therefore, the desorption
which will occur.
Equation 1 indicates that KL and av will predominantly influence the
desorption from primary clarifiers. The residence time is clearly an
important variable, but in practice it generally ranges from 1.5 to 2 h;
therefore, it is relatively constant. The interfacial surface area per
unit volume, av, is the clarifier depth for units with uniform cross sec-
tions. Figure 5 presents several curves of the fraction that can be expect-
ed to be desorbed from primary clarifiers as a function of the clarifier
depth and the Hc of the particular compound.
The data in Table 8 indicate that substantial amounts of all compounds
were found in the off-gas from the aeration basin of the spiked system.
Interpretation of the off -gas data is, however, quite involved since the
three mechanisms of sorption, biodegradation, and stripping may have been
occurring simultaneously for several of the compounds studied.
Roberts, et al. (18) have presented a model to predict stripping by
bubble aeration, in completely-mixed, clean water systems, in which the
reciprocal of the removal may be computed as :
- e-0Zg] (5)
CLE QL
where CLI and CLE are tne influent and effluent liquid phase concentrations,
M ® L ; HC is the Henry's law constant, g 9 m /g » m ; QQ is the gas
flow rate, nr o s"1; 0^ is the liquid flow rate, m o s~* . 0Zg is defined
as given below:
0Z , KLa • VL (6)
9 s HC • QG
where K^a is the overall mass transfer coefficient, s , and V-, is the
liquid volume, m^.
The fraction stripped, n, may be computed by:
n = 1
The model was used to estimate stripping losses from the aeration
basin utilized during this study. A computer program was used to model the
basin as four completely-mixed reactors in series and compute effluent
concentrations for values of Hc ranging from 0.01 to 2.1. Two different
581
-------
CO 5
DC
LU
h-
LLJ
Q- 3
LU
Q
DC
LL
DC
o 1
0
0 10 20 30 40 50 60
FRACTION DESORBED - PERCENT
Figure 5. Predicted desorption from primary clarifiers as a function
of clarifier depth, HC> and mass transfer coefficients.
582
-------
sets of conditions were evaluated; one with high gas to liquid flow ratios
and high KLa's, the other with low values for the same variables. The
fraction desorbed, n, was then plotted as a function of the different Hc's.
The results are presented in Figure 6, where curves A and B represent
the high and low values of QG/QL and KLa, respectively. For the case with
high K^g's, 90 percent removal due to stripping is predicted for compounds
with Hc greater than 0.03, and for low KLS conditions, 90 percent removal
is predicted at Hc of 0.07.
The fraction of each compound removed by stripping, observed during
this study, is plotted in Figure 6 versus the compound's Hc. The observed
removals due to stripping are considerably lower than the removals predicted
by the model of Roberts, et al. (18). It is important to note that the
slopes of the experimental data and the predicted removals are almost
identical. The data indicate that some mechanism is reducing the stripping
from the aeration basin.
Sorption onto the biomass is the principal mechanism which will reduce
the amount of material stripped from the aeration basin, although other
factors, such as matrix effects on solubility, may be important. Matter-
Muller, et al. (19) have discussed the role of sorption as it relates to
the removal of organic compounds in the activated sludge process. A posi-
tive correlation between the adsorption constant, the milligrams of a
compound adsorbed per kg of total solids, and the KQW was observed.
Some preliminary investigations were conducted during this study to
evaluate the rate at which sorption to the biomass occurs. A 1.5 1 sample
of mixed liquor was placed in a 2 1 beaker, and then spiked with a mixture
of several of the compounds being studied. A Teflon® plug, with a 1/4 in.
stainless steel sample line, was then placed on top of the sample. The
plug produced a zero-headspace, air-tight sample container. The sample was
then mixed with a magnetic stirrer.
Samples were withdrawn, by depressing the Teflon® plug, after 5, 10,
15, 30, and 60 minutes. The samples were immediately centrifuged and the
liquid phase organic compound concentrations determined by GC/MS using the
purge-and-trap method previously described.
The concentration versus time curves indicated that the sorption was
first order, and the adsorption coefficients were computed accordingly.
Sufficient data are not yet available to properly quantitate the
adsorption coefficients, Ks, for the compounds studied. Additionally, the
influence of variables, such as the MLSS concentration and the SRT, have
not been evaluated. The observed values of Kg have, however, been large
enough to account for the differences between the predicted and the observed
stripping removals. Figure 7 is a plot of the Ks's obtained for one study
as a function of the Kow's. The correlation is quite good (r = 0.95), but
additional data, gathered under varying conditions, are required before any
attempt at generalization can be made.
583
-------
Ul
00
i-l
(B
/-^ HI yo
n e
C 3 3
i-t O O
0>
CO
p. w
O M
3 to
HI C
0)
nc
rr
• O
3 -O CO
CL ft ft
0. O.
0>
ft O T3
01 rt H-
n> 3
i-h a-OP
i-t
§•^3
rt : 0>
sr o re
H- M i-t
CO (B 0)
01 rt
CO 3 H-
rt O
C « 3
O. Oi
*< rt CT
• n> 01
CL o>
ID CD
FRACTION REMOVED BY STRIPPING - PERCENT
ro
O
GO
o
01
o
o>
o
oo
o
(O
o
o
o
p
b
I
o
(— I— KJ ^
*^J >^-J ^^1 1 Q G-,
—I H£3
CT^ Cn rsj rxj
-tr -tr v>j O4
i^/n i_n cn cn
r^o ^o ^j ijj
CD CD CD d.
-------
15
12
0
Ks = 0.007 Kow+ 3.02
R = 0.95
SRT a 3 DAYS
6
K
ow
9
x 100
12
15
Figure 7. First-order sorption coefficient, Kg, to the mixed liquor
as a function of the KQW.
585
-------
The biodegradability of a compound will obviously influence the extent
to which the compound is removed by stripping. One intuitively expects the
biorefractory compounds to be more strippable than these materials which
are easily degraded. For the volatile compounds, which are structurally
simple molecules, the extent of halogenation should influence the relative
biodegradability of the compound.
Figure 8 is a plot of the percent halogen by weight of each compound
versus the percent of each compound found in the aeration basin off-gas.
586
-------
100 r—
100
PERCENT IN AERATION BASIN OFF GAS
Figure 8. The influence of the degree of halogenation on the
amount of a compound removed by stripping in the
aeration basin.
587
-------
CONCLUSIONS
This study was conducted to evaluate the removal of volatile priority
pollutants in a conventional POTW and investigate the factors that determine
how the compounds partition in the treatment processes. Several important
conclusions can be drawn from the results of this investigation:
1. The majority of the volatile priority pollutants studied were
removed very effectively by the pilot-scale POTW. Removals greater
than 99 percent were observed for 9 of the 16 compounds investigat-
ed. Only 1,1,2-trichloroethane and dibromochloromethane had mean
removals less than 90 percent.
2. Appreciable removals can be expected to occur in the primary
clarifier due to desorption. The removals follow existing two-film
models reasonably well, and gas and liquid phase transfer coeffi-
cients have been determined.
3. Partitioning to the solids during primary clarification was not
a significant removal mechanism. However, the partitioning that
did occur was observed to be functionally related to the KQW.
4. For many of the compounds studied, stripping from the aeration
basin was the principal removal mechanism.
5. A model which predicts stripping from clean water systems was
compared with the stripping observed in this study. The predicted
values were higher than the observed values, which suggests that
some mechanism was reducing the stripping losses. Sorption to the
biomass was found to be sufficiently rapid to account for the
observed differences.
6. The adsorption coefficient, Ks, for organics to the biomass was
related to the KQW, which is consistent with previously-reported
findings.
7. The biodegradability of a compound will infuence the extent to
which the compound is removed by stripping. The more biorefractory
the compound, the more likely the compound is to be stripped.
8. The percent of the molecular weight contributed by the halogens
was shown to be a relative indicator of biodegradability.
9. Those materials which do partition to the biomass are biodegraded,
or otherwise altered, since only low concentrations were observed
in the waste activated sludge.
588
-------
RECOMMENDATIONS
1. At the present time, the partitioning of the volatile priority
pollutants in primary clarifiers appears to be predictable with
reasonable accuracy. Some additional work should be conducted to
confirm the existing models.
2. Stripping from aeration basins is not predictable at this time.
Additional research is needed to quantitate the sorption to the
biomass and the influence of biodegradability on stripping.
3. In order to fully understand the removal mechanisms, research
should be conducted to determine whether metabolic intermediates
are produced, or whether the compounds are directly mineralized.
589
-------
REFERENCES
1. Petrasek, A.C., et al. Fate of Toxic Organic Compounds in Wastewater
Treatment Plants. J. Water Pollut. Control Fed. (In press).
2. Petrasek, A.C. and Kugelman, I.J. Metals Removals and Partitioning
in Conventional Wastewater Treatment Plants. J. Water Pollut. Control
Fed. (In press).
3. Method 624, Organics by Purge and Trap. U.S. Environmental Protection
Agency, Environmental Monitoring and Support Laboratory, Cincinnati,
Ohio, 1979.
4. Peltier, W. Methods for Measuring the Acute Toxicity of Effluents to
Aquatic Organisms. EPA-600/4-78-012. U.S. Environmental Protection
Agency, 1978.
5. Neiheisel, T.W., et al. Effects on Toxicity of Volatile Priority
Pollutants Added to a Conventional Wastewater Treatment System. In-
house report, U.S. Environmental Protection Agency, ERC-Duluth, NFTS,
Cincinnati, Ohio, 1982.
6. Neely, W.B., et al. Partition Coefficient to Measure Bioconcentration
Potential of Organic Chemicals in Fish. Environ. Sci. & Tech. 8:
1113-1115, December 1974.
7. Lyman, W.J., et al. Handbook of Chemical Property Estimation Methods
- Environmental Behavior of Organic Compounds. McGraw-Hill, N.Y.,
1982^
8. Chiou, C.T., et al. Partition Coefficient and Bioaccumulation of
Selected Organic Chemicals. Environ. Sci. & Tech. 11: 5, 475-478,
May 1977.
9. Thibodeaux, L.J. Chemodynamics - Environmental Movement of Chemicals
in Air, Water, and Soil. John Wiley & Sons, N.Y., 1979.
10. Liss, P.S. and Slater, P.G. Flux of Gases Across the Air-Sea Interface.
Nature. 247: 181-184, January 1974.
11. Mackay, D. and Leinonen, P.J. Rate of Evaporation of Low-Solubility
Contaminants from Water Bodies to Atmosphere. Environ. Sci. & Tech.
9: 13, 1178-1180, December 1975.
12. Mackay, D. and Wolkoff, A.W. Rate of Evaporation of Low-Solubility
Contaminants from Water Bodies to Atmosphere. Environ. Sci. & Tech.
7: 7, 611-614, July 1973.
13. Dilling, W.L., et al. Evaporation Rates and Reactivities of Methylene
Chloride, Chloroform, 1,1,1-Trichloroethane, Trichloroethylene, Tetra-
590
-------
chloroethylene, and Other Chlorinated Compounds in Dilute Aqueous
Solutions. Environ. Sci. & Tech. 9: 9, 833-838, September 1975.
14. Billing, W.L. Interphase Transfer Processes. II. Evaporation Rates
of Chloromethanes, Ethanes, Ethylenes, Propanes, and Propylenes from
Dilute Aqueous Solutions. Comparisons with Theoretical Predictions.
Environ. Sci. & Tech. 11: 4, 405-409, April 1977.
15. Liss, P.S. Process of Gas Exchange Across An Air-Water Interface.
Deep-Sea Res. 20: 221-238, 1973.
16. Smith, J.H., et al. Prediction of the Volatilization Rates of High-
Volatility Chemicals from Natural Water Bodies. Environ. Sci. & Tech.
14: 11, 1332-1337, November 1980.
17. Matter-Muller, C., et al. Transfer of Volatile Substances from Water
to the Atmosphere. Water Res. 15: 1271-1279, 1981.
18. Roberts, P.V., et al. Volatilization of Organic Pollutants in Waste-
water Treatment - Model Studies. Draft final report. EPA-R-806631.
Project officer H.P. Warner, Mun. Environ. Res. Lab., Cincinnati,
Ohio, January 1982.
19. Matter-Muller, C. et al. Non-Biological Elimination Mechanisms In A
Biological Sewage Treatment Plant. Prog. Wat. Tech. 12: 299-314,
1980.
20. Kyosai, S., et al. Desorption of Volatile Priority Pollutants in
Sewers. Internal report, U.S. Environmental Protection Agency, Mun.
Environ. Res. Lab., Cincinnati, Ohio, December 1980.
591
-------
Energy Use at Municipal Wastewater Treatment Plants
Overview and Case Studies
by
Gary R. Lubin
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
593
-------
ENERGY USE AT MUNICIPAL WASTEWATER TREATMENT
PLANTS-OVERVIEW AND CASE STUDIES
Serious concern for the cost and availability of energy began in
the U.S. in the early 70's. Energy utilization continues to be a major
consideration in the pursuit of affordable and cost-effective solutions
to wastewater and sludge collection, treatment and disposal problems in
the U.S. making it necessary to seriously study ways to maximize the
utilization of energy in the design and operation of wastewater treat-
ment facilities. It is the purpose of this paper to: first provide a
brief review and perspective of the energy problem in the U.S. as it
relates to municipal wastewater treatment and second, to provide a
series of three case studies of innovative energy saving technologies
(1) presently being planned (2), under construction and (3) under
operation.
Information from the 1982 EPA Needs Survey (1) which provides some
first order approximations regarding number, type, costs, etc. of
municipal wastewater treatment facilities, is presented in Table 1.
According to the survey, there were a total of 15,425 municipal waste-
water treatment plants operating in the U.S. in 1980 designed to treat
a flow of 1.34 X I08m3/d (35.3 bgd) (actual treated flow equalled 1.02 X
108m3/d (26.9 bgd)) from a service population of 163,000,000 (71%
served). The survey projected that a total of 21,011 municipal
wastewater treatment plants would be operational by the year 2000 with
design capacity of 1.62 X lO^m^/d (42.7 bgd) to handle wastewater from
a sevice population estimated to increase to 257,000,000 (92% served).
This represents an increase of 36% in number of operating plants, 21% in
design flow capacity and 58% in service population. The net increase
of 5,586 operational plants reflects about 1,480 plants to be abandoned,
446 plants under construction (as of 1980) and 6,620 plants to be built
by the year 2000.
Overall effluent quality is also projected to improve with vastly
reduced use of primary and advanced primary treatment - down to a total
of 12 plants treating 5.54 X lO^mS/d (l,464mgd); and an overall increase
of 8,693 in number of secondary, advanced secondary, advanced wastewater
tertiary treatment, and no discharge facilities to treat an attendant
increase in flow of 4.69 X 107 m3/d (12,400 mgd).
It is clear that energy expended for the treatment of municipal
wastewater in the U.S. will necessarily continue to increase for two
basic reasons: increase in actual number of facilities and amount of
wastewater treated and increase in the overall level of effluent
quality.
According to the EPA publication, "Energy Conservation in Municipal
Wastewater Treatment," (2) in 1977, about 150.73 X 1012kJ/yr (142.87 X
10^2 Btu/yr) were used in 1977 for treatment of municipal wastewater in
publicly owned treatment works. This amounted to 0.17% of the annual
U.S. energy use estimated to be 86 quads (1 quad = 1.055 EJ (1.0 X
594
-------
Ln
^D
Ul
TABLE 1
NUMBER, TYPE, AND SIZE OF PUBLICLY OWNED MUNICIPAL WASTEWATER TREATMENT
FACILITIES IN THE U.S. IN 1980 AND PROJECTED FOR THE YEAR 2000(1)
CATEGORY OF TREATMENT
1980
Facilities
Count
% of total
Act. '80 flow*
% of total
Design flow*
% of total
Year 2000
Facilities
Count
% of total
Design flow*
% of total
Change
Count
% increase
Design flow*
% increase
No
Discharge
1600
10.4
491
1.8
759
2.2
2736
13.0
1540
3.6
+1136
+71.0
+781
+102.9
Primary
1036
6.7
2474
9.2
3047
8.6
3
<0.1
220
0.5
-1033
-99.7
-2827
-92.8
Advanced
Primary
2083
13.5
2825
10.5
3391
9.6
9
<0.1
1244
2.9
-2074
-99.6
+2147
-63.3
Secondary
7946
51.5
11,008
40.9
14,291
40.6
11,748
55.9
17,474
40.9
+3802
+47.8
+3183
+ 22.3
Advanced
Secondary
2529
16.4
9376
34.9
12,288
35.6
5845
27.8
19,288
45.3
+3316
+131.1
+6729
+ 53.6
AWT
Tertiary
231
1.5
714
2.7
1215
3.4
670
3.2
2922
6.8
+439
+190.0
+ 1707
+140.5
Total
15,425
100
26,891
100
35,265
100
21,011
100
42,691
100
+5586
+ 36.2
+7426
+21.1
* All Flows in mgd, 1 mgd = 3785 m3/d
-------
1015 Btu)) at the time. For 1990, the report projected that 271.02 X
1012 kJ/yr (256.91 X 1012 Btu/yr) would be required for wastewater
treatment or 0.23% of the national energy use projected to be 114
quads. A more recent EPA report, "Energy Requirements of Present
Pollution Control Technology" (3) indicates operating energy required
for municipal wastewater treatment plants was 284.85 X lO15^ |
-------
TABLE 2. NET PRIMARY ENERGY REQUIREMENTS FOR THE OPERATION OF PUBLICLY
OWNED MUNICIPAL WASTEWATER TREATMENT FACILITIES IN THE U.S. IN
1980 AND PROJECTED FOR THE YEAR 2000
Ibgd = 3.785 X 106 m3/d
IBtu = 1.055 kJ
1980 2000 % Increase
No. of Wastewater 15,425 21,011 36
Treatment Plants
Design Flow (bgd) 35.3 42.7 21
Population Served 163,000,000 257,000,000 58
Energy Required 245 436 78
(10*2 Btu)
National Energy Budget
(quads) 87 140 61
% Municipal Wastewater
Energy of National 0.28 0.31 11
Energy Budget
597
-------
Ln
vo
00
X
Ul
Q
~ 3
Q.
LU
D LABOR INDEX
A POWER INDEX
71
73 75 77 79
YEAR
81
FIGURE 1. RELATIVE LABOR AND POWER COST INCREASES (7)
-------
same operation and maintenance cost index information, in 1967, the
cost of power comprised 19.5% (8) of total operation and maintenance
costs in a wastewater treatment plant and has increased to 26 - 27% as
of 1982.
Recent U.S. Department of Energy projections indicate that the
costs of power and fuel will continue to rise. For example, in the
commercial sectors, the cost of electricity is projected to increase to
$20.00/106kJ ($21.10/106 Btu) by 1990, a 23% rise compared to 1981
prices. In a similar fashion, the cost of natural gas is projected to
increase to $5.70/lo6kJ ($6.01/106 Btu), a 51% increase.
Information from the 1980 EPA Needs Survey (10) indicates that
about $3.3 billion (1980 dollars) were expended for operation and main-
tenance of 15,250 publicly owned municipal wastewater treatment plants
estimated to be treating an actual flow of 0.97 X 103m3/d (25.7 bgd)
(This is equivalent to 9tf/m3 treated (35^/1000 gal)). The annual energy
requirement for operation and maintenance of these facilities is esti-
mated to be about 248 X 1012kJ (235 X 1012 Btu) or about 1.45 X 1010 kWh
for power (65% of the total) and 8.68 X 1013kJ (8.23 X 1013 Btu) for
fuel (35% of the total) (4). Applying adjusted energy cost information
to these figures, energy costs are estimated to be about $0.69 B (1978
dollars), which is 26% of the total. It is fair to conclude that, on
the average, energy costs comprise from 20%-30% of the total budget for
operation and maintenance.
As a case in point, in 1982, the City of Cincinnati, Ohio (11)
expended $6,535,000 for energy, which amounted to 20.4% of a total
budget of $31,992,000 to operate and maintain wastewater treatment
facilities. About 39% of the Cincinnati energy budget is directed to
wastewater collection and treatment. In other specific cases, energy
costs can be much higher.
Energy usage and cost estimates for operation and maintenance of
municipal wastewater treatment facilities in the U.S. are useful for
purposes of problem definition; but from the standpoint of targeting
conservation, the energy requirements of individual unit processes and
components is of fundamental importance. An estimate of energy used
for plant operation is shown in Table 3 (4) for activated sludge treat-
ment of municipal wastewater. Energy used to operate the treatment
plant includes: electrical energy and heat energy for digester heating,
building heat, sludge incineration and hauling of sludge to land dis-
posal. Electrical energy represents 63% - 76% of the energy used for
plant operation. Building heat requirements are estimated at only 5%-
10% of the operating energy. Approximate estimates for the electrical
energy requirements for various unit processes is shown in Table 4(4).
At the 3785 m3/d (1 mgd) size, a trickling filter requires 80% more
energy than a primary plant; and the activated sludge plant requires
roughly three times as much energy as the primary plant. An economy of
scale is apparent whereby 3.8 X I05m3/d (100 mgd) primary, trickling
filter and activated sludge plants respectively utilize about 50%. 57%,
76% of the unit electrical energy consumption as with a 3785 m3/d (1
mgd) facility(4).
599
-------
TABLE 3. ESTIMATED OPERATING ENERGY BUDGET FOR MUNICIPAL
WASTEWATER TREATMENT PLANTS (kwh/mg) (4)
Size of Plant
1 mgd 10 mgd 100 mgd
Electrical Energy
Digester Heating
Building Heat
Sludge Hauling
Sludge Incineration
Total
1100
168
160
20
—
1448
893
168
59
—
230
1350
835
168
86
—
230
1319
In terms of kilowatt-hours per million gallons of wastewater treated. Es-
timates are based on activated sludge plants with anaerobic digestion. Sludge
disposal is by incineration at the 3.8X104 m3/d (10 mgd) and 3.8X105 m3/d (100
mgd) sizes by hauling dewatered sludge 64.4km (40 miles) one-way to land
spreading at the 3785 m3/d (1 m9d) size. Energy recovery is by generation of
electrical power with 1C engine using digester gas as fuel. The waste heat
from the 1C engines is used to heat the digesters. Energy wheels are utilized
to conserve building heat. Img = 3785m3
600
-------
TABLE 4. ESTIMATED ELECTRICAL ENERGY CONSUMPTION FOR OPERATION
OF MUNICIPAL WASTEWATER TREATMENT PROCESSES (kWh/mg)*(4)
Preliminary Treatment
Influent Pumping (30 ft TDH)**
Primary Sedimentation
Reci rculation Pumping
-Trickling Filters
(Qp/Q = 3.0)
-Activated Sludge
(Qp/Q = 0.5)
Diffused Air Aeration
(AEF = 6%)
Mechanical Aeration
(2 Ib 02/hp-hr)
Final Sedimentation
Chi ori nation
Sludge Pumping
Gravity Thickening
Air Flotation Thickening
Anaerobic Digestion
Vacuum Filtration
Incineration
Lights and Misc. Power
1 mgd
18.5
153.0
30.6
183.0
45.0
532.0
404.0
30.6
0.7
2.7
10.2
70.0
123.6
58.5
65.0
57.0
Size of Plant
10 mgd
6.6
145.1
12.2
174.0
42.3
532.0
404.0
12.2
0.7
2.7
2.0
60.8
45.6
34.6
28.7
21.0
100 mgd
2.5
129.3
7.3
155.2
31.3
532.0
404.0
7.3
2.7
2.7
0.4
46.9
19.1
36.4
25.9
24.0
*1 mg=3785m3
**TDH = total dynamic pumping head, Qr/Q = return flow rate/average daily
flow rate
AEF = aeration efficiency in percent for diffused air and Ib
02/hp-hr for mechanical aeration
601
-------
In activated sludge plants, about 57% of the electrical energy is
used for aeration, about 20% for pumping influent and return flows and
6% for mixing and heating the anaerobic digester.
The radically changing relationships in cost and availability of
energy resources over the past decade have provided the driving
force to seek energy saving solutions to wastewater problems at the
national level. The Clean Water Act of 1977 (PL95-217), as amended by
the Municipal Wastewater Treatment Construction Grant Amendments of
1981 (PL97-117), contains a number of provisions to encourage the
development and implementation of innovative and alternative (I/A)
wastewater technology that provide for greater use of energy recovery
and conservation (7, 13).
In development of the Clean Water Act, the Congress recognized
that energy self sufficiency is possible through use of alternate
energy sources in publicly owned treatment works constructed with
Federal support. In fact, a 115% cost-effectiveness preference was
established which encourages construction of I/A technology systems
in order to reduce the demand for non-renewable energy resources over
the long term.
The EPA's I/A Technology Program widens the range of available
solutions to address wastewater and sludge problems. Since the incep-
tion of the I/A Technology Program in October 1978, over 2,000 supporting
grants have been awarded by the EPA to municipalities which have adopted
I/A technology solutions (13, 14). Over 25% of the innovative tech-
nology projects funded resulted in direct savings of net primary energy
and over 10% of the alternative technology projects funded were for
energy recovery or conservation. These have included: co-disposal of
sludge and refuse; anaerobic sludge digestion with productive use of
recovered methane; self sustaining and starved air sludge combustion;
use of alternate energy such as active and passive solar energy including
photovoltaic cells, windmills, low head hydroelectric, and heat pumps;
use of efficient aeration devices such as draft tube aeration; use of
energy efficient unit processes such as inchannel clarification in an
oxidation ditch.
Energy is also conserved indirectly by utilizing energy efficient
I/A treatment technology such as land application and subsurface dis-
posal systems. It has been previously estimated (13) that 17.3 X 10^
kWh/yr in energy requirements could be saved through adoption of I/A
technology in new construction through the EPA Construction Grants
Program. This is 7%- 8% of the estimated wastewater treatment energy
budget for 1980.
In addition to these savings, energy will be conserved through
future retrofit modifications to existing treatment facilities, improved
energy management in ongoing operations and a projected increase in the
use of trickling filters, oxidation lagoons, etc. as secondary treatment
technology in certain cases.
602
-------
The remainder of this paper presents three examples, or case his-
tories, of alternative energy technologies at municipal wastewater
treatment plants:
1. Use of low-head hydroelectric generation at Bonney Lake,
Washington
2. Use of active/passive solar, heat pumps at Wilton, Maine
3. Use of windmill derived power at Southtown, N.Y.
BONNEY LAKE. WASHINGTON (15)
BACKGROUND
Wastewater is generated from residences and businesses around Lake
Tapps near the City of Bonney Lake, Washington. Lake Tapps is a storage
reservoir for the White River Hydroelectric Plant. According to initial
planning efforts, wastewater collected from the area is to be lifted
over a ridge and dropped approximately 122 m (400 ft) vertical distance
over approximately 1,097 m (3,600 ft) horizontal distance to the Puyal-
lup River flood plain after which it will flow by gravity to an existing
sewage treatment plant at Sumner, Washington.
Initially proposed was use of a gravity sewer interceptor to
transmit flow to another treatment plant site on the floor of the
Puyallup Valley at Alderton, Washington. This was not considered to be
environmentally acceptable by the residents of the region, who preferred
routing the wastewater to the City of Sumner Wastewater Treatment
Plant. The Sumner option has one disadvantage: it is energy-intensive
and requires a large lift station to pump wastewater over a hill and
into the valley. The energy necessary for pumping provided an incentive
to find a way of reducing energy costs.
SYSTEM DESCRIPTION
The wastewater collection area lies near a glacially-formed escarp-
ment rising from the Puyallup River flood plain. The interceptor
crosses the escarpment en route to the Sumner Regional Wastewater
Treatment Plant. Various methods were considered for dissipating
energy across the escarpment. Deep-drop manholes presented difficult
construction and maintenance problems. A pressure sewer with energy
dissipation features presented erosion, cavitation, and foaming pro-
blems. Reclaiming energy with a turbine generator was the most cost-
effective solution with energy revenues offsetting the lift station
energy costs. This system would provide a shelter against ever-increas-
ing lift station energy costs. Under the EPA innovative and alternative
technology program, wastewater transmission and treatment systems that
effect significant reduction in net power consumption are encouraged.
The Lake Tapps energy recovery station fulfilled these criteria and was
approved by EPA in December 1980.
603
-------
Planning and preliminary concept design for the Bonney Lake project
has been conducted by the firm Philip M. Botch, Inc., Bellevue, Washing-
ton. Design of this innovative project was underway; however, due to
recent problems of implementing a regional alternative, the project may
not reach construction.
COMPONENT DESCRIPTION AND DESIGN CRITERIA
The proposed innovative alternative includes the use of 1,095 m
(3,592 ft) of 45.7-cm (18-in) ductile iron (DI) penstock (hydrostati-
cally-pressurized force main) and a hydroelectric generating station
that would tie directly into the utility power grid. The generation
station would include a two-jet impulse turbine and induction generator.
A schematic of the project is shown in Figure 2. Characteristics and
performance information follows:
Penstock diameter
Penstock length
Verticle drop
Turbine/generator rating
Average flow -- 1982
Average flow -- 2002
45.7 cm
1,095 m
112.8 m
125 kW
2,575
8,325 m3/d
Yearly power production -- 1982
Yearly power production -- 2002
217,800 kWh
697,600 kWh
Value of power in 1982 at $0.04/kWh
Value of power in 2002 with a 9 1/3 per-
cent annual compounded escalation rate
Turbine type
Number of nozzles
Governor
Generator type
Method of operation
Type of plant
$ 8,712
$166,132
Pelton-impulse
One
None
Induction
Automatic, unattended
"Run of river"
604
-------
18" Pressure Sewer
24" & 18" Gravity
3330' Vitrified Clay Pipe
18" Penstock
36" Gravity
15,000' Vitrified Clay Pipe
Comminutors
(2)
446.0' , .
Forebay
Pumps (1) Spare
Motorized Valve (TSV)
Nozzle
Hydraulic Safety
By-Pass Valves
- Manual Safety
Bypass Valve
/-—El. 80.0'
To Treatment Plant
Figure 2.
Schematic-energy recovery system.
Source: P.M. Botch and Associates, Inc.
-------
A preliminary treatment station consisting of a comminutor, grit
collector, and screen, would be located in the interceptor ahead of the
penstock. The turbine would have an automatic jet deflector to prevent
overspeed, and a surge-relief valve would protect against inadvertent
flow surges. A blowout rupture disc is provided in the event the surge
relief valve malfunction. If the turbine is down for repair, bypass
throttling valves will automatically maintain the proper water level in
the forebay.
A special variable opening nozzle would be designed to substitute
for the nozzle commonly used in a Pelton turbine. The nozzle commonly
used in a Pelton turbine employs a controlled needle opening. The
small annular space around the needle at low loads and the proceeding
straightening vanes presented potential clogging problems. The nozzles
would be fixed in an open position and operated without needles. If the
project is implemented, the special nozzle will be tested in a hydraulic
laboratory before incorporating it into the turbine design.
ENERGY SYSTEM PERFORMANCE DATA
The energy analysis indicates that the five lift stations will
require 137,984 kWh/yr at startup (2,575 m3/d or 0.68 mgd)and 461,925
kWhr/yr in the year 2000 (8,325 m3/d or 2.19 mgd). The generating
station will produce 218,665 kWh/yr and 704,230 kWh/yr at these same
flows. Therefore, the net energy production of the proposed innovative
alternative is 80,681 kWh/yr at start up and year 2000, respectively.
SOUTHTOWN SEWAGE TREATMENT CENTER (WOODLAWN, NEW YORK) (16)
BACKGROUND
The new wastewater treatment facilities at the Southtown Sewage
Treatment Center in Woodlawn, New York, will be powered by a wind turbine
generator. The Southtown facility is located on the shore of Lake
Erie, near Buffalo, New York, which is in an area of strong persistent
winds.
Initial construction of the treatment facility began at Southtown
in the fall of 1977 with support from the EPA Construction Grants
Program, and all construction, including the innovative wind turbine
generator system, is expected to be finished in Spring 1984. Design
flow for the Southtown Sewage Treatment Center is 60,560 m^/d (16 mgd).
Major unit processes include pure oxygen activated sludge, chemical
addition for phosphorus removal, sand filtration, and chlorination.
Sludge will be incinerated. The effluent will be discharged to Lake
Erie.
WTG Energy Systems, Inc., Buffalo, New York, developed and designed
the wind power system. URS Engineers, Montvale, N.J., is the designer
of the treatment plant.
606
-------
The use of wind-generated electricity at the Southtown Sewage
Treatment Plant will place Erie County in a unique position as one of
the first commercial installations utilizing a wind generator at a
municipal wastewater treatment facility in the U.S. The only other
known application of windmills is at Livingston, Montana where four 25
kW rated Carter Wind System (Burkburnett, Texas) units have been operat-
ing since December 1981 to provide the wastewater treatment plant with
power.
When the Southtown Sewage Treatment Center reaches design oper-
ation, it is estimated that the power utilization will be about
12,570,000 kWh/yr. The use of one 600 kW wind turbine generator will
provide from 980,000 to 1,215,000 kWh/yr depending upon wind regime.
Based on a cost-effectiveness analysis, net annual power cost savings
from the wind turbine generator system are estimated to be a minimum of
$27,000 (October 1982 $).
SYSTEM DESCRIPTION
One 600-kW wind turbine generators (model MP1-600, supplied by WTG
Energy Systems, Inc.) will provide the power. A typical wind turbine
generator is shown in Figure 3.
The model MP1-600 consists of: a 38.1 m (125 ft) diameter, three
blade upwind rotor driving a 600 kW, 2400-V, 60 cycle AC generator
through a 1 to 48 ratio speed-increaser; and a rotor, gear drive assem-
bly, generator and hydraulic system mounted on a rotating base and
enclosed within a machine cabin. This assembly is mounted on top of a
pinned truss steel tower, and is yawed by a hydraulically-controlled
bull-gear unit that provides 360° positioning to ensure maximum upwind
efficiency of the rotor.
The rotor blades are a fixed pitch GA(w)-l airfoil design incorpor-
ating blade-tip drag flaps that are automatically activated to stop the
rotor under conditions of excessive wind speed, vibration, or any
system malfunction such as icing. This "fail-safe" system permits
unattended operation of the wind turbine, and prevents any aggravated
system failures.
Electrical generation begins at wind velocity of 3.0 m/s (10 mph)
at hub height. The rated generator output of 600 kW is achieved at 13.4
m/s (30 mph), and the maximum generator output of 750 kW is reached at
a wind velocity of 15.2 m/s (35 mph). Shutdown occurs at 24.6 m/s (55
mph). The survival wind velocity is 67.1 m/s (150 mph). Throughout
the operating range, the rotor of the MP1-600 system will maintain a
constant 25 rpm for the production of constant frequency 60-Hz power.
The wind regime at Southtown is expected to be 5.5 m/s (12.4 mph)
providing an output of 980,000 kWh/yr for the wind turbine system.
The control unit of the MP1-600 system is a solid-state micropro-
cessor located in the control house at the base of the tower. This
607
-------
Typical Wind Turbine Generator System
WTG Energy Systems, Inc.
Figure 3.
Source:
608
-------
preprogrammed computer continually monitors and controls all generating
and operational parameters including wind velocity and range; and the
maximum possible power output is introduced into the utility grid
system at precision-controlled voltage and frequency. Even if the
MP1-600 system is the only generator on the transmission line system,
precise voltage and frequency will still be maintained.
COSTS AND REQUIREMENTS FOR OPERATION AND MAINTENANCE
The capital and installation costs (October 1982 $) for the wind
turbine generator system, consisting of one 600-kW unit, are as follows:
One 600 kW wind turbine generator $1,100,000
Foundation/Erection $ 186,000
480-V distribution (305 m) $ 58,000
Testing $ 3,350
Total installed cost $1,347,350
The estimated manpower requirements are based on operating experi-
ence from other WTG, Inc. installations. The system is designed for
unattended operation; however, the system will require an annual alloc-
ation of approximately 78 man-hours for scheduled maintenance. The
estimated annual maintenance requirement is based on data obtained from
a wind analysis program conducted for the Southtown facility indicating
annual machine availability at 90 percent (minimum) and annual machine
operating time at 5,804 hr (66 percent of the year).
The estimated operation and maintenance requirements and costs are
as follows:
Lubricants and spare parts $4,500
Labor $2,340
Total annual operating costs $6,840
WILTON, MAINE USE OF INTEGRATED ALTERNATE ENERGY SYSTEMS (17)
BACKGROUND
The Wilton, Maine wastewater treatment plant was designed by Wright-
Pierce Architechts and Engineers, Topsham, Maine. The 1,700 m3/d (0.45
mgd) facility began operation in September 1978 and was one of the first
municipal wastewater treatment plants in the U.S. to use alternative
energy technology. A research project supported by the Municipal Envi-
ronmental Research Laboratory was conducted from May 1977 to March 1981
609
-------
to monitor and evaluate the performance of the energy systems installed
at the Wilton treatment plant. As of March 1980, actual flow treated
at the plant was 450 m3/d (0.12 mgd) or 26% of design.
A primary objective of the design of the Wilton facility was to
reduce net primary energy consumption by use of (1) alternate energy
sources, (2) less energy intensive process equipment, (3) an overall
architectural and engineering energy saving design.
SYSTEM DESCRIPTION
The Wilton Wastewater Treatment Plant is located at 45° north
latitude. Monthly average ambient temperatures range from a low of -
4.4°C in January to a high of 21°C in July.
The Wilton plant was totally enclosed in two structures, and unit
processes were built in close proximity to each other to reduce exposed
surface area and to reduce length of hydraulic runs. Flow by gravity
was used wherever possible. The control building was well insulated,
and zone heating is practiced. Concrete block and brick with interspace
insulation were used for construction materials to provide a large heat
retaining mass.
The roof design provides for retention of snow as a natural
insulator. The building was built into a hillside with little northern
exposure to minimize outside surfaces.
In order to reduce the need to import energy, active and passive
solar energy producing systems were designed. A southern exposure was
used to maximize production. The primary purpose of the active solar
system is anaerobic digester heating but is also used for building heat
and the hot water supply. Passive solar is used to provide heating of
the clarifier room.
The heating system also included: a water-to-water heat pump to
extract energy from the 7° - 10°C effluent; a digester gas fired boiler;
and air-to-air heat exchanger to recover 60% of the heat from exhaust
ventilation system air to preheat incoming cold air; and electrical
generator cooling jacket heat recovery. The anaerobic digester system
consisted of primary and secondary digesters with attendant high and
low pressure gas recovery, storage and utilization. The design approach
intended to provide active solar digester heating thus freeing digester
gas to be stored in the form of a compressible, combustible high grade
energy source for use in a boiler for building heating, running the
electric generator and long term storage.
Figure 4 shows the plant process flow diagram and design criteria.
Wastewater is lifted into the plant by use of screw pumps which use
less energy than conventional pumps. Wastewater flow is by gravity
throughout the remainder of the plant. Pretreatment is accomplished by
comminution and grit removal. Rotary screens are used to remove solids
and secondary treatment is provided by rotating biological contactors
610
-------
1 SCREW PUMPS
2 GRIT CHAMBER
3 COMMINUTOR
4 BAR SCREEN BY-PASS
5 FLOW MEASURING & SAMPLING
6 PRIMARY SCREENS
7 ROTATING BIO-CONTACTORS
8 SECONDARY CLARIFIERS
9 FLOW MEASURING & SAMPLING
10 CHLORINE CONTACT CHAMBER
11 PLANT EFFLUENT
12 SPRAY IRRIGATION
13 PRIMARY SLUDGE
14 SECONDARY SLUDGE
15 SECONDARY SKIMMINGS
16 SLUDGE HOLDING
17 SLUDGE TRANSFER
18 SLUDGE HEATER
19 SLUDGE RECYCLE PUMPS
20 ANAEROBIC SLUDGE DIGESTERS
21 SLUDGE HOLDING
22 SLUDGE DEWATERING PUMP
23 DEWATERING UNIT
24 DEWATERED SLUDGE
25 HYPOCHLORITE GENERATION
26 HYPOCHLORITE STORAGE
27 METERING PUMPS
DESIGN CRITERIA
Quantity of sewage
0.02 mVs
Influent BOD
200 mg/1 (340 kg/d)
Influent suspended solids
2OOmg/l (340 kg/d)
Effluent BOD
20mg/l (34 kg/d): 90% removal
Effluent suspended solids
20mg/l (34 kg/d): 90% removal
Sludge quantity to digesters
9.5 m3/d ol 3.5% solids
Methane yield
110 to 125 mVd
Methane heat value
22,400 kJ/m3or 2.4 to 2.7 GJ/d
Figure 4. Wilton, Maine Process Flow Diagram (17)
611
-------
which use less energy as compared to activated sludge processes.
Secondary clarifiers provide final solids removal. Combined primary
screened and secondary settled solids are anaerobically digested prior
to dewatering and land application.
A conceptual energy flow diagram is shown in Figure 5 which
illustrates the unique interdependency of energy sources and users at
the Wilton plant. In the design, use of solar energy is maximized as
the primary energy source; digester gas is the intended secondary energy
source; and recovered effluent heat is intended as a back-up and final
supplementary source. The generator was to provide stand-by heating in
the event of a power failure and to provide power for general use when
excess methane became available.
The active solar system is a hydronic type comprised of flat plate
collector panels mounted as part of the building roof, an ethylene
glycol/water collection loop, a heat exchanger and storage system. The
collector panels cover 139.4 m2 (1500 ft2) gross area and consist of an
extruded aluminum plate and frame, copper tubing to transport the col-
lector fluid and two panes of low iron content tempered glass. The
backs of the collectors are insulated with 114 mm thick rigid foam
board insulation. The antifreeze solution is pumped through the panels
and heated to 48.9°C to 60°C (120°F - 140°F). Energy from the heated
ethylene glycol is exchanged with the plant's circulating hot water
system. The array of 54 double glazed panels face 2° west of south at
an angle of 60° to the horizontal. The resultant effective collection
area is 119.5 m2 (1,286 ft2).
The passive solar system is built into the south wall at two levels
in order to provide heating and lighting to the clarifier room. The
array consists of 83.2 m2 (812 ft2) of glazed insulated, translucent
fiberglass panels. These panels are also oriented 2° west of south at
60° to the horizontal. The effective collection area is 75.4 m2 (812
ft2). The transmissivity of the panels is 66%. Panel construction con-
sists of four layers of fiberglass sheeting supported with aluminum
braci ng.
The water to water heat pump is used for hot water heating when
digester gas is not available and solar production is inadequate. Due
to problems with anaerobic digestion including start up difficulties
and operation at under loaded conditions, and due to the fact that
solar energy proved to be inadequate, the heat pump was the major
source of heating during winter. The heat pump recovers heat from
treatment plant effluent prior to discharge. Specification information
for the heat pump is shown in Figure 6.
ENERGY AUDIT FINDINGS
Projected energy requirements for building heat, digester heating
and electrical equipment serve as the basis for evaluating the actual
observed performance of the respective systems. These are summarized
in Table 5. Based on an equivalent energy comparative analysis, 86% of
612
-------
1 PROPANE
| (STANDBY)"!
PLANT
EFFLUENT
t
ELECTRIC^!
POWER ^
t
HYDRONIC
SOLAR
COLLECTORS
HEAT
EXCHANGER
METHANE
BOILER
ELECTRIC
GENERATOR
SOLAR
STORAGE
L-ELECTRIC
POWER
HEAT
DISTRIBUTION
SYSTEM
ELECTRIC POWER
(SUPPLEMENTARY)
HEAT RECOVERY
Figure 5. Conceptual Energy Flow Diagram for Uilton, Maine (17)
-------
FIGURE 6 (17)
HEAT PUMP SPECIFICATION DATA
A. Manufacturer: Carrier
B. Total Heat Output Capacity: 320,000 Btu/hr
C. Condenser side:
1. 40 gpm heating system water.
2. Leaving water temperature: 130°F.
3. Entering water temperature: 114°F.
4. Water pressure drop: 13.5 ft.
5. Refrigerant saturated discharge temperature: 140°F.
6. Electric input at full load: 28.4 KW.
7. COP = Heat Output = 3.3
Electrical Input
D. Evaporator Side:
1. Fluid: Sewage effluent with 10 ppm chlorine residual and minimal
suspended solids.
2. Fluid Flow: 60 gpm
3. Entering Water Temperature: 50°F.
4. Leaving Water Temperature: As required.
5. Maximum water pressure drop: 5 PSI
E. Refrigerant: R-22
F. Saturated suction temperature: 36°F
614
-------
TABLE 5 (17)
PROJECTED ENERGY REQUIREMENTS SUMMARY
Bldg. Heating
Electrical (kWh)
Month
Jan.
Feb.
March
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
ANNUAL
and
Ventilating
(GJ)
78.85
74.57
53.27
27.70
4.26
0
0
0
0
14.91
38.37
53.27
345.20
Digester
Heating
(GJ)
33.43
31.09
31.92
27.76
24.72
20.66
17.63
17.86
18.82
22.81
25.92
30.51
303.13
Total
Heating
(GJ)
112.28
105.66
85.19
55.46
28.98
20.66
17.63
17.86
18.82
37.72
64.29
83.78
648.33
Process
Equipment
19,860
19,860
19,860
19,860
19,860
19,860
19,860
19,860
19,860
19,860
19,860
19,860
238,320
Heating and
Ventilating
Equipment
14,560
12,850
10,460
8,340
6,560
6,550
6,540
6,540
6,540
6,550
9,370
11,710
106,570
Lighting
520
520
520
520
520
520
520
520
520
520
520
520
6,240
Total
Electrical
34,940
33,230
30,840
28,720
26,940
26,930
26,920
26,920
26,920
26,930
29,750
32,090
351,130
-------
the total was projected for electrical energy leaving 14% for building
and digester heating. Of significance is that 58% of the electrical
energy requirement was projected for operation of process equipment.
Table 6 indicates the projected sources of energy to satisfy the
heating energy demands shown in Table 5. Table 7 presents the actual
energy used and produced during the ten month study. All data for
energy users was monitored at the point of use. Distribution losses in
addition to accuracy in monitoring account for the differences in total
energy produced and total utilized.
Table 8 summarizes actual power used and actual produced heat
energy as monitored during the study. Total power used over the ten
month period equalled 258,440 kWh which was only 87.5% of the anticipated
use . At an average flow of 454 m3/d (0.12 mgd), this is equivalent to
1.79 kWh/m3 (6,759 kWh/mg) which is a rather high rate of use. Total
energy used at the facility was 3,403 GJ, 84% of which was for electric
power. As actual flow treated reaches design capacity, the energy
requirements will approach a more reasonable figure of 0.48 - 0.50 kWh/m"3
(1800 - 1900 kWh/mg) treated.
Shown in Figure 7 is a bar chart with the total energies produced
by each heating system component during the ten month study.
Figure 8 illustrates estimated design and observed actual energy
use and production on a system component basis.
Projected and actual percent energy source contribution for heating
is presented in Table 9. It is notable that the heat pump provided
60% of the total annual energy produced by all five systems. During
the months of October 1977 to March 1978, the heat pump provided the
primary source of heating energy. The coefficient of performance (COP)
of the heat pump varied with the temperature of the effluent. Table 10
presents a summary of heat pump performance information. The average
COP observed during the study was 2.9.
The only months during which the actual collected energy by the
active solar system equalled or exceeded the projected total were
September and December 1981. The calculated long-term collection
efficiency averaged 23% which is the net energy collected divided by
total incident energy available. This is significantly lower than
anticipated. The total solar energy collected was 122 GJ which was
only 64% of that estimated. However, because overall actual heating
demand was lower than expected, the active solar energy systems provided
82% of its expected share of energy. Reasons offered for the observed
lower collection efficiency included:
1. Data/instrumentation error.
2. Collector heat loss factor
a. Inadequate thermal isolation.
b. Possible convective losses between the absorber plate
and the rigid insulation.
616
-------
TABLE 6 (17)
PROJECTED HEATING ENERGY SOURCES (GJ)
Passive
Solar
Active
Solar
Emergency
Generator
Methane
Boiler
Heat
Pump
Total
Heating
Month Contribution
Jan.
Feb.
March
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
ANNUAL
12.5
15.6
13.9
7.0
0
0
0
0
0
2.2
8.4
10.0
69.6
Contribution
10.23
14.60
17.74
15.64
15.14
14.90
17.12
17.86
18.82
19.26
10.98
8.18
108.47
Contribution
1.2
1.2
1.2
1.2
1.2
1.2
0.5
0
0
1.2
1.2
1.2
11.3
Contribution
15.25
14.13
15.25
14.69
12.67
4.60
0
0
0
15.09
16.71
15.25
123.64
Contribution
73.19
60.16
37.12
17.01
0
0
0
0
0
0
26.99
49.18
263.65
Contribut
112.37
105.69
85.21
55.54
29.01
20.70
17.62
17.86
18.82
37.75
64.28
83.81
648.66
-------
TABLE 7 (17)
ACTUAL HEATING ENERGY CONTRIBUTION SUMMARY - USERS AND PRODUCERS (GJ)
USERS JUNE JULY AUGUST SEPT OCT NOV DEC JAN FEB MARCH
Digester Heating 9.774 7.603 11.561 19.107 22.335 21.177 31.363 33.531 22.917 33.624
Bldg. Htg/Ventilating 0.23 .06 .03 0.32 3.51 12.67 36.91 46.12 39.75 29.44
TOTAL 10.01 7.66 11.59 19.43 25.85 33.85 68.27 79.66 62.67 63.07
PRODUCERS
Active Solar 10.315 8.932 12.907 25.821 10.663 8.225 11.341 7.453 13.254 14.067
Passive Solar 0000 2.93 6.82 10.08 11.27 13.41 11.07
Generator Heat Recovery 0.327 1.047 0.445 0.457 0.345 0.548 1.192 1.065 1.333 1.665
Boiler 5.760 0.007 0.020 0 0.045 0 12.053 8.292 0.007 0.017
Heat Pump 0.559 0.005 3.784 3.057 32.594 31.653 52.778 73.548 64.159 64.728
TOTAL 16.96 9.99 17.16 29.34 46.58 47.25 87.44 101.63 92.16 91.55
-------
TABLE 8 (17)
TOTAL ELECTRICAL ENERGY USAGE
AND HEATING ENERGY PRODUCED
Month
January
February
March
April
May
June
July
August
September
October
November
December
TOTAL
Measured
Power
(kWh)
29,600
29,920
30,200
-
-
22,680
22,120
26,200
21,000
25,840
23,000
27,880
258,440
Equivalent Elec.
Heat Energy
(GJ)
328
331
335
-
-
251
245
290
233
286
255
309
2863
Produced
Heat Energy
(GJ)
102
92
92
-
-
17
10
17
29
47
47
87
540
619
-------
100- •
OS 90- •
Q
UJ
<
IX
UJ
80- •
>-
O
cr
UJ
u] 70
o
§ 60--
50--
40- -
w -^n
t? 3O
H 20--
10 ••
•I ACTIVE SOLAR
E3 PASSIVE SOLAR
EZ3 HEAT PUMP
023 BOILER
HD GENERATOR
MBTUx 1.0551 = GJ
JUNE JULY AUG SEPT OCT NOV DEC
JAN
FEB
MAR
Figure 7. TOTAL ENERGY CONTRIBUTION BY EACH HEATING SYSTEM COMPONENT (17)
-------
p 80
— 60
1 40
S
S 20
I 0-
ENERGY USERS
Ib . . .uli
JFMAMJJASOND
ENERGY PRODUCERS
g
2 20
K
£ "°
5 0
Hill
JFMAMJJASOND
25
20
15
10
1
20
ll III
J F M A M J J ASOND
JFMAMJJASOND
80
60
— 40
a.
20
I
20
15
10
5
I
JFMAMJJASOND
JFMAMJJASOND
u 2.0
UJ
-------
TABLE 9 (17)
PROJECTED AND ACTUAL PERCENT ENERGY SOURCE CONTRIBUTION FOR HEATING
Month
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
ANNUAL
Passive
Solar
Proj. Act.
11
15
16
13
0
0
0
0
0
6
13
12
11
11
15
I?.
-
-
0
0
0
0
6
15
12
10
Active
Solar
Proj. Act.
9
14
21
28
52
72
97
100
100
51
17
10
28
7
14
15
-
-
61
89
75
88
23
17
13
23
Emergency
Generator
Proj. Act.
1
1
2
2
4
6
3
0
0
3
2
1
2
1
1
2
-
-
2
11
3
2
1
1
1
2
Methane
Boiler
Proj. Act.
14
13
18
27
44
22
0
0
0
40
26
18
19
8
0
0
-
-
34
0
0
0
0
0
14
5
Heat
Pump
Proj. Act
65
57
43
31
0
0
0
0
0
0
42
59
40
73
70
71
-
-
3
0
22
10
70
67
60
60
622
-------
Month
TABLE 10 (17)
HEAT PUMP PERFORMANCE SUMMARY
Effluent Temp
Annual
* Estimated
** IkWh = 3.6 x 106 J
Energy Input
(icWh)**
Energy Output
(GJ)
33,660
1010
360.89
COP
January
February
March
April*
May*
June
July
August
September
October
November
December
7.8
6.8
6.1
—
-
15.7
18.3
20.0
19.3
16.7
13.7
10.2
Compressor
6807
6717
6388
(2112)
(2327)
40.5
0
241.9
224.9
2327
2112
4363
Pump
204
202
192
(63)
(70)
1
0
7
7
70
63
131
68.80
64.16
62.64
(25.3)
(28.4)
0.51
0
3.54
2.75
28.39
25.32
51.08
2.73
2.58
2.64
_
-
3.43
_
3.95
3.29
3.29
3.23
3.16
2.90
623
-------
3. Collector heat transfer losses
a. Air within the fluid loop.
b. Effect of the glycol solution.
4. Control sequencing and response.
5. Collector response sensitivity.
6. Collector efficiency losses due to dirt accumlated during
construction.
The discrepancies between design predictions and operating data
are attributed to the lack of a reliable design procedure to accurately
distinguish between instantaneous collector efficiency and year long
collector efficiency. Reliance on instantaneous efficiencies results
in an over optimistic long-term performance expectation due to the phe-
nomena of threshold temperature activation levels in relation to avail-
able insolation, cloud cover, etc. Presently available procedures of
applying mean expected percent sunshine to heat harvest tables for
prediction of available solar insolation have been found to be over
optimistic because of the highly variable nature of sunshine. For
example, on a partly cloudy day, even though the sun may shine, for 30%
of the day, this may be in intermittent bursts which may not be of
sufficient sustained intensity to reach threshold activation temperature
levels. Also, percent sunshine tables fail to indicate time of day or
intensity i.e., sunshine during midday is more productive than at other
times.
Calculations indicated that the passive solar energy system pro-
vided a total of 10% of the actual annual energy used for heating
which is 91% of the projected share. The manufacturer indicated a
transmissivity for the panels to be 66%. The observed peak noon time
transmissivity ranged from 35% in July to 57% in January. Part of the
reduction is attributed to the overhang used for shading during
summer. The remainder is attributed to other factors such as accumu-
lated dirt and surface reflection.
The purpose of conserving energy at the Wilton facility was to
ultimately reduce operating costs for electricity and fuel. Each energy
producing component was evaluated for energy conservation as well as
cost-effectiveness using a payback period approach. The results of
this evaluation are shown in Table 11. Each component, except for di-
gester gas production, was a net energy producer and net fuel cost
saver. The use of an effluent heat pump and air to air heat recovery
are most definitely cost-effective with good payback periods of 11 and
8 years, respectively. However, use of active solar energy at the
Wilton facility is difficult to justify on a cost-effectiveness basis -
the calculated payback period is 44 years.
Use of the passive solar energy system to heat the clarifier room
at Wilton is judged to be marginally cost-effective. Use of passive
solar to heat occupied areas where there is no exposure to water surface
would improve cost-effectiveness and is a preferred method.
624
-------
TABLE 11 (17)
ENERGY AND COST EFFECTIVENESS SUMMARY
N>
Ln
Component
Active Solar
Passive Solar
Heat Pump
Generator Heat
Recovery
Air-to-Air Heat
Recovery
Digester Gas
Production
Output
GJ ($)
153.7
34.26
360.89
10.13
58.13
325
1,302
290
3,057
86
492
2,750
GJ
13.
0
124.
0.
6.
551
Input
($)
4 368
0
85 2,060
09 1
46 81
3,837
Initial
Investment
($)
41,000
7,000
11,000
2,900
3,300
N/A
Energy
Output/Input
Ratio
11.5
N/A
2.9
113
9.0
0.59
Value
Output/Input
Ratio
3.5
N/A
1.5
86
6.1
0.72
Simple
Payback
(Years)
44
24
11
34
8
N/A
-------
The findings at Wilton regarding cost effectiveness of active
solar energy can be generalized to an extent. Based on a technology
assessment of solar thermal energy applications in wastewater treatment
(18), active solar heated anaerobic digestion proved uneconomical
throughout the U.S. A sensitivity analysis indicates that collector
system cost is the single most significant cost item. In order to be
economically viable on a payback basis, collector system costs would
have to be reduced from $538/m2 ($50/ft2) to a range of $162/m2 to
$323/m2 ($15 to 30/ft2).
626
-------
REFERENCES
1. "1982 Needs Survey - Conveyance, Treatment, and Control of Municipal
Wastewater, Combined Sewer Overflows, and Stormwater Runoff -
Summaries of Technical Data" EPA 430/9-83-002 U.S. Environmental
Protection Agency, Washington, D.C., May 1983.
2. "Energy Conservation in Municipal Wastewater Treatment" EPA 430/9-
77-011 U.S. Environmental Protection Agency, Washington, D.C.,
March 1978.
3. "Energy Requirements of Present Pollution Control Technology -
Interagency Energy/Environmental R&D Program Report" EPA 600/7-78-
084 U.S. Environmental Protection Agency, Cincinnati, Ohio, May
1978.
4. "Total Energy Consumption for Municipal Wastewater Treatment" EPA-
600/2-78-149 U.S. Environmental Protection Agency, Cincinnati,
Ohio, August 1978.
5. Owen. W.F., "Energy Requirements and the Potential for Energy
Conservation in Municipal Wastewater Treatment," Proceedings of
the U.S. Department of Energy Energy Optimization of Water and
Wastewater Management for Municipal and Industrial Applications
Conference, ANL/EES-TM-96, New Orleans, Louisiana, December, 1979,
Volume 1 p. 73.
6. "Energy - Environment Interface: Where the Environmental Action
Will be in the 1980"s" Civil Engineering Magazine, American
Society of Civil Engineers, September, 1980, p. 74.
7. "Innovative and Alternative Technology Assessment Manual" EPA
430/9-78-009, U.S. Environmental Protection Agency, Cincinnati,
Ohio, February 1980,
8. "Index of Direct Costs for Operation, Maintenance and Repair Based
on Composite 5 MGD Municipal Wastewater Treatment Plants, 3rd
Quarter CY1982" U.S. Environmental Protection Agency Office of
Water Program Operations.
9. Department of Energy, Office of Conservation and Renewable Energy,
10CFR 436, Federal Register, Volume 46, No. 222, November 18,
1981, p. 56711:
10. "1980 Needs Survey - Cost Estimates for Construction of Publicly-
Owned Wastewater Treatment Facilities" EPA 430/9-81-001, U.S.
Environmental Protection Agency, Washington, D.C., February, 1981.
627
-------
11. Bechtel, H. Comptroller, City of Cincinnati Metropolitan Sewer
District, Personal Communication.
12. Rushbrook, E.L., and Wilke, D.A. "Energy Conservation and Alter-
native Energy Sources in Wastewater Treatment" Journal, Water
Pollution Control Federation Vol. 52, No. 10, October 1980 p. 2477
13. Smith, J.M. and Lubin, G.R., "The Costs Problems and Benefits of
Innovative and Alternative Technology", Proceedings of the Eighth
National Individual Onsite Wastewater Systems Conference 1981,
National Sanitation Foundation, Ann Arbor, Michigan.
14. "Innovative and Alternative Technologies for Wastewater Treatment,"
U.S. Environmental Protection Agency, Cincinnati, Ohio, October
1982.
15. Internal Technical Review Memorandum for Bonney Lake, Washington,
U.S. Environmental Protection Agency, Cincinnati, Ohio, August
1980.
16. Internal Technical Review Memorandum for Southtown, New York, U.S.
Environmental Protection Agency, Cincinnati, Ohio, January 1981.
17. Fuller, D.H., Wilke, D.A., Thomas, P.L. and Lisa, A.J., "Monitoring
Integrated Energy Systems at a Wastewater Treatment Plant in
Maine", U.S. Environmental Protection Agency, Contract No 68-03-
2587, U.S. Environmental Protection Agency, Cincinnati, Ohio, July
1983.
628
-------
ENERGY RECOVERY, REUSE, AND CONSERVATION AT METRO CHICAGO
by
Cecil Lue-Hing
Hugh McMillan
Raymond R. Rimkus
Forrest C. Neil
The Metropolitan Sanitary District
of Greater Chicago
Chicago, Illinois
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
629
-------
ENERGY RECOVERY, REUSE, AND CONSERVATION AT METRO CHICAGO
by: Cecil Lue-Hing
Hugh McMillan
Raymond R. Rimkus
Forrest C. Neil
The Metropolitan Sanitary District of Greater Chicago
Chicago, IL 60611
ABSTRACT
In the aftermath of what, in 1973, was termed an "energy crisis," energy
prices in the United States and elsewhere began to escalate rapidly. In an
effort to contain costs and conserve limited natural resources, the Metro-
politan Sanitary District of Greater Chicago (District) began a detailed in-
vestigation of its energy uses and costs. This paper presents a series of
case studies which describe how the District reduced energy usage at its
John E. Egan, O'Hare, and West-Southwest treatment facilities without any
concomitant reduction in treatment efficiency.
At the John E. Egan facility the major energy saving steps were conver-
sion from a two-stage to a single-stage nitrification system, modification of
the sludge thickening process, and increased digester gas utilization. At
the O'Hare facility, the major energy saving steps were conversion from a
two-stage to a single-stage nitrification system and elimination of tertiary
filtration. At the West-Southwest facility, the major energy saving steps
were conversion of steam-driven blowers and pumps to electrically driven
blowers and pumps, increased use of digester gas, elimination of the heat-
drying process for sludge disposal, and reduction in air usage in the aera-
tion tanks.
Total energy savings at these three facilities will be approximately
$15.4 million/year once all of the modifications are completed.
630
-------
INTRODUCTION
Historians looking back at the decade of the 1970s will probably con-
clude that the end of an era of inexpensive energy supplies was the dominant
event of the period. In the aftermath of what, in 1973, was termed an
"energy crisis," energy prices in the United States and elsewhere began to
escalate rapidly. Prices of energy sources rose somewhat erratically be-
tween 1973 and 1978, and in 1979 again increased at an accelerated rate.
Although petroleum prices were the first to rise, various market forces
soon caused the prices of virtually all other energy sources to rise in vary-
ing degrees. Consequently, most energy users, including the Metropolitan
Sanitary District of Greater Chicago (District), experienced significant
increases in their operating costs. For example, the estimated costs for
natural gas and electricity at the District's West-Southwest Sewage Treatment
Works increased about 39 percent from a total of $13.7 million in 1977 to
$19 million in 1979. In an effort to contain costs and conserve limited
natural resources, the District began a detailed investigation of its energy
uses and costs.
The District serves a large area and operates numerous facilities; thus,
its approach was to investigate all its installations and prepare an inven-
tory of energy use. Although the development of such an inventory may appear
obvious, it was a rather complex task for a body responsible for the collec-
tion and treatment of wastewater throughout the Chicago metropolitan area,
encompassing virtually all of Cook County, Illinois. The District's service
area extends over approximately 860 sq miles (2,230 km^), and embraces a pop-
ulation of nearly six million people; and its various facilities receive
and treat, to secondary or tertiary levels, wastewater flows that, in 1978,
averaged nearly 1,400 MGD (61.0 m3/s). What follows is a series of case
studies which describe how the District focused its attention upon areas
that could potentially result in cost and energy savings without any concomi-
tant reduction in efficiency or service to its constituency.
CASE STUDIES
ENERGY SAVINGS AT THE JOHN E. EGAN WATER RECLAMATION PLANT
The John E. Egan Water Reclamation Plant (WRP) one of the seven District
facilities, is located in northwest Cook County in an unincorporated area of
Schaumburg and serves an area of approximately 44 square miles (114 km^).
This area encompasses most of the upper Salt Creek drainage basin and in-
cludes all or parts of Palatine, Schaumburg, Hoffman Estates, Arlington
Heights, Roselle, Elk Grove Village, Rolling Meadows and Inverness. Con-
631
-------
struction of the plant began in 1971 and the plant started treating sewage
on December 16, 1975. The plant was constructed at a cost of about $43
million.
The plant is designed as a 30-MGD (1.31 m3/s) , two-stage nitrification
system with dual media filtration for tertiaiy treatment. The plant consists
of control, maintenance, pretreatment, filter, digester, laboratory, and
thickener buildings; three pump houses; four aeration tanks; four digesters;
and twelve settling tanks. The plant is capable of providing complete treat-
ment for flows as high as 50 MGD (2.19 m3/s). Primary treatment can be pro-
vided for an additional 75 MGD (3.28 m3/s). All effluent flows are chlori-
nated.
The facilities provided (Figure 1) comprise coarse screening; pumping;
fine screening; grit removal; two stages of aeration,each followed by set-
tling; gravity filtration through dual-media filters; and chlorination.
Facilities for handling waste-activated sludge from the two aeration
stages include flotation thickeners and anaerobic digesters. A centrifuge
building to provide dewatering of the digested sludge was recently completed.
One of the design criteria aims for the John E. Egan WRP was to provide
the maximum amount of automation to minimize the labor needed for plant
operation and to provide steady and efficient treatment. To implement this
criterion the plant contains a total of 1,177 instruments, transmitters and
sensing elements. Most of the signals from the local instrumentation are
transmitted to the control room instrumentation panel which contains a
schematic of the plant with indicator lights for the major valves and equip-
ment, as well as a multitude of recorders, indicators, and controllers. All
of the analog and digital signals from the panel are entered into a dual
computer system (one computer for backup).
An automatic dissolved oxygen control system maintains the oxygen con-
tent in each of the aeration tank's three passes. A typical dissolved oxygen
pattern is 1.0, 1.5, and.2.0 mg/L in the first, second, and third pass,
respectively. Air for the aeration system can be controlled by remote valve
set point, flow set point, or cascaded via a dissolved oxygen set point from
the dissolved oxygen probes. All control commands can be directed from the
control room at the operator's selection. The plant's blowers, although
turned on and off locally, are flow controlled via influent vanes which are
varied automatically to maintain a set pressure.
The operational philosophy for the John E. Egan WRP follows the Dis-
trict's policy of providing the maximum degree of treatment to the maximum
possible sewage quantity at minimum cost. To this end, the blowers and
mechanical aeration devices are operated to maintain system air pressure at
minimum levels. Air to distribution channels is reduced to minimum levels
necessary to prevent solids settling. The overall air management procedure
is to maintain sufficient aeration rates to achieve effluent standards with-
out over aerating.
Plant personnel began a study in late 1979 to determine where energy
632
-------
PDE TKATMEIIT BID6
I '
imi
ffil *""*
^=/=Jff.~^_ '- ; -i-fca,. w v>77
" i-OC£2sK' TT^'T'^'-^r^
COMSI
scmiiB
H«S1 SIM( SICOHO SU6I
«1MIIO« BASK SltHMfNUTIOII lUW AIR1IIOK »A5I« SIOIMINl/lTIOH »»SIN
ruiirt
now
SOLIDS MANAGEMENT
Figure 1. Schematic of the John E. Egan Water Reclamation Plant.
-------
consumption could be reduced at the John E. Egan WRP. Process changes and
methods suggested by the study were reviewed in terms of cost effectiveness
and impact on treatment and plant environment. Where possible, energy con-
sumed during each phase of the treatment process was determined. This study
resulted in a series of operational changes and process flow modifications
to sewage treatment and sludge handling processes that significantly reduced
energy consumption.
In July 1981, the basic treatment process was changed from a two-stage
nitrification process to a single-stage nitrification process, with the
first-stage final settling tanks converted to primary tanks. Since the plant
design and piping are arranged so that conventional activated sludge, con-
tact stabilization, step aeration or any combination of the above process
schemes can be utilized, no construction of any kind was required. It was
believed that the change to a single-stage nitrification system could be
successfully accomplished, since the plant was currently operating at only
two-thirds of design capacity, thereby allowing sufficient hydraulic deten-
tion time for a single-stage nitrification system.
The change to a single-stage nitrification process was accomplished
without any deterioration in effluent quality. Table 1 shows the final
effluent suspended solids concentration and number of backwashes for 1981
and 1982. The 1981 data represents effluent quality before filtration as a
two-stage operation, and 1982 data represents effluent quality before filtra-
tion as a single-stage activated sludge operation. As can be seen from this
data, there was a decrease in effluent suspended solids and number of filter
backwashes for relatively the same volume of sewage treated.
Table 2 shows annual averages of air used in the aeration tanks from
1980 through 1982. There was a decrease in air requirements of 3.7 MCFD
(104,784 m^/day). In addition, the air-to-sewage ratio decreased by 0.26
ft-Vgal (1.9 m-Vm^) for the same period. These air usage decreases are due
to conscientious use of the automatic dissolved oxygen control system and
lower oxygen requirements for the single-stage system.
In conjunction with the change to the single-stage activated sludge
process, the sludge thickener operation was eliminated. The waste-activated
sludge is now pumped to the head of the plant and removed in the primary
settling tanks. These primary tanks are operated with a high sludge blanket
to allow for greater sludge concentration. The sludge is withdrawn at
approximately 2.5 percent solids concentration and pumped directly to the
anaerobic digesters.
Natural gas consumption has been reduced through modified digester oper-
ation at the John E. Egan WRP. Improved steam trap maintenance has led to
increased heat exchanger efficiency in the digester. In addition, a digester
gas utilization system to supply 500,000 therms per year (5.275 x 10 kJ)
for use in the John E. Egan WRP boilers was installed in 1982.
Cost saving associated with energy conservation measures mentioned above
are shown in Table 3. The major saving in the aeration system is accounted
for through reduction in air usage and power consumption for blower operation.
634
-------
All of the operating costs for the dissolved air flotation unit, except
sludge pumping cost, were saved. Digester gas utilization is expected to
supply 500,000 therms/year (5.275 x 1010kJ), which is 30 percent of the plant
requirements for boiler fuel. At a 1981 natural gas cost of $0.37/therm
($3.51/106 kJ), a saving of $185,000 per year is anticipated.
TABLE 1. MONTHLY AVERAGES OF EFFLUENT SUSPENDED SOLIDS PRIOR TO FILTRATION
AND NUMBER OF FILTER BACKWASHES FOR THE JOHN E. EGAN WATER
RECLAMATION PLANT
Month
January
February
March
April
May
June
Average
July
August
September
October
November
December
January
February
March
April
May
June
July
August
September
October
November
December
Average
No. of
Backwashes
1 QR1
10
15
12
10
13
2
12.4
Plant modified to single-stage
NA*
NA
NA
NA
NA
1 QQ9
— j_yo£
4
4
12
7
3
2
4
3
3
3
9
16
5.8+
Flow
MGD
17.72
22.70
20.13
21.76
22.41
21.18
20.98
activated
NA
NA
NA
NA
NA
18.47
18.63
21.11
24.48
19.39
17.34
20.19
17.63
17.29
16.27
23.41
26.93
20.60f
SS
mg/L
14
17
17
10
11
4
12.2
sludge process
4
4
6
5
3
5
7
10
6
4
4
5
5
5
6
2
8
5.2
*NA = Not Available.
Average for 1982 only.
Note: MGD x 0.0438 = m3/s.
635
-------
TABLE 2. AIR USAGE IN THE AERATION TANKS AT THE JOHN E. EGAN WATER
RECLAMATION PLANT
1980
13.60
0.78
Annual Average
1981 1982
— _ _ -_vr'T7"n —
— — — "-JMU.ru —
11.60 9.90
_ — _ _ _ _ _ f<-3/oa1— — -
it-vgaj.— —
0.59 0.52
Amount Decrease
1980-1982
3.70
0.26
*MCFD = Million Cubic Feet Per Day.
Note: cu. ft. x 0.02832 = m3.
ft3/gal x 0.1336 = m3/m3.
TABLE 3. COST SAVINGS ASSOCIATED WITH ENERGY CONSERVATION AND PROCESS MODIFI-
CATION AT THE JOHN E. EGAN WATER RECLAMATION PLANT
Anticipated
Process Changes Made $ Savings/Year
Wastewater
1. a. Change from two-stage to $ 50,000
single-stage A/S system
b. Reduction in total air used
c. Reduction in air used/unit
volume of sewage treated
(air-to-sewage ratio)
2. Reduction in filter backwash A,000
frequency
Sludge
3. a. Elimination of dissolved flotation 80,000
thickeners
b. Pump W/AS to head end of plant for
removal and concentration to
approximately 2.5%
4. Increased use of digester gas to 185,000
supply approximately 30% of boiler
fuel demand
TOTAL $319,000
636
-------
With the energy conservation measures at the John E. Egan WRP, a total
saving of $319,000 per year is expected. Substantial savings like these will
become a factor in meeting the challenge of maintaining high effluent quality
while controlling operating costs, even in the face of ever-increasing fuel
prices.
ENERGY SAVINGS AT THE O'HARE WATER RECLAMATION PLANT
The O'Hare Water Reclamation Plant (WRP) is the newest of the District's
seven sewage treatment facilities. Located in the city of Des Plaines, the
O'Hare WRP serves a 65.2 square mile (168.8 km^) area which includes the
communities of Arlington Heights, Mount Prospect, Prospect Heights, Wheeling,
Elk Grove Village, Rolling Meadows, Buffalo Grove, and a part of the City of
Des Plaines.
Sewage is conveyed to the plant through a 4.5*-mile (7.2 km) long, 20-
foot (6.1 m) diameter rock tunnel. The tunnel invert is 160 ft (48.8 m) be-
low grade at its entrance to the plant pumping station, and serves as both
a dry weather flow intercepting sewer and combined sewer overflow storage
reservoir. The O'Hare system is the first fully functional segment of the
District's Tunnel and Reservoir Plan (TARP) for storage and treatment of
combined sewer overflows.
The O'Hare WRP was designed to treat 72 MGD (3.15 m3/s), utilizing a
two-stage activated sludge process for ammonia removal and dual media sand
filtration to meet effluent standards of 4 mg/L BOD, 5 mg/L suspended solids,
and 1.5 mg/L NH4-N. The O'Hare WRP began operation in May 1980, and presently
treats an average daily sewage volume of 29 MGD (1.27 m-Vs) .
The O'Hare WRP is a particularly energy-intensive facility, as all sew-
age must be pumped from the rock tunnels-combined sewer overflow reservoir.
The normal discharge head on the raw sewage pumps is 195 feet (59.4 m). Raw
sewage pumping alone accounts for over 40 percent of the plant electrical
consumption. In addition, the plant design requires pumping of the activated
sludge plant effluent an additional 34 feet (10.4 m) up to the dual media
sand filters. Prior to plant start-up, electrical energy consumption was
projected at 2,500,000 KWH per month. Natural gas consumption for plant
heating was projected at 900,000 therms (1 therm = 100,000 Btu = 105,500 kJ)
annually.
Since any plant energy conservation program should consider all potential
areas of reduction in order of power demand, the initial priorities were
assigned to process equipment in order of magnitude of power consumption.
Thus, an area of high potential for large energy savings is the retiring of
capacity not currently in critical demand. This is especially true for a new
facility in which flows and loadings are not yet up to design limits.
A decision was made in May 1980 to operate the O'Hare WRP as a single-
stage activated sludge system, even though it was designed as a two-stage
system. This mode of operation will continue as long as effluent standards
are maintained. In 1981, the average ammonium nitrogen concentration of the
raw sewage was 13.7 mg/L and the average concentration of the final effluent
637
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was 0.2 mg/L. These figures represent an average ammonium nitrogen removal
efficiency of 98 percent.
The major benefits of operating as a single-stage system are the reduc-
tion of process air requirements and the associated cost for power consump-
tion. Table 4 shows annual average power consumption in KWH/day at the O'Hare
WRP for 1980 through 1982. There was a reduction of 6,700 KWH/day for
blowers used between 1980 and 1982.
TABLE 4. AVERAGE DAILY POWER CONSUMPTION AT THE O'HARE WATER RECLAMATION
PLANT
Raw Sewage Pumps
Blowers
Sand Filtration
Sludge Disposal
Heating and
Ventilation
Process Water
Lighting
Miscellaneous
Annual
1980
23,000
30,000
6,100
2,000
10,200
1,400
2,500
8,000
Average
1981
24,500
26,000
6,600
2,400
5,500
1,100
1,700
5,000
KWH/Day*
1982
25,500
23,300
0
2,400
3,900
800
1,300
4,700
(Increase)
Decrease
1980-1982
(2,500)
6,700
6,100
(400)
6,300
600
1,200
3,300
TOTAL 83,200 72,800 61,900 21,300
*KWH = Kilowatt Hours.
Table 5 summarizes how air use has been reduced since 1980. As can be seen,
the largest reduction was realized by reducing air rates to the raw sewage,
return sludge, and mixed liquor channels. Total channel length requiring
aeration is over 3,000 feet (914.4 m), with channel widths ranging from six
feet to 14 feet (1.83 to 4.27 m). Solids deposition in these channels was a
major concern; therefore, air rates were reduced on a trial-and-error basis
to present rates. Aeration tank air rates were also reduced by changing the
dissolved oxygen set point on a trial-and-error basis. Presently, the set
point is maintained at 2.0 mg/L approximately 100 feet (30.48 m) from the
effluent end of the aeration tanks.
On October 27, 1981, dual media filtration was discontinued. The second-
stage settling tanks were put in service to provide a second settling of the
first-stage effluent. There was no significant reduction in treatment
638
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efficiency, and effluent quality continued to exceed standards.
TABLE 5. AIR DISTRIBUTION AT THE O'HARE WATER RECLAMATION PLANT
*
Annual Average, MCFD
Area
Aeration Tanks
(ft.3/gal. Sewage)
Air Lift Pumps
Distribution Channels
Grit Channel
Post Aeration
(Overall, ft.3 /gal.)
Total Air Use (MCFD)
1980
15.70
(.64)
2.20
14.20
1.00
1.00
(1.31)
34.10
1981
14.70
(.58)
2.20
10.60
1.00
1.00
(1.06)
29.50
1982
12.20
(.50)
2.50
6.50
0.40
0.20
(0.76)
21.80
Increase (+)
Decrease (-)
1980-1982
-3.50
(-0.14)
+0.30
-7.70
-0.60
-0.80
(-0.55)
-12.30
*
MCFD = Million Cubic Feet Per Day.
Note: cu. ft. x 0.02832 = m3; ft.3/gal. x 0.1336 = m3/m3.
As shown in Table 6, the average plant effluent quality with filtration dur-
ing 1980 and 1981, was 2.4 and 2.2 mg/L BOD, 2.0 and 1.4 mg/L suspended
solids, and 0.7 and 0.2 mg/L NH4-N, respectively. The average plant effluent
quality, without filtration in 1982, was 2.3 mg/L BOD, 2.1 mg/L suspended
solids, and 0.3 mg/L NH4-N.
TABLE 6. ANNUAL AVERAGE EFFLUENT QUALITY AT THE O'HARE WATER RECLAMATION
PLANT
Year
1980
1981
1982
Treated
Flow, MGD
26.1
27.7
28.8
Suspended
Solids (mg/L)
2.0
1.4
2.1
BOD (mg/L)
2.4
2.2
2.3
NH4-N(mg/L)
0.7
0.2
0.3
Note: MGD x 0.0438 = m3/s.
639
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Annual reductions in electricity and natural gas consumption since 1980
are depicted in Figures 2 and 3. Plant electrical consumption has been re-
duced 26 percent from 2,546,674 KWH per month in 1980 to 1,882,654 KWH per
month in 1982. Natural gas consumption has been reduced 70 percent from
456,620 therms (4.82 x 1010 kJ) in 1980, to 137,500 therms (1.45 x 1010 kJ)
projected for 1983. It must be pointed out that these reductions are due to
numerous energy conservation measures initiated during the two and one-half
years since plant start-up. However, a large percent of the reductions are
attributed to taking the second-stage aeration system and dual media filtra-
tion out of service.
The dollar savings realized through conservation efforts have been sub-
stantial. Electricity bills averaged $105,050 per month in 1980 and $98,783
per month in 1982, and natural gas cost $137,846 in 1980, and $88,509 in
1982, representing an annual energy cost savings of approximately $125,000
in 1982 compared to 1980. Table 7 shows the cost savings for the major pro-
cess modifications at the O'Hare Water Reclamation Plant. It should be re-
membered, however , that the O'Hare WRP is currently operating at only 40 per-
cent of design flow, which allows for greater operating flexibility than one
might find at a more fully loaded plant. Therefore, energy cost savings may
have been easier to achieve than at a more fully loaded treatment plant.
TABLE 7. COST SAVINGS ASSOCIATED WITH ENERGY CONSERVATION AND PROCESS MODIFI-
CATION AT THE O'HARE WATER RECLAMATION PLANT
Process Changes Made
Anticipated
$ Savings/Year
1. a. Change from two-stage to
single-stage A/S system
b. Reduction in total air used
c. Reduction in air used/unit
volume of sewage treated
(air-to-sewage ratio)
$122,000
2.
3.
TOTAL
Elimination of dual media
filtration
Decrease in process water
usage
111,000
26,000
$259,000
ENERGY SAVINGS AT THE WEST-SOUTHWEST SEWAGE TREATMENT WORKS
The energy inventory that the District conducted indicated that the West-
Southwest Sewage Treatment Works (STW) is the District's largest energy con-
640
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o
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x
X
A M J J A
MONTH (1980- 1982)
Figure 2. Monthly electrical usage at the O'Hare Water Reclamation Plant.
-------
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sumer. The West-Southwest STW, believed to be the largest treatment facility
in the world, with a design capacity of 1,200 MGD (53.0 m-Vs) , is a conven-
tional activated sludge process facility, designed and constructed in the
late 1930s. The sewage treatment process train consists of course screening,
grit removal, fine screening, preliminary settling, secondary aeration, final
settling, and effluent chlorination. The sludge processing and disposal
systems consists of a combination of sand bed dewatering, anaerobic digestion,
vacuum filtration, heat-drying, centrifugation, and land application.
Since the late 1970s, four major operating changes have been made to
conserve energy at the facility. These four changes are described in the
following sections.
Conversion of Steam-Driven to Electric-Driven Equipment at the West-Southwest
Sewage Treatment Works
The West-Southwest STW currently uses a combination of steam and elec-
tricity to meet its energy requirements. Seven natural gas-fired boilers
supply moderate pressure 425 psig (2,930 kN/m^) steam to turbine-driven pumps
and blowers. In addition, approximately 80 percent of the average 15,000 kW
electrical demand is generated by turbine-driven generators, which permits
the West-Southwest STW to generate most of its energy needs from natural gas.
The boiler facility is also an integral part of the heat-dried fertilizer
process in which vacuum-filtered wastewater solids are contacted with boiler
flue gases in flash-drying units. Natural gas-fired afterburners are used to
incinerate aerosols resulting from the heat-drying process.
The investigations indicated that the boilers, steam turbine, and heat-
drying systems of the facility were very energy intensive and comprised the
largest uses of energy in the District. Of a current 271,200 kW total energy
demand at the West-Southwest STW, approximately 99 percent, or 267,600 kW, is
provided by natural gas; and one percent, or 3,600 kW is furnished by pur-
chased electricity. Of the 267,700 kW furnished by natural gas, approxi-
mately 78,400 kW is related to heat-drying; 36,400 kW is related to waste-
water treatment operations; and the balance, 152,800 kW, is lost in energy
conversion. In 1977, the annual energy costs for the West-Southwest STW in-
cluded $13 million for natural gas and $620,000 for electricity; for a total
of about $13.6 million. The present and future installed capacity and oper-
ating demand at the West-Southwest STW are contained in Tables 8 and 9, re-
spectively.
TABLE 8. PRESENT INSTALLED CAPACITY AND OPERATING DEMANDS (1977)
Installed Capacity Average Demand
Facilities
Electric motors
Steam-driven turbines
TOTAL
(kW)
36,700
39,900
76,600
(kW)
15,000
25,500
40,500
Steam-driven electric
generators 18,000 11,000
(Average Output]
643
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TABLE 9. FUTURE ENERGY CHARACTERISTICS (1995)
Facilities
WS wastewater pumpst
SW wastewater pumps §
Air compressors
Outfall pumps
Misc. equipment
TOTAL
Installed Capacity
(kW)
9,000
11,200
58,600
5,670
32,000
116,500
Normal Load*
(kW)
7,500
2,100
32,200
3,000
10,100
52,200
Heavy Load
(kW)
9,000
4,300
47,700
4,300
10,100
75,400
+Average daily flow of 903 MGD (39.6 m3/s), 205 days per year.
Average daily flow of 903 MGD (39.6 m3/s) plus Tunnel and Reservoir Plan
(TARP) dewatering flow; total flow of 1,360 MGD (59.5 m3/s) for 160 days
per year.
TWS = West Side (Imhoff Tank Facility).
§SW = Southwest (Primary Tank Facility).
With a view toward reducing the energy intensiveness of the facility,
eight alternative systems were proposed and studied in detail. They are as
follows.
Alternative 1 - Retain Existing System—The present steam turbine system
would be retained to meet the existing energy requirements. Additional elec-
tricity would be purchased from the local utility to meet future energy re-
quirements.
Alternative 2 - Purchased Electric Energy—All existing and future prime
movers would be electrically driven. The total electrical demand would be
supplied by purchased electricity.
Alternative 3 - District-Generated Electricity—All existing and future
prime movers would be electrically driven. A new multi-fueled electric gen-
erating plant would supply the total electrical demand.
Alternative 4 - Modernized Steam-Drive—All existing and future prime movers
would be turbine-driven. A new multi-fueled boiler system would supply steam
for the facility.
Alternative 5 - Gas Turbine Drive—The existing steam turbines would be re-
placed with natural gas turbines. All future prime movers would be elec-
trically driven. The energy demand would be supplied by a combination of
natural gas and purchased electricity.
Alternative 6 - Purchase Peaking Steam—All prime movers would be electrical-
ly driven. Electricity would be derived from two sources. Electricity for
the base load would be purchased at a constant rate from a local utility,
644
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but additional power demands would be generated from in-house turbine-driven
generators. Steam purchased over-the-fence would be used to drive the elec-
tric generators.
Alternative 7 - Purchase Peaking Electricity--This alternative is similar to
Alternative 6, except that the steam purchased over-the-fence would be u~ed
to generate base load requirements and electricity purchased from a local
utility would provide the balance of the demand.
Alternative 8 - Purchase Total Steam—This alternative is similar to Alterna-
tive 4, modernized steam drive, with the exception that the steam would be
purchased over-the-fence.
The alternatives were subjected to an economic analysis involving deter-
mination of annual and present worth costs. Because the analyses were pre-
pared over several years, all costs were related to the "Engineering News
Record" (ENR) Cost Index for Chicago of 2,600, corresponding to price levels
prevailing in 1977. Furthermore, all costs for in-house energy generation
were developed on the basis of using natural gas as the primary fuel. The
cost analysis, as presented in Table 10, indicates that Alternative 2 has an
annual cost of approximately $13.1 million, as compared to the analogous cost
of nearly $19 million for Alternative 1, which involves retaining the present
system. Thus, the implementation of Alternative 2 at the West-Southwest STW
would result in a projected annual savings of about $5.9 million.
In view of the uncertainty regarding the effect of inflation, any es-
timate of future costs is subject to question. For this reason, a sensitivity
analysis was prepared to evaluate the effects of varying the future values of
various economic parameters on the total present worth costs of each of the
alternatives. The annual escalation rate for operation and maintenance
(0 & M) and energy costs was varied to determine if changes in the inflation
rate could alter the economic analysis. The calculated data for four of the
eight alternatives that derive energy from a single source are presented in
Figure 4. Examination of Figure 4 clearly indicates that Alternative 2 will
result in the least present worth costs in all cases studied. A typical re-
sult of the present worth analysis is presented in Table 11.
The efforts to conserve energy should deal not only with monetary costs,
but also with the conservation of our primary energy resources. In the spirit
of conservation, the primary energy requirements of the eight aforementioned
alternatives were estimated, and are presented in Figure 5. The figure indi-
cates that implementation of Alternative 2 would result in an energy demand
of approximately 182,600 kW, as compared to 245,500 kW by the existing sys-
tem. Thus, a shift to Alternative 2 would yield a saving of 62,900 kW of
primary energy demand. Plans for implementing Alternative 2 are currently
underway and the system should be operational in 1985.
645
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TABLE 10^ ECONOMIC COMPARISON OF ALTERNATIVES, ANNUAL COST BASIS ($1,OOP/YEAR)
Amortized capital*
Operation and
Maintenance
Electricity
Natural gas'"
§
Steam
Digester gas credit
Total
Alt. 1
Retain
Existing
System
617
3,602
5,619
9,130
0
0
18,968
Alt. 2
Purchase
Elec.
Energy
1,282
986
10,830
—
—
—
13,098
Alt. 3
District-
Generated
Elec.
U.868
2,918
—
10,501
—
—
18,287
Alt. ll
Modern
Steam
Drive
M07
3,356
—
11,230
—
—
19,^93
Alt. 5
Gas
Turbine
Drive
1,812
3,602
5,619
8,076
—
—
19,109
Alt. 6
Purchase
Peak
Steam
3,8U5
1.81U
6,785
—
10,857
(788)
22,513
Alt. 7
Purchase
Peak
Elec.
3,8U5
1,687
^,327
—
1U.5U6
(788)
23,617
Alt. 8
Purchase
Total
Steam
3,565
3,172
—
—
21,613
(788)
27,562
™ -
Amortized capital cost; term = 30 years, interest = 6.
Electricity purchased at rate of $0.02ll4/KWH (January 1977).
^Natural gas purchased at rate of $0.l67/therm ($0.106/10° kJ), (January 1977).
Steam purchased from outside vendor at the following rates:
$3.15/106 Btu ($2.99/10° kJ) for Alternate 6.
$2.70/10°" Btu ($2.55/10° kJ) for Alternate 7-
„ $2.90/106 Btu ($2.75/106 kJ) for Alternate 8.
Digester gas sold at annual credit of $788,000 to steam producer.
-------
TOTAL PRESENT WORTH COSTS IN $ 100,000,000
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TABLE 11. ECONOMIC COMPARISON OF ALTERNATIVES. PRESENT WORTH BASIS ($ MILLION)
-p-
OO
Capital cost
Operation and
Maintenance '
Electricity^
Natural gas§
Steam
Digester gas
credit
Total
*Present worth
Alt. 1
Retain
Existing
System
8.0
51.9
106.3
199.0
—
—
365.2
calculated for
Alt. 2
Purchase
Elec.
Energy
16.5
14.2
204.9
—
—
—
235.6
term of 15
Alt. 3
District-
Generated
Elec.
62.8
42.1
—
228.9
—
—
333.8
years and
Alt. 4
Modern
Steam
Drive
63.3
48.4
—
244.8
—
—
356.5
interest
Alt. 5
Gas
Turbine
Drive
23.4
51.9
106.3
176.0
—
—
357.6
rate of
Alt. 6
Purchase
Peak
Steam
49.6
26.2
128.4
—
156.6
(11.4,
349.4
6.625%.
Alt. 7
Purchase
Peak
Elec.
49.6
24.3
81.9
—
209.8
(11.4)
354.2
Alt. 8
Purchase
Total
Steam
46.0
45.7
—
—
311.7
(11.4)
392.0
^
Annual escalation rate for operation and maintenance costs is 7%.
TAnnual escalation rate for electricity purchased is 11%.
^Annual escalation rate for natural gas purchased is 13%.
^Annual escalation rate for purchased steam is 7%.
* Annual escalation rate for digester gas credit is 7%.
-------
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Z
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200
150
100
u
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50
ALT. I ALT. 2 ALT. 3 ALT. 4 ALT. 5 ALT. 6 ALT. 7 ALT. 8
Note: ALT. 1 = RETAIN EXISTING SYSTEM
ALT. 2 = PURCHASE ELECTRICAL ENERGY
ALT. 3 = DISTRICT GENERATED ELECTRICITY
ALT. 4= MODERN STEAM DRIVE
ALT. 5= GAS TURBINE DRIVE
ALT. 6 = PURCHASE PEAK STEAM
ALT. 7 = PURCHASE PEAK ELECTRIC
ALT. 8= PURCHASE TOTAL STEAM
Figure 5. Resource energy utilization, comparison of alternatives.
Digester Gas Utilization Program at the West-Southwest Sewage Treatment Works
The West-Southwest STW has an anaerobic digestion complex consisting of
twelve 2,500,000-gallon (9.5 x 10" 1) floating-cover high-rate digestion
units. Each digestion unit is rated at 25 dry tons/day (22,680 kg/day) at a
3.3 percent solids feed. Digester operational data for 1977, based on
monthly averages, are: (1) solids feed—4.8 percent to 5,7 percent; (2) or-
ganic loading—0.082 Ib/cu ft/day to 0.130 Ib/cu ft/day (1.31 kg/m3/day to
2.08 kg/m^/day); (3) volatile solids destruction—18 percent to 40 percent;
(4) detention time'—15 days to 25 days; and (5) gas production-—13.1 cu ft/
Ib to 18.1 cu ft/lb (0.82 m3/kg to 1.13 m3/kg) of volatile solids destroyed.
Sludge heating and mixing is accomplished by continually circulating the
sludge through water tube heat exchangers, Hot water is supplied to the heat
exchangers from digester gas-fired fire-tube boilers. There are sixteen
boilers for twelve digesters. Feed to the digesters is predominately waste-
activated sludge.
649
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The first four digesters at the West-Southwest STW were built and placed
into service in 1964. At that time, the use of digester gas consisted only
of that amount required to maintain mesophilic conditions in the digesters
and to provide heat for the digester building. The economics at that time
indicated that the excess digester gas be flared off in waste gas burners.
Two additional sets of four digesters each were subsequently built in 1969
and 1973, and again the waste gas was flared off.
Since 1974, with the Middle East oil embargo and the shortage of domes-
tic energy, the cost of energy has skyrocketed and made the utilization of
this waste gas not only economical; but mandatory.
Digester Gas Production and Dollar Value—The gas produced in each digester
is metered and recorded by a chart and totalizer. The average total gas
production in 1977 was 2.7 x 106 cu ft/day (0.076 x 106 m3/day). Figure 6
shows the gas produced on a monthly basis in 1977, and the gas utilized to
maintain the digesters at 95°F (35°C). The difference between the two is
the digester gas wasted, or the amount of gas available for further utiliza-
tion. An average of 1.0 x 106 cu ft/day (0.028 x 106 m3/day) of digester gas
is available for additional utilization.
Digester gas is composed of approximately 65 percent methane, 30 percent
carbon dioxide, and five percent varying amounts of nitrogen, hydrogen, car-
bon monoxide, and oxygen. This gas is capable of supplying 650 Btu per
standard cu ft (24,214 kJ per standard m3). Thus, the 1.0 x 106 cu ft/day
(0.028 x 10^ m3/day) of excess digester gas has the energy equivalent of
650 x 106 Btu/day (686 x 10& kJ/day).
The major fuel source at the West-Southwest STW is purchased natural
gas. In 1979, the price of the natural gas averaged approximately $0.25/
therm ($2.37/106 kJ). Thus, the 6,500 therms (686 x 106 kJ) of unused di-
gester gas is worth approximately $l,625/day or $593,125/year at 1979 prices.
Method of Utilization—In order to actually realize this dollar savings, a
method had to be chosen to convert the digester gas to usable energy.
Methods of utilizing digester gas studied at the West-Southwest STW included
gas turbine generators, internal combustion engines, and water tube boilers.
Gas turbine-generating syster.is require a large capital investment. In
our particular case, this meant $2,500,000 to $3,000,000. Also, there was
much concern about cleaning the digester gas, which is a necessity for
keeping the combustion chamber clean.
Internal combustion engines, as observed in other facilities, had high
noise levels and an abundant amount of supporting equipment, such as lubri-
cation, ignition, carburetion, and cooling systems. It, appeared that there
would be a problem using digester gas on an internal combustion engine since
some plants had to redesign component parts of the engine to deal with the
corrosive nature of the gas. Additionally, there was no convenient direct
application to a pump or blower in the plant.
650
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O
U>
O
Ul
r4.0
TOTAL GAS PRODUCED
-3.0
-2.0
-1.0
1.0 MCFD
DAILY AVERAGE
WASTED,
NGAS AVAILABLE FOR
FURTHER UTILIZATION
1.65 MCFD
DAILY AVERAGE
USED
I
I
I
I
I
J
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1977
Figure 6. Digester gas production and utilization in 1977
at the West-Southwest STW.
The third alternative—ie., water tube boilers—was studied and became
our first choice for three reasons:
1. Low capital cost and quick return on investment. It was estimated
that the cost of material and labor to complete the project would be $870,000
(1979 prices). The cost of operation,including maintenance, is estimated at
$150,000/yr. As the value of the digester gas has been calculated to be
$593,125 annually, it can be seen that the project cost would be amortized
in less than three years.
651
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2. Complete utilization of low-pressure steam. The low-pressure steam
requirements and the source of steam were studied along with the amount of
steam generated from the excess digester gas. It was found that at no time
would the amount of low-pressure steam available from the excess digester gas
exceed the demand for low-pressure steam at the West-Southwest STW. Since
the demand for low-pressure steam is present, a consistent boiler operation
would be expected.
3. By 1985, the West-Southwest STW expects to replace six turbo-pumps
and seven turbo-blowers with electric drives. This equipment is being phased
out along with seven high-pressure steam generators due to their age and high
cost of maintenance and operation. Elimination of the high-pressure steam
generators will necessitate the installation of a new steam-generating
system.
Boiler Selection—Once it was decided to utilize the excess digester gas by
producing steam, it was necessary to determine the size and type of boiler
best suited for this application. An engineering analysis of the daily
variation in excess gas production and the steam-generating efficiency of
various boilers led to the conclusion that 22,200 Ib/hr (10,070 kg/hr) of
steam would be the average output of the boiler required to burn all the ex-
cess digester gas. The maximum and minimum loads were calculated to be
32,000 Ib/hr (14,515 kg/hr) and 10,000 Ib/hr (4,536 kg/hr), respectively.
From this it was decided to use two 35,000 Ib/hr (15,876 kg/hr) steam genera-
tors. Two units were chosen to provide the facility with a backup unit to
be used during repairs and also because there is a plan to increase the di-
gester complex by 50 percent.
Proposed Installation—A schematic of the overall digester gas utilization
system and the associated pressure control system designed to control this
system is shown in Figure 7. Two gas pressure transmitters are installed
in the gas header, one for each compressor. The transmitter puts out elec-
trical signals (4 mA-20 mA) to the d-c variable speed controller which
regulates the speed of the motor in a manner that maintains the pressure in
the digester header at a 5.25-inch (133 mm) water column, plus or minus 0.5
in. (12.7 mm).
At the steam-generating end, the gas at line pressure is stored in the
2,000-cu ft (56.64 m^) vessel which will function as a buffer for the system.
Due to the variable rate of gas production, it was felt that this vessel
would dampen the fluctuations in fuel supply to the boilers, thereby having
a more uniform steam output from the boilers.
Incorporated into the controls is an alarm system designed to provide
safety to the operation. The alarms, visual and audio, monitor such things
as low gas header and compressor suction pressure, high discharge pressure
and temperature, and the presence of methane gas in the area. In these
situations, the compressors are automatically shut down.
As of 1982, this proposed installation has been completed and is oper-
ating satisfactorily, providing the District with a substantial cost savings.
652
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Ln
OJ
DIGESTER GAS HEADER
GAS PRESSURE
TRANSMITTER
'P
DC VARIABLE SPEED^
CONTROLLER
AFTERCOOLER
\
COMPRESSOR
COMPRESSOR
100 TO 1750 RPM MOTOR
100 TO 1750 RPM MOTOR
STORAGE
ACCUMALATOR
GAS PRESSURE
TRANSMITTER
DC VARIABLE SPEED
CONTROLLER
Figure 7. Schematic of the digester gas utilization system.
-------
Elimination of Heat-Drying at the West-Southwest Sewage Treatment Works
The West-Southwest STW is, as the name implies, a combination of two
facilities, operating together now, on the same site. The older West Side
Sewage Treatment Works, which was placed into operation on June 6, 1930, is
a primary treatment facility providing primary settling and digestion in 108
Imhoff tanks. Imhoff tank sludge is air-dried on sand beds and then placed
into storage at the Harlem Avenue Solids Management Area (HASMA), two miles
west of it. The West Side STW operation continues today essentially as it
has in the past. The primary treatment provided by the West Side STW, how-
ever, proved inadequate for the increasing sewage flows generated in the
growing Chicagoland area in the 1930s. To meet the needs of the community
and to protect the water quality of the Chicago Sanitary and Ship Canal, an
activated sludge facility was needed; and thus, the Southwest STW was built
and placed into operation in 1939. The combined West-Southwest STW treats
the Imhoff tank effluent produced at the West Side STW, along with the pri-
mary tank effluent from the Southwest Side STW itself. After a number of
expansions through'the years, the existing West-Southwest STW has a secondary
treatment design capacity of 1,200 MGD (52.6 m3/s).
The Southwest STW was designed, in part, around a heat-drying process,
the solids disposal method selected in 1939 for processing waste-activated
sludge. Hot gases used for flash-drying sludge are produced in boilers
which also produced steam. This steam is then used to power all of the raw
sewage pumps, the blowers, and three generators used to produce plant elec-
tricity.
The heat-drying process works as follows (Figure 8). Waste-activated
sludge solids concentrated to approximately one to two percent solids content
in gravity concentration tanks are conditioned with ferric chloride and sent
to a bank of vacuum filters. At the vacuum filters, the conditioned sludge
is dewatered partially to produce a filter cake of approximately 15 percent
solids. The filter cake then drops onto a conveyor belt and is transported
to a mixer where it is combined with dried solids from the drying line to
obtain a mixture of approximately 55 percent solids,, which is fed to the
drying tower. Here hot gases of approximately 1,300°F (700°C) are mixed with
the solids, resulting in an instantaneous evaporation of water. The dried
solids are cooled, screened, and transmitted by conveyor belt to the fertili-
zer storage facilities. The material is an excellent soil conditioner and
fertilizer base and is presently sold to a broker on a competitive bid basis.
The broker in turn has developed a market of buyers who apply the solids to
land.
The drying equipment itself consists of 14 units, each having a capacity
to evaporate 25,000 Ibs of water per hour (11,340 kg/hr) from sludge by using
a blend of combustion gases and sludge vapor. Each unit consists of a sludge
mixer, drying tower, flash dryer, sludge mixer air lock, two cyclone separa-
tors having double flap discharge valves, combined surge and fuel bin, dry
return conveyor, dryer induced draft fan, and gas scrubber unit. Effluent
water is used for cleaning gases passing through the gas scrubber.
Since 1939, the heat-drying plant had run continuously except for brief
654
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Fecl3 V
GRAVITY
CONCENTRATION
TANK
1-2% SOLIDS
ROM GAS-FIRED
WTER WALL FURNACE
URNACE GAS 700°C
VACUUM
FILTER
15% SOLIDS
FILTER CAKE
SLUDGE SEPARATORS
SLUDGE
SURGE BIN
DRYING
TOWER
DRIED SLUDGE
COOLER
TO STORAGE
FACILITY
SLUDGE DRYER
Figure 8. West-Southwest Sewage Treatment Works heat-dried
fertilizer processing plant.
periods of time when the main conveyor belt needed repairs or replacement.
Table 12 shows the input solids for various years since 1940.
The load on the heat-drying plant was partially reduced when anaerobic
digesters were placed into operation in the 1960s and early 1970s. Even with
the construction of twelve digesters, however, heat-drying continued because
the average solids load in the plant (including recycle flows) exceeded the
capacity of the anaerobic digesters.
To understand the operational changes made to accomplish the cessation
of heat-drying without adding any new sludge processing facilities, it is
necessary to review the sludge handling situation at the West-Southwest STW.
655
-------
TABLE 12. SOLIDS INPUT TO THE HEAT^DRYING PLANT THROUGH THE YEARS
Year Dry Tons/Day
1940
1950
1960
1970
1976
1978
1980
1981
1982
156
163
500
415
205
165
175
90
0
Note: Tons x 907.2 = kg
Figure 9 shows monthly averages of the suspended solids loadings to the
aeration tanks coming from the West Side Imhoff tanks and the Southwest Side
primary tanks from 1979 to 1982. The West Side contributed 54.3 percent of
the load in 1979 and 60.9 percent in 1980. Furthermore, the West Side Imhoff
tanks spilled over great amounts of solids in the spring when they became
overloaded and could not be emptied because the winter cover of sludge on
the sand drying beds had not yet been dug. As a result, the recycles
occurred in the plant, raising the reported waste-activated sludge quantities.
At the same time the input solids to heat-drying and digestion in March thru
June went up 20 percent over the annual figure, and the plant became sludge-
bound at times. Ironically, at other times of the year, excess sludge
handling capacity existed in the plant.
To break this cycle, it was decided that ending the practice of sending
Southwest primary solids to the West Side Imhoff plant year-round would end
the overloading of the Imhoff tanks and would dampen the spring solids peak-
ing. Further, it was felt that the heat-drying operation itself was con-
tributing to in-plant recycles via the gas scrubbers, and that a reduction
in overall reported solids would occur once heat-drying ceased. This phenom-
enon had occurred in July and August of 1980 (Figure 9) when repairs to the
main fertilizer conveyor prompted a one-week shutdown. The shutdown was ex-
tended when it was observed that apparent plant solids had decreased markedly
while the heat-drying plant was out of service. Beginning in July of 1981,
Southwest primary sludge was sent to the digesters along with thickened
waste-activated sludge; and on August 4, 1981, the heat-drying plant was shut
down. As Figure 9 shows, the aeration tank loadings immediately changed; and
now more solids were coming from the Southwest plant than from West Side.
In the spring of 1982, the usual overflow of solids from West Side was great-
ly dampened; and although the solids loading to the digesters increased to
656
-------
Q
>v
en
1000 r-
900 -
800 -
700 -
600
500
400
300
200 L
100 -
LEGEND:
SW LOADING TO AERATION TANK
WS LOADING TO AERATION TANK
Note: tons x 907.2 = kg
HEAT DRYING
0/S FOR REPAIRS
HEAT DRYING ENDS
1979
WS=54.3%
OF LOAD
1980
WS=60.9%
OF LOAD
1981
WS = 50.8%
OF LOAD
1982
WS = 43.3%
OF LOAD
Figure 9. Aeration tank solids loading from West Side (WS) Imhoff tanks
and Southwest Side (SW) Primary tanks.
657
-------
capacity, there was no need to heat-dry.
The reduction in plant solids recycle has enabled the existing digester
facilities to handle all solids at the West-Southwest STW since August 1981;
and the heat-drying plant, the former mainstay for processing waste-activated
sludge, serves as a standby process.
Table 13 shows the changes in sludge production and processing at the
West-Southwest STW from 1976 to 1982, and the yearly natural gas usage for
the heat-drying system. The table shows that as the solids input to the
heat-drying plant was reduced beginning in 1981, the amount of sludge pro-
duction also was reduced, resulting in the anaerobic digesters having suffi-
cient capacity to handle the entire sludge production. In addition, natural
gas usage for heat-drying has been reduced from over 20 million therms/yr
(2.11 x 1012 kJ/yr) to zero. The elimination in August of 1981, of the heat
drying of sludge has resulted in a large savings in energy and money. Based
on average 1982 gas costs of $0.35/therm ($3.32/106 kJ), it is estimated that
it would have cost the District approximately $7.4 million in 1982 to heat-
dry sludge at the input rate of 175 dry tons of solids per day (158,760 kg/
day) which occurred in 1980, the last full year of heat-drying operation.
This is a major savings, since the total 1982 gas bill at the West-Southwest
STW was $12.7 million.
TABLE 13. SOLIDS PRODUCTION, PROCESSING, AND NATURAL GAS USAGE AT THE WEST-
SOUTHWEST SEWAGE TREATMENT WORKS (YEARLY AVERAGES)
Year
1976
1977
1978
1979
1980
1981
1982
Total Sludge*
(Dry Tons/Day)
497
514
494
523
517
461
417
Dry Tons/Day
To Heat Drying
205
210
165
236
175
90
0
Dry Tons /Day
to Digesters
292
314
329
287
342
371
417
Gas Usage
for Heat
Drying
(Therms /Yr)
25,495,000
21,950,000
17,205,000
24,665,000
21,161,000
8,159,000
0
*Excluding Imhoff tank sludge.
Note: Tons x 907.2 = kg; Therms x 105,500 = kJ.
Reduction of Air to the Aeration Tanks at the West-Southwest Sewage Treatment
Works
The West-Southwest STW is a conventional air-activated sludge treatment
facility consisting of four similar batteries of aeration tanks. Each bat-
tery is composed of eight tanks, with each tank consisting of four channels
in series. The channels are 43A feet (132 m) long, 34 feet (10.4 m) wide,
658
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and 15 feet (4.6 m) deep. Porous plate diffusers located along one side of
each channel produce a spiral-type flow pattern. The diffuser plates are 80-
permeability.
Compressed air is supplied by seven centrifugal blowers having a total
capacity to compress 780,000 cfm (368 m3/s) of free air to 8.5 psi (58.6 kN/
m2) . The blowers are driven by steam turbines, with the steam being produced
by seven gas-fired boilers. The boilers are two-drum, vertical, bent-tube
type with superheater, and will deliver from 70,000 to 110,000 Ibs (31,752 to
49,896 kg) of steam per hour each at 425 psi (2,928 kN/m2).
The energy cost to power the blowers is one of the largest operating
costs of the treatment process. In 1979, a total of 79.4 million therms of
natural gas was used at the West-Southwest STW (Note: 1 therm = 100,000 Btu =
105,500 kJ). The average cost of natural gas in 1979 was $0.25/therm ($2.37/
106 kJ), resulting in a total gas cost of $19.8 million. Of this amount,
approximately $7.9 million, or 40 percent of the total, was spent to produce
steam to power the air blowers.
Keeping the rapidly rising natural gas costs experienced in the late
1970s in mind, a program was begun in 1979 to determine whether the amount
of air supplied to the aeration tanks could be reduced without having a
detrimental effect on the excellent effluent quality which the West-Southwest
STW was then achieving. Of special interest, was the ability of the facility
to maintain year-round nitrification, which although not a current permit re-
quirement, could be a requirement, in the future. The major operational change
which took place was to modify the distribution of air to the four-channel
aeration tanks. Prior to 1979, the air was distributed fairly uniformly to
each channel resulting in low dissolved oxygen levels at the head end of the
aeration tanks. In 1979, a tapered aeration approach was implemented, in
which proportionately more air was supplied to the first channel of each
aeration tank, while less air was used in the remaining three channels. By
doing this, an overall reduction of approximately ten percent in air usage
was achieved while nitrification efficiency was actually increased.
Table 14 presents yearly averages of final effluent BOD, suspended
solids (SS) and NIty-N for the West-Southwest STW for 1977 to 1981. As can
be seen, final effluent BOD has stayed in a 5 to 7 mg/L range and final
effluent SS in a 6 to 8 mg/L range. Final effluent NIfy-N has decreased from
an average of 2.4 mg/L in 1979 to 1.4 mg/L in 1981.
TABLE 14. YEARLY AVERAGES OF FINAL EFFLUENT BOD, SUSPENDED SOLIDS, AND NH.-N
AT THE WEST-SOUTHWEST SEWAGE TREATMENT WORKS
Year
1977
1978
1979
1980
1981
BOD
(mg/L)
5
6
7
6
6
Final Effluent
SS
(mg/L)
7
8
8
6
6
NH4-N
(mg/L)
2.7
1.8
2.4
1.6
1.4
659
-------
Table 15 presents yearly averages of air and steam usage for 1977 to
1981. As can be seen, steam usage in the blowers has been reduced from an
average of 4.5 million Ibs/day (2.0 million kg/day) in the 1977 to 1978 per-
iod to an average of 3.9 million Ibs/day (1.8 million kg/day) in the 1980 to
1981 period. In 1981, the energy cost for producing steam was approximately
$5.00/1,000 Ibs steam produced ($11.00/1,000 kg). Thus, the average energy
savings in reduced steam usage has been approximately $3,000/day or $1,095,000
/year.
TABLE 15. YEARLY AVERAGES OF AIR AND STEAM USAGE AT THE WEST-SOUTHWEST
SEWAGE TREATMENT WORKS
Sewage Total Air Steam Usage
Flow Usage* in Blowers
Year (MGD) (106 ft.3/Day) (106 Ibs./Day)
1977 795 745 4.48
1978 819 735 4.52
1979 873 690 4.32
1980 808 665 4.09
1981 807 677 3.80
*Approximately 85% of the air used goes to the aeration tanks. The remaining
15% is used for the return sludge airlift pumps and the aerated grit cham-
bers.
Note: MGD x 0.0438 = m3/s; ft.3 x 0.028 = m3; Ibs x 0.454 = kg.
Total Cost Savings at the West-Southwest STW
Table 16 presents a summary of the cost savings achieved at the West-
Southwest STW since the late 1970s through process modifications and energy
conservation measures. As can be seen, these savings amount to over $14 mil-
lion/year, indicating the magnitude of the savings which can be achieved at
a major facility through a careful analysis of operating procedures.
CONCLUSIONS
In a time of rapidly changing energy prices, it is prudent to critically
review the design basis and assumptions that entered into the engineering
development of existing facilities. In many cases, current economic condi-
tions may dictate that substantial modifications be made to processes or
operations that are otherwise technologically advanced. A realization of a
changing economic environment caused the District to review all its facili-
ties, to prepare an inventory of its energy uses, to initiate a procedure to
focus in those areas where energy conservation would most probably be fruit-
ful, and, finally, to implement a plan that would reduce energy consumption
and related costs.
660
-------
The work described in this paper was not funded by the U.S. Environ-
mental Protection Agency, and therefore, the contents do not necessarily re-
flect the views of the Agency and no official endorsement should be inferred.
TABLE 16. COST SAVINGS ASSOCIATED WITH ENERGY CONSERVATION AND PROCESS
MODIFICATIONS AT THE WEST-SOUTHWEST SEWAGE TREATMENT WORKS
Item $ Savings/Year
1. Convert from steam driven turbines
to purchased electricity $5,900,000
2. Digester gas utilization
a. Amortized capital cost* - 86,000
b. 0 & M cost -150,000
c. Energy production +593,000
Net Savings 357,000
3. Elimination of heat-drying
a. Energy savings 7,400,000
b. 0 & M cost savings 1,500,000
c. Lost profit from fertilizer
sale -1,469,000
Net Savings 7,431,000
4. Savings due to reduction of air
to the aeration tanks 1,095,000
5. Total savings at the West-Southwest
STW 14,783,000
*Term = 20 years; Interest = 7.625%.
GLOSSARY OF TERMS
A/S = activated sludge
Btu = British thermal units
cfm = cubic feet per minute
cu ft = cubic feet
661
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d-c = direct current
ft3/gal = cubic feet per gallon
kJ = kilojoules
kN = kilonewtons
kW = kilowatts
KWH = Kilowatt-hours
Ibs = pounds
mA = milli-amperes
MCFD = million cubic feet per day
psi = pounds per square inch
SS = suspended solids
W/AS = waste-activated sludge
662
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PROGRESS IN SEQUENCING BATCH REACTOR TECHNOLOGY
by
E. F. Earth, B. N. Jackson, and J. J. Convery
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19 - 21, 1983
Tokyo, Japan
663
-------
PROGRESS IN SEQUENCING BATCH REACTOR TECHNOLOGY
by: E. F. Earth, B. N. Jackson, and J. J. Convery
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Office of Research and Development
Cincinnati, Ohio 45268
ABSTRACT
Sequencing batch reactor (SBR) technology is being implemented at various
municipal sites in both the United States and abroad. Total life-cycle cost
savings, ease of operation and reliability favor this technology at facili-
ties sized up to 19,000 m3 per day (5 mgd).
Current research investigations on SBR's concern controlling sludge
settleability, low energy options, and biological phosphorus removal.
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
INTRODUCTION
This paper will discuss progress of municipal implementation and labora-
tory research on batch reactors since the October 1981 United States/Japan
Conference on Sewage Treatment Technology. In the United States and several
other countries sequencing batch reactors (SBR) are being designed and con-
structed for municipal facilities to meet a variety of effluent requirements.
Laboratory studies are being conducted to seek operational patterns to a-
chieve nitrification, denitrification, and biological phosphorus removal.
664
-------
As a refresher, since the last presentation on the SBR process, Figure 1
provides an elevation view of an SBR reactor operating in a secondary treatment
sequence (1).
Because sequencing batch reactor technology is new to both designers and
treatment plant operators, the major applications are currently for facilities
of 19,000 m-^ per day (5 mgd), or less. This lack of experience on large size
facilities is no barrier to implementation. Between the years 1983 and 2000,
it is anticipated that 3,000 municipal facilities with design flows less than
7,500 m^ per day (2 mgd) will need to be constructed in the United States.
About 2.5 billion dollars will be expended on these sized treatment plants.
MUNICIPAL IMPLEMENTATION
The following list shows the locations where seqeuncing batch reactors
are being constructed to provide municipal wastewater treatment.
Location Size, m-Vd (mgd)
Poolesville, Maryland 2,200 (0.6)
Grundy Center, Iowa 3,200 (0.8)
Sabula, Iowa 1,900 (0.5)
LeClaire, Iowa 1,900 (0.5)
Union City, Tennessee 12,900 (3.4)
Jenuau, Alaska 19,000 (5.0)
Teullahoma, Tennessee 19,000 (5.0)
LaPaz, Mexico 200 (0.06)
Puerto Escondido, Mexico 1,000 (0.3)
Staten Island, New York 1,900 (0.5)
Taupo County, New Zealand County code for all
new facilities
The Grundy Center, Iowa SBR selection saved 18 percent construction cost
compared to the least costly conventional alternative, and a savings of 9
percent in electrical cost. The Sabula, Iowa facility plan showed a 22
percent energy savings, and a 15 percent life-cycle cost savings over
conventional activated sludge. Both facilities received an extra 10 percent
federal share of construction funds under the Innovative and Alternative
provisions of Public Law 95-217.
Taupo County, New Zealand has provided for SBR selection in all new
plant construction for several reasons (2). Chief among these reasons was
the need to provide economical treatment for nitrogen removal to protect
Lake Taupo from eutrophication. The County Engineer evaluated several options
for capital and operating costs and arrived at the following ranking for the
Acacia Bay portion of Lake Taupo:
665
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Acacia Bay, New Zealand, 2280 m3/d (0.6 mgd)
Process Option Total
Oxidation Pond
Sequencing Batch Reactor
Activated Sludge
Biological Filtration
Rotating Biological Contactor
Oxidation Channel
$
$
$
$
$
$1
Capital Cost
624,000
634,900
746,800
755,000
956,000
,006,000
Annual
Operating Cost
$ 9,800
$23,400
$28,100
$17,900
$17,700
$27,000
The decision analysis showed that the oxidation pond, activated sludge,
biological filter and rotating biological contactor processes could not be
easily managed for nitrogen removal; and all but the oxidation pond were
more capital expensive than the SBR. While the oxidation channel could be
operated for nitrogen removal, the capital cost was prohibitive. Even
though the analysis showed the SBR operating cost to be greater than three of
the options, on a cost per kilogram of nitrogen removal, the SBR was most
cost effective.
Whang and Hao developed computer simulation models for the process design
of the Poolesville, Maryland SBR. Software developed uses an iterative
process, from input data, to size reactors, give temporal concentrations of
substrate and active biomass, and oxygen utilization rates (3).
OPERATIONAL CONSIDERATIONS
Since the majority of the SBR's being constructed are of small size a
recent discussion of energy utilization at municipal facilities by Smith is
of interest (4). This discussion shows that in the 3,785 m3 per day (1 mgd)
size range energy consumption is only 8.1 percent of the operating cost and
labor accounts for 68.2 percent of the cost. Therefore, the SBR process with
automated valving, and a process controller which eliminates major labor
time, is a logical selection at small facilities. In Australia, where
modifications of the SBR have been employed for several years, it is common
to have one operator manage four facilities in a several hundred square
kilometer area. Also, designers are beginning to recognize the attributes of
the SBR in many situations. Barth has noted flexibility, equalization,
quiescent settling, elimination of recycle pump, and process reliability, as
criteria that direct selection of batch systems for many installations (5).
Bathija, has described various SBR tank designs and operational schemes
(6). Racetrack, rectangular (length to width ~ 4:1), and circular SBR
facilities have been constructed. Recommended side-water depth is 3 to 4.5 m
(10 to 15 ft). If both aeration and mixing are independently necessary, a
666
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jet type aeration device is preferred. If separate mixing only is not a
process requirement any non-clogging aeration system can be specified.
Bathija also suggests SBR solutions to two common problem areas in
municipal treatment; reduced hydraulic flow during the early design life of a
facility, and increased hydraulic flow during storm events. During the early
design life period of reduced flow, liquid level sensors can be set at a
fraction of tank capacity. In this way, the length of treatment cycles is
the same as design, and power is not wasted by over-aeration during an
excessively long cycle time. There are several approaches to manage increased
hydraulic flow during storm flows. If level sensors are left in their usual
position, increased flows will cause the number of cycles per day to increase.
If this should cause a reduction in efficiency the level sensors could be
raised, within free-board limits, to keep the cycle time near design
requirements. Either of these two management approaches could be coupled
with modification of the time periods within a cycle. For instance, the time
devoted to IDLE could be eliminated and that time period shifted to increase
REACT time, yet not alter the overall design cycle time.
The SBR process has an outstanding reliability feature during increased
hydraulic flows. The mixed liquor solids always remain in the reactor and
cannot be washed out by hydraulic surges. Also, there is no recycle flow
from a separate clarifier and, therefore, an SBR process does not rely on
return sludge capability to maintain an adequate level of mixed liquor solids
during increased hydraulic flow.
EQUIPMENT SELECTION
Because the SBR process is rather new, several types of instrumentation
are being pursued. Some designs are employing photoelectric level sensors,
others use float level switches for controlling reactor liquid level.
Automated valves for control of reactor influent and effluent range from
pneumatic devices to motorized gate valves.
Effluent discharge devices can be submerged standpipes, tipping weirs,
float supported collector pipes, or submberged pumps.
In all but the smallest systems, commercial process controllers are used
to time and control the process sequence. In systems under 20 m-Vday (5000
gpd) simple time clock and electrical solenoid valves would be recommended.
INDUSTRIAL APPLICATION
The Springfield Creamery in Springfield, Oregon, produces a waste that
has a large concentration of soluble oxygen demand, intermittent flow, and
extreme pH fluctuation. Flow is 40 m^/day (10,000 gpd). An adjoining meat
packing plant has a large concentration of suspended oxygen demand, intermit-
tent flow, and stable buffered pH of about 7.. Flow is 8 m3 per day (2000
gpd).
Upon learning of the inherent equalization of an SBR process, ease of
operation, wide flexibility of treatment options, and simple design con-
667
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siderations, the two companies plan to mix these waste streams for combined
treatment. The SBR will be an earthen basin with dimensions of 7.5mx4.5m
x 2.4 m (25 ft x 15 ft x 8 ft). Aeration will be provided by a submerged
pump with an air blower exhaust line tapped into the intake side of the pump.
Since the flow is intermittent, a single tank system will be adequate.
Due to the facts that SBR's can be operated to produce a defined residual
concentration of a pollutant with no possibility of short circuiting, and that
quiescent settling produces very clear effluent, the process has been select-
ed to treat a combination of landfill leachate and chemical manufacturing
wastes in Niagara, New York.
The plant wastes are generated from the industrial operations and the
leachate is collected from a remote landfill area via collection underdrains
and hauled by truck to the plant site. Both type wastes contain several of
the Consent Decree priority pollutants. Daily design flow is 600 m3.
The existing treatment at the industrial site consists of a storage
tank, neutralization tank and carbon absorption columns; with discharge of
the column effluent to the city sewer. Operation has shown that with this
physical/chemical process, excessive soluble organic matter quickly saturates
the absorption capacity of the carbon columns requiring frequent thermal
regeneration of the carbon. Upgrading construction will add two biological
SBR's, to reduce the soluble organics, and provision for adding ammonia and
phosphate to serve as nutrients for the SBR organisms.
Many of the organic components of the mixed waste have slow rates of
biodegradation. To insure efficient degradation, the SBR contents will be
monitored for total organic carbon during REACT until a predetermined concen-
tration is achieved. Thus, the SBR will decrease the organic loading to the
carbon columns and efficient settling will not overly burden the columns with
suspended solids. Waste activated sludge from the SBR's will be incinerated
to destroy any sorbed priority pollutants on the sludge surface.
Pilot SBR operation at a scale of 50 m3/day (13,000 gpd) has shown a 90
percent reduction of soluble organic carbon from the influent mixed waste.
It is therefore anticipated that the useful life of the carbon, before
regeneration is necessary, will be increased by almost a factor of 10. Figure
2 is a schematic of the full-scale process as it will exist in 1985.
LABORATORY RESEARCH ON SBR's
Control of Sludge Bulking
Working with 4 L SBR's, fed a soluble synthetic wastewater, Chiesa has
correlated sludge volume index (SV1) with aeration time during the FILL period
(7). He used the following strategies to manage the substrate tension in the
SBR's:
668
-------
Control
Strategy
A
B
C
D
E
F
Unaerated/Unmlxed
FILL, hr
2.00
1.75
1.50
1.25
1.00
0.00
Aerated
FILL, hr
0.00
0.25
0.50
0.75
1.00
2.00
Aerated
REACT, hr
4
4
4
4
4
4
SETTLE ,
and IDLE
2
2
2
2
2
2
DRAW
, hr
Very spectacular results were obtained as shown in Figure 3. To confirm
this observation, an SBR operated under control strategy F, with an SVI of
600 mL/g, was switched to strategy A; and in 15 days the SVI decreased to 100
mL/g.
The researchers explain these observations on the basis of competitive
growth of one group of organisms in opposition to other groups. They postulate
that strategy A, where substrate tension surrounding the organisms reaches a
high level during FILL, and subsequent oxidation of organics and endogenous
metabolism during REACT, which places the organisms in periodic starvation,
selectively encourages the growth of floe forming organisms. Filamentous
organisms survive best when the substrate tension is constantly maintained at
a low level such as in strategy F.
The sludge developed under strategy A had a greater specific oxygen
uptake rate than did the F strategy sludge; and the A sludge was much more
efficient in substrate removal rate than the F sludge.
The authors point out the great flexibility of the SBR process to control
substrate tension at any desired level. It can be noted in the above strate-
gies that A would be equivalent to contact stabilization and F would be simi-
lar to a completely mixed activated sludge process.
Unaerated SBR
Irvine has demonstrated with bench-scale SBR's that a weak domestic
wastewater can be treated without major power input for aeration (8). He
used 4 L SBR's that were mixed with a stirrer, with just enough energy to
keep the mixed liquor in suspension, during FILL and REACT. The organic
loading was 0.02 kg 8005 per day per kg mixed liquor solids. A 24 hour cycle
consisting of FILL 9 hr, REACT 12 hr, SETTLE 2 hr, DRAW 0.5 hr, and IDLE 0.5
hr; was used.
In this lightly loaded SBR process the aeration provided by surface
renewal due to stirring was sufficient for the oxygen requirements of the
organisms. The authors conclude that this low energy SBR process is analogous
to a wastewater lagoon system. With the added advantage that algal growth
will not occur, as is normal for conventional lagoons, because the mixed
liquor turbidity prevents sunlight penetration. Mixed liquor concentration
was 1800 mg/1, and the 2 hour SETTLE period allowed excellent liquid solids
separation.
669
-------
Results for this low energy system for removal of BOD5 are shown in
Figure 4. Suspended solids removal was equally as effective and averaged 10
g/m^ over the 60 day study period.
Biological Phosphorus Removal in an SBR
Discussions at the June 1982 "Workshop on Biological Phosphorus Removal"
showed a similar process feature for three proprietary phosphorus removal
systems (9). This feature is shown conceptually in Figure 5. When activated
sludge mixed liquor is subjected to an anaerobic or anoxic environment* with
influent organic substrate, there is coincident leaching of phosphorus from
the cellular material and sorbtion of organic matter. When environmental
conditions are changed to an aerobic state, phosphorus is removed from solution
and organics are oxidized.
The following several theories have been proposed to explain this finding
(9). Anaerobic-aerobic staging can result in selection of a biological
population that is capable of storing polyphosphates. The actual mechanism
for storage and release and the basis of population selection is not known.
The regulation of the adenosine diphosphate ratio to adenosine triphos-
phate (ADP/ATP) controlled by the reversible enzyme polyphosphate kinase has
been suggested as a mechanistic factor. When cells are placed in a "stress
condition" such as lack of oxygen during an anoxic period, large amounts of
polyphosphates are then stored in the cells when subsequent aerobic conditions
are provided and cellular growth is rapid.
Another theory suggests that polyphosphate storage ability of certain
bacteria allow them to compete and survive in an alternating anoxic-aerobic
environment. The energy derived by hydrolysis of polyphosphate (ATP) may be
used directly for transport of substrate across the cell membrane in the
anoxic condition.
Polyhydroxy butric acid (PHB) has also been suggested as an important
consideration. It has been noted that PHB is formed during anoxic conditions,
and organisms such as Acinetobacter can accumulate both PHB and phosphates.
These various mechanistic theories seem to show that some type condition-
ing occurs during the anoxic period; whether enzymatic hydrolysis, uptake of
a metabolite or environmental stress that confers a competitive advantage to
certain phosphate storing organisms when conditions are switched to an aerobic
state.
The term anaerobic refers to environments which have no measurable concentra-
tions of either oxygen or oxidized nitrogen. Often times appreciable concen-
trations of carbonaceous materials must be present to maintain this condi-
tion. Anoxic refers to environments which have no dissolved oxygen but have
oxidized nitrogen present. However, these two terms were used almost inter-
changeably in the workshop discussions.
670
-------
The PhoStrip process utilizes this anaerobic or anoxic leaching to
remove phosphorus from a portion of mixed liquor in a side stream stripper
tank. Both the A/0** and Bardenpho*** processes remove phosphorus by baffling
the biological reactor to maintain the mainstream flow environmental condi-
tions suitable for each process1 operation.
Also, all three processes were reported to be subject to inhibition of
phosphorus leaching during the anaerobic or anoxic phase if nitrate ion was
present. If nitrate was present, provision for denitrification before
phosphorus leaching had to be provided.
All of these applications for phosphorus removal are for continuous flow
systems. The Municipal Environmental Research Laboratory is employing an SBR
for studying biological phosphorus removal because the batch approach should
allow close control of environmental conditions. A schematic of the 4 L
bench-scale reactor used for these studies is shown in Figure 6. A vast
number of operational schemes can be employed using a microprocessor con-
trolled SBR. In order to achieve the release and uptake of phosphorus noted
in Figure 5 the following cycle scheme was employed:
Cycle Event
Time
Purpose
Note
FILL+
STRESS
AERATE
1 hr
4.5 hr
1 hr
Add substrate
Cause phosphorus
leaching and
denitrification
Cause phosphorus
uptake, and
oxidize organics
No aeration
Mixer on
No aeration
(Time overlaps
with FILL
time)
Aeration
WASTE SLUDGE
4 sec
Remove phosphorus
from reactor,
and control SRT
Aeration
SETTLE
15 min Form clear super-
natant
No aeration
Biospherics, Inc., 4928 Wyaconda Rd., Rockville, MD 20852
Air Products, Inc., Box 538, Allentown, PA 18105
**
***
EIMCO-PMD, 3839 S. West Temple, Salt Lake City, UT 84115
"^Primary effluent from Cincinnati's Muddy Creek treatment plant used.
671
-------
Cycle Event Time Purpose Note
DRAW 5 min Discharge effluent No aeration
IDLE 10 min Adjustment of cycle No aeration
length
The total cycle time was 6 hours and therefore the SBR emptied and filled
4 times each day.
The results achieved are shown in Figure 7. During FILL the phosphorus
concentration in the reactor is affected by the phosphorus content at the end
of the last cycle event (either DRAW or IDLE), the concentration in the feed
entering the reactor and the leaching of phosphorus from mixed liquor solids.
In the case depicted, the residual phosphorus in the SBR was diluted as primary
effluent, with a smaller concentration entered, and a gradual increase to 33
g/m^ occurred as mixed liquor cellular leaching occurred. During the STRESS
period a plateau concentration existed, until aeration was commenced, and
cellular uptake reduced the concentration to 2.5 g/m^. Effluent filtered
orthophosphorus concentrations approaching 0.0 g/m^ have occasionally been
noted.
Nitrate nitrogen remained at about 1 g/m^ during STRESS due to the
occurrence of denitrification. A dramatic increase of nitrate formation
occurs once aeration is commenced and dissolved oxygen increases.
The SBR was operated under this regime for 30 days (120 cycles) using
the Muddy Creek primary effluent. SBR effluent residual orthophosphorus was
routinely between 2.5 and 0.5 g/m^. Influent total phosphorus varied between
20 g/m^ and 15 g/m^, with orthophosphorus between 20 g/m^ and 6 g/m^. Muddy
Creek wastewater is primarily domestic waste.
The process management to control biological phosphorus removal can be
illustrated by referring to Figure 7. During FILL and STRESS, conditions
have to be provided to cause denitrification of any nitrate and insure that
leaching from the cellular mass occurs. STRESS periods ranging from 2 to 6
hours have been studied. Three hours appears to be the minimum time that can
be employed. An aeration period of at least 1 hour is necessary to reincorpo-
rate the leached phosphorus and oxidize organics. Aeration times greater
than this lead to less efficiency due to lysis of cells during endogenous
respiration. Wasting of sludge from the SBR must be done when the biological
solids have the highest content of phosphorus. This would be at the end of
AERATE, which yields a dilute waste activated sludge of the same solids
content as the mixed liquor. Or, wasting can be done near the end of SETTLE,
which provides a thickened waste activated sludge. Caution is required here
in case low dissolved oxygen in the sludge blanket causes leaching of phos-
phorus. Thus, overall efficiency of biological phosphorus removal dictates
that SETTLE time be as short as possible, yet provide good solids separation.
A minimum of 15 minutes and a maximum of 30 minutes has been satisfactory.
672
-------
Time devoted to DRAW is not critical to biological phosphorus uptake
directly. Mainly, on full-scale SBR's this time period would be related to
effluent weir design to insure proper hydraulics within the reactor, and
hydraulics of discharge appurtenances. Provision for an IDLE period is
optional in SBR operation for biological phosphorus removal. A short IDLE
period, either quiescent or aerated would have no impact on overall efficiency.
IDLE is simply a convenience of adjusting cycles between reactors if two
SBR's are operated alternately. The same SBR process cycle described above
was employed with wastewater from Cincinnati's Little Miami facility. This
waste contains a major fraction of wastes from a variety of industrial pro-
cesses. Consistent biological phosphorus removal could not be achieved.
Over a three month period variations to FILL, STRESS, and AERATE were attempt-
ed without success. Efficient removal with residual orthophosphorus values
of 0.5 to 1.0 g/m^, would be noted for several days; then deterioration of
efficiency would occur.
These SBR studies, on two wastewaters, have not revealed the controlling
parameters to insure consistent, highly reliable biological phosphorus remov-
al. This same conclusion was noted for the three continuous flow biological
phosphorus removal processes discussed at the Annapolis workshop (9).
Presently it would be recommended that any facility plan for biological
phosphorus removal be guided by pilot plant studies prior to final selection.
Additionaly, in those cases where a high reliability of phosphorus removal is
necessary, it would be recommended that a chemical addition system be installed
as backup equipment.
673
-------
REFERENCES
1. Earth, E.F. Sequencing batch reactors for municipal wastewater treatment.
8th US/Japan Conference on Sewage Treatment Technology, Cincinnati, Ohio.
October 1981.
2. Taupo County Council Sewerage Code for Lake Taupo Settlements, 72 Lake
Terrace, Taupo, New Zealand, November 1982.
3. Whang, J. S., and Hao, 0. J. Comprehensive design of sequencing batch
reactor systems. 9th U.S./Japan Conference on Sewage Treatment Technolo-
gy, Tokyo, Japan, October 1983.
4. Smith, J. M. Energy recovery and conservation for low-cost systems.
Workshop on low-cost treatment. Clemson University, April 1983.
5. Barth, E. F. (III). Sequencing batch reactors: doing more with less.
Federal Water Quality Association Newsletter, Vol. 10, No. 1, October
1982.
6. Bathija, P. R. The jet age in sequencing batch reactors. Seminar on
Emerging Technologies, Boston, Massachusetts, December 15, 1981.
7. Chiesa, S. C., and Irvine, R. L. Growth and control of filamentous
microbes in activated sludge. 55th Annual Conference Water Pollution
Control Federation, St. Louis, Missouri, October 1982.
8. Irvine, R. L., and Carvajal, E. B. Sequencing batch reactors for municipal
compliance over a wide range of effluent quality. Workshop on Low Cost
Treatment, Clemson University, April 1983.
9. Workshop on biological phosphorus removal in municipal wastwater treat-
ment. Summary report, Annaypolis, Maryland, June 1982.
10. Hong, S., et al. A biological wastewater treatment system for nutrient
removal. Air Products and Chemicals, Inc., June 22, 1982.
674
-------
WASTEWATER
1 HR
1
tx»—
3HR
\
AIR
, <*>-
1 HR
I
0.5 HR
rxj—
CXH-
CXI—
t*>-
0.5 HR
AIR
M—
_ TILL ^ —
| r*-^"«WV» V.V-I-- '-'^r-f. -r_ ^
REACT -,
^iUi(i:^(v^SSl^?^v@
r SETTLE -,
•i^l-^^I^Vii^-'^^
DRAW
V
::-:iH^^y^^VVv;::-/^^viU^
IDLE
^T7:7?^;^/: • '• r^TT: • : :^; f^Xv.- : •. : V. •/.•• •;•'•.
fttt&-:-XX*:*:X*Wt-^\
-END FILL }FREEBC
— CXI
— START FILL
— txj
— tx]
— txj
— M
— M
DISCHARGE
EFFLUENT
—cxi ^
M WASTE *
SLUDGE
— x
SEQUENCE OF EVENTS FOR
6 HOUR SBR CYCLE (ELEVATION VIEW]
LEGEND:
X AUTOMATIC VALVE
0.0 HR =1 INTERNAL CLOCK
T LIQUID LEVEL SENSOR
RY
Figure 1. Sequence of events for 6 hr SBR cycle.
(elevation view)
675
-------
f^hpmical
VX 1 1 ^ 1 1 • I Wfci •
Plant Waste
300 m3/d
300 m3/d
•^
Hauled in
x^ ^\
Storage
Blend
\ x
\ ^
>fc
*
/
\
rNH3
-PO|
-Lime
Mixer
r
d
"\
s V
T
^
i ^~^ j
v '7
Leachate ^-r-^ ^-, — '
Sludge to Landfill
Biological
SBR's
Air
-~-
< ! ^ E
' — - —
a
»-' Air|
t "~
^^ E
\AJ
i
-4—
U
),. j
"^
3-
o
3
^-/
T j
[7k
E
3
3
(0
v^
i I
To City
AQ t« Sewer
Incineration
Figure 2. SBR-Carbon adsorption for industrial waste.
-------
10 20 30 40
( ) Control Strategy
Figure 3. SVI as a function of control strategy.
(From Ref. 7).
677
-------
\
O)
Q
O
CO
140
120
100
80
Influent
Effluent
A
/ \
60
I
i A /
»/ \ /
-',' v
40
20
7 10 13 17 20 23 27 30 33 36 37 41 44 47 50 53 56 59 61
Time, days
Figure 4. BOD versus time for low energy SBR.
(From Ref. 8).
678
-------
Anaerobic
Aerobic
Environmental Conditions
Figure 5. Biological phosphorus and BODc removal due
to anaerobic-aerobic contacting. (Ref. 10)
679
-------
00
o
r 43 Mi
o
iil
Clock
Vs.
>
^
*?* 'a--
ruiv-
I~y^-:::>
T^
Microprocessor
Waste
Sludge ,
_f Pump
Effluent
Wastewater
Holding
Tank
Figure 6. 4 L Bench-scale SBR.
-------
SEQUENCING BATCH REACTOR BIOLOGICAL PHOSPHORUS
REMOVAL
- NOTES -
pH RANGE 6.6-7.0
TEMPERATURE 22°C
5.0-
2.5-
DISSOLVED OXYGEN IN SBR MIXED LIQUOR MLSS
MLSS
i '|"T~|^~^|^'T
3000 g/m3
5.9% P
f,'
' '
/
\
A
\
\
\
\
1 •
10-
3
5-
N03-N IN FILTRATE FROM SBR
s
/
••-.-_. .._^_..^..-....^_.^_.^..<_..^..^
1 i i 1 • i 1 i i 1 i T | • i 1
ORTHO PHOSPHOROUS IN FILTRATE FROM SBR
30-
3
15-
^^ .. + ,..--«- — * — -«^
\-
•
Figure 7. SBR Biological phosphorus removal.
-------
THE BIOLOGICAL AERATED FILTER-
PROGRESS OF DEVELOPMENT IN THE U.S.
by
Gary R. Lubin
Wastewater Research Division
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
683
-------
THE BIOLOGICAL AERATED FILTER-PROGRESS OF DEVELOPMENT IN THE U.S.
INTRODUCTION
Current projections (1) indicate that, by the year 2000, 21,027
municipal wastewater treatment facilities will be operating in the
United States (U.S.) to treat a flow of 161,778,000 m3/d (42.7 bgd)
(See Table 1). This compares to the 15,431 facilities presently oper-
ating. The net increase of 5596 operating facilities is based on
abandonment of 1477 existing plants, 447 plants under construction (as
of 1980) and 6627 new plants to be constructed by the year 2000.
Therefore, more than 30% of the plants to be operating by the year 2000
are yet to be built. A total of 5832 existing facilities are to be
enlarged and/or upgraded. Of the 21,027 facilities to be operating in
the year 2000, more than half of the design flow to be handled will be
treated to better than secondary levels. More than 80% of the total
number of facilities will be for design flow capacity less than 4000
m^/d (1.06 mgd); yet only 3% of the facilities will be treating more
than 65% of the flow.
In order to address the present and future needs in these areas,
the Wastewater Research Division of the U.S. EPA Municipal Environmental
Research Laboratory conducts a national program to support research, de-
velopment and evaluation of municipal wastewater and sludge collection,
treatment and disposal technologies. Focus is on solutions that reduce
capital and operating costs, use energy and resources more efficiently
and improve operational reliability. Presently, particular program
interest is directed to problems of small communities, operation and
maintenance, technology suitable for retrofit and testing and engi-
neering evaluation of conventional as well as "innovative and alter-
native" technologies.
As a result of these efforts, the range of available solutions will
be widened to address: continuing changes in cost and energy relation-
ships experienced in the economy; changes in water quality issues; and
changes in affordability and funding scenarios-particulary as they
relate to the recently passed "Municipal Wastewater Treatment Construc-
tion Grant Amendments of 1981" (PL97-117, 12/29/81).
THE BIOLOGICAL AERATED FILTER
As reported previously (2), a promising new technology development
for wastewater treatment appears to be the biological aerated filter
(BAF). The proprietary BAF process was developed in France by Omnium
de Traitments et Valorisation (OTV), a company involved in engineering,
equipment fabrication, and construction of wastewater treatment facili-
ties. The BAF process is presently marketed in the U.S. by the Eimco
684
-------
TABLE 1
NUMBER OF PUBLICLY OWNED MUNICIPAL WASTEWATER TREATMENT FACILITIES IN
THE U.S. ACCORDING TO SIZE RANGE IN 1980 AND PROJECTED FOR THE YEAR 2000*
FLOW (MGD)
(0-.105) (.106-1.05) (1.06-10.5)
(10.57-50.2) (50.2+) Total
1980
Facilities
Count
Total Flow
% Flow
% Facilities
2000
Facilities
Count
Total Flow
% Flow
% Facilities
Change
Count
% of total
Flow
% of total
% incr. count
% incr. flow
5120
261.8
.7
33.2
8701
437.5
1
41.4
3581
64.0
175.7
2.4
69.9
67.1
7031
2671.6
7.5
45.5
8460
3063.7
7.1
40.2
1429
25.5
392.1
5.2
20.3
14.7
2760
9114.9
25.8
17.9
3213
10,737.9
25.1
15.3
453
8.2
1623.0
21.7
16.4
17.8
421
9,333.4
26.4
2.7
524
11,211.4
26.2
2.5
103
1.8
1878
25.1
24.5
20.1
99
13,889.0
39.3
0.7
129
17,290.9
40.4
0.6
30
0.5
3401.9
45.6
30.3
24.5
15,431
32,270.7
100
100
21,027
42,741.4
100
100
5596
7470.7
36.3
21.2
* 1982 Needs Survey
-------
Process Equipment Company, Salt Lake City, Utah, under an exclusive
licensing arrangement.
Research interest in the U.S. is due to apparent simplicity of
operation, reduced reactor volume and space requirements, positive
effluent solids control eliminating the need for a secondary clarifier,
associated sludge control problems with activated sludge processes,
competitive power requirements and flexibility in treatment capability
as well as size range applicability. An attractive feature of the BAF
is the reduced land area requirement, which is about 20% of that for a
plastic media trickling filter and secondary clarifier and 10% of that
for conventional activated sludge systems.
GENERAL BAF DESCRIPTION
The BAF is a high rate, fixed film biological/solids filter.
Figure 1 presents a process flow elevation view of the BAF.
In the BAF, primary effluent, which is free of coarse and flotable
materials, is introduced to the top of the filter unit and flows by
gravity downward through a packed bed about 1.5 m to 1.8 m deep (5.0 to
6.5 ft deep) of granular, porous media, which is a 3 to 6 mm kiln fired
clay mined in the U.S. and which costs about $0.22/kg ($0.10/lb).
Filter media loss is reported as 2% a year, and media life is expected
to exceed 20 years. Free oil and grease must be reduced below about 20
mg/1 to avoid media plugging. A high biomass concentration is estab-
lished on the media, reportedly equivalent to 15,000 to 20,000 mg/1 of
mixed liquor volatile suspended solids (MLVSS). This is attributed to
a high media specific surface area of 1312 to 1640 m2/m3 (400 to 500
ft2/ft3). Oxygen for biological growth is supplied by sparging com-
pressed air directly into the packed media bed about 0.3 m to 0.5 m
(1.0 to 1.5 ft) above the underdrains through a PVC pipe distribution
system. The system is designed to ensure uniform air distribution
across the bed. The air moves upward, countercurrent to the waste-
water, but not at a sufficient velocity to expand the bed. Aeration
continuously loosens the filter bed to allow penetration of solids,
avoid plugging and make maximum use of the filter depth. Solids fil-
tration and BOD absorption/oxidation take place throughout the volume
of the filter, but the bed volume below the air sparger is undisturbed
and serves as a polishing zone for suspended solids (SS) removal. The
dissolved oxygen (DO) of the BAF effluent is reported to be about 0.5
mg/1. The BAF can potentially be used to achieve BOD and SS removal as
well as nitrify without the use of final clarification.
The air bubbles are 1 to 3 mm in diameter compared to the 3 to 6 mm
media size. As a result, contact time for the air bubble is extended
due to the circuitous path that must be followed through the media and
686
-------
BACKWASH
•INFLUENT
i i i i
PROCESS AIR
t
GRANULAR MEDIA
•^-EFFLUENT
|
BACKWASH WATER
— BACKWASH
AIR
FIGURE 1 (6)
BIOLOGICAL AERATED FILTER SYSTEM
687
-------
biofilm. Because of the low operating head of the unit, the manufac-
turer claims a relatively low blower discharge pressure of about 4.5 to
4.7 psi, offering the possibility of a low energy unit operation.
The BAF will typically be constructed above grade and requires
approximately 3.5 m to 3.7 m (11.5 to 12.0 ft) of head to enter the
module. Pumping may be required to feed the BAF. About 2.4 m (8 ft)
of head, however, can be recovered for downstream units such as cascade
aeration.
The total hydraulic residence time (HRT) in the packed bed will
generally range from 30 to 80 minutes dependent upon influent strength
and effluent required. Ninety-percent BODs removals reportedly can be
achieved at HRT's from 40 to 60 minutes at loadings of 3.2 to 5.0 kg
BOD5/ m3/d (200 to 310 Ib BOD5/1000 ft3/d).
Accumulation of biological growth and trapped biological solids
causes the head above the media bed to gradually increase from about
0.15 m (0.5 ft) under clean conditions to 0.61 m (2 ft) when a level
sensor (timer control can also be used) will initiate a periodic back-
washing procedure using water wash and air scour. Treated effluent is
used for the water wash at a rate of 0.65 m/min (16 gpm/ft?). Air is
introduced to the bottom of the bed at a rate of 0.9 m/min (3 scfm/ft2)
to scour excess solids from the media. It is claimed that from 4 to 6
complete cycles are normally necessary during backwash. The backwash
water is removed by a siphon located above the bed and returned to the
primary clarifiers. The settling characteristics are similar to trick-
ling filter slough with a sludge volume index (SVI) of 40 to 60. The
estimated sludge production is 0.4 to 0.7 kg/kg BOD removed. The total
volume of backwash water normally required is claimed to be about 2 to
2.5 times the bed volume or 5% of plant flow. The frequency of backwash
required is claimed to be 15 to 24 hr for BOD removal units achieving
secondary treatment and once every 24 hr for nitrification units. A
microbial slime layer remains on the media to resume treatment. One
backwash system can reportedly accomodate up to 20 BAF module units.
The BAF is presently made available through Eimco in the U.S. in the
form of modules which are pre-fabricated, shop assembled units including
air distribution piping, underdrain nozzles, backwash system, media and
controls. Each module is made of steel and consists of a series of
cells. A typical module is 3.7m x 12.8m x 3.7m (12ft x 42ft x 12ft)
high and is 46.5 m? (500 ft?) in cross section and contains a volume of
171.3 m3 (6048 ft3). Operation of the BAF is automatically controlled
by use of a programmable controller.
FRENCH DEVELOPMENT OF THE BAF
As reported by OTV and Eimco (3)(4)(5)(6), OTV first piloted the
688
-------
BAF concept at the Paris, France, Columbes treatment plant in 1975 for
both BOD removal and nitrification. Both granular activated carbon and
clay media (mined in France) were used in columns 0.11 m (4.4 in.)
diameter ranging from 1.6 to 3.0 m (5.2 ft to 9.8 ft) deep. Selection
of the media appropriate for such a filter would consider: the need for
a high surface area with a high pore volume to maximize bacteria popul-
ation, particle size, particle shape and density for hydraulic and air
distribution headloss considerations, resistance to abrasion during
backwashing, availability, and cost. Hydraulic application rates in
the pilot work were varied from 0.5 to 5.0 m/hr (0.2 to 2 gpm/ft2) of
primary effluent. The COD, BODs, SS and NH3-N of the primary feed
averaged 200 mg/1, 85 mg/1, 75 mg/1 and 22 mg/l, respectively. The
organic loading rate varied from 2.5 to 15 kg COD/mJ/d (66 to 400 Ib BODc
/1000 ft3/d), and liquid retention times based on total bed volume ranged
from 19 to 115 minutes. Reported BODs effluent concentrations averaged
less than 1Q mg/1 for loadings less than 5.1 kg BOD5/nr/d (318 Ib
BOD5/1000 ft^/d) (Figure 2). Effluent suspended solids averaged less
than 5 mg/1 for loadings over the full range. Further, the pilot study
indicated that the clay and carbon media performed similarly ( Figure
3). The primary effluent was increased in strength with beef extract
in order to study a stronger wastewater characterized with average
total COD, BOD5, SS and NH3-N as follows: 475 mg/1, 280 mg/1, 75 mg/1
and 50 mg/1. As indicated on Figure 4, BAF treatment of the higher
strength wastewater resulted in only a marginal increase in effluent
6005 at the same loadings.
At Colombes, France, while operating in a nitrification mode at
15°C at an organic loading rate of 2.2 kg BODg/m^/d (140 Ib BOD5/1000
ft3/d), BODc was reduced from 110 mg/1 to less than 10 mg/1 and NH3-N
from 20 mg/T to less than 1.0 mg/1. For BODc, loadings less than 5.1 kg
BODc/m3/d (313 ib BODC/1000 ft3/d), effluent SS averaged less than 5
mg/1.
A full-scale, 1893-m3/d (0.5-mgd) system was built in LeHavre,
France, and began operating in October 1978. The system consisted of
four cells with total bed surface area of 30.2 m2 (325 ft2) to treat a
primary effluent to provide advanced secondary industrial recycle water.
A media depth of 2.0 m (6.6 ft) is used. Loadings during an August-
September 1980 survey were 3.5 kg BODc/m3/d (220 Ib BODC/1000 ftj/d) and
1.8 m/hr (0.83 gpm/ft2). At 1514 m3/d (0.4 mgd), BOD5 was reportedly
reduced from 150 mg/1 to 16 mg/1 and SS from 130 mg/1 tO 7.5 mg/1.
Wastewater temperature was 15°C.
While operating as a second-stage nitrification mode, 800$ was
reported to be reduced from 25 mg/1 to less than 10 mg/1 and 'NH^-N
reduced from 20 mg/1 to 3 mg/1 at a loading rate of of 641 kg NFU-N/nr/d
(40 Ib NHo-N/ 1000ft3/d) and a temperature of 15°C. The LeHavre facility
has also "been reported to reduce NH3-N to 1.0 mg/1. The EPA also has
access to some raw as opposed to summary data from the LeHavre facility
treating a wastewater with a strong industrial component including high
organic nitrogen concentrations. Two cells were used for a nitrifi-
cation test from October 1978 to March 1979 indicating that the units
689
-------
100
PERCENT 9°
REMOVAL 80
70
60
CONG.
(mg/l)
40
20
DETENTION TIME (MIN.)
57.6 28.8
19.2
BOD REMOVAL
COD REMOVAL
ACTIVATED
CARBON
SYSTEM EFFLUENT
ACTIVATED CARBON MEDIA
•COD
BOD.
COD LOADING (kg/m°-day)
FIGURE 2 (6)
AVERAGE PERFORMANCE OF BIOLOGICAL AERATED FILTER FUNCTION OF
ORGANIC LOADING - DOntSTIC 'rtASTfiWATER USIwG Tut FKtNCH PILOT
UNIT (ACTUAL DATA NOT AVAILABLE)
-------
80
60-
CONC.
(mg/l)
40-
20 ••
DETENTION TIME (MIN.)
1 ,—
57.6
28.8
ACTIVATED CARBON-
MEDIA
5.0 10.0
COD LOADING (kg/m3-day)
19.2
15.0
FIGURE 3 (6)
EFFECT OF f^EDIA ON EFFLUENT COD CONCENTRATION USING THE
FRENCH PILOT UNIT (ACTUAL DATA NOT AVAILABLE)
-------
20
BOD_
o
CONC.
(mg/l)
10
(ACTIVATED CARBON MEDIA)
DOMESTIC + BEEF EXTRACT
DOMESTIC
i 5.0 10.0 15.0
COD LOADING (kg COD/m3-day)
FIGURE 4 (6)
AVERAGE PERFORMANCE OP BIOLOGICAL AERATED FILTER USING HIGHER
STRENGTH DOMESTIC - SYNTHETIC WASTEWATER USING THE FRENCH
PILOT UNIT (ACTUAL DATA NOT AVAILABLE)
-------
were capable of achieving an effluent NH3-N of 7 mg/1, which was the
objective of this particular test.
To date, in addition to the 1893-m3/d (0.5-mgd) LeHavre and 757-
m3/d (0.2-mgd) Columbes facilities, 15,519-m3/d (4.1-mgd) and 9463-m3/d
(2.5-mgd) facilities are in operation at Soissons and Valbonne, France.
Other facilities are under construction including 18,925-m3/d (5.0-mgd)
and 13,248 m3/d (3.5-mgd) facilities at Grasse and Hockfelden, France,
respectively.
DEVELOPMENT IN THE U.S.
During the late 60's and early 70's the use of packed bed reactors
(PBR) (a predacessor to the BAF) for nitrification progressed from the
laboratory stage to pilot-scale and full-scale commerical availability
(7). A PBR consists of a bed of media upon which biological growth
occurs overlaying an inlet chamber. Wastewater is evenly distributed
across the floor of the PBR by baffles, nozzles, or strainers. Several
types of media have been successfully used in PBR reactors for
nitrification including 2.5- to 3.9-cm stones, 5.0-mm gravel, 1.8-mm
(effective size) antracite and 9-cm plastic media. The BAF differs
from the PBR in several areas. The BAF is capable of removing signifi-
cant BOD and solids as well as nitrifying. Wastewater flow is downward
rather than upward. Air is supplied via an in-bed sparger rather than
via predissolution of oxygen or bubbling air across the floor of the
reactor.
A BAF proof-of-concept pilot plant study was carried out by Eimco
during the latter part of 1979 to treat primary treated wastewater at
Salt Lake City, Utah (6). The pilot reactor was 19 cm (7-1/2 in) in
diameter with a media depth of 1.6 m (5 ft-3 in). When run at 12.54 m3/d
(2.3 gpm), the unit reportedly achieved BODs and SS less than 10 mg/1.
At the University of Utah, a nitrification bench-scale study has
recently been completed as part of work by Ms. Barbara Campion under
the direction of Dr. H. David Stensel (8). Using a 0.17-m (6-1/2-in.)
diameter reactor, 4.0 m (13 ft) high, effluent NH3-N concentrations
less than 1 mg/1 were achieved at 17°C when treating an influent NH3-N
concentration ranging from 20 to 50 mg/1 in a 1.5-m (5-ft) deep anthra-
cite media bed at loadings of 399 kg NH3-N/nr/d (24.9 Ib NH3N/1000
ft3/d). During the study, it was noted that BODc dropped below about
20 mg/1 before significant nitrification occurred!. Effective size of
the anthracite is the same as the media to be used in the BAF although
specific surface area will vary due to differences in porosity and
shape.
More recently, four other field test pilot studies in the U.S. have
been completed at Park City, Utah (9), and Asheville, N.C.(IO), as well
as at Homestake Mining Company, Lead, S.O., and Spanish Fork, Utah.
The Park City, Utah, wastewater treatment facility is located near
Salt Lake City, Utah, at an elevation of 1966 m (6450 feet). Process
693
-------
water temperatures range down to 8°C. The effluent requirements of the
7192-m3/d (1.9-mgd) facility require nitrification with effluent sea-
sonal ammonia nitrogen concentrations ranging from 2.0 mg/1 in summer up
to 7.0 mg/1 in winter months.
A two-column pilot unit (rated at 1 gpm average flow per column)
(Figure 5) was tested during the spring of 1982 under the direction
of PM Engineers, Inc., Salt Lake City, Utah. The pilot study and results
have been reported by PM Engineers (9) and are summarized here. Each
column was 30.5 cm (12 in.) in diameter and constructed to represent the
actual vertical full-scale BAF unit including media depth, location of
underdrains, influent air, etc. Some mechanical and equipment problems
ocurred during the effort, but there were no problems encountered that
related to process feasibility. For example, during the shakedown
period, a compressor failure caused a 2-week delay until a replacement
could be installed. Also, primary effluent was delivered by pumping to
a 208-L (55-gal) drum surge tank. Pump suction was frequently lost
causing flow to the BAF unit to terminate. In another instance, the
primary clarifier, which was providing the feed to the BAF unit, was
removed from service for 3 days. During this period, air only was
fed to the BAF unit to maintain aerobic conditions. When primary
effluent feed was resumed, the pilot unit was performing as desired
within only 1 day. Problems were also encountered with foulants
plugging feeder valves and blinding of the bed. The bed, therefore,
required backwashing sooner than the regular 24-hr cycle. To solve
this problem, the filter was backwashed with a single cycle (as opposed
to 3 to 6 cycles in a full sequence). This had the effect of providing
partial cleaning of the filter bed and extending the filter run length
until the full backwash cycle could take place. As a result, the fol-
lowing procedure has been adopted by Eimco for recommended full-scale
design and operation. A timer control activates a full backwash cycle
on a regular 24-hr basis at night during low flow, and a level sensor
detects the need for and initiates the shorter pre-emptive cycle.
The wastewater at the Park City plant is atypical. Primary efflu-
ent can be characterized as follows: BODs = 50 mg/1, NH3-N = 15 mg/1,
Flow ranges from 2650 to 14,005 m3/d (0.7 to 3.7 mgd) due to presence of
infiltration/inflow. The pilot studies were conducted from April 19
through September 24, 1982 to determine if the Park City, Utah wastewater
could be treated for BOD and ammonia removal to achieve permit limits
without secondary clarification.
The most significant part of the study occurred from August 20 to
September 24 when loading rates were most consistant. Figure 6 presents
the results of the testing during this period when effluent BOQ ranged
from 5 to 15 mg/1 and averaged about 10 mg/1 and effluent NH-^-N5 ranged
from <1.0 mg/1 up to 7.0 mg/1 and averaged about 2.5 mg/1. Total
suspended solids were always below 5 mg/1. The consulting engineer
concluded that the following design loading rates should be used in
694
-------
e
O
J
CM
T-
1
r-
i!
II
II
II
|l
ll
II
_u
-fT L
•Ql-
'
t^- ~—~ -~- "^
I
IT,
' • > 1 J f M
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u u u
r~iLi • i..
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}( ^fl'
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*rr*
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VI
i
r BACKWASH SIPHON
ir^rf^ii
it
u
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n
12" BAF
COLUMN
CATALYST
r LEVEL (
"i A r-
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^••^^^^^^IVVM
^C
'V
~i
TIT'
BACKWASH
COLLECTOR
TANK -
AIR DISTRIB
PIPING
| i—i r-y .— ^ [
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*
r — i
TT=£i I
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ft
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FRONT ELEVATION
SIDE ELEVATION
FIGURE 5
BAF PILOT PLANT AT PARK CITY, UTAH
SOURCE: PM ENGINEERS, INC. (9)
695
-------
15
20
AUGUST
SEPTEMBER
BOD •
NH3 A
FIGURE 6.
PARK CITY PILOT TEST RESULTS
SOURCE: PM ENGINEERS, INC. (9)
696
-------
full-scale design to meet, the required effluent limits: 1.44 kg BOD5/
m3/d (90 Ib BOD5/1000 ft3/d) and 0.32 kg NH3-N/mJ/d (20 Ib NH3-N/1000
In Asheville, N.C.(IO), present plans are to expand the existing
94,625-m3/d (25-mgd) step aeration wastewater treatment plant to 170,325
m3/d (45 mgd). The plant treats a significant industrial wastewater
component. The City of Asheville and their consulting engineer, Harry
Hendon and Associates, Inc., Birmingham, Alabama, decided to seek a
treatment process which would handle industrial shock loads and which
would meet limited space requirements at the existing site. In May
1982, representatives of the treatment authority, the consulting engi-
neer and Eimco made on-site inspections of several BAF installations in
France. Subsequently, the BAF unit process was evaluated as part of a
cost-effective analysis. A decision was made to pilot the BAF process
at the treatment plant to determine if it would meet a BODs/SS require-
ment of 30/30 mg/1. The pilot study and results have been reported by
Harry Hendon and Associates and Eimco (10)(11) and are summarized here.
The BAF pilot unit used comprises four independently operated
cells, each measuring about 0.6 m x 1.1 m (2 ft x 3.5 ft) with a media bed
depth of 1.8 m (6 ft). The pilot unit was manufactured by Eimco for
such studies, is fully automated and includes a clean water effluent
storage tank, a dirty water backwash storage tank and the pumps, blowers
and control instrumentation needed for operation. As opposed to the
manual backwashing conducted at Park City, Utah, the Asheville pilot
unit was to backwash each cell automatically 4 to 6 times every 24 hr.
Each backwash cycle was to include the following procedures:
1. Feed, process air and effluent valves in the cell were closed.
2. Air scouring proceeded at approximately 0.9 m3/min/m^ (3 cfm/
for 45 seconds.
3. Simultaneous air scour and water wash at 16 to 18 gpm/ft?
proceeded until the liquid level in the cell reached a point
just below the siphon invert.
4. A 30-second quiescent period followed to allow media settling.
5. Washwater was again introduced and continued until the liquid
level in the cell reached an elevation just above the top of
the siphon.
6. Backwash water was siphoned to the dirty water backwash sump.
A counter automatically kept track of the total number of backwash
cycles for each cell in the pilot unit. These are summarized in Table 2.
The consulting engineer estimates that, at design flows and loadings,
about 7% of influent to the BAF would be used as backwash water. Due
697
-------
TABLE 2 (10)(11)
SUMMARY OF BAF BACKWASHING CYCLES AT ASHEVILLE, N.C.
Cell Number
Operation 1234
Loading (m/hr) 1.71 2.44 3.18 1.22
Number of Total Daily Timed
Cycles 5564
Number of Daily High Level
Cycles 2221
Number of Total Daily
Cycles 7785
Backwash Volume, m3 3404 3404 3890 2431
Backwash Water 10 7.1 6.5 10.2
(% Of Influent)
698
-------
to the fact that the siphon in the pilot unit was mounted 0.2 m (8 in.)
lower (for transportation purposes) than would be the case in full
scale design, the actual number of cycles expected may be lower in a
full-scale operation.
A survey of plant operating records indicated the maximum monthly
average primary effluent BODs to be 175 mg/1 , which served as the basis
for the proposed full-scale BAF design loading rates of 5.6 kg BODc/nr/d
(348 Ib BODc/1000 ft3/d), 0.09 m/min (2.24 gpm/ ft2) under maximum hy-
draulic conditions and 0.04 m/min (0.99 gpm/ft2) under average condi-
tions of flow. The pilot plant was set up to operate at 5.7 kg BODg/nr/d
(355 Ib BOD5/1000 ftj/d) and 0.09 m/min (2.26 gpm/ft2) maximum hydrau-
lic loading rate and 0.04 m/min (1.01 gpm/ft^) average hydraulic loading
rate.
During the total time of the pilot plant operation, the influent
BOD5 to the BAF ranged widely from 30 mg/1 to 189 mg/1 and averaged 107
mg/1, substantiating the proposed maximum design value of 175 mg/1 in
order to meet permit requirements at all times. Total oil and grease
averaged 4.1 mg/1 and ranged from 0.5 to 8.5 mg/1. After the startup
period, BAF unit performance was monitored for 38 days under constant
flow conditions at average flow in cell 2 and sustained overloading of
126% of average flow in cell 3 (Table 3). Average influent
during this period was 87 mg/1.
The effluent BODs averaged 20.3 mg/1 and 22.3 mg/1 in cell 2 and
cell 3, respectively. Range of effluent 8005 was from about 6 mg/1 to
41 mg/1 in the cell loaded at average conditions and from 6 mg/1 to 50
mg/1 in the overloaded cell. Effluent TSS were consistently low,
averaging less than 12 mg/1 in all cells. During this time period,
the plant's step aeration process was upset due to several industrial
shock loadings. For example, pH ranged from 6.1 to 9.1 over 24 hr and
high pH values of 11.0 were observed. As a result, the treatment plant
was unable to comply with permit limitations whereas the BAF pilot unit
continued acceptable performance. It is notable that, in spite of
higher hydraulic and organic loadings experienced by overloaded cell 3,
removal performance was within 10% of cell 2 when using effluent
as the measure.
Due to the lower-than-average strength primary effluent, organic
loadings never reached more than 62% of the actual design load during
the study. The consulting engineer conducted a linear regression
analysis of the data which indicated, as would be expected, higher
effluent BODg concentrations as organic load increased. The analysis
also predicts that for the Asheville wastewater, at design loadings of
5.7 kg BODc/m-Yd (355 Ib BOD5/1000 ft3/d), effluent BOD5 would be
less than 28 mg/1 .
The pilot unit was briefly tested over a 3-day period from
December 6 through December 8, 1982, to ascertain effects of diurnal
699
-------
TABLE 3 (10)(11)
LOADING RATES AND OBSERVED PERFORMANCE OF THE ASHEVILLE, N.C.
PILOT UNIT AT CONSTANT FLOW RATES
o
o
Cell
No.
1
2
3
4
Flow
(m3/d)
27.3
38.2
48.0
19.1
Hydraulic
Loading Rate
(m/hr)
1.7
2.4
3.2
1.2
% of Design
Hydraulic
Loading Rate
72
100
126
50
Organic
Loading Rate
(kg BOD/m3/d)
2.1
2.9
3.5
1.4
% of Design
Organic
Loading Rate
37
51
62
25
Average
Effluent
BOD (mg/1)
-
20.3
22.3
_
Average
Effluent
TSS (mg/1)
9.0
8.0
11.0
7.0
-------
loading conditions. Cell 2 was operated at a constant flow rate of 2.4
m/hr (1 gpm/ft^), the average hydraulic design low rate. Cells 1 and
3 were alternately operated at flow rates of 1.8 m/hr (0.72 gpm/ft2)
and 3.0 m/hr (1.25 gpm/ft?). Flow was adjusted in a step wise fashion
once each in the morning and at the end of the working day. The results
of this testing are summarized in Table 4. There is no distinguishable
difference in performance between cell 2 and cells 1 and 3.
UNIVERSITY OF UTAH/EPA FULL-SCALE DEMONSTRATION OF THE BAF
Design information is needed to determine BAF tank volume, air
requirements, blower horsepower and sludge production. Tank volume
is based on recommended volumetric organic loading to achieve a desired
effluent quality as a function of temperature and wastewater character-
istics. The hydraulic loading rate is used to determine the filter sur-
face area. The required process air feed rate is based on an assumed
value of 0.8 to 1.0 kg 02/kg BOD5 removed, an averge DO of 2 mg/1, a mid-
depth saturation DO concentration and an oxygen dissolution efficiency
of about 10.5% at standard conditions. Assumed values for alpha and
beta are required.
The present design approach originates from Eimco, is empirical
and is based on reported operation and performance data from OTV through
Eimco and the limited U.S. pilot work.
Due to the impacts of the U.S. EPA Innovative/Alternative Tech-
nology Program, there are two U.S. locations where the BAF is presently
under design based on this empirical approach for use as part of a full-
scale wastewater treatment facility. These include: 1) a 2270-m3/d
(0.6-mgd) facility at Wallace, N.C., to treat a clarified trickling
filter effluent for nitrification to achieve a 3.0-mg/l NH3-N effluent
and 2) a 3859-m3/d (1.0-mgd) facility at Clinton, Arkansas to treat an
equalized, pretreated domestic/poultry waste for nitrification to
achieve a 1.0-mg/l NH3-N effluent.
mng
Other locations where the
include:
BAF system has been considered in plan-
Location
Size
1. Asheville, N.C. 20.0 mgd
2. Wilmington, Ohio 2.3 mgd
3. Glendale, Ohio 0.5 mgd
4. Fairmont, N.C. 0.5 mgd
5. Greene County, Ohio 4.5 mgd
6. Lewisburg, Ohio 0.3 mgd
7. New Lebanon, Ohio 0.5 mgd
8. Park City, Utah 1.9 mgd
Treatment
BOD/nitrification
BOD/nitrification
BOD/nitrification
Nitrification
BOD/nitrification
Nitrification
BOD/nitrification
Nitrification
701
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TABLE 4 (10)(11)
DIURNAL FLOW TEST RESULTS FOR ASHEVILLE, N.C.
Average Influent Effluent Concentration
Concentration (mg/1) (mg/1)
December 6, 1982
BOD (mg/1)
TSS (mg/1)
December 7, 1982
BOD (mg/1)
TSS (mg/1)
December 8, 1982
BOD (mg/1)
TSS (mg/1)
Average Results
BOD (mg/1)
TSS (mg/1)
Cell 1 Cell 2 Cell 3
55
32
90
40
110
36
6.8
5
11
10
10
5
9
7
7
6
8
10
12
6
9
7
7.5
7
13
8
11
4
10
6
702
-------
In general terms, there are areas of risk in utilizing the BAF in
the U.S. stemming from differences in French and U.S. experiences
including media, wastewater characteristics and flows. Long-term full
scale operating experience in the U.S. has not substantiated projections
of media life and loss, performance, frequency of backwash and affect
of recycle on primary clarifier performance.
A more fundamental understanding of the process is desirable based
on fixed film mass transfer information including media surface area,
biomass per unit volume, liquid velocity, substrate type and concentra-
tion and bulk liquid DO concentration.
The EPA entered into a cooperative agreement with the University
of Utah in May 1982 to conduct a 1893-m3/d (0.5-mgd) (nominal flow
rate) demonstration project through March 1984 to independently assess
process feasibility and application of the BAF for treatment of a
primary effluent. The Wastewater Technology Center for Environment
Canada is also providing support for the project. Dr. H. David Stensel
is the principle research investigator for the University of Utah.
Progress of the demonstration project has been reported (12)(13) and is
summarized here.
The pilot unit is located at the South plant of the South Davis
Sewer Improvement District about 11.2 kilometers from Salt Lake City,
Utah. The South Davis South plant includes primary and trickling filter
treatment and is presently processing 9463 m^/d (2.5 mgd) of combined
domestic and industrial wastes. Domestic flow comprises 70 to 80% of the
total with the remaining industrial contribution originating from an
oil refinery, a tannery and a laundry. Primary treatment is accomp-
lished with two 16.8-m (55-ft) diameter clarifiers operated at an
average overflow rate of 21.4 m/d (526 gpd/ft2). Secondary processes
include a plastic media trickling filter followed by an intermediate
clarifier, final biological treatment using two parallel-operated rock
trickling filters and final settling. Underflow from the final clari-
fier is returned to the head of the plant. Figure 7 presents the
physical layout of the BAF demonstration project. Primary effluent is
pumped from the primary clarifier effluent wet well to the BAF through
a 15.2-cm (6-in.) feed line. Two self-priming centrifugal pumps rated
at 3 hp and 5 hp operate independently to supply primary effluent to
each cell of a 2 cell BAF half-size module (3.7 m (12 ft) x 6.4 m (21
ft) x 3.7 m (12 ft)). Each cell includes 1.8 m (6 ft) of media and
11.5 m^ (124.3 ft^) of cross sectional area. Variable drive feed pumps
are used to provide a variety of flow rates to each cell. A specially
built DC signal generator unit automatically controls the flow rates on
an hourly basis so as to simulate diurnal flow conditions. The signal
generator also controls influent and effluent composite sampling pump-
ing. Eimco provided the BAF tank with process air headers and a plas-
tic nozzle underdrain system, a 25-hp backwash air blower, two 10-
hp process air blowers, a 25-hp backwash water pump, a 1-1/2-hp com-
703
-------
N
PRIMARY CLARIFIER
EFFLUENT WET
WELL
BACKWASH COLLECTION TANK
BACKWASH BLOWER
PROCESS AIR
BACKWASH [*•
WATER 1
EFFLUENT [~
-*O o*-|
JJQ INFLUENT
0*-,
rH-o
FIGURE 7
PHYSICAL LAYOUT OF THE SOUTH DAVIS
BAF DEMONSTRATION PROJECT
BACKWASH AIR PROCESS
AIR
704
-------
pressor, a microprocessor controller and necessary pneumatic operating
valves. Sample taps were added at 0.3-m (1-ft) intervals through the
height of the bed and below the underdrains. Propeller meters are used
on the effluent lines to provide instantaneous and cumulative flow
measurements on a continous flow recorder. An existing aerated grit
chamber was divided for purposes of providing a backwash collection
tank and a backwash water supply clear well to receive effluent. The
dirty backwash water is returned to the head of the South Davis South
plant.
Objectives of the project include assessment of treatment perform-
ance, operational and maintenance requirements and equipment reliability.
Each cell is to be operated independently. Initially, loadings used
reflect Eimco recommended loading rates of 3 and 5 kg BODc/m3/d to
achieve effluent BODs/SS of 10/10 mg/1 and 20/20 mg/1, respectively.
Diurnal flows will be simulated ranging from peak to average flow
factors of 1.25 to 1.75.
At each loading condition, BOD and SS removals will be determined
as well as oxygen requirements, energy requirements, solids production
and characteristics and bed and media characteristics, including attri-
tion, film thickness, density and kinetics. A separate 16.5-cm (6-1/2
-in.) diameter column will be operated in parallel with one of the
cells in order to assess scale-up factors. If successful, current
plans are to use the column to evaluate nitrification performance of
the BAF process.
Daily composite samples are collected from the influent and efflu-
ent for analysis of total COD, soluble COD, total BODs, soluble BODs,
total suspended solids, volatile suspended solids and effluent turbidi-
ty. In-bed profiles of COD and suspended solids removals are obtained.
Effluent and in-bed measurements of DO are taken daily. Off-gas samples
of spent air are collected to determine oxygen uptake efficiencies.
Temperatures are monitored. After each backwash cycle, dirty backwash
water is measured for volume and sampled from an aerated, homogeneous
mix collected in the backwash water collection tank.
Sludge settling tests are run to determine SVI and zone settling
velocity. Sludge age is also determined. Headloss is measured across
sample tap locations using a manometer. Tracer studies with lithium
chloride will be conducted to define bed hydraulic characteristics.
Design of the project began in June 1982, and installation of the
BAF unit was finally completed by the end of November 1982. During
December, Eimco checked out the BAF equipment. About 19.5 bags of
media were then added to each cell. Each bag contained about 1.1 m^
(40 ft^) of media. As delivered, the media contained a significant
amount of fines which had to be removed by backwashing. Prior to start-
up, backwashing was conducted using tap water obtained by filling the
clear well using a garden hose. This cumbersome procedure limited the
number of backwashes to four and twelve for the west and east cells,
respectively.
705
-------
Startup occurred December 27, 1982, at a hydraulic loading of about
327 m3/d (60 gpm). After only 4 days of operation, shutdown was neces-
sary due to a series of mechanical problems with the air supply com-
pressor, flow meter, pneumatic control values and pressure release vent
pipe. After repairs were completed, the unit resumed operation on
January 14, 1983, but further operating problems were encountered due
to 1) inadequate backwash air rates caused by a faulty pressure release
valve in the backwash blower, 2) need for manual backwashing more
frequently than every 24 hr because the microprocessor control had not
been programmed, 3) media blinding causing influent to inappropriately
exit the backwash siphon and causing carryover of media into the back-
wash tank, 4) incorrect bypass air rate through the process air header
during backwash, 5) inadequate backwash air distribution and 6) the need
to replace circuit breakers for the process air blowers, replace cracked
PVC sample taps and correct air flow measurement equipment.
Excessive headloss due to media blinding were observed to occur
in the top part of the bed. This headloss could have been due to
fines plugging the bed, high biomass concentrations or air binding and/
or inadequate backwashing; but exact causes have not yet been identified.
Based on sieve analyses, it is noted that the effective size of the
media changed since startup from 2.3 to 3.0 mm as measured on April 5,
1983, indicating removal of fines. The above problems were corrected
by February 14 when the plant began fully automatic operation. Data
collected during the period from January 14 through February 14 is not
considered to completely represent BAF performance due to interrupt-
ions in flow and other problems encountered. Through March 8, the flow
fed to each cell was maintained at 327 m3/d (50 gpm) resulting in
average organic loadings of 1.2 to 1.4 kg BODr/nr/d (75 to 87 Ib BODc/
1000 ft3/d). Hydraulic loading was 1.2 m/hr (0.5 gpm/ft2) during this
period. The run times between timed backwashing for the east cell
improved to a 24-hr regular interval. The west cell frequently required
backwashing every 10 to 12 hr, possibly due to a sag in the underdrain
plate causing a non-uniform backwash air rate. This problem has been
solved by increasing the backwash air rate. Beginning on March 8,
1983, the flow rate to each cell was increased and a diurnal flow pattern
was to be initiated simulating peak to average flow factors of 1.25 and
1.75, but it was discovered that the process air distribution piping
holes were drilled too small causing high headlosses in order to provide
the necessary increase in air flow for the attendant increase in organic
load.
Media was removed from both cells, and the hole size was increased
to 1.5 mm by drilling in order to provide sufficient air flow. This
task was accomplished by April 8, 1983. The media was replaced by
April 11, and startup was again initiated at about 1.2 m/hr (0.5 gpm/
ft^), resulting in a loading of about 1.0 kg BOD5/nr/d (62.5 Ib BOD
5/1000.,ft /d). On April 22, loadings were increased to about 2.2 kg
BOD5/m-Yd (137 Ib BOD5/1000 ftj/d) and 3.5 kg BOD5/ mj/d (218 Ib BOD5/
706
-------
1000 ft3/d) on the east and west cells, respectively. Diurnal flow was
simulated using a peak to average flow factor of 1.3.
Organic loading rates and influent/effluent 8005 data for January
through March 1983 are presented in Figures 8 and 9 for the east and west
cells, respectively. Figures 10 and 11 present hydraulic loading rate
and effluent suspended solids for the east and west cells, respectively.
As mentioned previously, data collected up through February 14 do not
reflect representative BAF performance. Performance after automatic
operation is considered more representative.
This is illustrated by Table 5, which presents information on
ranges and averages of loading rates and effluent characteristics for
the east and west cells, both before and after automatic operation.
The smaller operating ranges of loadings after automatic operation
reflect improved process control resulting in significantly smaller
ranges in effluent BODs, incidental improvement in the range of efflu-
ent solids removals and significantly improved effluent 6005 concentr-
ations.
During the period January through March 1983, the average ROD5 and
total suspended solids effluent concentrations and removal efficiencies
are essentially the same for both cell-s in spite of the fact that the
west cell was loaded at higher organic and hydraulic rate?. Tables 6,
7, 8 and 9 present average process performance results of the west and
east cells both before and after automatic operation. After automatic
operation, 88% BODs removal and 91% SS removal efficiencies were
achieved resulting in 10 mg/1 8005 and 10 mg/1 SS in the effluent.
These results must be viewed in consideration that the system was loaded
at less than 50% of the 3 to 5 kg BODc/m3/d (187-312 Ib BODc/1000
ft-Vd) rates to be studied as part of the demonstration project and less
than the average hydraulic loading rate of 2.4 m/hr (1 gpm/ft2) recom-
mended by Eimco for typical conditions.
As with the Asheville, N.C., pilot work, the South Davis project has
been conducted to date under the constraint of a relatively weak and a
typical primary effluent concentration of 85 to 90 mg/1 8005.
Summaries of performance for the east and west BAF cells during
the 3-week period of April 25 - May 15, 1983, are shown in Tables 10
and 11, respectively. At the increased loading rates during this time
period, effluent BOD's averaged 11 mg/1 and 17 mg/1 for the east and west
cells, respectively, reflecting removals of 87% and 79%. Similarly,
effluent total suspended solids were 10 mg/1 and 18 mg/1 reflecting
removals of 91% and 85%. Table 12 presents a comparison of perform-
ance data for the time periods February 14 - March 8, 1983 (period 1)
and April 25 - May 15, 1983 (period 2). In the east cell, the organic
and hydraulic loading rates were increased by 1.9 times and observed
performance was about the same for both time periods. In the west
cell, however, at organic and hydraulic loading rates 2.5 to 2.6 times
707
-------
TOTAL BOD CONCENTRATION (mg/1)
ORGANIC LOADING RATE (kg BOD/m3-d)
O
00
o
v E£
o a
a M
H n
G O
^> ^>
^^ t^
I—I M
C/D 55
O
M w
s o
o o
2
co pa
^ S
3> o
H <
M >
o r1
a
M
h^ a
pa
o M
(-1 >
M CO
n H
H
n
t-1
o
H
33
M
CO
H
I—I
s
-------
AUTOMATIC OPERATION
3/11
TIME
FIGURE 9
ORGANIC LOADING AND BOD REMOVAL IN WEST CELL OF THE SOUTH DAVIS BAF
DEMONSTRATION PROJECT
709
-------
30
B
CO
Q
O
CO
1 10
2
W
PH
CO
CD
CO
h-J
-------
i.o r
O
C/3
n
w
w
H
O
H
30
20
10
AUTOMATIC
OPERATION
1/10
1/20
1/30
2/9
TIME
2/19
3/1
3/11
FIGURE 11
HYDRAULIC LOADING AND EFFLUENT SUSPENDED SOLIDS IN WEST CELL OF THE
SOUTH DAVIS BAF DEMONSTRATION PROJECT
711
-------
TABLE 5
PERFORMANCE OF BAF BEFORE AND AFTER AUTOMATIC OPERATION
AT THE SOUTH DAVIS BAF PROJECT
East Cell West Cell
Before After Before After
Ranges
Organic Load Rates (kgBOD/m3/d) 0.22-1.41 0.93-1.5 0.5-2.52 0.92-1.5
Hydraulic Load Rates (m/hr) 0.15-0.95 0.81-1.37 1.86-2.44 0.93-1.30
Effluent BOD (mg/1 ) 9-28 7-17 10-27 6-14
Effluent TSS (mg/1) 7-21 7-18 7-16 7-15
Averages
Organic Load Rates (kgBOD/m3/d) 0.73 1.19 1.17 1.39
Hydraulic Load Rates (m/hr) 0.51 1.08 1.00 1.20
Effluent BOD (mg/1) 17.4 12.1 17.4 11.6
Effluent TSS (mg/1) 10.8 10.5 11.8 10.1
712
-------
TABLE 6 (12)(13)
SOUTH DAVIS BAF
PROCESS PERFORMANCE IN WEST CELL BEFORE
AUTOMATIC OPERATION (1/12/83-2/13/83)
Parameter Avg. Influent Avg. Effluent Avg. Removal
Concentration Concentration Efficiency
(mg/1) (mg/1) (%)
TBOO 93 17 81
SBOD 26 10 63
TCOD 220 66 70
SCOD 90 50 44
TSS 116 12 90
VSS 83 9 90
Avg. Hydraulic Loading Rate = 1.00 m/hr
Avg. Organic Loading Rate = 1.17 kg TBODc/m3/d
Avg. Organic Loading Rate = 3.16 kg TCOD/m3/d
TABLE 7 (12)(13)
SOUTH DAVIS BAF
PROCESS PERFORMANCE IN EAST BAF CELL BEFORE
AUTOMATIC OPERATION (1/12/83-2/13/83)
Parameter Avg. Influent Avg. Effluent Avg. Removal
Concentration Concentration Efficiency
(mg/1) (mg/1) (%)
TBOD5 93 17 81
SBOD5 26 9 65
TCOD 220 62 72
SCOD 90 50 44
TSS 116 11 91
VSS 83 7 91
Avg. Hydraulic Loading Rate = 0.51 m/hr
Avg. Organic Loading Rate = 0.73 kg TBOD5/m3/d
Avg. Organic Loading Rate = 1.59 kg TCOD/m3/d
713
-------
TABLE 8 (12)(13)
SOUTH DAVIS BAF
PROCESS PERFORMANCE IN WEST BAF CELL AFTER
AUTOMATIC OPERATION (2/14/83-3/8/83)
Parameter
TBOD5
SBOn5
TCOD
SCOD
TSS
VSS
Avg. Influent
Concentration
(mg/1)
97
27
234
85
114
69
Avg. Effluent
Concentration
(mg/1)
12
6
51
39
10
7
Avg. Hydraulic Loading Rate = 1.2 m/hr
Avg. Organic Loading Rate = 1.39 kg TBODc/m3/d
Avg. Organic Loading Rate = 3.62 kg TCOD/m3/d
Avg. Removal
Efficiency
87
79
78
54
91
91
TABLE 9 (12)(13)
SOUTH DAVIS BAF
PROCESS PERFORMANCE IN EAST BAF CELL AFTER
AUTOMATIC OPERATION (2/14/83-3/8/83)
Parameter
TBOD5
SBOD5
TCOD
SCOD
TSS
VSS
Avg. Influent
Concentration
(mg/1)
97
26
234
85
114
69
Avg. Hydraulic Loading Rate =
Avg. Organic Loading Rate
Avg. Effluent
Concentration
(mg/1)
12
6
51
39
11
7
1.08 m/hr
1.19 kg TBODc/m3/d
Avg. Removal
Efficiency
85
74
78
54
91
90
Avg. Organic Loading Rate = 3.16 kg TCOD/m3/d
714
-------
TABLE 10 (12)(13)
BAF PROCESS PERFORMANCE SUMMARY
FOR EAST CELL 4/25-5/15/83
Time Period
4/25-5/1/83 5/2-5/8/83 5/9-5/15/83 AVG.
Flow Treated (m3/d) 511 596 595 566
Organic Loading Rate (kg BOD/m3/d) 1.92 2.13 2.63 2.24
Average Hydraulic Loading Rate (m/hr) 1.86 2.18 2.15 2.05
Average Detention Time (min) 61.3 50.7 50.9 54.5
Effluent BOD5 (mg/1) 9 12 12 11
Effluent TSS (mg/1) 10 12 9 10
Effluent DO (mg/1) 1.8 2.4 - 2.0
BOD Removal (%) 88 85 87 87
TSS Removal (%) 91 90 92 91
Wastewater Temperature (°C) 12.2 15.3 ll.fi 12.9
TABLE 11 (12)(13)
BAF PROCESS PERFORMANCE SUMMARY
FOR WEST CELL 4/25-5/15/83
Time Period
4/25-5/1/83 5/2-5/8/83 5/9-5/15/83 AVG.
Flow Treated (m3/d) 858 810 861 843
Organic Loading Rate (kg BOD/m3/d) 3.42 3.39 3.75 3.53
Average Hydraulic Laoding Rate (m/hr) 3.13 3.15 3.13 3.13
Average Detention Time (min) 36.4 35.0 35.1 35.5
Effluent BOD5 (mg/1) 17 19 16 17
Effluent TSS (mg/1) 19 17 17 18
Effluent DO (mg/1) 2.2 1.6 3.0 2.2
BOD Removal (%} 78 78 82 79
TSS Removal (%) 84 85 85 85
Wastewater Temperature (°C) 12.6 14.1 11 12.4
715
-------
TABLE 12
COMPARISON OF BAF PERFORMANCE IN THE EAST AND WEST
CELLS DURING 1) 2/14-3/8/83 and 2) 4/25-5/15/83
East Cell West Cell
Period 1 Period 2 Period 1 Period
Organic Load Rates (kg BOD/m-Vd) 1.19 2.24 1.39 3.53
Average Hydraulic Load Rate (m/hr) 1.08 2.05 1.20 3*13
Effluent BOD (mg/1) 12 11 12 17*
BOD Removal % 85 87 87 79
Effluent TSS (mg/1) 11 10 10 18
TSS Removal % 91 91 91 85
higher, effluent 8005 and total suspended solids increased to 17 mg/1
and 17.5 mg/1, respectively (time period 2), from 12 mg/1 and 10 mg/1
(time period 1) indicating that the west cell is beginning to approach
the limits of performance capability. The spring of 1983 has been an
unusually wet one for the Salt Lake City area. This has been due to
higher-than-normal rainfall and snow melt causing serious flooding in
the area. As the study proceeds, the wastewater strength is expected
to increase. Present plans are to increase loadings to about 3 kg
BODc/mJ/d (187 Ib BODc/1000 ft3/d) and 5 kg BOD5/m3/d (312 Ib BOD5/1000
ft3/d) on the east and west cells, respectively, and run at these cons-
tant loadings for a time.
716
-------
REFERENCES
1. "1982 Needs Survey - Conveyance, Treatment, and Control of Municipal
Wastewater, Combined Sewer Overflows, and Stormwater Runoff -
Summaries of Technical Data" EPA 430/9-83-002 U.S. Environmental
Protection Agency, Washington, O.C., May 1983.
nar
on
2. Brenner, R.C., "Status of Novel Biological Process Development in
the United States" Proceedings of the Interim Technical Semina
Between Seventh and Eighth United States/Japan Conferences o
Sewage Treatment Technology, Tokyo, Japan, May 1981.
3. Leglise, J.P., Gilles, P. and Moreaud, H., "A New Development in
the Biological Aerated Filter Bed Technology" Paper Presented at
the 53rd Annual Water Pollution Control Federation Conference, Las
Vegas, Nevada, October 1980.
4. Gilles, P., Leglise, J.P., and Moreaud, H., "New Developments in
Fixed Bed Biological Treatment" Omnium D1 Assainissement
Courbevoie, France, 1979.
5. DiGregorio, D., "Application of the Biological Aerated Filter to
Municipal Wastewater Treatment" Proceedings of the 1983 Annual
Meeting Utah Water Pollution Control Association Park City, Utah,
April 1983 p 49.
6. "Evaluation of the Biological Aerated Filter for Treatment of
Municipal Wastewater" Application Package, U.S. Environmental
Protection Agency Cooperative Agreement No. CS809217, University
of Utah, Salt Lake City, Utah, February 1982.
7. "Process Design Manual for Nitrogen Control" U.S. Environmental
Protection Agency, Cincinnati, Ohio, October, 1975.
8. Stensel, H.D., University of Utah, Salt Lake City, Utah, Personal
Communication.
9. Schilaty, D.J., "Nitrification Pilot Study Utilizing the Biological
Aerated Filter (BAF)" Proceedings of the 1983 Annual Meeting, Utah
Water Pollution Control Association, Park City, Utah, April 1983,
p. 52.
10. Robinson, L.R., and Coombs, J.M., "Space Limitation and Industrial
Wastewater Shock Load Problems Resolved Through Use of Biological
Aerated Filters" Paper Presented at the Sixth Annual Wastewater
Technical Conference of the Alabama Association for Water Pollution
Control, April 1983.
717
-------
11. "Summary of Biological Aerated Filter Demonstration Tests for the
Metropolitan Sewage District Buncombe County, North Carolina",
Eimco Process Equipment Company, Salt Lake City, Utah, January
1983.
12. Stensel, H.D., and Lee, K. "Biological Aerated Filter for Full
Scale EPA Demonstration Project" Proceedings of the 1983 Annual
Meeting, Utah Water Pollution Control Association Park City, Utah,
April 1983, p. 56.
13. "Evaluation of the Biological Aerated Filter for Treatment of
Municipal Wastewater" Progress Reports, University of Utah, Salt
Lake City, Utah, U.S. Environmental Protection Agency Cooperative
Agreement No. CS809217.
718
-------
SLUDGE MANAGEMENT PLANS AND PRACTICES AT
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
by
Cecil Lue-Hing
Hugh McMillan
Forrest C. Neil
Raymond R. Rimkus
The Metropolitan Sanitary District
of Greater Chicago
Chicago, Illinois
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
719
-------
SLUDGE MANAGEMENT PLANS AND PRACTICES AT
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
By: Cecil Lue-Hing
Hugh McMillan
Forrest C. Neil
Raymond R. Rimkus
The Metropolitan Sanitary District of Greater Chicago
Chicago, Illinois 60611
ABSTRACT
The Metropolitan Sanitary District of Greater Chicago (District)
services the city of Chicago and over 120 suburban communities. The com-
bined industrial and domestic loading, equivalent to 11 million people, ul-
timately results in 635 dry megagrams (Mg) of sludge solids per day that must
be managed.
The District has long believed that sludge utilization represents one
of the best sludge management alternatives. Since the late 1960s the
District has initiated projects throughout the state of Illinois utilizing
sludge for agricultural and land reclamation purposes. Two of these pro-
jects include: (1) A 48-hectare (ha) farm on the site of a 0.35 m3/s (8.1
MGD) water reclamation plant in a residential suburb, utilizing the 800 dry
Mg of sludge produced annually to grow corn; (2) Strip-mined land, 322 km
southwest of Chicago in Fulton County, reclaimed by the addition of sludge
solids.
At the Fulton County site, from 1972 to 1981, an average of 477 dry Mg
have been applied per hectare, increasing the organic carbon content of the
minespoil from 0.67 to 4.6 percent. Crops grown are sold for livestock
feed.
Current sludge processing methods at the District include new dewatering
methods that result in a sludge of over 60 percent total solids. This soil-
like product is being used to cover a closed, 91-hectare municipal landfill,
and to construct a winter recreational area.
Competitive bidding for contracts to handle sludge have been a manage-
ment option used by the District. Currently, an innovative contract for a
private firm to handle 20 percent of the District's raw sludge is being pre-
pared.
720
-------
INTRODUCTION
The Metropolitan Sanitary District of Greater Chicago (District) ser-
vice area encompasses almost all of Cook County, Illinois, which extends
over 2,227 km^ (860 sq miles) and includes the city of Chicago and more
than 120 suburban communities. Wastewater is collected and treated from a
domestic population of 5.5 million people. Added to this domestic loading,
the nondomestic and combined sewer load contribute an additional load
equivalent of 5.5 x 10^ people, bringing the total population equivalent
served to 11 x 10^. Approximately 635 megagrams/day (700 tons/d) of or-
ganic solids are processed for disposal.
Municipalities through the years have attempted to dispose of their
recovered wastewater solids through various combinations of long-term
storage in lagoons or stockpiles, landfilling, ocean disposal, and inciner-
ation. The relatively recent public awareness of such environmental issues
as air quality, land usage, and energy conservation is forcing a closer
look at this age-old problem-—how to effectively process and dispose of
wastewater solids without causing environmental damage.
During the past 50 years, while significant advances have been made in
the field of wastewater treatment and solids processing, the area of solids
disposal is just beginning to be explored intensively. No matter how much
processing is given to the recovered wastewater solids, there remains some
fraction that must be disposed of or utilized.
Faced with increasing solids production rates, escalating fuel costs,
and limited land availability for disposal, the Metropolitan Sanitary
District of Greater Chicago Board of Commissioners in the late 1960s adopt-
ed a policy of solids utilization. Today, the District believes that use
rather than disposal of the recovered solids from wastewater treatment
represents one of the best management alternatives.
The District has always endeavored whenever economically justified to
adopt the concept of solids utilization into its sludge management programs.
In this paper, the present and some of the past sludge management techniques
used by the District will be discussed.
AGRICULTURAL USE - FOOD CHAIN CROPS
HANOVER PARK LAND APPLICATION SITE
The District's Hanover Park Water Reclamation Plant (WRP) located in
the Village of Hanover Park, Illinois, treats the wastewater from a Sl-km^
(12-mi2) area which includes portions of 4 villages in the northwestern
part of Cook County, Illinois. In 1981, an average raw sewage flow of 0.35
m3/s (8.10 MGD) was treated.
In order to make the Hanover Park WRP a totally independent treatment
facility, a 48.5-ha (120-acre) farm was constructed in 1978 to utilize all
721
-------
the sludge generated. Sixteen fields were developed thusly:
1. Each field was graded to have a gentle slope so liquid sludge
could be applied at the high end through gated irrigation pipe;
2. Fields have terraces and dikes to divert surface runoff to the
lower end of each field; and
3. A tile drainage system in each field collects infiltration and
surface runoff and conveys this water back to the Hanover WEP.
In the winter when no sludge application is made to fields, digested
sludge from the WRP is stored in two lagoons. During the application season,
both the lagooned sludge and digester drawoff are applied, so that by the
end of the application season, ideally the storage lagoons are empty.
Sludge is pumped to the farm fields through a buried pipeline to sixteen
distribution points (one in each field) to which the above ground slotted
irrigation piping is connected.
The location of the plant and farm are shown in Figure 1 which also
shows the proximity of residential housing.
Sludge application began in 1979 when nine of the sixteen fields re-
ceived sludge. Table 1 presents the sludge application quantities for each
field in 1979, 1980, and 1981. Total dry megagrams (Mg) applied each year
were 127 (140 tons), 550 (607 tons), and 822 (906 tons) for 1979, 1980, and
1981, respectively. By 1981, the Hanover Park WRP farm was more than able
to accommodate the total annual sludge production from the WRP.
Digester output during 1931 totaled 784.5 dry llg (865 tons) or 2.14 dry
Mg/d (2.37 tons/day). During 1981, a total of 557 Mg (614 dry tons) of
digested sludge at 2.0 percent solids and 265 dry Mg (292 dry tons) of lagoon
sludge at 1.6 percent solids were applied to the Hanover Park WRP farm
fields.
Table 2 shows the mean chemical analysis of the sludge (digester draw-
off and lagooned sludge) applied to the fields for the first three years of
operation (1979-1981).
The fields are planted each year to either corn or grass. During the
first year of application (1979) all fields were planted to grass. In 1980
and 1981, several fields were planted to corn with averaged yields of 53.6
hectoliters/ha (61.6 bu/acre) in 1980 and 13.4 hectoliters/ha (15.5 bu/acre)
in 1981. Wet conditions were responsible for the low yield in 1981. All
harvested corn is sold to a local grain elevator.
Grain samples from each field were analyzed for total metal content.
These results are shown in Table 3 for the 1980 grain and Table 4 for the
1981 grain. As Tables 3 and 4 show, Cd content of corn grain from the
Hanover Park fields ranged from <0.02 (6 samples) to 0.13 rag/kg.
722
-------
OOOOOOoo
o o o o o o oo
LEGEND-
QFIELO NUMBER
O PUMP STATION
SINGLE -
FAMILY
HOUSING
200' 100' 0 200'
SCALE IN FEET
SINGLE -
FAMILY
HOUSING
©
IS Ac
9 5 Ac
Figure 1. Location of fields utilized for sludge application at the
Hanover Park Water Reclamation Plant.
723
-------
TABLE 1. HANOVER PARK WATER RECLAMATION PLANT FARM SLUDGE APPLICATION FOR
Field
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1979*
2.7
0
0
0
2.0
11.6
8.7
0
7.4
0
7.6
0
0.7
2.5
0
9.9
19801"
11.0
4.9
5.8
5.8
2.0
11.6
6.9
4.3
32.5
14.3
0.0
15.0
15.7
6.9
21.7
5.6
1981*
— Mg/ha
26.4
0
18.8
50.2
0
7.4
0
23.3
33.6
14.6
13.9
34.0
4.5
17.9
9.9
18.8
Total 1979-1981§
40.1
4.9
24.6
56.0
4.0
30.7
15.7
27.6
73.5
28.9
21.5
49.1
20.8
27.3
31.6
24.4
*In 1979, the total solids application was 127 Mg.
In 1980, 550 Mg.
|In 1981, 822 Mg.
The cumulative total for 1979-1981 was 1,499 Mg.
Costs associated with the 48.5~ha (120-acre) Hanover Park WRP farm in-
clude land purchase of $1,675,000 in 1970, construction (including flood
control system) of $3,299,800 in 1971, and annual operations and maintenance
(0 and M) costs as follows:
1) 1979, $74,832 expended,or $593 per Mg ($538/dry ton) applied.
2) 1980, $64,000 expended, or $116 per Mg ($105/dry ton) applied.
3) 1981, $69,882 expended, or $84.9 per Mg ($77/dry ton) applied.
These above unit cost figures indicate that the 0 and M cost has de-
creased as experience was gained and greater quantities of solids were applied
(Table 1) to the farm fields.
The Hanover Park WRP farm represents a sludge application to land pro-
ject in extremely close proximity to nearby single-family residences
724
-------
TABLE 2. ANALYSIS OF THE SLUDGE APPLIED TO FARM FIELDS AT THE HANOVER PARK
WATER RECLAMATION PLANT FROM 1979 THROUGH 1981. RESULTS ARE
BASED ON TWENTY-ONE MONTHLY DIGESTER DRAWOFF COMPOSITES
AND FOURTEEN MONTHLY LAGOON SLUDGE COMPOSITES.
Constituent
Digester Drawoff
Mean Min. Max.
Lagoon Sludge
Mean
Min.
Max.
Total solids
Total volatile solids
Total P
N-Kj eldahl
N-NH3
Al
Ca
Cd
Cr
Cu
Fe
K
Mg
Mn
Na
Ni
Pb
Zn
2.07
60.8
18.6
65.8
24.8
8.42
35.2
0.058
1.37
1.96
11.7
2.94
7.76
0.63
9.41
0.20
0.19
1.27
1.6
57.4
5.8
56.6
15.8
2.92
19.2
0.009
0.34
0.64
4.50
2.40
1.75
0.26
6.43
0.08
0.08
0.56
2.8
65.6
Iro /M
Kg/JM,
33.3
83.2
35.0
12.0
47.5
0.214
2.44
2.58
17.5
3.88
11.8
0.88
12.5
0.37
0.24
1.84
. ._ rr /]
2.47
51.8
16.6
51.7
20.5
7.48
37.5
0.063
0.77
1.48
15.6
5.79
15.1
0.46
15.7
0.15
0.22
1.81
0.13
40.4
3.44
39.2
8.19
0.77
10.5
0.015
0.19
0.23
3.46
2.16
4.22
0.18
3.75
0.08
0.03
0.38
4.8
57.6
23.5
89.5
60.5
12.8
70.0
0.243
1.07
2.05
18.6
20.0
38.5
0.58
83.1
0.28
0.27
2.98
Hg
5.25
1.87
0.85
10.8
(Figure 1). Some homes are within 30 m (100 ft) of sludge application fields,
The District has found that the public accepts the fact that a sewage sludge
farm is located almost in their backyards. Complaints from neighbors have
been minimal and in some years no complaints at all are received by plant
operating personnel. The Hanover Park WRP farm shows that a well-managed
and properly designed sludge application to land site is acceptable to the
general public.
725
-------
TABLE 3. SELECTED METALS ANALYSIS OF CORN GRAIN GROWN IN 1980 ON FARM FIELDS AT THE HANOVER PARK
WATER RECLAMATION PLANT. VALUES ARE MEANS OF DUPLICATE SAMPLES.
NJ
Field
2
3
5
6
7
8
14
16
Zn
17.9
20.5
20.5
18.7
19.4
19.2
18.3
19.2
Cd
<0.02
<0.02
<0.04
<0.02
<0.02
<0.02
<0.02
<0.02
Cu
4.63
2.03
1.57
1.47
1.42
1.74
1.89
1.98
Cr
1.51
0.84
1.06
0.62
1.82
1.99
2.24
1.92
Fe
/i
-mg/K.g
68.8
41.5
51.0
44.4
20.8
49.5
63.2
92.2
Ni
Pb
(oven-dried, (
0.50
0.26
0.34
0.34
0.34
0.52
0.44
0.40
0.09
0.04
0.04
<0.01
<0.04
0.03
0.19
0.09
K
' C O f-\ \
JD L;
3,539
3,966
3,922
3,584
3,678
3,731
4,151
3,751
Ca
221.0
59.8
67.7
53.8
40.0
108.0
107.0
172.0
Mg
1,471
1,435
1,453
1,254
1,519
1,516
1,728
1,556
Mn
4.57
4.58
4.98
4.58
5.60
5.39
5.16
7.38
TABLE 4. SELECTED METALS ANALYSIS OF CORN GRAIN GROWN IN 1981 ON FARM FIELDS AT THE HANOVER PARK
WATER RECLAMATION PLANT. VALUES ARE MEANS OF DUPLICATE SAMPLES.
Field
3
6
14
16
Zn
14.6
12.6
17.2
20.7
Cd
0.03
0.04
0.05
0.13
Cu
1.03
1.18
1.90
1.85
Cr
0.30
0.35
0.26
0.20
Fe
/,
- mg/ kg
12.8
13.6
18.0
20.1
Ni
(oven dried
1.01
1.12
1.05
1.24
Pb
, 65°C)
0.09
0.06
0.45
0.08
K
5,999
7,212
7,314
7,771
Ca
57.2
59.1
69.4
61.2
Mg
1,579
1,261
1,645
1,479
Mn
4.54
3.94
5.95
3.94
-------
AGRICULTURAL USE AND LAND RECLAMATION
FULTON COUNTY LAND APPLICATION SITE
The District's Fulton County project is the embodiment of the concept of
the agricultural utilization of sewage sludge as a sludge management alterna-
tive. As at the Hanover Park WRP farm site, sludge is applied as a fertil-
izer; but at the Fulton County site, this sludge utilization operation has
the added benefit of reclaiming previously surface-mined land.
Fulton County is located in West Central Illinois, approximately 300 km
(200 mi) southwest of Chicago. From the 1920''s to the 1960's, 16,000 ha
(40,000 acres) of former row crop land in Fulton County was strip-mined for
coal before the enactment of reclamation laws. The gently rolling fields of
fertile prairie soil were replaced by a corduroy topography of steep spoil
mounds and long, narrow lakes. While many strip-mined areas are characterized
by acidic soils and surface waters, Fulton County has neutral to alkaline
calcareous soils. This characterization increases the suitability of the
site for reclamation by sludge application, as the availability of metals for
plant uptake is substantially reduced in an alkaline environment.
Description of the Site
In 1970, the District initially purchased 2,898 ha (7,156 acres) of land
in Fulton County and currently owns 6,289 ha (15,528 acres). Over 60 percent
of the site had been strip-mined and was being used for livestock pasture.
It is the District's intention to reclaim the strip-mined spoil areas so that
they can be suitable again for row-crop agriculture. This will be accom-
plished by regrading of the land and increasing the nutrient and organic
matter content of the spoil by additions of sludge solids.
To store the sludge that would be barged down the Illinois River from
Chicago, holding basins were constructed. In 1971 two basins, each lined
with a two-foot layer of compacted clay, were formed with a combined capacity
of approximately 3.8 million cubic meters (5,000,000 yd3). During 1973,
holding basins #3A and #3B with a combined capacity of 2.3 million m3
(3,000,000 yd3) were constructed to store the supernatant from the other
two basins.
During this same period, extensive regrading was done to form fields
suitable for sludge application and row-crop agriculture. Each application
field was bermed, and drains to a runoff retention basin designed to capture
the regional 100-year storm event of 15.5 cm (6.1 in). The runoff water is
retained until it meets the State of Illinois permit standards which are cur-
rently TSSS99 mg/L, BODS33 mg/L^and fecal coliforml494 counts/100 ml. Ex-
tensive surface-water and groundwater environmental monitoring operations
were also initiated at the beginning of the project. Figure 2 shows an over-
view sketch of the Fulton County site and Figure 3 a typical application field.
By 1981, 110 fields of approximately 2,300 ha (5,700 acres) were being util-
ized for row-crop or forage production.
TSS = Total suspended solids; BOD = Biochemical oxygen demand.
727
-------
• JJW/ /,-—12 -2 '
L^Kif^-
36-1
proporty boundary-
Figure 2. Farm fields and runoff basins at Fulton County, Illinois.
728
-------
N3
TRACTOR DISK WITH
HOSE PIPELINE
SERMED FIELD
FIELD RUNOFF RETENTION
BASIN
(DESIGNED FOR 100 YEAR STORM)
STREAM
CONTROLLED RELEASE
TO STREAM
Figure 3. Typical field design with runoff water capture system
at Fulton County, Illinois.
-------
Operation of the Fulton County Site
The site became operational in August of 1971 when the first barge of
liquid sludge docked in Liverpool, Illinois. From 1971 to 1981 an average
of 1.27 million wet Mg (1.4 million tons) of sludge at 4-6 percent total
solids have been barged to the Fulton County site each year from the Dis-
trict's West-Southwest Sewage Treatment Works (STW). The sludge shipped to
Fulton County is normally drawn from heated (35°C) anaerobic high-rate di-
gesters at the West-Southwest STW treating waste-activated sludge and a small
percentage of primary sludge. This digested sludge had also been stored at
the Lawndale Avenue lagoons at the West-Southwest STW for many years; and
during the summer, barges can be filled with lagooned sludge or with a mix-
ture of both lagooned and freshly digested sludge. Since 1981 when a new
centrifuge facility at the West^Southwest STW became operational, the sludge
barged has been a mixture of liquid polymer-dosed centrifuged digested sludge
(15 percent TS) and digested sludge (3-4 percent TS) blended to 6-8 percent
total solids.
From the barge dock at Liverpool, Illinois, the sludge is pumped 17 km
(10.4 mi) through a pipeline to the holding basins. During warm weather,
the sludge is pumped from the basins via a surface pipe distribution system
to the fields. At the fields, the methods of sludge application have con-
tinually evolved over the years. Initially, spraying by a traveling sprinkler
was the main method; but it was totally replaced by 1977 by incorporation of
the sludge-using tractor-drawn tandem-disk incorporators with a sludge dis-
tribution manifold, which directs sludge to each disk blade as it tills the
soil. Incorporation became the method of choice for the following reasons:
(1) a greater amount of sludge can be applied in a shorter period of time;
(2) applications are more uniform as varying winds are not a factor; (3) the
reduced visibility of the sludge is aesthetically more acceptable; and (4)
the potential for odors is greatly reduced.
Since 1980, dewatered sludge solids at 55 percent from the holding basins
have been hauled to fields by means of a hydraulic ram ejector truck and self-
loading scraper. A bulldozer then spreads the sludge, which is then incor-
porated with a heavy disk.
The supernatant from the settling of the sludge in the holding basins
has been applied as an irrigant and fertilizer since 1977 to pasture fields
via gated pipe. An approximate average rate of 1,000,000 liters per hectare
(100,000 gal/acre) has been applied each year.
Sludge Quality and Application Rates
From 1972 to 1981 an average of 1.1 million wet Mg (1.3 million tons) of
liquid sludge have been applied each year to the Fulton County farm fields.
This sludge is typified by the 1981 analysis given in Table 5. The sludge is
well-stabilized at 46.9 percent volatile solids. One dry megagram contains
28 kg total phosphorus and 46 kg total Kjeldahl nitrogen. Sludge has been
applied at an approximate yearly rate of 50 dry Mg/ha (22 tons/acre) to mine-
spoil fields. Since sludge is being applied for reclamation, the rates have
been higher than typical agronomic rates based on crop nitrogen requirement.
730
-------
TABLE 5. MEM VALUES AND RANGE OF THE PRINCIPAL CONSTITUENTS OF THE SLUDGE
APPLIED AS FERTILIZER TO FULTON COUNTY FARM FIELDS FROM MAY 26 TO
OCTOBER 30, 1981 AND THE MEAN CONTENT PER DRY MEGAGRAM. RESULTS ARE
BASED ON TWENTY WEEKLY COMPOSITE SAMPLES
Minimum
Mean Content
Maximum Mean Per Dry Mg
PH
EC, dS/m
Total P
N-Kjeldahl
N-NH3
Alk. as CaC03
Cl
Fe
Zn
Cu
Ni
Mn
K
Na
Mg
Ca
Pb
Cr
Cd
Al
Hg
Total solids
Total volatile solids
7.4
3600
724
1387
542
3270
264
1900
133
77.8
18
19.1
8
7
470
1120
31.1
114
8.0
520
0.104
4.40
44.6
7.9
5800
,
mg/L —
2020
2888
1428
4660
508
3740
259
135
26
33.0
50
31
810
3950
66.0
241
17.9
830
0.533
6.00
49.3
7.6
4975
1455
2398
1038
3790
339
2351
181
95.6
22
25.1
30
18
647
1854
45.0
163
12.4
662
0.311
5.22
46.9
-
kg/Mg
27.9
45.9
19.9
73.0
6.5
45.0
3.47
1.83
1.68
0.48
0.6
0.3
12.4
35.5
0.86
3.12
0-.24
12.7
0.006
1000.00
469.00
(Ib/ton)
(55.7)
(91.9)
(39.8)
(145.0)
(13.0)
(90.1)
(6.93)
(3.66)
(0.84)
(0.96)
(1.1)
(0.7)
(24.8)
(71.0)
(1.72)
(6.24)
(0.48)
(25.4)
(0.012)
(2000.00)
(938.00)
Table 6 shows the annual application rates and cumulative applications
of sludge after ten years to the 21 minespoil fields that have grown at least
one crop of corn. An average of 477 dry Mg/ha (213 tons/acre) of sludge have
been applied as of the end of 1981.
Effect of Sludge Application on Mine-Spoil
In the spring of each year prior to sludge application, the plow layer
(0-15 cm) of soil is sa-npled and analyzed. Table 7 presents the yearly
averages and ranges of pH, electrical conductivity (EC) and organic carbon
found for the same 21 sludge-amended mine-spoil fields listed in Table 6.
731
-------
TABLE 6. ANNUAL AND -CUMULATIVE SLUDGE APPLICATION RATES FOR MINE-SPOIL FIELDS THAT HAVE
GROWN CORN AT THE FULTON COUNTY, ILLINOIS LAND RECLAMATION SITE FOR 1972-1981
Field
1
2
3
4
5
7
8
9
11
12
13
14
15
17
25
26
28
30
32
33
47
_ *
Xw
1972
0
0
13
0
0
0
0
5
0
0
0
0
0
5
0
0
0
0
0
0
0
8
1973
0
0
3
1
1
1
2
1
0
0
0
0
0
4
0
0
0
0
0
0
0
2
1974
43
54
55
55
52
48
27
37
66
38
36
15
65
43
22
61
39
45
8
9
0
41
1975
65
41
23
86
90
50
57
15
79
43
33
30
67
47
65
28
82
43
49
69
0
53
1976
121
129
83
117
81
13
72
46
119
61
40
23
133
34
0
98
95
101
64
91
46
78
1977 1978
-dry Mg/ha
0
83
0
67
0
64
0
28
0
58
81
64
91
84
112
108
0
126
0
0
85
81
116
36
83
0
53
59
64
67
109
0
44
75
19
19
85
88
79
23
75
98
90
67
1979
0
107
14
94
75
0
58
0
105
91
82
20
130
120
27
17
135
115
50
124
88
81
1980
94
51
90
48
73
64
76
93
60
26
74
85
70
26
85
97
37
104
16
32
74
65
1981
52
60
55
56
70
68
58
54
63
150
67
133
47
54
41
57
68
33
45
74
65
65
TOTAL
491
560
419
524
495
368
414
345
600
467
457
445
622
436
438
555
535
590
308
497
448
477
*The weighted mean (Xw) is the mean of only those fields that received sludge that
year.
-------
w
w
TABLE 7. MEANS (X) AND RANGES OF pH, ELECTRICAL CONDUCTIVITY (EC) AND ORGANIC CARBON
FOUND IN SOIL (0-15 cm) FROM 21 SLUDGE-AMENDED MINE-SPOIL CORN FIELDS
AT THE FULTON COUNTY, ILLINOIS ALND RECLAMATION SITE FROM 1972-1981
Year
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
X
7.54
7.70
7.65
7.11
7.14
6.79
6.80
6.70
6.64
6.49
Nf
11
6
40
42
40
42
42
60
42
42
PH
Min.
7.20
7.50
6.50
6.50
6.10
6.30
6.19
5.26
5.59
6.03
Max.
7.80
7.90
8.40
8.00
7.55
7.30
7.18
7.41
7.18
6.94
X
1.47
1.30
1.53
2.07
1.85
2.87
2.04
2.86
2.65
2.28
EC*
N
11
6
40
42
40
42
42
42
42
42
(dS/m)
Min.
0.45
0.67
0.16
0.86
0.50
0.74
0.49
0.99
0.60
0.64
Organic Cf (%)
Max.
3.00
2.50
3.40
4.60
3.50
4.80
3.60
4.50
4.40
3.68
X"
0.67
1.05
0.67
0.86
1.24
2.07
3.07
3.53
3.85
4.60
N
22
6
52
84
80
84
84
84
84
84
Min.
0.24
0.78
0.16
0.28
0.59
0.81
1.96
1.89
2.02
2.35
Max.
1.56
1.25
1.80
1.81
2.90
3.29
4.88
5.83
5.40
6.59
*Determined on 1:1 soil/water solution.
^Determined according to Walkley-Black method (1).
T= Number of analyses.
-------
Over a ten-year period, the pH has decreased from 7.54 to 6.49; EC has in-
creased from 1.47 to 2.28 dS/m; and organic C has increased from a low 0.67
percent in 1972 to 4.60 percent in 1981. If the pH of a farm field gets be-
low 6.5, agricultural limestone is applied to keep soil pH above this value.
For comparison, Table 8 shows the results from four -nine-sooil fields
that did not receive sludge application, although supernatant was applied one
year (1979 or 1980). These fields were inorganically fertilized with
commercial N-P205-K20 at a rate of 140-112-112 kg/ha (125-100-100 Ib/acre)
for a corn crop. As these fields were not put into service until 1976, the
table only presents data from 1976 to 1981. The three parameters have all
shown a slight increase over six years. The pH has increased from 7.03 to
7.29; EC from 1.78 to 2.05 dS/m; while organic carbon has increased only 0.36
percent from 0.68 to 1.04 percent, likely due to incorporation of crop
residues.
The application of sludge has increased the fertility of the mine-spoil
field soil as measured by nitrogen (N), phosphorus (P), and potassium (K)
levels. Table 9 gives the yearly means and ranges of these elements for the
sludge-amended mine^spoil fields. The available mineral N, as measured by
exchangeable Nlty-N and N03+N02-N, was 21 mg/kg in 1972 and 189 mg/kg in 1981.
Available P has increased from 24 mg/kg to 299 mg/kg of soil in 1981. The
exchangeable K has not increased as dramatically since the sludge is not high
in K. For example, the 1981 sludge applied contained 0.06 percent K. Ex-
changeable K increased from 122 mg/kg in 1972 to 326 mg/kg in 1981.
In comparison, the fertility of the inorganically fertilized mine-spoil
as measured by the same three parameters has not changed much. Table 10
shows a change of 7.3 to 34 mg/kg available mineral N, 7.5 to 12 mg/kg avail-
able P, and 98 to 220 mg/kg exchangeable K from 1976 to 1981.
In addition to the essential plant nutrients just discussed and other
essential trace elements, such as zinc, copper and iron, sewage sludge also
contains such metals as cadmium (Cd), Nickel (Ni), and lead (Pb). The
sludge fertilizer applied to fields from 1974 to 1981 has mean concentrations
of 290 mg Cd, 410 mg Ni and 900 mg Pb per dry kg of sludge. Using these
concentrations with the average cumulative sludge application of 477 Mg/ha,
approximately 138 kg Cd, 196 kg Ni and 429 kg Pb per ha have been applied to
an average mine-spoil field after ten years. Assuming that the 15-cm plow
layer of soil weighs 2.24 million kg (2,000,000 lb/acre-6 inch), concentra-
tions expected to be found with the above metal loadings would be 62 mg Cd,
88 mg Ni and 192 mg Pb per kg of soil. Table 11 gives the yearly means and
ranges of 0.1 N^ HC1 extractable Cd, Ni, and Pb. The average concentrations
found in 1981 of 60.1 mg Cd, 56.7 mg Ni and 175 mg Pb/kg compare favorably
with the above estimates. As the soil analysis is an extraction and not a
total digestion, lower values would be expected. Table 11 also shows the
yearly increases in concentration of the three elements Cd, Pb and Ni. As
would be expected, concentrations of these elements in mine-spoil fields with
commercial fertilization have not changed over the years as shown in Table
12. Any differences are probably due to sampling and analytical variability.
734
-------
—i
UJ
TABLE 8. MEANS (X) AND RANGES OF pH, ELECTRICAL CONDUCTIVITY (EC) AND ORGANIC CARBON FOUND IN
SOIL (0-15 cm) FROM FOUR INORGANICALLY FERTILIZED CORN FIELDS AT THE
FULTON COUNTY. ILLINOIS LAND RECLAMATION SITE FROM 1976-1981
pH* EC*(dS/m) Organic CT (%)
Year X Nt Min. Max. X M
1976 7.03 6 6.75 7.45 1.78 6
1977 6.77 2 6.47 7.07 0.18 2
1978 7.35 8 7.04 7.65 1.53 8
1979 7.67 8 7.47 8.07 1.32 8
1980 7.40 8 7.17 7.64 1.71 8
1981 7.29 8 7.01 7.41 2.05 8
Min. Max. X N Min. Max.
0.27 3.00 0.68 12 0.51 0.80
0.16 0.19 0.62 4 0.41 0.81
0.33 2.80 0.77 16 0.51 1.15
0.26 2.66 0.77 16 0.60 0.94
0.40 2.98 0.86 16 0.64 1.10
0.34 3.08 1.04 16 0.84 1.33
*Determined on 1:1 soil/water solution.
^Determined according to Walkley-Black method (1).
•fN = Number of analyses.
-------
TABLE 9. MEANS (X) AND RANGES OF AVAILABLE MINERAL NITROGEN AND PHOSPHORUS AND EXCHANGEABLE
POTASSIUM FOUND IN SOILS (0-15 cm) FROM 21 SLUDGE-AMENDED MINE-SPOIL CORN FIELDS AT
THE FULTON COUNTY, TLLTNOIS LAND RECLAMATION 3T.TE FROM 1972-1981
Mineral
Year
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
X
21
32
14
54
63
146
43
217
179
189
N§
22
12
80
84
80
84
82
84
84
84
N* (rag /kg)
Mln.
0
14
0
4
29
24
16
23
49
63
Max.
69
59
123
255
119
360
136
530
418
370
Available
X
24
13
10
23
59
146
214
393
269
299
N
22
12
52
84
80
84
84
84
84
84
Pf (rag/kg)
Min.
11
8
0
7
10
46
108
194
170
188
Max.
33
18
22
89
135
320
400
617
347
403
Exchangeable K^ (mg/kg)
X
122
92
72
130
122
171
219
225
281
326
N
22
12
48
84
80
84
84
84
84
84
Min.
98
79
26
71
66
103
104
103
148
112
Max.
173
102
121
222
205
563
527
421
454
469
*Available mineral N consists of exchangeable NH4-N and N03+N02-N extracted with 2N^ KC1 according
to Bremner (2).
"^Available phosphorus was determined by extraction with 0.03 N N^F + 0.025 N HC1 (3).
•{•Exchangeable potassium was determined by extraction with IN^ NH^AC (4) .
§N = Number of analyses.
-------
TABLE 10. MEANS (X) AND RANGES OF AVAILABLE MINERAL NITROGEN AND PHOSPHORUS AND EXCHANGEABLE
POTASSIUM FOUND IN SOILS (0-15 cm) FROM FOUR INORGANICALLY FERTILIZED CORN FIELDS AT THE
FULTON COUNTY, ILLINOIS LAND RECLAMATION SITE FROM 1976-1981
Year
_ Mineral N* (mg/kg)
X N§ Min. Max.
Available P (mg/kg)
X
N
Min. Max.
Exchangeable K^ (mg/kg)
X N Min. Max.
1976
7.3 12 3.2 12
7.5 8
0.4 20
98 12
80
132
1977 28.0
25.0 32
7.1
0.4 16
81
76
88
CO
1978 16.0 16 8.8 37 3.5 16 0.4 16
1979 11.0 16 6.1 15 27.0 16 7.5 56
125 16 104 149
110 16 39 220
1980 43.0 16 9.1 80
20.0 16
7.7 43
196 lo
326
1981 34.0 16 12.0 72
12.0 16
0.4 40
220 16 143
428
*Available mineral N consists of exchangeable NH4-N and N03+N02~N extracted with 21N KC1 according
to Bremner (2).
"^Available phosphorus was determined by extraction with 0.03 N NH4F + 0.025 N_ HC1 (3).
•{•Exchangeable potassium was determined by extraction with IN NH^OAC (4) .
§N = Number of analyses.
-------
00
TABLE 11. MEANS (X) AND RANGES OF EXTRACTABLE* CADMIUM, NICKEL AND LEAD FOUND IN SOIL (0-15 cm)
FROM 21 SLUDGE-AMENDED MINE-SPOIL CORN FIELDS AT THE FULTON COUNTY, ILLINOIS
LAND RECLAMATION SITE FROM 1972-1981
Cd (mg/kg)
Year
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
X
0.23
1.00
3.19
5.91
11.2
19.3
39.5
46.3
49.2
60.1
Nf
22
8
65
84
80
84
84
84
84
84
Min.
0.03
0.33
0.23
0.13
3.36
7.43
21.2
23.0
23.4
30.7
Max.
1.50
1.52
21.4
13.5
26.2
42.7
68.3
133.0
72.0
73.5
X
6.7
6.4
6.6
10.2
13.4
18.7
37.2
41.5
41.6
56.7
Ni
N
22
8
54
84
80
84
84
84
84
84
(mg/kg)
Min.
3.2
3.0
3.0
1.6
5.3
6.0
17.8
19.8
16.4
35.2
Pb (mg/kg)
Max.
10.0
10.0
10.3
19.1
29.6
35.5
54.7
111.0
69.9
70.2
X
3.63
2.44
5.58
16.1
27.0
50.2
101.0
136.0
129.0
175.0
N
22
8
54
84
80
84
84
84
84
84
Min.
0.33
0.33
3.97
5.70
10.8
16.8
63.0
78.3
53.9
110
Max.
8.50
6.12
7.24
35.6
59.8
114.0
151.0
219.0
189.0
215.0
*Metals were determined by extraction with 0.1 N^ HC1 (5).
tN = Number of analyses.
-------
TABLE 12. MEANS (X) AND RANGES OF EXTRACTABLE* CADMIUM, NICKEL AND LEAD FOUND IN SOILS (0-15 cm)
FROM FOUR INORGANICALLY FERTILIZED CORN FIELDS AT THE FULTON COUNTY, ILLINOIS
LAND RECLAMATION SITE FROM 1976-1981
Cd (mg/kg) Ni (mg/kg) Pb (mg/kg)
Year X N1" Min. Max. X N Min. Max. X N Min. Max.
1976 0.52 12 0.22 0.98 11.0 12 4.3 16.5 4.69 12 2.32 6.37
1977 0.43 4 0.26 0.67 3.3 4 3.3 3.3 3.58 4 3.10 4.02
1978 0.41 16 C.05 1.32 7.0 16 4.3 10.1 5.86 16 0.99 7.65
1979 0.40 16 0.33 0.95 6.7 16 3.3 9.9 5.59 16 0.33 15.50
1980 0.69 16 0.33 1.54 6.4 16 3.1 14.5 1.18 16 0.33 4.16
1981 0.39 16 0.33 0.97 6.5 16 3.2 11.6 3.95 16 0.33 6.62
*Metals were determined by extraction with 0.1 IJ HC1 (5).
^N=Number 'of analyses.
-------
Effect of Sludge Application on Corn
As the major agricultural crop in Illinois, corn is grown at' the Fulton
County site along with other crops such as soybeans, wheat and forage. A
three-year field rotation schedule is generally used—for two years, sludge
is applied; and in the third year a crop is grown to utilize the available
N and provide economic return. Corn yields have been variable as shown in
Table 13 and 14 for the sludge-amended and non-amended mine-spoil fields.
Yearly yield averages of sludged corn fields ranged from 0.7 to 6.1 Mg/ha
(11 to 97 bu/acre). No corn was grown on inorganically fertilized mine-spoil
until 1977.
TABLE 13. CORN GRAIN YIELDS FROM SLUDGE-AMENDED MINE-SPOIL FIELDS AT THE
FULTON COUNTY. ILLINOIS LAND RECLAMATION SITE FROM 1972-1981
Field 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981
-Mg/ha* (15.5% moisture)
1 0.9 3.7
2 3.0 1.4 6.2
3 3.3 3.0 0.6 4.0 2.0 5.7
4 2.2
5 1.2 1.9
7 1.6 3.0
8 1.3 1.3
9 2.7 2.4
11 0.7 0.6
12 1.8
13 0.4 2.5
14 5.1
15 1.0 1.9
17 2.3 2.1
25 2.4 4.1
26 2.8 4.2
28 0.7 0.7
30 1.6 2.0
32 1.3
33 0.6
47 6.0
X 2.8 2.5 0.7 2.8 2.0 1.1 1.9 4.3 1.3 6.1
*Mg/ha x 15.7 = bu/acre.
740
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TABLE 14. CORN GRAIN YIELDS FROM INORGANICALLY-FERTILIZED MINE-SPOIL FIELDS
AT THE FULTON COUNTY, ILLINOIS LAND RECLAMATION SITE FROM 1972-1981
Field 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981
-Mg/ha* (15.5% moisture)-
29
50
64
65
3.9
5.1
4.2
3.8
2.4
1.0
4.3
0.5
1.3
3.6
145
X
5.8
1.7 4.5 4.6
4.7
2.7
3.6
*Mg/ha x 15.7 = bu/acre.
From 1977 to 1981 the yearly means, as shown in Table 14, ranged from
1.7 to 4.6 Mg/ha (27 to 73 bu/acre). The average yield for non-mined land
throughout all of Fulton County from 1972 to 1981 was 6.4 Mg/ha (101 bu/acre)
and ranged from 4.7 to 7.7 Mg/ha (74-122 bu/acre). The years 1974, 1977 and
1980 were considered least favorable for corn production in Fulton County
(6). The average yields for these three years were only 0.7, 1.1 and 1.3
Mg/ha on sludged mine-spoil. Favorable weather conditions seem to be of
greater importance on mine-spoil than normal agricultural soils. No trend
of yield increase, as soil fertility increases from sludge addition, is dis-
cernible; but good yields are possible as shown in 1981.
The corn crops grown from 1972 to 1981 were sampled from trace metal
analysis. Table 15 presents the mean concentrations found each year in corn
grain grown on the same 21 sludge-amended mine-spoil fields previously dis-
cussed. It is obvious from the table that corn is an excellent crop for
sludge-fertilized land, as no evidence of metal accumulation in the grain is
shown.
TABLE 15. MEAN CONCENTRATIONS OF TRACE METALS FOUND IN CORN GRAIN GROWN ON
SLUDGE-AMENDED MINE-SPOIL AT THE FULTON COUNTY, ILLINOIS
LAND RECLAMATION SITE FROM 1972-1981
Year
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
Zn
91
27
28
34
30
36
38
42
33
26
Cd
—
0.2
0.1
0.3
0.3
0.5
0.5
0.6
0.2
0.1
Cu
i *
nig /Kg
2.8
3.4
2.5
2.4
2.1
1.9
2.9
4.0
2.3
2.1
Cr
(oven-dried,
1.7
0.2
1.0
0.5
0.1
0.3
0.2
0.5
3.7
0.9
Ni
/- c O fi \
OD L>)
1.4
0.6
1.5
1.4
0.8
1.1
1.7
5.7
0.7
0.8
Pb
—
0.3
0.2
0.5
0.1
0.1
0.1
0.2
<0.1
<0.1
Mn
10.0
7.2
8.6
8.9
4.8
6.7
6.6
7.0
7.2
4.1
Fe
98
21
45
32
23
38
31
28
32
28
741
-------
Table 16 gives the concentrations found in the corn grain from 1977 to
1981 for inorganically fertilized land. The Zn, Cd, Cu, Ni, Mn and Fe over-
all means are slightly lower than the sludge-amended corn concentrations for
the same period; but the differences are insignificant.
TABLE 16. MEAN CONCENTRATIONS OF TRACE METALS FOUND IN CORN GRAIN GROWN ON
INORGANICALLY-FERTILIZED MINE-SPOIL AT THE FULTON COUNTY, ILLINOIS
LAND RECLAMATION SITE FROM 1972-1981*
Year
1977
1978
1979
1980
1981
Zn
25
21
21
28
31
Cd
0.1
0.3
0.1
0.1
0.1
Cu Cr
/I ( A * r±A 1
1.1 0.1
2.3 0.2
2.9 1.0
2.0 3.8
1.7 0.6
Ni
f C O p \
3 )
0.7
0.6
1.6
0.5
0.7
Pb
<0.1
0.1
0.2
0.1
<0.1
Mn
4.4
5.6
4.5
7.8
5.4
Fe
24
18
27
26
20
*No corn was grown on inorganically-fertilized mine-spoil from 1972-1976.
Federal Regulations Concerning Sludge Application To Land
On September 13, 1979, the United States Environmental Protection Agency
(7) published "Criteria for Classification of Solid Waste Disposal Facilities
and Practices; Final., Interim Final, and Proposed Regulations" in the Federal
Register. These regulations allow two alternatives for sludge application
projects:
1. For land used to produce food chain crops other than animal feed:
a. Soil pH must be maintained at 6.5 or higher;
b. By 1987, the annual application of Cd cannot exceed 0.5 kg/ha
(0.44 Ib/acre); and
c. The cumulative application of Cd is limited by the soil cation
exchange capacity.
2. For land used to produce animal feed:
a. Soil pH must be maintained at 6.5 or greater;
b. A facility operating plan must show that the crops will be used
strictly for animal feed and if alternative land uses arise,
what measures will be taken to safeguard against possible Cd
health hazards; and
c. The land record or deed must stipulate that the property has
received high Cd application from solid waste, and food chain
crops should not be grown.
The average Cd concentration of the District's sludge applied to the
Fulton County site was 0.29 kg/Jry Mg (0.58 Ib/.ton) . Therefore, under the
742
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first alternative, only 1.7 dry Mg/ha (0.8 ton/acre) could be applied to keep
the annual Cd application below 0.5 kg/ha. As this low application rate is
unfeasible, the second alternative is followed by the District. Since 1979
all crops grown on sludge-amended fields have been grown for animal feed only
and have been sold to Norris Farms in Fulton County, a livestock feeding
operation.
Cost of the Fulton County Site
The 1981 costs for the Fulton County project are contained in Table 17.
The total cost per dry megagram was $346.45 ($314.23/dry ton). Transporta-
tion accounts for 52 percent of the costs and increased 23 percent over 1980.
Revenues from crop sales were $198,227; while 63,387 dry Mg (69,886 tons) of
solids were utilized, for a return of $3.13/Mg ($2.84/ton).
TABLE 17. COSTS FOR THE FULTON COUNTY LAND APPLICATION SITE FOR 1981
Cost
Item $/dry Mg $/dry ton
Capital
Land Costs and Taxes
Application
Barge Transportation
Anaerobic Digestion
Centrifugation
Monitoring
Revenue from Crop Sales
TOTAL
28.36
11.02
94.86
180.96
18.13
16.25
7.11
-3.13
353.56
25.72
10.00
86.04
164.13
16.44
14.74
6.45
-2.84
320.68
LAND RECLAMATION FOR RECREATIONAL USE AND NON-FOOD CHAIN AGRICULTURE
SLUDGE PROCESSING
On-Site Sludge Processing
Centrifuge Operation—A portion of the sludge produced at the District is
processed through continuous solid bowl centrifuges which are at the Dis-
trict's John E. Egan, West-Southwest and Calumet sewage treatment facilities.
These facilities also contain a liquid and dry polymer handling system and
743
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screw and belt conveyors for unloading the centrifuged sludge for truck and
rail transport. In these centrifuge facilities, liquid anaerobically di-
gested sludge with a solids content of 3 to 6 percent solids is concentrated
to a dewatered cake with a solids content of 14 to 21 percent.
Sand Bed Dewatering—At the West-Southwest STW, Imhoff digested sludge is
processed on sand drying beds. The Imhoff sludge is applied to the sand dry-
ing beds in liquid form at a solids concentration of about 7 percent solids
after being dosed with a liquid polymer at a rate of 8.5 kg/Mg (17 pounds
per dry ton) of sludge solids. The dewatered sludge is typically removed
from the sand drying beds in three to nine weeks time at a solids concentra-
tion of about 40 percent. In 1981, the sand bed dewatering system processed
an average of 48.9 dry Mg (54 dry tons) per day.
Heat Drying—In 1939 the heat-drying plant at the West-Southwest STW was put
in operation. Over the years capacity was increased; while air pollution
emissions were greatly reduced through conversion from coal to natural gas
and installation of gas scrubbers and afterburners. The system is as follows
(Figure 4):
Fecl3
GR
CONCE
1-20/
QR
VA
"
VACUUI
, FILTEF
15% SOL
FILTER Ci
AVI F Y *"
:NTRATION .,
TANK _^4 1 >»
I) SOLIDS
OM GAS-FIRED
TER WALL FURNACE
*NACE GAS 700°C
jr l<
\A
?
IDS
'VKE SLUDGE SEPARATORS
^
Jii
Jo
r^\ MIXER
•*— DRYING
TOWER
^
r^l J I J
vv
i i
\
^-DRYING
LINE
i
^SLUDGE
SURGE BIN
r
1 1
\
^DRIED SLUDGE
COOLER
r
o
FACILITY
SLUDGE DRYER
Figure 4. Heat-dried fertilizer processing plant.
744
-------
Waste-activated solids concentrated to approximately 1 to 2 percent solids
content in gravity concentration tanks are conditioned with ferric chloride
and sent to a bank of vacuum filters. At the vacuum filters the conditioned
sludge is dewatered partially to produce a filter cake of approximately 15
percent solids. The filter cake then drops onto a conveyor belt and is
transported to a mixer where it is combined with dried solids from the dry-
ing line to obtain a mixture of approximately 55 percent solids, which is
fed to the drying tower. Here hot gases of approximately 700°C (1,300°F) are
mixed with the solids, resulting in an instantaneous evaporation of water.
The dried solids are cooled, screened, and transmitted by conveyor belt to
the fertilizer storage facilities. The material is an excellent soil con-
ditioner and fertilizer base and is presently sold to a broker on a competi-
tive bid basis. The broker in turn has developed a market of buyers who
apply the solids to land.
Discontinuance of Heat-Drying Program—The use of the heat-drying process was
reduced considerably in 1981. During this year, input to the system averaged
81.6 dry Mg (90 dry tons) per day; while in 1980, it averaged 158 Mg (175 dry
tons) per day. On August 5, 1981, the heat-drying plant was put on standby
service. Stockpiles of heat-dried sludge are being sold to a broker until
exhausted. There are no current plans to start up the process.
The heat-drying process is an energy-intensive operation which uses
nearly 12 kilowatt hours of equivalent electrical power to process 1 kg
(2.2 Ibs.) of sludge. Land application, including stabilization, transpor-
tation and application energy, at the Fulton County utilization site uses
only about 1.30 kilowatt-hours per kg (0.59 kw-hr/lb.) of dry solids applied.
With the present energy costs in the U.S. and the need to conserve energy
resources, it is extremely unlikely that the process will be used again by
the District.
Off-Site Sludge Processing
Lagoon Dewatering—Some of the solids from the heated anaerobic digesters at
the District's West-Southwest STW is stored in large holding basins (lagoons).
Lagoon dewatering consists (Figure 5) of first establishing a drainage pro-
file within a lagoon to facilitate gravity dewatering of trapped water and
rainfall runoff through the drawoff box. The advantage of gravity flow is
significant in that pumping is not necessary and winter weather does not
curtail drainage operations. The lagoon then is allowed to remain at rest
with an established drainage profile through the following winter. A slack-
line cableway system is then used to further improve lagoon drainage. The
system as used is intended to scrape material from the center upwards toward
the sides of the lagoon. In this way it is intended that the following be
accomplished:
• In addition to the initial drainage gradient established along the
length of the lagoon, a drainage gradient is now established across
the width of the lagoon.
• The slackline first scrapes one side of the lagoon and then the
other.
745
-------
STEEL TRUSS
SUPPORT
IAAA
SUPERNATANT
PUMP 8 MIXERS
DRAWOFF BOX » LAGOON BOTTOM
SECTION A-A
(a) PRECONDITIONING
CRANE
L
SUPERNATANT
DRAWOFF BOX
F^ B yCRAf
_| ^S.
at-m
1
SLACKLINE
I
jfr*—BUCKET
; t
t
r^
J
PLAN
CATERPILLAR TRACTOR )
USED AS MOVABLE DEADMAN
(b) STRESSING THE SOLIDS
CRANE
CATERPILLER
(DEADMAN)
BUCKET SLACKLINE
EXCESS WATER
LAGOON BOTTOM
SECTION B-B
(c) STRESSING AND SHIFTING OF DRIER MATERIAL TO THE SIDES OF
THE LAGOON
Figure 5. Lagoon Solids Removal.
746
-------
Approximately 15 cm (6 in) of lagoon crust [material near the top of
the lagoon, the top 7 or 8 cm (3 in) of which has undergone appreci-
able evaporation] is scraped each time, and is piled up along the
sides of the lagoon for further dewatering and storage before excava-
tion and transportation. Stored material along the lagoon dikes is
loaded by dragline onto dump trucks. The lagoon dewatered sludge
typically has a solids concentration of about 33 percent.
Drying Cell Operation—A portion of the lagooned and centrifuged dewatered
sludge is further dried at several sites by a process called agitation dry-
ing. The agitation drying process consists of first applying the sludge to
clay-lined drying cells surrounded by soil berms. A bulldozer then spreads
the sludge to a depth of about 40.6 cm (16 in). As the wet sludge surface
dries in the atmosphere, a crust forms on the surface, inhibiting further
drying. In order to achieve continued drying, a bulldozer is driven through
the sludge daily, breaking the crust and exposing fresh wet material to the
elements. The process continues until a dry product is formed. The dry
product is then pushed into a windrow and removed in trucks. Depending upon
weather conditions and initial sludge solids content, the drying process can
take 40 to 70 days and can consistently achieve final solids concentrations
over 60 percent.
LAND RECLAMATION
City of Chicago, 103rd and Doty Site
In 1979, the District and the City of Chicago discussed the possibility
of a joint cooperative program to reclaim a City of Chicago owned landfill.
The landfill was 91 hectares (225 acres) in size and was used for the dis-
posal of municipal solid waste, construction debris, curb and gutter clear-
ings and tree removal wastes. As the site was licensed and operated before
the enactment of today's stricter environmental regulations, it did not have
a final cover, lacked runoff control, and had no vegetative cover.
In 1979, the City of Chicago and the District agreed to conduct a demon-
stration to show how District sludge might be used to convert the land site
at 103rd and Doty Avenue into an environmentally acceptable landfill which
would be aesthetically pleasing to the surrounding neighborhood. The
demonstration site was 14.9 ha (37 acres) in size. The site was covered
with a 0.6 m (2 ft) clay seal, and then 1.52 m (5 ft) of sludge from
District drying cells (60 percent solids or greater) was applied. The
whole area was then seeded with a rye grass mixture to establish erosion
control. The project was a complete success and a vigorous stand of grass
was produced.
The success of the demonstration project led to an intergovernmental
cooperative effort between the District and the City of Chicago. In 1982,
the City Council of Chicago passed an ordinance that established the Dis-
trict as the city agent in the final closure of the 103rd and Doty site.
The closure plan will be performed in 3 phases. Phase I will involve
747
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the development of a 23.4-ha (58-acre) winter recreation hill and parking
area. The site will first be capped with a 0.6-m (2-ft) clay seal, and then
a hill will be constructed from clean clay soil fill and District drying
cell solids. The entire site will be bermed and runoff directed to drainage
control ponds. The entire site will be landscaped with grass and trees.
Phase II will take place concurrently with Phase I. A 8.8 ha (22 acre)
site which represents the most highly visible portion of the entire site will
be capped with a 0.6-m (2-ft) clay seal and then 1.52 m (5 ft) of District
drying cell solids. Again, the entire site will be landscaped with grass
and trees and runoff directed to ponds.
It is anticipated that Phase I and II will be completed in late 1984.
Phase III will involve the reclamation of the remaining 58.6 ha (145
acres) of the 103rd and Doty site. The site will receive 1.5 m (5 ft) of
drying cell solids followed by 0.6-m (2-ft) clay cap and 0.6 m (2 ft) of
sludge as a base for vegetative cover. The District will contour the site
as dictated by the City of Chicago who have indicated that the site would
be used for a golf course, public park or tree nursery. It is anticipated
that this phase will take eight years to complete.
In 1981, the cost of digestion, lagooning, drying, transportation and
application of sewage solids to the 103rd and Doty site was $65/dry Mg
($59/dry ton).
Palzo Land Reclamation Site
In 1970, the U.S. Forest Service and the District became involved in a
joint effort to reclaim portions of the Palzo Mines in southern Illinois.
These acidic mine spoils, now part of the Shawnee National Forest, had
virtually no vegetation since surface mining ceased in 1961. The acidic
runoff had seriously affected a nearby receiving stream (Sugar Creek) and
the solution to this problem became a primary goal of the U.S. Forest Ser-
vice.
In 1977, the U.S. Forest Service reclaimed 52.6 (130 acres) of acidic
soil in the Shawnee National Forest using liquid lagooned digested sewage
sludge from the District's Calumet STW. The District supplied this sludge
at no charge to the U.S. Forest Service who applied the sludge at an average
rate of 657 Mg/ha (300 dry tons/acre). The total cost for this operation
including land grading, sludge transportation, and environmental monitoring
was $96/Mg dry sludge ($87/ton). District cost for sludge transportation
was $78/Mg ($71/ton).
Libby-Owens-Ford Land Reclamation Site
In 1969, sludge supplied free of charge by the District was used to
treat an alkali sand-filled lagoon with a pH of 10.5 near Ottawa, Illinois,
which was owned by the Libby-Owens-Ford Company. This lagoon was totally
devoid of vegetation, and during dry weather produced dust which was a
nuisance to surrounding residents. Liquid digested sewage sludge was in-
748
-------
corporated into the sand-filled lagoon by filling 0.6-m (2-ft) deep trenches
with liquid sludge and covering this with sand. Using this application
method, 380 Mg/ha (170 dry tons/acre) of sludge were mixed into the sand
surface. Grass was planted on the soil and has grown vigorously ever
since.
Liquid lagooned sludge was shipped from the District's West-Southwest
STW to Ottawa, Illinois, and applied to the site at a total cost to the
District of $85/dry Mg ($77.20/dry ton).
Ottawa Silica Sand Land Reclamation Site
The Ottawa Silica Sand Company owns a 60.7-ha (150 acres) strip-mined
site approximately 125 km (77 miles) southwest of the city of Chicago.
This site was strip mined by a coal company, and then sold to the Ottawa
Silica Sand Company. The company had hoped to mine the site for sand, but
abandoned such attempts because of the high cost of mining the rough strip-
mine topography. The Ottawa Silica Sand Company was aware that the site
created aesthetic and environmental problems. The site was barren and gen-
erated an acid runoff to the nearby Illinois River. The company wanted to
vegetate the site to reduce soil erosion and acid runoff and make the site
more aesthetically acceptable.
The District became aware of the Ottawa Silica Company site in the
late 1970s and approached the company with a proposal to use some of the
District's sludge as a soil amendment for vegetating the Ottawa site. It
was agreed that a reclamation effort using sewage sludge would be made on
a 0.81 ha (2 acre) portion of the 60.7-ha (150-acre) site owned by the
Ottawa Silica Sand Company, and the District agreed to pay for the total
costs for reclamation.
A total of 6,398 wet Mg (7,037 tons) of lagooned digested sludge was
shipped to the Ottawa site with an average concentration of 29 percent.
The actual application rate was about 2,000 Mg/ha (892 tons/acre). Mixing
of the lagooned sludge with the mine spoil was accomplished by placing the
sludge along the crests of the mine spoil ridges and after partial drainage,
the sludge was mixed with and pushed into the valley between the ridges.
The entire site was planted with grass. The grass was successfully es-
tablished and growing two years after the sludge application.
The total unit cost to the District including sludge transportation
and application was $81/dry Mg ($73/dry ton).
Nu Earth Program
Nu Earth is a wastewater solid that has been digested anaerobically
in the digestion compartment of Imhoff tanks, followed by air drying on
sand beds and haulage by rail to a stockpile area for further dewatering
over a period of years. Within the past few years, the District has de-
veloped its very successful local Nu Earth distribution program. Indi-
vidual users can order a minimum quantity of one 18.4 m^ (24 cu yd) truck-
load that is delivered free of charge within an 80 km (50 mile) radius of
749
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the distribution point. Nu Earth is a compost-like material resembling a
rich soil (about 55 percent solids content) and has proved acceptable to
the public for use in landscaping and flower gardening. It contains ap-
proximately 4 percent N, 6 percent P2°5» anc* ^1 Percent K2°-
In 1981, nearly 35,373 dry Mg (39,000 dry tons) of Nu Earth was dis-
tributed for non-food chain uses in the greater Chicago area. The cost
to the District for the Nu Earth program, including Imhoff digestion, sand
bed dewatering, solids storage and transportation, is about $70/dry Mg
($63/ton).
LANDFILLING OF SLUDGE WHEN REQUIRED
Solids from the District's storage lagoons also are removed on a compe-
titive bid contractual basis. The contractor is required to excavate and
dispose of the solids in a legal manner, and most of it in recent years has
been going to sanitary landfills. This method of solids disposal has been
used when the quantity of solids desired to be disposed of exceeds the land
application/utilization capacity of the existing market place, such as when
it is desired to dispose of large quantities in a short time period to
eliminate a lagoon to make space for plant expansion. Also, contract dis-
posal will be chosen when physical constraints in the lagoon complex do not
make slackline removal desirable. In 1981, 50,855 dry Mg (56,070 dry tons)
of solids were removed from lagoons via lagoon cleaning contracts. At the
present time there are no plans to utilize this mode of solids management
in the future, but this option will be considered if conditions so dictate.
This mode of solids management is one of the least expensive solids manage-
ment options used and averages about $80 to $100 per dry Mg ($88.2 to $110.3
per dry ton).
USE OF THE PRIVATE SECTOR IN MUNICIPAL SLUDGE MANAGEMENT
The District believes that in certain circumstances private contractors
can economically manage municipal sludge in a cost-effective and environ-
mentally safe manner. The District is therefore currently preparing a
contract by which private concerns can competitively bid for the right to
manage a portion of the District's sludge production.
The bidding organization must be prepared to manage 108.8 Mg (120 dry
tons) of District sludge using an option which is acceptable to local,
state, and federal agencies. The sludge will be provided in a slurry of
1 to 3 percent solids and will not be stabilized. The vendor must show
that he can manage the sludge for a 20-year period. Cost increases in-
curred by the vendor during the life of the contract will be reimbursed by
the District according to a predetermined formula. The lowest qualified
bidder will be awarded the contract, but the District has set a .predeter-
mined maximum capital and operation and maintenance cost and maximum ener-
gy usage which cannot be exceeded. Current plans call for bids to be
opened in May of 1983 for this sludge management option.
750
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SUMMARY
Wastewater solids management is the most difficult problem today facing
most of the operators of publicly owned wastewater treatment facilities.
With goals of the future being the elimination of combined sewer overflows
and increased treatment efficiencies, solids quantities for ultimate dis-
posal or utilization will increase, magnifying the already difficult solids
management problems.
The philosophy of today's wastewater solids managers at the District
is to maximize the degree of flexibility of each solids distribution pro-
gram. Research, experimentation, and venturing into unexplored avenues
holds the key to answering the solids management questions of the future.
The work described in this paper was not funded by the U.S. Environ-
mental Protection Agency. The contents do not necessarily reflect the
views of the Agency and no official endorsement should be inferred.
REFERENCES
1. Allison, L. E. Organic carbon. In; C. A. Black (ed.), Methods of
Soil Analysis. American Society of Agronomy, Madison, Wisconsin, 1965.
pp. 1376-1378.
2. Bremner, J. M. Inorganic forms of nitrogen. In; C. A. Black (ed.),
Methods of Soil Analysis. American Society of Agronomy, Madison,
Wisconsin, 1965. pp. 1179-1237.
3. Olsen, S. R. and Dean, L. A. Phosphorus. In; C. A. Black (ed.),
Methods of Soil Analysis. American Society of Agronomy, Madison,
Wisconsin, 1965. pp. 1035-1048.
4. Pratt, P. F. Potassium. In; C. A. Black (ed.), Methods of Soil
Analysis. American Society of Agronomy, Madison, Wisconsin, 1965.
pp. 1022-1030.
5. Viets, F. G., Jr. and Boawn, L. C. Zinc. In; C. A. Black (ed.),
Methods of Soil Analysis. American Society of Agronomy, Madison,
Wisconsin, 1965. pp. 1090-1101.
6. Tyner, E. H. Factors influencing corn yields on MSD property in Fulton
County, Illinois. Unpublished report, January, 1983.
7. United States Environmental Protection Agency. Criteria for Classifica-
tion of Solid Waste Disposal Practices. Federal Register, September 13,
1979. pp. 53438-53468.
751
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SLUDGE INCINERATOR
FUEL REDUCTION PROGRAM
by
Paul F. Gilbert, Plant Engineer
Hartford Water Pollution Control Plant
Hartford Metropolitan District Commission
Hartford, Connecticut
Eugene W. Waltz, Associate Director
Energy Engineering and Research Division
Indianapolis Center for Advanced Research
Indianapolis, Indiana
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
9th United States/Japan Conference
on Sewage Treatment Technology
September 19-21, 1983
Tokyo, Japan
753
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SLUDGE INCINERATOR FUEL REDUCTION PROGRAM
Paul F. Gilbert, Plant Engineer
Hartford Water Pollution Control Plant
Hartford Metropolitan District Commission
Hartford, Connecticut
Eugene W. Waltz, Associate Director
Energy Engineering and Research Division
Indianapolis Center for Advanced Research
Indianapolis, Indiana
ABSTRACT
The Hartford Metropolitan District Commission has successfully accom-
plished two major operational changes at its water pollution control plant
to significantly reduce sludge incinerator fuel consumption. The Hartford
Water Pollution Control Plant was one of the first municipal plant opera-
tions in the U.S. to use the continuous belt filter press. During the
period from 1979 to 1981, the Hartford Plant converted from vacuum filters
to all belt filter presses. The resulting improvement in solids production
and drier sludge cake enabled a 657,, reduction in specific fuel consumption.
In 1982, the Hartford incinerators were operated with a new, more fuel ef-
ficient operating mode adopted by the plant engineering staff with the
technical assistance of the Indianapolis Center for Advanced Research.
Routine operations with the new incinerator operating mode during 1982
achieved an additional 517= fuel reduction. The net change in the incinerator
specific fuel consumption from both of these operational changes between 1978
and 1982 was 104 gallons of oil per dry ton of sludge cake incinerated. The
1978 average fuel consumption of 125 gallons per dry ton was reduced to an
average of 21 gallons per dry ton for 1982 for an overall reduction of 837..
The average operational cost savings from this reduction and related savings
amounted to over $1,300,000 per year for 1982 as compared to 1978 operations.
With these two major operational changes, the Hartford Water Pollution Con-
trol Plant has become one of the most energy efficient sludge handling opera-
tions by incineration in the U.S.
754
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SLUDGE INCINERATOR FUEL REDUCTION PROGRAM
INTRODUCTION
The disposal of municipal sewage sludge by incineration most often re-
quires the use of large amounts of auxiliary fuel. Increasing energy costs
in recent years have made incinerator fuel consumption a major operational
cost problem for many municipal operations. To reduce this operational
cost, the Hartford Metropolitan District Commission conducted two major
operational changes at its Hartford Water Pollution Control Plant. The
Hartford plant was one of the first in the U.S. to convert to continuous
belt filter presses for sludge cake dewatering. This conversion took place
between 1979 and 1982 with the installation of four belt filter presses. The
conversion to belt filter presses resulted in dramatic fuel savings of 6570
and increased solids production. In late 1981, the Hartford plant engineer-
ing staff and incinerator operators adopted a new, more fuel efficient
operating mode with the technical assistance of the Indianpolis Center for
Advanced Research. The new incinerator operating mode has been exclusively
used in routine operations since January, 1982, and has resulted in an ad-
ditional 517o reduction in the specific fuel consumption. The combined re-
sult of these two major operational changes was an 837,, reduction in the
incinerator fuel consumption. These results are reviewed here as an example
of how improved dewatering equipment and incinerator operating technology
offer new options to those municipal plants which are currently bound, for
various reasons, to sludge disposal by incineration.
PAST OPERATIONS
The Hartford Water Pollution Control Plant performs primary and second-
ary wastewater treatment for more than 45 million gallons of wastewater per
day and generates in excess of 200 wet tons of filtered sludge cake per day.
The sludge handling facility was designed in 1968 with four dissolved air
flotation thickeners, five drum-type vacuum filters and three multiple (11)
hearth incinerators. The incinerators are equipped for either gas or oil
755
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operation and are rated at 12.5 wet tons per hour maximum capacity. In 1978,
before conversion to belt filter presses, the vacuum filters average 13.870
cake solids. Production required continuous operation of three of the five
vacuum filters with two of three incinerators operating around the clock,
on a five-day work week. The plant operation experienced the typical pro-
duction and maintenance problems associated with handling an extremely wet
sludge cake, that is, clinkers, broken teeth, plugged drop holes, excessive
refractory problems, broken shear pins, smoking, etc To compound
problems, the Hartford plant began receiving sludge from satellite plants in
East Hartford, Rocky Hill and from Glastonbury.
In view of these operating problems and the ever increasing cost of
fuel, the Hartford Metropolitan District Commission initiated a major pro-
gram effort to find new methods in plant operations and processes to re-
gain "control" of operating costs. The belt filter press conversion pro-
gram and the new incinerator operating mode development were two of the major
projects among others which have been undertaken.
BELT FILTER PRESS CONVERSION
Testing and Operational Experience
Hartford began pilot testing belt filter presses in the spring of 1978.
Test results showed that significantly drier sludge cake was produced at
higher production rates as compared to the performance of the existing
vacuum filters. The plant staff then conducted side-by-side performance
tests of the most qualified machines to select the first press for procure-
ment and installation. The first press was installed in 1979 with a care-
fully monitored start-up and shake-down period. Despite numerous mechanical
problems and excessive downtime, the belt filter press quickly proved it-
self so economically beneficial, the approval for acquiring the second press
was granted only four months after the first one was installed. The pay-
back period for the firsb press was only six weeks!
In selecting the second press, performance tests were again conducted
to evaluate overall performance, with emphasis placed on mechanical design,
and maintenance features to incorporate these requirements in the bid
specifications. The second press, which was supplied by a different manu-
facturer than the first, was installed in December, 1979, just eight months
after the first one.
During the first half of 1980, the Hartford plant operated with two
belt presses and one vacuum filter. The mechanical reliability sought with
the second press was realized, as well as, continued fuel savings and sludge
cake production improvements. With this continued operational success, the
District purchased a third press from this same supplier and installed it in
December, 1980. During 1981, the plant was able to operate almost exclusive-
ly with belt presses. A fourth press was placed into operation in June,
1982 to increase capacity and operational flexibility in pairing two presses
to each operating incinerator.
756
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Being one of the first plants to try the belt filter presses, the early
operational experiences were expectedly problematic. The initial press
operation was plagued with numerous mechanical problems with the bearings,
rollers, spray water pump, filter screen cleaning, filter screen tracking,
and filter screen seam closures. With assistance from the manufacturer,
the first press was retrofitted and upgraded for more reliable operation.
The second through fourth presses were from a different supplier, have had
few mechanical problems, and have been satisfactory in operation.
As more operational experience was gained, improvements were made in
several key operating conditions. The filter screen seam closure wearing
problem was reduced by using higher molecular weight plastic scraper blades
resulting in an increase in filter screen operating life from an average of
500 hours to an average of 1500 hours. A new filter link screen is being
tested with a potential increase in cake solids and an operating life in
excess of 2500 hours. Proper polymer conditioning of the sludge cake on all
the presses has been a problem. A two component liquid polymer mix was de-
veloped from experiments with the polymer supplier to reduce the dosage re-
quirements to the same level as was required for the vacuum filters.
Changes in the sludge conditioning tank to improve polymer sludge mixing
have also helped reduce dosage requirements and increased flexibility to
adjust to varying sludge characteristics. Maintaining a constant blend in
the mixing of the raw primary and waste activated sludges from four plants
requires close operator control. Sludge blend variations of only 57» to 107»
can cause the press screens to plug and the sludge to squeeze out the ends
of the rollers with a resulting loss in percent solids and production. In
spite of these operating problems associated with reducing a new operating
technology to routine production line practice, the operational improvements
and cost savings achieved with the belt filter presses in Hartford have been
dramatic.
Fuel Reduction Results
To provide an accurate baseline for comparing the fuel reduction achiev-
ed by converting to belt filter presses and by improvements in the incinera-
tor operating mode, a statistical analysis was made of the key operating
performance data for past operations and each of the years during which
changes were made. In addition, the correlation of specific fuel consump-
tion (SFC) measured in gallons of oil per dry ton with the absolute sludge
cake moisture to volatile ratio by weight (M/V) was computed to provide a
more comprehensive measure of change for comparison.
The average specific fuel consumption for the incinerator operations
in 1978 was 125 gallons of oil per dry ton. The sludge cake solids aver-
aged 13.87o, and the volatiles averaged 77.1%. The sludge cake M/V ratio
which is directly related to, and principally determines, the specific fuel
consumption demand was an average 8.6 which is relatively high.
The savings resulting from the belt filter presses is reflected in the
sharp reduction in the sludge cake M/V ratio, particularly in 1980 when the
major fuel reduction was achieved. The net reduction of an average of al-
most 82 gallons of oil per dry ton would translate into a savings of over
757
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EFFECT OF BELT FILTER PRESSES ON KEY
OPERATING PERFORMANCE VARIABLES FOR 1978 TO 1981
1978 to 1981
YEAR PERCENT
VARIABLE 1978 1979 1980 1981 CHANGE
—i
Ln
00
PERCENT SOLIDS 13.8 14.5 18.5 19.5 +41
SLUDGE CAKE M/V 8.6 8.
5.8 5.4 -37
FUEL CONSUMPTION
GALS./DRY TON
125.2 116.1 60.5 43.5 -65
TABLE I.
-------
848,000 gallons of oil at the 1982 dry ton production level of 10,351 dry
tons. Furthermore, the average incinerator-hours of operation per day also
dropped from 46.5 in 1978 to 35.7 in 1981, a 23% decrease.
These substantial results were accomplished after a considerable amount
of time and effort was invested by the Hartford plant management, staff and
operating personnel. The experience of Hartford with the belt filter
presses serves as a classic example of the opportunities that exist in many
plants throughout the country to achieve internal improvements with the
adoption and modification of new operating technologies. Most operations
would have been contented at this point with the lower fuel consumption
levels that had been achieved. However, in the case of the Hartford Metro-
politan District Commission and Staff, the dramatic success with the belt
filter presses encouraged us to pursue the adoption of other innovative
operating technologies to improve our operations further. One of the
technologies adopted was an improved incinerator operating technique which
had been developed by the City of Indianapolis Department of Public Works
with the Indianapolis Center for Advanced Research under sponsorship of
the U.S. EPA Municipal Environmental Research Laboratory.
NEW INCINERATOR OPERATING MODE
The development and testing of the new operating mode was the result of
a cooperative effort by the Hartford engineering and operating personnel
with combustion engineers from the Indianapolis Center for Advanced Research
(ICFAR). The new operating mode was derived from refined operating tech-
nology developed by ICFAR through a major operational research project con-
ducted on the Indianapolis incinerators. On-the-job instruction and training
in the use of the new operating mode was also performed to demonstrate the
potential fuel reduction and upgrade operator performance.
Operational Testing and Analysis
An operational analysis was made of the Hartford incinerator opera-
tions which included airflow measurements, exhaust gas analysis, assess-
ments of key instrumentation and controls, existing operator specific
practices, load rate management, incineration/dewatering modes, airflow
management, burner use profiles, combustion zone location and hearth tempera-
ture profiles. A kinetic incinerator analytical model was also used to
determine the most optimum load rate and plant operating mode which would
result in the minimum possible fuel consumption.
ICFAR made preliminary analysis of practices which were contributing
to excessive fuel consumption. Some of these findings were: 1) combustion
occurring too high in the incinerator, 2) high exhaust gas temperatures,
3) high draft settings and too much auxiliary air, 4) misuse of heated
rabble arm cooling return air, 5) improper burner use profiles, and 6) im-
proper techniques for controlling combustion zone location. Also contri-
buting to the high fuel consumption were other problem areas associated with
the lack of remote operator controls for airflow dampers and burners.
759
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The airflow measurement results were used to help correct the problems
found in the airflow management approaches being used, as well as, to assess
the relative impact of various previously proven techniques on the Hartford
incinerator set-up. A preliminary analysis indicated that through optimum
airflow management, the potential fuel reduction from these measures alone
was 70% with a sludge cake having a moisture to volatile ratio of 5.0 and
with an incinerator loading rate of 6 wet tons per hour. Furthermore, the
kinetic rate analysis for these conditions predicted that the potential fuel
consumption for the Hartford operation with such a dry cake was nearly
zerol This analytical result was in agreement with the preliminary estimate
drawn from airflow management techniques, since an additional 307o could be
reasonably expected from improved combustion zone location control, optimum
burner use profiles, improved load management, and the synergistic effect
of these operating mode techniques on fuel consumption. Based on these re-
sults and ICFAR's previous experience from similar programs in Indianapolis,
Buffalo, and Nashville, periods of autogenous combustion were expected with
the new operating mode. Autogenous combustion was achieved several times
during the operational trial and demonstration test for as long as eight
hours.
Based on the operational trial tests and analyses, a new operating mode
with specific instructions and operating settings was developed. The new
operating mode was then demonstrated in full plant operation for a two week
performance demonstration test period. On-the-job operator training in the
use of the new mode was also accomplished at the same time. After comple-
tion of the successful performance test, the operating mode was further
refined for routine operational use.
The new operating mode was characterized by the following general oper-
ating guidelines:
"Maximum use of heated rabble arm cooling air return
"Lowest possible draft to minimize excess air and leakage
"Combustion on hearth 7 or 8 to maximize drying area
"Eliminate airflow to top hearth burners
"Control combustion zone location with burner use profile
"Slow center shaft speed to improve sludge drying
"Discontinue use of hearth #5 burners
The specific operating instructions which constituted the .new operating mode
were given to the incinerator operators and included procedures for sludge
load management, incinerator operational control, general operating settings,
specific settings for normal operations, combustion zone location control,
standby and start-up operations, and techniques to control sludge cake
"burn-outs". The most effective incineration/dewatering mode was determined
from the trial tests to be two belt filter presses paired to each operating
760
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incinerator. The most optimum incinerator loading rate was found to be
6 wet tons per hour per incinerator based on analysis and trial tests of
load rates between 4.5 and 7 wet tons. The 6 ton per hour load rate was the
minimum rate associated with keeping up with the overall plant loading rate
and still minimize fuel consumption. The improved operating mode also en-
abled a further reduction in fuel usage because the new mode allowed the
presses to be slowed down resulting in a small increase in solids.
Fuel Reduction Results
The new incinerator operating mode was placed into routine operational
use directly following the two week performance test conducted in January
1982. At this time, the new operating mode has been in continous use by
Hartford for over a year. The operational data for the Hartford plant for
1982 was analyzed to measure and compare the fuel reduction achieved.
The next slide (graph) shows the average specific fuel consumption
for the Hartford operations from 1978 through 1982 for comparison of the
total historical change. The average specific fuel consumption for 1982
was 21.1 gallons per dry ton as compared to 43.5 for 1981, a 51.57,, reduc-
tion. With this improvement the total fuel reduction achieved by Hartford
between 1978 and 1982 amounted to 104 gallons per dry ton, or 837,, which at
the 1982 production level represented a savings of 1,076,000 gallons of #2
fuel oil as compared to 1978.
In addition to reducing direct fuel consumption, the new operating
mode provided increased operating flexibility with the equipment, since the
incinerators could now be efficiently operated at load rates 50 to 60 per-
cent of capacity which was not possible before without paying a tremendous
penalty in excess fuel consumption. The incinerator operation is also now
characterized by cooler maximum operating temperatures, more steady state
control, less particulate emissions and reduced maintenance on internal in-
cinerator parts. In particular, damage to the refractory has decreased,
rabble teeth have not been failing due to the lack of clinker formations,
the rabble arms are lasting longer, and the burner slagging problems has
been drastically reduced.
In spite of the significant fuel reduction achieved with the new op-
erating mode, the Hartford incinerator operation still has further fuel
reduction potential which has yet to be realized from the new operating
mode. There are several equipment related reasons which currently are limit-
ing further gains.
The conveyor system has posed numerous problems. The sludge cake from
the belt filter presses is delivered to the incinerators via a series of
belt conveyors. Due to the arrangement of the presses, one conveyor feeds
both operating incinerators. Diverting a fixed amount of sludge on a con-
tinuous basis off the conveyor is a difficult task. If dry cake builds on
the front of the diverter, the amount of feed to both incinerators will be
changed, upsetting the thermal equilibrium.
761
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Z9L
AVERAGE SPECIFIC FUEL CONSUMPTION
(GALLONS OF OIL PER DRY TON)
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Another critical equipment related problem has to do with the inadequacy
of the original rabble arm raking pattern which was originally set-up for
a wetter sludge cake. The drier cake commands a far different profile for
the number of rabble arms per hearth and the spacing between rabble teeth
depending on what hearth your considering. During the operational tests
an uneven sludge distribution problem was encountered several times. A
distorted burning pattern resulted with sludge combustion occurring on three
hearths simultaneously with uneven burning on one side of these hearths.
This condition also creates an increase in incinerator "burnouts" where the
dry sludge cake gets to a point of uncontrollable autogenous combustion and
the incinerator steady state thermal equilibrium is lost in the process.
Plans are underway to correct the rabbling pattern to adjust for. the drier
sludge cake. To a lesser extent, some improvement in the instrumentation
and remote operating controls would also enable improved operator perform-
ance.
COST SAVINGS
The nominal cost savings from reducing incinerator fuel consumption
on an annual basis was estimated from the change in the specific fuel con-
sumption from 125 to 21 gallons of oil per dry ton. Based on 1982 pro-
duction of 10,351 dry tons, the savings would be over $1,076,000 per year
using an estimated price for #2 fuel oil of $1.00 per gallon.
In addition to the incinerator fuel savings, there were also other
energy savings realized from the belt filter press conversion. Since the
plant started up in 1972, the activated sludge mixed liquor suspended
solids (MLSS) concentration had averaged 4,000 to 5,000 milligrams per
liter (mg/1) requiring approximately 100 million cubic feet of dissolved air
per day. With the belt filter presses, the sludge production increase has
enabled the MLSS level to be lowered to a more desirable 2,000 mg/1 range.
The resulting decrease in the dissolved oxygen demand reduced the daily air
usage to approximately 55 million cubic feet per day. This reduction, in
turn, reduced the electrical energy requirements of a 3,000 hp air com-
pressor by 207» which amounted to a $200,000 per year savings in electrical
costs. Also, each vacuum filter had a 71.5 hp requirement as compared to
22 hp for each belt press. This reduction in electrical use resulted in an
estimated savings of $25,000 per year. In addition, the elimination of the
vacuum pumps which required potable water at a rate of 30 GPM/filter re-
sulted in a savings of $6,000 per year. In total, these additional savings
amounted to over $231,000 per year.
The total plant estimated annual energy cost savings from converting
to belt filter presses and the new incinerator operating mode are shown on
Figure II. The sharply rising dashed line represents the annual total gas,
oil and electrical costs. The costs are actual to 1978 and have been esti-
mated to reflect the subsequent yearly costs if vacuum filters remained in
operation. The solid lower branch line represents the actual yearly costs
since the retrofitting to belt filter presses and the new incinerator oper-
ating mode.
763
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32 i—
< o
LJ '
Z (K
UJ >
H 2
CD
3,0
2 8
2.6
2.4
2.2
2 0
1.8
1.6
1.4
1.2
1.0
- BTU's xlO'VYR
ANNUAL ENERGY USAGE & COSTS
VACUUM FILTERS VERSUS BELT FILTER PRESSES
3.09
3.02
VACUUM FILTERS
(assumed)
BELT FILTER
PRESS (ACTUAL)
JL
1976
1977
ANNUAL
SAVINGS
50.8 % in DOLLARS
V 62.9% BTU's
1.14
_L
Figure I.
1978 1979 I960 1981 1982
PRESS I PRESSH PRESSin PRESSET
1C FAR
-------
The shaded area represents the annual cost savings. For example, our
1982 costs were cut in half by $1.5 million.
The upper increasing then sharply decreasing solid line, demonstrates
the continuously rising energy demand then the constant decrease during the
retrofit period. The total plant energy has been reduced by 62.97o between
our peak year of 1978 and 1982.
CONCLUSIONS AND RECOMMENDATIONS
1. Fuel consumption in multiple-hearth sewage sludge incinerators
can be significantly reduced by improved dewatering equipment
and also by using more fuel-efficient operating modes.
2. Further applications of improved operating techniques need
to be promoted as a cost effective approach to reducing in-
cinerator fuel consumption.
3. Low cost investments for improved instrumentation and controls
and operator training programs can result in major fuel savings
for many existing operations.
The work described in this paper was not funded by the U.S. Environ-
mental Protection Agency. The contents do not necessarily reflect the
views of the Agency and no official endorsement should be inferred.
7/20/83
MJS GOVERNMENT PRINTING OFFICE 1985/559-111/10826
765
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