United States
Environmental Protection
Agency
Office of
Water Program Operations
Washington DC 20460
November 1978
Symposium on
Advanced Equipment
and Facilities for
Wastewater Treatment
U.S.A.-U.S.S.R
Working Group
on the Prevention of
Water Pollution
from Municipal and
Industrial Sources
May 9-10, 1978
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Symposium on
Advanced Equipment
and Facilities for
Wastewater Treatment
U.S.A.-U.S.S.R.
Working Group
on the Prevention of
Water Pollution
from Municipal and
Industrial Sources
May 9-10, 1978
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Index Preface
Opening Remarks
John T. Rhett
Welcome
Harold P. Cahill, Jr.
Address
Francis T. Mayo
Papers Presented at the
USA/USSR Symposium
Westrick, James J., (US EPA), Removal of Volatile
Halogenated Organic Compounds by Activated Carbon
Myasnikov, I.N., Gandurina. L.V., (USSR), "Enhancement of
Mechanical Wastewater Treatment in the Petroleum Refining
Industry".
Crame, Leonard W., Henderson, U.V. (Texaco Inc., USA),
"Activated Sludge Enhancement: A Viable Alternative to
Tertiary Carbon Adsorption".
Genkin, V.E., Belevtsev, A.N., (USSR), "Electrochemical
Treatment of industrial Wastewaters".
Warner, Howard P., English, John N., Kugelman, Irwin J.,
(US EPA), "Wastewater Treatment for Reuse and its
Contribution to Water Supplies".
Vorobyova, N.Y., Myasnikov, I.N., Gandurina, L.V., Kedrov.
Yu. V., (USSR), "Methods of the Varnish Industry
Wastewater Treatment"
Sebastian, Frank P., Doodeman, E.A., Micketts, John P..
(Envirotech, USA), "Training for Use of Advanced Facilities
and Equipment for Wastewater Treatment".
Skirdov, I.V., Koltsova, S.I., Morozova, K.M.. (USSR),
"Methods of Improvement of the Secondary Settling Tanks
Operating Efficiency".
Opatken, Edward J., Venosa, Albert D., Meckes, Mark C.,
(US EPA), "Contactor Evaluation for Ozonation of
Wastewater"
Pisanko, N.V., (USSR), "Combined Treatment of Industrial
and Municipal Sewages".
Collins, John W., (US EPA), "Closed Process Water Loop in
NSSC Corrugating Medium Manufacture".
Protocol
Appendix 1
Participants
Appendix 2
Papers Presented
Appendix 3
Future Program
Appendix 4
Symposium Program
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The sixth cooperative USA/USSR symposium on Advanced
Equipment and Facilities for Wastewater Treatment was held
in Cincinnati, Ohio at the U.S. Environmental Protection
Agency on May 9th and 10th, 1978. This symposium was
conducted in accord with the sixth session of the Joint USA/
USSR Commission held in the USA in November, 1977.
This symposium was sponsored under the auspices of the
Working Group on the Prevention of Water Pollution from
Municipal and Industrial Sources. The co-chairman of the
Working Group are H.P. Cahill, Jr. of the United States
Environmental Protection Agency and S.V. Yakovlev of the
Department of Vodgeo in the Soviet Union.
The United States delegation was led by Harold P. Cahill,
Jr., Director, Municipal Construction Division, U.S.
Environmental Protection Agency. The Soviet delegation was
led by Roald Slavolyubov, Department Chief of Main
Administration, USSR State Committee on Building
Construction.
The eleven papers that were presented at the symposium (six
US and five USSR) are reprinted in English in this volume in
accord with the protocol signed by the delegation leaders on
May 16, 1978.
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Opening Remarks
John T. Rhett
It is a great pleasure to open this sixth Joint US/USSR
Symposium on Advanced Equipment and Facilities for
Wastewater Treatment and I am delighted to see the wide-
ranging interest and attendance. I would like to thank our
Soviet colleagues for their strong support of these conferences,
both here and in Moscow and my EPA colleagues here in the
Cincinnati Environmental Research Center and in Washington,
D.C. for their participation. I would also like to recognize the
contributions of private enterprise to these symposia, through
representatives, who are directly involved in environmental
concerns.
The high degree of cooperation and coordination that is
required to accomplish this international exchange of
information is impressive. Bilateral scientific cooperative efforts
like this to extend the boundaries of what is possible in
pollution control deserve the highest priority. I am happy to
see that the caliber and experience of the people involved
reflect a high degree of concern for environmental protection in
our respective governments.
As the sixth in a series, this is a logical extension of the
continuing scientific and technical inquiry of members of this
working group in methods of improving the generic types of
wastewater and sludge treatment systems and those systems
which allow recycling and reuse of wastewater, as an extension
of the conservation ethic.
During the months since our exchange of techniques and
ideas in Moscow last fall, we have enjoyed some significant
developments in the program for which I am responsible—the
federal government grant program to construct wastewater
treatment systems in our municipalities. Our fundamental
mandate, the Federal Water Pollution Control Act of 1972, was
amended in December by a new clean water act. This act was
passed by a substantial majority of members of the congress
and signed into law by President Carter.
With the new law, we received authorization for the addition
of significant funding to our program. Approximately $24.5
billion should be available to extend the program for 5 more
years, and allow us to plan ahead with more assurance that the
necessary funds will be provided.
I realize five-year planning periods are not new in the Soviet
Union, and I am not sure this type of planning system would
be appropriate for our country. But, the type of continuing
congressional and administration support we have been
receiving is somewhat unique among our capital construction
programs. Since we had completed committing more than $18
billion in federal funds to projects by last fall, and many of our
states had virtually exhausted their allotments, the arrival of
this authorization in December was very fortunate.
Communities can now proceed to make long-term
commitments to treatment facilities construction without great
concern for future provision of the federal share of 75 percent
of the costs.
Some major provisions of the new Clean Water Act were
designed to encourage the advancement of "alternative and
innovative" technologies, which depart from and are
significantly better than, the traditional treatment systems. 1
might add that the various incentives the Congress authorized
would allow 10 percent more federal funds to go to projects
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employing technologies which offer sufficient benefits and
would reserve certain percentages of the funds allotted to the
States exclusively for these types of projects. Further, these
projects would enjoy certain advantages in cost-benefit
comparisons with other projects to allow a higher initial capital
investment.
In providing these additional incentives, the Congressional
objective was to encourage municipalities to seriously examine
the feasibility of adopting treatment processes that reclaim and
recycle wastewater, and which consider land application and
land treatment with particular respect to the small and rural
communities. This is very much in concert with current
objectives of EPA's policies to give careful consideration to the
cost-effective alternatives. Further, our Agency Administrator,
Douglas Costle, stated in his policy memorandum last fall, "the
Agency is now fully in agreement with the intent of Congress
to encourage the development of wastewater management
policies that are consistent with the fundamental ecological
principle that materials should be returned to the cycles from
which they are generated."
The financial incentives I mentioned, coupled with the very
rea! problems of limited water supplies and energy constraints
which we have encountered, should be very influential in
persuading many communities to view this alternative more
positively than in the past. Groundwater and the prevention of
contamination of underground supplies, of course, will be a
principal concern in choice among the alternative solutions, and
the planning details.
The major intent of these policy directions is to promote the
type of technology that will:
• Cut costs: I
• Simplify systems; and
• Enhance the recycling and recovery options and other
resource saving benefits, such as energy, that can be
obtained.
These initiatives and some others designed to recognize the
special characteristics of small and rural communities allow the
program a great deal more flexibility in providing for
appropriate treatment. And this is a development of which I
heartily approve.
Another significant addition to the program allows States to
participate much more actively in program management
through the provision of a portion of their allotments for
securing the needed personnel resources. Not only the
Construction Grants Program but other portions of the water
pollution control effort, such as water quality planning and
point source discharge permitting activities, can be supported
through these allotments. As a corollary to this effort to add
more program management resources, we have contracted with
the U.S. Army Corps of Engineers to secure up to 600
engineers to aid us primarily in review of construction
activities.
I have related a greatly abbreviated and over-simplified
explanation of the intent of some of the major new water act
provisions as they affect construction grants. We are currently
in the process of issuing the pertinent regulations to implement
these new mandates. We have reached the stage of publishing
a proposed version of the regulations which includes a
considerable amount of public review and participation,
secured to date. Our process allows for a formal comment
period until the end of June, and we expect to issue our final
version of the regulations in September.
Congress developed the new amendments during a long and
intensive review of our program, and I would like to emphasize
that we are very pleased with the outcome of that review and
legislative effort. While it provided some important new
directions to our water pollution control effort, our basic
commitment and strategy for water quality remain the same,
namely, the restoration and maintenance of the chemical,
physical and biological integrity of our waters. The new
amendments sustain the primary proposition that the best way
to control the discharge of pollutants is through the application
of uniform treatment technologies to classes and categories of
discharges. At the same time, the amendments somewhat
reoriented the direction of our criteria for "best available
technology" away from any unnecessary control of additional
increments of the so-called "conventional pollutants" toward a
much more intense effort to identify land control toxic
pollutants.
The subject of this symposium is central to the increased
emphasis on toxics control. In the past 25 years, we have
experienced a vast growth in our chemical industry. The U.S.
Chemical Industry now has sales of $113 billion a year. Its
gross cost is twice that of our "Gross National Product."
International trade in chemicals amounts to $78 billion
annually. Evidence of adverse effects to public health is
accumulating at an increasingly rapid rate. And, incidents of
contamination that pose clear hazards to health are even more
alarming. Controlling toxic chemicals places a serious burden
of responsibility on government officials. Our countries, as
heavily industralized nations, share a mutual concern to
develop and apply the appropriate treatment technologies and
management systems. I look forward to sharing the fruits of
our mutual and continuing efforts in this field, and particularly
to the results of this symposium. D
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Welcome
Harold P. Cahill, Jr.
I always enjoy exchanging ideas with the people who are
recognized and respected experts in their profession because it
offers a challenge. And it is personally rewarding because of
the chain of enduring friendships with my Soviet colleagues.
which has grown out of these meetings and contacts.
At this Sixth Joint Symposium I am impressed, once again.
with the relevancy of the topics for presentation. I am also
impressed with their applicability to many of the problems in
our Construction Grants Program, and the depth of scientific
knowledge and experience that is represented.
I am looking forward to the papers to be delivered today.
and I am hopeful from the program perspective that some
methods to tame and subdue the "troika" of problems that are
currently pulling at our program will emerge. I refer to three
major problems ofconcern:
• First, toxic substances control;
• Second, runaway costs of conventional treatment,
particularly for the highly sophisticated systems and
particularly for the small and dispersed localities; and
• Third, strong pressures to develop new technological
methods to enhance the conservation ethic in our pollution
control systems and to develop the management approaches
to provide the necessary degree of cooperation in our
programs and flexibility in their application.
I am happy to note there are papers that would add to our
base of knowledge about each one of these concerns, with the
possible exception of management approaches. Our Deputy
Assistant Administrator, John Rhett spoke of the new Clean
Water Act amendments yesterday, and our EPA regulations
being prepared. I will direct my remarks to some of the
measures within EPA to meet this need to draw our programs
into closer relationship.
Our Agency is currently developing a Regulatory Reform
Program, and one of the problems it is designed to address is
the impact of excessive costs and inflation. In general, and
whenever possible we will be regulating only when we are
confident that the benefits exceed the costs; and where we find
more efficient ways of meeting environmental goals in the least
costly manner.
Our Administrator Douglas Costle undertook, as his primary
responsibility, the task of making EPA programs and
operations more rational. Three things are being done to
achieve this goal:
• We are improving our system for ranking environmental
problems in priority order, and this includes the social and
economic implications of achieving the goal.
• We are moving to improve the efficiency of our procedures,
by cutting out both the excessive requirements and
paperwork, and the uncertainty as to the requirements.
• And we are attempting to encourage the maximum amount
of innovation in solving the pollution control problems.
New regulations are subjected to a very intensive review
procedure by the public and others with particular expertise in
the areas affected. A number of alternatives are presented to
the Administrator, with analyses of their good and bad points,
and an assessment of costs-and benefits. The EPA system has
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proven attractive to other Federal agencies and served as a
model for part of an Executive Order on Regulatory Reform
recently issued by the President. That Executive Order, I might
add, calls for a careful analysis of all regulations that may have
significant economic, social, geographic or governmental
impact.
Our system for deciding what rules need to be written, and
when, is also being reviewed. Often Congress provides the
answers to these questions, or our Courts, but sometimes we
do have the discretion to make a decision. Some of our more
recent laws provide us more flexibility to address individual
problems.
The Clean Water Act, Clean Air Act and Resource
Conservation and Recovery Act, for example, provide special
consideration to the innovative approaches in pollution control.
It is in the form of a waiver allowing companies that can show
progress toward developing innovative technologies to get an
extension of time in which to meet the requirements. The basic
criterion, of course, is that the new approach must be able to
get the job done more cheaply, or more effectively, than what
is already available.
We are also working internally and with other Federal
agencies to be sure our regulations are consistent and
complementary, and our enforcement efforts are coordinated.
As Mr. Rhett mentioned yesterday, we are moving to
augment our program management resources through
encouraging State assumption of program responsibilities and
through employment of the Corps of Engineers to review
construction activities.
The issue of project integrity and the quality of projects is of
intense concern to us. We have more than 10,000 projects
underway—projects valued at over $21 billion are in the
construction phase. We are moving to assure the soundness of
projects under construction, and the incentives Congress
provided should greatly improve the prospects for obtaining
"quality" projects from planning. What do I mean by the term
"quality project"? More than the engineering specifications,
which are obviously essential, "quality" connotes the sensitive
match between the technological aspects of a facility and the
needs of the community it is designed to serve. This match
should be in terms of size and cost, means by which the
project is financed, its method of treatment, and the plans for
operation and maintenance.
EPA has begun two activities to ensure that better quality
projects are developed through facility planning. The first is to
encourage our professional engineering community to give
better consideration to innovative and alternative processes,
and the second is to involve our private citizens who might be
affected more actively in the planning process.
This Symposium should greatly aid in the expansion of the
available technology. We still have a long distance to travel
before we will have progressed as far as we need to go in the
development of the necessary technologies. But our efforts are
well grounded on solid scientific principles. There are a good
many avenues to explore, and I am looking forward to the
presentations today. D
Promoting the Use of New and
Innovative Municipal Wastewater
Treatment Technology in the
United States*
Francis T. Mayo**
•Presented at the Joint US/USSR Symposium—May 9-10, 1978—U. S.
Environmental Protection Agency, Cincinnati. Ohio.
"Director. Municipal Environmental Research Laboratory.
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The Present Situation
For some time now the Environmental Protection Agency has
been seeking effective means to implement the application of
new and innovative technology in the field of municipal
wastewater treatment in the United States. This has been
difficult to achieve in the absence of a significant program to
demonstrate the effectiveness and efficiency of new and
innovative technology at full scale installations.
New and innovative technologies are considered to be those
of recent development, not in common use throughout the
country but with sufficient demonstrated capability for
improved treatment success and efficiency to warrant broader
application.
To a limited extent new technologies are being developed
and marketed by private interests particularly if a proprietory
position can be maintained in marketing the technology.
Examples of this are: biological phosphorus removal (phostrip),
deep shaft aeration, ultraviolet light disinfection. Some large
municipalities, such as the Metropolitan Sanitary District of
Greater Chicago and the Los Angeles County Sanitary District
have taken other initiatives.
For the most part the pace has been slow in applying new
technology in the field of municipal wastewater treatment.
From 1966 to date the Federal Government has financed a
program for full scale demonstration of promising municipal
wastewater treatment technologies, several of which are in
more common use today. Some examples are high purity
oxygen aeration, phosphorus removal by chemical addition,
suspended growth and attached growth systems for nitrification
and/or denitrification. The level of financing has been very
modest in comparison to the need for demonstrations for the
past several years.
However, during the past decade a number of advances in
municipal wastewater treatment technology have taken place.
Many warrant more widespread application in order to fully
understand the advantages (or disadvantages) associated with
them and to provide further opportunities for improvement
with respect to operational stability, operation and maintenance
costs, conservation of energy and performance efficiency.
Table 1 identifies new and innovative technologies in three
broad classifications:
• Proven but not used extensively
• Tested but need field verification
• Good ideas that need testing
Research is currently underway for a number of these
technologies.
A New Program
In an effort to foster the more widespread application of
innovative municipal wastewater treatment technology the
Congress of the United States recently amended the Federal
Water Pollution Control Act to provide increased dollar
incentives to municipalities receiving Federal grants for the
construction of such facilities.
The Federal construction grant assistance program to support
the installation of municipal wastewater collection and
treatment facilities has been established at 5 billion dollars a
year for fiscal years 1979 through 1982. A minimum of
l/2 percent of each state's share of these funds is to be used to
support the application of innovative technology by increasing
the level of the Federal grant from 75% to 85% of the cost of
planning, design and construction of projects incorporating
innovative technology.
In addition the new legislation provides that Federal funds
may be used to fully replace such facilities if the innovative
technologies that are used prove to be ineffective or bring
about unreasonably high costs of operation and maintenance.
It is anticipated that these two major inducements will assist
in overcoming the principal obstacles that now impede putting
the newer technologies to use.
The new Federal legislation establishes a companion program
requiring an evaluation of each project employing innovative
technology and enjoying the 85% level of grant assistance. This
evaluation program will be a cornerstone in documenting the
effectiveness of the newer technologies and promoting more
widespread application.
The Environmental Protection Agency is in the early stages
of developing criteria for implementing of this new program to
promote the application of a significant variety of innovative
technologies in the field of municipal wastewater treatment
including technologies developed in other countries. Efforts are
now underway to develop a clearinghouse of information to
assist in selecting the technologies that will be pursued. Data
from the evaluation program mentioned earlier will be entered
in the clearinghouse for availability to all interested parties. We
fully expect that a number of innovative treatment technologies
will be applied in the next three to five years and that the fruits
of that effort will be increasingly apparent in the next decade in
the form of more effective, and more efficient technologies for
a wide range of municipal wastewater treatment needs.
Continuing Research Efforts
In order to enlarge our capability to test promising emerging
water pollution control process technologies we are presently
constructing a new Test and Evaluation Facility here in
Cincinnati at the site of the Mill Creek Sewage Treatment Plant
a short ten minute trip from here. The treatment plant has a
capacity of 450,000 cubic meters/day (120 mgd) and employs
primary treatment technology followed by single stage
nitrification. The new 2.6 million dollar Test and Evaluation
Facility will consist of a two story steel building with 3100
square meters (33,500 sq. ft.) of floor space including 2300
square meters .(25,000 sq. ft.) of two story experimental area
and 800 square meters (8,500 sq. ft.) of laboratory, storage and
office space. The principal laboratory analytical support will be
provided here at the Environmental Research Center.
The new test facility will support the research and
development programs of five EPA laboratories located in the
Cincinnati area. These are the Municipal Environmental
Research Laboratory, the Industrial Environmental Research
Laboratory, the Health Effects Research Laboratory, the
Environmental Monitoring and Support Laboratory and the
Newtown Fish Toxicology Station.
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The Mill Creek Treatment Plant, with its industrial waste tank
farm and its combination of industrial and municipal wastes
and wastewaters, provides an ideal location for centralized
inter-laboratory research on water pollution control. The
facility will enjoy an extraordinary degree of flexibility because
of the following features:
• Centralized service system with independently controllable
sources of wastewater and sludges from several points
within the treatment plant
• Overhead cranes and movable pilot equipment with quick
connect/disconnect piping
• Flexible computer system for process control research and
for data acquisition and processing
• Use of Automated Laboratory Services to provide rapid turn
around in analytical work
Research at the new facility will include:
• Evaluating new treatment approaches for municipal and
industrial wastes, wastewaters and sludges.
• Identifying toxic chemicals in and evaluating systems for
removal of toxic chemicals from municipal and industrial
wastewaters.
• Evaluating pollution control methods for combined sewer
discharges.
• Developing improved process control methods for waste and
wastewater treatment processes.
• Assessing environmental impacts, such as fish toxicity, of
effluents from various wastewater treatment processes.
• Producing municipal or industrial effluents and renovated
water for health effects research, such as mutagenicity
studies.
• Evaluating industrial energy conservation methods including
uses of wastes as fuels.
• Field testing of pollutant monitoring or sampling devices.
• Evaluating the treatment of drainage from sanitary landfills.
It will be our pleasure to continue to freely share the
knowledge gained from these new national programs.
Perhaps future Joint US/USSR Symposia will provide
opportunities to report on the success of our efforts. D
Table I
Innovative Technologies
Category and title
Classification
Tested
Proven but not but needs Good idea
used field that needs
extensively verification testing
A. Secondary Treatment
Alternatives
I. Intermittent Sand Filtration to
Upgrade Lagoons
2. Open Tank Oxygen Aeration
3. Automation of Secondary
Treatment Plants
4. Fluidized Bed-Oz Biological
Treatment
5. Carrousel (deep oxidation
ditch with mechanical
aeration)
6. Deep Shaft Aeration
7. Airco Fall Reactor (clip-on
upgrading technique)
8. Orbital (Raceway brush
aeration & flow equalization)
9. Activated Bio-Filter (sludge
return in a trickling filter)
10. Weighing Agent Upgrading
II. Rotating Biological Contactors
B. Disinfection Alternatives
I. Ultraviolet Radiation
2. Sulphur Dioxide
Dechlori nation
3. Ozone
Air
02
Electron Acceleration
4. Chlorine Dioxide
C. Nutrient Removal
1. Single-stage Nitrification-
Denitrification in an Extended
Aeration Plant
2. Fixed Film Nitrification and
Denitrification
3. Biological Phosphorus
Removal (Phostrip)
4. Digester Supernatant
Ammonia Recovery
5.
AARP—Ammonia Removal &
Recovery
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Category and title
Classification
Tested
Proven but not but needs Good idea
used field that needs
extensively verification testing
D. Toxics Removal (organics &
heavy metals)
1. Powdered Carbon Upgrading
to Activated Sludge Plants
with Regeneration
2. Powdered Carbon Upgrading
to Activated Sludge Plants
without Regeneration
3. Sodium sulfide or Ferrite
Upgrading for Heavy Metal
Removal
4. Independent Physical-
Chemical Treatment with
Nitrate Addition (no
regeneration)
E. Preliminary & Primary
Treatment Alternatives
I. Flow Equalization
Dry & or dry/wet weather
storage
2. SWIRL Primary
3. Stationary Screens (Bauer
Eng.) Discostrainer
F. Special Applications
1. Chemical Flocculation &
Flotation for Ocean Discharge
2. Renovation & Reuse through
Groundwater Recharge
3. Direct Municipal/Industrial
Reuse
4. Aluminum Sulphur
Impregnated Concrete Pipe
Trenchless Sewers
5. Integrated Municipal Utility
Services
Solid refuse
Sludge
Wastewater renovation
Power production
6. Solar Energy for Digester
Heating; Remote Facility
Pumping Stations
Category and title
Proven but not
used
extensively
Classification
Tested
but needs
field
verification
Good idea
that needs
testing
G. Small Flow Applications
I. Centralized Management of
Remote Treatment Facilities
2. Septage Treatment
3. Individual Home Water
Conservation Treatment &
Reuse Systems
4. Alternating Soil Absorption
Fields and Chemical
Rejuvenation
5. Recreational Vehicle Waste
Disposal Systems
H. Sludge Disposal Applications
I. Slude-Refuse Coincineration
Co-pyrolysis
2. Digester Supernatant
Treatment with Anaerobic
Trickling Filter
3. Coal Sludge Incineration
4. Sludge Pressure Dewatering &
Autothermal Incineration
5. Thermophilic Digestion
A erobic
Anaerobic
6. Multiple Hearth Pyrolysis
7. Composting (Alternate
Schemes)
8. Compost Sterilization w/Heat
9. Lime Stabilization
10. Sludge Trenching
11. Heat Treatment of Sludges
Prior to Digestion to Improve
Biodegradation
12. Sludge Disinfection by High
Energy Electron Irradiation
I. Wet Weather Flow Treatment
I. Vacuum Street Cleaning
2. Sewer Flushing
3. Porous Pavement
4. Helical Flow Regulator
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Removal of Volatile Halogenated
Organic Compounds by
Activated Carbon
James J. Westrick
The removal of nitrogen from municipal wastewaters is
required at various locations throughout the U.S.A. This can
be accomplished by biological processes or by physical-
chemical process. Biological processes are available which
oxidize ammonia to nitrate (nitrification) ion and then reduce
the nitrate nitrogen to elemental nitrogen (denitrification). Often
the only nitrogen control requirement is based on nitrogenous
oxygen demand, and can be satisfied by nitrification without
the necessity of denitrification.
In cases when nitrogen removal is required, physical-
chemical processes may be competitive. The process known as
breakpoint chlorination is one which has generated
considerable interest over the last five years. The process is
based upon the chemical oxidation of ammonia to elemental
nitrogen gas by aqueous chlorine. The probable overall reaction
is summarized by Eq. 1.
NHJ + 1.5 OC1-
.5N2 + 1.5 H2O + H
[Eq.l]
Equation 1 illustrates the stoichiometric chlorine requirement is
1.5 moles old aqueous chlorine per mole of ammonia oxidized
(7.6:1, weight basis). Other reactions, such as the formation of
nitrogen trichloride and nitrate also consume chlorine and can
result in a chlorine requirement on the order of 9:1 to 10:1
chlorine:ammonia-N (weight basis). Most municipal
wastewaters in the U.S.A. contain ammonia nitrogen in the
range 10-30 mg N/^, thus requiring up to 300 mg Cl// for
ammonia oxidation. There has been some concern that the
application of high dosages of chlorine to wastewater could
result in the formation of undesirable chlorinated organic
compounds. This was a special concern after it was learned
that chlorination of public drinking water supplies resulted in
the formation of trihalomethanes, most notably chloroform. In
the case of treatment of wastewater for discharge to a
waterway or aquifer which serves as a drinking water source,
production of chloro-organics could be a problem.
In order to examine the magnitude of the problem and the
effeptiveness of a possible remedy, a pilot plant study was
undertaken at the EPA facility in Cincinnati. The objective was
to operate a pilot plant system simulating as nearly as possible
a treatment train producing high quality (reuse quality) effluent
and using breakpoint chlorination for nitrogen control. The
problem of the formation of chlorinated organics would be
assessed together with the capability of activated carbon to
remove the chlorinated organics and to prevent their formation.
This paper addresses only the subject of the effectiveness of
granular activated carbon for removal of halogenated organics.
The system used was a continuous flow pilot plant which
would be subject to typical changes in wastewater
characteristics. The process sequence was:
I. Secondary treatment by a trickling filter system
2. Tertiary lime clarification
3. Neutralization
4. Granular media filtration (GMF)
5. Breakpoint chlorination (BPC)
6. Granular activated carbon adsorption (GAC)
10
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Because of the difficulty in measuring a large number of
chloro-organics, the trihalomethanes, chloroform (CHCI3),
bromodichloromethane (BrCHCl2), dibromochloromethane
(Br2CHCl) and bromoform (CHBr-,) together with carbon
tetrachloride (CC14) and 1,2-dichloroethane (C2H4C12) were the
halogenated organics measured routinely. There was a growing
body of data on these compounds in relation to water
treatment practice, and it would be possible to compare results
of wastewater chlorination with water treatment. The analytical
procedure was not overly time consuming, therefore, the large
number of samples would not impose an impossible burden on
the analytical staff. Conventional pollution parameters were
used to document the general efficiency of the system.
Description of Facilities
Raw wastewater was pumped continuously from a 1.8 m
interceptor sewer serving residential and industrial areas of the
City of Cincinnati. After treatment in a 0.6~s Y ! DETECT
HPID MIX
\— ,
FLOCCULATOR "
\
SLUDGE RECYCLE
•* *•
OR
D
N
/
r
(. ! CLARIFIER
i i
juu.
zso
p
d
LJ
4
)
V"
<•'- > ;
"' <.-'?
TO CARBON
SYSTEM
TO WASTE
COa
NEUTRALIZATION TRI-MEDIA
TANK FILTER
©- DENOTES SAMPLE POINT
DENOTES ELECTRONIC CONTROL LOOP
Figure I.
Flow Diagram, Tertiary Lime Clarification-Filtration.
A schematic diagram of the chlorination carbon systems is
shown in Fig. 2. Three activated carbon systems were operated
in parallel. All were two-stage series expanded bed systems
operating on filter effluent. In system 3, the filter effluent
underwent BPC before application to the first stage carbon
adsorber. In system 2, the BPC system was located between
the first and second stage adsorbers. System 1 had no BPC and
was used as a control.
Each activated carbon system contained 2.4 m (at repose) of
Filtrasorb 400* granular activated carbon per stage for a total
depth of 4.9 m. The hydraulic application rate to each adsorber
was 15 m/hr for a resultant contact time of 10 min/stage (based
*A product of Calgon Corporation. Pittsburgh, Pennsylvania.
on empty bed volume, carbon at repose). The rate of flow to
each carbon system was controlled by positive displacement
feed pumps and monitored by rotometers. The diameter of
each adsorber was 15 cm. The carbon was cleaned weekly by
air scour and upward flow water wash, applied separately. The
air rate was 150 m/hr and the water backwash rate
was 37 m/hr.
MEDIA
FILTER
©-DENOTES SAMPLE POINT
Figure 2.
Carbon-Chlorination System Schematic.
DK2, BK3 - BREAKPOINT
CHLORINATION
REACTORS
1A, 2A, 3A - 1st STAGE ACTIVATED
CARDON COLUMNS
ID, 2D, 3B - 2nd STAGE ACTIVATED
CARDON COLUMNS
A special sampling apparatus was fabricated for use in
obtaining composite samples for subsequent analysis of volatile
organic compounds. A schematic of the apparatus is shown in
Fig. 3. Effluents from the filter, breakpoint reactors and first
and second stage carbon columns were sampled with this
system. An in-house designed and fabricated electronic timer
opened the solenoid valve A to allow the sample to flush the
sample line for a selected time interval through a three-way
solenoid valve B to waste. The timer then energized the three-
way valve for an instant so that the sample was diverted into
the sample chamber. The sampling interval, the flush time and
the sample impulse time were all adjustable to allow for the
proper sample volume and to insure complete flushing of the
sample line. The electronic timer operated a total of nine
samplers. The composite sample chambers consisted of 2-liter
graduated cylinders equipped with flat bottoms and glass tube
inlet-outlet ports. Teflon floats were machined to fit each
sample chamber so that as the sample volume increased, the
floats would ride up on the sample surfaces. These float-
equipped chambers permitted the collection of composite
samples in closed containers, and minimized the loss of volatile
organics during the composite period. A few grains of sodium
thiosulfate were added to each chamber at the beginning of
each sampling period to prevent further reaction of chlorine
and precursors during the compositing period. Each sample
chamber contained a magnetic stirring bar which was used to
mix the sample at the end of the compositing period. An air-
driven magnetic mixer was located under the sample chamber
11
-------
to drive the stirring bar. The system was operated 24 hours/
day, 7 days/week for a period of 9 weeks. Composite samples
were collected three times per week for analysts.
TO OTHER SAMPLERS
FROM SYSTEM
SAMPLING POINT
SAMPLE
CHAMBER
TEFLON
FLOAT
MAGNETIC
MIXER
VALVE
TYPE
2-WAY
SOLENOID
3-WAY
SOLENOID
MANUAL
TOGGLE
MANUAL
NEEDLE
TO TO SAMPLE
WASTE VIAL
FUNCTION
DIRECT SAMPLE
TO VALVE B
DIRECT SAMPLE
TO CHAMBER
TRANSFER COMPOSITION
SAMPLE TO VIAL
& DRAIN REMAINDER
CONTROL MIXER
SPEED
Figure 3.
Automatic Composite Sampler for Volatile Halogenated Organic*.
At the end of the composite period, the contents of each of
the closed composite samplers were mixed with the stirring
bars for a short period of time to assure that a representative
sample would be withdrawn. Then valve "C" (see Fig. 3) was
opened manually to allow the contents of the chamber to flow
into the bottom of a 20 ml serum vial. The vial contents were
displaced several times to minimize air contact and a convex
meniscus was left at the top. The vials were then sealed with a
teflon disc held in place by a crimped aluminum cap. After the
samples were transferred to the sealed vials, the remaining
contents of the sample chambers were drained, and the floats
were lifted out. The sample chambers were rinsed with distilled
water, if necessary, and a few grains of sodium thiosulfate
were placed in each chamber for dechlorination of the next
composite sample. The floats were then reinserted, and the
sampler was ready for another composite period.
The experimental procedure was simply to operate the
system under steady conditions, monitor the production of
volatile halogenated organics (VHO) during breakpoint and
monitor the removal of VHO by the activated carbon systems.
The procedure of Bellar and Lichtenberg was used to
measure the six volatile halogenated organic compounds (I-2)-
The volatile substances were purged from the sample with
helium and collected on an adsorbent trap (Tenax). The
trapped organics were then introduced into a gas
chromatographic column (1.8 m x 4 mm glass column packed
with 60/80 mesh Tenax) by helium purging at elevated
temperature. The gas chromatograph was equipped with an
electrolytic conductivity detector operated in the halide mode.
Ammonia interference was overcome by acidifying the samples
before purging to avoid volatilization of ammonia. Peaks
obtained as the output of the detector were identified by
comparison with retention times of known standards.
Concentrations were determined by comparison of peak heights
with a standard curve.
Granular Activated Carbon Performance
Tables 1, 2 and 3 summarize the data on the six VHO
compounds in the influents to the carbon columns. Chloroform
was the only compound of the six VHO's that was detected
consistently and in significant quantity in the samples taken
around the activated carbon and BPC systems. Therefore, the
major emphasis in the analysis of carbon performance is on
chloroform removal.
Table 1
Concentration of Halogenated Organics
in influent io Columns 1A and 2A.
COMPOUND AVERAGE
CHCls
BrCHCh
BrzCHCI
CHBrs
ecu
C2H.l
1.7
CzH^CI: 0.5
All concentrations — fig/1
N.D. — not detected
MEDIAN
29
2.8
N.D.
N.D.
2.0
N.D.
MAX.
86
26
6.3
0.8
5.8
5.1
MIN.
2.5
N.D.
N.D.
N.D.
N.D.
N.D.
% OF DAYS
DETECTED
100
75
29
4
68
14
12
-------
Table 4
Carbon Column Identification
CARBON COLUMN CONTACT TIME
DESIGNATION (MIN) INFLUENT REMARKS
1A 10 — 1
IB 10 GMF 2
1AB 20 IA 1
2A 10 GMF I
2B 10 BK2 2
2AB — — 3
3A 10 K3 4
3B 10 3A 2
3AB 20 BK3 5
Remarks
1. Influent to IA. 1AB and 2A included the 2400 ^ig/l value of July 2.
Capacity and breakthrough data are not useful.
2. IB, 2B, and 3B all received wastewater treated with 10 min carbon
contact. The CHCI.-i concentrations in their influents are variable but
within a reasonable range. Capacity and breakthrough data from these
second-stage columns are useful.
3. 2AB cannot be treated as a single 20-min contact time adsorber because
of the chlorination reactor which altered the wastewater composition
between stages.
4. 3A was exhausted before the July 2. 900 ng/l influent concentration was
observed. The capacity and breakthrough data to the point of exhauston
can be used.
5. 3AB was not exhausted at the time the July 2. 900/xg/l influent
concentration was observed. Capacity and breakthrough data are only
marginally useful.
Referring to Fig. 2, each GAC system is treated as three
adsorption systems. For example, GAC system 1 has a 10-min
contact time adsorber treating GMF effluent (1 A), a 20-min
contact time adsorber treating GMF effluent (1A + IB,
designated here 1 AB) and a 10 min contact time adsorber
treating the effluent from adsorber 1A (IB). The carbon column
designations are shown in Table 4. Adsorber 2 AB cannot be
considered as a single 20-min system from a VHO removal
standpoint because of the breakpoint between stages. As Table
4 indicates, the interpretation of the chloroform removal data
for systems IA, 1AB, 2A and 3AB is hindered because of the
extremely large influent chloroform measurement in the
samples of July 2. The effect of the large influx of CHCl^ on
July 2 on GAC system 1 is shown in Fig. 4, in which the
CHC13 concentrations after 10 min and 20 min GAC contact
are shown in a time plot. After 10 min contact, the CHC13
concentration on July 2 was reduced from 2400 fj-g/t to 59 jttg/
f, while none was detected after 20 min contact time. After
July 2, the first stage effluent was usually higher than the
influent, while the second stage maintained low effluent levels
for some time. In fact, the second stage exhibited a fairly
uniform breakthrough curve, apparently unaffected by the July
2 event.
The CHC13 concentrations in the effluents from columns 3A,
3B, 2B and IB are shown as a function of volume of
wastewater treated in Figs. 5, 6, 7 and 8. These effluents were
unaffected by the July 2 slug and illustrate the shape of the
breakthrough curves and the relatively good fit of the smooth
curves to the data points. After the breakthrough of CHC13 in
the effluent of column 3A occurred (Fig. 5), the column was
kept in service. Its capacity for removal of CHC13 was
essentially exhausted, showing removal only when the influent
concentration rose to much higher levels than usual. The
effluent from 3 A was often higher in CHC13 than the influent
after breakthrough occurred. This was also observed in the
carbon treatment of chlorinated river water(3>.
The four breakthrough curves are shown together in Fig. 9
for comparison. Several superficial observations can be made
from examination of the breakthrough curves. Locating the
breakpoint chlorination system in the mid-carbon position
resulted in about 20% longer running time before carbon broke
through to a concentration of 5 fJ.g/f. Examination of the
breakthrough curves of system 3 for influence of contact time
results in a somewhat unexpected observation. Using CHC13
concentration of either 5 or 10 /u,g/^ as the exhaustion criterion,
20-min contact time allows over 3 times the run length to
exhaustion as 10-min contact time.
100
80
60
40
20
N.D,
I
2400 pg/\
in Influent
\
JUNE
JULY
AUG.
Figure 4.
CHCI., in Effluents of GAC System 1.
_L
50 100 150 200 250
VOLUME TREATED, cu. m.
300
350
Figure 5.
CHCI, Breakthrough, Column 3A.
13
-------
70
60
50
140
x
u
30
20
10
SO 100 ISO 200
VOLUME TREATED cu. m.
250
300
Figure 6.
CHCI Breakthrough, Column 3B.
150 200
VOLUME TREATED cu. i
250
300
Figure 7.
CHCI:I Breakthrough, Column 2B.
350
350
SO 100 ISO 200 250
VOLUME TREATED, eu. m.
300
350
Figure 8.
CHCI Breakthrough, Column IB.
50
u
X
u
£30
20
10
3A
100 200
VOLUME TREATED, cu. m.
300
Figure 9.
Breakthrough Curves, CHCI,.
Love, et al, found that doubling the contact time
approximately doubled the bed life<3). Other work on the
breakthrough of sewage organics showed a 20-min contactor
had less than twice the service life of a 10-min contactor with
TOC as the effluent criterion <4)- Approximately 50 cu m and
165 cu m had been treated in system 3 when the effluents from
14
-------
the first and second stages, respectively, reached a CHCI:, level
of 5 iJLg/f. Since the volume of the 10-min contactor was 0.041
cu m and the volume of the 20-min contactor was 0.082 cu m
the throughputs to an exhaustion criterion of 5 jug CHClJf in
the 10-min and 20-min contactors were 1200 and 2900 bed
volumes, respectively. Carbon utilization rate can be defined as
the weight of carbon exhausted per unit volume of wastewater
treated. Using a bed bulk density of 420 kg/cu m, a 20-min
contactor would be exhausted at a rate of 200 g carbon/cu m
wastewater treated, while the utilization rate of a 10-min
contactor would be 340 g/cu m. This is a significant difference
in performance which suggests that a weakly sorbed substance
such as chloroform, longer contact times may give improved
utilization of the carbon. A probable explanation is that
because more strongly adsorbed organics are removed in the
first stage, the competition for available adsorption sites is
reduced in the second stage. As will be seen later, removal of
competing organics in the first stage apparently allowed more
efficient chloroform adsorption in the second stage. This could
be especially important in considering treatment of polluted
surface waters with activated carbon for removal of
trihalomethanes. One approach often considered for installation
of GAC in drinking water treatment works is replacement of
filter sand with GAC. This approach usually results in contact
times of only 4-8 min. A careful examination of the effects of
contact time and removal of competing organics could result in
lower GAC regeneration requirements for trihalomethane
removal.
0 0.2 0.4 0.6 0.8 I
CUMULATIVE APPLIED CHCI3 LOADING, g CHCI3 /kg Carbon
Figure 10.
CHCI:, Breakthrough As a Function of Applied CHCI,.
Fig. 10 shows the pattern of chloroform breakthrough as a
function of cumulative weight of CHC13 applied to each 10-min
contactor. The cumulative applied loading was calculated from
the concentrations in the influent to each carbon column as
designated in Table 4, with columns 3A and 3B treated as
separate adsorbers. The "B" columns all were second-stage
columns treating wastewater that had already been treated with
10-min carbon contact. Column 3A operated on chlorinated
filter effluent. While the loading to each column was low, (<
0.3 g CHCls/kg carbon) all columns produced very low effluent
CHCI3. The differences in performance are only apparent as
the cumulative loading increases and breakthrough occurs.
Table 5 shows the capacity of the carbon for chloroform
removal in each of the 10-min columns. Carbon capacity is
defined as the cumulative weight of the CHC13 removed per
unit weight of carbon up to some point in the service time of
the carbon. Values shown are for effluent breakthrough
concentrations of 5 fj,g/S and 10 fj.g/f and also for the
maximum capacity observed before complete exhaustion. As is
evident from Fig. 10, nearly all the applied chloroform was
removed up to the time of breakthrough. Therefore, the values
in Table 5 reflect the same pattern as Fig. 10. Very little
difference in carbon capacity can be detected at a 5 ^tg/l
effluent level. At the 10/xg/1 effluent level, IB had removed
less CHC13 than 2B, while 3A and 3B had both removed
substantially greater amounts of CHCI3 than 2B. At the point
of zero removal or complete exhaustion, column 3B had
exhibited greater capacity for chloroform removal than 3A.
Table 5
Capacity of Carbon for CHCh Removal
10 minute contact time
MK CHCb removed/kg carbon
3A 3B 2B IB
At 5 /itg CHCLi breakthrough
At 10 MK CHCI, breakthrough
Maximum capacity
0.36
0.61
0.64
0.38
0.62
0.74
0.37
0.43
0.47
0.32
0.35
0.35
1.0
0.8
c 0.6
o
-Q
^0.4
u
UJ
2 <.
s d"1
x ^
S
0.2
O)
0.1
3A
2B
IB
I
10 20 40 60 80 100 200
AVERAGE INFLUENT CHClj
AT MAXIMUM CAPACITY,pg/\
Figure 11.
Capacity of 10-Minute Contactors for CHCI.-, Removal.
The maximum capacity values are further illustrated in Fig.
11 where they are plotted against the flow weighted average
concentration of CHCI, in the influents to each 10-min
contactor up to the time of zero removal in an equilibrium type
plot. The average influent concentration is analogous to the
equilibrium concentration of solute and the maximum capacity
can be considered the capacity at equilibrium. The three
second-stage columns fit a Freundlich type equation very well:
15
-------
X «•«
— max = 0.022
M w
[5]
X
where 77 max = maximum capacity at complete exhaustion,
gCHCL3 removed
kg carbon
Cinf = flow weighted average influent concentration, /ig
CHcy
The data point for column 3 A lies below this line of best fit
for the B columns indicating less efficient adsorption by 3A.
The B columns all received wastewater which had been treated
with 10 min contact with GAC, while 3A treated chlorinated
GMF effluent. It appears from Fig. 11 that the CHC13
adsorption characteristics of the three B columns were similar
even though the loading pattern was variable throughout the
study and among the three columns. Another point of interest
is that column 2B influent contained an average of 12 mg/f
total chlorine residual of which 8.4 rrtg/^ was free chlorine
residual. Fig. 11 indicates no effect of chlorine on the CHC13
removal capacity of column 2B.
The less efficient removal of CHC13 by column 3A is almost
certainly caused by competition of more strongly adsorbed
sewage organics for adsorption sites. Removal of these sewage
organics by the A columns reduces the competition for sites in
the B columns and permits more efficient removal of
chloroform in the second stage columns.
A laboratory batch equilibrium adsorption test was run using
CHC13 in carbon-treated distilled water to which minerals had
been added to simulate the salt content of sewage (5>. In this
test the resulting equilibrium expression resulted:
where
- = 0.033 C
M let,
[6]
where — = weight of CHC13 removed per unit weight of
M
carbon, g CHClg/kg carbon
Ceq = concentration of CHC13 in the liquid phase at
equilibrium, /xg CHClgT
While great significance should not be placed on the
comparison of the B column data with the results of one batch
test, it is encouraging that the capacity—concentration
relationship obtained from the column data taken over a period
of 9'/2weeks under highly variable conditions appears
reasonable in the light of the laboratory results. The system
was not designed to obtain data for comparisons between batch
and column tests. If that were the objective, numerous
isotherms run on the wastewater actually being fed to the
columns and columns spiked with known, constant
concentrations of CHC13 would have been more useful.
The column data indicates that in a wastewater of a given
quality, the capacity of carbon for removal of chloroform can
be directly related to the influent concentration by a
Freundlich-type expression. It is also apparent that the
presence of Competing organics can greatly reduce the
efficiency of chloroform removal. For example, if column 3A
had functioned as efficiently as the three B columns for CLC13
removal (if it had conformed to Eq [5] at its average influent
concentration of 119 /xg/
-------
Conclusions
A pilot plant was operated continuously for nine weeks.
Monitoring of six volatile halogenated organic compounds
around the breakpoint chlorination-activatee carbon systems
resulted in the following conclusions:
The breakthrough of chloroform in the effluents of the
carbon contactors was very sharp, with quite low effluent
concentrations (generally < 10 jug/O up to the point of
breakthrough. After exhaustion the chloroform concentration in
the carbon effluent was often higher than the influent
concentration.
The service life of the 20-minute contactor treating
chlorinated tertiary filter effluent was much more than twice
that of a 10-minute contactor. The carbon utilization rate of the
20-minute contactor treated as a single-stage contactor was 200
g/cu m, compared to a utilization rate of 340 g/cu m for the 10-
minute contactor, with 5 ju,g CHCl.V^ as the exhaustion
criterion.
The capacity of the second stage columns to remove
chloroform was a precise function of the average influent
concentration. The first stage column removed CHC13 less
efficiently than the second stage column, presumably because
more strongly adsorbable organics were preferentially adsorbed
in the first stage, thereby reducing the competition for
adsorption sites in the second stage.
The removal of chloroform by carbon was not affected by
the presence of 12 mg/
-------
Enhancement of Mechanical
Wastewater Treatment in the
Petroleum Refining Industry
I.N. Myasnikov., L.V. Gandurina
Mechanical treatment methods such as sedimentation and
pressure flotation play an important part in the treatment of
petroleum refinery wastes. These processes being utilized as a
primary treatment provide the removals of coarse dispersed
matter, emulsified oil substances, colloidal solids, which affect
significantly the operation of the biological system and the
treatment system as a whole.
Therefore ways of improving the effectiveness of pressure
flotation and sedimentation processes become of practical
importance. One of them is the treatment of wastewaters with
chemicals such as coagulants and flocculants. The application
of the latter maximizes removals of fine dispersed stable
colloids from wastewaters thus optimizing treatment efficiency
of the process.
In the USSR inorganic coagulants -salts of aluminum and
iron (1)- are most commonly employed for treating wastes. In
recent years waste materials from various industrial processes
containing aluminum, ferrous and ferric salts and mixtures of
them (2-4) are used as coagulant aids.
Lime milk is added to maintain the required pH in wastes.
To optimize chemical treatment inorganic coagulants are
increasingly replaced with high molecular weight organic
flocculants or used in combination with the latter. Cationic
flocculants are most effective in treating wastewaters. Several
types of flocculants applied in treatment of petroleum refinery
wastes are presented in Table I.
Table 1
Characteristics of cationic
flocculants
EXCHANGE
TRADE MARK VOLUME
OF MG-EQUIV/G AS
FLOCCULANT CI-ION
BPK-101
BA-102
BA-112
BA-212
UCs
BPC-411
4,56
2,8
3,2
3,6
1.5
4,67
(T)) IN O,I
SOLUTION OF
NaCI DL/G
—
0,3
0,4
0,2
0,3
0,5
T> VISCOSITY/
CONCENTRATION,
DL/G 1% AQUEOUS
SOLUTION
1,96
1,18
2,08
0,28
1,18
0,17
Efficiency of sedimentation treatment of petroleum refinery wastewaters. treated with
chemicals
Effect of inorganic coagulants on the level of petroleum
refinery wastes treatment and their optimum dosages depend
on pollutant concentration, their dispersion, the pH of wastes
being treated (1-4). It has been found that doses of inorganic
coagulants vary in the range of 50 to 150 mg/1. The residual
concentration of oil substances is 10-15 mg/1 with initial
concentration of 50-175 mg/1. Simultaneously reduction in SS
concentration and COD value takes place.
Nonionic and anionic flocculants used in conjunction with
inorganic coagulants allow to improve the efficiency of
clarification process, to reduce dosages of inorganic coagulant
(Fig. 1), and to replace completely inorganic coagulants if
cationic flocculants are employed (Fig. 2). From data given
above it is apparent that treatment efficiency depends on the
nature of a flocculant.
Among nonionic and aniomic flocculants, polyacrylamides
varying in molecular weights and degree of hydrolysis (PAA,
PAA-R, PAA-G) provide the most effective clarification of
18
-------
petroleum refinery wastes. Doses of above given flocculants
range from 0,5 to 1 mg/1.
According to decrease in effectiveness, tested cationic
flocculant may be schematically given in the following
sequence: BA-212> BA-112>BPK-101>12CH. Optimum
dosages of flocculants having the same nature (BA-112, -212,
12C8) is 10 mg/1, the optimum dose of BPK-101 flocculant is 5
mg/1. It seems to be due to higher value of total electrical
charge (exchange volume) of BPK-101 flocculant (Table 1).
ag/1
3.0
Dose of flocculant, Dg/1
Figure 1.
Treatment efficiency of petroleum refinery wastewater by sedimentation
process as a function of flocculant
(1-4) and coagulant (5) dosages.
l-4Concentration of A1,(SO,), is 24 mg/1;
Concentration of SS (initial) mg/1: 1-4- 57mg/l; 5- 81mg/l;
Flocculant: I- PBC-M, 2-PAA-G. 3-PAA. 4- PAA-R.
The most important factor which determines effectiveness of
purifying wastewaters, treated with any coagulant and
flocculany, is the achievement of optimum hydrodynamic
conditions for mixing and floe formation.
The first stage of mixing (rapid mixing) provides complete
and rapid distribution of chemicals in a body of water as well
as determines numerical concentration of initial particals in
coagulated suspension and their distribution on size.
The second stage (slow mixing) promotes the formation of
floes of certain size and structure thus providing optimum
condition for their separation.
Studies carried out have shown that optimum mixing is
achieved at velocity gradient G2 of 94-120 sec"1 and mixing
period t1 of 20-60 sec (Fig. 3). Optimum floe formation is
obtained at velocity gradient G2 of 20-25 sec"1, which
corresponds to Camp criterion G2 12 =24000-30000 and mixing
period of 20 min.
Kinetic relationships between efficient clarification of oil
wastes treated with BPK-101 and BPC-41 1 flocculants at
optimum floe formation conditions and detention period are
illustrated in Fig. 4. From data obtained it is apparent that
B_.
tn
Doee of flocculant, mg/1
Figure 2.
Concentration of suspended matter in treated petroleum refinery wastewater
as a function of flocculant doses.
Initial concentration of SS= 39.5 mg/1;
1- BPK-101; 2- I2C,; 3- BA-112; 4- BA-212.
most of the contaminant is removed by 30 minutes settling.
Residual concentration of suspended matter is from 4 to 11 mg/
I. As the results obtained from kinetic studies indicate,
treatment efficiency and settling velocity of floes decrease
under non-optimum mixing conditions (Fig. 4).
Therefore it is necessary to include mixing and floe
formation chambers in treatment scheme of petroleum refinery
wastewaters.
Flotation of coagulated and flocculated wastewaters.
In petroleum refinery waste treatment technology the following
flotation systems with addition of chemicals are used:
• full flow system, when all the flow of wastewater to be
treated enters a saturation tank;
• recycle system, when from 20% to 50% of clarified effluent
is supplied to a saturator.
Chemicals are fed into the system at the suction end of the
pump where wastes enter the saturation tank (Fig. 5a), or into
recirculating pipeline ahead of pressure tanks (Fig. 5b) or the
flotation cell (Fig. 5b).
The mixer and the flocformation chamber are included in the
latter treatment scheme in order to achieve optimum conditions
for mixing and floe formation.
19
-------
Time, hour
Figure 3.
Kinetic of sedimentation of petroleum refinery wastes treated by BPK-101
(1,2), BPO»11(3) flocculants.
I- nonoptimum conditions for floe formation:
2-3- optimum floe formation conditions.
Figure 4.
Relationship between suspended solids removal from petroleum refinery
wastes, treated by a flocculant and clarified during 0.5 hour, and mixing
conditions.
G,. sec-': 1.4.6-94; 2,3-117,5;
G,. sec-': 4,5,6- 25;
t1. sec: 1,4,5-60:2,3-20;
t,,min.: 1.2,5,6-20:3-10.
rK>
-a
coagulant
b)
air
coagulant
coagulant
c)
flocculant
air
Figure 5.
Typical schemes of flotation units.
a) direct flow, b,B)recycle
I-pump for wastewaler,
2- saturation tank, 3- flotation cell, 4- mixer,
5- floe formation chamber, 6- chamber for mixing wastewater and effluent from a
saturation tank.
As the majority of existing full-scale flotation facilities
operate according to schemes, making provision for chemical
addition to wastes prior to entering the saturation tank or the
pump, the study of effective applicability of chemicals in such
schemes is of practical concern.
The results of treating waste waters in a 600 cu.m/hour full
scale flotation unit, a schematic of which is shown on Fig. 5b,
are presented in Table 2. The unit consists of a typical radial
flotation chamber with a diameter of 15 m.(3), a saturation tank
of barbotage type (2) to saturate wastes with air, a chamber of
"tube in tube" type for mixing wastewater with an effluent
from a saturator (6), a pump (1). Air is supplied by an ejector
(5). A pressure of 58,8 Ib/sq. in. is maintained in a saturation
tank. 50 percent of treated wastewater is saturated with
dissolved air. Chemical (aluminium sulfate) is introduced into
the suction end of the pump ahead of the saturator. Aluminium
sulfate at dosages of 75 to 120 mg/1 and BPK-101 flocculant
have been tested. After passing through mechanical treatment
20
-------
Table 2
Effectiveness of treating petroleum refinery
wastes in the full scale flotation unit
CHARACTERISTICS OF WASTEWATER
REMOVAL EFFICIENCY
CHEMICAL
BPK-101
DOSE OF
CHEMICAL
MG/L
75
75
75
75
100
100
100
100
120
120
120
3.0
6.4
5.0
5.6
9.5
4.5
13
17
BEFORE
TREAT-
MENT
96
75
85
94
—
—
—
—
48
54
23
24
59
80
64
17
12.5
8
17.0
SSMG/L
AFTER
TREAT-
MENT
33
34
25
22
9.5
34
39
17
10
13
1.3
12.8
19.4
5.0
COD MGOz/L
BEFORE AFTER
TREAT- TREAT-
MENT MENT
327
354
362
319
221
—
245
442
197
155
—
177
181
180
198
293
304
281
316
225
212
216
162
106
—
107.5
185
150.5
97
—
129
155
64.6
—
170
189
170
177
OIL
SUBSTANCES
MG/L
BEFORE AFTER
TREAT- TREAT-
MENT MENT
41
52
50.8
37.5
63.4
50
67
28
30
26
37.5
56.5
86
96
77
29.5
36.5
49
39
16.3
18
1 1.3
9.1
II
18
29
11
2.0
7.0
II
—
19
22
19
4
8.0
9
27
ss
66
55
71
77
80
37
71
87.5
80
92
71
COD
31
40.1
40
49
52
58
24
37
27
70
64
42
39
39
44
OIL
SUB-
STANCES
60
65
78
76
82.5
65
57
61
93
73
71
78
77
75
86
78
81
31
facilities including grit tanks, oil intercepters and ponds for
additional sedimentation, wastes were treated by flotation.
From data presented in Table 2 it is evident that removal
efficiencies achieved by pressure flotation with aluminium
sulfate addition are 37%-80% for SS (initial concentration =
23-100mg/l), 57%-93% for oil substances (initial concentration
= 25-70 mg/1). The COD value is being reduced by 24%-58%
(COD initial = 155-442 mg/1).
The results obtained from full-scale flotation studies with
addition of BPK-101 flocculant at dosages of 2 to 15 mg/1 show
that optimum doses of a flocculant are in the range of 5 to 10
mg/1, which are one tenth-one fifteenth as much as that for an
inorganic coagulant (Table 2). Under optimum operating
conditions removal efficiencies achieved by the flotation
process are 71%-92% (initial concentration = 17-80 mg/1) for
suspended solids, 75%-85% for oil substances (initial
concentrations = 30-100 mg/1). Simultaneously the COD value
is reduced by 39%-70% (initial concentration = 180-293 mg
While carrying out full scale studies, it has been found that
moisture content of foam being produced during flotation
treatment of wastes, is reduced from 94%, if aluminium sulfate
is added as a coagulant, to 88%-91%, if BPK-101 flocculant is
employed.
Comparative analysis of data obtained shows that petroleum
refinery wastes can be treated effectively by using BPK-IOI
flocculant.
Introduction of chemicals through mixing and floe formation
chambers ahead of flotation cell (Fig 5B) allows to achieve high
degree of effluent quality (5). The addition of aluminium sulfate
as a coagulating aid provides 88%-%% removal for oil
substances (residual concentration is 1 to 6 mg/1). Removal
efficiency for SS is 8I%-93%, the COD value is reduced by
70%-77%.
Thus the results of pilot and full scale studies indicate that
the use of flocculants for intensification of mechanical
treatment of petroleum refinery wastes is appropriate.
21
-------
Activated Sludge Enhancement: A
Viable Alternative To Tertiary
Carbon Adsorption
Leonard W. Crame
Texaco Inc.
Presented by:
U.V. Henderson, Texaco Inc.
Introduction
In view of the possibility of more stringent 1983 BATEA (Best
Available Technology Economically Achievable) effluent
guidelines, 1'2-:t'4 petroleum refiners are faced with the dilemma
of an insufficient data base to determine the proper approach
for making cost-effective improvements. The EPA previously
proposed granular activated carbon adsorption after activated
sludge treatment as BATEA technology; however, the current
emphasis is to consider both effluent quality and the cost
effectiveness of attaining the desired results. Two proposed
approaches to BATEA technology are (1) increasing the sludge
age (or mean cell residence time) of the activated sludge
biomass to develop a more diverse population capable of
assimilating biorefractory organics or (2) adding powdered
carbon directly to activated sludge aeration basins. Both
alternatives to tertiary carbon adsorption would require little
capital investment and would lower operating costs.
Grutsch and Mallatt5-6'7-8-9-10-11 have proposed that the best
refinery end-of-pipe treatment for soluble organic removal
should include pH control, equalization, optimized dissolved air
flotation (DAF), and high sludge age (20-50 days) activated
sludge treatment. High sludge ages (SA) require mixed liquor
solids levels above conventional levels (5-10 days SA). These
higher levels increase solids flux and must be considered in
secondary clarifier solids loadings. Also high effluent TSS,
despite less frequent sludge wasting, can result in a loss of
mixed liquor solids.
Grutsch and Mallatt emphasize that optimized chemically-
assisted DAF pretreatment (or comparable pretreatment)
reduces the colloid charge (zeta potential) to maximize partical
agglomeration for efficient flotation, and reduces the organic
load on the activated sludge unit (ASU). Removing colloids
normally present in raw refinery wastewater allows better
bioflocculation and lower effluent total suspended solids (TSS)
since most refinery colloids and biosolids have repelling
negative charges. The microbial population could then
acclimate to the biorefractory organics by producing enzymes
which reduce these to simpler biodegradable substrates.
Current reports from within the petroleum industry seem to
indicate some benefits for increasing SA. Other investigators12
have reported that high SA (low food/microorganism ratio)
produces poor sludge settleability.
As a result of pilot studies at the Du Pont Chambers Works,
Hutton and Robertaccio w were issued a U.S. patent14 for the
Du Pont PACT process.I5 The PACT process basically
involves the addition of powdered carbon (or fuller's earth,
etc.) to an ASU, usually in a range of 50-400 mg/1 based on
influent flow. Du Pont has reported16-17'18 a number of
advantages of the PACT process which include:
(1) color removal,
(2) stability against shock loadings,
(3) improved BOD removal,
(4) improved refractory organic removal,
(5) resistance to toxic substances,
(6) improvement in hydraulic capacity,
(7) improved nitrification (mainly in municipal wastes),
(8) foam suppression, and
(9) improved sludge settling and increased clarifier capacity.
22
-------
A disadvantage of the PACT process is that the system can
become very expensive if powdered carbon addition rates
become high (hundreds of mg/l), even though powdered carbon
is cheaper than granular carbon.
DeJohn and Adams19>20>21 have developed a considerable
amount of pilot study data on activated sludge-powdered
carbon systems. They report significant enhancement in studies
involving refinery and petrochemical wastewaters. DeJohn and
Adams explain the powdered carbon enhancement mechanism
as localization and concentration of oxygen and pollutant as the
result of adsorption on carbon surfaces, resulting in a more
complete biooxidation. The adsorption of biorefractory organics
allows a longer residence time for these components in the
system. Other researchers22-23 have found similar
improvements using activated sludge-powdered carbon systems
and purpose analogous enhancement mechanisms.
Rizzo24 has reported a case history of a full-scale activated
sludge-powdered carbon demonstration run at the Corpus
Christi, Texas, Sun Oil refinery. Results included better system
stability, reduction of foaming, resistance to upset conditions,
lower effluent suspended solids and clearer effluent, and
improved organic removal. These improvements were achieved
by maintaining only a 450-mg/l powdered carbon reactor
concentration with a 10-mg/l powdered carbon dosing
requirement. The shortcoming of this investigation was that a
parallel control could not be run simultaneously and most
improvements reported could possibly have been attributed to
better clarification.
The merits of powdered carbon enhancement have been
further confused with the more recent development of several
types of powdered carbons with significantly different
properties.
Scope of Work
1. Objective
The objective of this study was to determine if the relatively
simple process changes of increased sludge age or the addition
of powdered activated carbon in conventional refinery activated
sludge systems can significantly enhance the removal of
organic wastewater contaminants to achieve or approach the
level of proposed BATE A (1983) technology more cost
effectively than the addition of granular activated carbon
contactors to BPCTCA (1977) technology.
2. Procedures
In Part I of this study, five completely-mixed (15 gal) ASLPs
were operated in parallel with identical 18-hr retention times
and 300-gpd/sq ft clarifier rise rates. A sixth ASU was run as a
second-stage unit with the same 18-hr retention time (Figure 1).
All biological reactors were located in a temperature controlled
room in an attempt to dampen influent wastewater temperature
variations and control biological reactions at about 85 F.
ASU's A and F served as controls, simulating conventional
refinery units with a 0.3 Ib TOC/lb MLVSS-day organic
loading. Separate controls were run to determine the effect of
optimized pretreatment on activated sludge treatment and
tertiary carbon adsorption. Equalized (24-hr) and pH-controlled
refinery wastewater was pretreated by dual-media (sand-
ACTIVATED
SLUDGE
CHEMICALS Ji
A
— »
B
C
F
~*
CONV.
0.3 F/M
HIGH SA
HIGH SA
PC-C
HIGH SA
PC-II
COHV.
0.3 F/M
HIGH SA
PC-II
s~~\ /~V~V~V^
-•O-^OUUL)-^
E
— • HIGH SA »
-*
»
-OOODO-
--
Figure 1
Treatment Schemes.
anthracite) filtration (4.6 gpm/sq ft) and a chemically assisted
DAF unit (1.5 gpm/sq ft) prior to control ASU's A and F,
respectively. The optimized DAF pretreatment neutralized the
negatively charged colloids, thus facilitating their removal and
producing a bio-unit feed that contained essentially only soluble
organics. Sodium phosphate (monobasic) was added to the
filter and DAF unit effluents for a minimum TOC: phosphorus
ratio of 100:2 to assure a proper nutrient level. Effluents from
ASU's A and F were continuously filtered through a dual-
media (sand-anthracite) tertiary filter for TSS removal before
passing through a series of four granular activated carbon
contactors to simulate proposed 1983 BATE A technology.
ASU's B, C, and D treated optimized DAF effluent with
sludge wasting calculated for a 50-day biological SA. A
commercially available, conventional-surface-area, powdered
carbon25 (designated PC-C) was added daily to ASU C to
maintain a 500-mg/l reactor operating level. Similarly, PC-H, a
high-surface-area powdered carbon,26 was added to ASU D to
investigate its enhancement capabilities.
ASU E was also operated at a 50-day SA treating ASU B
effluent to determine if there was any benefit to ASU staging.
In Part II of this study, the second-stage ASU E was placed
in parallel with other ASU's treating the DAF unit effluent as
shown in Figure 1 and redesignated as ASU G. PC-H was
added to ASU G to maintain a 2500-mg/l operating level while
powdered carbon levels were increased in ASU C and D to
1000 mg/l.
Effluents were collected daily, Monday through Friday, as
grab samples. Grab samples were taken in lieu of composites
for convenience since the pilot unit treatment scheme
contained significant equalization. Samples from the
equilization basin, biological reactors, and carbon columns
were filtered with Gelman type A/E glass fiber filters to give
the soluble contaminant (TOC, COD, S=) level. Glass fiber
filters were used instead of 0.45-micron filters because the
solids retained on glass fiber filters define the TSS
measurement. Samples were analyzed immediately after
collection or were preserved until analyzed using accepted
preservation methods.27
23
-------
All effluent data were compared after plotting values on log-
normal probability papers. Single straight line data fits were
determined by calculating 50th and 90th percentile values. The
50th percentile values equaled the antilog of the mean of the
log values of data sets. The 90th percentile values were
calculated assuming a single-tailed log-normal data distribution.
lnN4n= lnN™+ 1.282 In S"
50
where
Sd is the standard deviation.
Engineering judgment was used to determine which data sets
being compared appeared different and required additional
statistical analyses to confirm significance of median
differences. Median data values were compared to determine if
they were from the same population using a paired t-test2tt
assuming a log-normal distribution as follows:
compute t =
n(n-l)
d = mean of differences = ]T d ,/n where d, = In x,- In y,
i
for i = 1,2,3,.,.n of n data pairs
S,i = standard deviation of dj.
The test hypothesis is that data are from the same population,
therefore, their true medians are equal. This hypothesis is
rejected if the calculated t-value exceeds the tabled two-tailed t-
value for n-1 degrees of freedom for the selected (90 percent)
confidence level.
Results
/. Part I - Pretreatment
The blended refinery wastewater contained excessive amounts
of colloids and TSS coated with oil, complicating pretreatment.
The DAF unit chemical dosages were relatively high at 40 mg/I
filter alum (A12(SO4):(14.3 H2O and 20-40 mg/1 Dearborn 431
cationic polymer. Chemical dosages were initially optimized
using zeta potential titrations in conjunction with jar tests;
however, only jar tests were continued since zeta potential
calculations became tedious and inconsistent due to the high
wastewater specific conductivity (usually 4000-8000
micromhos/cm). This salinity was primarily due to the brackish
intake waters to the refinery and may have impeded chemical
coagulation at lower chemical dosages as reported by Grutsch
andMallatt."
The superiority of the optimized DAF unit (operating at 1.5
gpm/sq ft) as a pretreatment system over simple sand filtration
is clearly evident in the three weeks of run data represented in
Figure 2.
600
500
400
300
200
100
800
700
,j 600
I 500
200
100
*DESIGNED FOR LESS THAN OPTIMUM PRETREATMENT
J I I I I I I I I I
10 20 30 40 50 60 70 80 90
PERCENT OF TIME LESS THAN INDICATED VALUE
Figure 2.
Part I—TOC and COD Removal By Pretreatment.
DAF unit effluent 50th percentile TOC (158 mg/1) was 55
percent less than the 50th percentile TOC (352 mg/1) in the
equilization basin influent to the DAF unit, while the sand filter
gave only a 18-percent reduction. Since, at best, only a 31-
percent TOC reduction could be achieved by vacuum filtration
of equalization basin samples with glass fiber filters (which
define TSS), the true effectiveness (55 percent reduction) of
colloid and oil coagulation and removal in the chemically
assisted DAF unit can be seen. The DAF unit effluent
contained essentially only soluble organic contaminants.
The continuous dual-media filter (operating at 4.6 gpm/sq ft)
could only manage a TOC reduction of about one-third of the
DAF unit. There was no indication that a shorter run time
would improve the filter effluent significantly. It appeared that
due to the nature of the solids, chemical adddition to the filter
feed would have been required for an improved system. The
purpose of the filter, however, was to produce a biological
reactor feed with characteristics comparable to DAF treatment
without chemicals. It was observed, on occasions, that DAF
pretreatment was very poor when chemical feed pumps failed.
Figure 2 illustrates COD removal by both pretreatment
systems employed and again demonstrates the effectiveness of
optimized DAF treatment. As in subsequent graphs, the data
points are not shown to avoid congestion of data.
Fiftieth percentile oil and grease values during Part I of this
study were 101, 70, and 16 mg/1 for the equalization basin, filter
effluent and DAF unit effluent, respectively. The equalization
basin 50th percentile TSS level of 78.0 mg/1 was reduced to
57.5 mg/1 by the filter and to 19.0 mg/1 by the DAF unit. A
portion of the TSS in the DAF unit effluent was due to
biological growth rather than influent solids. It is possible that
part of the organics reduction through the DAF unit was the
result of biological activity which could also occur in full-scale
systems.
24
-------
2. Part I -Activated Sludge Performance
TOC and COD (filtered) effluent variability plots for pilot-
scale 18-hr retention ASU's are compared in Figure 3. These
results are from the initial 3-week data run.
J 100
3 90
£ 80
Ju 7°
oo 60
^ 50
t. Q
lj UJ
"g 40
EH 30
300
200
100
90
80
70
60
50
50TH PERCENTILE VALUES. MG/L
A, FILTER - LOW SA
B, DAF - HIGH SA
DAF - HIGH SA-500 MG/L PC-C
DAF - HIGH SA-500 MG/L PC-H
COD
US
108
97
89
116
105
10
20 30 40 50 60 70
PERCENT OF TIME LESS THAN INDICATED VALUE
Figure 3.
Part I—Activated Sludge TOC and COD Distributions.
Control ASU F produced a better effluent than control ASU
A, both operating at equal 0.3 Ib TOC/lb MLVSS-day (F/M)
loadings. MLVSS levels in ASU A averaged 1,148 mg/1, about
twice that of ASU F due to a twofold increase in feed TOC.
Considering both TOC and COD removal, ASU B, C, E, and
F did not show any significant overall difference in
performance. Fiftieth percentile TOC values ranged from 53-58
mg/1 while COD values were 97-116 mg/1 as shown in Figure 3.
Sludge age was not a controlling performance variable as ASU
B (50-day SA) and ASU F (about 10-day SA) differed greatly
in solids retention time with average MLSS levels of 1,621 mg/1
and 816 mg/1, respectively. Chemically assisted pretreatment
for removal of colloids and oil had the most significant effect
on organics removal. The high-surface-area powdered carbon
(designated PC-H) significantly enhanced organic removal in
ASU D, with a 50-day SA and a 500-mg/l PC-H operating
level. Enhancement was not evident in ASU C containing the
conventional-surface-area powdered activated carbon
(designated PC-C). Powdered carbon addition increased the
average ASU C MLSS level to 1,885 mg/1 with ASU D
averaging 1,976 mg/1.
Since a marginal enhancement occurred with the addition of
PC-H at a 500-mg/i level, the scope of this investigation was
expanded to evaluate powdered activated carbon addition at a
1000-mg/l level and only PC-H at approximately 2500 mg/1.
This would give a greater overview of the enhancement
capabilities of powdered carbon, especially the highly active
PC-H. ASU E was taken out of service since it was only
succeeding in lysing biological cells as a second stage following
ASU B. The reactor was placed in parallel with other units
being fed by the DAF unit and redesignated ASU G. The SA
maintained at 50 days and PC-H was built up to a reactor level
of about 2500 mg/1 for Part II of this study.
3. Part I - Granular Carbon Adsorption
Granular carbon Series A, treating ASU A effluent, exhausted
two 130-gram carbon beds during 17 days of a 3.4-gpm/sq ft
hydraulic loading in Part I. A 20-mg/l soluble (filtered) TOC
and a 44-mg/l soluble COD effluent (50th percentile, Figure 4)
was produced with 0.10 and 0.09-g TOC/g carbon accumulative
loadings at exhaustion. Carbon Series F, treating ASU F
effluent, reduced the 50th percentile effluent soluble TOC and
COD to 23 mg/1 and 40 mg/1, respectively. Because of the
relatively few data points used to establish Figure 4, there is
little significance'in the difference between carbon series A and
F 50th percentile values. A single carbon bed was exhausted to
a 0.12-g TOC/g carbon loading. TOC loadings of carbon
columns in Series A were comparable to an average of 0.11 g
TOC/g carbon reported for the granular carbon during the four
previous exhaustions prior to each regeneration.
Granular carbon effluents were of substantially better quality
.than all biological unit effluents. The 50th percentile soluble
TOC and COD reductions in carbon Series A were 44 mg/1 and
84 mg/1, respectively, whereas carbon Series F accounted for a
50th percentile 35-mg/l soluble TOC and 65-mg/l soluble COD
reduction.
200
8100
Q 90
3 80
g 70
5 60
£ 50
30
20
50
40
30
20
| 5
I 4
3
j I
l I I I I I
5 10 20 30 40 50 60 70 80 90
PERCENT OF TIME LESS THAN INDICATED VALUE
Figure 4.
Part I—Granular Carbon Column TOC and COD Distributions.
95
90
25
-------
4. Part II - Pretreatment
Pretreatment by filtration and chemically assisted DAF
treatment continued as in Part I of this study. Again, using
dosages of 40-mg/l filter alum and 20-40 mg/1 Dearborn 431,
optimized DAF pretreatment reduced the equalization basin
TOC and COD by more than 50 percent as shown in Figure 5.
Filtration could only remove gross quantities of oil and solids
without preliminary chemical coagulation. Although
equalization basin, filter, and DAF unit effluent 50th percentile
TOC and COD concentrations were approximately equal to
those experienced in Part I of this study, there existed a
greater degree of variability in Part II. A contributing variability
factor was the rainfall dilution of refinery wastewater streams
as an average of 0.21 in./day of rain fell during Part II
compared with 0.06 in./day during Part I.
70ft
600 _
500-
400.
300-
200-
100.
90-
80-
70-
60
*DESIGNED FOR LESS THAN OPTIMUM
I I l i l i I
PERCENT OF TIME LESS THAN INDICATED VALUE
Figure 5.
Part II—TOC and COD Removal by Pretreatment.
5. Part II -Activated Sludge Performance
The effluent quality for Part II, basis filtered TOC and COD, is
given in effluent frequency distributions. Figure 6, for the six-
week run period. Control ASU A (F/M = 0.3), without
optimized pretreatment, continued producing the most inferior
effluent and experienced three upsets due to the development
of a filamentous bulking sludge. The unit was restarted on each
upset occasion with new seed and allowed to acclimate for a
few days before effluent data were used for comparison with
parallel systems. ASU B, C, and F, as in Part I, produced
nearly equivalent effluents in terms of filtered TOC and COD
with neither high SA (50 days) nor 1000 mg/1 PC-C enhancing
biological treatment. PC-H added to ASU D and G at levels of
1000 and 2500 mg/1, respectively, reduced TOC and COD
substantially. Compared with high SA control ASU B, 50th
percentile TOC was reduced an additional 10 mg/1 and 22 mg/1
in reactors D and G, respectively. COD 50th percentile
reductions below reactor B were 22 mg/1 for ASU D (1000 mg/1
PC-H) and 39 mg/1 for ASU G (2500 mg/1 PC-H). The ASU G
run time was abbreviated, however, due to the time required
100
90
•; so
o 70
* 60
. 50
u 30
20
10
.200
8
100
ri 90
ft. 80
H 70
g 60
50TH PERCENTILE VALUES, MG/L
FILTER - LOW SA
DAF HIGH SA
DAF
DAF
DAF
DAF
HIGH SA-1000 MG/L PC-C
HIGH SA-1000 MG/L PC-H
LOW SA
HIGH SA-2500 MG/L PC-H
44
34
46
22
COD
157
111
119
89
108
72
10 20 30 40 50 60 70 80 yu
PERCENT OF TIME LESS THAN INDICATED VALUE
6.
Figure
Part II— Activated Sludge TOC and COD Distributions.
for acclimation at the higher PC-H level. As in Part 1 of this
study, it was observed that as powdered carbon levels were
suddenly increased in ASU C, D, and G, performance was
exceptionally good for a short period of time.
Phenols feed concentrations were higher in Part II of this
investigation as 90th percentile values reached 18 mg/1,
compared with 8.5 mg/1 in Part I. ASU D (see Table I) and G,
containing PC-H, provided the best phenols removal with 50th
percentile phenols levels of 0.05 mg/1 and 0.04 mg/1,
respectively. This was slightly lower than the high SA control
ASU B (0.06 mg/1) and low SA control ASU F (0.07 mg/1).
Although the lack of optimized pretreatment produced higher
50th percentile phenols levels (0.1 1 mg/1) in ASU A, even
poorer reductions were experienced with ASU C as in Part I.
Similar results were obtained in Part I. An occasional high
phenols value was measured in the effluents of ASU D and G
but not with the consistency or magnitude of ASU C.
Effluent oil and grease values, included in Table 1 , illustrate
the significance of removing most of the oil and grease before
biological treatment. The 18 mg/1 50th percentile oil and grease
effluent level of ASU A greatly exceeded the concentration of
5 mg/1, or less, discharged from reactors receiving optimized
pretreatment. The addition of PC-H to ASU D and G gave
slight oil and grease improvement with SA alone not being in
enhancement factor.
Effluent TSS levels were high in ASU A at a 50th percentile
level of 86 mg/1. TSS increased to more than 150 mg/1 when
filamentous sludge bulking occurred. However, ASU's with
DAF pretreatment produced a more settleable sludge. The high
SA control ASU B had a significantly higher effluent TSS level
than the lower SA control ASU F, but the high SA could be
maintained. ASU C and D experienced effluent TSS levels less
than control ASU B despite higher reactor solids due to
26
-------
Table 1
Part II—Effluent Summary
(ALL VALUES MG/L)
EFFLUENT
SAMPLE
EQ EASIN
FILTER
DAF UNIT
ASU A
ASUB
ASUC
ASUD
ASUG
ASUF
CARBON COL
(SERIES A)
CARBON COL.
(SERIES F)
PHENOLS
PERCENTILE
SOTH 90TH
7.3
—
—
0.11
0.06
0.15
0.05
0.04
0.07
0.04
0.02
18.0
—
—
0.16
0.14
0.38
0.20
0.13
0.17
4.8
0.08
OIL & CREASE
PERCENTILE
SOTH 90TH
108
69
14
18
5
3
< 3
< 3
4
< 3
< 3
191
130
19
38
7
9
5
3
7
6
4
TSS
PERCENTILE
SOTH 90TH
64.0
34.0
13.0
86.0
27.5
23.0
18.0
22.0
8.4
—
—
119
74.0
21.0
149
41.0
77.0
57.0
44.0
28.0
—
—
AMMONIA
PERCENTILE
SOTH 90TH
20.9
—
—
11.5
3.9
3.3
3.1
3.1
2.3
—
—
27.2
—
—
20.0
9.2
5.4
4.8
4.4
5.4
—
—
Table 2
Part II—Sludge Data
AVERAGE VALUE
NOMINAL LOADING
ACTUAL LOADING
MLSS, MG/L
MLVSS, MG/L
PC, MG/L
%vss
OXYGEN UPTAKE,
LBOz/LBCODREM
MG/L-M1N
SVI, ML/G
SETTLING VELOCITY, FT/
WIN
BIOMASS PRODUCTION
RATE"
TOTAL PRODUCTION
RATE6
• CONVENTIONAL-SURFACE-AREA.
6 HIGH-SURFACE-AREA.
c DISCRETE SETTLING.
" LB VSS/LB COD REMOVED.
e LB TSS/LB COD REMOVED (INCLUDES CARBON).
ACTIVATED SLUDGE UNIT
A
F/M= 0.3
F/M= 0.3
1,487
1,302
0
88
0.40
0.16
95
0.17
0.22
0.25
B
50-DAY SA
39-DAY SA
1.892
1.562
0
83
0.68
0.12
64
0.34
0.16
0.19
C
50-DAY SA
42-DAY SA
2.728
2.269
1.000"
83
0.71
0.12
41
0.38
0.12
0.17
D
50-DAY SA
44-DAY SA
2.720
2.416
1.000"
89
0.49
0.11
43
0.38
0.11
0.14
F
F/M= 0.3
F/M=0.3
745
689
0
92
0.61
0.11
91
N/AC
0.19
0.21
G
50-DAY SA
56-DAY SA
4.096
3,898
2.500"
95
0.47
0.10
30
0.39
0.08
0.09
powdered carbon. No effluent TSS increase was observed in
ASU G due to the higher (2500 mg/1) PC-H level.
Ammonia nitrogen removal in system A was less than the 80
percent achieved in the systems with optimized pretreatment.
The organic loading was higher and the sludge age was less
than in other systems. The factors controlling the degree of
nitrogen removal were not investigated. Nitrification during
Part II was not as complete as that obtained in Part I.
Sludge Characteristics and production rates are summarized
in Table 2 for all ASU's. As expected, ASU A had the highest
measured oxygen uptake averaging 0.16 mg oxygen/1-min due
to a higher influent organic concentration. Oxygen consumption
averaged 0.10-0.12 mg oxygen/1-min in other ASU mixed
liquors, but a relationship of increased oxygen demand and
enhanced biological treatment did not exist. The sludge volume
index (SVI), a measure of sludge compactability, significantly
improved with SA and powdered carbon addition. Sludge
settling velocities were exceptionally high with the worst rate
(ASU A) being 0.17 ft/min corresponding to a 1830-gpd/sq ft
clarifier rise rate. Other mixed liquors settled with zone settling
velocities of 0.34-0.39 ft/min. The average MLSS concentration
of 745 mg/1 in ASU F was too low for zone settling to occur.
One of the most surprising results of powdered carbon addition
was that less biomass was produced than in control systems.
ASU G produced an average of 0.08 Ib biomass/lb COD
removed compared with control rates of 0.22 for ASU A and
0.19 for ASU F. PC-H was more effective than PC-C at
reducing biomass production rates at the same SA. The total
sludge production of activated sludge powdered carbon systems
was not much higher than controls, due to lower biological
sludge production rates.
Powdered carbon inventories and makeup requirements for
ASU's are summarized in Table 3 for Parts I and II of this
study. PC-C losses were slightly higher than PC-H but still
reasonably close to 2 percent per day. Since biological sludge
was wasted at a rate of 2 percent per day in high SA reactors,
27
-------
Table 3
Powdered Carbon (PC) Requirements
ASU-PART
C-I
0-1
C-ll
0-11
Ci-11
PC-
LEVEL
500
500
1.000
1.000
2.500
PC
TYPE
PC-C
PC-H
PC-C
PC-H
PC-H
PC
INVEN-
TORY
(G)
2S.4
28.4
56.7
56.7
141.9
ACG PC
LOSS
(G/DAY)
0.68
0.56
1.50
1.12
2.21
PC
MAKEUP
2.4
2.0
2.6
2.0
1.6
it is a fairly good assumption that powdered carbon lost in
effluents was in the same proportion to biological sludge as in
the mixed liquor. Thus both biological and powdered carbon
SA may be assumed to be equal for simplification of powdered
carbon daily makeup requirements. The powdered carbons
must be wetted to prevent loss of floating carbon in the
clarifier. This was accomplished by boiling the carbon slurry in
this study. Vacuum degassing could also be used.
Another observation made during Part II was that activated
sludge-powdered carbon systems significantly reduced aeration
basin foaming compared with control systems. Foaming in
ASU aeration basins was not a problem but did occur
occasionally.
6. Part II - Granular Carbon Adsorption
A single granular carbon bed was exhausted from carbon
Series A with an accumulative organic loading of 0.15 g TOC/g
carbon during Part II. The data include three short runs. The
first two carbon beds required backwashing almost daily due to
high TSS levels which could not be continuously removed by
dual-media filtration. Fiftieth percentile effluent soluble TOC
was 30 mg/l (see Figure 7) for a reduction of 38 mg/1 from ASU
A. ASU A 50th percentile soluble COD was reduced by 84 mg/
1 to 79 mg/l. Although phenols levels were generally low (50th
percentile of 0.04 mg/l) a few very high effluent phenols levels
were detected in carbon Series A giving a 90th percentile
phenols value of 4.8 mg/l (Table 1). Phenols must have been
adsorbed, concentrated, and then'eluted in slugs from the
carbon beds to achieve such a high level. Effluent oil and
grease levels remained low with 50th percentile values less than
3 mg/l.
Carbon Series F exhausted a single carbon bed to an
accumulative organic loading of 0.13 g TOC/g carbon while
surpassing the performance of carbon Series A. The 50th
percentile soluble TOC was significantly lower at 18 mg/l for a
28 mg/l reduction (Figure 7) from ASU F. Fiftieth percentile
soluble effluent COD was 64 mg/l for a 44 mg/l reduction.
Phenols levels were extremely low at 0.02 mg/l (50th percentile)
and no sudden loss of adsorbed phenols was detected during
most of the Part II data run (Table 1). Oil and grease effluent
levels (50th percentile) were again less than 3 mg/l.
The lower dashed lines in Figure 7 represent the
performance of ASU G, the best of the activated sludge-
powdered carbon reactors. ASU G produced an effluent
superior to carbon Series A and approached the quality of
carbon Series F. The powdered carbon enhancement removed
about 85 percent of the soluble TOC adsorbed on carbon Series
F and about 60 percent of the COD based on 50th percentile
100,
90
80
70
^ 60
g 50
zo" 40
u o
20
10
200
1 I I
I I
I I I
3:
Us" 101
U* Q O|
uos 71
5 6l
£ 5'
4
3
2 5 10 ~20 3D 4TJ5050 70 80 90
PERCENT OF TIME LESS THAN INDICATED VALUE
Figure 7.
Part II—Granular Carbon TOC and COD Distributions.
effluent values. The 2,500 mg/l PC-H operating level in ASU G
significantly reduced effluent color to a level comparable with
granular carbon effluent color.
7. Economics
Although unequal in overall performance, a high SA activated
sludge-powdered carbon system (ASU G, 72 mg/l COD)
approached the level of granular carbon adsorption (carbon
Series F, 64 mg/l COD) to within 8 mg/l COD at the 50th
percentile point. Both systems would require extensive
pretreatment and tertiary suspended solids removal. All other
process components being essentially equal, daily carbon usage
costs were estimated for theoretical plant flows of 1-5 MM
The cost of virgin powdered carbon (PC-H or PC-C) was
estimated at $0.30/lb and it was assumed that wasted carbon
would be thrown away. To calculate the equivalent powdered
carbon dosage required for an 18-hr retention ASU it was
assumed a 50-day SA would be maintained, giving an average 2
percent powdered carbon makeup. This was the equivalent of a
37.1 mg/l powdered carbon addition rate based on influent
flow. A powdered carbon feeder and storage facilities were
included in powdered carbon costs using Du Pont economics16
and applying the 0.6 rule. It was assumed that the powdered
carbon feeder could handle a 50 mg/l addition rate.
Regenerated granular carbon adsorption costs were
estimated, using Brown and Root, Inc. economics,29 and
converted to 1977 dollars. Daily granular carbon costs were
estimated using 17.2 percent of the fixed investment for
operating and maintenance cost and 17.7 percent for
depreciation. The total daily costs for powdered carbon were
estimated using the same percentage allowances.
Daily estimated carbon costs are shown in Figure 8 for
theoretical flows of 1-5 MM gpd by scaling up ASU G and
28
-------
3500
3000
g 2500
OS
w
*" 2000
£ 1500
o
u
^ 1000
|
500
0
234
FLOW MM GPD
Figure 8.
Comparison of Estimated Carbon Costs.
J\J
40
a
$30
g
Id
pa
§20
§
«10
0
—
—
36
$0.61
IB COT)
44 8
$3.19
LB COS
$14.73
Lfc COB
POWDERED
CARBON
GRANULAR
CARBON
INCREMENTAL
IMPROVEMENT
Figure 9.
Estimated Effective Carbon Cost at 1 MM GPD.
carbon Series F carbon requirements. The cost effectiveness of
the relatively simple process change of adding powdered
activated carbon to the activated sludge process can be clearly
seen. Estimated daily cost savings would range from $987/day
at 1 MM gpd flow to $275Q/day at 5 MM gpd using high-
surface-area powdered carbon (PC-H) addition rather than
granular carbon adsorption. The incremental cost would be
about $14.73 per pound of COD at 1 MM gpd (see Figure 9).
Discussion
/. Increasing Sludge Age (SA)
Contrary to conventional activated sludge design techniques,
the increased SA did not result in sludge deflocculation, higher
SVI, and high effluent TSS. With the exception of a few days,
the high SA control ASU B easily achieved a high SA as a
result of good pretreatment as proposed by Grutsch and
Mallatt.I
-------
DeJohn19-30 explains that granular carbon columns are
sometimes undersized because the designer uses virgin carbon
and assumes that regenerated carbon will have the same
activity. The thermal regeneration process will enlarge some
carbon pores reducing the surface area and decreasing the
adsorption of small molecules which are not so strongly
adsorbed on larger pores. Assuming that many small molecules
require small powdered carbon pores for moderately strong
adsorption, PC-H may have been more effective than PC-C
because of pore size distribution, provided that the normally
biorefractory refinery organics were small molecules.
The mechanism of powdered carbon enhancement of the
activated sludge process was not defined in this study and
needs further investigation in Phase II. Target SA's of the
activated sludge-powdered carbon systems were 50 days.
Ideally, systems should be operated for periods of several SA's
to insure that equilibrium conditions have been reached and
that the low (2 percent) daily powdered carbon makeup rate
will continue to give consistent results.
The selection of the best powdered carbon for a particular
activated sludge enhancement is not a simple task since
powdered carbons vary in their adsorptivity. Carbon isotherms
performed on a refinery wastewater would exhibit a wide
variability and require a statistical analysis to select the best
powdered carbon. Isotherms would have to be performed on
the activated sludge effluent (as in Phase II of this study) to
determine enhancement strictly due to adsorption.
The powdered activated carbon (PC-H) utilized with very
good enhancement results is not, as of yet, commercially
available. Because of the relatively high cost of granular carbon
adsorption, other powdered carbons at similar and higher
operating levels would probably offer a significant improvement
in activated sludge performance and remain more cost effective
than granular carbon.
3. Granular Carbon Adsorption
Granular carbon adsorption data indicate that the quality of
end-of-pipe refinery wastewater treatment depends on
optimization of each treatment step from primary to tertiary
treatment. The use of equilibrium or regenerated granular
carbon in pilot studies will provide a more realistic data base,
recognizing that economics would favor regeneration for many
potential users.
The classical approach31-32-33-34 for handling carbon
adsorption data to establish breakthrough curves was virtually
useless in this study because it assumes the carbon column
influent has a single adsorbate. In the calculation of
accumulated TOC loadings at apparent breakthrough of carbon
columns there were several instances where organics were
eluted in slugs from carbons in both series. At times, phenols
were two orders of magnitude higher than normal. This
phenomenon is a very real problem and must be considered
when establishing stringent effluent discharge guidelines for
industry. Even the best available technology, disregarding
economics, has its limitations.
Summary
The EPA 1983 guidelines for the petroleum refining industry
have assumed that 1977-type technology must be upgraded by
the addition of costly systems, such as granular activated
carbon adsorption. The results of this API study indicate that,
should the EPA adhere to the granular carbon technology
originally proposed, it may be possible to achieve this level of
treatment technology by the much more cost-effective method
of adding powdered activated carbon to the 1977 activated
sludge system.
Process modifications including optimized pretreatment and
the addition of a high-surface-area powdered activated carbon
can be used to produce an effluent which is comparable in
quality to that obtained by granular carbon adsorption.
Increasing activated sludge age from the conventional mode of
operation (about 10 days) to about 50 days did not give a
significant system improvement; however, in conjunction with
powdered carbon addition, high sludge age allowed higher
equilibrium reactor concentrations (2500 mg/1) at low (2
percent) carbon makeup rates. This benefit has been
demonstrated with the high-surface-area carbon and it is
possible that it can also be obtained with increased levels of
conventional powdered carbon. The cost-effectiveness of any
powdered carbon will depend on the wastewater characteristics
and powdered carbon adsorptivity, which was greater for the
high-surface-area carbon (2462 sq m/g) than for the
conventional-surface-area carbon (550 sq m/g) investigated
here. Even granular carbon adsorption was found to have
limitations as slugs of phenols were eluted, on occasion, into
the effluent.
Acknowledgements
This study was funded in part by the American Petroleum
Institute, Division of Refining, CREC Liquid Waste
Subcommittee.
30
-------
REFERENCES
Environmental Protection Agency. "Petroleum Refining Point Source
Category Effluent Guidelines and Standards," Federal Register, Vol 38
(240) 34542 (December 14, 1973).
Environmental Protection Agency. "Petroleum Refinery Point Source
Category Effluent Guidelines and Standards," Federal Register, Vol 39 (91)
16560 (May 9, 1975).
Environmental Protection Agency, "Petroleum Refining Point Source
Category Effluent Guidelines and Standards." Federal Register, Vol 40 (98)
21951 (May 20, 1975).
Jones Associates. "Effluent Limitations in the Petroleum Refining
Industry," Vol IB, Prepared for the Office of General Counsel, American
Petroleum Institute (January, 1976).
J. F. Grutsch and R. C. Mallatl. "Optimize the Effluent System — Part 1:
Activated Sludge Process." Hydrocarbon Processing. Vol 55 (3) 105 (1976).
J. F. Grutsch and R, C. Mallatl. "Optimize the Effluent System —Part 2:
Intermediate Treatment." Hydrocarbon Processing. Vol 55 (4) 213 (1976).
J. F. Grutsch and R. C. Mallatt, "Optimize the Effluent System —Part 3:
Electrochemistry of Destabilization," Hydrocarbon Processing, Vol 55 (5)
221(1976).
J. F. Grutsch and R. C. Mallatt. "Optimize the Effluent System—Part 4:
Approach to Chemical Treatment." Hydrocarbon Processing, Vol 55 (6)
115(1976).
J. F. Grutsch and R. C. Mallatt. "Optimize the Effluent System —Part 5:
Multimedia Filters." Hydrocarbon Processing, Vol 55 (7) 113 (1976).
J. F. Grutsch and R. C. Mailatt. "Optimize the Effluent System —Part 6:
Biochemistry of Activated Sludge Process," Hydrocarbon Processing, Vol
55(8) 137(1976).
J. F. Grutsch and R. C. Mallatt, "A New Perspective on the Role of the
Activated Sludge Process and Ancillary Facilities." Presented at Joint
EPA-API-NPRA-TU Open Forum on Management of Petroleum Refinery
Wastewaters, Tulsa. Oklahoma (January 26-29, 1976).
D. L. Ford and W. W. Eckenfelder, Jr.. "Effect of Process Variables on
Sludge Floe Formation and Settling Characteristics, "Journal Water
Pollution Control Federation, Vol 39 (11) 1850 (1969).
G. Grulich. D. G. Hutton, F. L. Robertaccio, and H. L. Glotzer.
"Treatment of Organic Chemicals Plant Wastewater with the Du Pont
PACT Process," Presented at AIChE National Meeting (February. 1972).
D. G. Hutton and F. L. Robertaccio. U. S. Patent 3.904.518 (September }.
1975).
E. I. Du Pont DeNemours and Company. "Du Pont PACT Process."
Technical Bulletin.
B. P. Flynn and L. T. Barry. "Finding a Home for the Carbon: Aerator
(Powdered) or Column (Granular)," Proceedings of the 31st Annual Purdue
Waste Conference (May 5, 1976).
B. P. Flynn "A Methodology for Comparing Powdered Activated Carbons
for Activated Sludge." Presented at 168th National Meeting, ACS, Div. of
Petroleum Chemistry, Symposium on Disposal of Wastes from Petroleum
and Petrochemical Refineries (September 13, 1974).
B. P. Flynn, F. L. Robertaccio, and L. T. Barry, "Truth or Consequences:
Biological Fouling and Other Considerations in the Powdered Activated
Carbon — Activated Sludge System." Presented at 31st Annual Purdue
Waste Conference (May 5, 1976).,
P. B. DeJohn and A. D. Adams, "Treatment of Oil Refining Wastewaters
with Granular and Powdered Activated Carbon," Proceedings of 30th
Annual Purdue Industrial Waste Conference (May 6, 1975).
A. D. Adams. "Powdered Carbon: Is It Really That Good?." Water and
Wastes Engineering, Vol 11 (3) B-8 (1974).
P. B. DeJohn and A. D. Adams. "Activated Carbon Improves Wastewater
Treatment." Hydrocarbon Processing, Vol 54 (10) 104 (1975).
A. B. Scaramelli and F. A. DiGiano. "Upgrading the Activated Sludge
System by Addition of Powdered Carbon." Water and Sewage Works. Vol
120(9)90(1973).
A. E. Perrotti and C. A. Rodman. "Enhancement of Biological Waste
Treatment by Activated Carbon." Chemical Engineering Progress. Vol 69
(11)63(1973).
J. A. Rizzo. "Case History. Use of Powdered Activated Carbon in an
Activated Sludge Syslem," Presented at Joint EPA-API-NPRA-TU Open
Forum on Management of Petroleum Refinery Wastewaters (January 26-29.
1976).
IC1 United States Inc., "Powdered Hydrodarco Activated Carbons Improve
Activated Sludge Treatment." Product Bulletin PC-4 (October. 1974).
Amoco Research Corporation. Amoco Active Carbon Grade PX-21 Product
Information Sheet (May. 1976).
APH A. Standard Methods for the Examination of Water and Waslewater,
13th Ed.. New York, New York (1971).
H. E. Klugh, Statistics: The Essentials for Research. 2nd Ed.. John Wiley
& Sons, Inc.. New York. New York (1974).
Brown and Root. Inc.. "Economics of Refinery Wastewater Treatment.'
American Petroleum Institute Publication No. 4199(1973).
P. B. DeJohn. "Carbon from Lignite or Coal: Which is Better?." Chemical
Engineering- Vol 82 (9) 113 (1975).
Metcalfand Eddy. Inc.. Wastewater Engineering, McGraw-Hill, New York.
New York (1972).
W. W. Eckenfelder. Jr.. Industrial Water Pollution Control, McGraw-Hill.
New York. New York 11966).
H, J. Fornwalt and R. A. Hutchins. "Purifying Liquids with Activated
Carbon." Chemical Engineering. Vol 73 (8) 1976 (1966).
J. L. Rizzo and A. R. Shepherd. "Treating Industrial Wastewater With
Activated Carbon." Chemical Engineering. Vol 84 (1) 95 (1977).
31
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Electrochemical Treatment of
Industrial Wastewaters
V. E. Genkin., A. N. Belevtsev
The growth of various industries results in the increase in
volumes of industrial wastwater discharges and kinds of
chemical substances, entering surface water supplies.
Biological methods widely applied to many types of
wastewaters are generally impractical or don't provide the
necessary quality of treatment of wastes containing bio-
resistant substances. These facilities are large in size and
require high capital investment.
Therefore, in recent years, combined treatment methods
have been finding increased use: physical-chemical treatment
with subsequent biological; physical-chemical process
employed as tertiary treatment after biological treatment.
Flowsheets of treatment facilities using physical-chemical
methods alone are also being developed.
Physical-chemical treatment processes with chemicals
addition often involve use of high chemical doses and cause the
secondary pollution of liquids, that is, increase salt
concentration. Therefore, during recent years wastewater
treatment without addition of chemicals is becoming popular.
The development and the implementation of electrochemical
methods is an advanced trend in the technology of wastewater
treatment. The methods, in a number of cases, permit to
recover valuable products, to simplify flowsheets and operation
of treatmept facilities, to provide control of their operation and
to reduce area requirements.
Electrochemical methods usually don't lead to increase in
salt content of treated effluents and, in many cases, allow to
avoid sludge formation or to reduce substantially the volume of
sludge produced.
While treating wastewaters by the action of a direct current,
a number of processes take place: anodic oxidation and
cathodic reduction of impurities present in wastewaters;
solution of metallic anodes; discharge and coagulation of
colloidal particles; electrophoresis; the passage of ions through
semi-permeable membranes; flotation of solid particles by gas
bubbles produced on electrodes; precipitation of metallic ions
on cathod; regeneration and concentration of acids and alkalies;
desalination of water and other electrochemical and chemical
processes.
At the present time there are three main directions in the
development of electrochemical treatment processes applied to
wastewaters, containing various impurities:
1) Removal of dissolved impurities (mostly organic matter)
from waste effluents in the form of non-toxic (or less toxic)
and, in some cases, water insoluble products as a result of
anodic oxidation and cathodic reduction.
2) Removal of dissolved impurities (mainly inorganic matter)
from wastewaters by electrodialysis, simultaneously utilizing
recovered products.
3) Removal of dissolved and finely divided in dispersed state
(including emulsified) insoluble impurities (both organic and
inorganic) by electrocoagulation methods (wastewaters are
electrolyzed using soluble iron an
-------
Anodic oxidation and cathodic reduction of impurities present
in wastewaters.
Electrochemical methods resulting in the decomposition of
organic compounds may be applied to relatively concentrated
wastewaters discharged in small volumes to local plants.
These methods are finding use because of the absence of
biological treatment facilities at local plants as well as the
presence of non-biogradable substances in waste streams.
Due to high consumption of energy the methods may be
applied only when other methods either are not feasible or
hardly economic.
Wastewaters are electrolyzed using electrolytically insoluble
anodes (graphite carbon, magnetite, dioxides of lead,
manganese and ruthenium deposited on titanium substrate) at
relatively high current densities in electrolysis units operating
with or without diaphragm.
Destruction of molecules of various organic materials
resulting from oxidation at the anode by the action of current,
is often accomplished with their complete decomposition, the
products of which are carbonic acid, water, ammonia and other
products. In some instances, anodic oxidation of organic or
inorganic compounds results in the formation of more simple,
non-toxic or less toxic, bio-oxidizable products (e.g. at the
anode phenols are oxidized to maleic acids, cyanides to
cyanates, sulfides to sulfates and so on).
More recently, electrochemical methods have been
developed for the removal of dissolved impurities (cyanides,
rhodanides, nitro-compounds, amines, alcohols, aldehydes,
ketons, azo dyes, sulfides, mercaptans, anthraquinone
derivatives and others) from waste effluents arising from
mechanical engineering, instrumentation, chemical, petroleum-
refining, pulp-and-paper and others industries.
Matt
1
1 —
t
2
i
I
1
l__ -L
11
10
n
i!
u
8
y
i!
d
n
ii
U
n
a
n
y
,.,*.
Figure I.
The Scheme of Principal of the Installation for the Electro-Chemical
Purification of Wastewater from Cyanides.
1. —feeding of the wastewa«er;
2.—accumulator;
3,—tank for the preparation of the NaCI solution:
4.—electrolyser;
5.—feeding of the air;
6.—regulator of the current;
7.—the source of the constant current;
8.—fault in the sewerage system;
9.—return of the water for further treatment.
The removal of pointed out above-compounds from waste
effluents is based upon anodic oxidation and cathodic
reduction.
The principal flowsheets for removal of cyanide compounds
from wastewaters by electrochemical oxidation is given in Fig.
1. The process is carried out in electrolysis units operating
without diaphragm. Plates or rods of graphite carbon, which
are utilized in the production of chlorine and sodium hydrate
by electrochemical method, are used as anodes. The anodes
may be of magnetite and ruthenium dioxides (with titanium
substrate) as well. Plates of alloy steel serve as cathods. While
electrolyzing alkaline waste effluents, containing simple and
complex cyanides, the latter are oxidized to cyanates at the
anode:
CM- + 2OH- - 2e
+ H,O
(1-1)
C u(CN)32- + 6OH- - 6 e—> Cu+ + 3CNO~ + 3H2O (1.2)
As the concentration of cyanate ions in the solution
increases, they are further oxidized at the anode, the final
products of which are carbonates and gaseous nitrogen:
2CNO- -I- 6OH- - 6 e—»2HCO,- + N, + 2H,O
(1.3)
The discharge of H+ ions resulting in the generation of
gaseous hydrogen as well as precipitation of metals in the form
of cyanide complexes (copper, silver and others) takes place on
the cathod.
In order to increase the electroconductivity of wastewaters,
the rate of the process and to reduce power consumption, it is
advisable to add inorganic salts (predominantly sodium
chloride) to wastewaters prior to the electrolysis and to adjust
the pH to 9-10 by addition of alkalies.
When sodium chloride is added to waste effluent besides
electrochemical oxidation, cyanides are oxidized by metallic
chlorine, being generated at the anode as a result of
electrochemical decomposition of NaCI.
2CI- - 2e 2CI (1.4)
CM- + 2C1 -t- 2OH- CNO- + 2Ch + H2O (1.5)
The process is carried out at the anode current density of
20-lOOA/m2 with addition of 3-4kg/m3 of soda and sodium
chloride (volume density is 1-3 A/1). Power consumption
required for treating wastewaters containing cyanides at a
concentration of 30-200m/l varies between 4 to 40kwh/nr1
(about 0,2 kilowatt-hour per gram of cyanide ions). 100%
treatment efficiency is achieved. 80% of total amount of non-
ferrous metals present in wastewaters recovered as cathodic
deposits are utilized.
Cathodic reduction of organic compounds from wastewaters
is desirable if direct anode oxidation doesn't occur or requires
high power consumption, and products formed during cathodic
oxidation are either non-toxic or subjected to oxidation with
distruction.
33
-------
During the electrolysis of wastewaters containing heavy
metal ions, the ions are discharged at the cathod, thus
producing deposits of corresponding metals (copper, zinc and
others). Organic nitro-compounds (nitro-benzene, trinitro-
toluene and others) are removed from wastes in an electrolysis
cell with porous inert diaphragms made of synthetic materials
(Mipor, polyethylene, Miplast). Plates of lead, zinc, copper,
alloy steel are employed as cathods. Wastewater is introduced
into the cathod compartment.
After reduction of nitro-compounds, wastewaters are
subjected to secondary electrochemical treatment, that is,
amines formed are oxidized to non-toxic products at the anode.
Waste effluents, containing trinitro-toluene are treated by
electrochemical process employing steel cathods and graphite
anodes at current densities of 200-600 A/m2 and at temperature
of 30-50° C.
Power consumption required for removal of gram of trinitro-
toluene from wastewaters is 0,5 kwh. In some cases, cathodic
reduction of organic substances results in the formation of
water-insoluble precipitates.
Thus, for example, while treating.wastewaters from
anthraquinone sulfonic acid manufacturing process (semi-
product of the synthesis of anthraquinone dues) by
electrochemical process using mercury cathod, reaction of
desulftation (reduction) of anthraquinone sulfonic acid to
anthraquinone which precipitates, takes place. The product
may be utilized in the process.
Electrodiaiysis
Electrodialysis - is a process of separating salt ions which is
carried out in multi-cell electrodialysis unit operating with ion-
exchange membranes by the action of direct current, directed
perpendicularly to the surface of membranes.
At present, electrodialysis is widely used for desalination of
salty underground and sea waters. The principles of operation
of electrodialysis units are well known and details are not
discussed in this paper.
In recent years, this method has been finding increased use
in the treatment of wastewaters for removal of salts (mine
waste effluents) and, especially, in regeneration of valuable
components from various spent process solutions and
electrolytes. Relatively high specific consumption of power
required for treatment of strong wastewaters, in many cases, is
compensated by the cost of regenerated products (acids,
alkalies etc). The method may be applied at low flow rates of
concentrated wastes.
Methods of regeneration of some electrolytes using
electrodialysis process have been developed by Institute
VODGEO.
While electrolyzing spent chromic acid solutions in the anode
compartment employing electrochemically active cation-
exchange membranes, cations of iron, trivalent chrome,
copper, which contaminate given electrolyte, are removed from
anode liquor.
The regenerated chromic acid solution is reused in the
process, metal cathodic deposits may be utilized.
Power required for regeneration of one cu.m. of spent
solution varies between 800-2000 kilowatt-hours depending on
the concentration of other impurities. The method is expedient
due to high cost of the products being regenerated (chromic
acids, copper as a metal).
Electrodialysis employing ion-exchange membranes allows to
regenerate inorganic acids and to recover metals from spent
pickling solutions. Thereby, 80-90% of acids used in pickling
processes may be regenerated and reused.
Power consumption required to treat one cu.m. of spent
pickling solutions is 1000-1200 kilowatt-hours.
Electrochemical regeneration of spent solutions, originating
from pickling products of copper and its alloys in sulfuric acids,
is carried out employing lead anodes and copper cathods at
current densities of 2 A/dm2 Thereby the consumption of
sulfuric acid is reduced by a factor of two or three during the
pickling process, and the volume of spent solutions to be
discharged is reduced by a factor of five-six.
Electrolysis of wastewaters using soluble anodes.
The main advantages of so called electrocoagulation method
over coagulation with addition of chemicals are: the apparatus
(electrolysis cell) employed for detoxification is more compact
and its operation is simple; detention periods are shortened;
feeding equipment is reduced or absent; solid phase in sludge
produced is reduced.
Due to electrolytic dissolution of anodes of steel or
aluminium the latter in the neutral or weakly alkaline media
form hydroxides.
As a result, coagulation process takes place and is analogous
to the treatment with adequate salts of iron and aluminium.
However, during electrocoagulation, liquid is not enriched with
anions and salt content doesn't increase, which is of
importance, if treated effluent is recycled in industrial water
supply, in comparison with conventional treatment with
addition of chemicals.
During electrocoagulation treatment of wastewaters, the
following electrochemical, phisicochemical, chemical processes
take place: 1) electrophoresis, 2) cathodic and chemical
reduction of organic and inorganic matter and formation of
cathodic deposits of metals; 3) chemical interaction between
ions of iron and aluminium, formed during the dissoltion of
anodes, and anions present in wastewaters (sulfides,
phosphates and others), resulting in the formation of insoluble
compounds; 4) flotation of solid and emulsified impurities by
hydrogen gas bubbles produced on cathod (electroflotation
process); 5) sorption of ions and molecules of dissolved and
emulsified impurities on the surface of iron and aluminium
hydroxides having considerable sorption capacity during
formation process.
The methods applied in combination, in a number of cases,
provide relatively high removal efficiency of dispersed as well
as some dissolved impurities. The efficiency appears to be
higher than that achieved while treating wastewaters with the
same doses of salt coagulants (estimated on the metal used).
Electrolytic coagulation in conjunction with electroflotation
(or alone) is, mainly, employed for removal of dispersed
impurities, which form stable colloidal systems in liquid, from
wastewaters. The process has limited application in removal of
dissolved impurities. Generally, these impurities form insoluble
34
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compounds (sulfide-, phosphate-, fluoride-ions) with ions of
iron and aluminium.
The steel anodes are effective in the removal of chromate-
ions, which are present in wastewaters, discharged from
various industries.
The removal of hexavalent chrome compounds from
wastewaters is based upon the chemical reduction of
bichromate- and chromate-ions by divalent iron ions, formed
during electrolytic dissolution of anodes as well as
hydroprotoxide of iron according to the following equations:
6FE2+ + Ci-,02- + I4H4
6Fe3++ 2Cr<++7H20 (3.1)
in acid medium
Cr207
2-
6Fe(OH)2
3Fe(OH)2
I4H+
->• 6Fe3+ + 2Cr1+ +7H20 in acid medium (3.1)
Cr2072- + 7H20 -» 6Fe(OH)3 + 2Cr(OH)3
+20H~ in weakly alkaline and neutral
Cr042- + 4H20
3Fe(OH)3 + Cr(OH)3
(3.3)
Electrolysis, under these conditions, may result in partial
reduction of chromate- and bichromate -ions resulting from
cathodic electrochemical processes.
Cr2072- + 14H+
Cr042- + 4H20 -
Fe3+ + e
Fe2+ + 20H
6e
3e
Fe2+
> 2Cr»+ + 7H20
Cr(OH)3 + 50H-
Fe(OH)2
(3.4)
(3.5)
(3.6)
(3.7)
During the electrolysis the increase in the pH and formation
of hydroxides of metals, ions of which are present in
wastewaters, take place. As a result, simultaneously with
chrome compounds are removed ions of other heavy metals,
which is rather considerable (in some cases removal efficiency
is high). The principle flow sheet for treating chrome containing
wastewaters is given in Fig. 2.
It is advisable to apply the process at hexavaient chrome
concentration up to 100 mg/l. At higher concentrations
consumption of metal increases, rapid passivation of surfaces
of steel anodes occur; power consumption increases
considerably.
At optimum pH value of 3-5 and concentration of Cr6+ of
50-100 mg/l, consumption of metallic iron is 2 parts per 1 part
of Cr6+ by weight, which is lower than theoretical value
calculated according equations (3.1), (3.2), (3.3).
In practice power consumption required for complete
reduction of hexavalent chrome appears to be close to the
theoretical value.
The consumption of sheets during electrocoagulation limits
its wide implementation. In practice only less than 80% of
metals of electrodes is utilized.
These disadvantages may be eliminated by modification of
apparatus used for electrocoagulation and wastewater treatment
schemes. D
Figure 2.
The Scheme of the Principal of the Treatment of Wastewater, Containing
Chromium, by Means of the Electrocoagulation.
I.—feeding of the wastewater;
2.—accumulator:
3.—tank for the preparation of the NaCI solution;
4.—the source of the constant current;
5.—electrolyser;
6.—settler;
7.—installation for the dehydration of sludge;
8.—treated water;
9.—sludge for the fault.
35
-------
Wastewater Treatment for Reuse
and Its Contribution To Water
Supplies
Howard P. Warner,
JohnN. English,
Irwin J. Kugelman,
EPA
Disclaimer
This report has been reviewed by the Municipal Environmental
Research Laboratory, U. S. Environmental Protection Agency,
and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the
U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
Foreword
The Environmental Protection Agency was created because ol
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution and it involves defining the problem,
measuring its impact, and searching for solutions. The
Municipal Environmental Research Laboratory develops new
and improved technology and systems for the prevention,
treatment, and management of wastewater and solid and
hazardous waste pollutant discharges from municipal and
community sources, for the preservation and treatment of
public drinking water supplies, and to minimize the adverse
economic, social, health, and aesthetic effects of pollution. This
publication is one of the projects of that research; a most vital
communications link between the researcher and the user
community.
The study summarized in this report evaluates a combined
biological/physical-chemical pilot treatment system designed to
produce a high quality reusable water. Process reliability is
established and effluent constituents are related to similar
materials identified in finished drinking waters.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
36
-------
Abstract
An 18 month study using cost effective municipal wastewater
treatment technology coupled with a computerized data
handling system, was conducted at the EPA/Washington, D.C.
Blue Plains Pilot Plant to obtain data on the safety of the
effluent for discharge upstream of drinking water intakes, and
for potential domestic reuse purposes. Treatment reliability was
demonstrated and performance results showed the absence of
virus in the effluent. Effluent concentrations of radioactivity,
trihalomethanes and other volatile organics, heavy metals,
pesticides, TOC, turbidity, general inorganic compounds, and
pathogenic indicator organisms were shown to be similar to
those found in finished drinking waters during the EPA
National Organics Reconnaissance Survey in 1975. The specific
organic compounds identified in the effluent are also present in
finished drinking waters. Effluent organic concentrates did not
exhibit mutagenic properties, and results of an 80 element
survey did not detect the presence of significant quantities of
any hazardous inorganic material. Effluent endotoxin levels
were comparable to levels in public drinking water supplies.
This report was submitted in partial fulfillment of contract
No. 68-03-0344 by the District of Columbia Pilot Plant under
the sponsorship of the U.S. Environmental Protection Agency.
This report covers the period from April 1975 to September
1976.
Acknowledgments
A project of this magnitude, which covers 18 months of pilot
plant operations, could not have been accomplished without
the assistance of the entire EPA-DC Pilot Plant staff.
Mr. Paul Ragsdale supervised the mechanics and
instrumentation personnel. Mr. Calvin Taylor served as chief
operator. Laboratory analyses were performed under the
direction of Mr. David Rubis. The efforts of all the D.C.
mechanics, technicians, crew chiefs, operators and laboratory
personnel are gratefully acknowledged.
Mr. Thomas A. Pressley and Ms. Stephanie G. Roan, On-
site EPA staff, performed the detailed organic identification
work and virus analyses were conducted by the Cincinnati
EPA Virology Laboratory under the direction of Mr. Daniel R.
Dahling.
Special thanks are due Mr. Thomas P. O'Farrell, past Pilot
Plant Chief, for his efforts in the early stages of the project
which enabled a timely completion of fabrication of the
treatment system.
Introduction
We are living in a Nation where millions of people are
presently reusing wastewater indirectly for domestic purposes.
Severe contamination of many surface supplies has occurred,
as evidenced by the identification of carcinogenic organic
materials in finished drinking waters, and increasing instances
of groundwater contamination are being found. There is a
concern on the part of health agencies in areas that use surface
' supplies for domestic purposes as to the potential hazards of
the present covert reuse of wastewater discharged upstream of
drinking water intakes. Since the typical wastewater treatment
plant does not remove all of the contaminants from the
wastewater there is a basis for this concern, and thus a need to
know the appropriate levels of municipal treatment to ensure
the safety of water supply intakes in the vicinity of the
discharges.
The concerns of health agencies where covert reuse is
prevalent are also receiving attention by health agencies in the
more arid areas of the U.S. where water utilities are proposing
the overt domestic reuse of wastewater to supplement depleted
groundwater supplies and unreliable surface sources. Concerns
about both covert and overt reuse are the same since the
problems and the research data required to solve the problems
are the same. The questions that need answers are:
• What are the health effects of the covert/overt reuse of
wastewater?
• What technology is needed to remove potential hazardous
materials?
The Environmental Protection Agency (EPA) through its
Municipal Environmental Research Laboratory (MERL) in
Cincinnati, Ohio is addressing the technology question by
characterizing the ability of municipal wastewater treatment
systems to remove pollutants of health concern and providing
knowledge of treatment system performance variability and
reliability.
A combined biological/physical-chemical treatment system
designed to produce a high quality reusable water has been in
operation at MERL's Washington, D.C. Pilot Plant for 18
months as part of a project that had the following objectives:
• Identification of specific pollutants in the final effluent and
evaluation of the performance of the individual processes in
removing these pollutants.
• Provide data on process and system performance variability
and reliability with respect to pollutant removals.
Conclusions
Performance results showed the absence of virus in the
effluent, and concentrations of radioactivity, trihalomethanes
and other violatile organics, heavy metals, pesticides, TOC,
turbidity, and microbiological parameters similar to those found
in finished drinking waters during the EPA National Organics
Reconnaissance Survey in 1975. The specific organic
compounds identified in the effluent are also present in finished
drinking waters. Effluent organic concentrates did not exhibit
mutagenic properties and results of an 80 element survey did
not detect the presence of significant quantities of any
hazardous inorganic material. Effluent endotoxin levels were
comparable to levels in public drinking water supplies.
Treatment reliability was demonstrated as evidenced by the
frequency distribution of the day to day concentrations of
chemical, physical, and biological materials remaining in the
effluent. In full scale facilities employing similar treatment
processes and located upstream of drinking water intakes, or
designed for domestic reuse purposes, reliability can be further
enhanced by in-plant storage facilities to provide flexibility,
process control instrumentation, and dedicated operating
37
-------
personnel. In planned reuse situations where a monetary value
is set on the water, or where enforced legal restraints are
placed on effluent quality reliability will become very good.
Description of Treatment System
The treatment system is located on the grounds of the
Washington, D.C. Blue Plains wastewater treatment facility
and is supervised by MERL staff and operated in cooperation
with the Washington, D.C. Department of Environmental
Services. The system treats degritted D.C. municipal
wastewater using a screening device to remove coarse
materials, lime clarification, dispersed growth nitrification, fixed
film denitrification, carbon adsorption, dual media filtration,
and chlorination for disinfection. This sequence of processes
was chosen because of past experience with the performance
of the individual processes and compatibility of the unit
processes when combined into a treatment system that could
produce a reusable high quality water from municipal
wastewater. Also, a similar treatment system was identified at
a workshop on "Research Needs for the Potable Reuse of
Municipal Wastewater" (1> as one of four treatment systems
that had potential as a cost-effective treatment for potable
reuse.
A schematic flow diagram of the treatment system is
presented in Figure 1 and the design and operating conditions
are summarized in Table 1. The system operates continuously
at 35 gpm (2.2 1/s). The backwash water from the
denitrification, carbon adsorption, and filtration processes are
returned to the influent of the lime clarification processes. A
portion of the sludges from the lime clarification and
nitrification processes are wasted to maintain process
equilibrium.
BACKWASH IANK
H.° §I LIME CLARIFICATION s'°«»°'
BACKWASH WATER FROM:
DENITR1FICATION COLUMNS,
CARBON COLUMNS,
AND FILTERS WASTE
POLYMER KO
FINAL EFFLUENT
Figure I.
Schematic Flow Diagram
The treatment system was operated on a continuous basis
with operators assigned to three, 8 hour shifts each day.
Samples were taken manually by the operators and composited
in refrigerated containers as required. Twenty-four hour
composites were taken 5 days per week and no sampling was
done between Friday 8 a.m. and Sunday 8 a.m. Other types of
Table 1
Design Data and Operating Conditions
Parameter
Raw Wastewater (Constant Flow)
Screening Device
Type
Size of Openings
Lime Clarification
Lime Dosage (pH 10.0) (as CaO)
FeCb Dosage (as Fe)
Hydraulic Loading Rate
Detention Time
Sludge Wasting Rate
Percent Solids in Waste Sludge
Nitrification (Suspended Growth)
Detention Time
MLSS
SRT
Air Requirement
Clarifier Overflow Rate and
Detention Time
Denitrification (Fixed Film)
Media Size
Specific Surface Area
Hydraulic Loading Rate
Methanol/NO3-N Ratio
Bed Depth
Detention Time (Empty Bed)
Operation
Granular Carbon Adsorption
Detention Time (Empty Bed)
Hydraulic Loading Rate
Columns in Series
Carbon Size (Filtrasorb 300)
Operation
Filtration with Alum and Polymer
Hydraulic Loading Rate
Dual Media
Coal 1.2-1.4 mm
Sand 0.6-0.7 mm
Alum
Disinfection with Chlorine
Detention Time
Residual
Value
35 gpm (2. 2 x
Bauer Hydrasive Model 552
0.040 in. (1.02mm)
200mg/l
I5mg/l
I050gpd/sq. ft. (42.8m3/m2d)
2.7 hr.
2% to 3%
1. 5% to 2.0%
3.5 hr.
200mg/l
8 day
1450 cu. ft./lb BOD O0.6m:l/ka)
526gpd/sq. ft. (21.4m:)/m2d) 2-3.6 hr.
3 to 6 mm
245 sq. ft./cu. ft. (900m2/m3)
5.9gpm/sq. ft. (4.1 l/m2s)
2:1 to 4:1
15ft. (4.6m)
9.5 min.
Downflow Packed Bed
35 min.
7gpm/sq. ft. (4.8l/m2s)
4
8 x 30 Mesh
Downflow Packed Bed
3 gpm/sq. ft. (2.04 l/m2s)
2.0ft. (0.61 m)
1.0ft. (0.30m)
5 mg/1
20 min.
I mg/l Free Available
sampling were also done manually by the operators as
required.
Establishing the reliability of any treatment system requires a
long-term program of routine monitoring of the system
performance. A mass of valuable data was obtained as a result
of this program and an efficient computerized data storage and
retrieval system was developed to sort large quantities of data
per month from 37 performance or process monitoring stations.
The data storage and retrieval system was designed for use on
the EPA UNIVAC 1110 Computer located at EPA Research
Triangle Park in North Carolina. All the programs run in batch
or demand mode. The system is modular in design to allow the.
addition and modification of programs without affecting the
system integrity. Data is entered into and withdrawn from the
computer using a terminal hookup. Statistical reports, data
listing, as well as data plots can be obtained as required by
project personnel to aid in establishing the system performance
credibility.
Performance
Virus
Virus in wastewater effluents are of concern to health agencies
dealing with the use of contaminated surface drinking water
supplies and proposed domestic reuse situations. For this
reason it is important that virus analyses be included in any
38
-------
reuse technology monitoring program. Virus and other
pathogens were monitored at various points in the treatment
system on three occasions over a three month period using
methods described by Rao, V.C., et al<2) and Wallace, C, et al
(3)
Samples of the raw sewage, finished effluent, and dual media
filtration effluent were taken during the first sampling period.
As shown in Table 2 animal viruses in raw sewage samples
ranged from about 7000 to more than 17,000 PFU/100 gal
(1,850-4,500 PFU/100 1). No animal viruses were observed in
the dual media filtration effluent before chlorination, or the
finished effluent following concentration of 100-150 gal (379-
5681) of each effluent.
Table 2.
Virus
Sampling
Period
1
2
3
Influent
1.850-4.500
4,500-18.000
7.400-18.000
PR
Nitrification
—
N.D.
N.D.
Animal Virus pfu/100 liters
SS
Filtration
N.D.
Chlorination
N.D.
N.D.
N.D.
Sample Volumes— 189 liters to 900 liters.
N.D.—None Detected.
During the second and third months samples of the raw
sewage, finished effluent and effluent from the nitrifying
activated sludge were taken. Animal viruses in the raw sewage
from 17,000 to 68,000 PFU/100 gal (4,500-18,000 PFU/100 1)
and from 28,000 to 68,000 PFU/100 gal (7,400-18,000 PFU/100
1). Animal viruses were not detected in the final effluent in
either sampling period. A total of 7 samples were concentrated
during these periods ranging in volume from 50 to 238 gal (190-
9001). During the last two sampling periods, effluent from the
nitrifying sludge system was tested on five occasions following
concentration of 40 to 160 gal (151-605 1) of each system. In
this phase of treatment, animal viruses still could not be
detected. Assays were carried out on solids remaining on
prefilters used for clarifying both the nitrification and final
effluents. Viable animal viruses could not be detected after
processing these solids.
Radioactivity
Samples of effluent were periodically taken for gross beta and
gross alpha analyses and the results are summarized in Table 3.
These levels are well below the maximum contaminant level
set forth in the EPA Interim Primary Drinking Water
Regulations <4) for radioactivity and they are comparable to
those reported in finished drinking water supplies (5)-
Table 4.
Volatile Organics
COMPOUNDS
(All Units
INFLUENT
Chloroform
Bromodichloromethane
Dib romochloromet hane
Bromoform
Carbon Tetrachloride
1,2-Dichloroethane
NUMBER
OF
SAMPLES
14
14
14
14
13
14
ARITH.
MEAN
13
0.9
5.9
<0.1
5.6
9.7
RANGE
4.44
< 0.1-4.5
< 0.1-23
< 0.1-0.2
< 0.1-32
< 0.1-134
Volatile Organics
Four trihalomethanes, carbon tetrachloride, and 1,2-
dichloroethane were determined in the influent and effluent
from individual processes on a twice per month basis to
determine the effectiveness of the treatment system in
removing these materials. A summary of the influent and
effluent concentrations of the compounds compared to the
range of concentrations found in finished drinking water
supplies is included in Table 4. Figure 2 shows the variation of
the volatile organics through each process. Although the
concentrations are quite low there is definite indication that
chlorination increases the quantities of each of the six
compounds.
Table 3.
Radioactivity
Sampling Period
1
2
3
4
Average in Drinking
Water*
Effluent Values pci/l
Gross Alpha Gross Beta
< 0.3 7.9± 0.9
< 0.5 8.1 ±0.9
< 0.5
< 0.5
5.5
7.4 ± 0.9
5.0± 0.9
2.9
* Summary of Interstate Carrier Water Supply Radionuclide Data "Preliminary
Assessment of Suspected Carcinogens in Drinking Water" EPA. December 1975.
Table 5 shows the results of analyses of other volatile
organics in the pilot plant influent and in the effluent from
various unit processes. The types of compounds and their
corresponding concentrations are similar to those present in
finished drinking water supplies (5). Blanks in the tables indicate
the compounds were below the detection limit of the GC/MS
technique used (8).
Toxicity Screening
Organic materials were concentrated from 500 gal (1,900 I)
samples of effluent using a reverse osmosis technique that
employed cellulose acetate and nylon membranes in series <7>.
The concentrate from each type membrane was extracted with
pentane or methylene chloride at acidic (pH 2) and neutral (pH
7) conditions. The separate extracts and a composite of the
extracts were tested for mutagenicity using the Ames
procedure <8) that utilizes in vitro microbiological assays with
strains of Salmonella Typhimurium TA 98 and TA 100. No
mutagenicity was detected as shown by the data in Table 6.
EFFLUENT
NUMBER
OF
SAMPLES
12
12
12
12
11
12
ARITH.
MEAN
8.0
5.4
5.2
2.6
1.0
0.5
RANGE
< 0.1-22
< 0.1-21
< 0.1 -28
< 0.1-23
< 0.1-5. 2
< 0.1-2.6
* FINISHED
DRINKING
WATERS
RANGE OF
CONCENTRATIO
NS
< 0.1-311
0.3-116
< 0.4-1 10
< 0.8-92
< 2-3
< 0.2-6
DRINKING
WATER
WASHINGTON,
D.C.
(DELACARLIA
PLANT)
41
8
2
**N.D.
N.D.
<0.3
* Based on 80 samples from National Organics Reconnaissance Survey—"Preliminary Assessment of Suspected Carcinogens in Drinking Water. Report to Congress".
EPA, December 1975.
** N.D.—None Detected.
39
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0 CHLOROFORM
• BROMOD1CHIOROMETHANE
X DIBROMOCHLOROMETHANE
A BROMOFORM
OCARBON THRACHLORIDE
• 1,2 DICHLOROETHANE
Q
Z
3
o
Q.
S
O
u
Z
o
oc
O
o
>
Table 5.
Volatile Organics in Process Effluents
TREATMENT PROCESS
Figure 2.
Removal of Volatile Organics.
ARITHMETIC MEAN . 0.720
OfOMflliC MEAN - 0.6IS
MEDIAN - 0.495
STANDAID DEVIATION - 0.745
O.OO01
2 S
0.05OO 0.30OO 0.7000 0.9500 0.9950
FRACTION EQUAL TO OR LESS THAN GIVEN CONCENTRATION
Figure 3.
Frequency Distribution of Effluent Mercury.
Compound
(Unit Mg/D
Influent
TR.*
TR.
TR.
4
TR.
TR.
10
1
Nitri-
fication
TR.
TR.
TR.
TR.
3
TR.
TR.
TR.
TR.
TR.
Denitri-
fication
TR.
TR.
TR.
TR.
Carbon
TR.
TR.
1
TR.
5
Chlorina-
tion
TR.
TR.
TR.
TR.
7
4
Drinking
Waler««
J
J
J
J
Acetaldehyde
Methanol
Acetone
Dichloromethane
Acrolein
Carbon Disulfide
Chloroform
Bromodichloro-
methane
,1,1-Tri-
chloroethane
Chlorodi-
bromoethane •
Benzene
Dimethyl disul-
fide
Toluene
N-Hexanol
Tetrachloro-
ethylene
Xylene
Alkyl benzene
Benzaldehyde
Carbon
tetrachloride
• TR.—Trace (< I /xg/l).
** "Preliminary Assessment of Suspected Carcinogens in Drinking Water," Report
to Congress. EPA. Dec. 1975.
TR.
TR.
TR.
TR.
TR.
TR.
TR.
TR.
TR.
TR.
TR.
2
Tr.
•Mutagenic
Potential
Table 6
Mutagenicity of Organic Concentrates
R.O. Membrane and
Solvent Fraction
Cellulose Acetate
• Pentane **N.D.
• Methylene Chloride Neutral N.D.
• Methylene Chloride Acidic N.D.
Nylon
• Pentane N.D.
• Methylene Chloride Neutral N.D.
• Methylene Chloride Acidic N.D.
Composite N.D.
* In Vitro with strains of salmonella typhimurium TA98 and TAIOO.
*» N.D.—None Detected.
Table 7
Results of Bacterial Endotoxin Testing"
SOURCE
ENDOTOXIN EQUIVALENTS
ng/ml
2.5-12.5
Blue Plains Reuse System
Public Drinking Water Systems
I 1.25
2 12.5
3 2.5
4 12.5
5 0.625
6 500.0
7 125.0
8 10.0
9 2.5
10
* Limulus Assay Procedure—Jorgensen et al.. Applied and Environmental
Microbiology. September 1976.
40
-------
Table 8
Heavy Metals
Final Effluent
Metal
(Unit-/ig/l) n Aril. Mean Range
Mercury 47 0.666 0.100-1.25
Cadmium 44 0.143 0.020-0.530
Selenium 38 4.76 2.00-5.00
Chromium 57 2.24 0.600-4.30
Lead 53 0.308 0.030-1.07
Manganese 60 7.96 1.40-20.0
Arsenic 56 2.25 0.300-6.00
Iron(mg/l) 227 0.0599 N.D.-0.810
Barium 49 82.3 3.10-200
Copper 56 4.86 1.40-21.0
Zinc 57 10.6 5.10-19.1
Boron (mg/l) 8 0.313 0.300-0.400
Flouride (mg/l) 62 0.722 0.380-1.10
Silver 49 0.134 0.009-0.400
Cyanide 32 4.23 1.00-9.80
Aluminum (mg/l) 210 0.251 N.D.-0.900
* "Preliminary Assessment of Suspected Carcinogens in Drinking Water" Report to Congress. EPA. December 1975.
** National Interim Primary Drinking Water Regulations, EPA. Federal Register. Vol. 40. No. 248. December 1975.
Wa
shington, DC
Drinking
Water'
. 0.5
50
1.0
10
20
EPA
Regulations**
2
10
10
50
50
50
1000
1.8 (fi 64°F
50
Table 7 shows the results of bacterial endotoxin tests on
effluent samples as compared to similar data from ten public
drinking water systems. These results were reported by
Jorgensen, J.H., et al<9) from studies in which they used a
Limulus assay technique for the detection of bacterial
endotoxins. The concentration of endotoxins in the Blue Plains
effluent is comparable to the concentrations in public drinking
waters.
Metals
Data on the metals present in the influent and effluent are
presented in Table 8 along with a list of the concentrations
present in the Washington, D.C. drinking water, and the levels
allowed in finished drinking water supplies as contained in the
"EPA National Interim Primary Drinking Water Regulations".
December 1975 I4). None of the effluent samples taken
exceeded metal concentrations cited in the EPA regulations.
The reliability of the treatment system to meet these
regulations is further demonstrated by the frequency
distribution of effluent mercury for the second four month
period of operation as shown in Figure 3. All twenty two of the
data values were less than the 2 /u.g/1 standard. The median
value was 0.70/Ag/l.
In addition to determining metals in samples of the AWT
system influent and effluent, the effluent from the lime
clarification process was monitored for a four month period
since previous data has shown that heavy metals can be
removed by this process. Table 9 shows that concentration of
metals in the influent, after the lime process, and in the final
effluent. It is evident that the lime process is primarily
responsible for the reduction in the metal concentrations.
Pesticides
Pesticide analyses were made on a less frequent basis than
were analyses for metals. The data presented in Table 10 are
based on samples taken twice per month. The levels in the
effluent are significantly less than the EPA standards for
drinking water that are listed in the table.
Table 9
Heavj Metal Removal by Lime Clarification
Metal
(Unit-^g/l)
Mercury
Cadmium
Selenium
Chromium
Lead
Manganese
Arsenic
Iron (mg/l)
Barium
Copper
Zinc
Boron (mg/l)
Fluoride (mg/l)
Silver
Cyanide
Aluminum (mg/l)
Table 10
Pesticides
Pesticide
Unit—^g/l (ppli
Aldrin
DDT
Dieldrin
Endrin
Heptaclor
Heptaclor Epoxide
Lindane
Methoxychlor
Diazin
Guthion
Malathian
Parathian
Influent
0.813
1.92
4.76
16.9
23.4
149
1.49
1.30
54.3
48.9
111)
0.250
0.701
3.98
5.80
Lime
Clarification
0.931
—
—
5.59
0.862
19.5
1.05
—
34.3
7.72
10.7
—
0.679
0.333
—
Final
Effluent
0.802
0.143
4.76
3.18
0.399
5.04
0.967
0.0467
27.2
5.66
12.6
0.313
0.724
0.0987
4.23
0.251
Effluent*
4
10
1
5
0.7
I
~t
40
5
200
10
10
*EPA
Regulations
200
4000
I05
* EPA National Interim Primary Drinking Water Regulations. Federal Register. Vol.
40. No. 248. December 24, 1975.
** Average of 4 data values for each pesticide.
41
-------
Table 1 1
General Organics
PARAMETER i
, .. ,. Arithmetic
(units— mg/l) N* Mean
TOC 231 74.1
COD 229 240
BOD 245 106
MBAS 13 g.92
CCE _ _
CAE _ _
Phenol (jig/I) 9 12.9
UV (5 290 mn (%T) — _
* N — number of samples.
General Organics
NFLUENT EFFLUENT
Standard Arithmetic Standard
Deviation N Mean Deviation
11.0 234 2.79 1.35
30.5 226 6.53 3.12
15.7 221 3.12 2.15
1.71 35 0.14 0.08
— 2 0.75 0.64
— 2 2.25 0.64
4.02 54 3.66 1.52
— 19 96.9 0.87
Figure 4 is a frequency distribution of 77 pieces of TOC data
A summary of various gross measurements or organics in the taken during the fifth and last period of operation. Included in
influent and effluent is presented in Table 1 1 and includes the the figure for comparison purposes is a frequency distribution
average of the parameters for a 14 month operation period. The of the TOC data from 80 drinking waters taken during the
treatment system is capable of reliably producing a high quality National Organics Reconnaissance Survey in 1975 <5). The
effluent on a continuous basis as evidenced by the TOC data
presented in Table 12 and Figure 4. The 311 pieces of TOC
data were grouped into 5 periods covering 18 months of
median TOC concentrations were 1 .5 mg/l for the drinking
waters and 2.5 mg/l for the wastewater effluent. The lower
levels of TOC in the drinking water data may be attributed to
operation and the arithmetic averages and standard deviations the cities in the survey using groundwater supplies.
were determined. The average TOC in the finished drinking
waters from 80 U.S. cities (5) is included in Table 12 for
comparison purposes.
Table 12
Variability of Effluent TOC
Number of Arithmetic Standard
4 Month Periods Samples Mean (mg/l) Deviation
1 58 2.26 1.31
2 64 2.35 1.00
3 69 3.72 1.59
4 43 2.67 1.50
5 77 2.68 1.02
Total 311 2.76 —
'Finished Drinking Water 80 2.21 Range
In an attempt to determine if additional TOC reduction was
possible grab samples of effluent were ozonated on three
separate occasions. An ozone dosage of 60 mg/I in the gas
stream was introduced into a 1 liter sample using the reactor
system described by Roan, S. <10). The sample was reacted with
the ozone stream for 60 minutes. The initial average TOC
concentration was 1.21 mg/l and the final TOC was 0.84 mg/l
which is a reduction of 30 percent. In addition, a short term
side stream study was conducted using a strong acid cation
resin in series with an intermediate base anion resin to
determine the removal of the remaining TOC by ion exchange.
These resins reduced the effluent TOC about 40 percent.
Figure 5 shows a graph of the removal of TOC by each of
the processes in the treatment system. Ninety-two percent of
• "Preliminary Assessment of Suspected Carcinogens in Drinking Water." Report to the TOC JS Amoved in the lime Clarification and nitrification
Congress. EPA, December 1975.
•^
_
f°0
U
O
*~
g
- ^^ -
^^*
^^/
t^^T^
^ff^^ /^
^f^ '
^/p '
: .s^' I /• :
'..^^ / -
/ rERIOD S
/ N»77
ARITHMETIC MIAN - J.6t
GEOMETRIC MEAN - 1.50
MEDIAN- J.50
STANDARD DEVIATION - L02
• PRELIMINARY ASSESSMENT OF CARCINOGENS
IN DRINKING WATER*. EPA. DEC 1975
HNISHSO DRINKING WAIER-IO QTIES
1 1 1 1 III 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 III 1 1 1 1
processes. The increase in TOC in the denitrification process
effluent is due to some leakage of methanol.
~a Table 13 shows the variability of the effluent COD for each
of the five operating periods and Figure 6 shows a frequency
distribution of 74 pieces COD data taken during the fifth
operating period. The median COD value is 5.61.
Table 13
Variability of Effluent COD
_ 4 Month Number of Arithmetic Standard
°o » Periods Samples Mean (mg/l) Deviation
2 g 1 58 5.28 2.55
"2 64 5.96 3.09
3 67 7.64 2.54
4 37 7.45 3.29
5 74 6.25 2.20
Total 300 6.45 —
_
o
O.OOOI 0.0020 0.0500 O.30OO 0.7000 0.95OO 0.9950 0.9999
FRACTION EQUAL TO OH LESS THAN GIVEN CONCENTRATION
Figure 4.
Frequency Distribution of Effluent TOC.
42
-------
Table 14
General Inorganics
PARAMETER
(unit—mg/l)
pH
Total Alkalinity
Conductivity (^mhos/cm)
TDS
Hardness
CaCo, Stability
Chloride
Sulphate
Calcium
Magnesium
Sodium
Potassium
* N—number of samples.
N»
2274
2435
137
35
176
178
INFLUENT
Arithmetic
Mean
7.20
125
283
115
31.2
6.47
Standard
Deviation
0.118
15.1
28.6
7.65
2.73
0.579
N
1081
980
830
210
40
40
158
122
218
224
228
21
EFFLUENT
Arithmetic
Mean
7.34
102
514
357
162
0.198
68.6
50.1
56.6
5.49
34.1
8.23
Standard
Deviation
0.146
12.1
36.0
31.6
7.18
0.394
4.56
3.83
4.40
0.481
2.94
0.318
General Inorganics
A summary of the inorganic constituents in the influent and
effluent is presented in Table 14. The arithmetic means and
standard deviations of each constituent are shown. Samples of
the effluent were checked for 80 elements by the Proton
Induced X-ray Emission Procedure
-------
Nutrients
The concentration of the phosphorus and nitrogen compounds
are shown in Table 16. Over 200 pieces of data were used for
each parameter in determining the means and standard
deviations. No attempt was made to completely denitrify the
effluent. The amount of methanol added to the denitrification
process was based on allowing 2 to 4 mg/I of NON in the
effluent.
Suspended Matter
Turbidity, and suspended and total solids data for the treatment
system influent and effluent are shown in Table 17. The
effluent turbidity level is within the requirements of the EPA
National Interim Primary Drinking Water Regulations(4) which
establishes the standard at 1 turbidity unit on a monthly
average basis. The variability of the effluent turbidity is shown
in Table 18. At the beginning of the last four months of
operation (period 5) it was noted that the turbidimeter had not
been properly standardized when making readings.
Implementation of the correct standardization procedure
accounts for the lower turbidity values during the fifth period.
Figure 7 is a frequency distribution of the 332 turbidity values
for samples taken in period five. Between 98 and 99 percent of
the values were less than the standard of one. The median
turbidity was 0.39 FTU.
Microbiological and Disinfection Parameters
Data on the chlorine dosage, demand, and free residual in the
effluent are included in Table 19 along with data on the
concentration of various pathogenic indicator organisms. The
free residual chlorine concentration of 2.23 mg/1 and low
turbidity of I FTU have combined to produce an effluent that
consistently meets the EPA Drinking Water Regulations.
Esthetic Parameters
The effluent had no odor when compared to samples of odor
free water prepared for the threshold odor test, and exhibited a
level of color equal to 3.5 color units based on the platinum -
cobalt standard. This data along with the average influent and
effluent temperature are shown in Table 20.
Table 17
Suspended Matter
PARAMETER
(unit—
mg/I) N»
Turbidity (FTU) —
Suspended
Solids 241
Volatile
Suspended
Solids 294
Total Solids —
* N—number of samples.
INFLUENT
Arithmetic Standard
Mean Deviation
109
84.0
21.3
N
1395
225
EFFLUENT
Arithmetic Standard
Deviation
Mean
0.884
1.02
16.0 —
209 362
0.448
0.954
30.4
Table 18
Variability of Effluent Turbidity
Table 19
Microbiological and Disinfection Parameters
PARAMETER
Chlorine Dosage mg/I
Chlorine Demand mg/I
Chlorine Residual (free) mg/I
Total Coliforms cells/100 ml
Fecal Coliforms cells/100 ml
Pseudomonas Aeruginosa cells/100 ml
Salmonella cells/100 ml
Total Count cells/100 ml
* N—Number of samples.
Table 20
Esthetics
PARAMETER N*
Temperature 382
INFLUENT
Arithmetic S
Mean' I
20.9
Odor (TON) —
Color (P-C —
units)
* N—number of samples.
»• N.D.—none deleted.
Arithmetic
Mean (FTU)
0.730
0.885
1.06
1.26
0.418
0.884
Standard
Deviation
0.256
0.800
0.464
0
0
rs
EFFLUENT
Arithmetic
N* Mean
2030
43
57
114
119
36
40
44
idard
ialion N*
50 320
35
84
4.35
1.83
2.23
0.11
0.17
0.81
0
66.8
.520
.182
~
Standard
Deviation
—
1.62
1.45
0.39
0.50
1.53
0
42.3
EFFLUENT
Arithmetic Standard
Mean Deviation
22.0
*»N.D.
3.52
2.32
N.D.
0.37
44
-------
ARITHMETIC MEAN - 6.25
GEOMETRIC MEAN - 5.9?
MEDIAN - 5.61
STANDARD DEVIATION - 1.70
I I I I I I I I I I I I I I I I I
O.OOOI 0.007O 0.0500 0.3OOO 0.7000 0.9500 0.9950
FRACTION EQUAL TO OR IESS THAN GIVEN CONCENTRATION
Figure 6.
Frequency Distribution of Effluent COD.
PERIOD S
N= 3J2
ARITHMETIC MEAN - 0.42O
GEOMETRIC MEAN - 0.386
MEDIAN - 0.385
STANDARD DEVIATION - 0111
I I I I I I I I I I I I I I I I I
III 1 I I I
0.0500 0.3000 0.7000 0.9SOO 0.9950
FRACTION EQUAL TO OR LESS THAN GIVEN CONCENTRATION
REFERENCES
"Research Needs for the Potable Reuse of Municipal Wastewater", EPA-
600/9-75-007, Dec. 1975.
Roa, V. C., et al.. "A Sample Method of Concentrating and Detecting
Viruses in Wastewater" Water Research 6: 1565-1576, 1972.
Wallace, C.. et al., "A Portable Virus Concentrator for Testing Water in
"S the Field" Water Reserach6: 1249-1256, 1972.
° "National Interim Primary Drinking Water Regulations", EPA, Federal
Register. Vol. 40, No. 248. Dec. 1975.
"Preliminary Assessment of Suspected Carcinogens in Drinking Water"
Report to Congress, EPA, Dec. 1975.
Bellar, T. A., & Lichtenberg. J. J.. "The Determination of Volatile Organic
Compounds at the /ig/l Level in Water by Gas Chromatography". EPA-670/
4-75-009, Nov. 1974.
Smith, J. K., et al., "Characterization of Reusable Municipal Wastewater
Effluents and Concentration of Organic Constituents", EPA Contract
Project No. 68-03-2090 (Final Report in review stage).
Ames, B. N., et al.. Proceedings of the National Academy of Sciences. Vol.
70, p. 2281. 1973.
Jorgensen, J. H.. et al.. "Rapid Detection of Bacterial Endotoxins in
Drinking Water and Renovated Wastewater", Applied and Fnviron.
Microb.. Vol. 32. No. 3, p. 347, Sept. 1976.
Roan. S. G.. et al.. "Laboratory Ozonation of Municipal Wastewaters".
EPA-670/2-73-075, Sept. 1973.
: Sims, P. "Proton Induces X-ray Emission Procedure". Dept. of Physics.
Purdue University.
Figure 7.
Frequency Distribution of Effluent Turbidity.
45
-------
Methods of the Varnish Industry
Wastewater Treatment
Vorobypva N.Y., Myasnikov I.N.,
Gandurina L.V., Kedrov Yu.V.
The varnish industry wastewater originates in the process of
the production of the varnish resin, varnish, enamel,
semiprocessed goods, and also in the process of the washing of
the equipment, package, floors, premises. The varnish industry
wastewater contains a great amount of dissolved and
emulsifiable organic substancies, coarse dispersed matter.
Pigments, alkali, phthalic and maleate anhydrids and their
acids, xylene, toluene, white-spirit, phenol, glycol, acids of the
fat row, resinous substancies. Besides, the varnish industry
wastewater is characterized by the changeable quantitative
composition of the pollution, which is determined by the range
of the products and the technology of the production. Table 1
gives the characteristics of the two main groups of the varnish
plant wastewater. To the first group belong effluents polluted
by the coarse dispersed matter. The second group of effluents
contains organic substancies in dissoluble and colloidal
condition. The source of the wastewater pollution is the
effluents of separate shops, in particular, of the varnish-boiling
shop, of the synthetic resin shop, of the varnish-oil shop, of the
package washing shop, of the siccative department. That is
why the problem of the treatment of the varnish plant effluents
is solved in two aspects: finding the highly effective local
methods of the wastewater treatment and working out perfect
technological schemes of the treatment of the varnish plant
sewage.
Table 1
The Composition of Wastewater of a Varnish Plant
THE FIRST GROUP OF
WASTEWATER
APPROXI-
INDICES BETWEEN MATELY
PH
Roughly dispersed
admixtures, mg/l
Substances, distracted by
chloroform, mg/l
Oil products, mg/l
CUO/chemical use of oxygen.
mg/l
THE SECOND GROUP
OF WASTEWATER
APPROXI-
BETWEEN MATELY
7.4-12
40-6400
56-810
10-75
9.6
1500
200
40
5.4-8.6
11-300
24-400
4-100
6.7
120
150
30
400-14000
1500
350-5000 4000
The most effective methods of the varnish plant wastewater
treatment are the physico-chemical methods, which meet the
following main requirements:
• high efficiency;
• compactness of the structure;
• the simplicity of the construction and its operation;
• an ability to exercise automatic control over the process;
• the technical and economical efficiency of the methods.
To the physico-chemical methods of the wastewater treatment
belong:
• settlement
• flotation
• filtering
• chemical fall out
• chemical oxydation
• adsorption by activated coal
• evaporation
• extraction by dissolvents
46
-------
Thus, the polyester resin industry wastewater treatment
includes the settlement from the mechanical admixtures and
catalytic oxydation by the temperature of 200-250° C /!/. The
copper-chromium contact is used as a catalyst. The purified
water is used in the recirculation water supply system. The
adsorption method is used mainly to further purify the
wastewater, from which suspended and emulsifiable
substancies were extracted. The activated coal, the peat, the
activated anthracite are used as sorbents. The settlement,
flotation and seepage are widely used to separate the coarse
dispersed matter and also to further purify the wastewater
preliminarily treated by coagulants and flocculants. For
instance, 50-70% of the coarse dispersed matter can be
extracted by the wastewater settlement. The results of the
kinetic research /pic. I/ testify to this.
300
3
o
o
4o
t, min
Figure 1.
Kinetics of coarse dispersed matter removal from varnish industry wastes.
To intencificate the process of the separation of the coarse
dispersed matter the multilayer settlers are used. The use of
such settlers makes it possible to greatly intencificate the
process of clarification, to increase its efficiency. To remove
the aggregative-stable colloid pollution, which can not be
removed by mechanical settlement, the method of coagulation
with the further separation of the coagulated pollution by
flotation is used. The example of the use of this very method is
the treatment of the wastewater of the industrial amalgamation
"Lakokraska". The wastewater treatment on the installation of
pressure flotation with the use of sulphate aluminium as
coagulant makes it possible to reduce the coarse dispersed
matter from 586-920 mg/l to 101-1% mg/1 and the substancies.
extracted by sulphuric ether, from 140-1408 mg/l to 32-255 mg/
I. In the process of the further treatment of the varnish plant
wastewater on the flotation-sandy filter the content of the
ether-extracted substancies reduces to 3-20 mg/l. The quality of
such water meets the requirements made to the water used in
the recirculation water supply system. It made it possible to
reduce the use of the fresh water approximately twice.
The detailed research, held by VNII VODGEO, concerning
the problem of the treatment of the varnish plant wastewater
by means of the coagulation, settlement and flotation has
shown that the efficiency of the treatment depends on the type
and dose of the reagent, the place of its lead-in, the mixing up
conditions, the flocculation conditions, the concentration of the
wastewater pollution.
The best results were achieved when the sulphate aluminium
/the dose is 70-150 mg/l/ in combination with the poliacrilarnid /
the dose is 1-2 mg/l/ used as the coagulant. As the result of the
research the optimume schemes of the plant wastewater
treatment were chosen. The preliminary settlement with the
further treatment of the water by reagents and the separation of
the flocculated flakes by means of pressed flotation is
necessary for the wastewater, containing a great quantity of the
coarse dispersed matter/pic. 2, scheme I/.
scheme I
2. 3
£ IL zZ Zf
^*2>
scheme 2
Figure 2.
Principal treatment schemes of varnish industry wastes.
I — influent
2.3 — addition of reagents
4 — settling tank
5.6 —mixing chamber
7 — flocculation chamber
8 — flotation chamber
9 — saturator
10 — pump
11 — air from compressor
12 — effluent discharge
47
-------
The greatest depth of the purification of the wastewater of
the II group was reached by the coagulation by the sulphate
aluminium together with the poliacrilamid, by the settlement,
and further purification on the pressure flotation installation /
pic. 2, scheme II. The effect of the purification of the
wastewater of the I group amounts by the suspended
substancies to 84-90%, by CUO /chemical use of oxygen/ to
50-80%. The effect of the purification of the wastewater of the
II group amounts by the suspended substancies to 98%, by
CUO to 50-64%.
The specification of the optimume parameters of the physico-
mechanical purification of the wastewater was held on the
experimental-industrial installation, the capacity of which was
5m3/hour. The experimental-industrial installation includes the
reagent economy, multistage thin layer settler and flotation
installation, consisting of the flotation chamber of the radial
type, the barbotage saturant and the compressor. The flotation
installation worked according to the scheme of the single-pass
flow /all the water was passed to the saturant/ and recirculation
/25% of the purified water was passed to the saturant/. The
pressure in the saturant was 5 atm. In the case of the single-
pass scheme the reagents were passed before the settler or
before the saturant, in the case of these of the recirculation
scheme-only before the settler /3/.
•f/ao
days
Figure 3.
Curves indicating the decrease in the coarse dispersed matter in the effluent
from the pilot-plant installation.
1 — influent
2 — after settling tank
3 — after flotalor
The experimental research, carried out on the experimental-
industrial installation, made it possible to find out the
optimum scheme of the physico-chemical treatment of the
package washing shop wastewater. The results are given in
Table 2.
One can see, that the maximume effect is reached, when the
reagents are passed to the settler and the flotation installation
works according to the recirculation scheme. Such scheme
provides the best conditions for the mixing up of the reagents
with wastewater for flocculation, and the adsorption of
pollution on them.
The single-pass scheme of the flotation wastewater treatment
when the reagents are passed before the saturant is less
effective because of the destruction of the coagulated pollution
in the pump or saturant.
In the process of the experimental-industrial tests it was
determined that the humidity of foam amounts to 88%, the
humidity of the sediment from the settler amounts to 80%.
On the basis of the research work, carried out by the VNII
VODGEO, the combined structure for the process of the
physico-chemical treatment of the wastewater is suggested /pic.
4/. The mechanical distraction of the coarse dispersed matter,
its mixing up with the reagents, flocculation and flotation
purification is carried out in this structure. To carry out these
processes there is the settlement zone, the zone of mixing
before and after settlement, the flocculation zone, the zone of
the flotation separation of the coagulated pollution.
<
is: Le.
/
0
1
;>
G
r
o
_
»y_
/£
Figure 4.
Scheme of the installation for physical-chemical treatment of varnish industry
wastewaters.
I — influent
2,3.
4
5,7.
8
6
9
10
II
— addition of reagents
— mixing chambers
— settling zone
— flocculation chamber
— flotation zone
— effluent discharge
48
-------
Table 2
The Results of the Wastewater Treatment Carried Out on the Experimental-Industrial Installation
HIGHLY DISPERSED ADMIXTURES CHEMICAL USE OF OXYGEN
THE THE
BEFORE AFTER TREATMENT BEFORE AFTER TREATMENT
TREATMENT TREATMENT EFFECT TREATMENT TREATMENT EFFECT
THE WORKING REGEME MG/L MG/L % MG/L MG/L %
I. The single-pass scheme
a) the reagents are passed before the saturant 114-5080 12-200 69-98 250-1330 240-440 65-67
b) the reagents are passed before the settler 120-3230 15-150 70-99 612-2150 342-1000 30-75
2. The recirculation scheme, when the reagents
are passed before the settler 1150-6000 20-100 93-99 1400 110 92
The principle of the clarification of the water in the thin layer REFERENCES
is used to intencificate the settlement. The process of the A v. Sacharov. "The wastewater treatment and gas sweetening in the
clarification is carried out in the shelf nozzle of the single-pass varnish industry." CHIMIYA Publishing House. M., 1971.
type. The construction of the nozzle provides the even ..-.OIL ..-n. u -i A ,u • •• A
.. ., . - . ,, .... ; _ , . . V.S. Narysev. A.F. Stulakova, The varnish materials and their use. 6.
distribution of the flow in it without the use of the special 71 1974
water distributive arrangement. The mixing up chambers and
the flocculation chambers are equipped with the mechanical L.v Oandurina. I.N. MX^ "ikov YU.V. Kedrov. ••Chemical and oil
... , . •,,.,, • machinery engineering. TSINTYchimneftemash. 3.6. 1977.
mixers, which make it possible to provide the optimume
conditions to carry out the process and to reduce the hydraulic
losses.
The flotation chamber of the horizontal type is equipped with
the arrangements for the even distribution of the flow in the
structure and the arrangements for the distraction of the
surface foam and the settled sediment. The combined structure
has the equipment for the production and dosing of the
reagents, and the feeding of the recirculating expenditure of the
water to the flotation chamber.
So, the use of the physico-chemical methods of the
purification makes it possible to get the purified water of the
required quality, which meets, in most cases, the standards for
the reuse of wastewater in the recirculation water supply
systems. D
49
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Training for Use of Advanced
Facilities and Equipment for
Wastewater Treatment
Frank P. Sebastian, E. A. Doodeman, John P.
Micketts, Envirotech Corporation
Introduction
This paper will address one of the primary reasons for
inadequate performance of wastewater treatment facilities:
shortages of adequately trained operation and maintenance
personnel. It will review some of the training programs and
funding currently available through the United States
Environmental Protection Agency. It will also describe
Envirotech's Environmental Operating Services group method
of training new or inexperienced personnel in the operation and
maintenance of sophisticated waste treatment equipment and
systems. Finally, some specific examples of Envirotech's
successful involvement in the training of personnel and
operation and maintenance of two sewage plants will be given.
Legislative Background
The Federal Water Pollution Control Act (PL 92-500)
established goals for the national water quality program. The
Act was amended on October 18, 1972 to add a broad range of
authorities and major new programs to further these goals.
Since the enactment of PL 92-500 a large amount of federal
funds has been invested in new wastewater facilities. The
Federal Government and the municipalities had not been
providing sufficient funds for operator and management
training, however, to operate and maintain these new
wastewater facilities. This inadequate funding has created a
shortage of competent and qualified personnel at all levels
which in turn has led to operating problems of wastewater
treatment plants. Therefore, many plants are operating below
design efficiency.
Clean Water Report
EPA is required under PL 92-500 to conduct an annual survey
and report to Congress on the efficiency of federally funded
municipal wastewater treatment facilities. Findings of EPA
operation and maintenance inspections and evaluations of
existing wastewater treatment facilities are reported each year
in the Clean Water Report to Congress. The results of the
1973, 1974, and 1975-6 surveys show that one third of all
plants are operating below design BOD-removal efficiency.
Other deficiencies that have been identified are:
1. Inadequate laboratory testing, controls, and reporting by
States and municipalities.
2. Inadequate operation and maintenance management.
3. Unavailability of operation and maintenance manuals for a
high percentage of all plants in the surveys.
4. Inadequate training delivery systems.
5. Inadequate inspection follow-up to determine the nature of
plant deficiencies and needed assistance.
6. Low level of public awareness of, and support for, improved
municipal treatment plant performance.
These problems can virtually all be traced back to shortages of
adequately trained operation and maintenance personnel.
In an effort to correct these deficiencies EPA has been
conducting several training courses in the wastewater treatment
area through intensive one-week programs. EPA has also made
50
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monies available for the construction of State training facilities
to train operation and maintenance personnel. Additionally,
EPA has awarded several grants to the states, universities and
other training institutions to support operator training, as well
as training for treatment works operations and maintenance.
Grants awarded under Section 104 of the Water Pollution
Control Act represent a large part of EPA's funding to help
states and local governments in their training programs. EPA
has also been successful in having monies allocated by prime
sponsors under the Comprehensive Employment and Training
Act of 1973 for the employment and training of persons in the
water and waste water fields.
EPA Guidelines
In recognition of the need to place increased emphasis on the
effective operation of new waste treatment facilities constructed
with Federal grant monies, EPA in September of 1976
published guidelines to permit federal funding of sewage
treatment plant start-up costs. The following start-up services
were identified as eligible for Federal funding:
1. Training of plant operation and maintenance personnel
necessary to operate specific treatment processes used in the
facility.
2. Providing expert operational assistance for adjusting and
"fine tuning" of the treatment process and equipment to
optimize performance, safety and reliability under actual
operating conditions.
3. On-site training and instruction of plant personnel to insure
that the sampling and laboratory testing needs are fully
understood.
4. Training of the operation and maintenance staff to insure
establishment of a maintenance management system as outlined
in the plant's operation and maintenance manual.
5. Training of plant personnel to insure implementation of a
records management system as detailed in the operation and
maintenance manual.
6. Revision of the operation and maintenance manual based on
actual operating experience obtained during the start-up period.
To be eligible for Federal money, the start-up services must
be provided by thy grantee's consultant or appropriate
manufacturer or vendor. Subagreement covering start-up
services would be prepared on a direct cost reimbursable basis.
Funding of start-up services would generally be available for
two to three months, the guidelines say. For large or complex
systems where several seasons are needed to determine plant
performance, however, funding may be allowed for twelve
months. Grant eligible start-up services are expected to average
90 man-days but provisions for up to 300 man-days have been
made depending on the size and/or complexity of the plant.
Federal start-up funds would not be available for entry-level
training or operator improvement training. Cost of off-site
training and/or orientation programs would also be ineligible for
federal funding. Normal operating and maintenance costs of the
municipal waste treatment facility, as well as wet and dry
equipment facility testing, are not grant eligible either.
Envirotech's Environmental Operating Services
Recognizing the lack of consistent performance of solids
handling systems and advanced wastewater treatment
processes, Envirotech formed an Environmental Operating
Services Group which assumes complete responsibility for
start-up assistance, operator training and maintenance control
to insure equipment start-up and performance to design
standards.
The Operating Services group provides the technical
expertise necessary to start-up, operate and maintain
wastewater treatment plants. In providing a link between
design and operation Operating Services can reduce start-up
problems; maintain plant operations at required performance
levels; build a trained team of knowledgeable, skilled operators;
reduce operating costs; and increase equipment life. These
results are accomplished through implementation of an
organized training program. Appended to this paper is a step-
by-step training program outline which has been used
successfully by Envirotech in training personnel for the
operation of advanced sludge processing equipment.
The Operating Services operations coordinator, supported by
process, equipment, and computer experts, can provide the
following services:
1. Rapid "on-stream" operations.
2. Consistent and optimum process performance.
3. Computerized management information systems to monitor
and analyze unit processes performance, budgets, manpower
allocation, and equipment maintenance.
4. On-site personnel training for up to one year, including
classroom training; laboratory training; simulated safety and
emergency drills; computer training; testing and evaluation of
the operator's aptitude, performance and progress; and
demonstration of preventive maintenance programs.
5. Documentation, including step-by-step procedures based on
twelve months of actual performance.
The advantages of the Operating Services training program are
many. They include:
1. Protection of EPA investment through
A. Effective preventive maintenance program day one
B. Early achievement of design capacity
C. Avoidance of consequence or trial and error learning.
2. Achievement of effluent quality on routine basis by
A. Liquid treatment objectives
B. Air pollution requirements
C. Avoidance of by-pass, upsets and odors
3. Optimization energy and fuel consumption by
A. Dewatering and incineration system
B. Wet encl./dry encl. balance.
There are additional advantages to the one-year Operating
Services training program as compared with the three or six
months program:
1. Allows greater sewage loadings due to collection systems
completion.
51
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2. Provides the seasonal variations to be encountered.
3. Allows initial personnel turnover which occurs during the
first three months.
4. Provides an adequate period of debugged operation.
5. Allows for critical annual maintenance activities not available
within six months.
6. Cost approximately 30% more than six months program.
Case Histories
In the State of California Envirotech's Environmental
Operating Services training programs have helped treatment
plants in the City of Burlingame and the Fairfield-Suisun
District meet air quality standards set by the State and the Bay
Area Air Pollution Control District, respectively.
The Burlingame plant was originally installed in 1934 and
upgraded in 1968 to provide secondary treatment and a partial
effluent polishing. The State's effluent quality standards were
not consistently met by the city's sewage treatment plant. One
of the major problems the city was faced with was the lack of
personnel experienced in the operations of advanced
wastewater treatment facilities. -
The city decided to bring the Operating Services group in to
resolve its manpower shortages and bring the sewage treatment
plant's operations up to standards. They were able to bring
about a 51% and 27% improvement in the BOD and SS
removals, respectively, and an 89% reduction in the effluent
coliform count.
This was caccomplished by first of all transferring most of
the plant's staff to Envirotech's payroll. The field team was
supported by a home-office group which had computerized
data analysis and reporting procedures at its disposal. A
computerized preventive maintenance program was developed
which gave thorough attention to tight process control. The
city adopted several recommendations which resulted in
upgrading several unit operations, such as: repair of the
primary clarifier; alteration of the primary clarifier grease
skimmer and pump station operations; modification of the
primary sludge wasting schedule; adjustment of the mechanical
aerators; and revamping and unfreezing of the sludge uptake
tubes in the final clarifier.
Finally, the Operating Services group was able not only to
resolve the plant's manpower shortages and bring the plant's
operation up to design standards, but plant performance
actually exceeded the consultant's design criteria.
In January 1974 the Fairfield-Suisun District signed an
operation and maintenance contract with Envirotech for
seventeen months in an effort to solve some of the major
problems that were plaguing the District's sewer plant. For
example, the plant consistently failed Bay Area Air Pollution
Control District limitation tests; exhaust scrubber emissions
were exceeding standards by 300%; and the plant was unable
to handle the sludge volume and extremely foul smelling.
The plant's operating staff was transferred to Envirotech's
payroll. Trouble areas were identified and plans for corrective
action were developed. Fine tuning adjustments and
improvements to reduce emission proposed by the operations
and maintenance group were made, and, as a result, the plant
was able to meet Air Pollution District standards. The solids
handling problem was resolved by clearing blocked sludge lines
and eliminating recycling of scrubber ash. These and other
improvements resulted in a 48% increase in solids handling
capacity, and the plant was able to incinerate all sludge on a
40-hour week schedule rather than operate a 90-hour schedule.
Dramatic improvements were also accomplished in the
efficiency of the oxidation ponds. Performance objectives were
met and improved efficiency will protect the equipment life. A
Fairfield-Suisun Sewer District Board member had the
following to say about the results of the operation and
maintenance contract: "Rather than abrogating our
responsibility as sewer board members, the decision to use an
external operations and maintenance service has given us
greater executive control. No longer embroiled in day-to-day
operational problems, we can turn our attention tc the major
policy considerations and long-range planning necessary to
assure the welfare of our citizens."
Conclusion
As mentioned earlier, the effective operation of a wastewater
treatment plant depends on the knowledge, experience and
general capabilities of its personnel. Furthermore, both EPA
and private industry recognized the need to place increased
emphasis on the effective operation of new waste treatment
facilities constructed with Federal grant funds. The EPA
directive that permits federal funding of sewage plant start-up
costs has gone a long way toward establishing a more effective
transition from construction to operation of new wastewater
plants. In this same connection, Envirotech's Environmental
Operating Services program has proven to be highly successful
in the training of treatment facility staff and the complete plant
operation and maintenance. All plants operating under
Envirotech direction have met State effluent quality
requirements since the beginning of operational responsibility.
In addition, with proper operations and a daily on-the-job
training program operating costs are reduced, improved
operating performance is achieved, along with increased
equipment life. D
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Methods of Improvement of the
Secondary Settling Tanks Operating
Efficiency
Skirdov I.V., Koltsova S.I., Morozova K.M.
Secondary settling tanks of various types are widely used in
the system of facilities for biological treatment of waste waters.
They perform several functions: separation of mixed liquor,
clarification of supernatant and thickening of settled sludge.
These functions must be interrelated in such a way as to
ensure the necessary degree of the returned sludge thickening
sufficient for maintaining a given concentration of biomass in
aeration tanks at the lowest content of the effluent solids.
All other conditions being equal (such as the sludge volume
index (SVI), the sludge concentration in the aeration tank, and
the wastewater temperature) SS concentration in the effluent
depends on the hydraulic conditions in the settling tank
ensured by the type of sludge distributing and water collection
devices.
In practice of the treatment facilities construction in the
USSR vertical, rectangular and radial settling tanks are
employed. Schemes of these facilities are given in Fig. 1.
Vertical settling tanks are used at designing the treatment
facilities of low capacity while radial and rectangular ones are
used at aeration stations of medium and high capacity. Radial
settling tanks are practiced on the largest scale; they are
reliable in operation, sludge suckers or sludge scrapers provide
systematic sludge removal from the unit. However, radial
settling tanks have unsteady turbulent conditions subjected to
the influence of density and convective flows. These
disadvantages of radial settling tanks become redoubled during
separation of mixed liquors which density is higher than that of
the effluent in the settling tank.
Studies of hydraulic conditions of radial secondary settling
tanks were carried out at the Institute "VODGEO" during
investigation of a number of municipal and industrial treatment
facilities using the method of tracing by a fluorescent and a
radioactive isotope. The analysis of the obtained data permitted
an evaluation of the degree of hydraulic imperfection of settling
tanks. For radial settling tanks 20-40 m in diameter the
efficiency of the volume usage expressed by the relationship
between actual and designed retention time is equal to 0.3-
0.45. It means that 55-70% of the settling tank's volume are
occupied by practically stagnant zones.
Distribution of SS concentration in the settling tank's volume
(see Fig. 2), when in the central part SS concentration is 2-3
times lower than in the working flow from the settling tank,
and is indicative of the imperfection of hydraulic conditions. It
indicates that the upper central part is semi-stagnant. The
working flow is carried by the density flow down to the bottom
and, when moving towards the periphery, occupies
approximately '/:« of the tank's volume. Having reached the
edge of the tank at a high speed the working flow reflects and
generates the intensive circulation and the counter flow in the
upper part of the settling tank. In the vortex zone under the
collecting weir the increased SS concentration is observed,
with some part of SS being carried out with the effluent.
Density flows also render a pronounced effect on the
hydraulic conditions of vertical settling tanks. Having entered
the unit mixed liquor is spreading about the more thickened
sludge blanket, strikes against the edge and generates a circular
flow, which rapidly reaches the surface of the settling tank, and
the working flow overflows into the collecting trough. The
53
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a-' Radial settling tank
b} VertixJki settling tank
?ci) Rectangular settling tank
Figure 1.
Diagrams of secondard settling tanks.
4567
distance from the centre,m
8
10
Figure 2.
Field of concentrations in a radial settling tank. D - 20 m.
54
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efficiency of the volume usage of vertical secondary settling
tanks is equal to 0.25-0.3. The characteristic feature of
standard constructions of these facilities is the sludge
deposition on the slopes and in the corners of sludge hoppers
which sufficiently hampers the maintenance.
To a certain extent the negative effect of density flows is
characteristic of rectangular secondary settling tanks.
Drastic improvement of hydraulic conditions of secondary -
settling tanks is possible by two ways: 1) by reduction of the
difference between densities of feeding mixed liquor and
detained influent in the settling tank and 2) by employment of
rotating sludge distributing devices when the density flow is
eliminated by the velocity of the distributing device moving in
the opposite direction. The first method can be realized by
mixed liquor feeding directly into the sludge blanket.
After preliminary researches carried out on the model of the
settling tank this, method was verified at one of the operating
secondary settling tanks installed at treatment facilities of a
chemical complex. With this purpose one of the conventional
settling tanks was transformed into a tank with the rotary
bottom distributing device and developed surface water-
collecting device. The scheme is given in Fig. 3. Mixed liquor
is fed by means of a sag pipe 1 to the central rotating chamber
2. The chamber is connected with two sludge distributing pipes
located near the bottom of the tank. Sludge distributing pipes
Figure 3.
Settling tank with the rotating sludge-distributing device and developed water
collecting device.
are provided with outlets 4 near which jet-cutting segmental
diaphragms 5 are installed. Jet-guiding blades 6 are fixed on the
pipe behind the outlets. Thickened and settled activated sludge
is collected by two sludge suckers 7.
The clarified effluent collection is realized by four radially
located submerged pipes 8 connected with the rotating central
chamber 9 for clarified water. Rotating parts of the central
chamber are conjugated with the lower parts by means of air
valves 5 constantly fed by air. The excess air is discharged to
the atmosphere through special pipe sockets. The design of
water collecting and sludge distributing devices provides equal
detention time of each separate jet. Rotation speed of the
sludge sucker is 17.5 rev/min.
The settling tank with the rotating bottom distributing device
operates steadily at the variations of the hydraulic conditions
from 0.5 to 2.1 m/h. Effluent solids do not exceed 10 mg/l.
Within the period of investigations the sludge concentration in
the aeration tank varied from 1.1 to 1.6 g/1 and the SVI was
equal to 96-166 cm-Vg. The highest load by the solid phase was
3.2 kg/m2 hour.
Studies of hydraulics and the field of concentrations have
shown the absence of density flows in the settling tank. The
efficiency of the settling zone usage is 0.85-0.95.
The automatic system of stabilization of sludge and water
levels in the settling tank sufficiently simplifies the maintenance
of the unit.
The investigations and the experience of the radial settling
tanks maintenance proved the presence of semi-stagnant zones
(in the central part of the unit) and vortex zones with high
velocities caused by the effect of density flows. These
phenomena were studied at radial settling tanks of various
diameters: 20. 24, and 40 m. The SS concentration in the
central part of the settling tank is 2-3 times lower than in the
effluent. The same situation was observed during investigations
of vertical settling tanks.
Technological parameters of operation of various secondary
settling tanks may be compared by using the following
relationship:
C, = f(qr. ICa).
where C—effluent solids, mg/l
I—sludge volume index, cnr'Yg
Ca—sludge concentration in the aeration tank, g/1
Product IC0 is the generalized criterion characterizing settling
properties of various activated sludges. The graphical form of
this relationship for secondary settling tanks is given in Fig. 4.
It is seen from the Figure that the settling tank with the bottom
distribution is the least subjected to the influence of the
hydraulic load variations. These facilities steadily operate
within the load range from 0.1 to 0.48 nv'/m2 hour while the
other types of facilities at the normal effluent solids do not bear
the loads higher than 0.2-0.3 nrVm2 hour.
Higher operating data of settling tanks with the bottom
distributing device are ensured by the peculiarities of their
hydraulic conditions which make the conditions of turbulent
and gravity agglomeration close to optimum ones. These
facilities can be used with high MLSS concentrations (3-5 g/1)
when the effect of density flows becomes very considerable.
55
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?°
I 2 34 5678 9 rO ff <2 13 f4 *5 (6
Figure 4.
•Field of concentrations in a settling tank with the bottom distribution.
.-1
^ 50
s
G
e
3 ^n
53
4>
0
•+» 30
fl
•H
§ :
•H
nccntra
3 :
o
CO
to
0
a
K
i
c.
f
7/
^
_4 A-
a
X
- V ~
X
- -"A"
^3
"^
0,10 0,20 0,30 0.40 0,50 O^
loadine by the voluae concentration, a-'/.^i-.-u
Figure 5.
Sludge content in the effluent from secondary settling tanks of various types
depending on loading by the volume concentration.
1—vertical settling tanks, 2-3—radial settling tanks
4—settling tank with the bottom rotating distributor.
Conclusions
1. The hydraulic conditions of the secondary settling tanks
significantly affects their efficiency of operation. Due to the
density flows in vertical and rectangular settling tanks the
efficiency of the volume usage does not exceed 40%.
2. Elimination of density flows with the help of rotating
distributing devices will permit to increase the efficiency of the
volume usage up to 80-90%, the highest effect can be reached
by using bottom rotating distributing devices.
3. Improvement of hydraulic conditions of secondary settling
tanks will permit to increase their capacity. Thus the hydraulic
load on settling tanks with the bottom rotating distributor
reaches 2.2 m3/m2/hour at normal effluent solids up to 20 mg/1
which exceeds the load on radial settling tanks almost 2 times.
4. Operation of new secondary settling tanks was tested under
full-scale conditions. These facilities are recommended for
installation at a number of treatment plants. Their use at
treatment plants with capacity of 100,000 m-Vday will give the
economic benefit of 140,000 rubles per year. D
56
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Contractor Evaluation for
Ozonation of Wastewater
Edward J. Opatken,
Albert D. Venosa,
Mark C. Meckes,
EPA
Ozone is now in use as a waste water disinfectant. Up to 1974,
chlorine was used exclusively for disinfecting wastewaters
within the United States. Since that time, Indiantown, Florida
has practiced disinfection with ozone, a little later Woodlands,
Texas, and recently Estes Park, Colorado. The Meander Water
Pollution Control Facility, near Youngstown, Ohio, is
undergoing start-up of an ozone disinfection process and there
are several facilities under construction and a considerably
larger number under design. But if we look closely at the first
four systems I mentioned, three in practice and one undergoing
start-up we find that each system has a contactor that differs
from the other three. Each system is looking for that economic
edge that will place it in an advantageous position in regard to
its competitors.
And I agree that there are significant economic and sales
benefits that can be reaped from an optimum gas/liquid
contactor. The problem is to determine reliably which
contactor yields the most economical system for ozone
application.
A project was initiated at the Robert A. Taft Center in
Cincinnati to evaluate general type liquid-gas contactors. Five
generic contactors were selected as representative of typical
gas-liquid devices. These contactors are:
Gas-Liquid Contactors
1. Packed Column
2. Jet Scrubber
3. Bubble Diffuser
4. Pressure Injector
5. Turbine Agitated Reactor
Four of the above five contactors are in use today. The
packed column is at Woodlands, TX, the bubble diffuser at
Estes Park, CO, the pressure injector at Meander, and the
stirred reactor at Indiantown, FL.
With the selection of these contactors, ground rules were
established to insure that a comparative evaluation will be
conducted with minimal bias. These rules are:
I. The liquid flow will be fixed at 75 1/min and the 5 contactors
will be designed for this liquid flow rate.
2. Parallel evaluation—the same quality wastewater effluent
will be fed to the contactors at the same time, to neutralize the
effect of a changing wastewater.
3. Four contactors will be evaluated against the same
contactor, in our case, the packed column was designated as
the standard and performance will fall above or below the
standard.
4. Experiments will treat both contactors alike, that is, same
ozone dosage, same ozone concentration, same gas and liquid
flows.
5. Performance evaluation will include ozone transfer, ozone
utilization and reduction of total and fecal coliforms.
Lets now look at a flow schematic of the pilot plant, and
follow the wastewater as it flows through the system.
During the first few months of the project, effluent from the
Muddy Creek Wastewater Treatment Plant served as the
wastewater source for the ozone disinfection studies. This
plant, operated by the Metropolitan Sewer Board of Greater
57
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Cincinnati, is a conventional activated sludge system treating
approximately 57,000 nv'/day of domestic wastewater.
On the day of an experiment, 20 m:i of Muddy Creek effluent
were drawn into a tank truck and transported to the pilot plant.
The effluent was pumped from the tank truck and split into two
lines. Both lines were suitably valved to allow for any desired
flow configuration. One line passed through a rotameter and
control valve and finally into the top of the packed column.
The second line was fed into a pump, where the pressure was
boosted to 380 kPa. The wastewater then flowed through a
rotameter and into the jet scrubber.
Using the above mode of operation, an entire series of
experiments were performed on each contactor separately. This
experimental arrangement, which was essentially a batch
operation, permitted the same wastewater to be pumped to
each ozone contactor without the need for parallel,
simultaneous operation.
Secondary effluent was also obtained from the conventional
activated sludge pilot plant located at the Robert A. Taft
Laboratory. The raw wastewater entering the plant was of
mixed industrial and domestic origin ."'Effluent from the final
clarifier was split between the two contactors simultaneously
and the flow was monitored by rotameters. An optional multi-
media pressure filter was available for removing suspended
solids from the effluent prior to splitting the flow. Data
obtained under this arrangement were collected with both
contactors operating in parallel as specified in the ground rules.
Ozone Generation
The ozone generator was capable of producing ozone at a
maximum rate of 3500 mg/min. Since the pilot facilities were
designed for evaluating two contactors in parallel, the
maximum applied dosage per contactor was approximately 25
mg/l.
Service air from the Robert A. Taft Laboratory, supplied at
a pressure of 620 kPa, served as the source of air for ozone
generation.
The air was filtered for removal of particulates and
lubricants, then dried by adsorption of water vapor on
activated alumnina. The dryer consisted of two parallel dryer
beds, each containing 8 kg of activated alumina. The process
air was passed through one of the dryer beds, where the dew
point was lowered to -70° C. Approximately 15 percent of the
dried air was returned for regenerating the alumina in the other
dryer bed. The dryers then automatically reversed their
functions, placing the regenerated bed on line for drying air
while the other bed underwent regeneration. The dried air was
then filtered for removal of any carry-over adsorbant and
monitored for dryness by an in-line dew-point meter.
The dried air was reduced in pressure from 620 kPa to 60
kPa and then split into two lines, each equipped with a
rotameter and valve for flow control between 75 and 5001/min.
The gas then entered the dual ozonator, which was air-cooled
and contained six plates per unit. Power was applied between
200 and 2000 watts, depending upon the ozone concentration
and air flow desired for the particular experimental run. The
temperature of both ozone-enriched gas streams were measured
upon exiting the ozonator. The two streams were recombined
to obtain a homogenous mixture and then split before entering
rotameters with a range between 20 and 130 1/min. After the
rotameters, separate gas lines fed the packed column and the
jet scrubber.
Packed Column
The packed column was a 230 mm diameter glass column 3.1
m in length. The packing consisted of either 13 mm or 25 mm
ceramic intalox saddles. A teflon redistributor plate was located
midway in the column to redirect the liquid towards the center
of the column. Secondary effluent entered the top of the
column and exited at the bottom. The residence time of the
secondary effluent was 20 seconds at a flow rate of 75 1/min.
Ozone was injected at the bottom of the column, flowed
upward and countercurrent to the secondary effluent, and
exited at the top. Pressure taps were located in the gas line at
the bottom and top of the column for determining the
differential gas pressure during an experimental run.
Jet Scrubber Contactor
The jet scrubber was a stainless steel liquid-gas contactor in
which secondary effluent was pumped through an orifice into a
300 mm diameter chamber. The resulting pressure drop of 380
kPa caused minute droplets to form. The ozone entered near
the orifice and both components (secondary effluent and ozone)
flowed concurrently down the chamber. The combined stream
then flowed to a bottom outlet where the contacting gas was
separated from the effluent. A portion of the gas was aspirated
back into the upper chamber by the liquid flowing through the
orifice and recycled to the inlet area.
Ozone Decomposer
The exhaust gas from each of the contactors was directed to an
ozone decomposer. An electric heater was used to increase the
exit gas temperature to between 260° C and 290° C to insure
destruction of the ozone in the off-gases.
Sample Collection
Gas Samples
Ozone gas sampling ports were located at the outlet of the
ozone generator, the exhaust gas line from each contactor, and
the exit gas line following the ozone decomposer.
A grab influent gas sample was collected and analyzed
iodometrically at the start of an experiment. Continuous
measurement of ozone in the gas stream was made subsequent
to the grab analysis to provide assurance of a steady state
ozone concentration. The continuous monitoring was
accomplished by a Dasibi ozone analyzer.
Wastewater Samples
Valved sampling ports were located on the influent and effluent
lines of both ozone contactors. Samples were analyzed for
chemical characterization of the effluent before and after
ozonation. Bacteriological samples were tested for total and
fecal coliforms by the MPN method.
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Chemical and Physical Characterization of Wastes
Total chemical oxygen demand (TCOD), soluble chemical
oxygen demand (SCOD), total organic carbon (TOC), total
suspended solids (TSS), volatile suspended solids (VSS),
ammonia nitrogen (NH3-N), total Kjeldahl nitrogen (TKN),
manganese (Mn), iron (Fe), pH, and turbidity were determined.
Nitrate nitrogen (NO3) and nitrite nitrogen (NO2) were also
determined.
The surface tension of the wastewater before and after the
contactors was determined by the ring method using a DuNouy
type tensiometer. Viscosity was determined with the Cannon-
Fenske viscometer.
Determination of Mass Transfer Coefficients
Mass transfer coefficients in the packed column and jet
scrubber were determined using MCWTP effluent. Ozone was
contacted with the secondary effluent in the packed column
and jet scrubber. Gas flow rates were varied between 35 and
150 1/min. The liquid flow rate was held constant at 75 l/min.
and the ozone concentration was measured in the inlet and
exhaust gases, and in the liquid emerging from the contactors.
The quantity of ozone that can be absorbed by the
secondary effluent was related to the inlet ozone gas
concentration and Henry's constant. This relationship is
described by the following equation:
1. Partial Pressure of Ozone in Equilibrium with Dissolved Ozone
y* = Hx
where y* = partial pressure of ozone in the gas in equilibrium with the
dissolved ozone in the liquid (mm Hg)
H = Henry's constant (mm Hg/mol fraction of ozone in the liquid)
x = ozone concentration in the secondary effluent (mols 0,/mol
liquid).
Henry's constant defining ozone solubility in water was
obtained from the International Critical Tables. Since the units
on Henry's constant were tedious to manipulate, they were
converted at various temperatures from mm Hg/mol fraction of
ozone in the water to liters water/liter air. The magnitude of
Henry's constant is substantially affected by temperature, as
shown in the next slide.
The mass transfer coefficients for the packed column were
determined using the following equation:
2. Mass Transfer Coefficient
N = G (y, - y2) = KgVa (A ylm)
where N = ozone transferred from the gas phase into the secondary
effluent (mg/min)
G = gas flow rate (liters gas/min)
Y, = ozone concentration in the inlet gas (mg/l)
Y2 = ozone concentration in the exhaust gas (mg/l)
KgVa = overall mass transfer coefficient (liters gas/min)
Ay in, = log mean concentration difference of ozone in the gas phase
across the entire column (mg/l).
The term Aylm is defined by the following equation:
where yi = ozone concentration (mg/l) in the gas phase in equilibrium with
ozone residual in the liquid at the bottom of the column, as
defined by Henry's Law
and yz" = ozone concentration (mg/l) in the gas phase in equilibrium with
ozone residual in the liquid at the top of the column since the
incoming wastewater had no ozone residual, y.. = 0 in the
above equation.
The mass transfer coefficients for the jet scrubber were
computed in the same manner. However, since the flow
configuration in the jet scrubber was concurrent rather than
countercurrent, y,* = 0 because the liquid entering the
contactor contained no ozone residual. Thus, for the jet
scrubber, the equation for the log mean concentration
difference simplifies to:
- (y8
In
(y.)
The mass transfer coefficients for both contactors are
illustrated in the next slide. The data indicate that the mass
transfer coefficients for the packed column were more than
twice the value determined for the jet scrubber at the gas flow
rates studied. Henry's Law states by definition, that as ozone
residual increases, the ozone concentration in the gas phase in
equilibrium with the residual will also increase. This means that
transfer is inhibited by high ozone residuals. A countercurrent
flow configuration, such as in the packed column, has the
advantage not only of contacting the liquid containing the
highest ozone residual with the gas containing the highest
ozone concentration (i.e., at the bottom of the column), but
also of contacting the liquid containing the least ozone residual
with the gas containing the lowest concentration of ozone (i.e.,
at the top of the column). This tends to equalize the
concentration driving force and thus maintain a more uniform
mass transfer rate across the entire length of the column.
In contrast, the jet scrubber, which operates in a concurrent
flow configuration, maintains a high concentration gradient at
the inlet end. As the residual increases, the exit gas
concentration, which must be in equilibrium with the residual,
will also increase. This substantially limits ozone utilization in
the jet scrubber when compared with the packed column.
Both contactors had relatively short liquid contact times
(approximately 20 seconds for the packed column and 3
seconds for the jet scrubber, at a wastewater flow rate of 75 I/
min). This tended to hinder both mass transfer and ozone
utilization. Longer contact times would permit the dissolved
ozone to react with oxidizable constituents in the secondary
effluent, lowering the ozone residual and thus increasing the
overall ozone concentration driving force.
Ozone Utilization
Ozone utilization is defined by the following equation:
3. Percent Ozone Utilization
Vl "
%0, Utilized =
x 100
In
where y, = ozone concentration in the influent gas (mg Oj/l)
y2 =. ozone concentration in the exhaust gas (mg 0^1).
59
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The next slide summarizes the percent ozone utilization data in
both contactors as a function of applied ozone dose. Results
indicate that the percent ozone utilized by the packed column
was substantially greater than the jet scrubber. Thus, the
packed column was superior to the jet scrubber from the
standpoint of mass transfer coefficient and percent ozone
utilization efficiency.
Ozone Concentration
Dosage is defined as:
4. Applied Ozone Dosage
£>„ = y, G/L.
where D,, = applied dosage, mg O3/lni,
Vi = ozone concentration in the inlet gas (mg O3/l gas)
G = gas flow rate (lKas/min)
L = liquid flow rate (l,,q/min)
There are two ways to vary ozone dosage: (1) change the G/
L ratio while maintaining a constant gas concentration, or (2)
change the ozone gas concentration while maintaining a
constant G/L ratio. Ozone utilization will vary in the same
manner. However, utilization can also be changed by
maintaining dosage constant and increasing the concentration of
ozone in the gas (i.e., increase y, and decrease G/L). Figure 15
illustrates the change in percent ozone utilization in both
contactors as a function of y, at a constant dosage level. It is
clear that as G/L decreased (or y, increased), percent ozone
utilization increased, even though the applied dosage was
constant. Caution must be exercised in using these data,
because increased y, values require increased power input per
unit weight of ozone when the dosage is constant. Thus, power
must be factored into any evaluation to establish optimum
performance criteria. The most cost-effective operating
condition for ozone disinfection does not necessarily comprise
the lowest ozone dosage.
Effect of Packing Size on Packed Column Performance
After completing Phase I of the investigation, it was necessary
to switch from the MCWTP effluent to the R. A. Taft
Laboratory pilot plant effluent so that both contactors could be
operated in parallel and simultaneously. The overall quality of
the latter effluent was inferior to the MCWTP effluent. This
factor resulted in excessive pressure drops in the packed
column when the system was operated at a liquid flow rate of
75 l/min.
To compensate for the increased pressure drops in the
packed column, it was necessary to increase the packing size
from 13 mm to 25 mm ceramic intalox saddles. This
modification, in effect, lowered the surface area of the packing
and consequently enabled operation of the column at more
reasonable pressure drops (i.e., <30 cm H2O). However, this
also affected the mass transfer efficiency of the column. Table
I demonstrates the effect of packing size on the overall mass
transfer coefficients of the packed column at various gas flow
rates.
The overall mass transfer coefficient (KgVa) consists of the
product of the mass transfer coefficient (KgV) and the surface
area per unit volume of packing (a). Although the KgV did not
change with packing size, the total mass transfer of ozone into
the liquid over the entire column decreased as a direct result of
the decrease in surface area of the packing.
Contractor Performance
Total Coliform Log Reduction (TCLR)
During the three-month period between August 2, 1976, to
November 2, 1976, a total of 40 experiments were performed
with MCWTP effluent to evaluate the total coliform reduction
efficiency of the packed column and the jet scrubber. The data
were grouped into three segments according to the magnitude
of the applied ozone dosage (i.e., low, moderate, and high).
It is clear that the total coliform reduction efficiency in the
packed column was superior to the jet scrubber at the low,
moderate and high dosage level. When considering all dosage
levels combined (n = 40) TCLR in the packed column was
significantly greater than that in the jet scrubber.
Fecal Coliform Reduction
The fecal coliform data reflect the same trends as the total
coliform data. Thus, the packed column out performed the jet
scrubber with respect to fecal coliform reduction at low
intermediate and high dosage level. When considering all
dosage levels, the packed column was significantly better than
the jet scrubber with respect to FCLR.
Data from this study conclusively demonstrated a marked
difference in performance between two generic type ozone
contactors, the packed column and the jet scrubber.
The packed column was superior to the jet scrubber with
respect to percent ozone utilization, mass transfer of ozone,
and disinfection. This superiority was significant and consistent
at all dosage levels employed. The next step in the program is
to compare the performance of the packed column with a
pressure injector system. This evaluation is now underway and
will be followed by diffusers and a turbine agitated
contactor. D
Chemical Characterization
Parameter
Temperature (°C)
TCOD
SCOD
TOC
TSS
TURB(JTU)
TKN
NH3-N
ORG-N
Log Total Coliform Density
Log Fecal Coliform Density
Log Fecal Streptococci Density
Mean
(mg/1)
21
30
24
10.3
6.7
3.8
8.3
7.2
1.6
5.77
5.38
4.19
Standard
Deviation
3
10
9
5.2
3.8
1.5
8.2
7.6
1.0
0.51
0.64
0.71
Range
14-24
18-56
15-49
4.4-25.5
2.4-20
2.3-7.6
1.9-37.8
0.1-34
0.2-3.8
4.90-6.73
4.36-6.54
2.70-5.23
60
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SERVICE
AIR
fc5 ,
COMPRESSOR
EXCII.
SURGE
TANK
'"1
^CL
-cU
DKYLR
--.ru-i
U PRESSURE
FILTER KEG.
VENT
1
OI-ONATOI1
(2 PARtLLTL UNITS) I
pEcoAM-'osER,
-r*
TAMK 1UIJCK C f|-
FROM MUODY CREEK UsTRAV/ER
TREAT/Ag::MT PLANT
-f^.
PILOT
i'l AMI
MULTI-MEDIA
FILTER
™r :— — AIIJ, OZONE
Table 1
Effect of Packing Size on Overall Mass Transfer Coefficients (KgVa) of the
Packed Column at Various Gas Flow Rates
KgVa (I/rain)
13 mm Packing 25 mm Packing
(KgV, l/min/m) (KgV, l/min/m)
84 46
(0.135) (0.180)
163 66
(0.261) (0.258)
175 73
(0.280) (0.285)
205 86
(0.329) (0.336)
Difference in Total Coliform Log Reduction
Gas Flow Rate
g/min
37
74
110
147
Ozone Dosage (mg/1)
Level
Low
Intermediate
High
All
Range
2.4-4.6
5.9-10,0
II. 8-18.6
2.4-18.6
Mean
3.6
7.5
13.9
7.4
Number
of Data
Points
in)
14
18
8
40
Total Coliform
Log Reduction
Packed
Column
2.0
2.8
2.4
2.4
Jet
Scrubber
1.4
2.3
2.2
1.9
Difference in Fecal Coliform Log Reduction
Level
Low
Intermediate
High
All
;e (mg/l)
Range
2.6-4.6
5.9-10.0
11.8-18.6
2.6-18.6
Mean
3.6
7.5
14.0
7.5
Number
of Data
Points
In)'
13
17
8
38
Fecal Coliform
Log Reduction
Packed Jet
Column Scrubber
2.3
3.3
3.1
2.9
1.4
2.8
2.5
2.3
61
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10 20 30
TEMPERATURE (°C)
Variation of H With Temperature
40
C
6 7:0
JET SCSU3BEH
4 3 12 16
:iCCNDi!JY EFFLUENT CZONH DOSAGE (ng/l)
Effect of Ozone Dosage on % Ozone Utilization
I 60
o
tsl
o
t?
PACKED COLUMN
JEI SCBUDBCR
} 4 6 6 10 17 H
OZONE CAS CONCIIJIRATION |mg/l)
Effect of Ozone Concentration on Ozone Utilization at
Constant Dosage of 8 mg/1
so 100
GAS FLOW KATE (l/min)
Effect of Gas Flow on Mass Transfer Coefficient
ISO
62
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Combined Treatment of Industrial
and Municipal Sewages
N.V. Pisanko
At the present time the basic trends in the field of the efficient
use of water resources are as follows:
• creation of the closed water supply cycles with the treated
sewage reuse;
• introduction of the waterless technological processes;
• improvement of the existing treatment structures and
construction of the new modern ones;
• complete sewage treatment with the use of the sorbtioning
materials, desalting and ozoniting plants;
• introduction of the local systems of sewage treatment with
the extraction of valuable components and treated water
reuse;
• sewage sediment treatment and utilization.
In this respect our Institute develops the experimental and
standard projects of various structures and plants for water
supply and sewerage of many fields of industry.
Selection of optimum variants of water management
schemes, considering the technological processes is carried out
on electronic compluters.
In practice of the industrial water supply and sewerage the
technical solutions, developed by the Institute, on the
combined treatment of industrial and municipal sewages have
been realized, and a number of complex programs for the
selection of optimal variants of treatment structures by
electronic computers have been devised.
Treatment of Industrial-Complex Sewages Together With
Municipal Effluents
One of the promising solutions of the efficient use of water
resources is the broad introduction of recycle water supply
with the post-treated sewage recharge. Such a project has been
carried out by our Institute at the undertaking of the chemical
type
Treatment structures capacity is -95.0 th.cu.m/day, including:
industrial effluents (28.0 th.cu.m/day) and industrial-domestic
town's effluents (67.0 th.cu.m/day).
Industrial effluents and domestic effluents of the town flow
to the treatment structures' site through the independant
sewers and the separate mechanical treatment takes place (see
diagram Nl). Value of BOD2 in industrial effluents constitutes
780 mg/1, suspension content -110 mg/l, nitrogen of ammonium
salts - 40 mg/1.
Towns' effluents are characterized by BOD2=168 mg/1
suspension content - 135 mg/1 and nitrogen of ammonium salts
-40 mg/1.
Industrial-domestic effluents after the mechanized gratings
(1,) grit chambers (2,) primary settlers (3) (vertical -9,0 m dia,
8 pcs and radial -20m dia, 4 pcs) are directed to the mixer (6.)
Industrial effluents after the surge tanks 4(6000 cu.m. and
1680 cu.m capacities), primary settlers 5(vertical-9,0 m dia, 4
pcs and radial-20m dia, 3 pcs) are directed to the same mixer
6. Due to the lack of phosphorus in mixed sewages, it is added
as a superphosphate solution to the mixer from the building for
chemicals.
63
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IM/it*/ CFFUIfNTS,
dZI
OF
CAL nNXt&-f iO" CONTACT TANK.I 11"
Diagram I
Treatment of Industrial Union Sewage Combined with Municipal Effluents.
After mixing the effluents have the following characteristics:
BOD2-420 mg/l; suspension ' .itent - 65 mg/1, nitrogen of
ammonium salts - 38 mg/1. Effluents mixture is treated at the
biological treatment structure, cimprising the aeration tanks-
mixers 7 (24 and 44 th.cu.m capacities) and secondary radial
settlers 8 (20 m dia -12 pcs).
Effluents aeration in aero-tanks is pneumatic, residence
time— 22 hours. Aero-tank acidic power by BPK20 is accepted
as 22,0 g/cu.m/h.
After biological treatment, water with BOD20= 10-12 mg/1,
suspension content -14,0 mg/1, nitorgen of ammonium salts-
5,0 mg/1 flows for post-treatment to biological ponds 9 of 260
th.cu.m capacity. After post-treatment in biological ponds
(during 3 days) effluents possess the following data:
BOD20—6,4 mg/1, suspension content -3,9 mg/1, nitrogen of
ammonium salts -1,8 mg/1, dissolved oxygen- 8,0 mg/1.
After biological ponds sewages are desinfected with chlorine
in the contact tank 10 and pumped by the pumping station 11
to the filtration station 12, consisting of horizontal settlers and
sand filters. Before going to settlers water is treated with
coagulants. Water, treated at filtration station, with
BOD20=2.7-3,0 mg/1 and suspended solids content -1,6-1,9
mg/1 is supplied for the recycles recharge. Sediment from
primary settlers 5 of industrial effluents is pumped over into the
slime collecting pond of 425 th.cu.m capacity. Sediment from
primary settlers of municipal effluents is mixed with excessive
activated sludge, passed through the sludge compactors, and is
fed to methan tank, where it is fermentated in mesophylic
conditions (at temperature to +35° C).
Fermentated sediment is directed to sludge areas with
asphalt-concrete base. Because of the toxic substances in
sediment its use was not possible and after drying it was
directed to storage places.
g -
STATiOA/; 12."fil.rf.ATLa>/ STATiOM
Selection of Oplimum Variant of Sewave Post-Treatment
Structures By Electronic Computers
From the practice of treatment structures operation it is
obvious that, very often, to provide the normative sanitary-
hygienic indices of the reservoir (in the rated range) the sewage
post-treatment is to be provided.
In some cases for post-treatment structures the large plots of
land are required (biological ponds with natural aeration) but no
electric power is needed. In other cases—small area and
considerable electric power consumption (aerated biological
ponds, filters flotators) are required. So, when choosing the
optimum variant of effluents post-treatment the great and
labor-consuming work (which is some cases is not possible to
be performed by familiar methods of calculations) is to be
done.
The complex program of the selection of the optimal variants
of sewage post-treatment by the electronic computers is
developed by the Institute.
As a basis for the program (see diagram 2) the following
structures tested in practice and providing the sufficient sewage
post-treatment degree as to the single-stage diagram are
accepted:
1( Biological ponds with natural aeration (D-3);
2) Biological ponds with mechanical aeration (D-4);
3) Biological ponds with weirs-aerators (D-5);
4) Rotary gratings, granular filters, aeration devices (D-6);
5) Strainers and aerated filters (D1?);
6) Rotary gratings, granular filters with chemicals treatment (D-
8);
7) Strainers (D-9);
8) Flotators (D-10);
64
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STRUCTURES OF COMPLETE &/OLD&/CAL TK.EZTMEMT
FLOW K.A.TE Q"th.Cu.,
5 OH camp. ~ rr^jt
COMPLEX. OF SEWAGE POST-TKETIT
TEf. °£KATU*E
WM7 STRUCTURES CALCULATED . 6ir' BLECTKOtJIC. COKPUTEKS
-c\IZ-eU<-7te-v tt-7 13-g
UK3H&IOLO& 1CAL fONHS W/TH NATURAL AEKATlOfJ; \2J-W - &IOLQ&IC/IL PQAftS WITH MECHAfJlCJIL AEKATtOfJ;
[2>-5t -BlOLOff/CffL POA&S WITH WEIR; \Ihdj- FILTERS; J27-7|- X£e#TE3> FlLTE*S>
CHEIHICRL TREATMENT, \2)-'t Uf-/Ot FLQTATOKS.
Diagram 2
Selection of Optimal Variant of Sewage Post-Treatment Structures.
Various combinations of above single-stage diagrams of the
sewage post-treatment structures made it possible to develop
18 dual-stage diagrams, providing more complete post-
treatment, than single-stage system, and to get minimum
structures cost by means of correct-distribution of the
pollutants removal degree separately for each stage.
To calculate the sewage mixing with reservoir water the
following programs are developed: D-l (concentrated outlet)
and D-2 (diffusing outlet).
By the program D-l, the calculation of which is related to
the sewage inlet reservoir and its rated range, the values of
limiting-allowable concentrations of pollutants (to be discharged
into the given reservoir) by BODcomp|, suspended solids and
harmful substances, and temperature are determined.
Limiting-allowable concentrations, which do not disturb the
physical-chemical composition of the reservoir are to be
provided in the rated range.
Data, developed by the program D-l, are the final
parameters of all variants of sewage post-treatment structures
considered. These data are transferred to all variants of
structures.
Calculation of the diffusing outlet is performed by the
program D-2. This calculation takes place to examine the
possibilities of replacing the post-treatment structures by the
diffusing outlet and to remove, if necessary, the partial load on
post-treatment structures as well.
All variants of sewage post-treatment structures (single and
dual stages) are calculated in 2 combinations: a) with
concentrated outlet; b) with diffusing outlet.
Calculation of each variant is carried out in the following
order:
A) All technological parameters of sewage post-treatment
structures are calculated:
—ponds areas, the number of mechanical aerators, weir-
aerators for any climatic region of the country, considering the
temperature drop factor:
—filtration rate, filters area, filters type;
—flotation time, flotators number, power capacities.
Calculation culminates in the determination of all parameters
of structures in all operating conditions.
B) Estimate-economical parameters are determined from the
technological ones.
As a criterion of optimum factor the reported costs are
accepted.
Capital costs are dependent on the capacity and sizes of
structures and are estimated from the predetermined graphical
relationship, converted to mathematical language.
Based upon the operating efficiency of complete biological
treatment structures, the following values of pollutants
concentrations, entering the post-treatment structures are
accepted; by BOD,.,,mi,i. - 15, by suspension - 15 mg/I. by
dissolved oxygen - 0.5 - 2.0 mg/I. Sewage temperature ranges
from - 6 to - 30° C.
On the basis of data on residual concentrations of pollutants
after the co'mplete biological treatment as well as on harmful!
65
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substances when discharging into the reservoir and determined
from the calculation program on mixing (D-l; D-2) it was
by the following:
a) ability of the post-treatment structures to remove
pollutants, considering the partial load on the reservoir and
BOD in the rated range.
b) ability of the river itself to reduce the concentration of
discharged harmful substances in the rated range due to the
stream turbulence up to the limiting-allowable concentrations.
After the post-treatment structures the value of these
pollutants, according to programs D3 -=- D6 will be reduced up
to 5 mg/1 (by BODTOni|)l.) and - up to 4 mg/1 (by suspension);
according to the program D7 this value will drop up to 3 mg/1
(both by BOD and suspension) and according to the program
D9 it will be up to 11 mg/1 (by BOD20) and - up to 6 mg/1 (by
suspension).
The introduction of complex programs of choosing the
optimum variant of sewage post-treatment structures provides
the following:
1. To determine in the shortest time the optimum variant of
sewage post-treatment considering the sanitary and hydraulic
condition of the reservoir over the capacities range from 0.5 up
to5000th.cu.m/day.
2. To get the sizes of all structures, comprising
communications between structures, on each variant.
3. To determine the allowable pollutants concentrations
before biological treatment structures.
Application of Aeration Tanks-Clarifiers for Biological Sewage
Treatment
An aeration tank clarifier developed by our Institute is one of
the efficient structures, which will find wide application at
biological treatment stations. This structure is used for
combined treatment of sewage from metallurgical undertakings
in a town.
After mixing the sewage at the rate of 50 th.cu.m/day are
characterised by BOD20= 110 mg/1 and suspension content
=95mg/l.
After mechanical treatment (gratings, grit chambers and
primary settles) sewages are directed to biological treatment,
which is realized in aeration tanks-clarifiers. An aeration-tank-
clarifier measures 48,0x20,0 m, its capacity -10,0 th.cu.m/day,
and with forced operating conditions it accounts for 15,0
th.cu.m/day.
Aeration tanks-clarifiers are prefabricated-monolithic
structures, their design-flow diagram is presented in fig. 1.
An aeration tank-clarifler operates in the following way.
Sewage is fed through the delivering pipe dispersely along the
length of the structure to the aerations zone 2, where it is
mixed with air and circulating activated sludge. Air supply is
performed from the air-blowing station through the air pipes (3)
to channels with plate diffusers (4) and tubular aerators (10.)
Aerated sludge mixture through the holes in partitions (5,)
controlled with gate valves enters the clarification zone (8,)
meanwhile passing the stream baffling zone (4,) where the
separation of suspended air bubbles takes place as well. Zone
of stream pulse baffling is separated from the clarification zone
by the partition (14.) Further the stream runs along partitions
(13,) then enlarging it breaks down into parts. One part of the
stream goes upwards in the direction of the diverting trough. It
acts as a motive force for the formation of a suspended layer of
activated sludge 8, where organic pollutants are detained and
oxydized. Due to the enlargement of the stream, its movement
rate reduces, which is beneficial for better water clarification.
Another part of the stream flows downwards along the
partition. It acts as a motive force when forming the permanent
recirculation between aeration and clarification zones. The
circulation is also provided by the slot 8, through which the
stream is drained to aeration zone caused by the intensive
rising of air bubbles, produced by fine-bubble aeration 4.
In order to prevent clogging of recirculating channels, the
tubular aerators 10 of perforated pipings with 5mm dia holes
are provided in their lower part.
Wastewater, treated from pollutants and filtered in the sludge
suspended layer is removed uniformly from the whole surface
of the clarification zone by the water diverting troughs 11.
Between the suspended layer 8 and a level of the clarified
water overflow, the protective layer of clarified liquid 6, the
height of which varies from 1 to 1.5m, is formed.
Excessive activated sludge under hydrostatic pressure is
diverted through the piping 12 of 150mm diameter for the
following treatment. Operating experience of the existing
aeration tanks-clarifiers demonstrated, that with the sewage
treatment for 5 hours, pollutants concentration reduces to 8-9
mg/1, suspension content - to 7-11 mg/1.
Aeration tank-clarifier differs from the known biological
treatment structures mainly by the hydrodynamic improvement
of the structure design itself, which promoted the formation of
the steady suspended layer of activated sludge in clarification
zone and its higher buffer ability, provided an intensive mass
exchange between the aeration and clarification zones and
complete and rather intensive mixing inside the layer at a time.
An intensive exchange between the mass of activated sludge in
the suspended layer and aeration zone made it possible to
provide an activated biomass in the suspended layer with
oxygen and feed, uniformly with time and layer volume. The
combination of aeration and settling zones allowed for
producing the optimal conditions of vital activity of activated
sludge organisms. The activated sludge is always to be found in
aerobic conditions, as the flow rate of circulating streams is
superior to the flow rate of treated water 7-15 fold. The
peculiar form of aerated zone aids in rising the turbulence of
sewage liquid stream and, thus, in the intensification of the
process of oxygen mixing and disolution.
Due to the filtrational mixing of the mixture in the mass of
the suspended layer, the conditions of phases, contacting
between themselves are improved, the oxydizing rate therewith
increases 1.8-2 fold as opposed to "traditional" aeration
tanks.
The intensity of the exchange between the aeration and
clarification zones is high to such an extent, that a structure as
a whole is practically a reactor-mixer, in which the process is
accomplished in full volume, occupied by activated sludge, and
the whole reserve of the active biomass is involved in oxidizing
process at a time.
66
-------
1.- WATER 3ELIVERM0 f>!f>E] 2~AEKATIOfi/ £0V£; 5'AIK - PIPES', *f" CHAMELS WITH PLATE
; 5-HOLES //V PARTITIONS; G'CLAKlFICATIOfJ ZOV5; 1~STREAM BAFFLING 1OA/C;
LfCdER OF
11-V/ATEK.
LAK
Figure I.
Aeration Tank-Clarificr.
The sludge mixture flowing from aeration zone to the
clarification zone is separated in suspended layer by filtering.
Efficiency of separation of such a dispersed phase by filtering
is much higher than by settling; so the total effect of sewage
treatment in aeration tank-clarifiers is higher than in complexes
of aeration tanks with secondary settlers and in aeration tank-
settlers.
The suspended layer of activated sludge in clarification zones
is characterised by the high stability due to the fact that the
suspending factor in this case is not the sewage stream, but a
circulating stream getting energy from the aeration system,
which is smoothly controlled. This aeration system provides
the drop of hydrostatic pressures between the aeration and
clarification zones. The application of aeration tanks clarifiers
makes it possible:
—to give up the construction and operation of individually
standing secondary settlers as well as a system of pipings and
pumping units for pumping over the circulating activated
sludge;
—to increase the capacity of the biological treatment
structures 2-fold in the same aeration tanks volumes and in the
same areas;
—to decrease the air and electric energy consumption two-
fold.
When comparing the variants of sewage biological treatment
in aeration tanks-clarifiers and in aeration-tanks with secondary
settlers it was found, that in the first case the area to be built
drops from 4266 to 2880 sq.m, electric power—from 63.0 to
37.3 th.roubles/year.
SLU3SE
Concentration of organic matter in industrial sewages often
exceeds I g/l, which is considerably much higher than in
domestic effluents.
Usually in industrial effluents the biogen elements are not
available: phosphorus and nitrogen, which are present in
domestic effluents. So the combined treatment of domestic and
industrial effluents, as a rule, is more efficient, then the
treatment of industrial effluents themselves.
It is not unusual to find that only by way of combined
treatment of industrial and domestic sewages the required
degree of their treatment can be obtained.
The rapid industry and town development results in the
necessity of solving the more complicated problems in the field
of industrial and domestic sewages treatment.
Therefore the conducting of this symposium, where we have
the opportunity for the experience exchange, will promote
further progress in the field of sewage treatment and
environment protection. D
67
-------
Closed Process Water Loop in
NSSC Corrugating Medium
Manufacture
John W. Collins
EPA
Abstract
A 300t/day corrugating medium plant found that their machine
process water could be reused extensively reducing their
effluent BOD5 and suspended solids to acceptable levels.
Machine process water was reused on showers, dilution of
stock entering the centrifugal cleaners, before the refiners and
at the screw press and in the digestor. Volume surges were
controlled by a reverse osmosis unit capable of handling 28,000
gal/day. Problems with life of the modules and fouling of the
membranes are discussed briefly. Product yield increased some
5-6% with dissolbed solids showing little effect on the paper
board's acceptability. Costs for the reverse osmosis are
compared with double effect and vapor compression
evaporation.
Introduction
The preferred method of waste water treatment is to eliminate
the effluents by altering the manufacturing processes. Several
pulp and paper mills have been successful in doing this. One of
particular interest is an NSSC (neutral sulfite semichemical)
mill in Green Bay, Wisconsin. Working with the Institute of
Paper Chemistry and the Environmental Protection Agency,
the Green Bay Packaging Company has converted its operation
from one requiring extensive end-of-pipe treatment to one
requiring no effluent treatment. The mill produces a corrugating
medium from a mixture of mixed hardwood NSSC pulp and
recycled corrugated box plant waste fiber. Most of the solids
pulped from the wood are burned in a fluidized bed to recover
sodium sulfate which is sold to a kraft mill. The residual
pulping liquor organics (approximately 25%) accompany the
fibers to the paper machine. By running the white water at a
high solids concentration, the remaining organics are
incorporated in the board. Upsets in the system can create as
much as 28,000. gal/day of excess "white water". To process
this excess and recover the solids for recycling a reverse
osmosis unit is used. This report will review some of the
process changes and the adaptation of reverse osmosis to the
system.
Recycle System
A balanced operation of the final system is diagramed in Figure
1. The machine "white water" or process water is reused on
machine showers for dilution of stock to the centrifugal
cleaners, in the repulper and in dilution after the screw press,
at the screw press and in the digester. Clarification of the
process water for fourdrinier shower is now shown here.
Various storage tanks are not shown either.
Clarified white water and reverse osmosis concentrate 4-6%
dissolved solids are reused in the pulp mill eventually going to
the evaporators. The arrangement of the units are shown in
Figure 2. Evaporator condensate, cooling water, vacuum seal
water and reverse osmosis permeate make up the mills final
effluent which was reduced from 1.8 to 1.6 M2GD.
68
-------
SALT CAK
32' TONS/DA
STEAM .
WOOD
250 TONS/DA
CHEMICALS x
SODIUM SULFIT
30 TONS/DAY
SODIUM CARSONA
8 TONS/DAY
Figure .
Mill process.
CLARIFIED
WHITE WATER
f
- ^ FLUID1ZED
t BED REACTOR
T
STRONG
LIQUOR
CENTRIFUGAL
s^ . CLEANERS
_*/ Vl SCREW | ,| PRIMARY |_J FINISHING I -£~> f~
. T3 r\ PRESS RTH REFINERS te*l REFINER rZ*\ T*l
l^\^_^4C T W '
- CORRUGATING
CORRUGATING
MEDIUM
300 TONS/DAY
PAPER
1
MACHINE £
TE FIBER DILUTION *>
100 TONS/DAY 0
PROCESS g
WATER 0
DILUTION ^ °"
~~i
Fig
FLUIOIZED HIS
BED 4 1
REACTOR
fl
J
y
In
M
* IT f~~]
49,OOO j 45.OOO
42.000
"
-
1
^
A
A
A
* A
n
A
4
.' 1
A
A
kii
* "W"^
•LOWEST DAY
H bAfl- MONTHLY AV
* HIGHEST DAY
A
A A
A
A
* n
1970 1971 I97Z 1973 1974
lire 3.
torical mill discharge performance.
A
E
&
1975 1976
K-0 CUNCtNIHAIt |(f|L^
LIQUOR
©
•— _
^ H^
tW PULP MILL WASH £-} WASTE QUOR
DILUTION TANK STORAGE TANK
--
L J
L j ,
^ EVAPO
> °™™** 1 | p.".. |
RETURN f ^
TANK ""— — H
_— »»
CHE
MIX
— ~J
LEVEL
i • fi— t} BLOW
MICA) 1 1 ^^K
> 1 1
EMERGENCY
ALARM WASTE L OUOR
STORAGE TANK 1
_
RATORS
1 1
ftb
CT
EVAPORATED
WASTE
.^ LIQUOR
f Jl STORAGE
A YANK
MILL DISCHARGE
OW
-
f SOLIDS - 284
S. SOLIDS- I
DS - y
.60
77B/
22**/
32**/
MGD
DAY
DAY
DAY
fi
FLUIDIZED BEDJ p^-»
REACTOR | ©
H FLOW - 1. 20 MGO
S TOT. SOLIDS - 3450*VDAY
SUS. SOLIDS - I90**/OAY
BOD 5 - 115 YOAY
WOOD ROOM |
©/ /<-
s\ c
OO
SURGE STORAGE
)
O-SEE TABLE'l
BOILER FLYASH
POND
CITY WATER IN
FLOW - 0.7 MGD
TOT. SOLIDS - 750*/DAY
SUS. SOLIDS - 0*/OAY
BOD 5 - 0*/DAY
CORRUGATED
WASTE
REPULPER
I
PULP MILL
MACHINE ROOM
© ,. © ,
.0 „
Pulp mill—combustion plant liquor flow.
Effect of Mill Closure on Pollution Load from the Mill
Following strong liquor combustion, but, prior to the water
reuse program, the BOD5 averaged around 20,000 lbs/24 hrs.
Figure 3 shows the reduction of BOD5 in the effluent as the
program progressed. Currently some 1.6 M2GD of effluent are
discharged with around 1,000 Ibs of BODj/day. Two Figures, 4
and 5 compare the pollutants before and after the water reuse
program. BOD5 was reduced from 6,000 Ibs/day to 1,000 Ibs/
day, suspended solids from 1,122 to 420 Ibs/day. Further
reductions would require treatment of vacuum seal waters and
felt washings. If reverse osmosis were to accommodate the
plant volume would have to be four times the size. Figure 5
shows the condition of the River water. The discharge quality
is fairly close to the Fox river water. As the river water
improves, the mills discharge will improve.
Reverse Osmosis
Reverse osmosis is a concentrating process based on the
permeability of a membrane to water but not the dissolved
solutes. Pressurizing the solution to be concentrated against the
membrane provides the work required to overcome the osmotic
Figure 4.
Mill discharge stream—1971.
O-SEE TABLE-2
MILL DISCHARGE
FLOW - 1.6
TOT SOLIDS- 734
SUS. SOLIDS- 42
BOD 5 - IOO
FLUIDIZED BED
REACTOR
RIVER WATER
0 MGD
3 "/DAY
0*/DAY
8*/DAY
IN
FLOW - l.ao MGD
TOT SOLIDS - 3968tt/OAY
SUS SOLIDS - ?8I*/OAY
8005 - 83»/OAY
©
&
©
®/
L
WOOD
/
ROOM |
c
@\v
OO
SURGE STORAGE
>
—
D
PULP MILL
9 ,
1 BOILER FLYA:
r-l POND
H
CITY WATER IN
FLOW
TOT SOLIDS
SUS SOLIDS
BOD 5
-•
CORRUGATED
WASTE
REPULPER
L- 1
1
1 MACHINE
1
. 6 ,.i
05 MGO
- 700 "/DAY
Ott/OAY
O"/ DAY
1
1
1
1
1
1
1
i
ROOM
0 ,
P
Figure 5.
Mill discharge stream—1975.
69
-------
pressure. Assymetric cellulose acetate membranes were the
first found to give reasonable water flux and are preferred after
some 15 years following their discovery. Preliminary trials at
the Institute of Paper Chemistry and at the Green Bay Mill
resulted in the selection of a spun Fiberglas 'A> in diameter tube
lined on the inside with the thin membrane now manufactured
by Universal Oil Products.
The unit was situated in the overall scheme of water reuse as
shown in Figure 6. The actual setup of the 18 tube modules is
shown in Figure 7. Not shown is a heat exchanger to cool the
process water or the screens used to clarify the stream. The
feed pumps are high pressure centrifugal pumps with 47 stages
for pressurizing and 23 stages for recirculation. The plant can
process up to 28,000 gal/day at a flux rate of 5 gfd (gal/sq ft per
day). To control fouling of the membrane surface, considerable
effort was directed toward working out the most efficient
cleaning schedule. Currently the system operates with periodic
automatic pressure releases to allow some of the permeate to
repenetrate the membrane by osmosis, thereby, removing some
of the solids from the inner membrane surface. This shutdown
is carried out every 2 hours for 12 minutes. Once a day a high
velocity flush is carried out and once a month an enyzmatic
detergent cleaning and soak for 12-18 hours is carried out to
remove chemical scale which is mostly calcium oxalate.
Figure 6.
Process water reuse system.
Problems with the reverse osmosis equipment were also
experienced. The first set of support tubes were subject to
premature bursting. The Fiberglas support structure weakened
during the 600 psi operation. A careful examination of the
manufacturing process and the raw materials before and after
exposure to this 5% solids NSSC machine process water
revealed permeate etching of the Fiberglas strands. Certain
trace components were being leached out rendering glass
weakened and subject to fracture. Changing the composition of
the glass led to a new generation of modules. The life has been
extended from some 1,000 hours to 12,000 hours.
With so many operating variables, the system needs a
number of controls. Figure 8 shows the various control devices
used to protect the membranes and ensure a continuous
smooth operation.
CONCENTRATE
RETURN
MODULE RACK
TYPICAL I OF 6
Figure 7.
Reverse osmosis flow diagram.
CLARIFIED
PROCESS WATER
FEED
pH SENSOR
TEMPERATURE SENSOR
SOLUBLE SOLIDS ANALYZER
CONDUCTIVITY
SENSOR
FEED
PUMPS 12)
RECYCLE
PUMPS (61 |_F.tP.W_<:°NJ8Pi..i
SIGNAL
_P_RESSIJRE
CONTROL
CONCENTRATE
Figure 8.
Reverse osmosis plant control.
Product Quality
Table 1 shows the properties of the paper before and after the
water reuse measures. A drop in mullen was the only
significant change. Acceptance by the processors and consumer
did not change. Costs are summarized in Table 2. The
reverse osmosis processing is less expensive to operate than
the two effect evaporator but not the vapor compression
evaporator. Capital installed costs were most for the reverse
osmosis equipment. This relatively high cost is partly due to
the small size of the plant, the elaborate control required and
the extensive measures to control fouling.
70
-------
Table I
Strength Comparison—Open System, 1970, to Closed System, 1975
2. Year
1. Item 1970 1975
3. Paper machine
4. Basis weight (pounds/1000 sq. ft.) 26.3 26.1
5. Concora (pounds) 71.8 70.6
6. Mullen (pounds) 42.0 34.0
7. Corrugator
8. Flat crush (pounds/sq. in.)
9. A Flute 30.8 30.1
10. B Flute 48.1 55.0
II. C Flute 46.5 40.3
12. Standard box. top to bottom
compression strength (percent of
standard) 100.6 107.4
Table 2
1976 Capital and Installed Costs
4.
Comparable
2. 3. Vapor
1. Reverse Two Effect Compression
Total installed cost Osmosis Evaporator Evaporator
1. Total installed cost $324.572 $200.000 $250.000
5. 1974-1975 Operating Cost Experience
6. Operating cost—S/3.785 cubic meters (1000 gal.) purified water
7. Energy consumption $ 1.70 $ 8.60 $3.34
8. Depreciation 6.45 3.18 3.71
9. Maintenance and labor 2.58 .91 .99
10. Total cost—$/3.785 m* $10.73 $12.69 $8.04
Conclusions
1. A corrugating medium mill using hardwood NSSC pulp and
recycled corrugated box plant waste fiber has found it can
operate successfully discharging an effluent requiring no
treatment to meet current federal and state regulations.
2. Corrugating medium can be produced from a pulp slurry
containing process water 160° F and 5% dissolved solids.
3. Corrosion, scale, foam, slime and deposits can be controlled
by changes in equipment composition or by conventional
techniques.
4. Reverse osmosis can recover solids for the paper machine
thereby keeping BOD5, color and suspended solids from the
sewer.
5. The additional dissolved solids (5%) that are incorporated in
the sheet have had no significant effect on the paper board's
acceptability.
71
-------
Protocol
Of the Sixth Mi'i-tiiiK of the USA and USSR delegations on
the problem of Prevention of Wastewater Pollution from
Industrial and Municipal Sources {Cincinnati, Ohio, Chicago,
Illinois. Washington, D.C., USA, May 7-16, 1978)
In accordance with the Memorandum of the Sixth Meeting of
the Joint USA/USSR Commission on Cooperation in the Field
of Environmental Protection (Washington, D.C., November
19)7), the USSR and USA delegations meeting on the problem
of Wastewater Treatment was held May 7-16, 1978.
The Soviet Delegation was headed by Roald F. Slavolyubov,
Department Head Central Administration of Gosstroy, USSR.
The American Delegation was headed by Mr. Harold P.
Cahill, Jr., Director of the Municipal Construction Division,
U.S. Environmental Protection Agency.
The list of participants is attached in Appendix 1.
In the course of the visit, the following was accomplished:
1. A Symposium on the topic of Advanced Equipment and
Facilities for Wastewater Treatment was held in Cincinnati.
2. The results of fulfillment of the 1977-1978 Program of
Scientific Research Cooperation.
3. Coordination of research projects to be fulfilled in 1978.
4. Consideration of the possibility of the free exchange of the
design documentation for the construction of an experimental
municipal industrial Wastewater treatment facility.
1. In the course of the Symposium, 11 technical papers were
delivered: 5 papers from the Soviet side and 6 papers from the
U.S. side (Appendix 2).
All papers were received with great interest and were
followed by a lively discussion.
The delegations have agreed that each side will publish all
papers in'the required number of copies in its own language
prior to November I, 1978, and will distribute them among
interested organizations. The sides will exchange 10 copies
each of the published Proceedings of the Symposium.
2. During the Meeting, the delegation visited industrial and
municipal treatment facilities and laboratories in Cincinnati,
Ohio; Chicago, Naperville and Dyer, Illinois; and Whiting,
Indiana; and Occoquan, Virginia. The technology of
wastewater treatment was carried out there with the specialists
from the AH-Union Scientific Research Institute VODGEO,
Soyuz Vodokanalproekt, EPA, Metropolitan Sanitary District
of Greater Chicago, and the AMOCO Research Center.
72
-------
Both sides agreed that the seventh symposium on the
following topic will be held in the USSR:
• Facilities for Tertiary Treatment of Biologically Treated
Effluents Including Removal of Biogenous Elements (from
August 20-September 2, 1978).
In preparation for the forthcoming symposium the following
was agreed upon:
• Each side will prepare 5-6 technical papers;
• Both sides will exchange the titles of papers to be delivered
six weeks prior to the beginning of the symposium.
• Both sides will exchange the texts of the papers both in
Russian and in English one month prior to the symposium.
In 1978 a long term exchange for one month will be carried
out. American specialists will visit the Soviet Union in June-
July 1978. Soviet specialists will visit the USA in October-
November 1978. Expenses related to this exchange of
specialists will be carried out on the basis of "receiving-side
pays1' basis.
4.The delegations discussed the possibility of an exchange of
specialists and technical documentation for the use in
construction of an experimental municipal and industrial
wastewater and sludge treatment facilities in 1979-1980.
The sides developed and coordinated the working program
for 1979, taking into account exchanges carried out in this area
by U.S. and Soviet specialists of the paper and pulp, chemical
and petroleum industries. Namely: the visit to the U.S. by
Soviet paper and pulp specialists in February 1978, the visit to
the USSR of American paper and pulp specialists in July 1978,
as well as the planned visit to the U.S. by Soviet petroleum
industry specialists in October 1978.
The program envisages two meetings of the American and
Soviet specialists. The first meeting to take place in the USA in
the spring of 1979. During that meeting, the sides will review
the nonreimbursable projects recommended for the
experimental treatment facilities. At that time, a symposium
will be held on the treatment of oil refinery wastewaters and a
summary of experience on closed oxytank performance. The
second meeting will take place in the USSR in the summer of
1979. At this meeting, projects of advanced municipal and
industrial wastewater treatment technology recommended by
both sides, shall be presented and the facilities to be
constructed for experimental projects shall be determined.
The sides expressed satisfaction that the present meeting was
held on the high scientific-technical level in the atmosphere of
friendship and mutual understanding and contributed to the
further strengthening and development of the cooperation in
the field of the environmental protection.
The record of the proceedings of the meeting is signed on
the 16th of May 1978 in two copies in the English and in the
Russian languages, both texts are equally authentic.
Harold P. Cahill, Jr.
Head of the American Delegation
R. F. Slavolubov
Head of the Soviet Delegation
73
-------
Appendix i
List of Participants at the Symposium "Advanced Equipment
and Facilities for Wastewater Treatment"
From the American Side:
Harold P. Cahill, Jr.
Delegation Leader
Director, Municipal Construction Division, US EPA
John T. Rhett
Deputy Assistant Administrator for Water Program Operations,
US EPA
William J. Lacy
Deputy Leader of Delegation
Principal Engineering Science Advisor, Office of Research and
Development, US EPA
R. John Garner
Director, Health Effects Research Laboratory, Office R&D,
US EPA, Cincinnati, Ohio
Francis T. Mayo
Director, Municipal Environmental Research Laboratory, US
EPA, Cincinnati, Ohio
Frank P. Sebastian
Senior Vice President, ENV1ROTECH, Menlo Park,
California, USA
John W. Collins
Senior Scientist, US EPA, Cincinnati, Ohio
James Westrick
Senior Scientist, US EPA, Cincinnati, Ohio
John N. English
Senior Scientists, US EPA. Cincinnati, Ohio
Edward J. Opatken
Senior Scientist, US EPA, Cincinnati, Ohio
U. V, Henderson
Senior Researcher, Texaco, Inc., Port Arthur, Texas, USA
Prof. Alexey N. Malyshev
Interpreter, US Department of State
From the Soviet Side:
Roald F. Slavolyubov
Delegation Leader, Department Chief of Main Administration,
USSR State Committee on Building Construction, USSR
Aleksey N. Belevtsev
Senior Researcher, All-Union Research Institute of Water
Supply, Sewage, Hydrotechnical Construction and Engineering
Hydrogeology, VNII VODGEO, USSR
Khafiz K. Karimov
Manager, Tashkent Department of Water Economy of Industry
and Populated Areas, All-Union Research Institute of Water
Supply, Sewage, Hydrotechnical Construction and Engineering
Hydrogeology, VNII VODGEO, USSR
Kseniya M. Morozova
Senior Researcher, All-Union Research Institute of Water
Supply, Sewage, Hydrotechnical Construction and Engineering
Hydrogeology, VNII VODGEO, USSR
Nikolay V. Pisanko
Chief Engineer, State Project Institute, "Ukrvodokanal
Project," USSR State Committee on Building Construction
74
-------
Appendix 2
List of Papers Presented at the Symposium, "Advanced
Equipment and Facilities for Wastewater Treatment"
From the American Side:
Removal of Volatile Halogenated Organic Compounds by
Activated Carbon
James Westrick
Activated Sludge Enhancement: A Viable Alternative to
Tertiary Carbon and Absorption
U. V. Henderson
Wastewater Treatment for Reuse and Its Contribution to
Water Supplies
John N. English, Howard P. Warner, Irwin J. Kugelman
Training for Use of Advanced Wastewater Treatment
Equipment and Facilities
Frank Sebastian
Contractor Design for Ozonation of Wastewater
Edward J. Opatken
Closed Process Water Loop in NSSC Corrugating Medium
Manufacturer
John W. Collins
From Ike Soviet Side:
Intensification of Mechanical Methods of Cleaning Wastcwater
in Oil Refineries
\. N. Myasnikov, L. V. Gandulina, K. K. Karimov
Electrochemical Methods of Cleaning Wastewater
A. N. Belevtsev
Cleaning Wastewater in Lacquer and Paint Production
I. N. Myasnikov, N. Y. Vorobyeva. L. V. Gandulina. Y. V.
Kedrov
Construction to Facilities for Separating Sludge Mixture in
Biological Cleaning of Wastewater in the Chemical Industiy
I. V. Skirdov, S. I. Kolletsova, K. M. Morozova
Joint Cleaning of Mixed Industrial and Municipal Wastewater
N. V. Pisanko
75
-------
Appendix 3
USA-USSR Cooperation of Working Group on Prevention of Water Pollution from Industrial and Municipal Sources for 1979
TITLES
Modernization of existing and
development of new combined
facilities with high efficiency for
wastewater treatment, including
hydrocyclones. multistage
settlers, flotators, facilities with
utilization of technical oxygen.
investigation of usage of
flocculants and coagulants.
Development of hydrocyclones
and pressure flotation units.
Development of tubular and
plate settlers.
Development of open aeration
tanks of "Marox" type with the
usage of technical oxygen.
Development of closed combined
aeration tanks of "Oxitank"
type with the usage of technical
oxygen.
Development of multi-media
filters with gradually descending
particle size distribution
Development of multi-media
filters and facilities with
continuous washing.
Intensification of wastewater
treatment processes in
petrochemical, chemical.
petroleum refining and pulp and
paper industries.
Intensification of wastewater
treatment processes in petroleum
refining industry.
Intensification of wastewater
treatment processes in
petrochemical and pulp and
paper industries.
Development of highly efficient
methods and facilities for
municipal sewage treatment with
removal of biogenous elements:
usage of treated effluents in
recycling systems at industrial
enterprises.
Development of methods and
facilities for nitrates and nitrites
removal.
FORM OF WORK
Joint development of themes.
scientific information and
specialists delegation exchange.
Symposium on: "Treatment of
Wastewater Containing Oil"
(USA. April 1979)
RESPONSIBLE FOR
From the From the
USSR USA
VNH VODGEO
Gosstroy
USSR
EPA
VNII CODGEO
Gosstroy
USSR
EPA
EPA
EPA
VNII CODGEO
EPA
1979
Information and delegation
exchange
VNII VODGEO EPA
VNII VODGEO
Joint development of themes, in-
formation and delegations ex-
change.
EPA
VNII VODGEO EPA
TIME EXPECTED RESULTS
1979 Improvement of the efficiency of
existing and development of new
treatment facilities, reduction of
reagents and cost of wastewater
treatment.
1980 Recommendations for designing
hydrocyclones and pressure
flotation units.
1980 Recommendations for use of
settlers for wastewater
treatment.
1980 Development of open aeration
tank with the usage of technical
oxygen.
1979 Development of closed aeration
tanks with the usage of technical
oxygen.
1979 Recommendations for designing
filters for treatment and final
treatment of wastewaters.
Recommendations for
construction of multi-media
filters.
1979 Increasing of wastewater
treatment efficiency of existing
treatment plants, introduction of
new treatment schemes.
maximum usage of treated
effluents in recirculating
systems.
1979 Development of treatment
scheme of a petroleum refining
plant using mechanical, physical)
chemical and biochemical
methods.
1979 Development of treatment
scheme of pulp and paper
petrochemical enterprises using
reagents.
1980 Development of new treatment
facilities for prevention of water
basing euthrophication:
development of new treatment
systems with maximum usage of
treated effluents in recycling
systems at industrial enterprises.
76
-------
Appendix 4
Program
Joint US/USSR Symposium
May 9-10, 1978
Tuesday, May 9
8:30 a.m. Registration
9:00 a.m. Opening Remarks—John T. Rhett
9:15 a.m. Welcome—Dr. R. John Garner
9:30 a.m. Removal of Volatile Halogenated Organic Compounds
by Activated Carbon—James Westrick. EPA.
Cincinnati. Ohio
10:15 a.m. Break
10:30 a.m. Intensification of Mechnical Methods of Cleaning
Wastewater in Oil Refineries—I.N. Myasnikov. L.V.
Gandulina. K.K. Karimov. USSR
11:15 a.m. Activiated Sludge Enhancement: A Viable Alternative
to Tertiary Carbon and Absorption—U.V. Henderson.
Texaco. Inc.. Port Arthur. Texas
12:00 Noon Discussion
12:15 p.m. Lunch
1:30 p.m. Electrochemical Methods of Cleaning Wastewater—
A.N. Belevtsev. USSR
2:15 p.m. Wastewater Treatment for Reuse and Its Contribution
to Water Supplies—John N. English, Howard P.
Warner. Irwin J. Kugelman. EPA, Cincinnati. Ohio
3:00 p.m. Break
3:15 p.m. Cleaning Wastewater in Lacquer and Paint
Production—I.N. Myasnikov, N.Y. Norobyeva. L.V.
Gandulina. Y.V. Kedrov, USSR
Discussion
Adjourn
4:00 p.m.
4:30 p.m.
Wednesday,
9:00 a.m.
9:15 a.m.
9:30 a.m.
10:15 a.m.
10:30 a.m.
11:15 a.m.
12:00 Noon
12:15 p.m.
1:30 p.m.
2:15 p.m.
3:00 p.m.
3:30 p.m.
May 10
Opening Remarks—Harold P. Cahill. Jr.
Address—Francis T. Mayo
Training for Use of Advanced Wastewater Treatment
Equipment and Facilities—Fank Sebastian. Envirotech.
Menlo Park. California
Break
Construction to Facilities for Separating Sludge Mixture
in Biological Cleaning of Wastewater in the Chemical
Industry—I.V. Skirdov. S.I. KolTsova. K.M.
Morozova. USSR
Contactor Design for Ozonation of Wastewater—
Edward J. Opatken. EPA. Cincinnati. Ohio
Discussion
Lunch
Joint Cleaning of Mixed Industrial and Municipal
Wastewater—N.V. Pisanko, USSR
Closed Process Water Loop in NSSC Corrugating
Medium Manufacturer—John W. Collins. EPA.
Cincinnati, Ohio
Discussion
Adjourn
(•US. GOVERNMENT PRINTING OFFICE: 1978 620-007/3733 1-3
77
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