USA-USSR
WORKING GROUP
ON THE PREVENTION OF
WATER POLLUTION
FROM MUNICIPAL AND
INDUSTRIAL SOURCES
NOVEMBER 1975
SYMPOSIUM ON
PHYSICAL/CHEMICAL TREATMENT
FROM MUNICIPAL AND
INDUSTRIAL SOURCES
U.S. ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460
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USA-USSR SYMPOSIUM ON PHYSICAL/CHEMICAL TREATMENT FROM
MUNICIPAL AND INDUSTRIAL SOURCES
ADDENDA
Figures omitted from the text are attached. They are:
Page 4, Figures 1 and 2.
Page 8, Figure 6.
Page 9, Figure 7.
Page 16, Figure 1.
Page 17, Figures 2 and 3.
Page 20, Figure 1.
Page 21, Figure 2.
Page 24, Figure 5.
Page 25, Figure 6.
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USA-USSR Working Group
on the
Prevention of Water Pollution
from
Municipal and Industrial Sources
Symposium on
Physical-Chemical Treatment
from
Municipal and Industrial Sources
Taft Center
Cincinnati, Ohio
November 12-14,1975
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
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PREFACE
The second cooperative USA/USSR symposium on the physical-chemical treatment of waste
waters from municipal and industrial sources was held in Cincinnati, Ohio at the Taft Center
from November 12 through November 14, 1975. This symposium was conducted in accord
with the protocol of the Fourth Session of the Joint USA/USSR Commission held in
Washington, B.C. from October 28-31, 1975.
This symposium was sponsored under the auspices of the Working Group on the Prevention
of Water Pollution from Municipal and Industrial Sources. The United States delegation was
headed by Harold P. Cahiil of the United States Environmental Protection Agency and the
Soviet delegation was headed by R. F. Slavolyubov of the Department of Gosstroi in the Soviet
Union.
The sixteen papers that were presented at the symposium (nine US and seven USSR) are
reprinted in English in this volume. The two papers presented in Moscow in May of 1975 by the
Soviets that were never bound in the previous volume are included as an appendix.
This volume is reprinted in English in accord with the protocol signed by the delegation
leaders on November 21, 1975 in Washington, D.C.
U,S. Environmental Protection Agency
11
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INDEX
Press Release v
Opening Address - Dr. Andrew W. Breidenbach 1
Papers Presented at the USA/USSR SYMPOSIUM
1. Cohen, Jesse M. and Westrick, James J. (US EPA), "Overview of Physical-Chemical
Treatment" 4
2. Maysnikov, I.N., Gandurina, L.V. and Butzeva, L.N. (Vodgeo), "Studies on
Wastewater Treatment with Flocculants Application" 14
3. Polta, Robert (Metropolitan Waste Control Commission, Twin Cities Area), "The
Operation of the Physical-Chemical Treatment Plant at Rosemount, Minnesota" . . .20
4. Levchenko, M.N. (orgchim), "Treatment of Chemical Plant Effluents" 31
5. Weber, Walter J. Jr. (University of Minnesota), "The Role of Activated Carbon in
Physiochemical Treatment" 35
6. Miasnikov, I.N., Balakin, B.A. (Vodgeo), "The Removal of Volatile Suspended Solids
from Wastewaters" 50
7. Gulp, George L. (Gulp, Wesner and Gulp), "Design of Facilities for Physical-Chemical
Treatment of Raw Wastewater" 58
8. Korshak, V.V., Zubakova, L.B., Gandurina, L.B., Mendeleev, D.I. (Moscow Chemistry
Technological Institute), "Synthesis of Cationic Poly electrolytes for Treatment of
Natural and Waste Waters " 76
9. Lacy, William, J. and Cywin, Allen (US EPA), "Physical-Chemical Treatment of
Wastewaters from the Petroleum Refining-Petrochemical Industry " 81
10. Panova, V.A., Goriatchev, N.S., and Lurie, U.U. (Vodgeo) "Examination of
Oil-Containing Waste Waters Chemical Composition after their Treatment in Aeration
Tanks" 90
11. Dunlap, Robert W. and McMichael, Francis Clay (Professors, Carnegie-Mellon
University), "Comparison of Alternative Strategies for Coke Plant Wastewater
Disposal" 96
12. Belevtzev, A.N., and Maixmenko, Ju.L. (State Committee of Scientific and Technical
Affairs) "Studies on Oxidation Processes of Cyanides and Phenols in Waste and
Natural Waters by Using Chlorine Dioxide" .105
13. Gellman, Dr. Isaiah (National Council of the Paper Industry for Air and Stream
Improvement), "Current Status and Directions of Physical-Chemical Effluent
Treatment in the Paper Industry " 111
11 I
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14. Ponomarev, V.G. and Zakharina, S.B. (Vodgeo), Treatment of Concentrated Waste
Waters Containing Oil Emulsions" 120
15. Markek, Anton C. and Askins, William (American Cyanamid), "Advanced Wastewater
Treatment for an Organic Chemicals Manufacturing Complex" 124
16. Sebastian, Frank P. (Envirotech), "Cost Benefits of Physical-Chemical Treatment" . .136
Papers submitted late from May symposium in USSR
17. Ostrovsky, O.P., Souproun, U.M., Reznikov, U.N. (VNIPI Chermetenergoochistka)
"Processing and Neutralization of Industrial Wastes from Iron and Steel
Effluents Treatment" .144
18. Lukinykh, N.A. and Turovsky, I.S. (Moscow City Water Supply and Treatment),
"Fundamental Principles of Selecting the Methods for Processing Sewage
Sediments in Accordance with their Properties"' 150
Protocol 154
Appendix I Participants 156
Appendix II Reports 157
Appendix III Program 158
IV
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JOINT US/USSR SYMPOSIUM
ON PHYSICAL/CHEMICAL TREATMENT
AND US TOUR
NOVEMBER 9 - NOVEMBER 23
The U. S. Environmental Protection Agency is hosting a joint US-USSR Symposium on
Physical-Chemical Treatment the week of November 12-14, 1975 at the Robert Taft Research
in Cincinnati, Ohio. The Symposium is being held under the auspices of the Joint US/USSR
Bilaterial Environmental Agreement signed in the fall of 1972 by Presidents Nixon and
Podgorny. As part of their activities in the Cincinnati area, the Soviets will be escorted through
the new facilities (Environmental Research Laboratory) located at 26 Sinclair Street.
The program for the Symposium will include 9 papers on Physical/Chemical Treatment for
the U.S. side and 7 papers from the Soviet side.
In conjunction with the Symposium, a tour has been arranged for the 6 Soviets of several
East Coast wastewater treatment facilities. The tour begins on Saturday, November 15 with
visits planned for the Lamberts Point and Chesapeake-Elizabeth plants located in the Norfolk
area. Monday, November 17, the Soviets will visit the Williamsburg Treatment Plant. The
Soviets will visit several plants in the Harrisburg, Pennsylvania area before leaving for the Soviet
Union on November 23, 1975.
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Improving The Climate for Our International Environment
A SPEECH BY DR. ANDREW BREIDENBACH, ACTING ASSISTANT ADMINISTRATOR
FOR WATER AND HAZARDOUS MATERIALS,
U.S. ENVIRONMENTAL PROTECTION AGENCY,
TO THE US/USSR SYMPOSIUM
ON PHYSICAL CHEMICAL TREATMENT,
CINCINNATI, OHIO
NOVEMBER 12-14, 1975
INTRODUCTION
I am glad to be here today to speak before this
distinguished bilateral group which is concerned with
bringing about environmental improvement.
Both the Soviet and United States goals are similar in
our large scale national efforts to clean up lakes, streams,
and coastal waters, and the water that we drink. Both of
our nations have had long periods of history when
economic growth received such concentrated attention
that the equivalent need to maintain a healthy environ-
ment was often overlooked and neglected.
I am happy to say that attention to the environment
has taken a healthy turn for the better in each of our
countries. The work of this group is dramatic evidence
of this fact, and I wish you all success in your efforts.
Already, the interchange of information and visits
between the USSR and US participants have led to
worthwhile results. Each country has its own area of
outstanding expertise in environmental improvement
that we can share to our mutual benefit. Each country
has developed leads in technologies for water pollution
abatement that would have taken a long time and
significant expense to match if the information were not
to be inter-communicated.
Jointly, we have been determining where each of our
nations stand in controlling the major industries manu-
facturing iron and steel, pulp and paper, chemicals and
petroleum refining where the major part of our indus-
trial pollution occurs. And we can begin identifying the
specific areas of pollution abatement technology that
would provide the most benefit to our respective
nations, so we can concentrate our attention efficiently.
In municipal wastewater treatment control, we have
passed this stage and have begun to exchange
information on control methodologies that are most
beneficial. Municipal treatment, of course, is where our
citizens become even more directly involved in our
efforts and where the costs are directly borne through
local, state and federal bonding and tax revenues.
While on this subject, I am happy to note that citizen
support for our environmental improvement measures
has continued at a high level.
SUPPORT OF ENVIRONMENTAL IMPROVEMENT
Certainly, it is true that progress in improving the
environment cannot be sustained without the heartfelt
support of the citizens in each of our countries. I am
greatly encouraged by the fact that the United States'
program has been characterized by consistent, sustained
public support for environmental goals and efforts to
achieve those goals.
As you may know, one of the methods we use to
determine the desires and opinions of our citizens is the
polling of public opinion where we go out to segments
of the public and sample and record the response. On
the issue of the impact and cost of environmental
controls, all along, public opinion polls have demon-
strated considerable support for our environmental
programs—even during the recent period of recession and
rising prices. I am most heartened by the fact that this
support has not been fickle. In fact, a survey by a major
opinion research firm in August showed that 60% of the
public believe it is more important to pay the costs to
clean up the environment than it is to keep prices and
taxes down. And 90% say that if the environment is not
cleaned up now, it will cost more in the long run.
To me this is a dramatic public endorsement of our
efforts. I am happy to say that President Ford has given
high priority to the environmental effort and has
repeatedly supported requests for increased manpower
and funding. The Congress has also consistently acted to
indicate its support. And the States and local govern-
ments have joined in the national efforts with their own
funds and programs.
GOALS
The specific goals of the United States program are
swimmable and fishable waters by 1983 and no dis-
charge of pollutants by 1985. The U.S. Congress has had
the National Commission on Water Quality working on
the feasibility of these goals over the last two years and
we will shortly be receiving the final report of the
Commission. Presently, the draft report of the Commis-
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sion's staff answers the question as to whether or not
achieving the goals of our Federal Water Pollution
Control Act of 1972 will be too expensive for the
economy of the United States.
The staff report found that the "impacts of the
projected expenditures on water pollution abatement on
the general economy—GNP growth rate, general price
level, interest rates, etc.—are not significant."
In an analysis of the price impact of PL 92-500, the
report found that the annual price increase, at an
average, would be 3/10 of one percent—a very small
price, indeed, to pay for cleaner water.
And it must be remembered that the municipal
wastewater treatment construction grant program,
amounting to $18 billion, is creating more jobs, with
some 125,000 on-site and off-site jobs having already
been created as a result of the construction grant
program. That figure is expected to rise to 200,000 by
the end of fiscal year 1977. The multiplier effect in
other sectors of the economy will considerably augment
that figure.
EVIDENCE OF IMPROVEMENT
It is well to recognize that the kind of tangible results
we hope and expect to see resulting from PL 92-500 will
not show up overnight. We are, in a sense, in mid-stream
in this effort. The enormity of the task was not
anticipated either by the Congress or by the agency, and
we will require the dedication of more resources in funds
and people to the achievement of the goals.
Meanwhile, we can take heart at the successes we are
beginning to record in this effort, all across the nation.
We are moving, and we are moving in the right direction.
Just a decade ago, Lake Erie in our great lakes had
been given up for "dead" by biologists. And the
Escambia Bay in Florida faced a similar prognosis. In
both cases, federal, state and local efforts have dramat-
ically revived both bodies of water to the point where
fish life-and some species not seen for many years-not
only survives but is thriving.
In these and many other areas individuals are enjoy-
ing once again the pleasures of cleaner water and the
success of the water clean-up effort is being recorded.
Over 97% of all water discharges are either now in
compliance with pollution control standards or are on
definite water clean-up schedules-with these require-
ments backed up by strong penalties for violations.
Among this number are almost all of our big industries.
Over 4,000 individual municipal wastewater treat-
ment projects are now underway—and improvements in
the administration of the construction grants program
will move these and other new projects to successful
completion.
We are, in effect, winning the first round in the fight
to end water pollution.
FUTURE EFFORTS
The next round will be much more difficult and more
costly-because it will deal with pollution from sources
that will require not only the application of enormous
resources, but also the application of technologies that
are still being developed and are not often available.
In our construction grants program for building
treatment facilities for urban wastewaters, it is estimated
that only 50%, or some 9,000 of 18,000 municipal
treatment plants, will provide by 1977/78 the necessary
quality of treatment. Moreover, these 9,000 plants
represent less than 40% of the 1977 population because
the larger cities will not have completed necessary
construction by that time. Our figures indicate that it
will take over $46 billion to raise treatment up to
secondary, or higher, where required by water quality
standards.
In the case of industry it is tentatively estimated by
the National Water Quality Commission that it will take
somewhere between $59.6 billion and $174.8 billion to
eliminate pollution from industry sources. These are
preliminary figures, however, and they appear to be on
the high side.
Also, while on this subject, we are particularly
concerned about the problem of eliminating toxic and
hazardous industrial effluents from wastewaters that are
discharged directly into our waters or which go into
municipal treatment systems which are not prepared to
treat these special discharges. It will require a complex
and innovative effort to develop the necessary tech-
nologies to treat industrial wastes in many cases.
As part of our control effort for instance, our
guidelines for pretreatment standards, which are being
developed, will be presenting information on those
chemicals that would inhibit the treatment plant pro-
cesses. This approach would allow the individual plant
manager to set the criteria for influents into his plant to
prohibit any chemical, or level of chemicals, that would
damage his plant operations.
The development of more and more new industrial
chemicals makes this task of protecting our environment
and public health more and more difficult. Fortunately,
this group gathered here today will help to make the
task more easily and quickly accomplished. The problem
of industrial wastes and the special needs of treatment
are common to both of our countries. The progress that
we make exchanging ideas and innovations will reinforce
pollution abatement progress not only for our nations—
but for all nations on our earth. I see by the agenda that
the variety of important subjects and topics to be
discussed should significantly contribute to further
progress and achievements, and I am pleased to express
the appreciation of the United States for the participa-
tion of our Soviet colleagues.
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THE CINCINNATI CENTER
One final thought before concluding, EPA is heavily
committed to research efforts in the field of water
pollution abatement. And health effects research is one
area that will be receiving increased emphasis. I am
happy to have been a party to these activities and to
have worked to build the new laboratory center, here in
Cincinnati, which you have toured. Although not quite
finished, it was dedicated by President Ford and Mr.
Train, our EPA Administrator, during the past summer.
Already, research conducted in Cincinnati has shown
us how to prevent the growth of algae by removing
wastewater nutrients; clean up oil spills; and produce
safe drinking water, among other discoveries. And we
have extended the improvements through EPA's tech-
nical assistance programs, to communities and states all
across America.
We hope these and the future improvements we
expect to develop in wastwater treatment will be
similarly beneficial to the Soviet citizens. I assure you
we will effectively employ advances in research due to
the Soviet efforts, and while we continue these ex-
changes, I am mindful we are not only eliminating
wasteful duplication of effort but communicating the
benefits of our different approaches to improving
abatement controls and furthering the cause of coopera-
tion for environmental improvement throughout the
world.
Thank you.
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Overview of Physical—Chemical Treatment
Jesse M. Cohen*
James J. Westrick
INTRODUCTION
A little more than a decade of research has resulted in
significant changes in the technology of treating
municipal wastewater. The design engineer now has
process alternatives not available to him in the past.
These processes, based largely on physical-chemical
principles, have the capability of treating a wide^variety
of wastewaters to produce effluents ranging in quality
from "secondary" as defined by EPA to that which
would meet the most stringent state requirements. These
processes, in conjunction with biological processes, are
increasingly being used to produce effluents that are
suitable for reuse, including use as a source for potable
water.
The treatment system which is most advanced in
development is the series of unit processes illustrated in
Fig. 1 (1,2). Following conventional pretreatment such
as bar screening and grit removal, the raw sewage is
treated with a metal coagulant or precipitant which
effectively removes suspended and colloidal solids as
well as phosphates. This unit process also removes most,
but not all, metals. Filtration through granular media,
optionally located either before or after carbon
adsorption, further reduces suspended solids. In some
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plant designs the filtration step is omitted, and the
downflow carbon contactors serve the dual purposes of
filtration and adsorption.
The fully clarified effluent from chemical treatment
is contacted with activated carbon which removes
dissolved organic matter. Where required, disinfection,
usually with chlorine, completes the treatment system.
When the carbon has been exhausted and can no longer
produce the desired effluent quality, it is removed from
the contactor and thermally regenerated. Sludges
produced during chemical clarification are processed for
disposal.
CHEMICAL CLARIFICATION
Clarification Equipment
Chemical clarification is the initial series of
operations in a physical-chemical system. The processes
are essentially the same as those traditionally used in
water treatment practice. A common flow scheme for
clarification is shown in Fig. 2. Chemicals and
wastewater are mixed in a rapid mix basin which
provides about one minute detention at average flow.
Mechanical mixing is preferred to ensure complete
dispersion of the chemical in the wastewater. From the
rapid mix basin the coagulated wastewater then flows to
a gently stirred basin where it is retained for 10-15 min
to allow the particles to collide, adhere and grow to a
settleable size. Slow paddle mixers are commonly used
for this application. The flocculated water is then
directed to a clarifier where quiescent conditions permit
the solids to settle out. In many cases, it is advantageous
to recycle settled sludge to the rapid mix basin in order
to assist in precipitation and floe formation. The
remaining sludge is withdrawn for dewatering and
disposal.
Chemicals for Clarification
Several chemicals may be used alone or in
combination for wastewater clarification. These are
listed in Table 1 and include lime at various pH's (3,4),
salts of iron and aluminum (5), and organic polymers.
The choice of the chemical to use depends on several
factors listed in Table 2. All factors are ultimately based
on optimizing process economics to reach a desired
water quality (6).
The chemistry of coagulation-flocculation has been
extensively described in the literature (7). Typical results
of these reactions can be illustrated by a description of
ferric chloride treatment of raw wastewater shown in
Fig. 3 (5). Increasing dosage of ferric chloride, expressed
in the illustration as Fe^ + , results in precipitation of
phosphorus as ferric phosphate. Here, the optimum dose
for phosphorus precipitation was about 60 mg/1 of
1". Concurrently, ferric hydroxide is formed which
coagulates and flocculates the suspended and colloidal
solids. Minimum residual turbidity obtained here
coincided with the optimum for phosphorus removal at
a dose of 60 mg/1. Since the chemical hydrolysis of
ferric chloride consumes an equivalent amount of
alkalinity, pH of the effluent will decrease, depending on
the buffering capacity of the wastewater. In this
instance, pH decreased from about 7.8 to 6.5 at
optimum iron dosage. In addition to suspended and
colloidal solids flocculation, chemical treatment also
removes 20-35 percent of dissolved organic matter
expressed here as soluble COD.
Since each wastewater is unique in its chemistry, the
exact dosage of chemical required must be determined
for each wastewater. This determination can readily be
made by appropriate jar tests of all chemical options.
After the dosage has been determined, then other factors
such as cost of chemical and sludge disposal, can be
considered for the final choice of chemical.
Use of iron or aluminum salts results in a change in
composition of total dissolved solids. Depending on
dosage, some 50-100 mg/1 of additional chloride or
sulfate ion occurs in the effluent, while 20-30 mg/1
phosphate ion and 50-100 mg/1 of carbon dioxide are
removed, thus resulting in little or no net increase in
total dissolved solids. Lime, on the other hand, can
result in lowered total dissolved solids through softening
reactions that reduce calcium and magnesium content.
FIG, 3
FeC!3 TREATMENT OF RAW WASTEWATER
30
a
O
u
25 SO 75 100 125
Ferric Chloride Dosage, mg/i c. s ,- ^ ' J
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TABLE 1. CHOICE OF CHEMICALS FOR
CLARIFICATION
1. Ferric Chloride
2. Ferrous Sulfate Plus Base
3. Ferric Sulfate
4. Aluminum Sulfate (Alum)
5. Lime (Single-Stage)
6. Lime (Two-Stage)
7. Waste Pickle Liquor Plus Base
8. Sodium Aluminate
9. Organic Polymers
Note: Polymers frequently added to assist flocculation
TABLE 2. FACTORS AFFECTING CHOICE OF
CHEMICALS
1. Influent Phosphorus Level
2. Effluent Discharge Standard
3. Wastewater Characteristics
4. Plant Size
5. Chemical Costs Including Transportation
6. Sludge Handling Facilities
7. Sludge Disposal Facilities
8. Other Processes Utilized
Performance of Clarification
Chemical clarification, properly conducted, trans-
forms raw wastewater to a fully clarified effluent with
substantially reduced concentrations of phosphorus,
organic matter and metals. Typical results are shown in
Table 3 which provides data obtained at five plants.
Clarification typically removes 70-80 percent of the
organic matter, 90-98 percent of suspended solids and
80-98 percent of the phosphate (8). Lesser removals may
be obtained when chemical dosages are reduced and
when the wastewater contains a higher-than-usual
proportion of dissolved organic matter.
TABLE 3. TYPICAL PERFORMANCE
OF CHEMICAL CLARIFICATION
Plant
Chemical
Organic SS Rem. P. Rem.
Rem. % % %
Ewing-Lawrence 170mg/lFeCl3 80 95 90
New Rochelle (ZM) Lime pH 11.5 80 98 98
Westgate, Va. 125 mg/1 FeCl3 70
Salt Lake City 80-100 mg/1 FeCl3 75 - 80
Blue Plains Lime pH 11.5 80 90 95
Sludge Production
The addition of chemicals to raw wastewater
obviously increases the weight of sludge produced,
compared to simple gravity sedimentation, because of
greater removals of suspended solids and because of the
presence of precipitated hydroxides, carbonates and
phosphates. The total weight of sludge produced can be
estimated in several ways: by weighing the sludge from a
jar test or pilot facility or by calculating the amount
from a knowledge of the precipitation products and
suspended and colloidal solids removed. As a rough
approximation, the weights of chemical sludge produced
per unit weight of coagulant fed are: 0.86 for ferric
chloride, 0.36 for alum and 1-1.5 for hydrated lime (9).
Both the volume and weight of sludge produced by
chemical treatment of raw wastewater can vary
substantially from plant to plant because of varying
wastewater characteristics, kind and dosage of chemical
used and the type and method of operation of
clarification equipment. Data from several pilot plant
and full-scale operations are summarized in Table 4.
In order to put chemical sludges in the context of
familiar experience, the combined sludges produced by
conventional primary and secondary biological treat-
ment are included in the summary. In terms of sludge
volume, chemical and biological sludges are comparable.
Low pH lime precipitation will, in fact, produce less
than half the volume than combined biological sludge. In
terms of weight of dry solids, lime processes produce 2-4
times as much of sludge as biological, while iron and
aluminum precipitation will produce as much or one-half
as much. Another characteristic shown in Table 4 is
sludge solids concentration. Lime sludges are characteris-
tically high in solids ranging from 4.4-11.1 percent.
Sludges produced by iron or aluminum salts range for
1.2-2.25 percent which are comparable to the mixed
primary and waste activated sludge (10).
Chemical sludges, like primary and waste activated
sludges, can be handled in the usual ways; thickened,
digested (except for high pH lime), dewatered,
landfilled, land spread or incinerated. All of these
approaches are being considered in design of full-scale
plants or are in operation. A more complete description
TABLE 4. SLUDGE CHARACTERISTICS
CHEMICAL TREATMENT OF RAW SEWAGE
Sludge Solids Wt. of Solids Volume of Sludge
% Ib/MG KG/m3 Ib/MG 1/m3
Primary & Waste
Activated Sludge
Lime, low pH
Lime, High pH
Aluminum
Iron
1.0
11.1
4.4
1.2
2.25
2,200 0.26
5,630 0.680
9,567 1.15
1,323 0.159
2,755 0.333
22,000
8,924
28,254
23,000
21,922
22.0
8.9
28.2
23.0
21.9
Average of data from Blue Plains, Lebanon, Taft Center, Salt
Lake City.
-------
of sludge production and disposal is contained in an EPA
Technology Transfer publication entitled "Process
Design Manual for Sludge Treatment and Disposal."
(11).
GRANULAR MEDIA FILTRATION
The effluent from a chemical clarifier operating on
raw sewage will normally contain a small amount of
suspended solids, on the order of 25 mg/1 or less. These
suspended solids can be removed by filtering the clarifier
effluent through a bed of granular media (12). In some
system designs, that granular bed is a carbon contactor,
acting as both an adsorber of dissolved organics and as a
filter of suspended solids. Carbon contactors, however,
are often quite deep, e.g. 12-16 ft (4-5 m), and cleansing
the bed of accumulated solids can be difficult. Also,
there is no way to protect the carbon against upsets in
the clarifier which could lead to rapid plugging of the
bed. Finally, a packed bed of carbon is an inefficient
filter because the particle size gradation will be
hydraulically classified from finer particles at the top of
the bed to coarser particles at the bottom. Thus, many
designers prefer to assign the filtration role to a granular
media filter specifically designed for that single purpose.
A granular media filter could also be placed after an
adsorption system (13). For example, upflow expanded
bed granular carbon systems do not remove solids.
Moreover, such systems may in fact produce a small
amount of additional solids in the form of sloughing
biomass. Therefore, positioning the filter after fluidized
or expanded bed carbon contacting would provide for
removal of clarifier effluent solids (which pass through
the fluidized bed) and also any turbidity resulting from
the development of sloughing of biomass on the carbon.
Granular media filters are almost essential as a final
treatment step in powdered carbon systems in order to
prevent substantial quantities of the very small carbon
particles from being discharged in the effluent (5).
GRANULAR ACTIVATED CARBON
The principal role of activated carbon is the removal
of soluble organic material from wastewater. This is
accomplished primarily by the physical adsorption of
organic molecules on the surfaces of the carbon, which is
a material uniquely suitable for this purpose. The high
capacity for adsorption by carbon is derived from its
very large internal surface area (600-100 m^/g) and its
special surface properties which form during the
activation process. When the capacity of the carbon
surface to remove additional molecules is diminished to
a predetermined extent, the surface can be renewed by
treatment of the carbon in a thermal regeneration
system, where the adsorbed organic molecules are
volatilized or oxidized and driven off the carbon. The
carbon, thus reactivated, is reintroduced into the
adsorption system and reused. A typical flow diagram
illustrating the series of operations is shown in Fig. 4.
Maximizing Carbon Utilization
There are two fundamental objectives of carbon
contactor design. The first is to maintain wastewater and
carbon in contact for a sufficient period of time to
achieve the desired degree of organic removal. Most
studies on municipal wastewater have indicated opti-
mum contact times in the range of 20-40 min (based on
empty bed volume). The second objective is to provide
that contact in such a way as to maximize the utilization
of the capacity of the carbon to remove organics and
thus minimize the replacement rate (14).
From an adsorption standpoint, maximum utilization
of the carbon capacity is obtained by the use of
countercurrent operation. An examination of the
Freundlich equation, an empirical relationship that has
been shown to adequately describe equilibrium data, will
show why:
__
M
= kC
1/n
where X = weight of organics adsorbed
M = weight of carbon applied
C = concentration of organics in
solution at equilibrium
k,n = empirical constants
This equation shows that the carbon loading,
M
(amount adsorbed per unit weight of carbon),
increases as the equilibrium concentration of the
organic material in the solution increases. In counter-
current contacting the carbon and the wastewater move
through the contactor in opposite directions. Thus,
carbon just leaving the contactor is in equilibrium with
FIG, 1
ACTIVATED CA33ON
REGENERAT.OiV SYSTEM
CARBON
CONTACTOR
•PAkE
CARSON
REGti\ " V.IGN
/DEWATERING FURNrtC"
SCREW
REGENERATED
CARBON
QUENCH
TANK
-------
wastewater with the highest carbon loading, —,
M
possible. Fresh carbon just entering the system contacts
the wastewater lowest in organics and provides the best
possible effluent at that contact time.
Since it is difficult in practice to achieve continuous
countercurrent contacting, adsorption system designs
approximate countercurrent contacting by using pulsed
bed, multiple-staged series operation, or single-stage
parallel contacting.
Pulsed-bed operation is a close approximation to
continuous countercurrent contacting. Here wastewater
flows up through a packed carbon bed. Slugs of spent
carbon are periodically removed from the bottom of the
adsorber and replaced at the top with fresh carbon. The
system is analogous to incorporating a large number of
stages within a single contactor. This type of carbon
contacting is commonly used as a "polishing" step to
handle highly pretreated wastewater essentially free of
suspended solids.
The two most commonly used designs for treating
chemically clarified raw wastewater are shown in Fig. 5,
which illustrates single and two-stage contacting. As the
number of stages increase, the more closely counter-
current contacting is approached. However, more than
two stages generally become uneconomic because of the
complex piping and valving.
Series contacting essentially divides an adsorber into a
number of contactors in series. When the effluent
standard is reached or exceeded, the carbon in the lead
contactor is removed and replaced with fresh (virgin or
regenerated) carbon. That contactor is then positioned
as the trail column and all other contactors are advanced
one position in the train.
Single-stage contacting divides the total contactor
volume requirement into a number of parallel
contactors. By starting the contactors in staggered
sequence, it is possible to have on stream at any given
time contactors in various stages of exhaustion. Thus,
poorer quality effluents from more heavily loaded
contactors can be blended with higher quality effluents
to produce the desired effluent quality. When the
blended effluent quality reaches the allowable limit, the
carbon in the contactor which has been on stream the
longest is removed and replaced with fresh carbon (15).
Biological Activity
A major factor in the operation of granular carbon
systems on chemically clarified raw wastewater is the
potential for the development of biological growths in
the carbon. These growths can cause severe plugging
problems in very short times. Therefore, packed-bed
contactors should be designed so that they can be very
thoroughly backwashed. Auxiliary backwash aids such as
air-scour and surface wash should also be installed.
The biological growths in the carbon columns, which
cause plugging and headloss problems, also can extend
the life of the carbon. Carbon granules tend to serve as
an attachment medium for the microbes while also
providing an enriched concentration of substrate by
adsorption. The mechanism of the adsorption-biological
activity interaction is not clear, but carbon loadings far
in excess of those predicted by laboratory isotherm tests
have been observed in pilot tests conducted over a long
enough time for the biological activity to develop (16).
An adverse effect resulting from biological activity is
the production of the highly undesirable compound,
hydrogen sulfide. Several methods have been suggested
to cope with this problem and all have exhibited varying
degrees of success. The one procedure which has been
successful is addition of oxygen in the form of nitrate,
which can be added as sodium nitrate. At the Pomona,
California pilot facility, 33 mg NaNC^/l (19 mg/1 as
oxygen) plus daily backwashing of the column to reduce
solids accumulation, completely prevented the forma-
tion of sulfide (17). Concurrently, nitrate was reduced
to nitrogen gas. An unexpected, but welcome, result of
nitrate addition was the extension of the life (capacity)
of the carbon. The carbon column was operated for 18
months without replacement and without a significant
decline in organic removal efficiency. The apparent
loading during that time reached a phenomenal 3.5 g
COD removed/g carbon of which 1.54 g/g was soluble
COD. Considering that values in the range of 0.5 g COD
removed/g carbon are commonly accepted for carbon
loading in physical-chemical systems, it is apparent that
the mechanisms of filtration (2 g COD/g carbon due to
particulate COD) and nitrate assisted biological activity
contributed greatly to the organics removal.
Carbon Regeneration
When activated carbon can no longer produce the
required effluent quality, it must be removed from the
adsorption system, transported to a regeneration system
and restored to nearly its original condition. In
municipal wastewater treatment, regeneration of granu-
-------
lar carbon is accomplished thermally in a multiple-hearth
type of furnace (18). A typical furnace is shown in Fig.
6. The regeneration system consists of dewatering
equipment, a feed conveyor, the furnace, a steam
generator, a product quench tank and air pollution
control equipment. Spent carbon enters the top hearth
and is dried. As the carbon progresses down the hearths
and its temperature increases, adsorbed organics are
volatilized or pyrolyzed, leaving a char residue. Steam is
injected into the furnace to oxidize the char residue and
to restore the surfaces of the carbon to nearly its original
condition.
During regeneration some loss of carbon is experi-
enced through physical attrition and burning of carbon.
These losses can amount to 3-8 percent or more of the
volume of carbon and are an important part of the
economics of carbon technology, since fresh carbon
must be added to maintain adsorption capacity.
Additionally, changes in the physical characteristics
of carbon are incurred during successive loading and
regeneration cycles (19). These changes are illustrated in
Table 5. Mineral components of adsorbed organics and
TABLE 5. CHANGES IN CARBON PROPERTIES
ON SUCCESSIVE REGENERATIONS
Cycle
Initial
1
2
3
Ash
Content, %
5.7
7 6
8.6
9.5
I2 No.
1090
1040
935
940
Molasses
No
250
310
290
350
Bulk Density,
g/cc
0.469
0.468
0.469
0.473
particulate inorganic material contribute to the increase
in ash of the regenerated carbon. Progressive changes
also occur in the basic pore structure of the carbon
particle. Surface contributed by small pores - >10 A-<
28 A as measured by Iodine Number - tends to decrease
while surface contributed by the larger pores - > 28 A
as measured by Molasses Number, tends to increase.
Little or no changes occur in the bulk density. In spite
of these measured changes, the net effect on the
capacity of carbon to remove organics is relatively
unaffected.
Thermal regeneration of carbon produces a gaseous
effluent containing carbon particles and noxious gases.
Both must be controlled to avoid pollution of the
atmosphere. Air pollution was successfully controlled at
the Pomona, California pilot plant system by the system
shown in Fig. 7 (17). Flue gases from the furnace first
periodically discharges the accumulated dust by
automatic reversal of the air flow. The particle free gases
pass through an afterburner operated at 1300-1400°F
(700-760°C) which incinerates the organic material
which was volatilized from the carbon. Other systems
have used a water spray system to remove particulates
but also include the afterburner.
POWDERED ACTIVATED CARBON
Activated carbon is also produced in powdered
form (passing 300 mesh, 85 um). Recent research studies
have established that powdered carbon can be used
successfully to treat wastewater (20,21,22). Application
of this technology has lagged behind that of granular
carbon primarily because regeneration of powdered car-
bon has only recently been demonstrated. With this
development, application of powdered carbon tech-
nology need not be deterred.
Contacting Systems
Because of its small particle size, powdered activated
carbon (PAC) must be contacted with wastewater as a
slurry. Rate of adsorption onto PAC is very fast,
equilibrium being reached in less than 10 minutes.
Generally, the same kind of equipment used in chemical
clarification can be used for carbon contacting. A com-
mon type of equipment is a solids-contact clarifier which
can be used to mix, flocculate and settle the powdered
carbon. In addition, this kind of equipment allows the
development of a carbon sludge with a residence time in
the contactor of several days, thus promoting the de-
velopment of biological activity which, as was discussed
earlier, contributes greatly to carbon's capacity to
remove organics (5).
After gravity clarification, the wastewater should be
directed to a granular media filter for final polishing and,
more importantly, for capture of powdered carbon
particles that escape the clarifier, and would otherwise
be lost from the system.
-------
To atmosphere
Fuel *
>
Air „,. .
Afterburner
7~)-•
r..-i
Combustion air- »
1 1 Cyclone
\ / Baghouse
Hearth ^
Furnace I L J
r XX
/Regenerated Dus* to T
S~ carbon out storage drum*
jf «A*
— Make-up water *
Dust to storage drum
I ) Quench tank
To carbon \ / ... ...
column -s ^^A — Motive Water
Eductor
'DIAGRAM OF THE AIR POLLUTION CONTROL SYSTEM
FIG, 7
PARTIALLY SPENT CARBON
INFLUENT
SPENT
CARBON
1st STAGE
CONTACTOR
CLARIFIER
CONTACTOR
CLARIFIER
FRESH CARBON
_, -•
u. t
9 -0 • ff'
^Pr.»'
.0^3 c
„ - „ , o
.C7^^C
GRANULAR
MEDIA
FILTER
— PRODUCT
FLOW DIAGRAF^l
TWO-STAGE COUNTERCURRENT
POWDERED ACTIVATED CARBON SYSTEM
FIG. 8
10
-------
Carbon Utilization
Adsorption - and concurrent biological activity -
normally takes place in a completely mixed vessel, which
can consist of a single stage of contact. To obtain higher
carbon loadings, two-stage countercurrent contacting is
desirable for high product quality. The rationale here is
the same as described for granular carbon. A typical two-
stage countercurrent contacting system is shown in Fig.
8. This system can treat raw wastewater directly or be
preceded by a chemical clarification system much as is
used for the granular carbon system. Fresh carbon is
added at the downstream clarifier, and is removed from
the system as a sludge from the first contactor. Carbon
solids separation may be obtained by metal coagulants
or preferably by organic polymers, since the latter con-
tributes no ash when the carbon is regenerated. In some
instances, flocculation occurs unaided and is adequate if
the clarifiers are operated at low overflow rates.
Regeneration
Within the past 2-3 years, it has been shown that
powdered carbon can be successfully regenerated
(22,23,24). The carbon sludge removed from the solids-
contact clarifier, is generally gravity thickened and then
dewatered. A vacuum filter has successfully produced a
carbon cake of about 23-25 percent solids. Regeneration
has been demonstrated in several types of thermal
devices, including fluidized bed reactor containing an
inert medium, transport reactor (commercial installation
regenerating 10 tons/day [9000 kg/day]), in a multiple
hearth furnace and in a wet-air oxidation system.
and 12 sq ft/1000 gal/day (0.30 m2 /m3 /day) capacity
for extended aeration and low-rate trickling filters. Since
the efficiency of the processes depend upon the laws of
physics and chemistry and not upon the well-being of a
huge population of living organisms with various en-
vironmental requirements, the P-C systems should per-
form in a more reliable manner. Operational flexibility
should allow more precise process control than is
possible with the biological systems. P-C processes
remove many materials which are toxic to biological
systems, and are, in general, unaffected by those toxi-
cants not removed. Removals of phosphorus, refractory
organics and metals are greater than those obtained by
biological systems. And finally, the effectiveness of P-C
treatment is not materially diminished by low waste-
water temperatures.
From the foregoing, however, it should not be
assumed that physical-chemical treatment is universally
applicable. The concentration and adsorbability of
soluble organics determine whether activated carbon
treatment is applicable. The higher the concentration of
organics, the more carbon will be required and the more
costly the process becomes. Certain organic material,
especially water soluble, low molecular weight organics,
are poorly or not at all adsorbed. Thus, physical-
chemical treatment would be unsuitable for treatment of
wastes containing a high proportion of non-adsorbable
materials. The basic processes of clarification and carbon
do not remove ammonia nitrogen, although high re-
movals of organic nitrogen are obtained. Physical-
chemical treatment thus must be considered as an
additional option when a wastewater treatment system is
being planned.
APPLICATION OF PHYSICAL-CHEMICAL SYSTEMS
Extensive bench and pilot scale research during the
past decade has resulted in physical-chemical systems
which are technically and economically feasible alter-
natives to biological systems. At the present time some
fifteen full-scale plants are in various stages of design and
construction, all of which will treat domestic/industrial
wastewater. Three plants are in the initial stages of
operation. Additionally, at least 12-15 plants are being
designed or constructed which will apply physical-
chemical systems to biological effluents to produce very
high quality effluents (15).
The reasons for choosing physical-chemical systems
over the alternative biological treatment are generally
based on the several advantages that physical-chemical
systems possess. The area requirements are minimal. As a
rough comparison, the combined area requirement of
the major liquid processing units in a P-C system is
roughly 2 sq ft/1000 gal/day (0.05 m2/m3/day) capacity
compared to values of 6 sq ft/1000 gal/day (0.15
m2 /m3 /day) capacity for conventional activated sludge
PERFORMANCE OF PHYSICAL-CHEMICAL
SYSTEMS
At present time, performance data from full-scale
operating plants are meager, although such information
should be available as plants come onstream. Per-
formance data have, however, been accumulated over
the past several years on fairly large (~50,000 gal/day
[190 m3/day]) pilot plant systems (2, 13, 16, 17).
Typical effluent quality from a physical-chemical
system treating degritted raw wastewater is shown in
Table 6 below. The systems consisted of chemical clari-
fication and granular activated carbon operating with or
without a granular media filter.
The range in product quality shown in the Table not
only reflects the usual expected variation, but also sug-
gests the flexibility that is inherent in the treatment
system. As an illustration, organic product quality —
COD, BOD— can be allowed to vary over a considerable
range simply by operating the carbon adsorption con-
tactors for longer periods thus decreasing the regenera-
tion frequency and concurrently the cost.
11
-------
TABLE 6. EFFLUENT QUALITY FROM
PHYSICAL-CHEMICAL SYSTEMS
Parameter
Concentration Range - mg/1
Suspended Solids
BOD5
COD
Phosphorus - P
Color - Units
Turbidity - JTU
2-10
5-15
10-25
0.2- 1.0
5-10
<10
Very high product quality is obtainable when physical-
chemical systems treat biological effluents. The product,
in many instances, is suitable for a variety of reuse
purposes including use as supplement to potable water
source. Product quality anticipated from this type of
system is illustrated in Table 7.
TABLE 7. EFFLUENT QUALITY FROM TERTIARY
PHYSICAL-CHEMICAL SYSTEMS
Parameter
Concentration - mg/1
<
1.
1-2
Suspended Solids
BOD5
TOC
COD
Total Nitrogen — N
Total Phosphorus - P
Metals meet drinking water standards
CoUform Bacteria, MPN/100 ml < 2.2
Fecal Coliform Bacteria, MPN/100 ml < 2.2
Virus 0
2.0
0.1
TABLE 8. PHYSICAL-CHEMICAL PILOT PLANT
POMONA, CALIFORNIA
Parameter
Raw Sewage Clarifier Effl. Carbon Effl.
TCOD, mg/1
DCOD, mg/1
SS, mg/1
Turbidity, mg/1
BOD5. mg/1
Color, Units
P, mg/1
N03-M, mg/1
PH
321
49
199
11.1
7.7
96
49
28
23
36
20
1.3
0.9
6.8
19
14
7
6
8
8
0.9
1.3
6.8
Clarifier
Flow - 60 gal/mm (3.8 I/sec) constant
Overflow rate - 1180 gal/day/sq ft (48 cu m/day/sq/m)
Weir loading - 10 gal/min/ft (2 1/sec/m)
Detention time - 84 min.
Alum dose - 25 mg Al/1
Polymer dose - 0.3 mg/1 anionic
Sludge Production - 2000 Jb/mil gal (250 mg/1)
Granular Carbon
Flow - 50 gal/min (3.2 I/sec) constant
Hydraulic loading - 4 gal/min/sq ft (10 cu m/hr/sq m)
Contactor type - single-stage, packed-bed downflow
Carbon size - 8 x 30 mesh (3 x 0.8 mm)
Empty bed contact time - 30 min.
Sodium nitrate dose — 33 NaNOj/l
1st cycle carbon loading - 3.5 g TCOD removed /g carbon
(1.5gDCOD/g)
1st cycle carbon utilization rate - 173 Ib/mil gal (21 mg/1)
Actual performance of a physical-chemical pilot plant
system operated at Pomona, California, for an extended
time—27 months—is shown in Table 8 (17). Also shown
are the engineering parameters of each of the two major
unit processes—chemical clarification and carbon ad-
sorption systems.
Note:
Carbon column ran 18 months (1st cycle) prior to regenera-
tion and was not exhausted. Three regeneration runs were
conducted in order to obtain regeneration data. Performance
data shown above is average data over entire 27-month
operation.
SUMMARY
Research during the past decade has provided the
design engineer with an array of unit processes which
provide, as never before, a capability to treat municipal
wastewater to almost any product quality. Increasingly,
these unit processes are being used alone or combined
with biological processes to satisfy the needs of any
specific plant. The number of possible combinations is
large. All that is needed for a successful operation is the
ingenuity of the design engineer.
REFERENCES
1. Cohen, J. M., Kugelman, I.J., "Physical-Chemical Treatment
for Wastewater," Water Research (GB), 6, 487 (1972).
2. Bishop, D. F., O'Farrell, T. P., Cassell, A. F., and Pinto,
A. P., "Physical-Chemical Treatment of Raw Municipal
Wastewater," EPA Technology Series, Washington, D.C.,
Report No. EPA 670-2-73-070.
3. Stamberg, J. B., Bishop, D. F., Warner, H. P., and Griggs,
S. H., "Lime Precipitation in Municipal Wastewaters,"
Chem. Engng. Prog. Symp. Series. Water-1970, 67, No. 107.
12
-------
4. Mulbarger, M. C, Grossman, E., Dean R. B., and Grant,
O. L., "Lime Clarification, Recovery, Reuse and Sludge
Dewatering Characteristics," Jour. Water Poll. Control Fed.,
41,2070(1969).
5. Burns, D. E., and Shell, G. L., "Physical-Chemical Treat-
ment of a Municipal Wastewater Using Powdered Carbon, "
EPA, Environmental Protection Technology Series, EPA-
R-2-73-264 (Aug. 1973).
6. "Process Design Manual for Phosphorus Removal," EPA
Technology Transfer, Washington, D C, (Oct. 1971).
7. Cohen, J. M., "Nutrient Removal from Wastewater by
Physical-Chemical Processes,"Chapter XII, NUTRIENTS IN
NATURAL WATERS. Edited by H. E. Allen and J. R.
Kramer. John Wiley & Sons, New York (1972).
8. Westnck, J. J., and Cohen, J. M., "Comparative Effects of
Chemical Pre-Treatment on Carbon Adsorption. " Presented
at 47th Annual Conference, Water Pollution Control Federa-
tion, Atlanta, Georgia, Oct. 1972 (In Press).
9. Isgard, E., "Chemical Methods in Present Swedish Sewage
Purification Techniques. " Paper presented to 7th Effluent &
Water Treatment Exhibition and Convention, London,
1971.
10. Adrian, D. D., and Smith, J. E., "Dewatering Physical-
Chemical Sludges." Applications of New Concepts of
Physical-Chemical Wastewater Treatment, Pergamon Press,
Inc., Sept. 1972
11 "Process Design Manual for Sludge Treatment and Dis-
posal. " EPA Technology Transfer, Washington, D.C., Oct
1974.
12. Culp, R. L., and Culp, G. L., ADVANCED WASTEWATER
TREATMENT, Van Nostrand Reinhold Co., New York,
1971.
13. Weber, W. J., Hopkins, C. B., and Bloom, R., "Physico-
chemical Treatment of Wastewater," Jour. Water Poll.
Control Fed.,42, 83 (1970).
14. Westrick, J J., "Physical-Chemical Treatment," EPA Tech-
nology Transfer Seminar (April 1975).
15. "Process Design Manual for Carbon Adsorption," EPA,
Technology Transfer, Washington, D.C. (Oct. 1973).
16. Hopkins, C. B., Weber, W. J., and Bloom, R., "Granular
Carbon Treatment of Raw Sewage," EPA Water Pollution
Control Research Series, ORD 17050 DAL (May 1970).
17 Directo, L. S., Chen, C. L., and Kugelman, I. J., "Pilot Plant
Study of Physical-Chemical Treatment." Presented at the
47th Annual Water Pollution Control Federation Confer-
ence, Denver, Colorado (Oct. 1974).
18. Cohen, J. M., and English, J. N., "Activated Carbon Re-
generation. " AIChE Symposium Series, Water-1974 -
Industrial Wastewater Treatment No. 144, 70 (1974).
19. Juhola, A. J., "Optimization of the Regeneration Procedure
for Granular Activated Carbon," EPA Water Pollution
Control Research Series, 17020 DAO 07/70 (July 1970).
20. Garland, C. F., and Beebe, R. L., "Advanced Wastewater
Treatment Using Powdered Activated Carbon in Recirculat-
ing Slurry Contactor-Clarifiers," FWQA Water Pollution
Research Series, ORD 17020 FKB 07/70 (1970).
21. Beebe, R. L., "Activated Carbon Treatment of Raw Sewage
in Solids-Contact Clarifiers," EPA Environmental Pro-
tection Technology Series EPA-R2-73-183 (March 1973).
22. Shuckrow, A. J., Dawson, G. W., and Bonner, W. F.,
"Physical-Chemical Treatment of Combined and Municipal
Sewage," EPA Environmental Protection Technology Series,
EPA-R2-73-149 (Feb 1973).
23. Smith, S. B., and Koches, C. F., "Plant Scale Thermal Re-
generation of Powdered Activated Carbon Used in Sugar
Purification. " Presented at 31st Annual Meeting, Sugar
Industry Technologists, Inc., Houston, Texas (May 1972).
24. Burns, D. W., Wallace, R. N., Cook, D. J., and Shell, G. L.,
"FinalReport EPA Research Contract No. 68-01-0183,"in
preparation.
13
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STUDIES ON WASTEWATER TREATMENT WITH FLOCCULANTS APPLICATION.
I. N. Maysnikov, L. V. Gandurina, L. N. Butzeva
(VNH VODGEO)
The industry growth and the rise of populated
areas accomplishment is attended with the formation of
a great number of wastes, which result in an environ-
ment pollution. In this connection great attention is paid
nowadays on environment control improvement, in-
cluding prevention of water sources pollution. Various
chemicals (oil products, acids, carbohydrates, alkalis,
cyanides, sugars, pesticides, detergents etc.) flowing
together with sewage break the natural processes taking
place in water reservoirs sometimes cause failure of
water supply of populated area and enterprised. Render-
ing such substances harmless at the mechanical and
biomechanical treatment stations presents considerable
pitfalls, and demands large capital and operating costs.
Besides, the removal effect of some contaminations, for
example oil products, heavy metals, organic compounds,
biochemically difficult oxidizable biogenous sub-
stances, is not in accord with sanitary standards and
causes the necessity of the subsequent post treatment.
At the same time requirements to the quality of
treated sewages disposed into the reservoirs or directed
to the reused systems are ever increasing.
It should be also noted that structures of mechanical
and biological treatment, used in most cases, have the
considerable sizes, treatment process in which requires
prolonged time and process control in these conditions
presents some difficulties.
So, currently, along with the successes achieved in the
field of mechanical and biochemical treatment other
possibilities of rising efficiency of rendering contamina-
tions in sewage harmless are being searched. The
combined use of mechanical, physical and chemical,
chemical and biological sewage treatment is one of such
trends.
Such treatment schemes find ever expanding
application in practice of rendering industrial and
domestic sewage harmless. The experience of mentioned
stations use shows that the performance of physical and
chemical, and biochemical treatment structures gives the
possibility to increase the efficiency of contaminations
removal, significantly reduce the time of liquid treat-
ment and etc.
In some cases, by application of mechanical, and
physical and chemical treatment only, the standards for
the treated effluents, intended for the reused purposes
may be achieved. The ever increasing attention to the
process of physical and chemical treatment derives also
from the fact, that they have a number of advantages,
for example, in comparison with biological treatment,
physical and chemical treatment structures require less
areas for their location, there is a possibility to remove
substances, toxic for active sludge microorganisms,
difficult oxidizable and biogenous contaminations and
to make the treatment process fully automatic and etc.
New highly efficient flocculants formation aids in
successful use of chemical process in physical and
chemical treatment while neutralizating industrial and
domestic wastewaters.
As a rule their use in small doses in water treatment
process makes it possible to get less quantity of sediment
and to intensify all the technological processes of the
industrial effluents.
However, at present, the majority of the present
physical and chemical treatment structures still use
mineral coagulants—aluminium salts, ferrum salts and
lime, which have some significant disadvantages: large
chemical doze, small strength of flock formation, low
rate of hydrolysis large sludge volume, difficulties
related to dewatering and utilizing of large quantities of
sludges.
The studies show that providing water supply in-
dustry with highly efficient flocculants makes it possible
to increase more the efficiency of physical and chemical
treatment structures.
This paper presents the results of studies on waste-
water treatment by applying flocculants and their
combinations with mineral coagulants. Experiments
were carried out on effluents of such industry fields as
chemical, petroleum chemical and paper and pulp.
Separation of solid phase (flock) and liquid was
performed by settling in cylinders for an hour or
two and filtering through paper filter, model filter
with the sand medium, compression flotation in labora-
tory installation with flotation camera of 100 mm
diameter and 1500 mm height.
As the majority of industrial effluent contaminations
has the negative charge, the studying of water soluble
cationic flocculants, macroion of which is positively
charged, is of particular interest. Such flocculants are
able to cause natural coagulation of negatively charged
particles.
There are also given the results, obtained by a number
of scientists.
The greatest emphasis in our work is placed on oil
contained sewage treatment studying, because of its
complex composition and substantial quantity of
organic substances with the difficulty oxydized ones
among them.
So, in order to study the high treatment rate of
oil contained sewage, the use of highly molecular syn-
thetic flocculants, both independently and together with
14
-------
TABLE I
Flocculants'
marks
1
HPS-46
HPS-47
HPS-48
HPS-49
HPS-411
HPS-11
HPS-7
Vinylpyndines Alkylat-
ing
agent
2 3
4-vinylpyridine CH3
~"~ C2H5
C3H7
C4H9
-"- C2H5Br
2-methyl-5 vinyl
piridine C2H5fir
_"_ _"_
_"— _"_
_"_ _"_
C2H5
Viscosity
character
/ /
delitre/
IB
4
0.75
0.76
0.70
0.20
0.78
0.4
2.26
4.0
9.4
0.4
M
10-S6
5
__
—
—
-
-
0.112
0.726
1.26
3.24
-
Exchange
volume
mg-equiv/
/g
6
3.94
3.23
3.47
3.48
4.05
4.44
4.2
4.16
3.80
3.5
mineral coagulants-aluminium sulphate, hydrolysis of
which occurrs with a rather high rate at pH 6.5 - 75, was
investigated.
Highly basic water soluble polyelectrolites of HPS
serie (highly molecular pyridine salts on vinylpyridine
base). Characteristics of the mentioned polyelectrolites
are presented in Table 1.
In this case from sewage with COD = 558 mg02/l, 64
mg/1 of suspended solids and 40.8 mg/1 of oil products,
Note. Molecular mass of polyelectrolites HPS-II was
calculated from the following formula
[n] =7.16°10-6M°94
In combined raw sewage treatment with the aluminium
sulphate and flocculants HPS-46, 47, 48, 49 with the subse-
quent settling during two hours, it was found that HPS-47 ap-
plication was the most efficient (Table 2).
Table 2
Flocculant
description
Influence of flocculant type on treat-
ment efficiency of petroleum contained
wastewaters with coagulation and set-
tling. (2 hours)
Dose mg/1
treatment efficiency, %
Al2(SO4>3 offloccu- COD suspended oil
lant solids product
73
70.5
69
77.5
HPS-46
HPS47
HPS-48
HPS-49
48
48
96
48
96
48
48
96
2.0
2.0
2.0
2.0
2.0
2.0
0
0
23.1
80
33.2
70
33.2
19.7
13.1
26.6
90.8
93.2
96.5
95.4
91.5
86.0
90.5
95.5
contaminations are removed by 80%, 93.2% and 73%
respectively.
It should be emphasized that in the same conditions
but without flocculant, the COD value decreases only by
13.1%. It is supposed, that high treatment efficiency is
achieved by interaction of flocculant with contamina-
tions found in the water not only in emulsifiable but in
dissolved condition.
From the mentioned materials it is apparent that the
rate of treatment from suspended solids and oil products
by applying HPS-47 is also increased. Doubling the
coagulants dose in this condition, in fact, does not
change the treatment efficiency from the suspended
, solids, yet causes the COD increase from 20 to 70% in
treated residual water.
So application of aluminium sulphate and flocculant
with 50 mg/1 and 2 mg/1 respectively concentrations
looks more promising in comparison with the usually
used at oil refineries doses of one coagulant, equaled to
100-150 mg/1.
The possibility of water treatment by the use of
flocculants only was also studied. The preliminary
experiments demonstrated low efficiency of 4 vinyl-
pyridine based flocculants in settling process of two
hours duration. Consequently, flocculated flocks
removal by filtering was studied.
The results obtained in wastewater treatment process,
at COD-52 mg/1 and 58 mg/1 of petroleum products
concentration, and treated with 10 mhmg/1 poly-
electrolyte, are given in Table 3.
It is apparent from the obtained data analyses that 2
methyl-5 vinylpyridine and 4 vinylpyridine based poly-
electrolytes alky late d with (ethyl bromide and ethyl
iodide (HPS47, HPS-411, HPS-11) were found to be
more efficient from all polymers flocculants in
flocculation and filtration process. These flocculants
15
-------
application makes it possible to reduce COD value by
87.5% and oil concentration by 93.4%. Molecular weight
increase of flocculant HPS-11 from 112000 to 726000
results in COD removal by 50%. This is due to the fact
that macromolecule size increase causes bonding of the
large number of colloid particles to the one polymeride
macromolecule forming therewith large flocks.
TABLE 3. TREATMENT EFFICIENCY WHEN
FLOCCULATION WITH FILTRATION USED.
mg 02/1 COD 40.7-172 mg/1 ether extracted ones, after
treatment by pressure flotation and cationic polyelec-
trolites preliminary introduced into sewage.
Flocculant
Treatment efficiency, %%
type
HPS-46
HPS47
HPS48
HPS-19
HPS-411
HPS-7
HPS-11 1^8=112000
HPS-11 M-V s=2726000
Petroleum Products
91.0
88.4
93.4
91
91
88.4
95.4
92.5
COD
14.1
87.5
37.9
-
87.5
65.6
38.2
87.5
In an effort to determine the influence of the floc-
culant molecular weight on treatment process, experi-
ments were performed on coagulated wastewater treat-
ment by means of settling and compression flotation.
Fig. 1 presents gained results. The displayed data
demonstrate that removal efficiency rises with the
increase of polyelectrolytes molecular weight. At the
same time flotation during 10 minute provides better
suspended solids removal in comparison with settling for
an hour. So flotation treatment of oil contained sewages
pretreated with polyelectrolyte HPS-11 (M=3.24.10'6)
and containing 57 and 75 mg/1 of suspended solids gave
their removal to the residual concentration 4.0 and 9.0
respectively that constitutes 80.5% and 93%.
Wastewater COD in the treatment process decreases
by 70.6 and 75.6%, oil products- by 75%. (Co = 36
mg/1).
From other types of polyelectrolites VA-2 (poly-
styrene based quarternary ammonium salt), P El (poly-
ethyleneimine), cationic polyacrilamide. The comparison
analysis of treatment rate of preflocculated wastewaters
by settling and filtration method, shows, that P El
(molecular weight = 80000) is the most efficient.
Optimum dose of P El determined by experimental
coagulating method averaged 5 mg/1.
Results obtained during oil contained sewage treat-
ment with flocculants, are given in Table 4.
In an effort to intensify the suspension removal from
water, treated with flocculant PEI (5 mg/1 dose), sewage
treatment by compressure flotation method was con-
ducted. The performed experiments demonstrated
considerable decrease of contaminations amounts in
sewage with 21 - 36.7 mg/1 suspended solids, 484-600
TABLE 4
Indices
Sewage composition
After oil separator
1
PH
COD mg/1
BOD mg Oj/l
Suspended solids
mg/1
K - P mg/1
Volatile phenols
with vapour, mg/1
Non ionogenous
detergents, mg/1
Chlorides
PEI mg/1
2
7.1 -
580 -
98.0 -
87.6 -
9.55 -
0.65 -
6.5 -
2950
7.7
1300
-130
- 133
- 155.8
-9.6
16.0
-5700
-
After physical and
chemical treatment
C -5 mg/1
3 PEI
7.1 - 7.8
270 - 660
15.0-24.5
2.1 -4.6
0.75 -5.4
0.6 - 8.9
5.5 - 14.5
—
0.003 - 0.07
16
-------
Thus, suspended solids concentration reduces by possible to evaluate the influence of flocculant nature
72-95%, etherextracted substances by - 89 - 91% and and its dose on treatment efficiency.
COD value - by 36 - 56%. Fig. 2, 3 give the curves of suspended solids decrease
It is a matter of general experience, that reagent
introducing place, plays a leading role in sewage treat-
ment by flotation. In most cases, for removal of the
major portion of contaminations, petroleum products
for example, the chemical supply into saturator is
efficient and in post treatment process of biologically
treated sewages; when easily broken flocks are removed,
coagulant is supplied to a flotation chamber.
It turned out in this case that polyethylene intro-
ducing place in flotation process has no practical in-
fluence on treatment efficiency.
The duration of water presence in flotator is one of
the factors responsible for process economy.
The study of influence of pressure flotation effi-
ciency on time, revealed that the bulk of contaminations
amount is removed in 5 minutes and in 10 minutes the
process is over. The following water presence in flotation
chamber leads to the foamy layer damage which causes
the water pollution again.
In ballast and industrial sewage treatment of petro-
leum transshipping reserves, the efficiency use of some
flocculants of cationic, anionic, and non ionic character
was studied.
Among cationic polyelectrolites polyethyleneimin,
poly-1.2 dymethyl-5 vinylpiry dine-methyl sulphate
(PPS), poly—1 ethyl-2 methyl-5 vinylpyridine-bromide
(HPS-11), polyelectrolites of VA serie: VA-212,
VA-112, VA-102 were tested. Among nonionogenous
and anionic flocculants metas (copolymeride of meta-
crylamide and metacrylitic acid), polyacrylamide and its
derivatives: PAA-H and RAA-R were used.
The comparative evaluation of mentioned polyelec-
trolites efficiency was made on the basis of the ex-
perimental sewage clarification for two hours in one litre
cylinders at various dose presence of studied substances.
When studying the simultaneous effect of aluminium
sulphate with anionic and nonionic flocculants on
treatment rate of ballast and industrial sewage it was
revealed that the highest treatment efficiency is achieved
by the use of polyacrylamide (C =1.0 mg/1) for ballast
waters and metas (c = 2 mg/1) for industrial waters.
Aluminium sulphate concentration constitutes 8 mg/1
(by aluminium ione). Thus at optimum chemicals doses
after an hour settling of ballast and industrial sewage of
oil transshipping reserves, suspended solids concentra-
tion reduces by 68 and 98%, and sewage COD-by 75%
and 30% respectively.
In order to achieve the same treatment rate after an
hour settling at sewage treatment with aluminium
sulphate, chemicals dose constitutes 25-32 mg/1 (by
ione Al3+).
Ballast and industrial sewage treatment with cationic
flocculant and subsequent sewage settling, makes it
17
-------
and ballast industrial sewage at settling. From the
obtained data it is clear that the most efficient were
flocculants VA-112, PPS and H C = 11 (mol. weight =
726000, the use of which at 5 mg/1 amount allows to
reduce suspended solids concentration by 75-83.5% and
COD-by 40-50%.
At flocculation and settling of industrial sewage of oil
transshipping reserves, best results were obtained by the
use of PPS strong basic polyelectrolite of 3 mg/1 con-
centration, for example PPS flocculant application
allows to reduce suspended solids concentration to 22
mg/1 (with initial =108 mg/1), COD - with initial = 170
mg/1.
In order to intensify the process of flocculated flocks
separation and sewage clarification, treatment by
compressure flotation method was also used, as a result
of conducted studies it was found that high treatment
effluency may be achieved either by application of
anionic and nonionic type flocculant, or by independent
use of cationic flocculants. Thus, flotation treatment of
ballast sewages, treated with aluminium sulphate (C = 8
mg/1 by A ione) and metas (C = 2 mg/1) gives the
possibility to reduce oil concentration to 1.7 mg/1 (with
the initial = 45 mg/1). The use of one coagulant (C = 8
mg/1) allows to reduce oil products concentration only
to 5 mg/1.
Among cationic type flocculants at flotation treat-
ment PPS—is the most efficient. So, at treatment with
the mentioned flocculant of 3 mg/1 concentration, the
suspended solids amount in sewage decreases from 30.5
to 11.0 mg/1, and petroleum products — from 7.6 to 2
mg/1.
Investigation of municipal sewage treatment by the
use of PEI, carried out at the Scientific Research
Institute of municipal water supply and sewage treat-
ment of the Academy of municipal management named
after Pamphilov, demostrated that PEI allows to remove
from sewage substances, being in the water both in
colloid and dissolved condition (dye-stuffs, naphthenic
acids and humic substances, ions of transitive metals).
The results of one serie of experiments, when pre-
coagulated water was subjected to settling and filtering,
are given in Table 5. Optimum PEI dose, determined by
the experimental coagulation method, ranges from 2 to
80 mg/1 and averages 10 mg/1. The increase of dose
higher than optimum one leads to the decrease of sewage
treatment efficiency.
As it was stated earlier, the available treatment
methods (mechanical and biochemical) do not allow
complete removal of difficulty oxidizable substances
from sewage; acid type dye-stuffs in particular.
Regarding this, high molecular flocculant application
for this purpose is of great practical interest.
Studies carried out by the Moscow chemical and
technological Institute named after Mendeleyev in
cooperation with the Central Scientific Research
Institute of wool, demonstrated that the use of poly-
electielites of serie HPS, results in a high degree of
sewage treatment from dye-stuffs.
Best results were got by using HPS-11 with 1.260000
molecular weight, as a precipitator. Polyelectrolite
molecular weight decrease is accompanied by the
increase of polymer recipitator dose. Besides, it should
be emphasized that dependence degree of dye-stuffs
removal from water solutions reaches its maximum at
increase of the polymeric precipitation dose.
lonogenous group presence both in dye-stuffs and
polyelectrolites molecules, gives the reason to expect
that dye-stuffs settling takes place as a result of chemical
interaction of these functional groups, condition of
which (dissociation rate) has the main influence on
flocculant settling ability.
The increase of polyelectrolite molecular weight
results in viscosity increase and consequently-in
increase of size and efficient charge of polyelectrolite
macromolecule. Settling ability of flocculant BBC
changes is also in the same way.
Optimum flocculant dose depends on dye-stuffs
concentration and ranges from 2 to 20 mg/1 and
averages 10 mg/1. The rate of sewage treatment ranges
from 75 to 100% depending on dye-stuffs' nature.
Correlating of the experimental results for dye-stuffs
of different types (polyelectrolite dose, settling rate)
points to the fact that dye-stuff molecules react to some
elementary flocculant links.
Sewage post treatment with chemical application.
Chemical treatment of sewage, biologically treated
with mineral coagulants with the subsequent separation
Table 5
Contamina-
tion type
or factor,
characte-
rising
water qua-
lity
1
BOD
COD
Suspended
solids
Protein
substances
Oil products
Detergents
Alizarine
Indigo
carmine
P205
0,2
Cr2
Ammonia
nytrogen
Water,
flow-
ing to
treat-
ment
2
87-139
200-435
120-168
79-417
10-40
3.1-5.8
0.84
0.63
20-31.5
2.3-4.0
7.7-10.3
8-32
Municipal sewage
Coagulated % of treatment
settled
3
40-61
99-191
26-61
74-98
0.8-3.6
0.64
0.35
12-25.5
0.5-1.6
1.7-3.4
8-28
mg/1
filtered
4
16-24
58-108
0.8-37
6.9-48
0-0.17
09-1.6
0.1
0.15
11-15
0.2-0.5
0.6-1.9
7.5-28
at
settling
5
51.0
53.0
76.7
69.3
_
-
2.38
44.4
38.0
68.0
48.6
5.0
at
settling
and
filtering
6
81.0
73.2
97.8
86.5
99.8
71.3
88.0
76.2
61.6
91.1
79-0
8.3
18
-------
of coagulated contaminations by pressure flotation
method is one of the efficient methods of post treat-
ment. Investigations were conducted on biologically
treated sewages of oil refinery (OR), integrated pulp and
paper (IPPM) and chemical mills (ICM).
Treated water characteristics are given in Table 6.
Table 6
Item
PH
Suspended solids mg/1
Ethersoluble mg/1
Sulphides mg/1
Chlorides mg/1
Phosphate, mg/1
Ammonia nitrogen mg/1
Nitrite nitrogen mg/1
Nitrate nitrogen mg/1
Phenol mg/1
Saltcontent, mg/1
COD mg/1 02
BOD full, mg/1 07
BOD5 mg/1 02
Dissolved oxygen, mg/1 02
OR
7.1
8.0-20.0
14-20
34
610
2
3.5
2.5
12.0
0.35
840
90-200
75
7.0
2.9
ICM
7.0
25.0
-
-
-
-
5.2
0.22
46.7
-
-
40
—
3.0
-
IP.PM
7.0
20-100
-
-
-
1.8
-
-
600
—
20-50
3.0
As a result of investigations carried out on coagula-
tion of sewages intergrated chemical and oil refinery
mills with aluminium sulphate, and subsequent treat-
ment by pressure flotation method, it was revealed, that
coagulant application at doses from 2 to 10 mg/1 is
accompanied by the increase of sewage treatment rate.
Thus, at aluminium sulphate dose of 10 mg/1, con-
centration of suspended solids reduces to 1.7 mg/1 (with
the initial = 9.0 mg/1; ethersolubles one-to 6.7 mg/1
(with the initial = 16.7 mg/1) COD value-to 84 mg/1
(with the initial =188 mg/1).
Studies on posttreatment sewages of the pulp and
paper industry by pressure flotation method, were
conducted both with coagulant application and without
it. Aluminium sulphate with concentration ranging from
2 to 20 mg/1 (by ion A) was used as a coagulant.
The optimum sulphate aluminium concentration,
consisting 10 mg/1, provides suspended solids removal
by 80-90%, phosphorus ones—by more than 50%.
BODs and COD values therewith reduces by 40% and
70% respectively. At the same time water saturation
with oxygen, the contents of which encreases 2-3 - fold
after a ten minutes flotation, takes place.
It may be said in conclusion, that in all cases floc-
culant application for treatment of sewages of different
composition is accompanied by the increase of treat-
ment rate. At present, polyelectrolites application in
sewage technology is often in particular need and
non-replaceable and sometimes it is more efficient
despite the high cost.
19
-------
THE OPERATION OF THE PHYSICAL-CHEMICAL PLANT AT ROSEMOUNT, MINNESOTA
Dr. Robert Polta
INTRODUCTION
The Metropolitan Sewer Board of the Twin Cities
Area was formed in 1969. In 1970 the MSB acquired the
33 wastewater treatment facilities and 320 miles of
interceptor in the 7 county metropolitan area. Of the 33
plants acquired only 4 produced treated effluents in
compliance with applicable water quality standards.
Twelve plants have been closed to date and several
others have been upgraded. Three new treatment facili-
ties have been put into service since 1972-one being the
Rosemount advanced wastewater treatment plant
(AWTP).
The original Rosemount treatment facility consisted
of a high rate trickling filter plant which discharged to
an effluent seepage pond from which the effluent
escaped by percolation and evaporation. No other outlet
was available for the effluent at that site and the seepage
pond was operating at capacity. Thus it was not possible
to expand the plant to meet the increasing hydraulic
loading.
The new plant was to discharge to Spring Lake which
is part of the Mississippi River. At that time however
studies were being made to determine the feasibility of
separating the lake from the Mississippi River and desig-
nating it for recreational use. The evaluation of the
water quality standards and their applicability to receiv-
ing waters of limited dilution capacity led to the
adoption of the following effluent quality limits for
design criteria:
BOD
Suspended Solids
Total Phosphorus
-10mg/l
-10mg/l
- 1 mg/1
20
-------
Ammonia Nitrogen
Total Coliform Organisms
- 1 mg/1
- lOOOMPN/lOOml
TABLE 1
ROSEMOUNT AWTP - ON-LINE PROCESSES
Several design alternatives were evaluated for a design
flow of 0.6 MGD. Estimated owning and operating costs
indicated that a physical-chemical treatment facility
would be most cost efficient. It was also recognized that
the use of these new treatment processes would serve to
fully evaluate the feasibility, economics and application
of individual unit processes for future treatment plant
construction elsewhere.
The decision was made in 1971 to build the Rose-
mount AWTP. The gate opened November 20, 1973 and
the facility has been in operation since that time.
PLANT DESCRIPTION
General
The plant is composed of process units totally
enclosed in a 15,000 sq. ft. steel building. After metering
and coarse screening the flow is pumped to one or two
parallel process trains each with a design capacity of
300,000 gal/day, Figure 1. The essential treatment units
in each process train are presented in Table 1 in the
order in which they appear in the plant.
Unit
Suspended solids
contact clarifier (1)
Dual media filters (2)
Granular activated carbon
colums (3)
Dual media filters (2)
Ion exchange columns
(clinoptilolite)
Function
BOD, suspended solids and
phosphorus removal
suspended solids removal
soluble organic removal
suspended solids removal
ammonia nitrogen removal
Considerable operational flexibility exists within each
train. The first stage filters (DMFj) can be bypassed.
The carbon columns may be operated in several modes.
The second stage filters (DMF2) may also be bypassed.
The flow from the two trains is mixed prior to
chlorination and discharged to the Mississippi River
(Spring Lake) through a forcemain approximately one
and one half miles long.
The support or off-line processes at the plant include
chemical feed systems, activated carbon transfer and
regeneration systems and a zeolite regeneration system.
21
-------
ON LINE PROCESSES
Clarification
A suspended solids contact clarifier is the first unit in
each process train. The units are 25 feet in diameter and
have a side water depth of approximately 13 feet-see
Figure 2. At design flow (208 gal per min. per unit) the
surface settling rate is 0.5 gal per min per square foot
and the detention time is approximately 3 hours and 45
minutes.
Each unit is equipped with a skimmer and grease box
as well as a rotating sludge plow. A variable speed
turbine type mixer is used to provide turbulence for
mixing the chemicals with the sewage flow. This turbine
also affects sludge recycle through the draft tube. Sludge
is removed from the clarifier on a flow proportional
basis, by gravity, and discharged to a holding tank. The
sludge is currently disposed of by hauling to another
MWCC facility or by subsurface injection on site.
The clarifier overflow is collected and discharged to a
weir box where sulfuric acid can be added for pH
control as required. The overflow rate is determined at
this point to allow for flow proportional chemical
additions in the clarifier.
© Rav.
(now Distributor]
Anthracite Coal
©
V Haste
IE
©
©
j^20
DUAL KEDIft FILTER
Rosemouni AUTP
Figure 3.
Filtration
The two primary and two secondary filters per train
are essentially identical. The backwash water storage
tank is located directly above the filter box as illustrated
in Figure 3. Each filter box is 8 feet in diameter pro-
viding for loading rates of 2 gal per min per square foot
at design flow. The loading rate doubles when one filter
of a pair is taken out of service for backwash. The filter
media consists of approximately 24 inches of anthracite
coal with an effective size of l.lmm and 12 inches of
sand with an effective size of 0.45 mm.
During normal operation the raw water enters valve
(A) and passes through the flow distributor and down
through the filtration media and underdrains, through
valve (B), up through the backwash storage compart-
ment and over the discharge weir. When backwash is
initiated valves (A) and (B) close and valve (C) opens to
drain down the filter box to that level. After this is
accomplished valve (C) closes and valve (E) opens and
valve (D) opens to allow air to pass up and scour the
media. Valve (D) then closes and valve (B) opens to
provide an upflow expanded bed wash. After backwash,
valve (E) closes and valve (A) opens. The filter is then
ready for service.
The available head allows for backwash rates of
approximately 15 gal per min per square foot. The air
scour rate is approximately 5 cubic feet per square foot
per minute. Backwash is presently initiated manually
although a program timer is available for automatic
initiation.
Carbon Adsorption
Each of the three carbon columns per train is 8 feet
in diameter and approximately 27 feet high-See Figure
4. A nominal depth of 12 feet of granular activated
carbon (Westvaco 12 x 40 mesh) is maintained in each
column. The piping and valve arrangement (32 air acti-
vated valves per carbon column train) allows consider-
able flexibility in terms of operating modes. Any 2 of
the 3 columns may be operated in the following modes:
series upflow, series downflow, primary upflow and
secondary downflow and parallel downflow. Series
upflow and series downflow have been the primary
operating modes to date.
The carbon columns are backwashed on a routine
basis to remove debris and to limit the accumulation of
biomass in the carbon bed. The procedure includes a 30
minute air scour and a 15 minute backwash at a rate of
12 gal per square foot per minute.
When the desired organic removals can not longer be
maintained across the carbon column, one of the
columns is taken out of service and replaced with a
column containing regenerated carbon. The spent carbon
is transported to the regeneration facility by an air aided
hydraulic transfer. Water is pumped through the back-
wash entrance and air supplied to the top of the column
22
-------
at 12 psi as the valve on the carbon transfer line is
opened. The carbon slurry is thus forced through the
transfer line and discharged to the spent carbon holding
tank. The 600 cubic feet of carbon can be transferred in
approximately 20 minutes.
Ion Exchange
The ion exchange columns are pressure vessels 8 feet
in diameter and, approximately 14 feet high. Each
column contains a 6 foot depth of the natural zeolite
clinoptilolite (20 x 50 mesh) supported on gravel pack-
ing and plastic strainers. The plant flow passes down
through two zeolite beds in series. When the NH3-N level
in the effluent of the second column reaches a pre-
determined level the primary column is taken out of
service for regeneration. The secondary column is moved
up to the primary position and a regenerated column is
placed in the secondary position.
downflow enter
carbon transfer air enter
underdrains
carbon depth 12 feet
/
o
upflow header
downflow exit
backwash enter
carbon transfer
Rosemount AUTP
CARBON COLUHfIS
Figure 4
OFF LINE PROCESSES
Chemical Feed Systems
Lime
Lime slurry is used to maintain an elevated pH in
the clarifier when required. The lime delivery system as
illustrated in Figure 5 consists of a lime storage silo with
capacity for approximately 30 tons hydrated lime, a
slurry mixing tank with a capacity of about 1650
gallons, slurry transfer pump, a slurry storage tank of
about 8000 gallons capacity and four, variable stroke,
diaphram chemical feed pumps. The lime slurry con-
centration is maintained at approximately 2.5%. The
slurry feed pumps have a maximum capacity of 5 gallons
per minute each and are used to maintain flow pro-
portional lime feed.
Ferric Chloride
Liquid ferric chloride (approximately 40% FeCl3) is
delivered to the plant and stored in a 6500 gallon fiber-
glass tank. The ferric chloride is used as a coagulant in
the clarifier. Four, variable stroke, diaphram chemical
feed pumps deliver the ferric chloride to the clarifiers on
a flow proportional basis. The pumps have a capacity of
15 gallons per hour each.
Polymer
An anionic polymer is used as a coagulant aid in the
clarifier. The polymer is delivered in liquid form and
diluted to a concentration of 0.25% in one of two
mixing tanks. Four, variable stroke, diaphram chemical
feed pumps feed the solution to the clarifier on a flow
portional basis. The pumps have a capacity of 7.5 gal-
lons per hour each.
Chlorine
Chlorine is supplied to the plant in one ton cylinders.
Two standard vacuum operated chlorinators with manual
rate control are used to deliver chlorine solution to the
effluent and at several points in the plant. The plant
effluent is served by a unit with a capacity of 100
pounds per day. The in-plant chlorine is supplied by a
unit with a capacity of 400 pounds per day.
Activated Carbon Regeneration
The carbon regeneration system is illustrated in
Figure 6. Spent carbon is transported to the dewatering
tank where gravity drainage reduces the moisture
content to appromately 50%. A variable speed screw
conveyer then delivers the carbon to a multiple hearth
furnace. The four hearth furnace is 54 inches in diameter
and is equipped with a wet scrubber and afterburner to
control stack emissions. During regeneration the hearth
temperatures are maintained in the following ranges:
23
-------
Hearth
1
2
3
4
Temp. Range —c
900 to 1050
1400 to 1500
1550 to 1650
1600 to 1700
Steam is injected into hearth number 4 to aid in the
regeneration process.
The carbon is quenched as it discharges from the
furnace and is transported to a storage tank similar
to the on-line carbon columns. Carbon is transferred
from the storage tank to one of the on-line columns by
the transfer technique previously described.
Zeolite Regeneration
When an ion exchange column is taken out of service
and the regeneration process is initiated the sequence is
as follows (Figure 7):
(1) The column is backwashed, upflow, at a rate of
approximately 8 gallons per square foot per minute.
(2) The hot brine is pumped through heat exchangers
1 and 2 and then the cooler — which protects the ion
exchange media against temperatures in excess of
80 F — and up through the media. The spent brine
returns through the heat exchangers and is discharged to
a storage tank.
(3) After a clean water rinse the ion exchange
column is again ready for service.
The spent brine is rejuvenated by the following pro-
ceduie:
(1) The pH of the spent brine is adjusted to 11.5 and
sodium carbonate is added. The CaCC>3 and Mg(OH)2
thus formed is allowed to concentrate in the tank
bottom and then pumped to the sludge storage tank.
(2) The desludged brine is then pumped through heat
exchanger 1 or 2 and discharged to the stripping tower.
(3) Steam is injected into the stripping tower at a
rate of approximately one pound per gallon of brine.
(4) The volatile NH3 along with water vapor are
discharged from the top of the tower to an air cooled
condenser.
24
-------
(5) The condensate discharges to a receiver at a
concentration of about 1%NH3-N.
(6) The regenerated brine is pumped from the
bottom of the stripping tower through the appropriate
heat exchanger and discharged to storage where the salt
concentration is adjusted to 1 normal NaCl.
Sulfuric acid and sodium hydroxide are added as
required for pH control in the two brine tanks.
PLANT PERFORMANCE
General
The Rosemount AWTP was put into operation in mid
November 1973 and since that time has been the only
treatment facility serving the City of Rosemount. During
the approximately 2 years of operation the facility has
produced a high, although somewhat variable, quality
effluent as illustrated by the monthly averages presented
in Figures 8, 9 and 10.
The initial plant start-up which was supervised by the
contractor's representatives lasted approximately 6
weeks. Steady state operating conditions were ap-
proached in January 1975. During 1974, however, the
plant was plagued by minor equipment failures that were
related to design and construction. As a result of these
circumstances a number of operating modes were
utilized throughout the year as required.
All of the on-line processes were operational in
November 1973, however, the two major off-line
processes, carbon regeneration and zeolite regeneration,
were not. Several attempts were made to regenerate
carbon in November 1974 but because of the inability to
maintain adequate temperatures in the furnace the
carbon was only partially regenerated. The first suc-
cessful regenerations were made in January 1975. The
zeolite regeneration system has been used on a sporadic
basis only because of minor problems which were again
related to design and construction.
EPA GRANT PERIOD
General
In June, 1973 the U.S. Environmental Protection
Agency awarded the Metropolitan Waste Control
Commission a research and development grant. The
objectives of the grant are to: evaluate the independent
physical-chemical treatment facility at Rosemount as a
25
-------
whole, evaluate the individual unit operations and
processes, and to determine the costs associated with
operation and maintenance. The grant was officially
initiated on June 1, 1975. Under the terms of the grant
agreement the plant is currently being operated in a
number of modes for 8 week periods to determine the
affect of plant configuration on performance.
Sampling and Analysis
Flow proportional composite samples of each process
effluent are collected on a daily basis. The routine
analyses and their frequency are presented in Table 2.
Other analyses, such as hardness, sulfate, total solids and
heavy metals, are made on a less frequent basis as
required. The analytical procedures utilized are as
described in Standard Methods (1) or Methods for
Chemical Analysis of Water and Wastes (2). The total
phosphorus and Kjeldahl nitrogen samples are stored and
analyzed on a weekly basis at the MWCC central
laboratory using automated chemistry techniques. All
other analyses with the exception of heavy metals are
performed at the Rosemount laboratory.
TABLE 2
SAMPLE - ANALYSIS FREQUENCY AT ROSEMOUNT AWTP
Analyses per Week
Raw Clar DMFj^CC DMF2AEC Eff
BOD - total
BOD _ filtrable*
COD - total
COD - filtrable*
TOC - total
TOC - filtrable*
Suspended solids
Phosphorus - total
total filtrable**
total ortho
filtrable ortho**
Nitrogen - Kjeldahl
— ammonia
PH
Alkalinity
Chloride
Temperature
Chlorine residual
Dissolved oxygen
*glass fiber filter
**0.45 filter
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
7
-
-
3
3
3
3
3
3
3
3
3
3
3
-
-
3 3
3
3
7
-
-
3
-
3
3
3
3
3
-
-
-
-
-
-
3
-
-
7
-
-
3
3
3
3
3
3
3
-
-
-
-
-
-
3
-
-
7
-
-
3
-
3
-
-
3
3
-
-
-
-
3
3
3
-
-
7
-
-
-
-
-
-
-
3
3
-
-
-
-
3
3
3
3
.
7
-
-
Steam
Air Cooled
Condenser
Ammonia
Solution
Heat Exchanger 1 or 2
Heat Exchancjer
Soda
Ash
Salt
Spent Brine
160°F
pH = 11.5
Brine
1 f! NaCI
170°F
pH = 10.5
Ion
Exchi.r
Column
Sludge
Heat Exchanger
-Cooler
Fron Filtc
Water Scor
To ;il ter Hater
Scoraqo 1
Rosoi'iount AWfP
Zeolite Regeneration System
Figure 7
26
-------
Operating Conditions
General
During the 8 week period June 7, 1975 to August 1,
1975, the plant was operated as follows:
clarifier - lime to pH 10.5, ferric chloride, polymer
DMFj - in service
GCC - 2 columns, upflow, series
DMF2 - in service
AEC - in service when available
300
200
CO
CO
1OO
0
v>
'*'''
J
-*«
F
M
—
A
1C
M
57
i —
J
A
J
r-K
A
—
S
— i
O
N
.
w
1
i
C
S
3
u
i.
)
r*i
J
Ra
X
F
w
M
—
—
A
...-i
-^
G
1
M
Q7
—
J
^
J
—
A
SO N D
Rosenount AUTP
MONTHLY AVERAGE SUSPENDED SOLIDS CONCENTRATIONS
Figure 8
3QQ
— ..— -..-^.
2QQ
Q
O
CD
10Q
0
_
1
•M
C
01
t
c
IQ
i
— —
IS" -'
T-
— 1
1
^P * "^*^
i
u
s_
QJ
i
(.
j
Raw
X
-^
i1'
-^rw^i
1
—
—
_n
i
— i
r-,
I
I
—
-U
*^°"^|___J ' -mrf^n^wj
JFMAMJJASONDJ FMAMJJASOND
fiosmunt ,'iMT?
MONTHLY AVERAGE BOD5 CONCENTRATIONS
Figure 9
27
-------
ID.
CL
ra
UH
J FMAMJ J ASONDJ FMAMJJ ASON
19 74 1.
During this period the raw flow averaged 221,430 gal
per day and the clarifier flow 277,350 gal per day. The
sources of recycle flow in the plant include backwash,
rinse and sample streams.
Clarifier
The average chemical dosages to the clarifier are
tabulated below:
ferric chloride
lime
polymer-Nalco 677
acid
42 mg/1 FeCl3 or 14 mg/1 Fe
560mg/lCa(OH)2or424
mg/1 CaO
2.9 mg/1
20,160 lbH2SO4 used
The pH in the mixing zone or draft tube was main-
tained at 10.5 based on average of 1290 hourly samples.
Approximately 400,000 gal of sludge were removed
from the clarifier at an average concentration of 4.6%.
Filters
First stage filters number 3 and 4 and second stage
filters number 7 and 8 (all in train 2) were used during
the 8 week period. Because of the limited capacity to
store backwash water in the plant the following schedule
was adopted:
filter backwash — day shift
carbon column backwash — 3-11 shift
zeolite regeneration — 11-7 shift
The filters are backwashed in the morning so that the
backwash pit, which is used to store backwash water
prior to recycle to the wet well, can be emptied by
1200-1400 hrs. The raw flow to the plant generally
starts to increase from a low of about 50 gal per min to
250 gal per min at this time. Additional filter back-
washing may be required during the day depending on
flow and clarifier performance. The backwash require-
ments of the four filters for the 8 week period are
tabulated below:
Filter No.
3
4
7
No. of Backwash Cycles
77
77
59
58
The backwash water requirement amounted to ap-
proximately 8.2% of the raw flow.
Carbon Columns
Carbon columns No. 4 and 5 were used during the 8
week test period. Both columns were put in service May
3, 1975, freshly regenerated, in the series, upflow mode.
Previous experience illustrated that a backwash fre-
quency of approximately once every 5 to 7 days was
sufficient to limit biological growth and the associated
problem of hydrogen sulfide generation.
Column No. 4 was backwashed 11 times and No. 5, 10
times during the 8 week period. The backwash water
requirement amounted to approximately 1.5% of the
raw flow.
Ion Exchange Columns
The ion exchange columns were in service for only 22
days during the 8 week period. The ion exchange
columns themselves were available for service but a
number of failures in the zeolite regeneration system
caused the prolonged down time.
Laboratory Data
The laboratory data summary is presented in Table 3.
For the 8 week period the removal efficiencies were:
Suspended Solids - 98%
BOD - 93%
Total P - 95%
NH3-N - 21%
TABLE 3
ROSEMOUNT AWTP LABORATORY DATA SUMMARY
(June 7 to August 1, 1975)
pH
Alkalinity -
Hardness -
Chloride
Suspended Solids
Turbidity - FTU
BOD - total
BOD - filtrable
COD - total
COD - filtrable
TOC - total (3)
TOC - filtrable (3)
P - Total
P - total filtrable
P - total ortho
P - filtrable ortho
Kjeldahl N
Notes
(1) temp recorders out of service
(2) DMF2 and AEC samples out of service
(3) TOC analyzer out of service for 2 weeks
Concentration -
Raw
7.7
i C03 397
:Os 306
267
ds 193
^U
151
3 39
382
B 111
) 77
i (3) 32
11.7
ble 8.3
9.1
tho 8.0
34
mg/1 at Sample Location
Clar
7.5
79
201
314
9
6
21
18
67 6
47
19
15
0.6
0.4
0.3
0.02
-
DMFj
7.6
-
-
-
5
4
16
-
57
44
16
15
-
-
-
-
-
GCC
7.6
-
-
-
7
6
14
10
42
25
10
8
-
-
-
-
-
Eff
7.7
75
187
351
4
5
11
8
36
25
9
8
0.6
0.4
0.3
22
22
28
-------
These data again illustrate that the major portion of the
removals of suspended solids, BOD and total phosphorus
were accomplished in the clarification process.
Organic removal across the carbon columns does not
appear encouraging. The effluent BOD of 11 iin Table 3
is slightly higher than the plant design standard. This was
partially due to an operational error when a pH
controller was inadvertently left in the standby position
for a period of about 15 hours. The high pH feed to the
carbon columns caused desorption of organics and the
effluent BOD rose to 37 and 22 mg/1 for two days
before returning to below 10 mg/1. The average effluent
BOD was 10 mg/1 when these two days are discounted.
During the 22 days the ammonia removal system was in
service, removals of approximately 60% were accom-
plished. The low removal efficiencies were apparently
caused by failure of the zeolite regeneration system to
achieve complete regenerations.
Costs
A separate cost accounting system was set up at the
Rosemount AWTP. The plant was divided into 17 cost
centers as illustrated in Table 4. Fifteen of the cost
centers are defined by physical boundaries. One cost
center, Laboratory Service, is defined by function. The
last cost center, Indirect Services, is used to identify
charges that cannot reasonably be identified with direct
plant operation.
During normal operation the three major costs for a
plant of this type are chemicals, labor and power. For
the 8 week period, June 7 to August 1, 1975, these three
categories accounted for 82% of the total operations and
maintenance costs, labor - 70%, chemicals - 7%, and
power - 5%. A chemical inventory is completed every
two weeks and usage determined. All MWCC employees
at the plant fill out two time cards on a biweekly basis,
the regular time card for pay purposes and a second card
to identify hours in the various cost centers. Electric
power and fuel usage are metered at the plant entrance
but not at the appropriate cost center. Fuel usuage in
the appropriate cost centers is readily estimated however
and electric power measurement instrumentation is
currently being installed on the larger motors.
Labor is by far the major cost factor for the Rosemount
AWTP. The operations and maintenance staff consists of
4 operators, 4 assistant operators, 1 pipefitter, 1
electrician, 2 laborers. A full time supervisor directs the
operating staff. The plant is staffed by a minimum of
two men around the clock. Maintenance is generally
performed during the day shift. The staffing require-
ments of the various cost centers are presented in Table
5. Time spent by the operator at the plant control panel
is charged to Indirect Services. The two plant processes
that require the most labor time are clarification (cost
center 30) and clinoptilolite regeneration (cost center
120). It is quite possible that the distribution of labor
time throughout the plant will change considerably
when all of the 'bugs' are worked out of the individual
processes.
Table 4
COST CENTER
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
Title and Description
PRELIMINARY TREATMENT - plant inlet to discharge to wet well, includes flow
measurement, bar screens, raw sampling pump
INFLUENT PUMPING STATION - wet well to discharge to SCC
CLARIFICATION & PHOSPHORUS REMOVAL - inlet to SCC to weir box on SCC
FILTRATION-1 - weir box on SCC to discharge to Storage^ 1
CARBON ADSORPTION - storage-1 to weir box feeding 2nd stage filters
FILTRATION-2 - weir box to and including storage—2
AMMONIA REMOVAL — ion exchange pumps to discharge from building
CHLORINATION - chlorine system for disinfection and odor control
EFFLUENT DISPOSAL - building to outfall
SLUDGE HANDLING & DISPOSAL - blowdown line (outside SCC) to discharge from
truck
CARBON REGENERATION - transfer and regeneration
CLINOPTILOLITE REGENERATION
AMMONIA RECOVERY SYSTEM - condenser and storage tank
AMMONIA DISPOSAL - disposition of stored ammonia solution
LABORATORY SERVICES - sampling, analysis, monitoring
BUILDING & GROUNDS - general systems including water, drain, compressed air,
heating, ventilation, cleaning, etc.
INDIRECT SERVICES - nondirect labor, plant supervision, project supervision, clerical
labor, data processing and other indirect services
29
-------
Table 5
Cost Center
Man Hours* (June 7 to Aug 1, 1975)
10— Preliminary Treatment
20 - Influent Pumping Station
30 - Clarification & P Removal
40 - Filtration - 1
50 - Carbon Adsorption
60 - Filtration - 2
70 — Ammonia Removal
80 — Chlorination
90 - Effluent Disposal
100 - Sludge Handling & Disposal
110 - Carbon Regeneration
120 — Clinoptilolite Regeneration
130 - Ammonia Recovery System
140 — Ammonia Disposal
150— Laboratory Service
160 - Building & Grounds
170— Indirect Service
* excludes vacation, sick leave, clearical and supervision
The total cost of operating and maintaining the facility
for the 8 week period on an actual flow basis was $4.82
per 1,000 gallons. The unit cost is extremely high
because the plant capacity and plant flow are low
enough to preclude any economy related to size, yet the
plant complexity requires full staffing. For plants of
moderate size, 5 to 10 MGD, and similar design the unit
cost of treatment would be reduced substantially.
Although power costs may be proportional to flow,
chemical unit costs decrease significantly when carload
deliveries are possible. From experience to date it does
not apperat that labor requirements will be directly
related to flow. If the plant had treated the design flow
of 600,000 gal/day for the 8 week period the unit cost
of treatment would have been $2.16/100 gal assuming
labor cost constant, chemical and power cost directly
proportional to flow and other miscellaneous costs
constant.
If the capacity and flow to the present facility was
increased to 2 MGD by using larger units rather than by
adding more units of the present size, the staffing level
required probably would not increase by more than 2 or
3 persons. It is obvious that as the plant capacity and
flow increase the operation and maintenance man hour
requirements per unit of flow decreases thus further
decreasing the unit cost of treatment.
SUMMARY
The 0.6 MGD Rosemount AWTP was constructed by the
Metropolitan Sewer Board (now Metropolitan Waste
maintenance w/o operation
110
25
540
58
58
133
32
25
8
40
24
521
85
23
937
1,249
970
Control Commission) to protect potential recreational
waters adjacent to the Mississippi River and to evaluate
the feasibility and economics of the unit processes
employed. The plant was put into service in November
1973 and since that time has been the only treatment
facility serving the City of Rosemount. The plant has
consistently discharged a high quality effluent.
A demonstration project jointly sponsored by the
USEPA and MWCC was initiated in June of 1975. The
purpose of the project is to evaluate the unit operation
and unit processes utilized at the Rosemount AWTP and
to determine the costs associated with the operation and
maintenance of the facility.
Operating experience to date illustrates that concentra-
tions of suspended solids, biochemical oxygen demand
and total phosphorus can be maintained at levels of 5
mg/1, 10 mg/1 and 1 mg/1 respectively. The ion
exchange system used to remove ammonia nitrogen has
not yet demonstrated its effectiveness because of numer-
ous problems with the zeolite regeneration system.
Although the unit cost of treatment is extremely high at
the current facility it is obvious that larger plants of the
same general design would operate at considerably lower
unit cost because of economic factors related to scale.
REFERENCES
(I)Standard Methods for the Examination of Water and Waste-
water, 18th ed., APHA, 1971
(2) Methods for Chemical Analysis of Water and Wastes, USEPA,
1974
30
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TREATMENT OF CHEMICAL PLANT EFFLUUENTS
M.N. Levchenko
Science and technology advance giving rise to a swift
growth of production volume during recent decades
makes the problem of pollution control especially
serious. Water pollution becomes so high that it appears
to be harmful and even disastrous for water reservoirs
and has an adverse effect on human's health. This leads
to the depletion of river, lake and underground water
sources on which the modern water management is
based.
Though our country occupies one of the first places
in the world as far as fresh water resources is concerned,
uneven distribution across the territory of the USSR and
a continuous growth of water consumption require a
search for ways of economic consumption of fresh water
and efficient treatment of effluents.
Chemical industry is one of the largest consumers of
water and at the same time it disposes to water reservoirs
large amounts of effluents.
In a great majority of chemical processes water is
widely used for cooling, material handling and directly
in technological processes. At the same time various
substances are used at chemical plants as raw materials,
intermediates and final products; part of them goes with
effluents to water reservoirs.
As a result the chemical industry being no leader in
terms of pollution quantities is among the first as far as
pollutants range is concerned.
The USSR for a long time has laws strictly limiting
pollution with effluents. In recent years the legislative
bodies of the USSR and Union republics have adopted
still stricter laws relating to pollution control and
economical use of natural resources.
For example, in accordance with published in 1975
new "Regulations for surface water Protection from
Pollution with effluents" in case of disposal to a water
reservoir of several substances with the same permissible
concentration and taking into account the pollutants
already disposed to the water reservoir from other
outlets the sum of concentration ratios
) of
each substance in the water reservoir to the correspond-
ing maximum permissible concentrations
should not exceed 1:
Cl +- C* 4. ... +. C» ._ < 1
Taking into account a large range of pollutants at the
chemical plants to be treated it is hardly permissible to
dispose even biologically treated effluents to rivers and
other water reservoirs.
Until recently a rapid growth of production volume
and range of chemicals produced was accompanied by an
almost proportional growth of fresh water consumption
and effluents amounts. However recent years witnessed a
clear trend towards the reduction of fresh water con-
sumption owing to
a) the development and use of new and improved
traditional technological processes without effluent for-
mation and with minimum water consumption:
b) maximum use of closed water circulation systems;
c) use in each technological process of local waste
water recycling with water treatment at a given process
stage and treated water recycling to the process;
d) after-treatment and recycling to the process of
effluents including conditionally clean and storm water;
e) a wider use of air cooling instead of water cooling,
etc.
Work being done in this direction gives certain
positive results. Thus during 1971-75 in spite of appre-
ciable growth of chemical production volume fresh
water consumption in the chemical industry as a whole
remained at 1970 level.
Today biological treatment is the main type of
effluent treatment at the chemical plants. Practically
each plant has its biological treatment facilities or sends
the effluents to the municipal treatment plant. As a rule
biological treatment of industrial effluents is conducted
together with the treatment of industrial and municipal
sewage. Effluents and sewage ratio varies greatly from
1:3 to 1:10 depending on the amount and type of
pollutants in industrial effluents, total amount of sew-
age, etc. Treatment efficiency is usually 95:98 per cent.
In our opinion good prospects exist for after-treatment
of biologically treated waste water with its further use
for industrial water supply. At Severodonetsk chemical
plant it is already for a long time that biologically
treated waste water is recycled to the process. Industrial
sewage and effluents and municipal sewage are treated
together at the biological treatment facilities with the
capacity of about 100000 m /day. The biological
treatment complex includes mechanical treatment of
industrial sewage, mechanical treatment of industrial
effluents, biological treatment including treatment of
residue. After-treatment is carried out in two-step buffer
ponds with total surface area of 16 ha. After three-days
residence of biologically treated waste water in buffer
ponds it is delivered to the industrial water supply
filtration plant and then to the additional feeding of
water circulation systems. Control of technological
processes and treatment degree is carried out by chem-
ical and bacteriological laboratories. According to the
analysis the efficiency of biochemical treatment of
sewage and effluents amounts to 97-98 per cent and is
characterized by the following values: biochemical oxy-
gen demand(<5/WcJ -4-H2 mg/1,suspended substances-7-12
mg/1, chlorides - 150 mg/1, sulphates - 100 mg/1,
temperature - 20-22°C, pH - 7-8. This water before the
delivery to the additional feeding of water circulation
systems is treated with ozone in special contact tanks for
additional treatment from organic contaminants and for
avoiding of biological overgrowing of cooling towers and
31
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other parts of water circulation systems.
At the synthetic fibre plant in Chernigov there are
biological treatment facilities with the capacity of 80000
m^/day. They simultaneously treat 68000 m-^/day of
municipal sewage and 12000 m-'/day of industrial
sewage and eflluents. After-treatment is carried out in
three-step cascade bioponds with total area of 40 ha.
Waste water from biological treatment facilities contains
20-70 mg/1 of suspended substances; BriKf is 14-18 mg/1.
After biological ponds the concentration of suspended
substances lowers to 8-20 mg/l,EflKfto 8-12 mg/1. After
the additional treatment in bioponds 12000 rn^/day of
waste water are recycled to the process and used for soft
water preparation.
Two-step after-treatment of biologically treated
waste water is used at nitrogen plant in Dorogobooge.
The 1st step-metallic drum filters with filter cloth cell
size 0,5x0,5 mm. The 2nd step-sand filters filled with
16-32 mm gravel up to 0,65 m and with 1-2,5 mm
quartz sand up to 1,2 m. Filtering rate in sand filters -
6-8 m/hr, filtering time - 12-14 hrs, washing rate -
13-15 I/sec, m^ washing time — 6-7 min. Washing is
carried out with filtered water which is then delivered to
the head of treatment facilities. Biologically treated
waste water contains up to 50 mg/1 of suspended
substances; EDKy is 15-20 mg/1. After additional
treatment the concentration of suspended substances
lowers to 5-6 mg/1, EDK,- lowers to 4-5 mg/1 and
after mixing with fresh river water the waste water is
sent to the water treatment plant and then to the
additional feeding of water circulation systems and
covering other production requirements.
The experience of the Ministry for Chemical Industry
shows sufficient reliability and efficiency of biological
treatment of all the sewage and effluents of a chemical
plant with their further after-treatment and recycling for
industrial water supply. However this is true for ammo-
nia, synthetic fibre and certain other plants where the
amount and contamination of industrial waste water are
relatively low. For plants producing organic, chloro-
organic and other products giving a large amount of
waste water and a large range of pollutants the optimum
variant in our opinion would be that of a local
physico-chemical treatment of industrial waste water in
all the water-demanding technological processes using
their own water circulation system. Industrial sewage
and partially industrial effluents should be treated at
all-plant treatment facilities when a local treatment is
undesirable.
In the USSR there was developed a complex route for
treatment and recycling of waste water of a large
production plant without disposal to open water reser-
voirs. The complex route includes the use of local
treatment plants in the production of suspension poly-
styrene, chlorine and caustic soda by a diaphragm
method and acetylene by a thermal oxidative pyrolysis
of natural gas. The waste water treated at local plants is
recycled to the water circulation system and to the
production process.
The waste water unfit for recycling is separated into
four types:
- organic polluted
- mineral polluted — above 3 g/1
- mineral polluted - under 3 g/1
sewage,
Mineral-polluted waste water with mineral content
above 3 g/1 after treatment (softening, separation of
suspended substances, conversion of insoluble salts into
soluble ones) is sent to a demineralization unit with
7-step evaporation in vertical film-type vessels. Deminer-
alized water with total salt content up to 50 mg/1 is
used for feeding boilers at a central heating-and-power
plant and for process requirements. Concentrated salt
solutions with salt content up to 50 g/1, formed during
demineralization, are pumped into deep layers of earth's
crust. Pumping is carried out to the depth of 1650-1750
m where stratal water was found with the same salt
composition but with a higher concentration — up to
150 g/1.
Organic-polluted water and sewage (of the production
plant and municipal) are sent to biological treatment
plant where they undergo separate mechanical treatment
and then joint biological treatment; after that they are
sent to a buffer pond.
Waste water with mineral content up to 3 g/1 and
storm (rain) water are sent to the same buffer pond
without preliminary treatment.
The complex route includes after-treatment of biolog-
ically treated and low-mineral waste water at adsorption
and ion-exchange units with the production of nitrogen
fertilizers from solutions used for regeneration of ion-
exchange resins.
Treated waste water from the buffer pond with salt
content up to 1500 mg/1 and chemical oxygen demand
XflK— 30- 130 mg/1 is delivered to an adsorption unit for
the separation of chloroorganic and other pollutants. An
adsorbent is an activated anthracite with 0,25-1 mm
particle size. Activated carbon is suspended in the
adsorber with constant relative expansion of adsorbent
bed being ^ =1,5.
Nc
Spent activated anthracite is discharged from the
lower part of the adsorber and sent to a vacuum filter
for water separation and then it is delivered to a reactor
of adsorbent thermal regeneration. Regeneration is
carried out at 850-950T by a mixture of stack gases and
steam. Activated anthracite losses during the cycle (up
to 10 per cent of adsorbent being regenerated) are
compensated using an anthracite activation unit.
Water after adsorption treatment goes to quartz press
filters for separation of entrained carbon dust (particles
up to 0,25 mm) and then to rapid filters. Waste water
treatment in prefilters and rapid filters is improved by
means of polyacrylamide introduction (up to 2 g/m^).
32
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Filtering rate in press filters and rapid filters is the same
— 8 m^/m^hr. The filters are periodically washed with a
reverse water current. Washing water is separated from
suspended carbon in precipitation tanks and recycled.
Waste water free of organic impurities and carbon
dust is delivered to the ion-exchange unit for lowering of
salt content.
A high-acid cationite KY-2 is used as cation-exchange
resin and a high-base anionite AB-17-8 is used as an
anion-exchange resin. At H-cationation cationites Ca++,
Mg++ and partially Na+ are extracted from the waste
water. After H-cationation water is separated from
carbon dioxide in a degasing vessel by venting off with
air. Water being separated of carbon dioxide undergoes
OH-anionation and then is used for additional feeding of
water circulation systems and for other production
requirements.
H-cationite filters are regenerated with 25 per cent
nitric acid; spent regeneration solution passes succes-
sively through 4 receivers, the capacity of each being
about % of the volume of all the regeneration solution.
Solution from the second receiver, the most saturated
with salts, is delivered to a mixer-neutralizer. Solutions
from the other receivers are successively used for further
regeneration.
OH-anionite filters are regenerated with 10 per cent
ammonia liquor. The most concentrated solution after
OH-filters regeneration passes to the mixer-neutralizer
where the mixture pH is raised to 7 adding, if necessary,
25 per cent nitric acid or 10 per cent ammonia liquor.
As a result of reaction between (NH^SC^ and
Ca(NC>3)2 sludge CaSC>4 2^0 is formed in the neutral-
izer; it is accumulated in the precipitation tank, centrifu-
gated for separation of solution and sent to heap.
The neutralized solution and centrifugate are collect-
ed in tanks from which they are continuosly sent to the
production of mineral fertilizers. The fertilizers contain
nitrates of ammonium, calcium, magnesium, sodium,
calcium sulfate and other compounds. Total fertilizer
nitrogen content is about 30 per cent.
Local plants are rather complicate treatment facilities
providing for waste water treatment, after-treatment, use
and utilization of sludge and other wastes, etc. Thus
waste water formed in acetylene production contains
carbon black, resin, phenol and other substances. The
treatment is carried out in horizontal vessels where
carbon black conies to the surface and by means of a
rake conveyor is delivered to a mixer and then to a waste
combustion unit. Water passed through carbon black
separators contains residual carbon black as wwell as
resins, phenols, aromatic compounds and other products
of incomplete combustion and methane pyrolysis. Be-
cause of the lack of treatment methods such waste water
is repeatedly used in a separate waste water circulation
system. Owing to water evaporation in the water
circulation system because of cooling salt content,
hardness, alkalinity, etc. rise and this has an adverse
effect on the production process. To stabilize recycled
water composition it is necessary to continuously purge
the circulation system. However because of a high
concentration of pollutants in the recycled water it is
not allowed to send it to biological treatment or dispose
it directly to a water reservoir. That is why the following
after-treatment was suggested:
a) coagulation in a suspended bed in clarifier using
coagulants of aluminium sulphate, ferric sulphate and
chloride. To keep the necessary pH value 5 per cent lime
milk is fed to the clarifier. Waste water treatment is
effected by means of coagulation on flake surface and
adsorption by flake is effected by means of filtering
large carbon black particles and small coagulant flakes
through the suspended bed.
Sludge formed during treatment (its volume is 0,2-0,5
per cent of the volume of water being treated) contains
carbon black, phenols, resins, etc; it is separated from
water in drum vacuum filters and sent to heap.
b) waste water treated in a suspended bed is delivered
to a contact vessel for treatment with ozone that
bubbles through the water layer. Ozone concentration is
20-30 mg/1.
Bubbling is effected through the system of porous
porolit pipes that allows to use all the ozone. Ozone-
treated water is recycled to acetylene production for
cooling of heat exchangers.
Investments in water supply and treatment facilities
of a production plant are lowered owing to the
reduction of fresh water consumption by 36 per cent
and possibility of nitrogen fertilizer production makes
operation of treatment facilities profitable because
operating expenditure would be justified by the cost of
fertilizers.
Development of a complex route allowing to com-
pletely eliminate waste water disposal to water reservoirs
indicates practical and economic way for solution of one
of the most acute problems — that of control of water
pollution with industrial effluents and economic use of
water resources.
As far as mineral fertilizer plants is concerned there
was also developed a water supply route providing for
industrial waste water treatment and recycling. These
plants are characterized by use of large amounts of water
for cooling and as a rule they have large water
circulation systems. Water circulation systems are con-
tinuously fed with fresh water to compensate losses
from evaporation, spray carrying away and water re-
moval to keep constant salt concentration of recycled
water.
Large amounts of water are also used in production
processes for scrubber refluxing when removing exhaust
gases, for washing of pipelines and vessels, for phospho-
rus washing in storage tanks and precipitators, for dust
removal, etc. Main pollutants in waste water here are
phosphorus compounds, phenols, cyanides, fluorides,
etc.
33
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Experience of operating mineral fertilizer plants
shows that it is enough to separate from recycled water
only those impurities that may complicate the produc-
tion process. Thus instead of deep treatment to sanitary
limits it is acceptable to carry out treatment to a degree
allowing to recycle water to various processes. So
phosphorus concentration may be 10 mg/1, that of
suspended substances - up to 100 mg/1; fluorine
concentration 20-30 mg/1. This is much higher than the
sanitary regulations allow and such water should not be
disposed to open water reservoirs but it may be recycled.
According to this route treatment plants consist of a
neutralization unit with the necessary reagent equipment
and facilities for various mechanical and physico-
chemical treatment of waste water.
Industrial effluents giving as a rule acid reaction (pH
= 1-5) are delivered to a horizontal sand trap for the
precipitation of large-size mechanical impurities. Then
the effluents are sent to a tank for averaging of waste
water amount and composition and levelling out of peak
concentrations of impurities including acids. Averaging is
carried out for 8 hours. The averaging tank consists of
two sections with corrosion-proof coating. There are
perforated vinyl pipes on the bottom of the tank for
compressed air delivery (air pressure being 10m of water
gaugs). The air contributes to better averaging and acid
gas venting off. Air flow rate is 2 m-* per 1 m^ of the
averaging tanks surface area. Waste water with the
averaged composition comes to a mixer where 10 per
cent lime milk is continuously added. There is an
automatic pH-meter at the mixer outlet for the control
of lime milk supply. Waste water from the mixer goes to
the precipitator where 0,5 per cent polyacrylamide is
added to improve precipitation efficiency and accelerate
phase separation. 20-50 g of polyacrylamide are added
per 1 tonne of dry matter of waste water suspended
substances. Polyacrylamide addition is controlled auto-
matically depending on the amount of waste water to be
treated. Neutralization reaction is completed in a reac-
tion chamber presenting a round concrete tank with a
capacity - 200 m^. Normal waste water residence time in
the reaction chamber is 30 min. Waste water mixing is
carried out by compressed air delivered by means of
perforated vinyl pipes. After the reaction chamber waste
water is sent to 1250 up horizontal precipitators for the
precipitation of suspended substances. Normal waste
water residence time in precipitators - 4 hours. The
neutralized waste water being clarified, sludge is collect-
ed in the lower conical part of the precipitators (sludge
humidity is 85-95 per cent). Clarified waste water is
recycled to the production process.
Sludge undergoes mechanical water removal in drum
vacuum filters. Filtering area of each vacuum filter - 10
m^, vacuum is kept to be 350-420 mm Hg, filter deposit
height - 6-8 mm. Dewa
Irretrievable water losses with sludge, during slag
granulation, etc. prevent accumulation of undesirable
impurities in a closed water circulation systems. Experi-
ence gained at mineral fertilizer plants indicated possi-
bility of water circulation system with a negative
balance, i.e. under such conditions when a closed system
should be continuosly fed with water from outer water
supply sources. As a such a source it is suggested to use
water removed from circulation system to keep constant
salt composition of recycled cooling water.
Today some mineral fertilizer plants are being con-
verted to water supply routes without waste water
disposal.
Practically at each chemical plant there may be used
one of the above-described water supply routes charac-
terized by absence of waste water disposal to open water
reservoirs and minimum consumption of fresh water
mainly for additional feeding of water circulation
systems and for covering central heating-and-power plant
requirements. According to the next five-year plan for
1976-1980 wide use of such routes is planned at
chemical plants.
34
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THE ROLE OF ACTIVATED CARBON IN PHYSICO-CHEMICAL TREATMENT(*)
Walter J. Weber, Jr.(**)
INTRODUCTION
Activated carbon is utilized in a number of environ-
mental process applications. Purification of gases with
activated carbon is an effective technique for air
pollution control, adsorption of dissolved impurities on
carbon is widely employed for water purification, and
adsorption on carbon is an integral part of most
physicochemical process schemes for wastewater treat-
ment and water reclamation.
The reasons for the choice of activated carbon as an
adsorbent in these applications are several fold. Carbon
has been demonstrated to have good sorption charac-
teristics for most organic compounds of interest in these
fields. This is attributable to its dual properties of large
surface area per unit weight (and bulk volume) and high
degree of surface activity. It can be produced with
relative ease and at reasonable cost from a number of
different raw materials and with a variety of surface
properties to meet the requirements of specific applica-
tions. Finally, activated carbon - particularly granular
activated carbon - can be efficiently regenerated for
multiple reuse as an adsorbent. Despite exhaustive
searches for alternatives, no other material has been
found which combines the desirable properties of an
adsorbent as effectively as does activated carbon.
This paper discusses salient features of the role of
activated carbon in physicochemical treatment systems
for municipal and industrial wastewaters, highlighting
advantages over other purification processes, and defin-
ing factors and considerations involved in the use of
carbon adsorption systems.
PRINCIPLES OF ADSORPTION
Adsorption occurs in large measure as a resultant of
forces active within phase boundaries, or surface bound-
aries. These forces result in characteristic boundary
energies. Classical chemistry defines the properties of a
system by the properties of its mass; for surface
phenomena the significant properties are those of the
surface or boundary.
Pure liquids tend to reduce their free surface energy
through the action of surface tension. A large number of
soluble materials (e.g., detergents) can effectively alter
the surfaces tension of a liquid. A material which is
active at surfaces will decrease the tension at the surface
of a liquid by virtue of its movement to the surface.
(*) Presented at the U.S./U.S.S.R. Symposium on Physical-
Chemical Treatment of Wastewaters, Environmental Re-
search Center, Cincinnati, Ohio, November 12-14, 1975.
(**) Professor of Environmental and Water Resources Engineer-
ing and Chairman, Water Resources Program, College of
Engineering, The University of Michigan, Ann Arbor,
Michigan, U.S.A.
Migration to the surface or boundary results in a net
reduction of the work required to enlarge the surface
area, the reduction being proportional to the concentra-
tion of sorbate at the surface. Hence the energy balance
of the system favors the adsorptive concentration of
such surface-active substances at the phase interface. The
tendency of an impurity to lower the surface tension of
water is referred to as hydrophobicity; that is, the
impurity "dislikes" water.
Adsorption of a dissolved impurity from water onto
activated carbon may result from the hydrophobicity of
the impurity, or it may be caused by a high affinity of
the solute for the carbon. For the majority of systems
encountered in water and waste treatment, adsorption
results from a combination of these factors.
The solubility of a substance in water is significant;
solubility can be thought of as the chemical compati-
bility between the water and the solute. The more
hydrophilic the substance the less likely it is to be
adsorbed. Conversely, a hydrophobic substance will
more likely be adsorbed.
In the context of solute affinity for the solid, it is
common to distinguish between three types of adsorp-
tion. The affinity may be predominantly due to: 1)
electrical attraction of the solute to the sorbent (ex-
change adsorption); 2) van der Waals attraction (physical
or ideal adsorption); or, 3) chemical reaction (chemi-
sorption or chemical adsorption).
Many adsorptions of organic substances by activated
carbon result from specific interactions between func-
tional groups on the sorbate and on the surface of the
sorbent. These interactions may be designated as "speci-
fic adsorptions." It is possible for specific adsorptions to
exhibit a large range of binding energies, from values
commonly associated with "physical" adsorption to
higher energies involved in "chemisorption." The adsorp-
tive interactions of aromatic hydroxyl and nitro-
substitutes compounds with active carbon, for example,
are specific adsorption processes resulting from the
formation of donor-acceptor complexes of the organic
molecule with surface carbonyl oxygen groups, with
adsorption continuing after these sites are exhausted via
complexation with the rings of the basal planes of the
carbon rmcrocrystallite.1
Adsorption results in the removal of solutes from
solution and their concentration at a surface, to such
time as the amount of solute remaining in solution is in
equilibrium with that at the surface. This equilibrium is
described by expressing the amount of solute adsorbed
per unit weight of sorbent qe, as a function of C, the
concentration of solute remaining in solution. An
expression of this type is termed an adsorption isotherm.
The adsorption isotherm is useful for representing the
35
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capacity of an activated carbon for adsorbing organics
from a waste, and in providing description of the
functional dependence of capacity on the concentration
of pollutant. The steeper the isotherm, the more
effective is the activated carbon; that is, the sharper the
rise of the isotherm to a given ultimate capacity as
concentration increases, the higher will be the effective
capacity at the concentration level desired for the
treated water. Experimental determination of the iso-
therm is routine practice in evaluating the feasibility of
adsorption for treatment, in selecting a carbon, and in
estimating carbon dosage requirements. Mathematic
description of the adsorption isotherm for a particular
system — that is, the functional dependence of capacity
of concentration — is also required for development of
predictive models for design applications.1-2 Details
of the conventional Langmuir and Freundlich isotherm
expressions are readily available in the literature.'1'
Mathews and Weber have recently described the use of a
more general and widely applicable three-parameter
isotherm model.3
The adsorption isotherm relates to an equilibrium
condition, however, and practical detention times used
in most treatment applications do not provide sufficient
time for true equilibrium to obtain. Rates of adsorption
are thus significant, for the more rapid the approach to
equilibrium, the greater is the fraction of equilibrium
capacity utilized in a given contact time. There are
essentially three consecutive steps in the adsorption of
materials from solution by porous sorbents such as
activated carbon. The first of these is the transport of
the adsorbate through a surface film to the exterior of
the adsorbent ("film diffusion").
Film, penetration, boundary layer, and other theories
have been postulated to explain mass transfer in the
region separating a turbulent bulk solution and a solid
surface. However, the fluid mechanics of this region are
not well defined. Boundary layer theory accounts for a
velocity distribution and is more realistic than film
theory, which assumes a laminar film surrounding the
particle. The term "film diffusion" is used here to
generally describe the resistance to mass transfer at the
surface of the particle. However, use of this term is not
intended to imply the existence of a definable film nor is
it meant to restrict treatment of data to the film theory.
The second of the three consecutive steps in sorption by
porous sorbents, with the exception of a small amount
of adsorption that occurs on the exterior surface of the
sorbent after transport across the exterior film, is the
diffusion of the sorbate within the pores of the sorbent
and/or along pore-wall surfaces ("intraparticle dif-
fusion"). The third and final step is adsorption of the
solute on the interior surfaces bounding the pore and
capillary spaces of the sorbent.
Consideration of rates at which interfacial tensions
are lowered by chemical compounds representative of
organic pollution materials gives indication that the
adsorption process itself is probably not rate-determin-
ing, and that a much slower process must control the
overall rate of uptake by porous carbon. Under certain
operating conditions, transport of the sorbate through
the "surface film" or boundary layer to the sorbent may
be rate-limiting; if sufficient turbulence is provided,
transport of the sorbate within the porous carbon may
control the rate of uptake. One of the most significant
factors to consider is, therefore, the nature of the step
which controls the speed at which the reaction proceeds,
in order that the process may be described in terms of
appropriate rate expressions and rate parameters.
Certain properties of the sorbate are useful in
determining the nature of the rate-controlling step. For
example, if intraparticle transport determines the rate of
reaction, the size and structure of an individual solute
ion or molecule will affect this rate to the extent that it
affects molecular mobility.
The rate-controlling step can also be characterized in
part by the observed activation energy for the process. A
study of the effect of temperature on rate, in addition to
yielding information relative to optimum conditions of
operation, permits evaluation of the activation energy
and is, consequently, a further means for determining
the nature of rate-limiting reactions.
For a process in which the overall rate is controlled
by a strictly adsorptive reaction the variation of rate
should be directly proportional to the concentration of
solute, and for very simple diffusion the rate is expected
also to be proportional to the first power of concentra-
tion. However, complex mathematic expressions for
intraparticle transport indicate that the relationship
between concentration and the rate of the reaction will
not be one of direct proportionality. 2'3 Since con-
centration affects a number of the parameters of these
equations, it is not possible to predict an exact con-
centration-rate relation for this reaction. Qualitatively, if
diffusion of solute within the pores and capillaries of the
carbon limits the rate, the variation of rate with
concentration is not expected to be linear, whereas a
direct proportionality is anticipated for strictly adsorp-
tive reactions. Thus the concentration-dependence of the
rate of reaction may be used as a partial test of
hypotheses regarding the nature of the rate-controlling
step. The effect of the concentration of solute on the
speed at which its sorptive uptake proceeds is also
significant for any prediction of the most efficient
manner in which adsorption can be utilized for removal
of the solute from solution.
For processes in which the rate-limiting reaction is
adsorption on the exterior surfaces of the sorbent or
transport through an external surface film, the rate is
expected to vary as the reciprocal of the diameter of the
sorbent particles for a given total weight of sorbent; this
because the rate is in this case a first-order function of
exterior surface area, which in turn is inversely propor-
tional to particle diameter. Conversely, according to
36
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appropriate mathematical expressions for transport re-
lationships, the rate of diffusion of solute into the pores
of a particle will vary as the reciprocal of some higher
power of the diameter of the particle. Variation of rate
with particle size is then another method which is useful
for the characterization of the rate-limiting step for a
particular system. Particle size is an important considera-
tion also for achieving optimum utilization of a sorbent
in treatment operations.
COMPONENTS AND CONDITIONS
Properties of Activated Carbon
Activated carbon is a generic term for a broad range
of amorphous carbon-based materials so prepared as to
exhibit a high degree of porosity and an extensive
associated surface area. Hundreds of different com-
mercial activated carbons with unique properties, and
therefore different application suitability, exist.
The purification properties of carbons, or at least
charcoal, have been known for over 30 centuries, but the
first commercial application appears to have been the
use of bone char for decolorization in the cane sugar
industry in the 1780's, and bone char is yet the most
commonly used sorbent in the cane sugar industry
today.'4)
During the 19th century different relatively crude
activated carbons were prepared from a variety of raw
materials, but manufacturing problems, and the absence
of a real need to find anything significantly better than
bone char stifled product development. The first acti-
vated carbon preparation and use for purification of
potable water occurred in 1862.1^'
In the late 1890's and early 1900's Ostrejko develop-
ed two improved processes for the manufacture of
activated carbon.(*>' The first involved the carbonization
of vegetable substances impregnated with metallic chlo-
rides; the second the activation of charcoal with carbon
dioxide and steam at high temperatures. Virtually all
activated carbons are yet made by one or the other of
these two processes, either low temperature chemical
activation or high temperature gaseous oxidation. The
low temperature chemical activation involves chemical
dehydration and charring of a carbonaceous raw materi-
al, and usually is carried out at temperatures between
200and650°C.
Porosity is developed by the action of dehydrating
chemicals—normally phosphoric acid, zinc chloride
and/or sulfuric acid-on the cellulose structure of the
starting material, or by the action of oxidizing gases
generated in the process. In the high temperature
oxidation of a previously charred carbonaceous sub-
stance, a porous structure is developed in the low surface
area carbonaceous starting material by controlled oxida-
tion at temperatures between 800 and 950°C with steam,
flue gas, or some other oxidizing gas mixture. Bone
charcoal is manufactured by a different process, in
which collagen and other carbon containing components
of bone are carbonized at high temperatures in the
absence of oxidizing gases to form carbon deposits
within the hydroxyapatite structure of bone.
The properties of an activated carbon depend on the
nature of the raw material used, the conditions under
which carbonization is accomplished, the activation
process and conditions, and post treatment of the
product.
Surface areas usually range between 450 and 1500
m^/g. Bone charcoal is an exception, having, in the
freshly prepared form, an area of about 100 m^/g char.
Bone char, however, contains only 5 to 12% by weight
of carbon, which accounts for 50% of its surface. The
carbon present is truly in an activated state, having an
area of between 400 and 1000 m^/g carbon, depending
on the composition of the char.
The surface areas of some typical carbons are shown
in Table 1.7
TABLE 1.
SURFACE AREAS OF TYPICAL ACTIVATED CARBONS
Name
Origin
Area,
Actibon S
Columbia G
Columbia AC
Darco S51
Darco G60
Darco KB
Filtrasorb 100 & 200
Filtrasorb 300
Filtrasorb 400
Norit
Nuchar Aqua
Nuchar WV-W
Nuchar WV-G
Witco718
Wood
Coconut shell
Coconut shell
Lignite
Lignite
Wood
Coal
Coal
Coal
Wood
Pupl mill residue
Coal
Coal
Petroleum residue
850-
1100-
1200-
500-
750-
950-
850-
950-
1050-
600-
550-
800-
1000-
1100-
900
1150
1400
550
800
1000
900
1050
1200
800
650
900
1100
1200
Surface area is normally determined by measuring the
volume of nitrogen gas adsorbed at liquid nitrogen
temperature (-195°C) at various pressures. From this
data one can calculate, using the BET equation, the
monolayer coverage and the surface area.1 The actual
area available for adsorption of a specific compound
from water can be considerably less than the total
surface area determined by nitrogen adsorption.
For gas adsorbing carbons, for example, most of the
surface area is in micropores, and these carbons have
little capacity for molecules too large to enter a pore less
than about 200 A in diameter. As another example,
bone char has a surface area of about 65 m^/g. Typical
commercial granular activated carbons may have areas in
excess of 100 m^/g; these, however, have only between
5 and 10 times the capacity of bone char in a use such as
sugar decolorization. Based on total surface area alone
they should be over 15 times as active, but bone char has
a much lower proportion of its surface in micropores
37
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and thus more readily available for sorption of the large
color bodies. The conclusion that must be reached then
is that total surface area is not by itself a satisfactory
measure of available surface for liquid phase applic-
ations. Rather, it is the distribution of surface area as a
function of pore size within the sorbent which is
important.
Pore volume distribution can be determined by a
combination of mercury porosimetry and gas adsorp-
tion-desorption measurements. Gas carbons are charac-
terized by a large percentage of pore volume in
micropores, the almost total absence of pore volume in
transitional pores, and a secondary maximum in macro-
pores. Conversely, liquid phase carbons have a pronounc-
ed percentage of pore volume in transitional pores
together with capacity in both micro and macropores.
Thus, just as with total surface area, total pore volume is
not acceptable by itself as a measure of capacity. Total
pore volumes of gas and liquid phase carbons are similar,
but it is the pore volume in large pores which determines
in large measure the capacity of liquid phase carbons.
Together, total surface area and total pore volume thus
given some measure of the potential capacity of a
carbon, which depends on the distribution of area or
volume with pore size, and the distribution of molecular
sizes to be adsorbed.
The chemical properties of the surface of the activa-
ted carbon are also important in determining activity;
that is, capacity for a specific adsorbate. The chemical
properties of the surface depend on the starting material,
the activation process, and the conditions employed in
activation.
Activated carbon can be considered to consist of
essentially two types of surfaces, excluding contribu-
tions from inorganic impurities. The first are planar,
non-polar surfaces, which comprise the bulk of the
surface for most carbons. Adsorption on this surface
would be largely of the van der Waals type. The second
type of surface is comprised of the heterogeneous edges
of the carbon planes, which made up the crystallites,
whereon carbon-oxygen functional groups formed by
oxidation in the manufacturing process are located.
These groups, which include phenolic hydroxyl, alco-
holic hydroxyl, carboxyl, n-lactone, f-lactone and
chromene groups, enable activated carbon surfaces to
undergo halogenation, hydrogenation, oxidation, and to
act as a catalyst in many reactions.
The surface properties of different carbons can have
profound effects on both rate and capacity for adsorp-
tion. The surface chemistry of active carbon has been a
subject of much interest for some time, yet surprisingly
little is known about the nature of the surface functional
groups of this material. Recent work in our laboratories
has provided an examination of the character of func-
tional groups formed on active.carbon under different
conditions of activation, using the technique of multiple
internal reflectance spectroscopy (MIRS) as a means for
characterizing surface functional groups.1
While the activity of a sorbent is related to its
distribution of surface area and the chemistry of that
surface, it must be recognized that activity or capacity is
only one parameter which must be taken into account
when selecting a carbon for a particular process. Other
properties to be considered include hardness and head-
loss characteristics for granular carbons, filterability and
bulk density for powdered carbons, water solubility of
impurities, and pH.
As already noted it is not possible to determine
activity or capacity from basic carbon properties such as
surface area, not to relate activity for a water or effluent
application to capacity for a reference sorbate, such as
iodine or methylene blue. Activity or capacity must be
determined directly on the system of interest. For
granular carbons, hardness is probably second in impor-
tance to capacity among properties to be considered in
carbon selection. Hardness determines, in large measure,
the loss on each adsorption-regeneration cycle. Losses
result from attrition on handling and burn-off during
reactivation. For coalbased carbons, losses of about 5%
per cycle can be expected; losses for softer carbons can
be as high as 15% or more.
Head-loss or pressure drop in downflow columns and
bed expansion in upflow columns of granular carbon are
determined in part by particle size and size distribution;
these properties are therefore factors influencing design
installation and capital costs. In general, the smallest size
of particle that conditions of efficient operation permit
should be used, for this increases the adsorption rate and
thus reduces the size of the plant required. For
powdered carbon, which usually must be removed from
the treated water by filtration, filterability is affected by
particle shape, size and size distribution.
Bulk density is also important in the selection of a
powdered carbon, for it determines, to a large extent,
the length of the filtration cycle. Filterability is impor-
tant, for poor filtration results in the use of more carbon
and filter aid, and the need to provide a larger plant.
All carbons contain some soluble impurities depend-
ing on the nature of the starting material, the activation
process, and final treatment. The amounts and the
nature of the compounds which can be tolerated will be
governed by the purity requirements of the treated
water or effluent.
The "pH" of a carbon is actually the pH measured on
a water extract from the carbon. It is a function
primarily of the nature of the activation process; steam
activation usually yields alkaline carbons, while activa-
tion with phosphoric acid, for example, gives carbon pH
values below 5. The pH of carbon can be modified by
washing. Steam activated carbons can be acid washed to
give products with pH values between 5 and 7, while
phosphoric acid carbons can be "neutralized" by caustic
wash. The adsorption of many solutes can be related to
solubility, which in turn is affected by pH. The optimum
38
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pH of the carbon, as well as of the solution, can be
determined only by experiment with the specific waste
water to be treated.
Solute Properties
In general, an inverse relationship between the extent
of adsorption of a solute and its water solubility can be
anticipated. The water solubility of organic compounds
within a particular chemical class decreases with
increasing chain length, because the compound becomes
more hydrocarbon-like as the number of carbon atoms
becomes greater. Thus, adsorption from aqueous
solution increases as an homologous series is ascended,
largely because the expulsion of increasingly large
hydrophobic molecules from water permits an increasing
number of water-water bonds to reform.
Molecular size is of significance if the adsorption rate
is controlled by intraparticle transport, in which case the
reaction generally proceeds more rapidly the smaller the
adsorbate molecule. It must be emphasized, however,
that the rate depends on class or series of molecules.
Large molecules of one chemical class may sorb more
rapidly than smaller ones of another if higher energies
(driving forces) are involved.1
Many organic compounds exist, or have the potential
of existing, as ionic species. Fatty acids, phenolic
species, amines, and many pesticides are a few materials
having the property of ionizing under appropriate
conditions of pH. Activated carbon commonly carries a
net negative surface charge; further, many of the
physical and chemical properties of certain compounds
undergo changes upon ionization. Most observations
point to the generalization that as long as compounds
are structurally simple, sorption is at a minimum for
charged species and at a maximum for neutral species.
As compounds become more complex, the effect of
ionization decreases. Studies of amphoteric compounds
indicate an adsorption maximum at the isoelectric point,
consistent with other observations that adsorption is at a
maximum for neutral species. A polar solute will be
strongly sorbed from a non-polar solvent by a polar
sorbent, but will prefer a polar solvent to a non-polar
sorbent. Polarity of organic compounds is a function of
charge separation within the molecule. Almost any
asymmetric compound will be more or less polar, but
several types of functional groups tend to produce fairly
high polarities in compounds. Examples of these are
hydroxyl. carboxyl, nitro, nitrile, carbonyl, sulfonate,
and amine. Thus ethanol, C2H50H, is polar, having an
incremental negative charge on the hydroxyl and a
corresponding positive charge on the ethyl group.
Because solvation by water involves formation of a
hydrogen bond from one of the positively charged
hydrogens of the water to a group bearing more or less
of a negative charge along with some bonding in the
reverse direction to the water oxygen, water solubility is
expected to increase with increasing polarity. It
therefore follows that adsorption decreases as polarity
increases, even though active carbon is a polar sorbent.
Because hydrogen and hydroxide ions are sorbed
quite strongly, the adsorption of other ions is influenced
by the pH of the solution. Further, to the extent to
which ionization of an acidic or basic compound affects
its adsorption, pH affects adsorption in that it governs
the degree of ionization. In general, adsorption of
typical organic pollutants from water is increased with
decreasing pH.
Adsorption reactions are normally exothermic; thus
the extent of adsorption generally increases with
decreasing temperature. The changes in enthalpy for
adsorption are usually of the order of those for
condensation or crystallization reactions, thus small
variations in temperature tend not to alter the
adsorption process in water and effluent treatment to a
significant extent.
The organic components of a waste mixture may
mutually enhance adsorption, may act relatively
independently, or may interfere with one another.
Mutual inhibition can be expected if the adsorption
affinities of the solutes do not differ by several orders of
magnitude and there is no specific interaction between
solutes enhancing adsorption. Similarly, because the
adsorption of one substance will tend to reduce the
number of open sites and, hence, the "concentration" of
adsorbent available, mutually depressing effects on rates
of adsorption may be predicted.
It should be apparent from the foregoing discussion
of the effects of solute character on adsorption that an
analytical characterization of the impurities present is
helpful to a thoughtful prediction of the effectiveness of
activated carbon in wastewater purification.
ADSORBER SYSTEMS
The type of reactor system in which to contact
carbon most effectively with the wastewater to be
treated is of particular significance for large-scale
treatment operations. Rates of adsorption on granular
carbon have been found to depend, in significant
measure, upon the particle size of the carbon.1 It is
desirable to employ carbon of as small a diameter as
conditions of efficient operation permit, so that high
rates of sorption obtain. The term "efficient operation"
is a key here, for the size of particle chosen will dictate
to some extent the type of reactor system in which
contact of the carbon with the wastewater will be
accomplished. For example, powdered carbon must be
used in either a batch or stirred-tank flow reactor; head
loss through a bed or column reactor would be
prohibitive in most cases. The type of reactor, on the
other hand, will dictate to some extent the efficiency of
contact, and therefore the efficiency of the sorption
reaction.
39
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In batch-type contact processes, a quantity of carbon
is mixed continuously with a specific volume of waste
until the contaminants have been decreased to a desired
level. The carbon is then removed and either discarded
or regenerated for use with another volume of solution.
If powdered carbon is used in this type of system,
separation of the spent sorbent from the water may
present difficulties. Conversely, the use of large particles,
which may be removed more readily when exhausted,
requires longer periods of contact, necessitating larger
reactors.
Continuous-flow operations have an advantage over
batch-type operations because rates of adsorption
depend upon the concentration of solute in the solution
being treated. Further, plug-flow (PF) or column,
reactors have this same type of advantage over com-
pletely-mixed-flow (CMF) reactors.1 For column opera-
tion, the carbon is continuously in contact with fresh
solution. Consequently, the concentration in the solu-
tion in contact with a given layer of carbon in a column
changes very slowly. For batch treatment, the concentra-
tion of solute in contact with a specific quantity of
carbon decreases much more rapidly as sorption pro-
ceeds, thereby decreasing the effectiveness of the carbon
for removing the solute. These considerations regarding
reactor efficiencies, coupled with the difficulty associ-
ated with regeneration of powdered carbon, make
granular carbon the choice for most municipal and
industrial wastewater treatment operations.
Common adsorber systems are illustrated in Figure 1.
For any system, a particular combination of flow rate
and bed depth is used to give an effective design
"contact time," the time required to reduce the organic
contaminants from the influent level to the desired
effluent level. Flow rates under 10 gpm/ft2 (407
l/min/m^) are usually employed to minimize pumping
costs associated with high head loss.
Municipal wastewater treatment experience has
indicated good treatment at contact times between 30
and 60 minutes. Significantly longer contact times are
normally required for industrial waste streams, consis-
tent with generally higher organic concentrations.
Adsorption theory and practice indicate that treatment
efficiency and economics are favored by higher
concentration. Thus, at some industrial installations,
concentrated waste streams are treated individually at
their respective sources to optimize overall treatment
system design and economics.
To provide sufficient removal of the organic loads
normally associated with wastewater, and to utilize the
carbon most effectively, an approach to countercurrent
contact is commonly required. This can be achieved with
moving bed adsorbers, or approximated with a number
of fixed bed adsorbers in series. In the latter case the
lead contactor in a series of adsorption columns is
removed from service when the carbon it contains is
exhausted (or nearly so) and, after being refilled with
fresh carbon, is placed at the end of the series. Each
contactor is thus advanced one position in the series by
piping and valving arrangements which permit shifting of
inflow and outflow points of the series accordingly. As
the number of stages increases, the piping and valving
arrangement becomes more complex and costly. A
compromise between the advantage of employing
multiple stages to more effectively utilize the carbon and
the cost of each additional stage must be achieved.
Upflow, expanded operation of fixed beds of granular
carbon permits the use of small particle sizes for faster
adsorption rates, without the associated problems of
excessive headloss, air-binding, and fouling with
MOVING 3ED
-out
DOWN FLOW IN SERIES
• Counter-current carbon UM
• Prior tutpsnded solids removi!
• Smaller volu
• Coimter-currjntctrbonuM
• Miilmumlin«ir velocity
• Ljrga voluma t y»t«m>
DOWN FLOW IN PARALLEL
1-, ~1
UPFLOW-EXPANOED IN SERIES
• Filtration & adsorption
• Miximum lineir vtloo
• Lirj« voluma lyftemt
• CounUr-current ctrtoon use
• Minimum ha^d lost
• Minimum prtlreiimtnt
Figure 1. Common Types of Adsorber Systems
40
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particulate matter common to packed-bed operation
with fine media. In expanded-bed operation, the water
flows upward through a column of relatively fine
granular carbon. The advantages of expanded-bed
adsorbers over packed-bed adsorbers have been demon-
strated and discussed.8
For fixed-bed (either packed or expanded) sorption
operations, the wastewater to be treated is passed
through a stationary bed. Non-steady-state conditions
prevail in that the carbon continues to remove increasing
amounts of impurities from solution over the entire
period of useful operation.
Figure 2 is a plot of the sorption pattern which
normally obtains for a fixed-bed non-steady-state sorber.
The impurity is sorbed most rapidly and effectively by
the first few layers of fresh sorbent during the initial
stages of operation. These first layers are in contact with
the solution at its highest concentration level, C0. The
small amounts of solute which escape adsorption in the
first few layers are then removed from solution in
subsequent strata, and essentially no solute escapes from
the sorber initially. The primary sorption zone is
concentrated near the influent end of the column, the
first layers of carbon become practically saturated with
solute and less effective for further sorption. Thus, the
primary sorption zone moves through the column to
regions of fresher sorbent. The wave-like movement of
this zone, accompanied by a movement of the C0
concentration front, occurs at a rate much slower than
the linear velocity of the water or effluent. As the
primary sorption zone moves through the bed, more and
more solute tends to escape in the column effluent, as
indicated in the sequence of schematic drawings in
Figure 2. The plot of C/CO vs time (for a constant flow
rate), or volume treated, depicts the increase in the ratio
of effluent to influent concentrations as the zone moves
through the column. The breakpoint on this curve
represents that point in operation where—for all
practical purposes—the column is in equilibrium with the
influent water, and beyond which little additional
removal of solute occurs. At this point, it is desirable to
reactivate or replace the carbon.
The method chosen for operation of fixed-bed sorber
is dependent on the shape of the curve given by plotting
C/CO vs time or volume. As noted previously, this curve
is referred to as a breakthrough curve. For most sorption
operations in water and effluent treatment, break-
through curves exhibit characteristic non-symmetric "S"
shapes, but with varying degrees of steepness and
positions of break-point. Factors which affect the actual
shape of the curve include the shape of the adsorption
isotherm, solute concentration, pH, rate-limiting mecha-
nism for adsorption and nature of the equilibrium
conditions, particle size, depth of the column or bed,
and the velocity of flow.1 As a general rule, the time
to break-point is decreased by: 1) increased particle size
of the sorbent; 2) increased concentration of solute in
the influent; 3) increased pH of the water; 4) increased
flow rate; and, 5) decreased bed depth. If the total bed
depth is smaller than the length of the primary sorption
zone required for effective removal of solute from
solution, then the concentration of solute in the effluent
will rise sharply from the time the effluent is first
discharged from the adsorber. Thus, for each type of
sorption operation there exists a critical minimum bed
depth.
Quantitive prediction of the performance of fixed-
bed sorbers involves prediction of the shape and position
Time, or Volume of Wa!er Trsats
Figure 2. Adsorntjo-i Pattern in a Fixed-Bed Adsorbe
41
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of the breakthrough curve, representing the movement
of the sorption front through an adsorber. Much of the
time and expense in planning and designing adsorption
facilities is involved in predicting or forecasting the
operational dynamics of the adsorption process for a
given waste water stream; this generally requires exten-
sive experimental pilot study. Both the time and expense
for such prediction can be minimized by a general
modeling scheme which is capable of describing the
dynamics of adsorption processes given certain basic
information about the system of interest. At a very
minimum, a general modeling scheme aids design of
programs to be carried out at the pilot level and
evaluation of the effects of process and operational
variables, thereby easing the transition from pilot to full
scale, conserving time and money, and ensuring more
optimum full scale design and operation.
Although a detailed discussion of various types of
modeling procedures that have been developed for
adsorber design is beyond the scope of this paper, it will
be noted that Weber and Crittenden have recently
developed a general modeling scheme termed MADAM I;
Michigan Adsorption Design and Applications Model -
1.2 Based on numeric solution techniques, MADAM I is
not restricted to simplified rate and equilibrium expres-
sions to facilitate analytic solution. Rather it can
accomodate the dynamic aspects of fluid dispersion,
solids mixing, multisolute interactions, and biological
growth on activated carbon surfaces, aspects which must
be excluded because of mathematic complexity from
models which are based on analytic solution techniques.
MUNICIPAL WASTEWATER TREATMENT
A number of physicochemical separation and
conversion processes have been studied over the past two
decades for potential applications to wastewater
treatment. Among these have been adsorption, coagula-
tion, chemical oxidation, solvent extraction, ion
exchange, distillation, freezing, reverse osmosis, ultra-
filtration, electrodialysis, electrochemical degradation,
flotation, and foam separation/9"11^ The process
combination of coagulation and precipitation for
removal of insoluble impurities followed by sorption on
activated carbon for removal of soluble organic
impurities has emerged as the treatment sequence of
greatest promise in terms of both technologic and
economic feasibility.
Development of physicochemical processes for higher
levels of treatment centered initially on "tertiary"
systems designed to follow "primary" sedimentation and
"secondary" biological treatment/10-1D There are
however, several fundamental shortcomings to this
approach. First, the implementation of tertiary systems
depends upon prior implementation of primary and
secondary systems. Second, the addition of tertiary
processes to primary and secondary processes incurs
capital and operating expenses of such magnitude as to
discourage this development in many instances. Third,
the effective operation of a tertiary process is dependent
to a large extent on the consistent and efficient
operation of a biological secondary process, which is
normally subject to problems arising from transients in
waste composition and flow (often requiring at least
partial diversion) and from the occasional presence of
toxic materials.
The concept of applying coagulation-sorption pro-
cesses directly to raw wastes rather than to secondary
effluents therefore has derived partially from considera-
tions regarding the effectiveness and reliability of
treatment and partially from the relative economics of
"direct" versus "tertiary" treatment systems.12 Direct
physicochemical treatment employing coagulation and
adsorption subsequently has been demonstrated to be an
attractive technical and economic alternative to
biological treatment.1^"18
TABLE 1.
OPERATING RESULTS OF PILOT PHYSICOCHEMICAL TREATMENT PLANTS
Plant Organic Effluent
Removal, % Concentration
Ewing-Lawrence (New Jersey) 95-98 TOCW @ 3-5
Blue Plains (Washington, D.C.) 95-98 TOC = 6
Lebanon (Ohio)
a. powdered carbonq 95 TOC = 11
b. granular carbon 97 TOC = 6
New Rochelle (New York) 95 COD(ii) = 8
Rocky River (Ohio) 93 BOD(ui) = 8
Salt Lake City (Utah)
powdered carbon 91 BOD = 13
Owosso (Michigan) 94 BOD = 8
(i) TOC - total organic carbon
(ii) COD — chemical oxygen demand
(iii) BOD — biochemical oxygen demand
42
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With pretreatment of raw waste by chemical
clarification—which results in significant removal of both
total and soluble organic matter, phosphates and
suspended solids—activated carbon treatment commonly
produces a clear effluent of low organic content, suitable
to meet requirements for pollution control and for many
reuse applications.
To give some illustration of this, Table 1 summarizes
overall treatment results obtained at several different
pilot installations of physicochemical treatment by
coagulations and adsorption. More than twenty munici-
palities in the United States are currently designing,
constructing or operating physicochemical facilities for
wastewater treatment. The number of industrial
treatment facilities using physicochemical processes is an
order of magnitude larger; these numbers can be
expected to increase sharply within the next decade.
The most common type of adsorber system is one in
which the effluent is passed through fixed beds of
granular carbon. In such systems hydraulic application
rates generally range from 2 gpm/ft^ to 8 gpm/ft^
(81-326 1/min/m^). In this flow range essentially
equivalent sorption efficiency is obtained for equivalent
contact times. At flow rates below 2 gpm/ft (81
l/min/m^) sorption efficiency is reduced, while at flow
rates above 8 gpm/ft^ (326 l/min/m^) excessive
pressure drop takes place in packed beds. Contact times
employed are in the range of 30 minutes to 60 minutes
on an empty bed basis. In general, increases in contact
time up to 30 minutes yield proportionate increases in
organic removal. Beyond 30 minutes the rate of increase
falls off with increases in contact time, and at about 60
minutes the effects of additional contact time become
negligible. Carbon beds operated at the lower end of the
flow range are generally designed for gravity flow.
Systems designed for higher flow rates must employ
pressure vessels if packed beds are used. A pressure vessel
is more expensive to construct than a gravity flow vessel,
but commonly requires less land area, and provides
greater ability to handle fluctuations in flow.
Provision must be made to regularly backwash
packed-bed carbon systems because they collect
suspended solids and tend to develop attached biologic
growths in this application. Backwashing alone generally
relieves clogging due to suspended solids, but does not
completely remove attached biologic growth. It is
advisable to include a surface wash and air scour to be
assured of removal of gelatinous biologic growth.
This attached growth can lead to development of
anaerobic conditions in packed beds. Aeration of the
feed is partially effective in preventing anaerobic
conditions, but this also accelerates biologic growth to
the extent that excessive backwash is required;
air-binding can also result. Effective control of biological
growth can be accomplished in most instances by regular
chlorination of the influent to the adsorbers, and/or by
chlorination or caustic addition during regular backwash
operations.
Packed beds of granular carbon are well suited for
treatment of effluents containing little or no suspended
solids, and under such circumstances normally operate
effectively for extended periods without clogging or
excessive pressure loss. However, the suspended solids
invariably present in many wastewaters, and the
potential for biologic growth on the surfaces of the
carbon can present problems for the use of packed beds.
Because solids and biologic activity usually cause
progressive clogging and high head loss in packed beds,
increased interest has developed in the potential of
expanded-bed adsorbers, which have certain inherent
operating advantages over packed-bed adsorbers for
treating solutions containing suspended solids. By
passing wastewater upward through a bed of carbon at
velocities sufficient to expand the bed, problems of
fouling, plugging and increasing pressure drop are
minimized. Effective operation over longer periods of
time results, as has been demonstrated in comparative
laboratory studies and in field investigations in both
"tertiary" and direct physicochemical applic-
ations.8'15'16 Another advantage of the expanded bed,
as noted earlier, is the relatively small dependence of
pressure drop on particle size. It is possible to use carbon
of smaller particle size in an expanded bed than is
practical in a packed bed, thus taking advantage of
somewhat higher adsorption rates which obtain for
smaller particles.
Perhaps the most significant potential benefit
provided by expanded-bed adsorption systems for
effluent treatment is the apparent extension of the
operational capacity of activated carbon observed by
Weber et al15'16 who found that apparent sorption
capacities in excess of 100 weight-percent as organic
matter and 150 weight-percent as chemical oxygen
demand (COD) could be obtained in expanded-beds of
activated carbon in which biologic growth has allowed to
fully develop.16 Because expanded beds require little
maintenance, extended periods of undisturbed operation
facilitate the development and continuous growth of
bacteria on the carbon surfaces. This biologic growth
functions both to biosorb and degrade some organic
compounds that would not ordinarily adsorb well on the
carbon, and to degrade some of the organic matter
which does adsorb on the carbon, functioning to provide
in-situ partial regeneration by renewing a portion of the
carbon surface for continued sorption. Prevention of
septic conditions and hydrogen sulfide generation in
biologically active adsorbers can be accomplished by
addition of small amounts of oxygen or nitrate to the
feed to the adsorbers.
Table 2 gives carbon capacities obtained in field
operations at several physicochemical pilot plants. In
that the wastes, effluent criteria, number of contact
states, etc. varied from plant to plant, it is not surprising
that some spread in the results is observed. For general
43
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planning purposes a COD capacity of 50 weight-percent
is reasonable if no biologic extension of carbon capacity
is taken into account. This is approximately equivalent
to a requirement of 500 pounds of activated carbon per
million gallons (60 grams per cubic meter) of sewage
treated. However, the results obtained by Weber et al,
16 with biologically-extended adsorption systems
suggest that it may be possible to achieve higher
effective capacities, reducing the carbon exhaustion rate
to less than 200-250 pounds per million gallons (24-30
grams per cubic meter).
TABLE 2.
CARBON CAPACITIES OBTAINED IN PHYSICO-
CHEMICAL PILOT PLANTS
Plant
Blue Plains (Washington)
Ewing—Lawrence (New Jersey)*
New Rochelle (New York)
Lebanon (Ohio)
Owosso (Michigan)
Salt Lake City (Utah)
Capacities,
TOC
15
50
20-24
22
weight-percent
COD
41
150
60
50
65
36
16
* Biologically-extended expanded-bed operation
Even for the highest capacities observed, the initial
cost of carbon are such as to make regeneration and
reuse of this material highly desirable. Technically and
economically feasible regeneration of granular activated
carbon can be accomplished by controlled heating in a
multiple-hearth or rotary-kiln furnace in the presence of
steam. During each regeneration cycle some carbon is
lost by burning and attrition, and some by alteration of
surface properties. The overall loss, expressed as percent
by weight of virgin carbon required to restore the total
original capacity of the batch, ranges from 5 to 10
percent. For planning purposes, carbon make-up
requirements in municipal treatment can be considered
to range from 25 to 50 Ibs. per million gallons (3-6
grams per cubic meter) of wastewater treated, again not
taking account of in-situ biological regeneration.
At present, regeneration systems for powdered
carbon are being developed and tested. A successful
process for regeneration of the powdered form would
represent a significant step toward making treatment
system utilizing this lower cost material a technical and
economic reality. The key factor will be maintaining
carbon loss at a sufficiently low level during
regeneration.
A suggested flow sheet for physicochemical treatment
of waste waters is given in Figure 3. In this scheme,
coagulant is added to the effluent, and flocculation takes
place in a chamber which provides moderate agitation
for an average detention time of 15 minutes.
Clarification takes place in a sedimentation basin with an
average detention time of two hours. The particular flow
sheet presented here is a single-stage coagulation system.
The clarified effluent is then passed through activated
carbon adsorption units for removal of dissolved
organics. The preferred mode of operation is an
expanded bed, which permits the use of simple open-top
concrete contacting basins and relatively trouble-free
operation. The use of open tanks with overflow weirs at
the surface of the contacting basin provides a means for
additional aeration of the wastewater during treatment,
thus helping to control anaerobic conditions in
subsequent reactors. Two-stage contacting of the
activated carbon is outlined in the treatment sequence
given in Figure 3. However, a larger number of stages can
be utilized if desired for a particular application. A
typical plant layout for a design capacity of 10 million
gallons (37,850 cubic meters) per day might be based on
five parallel adsorption units of two stages each. When
HAW SEW-'-SE
2-STAGE
CARBON CONTACTORS
EXPANDED BEOS
I CARBON REGENERATION
I '
Ln
DRAIN
TANK
i I
MULTl- STORAGE
HEARTH TANK
FURNACE
Figure 3. Schematic Diagram of A Typical.
Physicochemical Treatment System
44
-------
the granular carbon in the first stage of one unit is spent,
that unit can be taken off stream while the spent carbon
is removed and regenerated in a furnace provided for this
purpose. During the time this unit is off-stream for
regeneration, the other four units can run at 25% higher
feed rate each. Upon completion of the regeneration, the
carbon is returned to the adsorber, which then becomes
the second stage of that unit; the former second stage
with partially spent carbon becoming the first stage.
Feed is then evenly divided to the five units until
another carbon bed is spent.
The water resulting from the clarification and
activated carbon treatment of municipal wastewaters
will enhance the quality of most surface waters, and
with disinfection is suitable for many reuse applications.
A final filtration may be desirable to insure a crystal
clear effluent. This post-filtration would remove any
suspended matter passing through, or biologically
generated in, the carbon columns.
INDUSTRIAL WASTEWATER TREATMENT
Industrial wastewater treatment is perhaps one of the
most effective and widespread environmental application
areas for adsorption processes. Experience with a broad
range of different types of industrial effluents indicates
that treatment by activated carbon is technically and
economically suitable for many such applications.
In addition to its use as a sole treatment process, with
appropriate pretreatment as required, activated carbon
treatment has been applied in some instances to the
effluents from biological treatment processes, and in
other instances to the influents to biological treatment
processes. In the former case adsorption usually is
intended for removal of biologically resistant chemicals,
such as nitrated aromatics in some chemicals industries.
In the latter case, the purpose of adsorption is to remove
substances, such as chlorophenol in the pesticide
industries, which may be toxic or otherwise capable of
inhibiting biological treatment processes.
Pretreatment Requirements
Granular carbon rather than powdered carbon is most
commonly utilized for industrial waste treatment; this
normally involves the use of either fixed-bed or
moving-bed contact systems. Pretreatment in these cases
is primarily for removal of excess suspended solids, oils,
and greases; materials which, although they can be
removed effectively by the adsorption bed, will likely
cause problems of head loss, fouling, and plugging of the
adsorber.
Suspended solids in amounts exceeding approxi-
mately 50 mg/1 should be removed prior to adsorption.
Oils and greases in concentrations above about 10 mg/1
should not be applied directly to adsorption beds. In
addition to causing head loss problems, these materials,
particularly oils and greases, can coat the carbon
particles and reduce adsorption effectiveness dramati-
cally.
For concentrations of suspended solids, oils, and
greases below the values given above, carbon beds are
frequently used for the dual role of filtration and
adsorption. Carbon bed engineering incorporates well
established filtration experience regarding backwash
requirements, surface wash or air scour features, and
appropriate flow rates conducive to filtration. In
applying established filtration experience to carbon
beds, which are normally deeper than ordinary filters, it
has been demonstrated that the top few feet of the
carbon bed function in the same manner as the
equivalent depth of a conventional single media filter.
Backwash bed expansion should be based on this
effective filtration depth rather than the total adsorption
bed depth.
Chemical clarification, air flotation and filtration are
common pretreatment processes. It is not unusual,
however, to find that pretreatment is not required when
adsorption is applied at the point of origin of the
contaminant of concern. Treatment of combined waste
streams, on the other hand, invariably requires
pretreatment for removal of suspended solids, oil, and
grease.
Adjustment of pH is sometimes employed to enhance
adsorption efficiency. Dissolved organic compounds are
normally adsorbed best at the pH of minimum polarity.
For example, weak acids, such as phenol, are better
adsorbed at lower pH values, while amines can be
expected to adsorb best at higher pH values. Potential
advantages of pH adjustment can be quickly determined
by laboratory tests.
Flow equalization is desirable for many industrial
effluent treatment processes. While adsorber systems can
be designed to meet fluctuating influent hydraulic loads
and organic concentrations, the treatment system can be
more economically designed and operated when these
fluctuations are minimized.
Treatability Evaluation
Adsorption isotherm tests are standard first-step
procedures for determining the feasibility of adsorption
for a specific application. The isotherm indicates the
degree of treatment that might be achieved and the
approximate amount of carbon required to reach a
treatment objective. It also indicates the dependence of
the amount of adsorption on contaminant concentra-
tion.1
The Calgon Corporation has recently tested 222
samples of different industrial effluents, representing 68
different mam facturing operations, to evaluate the
removal of organic contaminants by activated car-
bon.19
In the work reported by Calgon, samples were
45
-------
membrane filtered prior to the adsorption tests to
remove suspended material which otherwise could be
incorrectly associated with adsorption treatment. This is
generally a good experimental procedure, and the type
and concentration of suspended material removed in this
step gives a preliminary indication of the desirability of
pretreatment.
The adsorption isotherm results are summarized
below, grouped according to SIC classification (Standard
Industrial Classification, U.S. Dept. of Commerce) of the
wastewater treated. This grouping allows comparison of
adsorption performance on like organic contaminants
and provides a reference list for indication of the
feasibility of adsorption as a treatment for each class of
effluent.
The list is a useful reference when considering
treatment alternatives available for a specific industrial
effluent problem, with respect to a preliminary
indication of the feasibility of adsorption treatment. The
data presented can be further catagorized according
to organic concentration. This categorization is given
in Table 4.
Because of the generally high levels of TOC evidenced
in most untreated industrial effluents, it is likely that a
combination of treatment processes will be required to
meet rigorous TOC reduction objectives at lowest cost.
The selectivity of adsorption on activated carbon for
color and phenol suggests the possibility of using
adsorption as a pretreatment to biological systems to
remove toxic, inhibitory and bio-resistant substances.
Adsorption treatment of industrial effluents for selective
removal of specific substances prior to discharge to
municipal systems appears to be technically and
economically feasible in many instances.
TABLE 3. RESULTS OF ADSORPTION ISOTHERM
SIC
number
2000
2100
2200
2300
2600
2700
2800
2900
Type of
industry
Food and
kindered
products
Tobacco
manufac-
turers
Textile
mill
products
Apparels
and
allied
products
Paper
and
allied
products
Printing,
publish-
ing and
allied
indus-
tries
Chemicals
and
allied
products
Petrol-
eum
refining
and
related
indus-
tries
Num
testei
16
1
33
28
2
9
1
2
137
13
18
17
3
Carbon
Initial TOC Initial exhaustion
Number (or phenol), color, Average % rate, lb/
mg/1 O.D. reduction 1000 gal
25-5,300
1,030
9-4,670
390-875
100-3,500 —
1.4
34-170
36-4,400
(7-270)
90 0.8-345
97
75
98
19-75,500 — 85
(0.1-5,325) — 99
0.7-275 98
92
99
58
93 1-246
0.1-5.4 97 0.1-83
12-43
90 3.2-156
94 3.7
4.3-4.6
0.7-2,905
1.7-185
1.2-1,328
1.1-141
6-24
46
-------
TABLE 4. SUMMARY OF ADSORPTION DATA
ON INDUSTRIAL WASTES
Category
Initial TOC < 100mg/l
Initial TOC = 100-1000 mg/1
Initial TOC = 1,000-10,000 mg/1
Initial TOC > 10,000 mg/1
TOC reduction > 90%
TOC reduction = 85-90%
TOC reduction < 85%
Color reduction > 95%
Color reduction = 90-95%
Color reduction < 90%
Phenol reduction > 99%
Phenol reduction < 99%
Number of samples
24
100
86
12
140
29
53
36
5
1
12
1
Carbon exhaustion rates for industrial effluents are
clearly in excess of those associated with municipal
effluent treatment. This is expected, considering the
relative levels of influent TOC. Municipal effluents can
be successfully treated at costs between 15-40 U.S. cents
per 1,000 gallons. For the most part, treatment of
industrial effluents costs in the dollars per 1,000 gallons
category for effective TOC reduction. For selective
removal of color or phenol, treatment costs might well
be in the cents per 1,000 gallons range.
For certain types of industrial effluents, such as those
from textile mill products operations, treatment by
adsorption alone appears suitable to meet organic
removal objectives. Experience with textile effluents
indicates the possibility of water reuse following
adsorption treatment. Such reuse can offset pollution
abatement costs. Cost reduction opportunities exist for
TEST ON DIFFERENT INDUSTRIAL WASTES
SIC
number
3000
3100
3200
3300
3400
3700
4200
Type of
industry
Rubber
and
miscel-
laneous
plastic
products
Leather
and
leather
products
Stone,
clay and
glass
products
Primary
metal
indus-
tires
Fab-
ricated
metal
products
Trans-
portation
equipment
Motor
freight
trans-
portation
and ware-
housing
Number
tested
8
2
7
8
1
2
4
Initial TOC Initial
(or phenol), color,
mg/1 O.D.
120-8,375
115-9,000 —
12-8,300
11-23,000 —
73,000
190-2,850
320-3,480
Average %
reduction
95
Carbon
exhaustion
rate,lb/
1000 gal.
5.2-164
95
87
90
25
91
87
3-315
2.8-300
0.5-1,857
606
12-361
20-72
47
-------
water reuse in many other industrial areas as well. Point
source treatment of specific wastes is also a substantial
factor in the use of adsorption technology for industrial
waste treatment.
REACTIVATION OF CARBON
Thermal reactivation of granular activated carbon has
been a successful practice for several decades. Rotary
kilns or multiple-hearth type furnaces operated at
temperatures between 1600-1800°F (870-980°C) are
normally used. The activation atmosphere in these
furnaces is maintained at low oxygen levels to effect
selective oxidation of adsorbed organic contaminants
rather than of the activated carbon. Carbon losses range
between 2-10% per cycle, with larger systems generally
experiencing smaller losses. Large systems are normally
designed for continuous operation, thereby facilitating
control of the process.
Afterburners and scrubbers are used to strip the
furnace exhaust gases of air pollutants. Industrial wastes
containing halogens or other corrosive substances require
special materials of construction in the kiln or furnace to
avoid corrosion problems. It is important that each
industrial effluent be evaluated from this standpoint.
The process and functional features of a thermal
reactivation system are illustrated in Figure 4. Detailed
engineering design features of granular activated carbon
reactivation systems are readily available in the
literal ure.20'21
Experience with chemical reactivation of granular
carbon has been largely unsuccessful to date. Recovery
of specific by-product adsorbates by extraction has been
demonstrated in some instances, but generally the
carbon does not sufficiently recover its adsorptive
properties. Additionally, by-product recovery frequently
suffers from the fact that the material of interest is in a
waste mixture and a pure product is difficult to recover.
ADSORBER
• .••. »• • •• .• •
V.V.- .••/:••;•'::-:
i'»« •»"'»•','• '.'•/•'
I •••••**<*•
ft':' .'•'•':•'•:'•••:'•'
'•'
DEWATERING
SCREW
FURNACE
FEED
TANK
FURNACE
t
SLURRY PUMP
48
-------
REFERENCES
1. Webei, W.J., Jr., Physicochemical Processes for Water
Quality Control, Wiley-Interscience, New York, N.Y. 1972.
2, Weber, W.J., Jr., and Crittenden, J.C., MADAM I - A
Numeric Method for Design of Adsorption Systems, Jour.
Water Pollution Control Fed., 47, 5, 924 (1975).
3. Mathews, A.P., and Weber, W.J., Jr., "Mathematical Model-
ing of Multicomponent Adsorption Kinetics," Symposium
on New Developments in Adsorption and Ion Exchange,
68th Meeting Amer. Inst. Chem. Engineers, Los Angeles,
CA. Nov. 16-20, 1975.
4. Deitz, V.R., Bibliography of Solid Adsorbents, National
Bureau of Standards, Washington, D.C., 1944.
5. Libscombe, I7., British Patent 2887, 1862.
6. Von Ostrejko, R., British Patents 14,224 (1900); 18,040
(1900). German Patent 136,792 (1901).
7. Abram, J.C., The characteristics of activated carbon, Pro-
ceedings, Activated Carbon in Water Treatment, Water
Research Assoc., Medmenham, Marlow, Bucks, England,
1974.
8. Weber, W.J., Jr., Hopkins, C.B. and Bloom, R., Jr., A
Comparison of Expanded-Bed and Packed-Bed Adsorption
Systems, Report No. TWRC-2 U.S. Dept. of the Interior,
Federal Water Pollution Control Administration, Cincinnati,
Ohio, 1968.
9. Morris, J.C. and Weber, W.J., Jr., Preliminary Appraisal of
Advanced Waste Treatment Processes, SEC TR W62-24, U.S.
Dept. of Health, Education and Welfare, Public Health
Service, R.A. Taft Sanitary Engineering Center, Cincinnati,
Ohio, 1962.
10. AWTR-1, Summary Report - The Advanced Waste Treat-
ment Research Program, 999-WP-24, U.S. Dept. of Health,
Education and Welfare, Public Health Service, R.A. Taft
Sanitary Engineering Center, Cincinnati, Ohio, 1962.
11. AWTR-14, Summary Report - The Advanced Waste Treat-
ment Research Program, 999-WP-24, U.S. Dept. of Health,
Education and Welfare, Public Health Service, R.A. Taft
Sanitary Engineering Center, Cincinnati, Ohio, 1965.
12. Weber, W.J., Jr. and Kim, J.G., Preliminary Evaluation of
The Treatment of Raw Sewage by Coagulation and Adsorp-
tion, Technical Memorandum, TM-2-65, San. and Water
Resources Eng. Div., The University of Michigan, Ann
Arbor, Michigan, 1965.
13. Rizzo, J.L. and Schade, R.E., Secondary Treatment with
Granular Activated Carbon, Water and Sewage Works, 116,
307, 1969.
14. Hager, D.G. and Reilly, D.B., "Clarification-Adsorption In
The Treatment of Municipal Waste-waters," Jour. Water
Pollution Control Fed., 42, 5, 794, 1970.
15. Weber, W.J., Jr., Hopkins, C.B. and Bloom, R., Jr.,
"Physicochemical Treatment of Wastewater," Jour. Water
Pollution Control Fed., 42, 1, 83, 1970.
16. Weber, W.J., Jr., Friedman, L.D. and Bloom, R., Jr.,
"Biologically-Extended Physicochemical Treatment," Pro-
ceedings Sixth Conference on Water Pollution Research,
Jerusalem, 18-24 June, 1972.
17. Bishop, D.F., O'Farrell, T.P. and Stamberg, J.D., "Physical-
Chemical Treatment of Municipal Wastewater, " Jour. Water
Pollution Control Fed., 44, 3, 361, 1972.
18. Hopkins, C.B., Weber, W.J., Jr. and Bloom, R., Jr., Granular
Carbon Treatment of Raw Sewage, Report No.
ORD-17050DAL05/70, Water Pollution Control Research
Series, U.S. Dept. of the Interior, Federal Water Quality
Administration, Cincinnati, Ohio, 1970.
19. Hager, D.G., "Industrial Wastewater Treatment by Granular
Activated Carbon, "Indust. Water Engin., 11, 1, 1974.
20. Smith, C.E., "Principles and Practice of Granular Carbon
Reactivation," in: Applications of New Concepts of Physi-
cal-Chemical Wastewater Treatment, Pergamon Press, Inc.,
(September 18-22, 1972), pp. 179-184.
21. Swindell-Dressier Company, A Division of Pullman Incor-
porated Process Design Manual for Carbon Adsorption, for
the Environmental Protection Agency, Technology Transfer,
October, 1971.
49
-------
THE REMOVAL OF VOLATILE SUSPENDED SOLIDS FROM WASTEWATERS.
I.N. Miasnikov, B.A. Balakin.
The process wastewaters from many industries are
contaminated with various volatile suspended solids. A
great number of these matters, especially, hydrogen
sulphide, carbon sulphide, carbon acid gas, sulphur
dioxide are contained in the wastewaters of chemical
industries. The wastes of sulphate pulp industries
contain hydrogen sulphide, methyl mercaptan, dimethyl
sulphide and dimethyl disulphide. A great number of
volatile matters are also contained in the wastes of oil
refinery industries and oil fields.
In some cases the volatile suspended solids are formed
in the wastewater while its rendering harmless, i.g. in
digestion tanks and while using various chemicals at the
waste treatment plants. The products of accessory
reactions in this case are hydrogen sulphide, methane,
carbonic acid gas and etc.
The quantity of volatile suspended solids in the
majority of the above mentioned wastes exceeds from
0.5 to I g/1. In addition, many of them are toxic even in
low concentrations. For instance, the allowable concen-
tration of carbon sulphide in the water of reservoirs is
not higher than I mg/1, hydrogen sulphide - 0. The
necessity of volatile suspended solids removal from
wastewaters is due to their toxic influence on biological
treatment processes, deterioration of conditions of
suspended solids settling, atmosphere contamination and
etc. Many of volatile suspended solids are the valuable
products and their return to production is also a great
national economy significance.
The removal of volatile suspended solids from wastes
is very difficult due to the great amount of waste liquid,
the availability of many cimponents in the solution to be
treated, various concentration of volatile suspended
solids and mechanical impurities of unequal commodity
value of these components, necessity of high rate
treatment. The solution of the problem is also
complicated, in most cases, by the absence of data on
physical and chemical parameters of wastewater
(density, viscosity etc.), the data of solubility of gases
and diffusion factors, which are necessary to take into
account in practical calculations, associated with the
liquid to be treated.
At present in most cases the all-plant wastes
contaminated with volatile suspended solids, enter the
reservoirs and sewage treatment facilities without
preliminary degassing. The operation experience of
sewage treatment facilities shows that at the expense of
natural degassing through the open surface the
satisfactory water treatment from volatile suspended
solids is not achieved. For instance, the wastewaters of
chemical fibre industries after the treatment facilities
contain some volatile components the quantity of which
several times exceeds sanitary standards. In addition in
the zone of the treatment plant the contamination of
atmosphere by the products to be treated is observed.
The efficiency of the natural degassing method
through the open water surface of the treatment
facilities does not exceed 50-60 per cent. Even when
using relatively prolonged settling of wastewaters (up to
15 days) the residual quantity of volatile suspended
solids is 3-5 mg/1. Consequently, this method of
removing volatile components cannot be recommended
neither for sanitary considerations nor for technical and
economical indices.
In home and foreign practice various degassing
processes are used for the removal of volatile suspended
solids from industrial wastes. Water blow-off with, air in
the open channels and settling tanks is used. Blow-off
products often enter the atmosphere.
For degassing separate categories of wastewaters and
process solutions the desorbers with the chord nozzle,
with the nozzle of Rashig's rings and hollow spraying
desorbers are used. The operation experience with
nozzle apparatuses and cascade apparatuses shows that
the rate of degassing of process solutions at the chemical
fibre industries does not exceed 90 per cent. These
apparatuses are advisable to use for wastewater
treatment.
The degassing of abrasive industries wastewaters from
hydrogen sulphide in the apparatus with the nozzle of
Rashig's rings provides, as our scientists show, the
elimination of dissolved gas by 95 per cent. The
nozzle-type and the cascade-type apparatuses are also
advisable to use for the removal of hydrogen sulphide,
mercaptan, dimethyl sulphide and dimethyl disulphide
from the wastewaters of pulp and paper industries.
Most scientists while considering the performance
of various desorbers emphasize the efficiency of liquid
treatment in the nozzle-type apparatuses. Alongside it is
necessary to note that the presense of suspended solids
in wastewaters makes the operation of the nozzle-type
apparatuses difficult that limitates their application
field.
For the degassing of waste liquid the temperature
effect is used. The wastewaters are heated when
increasing density up to the temperature higher than the
boiling point, and then they enter the evaporation
chamber though the reducing valve.
In the course of instant boiling the degassing alone
takes place. High-temperature vapour and gas mixture
formed enters the tubular heat exchanger, where it is
cooled at the expense of wastewater flowing to the
plant.
The degassing of the liquid in the apparatuses in
vacuum is used when it is necessary to perform thorough
elimination of dissolved gases when their residual
50
-------
content is I mg/1.
One of the methods of dewatering the volatile
suspended solids contained in the liquid, is their
transformation into the non-soluble compounds. Chlori-
nation of wastewater is used for rendering harmless
hydrogen sulphide and carbon sulphide. Chlorinated
lime and chlorine are used as chemicals. The oxidation
of carbon sulphide can be performed up to the neutral
sulphur or up to 863 with subsequent hydration to
H2S04. For the oxidation of I g of carbon sulphide into
sulphur 0.93 g of available chlorine is required, and for
the oxidation into 803 - 3.7. The rate of treatment is
dependent on the weight ratio of carbon sulphide and
chlorine; for example, at the ratio 1:2 it exceeds 50 per
cent, but at the ratio 1:8 it exceeds 90 per cent. The
oxidation proceeds in time.
The reaction of hydrogen sulphide with available
chlorine proceeds intensively and is completed with the
formation of sulphur. At the ratio of hydrogen sulphide
and chlorine equal to 1:1 in the acidic medium 65 per
cent of hydrogen sulphide is oxidized in an hour, but in
four hours - 80 per cent.
One of the efficient method for rendering harmless
hydrogen sulphide, methyl mercaptane and its natrium
salts is their air oxidation in ordinary conditions in the
presence of catalizers (hydrated oxides and iron oxides,
copper oxides, manganese oxides etc.).
At the first stage of oxidation the sulphides of these
metals are formed, which then are air oxidized into
subsequent compounds of elementary sulphur, thio-
sulphite and sulphate depending on the ph value.
As a catalizer graphite is also used which allows the
total oxidation of hydrogen sulphide-methyl mercaptan,
contained in the liquid, as well as the oxidation of their
natrium salts to thiosulphate for an hour. When
catalizers are absent their air oxidation is performed by
50 per cent during 24 hours.
While considering the given studies and the operation
experience of industrial apparatuses it is necessary to
note, that the rendering harmless of volatile suspended
solids generally does not exceed the sanitary standard.
In addition, the published studies do not contain
sufficient data describing the kinetics of treatment
process, as well as its structural design. This makes the
use of degassing methods in practice difficult and
necessitates the usage of subsequent studies with the
purpose of determination general process parameters of
overall removal of components from the wastewaters at
minimum consumption of desorber agent, as well as the
specifying of the calculation method for desorbers and
determination of technical and economical indices of
degassing installations.
With this purpose the institute VNII VODGEO in
cooperation with a number of organizations has
accomplished the studies as to desorption of dissolved
gases in the nozzle-type apparatuses of Rashig's rings
with the barbotage layer of liquid, as well as spraying
degassing units. The experiment is realized at pilot-scale
and full-scale installations, using real wastewaters of
various industries.
When calculating the desorption apparatuses it is
necessary to take into account a number of physical and
chemical parameters of wastewater and the components
to be removed. The absense of these data does not allow
to carry out the design of degassing works. That's why
the attention was given to the determination of
quantitative values of density, viscosity of wastewater,
equilibrium constants of the components to be removed,
as well as to the other physical and chemical indices of
liquid and volatile suspended solids.
The equilibrium constant m is dependent on the
qualitative characteristic of wastewaters, its value is
considerably ranges. The quantitative values of equilib-
rium constants for carbon sulphide, hydrogen sulphide
and carbon acid which are in a free state in the
wastewater, containing not more than 3 kilo-
moles/cu.m. of mattars were determined according to
the following formula:
where
i^ojm - the equilibrium constant of the component
for water and wastewaters.
C - concentration of the matter to mole/cu.m.
The values of equilibrium constants of carbon
sulphide and hydrogen sulphide for water and
wastewater from the chemical fibre industries, contain-
ing from O.I to 0.2 moles of the electrolite are given in
the table.
During the operation of desorbers the degree of water
treatment was studied depending on its temperature, pH
value, concentration of volatile components and
suspended solids, consumption of liquid and desorbing
agent, pressure in the apparatus, construction of the
water spraying device, geometric parameters of desorbers
etc.
The conducted studies allowed to establish the
optimum parameters of the wastewater treatment
process and to determine the desorbers application field.
Desorption in the nozzle-type apparatus of Rashig's
rings.
The removal of volatile suspended solids from
wastewaters is performed in the apparatus under vacuum
and at the atmospheric pressure. As a nozzle which is
located in order or conversely the ceramic Rashig's rings
are used with dimensions 25 x 25 x 3 and 50 x 50 x 5.
The liquid supply to the desorber is performed through
the nozzles with the outlet opening 5 or 10 mm, being
located at the height of 0.5 - 0.7 m above the nozzle.
The application of regulable nozzles allows the
uniform distribution of liquid to the upper layer of the
nozzle.
51
-------
The desorbing agent is fed under the nozzle through
the perforated piping. When using the nozzle the
conditions of modelling are taken into account, the ratio
of maximum dimension of the element to the desorber
diameter is less than 0.125, the nozzle height to the
diameter of the apparatus 5, but the ratio of the nozzle
height to the diameter of the element 40. On the upper
part of the apparatus at the height of 0.3 m above the
nozzles the drop removing device of Rashig's rings is
placed, the dimensions being 25 x 25 x 3, the height of
layer is 0.2 m. The apparatuses are operated at the
nozzle spraying density up to 160 cu.m/sq.m/hr.
The amount of the matter being transformed from
the liquid into the gaseous phase (and conversely) is
determined as to the known mass transfer equation:
WA= KX.F. A aver. (I)
where W^ - quantity of desorbed component,
Kx - mass transter factor related to the unit surface con-
tact of phases;
A - average driving force of the process. The driving force
of the process was determined according to the formula
widely used in practice:
wheie XjX2 - the concentration of the component at the
outlet and inlet in the apparatus;
inlet =
V
m
V2
outlet = —
m
equilibrium concentrations;
m — equilibrium constant.
When \2 K equal to zero and the value Xp inlet is highly
low, the driving force is determined according to the
formula:
Xi-X2
2.3 Ig X] 3
A aver =
A aver =
j-Xp inlet)-(Xc-Xp outlet
2.3 1 g
j—Xp inlet
t—Xn outlet
When using the formula (3), the possibility of error as
the calculations showed, is 8: + 4 per cent.
The mass transfer factor is the main parameter, which
characterizes the operation intensity of the desorption
apparatuses. It is dependent on the direction of phases
movement, proportional to the spraying density of the
nozzle in the range of 10-160 cu.m. sq.m/hr of
wastewater. Stable operation of the apparatus is
observed when spraying density is not less than 10 cu.m.
sq.m./hr. The nozzle resistance does not exceed 20 mm
Hg. The optimum unit air consumption for the
apparatus operation under vacuum is 3 cu.m/sq.m/hr.
J'htuie equllib
( Figurea In
point of cr.
"'i' • ' « vjiurj fir- o(i.., mi, .lnt'cm, o. o.ubc'i. .i;l;iv.(,'~ .
qui'UPL.tj- brebkt, are obtained u, ,. ,il cul;>.t ion ueth(.'ii iVr tciipc: ntui'i- .ibuvr t!rj L',JII'J
,i~V n MUphide)
Naoie oi
liquid
A.+.P-
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(0.01 m/sec), at normal pressure -10 cu.m/sq.m/hr. The
increase of air velocity in the desorber up to 0.13 m/sec
doesn't practically influence the rate of wastewater
treatment.
The main quantity of volatile components (up to
60-80 per cent) is removed from the liquid at the
expense of the operation of the spraying devices; the
height of their location above the nozzle being 0.7 m. In
this case the liquid flows to the nozzle with insignificant
amount of gaseous component. As the wastewater flows
through the nozzle the volatile products are removed
from the liquid.
The value Kx is inversely proportional to pH. The
optimum value during the wastewater treatment in the
apparatus in vacuum is 6.5. The degree of desorption is
85 per cent. The coefficient of desorption is also
dependent on the vacuum value, especially at high
spraying densities.
The mass transfer intensity doesn't vary at the
increase of the ratio H / more than 3(H - the height
of the nozzle, - diameter of the apparatus). The
method of nozzle location doesn't greatly influence the
treatment effect. The presence of suspended solids in the
wastewater which have adhesive properties reduces the
time of the operation run of the nozzle. So, for the
treatment f wastewaters from the chemical fibre
industries not more than 80 mg/1 of suspended solids is
allowed but for (hard) solids, not having adhesive
properties, their content may exceed I g/1 and more.
As a result of generalization of the experimental data
(when using the theory of similarity and the method of
analysis of dimensions) the following criterion equation
is obtained for the desorption process in the nozzle-type
apparatus:
a) for carbon sulphide N4 = A.Re °-83. Pr °-5 (4)
b) for hydrogen sulphide N4 = A.ReL26.Pr °-S (5)
where Nr4,Re,Pr - the criteria of Nusselt, Reynolds,
Prandtlja. The value of the coefficient A is dependent on
the vacuum depth; for carbon sulphide it is in the range
of 3.0 (at 200mmHg) to 4.5 (at 600 mm Hg): for
hydrogen sulphide - 0.0 and 0.075 respectively.
Values of Reynold's criterion index for carbon
sulphide are confirmed by prolonged operation of
desorbers when wastewater treatment. The difference of
indices is due to the complexity of wastewater
composition, to the variety of forms presented in the
components to be removed etc.
Thus the given criterion equation allows to determine
by the calculation method the mass transfer factor when
wastewater treatment. The efficiency of volatile
components removal exceeds 98 per cent (the residual
content is less than 2 mg/1).
The cost of treatment of I cu.m. wastewater in the
nozzle-type apparatus operating in vacuum is 0.7
copeck, but at the atmospheric pressure it is 2 copecks.
The latter cost is obtained for the conditions of
treatment the foamy liquids in the apparatuses (the
influent contains foamy substances) and for air supply
by the gas blower. In case of using the fan to feed the
desorbing agent the treatment cost of I cu.m. influent is
only 0.5 copeck.
When returning valuable components to the process
the treatment of influent may become paying.
The desorption in the apparatus with the barbotage layer
of liquid.
One of the main components which determine the
apparatus design and the method of rendering the
volatile contaminants harmless are the suspended solids.
In most cases they have adhesive properties; their
concentration approaches I g/1 and more that, in turn,
excludes the possibility of application such efficient
desorbers as the nozzle-type apparatuses.
For rendering these wastewaters harmless it is
advisable to use degassors with entire barbotage liquid
layer. They are efficient for removing from wastewaters
weakly soluble gases in which the main resistance during
diffusion is represented by the liquid film. At barbotage
along with the desorption of volatile contaminations the
adsorption of oxygen takes place; as a result, the
oxidation processes occur and BOD liquid is reduced in
30-50 per cent and more, that is very significant when
wastewater rendering harmless.
To remove the volatile components from the
wastewaters which contain some amount of suspended
solids it is advisable to use the apparatuses with the
barbotage layer of liquid (figure I). The feature of the
apparatus is that its design provides for spraying and
barbotage of the liquid.
The desorber is in operation both in vacuum and at
atmospheric pressure. The air is fed through the
removable barbotage device with perforated disc, the dia
of openings is equal to 1.8 mm. Similar as in the
nozzle-type apparatus the liquid is fed through the
variety of nozzles with 10 mm outlet opening. The
operation of nozzles successfully provides for foam
reduction; when they are absent the possibility of the
apparatus operation is excluded when the influent
containing surface-active agents is treated in it.
The apparatus allows to change (according to the
operational conditions) the height of the barbotage layer
of liquid by subsequent erection of pipings (9,11,13). The
release, of micro bubbles from the liquid, which are go
away from the barbotage layer takes place in the vat
(10); the gas obtained enters the apparatus through the
pipings (13).
The operation of the desorber was studied at the
spraying density being 3-66 cu.m/sq.m/hr, and the
barbotage intensity 16-360 cu.m/sq.m/hr.
During the operation along with the other parameters
static ( h st) and working (work) height of liquid layer
barbotage is determined and this allowed to establish gas
content of the layer - the value ^ , which is the most
53
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important characteristics.
The average diameter of the air bubble for the above
mentioned wastewater barbotage conditions may be
assumed as 3.8 mm on the basis of calculations. Contact
surface of phases when barbotage may be presented as
summary surface of gas bubbles of gas liquid system. In
this case the unit contact surface of phases related to I
cu.m. of the gas liquid layer is determined according to
the known formula:
Contact surface of phases, related to I sq.m. of the
desorber cross-section is determined according to the
^ , ip-h b 80 Nu = A.Re °-34.Pr °-5 (10) For the
desorption of hydrogen sulphide at Re< 80
Nu = A.Re. O-5*8 .Pr 0-5 (n)
The value of coefficient A for the desorption of
carbon sulphide for the term, Re < 80, is equal to 2.3 in
vacuum 600mm Hg and 2 mm in vacuum from 200 to 0.
For the desorption of hydrogen sulphide they are equal
to 0.7 in vacuum 600 Hg and 0.6 in vacuum from
200 to 0.
The A values are also defined for the terms when Re )
80.
The degassing rate of various types of wastewaters is
generally 98-99 per cent (the residual content of the
volatile component is 0.4 - 1.5 mg/1). In their case the
post-treatment of wastewaters from volatile components
is not required. In the course of degassing at normal
54
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pressure the wastewater saturation with air oxygen takes
place in the apparatus that is very significant.
The treatment cost of I cu.m. of wastewater (without
considering the utilization of valuable matters and the
decrease of the BOD value) in the apparatus, operating
in vacuum, is I copeck, but at normal pressure it is 5
copecks. The given cost may be considerably reduced, if
the volatile components are the valuable products.
Desorption in the spraying apparatus
The hollow apparatus similar to the nozzle-type
desorber is proposed for removing the volatile
components from the wastewaters by the liquid spraying
process. The desorption in the hollow spraying apparatus
is realized at the expense of diffusion of volatile
components through the surface of drops at their fall, as
well as partially, at the expense of the false bottom
operation as a fall-through plate, and insignificantly, at
water flow through the inside surface of desorbers. The
height of drops fall (up to the false bottom) is 4 m. For
liquid spraying various types of nozzles with the 10 mm
outlet opening are used. The hollow desorbers operate at
the spraying density 12-120 cu.m/sq.m.hr.
When defining the contact surface of phases while
spraying the wastewater with the used nozzles (with the
10 mm Cutlet opening) it is assumed that the average
diametejKjof drops is equal, to 1.5 mm. The drop velocity
of such a drop is 4.5 m/sec., that significantly exceeds
the air velocity at the counter current for the given cases
of treatment wastes in the desorber.
Using the known formula for the definition of the
contact surface of the phases a = 6 /Wk.d cp and
substituting the accepted values in it, we shall obtain for
the discussed cases of wastewater treatment the
following:
1000 M
1.125
where a - unit contact surface of phases in I cu.m. of
hollow spraying apparatus;
H - spraying density, cu.m/sq.m.sec.
The desorber operation results show that the achieved
rate of water treatment is 80-85 per cent, but in some
cases it is up to 92%.
The mass transfer factor is inversely proportional to
the spraying density. It remains practically constant at
air consumption more than 800 cu.m./sq.m.hr. (the unit
consumption is about 30). When feeding the waste liquid
through the perforated pipeline (instead of nozzles) the
treatment effect is reduced in 10-15 per cent.
The Kx coefficient is dependent on the vacuum value.
It is also increased at the ejector air inlet to the pipeline
ahead of the nozzle. The main amount of volatile
components (up to 70-80 per cent) is removed from the
Applicat:
LJ
eas
r~
i
.on field of various type degassors
OfPT*
hollow spraying, normal pressure
"worlc * um^ opt • * 02
K^ = 0.00035
1
hollow, spraying, vacuum = 600 mm Hg
H work =I*7 m« v unit opt=I0' nO2r°'ali
K2 =0.0004
barbotage, normal pressure
Hsfe =I*' m5 vunit opt =1°: hox=°-
K~ = O.OOIIj
barbotage, vacuum = 600 mm Hg i
Hgt = I m; Vunit opt = 5; hox = 0.22; K^ = 0.002?;
With nozzle of Eashig's rings; normal
^nozzle = I m; Yunj-h opt = 10; h-^. =0.
KT =0.0023
With the nozzle of Eashig's rings; vacuum = 600 rnnHg;
Hnozzle = I m; V viD±t opt = 3; h^ = 0.2; K^.004;
64;
pressure
34;
-?o° 2 4 6 s fa' 2 4
Concentration. CS2, mg/1
Liquic
gas.CvGL'10
£ 8 fo £
.,GI
Eg/
55
-------
wastewater when the drops are falling at the distance of
0.7-1 m from the nozzle.
The optimum pressure ahead of the nozzle is a liquid
head equal to 0.7 -1 atm. On the basis of generalization
of the operation data on the plant-scale and full-scale
hollow spraying-type apparatus the criterion equation is
obtained for trie desorption process of carbon sulphide
from wastewaters.
where A - for vacuum 600 m. Hg - 400, for vacuum 200
mm Hg - 250, for normal pressure - 200 mm Hg. In the
criteria of Nussolt and Reynolds average drop diameter
is accepted for the typical dimension. Since the lower
concentrated mixture is formed in the spraying desorber
the cost of valuable components as returned to the
manufacture will be higher than for the nozzle-type and
the barbotage-type apparatus.
When generalizing the performance results of the
nozzle-type desorbers of Rashig's rings with barbotage
layer of liquid and hollow sprayer-type ones, it is
necessary to note that these data allow to compare the
discussed desorbers as to the achieved efficiency of the
wastewater disinfection, they afford the opportunity to
perform the process design of these facilities and to
recommend them for wastewater treatment practice
from various industries. In the above-mentioned
desorbers the waste liquid depth (under otherwise equal
conditions) is clearly shown in the figure 2. The
selection of the wastewater treatment process is
performed depending on the local conditions. The
discussed methods of desorption and designing appara-
tuses have recently found the application in chemical,
pulp and paper and food industries. The schematic
diagram of one of industrial installations is given in the
figure 3. The performance of this installation provides
for the high-rate treatment of water and vapour and gas
mixture. In addition the return of valuable substances
takes place.
The application field of various types of desorbers is
being expanded with the increase of requirements to the
sanitary protection of waters and atmosphere from gas
emission contaminations.
List of inscriptions to figures
Figure I. Barbotage-type degassor: 1,4 - water supply
pipeline; 2 - spraying nozzles; 3 - barbotage liquid layer;
5 - removable barbotage unit; 6 - drop removing layer; 7
- pipeline for vapour and gas mixture outlet; 8 -
explosion-proof device; 9 - pipeline for treated water
outlet; 10 - vat for separation micro bubbles from liquid;
I-I3 - Pipelines for outlet from the apparatus; 12 -
Hydiaulic vat.
Figure 2. Application field of various type degassors.
Spraying density = 12 cu.m/sq.m.hr, t = 60°C; spray-
ing device - controllable cylindrical nozzle (C.C.N.);
concentration of carbon sulphide in the vapour and gas
mixture CVGM =100 mg/1; mass transfer factor = Kx
kilomole/sq.m.sec; concentration of carbon sulphide in
water, Cj - at the apparatus inlet, €2 - at the apparatus
outlet; H nozzle - height of the nozzle, hox - unit
ito viin-
wastewatfir Tt~l.-l.ioi
~-> L_syj' f;snij
Shematic diagram of industrial desorption installation
56
-------
transfer height; U unit opt. - unit air consumption.
Figure 3. Schematic diagram of industrial installation for
desorption of carbon sulphide, hydrogen sulphide with
carbon sulphide recovery.
I. Water intake tank; 2 - pump; 3 - heat exchanger; 4 -
degassor; 5 - hydraulic gate valve (barometric vat); 6 -
cooler; 7 - condensate collector; 8 - vacuum pump; 9 -
Adsorber for hydrogen sulphide; 10 - adsorber for carbon
sulphide;
2. Hollow, spraying, vacuum = 600 mm Hg H work =
1.7 m; V unit opt. = 10; hox = 0.81; Kx = 0.004
3. barbotage, normal pressure H s^ = 1.5 m; V unit opt.
= 10; hox = 0.64; Kx = 0.0011
4. barbotage, vacuum = 600 mm Hg Hst = I m; V unit
opt. = 5; hox = 0.22; Kx = 0.0027;
5. With nozzle of Rashigs rings, normal pressure H
nozzle = 1 m; V unit opt. = 10; hox = 0.34; Kx =
0.0023
6. With the nozzle of Rashig's rings; vacuum = 60 mm
Hg; H nozzle = I m; V unit opt. = 3; hox = 0.2; Kx =
0.004;
57
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DESIGN OF FACILITIES FOR PHYSICAL-CHEMICAL TREATMENT OF RAW WASTEWATER
Presented by Gordon L. Gulp at Technology Transfer Seminars
Sponsored by the U.S. Environmental Protection Agency.
INTRODUCTION
The various approaches to physical-chemical treatment
of raw wastewater as described by other speakers in this
session, all involve the use of the same basic unit
processes of coagulation and settling for removal of
suspended solids and, in some cases, phosphorus; the use
of filtration for further removals of suspended solids and
phosphorus; and carbon adsorption for removal of
soluble organics.
This paper will discuss: typical design parameters for the
unit processes involved in physical-chemical treatment of
raw wastes; how the design engineer may determine the
design criteria best suited for a given wastewater; criteria
being used for full-scale plants; and the results obtained
in studies in several locales.
PLANT PERFORMANCE SPECIFICATIONS
For purposes of providing an illustrative example for
discussion of design considerations, the raw waste
characteristics and effluent requirements shown in Table
1 have been assumed. The effluent standards cannot be
met with secondary treatment alone as chemical
coagulation would be required to meet the phosphorus
standards and, at least, filtration of a secondary effluent
to meet the BOD and SS requirements. On the other
hand, the effluent standards are not so stringent to know
for certain that physical-chemical techniques must be
used in series with biological treatment. Therefore, a
design engineer faced with the above situation should
conduct the necessary tests to determine if the above
standards could be met by physical-chemical treatment
alone, and if so, what design criteria should be used. The
unit processes involved are proven to the degree that
extensive, on-site pilot tests are not necessary for most
wastewaters and design criteria can be obtained in
laboratory tests. Of course, if time and funds permit, an
TABLE 1
WASTEWATER CHARACTERISTICS AND EFFLUENT
QUALITY REQUIREMENTS
BOD
COD
Suspended Solids
Hardness, as CaCOj
Phosphorus
Alkalinity
Influent,
Average
(mg/1)
180
520
250
150
11.5
220
Effluent,
weekly
Average (mg/1)
15
30
10
on-site pilot test over several months will permit an even
more accurate determination of design criteria under a
wider variety of operating conditions. Should on-site
pilot studies be considered, the scale of the equipment
can be tailored to meet the individual needs of the
project. Small diameter filters and carbon columns
(about 6-inch diameter) are adequate for column studies
and can often be obtained from suppliers of carbon and
filter manufacturers on a loan or rental basis. Pilot
clarifiers of 6-10 feet in diameter can usually be rented
from clarifier manufacturers. In a like manner, pilot
sludge thickening and dewatering equipment can also be
rented. The overall cost of pilot studies will vary widely
depending upon the extent of the data collected. A
meaningful study should span several months if any
seasonal variations in raw wastewater quality are
anticipated. Although pilot studies unquestionably
provide a firmer basis of design, the author's experiences
indicate that, except in unusual circumstances, the
design criteria for the physical-chemical unit processes
undei consideration here can be determined with
suitable accuracy in properly conducted laboratory tests
on representative raw waste samples.
PRELIMINARY DATA COLLECTION
In order to proceed with the design on a rational basis, a
characterization of the raw wastewater in terms of its
amenability to physical-chemical treatment must be
made. The following description of tests on wastewater
illustrates techniques which may be used. Four 24-hour
composite samples collected during four different weeks
are used in the example.
The goals of these tests are to answer the following
major questions which must be answered before the
design can proceed:
• What is the best coagulant?
• How much sludge is produced?
• How well does the sludge dewater?
• Is coagulant recovery practical?
• What is the nonadsorbable fraction of organics in the
raw wastewater?
• How much carbon contact time will be required?
• What effluent quality can be expected?
SELECTION OF COAGULANT
There are four major classes of coagulants which may be
considered singularly or in combination:
58
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1. Polymers. Some investigators have reported success-
ful coagulation of raw sewage with polymers alone. The
author has examined polymers as the primary coagulant
on many wastewaters without finding them economic-
ally attractive when compared to the inorganic coagu-
lants available. The cost of polymers is $l-$2 per pound.
When used as the primary coagulant, polymers do not
provide phosphorus removal. One of the following
inorganic coagulants is required if phosphorus removal is
of concern. Polymers used in conjunction with an
inorganic coagulant are effective settling and filtration
aids.
2. Iron Salts. Ferric chloride or ferric sulfate may be
used for both suspended solids and phosphorus removal.
Experience has shown that efficient phosphorus removal
requires the stoichiometric amount of iron (1.8 mg/1 Fe
per mg/1 of P) to be supplemented by at least 10 mg/1
of iron for hydroxide formation. Typically, 15-30 mg/1
as Fe is required to provide phosphorus reductions of
85-90 per cent. When considering iron for coagulation of
raw wastes, it must be remembered that in an anaerobic
environment, as may be encountered in a downstream
carbon column, iron sulfide may be formed. This black
precipitate is obviously not desirable in the final
effluent.
3. Aluminum Salts. Both aluminum sulfate (alum) and
sodium aluminate have been used for coagulation of
wastewaters. Alum is generally a much more effective
coagulant than sodium aluminate. Alum doses of
200-300 mg/1 are typically required for 85-90 percent
phosphorus removal (an aluminum to phosphorus ratio
of 2-3). Disadvantages of both the iron and aluminum
salts are (1) both form gelatinous hydroxide floes which
are difficult to dewater in many cases; (2) no techniques
are available for recovery and reuse of the coagulant
when phosphorus removal is required; and (3) large
amounts of ions (chlorides or sulfates) are added to the
wastewater.
4. Lime. Lime has been successfully used in several
locales for wastewater coagulation and phosphorus
removal. The amount of lime required is independent of
the amount of phosphorus present; rather, it is a
function of the wastewater alkalinity and hardness.
When the pH reaches 9.5 due to the addition of lime, the
orthophosphate is converted to an insoluble form. In
some cases, additional quantities of lime may be
required to form a readily settable floe. Lime has been
recalcined and reused in some cases when used to
coagulate secondary effluent. However, as will be illus-
trated later, recalcining and reuse may often not be
practical when it is used to coagulate raw wastewaters
due to the large amount of inert materials present in the
combined raw sewage-chemical sludges. In any case, lime
sludges usually dewater more readily than those resulting
from iron or aluminum coagulation.
The choice of coagulant can usually be made rather
quickly by laboratory jar tests. The following illustrative
example is based on data collected on a raw wastewater
from a community in the Midwest.
In the technique used, six one-liter samples are dosed
with the coagulants being studied while being rapidly
mixed with a jar test device. In this example, 0.5 mg/1 of
an anionic polymer (nopcofloc 930, manufactured by
Diamond Shamrock) was added as a settling aid.
Following a 60-second rapid mix, the samples are slowly
mixed for about 5 minutes. These are then allowed to
stand quiecently to permit settling of the floe. Samples
of the supernatant are then obtained with a pipette from
a point just below the liquid surface in the jar. This is
done to avoid including any of the floating solids which
are invariably found in raw sewage. This supernatant
sample is then analyzed for turbidity, pH, hardness
(when lime is used as a coagulant), and phosphorus. A
portion of the remaining supernatant is filtered through
a Whatman No. 2 filter paper. The filtrate is analyzed for
turbidity, phosphorus, and in some cases, TOC, COD,
BOD and suspended solids. Past experience has shown
that the filtrate quality obtained with this filter paper
will be about the same as that which will be achieved
with a mixed-media filter.
Lime Coagulation
By plotting the jar test data, it was determined that the
lime dosages required to achieve a filtrate phosphorus
concentration of one mg/I were as follows:
Sample No. 1 = 132 mg/1 as Ca(OH)2
Sample No. 2 = 100 mg/1 as Ca(OH)2
Sample No. 3 = 110 mg/1 as Ca(OH)2
Sample No. 4 = 130 mg/1 as Ca(OH)2
One mg/1 phosphorus was achieved at a pH of 9.1-9.5.
The lime dosage required for optimum solids removal
varied from 100-130 mg/1. In general, a somewhat higher
dose of lime was required for optimum solids removal
than was required for phosphorus removal. A lime dose
of 200 mg/1 achieved adequate solids removal for all four
samples and this dose will be used in subsequent
calculation of the cost of lime coagulation.
Suspended solids analyses showed that settled superna-
tant contained less than 5 mg/1 suspended solids at this
dose and the filtered supernatant generally contained no
measurable suspended solids. A lime dose of 200 mg/1
results in an effluent phosphorus concentration of
0.07-0.26 mg/1 and a pH of 9.6-10.1. The lime and
polymer dosage produced a rapidly settling floe, as it
does in most wastewaters.
59
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Alum Coagulation
The alum dosages required to achieve a filtrate
phosphorus concentration of one mg/1 were as follows:
Sample No. 1 = 120 mg/1
Sample No. 2= 153 mg/1
Sample No. 3 = 165 mg/1
Sample No. 4= 150 mg/1
The pH was reduced to 6.7-7.1 by the above alum
dosages.
Adequate solids removal was achieved at alum doses
equal to or less than that required for phosphorus
removal.
Iron Coagulation
The ferric chloride dosages required to achieve a filtrate
phosphorus concentration of one mg/1 were as follows:
Sample No. 1 = 20 mg/1 as Fe
Sample No. 3 = 27 mg/1 as Fe
Sample No. 4 = 23 mg/1 as Fe
The required Fe/P ratios were 2.7, 2.4, and 2.5
respectively. It appeared that the dose required for
phosphorus removal would equal or exceed that required
for solids removal.
Comparison of Coagulant Costs
The cost of the various coagulants at the plant site is as
follows:
Lime = $16.75/ton of CaO
Alum = $70/ton
Ferric Chloride = $90/ton (or $262/ton of Fe)
The estimated costs for coagulation with the following
doses are as follows:
200 mg/1 lime [as Ca(OH)2] = $10.60/mg
160 mg/1 alum = $46.50/mg
23mg/lFe = $25.10/mg
It is apparent that lime is the lowest cost coagulant, even
when the lime dosage involved reduces the phosphorus
to less than 0.3 mg/1.
Of course, the total economic comparison must also
include the relative cost of sludge disposal associated
with each coagulant. Nearly always the lime sludges may
be disposed of at significantly lower costs than the
sludges resulting from either alum or iron coagulation.
Thus, in the above example, there is little doubt that
lime will remain the most economical coagulant when
sludge disposal costs are included.
The general dewatering characteristics of the sludge may
be determined by laboratory tests. A 100 ml sludge
sample is dewatered with a Whatman No. 2 filter paper
in a Buchner funnel with laboratory vacuum. The
volume of filtrate versus time is then plotted and
compared to similar data for sludges for which field
experience has also been obtained. Figure 1 presents an
example comparison which shows that the sludges
resulting from coagulation of this wastewater dewatered
even more readily in the lab than did another sludge
which later proved to dewater very well in a centrifuge.
Thus, the dewatering of the sludge does not appear to be
a limiting factor in this case.
It is difficult to obtain an accurate gravimetric
measurement of sludge quantities in a laboratory test
due to loss of solids during decanting, etc. However, it is
possible to estimate the quantities of lime sludge from
the chemistry involved and the data collected from the
jar tests. As shown in Table 2, about 4,050 pounds of
solids per million gallons would be expected with a lime
dose of 200 mg/1. Following incineration, the ash
quantities would be about 2,165 pounds per million
gallons.
With this information, it is then possible to determine
the feasibility of recalcining and reusing the lime. From
Table 2, it is apparent that if one were to recycle all of
820 pounds of the lime recovered per mg, that one
would also recycle 1,345 pounds of inert ashes.
Assuming that a 20 percent blowdown were practiced,
one would recycle 670 pounds lime and 1,080 pounds
inerts. After the second cycle, there would not be 1,345
+ 1,080 pounds of inerts in the furnace discharge or
2,425 pounds of inerts. Table 3 presents an illustrative
calculation of the buildup of inerts through 11 cycles
with 20 percent blowdown of the furnace product.
Eventually, one will be dewatering and incinerating
about 6,500 pounds of inerts per mg in order to recover
only 670 pounds of lime. The solids handling system
would have to be sized for a solids load corresponding to
a nonvolatile fraction of about 7,300 pounds/mg rather
than the 2,165 pounds/mg if the sludge was merely
incinerated and thrown away. One would be spending
far more to recover the lime than it would be worth. A
higher blowdown rate still does not make recalcining
practical in this example. It is far cheaper to use the lime
once and dispose of the sludge. Until a means is available
for very efficient separation of lime from the inerts in
the combined raw sewage-chemical sludge, lime recycle
will often not be practical when coagulating raw sewage
unless very high lime doses are involved. Envirotech is
developing a dry classification technique for this purpose
60
-------
300018
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S3SV3 H108 Nl
OE6 301d03dON I/DIM S'O
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ISON033S) 3WU
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OS
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TABLE 2
ESTIMATE OF LIME SLUDGE QUANTITIES
Raw Sewage Suspended Solids =250 mg/1
Raw Sewage PO4 = 34.5 mg/1
Add 200 mg/1 lime as Ca(OH)2 or 108 mg/1 Ca
Assume all 250 mg/1 raw sewage SS removed
Assume lime reacts with PC>4 to form
Ca5(OH) (P04)3
Weight of Ca5(OH) (PO4)3 formed =
Ca5(OH) (P04)3m.w. x Po conc = 502
(OP4)3 m.w.
Raw Hardness =
Treated Hardness =
Ca lost in effluent =
CainCa5(OH) (PO4)3 =
Ca in CaCO3 sludge =
Quantity of CaCO3 =
285
x 34.5 = 61 mg/1
x (185-150) = 14 mg/1
150 mg/1 as CaCO3 [as measured on Sample No. 4
with 200 mg/1 Ca(OH)2]
185 mg/1 asCaCO3
40
100
200
502
108
100
40
x 61 mg/1
- (24+ 14)
x 70
= 24 mg/1
= 70 mg/1
= 175 mg/1
Sludge Composition
Raw sewage Solids = 250 mg/1
Ca5(OH) (PO4)3 = 61 mg/1
CaCO3 = 175 mg/1
2080 Ibs/mg x .4
5101bs/mg x 1.0
1460 Ibs/mg x .56
4050 Ibs/mg
835 Ibs/mg
510 Ibs/mg
820 Ibs/mg
2165 Ibs/mg
61
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TABLE 3
EFFECT OF RECYCLING RECALCINED MATERIALS
Pounds per Million Gallons
Recycled Material
Furnace Discharge with 20% Slowdown
Cycle No. Lime Inerts
1
2
3
4
5
6
7
10
11
820
820
820
820
820
820
820
820
820
820
820
1345
2425
3285
3975
4525
4965
5315
5595
5825
6005
6145
Lime
670
670
670
670
670
670
670
670
670
670
670
Inerts
1080
1940
2630
3180
3620
3970
4250
4480
4660
4800
4915
Assumes 100% calcium recovery from sludge and makeup
lime to maintain 200 mg/1 lime dose
but no operational data are yet available. A plant under
construction in Contra Costa, California will make use of
this dry classification technique on sludges resulting
from lime coagulation of raw sewage.
CARBON ADSORPTION
There are organics (i.e., sugars) which may be readily
biodegradable but which are difficult to adsorb on
carbon. The amount of these nonadsorbable materials
will vary greatly from wastewater to wastewater and
their presence will be the governing factor concerning
the quality of effluent which can be achieved by carbon
adsorption. The same physical-chemical process may
produce a BOD of 10 mg/1 in one locale and 30 mg/1 in
another due to this fact. The ability to remove the
soluble organics may be measured in the laboratory by
two methods. /
One of these methods is a batch process in a beaker
while the other is a flow-through, carbon column
experiment. In the first case, the raw sewage is contacted
with 1,000 mg/1 of Aqua Nuchar A, a powdered carbon,
for one hour. Alternately, a sample of the granular
carbon under consideration may be ground and applied
to the sample. The sample is then coagulated, settled and
the supernatant filtered through Whatman No. 2 filter
paper prior to analysis. Past work done with powdered
carbon indicates that an Aqua Nuchar dose of 600 mg/1
and a contact time of five minutes is generally adequate
for removal of all adsorbable organics. Thus, the above
conditions insure that all adsorbable materials are, in
fact, removed. The above technique is a quick method of
determining the nonadsorbable fraction of organics. The
isotherm technique described by other speakers in this
session will provide more information.
The column test may be conducted using Calgon
Filtrasorb 400 carbon or equivalent in five %-inch
diameter columns in series. The columns are sized so
that cumulative contact times of 7.5, 15, 30,45 and 60
minutes are provided at the end of the respective
columns. Four to five gallons of raw sewage are
coagulated with either lime or alum, settled, the
supernatant decanted (the pH adjusted to 7 when lime is
used), and the clarified wastewater pumped through the
columns. This quantity of sewage will provide several
days of operation in columns of this size. The tests
should be continued as long as possible to accurately
determine the effects of biological activity. The sludge
should be saved for analysis. The results from these small
columns have been found by the author to be consistent
with those obtained in larger units. For example, in one
study spanning several months, the results concerning
contact time from small laboratory columns in the first
four weeks of the study were essentially the same
observed from both 6-inch diameter and 3-foot diameter
columns operated over several months.
The reasons for preferably conducting both the
powdered carbon and column tests are to determine if
the effluent from the columns could be lower in BOD
than that achieved by adsorption alone due to the
biological growth in a column and to determine the
effects of contact time on column performance.
Powdered Carbon Results
The effluent quality achieved by the powdered carbon
technique above should closely represent the non-
adsorbable fraction of the organics contained in the raw
waste sample tested. The results obtained with the
wastewater in question are as follows:
The three parameters show similar trends from sample to
sample, with the fourth sample containing substantially
less nonadsorbable organics than Samples 2 and 3 and
somewhat less than Sample 1. It appears that the BOD
of 2 mg/1 measured for Sample 4 may be low as the
COD/BOD ratio is considerably out of line with the
other samples. The COD appears valid as the COD/TOC
ratio compares closely with the other samples. However,
it is possible that there was a change in the nature of the
unadsorbable organics so that, in fact, a smaller portion
was biodegradable.
The nonadsorbable BOD ranged from 2-18 mg/1 with an
average of 12.2 mg/1 for the four samples.
62
-------
Column Tests
Figures 2 and 3 summarize the data collected from the
laboratory columns. As can be seen from the figures, the
benefits achieved by contact times greater than 30
minutes are slight. The carbon column effluent BOD
values after 60 minutes contact ranged from 5 to 15
mg/1 and averaged 11.0 mg/1. The BOD samples collected
at a 30-minute contact time averaged 12.5 mg/1.
An estimate of the required carbon dosage can be made
by assuming that carbon will be withdrawn for
regeneration when the carbon loading is 0.5 pounds of
COD removed per pound of carbon. This loading has
20
10
0
Ol
kt_ ORGANIC CARBON
o S
H
O
0
20
10
0
c
DAY 1
"\ ;
DAY 2
\
°
. °v DAY 3
o
X. •;
o
1 I
20 40 6C
CARBON DETENTION TIME. WIN.
30
20
10
0
D>
M. ORGANIC CARBON
S JJ
O
H
0
20
10
0
(
\ DAY 8
• -J
DAY 10
v
^o
-\ DAY 14
\^\
^^X ^v
_ \v. °-~-__^
DAY 22 X^^^ ^ ^£
) 20 40 60
CARBON DETENTION TIME. WIN.
FIGURE 2
PILOT CARBON COLUMN DATA
63
-------
CARBOK CONTACT TIME, MINUTES
FIGURE 3
PILOT CARBON COLUMN DATA
been achieved in several studies. An average soluble
influent COD of 86 mg/1 was achieved with lime
clarification in the four series of jar tests. The average
COD achieved in the four powdered carbon tests was 23
mg/1 and averaged 24 mg/1 after 30 minutes contact in
the columns. Thus, an average COD removal of about 62
mg/1 would be expected from these tests, The
corresponding carbon dosage is 1,030 pounds/mg.
Carbon dosages calculated from short-term laboratory
column tests are usually conservatively high, as
biological action usually results in greater permissible
loadings in a continuous, plant scale operation.
PROCESS DESIGN
The purpose of this section is to discuss those design
criteria necessary for plant design. Figure 4 illustrates
the flow sheet upon which the following discussion is
based.
Flow
Both the average and peak flows are of concern. In a
physical-chemical plant, there is a substantial volume of
flow recycled to the head of the plant from the
following major sources: (1) furnace scrubber under-
flow, (2) filter and activated carbon backwash flows, (3)
sludge thickener overflow, and (4) sludge dewatering
filtrate or centrate. For example, a 15 mgd average flow
rate may be associated with a peak hourly rate of 30
mgd. To these values must be added the volume of
recycle streams. If these recycle streams total 3.5 mgd in
the above example, then the design hydraulic flow rates
become 18.5 mgd average and 33.5 mgd peak hour.
Preliminary Treatment
Comminution and grit removal facilities designed in
accordance with standard sewage treatment design
practices should be provided.
Chemical Feed, Rapid Mix and Flocculation
These functions may all be carried out in accordance
with standard practices followed in the water treatment
field for years.
Proper rapid mixing is important to efficient utilization
of the coagulating chemicals. The use of a mechanical
rapid mixing device in the basins with a total of 2
minutes detention time of the average flow is
recommended. When using lime as coagulant, scaling of
the mixer shaft will occur and may cause excessive
bearing wear if not cleaned regularly. In any case,
provision of two parallel rapid mixing units each with a
nominal capacity of one-half the design flow is prudent
to provide flexibility in operation. Should one mixing
unit be down for repair, the entire flow can be passed
64
-------
J
r
0
RAW ^
SEWAGE
Q PEAK HOUR!
COMMINUTION
AND
GRIT REMOVAL
[A] DESIGN FLOW BASED ON
[*•
c
•}
RAPID MIX
AND
FLOCCULATION
t
COAGULANT(S)
Q PEAK HOUR PLUS
(A)
SLL
DGE
L
Q RECYCLE
SURGE
BACKWASH WASTEW-ATERS
t 1
1 1
i i
i i
i i
RECAHBONATON
COAG USED)
CHLORINE
POND I81 IB)
ASH , ,
1 t I
-
SLUDGE
THICKENING
(OPTIONAL!
SLUDGE CARBON
~* DEWATERING * INCINERATION DEGENERATION
1 1 1 1
1 CENTRATE crfjimnpo SCRU3TER
OVERFLOW OR UNDER 'lO-V UNDERFLO* AND
FILTRATE UNULK LUA< CA-,CON WA£J WA-rERS
_i __* _J _t
FIGURE 4
ILLUSTRATIVE SCHEMATIC OF
A PHYSICAL - CHEMICAL TREATMENT PLANT
through the remaining basin which will still provide one
minute mixing with the above criteria.
A mechanically mixed flocculator with 15 minutes
detention is generally adequate for wastewaters. In many
cases, the flocculation resulting from the large coagulant
doses added to wastewaters results in very rapid
flocculation and even shorter detention times may be
feasible. Provisions should be made to add up to one
mg/1 polymer at the rapid mix or at the flocculator inlet
or outlet or split among these points.
Clarifier Sizing
The critical design parameter is the peak hourly surface
overflow rate. Gross carryover of solids can cause the
downstream filter or adsorption processes to fail due to
excessive headloss which, in turn, will result in a total
failure of the plant. Thus, it is of little consolation to
know the clarifier will perform properly under average
flow conditions only to have a carryover of excessive
solids during the peak hourly flow shut the entire plant
down. A maximum peak hourly rate of 1,400 gpd/ft^
for conventional horizontal or radial flow clarifiers is
recommended when using lime as a coagulant unless
pilot tests indicate that other rates should be used. A
maximum average rate of 900 gpd/ft^ is recommended.
Whichever of these two criteria results in the larger
clarifier size should be used.
Several attempts have been made to use upflow, sludge
blanket type clarifiers on coagulated primary or
secondary effluents. Difficulty in holding a sludge
blanket has been reported in every case. Successful
operation has been achieved with these units by lowering
the overflow rate to conventional clarifier rates and
eliminating the sludge blanket, which in essence,
converts the unit to a conventional radial flow basin.
The instability of the sludge blanket or solids contact
units is due to the organics found in the raw sewage and
the wide variations in incoming flow. These units have
been most successful in treating groundwaters of
uniform composition at a constant flow rate. The author
does not recommend their use on coagulated waste-
waters.
Provision should be made for recirculation of controlled
amounts of sludge from the bottom of the clarifier to
the rapid mix inlet. The high pH of lime-treated water
will form deposits of calcium carbonate on structures
and in pipelines which it contacts. Lime sludge suction
lines should be glass lined to facilitate cleaning. Pro-
visions must also be made for regular cleaning of all
other pipelines which carry the high pH effluent. Use of
the new polyurethane cleaning pigs should be com-
patible with the layout of the pipelines. Mechanical
sludge collection equipment used in lime settling basins
should be of the bottom scraper type rather than the
vacuum pickup style because of the dense sludge to be
handled.
65
-------
Recarbonation
lime treatment of wastewaters for phosphorus removal
often raises the pH to values of 10-11. At this pH, the
water is unstable and calcium carbonate floe will
precipitate readily. This floe is very tenacious and would
encrust any downstream filters or carbon particles to a
serious degree. The pH may be lowered by injecting €62
gas obtained from the incinerator stack gases. Primary
recarbonation is used to reduce the pH from 11 to 9.3,
which is near that of minimum solubility for calcium
carbonate. In domestic wastewater, primary recarbon-
ation to pH = 9.3 results in the formation of a heavy,
rapidly settling floe which is principally calcium
carbonate, although some phosphorus is also removed
from solution by adsorption on the floe. If sufficient
reaction time, usually about 15 minutes in cold water, is
allowed for the primary recarbonation reaction to go to
completion, for the calcium carbonate floe does not
redissolve with subsequent further lowering of pH in
secondary recarbonation. If lime is to be reclaimed by
recalcining and reused, this settled primary recarbon-
ation floe is a rich source of calcium oxide, and may
represent as much as one third of the total recoverable
lime. If the pH were not reduced to less than about 8.8
before application to the filters and carbon beds,
extensive deposition of calcium carbonate would occur
on the surface of the grains. This could reduce filter
efficiency, and could also drastically reduce the
adsorptive capacity of granular activated carbon for
organics. It would produce rapid ash buildup in the
carbon pores upon regeneration of the carbon, and
would lead to early replacement of the carbon.
It is possible to reduce the pH of a treated wastewater
from 11 to 7 or to any other desired value in one stage
of recarbonation. Single-stage recarbonation eliminates
the need for the intermediate settling basin which is used
with two-stage systems. However, by applying sufficient
carbon dioxide in one step for the total pH reduction,
little, if any, calcium is precipitated with the bulk of
calcium remaining in solution, thus increasing the
calcium hardness of the finished water, and, in addition,
causing the loss of a large quantity of calcium carbonate
which could otherwise be settled out, recalcined to lime,
and reused. If lime is to be reclaimed or if calcium
reduction in the effluent is desired, then two-stage
recarbonation is required. Otherwise, single-stage re-
carbonation may be used with a substantial savings in
initial cost, and a reduction in the amount of lime sludge
to be handled.
In our example wastewater discussed earlier, there would
be no need for two-stage recarbonation because (1) no
reuse of lime is planned, (2) the phosphorus goals can be
achieved without the slight additional phosphorus which
may be provided by two-stage recarbonation, and (3) the
low lime dosage required does not add a significant
quantity of calcium to the effluent.
If two-stage recarbonation is being considered only for
the purposes of lime recovery, one should compare the
value of the lime recovered against the cost of providing
two-stage recarbonation. Peak hourly overflow rates for
the intermediate clarifier in two-stage recarbonation
should not exceed 1,400 gpd/ft^. Provision should be
made for polymer addition to the intermediate clarifier
influent.
The details of design for recarbonation systems may be
found in Advanced Wastewater Treatment.
Filtration
Whether or not filtration is needed prior to activated
carbon adsorption is subject to debate. There is no
question that filtration ahead of a downflow granular
carbon adsorption bed will reduce the rate at which the
pores of the activated carbon become plugged with inert
materials. Also, the use of an efficient filter permits
downstream use of upflow, packed carbon beds which
may be operated in the more efficient countercurrent
mode discussed later. The question is whether or not the
cost of providing the filtration exceeds the benefits
mentioned above. Only long-term operating data from
plants using granular carbon with and without prior
filtration will answer this question. In the interim, a
conseivative design will include filtration prior to carbon
adsorption. In addition to protecting carbon pores from
plugging by inerts, mixed media filtration also provides a
more efficient means of solids removal than carbon
alone, resulting in a higher effluent quality. Filtration
Equipment is available which will provide simple,
reliable and automatic operation. Carbon is not a
particularly effective filter because it acts as basically a
surface type filter and as such, is subject to all the
shortcomings of other surface filters applied to
wastewaters. Any high solids loading will blind a surface
type filter in short order. The use of dual media or
mixed, tri-media filters provides a much more efficient
filtration device which is capable of tolerating a much
higher solids loading than is a surface type filter. A
discussion of alternate filtration devices and a detailed
discussion of filter system design may be found in
Advanced Wastewater Treatment.
In instances where an upflow expanded bed carbon
contactor is used, the filter may be located downstream
of the carbon column to remove the bacterial floe which
is flushed from the carbon.
It is desirable to precede the filtration step with a flow
equalization pond so that the filters may be operated at
essentially a constant rate. Provisions should be made for
66
-------
a feed of polymer directly to the filter influent as a filter
aid. Filter effluent turbidity and head loss should be
monitored continuously with high filter head loss being
used to initiate an automated backwash program.
Granular Carbon Adsorption
Because of the unproven economics of recovery and
reuse of powdered carbon, the use of granular carbon is
the only current practical technique available for
removal of soluble organics from coagulated raw
wastewater. Chemical oxidation techniques are not yet
practical for the large quantities of organics involved.
The major design decisions facing the engineer is the
selection of a contact time (30 minutes in the example
discussed earlier), what dose of carbon is required (can
be conservatively estimated by assuming a removal of
0.5 pounds of COD per pound of carbon prior to
regeneration) and the configuration of carbon contactor
to be used. Typically, the carbon doses will be
substantially higher than when granular carbon is applied
to coagulated and filtered secondary effluent. In the
earlier example, a carbon dose of slightly more than
1,000 pounds per million gallons was estimated. This
magnitude of dose is not unusual when applying carbon
to coagulated raw sewage.
Contact time of about 30 minutes has been reported by
many investigators as marking the point of diminishing
returns. That is, a drastically longer contact time would
not provide any proportionately greater removal of
organics.
The two major alternate contactor configurations to
consider are open concrete vessels of either an upflow or
downflow type or upflow, countercurrent columns in
steel or concrete vessels. The countercurrent approach
(see Figure 5) offers a more efficient utilization of the
carbon as only the most saturated carbon is withdrawn
for generation. This result is aided by the fact that as the
carbon becomes saturated with organics, it becomes
heavier. When the carbon column is backwashed, the
CARBON COLUMN
-BYPASS VALVE
CLOSED
CARBON COLUMN
INFLUENT HEADER
VALVF-OPF.N
TYPICAL ARRANGEMENT FOR UPFLOW.
COUNTER CURRENT CARBON CONTACTOR
(MtOV LUI P a GULP)
67
-------
more saturated, heavier carbon tends to maintain a
position at the bottom of the column where it is
withdrawn for regeneration. A semi-countercurrent
approach can also be achieved by using two downflow
columns in series. As indicated on Figure 6, water is first
passed down through Column A, then down through
Column B. When the carbon in Column A is exhausted,
the carbon in Column B is only partially spent. At this
time, all carbon in Column A is removed for
regeneration and is replaced with fresh carbon. Column
B then becomes the lead column in the series. When the
carbon in Column B is spent, the carbon is removed for
regeneration and is replaced with fresh carbon. This type
of operation gives only some of the advantages of
countercurrent operation because only the carbon near
the inlet of the lead bed is fully saturated with
impurities removed from the water and some capacity is
unused in much of the rest of the carbon sent to
regeneration. Also, the piping and valving is more
complex and costly than for an upflow, countercurrent
column. Unless one is attempting to use the carbon for
the dual purpose for filtration and adsorption (which the
author does not recommend for most cases), there is no
advantage to using the downflow approach while there
are the disadvantages discussed above. The Technology
Transfer Manual, "Process Manual for Carbon Adsorp-
tion" (second edition, dated October, 1973) contains
several illustrative contactor designs.
The choice of contactor design is also dependent upon
the method selected for control of hydrogen sulfide
generation in the carbon columns. The hydrogen sulfide
is produced by sulfide-reducing bacteria under anaerobic
conditions. Conditions promoting or accelerating the
production of hydrogen sulfide in carbon contactors
include:
• Low concentrations or absence of dissolved oxygen
and nitrate in the carbon contactor influent.
• High concentrations of BOD and sulfates.
• Long detention times.
• Low flow-through velocities.
TO CARBON
RECLAfMfi'ir'
PIPING DlftG'tAM
FIRST
- FLOW A TO B,
RENEW CARSON IN A
THEN,
FLOWB TO A,
RENEW CARBON IN B
THEN,
FLOW A TO B AND
— CYCLE IS COMPLETE
TWO DOWNFLOW CARBON CONTACTORS IN SERIES
(FHOM CUI P & (Ul I1]
68
-------
It may be possible to prevent or correct problems of
hydrogen sulfide generation by eliminating one or more
of the conditions necessary to sustain growth of the
sulfate-reducing bacteria. Most of the preventive
measures must be provided in the design of the carbon
contacting system, but there are also some corrective
measures which can be taken in plant operation. The
amount of actual plant operation experience in this
regard is limited. To provide flexibility for dealing with
problems of hydrogen sulfide production in packed beds
of carbon, facilities for application of chlorine to the
influent should be provided. In addition, in upflow
expanded beds it may be desirable to provide for
introduction of air, oxygen or sodium nitrate (as a
source of oxygen). Because of the mass of cell growth
produced, it may be less desirable to introduce air or
oxygen ahead of packed beds because of potential
physical plugging of the beds. These growths are flushed
through expanded upflow beds, but may be removed in
sections of the plant which follow such as filters or
claiifiers.
Some measures available in the operation of carbon
facilities for control of hydrogen sulfide are:
• Columns may be backwashed at more frequent
intervals or backwashed more violently by use of air
scour or surface wash.
• Detention time may be reduced by taking some
carbon contactor units off the line, provided that the
reduced carbon contact time is still sufficient to
obtain the desired removal of organics and that head
losses in the carbon columns remaining on the line do
not become excessive.
• Chlorination or oxygen addition may be initiated.
In operations at the PCT pilot research facility at
Pomona, California where the carbon influent consisted
of chemically clarified raw wastewater, it was found
that:
• Continuous chlorination of the carbon column influ-
ent at dosages up to 50 mg/1 reduced significantly
but did not stop I^S production.
• Intermittent backwash, surface wash and oxygen
addition reduced but did not completely eliminate
H2S.
• Intermittent backwash, surface wash and continuous
oxygen addition to DO = 4 mg/1 reduced sulfide
formation but stimulated biological growth and head
loss in the carbon bed.
• The addition of air wash to normal backwash and
surface wash was not effective against H2S and 7
inches of carbon was lost from the bed.
• The continuous addition of sodium nitrate to the
carbon column influent at the rate of 4 to 5 mg/1 as
N03—N completely inhibited H2S generation in the
column.
At the Cleveland Westerly pilot plant, all efforts to
eliminate sufide odors in carbon columns following PCT
were found to be impractical. However, the BOD of the
carbon column influent at this plant ranged from 80 to
100 mg/1 as opposed to around 40 mg/1 at Pomona.
The control methods used were: (1) daily backwashing
at 10 gpm/sq. foot plus surface wash at 2 gpm/sq. foot
for 28 minutes, (2) continuous addition of NaN03 to
the influent, and (3) backwashing with water containing
27 mg/1 of chlorine (from NaOCI). At dosages of 100
mg/1 of NaNOg (expressed as NO^) sulfide production
was climated but this high dosage was not considered
economically practical.
Sulfides in the carbon column effluent can be removed
by precipitation with iron or by addition of chlorine.
However, at this time the most effective means of coping
with the H2S problem appears to be to maintain aerobic
conditions in the carbon contactors rather than trying
to remove H2S after it is formed. If the BOD applied to
the carbon is less than 5 mg/1 as is the case in most
tertiary treatment schemes, the H2S problem is easily
controlled. For applied BOD values substantially higher
than this, it appears that use of upflow, aerobic
expanded contactors followed by sedimentation or
filtration is preferable.
Also, breakpoint chlorination, prior to downflow beds,
although expensive, has been reported effective at Blue
Plains in controlling hydrogen sulfide. Since most of the
nitrogen can be expected to be on the ammonia form in
PCT applications, efficient nitrogen removal could also
be achieved with this approach. Higher operating
pressures and hence, greater carbon depths may be used
in steel pressure contactors. As a result, a concrete
contactor generally has a shallower carbon depth and a
greater surface area of carbon to maintain the same
contact time. Thus, there is substantially more
underdrain area and influent and effluent headers per
unit of contact time in the gravity concrete structures.
Economic comparisons between the two approaches
show that there is not a great deal of cost difference in
most cases. When using steel contactors, it is imperative
that the interior be properly protected from the very
corrosive effects of partially dewatered activated carbon.
Two 8-mil thick coatings of a coal tar epoxy has proven
to be effective at Tahoe over 4 years of continuous
operation. Fiberglass-polyester coatings would also be
effective although more costly than the coal-tar epoxy
coatings. Costs for shop-applied coatings will vary from
about $0.50/ft2 to $2.00/ft2 depending upon the
material and thickness selected. Costs for field applied
coatings will be about twice as high. Also, in most cases,
the costs for fabricating steel vessels in the field will be
substantially higher per pound of steel than for a shop
fabricated vessel.
69
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Carbon Regeneration
As granular activated carbon adsorbs organics from
wastewater, the carbon pores eventually become
saturated and the carbon must be regenerated for reuse.
The best way to restore the adsorptive capacity of the
carbon is by means of thermal regeneration. By heating
the carbon in a low-oxygen steam atmosphere in a
multiple-hearth furnace at temperatures of 1,650-1,750
degrees F, the dissolved organics are volatized and
released in gaseous form. The regenerated carbon is
cooled by water quenching. By proper treatment, carbon
can be restored to near virgin adsorptive capacity while
limiting burning and attrition losses to 5-10 percent.
Regeneration furnace off-gas odors can be controlled by
afterburning, if necessary, and particulates and soluble
gases can be removed by use of Venturi or jet
impingement type scrubbers. Figure 7 illustrates a
typical regeneration system.
The carbon furnace should be sized with recognition of
the fact that substantial downtime may be required for
maintenance of the furnace. An allowance of 40 percent
downtime in selecting the furnace size provides a
conservative basis for furnace selection. Details on the
design and operation of carbon regeneration systems
may be found in Advanced Wastewater Treatment and in
the EPA Technology Transfer Manual, "Process Design
Manual for Carbon Adsorption" (second edition,
October, 1973).
MAKEUP
CARBON
CARBON
SLURRY BIN
t— p
'*
\
Jk- —
*
T
==» SPENT CARBON DRAIN
AND FEED TANKS
. SCREW
/ CONVEYORS
X A
a
i r
i
SPENT CARBON FROM
'CARBON COLUMNS
CARBON
REGENERATION
FURNACE
CARBON
SLURRY
PUMPS
QUENCH
REGENERATED CARBON
DE-FINING AND
STORAGE TANKS
. REGENERATED CARBON
TO CARBON COLUMNS
FIGURE 7
ILLUSTRATIVE CARBON REGENERATION SYSTEM
(FROM CUI P 6 CULP)
70
-------
ALTERNATE SYSTEMS
Several alternate approaches now being used or
investigated for use in various parts of the country are
summarized in Figure 8 and some specific cases are
described below. The exact effluent quality by each
process will depend on the specific influent quality
involved; however, the effluent quality achieved in each
previous study indicates the general capabilities of each
process.
Rocky River, Ohio Study
Rizzo and Schade studied a physical-chemical system for
application at Rocky River, Ohio in a 10 mgd plant now
TABLE 4
under construction. The raw sewage was coagulated with
an anionic polymer (about 0.3 mg/1) settled, and then
applied to granular carbon columns essentially using the
schematic shown in Figure 8-C. The downflow carbon
columns serve the dual purpose of adsorption and
filtration. In order to provide the phosphorus removal,
an inorganic coagulant must be used in conjunction with
the polymer. The full-scale plant at Rocky River will use
ferric chloride in addition to the polymer to provide
phosphorus removal.
Rocky River pilot tests with four small carbon columns
in series were performed over a 31-day period. The
following table summarizes the results.
CARBON CONTACT
TIME, MINUTES
CLARIFIER
RAW EFFLUENT
14.0 23.4 32.6
Suspended Solids, mg/1
BOD, mg/1
COD, mg/1
107
118
235
65
57
177
13
21
67
15
11
50
44
COAGULANT
PRELIMINARY
/»
CLARIFICATION
fXPANDED
CARSON
ADSORPTION
FILTRATION
DISINFECTION
CARSON I
REGENERATION I
^COAGULANT
PRELIMINARY
TREATMENT
!,
CHEMICAL
CLARIFICATION
CARBON
ADSORPTION
DISINFECTION
CAR3
HtGENER
DN
ATION
FIGURES
TYPICAL PHYSICAL-CHEMICAL TREATMENT SCHEMES -
71
-------
Ewing-Lawrence Studies
Weber, et al, have reported on studies conducted at the
Ewing-Lawrence Sewerage Authority plant near Tren-
ton, New Jersey. The raw sewage was coagulated,
settled, filtered and passed upward through an expanded
carbon bed (Figure 8-b). Filtration was also evaluated
following the carbon treatment. The degritted raw
sewage was coagulated with an inorganic coagulant and
then pasted through a sedimentation basin at a rate of
about 700 gpd/sf. Weber found that there was no
significant difference in the adsorption efficiency of a
downflow, packed carbon bed and an expanded upflow
bed. The expanded beds offered the advantage of not
requiring backwash for removal of biological solids. The
wastewater used in these studies was very weak as
reflected by the primary effluent BOD of 40 to 60 mg/1,
with a clarified effluent BOD of only 10 to 20 mg/1
being applied to the carbon. The initial value of soluble
BOD is much lower than usually found in municipal
wastes. The soluble BOD applied to the carbon
stimulated biological growth within the carbon columns.
The biological activity is enhanced by the overall
capacity for removal of organics by oxidizing a portion
of the adsorbed organics. However, the benefit was
accompanied by a problem of generation of hydrogen
sulfide under the anaerobic conditions encountered in
the columns. Addition of hypochlorite to the carbon
influent was moderately effective in reducing the
hydrogen sulfide odor. Aeration of the carbon influent
partially reduced the odor but produced enough
biological floe to plug the packed bed adsorbers. The
approach finally used was to bleed oxygen into the
influent of an expanded, upflow bed whenever there was
evidence of hydrogen sulfide in the product water. The
5-day BOD of the carbon effluent averaged 2 to 3 mg/1.
Z-M Process
The basic flowsheet for this process consists of lime
coagulation at high pH (11), settling, recarbonation,
filtration and granular carbon adsorption. The basic
flowsheet of the type shown in Figure 8-a with the
requirement of high pH being an integral part of the
approach. The process developers claim that the
adsorption of the organics found in raw sewage may be
improved with the addition of lime to raise the raw
sewage pH to a very high value. They feel that this
causes hydrolysis of high-molecular-weight organic
molecules with resulting lower weight organics being
more readily adsorbed. Effluent COD values of 2 mg/1
have been claimed. The pH required to achieve the
claimed hydrolysis reaction varies from wastewater to
wastewater but is generally in the range of 11.8 and
higher.
Biological growths occurred in the carbon columns in
laboratory and pilot tests. Carbon contact time was 67
minutes in the pilot plant. The resulting potential
problem was controlled by backwashing the carbon
columns whenever the D.O. dropped more than 0.5
mg/1 during the passage through the column. With
stronger wastewaters, more typical of municipal wastes,
backwashing of the columns based on that D.O. would
be impractical. In addition to backwashing on the basis
of D.O. decrease, the last portion of the backwash water
was chlorinated to minimize biological growth.
During the "best monthly period" of the pilot plant
operation, the carbon influent COD of 65 mg/1 was
reduced to 2 to 14 mg/1 (average of 8.6 mg/1). During a
"stable period" of three weeks, the effluent COD
averaged 11 mg/1. The COD of 65 mg/1 applied to the
carbon is lower than will be the case for many
coagulated and settled raw municipal wastes.
For the Z-M process, large quantities of lime are required
to raise the pH to the desired range. Lime requirements
of 600 to 800 mg/1 are not unusual. This results in
larger quantities of sludge to be handled when compared
to the required coagulant dose for good coagulation and
phosphorus removal only. Also, the quantities of C02
required for pH adjustment are increased. Weber
reported on tests in which no benefit resulted from use
of the high pH proposed in the Z-M process. Similarly,
on-site pilot tests at Cleveland, Ohio which are described
below, did not show any benefit from use of a high pH
prior to carbon adsorption. Thus, extensive tests should
be conducted on any given wastewater to determine if
any benefits occurring by raising the pH to these high
values offset the additional costs.
Cleveland, Ohio Study
Laboratory investigations and pilot plant studies of
physical-chemical treatment of raw sewage at the
Westerly plan in Cleveland, Ohio were conducted from
July 1970 to April 1971. The study goal was to develop
design criteria for a 50 mgd plant now under
construction. The basic processes used were coagulation,
settling, filtration and granular carbon adsorption(Figure
8-a).
The raw sewage BOD averaged 235 mg/1 and the COD
523 mg/1 during the pilot study. The BOD applied to
the carbon averaged about 90 mg/1 and the COD 150
mg/1.
BOD and COD removals averaged 86.5 percent and 92.4
percent, respectively, which correspond to an average
effluent BOD of 31 mg/1 and COD of 40 mg/1. Severe
problems with generation of hydrogen sulfide in the
carbon columns also occurred, and no satisfactory
solution was developed during the pilot study.
72
-------
Blue Plains Study
FULL SCALE APPLICATIONS
Physical-chemical treatment of raw wastewater was
among the alternates studied by the EPA in their
Washington, D.C. pilot plant. The process consisted of
lime coagulation, sedimentation, filtration and granular
carbon adsorption (Figure 8-a). The raw sewage had an
average BOD of 129 mg/1 and a COD of 307 mg/1. Raw
sewage was lime coagulated in the pH range of 11.3 to
11.7. About 80 percent BOD removal was achieved by
lime coagulation only. Thus, the BOD applied to the
carbon was 20-30 mg/1.
Average carbon contact time was 27 minutes in four
series columns of downflow, packed bed configuration.
Hydrogen sulfide problems could not be controlled by
daily backwashing of the lead column. A caustic
backwash (600 mg/1 NaOH for 30 minutes) of the lead
column every other day reduced the biological activity
somewhat but F^S persisted at the 2.5 mg/1 level.
During early tests, the COD was reduced from 41 to 8
mg/1 but later reductions were substantially less, with an
effluent COD of 20 mg/1. At a carbon loading of 0.46
pounds per COD per pound of carbon, the carbon from
the first two columns was replaced.
Physical-chemical treatment of raw wastewater at Blue
Plains (consisting of 2-stage lime precipitation, filtration
and carbon adsorption) produced the following average
effluent quality over a 10 month period: BOD of 6.2
mg/1 (95% removal), COD of 15.5 mg/1 (95 percent
removal), and 0.13 mg/1 total phosphorus (99 percent
removal). The f^S problem was controlled and
ammonia removed by breakpoint chlorination ahead of
the carbon. Backwashing of the lead column everyday
coupled with feeding of 15 mg/1 oxygen to the lead
column and lesser amounts to each downstream column
also controlled the F^S problem.
Table 6 summarizes the status of several major projects
utilizing physical-chemical treatment of raw waste-
waters. The effluent data in Tables 5 and 6 and the
author's experience in the evaluation of many
wastewaters in the laboratory indicate that the PCT
approach is best suited for cases where the effluent BOD
requirements are in the 7-20 mg/1 range. Most raw
wastewaters contain enough non-adsorbable BOD to
prevent consistent achievement of BOD values of 1-7
mg/1 unless biological treatment precedes carbon
adsorption. However, as indicated in Table 6, there are
many instances where regulatory requirements fall in the
range which can be met by PCT.
SUMMARY
Physical-chemical treatment of raw wastewaters offers
performance advantages over biological treatment, in
that somewhat higher removals of BOD are generally
provided while substantially higher removals of sus-
pended solids and phosphorus are provided. The process
is not adversely affected by toxic materials. Substantial
savings in space are achieved with physical-chemical
treatment. Under some conditions, it may also offer
economic advantages.
Not all organics found in municipal wastewaters are
adsorbable on carbon. Thus, the limitation on BOD and
COD removal will depend on the quantities of these
non-adsorbable materials present in a given wastewater.
Generally, 90-95 percent BOD and COD removal can be
achieved. Techniques are presented which enable the
design engineer to evaluate the quantity of nonadsorb-
able organics present in a given wastewater. Techniques
for evaluation of alternate coagulants and the handling
of the resulting sludge are also presented.
TABLE 5
SUMMARY OF EFFICIENCY OF PHYSICAL-CHEMICAL
TREATMENT OF RAW WASTEWATERS
INFLUENT* EFFLUENT*
CHARACTERISTICS CHARACTERISTICS
TEST SITE
BOD COD SS
BOD COD SS
Rocky River, Ohio
Eqing—Lawrence, New Jersey
Z-M Pilot Plant at New Rochelle, N.Y.
Cleveland, Ohio
Blue Plains, D.C.
118
100
-
235
235
—
220
523
107
_
—
207
—
10
7.6
5.4
8
2-3
_
24
44
_
2-14
50
129 307 -
13
3.4 6.2 15.5 -
1
0.2
0.5
0.13
73
-------
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Design considerations for the unit processes of
coagulation, settling, filtration, carbon adsorption,
carbon regeneration and sludge handling are discussed.
Design and operational considerations for the control of
hydrogen sulfide generations within carbon contactors
are also discussed.
Experiences gained at several locales in pilot tests are
presented as well as a tabulation of the design criteria
being employed in several full-scale installations.
REFERENCES
1. Gulp, G.L., "Chemical Treatment of Raw Sewage," Water
and Wastes Engineering, p.61 (July 1967) and p.54 (October
1967).
2. Pearse, et al, "Chemical Treatment of Sewage," Sewage
Works Journal, p. 997 (1935).
3. Culp, R.L. and Culp, G.L., Advanced Wastewater Treat-
ment. Van Nostrand Reinhold, New York (1971).
4. Rizzo, J.L. and Schade, R.E., "Secondary Treatment with
Granular Activated Carbon," Water and Sewage Works, p.
307 (August 1969).
5. Anonymous, "Carbon Makes Debut in Secondary Treat-
ment, " Environmental Science and Technology, p. 809
(1969).
6. Kugelman, I.J. and Cohen, J.M., "Chemical-Physical Proc-
esses,., presented at the Advanced Waste Treatment and
Water Reuse Symposium, Cleveland, Ohio (March 1971).
7. Weber, W., Hopkins, C.B., and Bloom, R., "Physiochemical
Treatment of Wastewater, " Journal Water Pollution Control
Federation, p. 83 (1970).
8. Zuckerman, M. and Molof, A.H., "High Quality Reuse Water
by Chemical-Physical Wastewater Treatment (Discussion by
W. Weber)," Journal Water Pollution Control Federation, p.
437 (1970).
9. Molof, A.H. and Zuckerman, M., "High Quality Reuse Water
from a Newly Developed Chemical-Physical Treatment
Process," presented at the Fifth International Water Pollu-
tion Research Conference, San Francisco, California (July
1970).
10. Shuckrow, A.J., Bonner, W.F., Prescan, N.L., and Kaz-
mierczak, E.J., A Pilot Study of Physical-Chemical Treat-
ment of the Raw Wastewater at the Westerly Plant in
Cleveland, Ohio (unpublished, 1971).
11. Bishop, D.F., et al, "Advanced Waste Treatment at the EPA
District of Columbia Pilot Plant." Paper presented at the
68th National Meeting of the AICHE, Houston, Texas
(March 1971).
12. "Chemical-Physical Wastewater Treatment - Phase 2, Acti-
vated Carbon Adsorption and Polishing," Technical Paper
No. 17, New York State Department of Environmental
Conservation (January 1972).
13. "Miniature Treatment Plant Operates m Housing Com-
munity," p. 102, Water and Sewage Works, (May 1973).
14. "Town's (Garland, Texas) Sewage Treatment Plant Will Use
Ultra-High-Rate Filtration," Engineering News Record, p.
21 (February 22, 1973).
15. "Process Manual for Carbon Adsorption," Office of Tech-
nology Transfer, U.S. Environmental Protection Agency,
second edition (October 1973).
75
-------
SYNTHESIS OF CATIONIC POLYELECTROLYTES
FOR TREATMENT OF NATURAL AND WASTE WATERS.
Korshak V.V., Zubakova L.B.,
Gandurina L.B.
Mendeleev D.I. Moscow Chemistry
Technological Institute
VNIIVODGEO
Nowdays reagent treatment of waste waters with the
use of highly-molecular organic material-flocculants is
one of the most popular methods in practice of natural
and waste waters treatment.
Flocculants used together with mineral coagulant or
alone afford intensification of water treatment pro-
cesses, improving its quality, reducing of mineral
reagents doses and quantity of formed slime correspond-
ingly, improving of filtering and mechanical character-
istics of sludge.
The charge of colloidal particles and flocculant
macromolecules is of great significance for adsorption
and flocculation.
Coagulation process is facilitated at the expense of
electrostatic attraction of contrary charged particles in
case if charge of colloidal particles and macromolecules
of polymers is different by its sign. The best way to treat
natural and waste waters is to use polyelectrolytes with
highlybasic ionogenous groups, since the most waste
waters pollutants have negative charge.
In connection with this the problem of new cationic
polyelectrolytes synthesis and investigation of their
physical-chemical properties is of great practical interest.
Besides it must be noted that there is extremely a
small number of polymers having high efficiency in
processes of water and waste treatment of industrial
effluent.
Existing methods of cationic polyelectrolytes synthe-
sis may be directed into two main groups:
- polymersimilar transformation of polymerization
and poly condensation linear polymers,
- polymerization of nonlimitive ionogenous mono-
mers.
In the first case cationic polyelectrolytes are received
as the result of polymers chemical transformations
non-containing ionogenous groups (polystyrene, poly-
vinyl toluene) or containing lowbasic ionogenous groups
(poly vinylpiridine, polyvinylhynoline).
Nonionogenous polymers are chloreme thy late d and
amminated by various tertiary amines: triethylamine,
triethanolamine etc. For the purpose of receiving highly
basic polyelectrolites at the base of polymers containing
lowbasic functional groups, they are treated with
different alkylating agents (halogen alkyls, dialkylsul-
phates etc.).
However given methods of cationic polyelectrolytes
synthesis are distinguished by their multistage character,
complicating technological scheme of receiving them, by
existence of accessory reactions leading to structure
formation of polymers and creation of unregular in
content polymers. Besides received cationic polyelec-
trolites, are characterised by comparatively low values of
molecular weights.
Therefore one stage process of ionogenous unsatu-
rated monomers polymerization is more perspective as
far as it affords receiving highly molecular anionites with
maximum ionogenous groups content.
The initial material used for the synthesis of highly
basic water-soluble polyelectrolytes were quaternary
vinylpyridine salts (QVPS) on vinylpyridine and various
alkylating agents base that conditioned by extremely
high reactivity of these salts and also availability of
source of raw materials.
Monomeric vinylpyridine salts easily enter into
polymerization due to high polarization of double
connection when positive charge on nitrogen atom. As
the double connections are more polarizated in the
ortho-and para-positions it is not possible in most cases
to receive unlimited quaternary salts on the base of 2
and 4 vinylpyridines because the polymeric products are
immediately released in this case.
At the same time as a result of reaction of 2-methyl
and 5-vinylpyridines (2M5V) and various alkylating
agents the stable quaternary vinylpyridine salts (Q VPS)
are formed due to the less activity of the double
connection.
It was established that the releasing of poly-I-alkyl-2
methyl -5 - vinylpyridine halides (2 MSV - RX) and poly
- 1.2 demethyl - 5 - vinylpyridine - n - toluene
sulphonates (2 MSV - METSA) is determined by the
conditions of carrying out of the reaction: medium
polarity, temperature, duration and so on.
A great effect has the nature of alkylating agents
(table No I).
Table I
Releasing (weight in p.c.) of QWS depending on the
nature of halide alkyl and radical length.
R CH3 C2H5 C3H7 C4H9
J
Br
Cl
80
78
15
65
60
40
5.0
15.0
60
42
76
-------
Vinylpyridine salts polymerization was performed by
three methods:
- Spontanous QVPS polymerization in concentrated
water solutions by specific ion mechanism;
- radical QVPS polymerization in water ethanol
solutions;
- radical QVPS polymerization without their inter-
mediate isolation.
QVPS polymerization by three methods affords not
only exposing the influence of synthesis method choice
on yield and properties of received polyelectrolytes
(molecular weight, ionogenous groups concentration
etc.), but also comparing efficiency of different
synthesis methods for the purpose of receiving
polyelectrolytes suitable for natural and waste waters
treatment.
Till now general attention of researches was directed
at studying of spontanous polymerization of quarternary
vinylpyridine salts.
Kabanov discovered that the reaction is going by
specific anion mechanism after detailed kinetic investiga-
tions of non-limitive quarternary salts at the base of
vinylpyridine with dimethylsulphate spontanous poly-
merization reaction. In result quarternary polymer salts
of highly molecular weight are formed and it's significant
at their use as flocculants for natural and waste waters
treatment.
The fact that reaction is performed without initiators
at low lemperatures (25-30°C) is highly significant.
Investigations showed that there was rapid fall of
polymerization speed at reducing of monomeric salt
concentration in solution.
It should be noted that at QVPS concentration I
mole/1 and lower the reaction doesn't proceed.
TABLE 2
Analogical dependence has place for molecular
weights of received polymers (drw.I).
The nature of antiions has great influence on
spontanous polymerization QVPS speed.
If at 2M5V-METSA salt polymerization for 4 hours
yield is 17% of theoretical, at 2M5V-CH3B salt
polymerization yield is 52%; and that is highly probable
that it's the result of different nucleophility and
mobility of anions, initiating spontanous polymerization
reaction.
Total duration of spontanous polymerization reaction
in concentrated water solution is floatuating from 24 to
48 hours. Depending on the character of polymerized
monomer salt (table 2).
The second method of cationic polyelectrolytes
synthesis radical polymerization of QVPS, is
distinguished by high productivity (table 2).
It is seen at given data that reaction duration in this
case is 6-10 hours.
However, molecular weights characteristic viscosities
of synthesized polysalts are significantly lower than
those values for polyelectrolites, received by spontanous
polymerization. Characteristic peculiarity of quarternary
vinylpyridine salts radical polymerization is the
influence of media in which the reaction is performed
(3). First of all it's conditioned by existence of
ionogenous groups and the strength of inter-ionous and
inter-molecular interactions of reacting particles and
activity of reaction centres depend on the degree of
these groups dissotiation.
The speed of I - ethyl - 2 - methyl - 5 - vinylpyridine
bromide in water-spirit solutions. - increases
approximately 4 times at transfer to less ionizing solvent
(absolute standard) comparing with the same value in
Dependence of reaction duration and
poly vinylpyridine salts viscosity.
Characteristics on the way of receiving them.
Salt
descrip-
tion
Synthesis method
Reaction Polymer
duration yield
hr %
Polymer
hund. ml/g
2M5V—
Spontanous polymeri-
zation. 24 95 8.7
Radical polymerization 10 93 0.7
Without isolation of
monomer salt. 12 93 0.3
Spontanous polymeri-
zation. 48 91 3.9
Radical polymerization 8 98 0.6
Without isolation of
monomer salt 12 97 0.24
x) Characteristic viscosity — 0.05 normal solution KBr.
2M5V—
77
-------
highly polar solvent (water).
QVPS radical polymerization speed depends on
monomer salt nature.
So radical length increase at QVPS nitrogen atom
from CH3 to €3^ lead to reducing reaction rate
approximately three times.
Table 3 Values of initial rates and total constants
of QVPS polymerization in 50% water ethanol
solution.
Initiator - asodiisobutyronitrile.
Monomer Temperature VQ10 4mole/sec K-102
2M5V-CH3J
2M5V-C2H5J
2M5V-CH3Br
2M5V-C2H5Br
2M5V-C3H7Br
70
70
75
75
75
75
2.14
2.96
1.50
0.99
0.57
9.84
5.56
7.70
3.90
2.57
1.49
Comparing of iodine and bromine salts
polymerization rates constants shows that bromine salts
are polymerized slower than iodine salts (table 3). In all
probability the difference of kinetic characteristic of
these salts is connected with different degree of
monomers molecules ionization and growing
macroradicals (3).
Water soluble highly basic polyelectrolytes can be
received not only by methods of spontanous and radical
polymerization of non-limiting QVPS, but also by
radical polymerization of the latter ones, withouf'their
intermediate isolation.
This one stage method of cationic polyelectrolites
synthesis is of interest by two reasons:
Firstly using this method of receiving cationic
polyelectrolytes monomer vinylpyridine salts isolation is
not required that simplifies the process significantly.
Secondly, this method of polyelectrolytes synthesis is
unchangeable in cases when monomer salts are received
with low yields or can't be isolated from reaction sphere.
For example, monomer salts at the base, of 4 -
vinylpyridine and different haloid alkyls couldn't be
isolated and therefore the last method is the only
possible of all above mentioned ways for receiving
cationic polyelectrolytes.
Therefore it should be concluded that all three
methods may be used.
The choice of method is defined by definite area and
synthesized polymers application conditions.
Properties and application of cationic
polyelectrolytes at the base of 2-methyl-
-3-vinylpyridine.
For preliminary appreciation of cationic polyelectro-
lytes application possibilities as flocculants investigation
of their behaviour in water solutions is significant. In
particular, investigation of viscous and electrochemical
properties of polyelectrolytes solutions reveal the struc-
ture condition of polymer macromolecules in solution,
its ionogenous abilities, associations of antiions and
polyions.
As the result of these investigations it was established
that for water solutions of polymer quarternary salts at
vinylpyridines base non-linear increase of the viscosity
with dilution usual for polyelectrolites is observed.
However for polyelectrolites of highly molecular weight
received by spontanous polymerization of quarternary
vinylpyridine salts viscosity isotherms pass througn"
minimum at definite concentration (Cg) of
polyelectrolytes in solution, (drw. 2). At CQ concentra-
-io is
20 J~5~*To
51.
Itoaoner cooc8Htratioa,mole/L
Relationship between initial Bpeed of salt
polymerization 2ICY - CgH^Br and molecular
of resulting polyaeridea and initial concentration
of Bononer. Temperature - 25*0.
} - h.O; '1- - 8.J !
78
-------
tion the increase of the viscosity is observed, which is
explained by aggregation of macromolecules at the
expence of intermolecular interactions.
Studying of electroconductivity of polymer and
monomer vinylpyridine salts shows their significant
difference.
Firstly, equivalent electroconductivity of polymer
salts is lower than manomers (table 4). Secondly,
isotherms of electroconductivity for polymers have
curvilinear concave character.
Table 4
Equivalent electroconductivity of water
solutions of QVPS and polyelectrolites
at their base at concentration 0.015
mole/1.
Description . Equivalent electrical
polyelectro-
lite
HPS-I
HPS-6
HPS-7
HPS-8
HPS-10
HPS-1 1
i
Monomeric —
salt 1
2M5V-METSA
2M5V-CH3J
2M5V-C2H5J
2M5V-C3H?J
2M5V-CH3Br
2M5V-C2H5Br
conduction
i
monomer |
49
88.5
83.5
80.5
92.0
85.0
polymer
hund.
ml/g
16 2.0
17.9 1.0
15.2 1.2
12.85 0.9
30.6 3.2
36.5 4.0
These features of electrochemical properties of solu-
tions are conditioned by series of specific characteristics
distinctive only for polyelectrolytes (counterion connec-
tion, association of ions). Values of seeming constant
ionization calculated with the help of Kachalcky-Spitnik
equation have extremely high values with the range 3.9-
4.85 indicative of presence of counterion association in
polyelectrolytes water solutions.
Investigations associated with the treatment of natu-
ral and waste water with utilization of synthesized
polyelectrolytes showed their high efficiency.
So the investigation of flocculating capability of
polimeric halogen containing vinylpyridine salts for
removing of humus substances from natural water was
carried out together with Voronezh State University of
Lenin's Komsomol.
The investigations were carried out with water solu-
tions of humic acid and fulvic acid with 2-10 mg/L
concentration. The concentration of ionogenous groups
of fulvic acids was 5.57 mg.equiv/g. The content of
carboxylic groups and the summery concentration of
carboxylic and fenolic groups of humic acids are turned
out to be 1.41 mg.equiv/g and 3.52 mg.equiv/g. HPS-6,
HPS-7; HPS-II were used in salt and OH-form as the
flocculants. The conversion into the OH-form is accom-
panied by yield of weakly basic groups in polyelectro-
lytes.
It is determined by isomerization of hydroxide alkyl
vinylpyridine formed when changing the gallogen-ions to
OH-groups; as a result the methylene bases containing
tertiary amino groups are formed.
Exchange volume of polyelectrolite found according
to the highly basic groups and the summary of highly
and weakly basic groups is given in Table 5.
The flocculants volume determined on the basis of
data of potentiometric titration.
Table 5
The flocculants volume determined on the basis of
data of potentiometric titration.
Flocculant
description
Volume mg. eqiv./g
ace. to highly basic
groups
ace; to summary of
highly and weakly
basic groups
E2
HPS-6
HPS-7
HPS-H
2.41
3.45
3.45
4.27
4.32
5.50
The presence of acid groups in humus substances and
general functional groups in flocculants permit to
suppose that the yield of humic acid and fulvic acid is
occured at the expense of chemical interaction of these
groups. In this case the polymer consumption should be
calculated according to the formula:
•C
G - polyelectrolite dose, mg/L
C - concentration of humic and fulvic acids in the water,
mg
Ep ; EPA ; EHA - exchange volumes of the flocculant;
fulvic acid and humic acid, mg. equiv./g.
However, the designed doses for polyelectrolites in
OH — form extremely exceed the experimentally -found
doses of flocculants. (table 6).
It points to the fact that the flocculation process is
determined not only by the volume of humus substances
and polybasic but the size of molecule of these
compounds.
79
-------
Table 6
Designed and experimentally-definite doses of flocculants.
Designed doses of flocculants
Flocculant
description
mg/mg
i
EIHA l
HPS-6 0
HPS-7 0
HPS-II 0
I
59
41
42
EIF
i
E2HA|
1
1.46
1.02
1.06
[
EFA i
1
2.30
1.62
1.70
1
EIHA i
i
0.31
0.32
0.25
E
0
0
E2F
1
2HA ,
1
82
81
0.64
1
1
1
EFA 1
l
1.30
1.25
1.1
Experimental
doses
m
of acids
g/mg
1
humic 1
acid
0.8-0
0.9-1
0.6-1
1
i
9
0
2
fulvic
acid
0.6-0.7
0.6-0.7
0.6-0.7
As it was established the cationic polyelectrolites on
the basis of vinylpyridines may be used successfully for
industry waste water treatment. But highly molecular
polyvinylpyridine salts obtained with the help of sponta-
neous polymeryzation of QVPS are the most efficient
flocculants.
So the utilization of HPS-II flocculant with 700000
molecular weight permit the treatment of waste water
containing acid dyes, petroleum products, dissolved and
emulsificated organic substances for 95-100%. The re-
sults of using of synthesized polyelectrolytes for indus-
trial wastes treatment are given in the report "Investi-
gation of the waste water treatment with flocculant
utilization" made by I.N. Myasnikov; L.V. Gandurina;
and L.N. Butseva.
LITERATURE
1. V.A. Kabanov, T.I. Patrikeeva; V.A. Kargin; The report of
USSR Academy of Sciences, 168, 6, 1350 (1966)
2. V.A. Kabanov, O.V. Kargin; V.A. Petrovakaya. Highly
molecular compounds, 13, 1, 348 (1971)
3. V.R. Georgieva; V.P. Zubov; V.A. Kabanov. The Report of
USSR Academy of Sciences, 190, 5, 1128(1970)
80
-------
Physical - Chemical Treatment of Wastewaters from the petroleum Refininj - Petrochemical Industry*
by
William J. Lacy and Allen Cywin**
Introduction
Let us define wastes, for the moment, as misplaced
resources of human industry. I say momentarily because
all wastes have use in some time frame and in some
ecosystem. The time frame is impacted by technology
and need, time, need, place, and technology then, all
determine the scope of industrial wastes problems.
Yesterday's moldy bread is today's penicillin. Last
month's paper mill wastes could be tomorrow's road
binding materials, cooking sauces, medicinals, or acti-
vated carbon. Pollutants may, therefore, be considered
as the wrong substances in the wrong places at the wrong
time.
Industrial wastes are principal point sources of
controllable waterborne wastes. In terms of the generally
quoted measurements of BOD5 for strength and volume,
the gross wastes of manufacturing establishments are
about three times greater than those of the U.S. sewered
population. Moreover, the rate of U.S. industrial produc-
tion, which gives rise to industrial wastes, is increasing at
about 4.5 percent per year or over four times faster than
the population growth rate. Add to this the extensive
variations of composition of industrial wastes, and one
realizes that the solution to industrial water pollution is
of paramount importance in the environmental protec-
tion effort.
Some large refining and petrochemical plants in the
United States treat their wastes economically. However,
the use of the same technology may not be economical
for the treatment of wastes produced in similar but
smaller plants.
At present, some 34 refineries discharge their wastes
to the community sewer system and depend upon the
municipal sewage plant for the treatment. However,
most refineries do not have sewer systems readily
available and thus must provide their own treatment
facilities. It thus becomes important that more econom-
ical methods for the treatment of control of wastes be
developed by industry. Ideally, a process for treating
wastes from an industry should:
1. Effect the removal of the pollutant at minimum
cost.
* Presentation of the Joint US-USSR meeting on P-C treat-
ment, Cincinnati, Ohio November 1975.
** Respectively, Principal Engineering Science Advisor, Office
of Research and Development and Director Effluent Guidelines
Development Division Office, EPA, Washington, D.C. 20460
2. Provide for the economical recovery of any
valuable by- or co-products.
3. Comprise a technique that would permit the
recycling of recovered materials, including water, back
to the production operation.
4. Be simple and require minimum operating labor.
5. Require relatively low capital investment.
Reduction of industrial waste discharges is often
accomplished efficiently and economically by process
modivications, improved housekeeping, and reuse-
recycle water management practices. During the period
1954-1968, total water use by all U.S. industries
increased 70 percent, but water intake only increased 34
percent. All U.S. industries achieved a reuse ratio 2.30 in
1968. The plants with the 20 best recycling rates in
1970 have very high recycling rates because of low raw
water dissolved solids, low ambient air temperatures, and
use of high temperature cooling, all of which permit
higher recycle ratio (2). By contrast, the Organic
Chemicals Industry (which includes the petrochemical
industry and is categorized herein by SIC 2815: Cyclic
Organic Chemicals) had a reuse ratio of 1.90 in 1968, a
net decrease of 4 percent over that of 1964 census.
Although the total water usage increased only 20
percent, water intake increased 25 percent, indicating an
ineffective utilization by this industry of potential
recycled water and/or multiple use of water. In compari-
son, petroleum refining has achieved an average reuse
ratio of 5.25 in 1968, an increase of 63 percent since
1954.
In 1970, industry produced 15.3 trillion gallons of
wastewater, compared to 5.3 trillion gallons for the
sewered population of the U.S. (3). The industry process
water use only was equivalent to 63 percent of all
domestic consumption (4). It would appear that exten-
sive wastewater reuse by industry should, therefore, have
a substantial impact on water conservation in the U.S.
This is of particular significance now in water shortage
areas and, in the future, in water-abundant areas.
Although water reuse has remained essentially con-
stant during 1964-1968 for the Organic Chemicals
Industry, absolute and substantial increases in the reuse
ratio are potentially possible under appropriate circum-
stances. Past occurences of water reuse have been
motivated by the pressures of limited water supply, poor
water quality, and more recently, environmental consid-
erations. The latter, particularly in view of existing
legislation, should accelerate the trend in the near
future.
Gross water demand projections for the next 50
years were made on the basis of industry growth
81
-------
projections and on the assumption that the goal of
pollution discharge" is achievable by the vear 1
(Table 1).
year
'no
1985
1970
1985
2000
2020
TABLE 1
GROSS WATER DEMAND PROJECTIONS
Gross
Water Demand Consumption Intake Discharge
(Billion gallons per day)
11.6 0.42 4.20 4.8
23.2 0.84 0.84 0
35.8 1.30 1.30 0
72.4 2.62 2.62 0
It is obvious that after achieving closed loop systems
by 1985 that the volume of intake required approaches
being equal to consumption.
After 1985, intake rates are expected to increase in
direct relation with industrial production and gross
water demand.
Now, let us speak more explicitly of the petro-
chemical and petroleum refining industries. The major
sources of pollution in these industries may be deline-
ated as shown (5):
1. Crude oil processing: distillation; desalting
2. Cracking Processes: catalytic and thermal; coking
3. Hydrotreating
4. Petrochemical operations
5. Lube oil manufacturing
6. Boiler and cooling tower blowdowns
7. Sour water stripping
8. Contaminated storm runoff
9. Intake water treatment
10. Storage and transfer
11. Leaks and spills
Such wastewaters may contain various salts, acids and
alkalies, ammonia, sulfides, solids, and mixtures of
organics of varying biodegradability, phenols and other
taste- and odor-producing chemicals, and heavy and light
oils. Furthermore, wastewaters so generated typically
exhibit a BOD and COD range of 100 to 10,000 mg/1
and 200 to 15,000 mg/1, respectively, with an average of
1,150 mg/1 BOD and 3,100 mg/1 COD (6), (7), which is
TABLE 2. TYPICAL REFINERY AND PETROCHEMICAL WASTEWATER
CHARACTERISTICS (7) (8) (9)
Petrochemical
Principal Products
Phenol, Ethylene
Aery Ion itrile
Fatty Acids, Esters, Glycerol
Azo & Anthraquinone dyes
Ethylene, Alcohols, Phenol
Acrylonitrile, Acetonitrile, Hydrogen Cyanide
Butadiene, Alkalate, MEK, Styrene, Maleic Anhydride
Butadiene, Maleic Acid, Fumaric Acid,
Tetrahydrophthalic Anhydride
Phenols
Acids, Formaldehyde, Acetone,
Methanol, Ketones, Nitric
Acid, Nylon Salt, Vinyl
Acetate, Actaldehyde
Isocyanates, Polyols, Urethane
Foam
Acetaldehyde
Ethylene, Propylene, Butadiene,
Alpha Olefins, Polyethylenes
Butylene Isomers, Butadiene,
Maleic Anhydride, Fumaric
Acid, Tetrahydrophthalic
Anhydride, Alkalate, Aldehydes, Alcohol
Refinery — Class A
Refinery — Class B
Refinery — Class C
Refinery — Class D
Refinery - Class E
Waste Flow BOD
mgd
2.0
0.302
0.10
0.94
5.9
3.9
2.0
3.605
0.215
3.46
0.57
1.15
0.750
1.50
.22
.99
2.98
4.35
7.93
mg/1
COD
mg/1
SS
mg/1
300
—
10,000
352
1,700
390
1,870
959
1,200
1,200
14,000
1,760
3,600
830
—
1,525
300
239
—
152
610
106
10
-
6,600
530
421
20,000
155
1,960
20
250
300
160
200
13,200
10,130
1,200
50,000
380
2,980
120
750
1,080
510
520
160
50
200
120
40
180
240
130
90
82
-------
indicative of the strength of the wastewaters. In Table 2
are listed some typical wastewater characteristics result-
ing from these industries.
The treatment of wastewaters from refineries and
organic chemicals manufacture becomes apparent with
evaluation of the nature of waste to be treated — that of
its relative biodegradability and normally higher
strength. Figure 1 is an empirical diagrammatic represen-
tation of the biodegradability of wastes encountered in
this portion of petrochemical industry. Organics in
general and petrochemicals in particular may be charac-
terized typically as to their respective abilities to degrade
biochemically: Type (a) classical log growth curve,
similar to domestic waste; Type (b) requiring a longer lag
or retention time for the enzymatic systems of the
micro-organisms to become more fully developed — a
semi-biodegradable waste; Type (c) a long period of
"seed" acclimation required before assimilation of
organics proceeds — a semi-refractory waste; and Type
(d) essentially no biochemical action due to a refractory
waste. Petrochemical wastewaters generally fall into the
range of a type (b)-Type (c) waste as depicted by the
cross-hatched area in the figure. Several explanations
have been postulated for this anomalous behavior (11):
(a) reaction rates of individual components (organics)
may differ markedly, (b) the bio-mass present may not
utilize some of the constituents due to the absence of
the proper enzymes (catabolic and biosynthetic enzymes
and permeases must all be present in proper concentra-
tions), and (c) there may exist materials causing inhibi-
tion or repression (interference in the natural metabolic
pathway). An additional factor that must be taken into
account, and one that may be the most significant, is the
formation of intermediates and end-products of meta-
bolic pathways that diffuse out of or are released by cell
lysis. These products may exhibit a profound effect on
the biodegradability of the waste. Extracellular quan-
tities of these intermediates and metabolites often are
indistinguishable from the original waste components,
and due to the non-specificity of either the BOD or COD
analysis, such a change in concentration cannot be
monitored directly and "a waste which is biodegradable
may appear to be 'hard' because of the intermediates
which have passed into the medium during the given
detention time" (11, p. R488). Table 3 contains a list of
24 organic compounds found to be biorefractory (12).
Similar compounds have been identified in the municipal
raw water intakes (Mississippi River and tributaries) and/
or finished water supplies at or near New Orleans,
Louisiana (13). Therefore, it is apparent from the
previous discussion that petrochemical and refinery
waste treatment practices present the environmental/
chemical design engineer with a formidable challenge
including what physical-chemical treatment process to
utilize.
TABLE 3. REFRACTORY INDUSTRIAL WASTES (12).
*nitrobenzene
trichloroethane
tetrachloroethylene
chloroethyl ether
chloromethyl ethyl ether
chloropyridine
chloronitrobenzene
dichloroethyl ether
"benzene
*toluene
camphor
veratrole (1, 2-ditnethoxy
benzene)
guaiacol (methoxy phenol)
borneol (bornyl alcohol)
isoborneol
*ethylene dichloride
chloiobenzene
bromobenzene
dichlorobenzene
bromochlorobenzene
*ethylbenzene
chloroform
*styrene
isopropylbenzene
butylbenzene
dibromobenzene
*isocyanic acid
*methylchloride
bromophenylphenyl ether
*dinitrotoluene
methylbiphenyl
acetone
2-ethylhexanol
2-benzothiozole
TYPES OF PETROCHEMICAL WASTEY'CvTER
AND THEIR RELATIVE BIODEGRADAB'LITY
(10)
"These compounds also have been found to impart taste and
odor to drinking water supplies in trace amounts (13).
There are indications that industry is well aware
of the benefits of recyling cooling tower blowdowns
(14). One such example concerns a Class "E" refinery
where "the cooling towers are used to reduce the
concentration of organics and to concentrate the un-
desirable precipitates. Thus, all wastewaters originating
from plant operations and storm water runoff are either
recycles into the process streams and reused or recycled
in the cooling towers" (15,p. 242). If wastewater reuse is
developed and implemented to its maximum potential, it
could provide industry with a viable technique for
pollution control, which could conceivably be the least
expensive alternative for fulfilling future regulatory
requirements. In fact, if no discharges of wastewater are
achievable and practicable, the need to obtain a permit
83
-------
TABLE 4 NET RAW WASTE LOADS FROM PETROLEUM REFINING
INDUSTRY CATEGORIES (50 Percent Probability of Occurrence)
KILOGRAMS/1000 M3 (LB/1000 BBLS)
SUBCATEGORY BODS OIL/GREASE PHENOL AMMONIA
TOPPING
CRACKING
PETROCHEMICAL
LUBE
INTEGRATED
to discharge effluents would be precluded. Add to this
the water conservation aspect and the potential savings
resulting from reduced effluent monitoring, and the
total recycle concept has even greater appeal.
As shown in Table 4 the largest percentage of the
waste load entering our waterways is derived from the
more complex types of refinery operations. It should be
evident that more than half of each of the five important
water pollution loads originate from Class D to E
refineries.
The data presented in Table 5 show that Class D and
E refineries account for about one third of U.S. refining
capacity. It is, therefore, evident that, generally speak-
ing, unit waste loading per barrel of crude processed
increases with increasing refinery complexity. This
would indicate the need for higher efficiency pollution
control systems for the more complex refinery as
necessary, should it be desired to achieve the same water
discharge load per unit of capacity as for less complex
refineries. This data also indicate that the more complex
refineries have larger capacities and are the larger point
sources of waste loads.
3.43(1.2)
72.93(25.5)
171.6(60)
217(76)
197(69)
8.29(2.9)
31.17(10.9)
52.91(18.5)
120.1(42)
75(26)
0.034(0.012)
4.00(1.4)
7.72(2.7)
8.3(2.9)
3.8(1.3)
1.20(0.42)
28.31(9.9)
34.32(12)
24.1(8.5)
20.5(7.2)
TABLE 5. DISTRIBUTION OF REFINING CAPACITY
BY REFINERY COMPLEXITY (9)
Refinery
Classification
A
B
C
D
E
Number of Capacity % of Total U.S.
Refineries MBCPD Crude Capacity
13
72
27
11
13
13
46
116
92
227
2
25
25
8
24
Table 6 shows treatment control efficiencies possible
with use of applicable technologies such as biological
systems and activated carbon adsorption, as compared to
the overall industry average being achieved at this time.
It illustrates that substantial improvements to pollution
control may be attained by the refining industry by
application of either well-demonstrated technology
(biological systems) or newer and emerging physical-
chemical technology such as activated carbon adsorp-
tion.
TABLE 6
Typical Removal Efficiencies for Oil Refinery Treatment Processes
PROCESS
INFLUENT BOD5 COD TOC
REMOVAL EFFICIENCY
ss
OIL PHENOL AMMONIA SULFIDE
API Separator
Clarifier
Raw Waste
1
5-40
30-60
5-30
20-50
NA
NA
10-50
50-80
60-99
60-95
0-50
0-50
NA
NA
NA
NA
Dissolved Air
Flotation
Filter
Oxidation Pond
Aerated Lagoon
Activative Sludge
Tpickling Filter
Cooling Tower
Activated Carbon
Filter
Granular Media
Activated Carbon
Data Not Available
1
1
1
2,3,4
2,3,4
1
2,3,4
2,3,4
5-9
5-9 plus 11
20-70
40-70
40-95
75-95
80-99
60-85
50-90
70-95
NA
91-98
10-60
20-55
30-65
60-85
50-95
30-70
40-90
70-90
NA
86-94
NA
NA
60
NA
40-90
NA
10-70
50-80
50-65
50-80
50-85
75-95
20-70
40-65
60-85
60-85
50-85
60-90
75-95
60-90
10-85
65-90
50-90
70-90
80-99
50-80
60-75
75-95
65-95
70-95
10-75
5-20
60-99
90-99
95-99+
70-98
75-99+
90-100
5-20
90-99
NA
NA
0-15
10-45
33-99
15-90
60-95
7-33
NA
33-87
NA
NA
70-100
95-100
97-100
70-100
NA
NA
NA
NA
84
-------
In addition to wastewater treatment technology,
refineries also have pollution control concerns with
process sludges, waste chemicals and thermal discharges
in the form of cooling water. The question of toxic,
hazardous, and/or taste and odor constituents in refinery
discharges of any sort must also be faced.
WATER POLLUTION CONTROL TECHNOLOGY
Table 7 illustrates the technological areas that are, in
general, pertinent to effective pollution control for the
Organic Chemicals and Petroleum Refining Industries.
The specific solutions available to each plant will be
determined by several factors—and economics (overall
economics) will oftentimes be the most important of
these. By and large, one must recognize the need to
detoxify and/or degrade toxic wastes, control discharges
of nutrients and salts (possibly through by-product
recovery techniques), and reduce or eliminate inadver-
tent high strength wastewater releases to quantities that
produce little or no ecological effects on receiving
streams. Where the receiving waters are too sensitive to
any permissible waste discharge, the development and
implementation of "no discharge" systems of pollution
control may be required as the means to meet local or
national environmental standards (presently and in the
future).
Physical and chemical and lower cost methods of
control will, of necessity, continue to be developed and
demonstrated. Improving performance and upgrading
existing treatment technology in conjunction with sup-
plemental advanced wastewater treatment physico-
chemical add-on processes (i.e., tertiary treatment) may
be necessary, particularly for special side streams diffi-
cult to treat by biological methods, as well as alternative
methods for implementation by both old and new
facilities. Sludges and chemical wastes, specific pollu-
tants, (e.g., halogenated hydrocarbons, heavy and toxic
metals, etc.,) and comprehensive water pollution control
methods, including regionahzation, also must be further
TABLE 7. POLLUTION CONTROL TECHNOLOGY STATUS IN THE PETROCHEMICAL
AND PETROLEUM REFINING INDUSTRIES.
Technology
Biological oxidation
NEED FOR
Research Development Demonstration
some
some
yes
Sludge disposal
yes
yes
yes
Advanced treatment
yes
yes
yes
Closed loop systems
Comprehensive approach
yes
yes
yes
yes
yes
Applications & Objectives
(1) Multi-stage biox systems
(?) To achieve and maintain 90-95%
BOD removal for single stage systems.
(3) Need pre- and post-treatment process/
operations to improve performance
and reliability of both single- and
multi-stage Biox.
(1) Solids disposal:
a) Land assimulation
b) Incineration (fuel value)
c) Catalytic oxidation
d) Solvent extraction
e) Wet oxidation and pyrolysis
(1) Biox alternatives
(2) To achieve and maintain 95-99%
pollutant reductions
(3) By- and co-product recovery
(4) Refractory organic removal
(5) Biox supplement
(1) No discharge (closed cycled systems)
(2) Cost of water
(3) Water conservation and resue
(4) Containment of trace toxic chemicals
(1) Total environmental effects
(2) Basin planning
(3) Joint treatment
(4) Synergistic benefits
85
-------
developed and improved.
As a result of the EPA perspective of the state-of-the-
art, the Industrial Pollution Control program developed
to date in the Petroleum Refining and Organic Chemicals
Industries is depicted in Table 8. In recent years, a total
of 29 grants/contracts have been awarded covering
RD&D projects concerned with wastewater characteriza-
tion and treatment costs, base level of treatment (biox),
advanced waste treatment applications, and recovery
(by-product and recycle/reuse) techniques. EPA support
amounted to $5,428,700 or 47 percent of total estimat-
ed project costs of $ 11,481,600.
One recently completed development project (Project
No. 12020 EEQ) resulted in the successful operation of
a completely mixed activated sludge process for treat-
ment of a propylene glycol process wastewater. This
wastewater was characterized by a high salt content
(8-10 percent NaCl), a pH of 11-12, relatively high
concentrations of the glycol (500-1,000 mg/1), together
with small quantities of related reaction products (in
concentrations amounting to less than 100 gm/1),
namely, the oxide, the dichloride, the chlorohydrin, the
TABLE 8. EPA RDGD GRANTS FOR POLLUTION CONTROL IN THE
PETROLEUM REFINING AND ORGANIC CHEMICALS INDUSTRIES
Grantee
C.W. Rice**
Engineering Science**
Engineering Science**
E.I. du Pont
State of Louisiana
MCA
Union Carbide
State of Louisiana
Datagraphics**
Univ. of California
Texas A&M Univ.
Univ. of Missouri
Ga. Tech.
Union Carbide
Dow Chemical
Celanese
Dow Chemical
State of Louisiana
Dow Chemical
Delaware R.B.C.
Union Carbide
B. F. Goodrich
Dow Chemical
State of Alabama
CIBA - Geigy
General Tire & Rubber
International Ozone Inst.
Dow Chemical
Union Carbide
TOTAL
Total Cost
($1,000)
56.3
11.2
17.0
874.5
69.0
60.0
67.1
67.3
6.7
86.7
38.5
38.5
76.1
314.9
282.5
600.0
226.6
827.6
196.4
995.7
554.1
823.1
1300.4
989.5
1268.3
938.7
15.0
181.1
498.8
11481.6
EPA Grant
($1,000)
56.3
11.2
17.0
150.1
48.3
42.0
46.9
32.5
6.7
81.2
34.9
36.4
71.4
220.4
197.7
395.3
142.3
457.8
108.3
646.7
231.8
364.9
509.8
314.5
392.6
461.9
8.0
110.0
231.8
5428.7
Primary Effort Technological
R DV DM Objectives
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Treatment costs-general
Wastewater characteristics
State of the Art
Ocean dispersal of salt waste
Recovery: Membrane systems
Effects of Ci2 on treated organics
X *Biox: Anaerobic inhibitors
Concentration of wastes by
dialysis
Treatment costs-organics
Recovery: Volatile solvent extrac-
tion of organics
Recovery : Solvent extraction
AWT: Carbon sorption &
regeneration
AWT: Radiation treatment of high
strength chlorocarbon wastes
X X *Biox: Refractory organic wastes
X Biox: Polyhydric/saline wastes
X Biox: Chloraldehyde wastes
X Biox: Optimization thru
automation
X AWT: Refractory chlorocarbon wastes
X AWT: UV Cl2 of organic acids in
waste brines
X AWT: Joint industrial/municipal
wastes
X Recovery: Cooling water blowdowns
X Biox: PVC wastes
X AWT: Phenol/Acetic acid waste brines
X Deep well disposal of wastes
X *Biox: Plastic media trickling filters
X Recovery: Distillation for renovation
AWT: Ozone
X Zero discharge: R.O.— Electrodialysis
X X Zero discharge: voided processes
** Contract * Multi-stage systems
86
-------
chlorinated ether, and some acetol and acetic acid. A
unique mixed culture, which tolerates high salt content
and utilizes glycols as the only carbon source, was
developed; however, an acclimation period of 6 to 8
weeks was required. TOD removal efficiencies of over 90
percent were obtained at retention times of 8.0 to 9.0
hours and loadings of 2.0 to 3.0 Ibs TOD/lb MLVSS-day.
Based upon such favorable results and the demonstration
of the consistent reliability of the TOD and TOC
parameters for correct interpretation of the behavior and
fate of the organics in the wastewaters and for the
evaluation of the treatment process, a subsequent grant
was awarded (Project No. 800766) to develop control
systems such that an activated sludge process could be
operated as efficiently as a chemical process on a
continuous basis; the premise being that the perfor-
mance of an activated sludge process can be further
improved and its reliability increased under steady state
conditions. Such conditions can only be achieved by
instrumentation to control: (a) the food to micro-
organism ratio in the aeration vessel; (b) the nitrogen
and phosphorus requirements; and (c) the biomass/
organics reaction temperature. An additional require-
ment included the development of a dependable biologi-
cal toxic detector to sense and eliminate (through proper
feed forward and feed backward controls, the influent
wastewater may be temporarily diverted to a holding
basin) a toxic substance prior to its entry into the
aeration basin.
More recently, efforts are being directed toward the
development and evaluation of improved physico-
chemical techniques, both for pretreatment, special
segregated side streams, and tertiary treatment supple-
mentation for, or as alternatives to, biological systems.
Also, the emphasis continues to be placed upon closed-
loop water reuse technology and by-product recovery.
There exists today in an area of southwestern Puerto
Rico, a large integrated refinery/petrochemical complex,
including an electrical generating facility. The cumula-
tive wastewater discharge exceeds 400 MGD (cooling,
process, and boiler feed blowdowns) which includes
excess heat, organic matter, suspended solids, total
nitrogen and ammonia, oil and grease, and phenol. The
petrochemical complex produces 775 million #/yr of
ethylene and derivative products, including butadiene,
ethylene oxide, phenol, cumene, polyethylene, bis
phenol-A, plasticizers, refined ethylene and diethylene
glycols, ethyl-hexanol, istobutanol, and butanol (23)
(24); whereas the integrated refinery processes approxi-
mately 175,000 bbls/day of crudes for the production of
aviation and motor gasoline, jet fuel, kerosene, disel
cyclohexane, isobutanol, propylene, and ethylene(23). It
should be noted that a large percentage of the total
wastewater flow is cooling water. A grant (Project No.
801398) for a water reuse project has been awarded by
EPA. The demonstration phase of the proposed study,
which entails the utilization of an optimized AWT
system that will deliver treated water for use in heat
transfer systems, will be conducted at Ponce, Puerto
Rico. One of the major objectives of this project will be
to provide quality criteria for water usage in the
petro-chemical industry, including quality criteria that
TABLE 8.
Grantee
Univ. of Okla.
Texas A&M
Harvard
Illinois Tech
API
A-D-M Co.
American Oil
Shell Oil
American Oil
American Oil
Atlantic-
Richfield Oil
BPOil
TOTALS
Total Est.
Cost ($1000)
18
234
16
12
85
245
355
100
1738
226
1160
2625
6844
EPA Grant
($1000)
14
40
15
35
51
107
170
70
337
74
275
350
1538
Primary
R&D
yes
yes
yes
yes
yes
yes
yes
-
yes on
water
reuse
Effort
Demo
Pilot
Plant
yes
yes
yes
yes
yes
yes
yes
Technology
State of the Art
Catalyzed Oxidation of Phenol and
Amines
Pretreatment for Biox (Oil removal)
Pretreatment for Biox (Oil removal)
Improved Biox Assimulation
of oil
Pretreatment for Biox (Oil removal)
Oily Sludge and Chemicals Disposal
(fluid bed incineration)
Oily sludge disposal (soil cultivation)
Post-treatment for Biox (chem coag,
dissolved air flotation)
Post-treatment for Biox (mixed media
filtration)
Advanced treatment
(Activated carbon with joint treatment
alternate)
Advanced treatment (Rapid Sand
Filtration with Activated Carbon)
87
-------
are limiting factors with respect to reuse of renovated
wastewaters, namely boiler-ffed water, cooling water,
service water, and process water. The successful comple-
tion of this project will have immediate and obvious
impact on the environment of south central and western
Puerto Rico, and it is anticipated that the results should
show that a significant step can be achieved toward total
recycle and reuse of petrochemical wastewaters.
In a recent grant with the Dow Chemical Company
(Project No. 803085) the problem of zero discharge
from petrochemical plants is being studied. This project
will focus on the removal of refractory organic con-
taminants and the recovery of industrially reusable
brines by a reverse osmosiselectrodialysis process. The
proposed use of these brines is in the production
chlorine which can be utilized for production back in
the plant. If successful, this project will evaluate the
total reuse of petrochemical wastewaters.
The main objective of total water pollution control
within an Organic Chemicals Industrial complex is based
on the concept that water pollution abatement and
water conservation are economically compatible, partic-
ularly for the long term. As water availability becomes
more critical, the reuse of water will be dictated by
economics, with attendant inherent treatment costs
merely a normal operating expense.
A Los Angeles area refinery impounds the periodic
storm flow, treats it by contact with granular activated
carbon, and then discharges it into a local channel.
Because of the highly seasonal nature of the rainfall, it is
essential that the treatment system be able to start up
and shut down without delay or difficulty. Of course,
this eliminated any possibility for the use of biological
systems. The operation of this plant demonstrated the
reliability, economics, and efficiency of activated carbon
treatment of wastewaters on an intermittent basis.
At another refinery, the full scale activated carbon
plant was not performing as well as had been expected.
The addition of a Bio-Disk pilot plant prior to the
carbon columns greatly improved the effluent quality.
This follows logically, since the hydrocarbons that are
not removable by activated carbon (polar molecules) are
highly biodegradable. The reverse is also true, those
materials that are refractory usually show amenability to
carbon removal.
In another recently completed grant (12050 EZG)),
the disposal of oily sludges from petroleum refineries by
land spreading was evaluated. Some micro-organisms
normally present in soil will attack petroleum hydro-
carbons and utilize them as their sole source of carbon.
Poorly aerated soils become anaerobic, and under these
conditions, the micro-organisms decompose oily material
very slowly. Aeration of soil by frequent cultivation is a
means of supplying oxygen essential for the more rapid
acting aerobic microbes. Temperature, moisture, soil
properties, oily sludge properties, and nutrient content
all influence the rate at which the hydrocarbons are
decomposed.
According to an EPA national analysis of the indus-
try, the attainable concentrations from the application
of best practicable control technology currently avail-
able aie shown on table 9.
Table 9
Attainable Concentrations from the Application of
Best Practicable Control Technology Currently Available
Parameter
BOD5
COD
TOC
ss
O&G
Phenol
NH3-N
Sulfide
CrT
Cr6
Concentration mg/1
15
80-115
(2.2XBOD,)
10 5
5
0.1
2-10
0.1
.25
.005
CONCLUSION
The Research, Development, and Demonstration
grants program of EPA has been implemented to meet
current and emerging needs for water pollution control
and energy conservation in the Petroleum Refining and
Organic Chemicals Industries.
Since the trend toward industrial water reuse has
already commenced (e.g., the Petroleum Refining Indus-
try), the exception ocurring in some areas of the Organic
Chemicals Industry, acceleration of the trend would
provide a sound basis for future industrial expansion.
Since current and future environmental standards are
expected to increase greatly the pressures to reduce
dramatically, or eliminate altogether, pollutional loads
and effluent discharges, reuse and recycle to the point of
providing an industrial closed water cycle should be
planned. On this point, Federal legislation calls for the
elimination of the discharge of pollutants into navigable
waters by 1985, as a goal.
88
-------
REFERENCES
1. Industrial Water Reuse Future Pollution Solution, G. Key,
W.J. Lacy, A. Cywin, Environmental Science and Tech-
nology, Sept. 1971.
2. 1967 Census of Manufacturers: Water Reuse in Manufactur-
ing, April 1971, U.S. Department of Commerce.
3. Achieving Pollution Abatement, K.L. Kollar and Robert
Brewer, Construction Review, Department of Commerce,
Vol. 19, No. 7, July 1973.
4. The Water Encyclopedia, O.K. Todd, ed., 1970. Water
Information Center, Port Washington, New York.
5. Minimizing Waste in the Petrochemical Industry, S.K.
Mencher, 1967, Chemical Engineering Progress, Vol. 63, No.
10, pp. 83-84.
6. Petrochemical Effluents Treatment Practices, Summary
Report, February 1970. Engineering Science, Inc., Austin,
Texas, FWPCA Contract No. 14-12461, pp. 35-37.
7. Projected Wastewater Treatment Costs in the Organic Chem-
ical Industry, July 1971. Datagraphics, Inc., Pittsburg, Pa.,
EPA Project No. 12020 GND, p. 54.
8. Extended Aeration Activated Sludge Treatment of Petro-
chemical Wastes at the Houston Plant of Petro-Tex Chemical
Corporation, Pruessner, R.D. and Mancini, J., 1966. Paper
presented at the 21st Annual Purdue Industrial Waste
Conference, May 1966, Purdue University, Lafayette, Indi-
ana, p. 2.
9. Petroleum Industry Raw Waste Load Survey, December
1972. Committee on Environmental Affairs, American Petro-
leum Institute, 1801 K. Street, N.W., Washington, D.C.
10. The EPA Program for Environmental Control in the United
States and Puerto Rican Petrochemical Industry, desRosiers,
P.E., and G. Rey, 1972. Papter presented at the Water
Pollution Control Federation Reconvened Session, San Juan,
Puerto Rico, October 15-18.
11. Factors Responsible for Non-Biodegradability of Industrial
Wastes, Irvine, R.L. and A.W. Busch, 1969, JWPCF, Vol. 41,
No. 11, Part 2, pp. R482491.
12. EPA Research and Tertiary Treatment, Myers, L.H. and L.F.
Mayhue, 1972. Paper presented at the 65th Annual AIChE
Meeting, November 26-30, 1972, New York City, P.4.
13. Industrial Pollution of the Lower Mississippi River in
Louisiana, 1972. EPA Region VI, Dallas, Texas. Surveillance
and Analysis Division, April 1972.
14. Industrial Water Closed Cycles Research Progress and Needs,
Rey, G. and W.L. Lacy, 1972. Paper presented at September
12, 1972, Seminar: Closed Cycle Operations by Industry,
Rider College, Trenton, New Jersey.
15. Water Reuse in Industry, Gloyna, E.F., D.L. Ford, and J.
Eller, 1970. JWPCF, Vol. 42, No. 2, Part 1, pp. 237-242.
16. Pilot Plant Activated Carbon Treatment of Petroleum Re-
finery Wastewaters, Short, T.E. and L.H. Myers, Robert S.
Kerr Environmental Research Laboratory, Ada, Oklahoma.
17. Anaerobic Treatment of Synthetic Organic Wastes, January
1972. Union Carbide Corporation, South Charleston, West
Virginia, EPA Project No. 12020 DIS.
18. Treatment of Wastewater from the Production of Polyhydric
Organics, October 1971. The Dow Chemical Company,
Freeport, Texas, EPA Project No. 12020 EEQ.
19. Biological Treatment of Chlorophenolic Wastes, June 1971.
The City of Jacksonville, Arkansas, EPA Project No. 12130
EGK.
20. Interim Report - Deepwater Pilot Plant Treatability Study,
July 1971. Delaware River Basin Commission, Trenton, New
Jersey, EPA Project No. 12130 DRO.
21. Anaerobic Degradation of Selected Chlorinated Hydrocarbon
Pesticides, Hill, D.W. and P.L. McCarty, 1967. JWPCF, Vol.
39, No. 8, pp. 1259-1977.
22. Biological Degradation of Tertiary Butyl Alcohol, Horn,
J.A., J.E. Moyer, and J.H. Hale, 1970. Paper presented at the
25th Annual Purdue Industrial Conference, Purdue Univer-
sity, Lafayette, Indiana.
23. Environmental Effectus of Petrochemical Waste Discharges
of Tallaboa and Guaynilla Bays, Puerto Rico, Lair, M.D.,
R.G. Rogers, and Weldon, M.R., 1971. Technical Study TS
03-208-02. EPA, Region, IV, Surveillance and Analysis
Division, Athens, Georgia.
24. Wastewater Control Facilities in a Petrochemical Plant,
Rucker, J.E. and R.W. Oeben, 1970. Chemical Engineering
Progress, Vol. 66, No. 11, pp. 63-66.
89
-------
EXAMINATION OF OIL-CONTAINING WASTE WATERS CHEMICAL COMPOSITION
AFTER THEIR TREATMENT IN AERATION TANKS.
by V. A. Panova, N. S. Goriatchev and
U. U. Lurie
All-Union Scientific-Research Institute
VODGEO
On the basis of examinations carried out at the
Institute VODGEO waste waters from oil-refining plants
after being treated in aeration tanks were found still
toxic. To prevent their detrimental effect on acquatic
life they must be diluted 16-60 times.
Up to now it was not possible to answer what
determines this toxicity and what kind of substances
present in waste water is toxic.
We should note that oil-containing waste waters
composition is changeable and depends on the degree of
treatment, that is why for determination of organic
substances in biochemically treated oil-containing waste
water four methods of concentrating were used with the
simultaneous division of organic substances mixture into
several groups depending on chemical composition of
separate components: I) extraction by diethyl ether, 2)
adsorbtion on activated carbon with desorption by
various solvents, 3) distillation from alkaline medium
with the application of freezing for neutral compounds
concentrating, 4) distillation from acid medium with the
application of the same freezing process for neutral
compounds.
In all cases this division is based upon specific affinity
of the mixture components towards solvents and on
their various acidic and basic properties.
It had been stated before, that evolution of organic
substances from biochemically treated oil-containing
waste water by direct extraction method with diethyl
ether and sorption on activated carbon leads for several
reasons to the considerable loss of some part of volatile
organic compounds. Besides, at direct extraction method
too low degree of organic compounds removal from
waste waters is obtained owing to the fact that many of
these compounds have low distribution factor in the
water - diethyl ether system.
Schemes developed by the authors were used in the
investigations carried out for separating and concentrat-
ing of organic substances from waste water and for their
division into groups.
According to these schemes waste water to be
analysed is suggested to be subjected to thrice-repeated
concentrating in order to raise extraction efficiency of
organic substances from water by ether. Separation is
commenced with the distillation of volatile bases and
neutral compounds from alkaline or acid medium.
Therevy all acids and phenols in the form of their salts
remain concentrated in a small volume of the distillation
residue. The distillation residue is being acidified and
extracted repeatedly at water to ether ratio 1:1. At such
extracting practically all volatile acids are being evolved
by ether. All oxy- and polyacids with the distribution
factor =0.1 polyalkohols, aminoacids, sulfoacids, sugars,
urea remain in the water layer. Then separation of acids
from phenols is being conducted, and after this in each
group obtained further division on volatile and non-
volatile substances is being carried on.
The group of organic bases is concentrated the same
way. After acidification of the distillate in which volatile
bases and neutral compounds are present, the latter are
distilled and salts of volatile bases being repeatedly
extracted by ether after acidification remain in the
distillation residue in a small amount. And finally the
group of neutral compounds is subjected to concentrat-
ing by freezing with their subsequent extraction with
diethyl ether.
At a slow freezing losses of neutral compounds with
ice were determined to make up no more than 10%. At a
rapid freezing, when the solution is placed directly into
the freezing chamber of the refrigerator, losses make up
40-50%.
The group of hydrophilic compounds (oxy- and
polyacids, polyalkohols, sulfoacids, aminoacids, sugars,
urea etc.) practically not extracted by ether (Their
distribution factor = O.I) is extracted at first together
with the mineral salts and then after being evaporated
dry is treated by dewatered ethanol for separation from
mineral substances. This group of compounds may be
subjected to further analysis for division into acids, bases
and neutral compounds with the help of cephadexes and
ion-exchange celluloses.
As a result of such treatment organic compounds
from oil-containing waste waters treated are divided into
four large groups: neutral, acidic, basic and hydrophilic
compounds. These groups are divided in their turn into
separate subgroups: volatile phenols, non-volatile phe-
nols, volatile acids, non-volatile acids, including naphthe-
nic acids, volatile organic bases, non-volatile organic
bases, volatile and non-volatile neutral compounds.
Quantitative characteristics of each separate group of
compounds evolved are represented in Table I. Oil-con-
taining waste water of an oil-refining plant was examined
after being biochemically treated. The result of the
analysis is given in Summary Table 2.
Analysis of the organic part of oil-containing waste
water was not limited by determination of weight of
separated groups of organic compounds: investigations
SO
-------
Table I Organic compounds in oil-containing waste water after biochemical treatment.
Separated groups of compounds
Neutral aldehydes and ketones
compounds oily substances
quinones
other neutral compounds
The sume of neutral compounds
Acidic Strong organic acids 44—67
compounds including: volatile
non-volatile
napthenic
other non-volatile acids
Very weak organic acids 6—8
phenols
other very weak organic acids
sum total of all acids
Basic Basic compounds in the form of
compounds hydrochloric salts
Compounds soluble in water and
not-extracted by ether (aminoacids,
oxyacids, sulfoacids, polyalkohols,
urea, sugars etc)
Sum total of all organic compounds
fluctuation of component
during observation period
mg/1 (1971, 1972, 1973)
1.8-2.0
0.8-3.5
0.3-1.1
6.0-95
10-100
14-35
20-53
2-4
16-51
0.1-3
5-8
50-75
7-55
90-102
150-330
Table 2 Summarized data of oil-containing waste waters chemical composition.
Ingredients defined
Waste water after
sand filtration biochemical treatment
Colour
Odour
pH
COD mg 0/1
BOD, mg 02/1
oil substances, filtrated, mg/1
oil substances, non-filtered, mg/1
Naphthenic acids, mg/1
Other non-volatile acids, mg/1
Volatile organic acids, mg/1
Volatile phenols with vapour, mg/1
Quinones, mg/1
Surfactants, mg/1
Dry residue, mg/1
Tempered residue, mg/1
Chlorides (CD, me/1
Phosphates (PO4^) mg/1
Sulfates(SO42-), mg/i
Nitrogen, ammonia mg/1
Nitrogen, nitrate mg/1
Nitrogen, nitrite mg/1
Calcium, mg/1
Magnesium, mg/1
Sodium, mg/1
Potassium, mg/1
Waste water before treatment in aeration tanks is diluted by sewage
1.5 - 1.8 times.
dirty-grey
oily
6.9-7.3
270-1050
26-58
—
18-64
8-20
54-140
30-70
1-11
—
8-13
8000-10000
7400-9300
4900-6100
—
_
8-29
0.2-1.3 single
0-0.1 determi-
nations
660
100
340 -
70
light-yellow
light oily
7.2-7.6
80-120
1.6-3.5
0.7-3.5
1.5-5.0
2.0-4.7
15-50
3.0-35
0.01-3.7
0.3-1.1
2.4-6.5
4900-6000
4200-4800
2700-3450
0.6-0.8
43-75
0.4-1.1
7.8-8.4
0.03-0.33
100-370
40-65
200
50
91
-------
were continued within each group. Two very important
groups of compounds were tested in detail, that is
neutral and acidic compounds, as they contain sub-
stances causing water toxicity (quinones, naphthenic
acids).
Group of Neutral Compounds
The group contains a great number of separate
components, namely non-oxidated hydrocarbones,
ethers and esters, aldehydes, ketones, alkohols,
quinones, anhydrides, lactones, fatty and aromatic
halogen-bearing compounds.
Three groups of neutral compounds were analysed,
namely neutral compounds evolved from water by direct
extraction with diethyl ether; by sorption on activated
carbon and by distillation from acidic and alkaline media
with the subsequent concentrating by freezing. The
latter method of neutral compounds separation indi-
cated the presence of more considerable amount of
organic compounds in the group as compared to those
evolved by two other methods. At evolution of neutral
compounds by above mentioned methods their contents
in water were 21.5, 41 and 100 mg/1 respectively. It
brings the evidence to the fact, that the used method of
concentrating of organic compounds by freezing after
removal of acidic and basic groups of organic com-
pounds gives us the possibility to preserve fully the
high-volatile part of organic compounds, that is neutral
compounds.
Analysis with the help of IR-spectroscopy has shown
that adsorption spectra of these three groups of neutral
compounds separated from water by various means (by
extraction, sorption and distillation) did not differ
greatly from one another. The three spectra were
characterized by the presence of a large area of carbonyl
compounds in them. Spectrum region at 1680 - 1780
cm"' testifies to the presence of aldehydes, ketones,
esters and lactones.
Gas chromatographic analysis of the neutral group of
compounds indicated the presence of 16 components in
it. In the group of neutral compounds substances
mentioned below were extracted and defined (see Table
I):
• aldehydes and ketones; their content in ditterent
water samples varied from 1.8 to 2.0 mg/1;
• hydrocarbons concentration from 0.8 to 3.5 mg/1;
• quinones concentration from 0.3 to I.I mg/1;
• the content of other neutral compounds in treated
water was 6 - 95 mg/1.
This group also contains alkohols, esters, lactones.
Summing up the results of investigations of the
composition of the neutral group it should be noted that
the above-mentioned data testify to the fact that
intermediate products of petroleum hydrocarbons bio-
chemical oxidation, lhat is oxygen-containing com-
pounds, are very numerous and present in water in
considerable quantities.
Special attention should be paid to the high content
of high-toxic and relatively stable quinones in waste
water.
Quinones appear as intermediate products of aro-
matic hydrocarbons biochemical oxidation (oil from
oil-refining plants bears up to 20% of aromatic hydro-
carbons).
Examination of the neutral group composition
should be completed by characteristics of those 10-15%
of hydrocarbons resistabt to oxidation and remained in
waste water after biochemical oxidation.
Having used a new gas chromatographic method of
hydrocarbons determination with their distribution
according to boiling temperatures the authors managed
to define which of hydrocarbons remained in waste
water after biochemical treatment.
The results of investigations given in Fig.I and in
Table 3 illustrate hydrocarbons distribution according to
their temperatures of boiling and testify to the fact that
hydrocarbons boiling at temperatures lower than 250 -
300°C. are practically absent in biochemically treated
waste water. These hydrocarbons usually have up to Cj4
- Cj7 carbon atoms in the molecule. They are mainly
oxidized, partly blown off in the course of treatment.
The content of hydrocarbons boiling at higher tempera-
tures decreases considerably as well. They remain in
quantity of about 15-20% of their initial content.
Two chromatograms are given in Figure I. The first
one (A) is given for waste water after sand filtration,
that is before biochemical treatment. The chromato-
grams clearly demonstrate that before treatment oil-con-
taining waste waters are polluted by raw oil, what can be
seen from a fractional composition and uniform distribu-
tion of normal hydrocarbons peaks with a small incer-
tion of their isomers and aromatic hydrocarbons.
As a result of treatment (see chromatogram "B") all
volatile and isomeric hydrocarbons were removed from
waste water - benzine and kerosene fractions are
practically absent in waste water.
Fig. 2 demonstrates more clearly which hydrocarbons
remain in waste water after biochemical treatment.
Remaining hydrocarbons with 25 carbon atoms in the
molecule give the highest peaks.
Summing up featuring of the neutral group of
compounds it should be men tioned once more that this
group is one of the largest judging by a number of
components constituting it. It consists of toxic com-
pounds along with non-toxic ones (aldehydes, ketones,
anhydrides, esters and lactones).
Group of Acidic Compounds.
The group is divided into two subgroups: strong
organic acids (acids with less than 10 carbon atoms in the
molecule) and weak organic acids with pK value > 10,
92
-------
J n fj-n [ •)
SI
-4-_.
4 ....
rr~
TableS.
Distribution of hydrocarbons in oil-containing waste waters of
an oil-refining plant according to boiling temperatures.
Number Ranges of
of
fraction
T
boil.
in" C
Waste water
before treatment
(after sand filteration)
Waste water after
biochemical treatment
Hydrocarbons
content
Hydrocarbons
content
weight %
mg/1 Weight
mg/1
1
2
3
4
5
6
1
8
9
10
11
12
13
14
100-130
130-160
160-190
190-220
220-250
250-280
280-310
310-340
340-370
370-400
400-430
430-460
460-490
490 and more
1.5
3
4
13
13
19
13
11
11
6
2.5
1.5
1
0.5
100
0.57
1.14
1.53
4.95
4.95
7.24
4.95
4.20
4.20
2.29
0.97
0.57
0.38
0.19
—
—
—
_
5
5
10
10
18
22
11
9
5
3
38.2
100
0.18
0.18
0.35
0.35
0.63
0.76
0.39
0.32
0.17
0.10
3.5
93
-------
sas^m xrf ~ q
as -"JK a-f - T
The group of acid compounds is the main one because
biochemical processes proceed with the formation of
acids. Various methods of analysis were used for its
examination.
As a result of the examination carries out the total
content of all acids, and non-volatile acids and volatile
acids contents defined separately, the total content of
innnocuous non-volatile acids and the content of some
other acids were found.
Besides, the content of naphthenic acids and other
highmolecular petroleum acids were determined. Sum-
mary data for organic acids content in waste waters are
given in Table 4.
Formic, acetic, propyonic and butyric acids were
found in all samples of oil-containing waste waters
treated in aeration tanks in the course of low-molecular
monocarboxylic acids determinations by a gas chromati-
graphic method. Valeric and caproic acids were found
only in one of the water samples. The fact that the
content of acetic acid exceeds that of other acids and
reaches 30-50% of all low-molecular monocarboxylic
acids has appeared general for all water samples. These
data are in agreement with the information on the role
acetate plays in the metabolism of acquatic organisms.
Special attention was paid to the non-volatile acids as
the contain both quite innocuous acids usually present
in water sources, and high-molecular acids including
naphthenic acids responsible for water toxicity.
Having analysed the data given in Table 4 one can
come to the following conclusion: the group of acidic
compounds has appeared, as expected, to be quite
numerous (up to 30% of all organic compounds are
included in it) and diverse by its composition. It
contains acids differing in structure, molecular weight,
chemical and physical properties. Strong organic acids
content in it varies from 44 to 74 mg/1. From 20 to 50
mg/1 of this content fall to the share of non-volatile
acids and only 24 mg/1 to naphthenic acids.
Table 4. Organic acids in oil-containing waste water after
biochemical treatment.
Fluctuations during obser-
vation period 1971, 1972,
1973 mg/1
I. Strong organic acids 44 - 74
a) Volatile acids 14 - 35
formic acid
acetic acid
propionic acid
butyric acid
Other volatile acids
calculating on valeric
acid
b) Non-volatile acids 20-53
naphthenic acids
lactic acid
amber acid
fumaric acid
glutaric acid
adipinic acid
pyruvic acid
oxalic acid
malonic acid
and other not identified
malic acid
and other acids
not identified
Other high-molecular
acids
II. Very weak organic acids 6-8
a) phenols (volatile with vapour)
b) other very weak organic acids
(phenols with the place substituted in
p-position, estersof
phenolic acids
Sum total of all organic acids
3-8
8-15
3-5
4-7
_
2-4
1 -4
1 -3
1 -4
0.3-5
11-35
0.-3
5-6
50-82
Summing up the results of analysis of organic
compounds in biochemically treated oil-containing waste
waters it should be mentioned once more that the
composition of such waters is very changeable and
94
-------
depends on the degree of organic compounds bio-
chemical oxidation.
The data obtained on waste waters being examined
testify to the fact that ether-extracted compounds to
which special attention had been attracted before,
represent only a minute part of organic substances, in
order of 35 mg/1 or 10-15% of the total quantity of
organic substances.
Conclusions
I. Analyses of chemical composition of oil-containing
waste waters carried out in accordance with the new
schemes for organic substances removal from waste
waters permit to preserve all volatile compounds, while
the methods considered before, such as direct extraction
by diethyl ether and sorption on activated carbon led for
different reasons to the loss of volatile substances.
2. It is shown that biochemically treated waste water
contains substantial quantity of various oxygen-contain-
ing organic compounds besides hydrocarbons remained.
Volatile, non-volatile acids, including naphthenic ones
and neutral compounds, such as hydrocarbons,
quinones, alkohols, aldehydes, ketones, alkohols, and
esters were extracted and determined quantitatively. The
total content of such hydrophilic compounds as sugars,
aminoacids, oxyacids, sulfoacids, polyalkohols etc. in
water was found along with the total content of organic
bases. IR-spectrum and chromatograms indicated quali-
titatively several other substances as well.
3. It was reaffirmed that about 10-15% of initially
present petroleum hydrocarbons remain in waste waters
treated in aeration tanks. Gas chromatographic analysis
has indicated that they belong to the compounds
containing more than 14 carbon atoms in the molecule
which is indicative of the absence of hydrocarbons of
benzine and kerosene fractions in the waste water
treated.
4. The investigations have shown that at biochemical
treatment of oil-containing waste waters petroleum
hydrocarbons undergo deep chemical changes. A con-
siderable part of them in the form of intermediate
products of different degree of oxidation remains in the
waste water and causes high COD value of waste waters
treated (in order of 100-150 mg 0/1) and their toxicity.
It was found that the following compounds are responsi-
ble for toxicity of biochemically treated oil-containing
waste water:
• quinones containing in waste water at concentration
up to I mg/1, which 10 times exceeds maximum
permissible concentrations,
• neutral compounds at concentration of 25 mg/1 and
more that also exceeds their non-toxic level. Toxicity of
this group is caused apparently, to a considerable extent,
by the presence of quinones in it,
• minerals salts (water salinity > 5 g/1),
• phenols, reduced to quinones as a result of biochem-
ical oxidation.
• As the toxicity of ciochemically treated waste water
decreases and even fully disappears with the time passes,
detention of treated waste waters in ponds before being
discharged is considered to be advisible.
95
-------
COMPARISON OF ALTERNATIVE STRATEGIES FOR COKE PLANT WASTEWATER DISPOSAL
by ROBERT W. DUNLAP Professor of Engineering and
Public Affairs Director, Environmental Studies Institute
FRANCIS CLA Y McMICHAEL Associate Professor of
Civil Engineering and Public Affairs
Trends in Cuke Making
Fifty years ago, the production of coke from by-
product ovens first surpassed the production from
beehive ovens. For many of these same years, the
by-product process was praised for two significant
advances over beehive coking; first, the fact that
by-product processing introduced significant chemical
recovery into coke making and second, that by-product
processing significantly reduced air pollution problems
associated with coking. The last 20-25 years, however,
have brought a changed perspective. While oven-coke
production has remained stable at 54-64 million metric
tons per year over the last quarter century, chemical
recovery has grown increasingly less advantageous. In
1950, twenty-two percent of product values from the
coke plant were associated with the value of coal
chemicals*. By 1973, coal chemicals represented only
twelve percent of total product value. At the same time
these changes were taking place, increasing attention has
been focused on the other principal difference between
by-product and beehive coking, namely the introduction
of significant water pollution problems which are a
direct consequence of the gas processing.
Effluent Guidelines
Coke plant effluent limitations have been imposed by
the Environmental Protection Agency2. It is recogniz-
ed that coke plant wastewaters are typically as saline as
sea water and contain a broad range of organics.
Limitations are set for oil and grease, suspended solids,
pH and sulfides, but the principal attention for the
guidelines are for the control of ammonia, cyanide and
phenolics. By 1977, the guidelines call for more than 90
percent reduction of these pollutants from the levels in
typical untreated process waters. Further control by
1983 is expected to reduce discharges of the three by
more than 99 percent (Table A).
TABLE A
Effluent Limitations for Selected
Coke Plant Pollutants (as kilograms)
per million kilograms of coke)
Typical Raw BPCTCA BATEA
Pollutant Wastewaters (1977) (1983)
Ammonia 914 91.2 4.2
Cyanide 120 21.9 0.1
Phenol 262 1.5 0.2
Average Percent Removal 0.0% 91.2% 99.7%
The intent of this study is to address the coke plant
wastewater problem by examining a number of topics.
What are the specific sources of the wastewaters? Can
they be reduced in quantity through process changes?
How do process objectives and environmental demands
like control of air pollution influence waste character-
istics? How can we evaluate the environmental impacts
to air, water, and land which result from process
effluents or are associated with the energy demands of
process control?
Coke Plant Wastewater Sources
By-product coke plants vary widely in size, extent
and type of by-product recovery, and wastewater prac-
tices. Wastewaters in coking originate from three princi-
pal sources: coal moisture, water of decomposition, and
process waters added during gas treatment and by-
product recovery. The process waters are the largest
fraction of the total wastewaters and typically account
for 60 to 85 percent of the total flow, which may range
from 500 to 1700 liters per metric ton depending on the
level of process water recycle. Typical gas processing and
recovery steps are shown in Figure A, which indicates
the six categories of wastes normally identified; (1) tar
still wastewater, (2) excess or waste ammonia liquor
(WAL) from the primary cooler, (3) ammonia absorber
and crystallizer blowdown, (4) final cooler wastewater
blowdown, (5) light oil (Benzol) plant wastewater, (6)
gas desulfurizer and cyanide stripper wastewater. Table
B indicates the level of wastewater flow and mass
emissions of cyanide, ammonia, and phenol for each of
the wastewater streams. Loose or tight recycle is a
measure of the flow reduction achieved through recycle
and process modification in the final cooler and the
benzol plant. Mass emissions are essentially the same for
both configurations with the exception of some loss of
pollutants assumed for tight recycle due to by-product
contamination, volatilization to the atmosphere in open
cooling towers, and development of corrosion products
in the coke oven gas distribution system.
The environmental impact of these wastewater
streams can be summed up by considering the overall
mass balance of emissions to the air, water, and the land.
The coke plant necessarily consists of coke ovens, the
quench towers for the incandescent coke, the by-
product plant, and an associated wastewater plant to
treat the wastes to meet the guidelines. Figure B shows
the principal plant input, coal, and the main outputs of
96
-------
Evaporated
Water Water (150 gal/ton)
COKE
QUENCH
i
Coke
^coke COKE gas
OVENS
1
Coal
(4200 tons/day) (6000 tons/day)
\ _ FINAL
/* COOLER
"3
ste
gas
DOO gpm
WASH OIL COOLING
AND
RECYCLE
t
300 gpn (loose)
30 gp
m (tight)
__. PRIMARY COOLER
t TAR DECANTER
.
< — stea
TAR
STILL
am CL)S 9pm
LIGHT OIL
'
WASH OIL
DECANTER
..
G
gas
J
gas
) 100 gpm
BENZOL
PLAN
GAS BLANKETING
AND HEAT EXCHANGE
T
AMMONIA ABSORBER ^/T^
AND CRYSTALLIZER X_/
11
COOLING TOWER
WITH RECYCLE
00 gpm
^3 )lOO gpin
DESULFURIZER
AND CYANIDE
STRIPPER
1
REBOILER
©360 gpm {loos
65 gpm (tigh
Clean
"— Gas
10
40 gpm
e
t)
Figure A. Srli"Utlc of Coke Plant Wastes.
Table B. Characteristics of Coke
Basis:
Plant Wastewater Streams
5443 kkg/day coal charged at
10% moisture
with 70% coke yield, equivalent to
3810 kkg/day coke product.
Mass Flow
Flow
Cyanide Ammonia Phenol
Flow tiwh Loose Recycle (gpm) (1pm)
1. Tar Still
2. WAL
3. NH3 Crystallizer
4. Final Cooler
5. Benzol
6. Desulfurizer
Total
5
20
100 380
100 380
300 1140
360 1360
40 150
905 3430
(kg/day) (kg/day)
2
33
8
164
4
246
457
136
3270
6
65
6
0
3483
(kg/day)
132
794
2
63
10
0
1001
Mass Flow
Flow with Tight Recycle
1. Tar Still
2. WAL
3. NG3Crystallizer
4. Final Cooler
5. Benzol
6. Desulfurizer
Flow
Cyanide Ammonia
(gpm) (1pm)
5
20
100 380
100 380
30 1
10
65 250
40 1150
(kg/day) (kg/day)
2
33
8
82
2
246
136
3270
6
33
2
0
Phenol
(kg/day)
132
794
2
40
3
0
Total
340
1290 373
3447
971
97
-------
COKE OVENS
QUENCH TOWER
UASTEWATER
TREATMENT
PLANT
BY-PRODUCT PLANT
STEAK
ELECTRICITY
COAL CHEMICALS
COKE OVEN GAS
AIR EMISSIONS
• QUENCH HATER
• COOLING TOWER VOLATILES
HATER EMISSIONS
• PROCESS WASTEWATERS
LAND EMISSIONS
• TREATMENT PLANT SLUDGE
FIGURE I
coke, coal chemicals, and coke oven gas. The mass
balance must also include air emissions from the open
cooling tower and the quench tower in the form of
volatiles and particulate matter. Water emissions may be
adequately represented by ammonia, cyanide, and
phenol. To control the wastewater effluents to the
degree required by current regulations, a new element
must be added—energy in the form of steam and
electricity is needed to operate the treatment systems.
Energy for Wastewater Control-Alternate Strategies
The energy system is examined more closely in Figure
C. It consists of a power plant, assumed to be a
coal-fired boiler, to raise steam and to generate elec-
tricity for the wastewater treatment plant. The power
plant also produces environmental emissions even
though the plant is configured to meet applicable air and
water regulations. Particulate matter, sulfur dioxide,
nitrogen oxides, and waste heat are emitted to the air.
Waste heat goes to the water, while land emissions are
ash and SC>2 scrubber sludge from the power plant, as
well as demineralization or softening sludge from the
boiler water treatment plant. An interesting problem
now arises. It appears that as one problem is solved-the
wastewater effluent problem from the coke plant-
another emission problem is created, namely the disposal
of effluents produced from generation of the required
steam and electricity. Furthermore, it seems obvious
that more and more energy will be required as the level
of wastewater treatment becomes more stringent. To
decrease the effluents from the coke plant, one must
the boiler plant. Several questions are posed. Are we
working at cross purposes? What is the net environ-
mental impact? How do we obtain an optimum level of
wastewater treatment which achieves the maximum
environmental improvement, considering all effects? To
answer these questions it is necessary to perform a
careful environmental assessment of the coking opera-
tion, including an examination of alternate strategies for
handling the wastewaters. Table C lists eight alternate
strategies (Cases 0 through 7) for controlling wastewater
discharges. Each strategy involves one of three levels of
wastewater treatment (Raw wastewater, Level I, Level
II), one of two levels of recycle (Loose, Tight), and one
of two quenching practices (Clean, Wastewater).
Flow processes for the wastewater treatment strate-
gies are shown in Figures D & E for a hypothetical coke
plant configured for this study. The wastewater flows
are generated from recovery operations found in many
steel plants. With a daily coal charge of 6000 tons (5443
kkg) and a daily furnace coke production of 4200 tons
(3810 kkg), such a plant would be among the largest 25
plants in the country. Level I treatment is wholly a
physical-chemical system employing a method of cya-
nide stripping based on existing technology developed
by Bethlehem Steel Corporation3, ammonia removal
using a conventional still, and phenol extraction based
on existing technology developed by Jones and Laughlin
Steel Corporation4. Level II is a higher level of
treatment, combining physical-chemical operations with
biological waste treatment. The biological plant is similar
to an existing facility at Bethlehem Steel and is designed
to reduce the carbonaceous oxygen demand, with
performance primarily set for phenolics reduction. These
treatment systems do not precisely correspond to
treatment levels designed to meet current EPA BPCTCA
or BATEA limits. However, Level I meets BPCTCA
guidelines for cyanide and ammonia; Level II meets all
BPCTCA guidelines and the BATEA guideline for
phenol.
The eight different control strategies each result in
pollutant emissions to the air, water, and land. Air
emissions originate from the coke quench tower, from
98
-------
ELECTRICITY
COAL
(FUEL)
STEAK
COKE PLANT WASTEWATER
TREATMENT PLANT
ENERGY PLANT
BOILER WATER TREATMENT PLANT
UTILITY AND POWER PLANT
STEAM GENERATION
ELECTRICITY GENERATION
LAND EMISSIONS
• ASH
• SLUDGE
HATER EMISSIONS
WASTE HEAT
AIR EMISSIONS
PM
I'ASTE HEAT
Table C. Coke Plant Wastewater Control Strategies
Case Treatment
Level of Recycle Type Quency
Loose Tight Clean Wastewater
0
1
2
3
4
5
6
7
Raw Wastewater
Raw Wastewater
Raw Wastewater
Raw Wastewater
Level I
Level I
Level II
Level II
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
the open cooling towers, and from the power plant
supplying electricity and/or steam to the treatment
process units. Water emissions arise from coke plant
wastewaters, from blast furnace wastewaters which
account for pollutants transferred by wastewater
quenching, and from power plant waste heat discharges.
Land emissions originate at the power plant, the quench
tower, the boiler water treatment plant, the coke plant
ammonia still, and the coke plant biological treatment
plant.
The foundation of the analysis is the construction of
an inventory of all principal pollutants emitted to air,
water, and land for each of the selected control
strategies. Figure F shows the daily emissions for a
selected list of pollutants from each of the active
operations for each control strategy. Measures were
generated for eight pollutants emitted to the air, six
pollutants to the water, and five pollutants to the land.
By itself, this accounting of the residuals shows the
relative complexity of the problem. It remains for the
community and the regulatory agency to develop an
aggregate summation of these different residuals in order
to select an overall best strategy for the environment as a
whole.
Cross-Media Analysis
Comparing the complete inventory of emissions with
the original wastewater loads (Figure F, Case 0) shows
that the reduction of emissions of ammonia, cyanide,
and phenol to the water involves the generation and
discharge of many other pollutants and treatment
residuals to the air and land. A comparison of the
relative environmental impact of the different strategies
demands the ability to compare trade-off effects, i.e.,
the effect on the environment of reducing mass emis-
sions of pollutants to the water while increasing mass
discharges of other pollutants to the air and land.
Reiquam, Dee, and Choi at the Battelle Memorial
Institute under a contract sponsored by the Council on
Environmental Quality and the EPA developed a tech-
nique for this purpose, termed Cross-Meida Analysis5.
This analysis starts with a mass emission inventory. A
hierarchical arrangement of weights is developed consist-
ing of two levels, media weights and pollutant weights.
99
-------
The first level of weights for air, water, and land may be
regional or applicable to the country as a whole. The
second level of pollutant weights establishes a mechan-
ism for allocating relative fractions of each of the media
weight totals to each pollutant. Choices between alter-
nate strategies are based on the relative values of a
numerical index calculated from the Cross-Media Analy-
sis.
The environmental degradation index (EDI) is ihs
arithmetic sum of the weighted damages for each
pollutant in each media,
EDI - z" d>-5 w> MP
where p is the pollutant index and
dp?s is the damage function for a selected strategy, s,
with
(0s
-------
air and water both ranked above the land. The CMU
system distributes the pollutant weights less evenly than
BMI and focuses on phenol in water as being the most
critical pollutant to control.
The mass emission inventory shown graphically in
Figure F must be converted to a set of numbers between
0 and 1, to be expressed as the damage function, dn, for
the cross-meida analysis. This study examined the
sensitivity of the environmental degradation index to the
procedure used for calculating damage. The simplest
damage function imaginable scale damage as a linear
function of the mass of pollutant discharged. One may
choose damage functions to scale relative emissions
non-linearly, so as to place heavy damage on any small
emission or to delay assignment of damage until a large
fraction of the largest possible emission is reached
(Figure G). The results of the sensitivity of the relative
rank of the coke plant strategies for nine damage
functions are shown in Table E. Using either the CMU or
the BMI weighting functions and the various damage
functions, the relative ranks of the coke plant waste-
AIR EMISSIONS c,
[HEAT*
10'
10
/1 \ /, 1I ' ix—r-3"
/\\ !ti\±£r:
water strategies are nearly the same. By comparing
absolute values of the SEI calculations as well as the
sensitivity of the ranks for each strategy, it is possible to
assemble a qualitative grouping of the coke plant
strategies shown in Table F.
Comparison of Wastewater Control Strategies
Table G shows that control of coke plant wastewaters
does result in environmental improvement for the
watercourse to which the plant discharges its wastes.
Control strategy Case 0 (loose recycle, no wastewater
treatment, discharge to the river) is chosen as the base
case against which all other strategies are compared. The
least desirable control strategies have negative SEI
values, indicating a net environmental damage compared
to the base case. In contrast, a large positive total SEI
value for a control strategy indicates net environmental
improvement compared to the base case. For all control
strategies, and either weighting method, positive SEI
values occur for the water media, indicating environ-
mental improvement over the base case.
Note, however, that environmental improvement for
the watercourse is coupled in every situation with
degradation of the air and land media. Values of zero for
the SEI mean that these cases are identical to the base
case. Furthermore, in some cases the net environmental
degradation of the air and land media are large enough
to negate the improvement which has taken place in the
watercourse. Environmental improvement in one media -
' here, water - is inextricably associated with deleterious
I I I I I I I
01234567
CASE
WATER EMISSIONS
LAND EMISSIONS
EC y
^ in£
o
a
0.1
FIGURE F. EMISSIONS INVENTORY FOR 3S10 KKG/DAY (1200 TON/DAY) COKE PLANT FOR LIGHT
SELECTED STRATEGIES.
•HEAT IN 106 BTU PER DAY
101
-------
Table D. Pollutant Weights (Wp) and Modifier Function (Mp)
for Coke Plant Wastewater Study
CMU Weights
Pollutant
To Water:
NH3
1OH
CN
SCN
Cl
Heat
Sum
To Land:
Ash, Coke Breeze
SO2-Lime Sludge
NH3-Lime Sludge
Boiler Water Sludge
Biological Sludge
Sum
To Air:
NOX
SO 2
PM
NHs
tOH
CN
Cl
Heat
Sum
Total
wp
5
321
22
3
1
22
374
41
54
54
54
54
255
30
70
60
26
48
82
25
30
371
1000
Mp
0.6
0.5
0.5
0.5
0.6
0.5
0.5
0.6
0.6
0.6
0.6
0.5
0.7
0.8
0.5
0.4
0.4
0.4
0.5
WpMp
3
160
11
2
1
11
20
32
32
32
32
15
49
48
13
19
33
10
15
BMI Weights
wp
52
84
74
56
33
74
373
42
58
58
58
58
274
22
43
56
47
56
60
47
22
353
1000
Mp
0.6
0.5
0.5
0.5
0.6
0.5
0.5
0.6
0.6
0.6
0.6
0.5
0.7
0.8
0.5
0.4
0.4
0.4
0.5
WpMp
31
42
37
28
20
37
21
35
35
35
35
11
30
45
24
22
24
19
11
Table E. Frequency Distribution of Alternative Strategies by Rank
" for Nine Damage Function Choice^
Number of Times Case Ranked As Shown (CMU Weights)
"~\Ronk
Case ^-\
0
1
2
3
4
5
6
7
1
X
I
X
6
2
X
X
X
2
1
1
X
1
4
2
X
X
3
X
X
X
X
2
7
X
X
4
2
4
1
2
X
X
X
X
5
2
1
5
X
1
X
X
X
6
3
1
3
X
X
X
2
X
7
1
1
X
X
X
X
7
X
8
X
X
X
X
X
X
X
9
Average
Rark
5.00
4.11
5.22
1.78
2.33
2.78
6.78
8.00
Number of Times Case Ranked As Shown (EMI Weights)
~^^Rank
Case — ~^
0
1
2
3
4
5
6
7
1
X
3
X
6
X
X
X
X
2
2
2
X
2
X
3
X
X
3
1
1
2
X
1
4
X
X
4
X
X
2
1
4
2
X
X
5
1
3
5
X
X
X
X
X
6
5
X
X
X
4
X
X
X
7
X
X
X
X
X
X
X
9
8
X
X
X
X
X
X
9
X
Average
Rank
4 67
2.73
4.33
1.56
4.78
2 89
8 00
7.00
102
-------
Case
TABLE F
Grouping of Wastewater Treatment Strategies
Treatment
Raw wastewater effluent; loose recycle;
wastewater quench
Level I treatment; tight recycle; waste-
water discharge to watercourse
Level II treatment; tight recycle;
wastewater discharge to watercourse
Level II treatment; tight recycle;
wastewater quench
Qualitative
Ranking
3 Raw wastewater effluent; tight recycle; Preferred
wastewater quench ~
5 Level I treatment; tight recycle; waste- Preferred
water quench
Better
than Base
Case
2 Raw wastewater effluent; tight recycle;
wastewater discharge to watercourse Base Case
0 Raw wastewater effluent; loose recycle;
wastewater discharge to watercourse
Not Pre-
ferred
TABLE G
Net Environmental Impact for Two Selected
Sets of Pollutant Weights and a S-shaped
Damage Function
(a = B = 1.5)
STRATEGY EFFECTIVENESS INDEX (CMU Weights).
Case
0
1
2
3
4
5
6
7
Case
0
1
2
3
4
5
6
7
Air
0
-39
- 5
-75
-16
-30
-28
-39
STRATEGY
Air
0
-47
- 3
-89
-12
-34
-20
-40
Water
0
85
3
172
162
170
164
166
Land
0
0
0
0
- 70
- 70
-148
-148
EFFECTIVENESS INDEX
Water
0
77
5
154
92
136
82
120
Land
0
0
0
0
- 76
- 76
-161
-161
Total
0
46
- 2
97
76
70
-12
-21
Rank
5
4
6
1
2
3
7
8
(BMI Weights)
Total
0
30
2
65
4
26
-99
-81
Rank
5
2
6
1
4
3
8
7
Figure G The Dajnage Function
Domage
Function
dP,s
Relative Moss Emission
The damage function is assumed to be the cumulative Beta Function
based on two parameters, a and p
Mean of distribution is [a/(u-* p)j and the variance of the distribu-
tion is [ap/Ca + p)2 (a + p + 1}] .
For nil cas>es , the damage function is 1 when the relative emission is
1, that is the actual emission is maximum When the actual emission
is zero, the damage function is zero
The following ranges of a and p were studied.
^\ p
a ^\
1.0
1 0
3 0
1 0
X
X
X
1 0
X
X
X
3 0
.\
X
X
cross-media effects, which may be large enough them-
selves to provide no net environmental improvement for
the control effort.
Conclusions
The prinicpal findings of this study apply to the coke
plant problem in particular, but suggest there may be
grave consequences whenever there is stringent effluent
regulation for separate media. Wastewater treatment
provides environmental improvement for one media,
water, but will lead to the degradation of the other
media, air and land. This is the phenomenon of
cross-media impact; energy requirements for treatment
processes create new pollutant residuals which are
smeared across all media. For some wastewater treat-
ment practices, the net environmental improvement due
to the practice is negative, i.e., cross-media effects are so
large as to negate the beneficial effects of improving the
water media. The frequency for which net degradation
of the environment is forecast from this analysis depends
on input parameter values and assumptions; this fre-
quency rises sharply with the stringency of wastewater
treatment.
It is useful to characterize the coke plant problem in
three ways - by type of quench water, by level of process
water recycle, and by level of treatment selected for
wastewaters. The cross-media analysis leads to the
following observations:
103
-------
• Quenching with coke plant effluents, regardless of
their level of treatment, appears to be a preferred
practice for the greatest net improvement of the
environment. This practice is preferred over discharge of
that effluent (at the same level of treatment) to
watercourse.
• Tight recycle of cooling waters rather than loose
recycle appears to be preferred for the greatest net
environmental improvement.
• For the wastewater control case in which tight
recycle of cooling waters is employed and the final
effluent is used for wastewater quenching, no waste-
water treatment is a preferred practice over either Level
I or Level II treatment, if the greatest net environmental
improvement is to achieved.
• For the wastewater control case in which tight
recycle of cooling waters is employed and the final
effluent is discharged to a watercourse, Level I is the
preferred wastewater treatment, if the greatest net
environmental improvement is to be realized. For this
case, this treatment level is preferred over the alterna-
tives of no treatment of Level II treatment.
• These results suggest that the current EPA effluent
standards for by-product coke plants, particularly the
BATEA (1983) limits, are too stringent to maximize the
net environmental improvement which can result from
the treatment and disposal of coke plant wastewaters.
The results of this study clearly support the conten-
tion that levels of environmental control must be
considered very carefully if maximum improvement of
the environment is to take place; stringent control of
emissions is not necessary the best course of action.
However, this analysis, like all analyses, is an approxi-
mation of reality, and not reality itself. In particular, the
cross-media technique requires many assumptions which
are open to question and interpretation. Nevertheless,
the results of the study appear robust enough that strong
conclusions can be stated regarding current by-product
coke plant effluent limitations. This analysis is offered
not to exacerbate the current controversy regarding
treatment and disposal of coke plant wastewaters but to
move the controversy toward more rational emphasis on
net improvement of the environment, rather than
emphasis on single media regulations and solutions.
References
1. U.S. Bureau of the Census, Statistical Abstract of the United
States- 1973 (94th Edition), Washington, D.C., 1973.
2. Iron and Steel Manufacturing Point Source Category, Effluent
Guidelines and Standards, Federal Register, Vol. 39, No. 126,
June 28, 1974.
3. Kurtz, J.K., "Recovery and Utilization of Sulfur from Coke
Oven Gas," in Problems and Control of Air Pollution, ed. by
F.S. Mallette, Remhold Publishing Corp., 1955.
4. Lauer, F., E.J. Littlewood, and J.J. Butler, "New Solvent
Extraction Process for Recovery of Phenols from Coke Plant
Aqueous Waste," Jones and Laughlin Steel Corporation.
Presented at Eastern States Blast Furnace and Coke Oven
Association Meeting, Pittsburgh, Pa., February 14, 1969.
5. Reiquam, H., N. Dee, and P. Choi, "Development of
Cross-Media Evaluation Methodology," Final Report to Coun-
cil on Environmental Quality and U.S. Environmental Protec-
tion Agency, Contract No. EQC315, Battelle Memorial
Institute, Columbus, Ohio, Volumes I and II, January 14,
1974 (PB232414/3WP); also "Assessing Cross-Media Im-
pacts," Environmental Science and Technology, Vol. 9, No.
2, February 1975.
6. Dunlap, R.W. and F.C. McMichael, "Environmental Impact of
Coke Plant Wastewater Treatment and Disposal," Journal of
Ironmaking and Steelmaking, in press.
7. Dunlap, R.W. and F.C. McMichael, "Air, Land, or Water: The
Dilemma of Coke Plant Wastewater Disposal," Environmental
Science and Technology, in press
104
-------
STUDIES ON OXIDATION PROCESSES OF CIANIDES AND
PHENOLS IN WASTE AND NATURAL WATERS BY USING CHLORINE DIOXIDE.
by A.N. Belevtzev, Ju.L. Maximenko.
Hypochlorite, chlorine and chloride of lime are
usually used as bactericidal and oxidizing agents in water
and waste treatment processes. However their usage
doesn't often produce significant effect.
Therefore the intensive searches of new oxidizing and
bactericidal agents for water treatment are lately carry-
ing out. At the institute VODGEO it was studied the
possibility of chlorine dioxide utilization for above
mentioned purposes in addition to testing for oxidation
processes of various substances contained in natural and
waste waters by using hypoclorites, ozone oxygen in the
air and other oxidizing agents. This oxidazmg agent was
selected due to a number of its advantages over other
oxidizing agents such as relative stability in water
solutions, high oxidation potential.
In the performed tests the main attention was given
to studyin the oxidation processes of simple and
complex cyanides, rhodonides, sulfides and phenols
because these compounds often occur in waste effluents
of various industries and also in stream waters.
The considered compounds are strong toxic, posess
offencive organoleptic properties and are converted to
nontoxic ones during oxidation distruction.
The present paper deals with the results of investiga-
tions in the field of oxidation of cyanide and phenolic
compounds.
Chemical effects of chlorine dioxide.
In the case chlorine dioxide interaction with reducers
it gains 1 or 5 electrons and is reduced to chlorite or
chloride ions that may be described by the following
reactions (1 - 6):
On the basis of known normal redox potentials of the
systems as 1 (Eg = 1.27 v) and 2(EQ = 1.5) and be using
Luter's rule.
(to - p)- Eonj/p = (m-n) • E om/n •'(ft-p) - E on/p
where m, n, p denote the degtee of valency and m > n >
P
as well as by using Nernet's equation.
where n is the quantity of transfered electrons the
normal redox potentials of systems as (3), (4), (5), (6)
were estimated that proved to be equal respectively
0.84V; 1.56v; 1.15v;0.77v.
The conducted calculations allowed chlorine dioxide
reduction to be presented in flow diagram in the
following oxidation reactions as:
in acid media
:0-'i,27,
- 1 1
» 1
£0-t,ttt
GO,
in alkaline media
The schemes show that in acid media chlorine dioxide
should be mainly reduced to chlorides as the redox
potential of system CL02/CL = l.5v more of that for
systems CL02/HCL02 = 1.21 v.
In alkaline media chlorine dioxide is reduced to
chlorite ions at a faster rate as the normal redox
potential of system CLO CLO2 = 1.15v is more of that
for system CLO2/CL = 0.85v.
Insofar as the potential of redox reaction is a
function of several other factors in the direction of
reactions it may be deviations depending on particular
conditions.
However the general regularity should be maintained.
By using the normal redox potential we estimated the
reaction potentials of chlorine dioxide interaction with
oxidable substances under various conditions, thereby
we selected the conditions of their carrying out, sched-
uled the proposed directions of reactions and their
products.
Oxidation of cyanides
All the water soluble cyanides except for the complex
CS'
105
-------
cyanides of iron are very toxic compounds. As a rule
cyanides affected by oxidizing agents are oxidized to
cyanates as follows:
which are then hydrolyzed forming carbonate and
ammonium ions that is described by the equation (8).
The estimations based on determination of the
reaction potential difference show that during the
oxidation process of cyanides chlorine dioxide should be
mainly reduced to chlorite ions as in alkaline media the
potential difference of systems C1O2/C1O2" and
CNO'/CN" is more of that for systems C1O2/C1" and
CNO-/CN-.
The estimations were experimentally confirmed dur-
ing cyanide oxidation of alkaline metals as well as
cyanides bound to complexes with zinc and cadmium.
The results of researches showed that simple cyanides
and cyanides bound to complexes with zinc and cad-
mium were oxidized to cyanates at the rate of chlorine
dioxide described by the following equations as: (9),
(10), (Fig. 1).
10
where Me = Zn^+ or Cd^+ (5, 2 mg per 1 mg of cyanide
ions).
In strong alkaline media (pH > 10) the reactions
proceed at faster rate. Oxidation of cyanides bound to
complexes with copper followed otherwise. In spite of
the fact that copper-cyanide complexes are more stable
versus ones contained zinc and cadmium they are
oxidized more readily at chlorine dioxide rate decreased
almost by five times.
The process is effected in two consecutive stages, at
first cyanides are oxidized to cyanates while chlorine
dioxide is reduced to chlorite ions that's given by
equation (1 1).
n
then the formed chlorite catalytically oxidizes the rest
cyanides thereby being reduced to chloride ions, as
follows:
12
In summation the process may be reproduced by the
following equation:
2 13
So on the basis of conducted investigations we may
state that cyanides bound to complexes with copper are
catalitically oxidized, as a result chlorine dioxide gains
five electrons and is reduced to chlorides.
The rate of process significantly depends on quantity
of copper in the complex.
The catalysis was found to take place if ratio
/Cu/;/CN-/ corresponded to complexes respectively
Cu(CN)^ and Cu(CN)2
The catalysis was not observed in the presence of the
complex Cu(CN)3" and of free cyanide ions in solution.
(Fig. 2).
The estimations of constants concerning complex
instability and the experimental data allow the assump-
/ro
Ion ratio (cjf"):(-l.*l)= '•:<- 1 o-zre.
] ! ' 2,51- 2 surve.
i ! i 2,j;3,1 - 3 :urve
1 ' ' a. = - •*• c-_rve.
Pig.1. Efiect of Chlorine Dioxide Rote on Oxidation
Proceaa of Cianidee.
106.
-------
tion to be made that the catalizators of process are itself
copper-cyanide complexes Cu(CN)2and Cu(CN)?".
At introducing copper ions into solutions of complex
cyanides of zince and cadmium the catalytic effect of
copper-cyanide complexes on oxidation process was
found out.
The oxidation process of cyanides bound to com-
plexes with nickel and cobalt proceeds with great
difficulties by the equation (14) and (15) when chloride
dioxide rate is of much above the theoretical one (8-10
mg/mg)
14
2 15
It was due to large losses of CLC>2 as a result of its
destruction caused by the low rate of oxidation process.
Chlorine dioxide cyanides bound to complexes with
iron are not oxidized. Chlorine dioxide effect on
ferrocyanides results in their oxidation only to ferro-
cyanides, i.e. oxidation of only metall in complex.
The formed cyanates produced from oxidation of
cyanides are oxidized by chlorine dioxide with much
more difficulty. The reaction occurs at marked rate only
at pH < 6. The products of oxidation there to proved to
be elementary nitrogen and bicarbonate ions.
So chlorine dioxide is reduced to chloride and
chloride ions as:
16
17
At the same time hydrolysis of cyanates with
subsequent formation of ammonium ions takes place at
pH < 5. The rates of both processes are proportional at
pH values in the range of 3.5 - 4.2.
Chlorine dioxide rate required for oxidation 1 mg of
cyanate ion is a function of pH value. It is on average
equal to 3.4 mg at pH values of 3.5-5.0, theoretical rate
by the reactions (1 6) and (17) amounts respectively 0.96
mg/mg and 4.82 mg/mg.
Oxidation of phenoiic compounds.
In complex problem of potable and waste water
treatment the removing of phenols refers to category of
technologic processes that require to be thoroughly
investigated. Some of researches have studied phenol
interaction with chlorine dioxide. However the obtained
results are contradictory in many respects especially as
concerns kinetics, mechanism and products of oxidation
reactions.
The investigators of our country disclosed that in acid
and neutral media phenol (carbolic acid) is readily
oxidized by chlorine dioxide at the rate of 1.2 mg/mg
(Figs. 3,4); the main products of oxidation is n6-
benzoquinone.
a
o
o
a
o
o
H
8
u
si
1st
dose,mg,per 1mg
of phenol.
Pig.J. Phenol concentration vari-
ations ve.CLOp dose.
60 120 YJ<7 Z1D
Time in minutes.
Fig.4. Kinetics of phenol oxidation
by using various CLOg doses.
107
-------
The oxidation rate and the required excess of
chlorine dioxide are functions both of initial phenol
concentration and of temperature.
Phenol concentrations vary from 50 to 0.02 mg/1
while the rate of CL02 increases in the 1.2-2.7 mg/mg
range.
Lowering the temperature results in decrease in
reaction rate. An increase in reaction rate at low
temperatures is achieved either by adding large quan-
tities of CL02 (for complete oxidation of phenol at the
temperature of 5°C the oxidizing agent is required to be
2-2.5 times of that at the temperature of 20°C) or by
increase in time constant up to 4-6 hours (Figs. 5-6).
Mechanism of one especially depend on pH value and
if in acid and neutral media the oxidation process occurs
only to benzoquinone whereas in alkaline solution the
reaction proceeds more deeply. Quinone formed at the
first stage is then oxidized to carbonic acid (Figs. 7, 8).
Pig.5
2 3 * S
CL02 rste Eg per 1 mg of phenol.
Effect of temperature onCLOp rate
required for complete phenol oxidation.
20
to &D JD
time in minutea.
.6 Effect pH value and temperature on phenol
oxidation rate.
2,5 3
6 r
pH value
Pig.7 Effect pH value nn phenol and n-benzoqulnone
trations at varioue CIOp doees.
1- 0,7 rag/rae.; 2-1,0 rag/me.t 3-1,2 mg/mg.(
5-5 mg/ -) rag phenol.
SO
Phenol tnc r>- oe::icc--r:i
tratlot vanaticlif. vr.
at •or. - 1-.C.
108
-------
By using physical-chemical methods of analysis for
acid fraction (on absorption spectre both in the ultra-
violet and polaro-graphically) malcic acid was identified
as a main product of oxidation. Oxalic acid is also
identified and a group of volatile acids is isolated (acetic
and formic acids are assumed to be among the acids).
During phenol oxidation chlorine dioxide is mainly
reduced to chloride ions. The process may be presented
by the following summarized equations:
in acid and neutral media
18
in alkaline media
CH-COOH
CH-COOH ,9
In alkaline media chlorine dioxide is partly reduced
to chlorite ions as:
CH-COOH
CH-COOH
20
Therefore chlorine dioxide rate required for oxida-
tion of one weight part of phenol in alkaline media
constitutes five weight parts that is some more of that
by equation (19) (2.4 mg/mg) and it is greatly less of
that by equation (2.0), therewith CLC>2 being reduced
to chlorite (12mg/mg).
Cresols and multiatomic phenols (hydroquinone,
resorcinol, pyrogallol, pyrocatechol) occur in addition to
simple phenol (carbolic acid) in waste effluents of
several industries and hence in water of streams into
which the mentioned effluents are discharged.
During chlorizating process cresols similarly carbolic
acid may form chloroderivatives the presence of which
in water is dangerous in organoleptic respect as in the
case of phenol content.
Multiatomic phenols are toxically harmful. Not so
much important cited in the literature on oxidation both
of cresols and multiatomic phenols either by chlorine
dioxide or other oxidizing agents justify that they are
more readily oxidized than carbolic acid especially in
alkaline media. As a result of their oxidation the proper
compounds of quinone structure assumed thereto to be
formed. The data as concerns subsequent conversions of
such compounds being influenced by various oxidizing
agents are not complete.
We attempted to disclose the mechanisms of oxida-
tion of cresols, quinones and multi- atomic phenols by
chlorine dioxide as well as to identify the products
produced during reactions.
The oxidation processes are considered on the follow-
ing examples:
— cresol oxidation on that of metacresols,
- quinone oxidation on that of n-benzoquinone,
- multiatomic phenols oxidation on that
resorcinol.
of
The studies on metacresol oxidation showed that it is
readily oxidized by chlorine dioxide. Both its oxidation
efficiency and specific rate of chlorine dioxide are only a
slight dependent on pH value in the 3-10 range.
The main products of reaction are quinone com-
pounds (it is likely their methyl-derivatives). However
their quantity didn't correspond to one of oxidized
cresol and didn't depend on pH value. So during
complete oxidation of cresol in amounts of 51 mg/1
quinone compounds were determined to be 23329
mg/1., i.e. only 55-60% of cresol was oxidized to
quinone.
It is possible to assume that at any pH value cresol
being affected by CLC>2 in addition to oxidation to
methilquinone undergoes more deep destruction by
forming the decomposition products of benzol zinc (for
example of methylmaleic acid) that are not identified in
our paper.
Chlorine dioxide rate during oxidation insignificantly
raised as pH value increases (over the range from 3 to
10) and was in amounts of 1.2 - 1.3 mg/mg.
The tests on n-benzoquinone interaction with chlo-
rine dioxide showed that inter n-benzoquinone was not
oxidized by chlorine dioxide in acid and neutral media.
The oxidation of n-benzoquinone effectively occurs in
alkaline media (pH^lO) at chlorine dioxide rate of 3 mg
per 1 mg of quinone.
N - quinone oxidation by chlorine dioxide in alkaline
media was found to be followed by forming carboxylic
acids among which maleic acid is the basic one.
The oxidation process may be described by the
equations (21), (22), as follows
0
CH-COOH
= If
CH-COOH
CH-COOH
During oxidation process chlorine dioxide is reduced
to chlorite and chloride ions that is confirmed by its rate
(3 mg/mg i.e. twice as much of that by equation (20)
(1.5 mg/mg) and 2.5 times as less of that by equation
(21) (7.5 mg/mg).
On the basis of performed investigations into oxida-
tion both carbolic acid and n-benzoquinone there may
be stated that hydroquinone will be oxidized only to
n-benzoquinone in acid and neutral media.
109
-------
In alkaline media the process proceeds similarly to
oxidation of quinone by breaking a ring and forming
carboxylic acid. For this reason it was of interest to
study oxidation process of other biatomic phenols
interarrangement of hydroxylic groups of which proved
to be either in meta or orto position rather than in para
one.
The resorcinol solutions (m - dioxybenzol) were
subjected to chlorine dioxide treatment. The investiga-
tion showed that oxidation intensity of resocinol insig-
nificantly raises as pH value increases (Fig. 9). So at
introducing CLC>2 in amounts of 0.5 mg per one mg. of
resorcinol the last was oxidozed by 84% at pH=3; by
91% at pH=5.5; by 94% at pH=8; by 100% at pH= value
in the range of 10.3-10.6. By using 2 mg of CLC>2 per 1
mg of resorcinol the last was oxidized completely at any
pH value. The process occurs by forming intermediate
compounds of quinone structure (OXY - para-quinone is
assumed to be).
In acid media the formed intermediate compounds
are simultaneously oxidized with resorcinol. In neutral
acid media the last do not subject to destruction until
the whole resorcinol is completely oxidized.
The process rate is enough high and the following
conditions are accepted to be optimal:
— the rate of oxidizing agent is of order of 1.5-2 mg
per one mg. of resorcinol,
— pH value is in 5.5 - 8 range.
— the contact time is over 20-30 minutes.
Organic acids and CC>2 are the end products of
reaction. Both maleic and oxalic acids among organic
ones are identified muconic acid is assumed to be
present.
On the basis of carried out investigations into
oxidation of n-benzoquinone and resorcinol as well as
after studying the numerous researches works we can
conclude:
— The oxidation process rate of diatomic phenols
(and quinones) depends on the interarrangement of
hydroxyl groups (and quinone grouping). The benzol
ring of phenol (or proper quinone) is less subjected to
breaking up under chlorine dioxide action if hydroxyl
groups (or quinone grouping) are in para-position rela-
tive to each other (hydroquinone, para-bezoquinone)
and they are distructed more readily when the group
arrangement is reproduced either in meta position
(resorcinol) or in orto position (pyrocatechol,
O-quinone).
Methyl-derivatives of quinone do not undergo to
destruction. Phenols having methyl substituent in side
chains are oxidized only to methyl-quinone.
Having studied chlorine dioxide reaction in the
presence of some specific substances we examined
chlorine dioxide effect on waste effluents containing
such compounds.
The biochemically treated refinery plant effluents
that contained nonoxidized oily hydrocarbons and the
products with various degree of their oxidation (COD is
of 100-150 mg/1) were affected by chlorine dioxide
effect.
The performed experiments showed that the sub-
stances retained in mentioned waste effluents being
biochemically treated are oxidized only in the presence
of large excess quantity of CLO2 with maximum effect
in strong alkaline media.
Removing COD by 90-95% is achieved by using
chlorine dioxide rate of 800-1000 mg/1 (5 - 8 mg per 1
mg of removed COD).
Phenols that contained in refinery plant effluents
being biochemically treated and in smallconcentrations
(0.1-1 mg/1) are effectively oxidized by chlorine diox-
ide. Their complete oxidation is obtained at CL02 rate
of 5 mg/1 over the period of 10-15 minutes.
The results of comparative tests on phenol oxidation
by calcium hydrochlorite in the same effluent indicated
that for achieving such effect "the activated chlorine"
required to be twenty times as much (100 mg/1).
Therefore chlorine dioxide utilization holds much
promise for advanced treatment of waste waters with
phenols content in small concentrations.
Fig. 9 3s sor •:-*}:;- inc. ^uin^i* t3ncs^^r=.:i7n
ve. CLC-v ^jse a" var» ju3 ^n vdiUC3.
110
-------
CURRENT STATUS AND DIRECTIONS OF DEVELOPMENT OF
PHYSICAL-CHEMICAL EFFLUENT TREATMENT IN THE PAPER INDUSTRY
Dr. Isaiah Gellman, Technical Director National Council
of the Paper Industry for Air and Stream Improvement,
Inc.
INTRODUCTION
For purposes of this discussion we feel it is desirable
to advance a definition of physical-chemical treatment
sufficiently broad to encompass the following ap-
proaches :
• chemical assistance to separation processes normally
defined as physical, such as flotation, sedimentation,
and filtration, particularly for removal of suspended
materials and dewatering of a variety of sludges,
• use of chemical reactants to remove or chemically
alter organic constituents of effluents whose presence
is not desired in the receiving stream,
• physical treatment of specific process effluent
streams to remove undesired chemical constituents, as
in steam-or air-stripping of spent kraft or sulfite
liquor condensates.
Viewed in these broad terms, physical-chemical treat-
ment is seen to have had a lengthy history of attention
in our industry, and therefore been the subject of
changing emphasis as well. Initially it took the form of
coagulant-assisted clarification of wastewater, particu-
larly at waste paperboard mills, for enhanced removal of
waste paper fines, and more highly clarified Whitewater
for improved in-process reuse.
More recently the emphasis has shifted toward (a)
possibilities for substituting physical-chemical treatment
for biological treatment as a means of meeting effluent
standards in such areas as fine paper and tissue produc-
tion, (b) removal of biologically refractive constituents
of pulping and bleaching effluents responsible for their
color, (c) enhanced dewatering of sludges high in
content of hydrophilic materials, and finally (d) selective
reduction of oxygen-demanding organic constituents of
particular process wastes as part of an approach toward
optimization of design of wastewater management sys-
tems combining physical-chemical and biological stages
deployed both within and external to the manufacturing
process.
The problems toward which physical-chemical treat-
ment is being directed are therefore numerous and
include the following, (a) improved effluent clarity
following either primary or secondary treatment, (b)
improved dewatering of sludges generated in either
treatment system, (c) enhanced opportunities for waste-
water reuse in papermaking through removal of sus-
pended matter and objectionable organic constituents,
(d) relief of overload conditions at biotreatment facil-
ities, (e) decolorization of pulping and bleaching efflu-
ents to avoid receiving water discoloration or other
undesired effects, (f) reduced possibilities for odor
emission at biotreatment facilities, (g) improved means
for processing neutral sulfite semichemical (NSSC) spent
liquors at non-integrated mills, and finally (h) economic
and technical optimization of wastewater management
systems.
The technologies included in consideration of phy-
sical-chemical treatment are therefore also quite num-
erous and include (a) sedimentation, (b) flotation, (c)
fine screening, (d) filtration through granular media, (e)
chemical precipitation, (f) chemical oxidation, (g) activ-
ated carbon adsorption, (h) steam or air stripping, (i) ion
exchange, (j) reverse osmosis and ultrafiltration,and (k)
solvent extraction, and perhaps others as well.
What follows in this paper is a systematic yet
necessarily brief and somewhat summary discussion of
this broad range of physical-chemical treatment ap-
proaches, and finally some comments as to the direc-
tions along which their further development and applic-
ation may lie.
SEPARATION OF RESIDUAL SUSPENDED SOLIDS
As suggested earlier, this approach has been pursued
more extensively at non-integrated fine paper and tissue
mills than at integrated chemical pulp and paper mills.
This is particularly the case with regard to further
clarification of excess machine white water before
discharge and has included chemically-assisted flotation,
pressure filtration, multimedia gravity filtration and
microstraining. More recently consideration has also
been given to improving the clarity of biotreated
effluents from both integrated and non-integrated mills.
Clarification of Non-Biologically Treated Effluent
Flotation Clarification of Tissue Mill Effluent - One
example of this approach is provided by the Scott Paper
Company facility at Fort Edward, New York. Pilot-scale
trails at this tissue mill led to a control installation
consisting of a pressurized air flotation system followed
by continuous centrifuge sludge dewatering. Chemical
treatment proposed for full-scale operation included a
standard cationic polyelectrolytic retention aid for
flotation, alum and caustic to aid floe formation and
activated silica for improved floe strength. Chemcial
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treatment costs were estimated in 1967 at $110,000
annually for treatment of 6 MGD. Since placing the
system in operation in 1972 there have been a series of
trails of various cationic polyelectrolytes, substitution of
lime for caustic for flocculation pH control, and
modification of the centrifuge as well. It is believed that
this process is capable of removal of 85 to 90 percent of
the suspended solids remaining after normal fibre re-
covery and 60 to 80 percent of the residual BOD.
Pressure Filtration of Fine Paper Mill Effluent
Weyerhaeuser's Miquon, Pennsylvania mill produces 250
TPD of fine printing papers using pulps delivered from
other mills, and employed 12,000 gallons of water per
ton at the time this control system was installed. The
mill was equipped with an alum and caustic-assisted
clarifier. Uncertainties regarding future water supply
sources and a desire to meet expected effluent standards
by means other than biological treatment prompted a
program that would lead to both improved effluent
quality and more extensive reuse. A pressure filter
evaluation program led to a decision to employ such a
filter believed capable of reducing clarifier effluent
suspended solids from 0.6 Ibs per 1000 gallons by 85
percent to 0.1 Ibs per 1000 gallons. In actual practice,
however, full-scale operation produced only 50 percent
reduction, attributed to floe degradation resulting from
excessive agitation of the filter feed.(l)
Further improvement has, however, been effected by
addition of a starch hydrolysis enzyme prior to clarif-
ication to eliminate the turbidity and suspension-
stabilizing properties of residual starch. Under these
conditions filtered effluent solids have been reduced to
0.05 Ibs per 1000 gallons from a clarifier influent level
of 5.6 Ibs per 1000 gallons. BOD reduction has,
however, remained below 20 percent.
Microstrainer Clarification of Fine Papermill Effluent
— Currently serving the Esleeck and Strathmore Paper
Company mills at Turners Falls, Massachusetts is a
microstrainer system consisting of two 10 foot diameter
x 10 foot length units with 23 and 35 micron screen
openings, handling 1.7 MGD. Coagulation and filtration
aids now in use include an anionic polyelectrolyte at a 1
ppm dosage, and either alum or caustic for pH adjust-
ment. Coupled with measure to (a) reduce starch usage
and improve retention, and (b) tighten control over
water usage, turbidity, suspended solids and BOD
reduction have reached 93, 98 and 88 percent respec-
tively. Deposition on the screens which interferes with
successful operation is overcome by periodic treatment
with 10 percent phosphoric acid. The sludge produced is
dewatered in a nearby municipal system at a cost of $ 1
per ton of paper production in addition to the normal
operating costs of $2.50 (1973 data) for the micro-
strainer system. (2) (3).
Polishing Filtration of Primary Effluent - Studies by
our organization at a coated fine paper mill have shown
erratic results stemming from frequent grade changes
and resultant changes in effluent composition. Using
polymeric addition to an alum and caustic-assisted
clarifier effluent, BOD reductions during polishing re-
mained below 40 percent while suspended solids and
turbidity were reduced by 80 and 60 percent respective-
ly. No provisions were developed for disposal of the
backwashed solids and this problem still remains to be
resolved. (4)
Clarification of Biologically Treated Effluent
The specifications of a small full-scale system serving
a tissue mill, and the results of several pilot plant trails
are summarized below.
Clarification of Tissue Mill Effluent - Ponderosa
Products at Flagstaff, Arizona currently produces 40
TPD non-integrated tissue and provides 10 days aerated
stabilization basin treatment followed by effluent polish-
ing in two anthracite/sand mixed media gravity filters
operated at 2 to 4 gallons/sq. ft./min. The filtrate is
chlorinated and recycled to the mill as process water.
Clarification of Kraft-NSSC Cross-Recovery Mill
Effluent — The Great Southern Paper Company at Cedar
Springs, Georgia discharges an aerated stabilization basin
effluent containing 65 ppm suspended solids. Coagula-
tion tests indicated an alum requirement for flocculation
of 70 ppm. Using multimedia filtration and no chemical
treatment a reduction of 50 percent suspended solids
was achieved at 2 gal/sq.ft./min with no measurable
BOD reduction. Alum dosage produced no discernible
benefits in either BOD or suspended solids reduction.
Scaleup costs for a 20 MGD system serving a 2000 TPD
mill indicated that costs for reducing suspended solids
from 12.5 to 4.2 Ibs per ton product would exceed $3
per ton. (5).
Polishing Filtration of Secondary Effluents — Studies
by our organization using three different filtration
approaches indicated modest suspended solids and BOD
reduction benefits with alum and polymer additions,
with the problems of filter backwash disposal still
remaining to be resolved. (4)
Microstraining of Secondary Effluent — The micro-
staining process is currently being commercialized at an
integrated bleached kraft mill practicing activated sludge
treatment. The system will contain three 6 foot diam. x
8 foot units using a 21 micron polyester fabric, loaded at
1300 gal/minute/filter. Backwash flow is to consume 2
percent of the throughput. Pilot plant results indicate
expected removals of 70 percent suspended solids and
30 percent BOD. (6)
Upgrading of Filtered Effluents for Process Reuse
The Weyerhaeuser, Miquon mill has also explored
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reuse possibilities for its pressure-filtered primary efflu-
ent. Filtrate color presents one obstacle to such reuse
due to the variety of white and colored grades produced.
This problem has been minimized by filtrate chlorina-
tion at a 3.5 ppm dosage rate. Slime accumulations
accompanying reuse were also minimized by a special
tank cleaning schedule. A major improvement in resue
capability was, however, achieved by introduction of
enzymes for residual starch hydrolysis as noted earlier.
Currently, recycled effluent accounts for 50 percent of
total daily water use.
SEPARATION OF DISSOLVED ORGANIC MATER
IALS
Among the physical-chemical treatment approaches
considered here are (a) condensate stripping and process-
ing, (b) NSSC spent liquor processing and integration of
reverse osmosis in the NSSC machine water system, and
(c) use of activated carbon in papermill effluent systems.
Processing of Chemical Pulping Liquor Recovery Con-
densates
Progress has been recorded recently in this area for
both kraft and sulfite liquor condensates as follows:
Kraft Condensate Processing — An early approach to
condensate stripping for BOD load reduction was report-
ed by Estridge (7) in which evaporator condensates,
barometric condenser water and turpentine decanter
underflow at an 850 ton per day linerboard mill were
recycled to a cooling tower. Aeration of these process
streams in this manner achieved a load reduction of
10,000 Ibs BOD per day due almost exclusively to air
stripping of methanol and other volatiles. An inherent
drawback lay, however, in the transfer of odorous
volatiles such as terpenes and organic sulfides to the
atmosphere.
This deficiency has been met by systems employing
either air or steam stripping with the stripped material
being burned at a subsequent combustion unit. An
example of such a system is that in operation at the
Mead Corporation mill at Escanaba, Michigan. Initially
this 800 ton bleached kraft mill installed a steam
stripper handling hot water accumulator overflow, tur-
pentine decanter overflow, evaporator condensates and
miscellaneous hot odorous streams. The initial objective
was to reduce odor release at the biotreatment system.
This was accomplished using a fractional distillation
column 53 feet high containing 24 trays, and steamed at
a 2.5 percent rate, with non-condensibles and collected
foul air burned in the lime kiln (8).
In 1973 a program was begun to determine whether
the mill BOD load could be significantly reduced as well.
Analysis showed that the stripper bottoms contained 15
to 18,000 Ibs BOD daily and that 90 percent of this
was accounted for by the methanol present in the
condensates. Modifications to the system enabled the
steam feed to be increased to 8 percent so that the
residual BOD was reduced to 4 to 5,000 Ibs daily for a
net reduction of 11 to 13,000 Ibs daily. Total steam and
power requirements are reported as 8000 Ibs/hr of 60 psi
steam and 65 HP for pumping condensates.
Sulfite Condensate Processing - Currently underway
at the Flambeau Paper Company, Park Falls, Wisconsin
sulfite mill is a project directed toward demonstrating
the possibilities for recovering methanol, furfural and
acetic acid as ethyl acetate from sulfate liquor evapo-
ration condensates. The process being investigated in-
volves steam stripping and activated carbon adsorption
to achieve removal and separation of these components.
This investigation expands on a project previously
conducted at the Institute of Paper Chemistry. (9)
Another physical-chemical treatment approach perti-
nent to sulfite liquor condensates involves the upward
adjustment of spent liquor pH prior to evaporation so as
to retain the volatile acids in the liquor concentrate,
permitting their destruction in the liquor furnace, rather
than allowing their entry into the condensates. Previous
studies have shown that upward adjustment of liquor pH
from 2.5 to 4.0 could result in condensate BOD load
reduction from 150 to 200 Ibs per ton to 50 Ibs per ton.
(10).
Processing of NSSC Spent Liquor and Excess Machine
Water
Spent Liquor Processing — Sonoco Products, Inc. at
Hartsville, S.C. recently has patented and commercial-
ized a novel process which facilitates the incineration of,
and subsequent chemical recovery from its spent sodi-
um-base NSSC liquor. Essentially, the NSSC liquor is
concentrated in multiple effect evaporators to 40 to 50
percent solids and mixed with finely divided reactive
alumina hydrate to form sodium aluminate which results
in solidification of the liquor concentrate. A rotary
pelletizer converts the solidified liquor to small pellets
with desirable incineration properties. First, a reducing
atmosphere is maintained within the pellet, leading
ultimately to formation of sodium aluminate and SO2.
Second, elevated temperature burning is possible at
1800°F. The ash is dissolved and used to scrub the SO2,
thereby releasing a hydrated alumina cake for recycle
and producing sodium sulfite solution for use in new
NSSC cook liquor. (11)
Processing of Excess NSSC Machine Water - Green
Bay Packaging Company at Green Bay, Wisconsin has
made a novel installation of reverse osmosis technology
designed to assist the operation of a high dissolved solids
machine water system. Excess water is bled out of the
system through a small 20 gpm reverse osmosis unit
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containing 300 separation modules, and reused as fresh
water for pump seals. This has assisted in reducing mill
BOD load to less than 10 Ibs per ton product. (12)
Removal of Organic Materials from Paper Mill Effluents
Using Activated Carbon
Explorations of activated carbon treatment have been
undertaken at a number of non-integrated paper mills
involving in several instances combined treatment with
municipal sewage. Included among these are (a) St.
Regis, Bucksport, Maine, (b) Fitchburg Papers, Fitch-
burg, Massachusetts, (c) Mohawk Papers, Wateford, New
York and (d) Neenah, Menasha, Wisconsin. Details of
several such projects are as follows:
Fitchburg, Mass. - Pilot studies for a full scale
project involving 14 MGD from two paper mills and 1.25
MGD municipal effluent were conducted using a process
consisting of chemical coagulation with alum, sedimenta-
tion and activated carbon column treatment. Process
results indicated an anticipated 50 percent BOD reduc-
tion through coagulation, followed by 82 and 86 percent
reduction in COD and BOD passing through four carbon
columns at 3.4 gal/sq. ft./min. The activated carbon
process design criteria selected were 7.2 Ibs carbon/lb
BOD at exhaustion, 30 minutes contact time, and
reactivation in a multiple hearth furnace. Costs were
estimated at $2.1 million for construction of the carbon
system in 1970, and $140,000 for annual operation, of
which 70 percent is carbon makeup. The facility has
been constructed, but operating results are not yet
available. (13)
Neenah - Menasha, Wisconsin — A pilot plant study
was performed using municipal sewage containing 80
percent paper mill effluent. The process studied involved
chemical coagulation with ferric chloride, sedimentation,
high rate filtration at 12 gal/sq. ft/min. to remove
fibrous material followed by a second filtration stage at
9 gal/sq. ft/min through PVC media, and upflow
expanded bed filtration through 1440 mesh carbon at 3
to 5 gal/sq. ft./min. Results obtained by the IPC study
group indicated removals of BOD, COD and suspended
solids prior to carbon treatment of 76, 83 and 98
percent respectively. Following carbon treatment, over-
all reductions were increased to 93,95 and 99.5 percent
respectively. Project costs were estimated in 1973 at 17
cents per 1000 gal capital and 35 cents per 1000 gal
operating for a total of 52 cents per 1000 gal for a 10
MGD plant. (14)
DECOLORIZATION OF KRAFT PULPING AND
BLEACHING EFFLUENTS
Basic Elements of Effluent Decolorization Problem
Definition
Measurement of Effluent and Receiving Water Color
Levels - Selection of methods for measurement of
pulping- and bleaching- derived color has always
proceeded from the observed similarity in hue between
so-called natural water color of swmp or decaying
vegetation origin and that of mill effluents. Starting with
color wheel visual comparators we have evolved most
recently to single wavelength spectrophotometric
measurements in the spectral range of 450 to 480 mu
where both effluents and the cobalt-chloroplatinate
standard display flat adsorption curves.
The procedure most recently found useful (15)
involves pH adjustment to 7.6 followed by filtration
through an 0.8 micron porosity membrane filter so as to
produce a high clarity sample without significant re-
moval of non-filterable color. Color is then determined
by light absorption measurement at 465 mu and
expressed in standard color units read against a calibra-
tion curve prepared with the above standard. While this
procedure is not as yet incorporated in Standard
Methods it has been recognized by EPA in its proposed
effluent color standards.
Detectible Changes in Receiving Water Color - One
major problem definition deficiency continues to exist
in the most important area of all, namely a determina-
tion of the variability in level of color detectibility in
different receiving waters, and at different points along
or overlooking such waters. We have recently completed
a pioneering investigation of this problem. These studies
have employed professionally screened observer panels
to determine (a) absolute thresholds of detectible color
level, (b) perceptible changes from a given visually
observable reference color level, and (c) the influence of
lighting conditions, water depth and quality, and observ-
er angle. The importance of such information in estab-
lishing rational water quality standards and ultimately
defining the goals of decolorization technology research
is seemingly obvious, yet such work has not bee
previously reported.
Adverse or Beneficial Effects of Receiving Water
Color — Aside from human objection to receiving water
discoloration on aesthetic grounds, little of substance
has been heard concerning other adverse effects. Occa-
sional comments are made concerning possible inter-
ference with light energy penetration for support of
photosynthetic primary productivity processes, yet no
evidence is presented to this effect. On the contrary, our
own aquatic biology productivity work using high
concentrations of biotreated colored effluents indicate
the absence of effects above color levels that would
probably be detected by humans. Downstream water
supply treatment problems receive only isolated mention
as a basis for setting decolorization requirements.
Inventory of Mill Process Color Loads and Sources —
Color load inventories are proceeding actively at selected
mills where decolorization needs have already been
identified as a consequence of inadequate receiving
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water dilution. Often these reflect application of some
control measures, and do not therefore provide neces-
sary broad background information. We have recently
completed a field survey of both bleached and unbleach-
ed chemical pulp mills, supplemented by determination
of the color contribution potential of numerous spent
pulping liquors, since these are the major source of pulp
mill color load. Preliminary findings for kraft mills
indicate a color equivalency of 2 Ibs of color units per Ib
of hardwood liquor solids, and 1.2 Ibs for softwood
liquors. On a mill-wide basis the average pulp mill color
load appears to fall between 100 and 200 Ibs per ton.
With regard to the bleach plant itself, the survey
indicates that the first two stages (chlorination and
caustic extraction) account for 200 Ibs color per ton at
hardwood mills, while in softwood operations the load is
350 Ibs.
Chemical Precipitation Processes for Effluent De-
colorization
General Basis for Precipitation Processes and their
Current Variants — The principal approach to chemical
precipitation has involved use of lime for that purpose.
More recently magnesium oxide has received attention
for NSSC effluent decolorization, while alum has recent-
ly found application for kraft effluent. As determined
by fundamental investigation at the New York State
College of Forestry at Syracuse University (16) (17) the
metal ion precipitation processes are all dependent on
the relatively low solubility of the metallic salts of the
colored weak organic acids.
A number of mill-scale variations on the lime precipi-
tation process have evolved in the last fifteen years
including:
• The massive lime process involving slaking of
reburned lime in caustic extract followed by re-solution
of the precipitated color in the recausticizing process
and ultimately burning of the colored organics in the
recovery furnace,
• addition of minimal lime dosages to total unbleach-
ed kraft effluent in the primary clarifier, precipitating
the color and dewatering the sludge in admixture with
the lime mud, and burning the color in the lime kiln,
• precipitation of colored substances in the caustic
extract or other specific colored effluents using minimal
amounts of lime slurry followed by dewatering in
admixture with lime mud and burning of the colored
organics in the lime kiln, or use of lime mud, fortified
with additional reburned lime or hydrate, to precipitate
color and again destruction in the kiln.
Massive Lime Treatment - This process received
large-scale studies at International Paper's Springhill,
Louisiana mill from 1970 to 1971 and was foimd to
remove over 90 percent of the caustic extract and
unbleached decker effluent, or about 60 to 70 percent
the process color load. A dosage of 20,000 ppm lime
produced a sludge settleable to 18 to 22 percent solids
and filterable to 50 percent for subsequent recausticizing
use. The demonstration plant was rated at 530 gpm
flow. An ability to produce a 740 color unit effluent was
demonstrated using the entire lime kiln output to treat
one-seventh of the mill flow. Costs were found to
approximate $1.80 per ton of bleached pulp. While the
reuse of white liquor was not affected, needs for
expansion of pulping liquor preparation and recovery
were identified. These have included (a) 15 to 20
percent additional capacity for green liquor slaking and
causticizing, white liquor clarification and lime mud
washing, and (b) 2 to 8 percent increases in pulp
washing, black liquor evaporation, recovery furnace and
accessories, and lime mud filtration and lime kiln
facilities. (18)
Since completion of the EPA contract mentioned
above, the demonstration facilities have been operated
using the lime mud modification with sweetener lime
added as needed to meet stoichiometric lime require-
ments. Both caustic extract and pulp mill decker
effluent have been studied with apparent success as
regards effluent decolorization and quality of the re-
burned lime, although caustic extract alone appears to
be more readily decolorized using the massive lime
alternative.
Lime Precipitation of Color During Primary Clarif-
ication — The first trial of this decolorization approach
was undertaken by Interstate Paper Company with EPA
support at the Riceboro, Georgia unbleached kraft
linerboard mill in 1968. Initial state permit requirements
for discharge to an extremely low flow estuary allowed a
color level of 30 units, so as to prevent excessive
discharge of slowly degradable lignin-derived organic
matter that would remain unoxidized during biotreat-
ment.
A lime precipitation process was installed at the
primary clarifier of this initially 4000 TPD mill at a
$451,000 cost. A dosage of 1000 ppm lime reduced the
color level from 1200 units to as little as 125 units. The
resultant sludge was sent to lagoon storage. Recarbon-
ation trials have shown that 20 minutes residence time
and lime kiln stack gas reduces residual lime from 750
ppm to 120 ppm. During these trials recarbonation
occured naturally in a large nonaerated biooxidation
basin. Here some color reversion ocurred, probably as a
result of alkaline extraction from the lagoon bottom.
Costs were estimated at $2 per ton total. (19)
The Continental Can Company, Hodge, Louisiana
mill recently completed work on an EPA-supported
contract involving full-scale demonstration of yet
another patented lime process modification (20) (21).
The process involves use of low lime dosages at the point
of primary clarification of unbleached kraft and NSSC
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boardmill effluents, followed by solid bowl centrifuga-
tion and calcining in the lime kiln for both fibrous
sludge disposal and lime recovery. The decolorized
effluent is recarbonated and clarified again with the
additional sludge dewatered on the lime mud vacuum
filter before calcining. Color reduction averaged 80
percent during periods of no NSSC production, and at
least 15 percent less with NSSC pulping operations. The
process is believed capable of over 90 percent decoloriza-
tion when operating on kraft alone. Operating costs
alone were estimated at 50
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osmosis processing of a number of pulp and paper waste
streams were reported in 1972 by Wiley et al. (19) (20)
Color rejection from kraft caustic bleach effluent was in
excess of 99 percent at inlet pressures of 500 psi at 35°C,
using cellulose acetate membranes. Optimum perform-
ance was achieved when concentrating the dilute feed by
a factor of about 10 for further separate processing and
chemical recovery of the concentrate.
It was, however, not possible to demonstrate sustain-
ed, long-term process operating feasibility in the extend-
ed life performance tests of the membrane equipment
available for these studies because of the low levels of
reliability of available membrane equipment. A tentative
cost estimate of $0.82 per 1000 gal. of product water
produced from caustic bleach effluent was reported.
Process costs appear quite sensitive to membrane module
replacement and maintenance charges, to membrane
permeation rates, and to increases in osmotic pressure as
concentration increases. Membrane fouling due to mater-
ial buildup on the membrane surface is also cited as
responsible for permeate yield rate decrease, and may
therefore require extensive pretreatment or cross-flow
application at high velocities.
Ultrafiltration — Reduction of color in pulp mill
effluents by ultrafiltration has been examined by
Champion International Corporation with partial assist-
ance form EPA with a 10,000 gallon per day (gpd) pilot
plant. This approach was justified on the basis that the
colored materials are of high molecular weight (> 1000).
Treated streams included decker effluents and pine
bleachery caustic extraction filtrate, which together
comprise about 80 percent of the color from a bleached
kraft mill. The pilot plant consisted of a five-stage
circular wound cellulose acetate membrane unit. High
color removal (90 to 97 percent) was demonstrated
when operating at water recovery ratios of 98.5 to 99
percent. Pilot plant capacity (membrane flux) was 15 to
20 gal/day/ft-' when operation proceeded smoothly.
However, plugging of the membrane cartridges by
residual particulates (even after precoat filtration) was
troublesome.
Several prefiltration, concentrate disposal, and water
reuse alternatives were evaluated.
Full-scale plant designs, and approximate capital and
operating costs were estimated for systems of 1 and 2
MGD capacity. Capital costs were projected at about
$700,000 for a 1 MGD plant, and $1,200,000 for a 2
MGD plant. Corresponding operating costs were projec-
ted at about 45o:/1000 gal (1 MGD) and 38
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agement concerning commercialization of ozone de-
colorization.
An example of the chlorination approach lies in
limited use at perhaps five to ten mills and involves
substitution of a hypochlorite stage for the conventional
caustic extraction stage. Since the latter contributes at
least 75 to 80 percent of the bleach plant color load, its
elimination can result in major load reduction. The
process change does not appear to be universally
applicable and results in substantial chemical cost
increments. Most recently investigators at Hooker
Chemical have proposed this modification as an "anti-
pollution," or APS, sequence yielding a 62 to 82 percent
color reduction. The change involves using large amounts
of chlorine dioxide immediately before the chlorination
stage in addition to substitution of sodium hypochlorite
for the caustic extraction stage (34).
A preliminary investigation of radiation-enhanced
oxidation of pulpmill effluents for color reduction has
been completed under our sponsorship at the Oak Ridge
National Laboratory (35). The results indicate that
exposure to 10 Roentgens in the presence of 500 psi
oxygen can achieve 90 percent decolorization.
DEWATERING OF HYDROUS SLUDGES
Sludges of a hydrous nature are being encountered
with increasing frequency as a consequence of (a)
improved capture of long-fibre sludge components, (b)
generation of excess biological cell material sludges in
activated sludge treatment, (c) production of organic
sludges during lime and alum-assisted coagulation or
precipitation of fibre fines and colored materials, respec-
ively. Polymer-assisted dewatering of such sludges is
receiving increased attention, as are efforts to improve
their dewatering characteristics through changes in phys-
ical state (freezing and thawing, and pressurized steam
treatment).
More recently interest has been renewed in solvent
addition processes capable of separating water from such
sludges, followed by distillation of the solvent from the
aqueous phase for reuse, as well as its recovery from the
sludge as it is subsequently dried. Triethylamine is
currently receiving consideration for this purpose.
(1) The need for development of more efficient
control systems to match the continued growth in size
and complexity of pulp and paper manufacturing facil-
ities at locations presenting substantial water quality
protection problems.
(2) The need for new control technologies capable of
removing effluent constituents that are only minimally
influenced by the more conventional sedimentation-bio-
treatment technology, such as effluent color, and possi-
bly foam generation.
(3) The desire to assemble optimized waste water
management systems combining a variety of control
technologies so as to assure their most cost effective and
dependable operation.
(4) The desire to increase opportunities for reuse of
treated process wastewater both for water conservation
purposes and to minimize discharge.
Some of the areas that suggest themselves for possible
cooperative study include the following:
(1) Determination of water quality needs for both
pulp and paper manufacture as a guide to development
of specific effluent treatment objectives — hence identi-
fying further physical-chemical treatment possibilities.
(2) Development of standardized test procedures for
evaluation of polymeric or other chemical aids to the
dewatering of sludges and the clarification of effluents.
(3) Examination of the effectiveness of various in-
process streams for regeneration of resin systems used
for decolorization, as well as activated carbon.
(4) Examination of chemical recovery steps available
for achieving reuse of calcium and aluminum cations for
precipitation of colored effluent components.
Finally, common attention might be given to an
examination of those environmental quality problems
confronting our industry which our limited experience
in physical-chemical treatment leads us to believe should
be addressed by such technology in proper combination
with the more widespread sedimentation-biotreatment
technology.
SUMMARY - DEVELOPMENTAL TRENDS AND
POSSIBLE AREAS FOR COOPERATIVE STUDY
It should be evident from this necessarily brief review
of physical-chemical treatment applications and possibil-
ities that they cover a wide range of approaches,
objectives and technologies. While such treatment is only
beginning to gain a position in the spectrum of control
technologies in actual use, the possibilities are encourag-
ing for their further development. This stems from four
basic considerations, as follows:
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E.L., U.S. Patent 3,639,206 (February
E.L. "Color Removal and Sludge Re-
(15) "An Investigation of Improved Procedures for
Measurement of Mill Effluent and Receiving Water
Color," NCASI Technical Bulletin No. 253 (December
1971)
(16) "The Mechanisms of Color Removal in the
Treatment of Pulping and Bleaching Effluents with
Lime-I Treatment of Caustic Extraction Stage Bleaching
Effluent," NCASI Technical Bulleting No. 239 (July
1970)
(17) "The Mechanisms of Color Removal in the
Treatment of Pulping and Bleaching Effluents with
Lime-II Treatment of Chlorination Stage Bleaching
Effluents," NCASI Technical Bulletin No. 242 (Dec-
ember 1970)
(18) "Color Removal from Kraft Pulp Mill Effluents
by Massive Lime Treatment," EPA Report 122-73-086
(February 1973)
(19) "Color Removal from Kraft Pulping Effluent by
lime Addition," EPA Technology Transfer, 2nd Capsule
Report (1973)
(20) Spruill,
1972)
(21) Spruill,
covery from Total Mill Effluent," Tappi 56 (4) :98
(1973)
(22) Environmental Applications of Advanced
Instrument Analyses: Assistance Project F7 69-71, p. 50
EPA Report R2-74-155 (May 1973)
(23) Gould, M., U.S. Patent 3,531,370 (September
1970)
(24) Fuller, R.R., U.S. Patent 3,627,679 (December
1971)
(25) Berger, H.F. and Smith, D.R., "Waste Water
Renovation," Tappi 51 (10) 37A (1968)
(26) McGlasson, W.G., Thibodeaux, L.J. and Berger,
H.F., "Potential Uses of Activated Carbon for Waste-
water Renovation," Tappi 49 (12) 521 (1966)
(27) NCASI Stream Improvement Technical Bulletin
No. 199, "Treatment of Pulp Mill Effluents with
Activated Carbn," (1967)
(28) Wiley, A.J., Dubey, G.A. and Bansal, I.K.,
"Reverse Osmosis Concentration of Dilute Pulp and
Paper Effluents," EPA Final Report Project No. 12040
EEL (1972)
(29) Wiley, A.J., Schaarpf, K. Bansal, I.K. and Arps,
D., Tappi55(12} 1671(1972)
(30) Rohm and Haas Co., "Decolorization of Kraft
Bleaching Effluents Using Amberlite XAD-8 Polymeric
Adsorbent," (Aug. 1971)
(31) Sanks, R.K., "Ion Exchange Color and Mineral
Removal from Kraft Bleach Wastes," EPA Report
R2-73-255 (May 1973)
(32) Chamberlin, T.A. etal "Color Removal From
Bleached Kraft Effluents," Proc. 1975 TAPPI Environ-
mental Conference
(33) "Preliminary Laboratory Studies of the De-
colorization and Bactericidal Properties of Ozone in Pulp
and Paper Mill Effluents," NCASI Technical Bulletin
No. 269 (January 1974)
(34) Lowe, K.E., "Bleaching at Crossroads," Pulp &
Paper p. 88 (August 1973)
(35) "A Preliminary Investigation of Radiation and
Enhanced Oxidation of Pulp Mill Effluents for Color
Reduction," NCASI Technical Bulletin No. 271 (Febru-
ary 1974)
119
-------
TREATMENT OF CONCENTRATED WASTE WATERS CONTAINING OIL EMULSIONS.
by V.G. Ponomarev and S.B. Zakharina Ail-Union
Scientific-Research Institute VODGEO.
For metal cutting in mechanical shops special cutting
oils and coolants are used representing stable emulsions
with the mineral oil content up to 50 g/1.
For the preparation of such coolants cutting emul-
sions are used, defined as concentrated emulsions of
mineral oil and emulsifying agents of the type "water in
oil". Various organic matters can be used as emulsifying
agents. When cutting emulsions are mixed with water,
phase reversel takes place and "oil in water" emulsion
generates spontaneously. Cutting emulsion content in
the emulsion generated is equal to 5-10 per cent.
Sometimes soda is introduced into it in quantity of
0.03%, pH of the emulsions used varies from 7 to 10.
An Analysis of the emulsion content in the process of
its use at the machine-building plant has revealed that
during its service-life all its components are present in it
in proportional quantities. Any significant changes in oil
and emulsifying agents contents or in the alkalinity are
not observed.
Despite high resistance to degradation, service life of
emulsions averages about a month, after this they are
renewed.
Increase in the coolant's viscosity as a result of the
liquid phase evaporation serves as one of the reasons for
its service life reduction. To prevent it water is periodic-
ally added to the coolant.
In the process of its use the coolant is polluted by
mechanical impurities, the main part of which consists
of metal particles and of grinding materials. These
admixtures concentration is constantly increasing, which
can make the further use of the emulsion impossible. In
order to prolong its service life the waste emulsion
should be subjected to mechanical treatment. At the
Soviet enterprises waste emulsion before its return for
reuse is usually fed to installations for mechanical
treatment, such as settling tanks, magnetic separators
and filters manufactured from different materials.
Coolant's decay as a result of the anaeobic micro
flora of sulphate-reducing bacteria growth in it is the
third reason for the coolant service life reduction.
Bacteria reduce sulphate present in the emulsion to
hydrogen sulphide.
To prevent emulsion decay in the course of its service
it is recommended to blow it off by air, thus creating
aerobic conditions and preventing anaerobic bacteria
growth.
Blowing off is recommended to carry out in collect-
ing reservoires installed near the lathes, so compressed
air should be fed to the lathes.
At the enterprises in operation where construction of
air conduits is not possible, for decay prevention
bactericidal matters such as hexachlorophen are added
to the emulsion in quantity of 0.02% of the emulsion
volume. As analyses showed, addition of hexachloro-
phen prolongs service life of the emulsion up to 4
months.
Based on the bench-scale and industrial tests a general
technological scheme of an installation for waste emul-
sion regeneration was developed (Fig. I). According to
this scheme polluted emulsion is fed to the setting tank
(I), where suspended matter and oil are separated.
Floated oil is fed to the oil collector (5), and suspended
matter collected in the conic part is introduced to the
sludge-holding tank (4). Treatment of emulsion from
fine suspended solids is conducted on filters (2). After
being treated on filters the emulsion is pumped over to
the seltling-reacting tank (3) to which if necessary and if
there is odour of hydrogen sulphide 15 mg/1 of KMnO4,
I g/1 of sodium nitrate and 0.2 g/1 of hexachlorophen in
the alkali solution are added. Besides, to renew emulsion
properties cutting emulsion and water are to be added to
it. After all components were added to the emulsion, it
is mixed with the compressed air, then settled to remove
non-ernulsified oil and then is fed to the shop. Oil
isolated in the settling-reacting tank is pumped over to
the oil collector (5) and then is fed to regeneration.
Sludge from the sludge-holding tank is fed to the filter
presses for dehydration (6).
Technical-economic evaluation of the suggested emul-
sion regeneration scheme shows that regeneration of 10
m^/day of the emulsion will permit to save about 21000
rubles per year.
It waste emulsions can not regenerate, they should be
decontaminated at the installations for their breaking.
While emulsions are settling within 1-3 months oil
concentration in them decreases only by 10-20 per cent.
Due to high stability of emulsive waste waters they
should be treated with the use of such chemical-physical
methods as coagulation, pressure flotation with the
addition of reagents and centrifugation.
In the emulsion coagulation analyses ferric salts, salts
of aluminium, calcium, magnesium, which at hydrolysis
give positively charged colloids of hydroxides, were used
as reagents. At their interaction with the negatively
charged micelles of the emulsion mutual coagulation
takes place with the formation of suspensions, contain-
ing particles of metal hydroxides, sorbing at their
surfaces drops of oil and of emulsifying agents.
Application of ferric sulfate with the addition of
lime, ferric chlorate with sulfuric acid and aluminium
sulfate with lime or sodium hydrate have appeared to be
the most effective for emulsion breaking. Dosage of
coagulants varies within the range of 3-7 g/1 depending
on the emulsified oil content.
120
-------
steaai
chlorophen
Fig.I Scheme of emulsion regeneration
As analyses indicated, the volume of the sludge
separated averages 17-20 per cent of the total effluent.
Depending on the oil concentration the sludge can take
different positions in the settling tank, that is to settle to
the bottom of the tank, or to float to the surface. In a
number of cases the sludge formed is located in the form
of floes along the whole volume of the settling tank.
That is why the determination of the method for sludge
separation from the waste emulsion is one of the
important problems.
The method of pressure flotation with the application
of reagents was investigated, and the investigations
showed that this method is possible to be applied for the
purpose in view. It was discovered at the pilot plant that
saturation of the emulsion with the air should be
conducted at the pressure of 3 atm., and the saturation
filter-press . ^ regeneration
Pig.2 Scheme of emulsion breaking by flotation
121
-------
duration is 5 minutes and the flotation period should be
abaut 15-20 minutes. Reagents should be added to the
emulsion immediately before the saturator.
Optimum doses of coagulating agents at the emulsion
oil content of 30 g/1 are equal to:
aluminium sulfate
ferrous sulfate
ferrous chloride
g/1
g/1
6
7
4 g/1
with addition of sulfuric acid 6 g/1
The volume of the foam formed is equal to 20-25% of
the effluent being treated volume.
The content of ether soluble matters in the treated
waste is equal to 0.15 - 0.3 g/1. The analysis showed that
mineral oil concentration was equal to 50-70 mg/1, and
the residual ether soluble matters are emulsifying agents.
With the aim of the foam volume decrease in view,
tests were carried out with the Soviet flocculating agents
available, such as the "Komet" flocculating agent and
polyacrylamide. It was established that at these floc-
culating agents dose of 10-100 mg/1 the foam volume is
possible to be decreased by 30-50%. "The Komet"
flocculating agent has appeared to be the most effective.
As a result of the investigations in the centrifugal
field ability for waste emulsion degradation it was
established that emulsions were broken at separation
factor of 7500, centrifugation period being equal to
15-60 minutes and depends on the emulsion composi-
tion. Before centrifugation the emulsion should be
treated by sulfuric acid to reach minimum pH value,
taking into consideration corrosive properties of the
metal, the centrifuge is made of (Fig. 3).
Being acidified to pH = 7 emulsions are broken by
60-80%. Several types of the emulsions used may be
broken in the centrifugal field by 90-98% at their
acidification up to pH = 3.
Centrifugation may be used as an independent
method for emulsive effluent treatment when acid-proof
equipment is available. Final treatment of the effluent
may be conducted jointly with the total effluent of the
enterprise.
On the basis of the investigations carried out, a
scheme of the full-scale installation for waste oil
emulsions degradation was developed which is now being
built at several industrial plants (Fig. 2).
According to this scheme waste emulsion is directed
from the shop to the settling tank (I) to which sulfuric
acid is fed. Mixing with the acid is carried on by means
of compressed air. Thus pH of the emulsion is reduced
to 6-7. After waste emulsion was settled during an hour
floated oil is fed to the oil collector (2), and the sludge is
introduced to the sludge-holing tank (3). Emulsion,
which was not broken in the settling tank is fed to the
flotation unit, where the second stage of its treatment is
carried on.
Coagulating agent, which is fed from the dose, is
mixed with the effluent before the saturator (4). The
saturator should be designed in such a way, that all
discharge of the emulsive effluent passes through it.
Emulsion saturated with the air is introduced to the
flotation compartment (5). The condensed foam is
skimmed off the surface of the flotation compartment
and is fed to the foam collector (6). Clarified liquid is
neutralized by means of NaOh, water or lime to pH = 7,
and then is discharged to the sewerage system where it is
mixed with the waste waters from the enterprises and
goes to the treatment facilities of the plant for the
full-scale treatment.
Foam from the flocculation unit is fed to the burners
for incineration or is mixed with the sludge separated
from the total effluent of the enterprise to be treated
jointly.
Technical-economic evaluation of the scheme con-
sidered has shown that the cost of the oil and emulsion
bearing effluent by physical-chemical methods is 60-70
copecks/m-'.
Hyperfiltration as one of the methods may be
recommended for the use at the enterprises discharging
sludge-holding tank
Pig.3 Scheme of emulsion breaking by separation
122
-------
small amounts of emulsive effluents, in order of 1-5
m-'/day.
Preliminary investigations show that at the initial oil
concentration of 30-40 g/1 concentration up to 350 g/1
is reached without any decrease of membrane productiv-
ity; oil content in the treated water is 7-8 mg/1 at the
membrane selectivity of 75-80% by sodium chloride.
Further concentration may lead to a slip of contamina-
tions.
Researches on this method to be used for oil and
emulsion containing waste waters are still being carried
on.
The choice of the method for emulsive waste water
treatment should be made in accordance with the local
conditions of the enterprise. Here the ratio between
emulsive effluent and the total effluent of the enterprise
should be taken into consideration as well as the
properties of the emulsions discharged and also the
presence of free industrial areas. The final scheme of
treatment should be confirmed by a technical-economic
calculation.
123
-------
ADVANCED WASTEWATER TREATMENT FOR AN
ORGANIC CHEMICALS MANUFACTURING COMPLEX
by
Anton C. Marek, Jr - Chief Sanitary Engineer Organic
Chemicals Division
William Askins - Environmental Engineer Engineering
and Construction Division
ABSTRACT
The Bound Brook plant of the American Cyanamid
Company manufactures dyes, chemical intermediates,
organic pigments, plastic additives, Pharmaceuticals, fine
chemicals, agricultural chemicals, elastomers and rubber
chemicals. The plant's extremely complex wastewater
stream now receives primary and secondary treatment.
Because of State and Federal regulation and because of
the effluent's impact on the receiving water, American
Cyanamid is designing an advanced wastewater treat-
ment system consisting of trimedia filtration and carbon
adsorption to further treat the Bound Brook plant
effluent. Alternative treatment processes were con-
sidered in paper studies and in laboratory bench scale
studies and were rejected. Both filtration and carbon
adsorption processes were tested in pilot studies, and
selected versions of both processes are being further
evaluated in on-going prototype demonstrations. The
full scale system is currently under design, and the
system will be fully operational in December 1977.
ACKNOWLEDGMENTS
The authors gratefully acknowledge Messrs. W. Allen, G.
Apfel, N.A. Kaye, H.R. Kemme, S.A. Leshaw, A.G.
Potter, C.P. Priesing, F.B. Van Cor and D.R. Wilcox of
American Cyanamid Company for their guidance and
technical support throughout this project and the
preparation of this paper.
The authors also wish to express their appreciation for
the technical assistance provided by the Calgon Corpora-
tion, Pittsburgh, Pennsylvania; Gulp Wesner Culp, El
Dorado Hills, California; E.I. Du Pont de Nemours and
Company, Wilmington, Delaware; Envirotech Corpora-
tion, Salt Lake City, Utah; ICI United States, Wilming-
ton, Delaware; Metcalf & Eddy Inc., Boston, Massachu-
setts; Neptune Microfloc, Inc., Corvallis, Oregon;Nichols
Engineering and Research Corporation, Belle Mead, New
Jersey and Zurn Industries, Rochester, New York.
FIGURES
Figure No.
1
2
3
4
5
6
7
9
10
Flow Diagram — Primary and
Secondary Treatment Facilities
TOC Isotherm Plot
Flow Diagram - 5-In Diameter GAC
Pilot Plant
TOC Breakthrough Curve
Flow Diagram - 30-In Diameter Pilot
Column
TOC Removal - 30-In Diameter Column
Headloss Profile Without Coagulant
Aid
Headloss Profile With Coagulant Aid
Cluster Filter Configuration
Flow Diagram — AWT Facilities
TABLES
Table No.
1
2
Influent Wastewater Characteristics
Typical Removal Efficiencies in Bio-
logical Treatment System
5-In Diameter GAC Pilot Plant -
Dissolved Solids Data
5-In Diameter GAC Pilot Plant -
Ammonia and Organic Nitrogen
Data
Powdered Activated Carbon Pilot
Studies I — Performance Summary
Powdered Activated Carbon Pilot
Studies II - Performance Summary
Summary of Pilot Filter Media
124
-------
The Bound Brook, New Jersey plant of American
Cynamid Company employs 2,200 persons and pro-
duces over 1,000 different products including dyes,
chemical intermediates, organic pigments, plastic addi-
tives, Pharmaceuticals, fine chemicals, agricultural chem-
icals, elastomers and rubber chemicals. The multiple
waste discharges from the production operations are
combined with cooling water, sanitary sewage and storm
water runoff from the plant area to form a single
effluent stream that is processed in an existing waste
treatment facility. Typical ranges of biochemical oxygen
demand (BOD), chemical oxygen demand (COD), color
and total organic carbon (TOC) in the raw waste stream
are shown in Table 1.
TABLE 1
Influent Wastewater Characteristics
Parameter
BOD
COD
TOC
Color
Concentration Range
270-400 mg/1
1,000-1,400 mg/1
260-350 mg/1
400-600 CDAPHA units
Wastewater treatment has been a major part of the
Bound Brook operation for over 30 years. As wastewater
technology has progressed with time, the Bound Brook
Plant has made significant improvements to its waste-
water treatment facilities. Figure 1 shows a flow diagram
of the existing facilities. In the late 1930's, a primary
treatment plant was installed at a cost of $500,000. This
plant included a 19 million gallon (7.2 x 10^ cu m)
equalization basin, a lime neutralization facility with a
capacity to neutralize an equivalent of 30 tons (27.2
metric tons) of sulfuric acid a day, and a 60 million
gallon (2.3 x 10^ cu m) primary settling lagoon.
Beginning in 1949, extensive laboratory and pilot
plant studies were initiated to procure desing data for
the construction of an activated sludge treatment plant.
This facility was built in 1957 at a cost of $4,500,000
and placed into operation in 1958. The secondary waste
treatment facilities consist of six aeration basins, each
having a capacity of 3-1/3 million gallons (1.3 x 10^ cu
m), six secondary clarifiers, and a chlorine contact
chamber. In addition to treating its industrial waste, the
Bound Brook plant provides secondary treatment for up
to 5 mgd (1.9 x 10^ cu m/day) a day of primary treated
waste from a regional municipal wastewater treatment
authority serving the region surrounding the Bound
Brook plant. Our contract with the Authority will expire
in 1977, and their wastewaters will not be included in
our advanced wastewater treatment system.
Our present waste treatment facilities provide better
than a 90% reduction in the BOD loading and approxi-
mately a 65% reduction in TOC and COD. The color
bodies present in our raw wastes are resistant to
biodegradation and as a result, little color is removed
through our existing facilities. Table 2 summarizes the
BOD, COD and TOC removals obtained in our treatment
facilities.
FIGURE 1
WASTE TREATMENT PLANT FLOW DIAGRAM
PLANT SEWERS AMERICAN CYANAMID COMPANY
BOUND BROOK, NEW JERSEY
AERATION BASINS
INFLUENT
PUMPS
SOMERSET
RAHITAN VALLEY
SEWERAGE
AUTHORITY
«— CHLORINE
(bfb
AIR BLOWERS
3 *
J >
3 "
) \
;
"a
* ^
o
1 ^
4
O
'O
4
"o:
2
J
f
i
i
i
i
,Q.
* t=
O
¥
o
o,
.t
i «
o
4
i
t
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T
1
1
1
6*
* *
o
a s
,f,
0
'a
t
o,
6
J
f
1
1
CLARIFIERS
/~6^\
1
y-i '
/ '/T\ .
/ ^ •
1 ' /^l\
I (Oil
n x_y
" /X^A
11 ' / /^r\
r-Hlf®-
MM /^
i, H IK' /T\
"II 1 1 x
1 1 1 1 1 1 1 III
1 1 1 IJ. 1 1 1 ». w
t "Hill '
1 1 1 1 1
CHLORINE
CONTACT
.'CHAMBER
O>TO RIVER
ASTE SLUDGE
PPPCOP RETURN
rrTTTT SVUDGE
RETURN SLUDGE TT f { ( PUMPS
125
-------
TABLE 2
Typical Removal Efficiencies in
Biological Treatment System
Parameter
BOD
COD
TOC
9 Removal
90-95
55-70
60-70
Unfortunately, many of the organic compounds present
in our raw wastewater are resistant to biodegradation,
and significant quantities of nonbiodegradable organics
are present in our secondary effluent. In 1971 it became
evident that additional treatment would be required,
particularly for color, odor, toxicity and suspended
solids.
For an understanding of the problem one must consider
the relationship between the Bound Brook plant dis-
charge and the flow in the receiving stream, the Raritan
River. The Raritan River has an average flow of
approximately 1 billion gallons per day (3.8 x 10^ cu
m/day) at the location of the Bound Brook discharge.
Seasonal variations, however, can be significant. Mini-
mum low flow is maintained at 90 million gallons per
day (3.4 x 10-* cu m/day) by release of water form an
upstream reservoir. Under these low flow conditions
which occur sporadically throughout the year, the
Bound Brook plant effluent makes up approximately
25% of the river flow.
Two alternatives were considered for upgrading the
Bound Brook plant effluent. They were: 1) heavier
emphasis on at-source treatment or control in the
manufacturing areas and, 2) additional end-of-pipe treat-
ment (advanced wastewater treatment) to supplement
biological treatment. Consideration was given to a study
program to isolate and treat concentrated waste streams
containing refractory organics within the manufacturing
area. However, manpower requirements and costs for
individual waste treatment facilities scattered through-
out the plant would have been excessive. The constantly
changing product mix, and the possibility of process
upsets and spills during transportation of raw materials
from building to building, contributed to the doubt that
this effort would be worthwhile. It would have been
extremely difficult to predict the effects of removing
components from the main waste stream, particularly
what new toxicants might be created by the admixture
of waste streams that in themselves are nontoxic. As a
result, it was decided to proceed with further investiga-
tion of advanced wastewater treatment techniques.
Preliminary literature reviews and bench scale studies
were conducted to evaluate activated carbon adsorption,
high lime treatment and ozonation. High lime treatment
produced no significant reductions in either color or
organic matter. Ozone requirements to reduce the color
and refractory levels to those achievable with activated
carbon were impractical. Capital and operating cost for
an ozonation plant were well beyond that for an
activated carbon treatment facility. However, carbon
isotherms conducted during the preliminary develop-
ment work indicated that carbon would substantially
reduce color, foam and refractory organics.
Since our preliminary isotherms were conducted in
1971, we have run approximately 100 additional iso-
therms on samples of our final effluent. Figure 2 shows
the extreme variation in adsorption capacity of virgin
carbon that is experienced with our particular waste-
water.
Both granular and powdered activated carbons were
investigated in pilot plant studies to evaluate the
feasibility of their use of improving the Bound Brook
effluent. Granular activated carbon (GAC) adsorption
studies were conducted in pilot units consisting of four 6
ft x 5 in inside diameter (1.8 m x 12.7 cm) columns
mounted on steel frames and piped with 1/2 in (1.3 cm)
polyethylene tubing. The use of polyethylene tubing
TOTAL ORGANIC CARBON
ISOTHERMS
00
QC
0 40
O
Q 0 20
LU
O
o 10
0 03
0 06
DC
(rj 0 04
O
o
I— 0 02
C/3
40 60 80 100
200
TOTAL ORGANIC CARBON mg/l
126
-------
provided the flexibility for connecting the columns for
either parallel or series operation as a particular test
required. Figure 3 is a flow diagram of our GAC pilot
system which was used for most of these studies. A side
stream of clarified effluent taken from one of our
existing clarifiers was pumped to a temporary storage
drum and thence to the pilot columns. One set of
columns was piped for parallel operation and packed
with filtration media to prefilter the effluent for test
Runs 2, 3 and 4. The second set of columns was packed
with granular carbon and piped for either series or
parallel operation depending on the test program. The
adsorption data obtained from these studies were used
to develop the process design for our full scale granular
activated carbon facilities. During each of the runs,
samples of effluent to the pilot plant system and
effluent from each column were analyzed daily for TOC,
COD, color and suspended solids.
Runs 1 and 2 were conducted for the purpose of
obtaining breakthrough data for TOC, COD and color.
For these runs, the 5-in (12.7 cm) diameter pilot plant
was operated in a downflow packed bed mode with the
four adsorption columns piped in series. For Run 1, the
adsorption columns were fed unfiltered clarified effluent
and were operated at a hydraulic loading rate of 1.9
gpm/sq ft (77.3 1/min/sq m). For Run 2, the influent
was prefiltered through a mixed media of coal, sand and
garnet before being fed to the adsorption columns. The
flow rate for Run 2 was 3.4 gpm/sq ft (138 1/min/sq m).
Figure 4 shows the breakthrough curve for TOC develop-
ed for Run 2.
In addition to the routine TOC, COD, color and
suspended solids analyses, special samples from Run 1
were analyzed for dissolved solids, ammonia and organic
nitrogen. Based on 20 analyses performed throughout
Run 1, the average reduction in total dissolved solids
through the adsorption columns was only 3%. Ammonia
and organic nitrogen analyses were performed during the
first 16 days of operation. During this period there was
no observed reduction in the ammonia nitrogen con-
centration, however, there was an observed 85% reduc-
tion in the organic nitrogen concentration. Tables 3 and
4 summarize the dissolved solids, ammonia and organic
nitrogen data collected through Run 1.
Exhaused carbon from Runs 1 and 2 was sent to an
outside laboratory for regeneration studies and reused in
succeeding runs. Run 3 was conducted to obtain
adsorption data using a downflow moving bed system
with regenerated carbon. The feed for this run was
prefiltered. In the run, all four columns were initially
charged with approximately 4 ft (1.2 m) of virgin
activated carbon. As the carbon in the lead column
became exhaused, the column was removed from service,
repacked with regenerated carbon from Run 1 plus a 5%
virgin makeup and placed back on stream at the end of
the four column series.
5" DIAMETER GRANULAR ACTIVATED CARBON PILOT PLANT
BACKWASH
*" OUTLET
FILTRATION
MEDIA
GRANULAR
ACTIVATED CARBON
APPROX 1 0'
127
-------
BREAKTHROUGH CURVE for TOTAL ORGANIC CARBON
RUN 2 - 5" DIAMETER COLUMNS
90
80
O
CD
DC
O
O
o
_i
<
»-
o
30
10
30
TIME - DAYS
As part of our regeneration program, the efficiency of
the regenerated carbon compared to virgin carbon was
evaluated in order to establish design parameters for a
full scale regeneration facility. Based on the information
TABLE 3
5-In Diameter GAC Pilot Plant -
Dissolved Solids Data
Effluent
Concentration
mg/1
2,843
2,176
2,578
3,802
2,427
2,668
1,863
2,210
2,019
2,017
2,394
2,268
2,524
2,718
2,172
2,341
1,876
2,413
2,470
2,300
2,354 mg/1
Average Reduction = 3%
Cumulative Flow
248
5,638
11,115
11,886
13,050
13,807
14,374
14,764
15,567
16,007
18,233
21,237
22,765
23,594
24,344
25,459
25,852
26,616
27,780
28,160
Average Concentration
Influent
Concentration
mg/1
3,002
2,268
2,689
2,913
2,511
2,777
1,942
2,236
2,059
2,068
2,467
2,380
2,529
2,752
2,238
2,361
1,870
2,449
2,595
2,335
2,422 mg/1
available in the literature at the time, we expected
adsorption activity losses in the range of 10-15% based
on one regeneration cycle. Comparisons of the once
regenerated carbon with virgin carbon using the adsorp-
tion isotherms, indicated that activity losses in the range
of 30-50% were being experienced. As a result, our pilot
plant program was extended in order to conduct
TABLE 4
Organic
Nitrogen Concentration
3
3
1
1
1
3
2
3
2
1
1
1
t^
2 mg/1
Cumulative Flo'
Gal
641
1.421
1,829
2,209
2,389
2,976
3.353
4,107
4,487
4,861
5,251
5,d38
6,038
Average
5-In Diameter GAC Pilot Plant -
Ammonia and Organic Nitrogen Data
Ammonia
Nitrogen Concentration
rf Influent Effluent
34 33
34 33
27 27
28 28
34 33
41 39
45 42
42 40
51 54
58 56
49 49
45 44
44 43_
41 mg/1 40 mg/1
128
-------
additional column studies during which different car-
bons and regeneration conditions were evaluated for
adsorption capacity through multiple regenerations. For
these tests, the pilot columns were piped in parallel so
that each column was fed the same wastewater. In each
of the four exhaustion runs one column was used as a
control and was packed with virgin carbon; a second
column contained carbon that had been acid washed
prior to regeneration using 1.5% hydrochloric acid
solution; a third column contained regenerated carbon
from the previous run without pretreatment; and the
fourth column contained a competitive carbon which
was being used for comparative purposes. Based on a
comparison of adsorption capacities for total organic
carbon after three cycles of regeneration, a carbon was
found that could be regenerated to approximately
75-80% of its virgin adsorption capacity while keeping
its physical losses to within 7%.
The use of powdered activated carbon to upgrade the
Bound Brook plant effluent was also evaluated during
two separate pilot plant studies. Both studies employed
a process in which the controlled addition of powdered
activated carbon (PAC) to aeration chambers in acti-
vated sludge units was evaluated. The studies were
conducted using the Bound Brook primary treated
effluent as feed to the activated sludge systems.
A preliminary PAC study was conducted during the first
quarter of 1973. For this study the beneficial effects of
adding low dosages of powdered activated carbon to our
activated sludge system were investigated on a pilot
scale. At the time of this evaluation, there were no
proven techniques to separate exhausted powdered
activated carbon from the biological sludge to regenerate
it for reuse. The investigation, therefore, was based on
the addition of powdered activated carbon on a throw-
away basis. For this study two 115-gallon (0.44 cu m)
capacity activated sludge systems were established. Both
units were operated to simulate the existing activated
sludge plant without the addition of the primary treated
waste from the Somerset-Raritan Valley Sewage Au-
thority.
The pilot plants were operated as plug flow units with a
20-hour detention time, a 30% return sludge ratio and a
mixed liquor suspended solids concentration ranging
from 3,500-5,500 mg/1. Following the initial start-up,
the units were allowed to run for 22 days to reach
steady state conditions and a stable BOD removal
efficiency.
Four separate dosage levels; 42 mg/1, 84 mg/1, 126
mg/1 and 168 mg/1; of powdered activated carbon were
evaluated in the pilot units. The second unit was
operated as a control throughout the study. Table 5
summarizes the results of this 3-month study. In general,
there were no significant reductions in the TOC or COD
levels in the effluent of the powdered activated carbon
system even at dosage rates of 168 mg of powdered
carbon per liter of influent waste. The most significant
improvement was in the color removal at the 168 mg/1
dosage level. The color removal efficiency was increased
to 33% compared to a 7% level for the control unit. The
residual color, however, averaged 331 CDAPHA units
and was still readily noticeable. It was obvious from this
preliminary investigation that much greater carbon
dosage rates would be necessary in order to produce a
powdered activated carbon system effluent that would
be comparable to that achieved with granular activated
carbon.
The second PAC process investigation was initiated in
January 1974. At that time, powdered activated carbon
had been successfully regenerated using a modified
transport reactor. As a result of this work, the addition
TABLE 5
Powdered Activated Carbon Pilot Studies I - Performance Summary
Activated
Sludge Unit
Control
PAC 4 2 mg/1
Control
PAC 84 mg/1
Control
PAC126mg/l
Control
PAC 168 mg/1
BOD
Influent
mg/1
263
350
333
312
Effluent
mg/1
19
25
12
20
24
13
9
9
Removal
%
93
90
97
94
93
96
97
97
TOC
Influent
mg/1
205
280
254
263
Effluent
mg/1
77
77
73
84
81
73
70
60
Removal
%
62
62
74
70
68
71
73
77
COLOR
Influent
CDAPHA
414
452
417
491
Effluent
CDAPHA
430
399
398
332
450
341
459
331
Removal
(4)
4
12
27
(8)
18
7
33
PAC = Powdered Activated Carbon
129
-------
of powdered activated carbon to the existing activated
sludge plant at dosage rates in excess of 200 mg/1
became attractive. The purpose of this second study was
to determine the powdered activated carbon dosage
requirements necessary to produce an effluent of similar
quality to that obtained with granular activated carbon.
This study was conducted using four completely mixed
biounits. Each unit consisted of a 6.3-liter aeration
chamber and a 4-liter gravity clarifier section. Return
sludge was drawn automatically from the clarifier
bottoms into the aeration chambers. One biounit was set
up as a control, and the other three were run at various
powdered activated carbon feed concentrations. All four
units were operated with an average detention time of
14 hours and a sludge age ranging from 10-14 days.
Powdered activated carbon feed rates ranging from 340
to 990 mg/1 of carbon were investigated. Table 6
summarizes the results of this study. It was concluded
that the powdered activated carbon process would
require exorbitant carbon dosages in order to produce a
final effluent with low color and TOC. It was further
concluded that these dosage requirements were neither
economical nor practical.
Data generated in the 5-in (12.7 cm) diameter column
studies and the PAC studies were ultimately used to
evaluate 17 possible alternative processes for upgrading
the Bound Brook system. These processes included
granular systems, powdered activated carbon systems
and combined powdered/granular activated carbon sys-
tems. The most attractive process from a technical
standpoint and a capital and operating cost was the
upflow, expanded, pulse-bed design.
To further test this design a larger granular activated
carbon prototype was installed in 1974. Figure 5 shows
the flow diagram of the 30-in (76.2 cm) diameter pilot
system. The carbon column is 30-in (76.2 cm) in
diameter x 35 ft (10.7 m) on the straight side with a 60°
cone bottom and is constructed of fiber glass. Filtered
wastewater is pumped into the bottom of the column
through five 1-in (2.5 cm) diameter nozzles located in
the cone section. The feedwater passes up through the
bed at a hydraulic flow rate of 8 gpm/sq ft (326
1/min/sq m). Each day a pulse of exhausted carbon
ranging from 2.5 to 5%, depending on the organic
loading, is removed from the bottom of the column,
while an equivalent amount of fresh carbon is added to
the top of the bed.
Currently, the column is only being pulsed at a 2.5%
rate. The bed depth of the column is maintained at
approximately 30 ft (9.2 m), thereby providing a
detention time of approximately 30 minutes. Presently,
the column is being pulsed using virgin carbon; however,
by the end of the year, we will begin using regenerated
carbon for pulsing. Our test program is designed to run
through five complete cycles of regeneration with the
carbon now being exhausted. Our purpose is to further
optimize the regeneration conditions for our spent
carbon and to better define the adsorption capacity of
the carbon after several regenerations.
Exhausted carbon from this column is being regenerated
in a 3-ft (0.92 m) diameter x 6-hearth multiple hearth
pilot furnace. Figure 6 shows recent influent and
effluent TOC concentrations to the column based on a
2.5% pulse. The TOC removal through the column for
this period averaged 68%.
Initially it was planned to operate the advanced waste-
water treatment system without filtration of the waste-
water, and it was believed that the upflow expanded bed
could accommodate the range of suspended solids
loading anticipated from the secondary treatment sys-
tem. However, two factors caused us to include a
filtration system in our design: 1) stringent limitations
placed by the EPA on our effluent suspended solids and
2) poor operating experience in our prototype carbon
studies caused in part by high suspended solids levels in
the secondary effluent.
The EPA imposed a suspended solid limitation of our
wastewater discharge of 1,950 pounds per day (885
TABLE 6
Powdered Activated Carbon Pilot Studies II - Performance Summary
BOD
Activated
Sludge Unit
Control
PAC 340 mg/1
PAC 580 mg/1
Control
PAC 7 90 mg/1
PAC 990 mg/1
Influent
mg/1
366
396
Effluent
mg/1
21
32
28
10
Removal
94
91
92
97
98
98
Influent
mg/1
261
267
TOC
Effluent
mg/1
114
97
76
101
34
33
Removal
%
54
63
71
62
87
88
COLOR
Influent
CDAPHA
502
435
Effluent
CDAPHA
515
150
94
465
73
67
Removal
(3)
70
81
(7)
83
85
130
-------
30" DIAMETER GAG PILOT PLANT SYSTEM
CLAHIFIER
SUMP
kg/day) daily average and 3,440 pounds per day (1,560
kg/day) daily maximum, which equates to 12 mg/1 daily
average and 21 mg/1 daily maximum at a design flow of
20 mgd (7.6 x 10^ cu m/day). Even with greatly
improved control of the solids concentration in our
aeration basins, we anticipate an average concentration
of approximately 30 mg/1 suspended solids in the
secondary effluent. Therefore, it was necessary to
include filtration of effluent in our design.
The second factor was not anticipated and manifested
itself only after the carbon prototype had been in
operation for 5 days. Without warning, 13 ft (4.0 m) of
the 28 ft (8.5 m) of carbon in the column was carried
TOTAL ORGANIC CARBON REMOVAL
30" DIAMETER PILOT CARBON COLUMN
2
o
m
cc
<
o
o
2~
<; D>
SE
cc
O
PULSE CONDITIONS:
VIRGIN CARBON
2.5% per day
FLOW RATE:
8 gpm/ft2
INFLUENT
EFFLUENT
. ^ . — ^X-
1 1 1 1 1 1 1
1 5
10 15 20 25 30
TIME - DAYS
131
-------
out of the column by the effluent flow. This phenom-
enon occurred two more times during the initial runs
without effluent filtration. It was postulated that solids
accumulation in the lower portions of the carbon bed
and the possible buildup of gas bubbles in the bed
contributed to these carbon carry-overs. It was decided
that the expense of wastewater filtration was justified
because large carbon losses of the type just described
would be intolerable in the full scale system. Therefore,
independent of the regulatory considerations, it was
decided to include a wastewater filtration system in our
design and to place the system ahead of the carbon
columns.
To determine the type of filtration system that will yield
the best results at the least cost, three small pilot
columns, an upflow prototype column and a larger
prototype downflow column were utilized. The pilot
columns were used primarily to select the type of
filter media for use in a downflow configuration. The
prototype filters were used to decide between an upflow
and downflow configuration and to determine design
parameters, utilizing the media type selected in the pilot
columns.
The pilot columns were leased from a filter media
supplier and consisted of 4-1/2 in (11.4 cm) diameter
clear plastic columns with connections for operation in a
downflow configuration and for backwashing with
water. Three types of dual media and three types of
trimedia were tested. The dual media consisted of a base
layer of sand and a top layer of coal. The trimedia
consisted of a bottom layer of garnet, a middle layer of
sand, and a top layer of coal. Table 7 shows the grain
size ranges of the sand and coal in the three types of
dual media and the grain size ranges of the garnet, sand
and coal in the three types of trimedia.
It was determined that trimedia Type C yielded the
highest removal of suspended solids within an acceptable
range of head loss. Not that this filtration media has a
higher percentage of fine garnet than the other media
tested, and closely resembles media typically used in
water treatment. Examination of the suspended solids in
the secondary effluent shows that the particles are
smaller than those in a "typical" secondary effluent and
that they lie within a very narrow range of particle sizes.
This examination gives strength to the decision for small
grain size filter media.
The upflow prototype unit consisted of a 16-in (40.6
cm) diameter column filled with 6 ft (1.8 m) of graded
media ranging from coarse gravel to fine sand. Suspend-
ed solids removal efficiency, headloss buildup and
breakthrough were determined both with and without
coagulant aid. It was determined that the unit could be
operated at rates up to 10 gpm/sq ft (407 1/min/sqm),
but that breakthrough occurred without warning and
TABLE 7
Summary of Pilot Filter Media
Type
Component Depth, In
Effective Size, Uniformity
mm Coefficient
Dual Media A
Dual Media B
Dual Media C
Trimedia A
Trimedia B
Trimedia C
Coal
Sand
Coal
Sand
Coal
Sand
Coal
Sand
Garnet
Coal
Coal
Sand
Garnet
Coal
Sand
Garnet
24
10
24
10
24
12
24
9
3
16
8
9
3
16
14
6
1.2
0.5
1.4
0.5
1.2-1.4
0.6-0.7
1.0
0.45
0.2
2.0
1.0
0.45
0.2
1.0
0.45
0.2
1.3
1.3
1.3
1.3
1.6
1.7
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
132
-------
that the filter could not be backwashed sufficiently
without expenditure of excessive amounts of energy and
time. It was also determined that a gravity downflow
configuration was more economical to install.
The large prototype downflow filter is 4 ft (1.2 m) in
diameter and is 35 ft (10.7 m) high. The filter is
provided with instrumentation to measure flow rate
through the filter, headloss across the filter, differential
pressure drop across 2-3A in (7 cm) increments of bed
depth and backwash flow rate.
Tests were run to determine optimal feed rate, suspend-
ed solids removal efficiency, headloss buildup, break-
through and backwash water characters!tics. In addition,
profiles of pressure drop through the bed were drawn to
determine how much of the filter bed was being utilized
and whether there was excessive headloss across the
media interfaces. It was found that suspended solids
removal efficiency varied from 64 to 84% at suspended
solids feed concentrations varying from 16 to 37 mg/1.
Headloss buildup was extremely slow with some filter
runs exceeding 24 hours before the filter was back-
washed. The filter was operated successfully at rates up
to 8 gpm/sq ft (326 1/min/sq m). Figure 7 shows a
typical headloss profile through the filter bed with no
coagulant aid used. Note the peaks occurring at the
media interface locations, indicating that substantial
quantities of solids are being trapped at these interfaces.
Figure 8 shows a typical headloss profile through the
bed when a coagulant aid was used. Note that although
solids removal efficiency remains high, the solids built
up at the surface of the filter, and filter runs were
drastically shortened.
It was decided from the results of the prototype studies
that a downflow filter packed with trimedia would be
used. Air backwash will be employed to ensure that the
suspended solids trapped in the lower portions of the
bed will be removed. The backwash cycle will be
initiated by headloss buildup rather than solids break-
through.
The results of all the paper studies, pilot tests and
HEADLOSS PROFILE
WITHOUT
COAGULANT AID
4' DIAMETER PILOT FILTER
COAL
FLOW RATE: 6 gpm/sq. It.
TPI-MEDIA TYPE C
SAND
GARNET*
2 4 6 8 10 12 14
INCREMENTAL HEADLOSS
INCHES PER 2.75" of
FILTRATION MEDIA
HEADLOSS PROFILE WITH
COAGULANT AID
4' DIAMETER PILOT FILTER
LU
I
o
X 20
1-
Q.
LU
Q
Q
LU
CD
FLOW RATE 6 gpm/sq ft.
TRI-MEDIA TYPE C
COAL
SAND
GARNET
02 6 10 14 18 22 26 30
INCREMENTAL HEADLOSS
INCHES PER 2.75" of
FILTRATION MEDIA
133
-------
prototype studies were analyzed to determine design
parameters for the full scale plant. The trimedia filters
are designed for a hydraulic loading of 5 gpm/sq ft (204
1/min/sq m) with one filter cell out of service for
backwashing. The backwash cycle will consist of drawing
down of the liquid level in the cell being back washed to
within 6 in (15.2 cm) of the media surface, air scouring
at a rate of 3-5 cfm/sq ft (0.9-1.5 cu m/min/sq m) for 5
minutes, air scouring at the same rate plus water
backwashing at a rate of 3-5 gpm/sq ft (122-204
1/min/sq m) for 2-3 minutes, water backwashing alone
at a rate of 15 gpm/sq ft (611 1/min/sq m) for up to 10
minutes, and gradually shutting off the backwash water
over a period of 4 minutes in order to reclassify the filter
media.
The physical configuration of the filters is shown in
Figure 9, and is known as a cluster filter design. The
actual filter will consist of two of these clusters with the
flow split between them. Each cell of the cluster acts as
an individual filter and can be isolated from the other
seven cells. Each cell will be 22 x 23 ft (6.7 x 7.0 m),
and will contain approximately 900 nozzles set at 9-in
(22.9 cm) centers in a false bottom. Liquid flows into a
splitter box located above the center column and divides
evenly among the four cells in the cluster. Flow
continues by gravity through the media and nozzles into
a false bottom, then discharges into an effluent channel,
and drops over a weir into a sump. When backwash is
initiated by a high water level above the media, the
water is drawn down through a siphon. Air is pumped
into the false bottom, and is distributed evenly among
the nozzles during the air scour. A water backwash is
then initiated with water distributing evenly among the
nozzles to complete the backwash cycle.
The carbon columns are designed for a hydraulic loading
of 8 gpm/sq ft (326 1/mm/sq m) with 5% of the carbon
bed volume being pulsed each day on the average. The
physical configuration of the columns consists of ten
16-ft (4.9 m) diameter x 40-ft (12.2 m) straight side
columns with 45° cone bottoms. The ten columns will
be piped in parallel and will be charged with 30 ft (9.2
m) of carbon. Waste water will be introduced to the
bottom of each column through eight inlet ports
projecting into the cone bottom. At the design hydraulic
loading of 8 gpm/sq ft (326 1/min/sq m), a linear
velocity of approximately 1 ft/min (0.31 m/min) will be
DOWNFLOW CLUSTER FILTER
Courtesy of General Filter Company
134
-------
experienced, and a contact time of 30 minutes will
result. The carbon bed is not restrained vertically, and
operates as an upflow expanded bed. A unique feature
of this design is that spent carbon can be removed
simultaneously with the addition of fresh carbon with-
out altering the flow rate through the column. The pulse
design allows operation of the columns in a manner that
approximates countercurrent movement of the waste-
water and carbon, thereby providing efficient utilization
of the carbon.
Figure 10 shows the general arrangement of the com-
ponents of the advanced wastewater treatment system,
including the carbon transport system and carbon
regeneration system. A spent pulse of carbon will be
transferred as a slurry to a spent carbon storage tank and
then to a dewatering screw. The dewatering screw will
permit the carbon to drain to approximately 50%
moisture before it is fed into the 26-ft (7.9 m) diameter
multiple hearth furnace for regeneration. The spent
carbon will be regenerated thermally in a closely
controlled atmosphere and temperature profile with a
maximum temperature of approximately 1,750°F
(954°C). Steam will be injected into the furnace to
enhance the reactivation step. Following regeneration,
the carbon will be water quenched to reduce the
temperature to below 100°F (38°C). From the quench
tank, the carbon will be transferred to the regenerated
carbon storage tank for reuse in the system.
Under average loading conditions, approximately
100,000 pounds (45,400 kg) of carbon per day will be
regenerated. Carbon attrition losses are estimated to be
7% per cycle, so that an estimated 7,000 pounds (3,180
kg) of virgin carbon will have to be added daily to
maintain the carbon inventory. The total carbon inven-
tory in the system will be 2.5 million pounds (1.14 x
106kg).
Construction of the advanced wastewater treatment
facilities and a waste activated sludge disposal plant will
begin in the first quarter 1976.
Mechanical completion is scheduled for June 1977 with
standard operation in December 1977. The capital cost
for these facilities is estimated to be $22.4 million and
will bring the total capital investment for water pollu-
tion control for the Bound Brook plant to over $35
million. Operating cost for water pollution control
facilities will exceed $8 million per year.
FIGURE 10
AWT
CARBON SLURRY
TREATED WATER
TO CHLOR1NATION
ADSORBERS
135
-------
Cost Benefits of Physical Chemical Treatment
by Frank P. Sebastian Senior Vice President
Envirotech Corporation
The Clean Water Act of 1972 established a national goal
and a national policy for the United States. So far as
industrial water pollution control is concerned, it estab-
lished a timetable of 1977 for the best practicable
control technology, and 1983 for the best available
control technology.
In the municipal sector, the 1977 timetable is for
secondary treatment, with water reclamation and reuse
factors to be considered after June 30, 1974, and by
1983 the best practicable technology.
In summary, the Act calls for clean streams for
swimming, recreation, and the safety of fish and wildlife,
by 1985, with full consideration for reclamation and
reuse possibilities for projects after mid-1974.
The technology exists today to more than meet all the
municipal wastewater requirements. Accordingly, guide-
lines have been issued for most industrial effluent
categories. Any list of examples of advanced waste
treatment that might be utilized to bring the nation to
the fruition of its water pollution control goals would
include Tahoe, Colorado Springs and Windhoek as
instances of existing plants, as well as Occoquan in
Washington, D.C.; Garland, Texas, and numerous others,
as examples of advanced treatment plants under design
and construction in the U.S. Overall there are some 113
plants under design or construction utilizing various
aspects of advanced waste treatment to meet the 1977
goals previously established under the 1972 Act.
Let's take a closeup look at Colorado Springs as an
example of upgradability of present biological technol-
ogy, flexibility for the future utilization of more
advanced technology, and water reclamation and reuse.
Colorado Springs was an overloaded 30-million gallon a
day primary secondary treatment plant to which more
biological treatment was added. The Colorado Springs
facility has also incorporated a two-million gallon a day
tertiary treatment system utilizing lime and granular
carbon.
The lime is added to a Reactor-Clarifier, the effluent
from which passes through a multi-media filter and then
on through a battery of granular carbon columns. The
lime sludge removed from the bottom of the Reactor-
Clarifier tank is recalcined in a multiple hearth furnace
for reuse. In the same way, the spent carbon, after
having removed soluble organic material, trace pesticides
and refractory organics from the effluent, is regenerated
on site with losses as low as 3% and averaging only 5-7%.
The resulting product from the Colorado Springs Water
Reclamation plant is a good indication of the potential
payoff that can result from the nation's newly adopted
water pollution goals. The reclaimed water was planned
to be piped to an electric power station for use as
cooling water makeup. The reclaimed water is valued at
26
-------
step in the process is to separate the liquids and solids by
the use of gravity and lime. This is done in a two-stage
process involving sedimentation equipment such as a
Reactor-Qarifier. The lime is mixed with raw influent,
not secondary effluent, as it enters the Reactor-Clarifier.
The lime facilitates the settling of the solid material and
the clarification of the effluent. It also renders the
phosphates insoluble which promotes settling. The car-
bon dioxide, shown entering this basin, is used to
neutralize the water after it has been made highly
alkaline through the addition of lime. The CC>2 source
will be explained later. The output of this separation
step consists of chemically clarified water, which is
shown coming off to the top right; and the settled solids,
that is, sludge and lime, which are shown coming down
from the bottom of the basin. The lime that was used in
the Reactor-Clarifier is reclaimed in a multiple hearth
furnace reclamation process which produces the needed
CC>2 as a product of the stack gas. Thus, the furnace
stack gas, which approaches zero air pollution levels,
provides the carbon dioxide, which is shown as it is
bubbled back through the water to neutralize it, as
mentioned earlier.
The principle product of the multiple hearth lime
reclaiming furnace, which is called a Plural Purpose
Furnace, and on which Envirotech has process patents, is
the reclaimed lime, which combined with makeup lime,
is recycled in the process. In this step the insoluble DDT,
PCB, and indeed all the chlorinated hydrocarbons that
settle out are decomposed and removed from the
environment. Additionally, there is a certain amount of
ash coming off the lime reclaiming furnace which will be
discussed later.
Although a principal source of energy in the lime
reclaiming furnace is the fuel value contained in the
sludge solids removed from the wastewater, auxiliary
fuel is required. The fuel traditionally burned has been
natural gas. However, due to the developing natural gas
shortage, an alternative fuel burning capacity will be
needed. A Hydroburner has been developed for use in
multiple hearth and Plural Purpose furnaces which is
capable of burning #2, #4 and #6 oil fuels. The normal
4:1 turndown ratio, flame stability and system control
have been achieved with this new burner. This innova-
tion is expected to further enhance the practicability of
recalcining lime while also reducing operating expenses.
The next step in the liquid stage is for the chemically
clarified water to be piped to a multi-media filter, which
functions to capture any suspended solids that remain
after lime treatment and neutralization. This filtration
prevents carryover onto the carbon column step which
follows.
The carbon adsorption and regeneration phases come
next. These processes are the same as the ones that have
been used so successfully at the Lake Tahoe plant since
1965. These are the steps that remove the taste, odor,
color, detergents, inorganics including the solvable prob-
lems of pesticides, chlorinated hydrocrabons, and trace
organics from the wastewater. After the carbon polishing
phase, the final product water is either chlorinated and
put to use, or perhaps returned to the water course. The
spent carbon, laden with the dissolved material it has
adsorbed from the wastewater in the next to last stage of
treatment, is regenerated on site in a multiple hearth
furnace. During this regeneration process, the organic
material is pyrolyzed or distilled off the carbon and is
then totally oxidized before being scrubbed and exhaust-
ed so that the only highly cleansed air is released into
m Z-M PROCESS
T CHEMICALLY CLARIFIED WATER f
RECLAIMED
LIME
AUXILIARY FUEL
'•C
jK
V
k»l
"JSJ2"
_ *-u
^n?
u
$;i
i*i
•fe-
;VH^
CLEAN CAS
CO , TO ATMOSPHERE
137
-------
the atmosphere. It is this regeneration step that the final
trace amounts of pesticides, which were removed from
the water, are decomposed and thus, eliminated from
the environment.
PCBs, which are the most thermally resistant of these
materials, are appearing in the natural environment in
increasing quantities. According to the October 10,1975
issue of Wall Street Journal, "Persistent PCBs loom as a
worse menace than DDT." PCBs have recently proved
more resistant to natural degradation than DDT. Many
areas now have PCB accumulations exceeding those of
DDT. Additionally, researchers have discovered that
these substances are more toxic than previously thought.
In fact, the maximum allowable PCB feed concentration
of 5 ppm, as set by the Food and Drug Administration
in 1973, is presently considered unsafe by many
scientists. A number of animal studies substantiate the
acute toxic effects of PCB. For instance, a study
reported by the Wall Street Journal article previously
mentioned found increased incidence of morbidity in
primates fed PCB doses of only 2.5 ppm. PCBs have
proliferated so widely that they are even being detected
in artificial lakes having no link to either municipal or
industrial effluents. Such a lake is ten-year old Lake
Anne in Reston, Virginia, where fish samples were found
having accumulated significant concentrations of PCBs
(1). Samplings of trout and salmon from Lake Michigan
have averaged 22.9 and 10.5 ppm of PCB, respectively.
Fish samples from the waters of the Hudson, Ohio and
Milwaukee rivers have also shown worrisome PCB levels.
However, the problems associated with PCBs can be
reduced through sound technological practices. One of
the best economical methods for disposing of PCBs is
through the normal incineration procedure in multiple
hearth furnaces. Tests show that 99.9% of PCBs aie
decomposed in the multiple hearth furnace at 1100°F
using a 0.1 second exhaust gas detection time (2).
Indeed, according to a United States Geological Service
survey, there appears to be no other way of removing
these highly persistent materials from the natural envi-
ronment - except in a sewage treatment plant which has
a furnace incorporated into its treatment process. One of
the recently determined benefits of the total oxidation
of sludge in the multiple hearth furnace is that 95% of
the PCBs are destroyed in the normal operation tempera-
ture of the sludge furnace - which is only 700° F using a
0.1 second exhaust gas retention time. This lowered
temperature represents a substantial fuel savings com-
pared to alternate methods, while at no additional
expense it destroys 95% of PCB pollutants and also
complies with EPA recommended performance stand-
ards for furnaces burning sludges found to contain PCBs.
To illustrate how incinerators perform in terms of air
pollution standards, I quote from the June 1975 EPA
Technology Transfer publication (4), "Air Pollution
Aspects of Sludge Incineration," which states:
". .. the newly promulgated Federal NSPS (New
Source Performance Standards) are based on demon-
strated performance of an operating facility, indicates
that use of proper emission controls and proper
operation of the incineration system will enable a
facility to meet all existing particulate matter regula-
tions."
In connection with a Livermore, California, treatment
facility, the San Francisco Bay Area Air Pollution
Control District, one of the most stringent air pollution
control districts in this country, rules that multiple
hearth incinerators are an insignificant source of air
pollution (5).
The toxicity of metals has caused increasing concern
over their discharge in recent years. In response to the
dangers of toxic concentrations of metals entering
potable water supplies, plus the risks from biomagnifica-
tion, the EPA has promulgated standards for metals
discharge (6, 7). IPCT processes like the EPA flowsheet
mentioned and high lime-carbon processes have demon-
strated the removal of substantial quantities of toxic and
undesirable metals from wastewater. A study by Maruy-
ama et al. (8) used various pilot plants to evaluate raw
sewage metal removal efficiency using IPCT processes. A
high and a low lime system were utilized. The high lime
system used a lime concentration of 600 mg/1 with a
resultant pH of 11.5, while the low lime system used a
lime concentration of 260 mg/1 and 20 mg/1 of ferric
sulfate with a resultant sludge pH of 10. The results of
this study are summarized in Tables I and II. The "new"
TABLE I
Removal of Metals by Low Lime System
Removal (%)
80
85
90
95
-85
-90
-95
- 100
With New
Carbon Column
As
Zn
Mn
Cr+3, Pb, Ni, Cr+6
With Old
Carbon Column
As, Cr+6
Zn, Cn
Cr+3, Pb, Ni
TABLE II
Removal of Metals by High Lime System
Removal (%)
75
80
85
90
95
- 80
-85
- 90
-95
- 100
With New
Carbon Column
Ba
Zn As
Cu Hg
Cr+3, Pb, Ni
Mn, Cd, Cr+6
With Old
Carbon Column
Zn
As
Ba
Cu Hg
Cr43, Pb, Ni
Mn Cd Cr+3
138
-------
carbon column was a virgin carbon column, while the
"old" carbon column had been in operation about a year
and was described as needing regeneration. Notice that
although each process has different removal efficiencies
for particular metals, the removal efficiencies are gener-
ally greater than 90% for both lime processes.
A physical chemical process that is, again, similar to the-
Tahoe tertiary phase is the high lime-carbon adsorption
process, which has been demonstrated full scale at the
South Tahoe Water Reclamation plant (9). Several full
scale municipal plants that will use this process are now
under construction. Although not ideally suited for
waste streams, where suitable, there are numerous
advantages of using independent physical chemical treat-
ment processes over conventional biological treatment.
An important advantage of this process, and indeed all
lime carbon IPCT processes, is that they are not
susceptible to toxic or shock loads as is the case with
conventional biological treatment plants.
Another variation of the high-lime carbon adsorption
process is being installed in California at the Central
Contra Costa Water Reclamation Project plant. Sched-
uled for completion in early 1976, the 30 mgd plant,
with an ultimate design capacity of 120 mgd, will
incorporate both the lime addition to raw sewage and
recalcination processes, but in a modified flowsheet. In
this modified process, removal of both metals and
organics occurs in the recalcining process. As I mention-
ed earlier, the principal product of the Plural Purpose
Furnace is reclaimed lime, which comes from sludge
heavily laden with organics, phosphorus, metallics and
other toxic substances. To avoid the overloading on the
solids processing, these substances are removed from the
lime-containing sludge before the recalcination step. This
separation and removal process prevents the solids
processing facility from being overloaded by metals,
organics and other inerts. Incidentally, pilot test results
for the Central Contra Costa Sanitary District plant
found that the removal of suspended solids and biolog-
ical oxygen demand was 99%, while phosphorus and
nitrogen removal efficiencies were 96% and 94%, respec-
tively (10).
Ash, mentioned previously, which is a major product of
both lime reclaiming and sludge incineration, is being
used experimentally at both Lower Allen Township,
Pennsylvania, and Japan for fertilizer. Ash could also be
utilized for such purposes as building materials, and
perhaps even to aid in the salting of winter roads. Table
III contains some typical analyses of ash taken from a
tertiary sewage treatment plant.
The unique cost saving benefit using independent phys-
ical chemical treatment for primary treatment in new
plants seeking to achieve clean water goals, is in terms of
making an equipment investment that can meet long
term objectives of higher quality effluent. This savings
can be demonstrated by looking at some cost compar-
isons.
Since the purpose of this discussion is to investigate the
costs of traditional primary secondary and tertiary
treatment, hereafter called "tertiary", to independent
physical chemical treatment, IPCT, a hypothetical "aver-
age" wastewater was used. The plant influent parameters
are presented in Table IV. It is recognized that such an
average waste stream does not exist, except for compara-
tive purposes. Costs were estimated using the economic
criteria set forth in Table V, and were derived through
the use of the Envirotech computer program (11). In no
way are the costs considered precise or totally reflective
of the actual expenses, but rather the level of accuracy
has been designed for comparative analyses. The pre-
dicted experimental error for capital costs are ± 10%,
while the operational costs are believed to vary ± 15%.
TABLE III
TYPICAL ANALYSIS OF ASH FROM TERTIARY
QUALITY ADVANCED WASTE TREATMENT
SYSTEM
Percent of Total
Content
Silica (SiO2)
Alumina (A12O3)
Iron oxide (Fe2C>3)
Magnesium oxide (MgO)
Total calcium oxide (CaO)
Available (free) calcium oxide
(CaO)
Sodium (Na)
Potassium (K)
Boron (B)
Phosphorus pentoxide (P2O5)
Sulfate ion (804)
Sample 1
Lake Tahoe
11/19/69
23.85
16.34
3.44
2.12
29.76
1.16
0.73
0.14
0.02
6.87
2.79
Sample 2
Lake Tahoe
11/25/69
23.72
22.10
2.65
2.17
24.47
1.37
0.35
0.11
0.02
15.35
2.84
TABLE IV
Raw Stream Characteristics
BOD5
COD
Flow
Suspended Solids
Alkalinity and Hardness
250 mg/1
450 mg/1
30 mgd
250 mg/1
250 mg/1 as CaCO3
139
-------
Item
TABLE V
Economic Criteria
Basis
Rate
Labor
Benefits
Fuel
Power
Maintenance Labor
Supplies
Solids Disposal Hauling
Amortization
Lime, virgin
Carbon, virgin
Carbon makeup
Lime recalcination Rate
Amounts per unit from
(1) 168 hr/wk, 52 wk/yr
Amounts per unit from (1)
Amounts per unit from (1)
25 years
$5/hr(3.8 rubles/hr)
20% of labor
$2.80/million Btu (w kopecks/
million kg meters)
2t/KWH(4.1 kopecks/
million kg/m)
$5/hr(3.8 rubles/hr)
$10/ton(.8 kopecks/kg)
7% interest
$40/ton (3.4 kopecks/kg)
47
-------
PRIMARY-SECONDARY TREATMENT WITH PHOSPHOROUS REMOVAL
LIME
MULTIPLE
HEARTH
FURNACE
FJGURF C
PRIMARY-SECONDARY-TERTIARY TREATflENT PLANT
LIME
141
-------
PHYSICAL CHEMICAL TREATMENT PLANT
SLUDGE
MULTIPLE
HEARTH
FURNACE
RETURN LIME
Two processes which have been shown to produce a
"drinkable quality" water are traditional primary-
secondary and tertiary treatment, and independent
physical chemical treatment, IPCT-II (where applicable).
The capital cost of the tertiary process is $32.8 million
for a sample 30-million gpd plant, as compared to $28.7
million for the IPCT-II plant. The operating cost,
including amortization, of the tertiary plant is
63.2
-------
costs encountered in IPCT-II facilities over biological
plants having tertiary treatment (carbon columns)
added. Water reclamation, which is now being seriously
considered by more industries and communities in both
the U.S. and Soviet Union, can be a cost effective
procedure for IPCT plants. The California State Water
Resources Control Board considers the cost of reclaimed
water as reflective of collection and treatment expenses
incurred through the secondary level of treatment. Since
this is mandated into law, utilizing this concept yields
reclaimed water at less than half the price from our
sample IPCT-II plant (where the influent is applicable)
compared to the same water from the tertiary flowsheet
discussed. The cost for tertiary plant reclaimed water is
14.1
-------
PROCESSING AND NEUTRALIZATION OF INDUSTRIAL
WASTES FROM IRON AND STEEL EFFLUENTS TREATMENT
O.P. Ostrovsky, U.M. Souproun,
U.N. Reznikov
VNIPIChermetenergoochistka
The iron and steel enterprises effluents contain some
contaminants which are specific for the branch of
industry. The contaminants may be subdivided into 3
groups: soluble and insoluble mineral and organic
compounds.
During the effluent treatment and the stabilization of
water supply systems the following waste materials are
formed — sludges, high mineralized effluents and wastes
with organic compounds.
Sludges
The iron and steel plant sludges may be divided as
follows:
—iron containing sludges. The group involves mill
scale, sludges from the gas cleaning of sintering, blast
furnace, open hearth, converter and electric steel plants;
—gypsum containing sludges. They include sludges.
They include sludges which are formed in the lime gas
desulphuration process in the neutralization process of
the effluents containing sulphur oxides;
—others. They involve treatment products formed in
small quantities: sludges from casting machines, ferro-
alloy furnace gas cleaning plants, scarfing machines etc.
The materials ratio is as follows.
Iron containing sludges including: — 89,16%
a/ sintering plants - 32,50%
b/ blast furnace stockhouse - 10,83%
c/ blast furnace gas cleaning plants - 19,17%
d/ open hearth furnace gas cleaning plants - 3,16%
e/ converter gas cleaning - 3,00%
f/ electric furnace gas cleaning plants — 0,50%
g/ mill scale - 20,00%
Gypsum containing sludges including: — 6,67%
— desulphuration sludges — 2,5%
— sludges from neutralized sulphur effluents 4,17%
Other sludges and dusts - 4,17%
TOTAL
- 100%
Sintering plant sludges
Up to 90 - 95% sludges are formed in sintering
housings during hydraulic blasting of gas collectors filter
bags, fan system collectors during hydraulic cleaning of
rooms and pipelines from dry and wet cleaning units for
waste gases and fan systems.
The remaining 5-10% sludges come from other
sintering plant departments: charge treatment housing,
lime calcination housing, stock yards, car dumpers and
so on. The main sources of their formation are fan
systems and charge materials falls. The sludges from
equipment and pipelines washing as well as sludges from
hydraulic rooms cleaning are supplied at a time and
irregularly.
Great bulk of sludges consists of sinter particles as
well as raw materials: ore, coke, coal, limestone. As a
rule sintering plants products are of rather coarse size
distribution. Sludges from dust bags of gas collectors and
hydraulic cleaning include 60-65% particles > 0,3 mm,
from installations for dry and wet cleaning up to 10%
particles > 0,3 mm, the greatest part of fines is in the
sludges from fans.
All sludges contain a large quantity (26 to 36%) of
particles sizes of which are 0,15-0,05 mm. Some sludges
have a lot of particles < 0,005 mm, and it may be
accounted for more efficient cleaning process of waste
gases. Solid phase density of sludges from sintering
plants is 3 to 4 g/cm^.
Sludges from stock houses of blast furnace shops
Sources of sludges formation are falls from conveying
and production equipment; dust deposition on building
and equipment elements, as well as dust from wet and
dry air cleaning systems.
Composition of sludges from stock houses is similar
to those from sintering plants and gas cleaning installa-
tions of blast furnaces. As to the particles size they may
be classified as coarse-sized ones (up to 60% particles of
0,01-0,05 mm size). Solid phase density of sludges from
the under-bins premises is from 3,9 to 4,2 g/cm^.
Sludges from gas cleaning installations
of blast furnaces
Sludges are formed during the scrubbing of blast
furnace gases and they are a mixture of fine particles of
the ore, fluxes, coke, entrained from the blast furnace
by the gas stream. Passing through a reducing zone of
the furnace they are partially reduced and partially
oxidized and combine. As a result of it sludges contain
primary ore elements and new compounds created in the
blast furnace.
Size distribution of sludges from the gas cleaning
plants of blast furnaces is similar to the size distribution
of sintering plants sludges and in some cases at the high
efficiency of blast furnace gases in dry dust catchers,
their particles are similar.
144
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As to the chemical composition sludges of effluents
from gas cleaning installations of blast furnaces, espe-
cially coarse-sized are also similar to sintering plants
sludges. Fines contain a smaller amount of iron com-
pounds and a greater amount of silicon oxides. Solid
phase density of sludges from gas cleaning installations
of blast furnaces is 2,2 to 4 g/cm^.
Sludges from gas cleaning installations
of converter and open hearth furnaces
shops
Sludges include the finest particles of oxides of iron,
aluminum, calcium, manganese and other elements. The
main component consists of iron oxides. As to the
structure the particles are regular spheres of different
sizes coated with a thin reddish crust. Size distribution
of sludges is mainly presented by the finest particles
with a diameter 0 to 50 . Density of a solid part of
sludges from the gas cleaning installations of converter is
3,3 to 4,4 g/cm3, of open hearth shops - 4,3 to 4,9
g/cm3 due to a high iron content in sludges.
Sludges from gas cleaning plants of electric
melting furnaces
Sludge composition depends on the charge ratio or on
kinds of the output being melted grade of steel, type of
alloy). Sludges include a relatively large quantity of iron
compounds /30 to 40%/, as well as of heavy and
non-ferrous metals (chrome, nickel, manganese, magne-
sium). In some sludges chrome content may reach 10%,
nickel - 8%, manganese - 7%, magnesium - 20%.
Sludges may also include titanium, tungstem, vanadium
and other elements. As to their particles size these
sludges are similar to sludges from the gas cleaning of
converter and open hearth furnace shops. Solid phase
density in these sludges makes up 2 to 4 g/cm3.
Mill scale
The sludge consists of iron oxides with content 33,0
to 65,0% FeO and 63,0 to 27,0% Fe2O3- In addition to
the solid phase the scale comprises 5 to 20% oil. Mill
rolls, rollers, roll tables, hot and cold saws cooling water,
descaling and roll table pit washing wastes are contami-
nated with scale and lubricating oils. The scale content
of wastes is 2 to 4% rolled metal weight. Scale falling
under mill and roll tables is conveyed to a primary
settling basin which is a scale pit for settling 80 to 85%
coarse scale.
Preliminary clarified waste waters are directed by
gravity from the primary settling basin to a secondary
one where fine scale is settled in quantity about 10%
coarse one.
The scale is classified to coarse (>10mm), inter-
mediate which is washed out from a pit under the mill
and brought away along channel bottom (10mm and
less) and fine (<2mm). The amount of intermediate and
fine scale varies depending on mill type and rolled metal
grade.
Scale solid phase density is 5,15 to 5,0 g/cm^.
Desulphuration sludge
The sludge forms in the process of wet limestone
scrubbing of sintering off-gases.
It consists principally from calcium carbonate and
sulphite.
Sludge particle size distribution varies greatly and is a
function of limestone grinding fineness while a desulph-
uration suspension preparing. The sludge solid phase
density is 2,6 to 2,7 g/cirP.
Neutralized sulphuric acid waste sludge
The sludge forms while neutralizing waste pickling
liquors and pickling line washing waters. The wastes are
usually neutralized with lime suspension. The neutraliz-
ing precipitates contain principally gypsum and iron
hydrooxides. The sludge solids are very dispersed and
precipitated with great difficulty.
Other sludges
The sludges form in very small amounts, and their
utilization is not a serious problem in comparison with a
total volume of all solid wastes through utilization
methods are required to be determined in every concrete
circumstances for these wastes too.
HIGH-MINERALIZED WASTE WATERS
These wastes include neutralized washing waters and
waste pickling liquors, regeneration and washing waters
of reagent water treating systems, recirculation system
blowing-down waters from metal working process and
wet gas cleaning units. The wastes are characterized by
multicomponent salt composition and salt content
exceeding sanitary standards. The most of these waters
are saturated with CaSO^ The total amount of the
waste waters to be neutralized at steel or metal working
plants can approach 500 m^/h.
ORGANIC WASTES
Waste rolling oils
The wastes form while treating or decomposing
lubricating and cooling emulsions. The lubricating and
cooling emulsion treating oil wastes contain 20 to 50%
water and up to 10% mechanical impurities. Oil wastes
that are formed while decomposing an emulsion after
clarifying contain up to 5% water and about 3%
145
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mechanical impurities. The impurities consist mainly
from fine iron oxides. Oil waste specific yield is 0,5 to
1,5 kg/t rolled product.
Waste decreasing solutions
The wastes include emulsified oils, anorganic deter-
gents (Na2C03, NaOH, Na3P04 etc) as well as different
surfactants. There are up to 0,5% oil, up to 100 g/1
anorganic detergents, up to 1% surfactants. The waste
degreasing solutions yield approaches 3-5 m /h at an
intermediate capacity metal working plant.
WASTES UTILIZATION, TREATMENT AND
NEUTRALIZATION
Sludges
Iron containing sludges can be utilized in sintering,
blast-furnace and steel production processes according to
wastes composition. They can be used at sintering plants
without any preliminary pelletizing and at others in
briquettes or pellet form. The iron containing sludges
dumping together with other sludges in settling pond as
practicized at some mainly old works results in metal
losses and surrounding pollution. Therefore modern steel
plants are commissioned in conjunction with iron
containing sludges treatment and utilization systems.
According to references a total utilized iron contain-
ing sludges amount is now about 63.0%.The sludges are
used the most successfully at sintering plants. The most
of them are the same plants sludges. Sometimes they
include also steel production and seldom blast furnaces
gas cleaning systems sludges.
The sludges using without any special dewatering
units is hindered because their high humidity makes
their conveyance difficult, results in the plant site,
equipment and hall pollution. A preliminary preparing
operation in special units (dewatering and drying) is
necessary as well while utilizing steel production gas
cleaning systems sludges in pelletized form (as briquettes
or pellets) in blast-furnace and steel production proc-
esses.
Gypsum containing sludges can be efficiently utilized
to reclaim and fertilize acid soils. The studies performed
have shown corn crops to increase by 25 to 50% as a
result of desulphuration systems and sulphuric acid
liquors neutralization units sludges applying in amount
of 4 to 5 t per ha.
The sludges must be dewatered to 6 to 8% humidity
before being applied. They can be utilized also as a base
for a constructional 250-350 grade cement and further
for constructional concretes and elements.
Thus, a prinicpal condition of successful sludge
utilization is special dewatering (preparing) systems
development.
Sludges dewatering equipment and methods
Sludges dewatering units are following: classifiers,
vacuum filters, press filters, centrifuges.
Classifiers. They are used to classify multisized
suspension solids with size up to 1 to 5 mm into 2 or
more fractions. The classifiers can be of two main types:
settling or centrifugal units. As to settling classifiers
horizontal clarifiers, spiral and elevator classifiers are put
in practice to dewater waste water sludges. Out of
centrifugal classifiers bent sieves or conical screens,
hydrocyclones and settling centrifuges are employed.
Horizontal clarifiers are the simplest classifiers. They
are put in rather wide practice of metallurgical waste
treatment. The clarifiers are not quite efficient. A fault
of them is low sludge dewatering rate.
Because of relatively low classification rate, poor
discharge mechanization and small dewatering rate the
clarifiers are designed no longer but are to be replaced
by more perfect equipment.
Spiral classifiers. These devices have been used for a
long time in ore-treating industry. They are more widely
spread in the sludge dewatering practice of metallurgical
plants than all the other types of mechanical classifiers.
In designs of batch produced spiral classifiers, bath
and conveyer parameters are chosen according to the
working conditions on ore pulps, which as a rule contain
a considerable amount of solid phase. However, in the
conditions of dewatering units treating metallurgical
plant sludges, considerably diluted suspensions are
mostly supplied to the classification. The adopted
relations of bath and discharging conveyer parameters of
batch designs are not optimal in this case.
Due to this fact one should reconstruct spiral
classifier baths to increase the drainage loading.
Elevator classifiers or dredging sumps.
These devices are taken from coal concentration
industry. The design is quite simple — they consist of
sump, in which the dewatering elevator boot is placed
for sedimented sludge output. Their operation on
metallurgical plant sludges is not practically investi-
gated. The loadings are taken on analogy with those on
coal concentration plants, though the difference in
working conditions is even more in this case then in
previously discussed one with spiral classifiers.
Bent and conical sieves are also taken from coal
concentration field. These units are characterized by
simple design, high production rate and operational
reliability. Yet they are rarely used in sludge dewatering
practice of treating metallurgical plant wastes, but seem
quite promising.
Hydrocyclones are widely used in water treatment
and sludge dewatering practice. Design methods applied
to different types of ore sludges are available. As for
146
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metallurgical plant sludges, these methods need some
specifications.
Bowl centrifuges are often treated as dewatering
equipment not of classifying type, though practically
they are classifiers, because of quite low meaning of
boundary grain size and that is why they will be
discussed later on.
Vacuum filters. Band, disk and drum vacuum filters
are used in the precipitate treatment of metallurgical
plant.
Band vacuum filters are used for coarse sludge
dewatering as well as for not-classified sludge, when the
unit production rate is low. Both band and drum
vacuum filters are characterized by small filtering surface
per unit of area occupied.
Disk vacuum filters are used for sludge dewatering
with size 0,3 to 0,1 mm from gas cleaning units of
sintering, blast furnace and converter processes. They are
most widely spread than other types of filters.
Drum vacuum filters are used in the same cases as the
disk ones. In our country drum filters are relatively rare.
Press filters. In practice of waste water precipitate
treatment of metallurgical plants press filters are applied
to dewatering of precipitates which are hard to dewater
(sludges of open-hearth gas cleaning units; sulphuric acid
liquor neutralization sludges, etc)
High classifying rate is guaranteed: the precipitate
contains a minimum quantity of moisture, and the
filtrate is of maximum purity. Press filters have relatively
simple design, highly developed filtering surface per unit
of occupied area and allow to use high pressure drop
that is especially important when dewatering suspensions
with high-dispersed solid phase.
In practice of precipitate dewatering of metallurgical
plant waste waters automatic chamber type press filters
with plate clam of FPACM type (institute UkrNIIChi-
mmash and Berdichev chemical machine works "Prog-
ress" design) got some spreading.
Press filters are produced with filtering surface of 2,5;
5; 10; 25 and 50 m2. FPACM press filter metal
consumption per weight unit of filtered products is 2-3
times lower than that of frame press filters, and
production rate is 4-6 times higher. All the filtering
processes are automatized.
Centrifuges. Centrifuges are not widely spread in the
practice of waste water precipitate treatment at metal-
lurgical plants in our country.
At present investigations are carried out on applica-
tion of bowl centrifuges with screw discharge conveyor
for dewatering different sludges.
Application — of such equipment provides consider-
able simplification of sludge dewatering methods, as it
allows to reduce a number of equipment units and
dewatering units room volume.
Process flow diagrams. Conditionally one can dis-
tinguish three types of process flow diagrams:
1) for multisized sludge dewatering
2) for dewatering of monodispersed sludge of inter-
mediate size
3) for high dispersed sludge dewatering.
The first type is characterized by sludge classification
to 2-3 fractions, each of them is dewatered separately on
its type of equipment.
Usually the largest fraction is dewatered in classifiers,
the fraction of intermediate size — in band vacuum
filters and the finest fraction in disk or drum vacuum
filters. Sometimes both intermediate and fine fractions
are dewatered together in disk or drum vacuum filters.
The second type diagram is widely used for dewater-
ing of converter gas cleaning units sludge, and includes
disk and drum vacuum filters as dewatering devices. The
third type can be used for dewatering of open hearth
and electromelting furnaces gas cleaning units sludges
and for neutralized sulphuric acid sludge; it is character-
ized by press filter application.
Equipment operational parameters depend on physical
and mechanical properties of suspension being dewater-
ed.
For the present a considerable number of studies on
operational parameters of vacuum filters, press filters,
centrifuges and classifiers for different sludges has been
carried out.
Investigations on sintering sludge dewatering resulted
in determining band and disk vacuum filters operational
parameters. For band vacuum filters while dewatering
+0,25(0,3) mm sintering sludge with primary pulp
concentration 400-600 g/1, it is recommended loading
of 4,0 to 5,0 t/m2 h and dewatered precipitate moisture
-13 to 15%.
For disk vacuum filters loadings are maintained in
dependence of feeding - 30 fraction content with
concentration of solids 400 g/1.
Table 1
Specific production rate of disk vacuum
filters versus size distribution of solids in
feeding.
Specific production rate
kg/ml h while concentra-
tion of solids in feeding is
400 g/1
30 u fraction content
in filter feeding, %
450
400
320
250
150
100
10
20
30
40
50
60
147
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Following correction factors taking into account the
concentration are introduced: 500 g/1 - 1,05; 600 g/1 -
1,30; 700 g/1 - 1,65; 800 g/1 - 2,20; 900 g/1 - 2,60.
Dewatered pricipitate humidity after disk vacuum
filters depends upon the solid phase granulometric
composition, used vacuum rate, precipitate depth and
other factors. It may vary within close range 18 to 22%.
While de watering converter gas cleaning system sludge
production rate of disk vacuum filters is 0,07 to 0,1
t/m2/h, dewatered sludge humidity is within range 27 to
35%. Due to rather high humidity dewatered converter
sludge is usually subjected to thermal drying after
vacuum filters.
While dewatering sludge formed in sintering plants
limestone gas desulphuration process on vacuum filters
following data were obtained: unit load - 50 - 125
kg/m2h (corresponding to concentration extreme values
of initial suspension 100 - 500 kg/m2h), precipitate
humidity 28 to 30%.
Conditions of press filters working on various types
of precipitates were investigated. The studies were
carried out on sludge of open hearth, converter and
electric steel furnace gas cleaning systems, on desulphur-
ation units sludge of sintering plants and also on sludge
obtained while neutralizing sulphur acid effluents. Table
2 illustrates data on dewatering of open hearth, con-
verter and electric steel furnace gas cleaning systems
sludges from different plants.
Press filter production rate depending upon physical
and mechanical sludge properties, pulp concentration
and cycle characteristic was within range 40 to 95
kg/m2h at precipitate humidity - 14 to 33%.
In experiments with dewatering of sludge, formed in
the limestone gas cleaning desulphuration process, speci-
fic production rate on press filters FPACM was 150 to
330 kg/m2h (corresponding to concentration extreme
values of initial suspension - 150 to 400 g/1) and
dewatered precipitate humidity - 15 to 18%.
While dewatering sludge formed as a result of
sulphuric acid waste neutralization by lime milk specific
production rate of press filters was 5 to 12 kg/m2h at
solid content in initial pulp 1,5 to 5% respectively and
Data on dewatering of sludge from steel furnaces gas-cleaning
system on filter-press tfTlKM -0,5
Table 2
Typo
of
sludge
1
Open-hearth gas-cleaning
system (plant A)
Open-hearth gas-cleaning
system (plant B)
Open-hearth gas-cleaning
system (plant D)
Converter gas-cleaning
system (plant A)
Converter gas-cleaning
system (plant B)
Converter gas-cleaning
system (plant C)
Electric steel furnace
gas-cleaning system
(plant A)
Electric steel furnace
gas-cleaning system
(plant B)
Electric steel furnace
gas-cleaning system
(plant C)
Solid pha-
se content
in suspen-
sion,
s/i
2
450-470
270-300
250-280
360-J80
250-270
530-350
270-300
370-400
240-260
Working
pres-
sure,
atm
3
4.0
4.5
4.0
5.0
4.0
4.0
4.0
4.0
4.0
Cycle characteristic
total
dura-
tion,
min
4
8
16
8
14
15
10
18
9
7
filt-
ration
*ime,
min
5
3
12
4
10
11
6
13
5
3
preci-
pitate
drying
time,
min
6
3
2
2
2
2
2
3
2
2
Obtained data
precipi-
tate
depth,
mm
7
4-5
S-7
4-5
10-12
6-7
11-12
4-5
10-11
8-9
precipi-
tate hu-
midity,
%
8
17-18
20-20.5
19-20
32-33
19-20
25-26
14-15
29-30
21-22
iltrate
olid
ontent,
g/1
9
up to 4
up to 3
up to 3
up to 3
up to 3
ip to 3
ip to 4
ip to 3
ip to 4
pecific
roduc-
ion ratex
.g/m2 h
10
60-70
40-45
55-60
60-65
50-55
90-95
45-50
75-80
75-60
148
-------
precipitate humidity was 58 to 61%.
It was stated that in addition to physical and
mechanical solid properties the production rate of press
filters used for dewatering of hot rolling mills scale in
secondary settling basins is greatly influenced by oil
content in pulp. Thus at a plant in a process of
dewatering scale containing 20% oil (in reference to
oiled solids) specific production rate on press filters
FPACM was 10 to 25 kg/m2 h (at solid concentration
140 to 550 g/1 respectively) while at another plant with
the same concentrations of scale, containing 8% oil,
specific production rate was about 25 to 75 kg/m2h.
Filtration of oiled pulp was shown to be greatly
improved by addition of lime milk. While dewatering the
said scale containing 20% oil lime addition to the pulp in
theoretical amount of 2 g CaO/1 resulted in 2,5 — 3
times increase of specific production rate. The lime
addition did not influence greatly on precipitate humid-
ity which was within range 10 to 12%.
Under relatively small oil content in scale (up to 10%)
the lime addition influence much less on production
rate.
Both dewatering and deoiling are the aim of the
process of scale treatment before utilization. However,
filtration process cannot provide effective oil separation
since oil passing through precipitate filter layer is
adsorbed on solid phase particle surface, as a result of
which process its considerable part is left in precipitate.
With the aim of searching out more effective methods
of such a sludge treatment the dewatering and deoiling
processes of the secondary settling basin scale in bowl
centrifuges with screw conveyer discharge of sludge were
studied. These studies showed that as to deoiling
the centrifugation process in bowl centrifuge has a
considerable advantage in comparison with the filtration
process, especially for the scale with the great oil
content.
These studies were carried in full-scale centrifuge of
NOGSh-32S type. The centrifuge throughput on pulp
was 2.5 to 4.0 rrP/h with the solids content 50 to 350
g/1.
The humidity of dewatered precipitate was in the
range" of 10 to 20%, and the oil content in the range of 2
to 5%.
The using of bowl centrifuges may be also very
promising for treatment of the other precipitates.
However, it requires the carrying out of definite studies
connected with finishing and putting into the practice of
this equipment.
In conclusion it should be noted that in present some
decisions on process flow diagrams of main steel plants
sludges dewatering are available and this does not hinder
putting into practice modern dewatering units. The main
factor decelerating the construction of these plants are
too slow rates of construction, although namely these
plants are one of the important resources of raw material
utilizing methods improving in steel-making industry.
HIGH MINERALIZED WASTES
One of the main trends in high mineralized wastes
neutralization is thermal desalting. The wastes desalting
problem is the complex of problems connected with
high concentration, obtaining of dry salts, their utiliza-
tion and storage.
The most of steel plants wastes are saturated with
components capable to form the scale on the heating
surfaces, that is why the main difficulties while high
concentrating such wastes are connected with the
control of scale formation.
In present, in steel-making industry one pilot plant
for thermal desalting is operated with production rate
100 m^/h. For high concentrating scale-forming wastes
tubular vaporizers with forced circulation are applied.
Studies data and plants operation practice for sea
water desalting show the following types of wastes deep
concentrating plants are the most reasonable.
1. Vaporizers with adiabatic evaporators and heating
of evaporating water in contact heaters with water-
repellent or gaseous heat-transfer agent.
2. Vaporizers with tubular evaporators and prelimi-
nary softening of water by thermal and reagent methods.
For small production rate plants vaporizers consisting
of two or three tubular devices with forced circulation
of water concentrated by evaporation.
In present, two types of vaporizers for high con-
centrating and drying of drop-forming wastes have been
developed. Multibodied vaporizer with tubular evapora-
tors and thermal softening of initial water which is to be
constructed at one of the Ural plants, as well as a
multibodied plant with adiabatic evaporators and heat-
ing of water concentrated by evaporation in contact
device with water-repellent heat-transfer agent is also to
be constructed at one of the Ukraine plants.
The still residue drying at these plants is provided for
in fluidized bed furnaces.
The problems of salt utilization are being studied in
laboratory conditions.
WASTES WITH ORGANIC COMPOUND CONTENT
One of the main methods of liquid wastes neutraliza-
tion containing organic compounds in different branches
of the USSR industry is flame method. Lately, the most
widespreaded agregates for flame neutralization are
cyclone furnaces.
For burning of oil wastes and for waste degreasing
solutions flame neutralization the cyclone furnaces of
different production rate have been developed. The
cyclone type devices are being constructed at some
steel-making and metal working plants. They are char-
acterized by high specific parameters. Volume specific
intencity when burning oil wastes is about 5.10"
kcal/m-%. Volume specific loading while solution neu-
tralizating is approximately 1 t/m^h.
149
-------
FUNDAMENTAL PRINCIPLES OF SELECTING THE METHOD FOR PROCESSING
SEWAGE SEDIMENTS IN ACCORDANCE WITH THEIR PROPERTIES
Prof. N.A. Lukinykh, D.Sc. (Eng.), Deputy Director of
Research for City Water Supply and Treatment
I.S. Turovsky, Cand.Sc. (Eng.), Head of Sediment
Treatment and Utilization.
One of the most intricate problems associated with
protection of water reservoirs from pollution is the
treatment of the sediment.
Sewage sediments belong to the class of hard-to-filter
silt suspensions, their treatment is complicated by their
large size and high humidity.
The sediment treatment methods include fermenta-
tion in anaerobic and aerobic conditions, drying on silt
pads and ponds; dehydration on vacuum filters, centri-
fuges, filter presses and other devices, and decontamina-
tion by thermal treatment or incineration.
Silty pads and silt ponds, which are widely used for
drying sediments, are extremely inefficient and occupy
large areas in city outskirts.
The use of mechanical dehydration makes it possible
to considerably reduce the areas and time required for
sediment drying, with simultaneous mechanization and
automation of the process.
Mechanical dehydration can be applied both to
fermented and unfermented sediments.
Among the methods for mechanical dehydration,
drum-type vacuum filters are most widely used.
The capacity of vacuum filters depends on the
composition and properties of the sediments, the ratio
between the sediment from the primary settlers and
active silt in the mixture, and also on the methods for
preparation of the sediments for dehydration. Of great
importance is the composition of the sewage under
treatment. All these factors differ from aeration station
to another.
The extent of water removal from the sediment is
indicated by the specific resistance of the sediment to
filtration.
The specific resistance of a sediment is found from
the formula.
where:
is the specific resistance of the sediment,
is the pressure (vacuum),
is the filtering area,
is the filtrate viscosity,
is the concentration of dry matter in the
sediment,
is a parameter characterizing water
removal from the sediment,
is the filtering time after the pressure was
set up,
is the filtrate volume obtained after a
constant pressure was set up.
In determining the specific resistance of the sediment
the parameter "b" can be obtained experimentally,
while the value of "r" can be calculated from Eq.(l) /!/.
The specific resistance of sediments at city aeration
stations varies widely. An analysis of specific resistance
values shows that unfermented sediments in primary
settlers and uncompacted active silt have a much lower
specific resistance than fermented sediments.
A sediment fermented in thermophilic conditions has
the highest specific resistance. It has also been establish-
ed that the higher the specific resistance, the lower is the
capacity of the vacuum-filters and the more thorough
the treatment which must be undergone by the sediment
prior to mechanical dehydration. /!/.
Calculation formulas have been proposed which
enable one to determine the amount of eater necessary
for washing the fermented sediments, the doze of the
chemical reagents required for sediment coagulation, the
expected capacity of the vacuum filters, and also the
optimum conditions of their operation /2/.
The specific resistance of the fermented particles by
washing with water or purified sewage. The curves of
reduction in the specific resistance of the fermented
sediments in the course of their washing can be
approximated by the equation
R0-
-an
where:
"o = ro . 10~1^ is the specific resistance of
the washed sediment, cm/g;
RH = rn . lO'lO is the specific resistance of
the washed sediment, cm/g;
n = is the amount of washing water, cu m
per 1 cu m sediment;
a = is a coefficient depending on the
concentration of the initial and washed
sediment, the removal of the suspended
matter with the drain water, and other
factors, which varies within the range
from 0.04 to 0.14.
The filtering devices show stable operation when the
specific resistance of the sediments reduces from the
initial value to (5 - 50 x 10^ cm/g, respectively. For
most sediments, the above reduction is achieved by
coagulation or flocculation with the aid of chemical
reagents.
The optimum dose of reagents is established from the
curves of reduction in the specific resistance of the
150
-------
sediment during experimental coagulation with different
doses.
The reagent dose can be tentatively determined from
the formula:
D = k(VIvV-§-- 0.001 alk), 3
where:
D is the reagent dose in per cent of the
sediment dry weight;
R r . 10~10 is the sediment specific resist-
ance, cm/g;
h is the sediment humidity, %;
c is the concentration of the sediment dry
matter, %;
alk is the sediment alkalinity, mg/1;
k is a coefficient depending on the type and
chemical composition of the reagent
used.
The efficiency of the drum-type filters is determined
from the formula:
where:
LI is the vacuum filter capacity, kg/m^ per
hour, with reference to the sediment dry
matter;
hi lid is the humidity of the initial and dehydra-
ted sediment, respectively, %
f is the density of the initial sediment,
t/m3;
in is the duration of the vacuum effect in
relation to the total filtering cycle, %;
P is the working vacuum, mm Hg;
£ is the filtrate viscosity, cp;
M is the drum revolution time, min.
Slimes with a low specific resistance often do not
require any treatment prior to dehydration. They can
also be used for reducing the specific resistance of
sediments in city sewage. In particular, such slimes
include products of neutralization of sulphuric-acid -
containing etching solution with lime, and waste from
some industrial enterprises.
When choosing the sediment treatment method, a
study into the mechanism of binding of the water the
solid particles of the sediment is of considerable impor-
tance as well as specific resistance evaluation /2/.
From the classification of the types of water binding
proposed by Rebinder it follows that breaking of the
water-solid bonds requires the expenditure of a definite
energy. The vacuum at which the sediments are dehydra-
ted on the vacuum filters equals 400 to 500 mm Hg. The
theoretical limit for water removal by vacuum filtering is
the water content of microcappilaries with a radius of
not less than 0.005 mm. Filter pressing or centrifuging
during which higher pressures are developed removes a
greater amount of water from the sediments, and the
filtered sediment has a lower water content as compared
with vacuum filtering. The maximum amount of water
removed from the sediments by mechanical dehydration
is characterized by the position of the first critical
humidity point (Fig. 1) and depends on the type of
sediment and the degree of its readiness for mechanical
dehydration.
It can be seen from the figure that compacted active
silt contains more hard-to-remove water than a ferment-
ed sediment, while the latter contains more such water
than the unfermented sediment from the primary
settlers.
The water content of the active silt on section b,c
reduces from 98 to 87.5%, that of the fermented
mixture, from 97.5 to 84.6%, and that of the unfer-
mented sediment from the primary settlera, from 94.6
to 73%.
When sediments are coagulated with chemical rea-
gents, part of the water bound by the physicomechanical
and physicochemical bond is released and the amount of
adsorption-bound water is reduced. The value of the first
critical point decreases as well.
Aeration stations with a capacity of up to 50 thous.
nr'/day use the sediment centrifuging method.
Centrifuging can be effected either with or without
the use of chemical reagents. A disadvantage of this
method, which limits the scope of its application, is the
large amount of suspended solid carried away with the
fugate.
The efficiency of retention of the sediment dry
matter during centrifuging is determined from the
formula
where: Csec}, Cc and Cf are, respectively, the concentra-
tions of the initial sediment, the cake, and the fugate.
Investigations show that in approximate calculation
of the dry matter retention efficiency one can use data
obtained on laboratory cup centrifuges.
c - Jrt erttt«»l
dlty polat
Fig. I. Curve* Of •adl»*nt drying lnt«a«Vtj
I- compacted active silt
2- fezwatetf BediMBt
3- tmfvraeoted sediment,
151
-------
The centrifuge capa city index is expressed by the
relation
E = F • S,m2, 6
where:
F is the surface area of the centrifuge
draining cylinder;
S is the separation factor.
where: ' g
W is the rotor angular radius, m;
R is the rotor radius, m;
g is the gravity acceleration, m/sec^.
In order to determine the type and size of the
centrifuge, one can change the surface area of the
draining cylinder by varying the diameter of the draining
orifice only within a small range, whereas the separation
factor can be varied up to 2000-3500 for the same
machine.
The sediment residence time in the rotor of an
industrial centrifuge, which depends on the capacity
index, is changed mainly by regulating the centrifuge
capacity. Hence, the principal parameters to be deter-
mined when simulating the process is the separation
factor and the centrifuging time. The effect of the
separation factor and centrifuging time on the efficiency
of sediment separation is easily determined on a labora-
tory-type cup centrifuge.
A comparison of the results of experiments on a
laboratory and an industrial centrifuge suggested a
method for tentative estimation on the dry matter
retention efficiency with an industrial centrifuge from
laboratory data with the use of the "centrifuging index"
proposed by us /3/:
V
where:
V is the volume of the compacted sediment,
cm-
V0 is the volume of the initial sediment,
cm-',
C is the concentration of the initial sedi-
ment, g/1.
The results of the experiments carried out on a
laboratory-type centrifuge show that the process of
separation of all types of sediment is stable when
centrifuging lasts over 2 min and the speed of the
centrifuge rotor is 6000 rpm; the centrifuging index is
actually independent of the concentration of the initial
sediment and remains constant for a definite type of
sediment.
Based on the data obtained with a laboratory-type
centrifuge -3 and an industrial centrifuge HO -325,
we derived the dependence of the sediment dry matter
retention efficiency on the centrifuging index (Fig. 2),
which is approximated by the expression:
14
12
°. 10
X
4>
•a
Ofl
'So
§ 4
10 20 30 40 50 60
b - dry matter retention efficiency,
The use of the centrifuging index as a criterion
enables one to estimate the increase in dry matter
retention efficiency in preliminary treatment of sedi-
ments with chemical reagents, by freezing and thawing,
heating, prolonged aeration, etc.
Mechanically dehydrated sediments belong to the
group of paste-like, colloidal, capillary-porous bodies
whose intensive drying involves difficulties.
Investigations on thermal drying of sediments de-
hydrated on vacuum filters, filter presses, and centri-
fuges show that the drying curves have the same shape
for different types of sediment and differ only in the
position of the critical points, which mainly depends on
the initial water content of the sediments (Fig. 3).
Sediments are dried in two stages, at a constant (period
I) and a reducing (period II) velocity.
•I - U'i,
- Mdiaut «t«» eont.nl u,*,
Fig. 3. Dr»l"?
of dahydratud *t&imm*
152
-------
In the first stage the drying rate depends on the
conditions of external mass- and heat-exchange between
the surface of the material and the drying agent. In the
second stage the drying rate depends on the conditions
of redistribution of humidity and heat inside the layer of
material.
To avoid overdrying of the surface layer, the rate of
evaporation must correspond to the moisture diffusion
from the inside of the material.
When intensive drying regimes are used, with high
velocities and temperatures of the drying agent (which is
typical of the drying of sediments in the suspended
state), the first drying stage considerably reduces. For
materials which dry like sediments with the formation of
a dry crust on the surface it is advisable to resume the
constant-drying-rate stage by breaking the crust and
thereby exposing the humid surfaces. This kind of
regime is achieved by drying in gas suspension counter-
currents /4/.
Treatment of experimental data in criterial depend-
ence Nuef =f(Re) shows that the experimental data are
correlated by the formula Nuef = 9.5 x lO'-'Re within
the range 200 < Re <500.
To complete sediment drying in the second stage it is
expedient to use the air fountain regime.
Conclusions
1. The main factors characterizing water removal
from sewage sediments are the specific resistance of the
filtration sediment, the centrifuging index, and the
position of the first critical humidity point.
2. Some relations are recommended which make it
possible to select the sediment treatment method and
determine the degree of its readiness for mechanical
dehydration and also the operating conditions of the
filtering devices according to the value of the specific
resistance of the sediment, the centrifuging index, and
the critical points of the water-solid bond.
3. The most efficient technique for thermal drying of
dehydrated sewage sediments is the method of gas
suspension counter-currents coupled with the air foun-
tain regime.
REFERENCES
1. I.S. Turovsky. Dehydration of sewage sediments on
drum-type vacuum filters. Stroyizdat, 1966.
2. I.S. Turovsky. Investigation into the Effect of Properties
of Sewage Sediments in the Course of Mechanical Dehydration
and Drying. Zhurnal prikladnoy khimii, V. XIV, 1972.
3. R.Ya. Agranonik, I.S. Turovsky. Evaluation of Efficiency
of Screw-type Centrifuges in Treatment of Seage Sediments.
Vodosnabzheniye i sanitarnaya tekhnika, 1970, No. 3.
4. I.S. Turovsky, L.L. Goldfarb. Investigation into the
Parameters of Materials Drying in Gas Suspension Countercur-
rents. Inzhenerno-fizicheskii zhurnal, AN BSSR, V.XXIII, No. 4,
1972.
CAPTIONS TO FIGURES
Fig. 1 Curves of sediment drying intensity: 1-com-
pacted active silt; 2-fermented sediment; 3-unfer-
mented sediment; c-lst critical humidity point;
d-2nd critical humidity point; A-drying intensity,
mg/min.cm , B-humidity, %.
Fig. 2 Dependence of dry matter retention efficiency
on centrifuging index in sediment dehydration
on centrifuge HOPP-325 with Q=3 - 4 m3/hr:
a-centrifuging index, cm3/g; b-dry matter reten-
tion efficiency, %.
Fig. 3 Drying kinetics of dehydrated sediments: a-sedi-
ment water content u, %; b-drying time T ,
min; c-drying rate du s % 5/min; d-u"cr;
e-u'cr. d r
153
-------
PROTOCOL
of the second Meeting of the USA and USSR delegations
on the problem of prevention of Water Pollution from
industrial and Municipal Sources
(Cincinnati, USA, November 9-23, 1975)
Between November 9-23 the Meeting of the USA-
USSR delegations on the problem of waste water
treatment took place.
The American delegation was led by Mr. Harold P.
Cahill, Jr., Director of Municipal Construction Division,
US Environmental Protection Agency.
The Soviet delegation was led by R.F. Slavolyubov,
Chief of the Glavpromstroi Proyekt Department, Gos-
stroi USSR.
The list of participants is attached in Appendix 1.
In the course of the meeting the following was
accomplished:
1. A symposium on physical-chemical treatment of
waste waters.
2. The accomplishments of the 1975 program of
cooperation were discussed.
3. Coordination of the Working Program for 1976.
I
At the Symposium 16 reports devoted to the prob-
lems of physical-chemical waste water treatment were
delivered: the US delegation delivered 9 reports: the
Soviet delegation 7 reports.
The list of reports delivered is attached as Appendix
II.
Of particular interest were papers by Soviet specialists
on new polyelectrolytes and on waste water treatment
from concentrated oil and emulsion, and reports of
American specialists on activated carbon absorbtion
waste water treatment and on physical-chemical with
utilization of coagulants.
The delegations have agreed that each side will
publish all reports presented at the Symposium in the
necessary number of copies in its own language prior to
May 1, 1976, and will distribute them among interested
organizations.
II
Concerning the results of the 1975 program of
cooperation, the following was noted:
The sides discussed twice the results of current
research, exchanged scientific and technical literature
and carried out two US-USSR symposia on sludge
management (USSR, Moscow, May 1975) and on
physical-chemical waste water treatment (USA. Cin-
cinnati, November 1975).
HI
The delegations determined and coordinated the
program of cooperation for 1976 (Appendix III).
The sides will yearly execute exchange of information
about the course of the work. The questions of the
exchange of results will be decided for each separate case
in conformity with the existing agreements between the
USA and the USSR in this field.
For the preparation of the forthcoming Symposium
"Intensification of Biochemical Methods of Waste
Waters Treatment" (USSR, Moscow, May 12-26, 1976),
the following was agreed upon:
• each side will present 5-6 reports to the Sympos-
ium;
• the sides will exchange the report titles prior to
February 1, 1976;
• the texts of the reports shall be exchanged in two
copies in Russian and English, prior to April 15,
1976;
Both sides noted that organization work for carrying
out the Sumposium "Waste Water Treatment — Physical-
Mecahnical Treatment Facilities" to be planned for
September 1976 in the USA will be considered in the
course of delegations meeting in May 1976.
Paying great attention to increasing the efficiency of
cooperation, the delegations consider it advisable to
carry out in the future long-term exchange of specialists
on various problems of waste water and sludge treat-
ment.
The delegations agreed to carry out a long-term
exchange of specialists during 1977:
• of Soviet specialists in the US on the problem of
the use of technical oxygen in biological treat-
ment, and
• of American specialists in the USSR on the
problems of biological treatment plants' oper-
ations.
The detailed exchange program will be agreed five
months prior to the date of the participants' departure.
This exchange will be carried out on the basis of equal
and "receiving-side-pays" basis.
In the course of this visit to the US the Soviet
delegation visited water treatment plants in or around
the cities of Norfolk, Philadelphia, Harrisburg, and Erie,
154
-------
the Taft Scientific Research Institute and the Cyanamid
Company.
Both sides expressed their satisfaction that the
meeting was conducted in an atmosphere of friendship
and in a spirit of mutual understanding, thus contribut-
ing to the further development and strengthening of
cooperation in the field of environmental protection.
This protocol was signed on November 21, 1975, in
Washington, D.C. in two copies, in English and Russian,
both texts being equally authentic.
From the Soviet Side From the US Side
R. Slavolyubov Harold P. Cahill, Jr.
Chief of Delegation Chief of Delegation
155
-------
APPENDIX I
LIST OF SOVIET PARTICIPANTS
1. R. Slavolyubov
2. V. Ponomarev
3. I. Myasnikov
4. A. Belevtsev
5. I. Maksinmenko
6. M. Levchenko
LIST OF AMERICAN PARTICIPANTS
1. Harold P. Cahill, Jr.
2. A. Breidenbach
3. A. Paretti
4. Jesse M. Cohen
5. Walter J. Weber
6. Russell Gulp
7. Robert Polta
8. A. Cywin
9. I. Gellman
10 R, Dunlap
11. A. Marek
12. F. Sebastian
Chief of the Department, GLAVPROMSTROYPROEKT,
GOSSTROY, USSR Chairman of the USSR Delegation
Head of the Laboratory, VNII VODGEO, GOSSTROY, USSR
Head of the Sector, VNII VODGEO GOSSTROY, USSR
Senior Researcher, VNII VODGEO GOSSTROY, USSR
Senior Researcher, Interdepartmental Environmental Protec-
tion Council of State Committee of Scientific and Technical
Affairs
Deputy Manager, Trust "ORGCHIM" MINCHIMPROM
Chairman of the U.S. Delegation, Director Municipal Construc-
tion Division, US EPA Washington, D.C.
Assistant Administrator for Water and Hazardous Materials,
EPA, Washington, D.C.
Consultant, Water Programs, EPA, Washington, D.C.
U.S. EPA, Cincinatti, Ohio
University of Michigan, Ann Arbor, Michigan
Gulp, Wesner & Gulp, El Dorado Hills, California
Metropolitan Waste Control Commission St. Paul, Minnesota
Director, Effluent Guidelines, EPA Washington, D.C.
NCASI, Pulp and Paper Industry, New York New York
Carnegie-Mellon University, Pittsburgh, Pa.
American Cyanamid, Bound Brook, New Jersey
ENVIROTECH, Menlo Park, California
156
-------
APPENDIX II
LIST OF REPORTS PRESENTED AT THE USSR-US SYMPOSIUM "WASTE WATER TREATMENT -
PHYSICAL-CHEMICAL TREATMENT FACILITIES"
FROM THE USSR
1. Levchenko, M, N. "Treatment of Waste Water from Chemical Plants"
2. Myasnikov, I.N., Gandurina, L.V., Butzeva, L.N. "Studies on Waste Water Treatment with Flocculants
Application"
3. Korshak, V.V., Zubakova, L.B., Gandurina, L.B., "Synthesis of Cationic Polyelectrolytes for Treatment of
Natural and Waste Waters"
4. Myasnikov, I.N., Balakin, B.A. "The Removal of Volatile Suspended Solids from Waste Waters"
5. Belevtsev, A.N., Maksinmenko, Yu. L. "Studies on Oxidation Processes of Cianides and Phenols in Waste and
Natural Waters by Using Chlorine Dioxide"
6. Panova, V.A., Goriatchev, N.S., Lurie, U.U. "Examination of Oil-Containing Waste Waters Chemical
Composition after their Treatment in Aeration Tanks"
7. Ponomarev, V.G., Zakharina, S.B. "Treatment of Concentrated Waste Water Containing Oil Emulsions"
FROM THE US
1. Cohen, Jesse M. "An Overview of Physical-Chemical Treatment"
2. Weber, Walter J. "The Role of Activated Carbon in Physical-Chemical Treatment"
3. Gulp, Russell "Design of Facilities for Physical-Treatment of Raw Wastewater"
4. Polta, Robert "The Operation of the Physical-Chemical Treatment Plant at Rosemount, Minnesota"
5. Lacy, William, Cywin, Allen "Physical-Chemical Treatment of Waste Waters from the Petroleum Refining-
Petrochemical Industries"
6. Gellman, Isaiah "Current Status and Directions of Development of Physical-Chemical Effluent in the Paper
Industry"
7. Dunlap, Robert, McMichael, Francis "Dilemma of Coke Wastewater Disposal"
8. Marek, Anton, Askins, William "Advanced Wastewater Treatment for an Organic Manufacturing Complex"
9. Sebastian, Frank "Cost Benefits of Physical-Chemical Treatment"
157
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APPENDIX III
PROGRAM
USSR-USA COOPERATION Of WORKING GROUP ON PREVENTION OF WATER POLLUTION
FROM INDUSTRIAL AND MUNICIPAL SOURCES
.No
Title
Responible for
Form of Work From the From the Time
USSR USA
Expected Result
I Modernization of existing and
development of new combined
facilities with high efficiency
for wastewater treatment,
including hydrocyclones, mul-
tistage settlers, flotators,
facilities for usage of technical
oxygen, investigations of usage
of flocculants and coagulants
Development of hydrocyclones
and flotation facilities;
scheme of usage of coagulants
- Development of tubular and
plate settlers and facilities
for usage of technical oxygen;
scheme of usage of flocculants.
2. Intensification of wastewater
process in petrochemical,
chemical, petroleum refining,
pulp and paper, and metallurgical
industries.
Intensification of wastewater
treatment process in metallur-
gical and petroluem-refining
industries
Joint development of
themes, scientific
information and
specialists
delegation exchange
Symposium on
"Improvement of
Biochemical waste
water treatment
methods" (USSR,
May, 1976, 16 days,
7 specialists)
Symposium on theme;
"Wastewater treatment
Physical-Mechanical
Treatment Facilities"
(USA, September. 1976
16 days, 7 specialists)
VNII VODGEO
GOSSTROY
USSR
EPA Through 1978
Information and dele-
gation exchange
Information and
delegation exchange
VNII VODGEO
Gosstroy
USSR
VNII VODGEO
GOSSTROY
USSR
EPA
EPA Through 1978
VNII VODGEO
GOSSTROY
USSR
Improvement of
the efficiency
of existing
and development
of new treat-
ment facilities
reduction of
space for loc-
tion, reduction
of reagents as
cost price of
waste water
treatment
Increasing of
wastewater
treatment ef-
ficiency
introduction of
new treatment
schemes, maxi-
mize usage of
treated waters
in recircula-
tion
Intensification of wastewater
treatment process in petrochemical
and pulp and paper industries.
EPA
158
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PROGRAM
USSR-USA COOPERATION Op WORKING GROUP ON PREVENTION OF WATER POLLUTION
FROM INDUSTRIAL AND MUNICIPAL SOURCES
Responible for
No Title Form of Work From the From the Time Expected Result
USSR USA
3. Development of highly efficient
methods and facilities for re-
moval of nutrients and treatment
of municipal wastewaters
Development of methods and
facilities for removal of
nutrients and treatment of
municipal wastewaters.
Usage of treated water in
recycling systems at
industrial plants.
Treatment of wastewater
sludges.
Stabilization and dewatering
of wastewater sludges
Joint development
of themes, informa-
tionand delegation
exchange
VNII VODGEO
GOSSTROY
USSR
EPA 1977
VNII VODGEO
GOSSTROY
USSR
EPA
Information and
delegation
exchange.
VNII VODGEO
GOSSTROY
USSR
Development of
new treatment
facilities for
prevention of
water basin
entrophication
and development
of new treat-
ment systems
with the maxi-
mum usage of
treated water
in recircula-
tion at indus-
trial plants.
Reduction of
cost price of
waste water
sludge treat-
ment increasing
of treatment
facilities
efficiency.
Technology and facilities for
utilization and treatment of
wastewater sludges.
EPA
5. Exchange of two Soviet specia-
lists for 4 months in US on
the problems of usage of
technical oxygen at bio-
logical waste water treatment
plants.
Exchange of two American
specialists for 4 months
m the USSR on the problem
of biological industrial and
municipal waste water treatment
plants.
Study of research
work of American
companies and
organizations,
participation in
scientific studies
Acquaintance with
research work of
the Soviet organiza-
tions and institutes,
participation in
scientific studies.
II Quarter
1977
III Quarter
1977
Studying of
the US
experience in
the field of
waste water
treatment.
Studying of the
USSR experience
in the field of
waste water
treatment.
159
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