WATER POLLUTION CONTROL RESEARCH SERIES • DAST 37
1102O-- 03/70
Combined Sewer Overflow
Seminar Papers
November 1969
U.S. DEPARTMENT OP THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
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Combined Sewer Overflow Seminar Papers
A compilation of technical papers and
discussions presented at a Seminar at
Hudson-Delaware Basins Office
Edison, New Jersey
November U-5, 1969
UoSo Department of the Interior
Federal Water Pollution Control Administration
Office of Research and Development
Division of Applied Science and Technology
Storm and Combined Sewer Pollution Control Branch
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CONTENTS
TITLE PAGE
Opening Remarks 1
Overview of Control Methods 9
Storage and Treatment of Combined Sewage as an Alternate to Sepa-
ration 19
Polymers for Sewer Flow Control 37
Overview of Treatment Methods 53
Microstraining - With Ozonation or Chlorination - of Combined Sewer
Overflows ... 59
The Use of Screening/Dissolved-Air Flotation for Treating Combined
Sewer Overflow 101
Overview of Combined Control and Treatment Methods 119
Assessment of Alternative Methods for Control/Treatment of Combined
Sewer Overflows for Washington, D»C 123
Assessment of Combined Sewer Problems 139
A Simulation Technique for Assessing Storm and Combined Sewer
Systems. 151
Summary „ 171
Building for the Future - The Boston Deep Tunnel Plan (Printed with
permission; paper not delivered at the Seminar) .......... 173
List of Attendees . . . . o 193
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OPENING REMARKS
*y
William A. Rosenkranz
As Mr. Dewling indicated, my purpose at this particular point
of the program is to give you a general idea as to how the program
works, some information about the background of its initiation and
how you would go about implementing a project with the assistance
of grant or contract through the Federal Water Pollution Control
Administration. Some of you may already be familiar with the
history but I will give you a bit of it to keep you on board.
Back in 196U, FWPCA, at that time Public Health Service,
completed a general assessment of the storm and combined sewer
problem in the United States. The report included an estimate
that it would cost about $30 million to correct this problem on
a national basis by means of sewer separation. The principal
recommendation was that alternatives to separation of sewers be
studied to find ways to do the job at less cost with the same or
better efficiencies. As a result of that report and other infor-
mation available to the Congress, the Water Quality Act of 1965
included the establishment of a demonstration grant program which
was at that time called Facilities Demonstration Grants. It was set
up on a basis of 50% grants. Contracts were also authorized and
the program was actually initiated on an active scale during the
spring of 1966. The first grant was made in June of 1966 and we
have gone on from there.
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The program was changed in the Fall of 1966 with the passage of
the Clean Water Restoration Act of 1966. At that time the amount of
participation in individual projects by means of grants was changed
from 50/0 to 75$. Additional demonstration grant programs were author-
ized at the same time in the fields of advance waste treatment; industrial
waste treatment and joint municipal industrial treatment. Since there
was no appropriation made at that time, the Congress authorized the
funds originally provided for the Storm and Combined Sewer Program
to be used during this first year and thereafter for implementation
of some of these programs to get them off the ground. The first
year of the Clean Water Restoration Act saw some of the funds that
had been allocated to the Storm and Combined Sewer Program used
for the first grant projects and contracts in the other technical
areas. The additional programs were funded the following year.
At the present time we have initiated 82 projects, the project
cost involved is $65 million and the Federal grant and contract funds
supporting these projects is about $28 million. So you can see
that the program is active, there is a lot of work going on and we
are still looking for additional demonstration and developmental
projects to carry us further down the road.
Once the program was initiated, it was obvious that additional
work was needed to bring the assessment of the problem on a national
basis more up to date. The information and data contained in the
196U report that I referenced earlier actually was data prior to
196U and it was felt that we ought to update not only the assessment
of the impact of combined sewers, their location and similar infor-
mation, but also update the estimate of cost for remedial measures.
Therefore, in 196? a contract was initiated with the American Public
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Works Association to do this job for us. As a result of that study
the AFWA estimated that it would cost $^8 billion to provide separate
storm and sanitary sewers in areas now served by combined sewers.
This included the work that would be required on private property
to separate plumbing from the combined sewers and reconnect to
sanitary sewers. The report also pointed out specific areas
where additional research and development is needed. Research and
demonstration projects to look into these particular areas are being
implemented as fast as it can be done.
With regard to procedures, let me say first that with regard to
demonstration grants the Federal funds are usually used to support
full scale projects. We are looking for projects that take a new
and/or improved method and apply it to a community problem at full
scale, so that the community does achieve a significant improvement
in their sewer system, a significant level of water pollution control
is obtained and data is obtained and evaluated so that other people,
such as yourselves, will have this information available and be able
to apply it on jobs that you may have. The participation, as indi-
cated earlier, is at the level of a maximum of 75% federal partici-
pation in the project. In return, we are actually buying information
so that we can disseminate it to others that have the need to use
it. We do participate in construction costs on the projects, however,
this is not our prime objective. This is not a construction program,
it is a research and demonstration program. Therefore, from other
standpoints, we prefer to keep participation in construction costs
as low as possible. We recognize that we must build a facility to
evaluate it, therefore, we do participate in construction costs to the
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extent possible, retaining compatability with the demonstration
objective. Grants can be made only to official government bodies.
We can make them to sanitary districts, municipalities, metro
organizations, state agencies, and counties; but we cannot make
grants in this program to profit making industrial organizations
or firms. Grantees must "be responsible for either the construction
or operation of maintenance of a system.
As Mr. Dewliog mentioned, we have kits here today, including
the application forms, instructions for completing them, copies of
the regulations involved and other pertinent information. If you
are interested in implementing a demonstration project with Federal
assistance we will give you the kits for filing an application. The
applications must be approved by the official water pollution control-
agency in the state where the project is to be done. In this way,
it functions very similar to the more normal construction grant
program, which requires state approval as well. The only difference
being that there is no state allocation of funds. As you know, in
the construction grant program each state is given a funding allo-
cation. In the research and demonstration program this is not done.
Contracts can be utilized to deal with government agencies,
industry, consulting firms, universities—almost anyone who has a
good project proposal. An organization, for example, the American
Public Works Association, can be either profit or non-profit to be
eligible for contract work. Contracts are generally used for develop-
mental work—investigations to explore difficult technical areas. Or,
in some cases, non-technical areas such as the nationwide study done
by American Public Works Association. We hope that if we have a
viable process come out of a developmental contract we can then
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follow it up and demonstrate the method at full scale by means
of a grant. This approach permits us to develop a piece of equip-
ment, a technique or method we can study at pilot scale and move
right into full scale operations by means of a suitable demonstration
grant project.
Special forms are not needed for contract proposals. It is
up to the person with the idea to state his idea, tell us how he
is going to carry it out, what his objectives are, what manpower he
needs, what kind of water quality sampling, monitoring or lab work
he will require together with his estimates of total cost that will
be involved in completing the proposed work.
You are probably interested in some of the technical areas in
which we are looking for work. When preparing material for the
Seminar, I came up with a list of something over 60 individual
kinds of projects that we would like to initiate. I am not going
to read the entire list to you this morning, but I would like to
mention several of them to give you an idea of some of the things
we would like to do. These are areas where work has not been done
and areas in which we have no real data for field use. Potential
project areas include removal of storm flow and infiltration from
sanitary sewers, thru elimination of illicit storm water connections
and similar approaches. Is there a good way to go about this task
efficiently and at reasonable cost to a community?
¥e need to assess the extent and significance of discharge of
sanitary wastes to storm sewers. Control techniques, if such control
is really warranted by an assessment of the problem, need to be
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developed and applied. Is this problem significant enough to
warrant extensive work?
We are interested in looking at special conveyance systems
such as pressure or vacuum sewers as an alternate means of sewer
separation. The American Society of Civil Engineers has examined
pressure sewers for us. The report is now at the printers and the
concept is being explored further by means of a demonstration
grant with the State of New York.
We need to do some work in infiltration control. I think
of you working on projects, especially the consulting engineers and
municipal people, find that infiltration is a major problem. The
American Public Works Association has found that this is true in
their earlier work and are now doing an assessment of the state-
of-the-art involved. Improved sealing materials have been explored
and you have a report on our first attempt at the conference tables.
Additional work is needed to further develop the materials and their
application.
A close look at improved materials and construction practices
with regard to all types of construction, including sewers, is
needed. Faulty bedding, poor jointing and inspection are causes
of major sewer problems. New construction materials and methods
for tanks, housing and all types of facilities are needed to reduce
cost of remedial measures. System analysis techniques are now being
developed and you will hear a paper on that later today. We want to
demonstrate the use of systems analysis in designing and investi-
gating problems in the sewerage system and implement an integrated
control system for an entire drainage area.
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A need, exists to demonstrate full scale some of the new methods
of treatment now under development. Here we are looking at treatment
methods and techniques which will be of a much higher through-put
rate than we now have. We are evaluating bio-disc treatment by means
of a contract pilot operation, dissolved-air flotation with high
surface loading rates, screening and microstraining, high-rate
filtration (both physical and biological). We think that sufficient
progress has been made in several of these methods to permit appli-
cation to combined sewage treatment on a fall-scale basis and at
reasonable cost at individual overflow points. Considerable work is
needed to field develop and apply system regulators. We will shortly
have a published report on the development of a"Fluidic Regulator"
which we think will have the potential to operate much more efficiently
than existing mechanical types of regulators. Many of you, especially
if you are in a municipal or consulting field, recognize that our
capabilities for measuring flow are not very good. They are diffi-
cult to apply, costly, require a great deal of equipment. A major
impact on the field could be made if we could come up with more
efficient and accurate flow measuring techniques which can be easily
and economically applied. We need to improve our water quality moni-
toring capability, including sampling techniques.
Thus far I have talked almost entirely about combined sewage.
Perhaps I ought to indicate that we are also interested in storm water
control and treatment. Very little work is going on in this area at
this time. We would like to see some good projects aimed at treating
and/or controlling urban runoff. Within our over-all Research and
Development programs, our particular Branch is also charged with the
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responsibility for determining the nature and extent of problems
existing and what potential remedial measures can be applied to
non-sewered runoff. This is runoff that does not reach the
collection system—storm, sanitary or combined.
In approaching and executing storm and combined sewer projects,
particularly the engineering investigations and determination of the
way to go, the municipalities and the engineers involved should keep
in mind that while we need to apply conventional engineering practice,
the problem itself doesn't lend itself to a straightforward engineering
solution. The problem is more complicated and difficult in that we
need to keep in mind that we have to apply originality and ingenuity
in solving these problems. We need good knowledge of the type and
magnitude of the local problem in order to properly jell a project
which may be feasible from both technical and economic standpoints.
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OVERVIEW OF CONTROL METHODS
by
Francis J. Condon
Most of what we will talk about this morning is the control
problems of combine sewers. The predominant pollutional sources
are in the combined sewer area and, therefore, to date, the pre-
dominance of our efforts have been in solving these problems. A
little closer definition of combined sewers as we use the term
should be given. The classic definition is well known, but there
are ostensibly separate systems which are in fact combined mainly
due to large infiltration problems. There are separate systems
built in outlying areas from the old urban areas which flow into
combined- sewers and then there are the problems of construction
such as the cross connections which were made for expediency.
Finally there is poor construction practices. The result is
that many of the so-called separate systems are cross connected
with combined or act as combined sewers.
Strangely enough in many parts of the country there is a reluc-
tance to enforce the ordinances necessary to make a separate system
separate. Examples of this are downspouts and foundation drains
that are connected into separate systems. The local populace want
it that way and the ordinances aren't enforced. Actually there are
some combined sewers yet being constructed although the general
practice is supposed to be that all new construction will be
separate systems.
The design of the recent collection systems and some of our
current interceptor designs, which take both separate and combined
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sewage, is done by old practices. The ratio of three to seven
wet weather flow to dry weather flow is usually used when the
design considerations are weighed, the governing factor is eco-
nomics. The data are interpreted so that they indicate that the
flow ratio selected, in that range, is the proper ratio to use
in order to intercept most of the storm flows. We have shown
in many cases where that rule of thumb of selecting a three or
five to one ratio is grosely in error. It is not uncommon to have
50 to 200 times dry weather flow in urban runoff.
Before we talk about where control is needed and what can be
done, we should briefly discuss the reason for those flows. The
first and most obvious is the rain event itself. Going back to the
ratio of flows we can use a specific example to illustrate the point.
There is a New England state which has a large number of middle
sized cities all of which were sewered with combined sewers and
very few of which have treatment plants. They discharge raw into
the receiving waters. The intent of the state is to build treatment
plants with some auxiliary facility to handle excess combined flows.
The justification for our entering into a demonstration grant with
one of the cities was that the design criteria for the state would
be set on our demonstration project for use in future treatment plant
construction thruout the state. To establish the volumes and rates
which could be expected and verify current runoff estimating practices,
it was decided to cross check estimating techniques. As a result
there were three groups whom we asked to calculate the rate and
amount of runoff during a rain event. First was the design engineers,
a large and reputable firm. They would naturally have to design
for the volumes of flows that would have to be taken by both the
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treatment plant and the auxiliary facility. Then we asked the
city engineer to make his calculations. Finally we had a research
and development group, who are doing pre-constmction evaluation,
to actually measure and back calculate the runoff factor. It was
extremely interesting, everyone knew what the other fellow was
doing. They all did a thorough job. I believe the engineering
firm used a modified rationale method; the city engineer used the
Chicago method. The research and development -firm actually measured
all flows and back calculated over a full year. There are so many
elements which enter in to how much runoff you get that the old
simplified equations were inadequate. The design engineers cal-
culations of volume for a given rain event, on the average, was
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the majority of flow comes from the service connections. Not only
the joints in the sub-system, the mains, and the laterals but as
indicated from one recent study about 70f0 of the volume came from
the length of line from the house to where it connected to the
lateral. How do you repair instead of replacing U inch service lines?
We are looking diligently for a project in this area and that will
be a major accomplishment if we can make any gains towards that
problem solution.
Another source of excess flow is malfunctioning regulators.
Again operations people in the room know the tough problem that
they present. The mechanical systems need constant maintenance
and looking after; even then they don't often perform as they were
designed. This morning there was mentioned the fluidic regulator
which we have great hopes for and there is another proje.ct in
New York City utilizing the Ponsar regulator.
Another result of the excess flows is the bypass at the treat-
ment plant and just as important the plant upset. So control at
the plant site itself with devices or facilities to handle excess
flow is another area which we are investigating. To summarize the
sources or causes of flow problems: one, it's underestimated runoff
from a given rainfall; two, infiltration from many sources; and
three, the regulators and four under designed treatment plants.
Therefore, we now come to what methods are being presently investi-
gated and what further needs to be done.
Firstly, drainage area control, this is a Pandora's box. The
term control applies both in the hydraulic volume and pollutant
load. We have projects in this vein and there will be a paper today
on one technique. The method to be discussed is up-system storage,
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•urban lakes, and surface lakes, which include recreation. In our
urban areas this is a very important element. Sub-surface storage
in caverns or tunnels and utilizing the geology itself is another
method. The so-called geological hidden valleys which are areas
of high permeability and void space may be used for storage. The
problem in utilizing this method of permeable stratum is polluted
water in the ground and, if needed, taking it back out. Barriers
to keep the polluted water from moving after it is in sub-surface
storage is an area to be investigated.
Another area of the investigation is the collection system
control and here again we have a wide range of ideas and projects
which we could look at. Special conveyance systems of pressure and
vacuum lines were one method already mentioned.
Catch basin improvements is an area to be researched and for
a while I thought that catch basins were no longer being constructed.
But we have found that they are still being designed in collection
systems. They serve a purpose in some cases, the idea is to make
them better and more functional.
Reducing the infiltration and ex-filtration as we mentioned
is a large problem but that is also part of the collection system
control.
In-line storage routing is a very interesting area. There
are projects in Milwaukee, Detroit, Minneapolis and St. Paul where
they utilize the storage concept in the collection system itself.
The purpose is to route the sewage and have it hit the plant not
as a large slug but as a slowly built-up volume that the plant
can handle without upsetting.
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There are some areas in instrumentation, monitoring, sensing
devices, and automated real-time control where much has been learned.
In-line detention also means flushing. Flushing becomes important
not only where we have the flat grades but also if we are going to
use in-line storage. In holding the sewage in large sewers we
have primary settling. Then the problem is after we have stored
how do we get those settled polluting materials back to plant again
without a slug effect.
There are flow additives to increase the capacity of the flow
characteristics. We have a very interesting paper on this today.
The use of polymers, whereby the flow is increased at the same head
is the concept utilized. There, appears to be reduction of internal
fluid friction and perhaps a boundary layer effect. This is a
most interesting phenomenon.
As mentioned there are many spinoffs from these projects and
it is difficult to categorize and talk about them because each
project incorporates so many of the side issues. Instrumentation,
sampling devices, sampling techniques and the methods are part of
almost all of our projects.
Another method of control is control at the overflow point. We
have projects, and these were our first cut efforts, such as tanks
or storage facilities where they were above ground, below ground or
underneath the water. These tanks would hold and take the first
surge with the heavy pollution load, if that is the case, then
treat what they had to bypass. The stored volume would be fed
back into the system. The treatment is usually aeration and
chlorination when the excess is discharged. An interesting point
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in the storage devices, whatever they may be, is the idea that
we have only a short time to hold because you couldn't economically
design to retain every storm. We want to get maximum treatment
in a short time, so with say a ten minute detention time how can
we get the maximum sedimentation. This is usually the treatment
that goes on at the detention facility. Our experience indicates
that primary sedimentation tank design is really far behind. There
are many things that could be done, and we are attempting to develop
projects now to improve settling tank design. We believe it would be
a major step if we could improve primary sedimentation in a shorter
holding period. There are also chemical and mechanical treatment
processes we are developing in this respect.
Now the last area. There are the modifications or additions to
existing treatment plants to contain or retreat excess flows both
by biological and mechanical techniques. There are several interesting
projects, I believe. One which is listed in your handbook is Kenosha,
Wisconsin. There we used a biological treatment method. The concept
is to keep a bio-mass viable during a dry period and have it available
for treatment of the excess flows as activated sludge.
Another concept is to concentrate the pollutants which actually
do go to the treatment plant. We had one of our very early projects
in this area where we attempted to use the pipe itself as a filter.
The idea was when the fluid head on the pipe caused surcharging,
the pipe would expand and in expanding it would become permeable.
The excess water would seep out the sides, it would be captured
and chlorinated but the solids would remain concentrated in the
smaller, contained stream which would go to the treatment plant
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thereby not hydraulically upsetting the plant. Unfortunately, tfhat
one has more application to some industrial waste projects and was
not feasible in combined sewage. We couldn't get the self-cleaning
aspect to the high degree which was needed on that concept. The
project did introduce many new ideas for other people.
Many of these treatment and control methods we talked about
with respect to combined sewage apply also to storm water. Urban
runoff itself is surprisingly loaded with polluting materials. One
could expect, especially in the COD readings, that urban runoff is
heavily polluted. In addition, coming from urban areas are pesticides
and insecticides which induce a fairly high toxic level in the
receiving waters. So that the storm runoff itself needs a good
deal of the attention in treatment especially in control measures.
In summary it can be said that:
(l) Work is currently going on in predicting more accurately
the volume and pollutional load of excess combined sewage
and urban runoff. Verification of the methods being
developed is still needed.
(2) Projects are active for in-system routing and storage.
There needs to be refinement in what has been developed
to date.
(3) Projects are active in off-system and outfall storage and
treatment. This is a very broad area and the ideas which
could be applied here have not been exhausted. The
combination of pollution abatement and recreational use
could certainly be explored further.
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There axe activities in bettering construction materials
and practices in addition to in-situ repair of pipe. This
is an area where not only pollution control but economic
benefits or gains could be very large. A large amount of
research awaits future efforts.
(5) Dual use treatment concepts at treatment plants where
facilities for treatment of excess flows could be utilized
for tertiary treatment of dry-weather flow is a wide open
research and development area.
(6) Appurtenance development such as improved regulators, tide
gates, catch basins, volume or rate measuring devices,
sampling devices, instrumentation in general, and many
other related items need further investigation.
There followed an open discussion of the fluidic regulator.
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STORAGE AND TREATMENT OF COMBINED SEWAGE
AS AN ALTERNATE TO SEPARATION
By A. W. Banister, P.E.
Partner, Banister Engineering Company
St. Paul, Minnesota
INTRODUCTION AND ACKNOWLEDGEMENT;
The City of Chippewa Falls, Wisconsin was confronted with the need to complete a
program of separating storm water from its sanitary sewage and waste collection
and treatment facilities or to provide a method of treating the combined sewage
and wastes.
The State Regulatory Agency basically had requested separation, although, upon
questioning, would approve an "alternate to separation" if the ultimate objectives
could be achieved.
A thorough investigation and study was undertaken, which indicated substantially
the same apparent objective could be achieved either by storage and treatment of
the combined sewage and wastes or by separation.
In evaluating the two possible procedures, the comparison was made on the basis of
complying with a regulatory agency order. Certain fringe benefits such as elim-
ination of flooding of basements during heavy rainfall and the occasional extreme
hxgh river water in the Spring were not considered in the evaluation, although these
advantages became apparent during the course of the studies necessary to reach a
conclusion. The fringe benefits which resulted were an extra bonus.
This paper will present the alternatives, the recommended project, and what results
have been achieved.
Too much cannot possibly be said about the complete and enthusiastic support and
assistance provided by the City officials and staff and especially Superintendent
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of Public Utilities, Clyde Lehman.
BACKGROUND:
The City of Chippewa Falls, Wisconsin was faced with the problem that many of its
sewers were of the combined type; the City was required to establish a system of
"separate" sewers. This problem is the same one confronting many of the older
cities throughout the United States today, whether large or small. The financial
impact upon any city is substantially the same, regardless of size, when related
to the number of taxpayers and the tax base. In many respects, the development
of the various centers of population throughout the United States probably followed
the same general pattern as that in Chippewa Falls. A brief background of the
City appears appropriate.
The City of Chippewa Falls has been incorporated for 105 years. Its development
and initial reason for establishment was due to the lumbering industry. Of course,
lumbering in the area is now almost non-existent. The City is situated on the
Chippewa River, with about 40 per cent of the area being south and 60 per cent being
north of the river. That portion of the City lying north of the river is bisected
by Duncan Creek. The Chippewa River in the vicinity of Chippewa Falls is controlled
by two hydroelectric dams, one of them being in the City. At one time both Duncan
Creek and the Chippewa River were used to float logs downstream to sawmills located
in Chippewa Falls. As development occurred, a further use of the river and of Duncan
Creek was to receive and carry away surface runoff and sewage and industrial wastes.
7;he matter of water pollution was never considered. Thusly, prior to about 1935,
practically all of the sewers constructed in Chippewa Falls were of the combined
type which discharged directly into either the Chippewa River or Duncan Creek.
I>n 1937 the Wisconsin State Board of Health strongly urged the City to provide treat-
ment of its sanitary sewage; in 1939, the City commenced construction of intercepting
sewers on both sides of Duncan Creek, which, when completed, would prevent all dry
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weather flows from entering the Creek. A plan had also been developed for the
construction of intercepting sewers on the north bank of the Chippewa River, and a
site for a waste water treatment plant was obtained.
World War II resulted in the stoppage of all sewer construction in the City and no
further progress was made until 1950, at which time the State Board of Health and
the Wisconsin Committee on Water Pollution issued an order requiring the completion
of intercepting sewers and the construction of a primary waste water treatment plant.
Construction of this was completed in 1952. Since the end of World War II all sewer
construction within the City has been of the "separate" type.
In 1954 the State Board of Health and the Committee on Water Pollution requested the
City to prepare a master plan for storm sewer separation. This plan was completed
and, as a result, the City began a program to construct separate storm sewers and
elimination of surface water entering the combined system. Each year the Director
of Public Works would include in his budget a sum of money for implementation of the
separation program. However, occasionally the need for constructing sanitary sewer
extensions occurred and some of the separation was not done. Obviously, separation
in fhe "downtown" area would be more costly and inconvenient per "amount of separation"
than j.n the residential areas. In 1965 the State Regulatory Agency directed that the
City establish a definite time schedule for the completion of the separation program.
Substantially, all of the separation in the residential areas had been completed by
this time,- but the "downtown" area contributed the vast majority of surface runoff
tributary to the combined system.
The same order requiring that the City establish a definite timetable for completion
of the separation program also included a requirement that improvements be made to
the waste water treatment plant to provide the degree of treatment intended. As a
point of information, the "degree of treatment intended" was primary treatment.
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By State interpretation "primary treatment" was a minimum of 30 per cent removal
of 5 day BOD and suspended solids. Industrial development and population increase
has occurred beyond expectation. Our firm designed the original intercepting sewers
and waste water treatment plant; the City again engaged us to assist them in this
project. In reviewing the treatment required by the State Agency, it became obvious
that improving the facilities at the waste water treatment plant to provide the
minimum 30 per cent removal would not be a sound approach because it was anticipated
that secondary treatment would be required within two years. Accordingly, a program
Was recommended to include secondary treatment incorporating the activated sludge
process to provide in excess 90 per cent removal of 5 day BOD and suspended solids.
It must be realized that great emphasis in Wisconsin is being placed on recreational
use pf many of the rivers, including use for whole body contact. The whole theory
pf, using the assimilative capacity of the receiving streams can no longer be used
in determining the degree of treatment to be provided. While the waste water treat-
ment plant, per se, may not appear a part of the storage and treatment of combined
sewage, certain parts of the plant could be affected if large volumes of combined
sewage were to be treated therein.
F,W,P,C,A. DEMONSTRATION PROGRAM?
At the Water Pollution Control Federation convention in Kansas City, F.W.P.C.A.
Commissioner Quigley announced that the F.W.P.C.A. had been authorized, and money
appropriated, an amount of $20,000,000 for demonstration projects for alternates
tp storm water separation.
This information was presented to the Chippewa Falls Common Council, with a possible
program of an alternate to separation. The City agreed to finance preliminary
investigations and feasibility study for such an alternate.
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The results of the study indicated that it would be feasible to construct a large
storage pond to store combined sewage and wastes which would otherwise bypass to the
Chippewa River and Duncan Creek during periods of surface runoff. It was also
found feasible to construct separate storm sewers.
The estimated cost of storage, with certain minor separation still being required
and construction of certain trunk sewers being required, was only slightly less than
the cost of separation. Comparative cost estimates were prepared for both programs.
In considering separation, it was assumed that the City could program the separation
over about ten years and pay for each year's work from the annual budget; no
financing and interest costs would be involved. It was also assumed that construction
costs would increase between two and two and one half per cent per year.
It was therefore recommended that the alternate to separation was advantageous to
the City only if a major grant-in-aid could be obtained, otherwise, the conventional
separation program should be adopted.
The City made an application for a F.W.P.C.A. Demonstration Grant. The grant was
reduced from the authorized 75 per cent to 55 per cent because of a rash of "last
minute" applications. However, the State of Wisconsin also has a grant-in-aid
plan of 25 per cent, for which the City applied and received. Hence, the net cost
to the City was 20 per cent of the cost plus the cost of land.
SELECTED PROJECT;
The project selected consisted of certain combined trunk sewers, increasing the
pumping capacity of the Bay Street Sewage Pumping Station, certain minor separate
storm sewers, a combined sewage (storm water) pumping station, and a combined
sewage storage pond.
In addition, certain conduit and sewage pumping capacity at the Waste Water Treatment
Plant had to be increased and each of the final two settling tanks at the plant were
23
-------
increased from 55 foot diameter to 65 foot diameter. No increase in size was made to
the primary settling tanks, aeration tanks, blower capacity or chlorine contact tank.
The total cost of this project, including the enlargements at 'the Waste Water Treatment
Plant, was $620,701. The general overall project is shown in Figure 1.
Studies by McKee in Boston have shown that for a rainfall intensity of 0.1 inches per
hour the percentage of sanitary sewage escaping from the sewers was as much as 80
per cent of the total sanitary sewage, when the intercepting sewer had a capacity of
two (2) times average dry weather flow. When the rainfall intensity was 0.5 inches
per hour, the percentage of sanitary sewage escaping increased to 95 per cent.
Although studies of the overflow points in the Chippewa Falls sewer system have not
been undertaken, casual observances tend to indicate that such studies would probably
show results similar to the foregoing. Practically every rainfall, no matter how low
the intensity may be, would have caused overflowing from the combined sewer system.
The first problem was locating a storage pond site where interception of the overflow
from the combined sewers could be done without long distances of large diameter pipe
being required. A problem of equal importance was to determine the size of the pond.
There was a low- area lying between the downtown business district and the Chippewa
Riyer, The main overflow point for the downtown area combined sewers was adjacent
to this site and the former overflow was carried across this low area in a 42 inch
corrugated metal pipe discharging into the Chippewa River. There is a railroad trackage
along one edge of the low area but at an elevation high enough so as not to be
endangered by the storage of storm water.
This was the only feasible location for the pond. By using this location, the maximum
size of the pond was established by geographical features of the area. Approximately
three acres was available for pond construction and the average area within the pond
could be about 1.33 acres.
-------
£X
STRUNK
WASTE WATER
TREATMENT
PLANT
FIGURE-1
PROJECT LOCATION
-------
The total volume of rainfall which the pond was designed to store was determined from
the mass rainfall curve, shown in Figure 2, which shows the total rainfall from the
beginning of the storm and also shows a plot of the theoretical percolation expected.
The percolation assumed was 0.3 inches per hour and the frequency of storm arbitrarily
selected was a ten year storm. As illustrated, the maximum runoff for the given
conditions was computed to be 1.6 inches. The total volume of runoff from the 90 acre
tributary area would calculate to be:
Volume of runoff = ^'^ x 90 acres = 12 acre feet
12
It may be interesting to note that the theoretical volume of runoff for a five year
storm would be approximately 10 acre feet and for a two year storm would be about
7,5 acre feet.
The total length of the design storm may be calculated by using a three point hydro-
graph such as is shown in Figure No. 3.
The peak rate of flow to the pond (Qmax) must be determined. An analysis of the
downtown area drainage using the rational method for storm sewer design showed an
expected peak storm runoff of 164 cfs. However, since these were combined sewers,
it was necessary that "bottlenecks" in the existing sewer system be eliminated and
no new ones created. Hence, all new combined sewers were designed having capacities
at least equal to all of the upstream pipes. The design was not based on just the
flows determined by the rational method.
Using 164 cfs as the peak rate of runoff from the design storm, the length of the
design storm was calculated as:
T = 2^'2 Vr = 2- •*?••/ 12 = 1.77 hours = 1 hour 46 minutes
Qmax 164
26
-------
i-1
i
TIME
OF SJORA\
I&O TOO
AMMUTErS
I^ASS RAIMFALL CUf^Vt
-------
•
('
REAM FLOW f&d-C.FS. - Q*A>C.
VOL.OF RUMOFF
T =* L&klbTW OF
STORM = 1 HOUR 4£> AMU.
O to 40 ao &o K3D
TlN\t FROM E>E:6!MMIMG OF STORM - /V\lklUT&5
FIGURE -5-
rzo
5 • PO1UT UVDROG,£APH-
-------
The existing Bay Street Sewage Pumping Station had a pumping capacity of 4000 gpm
but the maximum rate permitted by the force main and intercepting sewer could be 6000
gpm. Hence, the pump capacity was increased to 6000 gpm. The estimated peak flow
of domestic sewage was 2000 gpm, so that up to 4000 gpm of the storm runoff could be
pumped to the intercepting sewer and the waste treatment plant without overflowing
to the storage pond.
During the period of the storm, the sewage pumping station will deliver:
4000 gpm x 106 minutes = 424,000 gallons of storm water to the Treatment Plant,
which is 1.3 acre feet and represents the amount by which the total volume of runoff
could be reduced when calculating the size of the pond.
Thus, in this case, we designed the pond for a volume of 12.0 - 1.3 = 10.7 acre feet.
This requires a water depth in the pond of 8 feet.
The elevation of the invert of the trunk sewers where they enter the Bay Street Pumping
Station is only 0.4 feet above normal river level. Gravity flow to an above ground
Storage could not be obtained. Therefore, a combined sewage pumping station was con-
structed to pump all combined sewage to the storage pond. This station has a capacity
of 75,000 gpm, which is the total capacity of the tributary trunk sewers.
The storm water pond was constructed of earth dikes with the top of the dike at
one foot above the top of the overflow elevation.
The design provided that, after the pond is emptied, the bottom would be flushed with
river water or from a fire hydrant to wash solids to the inlet to the Bay Street
Pumping Station to minimize the leaving of solids after draining. The pond interior
was surfaced with a bituminous mat to facilitate cleaning and to allow vehicular
traffic within the pond for maintenance of structures and removal of grit.
29
-------
Relief valves were placed in the pond bottom so that when the river level rises above
the pond bottom, it will flood rather than being in danger of floating. The earth dikes
adjacent to the Chippewa River are fully protected by riprap to prevent erosion during
the periods of high river level.
The entire volume of combined sewage from the pond flows by gravity, through a
regulating valve, to the Bay Street Sewage Pumping Station and thence to the waste
treatment plant for treatment and disposal.
The W,aste Water Treatment Plant now has secondary treatment utilizing the activated
sludge process. The aeration tanks were designed on the basis of 50 pounds of 5 day
BOD per 1000 cubic feet of volume. There are four separate aeration tanks so designed
that they can be operated utilizing conventional activated sludge, contact stabilization
or step aeration.
The final settling tanks were designed on a solids basis, not the usual overflow or
detention basis. In the design, once it had been decided that combined sewage would
be treated during periods of runoff, further consideration to the final settling tank
size was given. It was decided that no increase in size would be required if the
Increased flow could be passed through the plant within about three hours. It was
agreed that higher flows beyond this time would "flush out" all of the activated
sludge.
No change in chlorine contact tank size was made.
For information, the plant was designed for an average dry weather flow of 3.5 mgd.
The characteristics of the sewage and waste used in the design provided for a BOD
of 320 mg/L (8500 pounds) and suspended solids of 290 mg/L (7500 pounds).
The present connected population is about 13,500 persons within the City plus 3,500
persons at the Northern Wisconsin Hospital and Training School, which is about one mile
east of the City and is the reportedly largest single institution in the State.
30
-------
The present BOD load is about 6000 pounds per day. There are four "wet" industries
which must be considered: Peters Packing Company, Leinenkugel Brewing Company,
Bowman Dairy and Clover Dairies. The wastes from the Brewery and Clover Dairies are
tributary to those sewers which overflow to the combined sewage storage pond. The
wastes from Peters Meat Packing Company and Bowman Dairy enter the intercepting
sewer near the Waste Water Treatment Plant, and are not in any way tributary to the
pond.
RESULTS;
In any new or different type of project, the results are the major consideration.
The entire project was designed using sound and proven engineering principles,
except that they had never all been put together in this manner in a single project.
Figure 4 is a tabulation of preliminary data to date. The table gives the total
precipitation on a given day, but not, at this time, the duration or intensity of
precipitation. Samples of the sewage and wastes entering the pond are collected
at five minute intervals by an automatic sampler. These are subsequently analyzed
in the laboratory at the Waste Water Treatment Plant. A similar program of sampling
the pond overflow to the river also is accomplished. All sewage and wastes tributary
to the pond are metered through a flume. The volume of sewage and wastes overflowing
the pond are currently not metered, although this could be done.
It will be noted that if the pond was not present, combined sewage would have overflowed
to the river in excess of sixteen times between April 20 and September 29, 1969.
At the time this paper is written, data has not been tabulated as to how many occurrences,
in excess of sixteen, would have overflowed to the river. With an average maximum dry
weather flow to the Bay Street Pumping Station of 2000 gpm and a new pumping capacity
of 6000 gpm, it is obvious that the first 4000 gpm of surface, runoff never entered the
pond. Between April 8 and September 29, 1969 there were 32 days having a measurable
precipitation. It is not known at this time whether there would have been a discharge
31
-------
DATA ON DAYS OF PRECIPITATION
1
DATE
kpril 8
14
20
26
27
toy 1
5
6
10
17
19
21
26
31
June 11
12
22
25
July 2
4
8
14
24
26
Xug, 4
29
Sept. 14
22
25
29
PRECIP-
ITATION
IN
INCHES
.07
0.14
0.20
0.13
0.48
.81
.05
,17
.02
.66
.22
.12
.10
.21
.88
.53
.48
.68
.69
.15
1.01
2.53
.03
.24
.4
1,97
.14
.18
,36
.22
.15
DUR-
ATION
OF DIS-
CHARGE
TO POND
IN MIN.
„
_
25
25
-
20
305
_
T-
_
_
_
_
_
-
90
_
50
80
60
_
90
115
_
55
110
110
-
60
65
_
35
B.O.D. TO POND
AVG
140
224
211
117
1ST
SAMPLE
196
223
191
151
156
182
55
125
78
170
98
110
383
315
154
179
72
229
81
141
142
142
368
261
121
2ND
SAMPLE
177
135
175
112
197
144
246
188
154
3KD
SAMPLE
195
212
44
227
140
296
233
184
4TH
SAMPLE
252
129
169
317
271
315
5TH
SAMPLE
260
323
483
LAST
SAMPLE
59
POND
OVERFLOW
TO RIVER
TIME
IN MIN.
_
-
-
-
-
-
—
-
-
-
-
-
-
-
—
-
-
-
-
-
-
-
120
-
-
-
60
_
-
-
-
KOD
AVG
61
27
PLANT SEWAGE
FLOW
MGD.
2.7
2.2
1.9
2.0
1.6
3.4
2.2
2.4
2.2
3.2
2.0
1.9
1.8
1.5
4.3
3.0
2.8
3.2
2.8
2.6
3.8
4.9
3.0
3.6
7.5
2.5
2.6
3.3
2.5
2.4
KOW
BOD
177
398
462
260
242
204
369
315
364
369
315
366
354
343
347
240
199
196
213
294
178
272
209
138
250
262
311
353
174
FINAL
BOD
53
69
22
32
21
52
15
12
25
15
12
30
22
20
22
23
32
8
13
26
4
14
6
25
3b
261e
17
11
22
aves
FIGURE 4
32
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to the pond if the pumping capacity of the Bay Street Pumping Station did not take
about the first 4000 gpm of runoff.
It must be realized that this is an unusually low frequency of rainfall. The area
experienced a severe drought in August and September. It would be nice if the weather
were more co-operative when an evaluation program is undertaken.
It will be noted, however, that on only two occasions did the pond overflow. One
of these occurred on July 14 when a total rainfall of 2.53 inches occurred and 1.45
inches of this occurred in about 35 minutes. This overflow lasted for two hours
and the five day BOD of the overflow was 61 mg/L. The second overflow occurred
on August 4, 1969 when there were two separate rainfalls. The first started at about
9:30 A.M. and entered the pond starting at about 9:45 A.M.. The pond had not been
*
emptied when a second rainfall of 1.97 inches started at about 9:20 P.M.. The second
rainfall lasted about one hour and about 1.35 inches fell in 40 minutes. The five
day BOD on this date was 27 mg/L.
The original worry of problems of sludge deposits on the pond bottom has been overcome.
The total time to clean the pond since April has been as follows:
April 15 Manhours
May 3 Hours - Street Sweeper
June 21 Manhours
July 22-1/2 Manhours
August 18 Manhours
September 3r-l/2 Hours ^ Street Sweeper
Experience has shown that the quickest and most economical means of cleaning sludge
from the pond is using a street sweeper. However, availability of the unit and
operator is sometimes a problem.
33
-------
Only two of the four aeration tanks are in use. The use of the other two has not
been required to date. Figure 4 also shows the 5 day BOD of the sewage and wastes
tributary to the Waste Water Treatment Plant and the final effluent on days of
precipitation. A review of this data indicates that the introduction of combined
sewage and treatment thereof has not been deleterious to the plant efficiency or
quality of final effluent when it is discharged to the plant at reasonable rates.
Attention is directed to the relatively poor effluent equality in April and early May.
The new facility was placed in operation in February From the start, and until
the first week in August, the return activated sludge pumps were not operating
properly or at capacity. This was a combination of faulty pumps and motors and
poor co-ordination between the motor and control manufacturers. The pumps were variable
speed units.
for information, the average volume of sewage and wastes, 5 day BOD thereof, and
final effluent from the plant have been:
MONTH BOD INFLUENT BOD EFFLUENT % REMOVED
February
March
April
May
June
July
Augus t
446
401
345
327
236
229
193
27
38
35
26
21
18
21
93.9
90.5
89.8
92
91.1
92.1
89.5
In the Spring of 1969 much of the upper Midwest experienced the second worst floods
in history. Chippewa Falls also had extreme high water , and the pond was flooded
with rjtyer water to prevent damage. After the river receded and the pond was drained
a fibrous material appearing to be similar to papermill wastes covered the pond bottom.
-------
This material was about 1/4 to 3/8 inch thick. In was readily removed in pieces,
some as large as about a square yard.
Two "bonus" results have resulted. The first of these resulted from the new trunk
sewers, which removed all "bottlenecks". Previously, whenever a rainfall, some of
lesser intensity than those encountered this year, many basements flooded because
of sewer "backup". There has not been a single flooded basement because of sewer
backup,
A second bonus became evident during the Spring flood. Previously, whenever there
was a flood, basements in buildings near the river flooded because of sewer backup.
In the Spring of 1969, not a single basement was flooded.
Some discussion appears appropriate concerning the characteristics of the combined
sewage entering the pond and which would otherwise overflow to the river. It was
once a general opinion that the "first flush" of runoff flow would produce the
highest BOD. Later some authorities have proposed that the flow sometime after
the ^first flush" would produce the highest BOD. Because about the first 4000 gpm
of flow from runoff in this instance is not sampled, the characteristics of the
first flush are not known. It appears, however, that the 5 day BOD of the flow
tributary to the pond increases for up to about 25 minutes. This would substantiate
the theory that the "first flush" is not the problem but rather a sustained flow.
The project has now been accepted by the general public as a major improvement.
Initially, the public was convinced that odors would result. There have been no
odors. Basement flooding has been eliminated. The public is happy about it.
The newspaper editor has had a sign prepared and the combined sewage storage pond
is now named "LAKE LEHMAN" for Superintendent of Public Utilities, Clyde Lehman.
35
-------
CONCLUSIONS:
A project of this type will achieve the required results if properly located, designed
and operated. Its use must be studied, based on land availability, feasibility and
economics. Of course, the requirements of the State Regulatory Agency must be considered.
It must always be remembered that any program of storm water separation can probably
never be 100 per cent accomplished if there has once been a combined system. Probably
the only way it could be accomplished would be to test every catch basin, televise
every sewer, and demolish every building where roof drains do not discharge above
ground and where it is positively known that there are not any footing and foundation
drains. There still remains those buildings having leaking basements and the water
goes to a floor drain.
The F,W.P,C,A, appointed a special task committee to review the project and observe
the sampling and testing program. At the time of writing this paper, the task review
committee has not submitted its report. However, the chairman of the committee has
advised that the only physical change they would recommend is the installation of
a baffle preceding the pond overflow structure. This baffle theoretically would
minimize the floating solids- from overflowing to the river. The committee expects
to recommend some changes in the tests now being conducted, especially the obtaining
of D.O. in the river.
36
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Polymers for Sewer Flow Control
by
George A. Kirkpatrick, P.E.*
"Polymers for Sewer Flow Control" is a report completed in
August 1969 by The Western Company of Richardson, Texas. It
describes the work performed during a 29-month contract period to
develop and demonstrate the use of high molecular weight polymers
to reduce pipe friction and, thereby, increase flow rates in sewers.
The additives thus used were tested for toxicity and their effect
on aquatic life. The effects of the polymers on sewage parameters
such as dissolved oxygen, biochemical oxygen demand, change in
settleable solids, and sludge drying were studied. Limited work
was performed to determine their effects on sedimentation, filtration,
and sludge drying in an actual wastewater treatment plant.
For those not familiar with them, polymers can be defined as
products resulting from the joining together of a number of identical
molecules of a simple substance. Rubber is an example of a polymer
which is made up of a long chain of isoprene molecules. It has been
learned that water can be polymerized to form a so-called "polywater", a
substance Uo percent more dense than normal water. In the wastewater
treatment field, certain polymers are used to induce coagulation of
colloids and assist in sedimentation and filtration processes.
*Storm & Combined Sewer Pollution Control Branch, Federal Water
Pollution Control Administration, Washington, B.C. 202^*2
37
-------
The chemical and physical changes which polymers impart to
fluids to reduce viscous friction have not been fully explained.
A simplified explanation given by The Western Company is:
"...that polymers probably tend to act as 'turbulence dampers' and,
in effect, damp out the very irregular paths of the fluid particles near
the wall and extend the laminar boundary layer further into the turbulent
flow core. This damping effect causes the laminar sublayer to increase
in thickness, resulting in a reduction in the wall velocity gradient
and shear stress gradient which provides a reduction in the frictional
resistance to flow, since the action of wall shear stress is to slow
down the fluid near the wall."
Based on a literature survey, and on the Contractor's previous
experience, six polymers were selected for evaluation. Preliminary
tests of these potentially "best" polymers were made in an existing
small-scale test rig, and five of them indicated sufficient potential
to warrant further testing.
A six-inch diameter, 100-ft long, asbestos-cement sewer pipe,
with one transparent section of pipe, was constructed to evaluate
the effects of polymers under different flow conditions of sewage.
(See figure l). Provision was made for varying the slope of the facility
between 0.3 and 2.0 percent, controlling the temperature of the sewage
between 38 and 90 F, varying the flow rate from 0 to 750 gpm, and the
polymer concentration from 0 to 1,500 mg/1. Sewage concentration could
be varied as required.
To disperse the polymers throughout the fluid for rapid absorption,
it was found necessary to first prepare them in a slurry form. For this
38
-------
Figure 1. Overall View of 6-Inch Diameter Flow Test Facility at Richardson, Texas
-------
purpose they were predispersed in a nonsolvent, either a product
called Cellosolve or anhydrous isopropanol, which was jelled with
a cellulose ether. The slurry consisted of hCffo polymer, 59-5$ non-
solvent, and 0,5^ gelling agent. Because one of the five candidate
polymers did not lend itself to this treatment, it was eliminated from
further testing.
Pressure drop, temperature, and flow rate through a 30-ft test
section were measured in the test facility. During each test the
flow rate was held constant. Each polymer was tested at various flow
rates, polymer concentrations, sewage concentrations, and temperatures.
Results of these tests are presented 3/i terms of percentage flow
increase (see figure 2), which was derived from measured pressure drop
using curves of relationship between pressure drop and flow rate,
as shown in figure 3- The three most effective polymers with respect
to flow increase at constant pressure drop, in order of decreasing
effectiveness, are Polyox Coagulant - 701 and WSR - 301 (both supplied by
Union Carbide Co.), and AP - 30 (supplied by Dow Chemical Co.). Flow
increases of more than lUO percent (2.^0 times original flow) were
attained with polymer concentrations of 150-200 ppm. Effectiveness of
these polymers varies significantly with sewage temperature and solids
concentration, with AP - 30 being least effected by temperature and
solids. (See figures k-6).
Following tests in the six-inch sewer line, a section of a 2^-inch
interceptor sewer line in the City of Dallas, Texas was instrumented
as shown in figure 7 for testing under actual field conditions. This
ho
-------
140
(300) gpm
(250) gpm
50 100 150 200
POLYMER CONCENTRATION-PPM
Figure 2., Polyox Coagulant-701 in Six-Inch
Test Facility at 73°F in Water.
25O
!/ FEET
O 01 m -j m
DROP- //VCaCS of WATER for 3C
ro w
PRESSURE
,
.
/
/
(
V
/
/
/
(
••
^/
JS-
/
ft
/
/
/
1
/
£,
*|
{_
/
/
/
P
1
/
/
/
1
?
D
7
50[
/
I'll
/'
''
Oppm
y200
tprn
300 400 500 600 TOO 800 9
M
FLOW RATE-flo/7?
Figure 3. Polyox Coagulant-701 in Six-Inch Test
Facility at 73°F in Water.
-------
140
120
100
k
1
c
80
I
IX
(A
<
Ul
cr
60
cr
ui
o
40
20
35 40
v-WSR 301 @ 200 PPM
a -POLYOX COAGULANT 701 @ 100 PPM
o -AP- 30 @ 250 PPM
o -D252 (cb 250 PPM
n-FR-4 @ 250 PPM
X -J-2FP@ 500 PPM
50 60 70
TEMPERATURE °F
80
9O
Figure ¥. Comparison of the Effectiveness of Six Additives
in Water as a Function of Temperature.
-------
h
I
1
I
140
120
IOO
80
l/J
•!
HI
rr:
o
60
I
40
20
o 200 mg/I POLYMER
A 100 mg/l POLYMER
D 50 mg/l POLYMER
140
100 200 300 400
SEWAGE CONCENTRATION-(mg/l)
500
0 mg/l SEWAGE
1500-mg/l SEWAGE
2700 mg/l SEWAGE
IOO 20O 30O 400
POLYMER CONCENTRATION-(mg/l)
500
Figure 5- Percentage Flow Increase vs Sewage Concentration
(mg/l) Polyox Coagulant-701 Polymer.
Figure 6.
Polymer (mg/l) vs Percent Increase With a Given
Sewage Concentration, Polyox Coagulant-701 Polymer.
-------
Figure 7. Plan and Profile of
Z4-Inch Sanitary
Sewer.
-------
sewer receives flow from a 36-inch interceptor line and discharges
into a 30-inch diameter sewer downstream. During peak daily flow
periods, the line is surcharged to heights between four and eight
feet above the top of the pipe.
Seven manholes were used in a 1,563-foot length of the sewer
line, and of the 36-inch line just upstream. Piezometers were
installed in six of the manholes - three to be read manually and three
ecjuipt with level recorders. Provision was made for taking temperatures
and collecting samples of the sewage. Sewage flow was measured by using
a dye tracer and a fluorometer for determining dye concentration.
Two mobile units for mixing, transporting, and injecting polymers
were constructed for the tests. Figure 8 shows the mixing and trans-
porting unit, which is primarily a 1,1^0-gallon tank. The second unit
containing the injection device with a capacity of 250 gallons per
minute, measured with a magnetic flow meter, is shown in figure 9.
Polymers were injected as a slurry consisting of 69.25$ isopropyl
alcohol, 0.75$ gelling agent, and 30$ polymer. In figure 10, the slurry
mixing and storage tank, the injector, and auxiliary equipment are shown
connected to the 2^-inch sewer line.
Four tests runs each were made to test Polyox WSR - 301 and
Polyox Coagulant - 701, using polymer concentrations varying between
35 and 100 mg/1. In each test, polymer injection was stopped when head
on the line was reduced enough to eliminate a surcharged condition. Both
polymers were effective in obtaining the desired head reduction, although
Polyox Coagulant - 701 provided a more rapid head reduction for the same
-------
Figure 8. Slurry Mixing Tank
Figure 9. Injection Unit
-------
'
Figure 10. The Injector, Slurry Mixing and Storage Tank, and
Auxiliary Equipment Connected to the 2^-Inch Sewer Line
-------
polymer concentration. A hydrograph of flow and changes in surcharge
elevation before, during, and after injecting polyox coagulant - 701
are presented in figure 11.
Based on information gained from these tests, and on an analysis
of frequency and intensity of rainfall in the area, the annual cost
of using polymers to control overflows, from a 15-inch sewer at Garland,
Texas, was estimated to be about $6,^00 per year. Based on actual bid
costs for construction, and on average sewer operation and maintenance
costs in Garland, the estimated cost of a relief sewer would be about
$27,000 per year, or more than four times as great.
While tests were being run to demonstrate the effectiveness of
polymers on flow increase, laboratory tests were conducted on the
originally selected six polymers to determine their effects on aquatic
life. Concentrations of polymer of up to 500 mg/1 were used. Tests
were made using polymers in both a slurry and non-slurry form, and using
nonsolvents without polymers. From these tests, the following conclusions
were reached:
1. The polymers evaluated are nontoxic to bacteria found
in raw sewage under the conditions of the tests. Therefore, they
should not be detrimental to the micro-biological treatment process in a
wastewater treatment plant.
2. The polymers tested have neither toxic or nutrient effect on
algae under the concentration and conditions tested.
3. The use of polymers as friction reducers in sewers will not
contribute indirectly to lake or stream pollution by having a toxic affect
upon fish life.
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•
2:00
Figure //. Hyclrograph of Flow and Surcharge of Monitoring Manholes Before, During, and After Injecting Polyox Coagulant-701.
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Tests of the effects of the polymers on certain sewage
parameters resulted in the following conclusions:
1. All the polymers demonstrate the capability to increase
sedimentation. Although some loss of polymer injected into a
sewer may occur due to sedimentation, this loss would be small
because of turbulent conditions when the sewer would be surcharged
and the polymers would be used.
2. The 5-day BOD for all polymers averages 1.56 mg/1 for a
polymer concentration of 500 mg/1. This value of'oxygen demand is
negligible when compared with that of the raw sewage used in the
tests, about 200 mg/1.
3. Use of polymers decreases the water retention capacity
of sludge, thereby yielding a dryer sludge cake for earlier disposal. .
The wastewater treatment plant at Lewisville, Texas, was
instrumented and tests with polymers were run to determine their
effects on sedimentation, filtration, and sludge drying under actual
wastewater treatment plant conditions. Unfortunately, due to plant
machinery breakdown and other plant operational difficulties during
the testing, results of the work are inconclusive. Although no
definite improvements in filtration and sedimentation rates could be
detected, apparently no adverse effects developed under the conditions
of polymer application at the plant.
Additional experimentation with use of polymers for sewer flow
control is recommended to include the following:
50
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1. Investigate polymer modification to permit dry feeding
directly into the wastewater, without use of a slurry.
2. Study the effects of mechanical agitation, such as pump-
ing, on degradation of polymer effectiveness.
3. Test the effectiveness of polymers on flow increase in
pipes of larger diameter.
h. Study the effects of friction reducing polymers on filter-
rock biota and the activated sludge treatment process.
5. Determine the effects of various industrial wastes upon
the friction reduction capabilities of polymers.
The City of Dallas, Texas, with the assistance of The Western
Company, has commenced a project to install permanent equipment to
inject polymers into a 30-inch sewer line to increase flow rate and
control overflows. Possible degradation of polymer effectiveness when
flow passes through a pumping station will be investigated. Nearly
75 percent of the cost of this project is to be funded by an FWPCA
demonstration grant.
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OVERVIEW OF TREATMENT METHODS
by
Darwin R. Wright
If I were a college professor at this time, I would tell you
to open up your text book to the section on combined sewer overflow
treatment, but there is one problem. There isn't a book on the
treatment of combined sewer overflows. Why? Because we are treating
a different waste with a different flow pattern; we are treating a
random waste, not a steady-state waste. As we proceed, I think that
you will find why this is true.
I would like to make two points. Number 1, as we say in Washington
after we got Vince Lombardi and Ted Williams, it is an all new ballgame.
Just taking quality alone, it is not unusual to have the suspended solids
range from a few mg/1 to 2000-5000 mg/1 and these changes can occur
rapidly. There is also a difference in the COD/BOD relationship, being
greater than domestic sewage. As was mentioned earlier, I am not convinced
that there is or is not a first-flush phenomenon. The important thing
is that you are going to have to treat a varying waste. You are liable
to get this "first flush" at any time. The quality will be constantly
changing since the flow pattern is constantly changing. You are treating
a storm hydrograph. You are not talking about a peak dry-weather flow
that may be twice the daily average flow. You may be talking of a peak
flow of a hundred to a thousand times dry-weather flow. I was in
Philadelphia yesterday and although I don't think you would design for
a hundred year storm, one outfall has a dry weather flow of about 25 cfs
(intercepted) and over 3000 cfs storm flow was recorded. That is high,
but this same sewer is capable of going up 20 or 30 times the normal
53
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dry weather flow or peak dry weather flow for a one-year storm. Since
we have the two problems of varying quality and quantity, it appears
that some type of a storage or surge facility ahead of the treatment
unit will "be required. One of our speakers this afternoon will discuss,
in some detail, the tradeoffs that were made between storage required
versus treatment facility size.
We are basically looking at all three of the treatment methods--
physical treatment, biological treatment and physical-chemical. Under
the physical treatment methods, the two that are going to be talked
about after lunch appear at this time to be the most promising. One
is screening from bar screens down to micro strainers with 15 to 20
micron size openings. The other promising metliod is dissolved air
•flotation. We have gone through a .5 mgd pilot plant scale. We now
have a 5 mgd- plant, which you will hear about this afternoon, in
Milwaukee; and we have the plans and specifications for a 2k mgd plant
in San Francisco. When we talk about high-rate filtration we are talking
about "high-rate" filtration. "High-rate" filtration will be covered
by the Crane Company speaker today, but we're talking now about ^5
gallons per minute per square foot. We are attempting to achieve
the equivalent of secondary treatment, or 70-80 percent removal of
solids. I might point out here that since we are treating a different
waste, if we can get out 70 or 80 percent of the solids, we can get
maybe 60 or 70 percent BOD removal. A couple of other techniques that
we have tried in the filtration area is one in which we used an ultra-
sonic filtration system where we could go down to 10 microns pore
openings. It turned out that after providing the pre-treatment
required, because of the nature of the combined sewer overflows, the
plastic filter elements were not effective. We tried also using the
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diatamaceous earth filter and again that was unsuccessful for the
same reason.
The SWECO screen is a vibratory rotating screen which we have
successfully tested in Portland on combined sewer overflows. Utilizing
mesh screens instead of micro screens, UO percent to 50 percent removals
have been achieved.
When it comes to biological treatment, we suddenly wonder what
happens when you have a large influx of flow. Here again we are talking
of 15-20 times dry weather flow on a routine basis. The one we have
investigated that looks promising for high flow rates, is the Allis
Chalmers' bio-disc, the rotating biological contactor method. The
dry weather flow going through the plant is 1 mgd and the peak flow is
about 2k mgd. As with the other treatment processes, it appears that
a surge facility will be required. This particular type of biological
treatment involves a large concentration of bio mass. Sloughing is a
problem and the bio-mass is very easy to settle. Therefore, a final
clarifier is needed.
In New Providence, New Jersey, we have under construction a high-
rate rock filter and a plastic media filter. We are attempting to
determine how a high-rate filter compared to a standard trickling
filter will react to treating storm overflows. Part of this project
is a surge facility. New Providence can only discharge into the inter-
ceptor sewer one-half mgd per 8 hours. Since normal daily variation of
flow just doesn't follow the above condition, the surge facility will
be used to enable the City to discharge at a constant rate of 0.5 mga
per 8 hours. The surge facility will also reduce peak storm waters and
level out the flows to the treatment facility.
55
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Mention was made earlier of the Kenosha project involving a bio-
solids reservoir. There will be a 15 to 30 minute contact tank which
will be empty during dry weather conditions. Storm flow will be
diverted into the contact tank, as will bio mass., thus providing solids
stabilization. Chlorination will also be provided.
We have one project where we have built a 10-acre oxidation pond
for treating combined sewer overflows. The results are inconclusive,
but tend to be on the negative side. As built, the pond needs further
refinement. We have under construction a deep lagoon project in which
we will have anaerobic treatment at the bottom and aerobic treatment
at the top.
Under the physical-chemical treatment processes, the feasibility of
activated carbon adsorption followed by or with coagulation, flocculation
or sedimentation is being investigated. It appears that carbon regeneration
may be a problem. In-house and contract work for FWPCA indicate that
economical methods of carbon regeneration may be available soon.
As far as disinfection is concerned, which would be the final
stage, we are investigating in New Orleans chlorination with gaseous
chlorine versus sodium hypochlorite. We are attempting to treat 11,000
cfs during a peak storm flow. To provide large quantities of sodium
hypochlorite the Grantee built an automatic hypochlorite plant. We
are investigating use of ozone in our microstrainer project.
We have also done exploratory studies on some of the other ones
like bromine. This report will be out soon.
An interesting question is, "What degree of treatment do we want?"
We haven't really formulated a policy yet on what degree of treatment
is required. The key issue depends upon the existing water quality
standard. To protect a beach area, reduction of bacteriological
56
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pollution would be the important parameter. This is basically the
problem which we face now with our San Francisco dissolved-air flotation
grant. Of prime concern is cleaning up a beach area, making it safe
from a bacteriological standpoint and removing the flotable solids--
grease balls and other visible materials.
If you have a stream which already is overloaded from any oxygen
demanding material or unsitely sludge deposits, the BOD or solids must
be controlled. Another problem in analyzing your system is industry
wastes or some other toxic material which may be contained in the over-
flow. The other thing to consider in the control of overflows is
what effect will this control have on the existing sewage treatment
plant. If you store all the waste from 30 overflows, where are you
going to treat it? If you already have an overloaded sewage treatment
plant, you are going to have to provide additional facilities. Consideration
should be given in the planning for making the facilities multiple
purpose. The facilities could operate during dry weather flow to
provide a higher overall degree of treatment. During periods of
runoff you would treat the overflows. The net result is a greater
overall system efficiency. In planning new treatment facilities, such
as new dry weather treatment plants or additions, consideration must
be given to the storm water overflow problem. If you do provide
storage facilities, you are going to have to treat that stored waste
somewhere. One of the gaps which we still have in our program,
because we have not completed all our projects, is the cost data, as
pointed out in the storage problem at Chippewa Falls, the alternate
solution was nearly equal to what the separation cost was except for
the intangible benefits. One thing with that particular project or
with all projects, if you separate you will have to live with adverse
57
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quality of the separate storm water. Ten to 15 of our demonstration
studies have sampled straight storm water. For highest water quality
uses associated with the water quality standards storm water discharges
impart a significant load. This load would probably not meet the existing
standards. One of the problems which needs resolving is the intangible
costs or benefits. To come up with a true cost, both tangible and
intangible costs must be considered. There seems to be a problem as
to how to express the combined sewer abatement cost. The typical
terminology used for treatment costs is cents per thousand gallons.
Is this a realistic cost to use when you are only talking about
operating these facilities maybe 3$> of the time? In this general
area here in the Northeast it rains about 3 percent of the time, over-
flows occur 3 to 5 percent of the time. Should treatment be expressed
in terms of dollars per acre, which would give an equivalent separation
cost. Regardless of how the cost is expressed, we must accept the
fact that there is not an economical solution utilizing either treat-
ment or in storage. The route we are taking on these projects is the
development of cost curves based upon flow rates or treatment efficiencies.
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MICROSTRAINING - WITH OZONATION OR
CHLORINATION - OF COMBINED
SEWER OVERFLOWS
PRELIMINARY REPORT
By: W. A. Keilbaugh, Manager, R & D
G. E. Glover, Research Engineer
P. M. Yatsuk, Engineer
COCHRANE DIVISION, CRANE CO.
King of Prussia, Pa,
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
CONTRACT No. 14.12.136
For Presentation, FWPCA Seminar - Combined Sewer
Overflows, Edison, N.J,, Nov. 4-5, 1969
59
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ABSTRACT
(C)
Micros-training, using a nominal 23 micron aperture Microstrainer screen,
has removed up to 98% of the suspended solids from a combined sewer over-
flow. The sewer, which has an average sanitary sewage flow of 1,000 gph,
serves a residential area of 11 acres in the City.of Philadelphia. The
maximum combined sewer flow recorded during rainstorms in one year of
operation has been 305,000 gph.
Volatile suspended solids removals with the 23 micron Microstrainer screen
have averaged 68% and 71% during different test periods.
BOD removals, as measured by BOD tests, and coliform bacteria concentra-
tions in the Microstrained effluents have varied widely, Postulations
as to the effects of Microstraining on these results are given.
Results to date indicate that there is a slightly better colon group
bacterial kill with chlorine in the Microstrainer effluents than when
ozone is used, when both are used at'an initial nominal concentration
of 5 ppm with 5-12 minutes detention time. However, chlorine applica-
tion has been better controlled and it has not been possible to optimize
requirements for these chemical feeds.
Preliminary estimates have been njade for the costs of treatment for a
combined sewer via the Microstraining process. It is estimated that the
costs per acre of drainage for a full scale plant in our test area would
range from approximately $9,500 to $11,800 for Microstraining alone,
$10,500 to $12,800 for Microstraining plus chlorination, $18,000 to
$21,300 for Microstraining plus ozonation. These costs compare favorably
with other techniques that have been proposed; e.g., the costs associated
with construction of separate storm and sanitary sewers have, in several
cases, been estimated to range between $20,000 and $23,000 per acre,
Cost estimates at a higher confidence level for Microstraining could be
derived through additional investigation at the higher throughput rates,
the consideration of which was begun during the latter part of the pro-
gram. We have also performed preliminary calculations, which show that
larger installations; e.g., 10 x the above, may produce costs 20% to
30% lower than these estimates, on a per acre basis.
Moreover, should the market for Microstrainers substantially increase
over present levels, it is probable that a higher production volume
would result in lower production costs, which could be passed on in
savings to users.
(C)
v 'Copyrighted Trade Name - Crane Co., Glenfield & Kennedy Div,
60
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This work has been conducted with the cooperation of the City of
Philadelphia under Contract NO- 14.12.136 from the Federal Water Pollution
Control Administration, U.S. Department, of the interior.
61
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INTRODUCTION
The pollution problems associated with combined sewer overflows in our
cities have multiplied and grown enormously over the past 20-30 years.
The increased concentration and growth of urban activities have brought
this about, and these problems have been subjected to much technical
and economic study. The studies have been intensified and broadened,
particularly over the past 15 years or so, because of increased public
awareness of the severity of the overall problem of pollution of our
streams and coastal waters.
Exact figures are difficult to obtain — and they are
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of opinion that the quality of separated urban atorm water is such that
this separated storm water should be treated in some manner prior to
ultimate discharge.
It now seems obvious that, for a variety of reasons, the separate storm
and sanitary system concept is not, at least by itself, the answer to
the problem. Rather, conclusions from information gathered in an
extensive survey' 'point out that different solutions and combinations
of solutions will be required in different localities depending upon
local circumstances. These circumstances include not only the dis-
charge systems, rainfall, areal characteristics, etc., but also the
desired character of the effluents as they relate to the receiving
stream or body of water.
The work reported here should provide a basis for the application of
additional tools that can be employed in combatting a most complex
pollution problem.
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SUMMARY
The information developed in this work to data preliminarily indicates
that treatment of combined sewer overflows via Microstraining can
furnish a high degree of solids removal for a per acre-cost of approx-
imately 40-50% of the cost of sewer separation in cities where separation
has been considered, such as Washington, D.C., Philadelphia, and Chicago.
Treatment of an actual overflow in a residential area of Philadelphia
has produced solids removals of up to 98%. Limited data, for a fine
Mark "0" (23 micron) screen, under relatively high throughput conditions,
show removal figures ranging from 78% to 98%, with an average of 91%.
Figures for a larger number of tests made with lower throughputs show
a solids removal range of 62% to 96%, with an average of 80%.
Volatile suspended solids removals have roughly parallelled the
experience with total suspended solids. These removals for the Mark "I"
(35 micron) screen averaged 47% and, for three modes of operation using
the Mark "0" screen, have averaged 68%, 71% and 71%.
Bacteriological results measured across the Microstrainer screens
exhibit anomolies, both reductions and increases in total and fecal
coliform being measured. Further major total coliform reductions can,
of course, be achieved with chlorine or ozone. Our results, with both
ozone and chlorine, although again anomolous in some instances, indicate
a slightly better performance with chlorine. Both chemicals have been
used at a nominal 5 ppm feed rate, the chlorine detention time being
varied at 5 and 10 minutes, and the ozone reaction period regulated
at about 12 minutes. Average values for total coliform residuals after
treatment were (per 100 ml) 166,000, 129,000 and 619,000 respectively.
These values for fecal coliform residuals were 41,000, 81,000 and 42,000.
We attribute the ostensibly better performance of the chlorine to a
more positive mode of chlorine addition than has been possible with the
ozone.
BOD removals across the Microstrainer have been difficult to measure.
In those cases where reductions have been recorded, the average re-
duction has been 65% across the Mark "0" screen. However, in 8 of the
17 measurements, increases in BOD are shown across the Microstrainer.
Several postulations have been made for the observed increases:
1. Natural predators for bacteria are largely removed by Microstraining
and are thus not present in large number on the discharge side.
2. Large colonies of bacteria are subdivided into larger numbers by
passage through the screen.
3. The bacterial food supply is made more available — more surface
6k
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area is produced on the e-ca^iru} so lido -- by tine screening process
and growth kinetics are fcnh^ncaa. This is perhaps reflected in the
observed BOD increases.
We lean toward the last-named explanation, and believe that such effects
of the Microstraining process can be desirable in the treatment of storm
water:
1. Smaller particles will have a lesser tendency to occlude bacteria.
They are thus more vulnerable to attack from ozone or chlorine.
2. If the BOD peaks largely over an early, shorter time period, down-
stream effects are likely to be less persistant.
This work has consisted of the design, installation, operation and
evaluation of Microstraining equipment, and of ozonation and chlorination
at a combined sewer overflow judged to be typical. At the time of this
report, operation has not been concluded and complete evaluations have
not been made. However, enough information is available to permit
preliminary conclusions regarding Microstrainer operation on this type
of combined sewer overflow.
Initially, the Microstrainer was fitted with a Mark "I" screen. Results
indicating effluents of intermediate quality were obtained from 9 rain-
falls of utilizable intensity and duration over a 6-month period,
A finer, Mark 1!0" screen, was then fitted to the Microstrainer.
Effluent qualities, with respect to removals of total and volatile
suspended solids increased measurably.
After an additional 8 useable rainfalls, the Microstrainer controls
were altered so as to produce a pre-established constant differential
head across the Microstrainer screen. Results from 6 sets of samples
during 3 different rainfalls indicated still further improvement in
suspended solids removals.
Finally, the differential head has been increased well above the normal
level noted above by blanking off much of the screen area designed
into the Microstrainer model employed. This reduction in screen area
amounts to about 80% of that available for filtering and has resulted
in high quality results in terms of suspended solids removals. These
results are most significant because they point the way to higher
hydraulic loadings with attendant lower capital costs.
These last tests, although few in number, indicate that the Microstrainer
Mark "0" screen in this service is superior to the Mark "I" coarser
screen, and that the Mark "0" performs well at a higher hydraulic load-
ing. No evidence of screen pluggage has been observed at any time.
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"Pretreatment" of the Micros-trainer influent by means of a heavy solids
trap and a bar screen are recommended for Cull scale installations.
Early approximate estimates for installed capital costs for such an
installation, and based on our 11 acre drainage area are:
1. Bar Screening and Microstraining $ 9,500 - $11,800 per acre
2. Bar Screening, Microstraining plus
Chlorination @ 5-20 ppm $10,500 - $12,800 per acre
3. Bar Screening, Microstraining plus
Ozonation @ 5 ppm $18,000 - $21,300 per acre
We hope to do further work to further define Microstrainer performance
at higher, heretofore unexplored ratings, and to optimize chlorine and
ozone requirements.
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EXPERIMENTAL
EQUIPMENT & TEST SITE
Microstrainer
The test system incorporates Microstraining for the removal of suspended
solids and associated impurities, followed by ozonation and/or chlorination
for disinfection. The Microstrainer comprises a 5 ft diameter by 3 ft
long drum, fitted on the periphery with a specially woven wire fabric of
stainless steel, having microscopic apertures. In this work, two
different types of screen have been employed, the Mark "I" (nominal
aperture 35 microns) and the Mark "0" (23 microns). In operation, the
drum is submerged in the flowing water to approximately two-thirds of
its depth. Raw water enters through the upstream end of the drum and
flows radially outwards through the microfabric, leaving suspended solids
deposited on the inside of the mesh. The drum rotates continuously, at
variable speeds, carrying the dirty fabric out. of the water and under
backwashing jets mounted across the top of the drum.
Intercepted solids are flushed into a receiving hopper fitted inside
the drum, with its lip above the top water level. in a full scale
project, these solids would be returned to the interceptor sewer for
disposal to the nearest sewage treatment plant.
Microstrainers of this type have been employed since 1945 for the
filtration of municipal and industrial water supplies, and more recently
for "tertiary" treatment of sewage effluents^ '
Chemical Equipment
After water passes through the Microstrainer, it is collected in a 1,200
gallon storage tank, before ozonation or chlorination. Ozone, is
generated in an Otto* Plate Type (Model 3-63) Ozonizer. This ozonizer
has 15 plate type elements and is rated at 300 grams of ozone/hour at a
concentration of 20 grams/cubic meter of air at a maximum power load of
7 kw. Supply to the high voltage electrodes is variable over a 7,000 -
15,000 volt range. The maximum cooling water requirement is 11 gal/min
at 15 foot head. Air drying equipment including a refrigerator and
dessicator, and electrical control panels are also provided. The air-
is supplied by a 1/2 hp blower and is filtered. It is cooled to 2-5° C
prior to dessication in silica gel columns to a dew point of -40° C.
The concentration of ozone in air and the amount of ozone introduced
into the water can be varied by adjusting the air flow and the voltage
of ozone production.
*Supplied by La Compagnie des Eaux et de 1'Ozone (CEO) of Paris, France.
67
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in the CEO Otto system that, we are usirv-j (Figure i) , hydraulic injectors
are used to mix ozonized air with the water to be treated in two contact
columns. The water is puraped to a first injector, where it mixes with
residual ozone and air from the second contact column. Both water and
ozonized air travel down through a centrally located (1*5 in D) pipe in
the deep (17' L x 12" D) column, in which the water level is regulated
at about 16 ft in depth, exiting at the bottom of this pipe and passing
upward through the first column. Air and unused ozone exhaust at the
top of this column. The effluent water from the first column is pumped
to a second injector for absorption of the initially generated ozone,
and this gas mixture passes through a second identical contact column.
The finally treated water is discharged to an inspection tank and then
to the surface stream.
It can be seen that this system can be described as a combination co-
current — counter-current contactor.
In* an actual plant, where operation is intermittent, it would seem
desirable from a capital cost standpoint to use an oxygen, rather than
an air, supply to the ozonizer. Using oxygen, the concentration of
ozone in the ozonizer effluent gas is twice that with air. Thus any
ozone generator will, produce twice as much ozone from oxygen as from
air.
We suggest that oxygen would be used on a once-through basis, with no
oxygen recycle.
Chlorination equipment supplied for the plant consisted of a gaseous
addition system**. Originally, water was treated by means of this
system, and attempts were made to retain the chlorinated effluent for
varying periods of time. However, the short duration of very many of
the useable rainstorms created metering and regulation problems. This,
coupled with the need for a supply of water for relatively long periods
of time for operation of the ozonator, forced a change in the method
of chlorine treatment. Manual addition of a solution of sodium
hypochlorite to samples of Microstrainer effluent from the holding
tank was adopted. Close control of chlorine addition was then possible
and the residual,— after chosen retention times -- was destroyed by
the addition of thiosuifate prior to refrigerated storage while awaiting
analysis.
Test Site
The test site is located on the western side of Philadelphia on a sewer
outfall which enters a tributary stream of Cobbs Creek, flowing
eventually into the Delaware River. The outfall serves an area of
**Wallace and Tiernan
68
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OZ.ONIZED AIR
ROTAMETER
CHLORINATOR
INJECTOR
REFRIGERATOR
AIR BLOWER
AIR FJLTGR
-SAMPLE
POINT
FLOOR LEVEL
DESSICATOR
ROTAMETER
CHLORINE CONTACT
AND STORAGE TANK
INSPECTION
7 A N K
MICROSTRAINER
FLOW
/METER ^SUPPLY PUMP5
2ND OZO^E
INJECTION
PUf/lP
FLOW RECORDER
-LOGS LcV£L
TC STREAM
1ST OZONE
INJEC
PUMP
SEWER
OUTFALL
MEASURING
COMTACT
COLUMN
CONTACT
COLUMN
EQUIPMENT INSTALLATION- SCHEMATIC
Figure 1
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approximately 11.2 acres, principally dwelling houses with paved roads
and sidewalks (Figure 2). Dry weather flow in the sewer averages
1,000 gallons per hour, and at the setting employed during the tests,
the interceptor will collect up to four times this flow. In Figure 2,
the dotted lines define sub-drainage areas, and the solid lines connect-
ing the small circles (catch basins) are the sewer lines. The outfall
is located at elevation 148, about 3 feet below the 150.7" intercepting
elevation.
Overflows normally take place when storms in the area exceed a rate of
0.1 in/hr which occurs approximately 40 times a year, mostly during the
spring and summer. However, our plant is such that it is usually not
properly activated unless the rate reaches 0.2-0.3 in/hr for about 1 hour.
The rate of flow into the outfall can reach as much as one million gallons
per hour during an intense storm of six inches per hour, which is attained
on average once every five years.
The sewer outfall was modified to incorporate a collection sump (Figure 3)
from which the storm water runoff is pumped into the test installation.
Rate of flow from the outfall is measured by means of a weir fixed at
the sump outlet, and is continuously recorded. A baffle wall was con-
structed in front of the weir to prevent surges of water upsetting the
measurement of flow rate.
Two Microstrainer supply pumps are installed between the baffle wall
and the measuring weir one having a maximum flow capacity of 12,000 gph,
the other having 5,000 gph capacity. These pumps have been used together
and separately so as to supply water at rates of 5,000 and 17,000 gph,
with some intermediate and lower rates, depending on the supply heads
available. Intakes to the pumps are protected by a screen, having 1/2"
square openings.
Operation
As water enters the collection sump, the level rises starting the pump(s)
and initiating a timer connected to the sampling devices inside the
test installation.
The rate of flow pumped into the Microstrainer is recorded continuously.
The pumped flow from the sump, together with the recorded overflow yield
an indication of the total storm flow.
As water enters the Microstrainer drum, head loss through the fabric
increases causing the drum speed to increase by means of an automatic
control system. Water for backwashing is drawn from the downstream
side of the strainer by means of a small pump, kept supplied during dry
periods from a storage tank containing city water. The Microstrainer
thus commences its filtering action at the beginning of a storm, passing
70
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Figure 2
OUTFALL
67TH&CALLOWH!Li.
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-TROUG-H
SEWER
OVERFLOW
MICRO
STRAINER
2.43
SCREEN-
a
Hi
life
.PUMPS
SEWER OVERFLOW TROUGH
M/CROSTRAJNER SUPPLY
Figure 3
-------
strained water into the collection tank. Water not stored lor further
tests is bypassed and returns to tht stream.
Sampling
Composite samples of the raw and strained water are extracted automatically
during a storm and stored in refrigerated containers from where they are
collected and tested by the Philadelphia Water Department. Ozonation
and chlorination are carried out as soon as possible, and further samples
are taken before and after treatment.
The Philadelphia Water Department performs the laboratory analysis of
samples, maintains the recording rain gauge and cleans the outfall sewer
after each overflow.
73
-------
RAINFALL AND RUNOFF
Rainfall Intensity-Return Frequency curves for the City of Philadelphia
are approximated in Figure 4, as furnished by the City Water Department.
Figure 5 shows the rainfall intensities and durations that we have
measured during the course of the testing from a rain gage located
about 100 yds from the test site, along with calculated corresponding
runoff coefficients. Total flows are measured by a rectangular weir
mounted at the discharge of the combined sewer trough and the metered
quantities that are pumped to the Microstrainer. The sanitary flow is
subtracted, according to the corresponding flow expected during the
same period, along with the pre-calibrated portion that flows into the
interceptor through a "drop" weir preceding the outfall. in relation
to our higher total flows, this constitutes a minor correction, since
the drop weir is set to accept only 4 x the average dry weather flow
(1,000 gallons/hour).
It can be seen that the highest rainfall recorded during our work has
been about 3.3 in/hr for 10 minutes but that the highest runoff
coefficients (0.8) do not coincide with these periods. We also have
shown, for some points in Figure 5, the intervals in days since the
previous rainfall. These figures do not appear to be adequate for
interpretation of the differences in the runoff coefficients.
The highest flow at which the combined sewer discharged into its
receiving sump was thus approximately 300,000 gal per hour for about
.08 hours. The corresponding runoff coefficient was calculated at 0.5.
For the 11 acre area involved, which has an imperviousness factor of
61%, this runoff amounts to 450 gal per min per acre.
The lowest runoff figures, recorded for which operating test data were
acquired, were approximately 10,000 gal per hour.
-------
2OO
rim
15.0
Figure 4
FREQUENCY ANALYSIS BY METHOD
£KTREME VALUES, AFTER G-UMBEL
II
IS 20 30 40 5060 3
MINUTES QUKM1ION
4 5 0 JO 12
PHILADELPHIA . PFMNSYLVAMIA
1903- 195)
75
-------
Fiqure 5
300,000
§
I
2?
K
•a:
o
200.000
UJ
i
u.
o
i
oc 100,000
£
GC
i
ID
3E
X
ITTT
o.io
8--H
-f Maximum Intensity over 5 minutes
O Mavimum Intensity over 10minutes
(NO.)DAYS SINCE LAST STORM
1,
1 - -1 l_
o
JLLLLJJ
1.0 2.0 30 4.0 5.0
RAIN FALL INTENSITY INCHES/HOUR
MAXIMUM STORM RUN-OFF
V3
RAINFALL II^TEWSITY
: .UJJL
7
-------
COMBINED SEWER OVERFLOW QUALITY
As expected, our data show that the quality of the overflow tends to
change with both the quantity and the duration of the rainfall. For
example, in Table 1, for the storm of 7/23/69, it is seen that the
suspended solids concentration of the Microstrainer influent was 55 ppm
during the early storm period, increasing to 97 ppm at a second later
sampling, and then falling to a lower 21 ppm nearer the end of the last
period. The same phenomena are shown for the storm of 7/28/69. Figure 6,
which combines elements of both time and rainfall intensity, illustrates
the relationship between overflow flow rate and suspended solids over a
larger number of storms for which both flow rate and suspended solids
data are available. From this limited information there is a direct
relationship. These data were accumulated over relatively short periods,
and it would seem that, with high intensities for longer periods, this
relationship will not hold. Unfortunately, data for varying flow vs
individual suspended solids information within storm periods are not
available.
Fecal coliform results are generally higher at the beginning or toward
the middle of a storm and lower at the conclusion (Table 2). BOD results
tend to follow the same coursetthat of the total suspended solids for
7/28/69 and 9/3/69, as do volatile suspended solids (Table 3).
77
-------
AJJLM i /
Suspended Solids, mo/1
Date
In
Out
% Reduction
BOD, ma/1
In
Out
% Reduction
MARK "I" SCREEN
oo
12-3-68
1-23-69
4-11-69
4-18-69
4-19-69
4-21-69
5-9-69
5-19-69
5-20-59
AVG.
MARK "0"
6-15-69
6-13-69
6-23-69
6-25-69
7-7-69
7-23-69
7-23-69
7-23-69
AVG.
104
71
202
223
457
115
108
173
372
203
SCREEN
107
103
159
157
118
55
97
21
102
57
62
90
150
251
71
44
89
139
106
71
17
48
24
49
29
43
17
37
45
13
55
33
45
38
59
49
63
44
34
84
70
85
58
47
56
19
57
21
17
36
29
27
40
39
43
44
33
18
782
23
21
20
12
18
26
252
130
20
112
11
38
30
41
135
5
49
9
38
15
6
48
3
7
4
16
14
Incr.
36
28
26
70
54
53
Incr.
55
66
Incr.
84
Incr.
93
95
20
-------
TABLE 1_ (continued)
SUSPENDED SOLIDS AND BOD, MICROSTRAINER INFLUENT, EFFLUENT
Suspended Solids, mg/1
Date Jn
-"•*" *• '- •• ^TT^* -- ••••— ^"-'- ' ™ • •
MARK "0" SCREEN
Control change , Max.
differential increased.
7-28-69 175
7-28-69 498
7-28-69 288
7-29-69 139
7-29-69 189
8-4-69 163
AVG. 242
MARK "0 " SCREEN
Filter Area Reduced
9-3-69 111
9-3-69 419
9-3-69 69
AVG . 200
Out
66
55
72
50
17
6
44
2
17
15
11
% Reduction
62
89
75
64
91
96
80
98
96
78
91
BOP, mq/1
In
135
740
13
296
Out
8
385
13
14
260
438
186
6
76
210
16
370
584
211
740
208
45
331
% Reduction
25
80
Incr.
Incr.
Incr.
Incr.
Incr.
72
Incr.
-------
5001
0
100 200
GAL. PER HOUR X 1000
300
INFLUENCE OF flUN-OFF RATE ON
SUSPENDED SOLIDS
-------
TABLE 2
CO
H
Date
MARK "I"
12-3-68
1-23-69
4-11-69
4-18-69
4-19-69
4-21-69
5-9-69
5-19-69
5-20-69
MARK "0"
6-15-69
6-18-69
6-23-69
6-25-69
7-7-69
7-23-69
In
SCREEN
330
1,300
510
1,610
1,460
690
9,000
28,000
1,500
3,000
2,100
SCREEN
13,400
4,400
100
6,700
27,000
2,200
3,700
2,800
FECAL COLIFORM^
After Chlorination
Out 5 ppm-5 min 5 ppm-10 min
655
900
670 5
1,630
1,940
5,700
8,800 100 670
-
28,000
2,500
4,800
3,000
6,200 77,000(3) 58
_
2,600 77 0
-
2,800 63 22
-
590 91 8.4
-
30,000
11,000 0 1
-
2,700
810
1,100 0.1 25
After Ozonation Residual Ch, ppm
5 ppm(2)
_ _
- -
- -
-
-
- -
140
110
-
33 1.9
0.2 1.3
0.3
32, 000(3) 1.6
23,000(3)
44 1.9
23
200 0.6
57
5,700 1.-3
2,800
-
6.8
4.3
-
- -
0.6 0
(%er 100 mix 1,000
(2)Nominal Feed Rate
(^Values Not Used in Calculation of Averages
-------
Date
TABLE 2 (continued)
FECAL COLIFORM(1)
After Chlorination
5 ppm-5min 5 ppm-10 min
After Ozonation
5
Residual P.?, ppm_
MARK "0 " SCREEN
Controls changed
relation between
to produce fixed
differential and
drum speed. Max. differential
increased .
7-28-69
7-29-69
8-4-69
240 190
120 0 -
11 0.5 5.4
- -
0 76 25
- -
25 31
- —
5 90 -
110 120
200 18 0 0
"* —
-
-
0.6
1.8
7
2.6
17
19
-
-
2.3
25
SCREEN FILTERING AREA REDUCED
9-3-69 5,
7,
2,
200 3,900
300 6,000
600 3,800
_
-
-
0.3
0.6
100 mix 1,000
(2) Nominal Feed Rate
-------
00
UJ
TAJJLEJL
VOLATILE SUSPENDED SOLIDS, MICROSTRAINER
Date _^__________^
12-3-69
1-23-69
4-11-69
4-18-69
4-19-69
4-21-69
5-9-69
5-9-69
5-19-69
5-19-69
5-ZQ-69
5-20-69
AVG.
MARK "0 " SCREEN
6-15-69
6-18-59
6-23-69
6-25-69
7-7-59
?-23~69
7-23-69
7-23-69
AVG .
fncji/1
In
60
33
41
63
111
44
51
69
79
42
90
42
60
34
35
31
81
53
21
39
9
38
Out
60
27
21
38
52
22
21
27
38
20
30
1?
31
12
4
12
8
28
7
13
4
11
% Reduction
0
18
49
40
S3
50
59
61
52
52
67
60
47
65
89
61
90
47
67
67
56
68
-------
TABLE 3 (continued)
VOLATILE SUSPENDED SOLIDS, MICROSTRAINER
Date
MARK "0 " SCREEN
7-28-69
7-28-69
7-28-69
7-29-69
7-29-69
8-4-69
AVG.
MARK "0 " SCREEN
9-3-69
9-3-69
9-3-69
AVG.
ma/1
In
- Controls Changed
37
63
48
44
38
54
47
- Area Reduced
21
42
18
27
Out
9
13
22
19
9
3
12
9
7
5
7
% Reduction
76
79
46
57
76
94
71
57
83
72
71
-------
MICROSTRAINING RESULTS
Total Suspended Solids
As initially started up, the Microstrainer was fitted with the Mark "I"
screen (nominal aperture size - 35 microns). As work progressed, it
became evident that the backwash jets, in conjunction with slime pre-
vention by means of the ultra violet light employed, would prevent
pluggage and fouling of the screen, and that the influents that were
received could be more than adequately handled. Accordingly, after
about 6 months of operation, the finer Mark "0" screen was installed
to determine if increased quality of the effluent could be realized
without pluggage.
Furthermore, after an additional approximately 2 months of operation,
the Microstrainer controls were altered so that it would operate at a
drum speed more closely related to differential head. And, finally,
80% of the filter screen area was blanked off by inserting plastic film
inside of the screen.
At the same time the backwash jets normally serving the blanked off
area were turned off.
These last-named steps were taken to increase the Microstrainer
hydraulic rating — important because of possible reduction in capital
cost of a full scale installation — and to determine the effects of
this increase on the quality of the effluent.
As can be seen in Table 1, and Figures 7, 8, 9, the removals of total
suspended solids ranged from 13% to 98%, the higher values being
characteristic of the Mark "0" screen, and better-regulated drum speeds.
Although the data are scattered, regressions are shown for suspended
solids in the feed vs % reduction of suspended solids in Figures 7 and 8.
These illustrate the improvement in performance gained through the use
of the Mark "0" screen, and also show the tendency for increased sus-
pended solids removal efficiency with an increase in the influent sus-
pended solids concentration. Over the range of data that we acquired,
straight line regressions offered the best fit.
The results for removal of volatile suspended solids are shown in
Table 3 and Figure 10. These results parallel those for total suspended
solids, ranging to an average value of 71% removal for the Mark "0"
screen and the higher differentials.
BOD
Removals of BOD are scattered (Table 1, Figure 11)
85
-------
100
80i
LU
CC
70
CO
Hi
p
co SQj-
I 50
"o
40 j—
30[-
I
i
20J-
10 !r-
I—i—i i r
(D
-J
1_1
y=35.4+ . 044 (ss FEED) _
1_I
100 200 300 400 500
SUSPENDED SOLIDS IN FEED, ppm
-------
CD
-q
toy
so
_ ! ' ioJ
! i 1 1 . \ \ ! i
^ O "™"
CO
CXSBTM9
O
CO
CO
„-,,
o
4151-
». l» f
f-';/'5'
-------
•?^n r
«u-y {
CO
o
co
CO
Mr-I1
o
o
i
CT/"* I
').! ';) i. — i-
60
20
lit!
100
200
300
400
500
SUSPENDED SOLIDS IN FEED,mg/i
SUSPENDED SQUDS REDUCTION
MARK '0' SCREES! REi
03
C
-------
ISGHESN
MARK 0 SCREEN
0 SCR8N
CONTROL comet
70
<**.•*>
oO;
-co £Q!—
<-, ~ w -"
40!
oLl
AV. LEVEL EFFLUENT
, r-g/>
u
MARK 0 SCREEN
RtDUCEO P.R5A
12-3-58
Figure 10
9-3-S9
-------
1 450%
VQ
O
100
AV LEVEL EFFLUENT, 130
mg/i
12-3-68
L J
Figure 11
9-3-69
-------
We postulate that the volatile suspended solids that pass the screens
are present in -the effluent, in a much more, finely divided form. We
further suggest that the resulting increased surface area of these
solids may serve as a more rapid and more efficient growth medium for
bacteria.
It is thus probable that downstream effects, after Microstraining, will
be less persistent — and particularly so in view of the major reductioi
in the volatile suspended solids fraction. Moreover, it appears certaii
that post-treatment with chlorine or ozone, if practiced, should be
markedly enhanced, considering the reduction in the number of larger
particles that tend to occlude organisms, protecting them from the
action of these treatments.
Fecal and Total Coliform
As shown in Tables 2 and 4, both fecal and total coliform bacteria quite
frequently exhibit increases in their concentrations in the Microstraine
effluent. This phenomenon has previously been noted by Boucher(8).
Clearly.no net "removal" of these organisms can be attributed to the
Microstraining process.
Several postulations have been made for these observed increases:
1. Natural predators are largely removed by Microstraining and are
thus not present in large numbers on the discharge side.
2. Large colonies of bacteria are subdivided into larger numbers by
passing through the screen.
3. The bacterial, food supply is made more available by the screen-
ing process and the growth kinetics during the 5 day measurement
period are enhanced.
As related above, we tend to accept the last-named postulation, but
it must be emphasized that the question has not been resolved.
91
-------
TABLE 4
Date
MARX "I"
12-3-68
1-23-69
4-11-69
4-13-59
4-19-69
4-21-69
5-3-6S
5-19-69
5-20-69
MARK "0"
6-15-69
5-18-59
5-23-69
6-25-59
7-7-69
7-23-69
In
SCREEN
1,
2,
2,
\
10 '
100,
8,
2,
5,
SCREEN
19,
3,
1,
10,
28,
1,
666
607
720
600
310
310
300
000
700
700
200
900
600
200
000
000
800
Out
1
2
2
9
8
93
4
3
6
8
5
14
11
1
740
,280
840
,970
,380
,800
,500
,000
,000
,600
,700
,600
,900
,000
860
,000
,100
TOTAL COLIFORMW
After Chlorination
5 Q Dm*™ Bruin 5 DQin*"lQ inln
3
-
800
-
-
-
-
-
98, 000(3)
290
-
240
-
150
-
5.1
-
0.2
6
-
760
_
-
-
-
—
130
0
-
79
-
18
-
100
-
110
After Ozonation
5 Dpm'2)
-
—
330
580
-
33
0.2
0.4
60,000^
36, 000 (3)
100
120
500
220
7,600
3,900
18
13
4.8
Residual
_
—
-
-
-
1
1
w
1
1
-
0
-
1
-
-
-
0
O3*PPm
.9
.3
.6
.9
.6
.3
2r 100 mix 1,000
(2) nominal Feed Rate
^Values Not Used in Calculation of Averages
-------
TABLE 4 (continued)
UO
Date
MARK "0
Controls
relation
TOTAL COLIFORM^)
After Chlorination
In Out 5 ppm-5 min 5 ppm-10 min
" SCREEN
changed to produce fixed
between differential and
After Ozonation Residual Os , ppm
5 ppm(2)
drum speed. Max. differential
increased .
7-2,8-69
7-29-69
8-4-69
SCREEN
9-3-69
170 0 330 200
-
44 11 0.8 12
-
78 200
3.1
-
130 330 - -
150 230
15 8 0 0
"• ™
FILTERING AREA REDUCED
12,000 16,000
20,000 13,000
12,000 20,000
30
8 ~
0.5 0.3
5.4
-
100
23
- -
- • -
3.8 0.6
32
_ _
- -
- -
100 mix 1,000
'2'Nominal Feed Rate
-------
CH1.OR1NAT1ON ftNl OZOMATT.i
Average total r.oli. form concentre, t ions for the final effluents in all of
our work., under varying conditions imposed on the Microstrainer, using
5 ppm of chlorine for 5 and 10 minute retention times, were 166,000/100 ml
and 129,000/100 ml, respectively. For fecal coliform concentrations,
these values, in the same order, were 41,000 and 81,000. Similar re-
sults for ozone at a nominal concentration of 5 ppm and a detention time
of about 12 minutes were 619,000 and 42,000. The corresponding total
coliform results for the Microstrainer effluent (prior to chemical
treatment) ranged from "0" (in one instance) to a high of 93,000,000,
and the fecal coliform counts ranged from "0" to 30,000,000.
Ozone, of course, is more desirable should a colorless final effluent
be desired, or in those cases where a less stable, less persistent down-
stream chemical residual is needed.
Higher chemical feeds and/or longer detention times are indicated for
a more complete bacterial kill. In this treatment situation it is
obvious that the former is more desirable because of the increased cost
associated with provision of storage for detention. Whether additional
"detention time" would be available in the discharge, downstream of an
actual plant of this type, would depend on individual circumstances.
Table 5 gives average values for final effluent coliform concentrations.
Time has permitted the investigation of the use of larger amounts of
chemicals with shorter detention times to only a limited degree, but
some results with chlorine* indicate the probability of greater bacterial
kills with larger amounts of chlorine and shorter detention times. For
example: in one test on different portions of the same sample, total
coliform were 110,000/100 ml for 10 ppm - 2 minutes and 7,500/100 ml
for 15 ppm - 2 minutes.
*These last-acquired results are not listed in any of the Tables.
-------
TABLE 5
TOTAL COLIFORM, FINAL EFFLUENT
AVERAGE VALUES (per 100 ml x 1,000)
CHLORINATION (5 ppm) OZONATION (5 ppm)
5 min 10 min
166 129 619
FECAL COLIFORM, FINAL EFFLUENT
AVERAGE VALUES (per 100 ml x 1,000)
CFILORINATION (5 ppm) OZONATION (5 ppm)
5 min 10 min
41 81 42
95
-------
ECONOMICS
The possible solutions to the combined sewer overflow problem appear
to be varied, depending upon individual circumstances^ . Among these
circumstances can be listed such items as the character of the existing
collection system, types of receiving waters, population density, rain-
fall, land use factors (i.e., residential, commercial, industrial) type
of catchment area and size of catchment area.
In many cases, it would appear that large areas are not available for
the construction of holding basins. And, in some cases, the prospect
of retaining large volumes of sewage for the times required for dis-
charge at low rates either to a receiving stream or to the sewer system
and a disposal plant, would appear unattractive from both aesthetic and
practical standpoints.
Although large detention basins, such as have been mentioned for Columbus,
Ohio, and Boston, Mass. (4) , will presumably continue to be employed
where huge overflow volumes are involved, in instances where large amounts
of land are not available, and where ultimate disposal is difficult,
or where the local environment is not suitable for detention tank
installation, the Microstrainer can be considered.
In this connection, a recent publication ' points out that 25% of the
catchment areas in Washington, B.C., are 25 acres or less in size, and
that a similar survey of Milwaukee, Wis., revealed that 50% of these
areas are of 25 acres or less. There is no intent to imply that the
use of Microstraining should be limited to the smaller areas, but these
figures illustrate the number of smaller subdivisions of a drainage
basin that might be handled locally.
The cost analysis quoted below illustrates the expenditure that could
be expected for a drainage area of the type for which this program
was conducted.
Plant design for Microstraining only envisions the treatment of 540x
average dry weather flow. Where chlorination (in 2 minutes retention
time) would be employed with Microstraining, the design contemplates
chlorination of an additional 540x; that is, when the overflow occurred
at 540x or below, both Microstraining and chlorination would be used,
and when the flow exceeded 540x, the excess up to a total of l,080x
would be only chlorinated. The 540x, at the target plant, is 20 cfs.
Flows over l,080x would bypass the entire plant.
A similar provision for ozonation capacity for the flows between 540x
and 1,0 80x was not included.
96
-------
It is calculated that, at tre 5 tOx figure, abc/ut !;5>t'. of th..> overflows
occurring in one year w<:uL'J be xalj.y treated*- '
These capital cost estimates include equipment, installation, and
engineering costs for Micros training, chlorination via sodium hypochlorate
or ozonation, the last-named operation being carried out with an oxygen
rather than an air feed. The use of oxygen -- on a once-through basis --
eliminates the first costs and maintenance changes associated with air
preparation or oxygen recycle equipment.
Dollar estimates for plant operation and maintenance have not been made.
However, operation costs of Microstrainer-chlorination plants should
be low. On a single plant basis, for Microstraining -chlorination, we
feel that maintenance labor costs should not exceed 4 hours per week
for 2 employees. Where multiple plants were installed, this estimate
would be materially reduced.
Where ozonation is used, operation and maintenance costs would be
expected to be somewhat higher.
97
-------
ACKNOWLEDGEMENTS
The cooperation of the City of Philadelphia Water Department, Mr. S.
Baxter, Commissioner, their Water Pollution Control Division under
Mr. C. F. Guarino, the Research and Development Group under Mr. J. V.
Radzuil and the analytical group at the Northeast Laboratories under
G. Carpenter, are gratefully acknowleged.
Plant design and its early operation were carried out by Messrs.
E. W. J. Diaper, Manager of Municipal Water and Waste Treatment and
Mr. J. D. Reilly, both of the Cochrane Division,Crane Co.
This program is sponsored by the FWPCA of the U.S. Department of the
Interior under Contract No. 14.12.136.
-------
(1) "PolLutionai Effects of Srorrr^ater and Overflows From Combined
Sewer Systems", U.S. Dept. of Health, Education and Welfare,
PHS, Nov. 1964,
(2) Davidson, R. N. and Gameson, A. L- H., "Field Studies on the
Flow and Composition of Storm Sewage", Symposium on Storm
Sewage Overflows, Institute of Civil Engineers, William Clowes
& Sons, Ltd., London, 1967.
(3) -Burrn, R. J. , "The Bacteriological Effect of Combined Sewer
Overflows on the Detroit River:, J. Water Pollution Control
Federation, 1967, 39 (Mar.) 410-425.
(4) Bacon, V. W., Leland, R. , Sosewitz, B. , "Separation of Sewage
From Storm Water", Symposium on Storm Sewage Overflows, Institution
of Civil Engineers, 1967, William Clowes & Sons, Ltd., London.
(5) "Problems of Combined Sewer Facilities and Overflows", WP-20-11,
American Public Works Association - Research Foundation for the
U.S. Dept. of Interior Fed. Water Pollution Control Administration.
(6) "Water Pollution Aspects of Urban Runoff; The Causes and Remedies
of Water Pollution From Surface Drainage of Urban Areas", WP-20-15,
Am. Public Works Association - Research Foundation for the U.S.
Dept. of Interior Fed. Water Pollution Control Administration.
(7) Lynam, B. , Ettelt, G. , and McAloon, T., "Tertiary Treatment at
Metro Chicago by Means of Sand Filtration and Microstrainers",
Journal Water Pollution Control Federation, Vol. 41, No. 2,
Part 1, Feb, 1969.
(8) Boucher, P.L., "Microstraining and Ozonation of Water and Waste
Water", 22nd Purdue industrial Waste Conference, May, 1967.
(9) Tucker, L. S-, "Sewered Drainage Catchments in Major Cities",
ASCE Urban Water Resources Research Program, Tech. Memorandum
No. 10, American Society of Civil Engineers, New York, N.Y.,
March, 1969.
(10) City of Philadelphia Data.
99
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THE USE OF SCREENING/DISSOLVED-AIR FLOTATION FOR TREATING COMBINED SEWER OVERFLOW
Authored by:
Donald G. Mason*
Presented at the Seminar on the Storm and Combined Sewer Pollution Problems
November 4 and 5, 1969
Edison, New Jersey
*Manager-Systerns Research
Technical Center
REX CHAINBELT INC.
Milwaukee, Wisconsin
101
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INTRODUCTION
The pollutional characteristics of combined sewer overflow are
being documented through the many federally sponsored projects
which are now underway. Preliminary results indicate that the
majority of the pollutional substances present in combined sewer
overflow are in the form of particulate matter. This indicates
that a high degree of treatment could be obtained by utilizing
an efficient solids/liquid separation process. The objectives
of this project (FWPCA Contract #14-12-40) are to determine the
design criteria, effectiveness, and economic feasibility of
using screening and dissolved air flotation to treat combined
sewer overflows.
The project is currently underway. Completion is expected by
late spring or early summer of 1970. The following discussion
is a review of the results obtained to date, tentative design
criteria, and expected removal rates.
DESIGN OF TEST FACILITY
During the fall and spring of 1967, the Hawley Road Combined
Sewer in Milwaukee, Wisconsin was monitored. A total of 12
overflows were sampled. Laboratory scale testing on these
samples included screening with various size media, chemical
oxidation, flotation, and disinfection. Laboratory analyses on
the untreated overflow as well as the effluents from the labora-
tory bench tests were analyzed for BOD, COD, SS, VSS, and dis-
102
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infection requirements. It was determined from this testing
that chemical oxidation did not appear technically feasible (1).
However, encouraging results were obtained from the screening
and flotation tests. These tests served as input data in the
design of a test facility utilizing screening and dissolved air
flotation. A process flow sheet for the system is shown in
Figure 1.
The system basically consists of a screen chamber and a flota-
tion chamber. The screen is an open ended drum into which the
raw waste flows after passing a 1/2" bar rack. The water passes
through the screen media and into a screened water chamber
directly below the drum. The drum rotates and carries the
removed solids to the spray water cleaning system where they
are flushed from the screen. Screened water is used for flushing.
The spray water and drum rotation are controlled by liquid level
switches set to operate at 6 inches of head loss through the
screen. The flotation chamber is a rectangular basin with a
surface skimming system to remove floated scum. Screened water
is pressurized and mixed along with air in an air solution tank.
The liquid becomes saturated with air and when the pressure is
reduced, minute air bubbles (less than 100 micron diameter) are
formed. This air-charged stream is then mixed with the remaining
screened water flow. The bubbles attach to particulate matter
and float it to the surface for subsequent removal by the skimmers.
Chemical flocculants may be added to enhance the removal efficiency
of finely divided particulate matter.
103
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AIRSOUJTION
TM
RAW
FLDW
SOLIuS
SCREENINGS
CHEMICAL FUDCCULAiiT
ADDITION
FLDTATiai CHAMBER
TREATEu
FLCW
FIDATEJ SOW
-------
>
Figure la. Screening and Dissolved-Air Flotation Unit
-------
The design criteria utilized in the design of the test facility
are shown in Figure 2. These criteria provide the wide" flexibility
necessary in a test facility. More precise design criteria will be
given later. The system was designed to treat 5 MGD of combined
overflow.
All pumps and auxiliary equipment were sized on this flow. The
flotation tank is compartmentalized to allow variation in the
surface loading without changing the raw flow rate. Pressurized
flow rate and operating pressures can be maintained over a wide
range of values.
RESULTS OF OPEKATION
The test facility was completed and put on stream in May of 1969.
Since that time, 28 overflows have been monitored. It has been
observed that about 25% of these overflows have high pollutional
load during the first portion of the overflow. This period of
first flushes has never lasted longer than one hour and has been
as short as 10-15 minutes. After these flushes pass, the charac-
teristics of the overflow become quite constant. This period has
been called the extended overflow period. The range of pollution
parameters measured for these 28 storms at the 95% confidence
level is shown in Figure 3. It may be observed that the first
flushes data has quite a wide range of values, while the extended
overflow data has a relatively narrow range. All laboratory
analysis were performed according to Standard Methods (2). The
106
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SCREEN
1, RAW FUDW RATE 3500 GPM
2, HYDRAULIC LOADING 50 GPM/SQ FT
3, SCREEN SIZE 50x50 297 MICRON OPEN INGS
4, SCREEN WASH 150 GPM MAXIMUM
FLOTATION TA1K
1, FUJW [^AlE 3500 GPM
2, SURFACE LOADIiiG 3-9 GPM/SQ FT
3, HORIZONTAL VELOCITY 3 FPM
4, PRESSURIZED FIDW PAlt W-UOO GPM
5, OPERATING PRESSURE 40-70 PSIG
6, MINIMUM PARTIAL RISE RATE 0,5-1,5 FPM
FIGURE 2
CRITERIA
FOR itf Q-£TCATI(W SYSB1
107
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FIRST FLUSHES
, , ..... ,,,,,,,, ....... 500-765
1 70-1 f!°
..... t i i i i i i • i i , ,,,,,, 1/U lCk_
• i i i i i i i i • i i i • i i i i i i i i i
i i i i i i i i i i i i i i i i i ,,,,
TOTAL ii .................... 17-2'i
COEii£iJ OVERFLD1K
, H5-1G5
OC 1 "! " 1 7/ '
<^>-' * i i i i i i i i i i i i i i i i i i i i i i i J~ I /H
\A\' l'<~' <7
VOO i i i i i i i i i i i i i i i i i i i i i i _X)~U/
TOTAL li .................... 3-6
ALL VALUES IN M6/L AT 95/o CQ'JFIDENCE LEVEL
COLIFORT1 310 X llP TD 1,5 X liP PER ML
HUJlt 3
GiAi
-------
data presented correlates well with combined overflow data from
the Detroit Milk River Study (3) and other published data (4).
The operation of the previously described test facility during
the spring, summer and fall of 1969 has provided valuable data
on operational characteristics and removal rates. Figure 4
shows the data associated with operational variables. The
average run had a length of 1-4 hours. Approximately 1/2 hour
is required to allow the flotation tank to come to equilibrium.
The flow rate for these runs was held constant at 3500 gpm.
Pressurized flow was varied over the range of 400-900 gpm and
the operating pressure from 40-60 psig. Of considerable
importance in the design of this type of system is the volume
of residual solids produced during operation. As shown in
Figure 4, the volume of water required to backwash and clean
the screen ranges from 0.29 to 0.64 percent of the raw flow
rate, while the volume of floated scum ranges from 0.43-0.85
percent at the 95 percent confidence level. Solids concentra-
tions in these streams generally is in the range of 1 to 2
percent, and at this concentration they easily flow by gravity.
Disposal methods utilized for these solids streams should be
sufficient to handle the upper limit of the expected sludge
volumes. Under the current contract, we are disposing of these
streams via an interceptor sewer which directs them to the
sewage treatment plant.
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LtNblUOF WWFUJW SCREEN HflSH FLOATED SON PRESSURIZED OPERATING
RUN RATE ASEOFFLOUi AS % OF FLO^ FLDW RATE PRESSURE
HOURS GPM % % GPM PSIG
5500 0,29-0,64 0,43-0,8 TO-900 40-50
(1) AT 95/o CONFIDENCE LEVEL
FIGURE 4
OPERATION IATA FRDT1 HMJEY
R3AD
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The efficiency of contaminant removal experienced for the over-
flows monitored to date is shown in Figure 5. Two time periods
are shown — spring storms and summer/fall storms. By observing
the screen data in Figure 5, it may be seen that during the
spring storms removals ranged from 23-33 percent for all listed
parameters. This was consistent with the preliminary data col-
lected the previous year. During the summer/fall storms, how-
ever, COD removals decreased indicating a change in the charac-
teristics of the overflow. It was determined that an increase
in soluble COD had occurred which was the probable cause for the
noted decrease in COD removal across the screen. The mechanical
operation of the screen has been very satisfactory. The media
utilized was type 304SS. No permanent media blinding has been
experienced. No build-up of greases or fats has occurred. Some
clogging problems have been experienced with the spray nozzles,
but this was caused by a sealing problem around the screen which
allowed unscreened water to pass into the screened water chamber.
The overall removals, i.e. screening plus flotation, are also
shown in Figure 5. Removals are shown with and without the
addition of chemical flocculants. The chemical flocculants,
when utilized, were a cationic polyelectrolyte (Dow C-31) and a
flocculant aid (Calgon A25). The polyelectrolyte dosage was
4 mg/1 and the coagulant aid dosage was 8 mg/1. Contaminant
removal without chemical addition was about 50% for all para-
meters as shown in Figure 5. Adding chemicals caused an increase
111
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SCREWING
MNG AND FLOTATION
BOU
GOD
SS
VSS
SPRIiiG
23,4 ±9,3
33,9 ±10,7
28,8 ± 10,5
28,2 ± 13, G
SUrie-FALL
20,3 ± 6,5
22,4 ±5,0
24,9 ±9,8
24,4 ± 13,2
y/o ciipncAL
rL_LJLjv>LJI_/'\i''i 1 o
(SPRING)
48,4±J5,7
52,9 ± 8,7
53,7 + 11,7
51,0 ± 15,9
(SUMMER-FALL)
50,8 ±12,5
53,4 ± 8,6
68,3 ± 8,4
64,8 ±10,0
NOTES: REMOVALS AS £ a 9S2 CONFIDENCE LEVEL
SCREEN OPENINGS 297 MICRCtJS
SURFACE LOADING 3 GPM/SQ FT
FIGURE 5
ON1MNWT RB'IOVALS IN ERCBfT BY SCREBUNG Aiffl FUJTATKW
-------
in SS and VSS removals to around 70%. COD and BOD removals,
however, did not increase significantly. This was probably a
result of the increase in soluble organics associated with the
summer/fall overflows. Chemical addition also provided a
strengthening effect on the floated sludge blanket, which is
very desirable from the materials handling aspect. Mechanical
operation of the flotation tank has been excellent. No mechanical
problems have been experienced. Maintenance on the entire system
is limited to periodic lubrication and requires less than 6 man
hours per month.
Another important aspect in the treatment of combined overflow is
disinfection. Figure 6 shows the effect of chlorination on total
coliform density from various overflows. In.storms 5 through 11,
chlorine was added in the pressurized flow line prior to blending
with the remainder of the flow in the flotation tank. The dosage
was 10 mg/1. The dosage may have actually been lower in some of
the runs, since sodium hypochlorite was utilized as the source
of chlorine and this solution decreases in strength over a
relatively short period of time. Introduction of the chlorine
in the pressurized flow allowed approximately 15 minute contact
time before discharge from the unit. In storms 19 through 22,
chlorine was added to the effluent from the flotation basin and
allowed to react for a ten minute period. The chlorine was then
deactivated with sodium sulfite and coliform analyses were per-
formed. It may be observed in Figure 6 that coliform reduction
was related to initial coliform density when using a constant
chlorine dosage. In the spring and early summer when coliform
113
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COLIFOPli EFFLUENT COLIPDRM
£
STORi I ii
5
5
7
8
9
11
19
20
21
22
DbiSITY
PER ML
36,000
5700
1,300
7,800
6,200
20,000
310,000
160,000
55,000
£,000
QllDRIit UOSAE
MG/L
10
ID
10
10
10
10
10
10
10
ID
(DuTACF THE
MIN,
15
15
15
15
15
15
10
10
10
10
DENSTIY
PER 100 ML
0
0
0
0
2
10
600
400
0
1500
FIGURE 6
IATA R)R GQHBIifiJ GVQR0S AT ii/M£Y ROAD
-------
densities were low, good disinfection was obtained. However, in
late summer when coliform density increased, the effluent contained
increased numbers of coliform organisms. Chlorine demand tests
were run on some storms. The chlorine demand was generally in
the range of 13 to 17 mg/1.
SUMMARY AND CONCLUSIONS
Based on the data taken during 28 overflows, Figure 7 presents the
recommended design criteria for screening and dissolved air flota-
tion systems treating combined sewer overflow. This criteria is
tentative, since the project has not yet been completed. The most
important criteria associated with screen design include hydraulic
loading and solids loading. The recommended values are those which
were found satisfactory in the operation of the Hawley Road facility.
With regard to the flotation design criteria, the surface loading
variable is the only one which has not been fully evaluated. Higher
rates will be investigated, and the effect of these rates on removal
efficiencies will be evaluated. The other criteria for flotation
shown in Figure 7 have been thoroughly evaluated and proven adequate
for combined sewer overflow treatment.
The cost of a flotation system for treating combined overflows
is directly related to the surface loading variable which is still
under investigation. Based on a 3 gpm/sq ft surface loading and
the other design parameters of Figure 7, capital cost of a screening/
flotation system should be in the range of $5,000 to $8,000 per
115
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fEDIA - 50 x 50 (297 MICRON OPENINGS)
HYDRAULIC LOADING - 50 GPM/SQ FT
HHAu LOSS CAPABILITY - 14 INCHES WATER
SOLIDS LOADING - Q.M DS/JDO so. FT
CLEANING HATER - 0,752 SCREENED FLOW
ON
FLOTATION'
SURFACE LOADING - 3 GPM/SQ
UORIZQiTAL VELDCITY - 3 PM
PRESSURIZED RDM - 15S
OPERATING PRESSURE - 50 PSIG
FLOATED SOI1! VOLUE - 0,95% OF RDM
PKVISIQ-IS FOR TOP AiiD BOTTOM SKIitUNG
QiBilCAL FUXCULANT ADDITIQ'^
(I) THIS VALUE MAY BE CONSERVATIVE/ HIGHER VALUES NOW BEING TESTED,
FIGURE/
REGOffEJDEiJ LESIGN CRITERIA FOR SCREEiJlilG AI^D FLOTATION
-------
MGD capacity for large capacity plants (>50 MGD). Detailed cost
analysis have not yet been performed and these costs are therefore
only ball park figures which could increase or decrease as more
information is obtained. These cost estimates do not include
land costs, which could vary considerably.
Operating costs for a screening and flotation system will be low
due to the expected periodic usage when treating combined over-
flow. Chemical costs should be in the range of 2 to 2.5 C/1000
gallons, while operating, maintenance and power costs are expected
to be less than 2 C/1000 gallons.
In summary, it appears that dissolved air flotation can be
utilized as a partial solution to the combined sewer overflow
problem. Significant removals of BOD, COD, SS, and VSS can be
obtained utilizing screening/flotation. While a detailed cost
analysis has not yet been completed, preliminary cost informa-
tion appears to justify the economic feasibility of the system.
117
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BIBLIOGRAPHY
1. Mason, D. G., "Interim Summary Report FWPCA Contract
#14-12-40, July 1968.
2. Standard Methods for the Examination of Water and Wastewater,
12th Edition, American Public Health Association.
3. Christensen, Ralph, Private Communication, FWPCA, Chicago,
Illinois.
4. Gannon, J. and Streck, L., "Current Developments in Separate
vs Combined Storm and Sanitary Sewage Collection and Treatment",
Presented 42nd Michigan WPCA Conference, June 1967.
118
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OVERVIEW OF COMBINED CONTROL AND TREATMENT METHODS
*y
William A. Rosenkranz
The discussions thus far have dealt with several methods of
control, or treatment. We have discussed the containment or
hydraulic control of the flov. Implementation involves modifying
an over-all system with some sort of treatment device or control
devices or utilization of combinations of these.
Today's papers and discussions thus far illustrate or bring
to our attention several important points:
First of all, there is likely to be no single method
of either control or treatment applicable as a
complete answer to combined sewer problems. I believe
that it is safe to say that this is true even when
considering sewer separation as a corrective measure.
We have to think in terms of individual outfall
control and treatment. Over-all systems which would
achieve control over individual drainage areas is of
great importance. Systems which can handle the entire
problem for a given community or even perhaps a metro-
politan area must be considered and evaluated. In
other words, drainage area approach must be applied
when investigating solutions to overflow problems.
While the point source control or treatment application
must also be utilized, they will fail unless the entire
119
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drainage area problems are assessed. This is applicable
to the entire community or metropolitan area as well
as the individual portions within the area.
Proper planning must consider and evaluate all of the different
kinds of treatment that might be utilized in an integrated control/
treatment system. We need to carefully examine the compatibility
of the methodology used in order to properly develop integrated and
coordinated systems.
The c!oncept of storage that we use in our program involves any
kind of storage that you want to talk about—concrete tanks, design
and construction of buildings or modification of roof designs to
permit use of roof-top storage, off-shore storage by means of
retention basins,underwater bags, many surface ponds, deep tunnels
or lined caversn--many different methods and in many different configura-
tions. Each of these methods may have a particular application to a
given situation due to the geology of the area, the topography of the
land, the location of the sewers, type of receiving waters, water quality
required and many other factors.
Engineering studies must consider all potential alternatives when
seeking to determine what is most applicable, what is efficient and
what is economical. In order to achieve an "optimal" system physical
control by storage must be considered in conjunction with potentially
applicable treatment methods. This would include as possible solutions
the use of storage or surge basins in combination with screening,
dissolved air flotation, bio-disc treatment, high rate biological
120
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filtration or any other treatment configuration. In-system flow
control, flood routing in the system, and storage of waste waters
from the system - off the system. In other words, remove wastewater
from the system--perhaps even in the upper portions of the drainage
area for feed back into the system when the storm is over. Improved
regulators, remote control, surge tanks combined with existing or
expanded sewage treatment plants, surface storage or retention basins
and microstrainers should be examined as possibilities. For example:
Infiltration control to achieve reduction of flows, in-system storage
or control combined with controlled release to a sewage treatment
plant might make a workable system. I am sure that in your own minds
you can dream up many possible combinations. The big problem, of
course, is the one that is the center of focus for our program activities,
That is the determination of what is feasible, what is economical and
how it (or they) can be used. Other papers to be presented during the
afternoon will deal with this aspect of the problem and the slides
which I will show will serve to illustrate some of the techniques and
devices currently being studies or demonstrated.
121
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ASSESSMENT OF ALTERNATIVE METHODS
FOR CONTROL/TREATMENT OF
COMBINED SEWER OVERFLOWS
FOR WASHINGTON, D.C.1
by 9
John A. DeFilippi, P.E.^
INTRODUCTION
The majority of United States cities today are served by both combined sewers and sep-
arated sanitary and storm sewers. The District of Columbia follows this pattern with an area
of approximately 20 square miles being served by combined sewers. These, of course, are
sewers which carry sanitary sewage during dry periods and, during periods of precipitation,
carry sanitary and storm sewer flows. The hydraulic, capacity of the system is often
exceeded during times of precipitation and raw sewage mixed with surface runoff is spilled
into the water courses of the District.
An investigation, sponsored by FWPCA, is now being completed which deals with the
assessment of alternative methods for control/treatment of combined sewer overflows for
the District of Columbia. The investigation, as presented herein, had three major
components: (1) problem definition, (2) the study of the feasibility of high-rate filtration
for treatment of combined sewer flows and, (3) the study of alternative methods of solu-
tion. Problem definition dealt with attempting to define hydraulic properties and water
quality characteristics of combined and separated storm sewer flows. This was accomplished
by both desk top hydrology and hydraulic studies and by field sample collection. The
second major area of study, high-rate filtration, was investigated by bench-scale laboratory
1 Research upon which this publication is based was performed pursuant to Contract
Number 14-12-403, with the Federal Water Pollution Control Administration, De-
partment of Interior.
Presented at the FWPCA Storm and Combined Sewer Overflows Seminar, Edison
Water Quality Laboratory, Edison, New Jersey, November 4-5, 1969.
2Manager, ROY F. WESTON New York Office, Roslyn, New York.
123
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experiments. The third part of the investigation, the study of alternatives, was accomplished
by analyzing various approaches used in other parts of the country relative to their appli-
cability to the Washington, D.C. system.
This paper will present a discussion of the three major portions of the investigation. The
approaches will first be described and then appropriate conclusions presented.
PROBLEM DEFINITION
Problem definition must first concern itself with an inventory of basic data of the combined
sewer area. The basic data must include the following types of information: schematic and
detailed maps of the system, drainage basin delineations, land use characteristics, slopes and
hydraulic capacities of collector lines and interceptors, overflow points, diversion points,
etc. Once this basic inventory of information is available, more precise problem definition
can follow. Fortunately, in the case of the District of Columbia this basic information was
readily available.
Following the inventory, attention was directed at attempting to quantify flow rates and
flow patterns which prevail in the system. The first approach which was used was the
Rational Method. The Rational Method can only estimate peak flow rates; it cannot provide
the second necessary component of flow determination, hydrographs of flow.
In order to determine the hydrographs, two methods were initially attempted. The first was
a method developed in the City of Chicago and reported quite extensively in the literature.
It will not be dwelled upon here except to say that it is a relatively elaborate procedure
which relates rainfall patterns to resultant flow hydrographs in sewers. The second attempt
at defining hydrographs used the unit hydrograph method. When both of these methods
were attempted, they did not agree nor did they match the results which were obtained by
using the Rational Method. Therefore, a third, more simplified approach was used.
-------
This approach used the Rational Method to predict the peak flow rate; this peak flow rate
was plotted at the time of concentration for each drainage basin. Following this, the volume
of runoff for a particular storm was estimated by the total amount of rainfall and the runoff
coefficient assumed for the drainage area. Knowing the peak runoff and the total volume of
runoff, a simple triangular hydrograph was assumed and plotted.
It was realized that this would not provide highly accurate depictions of flow patterns in the
sewers. However, it was felt that the hydrographs would be sufficiently accurate for the
purposes and goals of the study. As it turned out when actual field data was collected, the
assumed hydrographs rather closely estimated actual flow conditions.
The simplified triangular hydrograph approach was quite appropriate to the investigation.
The hydrographs were quickly compiled and reflected, with sufficient accuracy, the actual
flow conditions. Moreover, they could easily be routed along interceptor routes because of
their fixed geometric properties. Routing was accomplished very simply by graphical
methods. The hydrographs were plotted along the x-axis (time axis) and lagged by the
assumed flow times between individual drainage basin discharge points. The resultant hydro-
graphs at any particular point along an actual or proposed interceptor could then be
compiled by simple addition of the cumulative ordinates.
WA TER QUALITY DETERMINA TION
Water quality determination proved to be significantly more difficult. Prior water quality
data in the literature had dealt primarily with composite samples which were collected over
the entire duration of a storm. In this particular investigation, it was necessary to define
water quality characteristics at discrete time points during the course of a storm. To ac-
complish this, completely automated monitoring stations were constructed and operated in
the field.
125
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Prior to constructing the monitoring stations, drainage basins for sampling were selected.
The selection was critical in order that representative data might be collected. The choice of
drainage areas for sampling was based upon the following criteria:
1. The size of the drainage area had to be sufficiently large to be representative of
the system but it also had to be small enough to be monitored economically.
2. Population density and land use within a monitored basin should be representa-
tive of the entire combined sewer area.
3. In order to have a valid correlation between runoff and rainfall, multiple diversion
or a large number of intercepting points were not desirable.
4. The geographical configuration at each proposed monitoring site should be flat
and accessible in order that monitoring equipment could be installed.
5. Traffic and public impact had to be kept to a minimum.
6. The size of the sampling sewer had to be sufficiently large to allow the installation
of equipment.
7. Extensive underground utilities could not be present to prohibit excavation.
Applying each of these criteria, three drainage areas were selected for sampling. Two of the
drainage areas were served by combined sewers. The third drainage area was served by a
separated storm sewer. The storm sewer was sampled to act as a control and to provide a
comparative basis.
126
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When the sampling basins and sites had been selected, construction of the sampling stations
began. At this point, it was determined that completely automatic sampling would be
required. This was decided because of the extreme difficulty of predicting accurately when
rainfall would occur and because of the further difficulties associated with compiling re-
quired manpower on short notice. This was a wise decision and it should be strongly urged
that further monitoring be accomplished automatically.
Each monitoring station required the construction and installation of equipment at an
upstream and a subsequent downstream manhole. The upstream manhole was used to trigger
the sampling process and to release a tracer element into the sewer flow for subsequent
sampling and measurement at the downstream manhole. By measuring the tracer concen-
tration at the downstream manhole and by knowing at what concentration and rate it was
introduced at the upstream manhole, accurate flow measurements could be made. The use
of depth of flow measurements and a steady state equation like the Manning Formula are
not applicable in this case because flow in combined sewers during times of precipitation is
not a steady state phenomena.
The downstream manhole was used for collecting the actual samples. A pump was located in
the sewer; this pump lifted wastewaters to a receiving tank in a shed above grade. Samples
were removed from the receiving tank at distinct time intervals and stored in a refrigerated
sample collector for subsequent analyses. For the majority of the storms, samples were
taken at five minute intervals.
Upon installation of the equipment, the systems had to be made operative and reliable
during periods of high flow. This proved to be difficult because of the extreme flow ranges
encountered and the very destructive debris which finds its way into a combined or storm
sewer. However, after much effort, the three monitoring installations were made operative
and performed extremely well during the summer of 1969.
12?
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There were a total of 150 samples collected and subsequently analyzed. These resulted from
22 storms occurring on the combined sewer drainage areas and 9 storms occurring on the
separated storm sewer area.
The data is still in the process of being reduced and organized but the following table
provides representative information. It is quite obvious that significant pollution occurs
from combined sewer overflows in terms of BOD, solids, COD, nutrients and coliforms. It is
perhaps even more surprising to note that significant pollution can occur from separated
storm sewers as well.
By integrating the combined sewer quality data, it is estimated that averages of 9.5 million
pounds of BOD, 224 million pounds of suspended solids, 3.5 million pounds of total
phosphate, and 1.0 million pounds of total nitrogen are discharged annually from combined
sewer overflows in the District of Columbia.
Organic contents are lower in the storm sewers than in the combined sewers but solids
loadings are much higher in the storm sewer than in the combined sewer. COD loadings are
about the same in both cases.
Initial flushing effects were very definitely shown but water quality remained poor through-
out the entire duration of the storm. That is, even after the initial flushing effects, there was
still significant pollution load being added to the water courses. Furthermore, combined
sewer water quality was not necessarily at its worst condition on the initial flush; quality did
get worse in several cases on subsequent flushes.
A potential problem with storm sewer flows is that biodegradability may be retarded by the
high solids content. The low BOD values may have resulted because high solids hampered
bacteria growth and therefore delayed biodegradability. This would result in lower five day
BOD values than in the combined sewer data but ultimate BOD may be equally as high.
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Table 1
Approximate Ranges of Water Quality Parameters
Flow
BOD
Suspended Solids
Total Solids
COD
Total Phosphate
(as Phosphorus)
Total Nitrogen
(as Nitrogen)
Total Coliforms
Fecal Coliform
Combined Sewer
4,000 - 600,000 gpm
10-500mg/L
100-2,000 mg/L
400 - 3,000 mg/L
30 - 2,000 mg/L
0.1 -8 mg/L
1-17 mg/L
60,000 - 6,000,000 counts/100 ml
300,000 - 5,000,000 counts/100 ml
Storm Sewer
2,000 - 75,000 gpm
10-650 mg/L
150-11,000 mg/L
400- 14,000 mg/L
40-1,500 mg/L
0.4 - 5 mg/L
0.6 - 6.5 mg/L
20,000 - 1,500,000 counts/100 ml
0 -1,300,000 counts/100 ml
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A further observation is that severe peaking hydrographs were recorded in the sewers. This
adds further proof to the concept that the application of a steady state formula for
estimating sewers flows based on flow depths is not applicable.
The data collected in the field has proven to be extremely valuable. It has demonstrated that
combined sewer flows exhibit significantly different water quality characteristics than those
which are to be found in domestic sewage. Total solids are completely out of the range of
expected values; the BOD/COD relationship is very much different than would be expected.
It is plain to see that we are dealing with a different set of conditions in combined sewer
flows and additional work is necessary to quantify and qualify the quality characteristics of
these flows. Assumptions that the water quality parallels that of domestic waste is simply
invalid. Treatment schemes and conclusions drawn on this basis cannot help but fall short of
their goals.
HIGH-RA TE FIL TRA TION FOR TREA TING COMBINED SEWER FLOWS
Having defined peak flow rates and water quality characteristics of combined sewer flows in
Washington, D.C., the efforts of the study were then turned to the laboratory analysis of
high-rate filtration for the treatment of combined sewer flows. High-rate filtration was
defined in this study as filtration rates equal to or greater than 15 gallons per minute per
square foot of filter area.
The overall objectives of the filtration study were:
1. To evaluate the applicability of high-rate filtration for the treatment of combined
sewer overflows.
2. To determine flocculation materials and procedures which will optimize solids
and BOD removal.
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3. To provide a design basis for pilot-scale or full-scale treatment units.
In view of the objectives, the variables which were evaluated in the laboratory study are as
follows:
1. Filter media including type, depth, size, and arrangement.
2. Flocculant and flocculant aid including types, dosages, and combinations.
3. Filtration rates.
Wastewater characteristics which were studied were size and concentration of suspended
solids, BOD concentrations, and temperature. The operating variables were backwash rate
and quantity, air scouring rate including duration and pressure, and pressure. Performance
was evaluated in terms of effluent quality, length of filter run, suspended solids penetration,
and head requirements.
The filtration system consisted of three filters each 4" in diameter and equipped with
associated instrumentation to monitor and control filtration rate, operating pressure, head
loss, and temperature. The filter columns were designed to have adequate strength to with-
stand elevated pressures, adequate depth for deep-bed filtration, and could be easily dis-
assembled for the purpose of exchanging and/or modifying the filter media. Wastewater
storage facilities of sufficient capacity were also provided to assure a maximum anticipated
volume of wastewater which the system would process. Transmission facilities were required
between the storage tanks and the filters. The transmission facilities were capable of
delivering the wastewater over the desired ranges of flow and pressure without materially
affecting the characteristics of the wastewater. Flocculating material supply and injection
systems were developed which were capable of delivering and mixing the numerous
f locculants and flocculant aids which were under consideration.
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A supply of wastewater was provided for testing the filters. The wastewater was developed
by diluting domestic sewage and adding clays and silts to provide a waste comparable to the
combined sewer flows being measured at the time in Washington, D.C. Finally, overall
system safeguards and monitoring and control devices were installed to protect and coordi-
nate the system components.
The equipment was arranged into three separate filtration systems which were parallel and
independent of each other. Each filter consisted of a 9 foot jointed glass pipe of 4" inside
diameter. Each filter is fed by a pump taking suction from the wastewater storage tanks; the
pump maintains a constant operating pressure on the filter. Eleven hundred gallons of
storage was provided for each filter.
Three different filter media were investigated. The first media was composed of fiberglass;
flow was in a downward direction. A second filter consisted of a 9" gravel base, 3" of coarse
garnet, 24" of a garnet/sand mixture, and 36" of anthracite; this was also a down-flow filter.
The third filter consisted of a 9" gravel base, 9" of coarse garnet, and 48" of medium
garnet; it was designed and operated as an upflow filter.
A total of 40 filter runs were performed with influent solids ranging from 4 to 900 mg/L
and influent BOD ranging from 40 to 90 mg/L. For each filter run, all necessary parameters
were measured and samples were periodically collected for subsequent laboratory analyses
to determine efficiency.
This data is now in the process of being reduced and analyzed but certain general con-
clusions can be drawn. The upflow filter could only operate satisfactorily between the
ranges of 5 and 15 gallons per minute per square foot. Within that range, suspended solids
removal were approximately 60 percent and a BOD removal of approximately 45 percent
was achieved. However, as the filtration rates were raised above 15 gallons per minute per
square foot, efficiency dropped off remarkably.
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Filter number two, the tri-media filter, performed very well at a loading of 10 gallons per
minute per square foot. At this filtration rate, suspended solids removal of 80 to 95 percent
were achieved and BOD removals in the range of 50 to 80 percent were also achieved. Filter
runs were approximately of two hours duration before head losses reached a point where
backwash was required. As the filtration rate was increased to 20 gallons per minute per
square foot, the same approximate efficiency was maintained. However, the length of
'filtration runs was reduced from approximately two hours to approximately one-half hour.
The third filter media, fiberglass, performed significantly better than the other two granular
media. The fiberglass was tested within the range of 15 gallons per minute per square foot
up to as high a loading rate as 50 gallons per minute per square foot. At 15 gallons per
minute per square foot, suspended solids removals were in excess of 95 percent and BOD
removals were in the range of 60 to 90 percent removal. Filter runs lasted from two to five
hours and no flocculant or flocculant aid was required.
As the filtration loading rates were increased from 15 to 50 gallons per minute per square
foot, suspended solids removals were in the range of 87 to 95 percent. BOD and COD
removals ranged between 60 to 75 percent and 50 to 75 percent respectively. Filter runs
lasted from one-half to one hour. At this particular point, there were 750 to 1,000 mg/L of
suspended solids in the influent.
As mentioned, it was found that flocculants and flocculant aids did not significantly
increase the efficiency of the fiberglass filter. However, this was not the case with the
granular media. For these two filters, it was found that alum in a dosage of 150 mg/L and
C-5 at a concentration of 4 mg/L were the optimum combination of flocculant and
flocculant aid.
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As a result of the laboratory filtration studies, a number of conclusions can be drawn. First,
and of major importance, is the fact that physical treatment can be used to effectively
reduce suspended solids and BOD concentrations. This is a significant finding because, as
developed in the problem definition part of the investigation, very high flows are to be
encountered in relatively short durations of time. This means that biological systems
probably cannot be utilized for the treatment of combined sewer flows unless large storage
facilities are provided for. Even in this case, it is questionable whether or not a biological
system can be kept active and sufficiently alive to adequately treat the wastes. Physical
treatment, on the other hand, can be used effectively on an intermittent basis.
Of the various media investigated, there is no question but that the fiberglass media per-
formed best and appears to definitely have an applicability for treating combined sewer
flows. Additional laboratory work is needed to develop data on depth of fiberglass bed,
desirability of combining granular and fiberglass beds, density gradation of fiberglass, and
backwash requirements. However, based upon the results in this study, the laboratory study
of fiberglass media should be continued and a pilot-scale facility operated for a final
evaluation.
STUD YOFAL TERN A Tl VES
Having defined the problem and having shown that physical treatment of combined sewer
flows is probably possible, the efforts of the study now concentrated upon the analysis of
alternative methods which might be applied in solving the combined sewer problem in
Washington, D.C.
The various alternative methods which are being considered, separately or in combination,
can be classified under four headings:
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1. Sewer Separation
2. Off-System Storage
3. In-Line Treatment
4. Miscellaneous
However, as has been shown, separation in itself may not be a solution in view of the high
pollutant loads which are delivered to the water courses from urban areas where separated
storm sewers exist.
In the study of Washington, D.C., four specific alternatives were developed. These were
developed based upon the physical layout of the combined sewer system and applicability
of various concepts to the Washington, D.C. system. Capital and annual cost estimates are
being prepared to provide a comparative basis.
*
The alternatives considered generally tunnel storage, local underground tank storage, treat-
ment of combined sewer flows for small drainage areas, and separation. Separation was not
studied in detail since it had been studied quite extensively in a previous investigation. The
results of the previous investigation were accepted and the earlier cost estimates were
brought up-to-date by the use of construction cost indexes.
Storage was studied in terms of volumes required and type of storage facility. In certain
cases, for the small drainage areas, local underground reinforced concrete storage tanks were
considered. Herein, the tanks would be constructed at the overflow points below grade. Top
soil would be added above and a park or other open space use would be made of the land
above the tank. For the larger drainage areas, underground tunnels were considered. These
would be bored in rock at an approximate depth of 800 feet. In both storage approaches,
the combined sewer flows are held during periods of peak runoff and fed back into the
system after precipitation has stopped for subsequent treatment. In each storage alternative
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it was assumed that existing hydraulic capacity of interceptors would be utilized as much as
possible. Therefore, during times of precipitation, the interceptors would be flowing full or
nearly full and treatment plant capacity would be exceeded. Incremental capacity was
assumed to be added at the plant during these periods and cost estimates included.
Specifically, the alternatives were developed as follows:
Alternative I: For the smaller drainage areas, storage would be provided at each
individual site by underground storage tanks. For the larger drainage areas, storage would be
provided in tunnels. After precipitation had stopped, the stored flows would be pumped
back into the system for subsequent treatment at the existing treatment plant.
Since the anticipated plant capacity would still be exceeded during times of precipitation, it
was assumed that physical treatment facilities would be necessary at the plant. These fa-
cilities would treat the non-stored flows and could act in series with the biological systems
during dry weather.
Alternative II: Herein, physical treatment would be provided at overflow points in the
system. However, due to the extremely high flow rates on even the smallest drainage areas,
storage chambers would be required to act as surge facilities. The same storage system was
assumed as in Alternative I.
A number of physical treatment processes are being studied including filtration, micro-
straining, screening, etc. The research on these processes is still in early phases. However, it
has been shown that physical treatment is apparently feasible. In order to derive com-
parative cost estimates, high rate filtration was assumed for this alternative.
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Alternative III: This alternative provided tunnel storage for all overflows with
subsequent treatment at the existing plant. It is similar to Alternative I except the overflows
at the smaller drainage areas would also be stored in tunnels.
Alternative IV: This method assumed separation and, as pointed out previously, was
not studied in detail because of prior studies and the question of effectiveness.
Capital and annual cost estimates are being prepared for each of the alternatives. These are
not sufficiently developed to be presented at this time but it appears that the first three
alternatives will have capital costs in the range of 100 million to 200 million dollars.
Separation, at the present level of construction costs, would have a capital cost in the range
of 300 to 400 million dollars.
If physical treatment can be developed as anticipated, the first three alternatives should
provide essentially equal pollution control and reduction. Separation would not be as
effective.
Operationally, separation would be far simpler once it had been accomplished. Storage
facilities will inherently require greater operational efforts, especially sludge handling and
removal. Physical treatment installations will require more maintenance and operation but it
is felt that, due to the nature of physical treatment, these systems can be automated to a
substantial degree.
If the final cost estimates develop as anticipated, one of the first three alternatives will be
recommended. Lower cost and increased pollution abatement will outweigh the operational
advantages of separation.
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SUMMARY
The study has successfully demonstrated an approach in analyzing solutions to combined
sewer problems for an urban area. The first two main areas of concentration - problem
definition and feasibility of physical treatment - allowed the development of a compre-
hensive master plan for eliminating raw sewage discharges from a combined sewer area.
The principles and method of approach developed herein can be applied to other combined
sewer areas to insure an optimum approach in eliminating combined sewer overflows.
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ASSESSMENT OF COMBINED SEWER PROBLEMS
by Richard H. Sullivan
Assistant Executive Director
for Technical Services
American Public Works Association
The water pollution problems which have become the target of public
opinion and public official concern are the sins of the past being imposed
on the present. We are today racing headlong to catch up with yesterday's
custom of using rivers to rid man's environment of his undesirable waste into
the waters most convenient to his urban habitat. Now that there is a national
desire to clean up the discharge of sewage and industrial waste by construction
of treatment plants of adequate processing effectiveness, attention is turned
to another sin of the past that is being imposed on the present—the discharge
of excess flows from combined sewers everytime it rains.
The problem stems from the early use of storm drains to handle domestic
sewage by admitted sanitary flows to these conduits. When sewage treatment
was not practiced, the fact that combined sewers spilled their waste water
into receiving streams was not a matter of concern, but when treatment was
provided for sanitary sewage it becomes necessary to install in combined sewer
interceptors, regulator devices which would divert dry weather flow to the
treatment plant and during storm run-off period to (excessive flows)
receiving waters.
In urban areas where adequate sewage treatment is provided, these periodic
overflows stand as a negative effect which minimizes investment in pollution
control. A water course that is polluted periodically is only little more
usable for most purposes than one that is continuously polluted. As more and
more sewage treatment facilities are provided, meeting Federal and State
Standards for high degrees of treatment, the anomaly of combined sewer overflows
becomes more and more obvious.
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In 1966, for the first time, substantial funds became available for
research in the field of water pollution. We have witnessed an excellent start
toward arriving at a rational engineering approach to reducing pollution from
many sources — including combined sewers. The work to date has not resulted
in defining a solution, but rather has stressed the need for a complete
engineering evaluation to determine the best solution for the physical parameters
which exist.
COMBINED SEWER FACILITY INVENTORY
In 1967, at the request of the Federal Water Pollution Control Adminis-
tration, the American Public Works Association undertook to make an inventory
of combined sewer facilities in the United States. Every local jurisdicition
with combined sewers whose population exceeded 25,000 was personally interviewed,
as well as a large sampling of other jurisdictions — including communities
with a population of less than 500. In all, 641 jurisdictions were interviewed.
We estimated that 46 percent of the communities with 94 percent of the population
and 84 percent of the area served by combined sewers were directly interviewed.
The results of the survey indicated that 36,236,000 people, living on
3,029,000 acres were served by combined sewers. This total indicates that
approximately 29 percent of the nations total sewered population is served by
combined sewers.
Mere numbers do not in themselves make a problem. In the past ten to
fifteen years, there has been a substantial effort to construct waste water
treatment facilities. Overflows from combined sewers are gradually being
identified as one of the continuing sources of pollution. The early rationale
that held that since the overflow was 99 plus percent storm water it was "clean"
has been disproved. Overflows are polluted.
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The small flows of sanitary sewerage in large combined sewers results in
low velocities. Solids are therefore settled out along the sewer line. Storm
flows tend to scour out this material and carry it to the overflow. A large
proportion of the sanitary sewerage also escapes in the overflow. It has been
estimated that from three to five percent of the total organic load reaching
the sewer leaves by the overflow.
A part of the problem of combined sewer overflows is the location of the
overflow facilities and the nature of the receiving waters. Nationally, most
overflows are adjacent to residential or industrially zoned land. The major
receiving waters are dry water courses or waters used for limited body contact
recreation or fishing.
These land and water uses are not suitable places for the discharge of
sewage. Presence of the combined sewer overflows may have a serious impact
upon land development and land values. For a hundred acre tract in one Michigan
City, influenced by one combined sewer overflow, our appraiser estimated that
a value loss of $600,000 and to the immediately adjacent area of 1,333 acres,
$4,476,000. This loss of value results in a tax loss to the City alone of
$70,000 per year.
The American Public Works Association, as a part of its 196? study, was
asked to estimate the cost of separating combined sewers nationwide. We
analyzed figures for weeks, adjusted for prices, inflation and about everything
else, and ended up with $48 billion in 1967 dollars as the answer. Of this,
$30 billion was for work in the public right-ofn*ay and $18 billion for changing
the plumbing on private property. The complete incapability of many of our
major urban areas to bear the disruption of their major commercial areas and
major streets makes complete separation and unlikely goal. Therefore we also
investigated alternatives and from the information available we estimated that
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the cost of alternate methods of treatment or control would amount to about
$15 billion. Such methods include in-system and off-system holding and
drainage area control.
The States, in particular, and many other agencies have enacted regulations
which prohibit the construction of new combined sewer systems or the additions
to existing systems. Unhappily some of the progress which is being made in
metropolitan areas is in new suburban developments where separate sanitary
sewers in a great many cases discharge into combined sewers and add higher
concentration of sanitary sewage to the overflows.
Another major finding from our interviews was the determination that less
than 20 percent of the combined sewer overflow regulators were of a true dynamic
type, that is they could be adjusted to meet various flow criteria. Of the
10,025 regulators found in the jurisdictions interviewed, /£ percent were
nothing more than simple weirs, many with design features which are not re-
sponsive to overflow regulation. In fact many were merely a hole in a manhole
to relieve the system.
The use of improper types of regulators for the existing conditions as
well as poor maintenance practices appeared to be one of the major reasons
for unnecessary and prolonged overflows.
Another finding was that infiltration was recognized as being excessive
in a great many systems. Although few jurisdictions had apparently surveyed
their systems treatment plant records indicate the excessive wet weather flows.
Sewer personnel across the country told us of their efforts to discontinue
the connection of roof gutters, area drains and foundation drains to the
combined sewer system. The flow from these sources is generally credited with
overloading the sewer system, causing both basement flooding, innundation of
mid-city areas and more frequent and prolonged overflows.
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Questions were also asked of each jurisdiction as to the number of per-
sonnel and the level of training of employees associated with the operation
and maintenance of the sewer system. In jurisdictions of less than 25,000, on
the average less than one-half have a full time registered engineer or an
engineer in training. For the 52 jurisdictions from 10,000 to 50,000, the
average was only 3-3 registered engineers in training per jurisdiction.
This group also averaged 5.4 certified plant operators per jurisdiction. Thus
it appears that generally, there may be an inadequate number of trained
personnel available to make maximum utilization of today's technology.
The full report is available from the FWPCA as publication WP 20-11.
STUDY OF URBAN STORM WATER POLLUTION
With sewage and industrial waste treatment a reality and the water resources
of the nation — or at least or major watersheds — protected; and with the
overflows of combined sewers effectively regulated and minimized, in terms
of the "two Q's" of quantity and quality of the spilled waste water to
receiving waters, still another "sin" of the past will still stand as a challenge
to the present and the future.
This will involve the evolution of a new concept of the pollutional impact
of separate storm water discharges on water courses, lakes and coastal waters.
Since everything is relative it is understandable that storm water has in the
past been considered harmless as compared with the pollutional nature of un-
treated or inadequately treated sewage and industrial wastes and the nature of
combined sewer overflows of admixtures of sewage and storm water runoff.
But with the elimination of minimization of these two obvious sources of
pollution, it will not be surprising that attention will eventually come to bear
on storm water spills. Are they a source of pollution? What are these sources?
What could be done about urban runoff waste waters? What is the role of
agricultoral land runoff in the total water pollution control picture and the
problem of protecting the nation's water resources for use and reuse purposes?
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Some of the answers to these basic questions are found in the study of
Water Pollution Aspects of Urban Runoff which was carried out from 1966 to
1968 by the AIWA under a contract with the FWPCA. The report on the study
is published as WP-20-15.
"Clean" storm water is polluted. Rain scavenges air pollution out of
the atmosphere; flows across roofs, across grass sprayed with insecticides
and fertilized with nitrogen and phosphorous, pets and birds; along street
gutters which may average a daily accumulation of more than a pound of debris
each day per 100 ft. of curb; and finally through cat chr-ba sins where the flow
.displaces perhaps two cubic yards of stagnate water and carries with it some
of the digested solids from the bottom of the catch-basin. By the time the
storm water reaches the sewer, it may exceed the strength of sanitary sewage.
When salts from snow and ice control, phenols from automobile eadiausts and
other contaminates are added, the storm water may have a .wide range of
unde sirable characteristic s.
TYPES OF PROBIEM3
The pollution problems which have been generally identified with combined
sewers include the following:
1. Pollution of receiving waters
a. too frequent overflows
b. dry weather overflows
c. prolonged overflows
d. carryover of solids
e. by-passing to protect waste water treatment plant facilities
2. Disruption of waste water treatment plants
a. concentration of solids and debris in primary treatment
b. wash-out of secondary treatment process due to low strength flows
salt water instrusion
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At the heart of most of these problems appears to be the combined sewer
regulator and the capacity of the treatment plant.
Most jurisdictions have not attempted to assess the extent of the pollution
of receiving waters. In many areas the effects of combined sewer overflows are
masked by other major sources of pollution, such as untreated or poorly treated
sanitary sewage, industrial waste, agricultural land run-off, feed lot run-off,
and urban storm water run-off.
The disruptive aspects of combined sewer flow at the waste treatment plant
are readp.y determined by plant operators. In many instances this has led to
even further diversion or by-passing to minimize treatment plant problems.
The AI¥A Research Foundation, under contract with the Federal Water
Pollution Control Administration and some 30 local governmental agencies, is
engaged in a cooperative study of combined sewer system overflow regulator
facilities and practices. This study covers design, application, construction,
control and operation and maintenance procedures. The specific purpose of this
Project is to analyze and evaluate the effectiveness of these practices and to
establish long-needed guidelines for more efficient and dependable control of
overflows and for reduction in the frequency and duration of combined sewer
flows and the resultant pollution in waters -receiving such spills.
The need for better practices was disclosed in the 196? study previously
described. The study resulted in a specific recommendation that an in-depth
investigation of regulator practices be carried out to determine if definitive
parameters of design, application, construction, control and management of such
facilities could be substituted for present and past procedures and to stimulate
acceptance of these improved practices in the rehabilitation of existing regulator
facilities and in the planning and installation of new regulator works. The
current Project is the result of this recommendation and FWPCA's belief that
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better practices can help resolve pollution problems restating from combined
sewer overflows.
The Function of Regulator Devices; The volume of liquid flowing in a
combined sanitary and storm water sewer is greater than the carrying capacity
of the interceptor sewer system, the pumping capacity of a pumping station or
the capacity of a sewage treatment plant, during periods of storm and runoff.
It is the function of a regulating device and the chamber in which it is installed
to regulate or control the amount of the flow which is allowed to enter the
interceptor system and to divert the balance to holding or treatment facilities,
or to discharge this balance to a point of disposal in nearby receiving waters.
The regulator, thus, has the function to transmit an dry weather flow to the
interceptor and hence to sewage treatment works, and to "split" the total
combined storm and sanitary flow during periods of runoff so that a portion of
the flow enters the interceptor and the balance is diverted to the other points
listed above.
Regulators may be of various kinds — such as stationary, movable,
mechanical, hydraulic, electrical, fluidic, variable, non-variable, etc. — but
their function is as described. The 196? study of overflow problems indicated
the need for improvement in regulator devices and in their operation and
maintenance. Over and above today's regulator facilities, the field of combined
sewer service would be benefited by the availability of other types of devices
and modifications of existing equipment. Among the challenges are greater
sophistication in control and actuating facilities, including onsite and remote
sensing and control of intercepted flows, paced by conditions in interceptor and
treatment works, and desired diversion of flows into holding and treatment
processes for the effective reduction in storm water overflow pollution.
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The problem of design, manufacture, application and handling of regulators
is made difficult by the conditions under which these devices and regulator
chambers must function. These include complex and often unpredictable hydraulic
conditions imposed by dramatic changes in runoff due to storms; the heterogeneous
nature of the sewage-storm water which is handled, including grit, course debris
and other clogging producing wastes; the corrosive nature of the liquids; and
the humid and corrosive-gaseous conditions in the regulator chambers. Further
complications are created by tide water backflows and other hard-to-predict
hydraulic conditions in interceptor-treatment plant networks.
Our study of combined sewer regulators has involved the interviewing of a
group of jurisdictions and then in cooperation with a panel of consulting
*
engineers preparing both a report and a manual of practice. Representatives of
financially participating jurisdictions as well as the WPCF and the ASCE are
serving on the steering committees for the study.
The study is well along and should be completed by early Spring of 1970.
Our detailed, extensive interviews of some seventeen jurisdiction has
found only three where the operation of the regulators has been designed to
minimize pollutions by assuring that the interceptor sewer is fully charged.
In Seattle, this is accomplished by a hydraulically operated gate controlled
by a bubbler unit downstream in the interceptor. In Minneapolis-St. Paul
Sanitary Distirct, control is achieved through the use of an inflatable dam,
increasing the head of the orifice discharge to the interceptor sewer. Detroit
is also using a form cf "traffic" control to maximize flow in the interceptor.
An additional principle of operation to minimize pollution is to maximize
in-system storage. The Seattle system in particular insures that all of the
collector storage capability is utilized prior to an overflow event. This
capability does much to eliminate dry-leather overflows and minimize pollution.
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Engineering investigations are being made in Seattle to determine where
there is justification for upgrading the facilities. The study is conducted
by monitoring a facility for the length of time and quantity of flow during
overflow events. From the characteristics of the contributory sewer system,
a mass hydrograph is constructed to analyze the quantity and time of flow
should a controlled facility be installed. One recent study indicated that
for a short period of time when eight (8) events occurred which overflowed
6.4 million gallons, that had a synamic regulator been installed only one event
of 2.7 million gallons would have occurred, a reduction of 85 percent in fre-
quency and 42 percent in volume.
When information of this type is available, the value of upgrading facilities
can be made. There are no magic numbers or rules of thumb — an engineering
study is needed in each case.
ROLE OF INFILTRATION CONTROL
Expenditures for sanitary and combined sewers and treatment facilities amount
to many millions of dollars annually and form a major part of the total amount
budgeted for operations and capital improvement programs in every urban community.
Unfortunately, in most urban areas, little attention has been given to
making sure that costly sanitary and combined sewers and sewage treatment facilities
function properly, if at all, under wet gound conditions. So-called ''separate-
sanitary sewer systems often collect such large infiltration flows that they are
ineffective in performing their primary function. Infiltration in sanitary
sewers usually causes flows which exceed treatment plant capacity and, as a result,
biological processes are either upset or raw sewage is by-passed into waterways
which were intended to be protected from such contamination.
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Infiltration was revealed as a major contributing factor in combined sewer
overflows in a report prepared in 196? by the AFWA Research Foundation which was
previously described. Thirty-four percent of the cities interviewed indicated
that infiltration exceeded their specification. The increased flow in com-
bined sewers due to infiltration decreases its in-system storage capability
and results in more frequent and longer duration of overflows.
Most engineering consultants, scientists, and administrators in the field
of design, operation and management of sanitary sewage collection systems have
little quantitative data available to use in estimating the extent of infiltration
and in making value judgements for the most effective means of prevention and
control.
The AFWA. Research Foundation in cooperation with 35 local jurisdictions
and the FWPCA has undertaken a study of economics of infiltration control,
design and construction practices for new construction and remedies for existing
systems where the cost benefit ratio of control indicates that such action is
desirable. This study should be completed in the Summer of 1970.
In this study, the factors contributing to storm and gound water infiltration
win be evaluated and analyzed to produce guidelines which will be of tangible
value to designers, administrators and operators of combined and sanitary sewage
collection systems and treatment plants.
The study is designed to aid in the formulation of an effective research
and development program to reduce pollution resulting from combined sewer
overflows and treatment plant by-passing attributable to infiltration.
-------
A SIMULATION TECHNIQUE FOR
ASSESSING STORM AND COMBINED SEWER SYSTEMS*
by
JOHN A. LAGER, P. E.**
INTRODUCTION
There are many methods under development for solving problems
related to storm and combined sewer discharges to receiving waters (1).
This paper describes work in progress to develop an assessment technique
for comparing alternate solutions through a comprehensive computerized
program capable of
"representing urban stormwater runoff phenomena,
both quantity and quality, from the onset of precipitation on
the basin, through collection, conveyance (both combined
and separate systems), storage, and treatment systems to
points downstream from outfalls which are significantly
affected by storm discharges. "
This work is an 18-month cooperative project undertaken by FWPCA.
(Federal Water Pollution Control Administration), Metcalf & Eddy Engi-
neers, Inc., Water Resources Engineers, Inc., and the University of
Florida, with overall coordination and management provided by Metcalf
& Eddy. Seven months have elapsed since the start of the work. The
developed model is to be essentially complete at the end of 12 months.
The concluding six months will be devoted to demonstration, testing, and
finalization of the program. Demonstration cities will be selected by the
FWPCA on the basis of available monitoring equipment, data, and appli-
cability, and may include catchment areas of 50 to 5,000 acres.
*Prepared for presentation at the Seminar on Storm and Combined Sewer
Pollution Problems and Alternative Solutions, November 4 and 5, 1969,
at the FWPCA Field Laboratory, Edison, New Jersey.
**Project Manager, FWPCA Contract No. 14-12-502, Metcalf & Eddy
Engineers, Inc., Palo Alto, California.
151
METCALF & EDDY
-------
It would be impractical to describe, in equal detail, all aspects
of this comprehensive program in the time allotted; therefore, the fol-
lowing presentation format will be adhered to:
1. A brief description of the comprehensive program elements
and basic concepts,
2. A summary of the project status as portrayed by recent de-
monstration of linked hydraulic subroutines and preliminary
comparisons with reported hydraulic data,
3. A more detailed accounting of the quality aspects in the pro-
gram development (selected on the basis of the writer's
personal familiarity and the apparent lack of comparable
approaches in the generally available literature), and
4. Views on the possible applications of the final program.
COMPREHENSIVE PROGRAM ELEMENTS AND CONCEPTS
The program is intended for use by municipalities, government
agencies, and consultants as a tool for evaluating the pollution potential
of existing systems, present and future, and for comparing alternate
courses of remedial action. Although cost-effectiveness techniques will
be fully utilized, the preponderance of human elements inherent in this
field of work precludes, in the writer's opinion, the achievement of an
optimal solution. For example, the removal of one pollution unit from
a receiving water will have different values to different people at differ-
ent times.
The simulation technique -- that is, the representation of the
physical systems identifiable within the model -- was selected because
it permits relatively easy interpretation and because it permits the loca-
tion of remedial devices (such as a storage tank or relief lines) and/or
denotes localized problems (such as flooding) at a great number of points
in the physical system.
152
-------
Since the program objectives were particularly directed toward
complete time and spacial effects, as opposed to simple maxima (such
as the Rational Formula approach) or gross effects (such as total pounds
of pollutant discharged in a given storm), it was considered essential to
work with continuous curves (magnitude vs. time), referred to as hydro-
graphs and "polluto graphs."
Because of the multitude of figures to be stored and manipulated
and because the program is expected to have general application, the
digital computer is the obvious operational vehicle. More specifically,
the developed program will be demonstrated on the Department of the
Interior's IBM 360/65.
An overview of the model structure is shown in Figure 1. Princi-
pal development responsibilities among the contractors are indicated,
and the elementary sequencing through the program is presented. In
simplest terms the program is built up as follows:
1. The input sources: Runoff as generated by any rainfall
hyetograph, antecedent experience, and land conditions;
Dry Weather Sanitary Flow as generated by land use, popu-
lation density, etc.; and Infiltration as generated by available
groundwater and the condition and age of the pipe elements.
2. The central core: Transport model which carries and com-
bines the inputs from node to node in accordance with Manning's
equations, and the theories of continuity, and complete mixing.
All inputs are considered as occurring at nodes, and the series
of linked nodes constitute the prototype collection system.
3. The correctional devices; Storage and Treatment models,
which receive hydrographs and corresponding pollutographs
from any selected point in the transport model, perform the
designated task based upon retention time, efficiency of treat-
ment, and other design parameters, and return the corrected
153
-------
hydrographs and pollutographs to the selected point within the
transport model or the receiving water.
4. The output: Receiving Water models or, in the case of a dry
bed, the storm stream discharge. The receiving water may
be a river, lake or estuary as identified by multi-linked nodes
and operated upon by geometry, upstream flows, tides, other
discharges, controls, etc. Comparison of maximum nodal
values to established water quality criteria may 'loop" back
to the correctional devices (requiring added increments of
construction) until the quality criteria are satisfied.
PROJECT STATUS - HYDRAULIC
At the September quarterly project meeting, a computer program
was executed that demonstrated the feasibility of linking several functioning
subprograms into a single operating unit requiring only one set of data and
"one punch of the computer execute'button. " The test case involved six
identical subcatchment areas (identical only to simplify the data takeoff)
with runoff discharging to the transport model at six different points,
which in turn discharged into a storage basin that overflowed into a simu-
lated estuary receiving water. Figure 2 shows a schematic plan of the
system. Figure 3 illustrates the initial rainfall hyetograph and succes-
sive hydrographs as the flow is routed through the system. Sample corres-
ponding output data are given in Tables 1 and 2.
Individual hydraulic subprograms have been successfully tested
against reported data for the Oakdale area in Chicago, the Northwood
area in Baltimore, and the Selby Street area in San Francisco, but time
does not permit presentation or elaboration on these results (2, 3,4).
M ETCALF ft EDDY
-------
PROJECT STATUS - QUALITY
Whereas the literature abounds with data and theories for modeling
the hydraulic aspects of rainfall-runoff and routing, very little has been
found in the area of quality models and/or data with notable exceptions
(5, 6,7,4, 8, 9,10). Thus, having a "free hand, " an approach was developed
(which continues to be improved upon) of breaking down the problem into
basic source elements, identified in the case of combined systems as sur-
face runoff quality, catchbasin effects, dry weather flow quality, dis-
placement phenomenon, and flushing; attacking each as a separate problem;
then recombining the parts to determine the final effect. The source
elements were further broken down by the nature of the pollutant (soluble
or nonsoluble), the amount of material accumulated at the start of the
storm, and the rate of removal of this material as a function of the storm
where applicable or, in the case of sanitary sewage, the hour of the day.
Surface Runoff Quality
The estimate of accumulative pollutants on the ground surface at
the start of the storm is based almost entirely on data presented in an
FWPC A-sponsored APWA study in Chicago, which reported dust and dirt
accumulations on urban streets as a function of time, land use, curb
length, antecedent rainfall, and street cleaning practice (8). The study
reported that this dust and dirt fraction was the best identifiable source
of pollutants in urban runoff and described its soluble constituents in
terms of BOD and other pollutants, all according to land use. While it
is not claimed that all urban areas will accumulate dust and dirt at the
specific rates measured in Chicago, these data are presently being used
without modification. (Some modification could and may be systemized
subsequently on the basis of a monitored air pollution index, such as
dustfall.) The reported frequency-efficiency-pass relationships of
street sweeping practice are also included in the model; thus, the effects
of changes in practice can be indicated.
155
METCALF 8c EDDY
-------
The removal of soluble pollutants from the streets to the storm
inlets or catchbasins is based on the following first order equation de-
veloped by Allen J. Burdoin, Consultant to Metcalf & Eddy:
P -P = P (l-e-4'6rt)
o o
Where P = total pounds of pollutant available on the ground at
o
the start of the period
p = amount remaining after time t
r = rate of runoff in inches per hour
t = time in hours from condition PQ to P
4. 6 = constant for the above units assuming that 90 percent
of the pollution will be washed off in one hour by a
runoff intensity of 0. 5 inches per hour.
The removal of nonsoluble pollutants (suspended solids and grit)
requires not only contact with the runoff but also physical transport by
the runoff; hence an availability factor is applied to the accumulated dust
and dirt before executing EQ.l.
The presently used availability factor is computed from the fol-
lowing equation:
A = 0. 57 + 1. 4rL 1 . . . . ................ EQ' 2
Where A = fraction of total dust and dirt available during the time
increment
r = rate of runoff in inches per hour during the time
increment.
156
-------
Studies are in progress for a more theoretical determination based
upon particle size distribution and average surface velocities computed for
each time increment.
The results of an application of the Surface Runoff Quality model
to a separate storm system serving a 27-acre area in Cincinnati (6) is
shown in Figure 4, and sample output data are given in Table 3
Catchbasin Effects
Catchbasins traditionally have been built on inlets to combined
sewer systems for the purpose of removing heavy grit whirh might other-
wise settle in the collection system and for providing a liquid barrier to
prevent sewage odors from reaching the streets. The APWA study and
other studies have indicated that these basins are a significant source of
pollution, reporting BOD concentrations of 60 mg/L (milligrams per
liter) for a residential area in Chicago (8), and 125 mg/L in Washington,
D.C. (11). The APWA study further reported the rate of removal of this
soluble pollution based upon test cases using salt solutions. In these
cases a catchbasin was subjected to varying inflows, and effluent salt
concentrations with time were noted. An empirical equation has been
fitted to these data by Burdoin. This equation further accounts for varying
basin liquid volumes and volume changes during discharge:
R = (1.0 - e~CL5V]) x 100 EQ. 3
Where R = percent of catchbasin source pollution removed
x = accumulative inflow to catchbasin in gallons
V = trapped volume of liquid in basin before storm in
gallons.
157
M ETC A LF 8. EDDY
-------
Dry Weather Flow Quality
This source element presents no unusual problems. Generalized
aggregate values will be available by direct measurement or from sewage
treatment plant operating records. The computer program takes these
data when they are available, corrects them for infiltration (which is
assumed to be free of pollutants), further corrects them for known indus-
trial process flow contributions, and then distributes the balance over the
study area in accordance with land use, sewage flow, family income, and
the percentage of dwelling units having garbage grinders. If measured
or plant data are not available, estimated average values are substituted
prior to the distribution. A sample program output is presented in
Table 4. Corrections to average values are included to account for the
hourly flow and strength variations (also taken from treatment plant data)
where the time of the start of rainfall is known, as in the verification of
recorded storm data.
Displacement Phenomenon
When runoff to a combined sewer begins, a major portion of the
sanitary now then present in the system is trapped and mixed or accel-
erated as plug flow by the new hydraulic influx. Depending upon the size
of the system, the capacity of the interceptor, and the prevailing rates
of storm and dry weather now, a substantial portion of this residual
sanitary now (as distinguished from that introduced to the system while
the storm is in progress) may appear in the overflow. By starting the
simulation in the model ahead of the beginning of actual runoff, thus
allowing the model to establish a base sanitary flow, it is expected that
this phenomenon will be properly accounted for.
Flushing
A deposition and scour model is being developed that will allow
solids to accumulate in the system in areas of low velocities during dry
weather now periods and thus will provide source material for the "first
158
METCALF & EDDY
-------
flush" of a storm. Removal of deposits will be expected to follow the tra-
ditional scour equations, hence, particle size distribution and availability
will be the control factors as in the Surface Runoff Quality model.
Computed results for a measured storm on the Laguna Street area
of San Francisco (4) are compared with the reported results in Figure 5 .
The Laguna Street system, unlike that in Cincinnati, has a combined system
and includes catchbasins, dry weather flow, and displacement. Since the
general grades are relatively steep (the main trunk rises 300 feet from
sea level in a mile and a half), no deposition or scour is accounted for.
Transport
The routing of pollutographs has been found to require much the
same analysis as that required for the routing of hydrographs, although
they do not behave identically. Simple time-off set routines are believed
inadequate so a complete mixing (between inlets), mass balance approach
has been adopted.
Treatment
Simplified models for treatment, other than direct sedimentation
(which is handled in a manner similar to that for pipe deposition but with
basin turbulence factors), are awaiting design criteria and operating
data on methods such as those being discussed at this Seminar before
being given serious consideration.
APPLICATIONS OF THE FINAL PROGRAM
As anticipated programs of relief may require expenditures of
billions of dollars, it is believed that the final program will provide a
worthwhile and relatively convenient tool for decision making.
Attention may be directed to the results in terms of pollution
of a number of storms at various intensities, durations, and frequencies
as opposed to the traditional design storm concept which deals with a
single occurrence.
159
METCALF flc EDDY
-------
Different treatment and storage alternates and unit sizes may be
compared in a short time space and at, perhaps, modest cost.
Results of a particular storm on a particular treatment system
may be transferred to nearby catchment areas with, hopefully, confidence
of the outcome.
Finally, much of the initial takeoff data which describe the existing
system and receiving waters need only be collected once and stored on tape
to be readily available to test new alternatives.
CONCLUSION
A program, now under development, has been described and its
potential usefulness explored. This program uses the resources of the
digital computer and the consortium of contractors to provide a simula-
tion technique for modeling and assessing storm and combined sewer
systems. A general overview of the program has been given, a sampling
of the approach methods explained, and preliminary results shown.
ACKNOWLEDGEMENTS
The work described herein is largely the product of my working
associates and our associated contractors whose efforts are hereby
gratefully acknowledged.
This project is being funded by the FWPCA through Research and
Demonstration Grants 14-12-502, 14-12-501, and 14-12-503.
160
METCALF ft EDDY
-------
RUNOFF
DWF
QUANTITY
SOLUBLE
QUALITY
NON-SOLUBLE
SCOUR a DEPOSITION
DISPLACEMENT
PHENOMENA
COMPLETE
MIXING AT
INLET
TRANSPORT
NON-SOLUBLE
QUALITY
RECEIVING
WATER HYDRAULIC
DWF
QUALITY
INFILTRATION
STORAGE
HYDRAULIC
STORAGE
TREATMENT
RECEIVING
WATER QUALITY
FIGURE I
OVERVIEW OF MASTER MODEL STRUCTURE
-------
SUBAREAS
n
30"
(10)
19
30"
17
(18)
SUBAREAS-EACH
47 ACRES
AVE. % IMP. 28%
ALL SEWERS 300* LONG
STORAGE BASIN
MAX. CAPACITY 1,000,000 GAL.
OUTLET CONTROL-FIXED ORIFICE
AREA OF OPENING - 8 SO. FT.
30
(8)
<0
A15 30"
— - '3 30"
(14) (12)
30"
(16)
-------
300.0
250.0
200.0
V)
u,
'.-•
3.0 r — 150.0
s
O
LO
2.0
li
? 1.0
<
or
0.0
100.0
50.0
0.0
RUNOFF AT POINT I
ALL SUBAREAS
CONTRIBUTING
RUNOFF AT POINT 0
AFTER STORAGE
\/- RUNOFF AT POINT
ONE SUBAREA
\ CONTRIBUTING
\
20
60 80
TIME IN MINUTES
100
120
140
160
FIGURE 3
COMPUTED HYDROGRAPHS
DEMONSTRATION MODEL
-------
-,1
~ 0.00
I
Z
0.10
D f 0.20
K
40.0
30.0
X
e>
o
o
CD
20.0
10.0
0.0
CINCINNATI MT. WASHINGTON
SEPARATE STORM SEWER
27 ACRES
LIGHT COMMERCIAL- RESIDENTIAL
9 PERSONS /ACRE
.*•---
REPORTED AVE. SS VALUES'
-COMPUTED BOD RESULTS
fr^iff^f'^ff .•^pv^m n mtmtn
-------
(544)
(534)
SAN FRANCISCO-LAGUNA ST
COMBINED SEWER
MARCH 10, 1967 STORM
[/
rl I
I I
'»
370 ACRES
MULTI-FAMILY RESIDENTIAL
68 PERSONS/ACRE
b
I'
D
DC
0.00
0.10
o.zo
250
200
Q
o
BQ
.^-REPORTED SS
VALUES
r-COMPUTED
\BOD RESULTS
REPORTED BOD VALUES
400
350
300
250
200
150
100
150
100
TIME
FIGURE 5
QUALITY MODEL RESULTS
COMBINED SEWERS
FOR
-------
.000
.000
.000
•noo
.000
.000
.000
.000
.000
e XT ER NA L
*E LE CT EO
OUTFLOW HYDRO GRAPHS
ELEMENT ""TIME "STEP
NUMBER 1
1 .000
12.704
94 .8 32
- l5StS7J
IC/> 91.779
£ f 270.003
2* 56 .2 IS
YTOn ~ 117.576
g^ > m H 162.628
f» >"" 215.084
§0? 127.775
"I} m "308.420
3-D 67.320
>S - 26.355
5 11.566
^O 8.121
g5 5.369
H> ~ 5.147
5.087
v 5. 056
'"3 .000
28.536
96.445
166.661
97.397
259.580
51.300
1 37 .4 55
163.202
224 »5P8
1 33.641
295.028
63.538
2
.000
52.1 36
97.899
170.383
1 OS .7 36
232.696
50 .4 90
1 78.325
163.334
221 .860
113.472
266.942 "
61 .181
"" 2^.632
11 .082
7.425
5.333
5.137
5.083
5.054
.1 97
72.357
93.173
1 73.224
1 12.448
216.543
45.527
200.585
163.255
2 23. 5 It
1 49.947
247.308
57 .689
3
.!«
100.441
98.609
167.890
120. ?51
151.389
44.636
222.159
1 61 .n 91
215.283
1 58.705
218,515
56.492
22.865
10.784
7.232
5. "501
5.129
5.080
5.051
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1 16.34Q
98.593
1 64.542
1 27.407
1 77.539
44.601
234.361
1 60.S73
211 .953
165.013
204.490
51 .a *!G
4
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\ 22.244
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155.1 16
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51.344
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200.556
156.321
44.336
IS. 334
10.011
5.698
5.246
5.116
5.C73
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1 26 .4 72
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1 63. 4 47
124 .823
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223.433
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2 10.047
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I 31.0 '35
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229.431
134.732
40.318
15.608
9.510
5.614
5.223
5.110
5.070
5.045
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1 19.620
78.221
106.714
203.756
103.402
59.364
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145.564
241 .773
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1 15.792
38.674
14.527
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5.203
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109.591
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-------
STORAGE ROUTING SOLUTION* FOR 200 TIME-STFPS THROUGH UNIT NO. 1» IS
RES
"" """" ' " " """ ' NO.
1
1
1
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< MI M)
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20.0
21.0
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32.0
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98.0
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2.37
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1 . '"9
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2.55
3.10
3. ?n
-------
TOTAL QUANTITIES RENGVRD FROM ALL AREAS IN F.ACH TIVFE INCREMENT
H
oo
W
c
10 (/>
£*
m H
^0 1^
c: o CD
zcr-
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TO
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TIME
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9:15
9:30
9:45
10: C
10:15
10:30
10:45
11: 0
.11815
11:30
11:45
12: C
12:15
12:3C
12:45
RUNCFl
CFS
0.10
0.35
0.50
0.60
0.85
1.10
1.30
1.45
1.55
1 .90
2.45
2.55
2.80
3.95
4.25
3.10
1.20
0.00
0.00
KUNUFF
IN/HR
o.oo
0.01
0.02
0.02
0.03
0.04
0.05
0.05
0.06
0.07
0.09
0.09
0.10
0.15
0.16
0.11
0.04
0.00
0.00
BCC
LBS/DT
0.15
0.52
C.73
C.86
1.17
1.46
1.64
1.72
1.73
1.97
2.31
2.16
2.12
2.59
2.34
1.46
0.52
0.00
O.OC
BCD
MG/L
26.7
26.5
26.0
25.4
24.6
23.6
22.4
21.2
19.8
18.4
16.8
15.1
13.5
11.7
9.8
8.4
7.7
0.0
0.0
ss
LBS/DT
1.92
7.03
10.08
11.98
16.95
21.59
24.72
26.37
26 . 70
31.43
38.81
36.65
36.80
50.27
46.83
25.07
5.53
0.0'D
o.oo
SS
MG/L
341.6
357.5
359.1
355.5
355.0
349.5
333.5
323.8
306.7
294.5
282.1
255.9
234.1
226.6
196.2
144.0
82.0
0.0
Q.'o
-------
SOLUTIONS FOR DRY HEATHER FLCH QUANTITY AND
QUALITY
TIME INCREMENT =
CASE =
12.21
1.83
10.38
10. MINUTES
1
9.03 10795.31 9048.60 3561.40 9901.27
A1BOD » 1CSC.67LBSPEROAY/CFS
A1SS = 1370.73 LBSPEROAY/CFS
ON
VO
m
TJ
-n r
i~ m
OH
^ >-
ODD
OCE
c nrn
> -o
o
c
M INPUT
1
2
3
4
5
6
7
8
9
10
11
12
13
10
11
13
20
22
14
30
31
40
5C
16
17
60
CWF
CFS
C.48
C.26
0.11
C.48
0.20
C.26
SUBTOTALS
1.79
0.93
C.12
0.71
C.21
0.40
SUBTOTALS
4.16
0.11
0.34
GQ
CFS
0.07
C.C4
0.02
C.C7
C.03
0.04
0.27
0.14
O.C2
0.11
0.03
C.C6
0.62
C.C2
0.05
QQOWF KLAND
CFS
0.55
0.30
0.13
0.55
0.22
0.30
2.06
1.07
0.14
0.82
0.24
0.46
4.79
0.12
0.39
2
2
2
2
2
2
2
2
2
2
2
2
1
OWBOD
LBS/DT
3.07
2.03
0.89
3.83
1.54
2.05
13.41
7.36
0.94
4.38
1.31
3.13
30.53
0.83
2.75
DWSS
LBS/DT
3.84
2.54
1.11
4.78
1.93
2.56
16.76
9.20
1.17
5.48
1.64
3.91
38.16
1.04
3.44
TOTPOP
PERSONS
BODCONC
MG/L
SSCOMC
MG/L
17601,
174.
217.
37364,
170,
213,
-------
REFERENCES
(1) Rosenkranz, William A., "Developments in Storm and Combined
Sewer Pollution Control, " presented at the Spring Meeting of the
New England Water Pollution Control Association, June 11, 1968.
(2) Tucker, L.S., "Oakdale Gaging Installation, Chicago - Instrumen-
tation and Data, " ASCE Urban Water Resources Research Program
Technical Memorandum No. 2, Aug. 1968. ~
(3) Tucker, L.S., "Northwood Gaging Installation, Baltimore - Instru-
mentation and Data, " ASCE Urban Water Resources Research
Program Technical Memorandum No. 1, Aug. 1968.
(4) Engineering-Science, Inc., "Characterization and Treatment of
Combined Sewer Overflows, " City and County of San Francisco,
Department of Public Works, FWPCA Grant WPD-112-01-66, Nov. 1967.
(5) Gameson, A.L.H. and Davidson, R.N., "Storm-Water Investigations
at Northampton, " J. Inst. Sew. Purif., 1963.
(6) Evans, F.L. m et al, "Treatment of Urban Stormwater Runoff,"
JWPCF, Vol. 40, No. 5, May 1968.
(7) Palmer, C.L., "Feasibility of Combined Sewer Systems, " JWPCF,
Vol. 35, No. 2, Feb. 1963.
(8) American Public Works Association, 'Water Pollution Aspects of
Urban Runoff, " FWPCA Contract No. WA 66-23, Jan. 1969.
(9) Pravoshinsky, N.A. and Gatillo, P.D., "Calculation of Water
Pollution by Surface Runoff, " International Association on Water
Pollution Research, Minsk, U.S.S.R., 1969.
/
(10) Metcalf & Eddy Engineers, Inc., "Stormwater Problems and Control
in Sanitary Sewers - Oakland and Berkeley, California," FWPCA
Contract No. 14-12-407, Sept. 1969.
(11) Johnson, C.F., "Equipment, Methods, and Results from Washington,
D.C. Combined Sewer Overflow Studies," JWPCF, Vol. 33, No. 7,
July 1961.
170
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WILLIAM A. ROSEWKRANZ - SUMMARY
A few minutes might be well-spent to summarize what has
taken place today and to offer a couple of comments of my own.
First of all, the matter of disposal of solids that may
be removed by a treatment process or collected in a storage or
sedimentation basin has not been the subject of much discussion.
When looking at alternatives, consideration must be given to the
solids and what are we going to do with them. Of course, there
are quite a few alternatives to be considered. We have discussed
today putting them back into the system with transport to waste-
water treatment plant. In this regard another comment is pertinent.
The Minneapolis-St. Paul and Detroit projects are using in-system
control, routing, storage, etc. in the system. They are now
noticing using solids concentrations in the treatment plant implement
and are getting complaints from the sewage treatment plant operators
related to increased solids handling problems at the treatment plant.
Obviously, they are accomplishing something. The solids are not.
going into the river but they are increasing the solids loads on
the treatment plant. This is a problem that has to be faced.
A couple of quick summary items. Alternatives must be
examined in terms of both technical and economic feasibility. We
are needful of designing coordinative and compatible systems. Where
more than one treatment point is involved, the analyzing of alternatives
171
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and selection of the control and/or treatment sytem, the total
pollution load discharged must be considered as well as the
instantaneous quality of a waste stream at any particular point
and time.
This is particularly true since both intra-state and inter-
state enforcement actions are now including this type of consideration.
The total pounds of allowable discharge are likely to be established
and the water quality standards set in this vain. Use of such an
approach will be increasing and it is going to place an additional
burden on communities with combined sewer systems.
The seminar that we had here today has presented what ammounts
to an interim report on the progress that we have made to date with
the help of some 80 grantees and contractors. Much more information
on performance and cost facilities is needed. Individual sewerage
systems present individually unique problems requiring unique solutions.
Our research and development program is still looking for good
demonstration projects to help fill these information gaps. I hope
you all contribute something to it. Thank you very much for being here.
172
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BUILDING FOR THE FUTURE - THE BOSTON DEEP TUNNEL PLAN
by
CHARLES A. PARTHUM
In early 1966, the City of Boston engaged the consulting firm of Camp, Dresser
& McKee to prepare a report on improvements to the Boston Main Drainage System. This
report, completed in late 1967, offered a plan of improvements which (1) correlated the
»
work of many urban renewal projects, (2) replaced old and antiquated sewers, (3) considered
the problems of an old combined sewer system, and (4) produced a course of action which
will keep sanitary sewage construction in the City moving ahead with the New Boston.
One of the recommendations in this report was the construction of a Deep Tunnel System
to receive and dispose of all overflows of mixed sewage and storm water and surface runoff.
Early History
Boston was settled in about 1630. By the year 1701 the population had increased
to about 8,000 and problems were being created by frequent digging of streets to lay or
repair sewers. Until the year 1823, however, the sewers in Boston were constructed, repaired,
and owned by private individuals. The purpose for which the sewers were constructed at
that time was for the draining of cellars and lands and toilet and privy vault wastes were
specifically excluded from the sewers.
In 1823 when the City of Boston was granted its charter, it assumed control of all
existing sewers and of the construction and maintenance of new ones, but not until 1833
was it determined that the Mayor and Aldermen at their discretion might permit fecal matter
to be discharged to the sewers. Between 1834 and 1870 the City conducted extensive
Partner, Camp, Dresser & McKee, Consulting Engineers, Boston, Massachusetts. This paper
was presented at the 42nd annual conference of the Water Pollution Control Federation,
Dallas, Texas, October 5 - 10, 1969.
-------
operations for reclaiming and filling tidal areas bordering the old shorelines of Boston.
To meet these changing conditions, sewers were extended long distances at practically
no grade to reach new points of discharge into the harbor. As a result, the deposit of
sludge and debris within the sewers and upon the tidal flats around the City occurred.
In 1870 the City declared that a better system of sewerage was urgent, but it was not
until the period betweeen 1877 and 1884 that the City of Boston constructed what is
known as the Boston Main Drainage System. This system consisted of 25 miles (39.5 km)
of main and branch intercepting sewers and a pumping station and outfall sewer to Moon
Island where sewage was discharged raw on the outgoing tide. The sanitary sewage
collected by the Boston Main Drainage System now is discharged to the new Metropolitan
District Commission sewerage system where it receives primary treatment and chlorfnation.
Still the combined sewer overflows exist.
The Problem
At the present time, there are about 1360 miles (2150 km) of sewers in the City
of Boston, many of which were built over 100 years ago. Most of these sewers, particularly
in the older sections of the city, are combined and their condition is questionable. Much
of the Boston Main Drainage System is surcharged and several sections have collapsed.
It is estimated that at the present time there are about 90 outlets in Boston which
discharge dry weather flows of sewage frequently or mixed sewage and storm water continuously
during wet weather. Of the approximately 30,500 acres (12,400 ha) of total sewered area
in the City of Boston, it is estimated that aboot 7,000 acres (2340 ha) are served directly
by combined sewers and about 10,100 additional acresUlOO ha) are now served directly
by separate systems which discharge to combined sewer outlets.
-------
Recent federal and state legislation has resulted in the classification of coastal
and inland waters in the vicinity of the City of Boston. This classification, adopted by
the State on June 20, 1967, and approved by the Federal Government, means that the
continued discharge of untreated sewage and mixed sewage and storm water is a violation.
Abatement of pollution from combined sewer system overflows presents a most formidable
problem for some of our older and larger cities. Until the problem is solved, however,
compliance with State and Federal water quality standards cannot be achieved. It was
most important, therefore, that the City of Boston have a feasible plan to present to State
and Federal authorities in its efforts to improve its sewerage system and to dispose properly
of its mixed sewage and storm water discharges.
Alternative Methods to Handle Mixed Sewage and Storm Water Flows
A number of communities neighboring Boston (Brookline, Cambridge, Chelsea and
Somerville) also have combined sewer systems which now discharge through outlets into
Boston Harbor and adjacent waters. It was concluded that methods for handling discharges
of sewage or mixed sewage and storm water from combined systems should include the appli-
cable areas in each of these communities. The tributary area in all five communities is
referred to collectively hereafter as the regional area.
To determine the most feasible method of handling mixed sewage and storm water
discharges to Boston Harbor and adjacent waters, a number of alternative methods were
investigated which, in addition to the Deep Tunnel Plan, included complete separation,
construction of chlorination detention tanks and construction of holding tanks.
Complete Separation
Separation has been the policy of the City of Boston for about 60 years. Separation,
if completely accomplished, would eliminate all discharges of overflows of mixed sewage
and storm water. In Boston and neighboring municipalities where systems are now combined,
175
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separation would require the construction of a new sanitary sewer in every street where
a combined sewer now exists. It would also involve new separate plumbing connnections
to all of the existing buildings, and the re-plumbing of many entire buildings to separate
roof drainage from the sanitary sewerage system. In many areas, yard drainage which now
discharges into the combined system would also have to be repiped to the separate storm
water systems. The construction of new separate sanitary sewers in the combined areas
of the city would result in enormous traffic problems that would interfere with every day
activities. New sanitary sewers would be required to serve 7,000 acres (2340 ha) in Boston ,
and an additional 5,000 acres (2020 ha) in the regional area.
It was not considered feasible or practical to completely separate existing building
plumbing into separate sanitary and storm systems. The great problem of enforcement of
such separation in private dwellings by owners would have to be carried out under city
ordinance by teams of inspectors. The only other possible way to affect separation of building
plumbing would be for the City to go into each building and accomplish the separation
itself. Separation in many buildings would require extensive renovations to the buildings
themselves.
Construction of Chlorination Detention Tanks
A second alternative method for handling mixed sewage and storm water discharges
involves construction in the vicinity of selected outlets, of chlorination detention tanks,
which would collect, detain and chlorinate discharges or overflows of dry weather
flow or mixed sewage and storm water before discharging to near-by watercourses. As
stated heretofore, there are about 90 outlets into Boston Harbor and adjacent waters from
the combined systems in Boston alone. An equal number of such outlets exist in neighboring
communities. It was estimated that about 30 ranks would be required to serve outlets in
176
-------
Boston alone. Near each outlet or combination of outlets must be available sufficient
land area for construction gf such tanks in order to make this method feasible. It was
estimated that these tanks would require a total land area of about 100 acres (40 ha)
to serve 10,300 acres (4180 ha) in Boston alone and about 160 acres (65 ha) to serve
17,000 acres (6900 ha) in the regional area. The cost of taking land for this method
even if it were to be made available would be prohibitive.
The enormous problem connected with the operation and maintenance of pumping,
chlorination and cleaning facilities in addition to land costs and construction costs for
chlorination detention tanks did not present a practical solution.
Construction of Holding Tanks
A third alternative method of handling mixed sewage and storm water discharges
involves construction of holding tanks in the vicinity of the outlets, which would store the
discharges or overflows until the storm subsides. The stored flows could then be released
back into the dry weather interceptor system for disposal with the normal sewage flow in
the sewerage system. The holding tanks would be much larger than chlorination detention
tanks, more land area would be required, and the resultant costs would be higher. Therefore,
holding tanks did not offer a practical solution.
Comparison of Costs
Shortly after beginning this study, the firms of Harza Engineering Company and
Bauer Engineering Inc. proposed a deep tunnel storage plan for the Metropolitan Sanitary
District of Greater Chicago. After a thorough review of the Chicago plan, including
discussions with the engineers involved it was concluded that the basic concept of deep
rock tunnels for storing overflows is most attractive and offers possibilities that other
methods do not.
A comparison of costs of the above three alternative methods together with the
Proposed Deep Tunnel Plan, to be described hereinafter, is as follows:
177
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ESTIMATED COSTS OF ALTERNATIVE
METHODS FOR THE BOSTON REGION
Estimated Costs, Million Dollars
Capitalized
Operation
and
Method
Complete Separation
Chlorination Detention
Tanks
Holding Tanks
Proposed Deep Tunnel
Plan 430.0 66.0 496.0
Construction
550.0
400.0
715.0
Maintenance *
34.0
133.0
99.0
Total
584.0
533.0
814.0
*At interest rate of 4.00%
It was concluded that of the various alternative methods studied, only the method
of storing overflows in deep rock storage tunnels would provide the Boston region with
a positive and feasible method of completely solving the problem of combined sewers.
Proposed Deep Tunnel Plan
The Deep Tunnel Plan is proposed to be of sufficient size and capacity and suitably
located to serve the tributary areas of Boston and the four neighboring communities which
have combined sewer systems, thus solving on a regional basis the problem of water pollu-
tion abatement. The total area to be served by the proposed Deep Tunnel Plan was estimated
at about 17,000 acres (6900 ha).
178
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Rainfall
In design considerations of a tunnel storage plan, the volume and intensity of
rainfall are very important factors. Two significant rainstorms were considered:
(1) a 5-in (13 cm) storm in 24 hours, with a frequency of recurrent of about 15 years,
which could be handled without surcharging the tunnels and (2) an 8.40-?n (21 cm) storm
in 24 hours which could be handled with surcharging of the tunnels. The total rainfall depth
shown on Fig. 1 "Depth of Rainfall vs. Frequency for Boston, Massachusetts" for a
storm of one-day duration and 100-year frequency is about 7.0-inches (18 cm). The
maximum recorded 24-hour rainfall in Boston is 8.40-inches (21 cm).
Whereas, it is obvious that a tunnel system designed on the basis of 5-in (13 cm)
and 8.40-in (21 cm) storms in 24 hours will not be adequate for a 24-hour rainfall in
excess of 8.40-in (21 cm), such excessive rainfalls, even though not ever recorded,
nevertheless were considered. The capacity of the present sewerage system is such,
however, that it is unable to deliver enough flow to exceed the proposed tunnel system
design capacity of 8.40-in (21 cm) in 24 hours, and the excess flow must, therefore,
be stored at the surface or runoff overland to the nearest watercourse. Even when replace-
ments are made to the surface collection system to increase its capacity, it is expected
that its total capacity to deliver flows to the tunnel system will not exceed the runoff
from an 8.40-in (21 cm) storm. Nevertheless, the pumps proposed have adequate capacity
to pump flows from such excessive storms if the long outfall is by-passed and an alternate
short outfall is employed.
Based on the set of curves shown on Fig. 1 , the total volume of rainfall in
one day expected for a storm frequency of about once in 15 years is about 5-in (13 cm)
over the entire tributary area. From the curves, it is apparent that a depth of
5-in (13 cm) would be expected from a storm of 48-hours duration about once in 4-1/2
179
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3! '0
u
* 8
a.
Ill
O
Ih
z
I
Totol Rainfall Dtpthi
Adopttd for Dtsign
10
Y I! A R S
FREQUENCY OF RECURRENCE
DEPTH OF RAINFALL VS FREQUENCY FOR BOSTON, MASSACHUSETTS
FIG. I
-------
years, and from a 4-day duration storm once in 3 years. Four inches (10 cm) would be
expected from a one-day storm about once in 5 years. The curves in Fig. 1 were
developed from data in United States Weather Bureau Technical Papers No. 40 and 49
for recurrence intervals from 2 to 100 years. Data for recurrence intervals from 2 months
to 2 years were based on analysis of Boston rainfall records for the 10-year period 1955
through 1964.
As a result of these studies, it appeared reasonable that a deep tunnel storage plan
could be constructed that would handle the runoff resulting from a 15-year frequency
rain storm of 24-hour duration (total rainfall depth 5-in (13 cm) and dispose of this runoff
within a 2-day period without surcharging the tunnels at any time. If the tunnels are
permitted to surcharge, the runoff from a storm equal to the maximum which has been
experienced in Boston may be handled. Essentially such a deep tunnel plan would eliminate
all overflows to Boston Harbor and adjacent waters and practically all flooding of land
areas and basements.
Storage vs. Pumping
There are numerous alternative arrangements possible in the development of
a deep tunnel plan with relation to the volume of storage and the rate of pumping.
These alternatives range from an arrangement of maximum pumping capacity with no
effective storage to very large volume of storage and minimum pumping capacity. The
estimated cost of a deep tunnel storage plan is dependent in large measure on the cost to
excavate rock. During the course of studies to determine reasonable tunnel capacities,
eight separate arrangements ranging from a pumping rate of 1370 cfs ( 2340 cu m/min)
and 35 miles (55 km) of 33 ft (10 m) diameter storage tunnels to a pumping capacity of
181
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2400 cfs (4100 cu m/min) and 15 miles (24 km) of 33 ft (10m) diameter storage tunnels
were investigated. It was determined from studies of relative costs that the cost increase
connected with increasing the pumping capacity is far less than the cost of increasing
the storage capacity. It was therefore concluded that a length of storage tunnels of about
17.2 miles (27 km) should be provided.
This analysis resulted, after some refinement, in a required minimum pumping capacity
of about 2400 cfs (4100 cu m /min) to handle a 5-in (13 cm) rainstorm:, together with a
storage volume equivalent to a length of about 17.2 miles (27 km) of 33 ft (10m) diameter
runnels, if the tunnels are not permitted to surcharge. By permitting the tunnels to surcharge
for a rainstorm of 8.40-in (21 cm) in 24 hours, a pumping capacity of about 5200 cfs (8850
cu m/min) may be obtained using the same pumps as are required for 2400 cfs (4100 cu m/min)
without surcharging. Moreover, for rainstorms in excess of 8.40-5n (21 cm) in 24 hours
the same pumps could serve if the whole flow were discharged to the sea through a short
outfall at the pumping station at Deer Island.
Fig. 2, "Deep Tunnel Storage Volume and Pumping Rates", is a mass or cumulative
curve of inflow to the proposed main pumping station. It indicates that pumping at a
continuous rate of 2400 cfs (4100 cu m/min) starting at about the 5th hour following the
start of the 5-in (13 cm) design rainfall will empty the tunnel storage reservoir by the
end of the 36th hour. For a pumping rate of about 5200 cfs (8850 cu m/min) the tunnels
could be emptied in a shorter period of time.
Alternatives Considered in the Development of the Proposed Deep Tunnel Plan
As mentioned before, many alternatives were considered in developing the proposed
Deep Tunnel Plan. The size and length of tunnels, the depth and length of outfalls, the
size and location of chambers and the main pumping station all were variables. After much
182
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467 Million Cu. Ft.—-j
450
Inflow to Main Pumping
Station from 8. 40-in.
Storm
276 Million Cu.Ft
Inflow to Main Pumping Station
from 5.00-in. Storm
Required Storage
Volume = 80 Million Cu.Ft
BOSTON, MASSACHUSETTS
DEEP TUNNEL
STORAGE VOLUME
AND
PUMPING RATES
e 16
TIME FROM START OF RAINFALL - HOURS
183
FIG. 2
-------
consideration, the radial storage tunnel arrangement shown on the plan of Fig. 3
was adopted in order to most effectively locate the tunnels such that access to them
for all parts of the area served by combined sewer outfalls would be achieved.
Ocean Outfall
Proper disposal of sewage effluent or mixed sewage and storm water to large
bodies of water requires an effective mingling of those polluted waters within the water
body to prevent the identification of the discharged wastewater, prevent odor nuisance,
and reduce bacterial concentrations. It was concluded, therefore, that the disposal of
all mixed sewage and storm water through a long outfall to sea would be the most effective
means of abating the pollution of Boston Harbor.
During these studies and in conjunction with the design of the proposed main pumping
station, seven different pumping rates through a single pipe outfall and a double pipe
outfall were considered. Preliminary costs were prepared for each alternative and compared
with the corresponding cost estimates for the tunnels and the pumping station.
The most economical combination included a single 9.5 mile (15 km) 20 ft (6 m)
diameter outfall with twin 14 ft (4.3 m) diameter diffuser pipes. At pumping rate of
2400 cfs (4100 cu m/min) the velocity in the outfall pipe would be about 7.5 fps, (2.3 mps)
and with 7-in (18 cm) diameter nozzles in the diffuser pipes 15 fps (4.6 mps) nozzle velocities
would be achieved.
Our studies indicate that with a pumping rate of 2400 cfs, (4100 cu m/min) a nozzle
discharge of 4 cfs (6.8 cu m/min) and a water depth of about 110 ft (33.4 m) at the diffusers,
an estimated dilution ratio of about 200 parts of sea water to 1 part wastewater would be
achieved in the rising plume of wastewater, if the dispersing effect of ocean currents is
ignored.
16%
-------
!
^ I MAIN PUMPING |" '
M ISTATI°N I'
WIND I DIAGRAM
PROPOSED
DEEP TUNNEL PLAN
FOR
BOSTON REGION
^w^rercHAMi
i N!
•••^^ PROPOSED STORAGE TUNNELS. OUTFALL ft DIFFUSERS
•••» PROPOSED ACCesS TUNNEL
^^— PROPOS
----- EXISTING CONDUITS
. " -• •
\
FIG. 3
-------
As a result of factors such as ocean currents, distance towards shore and composition
of the wastewater, dilution ratios are expected to range from about 200 to V to perhaps
6,000 to 1. Comparable reductions in the concentrations of bacteria and viruses and other
polluting substances would, as a result, range from about 99.50 per cent to 99.98 per cent
even without chlorination. These reductions are to be compared with about 90 to 95 per cent
removal of organic matter to be expected by conventional "complete" treatment. In other
words, the concentration of polluting substances remaining after treatment by this method
may be less than 10 per cent of that which can be expected following conventional treatment
facilities. In order to provide positive kill of bacteria and viruses, it is proposed that a
heavy chlorine dose be applied throughout the year for protection of recreation and shellfish
taking.
The alternative of discharging the storm runoff into a surface storage reservoir at
Deer Island and passing it through the existing sewage treatment plant at a controlled rate
following a storm was considered but not recommended because:
1. An expenditure of 60 million dollars for a surface storage reservoir did not
appear feasible because the mixed sewage and storm water volume must still
be disposed of within about a 2-day period, either through the plant or through
a separate outlet, in order to have the reservoir empty before the next storm.
2. The efficiency of the existing sewage treatment plant would be reduced for
extended periods following storms.
3. The operation, cleaning and maintenance of such a surface reservoir will require
large expenditures.
186
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Description of Proposed Deep Tunnel Plan
The proposed Deep Tunnel Plan has been developed for collection and disposal
of mixed sewage and storm water flows from 17,000 acres (6900 ha) in the Boston region
and is shown on Fig. 3. The plan comprises the following principal elements:
1. Surface connections consisting of interception chambers located on outlet conduits
downstream of existing or proposed control chambers which will divert dry weather
flows to the existing sewerage system where it will receive primary treatment and
chlorination at the existing MDC treatment works at Deer Island. Excess flows of
mixed sewage and storm water flows would be discharged to the drop shafts, described
below, by the surface conduits.
2. Drop shafts, either vertical or inclined, to conduct the flows from the surface
connections to transmission tunnels or directly to the deep rock tunnels.
3. Transmission tunnels in rock to carry flows from drop shafts to the storage tunnels.
4. An underground reservoir consisting of a system of 33 ft. (10m) diameter deep
rock storage tunnels in a radial pattern sloping gently to a central chamber
located at Columbus Park, and a 33 ft. (10 m) diameter main storage tunnel
extending from the Central Chamber at Columbus Park beneath Boston Harbor to
a main pumping station at Deer Island, as shown by heavy black lines on Fig. 3.
The total length of five radial storage tunnels is about 12.7 miles (20 km). The
main storage tunnel would be about 4.5 miles (7.1 km) in length and would be
approximately parallel to and on the south side of the existing MDC sewage
tunnel (not shown on Fig. 3). The total length of storage tunnels is, therefore,
about 17.2 miles (27 km).
5. A central chamber located in rock, with sluice gates, tunnel ventilation and
control facilities.
187
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6. A sloping access tunnel extending from the central chamber to the
vicinity of the Reserved Channel in South Boston. Its purpose would be to
provide access during construction and for maintenance and inspection purposes
thereafter.
7. A main pumping station located in a rock chamber at Deer Island with control
building, power supply and chlorination facilities, etc., in a surface structure.
8. A 20 ft. (6 m) diameter subaqueous outfall pipe extending about 45,000 ft.
(13,700 m) generally east northeast into Massachusetts Bay terminating in two
14 ft. (4.2 m) diameter diffuser pipes, each about 5800 ft. long (1770 m).
The estimated cost of the Proposed Deep Tunnel Plan is as follows:
Estimated Cost
Item million dollars
Deep Storage Tunnels (including Central
Chamber and Drop Shafts) 213.0
Main Pumping Station (Deer Island 39.0
Ocean Outfall and Diffusers 54.0
Surface Connections 26.0
Transmission Tunnels (including drop shafts) 88.0
Separation (of minor areas) 10.0
TOTAL ESTIMATED CONSTRUCTION COST 430.0
Capitalized Annual Operation and
Maintenance Cost (at 4% interest) 66.0
TOTAL ESTIMATED COST (for comparison with 496.0
alternative schemes)
188
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Pertinent Features of the Proposed Deep Tunnel Plan
Main Pumping Station
The location of the Main Pumping Station would be to the east of the existing
MDC sewage treatment plant on Deer Island. It would consist of a circular chamber some
180 ft. (55 m) in diameter excavated in solid rock.
The station would have design capacities of 2400 cfs (4100 cu m/min) at a total
head of about 350 ft (106 m) with required operating horsepower of about 110,000
and 5200 cfs (8850 cu m/min) at a total head of about 200 ft (60 m) with a maximum
required horsepower of about 150,000 with the tunnels surcharged.
Storage Tunnels
The storage tunnels consisting of the five radial storage tunnels and the main
storage tunnel to Deer Island are proposed to be excavated to cross sectional area equivalent
to about a 33 ft (10 m) diameter circle.
The method of construction of these tunnels at the present time would appear to
be by the drill and blast method. This project was discussed with contractors experienced
in tunnel work. The access tunnel sloping at about 8 per cent grade from the ground surface
to the central chamber at Columbus Park was proposed as an efficient means for access
to the area while the tunnels are being constructed, for easy transportation of the muck to the
surface for disposal either as fill in the immediate area or on barges to be disposed of
elsewhere. The length of rhe five radial storage tunnels under Boston is such that the trans-
portation of the muck from the tunnels to the surface should pose no unusual tunnel construc-
tion. It is thought at this time that the sides and top of the tunnels would not have to be
lined except where unstable rock is encountered or where rock bolts are needed for stability.
The cost of the deep storage tunnels includes 25 per cent of the tunnel length full lined,
189
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75 per cent of the tunnel length with paved invert only and 40 per cent of the tunnel
length supported by rock bolts. The bottom of the tunnels is proposed to be lined with
concrete to assist in the operation and maintenance of the tunnel system and also to provide
a relatively smooth surface on which the contractors' trucks may operate.
Because the primary function of these tunnels is to provide storage volume and
not flow capacity for hydraulic transmission, the shape of the tunnel cross section is not
critical, and a horseshoe or other section could be used instead of the circular section if
it appears more advantageous and economical.
The depth of the storage tunnels is about 300 ft (91 m) below the surface. The
required depth is controlled by the location of the rock surface along its profile. The invert
of one radial storage tunnel and the main storage are proposed to be slightly below that of the
existing MDC Boston sewage runnel to permit dewatering the existing tunnel if required.
Considerable research and experimentation on rock boring machines (moles) with
rotary cutting heads in diameters as large as 33 to 36 ft (10 to 11 m) is being done in this
country and in Europe. The rock formations in Boston are hard and of varying strength.
It appears likely that in the next five to ten years the excavation of hard rock by rock
boring machines will become routine. If the proposed tunnels can be constructed by machines,
the interior of the tunnels will be of circular cross-section and quite smooth, eliminating
in general the need for concrete linings or inverts. Of great significance is the probability
that the development of rock boring machines will reduce excavation costs for rock such
that the costs of tunnels excavated by boring machines may within a few years be sub-
stantially less than those of tunnels excavated by drilling and blasting methods.
190
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Ocean Outfall and Diffusers
The outfall is proposed to extend 45,000 ft. (13,700 m) generally east northeast
into Massachusetts Bay. The pipe would be of reinforced concrete and be provided with
special flexible joints. The pipe would be laid on the bottom of the bay in a trench
sufficiently deep to prevent movement of the pipe. It would be buried where it crosses the
main ship channel.
The diameter of the diffuser nozzles would be 7-in (18 cm) with a spacing on each
side of the diffuser pipe of about 19.2 ft (5.8 m). The diffuser pipes would be located
at approximately right angles to prevailing ocean currents in the area. The diffuser pipes
would be located at about 110 ft (33 m) below mean sea level.
Advantages of the Proposed Deep Tunnel Plan for the Boston Region
1. The Deep Tunnel Plan provides the best and most practical regional solution
to the problem of handling mixed sewage and storm water and assures the
abatement of water pollution due to both sewage and surface runoff.
2. It is adaptable to serve any conceivable development in the region in the future
and is the most economical of the methods studied for eliminating overflows to
the surrounding waters. This plan may become relatively less expensive in
the future as rock boring technology improves.
3. The Deep Tunnel Plan will occupy very little valuable land area, its construction
will not cause interference with traffic or surface activities and it will permit
the efficient draining of all areas that now flood during heavy rains and high
tides.
4. The Deep Tunnel Plan provides the means for safely disposing of all polluted
surface water and sewage well out to sea away from any inhabitated areas.
191
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5. Sections of the deep storage tunnels will parallel the MDC sewerage
tunnel and have lower inverts to complement the existing MDC sewerage
system.
6. The large quantity of rock excavated from the tunnels will be available at
low cost for fill in connection with the expansion of Logan International
Airport, site development for the proposed 1976 Worlds Fair or other fill
operations in and around Boston Harbor.
Conclusions
It is not reasonable to expect the City of Boston alone to effectively dispose of its
mixed sewage and storm water overflows unless neighboring cities and towns having similar
combined systems and overflow problems do likewise. For this reason, the Deep Tunnel
Plan should be constructed as a regional operation.
Although the proposed Deep Tunnel Plan is less expensive than complete separation
of the system, it nevertheless represents a major expenditure. At the present time
State and Federal grants do not appear adequate, either in funds or in scope of existing
grant programs to materially assist in the construction of such a proposed plan.
The City of Boston has adopted this plan and has presented it to the State and the
Federal Government as its solution to the total water pollution problem.
A concerted effort by these large cities to join together and obtain substantial
financial assistance from the Federal Government appears the only feasible means for
correcting the mixed sewage and storm water overflow problem in many of the larger
cities in the U. S.
192
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LIST OF ATTENDEES AT THE SEMINAR
"STORM AND COMBINED SEWER OVERFLOWS"
November U-5, 1969
Allen, Harry S.
Exec. Vice President
Charles J. Kupper, Inc.
15 Stelton Road
Piscataway, N. J. 0885!+
Andrek, George
Planner III
Nassau County Planning Dept.
2*4-0 Old Country Road
Mineola, N. Y. 11501
Banister, A. W.
Banister Engineering Co.
310 North Snelling Ave.
St. Paul, Minn. 5510U
Bankard, Harry T.
Project Manager
John J. Cassner Inc.
250 Broadway
New York, N. Y. 1000?
Barnes, William W. Jr.
Interceptor Serv. Supervisor
City of Philadelphia Water Dept,
3900 Richmond Street
Philadelphia, Pa. 19137
Bigler, Daniel E.
Superintendent
Treatment Plants & Sewers
Township of North Bergen
Dept. of Public Works
U3rd Street & Kennedy Blvd.
North Bergen, N. J.. 070^7
Boox, Louis 0.
Engineer
291 State Street
Perth Amboy, N. J.
08861
Brokaw, Arthur
American Public Works Association
2300 Yardley Road
Yardley, Pa. 1906?
Bromberg, Albert W.
Chief, Operations Branch
FWPCA
Edison, N. J. 088l?
Brown, Calvin G., P.E.
Nassbaumer & Clarke, Inc.
310 Delaware Avenue
Buffalo, N. Y. 1^202
Bryon, John C.
Chief Sanitary Engineer
N. Y. State Office of Gen. Services
Bldg. k, State Campus
Albany, N. Y. 12226
Burger, Theodore B., P.E.
Public Health Engineer II
Bureau of Water Pollution Control
Nassau County Health Dept.
2^0 Old Country Road
Mineola, N. Y. 11501
Bush, Joseph G.
Operator
N. J. Training School State of N. J.
P. 0. Box 169-
Totowa Boro, N. J. 07511
Butler, William
FWPCA
Needham Heights, Mass,
0219^
Buzzi, John L.
Secretary
Charles J. Kupper Inc.
15 Stelton Road
Piscataway, N. J. 0885^
Calocerinos, Emanuel
Partner, Calocerinos & Spina
Cons. Engineers
1000 Seventh North Street
Liverpool, W. Y. 13088
193
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Cameron, Stewart M.
Mechanical Engineer
City of Philadelphia Water Dept.
Water Pollution Control Plants
3900 Richmond Street
Philadelphia, Pa. 19137
•Carstensen, Erik
Public Works, Erie County
^5 Church Street
Buffalo, N. Y. 1^202
Casper, Lawrence
Chemist
FWPCA
Edison, N. J. 08817
Castrigno, Leonard
Design Engineer
Charles R. Volzy Associates, Inc.
300 Martin Avenue
White Plains, N. Y. 10601
Cevallos, Aldo
Sanitary Engineer
John G. Reutter Associates
729 Federal Street
Camden, N. J. 08103
Clausen, Hans
Project Manager
Charles R. Velzy Associates, Inc.
300 Martin Avenue
White Plains, N. Y. 10601
Condon, Francis J.
Sanitary Engineer
FWPCA
Washington, B.C. 202U2
Cornell, I.
Middlesex County Sewerage Authority
P. 0. Box U6l
Sayreville, N. J. 08872
Cosulich, William F.
Consulting Engineer
95 Commercial Avenue
Plainview, N. Y. 11803
De Fillippi, John A.
Roy F. Weston, Inc.
lOhk Northern Blvd.
Roslyn, N. Y. 11576
Dewling, Richard T.
Chief, Laboratory Branch
FWPCA
Edison, N. J. 08817
Di Memmo, John
Hamilton Township Engineer
2090 Greenwood Avenue
Hamilton, N. J. 08609
Durfor, Charles N.
Chief, Basin Planning & Water Resources
FWPCA
Edison, N. J. 08817
Feder, Robert L.
Director R&D Office
Ohio Basin Region
FWPCA
Cincinnati, Ohio ^5226
Feldman, Benjamin
Consulting Sanitary Engineer
23 Basswood Road
Levittown, Pa. 19057
Felton, Paul M.
Executive Director
Water Resources of the Delaware
River Basin
21 South 12th Street
Philadelphia, Pa. 19107
Feuerstein, Donald L., Dr.
Manager, Waste Management Systems
Environmental Systems Division
Aerojet-General Corporation
9200 East Flair Drive
El Monte, California 9173^
Fitzpatrick, Edward V.
Deputy Director
FWPCA
Edison, N. J. 08817
Flanagan, M. J.
Project Engineer
Tippetts, Abbett, McCarthy, Stratton
3^5 Park Avenue
New York, N. Y. 10022
Dudeck, Michael S.
Assistant Engineer
Township of Hamilton
2090 Greenwood Avenue
Hamilton, N. J. 08609
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Foerster, E. R.
Partner
Greeley & Hansen Engineers
233 Broadway '
Room 1380
New Yor, N. Y. 1000?
Gallagher, Tom
Engineer
Hydroscience, Inc.
310 Broad Avenue
Leonia, N. J. 07605
Gidlund, Erick R.
Associated Consultant
Teeter-Dobbins Consulting Engineers
MacArthur Airport
Ronkonkoma, N. Y. 11779
Glover, George
Research Engineer
Cochman Division
Crane & Co.
King of Prussia, Pa. 19*4-06
Goldberg, Alexander
Director
Passaic Valley Sewerage Commission
790 Broad Street
Newark, N. J. 07102
Greene, William L.
Supervisor, R&D
Philadelphia Water Dept.
1110 Municipal Service Bldg.
Philadelphia, Pa. 19107
Guthrie, Byron
Sanitary Engineer
Parsons, Brinkerhoff, Quade & Douglas
111 John Street
New York, N. Y. 10038
Hamilton, David
Sanitary Engineer
Middletown Township Health Dept.
Kings Highway
Middletown, N. J. 077*4-8
Harte, Kenneth E.
Director & Project Engineer
Lehigh River Restoration Association
120 North Ellsworth Street
Allentown, Pa. 18103
Herkert, E. C.
Associate Lab Director
E. T. Killam Associates, Inc.
*4-8 Essex Street
Millburn, N. J. 070*4-1
Hillman, M. H.
Project Manager
Seelye, Stevenson, Value & Knecht
99 Park Avenue
New York, N. Y. 10016
Hoder, Emil J.
Vice President
Charles J. Kupper, Inc.
15 Stelton Road
Piscataway, N. J. 0885*4-
Hoffman, Christian T., Jr.
Supervising Public Health Engineer
N. J. State Dept. of Health
P. 0. Box 15*+0
Trenton, N. J. 08625
Hohman, Merrill S.
Planning & Program Management
FWPCA
Boston, Massachusetts 02203
Howe, Joseph C.
Project Engineer
Metcalf & Eddy Engineers
60 East *4-2nd Street
New York, N. Y. 10017
Harry Ike
Civil Engineer
FWPCA, Construction Grants
Edison, N. J. 08817
Jacobson, Martin
Sanitary Engineer
FWPCA, Construction Grants
Edison, N. J. 08817
Jeske, Richard J.
President
Richard J. Jeske Inc.
26 Linden Avenue
Springfield, N. J. 07081
195
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Jorlett, Joseph A.
Engineer of Design
Fernandez, Jorlett, Kief & Tracey
l6th and Long Beach Blvd.
Ship Bottom, N. J. 08008
Juczak, S., Jr., P. E.
Director
Bureau of Water Pollution Control
Nassau County Health Dept.
2hO Old Country Road
Mineola, N. Y. 11501
Kachorsky, Michael S.
President
M. S. Kachorsky & Associates
P. 0. Box 68
Manville, N. J. 08835
Kahn, Lloyd
Acting Chief Chemistry Section
FWPCA
Edison, N. J. 08817
Kane, Robert C.
City Engineer
City of New Brunswick
City Hall & Barnyard Street
New Brunswick, N. J. 08902
Karvelis, Ernest G.
Chief, Biology Section
FWPCA
Edison, N. J. 08817
Keilbaugh, William
Project Manager
Cochman Division
Crane & Co.
King of Prussia, Pa. 19^06
Kestner, Joseph A., Jr.
Consulting Engineer
One Kestner Lane
Troy, New York 12180
Kirkpatrick, George A.
Hydrologist
FWPCA
Washington, D.C. 202^2
Kopolowitz, Sol
Associate
Havens & Emerson
233 Broadway "
New York, N. Y. 1000?
Krohn, Marc, Dr.
Health Officer
Middletown Township Health Dept.
Kings Highway
Middletown, N. J. 077^8
Kupper, Charles J., Jr.
President
Charles J. Kupper Inc.
15 Stelton Road
Piscataway, N. J. 0885^
Lach, Alexander A.
Plant Superintendent
Middlesex County Sewerage Authority
P. 0. Box U6l
Sayreville, N. J. 08872
Lager, John A.
Metcalf & Eddy, Inc.
Palo Alto, Calif. 9^303
Lewis, Allen J.
Head, Division of Engineering
Township of Woodbridge
1 Main Street
Woodbridge, N. J. 07095
Lubetkin, S. A.
Chief Engineer
Passaic Valley Sewerage Commission
790 Broad Street
Newark, N. J. 07102
Manganero, Charles
Consulting Engineer
Passaic Valley Sewerage Commission
790 Broad Street
Newark, N. J. 07102
Mariniansky, E.
Project Engineer
Seelye, Stevenson, Value & Knecht
99 Park Avenue
New York, N. Y. 10016
196
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Martin, Thayer F.
Sanitary Engineer
Standard Engineering
17^3 Western Avenue
Albany, N. Y. 12203
McCann, John T.
Borough Engineer
Borough of New Providence
Park Place
New Providence, N. J.
Park Place
New Providence, N. J. 0797^
McKenna, Gerard
Chemist
FWPCA
Edison, N. J. 08817
Metzger, Ivan
Professor
Newark College of Engineering
323 High Street
^Newark, N. J. 07102
Miles, Charles F., Jr.
Associate Sanitary Engineer
New York State Health Dept.
270 Madison Avenue
New York,New York 1122U
Moller, Edward J.
Deputy Engineer
Passaic Valley Sewerage Commission
790 Broad Street
Newark, N. J. 07102
Moore, Robert C.
Vice President
Elson T. Killam Associates, Inc.
U8 Essex Street
Millburn, N. J. 070^1
Muss, Milton
Township Engineer of North Bergen
U3rd Street & Kennedy Blvd.
North Bergen, N. J. 070^7
Mytelka, Alan I., Ph.D.
Assistant Chief Engineer
Interstate Sanitation Commission
10 Columbus Circle
Room 1620
New York, N. Y. 10019
0 ' Sullivan , John
Project Engineer
Brinnier & Larios Consulting Engrs.
67 Maiden Lane
Kingston, N. Y. 12^01
Palasits, Robert B.
Alfred Crew Consulting Engineers
75 North Maple Avenue
Ridgewood, N. J. 07^50
Palevsky, Gerald
Assistant Professor Civil Engineering
CCNY
Convent Avenue at 138 Street
New York, N. Y. 10031
Park, George M., Jr.
Project Engineer
Gannett, Fleming Corddry & Carpenter, Inc.
P. 0. Box 1963
Harrisburg, Pa. 17105
Paul, Carl
Hydrologist
FWPCA
Edison, N. J.
08817
Paul, P. E.
Sanitary Engineer
Gannett, Fleming, Corddry & Carpenter
P. 0. Box 1963
Harrisburg, Pa. 17105
Perna, Thomas F., P. E.
Engineer Co-ordinator
N. Y. State Pure Waters Authority
5^5 Madison Avenue
New York, New York 10022
Pierce, James C.
Sanitary Engineer
Van Note-Harvey Associates
23^ Nassau Street
Princeton, N. J. 085^0
Porter, William H»
Leon H. Wendel, Consulting Engr.
7^05 Canal Road
Lockport, N. Y.
197
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Qasum, Syed R.
Battelle Memorial Institute
505 King Avenue
Columbus, Ohio ^3201
Radziul, Joseph V.
Chief, R&D
Phila. Water Kept.
1110 Municipal Service Bldg.
Phila., Pa. 1910?
Ramanathan, M.
Design Engineer
John G. Reutter Associates
729 Federal Street
Camden, N. J. 08103
Ray. Don L.
Student - Ph.D. Candidate
University of Massachusetts
Amherst, Mass. 01003
Richardson, AUyn
Chief, Technical Liaison Section
FWPCA
Boston, Mass. 02203
Riis-Carstensen, Eric
Consulting Engineer
28 Clarendon Place
Buffalo, N. Y. 1U209
Ricks, Ronald E.
Resident Engineer
Havens & Emerson Cons. Engrs.
50 North Franklin Turnpike
Ho Ho Kus, N. J. 07^23
Rosenkranz, William A.
Chief, Storm and Combined Sewer
Pollution Control Branch
FWPCA
Washington, B.C. 202^2
Sarsenski, Joseph E.
Instructor & Professor of
Civil Engrg.
University of Conn.
Storrs, Conn. 06268
Scottron, V. E.
Instructor & Professor of
Civil Engrg.
University of Conn.
Storrs, Conn. 06268
Shyfelt, Clyde
FWPCA
Needham Heights, Mass. 0219^
Smith, Arnold R.
Partner
Nebolsine, Toth & McPhee Assoc.
P. 0. Box 109
Ft. Lee, N. J. 0702U
Smith, Herbert R.
Associate
Robert G. Werden & Assoc.
P. 0. Box hlh
Fenkintown, Pa. 190*4-6
Inc.
Smith, Robert L.
Delaware Water and Air Resources
P. 0. Box 916
Dover, Delaware 19901
Sobeck, Robert G.
Superintendent
Jersey City Sewerage Authority
P. 0. Box 68V7
Journal Square Station
Jersey City, N. J. 07305
Soylemez, Yener
Senior Public Health Engineer
N. J. State Health Dept.
206-B Hollywood Drive
Trenton, N. J. 08609
Strandberg, Leonard J.
Hydraulic Engineer
John J. Cassner Inc.
250 Broadway
New York, N. Y. 10007
Sullivan, R. H.
Assistant Executive Director
for Technical Services
American Public Health Assoc.
Chicago, 111.
Ulrich, Fred
Senior Sanitary Engineer
Interstate Sanitation Commission
10 Columbus Circle
New York, N. Y.
198
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Ure, James E.
Associate
Alexander Potter Associates
99 Church Street
New York, N. Y. 1000?
Van Wagenen, Paul
Project Engineer
Brinnier & Larios Consulting Engineers
67 Maiden Lane
Kingston, N. Y.
12^01
Voegler, G. P.
Sanitary Engineer
Gannett, Fleming, Corddry &
Carpenter
P. 0. Box 1963
Harrisburg, Pa. 17105
Vogler, John F.
General Superintendent &
Chief Engineer
City of Trenton
City Hall
Trenton, W. J. 08609
Warburton, Leonard, P. E.
Manager
Water Resources Division
Goodking & O'Dea
1190 Dixwell Avenue
Handen, Conn. 065lU
Waters, John E.
Senior Project Engineer
Sanitary Division
Gannett, Fleming, Corddry,
& Carpenter, Inc.
P. 0. Box 1963
Harrisburg, Pa. 17105
Weber-, Paul
Supervisor
Deepwater Project
Delaware River Basin Commission
25 Scotch Road
Trenton, N. J. 08628
Witkowski, John
Sanitary Engineer
FWPCA
Edison, N. J. 08817
Wright, Darwin R.
Sanitary Engineer
FWPCA
Washington, D.C. 202^2
Wylen, Anthony L,
Associate
Teetor-Dobbins Cons. Engr.
Veterans Memorial Highway
& Johnson Ave.
Ronkonkoma, N. Y. 1*1779
Wyszkowski, Paul E.
Treasurer
Charles J. Kupper, Inc.
15 Stelton Road
PisCataway, N. J. 088514-
Yatsuk, Peter
Cochman Division
Crane & Co.
King of Prussia, Pa.
19*4-06
Yuda, William A.
William A. Yuda Associates
95 West Nyack Way
West Nyack, N. Y. 1099^
Zablatsky, Herman B.
Superintendent
Bergen County Sewer Authority
P. 0. Box 122
Trenton, N. J. 08625
199
U. S. GOVERNMENT PRINTING OFFICE : 1970 O - 382-275
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