EPA-670/9-75-005
MAY 1975
PROCEEDINGS
THIRD U.S.-JAPAN CONFERENCE ON
SEWAGE TREATMENT TECHNOLOGY
February 12-16, 1974
TOKYO, JAPAN
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EPA-670/9-75-005
May 1975
THIRD
U.S. - JAPAN
CONFERENCE ON
SEWAGE TREATMENT TECHNOLOGY
PROCEEDINGS
February 12-16, 1974
Tokyo, Japan
OFFICE OF INTERNATIONAL ACTIVITIES
OFFICE OF RESEARCH AND DEVELOPMENT
OFFICE OF WATER AND HAZARDOUS MATERIALS
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
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REVIEW NOTICE
This publication has been reviewed by
the U.S. Environmental Protection Agency and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views of the Agency nor does the mention
of trade names or commercial products constitute
endorsement or recommendation for use.
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FOREWORD
The United States and Japan share a common
concern for the protection of man's environment.
Both nations have recognized that their highly
developed technological talents should be turned
to the solution of environmental problems which
confront us today. In the past they have made
important advances, both individually and in
cooperation with others, to preserve and enhance
the quality of life.
The advantages which accrue from cooperative
effort on problems of mutual concern are undeniable.
Building on two earlier successful meetings, the
Third U.S./Japan Conference on Sewage Treatment
Technology, held in Japan in 1974, is a recent
example of effective cooperation for mutual benefit.
These Proceedings will be of real value to future
efforts in the field.
We look forward tq,_siinilar productive cooperation
in the future. -
('-"" \ I 1
\L\ ii\JT (
Rusdell IE. Train
Adnlinistrator
Washington, D.C.
April, 1975
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CONTENTS
FOREWORD iii
JAPANESE DELEGATION v
U.S. DELEGATION vi
JOINT COMMUNIQUE 1
JAPANESE AGENDA 4
JAPANESE PAPERS
OFFICIAL CONFERENCE 5
AMERICAN AGENDA 189
AMERICAN PAPERS
OFFICIAL CONFERENCE 190
IV
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JAPANESE DELEGATION
THIRD US/JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
Dr. Takeshi Kubo
Mr. Katsuto Inomae
Dr. Mamoru Kashiwaya
Mr. Kenjiro Saito
Mr. Shigeru Ando
Mr. Katsumi Yamamura
Mr. Kenichi Hanada
Dr. Shoichi Nanbu
Dr. Akinori Sugiki
Mr. Satoru Toyama
Mr. Masayuki Sato
Mr. Seiichi Yasuda
Mr. Hideo Fuji!
Head of Delegation
Director General
Department of Sewerage & Sewage Purification
Ministry of Construction
Head
Sewage Works Division
Department of Sewerage & Sewage Purification
Ministry of Construction
Chief
Water Quality Section
Public Works Research Institute
Ministry of Construction
Chief
Sewage Works Section
Public Works Research Institute
Ministry of Construction
Chief
Advanced Waste Treatment Section
Public Works Research Institute
Ministry of Construction
Head
Water Quality Control Division
Water Quality Bureau
Environmental Agency
Head
Water Pollution Control Division
National Research Institute for Pollution
and Resources
Ministry of Commerce and Industry
Head
Sanitary Engineering Division
National Public Health Institute
Ministry of Health and Welfare
Head
Research and Technology Development Division
National Sewage Works Corporation
Head
Engineering Division
National Sewage Works Corporation
Director
Sewage Works Bureau
Yokohama City Office
Director
Sewage Works Bureau
Kyoto City Office
Head
Technology Development Division
Sewage Works Bureau
Tokyo Metropolitan Government
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U.S. DELEGATION
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
Francis M. Middleton, Team Leader
Jesse M. Cohen
Edwin F. Earth
Dr. Joseph B. Farrell
Francis J. Condon
Charles H. Sutfin
Andrew M. Caraker
Bart Lynam
Richard Whittington
Deputy Director
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Ohio 45268
Chief, Physical-Chemical Treatment Section
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Ohio 45268
Chief, Biological Treatment Section
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Ohio 45268
Chief, Ultimate Disposal Section
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Ohio 45268
Staff Chemical Engineer
Municipal Pollution Control Division
Office of Research & Development
Environmental Protection Agency
Washington, D.C. 20460
Chief, Process Technology Branch
Municipal Wastewater Systems Division
Office of Water Programs
Environmental Protection Agency
Washington, D. C. 20460
Coordinator for Japanese Affairs
Office of International Activities
Environmental Protection Agency
Washington, D.C. 20460
Superintendent, Metropolitan Sanitary
District of Greater Chicago
100 East Erie Street
Chicago, Illinois 60611
Deputy Director, Texas Water Quality Board
3101 Highland Terrace, W.
Austin, Texas 78731
VI
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JOINT COMMUNIQUE
THIRD U.S./JAPAN CONFERENCE
ON
SEWAGE TREATMENT TECHNOLOGY
Tokyo, Japan
February 16, 1974
1. The Third U.S./Japan Conference on Sewage Treatment
Technology was held in Tokyo from February 12-16, 1974 by
mutual agreement between Mr. Russell E. Train, Administrator
of the U.S. Environmental Protection Agency (EPA) and Mr. Takao
Kameoka, Ministry of Construction.
2. The U.S. Delegation headed by Mr. Francis M. Middleton,
Deputy Director of The National Environmental Research Center
(NERC), Cincinnati, Ohio, EPA was accompanied by seven repre-
sentatives from the U.S. EPA, state and local governments.
3. The Japanese delegation headed by Dr. Takeshi Kubo,
Director General, Department of Sewerage and Sewage Purification,
Ministry of Construction, was composed of eight National officials,
three local government officials, and two representatives from the
Japan Sewage Works Corporation.
4. Prior to the Conference the U.S. delegates visited Saitama
Prefecture Arakawa Sewage Treatment Plant, Tokyo Metropolitan Government
Ukima Works and Ochiai Works, Yokohama City Torihama Industrial Waste
Treatment Works, Yokosuka City Shitamachi Sewage Treatment Plant,
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Zushi City Water Pollution Control Center, Fujisawa City South Sewage
Treatment Plant, Atami City Nishikigaura Sewage Treatment Plant, Kyoto
City Toba Sewage Treatment Plant and Kisshoin Sewage Treatment Plant,
Nara Prefecture Yamato River Purification Center and advanced waste
treatment pilot plants at Yokosuka and Kyoto which were conducted by the
Ministry of Construction.
5. Each field visit involved the subject matter to be discussed during
the Conference.
6. The U.S./Japan Conference on Sewage Treatment Technology grew out of
the Second U.S./Japan Ministerial Conference on Environmental Pollution held
at Washington, D.C. in June, 1971 between Chairman Russell E. Train, then
Head of the Council on Environmental Quality and then Japanese Minister
Sadanori Yamanaka. The First Conference was held at Tokyo, Japan in 1971
and the Second Conference was held at Washington, D.C. in 1972.
7. Principal topics of the Third Conference were Federal Water Pollution
Control Act Amendments of 1972, sludge treatment and disposal, combined muni-
cipal and industrial waste treatment and advanced waste treatment technology.
During the Conference the presentations were followed by vigorous discussions
from both sides.
8. In addition to the Conference, the Municipal Design Seminars were
opened to about two hundred members of the Japan Sewage Works Association
on the subjects of physical-chemical treatment technology, pure oxygen
activated sludge technology, upgrading of existing plants, and combined
sewer and stormwater technology.
9. A video tape concerning research on environmental pollution at the
Robert A. Taft Center, NERC, EPA, Cincinnati, Ohio was narrated in Japanese
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by Mr. Tokuji Annaka, research engineer, Public Works Research Institute,
Ministry of Construction. Mr. Annaka is spending one year in Cincinnati
by an exchange program of technical personnel between two countries in a
follow-up of conclusions reached at the Second Conference held at Washington,
D.C. in 1972.
10. The Conference was successful and fruitful in the exchange of knowledge
and experience with each country. Future emphasis will be placed upon closer
exchange of experts and information between the two countries.
A progress report of these three Conferences since 1971 will be pre-
sented by both sides for the coming U.S./Japan Ministerial Conference on
Environmental Pollution.
11. The delegations agreed to explore and identify research projects,
which might be undertaken jointly by both U.S. and Japanese experts, and
also to look for the possibility of attendance of officials from Asian
countries to the future conferences.
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AGENDA
JAPANESE PRESENTATIONS
TUESDAY, FEBRUARY 12:
JAPANESE SIDE VIEWS ON U.S. FEDERAL WATER POLLUTION
CONTROL ACT AMENDMENTS OF 1972
WEDNESDAY, FEBRUARY 13:
HEAT TREATMENT OF SEWAGE SLUDGE
COMBINED TREATMENT OF MUNICIPAL AND INDUSTRIAL WASTEWATER
THURSDAY, FEBRUARY 14:
STUDIES ON ADVANCED WASTE TREATMENT
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Third US/JAPAN Conference
JAPANESE SIDE VIEWS ON THE FEDERAL WATER
POLLUTION CONTROL ACT AMENDMENTS OF 1972
WATER QUALITY STANDARDS, EFFLUENT STANDARDS
presented by
Katsumi Yamamura
Head, Water Quality Control Division,
Water Quality Bureau,
Environment Agency
GRANTS FOR CONSTRUCTION OF TREATMENT WORKS,
RESEARCH AND RELATED PROGRAMS
presented by
Takeshi Kubo
Director, Department of Sewerage & Sewage Purification,
City Bureau,
Ministry of Construction
February 12-16, 1974
Ministry of Construction
Japanese Government
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CONTENTS
Page
1. Water Quality Standards, Effluent Standards ...............
2. Grants -for Construction of Treatment Works, Research and
Related Programs ..........................................
2.1 Introduction ............................................ "
2.2 Target Dates ............................................ 10
2.3 State Grants for Construction of Treatment Works ........ 10
2.4 Reactions for guidelines from professional engineers .... H
2.5 Secondary Treatment Information ......................... 12
2.6 Information on Alternative Waste Treatment Management ... 12
2 . 7 Infiltration/Inflow ..................................... 13
2.8 Allotment of Federal Grants for Construction of Treatment
Works ....................................... : ........... ^
2 . 9 Public Participation .................................... 1^
2.10 Cost-Effective Analysis ................................. 15
2.11 Pretreatment Standards .................................. 15
2.12 User Charges ..... ....................................... 16
2.13 Industrial Cost Recovery ................................ IT
2.14 Consideration on Reclaiming or Recycling of Water ...... 18
2 . 15 Planning of Storage for Water .......................... 18
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1. Water Quality Standards, Effluent Standards
As the contents and intentions of the Federal Water Pollution Control
Act of 1972 were made clear through the Guidelines and other informations
x
recently issued, we, as Government officials responsible for water pollu-
tion control, highly appreciate such informations and the Act itself as
good references for considering the measures to combat water pollution
such as establishment of regulatory standards and as basic informations
for reviewing the measures already taken.
First, we feel that the FWPCA of 1972, which most comprehensively
provides for the policy to protect and improve water quality, is more
functional than the statutory system in Japan, composed of several laws
i.e. the Basic Law for Environmental Pollution Control which is the
basic law for pollution control policy in general and provides for the
establishment of Water Quality Standards, and the Water Pllution Control
Law which provides for various regulatory measures and other laws to
carry out pollution control projects including construction of sewerage.
The second point I want to say is on Water Quality Standards.
The Water Quality Standards under the FWPCA of 1972 are to be established
to attain a very high quality of the environment so as to protect fishes
and other aquatic living organisms and their culture, and to maintain
the natural beauty and the amenity for peaple's recreation activities.
We would highly appreciate such intensive water pollution control policy
when considering its difficulty in attaining such high quality in any
water bodies which are already polluted to some extent including closed
waters such as harbors around industrial zones.
The third point is on effluent standards.
I think that you have made great change in ways of thinking and those
provisions on best practicable or best available technology are to be
applied in all bodies of water. This would give great influence on
water management policy in Japan.
According to the informations already published, the effluent
standards have been set as maximum emission units e.g. maximum COD
emission amount per unit raw material in cases when best practicable
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or best available technologies are adopted. We have not been able to
examine the effluent standards in detail but we have found that some of
them are very stringent. We think that, in order to establish such
standards, you had to consider current effluent treatment technologies,
differences in manufacturing processes, possible effects on production
costs, etc., and we highly appreciate the efforts you have made.
I would like to ask you a few questions on the FWPCA of 1972, the
Guidelines and related matters.
(l) Any State Governor has to consult with the Administrator of EPA
when he wants to work out a plan for pollution control, development and
use of water resouces (including restoration, conservation and protectioi
of them) with the view to preventing water pollution. I want to know
the methods and procedures of the consultation and environmental impact
assessment between State Governor and the Administrator.
(2) You have established to effluent standards as emission amount of
pollutant per unit raw materials. I think that continuous manitoring
systems of quality and quantity of effluent and of consumption of raw
materials should be established. How do you carry out such monitoring?
What like are the cases when the establishment of least water
quality standards is considered impossible because of natural conditions
of water, man-made pollution and special purpose of use of water? I
think that the acidic waters caused by mines is one of those cases.
How do you establish water quality standards in this case? And do you
carry out any measures to improve the quality of such acidic waters?
(4) Some bottom deposits may give bad influence on fishes, ecosystem
and water quality. Organic deposits will influence on eutrophication.
For example, mercury in fishes of Minamata Bay is considered to be
caused by contaminated deposits. In order to combat pollution by
mercury and its compounds, we established the Provisional Standards for
Removing Bottom Deposits Containing mercury on June 30, 1973- Do you
have any intention to establish standards for removing bottom deposits
and to enforce them?
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2. Grants for Construction of Treatment Works, Research and Related
Programs
2.1 Introduction
Environmental pollution control has teen one of the important policies
recently in Japan especially for these several years and it is further
recognized that the policy of the environmental pollution control shall
be placed on a top priority among various national policies from now on.
Because, initially the pollution problem was attacked on a fragmentary
basis with various local governmental units coped with the independent
countermeasure for special types of pollutant, but the environmental prob-
lems, particularly water pollution problems relating to rivers, lakes and
coastal waters are accused by the public not only in the industrial area
of the large cities, but also in the rural area of all over Japan, and
so the public has become more aware of water pollution and its attendant
environmentally degrading problems in such a way of the fishermen's
union's demonstration against pollution in various part of Japan. Under
these circumstances the positive protective actions have been seriously
demanded with increasingly periodicity.
Japanese Government has been trying to establish powerful legislation
on pollution control and also to promote the countermeasure against water
pollution prevention such as sewage treatment construction planning.
This is my understanding that the Federal Water Pollution Control Act
Amendments of 1972 (the Act) is a very comprehensive and complex law that
addresses all types of water pollution, and so far in Japan we could not
go through such a experience on its comprehensiveness and its ambitious
national goals. In the beginning of the Act the national goals are
declared in taking up a positive attitude. The ultimate goal is to
eliminate the discharge of pollutants into the navigable waters of the
United States by 1985 and the interium goal is to achieve the water
quality by July 1, 1983 which provides for the protection and propaga-
tion of fish, shelfish and wildlife and provides for recreation in and
on the United States waters. Further, the national policy is that the
discharge of toxic pollutants in toxic amounts be prohibited. The
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concrete measure and the definite procedure to attain the goal can be
realized through the regulations and guidelines pursuant to each section
of the Act.
It is understandable that the regulations establish the terms of
requirements for each specific piece of the Act and the guidelines ex-
plain, amplify in detail, and provide guidance to supplement the regula-
tions, and in these connections the regulations are formal documents that
provide the legal framework for the implementation of the Act and on the
other hand the guidelines are explanatory and assist in the understanding
of the regulations. I have gotten through with reading some regulations
and guidelines and I would like to present the Japanese side views and
to make some comments on the Act, regulations and guidelines.
2.2 Target Dates
In order to achieve the ultimate national goal you have only ten
years more. With full implementation of the Act including target dates
for the use of "best practicable" technology subsquently "best available"
technology, and finally zero discharge of pollutants, and in these con-
nections you shall have to carry out the extraordinarily large waste
treatment works program. It seems to me that it takes time to explore
to make the most reasonable planning and also designing with waste
treatment facilities from view point of engineering, and as might be
expected in such a development, by now it is highly doubtful that any
local government would meet its responsibility to control water pollution
unless the maximum authorized federal grant is provided, and the 18
billion dollars federal grant program will be increasing due to construc-
tion cost rising, and also there must be many difficulties to cope with
the time limitation of the Act for small communities and small industries.
From these points of view I am obliged to acknowledge that it will be
too short to attain the target dates for the ambitious national goals.
2.3 State Grants for Construction of Treatment Works
Before enactment of 1972 Amendments Act, the program was aimed at
providing an incentive for State Governments and local municipalities
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and offered 10$ bonus federal grant in the case of combination of state
grant program and of regional waste treatment plant construction. It
seems that such an incentive policy would be quite effective to promote
construction program with each financially sharing basis among Federal,
State and local municipality. The national goals of the Act should be
the mutual goals of all concenrned with protection of U.S. Nation's
waters and in order to achieve the national goals it should be absolutely
necessary to keep a coordinate effort with each other among EPA, State
agencies, municipalities, design engineers, and industries. In order
to keep such a partnership some kinds of incentive with each other would
be desirable. The current program promises seventy-five percentage
federal grant of the construction cost of sewage treatment plants and
sewers for publicly owned facilities of any size and in this case there
is no incentive between EPA and state agencies. I would say that collabora-
tion and cooperation should be maintained at the federal, state and regional
level. Through the experience in the past Act is there any bad effects
in such an incentive way of federal grant system between federal and
states.
2.4 Reactions for Guidelines from Professional Engineers
It seems that the regulations and guidelines establish a very power-
ful frame work for the purpose of establishing minimum requirements to be
followed by all planners and designers of municipal water pollution
control facilities, and I can imagine that there must be the tendency
of guidelines to be used as standards. The objective of the Act is to
restore and maintain the chemical, physical and biological integrity of
the Nation's waters and this tendency should not cause the regulations
and the guidelines to become too confining, because this tendency could
stifle the creativity of the professional designers. I think that
standardization on design criteria of facilities sometimes will give a
bad effect to creative improvement from view ponts of engineering. Do
you have any reactions or arguments from the professional designer's
field on the matters of standardization caused by establishing the
regulations and guidelines of the Act?
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2.5 Secondary Treatment Information
Pursuant to section 304 (d) (l) the information, in terms of the
parameters of biochemical oxygen demand, suspended solids, fecal coliform
bacteria and pH on the degree of effluent reduction attainable through
the application of• secondary treatment. Terms '1-week' and '1-month' as
used in effleunt samples are expressed in a period of seven consecutive
days and thirty consecutive days. It is reasonable in this way to have
the parameters of BOD, SS and fecal coliform bacteria. It is understand-
able that in the case of comb'ined sewer system during wet weather require-
ments should be made case by case, but it seems to me that there should
be some guidelines to make the decision of the attainable percentage
removal level in combined sewer during wet weather. In 'most of large
cities in Japan the combined system has been taken and many storm-overflows
do exist exactly on sewers. In these cases it is not so practicable to
decide the requirements even in case by case. I understand in the regula-
tions that when industrial wastes discharge into publicly owned treatment
works, effluent standard can be adjus'ted upwards to only those cases in
which the flow or loading from an industrial category exceeds 10 percent
of the design flow or loading of the treatment works. Actually the per-
centage of the flow or loading of industrial waste into publicly owned
treatment works may vary from time to time, and this means that the
effluent standards from the corresponding publicly owned treatment works
may vary from time to time being adjusted proportionally- Who is taking
responsibility to decide the effluent standards for such a case by case
such as combind sewer and industrial waste problem? I shall be much
obliged if someone explain the practice in U.S.A. more in detail for
combind sewer and industrial waste.
2.6 Information on Alterrative Waste Treatment Management
Pursuant to section 304 (d) (2) of the Act, information on alter-
native waste treatment management techniques and systems available .to
implement section 201 of the Act, is published in dividing into three
categories (l) treatment and discharge into navigable waters (2) land
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application techniques and (3) wastewater reuse. In navigable waters,
where water quality standard are more stringent, effluents based on
those standards will apply and more stringent effluent limitations
including additional parameters such as ultimate oxygen demand and ulti-
mate biochemical oxygen demand will be decided. The use of the parameters
of ultimate exygen demand means the total oxygen demand of the waste-
water effluent including organic nitrogen, especially in the form of
ammonia. I seems to me that technology to satisfy the ammonia biologi-
cal demand is more costly and less widely achievable and is not always
practicable at the moment. I wonder whether this kind of technology
should be called to be best practicable or not.
2.7 Infiltration/Inflow
Pursuant to section 201 (g) (3) of the Act, the EPA Administrator
shall not approve any grant after July 1, 1973, for treatment works
under this section unless the applicant shows to the satisfaction of the
Administrator that each sewer collection system discharging into such
treatment works is not subject to excessive infiltration. It is recog-
nized that sewage treatment of infiltration/inflow requires larger
treatment works with increased cost for capital, operation and mainte-
nance, and elimination of infiltration/inflow by sewer system rehabilita-
tion can often reduce the cost of sewage collection can often reduce the
cost of sewage collection and treatment, therefore a logical and systematic
on the total system over sewage collection and treatment is necessary to
determine the cost-effectiveness through the cost-effective analysis.
The cost-effective enalysis should be based on the comparison of the
estimated cost for treatment of infiltration/inflow and the estimate
cost for rehabilitation of the sewer system. It seems to me that in this
case the estimate cost for treatment of infiltration/inflow may vary
sharply in either case of estimating the cost for best practicable or
best available process, in other words for secondary treatment or advanced
waste treatment.
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2.8 Allotment of Federal Grants for Construction of Treatment Works
As for allotment of federal grant and state determination and certi-
fication of project priority, pursuant to section 205 (a) the federal
grant of plant construction shall be allotted among the States in accord-
ance with regulations in the ratio that the estimated cost of constructing
all needed publicly owned treatment works in each state bears to the
estimated cost of construction of all needed publicly owned treatment
works in all of the states. I understand.that pursuant to section 516
(b) (2) a detailed estimate, biennially revised, of the cost of construc-
tion of all needed publicly owned treatment'works in all of the States
and of the cost of construction of all needed publicly owned treatment
works in each of the States and the applicable percentages to be used in
computing State allotment every two years. On other hand the EPA
Administrator, pursuant to section 516 (b) (3) (4), shall make a com-
prehensive study of the economic impact on affected units of government
of the cost of installation of treatment facilities, and a comprehensive
analysis of the national requirement for effluent to attain water quality
objectives as established by the Act. Is there any possibility for the
Administrator to correct the allotment of funds at the results of the
comprehensive study and analysis pursuant to section 516 (b) (3) (4)?
Pursuant to the regulation of grants for construction of treatment works,
construction grants will be awarded from allotments available in accord-
ance with a State System for certification of priority for construction
grant project. What kind of criteria is'used in Texas State priority
system?
2.9 Public Participation
It is required by the regulation that the State agency has afford
adequate opportunity for the public participation such as oral or written
municipal and public comment upon the State priority system. Further,
pursuant to section 101 (e), the EPA Administrator, in cooperation with
the States, shall develop and publish regulations specifying minimum
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guidelines for public participation in such processes. Could you explain
the public participation in the development of water pollution control
program in the case of Texas State agency?
2.10 Cost-Effective Analysis
In cost-effective analysis procedure of the guidelines pursuant to
section 212 (2) (c) of the Act it is required that the planning period
for the cost-effective analysis shall be 20 years. On the other hand
pursuant to section 208 (b) (2), any plan prepared'under such process
shall include the idenfication of treatment works necessary to meet the
anticipated municipal and industrial waste treatment needs of the area
over a twenty years period including any requirements for the acquisition
of land for treatment purposes; the necessary wastewater collection and
urban storm runoff systems; and a program to provide the necessary
financial arrangements for the development of such treatment works.
I wonder why a twenty-year period is fixed' in those cases, because pursuant
to the same guidelines of cost-effective analysis the service life shall
•be taken in accordance with such situations as follows;
Land permanent
Structures 30 ~ 50 years
Process equipment 15 ~ 30 years
Auxiliary equipment 10 ~ 15 years
2.11 Pretreatment Standards
It seems that the federal pretreatment standards pursuant to section
307 (b) of the Act are intended to be national level in scope and in
many cases it will be necessary for a State or a municipality to supple-
ment the Federal Standards with additional pretreatment requirements in
accordance with the local condition pursuant to section 304 (f) (l) and
guidelines. Pretreatment for removal of compatible pollutants such as
BOD, SS and so on, is not required by the Federal Pretreatment Standards.
I understand this indicates that the compatible industrial wastewater
will be encouraged to be treated in publicly owned treatment works by
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joint treatment under the user charge systems. I understand also that
under the National Pollutant Discharge Elimination System pursuant to
section 402, all point sources including publicly owned treatment works
must obtain a permit for' the discharge of wastewaters to the navigable
in the United States, permits, however, will not be required for industrial
sources discharging into publicly owned treatment works, and effluent
limitations for publicly owned treatment works is required including (a)
secondary treatment information, section 304 (d) (l) (b) toxic effluent
standards, section 30? (a) (c) Water quality standard, section 303 of the
Act, and the most stringent limitation for each pollutant will govern.
Accordingly I understand that it may be necessary to establish a local
system which will allocate waste loads to industrial users so that
biological treatment processes are not inhibited and to ensure that
effluent limitations are met. Finally there is one thing in pretreatment
for the incompatible pollutants such as heavy metals. In the case of
pretreatment to remove heavy metals there must be some difference on
quality limitation between publicly owned biological treatment works and
physical chemical treatment works. Supposing that small amount of heavy
metals through legal pretreatment limitation are discharged into publicly
owned treatment works and such heavy metals will be concentrated in the
sludge, and there will happen to cause difficulties in sludge treatment
and disposal. In this connection there"are serious discussions in Japan
in which any heavy metals in any amount into publicly owned treatment
works should be prohibited from industrial sources including small
industries, and publicly owned treatment works should not take respon-
sibility of recieving any heavy metals from industry.
2.12 User Charge
It seems that the user charge systems are intended to enable the
treatment authority to be financially self-sufficient with respect to
operation and maintenance, because the term of operation and maintenance
in this case includes replacement, and the expenditures for replacement
are the expenditures for installing equipment or appurtenances which are
necessary during the service life of the treatment works to maintain the
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capacity and performance for which such works were designed and constructed,
and also user charges must be included in the charges made by treatment
authorities for wastewater collection and treatment such as payments for
local debt service for previous construction and local share of the works.
I understand that the user charge system may be a policy under which
sewage treatment works should be financially self-suport excluding re-
construction and expansion works.
As for industrial cost recovery, it seems that the definition of an
industrial user is too broad, especially with regard to Division I -
Service - of the Standard Industrial Classification Manual, 1972, Office
of Management, because some kinds of service industries which are having
close contact with civic life discharge primarily domestic type waste,
and are different from industries contributing significant quantities of
process wastes- In Japan discussions are now going on with regard to
the definition of the industrial user particularly relating to service
industry, because we are going to establish the specifyed sewer charging
system for industrial users in accordance with the polluters pay principle,
ppp. Finally I would like to raise questions concerning with treatment
of stormwater and infiltration. How the cost for stormwater treatment
and infiltration water treatment will be financed? In our Japanese
practices user charges are levied by the way of system based on water
quantity measured by water meters installed in each house, and of course
such water quantity does not include stormwater and infiltration water,
and we cannot distribute such portion of such cost of stormwater and
infiltration water treatment to users.
2.13 Industrial Cost Recovery
The regulations require that all grantees recover from industrial
users that portion of the grant amount of the treatment of wastewater
from such users, and an industrial users' share shall not include an
interest component. The regulation also provides that a grantee may
retain an amount of the revenues recovered from industry equal to (l)
the amount of the non-Federal cost of the project paid by the grantee,
plus (2) the amount necessary for future reconstruction and expansion of
17
-------
the project. The total amount retained, however, cannot exceed 50 percent
of the amount recovered. There are three points arising here that the
first one is the reason why 50 percent limitation in retainment is taken
and the second one is the fact that the corresponding treating authority
may make a profit in this portion through industrial recovery system, and
the third one is that there must be arguments in which industrial users
may not pay the interest component, but other industries which do not
happen to discharge their wastewater into public sewers due to their
location cannot help providing their own plants and operating the plants
by their own expenditures including the interest component.
2.14 Consideration on Reclaiming or Recycling of Water
Pursuant to section 201 (g) (2) (B) provides that the works proposed
for grant assistance will take into account and allow to the extent
practicable the application of technology at a later date which will
provide for reclaiming or recycling of water. At the planning or design-
ing basis what kind of consideration should be definitely paid for
reclaiming or recycling of water?
2.15 Planning of Storage for Water
Pursuant to section 102 (b) (l) (2) (3) (4) (5) of the Act, in the
planning of storage for water quantity and regulation of stream flow
consideration shall be given by the Corps of Engineers, Bureau of
Reclamation, or other Federal agency. The Act provides also that the
need for value of storage for regulation of stream flow shall be determined
by the Corps of Engineers, Bureau of Reclamation and the value of storage
for quality control shall be determined by the EPA Administrator. It
seems that the program of quality control and the program of quantity
control should not be separated and should be unified at least in the
planning basis. It is reported that in Britain reorganization in the
field of water service is going to be established and 10 New Regional Water
Authorities will be established in England and Wales, and they will take
responsibility of all water problems including quantity control, regula-
tion of stream flow, water pollution control, water supply, sewage
18
-------
purification and disposal and so on. The regional water authority which
will be established in its river .basin wide base is really single organi-
zation for water quality and quantity in all water problems.
The British practice in this way may be of some value for our
discussion.
19
-------
Third US/JAPAN Conference
HEAT TREATMENT OF SEWAGE SLUDGE
presented by
Kenjiro Saito
Chief, Sewage Works Section
Public Works Research Institute
Ministry of Construction
February 12-16, 1974
Ministry of Construction
Japanese Government
20
-------
CONTENTS
1. Introduction .............................................. 23
1.1 Antecedents ....... . ......... . ................ . ....... ... 23
1.2 Laboratory tests on heat treatment ..................... 27
2. Results of operations and problems ....................... . 36
2.1 Results of operations .................................. 36
2.2 Problems on operations ................................. 36
2.2.1 Erosion and scale deposition of heat exchanger ..... 36
2.2.2 Smells ............................................. ^0
2.2.3 Treatment of supernatant ........................... Uo
2.2.4 Noise .............................................. 4l
2.2.5 Plant maintenance and operation .................... 4l
3. Tests and investigations for improvement of heat treatment
process [[[ ^2
3-1 Wear, corrosion and baking of organic substances in
the heat exchanger ..... ................................ ^3
3.1.1 Improvement of heat exchanger
3.1.2 Corrosion test within reactor
3.2 Deodorization
3.2.1 Catalytic combustion method
3.2.2 Ozone oxidation method
-------
Page
3-3 Studies concerning the treatment of supernatant ....... 50
3-3.1 Conventional activated sludge process 50
3-3-2 Step aeration process « • 52
3.3.3 Extended aeration process • 55
3-3-4 Aerobic digestion process 55
3-4 Studies on the dissolution of heavy metals 56
4- Cost estimate for installation, operation and maintenance
of the heat treating facilities 58
4-1 Method of estimating costs 58
4-2 Capital costs and operation and maintenance expenses ... 58
5- Conclusions 62
22
-------
HEAT TREATMENT OP SEWAGE SLUDGE
1. Introduction
1.1 Antecedents
As of 1972, 254 sewage plants were operated in Japan, and the
number now is on the constant increase'. Those plants were running
mostly on a method embracing a series of processes including
anaerobic digestion, mechanical dewatering, dumping or incinera-
tion. As for the dewatering process, the mechanical method seems
to have become more increasingly practised in recent years. This
is primarily because the process resting on anaerobic digestion,
drying with bed and dumping is being discouraged by an offensive
taken by nearby inhabitants against nuisance stink, difficulties
in acquiring suitable plant sites, labour shortage, etc.
On the other hand, as more and more the mechanical dewatering
process has been disseminated, its characteristic problems have
come to light.
The following is a list of major problems and a breif explanation
of each -
l) Economics
The mechanical dewatering process requires a pretreatment in
which coagulant is dosed to thickned sludge for increasing
dewatering efficiency.
In Japan, combined use of ferric chloride (Fed,) and lime
is. the most commonest of all as a coagulant dose. In some
cases, however, ferric sulfate (FeSO,) is used instead of
ferric chloride. Anyway, the chemicals accounts for as much
as 20 to 45$ of the total operating cost of the sludge treat-
ment .
23
-------
2) Working efficiency
It is often that the content of organic substances reaches no
less than QQ% or more in the sludge to be handled at sewage
plants of large housing communities, local cities and especially
those designed as a separate sewer system conveying mostly
domestic sewage. This kind of sludge is very fine in size,
and is hard to cencentrate; if it is retained in a thickener
for 2 to 3 hours, it will readily come afloat as scum, and
worse the moisture content of the cake cannot be kept at the
level of 75 to 80% unless the plant operator doses more
coagulants than usually required.
Increase in the content of lime in the sludge cake increases
sludge volume as a whole, over loading the incinerator.
Since the separate sewer system is expected to gain popularity
in the future, the above problems will emerge as a reality.
3) Working conditions
The vacuum filters, filter presses and other machines widely
used for the mechanical dewatering process cannot do without
constant inspection, cleaning and overhaul, and the operators
are forced to attend them all the time. Meantime, the working
environment in the sludge treatment process is insalubrious
compared to the rest of the sewage treatment system. Lime
handling is really a peeve, because this fine powder is liable
to fly about.
24
-------
As a consequence, it poses grave concern over labour settle-
ment and occupational hygiene to add to the fact that the
sludge treatment is an extraordinarily costly business what
with upkeep, maintenance, inspection and soaring labour cost.
4) Durability of equipment
Ferric chloride used as a coagulant is very active upon metal
structures such so chemical storage tank, mixing tank, piping,
valves, gas ducts and fans in incinerator, costing replacement
and repair too much. The improvement in the materials of such
equipment is a matter of primary concern.
To cope with these and other various problems, emphasis has been
placed on the development of new systems with which to increase
dewaterability and realize remote and automated control.
To ward off the problems resulting from the use of chemicals, heat
treatment process has attracted keen attention as a promising
pretreatment method of sludge. In Japan, this process was consider-
ed for the first time in 1970 when the modification of a sludge
handling system of Shyojaku Plant was projected, and eventually
was practised after investigation of a test plant.
In this process, sludge is heated in order to coagulate protein
in it into hydrophobic one, remove bonding water as well as to
improve sedimentability and dewaterability by accelerating the
flocculation of suspended solids. It is evident that the process
will save installation space and cut labour by automation. The
process is also favoured from the viewpoint of sanitation that the
heating annihilates baccili and parasite eggs.
The Ministry of Construction, while believing in the process,
urged to appraise it from various angles of view, turn up problems
and provide measures against them before implementation as it was
25
-------
concerned about the safety and durability of the equipment and
offensive byproducts such as stink and high, concentrate supernatant.
To push forward the Ministry's policy, full-scale plants were in-
stalled in Sakai (Semboku Plant), Fujisawa (Nambu Plant) and Sapporo
(Toyohiragawa Plant), so that the performance of the plant facili-
ties could be assessed. Also, the Committee for Investigation into
Sludge Handling and Disposal of the Japan Society of Civil Engineers
was entrusted with the task of conducting fundamental studies,
evaluation of plant achievements and retrieval of problems.
Realizing the significance of the mission assigned'to it, the
Committee immediately organized a subcommittee comprising civil
engineers, sanitary engineers, metallurgists, mechanical engineers,
and of course sewage engineers from the municipalities operating
the full-scale plants, and embarked on research work from 1970.
Their principal subjects were:
l) Literature research on the process achievements in European
countries
2) Laboratory test on sludge available here in Japan to elucidate
the principles, effects and problems of the heat treatment
process
3) Assessment of full-scale plants based on actual operation data
from the viewpoint of economics, durability of facilities and
operatability, etc.
4) Examination of characteristics of supernatant and development
of its treatment techniques
5) Detection of stink factors and examination of methods for
removing them
6) Research of the equipment with respect to corrosion and bank-
ing, etc.
26
-------
These surveys were actively promoted in both field and laboratory.
The proceedings were made public annually in the form of interim
report, and some of them were submitted to the Second U.S.-Japan
Conference on Sewage' Treatment Technology.
Submitted herewith is the summary of the final report covering the
three-year research activities of the committee and its conclusions.
1.2 Laboratory tests on heat treatment
In corroboration of the principles of heat treatment and for the
purpose of obtaining the optimum treating conditions, fundamental
laboratory tests were conducted -using sludges from Semboku Plant,
Nambu Slant and Toba Plant, Kyoto.
The results were as follows.
l) Both excess activated sludge and sludge from the primary sedi-
mentation tank tended to be filtered quickly when treated at
temperatures above 180 G. The higher the temperature, the
lower the moisture content in the cake. The heat treating
time was not a significant factor for both sludges, but with
the temperature and time fixed, the sludge from the primary
sedimentation tank could create the cake of lower moisture
content than the excess activated sludge did.
2) The higher the heat treating temperature and the longer the
heat treating time, the faster the filtration rate. With the
treating time fixed, the filtration rate increased in propor-
tion to the temperature.
3) While the specific resistance of sludge had no significant
i-\
correlations with heating temperature and time, if up to 180 C,
as it was largely affected by the content of organic substances,
it plunged down at temperatures above 190 C.
27
-------
4) For both excess activated sludge and sludge from the primary
sedimentation tank, BOD, COD and ammonia nitrogen in super-
natant increased sharply from temperatures 180 C and above;
their concentrations became higher on the higher temperatures
and on the longer time. Similar tendency was noticed with
respect to the colour of the supernatant.
5) The solubility of heat treated sludge was higher as the
organic content increased; namely, the highest was the excess'
activated sludge, followed by mixed sludge and sludge from
primary sedimentation tank in turn. It was inferred that some
50 per cent of solids contained in the activated sludge would
dissolve in some 30 min. of heat treating.
6) The baking of heat exchanger become violent when the heating
temperature was increased more than 200 C. The tendency for
the heat exchanger to have scorches was stronger as the
organic content increased.
7) It was concluded that the heat treatment as a pretreatment of
sludge for dewatering can be carried out effectively even with
temperature set at 180 C and time at 30 to 60 min. if the
organic content in sludge is in the range of 50 to 60$, while
if the organic content varies or exceeds 60$, the heat treating
conditions should be set at 190°G to 200°C and 30 to 60 min.
Sewage treatment plants where full-scale facilities were installed
are listed in Table 1.1. They all were designed to handle for the
most part domestic sewage.
Table 1.1 shows the design data for each of the plants. Their
heat treatment facilities are outlined in Table 1.2, and the
process flow of sludge treatment section is given in Pig. 1.1.
28
-------
Table 1.1 Design data for heat treatment facilities in projected sites
Plant
ro
VD
Items
Date of operation
(l) Sewer system
(2) Description
Plant area
Served area
Served population
Volume of sewage
flow, avg.
(3) Sewage treatment
process
(4) Heat treatment
system
Toyohiragawa, Sapporo
Oct., 1970
Combined sewer
(domestic sewage only)
8.557 ha
2,202 ha
200,000
64,OOO
Activated sludge
process (step
aeration possible)
Porteous system
Nambu, Fujisawa
Aug., 1964
Combined sewer
(partly combined &
partly incl. in-
dustrial effluents)
9-24 ha
1,713 ha
228,000
76,730 mVday
Activated sludge
process (step
aeration system)
Von-Roll system
Semboku, Sakai
Mar., 1969
Separate sewer
(domestic sewage only)
8.40 ha
1,845 ha
221,000
86,190 mVday
Activated sludge
process (step
aeration system)
Porteous system
-------
co
o
^^Jlant
Items — ^^^^
(5) Design data
l) Quality of
influent
2) Total solid of
raw sludge
3) Moisture content
of raw sludge
4) Volume of raw
sludge
5) Moisture content
of thickened sludge
6) Volume of thickened
sludge
7) Moisture content
of heated sludge
8) Total solid of
heated sludge
9) Volume of heated
sludge
Toyohiragawa, Sapporo
B.O.D. 200 ppm
S.S. 250 ppm
20.16 t/day
99$
2,345.3 mVday
95$
403 mVday
90$
16.12 t/day
161.2 t/day
Numbu, Pujisawa
B.O.D. 200 ppm
S.S. 250 ppm
5.8 t/day
98$
288 mVday
96$
144 nr/day
92$
4.6 t/day
57.7 t/day
Semboku, Sakai
B.O.D. 200 ppm
S.S. 300 ppm
7.84 t/day
98$
392 m3/day
96$
196 m3/day
90$
5.84 t/day
54.9 t/day
-------
^~~~~~^~~-~^_^^^ Plant
Items ^~~~~~- — ^^_^
10 ) Moisture content
of cake
11 ) Cake volume
(6) Heat treatment
facilities and
operating conditions
l) Raw sludge
temperature
2) Outlet temperature
of heat exchanger
3) Heat treating
temperature in
reactor
4) Outlet temperature
of heat exchanger
5) Sludge cooler out-
let temperature
6) Conditioning time
in reactor
Toyohiragawa, Sapporo
M%
30.4 t/day
10°C
165°C
200 °C
55.3°C
(excl. from 1st stage)
45 min.
Numbu, Pujisawa
40$
1.1 t/day
20°C
160°C
200°C
62°C
25°C
60 _ 120 min.
Semboku, Sakai
50$
9.97 t/day
15°C
160 °C (from reactor)
200°C
60°C (to reactor)
Influent temp. + 15°C
30 _ 60 nrLnr
-------
Table 1.2 Main plant facilities
CO
IN3,
^\. Plant
Facilities \^
& units ^\^
(l) Appurtenances
Sludge screen
Thickner
Sludge pump
Ho. 1 crusher
Scale prevent-
ing device
No. 2 crusher
Toyohiragawa, Sapporo
Specifications
Automatic bar
screen screw
press
/I 5 m x 3.3 m
Solid pump,
/80 _ 50 x
0.3 m-ymin x
9 m x 3.7 kW
Disintegrator,
/200 mm x
30 mVhr x 2.4 m
x 5.5 kW
Electromagnetic
type?
/I 50 x 19 nP/hr
In-line type,
/200 x 38 nP/hr
x 18.5 kW
Q'ty
(a)
1
4
4
3
3
3
(b)
' 1
2
2
2
2
2
Numbu, Pujisawa
Specifications
-
/1 50 mm x
2 . 5 m^/min x
17 m x 22 fcW
/200 _ /I 50 mm
x 1 m^/min x 6 m
x 11 kW
-
Q'ty
(a)
0
3
2
0
0
(b)
0
2
2
0
0
Semboku, Sakai
Specifications
_
fill .6 m x 5-5
(3-5) m
Solid pump,
/80 _ 50 x
0.45 nr/min x
15 m x 7.5 kW
Disintegrator,
$200 °mm x
30 mVhr *
3 . 5 m x 11 kW
Electromagnetic
type,
^100 mm x
13-5 mVhr
In-line type ,
^200 mm x
13-5 nr/min x
11 kW
Q'ty
(a)
0
2
2
3
3
3
(b)
0
1
2
1
1
1
-------
oo
GO
^^\^^ Plant
Facilities
& units ^^\^
(2) Heat treatment
facilities
High pressure
sludge pump
Heat exchanger
Reactor
Sludge cooler
Heat treated
sludge
thickner
Toyohiragawa, Sapporo
Specifications
Diaphragm type,
^65 _ /100 x
19 m3/hr x
200 m x 30 kW
Counterflow
double/ pipe type,
16.8 mVhr x
18 kg/cm2 x
220 m2
Vertical
cyl inde r
^1,798 x 7,000 H
x 16.8 m3
Count erf low
dual pipe type,
16.8 m3/hr x
18 kg/cm2 x
59 m2
/7 m x 4 m x
154 m3
Q'ty
(a)
3
3
3
3
2
ss.
(b)
2
1
1
0
1
s.
Numbu, Fujisawa
Specifications
Diaphragm type,
jzfeo mm x 3 —
10 m3/hr x 30
kg/cm2 x 18.5 kW
Counterflow
double pipe type
3 - 10 mVhr x
18 kg/cm2 x
150 m2
Vertical
cylinder
>£L>750 x 7,000 H
x 14 m3
(Built in the
heat exchanger)
7,600W x 7,600L
x 5,000 W.D.
Q'ty
(a)
3
3
3
3
2
ss .
(b)
2
1
1
1
1
s.
Semboku, Sakai
Specifications
Diaphragm type,
/i65 mm x 10 m3/hi
x 250 m x 15 kW
Cojnterflow
double pipe type,
10 mVhr x
18 kg/cm2 x
approx. 165 m
Vertical
cylinder
^1,600 x 7,000 H
x 12.5 m3
Co jnterflow
dual pipe type ,
10 mVhr x
18 kg/cm2 x
40 m2
/10.8 m x
3-6 mH x 325 m5
Q'ty
(a)
3
3
3
3
Is.
(b)
1
1
1
1
Is.
-------
oo
^""\^^ Plant
Facilities^\^^
& units ^^\^^
Heat treated
sludge storage
tank
(3) Sludge dewater-
ing facilities
Filter press
& ancillary
equipment
(4) Steam generat-
ing facilities
Heavy oil fired
boiler
Toyohiragawa, Sapporo
Specifications
3»5 m x 10 m
x 2 mH x 70 m2
Horizontal type,
1,500 x 1,500 x
50 compartments
x filter area
194.5 m2
Q'ty
(a)
Is.
5
2
(b)
Is.
3
2
Numbu, Fujisawa
Specifications
-
Vertical type,
filter area,
25 m2
Q'ty
(a)
0
2
2
(b)
0
1
2
Semboku, Sakai
Specifications
/6 m x 2.7 mH
x 85 m3
Horizontal type,
1,500 x 1,500
x 75 compartments
x filter area,
292 m2
Q'ty
(a)
.s .
3
2
(b)
Is.
1
2
Note: (a): Overall
(b) : Number of installations this time
-------
•1 f-1. Example of process
V
of jluJoe, treatment section
GO
en
thsckener
Heat treated s/odje sttraje tank.
3) iS/uJje CratAer
Hijh pressure sluJte pump
f) Heat etcharnet
7) Reaettt
7X
Deodar:j/ra f awl: ties
9) Heat treated s/uJjc
Boiler
//) Hyh pressure •sludje
Filter
'J) Tram fit
Cake
a
V
»>
V
-------
2. Results of operations and problems
2.1 Results of operations
The three plants surveyed where put in operation on different
dates as shown in Table 2.1. Their operational results in one
year or two are summarized in Table 2.2, from which it appears
that the sedimentability and dewaterability of sludge have been
largely improved by heat treatment, and that dewatering by filter
press has reduced the moisture content of cake to some 36 to 48%,
sharply reducing the cake volume to be handled and making it
feasible to carry out landfill with cake or burn it without any
fuel.
Table 2.1
Plant Toyohiragawa, Nambu, Semboku,
Sapporo Fujisawa Sakai
Construction April, 1970 June, 1971 Nov., 1970
started
Operation Mar., 1971 Mar., 1972 Oct., 1971
started
2.2 Problems on operations
The problems which have been concerned with the heat treatment
system are as follows.
2.2.1 Erosion and scale deposition of heat exchanger
At Toyohiragawa Plant, the heat exchanger* in its intial 18
months of operation had part of the extension of the inside
tube and around T-tube in the bottom worn out to break part
of the latter.
36
-------
As a temporary repair, a sleeve tube was put on the broken
part, along with such measures as improvement of grit removal
units, installation of cushion tank, and injection of water
at reactor outlet.
At Nambu Plant, after 6 months of operation, some 0.7 mm of,
abrasion was noticed at two places in the inside tube on the
high temperature section, and the tube was renewed accordingly.
Also, the sludge crushing pump and heat treated sludge dis-
charge valve were found scored.
At Semboku Plant, after one year of operation, one out of 108
inside tubes in the high temperature section developed an
abrasion of some 0.7 mm on the outside, and was renewed. Also,
the blades of sludge crusher were found fretted.
The troubles common to all the three plants were baking-up of
organic substances to the heat exchanger, which resulted in
degradation of heat conduction and increase in heavy oil con-
sumption, not to say deterrence in plant operation.
(sludge-to-sludge heat exchanger _ hereinafter sometimes
referred to as direct type heat exchanger _ with raw sludge
running through inside tube and heat treated sludge through
annular space between the inside tube and outside tube)
37
-------
Table 2.2 Operational data of heat treatment plants (from April, 1972 to Mar., 1973)
CO
oo
^^\^^ PI ant
I tern ^^\^
Average sludge
solid, tons/month
Monthly average
moisture content,
%
Heat treatment
capacity, m3/hr
Heat treating
temperature, °C
Heating time,
min.
Moisture- content
of heat treated
sludge , %
Moisture content
of sludge cake, %
Toyohiragawa, Sapporo
Max.
200
34
86.5
37.2
Mean
562
95.3
25.0
198
30
84.3
36.1
Min.
195
27
81.4
35.1
Nambu, Pujisawa
Max.
201
120
85.1
46.3
Mean
112
96.7
6.5
195
120
78.1
37.2
Min.
180
60
71.3
33.1-
Semboku, Sakai
Max.
200
Mean
107
96.1
10.2
194
Apr. _ Aug.
29.4
27.5
Sept. - Mar.
47.9
94-9
54-6
45-5
87.8
47.8
Min.
190
26.3
42.9
83
40.6
-------
CO
^"^-\^ Plant
Item ^^\^.^
Properties of
supernatant :-
T emperat ure , °C
pH
Total solid,
mg/lit.
Dissolved
matt e r , mg/1 i t .
S3, mg/lit.
GOD (KMn04.) ,
mg/lit .
BOD 5, mg/lit.
T-N, mg/lit.
Properties of
ef fluent :-
BOD5, mg/lit.
SS, mg/lit.
Supernatant
t re at ment
Toyohiragawa, Sapporo
Max.
53
5.7
5,950
4,040 .
2,260
1,800
6,000
17.3
41.4
Mean
43.3
5.5
5,232
3,908
1,325
1,590
5,155
11.4
25.9
Min.
28
5.3
4,838
3,690
978
1,280
3,520
5.2
18.3
Supernatant diluted
300%, aerated 24 hrs,
and then fed back to
pre-aeration tank
Nambu, Fujisawa
Max.
36.1
5.8
8,100
7,900
650
4,700
6,100
1,100
25-0
29
Mean
29-1
5.7
5,978
5,575
403
2,975
4,413
664
14.4
14.6
Min.
22.1
5.4
4,160
3,690
200
2,050
3,400
410
5.5
7
Directly discharged
to raw sewage
Semboku, Sakai
Max.
29-0
5.8
9,899
9,252
1,008
3,520
7,660
1,349
18.2
34
Mean
24.8
5-2
7,191
6,644
547
2,615
5,847
704
12.8
19-5
Min.
19.0
4.6
4,362
3,946
118
1,600
4,204
258
7.9
9
Directly discharged
to raw sewage
-------
2.2.2 Smells
The sources of offensive odors were waste gases mainly from
the reactor and thickener and partly from filter room and cake
hopper. Other plant equipment were piped together to form a
closed system, and were scarcely any outlet of such stink.
In each plant, the waste gas from the reactor was run through
a gas separator and fired in1 a heavy oil fired boiler or in-
cinerator, together with the gas coming from the thickener.
Smelly gas from filter and cake hopper was burnt partly in
the incinerator and partly vented out of the stack (Toyohiragawa
Plant) or was scrubbed with water and sprayed with deodorant
(Nambu Plant).
2.2.3 Treatment of supernatant
Table 2.2 shows the results of quantitative analyses of super-
natant and effluent before and after heat treatment at each
plant. The volume of the supernatant to be handled was largely
dependent upon the heating temperature, heating time, and
thickening rate of raw sludge and heat treated sludge, but was
about 0.5 per cent of the inflow on the average. The character-
istics of supernatant were roughly represented by the follow-
ing, though different according to specific conditions.
pH : 5 - 6
COD (KMi04) : 1,300 - 5,000 mg/lit.
Total solid : 4,200 - 10,000 "
BOD : 3,500 - 8,000 "
T - N : 300 - 1,400 "
The supernatant is high in concentration, and if it were
returned to the intake of the plant for retreatment together
with raw sewage, BOD load would be sent up by 10 to 20$.
40
-------
At Toyohiragawa Plant, the supernatant was diluted thrice with
'plant effluent, subjected to 24 hrs of aeration and returned
to the preaeration tank, turning out satisfactorily processed
effluent.
At Nambu Plant, the supernatant was directly discharged to the
intake of the plant, developing some smell and dark brown hue
in the effluent.
At Semboku Plant, the supernatant was directly discharged to
the raw sewage, and an experiment on the treatment of super-
natant from heat treatment process by a step aeration process
was carried out by making use of one of the existing tanks
with significant results.
2.2.4 Noise
High-pressure sludge pump, air compressor, boiler and sludge
discharge valve were noise sources.
The high-pressure sludge pump, for example, roared at a noise
level of some 80 phon 1 m apart. But those noise-generating
equipment were all hived into an underground cell with its
ceiling lined with sound-proof materials, and served no
problems to the nearby inhabitants.
2.2.5 Plant maintenance and operation
Toyohiragawa Plant has been maintained and operated by the
officials of Sapporo Municipal Government.
Semboku Plant was operated by a private company during tiral
run, but, now is operated and maintained by the officials of
Sakai Municipal Government.
41
-------
On the contrary, the operation and maintenance of the Nambu
Plant has been consigned to a private business because of
difficulties in keeping operators.
Toyohiragawa Plant was stopped for 7 days because of pipe
breakdown troubles and another 7 days for two periodic inspec-
tions (14 days in total). During the period, sludge was
stored.
At Nambu Plant, 10 days were wasted away for reasons of machine
troubles, and 17 days were spared for periodic inspection.
During the plant suspension, the sludge treatment was taken
over by the now stand-by facilities used for chemical dose and
vacuum filtration.
At Semboku Plant, 19 days were wasted away for periodic in-
spection, and sludge during the period was stored as in the
case of Toyohiragawa Plant.
Since 10 to 20 days are necessary for periodic inspection and
repair, at least one train of standby facilities is indispen-
sable, together with a reservoir to store sludge which will
result from the reduction of plant capacity during that period.
Another problem is the compulsory manning requirements.
According to the "Pressure Vessel Safety Rules", this kind of
heat treatment facilities is required to have a certified
chief engineer for boiler operation and a certified chief
engineer for danger handling.
3. Tests and investigations for improvement of heat treatment process
In order to settle the problems which were turned up by the running
of the full-scale plants, the members of the subcommittee took the
lead in conducting some fundamental experiments.
42
-------
3-1 Wear, corrosion and baking of organic substances in the heat
exchanger
3-1-1 Improvement of heat exchanger
The heat exchangers employed were originally of the direct
"kyPej as shown in Figs. 3-1 and 3.2, in which the inner tube
carried low temperature raw sludge while the annular space,
between the inner and outer tubes conveyed high temperature
heat treated sludge.
Rather simple in construction though it was, wear, corrosion
and baking of organic matter were brought about in the annular
space and T-tube which were conveying heat treated sludge.
To solve these problems, the following measures were provided,
and the results were analyzed after three months of operation.
(a) Conversion of heat exchanger from direct type to sludge-
to-water type (indirect type) as illustrated in Pig. 3-3.
With this modification, the heat treated sludge could
always be run through the inner tube without necessity
of negotiating difficult places where flow pattern was
sharply changed in section or direction, thus smoothing
the flow and reducing turbulence.
(b) Installation of a cushion tank just upstream of the
automatic sludge valve.
With this, abrupt pressure change at the time of sludge
valve operation could be abated, minimizing abrasion and
corrosion.
(c) Pre-cooling of heat treated sludge by water injection at
the outlet of reactor.
43
-------
(d) Adoption of a special cleaning method in which a cleaning
bullet is forced through the inner tube hydraulic ally
with between the bullet loading and unloading ports pre-
pared at the inlet and outlet of the heat exchanger.
With this, the cleaning time was saved, doing away with
the overhaul of the heat exchanger.
Reactor
AW sludge.
storage tank
Heat exchanger
A
~I
tSteam boiler
Heat treated s/ve/oe
Heat treated sic/doe
thickener ^
Raiu •sludtt
Section A -A'
Fig. 3.1 Process flow sheet of direct type
heat exchanger
44
-------
Cap
. 3-2 Detail of direct type heat exchanger
RO.II> studoe
suoe
e ton
Reactor
HO. I heo.i exchanger
H.P sludge B
^ (inner-
NO. Z htod exchanger
C ^/W?e
\j
Crusher
/Section B—B
^Section C-C
(heat treated -studae )
Pig. 3-3 Process flow sheet of indirect type
heat exchanger (sludge-to-water)
45
-------
In three months after improvement, the heat exchanger was
disassembled and examined. It was found that the high
temperature section of the inner tube was covered with a black
hard organic scorch of 0.1 to 0.2 mm in thickness while other
parts were laid with the same but 2 to 3 mm in thickness.
There was no abrasion nor corrosion to make mention of. The
low temperature section had a soft organic layer of 0.1 to 1.0
mm thick, but had neither abrasion nor corrosion whatsoever.
These depositions could easily be removed by running the
cleaning bullet. The outer tube was covered with an oxide
film in good condition.
With all these, the improvement measures taken were verified
effective.
3.1.2 Corrosion test within reactor
The heat treating reactor is ill situated so far as corrosion
is concerned, because it is always to bear the brunt of high
temperature and high pressure in addition to constant attack
from chemically active water which contains much solid and is
not deoxygenated.
For this reason, the reactor corrosion problems were studied
from the metallurgical point of view by conducting corrosion
tests on mild steel for boiler use (SB42 - JIS G3103) in
reactors at Toyohiragawa and Semboku while stress corrosion
tests were conducted at Nambu using stainless steel (SUS32).
At Toyohiragawa and Semboku, mild steel test pieces indentical
to reactor material were set in a running reactor for 12 months.
The results were as follows.
46
-------
(a) The test pieces were deprived of nasty layer, and their
remaining thicknesses were measured. The measurements
proved to be almost the same as before test, evincing that
the corrosion rate was very small.
(b) Microscopically, the corrosion was found uniform over the
entire surface of each test piece.
(c) Also, it was found that the test pieces were protected
with a firm film of Fe,0 to reduce corrosion to a
minimum, and therefore that the reactor material was
o
strong enough to sustain the corrosion under service
conditions.
At Nambu Plant, three kinds of stainless steel test pieces
(SUS32, SUS27 and 18Cr steel) which were prestressed were set
in a reactor for 9 months for corrosion test. The results
were as follows.
(a) SUS32 which was the same material as reactor's was free
from any problematic corrosion symptoms like stress
corrosion cracking, pitting and inter-granular corrosion.
(b) BUS27 yielded to stress corrosion cracking, and was
judged unfit for the reactor.
(c) 18Cr steel showed no stress corrosion cracking or pitting
and were considered to be a substitute for SUS32.
3.2 Deodorization
As already mentioned, each plant was burning away smelly gases of
the heat treating process in boiler or incinerator after possing
through a gas separator. In order to realize a more effective
47
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way of odor removal, catalytic combustion method and ozone oxida-
tion method were studied at Semboku Plant for 2 years- On the
other hand, Nambu Plant was applied with a so-called scrubbing
method.
3.2.1 Catalytic combustion method
This method was picked up because it was first believed that
the plant economy would be improved if smelly gas could be
disposed of catalytically at some 200°G as 200°C steam source
was already available for the heat treating process.
Odorous gases from reactor, heat treated sludge storage tank,
heat treated sludge thickener and supernatant storage tank
were forced into a 400 / x 2,400 mm catalyzer-packed column
and burned at 200°C to 300°C. Then, combustion gas was
analyzed.
Instinctive test verified the complete removal of odor when
the combustion was done at 200 C to 250 C.
The combustion gas analyses disclosed that R~S and NH_ were
completely removed at 250°C to 300°C and 200°C to 300 C
respectively while CO was removed some 80$ at 200°C to 300°C
and hydrocarbons removed, some 50$ at 300 C.
A gas chromatographic analysis showed the peak of hydrocarbon
spectrum was shifted toward smaller molecular weight since
molecular chains were disjoined by catalyzer. Compounds
which were identified as responsible for offensive odors in-
cluded WE,, HgS, ethyl amine, ethyl mercaptan, .diethyl amine,
propyl mercaptan, etc.
M2 - group and SH - group of amines and mercaptans were found
on a gas chromatograph to have their peak reduced or completely
extirpated when passed through the catalyzer layer, verifying
48
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that the catalyzer was effective to kill radicals responsible
for smells.
The catalytic combustion method was thus justified as an
effective way to abate stink generated from the reactor.
3.2.2 Ozone oxidation method
An ozone oxidation method was examined because the exhaust
from filter room of which majority was occupied by air diluting
offensive odor was considered to jumbonize the catalytic
combustion system if it was applied. In a 200 $ x 3,600 mm
reactor, smelly-compounds and ozone were worked upon each other
under humidified conditions, and the results were judged ex-
cellent on an instinctive test. There was 'no sensible trace •
of odor when ozone Was charged several tens of ppm. Gas
analyses, however, revealed that the removal rate of total
hydrocarbon was only 10 to 15%. Although ozone was useful to
cut HH? - or SH - group and abate offensive odor, it would
have been not so powerful as to dissociate hydrocarbons.
Anyway, the ozone method manifested itself as practically
warrantable for odor-killing.
3.2.3 Scrubbing method
At Nambu Plant, high-concentration foul gases coming from
reactor and heat-treated sludge thickener were burned in the
form of secondary air, -and other subtle room odors were led
to a scrubbing tower to wash away their soluble compounds
with the effluent from the secondary sedimentation tank (ikg
water/kg gas).
After scrubbing, the exhaust gas was almost odorless, sub-
stantiating the practicability of this method.
49
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3-3 Studies concerning the treatment of supernatant
As explained in the foregoing, the supernatant produced by the
heat treatment system is higher in concentration than that from
the ordinary sludge treatment facilities. If it is returned to
the raw sewage where it joins influent sewage, it will increase
B3D load by 10 to
In order to mitigate the raw sludge treatment system from BOD
overload due to the returning of supernatant, the following
experimental treatments of supernatant were conducted at the
plants.
(l) Conventional activated sludge process (at Toyohiragawa Plant
and Semboku Plant)
(2) Step aeration process (at Semboku Plant)
(3) Extended aeration process (at Semboku and Toyohiragawa Plant)
(4) Aerobic digestion (at Nambu Plant)
3.3.1 Conventional activated sludge process
A combined sewage treatment by the conventional activated
sludge process of supernatant and sewage running in at a rate
of 1 lit./min. was conducted at a pilot plant of Toyohiragawa
Plant. 1 to 2 per cent of supernatant was mixed with the
influent sewage,though in the actual plant the supernatant
was about 0.5 per cent of influent sewage. This is because
the experiment was designed to cover a case where it is
required to centrally process various kinds of sludge.
The BOD loads were as shown in Table 3.1 below.
50
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Table 3.1 Test conditions (BOD loads.)
BOD load
Control
Case 1 (l$)
Case 2 (2$)
BOD kg/kg MLSS/d
0.08 - 0.18
0.13 - 0.28
0.23
BOD kg/m3/d
0.29 - 0.47
0.46. - 0.68
0.65
Prom the tests, following conclusions were obtained.
(l) 1 per-cent addition of supernatant brought about some
0.2 kg/nr/d increase in BOD load if the conventional
activated sludge process is applied.
(2) 1 to 2 percent addition made 0.13 to 0.28 kg/kg MLSS/d
of BOD load. In case 1, the retention time in the
conventional activated sludge process was more than 5
.hrs, and BOD removal was some 95 per cent, showing no
significant difference from the control.
(3) COD(Cr) vas somewhat higher than the control's, but the
removal rate was more than 80 per cent.
(4) Effluent presented light yellowish brown or was evidently
colored compared with the control.
(5) By the addition of supernatant, nitrogen compounds were
dissolved into effluent with 1 to 2 ppm higher in con-
centration than the control. But, with the readsorption
of metals into activated sludge, the concentration of
metals in the effluent was held almost constant.
51
-------
(6) The growth rate of activated sludge was 1.5 to 2 times as
much as the control. In case 1, settling characteristic
of sludge was not affected, but in case 2, it was degraded.
(?) The above can be summarized that the treatment of supernatant
by the conventional activated sludge process is little or
no problem if the adding ratio of supernatant is less
than 1 per cent, except that the effluent is tinged with
light yellowish brown and that the concentration of
nitrogen compounds is increased by 1 to 2 nig/lit-
3.3.2 Step aeration process
At Semboku Plant, the supernatant and sewage had been treated
together on the conventional activated sludge process, but
effluent BOD had been as high as 20 mg/lit., in addition to
the problem that the effluent had been tinged with light
yellow.
In order to process the supernatant from the heat treat-
ment process which was high in HDD, the step seration
process was considered as activated sludge in its log growth
phase was considered preferable for the treatment of supernatant
which was high in BOD. One of the existing tanks ( effective
capacity of 3,080 m^) was modified for step aeration process,
and the sludge raturnr.ate, feeding points, and other factors
were changed to obtain the optimum operating conditions by a
comparative method.
Pig. 3-4 shows a schematic diagram of the step aeration process
in which the aeration tank is divided into six sections, the
first sectio., of which takes in supernatant and 30^ of return
sludge, the second section receives the remaining return
sludge and one-fifth of the primary and the third through
sixth section equally share the remaining sewage among them.
52
-------
In the first section, supernatant took retention time of
24 hrs, and the combined sewage took 3.4 to 3-9 hrs in other
sections. Since SVI was a little increased by the admixture
of supernatant, the overflow rate of the final sedimentation
— O
tank was reduced to 12.9 nr/m /d. Under these operating con-
ditions, the results were acceptable as follows.
(a) Where the supernatant was added 0.52 to 0.72 per cent to
the primary effluent, the effluent (from the final sedi-
mentation tank) contained 5-7 to 11.0 rag/lit, of BOD,
5.7 to 18.8 rg/lit of COD (KMn04) (28.3 mg/lit.COD(Cr)),10
to 15 mg/lit. of NH^-N, and less than 10 mg/lit. of S3.
The effluent was almost colorless and transparent .
(b) Odor from the aeration tank was very little, and the
pretreatment tank presented no bubbling.
53
-------
Schematic d/aQram of iStep ae.ro.tion
Effluent
en
Find
•sedh
tank
Return
treated
of
- aeration tank
i 'mentation
tank
30%
tank
-------
3-3-3 "Extended aeration process
At Semboku Plant, direct aeration of undiluted supernatant
was tried. In an 18-hr aeration, BOD removal was removed 59
to 66 per cent, but violent foaming carried sludge floes away-
At Toyohiragawa Plant, a spare tank (806 m') was used.to
examine two cases; aeration of undiluted supernatant and
r
aeration of supernatant diluted with the secondary effluent.
In undiluted case, BOD was removed about 47 per cent in four
days of aeration, and foaming was noticeable just as in the
case of Semboku Plant.
When 300^ diluted supernatant was aerated for a long time
with the aeration set at 3 m-Vhr/aeration tank, irr, the
following results were obtained.
In a retention time of 32.2 hrs, supematant's BOD was removed
84 per cent, and COD ( KMuOU ) .28 per cent.
In an additional 24-hr aeration, BOD removal rate reached
approximately 90 per cent. But the supernatant, which was
high in temperature, generated odorous gas and vapour too
much, leaving much to be studied for their removal.
3-3-4 Aerobic digestion process
At Nambu Plant, the supernatant was laboratory tested by an
aerobic digestion method.
Fig. 3.5 shows an example of digestion time vs. BOD of mixed
liquor and effluent.
The test results were as summarized below.
55
-------
(a) Aerobic digestion of supernatant under BOD load of 0.1
kg/kg MLSS/d resulted in 95$ BOD removal-
(b) Judging from BOD removal and growth rate, the digestion
time would require more than 20 days.
(c) Total nitrogen decreased with increase in digestion time;
the nitrogen removal was 16 per cent for 20-day digestion
and 56 per cent for 60-day digestion.
(d) With increase in digestion time, the hue was improved
slightly, but thick brown colour characteristic to the
supernatant was still dominant.
2.000,
BOD
rSOO
-Jffff
200
/OO
o
' 0 It 20 JO *0 SO "' 'it
Digestion time
Fig- 3-5 Digestion time vs. BOD
3-4 Studies on the dissolution of heavy metals
At Nambu Plant and Toyohiragawa Plant, studies were made about
the effects of heat treatment on the bahaviours of heavy metals
contained in the sludge, especially with center around their
dissolution into supernatant.
56
-------
At Fambu Plant, have iron, chromium, copper, cadmium, zinc, lead
and arsenic (seven elements in all) were analyzed, and heavy
elements - lead, zinc, iron, copper and cadmium at Toyohiragawa.
Prom the studies, the following were made clear.
(a) The dissolving ratio which is defined as a ratio of the total
amount of each heavy metal in the supernatant to that in the
raw sludge was 4-19 to 5-41 per cent for Fe, 0-51 to 3-41 per
cent for Or, 4-19 p.er cent for As, 0.05 to 4.19 per cent for
Cu, 0.7 to 9-61 per cent for Cd, 2..67 to 3-70 per cent for
Pb, 0.42 to 1.28 per cent for Zn, all in Nambu Plant.
In Toyohiragawa, Fe was 8.00 per cent; Pb, 0.80 per cent; Zn,
1.3 per cent, respectively- Namely, the dissolving ratio of
heavy metals and arsenic was less than 10 per cent on the
whole.
(b) In spite of heat treatment, more than 90 per cent of sludge
heavy metals was retained in the cake to be disposed of.
Accordingly, exhaust gas produced by the incineration of
cake should be processed through a suitable precipitator in
order to trap heavy metals.
(c) Increase in the concentration of heavy metals in the effluent
due to dissolution into supernatant registered a maximum of
0.6 mg/lit. for Fe.
Of the heavy metals controlled by the Water Quality Standards
for Toxic Substances, such metals as Cr. , Cd and Pb were a
-U
maximum of the order of 10 mg/lit., which was considered
not detrimental to the effluent.
57
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4- Cost estimate for installation, operation and maintenance of the
heat treating facilities
In order to appraise the economics of the heat treatment process,
the capital cost, operation and maintenance costs were estimated
for each plant and compared with the anaerobic digestion-chemical
coagulation-vacujm filtration process which is now prevailing as a
sludge treatment method.
4.1 Method of estimating costs
For each plant, the costs were deflated to those in the 1972 yen,
and the costs necessitated for the treatment of supernatant and
deodorization were included.
4.2 Capital costs and operation and maintenance expenses
Table 4-1 shows a comparison in capital costs between the heat
treatment system and the digestion-chemical coagulation-vacuum
filtration system- Table 4-2 shows a comparison between the two
systems with reference to operation and maintenance costs and
depreciation costs.
Whether the processing is to cover up to dewatering or up to
incineration, there is no significant difference in the capital
cost per solid tonnage per day between the two systems, except
for Toyohiragawa Plant. Up to dewatering, the capital cost reaches
¥ 45 to 47 million, while up to incineration it amounts to ¥' 53
to 60 million.
The costs for operation, maintenance and depreciation are almost
the same for both the heat treatment system and the digestion-
chemical coagulation-vacuum filtration system if dewatering is
included. If extended to incineration, the situation turns out
to the advantage of the heat treatment system. But if sophisticat-
ed deodorizing facilities, and treatment of supernatant, etc. are
58
-------
taken into account, the advantage cannot always go to the heat
treatment system.
In brief, the costs for construction, operation and maintenance
are almost the same for both system for the time being.
59
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Table 4.1 Comparison of capital costs between heat treating system
and digestion-dewatering system
Plant
Toyohiragawa
Nambu
Semboku
Sludge
solid,
DS_T/day
40-3
17.3
23.5
Heat treatment system
up to
dewatering
¥ million
(per DS-T)
985
(24-4)
820
(47.4)
1,114
(41.4)
up to
incineration,
¥ million
.(per DS-T)
1,331
(33.0)
-
1,234
(52.5)
Space,
m2
3,150
2,460
2,730
Digestion-chemical coagulation-
vacuum filtration
up to
dewatering
¥ million
(per DS-T)
1,390
(34-5)
811
(46-9)
1,051
(44.7)
up to
incineration,
¥ million
(per DS-T)
1,801
(44.7)
1,039
(60.1)
1,329
(56.6)
Space,
m2
5,000
3,000
4,200
cr>
o
B.B.: Values parenthesized refer to unity ton of daily processing sludge (DS).
-------
Table 4-2 Comparison of upkeep costs and depreciation costs between heat treating system
and digestion-dewatering system Ti d ")
Plant
T oy ohi ragawa
Nambu
Semboku
Heat treating system
Up to dewate:ri.ng
Upkeep
6,715
11,370
-
Depr.
3,620
6,630
-
Total
10,335
18,000
-
Up to incineration
Upkeep
7,130
-
6,860
Depr.
4,950
-
7,640
Total
12,080
-
14,500
Digestion-dewatering system
Up to dewatering
Upkeep
7,000
10,640
9,140
Depr.
4,070
5,590
5,220
Total
11,070
16,230
14,360
Up to incineration
Upkeep
9,000
12,600
11,100
Depr.
6,160
8,300
7,650
Total
15,160
20,900
18,750
en
-------
5. Conclusions
The following is the summary of the opinions formed by the committee
in regard to the heat treatment process.
The heat treatment process is still in its developing stage, and
has many problems, accordingly. The Committee has obtained the
first-hand knowledge about the process based on the three-year
investigation program. The heat treating facilities themselves
will be little problem if proper measures were taken for the
prevention of corrosion and organic deposition. Dewaterability
of heat treated sludge is excellent, and dewatered sludge can burn
well without any additional fuel. But, the following problems
still remain unsettled.
(l) Deodorization of stink from heat treatment process.
(2) Treatment of supernatant with high BOD (incl. removal of
heavy metals and nitrogen compounds).
(3) Establishment of operation and maintenance system including
periodic inspection.
If there are municipalities which are inclined to construct the
heat treatment system, they should carefully examine the necessity
of sludge incineration, space availability, prospects of manning
for system operation and maintenance, and above all the costs for
construction, operation and maintenance.
Before the heat treatment system would establish itself and become
accepted widely by sewage plants, it might possibly presuppose the
following developments, along with the solution of the problems
pointed out by the Committee.
62
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(l) Determination of optimum operating conditions
Quality of sludge varies with plants, and the optimum operating
conditions should be determined for each plant by basic experi-
ments.
Considering the quality of supernatant, scorching of organic
substances and overall economy, the heat treating temperature
and time should be as low and short as possible so long as the
aimed dewatering rate can be attained. Namely, the heat treat-
ing conditions should be optimized in consideration of the
entire sewage treatment process.
(2) Establishment of closed system for heat treatment facilities
The cake obtained from heat treated sludge is low in moisture
content and high in calorific value. Namely, it is desirable
to recuperate the heat from incineration of cake for the heat
treatment, to use smelly gases as incinerator combustion air
for complete deodorization and also to reduce the discharges
only to ash and combustion exhaust.
In this context, the advent of an incinerator with a heat
recuperative boiler compatible to the heat treatment process
is strongly hoped for.
(3) Unitization of equipment
The standardization and unitization of equipment should be
pushed forward for the purpose of simplifying the facilities,
facilitating quality control and saving costs.
In support of the conclusions and opinions formed by the Committee,
the Ministry of Construction has agreed in principle to recognize
the heat treatment system as eligible for government subsidy pro-
grams.
-------
To complete the eligibility, however, it is necessary- to develop
new equipment meeting the abov emeriti one d requirements.
In the pursuit of this purpose, the Ministry is starting the
assessment of the development and improvement of equipment, and
the Institute of the National Sewage Works Corp. will play a key
role in this.
64
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Third US/JAPAN Conference
COMBINED TREATMENT OF MUNICIPAL AND
INDUSTRIAL WASTEWATER
presented by
Masayuki Sat^
Director, Sewage Works Bureau
Yokohama City Office,
Hideo Fujii
Head, Technology Development Division
Sewage Works Bureau
Tokyo Metropolitan Government
and
Seiichi Yasuda
Director, Sewage Works Bureau
Kyoto City Office
February 12-16, 1974
Ministry of Construction
Japanese Government
er,
-------
I. -GENERAL
CONTENTS
Page
1. Treatment Systems of Industrial Wastewater 67
2. Considerations Required in Combined Treatment 70
66
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COMBINED TREATMENT OF MUNICIPAL AND INDUSTRIAL WASTE WATER
§ I. GENERAL
1. Treatment systems of industrial waste water
2. Considerations required in combined treatment
(l) Technical considerations
(2) Allotment of expenses
(3) Administrative measures
With the expansion of today's industrial and economic world which is
built on such fundamental materials as metals and petroleums, pollution
of public waters by industrial waste water has spread not only over
heavily industrialized major cities and their suburbs, but also over
farming and fishing areas, posing a serious threat to water source and
to human health and life.
Under these circumstances, the importance of public sewerage, the role
of which is to treat and dispose of municipal waste water which is
discharged continuously, has become increasingly large. To protect
public waters and human health and life from pollution, work on public
sewerage and industrial waste water must be effectively carried out,
but it is important that we make efforts to find possible and effective
approaches for pollution control in combination of them.
Possible countermeasures may vary according to the circumstances in
which a country or district finds itself, but in our present state, we
believe it is urgent that better solutions to processing techniques,
expense allotments and administrative systems be sought through ex-
changing information among those who are confronted by similar problems.
1. Treatment systems of industrial wastewater
The biochemical oxygen demand (BOD) load of industrial wastewater
is'said to be several times more than that of domestic wastewater,
67
-------
suggesting that the former accounts for a significant proportion of
the water pollution problem. Furthermore, industrial wastewater is
a major source of contaminants which are threats to human health and
life.
In considering the industrial wastewater problem, possible counter-
measures to be taken may be classified as follows:
(l) Independent treatment ... where industrial wastewater is
separately treated and then released directly into public
waters.
a) Individual and independent treatment (A) ... where individual
firms and plants treat waste water independently.
b) Joint independent treatment (B) ... where wastewater is
treated on a joint treatment basis.
(2) Combined treatment ... where industrial wastewater accepted by
public sewerage.
a) Accepted with pretreatment
l) Individual pretreatment (c) ... where individual firms and
plants pretreat wastewater
2) Joint pretreatment (D) ... where pretreatment is made on
a joint treatment basis.
b) Accepted without pretreatment (E-)
The above classification may be illustrated as follows:
68
-------
Fig. Treatment Systems of Industrial waste water
Independent treatment
Individual and independent
treatment
Joint independent treatment
Combined treatment
Individual pretreatment
Joint pretreatment
Public
Sewarage
c/l
f-1
0)
I
There are many factors that must be taken into consideration, such
as location of factories, and quantities and qualities of sewage
water, before selection of a treatment system can be made. To meet
requirements of large areas, a combination of two or more of these
systems may be employed.
From the standpoint of taking measures based on "control over the
sources", independent treatment systems A or B appear to be most
desirable, but in many cases, we have to adopt a combination of
systems C, D and E.
Where there are no effluent routes other than public sewerage, it
may be more efficient in attaining water pollution prevention to
take appropriate administrative steps rather than to force small
and medium enterprises that can hardly afford, technically and
financially, an independent treatment.
69
-------
We_will now discuss some.-of the problems that may be encountered in
employing a combined treatment.
Considerations required in combined treatment
The problems in planning of a combined treatment are divided into
three principal items; technical measures, allotment of expenses
and administrative measures.
(l) Technical measures
It is generally said that "control over the sources of contami-
nation" is the principal rule of combating public nuisances.
However, at the same time, a strong case can also be made for
the efficiencies of scale.
In air pollution control, no measures can be other than to do
something about the very sources of contamination.
This is mainly because collecting emissions, once discharge
into the atmosphere, is prohibitively expensive.
In wastewater control., on the other hand, the gravity flow system
is a skillful approach to collecting pollutants. The premise
of a combined treatment - collecting and combining flows - is
physically and economically feasible.
If conditions given below are all met in wastewater treatment,
a combined treatment is both useful and practical.
l) Will not damage sewerage facilities.
2) Will not disturb biological treatment process and can meet
effluent requirements of treated water.
3) Will not contain dangerous substances in excess of established
limits.
In order to satisfy these conditions, the standards of pretreat-
ment techniques play an important role throughout all phases of
•
construction, maintenance and management of a treatment plant.
70
-------
The following considerations, in particular, are of paramount
importance:
(a) Technical and financial guidance and assistance to medium'
and small enterprises that are producing undesirable
industrial wastewater.
(ID) Selection and development of sludge treatment and disposal
methods employed during pretreatment of undesirable indus-
trial wastewater containing dangerous substances.
(2) Allotment of expenses
Expenses of a combined treatment should be on a "Polluter-Pay-
Principle" (P.P.P.) basis. However, because of difficulties in
determining quantities and qualities of industrial wastewater
running into common public sewerage in early stages of building
a treatment plant, the trend in Japan is toward having users
share these expenses in the form of fees.
As for the problem of expense allotment, our considerations
should not be limited to a simple balance of allotment. A
system based on water qualities and ajprogressive charging system
should also be considered so as to provide an incentive for
suppressing discharge pollutants.
Administrative measures
For the purpose of increasing effectiveness of a combined
treatment, it is necessary that wastewater discharge from in-
dividual firms be monitored so that it be kept within appropriate
limits, along with enforcement of strict wastewater' discharge
restrictions including greater penalties to offenders.
For a satisfactory result in administrative measures taken,
appropriate guidance and assistance should be employed, rather
than relying on restrictions alone. Among such s"teps may be
technical assistance covering improvements in production processes,
particularly in medium and small enterprises, and expansion of
financing systems for the installation of pretreatment facilities.
71
-------
It is an effective approach that the municipal authority plans
and constructs joint pretreatment systems. And, on a greater
scale, basic policies such as formation of new industrial
districts in harmony with city planning are necessary.
So far we have discussed basic considerations required for a
combined treatment of industrial waste water, and now we will
briefly report on some examples of combined treatment in service
in Tokyo, Yokohama and Kyoto.
Yokohama Operating conditions of common pretreatment facilities
based on the system "D" where wastewater'is collected according
to the qualities of water to be drained are discussed along
with related problems and countermeasures.
Tokyo Chronological processes of common pretreatment facilities
that were initially started in the "D" system and were later
combined with the "C" system for processing wastewater containing
dangerous substances to meet restricted requirements on waste-
water discharge, are discussed along with future plans to introduce
public sewage treatment plants and the latest technical develop-
ments for deep aeration.
Kyoto Results of recent experiments on improving activated
sludge methods (double-stage process and oxygen aeration) con-
ducted in the public sewage treatment plant where a combined
treatment is being carried out with the systems "C" and "E" for
processing industrial wastewater from dyeing plants, are presented.
72
-------
§ II. TORIHAMA INDUSTRIAL WASTE WATER PRETREATMENT PLANT:
HOW IT OPERATES AND PROBLEMS POK FUTURE IMPROVEMENTS
- The 6ity of Yokohama -
CONTENTS
Page
Introduction
1. Present Servicing Status of Torihama Industrial Waste-
water Treatment Plant ................................ 77
2. Problems Encountered at This Plant and Their
Countermeasures ...................................... °5
73
-------
§ II. TORIHAMA INDUSTRIAL WASTEWATER PRETREATMENT PLANT:
HOW IT OPERATES AND PROBLEMS FOR FUTURE IMPROVEMENTS
- The City of Yokohama -
Introduction
At the recent Second U.S.-Japan Conference on Sewage Treatment Technology,
combined treatment of industrial and municipal wastewaters in Yokohama
City was reported on along with an example of industrial wastewater treat-
ment processes as practiced in Torihama, a coastal industrial district
in Yokohama.
Major features and treatment methods reported are summarized as follows:
(l) Features
l) The construction and maintenance costs relating to the joint
treatment of industrial wastewater is a full charge to constituent
enterprises, and the construction and maintenance activities are
placed under the control of the City.
2) Industrial waste water is classified into three types: mis-
cellaneous wastewater (from water closets, kichens, etc.)
general process wastewater (containing organic matter, oils, etc.),
and pickling and plating process wastewater (discharged from
pickling and plating factories). Wastewater from plating and
pickling processes is further divided into two types, that con-
taining cyanide and that containing heavy metals.
Each type of wastewater is properly treated according to its
particular physical and chemical properties and conditions.
3) Loans of comparatively low interest are being offered by the
City to medium and small firms as a public nuisance prevention
fund to help them finance their shares of the common wastewater
treatment plant construction costs.
4) Miscellaneous wastewater, general process wastewater, cyanide
wastewater and heavy-metals wastewater, discharged from the
74
-------
industrial district, are separately drained through individually
provided pipings and then treated separately according to their
physical and chemical properties and conditions before they are
sent' to a sewage treatment plant where all the wastewaters are
combined, mixed together and treated by an activated sludge
process.
A flow-sheet of these"treatment processes is shown in Fig. 1.
This paper covers the operating conditions at the Torihama
Treatment Plant since the previous report and problems
encountered that require further consideration.
75
-------
Fig. 1 Flow-sheet showing treatment processes at Torihama
Industrial Waste Water Pretreatment Plant
Plant No. 1
Plant No
2 .
( Heavy metals waste water )
( Cyanide waste water
1
Pump
J
Pump
!
friary oxidation storage tank
i
Secondary
tion tank
|_
General process
waste water
Miscellaneous
waste water
i
oxida- Reduction tank
I
Filtrate
Mixing tank
J
SiM&n^nl^P^ Vacuum filter
1
Filter
J
pH controller
Relay pump
Relay pump
(NOTE) Miscellaneous » TTT ^/Hav
r waste water 4, .35.5 my day
General process 7/171 ^/A™,
Designed capacities was!e wa^er 3,421 nf/day
-£a~l?edwater 60 rf/day J
L wa§¥e~-wit§rs 340 n3/day SI
r Plant No. 1 1,097 nf/day
Plant area LPlantNo.2 3,300 rf/day
udge cake
>
J
,
Screen Screen
i . J
Pump Pump
I 1
Aerate
chambe]
,
1 priH
Oil separator
J
pH controller
j
Mixing
,
tank
sludgei Coagulation-sedi-
1 mentation tank
T-n •
.
»6
Centr
Slud
ener hp
storage
ifuge -
\
;e cake
grld
\
r
^-Supernatant
Pressure pump
*- Centrate
Nambu Sew
age Treat
-------
1. Present Servicing Status of Torihama Industrial Wastewater Treatment
Plant
The Torihama Treatment Plant No.2 has been in operation since April
of 1972. However, due to the fact that the volume of influent has
been much smaller than initially expected and that most of the waste-
water processed contains oils, the oil separating units have been
operated intermittently.
The Torihama Treatment Plant No.l, on the other hand, has been in
operation since March of 1973, and following a two month trial period,
it has been operating satisfactorily.
(l) The number of constituent enterprises and the amount of waste-
water
The number of constituent enterprises as of the end of August,
1973, and the amount of influent classified by it's type are shown
in Table 1.
77
-------
Table 1 Number of enterprises and the amount of wastewater
"— -v,! terns
Types of \.
wastewater ^\^^
Miscellaneous
General process
Pickling and
plating process
Enterprises
Planned
169
61
6
Existing
81
41
4
Rate($)
48
67
67
Total
Wastewater
Designed
4,333m3
/day
3,421
400
8,154
Present
430m3
/day
586
270
1,286
Rate($)
10
17
67
16
Note: Breakdown of pickling/plating process wastewater
^""^-^^Vp lume
Types \^
Cyanide
Heavy metals
Total
Designed
60m^/day
340
400
Present
60m^/day
210
270
Rate($)
100
58
67
As shown in Table 1, the number of constituent enterprises entered
has reached approximately 50$ of the designed number while the
present volume of wastewater comes to only 16$ of the designed
level. The designed volume has been reached only by wastewater
containing cyanide, while at present, the volume of wastewater
containing heavy metals is only 58$ of the designed volume.
(2) Qualities of the influent and the effluent
The quality of influent and that of effluent at Torihama Industrial
Wastewater Treatment Plant are shown in Tables 2 and 3.
78
-------
Table 2 Record of Treatment of Plant No. 1 (Pickling/plating process wastewater)
Item
Date
1973.6.11
6.13
6.27
7. 4
7.11
7.25
8. 1
8. 8
8.22
9.12
9.26
Type of
wastewater
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Cyanide
Metals
Effluent
Hue
Yellow
Yellow
Light jellow
Light yellow
Yellow
Lignt yellow
Light yellow
Yellow
Light yellow
Colorless
Yellow
Yellow
Colorless
Yellow
Light yellow
Colorless
Yellow
Light yellow
Colorless
Yellow
Light yellow
Colorless
Yellow
Light yellow
Colorless
Yellow
Colorless
Colorless
Yellow
Colorless
Colorless
Yellow
Light yellow
Desired level
Odor
None
Cresol
Slightly cresol
None
Cresol
None
None
Cresol
Slightly crosol
None
Cresol
Slightly cresol
None
Cresol
Mineral oil
None
Cresol
Slightly cresol
None
Cresol
Slightly cresol
None
Cresol
Slightly cresol
None
Cresol
Slightly cresol
None
Cresol
Slightly cresol
None
Cresol
Slightly cresol
Water
temp.(°C)
16.0
16.5
16.5
19.0
19.0
19.0
21.0
22.0
21.0
22.0
22,0
22.5
29.0
26.0
28.0
25-5
27.0
28.0
27.0
26.0
27.5
27.0
28.0
29-0 _,
29.0
28.0
29.0
25.5
26.0
26.0
26.0
26.0
26.0
pH
11.0
11.3
7.4
11.1
3.2
8.2
10.9
2.8
8.3
10.9
2.4
6.9
10.5
2.3
11.7
11.0
6.0
8.3
11.1
1.9
8.1
11.0
3.0
8.3
11.6
2.6
7.4
9.5
3.0
7.3
11.1
2.7
8.7
5~9
CN
(me/I)
190
13.0
12.0
160
28.0
Trace
350
8.8
4.0
_
-
0
290
1.1
23.0
290
13.0
0.7
-
-
5.8
140
0.1
0.1
150
22.0
0.3
160
3-5
Trace
190
2.0
0.1
1
and
less
T-Cr
(mg/l)
1.6
130
0.4
3-6
51
1.3
0.7
47
0.2
0.6
37
0.8
36
0.3
0.2
35
0.3
30
8.4
0.2
64
1.4
0.5
14
0.3
0.4
420
Trace
1.3
120
1.5
2
and
lie s a
Cr+6
(mg/l)
_
-
0
-
-
-
0
22
0
-
19
0
-
11
0
0
14
1.8
0
8.5
5.5
0
52
1.1
0
4.8
0
0
5.5
0
0
41
1.1
0.5
and
iless
S-Fe
(mg/1)
_
1.6
0.1
3.6
8.2
0.2
4.0
5.4
-
-
-
-
27
0.1
2.2
3.0
0.2
2.5
6.3
0.4
1.8
3.0
-
2.8
7.8
0.3
1.6
16
0.3
1.7
63
0.3
10
and
•less
Ni
(mg/l)
0.9
20
32
2.0
15
0.5
2.5
14
9-4
2.9
16
17
-
15
18
-
-
-
-
-
-
-
-
-
~
_
-
-
-
-
-
-
-
-
Cu
(mg/1)
4.3
4.2
8.5
6.4
2.9
0.6
3.2
7-5
0.4
5.3
3-3
5.6
-
4.6
4-4
5.8
38
1.3
3-4
3.7
4-5
2.3
2.4
0.1
2.1
5-0
4.5
1.2
15.0
0.3
1.7
37.0
Trace
3
and
Iless
Zn
(mg/l)
110
17
1.4
120
56
1.2
190
43
0.2
120
55
23
-
61
30
90
37
0.3
90
50
0.7
64
32
0.2
87
22
1.0
150
22
Trace
110
80
0.4
5
and
' less
Pb
(mg/l)
0.2
0.1
0.3
0.4
0.1
0.1
0.1
0.3
0.1
0.5
0.2
0.3
-
1.8
0.1
0
0.1
0
0
0.2
0
0.1
0.3
0.2
0.1
0.2
0
0
0.4
0
Trace
0.5
0
1
and
iless
Cd
(mg/l)
0.04
Trace
Trace
0.02
0.01
Trace
0
0.02
0.01
0
0
0.03
-
0.01
0.02
0
0
Trace
0
Trace
Trace
0.03
Trace
0
0
0.02
Trace
0.01
0.01
0
0
0.02
0.01
0.1
and
lleas
Remarks
Avg. vol. during June
190 m3/day
Avg. vol. during July
240 rnVday
Avg. vol. during August
270 m^/day
Avg. vol during September
270 m3/day
to
NOTE: Waste waters containing cyanide and heavy metals are treated respectively before they are mixed together, and then conveyed
to Nambu Treatment Plant.
-------
Table 3 Record of Treatment at
Plant No.2 (general process waste water)
^\Item
Date ^^^
1973.6.20
7.18
8.15
9-19
Desired
Types
Influent
Effluent
Influent
h Effluent
Influent
Effluent
Influent
Effluent
level
Hue
Turbid
black
Turbid
black
Turbid
grey
Color-
less
Light
grey
Dark
grey
Turbid
grey
Turbid
grey
Odor
Mineral
oil
Mineral
oil
Mineral
oil
Mineral
oil
Mineral
oil
Mineral
oil
Mineral
oil
Mineral
oil
Water
temp. (c)
22.0
22.0
25.0
25.0
29.0
26.0
24-0
24-0
PH
9-9
9-1
9.1
8.6
7-7
8.5
7.6
7.5
5~9
BOD
(mg/l)
540
300
170
180
340
110
210
170
300
and
more
COD
(mg/l)
180
140
140
160
104
54
153
147
S3
Jmg/l)_
650
120
240
78
1,900
280
270
28
300
and
more
I 2 demand
lOae/l)
13
15
67
43
6
25
22
140
Cl
(ffig/1)
4,100
2,900
6,900
4,800
6,100
4,300
2,600
3,900
Oil
(mg/l)
350
100
170
15
1,200
140
110
__43_J
35
and
more
Reraarks
Avg. vol. during June
350 mVday
Avg. vol. during July
450 m^/day
Avg. vol. during August
590 rn^/day
Avg. vol. during Sept.
607 m5/day
00
o
-------
As indicated in Table 2, the cyanide content in the treated water
exceeded the desired level particularly during the early periods
of plant operation. This was due to the fact that cyanide had
been discharged and mixed with waste water which contained heavy
metals as a result of misoperation by some station operators.
After giving them proper instructions, these kinds of accidents
have been considerably reduced and are rarely encountered today.
You may notice that the 6-valent chromium content in the treated
water exceeded the desired level on the 25th of July, 1st and 8th
of August, and 26th of September. This was supposedly due to an
excess amount of sodium hypochlorite introduced for decomposition
of cyanide, causing the reduced trivalent chromium to be oxidized
again to 6-valent chromium when mixed with chromium containing
wastewater. Also, unsatisfactory treatment of copper is generally
attributable to difficulties in the formation of cupric hydroxide
through coagulation as a result of the formation of complex
cyanide.
In Table 3, it can be seen that the concentration of oils and fats
in treated water exceeds the desired value. The major causes are,
it is assumed, (l) degradation of efficiency in removing oils
because of processing various kinds of oils flowing into wastewater
being processed, (2) shortened retention period due to, a short-
circuit produced in the separation tank, and (3) insufficient oil
separation in the natural aeration system.
Although removal of B 0 D and S S is today done only by gravity s
sedimentation rather than a chemical coagulation/sedimentation,
obtained values of this plant show that they are well within
the desired values.
(.3} Operation/maintenance cost
Operation and maintenance costs including chemicals, lighting,
heating expenses, power, personnel, sludge disposal and pipe
cleaning expenses are totally charged to constituent enterprises.
81
-------
Allotment of these expenses is based upon the quantities and
qualities of waste waters discharged from individual firms. Shown
in Table 4 is the Operation/maintenance cost per one cubic meter
of wastewater, computed from the present conditions of plant
operation.
Table 4. Operation/maintenance cost per 1 m^ of wastewater
^""~~^-_^^ C o s t s
Types ^~~^\^^^
Miscellaneous
General process
Pickling/plating
process
For present
15 yen
Average 60 yen
*Average 210 yen
For designed
10 yen
Average 34 yen
Average 1J6 yen
* Sludge disposal cost are not included.
The operation and maintenance cost for general process and mis-
cellaneous wastewaters runs higher than its designed cost. This
is because the volume of wastewater is comparatively small and
the fixed cost, such as personnel expenses, is almost constant
irrespective of the amount of waste water. As for pickling/plating
process wastewater, the amount of chemicals used is twice or
thrice the designed amount, thus pushing up the cost to a very
high level.
(4) Operation and maintenance system
Operation and maintenance of plant No.l and No.2 is conducted by
two daytime personnel shifts and one night shift, on a four-man
shift basis. Tasks performed by the operators consists primarily
of machine operation, feeding chemicals into chemical tanks,
maintenance and inspection of equipment and instrumentation,
keeping daily operation reports, and conducting simple water
quality tests.
82
-------
(5) Sludge and waste oils, and their disposal
l) Sludge disposal
During treatment of pickling/plating process wastewater, 600 to
800 kg (water content QQffo] of sludge containing such dangerous
materials as heavy metals are produced daily. These substances
should not ooze out of the sludge when disposed, and we are
presently concentrating our efforts on developing desirable
methods of disposal.
For the time being, sludge is stored in sealed containers within
the sewage treatment plant yard until a desirable method of
disposal is found. Under study is a method in which sludge
cakes containing dangerous substances are mixed with such
additives as clay, glass chips and sludge from waterworks and
then heated to 1,100 to 1,200°C in a furnace. During this high
temperature treatment, components in the additives (mainly SiOp>
Al20;j> Fe2CU, etc.) react with heavy metals in the sludge in a
solid-state mutual reaction to form a glass-phase, in which
heavy metals in the sludge are sealed inside permanently, and
the dangerous substances enclosed are thus prevented from oozing
out upon disposal. The flow - sheet below shows this process
which is now under study.
(a) Sludge treatment flow-sheet under study
Plating
sludge
Sinterim
additives
1V1-L AC I
Burne
.
f
l\
T-.
Liryer
S
— 1
To atmosphere
1 -*
Sintered sludge
(artificial gravel)
300°O800°C
83
-------
:) Test results obtained
i) The experiment has been conducted by processing dry sludge
in a laboratory type fixed furnace.
ii) Tabulated below are the sintering additives and temperatures
used.
Sintering additives
Clay
Sludge produced from the
municipal waterworks
• Sintering temperatures
1,180 to 1,220
1,150 to 1,180
NOTE: Blending ratio of plating sludge to sintering
additives is roughly 25 to 75
Sintering temperatures decrease with an increase in Ca
content, but furnace operation at lower temperatures
poses a problem in maintaining desired temperatures because
it subsequently reduces allowable baking temperature ranges.
iii) Solubility test of heavy metals from sintered sludge
u
5-
4-
3-
2-
1-
o-kb-
Blending ratio
Clay : Plating sludge
_Le_ga_l_upp_er J-imit_ .OLSmg/l)
yoo
y.50 y.70
Sintering temp. (°C)
NOTE: The sample is dipped three hours at 100 C
84
-------
When sludge is processed at high temperatures, emission of
heavy metals into the atmosphere poses a serious problem.
We are now studying methods of reducing emissions into the
atmosphere to an absolute minimum.
Among the approaches under study are to lower sintering
temperatures by adding materials for preventing sublimation
of the heavy metals contained, and to sinter heavy metals
within a closed circuit furnace so that-emission of furnace
gases into the atmosphere is totally eliminated.
2) Disposal of waste oils
Waste oils produced during the treatment of general process
wastewater amount to 400 to 600'liters a day (water content 50$).
These waste oils are removed by waste oil disposal licencees
licenced by the Mayor.
In this regard, storage methods of waste oils in treatment plant
are subject to the restrictions specified under the Fire Act
from the standpoint of fire prevention.
2. Problems Encountered at This Plant and Their Countermeasures
(l) Processing capability of the joint pretreatment plant
The initial cost of the joint pretreatment facilities are totally
charged to constituent enterprises and the processing capacity
of this plant was decided on the basis of estimates provided in
reports from individual enterprises as to the quantities and
quanlities of wastewater they were to discharge before the plant
was constructed. However, the quantitative and qualitative waste-
water data reported were in most cases underestimated, so that
today the plant constructed based on these underestimates hardly
provides any surplus processing capacity. As a result, it is
difficult for the plant to allow constituent enterprises to
increace their drainage volumes or change the qualities of their
wastewater along with the development and expansion of their
business activities.
85
-------
In view of our experience, therefore, when a new wastewater
treatment plant is to be built, it is suggested that the City pay
part of the construction cost for the enterprises concerned so that
a plant with a capacity flexible and large enough to accommodate
future expansion can be built.
At the Torihama Plant, there had been a demand for an increase of
640 cubic meters a day of general process wastewater after the
construction of the plant was completed. This demand has been
admitted on the condition that additional facilities for this
plant will be realized in the near future.
(2) Joint pretreatment of waste water which contains oils
Because a joint pretreatment system has been adopted here for
processing wastewater containing oils, the following problems
have been encountered:
i) Although oil separation facilities were originally designed
as a aeration system, it has been found that oil separation
performance is inadequate today, partly because actual
influent contains a wide variety of oils, and partly because
the concentrations of some of these oils have far exceeded
earlier expectations.
To cope with this problem, we plan to take steps which will
extend their retention period and to improve plant capabilities
upon thorough investigation of physical and chemical properties
and inflow rates of oily wastewater which are expected to
further increase.
ii) All enterprises which have gasoline filling stations and storage
facilities are required under the Fire Act to have oil separa-
tion facilities within their premises, but unless management
of these facilities is well maintained, there is always a
possibility of a large amount of gasoline, oil, etc., in
addition to waste-oils from other enterprises, being drained
into the sewage pipes.
86
-------
Since these offenses could lead to fire hazards in sewage
pipes and facilities, or present difficulties in proper
treatment processes, we have been keeping in touch with enter-
prise operators and providing them with necessary information
by distributing literature and holding guidance sessions.
Facilities for pickling and plating wastewater treatment
l) It was originally intended that pickling and plating waste-
water be treated in three separate systems by dividing it
into cyanide, chromium and acid/alkaline wastewaters, but due
to the complexity and technical difficulties of piping,
chromium and acid/alkaline wastewaters are combined and
allowed to flow in one piping system. As a result, we face
the following problems:
(a) Since heavy-metals wastewater and acid/alkaline wastewater
are conveyed in one piping system, trivalent iron ions
contained in acid/alkaline wastewater is reduced to bivalent
iron ions when reduction of 6-valent chromium takes place.
This causes the consumption of reducing agents to increase.
Treatment of 6-valent chromium is as follows: it is reduced
first by lowering its pH value and then, by increasing its
pH value, it is separated and removed as hydroxides. The
pH value in acid/alkaline wastewater also changes during this
process, so the consumption of a pH adjusting agent increases.
(b) Bivalent iron hydroxide (ferrous hydroxide) is inferior to
trivalent iron hydroxide (ferric hydroxide) in coagulation
and dehydration properties.
In consideration of the above, it is desirable that pickling
and plating process wastewater be processes in three
separate systems.
2) Vacuum filters are used for dehydration of sludge, but due to
such problems as poor quality filtrate and filtering fabric
wash fluids in addition to large volumes of filtrate being
87
-------
processed, their loads greatly increase when the fluids are
returned to the treating system. This makes smooth system
operation difficult.
In the meantime, abundant use'of calcium hydroxide for
increased dehydration efficiency has increased the consump-
tion of sulfuric acid and resulted in production of extra
sludge.
We plan to install more dehydrating machines, the numbe'i1 of
which will be based on the results of ,the operation of exist-
ing units. Types of new machines will also be thoroughly
considered for improvement in overall capabilities at our
plant.
3) We require that strong waste liquids produced at plating
factories be stored temporarily within the plants and then
discharged continuously in small quantities sufficiently
dilluted with routine wastewater.
In the early days of operations, however, dilluting operations
by individual firms weren't always performed satisfactorily.
As a result, considerable variations occurred and the process
efficiencies were affected. Today, however, owing to the
intensive guidance we have given operators in factries, this
kind of problem is seldom experienced.
In view of the fact that highly concentrated wastewater is
small in quantity, it is desirable to treat it separately so
that a uniform concentration of sewage can more easily be
maintained.
(4) Quantitative and qualitative determination of wastewater for
user charges
The volume of drained water at individual enterprises is esti-
mated by means of a water meter installed on the inlet side of
its water supply. In cases where users consume clean water in
88
-------
the manufacture of their products, for example, at a raw concrete
mill, the quantity of drained water may differ substantially
from the supplied water consumption. This is where the difficulty
in drained water volume determination lies.
As for the determination of quality of wastewater, individual
operators in factories are required to submit a report on it.
We found, however, that these stated qualities differ greatly from
the fact and lack reliability. Therefore, though time-consuming,
it is desirable that determination be made by city officials.
(5) Operation and. maintenance costs
Operation and maintenance costs are computed on a liquidation
principle at this plant, and this system has experienced such
shortcomings as:
l) Operation and maintenance costs vary year by year, therefore
their computation is quite complex and time-consuming.
2) Since fixed expenses, such as personnel, lighting, heating
and water expenses, remain constant irrespective of the volume
of wastewater discharged, early enterprises in the industrial
district are charged at a higher rate than new ones.
3) Since the treatment plants are run with expenses "totally borne
by member enterprises, it is a prerequisite that unanimous
consent of all participant enterprises be obtained before
giving a go-ahead to any plan for improvement or expansion
of facilities.
As a solution to the problems presented above, a new expense-
allotment system based on revising user charges every two or
three years to correct for variations in plant operation ex-
penses may have to be worked out, rather than relying upon a
liquidation principle.
89
-------
(6) Others
Although it is difficult in small scale facilities such as
Torihama plant to prepare alternative treatment systems for
emergencies, it is desirable to have spare parts for instru-
ments, pumps and valves.
90
-------
§ III. COMBINED TREATMENT OF INDUSTRIAL AND DOMESTIC WASTEWATER
AT SHINGASHI VALLEY
- Tokyo Metropolitan Government -
CONTENTS
Page
Introduction •> 92
1. Effluent Standard ..- 9_k
2. Sludge Handling 97
3. Surcharge ,... 97
4. Shingashi Treatment Plant 98
5. Discription of Shingashi Plant 99
91
-------
§ III. COMBINED TREATMENT OF INDUSTRIAL AND DOMESTIC WASTEWATER AT
SHINGASHI VALLEY
- Tokyo Metropolitan Government -
Introduction
Crude trade wastewater discharged from the heavy industrial area in
Shingashi valley was a major pollution source to the Sumida River.
In order to remove the pollutants and renovate the river, design of
a new waste treatment plant was'Started in 1962. About 730 industries
and 200,000 people were to be served by the plant. This was the first
attempt in Japan to -build a plant for treatment of a mixture of many
kinds of industrial wastewater. The plant which is named Dkima has
been under operation since 1966. This paper depicts an anecdot" of
Ukima's rise and fall.
The Ukima Plant was designed to take care of almost all of the in-
dustrial wastewater produced in Shingashi valley. Wastes were mainly
from metallurgical, chemical, metal plating, food processing, pharma-
ceutical, pulp and paper, and dye industries. Before the plant began
operation the wastes were discharged directly to the Sumida River.
At present, the Ukima Plant treats 160,000 cubic meters of liquid
wastes daily. Detailed information on design criteria, process
basis and historical background of the Ukima Plant was previously
reported at the first US - Japan Conference on Sewage Treatment
Technology in Tokyo during 1971.
92
-------
^** **N. ^ « . •*
Industrial^ Grit / ^ \, j£j£j_ Eaualization
tfAatea Chamber V ) Tank"6 ' Tank
PH Control
Coagulan
1
_ . . /^^\*" ^ deration & Rapid
_•. [ Pump ] Control -». Regulation -*• Mixing -
Chamber V / m , _ ,
^ / Tank Tank Tank
1
ts
Slow
Mixing
&
Floccu-
lation
Tank
Pumping
Station
Ukima Treatment
Plant
Final
— Settl-
ing
Tank
for
».
ShingasM
Excess
Handling
factory
Sludge
'ig. 1 Flow Diagram of Ukima Plant
Since inauguration of the Ukima Plant operation public concern of
pollution has developed very rapidly, with a number of new regulations
installed. It may be likened to a "kaleidoscopic change". Living
environmental standards, water quality laws, and effluent standard
modifications are examples. Pollution is now a popular topic in
nearly all daily newspapers and seldom does a day pass without TV or
radio reports on pollution. The public is very sensitive to the
degree of pollution that exists and this circumstance has resulted
in an alteration of the basic idea of Ukima 's design basis. Although
it consistently serves to save the Sumida River from organic pollution,
the Ukima plant is not a panacea. We have come to the conclusion that
the (l) effluent standard, (2) sludge handling method, and (3) surcharge
system should be revised.
-------
60-
50-
40-
30-
20-
10-
1961 62 63 64 65 66 67 68 69 70 71 72
Pig. 2 Strain Quality of the Shingashi River
(the major tributary of the Sumida)
1. Effluent Standard
BODc; of 120 mg/1 and S3 of 150 mg/1 were stringent enough for the
initial purpose of the Sumida River Pollution Abatement Program.
However, in 1971, Tokyo began to believe that the effluent quality
should be improved to 20 mg/1 BOD^ and 70 mg/1 SS. In addition to
these levels the Japanese Central Government regulatory agency
announced the following standards to apply to all waste discharges
to the River:
(l) Hexane extract
(2) Phenol
(j>) Cyanide
(4) Alkyl mercury
(5) Organi c pho sphorus
(6) Cadmium
(7) Lead
(8) Hexavalent chromium
Mineral oil and grease
Vegetable and animal grease
5 mg/1
1 mg/1
N.D.
1 mg/1
0.1 mg/1
1 mg/1
0.5 mg/1
5 mg/1
30 mg/1
94
-------
(9) Arsenic
(lO) Total mercury
(ll) Total chromium
(12) Copper
(13) Zinc
(14) Soluble iron
(15) Soluble manganese
(16) Fluorine
0.5 mg/1
N.D.
1 mg/1
3 mg/1
5 mg/1
10 mg/1
10 mg/1
15 mg/1
These are named the "health hazard substances" and the traditional
municipal sewage plant is not capable of adequately removing these
substances. The only way that the treatment plant effluent quality
could satisfy the standard was for the plant to refuse acceptance of
the substances. In other words, these materials should be controlled
at their source. Every industry is now required to install its own
pretreatment equipment for removing the "health hazard substances"
before discharging the wastewater to any Tokyo municipal sewer.
Table-1 shows the yearly change of the influent quality, which shows
a decreasing trend.
Table-1 Yearly Change of the Ukima Influent and Effluent
Quality
^^ ^__
PH
SS
BOD
COD
T-N
inf.
eff .
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
1970
6.9~8.7
7.2-7.6
239
71
270
88
321
187
85.7
59.5
1971
6.7-8.6
7.1-7-7
203
78
193
64
209
97
70.5
57.7
1973
7.3~8.3
7.4-8.0
224
79
197
64
198
92
41.7
36.9
mg/i
95
-------
Table-1 Yearly C
Table-1 Yearly Change of the Ukima Influent and Effluent
Quality (Continued)
^^^ — _____
CN
phenol
T-Cr
Cr+6
Cu
Cd
As
Pb
T-Hg
T-Fe
Soluble Fe
Soluble Mn
F
Zn
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
' inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
inf.
eff.
1970
0.2
0.1
2.3
0.5
4.3
2.9
-
-
2.3
1.1
0.21
0.16
ED
ED
11.7
6.3
0.17
0.12
-
-
-
-
-
-
-
-
-
-
1971
0.2
0.1
-
-
3-6
1.9
1.0
0.54
1.9
0.8
0.07
0.03
0.03
0.03
6.8
3.4
ED
ED
-
-
-
-
-
-
-
-
-
-
1973
0.2
0.1
0.4
0.1
1.4
0.9
0.5
0.1
1.6
1.4
0.04
0.02
0.01
0.007
5.5
2.5
ED
ED
23.0
16.5
1.2
2.0
0.6
0.5
L 4.0
4.0
3-8
2.0
mg/1
96
-------
2. Sludge Handling
Although concentrations of the "health hazard substances" in the
influent are less than the standard they accumulate in the primary
or excess sludge. Some, heavy metals are found at concentrations of
100 to 1000 times more in the sludge as compared to the influent.
Analytical data of the heavy metals contained in the sludge are listed
in Table-2. Each value in the table is considerably greater than
found in normal municipal sewage sludge. Referring to the "industrial
and municipal refuse law," one may see that the numbers are so large
that the Ukima plant sludge is considered to be "poisonous sludge"
which is strictly regulated for final disposal. During ultimate
disposal of the sludge special care must be taken to protect surface
or ground water from sludge seepage.
Table 2 Heavy Metals Contained in Ukima Sludge and Ash
^^-^^
Thickened
Sludge
Ash
date
71-5
72-3
73-6
72-5
72-10
73-6
73-6
T-Hg
-
-
28.4
0.024
0.008
0.101
-
Cd
516
361
150
38.0
56.0
47.8
30.8
T-Cr
11,719
14,562
14,000
6,500
9,000
6,580
5,625
Cr+6
-
-
0
-
2,550
1,380
1,200
Pb
6,484
7,522
10,300
15,000
11,500
4,220
1,875
Zn
-
-
2,170
9,500
8,000
9,490
-
Cu
-
-
8,950
4,500
5,500
4,050
-
.g/kg - dry solid
m,
3- Surcharge
A portion of Ukima's running cost is financed by a surcharge paid by
the industries. The basic formula for the surcharge calculation is
as follows:
C = A + 1.7 (B + S) + 180P
C : Basic factor for surcharge rate
A : Acidity or alkalinity load which exceeds pH 5-6 or 8.7
respectively.
97
-------
B : BOD (mg/l) fraction which exceeds 300 mg/1
S : SS
P : CN + Cr, Cyanide (mg/l) fraction which exceeds 2 mg/1
Chromium (mg/l) fraction which exceeds 3 mg/1
In this formula the third item, 180P, on the right hand side amounts
to a large portion of surcharge. The original intention of the item
was rather for the purpose of rejecting such toxicants as cyanide
and chromium, or for applying a penalty for their presence. It was
also expected that the penalty would provide a financial incentive to
the industries to control strength of their wastewater. However,
contrary to the expectation, the industries chose to pay for discharge
of the toxicant substances. This resulted in several problems in
sewer pipes and plant performance. Therefore, as previously noted,
each industry was forced to have its own pretreatment plant and since
early 1973 no surcharge has been collected.
However, we are thinking of a new concept of surcharge which is to
be applied not only to Shingashi valley but also to the whole of
Tokyo. It is based on both BODt and SS concentrations in the waste-
water discharge. All waste discharges whose BOD^ and SS are stronger
than the standard domestic sewage are subject to the new surcharge.
The new surcharge concept is expected to provide an equitable solution
for all users of the Tokyo waste treatment facilities.
4- Shingashi Treatment Plant
When the original Ukima Plant was planned, BODj- of 120 mg/l and SS of
150 mg/l were the controlling design criteria of the final effluent.
The new requirement for BODc and suspended solids is 20 and 70 mg/l
respectively. The Shingashi Plant is now under construction to
provide additional treatment of the Ukima Plant effluent. Even
though toxic matter is removed at the very beginning, before dis-
charge to the municipal sewer, refractory substances still exist
in the influent. With a single-stage biological system it is
difficult to produce an effluent containing less that 20 mg/l BODR
98
-------
and 70 mg/1 suspended solids. A year of study concluded that if the
Ukima plant effluent was diluted with crude domestic sewage it could
be made bio-degradable. Thus, a two stage biological system is now
intended, consisting of the Ukima Plant and the Shingashi Plant.
In 1974, a part of the full system will be operating, and in the near
future a tertiary plant may be included.
5. Description of Shingashi Plant
A flow diagram and plant layout are shown in Figure 3 and Figure 4
respectively.
Industrial
wastes
222,000
Domestic Sewage
1,009,800 m3
Ukima treatment
plant
Tertiary '
treatment i
i
outfall
outfall
Shingashi Sewage Treatment Plant
Fig. 3 Flow Diagram of Whole System Plants
99
-------
Sludge thickner
incinerator
o
Sludge
Handling
Factory
O
O
>-3
P>
a
fv
Regulation
Aeration &
Floccutation Tank
3
3
PJ
01
a>
rl-
i— '
H-
3
0>f
i»
s
fr
Administration
Building
Aeration Tank
Final
Settling
Tank
Pig. 4 Dkima & Shingashi Plant
-------
Two level settling tanks (primary and secondary) and deep aeration
tanks are interesting design features. The aeration tank is designed
to provide a straight one way flow pattern, while traditional aeration
tanks have a back and forth flow pattern. Thus a considerable saving
of space and head loss are expected.
Table 3 Settling tank in Shingashi Plant
Primary Secondary
Structure 2 decks 2 decks
Plow pattern parallel, one way parallel, one way
Retention period 1.7 hr 2.'^ '*"*
Overflow rate 50 m3/m2/day Z^^tf mVm2/day
Dimension, upper 20^ 44^ 3.5^ 20 39-^ 3.6
lower 20 51 3-5 20 55 3-6
Space saving is one of the important design factors.
The local people do not like having a sewage treatment plant for
a neighbor. Thus, obtaining land for a sewage treatment plant is
a time consuming business. The two deck secondary settling tanks
at the Ochiai plant was the first trial of this concept. It was
first installed as early as 1962.
For the past three years a deep aeration activated sludge process
has been our research subject. Since May, 1973 the pure oxygen
process has also been under pilot study. The following comments
relate to the development of the deep aeration tank concept.
(l) Oxygen transfer rate, KLa, is proportional to the 0.7 power of
the diffuser depth, and electrical consumption is also proportional
to the same number. Therefore, energy efficiency is independent
of the depth. Table 4 shows changes of KLa relatiye to the diffuser
depth.
The deep aeration system may be considered effective when applied
to mixed liquor whose oxygen consumption rate is large. The
Shingashi's aeration tank is such a case.
101
-------
Table 4 Changes of KLa Relative to the Diffuser Depth
Aeration
Tank
Depth
H(M)
6
(iSfeet)
12
(36feet)
18
(54-feet)
Diffuser
Depth
H'(M)
5.9
11.9
17.9
Tank
Volume
V(M3)
75.4
150.7
226
Air Volume
Ql
(raVzr)
47.1
85.1
46.8
83.3
167.0
60.9
122.9
227.6
Q2=QlA
(mVHr/M5)
0.62
1.13
0.31
0.55
1.11
0.27
0.54
1.01
Air
ratio
3-1
5.6
1.6
2.8
5-5
1.3
2.9
5.0
KLa
KLa(T)
(1/Hr)
0.81
1.95
0.64
1.66
3-30
1.08
5-71
9.21
KLa(20)
(1/Hr)
0.82
1.96
0.66
1.68
3.37
1.09
5.78
9.28
Air ratio = Ratio of air flow rate to influent flow rate
(2) Aeration tank' depths of 60 feet do not significantly influence the
activated sludge activity.
(3) When air is diffused at a location deeper than 17 feet, biological
floe won't settle in the secondary settling tank due to entrainment
of fine air bubbles. Super-saturation causes fine bubbles to ac-
cumulate near the water surface and became attached to the floes.
It is the same phenomena that occurs in the air floatation process.
(4) Unless methods of improving the floe settlability obtained,
the diffuser should not be submerged deeper than 17 feet; however
the tank depth is not limited.
(5) Design criteria for the deep tank, with dimensions up to 30 feet
depth, have been derived and confirmed. Use of tanks with depths
as much as 60 feet are now being developed.
102
-------
§ IV. COMBINED TREATMENT OF MUNICIPAL AND INDUSTRIAL WASTEWATER
IN KYOTO
- The City of Kyoto -
CONTENTS
Page
I. Present Conditions of the Area Covered by the Sewage
Treatment Plant Concerned .................................. 10U
1-1. Actual Situations of Factories and the Quantity of
Inflowing Sewage ......................................
1-2. The Characteristics of the Inflowing Sewage ........... 106
II. The Treatment Experiments of the Inflow of Route B ......... 10Q
II-l. The Treatment Experiments at a Low Load by Existing
Facilities ............................................ 109
II-2. The Two Stage Treatment Experiments by the Activated
Sludge Process at a Pilot Plant ....................... Ill
II-3. The Treatment Experiments by the Activated Sludge
Process with the Pure Oxygen Aeration ................. 115
III. Conclusion ................................................. 127
103
-------
§ IV. COMBINED TREATMENT OP MUNICIPAL AND INDUSTRIAL WASTEWATER
IN KIOTO
- The City of Kyoto -
I. Present Conditions of the Area Covered by the Sewage Treatment
Plant Concerned
1-1. Actual Situations of Factoties and the Quantity of Inflowing
Sewage
At the Kisshoin Sewage Treatment Plant, there are two units of
the treatment facilities named Route A facilities and Route B
facilities, respectively. Route A facilities are for Sujaku Line
sewage and a part of Karahashi Line sewage, and Route B facilities
are for only Karahashi Line sewage.
Karahashi Line covers an area of 128 hectares in the south of
Kyoto City, where are a number of factories for dyeing, electric
appliance manufacturing, gilding, and others. As shown by Figure
1-1, 48$ of Karahashi Line sewage is treated by Route B facilities.
Karahashi Line
Sujaku Line
60,000
Route B
facilities
Route A
facilities
Q
Discharge
Fig. 1-1 Flow Sheet of Kisshoin Treatment Plant
104
-------
The pH value of the sewage from such factories largely fluctuates
and, therefore, the sewage can hardly be treated by the ordinary
activated sludge process satisfactorily. As a result, a two stage
treatment has been conducted at the Plant now by leading the
effluent from Route B facilities to Route A facilities.
Tables 1-1 and 1-2 show the results of the research which were
made in 1969 on the Karahashi Line sewage. According to Table 1-1,
41$ of the area covered by the Line is residential areas and only
20$ is factory sites. Table 1-2 indicates that only 13$ of the
total number of factories is dyeing industry but that it occupies
32$, the largest portion, of the total factory sites.
Table 1-1 Area Ratio by Land Use
Factories
20.0
Residences
41.0
Offices
6.0
Roads & Parks
21.8
Railway Sites
11.2
Total
100
Table 1-2 Factory Ratio by Industrial Type
Dyeing
Machine Mfg.
Metal Work
Food Mfg.
Electrical, Mechanical
Work
Others
Total
Number of
Factories
12.5
29.8
15.4
8.1
6.7
32.5
100
Area
31.9
31.2
3-5
1.7
3.7
28.0
100
Sewage
Discharged
64.6
9.1
4.7
10.0
3.3
8.3
100
Out of the inflowing sewage amounting to 30,000 m^/day, 22,900
mVday, 76$, is the waste of factories, while the remaining 24$
is the domestic sewage and others. Of the factory sewage, 14,800
m^/day, 65$, is the dye waste.
105
-------
1-2. The Characteristics of the Inflowing Sewage
Table 1-3 The Quality of the Inflowing Sewage (in 1972)
Temperature °C
pH
BOD mg/1
C 0 D Mn mg/1
Total Solids mg/1
Fixed Solids mg/1
Suspended Solids mg/1
Soluble Matter mg/1
Total Nitrogen mg/1
Ammonia Nitrogen mg/1
Albuminoid Nitrogen mg/1
Nitrite Nitrogen mg/1
Nitrate Nitrogen mg/1
Iodine Consumed mg/1
Chlorine Ion mg/1
Total Phosphorus mg/1
Phenol mg/1
Anionic Detergents mg/1
No. of Coliform Colonies
colonies/ml
Inflow to Route B
Average
26.3
8.9
363-3
215.1
1,461
1,039
116
1,355
38.21
2.78
14.43
0.27
0.28
124.6
112.9
2.37
0.35
8.7
12,000
Maximum
30.6
9.8
632.5
348.0
2,075
1,287
147
1,875
67.51
9.65
45.15
0.98
0.56
300.8
199.5
3.00 -
1.23
24.0
34,000
Minimum
22.0
7.4
193-8
28.1
834
618
77
746
14.41
0.16
2.20
0.04
0.04
7.9
12.1
0.77
0.00
1.4 -
19
As shown by Table 1-3, the inflow to Route B has been greatly
affected by industrial waste, especially by dye waste. Now the
special features of the waste quality, which should be taken into
consideration for the treatment, and their causes are examined.
(l) pH
Often the inflowing waste is alkaline. Since a great amount
of alkali, such as sodium hydroxide (NaOH) and sodium silicate
ioe
-------
, is used for the dyeing, the waste is surmised to be
alkalized. At the maximum, pH in the waste reaches 10, but
sometimes the waste is acidified to pH 4 to 6.
(2) BOD
Compared with the ordinary municipal sewage, the inflow usually
has a higher BOD and its amount largely fluctuates. The average
BOD is 300 mg/1, and it often exceeds 400 mg/1. On Sundays and
national holidays, it comes down to as low as 100 mg/1.
Further even.within a single day, it largely fluctuates as
shown by Figure 1-2. At the peak hour it reaches as high as
600 to 800 mg/1.
BOD
mg/1
1000-
11
13 15 17 19 21 23
Time (hundred hours)
Fig. 1-2 Hourly Variation of BOD
In the inflowing waste, 80$ of the BOD is soluble BOD. Only
0 to 20$ of the BOD can be removed at the primary sedimentation
tank and consequently the BOD load in the aeration tank has
become high.
107
-------
(3) Reducing Agent
Sometimes by the waste as much as 300 mg/1 of iodine, is con-
sumed. It is surmised to be due to the reducing agent contained
in the waste. Actually reducing agent, such as sodium thiosulfate
(NapSpOv), sodium sulfite (Na2SO^), and sodium sulfide (^28),
is used as an auxiliary agent for dyeing.
(4) Soluble Matter and Suspended Solids
In the inflowing waste, the total solids,is approximately 1500
mg/1 on the average. Of the solids, the suspended solids is
only about 100 mg/1 and most of the solids is soluble matter.
Further, of the total solids, the volatile matter is only 35%.
It means that the waste is highly contaminated by inorganic
soluble matter.
(5) Nitrogen and Phosphorus
There is not much ammonia nitrogen but is a considerable
amount of organic nitrogen in the waste.
The amount of phosphorus is a little and the total phosphorus
is approximately 2 mg/1.
(6) Coloring by Dyestuff
Since the waste has been colored by dyes, it brings about a
feeling of contamination.
108
-------
II. The Treatment Experiments of Inflow to Route B
Any organisms peculiar to the activated sludge can hardly be found
in the aeration tank of Route B. It means that the inflow to Route
B can scarcely be treated by the ordinary process. Further if the
mixed liquor suspended solid is given more than usual, the activated
sludge is decomposed because of poor supply of oxygen, and the
treatment efficiency is impaired on a large scale.
At present the BOD removal is 30 to 50% and the SS removal is 10 to
30% by the Route B facilities. Therefore, by existing facilities
and at a pilot plant, various experiments were conducted on the
treatment of Route B sewage.
II-l. The Treatment Experiment at a Low Load by Existing Facilities
¥ith the quantity of the inflow limited to 200 in-Vhr and with the
conditions fixed as shown by Table II-l, an experiment was con-
ducted. The results are shown by Table II-2.
Table II-l Conditions of Experiment
Inflow m /day
Air Supplied
Aeration Period
M L S S
R S S S
BOD-SS Load
Detention Period in Final
m* air/in-^ sewage
hrs
mg/1
mg/1
kg/SS kg- day
Sedimentation Tank hrs
4,260
15.8
11.4
2,336
6,262
0.129
4.10
"(l)
The pH in the inflow fluctuates between 10.5 and 9.2 and its
average is about 10. In the grid chamber, pH is adjusted, but
pH in the effluent from the primary sedimentation tank still
fluctuates between 8.9 and 6.3- This fluctuation, however,
does not hamper the biological treatment. The pH in the
effluent from the final sedimentation tank is only 7.5 to 7-1.
109
-------
Table II-2 Results of Experiment
Hundred
Hours
9
11
13
15
17
19
21
23
1
3
5
7
Average
PH
Inflow
10.0
9-9
9.5
10.1
10.4
9.9
9.6
10.2
10.2
10.5
9.2
10.3
10.5-
9.2
Primary
Effl.
6.3
6.3
6.7
8.4
8.9
8.9
8.7
7-8
7.9
8.0
8.3
7.6
8.9~
6.3
Final
Effl.
7-4
7 = 3
7.2
7.1
7.2
7.4
7-5
7.4
7.4
7.4
7.4
7.4
7.5-
7.1
BOD mg/1
Inflow
239
526
206
289
211
252
220
177
206
95
160
137
226
Primary
Effl.
200
283
278
244
241
272
328
223
203
210
142
156
232
Final
Effl.
19
2.1
24
24
25
25
23
25
24
21
16
17
22
SS mg/1
Inflow
75
106
73
262
97
81
73
31
20
13
29
18
74
Primary
Effl.
54
146
62
108
84
68
113
22
51
29
53
39
69
Final
Effl.
12
25
45
47
44
28
23
38
25
50
27
39
33
(2) BOD
The BOD in the inflow largely fluctuates between 526 and 95
mg/1. The average is 226 mg/1. The fluctuation of BOD in the
effluent from the primary sedimentation tank is small being
between 328 and 142 mg/1, but BOD has not been removed in the
tank. In the effluent from the final sedimentation tank,
however, BOD is 22 mg/1 on the average having been removed
satisfactorily.
(3) S S
Suspended solids in the inflow is between 262 and 13 mg/1 and
the average is 74 mg/1. SS can hardly be removed in the primary
sedimentation tank, and the primary sedimentation tank of Route
B functions only to average the inflow quality.
By the conditions that greatly differ from the ordinary
activated sludge process, as shown by Table II-l, the ciliata
110
-------
peculiar to the activated sludge are proliferated and the
effluent is satisfactory.
II-2. The Two Stage Treatment Experiment by the Activated Sludge
Process at a Pilot Plant
The aforementioned experiments prove the fact that to treat the
Karahashi Line -sewage the load has to be made lower than the
standard conditions of the activated sludge process. It is,
however, inadvisable to newly build and maintain such low load
facilities. Therefore, in the hope that a more effective process
might be found, a two stage treatment by activated sludge was
experimented.
1st stage
2nd stage
primary
Effluent
Aeration
Sedimen-
tation
Effluent 1
Aeration
Sedimen-
tation
Effluent 2
Aero-accelator
Fig. II-l Flow Sheet of Two Stage Treatment
As shown by Figure II-l, after the aero-accelator the effluent
is to go through another aeration and sedimentation tank. By
this method, two experiments were conducted with the operation
conditions different from one another.
(l) Experiment I
Table II-3
Conditions of Experiment I
Air Supplied
Aeration Period
M L S S
R S S S
BOD-SS Load
Detention Period
UK air/irr sewage
hrs
mg/1
mg/1
kg/SSkg-day
in Sedimentation Tank hrs
1st stage
8.2
1.63
3,000
0.89
1.5
2nd stage
8.9
4.33
1,900
7,000
0.35
1.28
111
-------
Most of the conditions, as shown in the Table, are standard
except the supplied air which is much more than usual. The
results are as shown in Table II-4. According to the Table,
BOD in the effluent 2 is 18 mg/1 on the average. The BOD
removal is 47.4$ at the first stage and 75-4^ at the second
stage. In the second stage there can be seen a considerable
number of ciliata peculiar to activated sludge and the result
is satisfactory.
Table II-4 Results of Experiment I
pH
T S mg/1
S S mg/1
BOD mg/1
BOD Removal %
Inflow
11.5 - 4.3
7.5
725
68
476 - 23
163
Primary
10.3 - 4.6
7.7
659
46
324 - 35
139
14.7
Effl. 1
8.8 - 6.9
7-7
536
23
129 - 14
73
47.4
Effl. 2
7.7 - 7.2
7.5
482
21
37-4
18
75.4
(2) Experiment II
For Experiment II, five sets of conditions were employed for
the second stage while the load of the first stage was kept
constant, so that the most effective conditions for the
treatment might be found.
Table II-5 Conditions of Experiment II
M L S S mg/1
BOD-SS Load kg/SSkg-
day
Aeration Period hrs
Air Supplied
EKair/m3sewage
Det. Per. in Sed
Tank hrs
Period of Experiment
1st stage
II-1-5
3,000
0.81
1.0
5
1.15
Oct 1 ~
Nov 21
2nd stage
II-l
2,000
0.150
6.0
14.7.
1.77
Oct 1~
Octl2
II-2
1,850
0.195
5.0
12.2
1.47
Oct 13~
Oct 23
H-3
1,400
0.255
5.0
12.2
1.47
Oct 24-
Nov 2
II-4
1,200
0.302
5.0
12.2
1.47
Nov' 3~
Nov 9
II-5
1,250
0.402
4.0
9.8
1.18
Nov 10~
Nov 21
112
-------
While the experiments were carried out, the quality of each
effluent was tested. The results are shown by Table II-6.
The BOD-SS load at the first stage is between 0.78 and 1.13
kg/SSkg-day. The BOD removal at the first stage is approximately
45$ at the Experiments II-l and II-3, but at other experiments
it is 20$ on the average. At the second stage, the Experiment
II-l shows the maximum BOD removal, 80.9$. At the other
experiments it is 68$ on the average.
No ciliata peculiar to activated sludge can be seen in the
effluent from the first stage, but after the second stage the
ciliata can be seen.
The conditions and the results of the two stage treatment ex-
periments at a pilot plant are as follows. At the first stage
under the following conditions, the BOD removal is 40 to 50$.
BOD-SS load approx. 0.8 kg/SSkg-day
Aeration period .... 1.6 hours
pH * lower than 10
After the second stage, which is operated with the following
conditions, the BOD removal becomes satisfactory with BOD in
the Effluent 2 being less than 20 mg/1.
BOD-SS load 0.15 to 0.2 kg/SSkg-day
Aeration period .... approx. 6 hours
Ca-T (MLSS (mg/1) x Aeration period ... 12,000 - 13,000 up
Air supolied 15 HK air/m^ sewage
113
-------
Table II-6 Results of Experiment II
Dates of Tests
Primary Effluent
BOD mg/1
PH
T S mg/1
S S mg/1
1st Stage
BOD mg/1
BOD Removal %
pH
T S mg/1
S S mg/1
M L S S mg/1
Aeration Period hrs
S V I mg/1
BOD-SS Load kg/SSkg •
day
2nd Stage
BOD mg/1
BOD Removal %
PH
T S mg/1
S S mg/1
M L S S mg/1
Ca-T
Aeratio'n Period hrs
S V I mg/1
BOD-SS Load kg/SSkg.
day
II-l
Oct 11
Oct 12
153-3
10.6-6.0
710
84
80.8
47.2
9-5-6.9
634
59
3,127
1.0
63.3
0.85'
15.5
80.9
7.9-7.6
610
43
2,012
12 , 070
6.0
80.9
0.123
II-2
Oct 22
Oct 23
158.8
10.8-5.7
•1,032
134
124.0
21.9
10.2-7.2
964
96
3,455
1.0
58.8
0.80
34.0
72.6
7-9-7.7
900
68
1,700
8,500
5.0
75.4
0.270
II-3
Nov 1
Nov 2
186.7
10.7-5-9
1,022
123
•105.4
43-5
9-3-7.0
961
122
3,580
1.0
56.5
0.90
33.6
68.1
7.9-7.4
913
62
1,372
6,860
5.0
73.1
0.285
II-4
Nov 8
Nov 9
188.1
11.3-5.1
1,091
130
136.6
27.3
10.4-7.2
1,009
112
4,169
1.0
53.4
0.78
41.4
69.7
9.2-7.9
933
118
1,357
6,790
5-0
79.5
0.373
II-5
Nov 20
Nov 21
217-5
11.1-4-7
1,167
130
195.5
10.2
10.3-6.3
1,119
127
3,334
1.0
49.5
1.13
77.7
60.3
8.4-7.2
979
86
2,123
10,620
5.0
73-5
0.343
114
-------
II-3- The Treatment Experiments by the Activated Sludge Process with
the Pure Oxygen Aeration
As mentioned above, to treat the sewage of Route B by the activated
sludge process, a remarkably large amount of oxygen is required in
the aeration tank. That is, to supply oxygen enough for the treatment,
the amount of air and the aeration period has to be made three times
than usual, respectively. It is inadvisable to build and maintain
such air system facilities as to meet the requirements aforementioned.
Therefore, the pure oxygen aeration process, which was surmised to
easily increase the supply of oxygen, was experimented at a pilot
plant, which is illustrated by Figure II-2.
Oxygen bomb
Gas
exhaust
Primary Adjusting
sedimentation tank
tank of
Rout B
Legend:
© Compressor
d> Pump
(|p Motor
Valve
Gas meter
Return sludge
Excess sludge
sampling points
© Inflow
© Effluent
0 Mixed Liquor
© Return sludge
Fig. II-2 Flow Sheet of Pure Oxygen Aeration Process
115
-------
Conditions of Experiments
The outline of the experiments of the treatment by the pure
oxygen aeration process is shown by Table II-7- For the Ex-
periments I and II, the effluent from the primary sedimentation
tank of Route B was used as the inflow.
Table II-7 Conditions of Experiments
Ace .
Exp
I
Exp
II
Exp
III
1
2
1
2
A.
1
Remarks
Acclimation
of Activat-
ed Sludge
Quantity of
Inflow
Constant
Quantity of
Inflow
Variable
Mixed
Ordinary
Municipal
Sewage
Inflow
Variable
Period
31 days
Jan 18 to
Feb 17
16 days
Feb 18 to
Mar 5
30 days
Mar 6 to
Apr 4
32 days
Apr 5 to
May 6
21 days
May 7 to
May 27
9 days
May 28 to
Jun 5
9 days
Jun 6 to
Jun 14
Quantity
of Sewage
m3/d
48
36
48
48
37.6
48
57.8
Aeration Period
Q
hrs
3
4
3
3
3.8
3
2.5
Q + R
hrs
2.2
2.9
2.1
2.2
3.0
2.4
1.9
Detention
Period at
Final Sed.
Tank hrs
3-3
4.3
3.2
3-3
4.5
3-6
2.9
Legend: Q ... Quantity of inflow
R ... Quantity of return sludge
Ace. & A. ... Acclimation
116
-------
Firstly, by the Experiment I, the conditions that make the
treatment effective at a constant inflow were found out. Then
at Experiment II, it was aimed to find out, with the finding
of Experiment I made use of, the most appropriate conditions
for the treatment of variable inflow which is similar to that
of Route B.
The Experiment III was made to see the efficiency of the mixed
treatment of Route B sewage and the ordinary municipal sewage.
The mixing of those two types of sewage was done in the ratio
of 1 to 1 and the hourly variation of inflow was made in the
same pattern as that of Experiment II.
(2) The Results of Experiment
To complete the experiments, it took nearly five months from
January 28 to June 14 of 1973. Tables I1-8, II-9, and 11-10
show the average values at each experiment of the operation
conditions, the water quality examinations, and the activated
sludge examinations, respectively.
117
-------
Table I1-8 Operation Conditions
Quantity of Inflow m3/day
Return Sludge mVday
Ratio of Ret Sludge %
Aeration
Period
Oxygen
Q hrs
• Q + R hrs
Supplied m3/day
Exhausted m3/aay
Ratio in Exhausted %
Used kg/day
Ratio of Used fo
BOD-SS Load kg/SSkg-day
BOD-VSS Load kg/VSSkg-day
BOD Load Rate kg/m3-day
Final
Sedi.
Tank
Overflow Rate m3/m2-day.
Solid Load kg/m^-'day
Detent. Per. hrs
Depth of Sludge cm
Blanket
Excess Sludge m^/day
Excess
Sludge
SS kg/day
VSS kg/day
Exc S3 per Rem BOD kg/kg
Oxy used p Rem BOD kg/kg
Ace.
48
19
40
3.0
2.2
8.44
1.61
54
10.83
89.7
0.33
0.53 '
1.67
14.8
103.4
3-3
198
0.14
2.45
1.77
0.28
1-25
Exp. I
1
36
14
38
4.0
2.9
8.47
1.89
56
10.60
87.5
0.27
0.41
1.52
11.0
85.3 '
4.3
181
0.15
3.12
2.15
0.38
1.28
2
48
20
43
3-0
' 2.1
14.00
2.40
57
17.99
89.4
0.37
0.56
2.35
15.0
137-4
3.2
175
0.22
4.65
3.03
0.39
1.42
Exp. II
1
48
17
35
3-0
2.2
16.33
5.89
53
17.59
78.1
0.28
0.41
1.80
15-0
131.1
3-3
136
0.21
5.37
4.07
0.54
1.95
2
37.6
11
29
3.8
3.0
16.13
8.09
56
14.15
68.3
0.25
0.37
1.62
12.0
96.8
4.5
81.
0.07
2.47
1.67
0.26
1.76
Exp. Ill
A.
47.9
12
26
3.0
3.4
14.67
8.00
55
14.71
70.1
0.34
0.48
1.94
15.0
107.5
3-6
110
0.09
3.26
2.30
0.29
1.32
1
57.8
17
30
2.5
1.9
16.46
8.85
57
16.34
69.4
0.32
0.45
1.87
18.0
135.3
2.9
170
0.18
5.04
3.61
0.47
1.78
Legend:
Ace. and A
Exe SS per Rem BOD
Oxy used p Rem BOD
Acclimation
Excess S3 per Removed BOD
Oxygen Used per Removed BOD
118
-------
Table II-9 Results of Water Quality Examination
Temperature °C
E
Transparency cm
E
PH
Max
I Win
Ave
Max
E Min
Ave
Total Solids I
mg/1 E
Soluble
Matter
Suspended
Solids
Volatile
Matter
Dissolved
Oxygen
BOD
Soluble
BOD
CODCr
Soluble
CODcr
CODMn
Soluble
CODMn
Alkalinity
Total
Nitrogen
I
mg/1 E
mg/1 I
E
Rem %
I
mg/1 E
Rem %
mg/1
E
I
mg/1 E
Rem %
mg/1
E
I
mg/1 E
Rem %
I
mg/1 E
Rem $
I
E
Rem fo
mg/1
E
mg/1
E
mg/1
E
Ace.
20.0
19.0
3-5
6.5
9.0
3.2
7.0
6.9
5.7
6.2
995
790
890
745
82
26
68.3
49
16
67.4
0.0
0.4
210.5
30.0
85.8
170.4
22.2
432.4
171.0
60.5
330.5
152.8
53-8
115.8
65.0
41.6
108.8
61.3
102.5
99.0
51.27
33.31
1-1
20.4
19.6
3.0
6.0
9.3
3-6
7.6
6.7
6.1
6.4
1,330
1,230
1,180
1,160
122
51
58.2
61
23
62.3
0.0
0.8
253-9
23.6
90.7
210.4
11.8
413-0
161.7
60.9
277.5
142.5
48.7
125.8
63.0
49.1
100.0
50.0
97.0
110.0
39.50
33-55
1-2
21.7
20.8
4.2
9.9
10.2
4.0
8.2
8.4
6.0
6.5
1,340
1,170
1,230
1,120
127
49
60.5
65
21
65.5
0.0
0.7
328.1
28.0
92.9
255.8
13-7
478.9
139.6
70.6
385.8
125-3
67-3
142.6
61.6
53-2
104.8
55.5
187.0
217.0
51.53
40.65
II-l
22.1
23.0
5-5
12.6
9.3
5.2
7-6
6.7
6.0
6.3
1,177
973
1,077
923
92
36
58.4
52
18
63.0
0.0
0.4
224.8
26.7
89-3
192.3
26.7
521.7
161.6
67.2
370.5
120.8
56.2
12-6.1
65-4
48.1
92.8
52.8
234.0
284.0
55-90
43-33
II-2
23-5
24.7
5.3
11.6
9.4
5.7
7.8
6.5
6.1
6.4
850
780
780
760
97
45
53-3
58
22
61.7
0.0
1.2
270.6
13.1
95.2
213.8
9.6
535.3
159.3
70.2
416.0
128.3
69-2
131.9
66.1
50.4
104.7
53-7
;
54.04
53-65
III-A
22.3
24.1
6.0
18.3
8.9
6.8
7.4
6.6
6.1
6.3
805
625
750
605
58
19
67-5
43
12
72.1
0.0
1.5 -
242.6
10.7
95.6
199-7
6.7
368.3
99-3
73.0
360.0
97.0
73.1
92.0
43-3
52.8
84.0
42.0
13.0
21.0
. 61.27
58.63
III-l
23.0
23.9
5-8
21.6
8.4
7.1
7.6
6.7
6.2
6.4
—
75
12
83.6
51
7
86.3
0.0
1.0
194.4
7.6
96.1
172.5
6.8
364-8
95.5
73-8
267.0
86.5
67.6
102.3
45.3
55.8
73-0
33-0
~"
32.34
25.59
119
-------
Ammonia I
Nitrogen mg/1
Albuminoid I
Nitrogen mg/1
£j
Nitrite I
Nitrogen mg/1
E
Nitrate I
Nitrogen mg/1
rj
Total I
Phosphorus mg/1
b
No. of Coliform I
Colonies
colonies/ml
Aoc.
2.90
18.86
39.29
3.19
0.55
0.62
0.05
0.04
2.37
1.03
104,000
11,000
1-1
3.13
22.17
16.76
5-30
0.79
0.62
0.09
o:oe
2.71
1.31
51,000
6,700
1-2
12.31
25.43
19.05
3-29
0.93
0/67
0.04
0.04
7.56
6.24
27,000
1,800
II-l
8. -16
26.11
33.70 -
3-67
1.08
0.93
0.18
0.14
4.67
3.83
19,800
1,900
II-2
10.16
42.45
22.51
2.60
0.27
0.30
0.07
0.07
2.92
2.29
25,000
840
III-A
10.87
42.40
50.37
16.23
0.41
0.59
0.04
0.06
3.28
2.51
55,000
3,200
III-l
6.44
16.64
25.90
8.95
0.11
0.08
0.02
0.02
2.54
1.64
160,000
3,300
Legend:
Ace Acclimation
A Acclimation
I Inflow
E Effluent
Rem % Removal %
120
-------
Table 11-10 Results of Activated Sludge Examination
Suspended I" ML
Solids mg/1 I RS
Volatile /. f ML
Matter ^/l {
v ItO
Ratio VSS/SS ML
SV % fffi
LRS
S V- I ML
Sludge Age day ML
Dissolved <
Oxygen mg/1
Oxygen Uptake
Rate mg/l-hr '
"AT 1
AT 2
AT 3
AT 4
.A AT
'AT 1
AT 2
AT 3
-AT 4
Sludge Preoip. ML
Rate om/min
Aco.
5,156
17,855
3,668
12,846
73.5
45
96
91
7.7
6.0
7.9
9.0
9.4
8.1
23
29
40
31
1.00
Exp I
1
5,539
20,971
3,692
14,307
66.7
38
97
69
7.6
6.0
7.2
7.8
8.3
7.3
65
49
39
31
1.48
2
6,472
22,110
4,210
14,414
65.1
35
95
54
7.0
6.0
6.6
8.4
8.6
7.3
46
49
48
41
1.80
Exp II
1
6,480
28,417
4,339
19,061
67.2
29
96
44
8.6
5-3
6.0
7.2
7.8
6.6
62
60
62
50
2.98
2 j
6,437
35,299
4,348
23,813
67.5
25
98
38
10.6
5.5
6.1
7.8
9.2
7.2
53
52
51
44
3-53
Exp III
A
5,739
35,866
4,054
25,272
70.6
21
97
37
12.4
5.8
6.4
7.9
9.0
7.3
51
60
48
41
4.11
1
5,784
28,012
4,136
20,047
71.5
23
97
39
8.0
5.7
6.3
8.2
9-3
7.4
51
52
50
48
3-59
Legend:
Ace. & A
ML
RS ......
SV '
AT
A AT
Acclimation
Mixed Liquor
Return Sludge
Volume of Sludge Settled in 30 Min.
Aeration Tank
Average in Aeration Tank
121
-------
(l) BOD
As shown by Figures II-3 and II-4, if only the Route B sewage
is aerated for 3 hours and its BOD-SS load is 0.3 kg/SSkg-day
or over, the BOD removal largely fluctuates and BOD in the
effluent exceeds 20 mg/1. If it is aerated for 3-8 hours and
its BOD-SS load is 0.5 kg/SSkg-day, the result is satisfactory
as its BOD removal is 90$ up and BOD in the effluent is less
than 20 mg/1.
Fig. II-3 Relation between BOD-SS
Load and BOD Removal
Fig. II-4 Relation between BOD-SS
Load and BOD in the
Effluent
95
XX
X * X X
»
•.. * . •
90
80
70
,60
H
cti
O
a
s
e85
o
m
i,
• ft
• §40
• -p
P!
§30
• Exp. II-l £
CH
xExp. II-2 H20
/
A
• •
1
10
80 1 1_ L. .. i. i« .. .j n
-
•
• .*
••
• •• *x * *
X w • A
»«k x**
X, X «* •• X^ X
x><
I 1 1 1 1 i
0.1 0.2 0.3 0.4 0.5 0.6
-BOD-SS Load (kg/SSkg-day)
• Exp. II-l
* Exp. II-2
'0 0.1 0.2 0.3 0.4 0.5 0.6
BOD-SS Load (kg/SSkg'day)
122
-------
As shown by Figures II-5 and II-6, the combined treatment of
the ordinary municipal sewage and Route B sewage brings about
a very stable, efficient result. In case that the aeration
period is 2.5 hours and that the BOD-SS load is. in a wide range
of 0.1 to 0.5 kg/SSkg-day, the BOD removal is 95$ up and BOD in
the effluent is less than 20 mg/1.
In other words, if only the high load sewage of Route B is
treated by the pure oxygen aeration process so as to purify
the effluent to the degree of the discharge water quality
standard at the peak of the worst inflow, it requires approxi-
mately 3 hour aeration, (in this case, aeration period on the
average flow is J.8 hours.) If, however, the ordinary municipal
sewage is mixed with Route B sewage in the even ratio, the
aeration period on the average flow can be shortened to 2.5
hours or less. Further it is found by the experiment that the
BOD-SS load should range from 0.2 to 0.4 kg/SSkg-day for the
most stable, efficient treatment.
When the temperature of the sewage is high, SVI goes down to
40 or so and the return sludge suspended solids reaches 30,000
to 38,000 mg/1 and further MLSS can be maintained as high as
6,000 to 7,000 mg/1.
123
-------
Fig. II-5 Relation between BOD-SS Fig. I1-6
Load and BOD Removal
Relation between BOD-SS
Load and BOD in the
Effluent
98
95
^5?
s^-x
i — i
cd
^
o
§
P=!
P
m
!
on
-
X
• X
x x
" X *• ••
x * • <
S3 20
9
x
n
0
x w
-p
s
0}
^ 10
^H
- H
• Exp. III-l
. xExp. III-A
-
x
•
X
r XX
X XV
X • • •
0
• • • •
• Exp. III-l
xExp. III-A
1 1 1 1 1 1
i i i i i~ -i n n 1 mmn/inKHR
0.1 0.2 0.3 0.4 0.5 0.6
* BOD-SS Load (kg/SSkg-day)
—•-BOD-SS Load (kg/SSkg-day)
(2) S S
As shown by Figure II-7, in case that only Route B sewage is
treated, the SS removal largely fluctuates between 20 and 90$
and is quite unstable disregarding the BOD-SS load. As shown
by Figure II-8, however, in case that the municipal and Route
B sewage are mixed, the result is stable with the removal
being 75$ and over and SS in the effluent being less than
20 mg/1.
124
-------
a
820h
10
0
X
•
Pig. II-7 Relation between BOD-SS
Load and SS Removal
100
90
80
70
60
50
X .
••• .
.
x
• Exp. II-l
* Exp. H-2
Fig. II-8 Relation between BOD-SS
Load and SS Removal
100
90
0 0.1 0.2 0.3 0.4 0.5 a 6
—-BOD-SS Load (kg/SSkg• day)
60
50
40
• Exp. III-l
x Exp. III-A
ot
0 0.1 0.2 0.3 0.4 0.5 0.6
—» BOD-SS Load (kg/SSkg•day)
(3) Consumption of Oxygen
To remove 1 kg of BOD, 1.0 to 2.0 kg of oxygen is required.
Compared with the treatment of ordinary municipal sewage, this
amount of oxygen is fairly big. As for 'the relation between DO
in mixed liquor and the treatment efficiency, if the DO at
the 1st section of the aeration tank is low and that of the
4th section is high, the treatment is done efficiently, but
if the DO of the 1st section is as stipulated and that of the
4th section lowers, the treatment deteriorates.
125
-------
(4) Characteristics of Activated Sludge
The flock of activated sludge is microscopic and the zoogloea
that forms the flock does not branch out but is spherical.
When the sludge shows a good precipitation, the SVI is around
40 and the sludge precipitation rate is as big as 3.0 to 4.0
cm/min, and the return sludge suspended solids is as high as
30,000 to 38,000 mg/1.
(5) Production of Excess Sludge
The production of excess sludge solids is 0.38 kg per 1 kg of
removed BOD and 68^ of it is volatile solids. The amount of
sludge solids is 87g per 1 cubic meter of the sewage treated
on the average. Usually the volume of sludge with moisture is
0.34^ of the sewage treated. At the ordinary air system it is
said to be ifo but by this process it is only 1/3.
126
-------
III. Conclusion
Through, various experiments, which were conducted to treat Route
B sewage to the degree of discharge water quality standard, the
following differences were made clear between the pure oxygen
aeration process and the ordinary air system.
l) The ordinary air system requires 10 hours of aeration period and
over (by the two stage treatment process it is 7 hours), while
the pure exygen process requires only 4 hours.
2) The BOD-SS load is 0.15 kg/SSkg-day for the ordinary air system,
the same is 0.2 to 0.4 kg/SSkg-day for the pure oxygen process.
3) The air supplied is approximately 15 m3 air/m3 sewage at the
ordinary air system, while at the pure oxygen aeration process
the amount of oxygen consumed for the removal of 1 kg of BOD is
1.0 to 2.0 kg. Consequently, compared with the ordinary air
system, the pure oxygen process.
(a) well removes BOD at the higher BOD-SS load, and
(b) produces less excess sludge.
Therefore, it is now evident that the pure oxygen aeration process
in quite useful for the treatment of the highly polluted sewage with
a largely variable load, such as the one inflowing to Kisshoin Sewage
Treatment Plant of Kyoto.
127
-------
Third US/JAPAN Conference
STUDIES ON ADVANCED WASTE TREATMENT
presented by
Dr. Mamorii Kashiwaya
Chief, Water Quality Section
Public Works Research Institute
Ministry of Construction
and
Dr. Shoichi Nanbu
Head, Sanitary Engineering Division
National Public Health Institute
Ministry of Health and Welfare
February 12-16, 1974
Ministry of Construction
Japanese Government
128
-------
STUDIES ON ADVANCED ¥ASTE TREATMENT
CONTENTS
Page
1. Laboratory Tests 130
2. Yokosuka Pilot Plant Studies 1^1
J. Kyoto Pilot Plant Studies 157
4. Evaluation of Treatability Depending Upon Water
Quality Matrices 175
129
-------
1. Laboratory tests
1.1 Lime precipitation in municipal wastewater
At the Second U.S. -Japan Conference on Sewage Treatment Technology
held in Washington, B.C. and Cincinnati, Ohio in 1972, some of the
results of laboratory test concerning with lime precipitation in
municipal waste water along with an outline of a pilot plant
installed at the Shita-machi Sewage Treatment Plant in Yokosuka
and some of pilot-scale investigation results were reported.
These results are briefed as follows:
a. In pH of wastewater was raised up more than 10.5 by lime dose,
the concentration of total phosphorus in the supernatant could
be reduced to lower than 0.5 mg/1 regardless the wastewater,
that is, raw sewage, primary or secondary effluent.
b. The lime dose required to raise pH of the wastewater more than
11.0 was as shown in Table 1.1.
c. The effects of the reduction of phosphorus by lime precipi-
tation on the concentration of magnesium in wastewater were
as follows;
While the reduction of metaphosphate depended on the reduction
of magnesium hydroxide, the reduction of orthophosphate was
not related to the reduction of magnesium hydroxide.
d. Using an X-ray diffraction method, it was disclosed that the
final products of calcium and phosphate reaction in lime pre-
cipitation process are calcium hydroxylapatite Ca
Scales of calcium carbonete sampled from inside of some tanks
at the Yokosuka pilot plant was identified by both electronic
microscopy and X-ray diffractmetry to be a mixture of aragonite
and calcite. These scales assumed a slab form on the inside
wall and a granular shape on the water in the tanks.
130
-------
The Ministry of Construction gave birth to a project team compris-
ing engineers of eight municipalities which are considered to
implement the advanced waste treatment of their own municipal waste-
water in the future. It is called "Joint Working Group on Advanced
Wastewater Treatment Technology" and undertakes the collection and
exchange of information, laboratory and pilot plant tests data
gathering and discussion among members over findings. From Tokyo
Metropolitan Government, Yokohama City, Nagoya City, Kyoto City,
Nagoya City, Kyoto City, Osaka City, Kobe City, Kita-kyushu City
and Yokosuka City have come two engineers each to participate in
JWGAWTT. From April, 197-2 to March, 1973, participate in JWGAWTT.
From April, 1972 to March, 1973, the project team members had
been mostly involved in laboratory tests of lime precipitation
using primary influent and secondary effluent of their own facilities.
During this one-year period, the laboraty tests were conducted twice
- one in Summer and one in Winter. In the laboratory tests, the
conditions were normalized that the flush mixing was set at 150 rpm
for 5 min., flocculation at 30 rpm for 25 min. and the settling for
30 min.
The results of analyses of the samples subjected to the laboratory
tests are given in Tables 1.2 and 1.3-
As will be clear from tables, the concentration of total phoshorus
in the primary influent was in the range of 1.34 mg/1 to 69.8 rug/I,
while 80 per cent of the samples of influent showed a concentration
of total phosphorus of less than 10 mg/1. On the other hand, the
concentration of total phosphorus in the secondary effluents ranged
from 0.37 mg/1 to 5-38 mg/1, whereas 72 per cent of the samples
of the secondary effluents showed a concentration of total phosphorus
of-not more than 1 mg/1. These values are by far lesser than those
reported in the United States.
The test results are summarized below:
a. All of the samples consisting of primary influents and secondary
effluents were normalized to have a pH value of 10.9 to 11.5
131
-------
before precipitation. In this case, 43 per cent of the samples
less than 0.4 mg/1 of total phosphorus concentfation in the
supernatant. On the other hand, the concentration of total
dissolved, phosphorus in the supernatant obtained from 68 per
cent of the samples was less than 0.4 mg/1.
In the tests, there were found no definite relationship between
the concentration of total phosphorus in the samples and the
concentration of total phosphorus and total dissolved phosphorus
in the supernatants.
The concentration of total phosphorus and the concentration of
total dissolved phosphorus, both in the supernatant were com-
pared to each other by the same treatment facilities.
It was disclosed that the lime-precipitated secondary effluent
generally showed lower concentration in both total phosphorus
and total dissolved phosphorus than the limeprecipitated primary
influent. (As regards the total phosphorus, 13 out of 18
samples showed lower values, and as regards total dissolved
phosphorus, 14 out of 15 samples showed lower values.)
Thus, it was concluded that in order to reduce the concentration
of total phosphorus the lime precipitation of the secondary
effluent should be preceded by biological treatment of the
primary influent. (See Table 1.4)
The concentration of total phosphorus and the concentration
of the total dissolved phosphorus, both in the supernatant,
were compared to each other by treatment plant and by season.
The comparative study revealed that the tests conducted in the
summer when water temperature is high goes a long way toward
reducing the concentration of both the total phosphorus and
total dissolved phosphorus rather than the tests in the winter
when water temperature is low.
(As regards the total phosphorus, 13 out of 18 samples showed
lower values, and as regards the total dissolved phosphorus
15 out of 18 samples showed lower values.) (See Table 1.5)
132
-------
d. It was also made clear that the lime dose was necessary to raise
pH of the primary influent and secondary effluent up to 11.0
changes with the buffer capacity of wastewater samples.
M-alkalinity of the samples was 50 to 200 mg/1, and the lime
dose required was 100 to 400 mg/1.
e. Primary influent and secondary effluent showed a magnesium
concentration of not more than 60 mg/1. The magnesium in
wastewater could be transformed into magnesium hydroxide by
adjusting the samples' pH up to 11.0.
Magnesium hydroxide affected as a flocculation aid, achieving
a substantive result in removing total suspended phosphorus
in lime-precipitated supernatant.
It was found that the residue of the total suspended phosphorus
in lime-precipitated supernatant is related to the concentra-
tion of magnesium hydoroxide produced.
f. Lime-precipitated sludge being rich with magnesium hydroxide
presents a low settleability, and increases its volume.
(See Fig. l.l)
g. The increase in pH is depressed by the increase in magnesium
concentration in wastewater.
In order to carry out lime precipitation of wastewater contain-
ing much magnesium, the lime dose should be enough to cover
up OH which is required for the conversion of magnesium-ion
into magnesium hydroxide.
h. Increase in calcium concentration in wastewater due to lime
dosage varied largely in the range of 20 to 140 mg/1. (lime
dose: 400 mg/1)
This increase had a correlation with M-alkalinity in waste-
water; the higher the M-alkalinity was, the lower the increase
in calcium in the supernatant resulted.
133
-------
i. The reduction of organic matter in wastewater by lime precipi-
tation was 30 to 70$ for the primary influent and 20 to 50$
for the secondary effluent, both in EMh04-COD(CODMn) index.
1.2 Investigations now in progress
a. Chemical precipitation of municipal wastewater by metal salts.
JWGAWTT and the Public Works Research Institute are carrying
cut some laboratory tests of chemical precipitation of'removing
phosphorus, suspended solids and organic matter by making dose
of three kinds of coagulant - aluminum sulfate, ferric chloride
and a mixture of aluminum salt and ferric salt (which is avail-
able on market and costs less than aluminum sulfate).
b. Reduction of ammoniacal nitrogen by break-point chlorination.
In the search for the design criteria of a break-point chlori-
nation process to be built in the Kyoto advanced waste treat-
ment pilot plant, the experimental work has been pushed forward.
1.3 Aspects of future studies
a. With a laboratory lime recalcining furnace installed at the
Public Works Research Institute, experimental investigations
will be conducted as to recovery and reuse of dewatered lime-
precipitated sludge. This furnace will be a modification of
a multiple hearth furnace of which only a single hearth is
taken out.
b. Also, the same furnace will be used for the regeneration of
exhausted granular activated carbon laboratory test.
c. Fundamental investigations on reverse osmosis are planned to
be carried out by making use of a flat plate type laboratory
use reverse osmotic equipment.
d. For the reduction of phosphate and nitrate in wastewater,
ion-exchange method will be examined.
134
-------
Table 1.1 Lime Dosage to raise pH up to 11.0
ing I'1 as Ca(OH)2
Item
Range
Average
Raw Sewage with
Digester
Supernatant
172 ~ 396
293
Raw
Sewage
135 - 450
323
Primary Sedi-
mentation
Tank Effluent
146 ~ 401
255
Secondary
Sedimentation
Tank Effluent
146 ~ 296
235
135
-------
Table 1.2 Primary Influent Quality Subject to the Laboratory Tests
Season
Summer
Winter
City
Tokyo
Yokohama
Yokosuka
Hagoya
Kyoto
Osaka
Kobe
Kita-Kyusyu
Plant
Ochiai
Chubu
Hokubu
Uwa-Machi
Shita-Machi
Meijo
Chitose
Toba
Kisshoin
Nakahama-
Nishi
Sumiyoshi
Chubu
Higashinada
Hiakari
Kogozaki
Mean
Range
Tokyo
Yokohama
Yokosuka
Nagoya
Kyoto
Osaka
Kobe
Kita-Kyusyu
Ochiai
Chubu
Shita-Machi
Meijo
Toba
Hakahama-
Nishi
Sumiyoshi
Chubu
Hiakari
Kogozaki
Mean
Range
Mean
Range
¥ater
Temper-
ature
(°c)
18.9
21.5
21.5
22.0
22.6
22.0
21.0
23.5
23-3
23-0
23.8
23-2
23-5
22.7
22.0
22.3
18. 9~
23.8
10.0
15.6
15-0
12.5
14.3
15.3
16.0
13.8
14.0
13-7
14.1
10.8-
16.8
-
-
pH
7.50
7.39
7.20
7-40
7.25
7-14
7.00
7-31
7.37
6.90
7.28
8.34
7.30
7.40
6.95
7.32
6.90-
8.34
7.45
7.70
7.67
8.40
7-52
7.28
7.30
7.60
8.55
7.16
7.66
7.16-
8.40
7.46
6.90-
8.40
P
(mg/l)
4.46
4.18
2.18
1.84
3-98
8.59
4.33
3-23
2.61
10.0
26.9
7.90
5-30
23-3
4.02
7.52
1.84-
26.9
5-49
4.68
1.93
10.0
1-34
9.80
69.8
9.80
6.84
4-30
12.4
1.34-
69.8
9-47
1.34-
69.8
P.D
(mg/l)
4.10
2.92
0.160
1.02
2.60
6.85
1.57
2.12
2.06
2.66
2.13
5.60
3-40
3.26
2.61
2.87
0.160-
6.85
4-56
3.88
1.77
9.76
1.12
3-30
3.18
7.55
1.15
0.900
3-72
0.900-
9.76
3.21
0.160
9-76
CODun
(mg/l)
85.0
43-3
37.7
45.1
77.0
77.5
34-2
74.1
53-4
106
170
109
62.6
445
46.6
97.8
34.2-
445
143
57.0
22.0
144
53-3
115
322
212
148
248
146
22.0-
322
117
22.0-
445
1)
Tur-
bidity
(mg/l)
111
116
71.1
22.0
62.0
396
50.0
-
272
975
260
90.0
1,300
85.0
293
50.0-
1,300
170
268
50.5
540
343
1,824
200
750
1,800
661
50.5-
1,824
444
50.0-
1,824
Ca
(mg/l)
27.2
38.5
44.0
34-0
140
20.0
70.0
29-4
24.7
49-0
48.5
41.0
36.3
54-4
39-5
46.4-
20.0-
140
14.9
31.0
-
9.6
14.8
39.9
24.5
41.0
22.0
24.7
9.6-
41.0
38.9
9.6-
140
Mg
(mg/l)
8.5
43-0
12.0
23-1
382
42.7
96.0
9.2
7.4
4.9
15-2
67.0
46.4
43-7
13.8
54-3
4.9-
382
12.7
30.7
-
6.1
-
5.8
30.1
21.7
41.9
9.30
19-8
5.8-
41.9
42.3
4.9-
382
Ill-
Alkali-
nity
(mg/l)
135
141
154
111
98.5
113
132
81.5
124
87.5
144
20.1
174
243
155
128
20.1-
243
90.5
148
57
220
168
86.0
197
181
198
151
150
57-
220
137
20.1-
243
l) Turbidity in mg-kaoline/1
* Samples collected at 9:30 a.m.
136
-------
Table-1.3 Secondary Effluent Quality Subject to the Laboratory Tests
Season
Summer
Winter
City
Tokyo
Yokohama
Yokosuka
Nagoya
Kyoto
Osaka
Kobe
Kita-Kyusyu
Plant
Ochiai
Chubu
Hokubu
Uwa-Machi
Shita-Machi
Meijo
Chitose
Toba
Kisshoin
Nakahama-
Nishi
Sumiyoshi
Chubu
Higashinada
Hiakari
Kogozaki
Mean
Range
Tokyo
Yokohama
Yokosuka
Nagoya
Kyoto
Osaka
Kobe
Kita-Kyusyu
Ochiai
Chubu
Shita-Machi
Meijo
Toba
Nakahama-
Nishi
Sumiyoshi
Chubu
Hiakari
Kogozaki
Mean
Range
Mean
Range
Water
Temper-
ature
(°c)
20.3
22.2
22.0
22.5
22.0
21.5
21.0
23.6
23.3
23.0
23.7
24.9
23.8
22.9
21.3
22.5
20.3-
24.9
16.3
14.5
15.8
13.6
14-7
14.5
13.8
17.1
12.6
14.6
14.3
11.3-
17.1
-
-
pH
7.00
7. '05
7.30
7.40
7.35
7.21
7.10
7.55
7,82
6.80
7.31
6.88
7.80
7.03
7.00
7.24
6.80-
7.82
7.31
7.50
7.08
7.00
7.05
7-38
7.52
7.00
7-30
7.13
7.27
7.00-
7.52
7-25
6.80-
7.82
P
(mg/1)
0.780
1.04
1-43
0.450
0.756
1.47
0.260
0.480
0.548
1.33
0.950
5.38
3-38
2.90
1.62
1.52
0.260-
5.38
0.370
2.60
0.713
4.16
0.969
3.23
0.322
3.06
0.859
1.62
1.79
0.370
4.16
1.63
0.260-
5.38
P.D
(mg/1)
0.670
0.955
1-34
0.389
0.679
0.718
0.240
0.480
0.350
0.888
0.320
4.28
2.60
2.74
1.42
1.20
0.240-
4.28
0.281
2.40
0.690
3.60
0.908
2.28
0.119
2.86
0.782
1.40
1.53
0.119-
3.60
1-33
0.119-
4.28
CODMn
(mg/1)
16.5
5-5
6.8
3-5
7.4
25-3
8.2
14.0
36.8
16.8
17.3
32.8
17.6
5.3
5.0
14.6
3-5-
36.8
11.0
9-9
4.8
23.6
22.8
20.4
14.3
21.9
11.3
11.9
15.2
4.8-
23.6
14.8
3.5-
36.8
1)
Tur-
bidity
(mg/1)
-
4.4
3.1
1.9
1.4
46.4
3.0
21.5
30.6
40.0
14.0
15.0
7.5
15.7
1.9-
46.4
11.0
11.0
2.5
50.8
-
26.3
17.8
20.0
15.2
21.2
19.5
2.5-
50.0
17.3
1.9-
50.8
Ca
(mg/l)
25.6
40.0
31-3
30.0
156
12.8
76.0
26.9
23-3
22.0
48.5
52.6
34-3
60.0
30.2
44-6
12.8-
156
15.3
35-3
-
-
-
16.7
40.8
25.1
68.1
20.4
31.7
15.3-
68.1
40.1
12.8-
156
Mg
(mg/1)
5.8
34-0
10.0
12.2
484
17.0
161
8.4
8.1
3-4
17.4
115
28.4
31.6
7.2
62.9
3-4-
484
10.6
37-3
-
-
2.9
30.4
32.8
33-3
9.9
22.5
2.9-
37.3
50.0
2.9-
484
M-
Alkali-
nity
(mg/l)
99-0
72.3
65.0
74.0
97.0
83.0
100
77.3
89.9
75-0
169
77-3
186
83.0
38.0
92.4
38.0-
186
83-5
97.5
39.5
147
166
81.0
123
168
213
105
122
39-5-
213
104
38.0-
213
l) Turbidity in mg-kaoline/1
* Samples collected at 9 = 30 a.m
137
-------
Table 1.4 Phosphorus and Dissolved Phosphorus in the Lime
Coagulated Supernatants of Primary Influent and
Secondary Effluent (Summer Samples)
Plant
Ochiai
Chubu
( Yokohama )
Hokubu
Dwa-Machi
Shita-Machi
Meijo
Chitose
Toba
Kisshoin
Wakahama-Ni shi
Sumiyoshi
Chubu (Kobe)
Higashinada
Hiakari
Kogozaki
PH
11.70
11.70
11.00
10.80
11.41
11.30
11.51
11.42
11.21
10.65
11.71
11.66
10.9
10.5
12,22
12.25
12.16
12.02
11.3
11.2
11.41
11.04
11.44
11.14
!!•. 62
11.42
10.52
10.24
11.45
11.40
Ca(OH)2
(mg/l)
400
400
400
200
400
300
400
400
400
400
400
400
400
400
400
400
400
400
400
400
400
300
400
300
400
400
400
100
400
200
P
(mg/l)
0.25
0.07
0.052
0.030
0.062
0.041
0.100
0.059
0.164
0.033
0.870
0.278
0.20
0.090
0.350
0.201
0-770
0.195
0.72
0.25
0.66
0.023
0.148
0.067
0.095
0.132
0.822
0.456
0.208
0.248
P.D
(mg/l)
0.13
0.02
0.020
0.008
0.028
0.010
0.052
0.024
0.137
0.017
0.160
0.222
0.11
0.09
0.165
0.152
0.205
0.090
0.50
0.14
0.50
0.07
0.141
0.041
0.066
0.030
0.254
0.104
0.164
0.040
Secondary Effluent/
Primary Influent
as P
0.28
0.58
0.66
0.59
0.20
0.32
0.45
0.57
0.25
0.35
0.03
0.45
1.39
0.55
1.19
as P.D
0.15
0.40
0.36
0.46
0.12
1.39
0.82
0.92
0.44
0.28
0.70
0.29
0.45
0.41
0.24
* Upper figures in colomns : primary influent
* Lower figures in colomns : secondary effluent
138
-------
Table 1.5 Phosphorus and Dissolved Phosphorus in the Lime Coagulated Supernatants
of Summer Samples and Winter Samples
Plant
Ochiai
Chubu
(Yokohama)
Shita-Machi
Mei jo
Toba
Sumiyoshi
Nakahama-Ni shi
Hiakari
Kogozaki
Primary Influent
pH
11.70
11.88
11.00
11.30
11.21
11.24
11.34
11.52
11.03
11.42
11.41
11.44
11.30
11.57
10.52
11.15
11.45
11.73
Ca(OH)2
(mg/1)
400
300
400
300
400
200
300
400
200
300
400
400
400
200
400
300
400
300
P
(mg/1)
0.25
0.310
0.052
0.28
0.164
0.408
4-21
4.16
1.45
0.806
0.66
0.945
0.72
1.81
0.822
0.323
0.208
0.409
P.D
(mg/1)
0.13
0.212
0.020
0.23
0.137
0.325
0.180
3.12
0.485
0.570
0.50
0.688
0.50
0.635
0.254
0.056
0.164
0.158
Summer/Winter
as P
0.80
0.18
0.40
1.01
1.79
0.69
0.39
2.54
0.50
as P.D
0.61
0.09
0.42
0.06
0.84
0.73
0.79
4.54
1.04
Secondary Effluent
pH
11.70
11.84
11.40
11.8
10.65
11.65
11.48
11.60
11.10
11.43
11.45
11.55
11.2
11.50
10.68
10.79
11.14
11.30
Ca(OH)2
(mg/1)
400
300
400
400
400
400
300
400
150
400
400
300
400
150
150
400
150
400
P
(mg/1)
0.07
0.093
0.008
0.03
0.033
0.068
0.340
1.680
0.284
0.580
0.05
0.053
0.25
2.120
0.205
0.091
0.840
0.045
P.D
(mg/1)
0.02
0.047
0.0
0.03
0.017
0.040
0.216
1.480
0.280
0.452
0.03
0.049
0.14
0.900
0.020
0.062
0.166
0.050
Summer/Winter
as P
0.75
0.27
0.49
0.20
0.49
0.94
0.12
2.25
18.69
as P.D
0.43
0
0.43
0.15
0.62
0.61
0.16
0.32
3.32
CO
* Upper figures in columns : Summer samples (mean water temp. 22.4°C)
* lower figures in columns : winter samples (mean water temp. 14.2°C)
-------
0
ftf)
CO
0
H
-P
-P
0
CO
o
O
/O
Magnesium Concentration in Sample (mg/l)
Fig. 1.1 Influence of Magnesium on Sludge
Volume and pH of Lime Treated
Wastewater ( Ca(OH)2 = 400 mg/l )
140
-------
2. Yokosuka pilot plant studies
2.1 Operating conditions of pilot plant
A flow diagram of the pilot plant is shown in Fig. 2.1, and its
operating conditions are given in Table' 2.1.
The lime dose was 300 mg/1 as hydrated lime during the period from
June 22, 1972 to March 22, 1973 (hereinafter referred to as "A"
series) and 1,000 mg/1 as hydrated lime during the period from
May 9, 1973 to October 13, 1973 (hereinafter referred to as "B"
series).
pH of the wastewater after adjustment by lime dose was 10.45 on
the average in "A" series and 10.95 on the average in "B" series.
2.2 Characteristics of pilot plant influent
Shita-machi Sewage Treatment Plant, Yokosuka, where the pilot plant
under discussion is installed, takes in domestic sewage as well as
wastes from marine products processing factories which use much
seawater. Also, seawater permeates into the sewar pipes laid along
the coastal line. Therefore, the influent to the treatment plant
contains significant amount of seawater, and magnesium concentra-
tion is relatively high. In the lime precipitation, "this high
concentration of magnesium restrains the rise of pH; even when as
much as 1,000 mg/1 of hydrated lime was dosed, pH of wastewater
after pH adjustment was 10.95 on the average.
Yokosuka city is planning to reuse the treated effluent as industrial
water in the future, and is in the process of investigating the
sewer system reconstruction in order to prevent infiltration of
seawater.
The lime precipitation of wastewster containing much magnesium
brings about diversified effects- due to a large amount of precipi-
tated magnesium hydroxide as already described in Section 1.1.
"Lime precipitation in municipal wastewater.tf
141
-------
Namely, magnesium hydroxide acts as a coagulant aid, while it retards
the rise of pH of wastewater (see Fig. 2.2), forms light floes with
poor settleability, sludge thickening rate and dewaterability, and
may cause the accumulation of magnesium in recalcined lime when lime
is recovered.
The concentration of magnesium in the wastewater handled by Shita-
machi Sewage Treatment Plant is 300 to 400 mg/1 as against about
10 mg/1 in the typical municipal wastewater in Japan.
2.3 Outline of the test results
Table 2.2 shows the mean values and ranges of influent and effluent
quality and average removal concerning "A" and "B" series at the
pilot plant.
Average suspended solids concentration of the influent were 5-4 mg/1
in "A" series and 2.6 mg/1 in "B" series. The turbidity was 5.8
mg/1 and 3-6 mg/1, respectively.
On the other hand, suspended solids and turbidity of the lime
sedimentation tank effluent were much more than those in the in-
fluent; namely,- the suspended solids were 12.3 times as much in "A"
series and 13-9 times as much in "B" series. This is because the
precipitates, such as calcium carbonate and magnesium hydroxide,
could not be settled down to the level of the suspended solids of
the influent.
In the calcium carbonate settling tank, a considerable portion of
suspended solids and turbidity was removed. In "A" series, suspended
solids and turbidity in the effluent of the calcium carbonate
settling tank was 5-0 per cent and 7.8 per cent of those in the
effluent of the lime sedimentation tank.
In the dual-media filter, both suspended solids and turbidity were
removed quite well. It is worthwhile that the removal of suspended
solids was almost 100 per cent for both "A" and "B" series. The
turbidity of the effluent of the dual-media filter was 0.3 mg-
Kaoline/1 for "A" series and 0.08 mg-Kaoline/1 for "B" series.
142
-------
The total phosphorus contents of the influent was 1.21 mg/1 for "A"
series and 1.43 mg/1 for "B" series. The concentration of total
phosphorus of the lime sedimentation tank effluent was 0.344 mg/1
for "A" series and 0.125 mg/1 for "B" series. pH of the lime
sedimentation tank effluent was 10.28 and 10.81 for "A" and "B"
series, respectively.
The removal of total phosphorus by lime precipitation in "A" series
was lower than that in "B" series. The total phosphorus in the
effluent of the calcium carbonate settling tank was 0.114 mg/1 or
90.5 per cent removal in "A" series. And the total phosphorus in
the effluent of the dual-media filter was 0.102 mg/1 and 0.04 mg/1
or 91-6 per cent and and 97.1 per cent for "A" and "B" series,
respectively.
The ratio of orthophosphate to the total phosphorus was 87 per cent
for both' "A" and "B" series so long as the pilot plant influent
was concerned. On the contrary, the ratio of orthophosphate in the
effluent of dual-media filter was 64 per cent and 77 per cent for
"A" and "B" series, respectively.
CODcr an<* TOG in the pilot plant influent was 40.2 mg/1 and 40.4
mg/1 for "A" series and 41-9 mg/1 and 49-2 mg/1 for "B" series,
respectively. CODcr &n(i TOG were removed little by little in each
unit process. The over-all removal of CODQr throughout the whole
processes was 44-3 per cent and 50.0 per cent for "A" and "B" series,
respectively, and that of TOG was 25-3 per cent and 28.9 per cent,
respectively, with the result that the removal of CODQr was larger
than that of TOG.
The regression line of COD0r with respect to TOG was found as
follows,
CODCr = 0.673 • TOG + 5-90
The correlation coefficient was 0.761.
The total nitrogen in the pilot plant influent was 7-12 mg/1 and
7.83 mg/1 for "A" and "B" series, respectively.
143
-------
The over-all removal of the total nitrogen throughout the whole
processes was 10.8 per cent and 30-3 per cent for "A" and "B" series^
respectively.
The ratio of ammoniacal nitrogen (NH^-N) to the total nitrogen in
the pilot plant influent was 19 per cent and 50 per cent for "A"
and "B" series, respectively. The ratio was 7.6 per cent and 36
per cent for "A" and "B" series, respectively, in the dual-media
filter effluent.
The removal of ammoniacal nitrogen by the ammonia stripping tower
was as low as 31.6 and 39-9 per cent for "A" and "B" series,
respectively. This may be ascribable to the fact that the air-liquid
ratio was as small as 700 to 2,000. The air-liquid ratio was first
designed to be in the range of 1,000 to 4,000 M^-air/m^'liquid, but
the actual head' loss in the tower exceeded the estimated value to
reduce it to the aforesaid value. At the air-liquid ratios, 700
and 1,500, the removal of ammoniacal nitrogen was 20 per cent and
50 per cent, respectively. The*variation of liquid temperature was
in the range of 15°C to 23°C, during the period of the experiment,
and does not seem to have significant effect on the removal of the
ammoniacal nitrogen.
2.4 Considerations to phosphorus removal
The mean values of total phosphorus and their standard deviations
are related to the mean liquid temperatures of the dual-media
filter effluent for "A" series as shown in Fig. 2.3.
The figure indicates that with the lime dose of 300 mg/1, the higher
the liquid temperature is, the lower becomes the concentration of
the total phosphorus in the dual-media filter effluent and also
the smaller becomes the fluctuations.
Comparing "A" series (mean liquid temperature: 22.7°c) with "B"
series (mean liquid temperature: 13.0°C) in the figure, it appears
that an increase of about 10 degrees centigrade in liquid temper-
ature acts to reduce the total phosphorus from 0.128 mg/1 to 0.050
144
-------
mg/1 and to increase the standard deviation from 0.081 mg/1 to
0.25. mg/1.
In "A" series, where lime dose was 300 mg/1, the effects of the
overflow rate of lime sedimentation tank and sludge recirculation
ratio upon the removal of phosphorus are shown in Table 2.3. As
may be seen in Table 2.3> a lowering of the overflow rate of the
lime sedimentation tank and the application of sludge recircutation
not only reduce the total phosphorus in the effluent of the lime
sedimentation tank, but also make its fluctuation smaller.
In "B" series, where lime dose was 1,000 mg/1, there were little
or no effects of the overflow rate and sludge recirculation.
As evidenced by the comparison between "A" series and "B" series,
the change of lime dose from 300 mg/1 to 1,000 mg/1 resulted in the
reduction of total phosphorus in the effluent both of the lime
sedimentation tank and of the dual-media filter, and diminished the
fluctuation of the total phosphorus concentration.
2.5 Scale formation of calcium carbonate
In this pilot plant, development of scale of calcium carbonate was
noticed. It spreaded from the flush mixing tank to flocculation
tank, and was remarkable in winter rather than in summer. Photo
2.1 shows a formation of scale on the flush mixing tank. 'In winter,
development of scale was so serious that the predetermined flow
rate for the pilot plant operation could not maintain owing to
resultant reduction in the cross-sectional area of a pipe connect-
ing each tank and increase of roughness inside of the pipe. When
the scale development was most serious,, the predetermined flow
rate of 9 m3/hr could be maintained only for the first 8 days
after cleaning, with gradual decrease afterwards, and on the 16th
day the flow rate was decreased to about 1 nK/hr.
Table 2.4 lists the compositions of scale formed in the tanks and
pipes of the pilot plant. For the preparation of the table, 10
samples were collected from the extension between the flush mixing
tank to the ammonia stripping tower and analyzed.
145
-------
No significant difference was found in the analytical results of
10 sample.
CaCO^ equivalent of CaO listed in the table was 89\4 per cent,
signifying that calcium carbonate accounted for .abou^ 90 per pent
of scale compounds.
In "A" series (lime dose: 300 mg/1; average pH value of ammonia
stripping tower effluent: 10.2&; liquid temperature: 10° to
24°C), no scale formation was noticed, except for a slight deposi-
tion over the filler surfaces in the ammonia' stripping tower.
In "B" series, on the other hand, scale formation in, "B" series
(lime dose: 1,000 mg/1; average pH value of the ammonia stripping
tower effluent: 10.81; and liquid temperature: 15° to 27°C) was
noticeable; during 5 months of operation, scale depbsition over
the filler surfaces was 0..5 to 1.5 cm in thickness.
In the lime precipitation-ammonia stripping processes, the most
serious problems is considered the scale formation.
Improvements taken so far for the pilot plant against scale problem
are as follows.
a. Connection between tanks was changed from pipe system to open
channel type for ease of monitoring and removing scale.
b. A part of the open channel was attached with a scale preventive
device which applys feeble current and magnetic field. Its
functional effects are under study.
2.6 Investigations now in progress
The Investigation now in progress are compared with those in the
past in the following.
a. In the past, powdered lime was dosed in the form of slurry,
while at present quick lime is slaked and then dosed in the
flush mixing tank.
b. In order to improve settleability in the lime precipitation
tank, an anionic polymer is dosed as the flo'cculant aid.
146
-------
c. Metal salts precipitation process is being studied in parallel
with the lime precipitation process.
d. Granular activated carbon adsorption contractors are provided
following the dual-media filter.
e. Capacity of ventilator for the ammonia stripping tower is
increased to increase air-liquid ratio up to 2,000 to 5,000.
f. Scale preventive device is installed for lime precipitation
process.
A part of the results of the experiments now under way is summarized
in Table 2.5.
2.7 Aspects of future studies
The facilities and investigations planned for the future are listed
below.
a. Rearrangement of piping to transfer metal salts precipitated
effluent to one of the existing dual-media filters.
b, Installation of control devices which are able to regulate lime
and metal salts coagulants dose in response to the changes in
the quality fluctuations of influent.
The lime dose will be controlled depending on either pH or
alkalinity in the influent, and also metal salts will be
controlled depending on either concentration of phosphate in
influent, pH of liquid in flush mixing tank or turbidity of
sedimentation tank effluent. Control system for the pilot
plant is still undecided.
c. Installation of centrifuge for sludge dewatering. Operating
conditions of the centrifuge, especially for lime sludge
dewatering to separate calcium carbonate from other compounds
will be determined.
147
-------
Lime
(Ca(OH)2)
Influent
(Secondary
effluent)
Holding Measuring
Tank Tank
Plush Mixing Tank
Flocculation Tank
Sludge Holding Tank
Lime Sedimentation Tank
oo
Holding
Tank
M
pa Qnr*"i 1
nj3- T-
fn"! r)i riv
Ammonia
Stripping Tower
Pump Measuring Recorbo-
Tank nation
Tank
Calcium Neutralization
Carbonate Tank
Settling
Tank
Effluent
Holding Tank
Dual-Media Measuring
Filter Tank
Pig. 2.1 Plow Diagram of Yokosuka
Advanced ¥aste Treatment
Pilot Plant
-------
Table 2.1 Operation Conditions of the Pilot Plant
Pilot Plant Influent
Lime Sedimentation
Tank
Ammonia Stripping
Tower
Calcium Carbonate
Settling Tank
Dual-Media Filter
Secondary Effluent
Flow Rate
Overflow Rate
Detention Time
Sludge Recirculation
Ratio
Flow Rate
Hydraulic Loading
Air-liquid Ratio
Flow Rate
Overflow Rate
Detention Time
Flow Rate
Filtration Rate
6-9 m3/h
30 ~ 50 m3/m2/d
2.3 ~ 1.5 h
0 ~ 20 %
3~8.5 m3/h
60 ~ 200 ni3/in2/d
700 ~ 2000 m^.air/
m3 liquid
2.5~6 m3/h
30 ~ 80 m3/m2/d
1.8 ~ 0.62 h
2-5.5 m3/h
120 - 350 m/d
149
-------
Secondary Effluent of "0" Sewage
Treatment Plant; Mg = 10.6 mg/1
Secondary Effluent of Shita-Machi
Sewage Treatment Plant; Mg = 300 mg/1
H2S04
NaOH
Titration
geq.)
Fig. 2.2 Titration Curves for Wastewaters of Different
Magnesium Concentration
150
-------
Table 2.2 Mean
Range of Water Quality in Each Process, and Accumulated % Removal
tn
mean
PH
range
, mean
1)
Turbidity range
(mg/i; removal^)
mean
Suspended
Solids ran«e
(mg/l) removal '
mean
(mg/l) ranse
removal ^
mean
/ , x range
(DMT/I) b ,
removal^
mean
P,ortho,
range
/ ...,,/T \ .., r-,\
W/1^ removal"^
mean
TOC
(nWl) range .
removal'' I
mean
UUi)Cr
range
1 mr-/1 1 M
^me/1' removal^
mean
(mg/l) range
removal '
mean
, , ,, range
(ms/1) ° .
removal'' '
Influent
(Secondary
Effluent)
6.96
6.90-
7-90
5.8
0.8-
33-5
-
5.4
0.4-
48.0
-
1.21
0.403-
3.21
_
-
-
-
1.05
0.503-
2.48
-
40.4
2.4-
114
-
40.2
4.0-
104
-
7.12
2.12-
11.8
-
1,36
0 -
7.41
-
(1972
lime
Sedimen-
tation
Tank
Effluent
10.28
9.30-
11.20
39.8
2.0-
510
-
66.5
8.0-
400
-
0.344
0.024-
3.28
71.5
-
-
0.352
0.026-
3.68
66.5
37.2
3.3~
94.8
7.9
38.1
4.0-
152
2.7
7.08
2.95-
12.3
0.6
1.33
0 -
6.22
2.2
A Series
.6.12 - 197
.Ammonia
Stripping
Tower
Effluent
9.90
9.20-
10.75
-
-
-
_
-
-
-
-
_
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
0.91
0 -
4.35
33.1
3-3.22)
Calcium
Carbonate
Settling
Tank
Effluent.
8.43 •""•'•
6.00-
10 . 60 .-
3.1'
0.8-
20.5
46.5
3.3
0 -
22.0
38.9
0.114
0 -
0.705
90.5
-
-
-
0.075
0 -
0.353
92.9
30.2
1.4-
86.4
25.3
30.9
2.4-
99.2
23.1
-
-
-
-
-
-
Dual-
Media
Filter
Effluent
7-95
6.30-
10.50
0.3
0 -
21.0
94.8
0
0
100
0.102
0.475
91.6
-
-
-
0.073
0 -
0.394
93.0
30.2
6.2-
89.2
25.3
22.4
3.2-
60.8
44.3
63.9
6.54-
10.5
10.3
0.48
0 -
3-73
64.7
Influent
(Secondary
Effluent)
7.65
6.90-
9.15
3-6
1.5-
11.0
-
2.6
0.4-
8.2
-
1.43
0.702-
4.35
_
1.33
0.630-
2.87
-
1.24
0.450-
2.80
-
49-2
6.9~
78.9
-
41.9
13.8-
88.9
-
7.83
3-49-
9.57
_
3.89
0.51-
7.61
-
(1973
Lime
Sedimen-
tation
Tank
Effluent
10.81
10.00-
12.40
23.8
3.0-
130
-
36.1
7.0-
68.0
-
0.125
0.004-
0.696
91.3
0.102
0.006-
0.595
92.3
0.086
0.004-
0.486
93.1
39.1
14.9-
96.5
20.5
33.6
11.7-
68.9
19.8
-
-
_
4.14
1.10-
6.03
-
B Series
.5.9 ~ 1973
Ammonia
Stripping
Tower
Effluent
10.29
8.70-
12.50
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
_
2.49
0.66-
3.82
35-9
.10.13)
Calcium
Carbonate
Settling
Tank
Effluent
9.65
6.38-
11.90
6.0
0.2-
45.5
-
6.2
0 -
40.0
-
-
-
-
-
-
-
-
-
-
31.2
12.5-
58.1
36.6
24.6
9.36
42.0
41.3
-
-
_
_
-
-
Dual-
Media
Filter
Effluent
7.24
5.70-
10.90
0.08
0 -
0.65
97.8
0
0
100
0.042
0.004-
0.201
97.1
0.035
0.006-
0.178
97.4
0.027
0.002-
0.400
97.8
35.0
9-7-
70.1
28.9
21.0
6.1-
54.6
50.0
5.46
2.13-
8.15
303
1.99
0.70-
3-38
48.8
l) Unit of Turbidity is mg'kaoline/1.
2) % removal is based on influent concentration.
* M-alkalinity of influent were 92 mg/l (67-119) in "A" series and 64 mg/l (30-88) in "B" seri
* pH of wastewater after pH adjustment were 10.45 (10.01-10.81) in "A" series and 10.95 (10.00'
* MLSS in flocculation tank were 994 mg/l (106-4,180) in "A" series and 1,550 mg/l (572-3 180)
es.
'-12.60) in "B" series.
in "B" series.
-------
0,24
a 20
cut,
0,12
0.08
0.04
O O
9 P
_ Standard
Deviation
0,08
406 JT
a
o
•H
-P
cd
0.^4 S
PI
0.02
O
CO
/2 /4 /6 /8 20 22 24
Water Temperature (°C)
Fig. 2.3 Relationships between Total Phosphorus
in Dual-Media Filter and its Standard
Deviation, and Water Temperature
("A" series)
152
-------
Table 2.3 Effects of Overflow Rate of Lime Sedimentation Tank and Sludge Recirculation Rate on Phosphorus Removal
Case
Al
A2
A3
Flow Rate
(mVh)
9
6
8
Sludge
Recircu-
lation
Ratio ($)
0
0
20
Overflow
Rate
(mVni2-cO
50
33-3
44.4
MLSS in Floccuta-
tation Tank (mg/l)
mean
750
590
1,600
range
300-1,560
140-1,440
1,140-2,460
P in Lime Sedimentation Tank
Effluent (mg/l)
mean
0.376
0.242
0.210
Standard
deviation
0.146
0.107
0.090
range
0.164-0.634
0.039-0.417
0.107-0.394
P in Dual-Media
Filter Effluent
(mg/l)
0.050
0.048
0.049
en
CO
* Lime Dose 300 mg/1 ( as Ca(OE)2 )
-------
Photo 2.1
Scale on the Flush
Mixing Tank
154
-------
Table 2.4 Composition of Scale
Range
Mean
Ignition
Loss
45.8-47-2
46.4
2)
Impurities
0.29-1.87
0.85
CaO
44.3-51.5
49.5
MgO
2.2-6.4
3.5
Total
99-1-102.7
100.2
l) at 1,000+;50C; includes adhesive moisture, crystal water
and
2) includes Si02 and
3) 49.5$ as CaO is equivalent to 89.4$ as
155
-------
Table 2.5 Interin Summary for the Experiments Being Under Way
PH mean
n ^ mean^)
Turbidity1'' ,5)
removal^ '
Suspended mean^'
Solids removalS)
mean4)
removal'''
mean4)
P,ortho cl
removal J '
mean''''
TOC ,c)
removal-^ '
' COD mean*}
removal' '
mean4)
• cl
removal-1 '
Influent
(Secondary
Effluent)
7.26
5.69
_
5.8
_
1.37
-
1.17
-
28.6
-
23.4
_
4.86
-
Lime
Sedimenta-
tion
Tank
Effluent
10.40
14.5
-
34
_
0.322
76.5
0.206
82.4
20.9
26.9
21.9
6.4
5.00
-
Ammonia
Stripping
Tower
Effluent
10.06
-
.
-
_
_
-
-
-
_
-
-
_
Calcium
Carbonate
Setting
Tank
Effluent
7-70
4.70
17.3
5.6
3.4
-
-
-
-
24.5
14.3
16.6
29.1
-
Dual-Media
Filter
Effluent
7.36
0.49
91.4
0
100
0.209
84.7
-0.174
85.1
16.3
43.0
12.0
48.7
4.28
11.9
3)
Sedimenta-
tion Tank
Effluent
Treated by
A12(S04)3
6.85
5.70
-
7.6
-
0.433
68.4
0.379
67.6
22.8
20.3
19.9
15.0
3.89
20.0
l) Unit of turbidity is mg-kaoline/1
2) lime dose = 300 mg/1 as Ca(OH)2
3) mole ratio of Al/P = 3.28
4) mg/1
5) %\ based on influent concentration
156
-------
3. Kyoto pilo't plant studies
Advanced waste water treatment plant was partly completed at Toba
Seawage Treatment Plant, Kyoto, in February, 1973 > and experiments
on the down-flow filtration process have been carried out from this
March. The down-flow filtration process is designed to remove
suspended solids from the conventional activated sludge process
effluent.
In Japan, the activated sludge process accounts for 71 per cent of
the total number of municipal sewage treatment plants. However, at
the final settling tanks of the activated sludge process, organic
suspended solids (i.e. biological floes) may not be removed enough
from the effluent.
For this reason, a design manual for the facilities to remove them
has been expected to prepare quickly as possible.
To fulfil the demand, Kyoto pilot plant began with the down-flow
filtration process for which some information on design and maintenance
is available from our own experience of supplying in-plant water.
3.1 Experimental instrumentations and methods of experiments
A pilot filter system was installed, which consists of 3 filters,
each having and filter area of 1.2 m% a media depth adjustable in
the range of 0.6 to 1.0 m, and a maximum filtration head adjustable
in the range of 2.4 to 3.0 m. The flow control is carried out by
means of a sluice valve, and the filtration head loss is continously
measured using an automatic level gauge. Flow rate of effluent is
measured continuously by a 30° V-notch weir equipped with an
automatic level gauge. The filter is cleaned by fixed surface
washing and back washing.
The cleaning wastewater is measured by means of a 90° V-notch weir
and sampled when it is necessary.
The filter media size used for the experiments are as listed in
Table 3.1. The filter media are packed as illustrated in Table
3.2.
157
-------
As a first phase experiment, the effects of the ratio of anthracite
coal depth to silica sand depth in the dual-media filter on the
filtration efficiency and overall economics were examined by com-
paring the filters No.l and No.2, along with a comparative study
of filters No.2 and No.3 on the effects of the difference between
the dual-media system and tri-media system. For the experiments,
a declining filtration method was used with the maxium filtration
head set at 3.0 m. The initial filtration flow-rate of filters
was set at 120 m3/m2-d, 240 mVm2.d, 360 mVm2-d, 480 m3/m2-d and
540 m3/m2'd, respectively.
The surface washing rate and its duration time for the fixed
surface washing were set at 0.15 to 0.2 mVm2'min' an(i 6 "to 10 min.,
respectively, and the expansion rate of filter media and washing
time for the back washing at 20 to 25 per cent and 6 to 12 min.,
respectively. In case the expansion rate for the back washing was
25 per cent, the back washing rates of filters No.l, No.2 and
No.3, were 0.78 mVni2• min. , 0.6? m^/m2'min• and 0.70 m3/m2•min.,
respectively. The fixed surface washing and back washing were
overlapped in the time range of 1 to 7 min.
3.2 Relationships between run-length and filtration flow-rate
The relationships between the run-length and filtration flow-rate
are shown in Pig. 3.1.
The run-length of No.l filter was such less than that of filters
No.2 and No.3.
The run-length of filter No.2 showed a tendency to become a little
longer than that of filter No.3. Namely, it is found that the
thickness of anthracite coal medium has a great influence on the
run-length, and that the thickness of anthracite coal media to
total media depth governs the economics of the filter process,
accordingly.
In the declining filtration method used for the experiments, the
decline in the filtration flow-rate was as shown in Table 3.3.
158
-------
The decline in the filtration flow-rate with increase in the
filtration head-loss was larger as the initial filtration flow-
rate becomes large. Beyond an initial filtration flow-rate of
360 m^/m^'d, the flow-rate declined soon after the start of filtra-
tion. With reference to Fig. 3-3 in which the typical sewage flow
pattern of Toba Sewage Treatment Plant is given, the flow-rate is
relatively constant over a period of about 9 hrs (from 10:00 a.m.
to 7:00 p.m.). Prom 7:00 p.m., however, the sewage hourly flow-
rate to the treatment plant was on the decline. For this reason,
if the actual treatment plant should be operated in declining
filtration method as in the experiments (i.e., if media size and
depth of filter No.2 or No.3 is applied), and if the filter should
be washed once every day, the initial filtration flow-rate might
have to be selected less than 360 m^/m^-d.
3.3 Effluent quality
The quality of the influent and effluent of the filter is shown in
Table 3-4- The quality of filtrate was largely influenced by the
quality of biological treatment effluent, making the effects of
filtration flow-rate uncertain.
Filtrate quality was degraded when experiments were carried out at
a filtration flow-rate of 480 mVm^'d. This is because of the
breakdown of the sewage sludge treatment facility during that
period, which forced to accumulate sludge in the primary sedimenta-
tion and biological treatment facilities.
There were differences in the quality of filtrate among the three
filters; filter No.l was better than filters No.2 and No. 3, and
filter No.2 was slightly inferior to filter No.3- It was also
found that the difference in filtrate quality among the three
filters was noticeably increased when the initial filtration flow-
rate was large. But, it was inferred that the difference would be
very little if the filtration flow-rate was lower than 360 m^/m^-d.
When three filters applying declining filtration method with media
159
-------
thickness set at 1.0 m and maximum filtration head at 3-0 m was
carried out, the change in the filtrate quality during the filtrat-
ing period was very little. Table 3-5 shows the above two examples.
With all, it is concluded that when the filtration is to be conducted
at a filtration flow-rate of less than 360 m3/m2-d, the ratio of the
anthracite coal layer to the total media depth be preferably around
60 per cent, just as in the filter system configuration preferred
in this filters Wo.2 and No.3. It is proved with this arrangement
that not only can be run-length increased like the example shown
in Fig. 3.1, but the filtrate quality can be maintained satisfactory.
There was no significant difference in both run-length and filtrate
quality between the dual-media filter No. 2 and tri-media filter
No.3- This may be attributable to the selection of the size of
gannet sand used as a medium.
3.4 Organic loads by washed waste water
The washed wastewater from the filter system is returned to inlet
of primary sedimentation tanks of the treatment plant. In the
existing sewage treatment system, the loading by this washed
wastewater cannot be ignored. For this reason, the volume of
washed wastewater and the loading by it were examined. Fig. 3-2
shows an example.
In case the back washing was carried out with the media expansion
ratio set at 20 to 25 per cent, it took about 5 min. for the filter
No.l (with short run-length) and 7-5 to 8 min. for the filters
No.2 and No.3 to attain a practical refreshness. As regards the
example shown in Fig. 3-2, run-length was 13 hrs for the filter
No.l, 25 hrs for the filter No.2 and 24 hrs for the filter No.3.
At the time of the back washing, the maximum BOD concentration
was 939 mg/1, 1,639 mg/1 and 1,306 mg/1 for the filters No.l, No.2
and No.3, respectively.
The maximum suspended solids concentration was 1,220 mg/1, 2,320
mg/1 and 2,070 mg/1, respectively. However, during the required
160
-------
washing time in which excess washing time was not included (5 min.
for filter No.l; 8 min. for filters Wo. 2 and No. 3), the mean BOD
concentration was 28? mg/1, 410 mg/1 and 411 mg/1 for filters No.l,
No . 2 and No. 3, respectively. Also, the mean suspended solids con-
centration was 384 mg/1, 551 mg/1 and 575 mg/1, respectively.
While the maximum BOD concentration and maximum suspended solids
concentration were so high as above, the mean values were about 2
to 3 times those of the primary influent. The washing water
required was 5-9 to 7.6 m^/filter m2, and retio of washing water
to filtrate volume was less than 2.5 per , cent.
3.5 Influences of filter washed wastewater on primary sedimentation
tank of existing facilities
Investigations were conducted on the influences of washed waste-
water created by once-a-day washing of the filter over the functions
of the primary sedimentation tank of the existing facilities into
which it would be return. Fig. 3-3 is an example showing the
influent load to the primary sedimentation tank of Toba Sewage
Treatment Plant. During the survey, the sewage influent at the
Plant was 362 x 1CP
The Toba Plant handles the sludge of the nearby Kisshoin Sewage
Treatment Plant and treats supernatant coming from another anaerobic
digestion facility which was treating night soil. As a consequence,
the return waste water from the plant at that time was as much as
41 x ID? m3/d running into the primary sedimentation tanks. The
over-all influent of the primary sedimentation tanks was 403 x 10^
m^/d, and the mean surface loading of the tanks was 22.7 m-Vm^-d.
The average removals of suspended solids and BOD were 76.5 and 59-2
per cent respectively. As given in Pig. 3.3, the influent load to
the primary sedimentation tanks was more than 20 x 10^ m-Vhr
during a 10-hr daytime, declining gradually from 7:00 p.m. to
6:00 a.m., and thence increased sharply during the period from
6:00 a.m. to 10:00 a.m.
161
-------
Both the influent suspended solids load and BOD load showed a
tendency to decrease from midnight to early morning.
Assuming that at Toba Plant a dual-media or tri-media filter
system is installed and operated at a filtration flow-rate of 300
m3/m2'd with washing once a day, the number of filters required
will be a dozen or so. If the filters are to be recleaned one by
one sequentially, the washed wastewater load on the primary sedimen-
tation tank will be equalized over some period of time. The hatched
part appearing in Fig. 3-3 is an example showing the case where the
filters are washed during 2:00 a.m. to 8:00 a.m. period. In this
example, the overflow rate of the primary sedimentation tanks will
be only 21.4 m^/m^-a even at 2:00 a.m. when the situation is most
critical. This is almost on the same level as the mean overflow
rate of 22.8 m3/m2.£ Of the primary sedimentation tanks without
filters.
BOD loading and suspended solids loading are not more than 1/5 the
mean values when filters are not installed. Namely, the filter
washing, if taken from midnight to early morning, would not affect
the existing sewage treatment facilities and could do without ex-
pansion of the existing facilities.
Feasibility of treating the washed wastewater in the primary
sedimentation tank was also examined using a settling column. The
results revealed that suspended solids in the washed wastewater
could satisfactorily settle out and be removed even without dosage
of a catonic polymer as the flocculant aid. (see Fig. 3.2)
3.6 Investigations now in progress
(l) As described in the foregoing, comparative studies on the three
down-flow filters have been carried out so far. It was reported
that in England the up-flow filtration has been sucessfully used
for polishing of the secondary effluent.
To follow suit, one Body Immedium Filter (filtration area: 1.2
m^) was installed at this plant, and has been studied in comparison
with other three media filters.
162
-------
The media (silica sand) used for the up-flow filter are in two
layers - one having an effective size of 1.16 mm and a uniformity
coefficient of 1.33 and another having 2.01 mm and 1.31> re-
spectively. The over-all media depth of the filter is 1.55 m.
The up-flow filter is cleaned by air agitation and back washing.
For the filter washing water, the secondary effluent is used.
As shown in Table 3.6, the filtrate quality obtained is little
different from that by the down-flow filters No.2 and No.3.
But, the up-flow filter requires twice or more time in washing
than the down-flow filter does. However,, the up-flow filter,
permits to used the secondary effluent directly as the filter
washing water, and to dispose the effluent without post aeration
because dissolved oxygen concentration in the filtrate is
relatively high.
(2) At the primary and secondary processes of large-scale sewage
treatment plants in Japan, where wastewater flows in from com-
bined sewarage systems, phosphorus is removed more than 6C$>
from influent of primary sedimentation tank in which digested
supernatant is contained with raw sewage. In some cases,
removal of phosphorus in the effluent is attained more than 80fo.
However, stringent effluent standard for phosphorus may be set
for sewage treatment plant effluent, and additional removal of
phosphorus may be required. It will therefore be of great
necessity to find an economical way for the reduction of residual
phosphorus in secondary effluent.
Certain data from the United States indicate that the concentra-
tion of phosphorus in secondary effluent is 6 mg/1 or higher in
the U.S., while that in Japan is 2 mg/1 or lower at large-scale
sewage treatment plant at present. Therefore, less removal
of phosphorus from secondary effluent might be allowed in Japan.
Investigations are in progress as to the influences of flush
mixing with coagulant addition as a pretreatment of filtration
over the filtrability, and quality of filtered 'water and washed
163
-------
wastewater. According to a laboratory test, it is found that
the method improves removal of phosphates and CODj/^. The mole
ratio of Al+^ to the concentration of phosphorus in secondary
effluent, however, is required to be 2.5 to 3 for maintaining
the concentration in filter effluent lower than 0.5 mg/1, and
the economical aspect of phosphorus removal should be examined
carefully.
(3) Since the reduction of CODjy^ is not enough when only direct
filtration of secondary effluent is applied for an additional
process, experiments on, granular activated carbon adsorption
process have been started. The granular activated carbon
adsorption system used is composed of six down-flow gravity
f~>
type pilot contactors each having an adsorption area of 0.7 m .
The system is designed to be modified into three running modes
- 1-tank 6-parallel, 2-tank 3-parallel and 3-tank 2-parallel -
whichever is desired. In the experiments by 2-tank 3-parallel
or 3-tank 2-paralleT, the so-called merry-go-round operation is
possible.
The season why the granular activated carbon adsorption tank is
made of the down-flow gravity type is that when this kind of
facility is installed in the future its main body is expected
to be constructed in reinforced concrete structure.
The effluent of the activated carbon adsorption contactors is
continuously measured with a 30° V-notch weir equipped with an
automatic level gauge.
For the measurement and sampling of washed waste water, a 90°
V-notch weir box is installed. The experimental facility can
be operated semi-automatically or full automatically or manually.
At present, 2-tank 3-parallel operating mode is.employed, and
granular activated carbon of Calgon 8 x 30 meshes, Calgon 12 x 40
meshes and Shirasagi 8 x 30 meshes is tested. Carbon bed depth
is 3-0 m for all of the contactors..
164
-------
Influent is 240 m^/m^-d, and back washing of carbon bed is
carried out once a day. An example of the water quality data
is shown in Table 5-7-
3.7 Aspects of future studies
At the pilot plant located at Toba Sewage Treatment Plant, Kyoto,
a furnace for regeneration of exhausted granular activated
carbon will be installed in order to test the replicate use of
regenerated activated carbon. Also, up-flow type granular acti-
vated carbon adsorption contactors will be installed for the
comparative study with the down-flow type granular activated
carbon adsorption system.
As regards to the ammonia removal, laboratory tests have already
been pushed forward for the installation of a break-point
chlorination pilot facility. It is in the stage of design of
the instrumentation. In Japan, water pollution problems due to
excess nitrogen in river and lake water and irrigation water
have come to stay, and the development of an economical way of
removing nitrogen has been voiced for.
Unfortunately, however, each sewage treatment plant barely
possess space to enlarge the facilities, and has only a limited
space to accommodate such extra work. With this in mind,
experiments of removing nitrogen are started on the break-point
chlorination process for which space can be small.
The soda industry here in Japan has been urged to change its
production process from mercury process to membrane one and it
remains uncertain whether so much chlorine gas will be avilable
for the break-point chlorination process from now on. Therefore,
it is necessary to investigate nitrogen removal processes more
extensively.
Another facility to be installed will be ion-exchange processes
for the removal of nitrate and phosphate, and also ammonia.
165
-------
Table 3.1 Media Size Using Experiment
Media
Anthercite Coal
Silica Sand
Garnnet Sand
Effective
Size (mm)
1.22
0.87
0.54
Uniformity
Coeficient
1.21
1.21
1.41
Table 3.2 Media Depth of Each Pilot Filter
^^^^^ "BH ~| f pT»
•n/r -, . ^^-^J- -1- J- wC-L
Media ^^L^^
Anthercite Coal
Silica Sand
Garnnet Sand
Total
No.l
(mm)
150
850
-
1,000
No. 2
(mm)
625
375
-
1,000
No. 3
(mm)
625
300
75
1,000
166
-------
Pig. 3.1
cr>
c\J
a
o,
a
0)
-p
cd
•H
-p
•H
a
M
Relationship Between Initial Flow-rate and
Average Run-Length of Pilot Filters
240 -
/20
Filter No,
Filter No,
Filter No.
O
20
/OO /2O
Run-Length (hrs)
-------
Table 3-3 Relationship between Filtration Plow-rate
Declined and Filtration Head-Loss
Initial
Flow-rate
(m3/m2.d)
120
240
360
480
540
Filtration Head-Loss (cm)
50
118
232
358
480
540
100
108
218
325
462
500
150
98
. 200
307
410
472
200
85
182
278
365
405
250
78
158
236
322
350
300
58
124
197
258
292
168
-------
Table 3-4 Influent and Filtrate Quality of Pilot-Filters
Initial Filtration
Flow-rate (m-'/m -d)
^^~^~~^Inf luent or
^""""""---JJiltrate
Items -\^__^^
Nos. of Data
S.S.
(mg/l)
BOD
(mg/l)
CODMn
(mg/l)
max.
min.
Av.
max.
min.
Av.
max.
min.
Av.
120
Inf.
8
26.3
7.9
14-8
29.1
12.5
22.4
20.7
9.8
15.6
Filtrate
No.l
5
8.3
1.0
3-7
10.9
1.7
3-9
14-3
8.4
10.4
No. 2
8
8.1
1.2
4-0
11.2
2.1
4.1
15.1
8.4
11.4
No. 3
8
7.4
1.6
3-9
9-9
2.2
3.8
14-9
8.4
11.3
240
Inf.
9
10.8
4.6
7.5
17.9
6.0
10.9
15.7
5-4
12.2
Filtrate
No.l
8
3-7
0.5
2.2
4.0
1.9
3.2
12.8
1.0
9.8
No. 2
9
3.8
1.0
2.7
7.3
1.8
4-3
13-7
1.0
10.2
No. 3
9
3.1
1.0
2.5
6.8
2.2
4-3
13.0
1.0
9.8
360
Inf.
10
28.8
3.1
9.7
16.9
2.5
10.8
23.8
6.1
12.5
Filtrate
No.l
7
2.4
0.3
1.3
4.1
1.0
2.1
16.4
4.5
10.4
No. 2
10
3.2
0.2
1.4
3-6
1.4
2.2
16.4
4.9
10.1
No. 3
10
3-0
0.1
1.3
3-4
0.6
2.0
16.7
4.8
9.8
480
Inf.
10
67.7
5.0
22.8
32.0
4-4
18.0
28.6
8.8
16.0
Filtrate
No.l
7
29-0
0.5
6.6
7.5
1.0
2.9
17-9
5-5
9.9
No. 2
10
43-5
0.8
11.4
19-4
1.4
6.4
20.6
5.9
12.0
No. 3
10
46.5
0.7
12.0
21.0
1.3
6.3
21.5
5.4
11.9
540
Inf.
9
33-5
4.2
13.8
29.9
6.3
15-8
26.0
9-0
16.5
Filtrate
No.l
7
5.6
1-4
3-5
7.1
1.5
4.1
16.0
8.2
12.6
No. 2
9
19.0
1.2
5.4
20.2
1.3
5.6
21.2
8.1
12.8
No. 3
9
18.3
1.1
5.2
16.1
1.0
4.8
21.7
8.4
13.0
CTl
-------
Table 3.5 Comparision to Filtrate of Three Filters after Filtration Start
How-rate
U3/m2-d)
240
^~~^^^^_Influent or
^^^Jfiltrate
Items ^^^-^^
Sampling Time after
Filtration Start (hrsrmin)
Liquid Temp (°C)
Dissolved Oxygen (mg/l)
S.S.
BOD
CODMn
cone. (mg/l)
rem. (fo)
cone. (mg/l)
rem. (%)
cone. (mg/l)
rem. ($)
Inf.
2:45
24.6
0.5
8.0
-
6.2
-
10.4
-
Filtrate
No.l
25.5
0.5
3-7
53-7
3-5
43.6
9.2
11.5
No. 2
3:00
25-5
0.3
2.9
63-8
3-1
50.0
10.1
28.8
No. 3
25.5
0.3
3.1
61.2
3-3
46.8
10.4
0.0
Inf.
26:25
24.8
0.2
10.7
-
12.9
-
12.4
-
Filtrate
No.l
25.2
0.2
2.6
75.7
3-4
73-5
9.3
25.0
No. 2
27:00
25.2
0.2
3.3
69.1
3-4
73-5
9.7
21.8
No. 3
25.2
0.2
2.7
74.7
3-2
75.1
9.7
21.8
Inf.
46:25
24.5
0.4
6.4
-
12.5
-
12.6
-
Filtrate
No.l
25.0
0.2
2.8
56.6
4.0
68.0
11.2
11.1
No. 2
47:00
25.0
0.2
2.9
54.8
3-8
69-5
11.0
12.7
No. 3
25.0
0.2
2.8
56.3
3.2
74.5
9.5
24.6
480
Sampling Time after
Filtration Start (hrs:min)
Liquid Temp. (°c)
Dissolved Oxygen (mg/l)
S.S.
BOD
CODMn
cone. (mg/l)
rem. (%}
cone. (mg/l)
rem. (fo)
cone. (mg/l)
rem. (fo)
2:43
26.2
0.2
8.0
-
6-. 2
-
9.8
-
3:00
26.8
0.2
1.8
77.5
2.0
67.7
8.4
14-3
26.8
0.2
1.7
78.8
1.6
74.1
8.5
13.3
26.8
0.2
1.7
78.8
1.6
74.1
8.1
17.4
24:43
26.0
1.7
8.2
-
4.4
-
9.6
-
25:00
26.5
0.2
2.0
75.6
1.4
68.2
9.0
6.3
26.5
0.1
1.5
81.7
1.4
68.2
9.0
6.3
26.5
0.1
1.7
79.4
1.7
61.5
9.0
6.3
-------
(a) Sewage Flow
20-
15-
10
Filters Washed Waste
Flow
2.73x10? m3
Average Hourly Flow
with Filter Washed WasteXFlow
13 (P.m.) 17
21
1 (am.) 5
(b) BOD Load
15-
*5>
i-H
H
nz)
I
o
o
m
Filters Washed Waste
. BOD Load
0.94x104 kg/hr ,
13 (p.m.) 17
21
1 (a.m..) 5
Time
(o) Influent Suspended Solids Load
10
5-
Filters Washed Waste
Sus. Solids Load
1.31x103 kg/hr
'3 (p.m) 17
1 (a. m.) 5
Time
Fig. 3.3 Typical Flow and Load Pattern to Primary Sedimentation Tanks
Assuming to be Equipped Filters, Toba Sewage Treatment Plant, Kyoto
171
-------
Pig. 3.2 Settling Column Tests of Filter
Washed Wastewater
Column height 2.2 m
Column Diameter 0.3 m
100
o
a
Q)
PH
CO
CO
Co:
Washed Waste Only
Mixed Waste of Wasted
Waste with Raw Sewage
(Ratio 1:10)
Washed Waste dosed a
Cationic Polymer
(Dose 1 mg/l)
Initial Cone, of Suspended
Solids
/oo
Overflow-rate
-d)
172
-------
Table 3-6 Comparision to Filtrate both Down-flow
Filters and Up-flow Filter
^~"~~^^Inf luent or
TJ. ^^"~~^\ Filtrate
Items ^\^^
Liquid Temp. (°c)
Dissolved Oxygen
(mg/l)
Turbidity (mg/l)
S.S.
BOD
C0%n
TOG
cone, (mg/l)
red. (fo)
cone, (mg/l)
red. (%}
cone, (mg/l)
red. (%}
cone, (mg/l)
red. (%)
Influent
20.3
0.5
7.5
11.2
-
17.8
-
13.7
-
14.2
-
Filtrate
No.l
20.7
0.5
2.65
2.7
75.8
5.5
69.2
11.7
14.6
9.6
32.4
Wo. 2
20.7
0.5
2.55
3.3
71.3
7.1
60.1
10.9
20.4
11.2
21.1
No. 3
20.7
0.5
3.60
4.9
56.2
9.2
45.5
11.7
14.6
10.0
29.6
Wo. 4
20.7
6.2
3.20
3.9
65.0
8.2
54.0
11.9
13.1
10.8
23-9
Remark: Filtration Flow-rate
Down-flow Filter
Up-flow Filter
240 m3/ni-d
No.l, No.2, No.3
(refer to Table 3.1 & 3.2)
No. 4
173
-------
Table 3.7 Influent and Effluent Quality of Pilot Granular
Activated Carbon Adsorption Contactors
^^•^-^Influent or
T, ^^^^~^Eff luent
Items ^~~~^~~~~^
Liquid Temp. (°C)
Dissolved Oxygen
(mg/l)
S.S.
BOD
CODMn
Kjeldahl
Nitrogen
cone, (mg/l)
rem. (fa)
cone, (mg/l)
rem. ($)
cone, (mg/l)
rem. (fo)
cone, (mg/l)
rem. ($)
In-
fluent
18.0
9-3
3.0
-
5.3
-
11.3
-
6.3
-
Effluent
No.l
17.4
0.4
3-5
-
5.1
3.8
7-7
39.7
3.8
39.7
No. 2
17.4
1.0
1.9
36.7
5.0
5.7
4.6
59.3
3.2
49-3
No. 3
17.4
1.2
2.8
6.7
5.1
3.8
6.6
41.6
4.8
23.8
No. 4
17.4
0.7
2.3
23.3
3-8
28.3
3.5
69.0
2.4
61.9
No. 5
17-4
0.7
3.6
-
4.6
13.2
7.2
36.3
4.2
33-3
No. 6
17.4
0.6
2.4
20.0
4.3
18.9
4.8
57.5
2.4
61.9
Remark: Arrangement of Granular Activated Carbon Adsorption Contactors
Influent
Filtrated
wastewater
Contactor
No.l
E
Contactor
No. 3
E
Contactor
No. 5
E
r
ffluer
No.l
J
ffluer
No. 2
1
ffluer
No. 5
Contactor
No. 2
it
Contactor
No. 4
it
Contactor
No. 6
it
•> Effluent (c.algon 8x32]
No. 2
Effluent [Calgon 12x40J
No. 4
^ Effluent [Shirasagi
No. 6
Adsorption Time in Each Contactor : ,15 min
174
-------
4. Evaluation of treatability depending upon water quality matrices
Connecting with the treatability of waste water, the status of the
impurities could be represented by three components such as the
impurity size, chemical property and cencentration (l), (2), (3).
Thus if the impurity sizes are. devided into several classes by means
of mechanical, optical or gel chromatographical technique, a water
quality matrix will be able to be established schematically as shown
in Figure 4.1.
X. j
i\
1
2
•
•
•
•
•
n-1
n
1
Cn
C2)
•
•
Cui
2
C,2
•
•
.
•
Cu
•
•
Coli
im
•
•
*• Y
n
m-l
ow
m.
Cm
Cnnv
Pig. 4.1 Water Quality Matrix
Fig. 4.2 Water Quality Conversion Matrices
175
-------
The water quality conversion matrices as shown in Figure 4.2 are
prepared for each process of water treatment. The indices of the
columns and rows are the same with the water quality matrix, but the
elements are written as the percentage of removal, fi(ij), instead of
the concentration, C(ij), of the water quality matrixes. If the
concentration is greatly different from each other, different treat-
ment process shall be proposed or the different percentages of
removal shall be put into the matrix elements. Thus, water quality
conversion matrices should be shown as the three dimensional matrices
to take the concentration effects into account.
In these water quality conversion matrices, while no removal is
anticipated, the element R(ijk) is zero., and for the removed part
the element R(ijk) takes a positive value. In one case when some
new components such as a metabolic waste of biological treatments
are added by the treatment, the elements become negative. In another
case when no water quality elements exist prior to the treatment at
the components, basic elements to be taken into the calculation
should be pointed out. In addition, if the element R(ijk) cannot
be decided independedtly, the relationship between other connected
components should be described.
In order to develope comprehensive technology for water quality
management on the basis of an idea as mentioned above, the research
project supported by Special Fund for Promoting of Multiministerial
Research Project under the Jurisdiction of the Science and Technology
Agency has been carried on since 1972 to 1974. The project director
is prof. Zenji Tambo, Hokkaido University and the grantees are The
Institute of Public Health, Ministry of Health and Welfare and Kinki
Regional Construction Bureau, Ministry of Construction.
4.1 Experiments for the verification of the concept
A series of laboratory experiments and pilot plant operations were
carried out to evaluate the feasibility of the above mentioned
concept. To obtain general results without falling into local
176
-------
conditions, many kinds of raw waters and treated waters in widely
spread areas of Japan were used for the experimental works.
l) Laboratory scale coagulation and carbon adsorption experiments
The major purpose of those laboratory scale experiments was to
study performance of the activated sludge process and chemical
coagulation process together with the results of followed activated
carbon adsorption process. For the purpose, the following ex-
perimental studies were carried out.
1. Treatment of raw sewage by combination of alum or lime
coagulation, sedimentation, filtration, and activated
carbon adsorption.
2. Treatment of the activated sludge process plant (Makomanai,
Sapporo) effluent by combination of alum coagulation, sand
filtration, and activated carbon adsorption.
3. Treatment of the activated sludge process plant (Pusiko,
Sapporo) effluent by combination of a simple sand filtration
without coagulation and activated carbon adsorption.
The laboratory scale semi-continuous treatment apparatus as shown
in Figure 4.3 consisted of a 200 liter of settling tank with
coagulation facility, a rapid sand filter, a filtered water
storage, and four down flow granular activated carbon columns
in series.
waste water
I T
A
TJ
TJ
¥_
effluent
A: Settling Tank
B: Sand Filter
C: Storage Tank
D: Carbon Beds
Fig. 4.3 Flow diagram of laboratory scale apparatus
177
-------
Standard jar tests were used to determine the coagulant dosage.
A coagulant was added to the settling tank, then, rapidly mixed
for 5 minutes, flocculated for 30 minutes, and settled for 1
hour. The supernatant from the tank was applied to the sand
filter with 50 cm of sand bed at constant rate of 50 m/day. The
filtered water was once put into the storage tank, then fed to
the four activated carbon columns arranged in series. The size
of the carbon column was 3 cm in diameter and 40 cm in length.
Pittsburg CAL activated carbon was placed in those columns with
25 cm depth. The rate of the flow through the adsorption columns
was set as 144 m/day.
In parallel with the laboratory scale continuous adsorption ex-
periments, batch adsorption tests were also carried out by using
powdered activated carbon.
The turbidity was measured by a photo-turbidimeter which was
calibrated with standard kaolinite solution. The total organic
carbon (TOG) concentration was determined by a Toshiba-Beckman
Carbonaceous Analyzer. Sample water having organic carbon con-
centrations below 1 to 2 mg/1 was concentrated under reduced
pressure at the normal temperature prior to the TOG determination.
Sometimes, the pH of the water samples was adjusted at pH=2 and
the samples were shaken or aerated with N2 gas so as to remove
inorganic carbon which was apt to hinder the TOG determination.
Ultraviolet absorbances were determined by a Hitachi 124 double
beam spectrophotometer. The concentrations of protein (Polin-
Chiocalteu test), amino acids (Ninhydrin test), and carbohydrates
(Anthrone test) were also determined for the same samples. The
COD and major inorganic constituents were also determined after
the standard methods (4).
2) Physico-chemical treatment of sulphide pulp waste water
A physico-chemical treatment of sulphide pulp waste water from
a pulp mill in Tomakomai, Hokkaido, by using activated carbon
produced from the lignin of the pulp waste water, was carried
178
-------
out to verify the applicability of the concept to the outside of
the municipal waste water treatment.
The flow sheet of the sulphide pulp waste water treatment processes
and the lignin base activated carbon production from the waste
water is shown in Figure 4-4-
PULP WASTEWATER ——> LIME CLARIFICATION ^ BATCH OR FLUIDIZED
t
Ca(OH)2
SETTLED LIME=LIGNIN
FLOG (SLUDGE) ACTIVATION
150°-180°c
£ H2S04—=* 2 hours
LIBERATED *
>• CONCENTRATION
LIGNIN SOLUTION OUI\^INIBAIXUI\
Fig. 4-4 Flow sheet of the pulp wastewater treatment and the
production of powdered activated carbon from lignin
of the waste water.
3) Pilot plant operations
To confirm the results of the laboratory scale experiments and
solidify the concept, two series of the same type physico-chemical
pilot plants were constructed and operated at Soseigawa sewage
treatment plant in Sapporo. A series of the plants treated raw
sewage which was pumped up from the primary settling tank over-
flow of the Soseigawa sewage treatment plant. Another series
of the pilot plant treated the activated sludge process effluent
of the sewage treatment plant for the purpose of the tertiary
physico-chemical treatment processes with or without chemical
coagulation process.
A schematic flow diagram of a series of the pilot plant processes
is shown in Figure 4-5- The operational flow chart including
operation conditions is written in Figure 4-6.
179
-------
1
A
t
^1
i-
c
3
-\
^
I
L
^
*
t
r
r
3-
\
. \
\
r
-if-
-»•
~1 r
_F
\
T
I1
T
J
r
JJ
r
1
T
^L
c
^
i
IL
A
B
C
D
E
F
G
Coagulant Tank
Waste Water Inflow
Rapidly Mixing Tank
Flocculator
Sedimentation Tank
Over flow rate 0,88cm/min
Detention time 150min
Rapid Sand Filter
Filtration rate 1^0 m/d
Activated Carbon Beds
Total depth 300 cm
I.V. lUlt m/d
Fig. 4.5 Flow diagram of the pilot plant
RAW SEWAGE
-*ACTIVATED SLUDGE TREATMENT PLANT
ALUM COAGULATION
I Dosage 150 ppm
FLOCCULATION
SEDIMENTATION
I
RAPID SAND FILTRATION
I
ACTIVATED CARBON ADSORPTION
I
(DIRECT PHYSICO-CHEMICAL
TREATMENT SYSTEM)
J
SAND FILTRATION
ACTIVATED CARBON
ADSORPTION
(TERTIARY TREATMENT
WITHOUT COAGULATION)
ALUM COAGULATION
J Dosage 40 ppm
FLOCCULATION
4r
SEDIMENTATION
4
RAPID SAND FILTRATION
4
ACTIVATED CARBON ADSORPTION
*
(TERTIARY TREATMENT
WITH COAGULATION)
Fig. 4.6 Operational flow chart of the pilot plants.
4) Gel chromatogram
The impurity size distribution of minute fractions of those
samples which had passed through 0.45 micron meter membrane
filters was determined by a gel filtration mainly on a column of
Sephadex G-15. For some samples, Sephadex G-25 or G-50 was
also used. Those gels were swelled for 24 hours prior to setting
into the columns. The resulting slurry of the gel was then
poured into the glass columns of 2.5 to 4 cm in diameter and 100
cm in length with 90 cm of the gel bed height.
180
-------
Most water samples were once filtered by 0.45 micron meter
membrane filter and concentrated into suitable concentrations
by rotary vacuum evaporators at the temperatures of 25 to 30°C
before applying to the column. Concentrated samples of 10 to
30 ml were placed at the top of the gel beds. Distilled water
was introduced into the column from the top at a constant rate
of flow for the elution. The rate of flow was 20 to 50 ml/min.
Effluent from the column bottom was collected in the test tubes
by an automatic fraction collector as 10 to 20 ml of successive
fractions. For each fraction, measurements were carried out for
TOG content and 220 to 280 millimicron meters of ultraviolet
absorbance.
The impurity size distribution characteristics of the gel
chromatogram were calibrated from the elution volume of Blue
Dextran (M.¥. 2 millions), raffinose (M.¥. 504), maltose (M.¥.
342), glucose (M.W. 180), ethylene glycol (M.W. 62), methanol
(M.W. 32), and DBS (M.W. 349).
4.2 Results of Experiments
l) Results of laboratory scale coagulation and carbon adsorption
experiments
The effectiveness of alum coagulation followed by carbon adsorp-
tion is appreciated by comparing Tables 4-2 and 4-2. .Some amount
of leakage of KMnO^ COD and E250 (Absorbance at 250 millimicron
meters) constituents are recognized when the coagulation process
is omitted. Whereas, in the case when alum coagulation process
is included, the leakage from the carbon bed is very scarce in
spite of ~a relatively higher raw water concentration.
181
-------
Table 4.1 Non coagulated, filtered and carbon adsorbed
secondary effluent.
Hours of
operation
48
96
168
336
COD(KM
Filtered
4-5
5.0
4.5
5.0
nO^ ) ppm
Adsorbed
1.0
1.0
0.9
1.2
E250
Filtered
0.122
0.109
0.110
0.137
Adsorbed
0.024
0.018
0.020
0.022
Table 4.2 Alum coagulated, filtered and carbon adsorbed
secondary effluent.
Hours of
operation
40
88
160
358
COD (KM
Filtered
8.2
8.5
8.3
8.0
hO^) ppm
Adsorbed
0.3
0.2
0.9
0.9
E250
Filtered
0.094
0.137
0.100
0.098
Adsorbed
0.000
0.006
0.006
0.002
The gel chromatographic studies shown in Figures 4-7 and 4.8 reveal
that without coagulation there exists typical leakage of larger
size impurities in the Zones 1 and 2 in the carbon adsorption bed
effluent. Inefficiency of activated carbon adsorption in removing
larger size impurities should be marked.
A result of physico-chemical raw domestic sewage treatment (co-
agulation, filtration, and carbon adsorption) without biological
process is shown in Figure 4.9. There is the leakage of COD from
the very early stage of the run. The major constituents of the
leaked COD are lower molecular weight substances such as amino
acids, low molecular fatty acids, and carbohydrates which could
be rather easily removed by biological processes.
182
-------
0,8
0-7.
0.1
ZONE 7
30 40 SO 60 70
FRACTION NUMBER X 15ml
Fig. 4»7 Gel chromatogram of
secondary effluent
F2SO
O.Z
30 to io 60 70
FRACTION NUMBER X 15ml
Fig. 4.8 Gel chromatogram of carbon adsorbed
secondary effluent without coagulation
1.0
0.8
C/Co 0.6
0.4
0.2
0
CARBOHYDRATE
Raw Water Cone.
COD 122 ppm
Carbohydrate 152 ppm
Column depth 20 cm
2 46 8 10 12 14 16
Time hours
Fig. 4.9 Physico-chemical treatment effluent of
domestic raw sewage.
183
-------
2) Results of sulphide pulp waste water treatment studies
For the physico-chemical treatment of sulphide pulp waste by
using lime or alum coagulation and the laboratory-made lignin
waste activated carbon adsorption, the usefulness of the above
mentioned chromatographic characteristics are verified as follows.
Ineffectiveness of activated carbon adsorption and effectiveness
of alum or lime coagulation in removing larger molecular substances
are also found by the results being shown in Figures 4.10 and 4.11.
The treatment system connecting both of the lime coagulation and
fluidized carbon adsorption bed in series gives a satisfactory
removal of the lignin content from the pulp waste water. The
spent lignin carbon saturated with the wastewater contents is
possible to be regenerated by concentrated sulphuric acid at the
temperatures of 150 to 180°C for the reaction period of two hours.
E 260
2.0
1.0
BLUE DEXTRAN
t
SUPERNATANT
X
t
'.RESOLVED SEDIMEN
\^ SOLUTION
100 300 500 700 900 1100 1300 ml
ELUATE
£ 280
4.0
3.0
2.0
1.0
0
PULP WASTE WATER
L ntTTr. nr-vn^A*, — ADSORPTION 5 jhin.
- BLUE DEXTRAN —-ADSORPTION 9 hrs.
300 500 700 900 1100 1300. ml
ELUATE
water. Sephadex G-50
Fig. 4.10 Gel chromatograms of Fig. 4-11 Gel Chromatograms of
supernatant and resolved pulp wastewater and
sediment solution of lime carbon adsorbed waste-
coagulation.
Sephadex G-50
^} Result of pilot plant studies
Typical gel chromatograms obtained from the pilot plant studies
are shown in Figures 4-12, 4-13, 4.14, 4-15, 4.16 and 4-17.
184
-------
As is seen in Figure 4-12, so called soluble impurities in the
municipal wastewater could be divided into five groups by the
Sephadex G-15 gel chromatography by using TOG, E260, and E220
as the water quality indices. This grouping is recognized as a
popular one by many analyses of the samples obtained from many
sewage treatment plants and natural rivers and lakes being polluted
by municipal wastewaters.
Comparison of Figure 4.12 with Figure 4.13 shows that activated
sludge treatment processes can effectively remove only a portion
of TOG which is insensitive to the ultraviolet absorbance at 260
millimicron meters, i.e., E260. Thus, for the removal of TOG
contents corresponding to E260, activated sludge processes are
not effective. The increase of ultraviolet absorbance at 220
millimicron meters, i.e., E220, in the Zone 4 would be caused by
some metabolic wastes of the biological activities.
Chemical coagulation followed by sedimentation and sand filtration
is effective for the removal of impurities in the Zone 1 and less
effective for smaller impurities in the Zones 2 to 5 as clearly
seen by the comparisons of Figure 4.13 with 4.14 and Figure 4-12
with 4.16.
However, a noticeable amount of TOG removal in the Zone 3 is
detected through the direct physico-chemical treatment process
as shown in Figures 4.16 and 4-17. This phenomenon might be
caused by some biological actions in the sand bed and carbon
adsorption bed. Incidentally, no removal in the Zone 3 is observed
in case of batch treatments using paper filters and powdered
activated carbon or short period experiments performed by small
scale laboratory tests. The total TOG contents removed by the
activated carbon column in the pilot plant are far beyond the
saturation adsorption capacity measured by batch tests.
185
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01
u
o
o
fc!
FRACTION
NUMBER x 10ml
FRACTION
NUMBERxlOml
Fig. 4-12 Gel chromatogram of
raw sewage
Fig. 4.13 Gel chromatogram of
secondary effluent
i NUMBER x 10ml
-------
0
5
NUMBER^ iQmi g!jj -
Zone
1
20
•
2
i ^"-J
l
3
j
\30 ,
\S^~s
\
i
i
ja!
A,!
(^ -^
1
1
1
1
1
1
1
— E 22(
--E 260
-"iRACTI
NUMBER
x 10ml
Fig. 4-16 Gel chromatogram of
coagulated raw sewage
Fig. 4.17 G-el chromatogram of
coagulated and adsorbed
raw sewage
The TOG.constituents in the Zone 3 are mainly low molecular
carbohydrates, amino acids, and low molecular fatty acids that
are easily decomposed by biological actions.
By the combinations of the above mentioned phenomena, as is seen
in. Figure 4.15, almost no organic substances are detected in the
effluent which has passed through activated sludge, alum or lime
coagulation with sedimentation and sand filtration, and the activated
carbon adsorption process arranged in series.
Inorganic impurities in the Zone 4 are effectively removed by the
processes of electrodialysis, ion exchange and so on. For the
portion, electric conductivity is available to use as a compre-
hensive water quality index.
4-3 Conclusion
For the removal of organics from wastewater, three comprehensive
water quality indices such as TOG, E260 m|i, and E220 imj, connected
with impurity size distributions could describe the treatability of
various types of treatment process such as biological process,
chemical coagulation, carbon adsorption, and so on.
187
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REFERENCES
l) Tambo,N., Lecture note of water treatment engineering, Department
of Sanitary Engineering, Hokkaido University, Sapporo, Japan (1968)
2) Tambo,N., Kamei,T., and Tanaka,T., An investigation of advanced
sewage treatment for the processes of coagulation and carbon
adsorption, Committee report on waste water reuse, Japan industrial
water and wastewater association (1971)
3) Tambo,N., Kamei,T., and Uasa,A., Behaviors of organic pollutants
in the physico-chemical treatment processes, Committee report on
higher order water and wastewater controls, Japan society of civil
engineering, Sanitary engineering committee (l97l)
4) Standard method for the examination of water and wastewater, IJth
edition, APHA, AWA, ¥PCF (l97l)
188
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AGENDA
AMERICAN PRESENTATIONS
TUESDAY, FEBRUARY 12:
THE FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
FEDERAL VIEWPOINTS
THE FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
STATE VIEWPOINTS
EPA OVERALL RESEARCH PROGRAM AND WASTEWATER TREATMENT RESEARCH
WEDNESDAY, FEBRUARY 13:
TREATMENT AND DISPOSAL OF SLUDGE FROM MUNICIPAL WASTEWATER
PLANTS IN THE UNITED STATES
EXPERIENCES WITH SLUDGE HANDLING IN TEXAS
THURSDAY, FEBRUARY 14:
PHYSICAL-CHEMICAL NITROGEN REMOVAL WASTEWATER TREATMENT
SLUDGES GENERATED IN PHOSPHATE REMOVAL PROCESSES
EPA EXPERIENCES IN OXYGEN-ACTIVATED SLUDGE
AERATION SYSTEMS FOR METRO CHICAGO
OXYGEN ACTIVATED SLUDGE SYSTEMS IN TEXAS
SUSPENDED SOLIDS REMOVAL PROCESSES STUDIED AT METRO CHICAGO
METRO CHICAGO - STUDIES ON NITRIFICATION
STORM AND COMBINED SEWER ABATEMENT TECHNOLOGY IN THE UNITED STATES
- AN OVERVIEW -
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THE FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
FEDERAL VIEWPOINTS
CHARLES H. SUTFIN
MUNICIPAL WASTE WATER SYSTEMS DIVISION
OFFICE OF WATER PROGRAM OPERATIONS
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
190
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THE FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
FEDERAL VIEWPOINTS
INTRODUCTION
In the United States, improving and maintaining the quality of our
waters requires a total national commitment at all levels. For a long time
in the United States water pollution was considered to be a matter for only
local concern. Since 1956, however, the Federal government and the States
have been actively assisting local communities with funds and technical
assistance. Still this effort was not enough. The pollution of the waters
grew to be a larger problem chiefly because of increased urbanization and
industrialization.
Faced with this situation, our Congress developed the Federal Water
Pollution Control Act Amendments of 1972 to provide planning and actions to
deal with water pollution. This legislation covers a wide range of activi-
ties. However, the objectives and goals are expressed in the very first
paragraphs of the Act, to wit:
1. By 1985, elimination of discharges of pollutants into
navigable waters.
2. By 1983, the attainment of water quality which provides
for the protection and propagation of fish, shellfish, and
wildlife, and recreation in and on the waters.
3. Prohibition of the discharge of toxic pollutants in toxic
amounts.
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4. Federal financial assistance for the construction of
publicly owned waste treatment works.
5. Fostering of areawide waste treatment management
planning processes.
6. Maintaining a major research and demonstration effort
to develop technology necessary to eliminate the discharge
of pollutants into the navigable waters, waters of the
contiguous zone, and the ocean.
At our last conference in December of 1972 we were just beginning
to implement the Act. Since then we have worked very hard, learned much
and in doing so have made significant progress toward full implementation
of the Act. Today, I would like to describe to you our efforts over the
past year. Since my specific area of responsibility is in municipal
wastewater treatment technology, I will emphasize that subject area while
giving a broad overview of the other portions of EPA's responsibility
under the Act.
EFFLUENT LIMITATIONS
In general, the new legislation provides for definite effluent
limitations for discharges into receiving waters, rather than application
of the former provisions whereby water quality standards for the particular
waters governed. Municipalities must have secondary treatment of their
wastewaters by July 1977 or 1978 under the law. However, where waste-
waters given secondary treatment will not achieve the water quality
standards of the receiving body of water, higher than secondary treatment
must be provided. This means, for example, that a State may set higher
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standards than secondary treatment for a particular lake, river, or estuary.
These higher standards will determine the degree of treatment that must be
provided to wastewaters discharged to the waterway.
On August 17, 1973 EPA published a final regulation which establish-
es the definition for the achievement of secondary treatment. It requires,
in general, 85 per cent removal or 30 mg/1 of BOD and suspended solids,
whichever is more stringent. All municipalities must provide treatment
of their wastewaters, at least to this standard, by July 1977 with some
extensions to 1978 in the case of plants that are under construction.
The law also provides that no grant can be made with 1975 funds
(available January 1, 1974) unless the treatment process involves the
use of the best practicable technology currently available and further —
all municipalities, whether or not they receive grants, must have the best
practicable treatment by 1983. We have drafted the best practicable tech-
nology regulation and it is now in the final stages of approval for publi-
cation as a proposal. We have provided you with copies and welcome your
comments and suggestions. Basically, the regulation establishes criteria
for three basic alternative waste management techniques which must be
considered and evaluated for cost-effectiveness. The alternatives and
criteria are summarized as follows:
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Treatment and Discharge
Monthly/Weekly
Averages
BOD- 30/45 mg/1
ss 30/45 mg/1 (Equivalent to
Secondary Treatment)
Fecal Coliform 200/400/100 ml
PH (6-9)
For treatment works over 1.0 MGD or 10,000 pop. or not discharing
to the open ocean.
UOD 50/75 mg/1 @ 20°C+
UBOD 30/45 mg/1 @ 20°C -
UOD = 1.5(BOD ) + 4.6(NH as N) - 1.0(D.O.)
5 3
UBOD = 1.5(BOD - 1.0(D.O.)
Land Application
Permanent Ground Water Criteria
Chemical Parameters EPA Drinking
Water Supply
Standards
Pesticides/Organics EPA Drinking
Water Supply
Standards
Point Source Discharge Criteria
Same as Treatment and Discharge Levels
Reuse
Not to Exceed the Above Levels
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In the case of industrial discharges, the effluent limitations
to be imposed must be derived from effluent guidelines now being developed
for 28 basic industrial categories that contribute significantly to water
quality problems. These guidelines for industry put into definite terms
the 1972 law's goals, i.e. "best practicable technology" by 1977 and then
"best available technology" by 1983.
PERMITS
The Act establishes a new system of permits for discharges into
the Nation's waters, replacing the 1899 refuse Act permit program. No
discharge from any point source is allowed without a permit. These must
be obtained for publicly owned treatment plants as well as industrial
dischargers. Over 20,000 municipal treatment plants must obtain permits
by December 1974. A typical permit will contain a schedule for upgrading
treatment to come within prescribed effluent limitations.
Any discharge not in conformity with a permit will be unlawful,
and, if willful and negligent, will be subject to a penalty of from
$2500 to $25,000 per day of violation. On the part of EPA, court actions
will be used as a last resort. We propose to give industries and munici-
palities the ample opportunity to comply with the requirements on a
voluntary basis.
PRETREATMENT STANDARDS AND GUIDELINES
The pretreatment standards can be described in terms of the two
major objectives outlined by Congress.
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The first objective, to prevent the introduction of pollutants
which would pass through inadequately treated, requires that the term
"inadequately treated" be defined. The regulations are based on the
premise that incompatible pollutants introduced by an industry are
inadequately treated if they pass through publicly owned treatment works
in amounts greater than would be permitted if the user discharged directly
to the receiving waters. Accordingly, the pretreatment standards for in-
compatible pollutants are the same as the requirements for direct discharge.
These requirements are to be based upon application of the best practicable
control technology currently available.
An incompatible pollutant is defined as any pollutant other than
BOD, suspended solids, pH and fecal coliform bacteria plus those pollutants
that the municipal plant was specifically designed to treat. A less strin-
gent pretreatment standard is permitted for thos incompatible pollutants
which the municipality is committed to remove in its permit for the publicly
owned treatment works.
The standards for incompatible pollutants apply only to major indus-
tries so as to reduce the number of industries which would have to pretreat
and yet cover those industries that could have a significant impact upon
the municipal plant.
The second objective which the standards must address is to protect
the operation of the publicly owned treatment works. Under this objective,
four prohibited discharges are listed in the standards.
There will be situations when the Federal pretreatment standards
will not be sufficient to protect the operation of the publicly owned
treatment works or prevent the discharge of industrial pollutants inade-
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quately treated. In such cases, the municipality would have to supplement
the Federal Standards. The pretreatment guidelines are intended to assist
municipalities in accomplishing this.
CONSTRUCTION GRANT REGULATIONS
To enable municipalities to meet effluent limitations and permit
requirements, the new amendments authorize Federal grants to municipalities
for assistance in building sewage treatment facilities. These grants are
mandated at the rate of 75 percent of eligible costs of approved projects.
To facilitate the processing of these grants, EPA has issued the
"Title II Regulations." These regulations set forth policies and procedures
concerning the processing of applications for grant assistance. Included
is the provision that all projects must meet planning requirements and
receive a priority certification from the State.
The regulations have been written with a view toward giving communi-
ties and States as much autonomy in making decisions as is possible under
law. For example, the responsibility for review of plans and specifications
for projects is to be passed to States as rapidly as States become able.
An innovation in the regulations is the introduction of a three-
step grant process. Step !_ allows a separate grant for the preparation
of preliminary studies and engineering. Step 2 provides for a grant for
the preparation of construction drawings and specifications, and Step 3
is for a grant for the building and erection of the treatment works.
This division of the financing of a grant for a project will accelerate
payments to the communities and allow available funds to be spread over
a larger number of projects. We believe that this procedure will be of
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great assistance to communities. It has already allowed a larger number
of projects to go forward in most areas than would have been the case
under the former regulations and law.
Final "Title II Regulations" will be published soon.
I would like to briefly mention some other requirements under
the Act that you will be interested in:
PLANNING
The law lays down firm requirements for the planning of pollution
abatement programs, and for control programs tied directly to the plans.
For example, each State must have a continuing planning process which will
result in water quality control plans for all navigable waters within the
State. Included in such plans must be an inventory and ranking, in order
of priority, of needs for construction of wastewater treatment plants re-
quired to meet the applicable standards. In addition, each sewage treatment
works must have a facility plan which will consider not only the technical
but also the social and economic aspects of a project. Involved here are
environmental impact statements prepared by EPA when major controversies
are unresolved.
INFILTRATION/INFLOW
Section 201 of the Act states that the EPA Administrator shall not
approve a grant after July 1, 1973 unless the applicant shows that each
sewer system discharging into the treatment works is not subject to excessive
infiltration. The construction grant regulations require that an analysis
be made of the sewer system involved to determine if there are indications
of excessive infiltration. If so, an infiltration study has to be made to
determine action to handle the infiltration problem economically. Such
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studies are eligible grant costs, usually as part of the Step 2 grant
process. There will be cases, where it will be more economic, on a cost-
effective basis to treat infiltration by building a larger plant, rather
than trying to seal a sewer system. Also, it is recognized that in many
cases it may not be feasible to remedy infiltration/inflow immediately.
A reasonable and satisfactory abatement schedule may be agreed upon while
the project goes forward.
An infiltration/inflow analysis has always been part of a well-
planned project. Therefore, we do not look upon this requirement as being
burdensome in the design of sewage treatment systems. Guidelines on infil-
tration/inflow analysis will be published shortly at about the same time
as final construction grant regulations.
COST-EFFECTIVENESS
Section 212 of the Act also specifies that the Administrator shall
publish guidelines on methods of cost-effectiveness analysis for the con-
struction of treatment works. These guidelines were published in final
form on September 10, 1973. Basically, the guidelines contain uniform
economic analysis procedures which must be incorporated into all grant
applications. This will assure adequate data and analysis demonstrating
the project to be the most cost-effective over the design life of the
works. The analysis must include consideration of both capital and oper-
ation and maintenance costs.
Again, cost effectiveness analysis has normally been undertaken
as part of any sound engineering analysis, even though it may not have
been labeled as such. The law formalizes the procedures. The requirement
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is not expected to cause any great problems since the process is familiar
to those in the profession.
USER CHARGES AND INDUSTRIAL COST RECOVERY
Having provided for Federal assistance in building wastewater
treatment facilities, the Act seeks to assure that the facilities will
be properly maintained and operated. To accomplish this, communities
that are assisted with grants are required to have a user charge system
that insures that all users will pay their proportionate share of operation
and maintenance costs. In addition, the law provides that industry, discharg-
ing into the system, must pay back its proportionate share of the Federal
grant. Fifty percent of this payback may be used for liquidating the
community's cost of the project and for future expansion and reconstruction
of the project. The remaining 50 percent reverts to the U.S. Treasury.
Final user charge and cost recovery regulations were published on August 21,
1973.
FINANCIAL NEEDS OF THE PROGRAM
To achieve the goals of the program will be a costly venture.
Recent estimates indicate that it will require industry to expend for
capital improvements $12.9 billion to bring about the use of best practicable
technology by 1977 and an additional $7.8 billion to apply best economically
available technology by 1983.
The needs of municipalities for financing has been the subject of
a recent survey. The objective of the survey was to ascertain the funds
that would be required to meet the 1977 goals of attaining secondary
treatment or higher where water quality standards are higher. The total
amount came to a total of over $60 billion. $16.6 billion is required to
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improve treatment plants to achieve secondary treatment, with an
additional $5.6 billion for further removing specific pollutants such
as phosphorus, nitrogen and organics to the extent required by legally
binding Federal, State, international and local actions. $700 million is
required for eliminating infiltration/inflow conditions, $13.6 billion is
necessary for building new interceptors, force mains, and pumping stations,
$11 billion is estimated for new collection systems, and $12.7 billion is
required for the reduction of combined sewer overflows. We know that some
of these figures are not absolutely accurate because of an inadequate data
base that we are even now engaged in strengthening. We believe, however,
that the combined total of $36 billion for treatment plants, removal of
other pollutants, and the building of new interceptors is reasonably accurate.
The remaining $24 billion is probably too low a figure.
FEDERAL FINANCIAL ASSISTANCE
The Federal government between 1956 and 1972 expended over $5 billion
to assist municipalities in building waste treatment facilities. At present
another $9 billion is available for grants at 75 percent of construction
costs. Four billion of this total was just added on January 1, 1974.
Further financing for after that date is now under study and review.
CONCLUSION
The magnitude of the United States' program which I have just
described leads to my concluding remarks. To make such a program viable
will require the utmost use of new technology and innovations. Even samll
advances in improving the efficiency and effectiveness of sewage treatment
systems will result in major savings overall; significant advances will
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reduce the load on our taxpayers who must pay for the improvements in
water quality.
Your efforts in Japan to improve and maintain water quality must
present the same strains on your economic and social systems. By joining
together to bring about the most efficient and effective application of
technology and ideas to the treatment of wastewaters, we can achieve more
than each of us can alone. Our visit to Japan so far has been most bene-
ficial in this respect. I look forward to a successful conclusion of this
Conference.
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THE FEDERAL WATER POLLUTION CONTROL ACT AMENDMENTS OF 1972
STATE VIEWPOINT
DICK WHITTINGTON, P.E., DEPUTY DIRECTOR
TEXAS WATER QUALITY BOARD
AUSTIN, TEXAS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
203
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FEDERAL WATER POLLUTION CONTROL ACT
AMENDMENTS OF 1972—STATE VIEWPOINT
I believe it appropriate in the beginning to provide a limited
overview of the American system of state-federal relations inasmuch as
this will help you understand my view and the interactions of federal,
state, and local governments in the United States.
The U.S. Constitution, written by representatives from the several
states, provides for a division of governmental powers between the federal
and state governments. The division was accomplished by delegating to the
federal government specified powers plus the powers inherently required to
execute the delegated powers—all undelegated powers to remain with the
states.
Under this division of powers, the control of water pollution was
for many years considered to be primarily a function of state government.
The federal government was considered as having the prime function when
its ability to discharge its delegated powers were endangered. Along
these lines, the federal government in 1899 enacted a refuse act which
placed it into the water pollution effort in a very limited way—only
to protect navigation channels from excessive siltation or clogging.
The 1899 Refuse Act required a federal permit to discharge refuse-laden
wastewaters into navigable waters. Several years ago, as a result of a
judicial decision, the 1899 Refuse Act was expanded in scope, wrongly
in the opinion of many, to consider all pollutants—not only suspended
solids. The 1972 Amendments, at least to some degree, is an outgrowth
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of the 1899 Refuse Act since it sets up a comprehensive federal waste
discharge permit system.
The U.S. Constitution has generally been interpreted so as to
provide federal supremacy over state government when there is a conflict
involving the national interest. This is the case with the 1972 Amendments
where it was decided that the national interest was being endangered because
of the failure of the several states as a whole to adequately control water
pollution. When this is done, a state's power to cope with its own problems
as it sees fit is to a considerable degree set aside—even though a particular
state may be doing its job satisfactorily.
Under the division of powers previously discussed, the State of
Texas proceeded many years ago to inaugurate programs to control water
pollution—other states also inaugurated programs, some very good, some
very bad. I think Texas has a good program. We have required secondary
treatment of domestic sewage for some 30 years. We have had a permit
program covering both municipal and industrial discharges, including
agriculture, since 1962. We have had a mandatory self-monitoring program
in operation since 1970. All of these programs and more are now incorpor-
ated into the 1972 Amendments and made federal programs. This fact,
coupled with detailed regulations promulgated under the Act requires
that all our programs be revamped and restructured to fit the pattern
mandated by the federal government. This necessarily involves a great
deal of lost motion and unnecessary expense. In this case, states who
did not have comprehensive programs as of the passage of the Act are
probably in an advantageous position since they will be able to structure
programs from the beginning to fit the federal mold. As each of you know,
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it is easier to construct a new house to detailed specifications than it
is to rebuild an old one—even though the old structure may be sound and
sturdy. We are in that position in Texas and we are trying to rebuild our
house since we recognize the Act as the law of the land.
I think it would be appropriate at this time to say that the various
state governments have no single viewpoint on the merits of the 1972 Act.
This same divergence of opinion exists even within individual states between
state civil servants, the political leadership, and the people. In general,
I think it would be true that: (1) the state civil servants, almost to a man,
think the law has serious flaws and has been wrongly implemented; (2) the
political leadership recognizes the law as a political necessity; and (3) the
people have no specific view—they are merely dissatisfied with the progress
the states have made in correcting pollution problems. In these regards, I
shall only attempt to discuss the Texas viewpoint, generally as seen by state
pollution control officials.
Within the time allotted to me, let us look at some aspects of the
law or regulations promulgated therunder which we consider problems.
Section 101(b) states that it is the intent of Congress that the
rights of the states to protect and use its waters be preserved. In
actuality, the federal role is all pervasive and conformity to the federal
mold is much more mandatory than statutory language would require. This,
we think, is a mistake since it fails to take into account regional differ-
ences between the states in law, custom, history, land use, topography, etc.
The insistence on uniformity has caused considerable wear and tear on nerves
and tempers, and has served no good purpose.
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Section 101(a) sets forth the goals of the Act—recreational use
water quality in all streams by 1983 and no discharge of pollutants by
1985. I think these goals are unrealistic, particularly the schedules.
Such environmental daydreaming will never take the. place of common sense
and sound technical judgment.
Section 301(b) (1) (c) of the Act says in effect that by July 1,
1977, publicly owned treatment works shall produce either a secondary treated
effluent, or an effluent subject to advanced waste treatment if this is
required to meet stream standards. Federal waste discharge permits as
provided for in Section. 402 of the Act will be used to implement these
requirements including the schedules. So far, all is well and proper,
except possibly the schedule.
When, however, the permit program is coupled with the grant program
for publicly owned treatment works as established under Title II of the Act—
a real dilemma results.
Section 202(a) provides that the federal shore of the costs of
publicly owned treatment works shall be 75%. A survey conducted under
Section 516(b) (2) of the Act to determine the needs of all the states
resulted in a need for Texas in excess of 800 million dollars, and we
think at the state level this is too low. The actual level of funding
as evidenced by past actions will fall far short of the need. Thus,
taking into consideration both the permit program and the grant program,
it would appear to us that the federal government is telling state and
local government on the one hand through the permit system to construct
rapidly the needed works; and on the other hand telling these same
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governments through the grant program that they are entitled to 75%
federal funding, but that it will not be forthcoming in many cases in
time to meet the 1977 deadline. This in our judgment is confusing. We
are very hopeful that the Congress will resolve this problem so that our
nation can proceed harmoniously to construct the necessary works to finish
the task of cleaning up our waters.
Title IV of the Act provides for a permit program to control waste-
water discharges, and provides that the federal government can delegate
under certain conditions the responsibility for the administration of this
program to the states. EPA has promulgated restrictive regulations concern-
ing the prerequisite to receive delegation and has interpreted the regulations
narrowly. They appear to be attempting to find reasons why a state should
not be given delegation, rather than how to overcome obstacles to delegation.
We think this is a mistake and that this fails to properly utilize existing
trained manpower available in state organizations. In order to partially
overcome this problem, our state and the EPA Region in which we are located
have worked out an informal arrangement to make our resources available.
Many other issues could be raised; however, suffice it to say that we
think that inadequate attention has been given in the law and its implementa-
tion toward effectively utilizing existing state organizations. This is,
we believe, primarily due to an attempt to fit all state programs—good and
bad—into one rigid mold.
Contrary to what you may think at this point in my presentation,
I do not think all aspects of the Act are bad. The concept of setting
water quality standards for the nation's waters is sound and necessary.
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The concept of specifying minimum treatment levels regardless of stream
requirements is sound—we have followed this concept in Texas in the case
of municipal sewage for over 30 years. The continuing planning process
mandated by Section 303 (e) of the Act is a sound concept. It has enabled
us to take a more effective look at the overall water quality needs in each
river basin and will result in a much more coordinated control program than
has heretofore been the case. The self-monitoring program wherein each
waste discharger is required to monitor the quantity of pollutants he dis-
charges to public waters and report this information to the government is
sound. We have had such a program in operation in Texas since 1970 and it
has been one of the most effective tools we have found in recent years in
abating pollution. There are many other aspects of the Act which are
worthwhile and necessary.
In summary, let me say that while I have obvious concerns about the
Act itself and the manner in which EPA has implemented the Act, it is a far-
reaching Act clearly setting forth our government and our people's determi-
nation to solve our nation's water pollution problems. I am personally
very confident that in a short time the rough spots will be smoothed over,
and we will complete the job of cleaning our nation's waters, started so
many years ago. I started in this business over 20 years ago, and I am
glad to see the climate of public opinion change to support the clean-up
effort. Without the public's support, the job will not be done. The
passage of the 1972 Act is very significant in that it clearly signals
our nation's commitment to clean water.
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EPA OVERALL RESEARCH PROGRAM
AND WASTEWATER TREATMENT RESEARCH
F. M. MIDDLETON
DEPUTY DIRECTOR
NATIONAL ENVIRONMENTAL RESEARCH CENTER
ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
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EPA OVERALL RESEARCH PROGRAM
AND WASTEWATER TREATMENT RESEARCH
ORGANIZATION
The Environmental Protection Agency is headed by an Administrator,
now Mr. Russell E. Train. To carry out the EPA programs there are Assistant
Administrators for various programs as shown in Chart I.
Research is directed by the Assistant Administrator for Research and
Development, Dr. Stanley M. Greenfield. His office is in Washington, D.C.
The Office of Research and Development has about 1800 employees and a budget
of about $120,000,000 per year. Chart II shows how the Office is organized.
To conduct the research for EPA, four National Environmental Research
Centers have been established. These NERC's are located at Cincinnati, Ohio;
Corvallis, Oregon; Research Triangle Park, North Carolina and Las Vegas,
Nevada. There are about ten smaller laboratories in other locations that
are administered by the NERC's. The brochures you have been provided explain
the programs of the NERC's further. Chart III shows the organization of the
Cincinnati NERC - The Robert A. Taft Laboratory.
HOW OUR RESEARCH IS CONDUCTED
Wastewater treatment research is conducted by the Advanced Waste
Treatment Research Laboratory in Cincinnati. Industrial waste treatment
research is conducted at Edison, New Jersey and at some other NERC's. Our
Storm and Combined Sewer Research Program is also located at Edison, New
Jersey.
211
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About 150 people work in the programs devoted to domestic and
industrial waste treatment. The budget for domestic wastewater is about
$10,000,000 and the industrial waste budget is about the same.
The objectives of our treatment research programs are to improve
old methods and devise new methods for the management and control of waste-
waters to enhance the quality of the Nation's water and meet the quality
standards required.
How do we decide upon research projects? First of all, the EPA is
guided by certain laws that have been enacted. Much of our work in water
pollution is directed by the Federal Water Pollution Amendments Act of 1972 -
Public Law 92-500. Within the policies of the EPA, the Office of Research
and Development develops a basic strategy to meet the Agency needs. Research
needs are solicited from EPA Headquarters and field programs. Using these
needs and the strategy documents, our Washington Headquarters, with help
from the laboratories, draws up a general research plan and designates the
amount of money to be spent in each area of work. It is then the job of
the research staff to design detailed work plans. After the work plans
are approved, the project gets underway. We project our research for five
to seven years. We perform research in our own laboratories but we also
make extensive use of cities, industries, commercial research groups and
universities to conduct research for us. Chart IV shws our planning
process in graphical form. Chart V is a list of major topics we are
conducting research on in the municipal and industrial waste field.
Chart VI shwos a summary sheet on one project and a graphical network
diagram of the project.
212
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TECHNOLOGY TRANSFER
Once the research is completed, it is made available to the Agency
programs that has requested it and to others. There are now several hundred
reports on the research that has been done. These reports are available to
you.
To expedite the use of new technology, EPA has special teams of
researchers and outside consultants put on special two- or three-day seminars
all over the country for consulting engineers, state authorities, city
governments and the like. We also produce manuals on various subjects
and distribute them widely. You are already familiar with our Advanced
Waste Treatment Manuals.
213
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CHART I
U. S. tNVlRONMENTAL PROTECTION AGENCY
OFFICE OF CIVIL UGHIS
AND UCBAN AFFAIRS
CAROL fHOMAJ 7S5-Oi«
OFFICE OF FEDERAL ACTIVITIES
SHUDCN MEYERS
755-0777
ADMINIS1RAIC*
RUSSfLL TWIN
755-7700
DEPUTY ADMINISTRATOR
JOHN OUARLES, JR.
755-77 IT
ro
^ OFF ICC Of INIEaNATlONAL ACHVITKS
FHZHUGH GRECN
755-27 M
OFFICE OF PUBLIC AFFAIRS
ANN DOR(
755-0700
AiST. ADMINISIRATOS
FOR A H AND
WAIE8 PROOtAMS
ROBERT SANSOM
7i5-?6*0
OFFICE OF
All QUALITY
PLANNING AND
STANDARDS
1. J. STEIGtCV/ALD
(9)9) (.33-8576
OFFICE OF
MOBILE SOURCE
AIR POLLUTION
CONTROL
ERIC STORK
426-3464
OFFICE Of
WATtft PLANNING
AND STANDARDS
LILLIAN RCGELSON
7SS-Qt02
OFFICE OF
WATER PSOGRAM
OFLRAT1ONS
itctON i . sc;rcN
JOHN MeGLtNNON
(417) 223-7210
«GlO^; il - Nf.v VO«K
GERALD KAN SI El
(212) 2M-K23
•ECtOM III ' fHfLADELPHIA
D. SNYOEB III
(3151 597-9801
UGION TV - ATLANTA
JACK RAVAN
(404) 5Ji-5777
MGION V -CHICAGO
flANClSMAYO
(317) 313-5*50
REGION VI - DALLAS
ARIHUfl BUSCH
(JU) 7-49-1962
•EGION VII- KANSAS CUV
JE8OME SVOfte
(8)4) 374-5493
REGION VIII - OENVtl
JOHN CRHN
(3331 837-3B»
UClON IX - SAN MANOSCO
PAUL OaFALCO, Jt.
{415) 5U-232D
-------
CHART II
OFFICE OF RESEARCH AND DEVELOPMENT
ASSISTANT ADMINISTRATOR
FOR
RESEARCH AND DEVELOPMENT
STANLEY GREENFIELD
755-2600
DEPUTY ASSISTANT ADMINISTRATOR
FOR
PROGRAM INTEGRATION
LELAND ATTAWAY
755-2611
DEPUTY ASSISTANT ADMINISTRATOR
FOR
ENVIRONMENTAL ENGINEERING
A. C. TRAKOWSKI
755-2532
MUNICIPAL POLLUTION
CONTROL DIVISION
WM. ROSENKRANZ
522-0363
TECHNOLOGY
TRANSFER STAFF
ROBERT CROWE
755-0851
INDUSTRIAL POLLUTION
CONTROL DIVISION
WM. LACEY
522-0363
NON-POINT POLLUTION
CONTROL DIVISION
THOMAS MURPHY
755-0628
AIR POLLUTION
CONTROL DIVISION
RICHARD HARRINGTON
755-0628
OFFICE CF PRINCIPAL
SCIENCE ADVISER
(VACANT)
SCIENCE ADVISORY BOARD
OFFICE OF PROGRAM MANAGEMENT
DAVID STEPHEN
755-0475
DEPUTY ASSISTANT ADMINISTRATOR
FOR
ENVIRONMENTAL SCIENCES
HERBERT WISER
755-0655
_L
DEPUTY ASSISTANT ADMINISTRATOR
FOR
MONITORING SYSTEMS
WILLIS FOSTER
755-2606
SPECIAL ASSISTANT
FOR WATER SUPPLY
RESEARCH
H. GORCHEV 755-2582
HEALTH EFFECTS
DIVISION
J. WESLEY CLAYTON
755-0614
ECOLOGICAL PROCESSES
AND EFFECTS DIVISION
(VACANT)
PLANNING AND
REVIEW STAFF
WM. SAVERS
755-2553
EQUIPMENT AND
TECHNIQUES DIVISION
HENRY ENOS
755-0448
WASHINGTON ENVIRONMENTAL
RESEARCH CENTER
LARRY RUFF
755-0477
QUALITY ASSURANCE
DIVISION
GUNTIS OZOLINS .
755-0434
DATA & INFORA.1ATION
RESEARCH DIVISION
MATTHEW BILLS
755-0468
NATIONAL ENVIRONMENTAL RESEARCH CENTERS
CINCINNATI LAS VEGAS
CORVALLIS RESEARCH TRIANGLE PARK
ASSOCIATED LABORATORIES
-------
rv>
CHART III
ORGANIZATION FOR NATIONAL ENVIRONMENTAL RESEARCH CENTER
THE ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI,-OHIO
PROGRAM
STAFF
i i
ADVANCED
WASTE TREATMENT
RESEARCH
LABORATORY
BRANCHES:
Treatment Process
Development
Systems and
Engineering
Evaluation
Technology
Development
Support
INDUSTRIAL
WASTE TREATMENT
RESEARCH
LABORATORY
BRANCHES:
Oil Spill Technology
Hazardous Spill
Technology
Industrial Pollution
Control
Watercraft and
Recreational
Pollution Control
Mining Pollution
Control
'
DIRECTOR
DEPUTY
I
SOLID AND HAZARDOUS
WASTE
RES
^RCU
LABORATORY
BRANCHES:
Disposal
Processing
DIRE'TOR
I
PUBLIC
AFFAIRS STAFF
1 .
WATER SUPPLY
RESEARCH
LABORATORY
BRANCHES:
Criteria Development
Standards Attainment
METHODS DEVELOPMENT
AND QUALITY ASSURANCE
RESEARCH
LABORATORY
BRANCHES:
Physical-Chemical
Methods
Biological Methods
Quality Assurance and
Laboratory Evaluation
Instrumentation
Development
Radiochemlstry and
Nuclear Engineering
1
ENVIRONMENTAL
TOXICOLOGY
RESEARCH
LABORATORY
BRANCHES:
Experimental Toxicology
Exposure Systems
and Assessment
Biological Effects
September 74. 1973
-------
CHART IV
OFFICE OF RESEARCH AND DEVELOPMENT PLANNING PROJECTS
EPA POLICIES AND
LEGAL RESPONSIBILITIES
OFFICE OF RESEARCH AND DEVELOPMENT
RESEARCH NEEDS RECEIVED FROM OTHER
EPA PROGRAMS, STATES, ETC.
STRATEGY PLAN
CONCURRED IN BY OTHER EPA PROGRAMS
GENERAL PROJECT PLANS
MONEY ESTIMATES PREPARED
LABORATORY RESEARCH PERSONNEL
DESIGN DETAILED STUDIES
APPROVAL OF PLANS
WORK BEGINS
217
-------
CHART ¥
RESEARCH PROJECTS IN DOMESTIC AND INDUSTRIAL WASTE TREATMENT AND CONTROL
NERC-CINCINNATI
1974
Advanced Waste Treatment Research Laboratory
Title
Demonstrate Combinations of Processes to Meet Water
Quality Needs
Methods & Processes to Provide Improved Operation &
Maintanence, In-System treatment, & Treatment of Joint
Municipal & Industrial Wastes
Research & Investigation of Joint Liquid-Solid Waste
Collection & Treatment
Treatment of Combined Sewer Overflows & Storm Water Discharges
Technology for Hydraulic & Pollutant Control of Urban Runoff
Simulation Models for Total Management of Sewerage Systems
Methods, Processes, & Systems to Reduce Water Use & Total
Sewage Flow
Research, Development, & Pilot Projects to Eliminate
Pollution from Sewage in Rural or Other Areas Generating
Small Flows
Wastewater Renovation and Reuse
Wastewater System Instrumentation & Automation
Wastewater Sludge Processing & Treatment
Wastewater Treatment Sludge Disposal
Control of Nutrients in Wastewater
Suspended & Colloidal Solids Removal from Municipal Wastewater
Biological Treatment Process Improvements for Municipal
Wastewater Applications
Municipal Wastewater Disinfection Process Development and
Demonstration
Reduction of Total Dissolved Solids (TDS) & Heavy Metals
in Municipal Wastewaters
Control of Dissolved Organics in Municipal Wastewater b\
Physical-Chemical Processes
218
-------
CHART V (continued)
Industriaj^_Waste Troatinent Research Laboratory
Technology Research for the Elimination of the Discharge of
Pollutants from the Inorganic & Miscellaneous Chemicals
Industries
Technology Research for the Elimination of the Discharge of
Pollutants from the Non-Ferrous Metals & Electroplating
Industries
Technology Research for the Elimination of the Discharge of
Pollutants from the Rubber & Plastics Industries
Completion of FY-73 Work Plan ROAPs 21 APK, 21 APL and
21 APO
Treatment of Mine Drainage
Pollution Control Methods for Surface Mining
Control of Pollution from Underground Mining of Solid Fuels
New Mining Methods
Mine Water Pollution Control Demonstrations - Section 107
OHMSETT Support
Chemical Identification of Oil Spills
Oil Spill Containment Devices
Equipment for Physically Removing Oil Spilled in the
Environment
Waste Oil Recycling
Prevention of Hazardous Material Spills
Hazardous Material Spill Emergency Response
Hazardous Material Spill Control and Removal
Separation & Recovery of Removed Spilled Hazardous Materials
Environmental Evaluation of Devices & Techniques to Control
Hazardous Material Spills
219
-------
Off ice-of Ccscarcli iiml MonUon'ny
RESEARCH Ci'.JfiCTIVi: ACilJCVIII-SilT PLAM SUMMARY
.f-0-OiK.VI tur_M
Treatment Process Development
and Optimization
Municipal Technology
i.o.
21-AST
.'i'-.-^i Lir::.'i: :.3.
1B2043
EI:OS/i...V HUE:
Reduction of Total Dissolved Solids (TDS) and
Heavy Metals in Municipal Wastewaters
21ABO
21AAP
21AAQ
21AAS
Design guidelines for. cost-optimized reverse osmosis, ion exchange and distillation
processes based on large-scale demonstrations. Reports on capabilities of vaste
treatment processes to remove heavy metals and possible process modifications to
enhance removal of metals and toxic non-metals,
c;)
Fcr,.i.
JLL9JL
.AQ.i
356
1.2
FY. 74
68
2.3
Sponsor
Region V
HEEO SPfiSORS
Priority
Cinti
131/171
17/62
191/454
05AC(
FY 75
220
2:3
Clannod
196!
FY 76
375
2.3
ActuU
1F6T"
FY77
600
CRG^'iiJATiC1; r.iS?:::siri.-L FG?.
FFC£PA?.;NJ A;;3 i.".?L£:'.c.'iT::;3 ".CA
L/3/oiv
(fivs di
67024
Sf:0 KLATIQ
Supporting FJ !:o'
FT 78
510
2.3
Pr.C;P.AM AREA PK10.71TY
A;slr;icd Ty Priority
16 -VKJJJ[
24 AXl'i!
FY 79
663
O.i
-------
17
a i AST
LEDUCTIOS OF TOTAL DISSOLVED SOLIDS (TDS) ANDJ
HEAVY HKTALS IN MUlilCIl'^L S'ASTEWATERS
ADVANCED BASTE TREATMENT RESEARCH LAOORATOHYj
HERC-C1MTVVAT1
OF REMOVING ADDITIONAL TOXIC
METALS & NON-METALS IN P-C
PILOT PLANT
Inhouse
Begin; 1973/2nd End: 1974/2nd Qti
.LUATIO.V OF" PROCESS $110,000
[MODIFICATION'S TO ENHANCE'
BEMOVAL5 OF SPECIFIC METALS
AND INORGANIC NON-METALS
Jnhouse
in- 1974/3rd End: 1976/2|id Qtr
/-T7>\ l8
( DecisionX
Data To 1
iDemonstrate/
\ 1977/1 /
SHORT EVXLUATIO^S OF
'-ETAL-Rf-'OVAL PRCCKS
TREATKEST PLANTS
lie-jin: j376/3rd End:
$152,500
ES AT
1978/2nd Qtr
23
I'REPARE MANUAL OF
PRACTICE FOR METALS
Becin: 197S/3rd End
S 7SjOOO
REyOVAL
1979/Znd
Qtr
B.REVERSE OSMOSIS.
01. 05, 07, 10, 11
[LABORATORY A.VD PILOT STUDIES!]
| OF REVERSE OSMOSIS |
DEMONSTRATE CURRENT RO 5311,000
TECHNOLOGY AT 150,000 GPD
17
RO DEMONSTRATION' 5195,000
USIN-G CHEMICALLY TREATED RAW
ffASTEWATES KITH OR WITHOUT
ACTIVATED CARBON
Begin: 1975/3rd End: 1976/?nd Qtr
/
\
00,000
ASSEMBLIES OH CONFIGURATIONS
Inhouse
[Begin: 1976/3rd End: 1977/?nd Qt
no
DEMONSTRATE NEWT RO
MEMBIUXE ASSEMBLY OR
COSTIC'JRATION
Demonstration Grant
fpREPARE MANUAL OK5100,000
PRACTICE FOH REVERSE OSMOSIS
137973rd End: X9
E.ECOHOM1C ftKALYSIg
C.ION EXCHANGE
03, o«, 06 [PILOT_ STUDIES" OT" ION EXCR.VMCE fr
OKSTRATE FIXED BED S2SO,000
ION-EXCHANGE AT 100,000 GPD
Demonstration Grant
Begin: 1974/3rd End: 1976/2KJ Pt
[DEVELOP PROCESS FOR S15~57ot
'''.ECCVESV OF SH_ FROM ION'
-:.XCHASGZ REGEStRANT AND
DISPOSAL OF RESIDUAL BRINE
fetepi:
1976/3rd End: 1978/lnd
; TO
5100,000
: OF
LICATION FOR EACH
DEMINERALIZATION PROCESS
'Contract
Begin: 1979/3rd End: 198Q/2nd Qtr
PARE MANUAL OK 3100,000
.PRACTICE FOB ION £XCHASOE
IContract
[Begin: 1976/3rd End: I979/2nd Qtr
IREGENERAFION 'OF NOVEL
,ION EXCHANGE MATERIAL
(Contract
PREPARE 1IANUA
PRACTICE FOR
Contract
BcK'n: 1980^3
1, Oh' S IOO ,l>00
DISTILLATION
r
-------
TREATMENT AND DISPOSAL OF SLUDGE FROM MUNICIPAL
WASTEWATER PLANTS IN THE UNITED STATES
DR. JOSEPH B. FARRELL, CHIEF
ULTIMATE DISPOSAL SECTION
TREATMENT PROCESS DEVELOPMENT BRANCH
ADVANCED WASTE TREATMENT RESEARCH LABORATORY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
222
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TREATMENT AND DISPOSAL OF SLUDGE FROM MUNICIPAL
WASTEWATER PLANTS IN THE UNITED STATES *
Most communities in the United States have primary treatment and
secondary treatment is a national goal. The quantities of sludge which
must be handled are large (Table l). We expect a large increase in the
amount of secondary and chemical sludges. As Table 1 shows, most of our
sludge is disposed to the land. A substantial proportion is incinerated
and the ash is disposed to land. Ocean disposal of sludge is expected to
be greatly reduced in the future.
Composition of Sludge
Municipal sludge is chiefly composed of paper fiber, human wastes,
food wastes, a proportion of industrial wastes, and, when stormwater is
included in the sewers, soil and dirt from roads. Raw sludges may contain
70 to 85 percent volatile solids (30 to 15$ ash) and digested sludge 50
to 65 percent volatile solids (50 to 35$ ash). Sludge from a community
contains trace amounts of hazardous materials. Typical values are
presented in Tables 2 and 3- The range of values can be extremely high.
It is important that communities periodically analyze their wastewater
sludge to determine whether hazardous levels of certain contaminants will
place restraints on their method of disposal.
Ocean Disposal**
The United States Council for Environmental Quality has spoken out
for an eventual cessation of the disposal of sewage sludge by barging to
* Presented at Third U.S./Japan Conference on Sewage Treatment Technology,
Tokyo, Japan, February 13, 1974.
** The author of this paper has not dealt intimately with ocean disposal and
is not an authority on EPA's Ocean Dumping Policy. The discussion is
presented for general guidance only.
223
-------
disposal sites in the ocean. Most barging is conducted on our East Coast
where the sludge is dumped in the relatively shallow waters of the Con-
tinental Shelf. Regulations have been published in the Federal Register^ '
and the Code of Federal Regulations^2' listing maximum concentrations of
certain metals and compounds which should not be exceeded in material
being dumped. For example, it is stated that mercury in the solid phase
should not exceed 0.75 mg/kg- Virtually any municipal sludge contains at
least several times this concentration of mercury. There is pressure to
raise these levels but it is unlikely that changes will be made. The
United States Environmental Protection Agency is issuing permits for
dumping of sewage sludges which are described as interim permits.
Municipalities are required to prepare a plan for meeting the desired
concentrations and reapply annually for a permit. It is anticipated
that municipalities will find other disposal methods less costly than
meeting the ocean disposal regulations. The EPA has prepared a report
describing the progress of the ocean dumping program'3/.
For years, cities in California have discharged digested sludges by
pipeline to outfalls into the ocean. There is essentially no continental
shelf on the Western Coast of the U. S. Nevertheless, California has a
policy which will probably prohibit ocean disposal of sludges in the
foreseeable future.
Stabilization
Anaerobic Digestion — There has been a renewed interest in anaerobic
digestion because of the energy shortage. Most of the interest is related
to agricultural and animal wastes and municipal solid wastes. The quantity
224
-------
of recoverable methane from sewage sludge digestion is too low to have an
impact on the national needs. However, it can help the economics of
individual plants. Most wastewater treatment plants which utilize
anaerobic digestion waste the surplus gas over their needs for sludge
heating. Los Angeles is a notable exception. Both the city and the
county sell their excess gas production to nearby utilities. There will
probably be more efforts made to utilize excess gas for in-plant power
generation and fuel needs. Its impact will be small.
Aerobic Digestion — Aerobic digestion is practiced at many small
plants where it is often followed by land disposal of liquid sludge. We
have supported research work aimed at improving plant scale operation and
establishing design information*- '. We have also supported work on thermo-
philic aerobic digestion (about 60° C) utilizing oxygen. This work,
although in its early stages, has been encouraging. It has the potential
of faster digestion (hence smaller equipment) and will produce a sludge
containing no pathogens.
Chlorine Stabilization — Stabilization of sludge by treating it with
high concentrations of chlorine (about 2000 mg/l) produces a stable and
sterile sludge. This process is being used at numerous small plants. We
are concerned that the drainings from this sludge may contain toxic
chlorinated compounds. We recommend that all drainings be recirculated
to the incoming sewage.
Lime Stabilization — Our studies^) show that addition of lime to
liquid sludge will stabilize the sludge for a sufficiently long time to
permit nuisance-free disposal. We now recommend adding lime to liquid
225
-------
sludge to raise pH to 12. This will require less than 0.15 kg Ca(OH)2
per kg of sludge (dry solids basis). The sludge and lime are preferably
mixed by air, which removes the odor of ammonia. Pathogenic bacteria are
eliminated. The sludge can be dried on sand beds, disposed to a landfill,
or spread in liquid form on farm land. It should not be discharged to a
lagoon or left in deep piles on the surface, because pH will eventually
drop and putrefaction can occur-
Microbiological Destruction
The disposal of digested sludge to landfills should represent no
serious microbiological problem. Solid waste is substantially higher
in pathogenic activity than digested sludges.
When there is any large-scale disposal of digested sludge to agri-
cultural land, the question of microbial contamination is generally brought
forth. If proper precautions are taken, there is no evidence of an undue
hazard. In some countries, however, pasteurization is required during
the summer. Recently, a plant utilizing nuclear isotopes to irradiate
sludge went on stream in Geiselbullach, Germany. It is believed that
their concern is chiefly worm eggs and cysts. It is possible that many
local jurisdictions will lean in the direction of extreme caution and
will require the equivalent of pasteurization for large scale agricultural
utilization of sludge.
Sludge Conditioning
Chemicals -- The use of inorganic chemicals such as ferric chloride
and lime continues to lose ground. Anionic, cationic, and nonionic
polymers are used in increasing amounts to condition sludges for the
226
-------
elutriation process, for gravity and air flotation thickening, and for
dewatering. The EPA has not found it necessary to stimulate development
in this field by grants and contracts. Several very competent chemical
companies are engaged in research and development of polymer conditioning
agents and are heavily committed to developing this market.
The use of polymers has made it possible to continue the use of
elutriation as a preliminary step for dewatering digested sludge. When
primary and activated sludge are digested together, elutriation often
washes out a large proportion of fines. These fines are returned to
process where they cause deterioration in effluent quality. EPA con-
sidered making elutriation ineligible for construction grant funds.
However, the use of polymers has improved elatriation performance suffi-
ciently that it is still possible to get approval for construction grants
for elutriation facilities.
Thermal Conditioning — The use of heat to condition sludge for
dewatering has seen rapid growth in recent years. For example, from 1970
through about the first six months of 1973, Zimpro Division of Sterling
Drug installed or has under construction its low pressure sludge oxidation
system for a population equivalent of about 10 million people. Other
companies such as Envirotech (Porteous Heat Treatment Process) have had
a similar experience.
Experience of communities with sludge conditioning equipment is mixed.
Some communities are very pleased with the process whereas others have had
many difficulties. The usual complaints are failure of equipment (often
related to stones and metal in the sludge), odor, excessive cost, and
227
-------
high BOD load and color in the supernatant. Limited bench-scale studies
at the Taft Center showed no substantial change in performance of the
activated sludge process when heat treatment supernatant was included in
the incoming primary effluent (COD load was held constant) except for a
persistent yellow color in the final effluent. Zimpro and others^"/
have found that activated carbon removes this color effectively.
The heat treatment of sludge has many vigorous advocates and equally
vigorous opponents. It is this writer's opinion that, barring the unlikely
discovery that heat treatment causes formation of materials extremely
hazardous to health, heat conditioning of sludge is a viable wastewater
treatment process. When its use is considered, its impact on the cost of
the entire processing sequence should be considered. The bad experiences
at some plants indicate that manufacturer's recommendations of operating
and maintenance costs and off-stream time for repairs should be adjusted
upwards when cost estimates are made.
Dewatering
High Solids — A new factor—the solids content of the dewatered
sludge—is becoming important in dewatering technology in the United States.
In the higher rainfall areas of the United States, sludge which is disposed
to a landfill should carry with it a minimum amount of water- If the
dewatered sludge is relatively dry, it will be easier to handle and will
contribute less to leachate than a wetter sludge. Several states have
put restrictions on solids content that range from general statements to
the effect that the sludge shall be easily handled by conventional land-
fill equipment to a specific statement by one state that the sludge shall
contain at least 50 percent dry solids.
228
-------
A second consideration which makes solid content important is the
energy shortage. If sludge is being incinerated, supplementary fuel will
be needed during burning unless the solids content is above about 30 percent.
With the cost of desirable fuels such as gas and fuel oil expected to double
in price and often be unavailable, there will be heavy pressure to produce
a high solids dewatered sludge.
Vacuum filters and centrifuges rarely produce cake solids greater than
about 22 percent solids when dewatering a mixture of primary and activated
sludges. Pressure filters can produce sludge cake in the desired moisture
range. Up until now, pressure filtration has been very slow in penetrating
the United States market, chiefly because the capital cost is so high.
We are clearly in need of innovative means to produce dewatered sludge
with solids content in excess of 30 percent solids. The development of
equipment which can remove additional water from sludge cake after it
leaves a centrifuge or vacuum filter is especially attractive.
Belt Filters -- Two primary types of belt filters have become available
in the United States: the Carter Belt-Filter press and the Westinghouse
Capillary Suction Dewatering System.
The Carter Belt-Filter press is a German development. It comprises
three dewatering zones: initial draining, pressing, and shearing. Sludge
is contained between two woven belts (0.2 to 1.5 mm openings). Rollers
are carefully positioned to apply pressing and shearing action to the
sludge. There were approximately 1,000 of these units installed in Germany
by 1971.
229
-------
The Westinghouse (infilco Division) Capillary Suction Dewatering
System has been developed with partial assistance from EPA. It utilizes
a porous belt which removes water from sludge by "capillary suction."
Near the end of the belt travel, a smooth roll, driven at the same linear
speed as the belt presses against it. The pressure forces additional
water from the sludge into the capillary belt. The sludge cake transfers
to the smooth roll where it is scraped off and conveyed away. This
device works well on sludges which are difficult to dewater. Polymer
demands are low and production rate is high. A demonstration unit is
being evaluated at St. Charles, Illinois.
Both of these devices offer possibilities of slightly higher sludge
solids than solid-bowl centrifuges or vacuum filters. They are simple
to operate and should have low maintenance costs.
Top-Feed Filter — Difficulty is often encountered in conventional
vacuum filtration with pickup from the sludge pan, and with cake release.
Experiments have been conducted at Milwaukee with the aid of an EPA grant
with a vacuum filter in which the sludge pan was moved from the usual
4:00 o'clock to 8:00 o'clock position on the drum up to the 8:00 o'clock
to 11:00 o'clock position. Difficulty encountered with sealing the pan
was overcome. Sludge pickup was excellent. Cake release also was excellent.
The cake release point was at the 8:00 o'clock position. The force of
gravity was an important aid in removing cake from the filter cloth.
Cake solids and filter yield were increased. A grant to demonstrate the
top-feed filter on a large scale has been made to Milwaukee.
230
-------
Centrifugation — Los Angeles County has demonstrated the utility of
a centrifuge of the vertical basket-type (solid wall basket) for removing
fine solids from sludge vith a high recovery. The minimum cost method
for Los Angeles to improve the performance of their solid-bowl centrifuges
and produce a high solids cake was to process the centrate through the
basket-type centrifuge. The basket-type centrifuge can give high recovery
of solids at low conditioning chemical cost. However, cake solids is lower
than obtained with the solid-bowl centrifuge.
Disposal
Incineration — An EPA Task Force conducted a series of tests on
sewage sludge incinerators and reported its results on air pollution and
(7\
metals concentration in particulates in a Task Force Reportv '. The recom-
mendations of the Task Force are found in another publication'"'. On the
basis of the above-mentioned tests, proposed standards of performance for
(q\
new stationary sources have been published^'. The standards specify only
that the exhaust gas contain less than TO mg/Wm3 (0.031 grain/dry scf) of
particulate matter. This writer believes that in applying this standard,
wet scrubbing will be required, probably with a venturi-type scrubber or
similar (ca. 100 cm water pressure drop). Some manufacturers maintain that
a low pressure drop scrubber (ca. 15 cm water) will clean the gases adequately
and are attempting to change this requirement.
The Task Force on incineration recommended that afterburners be used
to insure that polychlorinated biphenyls and other organic materials are
destroyed. The suggested conditions were l600° F (870° C) for 2.0 seconds
or a combustion condition that accomplishes the desired destruction. Tests
231
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by manufacturers indicate that an afterburner temperature of 1100° F
(590° C) and about 0.5 second accomplishes virtually complete destruction
of these materials when they are incinerated with sewage sludge in a
multiple hearth incinerator.
Incinerators can be made to meet virtually any reasonable air pollu-
tion requirement without becoming extremely costly. There is a report of
an incinerator being permitted in the San Francisco Air Pollution Control
District because it would produce less pollution than would the trucks
needed to transport the sludge cake to a suitable sanitary landfill.
Landfill — Proposed guidelines have been published for land disposal
of solid wastes^ '. These guidelines are not a binding obligation. The
disposal of digested sewage sludges is permitted in sanitary landfills
where there is provision for handling these sludges. The sludges must
be digested and must contain no "free" water ("free" water is not defined).
Much sewage sludge is disposed by municipalities in what might be
called "private" landfills, but which are often nothing more than dumping
grounds. It is our intent to promptly commence the development of an
environmentally acceptable procedure for disposal of sludge from small
wastewater plants to private landfills.
Land Spreading — A critical review of land spreading practice in the
United States has been made^11' and will be published soon. No detailed
discussion will be presented here. Up until recently, most of our attention
/
has been given to nitrogen as the factor that limits the rate of application
of sludges to the land. For communities with a high proportion of industrial
232
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wastes, the presence of certain metals which can be taken up by growing
crops will prevent the use of land spreading or limit loading rates to
uneconomical levels. The loading levels of metals which are eventually
permitted in land spreading applications will decide whether this con-
serving use of sludge will be an economically viable alternative to other
disposal methods.
J. B. Farrell
January 31,
233
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LITERATURE CITED
1. Federal Register, 38, No. 198, Part II, "Ocean Dumping, Final Regula-
tions and Criteria," Oct. 15, 19T3-
2. Code of Federal Regulations, 40 CFR, 220-227-
3. "Annual Report on the Administration of the Ocean Dumping Program,
Fiscal Year 1973," pub. U. S. EPA.
U. Cohen, D. B., and J. L. Puntenny, "Metro Denver's Experiences with
Large Scale Aerobic Digestion of Waste Activated Sludge," presented
at 47th Annual Conf. WPCF, Cleveland, Ohio, Oct. U, 1973-
5. Farrell, J. B., J. E. Smith, Jr., S. W. Hathaway, and R. B. Dean,
"Lime Stabilization of Chemical-Primary Sludges at 1.15 MGD," presented
at the 45th Annual Conf. WPCF, Atlanta, Georgia, Oct. 8-13, 1972.
6. Corrie, K. D., "Use of Activated Carbon in the Treatment of Heat-
Treatment Plant Liquor," Water Poll. Control, 629-635 (1972).
7. U. S. EPA, "Report of Task Force on Sewage Sludge Incineration,"
Jan. 1972, available NTIS, No. PB 211 323.
8. U. S. EPA, "Ocean Disposal Practices and Effects, A Report of a Meeting
held by the President's Water Pollution Control Advisory Board, Sept. 26-29,
1972," p. 22, U. S. Govt. Printing Office: 1972-514-150 (126).
9. Federal Register, 3_8, No. Ill, June 11, 1973, "Standards of Performance
for New Stationary Sources, Proposed Standards for Seven Source Categories."
10. Federal Register, 38, No. 8l, Part II, Apr. 27, 1973, EPA, 'Solid Waste
Disposal: Proposed Guidelines for Thermal Processing and Land Disposal of
Solid Wastes."
11. Battelle Memorial Institute, Columbus, Ohio, Contract 68-03-0140, "A
Critical Review of Experience with Land Spreading of Liquid Sewage Sludge,"
to be published.
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TABLE 1: MUNICIPAL SLUDGES FOR DISPOSAL
QUANTITIES
ro
GO
en
SLUDGE TYPE
Primary (0.12 Ib/cap-da)
Secondary (0.08 Ib/cap-da)
Chemical (0.05 Ib/cap-da)
DISPOSAL METHODS
Landfill
Utilized on Land
Incineration
Ocean (Dumping and Outfalls)
POPULATION TON/YR.
(MILL.)
3,170,000
101 1,U80,000
10 91,000
1972
POPULATION TON/YR.
(MILL.)
170
170
50
(% of Pof>ulation)
20
25
15
3,720,000
2,^80,000
^55,000
1985
hO
30
30
0
-------
Metal
Beryllium
Cadmium
Chromium
Copper
Mercury **
Lead
Zinc
TABLE 2
CONCENTRATION OF METALS IN SLUDGE —
SEVEN U. S. LOCATIONS
Median (mg/kg)
0
200
1,800
1,700
4.5
2,800
1,600
Range (mg/kg)
N.D. *
N.D. to 800
400 - 5,900
900 to 6,000
3-0 to 5-5
800 to 6,900
400 to 8,UOO
* N.D. = not detected
** Only 3 sludges analyzed
236
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Dieldrin
Chlordane
DDD
DDT
PCB
TABLE 3
PESTICIDE AND PCB LEVELS IN SLUDGES
Compound
Aldrin
Number of
Sites Sampled
3
Median
(mg/kg)
N.D. *
Range
(mg/kg)
16 (in on
5
5
5
5
10
0.3
18.U
0.2
0.2
2.8
sample only)
0.08 to 2.0
3.0 to 32
N.D. to 0.5
N.D. to 1.1
N.D. to 105
N.D. = not detected
237
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EXPERIENCES WITH SLUDGE HANDLING IN TEXAS
DICK WHITTINGTON, P.E., DEPUTY DIRECTOR
TEXAS WATER QUALITY BOARD
AUSTIN, TEXAS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
238
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EXPERIENCES WITH SLUDGE HANDLING IN TEXAS
Texas, located in the southwestern part of the United States,
is a large state covering 267,339 square miles (692,408 square kilometers.)(D
Some areas are highly urbanized, others are barely inhabited. For example,
Dallas County has a population density of about 1500 persons per square mile
(580 persons/square kilometer); while Kenedy County has a population density
of about 0.5 person per square mile (0.2 person/square kilometer.)(D As a
consequence of the varying degrees of urbanization, Texas has both large sew-
age treatment plants and very small sewage treatment plants—ranging in treat-
ment capacities from roughly 100 MGD (380,000 m /day) to 2000 gallons per day
(7.6 m3/day.) This same factor dictates that plants are located in both
highly populated areas and very remote rural areas. The climate in Texas
varies from humid in the East to arid in the West—rainfall variations from
roughly 50 inches per year (127 cm/year) to less than 8 inches per year (20
cm/year.) These diversities lead to a host of sludge handling and disposal
techniques.
The predominate sludge disposal technique utilized by small plants
in rural areas in Texas is anaerobic digestion with dewatering on open beds
and subsequent land application. This technique is satisfactory and will
continue in popularity.
At small plants in urban areas, the trend is away from anaerobic
digestion and toward aerobic digestion. This trend is created by two
considerations: (1) the extensive use of contact stabilization process
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treatment plants and the amenability of aerobic digestion with this process,
and (2) nuisance problems associated with handling anaerobic sludges.
Where small plants utilizing aerobic digestion are constructed
within economical hauling range of a large plant with sludge handling
capability, drying beds are not constructed—the excess sludge produced
being transported to a sludge plant for dewatering and disposal. Since
many of these plants depend upon contract hauling of the sludge with the
attendant unreliability of transportation, difficulties have been experienced
with sludge buildup within the treatment process and subsequent deterioration
of effluent quality. This is, of course, not inherent in the scheme—rather,
a defect in the management and implementation.
The City of Houston employs a novel technique for transporting excess
activated sludge from plants with no dewatering facilities to a sludge process-
ing plant. The City is located on the coastal plain which has a flat topo-
graphy. Because of topography and other factors, the City has thirteen
permanent sewage treatment plants and other temporary plants. Only two
plants, the two largest, are equipped with sludge dewatering facilities.
The excess activated sludge from some of the plants is pumped via pressure
conduit to the nearest sanitary sewer which flows to the major plants equipped
with sludge dewatering facilities. No problems have arisen as a result of
this transportation technique.
Where sludge facilities are not within economical or practical
hauling distance, small treatment plants utilizing aerobic digestion are
equipped with sludge drying beds. Difficulties have been encountered in
dewatering such sludges on drying beds—primarily the blinding of the bed.
In coping with this problem, operators have learned to draw sludge onto
240
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the beds very slowly. This permits the supernatant to flow over the
settled and settling sludge and drain through the sand bed ahead of the
encroaching sludge. At some plants, arrangements have been made to fill
the bed, allow the sludge to settle, and decant the supernatant. The
addition of polymers to the sludge as it is being drawn is reported to
help overcome the blinding of the bed. The polymer is added to the aerobic
digester about 12 hours before drawing.^4^ The addition of polymers to the
sludge as it is being drawn is reported to help overcome this problem.
At large plants in Texas, various sludge disposal techniques are
employed.
The City of Houston, at the two major facilities previously
mentioned, utilizes the activated sludge process without primary sedi-
mentation. The excess sludge is chemically conditioned with ferric chloride
(75 Ibs. per ton of dry solids - 3.75%), dewatered on rotary vacuum filters,
flash dried and, subsequently, sold as a fertilizer under the name of
"Hou-Actinite." The sludge to the filters typically average around 4%
solids, the filter cake about 15%, and the completely dried processed
sludge about 95.7%.^ ' The fertilizer typically has a moisture content of
around 5%; ash content of 35%; nitrogen content of 5%; and available phos-
phoric acid, 4%.(2) The revenue to the City in the first six months of
1972 from fertilizer sales was reported to be $21 per ton (907 kg.) ^
The City of Houston is presently building an additional 30-ton-per-
day (27,000 kg/day) sludge processing plant at its Alameda Plaza sewage
treatment plant. This plant is to employ pressure filtration in lieu of
vacuum filtration ahead of flash drying. In order to produce a filterable
sludge, the sludge must be conditioned with both ferric chloride and lime.(3
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It is estimated that the pressure filter cake will have a solids content of
about 35% as contrasted to vacuum filter cake with a solids content of 15%.(3)
The increased solids content permits the drying step to be accomplished with
smaller flash dryers and a decreased fuel consumption. The savings in drying
cost by using the pressure filters dictated the design change from vacuum
filters. One disadvantage of the design change has been to lower the value
of the fertilizer produced. This is brought about by the dilution of the
nutrient value of the fertilizer by lime used in sludge conditioning and
diatomaceous earth used to precoat the filters. It is estimated that the
ash content will be increased to 49% and the nitrogen content lowered to
about 4%.(3) The pressure filter-flash dryer system is estimated to save
the City about 2.5 million dollars over the next nine years. '
The Gulf Coast Waste Disposal Authority operates a large industrial
waste treatment plant in the Houston area known as the Champion plant. The
plant treats paper mill waste with a small amount of other waste, primarily
petroleum refining waste. The plant employs the activated sludge process and
has a treatment capacity of 44 mgd (166,500 m /day).
Centrifuges are used to dewater excess activated sludge. The dewatered
sludge is conveyed to barges moored in the ship channel for transportation to
ultimate disposal in lagoons constructed in the coastal wetlands. The sludge
is conditioned with polymer prior to cer.trifugation. A 20% solids cake is
generally produced. The centrifuges in this operation experience unusually
high levels of abrasion wear. This wear is attributed to the lime and titanium
content of the sludge derived from the paper-making process.^ Because of
the centrifuge problem and the likelihood that the lagooning operation in
the coastal wetlands will be declared unacceptable by the regulatory agencies,
242
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the Authority is looking toward other sludge disposal techniques. They have
tentatively decided upon pressure filtration and land filling. The primary
factors influencing the decision to go to pressure filters over vacuum filters,
(2) chemical conditioning cost associated with vacuum filters, and (3) the
dryer cake produced by the pressure filters.(4) The dryer cake facilitates
subsequent drying and/or incineration should these steps be ultimately required,
and also permits transportation of the cake in open dump trucks without drip-
ping liquids on the public roadways should an inland landfill site be chosen.
The City of Austin Govalle sewage treatment plant utilizes lagooning
to dispose of its excess activated sludge. The plant is a 40 mgd (151,400
m3/day) contact stabilization plant. The lagoons are constructed above grade
and the only liquids they receive are excess activated sludge, the rain that
falls on their surface, and river water pumped into them to maintain a constant
water level. River water pumpage is necessary to keep a constant water level
since the excess activated sludge is not sufficient to make up for evapora-
tion losses. The ponds cover some 191 acres (77.3 hectares) and are so
constructed that they have a uniform depth of 8 feet *2.43 m) and smooth
sides with a 1/4 slope. A paddle boat is provided to break up scum which
sometimes forms. This system has worked extremely well and no problems
have been encountered with nuisance conditions. In fact, the ponds are one
of the favorite areas of bird watchers in the winter when the ponds are
visited by great numbers of water fowl and shore birds.
The City of San Antonio also employs sludge lagooning at its Rilling
Road plant. This plant is a 94 mgd (355,790 m3/day) conventional activated
sludge plant. Only the excess activated sludge is lagooned—the primary
sludge is subjected to anaerobic digestion and drying on open beds. The
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sludge lagoon is known as Mitchell Lake. It is actually an articicial
impoundment covering some 850 acres (344 hectares) with a watershed area of
5000 acres (2023 hectares). The lake has been in continuous service as a
sludge lagoon for 70 years, and it is interesting to note that the sludge
accumulation over the lake bottom varies from about 3 feet (.91 m) in the
upper and to about 1 foot (.305 m) in the lower end. Nuisance conditions
frequently exist at this lagoon. These conditions are created by extensive
shallows which are frequently exposed to the atmosphere by the fluctuating
water level in the lake. The water level in the lake is allowed to fluctuate,
getting low in dry weather and overflowing in periods of adequate rainfall.
Due to the public dissatisfaction with Mitchell Lake, the City is presently
considering alternate sludge disposal techniques.
It is our expectation that large plants in Texas in the more arid
portions of the State will continue to utilize sludge lagooning where feas-
ible. In heavily populated areas where ultimate disposal is fertilizer
production or long distance landfill, particularly where the landfill must
be reached via public roads, we expect a trend away from vacuum filters to
pressure filters. Where ultimate disposal is nearby landfill, vacuum filters
will most likely continue to be the most viable method of dewatering.
REFERENCES
1. A. H. Belo Corporation, Texas Almanac and State Industrial Guide, 1972-73.
2. Bryan, A. C. and Garrett, M. T., Jr., What Do You Do With Sludge? Public
Works, December 1972.
3. Binkley, James A., Engineering Report to the City of Houston Public Works
Department - Sludge Disposal Methods, Almeda Plaza Sewage Treatment and
Sludge Disposal Facilities, Job. No. 3304, September 10, 1971.
4. Teller, Joe P., Personal Communication, December 5, 1973.
244
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PHYSICAL-CHEMICAL NITROGEN REMOVAL
WASTEWATER TREATMENT
JESSE M. COHEN, CHIEF*
PHYSICAL-CHEMICAL TREATMENT SECTION
TREATMENT PROCESS DEVELOPMENT BRANCH
ADVANCED WASTE TREATMENT RESEARCH LABORATORY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
CINCINNATI, OHIO
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
ENVIRONMENTAL PROTECTION AGENCY* Technology Transfer
July 1974
*The presentation was based on this Bulletin.
245
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ACKNOWLEDGMENTS
This seminar publication contains materials prepared for the
U.S. Environmental Protection Agency Technology Transfer Program
and has been presented at Technology Transfer design seminars
throughout the United States.
The information in this publication was prepared by Gordon
Gulp, representing Gulp, Wesner, Gulp—Clean Water Consultants,
Eldorado Hills, Calif.
NOTICE
The mention of trade names or commercial products in this publication
is for illustration purposes, and does not constitute endorsement or recom-
mendation for use by the U.S. Environmental Protection Agency.
246
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CONTENTS
Page
Introduction 248
Chapter I. Ammonia Stripping 249
Chapter II. Selective Ion Exchange 257
Chapter III. Breakpoint Chlorination 263
Chapter IV. Comparison of Processes 267
References 268
247
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INTRODUCTION
There are three basic physical-chemical nitrogen-removal techniques available for application
today. These three processes are
• Ammonia stripping (ch. I)
• Selective ion exchange (ch. II)
• Breakpoint chlorination (ch. Ill)
All of these approaches have the advantage that they are based on the removal of nitrogen in
ammonia form, which eliminates the costs of converting the ammonia to nitrate in the biologic-
treatment step. They also have the advantages that they are unaffected by toxic compounds that
can disrupt the performance of a biologic nitrogen-removal system, they are predictable in perform-
ance, and the space requirements for the treatment units are less than for biologic-treatment units.
The advantages and disadvantages of each of these physical-chemical processes are discussed
in detail and the processes are compared in the chapters that follow. Discussion of these processes
includes application at the following facilities, either in existence or under design:
• South Lake Tahoe, Calif.
• Orange County, Calif.
• Windhoek, South Africa
• Blue Plains, B.C.
• Upper Occoquan Sewage Authority, Va.
• Rosemount, Minn.
• North Lake Tahoe, Calif.
• Montgomery County, Md.
• Cortland, N.Y.
248
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Chapter I
AMMONIA STRIPPING
The only nitrogen-removal process that actually has been used on a plant scale in wastewater
treatment is ammonia stripping. This process has been in use for ammonia nitrogen at the South
Lake Tahoe plant for about 4 years. Both the advantages and limitations of this process have been
clearly demonstrated.
The ammonia-stripping process itself consists of
• Raising the pH of the water to values in the range of 10.8 to 11.5, generally with the lime
used for phosphorus removal
• Formation and re-formation of water droplets in a stripping tower
• Providing air-water contact and droplet agitation by circulation of large quantities of air
through the tower
The towers used for ammonia stripping closely resemble conventional cooling towers.
Questions are sometimes raised concerning the fate of ammonia discharged to the atmosphere.
Are we merely converting a water-pollution problem to an air-pollution problem? Does the
ammonia stripped from the wastewater cause an air-pollution problem or find its way back to the
receiving stream owing to scavenging by precipitation?
The concentration of ammonia in the stripping-tower discharge is only about 6 mg/m3 for
domestic wastewaters (at an air flow of 500 ft3/gal and at an ammonia concentration of 23 mg/1
in the tower influent). As the odor threshold of ammonia is 35 mg/m3, the process does not
present a pollution problem in this respect. The ammonia discharged to the atmosphere is a stable
material that is not oxidized to nitrogen oxides in the atmosphere. The natural production and
release of ammonia as part of the natural nitrogen cycle is about 50 billion tons per year. Roughly
99.9 percent of the atmosphere's ammonia concentration is produced by natural biological
processes.1 There is a large turnover of ammonia in the atmosphere, with the total ammonia content
being displaced once a week on the average. Ammonia is returned to the earth through gaseous
deposition (60 percent), aerosol deposition (22 percent), and precipitation (18 percent). Ammonia
is not considered an air pollutant because there are no known public health implications, and
because it is a natural constituent of the atmosphere derived almost entirely from natural sources.
For example, a single cow releases as much nitrogen to the atmosphere in feces and urine as 12
people would contribute if all of their ammonia production were stripped to the atmosphere.
There are no standards in the United States for ammonia concentrations in the atmosphere.
Some foreign standards1 have been established.
• Czechoslovakia, 100 mg/m3 (24 hours)
• U.S.S.R., 200 mg/m3 (24 hours)
• Ontario, Canada, 3,500 mg/m3 (30 minutes)
249
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All of these standards are far above the 6 mg/m3 that will occur right at the tower discharge. The
process cannot be dismissed from consideration because of air pollution.
A remaining question is the fate of the ammonia discharge to the air. Is it likely to find its
way into the receiving stream by being scavenged from the atmosphere by precipitation?
Ammonia may be washed from air by rainfall, but not by snowfall. The natural background
concentration of ammonia in the atmosphere is 5-7 ppb. In rainfall the natural background ranges
from 0.01 to 1 mg/1, with the most frequently reported values of 0.1 to 0.2 mg/1. The amount of
ammonia in rainfall is related directly to the concentration of ammonia in the atmosphere. Thus,
an increase in the ammonia in rainfall wuuld occur only in that area where the stripping-tower
discharge increases the natural background ammonia concentration in the atmosphere.
Calculations for the ammonia washout in a rainfall rate of 3 mm/h (0.12 in./h) have been
made for the Orange County, Calif., project. The ammonia concentrations of ammonia in the
rainfall would approach natural background levels within 16,000 feet of the tower. Of course, the
ammonia discharge during dry periods diffuses into the atmosphere quickly so that the background
concentration and resulting washout rate of ammonia at greater distances from the tower are not
affected during a subsequent storm. The ultimate fate of the ammonia that is washed out by rain-
fall within the 16,000-foot downwind distance depends on the nature of the surface upon which
it falls. Most soils will retain the ammonia. That portion which lands on paved areas or directly
on a stream surface will appear in the runoff from that area. Even though a portion of the ammonia
washed out by precipitation will find its way into surface runoff, the net discharge of ammonia to
the aquatic environment in the vicinity of the plant would be very substantially reduced.
One of the great advantages of this method of nitrogen removal is its extreme simplicity. Water
is merely pumped to the top of the tower at a high pH, air is drawn through the fill, and the am-
monia is stripped from the water droplets. The only control required is the proper pH in the
influent water. This simplicity of operation also enhances the reliability of the process.
Several factors affect the efficiency of the ammonia-stripping process.
• Type of stripping unit
o pH
• Temperature
« Loading rate
• Scale of deposition
There are three basic types of stripping units now being used in full-scale applications.
• Countercurrent towers
• Crossflow towers
• Stripping ponds
Countercurrent towers (the entire airflow enters at the bottom of the tower while the water enters
the top of the tower and falls to the bottom) have been found to be the most efficient. In the
crossflow towers, the air is pulled into the tower through its sides throughout the height of the
250
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packing. This type of tower has been found to be more prone to scaling problems. The stripping-
pond approach will be discussed in more detail later.
The pH of the water has a major effect on the efficiency of the process. The pH must be
raised to the point that all of the ammonium ion is converted to ammonia gas. The pH required
varies somewhat with temperature,2 but is generally about 11.0.
Another critical factor is the air temperature. The water temperature has less effect on per-
formance because the water temperature reaches equilibrium with the air temperature in the top
few inches of the stripping tower. The efficiency of the process decreases as the temperature de-
creases. For example, at 20° C 90 percent removal of ammonia is typically achieved. At 10° C,
the maximum removal efficiency drops to about 75 percent. When air temperatures reach freezing,
the tower operation must generally be shut down owing to icing problems.
The hydraulic loading rate of the tower is also an important factor. This rate typically is ex-
pressed in terms of gallons per minute applied to each square foot of the plan area of the tower
packing. When the hydraulic loading rates become too high, good droplet formation is disrupted
and the water begins to flow in sheets. Tower loading rates of 2 gal/min/ft2 have been shown to be
compatible with optimum tower performance.2 It is critical that the water and air be uniformly
distributed over the tower area.
Another factor that may have an adverse effect on tower efficiency is scaling of the tower
packing resulting from deposition of calcium carbonate from the unstable, high-pH water flowing
through the tower. The original crossflow tower at the South Lake Tahoe plant has suffered a
severe scaling problem. The severity of the scaling problem was not anticipated from the pilot
studies in which a countercurrent tower was used. As a result, the full-scale crossflow-tower packing
was not designed with access for scale removal in mind. Thus, portions of the tower packing are
inaccessible for cleaning. Those portions that were accessible were readily cleaned by high-pressure
hosing. The potential scaling problem must be recognized in design. The use of countercurrent
towers and design of the packing with access for cleaning can adequately combat this problem.
An example of design for scale control is the 15-mgd tower now under construction at the
Orange County, Calif., Water District plant (fig. 1-1). There the tower packing has been designed
to be readily removable for cleaning as a precaution against scaling problems, although no signifi-
cant scaling problem has been observed in several months of pilot tests at Orange County.3 Scaling
has also been reported not to be a significant problem at the Windhoek, South Africa, plant where
only a soft, easily removed scale was encountered.4 On the other hand, tests at the Blue Plains
pilot plant encountered a hard scale that was extremely difficult to remove.5 The hardness of the
scale at Blue Plains was affected by operating pH, with a harder scale forming at pH 11.5 than at
pH 10.8.
Typical design criteria are
• Hydraulic loading, 1 to 3 gal/min/ft2
• Air-to-water ratio, 300 to 500 ft3/min per gal/min
• Air-pressure drop, 0.5 to 1.25 inches water
• Fan-tip speed, 9,000 to 12,000 ft/min
• Fan-motor speed, 1 or 2 speed
• Packing depth, 20 to 25 feet
251
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Figure 1-1. Ammonia-stripping tower design. Orange County, Calif.
• Packing spacing, 2 to 4 inches horizontal and vertical
• Packing material, wood, plastic (Vfc-in. PVC pipe being used at Orange County)
A curve for estimating the costs of the ammonia-stripping process for various-size plants is
presented in figure 1-2. This curve is based on a loading rate of 2 gal/min/ft2. Because some applica-
tions may require ammonia removal only during warm weather months, operating costs are shown
for both 6-month and 12-month operation.
The South Tahoe system is being modified to reduce the impact of temperature and scaling
limitations encountered at this plant.6 Basically, the modified process will consist of three steps
(see figs. 1-3,1-4, and 1-5).
252
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10.000
5,000
3,000
° 2,000
8
u
oT
<
o
1,000
400
300
200
Operating and maintenance
12 months' operation
Operating and maintenance
6 months' operation
I I I I I
I
J I
1,000
400
300
200
LJ
100 ^
<
5
Q
Z
50
40
30
20
Z
I-
ir
LU
o.
O
Z
5 6 7 8 910 20 30 40 50
PLANT CAPACITY, mgd
100
200
Figure 1-2. Ammonia-stripping costs. (EPA STP Index = 200; includes engineering, legal, administrative,
construction financing, and contingencies.)
• Holding in high-pH, surface-agitated ponds
• Stripping in a modified, crossflow forced-draft tower through air sprays installed in the
tower
• Breakpoint chlorination
This system was inspired by observations in Israel of ammonia nitrogen losses from high-pH
holding ponds.7
Pilot tests at South Tahoe indicated that the release of ammonia from high-pH ponds could be
accelerated by agitation of the pond surface. In the modified Tahoe system, the high-pH effluent
from the lime clarification process will flow to holding ponds. Holding pond detention times of
7-18 hours will be used in the modified South Tahoe plant. The pond contents will be agitated
and recycled 4-13 times by pumping the pond contents through vertical spray nozzles into the air
above the ponds. At least 37 .percent ammonia removal is aniticipated, even in cold weather condi-
tions, in the ponds. The pond contents then will be sprayed into the forced-draft tower. The pack-
ing will be removed from the tower and the entire area of the tower will be equipped with water
sprays. At least 42 percent removal of the ammonia in the pond effluent is anticipated, based on
pilot tests, from this added spraying in cold weather, which will include recycling of the pond
effluent through the tower to achieve 2-5 spraying cycles. The ammonia escaping this process then
253
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,,R SPRAYING OF RECYCLED POND WATER
IN THE SECOND OF TWO PONDS
IN SECOND POND. TWO
RECYCLE PUMPS
34mgd CAPACITY
4'/. TO 13'A RECYCLES
TWO HIGH pH PONDS IN SERIES
7 TO 18 HOURS DETENTION TIME
FLOW VARIES. 2 5 TO 7.5 mgd
Figure 1-3. Proposed new and modified ammonia nitrogen removal processes. South Lake Tahoe:
New high-pH flow-equalization ponds.
EXISTING CROSS FLOW AMMONIA
STRIPPING TOWER
Figure 1-4. Proposed new and modified ammonia nitrogen removal processes, South Lake Tahoe: Existing
stripping tower modified with new sprays.
CO, OR Cl,
CO,
Cl,
pH 10 8 i
^^^
^
4
h
«-^— ^^_^_ ^-._ ^^_j
i
>
s*^*^
™*W-*V_^>»
pH = 70
f EXISTING 2 STAGE NEW BREAKPOINT EXISTING 1 MG
t RECARBONATION CHLORINATION BALLAST POND
vmmJ BASIN CHAMBER FOR CHLORINE CON
pH = 70
TO FILTERS AND
CARBON COLUMN
TACT
Figure 1-5. Proposed new and modified ammonia nitrogen removal processes, South Lake Tahoe:
Breakpoint chlorination (new).
254
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will be removed by downstream breakpoint chlorination. The quantity of ammonia to be removed
by breakpoint chlorination will vary from 5 to 16 mg/1, depending on the plant flow and
temperatures.
Another approach to overcoming the limitations of the stripping process has been developed
by CH2M/HILL Consulting Engineers.8 Although the process is only in its initial stages of develop-
ment, preliminary tests indicate it may be a significant advance in the state of the art of nitrogen
removal. It appears that the new process overcomes most of the foregoing limitations and has the
advantage of recovery of ammonia as a byproduct.
The improved process, shown diagrammatically in figure 1-6, includes an ammonia-stripping unit
and an ammonia-absorption unit. Both of these units are essentially sealed from the outside air but
are connected by appropriate ducting. The stripping gas, which initially is air, is maintained in a
closed cycle. The stripping unit operates essentially in the same manner that is now being or has
been used in a number of systems, except that this system recycles the gas stream rather than using
single-pass outside air.
Most of the ammonia discharged to the gas stream from the stripping unit is removed in the
absorption unit. The absorbing liquid is maintained at a low pH to convert absorbed and dissolved
ammonia gas to ammonium ion. This technique effectively traps the ammonia and also has the
effect of maintaining the full driving force for absorbing the ammonia, since dissolved ammonia
WASTEWATER
CONTAINING _
DISSOLVED
AMMONIA (NH3)
FAN (TYPICAL)
I
RECYCLE
ALTERNATE I
DUCTING (TYPICAL)
PUMP
~A A A A
STRIPPING
UNIT
A A A A
ABSORPTION
UNIT
J
GAS STREAM-AMMONIA
REDUCED BY ABSORPTION
l.
t
RECYCLED
ABSORBENT
LIQUID
PUMP
WASTEWATER STRIPPED OF NEARLY
"*" ALL OR PART OF AMMONIA (NH3)
ACID AND
WATER MAKEUP
AMMONIUM SALT
SLOWDOWN (LIQUID
OR SOLID), OR
DISCHARGE TO STEAM
STRIPPER FOR AMMONIA
GAS REMOVAL AND
RECOVERY
Figure 1-6. Process for ammonia removal and recovery.
255
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gas does not build up in the absorbent liquid. The absorption unit can be a slat tower, packed tower,
or sprays similar to the stripping unit, but will usually be smaller owing to kinetics of the absorption
process.
The absorbent liquid initially is water with acid added to obtain low pH, usually below 7.0.
In the simplest case, as ammonia gas is dissolved in the absorbent and converted to ammonium ions,
acid is added to maintain the desired pH. If sulfuric acid is added, for example, an ammonium sul-
fate salt solution is formed. This salt solution continues to build up in concentration and the
ammonia is finally discharged from the absorption device as a liquid or solid (precipitate) blowdown
of the absorbent. With current shortages of ammonia-based fertilizers, a salable byproduct may
result.
Other methods of removal of the ammonia from the absorbent may also be applicable, depend-
ing on the acid used and the desired byproduct. Ammonia gas or aqua ammonia could be produced,
for example, by steam stripping the absorbent. In this case, acid makeup would be unnecessary.
It is believed that the usual scaling problem associated with ammonia-stripping towers will be
eliminated by the improved process, since the carbon dioxide which normally reacts with the cal-
cium and hydroxide ions in the water to form the calcium carbonate scale is eliminated from the
stripping air during the first few passes. The freezing problem is eliminated owing to the exclusion
of nearly all outside air. The treatment system will normally operate at the temperature of the
waste water.
256
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Chapter II
SELECTIVE ION EXCHANGE
The selective ion exchange process derives its name from the use of zeolites that are selective
for ammonia relative to calcium, magnesium, and sodium. The zeolite currently favored for this use
is clinoptilolite, which occurs naturally in several extensive deposits in the Western United States.
Studies of the process have been conducted by Battelle Northwest9 and the University of Cali-
fornia.10 Clinoptilolite used in studies conducted by Battelle Northwest for EPA was obtained
from the Hector, Calif., leases of the Baroid Division of the National Lead Company, Houston, Tex.
The clinoptilolite is crushed and sieved to obtain a 20 by 50 mesh size. Ammonia is removed by
passing the wastewater through a bed of clinoptilolite at a rate of about 10 bed volumes per hour.
The use of clinoptilolite was investigated at the University of California with the objective of
optimizing its application to ammonia removal from wastewaters. Pilot-plant operations were
carried out at three different municipal sewage-treatment plants. An average ammonia removal of
96 percent was obtained in these operations with influent ammonia nitrogen concentrations of
about 20 mg/1.
The ammonia capacity of the clinoptilolite was found to be nearly constant over the pH range
of 4.0 to 8.0, but diminished rapidly outside this range. The effect of wastewater composition on
the ammonia exchange capacity was analyzed by exhausting clinoptilolite beds with waters having
different chemical compositions. For relatively constant influent ammonia concentrations, the
ammonia exchange capacity was observed to decrease sharply with increasing competing action con-
centrations up to about 0.01 molar. Increases of cation concentrations above this value continued
to decrease the exchange capacity, but to a much lesser degree. Ammonia removal to residual levels
less than 0.5 mg/1 ammonia nitrogen is technically feasible, but only with shorter service cycles and
greater regeneration requirements. Flow rates in the range of 7.5 to 15 bed volumes per hour had
no effect on ammonia effluent values.
Battelle Northwest conducted pilot studies of the clinoptilolite process applied to secondary
effluents, advanced waste treatment effluents, and clarified raw sewage.9 -11 Ammonia removals
ranging from 93 to 97 percent were demonstrated using a 100,000-gal/d mobile pilot plant. These
studies were conducted at several different locations across the United States.
After about 150-200 bed volumes of normal-strength municipal waste have passed through the
bed, the capacity of the clinoptilolite has been used to the point that ammonia begins to leak through
the bed. At this point, the clinoptilolite must be regenerated so that its capacity to remove ammonia
is restored.
The key to the applicability of this process is the method of handling the spent regenerant. The
resin is regenerated by passing concentrated salt solutions through the exchange bed when the am-
monia concentration has reached the maximum desirable level. Following regeneration, the
ammonia-laden spent-regenerant volume is about 2.5 to 5 percent of the throughput treated before
regeneration.
257
-------
The original approach to recovering and reusing the regenerant was to use a lime slurry as the
regenerant so that the ammonium stripped from the bed during regeneration would be converted to
gaseous ammonia, which could then be removed from the regenerant by air stripping.9
Regeneration with lime alone was found to be a rather slow process; therefore, the ionic
strength of the regenerant solution was increased by the addition of salt (NaCl). The increased
ionic strength of the regenerant plus the presence of sodium ion accelerates the removal of ammonia
from the zeolite. Although most of the sodium chloride added to the regenerant is converted to
calcium chloride by continuous recycle of the regenerant, sufficient sodium ion remains under
steady state conditions to promote the elution of the ammonium ions. The sodium ion has a
higher diffusion coefficient than calcium ion, which is believed responsible for increasing the am-
monia elution rate. With the lime-slurry regenerant, the regenerant stripping tower handles only a
small fraction of the total plant throughput. Heating the stripping tower, even during cold weather
periods, is then practical.
The use of the high-pH regenerant is accompanied by an operational problem. Some plugging
of the bed with Mg(OH)2 and CaCO3 occurs when the high-pH regenerant is used. Attrition of the
zeolite is aggravated by the violent backwashing needed to remove these solids, and is 0.17-0.25
percent per cycle, making makeup clinoptilolite costs a significant factor. These problems make more
recently developed methods of regenerant recovery more attractive.
In one approach, ammonia in the regenerant solution may be converted to nitrogen gas by
reaction with chlorine which is generated electrolytically from the chlorides already present in the
regenerant solution. This process can be carried out with a regenerant of neutral pH so that the
problem of precipitation of Mg(OH)2 and CaCO3 within the bed during regeneration is eliminated.
Also, cold weather does not affect the regenerant recovery process. The regenerant solutions used
are rich in NaCl and CaCl2 which provide the chlorine produced at the anode of the electrolysis
cell. The reactions for the destruction of ammonia by chlorine are the same as for breakpoint
chlorination.
During regeneration of the ion exchange bed, a large amount of calcium is eluted from the
zeolite along with the ammonia. This calcium may be removed from the spent regenerant solution
by soda ash softening before passing the spent regenerant through the electrolytic cells. The soften-
ing step would lower the calcium concentration below the level that would cause calcium hydroxide
formation in the electrolytic cells. High flow velocities through the electrolysis cells are required in
addition to a low concentration of MgCI2 to minimize scaling of the cathode by calcium hydroxide
and calcium carbonate. Acid flushing of the cells would be necessary to remove this scale when the
cell resistance becomes too high for economical operation.
In pilot tests of the electrolytic treatment of the regenerant at Blue Plains, Battelle Northwest
found that about 50 Wh of power were required to destroy 1 gram of ammonia nitrogen (NH3-NT).
When related to the treatment of water containing 25 mg/1 NH3-N, the energy consumed would be
4.7 kWh per 1,000 gallons. Tests at South Tahoe also indicated that a value of 50 Wh per gram is
reasonable for design.12 Preliminary capital and operating costs of $1.5 million and 9 cents per
1,000 gallons, respectively, were estimated by Battelle for a 10-mgd plant using electrolytic destruc-
tion of ammonia in recycled regenerant containing chloride salts of calcium, sodium, and magnesium.
Electrolytic treatment of the regenerant avoids the disposal of ammonia to the atmosphere or dis-
posal of aqueous ammonia concentrates. Total costs, including capital amortization, were estimated
at 12.7 cents per 1,000 gallons.11
A 22.5-mgd plant designed by CH2M/HILL for the Upper Occoquan Sewage Authority in the
State of Virginia will employ selective ion exchange with electrolytic treatment of the regenerant
for ammonia removal. This plant will utilize soda ash softening of the regenerant to avoid cathodic
scaling of the electrolysis cells. A simplified flow schematic of the regeneration system is illustrated
258
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in figure II-l. The regeneration of the clinoptilolite beds will be accomplished with a 2-percent
solution of NaCl. The spent regenerant will be collected in a large holding tank to minimize varia-
tion in the calcium content before soda ash addition for calcium removal. After the soda ash addi-
tion, the regenerant will be clarified and transferred to another holding tank where the regenerant
will be recirculated through electrolysis cells for ammonia destruction.
Design criteria for the ammonia-removal plant for the Upper Occoquan District are summarized
in table II-l. The electrolysis cell to be used by this plant is a 500-Ampere unit manufactured by
Pacific Engineering and Production Company of Nevada, Henderson, Nev. The cell consists of a
lead dioxide coated graphite anode in a cylindrical stainless steel vessel which is the cathode. The
lead dioxide is highly resistant to attack by chlorine or oxychloroacids. The estimated total cost
for this plant is 12.6 cents per 1,000 gallons for the selective ion exchange process.
In order to develop the design criteria for the Occoquan plant, CH2M/HILL conducted pilot
tests of the process at the South Tahoe plant.12 The ammonia concentration in the wastewater at
South Tahoe ranged from 21 to 28 mg/1 during these pilot tests. After about 6 weeks of pilot-plant
operation, the calcium concentration of the influent increased from about 55 mg/1 to about 80 mg/1.
This increased calcium concentration together with concurrently occurring lower influent tempera-
tures reduced the quantity of ammonia that could be loaded onto the clinoptilolite before a break-
through of 1 mg/1 of ammonia. The average loading to the clinoptilolite column before breakthrough
of 1 mg/1 of ammonia was 144 bed volumes with an influent containing 55 mg/1 calcium at 22° C.
When the influent calcium increased to 80 mg/1 and the temperature dropped to 14° C, the loading
capacity of the clinoptilolite column dropped to 104 bed volumes. Ammonia removals achieved
were in excess of 95 percent.
Na2CO3
NaOH
ZEOLITE
BED
SPENT
REGENERANT
HOLDING
TANK
CLARIFIER
REGENERANT
OUT
ANODE
RENOVATED
REGENERANT
HOLDING
TANK
SLUDGE
REGENERANT
on
CO
O
DC
LU -J
-I UJ
01 O
REGENERANT
IN
CATHODE
RECTIFIER
Figure 11-1. Simplified flow diagram of Upper Occoquan regenerant treatment system.
259
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Table \\-1.-Design criteria for the Upper Occoquan ammonia removal plant at 22.5-mgd flovj rate
Exchange beds:
Size and type
Number
Media
Media size
Bed depth
Bed length
Bed width
Service cycle loading:
Average
Maximum
Hydraulic loading:
Average
Maximum
Flow:
Average
Maximum
Length of service cycle
Bed loading
Backwash water
Backwash rate
Exchange-bed regeneration:
Length of cycle
Regeneration rate . . .
Regenerant recovery:
Method
Power requirement
NH3 destruction rate
Number of electrolytic cells in service
Total number of cells provided
Rectifiers:
Number
Capacity
Salt requirements
10-foot-diameter X 50-foot-long horizontal
pressure units
8
Clinoptilolite
20 X 50 mesh
4 feet
50 feet
10 feet
9.1 BV/h
14.1 BV/h
4.4 gal/min/ft2
6.9 gal/min/ft2
3.2 mgd per bed
5 mgd per bed
200 BV
365 pounds NH3 per bed cycle
Carbon-column effluent
8 gal/min/ft2
3.1 hours
10 BV/h
Electrolysis
40 Wh per gram NH3-N destroyed
0.16 pound NH3-N per hour per cell
480
720
3
750 kW
13,900 Ib/d
The pilot column was regenerated successfully with a 2-percent sodium chloride solution at
neutral pH. No loss of Clinoptilolite by attrition was observed when using the neutral regenerant,
and no difficulties in backwashing were observed. Although the neutral regeneration scheme was
found to involve 30-40 bed volumes of regenerant rather than the 10 or less needed by others with
the high-pH schemes, the minimization of attrition losses is achieved without significant disadvan-
tage. The closed-loop regenerant-recovery system results only in added downtime for regeneration.
Scaling within the electrolytic cell used for regenerant recovery was the primary concern of the
Occoquan pilot-plant study; therefore, the electrolytic cell was routinely dismantled and inspected
for scaling. The flow rate through the cell was set initially at velocities of 0.13 to 0.16 ft/s, and a
thin buildup of scale was observed on the cathode at the bottom-cell-inlet end after 160 hours of
operation. After 230 hours of operation, the flow velocity was reduced to 0.06 ft/s, and very light
scale buildup was observed depositing over the entire cathode area.
260
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Scale was removed from a 1-in.2 area of the cathode, and the flow velocity through the cell
was increased to 0.21 ft/s to determine the effect of scaling at higher cell velocities. At this in-
creased flow, which was maintained for most of the period of the pilot-plant study, no new scale
was deposited on the cathode. Visually, it appeared that from 25 to 50 percent of the previously
deposited scale was removed. These observations suggest that scaling within the cell can be con-
trolled by sufficient flow velocities. The average power requirements for regenerant recovery were
measured as 43.3 Wh per gram ammonia destroyed. To allow for normal system losses, a design
value of 50 Wh/g appears reasonable.
An alternative to air stripping or electrolysis of the regenerant is steam stripping. A 0.6-mgd
plant in Rosemount, Minn., which is now entering its startup period, utilizes this technique.13'14
At Rosemount ammonia is recovered from the spent ion exchange regenerant in an ammonia
stripper. Steam is injected into a distillation column countercurrent with the regenerant solution
to strip off the ammonia. An air-cooled plate-and-tube condenser then condenses the vapor for
collection in a covered tank as 1-percent aqueous ammonia for sale as a fertilizer, However, it is
a dilute (1 percent) ammonia solution, which reduces its potential for sale as a fertilizer, since
commercial fertilizers require handling of only 1/10 the volume of liquid for the same ammonia
application.
No detailed data on the Rosemount design and anticipated operating parameters were available
at the time of this report. An EPA evaluation of the plant will be made in 1974 after the initial
shakedown problems are resolved. The steam-stripping process is based on the use of the high-pH
regenerant, which has the disadvantages noted earlier. Battelle Northwest's evaluation of steam
stripping3 indicates that it is economically feasible if the regenerant volume is held to 4 bed volumes
per cycle, which is achievable with high-pH regenerant. The steam requirements were estimated to
be 15 pounds per 1,000 gallons. At a steam cost of $2 per 1,000 pounds, the steam costs would
be only 0.03 cent per 1,000 gallons. Heat recovery by contacting the cold regenerant with stripped
regenerant and by contacting it with the condenser would be necessary to achieve economical
operation. Because of the unstable, high-pH regenerant, scaling problems on the heat exchanges
could be anticipated.
Another technique for regenerant recovery is the use of the stripping-recovery process (shown
in fig. 1-4) on the spent regenerant. A 6-mgd plant at North Lake Tahoe is being designed using
this approach. Tests to date indicate that ammonia sulfate concentrations of 50 percent are readily
achievable in the absorption tower. The estimated costs of the selective ion exchange approach based
on this technique of regenerant recovery are shown in figure II-2. No credit for potential sale of
ammonium sulfate has been included.
aB. W. Mercer, BatteP.e Northwest, personal communication, Dec. 14, 1973.
261
-------
20,000
10,000
5,000
o 3,000
x
I 2,000
o
T3
CO
O
O
E
<
O
1,000
500
400
300
200
Capital
Operating and maintenance
J L
I I i I
JL
J L
2,000
1,000
500
400
300
200
100
50
40
30
20
4 5 6 7 8 910
20
30 40 50
100
200
PLANT CAPACITY, mgd
o
X
05
CO
O
o
LU
O
<
LU
z
5
Q
<
U
Z
<
DC
LU
CL
O
Z
Figure 11-2. Ammonia removal by selective ion exchange. (EPA STP Index = 200; includes engineering, legal,
administrative, construction financing, and contingencies.)
262
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Chapter III
BREAKPOINT CHLORINATION
When chlorine is added to a waste water containing ammonia nitrogen, ammonia reacts with
the hypochlorous acid formed to produce chloramines. Further addition of chlorine to the break-
point converts the chloramines to nitrogen gas. The chlorine and ammonia reactions in dilute
solutions are
NH4 + HOC1 -»• NH2C1 (monochloramine) + H2O + H+
NH2C1 + HOC1 -* NHC12 (diochloramine) + H2O
NCH12 + HOC1 -» NC13 (nitrogen trichloride) + H2O
The reactions are dependent on pH, temperature, contact time, and initial chlorine-to-ammonia
ratio. Chlorine is added to the wastewater being treated until the chlorine residual has reached a
minimum (the breakpoint) and the ammonia is'removed. A typical breakpoint curve is shown in
figure III-l. The reaction with ammonia is very rapid. Less than 1 minute, in the pH range of 7.0
to 8.0, and all of the free chlorine is converted to monochloramine at a 5:1 weight ratio of
chlorinerammonia nitrogen. As the weight ratio exceeds 5:1, the monochloramine breaks down and
forms dichloramine and ammonia,
2NH2Cl->-NHCl2 +NH3
Monochloramine is then oxidized by excess chlorine under slightly alkaline conditions to nitrogen
gas,
2NH2C1 + HOC1 ->• N2t +3HC1 + H2O
Stoichiometrically, a weight ratio of 7.6:1 of chlorine to ammonia nitrogen is required to oxidize
ammonia to nitrogen gas.
Breakpoint chlorination tests on domestic wastewaters at the Blue Plains plant indicate that
95 to 99 percent of the ammonia is converted to nitrogen gas and that no. significant amount of
nitrous oxide is formed.15 The quantity of chlorine required to achieve breakpoint was found to
decrease with an increasing degree of treatment before the breakpoint process. The quantity of
chlorine required for breakpoint chlorination of raw wastewater was found to be 10 parts by weight
of C12 to 1 part of NH3 nitrogen. This ratio decreased to 9:1 C12 :NH3 nitrogen for secondary
effluents, and 8:1 C12 :NH3 nitrogen for lime-clarified and filtered secondary effluent. The Blue
Plains tests found that the chlorine dose was minimized at pH values between 6.0 and 7.0. The
minimum NO3 production (1.5 percent of the NH3-N) occurred at pH 5.0. At pH 8.0, the nitrate
production increased to 10 percent of the influent NH3 nitrogen. NC13 production at the break-
point decreased from 1.5 percent to the influent at pH 5.0 to 0.25 percent at pH 8.0. Temperature
did not affect the product distribution or the required chlorine dose in the range 5° to 40° C.
263
-------
10 1
0.5
MOLE RATIO, CI2 : NH4-I\I
1 1.5
COMBINED CHLORINE
RESIDUALS PREDOMINANT
FREE CHLORINE
RESIDUAL
PREDOMINANT
23456789
CHLORINE DOSAGE, mg/|
Figure 111-1. Typical breakpoint-chlorination curve.
10
11
12
The use of chlorine produces an equivalent weight of hydrochloric acid which may depress the
pH of the wastewater unless the natural alkalinity is adequate or a base such as sodium hydroxide is
added. If the pH is allowed to fall, highly odorous nitrogen trichloride (NC13) is formed, which is
an intolerable end product. If a base is used to prevent pH depression, the mixing of the wastewater,
chlorine, and base must be extremely violent to avoid local areas of low pH which would generate
NC13. Tests at Blue Plains showed that eductors do not give adequate chlorine-wastewater mixing,
which did result in localized low-pH regions in which objectionable quantities of NC13 formed.
Violent mechanical mixing is required. The use of sodium hypochlorite rather than chlorine does
not depress the pH and avoids the foregoing problem.
The use of chlorine gas may produce more acid than can be neutralized by the wastewater.
According to the EPA study reported by Pressley,15 14.3 mg/1 of alkalinity (as CaCO3) are required
to neutralize the acid produced by the oxidation of 1 mg/1 NH3-N to N2. Either sodium hydroxide
or lime may be used for pH control if the wastewater is deficient in alkalinity. A wastewater con-
taining 25 mg/1 NH3-N requires an alkalinity of about 357 mg/1 if chlorine gas is used.
A significant factor in considering this process for application in some cases is the addition of
dissolved solids inherent to the process. If, for example, chlorine gas were used and the influent
ammonia nitrogen concentration were 25 mg/1, the dissolved solids would be increased by 156 mg/1.
Neutralizing with lime would result in a total increase of 306 mg/1 of total solids. If the chlorinating
agent were sodium hypochlorite, the increase in dissolved solids would be 177 mg/1.16
264
-------
The effects of breakpoint chlorination on organic nitrogen are somewhat uncertain. The Blue
Plains tests15 found only a "slight reduction in organic nitrogen within the two hour contact time."
Other tests17 observed a decrease in organic nitrogen content as the C12:N ratio increased. Reduc-
tions from 3.2-3.5 mg/1 to 0.2-0.4 mg/1 organic nitrogen were reported for the breakpoint process.
The authors,17 however, felt that such apparent removals result from an analytical anomaly in
which the organochloramine formed is not measured as nitrogen in the Kjeldahl organic nitrogen
analysis. At higher chlorine dosages, however, their literature review indicated that organochloramines
will be oxidized to aldehydes and nitrogen gas. The breakpoint reactions of organochloramines pro-
ceed more slowly than the ammonia chloramines, and probably will not be complete in a 30-minute
contact time.
Several recent studies16'17'18-19 have investigated the possibility of adding only enough
chlorine to form monochloramines and then removing the monochloramines on activated carbon.
Some advantages would be realized if monochloramine could be removed by activated carbon. The
theoretical C1:N ratio for 100 percent ammonia removal would drop from 7.6:1 for breakpoint to
about 5:1 for the formation of monochloramine. The dissolved solids added to the system and the
alkalinity requirements would be significantly reduced. Two studies16'17 found that ammonia
removals of about 50 percent could be achieved at C1:N ratio of 5:1 when the breakpoint process
was followed by activated-carbon adsorption. Complete removal still required dosages of about 9:1
in three studies.16'17'18 Carbon contact times of 10 minutes were found to be adequate for com-
plete dechlorination of the effluent.16
Experiences with the breakpoint process in South Africa20 confirm that automatic control of
the process is important. The African researchers concluded that monitoring of the ammonia
coupled with automatically controlled chlorine dosing is a necessity. A successful, automated-
computer-control system has been developed and demonstrated at the Blue Plains pilot plant.21
This system matches the quantity of chlorine fed to the quantity of incoming nitrogen, and also
controls the pH to 7.0 to minimize the formation of NC13 and NO3. (See fig. III-2.)
There are several projects in the design or construction stage utilizing the breakpoint-chlorina-
tion process. The 7.5-mgd. South Lake Tahoe plant is adding facilities to provide breakpoint chlorina-
tion of the quantities of ammonia which escape the upstream nitrogen-removal processes (5-16 mg/1).6
The Orange County, Calif., 15-mgd wastewater reclamation plant now nearing completion will
include facilities to remove the 2-3 mg/1 of ammonia that will escape the upstream ammonia-stripping
process.22 Chlorine gas will be supplied from purchased 1-ton cylinders and by an on-site electrolytic
generator rated at 2,000 Ib/d. The chlorine generation system will utilize an electrochemical cell
to electrolyze sodium chloride brine to chlorine gas and sodium hydroxide solution. The sodium
hydroxide solution will be used in an adjacent sea water desalting plant.
A 60-mgd facility is under design for Montgomery County, Md., by CH2M/HILL, which will
utilize the breakpoint process as the primary nitrogen-removal process. In this plant, sodium hypo-
chlorite will be produced on site by electrolysis of a salt brine. The Cortland, N.Y., 10-mgd
physical-chemical plant design includes facilities for breakpoint chlorination of the portion of the
flow required to meet stream standards.
The costs of the process applied to the 309-mgd plant at Blue Plains were estimated at 6.7 cents
per 1,000 gallons, with chemical costs constituting 5.9 cents of this value. These costs were based
on a chlorine cost of only $75 per ton and a dose of only 120 mg/1. The control of pH was assumed
to be by lime addition (1 pound of lime per pound of chlorine) at a lime cost of $24 per ton. In any
case, the cost of the chlorine itself constitutes a large portion of the total project costs. Assuming a
chlorine cost of 0.07 cent per pound and a C1:N ratio of 8:1, the chlorine cost for removal of 25
mg/1 ammonia would be 11.8 cents per 1,000 gallons. The chlorine demand for this dose is equiva-
lent to 1,668 Ib/mg.
265
-------
INFLUENT
Figure 111-2. Breakpoint-chlorination control system.
The breakpoint process is useful for eliminating low concentrations of ammonia as a polishing
step following another nitrogen-removal process.
266
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Chapter IV
COMPARISON OF PROCESSES
Each of the processes discussed earlier has its advantages and disadvantages. Unfortunately,
no single process for nitrogen removal is superior to others both in terms of performance and
economics.
The ammonia-stripping process has the advantages of low cost, removal of ammonia with a
minimal addition of dissolved solids, simplicity, and reliability. However, it has the disadvantages
of poor efficiency in cold weather and the potential for scaling problems that may reduce its effi-
ciency, and it raises concerns, whether valid or not, over ammonia gas discharge. The new stripping-
recovery system overcomes many of these problems, but at the sacrifice of low process costs.
The selective ion exchange process has the advantages of high efficiency, insensitivity to tem-
perature fluctuations, removal of ammonia with a minimal addition of dissolved solids, and the
ability to eliminate any discharges of nitrogen to the atmosphere other than nitrogen gas. This
process has the disadvantage of relatively high cost, and process control and operation are relatively
complex.
The breakpoint chlorination process has the advantages of low capital cost, a high degree of
efficiency and reliability, insensitivity to cold weather, and the release of nitrogen as nitrogen gas.
It has the disadvantage of adding a substantial quantity of dissolved solids to the effluent in the
process of removing the ammonia, it will raise public concerns over handling of chlorine gas, the
process controls required are relatively complex, and it requires a downstream dechlorination
process.
The relative costs of the physical-chemical nitrogen processes for a 10-mgd plant are
• Ammonia stripping, 5 cents per 1,000 gallons
Selective ion exchange, 10-13 cents per 1,000 gallons
Breakpoint chlorination, 11 cents per 1,000 gallons
These costs all are based on the removal of 25 mg/1 ammonia nitrogen. The cost of biological
nitrogen removal by the three-stage activated-sludge process has been estimated23'24 at about 13
cents per 1,000 gallons. Preliminary estimates on the costs of the new ammonia-stripping/ammonia-
recovery process discussed earlier, which minimizes the seasonal restrictions on the ammonia-
stripping process, indicate that the cost will be 8-10 cents per 1,000 gallons. It can be seen from
the above costs that there is little economic incentive to select one process over another if faced
with a requirement for cold weather removal of ammonia. The choice must be made by weighing
the advantages and disadvantages of each approach in light of the circumstances applicable to a
specific project.
267
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REFERENCES
1S. Miner, "Preliminary Air Pollution Survey of Ammonia," U.S. Public Health Service,
Contract No. PH22-68-25, Oct. 1969.
2A. F. Slechta and G. L. Gulp, "Water Reclamation Studies at the South Tahoe Public Utility
District," J. Water Pollut. Cont. Fed., 39, 787, May 1967.
3G. M. Wesner and R. L. Gulp, "Wastewater Reclamation and Seawater Desalination," J. Water
Pollut. Cont. Fed., 44, 1932, Oct. 1972.
4R. B. Dean, ed., Nitrogen Removal from Wastewaters, Federal Water Quality Administration
Division of Research and Development, Advanced Waste Treatment Research Laboratory, Cincinnati,
Ohio, May 1970.
5T. P. O'Farrell et al., "Nitrogen Removal by Ammonia Stripping," J. Water Pollut. Cont.
Fed., 44, No. 8, 1527, Aug. 1972.
6 J. G. Gonzales and R. L. Gulp, "New Developments in Ammonia Stripping," Pub. Works,
May and June 1973.
7Y. Folkman and A. M. Wachs, "Nitrogen Removal Through Ammonia Release from Ponds,"
Proceedings, 6th Annual International Water Pollution Research Conference, 1972.
8L. G. Kepple, "New Ammonia Removal and Recovery Process," Water Waste, in press, 1974.
9Battelle Northwest, "Ammonia Removal From Agricultural Runoff and Secondary Effluents
by Selective Ion Exchange," Robert A. Taft Water Research Center Rep. No. TWRC-5, Mar. 1969.
10 University of California, "Optimization of Ammonia Removal by Ion Exchange Using Clinop-
tilolite," U.S. Environmental Protection Agency Water Pollution Control Research Series No. 17080
DAR 09/71, Sept. 1971.
11Battelle Northwest and South Tahoe Public Utility District, "Wastewater Ammonia Removal
by Ion Exchange," U.S. Environmental Protection Agency Water Pollution Control Research Series
No. 17010 ECZ 02/71, Feb. 1971.
12R. Prettyman et al., "Ammonia Removal by Ion Exchange and Electrolytic Regeneration,"
unpublished report, CH2M/HILL Engineers, Dec. 1973.
13"Physical/Chemical Plant Treats Sewage Near the Twin Cities," Water Sewage Works, 120,
86, Sept. 1973.
14D. Larkman, "Physical/Chemical Treatment," Chem. Eng., Deskbook Issue, 87, June 18, 1973.
15T. A. Pressley et al., "Ammonia Removal by Breakpoint Chlorination," Environ. Sci. Technol.,
6, No. 7, 622, July 1972.
16W. N. Stasuik, L. J. Hetling, and W. W. Shuster, "Removal of Ammonia Nitrogen by Break-
point Chlorination Using an Activated Carbon Catalyst," New York State Department of Environ-
mental Conservation Tech. Paper No. 26, Apr. 1973.
17A. W. Lawrence et al., "Ammonia Nitrogen Removal from Wastewater Effluents by Chlorina-
tion," presented at 4th Mid-Atlanta Industrial Waste Conference, University of Delaware, Nov. 1970.
18P. F. Atkins, Jr., D. A. Scherger, and R. A. Barnes, "Ammonia Removal in a Physical Chemical
Wastewater Treatment Plant," presented at 27th Purdue Industrial Waste Conference, May 1972.
19R. C. Bauer and V. L. Snoeyink, "Reactions of Chloramines with Active Carbon," J. Water
Pollut. Cont. Fed., 45, 2990, Nov. 1973.
20L. R. J. Van Vuuren et al., "Stander Water Reclamation Plant: Chlorination Unit Process,"
Project Rep. 21, Pretoria, South Africa, Nov. 1972.
21D. F. Bishop et al., "Computer Control of Physical Chemical Wastewater Treatment," Pollu-
tion Engineering and Scientific Solutions, vol. 2, Plenum Press, 1973.
268
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22G. M. Wesner, "Water Factory 21—Waste Water Reclamation and Sea Water Barrier Facilities,"
Orange County Water District Rep., Feb. 1973.
23Bechtel, Inc., "A Guide to Selection of Cost Effective Wastewater Treatment Systems," draft
rep. for EPA U.S. Environmental Protection Agency, May 1973.
24R. Smith, "Updated Cost of Dispersed Floe Nitrification and Denitrification for Removal of
Nitrogen From Wastewater," U.S. Environmental Protection Agency Memorandum, Cincinnati,
Ohio, Apr. 13,1973.
269
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SLUDGES GENERATED IN PHOSPHATE REMOVAL PROCESSES
DR. JOSEPH B. FARRELL, CHIEF
ULTIMATE DISPOSAL SECTION
TREATMENT PROCESS DEVELOPMENT BRANCH
ADVANCED WASTE TREATMENT RESEARCH LABORATORY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
270
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SLUDGES GFTVRATED IN PgQSFHAIE
FJE-fOVAL PROCESSES*
Aluminum and iron salts and lime have been used in the physical-
chemical treatment of uastewater to remove phosphate. Use of these
chemicals increases the mass of sludge and affects its dewatering
properties.
Quantity
Isgird,^ ' in discussing Swedish experience, has presented a table
vhich relates sludge production to chemical dose (Table l). It is
believed that he was referring to experience with tertiary treatment.
The quantities of alum and iron sludges are easily calculated from the
chemical equations showing the reactions of Al^+ and Fe3+ (see Table 2).
The dose of Al or Fe used is related to the phosphorus level in the vaste-
water. It usually ranges from 1.8 to 2.2 atoms per atom of P. Isgird's
figures are seen to be quite reasonable.
When aluminum and iron salts are added at the primary clarification
stage, much more primary sludge is produced than predicted by the chemical
equations. The reason is the substantial increase in the efficiency of
the clarifier. Tables 3 and 4 show the anticipated increase in sludge
mass when Al and Fe are added at various points in the wastewater treatment
process.
The illustration in Table 3 compares sludge production when Al and Fe
are added to the primary clarifier with sludge production when they are
* Presented at the Third U.S./Japan Conference on Sewage Treatment Technology,
Tokyo, Japan, February 14, 1974.
271
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added to the aerator. Less sludge is produced when the chemicals are added
to the aerator. This is true "because the BOO load on the aerator is much
reduced when the chemicals are added to the primary. Since the EOD load
is reduced, there is much less conversion of organic material to carbon
dioxide; consequently total mass of sludge is higher.
The mass of sludge formed vrhen lime is added to wastewater can also be
calculated from the chemical equations (see Table 5). It is necessary to
know the chemical analysis of the water before treatment and estimate it
after treatment. The major difference in calculation method is that the
initial dose of Ca(CH)2 is estimated from the alkalinity of the vastewater
rather than from a relationship between the phosphorus level in the waste-
water and the Ca(OH)2 dose. Figure 2 shows a correlation of lime dose
with alkalinity of the wastewater.
Dewaterin.'; Properties
There are a few generalizations that can be made about the sludges
generated by Al, Fe, and Ca(OH)2 addition. Aluminum and iron salts
generally reduce the solids content of the primary clarifier sludge.
Sludges cannot be thickened to as high a solids content. The effect is
often unnoticed at lower doses, but when the ratio of metal dose to waste-
vater suspended solids increases, the effect is substantial. For example,
if enough Al or Fe is added to a typical United States wastewater to remove
90 percent of the phosphate, the sludge thickening and dewatering properties
will be noticeably poorer.
272
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With liir.3, the effect is the opposite. Lice improves thickening and
devatcring properties substantially. It is often possible to eliminate
sludge conditioning agents. Mass of sludge is generally much higher but
volucs is often lower than if Al or Fs salts were used.
Table 6 attempts to express theoe qualitative statements in a semi-
quantitative way. It should only be xised as an approximate guideline for
anticipated results.
Examples
Barrie. Tests were reported by Ian Grayx ' of the Ontario Ministry
of the Environment (Canada). The plant conditions are as follows:
3.0 MGD (11, 1KX> m3/da)
bar screens, grit removal
primary clarifier
activated sludge
final clarifier
two stage digestion
waste activated sludge recycled to plant inlet
Alum addition to the primary was compared to alum addition to the aerator.
A high dose of alum (200 mg/1 of alum, equivalent to 200 x 0.091 =
18.2 E3/1 Al) significantly lowered sludge solids.
If alum dose was less than 150 mg/1 of alum, there was no effect on
sludge density.
The point of alum addition (to the primary or to the aerator) did not
affect sludge density.
273
-------
Littlo Paver. This is a email primary plant (15,000 m^/da) in the
city of Windsor, Ontario. ^' Data are surtaarized in Table 7« Alum and
lime addition are compared to each other and to a control period (the
previous year). Altai addition caused a slight reduction in filter yield
and cost of conditioning chemicals increased. Lime caused a substantial
increase in sludge concentration and filter yield, and reduced chemical
conditioning costs.
Blue Plains. This is the principal plant in Washington, D. C.
Table 8 describes the processing sequence at this plant. During a
lengthy test period, J]Q mg/1 of alum (9.1$ Al) was added to the aerators.
Effects are summarized below:
A. Thickening. Sludge is 7.5$. Ho change.
B. Digestion. Sludge leaves at 3«5$« No change. Ho
interference with digestion.
C. Elutriation. Higher polymer dose is needed to retain
fines. Cost is $7/dry ton vs. $3/dry ton.
D. Filtration. Filter yield is about the same, but solids
content of cake is 20% vs. 23%. Chemical cost is
$7/dry ton, slightly over $l/dry ton higher than previously.
Contra Costa, California. This system utilizes chemical treatment in
the primary clarifier for phosphorus removal, followed first by carbonaceous
removal and nitrification in a single aeration stage, and finally by
denitrification.^ ' Lime will be used to pH 11 with 14 mg/1 ferric
chloride. The lime addition reduces the biological load to the second
stage, allowing longer sludge age needed for nitrification. It also
provides heavy metals removal, and offsets the acid formed in nitrification.
274
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Waste biological solids are returned to the primary clarifier.
Solids in the primary clarifier underflow are 5-9 percent. Sludge is
first centrifugcd in a solid bowl centrifuge without polymer. The
cake contains most of the calcium carbonate, and the centrate contains
most of the calcium phosphate, magnesium hydroxide, and organic
material. The ceatrate is once again centrifuged using a higher rota-
tional speed and polymer. The first cake can be calcined to produce
reusable lime. The cake from the centrate is incinerated for disposal.
Salt Lake City. Addition of Al, Fe, and Ca(OH)2 have been investigated
on a large pilot plant scale by the Eimco Corporation at Salt Lake City,
Utah.^' Results are summarized in Tables 9 and 10. Results for the Al
and Fe cases are based on a very limited amount of data.
Results indicate excellent sludge characteristics with line. Results
with Al and Fe are poor, primarily because the experimenters could not
thicken the sludge. This work has continued. Much more information has
been collected but is not yet available. A modification in the design
of the clarifier has allowed the Al and Fe sludges to settle to higher
solids, giving better filter yields.
275
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LITERATURE CITED
(1) Isgird, Erik, "Chemical Methods in Present Swedish Sewage Purification
Techniques," presented at the 7th Effluent and Water Treatment Exhibition
and Convention, London, June 25f 1971*
(2) Gray, IEJI M., "Phosphorus Removal at Earrie WPCP," Ontario Ministry of
the Environment, Dec. 1972.
(3) Buratto, D. A., and L. S. Romano, "Phosphorus Removal at City of Windsor's
Little River Plant," in Proc. of Tech. Seminar on Physical-Chemical
Treatment, Mar. 9> 1972, Ontario Ministry of the Environment.
(4) Parker, D. S., F. J. Zadick, and K. E. Train, "Sludge Processing for
Confined Physical-Chemical-Biological Sludges," Environmental Protection
Technology Series, EPA-R2-73-250, July 1973.
(5) Burns, D. E., and G. L. Shell, "Physical-Chemical Treatment of a
Municipal Wastewater Using Powdered Carbon," Environmental Protection
Technology Series, EPA-R2-73-264, Aug. 1973.
276
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TABLE 1 — SLUDGE PRODUCED
BY CHEMICAL ADDITION
ALUM : ADD 4 x mg/1 of Al
FERRIC: ADD 2.5 x mg/1 of Fe
LIME : ADD 1 to 1.5 mg/1 of Ca(OH)2
(AFTER E. ISGARD - SWEDISH EXPERIENCE)
9 — Al and Fe SLUDGE PRODUCTION
Al + PO^ =
1 kg 4.52 kg
Al + 30H = Al(OH)3
1 kg 2.89 kg
Fe + PO. = FePO^
1 kg 2.70 kg
Fe + 3QH = Fe(OH)
1 kg 1.91 kg
277
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Table 3 : Calculated Sludge Mass (ib/M.G.)
Fe to Fe to Al to Al to TF
Conventional Primary Aerator Aerator Clarifier
Primary
SS"Removal
Sludge Solids
Fe Solids
Al Solids
Total
Activated Sludge
Secondary Solids
Fe Solids
Al Solids
Trickling Filter
Secondary Solids
Al Solids
Totals
1250
0
0
1250
715
(656)
1965
536
804
541
75^
1875 1250 1250
605
2480 1250 1250
8o4
425
1250
1250
3016
2595
2479
745
483
2478
Table k Basis for Sludge Mass Calculation
in Table 3
Cation/P Dose
(n:ol/rnol)
1.5
1.75
lb Chemical Sludge/lb Cation
Ib/Ib AlIb/lb Fe"
3.9
3.8
2.4
2.3
Assumptions:
Cation/P Dose
Cation/P Dose
1.5 nol/Eiol to aerator
1.75 Riol/mol to primary or before
Trickling Filter clarifier
Influent Sevage
BOD = 230 mg/1
SS - 300 iag/1
P = 10 mg/1
278
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TABLE 5 — REACTION OF LIMB WITH WASTEWATER
5Ca(OH)2
Ca(OH)2
Mg
HCOo
*J
Ca(OH)
CaC03 +
20H = Mg(OH),
= Ca + 20H
90H
+ OH
TABLE 6 — FZLTRABILIIY OF PHOSPHATE SLUDGES
CEEMCAL
3+
A1
LIME
PRIMARY
YIELD COST*
0.5-0.8 MJCH MORE
0.5-0.8 14UCH MORE
1.1-1.5 LESS
PRBIARY + WAS
COST*
YTET.D
0.7-1.0 MORE
0.7-1.0 MORE
1.3-1.8 MUCH LESS
* COST OF CONDITIONING CHEMICAL
279
-------
TAELE_T — LITTLE RIVER WPCP. WINDSOR,
PRIMARY PLAINT (15,000 m3/da.)
DOSE (ns/1)
SLUDGE (mg/1)
SLUDGE CONCW.(#)
FILTER YIELD
CONTROL
0
158
6.2
25
ALUM
150
310
5.8
23
LIME
125-150
338
11.1
35
THKG COST-*
($/metric ton)
IT.TO
19.60
13.00
Fed-, and LIME
TABLE 8 — BLUE HAJTS WFCP, WASHINGTON, D.C.
CAPACITY 300 MGD (1,130 x
KWCESS PRIMARY CLARIFICAHOW
HIGH-RAIE ACnVATJED SLUDGE
SLUDGE PROCESSDTg
A. PRB-IARY IS MIXED WITH V7ASTE A.S.
and THICKENED
B. DIGESTION
C. TWO-ST^.GE ELUTRIATION
D. FILTRATION (POLH-ER + Fed,)
280
-------
TABLE 9 — SALT LAKE CITY PILOT PLAHT,
PRIMARY DULY
DOSE (rag/1)
SLUDGE (mg/1)
SLUDGE CONC1T.($)
GRAVITY
SOLIDS LOADHIG (kg/m2-da)
UNDERFLOW SOLIDS
FeClg ALUM Ca(OH)2
120 150 460
168 144 840
1.3 0.3 12.0
r4 24 210
3.0 1.5 20.0
TABLE 10 — SALT LAIS CITT PILOT PLAKT.
PRIMARY GllLY
DOSE (ma/1)
VACUUM FILTRATION
Ca(03)2 DOSE (kg/kg)
YIELD (kg/m2-hr)
CAKE SOLIDS (<)
FeClg
120
0.2
5-9
20
ALUM
150
0.2
3.9
20
Ca(OH)2
460
0
49
4o
281
-------
ro
oo
ro
u_
12
DC
LU 11
LLJ
co 10
7
1 III II
^**&~°
a SX^
n X*v A ^
s A
0
y^ SYMBOL ALKALINITY
/A (mg/I)
y^ A 100-125
/ o 226
^ a 440-460
X
X
^x 0 277
^ 450
* 300
1 III IS
- - -
REF
1.
2.
3.
4.
5.
5.
— —
—
i
. LOCATION
WASH., D.C.
S. TAHOE, CA.
NINE SPRINGS.
Wl
LEBANON, OH
LEBANON, OH
BATAVIA, OH-
0.3
0.5
3.0
0.7 1.0 2.0
CaO/ALKALINITY
FIG. 2: RATIO OF LIME DOSE (mg/I) TO INITIAL WASTEWATER
ALKALINITY (mg/I)
-------
EPA EXPERIENCES IN OXYGEN-ACTIVATED SLUDGE
EDWIN F. EARTH, CHIEF*
BIOLOGICAL TREATMENT SECTION
TREATMENT PROCESS DEVELOPMENT BRANCH
ADVANCED WASTE TREATMENT RESEARCH LABORATORY
NATIONAL ENVIRONMENTAL RESEARCH CENTER
CINCINNATI, OHIO
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
'The presentation was based on material prepared by Richard C. Brenner for the
U.S. Environmental Protection Agency - Technology Transfer Design Seminar Program
283
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EPA EXPERIENCES IN OXYGEN-ACTIVATED SLUDGE
Richard C. Brenner
INTRODUCTION
Utilization of oxygen aeration for activated sludge treatment is
receiving increasing attention in wastewater treatment plant construction
in the United States. The concept, although more than 20 years old, has
received serious consideration only during the last six years with the
development of several cost-effective systems for dissolving and utilizing
oxygen gas in an aeration tank environment.
The rapid transition from the drawing boards to full-scale imple-
mentation has been possible because of intensive government and private
research and development programs., The U.S. Environmental Protection
Agency (EPA) and its predecessor organizations have contributed signi-
ficantly to the total research and development effort. The purpose of
this paper is to summarize the role of EPA during the period of 1968-1974
as the oxygen aeration process progressed to its current level of development.
As outlined in Table 1, EPA has pursued seven active projects to date.
The projects include in-house pilot plant studies to examine process
kinetics, extramural feasibility grants and contracts, extramural materials
and safety projects, and extramural demonstration grants.
The EPA contribution to the projects described in Table 1 exceeded
$3.4 million through Fiscal Year 1974 (ended June 30, 1974).
The cost breakdown by project is given in Table 2.
Test facilities, experimental plans, and results (where available)
for each of the above projects are summarized in the following sections.
THE BATAVIA PROJECTS
A research and development contract was awarded to the Union Carbide
Corporation in October 1968 to evaluate a proprietary staged, covered-
tank oxygenation system at the Batavia, New York, Water Pollution Control
Plant. Union Carbide was awarded a follow-up contract in June 1970 to
284
-------
TABLE 1. EPA RESEARCH AND DEVELOPMENT
PROJECTS ON OXYGEN AERATION
Project
Objective
1. Batavia 1 and II
(Union Carbide Corporation)
2. Newtown Creek
(New York City)
3. Las Virgenes (California)
Municipal Water District
4. FMC Corporation
5. EPA/District of Columbia
(Blue Plains) Pilot Plant
6. Bureau of Reclamation
7. Rocketdyne Division of
Rockwell International
Establish feasibility of multi-stage,
covered-tank oxygenation concept.
Scaled-up demonstration of multi-stage,
covered-tank oxygenation system.
Demonstration of single-stage, covered-
tank oxygenation system.
Establish feasibility of open-tank
oxygenation concept.
Determine process kinetics over wide
range of operating conditions.
Materials of construction corrosion
testing.
Define safety requirements and
develop safety manual and checklist.
TABLE 2. EPA RESEARCH AND DEVELOPMENT EXPENDITURES
ON OXYGEN AERATION THROUGH FY-73
Project
Cost to EPA Type of Project
Union Carbide Corporation (Batavia I and II) $ 795,000
New York City (Newtown Creek) $1,574,000
Las Virgenes (California) Municipal Water $ 186,000
District
FMC Corporation $ 142,000
EPA/District of Columbia (Blue Plains) $ 500,000
Pilot Plant
Bureau of Reclamation $ 165,000
Rocketdyne Division of Rockwell International $ 92,000
TOTAL $3,454,000
Contracts
Grant
Grant
Grant
Contracts and
Inhouse
Contract
Contract
285
-------
better define soluble organic removals and excess biological sludge pro-
duction and to undertake initial pilot plant studies on oxygen sludge
dewatering and stabilization. The oxygenation system was installed in
one of two existing air-activated sludge trains at Batavia. During the
first contract, the performance of the oxygen train was evaluated against
that of the intact air train. A schematic diagram of the Batavia Plant
after installation of the oxygen system is shown in Figure 1.
The oxygen system configuration evaluated at Batavia was the first
large-scale embodiment of the now well known "UNOX" process.* A typical
three-stage "UNOX" aerator is shown schematically in Figure 2. The aerator
operates as a series of completely mixed stages, thereby approximating plug
flow. Oxygen gas is fed under the aeration tank cover at the inlet end of
the tank only and flows co-currently with the liquid stream from stage to
stage. Gas is recirculated in each stage by centrifugal compressors which
force the gas down hollow shafts out through submerged rotating spargers.
Submerged turbines maintain suspension of the mixed liquor solids and
disperse the oxygen gas. A mixture of unused oxygen gas, cell respiration
by-product carbon dioxide, and inert gases is exhausted from the final stage,
typically at an oxygen composition of about 50% and a flow rate equal to
10-20% of the incoming gas flow rate. Using co-current gas and liquid flow
to match the decreasing dissolution driving force inherent in continually
decreasing oxygen gas composition with the decreasing oxygen demand of
wastewater undergoing biological treatment has proven to be a very efficient
oxygen contacting and utilization technique.
A second-generation multi-stage process has been developed and utilized
both by Union Carbide and Air Products and Chemicals, Inc. This adaptation of
the original covered-tank concept replaces the recirculating compressors and
rotating spargers with surface aerators. Oxygen transfer is accomplished by
gas entrainment and dissolution. Submerged turbines are 'also used optionally
where tank geometry requires additional mixing capability. As shown in Figure 3,
all other aspects of the system are unchanged. The first Air Products and
Chemicals version of the covered-tank, surface-aerator concept has been oper-
ating for approximately three yearsat tne Westgate Treatment Plant in Fairfax
County, Virginia (design flow 12 mgd). Operation commenced in July 1972
^Mention of a trade name or commercial products does not constitute Environ-
mental Protection Agency endorsement or recommendation for use.
286
-------
PLANT
,,EFFLUENT
IV)
oo
CHLORINE
CONTACT
TANKS
02
STORAGE
KEY
SEWAGE FLOW
SLUDGE FLOW
DESIGN POPULATION 25,000
&VG FLOW 2.5 MIL GAL /DAY
MAX.FLOW 6.25 MIL GAL /DAY
MAIN PUMP STATION
FIGURE 1. SCHEMATIC FLOW DIAGRAM FOR WATER POLLUTION CONTROL PLANT, CITY OF BATAV1A, NEW YORK
-------
IN3
00
00
AERATION
TANK COVER
OXYGEN
PEED GAS
WASTE
LIQUOR
FEED
RECYCLE
SLUDGE"
PROPELLER
DRIVE
GAS RECIRCULATION
COMPRESSORS
EXHAUST
"GAS
MIXED LIQUOR
"EFFLUENT TO
CLARIFIER
PROPELLER
SPARGER
FIGURE 2. SCHEMATIC DIAGRAM OF MULTI-STAGE, COVERED-TANK OXYGENATION
SYSTEM WITH GAS RECIRCULATION COMPRESSORS AND SUBMERGED
TURBINE/SPARGERS
-------
AERATION TANK COVER
SURFACE AERATOR
ro
oo
OXYGEN
FEED GAS
WASTEWATER
FEED
RECYCLE
SLUDGE
MIXER DRIVE
EXHAUST
GAS
MIXED LIQUOR
EFFLUENT TO
CLARIFIER
SUBMERGED PROPELLER (OPTIONAI)
FIGURE 3. SCHEMATIC DIAGRAM OF MULTI-STAGE, COVERED-TANK OXYGENATION SYSTEM
WITH SURFACE AERATORS
-------
at Speedway, Indiana, the first municipal plant to utilize the Union
Carbide surface aerator system (design flow 7.5 mgd). The surface aerator
modification of the basic multi-stage process has exhibited better cost
effectiveness for tanks up to approximately 15 feet deep and is being used
increasingly in full-scale design. Market forecasts and actual experience
to date of firms selling multi-stage, covered tank oxygen systems indicate
that 80-85% of the plants that eventually utilize this oxygen system concept
will employ surface aerator designs. A report currently being prepared for
EPA by Air Products and Chemicals documenting the Fairfax County, Virginia
case history from inception through two years of operation with the oxygen
system will be available by mid-1975.
The results of the Batavia projects have been widely disseminated in
two EPA Water Pollution Control Research Series Reports (17050 DNW 05/70)
(17050 DNW 02/72). One of the conclusions expressed in these reports is
that oxygen aeration can provide equal treatment efficiency to air aeration
with only one-third as much aeration volume. This conclusion has been sub-
ject to widespread criticism. In that this generalization was reached by
comparing an efficient oxygen contacting system with a relatively inefficient
coarse-bubble air aeration system, the criticism appears to be justified.
The increasing variety of air aeration equipment being marketed offers a
wide range of oxygen transfer kinetics. Some of this equipment has been
shown to be capable of supporting the higher mixed liquor solids concen-
trations necessary for justifying smaller volume biological reactors (e.g.,
the INKA aeration system, Divet, et al., 1963). Design engineers are urged
to investigate and prepare cost estimates for both air and oxygen systems
as a basis for process selection. Process selection should be made from a
total integrated system comparison, including aeration, secondary clarifi-
cation, and excess biological sludge handling and disposal requirements.
Pertinent results of the two Batavia projects relating only to oxygen
system performance are summarized below:
1. The feasibility of achieving high oxygen gas utilization (91-95%)
was established.
2. Efficient biological performance (90-95% BOD^ and suspended solids
removals, 80-85% COD removal) was demonstrated with short aerator
detention periods (1.4-2.8 hours based on Q) and high organic
volumetric loadings (140-230 Ib BOD5/day/l,000 ft3).
290
-------
3. High mixed liquor dissolved oxygen (D.O.) levels (8-12 mg/1) were
maintained at high mixed liquor suspended solids (MLSS) concentration
(3,500-7000 mg/1).
4. Warm weather secondary clarifier performance deteriorated above
2
an average surface loading of 1,600 gpd/ft .
5. Oxygen sludge exhibited excellent thickening properties during
secondary clarification (settled sludge of 1.5-3.0% solids).
6. Aerobic digestion of oxygen waste activated sludge with oxygen
produced comparable volatile suspended solids (VSS) reduction
rates to those given in the literature for air aerobic digestion
processes. Reductions in oxygen sludge VSS concentrations of 25
and 40% were achieved with 7 and 15 days of aerobic stabilization,
respectively.
7. Direct vacuum filtration of undigested oxygen waste activated
sludge was shown to be feasible using 10% ferric chloride for
2
conditioning. Cake yields of 3.5-4.5 Ib/hr/ft and moisture
contents of 83-85% were achieved at a cycle time of 2.4 min/rev.
Moisture content improved to 75-80% but cake yield dropped to
2
1.5-2o5 Ib/hr/ft at a cycle time of 6.3 min/rev.
8. Vacuum filtration of aerobically digested oxygen waste activated
sludge proved to be infeasible with the chemical conditioners
tested.
THE NEWTOWN CREEK PROJECT
Results of the initial Batavia contract were judged sufficiently
encouraging to justify a scaled-up demonstration of the multi-stage oxygen
system in a large municipal plant. A research and development grant was
awarded to New York City in June 1970 to convert one of sixteen parallel
bays at its Newtown Creek facility to oxygen using the recirculating com-
pressor/submerged turbine version of the "UNOX" process. The design flow
of the test bay is 20 mgd, roughly 10 times higher than the capacity of the
Batavia oxygen system. In addition to the $1.574 million EPA grant, New York
City provided over $1.2 million in city funds in support of the project.
The Newtown Creek plant was designed on the modified aeration principle
for 1.5 hours of aeration time (based on Q) and treatment efficiencies in
the range of 65-70%. The city is now confronted with an upgrading problem
in a land-locked neighborhood (see Figure 4), a situation common to many
291
-------
N
CK
l/l
z
<
u
STREET
/////A
1 SLUDGE
DIGESTION
OXYGEN AERATION
TEST BAY
o o
)O O
p° °
po o
A If
-------
large urban plants in the United States. Oxygen was believed to be a good
candidate for achieving the required 90% BODj. removal within the confines
of the existing aeration tanks and secondary clarifiers. Future conversion
of the entire 310 mgd facility to oxygen was the ultimate objective provided
a removal up to the 90% ± 8005 level could be consistently demonstrated in the
test hay. Two views of the Newtown Creek test bay are jshown in Figure 5.
The test bay went on stream in early June 1972. Extensive mechanical
problems and unreliable meters prevented accurate data collection during
the start-up phase (June 4, 1972-September 16, 1972) during which time the
influent flow was increased from 11 mgd to the design level of 20 mgd. Data
for this period are limited to effluent quality as summarized in Table 3.
TABLE 3. EFFLUENT QUALITY AT NEWTOWN CREEK
DURING START-UP (6/4/72-9/16/72)
Flow
(mgd)
11 _+ 2*
14 ± 3b
20 + 4C
Duration
(weeks)
Effluent Concentration (mg/1)
Total
4 10
5 8
6 15
Soluble Total
BOD COD
4 68
3 55
4 62
Soluble
COD
50
41
47
Suspended
Solids
18
19
18.
aMLSS = 4,865 mg/1, Detention Time (based on Q) = 2.7 hr +.
MLSS = 5,920 mg/1, Detention Time (based on Q) = 2.1 hr _+.
CMLSS = 4,260 mg/1, Detention Time (based on Q) = 1.5 hr +.
Metering difficulties were finally resolved by mid-September 1972 permitting
commencement of the extensive data collection program planned for this project.
From September 17, 1972 through September 1, 1973, seven phases of a ten-phase
experimental program were completed. The influent flow conditions for these seven
phases are summarized in Table 4. Diurnal peak, average, and minimum flow rates
for Phases 4 through 7 are given in Table 5. With the exception of Phase 7, the
diurnal fluctuation patterns were selected to simulate the actual influent flow
pattern., o± the Newtown Creek facility.
293
-------
RAW
SEWAGE
FIVE GAS RECIRCULATING
COMPRESSORS
EIGHT SUBMERGED
PUMPS
[
RAW
SEWAGE
ijT
V
'
D D D D D
0
0
o
o
o
o
^
0
X
X' PROPELLER MIXERS
t
55'
I
=
-* Ann1 v
SECONDARY
EFFLUENT
MIXER
ASSEMBLY
DRIVE
PROPELLER
SPARGER
PLAN VIEW
NO SCALE
GRIT
CHAMBER I
FOUR-STAGE OXYGEN AERATOR
SECONDARY
EFFLUENT
SECONDARY
CLARIFIER
SLUDGE
RECYCLE
ELEVATION
NO SCALE
SLUDGE
WASTING
FIGURE 5. PLAN AND ELEVATION VIEWS OF OXYGEN AERATION TEST BAY, NEWTOWN CREEK
-------
TABLE 4. EXPERIMENTAL SCHEDULE FOR NEWTOWN
CREEK PROJECT (9/17/72-9/1/73)
Phase
Dates
Influent Flow Condition
9/17/72 11/25/72
12/10/72 2/1/73
20.8 mgd (Constant)
14 > 20 > 15 mgd
Avg. 17.7 mgd (Winter Upset)
_> t-i JLO/ /j H-/ // /o o 7 ^.u mgd
AVG. 15.1 mgd (Winter Restart)
4
5
6
7
4/8/73
6/3/73
7/8/73
8/12/73
6/2/73
- 7/7/73
- 8/11/73
- 9/1/73
20.6 mgd
25.3 mgd
30.0 mgd
35 o 4 mgd
(Diurnal)
(Diurnal)
(Diurnal)
(Diurnal)
TABLE 5. DIURNAL FLUCTUATION PATTERNS FOR
NEWTOWN CREEK (4/8/73-9/1/73)
Phase
4
5
6
7
Avg. Flow
(mgd)
20.6
25.3
30.0
35.4
Peak Flow
(mgd)
24
30
36
37.5*
Minimum Flow
(mgd)
14
17
19
30
*Maximum influent pumping capacity.
295
-------
A performance summary for the oxygenation system for Phases 1 through
7 is presented in Table 6. System sludge characteristics, aerator
loadings, and secondary clarifier loadings are summarized in Tables
7, 8, and 9, respectively.
TABLE 6. PERFORMANCE SUMMARY FOR NEWTOWN CREEK
(9/17/72-9/1/73)
Total BOD In
(mg/D*
Total BOD Out (mg/1)
% Removed
Soluble BOD
Soluble BOD
% Removed
Total COD In
Total COD Out
% Removed
In (mg/D*
Out (mg/1)
(mg/D*
(mg/1)
1
156
9
94
84
4
95
356
61
83
2
157
21
87
78
13
83
365
88
76
3
152
17
89
91
12
87
365
76
79
Phase
4
171
17
90
102
11
89
365
77
79
5
213
22
90
113
13
88
307
70
77
6
218
21
90
99
11
89
290
64
78
7
212
23
89
88
15
83
308
62
80
Soluble COD Out (mg/1) 50 69 63 69 58 49 46
Susp. Solids In (mg/D* 149 146 144 159 147 125 131
Susp. Solids Out (mg/1) 12 22 17 18 24 17 17
7o Removed 92 85 88 89 84 86 87
Sewage Temp. Range (°F) 7.7 64 51 53 62 71 72
^ ty ^ + + ^ 4,
56 53 61 69 74 77 78
*No primary sedimentation. Concentrations shown are for raw sewage
influent to oxygen aerator.
296
-------
TABLE 7. AVERAGE SYSTEM SLUDGE CHARACTERISTICS
FOR NEWTOWN CREEK (9/17/72-9/1/73)
Phase
1
2
3
4
5
6
7
MLSS
(mg/1)
4,890
5,060
4,000
3,875
4,550
4,155
3,090
MLVSS
(mg/1)
4,110
4,150
3,200
3,110
3,640
3,340
2,485
Return
Sludge
Flow
(% of Q)
30
40
50
45
44
34
25
Return
Sludge
TSS
(mg/1)
16,260
12,835
11,370
13,420
15,975
16,330
12,685
SVI
(ml/gram)
45
59
77
53
42
43
48
SRT
(days)
_#
-•$:-
_#
1.35
1.37
1.24
0.77
^Sludge wasting data not reliable.
TABLE 8. AVERAGE AERATOR LOADINGS FOR
NEWTOWN CREEK (9/17/72-9/1/73)
Phase
1
2
3
4
5
6
7
Detention Time
-Based on Q-
(hr)
1.43
1.68
1.96
1.44
1.17
0.99
0.84
F/M Loading
/lb BODs/day\
Y lb MLVSS /
0.65
0.57
0.57
0.92
1.19
1.62
2.44
Volumetric Organic
Loading
/lb BOD5/day\
\^ 1,000 ft^ )
163
140
110
178
272
331
379
297
-------
TABLE 9. AVERAGE SECONDARY CLARIFIER LOADINGS
FOR NEWTOWN CREEK (9/17/72-9/1/73)
Phase
]
2
3
4
5
6
7
Surface Overflow
Rate
(gpd/ft2)
945
805
686
936
1,150
1,364
1,609
Mass Loading
Ab TSS/ft2\
\ day )
50.1
48.2
32.6
43.7
63.0
63.3
52.0
Weir
Loading
(gpd/ lineal ft)
129,000
110,000
93,000
127,000
157,000
186,000
219,000
From the beginning of the project, New York City officials
considered performance of the oxygen test bay during cold weather the
most critical segment of the experimental program. It was during the
prolonged severe weather period that the true upgrading potential of
oxygen for Newtown Creek would be most evident. A discussion of the
data collected through September 1, 1973 at Newtown Creek is first pre-
faced, therefore, with a summary description of the operational difficulties
encountered during the 1972-73 winter season.
During Phase 1 (autumn 1972), operation went smoothly and perfor-
mance was obviously excellent. On November 25, 1972, the test bay was
shut down temporarily to replace a bearing on the sludge recycle pump.
What was planned to be a two-day outage turned into a two-week shutdown
when the stocked spare bearing proved to be the wrong size and a new one
had to be located. During the outage, sludge in the reactor was continually
oxygenated while the sludge in the secondary clarifier was devoid
of oxygen. Due to the imminence of the upcoming cold weather, it was
decided to restart the system using the existing sludge rather than empty
the tanks and take the time necessary to generate a new biomass. The
oxygen test bay was put back into service on December 10, 1972.
298
-------
For the first several weeks of Phase 2, performance was satisfactory
as the influent flow rate was gradually increased to the design level of
20 mgd. Shortly thereafter sludge settling properties began to deteriorate
and effluent BOD , COD, and suspended solids residuals exhibited a slowly
increasing trend. Microscopic examination of the mixed liquor revealed
the appearance of filamentous organisms of both apparent bacterial and
fungus origin. Influent flow was then decreased in several increments
during the month of January 1973 in an attempt to starve or "burn out" the
filamentous culture or cultures and reestablish a "healthy" population.
Instead of eradicating the filamentous organisms, reduction of flow
and organic loading seemed to have the opposite effect of stimulating
proliferation. This proliferation was accompanied by the usual indicators
of a bulking sludge, i.e., a substantial increase in SVI, a rising sludge
blanket in the secondary clarifier, increasing suspended solids carry-over
in the final effluent, and operational difficulty in managing total system
sludge inventory.
In trying to determine the source of the filamentous intrusion, it was
postulated that the bacterial species (Sphaerotilus) may have developed in
the secondary clarifier sludge blanket during the aforementioned shutdown.
A local pharmaceutical firm is known to discharge mycelia into the Newtown
Creek sewer system and this was suspected as the source of the fungus
organisms., By the end of January 1973, with the influent flow reduced to
15 mgd, the SVI had risen from a summer background level of 45-50 to 85-100,
effluent suspended solids were exceeding 30 mg/1, effluent soluble BOD had
increased to over 20 mg/1, and the clarifier sludge blanket was continuing
to rise. At this point a decision was made to "dump" the entire sludge
inventory, hose all settled sludge pockets out of the reactor and clarifier,
and start over. This second shutdown began on February 1, 1973.
After taking some additional time to make repairs to the sludge collection
mechanism while the clarifier was dewatered, Phase 3 commenced on February 18,
1973. Conservative loading rates were utilized initially based on the premise
that the best chance to prevent a reoccurrence of the filamentous condition
was a program of gradual and modest increases in F/M loading until the 20 mgd
design flow rate was reached. Relatively high MLSS concentrations of 5,000 mg/lt
299
-------
were maintained as a further measure to minimize F/M loading. However,
within several weeks a repeat of the experience encountered in Phase 2
became evident with the initial appearance of filaments in the oxygen
sludge. This time the organisms were definitely identified as fungus.
One possible reason for explaining the higher 1972-73 winter incidence and
enrichment pattern of these fungus organisms in the Newtown Creek oxygen
sludge as opposed to that facility's air sludges is the lower mixed
liquor pH inherent to the operation of the covered-tank oxygen system.
With the prospect of impending project failure a real possibility,
a joint decision (New York City, Union Carbide, and EPA) was reached to
accept the presence and proliferation of the fungus organisms as a cold
weather phenomenon and attempt to find an operating mode that would permit
satisfactory winter performance at design flow in spite of them. Accordingly,
a program of increased sludge wasting was initiated which eventually lowered
the MLSS concentration to less than 4,000 mg/1 and the SRT* to slightly
more than one day. At the same time influent flow was elevated in several
fairly rapid increments to 20 mgd (equivalent to an aerator detention time
of 1.5 hours based on Q). These steps yielded an F/M at the end of the
phase in the range of 0.75-0.80, considerably higher than the average of
0.57 for all of Phase 3. The altered operating philosophy proved to be
the correct decision, resulting in a controllable clarifier sludge blanket
and stable cold weather performance at design flow. Percentage removals
for the remainder of Phase 3, although not as high as Phase 1, were within
satisfactory limits. As the wastewater temperature increased during early
spring, the concentration of filamentous organisms diminished, and they
eventually disappeared in early May 1973.
During the summer of 1973,the Newtown Creek oxygen system exhibited
remarkable capability for absorbing high hydraulic and organic loadings
while still producing a high quality secondary effluent. Four diurnal
phases (Phases 4-7) conducted from April 8, 1973 through September 1, 1973
successively increased the average influent flow from 20.6 to 35.4 mgd.
During Phase 7 the average nominal aerator detention time was only 52 minutes
with corresponding average F/M, volumetric, and clarifier surface loadings of
* Defined as Ib VSS under aeration/Ib VSS wasted in the waste sludge and
final effluent/day.
300
-------
2.44 Ib BOD5/day/lb MLVSS, 379 Ib BOD5/day/l,000 ft , and 1,609 gpd/ft2,
respectively. These results confirmed and exceeded the high-rate
loading potential of oxygen-activated sludge first seen at Batavia.
At this point in the project it was possible to offer the following
interim status remarks:
!„ The high-rate loading capability (nominal aeration time < one
hour) of oxygen aeration operating on Newtown Creek wastewater
during warm weather was conclusively demonstrated.
2. Prospects appeared promising that a modified method of operation
evaluated in late winter 1972-73 could circumvent the negative
effects of what may be an indigenous cold weather filamentous
condition with oxygen at Newtown Creek and permit satisfactory
performance at a flow rate at least equal to the design level
of 20 mgd (1.5 hours of nominal aeration time).
3. The operational measures employed to effect the improved
performance in late winter 1972-73, namely high F/M's and low
SRT's, occurred naturally to an even greater degree during the
high loading phases of summer 1973.
4. The above comments provide a tentative basis for speculating
that in some cases oxygen aeration may most beneficially be
employed at ultra high loading rates substantially exceeding any
which have been approved to date by State agencies.
Because of the importance attached to winter operation and performance,
the project was extended to the end of April 1974. The two major questions
which were to be addressed during the extended period were whether filamentous
organisms (particularly fungus) would again infest the oxygen sludge as
wastewater temperature dropped and, if so, would the modified method of
winter operation previously described permit continuous efficient per-
formance with a diurnal loading pattern centered around an average influent
flow rate of 20 mgd. If the first few months progressed without upset,
the flow rate was to be increased to 25 mgd and subsequently to 30 mgd
in the last 2-3 months of the winter season. The reason for holding this
latter option open was that if a year-round loading capability of 30 mgd
301
-------
could be demonstrated, the Newtown Creek Treatment Plant could conceivably
be satisfactorily upgraded by converting only 11 or 12 of the existing 16
bays from air aeration to oxygen aeration.
Data for the extended operating period (September 1973 through April
1974) are summarized along with the first seven project phases in a paper
entitled "Upgrading New York City Modified Aeration with Pure Oxygen."
This paper was prepared by New York City personnel (Nash, et al.) and
presented at the 47th Annual Conference of the Water Pollution Control
Federation. It is recommended that both this Technology Transfer report and
the New York City paper be reviewed in evaluating the Newtown Creek project.
The project will also be extensively documented and analyzed in the final
grant report now being prepared by the City. It is anticipated this report
will be available for distribution by mid-1975.
Another aspect of the project is discussed briefly below. Initially
the performance of the four-bed Pressure Swing Adsorption (PSA) Oxygen
Generator was less than satisfactory. During the 1972 summer startup
phase the unit was out of service due to mechanical problems roughly
40 percent of the time. These problems have since been largely corrected
and the generator now functions with a down-time that varies between
5 and 10 percent. During the 1972 startup difficulties one of the four
beds inadvertently became "loaded up" with water vapor. Subsequently, the
maximum achievable output of the unit was 10 tons of gas per day at
90 percent oxygen purity versus a design output of 16.7 tons of gas per
day at 90 percent oxygen purity. This necessitated an increase in
consumption of and reliance on the back-up liquid oxygen reservoir during
peak oxygen demand periods. The simplified three-bed (moving parts decreased
50 percent) PSA unit installed at Speedway, Indiana, has reportedly operated
at design output with high mechanical reliability following its installation
and startup in mid-summer 1972.
302
-------
THE LAS VIRGENES PROJECT
A single-stage, covered-tank oxygenation system has been designed by
the Cosmodyne Division of Cordon International Corporation. The system,
given the name "SIMPLOX" and shown schematically in Figure 6, utilizes an
inflated dome-type cover to contain the oxygen-rich atmosphere over the
aerator. This concept is intended primarily for upgrading existing air
activated sludge plants with a minimum capital expenditure by utilizing
conventional air blowers and coarse-bubble air diffusers to recirculate
oxygen gas. Air blowers used in this service must be corrosion proofed
and otherwise modified to be compatible with oxygen gas. Virgin oxygen
gas is introduced to the aerator through a fine-bubble sparger located
on the tank bottom and on the opposite side wall from the conventional air
diffusers. Power required for oxygen dissolution is greater for the
"SIMPLOX" process than for the multi-stage systems because: (1) the
equipment used for transferring oxygen is modified air aeration equipment
and not specifically tailored to oxygen gas kinetics and (2) the gas phase
above the mixed liquor is completely mixed and assumes the same oxygen
composition as the exhaust gas stream; thus, the driving force for dissolving
oxygen in wastewater is less than in the lead stages of multi-stage aerators.
However, capital costs for converting an existing aerator from air to oxygen
service should be significantly less with the "SIMPLOX" approach because
staging baffles and multiple oxygen dissolution equipment assemblies are
not required. Since the gas phase is completely mixed, exhaust oxygen,
carbon dioxide, and inert gases can be bled from any point of the inflated
dome and any of several activated sludge flow configurations, including plug
flow, complete mix, and step aeration, can be used as desired.
A research and development grant was awarded to the Las Virgenes (Cali-
fornia) Municipal Water District (a suburb of Los Angeles) in June 1971 to
evaluate the "SIMPLOX" system at its Tapia Water Reclamation Facility. The
experimental program concluded on September 10, 1973. The District contributed
$62,000 in support of the project, supplementing the $186,000 EPA grant. An
empty nominal one mgd train was available for the oxygen study because of a
recent expansion at the Tapia facility. The manner in which the oxygen system
was incorporated into this existing train is shown in plan view in Figure 7.
303
-------
r
V
"* ' " ' '" 1
(LIQUID 02
STORAGE
02
APORIZER
EXHAUST
GAS
)
r
PURE 02
FEED
|
1
1
CO
O
PRIMARY
EFFLUENT
1
INFLATED DOME
GAS PHASE-COMPLETELY MIXED
RECIRCULATING
COMPRESSOR
MODIFIED AERATION TANK
02 SPARGER
U_LU
rn m U M Lf
SECONDARY
EFFLUENT
RECYCLE
WASTE
SLUDGE
FIGURE 6. SCHEMATIC DIAGRAM OF DIFFUSED AIR AERATION SYSTEM MODIFIED TO
RECIRCULATE OXYGEN GAS, LAS VIRGENES PROJECT
-------
COVERED AERATION TANK
118'x30!xl5' WD
PRIMARY EFFLUENT
STEP FEED
PURE 02
GAS FEED
CO
0
cn
" 1 i
v°
,\
2 SPARGER
AIR DIFFUSERS
?????????
A 6 A 6
1
A A A | A A
i J
j_
/ CIRCULAR \
^/ CLARIFIER \
1 45' DIAxlO' / |
\J»°y \
RECTANGULAR
CLARIFIER
120'x20'xlO' WD
SECONDARY
EFFLUENT
_-^
RECIRCULATING
AIR COMPRESSOR
RECYCLE GAS I
EXHAUST
I »S GAS
FIGURE 7. FLOW DIAGRAM FOR LAS VIRGENES OXYGENAT10N SYSTEM
-------
Tha schedule followed during the experimental program for the project is
outlined in Table 10. The range of aerator loadings examined was not as
broad as at Newtown Creek due to influent flow limitations and a weaker
aerator feed (primary effluent at Las Virgenes, raw sewage at Newtown
Creek)„ The experimental program consisted of seven phases characterized
by increasing flow and system loadings. To effect a more pronounced
increase in aerator loading, only 45 percent of the available aerator
volume was utilized in the last five phases. This was accomplished via
the installation of a temporary bulkhead across the width of the aeration
tank after Phase 2.
TABLE 10. EXPERIMENTAL SCHEDULE .FOR LAS VIRGENES
PROJECT (4/25/72-9/10/73)
Phase
1
2
3
4
5
6
7
Dates
4/25/72
9/11/72
1/22/73
3/9/73
4/4/73
5/1/73
5/15/73
- 7/31/72
-11/13/72
3/8/73
4/3/73
4/30/73
5/14/73
9/10/73
Influent
Flow
(mgd)
1.0
2.0
1.0
1.13
1.3
1.54
1.85
% of Aerator
In Use
100
100
45
45
45
45
45
No. of
Clarif iers
In Use
1
2
1
2
2
2
2
System performance for the Las Virgenes project is summarized in
Table 11. Tables 12, 13, and 14 summarize, respectively, system
sludge characteristics, aerator loadings, and secondary
clarifier loadings. Project data and information are presented in
more thorough fashion in the final grant report. This report, currently
being reviewed by EPA, is scheduled to be available for distribution by
the end of the first quarter of 1975
306
-------
TABLE 11. PERFORMANCE SUMMARY FOR LAS VIRGENES
(4/25/72 9/10/73)
Total BOD5 In (mg/1)*
Total BOD5 Out (mg/1)
% Removed
Total COD In (mg/1)*
Total COD Out (mg/1)
% Removed
Soluble COD In (mg/1)*
Soluble COD Out (mg/1)
% Removed
Susp. Solids In (mg/1)*
Susp. Solids Out (mg/1)
% Removed
1
82
2
97
153
35
77
58
16
72
73
9
88
2
69
4
94
136
35
74
43
19
56
67
7
90
3
79
2
97
170
29
83
76
23
70
39
4
90
Phase
4
107
5
95
218
35
84
93
26
72
53
7
87
5
115
9
92
262
37
86
101
31
69
63
5
92
6
103
9
91
242
40
83
101
31
69
59
4
93
7
95
10
89
238
50
79
100
32
68
44
6
86
Turbidity Out (JTU) 232 3223
NH3-N In (mg/1)* 13.0 6.8 10.7 14.2 15.6 15.8 15.6
NH3-N Out (mg/1) 0.4 0.1 0.2 4.1 4.8 2.8 3.1
% Removed 97 99 98 71 69 82 80
N03-N Out (mg/1) 16.2 15.3 8.8 6.9 5.6 7.5 8.0
^Concentrations shown are for primary effluent feed to oxygen aerator.
307
-------
TABLE 12. AVERAGE SYSTEM SLUDGE CHARACTERISTICS
FOR LAS VIRGENES (4/25/72-9/10/73)
Phase MLSS MLVSS
(mg/1) (mg/1)
1 3,700 2,950
2 3,750 3,050
3 3,815 2,950
4 3,570 2,715
5 3,050 2,485
6 2,595 2,170
7 2,535 2,115
TABLE 13. AVERAGE
Return Return
Sludge Sludge
Flow TSS
(% of Q) (mg/1)
30 14,325
30 13,295
32 12,890
32 9,230
40 7,105
39 6,705
40 8,350
AERATOR LOADINGS FOR
SVI SRT
(ml /gram) (days)
99 79
179 68
175 46
200 30
247 12
191 9
117 12
LAS VIRGENES (4/25/72-9/10/73)
Phase Detention Time
-Based on Q-
(hr)
1 9.56
2 4o78
3 4.30
4 3.81
5 3o31
6 2.79
7 2.32
F/M Loading
fib BOD5/day \
\ Ib MLVSS /
0.07
0.11
0.15
0.24
0.33
0.41
0.46
Volumetric Organic
Loading
fib BODs/day^
V 1,000 ft?/
13
22
27
42
52
56
62
308
-------
TABLE 14. AVERAGE SECONDARY CLARIFIER LOADINGS
FOR LAS VIRGENES (4/25/72-9/10/73)
Phase Surface Overflow Mass Loading
Rate /lb TSS/ft2 \
1
2
3
4
5
6
7
(gpd/ft2)
417
501
417
283
326
386
464
V day )
16.7
20.4
17.5
11.1
11.6
11.6
13.7
A cursory review of Table 11 reveals that effluent quality for the
entire Las Virgenes project was superb and surpassed that observed at
Newtown Creek. This can be attributed to three factors: (1) the lower
aerator organic loadings which permitted a high degree of COD insolubili-
zation, (2) the very conservative secondary clarifier surface and mass
loadings which promoted highly effective solids capture, and (3) the lack
of any significant industrial waste contributions. A major objective of
wastewater treatment in the Las Virgenes District is the production of an
ultra high quality secondary effluent after chlorination suitable for
agricultural reuse. The thrust of this project, therefore, was geared
not so much to maximizing system loadings (as was the case at Newtown Creek)
as maintaining truly superb quality effluent and determining the effect of
a relative conservative progression in system loadings on single-stage
nitrification. As shown in Table 15, virtually complete nitrification
was observed with F/M loadings between 0.07 and 0.15 lb BOD5/day/lb MLVSS.
For F/M loadings between 0.24 and 0.46 lb BOD /day/lb MLVSS, nitrification
was only 69-82 percent complete. Lower wastewater temperatures may also
have played a role in the decreased nitrification of the latter four phases.
309
-------
TABLE 15. EFFECT OF ORGANIC LOADING AND
WASTEWATER TEMPERATURE ON NITRIFICATION
AT LAS VIRGENES (4/25/72-9/10/73)
Phase
1
2
3
4
5
6
7
F/M
/lb BODs/day\
^ lb MLVSS J
0.07
0.11
0.15
0.24
0.33
0.41
0.46
SRT
(days)
79
68
46
30
12
9
12
Wastewater
Temp . Range
(°F)
70-77
73-79
65-67
65-67
67-70
68-71
70-75
% NH3-N
Removed
97
99
98
71
69
82
80
Fin. Eff.
N03-N
(mg/1)
16.2
15.3
8.8
6.9
5.6
7.5
8.0
Another major goal of the Las Virgenes staff was to minimize excess
biological sludge production as much as possible. This goal probably led
to the most significant problem area encountered on the project, a very
evident bulking sludge. No sludge was intentionally wasted from the
system during Phases 1 and 2. Wastage of suspended solids in the final
effluent and final clarifier skimmings was sufficient to balance net system
biomass growth at the low F/M loadings employed. Resulting SRT's were as
high as 79 days and the SVI climbed to a level near 200 ml/gram. Despite
the instigation of a scheduled wasting program in Phase 3, the sludge
continued to bulk and the SVI climbed even higher. It was not until Phase 7
at an SRT of 12 days and an F/M loading of 0.46 lb BOD /day/lb MLVSS that a
significant drop in SVI occurred. The bulking sludge condition is attributed
here to a combination of Sphaerotilus filamentous development due to the
inordinately high SRT's and the accumulation of other poor settling debris
in the floe matrices. It was only because of the low clarifier loadings
that efficient overall performance was sustained. Sludge blanket levels
frequently rose to within a few feet of the clarifier weirs. The Las Vir-
genes experience illustrates the potential operating difficulties that can
and probably will occur at very low oxygen system loading rates.
310
-------
One definite conclusion reached during the project is that the inflated
tent (dome) concept is not suitable for permanent installation. New leaks
developed repeatedly in the polyvinyl material due to separation of the
tent/tank interface, abrasion against the tent support structure during
high winds, and bullets from pranksters' guns. The gas leak problem made
accurate oxygen consumption monitoring impossible, and during the latter
higher loading phases, the leaks became sufficiently frequent and large
that it was extremely difficult to maintain a mixed liquor D.O. above
1-2 mg/1. The rationale for using an inflated dome in lieu of a flat cover
on this research project was to permit access to the tank interior, a
procedure effectively utilized on several occasions. A permanent install-
ation would probably require a flat, more rigid cover for longevity and
minimization of leaks.
The Cosmodyne Division of Cordon International has not attempted to
establish a proprietary position with respect to the "SIMPLOX" system.
Notwithstanding the attractive capital cost features of this oxygen
dissolution concept for upgrading existing air-activated sludge plants,
without the support of a proprietary interest and an aggressive marketing
effort, utilization of this process in treatment plant construction will
most likely proceed at a much slower rate than with other oxygen processes.
THE FMC PROJECT
The FMC Corporation has developed a unique fine-bubble diffuser capable
of producing uniform oxygen bubbles of less than 0.2 mm in diameter. The
diffuser works on the shear principle of passing a high velocity liquid
stream at right angles to oxygen bubbles discharging into a vertical slot
from capillary tubes. Oxygen gas is introduced to the capillary tubes at
30 psi pressure., A graph provided by FMC showing water depth required for
complete dissolution of varying size oxygen gas bubbles is reprinted in Figure
8.# The large effect of a relatively small change in bubble size on the water
depth required for 100 percent dissolution is readily evident. For a bubble
diameter of 0.20 mm, a 17.5 foot deep tank would be required. The required
depth decreases to 8.5 feet for a 0.15 mm diameter bubble.
One of the many potential applications for this diffuser is in an open-
#This graph was prepared using tap water. Dissolution characteristics for
various size oxygen gas bubbles may and probably do differ for a wastewater
undergoing biological treatment.
311
-------
0.25
CO
i—'
no
w
H
W
,-J
cq
cq
CQ
w
o
0.20
0.15
0.10
0.05
PARTIAL ESCAPE OF BUBBLES
BUBBLES COMPLETELY DISSOLVED
2 3 4 5 6 7 8 9 10 15
DEPTH OF WATER REQUIRED FOR 100% DISSOLUTION - FEET
20
30
40
FIGURE 8. OXYGEN GAS BUBBLE DIAMETER VS. WATER DEPTH FOR COMPLETE DISSOLUTION
-------
tank oxygen-activated sludge process. To evaluate the feasibility of an
open-tank oxygenation approach, a research and development grant for
$142,000 was awarded to FMC in September 1972 for a nominal 30 gpm pilot
plant study. The firm is contributing over $75,000 of their funds to the
project. The pilot plant has been installed on the grounds of the Engle-
wood, Colorado (suburb of Denver), trickling filter plant and receives a
feed stream of primary effluent from that plant. Pilot plant configuration
and dimensions are shown in Figure 9. The aeration tank is provided with
two baffles to approximate a plug flow (three-stage) condition. Diffusers
are located in each of the stages. Mixed liquor is recirculated through
the diffusers by low head centrifugal pumps. Pump suction is taken near
the liquid surface to promote mixing and tank turnover. Throttling of the
oxygen feed is accomplished automatically by D.O. sensing and control.
Major points of research interest in the project are: (1) oxygen
utilization efficiency in an open-tank setting, (2) oxygen feed control
response based on a D.O. monitoring approach, (3) mixed liquor recirculation
rates and power requirements, (4) diffuser self cleansing (non-clogging)
capabilities, and (5) shearing effect, if any, on mixed liquor particles
caused by continuous recirculation through the pumps and diffusers. In
the event that floe disruption did occiu , a short detention biological
reflocculation tank (gentle mixing, no chemicals) was interposed
between the aerator and secondary clarifier. Two aspects of system design
which cannot be adequately defined at the scale of this pilot plant study
are diffuser mixing characteristics and additional mixing requirements,
if any, for large aeration tanks. This task is being addressed by FMC in deep
tank tests using tap water at both die firm's Englewood and Santa Clara
laboratories.
Pilot plant fabrication was completed in late June 1973. System
startup required the first 20 days of July. The experimental program which
followed was divided into eight phases and is outlined in Table 16. Perform-
ance data for the four highest flow phases (Phase 4 through 7) are summarized
in Table 17. Sludge characteristics, aerator loadings, and secondary clarifier
loadings for the same four phases are presented in Tables 18, 19 and 20
respectively. Data for the first three conservative load phases as well as
Phase 8 which was still in progress at the date of this writing will be included
by FMC in the final project report. Availability of this report is expected
by mid-1975.
313
-------
MIXED LIQUOR
MIXED LIQUOR
FLOCCULATION TANK
(IF NECESSARY)
CIRCULAR CLARIFIER
CENTER-FEED, RIM TAKEOFF
10' DIA x 10' WD
CO
I—>
-pi
FROM GASEOUS
OXYGEN SUPPLY
THREE-STAGE
OPEN TANK AERATOR
8' LONG x 4' WIDE x 11' WD
SECONDARY
EFFLUENT
RECIRCULATING PUMPS
PRIMARY
EFFLUENT
FINE BUBBLE
DIFFUSER
RECYCLE SLUDGE
WASTE
SLUDGE
FIGURE 9. FMC OPEN-TANK OXYGENATION PILOT SYSTEM
-------
TABLE 16. PLANNED EXPERIMENTAL PROGRAM FOR FMC PROJECT
Phase
1
2
3
4
5
6
7
8
Dates
7/21/73
9/6/73
12/6/73
4/8/74
5/1/74
6/1/74
7/1/74
10/1/74
- 9/5/73
- 9/30/73
- 1/28/74
4/30/74
5/31/74
- 6/30/74
- 7/31/74
10/31/74
Influent Flow
Condition
10 gpm (Constant)
10 gpm (Diurnal)
15 gpm (Constant)
25 gpm (Constant)
35 gpm (Constant
30 gpm (Diurnal)
20 gpm (Diurnal)
15 gpm (Constant)
No. of
Clarifiers
in use
1
1
1
2
2
2
1
1
TABLE 17. PERFORMANCE SUMMARY FOR FMC PROJECT
(4/8/74 - 7/31/74)
Total BOD5 In (mg/1)*
Total BOD5 Out (mg/1)
% Removed
Total COD In (mg/1)*
Total COD Out (mg/1)
% Removed
Suspended Solids In (mg/1)-"
Suspended Solids Out (mg/1)
% Removed
Turbidity Out (JTU)
Sewage Temperature (°F)
4
153
-13
92
332
95
71
110
13
88
6
57
5
159
18
89
315
74
77
85
15
82
6
62
Phase
6
180
16
91
259
57
78
85
12
86
4
67
7
208
16
92
322
61
81
115
15
87
5
71
* Concentrations shown are for primary effluent feed to oxygen aerator.
315
-------
TABLE 18. AVERAGE SYSTEM SLUDGE CHARACTERISTICS
FOR FMC PROJECT (4/8/74 - 7/31/74)
Phase
4
5
6
7
MLSS
(mg/1)
5,120
4,030
4,745
3,960
MLVSS
(mg/1)
4,010
3,435
3,860
3,365
Return
Sludge
Flow
(% of Q)
11,585
10,485
12,220
10,850
Return
Sludge
TSS
(mg/1)
60
52
57
50
SVI
(ml/gram)
71
70
67
73
SRT
(days)
2.0
1.5
2.1
2.6
TABLE 19. AVERAGE AERATOR LOADINGS FOR
FMC PROJECT (4/8/74-7/31/74)
Phase
4
5
6
7
Detention Time
-Based on Q-
(hr)
1.32
0.94
1.10
1.65
F/M Loading
/lb BOD5/day\
\ lb MLVSS J
0.69
1.17
1.01
0.91
Volumetric Organic
Loading
/lb BOD5/day\
^ 1,000 ft3 J
173
253
244
190
TABLE 20. AVERAGE SECONDARY CLARIFIER LOADINGS
FOR FMC PROJECT (4/8/74-7/31/74)
Phase
4
5
6
x 7
* Excludes
Surface Overflow
Rate
(gpd/ft2)*
514
720
617
823
influent center-well annular
Mass Loading
/ lb Tss/ft2 y<-
\ dav /
35
37
38
41
area which = 9.1% of total
clarifier surface area.
316
-------
As shown in Table 17, BOD^ and suspended solids removals during the
high loading conditions of Phases 4, 5, 6, and 7 were excellent. One of
the significant observations forthcoming from the project was that the
feared disruption of sludge settling properties due to floe shearing as the
mixed liquor was continually recirculated through the centrifugal pumps
and diffusers did not materialize. SVI for the above four phases averaged
a very acceptable 70 nil/gram. A highly concentrated float (4-6 percent TSS)
approximately six inches thick quickly developed on the surface of the
aerator after startup. This combination aeration/flotation effect was
anticipated in light of the fine bubbles created by the oxygen diffusers.
It was found that the thickness of the float can be controlled by adjusting
the elevation at which the mixed liquor recirculation suction is taken.
FMC personnel believe this feature offers a potential economically attractive
alternative location for extracting waste sludge from an activated sludge
system.
In a full-scale embodiment of this open-tank oxygen concept, mixed
liquor recirculation would not be accomplished by centrifugal pumps.
Instead, FMC envisions a propeller-type pump mounted inside a downcomer
draft tube. The draft tube in turn is to be connected to a pipe header
containing many gas bar diffusers. The whole assembly will rest on the
aeration tank floor and will be prevented from moving sideways by lateral
catwalks which are tied into the top of the draft tubes. Elevation, plan,
and side views of a full-scale aerator assembly as currently proposed are
pictured in Figure 10. A perspective view of a typical aeration tank
containing several of these assemblies and the resulting fluid mixing
pattern are shown in Figure 11. This system appears to possess the
essential ingredients for significantly impacting the wastewater treatment
construction industry.
317
-------
CJ
I—*
00
MOTOR PEDESTAL
THRUST BEARING
TOP OF COPING -
WEATHER-PROOF
- MOTOR ""•
-MOTOR PEDESTAL '.'.'_, WALKWAY
V
• / '
' i '
i\
\ -O-O '
a- -^- — r
1:
I
l!
*
•• DRAFT TUBE —
\ ' 1
// ^ \
^ x 7 \x y-
' /\ * w
.~.--7~r ; . . .". '~
s \
\
/ r.
' /' '•
'.'.-*' ' °
- "T^— :•-!
SUPPORT —
SECTION A-A
FIGURE 10. ELEVATION, PLAN, AND SIDE VIEWS OF ENVISIONED FULL-SCALE
EMBODIMENT OF FMC "MAROX" OPEN-TANK OXYGENATION SYSTEM
-------
FIGURE 11. PERSPECTIVE VIEW OF ENVISIONED
FULL-SCALE "MAROX" OPEN-TANK OXYGEN SYSTEM
-------
THE BLUE PLAINS PROJECT
A multi-stage, covered tank oxygenation pilot system of Union Carbide
design (see Figure 12) was operated continuously from June 1970 through
September 1972 at the Joint EPA/District of Columbia (Blue Plains) Pilot
Plant. Nominal design throughput for the system was 70 gpm (100,000 gpd).
The results generated in over two years of work (believed to be the single
longest continuous oxygenation pilot plant study on record) were extensively
reported at the 1972 Water Pollution Control Federation Conference (Stamberg,
et al., 1972). For a detailed summary of monthly operating data, the reader
is referred to the upcoming publication of this paper in the Federation
Journal. Discussion of the project here is limited to generalized results
and observations.
The oxygen system was operated over a wide range of SRT's from 1.3
to 13«0 days. Hqwever, on District of Columbia (D.C.) primary effluent,
filamentous organisms propagate rapidly with either oxygen or air if the
SRT is held below approximately five days for any extended period of time,
producing a bulking sludge with greatly retarded settling rates. Conse-
quently, the majority of the Blue Plains operation has been intentionally
restricted to SRT's greater than five days. A technique devised by pro-
ject staff personnel of reducing the incoming flow and twin dosing the
sludge recycle stream with 200 mg/1 of hydrogen peroxide (based on influent
flow) for 24-hour periods at a one-week interval proved to be an effective
method for purging entrenched filamentous bacterial growths from an acti-
vated sludge system. The technique provides lasting benefit only if
subsequent F/M loadings are adjusted to maintain an SRT outside the critical
filamentous growth range. The conditions under which filamentous cultures
propagate and flourish are unique to each wastewater and location. Some
plants can operate in any desired loading range without encountering fila-
mentous problems. Oxygen mixed liquor at Blue Plains was normally well
bioflocculated and essentially free of fragmented debris between discrete
particles.
Above an SRT of five days, average system F/M loadings remained in
the range of 0.27-0.50 Ib BOD /day/lb MLVSS. On those few occasions when
320
-------
OJ
02 RECYCLE
—cfc-i
INFLUENT
r<->0
00
n
oo
CO
T
SLUDGE RECYCLE
EXHAUST GAS
J
L
EFFLUENT
WASTE
SLUDGE
FIGURE 12. SCHEMATIC DIAGRAM OF BLUE PLAINS OXYGENATION SYSTEMa
Reprinted with permission (Stamberg, et al., 1972)
-------
the system was operated at an SRT less than five days, F/M loadings rose
to levels as high as 1.0 Ib BOD /day/Ib MLVSS. Corresponding average
volumetric organic loadings at an SRT above five days ranged from 57-185 Ib
o
BOD /day/1000 ft . Aerator detention times (based on Q) were varied between
1.5 and 2.8 hours throughout the two-year+ period. For all loadings
investigated, BOD insolubilization was virtually complete. Effluent
soluble BOD residuals were never greater than 5 mg/1 and consistently
averaged 2-3 mg/1. Total BOD and suspended solids removal were a direct
function of clarifier performance. Effluent COD and TOC concentrations
typically ranged from 35-60 and 15-20 mg/1, respectively.
During the spring periods of rising wastewater temperature, nitrifi-
cation was established more slowly in the Blue Plains single sludge oxygen
system than in a parallel conventional single sludge air aerated pilot
system probably due to the lower mixed liquor pH inherent in operation of a
covered biological reactor. Once established, however, substantial nitri-
fication was exhibited by the oxygen system during warm weather. With
decreasing wastewater temperature in the fall, deterioration of nitri
cation was directly related to SRT. At an SRT of 9.0 days and a wastewater
temperature of 63°F, at least partial nitrification was sustained. However,
once the wastewater temperature decreased to about 60°F, no nitrification
was observed in the Blue Plains oxygen system up to an SRT of 13.0 days.
Phosphorus removal experiments were conducted by adding aluminum
sulfate (alum) directly to the oxygen mixed liquor. At an Al /P weight
ratio of 1.4/1.0, phosphorus removal averaged 80% with total and soluble
phosphorus residuals of 1.8 and 1.6 mg/1 (as P) , respectively. Increasing
the alum dose to an Al /P weight ratio of 1.8/1.0 decreased total and
soluble residuals to 0.62 and 0.53 mg/1 (as P), respectively, but it also
lowered mixed liquor pH from 6,5 to 6.0. At the lowered pH, the oxygen
biota eventually dispersed and the experiments were discontinued. For low
alkalinity wastewaters such as the District of Columbia's, pH control may
be necessary to achieve efficient (90% or greater) phosphorus removal when
acidic metallic salts are added directly to oxygen-activated sludge mixed
liquor.
322
-------
Oxygen clarifier performance at Blue Plains and its effect on total
system operation are addressed in a later section. Continued experiments
only recently completed at Blue Plains included evaluation of oxygen in a
step aeration flow regime and examination of the nitrification kinetics of a
second-stage oxygen system operating on full-scale D.C. modified aeration
effluent feed. Reports on these activities are in preparation.
THE BUREAU OF RECLAMATION PROJECT
The Bureau of Reclamation's Engineering and Research Center in Denver,
under an interagency agreement with EPA, has recently completed the second year
of a three-year project to test many different materials of construction to
evaluate their suitability for use with oxygen aeration wastewater treatment
systems. The materials being tested include three different types of con-
crete, twelve different metals, and eleven protective coatings, linings,
joint sealers, and gaskets.
The materials are being exposed for varying lengths of time to oxygen-
rich mixed liquor, oxygen-rich vapor above the mixed liquor, and to the
interface between the two phases and then withdrawn for examination. Oxygen
reactors being utilized for these tests include Las Virgenes; Speedway,
Indiana; and Fairfax County, Virginia. Interim results are available by writing
to EPA, Office of Environmental Engineering, Washington, D.C. (20460).
CRITICAL PROCESS PARAMETERS
Certain process parameters are vital to the successful operation and
economic attractiveness of all waste treatment processes. For oxygen
iteration systems, four of these process parameters are oxygen utilization
and consumption, sludge production, power consumption, and biological
performance versus biomass loading. Available data for the projects des-
cribed above are summarized below for each of the four parameters.
Oxygen Utilization and Consumption
A misconception which seems to have accompanied the development of the
oxygcnation processes is that oxygen gas possesses mystical qualities and
can oxidize organics and ammonia nitrogen with less oxygen consumption than
air systemst In reality, of course, the same amount of oxygen is required
323
-------
to oxidize a given amount of organic carbon to carbon dioxide and water
or a given amount of ammonia nitrogen to nitrate nitrogen regardless of
the source of oxygen or the method in which it is delivered to a biologi-
cal system.
The conventional method of calculating oxygen consumption in a
covered-tank oxygen system is to monitor inlet and exhaust gas flows
and effluent D.O. and assume that all oxygen not accounted for was con-
sumed. This method will not detect any gas leaks which may develop in
and at the joints of the reactor cover. A second method which is sensitive
to detecting sizeable leaks and can be used to check the gross accuracy of
the oxygen metering equipment is an oxygen balance technique recommended
by the Blue Plains staff (Stamberg, et al., 1972) and shown in Table 21.
The method assumes that one pound of oxygen is consumed for every pound
of COD destroyed (not to be confused with COD removed from the substrate)
and that 4.57 pounds of oxygen are consumed for every pound of ammonia
nitrogen converted to nitrate nitrogen. The method is reasonably accurate
provided the wastewater does not contain certain industrial components
which do not consume oxygen in a COD determination but will utilize oxygen
in a biological system.
Oxygen utilization and supply data for Newtown Creek, Batavia,
Blue Plains, and the FMC project are summarized in Table 22. Accurate
measurement of oxygen utilization at Las Virgenes was hampered due to
excessive gas leaks in the tent cover previously described. The table
indicates a lack of informity for all three methods selected for
indicating specific oxygen supply requirements. Generally, in the
absence of nitrification, slightly more than one pound of oxygen should
theoretically be supplied for each pound of COD destroyed. The Newtown
Creek value of 0.8 for the period of September 17, 1972 through October 14,
1972 cannot possibly be correct and indicates probably either low inlet
gas measurements or low waste sludge COD determinations. Of the three
.methods shown, designing oxygen supply requirements on the basis of antic-
ipated BOD5 removal is the least reliable. Since COD destroyed usually
324
-------
TABLE 21. OXYGEN BALANCE METHODS
Method 1: Ib/mil gal Oxygen Supplied
( ) Ib/mil gal Exhaust Oxygen
Ib/mil gal Oxygen Utilized
Ib/mil gal Secondary Effluent D.O.
(=) Ib/mil gal Oxygen Consumed
Method 2: Ib/mil gal Aerator Influent COD
(-) Ib/mil gal Secondary Effluent COD
( ) Ib/mil gal Waste Sludge COD
(=) Ib/mil gal COD Destroyed3
(+) Ib/mil gal Nitrate Nitrogen Oxygen Demand
(+) Ib/mil gal Exhaust Oxygen
(+) Ib/mil gal Secondary Effluent D.O.
(=) Ib/mil gal Oxygen Supplied (Theoretically)
rt
Assumes 1 Ib COD destroyed consumes 1 Ib 09.
. ^
Assumes 1 Ib NH -N converted to 1 Ib NO.-N consumes 4.57 Ib 0~.
cannot be accurately predicted in advance, using an oxygen required/
anticipated COD removal weight ratio of 0.60-0.75 and adding this to anticipated
nitrification oxygen demand, if any, is probably the best technique avail-
able for sizing oxygen supply equipment. The effect of nitrification on
oxygen supply and consumption is readily apparent at Blue Plains in May
1972. Generally, but not always, less oxygen was consumed per pound of
BOD removed as the F/M loading increased. A similar pattern was not evi-
dent for oxygen consumed per pound of COD removed.
325
-------
TABLE 22. SUMMARY OF OXYGEN UTILIZATION AND SUPPLY
GO
ro
cr>
Plant
°2
Newtown Creek
Phase 1
Phase 2
Phase 3
Phase 4
Phase 5
Phase 6
Phase 7
Batavia
5/12/69-11/10/69
9/1/70-11/30/70
Blue Plains
May 1971°
May 1972d
FMC Proiect
Phase 4
Phase 5
Phase 6
Phase 7
Metered
Utilization
>90
>90
>90
>90
>90
>90
>90
93
92
97
97
-
-
-
F/M
/lb BOD5/day\
^ lb MLVSS )
0.65
0.57
0.57
0.92
1.19
1.62
2.44
0.59
0.87
0.97
0.36
0.69
1.17
1.01
0.91
lb Op Supplied
lb BOD Removed
1.09
1.20
1.39
1.02
0.88
0.83
0.79
0.94
1.36b
1.04
2.09
1.22
1.11
0.92
1.08
lb 02 Supplied
lb COD Removed
0.55
0.59
0.65
0.55
0.72
0.73
0.61
0.60
1.13b
0.60
1.03
0.72
0.65
0.75
0.79
lb 02 Supplied
lb COD Destroyed
0.80a
-
-
-
-
-
-
-
1.09
1.23
„
.
-
Covers the segment of Phase 1 from 9/17/72-10/14/72 only.
bValues are high due to high clarifier loadings resulting in significant solids carryover and
lowered BOD^ and COD removals.
CNo nitrification.
"Substantial nitrification.
-------
Sludge Production
Available data indicate that oxygen systems may produce less excess
biological sludge than air systems at comparable F/M loadings. The first
indication was provided by the two Batavia projects as shown in Figure 13.
In this figure, BOD removed per day per unit of MLVSS is plotted in the
conventional method against the inverse of SRT for both the air and oxygen
trains. The curves reveal an approximate 50% reduction in favor of oxygen.
Although both of these trains were operated in plug flow configuration, the
comparison is most likely heavily biased toward oxygen because of the severe
D.O. limitations under which the Batavia air reactor operated during these projects,
If oxygen does produce less sludge, it is probably due to the high mixed
liquor D.0« concentration maintained and the additional driving force it
provides for increasing oxygen penetration into and stimulating aerobic
activity within floe particle interiors. Air system sludge production
data in which the mixed liquor is not devoid of D.O. for a lengthy section
at the head of the aerator (in contrast to Batavia) will provide more
meaningful future comparisons with oxygen sludge production data.
Reliable sludge production data are available from Newtown Creek for
Phases 4-7. The data have been averaged for each phase and superimposed
on the Batavia sludge production curve in Figure 13. Three of the four
points plot reasonably close to the line of best fit (or that line extended)
for the Batavia excess sludge production data, lending credibility to this
projection of oxygen sludge production for raw wastewater feed. The fourth
point (Phase 4), which represents the least loaded condition of the four
phases plotted, falls considerably above the Batavia oxygen sludge pro-
duction curve. Additional sludge production data generated by the Newtown
Creek oxygen system during the extended operating period of September 1973
through April 1974 are presented in the previously mentioned New York City
authored paper "Upgrading New York City Modified Aeration with Pure
Oxygen." These additional data along with the data summarized in this report
provide an accurate representation of oxygen system sludge production at
Newtown Creek over a substantially broad range of loadings.
327
-------
1.3
- 1.31
V
1.1
1.0
0.9
o.e
BATAVIA OXYGENATION
SYSTEM SLUDGE PRODUCTION
CURVE EXTENDED
0.93
0.76
EXCESS VSS FORMATION
CORRELATIONS AND
95% CONFIDENCE LIMITS
FOR PREDICTED VALUES
1969 AND 1970
* BATAVIA
/ AIR AERATION SYSTEM
957. CONFIDENCE
LIMITS
• BATAVIA OPERATIONS
/_
O.7
. 0.73
0.5
0.4
0.3
0.2
O.I
A /
/
9
^crf-
BAT AVI A
OXYGENATION
SYSTEM
//
/
BATAVIA LEGEND FOR
WEEKLY DATA POINTS
/A
/
CODE
A
A
D
Q
O
O
SYSTEM
AIR
AIR
OXYGEN
OXYGEN
OXYGEN
OXYGEN
YEAR
1969
1969
1969
1969
1970
1970
PHASE
I
m
i
JL
i
or
NEWTOWN CREEK
LEGEND
PHASE 4 AVG.
PHASE 5 AVG.
- PHASE 6 AVG.
PHASE 7 AVG.
col
|H
CM
0.2
0.4
0.6
0.8
1.0.
1.2
L4"
l.«
2.0
LB BOD REMOVED/OAY/LB MLVSS
FIGURE 13'. NEWTOWN CREEK EXCESS OXYGEN SLUDGE PRODUCTION DATA SUPER-
IMPOSED ON BATAVIA EXCESS SLUDGE PRODUCTION CORRELATIONS PLOT
2.2
328
-------
Sludge production data for the Blue Plains oxygen system are compared
with data from a parallel step aeration air pilot system operated on the
same primary effluent feed in Figures 14 and 15 (Stamberg, et al., 1972).
Figure 14 plots SRT versus F/M loading and indicates that less volatile
mass under aeration was required with oxygen to reach any given SRT above
six days. Blue Plains personnel attribute the increased activity of the
oxygen volatile mass to maintaining mixed liquor D.O. between 4 and 8 mg/1
and the minimization of sludge pockets and dead spots afforded by independ-
ently controlled mixing. Figure 14 can be manipulated to produce Figure 15
by multiplying F/M values by the corresponding SRT values and inverting
the product to yield volatile solids produced per unit of BOD,, applied and
then replotting these new values against SRT. Figure 15 shows substantial
reduction in sludge production with oxygen again above an SRT of six days.
Below an SRT of about eight days, the step aeration system experienced
soluble BOD5 breakthrough and overall effluent quality was poorer than
that of the oxygen system. Because of the different flow configurations
utilized, sludge production information generated by these two systems
cannot be used directly to derive conclusions regarding the relative sludge
production rates of oxygen and air at comparable SRT's. The kinetics of
step aeration dictate that it will experience maximum sludge production
at a much higher SRT than a plug flow regime.
In an attempt to compare sludge production data from air and oxygen
systems with similar operating conditions and with the further restriction
that the air system is not oxygen transfer limited, data from the Hyperion
Plant in Los Angeles (Smith, 1969) are plotted against the Blue Plains data
in Figure 16 on a BOD,, removed basis and Figure 17 on a COD removed basis.
Hyperion is an air activated sludge plant with a consistent record of excellent
performance and adequate mixed liquor D.O. Both Hyperion and Blue Plains data
were collected on systems operated in a conventional plug flow mode on primary
effluent feed. In Figure 16 a majority of the oxygen points fall below the
Hyperion regression curve and Smith's computer program curve for Hyperion.
In Figure 17 all but two of the oxygen points fall below the air curve, many
of them well below. These two figures lend additional support to the position
329
-------
CO
CO
O
1.0,-
0.8
GO
GO
S 0.6
0.4
0.2
STEP AERATION
I
I
I
I
0 2 4 6 8 10 12
SLUDGE RETENTION TIME-SRT (days)
FIGURE 14. BIOLOGICAL ACTIVITY RELATIONSHIPS - BLUE PLAINS
aReprinted with permission (Stamberg, et al., 1972)
14
16
-------
CO
CO
ca
1.0
0.8
CO
s 0.6
en
o_
oo
0.4
0.2
I
46 8 10 12
SLUDGE RETENTION TIME-SRT (days)
14 16
FIGURE 15. EXCESS BIOLOGICAL SLUDGE PRODUCTION - BLUE PLAINS
aReprinted with permission (Stamberg, et al. , 1972)
-------
1.0 i—
00
CO
IX)
Ci
LU
co
CO
co
< 0.5
Q
Q
LU
Q
O
a.
CO
CO
—i
II
t—
CO
O =HYPERION (AIR)
A =BLUE PLAINS
(OXYGEN )
_L
0.2 0.4 0.6 0.8 1.0
LB BOD5 REMOVED/DAY/LB MLVSS IN AERATOR
1.2
FIGURE 16 . COMPARISON OF SLUDGE PRODUCTION FOR AIR AND OXYGEN SYSTEMS
ON PRIMARY EFFLUENT FEED (BOD5 REMOVED BASIS)
-------
1.0 i—
CO
CO
CO
cm
LU
to
to
ca
O
LU
U
ID
Q
O
01
CO
03
_i
II
h-
CO
0.5
1
0=HYPER!ON (AIR)
A=BLUE PLAINS
(OXYGEN)
I
I
I
I
I
0.4 0.8 1.2 1.6 2.0
LB COD REMOVED/DAY/LB MLVSS IN AERATOR
o -
2.4
FIGURE 17. COMPARISON OF SLUDGE PRODUCTION FOR AIR AND OXYGEN SYSTEMS ON
^PRIMARY EFFLUENT FEED (COD REMOVED BASIS)
-------
that reduced sludge production is probable with oxygen, but not to the
degree predicted from the Batavia projects. Additional comparative data
under similar operating conditions and on the same wastewater feed are
neededo The current Detroit expansion is a good cand- date for supplying
such information when large-scale air and oxygen modules now in the
final stages of construction and/or startup are ready for parallel
operation.
Available sludge production data for Newtown Creek, Batavia, Las
Virgenes, and the FMC project and two typical months of data for Blue
Plains are summarized in three forms in Table 23 along with the corres-
ponding F/M loadingSo This table illustrates the general futility of
attempting to correlate sludge production data from one location to
another by any of the three methods shown. Many local factors including
wastewater composition, wastewater temperature, mixed liquor D.O., and the
biodegradability rate of various organic constituents combine to influence
the amount of excess sludge that will be formed at different plants under
similar loading conditions= Table 23 also shows that even at a single
plant, unit sludge production on a BOD or COD removed basis does not
necessarily increase with increasing F/M loading, or vice versa. If any
rational method exists for representing sludge production at a single
location or comparing sludge production among locations, it is probably
the basic inverse SRT method utilized in Figures 13, 16, and 17, or one
of several published modifications of this basic method,
Power Consumption
One of the more attractive economic aspects projected for oxygenation
systems from the Batavia work is greatly reduced power requirements for
oxygen supply (generation) and transfer (dissolution) compared with the
power requirements of air blowers. Estimated installed HP load require-
ments as projected from the Batavia work are plotted against plant size
and BOD aerator loading for both oxygen and air systems in Figure 18.
The oxygen system band represents the additional power requirement for
mixing as aerator volume is increased from one hour detention to two hours
detention (based on Q). The air system band encompasses blower supply
rates from 0.8 to 2.4 cubic feet of air supplied per gallon of wastewater
334
-------
TABLE 23. SUMMARY OF OXYGEN SYSTEM SLUDGE PRODUCTION
OJ
CO
en
Plant
Newtown Creekc
Phse 4
Phase 5
Phase 6
Phase 7
Bataviac
7/21/69-9/7/69
8/30/70-10/25/70
Las Virgenesd
Phase 1
Phase 2
Phase 3
Phase 4
Phase 5
Phase 6
Phase 7
FMC Projectd
Phase 4
Phase 5
Phase 6
Phase 7
Blue Plainsd
Sept. 1971
Feb. 1972
F/M Loading lb
/lb BOD^/day\
^ lb MLVSS )
0.92
1.19
1.62
2.44
0.79
0.52
0.07
0.11
0.15
0.24
0.33
0.41
0.46
0.69
1.17
1.01
0.91
0.39
0.30
Waste Sludge TSSa
mil gal
1,300
1,185
1,055
1,025
970
1,250
-
91
103
250
250
123
1,086
730
752
878
620
430
lb VSS Produced*3
lb BOD Removed
0.94
0.73
0.59
0.60
0.41
0.52
0.19
0.14
0.15
0.14
0.27
0.31
0.21
0.80
0.62
0.50
0.53
0.38
0.47
lb VSS Produced13
lb COD Removed
0.49
0.59
0.51
0.46
0.35
0.29
0.13
0.09
0.08
0.05
0.13
0.15
0.09
0.47
0.36
0.41
0.39
0.25
0.23
•Includes waste sludge TSS only. cRaw sewage feed.
blncludes waste sludge and final effluent VSS. d'Srima.ry effluent feed.
-------
oc
LU
U-
10
Z
O
Z
a.
a.
to
Z
LLJ
O
X
O
u_
D
O
a.
CO
Z
10,000
LB BOD5 APPLIED TO AERATOR PER DAY
1,000 10,000 100,000
™
/ m
1,000
100
10
I I I I I I
AIR SYSTEM BLOWERS
OXYGEN SYSTEM
DISSOLUTION AND
GENERATION
EQUIPMENT
SYSTEM POWER ESTIMATES
BASED ON BATAVIA DATA
0.8 FT3/GAL
1.6 FT 3/GAL
2.4 FT3/GAL A
1,005 HP
1,041 HP
905 HP
1 HR DETENTION
2 HRS DETENTION
0 NEWTOWN GREEK-
DESIGN CONDITION
NEWTOWN CREEK-
OPERATING CONDITIONS
A — PHASE 1 AVG.
EJ— PHASE 7 AVG.
I I I I I I
1 1 1111
1 10 100
PLANT SIZE-MGD
(BASED ON AVG. AERATOR INFLUENT BOD5 OF 130 mg/l)
FIGURE 18. NEWTOWN CREEK POWER CONSUMPTION SUPERIMPOSED
ON BATAVIA POWER PROJECTION CURVES
336
-------
treated. Using the median of the bands, 50% and 65% reductions in aeration
power requirements are projected for oxygen over air at plant sizes of 1
and 100 mgd, respectively.
Plotting the installed HP load for oxygen supply and dissolution at
Newtown Creek on this curve indicates oxygen system power requirements
estimated from Batavia may be somewhat optimistic. The installed HP load
at Newtown Creek is 1041 HP, as broken down in Table 24, for a design load
of 41,700 pounds of BOD per day (calculated using a BOD5 of 250 mg/1 at
20 mgd). The Batavia curve predicts an installed nameplate requirement of
only 550-800 HP for the same design BOD load.
TABLE 24. INSTALLED HP AT NEWTOWN CREEK FOR
OXYGEN GENERATION AND DISSOLUTION
Item Nameplate HP
1. PSA Compressor 450
2. Liquid Oxygen Vaporizer 96
3. 1st Stage Compressors at 40 HP ea 80
4. 2nd, 3rd, and 4th Stage Compressors at 40 HP ea 120
5. 1st Stage Mixers at 50 HP ea 100
6. 2nd, 3rd, and 4th Stage Mixers at 30 HP ea 180
7. PSA Cooling Tower Pumps 8
8. Instrument Air Compressor 7
Total 1,041
The strength of the Newtown Creek wastewater during the project
was somewhat weaker than the design projection. The actual BOD^ load
for Phase 1 averaged only 29,650 pounds per day (29 percent less than
the design load) even though the average flow of 20.8 mgd was slightly
higher than the design flow of 20 mgd. However, actual power consumption
for the same period averaged 905 HP, a decrease of only 13 percent from
the installed load. This demonstrates a well-known fact that non-variable
speed drives operating below design load will consume almost as much power
337
-------
as when operating at design conditions. Consequently, power consumption
for Phase 1 when superimposed on Figure 18 falls well above the oxygen
band and up near the median of the air band.
The converse situation is illustrated in Phase 7 when, due to the
increased average influent flow of 35.4 mgd, the BODj. load to the aerator
averaged 62,645 pounds per day. Oxygen supply and dissolution requirements
consumed an average power draw of 750 kilowatts (equivalent to 1,005 HP).
Thus, with an actual power consumption 3.5 percent less the installed load,
the system satisfactorily treated a BOD,, loading 50 percent greater than the
design load. For this phase, power consumption plots near the median of the
Batavia oxygen band in Figure 18.
From the above data it is apparent that actual unit power consumption
for oxygenation systems will approach installed unit power consumption
only when operating at or near design organic load. Another conclusion which
can be drawn from Newtown Creek experiences is that the oxygen module1 s oxygen
transfer equipment was substantially overdesigned for the projected
BOD load.
5
Biological Performance Versus Biomass Loading
A strong point of oxygenation system performance noted wherever oxygen
has been tested is the relative insensitiveness of effluent quality to
changes in F/M loading. Data accumulated from Batavia, Newtown Creek, Blue
Plains, and Las Virgenes are plotted in Figure 19. These data indicate
plateaus for soluble BOD,, and soluble COD breakthrough of only about 15 and
60 mg/ls respectively, up to F/M loadings of 2.4 Ib total BODs applied/day/lb
MLVSS. This denotes consistent and impressive performance under stressed
conditions. At the lower loadings employed at Blue Plains, essentially
complete insolubilization of BOD is evident. For all F/M loading rates,
however, total system efficiency for oxygen processes will be more directly
dependent on solids capture efficiency (clarifier performance) than on
biological performance deterioration.
338
-------
CO
CO
80
Q
§
W
J
§ 8
W 0
O =BATAVIA
A =NEWTOV/N CREEK
D =BLUE PLAINS
X =LAS VIRGENES
O
GO,
I I
I 1 I I
I
0.5
1.0 1.5
F/M LOADING - LB BOD5 APPLIED/DAY/LB MLVSS
2.0
80
0
16
O
O
w
O
C/D
Pu
tu
W
j i i I
2.5
FIGURE 19. EFFECT OF F/M LOADING ON OXYGEN
SYSTEM EFFLUENT SOLUBLE BOD5 AND COD
-------
SLUDGE SETTLING AND SYSTEM DESIGN
Perhaps the most important information generated by the Blue Plains
project has been a delineation of some of the factors affecting sludge
settling at that site and its resultant effect on system design (Stamberg,
et al., 1972)o In addition to the retardent effect on sludge settling
previously mentioned due to filamentous infection of mixed liquor, other
factors which affected oxygen sludge settling rates at Blue Plains included
solids concentration, bulk sludge density (volatile solids fraction), and
wastewater temperature.
In the range of MLSS concentrations at which hindered or zone
settling occurs, it has been found that an equation in the form of v.= aC.
where v. = initial settling velocity
C. = initial solids concentration
i
a = intercept constant
n = slope constant
when plotted on log-log paper yields a straight line. Further, it has been
shown such a relationship exists for each of the three types of settling,
discrete particle, hindered, and consolidation settling (Dick, 1970)(Duncan,
et al., 1968). The change in slope between discreet particle settling and
hindered settling normally occurs at a C. between 2000 and 3000 mg/1. The
hindered settling zone is characterized by a discrete subsiding interface and
a zone of homogenously mixed settling particles. Clarifiers operating with
initial hindered settling are in reality operating as sludge thickeners.
It is essential that both hydraulic and mass loadings be considered in the
340
-------
design of secondary clarifiers for high solids systems. In many cases,
thickening (mass loading) requirements will control the design. The
best available approach for evaluating thickening requirements appears
to be the batch flux (mass x settling velocity) method (Dick, 1970).
Bulk sludge density is a function of volatile solids fraction, i.e.,
density increases with decreasing volatile fraction. The incorporation
of denser inerts into the sludge mass is the primary reason why biomasses
developed on raw wastewater will generally settle better than those
developed on primary effluent. Another manner in which sludge density
is temporarily affected is the washing of accumulated inerts into a plant
from its sewer system during rain storms. This point was vividly illus-
trated at Blue Plains during a tropical storm the summer of 1972 as shown
in Figure 20 «
The least, recognized parameter prior to plant startup that eventually
strongly affected oxygen sludge settling rates at Blue Plains was waste-
water temperature. Settling rates decreased significantly from summer to
winter operation. For example, during September and October 1971 (a
period when the oxygen clarifier was operated with a deep center feed
below the sludge blanket to capture unsettleable particles) as wastewater
temperature dropped from 81° to 71°F, the initial settling rate (ISR)
decreased from 10 ft/hr to 7 ft/hr in a 1-liter graduated cylinder test
at an MLSS concentration of 6000 mg/1 (see Figure 21). In November of
the same year the center feed was raised above the blanket in an attempt
to purge unsettleable particles from the system and increase bulk sludge
density. While this technique did increase the sludge density and tem-
porarily the ISR, a similar temperature effect was noted over the two-
month period of November and December 1971. As wastewater temperature
dropped from 70° to 63°F, the ISR decreased from 14 ft/hr to 9 ft/hr at
an MLSS concentration of 4500 mg/1 (see Figure 22). Conversely, as Blue
Plains wastewater temperature increased in the spring and summer of 1972,
substantial increasing settling rates were observed as illustrated in
Figure 23. The net result of this phenomenon was that a peak oxygen
2
clarifier overflow rate of 1940 gpd/ft was possible in the summer of 1970
with an MLSS of 8000 mg/1, while the peak overflow rate that could be
341
-------
100
80
60
50
40
~ 30
-c=
4± 20
CL3
S 10
UJ
:>• 8
2= 6
•=; 5
t 4
oo
JUNE 22-JULY 3, 1972
(TROPICAL STORM)
10-20, 1972
I I
3 4 5678910
20 30 40 60 80 100
INITIAL MLSS CONCENTRATION (gm/l)
FIGURE 20. ILLUSTRATION OF INCREASED SLUDGE DENSITY CAUSED BY RAIN a
STORM AND ITS EFFECT ON INITIAL SLUDGE SETTLING VELOCITY
Reprinted with permission (Stamberg, et al., 1972)
342
-------
30
20
j= 15
^ 10
£ 8
o
UJ n
>• D
SE
e 4
UJ
^ '3
1
D.C.-Sept 1971-[78-81°F)
D.C.-Oct 1971-[71-73°F)
I I
1 2 34 6 8 10 15 20 30
INITIAL MIXED LIQUOR CONCENTRATION (gm/l)
FIGURE 21. EFFECT OF DECREASING WASTEWATER TEMPERATURE ON INITIAL SLUDGE
SETTLING VELOCITY (SEPTEMBER-OCTOBER, 1971)&
Q
Reprinted with permission (Stamberg, et al., 1972)
343
-------
30
20
]jf 15
S 10
£3 Q
£ B
CD
I 4
LU
^ 3
«C
t:
1
D.C. -Nov 1971-(68-70°F)
D.C.-Dec 1971-(63~64°F)
1 I
I I I
I !
I
1 234 6 8 10 15 20 30
INITIAL MIXED LIQUOR CONCENTRATION (gm/l)
FIGURE 22. EFFECT OF DECREASING WASTEWATER TEMPERATUREaON INITIAL SLUDGE
SETTLING VELOCITY (NOVEMBER-DECEMBER, 1971)
a
Reprinted with permission (Stamberg, et al.} 1972)
344
-------
40
30
20
1972
JUNE 10-
[70°F-74
i i i i i r
JUNE 22-JULY 3,
(72°F-76°F]
CD
10
8
7
6
5
MAY 20-31,
(66°F-71°F)
1-
(63°F-65°F)
JULY
10-25,
F-79°F)
3 456 8 10
INITIAL MLSS CONCENTRATION (gm/l)
FIGURE 23. EFFECT OF RISING WASTEWATER TEMPERATURE ON INITIAL
SLUDGE SETTLING VELOCITY (SPRING-SUMMER, 1972)a
&Reprintcd with permission (Stamberg, et al., 1972)
345
-------
sustained in either the 1970-71 or 1971-72 winters without clarifier
2
failure was 975 gpd/ft at MLSS levels that varied from 3900-5300 mg/1.
Undoubtedly all of the factors discussed above contributed to the reduced
overflow rates necessary at Blue Plains to maintain satisfactory winter clarifier
operation. However, it appears that wastewater temperature played a
major role at this site. It is strongly emphasized though that the con-
clusions drawn from the Blue Plains project regarding wastewater tempera-
ture and sludge settling are not intended to imply that a similar effect
will be noted universally. Much additional data are needed to reach a
more definitive conclusion. Some additional data were collected over a
period of about 20 months at Newtown Creek (raw wastewater feed) and
Speedway, Indiana (primary effluent feed),, Batch flux settling tests
were conducted periodically at both sites using slowly stirred
six-inch diameter, eight-foot long settling columns. Settling
velocity profiles as a function of initial MLSS concentration are plotted in
Fig. 24 for three runs conducted at Newtown Creek in December 1972 and June and
August 1973. These plots tend to verify the temperature effect observed
at Blue Plains. The decreased settling rates noted in the winter at Newtown
Creek are probably due to a combination of increased viscosity and drag of
the wastewater and alteration of biomass characteristics (proliferation of
filamentous organisms) at the colder water temperature.
Results of the long-term Blue Plains work illustrate clearly that
oxygen system design should be thought of as an integrated package con-
sisting of a biological reactor, a secondary clarifier, and sludge handling
facilities. The system should be designed for the worst anticipated climatic
conditions at a given site. Clarifier sizing should be specifically tailored
to the design and anticipated operating conditions of the reactor. There
are two basic ways of achieving a desired F/M loading: (1) a small reactor
and high MLSS or (2) a larger reactor and lower MLSS. If the first method
is selected to save on reactor costs, a larger clarifier will be necessary.
Both a small reactor and a small clarifier cannot be successfully mated in
a design unless greatly reduced MLSS concentrations are utilized. However,
opting for this selection will increase F/M loading, excess biological
sludge production, and required sludge handling capacity and costs.
346
-------
Pi
H
H
U
O
,-)
W
H
W
C/3
i-J
<
H
H
H
z;
40
30
20
15
10
8
4
3
June 20, 1973 (22°C)
Aug. 8, 1973 (26°C)
Dec. 10, 1972 (17°C)
2 34 6 8 10 15 20 30
INITIAL MIXED LIQUOR CONCENTRATION (GM/L)
FIGURE 24. SETTLING VELOCITY PROFILES FOR BATCH
FLUX SETTLING TESTS CONDUCTED AT NEWTOWN CREEK
347
-------
PROCESS ECONOMICS
No updating of the comparative cost estimates presented for air and
oxygen systems in the Batavia II final project report (17050 DNW 02/72)
has been attempted in this paper. Figure 25 summarizes estimated total
treatment costs (including amortization, operation, and maintenance) for
air and oxygen systems of 1-100 mgd capacity as taken from the Batavia II
final report. Interest was figured at 5-1/2% over 25 years. Oxygen
supply costs are based on on-site generation plant purchase by the
municipality. Projected savings in the cost of oxygen by buying and
operating your own plant as opposed to commodity across-the-fence purchase
current at the time of printing of the Batavia I final project report
(17050 DNW 05/70) are shown in Figure 26.
Figure 25 projects average savings in total treatment costs of about
20% with oxygen for plants of 20-100 mgd« It must be remembered, however,
that built into these curves are: (1) the assumption questioned by many
observers that oxygen reactors will universally be one-third as large as
air reactors for equal treatment and (2) what is believed to be overly
optimistic estimates of the difference in sludge production rates between
air and oxygen processes. The author concludes the one area in which
oxygenation may have a very decided economic advantage is in the upgrading
of existing overloaded secondary plants, such as Newtown Creek. Also it
is likely that many decisions to install oxygen are not made so much on
the basis of economics as on the basis of the high process reliability
and stability and the rapid recovery following toxic upsets afforded by
an enriched oxygen biological system.
348
-------
20
40 60
PLANT SIZE-MGD
80
100
FIGURE 25. TYPICAL RANGES FOR TOTAL TREATMENT COSTS FOR NEW PLANTS
WITH PRIMARY SEDIMENTATION PROJECTED FROM BATAVIA STUDIES
349
-------
GO
en
O
120
100
80
y eo
cr
a.
UJ
o
x 40
O
20
ON-SITE GAS PURCHASE
ON-SITE
PLANT PURCHASE
J 1
J I
I I
0.2 0.5 I 2 5 10 20 50
OXYGEN USAGE RATE — TONS / DAY
100 200 500 1000
FIGURE 26. OXYGEN COSTS AS A FJNCTION OF USAGE RATE
-------
CONTINUING DEVELOPMENTS
Continuing Research and Development Projects
Continuing EPA research and development efforts are underway or recently
completed in the following areas: (1) evaluation of second-generation oxygen
dissolution approaches, (2) examination of oxygen nitrification kinetics both
in single-stage and two-stage systems, (3) definition of viable alternatives
for combining chemical phosphorus removal with oxygen aeration, (4) determin-
ation of the most cost-effective sludge handling and dewatering techniques for
taking advantage of the excellent thickening properties of oxygen sludge,
(5) examination of sludge settling characteristics, (6) investigation of
aerobic sludge digestion with oxygen gas, and (7) a study of the safety
aspects of using oxygen in a wastewater treatment plant environment.
The development and maturation of new wastewater treatment processes are
usually accelerated by the parallel development of several proprietary systems.
However, because of this more rapid development, certain process details and
aspects not directly associated with the treatment of wastewater often do
not receive as thorough an evaluation as may be desirable and prudent.
The safety aspects and requirements of utilizing oxygen in activated sludge
treatment (No. 7 on the above list) are believed to represent one such aspect.
Although each firm marketing an oxygen aeration system has undoubtedly
considered safety features and requirements for its particular system,
no comprehensive generalized treatment of the subject has been undertaken,
until recently. Of particular concern is the processing of wastewaters
which periodically contain hydrocarbons and other volatile substances in
covered aeration systems with oxygen atmospheres ranging anywhere from 50
to 95%. The fundamental safety ramifications of using oxygen in this type
of duty have needed an in-depth review and evaluation by an independent
investigative team. A standard safety manual has also been urgently needed
to instruct waste treatment plant designers and operators in the safe and
proper handling of oxygen and to identify essential safety equipment and
instrumentation. Such a manual must be sufficiently broad and comprehensive
to apply to any rational concept for dissolving oxygen in wastewater.
351
-------
Due to lack of funds, this project was delayed for more than
a year. In June 1974, however, a contract was awarded to the Rocketdyne
Division of Rockwell International to undertake this study. The
purpose of the project is twofold:
(1) To evaluate the fundamental ramifications and implications from
a safety standpoint of using-oxygen gas or oxygen enriched air
for aeration of activated sludge systems and based on this
evaluation to recommend an implementive course of action which
will ensure the safety and security of wastewater treatment plant
personnel and facilities.
(2) To develop a standard safety manual and safety checklist for
the safe and proper handling of oxygen in a wastewater treat-
ment plant environment that will apply in principle to any
rational oxygen dissolution concept.
Oxygen Process Implementation
Oxygenation systems are being designed and constructed for many
treatment plants across the country to meet a variety of new plant con-
struction and plant upgrading needs. At the time of this writing, 48
known municipal oxygen systems are in various stages of design, construction,
startup, or operation. As summarized in order of decreasing size
in Table 25, the total design flow of these 48 plants is 2S714.8 mgd ranging
in capacity from 0.9 to 600 mgd. Of the 48 plants,37 are designed using
surface aerators for oxygen dissolution,eight with submerged turbines, one
with fine-bubble diffusers (open-tank), one (Las Virgenes) employed a
converted air blower and air diffusers, and one is still undetermined.
Oxygenation is also beginning to make inroads into the industrial
wastewater treatment picture. As indicated in Table 26, eight systems
are currently being constructed and/or operated to treat a variety of
industrial wastes. The total design flow of these_eight systems is 62.9
mgd ranging in size from 1 to 25 mgd. Six oxygenation systems are now also
on-line in Japan.
Preliminary oxygen designs are being prepared for 30-40 additional
plants still in the negotiating phase. It appears that oxygen aeration
is definitely here to stay.
352
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TABLE 25. MUNICIPAL WASTEWATER TREATMENT PLANTS UTILIZING OXYGEN
Plant
1.
2.
3.
Detroit, Mich.
Detroit, Mich.
Philadelphia, Pa.
Design
Flow
(mgd)
600
300
210
Type of
Dissolution
System
Submerged Turbines
Submerged Turbines
Surface Aerators
Status
(Oct. 1974)
Design
Startup
Design
(Southwest)
Philadelphia, Pa.
(Northeast)
New Orleans, La.
Middlesex County, N.Jo
7- Oakland, Calif.
(East Bay M.U.D.)
8. Dade County, Fla.
9. Louisville, Ky.
10. Wyandotte, Mich.
11. Denver, Colo.
12. Baltimore, Mel.
13. Tampa, Fla.a
14. Miami, Fla.
15. Duluth, Minn.
16. Hollywood, Fla.
17. Cedar Rapids, Iowa
18. Ilarrisburg, Pa.
19. Springfield, MD.
20. Salem, Ore.
21. Danville, Va.
22. Euclid, Ohio
23. Ft. Lauderdale, Fla.
24. Littleton/Englewood, Colo.
25. New York, N.Y. (Newtown Creek)
26. Decatur, 111.
150
Surface Aerators
122 Surface Aerators
120 Submerged Turbines
120 Submerged Turbines
120 Surface Aerators
105 Submerged Turbines
100 Submerged Turbines
97 Surface Aerators
73 Surface Aerators
60 Surface Aerators
55 Surface Aerators
42 Surface Aerators
36 Surface Aerators
32.9 Surface Aerators
31 Surface Aerators
30 Surface Aerators
26.5 Surface Aerators
24 Surface Aerators
22 Surface Aerators
22 Surface Aerators
20 Surface Aerators
20 Submerged Turbines
17.7 Surface Aerators
Design
Const.
Const.
Const.
Design
Const.
Const.
Const.
Design
Design
Design
Design
Const.
Design
Design
Design
Const.
Const.
Const.
Design
Design
Oper.
Const.
aTwo-stage oxygenation system.
(CONTINUED)
353
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(CONTINUED)
TABLE 25. MUNICIPAL WASTEWATER TREATMENT PLANTS UTILIZING OXYGEN
Plant
27.
28 0
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45 o
46.
47-
48.
Fay ett evil le, N.C.
Chicopee, Mass.
New Rochelle, N.Y.
Muscatine, Iowa
Winnipeg, Manitoba
Fairfax County, Va.
Brunswick, Ga.
Tauton, Mass.
Morgantown, N.C,,
Lebanon, Pa.
Fairbanks, Alaska
Speedway, Ind.
Deer Park, Tex.
Lewisville, Tex,,
Mahoning County, Ohio
Jacksonville, Fla.
Calabasas, Calif.
(Las Virgenes, M.W.D.)
Littleton, Colo.
Cincinnati, Ohio
Hamburg, N.Y.
Minneapolis, Minn.
Chaska, Minn.
Design
Flow
(mgd)
16
15
14
13
12
12
10
8.4
8
8
8
7.5
6
6
4
3.4
1.8
1.5
1.2
1
1
0.9
Type of Status
Dissolution (Oct. 1974)
System
Surface Aerators
Surface Aerators
Submerged Turbines
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Undetermined
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Surface Aerators
Converted Air
Diffusers
Surface Aerators
Surface Aerators
Surface Aerators
Fine- Bubble
Diffusers (Open Tank)
Surface Aerators
Const .
Design
Design
Const „
Oper.
Oper.
Oper.
Design
Const .
Design
Rebid
Oper.
Oper.
Const .
Const .
Startup
Oper.
Discontinued
Oper.
Const.
Oper.
Const .
Oper.
2,714.8
Treatment of Zimpro supernatant.
354
-------
TABLE 26. INDUSTRIAL
PLANTS
WASTEWATER TREATMENT
UTILIZING OXYGEN
Plant
Design
Flow
(mgd)
Type of
Dissolution
System
Status
(Oct. 1973)
1. Container Corp.
(Fernandina Beach, Fla.)
a
2. Chesapeake Corp.
(West Point, Va.)
3. Gulf States Paper, Inc.a
(Tuscaloosa, Ala.)
4. Union Carbide Corp.
(Sistersville, W. Va.)
5. Uniori Carbide Corp.
(Taft, La.)
Q
6. American Cyanamid Co.
(Pearl River, N.Y.)
7. Standard Brands
(Peeksville, N.Y.
b
8. Hercules, Inc.
(Wilmington, N.C.
25
Surface Aerators
Const.
16.3 Surface Aerators Oper.
10
Surface Aerators Startup
4.3 Surface Aerators Oper.
3.8 Submerged Turbines Const,
1.5 Surface Aerators Oper.
1 Surface Aerators Oper.
Surface Aerators Oper.
62.9
Pulp and Paper
Petrochemical
-»
"Pharmaceutical
Distillery
355
-------
SUMMARY
1. Oxygenation systems are equally applicable to new plant construction
and upgrading of existing overloaded secondary treatment plants.
2. Oxygenation systems should be designed as integrated packages consisting
of a biological reactor, a secondary clarifier, and sludge handling
facilities.
3. There are genuine indications that reduced excess biological sludge
production is possible with Oxygenation; however, additional verifying
data are needed.
4. Research and development will continue on many areas of the total
Oxygenation process to fully exploit the potential of the process.
356
-------
REFERENCES
"Continued Evaluation of Oxygen Use in Conventional Activated Sludge
Processing", U. S. Environmental Protection Agency, Water Pollution
Control Research Series Report Number 17050 DNW 02/72, February 1972.
Dick, R. I., "Thickening" in Water Quality Improvement by Physical and
Chemical Processes, Volume II, University of Texas Press, 1970.
Divet, L., P. Brouzes, and P. Pelzer, "Short Period Aeration Studies at
Paris", presented at Annual Meeting of New York Water Pollution Control
Association, New York City, January 1963.
Duncan, J. and K. Hawata, "Evaluation of Sludge Thickening Theories",
Journal Sanitary Engineering Division, ASCE, 94, Number SA2, April
1968.
"Investigation of the Use of High Purity Oxygen Aeration in the Conventional
Activated Sludge Process", U. S. Department of the Interior, Federal
WaterQjality Administration, Water Pollution Control Research Series
Report Number 17050 DNW 05/70, May 1970.
Smith, R. and R. G. Eilers, "A Generalized Computer Model for Steady-State
Performance of the Activated Sludge Process", U. S. Environmental Pro-
tection Agency, Water Pollution Control Research Series Report Number
17090 ... 10/69, October 1969.
Stamberg, J. B., D. F- Bishop, A. B. Hais, and S. M. Bennet, "System Al-
ternatives in Oxygen Activated Sludge", presented at 45th Annual Water
Pollution Control Federation Conference, Atlanta, October 1972.
357
-------
AERATION SYSTEMS FOR METRO CHICAGO
BART T. LYNAM, GENERAL SUPERINTENDENT
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CHICAGO, ILLINOIS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
CO-AUTHORS: STEVE GRAEF, SENIOR CIVIL ENGINEER
DON WUNDERLICH, ASSOCIATE CIVIL ENGINEER
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CHICAGO, ILLINOIS
358
-------
ABSTRACT
Aeration Systems for Metro Chicago
The Metropolitan Sanitary District of Greater Chicago
has experimented with aeration system design and operation
since 1920- Initial efforts involved full scale field
studies on activated sludge in advance of the design of the
three major treatment plants at North Side, Calumet and
West-Southwest. Both diffused air and mechanical aeration
were extensively evaluated. Evaluations included location
in tank, tank configuration, rate of oxygen transfer, diffuser
and aeration characteristics, and, finally, large scale oper-
ating problems. The District's present aeration practice
evolved from this experimental program and many of the
practices developed are employed in plant designs throughout
the country.
The flow diagram for a typical District facility would
include an air intake, primary and secondary air filters,
centrifugal or positive displacement blowers, air transport
system and porous diffuser plates located in the base of
each aeration tank to provide a spiral flow regime. Sizes
and quantities are presented for the District's design and
operating practices and reference is made to detailed studies
which led to the present technology.
359
-------
CONTENTS
Page
I. Introduction 362
A. Services and Area
B. Quantities Treated
C. Plants - sizes, types of aeration
II. Development of Aeration Technology at the District 364
A. Early Years 364
1. Founding and Reversal
2. Design for natural stream assimilation
B. Experimentation with Secondary Treatment 364
1. DesPlaines River and Calumet Plants
2. Design and Operational parameters investigated
C. First Major Plant Design - Criteria 365
D. Diffuser Plate Studies 366
1. Permeability
2. Uniformity
3. Diffuser plate rating
E. Second Major Plant Design 367
1. Criteria
2. Clogging problems
F. Operational Life of Diffuser Plates
1. Problems at major plants
2. Identification of particulate clogging
3. Filter testing
G. Evolved Aeration System for West-Southwest
1. Increased permeability
2. Improved filtration
3. Reduced air flow per diffuser plate
4. Cost effective treatment
360
368
369
-------
II. (Cont'd) Page
H. Recent Work with Aeration 371
1. Instream aeration
2. Basin aeration
3. Small plant design and modification
4. Salt Creek plant design
III. Fine Bubble Aeration Practice 375
A. Introduction 375
B. Intakes 375
1. Location
2. Blending for temperature control
C. Filters 377
1. Types
2. Function of dual system
3. Filtered air quality
4. Monitoring
D. Blowers 379
1. Types
2. Operating characteristics
3. Noise abatement
E. Air Mains 381
1. Sizes
2. Location
3. Protection
4. Couplings and valves
F. Aeration Tanks 383
1. Configuration
2. Diffuser placement
3. Spiral flow
4. Diffuser specifications
5. Clogging and rejuvenation
6. Plate aeration capacity
G. Other Uses of Low Pressure Air
IV. Summary 391
361
-------
Aeration Systems for Metro Chicago
Bart T. Lynam*
Introduction
The Metropolitan Sanitary District of Greater Chicago
provides wastewater treatment, water pollution control and
flood protection services to an area comprising 860 square
miles, including the City of Chicago and approximately 120
suburbs. Approximately 5.5 million people reside within the
service area, which includes an industrial community contri-
buting a wastewater discharge equivalent to 4.5 million
additional persons.
Three major wastewater treatment works handle the
bulk of the District's wastewater flow. The West-Southwest,
North Side and Calumet Plants provided secondary treatment
to 875, 350, and 200 MGD respectively in 1972. Each of these
plants employ activated sludge treatment with fine-bubble
aeration. The District also operates four additional plants
in the 1 to 6 MGD range. Two of the plants employ fine-
bubble aeration for secondary treatment while the others
incorporate mechanical aeration.
*General Superintendent, The Metropolitan Sanitary
District of Greater Chicago; Chicago, Illinois 60611
362
-------
It should also be noted that the District is anti-
cipating the start-up of its 30 MGD Salt Creek Water
Reclamation Plant in early 1975. This highly instru-
mented facility with computer assisted control will also
provide fine-bubble aeration to a two-stage activated
sludge process for nitrification.
363
-------
Development of Aeration Technology at the District
Early Years
When the Metropolitan Sanitary District was founded in
1889 its primary function was to prevent the pollution of
Lake Michigan and the city's water supply. The Chicago river
(which originally carried sewage wastes into the lake) was
reversed and substantial quantities of lake water (up to 10,000
cfs) were diverted into the Illinois River Basin for dilution.
Design and operation criteria was based upon the need for
natural stream assimilation capacity for a population equiva-
lent to 3,000,000 anticipated around 1920. Around 1910 the
District initiated treatment plant studies in anticipation of
the eventual population growth.
Experimentation with Secondary Treatment
Recognizing that natural stream assimilation was a temporary
measure for a service area undergoing accelerated growth the
District incorporated facilities for experimentally testing
secondary treatment in the designs for the Des Plaines River
and the original Calumet sewage treatment plants. Both went
into operation in 1922.
364
-------
The Des Plaines River plant incorporated full-scale activated
sludge treatment while the original .Calumet plant provided
Imhoff treatment with a portion of the flow passing through
full scale experimental activated sludge units.
Studies performed during the late 1920's at these plants
included plain aeration, tapered aeration and sludge reaera-
tion. Diffused aeration, mechanical aeration and various
combinations of the two were evaluated. By the beginning of
the 1930's the effect of process design and operational para-
meters, such as tank depth, residence time, return sludge rates,
air flow rates per unit volume, and both spiral flow and
ridge-and-furrow flow, had been investigated.
First Major Plant Design
The research activity at Des Plaines River and the original
Calumet Plants resulted in the 175 MOD North Side Activated
Sludge Plant which was placed in operation late in 1928. The
design consisted of 36 diffused air, spiral flow aeration tanks
providing a 6.3 hour detention time with 20% return sludge.
Two parallel rows of air diffuser plates were set in con-
crete holders at a depth of 15 feet. These diffusers were
fabricated with a permeability ranging between 11.7 and 18.5.
365
-------
Permeability is essentially defined as the air discharge in
cfm passing a one-foot-square plate under a pressure of two
inches of water. It should be noted that 18.5 was the highest
permeability manufactured at that time. A plate ratio
(surface area of plates/surface area of aeration tank) of
9.6% was employed. Compressed air was supplied to .the system
by 7 Turbo-Blowers having a combined capacity of 250,000 cfm
at 7.75 psig. Oil-coated impingement filters were used to
filter the incoming air.
Diffuser Plate Studies
An ongoing battery of diffuser tests were initiated
shortly after the North Side start-up to provide an economic
design for the proposed addition at Calumet and the new Southwest
plant. These studies by Beck (1) investigated the effects of
permeability and plate thickness on air rates, bubble size,
and pressure loss. Efforts were aimed at reducing diffuser
plate pressure losses in order to keep the cost of compress-
ing air as low as possible. It was soon recognized that
uniform air distribution through the diffuser plates was needed
to avoid operational problems. Later it was found that plates
with higher permeability gave better uniformity with only a
slight reduction in bubble area per unit of air.
366
-------
The studies also disclosed that lower pressure losses and
reduced plate clogging, resulting in longer life, could be
attained by operating the system with lov/er individual
plate air rates. Perhaps, the most significant result of
these early diffuser tests by Beck was the formulation of
an accurate method for rating diffuser plates.
Second Major Plant Design
Based on the success of the system at North Side, a new
136 MGD activated sludge plant was placed in service at Calumet
in 1935. The design for Calumet was similar to the North Side
design except that the specifications called for diffuser plates
with a higher permeability range (36 to 44). Contrary to the
North Side experience, operations at Calumet were seriously
handicapped by diffuser clogging due to industrial wastes
containing suspended and dissolved iron compounds. These
materials precipitated in the aeration tanks resulting in ferric
oxide which clogged the upper faces of the diffuser plates. The
clogging persisted for years. Extensive tests were made on raw
sewage composition, diffuser properties and cleaning techniques.
The problem was eventually solved by prohibiting discharge of
pickled liquor into the sewer system and by increasing the
air discharge rate through the diffusers to keep the particulate
matter in suspension.
367
-------
Operational Life of Diffuser Plates
By 1940 the Activated Sludge process was in service at the
West-Southwest Plant in addition to North Side and Calumet.
While iron deposits were hindering the Calumet Plant, diffuser
clogging problems developed at West-Southwest. As a result,
air distribution studies were initiated (2) at all of the
District's major plants to determine what steps could be taken
to extend the operational life of the diffuser plates.
The original diffuser plates installed at West-Southwest
were replaced with plates of 80 permeability in 1945. By 1947
the pressure losses had again become excessive. Tests revealed
that the plates clogged primarily from dust in the air supply.
The air supply was particularly dirty in the area of the
West-Southwest Plant due to soot from the coal-fired boilers.
Unfiltered air contained as much as 9 mg of particulate/1,000
cubic feet. Filtered air from the original impingement air
filters contained 3.5 mg/1,000 cubic feet. Many different fil-
ters and secondary filters were tested in order to reduce the
dust content.
It was decided to replace the old impingement filters with
Electro-Matic Filters in which unfiltered air passes through
an electrostatic field.
368
-------
Charged dust particles are then attracted by oppositely
charged plates covered with an oil film, where they are
ultimately captured. These filters were successful in
reducing the dust content of the air to 1 nig/1,000 cubic
feet. Early operation, however, pointed out the need to
temper outside air in colder weather to prevent icing on
the filters. Furthermore, the initial operation indicated
that the 1 mg/1,000 cubic feet was still excessive.
By 1948 tests concluded that precoated bag filters
should be installed at Southwest to reduce the dust in the
filtered air to less than 0.1 mg/1,000 cubic feet. Addi-
tionally, the bag filter was simple to operate and maintain,
had a low pressure loss across the filter, and was not
adversely affected by inclement weather conditions. As a
result it was decided to employ the bag filters as the
primary filtering system and to utilize the Electro-Matic
filters as a secondary system.
Evolved Aeration System at West-Southwest
In the design for the third activated sludge battery at
West-Southwest an economical air diffusion system had evolved
369
-------
consisting of bag filters and diffuser plates with an
80-permeability rating utilizing a comparatively low
air rate per plate. The low plate air rates required
additional plates and hence a higher first cost. Yet by
comparison the modified operating procedure was cost
effective based on reduced maintenance costs and longer
plate life. An exhaustive economic comparison was made
for various types of diffusers (plates, jets, and tubes).
The findings resulted in a system consisting of 1 inch
thick porous ceramic plates similar to the replacement
plates added to batteries A and B in 1945. The major
change coming out of this study was the placing of the
diffuser plates normal to the walls with 20% to 30%
additional plates in the influent half of the tanks. When
this change was considered with the improved air filtering
the District's engineers anticipated that the plates would
have a useful life of 14 years. Battery C was put in
operation in 1950 and the original plates are still operat-
ing satisfactory today.
The excellent operation of Battery C resulted in the
design of this system becoming the standard for the activated
sludge process within the District.
370
-------
The ease of operation, minimal maintenance required, and
excellent performance resulted in its adoption as the
aeration system for large plants.
Recent Work with Aeration
In addition to the design of a fourth activated sludge
battery at West-Southwest, the District has engaged in
aeration studies and applications in the following areas:
stream aeration, basin aeration, small plant design and
modification, and the Salt Creek plant design.
In order to meet regulations set by the IPCB requiring
that certain set dissolved oxygen concentrations be main-
tained in the waterways system, the District considered a
variety of in-stream aeration designs. The objective was to
artificially aerate the low points on the oxygen sag curve
along the District's Waterway system. Mechanical, diffused
air and pureoxygen aeration equipment was studied, sized
and evaluated. The design life was estimated at ten years
since it is anticipated that the proposed Chicago Underflow
Plan and major plant expansion to tertiary treatment would
render the project obsolete.
371
-------
The Chicago Underflow Plan (which would capture and treat
the stormwater run-off from Chicago by utilizing temporary
underground storage in tunnels and surface storage in
abandoned rock quarries with gradual pump back to the major
plants for complete treatment during dry weather) together
with the tertiary treatment of all wastewater from the
District's service area would insure adequate D.O. levels
in the waterways without the need for in-stream aeration.
An economic comparison indicated that total costs per pound
of oxygen transferred were lowest for floating mechanical
aerators primarily because of a lower capital cost. Unfor-
tunately the narrow width of the channel precluded the design
because of its potential navigational hinderance. A scheme,
whereby a portion of the stream would be withdrawn into a
pure oxygen aeration system and then reintroduced to the
stream was evaluated. Although the entire system could be
placed on shore out of the way of navigation, the total cost
(per pound of oxygen added) was slightly higher and was thus
passed over. Diffused aeration with porous diffusers was
ultimately selected because of its location in the channel
floor, out of the way of barge traffic. Its total cost
fell between that for mechanical aeration and pure oxygen
aeration.
372
-------
District experience with aeration basin design and opera-
tion has been almost exclusively with mechanical aeration.
For the most part, these aerators have had low capital costs,
been easy to install and operate and are best suited for the
relatively short design life of aeration basins.
In recent years the District has extended service to
several remote areas which were struggling to provide treat-
ment for their wastewater. In the course of expansion,
several small, overloaded plants were obtained by the District
through annexation. It was decided to employ mechanical
aeration at two facilities because of their relatively short
life spans in view of existing phase out schedules. In both
instances improved treatment of the existing trickling filter
plants required conversion to the activated sludge process. The
existing circular trickling filters made it more economical
and easier (as well as quicker) to install surface mechanical
aerators.
Most recently the District has undertaken the design and
construction of a highly instrumented, two stage activated
sludge Water Reclamation Plant at Salt Creek. Since the size
(30, expansible to 125 MGD) was on the border line between a
large and small plant, an economic comparison was made between
373
-------
mechanical and diffused air aeration. Mechanical aeration
was slightly lower in total cost for the initial 30 MGD
size. Both design concepts were then carefully reviewed.
Ultimately, diffused air was selected because of (1) its
econoroy in the light of anticipated plant expansion; (2) its
capability to provide step feed, contact stabilization, com-
plete mix and tapered aeration, in addition to conventional
activated sludge treatment; and (3) its excellent past
performance and reliability. This facility featuring com-
puter assisted operation is scheduled to go on .stream in
early 1975.
374
-------
FINE BUBBLE AERATION PRACTICE
Even though the equipment varies from plant to plant
aeration systems throughout the District are conceptually
similar. Although there are several uses for low pressure
air within the plant, the primary use of the air is to
transfer oxygen to the activated sludge process and keep the
mixed liquor in suspension. In a typical District design,
Figure 1, atmospheric air enters the system through an air
intake. Air passes from the intake through primary and
secondary filters before being compressed by the blowers.
It then discharges into air mains and headers which trans-
port the pressurized air to porous plate diffusers in the
aeration tanks.
Intakes
Air intakes are located to optimize the air quality
being drawn in and are usually equipped with louvers to
protect the air passages. Atmospheric air passes through
the intake into a chamber leading to the first of a dual set
of filters. Besides connecting the intake and the first set
of filters, the chamber also serves to blend warm building
exhaust air with atmospheric air in winter to maintain a
temperature above freezing through the filters. Without
such provision condensate could freeze in the filters.
375
-------
OUTSIDE AIR INTAKE HOOD
84" BLOWER DISCHARGE
CO
~-j
cr>
FILTERED AIR DUCT
f BLOWER
SUCTION
CHAMBER
n n
AH
INTAKE
SHAFT
PRIMARY PRECOATED BAB FILTERS
TO AERATION BATTERIES
TO AERATION BATTERIES
SECONDARY DRY MEDIUM FILTERS
AIR FLOW DIAGRAM AT WEST-SOUTHWEST PLANT (
AERATED GRIT CHAMBERS
AIR LIFT PUMPS
CONVEYANCE CONDUITS
FIGURE 1
-------
Filters
Air filters are the most vulnerable link in the
aeration system's chain of processes. Basically, there
are four types of filters which have been utilized over
the years. These include viscous filters, dry medium
filters, electronic filters and precoated bag filters.
The Metropolitan Sanitary District plants, like most
plants practicing diffused aeration, employ a dual set of
air filters. Primary filters remove most of the particu-
late matter. Secondary or back-up filters provided addi-
tional removal of particulates which pass the primary and
protect against system damage, should the primary filters
rupture or fail.
The primary filters at the West-Southwest plant are
the precoated bag type equipment. Incoming air passes up
through the center of the bag and then outward through the
precoated material on the primary filter. During normal
operation air passing the primary filters will contain
particulate matter in concentrations less than 0.05 mg per
1,000 cubic feet. To insure good filtration the precoated
bags are cleaned every year. One filter at a time is isolated
and then shaken rapidly, Figure 2, so as to remove the
precoat together with all accumulated dust.
377
-------
CO
-^j
oo
AIR -7
OUTLET
AIR
INLET
L
r
L
j;
^
\
...1_
x^
>;u
TS
Y"'
^
-tp
! ^
s
SHAKING
MECHANISM
X
ACCESS
DOOR
H SEPARATOR
PLATE
FIGURE 2
OQOQ
oooo
oooo
oc oo
DUST TUBE SECTION
-------
The used precoat and dust falls into a hopper at the bottom of
the filter unit and is removed. The bags are then recharged
and the unit is returned to service. It is important to
note that the absolute concentration leaving the filter is
far more important than the percent removal by the filter.
Filtered air quality is determined by drawing 50,000 cubic
feet of filtered air throxigh a tared sample thimble.
The secondary filters at the West-Southwest plant are of
the dry medium type and have the shape of a large sock or
mitten. These provide back-up and help to insure a long
service life before cleaning and rejuvenation of the .aeration
system is needed. Furthermore filter equipment is over-
designed in comparison to the blowers, since they comprise
the critical stage in an aeration system; they are designed
so that all blowers can be placed in service with one filter
unit out of service. An important part of filter operation
is a careful monitoring program. Important parameters include
time in service, pressure drop across the filters, air volume
filtered, air flow rate, and particulate concentration of the
effluent.
Blowers
Filtered air makes its way through butterfly doors into
a common air tunnel which feeds the plant blowers.
379
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The District employs several types of blowers including
vane axial, centrifugal and positive displacement varie-
ties. The new Salt Creek Water Reclamation Plant will
have a new type of blower which will permit a broader
range of operating capability because of its automatic
inlet guide vane control. The District's blowers range
in size from 1,500 cubic feet per minute up to 200,000
cubic feet per minute. These blowers are powered by
several types of prime movers including steam turbines,
electric motors and gas turbines. Blowers, which are
essentially low pressure compressors, produce an output
pressure between 7.5 and 10 psi. Since the friction
losses are in the order of 0.5 to 2.5 psi most of the blower
output pressure is needed to overcome the 15 to 17 feet
of hydrostatic head. Inherent in blower operation is
a substantial temperature increase in the air. For
example, with a blower discharge pressure of 8 psi the
air temperature rise would be approximately 100°F above
ambient temperature.
An important factor in the design and installation
of blower systems is noise reduction. Silencers are
installed in the air piping to maintain sound levels
within a reasonable range.
380
-------
In order to minimize noise on the largest blower at the
West-Southwest plant, an acoustical housing was fabricated
to enclose both the turbine and the blower. The insula-
tion consisted of three (3) inches of fiberglass material.
Air Mains
The discharge from the blowers is transported through
large air mains to the aeration tanks with small quantities
being routed to other processes such as aerated grit chambers
and air lift pumps. This air transport system consists of
piping ranging from 84-inch conduits to 4-inch diffuser header
pipes. Much of the piping is contained in service tunnels
and galleries, thus enabling workmen to inspect and service
them readily.
The general requirements for air piping are as follows:
(a) the outside of the pipe must be sufficiently corrosion
resistant for the location and (b) the inside of the pipe must
remain so clean and sound that it will not give off any
particles which would add to the clogging of the diffusers.
Procedures have been developed for protecting air piping
against corrosion and pitting. Large piping over 24 inches,
which is located inside buildings, galleries, or embedded
in concrete, is steel with the outside painted and inside bare
381
-------
The inside receives a grease coating during construction
and is washed clean with solvents before being placed in
operation. Smaller pipe, 8 to 24 inches, is spiral
galvanized steel. Piping 6 inches and under is standard
weight galvanized steel. Other piping which is submerged
or immediately above wastewater is galvanized cast iron
when 3 inches or larger.
These precautions are necessary for the following
reasons. Air comes from the blowers at about 100°F above
the atmospheric temperature, and as long as it remains a
few degrees above the atmosphere there is no condensation
to cause rusting. Therefore, no protective coating is
necessary for mains inside the buildings and galleries after
they are put in service. However, pipes too small for men
to enter for thorough cleaning just prior to placing in
service are galvanized to insure a clean interior.
Bituminous coatings and paints are not used for interior
coatings because oxidation of the coating or paint vehicle
releases particles which contribute to diffuser clogging.
Where pipes are submerged, condensation will occur
at times inside the pipes, due to the lowered temperatures,
and this requires a good coating to prevent rusting.
382
-------
Also, the outside of submerged pipes is subjected to
corrosive conditions which are somewhat unpredictable.
Important factors in pipeline design are the types
of couplings and joints. These must be capable of
handling the velocities and temperature of the air flow.
Extensive use of valving is incorporated in the system
for both controlling and isolating air flow. Automatic
and manually operated valves have been employed. The
District's new Salt Creek Water Reclamation plant will
have the capability of automatic air rate control. Dis-
solved oxygen sensors will regulate the automatic control
valves which distribute air into the aeration tanks.
Large diameter air mains at the District's major plants
are usually fitted with butterfly valves, while the small
diameter conduits consist of globe valves. An important
function in operating the air transport system is the care-
ful monitoring of air pressures and flows.
Aeration Tanks
Most of the aeration tanks, Figure 3, within the
Metropolitan Sanitary District consist of long, multipass
concrete channels having rectangular cross sections.
383
-------
(SEE FIGURE 4 FOR SECTIONAL VIEW).
GO
00
4i8-
L. r 4 NON-PRESSURE WALL
6- AIR HEADER
\
/
/
__
J-
^
-d.
1
4
s,
)-
*sS3-
l
. 6" AR PIPING UP TO 18" HEADER (TYPICAL)
I
DIFFUSER PLATE HOLDERS
-------
Porous plates tightly cemented in durable, solid concrete
plate holders are placed (six plates/holder) along one
of the channel walls. .Because of its effective air fil-
tration equipment, the District has been able to economize
by setting diffuser plates with mortar rather than remov-
able metal plate holders. A header pipe connects the air
main and the porous plate diffusers, Figure 4, thus permitt-
ing distribution of air into the base of the aeration tanks.
Since the diffusers are constructed adjacent to one of the
channel walls. Figure 5, a spiral or overturning flow
regime is established by the air distribution. As a result,
two benefits accrue. One air main serves two channels and
the spiral flow insures that the solids will remain in
suspension. King (3) reported results of an extensive study
of tank velocities at various horizontal and vertical loca-
tions.
Years of District experience with diffuser plates
have led to well defined specifications for these diffuser
plates. The plates are approximately 12" square and 1"
thick. The fabrication materials may be either a crystal
aluminum oxide bounded with a high alumina glass or a sili-
cious sand bonded with silicate. Rigid permeability (2)
and oxygen absorption rating (3,4) requirements must be
385
-------
6" ANGLE VALVE
CO
CO
DRAINAGE TRENCH
6" ANGLE VALVE
L__ 4 DRAINAGE TRENCH
NON-PRESSURE WALL
TYPICAL AERATION TANK
CROSS SECTION
FIGURE 4
-------
AIR MAIN
CO
00
TYPICAL INTERIOR NON-PRESSURE WALL WITHOUT AIR MAIN
(£ TYPICAL INTERIOR NON-PRESSURE WALL WITH AIP MAIN
TYPICAL CROSS SECTION OF SPIRAL FLOW AERATION TANK
FIGURE 5
-------
met as determined by specific empirical techniques.
After installation, pressure loss and volume of air
diffused are monitored closely. From time to time, the
air rate is temporarily raised and lowered to enable a
plot of pressure loss versus flow rate. A pronounced
upward curve is an indication that the plates are clogging.
Clogging can occur on the air side or the liquor side.
Except for the ferric oxide deposits at the Calumet plant,
most clogging has occurred on the air side. Besides
particulate problems, some pressure loss has occurred from
condensation in diffuser headers during the early spring
and summer. Two methods have been employed for rejuvenat-
ing the plates. The most effective has been removal and
kiln burning. The second, a temporary measure, is washing
the plates with an acid.
Recent District designs provide more than adequate
mixing velocities. This is insured by plate arrangements
which discharge 8 to 12 cfm of air per foot of tank length.
Several plates are placed side by side in rows to provide
a band of aeration between 6 and 12 feet in width. In the
past, fewer plates were placed in the effluent half of the
aeration tanks to produce a tapered aeration effect.
388
-------
This served well in the conventional activated sludge
process. The District now provides step feed capabili-
ties in its designs so a uniform plate area is provided
throughout the aeration tanks. The nominal distribution
capacity of an individual diffuser plate ranges from
1 to 4 cfm. MSD experience has demonstrated that a long
service life can be obtained from the porous plates if
adequate air filtration and careful placement of the
plates are practiced.
Other Uses of Low Pressure Air
The aerated grit chambers in the District plants
utilize air drawn from the blower system. This air is
diffused into the wastewater stream through submerged non-
porous diffusers located close to the bottom of the chamber,
The quantity of air used by the aerated grit chambers
ranges from 2% to 5 percent of the total blower output.
Another important use of low pressure air is the air lift
pumps serving the final clarifiers, primary settling tanks
and concentration tanks. The quantity utilized in these
locations ranges from twelve to twenty percent of the
total blower output.
389
-------
Low pressure air is also used in minor quantities
for aerating and mixing various wastewater conveyance
conduits. Moreover, it is utilized for post aeration
at the Hanover Park Water Reclamation Plant and the Salt
Creek Water Reclamation Plant.
390
-------
SUMMARY
The Metropolitan Sanitary District of Greater Chicago
has been engaged in aeration systems development since 1920,
Its principal contributions have been in diffuser perme-
ability criteria, design and operation of primary .and
secondary air filters, aeration tank configuration and
diffuser placement and the formulation of mathematical rela-
tionships for oxygen transfer. The result has been an
effective economical technology for the activated sludge
process.
391
-------
REFERENCES
.1. Beck, A. J., "Diffuser Plate Studies" Sewage
Works Journal, 8, 1, pg. 22 (1936)
2. Anderson, N. E., "Tests and Studies on Air
Diffusers for Activated Sludge", Sewage Works
Journal, 22, 4, pg. 461 (1950)
3. King, H. R., "Mechanics of Oxygen Absorption in
Spiral Flow Aeration Tanks. I. Derivation of
Formulas", Sewage and Industrial Wastes Journal,
22, 8, pg. 894 (1955)
4. King, H. R., "Mechanics of Oxygen Absorption in
Spiral Flow Aeration Tanks. II. Experimental
Work", Sewage and Industrial Waste Journal, 27,
9, pg. 1007 (1955)
5. Water Pollution Control Federation "Manual of
Practice No. 5 Aeration in Wastewater Treatment1
Published by WPCF, Washington D.C., 1971
392
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OXYGEN ACTIVATED SLUDGE SYSTEMS IN TEXAS
DICK WHITTINGTON, P.E., DEPUTY DIRECTOR
TEXAS WATER QUALITY BOA.RD
AUSTIN, TEXAS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
CO-AUTHOR: TIMOTHY B. TISCHLER, TEXAS WATER QUALITY BOARD, AUSTIN, TEXAS
393
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OXYGEN ACTIVATED SLUDGE SYSTEMS IN TEXAS
REVIEW OF OXYGEN USE IN WASTEWATER TREATMENT
Since D. A. Okun's first experiments with the Bio-Precipitation, a
pure oxygen process, in the late 1940's, the use of high purity oxygen in
wastewater treatment has created surges of interest followed by periods of
diminished interest in the academic community and in industry. These early
studies were conducted on laboratory scale and on pilot plant scale during
the 1950's. The pilot plant sutdies on municipal sewage concluded that the
use of pure oxygen resulted in a savings in reactor volume and total plant
area. These savings were due to the greater concentration of mixed-liquor
solids that can be maintained aerobic with oxygen. The power requirements
of the conventional system and the Bio-Precipitation process were found to
be essentially equal. In order for the Bio-Precipitation process to offer
an economic advantage, the cost savings resulting from the decreased size of
the reactor had to be greater than the additional costs associated with pro-
viding high purity oxygen. Evidently, the advantages were not sufficient,
as further research into the use of pure oxygen was not significant for nearly
ten years.
Interest in the use of pure oxygen was revived by the Linde Division
of Union Carbide Corporation in the late 1960's, when the Corporation began
seeking additional markets for its new oxygen production process. The Union
Carbide process utilized a multi-stage, covered system which it named the
Unox Process. This system was first evaluated at the Batavia, New York,
municipal sewage treatment plant where it was operated in parallel with a
394
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conventional activated sludge plant.'^' Since that initial investigation,
the applicability of the process to a wide range of wastewater characteristics
has been demonstrated by pilot plant studies throughout the United States. ^
THE UNOX PROCESS
The only significant application of pure oxygen to waste treatment
available today is the Unox Process. In the Unox Process, oxygen absorption
takes place within the mixed-liquor of the biological reactor. The system
utilizes a series of gas-liquid contacting units or cells. Mass transfer
and mixing within the cells is accomplished with a surface aerator or a
sparged-turbine system. The individual cells are gas-tight, allowing the
atmosphere in each cell to be collected and diffused into each succeeding
cell. High purity oxygen is added to the first cell, thus providing maximum
dissolved oxygen concentrations in the first cell where the oxygen demand is
greatest. At the end of the series of cells, the remaining gas, containing
a small fraction of the initial oxygen content, is vented to the atmosphere.
Liquid-solids separation is accomplished in conventional clarifiers.
THE UNOX PROCESS IN TEXAS
There are presently no large-scale Unox systems in operation or
under design in Texas. Four small to medium size Unox systems are under
construction or are being planned by Texas municipalities. A 6 MGD (22,800
m3/day) Unox plant is being built by the City of Deer Park. This plant is
scheduled to begin operation in the early part of 1974. Construction on
another 6 MGD (22,800 m3/day) plant for the City of Lewisville began in
January 1974. Additional Unox installations are planned by Pasadena and
Missouri City, Texas.
395
-------
There is no plant performance data available for any of the Texas
Unox installations at this time.
REPORTED ADVANTAGES OF UNOX
The reported advantages of the Unox Process include: reductions in
biological reactor volumes, higher oxygen-transfer efficiencies, improved
sludge handling characteristics, simplified process control and odor control.
Reduction in the size of the biological reactors is accomplished by
the use of a much higher mixed-liquor solids concentration in the Unox
Process. The higher concentration of biological solids can be maintained
in an aerobic condition by the greatly improved oxygen mass-transfer effi-
ciencies of pure oxygen. The higher mixed-liquor solids concentration
allows the designer to decrease the biological reactor volume while main-
taining the system mass-loading rate at a level comparable to that of
conventional designs. The savings realized from tankage reductions repre-
sents the main economic advantage of the oxygen system.
The more direct advantages resulting from the higher oxygen-transfer
efficiencies of pure oxygen include equipment-size reductions and reduction
in power usage. The lower equipment requirements of the oxygen system
produce a savings in a projects capital cost, and the reduced power consump-
tion a decrease in operating costs.
Other reported advantages of oxygen are improved sludge settling
characteristics and a reduction in the quantity of waste solids produced.
The greatly improved sludge settling characteristics of oxygenated
biological solids have been reported by a number of investigators.(3) The
advantages of an improved settling sludge are twofold. The improved clari-
396
-------
fier-underflow concentration allows the maintenance of the high operating
mixed-liquor solids concentrations and the thicker clarifier underflow
results in considerable savings in sludge handling.
The Union Carbide Corporation has reported a reduced sludge
production from their Unox Process and has attributed the decrease to a
highly aerobic sludge. They have postulated that the high dissolved oxygen
concentration of the Unox Process is able to penetrate large floe particles,
thus maintaining the entire sludge mass aerobic and active.^ These results
have been contradicted by independent investigations conducted on bench-
scale-sized pure oxygen units.'3^ The results of these experiments indicate
the Kinetics of activated sludge systems operated at a dissolved oxygen
concentration as great as 20 mg/1 do not vary significantly from the reported
Kinetics of conventional systems. Furthermore, studies of oxygen diffusion
through biological floe particles have shown that for dissolved oxygen con-
centrations and floe particle sizes normally encountered in the conventional
activated sludge process, the entire mass of the floe particle is aerobic.^ '
The dispute over excess solids production should be conclusively
answered in the next several years as an inventory of operating data is
accumulated.
The simplified process control of the Unox system also has its
advantages. A simple pressure control system is used to monitor the oxygen
requirements of the system, thereby permitting only the oxygen needed to be
applied. The system easily "tailors" the oxygen applied to the diurnal
demands of the wastewater. A considerable savings in power is realized by
this integrated system.
397
-------
The enhanced ability of the Unox Process to respond quickly and
automatically to varying oxygen demands, thereby maintaining a minimum
dissolved oxygen concentration of 1-2 mg/1, and to maintain higher return
sludge solids concentrations should improve the stability of the process
and minimize plant upsets. Should this be the case in actual plant
operations, the Unox Process would have a decided advantage over the
conventional activated sludge process.
Another advantage -of the covered tank system is that effective odor
control of the vent gas can be practically achieved. The total gas vented
from the system is reported to be about 1% of the gas vented from an air-
activated-sludge system.* '
POSSIBLE DISADVANTAGES OF THE UNOX SYSTEM
The Unox Process includes sophisticated mechanical and electrical
control systems that ordinary treatment plant operators may find difficult
to control and maintain. It is a sad fact, but true, that many of the
treatment plant operators in the State of Texas and in other states are
undereducated and underpaid. These personnel may not be capable of main-
taining the Unox Process even after extensive instruction. Municipalities
located in the industrial-urban areas of the State, where there is a reservoir
of persons trained in the maintenance of instrumentation and complex machinery,
can more readily assume this risk.
Another possible disadvantage of the Unox Process is the possibility
of volatile hydrocarbons entering the enclosed system which could lead to
a serious explosion. This possibility has been recognized by Union Carbide
and a sensitive hydrocarbon monitoring device is installed in every Unox
398
-------
unit sold. When significant hydrocarbon concentrations are detected by the
sensing device, the tanks are automatically purged of oxygen with air. Proper
maintenance of this monitoring device would seem to be mandatory.
FUTURE OF UNOX IN TEXAS
The Unox Process seems to be a viable alternative to the conventional
activated sludge process. Its greatest advantage seems to be the reduction
in tank volumes and land areas needed for treatment. These advantages would
be of primary importance in the renovation and expansion of existing large
sewage treatment plants in densely populated areas.
While the economic advantages of the Unox Process for large municipal
plants may be considerable, there may be no economic advantages for small
communities. Small communities should carefully consider the economics of
the Unox Process as compared to conventional designs, with special attention
being given to the complexity of operation and the need for highly trained
operators. In Texas, we are assuming a "wait and see" attitude before
reaching a decision on the merits of this process in actual operation.
REFERENCES
1. Environmental Protection Agency, "Oxygen Activated-Sludge Wastewater
Treatment Systems", Technology Transfer Publication, August 1973.
2. Mueller, Boyle and Lightfoot, "Oxygen Diffusion Through a Pure Culture
Floe of Zoogloea Ramigera", Proceedings of the 21st Purdue Industrial
Waste Conference.
3. Tischler, Timothy B., "Kinetics of the Pure Oxygen Activated Sludge
Process", Masters Thesis, Department of Environmental Health Engineering,
The University of Texas, Austin, 1973.
399
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SUSPENDED SOLIDS REMOVAL
PROCESSES STUDIED AT METRO CHICAGO
BART T. LYNAM, GENERAL SUPERINTENDENT
THE METROPOLITAN SANITARY DISTRICT OG GREATER CHICAGO
CHICAGO, ILLINOIS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
CO-AUTHORS: DAVID R. ZENZ, COORDINATOR OF RESEARCH
CECIL LUE-HING, DIRECTOR, RESEARCH AND DEVELOPMENT
GEORGE R. RICHARDSON, HEAD, WASTEWATER RESEARCH SECTION
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CHICAGO, ILLINOIS
400
-------
TABLE OF CONTENTS
Page
LIST OP TABLES 402
LIST OF FIGURES 403
I. SUSPENDED SOLIDS REMOVAL PROCESSES STUDIED AT
METRO CHICAGO 405
A. Background 405
B. Full-Scale Evaluation of Sand Filtration
and Microstraining at Hanover Park 408
C. Pilot Plant Studies At Hanover Park-Evaluation
of Three Sand Filtration Devices
1. The DeLaval Filter
2. The Neptune Microfloc Unit 423
3. The Graver Filter 424
4. Results and Conclusions 428, 435
D. Evaluation of 15 MGD Micros trainer At The
North Side Treatment Works Of MSDGC. 436
E. Summary Comparison Of Tests Results Of
Filtration Devices Tested 447
401
-------
LIST Of TABLES
Table 1. Hanover Park Sand Filters % Backwash
Table 2. Operation Of The DeLaval Filter At Various
Hydraulic Loadings
Page
417
429
Table 3. Operation Of The Neptune Microfloc Unit -
Treatment Of Secondary Effluent
430
Table 4. Comparison Of Operating And Performance
Parameters Of The Filtration Devices Tested
By MSD.
448
402
-------
LIST
0 F
FIGURES
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10-
Figure 11.
Figure 12.
Figure 13.
Continuous Flow Sand Filter Suspended
Solids Removal At High Head Without Co-
agulation
Continuous Flow Sand Filter Tertiary
Effluent Suspended Solids As A Function Of
Hydraulic Loading And Secondary Effluent
Suspended Solids Based On Regression of
y = 0.756X - 0.03X
Continuous Flow Sand Filter Tertiary
Effluent BOD As A Function Of Hydraulic
Loading And Secondary Effluent BOD Based On
Regression Of y = 0.906X - 0.012
Microstrainer-Suspended Solids Removal With
Idle Speed At 10% Of Maximum
Microstrainer-Tertiary Effluent Suspended
Solids As A Function Of Hydraulic Loading
And Secondary Effluent Suspended Solids
Based On Regression Of y = 0.739X - 0.011
Microstrainer-Tertiary Effluent BOD As A
Function Of Hydraulic Loading And Secondary
Effluent BOD Based On Regression y = 0.736X +
0.0006
Diagram Of The DeLaval Filter
Flow Diagram Of The Neptune Microfloc Unit
Diagram Of The Graver Filter
Suspended Solids Loadings And Removals For
The Graver Filter
Backwash Usage For The Graver Filter
Influent And Effluent Suspended Solids And
BOD For The Graver Filter
Cumulative Frequency Distribution Of Influent
Suspended Solids Loading To North Side Micro-
strainer
410
411
412
414
415
416
422
425
426
432
433
434
440
403
-------
LIST OF FIGURES
(Continued)
Page
Figure 14. Cumulative Frequency Distribution Of Flow
Thru North Side Microstrainer 441
Figure 15. Cumulative Frequency Distribution Of
Suspended Solids in ^orth Side Microstrainer 442
Figure 16. Cumulative Frequency Distribution Of BOD
Concentrations In North Side Microstrainer 444
Figure 17. Backwash Data For North Side Microstrainer 445
404
-------
SUSPENDED SOLIDS REMOVAL PROCESSES STUDIED AT METRO CHICAGO
The Metropolitan Sanitary District of Greater Chicago was
created by the Illinois State Legislature in 1889, to protect
Chicago's Lake Michigan drinking water supply from pollution.
This action was deemed necessary because in 1885, a heavy storm
of more than six inches over the Chicago area in a two day period,
flushed the streets, catch basins and sewers into the rivers and,
subsequently, polluted the lake far beyond the intake cribs which
supplied the city's drinking water. As a result, approximately
12 percent of the city's population died from such waterborne
diseases as cholera, typhoid and dysentery.
The initial treatment system consisted of reversing the flow
of the Chicago River by the construction of a man-made canal system,
so that it carried discharged polluted water away from the lake.
This system of treatment by dilution was the first step in pre-
venting raw sewage from entering Lake Michigan and providing a
minimum level of treatment.
Although the reversal of the Chicago River solved the prob-
lem for Chicago, neighboring states on the great lakes protested
that the District was draining the lake and sued the District to
prevent it from taking unlimited quantities of water from the lake.
As a result of the law suit, lake diversion was reduced from
10,000 to 3,000 cubic feet per second. Therefore, controlling
locks were constructed at Wilmette Harbor, the mouth of the Chicago
River and the Calumet River. These locks control the diversions
405
-------
from Lake Michigan.
The loss of diversion water and the constantly increasing
flows of the rapidly growing Chicago area required the building of
treatment plants to intercept and process the sewage flowing into
the canals in order to keep the rivers and waterways from becoming
overly polluted. Research work initiated by the District in 1911
enhanced by urging of the Supreme Court dealing with the diversion
matter, commenced a second phase in the District's waste treat-
ment program. The North Side plant, serving the northern portion
of the area, was completed in 1928 and expanded in 1937. The
West-Southwest plant, the world's largest sewage treatment plant,
was placed in operation in 1939. Together with the Calumet plant
these plants today treat over 1.3 billion gallons of sewage from
a population of about 6.0 million people and an equivalent of an
additional 4.5 million people from non domestic sources.
The District recognizes, however, that today secondary
treatment cannot be considered to be the ultimate objective in
sewage treatment as it was in the past. In addition, stricter
rules and regulations being imposed by the Illinois Pollution
Control Board (IPCB), makes it mandatory to discharge a higher
quality effluent relatively free of contaminants including organic
suspended solids.
IPCB rules and regulations take on added significance to
the Sanitary district when one considers that, during periods of
low flow up to 99% of the flow in the sanitary district's man-
made controlled waterway system consists of MSDGC effluent.
406
-------
According to the newly adopted rule, section 404 (f) (ii) , MSDGC
is subject to an effluent standard of 10 mg/1 of BOD5 and 12 mg/1
SS by December 13, 1977. For these reason the District has been
actively engaged in studying advanced wastewater treatment pro-
cesses on pilot or full-scale operation since 1968.
Because of the importance of effective suspended solids
removal to the production of high quality effluents, the MSDGC
has conducted extensive full scale and pilot studies in this
area. This paper presents some of the Districts experiences
resulting from these studies.
407
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FULL SCALE EVALUATION OF SAND FILTRATION
AND MICROSTRAINING AT HANOVER PARK
INTRODUCTION
The initial full-scale tertiary treatment studies in terms
of removal of solids were conducted at the Hanover Park Treatment
Plant in 1968. This work has been reported in detail by Lynam
et al.
Two methods of physical separation or removal of suspended
solids were investigated, namely sand filtration using the Hardinge
design rapid sand filter and microstraining using the Glenfield
and Kennedy microstrainerf The Hardinge sand filter utilizes a
silica sand with an effective size of 0.51 mm and a uniformity
coefficient of 1.62. These filters are continuously cleaned by
a traveling backwash mechanism so that no major down-time is
experienced during backwash procedures. This unit permits about
90% of the filter bed to be in continuous operation, the re-
maining 10% being that portion being automatically backwashed by
the travelling backwash mechanism.
Microstraining is a method of filtration in which a stain-
less steel fabric is used as a filtering medium. The microstrainer
used at Hanover Park has a drum 10 feet in diameter and 10 feet
long in which the fabric is mounted on the periphery of the re-
volving drum. The untreated water flows into the drum and radially
outward through the microfabric, leaving behind the suspended
solids removed by the fabric. The solids on the inside are
carried upward, where a row of backwash jets flush them into a
(1) Tertiary Treatment at Metro Chicago by Means of Rapid Sand
Filtration and Microstrainers
408
-------
hopper mounted on the hollow axle of the drum. The drum ipeed
and backwash pressure are automatically controlled by headloss
across the drum. The maximum headloss is 6 inches; drum speed
can vary from a minimum of 0.7 to a maximum of 4.3 rpm and corre-
spondingly, the backwash pressures vary from 20 to 55 psi.
In the process of analyzing the large amounts of data
collected it was discovered that plots of many parameters yield
poor correlations and were not useful in evaluating the efficiency
of the tertiary treatment process. However, a plot of suspended
solids removal versus suspended solids loading in terms of
Ibs/ft2/day yield a high degree of correlation. Consequently,
this method of data presentation will be used to summarize the
Hanover Park Operations.
RESULTS - SAND FILTRATION
The performance of the sand filter is shown in Figure 1. The
regression equation is y = 0.756X - 0.034 with a correlation
coefficient of 0.922. A family of curves may be constructed from
the regression equation of Figure 1^ to show a relationship between
tertiary effluent quality in terms of suspended solids and hy-
draulic loadings. This family of curves (Figure 2), demonstrates
the relationship between hydraulic loading and solids loading. The
dashed line shows both an upper limit of 6 gpm/ft2 for hydraulic
loading and a solids loading limit of 0.65 Ibs/ft2/day to produce
a tertiary suspended solids quality dependent upon the combination
of secondary effluent quality and hydraulic loading. The same
analysis was applied in terms of effluent BOD and the family of
409
-------
FIGURE 1
CONTINUOUS FLOW SAND FILTER
O
32
LU
OC
0.5
0.4
0.3
0.2
0.1
SUSPENDED SOLIDS REMOVAL AT HIGH HEAD WITHOUT COAGULATION
o.i
0.2
0.3
0.4
0.5
O.6
S S LOADING (!bs/sq. ft:/day)
-------
FIGURE 2
CONTINUOUS FLOW SAND FILTER
TERTIARY EFFLUENT SUSPENDED SOLIDS AS A FUNCTION OF HYDRAULIC LOADING AND SECONDARY EFFLUENT
SUSPENDED SOLIDS HIGH HEAD BASED ON REGRESSION OF Y = 0.756X - 0.034
10
9
a
7
6
5
4
3
2
1
\30 mg/l SECONDARY EFFLUENT
HYDRAULIC LOADING fapa/sq. ft.)
-------
0
o
C3
FIGURE 3
CONTINUOUS FLOW SAND FILTER
TERTIARY EFFLUENT BOD AS A FUNCTION OF HYDRAULIC LOADING AND
SECONDARY EFFLUENT BOD BASED ON REGRESSION OF Y = 0.906X - 0.012
mg/I SECONDARY EFFLUENT
HYDRAULIC LOADING (gpm/sq. ft.)
-------
curves developed is shown in Figure 3_.
MICROSTRAINER
Microstrainer performance at 10 percent idle speed (0.7-rpm)
is given in Figure £. The regression equation is y = 0.739X - 0.011
with a correlation coefficient of 0.922. The suspended solids
removal at 0.7-rpm was significantly greater than at a 20 percent
idle speed. It is believed that the slower speed allowed a greater
build-up of solids at the surface of the microstrainer fabric thus
yielding improved filtration. A family of curves, may be
constructed from Figure £ to show the relationship between tertiary
effluent suspended solids and hydraulic loading. This family of
curves is shown in Figure 5_. The dashed line shows an upper limit
of 6.5 gpm/ft2 for the hydraulic loading and 0.88 Ibs/ft2/day for
the pounds loading. A similar analysis was applied in terms of
BOD and a family of curves developed as presented in Figure 6_.
When one evaluates the overall efficiency of a physical
separation process consideration must be given to the amounts
of treated water used to backwash the unit after the maximum head
is reached. Table !_ presents backwash consumption for the sand
filter at flows of 1.0 through 6.0 gal/min/ft2. The backwash
exceeded 0.5% only once and that was at the maximum hydraulic
loading. The percent of treated water used in backwashing the
2
microstrainer increased to approximately 3 percent at 3.8 gal/min/ft
hydraulic loading.
413
-------
FIGURE 4
MICROSTRAINER
SUSPENDED SOLIDS REMOVAL WITH IDLE SPEED AT 10% OF MAXIMUM
O.8
>.
c
-a
0.3
JT3
O
3E
»/»
0.2
0.1
-------
FIGURE 5 miCROSTRAINER
TERTIARY EFFLUENT SUSPENDED SOLIDS AS A FUNCTION
OF HYDRAULIC LOADING AND SECONDARY EFFLUENT SUSPENDED SOLIDS
BASED ON REGRESSION OF Y= 0.739X - 0.011
mg/l SECONDARY EFFLUENT
HYDRAULIC LOADING (gpm/sq. it.)
-------
fr—
0
FIGURE 6
MICROSTRAINER
TERTIARY EFFLUENT BOD AS A FUNCTION OF HYDRAULIC LOADING AND
SECONDARY EFFLUENT BOD. BASED OH THE REGRESSION OF Y = 0.736X+0.006
U^OHHU
\
\
v
x
\
\
\
s
|^^^HQH13u
20- mg/l SECOt^
V. 15 mg/l
^^
v
^'^^
^*^
<»— «—=J
' »*.
JDARY EFFLUENT
mg/l
—
•*• m*u
5 mg/l
6
10
HYDRAULIC LOADING (gp.«n/sq.ft.)
-------
METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 1
HANOVER PARK SAND FILTERS
% BACKWASH
FLOW Gol/(Mln)(Sq Ft) % BACKWASH
1 0.31
1.5 0.33
2 0.33
2.5 0.35
3 0.34
3.5 0.36
4 0.37
4.5 0.40
5 0.42
5.5 0.48
6 0.65
417
-------
CONCLUSIONS
1. The maximum suspended solids loading to the sand
filter was 0.65 Ib/ft2/day.
2. The maximum hydraulic loading to the sand filter
was 6 gpm/ft2.
3. With an influent of 18 mg/1 of BOD and suspended
solids, an effluent quality of 2.5 and 5.5 mg/1
respectively can be obtained by the Hardinge sand
filter.
4. The maximum suspended solids loading to the
microstrainer was 0,88 Ibs/ft2/day.
5. The maximum hydraulic loading to the microstrainer
was 6.5 gpm/ft2.
6. With an influent of 18 mg/1 of BOD and suspended
solids an effluent quality of 4.0 and 5.0 mg/1
respectively can be obtained for the Glenfield-
Kennedy unit.
7. The sand filter backwash consumption was generally
less than 0.5% up to the maximum flow, while the
microstrainer reached 3% at the maximum flow.
418
-------
PILOT PLANT STUDIES AT THE HANOVER PARK TREATMENT
WORKS - EVALUATION OF 3 SAND FILTRATION DEVICES
INTRODUCTION
Following the studies conducted at the Hanover Treatment
Works involving the use of the Hardinge continuous flow sand fil-
ter, it was the decision of the staff of the District that other
sand devices should be evaluated. This was necessary because of
the large amount of funds which would be required to meet the 1977
Illinois S.S. and BOD criteria (30 day average not to exceed 12 mg/1
of S.S. and 10 mg/1 BOD) and the necessity to select a treatment
method which would yield the most cost effective solution to
achieving such criteria.
The MSDGC decided 3 pilot sand filtration devices would be
run in parallel and that this would enable direct comparison of
these processes without accounting for differences in feed source.
An experimental area was set aside in the existing Hanover
Tertiary treatment plant and three types of deep bed, high rate
sard filtration pilot plants were set up. The three devices were
a DeLaval upflow filler, a Neptune Microfloc mixed media filter
and a Graver dual media pressure filter.
The objective of the program was to investigate the perfor-
mance of each unit.
All of the units received a common influent, that is, second-
ary effluent from the Hanover Treatment Works. Direct simul-
taneous comparisons of effluent quality and operational parameters
were therefore readily possible.
419
-------
It should be noted here that all data presented is based upon
filter runs, that is, the sampling was so arranged that influent
and effluent samples were gathered between backwash cycles. There-
fore influent and effluent analysis as well as filter loadings are
based upon filter runs which were usually not of a 24-hour duration.
2
Loading and removal figures are given in Ibs/ft /filter run and
influent and effluent samples are not generally for 24-hour periods.
Utilizing influent and effluent analysis as well as the load-
ing and removal values based upon 24-hour samples is justified
for the previously discussed full scale Hanover studies, because
both the Hardinge sand filter and the Glenfield-Kennedy Micro-
strainer backwash virtually continuously. Attempting to orient
analysis of data upon runs for the microstrainer and Hardinge
filter is not theoretically possible while the Hardinge filter
backwashes .many times during a given 24-hour period.
Orienting analysis of data upon filter run for the 3 pilot
sand filters is justified due to the batch nature of the 3 devices
undergoing study. Loading and removal values based upon filter
runs yield the total Ibs of S.S. per square foot applied or re-
moved between backwashes and are more meaningful and correlatable
with other operational and performance criteria. Samples gather-
ed during a filter run while often not actually occurring during
a calendar day should be comparable with samples composited on a
24-hour calendar day.
EXPERIMENTAL APPARATUS
1. The DeLaval Filter
420
-------
The filter used was manufactured by the DeLaval Separator
Company and was an "Upflo Immedium filter Model OT-3". The filter
vessel was approximately 3 feet in diameter and 13 feet deep. The
filtering media was silica sand and gravel, with the filter bed
being approximately 7 feet deep. The bed had an effective surface
area of 6.75 square feet and at a maximum flow rate of approximately
2
6 gpm/ft , the unit can filter about 58,000 gallons daily.
As can been seen in Figure T_, the flow through the filter
was upward, with the influent entering the unit through a large
number of nozzles located in a distribution plate at the bottom of
the filter vessel. The filter media consisted of four layers, with
two of the layers being gravel and two of the layers being sand.
The two gravel layers served as support for the sand layers, as
well as distributing the flow uniformly and thereby reducing short
circuiting. The first gravel layer which was at the bottom, was
a 4 inch layer consisting of coarse gravel (1-1/4 to 1-1/2 inches).
The second layer of gravel was 10 inches thick and contained gra-
vel (3/8 to 5/8 inches). On top of the gravel layers was a 12
inch layer of coarse sand (2 to 3 mm). The filter bed was held in
place by a grid, which was buried near the top of the 60 inch fine
sand layer. This filter was designed to utilized the entire depth
of the filter for filtration and solids storage.
The backwash cycle was accomplished as follows: initially
the filtration cycle was terminated when the head loss through the
filter reached a preset level, which was usually 14 psi. With the
filtration cycle terminated, the backwash cycle was then initiated
421
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
SAND RETAINING GRID
INFLUENT
WASH
3ID_-\
\,
I
v
SANE
i
FLOW
SAND
)(
, i
-2mm)
i i .
2-3mm)
GRAVEL ( 3/8 -5/8a)
GRAVELd 1/4-1 \/2a)
\
N SYSTEM -
K/l
*,1VI
_A
N^3-
^~
N^l
WASTE
FILTRATE
AIR
TO DRAIN
FIGURE 7
DIAGRAM OF THE DeLAVAL FILTER
422
-------
by first draining the filter bed. The filter was then fluidized
by forcing air through the filter at low pressure ( 5 to 10 psi).
After 3 minutes of air flow, the filter was flushed with water at
a rate of about 10 - 13 gpm/ft2. After approximately ten minutes
of flushing the bed was allowed to settle for five minutes, with
the largest particles settling to the bottom and the finer par-
ticles to the top.
2. The Neptune Microfloc Unit
The unit used was manufactured by Neptune Microfloc Inc. and
was a "Reclamate SWB-27A." The principal tank was 5 feet square
and 6 feet deep, and was divided into three compartments: a floc-
culation chamber, a settling chamber, and a. filter chamber. The
settling chamber contained settling tubes and the filtering media
consisted of anthracite coal, silica sand, garnet, and gravel.
The filter bed was 5 feet deep and had a surface area of 4 square
^
feet, and a maximum flow through rate of 10 gpm/ft or about 58,000
gpd. The backwash storage tank was approximately 5 feet in dia-
meter and 7 feet deep. Flow through the filter was regulated by
an effluent pump and an effluent rate control valve which was
operated by a level transmitter positioned above the bed.
The filtering media consisted of from top to bottom: a 30
inch layer of anthracite coal (1.2 to 1.3 mm), a 12 inch layer of
silica sand (0.8 to 0.9 mm), a 6 inch layer of garnet (0.4 to 0.8
mm), and a 3 inch layer of support gravel 1.5 to 2.0 inches, and
at the bottom the entire bed rests on a 12 inch layer of gravel
(1/2 to 2 inches).
423
-------
As can be seen in Figure 8_ the "Reclamate SWB-27A" could be
operated in several different modes. The complete flow pattern
included chemical addition followed by flocculation, settling, and
removal. However as shown in Figure £ if chemical addition was not
desired, the flocculation and settling chambers could be bypassed.
Therefore, the appropriate mode of operation can be selected on the
basis of the quality of the influent wastewater, the nature of the
suspended solids, and degree of tertiary treatment desired within
the performance limits of the unit. The studies noted in this
paper will only include those tests when the flow bypassed the
flocculation and settling chambers and no coagulants were Utilized.
When the head loss through the unit increased to the setting
on the vacuum switch located between the filter and the effluent
pump, the backwash cycle was initiated. As shown in Figure 8,
both the filter and the settling chamber were cleaned during the
backwash cycle. The backwash flow was 20 gpm/ft2 and the volume
of water required for a backwash was approximately 650 gallons.
Settling after backwash restored .the anthracite coal, silica sand,
garnet and gravel layer to their proper positions in accordance
with their density differences.
3. The Graver Filter
The filter manufactured by the Graver Water Conditioning
Company was a "Monoscour Filter," and the Wastewater was pumped
down and through the filter. A diagram of the Graver filter is
shown, in Figure 9_. The filter vessel was 22 inches in diameter
and 7 feet 6 inches in height. The filtering media consisted of
424
-------
-P.
ro
en
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
w
V.-)
H
H
CHEMICAL
_EEE£L
FLQCCULATION
TANK
TUBE
SETTLERS
o
FIGURE 8
*
MIXED
MEDIA
FILTER
CHAMBER
EFFLUENT
BACKWASH
FLOW DIAGRAM OF THE NEPTUNE MICROFLOC UNIT
-------
SANITARY DISTRICT QF GREATER CHICAGO
BACKWASH
STORAGE
FLOW
ANTHRACITE
SAND
EFFLUENT
INFLUENT
BACKWASH
FIGURE 9
DIAGRAM OF THE GRAVER FILTER
426
-------
anthracite coal and silica sand, with the filter bed being approx-
imately 3 feet deep. The bed had an effective surface area of
2.65 square feet and at a maximum flow rate of 11.5 gpm/ft2 the
unit was capable of filtering about 43,000 gallons daily. As shown
in Figure £, the backwash storage compartment (6 feet in diameter
and 5 feet in height) was positioned directly above the filter
vessel.
A combination of anthracite coal and silica sand were used
during the test period with the \size of the anthracite being 1.0
to 1.4 mm and the size of silica sand being 0.6 to 0.7 mm.
As in the case of the other filters, the filtration cycle was
automatically stopped when the influent pressure to the filter
reached a preset level. The backwash cycle begins with the bed
being initially drained. After the bed was drained, the filter
bed was then air scoured for 5 minutes at a rate of 15 scfm at 5
psi. Following the air scouring the filter bed was allowed to
settle for 6 minutes, after which the filter bed was backwashed
for 5 minutes at a rate of about 15 gpm/ft2. The total volume of
water used during backwash was about 200 gallons. After back-
washing the filter bed, it was allowed to settle, with the sand
settling below the anthracite coal because of its greater density.
427
-------
RESULTS
DeLaval Filter
In Table 2 are contained results of the operation of the
DeLaval filter at three different flow rates.
Generally speaking, as the loading increased so did backwash
frequency and volume. Based uppn the data collected, it appears
that the unit is capable of treating loadings up to 1.24 lbs/ft2/
day with backwash rates of less than 4%.
It also appears, from the data collected, that the DeLaval
2
filter is capable of handling hydraulic loadings of 4-5 gpm/ft
with the effluent solids being about 5 - 7 mg/1 and the effluent
BOD about 5 -.9 mg/1.
Neptune Microfloc
The results obtained for the Neptune Microfloc unit are
represented in Table _3. The unit was tested at flow rates
of 2 and 5 gpm/ft . An increase in hydraulic loading, as com-
pared to the DeLaval unit, caused a reduction in loading. As one
would expect, backwash frequency and, therefore, backwash usage
increased with increased hydraulic loading. Effluent BOD and
S.S. were between 4 to 6 mg/1 and appeared to be independent of
hydraulic loading. The Neptune Microfloc unit appears to be cap-
able of achieving excellent effluent quality (less than 6 mg/1 of
S.S. and BOD) at hydraulic loadings of 4 gpm/ft with backwash
volumes less than 3%.
Graver Pressure Filter
Figure 10_ presents data on loading and removals of the Graver
428
-------
METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 2
OPERATION OF THE DE-LAVAL
AT VARIOUS HYDRAULIC LOADINGS
HYDRAULIC LOADING, GPM/SQ FT 4 4.7 5
Influent S.S., mg/l
Effluent S.S., mg/l
S.S. Removal, %
Influent BOD, mg/l
Effluent BOD, mg/l
BOD Removal, %
Length of Filter Runs, Hrs
S.S. Loading, Ib/sq ft/filter run
S.S. Removal, Ib/sq ft/filter run
Backwash Usage, %
12
7
44
7
5
26
43.0
1.04
0.45
2.5
14
7
54
17
9
48
37.0
1.23
0.67
2.7
H^BB^K£
14
5
62
18
5
72
35.4
1.24
0.70
3.7
429
-------
II 3
HYDRAULIC LOADING , GP^/SQ FT
laflyent S,S., aig/l
If!!udntS.S.,mg/l
S.S. Removal, %
Influent BOD, mg/l
Effluent BOD, mg/l
BOD Removal, %
Length of Filter Run, hours
S.S. Loading, Ib/sq f J/filtsr run
S.S. Removal, Ib/sq ft/filter run
Backwash Usage, %
2
14
4
73
23
6
74
106.3
1.53
1.12
1.3
4
BMMMHU
16
4
73
25
4
85
27.2
0.86
0.64
2.5
430
-------
Pressure Filter at flow rates from 2.2 to 9.0 gpm/ft2. In
general, loading and removal were closely grouped over the entire
range of flow rates. The highest loading was achieved at a flow
rate of 9.0 gpm/ft where 1.9 lbs/ft2 was achieved at that flow
rate.
Figure 11 presents results for backwash requirements of the
Graver filter. Clearly, backwash usage remained fairly constant
over the range of flow rates. This would seem to correlate with
the loading values given above in that if the loadings per filter
run remain consistent, backwash usage should also be so. In
general, backwash usage was low usually being less than 1% for all
flow rates tested.
Figure 12 presents the effluent quality for the Graver filter.
In general, for all hydraulic loadings, effluent solids range from
5 to 10 mg/1 while effluent BOD values range from 6 to 8 mg/1.
Apparently, effluent quality remains independent of hydraulic and
S.S. loading.
The Graver filter appears capable of handling hydraulic loads
of up to 9 gpm/ft2 and S.S. loadings up to 1.9 lbs/ft2 and achieve
effluent quality averaging about 6 mg/1 of S.S. and BOD.
431
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 10
SUSPENDED SOLIDS LOADINGS AND REMOVALS FOR THE GRAVER FILTER
2.0-1
1.5-
1.0
0.5
U>
S.S. LOADIN
S.S. REMOVAL
2.2 gpm/ft2 4.O gpm/ft* 5.9gpm/ft3 6.0 gpm/ft2 «.0 gpm/ft3 9.O gpm/ft*
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 11
BACKWASH USAGE FOR THE GRAVER FILTER
GO
CO
2.01
1.5*
1.0
1.14%
0.84%
0.65%
0.62%
0.51%
0.44%
2.2 gpm/fta 4.0 gpm/f»a 5.9 gpm/f»a 6.0 gpm/fta 8,0 gpm/fta 9.O gpm/ft1
-------
THE METROPOLITAN SAHITMY DISTRICT OF GUiMift
FIGURE 12
INFLUENT AND EFFLUENT SUSPENDED SOLIDS AND B.O.D. FOR THE GRAVER FILTER
CO
O»
E
O
•
ca
VI
"O
4>
25
20
15
10
INFLUENT
EFFLUENT
SS BOD
2.2 gpm/f»a
SS BOD
4.0 gmp/ft
SS BOD
5.9 gpm/ft *
SS BOD
6.0 gpn/ft a
SS
BOD
SS
BOD
8.0 gpm/ft 9.O gpm/ft
-------
CONCLUSIONS
From the results given on the previous pages, the following
may be concluded from the pilot plant studies conducted in the
Hanover Tertiary Building.
1. All the filtration units tested appeared to be capable
of producing effluent S.S. and BOD of less than 10 mg/1.
2. The Graver pressure filter was capable of operating at
higher hydraulic loadings (9.0 gpm/ft2) and S.S. loadings
(1.9 lbs/ft2) than the other units tested.
3. The Neptune Microfloc unit was capable of achieving the
best effluent quality (less than 6 mg/1 of S.S. and BOD).
435
-------
EVALUATION OF 15 M.G.D. RATED CAPACITY MICROSTRAINER
AT THE NORTH SIDE TREATMENT WORKS OF THE
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
INTRODUCTION
Following the sand filtration and microstrainer studies at
the District's Hanover Works, the staff of the MSD concluded that
the microstraining concept held promise for its North Side Treat-
ment Works. This was based mainly upon the low land area require-
ments of the microstrainer and the limited expansion space available
at the North Side plant-
Although the microstrainer studied at the Hanover Works
performed adequately, it was considered to be too small for
practical consideration at the North Side Sewage Works. The
microstrainer tested at Hanover (10' diameter drum, 10' long) was
rated at 2.9 mgd based upon the studies conducted at Hanover.
Clearly, for a 330 mgd (dry weather flow) plant, such a size unit
would produce an installation with far too many individual units.
Therefore, the MSDGC decided that single units whould have a least
a 15 M.G.D. capacity for the North Side Facility.
Because no manufacturer had produced a microstraining device
of 15 M.G.D. capacity, the MSD decided to issue a performance type
contract for only one such unit for the North Side Plant. Commen-
surate with standard bidding procedures utilized by the District,
a contract was issued to the low bidder for such a unit and a
microstrainer constructed at the North Side Facility-
The facility supplied to the District was a drum 40 ft. long
436
-------
by 10 ft. in diameter. Unlike the microstrainer at Hanover, this
unit receives influent from both ends of the drum. In addition,
the filtering fabric was not placed flat on the outer surface of
the drum, but in a corrugated pattern. The manufacturer stated
that this was done to provide as much filtering area as possible
for the drum size supplied.
The unit constructed at North Side was manufactured by the
Crane-CochraneCo. and utilized a Mark 0 stainless steel fabric
with triangular openings of 23 X 45 X 45 microns (160,000 openings
to the inch). Again, the fabric traps the solids and rotates with
the drum to bring the fabric under wash water sprays which wash
the solids into hoppers for gravity removal to disposal. After
the fabric is washed, it passes under ultraviolet lights to in^
hibit bacteriological growths. With the corrugated arrangement
of the fabric on the drum, it was possible for the manufacturer
to place the fabric in removable sections.
The drum speed and backwash pressure can be automatically
controlled by head loss through the drum. When a set head loss is
exceeded, the drum speed and backwash pressure are increased until
the set head loss is restored. The unit is built for maximum head
losses of 6 inches, drum speeds of about 1 to 5 rpm and backwash
pressure of about 35 to 37 psi.
The entire unit was housed in a heated all weather facility-
Federal funding for performance tests on the unit were obtained
and the unit began shakedown runs in November, 1971.
The unit was tested for flow capacity, that is its ability
437
-------
to filter secondary effluent from the North Side Plant at flow
rates approaching 15 MGD. Operation of the unit consisted of
achieving, as much as practicable, a head loss of 6 inches within
the constraint of the unit's drum speed and backwash pressure.
438
-------
RESULTS
In Figure 13 is presented a cuimnulative frequency of the
loadings (Ibs/ft /day) to the unit during the period of flow
capacity testing. The unit depicts an ability to take solids
loadings as high as 1.0 Ib/ft2/day. As noted previously for the
Hanover studies, it is believed that this expression enables
direct comparison between various types of units and sizes.
Clearly, such an expression has value since filtration devices are
designed primarily to remove S.S. and have an ability to remove
only a certain total weight per unit area given a specific head
loss and type of S.S.
In Figure 14 is presented a cummulative frquency curve of the
flows (24 hour) achieved by the microstrainer for the loadings
given in Figure 13. Clearly, the microstrainer rarely achieved
the 15 MGD capacity envisioned for it and actually produced flows
averaging (50 Percentile) 7.6 mgd.
Plotted in this same cummulative frequency chart are the
2
flows expressed as gpm/ft . It can be seen that the unit achieves
O
flows averaging 3.5 gpm/ft^ for the solids loading depicted in
Figure 13.
It should be npted here that the surface area of the fabric
was taken to be total fabric area or the total area of the micro-
strainer farbir taking into account its corrugated placement on
the drum.
In Figure 15_ is presented cummulative frequency charts of
the influent and effluent S.S. for the unit during the same flow
439
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CUMULATIVE FREQUENCY DISTRIBUTION OF INFLUENT
SUSPENDED SOLIDS LOADING
TO NORTH SIDE MICROSTRAINER
100-1
J" 60H
40H
20'
FIGURE 13
200
4OO
600
800
1000 1200
1400 16OO
Suspended Solids loading, Ibs./day
0'.1 O:2 O.3 O.4 O.S O.6 0.7 O.8 O-9 1.O
Sisptided Solids Loadi&g, Ibs./ft'/day
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CUMULATIVE FREQUENCY DISTRIBUTION OF FLOW
THROUGH NORTH SIDE MICROSTRAIfJER
1OO-1
80-
.3 60-
4O
20
FIGURE 14
1.0
2.0 3.0 4.0 5.0
Flow gol./Bin./ft?
6.0
7.0
•.0
2.0 4.0 6.0 8.O 10.O
Flow n.g.d.
12.0
14.0
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
ro
CUMULATIVE FREQUENCY DISTRIBUTION OF
SUSPENDED SOLIDS IN NORTH SIDE MICROSTRAINER
FIGURE 15
100
•0
INFLUENT!
EFFLUENT
10 12
14 16
18
I
20
Sispeided Solids mg/l
-------
capacity tests depicted in Figures 12^ and 13. It can be seen that
the secondary effluent from the North Side Plant is of high quality
having an average (50 Percentile) S.S. of 11.5 mg/1 and 87 percent
of the values less than 20 mg/1. It also can be seen that the
effluent S.S. from the unit is of high quality having an average
(50 Percentile) S.S. of 3.2 mg/1 with no value exceeding 12 mg/1.
In Figure 16 is presented a cummulative frequency distribution
of the influent and effluent BOD from the unit. The average BOD
(50 Percentile) of the influent to the unit was 10.0 mg/1 while
85% of the values were less than 15.0 mg/1. Effluent BOD averaged
(50 Percentile) 3.8 mg/1 while no value exceeded 13.0 mg/1.
Backwash consumption for the unit it depicted in Figure 17.
It can be seen that the backwash is a decreasing function of flow.
This is because for the North Side unit, backwash flow remains
fairly constant over the flow rates tested. Therefore, as flow
through the unit increases, percent backwash decreases.
The backwash data indicates that for the average flow (7.6 mgd)
processed by the unit during these tests, the unit required 4.6%
backwash while at maximum flow (15 mgd) required about 3.0%.
443
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CUMULATIVE FREQUENCY DISTRIBUTION OF B.O.D.
CONCENTRATIONS IN NORTH SIDE MICROSTRAINER
FIGURE 16
100
80
X 60
«
i_
O
O
— 40-
INFLUENT
EFFLUENT
2.0
4.0 6.0 8.0
B.O.D. mg/l
10.0
12.O
14.0
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
BACKWASH DATA FOR NORTH SIDE MICROSTRAINER
20.0i
16.0*
12.0-
en
8.0-
4.0
FIGURE 17
6 8
Flow ffl.g.d.
10
1.0
2.0
3.0
5.0
Flow aoI./Bii./fft.a
i«
6.0
-------
CONCLUSIONS
The results of the microstrainer tests at the North Side
Plant did not prove as promising as first envisioned. Although
effluent quality was satisfactory and well below present Illinois
standards (Illinois standards require 30-day average BOD values
of less than 10 mg/1 and S.S. less than 12.0 mg/1), the flow
capacity of the unit was well below that envisioned by the MSDGC.
The North Side unit has proven itself capable of taking flows
on the average (50 Percentile) of about 7.6 mgd with corresponding
solids loadings averaging (50 Percentile) about 0.5 Ibs/ft^/day.
Effluent quality for the Mark O stainless steel fabric appears to
be capable of meeting present Illinois S.S. and BOD standards.
Backwash valume for the unit operating at an average flow capacity
was about 4.6%.
446
-------
SUMMARY COMPARISON OF TEST RESULTS OF FILTRATION DEVICES
TESTED
In Table £ is contained a summary of the operating and per-
formance parameters for the filtration devices discussed in this
paper. The following may be concluded from a comparison of these
summarized results.
1. The North Side Microstrainer although capable of achieving
the maximum flow capacity of the Hanover Microstrainer
on a short-term basis, could not consistently achieve
the maximum flow for the Hanover unit. This could in-
dicate that microstrainer flow capacity is severly de-r
pendent on the type of effluent solids.
2. It appears that the microstraining devices cannot achieve
the S.S. removal performance of sand filters.
3. It appears that batch type filters are capable of loadings
over 1.2 Ibs/ft2/filter run.
447
-------
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
TABLE
COMPARISON OF OPERATING AND PERFORMANCE
PARAMETERS OF THE FILTRATION DEVICES
TESTED BY THE MSD
PARAMETER
HARDINGE DELAVAL MICKOFLOC GRAVER
HANOVER PARK NORTH SIDE SAND SAND SAND SAND
MICROSTRAINER MICROSTRAINER FILTER FILTER FILTER FILTER
00
FLOW RATE (GPM/SQ FT)
Maximum
Range Tested
LOADING
Maximum
BACKWASH (%)
At Max. Flow
Range
EFFLUENT BOD (MG/L)
At Max. Flow
Range
EFFLUENT S.S. (MG/L)
At Max. Flow
Range
6.6
0-6.6
0.88 **
0-0.88 **
4.0
0-3.0
4.0-
1-5
5.0 *
1-10
6.3
0-6.3
1.0**
0-1.0
2.9
0-16
0-11
0-12
6.0
0-6.0 0-5.0 0-4.0 0-9.0
0.65 **
0-0.65** 0-L24** 0-1.53 0-1.9*
0.65
0-0.65 0-3.7 0-2.5 0-1.14
2.3'
1-4
5.0 *
1-9
5-9
5-7
4.0-6.0 3.5-8.0
4.0
5.9
• For Influent BOD of 18 mg/l and Maximum Loading
A For Influont S.S. Equal* 18 mg/l and Maximum Loading
* Ibs/sq ft/filtor Run
** Ibs/sq ft/day
-------
.METRO CHICAGO
STUDIES ON NITRIFICATION
-BART T. LYNAM, GENERAL SUPERINTENDENT
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CHICAGO, ILLINOIS
PRESENTED AT
THIRD U.S./JAPAN CONFERENCE ON SEWAGE TREATMENT TECHNOLOGY
TOKYO, JAPAN
FEBRUARY 1974
CO-AUTHORS: DAVID R. ZENZ, COORDINATOR OF RESEARCH
CECIL LUE-HING, DIRECTOR, RESEARCH AND DEVELOPMENT
GEORGE R. RICHARDSON, HEAD, WASTEWATER RESEARCH DIVISION
BOOKER T. WASHINGTON, SANITARY CHEMIST I
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CHICAGO, ILLINOIS
449
-------
TABLE OF CONTENTS
List of Tables
List of Figures 452
I. INTRODUCTION 453
-II. TWO STAGE NITRIFICATION AT HAZELCREST, ILLINOIS 457
A. Introduction 457
B. Results 457
1. Phase I - Initial Testing Period
April 20 - July 30, 1969 458
2. Phase II - December 15 - March 24, 1970 464
C. Conclusion 469
III. CALUMET NITRIFICATION PILOT PLANT 47Q
A. Introduction 470
B. Results 472
C. Conclusions 435
IV. NITRIFICATION AT LEMONT, ILLINOIS - EXTENDED AERATION 487
V. SUMMARY 494
VI. NITRIFICATION OF A HIGH AMMONIA CONTENT SLUDGE
SUPERNATANT BY BIOLOGICAL PROCESSES 495
VII. REFERENCES 503
450
-------
LIST OF TABLES
Table 1. Calumet Raw Sewage Characteristics Monthly
Averages During Pilot Study
Table 2. Return Sludge Trace Metal Analyses - Averages
Table 3. Lemont - WRP November 1972
Table 4. Metals in Return Sludge of Lemont - WRP
Table 5. Chemical Characteristics of Sludge Lagoon
Supernatant from Fulton County
471
483
491
492
497
451
-------
LIST OF FIGURES
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
District Map
Time Series Plot of Raw NH3~N Effluent
N02-N03 and
Time Series Plot Second Stage BOD Loading
Time Series Plot Second Stage MLTSS
Time Series Plot Second Stage Ammonia
Loading
Time Series Plot Second Stage Effluent
NH3 and NO.-NO,
ft »J
Time Series Plot Second Stage BOD Loading
Time Series Plot Raw Sewage Temperature °F
Time Series Plot Second Stage MLTSS
Schematic of Second Stage Biological
Nitrification System
Pilot Plant Influent and Effluent NH3~N
Concentration
Frequency Distribution of Effluent TSS from
the Calumet Nitrification Pilot Plant
Weekly Variations in Aluminum Concentration
Weekly Variations in Chromium Concentration
Schematic of Lemont Water Reclaimation Plant
Performance of The Slurry System
Performance of the Rotating Disc System
454
459
460
461
463
465
466
467
468
473
475
478
481
482
488
499
500
452
-------
INTRODUCTION
The Metropolitan Sanitary District of Greater Chicago (MSDGC)
collects and treats more than one billion 250 million gallons
of domestic and industrial waste each day. It has a capacity
of 1,600,000,000 gallons a day and its growth and ungrading
continues in order to keep pace with the needs and demands of
the communities which it serves and to produce higher quality
effluents in order to upgrade all water resources in the State
of Illinois.
The District maintains a waterway system which consists
of 85 miles of navigable waters including canals, channels and
rivers (Figure ,1) . In addition, hundreds of miles of secondary
tributaries and storm sewers also drain into the main waterway
system. Because the District' s three maj.or sewage treatment
plants and four small treatment plants discharge effluent to
the drainage basin, more stringent criteria are being placed
on the quality of effluent discharged. These criteria cover
a wide spectra such as carbonaceous oxygen demand, toxic
substances, nutrients and oils and greases. The MSDGC has
directed considerable efforts toward the removal of nitrogen
and phosphorus nutrients in order to develop effective and
economical procedures.
It is now realized that besides it's role as an indicator
(1 2}
of pollution, ammonia itself is a serious pollutant. '
Ammonia nitrogen in waste treatment effluents has been held
undesirable due to the following reasons:
453
-------
DISTRICT MAP
FIGURE 1
THEjMETROPOLITAN SANITARY! DISTRICT OF\3REATER CHICAGO
LAKE
MICHIGAN
CHICAGO RIVER
SRUNDY CO !
£ a. D TREATMENT PLANTS
•d 3
STATIONS
lNTERCEPTING SEWERS
WEJST-SOUTHWEST
w [ - -i
454
-------
1. It reacts with chlorine during the disinfection
process and produces chloramines which are less
effective as disinfectants than free chlorine and
may subsequently cause an increase in the chlorine
demand.
2. This constituent exerts a toxic effect on aquatic
life at high concentrations. This has been demon-
strated by investigators to be particularly toxic
on fish life.
3. It exerts an oxygen demand on the receiving waterways
and will subsequently, when oxidized to other nitrogenous
forms act as a nutrient for undesirable algae forms.
The Illinois Pollution Control Board (IPCB) Rules and
Regulations, Chapter 3, Water Pollutions require in Rule 406 ^ '
that "No effluent from any source which discharges to the
Illinois River, the Chicago River System, or Calumet River
System, and whose untreated waste load is 50,000 or more popu-
lation equivalents shall contain more than 2.5 mg/1 of ammonia
nitrogen as N during the months of April through October, or
4 mg/1 at other times, after December 31, 1977." This rule
will require that the three major treatment plants of the
Metropolitan Sanitary District of Greater Chicago, namely the
455
-------
North Side Sewage Treatment Works, the West-Southwest Sewage
Treatment Works, and the Calumet Sewage Treatment Works remove
ammonia nitrogen from their effluents after December 31, 1977.
To this end the MSDGC has undertaken pilot process studies
to evaluate alternate procedures for removing ammonia nitrogen
from its secondary treatment effluents.
After serious consideration of the physical-chemical and
biological processes available for ammonia removal, it was
decided that secondary or unresolved problems made the physical-
(4 5)
chemical processes unfeasible at this time. '
Therefore, the MSDGC concentrated its efforts on the biological
processes for ammonia removal.
This paper will present some of the data collected on several
of the biological treatment projects conducted from 1969 through
1973. These data will be discussed in the following order:
1. Two-Stage Nitrification at. Hazelcrest, Illinois
11. Calumet Nitrification Pilot Plant
111. Nitrification at Lemont, Illinois - Single Stage
Extended Aeration
IV. Nitrification of a High Ammonia Content Sludge Super-
natant by Biological Processes
456
-------
Two-Stage Nitrification at Hazelcrest, Illinois
The 1.2 mgd design capacity treatment facilities at
Hazelcrest, Illinois, were converted from two parallel activated
sludge systems to a two-stage biological nitrification process.
The total capacity of the nitrification plant was approximately
0.6 mgd.
In April of 1969, the Hazelcrest facility began operating
as a two-stage nitrification process. However, it was not until
June of the same year that the system attained a satisfactory
level of nitrification. This level of nitrification continued
through the month of December 1969. During this period of
operation, the detention time ranged from 4.5 to 3.6 hours for
the first and second stage reactors. The first and second stage
clarifier detention times ranged from 1.95 to 1.56 hours and
3.22 to 4.03 hours respectively. These detention times were
calculated on an average flow of 0.8 and 1.0 mgd which were the
range of flows generally experienced by the plant.
Results
The summary data of the Hazelcrest project will be presented
in two phases. Phase I will show data for the initial start-up
and a period of successful operation. Phase II will show data
after the nitrification process was interrupted and steps were
taken to re-establish it.
457
-------
Phase I - Initial Testing Period (April 20 - July 30,
1969
As in any start-up period, there were fluctuations in
plant operation. Once the plant reached a point of steady state
operation, mixed liquor suspended solids in the first stage
reactor had to be maintained between 1HOO and 2000 mg/1. If
the mixed liquor solids were allowed to exceed 2000 mg/1, excess
solids were carried over into the second stage.
On May 1, solids wasting from the second stage was
discontinued to build up the mixed liquor solids. By following
this procedure mixed liquor solids concentrations were main-
tained between 2800 and 3000 mg/1. It was only necessary to
waste occasionally to prevent second stage effluent deterioration,
The data obtained during this period of study will be
presented in the next four figures. It can be seen from the
nitrate - nitrite and ammonia curves (Figure 2) that the plant
approached a satisfactory point of nitrification around June 23
and continued to nitrify at this level through July 30. The
average raw NH3~N concentration of 12 mg/1 was reduced to an
average concentration of 1.5 mg/1 in the second stage effluent.
The nitrate-nitrite concentration ranged from 10.0 to 17.0 mg/1.
The temperature ranged from 50°F to 64°F during this phase of
study.
As can be seen from Figures 3_ and _4, the second stage
reactor operated with an average loading of 0.10 Ib BOD/lb
458
-------
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 2
E
15-
10-
0-
20
15;
10
5
0
70-
60
50
I— 40
-SECOND STAGE NH3 AS N
\ i\
\J\rJ
-TEMPERATURE
SECOND STAGE NO2+NO3AS N
5 10 15 20 25 30
10 15 20 25 30
Jane
10 15 20 25
Jily
30
TIME SERIES PLOT OF RAW SEWAGE AMMONIA, EFFLUENT (NO 2 & N03)
AND EFFLUENT AMMONIA AND RAW SEWAGE TEMPERATURE AT HAZELCREST
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 3
a «/>
0.3
0.4
0.3
cr\
o
S
0.2-
0.1
20 25 30 5 10 15 20 25 30 5 10 15 20 25 30 5 10 15
April
May
June
Jily
TIME SERIES PLOT SECOND STAGE B.O.D. LOADING AT HAZELCREST
-------
KtETROPOUTAN SAUiTARY DISTRICT OF GREATER CHICAGO
-p.
cr>
£
^
V)
&E
30OO-
? 2000-
1OOO-
• i i
20 25 30 5 10 15 20 25 30 5 10 15 20 25 30 5 10 15 20 25
Joce
h\1
TIKE SERIES PLOT OF SECOND STAGE fcUTSS AT HAZELCREST
-------
MLTSS/day and a mixed liquor suspended solids range of 2500
to 3500 mg/1 from April 20 to July 30, 1969.
Figure 5 presents data on the NHj-N loading to the second
stage. The loading was generally less than 0.04 Ibs NHj/lb
MLTSS/day- The plant continued to nitrify at about 90% effi-
ciency with NH3-N less than 1.5 mg/1 through the month of
October.
To select or choose factors responsible for achieving
the degree of nitrification observed is difficult but one may
consider several factors. A comparison of the data presented
in the graphs for the period of satisfactory and unsatisfactory
nitrification is of interest. The organic loading to the second
stage was somewhat lower during satisfactory nitrification.
Also, sewage temperature appears to exert a significant effect
on nitrification. From April 20 through May 21, the temperature
was 50°F at which time there was no nitrification. There was
some nitrification when the temperature increased to 59and 60°F.
The temperature remained at this level for 30 days and the plant
was nitrifying at 50% efficiency. When the temperature increased
to 63 and 64°F the plant began to produce complete nitrification.
462
-------
CO
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 5
0.05-
M 0.04-
0.03-
O.O2*
0.01
0 25 30 5 10 15 20 25 30 5 10 15 20 25 30 5 10 15 20
April
May
Jine
J.ly
TIME SERIES PLOT OF SECOND STAGE AMMONIA LOADING
AT HAZELCREST
-------
Phase II - December 15, - March 24, 1970
As previously noted, the Hazelcrest Plant produced a well
nitrified effluent during the months of November and December.
However, about January 1, 1970 a decrease in second-stage
nitrate levels and a corresponding increase in the NH3-N level
occurred. This decrease in plant efficiency is depicted in
Figure 6^ A clear indication of the exact cause of the cessa-
tion of nitrification is not evident but certainly several
factors must be considered to have significantly contributed to
the effect.
The organic loading to the second stages (Figure _7) was
high, averaging about 0.3 Ib BOD/lb MLTSS/day. As indicated
in Phase I, a more reasonable figure for the second stage loading
would be 0.1 Ib BOD/lb MLTSS/day.
Another factor contributing to the lack of nitrification
was the relatively low raw sewage temperatures that occurred
January 1, 1970, and thereafter (Figure 8). This average
temperature of 47°F was much lower than the temperature experi-
enced in the spring of 1969, at which time partial nitrification
was obtained.
It was also possible (Figure 9_) that the relatively large
fluctuations in MLTSS did not contribute favorably to the nitri-
fication process. The inability to maintain a steady-state
operation with respect to the above parameters was certainly a
464
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 6
NH,
15 20 25 30 5 10 15 20 25 30 5 10 15 20 25 1 5 10 15 20
December
Janiory
February
ltd arch
TIME SERIES PLOT SECOND STAGE EFFLUENT AMMONIA
AND (N02 + N03) AT HAZELCREST
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 7
cr>
15 20 25 30 2 5 10 15 20 25 30 5 10 15 20 25 5 10 15 20
December January February March
TIME SERIES PLOT SECOND STAGE B.O.D. LOADING AT HAZELCREST
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
8
n.
01
—I
.,
45
40
15 20 25 30 5 10 15 20 25 30 5 10 15 20 25 1 5 10 15 20
December
February
Harch
TIME SERIES PLOT RAW SEWAGE TEftP. AT HAZELCREST ILL.
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 9
CTi
00
3500<
«/*
«£ 3000
25OO
2000
15 10 25 30 5 10 15 20 25 1 5 10 15 20 25
January
Febnary
March
TIME SERIES PLOT SECOND STAGE MLTSS AT HAZELCREST
-------
detriment to the system.
Due to the absence of flexibility in the operation of the
plant, it was difficult to determine precisely the total or
direct effect of the various parameters believed to exert adverse
changes on the nitrification process. However, the following
conclusions were drawn from the MSDGC experiences with this
study.
1. A two-stage activated sludge process can produce an
effluent high in nitrate - nitrite and low in ammonia
concentrations at a detention time of 3.0 to 5.0 hours
in the second stage.
2. It is necessary for the first-stage system to perform
efficiently in organic and suspended solids removal to
prevent detrimental carry-over of these materials into
the second stage.
3. Temperature effects appear to be a major factor in
initiating and maintaining nitrification.
4. A highly nitrified effluent can be produced when the
NH3 loading is less than 0.04 ibs/MLVSS/day to the
second stage.
469
-------
Calumet Nitrification Pilot Plant
Introduction
The Calumet Sewage Treatment Plant, located in the south-
eastern section of the City of Chicago and serving this general
portion of the city and Cook County, was placed into operation
in 1935. The present plant receives combined domestic and
industrial sewage from an area of approximately 270 square
miles. The plant's sewage processing facilities include preli-
minary and secondary treatment, anaerobic sludge digestion, and
contact chlorination.
There is a wide range of industries operating within the
Calumet Treatment Plant service area, such as steel mills,
coking plants, paint and chemical manufacturers, and grain and
transport companies. These and other regional industries contri-
buted an estimated 60 - 70 mgd of the average 199 mgd of sewage
volume which the Calumet Plant processed in 1972. Table 1^
lists some of the pertinent characteristics of the Calumet raw
sewage obtained during the six months in which the Calumet
Nitrification Pilot Plant was operated.
470
-------
THE METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 1
CALUMET NITRIFICATION PILOT PLANT
CALUMET RAW SEWAGE CHARACTERISTICS
MONTHLY AVERAGES DURING PILOT STUDY
TKN
NOV. 1972
DEC.
JAN. 1973
FEB.
MAR.
APR.
AVERAGES
24
29
28
.1
.9
.3
32.4
24
.4
22.8
27.0
NH^N
15.
6
17.8
18.0
23.7
17.
15.
6
7
pH
7.5
7.
5
7.4
7.
7.
7.
4
5
6
18.1
TSS
194
265
178
174
192
231
206
YSS
121
157
113
107
108
116
120
BOD
106
149
136
148
130
113
130
COD
245
330
287
312
262
234
278
Results expressed In mg/l, except for pH.
471
-------
Results
From November 1, 1972, through April 24, 1973, a two-stage
bench-scale nitrification feasibility study was conducted at
Battery C of the Calumet Sewage Treatment Plant. The final
effluent from Battery C was utilized as the influent feed to a
20.6 gallon, compartmentalized pilot reactor which constituted
the second stage of a two-stage biological treatment process.
A schematic of the pilot plant is shown in Figure 10. Within
three days of start-up of the pilot plant, significant nitrifi-
cation was observed and was maintained at approximately 90 per
cent ammonia nitrogen removal until the completion of the project,
The data collected for the nearly six months of operations
has been summarized as follows:
1. Substrate Loading and Substrate Removal
The influent feed ammonia nitrogen averaged 17.5
mg/1, with the weekly averages ranging from 10.1 to
24.9 mg/1; this included a supplemental 10 mg/1 NI^Cl
dosing to the reactor which was initiated during the
latter phase of the study. The average ammonia nitrogen
reactor loading rate was 0.126 Ibs NHs-N/lb MLVSS/day;
weekly averages ranged from 0.041 to 0.273 Ibs NH3~N/lb
MLVSS/day. Effluent ammonia nitrogen concentrations
averaged 2.1 mg/1, an average of 88 per cent removal.
The average ammonia nitrogen removal rate was 0.109
Ibs NH3-N/lb MLVSS/day.
472
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CALUMET NITRIFICATION PILOT PLANT
INFLUENT FEED
CO
REACTOR (20.6 GALLON CAPACITY)
RECYCLE TO REACTOR
EFFLUENT
(ASSUME NO WASTE)
FIGURE 10
SCHEMATIC OF 2ND- STAGE BIOLOGICAL NITRIFICATION SYSTEM
-------
Figure JL1 details the variability in ammonia
nitrogen for influent and effluent streams and the
resultant % removal for the initial five days of
start-up, and the subsequent 25 weekly averages. The
effluent ammonia nitrogen observed for weeks 15, 16,
and 17 were high, averaging 4.6 mg/1, due to insuffi-
cient mixing in the aeration tank which resulted in
inadequate oxygen transfer. However, as indicated, the
effluent quality was greatly improved by the 18th week,
following correction of the mixing problem. Again,
during the period between the 21st week and the 23rd
week of operations, operational difficulties (which in
this case was the loss of the nitrifying population as
a consequence of the reactor overflowing) resulted in
high ammonia nitrogen bleed-throughs to the effluent.
The residual effluent ammonia nitrogen obtained for
this period averaged 3.4 mg/1. As was previously stated,
effluent NH3-N averaged only 2.1 mg/1 over the full 25
weeks of the study.
2. Effect of Change in Detention Time
The nitrification reactor was successfully operated
at detention times of 4.0, 3.0 and 2.0 hours, based on
influent flow rate only, for periods of 82, 42 and 51
days, respectively. Throughout the study recycle sludge
474
-------
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 11
CALUMET NITRIFICATION PILOT PLANT
Pilot Plait liflieit »d Efflteot NH3-H Coiceitutlois
7» Removal of Ammonia
\ \
n i i i v \ i
013345
Start-up, Days
• 10 12 14 16
Weekly Averages
30 23
24
-------
was pumped to the head of the reactor at rates of
either 50% or 75% of the influent flow. Excluding
the initial start-up week, the average effluent ammonia
nitrogen was 0.9, 2.8 and 2.0 mg/1, respectively, for
the detention times investigated.
3. Solids Retention Time, SRT
For the first 11 to 12 weeks of this study, efforts
were not directed towards maintaining a sludge age of
any particular number of days. However, for the remaining
weeks of the study, attempts were made to control the
sludge age at an average of at least ten days. This
was done by periodically adding settled return sludge
from Battery C to the nitrification reactor whenever
effluent suspended solids losses and/or accidental
sludge wasting resulted in MLVSS levels of approximately
1000 mg/1 or less. The average SRT obtained during
this latter phase of operations was nine days at an
average reactor temperature of 15°C.
4. BOD and Suspended Solids Considerations
Influent BOD and TSS to the second-stage reactor
averaged 18 mg/1 and 13 mg/1, respectively, whereas
effluent BOD and TSS averaged, respectively, 29 mg/1
476
-------
and 26 mg/1. Typically, BOD and suspended solids
removal through the nitrification unit was not observed
once nitrification commenced. Figure 12_ indicates
the frequency distribution of effluent TSS which was
obtained for each of the two major clarifier overflow
rates at which the clarifier was operated/ namely 287
gal/sf/day and'382 gal/sf/day. As shown, the higher
effluent TSS were more often observed at the higher
clarifier overflow rate.
5. Maintenance of Mixed Liquor Volatile Suspended Solids
Weekly averages of mixed liquor suspended solids
ranged from 1151 rag/1 to 3642 mg/1, averaging 2115 mg/1
of which an average 1359 mg/1 (64.2%) was MLVSS. It
was necessary to periodically add settled return sludge
from Battery C to the nitrification unit in order to
maintain a level of 1000 - 1500 mg/1 MLVSS. The addition
of return sludge to the reactor occasionally resulted
in a transient upset in nitrification efficiency. This
was adjudged to be due to dilution of the nitrifying
population and was considerably lessened by a slow
addition of the solids to the reactor.
6. Temperature Observations
Since there were no provisions for controlling the
477
-------
oo
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CALUMET NITRIFICATION PILOT PLANT
FIGURE 12
60-
9
V
u
L.
40-
30-
Clorifier Overflew Rate = 287 gal/»f/day
Clarifier Overflow Rate = 382 gal/sf/day
i
o
o
n
I
o
n
o
T
o
Effluent TSS , mg/l
Frequency Distribution of Effluent TSS from the Calumet Nitrification Pilot Plant
-------
temperature of the nitrification unit, aeration
temperatures varied with changes in feed and ambient
temperatures. Average weekly reactor temperatures
ranged from 22°C to 13°C over the six months involved
in the study.
7. pH and Alkalinity Observations
pH control did not present any operating problems
with the Calumet Nitrification Pilot Plant. The influent
pH ranged from 7.4 to 7.7, and effluent pH ranged from
7.3 to 7.8 over the 25 weeks of the study. Sawyer,
(Ref. 6) from his studies at Marlborough, Mass.,
recommended a mixed liquor pH range of 7.6 to 7.8 in
order to allow carbon dioxide to escape to the atmosphere.
This pH range would still be sufficiently close to the
theoretical maximum pH of 8.4 to insure a high nitri-
fication rate. The pilot plant mixed liquor pH's ranged
from 6.9 to 7.7, and nitrification was apparently not
attentuated at these pH levels.
Effluent alkalinity concentrations ranged from 60
to 650 mg/1, averaging 174 mg/1. The average alkalinity
consumption was 5.2 Ibs alkalinity (as CaCO3)/lb NH3-N
oxidized and ranged from 1.2 to 7.8 ibs alk/lb NH3-N
oxidized.
479
-------
Trace Metal Effects
Two aspects of high trace metal concentrations
were considered in this study: (a) the effects of
influent concentrations of trace metals on the nitri-
fication process, and (b) the extent and effect of
trace metal accumulation in the return sludge. Of the
14 metals monitored/ none were found to be significantly
high in either the influent or effluent streams. Typically,
influent and effluent concentrations of metals were
about the same; this is reflected in Figures 13 and ^4
for two of the metals, Al and Cr. There were no occasions
when upsets in nitrification efficiency were attributable
to the concentrations of trace metals observed in the
influent stream*
Table !2 lists the average return sludge trace
metal concentrations for Calumet Battery C and also for
the nitrification pilot plant. As shown, some of the
pilot plant trace metal values exceeded those of Battery
C, whereas others were less. This merely reflected the
variability in trace metal concentrations that was
observed for the pilot plant return sludge. This
variability was due to periodic sludge losses through
accidental sludge wastage and high effluent suspended
solids, and sludge additions which were required to
replenish those losses. Thus, as assessment of trace
480
-------
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CALUMET NITKIfKATION PILOT PLANT
FIGURE 13
7.0-
00
3.0-
E
9
c
0.4-
^••i Influent, Average = 0.7 mg/l
'**** Effluent, Average = 0.9 mg/l
13
Weeks
16
JO
Wtekly Variations in Alinitum Coicentration
X
-------
00
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
CALUMET NITRIFICATION PILOT PLANT
FIGURE 14
o.o«
Influent, Average = 0.02 mg/l
Effluent, Average = 0.03 mg/l
0.06'
0.04
o
J:
u
0.02
v\/\
24
Weekly Variations in Chromium Concentration
-------
OF GREATER CHICAGO
CALUMET
T3ACE ;V£7:U ANALYSES & ATOAG2S
(Results Expressed in rag/1 except Hg. Hg ta ug/g)
Zn
Cd
Cu
Cr
Fa
HI
Pb
K
Na
CQ
Mg
Mn
Al
Hg
CALU^iT SATTESY 'C'
2.23
0.070
0.148
0.493
13.8
0.062
0.504
3.95
11.0
43.2
13.4
0.256
4.23
1.34
CAlU$n PILOT PLANT
1.86
0.053
0.135
0.531
14.7
0.037
0.431
3.41
19.4
37.9
13.5
1.121
4.37
2.22
HOTS: A91 Vohas Calculated on G dry weigh? basis.
483
-------
metal accumulation in the return sludge could not be
properly evaluated.
9. Dissolved Oxygen Considerations
The amount of air supplied to the reactor was
determined in great measure by the need to keep the
MLSS in suspension via the bubbling actions of the
compressed air. Thus, although the air input was
measured, as was also the reactor dissolved oxygen,
the values obtained were not reflective of what would
be expected in a full-scale plant.
484
-------
Conclusions
The following conclusions were derived from the results
obtained by operating the Calumet Nitrification Pilot Plant:
1. The Calumet Treatment Plant, with a second-stage
nitrification system, could reasonably be expected
to produce a nitrified effluent with an ammonia
nitrogen residual of less than 2.5 mg/1 under the
following conditions:
influent NH3-N, 10 - 25 mg/1
SRT, at least 10 days
minimum operating temperature, 12 - 15°C
It must be emphasized that the lowest average temperature
of 12QC recorded in the pilot plant aeration tank was
approximately 2 - 3°C higher than that observed in the
full-scale aeration tanks. Therefore, since a lower
second-stage aeration temperature would be expected in
an on-line plant, cold temperature nitrification studies
on the Calumet sewage will be undertaken.
2. The average alkalinity consumption of 5.2 Ibs alkalinity/
Ib NH3-N oxidized that was required in the nitrification
of Calumet Battery C effluent correlates reasonably
well with the theoretical demand of 7.2 Ibs/lb NH3-N
oxidized. Since Battery C effluent supplied this demand
485
-------
without resulting pH depressions through the nitri-
fication unit, it would be expected that future nitri-
fication of Calumet sewage would not entail supple-
mentation of the treatment stream alkalinity. However,
in alkalinity deficient or high ammonia content waste-
waters which are undergoing biological nitrification,
it is expected that alkalinity additions will be required,
3. The preceeding first-stage sludge of the carbonaceous
system apparently reduced influent concentrations of
trace metals to non-inhibitory levels. However, the
effects of trace metals upon nitrification in a single-
stage system, under the conditions listed, are not known.
486
-------
Nitrification at Lemont, Illinois - Extended Aeration
The Lemont Water Reclamation Plant (WRP) treats sewage
primarily from the Village of Lemont, a town of about 5000
located in southwestern Cook County. The plant was designed in
1969 and completed in mid 1972. The schematic (Figure 15) shows
the treatment processes employed at the plant. A brief descrip-
tion of plant facilities is as follows:
Design capacity 1.2 mgd
Maximum flow receiving complete treatment 3.0 mgd
A. Grit and screening
B. Primary settling
Two 45 ft. diameter tanks
Detention time at 1.2 mgd - 4.5 hr.
Surface settling rate - 380
C. Aeration tanks
Two single pass tanks 120 ft by 25 ft, 13.5
depth
Detention time at 1.2 mgd - 12 hr
Diffused aeration with 6000 cfm blower capacity
100% sludge return capacility
D. Final settling tanks
Two 36 ft. diameter center feed tanks
Detention time at 2.4 mgd mixed liquor flow - 3.7 hours
Surface settling rate at 2.4 mgd mixed liquor flow -
600 gal/ft/day
E. Micros trainers
Two 10 ft by 10 ft Zurn microstrainers
Design flow (each) - 1.2 mgd
Maximum flow (each) - 1.7 mgd
Screen size - 23 microns
487
-------
THE METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE J5
LEMONT WATER RECLAMATION PLANT SCHEMATIC DIAGRAM
RAW
SEWAGE
GRIT REMOVAL
AND SCREENING
PRIMARY
SEDIMENTATION
EXTENDED
AERATION
FINAL
SEDIMENTATION
MICROSCREENING
CHLORINATION
EFFLUENT
488
-------
F. Chlorination
Sodium hypochlorite with chlorine contact chamber.
G. Sludge treatment
Gravity sludge thickening tank
Two complete mix digesters with external heat exchangers,
3200 ft3 capacity
489
-------
The aeration facility was designed to utilize the extended
aeration process in order to provide nitrification as well as
BOD and suspended solids removal. The extended aeration process
has worked out rather well at this plant. The final clarifier
effluent ordinarily averages about 5 mg/1 BOD and 10 mg/1
suspended solids. Effluent ammonia generally is less than 0.5
rag/1.
Table 3_ summarizes the operating results for November 1972,
a fairly typical month. Influent ammonia nitrogen averaged
11.1 mg/1 and effluent ammonia nitrogen averaged only 0.2 mg/1,
a reduction of 98 per cent. Effluent nitrate nitrogen increased ac-
cordingly by an average of 12 mg/1. Plant flow averaged 1.26
mgd, resulting in an average aeration tank detention time of
11 hours. The MLSS averaged J460 mg/1 and it's interesting that
the plant has never encountered any serious settling problems.
The BOD loading and F/M ratio were as would be anticipated from
the extended aeration process very low.
The extended aeration process typically has long aeration
times and low sludge wastage rates. Average monthly aeration
tines have varied from 10 hours to 26 hours. Because of low
sludge production, weekly grab samples of the return sludge were
analyzed for metal content to ascertain if any concentration was
occurring. Table 4^ shows the average monthly results from
December 1972 through June 1973. There is to date no evidence
of metal concentration in the sludge.
490
-------
THE METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 3
OPERATING RESULTS OF LEMONT - WRP
NOVEMBER 1972
NH3-N Primary
NH3-H Final
Percent Reduction
N03-N and N02-N Primary
N03-N and N02-N Final
N03-N and N02-N Increase
Flow to Aeration Tanks
Detention Time
BOD Loading
MLSS
F/H
D.O. Final
Temperature Final
S.S. Raw
S.S. Primary
S.S. Secondary
BOD Raw
BOD Primary
BOD Secondary
11.1 mg/1
0.2 mg/1
98%
1.47 mg/1
13.60 mg/1
12.13 mg/1
1.26 mg/1
11 hours
13 Ibs/IOOOft3
3460 mg/1
One Ibs POP
" It MJ iff
8.2 mg/1
54°F
101 mg/1
85 mg/1
10 mg/1
128 mg/1
96 mg/1
5 mg/1
Range of Detention times for November 1972 were 5^ to 24 hours.
491
-------
THE METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 4
METALS IN RETURN SLUDGE OF
DECEMBER 1972 - JUNE 1973
Zn Cd Co Cr Fe Ni Pb
DEC.
JAN.
FEB.
MAR.
APR.
MAY.
JUNE
AVERAGE
1.33 0.01 0.22 0.02 5.6
0.75 0.00 0.16 0.02 3.4
0.53 0.00 0.14 0.01 1.7
0.83 0.01 0.12 0.01 3.1
1.18 0.01 0.24 0.02 5.8
0.79 0.01 0.20 0.01 4.5
0.99 0.00 0.25 0.01 5.4
0.91 0.01 0.19 0.01 4.2
0.00 0.59
0.00 0.36
0.01 0.27
0.02 0.38
0.03 0.62
0.00 0.38
0.01 0.46
0.01 0.42
AH values reported a* mg m«tal p«r gram return sludg* suspondod
• elidi. Data r«pr»s«nts monthly av*rag*s of w*«kly garb samples.
492
-------
Nitrification has been maintained without interruption since
June of 1972. Sewage temperatures at the plant have been as
low as 45°F without any impairment in aiomonia removal. Although
our current interest in single-stage nitrification lies primarily
in systems having shorter detention times, the data from the
Lemont WRP has demonstrated that the process, when operated
at long detention times, can consistently produce a well-nitrified
effluent. As the flow to the plant increases due to expansion
of the sewered population, we will determine what operational
changes may be required to maintain effective nitrification.
493
-------
Summary
As described in the preceding sections, the MSDGC past
pilot plant experiences in achieving nitrification of its
domestic wastewaters has been with the two-stage process. Also,
the District's 50 mgd Salt Creek water reclamation plant which
is currently under construction is designed as a two-stage plant.
However, it should be pointed out that the MSDGC policy toward
nitrification at any future plants or in the expansion of present
plants is still not completely resolved. Currently, the concept
of single-stage nitrification at all the major plants is being
tested on a pilot scale. In particular, a pilot plant currently
under construction at West"Southwest will have a maximum flow
capacity of 26 mgd, (detention time, 5.5 hours) with the return
sludge flow capability of 26 mgd.
494
-------
Nitrification of a Hign Ammonia Content Sludge Supernatant
by Biological Processes
As part of its land reclamation and sludge recycle program,
the MSDGC has been barging anaerobically digested sludge to
Fulton County, Illinois for application to strip-mined lands to
promote row crop production and grazing. Before the digested
sludge is spread on the land, it is held in large holding basins
or lagoons. Since the sludge remains in the lagoons for a signi-
ficant period of time, much compaction of the digested solids
occur and a substantial layer of supernatant, which is relatively
low in suspended solids, is formed. Because of the direct
influence of high nitrogen content on land demand, it was
imperative that the MSDGC develop methods for reducing the ammonia
content of the sludge lagoon supernatant (S.L.S.), since the
ammonia content of the S.L.S. constitutes up to 50% of the total
nitrogen content of the lagooned digested sludge.
Basically, there were two alternatives for reducing the
ammonia content of the S.L.S. Either the S.L.S. could be barged
back to the West-Southwest Treatment Plant in Stickney, Illinois
or the S.L.S. could be treated on site at Fulton County with
the effluent being discharged to the local waterways.
The overall goal of the investigation was to pursue the
second alternative and determine the feasibility of biologically
treating S.L.S. for stream discharge. Because of the small
amount of information available on the biological treatment of
495
-------
a high strength ammonia waste, particularly sludge supernatant,
it was of importance to initially establish the feasibility
of biologically nitrifying S.L.S. Two methods of biological
treatment were evaluated: namely, a conventional activated
sludge or biological slurry system and a system utilizing
partially submerged rotating discs. The use of a rotating
disc system was investigated because of its potentially low
maintenance and operating costs.
Throughout the study, S.L.S. from Fulton County was shipped
periodically by truck to theW-SW Treatment Plant where the
pilot tests were conducted. As can be seen in Table 5_, which
lists the chemical characteristics of the S.L.S. which was used
in the study, S.L.S. is a high strength ammonia waste water
with the NH-j-N averaging 547 mg/1. Since the oxygen required
to biologically oxidize ammonia to nitrates is 4.61bs 02/lb
NH3-N oxidized, the theoretical oxygen demand is considerable
and can be as high as 4050 mg/1 (when 879 mg/1 of NH3-N is
oxidized to nitrates). It. can also be seen in Table 5_ that
there was on the average only about 3.3 Ibs alkalinity per Ib
of NH3~N contained in the S.L.S.
Since the oxidation of NH3-N involves the theoretical
consumption of 1.2 Ibs of alkalinity per Ib of NH3-N oxidized,
the S.L.S. did not contain enough alkalinity to meet the demand.
This was important because the autotrophic bacteria which
oxidize ammonia require a pH of at least 6.5 - 7.0 in order to
496
-------
METROPOLITAN SANITARY DISTRICT
OF GREATER CHICAGO
TABLE 5
CHEMICAL CHARACTERISTICS
OF SLUDGE LAGOON SUPERNATANT
FROM FULTON COUNTY
CHEMICAL PARAMETER AVERAGE RANGE
pH 8.0-8.4
Alkalinity, mg/l 1834 1215-2843
Total Kjeldahl Nitrogen (TKN), mg/l 703 465-975
NH3-N, mg/l 547 292-879
N02-N, mg/l 0.21 0.04-0.86
N03-N, mg/l 0.40 0.26-0.74
Total Solids,mg/l 1190 813-1462
Total Suspended Solids, mg/l 150 52-231
Volatilo Suspended Solids, mg/l 97 39-126
Total BOD 64 28-121
Total COD 753 345-1119
Total P04-P 40.5 23.1-51.1
497
-------
function properly. If the pH goes below 6.5, the rate of
oxidation drops off radically. Therefore, throughout the
study, the pH was controlled in the range of 7.8 - 8.2 with
the addition of sodium carbonate.
The rotating disc pilot system consisted of a semi-circular
fiberglass tank which was divided into four equal volume compartments
The tank was equipped with 2' diameter plastic discs arranged
on a horizontally rotating shaft. The total surface area
provided by the discs was 250 ft2. The volume of the unit was
35 gallons, with the discs submerged 40% of the diameter. Disc
rotational speed was maintained at 3 rpm for the duration of the
study.
The slurry system consisted of a 50-gallon plexi-glas
aeration tank, which was separated into seven compartments to
simulate a plug-flow system, and a 6' high clarifier which
2
provided a maximum surface area of 2.25 ft . Air was supplied
by diffused aeration through porous membranes.
Before the continuous flow operation began, both units
were initially filled with S.L.S. diluted by 50% with tap water.
The bio-mass within each system was allowed approximately two
weeks of acclimation before continuous flow operation began.
The temperature throughout the study in both units was maintained
in the range of 22° - 28°C.
As can be seen in Figures 1£ and 17, which show the
performance of both the rotating disc system and the slurry
498
-------
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 16
PERFORMANCE OF THE SLURRY SYSTEM
v "'
I -
jO 6-
I *"
a—
-DETENTION TIME
INFLUENT NH3-N LOADING
so a 3
•4° JS
30 5^
10 E *ۥ
mx
10 M
.-
1-1
(85) (70)
34567*
T
10
I I I
n ia 13
Weeks of Continuous Flow Operation
-------
en
O
O
METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO
FIGURE 17
PERFORMANCE OF THE ROTATING DISC SYSTEM
14
-S3 10
•"
'I '
.2 *
O 4-
O
0 1-
H
MJ O1
•DETENTION TIME
INFLUENT NH3-N LOADING—i
..jr*!**""**
O.S
0.3
0.2
•O.I
.f ^
a o
E *?
10 11 12 13
Weeks of Continuous Flow Operation
Performance of the Rotating Disc System
-------
system, respectively, the S.L.S. was highly amenable to
biological nitrification. Except for the first two weeks of
operation, both systems performed extremely well through the
progressively higher ammonia loadings applied. The average
effluent NH3-N at the highest loadings for the rotating disc
system and slurry system was 2.5 mg/1 and 2.0 mg/1, respectively.
Except for the first few weeks when some ammonia was stripped
in both units (as determined by a nitrogen balance), the
effluent N03-N and NO2-N generally exceeded the ammonia removed,
which indicated a high amount of nitrification and conversion
of organic nitrogen to NH3-N and subsequent oxidation to N02~N
and N03-N. The overall total Kjeldahl nitrogen removal (TKN)
for both systems at the highest loading was approximately 99%.
Early in the study, there was some inhibition of the NO2-N
oxidation in both systems as the effluent N02-N generally was
much greater than the effluent NO3~N. However, at detention
times of ten days and lower, the effluent NC^-N was generally
less than 1.0 mg/1.
The air flow rate to the slurry system was controlled to
maintain a D.O. of at least 1-2 mg/1 in each of the compartments,
The D.O. in the rotating disc system was at least 2.0 mg/1 in
each compartment, even at the highest ammonia loadings. The
amount of Na;>CO3 required to maintain a pH of 7.8 to 8.2 in the
rotating disc system averaged about 3-4 Ibs of alkalinity
per Ib of NH4-N oxidized, while the slurry system averaged
501
-------
4 -5 Ibs of alkalinity per Ib of NHj-N oxidized.
In the temperature range of the study (2^-28°). it can be
concluded that high rates of ammonia oxidation in S^L.S. can
be achieved by both the slurry and rotating disc system as long
as the pH is properly maintained with Na2CO3. Further work is
being conducted to determine the effects of lower temperatures
on both processes. Also, a better assessment of the effluent
quality in terms of BOD and suspended solids of both systems
at the colder temperatures will likewise be investigated.
502
-------
REFERENCES
1. Sawyer, C.N., and McCarty, P.L. Chemistry for Sanitary
Engineers, Second Edition, McGraw-Hill Book Company.
2. Advanced Waste Treatment and Water Reuse Symposium, Volume
1, Pick Congress Hotel, Chicago, Illinois, February
23 - 24, 1971.
3. State of Illinois the Environmental Protection Agency,
Water Pollution Regulations of Illinois, March, 1972.
4. "Ammonia Removal from Agricultural Runoff and Secondary
Effluents by Selected Ion Exchange", Robert A. Taft
Water Research Center Report TWRC-5.
5. Gulp, R.L., Gulp, G.L., Advanced Wastewater Treatment, Van
Nostrand Reinhold Company, 1971.
6. "Nitrification and Denitrification Facilities," report by
Metcalf & Eddy, Inc. for Federal EPA Technology
Transfer Program, Chicago, Illinois (November 1972).
503
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STORM AND COMBINED SEWER
ABATEMENT TECHNOLOGY
IN THE UNITED STATES
- AN OVERVIEW -
Francis J. Condon, Supervisory Sanitary Engineer
Municipal Pollution Control Division
Environmental Protection Agency
Office of Research and Development
Washington, D.C.
Presented at
Third U.S./Japan Conference on Sewage Treatment Technology
Tokyo, Japan
February 1974
504
-------
*• Introduction
The Office of Research and Development of the U. S. Environmental
Protection Agency is organized so that program responsibility to develop
new technology for treatment and control of water pollution caused by
urban runoff falls within two organizational units. The Municipal
Pollution Control Division of the Washington Headquarters staff is
responsible for planning, coordinating and assessing the program. The
Advanced Waste Treatment Laboratory in Cincinnati, Ohio, is responsible
for implementation. There are, of co,urse, other activities within these
units but this seminar will be limited to urban runoff pollution abatement
technology.
The following are the principal sources of runoff induced pollution
as viewed in our program activities: combined sewer (domestic sewage
and runoff) overflows, sewered storm water discharges, sanitary sewers
surcharged by infiltration, treatment works or pump station bypass and
urban non-point or overland runoff.
Given these sources it follows that the specific causes are precipita-
tion and snow melt resulting in hydraulic overload relief of combined waste-
water collection and transport networks, pollutants flushed from urban
surfaces and bypass of excess wastewater flows at treatment facilities
to prevent process upset.
When the causes are considered in this context, it is evident that
remedial solutions must include elements of urban hydrology as well as
sanitary engineering. The superimposing of urban hydrology on the usual
sanitary engineering solution methods broadens the scope of problem
definition and abatement approach. Considering the situation in such a
505
-------
manner enters into the realm of metropolitan water balance systems or the
total system concept.
Consideration of the total system in problem definition and alternate
solution schemes is somewhat new to the practicing sanitary engineer in the
United States who traditionally views waste water treatment as the principal
means of water pollution abatement. Treatment of foul water will always be
necessary but improved technology development and application in prevention,
reduction and control of hydraulic and pollutant factors must be given high
priority when addressing storm and combined sewer overflow pollution sources.
Figure 1 is a schematic display of the total metropolitan hydrologic
system which must be examined in developing data and applying technology for
urban water quality improvement. It is illustrative of the scope in cause
and effected uses which should be considered in metropolitan runoff pollution.
Figure 1 may be used for outlining areas for which water quality and
quantity data must be obtained to assess relative significance or as a guide
to where applied research will have the most effect.
For example, the conditions of the urban land surface effects the quality
and quantity of: direct runoff (non-point), storm drainage discharge and,
where interconnected in combined systems, the normal domestic sewage flows.
Therefore, as a first cut in prevention one would evaluate the possibilities
and effectiveness of manipulating urban land surfaces in reducing water
pollution.
The Figure also serves as an example of the need to apply the system
concept in the analysis, planning and implementation of a Research,
Development, Demonstration Program.
506
-------
ATMOSPHERE
PRECIPITATION
EVAPOTRANSPI RATION
cn
o
<
<
£
o
tc
\
URBAN LAND SURFACE
MANIPULATED
DIRECT
RUNOFF
FLOW
AUGMENTATION
INDUSTRIAL
WATER
SURFACE WATER
MANIPULATED
ZONE OF
AERATION
t 1
J
H
CAPIl
R
.LARY
SE
SPRING
SEEPAGE
RECHARGE
WELLS
STORM
DRAINS
WASTE-
WATER
SEWERAGE
inf
eltratio i
ZONE OF SATURATION
DEEP INTRUSION
SURFACE
OUTFLOW
EFFLUENT
EXPORTED
WATER
GROUNDWATER
OUTFLOW
X INTERCONNECTED IN
COMBINED SYSTEMS
URBAN HYDROLOGIC SYSTEM
(ADAPTED FROM: "SUMMARY OF THE HYDROLOGICAL SITUXVTION IN LONG ISLAND. N.Y.. AS A GUIDE TO
WATER MANAGEMENT ALTERNATIVES". BY O.L. FRANKE AND N.E. MeCLYMONDS. U.S.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 627F. 1972)
c
-------
This last point is of importance. The large majority of research and
development efforts and resources in the United States, and apparently other
Nations of the world, have been devoted to the development of tools for the
treatment of wastewaters. Relatively little effort has gone into overall
problem solutions which include prevention and control. Within our program
attempts are being made to change the thrust from tool development to storm
and combined sewer problem solution development. That is, we hope to complete
preliminary National field measurement programs that when coupled with
performance data from categories of tools, i.e., liquid-solid separation,
flow control, rate attenuation, etc., will provide design criteria as
dictated by requirements of performance or by desired receiving water quality.
II. Problem Description
In the paper entitled, "Municipal Pollution Control Technology in the
United States of America" presented in Tokyo by Mr. Frank M. Middleton during
the 1971 Conference, it was noted that the single dissimilarity between the
municipal wastewater treatment programs of Japan and the United States was
the trend in Japan of continuing to build combined sewer systems. In
comparison, current construction in the United States is primarily separate
systems.
There is evidence of some change beginning to take place in the United
States away from the trend of constructing separate systems.
In cities where existing collection networks have portions which are
combined, consideration is now being given to continuing constructing
combined sewers as the collection network is expanded. The pollution loads
generated in urban runoff and the possible future need to reduce this source
is the motivating force for the change in trend.
508
-------
An example is the recommendations from the recent comprehensive report
of the Department of Public Works of San Francisco. This exhaustive
investigation determined that to attain the desired water quality in San
Francisco Bay, it would be necessary to treat a large portion of the urban
storm water runoff. Therefore, one of the principal recommendations of the
report is to continue to construct combined sewers predicted on the control
and treatment of wet weather flows.
To gain a perspective of the problem in the United States a brief
summary of the physical and pollutional aspects of the storm and combined
sewer discharges will be given. Tables 1 and 2 give the magnitude with
respect to population distribution and length of sewers.
In the combined interceptor sewers the ratio of wet-weather to dry-
weather capacity ranges from 1:1 to 8:1. The median ratio is 4:1. This,
however, is somewhat misleading in that the rain events over the urban areas
are .usually of the cell patterns and short, intense precipitation in a
catchment area will cause overflow at one interception point while unused
capacity is available in other portions of the system.
Several of our projects have documented that rainfall intensities as
low as 0.01 in/hr (0.025 cm/hr) cause overflow from combined sewers. Further,
common rainfall intensities of 1.0 in/hr (2.5 cm/hr) will cause flow rates
of 50 to 100 times the dry-weather flow at the interception point.
The incidence of overflow events for each relief point is about 30 per
year. Consideration of an entire metropolitan area, however, yields a range
of 60 to 100 events per year for the entire combined collection network. The
average duration of overflow is about 5 hours. In storm sewer discharges the
average number of events per year is 95 with an average duration of 7 hours.
509
-------
Table 1
Number, Population and Area of U.S. Communities
Served by Combined Sewers
Population
Groups
50
25
10
5
1
1
over
,001 -
,001 -
,001 -
,001 -
,001 -
,00 and
104
100,000
50,000
25,000
10,000
5,000
less
Total
U.S.
1
1
6
9
132
201
432
,134
,394
,613
,874
Population
Number (in 1 ,000 'si
Served by Served by
Cmb. Sewers Cmb. Sewers
75
86
119
203
227
458
161
26
3
2
1
,261
,854
,385
,865
911
874
86
Area
) (in 1,000's)
Served by
Cmb. Sewers
Acres
1,423 -
472 -
313 -
337 -
214 -
235 -
35 -
Ha
576
191
126
136
867
955
142
.7
.5
19,780
1,329
36,236
3,029 - 1
Of the total sewered population in the United States approximately 29
percent is served by combined sewers.
The breakdown in round figures is: unsewered 74 million, separate
sanitary 90 million, combined sewers 36 million.
Separate
Sanitary
Table 2
Combined
Sewers
Separate
Storm
Mi 1es Km
53,801 86,566
Miles Km
56,132 90,316
Miles Km
21,571 34,708
510
-------
(Network = 120 events)
There are 14,200 plus combined sewer relief points and an estimated 700
storm sewer discharge points. In the combined portion 72% have an interval
diameter of 24 inches (61 cm) or less. There are 10,000 plus regulators in
the combined networks.
Another factor to be considered in examing the physical characteristics
of combined sewer systems is that there are many cross overs between separate
sanitary and combined networks which are unrecorded and that many storm
systems are laid at shallow depths above the separate sanitary lines with
frequent exfiltration from the storm sewers and infiltration into the
separate sanitary sewers. Such infiltration and illegal inflow connections
result in many miles of sewers which are identified as separate to be, in
fact, acting as combined sewers.
When determining the receiving water pollution loading from combined
sewer overflows, several considerations not normally applied to dry-weather
domestic flows must be taken into account.
A summary is as follows:
A. Both strength and total mass emission of pollutants on an event basis
be considered in determining receiving water degradation potential.
B. The characteristics and concentrations of the polluting parameters
change with rate (cfs-1/sec), time from start of discharge and real
time of occurrence.
C. The rate of polluting parameter strength decrease is less than the
rate of hydraulic or flow increase, therefore, the total emission
of pollutants increases as the overflow intensity increases.
511
-------
D. There is, under the more common conditions, little dilution of the
slug load in the receiving water during the initial critical time
period. This includes flowing streams as well as lakes, bays and
estuaries.
E. In flowing streams dissolved oxygen deficits are usually more severe
at greater distances downstream of the overflow point source than the
distance and severity during normal treatment works operation. This
is caused by the slug load reaction time, the decrease in reaeration
rate due to increase volume in the stream, and increased flow rate.
F. The oxygen demanding characteristics of combined sewage cannot be
quantified in the same manner as dry weather sewage. For example,
the heavy metals from the street flush portion inhibit the micro-
biological action in the BOD analysis. Therefore, the 600$ reading
is not a valid indicator of oxygen demand potential in combined sewer
overflows. Additionally, oxidation of the heavy metals, which can
occur at a high rate, is masked in the standard BOD analysis.
G. There is greater differences in the vertical distribution of
pollutants in overflow relief flows than in normal dry-weather flow.
Sampling procedures are more critical in accurate determination of
pollution loads.
These observations apply to storm water discharges as well.
Tables 3 and 4 indicating pollutant concentration and loads for combined
and storm sewage discharges are given for comparative purposes.
512
-------
Table 3
Comparison of Quality (Strength) of Combined Wastewater Overflows
Type of
Wastewater
and City
Raw Sanitary Flow
Primary Effluent
Secondary Effluent
Combined Sewer Overflows
Atlanta, Ga.
Berkeley, Calif.
Brooklyn, N.Y.
Bucyrus, Ohio
Cincinnati , Ohio
Des Moines, Iowa
Detroit, Michigan
Kenosha, Wisconsin
Milwaukee, Wisconsin
Racine, Wisconsin
Sacramento, Calif.
San Francisco, Calif.
Washington, D.C.
BOD,
mg/T
Ave.
200
135
25
100
60
180
120
200
115
153
129
55
119
165
49
71
COD
mg/1
Ave.
500
330
55
.
200
-
400
250
-
115
464
177
-
238
155
382
SS
mg/1
Ave.
200
80
15
—
100
1,051
470
1,100
295
274
458
244
434
125
68
622
Total
Col i form
MPN/100 ml.
5x10?
2x10'
1x1 (T
IxlO7
-
- 7
1x10
-
-
~ g
2x1 Ob
-
^A.Ug
3x1 06
3x10
Table 4
Comparison of Quality (Strength) of Storm Water Discharges
City
Ann Arbor, Michigan
Des Moines, Iowa
Durham, N.C.
Los Angeles, Calif.
Madison, Wisconsin
New Orleans, La.
Sacramento, Calif.
Tulsa, Oklahoma
Washington, D.C.
BOD.
Ave?
28
36
32
9.4
-
12
106
11
19
COD
Ave.
.
-
224
-
-
-
58
85
335
SS
Ave.
2,080
505
-
1,013
81
26
71
247
1,697
Total
MPN/100 ml
_
-
3x105
-
~c.
1x10*
8.10?
1x1 OJ|
6x1 0D
513
-------
For comparison purposes the following generalizations with respect to
pollution loadings can be made although wide variations can exist at specific
locations.
A. For any given collection system the raw domestic sewage which is
carried out of the combined sewers by excess flows is about 5 to 7
percent of the total dry weather flow on an annual basis. With
respect to time, the accumulated overflow events total about 4% or
14 1/2 days per year.
B. On an annual basis the pounds of BOD5 discharged in combined sewer
overflows is approximately equal to the pounds discharged from a
secondary treatment plant serving the combined collection area.
C. On an event basis the organic loads placed on the receiving water
during combined sewer overflow are 8 to 12 times the secondary
treatment plant effluent load.
D. Urban runoff is similar to dilute industrial wastewater in many
respects. Calculations indicate that a moderate to heavy storm over
an urban area will wash more oxygen demanding load into the receiving
water than the same area's raw sanitary sewage during the same period
of time.
The impact of storm generated pollution on receiving waters is difficult
to quantify with precision. The relative significance of various runoff
pollution sources in a reach of water requires a long period of sampling
under a sufficient range of the primary variables.
However, it does appear the myth of dilution can be put to rest. The
high frequency, low intensity storms are the greatest offenders. The runoff
volume is low so that with respect to the receiving water volume there is
514
-------
little percent change. But the pollutant concentrations are so high that
significant levels of change are noted in the receiving water.
For example, rainfall intensities up to 0.4 in. (10 cm.) per hour
account for 98 of the average 120 runoff events per year but only 32 percent
of the total volume of runoff. Yet these low intensity events account for
over 85% of the pollutant mass emission.
Therefore, if there is a dilution factor it occurs only in the less
frequent long duration, constant precipitation rate storms.
This is a brief outline of the extent, cause, source and incidence of
the stormwater runoff problem. The one important and unanswered question is:
What ranking value iwth respect to cost effectiveness will we give the problem
relative to other sources of water pollution, e.g., industrial or municipal
treatment works? This of course would assign the priority -of remedial
construction funding. Attempts to resolve this question are currently
underway.
III. Strategy for Research and Development
The Federal Water Pollution Control Act Amendments of 1972 contains
sections which deal with technology research and development, urban runoff,
consideration in developing area wide plans, and permit conditions for
combined sewer overflows. There are requirements for quantifying the
pollution of stormwater runoff. There is, however, a large gap in current
construction funds for remedial hardware. The relative significance of the
problem must be determined with a high degree of certainty before immediate
remedial funding allocations can be justified.
Future corrective action, however, cannot be denied. As the conventional
pollution sources of municipal treatment works and industrial plants are
515
-------
brought under control, the significance of combined and stormwater discharges
will increase. In many cases, the receiving water quality standards will not
be attained until these sources are reduced or eliminated.
With the strong possibility of near future construction expenditures, it
would be well to review the strategy and tools developed for abatement.
The formulation of the program strategy for research and development
activities was influenced by four elements. These can be identified from
Figure 2. They are: (1) the requirements of the water pollution control
act, (2) the existing conditions, (3) the level of technology practiced along
with the State-of-the-Art of the technology, and (4) the funding available.
Initially, the strategy of the program, which began eight years ago, was
to carry out full-scale demonstration projects of new and improved abatement
tools wherein design, performance, benefits and cost data would be developed.
The goals of this program have been partially realized. Over the first few
years of the program emphasis was changed to other areas of environmental
pollution and fewer full-scale projects could be supported than had been
originally planned. As feedback from demonstrations was obtained, the thrust
of the program changed, as mentioned in the Introduction, to methods of
problem solution.
However, there have been several pilot and bench top projects completed,
along with some full-scale demonstrations in development of novel or improved
tools.
IV. Methods of Abatement
A brief summary of selected projects grouped by principal methods as
shown in Figure 2 will be given. It should be noted that many individual
projects cut across the category divisions and may incorporate two or more
516
-------
Figure 2
Storm and Combined Sewer
Pollution Control Program
517
-------
methods. However, for purpose of presentation, every project has been
assigned to one remedial method category.
A. Prevention or Input Management
Fourteen projects have been completed in the category. The
projects include: (1) quantity reduction (infiltration control),
(2) quality improvement (deicing methods), (3) runoff rate atten-
uation (porous pavements), and (4) improved materials (electro-
magnetic sub-surface profiling).
The rational of the objectives in this remedial method grouping
is best illustrated by referring to Figure 1. As mentioned, urban
land surface conditions effect the quality and quantity of non-point
runoff, storm discharges and combined sewer overflows. And, as
importantly, they effect the time of concentration. Therefore, any
manipulation or improvement of the urban surface conditions which
would reduce the volume of runoff or increase time of concentration
or improve the runoff quality is considered a prevention method.
An example of work in this area is the feasibility study
entitled "Investigation of Porous Pavements for Urban Runoff Control".
Various methods of construction to obtain permeable surface covering
were examined in the investigation. The material which indicated
the highest possibility of success is porous asphaltic concrete
roadways.
The reason for selecting permeable street surfaces is that the
urban street or roadway acts as a collector, a transport pathway and
generator of pollutants. Its use, physical characteristics, location
and method of construction makes a transition or hinge point between
519
-------
air, land and water pollution. Therefore, a likely pollution control
attack area is improvement in design, method of construction and
operation.
Viewed in this fashion there are many benefits. For example, if
a permeable surface is successful, part of the runoff will enter the
ground, reducing the volume and recharging urban ground waters. Part
will flow through the base material and thus be rough filtered and
the time of concentration will be increased. Therefore, we may
realize both prevention and control at a critical point in the
hydrologic system.
Based on the feasibility investigation there are two current
demonstration projects, recently initiated, in which design and
performance data are to be gathered on porous asphaltic parking lots
and low design residential streets. Other projects are being
considered in demonstration of improved curb and gutter design to
facilitate street cleaning and swirl separators at inlets, in place
of catch basins, to remove particulates (the majority of surface
runoff pollutants) by concentrating them in a relatively small
percentage of the runoff volume followed with storage and treatment.
B. Control or Flow Management
Ten projects have been completed in this method of abatement.
This is a somewhat misleading indication of the effort which has gone
into the category. Many of the effluent management or treatment
projects have significant work in control of flows. The projects
listed here are totally dedicated to flow management. The projects
include: (1) flow regulation (a manual of practice), (2) flow routing
520
-------
(a dispatching system), (3) storage (deep tunnels), and (4)
instrumentation (maximizing in-system capacity).
A capability profile will be given on the deep tunnel concept,
therefore, an example in this category will not be discussed. However,
a few words on the overall rational are in order.
Flow control in combined sewer pollution abatement appears to
be the most cost effective approach providing, of course, there is
adequate dry weather treatment facilities. In the United States
very few communities with combined sewers, in whole or in part, know
how their collection-transport systems react to runoff events. In
all of our problem definition and demonstration projects it has been
found that either through flow routing, improved regulation or in-
system storage, the rate of flow at a given relief point could be
controlled to some degree thereby reducing the volume and incidence
of raw sewage discharge. As an added benefit, the efficiency of the
treatment works can be markedly improved.
Our conclusion is that a well designed sewer monitoring and
sampling program integrated with in-depth rainfall and runoff
monitoring to obtain accurate basic data for use in the Storm Water
Management Model will return many times over the original investment
when an abatement scheme is to be chosen and construction started.
C. Treatment Methods or Effluent Management
The first groupings in this category are: (1) dual or multi use
facilities, (2) satellite plants or treatment at outfall points, and
(3) in-stream treatment.
521
-------
Each of these groupings could be broken down into similar
specific processes such as: physical, physio-chemical, bio-physical,
bio-chemical and chemical.
The total of thirteen projects have been completed in this
category. A brief summary of successful treatment modes developed
to pilot stage is as follows:
1. Physical:
(a) sedimentation and flow control (combined sewers)
(b) screening, dissolved air flotation (combined sewers)
(c) deep bed, dual media filtration (storm runoff and combined
sewers)
(d) swirl separation (combined sewers and storm runoff)
(e) microstraining and disinfection (combined sewers)
2. Physio-Chemical:
(a) powdered activated carbon (combined sewers)
(b) coagulation - flocculation aids (combined sewers)
Item (b) is in conjunction with physical mode projects in
(1) above.
3. Bio-Physical:
(a) detention with bio action and physical separation, includes
dual use (combined sewers)
4. Biological:
(a) dual use contact stabilization (combined sewers)
(b) dual use trickling filter (combined sewers)
5. & 6. Bio-Chemical and Chemical Modes have not been evaluated.
522
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Although bio oxidation through storage lagoon aeration are
among on-going projects, the operating data are not available. In
the 5 and 6 Subgroupings, the completed work is principally in methods
of disinfectant generation which have been modified to suit combined
sewer overflow treatment. Two methods for generating sodium
hypochlorite and one for chlorine dioxide have been developed.
Abstracts of completed projects are in the Appendix. A
capability profile will be given on a dual use, biological
demonstration facility.
As a final observation in this category, it appears that dual
use, in a physio-chemical or bio-physical mode of operation, is the
most cost effective treatment scheme and that in-stream treatment is
a poor risk for effectiveness.
D. Combinations or System Approach
In this category, the prevention, control and treatment methods
are brought together and mathematical modeling is added to develop
solution schemes, make cost effectiveness comparisons and examine
alternate solution methods. It is here where the total system
approach is developed. In all, six projects have been completed in
this category.
Our primary vehicle in approaching the total system concept is
the Storm Water Management Model. A capability profile will be given
on this project.
The remaining completed projects in this category are principally
engineering investigations of urban areas which develop methods of
examining alternate schemes and cost effectiveness comparisons. From
523
-------
these, we hope to arrive at a uniform means of: (1) predicting
pollution loads, (2) gathering and presenting evaluation data, and
(3) arriving at the true cost and receiving water benefits.
V. Capability Profile: Effluent Management
A. Dual Use Biological Treatment
The concept of this project is to modify an existing activated
sludge process in such a manner so as to provide contact stabilization
for excess wet weather flows which are being bypassed at the plant to
prevent process upset. The following discussion and tables are
extracted from a paper by Charles A.Hansen and Robert W. Agnew of
Rexnord Company on an EPA demonstration project sponsored by the
Municipal Pollution Control Division.
Before construction of the demonstration system, the treatment
train was grit removal, primary sedimentation, aeration (activated
sludge), sludge mixing for anaerobic digestion, sludge thickening,
clarification of the mixed liquor and chlorination. The original
plant treatment capacity was 23 MGD (1007 I/sec-). The interceptor
size at the plant wet well is 72 in. (183 cm.) with a 50 MGD
(2190 I/sec) capacity. Bypasses of excess flows were frequent.
A maximum design flow of 20 MGD (876 I/sec.) was selected for
the demonstration project. The total wet weather capacity then being
43 MGD (1890 I/sec.).
The demonstration system was designed for integration with the
original facilities. A constant portion of activated sludge from the
dry-weather operation is stored by balancing the biosolids reservoir
inflow and outflow. The stored material is used as a source of
524
-------
Figure 3
Kenosha, Wisconsin
Contact Stabilization Demonstration
Flow Diagram
o
3
CT
•o
O)
X
Wet
Well
Excess Flow
Wet Weather
Grit Basin
Stabilized
Sludge
Biosolids Reservior
Stabilization Basin
Normal Operation
Primary Tanks
Contact Tanks
Aeration Tanks
Sludge Transfer
Digesters
Blowers and
Sludge Thickener
Pump
Building
Chlorine
Contact
-> Effluent
525
-------
biological solids in the contact stabilization treatment of the
excess flows. This mode of treatment is also identified as physical
adsorption, biosorption and sludge reaeration. All refer to a
modification of the activated sludge process*
Modification and additions to the existing plant hardware are
as follows:
1. Installation of a 20 MGD (876 I/sec.) gas driven pump in the
existing wet well and diversion chamber. The pump delivers the
wet weather excess flow to the demonstration system and can be
used as standby for dry weather operation.
2. An unused mixing basin was converted to a grit tank. The tank
is 56.5 ft. (17.23 m) long, 225 ft. (68.62 m) wide and has a
mean depth of 9 ft. (2.74 m). At a flow of 20 MGD (876 I/sec.)
the horizontal velocity is less than 0.2 fps (0.06 m/sec.).
3. Construction of a contact and stabilization tank in one structure
divided by concrete walls into four smaller tanks. The contact
section was designed to handle a maximum raw flow of 20 MGD
(876 I/sec.) and a stabilized sludge flow of 5 MGD (219 I/sec.)
for a 15 minute contact period. The contact section can be
divided into two smaller units of different volumes to allow
experiments in varying the contact time while the total flow
remains constant. This also provides like raw flow pollutant
characteristics while comparing contact time effectiveness. One
unit of the contact tank has a volume of 164,000 gal. (620,740 1) ,
the second 80,500 gal. (304,792 1). Therefore, by using the units
either separately or simultaneously three effective volumes can
526
-------
be made available. The tank has a sidewall depth of 17.5 ft.
(5.34 m). Aeration is through a fixed air dispenser system along
the bottom of one wall in each unit. The system can deliver up
to 3,750 scfm (106.12 cu m/min.).
4. Following the contact section of the tank and divided by a
concrete wall is the stabilization basin (biosolids reservoir
section). This section is also divided into two parts so that
various stabilization times may be evaluated. Both units of this
section are 30 ft. (9.15 m) wide, 96 ft. (29.28 m) long and 17.5
ft. (5.34 m) deep. Aeration is by eight 50 hp (37.3 kw)
floating mechanical surface aerators. The arrangement allows
for stabilization times of up to seven days.
5. Construction of a new clarifier for use in both dry and wet
weather flows. The design surface overflow rate (SOR) is
1300 gpd/sq. ft. (0.047 lps/m2) resulted in a 140 ft. (42.7 m)
diameter, peripheral feed effluent clarifier. The surface area
is 15,400 sq. ft. (1420.6 sq. m) and a volume of 1.4 million
gal. (5.23 million 1). During wet weather operation the
clarifier is isolated from the dry weather plant.
6. The necessary piping, pumps, valves and instrumentation are
included.
The system is kept in readiness by maintaining a biosolids
reservoir fed by the dry weather plant operation.
When excess flows occur the raw flow pump automatically starts
and delivers the flows via the grit chamber to the contact section
where stabilized sludge from the biosolids reservoir is proportioned
527
-------
in. At the same time the pump for transferring sludge from the new
clarifier to the stabilization section is put into operation. The
air blower for the contact tank is also started at this time. Once
the demonstration system is operating the sludge detention time
in the stabilization tank is short. The time being dependent on the
flow rate entering the dry weather plant and the rate of transfer to
the contact section. The sludge flow rate to the contact section is
a function of the rate of raw combined sewage flow through the
contact tank. Meanwhile, at the new clarifier the flow from the dry
weather plant is diverted to the original clarifiers and the return
sludge line to the dry weather plant is shut, the return sludge line
from the new clarifier to the stabilization tank is opened. The
clarifier then receives the feed from the contact-stabilization tank.
The necessary synchronism of blower and chlorine feed increase is
manually started.
When the high flow condition has subsided the wet weather system
is manually taken out of service at the main control board. After
shutting down the wet weather mode of operation, the start-up
procedures are automatically reversed and the plant returns to normal
dry weather operation. The grit and contact tanks are then emptied
and the system made ready for the next event.
528
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en
IX)
UD
Table 5
Summary of Operating Conditions
Variable
Gal treated
Average flow rate
Duration of run
Return sludge
MLSS
Contact time
Reaeration time
Unit of Measure
mil gal
mgd
hours
% of raw flow
mg/1
minutes
hours
Stabilization time days
F/M
Stabilization
tank turnovers
Clarifier SOR
Clarifier
detention time
Clarifier
turnovers
Ib BOD/day
Ib MLSS
gpd/ft2
hours
Range
1.789-7.558
13.3-19.4
2.7-11.0
10-55'
975-5370
12.1-19.6
1.0-7.3
0.5-15
0.64-5.3
0.53-6.8
864-1257
1.3-1.85
1.7-8.2
Mean Metric
4.007 15.17X106L
16.6 727.2 L/sec.
5.8
37
3060
15.5
2.7
4.4 1.99 Kg
2.7
2.9
1078 305 cu m/min/ha
1.46
3.9
-------
Table 5
1972 Removal Summaries 23 Events, 92 Mil Gal. Treated
Arithmetic Mean Weiqhted Mean
Total Solids
T.V.S.
Suspended solids
s.v.s.
Total 300
Dissolved BOD
Total organic carbon
Dissolved organic carbon
Total Kjeldahl as M
Total P04 as P
Total coliform count/ml
Fecal cell form count/ml
Raw flow sample taken after grit removal.
2
Final sample taken prior to chlor(nation.
Raw1
706
270
325
126
115
27.6
121
25.4
1?,9
5.1
Raw
34,786
2,308
Final2
471
143
24.7
13.9
18.6
8.5
24.0
16.9
6.7
2.7
Geometric
Raw1
704
270
314
121
102
24.1
113
21.8
11.0
4.8
Mean
Final2
455
140
26.4
15.2
17.8
7.6
22.8
1 5 . 11
5.5
2.4
Fi nal 2
2,883
374
530
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The total construction cost for the system was $1.1 million. The
capital cost breaks down to $917 per acre (.405 ha) served or $55,000 per
MGD (43.808 I/sec.). Operating and maintenance cost cannot be determined
because all of the runs have been of experimental nature and no standard
procedure has been set. Future plants can be constructed at lower cost
because provisions will not be necessary for operating at different levels
for each variable.
The principal conclusions are:
1. The use of contact stabilization in treating excess flows at
aerated activated sludge plants is feasible and reliable.
2. Removal efficiencies of SS - 90%, BOD5 - 80% and TOC - 79%
can easily be maintained for excess flows.
3. Improved dry weather operation and performance can be realized
at the existing plant.
4. The capital cost in dollars per unit of capacity can be lowered
upon development of optimum variable operating ranges.
VI. Capability Profile: Storm Water Management Model
The Storm Water Management Model and other associated work completed and
on-going in mathematical modeling are intended as prime tools for use in
applying the total system concept in selecting alternatives for water
pollution control. Work is continuing on providing additional capability and
refinement of the SWMM and development of a family of models of varying
degrees of sophistication for use by planners, engineers and decision makers.
This profile is extracted, with quotations, from a paper entitled "A Model
for Assessing Impact of Stormwater Runoff and Combined Sewer Overflows and
Evaluating Abatement Alternatives: by Harry C. Torno, U.S. EPA., Municipal
531
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Pollution Control Division (RD-678), Washington, D.C. 20460. Copies of the
model program may be obtained by sending a blank 9-track 1600 hpi computer
tape to Mr. Torno and requesting the SWMM program. Program documentation
will be furnished or is available separately.
A users group has been established to exchange information and experience
on model applications and to act as a focal point for improvements. Further
details are available from Mr. Torno.
The entire SWMM is large. There are over 10,000 FORTRAN statements and
it requires a large computer for reasonable execution. For example, an IBM
360/65 with at least 512K bytes of core storage is required. Some users have
executed the program on smaller computers (IBM 1130) by overlaying, reducing
size and number of COMMON areas and by using portions of the program.
Using the rainfall (hyetograph) and system (catchment, conveyance,
storage/treatment and receiving water) characteristics as inputs the SWMM
determines quality and quantity of runoff, routes the runoff through a
combined (or separate system) with specified storage and treatment
facilities and operating policies, and thence into the receiving water, where
impacts are identified. The output of the model consists of tables, hydro-
graphs and pollutographs of BOD, suspended solids, dissolved oxygen and
coliform. These can be displayed for selected points within the system as
well as in the receiving waters.
The SWMM consists of 5 blocks, or groups of subroutines. They are:
A. EXECUTIVE Block - Provides control and service functions. All inter-
facing between the four computational blocks takes place through this
block. The block includes a subroutine called COMBINE (a network
aggretation routine) which allows collection of two or more output
532
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data sets, and allows combination of different data sets and manholes
into a single data set with one manhole. This aids in modeling of
large geographical areas.
B. RUNOFF Block - Computes the storm water runoff and its associated
pollution loadings for a given storm for each subcatchment and
stores the results in the form of hydrographs and pollutographs at
the inlets to the main sewer system. Overland flow simulation is
accomplished by a storage routing method using Manning's equation
and the continuity equation. Overland flow does not begin until
depression storages are full. Infiltration on previous areas is
computed by Horton's exponential function, and is subtracted from
water depth existing on the sub-catchment. Gutter flows are treated
as a succession of steady-state flows, with outing accomplished using
Manning's equation and the continuity equation. To use this block,
the user must input the rainfall hyetograph and a discretization of
the drainage basin into sub-basins of constant land from character-
istics. The location and chara-teristics of the gutters and pipes
also have to be described. In addition, the user must input street
cleaning frequency and catchbasin data as well as the land use and
other features of the different areas of the basin.
C. TRANSPORT Block - Routes flows through the sewer system. Prestorm
conditions in the sewers are set up by computing dry-weather flow and
infiltration and distributing them throughout the conveyance system.
The Transport Block then routes the storm runoff (as determined by
the RUNOFF Block), the dry weather flow (DWF), and the water that has
infiltrated into the system through the main sewer pipes, and through
a maximum of two optional "internal" storage tanks.
533
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The routing scheme is based on a finite-difference solution of
the St. Venant equations, in which normalized values of the flow and
conduit cross-sectional area are used. When a pipe is flowing full
and inflow exceeds outflow, the excess (surcharge) is stored at the
upstream manhole. The flows are routed to a maximum of five outlet
points. This block requires that the sewer system be discretized
into pipe segments of constant size, slope, and type jointed by
either manholes, control structures such as flow dividers, or
"internal" storage tanks. An "internal" storage tank is described
by its size, shape, outlet device, and unit cost. The outlet device
can be either a pump specified to go on or off at a specified tank
depth, a weir, or an orifice. The outlet device is used to specify
the operation policy of the storage tank.
The DWF and quantity entering the sewer system are calculated
by inputting to the model such parameters as daily and hourly
pollution correction factors, land use and population of the
subareas, and average market value of the dwellings in a subarea.
If more exact data is available such as average BOD of flows, this
can be used in place of some of the other data.
Infiltration is calculated by estimates of base dry weather
infiltration and groundwater and rainwater infiltration, and such
parameters as average joint distance. The use of the subroutines
calculating DWF quality and quantity and infiltration is optional.
D. STORAGE Block - Simulates the changes in the hydrographs and
pollutographs of the sewage as the sewage flows through one optional
special wastewater treatment facility. The facility has to be
534
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located at one of the outfalls specified in the Transport Block.
The treatment process is chosen by the user to consist of a sequence
chosen from the following unit processes: "external" storage (same
as "internal" storage except that it is located adjacent to an outlet
of the sewer system), bar racks, fine screens, dissolved air
flotation, sedimentation tanks, microstrainers, high rate filters,
effluent screens, swirl concentrators and chlorinators and other
chemical dispensers. The user can specify the sizes of the treatment
processes or else can specify that the model is to select the sizes
of the processes (except for "external" storage) such that a certain
user-selected percentage of the peak flow receives treatment. The
Storage Block also has the capability of calculating the capital,
land, and operation and maintenance costs of the treatment processes
chosen. The user has the option of either specifying the unit costs
or using default values provided by the simulation model. The
calculations in this block are based on the continuity equation.
E. RECEIVING WATER Block - Takes output from TRANSPORT or STORAGE and
computes the impact of the discharges upon the quality of the
receiving water. The receiving body of water is discretized by the
user to consist of a network of nodes connected by channels. An
option in the program allows two parallel channels to be used between
junctions, to aid in simulating receiving bodies such as marshes.
Each channel is of constant surface and cross-sectional area.
Boundary conditions can be specified as a weir (outfall from a lake)
or some tidal condition. The structure of the SWMM is schematically
depicted in Figure 4.
535
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INFILTRATION
3
DRY WEATHER FLOW
EXTERNAL
STORAGE
TREATMENT
TREATMENT
COST
±
RECEIVING WATER
FIG. 4
SWMM Structure
The model was originally developed to consider only storm a no
combined sewer abatement alternatives. It has become apparent that
the wet weather flows cannot be considered separately from the
conveyance and treatment of sanitary sewage. This is brought into
focus when considering the effects of various discharges (municipal
treatment works, combined sewer overflows and industrial discharges)
upon receiving waters. Modifications are now being made to include
dry weather treatment facilities in the SWMM and to increase the
capabilities for such pollutants as nitrogen, phosphorous, oil and
grease.
Model verification and refinement has been accomplished in
application to measured flow and analyzed water quality for catchments
in San Francisco, Cincinnati, Washington, Philadelphia, and
Lancaster, Pennsylvania.
Access to digital computers for execution of complex mathematical
models is becoming more available to the engineer and such tools
should be used in examining abatement alternatives to water pollution
abatement.
536
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VII. Summary
In the next three years there will be several EPA demonstration projects
in which the evaluation phase will be completed. These projects were
initiated as long as five years ago. Therefore, for the immediate future
the program plan may best be described as an assimulation period. The data
obtained from the full-scale facilities will be incorporated into data
matrices relating to cost effectiveness for use in developing problem solution
methods. Consequently, the start-up of full-scale demonstrations will be
curtailed.
The following tables are based on the data collected for a report now
in preparation*entitled "Urban Storm Water Management and Technology: An
Assessment".
The tables are skeleton outlines and summaries of the cost and performance
information collected which is pertinent to this paper.
Table 7
Estimated Costs of Sewer Separation
Estimated cost^ $/acre
Regional Costs Type 2^ (gravity)'
New England 35,580
Middle Atlantic 24,350
South Atlantic 24,530
Southern 16,720
Midwest 10,710
West 9,250
National average 18,260
a. Adjusted to ENR = 2000.
b. Type 2 is constructing new storm sewers and using existing combined
sewers for sanitary sewers.
Note: $/acre x 2.47 = S/hectare
^Published as Report EPA-670/2-74-040, December 1974,
537
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CO
c»
Table 8
Sewer Separation Versus Conceptual Alternatives
Capital costs?
Location, (REF.
Boston, Mass.
Bucyrus, Ohio
Chicago, 111.
Cleveland,
Ohio
Detroit, Mich.
Seattle, Wash.
Washington,
D.C.
) Separation
997,260,000
15,957,000
6,772,255,000
372,405,000
2,859,185,000
15,486,000
677,778,000
Alternative
779,692,000
9,220,000
1,322,378,000
111,842,000
2,859,000 1
8,185,000
353,333,000
a. Adjusted to ENR = 2000.
b. Ratio of separation cost to alternative cost.
c. Alternative costs are for first phases only and
Cost ratioD
1J3
1:7
5:1
3:3
,000:lc
i:9d
1:9
do not incl
Alternative
Deep tunnel
storage
Lagoon system
Storage tunnels
and quarries
Offshore stabil-
ization ponds
Sewer monitoring
& remote control
of existing com-
bined sewer stor-
age system
Computer controlled
in-sewer storage
system
Tunnels & mined
storage
ude future
total system.
d. Separation costs are only for southwest and east central Seattle, while
alternative costs are for the total combined sewer area.
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Table 9
Summary of Storage Costs for Various Cities9
Location
Seattle, Wash.
Control and monitoring system
Automated regulator station
^inneapolis-St. Paul, Minn.
Chippewa Falls, Wis.
Storage
Treatment
en
£o Jamaica Bay, New York City, N.Y.
Basin
Basin and sewer
Humboldt Avenue, Milwaukee, Wis.
Boston, Mass.
Cottage Farm Stormwater
Treatment Station
Chicago, 111
Storage and tunnels
Treatment
Storage basins
Collection, tunnel, and
pumping0
Storage,
mil gal.
—
—
32.0
—
2.8
--
10.0
23.0
4.0
1.3
5,570.0
--
2,736.0
2,834.0
Capital cost, $
3,500,000
3,900,000
7,400,000
3,000,000
744,000
186,000
21,200,000
21,200,000
2,010,000
6,200,000
1,323,000,000
1,550,000,000
568,000,000
755,000,000
Cost per
acre,
$/acre
—
__
--
--
8,260
2,070
6,530
6,530
3,560
—
5,500
6,460
2,370
3,150
Storage
cost,
$/gal.
--
--
0.23
—
0.26
—
2.12
0.92
0.50
4.74k
0.24
--
0.28
0.27
Annual
Operation S
maintenance
cost, $
--
--
250,000
--
--
--
--
00
--
65,000
--
—
--
~~
a. ENR = 2000.
b. Includes pumping station, chlorination facilities, and outfall.
c. Includes 193.1 km (120 miles) of tunnels.
Note: $/acre x 2.47 = $/hectare, $/gal. x 0.264 = $/liter, mil gal. x 3.785
= Ml
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Table 10
Cost of Sedimentation Facilities3
Location of facility
Capital cost,
mgd $/mgd
Annual
operation and
maintenance cost
$/mgd
Cambridge, Mass.
Cottage Farm Storm-
water Treatment
Station
Columbus, Ohio
Whittier Street
Alum Creek
Milwaukee, Wis.
Humboldt Avenue
New York, N.Y.
Spring Creek-
Jamaica Bay
62.4
192
43
192
480
100.000C
32,000
43,000
10,500
44,000
1,240
a. ENR = 2000.
b. Maximum capacity assuming 30-minute detention time.
c. Includes pump station and screening facilities.
Note: mgd x 43.808 = I/sec
540
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en
Table 11
Cost of Microstrainers and Ultrafine Screens for 25-Mgd Plants3
Loading
rate,
Influent gpm/
source sq ft
Micros trainers
Philadelphia, Pa.
Taft Institute
Hypothetical
Chicago, 111.
Ultrafine screens
Fort Wayne, Ind.
Storm 25
overflow
Activated 16
sludge
effluent
Sewage 5-10
effluent
Activated 6.6
sludge
ef f 1 uent
Storm
overflow
Modified Operation and
Capital capital maintenance cost
costb costc Annual
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Table 12
Capital and Operation and Maintenance Costs for Biological Treatment3
Item
Location
Contact
stabilization,
activated
sludge
Kenosha,
Wisconsin
Trickling
filter
New Providence,
New Jersey
Rotating
biological
contactor
Milwaukee,
Wisconsin
Oxidation pond
Shelbyville and
Springfield,
Illinois
Plant capacity, mgd
Capital cost
(construction cost,
excluding land,
$/mgd
Operation and Maintenance
(annual cost assuming
250 hr/yr of operation),
<£/l,000 gal.
20
78,300(
4.8
68,000d
10.4
30,000
4.4
0.3 to 2.2b
43,800 to 55,000
a. EMR = 2000.
b. Equivalent capacity which is a pond with a 10-day detention time.
c. Cost of pumps, aeration tanks, and final clarifier.
d. Includes cost of plastic media filter, final clarifier, side piping, and electrical work.
e. Approximate cost of dry weather flow.
f. Cost only for Springfield, Illinois.
Note: mgd x 43.8 = I/sec
$/mgd x 0.0228 = $/l/sec
$/l",000 gal. x 0.264 = <£/! ,000 1
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Table 13
Estimated Capital and Operation and Maintenance
Costs for Typical Physical-Chemical Treatment Plant
Capital costs, $
Location
Hypothetical
CAST a
Total
Annual
Hypothetical
PCTb
Total
Annual
South Lake
Tahoe, Calif.
Total
Annual
Albany, N.Y.C
Total
Annual
10 mgd
4,822,000
377,200
6,656,000
520,700
4,870,500
381 ,000
1,791,500
140,100
25 mgd
9,680,800
757,300
13,409,000
1,049,000
9,907,400
775,100
3,643,900
285,100
Operation and
maintenance costs,
<£/l,000 gal.
100 mgd 10 mgd 25 mgd 100 mgd
28,330,500
2,216,300 9.7 7.1 5.3
42,379,000
3,315,300 16.3 13.4 10.3
89,010,600
2,269,500 13.0 10.8 8.6
10,670,100
834,700 18.8 15.6 11.7
a. CAST = conventional activated sludge treatment (for comparison only).
b. PCT = physical-chemical treatment.
c. Combined Sewer Overflow Treatment based on 100,000 gal/day pilot plant.
Note: mgd x 43.808 = I/sec
(f/1,000 gal. x 0.264 = tf/1,000 1
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Table 14
Dissolved A1r Flotation Cost for 25 Mgda
Plant location
Construction cost
Including pre-
treatment devices"
Operation and
maintenance
Total cost,
£/l,000 gal.
Chemical cost
alone,
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Table 15
High Rate, Deep Bed, Dual Media Filtration Cost
Cleveland, Ohio, Pilot Facilities
Operation and
maintenance
cost, $/yr
44,000
55,000
98,000
129,000
a. The cost data are based on an EMR of 2000.
b. Based on 5 hour overflow event with only temporary sludge storage.
Sludge handling cost not included.
Plant capaci
cu m/min
64
132
263
526
tyb
mgd
25
50
100
200
Capital9
cost, $
1,580,000
2,390,000
4,370,000
7,430,000
545
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Table 16
Examples of System Operation Controls
Location
Seattle
Wash.
Boston,
Mass.
Dallas,
2 Tex.
CTl
= San Francisco,
1 Calif.
Operation
scale
Full
Full
Full
Full
Operation
controlled
Overflow
quantity
Overf 1 ow
quality
Sewer
surcharge
Overflow
quality
Monitoring devices
Level sensors, rain gages,
wind gages, automatic sam-
plers, telemetry units,
computer, position sensors.
Level sensors, automatic
sampler, Dall tube, re-
sidual chlorine analyzer.
Level sensor, magnetic
flowmeter, temperature
probe, computer.
Magnetic flowmeters, level
probes, differential pres-
sure sensor.
Control devices
Gate regulators, tide
gates, pumping stations.
Pumping station, sodium
hypochlorite feeder, gat
regulators.
Polymer injection feeder
Polyelectrolyte feeders,
solids pump, bypass
gates, dissolved air
Mt. Clemens,
Mich.
Full
Milwaukee,
Wis.
Minneapolis,
Minn.
Full
Full
Overflow Magnetic flowmeters, level
quality probes, automatic samplers,
differential pressure
sensors.
Overflow Level sensors, automatic
quantity samplers, magnetic
flowmeters.
Overflow Automatic samplers, rain
quantity gages, computer, pressure
sensors.
flotation units.
Pumping stations, aerated
lagoons, microstrainer,
pressure filters,
chlorine-chlorine dioxide
feeders.
Mixers, chlorinators, bar
screen, detention tank.
Fabridam regulators, gate
regulators.
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