USA-USSR
WORKING GROUP
ON THE PREVENTION OF
WATER POLLUTION
FROM MUNICIPAL AND
INDUSTRIAL SOURCES
Vodgeo Moscow, USSR
August 23-24, 1976
SYMPOSIUM ON
INTENSIFICATION OF
BIO-CHEMICAL
TREATMENT OF WASTEWATERS
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 'WASHINGTON DC 20460
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USA-USSR
WORKING GROUP
on the
Prevention of
Water Pollution
from
Municipal and
Industrial Sources
Symposium on
Intensification of
Bio-Chemical
Treatment of
Wastewaters
Vodgeo
Moscow, USSR
August 23-24, 1976
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INDEX
Preface 1
Opening Address - Mr. John T. Rhett 2
Papers Presented at the USA/USSR
SYMPOSIUM
Yakovlev, S.V., Skirdov, I.V., Rogovskaya, C.I.,
and Shvetsov, V.N. (Vodgeo), Kinetics of
Biochemical Oxidation 4
Cywin, Allen (US EPA), Chemical Additions to
Biological Treatment of Petroleum Refinery
Wastewater 16
Shifrin, S.M., Mishookov, E.G., Ivanov, G.V.
and Golookovskaya, E.K. (Leningrad), The
Trends in Intensification in Biochemical
Treatment of High Density Wastewater 22
Lacy, William (US EPA), Steel Industry
Wastewater Treatment Using Biological-
Chemical Technology 25
Gerber, V.Ya (Bashkirian Scientific Research
Institute of Petroleum Refining, USSR),
Facilities Improvement for Biochemical
Treatment of Petroleum Refinery Wastewater 30
Rosenkranz, William (US EPA), Biological
Methods for Control of Nitrogen in Municipal
Wastewaters 32
Skirdov, I.V., Shvetzov, V.N., Bondarev, A.A.,
Lurje, B.I., Bereykina, N.G., Katchkova, S.E.
(USSR), Operation Experience of Oxytanks 36
Sebastian, Frank and Lachtman, Dennis
(Envirotech), Improvements for Kraft Pulp and
Municipal Treatment Processess 41
Yakovlev, S.V. and Karjukhina, T.A. (USSR),
Biological Wastewater Treatment in the Presence
of Steroid Compound 50
Harper, Fred (Orange County Sanitation
Districts, California) A Comparison of
Conventional Activated Sludge Process and Pure
Oxygen Activated Sludge Process for a 75 MOD
Secondary Treatment Facility 54
Skirchiavichus, A.L. (The Kaunas Polytechnic
Institute of Snechkus A.) Studies of Artificial
Aeration in the Lithuanian SSR 60
Adams, Carl (Associated Water and Air
Resources Engineers, Inc) and Sumner, Billy
(American Consulting Engineers Council, Barge,
Waggoner, Sumner and Cannon), Wastewater
Treatment Concerns of the Organic Chemicals
Industry in the United States 62
Skirdov, I.V., Shvetzov, V.N., Morosova, K.M.,
Gubina, L.A. (USSR), Biochemical Treatment of
Highly Concentrated Wastewaters From Wool-
Scouring Operations 70
Love, William (Hampton Roads Sanitation
District, Norfolk, Virginia), Analytical and
Process Improvements in Biological Treatment of
Municipal Wastewaters 74
Ysrshov, A., Kyghel, M., Zemlyak, M.
(Candidates of Sciences), Development and
Improvement of the Municipal Sewage Biological
Treatment Facilities 78
Protocol 80
Appendix I Participants 81
Appendix II Reports 82
Appendix III Program 82
Appendix IV Itinerary 84
U.S. Environmental Protection Agency
M
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PREFACE
The third cooperative USA/USSR symposium on the
Intensification of Bio-Chemical Treatment of Wastewaters
from Municipal and Industrial Sources was held in Mos-
cow, USSR at the Vodgeo headquarters on August 24
through 25, 1976. This symposium was conducted in
accord with the protocol of the Fourth Session of the Joint
USA/USSR Commission held in Washington, D.C. from
October 28 through 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 John T. Rhett of the United
States Environmental Protection Agency and the Soviet
delegation by Professor S.V. Yakovlev of the Department
of Vodgeo in the Soviet Union.
The fifteen papers that were presented at the symposium
(seven US and eight USSR) are reprinted in English in this
volume.
This volume is reprinted in English in accord with the
protocol signed by the delegation leaders on September 4,
1976 in Moscow, USSR.
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OPENING
ADDRESS
John T. Rhett
Introduction
This third symposium of the U.S./U.S.S.R. "Working
Group on the Prevention of Water Pollution from
Municipal and Industrial Sources" represents another
milestone in the advancement of cooperation between our
nations in improvement of the earth's environment. It is
said that cooperation in environmental matters can serve as
a model of how two countries can cooperate for the mutual
benefit of themselves and of all nations. Certainly this has
proven to be so in our group where so much progress has
been made so swiftly in the areas to which we have
addressed ourselves.
It is especially significant to the world that our activities
have been directed not only to municipal treatment of
sanitary wastewaters, but also to industrial wastewaters. As
our countries are the two nations with the largest gross
national products of the world we have the greatest need to
treat industrial wastes as well as the greatest opportunity to
learn how methods of treatment can be improved so that
there is no threat to the environment. Not only industrial
strength is characteristic of our nations, but also the need to
give world leadership in industrial environmental control.
U.S. Municipal Wastewater Treatment
Systems
On the part of the United States, we have embarked on
one of the largest public works programs in the history of
the world in order to bring our waters up to fishable and
swimmable standards by 1983. This endeavor involves
18,000 municipalities with a combined population of over
200 million people. Our Congress has provided $18 billion
in grants to municipalities in order to initiate the clean-up
program. With this $18 billion, which represents 75% of the
total construction cost of $24 billion, 9,000 municipalities
will have established their sewerage systems by next year.
However, less than 40 percent of the 1977 population will be
served by secondary treatment or some higher level
necessary to meet water quality, principally because the
large cities will not have had time to complete construction.
We still have a long way to go, and it will require additional
large sums of money to accomplish our goal. Already,
however, we have 7,126 active projects underway, with
10,500 slated for next year.
One of our principal tasks has been to keep the
municipalities enthusiastic and moving on the program of
cleaning up their waters. We have found it necessary to have
seminars, briefings, and conferences that bring the message
to every potential community that is eligible for Federal
assistance. This endeavor has worked remarkably well and
has enabled national goals and standards to be integrated
into local government aims and needs. We are pleased by
the progress that has been made in this area and the
cooperation that has been fostered.
U.S. Industrial Wastewater Treatment
Systems
Environmental concerns have also been integrated into
the decision-making process in industry. Many industries
have actually found it more profitable to operate with
environmental concerns in mind and to recycle and
conserve water used in their processes and to recover
valuable resources from wastewaters. Together government
and industry expended about $15.7 billion in pollution
control last year and a goodly portion of this amount was in
control of wastewaters. Of special note is the fact that a new
pollution control industry has been created which employs
some one million workers.
Of course, our municipalities are also involved with
treating industrial wastes, just as Soviet industry and
municipalities cooperate in combined treatment systems.
Our working group has made significant contribution to
making knowledge known about how pretreatment of
industrial wastes can be accomplished so that municipal
systems can operate efficiently in treating the remaining in-
dustrial wastewaters.
First Working Group Symposium
I would now like to comment on the progress that has
been made by the Working Group on the Prevention of
Water Pollution from municipal and industrial sources.
Our first cooperative U.S./U.S.S.R. symposium on
municipal and industrial wastewater sludge, held in
Moscow in 1975, was a fundamental contribution to ways
of handling the increasing amounts of sludge that are being
generated by our improved wastewater treatment methods.
Depending upon the composition of a wastewater
treatment plant's sludge, the quantity involved, and the
disposal method, disposal of sludge can have an important
impact on the environment. It is therefore essential for
wastewater treatment installations to consider the proper
disposal of the sludge that is produced. In fact, this is one of
the most important factors that must be considered in the
design of any wastewater treatment facility.
Our insight in making sludge the first topic of our series
of symposia was a fortunate one. Time has proven that the
method of disposal of sludge is both a problem and an
opportunity. As our symposium indicated, the ultimate use
of sludge as a valuable resource for many worthwhile uses
has to be the ultimate goal of cur efforts. I believe that we
have made significant progress in the last year. In fact, EPA
has established a sludge Task Force which is just about to
issue its report on developments in this area and the first
symposium provided excellent background material for its
efforts.
Second Working Group Symposium
Our joint symposium last year at Cincinnati, Ohio exam-
ined physical/ chemical treatment of wastewaters from
municipal and industrial sources. It is here that we are at the
cutting edge of research and innovative methods in
wastewater treatment. The methods discussed at the
symposium are essential tools with which to work to
provide the most cost-effective treatment of difficult wastes
while at the same time providing the means to make
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possible the recycling and re-use of water resources. More
and more, our water resources are becoming scarce relative
to uses that have to be made of them. There is, of course, a
definite limit to the amounts of water that are available
from nature. Our only means of meeting the need for
increased use is through conservation and re-use. The
physical/chemical treatment methods offer us unparalleled
opportunities for re-use, as set forth at our symposiums. We
can be sure that that symposium will always be a landmark
in progress in treating wastewaters, if only for its
contributions to the science of re-use. But, of course, the
symposium was significant in a multitude of other areas of
scientific advance in wastewater treatment. The symposium
papers will need to continue to be mined for valuable
insights, data, and practical applications.
Third Working Group Symposium
Our third symposium, which we have convened today, on
"Intensification of Bio-Chemical Treatment of Waste-
waters", is another building block to the success of the
mutual efforts of our nations in bio-chemical methods of
treatment. Treatment methods are beginning to show
important advances and are a key to many difficult cases of
treatment needed.
It is especially notable here that a paper will be presented
from each of four related industry groups: chemical
technology; pulp and paper; femorous metallurgy and
petroleum refining; and petro-chemical. In addition,
municipal treatment processes will be discussed that use
bio-chemical treatment. These industrial groups represent a
great percent of the total wastewater flows to be treated by
industry. As such, we are really covering the problems and
opportunities of almost all of the industrial flows that must
be considered. Therefore, we can make real advances in
exchanging knowledge of bio-chemical, methods and
processes for treating industrial and municipal wastewaters.
I wish you great success in your efforts.
Fourth Working Group Symposium
I look forward to our fourth working group symposium
which will be convened in January 1977, again at the EPA
Cincinnati research complex. The subject of the symposium
will be Physical-Mechanical Wastewater Treatment." This
subject area will continue to round out our efforts to have a
comprehensive view of the subject field of municipal and
industrial wastewater treatment methods and opportunities.
Fortunately, you will be able to see our new research
facility at Cincinnati in full operation. You will remember
that in November of last year it was still being completed
and was unoccupied. We are happy that we are able to
extend to the working group an invitation to attend the
second Cincinnati meeting.
Conclusion
My review of the accomplishments of the symposia and
visit to the municipal and industrial treatment works of
both our countries, leads me to conclude my remarks by
expressing a certain amount of amazement that we have
been able to progress so far in a relatively brief time. We
have approached our mission in a spirit of cooperation and
creativeness. We have tackled first things first and have
made headway by our industrious and inspired efforts. We
have more than fulfilled the assignment that was placed
upon us, yet there is further progress that we can mutually
undertake. I congratulate you on all of your efforts and
results. Let us now move forward even more in improving
our own and the world's environment.
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Kinetics of Biochemical
Oxidation
by Yakovlev S.V., Skirdov I.V., Rogovskaya
C.I. and Shvetsov V.N.
All-Union Scientific Research Institutes
VODGEO
In the near future biological methods will continue to
play the principal role in the main body of wastewater
treatment technology due to a number of advantages the
biological treatment has as compared to the physical-
chemical methods known.
It should be noted however that the biochemical
treatment method has not yet. exhausted its abilities.
At present the improvement of the process by means of it
being affected by external factors is considered to be the
most practicable.
Methods of the biological treatment process improve-
ment in aeration tanks by increasing either concentration of
activated sludge microorganisms or dissolved oxygen
concentration (or its partial pressure) as well as increasing
the substrate concentration in first stages of the process
carried on in plug-flow aeration tanks have become a
practice in sanitary engineering.
The potential abilities of this method may be revealed in
full measure during the studies of the process kinetics taking
into account interrelation of the main factors.
In the cells of microorganisms of activated sludge, which
is the main agent of the biochemical treatment process,
many enzyme-catalysed reactions occur simultaneously, the
enzymes being closely linked together thus forming complex
polyenzymic systems. The peculiarity of biological enzymat-
ic systems is their ability to self-regulation.
Having the data about the principles of such self-
regulation it is possible to simplify the complex chains of
biochemical reactions essentially.
Under stationary conditions the amount of the material
passing through each separate stage of the process must
be the same, so the rates of each separate reaction must be
equal too. Under these conditions the rate of the process
will depend on the rate of the slowest reaction. This concept
developed by lerusalimsky (1) was called "the minimum
principle." It is postulated in it that "the rate of the total
process depends upon the rate change in the slowest stage
only" while the rate increase in the other stages doesn't
affect the process. The minimum principle explains such
peculiarities of enzymatic systems as their low conversion
and saturation. In stationary conditions the minimum
principle allows to follow only key reactions without taking
into account many secondary ones.
As distinct from non-enzymic reactions the enzyme-
catalyzed reaction rate increases with a gradual slowing-
down rather than proportionally to the substrate concentra-
tion increase and reaches a certain maximum, the value of
which depends on the enzyme concentration.
Kinetics of the enzymatic reactions is based on the
assumption that there is some enzyme-substrate complex
and that the reaction rate depends on the rate of its
degradation. The complex is assumed to be formed
instantly, because its concentration is constant and defined
by thermodynamic equilibrium between the enzyme,
substrate and this complex.
Assuming that the completion of an enzymatic reaction is
preceeded by formation of enzyme-substrate complex
Nichaelis and Menten (2) presented it by the following
scheme
"1,
+ E 4 _ SE
K-l
P + E
and thus obtained the well-known Equation
V + S
V = vmax a
(1)
where V is the reaction rate at substrate concentration S;
V maximum reaction rate without substrate limit-
ing;
Ks reaction constant.
In works by Monod (3) and lerusalimsky (1) the biomass
growth rate (A) was shown to be described by the
analogous equation:
where/^ = dtx ; * is the microorganisms concentration.
The relationship between substrate uptake rate and
biomass growth rate is usually expressed by the depend-
ence :
dx =-y ds
dt dt
where y is the proportionality factor, characterizing
biomass yield per unit of the substrate consumed (economic
coefficient).
Keeping in view dependence 2, the equation for the
substrate uptake rate can be written in the form:
ds = 1 mavS
dt y
x.
(4)
This equation and its modifications were successfully
used by Hinshelwood, Herbert, Dawning, Benedek, Gunter
et al (4, 5, 6, 7, 8) in mathematical models of biological
wastewater treatment systems.
A number of investigators stick to different, fully empiric
dependences, based on so-called two-phase theory of
substrate removal, proposed by Garret and Sawer (9). This
theory was used later by Eckenfelder, McCabe, Korolkov
and Bazyakina (10, 11, 12).
In accordance with this theory and on the basis of
experimental data the process of activated sludge microor-
ganisms growth can be conditionally divided into two
phases: in the first one the substrate concentration exceeds
the limit, necessary for the complete saturation of enzymic
systems, in the second one the saturation rate decreases as
the substrate is removed.
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For the first phase the following type of Equation is
assumed:
dx_ - KjX (5)
dt
and for the second one
&L = a • K',x • S, (6)
dt
where a is an empiric coefficient and coefficients K^ and X
are combined:
K'2x = K2.
In a transition point of these two phases where the growth
rates are equal according to Equations S and 6 Kix = afeS.
The further development of this theory by Wuhrman et al
(13) as applied to the multicomponent substrates has led to
the hypothesis according to which the waste water substrate
removal curve is the superposition of direct line segments
characterizing uptake of a particular substrate compounds
by activated sludge. •
With the help of this hypothesis a satisfactory agreement
of the calculated data with the experimental ones can be
obtained as shown by the work of Evilevitch et al (14).
It should be noted however that the use of theoretical
regularities known in modern biochemistry and microbiol-
ogy gives more possibilities for the mechanism of the
biological treatment process to be revealed as compared to
empiric formulae which have a particular character. It must
be born in mind that either for a single cell or for a complex
biocoenosis of activated sludge oxidizing multicomponent
substrate the minimum principle is apparently valid, that is
the limiting of the process by one, the most slow reaction.
Information obtained from the literature can't give a clear
unambiguous answer to the question about the character of
the relationship between the MLVSS and the rate of
organic matter oxidation in aeration tanks.
A number of recent investigations (15,16) show that there
is no proportional relationship between the MLVSS and the
rate of oxidation; sludge activity measurably decreases
when its concentration increases. Analogous phenomenon
is observed during the propagation of living organisms
population in the process of biological synthesis as well. In
general this phenomenon can be caused by the following
reasons:
— the mass exchange deterioration due to the change in
reological properties of mixed liquor;
— interspecied competition of microorganisms;
—microorganisms development suppression by products
of their metabolism.
The lack of information referring to the effect of the
MLVSS concentration upon the rate of biochemical
oxidation does not permit drawing a conclusion about the
mechanism of this phenomenon.
It should be noted that there is no agreement in the
works devoted to the dissolved oxygen concentration effect
upon the activated sludge microorganisms metabolism, and
the experimental results are very contradictory. Some
investigators point out to the existence of the dissolved
oxygen critical concentration above which the oxygen effect
on the process is not observed (17,18, 19). Concrete values
of this concentration according to the data obtained by
different investigators have an essential error. In other
works mainly referring to the enzymes production, a
suppressive or toxic effect of high D.O. concentrations was
observed (20, 21). In a number of recent works dealing with
the problem of oxygen use for biological treatment (22, 23)
an evident positive effect of the oxygen concentration up to
30 mg/1 was marked. In this case the rate of substrate
removal increases and the settling properties of mixed
liquors is being improved.
Disagreements in the evaluation of oxygen effect upon
the biological treatment process can be explained by the
influence of many secondary factors badly affecting the
experimental results, by the insufficient variation range of
the parameters under study and by the absence of uniform
methods and suitable equipment for such investigations.
It should be outlined especially that the theoretical
aspects of D.O. and MLVSS concentrations effect on the
kinetics of the biological treatment process have been
studied insufficiently.
It is known from biochemistry that the molecular oxygen
can be involved in the cellular metabolism in three ways:
1. as a terminal electrone acceptor in the respiration
chain;
2. at the direct incorporation into the substrate to be
oxidized;
3. for direct acceptance of hydrogen from dehydrogenases
with the hydrogen peroxide formation, without respiration
chain being involved.
The molecular oxygen role in the cellular metabolism is
extremely great, because it is one of the most important
components of the processes providing the microorganisms
with the energy and material for their biosynthesis.
The molecular oxygen does not only take part in the final
substrate oxidation but oxygenates a large number of
organic compounds in the initial stages of their metabolism,
and thus enables their being used by microorganisms.
Due to the conjugation of oxidation and phosphorilizing
oxygen influences on the energetic level practically all
enzyme-catalyzed processes proceeding in the cell. On this
basis one can assume that the oxygen effect must be
described mathematically by equations of enzymatic
reactions. Since the substrate and oxygen take part in the
oxidation process, this equation must be one of the
bisubstrate enzymatic reaction equations the type of which
may be determined after the analysis of experimental data.
The attention of investigators in the field of wastewater
treatment is especially attracted by the theoretical aspects of
the regularity between biochemical oxidation of organic
compounds and their physico-chemical structure, kinetics
of its biochemical destruction and enzymatic properties of
the microorganisms involved in the process.
When studying the effect of the material structure on the
biochemical destruction process Winter (29) has drawn a
conclusion that in most instances the rate of destruction
decreases as the molecular weight increases. The oxidation
rate decrease was observed in the homologous series of
alcohols with lengthening of hydrocarbon chains. By the
author's opinion the chain branching decreases the
oxidation rate essentially. It is valid, however, for the
aliphatic series only.
An unimportant change in the structural formula of a
substance produces a considerable effect on biological
oxidation. Substances with the hydroxide radical are
oxidized readily.
When studying the effect of various functional groups on
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the rate of the organic compounds destruction Winter
marks the continuous decrease in the rate of the biological
degradation involving the following succession: — SO2H,
— OH, —COOH, —NH2, —CN, —CHOH, — CH,OH,
—OOC, —CH2, —CH3.
Among the aromatic compounds benzene is the least
biodegradeable; compounds with a short side chain such as
toluene and ethylen benzene are a little more biodegradable.
Compounds with longer side chain inhibit biological
destruction almost completely.
The information available gives only approximate data
concerning the effect the molecular structure of substances
produces on their biochemical oxidation parameters.
In the majority of the well-known works (30, 31) the
quantitative evaluations are absent, many of the data are
contradictory since the investigations were conducted in
different conditions and under different methods. Criteria for
the experimental data evaluation various as well.
These circumstances caused the necessity for special
complex investigations to be conducted including techno-
logical, miclobiological and oxidation process of organics
belonging to different classes.
Methods of Investigations
It was shown previously that the metabolic activity of the
microorganisms depends on the external parameters and
first of all on the concentration of a carbon substrate and
D.O. concentration.
The lack of only one component in the environment causes
decrease in the metabolic activity, that is why investigation of
the external parameters affect the so-called "limited" media
are usually used, where the amount of only one component
under investigation is varied and the other components
necessary for the cell growth are present in excess.
In modern practice of biological studies in general and
studies of kinetics of wastewater organics biochemical
oxidation ' in particular, two approaches are used: the
continuous cultivation method and the method of investiga-
tions in batch conditions, each of them having its own
advantages and shortcomings.
On the basis of the properties of the subject under
investigation and the aims of investigations a method must
be chosen capable of providing the maximum reliable
information with the minimum of efforts and expenditures
spent.
Activated sludge has a number of specific properties the
most important of which are its biological inertia and
adaptation.
Biological adaptation of activated sludge is such a
phenomenon when the cell gradually rather than imme-
diately adopts to the environmental change. Increase in the
cell growth rate is connected with the preliminary increase
in the amount of ribosomes and other organelles responsi-
ble for protein synthesis. The process takes the time
comparable to the time for cell reproduction.
Adaptation of microorganisms to the particular environ-
mental conditions is connected with the reformation of the
cell enzymatic apparatus as well as the change in the specied
composition of the activated sludge as a result of natural
selection and mutation. When environmental conditions are
changed adaptation causes corresponding changes in
biochemical properties of the culture.
When evaluating the microorganisms properties one
should bear in mind that the substrate biological destruc-
tion is carried out by enzymatic reactions the duration of
which amounts to seconds.
As compared to the synthesis reactions of enzymatic
macromolecules or to the processes of the cell working
apparatus formation (ribosomes, mitochondrions, mem-
branes) the duration of which amounts to hours enzymatic
reactions may be considered very rapid ones.
Comparing the continuous- and batch-flow methods it
should be mentioned that in the closed system of batch
studies simultaneous change of several parameters with time
(substrate, oxygen, metabolite and biomass concentrations
etc.) is inevitable. This makes the evaluation of some
parameters under investigation difficult. Besides, the
phenomenon of biological inertia can sharply reveal itself
here.
The continuous-flow cultivation method does not possess
the above mentioned disadvantages of the batch method
because it theoretically allows to keep the biological system
studied in the given equilibrium state for unlimited period
of time. However when the continuous-flow process is
carried on in practice serious technical difficulties can occur,
breaking its stability and lowering its accuracy and the
reliability of experimental data. These difficulties are caused
by the necessity for the microamounts of substrate elements
to be dosed precisely as well as the necessity for stabilization
of biomass concentration, pH, aeration intensity or O2
concentration etc. Any reliable control devices for many of
these parameters have not been available yet.
On the other hand the change of external parameters in a
continuous-flow reactor ineritably leads to adaptation and
so to the chape in biochemical properties of activated sludge
that interferes with the analysis of the external factors affect
on biochemical properties of activated sludge that is upon
its enzymatic apparatus.
Thus none of the accepted methods can pretend to be the
universal one, each of them has its own field of application.
The continuous cultivation method is expedient to be
used for the growth of activated sludge biomass adopted to
a certain substrate. This method is irreplaceable for the study
of slow adaptation processes.
When the effect of the external parameters upon the
sludge enzymatic activity is studied the batch tests are
rationaly used.
In batch tests the right choice of the interval in which the
process rates are measured is of great importance. It must
be small enough in order for the substrate and activated
sludge not to take the time to alter significantly and the
metabolite concentration not to reach a noticeable value.
Besides, this interval must be large enough in order for the
equilibrium of the system, that is a quasi-stationary state of
kinetic parameters, to be reached.
On the basis of general considerations concerning the
methods of investigations into the kinetics of biochemical
oxidation the bench-scale studies were carried out on
continuous-flow models of aeration tanks of various
modifications as well as by means of running "sharp" tests
in batch-flow aeration tanks and respirometers.
In continuous-flow conditions the experiments were run
for comparison of D.O. concentration and MLVSS
concentration effect upon the biochemical oxidation rate
for various substrates. The necessity for these experiments
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to be run was dictated by the desire to bring the results of
bench-scale studies close to full-scale conditions since they
allow to take account of the activated sludge adaptation to
certain substrates and to other external conditions which
can take an important effect on the sludge activity and on its
physical characteristics, in particular upon the settling
properties.
During investigations a regular technological control for
the operation of the units was carried on. The microbial
content of activated sludges, its physical parameters (such
as sludge volume index (SVI), the size and the form of
zoogloen), ash content, COD and BOD of the effluent and
mixed liquor, MLSS, N, and P content of the effluent were
determined. Chemical analyses were conducted by Standard
Methods.
A Complete-mixing Aeration Tank
A conventional laboratory aeration tank served as a
model of the complete-mixing aeration tank (Fig. I).
Aeration tanks for operation with high MLSS concentra-
tions were rigidly fixed with the settling tanks.
Sludge recirculation was carried on either by a dosing
diaphragm pump or at the expense of the difference
between volume weights of air-water mixture.
The control for air supply was carried on manually in
accordance with the given oxygen profile. The D.O.
concentration was determined periodically by an electro-
chemical sensor.
A Counter-flow Aeration Tank
For determination of the counter-flow efficiency in the
process of oxygen absorption and its uptake by biochemical
oxidation the model of a counter-flow aeration tank was
used.
The counter-flow aeration tank operated in the regime of
a complete-mixing reactor; it was a closed circuit compris-
ing two vertical columns made of plexiglass (Fig, 2).
Recirculation of the liquid in the circuit was created by an
impeller pump (I) fixed in the upper part of the recirculation
column (2). This permits the necessary rates of the
downflow in the aeration zone to be obtained (column 3).
The rate of recirculation was measured by the head loss in
the measuring diaphtagm (5) and was regulated by a valve
(6). Influent was fed to the aeration tank through the tubing
(7) in the upper part of the aeration column. Either oxygen
or air was fed through the porous diffuser (4) in the lower
part of aeration zone.
The oxygen profile stabilization was fulfilled by automati-
zation of the air supply system on the basis of D.O.
analyser. This system provided the accuracy of D.O.
concentration ±1.0 mg Off 1 in the range of this parameter
change from 3 to 20 mg/1.
dozing pump
effluent
influent
°f * laboratory «>n«Pl«t« mixing aeration
Respirometers
The large part of experimental data was obtained as a
result of investigations conducted on respirometers.
The experiments were run in order to obtain kinetic
constants for equation of enzymatic reaction during
investigation of the effect, the' substrate, oxygen and
activated sludge microorganisms concentrations have upon
the process.
The respirometric method is widely used in biological
studies of such processes accompanied by gas-exchange as
plant 'photosynthesis, metabolism in tissues and respiration
of microorganisms.
The advantage of respirometric methods are their relative
simplicity and ability of making direct volumetric determi-
nations of the oxygen consumed as well as the continuous
observations with the automatic recording of the data.
Negligible inertia allows to work with the small amounts
of substrate.
The possibility of simultaneous gas-exchange analysis on
the basis of oxygen uptake and carbon dioxide release
places the respirometric method in a special position even as
compared to such modern methods of investigations as
polarography and CO2 analysis with the help of experimen-
-------
tal acoustic analysers.
Warburg manometric instruments were practiced on a
large scale for respirometric studies, but they have a number
of serious disadvantages such as a small volume of cultural
vessels, the impossibility to control during study the
following process parameters (oxygen profile, pH, substrate
composition and concentration).
sludge separator
£
effluent
(to the
darifier)
dosing pump
for sludge
recirculation
dozing pump for
excess sludge
removal
differential i
manometer
Figure 2 The scheme of a laboratory counter-flow
Automatic manometric instruments - respirometers -
have been used recently. They differ from Warburg
respirometers by large volume of cultural vessels, intensive
agitation, aeration of tne culture and forced absorption of
the carbon dioxide released.
In the laboratory of biological treatment a continuous-
flow respirometer was developed, the scheme of which is
given in Figure 3,
The respirometer consists of the following principal
units:
I. The unit of microorganisms cultivation consisting of
three hermetic vessels with impeller aerators;
II. The unit of automatic oxygen supply with wet
gasholders;
III. The unit of automatic recording of the oxygen
consumed;
IV. The unit for carbon dioxide removal from gas
mixture with mic/ocompressors and scrubbers;
V. The unit of temperature stabilization with contact
thermometers;
VI. The unit of D.O. concentration measurement with the
help of D.O. andlysers " -152.003".
VII. Sludge separation unit with vertical settling tanks;
VIII. System of sludge feeding and recirculation with
plunger pumps;
IX. pH stabilization system;
X. MLVSS stabilization system.
The respirometer was provided with three fermenters
each of them equipped by autonomous systems of air
supply, gas purification, temperature stabilization etc. This
allows to conduct parallel investigations in a wide range of
parameters change as well as technological researches of
multi-stage systems of wastewater treatment.
The instrument has the following technical characteris-
tics:
VIII
VII
Figure 3 Technological scheme of respirometer
I. The fermenter capacity is 3 1.
2. The oxygen feeding accuracy 0.4-0.8 cm'
3. One scale division of the consumed oxygen recorder -
6mg/l.
-------
4. Accuracy of the consumed oxygen registration is 1.5
mg/1.
5. The system of D.O. concentration recording is
automatic. The accuracy of recording is ±0.5 mg/1
when the instrument of the type -152.003 is used.
Variation range of D.O. concentration is 0.5-20
mg/1.
6. The system of control for the carbon dioxide released
(potentiometric titration with Ba(OH)2 is manual or
automatic. The accuracy of CO2 control is 2 mg/1.
7. Agitation and aeration is carried on with the help of
an impeller having 6-step reducer with 200-1500
rev/ min.
8. The system of temperature stabilization with heating
and cooling is automatic. The accuracy of stabiliza-
tion is ±0.25° C. The temperature variation range is
+5 - +40° C.
9. Feeding of the substrate is carried on by plunger
pumps with a continuous change from 0.01 to 10
cm3/min. The accuracy of feeding is ±5%.
10. Sludge recirculation is carried on by plunger pumps
with continuous change in discharge from 0.01 to 10
cm3/min. The accuracy of feeding is 5%.
Finishing the description of the methods of experiments
for biochemical oxidation kinetics determination one
should mention a very important peculiarity of biological
systems and of activated sludge in particular. This
peculiarity is the poor reproducibility of the experimental
data. It is caused by two factors: by inaccuracy of
instruments and to a large extent by their poor reproducibil-
ity (or by so-called time drift) which depends on biochemical
properties of activated sludge.
The dispersion of the results caused by the time drift
usually exceeds by the order the dispersion caused by
inaccuracy of measurements. Relatively law efficiency of
strictly successive methods of the experiment planning at
the researches of biochemical systems may be explained by
this fact.
In order to control disagreement of the results caused by
time drift it is appropriate to carry on the experiment in
such a way that all values of the parameter under
investigation could be studied in one run. Very often it is
not possible to do; then several series of tests should be
conducted, but in each series one test from the proceeding
one should be repeated. On the basis of the test repeated it
will be possible to determine the disagreement caused by
time drift.
Discussion of the Experimental Results
A. THE SUBSTRATE CONCENTRATION EFFECT
The dependence of the biochemical oxidation process
rate on the substrate concentration was studied in continu-
ous-flow conditions on models of complete-mixing aeration
tanks and in batch-flow conditions on respirometers,
Such pure chemicals as acetone, normal propyl alcohol,
isopropyl alcohol, propionic aldehyde and propylenglycol
etc. and real industrial wastewaters of yeast and antibiotics
production were used as substrates (as the sources of
organic carbon).
In accordance with the working hypothesis the substrate
concentration effect on the specific reaction rate is described
by the equation of enzymatic reactions (4) the kinetic
constants of which may be determined graphoanalytically
by Lineweaver - Berk method according to which the initial
Equation 4 is presented as reciprocal values
_L = 1 + Ks
V
'max
vmax ^
(5)
_1_ J_
In coordinates V ; S the graphical form of this equation
is a straight line intersecting the axis J_ in a point of 1
1 1 V V
and the axis — in the point of—. max
S Ks
The experimental data plotted to this graph have shown
that straight lines have different angles of inclination for
different series of tests but intersect in one point (_L_). It
-Ks
points out to the fact that one of the reaction components is
not homogenous, which is caused by the time drift of
activated sludge.
The existence of the common point of intersection shows
that the change of the sludge enzymatic activity affects the
function V = f(S) in accordance with the law of noncompe-
tent modification, the equation of which has the form:
V = V
f _Kj_\ s
maxl I
M + K. /K.+
1 3
(6)
where K, - kinetic constant of the modificator;
I - modificator concentration.
In reciprocal values the equation can be presented as
(7)
'max
It follows from the graphical form of the Equation 7 that
the relative activity of sludges for each series of tests differs
by the multiplier ( ) and may be evaluated through
the ratio of maximum values
L =
1/Vj
= VcPmax
1/V,
(8)
max
'max
where L - sludge activity coefficient for the given series
of tests.
VcPmax " meiinvalueofvmax
vlmax - valueofvmax for the 8iven series of tests.
Values of specific rates with correction for the sludge
activity time drift may be defined as
V'= V, d,, (91
where Vj is a reduced value of Vmax for the given series of
tests.
The corrected values of oxygen uptake rates and the
-------
initial data for their calculation are given in Fig. 4. It
follows from the graph that
max
= 99.4mgO2/g of VSS/hour.
I
'.',
1.0
Ks= 152 mg/1
The terminal form of the function V=f(S) for acetone,
oxidized by the activated sludge, is given in the Fig. 5 where
the points, obtained by the calculation in accordance with the
equation 4, are connected by a curve.
The corrected values of the experimental data agree with
the calculated curve, their maximum deviation does not
exceed 5 percent.
It should be noted that without time drift these ratios
reached 213%.
Analysis of the graphical forms of the function V=f(S)
(Fig. 4) shows that curves have smooth slopes with the
asymptotic approaching to V max, consequently the approx-
imating of this curve by the two straight lines is wrong from
the theoretical point of view.
!
-L
If:
Figure 4 Determination of kinetic constants by Lineweaver-Berk
method
;
0i
j.
t
[
~,
,.
•-
— ^
oa 2>
o»
3
ir(-/ff/-
•* V
V,'
-t
„., »f/,w
•Xft^t
•— • —
-------
be proved.
The biomass growth rate in the Ferhulst equation may be
expressed through the specific oxidation rate:
.dx. = 1 .x (11)
dt y n
(the designations are the same).
The specific oxidation rate for a particular kind of sludge
at x = 1 g/1 and other conditions being invariable is the
constant, that is i= E. (12)
With consideration of Equations 11 and 12 Equation 10 is
reduced to the following form:
JL = L (
1 E
x)
Introducing designations for constant coefficients
V. =Aand X. = B
E E
we obtain
= A -
(13)
Expression 13 is the direct line equation, that doesn't
correspond to the experimental data, given in the plot (Fig.
Hence, the Ferhulst equation can't be applied to the
activated sludge biocoenoses.
As previously mentioned the decrease m the sludge
activity may be caused by the products of metabolism
release, inhibiting biochemical oxidation process which
mechanism is described by the following equation
V =
(14)
where the inhibitor concentration according to lerusahmsky
(26) is proportional to the amount of microorganism
biomass.
1=
(15)
The rest designations are the same.
In Equation (14) in conditions of constant substrate
concentration or its excess (in these particular conditions a
comparison should be made) the members characterizing
the substrate effect may be expressed by a constant
= A
(16)
The specific oxidation rate at x = 1 g/1 for a particular
substrate may be considered a constant as well.
V. = E (17)
Then the Equation will assume the form:
V = A
Ki
(18)
Zx
The rates ratio with consideration of the assumptions
made may be expressed as follows:
V_
Vi
AKi
E(Zx + Ki)
(19)
For the graphical interpretation it is convenient to
present the Equation obtained (19) in the form:
-v
K. )
\_
A
(20)
For a concrete substrate the Z/Ki ratio is a constant.
So we can assume that Z/Ki = where Y is the
coefficient characteristic inhibiting of the process by
products of metabolism.
Then Equation 20 may be written in the following form
(21)
• = f(x) are
As can be seen from Fig. 7 the curves for
the straight lines. v
This facts serves as the proof of the applicability of bility.
The angle of inclination tangent gives the value of
Equation 14.
Analysing the position of direct lines for different
substrate concentrations one can note that tg decreases as
S increases to a certain value. Hence for determination of
coefficient it is necessary to use the data obtained without
limiting by substrate.
The specific rate value corresponding to the intersection
of direct lines in the plot of 1 = f(x) with the ordinate
V
axis (^corresponds to the rate A without inhibiting by
V
metabolites.
Thus the analysis of experimental data has shown that the
sludge activity decreasing with the increase of its concentra-
tion is described by the enzymatic reaction equation with
consideration of non-competente inhibiting by metabolites.
It should be noted that inhibiting in a certain range of
MLVSS variation is less than the increase in the total sludge
biomass activity, so with the MLVSS increase the essential
increase in the oxidation capacity of aeration tanks occurs.
For certain substrates the dependences of oxidizing capacity
on MLVSS is given in the plots (Fig. 8). Optimal value of
MLVSS (from the oxidizing capacity point of view) varies
in the range from to g/1 and depends on the constants
of the enzymic reaction equation, characterized by the
individual properties of the substrates.
C. EFFECT OF D.O. CONCENTRATION
Technological studies on the models of aeration tanks for
investigation of D.O. effect on the biochemical treatment
process were carried on with the acetone and phenol used as
11
-------
substrates.
Operation data of counter-flow aeration tanks when the
air is fed to one of them and the oxygen to the other one, are
given in Table 1 .
There is a significant increase in the process rate as
the D.O. concentration increases. Thus the acetone specific
oxidation rate increased from 3.4 to 1 12 mg/l/h (2.88 times)
as the D.O. concentration increased from 3 to 12.7 mg/1.
Similar data were obtained in tests conducted in batch
flow aeration tanks.
.t
V'rff*
7f
I
*^r<
Figure 7 Graphical form of 1/V = f(x) for determination of
inhibition factor Y at oxidation of acetone (1) secondary octyl
alcohol (2) and isobutyl alcohol (3).
on
>
10
If
&
-Jtf
30
Figure 8 Relative change in oxidizing capacity with the MLVSS
increase in aeration tanks at oxidation of acetone (1), octyl alcohol
(2) and pyrocatechol (3).
-le
Figure 9 Graphic of binary reciprocal values of the relationship
between oxygen uptake rate and its concentration.
J. substrate concentration of 94 mg/1
2. Substrate concentration of 360 mg/1
3. substrate concentration of 450 mg/1
A wide cycle of experiments was carried out on
respirometers in batch conditions for a more accurate
quantitative evaluation of the D.O. effect. These experi-
ments were carried on with substrate (acetone) concentra-
tion varying from 0.5 to 33 mg/1 and oxygen concentration
varying from 1.0 to 20 mg/1.
The experimental data are given in the plots of functions
of V = f(Co). (Fig. 9).
The plots of reciprocal values in coordinates 1/V - 1/S
were used for identifying the mechanism of D.O. effect.
It was noted in a number of recent works (27, 28) that the
process of oxygen and substrate interaction may be
described by several mechanisms. The mechanism of a two
stage substitution is possible, where the reduced enzyme
group reacts with the products of respiration chain.
The following equation corresponds to this mechanism:
•y
S Co
maxKsCo
KoS + SCo
(22)
where /dx/dtx-is the specific microorganism growth rate.
S - the substrate concentration.
Co - partial pressure of oxygen.
Ks and Ko- equilibrium constants.
When analysing experimental data with the help of
reciprocal values plots a large dissipation of points was
observed that can be explained by the time drift; of
activated sludge properties.
As applied to the two-stage substitution mechanism
(Equation 22) the time drift causes lowering of all points
obtained in the given series of experiments in the ordinate
axis by the same value as to the mean statistic value (Vcp)
for the given S.
The correction for the time drift (at the investigation of
D.O. effect) was defined as a value by which it is necessary
to remove the experimental lines along the ordinate axis for
the given series of experiments so that they pass through the
points corresponding to the mean statistic values of Vcp.
that is J} - Vcp-Vi (23)
On the basis of this correction a summar plot was made
(1/V = f(l/Co) (Fig. 10) with the help of which the values of
constants Vmax and Ko were determined, characterizing
D.O. concentrations effect at various substrate concentra-
tions.
A point with the coordinates 1 / Vmax cp was plotted on this
graph corresponding to the excess substrate concentration
(see Fig. 10). A direct line parallel to the other exper-
imental lines passed through it. Intersections of this
direct line with the coordinate axises give the reciprocal
values of unknown 1/Ko and I/Vmax.
For acetone V max = 133 mg O2/g/h and Ko = 2.38 me
02/1.
The experimental data analysis (see the plot for V = f(Co)
in figure 10) has shown their satisfactory agreement with the
calculation data according to Equation 22.
A remarkable peculiarity of the dependence obtained is
the fact that the greatest effect of D.O. concentration is
observed in excess substrate concentration conditions. The
role of Co parameter diminishes as the value of S decreases.
Hence the maximum increase in the oxidation rate at the
expense of D.O. concentration increase is possible when
conducting incomplete biological treatment or in initial
stages of multi-stage systems.
12
-------
Figure 10 Relationship between the oxygen uptake rate and its
convention:
1 - substrate concentration of 94mg/l (COD)
2 • substrate concentration of 360 mg/l
3 - substrate concentration of 450 mg/l
On the basis of Equations 21 and 22 a generalized
dependence may be obtained
V = Vmax
S -Co
!
Ks • S + KCo + SCo (1+yx)
(24)
The equation obtained considers the effect of the main
components of biochemical oxidation and is used by the
authors in mathematic modelling of the biological waste-
water treatment process.
D. EFFECT OF THE MATERIAL STRUCTURE ON
THE BIOCHEMICAL DESTRUCTION PROCESS
It is rational to analyse the effect of the organics structure
on parameters of biochemical treatment using conventional
characteristics of the physico-chemical properties of the
matter or on the basis of sanitary-chemical analyses. The
main data characterizing substances under study and
parameters of their biochemical oxidation are given in
Table 2. Figure II illustrates the relationship between BOD,
COD, specific oxidation rate j> , the sludge yield volume
and the molecular weight of a number of organics tested.
The run of BOD and COD curves (Fig. II) shows that
these parameters have the tendency to decrease as the
molecular weight grows. This tendency breaks as the
structure of the substance changes.
Analysing mutual position of COD and BOD curves one
should note that they draw together as the molecular weight
grows, that is the BOD/COD ratio increases. Activated
sludge growth curve repeats the run of BOD and COD
curves in general outline and slightly lowers as the
molecular weight of substances grows.
The value of the BOD/COD ratio also gives the
possibility for judging about the character of bacterial
metabolism responsible for oxidation process.
Catabolic ways of metabolism prevail at large values of
this ratio while the anabolic ways prevail at low values. One
can judge about this on the basis of the data given in Table
2, from which it is seen that energetic processes prevail over
constructive ones at large values of BOD/COD ratio which
is followed by low activated sludge yield and low total
bacterial number of 1 g of sludge respectively. Constructive
processes prevail in processes with relatively low BOD-
/COD ratio.
Figure 11 Dependences of BOD, COD of substance, the specific
rate of their oxidation and sludge yield on the molecular weight.
This relationship is proved by literary data.
Sharp diminishing of the difference between COD and
BOD of 1 mg of the substance as increases claims
attention.
This relationship is presented in Figure 12. It must be
noted that the growth of with the growth of BOD to
COD ratio agrees in outline with the ideas formed.
However, the data about various organics biochemical
degradeability have not been systematized yet and enable to
make the comparative qualitative evaluations only. In con-
nection with this more detailed analysis of relationship
between oxidation rate and BOD/ COD ratio is of interest,
because the values which form it, are accessible for
quantitative determinations with the use of standard
methods.
In Table 2 the data are given about BOD and COD of
particular substances and about specific rates of their
>xidation. In general these data are obtained as a result of
laboratory investigations carried out at the Institute
VODGEO.
Graphical forms of the following functions are construct-
ed for the analysis of these data :
= f (COD-BOD);j> = f
COD/'
M
\
to
t,t can-too
and
rnneRAn I*e'ationsniP betw«n specific oxidation rate
COD-BOD difference
x - according to VODGEO data
- according to construction norms and laws II. 74.
where C is a specific amount of organic carbon in a tested
substance expressed in g of C/g of substance.
It follows from here that despite the essential dissipation
of experimental points correlation between the rate of
oxidation and BOD/COD and COD-BOD values is
followed rather clearly.
Statistic analysis of the experimental data was carried on
13
-------
with the help of a computer "M P-2" and showed the
following:
a,o
1)
= f(COD-BOD) =
(25)
[a(COD-BOD) + B]2
a = 0.1164 b +0.1427.
The root-mean-square deviation (dispersion) of this
function from the majority of experimental points is equal
to 8.9350 mg Oz/g/hour.
The value of confidence interval E = 0.2262 at the number
of degrees of freedom K equal to number of points n - 42 is
K=/f-l =41.
The value of confidence of probability is equal to 0.96
(significance level is 28%).
2) for the dependence of the type
COD
I
(26)
/BOD\
[aVCOD/ + B]2
a = 0.002898 b = 0.4421
The value of confidence interval E = 0.1510. The root-
mean-square ratio of approximating function
6 =11.4548 mg°2
g/hour
Confidence probability P = 0.87 at the number of point
equal to 42.
Thus for practical evaluations the following dependence
providing more close correlation of parameters may be
recommended:
I
/O.I 164 (COD-BOD) + 0.1427/2
(27)
The dependence BOD = f(C) (Fig. 13) is described by the
straight line equation y = ax + b, where y = BOD, a = 4.7579
b = 1.1894, that is BOD = 4.76 • C - 1.19.
The total dispersion = 0.58195.
The confidence interval value E = 0.3142. Confidence
probability P = 0.99 at the number of experimental points
equal to 21.
Substituting BOD value from Equation 28 into Equation
27 we shall obtain the dependence
0.1164 [COD-(4.76 • C-1.19)] + 0.1427
(29)
which allows to determine the specific oxidation rate
without the BOD analysis.
Figure 13 Relationship between BOD and dissolved carbon
concentration.
While evaluating the accuracy of obtained dependences it
must be born in mind that the reproducibility of experi-
ments run for determination of biochemical oxidation rate
is comparatively poor; BOD and COD values are not
absolutely accurate either.
In the experiments run for determination of specific
oxidation rate ( ) the deviation from mean values may
exceed 50%; in the analysis for BOD total this error varies
within the limit of ±10%. The COD value is defined more
accurately but in this case the deviations from mean values
within the limit ±5% are the most probable. With the ratio
caused by errors of the experiment and the analysis taken
into account the relationship between COD and BOD is
more trustworthy.
The relationships obtained (27, 28, 29) are valid for pure
substances and their applicability to complex mixtures
characteristic of industrial wastewaters demands further
development. The methodical approach to the problem still
demands the further development. Apparently, the results
of this problem's solution cannot be obtained soon, but for
practical purposes the use of approximated relationships is
possible.
The experimental data analysis has shown also that the
correlation between V max and BOD/COD is observed
(Figure 14). It is interesting to note that the experimental
points formed two straight lines each of them is character-
ized by the value COD
14
-------
Dependence of constants Ks and on V max is given in
the plot (Figure 15). A rather clear dependence of on V
max can be seen here, but as far as the constant K is referred
the tendency for its increase as the V max decreases can be
marked. This aspect alongside with the relationship between
the biomass yield and substrate properties demands the
further researches.
s
y
Figure 14.Relationship between the maximum oxidation rate Vm
and BOD/COD ratio.
1 - at COD/C = 3.6 - 4.1 ;2 - at COD/C = 2.2 - 3.3.
0
,<•
I
•4
/ v>
J
I
»\
s
s
L-ft,
ff
r^~&
•
\
7^
...--
K3
2-
i— — ~
, /'
#=<-
jj
•* n
•
•^•M__
m> MB *w v* tat Mr nf
Figure 15 Relationship between Ks and constants and Vmo.
Conclusions
Investigations into biological treatment kinetics carried
out under laboratory conditions drew the following conclu-
sions :
1, Evaluation of the subject under consideration dynamic
properties is of great importance when choosing the methods
of investigation.
Researches with the so-called "sharp" tests run in batch
conditions are appropriate to be carried on during invest-
igations of slow inertial processes. During the study of
the processes with high inertia dealing with microorganisms
acclimatization the continuous-flow cultivation method
should be used.
2. The peculiarity of the experiments with activated
sludge is the poor reproducibility of the results due to the
time drift of activated sludge biochemical properties. This
should be taken into account in carrying out the experi-
ments and analysing the data obtained.
3. For investigations of the kinetics of low inertial
processes connected with the effect of substrate, D.O.,
activated sludge concentrations and pH, temperature etc, it
is appropriate to use manometric methods.
. Special kinds of instruments - respirometers - based on
this principle permit to run the experiments in a wide
variation range of parameters.
4. It is proved experimentally that the effect of substrate
concentration on the biological treatment rate may be
described by the Michaelis - Menten Equation. The effect of
MLVSS upon the rate of biological treatment is described
by the lerusalimsky Equation taking account of the process
inhibition by products of metabolism.
5. The joint effect of substrate and D.O. concentrations is
described quite satisfactorily by the equation of a bisub-
strate reaction proceeding in accordance with the two-stage
enzyme substitution.
6. The generalized kinetic equation was obtained
permitting the effect of the biochemical oxidation main
components to be objectively taken into account.
7. Increase in the number of carbon atoms in the
molecule of substance causes decrease in the biochemical
oxidation rate and intensification of biological synthesis
processes aliphatic alcohols serve as the example of this
phenomenon.
The various functional groups available and their
position in the molecule of substances produce an
important effect on the process kinetics.
The oxidation rate of izoalcohols is lower than that of
alcohols with normal structure. Biological degradability of
isoalcohols decreases from primary alcohol to the tertiary
one.
When the number of carbon atoms in the molecule is the
same and the various functional groups determining the
chemical properties are available, the highest destruction
rate is observed in normal alcohols and organic acids.
8. The analysis of literary and experimental data
obtained have shown that the relationship between the rate
of oxidation and molecular weight is very contradictory.
The most satisfactory correlation for individual substan-
ces is being observed between the specific rate of oxidation
and the difference between COD and BOD as well as
between and COD-carbon difference. Relationships
obtained as a result of statistical handling (27,29) allow us to
define the specific rates of oxidation for individual substan-
ces.
The applicability of these relationships to the multi-
component substrates needs to be experimentally verified.
15
-------
Chemical Additions to
Biological Treatment of
Petroleum Refinery
Wastewater
Allen Cywin*
U.S.E.P.A.
Introduction
The form contaminants take in petroleum refining
effluents is very important to the design and operation of
end-of-pipe treatment facilities and include suspended,
colloidal and soluble materials. In the raw waste loads, most
BOD and COD frequently occurs as suspended and
colloidal matter. Certainly, gross quantities of contamina-
tion tend to exist as colloidal and suspended matter,
whereas variability of soluble components is much more
limited. Therefore destabilization and chemical removal of
colloidal and suspended matter in a chemical pretreatment
step substantially lowers and equalizes contaminant levels
prior to secondary treatment. This of course leads to savings
in costs and energy in biological treatment.
Table I provides an overview of various treatment
processes that may be employed in producing an effluent of
drinking water quality from petroleum refinery wastes.
'Senior Science Advisor, Office of Water & Hazardous Mate-
rials
Presented at the Third U.S./USSR Symposium for waste water
treatment and control at Moscow, USSR, August 23-25, 1976.
The use of chemical systems for treating specific
petrochemical wastes, as an addition to biological treat-
ment, has been successfully employed. The most common
methods for chemically treating petrochemical wastes
include neutralization, precipitation, coagulation, and
oxidation, illustrated under the "Intermediate Treatment"
sequence of Table 1. (1) (2)
Pre- and primary treatment may be required to remove
certain materials which would adversely affect the biological
system. Oils are difficult for the organisms to metabolize
due to their low solubility. Inorganic and non-
biodegradable organic suspended solids will tend to build
up in a treatment system, decreasing the proportion of
active biological solids, and thus adversely affecting the
treatment efficiency. Sulfides react with dissolved oxygen
and reduce the oxygen available to the organisms. Heavy
metals are toxic at defined concentrations and must be
removed or reduced to safe levels. Also, waste streams with
potentially toxic organic compounds should be separated
and treated prior to treating in a biological system.
Sequence
Primary
treatment
Treatment
1. Removal
of gross
amounts
of hydro-
carbons
and solids
Processes
Primary API
separators
Objectives
Removal of free
oil and solids
Intermedi- 2. pH control Mixing and
ate neutrali-
treatment zation
Adjust pH to
proper range for sub-
sequent treatment by
immediate oxygen de-
mand (IOD) reduc-
tion, filtration and
ASP operation in nitri-
fication mode
3. Immediate Aeration and To reduce im-
oxygen
demand
(IOD)
reduction
4. Removal
of col-
loidally
dispersed
phase
Secondary 5.
Tertiary
Dissolved
organics
and
ammonia
removal
6. Phase
removal
mixing mediate oxygen
demand and peak
concentrations of con-
taminants by air
oxidation and
equalization in a
series of basins
Chemical To reduce oil,
coagulation biochemical
and filtration oxygen demand
(BOD) and chemical
oxygen demand
(COD). Removal of oil
makes ASP more op-
erable in desired mode.
Completely To maximize
mixed removal of am-
activated monia and BOD,
sludge process COD causing sub-
stances.
Filtration
Chemical Treatment
To maximize
effluent quality by re-
moving suspended sol-
ids and their associa-
ted BOD, COD and
threshold odor causing
substances.
Neutralization and pH Adjustment - Neutralization of
petrochemical wastes may be desired for several reasons,
including:
a) preparation of a waste for biological treatment,
b) preparation of a waste for direct discharge,
c) pretreatment for efficient coagulation,
d) prevention of attack and corrosion of conveyance or
process equipment, and
e) prevention of unwanted precipitation of waste compo-
nents.
Neutralization implies the adjustment of a wastewater pH
to values at or near neutral pH; i.e., pH seven. (However,
most petroleum refinery biological treatment systems
operate efficiently at pH 6-8.) Types of wastes generally
neutralized are (a) dilute acid or alkaline wash waters; (b)
spent caustics; (c) acid sludges from alkylation, sulfonation,
sulfation, and acid treating processes; and (d) spent acid
catalysts (3).
Acid streams can be neutralized by mixing the waste with
lime slurries, or by adding caustic soda (NaOH) or soda ash
(Na2COj). Limestone beds (CaCOs) are occasionally used,
16
-------
either as an upflow system or a downflow system.
Sulfuric acid (HiSO*) is the most common neutralizing
agent used to neutralize spent caustic wastes, although
hydrochloric (HC1) can also be used. Acid sludges are
normally hydrolyred to free acids prior to their use as
neutralizing agents. Spent caustic neutralization with an
acid can be designed as a batch or a continuous system. The
carbon dioxide in flue gases can also be used to neutralize
spent caustic solutions. Flue gas neutralization is economi-
cally feasible provided that the gases are available at high
enough pressures so that no compressor is required to inject
them into the spent caustic solution. It neutralizes alkaline
wastes by the forming of a weak carbonic acid. Spent acid
catalyst and sludges have been spread in pits filled with lime,
limestone, or oyster shells for neutralization. It should be
noted that pH adjustment is commonly used to facilitate
coagulation and precipitation.
Coagulation - Precipitation • The addition of coagulants
under proper conditions causes the formation of a settleable
precipitate containing waste materials which can be
removed by conventional sedimentation or flotation
processes. It should be noted that coagulation is always
followed by some type of solids-separation process. The
most commonly used coagulants are hydrated aluminum
sulfate (alum), ferrous sulfate, and ferric salts. The
conventional coagulation system utilizes a rapid mix tank
followed by slow agitation of the mixture to promote
growth of floe particles which settle. The sludge-blanket
clarifier, which provides mixing, flocculation, and settling in
the same unit, has had many industrial applications because
of its compact dimensions.
Coagulant aids are sometimes necessary to promote
bridging between floe particles and render the floe more
settleable. The most common coagulant aids are activated
silica, bentonite clays, the organic polyelectrolytes, and
water treatment clarifier sludge. The three types of
polyelectrolytes are categorized by their electrochemical
nature, specifically, cationic, anionic, and nonionic.
Organic polyelectrolytes are helpful in improving the
effectiveness of the air flotation process and in obtaining a
high degree of clarification. In many plants organic
emulsion breakers have replaced traditional alum treat-
ments.
Besides yielding a better quality effluent, organic
emulsion breaker programs, by reducing the dosage of
inorganic chemicals, can also reduce the amount of sludge
generated by 50-75%. A significant saving in further sludge
treatment, or truckout, can be realized because the sludge
resulting from the organic polyelectrolyte treatment
contains at least as much oil as in the inorganic sludges, but
in a much smaller volume. Plants that incinerate sludge
have realized a higher value (Btu per pound) with the
organic sludge.
Provisions must be made for the disposal of the sludges
formed by the settled precipitates from coagulation-pre-
cipitation processes. Landfills are the most common form of
inorganic sludge disposal, while organic sludges are usually
dewatered by some filtration method and subsequently
incinerated or buried.
High molecular weight cationic polyacrylamide floccu-
lants produce efficiencies in sludge dewatering processes.
Figure 1 illustrates in simple form the use of polyelectro-
lytes at other points in the biological process where
emulsion breakers may enhance the system.
These are usually applied after jar and/or pilot tests
determine which of the many polyelectrolytes available will
be most efficient. For high-rate and extended aeration
systems (F/M ratios >.6 +< .2, respectively) cationic "pol-
yamine" coagulants often work best. For conventional
aeration (F/M ratios 0.2 - 0.6) systems polyacrylamide
cationic coagulants are often preferred, as illustrated in
Figure 2.
A full comparison of an acid-alum-lime treatment system
and an organic polyelectrolyte emulsion breakers program
shows these advantages for the organic system:
(a) lower total dissolved solids in the effluent for plant re-
use;
(b) elimination of final clarification and lime or caustic
neutralization; and
(c) reduction in corrosion rates, alum usage, and sludge
generation.
Oxidation processes - Oxidation processes are used to
treat both organic and inorganic contaminants using
oxygen or other chemicals as the oxidizing agents. The
oxidation of sulfides to sulfates using steam and air is an
effective treatment method; however, wastes containing
high concentrations of phenol cannot be treated in this
manner because phenols interfere with sulfide oxidation. If
large quantities of mercaptans or mercaptides are present in
the waste, a reoxidizer may be required to insure complete
oxidation.
Catalytic oxidation is usually applied when the fuel value
of a waste is too low for conventional incineration. The
process was originally designed to operate in the vapor
phase but has been successfully applied to aqueous wastes.
Laboratory studies have shown that dilute aqueous organic
wastes could be effectively oxidized at temperatures below
600° C by using a copper-chromate catalyst. Investigations
have demonstrated that hydrocarbons also could be
oxidized by using metal oxide catalysts. The initial cost of
catalytic oxidation units may be 20 to 30 percent greater
than that for conventional incinerators, but for dilute
organic wastes the operating costs may be 15 to 20 percent
less.
n
(owl I-
IlltM
I*Ht
T
AM
laprtur
I1*M twi
. »1« Mrfyl"
(HMO**-** Bll to Dm) to*)
Figure 1
17
-------
-
|>H HtJJultWM U i-l
Figure 2
Chlorine (Ci) has been used successfully to oxidize
phenol and cyanide in petrochemical wastes. The oxidation
of phenols must be carried to completion to prevent the
release of chlorophenols which cause objectionable tastes
and odors in drinking water. Cyanides can be oxidized to
carbon dioxide and nitrogen by chlorination if the pH is
maintained in excess of 8.5 and sufficient chloride used, thus
preventing the release of toxic cyanogen chloride. Chloride
dioxide has been shown to overcome these and other
disadvantages of chlorine and hypochlorite oxidation,
although this treatment is very expensive.
Ozone (Os) has been proposed as an oxidizing agent for
phenols, cyanides and other unsaturated organics because it
is a considerably stronger oxidizing agent than chlorine.
The chief disadvantage in the United States is the high
initial cost of ozone generation equipment, although there
seems to be more experience in the USSR (for drinking
water) where the costs may be different. Ozone has several
advantages, one of which is its ability to react rapidly with
phenols and cyanide.
Miscellaneous Methods - Ion exchange has been used to
remove specific petrochemical pollutants. Quaternary
ammonium anion resins have successfully removed phenols
in the laboratory.
A full scale demonstration of a chemical-biological
treatment of petroleum refinery waste water has been
completed. The results of recent E.P.A. sponsored research
investigations (4) of the AMOCO company's Yorktown
refinery waste lagoon effluent and API separator effluent to
determine the applicability of coagulation/mixed-media
filtration on these streams illustrates the efficiency of
combining these techniques. This relates to step 4 of Table I
(removal of colloidal material).
Coagulation/mixed-media filtration - Mechanisms for
retention of solids within pores of filter media may be
separated into two principal processes: a transport step and
an attachment step. The transport step involves movement
of the dispersed phase material to the vicinity of the filter
media surface, and the attachment step involves attachment
of the particles on the media surface. The transport
mechanisms may involve diffusion, interception, sedimenta-
tion and hydrodynamic actions. The attachment mecha-
nisms may involve van der Waal forces, electrical double
layer interaction, mutual adsorption or hydrogen bonding
or ionic forces. Experimental comparisons of the filtration
of colloidal, ferric hydroxide suspensions with the filtration
of well flocculated suspensions of ferric hydroxide, both
performed under identical conditions of filtration, demon-
strate a much higher filtration efficiency for the floe. Studies
have shown that removal of colloidal suspensions by
filtration appears to be possible only when the colloidal
particles to be filtered carry an electro-kinetic charge
opposite to the charge of the filter media used. The removal
of the colloid is by electro-kinetic sorption of the colloidal
particles on the surface of the filter media. This kind of
"filtration" phenomena seems to have limited application to
the filtration of industrial waste water because of complica-
tions encountered in application, the complexity of which
are beyond the scope of this paper.
Colloidal Destabilization - In most cases, the application
of filtration to petroleum refining waste waters will not be
optimized unless the colloidal material in suspension is
destabilized by essentially neutralizing the surface charge on
the colloids. The neutralization of the charge using
conventional primary coagulants is simple, but must
recognize the condition of the water. Overdosing with alum,
for example, can be a most deleterious response to a direct
filtration system that is not performing satisfactorily.
Stumm and O'Melia (5) describe the equilibrium
composition of solutions in contact with precipitated
primary coagulants in the interesting manner shown in
Figures 3 and 4. These diagrams are calculated using
equilibrium constants for solubility and hydrolysis equili-
bria. The shaded areas A and B in each figure are
approximate operation regions for air flotation and
clarifiers (region A) and direct filtration (region B). Both
regions are assumed to cover a pH range of 6.0 to 8.5. The
coagulant dosage ranges from 33 to 200 mg/1 in region A
and 3.3 to 20 mg/1 in region B. These figures are useful in
the interpretation of some filtration results.
With reference to Figure 4, the isoelectric point for ferric
hydroxide coincides with the region of minimum solubility,
and operating regions for water treating (destabilization)
always yield a hydrolyzed primary coagulant with a
desirable, positive, zeta potential.
l-a!-
A - Ojwntlng Region for Air
noutlon md ciiririm
B - Operating Region for
Direct mtr.tlon
13(oa)^
« - «,<<<
r - Ai3'
Flgur* 3 Bqulltbriua competitions of solution! In
contact with Al(OB)3
18
-------
A - Operating Region for Air Flotation end Clarlflera
B - Operating Region for Direct Filtration
C - Fc(OH)£
\ ^^—— Fe(OB)j (a)
Figure 4. Equilibrium compositions of solutions in contact with
Fe(OH).i
In many refinery situations, however, it is difficult to use
this desirable condition because the presence of sulfides and
strongly reducing conditions cause the reduction of ferric to
ferrous iron and the formation of mixed iron sulfides with
no coagulation powers. In fact, in some refinery waters the
use of iron coagulants at modest dosages may contribute to
stabilizing solids rather than destabilizing them.
While alum has no redox or sulfide chemistry comparable
to iron, its amphoterism and solubility pose definite
limitations on alum usage. With reference to Figure 3, a
substantial portion of operating region B lies in the area
where alum is soluble and the predominant equilibrium
species is negative, A1(OH)4. In the more acidic part of
region B, however, the concentration of equilibrium ionic
species is very much lower and much less negative.
Considering these data, it is not unexpected that investiga-
tors consistently report optimal coagulation/flocculation
results with alum at a pH of 5-6.
With inspection of Figure 3, one may question why alum
is effective at all for neutralizing negatively charged colloids
in the indicated operating regions. One approach to
explaining observed performance requires understanding
that the data in Figure 3 are equilibrium data; but before
equilibrium is reached, substantially different conditions
exist.
Alum very readily hydrolyzes to form polymers in a
complex manner not well defined. The hydrolytic pathway
and reaction rates are affected by pH, temperature, other
ions, etc. The hydrolytic reactions are not instantaneous,
and as they proceed, positively charged hydroxo polymers
are formed which are available for colloid adsorption. The
hydrolyzed species have enhanced adsorption capabilities
possibly due to larger size, less hydration, and the presence
of coordinated hydroxide groups. In solutions more
alkaline than the isoelectric point, the positively charged
polymers are transient and, at equilibrium, anionic
polymers prevail. In modestly alkaline solutions, the
transient, positively charged polymers appear to contribute
to destabilization of colloids. On the other hand, in
solutions more acidic than the isoelectric point, the
positively charged polymers prevail at equilibrium and
destabilization of colloids is achieved at significantly lower
coagulation treatment levels.
While coagulation/flocculation of refinery waste water
can frequently be achieved over a wide pH range using
primary coagulants supplemented with polyelectrolytes,
typically there is a very definite optimal pH that may
simplify, or even be required by, direct filtration. Operating
at the optimal pH yields benefits of maximum removal of
discontinuous phase material with minimal coagulant
requirement and sludge generation.
Frequently, refinery waste waters only require 5 to 10
mg/1 of primary coagulant at a pH range of 6 to achieve
destabilization for filtration. When this level of chemical
treatment is observed in jar tests, the coagulant dosage may
be much below that required for generation of floe;
however, excellent filtration results are achieved. The
destabilized particles penetrate into the pores of the filter
media, the media aids the flocculation process, and the
particles are effectively trapped with high solids loadings.
Too much primary coagulant can be added at a pH of 6 and
some suspended matter restabilized. Too much coagulant
puts an unnecessarily heavy solids burden on the filter and
the result is rapidly increasing pressure drops, early
breakthrough and excess backwash sludge to handle.
At a pH of 8, substantially more primary coagulant may
be needed to neutralize the zeta potential. The dosage may
be 30 mg/1 or more with the generation of a substantial
floe size instead of the almost invisible pin-point floe of
suspensions successfully filtered at a pH of 6. The more
voluminous floe does not penetrate into the filter media as
well as does the pin-point floe and lower solids loading,
higher pressure drops, and more chemical usage, backwash
and sludge volumes result.
At a pH of 9, the zeta potential of the system may never
be neutralized and, of course, is not optimal as such for
direct filtration. With iron salts, chemical coagulation/floc-
culation at a pH of 9 or more can yield superb results with
some waters, but a different clarification mechanism is
involved. Comparatively large dosages of coagulant are
used which generate large, voluminous floe particles that
trap and enmesh the suspended matter in the water being
treated and retain the solids in the sludge blanket. This
approach is not optimal for direct filtration but requires
pretreatment in a clarifier to handle the voluminous sludge
volume generated. The clarifier water is then polished by
filtration using polyelectrolytes to destabilize the residual
suspended matter.
Figure 5 illustrates the effect of treating a refinery effluent
water with fixed levels of overdosage, underdosage, and
optimal dosage of primary coagulant at various pH levels.
For this example, the optimal dosage is defined as the
coagulant required to bring the zeta potential of the system
into the target zeta potential range of ±5 mV necessary for
destabilization of the suspended matter preparatory to
direct filtration. To emphasize the importance of pH for
these systems of over, under, and optimal treating with
coagulant, there is a pH range where the system is
destabilized and receptive to clarification by direct filtra-
tion.
For the optimal dosage in curve A, the system is
destabilized over the widest pH range of 5.5 to 8.4.
Underdosing (curve C) provides a destabilized system for
filtration only at a pH of about 6.5 or less. Overdosing
19
-------
(curve B) results in the narrowest pH range for effective
destabilization of about 0.6 pH units, i.e., 7.65 to 8.25.
Refinery effluent waters may vary rapidly in pH over a
short time span which makes it desirable to determine the
optimal coagulant-pH balance. Frequently, poor or no pH
control is available. In these cases, the destabilization of
suspended matter frequently can be "desensitized" to pH
somewhat by using coagulant/ polyelectrolyte combina-
tions. The preferred operating procedure that frequently
makes the filtration system essentially free from upset is a
two chemical system: a primary coagulant supplemented by
a polyelectrolyte. Two cases seem appropriate: 1) For the
operating range of 6-9 pH, an underdosage of primary
coagulant is used and is supplemented by addition of a
cationic polyelectrolyte. This combination of chemicals
broadens the effective pH range of destabilization of curve
C in Figure 5, and, additionally, the chemical properties
more adherent to the filter media. 2) For the operating
range of 5-7 pH, the polyelectrolyte used to supplement the
primary coagulant may be a non-ionic or very weakly
anionic. The non-ionic or very weakly anionic polyelectro-
lyte is useful in systems that tend to modest overdosage
situations with primary coagulant. Massive overdosing with
primary coagulant can be compensated for somewhat by
non-ionic or very weakly anionic polyelectrolytes but
rapidly blind the filter. These chemical treatments are also
useful when high hydraulic loadings are applied to the filter
or rapid rate increases occur, both of which may tend to
redisperse trapped solids and cause premature break-
through.
Strong, or very strong, anionic polymers usually perform
the poorest in tests comparing cationic, non-ionic, very
weakly anionic, weakly anionic, fairly strong anionic,
strongly anionic, and very strongly anionic polyelectrolytes.
In one instance, treatment with only a cationic polyelectro-
lyte at a less than 1 ppm outperformed all other
combinations of chemical treatment for destabilization of
suspended matter preparatory to filtration.
Another distinction that may be important is the nature
of the colloids to be destabilized: inert materials including
clays, silica, coke fines, oil particles, etc., or biocolloids
consisting chiefly of bacteria. Amoco's (4) work on colloid
destabilization at other refineries has been largely on inerts,
or a mixture of colloids predominately inerts with some
biocolloids. The work of McLellon et al. (6) and Stumm et
al (5) indicates that where principally biocolloids are
concerned, stability is less dependent on repulsive electro-
static interactions and relates primarily to the interaction
of the hydrophilic surface of the biocolloid with the aque-
ous solvent. The source of colloid surface charge is through
acid-base interactions of ionogenic functional groups. The
authors cited conclude that aggregation of biocolloids is by
chemical interaction of the hydroxy metallic polymers with
the ionogenic groups of the colloid followed by chemical
bridging. If the destabilization mechanism for biocolloids is
such a special case, the chemical pretreatment may be
optimized by emphasizing the use of organic polymers
known to form chemical bridges. The optimal chemical
pretreatment would then be expected to be a multichemical
system. -
Tests indicate that in warm brackish water a two-
chemical system at low concentrations was satisfactory
whereas for cold brackish water a three chemical system at
higher concentrations may be required.
•30
-JO
A - Optlul Iron Salt Dostgi
B - Ovtrdote wltb Iron
C - Under Doiige with Iron
D - Ttrgtt z«u PolentUl Ri
pH
Figure 5. Variation of final zeta potential with pH when treating
refinery effluent having negative zeta potential with three levels of
coagulant dosage
Polyelectrolytes screened vary widely in effectiveness, and
optimizing chemical pretreatment involves testing a series of
commercial polyelectrolytes at various combinations until
an optimal combination was found (7)
1. Two Chemical Systems
a) Optimize pH.
b) Use a primary coagulant plus an organic cationic
polyelectrolyte, or
c) Use a primary coagulant plus an organic non-ionic or
weakly anionic polyelectrolyte.
2. Three Chemical Systems
a) Optimize pH.
b) Use a primary coagulant/ organic cationic polyelec-
trolyte/weakly anionic polyelectrolyte treatment se-
quence.
Nutrients - Effective biological treatment of any organic
contaminant requires the availability of essential nutrients
for the organism. The mineral nutrients required by bacteria
are available in sufficient amounts in most wastewaters, but
nitrogen and phosphorus requirements are more critical and
many petrochemical wastes are deficient in one or both of
these elements. Nitrogen (N) and phosphorus (P) require-
ments for biological treatment have been related to the
magnitude of the degradable organic content of wastewater
as represented by BOD. Generally, a BOD:N:P ratio of
100:5:1 will provide sufficient amounts of these nutrients.
Nitrogen is most readily available in its reduced form as
ammonia, ammonium ion, or amino nitrogen. Organic
nitrogen, nitrates, nitrites, and organic compounds contain-
ing these forms can also be used, but a considerable
expenditure of energy is required to reduce these forms to
ammonia nitrogen. Phosphorus is usually added in the form
of phosphoric acid or soluble phosphorus salts since they
are most readily assimilable.
Summary
In summary, biological treatment is the key end-of-pipe
element in the overall treatment systems, for petroleum
20
-------
refinery wastes. Therefore the unit processes within the
treatment system should be optimized to utilize the
biological process for removal of soluble contaminants. In
the United States we have learned that the use of chemical
pretreatment as well as other physical processes (such as
dissolved air flotation and mixed media filtration) will
enhance the performance of the biological systems by
removing colloidal and suspended matter. This not only
improved the efficiency of the biological treatment process
but saves on cost of equipment and operations.
References
1. Grutch, J.F. and Mallatt, R.C., Optimize the Effluent
System, Hydrocarbon Processing (March 1976)
2. Lacy, W.J. and Cywin, Allen, Physical-Chemical
Treatment of Wastewaters from the Petroleum
Refining - Petrochemical Industry Joint U.S. - USSR
Symposium; Cincinnati, Ohio (November 1975)
3. Halper, Martin and Cywin, Allen, Development Docu-
ment for Effluent Limitations Guidelines and New
Source Performance Standards for the Petroleum
Refining Point Source Category, Environmental
Protection Agency, EPA - 440/1-74-014-1, (April
1974)
4. Grutch, J.F., Mallatt, R.C., and Peters, A.W., Chemical
Coagulation/Mixed-Media Filtration of Aerated
Lagoon Effluent, EPA - 660/2-75-025, (June 1975)
5. Stumm, W. and O'Melia, C.R., Stoichiometry of
Coagulations, Jour. AWWA 60:514 (1968)
6. McLellon, W.M., Kernath, T.M. and Chao, C.,
Coagulation of Colloidal and Solution Phase Impuri-
ties in Trickling Filter Effluent, Jour. WPCF,
60(1):77-91, (1972)
7. Surchek, J.G., and Tutein, T.R., Simplified Method
Determines Cost Performance of Polymeric Floccu-
lants. Water and Sewage Works (January 1976)
21
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MINISTRY OF HIGHER AND
VOCA TIONA L SECOND A R Y
EDUCATION OF THE USSR
LENINGRAD INSTITUTE OF CIVIL
ENGINEERING
S.M. Shifrin, B.C. Mishookov, G.V. Ivanov,
E.K.Goloobovskaya
The Trends in Intensification
in Biochemical Treatment of
High Density Wastewater
Intensification of biochemical treatment of waste water
which has high density of organic matter may be carried out
in a number of ways, the major ones being the following:
—increase in load imposed on microbial mass by
establishing the optimum conditions for activated sludge
behavior;
—usage of high density activated sludge;
—usage of thermophilic activated sludge.
The first trend is implemented by increasing the density of
microorganisms and reducing the retention period of liquid
inside the aeration tanks. When the density of microorga-
nisms increases, the rate of their removal goes up; the
relation between the treatment rate and the increase in
density of microorganisms is of non-uniform nature. Fig 1
shows an example of dependence (which has been
established by us) of treatment rate on the density of
microorganisms in sludge-liquid mixture in the aeration
tanks with the oxidation (under contact conditions of
organic matter in the influent coming from the food
industry enterprises.
The dependence of treatment rate on the organic matter
density is of S-shaped form and somewhat differs from well-
known patterns established by Michaelis-Menton; Monod
and others.
In general the rate of treatment may be represented as an
equation of trimolecular reaction
r= =-K (C)n(D)m(0)P
(D
where C,D,O - respectively, densities and concentration of
organic matter, activated sludge and dissolved oxygen in
the liquid;
K - the constant value of the reaction rate;
n,m,p - empirical values.
It is generally accepted that dissolved oxygen concentra-
tion in excess of 0.5-1.0 mg/1 is of little practical significance
for the biochemical treatment rate, provided the mass-
transfer of oxygen is not connected (as is the case in diffused
aeration systems, for example with the speed of agitation of
sludge-liquid mixture.) If the oxygen concentration and the
speed of agitation related to it do not restrict the treatment
rate, then the formula (1) turns into an equation of
bimolecular reaction. Within the wide range of concentra-
tion changes the values of "n" and "m" are the variables.
The value of "n" ranges from 2 to 0.5 with little and medium
loads on activated sludge and is reduced to zero when the
load increases. The value of "m" is frequently assumed to be
the constant (in case of narrow ranges of changes of "D"
value), although in general "m" decreases when "D"
increases. One can compare the efficiencies of treatment
only on the basis of rate "r" as with the changes of "n" and
"m", the value of "K" becomes incomparable. In view of this
it is advisable to apply the first criterion of Damkohler
Daj
Daj
- r. 1
v • c
(2)
Where r - Treatment rate;
1 - determining linear characteristic;
v - determining velocity of liquid movement;
c - concentration of matter going into reaction.
When applying this criterion to wastewater biochemical
treatment it is possible to change the criterion somehow
taking into account the equation (1):
Da,
kcnpmbp_
vC
Damkohler's modified criterion under the equation (3)
enables to compare efficiencies of treatment of a specific
kind of wastewater while changing the organic matter
density (C), the activated sludge dosage (D) and the
aeration duration.
The way the treatment rate changes (Fig. 1) indicates that
usage of one-stage facilities is not advisable since the
treatment average rate in such facilities turns out to be low.
Treatment in two-stage or three-stage aeration facilities in
which the optimum conditions for existence of specific
activated sludge are provided is economically more
preferable. On the basis of our research one may come to
the conclusion that the two-stage treatment is applicable
with the organic matter density of up to 8.0 - 12.0 g/1
(calculated at the bichromate COD), while the three-stage
treatment is advisable when the density calculated at the
COD is within 10.0 - 15.0 g/1. It should be borne in mind
that we are dealing here with the organic matter which
undergoes oxidation without great difficulties during the
biochemical treatment (wastewater from the food industry
enterprises, influent from live-stock farms etc.) The
establishment of optimum conditions for activated sludge
existence in each stage of aeration facilities provides for the
proper speed of agitation and supply of dissolved oxygen.
In the first stage of aeration facilities the proper agitation
and dissolved oxygen supply is achieved with the electric
power consumption of up to 100 watt/hour per 1m3 of
volume, in the second stage - up to 70 watt/h/m3, in the
third stage - up to 50 watt/hM3 (these power consumptions
hold good for the aeration facilites with the capacity of 150-
500 m3). Dissolved oxygen is contained in the liquid at a
level of 0.1-0.5 mg/1 in the first stage; 2.0-3.0 mg/1 in the
second stage; 3.0-4.0 mg/1 in the third stage. Nitrification
was observed in the second and third stages. The third stage
usually acts as an aeration-nitrification tank and at the same
time it acts as a preventive means to hold up the microbial
22
-------
mass which is periodically entrained by the effluent from the
second stage.
The organic matter oxidation rate amounts to 200-300
g/hour of COD per 1 m3 of volume of the first stage
aeration tank, 100-150 g/m'/h in the second stage, 10-30
g/m3/hour in the third stage, while the treatment efficiency
makes up approximately 50,80 - 90,95 - 97% of COD
respectively after the first, second and third stages of
aeration tanks.
The second trend in stepping up the treatment provides
for an increase in density of microbial mass in the facilities
(higher density of activated sludge). The increase in the
microbial mass volume results in the reduction of specific
velocity of organic matter removal per unit weight of
microorganisms. At first sight higher density of activated
sludge does not yield an anticipated result. However, it
should be borne in mind that activated sludge of higher
density has considerable Constance and is able to withstand
drastic changes in density with comparative ease, which is
typical of the high density wastewater. Higher density of
activated sludge is achieved through employment of
intensive means of microbial mass separation - by filtration,
flotation and prolonged settling. But not all these means are
applicable to hold up the microorganisms after the first
stage of aeration facilities. High rate treatment in the first
stage generates the microbial mass consisting of very fine,
badly flocculating particles, so that the holding up of this
mass is a rather complicated problem. The sedimentation
properties of microbial mass are influenced positively by the
inert solids in the form of specially introduced medium,
such as activated carbon, or in the form of suspended
matters contained in wastewater. In view of the current
practice of microbial mass separation the prolonged one-
stage or two-stage settling proves to be the least expensive
and the most feasible one.
In the multi-stage aero-accelators designed for treating
live-stock farm wastewater the activated sludge density was
maintained equal to 10-18 g/1 in the first and second stages
and 6.0-8!o g/1 in the third stage. The influence of the
activated sludge density on rate and efficiency of treatment
comes to be observed when the density is reduced to 6,0-8.0
g/1. After the microbial mass has passed through the
second stage of aeration tanks the sedimentation properties
of the mass becomes better and the density of suspended
matter in treated wastewater reduces to 100 mg/1 as a result
of settling.
It is of certain interest to establish the weight of live cells
of microorganisms in the sludge by the DNA content. The
research into this problem has shown that the live cell
weight in the first stage makes up 30% calculated on the
basis of the total weight of microbial mass, and 18% in the
second stage.'
The third trend in stepping up the treatment is prompted
by the high-rated biochemical treatment. When increasing
the density of organic matter up to 8.0-15.0 g/1 and the
treatment rate up to 100-300 g/m3/hour there takes place
the biothermal warming-up of the liquid caused by the
excessive energy emitted when the organic matter is
oxidized. For instance, in the operating aeration tanks
(located inside the building) the liquid temperature was
maintained spontaneously at 30-34° C while the influent and
the inside air had a temperature of 13-17°C. In view of this
fact it is advisable to carry out treatment in the first stages
under thermophilic conditions, i.e. at 50-55° C. The increase
in temperature will enable to increase the treatment rate by
1.5-1.8 times if there is high-rate agitation and sufficient
supply of dissolved oxygen. Thermophilic aerobic process
enables to destroy practically all the pathogenic organisms
in wastewater, which is a great advantage of this process.
The increased demand for air which is necessary to establish
aerobic conditions is the drawback of the process as it
increases the cost of treatment.
The combination of the above mentioned trends enables
to step up the treatment of high density waste-water and to
reduce capital investments and maintenance costs.
Positive results in the field of biological water treatment
intensification have been recently obtained by special
preparation of waste water before delivering it into the
aeration tank, the preparation is accomplished by the
preliminary treatment of waste waters according to the
method of electric flotation coagulation (EFC). As the
result the contamination concentration is considerably
reduced. F.e., the concentration of suspended matters of the
butchery by electric flotation coagulation method decreased
the density of suspended matters to 95-98 per cent (from
2000 to 10-60 g/m3), COD by 60-70 per cent (from 1700-
2000 to 400-800 g/m'), BOD has been changed as well.
After EFC BOD was 0.69, COD - 14.7 g/m3.
Studies of the biological treatment of waste waters
subjected to the electric flotation coagulation treatment in
the aeration tanks allowed to find out a number of specific
features. It was established that activated sludge differed
somewhat from the sludge treating the same effluent after
the usualy mechanical treatments its ash content was 15-
20%, sludge index was 180-200, dehydrogenation activity of
the regeneration activated sludge -5 -8 mg/g of the dry
weight. Usually sludge floes were finer and more dispersed.
The composition of sludge hydrobyonts was more variable.
The increase of the number of rotaria and setacious worms
was observed. The process of effluent purification after
RFG was rather intensive but the increase of sludge under
effluent conditions was only 12.7 mg/1 (2-3% of the
incoming BOD), and in the contact experiments was not
recorded at all. One could observe considerable increase of
sludge dehydrogenation activity (up to 30-50 mg/1), sludge
oxygen activity consumption, the increase of the microorga-
nism number and the number of bacteria. The absence of
notable growth of sludge may be explained by the fact that
under the byological treatment of the effluent containing
suspended matters the increase of sludge is connected with
the sludge floes sorption of the suspended matters
constituting the inert part of the activated sludge.
Suspended matters concentration in the case considered
amounted to no more than 50 mg/1, i.e., was several times
lower than after usual sedimentation.
High activity of sludge allowed to accomplish the
purification process at reduced sludge densities. The
concentrations from 0.3 to 3.9 g/1 were tested. The
increased doze from 0.3 to 0.8-1.0 g/1 proved to be
favourable for the process of contamination removal.
Changing the sludge concentration within 1.0 to 3.0 and
sludge loading from 1400 to 400 mg COD/g of dry sludge
respectively did not affect the duration of the process which
lasted 8 hours. In all the cases the complete purification was
ensured during this period of time (See Fig. 2).
23
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The tests carried out had also to determine the setting up
of sludge oxygen consumption and dehydrogenation
activity. The analyses have shown that the process of
impurities distraction from the liquid (sorption) and their
oxydation take place with varying velocities. If the
impurities removal from the effluent approximated 3 hours,
the oxidation of the removed impurities required 6-10
hours. Impurities oxidation took place not only with less
velocity but depended to a large degree on the sludge
concentration. The higher the sludge doze was, the higher
was the % of the oxidized impurities compared with those of
sorbed.
The results received somewhat opposed the wide spread
opinion that the necessary aeration time is the reverse ratio
of sludge concentration but they are quite consistent with
the laws established for natural ecological systems. Any
aeration tank can be considered to be a kind of an ecological
system as it has the same features: the limited capacity
(biological current); the certain amount of nutrition
(activated sludge); the process of energy transformation. In
any ecological system the stability of existence nutrition
conditions may be maintained by means of population
dynamics. With the increase of the population density the
growth rate is reduced. Unlike the natural ecological systems
the population density in the aeration tank is artificially
increased by the recirculation of activated sludge. The
increased doze of sludge is necessary as it sets up the process
and ensures the stability of water works operation but under
these circumstances the rate growth of populations is
decreased and thus their psysiological activity. By reducing
ferment activity aeration tank activated sludge compensates
to some extent artificially increased population density, i.e.,
in this way, the self-regulation of the aeration tank ecological
system is achieved. Within the required sludge density its
activity is determined depending upon the conditions of the
ecological system as a whole.
One of the main abiotic factors influencing the formation
of the ecological systems is the provision of feed. Under
natural conditions the number of populations is the function
of food amount. Any aeration tank does not differ in this
respect from a natural ecological system. The increase of
contamination concentration in the liquid treated results in
the increased number of populations and the increased
nutrition.
Hence the increased sludge dose is natural and efficient
only in the case of highly concentrated effluent.
Increasing the sludge dose above the natural possibilities
of the system causes'the relative increase of the inert
(ballast) part of sludge and does not set up the purification
process.
The lower the sludge doze is, the more effective works
every particle of the biomass, and so the same effect of
purification can be achieved under different sludge density
in the aeration tank.
The limits of sludge dozes when its self-regulating
qualities appear under other equal conditions are deter-
mined by feeding i.e., contamination concentration in the
water treated. Therefore the process of waste waters
treatment is determined not only by the sludge loading but
by impurities density in the aeration tank.
As sludge ensure the necessary efficiency of treatment it is
more advantageous to carry out the process at the minimum
sludge doze as in this case the conditions of oxygen sludge
supple are improved, and thus energy consumption per unit
of the contamination removed is reduced.
The EFC application as a means of preliminary effluent
treatment of the butchery allows considerably to reduce the
time of aeration with the subsequent treatment of this kind
of effluent. Simultaniously the amoung of excess activated
sludge is decreased.
HI stage Estage ' I stage
Figure 1. Oxidation impurities curves related in time.
123 6 8 10 12 14 16 18 20 22 i.Ai*
Figure 2. Kinetics of impurities distraction at various sludge doses.
Sludge dose, g/l Loading at the moment of stirring
mg COD/g of dry sludge
1 0.40
2 0.77
3 1.99
4 1.30
5 2.06
1420
643
643
400
712
24
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Steel Industry Wastewater
Treatment Using Biological-
Chemical Technology*
William J. Lacy, P.E.**
Introduction
The steel industry in the US is composed about 102
companies operating 420 plants. Of these, 63 are integrated
plants, 96 are nonintegrated, and 261 are hot and cold
working plants. These plants are located in almost every
state, but the principal concentration is in the northeast
quadrant of the country in the States of New York,
Pennsylvania, Ohio, Indiana, and Illinois, see Fig. 1.
Generalizations about steelmaking operations are diffi-
cult because exceptions can be found in every mill. Steel
mills in operation today range from older marginal mills
built early in this century to new modern facilities built in
the last several years.
Significant waterborn wastewaters result from all steel
mill manufacturing operations. These wastes are principally
suspended solids, oils, waste acids, ammonia, cyanides,
phenols, chlorides, fluorides, sulfides, heavy metals, and
heated discharges.
Basic processing operations shown in Figure 2, include:
by-product coke manufacturing; sintering operations; blast
furnaces; steel making (electric furnaces, basic oxygen
furnaces, and open hearth furnaces); vacuum degassing
operations; continuous casting; rolling mill operations; and
finishing operations.
•Presented at the Joint US-USSR Water Pollution Control
Symposium in Moscow, USSR, August 22-28, 1976.
** Principal Engineering Science Adviser, Office of Research and
Development, U.S. Environmental Protection Agency, Washing-
ton. D.C.
Source of Pollution
Each of these basic operations contains a large complexi-
ty of pollutant discharge into the environment. For the
coking operation, wastes are emitted from the waste
ammonia liquor, still wastes, final cooler wastes, and light
oil recovery wastes. The blast furnace, with similar
pollutants to the coking operation, has its main aqueous
waste resulting from gas cleaning with wet washers. The
actual steel making operation also generates liquid wastes
from the air pollution control equipment, such as: sparking
boxes, spray chambers, and venturi scrubbers. The
degassing operation has liquid wastes from the barometric
condenser cooling water. Cooling water discharge results
from the casting operations, whereas, dust control equip-
ment creates the sintering operations wastewater. The
rolling mill operation has wastewater from the scale,
lubricating oils, spend pickling operations, and pickling
rinse waters.
Treatment technology differs for each of the respective
unit operations. The coking operation employs, for the
waste ammonia liquor, anhydrous recovery, bio-oxidation
of cyanides and phenols, and ammonia denitrification, and
possibly total incineration. Closed loop is achievable for the
final cooler water with a minimum blowdown. Recycle is
available for the light oil recovery wastes. The vacuum
degassing operation treats its cooler water wastes by
sedimentation, filtration cooling and recycle. The continu-
ous casting mode recycles spray cooling waters with scale
pit sedimentation followed by filtration or cooling. The
sintering phase employs dry dust collection and gas cleaning
equipment for new plants whereas the wet systems
incorporate a complete recycle consisting of a thickener
(polyelectrolyte addition), vacuum filter and clarifier. The
recycle blowdown consists of, aeration for oil removal, lime
precipitation, fluoride neutralization, and final thickeners.
The rolling mill operation (Fig. 3) employe crude settling
chambers for scale and oil recovery, lime neutralization and
evaporation-condensation for strong pickling wastes,
recovery of oily wastewaters by primary belt skimming,
chemical coagulation, magnetic agglomeration, and deep
filtration. The main treatment operations employed in the
finishing operations include chrome reduction, cyanide
oxidation, sedimentation, and metal sludge filtration (Fig.
4).
Treatment Technology
The cyanides oxidation to cyanates (CNO-) or carbon
di&xides (CO2) by various oxidizers (alkaline chlorination
or hypochlorite) has been accomplished for this industrial
liquid wastes. Bioxidation is effective but generally
susceptible to shock loads and requires a long residence
time. Cyanide removal by ion exchange columns is effective
but expensive.
The phenolic wastes can also be removed by either liquid
extraction or vapor recirculation but these methods are not
very economical. The bio-oxidation of phenols is being
widely used and is economical.
Effective methods of ammonia recovery and removal
require the use of an ammonia still and gas liquid
adsorption. Biological nitrification-denitrification of ammo-
nia is not feasible currently because of inherent system
instabilities. However, I will discuss this process later in the
paper. The ion exchange removal approach looks promising
but little has been done.
Disposal of Spent Pickling Solutions
The simplest method is neutralization but this unfortu-
nately leaves a great deal of dissolved solids. Ion exchange
removal has been demonstrated for sulfuric (JUSCM) and
hydrochloric acid (HCL). Direct crystallization of FeSO*
from either sulfuric or FeCU from hydrochloric liquors is
'possible. The acid is regenerated in the process and the
entire procedure looks promising. Finally, spent pickling
solution separation by reverse osmosis is now only a matter
of speculation.
Industry Description
Approximately ninety-two percent (92%) of the 1972
total United States annual steel production was produced
by fifteen major steel corporations. (See fig 5)
Molten iron for subsequent steelmaking operations is
normally produced in a blast furnace. The blast furnace
process consists essentially of charging iron ore, limestone,
25
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and coke into the top of the furnace and blowing heated air
into the bottom. Combustion of the coke provides the heat
necessary to obtain the temperature at which the metallurgi-
cal reducing reactions take place. The function of the
limestone is to form a slag, fluid at the furnace temperature,
which combines with unwanted impurities in the ore.
The blast furnace auxiliaries consist of the stoves in which
the blast is preheated, the dry dust catchers in which the
bulk of the flue dust is recovered, primary wet cleaners in
which most of the remaining flue dust is removed by
washing with water, and secondary cleaners such as
electrostatic precipitators.
The principal steelmaking methods in use today are the
Basic Oxygen Furnace (BOF or BOP), the Open Hearth
Furnace, and the Electric Arc Furnace.
The steelmaking process consists essentially of oxidizing
constituents, particularly carbon, down to specified low
levels (less than 1%) and then adding various elements to
required amounts as determined by the grade of steel to be
produced (Fig. 6 shows hot slab and Fig. 7 continuous hot
forming of steel tubing).
The open hearth furnace allows the operator, in effect to
"cook" the steel to required specifications.
Since the introduction in the United States of the more
productive basic oxygen process, open hearth production
has declined from a peak of 93 million kkg in 1956 to 32
million kkg in 1971. The basic oxygen furnace is now clearly
the major steelmaking process.
The electric-arc furnace (see Fig. 8) is uniquely adapted to
the production of high-quality steels. Practically all stainless
steel is produced in electric-arc furnaces. Electric furnaces
range up to 9 meters in diameter and produce from 1.8 to
365 kkg per cycle in 1.5 to 5 hours.
Although electric-arc furnaces have been small in heat
capacity as compared to open hearth or basic oxygen
furnaces, a trend towards larger furnaces has recently
developed. Electric-arc furnaces are the principal steelmak-
ing process utilized by the so-called mini steel plants which
have been built since World War II.
Now, I would like to discuss two biological-chemical
treatments that can be applicable to steel manufacturing
wastewaters; namely: A) ammonia stripping and, B)
denitrification.
A. Ammonia Stripping
In the air stripping process for ammonia removal, four
considerations are most significant: 1) pH of the wastewa-
ter, 2) rate of gas transfer, 3) the air-to-liquid requirements,
and 4) the hydraulic loading.
In a wastestream, ammonium ions exist in equilibrium
with ammonia:
NHUOH NH3 + H2O
Below a neutral pH of 7, only ammonium ions (NHt) in true
solution are present while, at values greater than 12,
ammonia (NHa) exists in solution as a dissolved gas. In the
range of pH 7 to 12, ammonium ions and ammonia gas exist
together in equilibrium. As the pH of the wastewater is
increased above 7, the equilibrium shown in the equation
above is shifted to the right in favor of ammonia gas which
can be removed from the liquid by agitating the wastewater
with air additions. The relative percentages of ammonium
ions and ammonia as a function of pH and temperature are
presented in Fig. 9. Examination of this Figure illustrates
why very little ammonia stripping can be expected in a
biological system. Even at the optimum temperature arid
maximum percentage of ammonia in the form of strippable
gas (NHs) is only about 25 percent.
After the ammonium ion has been converted to ammonia
gas, there are two major factors which affect the rate of
transfer. They are: 1) surface tension of air-water interface
and, 2) the difference between the ammonia concentration
in the water and in the surrounding air. It has been found
that the surface tension is at a minimal value during the
process of forming water droplets, and after the water
droplet has been formed, gas transfer becomes negligible.
Therefore, repeated droplet formation, rupture, and
reformation greatly assist ammonia stripping operations
with regard to minimizing surface tension.
Minimizing the concentration of ammonia may be
accomplished by circulating large quantities of air rapidly
through the water droplets. These same principles of droplet
formation and reformation and the necessity of large
gas/ liquid requirements are inherent in conventional
cooling tower design and explain the" adaptability of these
towers to the ammonia stripping process. The material
value can be described as
Where:
G = Quantity of air flow, moles incoming air/ unit time
LQ = Quantity of water flow, moles incoming water/
unit time
YI = Concentration of ammonia in air at the bottom of
the tower, moles ammonia/ mole air
Yz + Concentration of ammonia in air at top of tower,
moles ammonia/ mole air
Xi = Concentration of ammonia in water at the bottom
of the tower, moles ammonia /mole water
Xz = Concentration of ammonia in water at top of
tower, moles ammonia/ mole water
This equation is based on a mass balance of input and
output and is valid regardless of the internal conditions
which control the process. Fortunately, the internal
equilibria are governed by Henry's Law for which adequate
knowledge exists and which will not be described. The
molar ratio of ammonia in the gas and liquid remain
constant at a specified temperature and pressure.
Design and Operational Considerations
Very few ammonia stripping towers have been designed
for treatment of wastewaters; generally, those towers which
have been constructed were the for treatment of low
strength municipal wastewaters. The same principles
utilized in the design of conventional cooling towers are also
applied to the design of ammonia-stripping towers. The
crosscurrent design is the more prevalent. Although the
counter-current type may become popular as more field
data become available.
There is greater efficiency of ammonia removal with
increased depth of tower packing. It should be noted that
the minimum air/ liquid loading required to obtain 90
percent removal is approximately 2,000 liters of air per liter
of wastewater. The increased removals at greater depths are
probably due to the greater number of droplet formations
and the subsequent air-water contact afforded by the greater
depth of packing.
26
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Deeper tower packing shows little effect of hydraulic flow
rate, at less than 100 L min/m2, at hydraulic loadings
greater than 100, sheeting of the water is observed which
decreases the number of droplet formations and subse-
quently reduces the tower efficiency.
Aside from economic considerations, the major advan-
tage of ammonia stripping over other methods of ammonia
removal is the ability to control the level of ammonia
removed in the process. Disadvantages are also inherent to
the air stripping process as outlined below:
1. Cold weather operation
a. Ammonia solubility greatly increases with lower
temperature
b. Inability to operate tower at wet bulb temperatures
less than 0°C
c. Fogging and icing problems
2. Deposition of calcium deposits within tower from pH
adjustment with lime.
3. Air pollution problems.
4. Ammonia reaction with sulfur dioxide to form
aerosols.
5. Deterioration of wood packing due to high pH of
wastewaters.
In the case of industrial wastes where the ammonia
concentration of the wastewater may be extremely high, on
the order of several thousand mg/1, an air pollution
problem may develop. Other potentially troublesome
problems may develop near large metropolitan areas or
other regions in which high concentrations of sulfur dioxide
form an aerosol or fog. In light of the above disadvantages,
ammonia stripping is a practical, reliable method for
nitrogen removal under the right climatic conditions and
with the proper precautions regarding scale prevention or
removal.
B. Nitrification-Denitrification
In the destruction and assimilation of organic com-
pounds, biological organisms will require, as nutrients,
approximately 1 kg of nitrogen per 23 kg of BOD removed.
In estimating nitrogen removal through a system by
synthesis, only the BOD removed and not that applied
should be considered. The nitrogen which is removed by
synthesis is incorporated, at least temporarily, into the
microbial cell, and is eliminated by removal of excess sludge
from the system. A system with poor settleability properties
cannot be expected to demonstrate a total removal of 1 kg
of nitrigen per 23 kg BOD due to the high carry-over of
organisms in the effluent. In this case, mixed media
nitration may be required to achieve the desired effluent
quality. Also, if the system has an excessive detention time
or over 6-8 days sludge age, nitrogen in the form of
ammonia or organic nitrogen may be released back into
solution so that once again an assumed removal of 1
kgN/23 kg BOD removed would not be valid.
During the process of biological nitrification, ammonia
and some organic nitrogen forms are converted to nitrite
and nitrate compounds by a specific set'of organisms,
Nltrosomonas and Nitrobacter. These organisms are strictly
aerobic autotrophs, i.e., they obtain carbon from inorganic
sources such as COa, HCO3, etc., and do not employ the
same metabolic mechanisms as those organisms which
assimilate BOD materials. The nitrifiers reproduce and
grow at much lower rates than the BOD removing
organisms and thus compete in the same environment. For
example, in an activated sludge system a constant
concentration of organisms or suspended solids (MLVSS) is
desired, so that all excess sludge which is produced and
accumulates is periodically wasted. If the BOD removing
organisms are producing at a rapid rate, they will increase
the required wastage of sludge from the system, which will
generally be much higher than the wasting rate compatible
with maintenance of an adequate population of nitrifiers.
Thus, insufficient nitrification will result unless the wastage
rate is lowered to accommodate the nitrifier requirements.
The wastage rate is usually controlled to maintain a
sufficient, "sludge age" in the system for nitrification.
It is claimed that a sludge age greater than 4 days in the
activated sludge process is adequate for 90 percent
nitrification at 20° C. I caution you that this information
was developed for municipal wastes and should never be
applied to higher strength industrial discharges without
extensive pilot studies.
Biological nitrification of ammonia concentrations as
high as 500 mg/1 with greater than 90 percent removal can
be obtained with the single-stage activated sludge process.
Two-stage systems have achieved greater than 97 percent
removal with these high influent levels. The biological
process can be applied to high as well as low concentrations
of ammonia assuming proper conditions of pH, tempera-
ture, absence of inhibitors, etc.
The nitrifiers are biological organisms, and are subjected
to the same constraints which limit most biological systems,
i.e., temperature, toxicity, shock loading, pH, etc. Nitrifica-
tion has generally been found most efficient in the pH range
of 7.8 to 8.3, and pilot results have indicated that inefficient
nitrification systems can be improved by adjusting the
influent pH level so that the aeration basin contents are
within the optimum range. Sodium hydroxide is recom-
mended for the pH adjustment since lime may precipate
calcium carbonate and limit the system from the standpoint
of available inorganic carbon, particularly with high
ammonia wastes. Lime may be satisfactory for low-strength
ammonia wastewaters.
Compounds toxic to nitrifiers include heavy metals,
cyanides, halogenated compounds, phenols, mercaptans,
and thiourea. Trace amounts of these constituents may not
nullify nitrification, but could lower the rate coefficient, kn.
Pilot studies would then be required prior to design or
"washout" because retarded growth rate may occur in the
final system.
Optimum temperature for nitrification has been cited as
28-32° C with nitrification ceasing below 5°C. If severe
temperatures are anticipated (less than 12-15°C in the
aeration basin), then serious consideration should be given
to the feasibility of nitrification. It is possible to preheat the
influent wastestreams, but this is not a practical solution
with most large streams.
Nitrate and nitrated compounds are very difficult to treat
by physical and chemical techniques other than ion
exchange. However, ion exchange technology for nitrogen
compounds is applicable to a small percentage of wastewa-
ters. Consequently, biological mechanisms remain the most
practical and dependable methods for removing nitrate
constituents from wastewaters. Biological nitrate reduction
can be accomplished by assimilatory or dissimilatory
mechanisms. Assimilatory reduction occurs when nitrate-
27
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nitrogen is utilized as a source of nitrogen for synthesis by
initial conversion to ammonia and subsequent incorpora-
tion into the cell. Nitrate dissimilation involves biological
oxidation of organic compounds where nitrate serves as the
terminal hydrogen acceptor in place of molecular oxygen.
The end product of this reaction may be nitrite, ammonia,
nitrous oxide or nitrogen gas depending on the organisms
and the pH of the system. Practically, the anaerobic
denitrification process will oxidize degradable organic
carbon compounds and reduce nitrate to harmless nitrogen
gas.
The denitrification process has been effectively applied to
nitrate levels as high as 10,000 mg/1. Currently, three
denitrification systems, anaerobic activated sludge, anaer-
obic ponds, and upflow anaerobic filters offer good reli-
ability with variable economy. If the nitrate treatment oc-
curs after BOD removal, there may be insufficient carbon
present for reduction of the nitrate and an external source
will be required. Methanol has been most commonly cited
as the most economical external carbon source based on
cost and available carbon. Carbon addition, whether
methanol or a suitable industrial waste, is required for all
denitrifying systems which follow organic removal proc-
esses. In many instances, particularly in those with high
strength industrial wastes, the economy of the system will
depend on the external carbon source chosen..
With many industrial processes, e.g., where nitric acid is
employed in-plant, it is much more desirable to pretreat the
waste for nitrate reduction ahead of a BOD removal system,
such as activated sludge. In this manner, readily-available
carbonaceous BOD in the raw waste is utilized for the
denitrifying carbon source. This concept not only reduces
the costs for external carbon in a post-treatment scheme,
but will also reduce the subsequent aeration volume and
Figure 1. The Nation's Top 10 (1)
horsepower needed for the activated sludge system due to
the BOD reduction through the denitrification system.
Besides ammonium stripping and denitrification, some
other technologies to be implemented in the near future
include: slag and sludge dewatering and disposal, technol-
ogy development for a closed loop in an interested steel mill
reducing phosphates and heavy metals, employment of
electro-membranes in the HiSO4 pickling operation to
achieve a step towards closed cycle, and finally a new
technology is emerging using direct reduction of low grade
taconite ore effectively eliminating the blast furnace and
coking operation to achieve total environmental control.
All of these aforementioned technologies will be
attempted in the near future by the Environmental
Protection Agency to improve the steelrnaking industries'
technology and to preserve the integrity of the United States
waterways.
References
1. Lacy, W.J., G. Rey and H.G. Keeler, Projects of the
Industrial Pollution Control Division, U.S. Environ-
mental Protection Agency, Office of Research and
Development, Washington, D.C. 1974.
2. Cywin, A., E. Dulaney, Development Document for
Effluent Limitation Guidelines for the Steel Making
Segment of the Iron and Steel Manufacturing Point
Source Category, USEPA, Office of Water and Hazard-
ous Materials, Washington, D.C., June 1974.
3. Adams, C.E., W.W. Eckenfelder, Process Design
Techniques for Industrial Waste Treatment," Enviro
Press, Nashville, Tennessee, 1974.
4. Lacy, W.J. Point Source Control—EPA Industry R&D
Cooperation, Chemical Technology, Vol. 5, pp. 742-747,
December 1975.
5. Pollution Abatement Costs and Expenditures 1973.,
U.S. Department of Commerce, MA 200(73)-2, Issued
3/19/76
; NATIONAL
STEEL
CORPORATION
28
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Figure 1. Steel Production Processes (2)
Table 1 United States Annual Steel Production Major Producers
(2) 1972
United States Steel
Bethlehem Steel
Republic Steel
National Steel
Armco Steel
Jones and Laughlin Steel
Inland Steel
Youngstown Sheet and Tube
Wheeling Pittsburgh
Kaiser
McLouth
Colorado Fuel and Iron
Sharon
Interlake
Alan Wood
Metric Tons/ Year
31,750,000
19,960,000
9,980,000
9,520,000
7,710,000
7,280,000
6,800,000
5,440,000
3,540,000
2,720,000
1,819,000
1,360,000
1,360,000
907,000
907,000
8 BIRLEC 50 Ton Electric Arc Furnace at Manchester Steel
Inland Steel Company's highly automated slabbing mill can handle
ingots weighing as much as 55,000 pounds . . . either singly or two
in tandem. It can roll the top, bottom, and both edges
simultaneously resulting in better, more uniform grain structure
and increased yield.
i
Z
HX)
Figure 3. Distribution of Ammonia and Ammonium Ion with pH
and Temperature (3)
Fig. 7 I.acleda Steel's Six Stand Horizontal/Vertical Forming &
Welding Mill
29
-------
Fig. 3 Inland Steel's 80 inch Five Stand Cold Rolling Mill and
Pickle Line.
Facilities Improvement for
Biochemical Treatment of
Petroleum Refinery
Wastewater.
V.Ya. Gerber
Bashkirian Scientific Research Institute of
Petroleum Refining (USSR)
Summary
This paper presents estimated performance specifications
for designing biochemical treatment facilities at refineries
and petrochemical plants.
The choice of single- and two-stage treatment systems for
refinery and petrochemical sewage is recommended depend-
ing on the quality of the sewage.
There are provided some operational data for refinery
and petrochemical sewage treatment and advanced treat-
ment as well as the flow diagrams and structures of
activated sludge units used. The advantages of activated
sludge units over biological filters and those of two-stage
systems over single-stage systems are demonstrated.
The quality of biological sewage treatment effluent and
the ratio of dilution for it to be harmless for receiving water
is reported.
In the Soviet Union biochemical treatment is one of the
basic treatment processes preceding the refinery waste
discharge into receiving waters.
The biochemical treatment has widely been used for
treating refinery wastes. Treatment facilities of all the
petroleum refineries and petrochemical plants situated in
the Volga and Urals basins include biochemical treatment
plants. The latter plants are foreseen for all the petroleum
refineries and petrochemical plants under construction.
Refinery wastewater can be subjected to biochemical
treatment either alone or diluted with domestic and
chemical wastewaters. In the first case biogenous elements,
especially nitrogen and phosphorus, are to be added to the
wastewater.
The biochemical treatment equipment of Soviet refineries
is mainly presented by activated sludge systems, especially
those with a many-point waste feeding and a complete
mixing. Most commonly conventional activated sludge
units (with a one-point waste and activated sludge feeding
to the first channel of the unit) are used at the second
treatment step.
As a matter of fact, no use is made of biological filters for
oil-containing waste treatment at the Soviet refineries, as
the operating experience at a refinery has shown them to be
insufficiently efficient, BODs, oil, and phenols removals
being as low as 73, 29, and 72%, respectively. The use of
activated sludge units at the same refinery has improved the
BOD, oil, and phenols removals up to 93 to 95%, 80 to 84%
99 to 100%, respectively.
Oxidation ponds at domestic refineries only serve for
after-treatment of a biochemical treatment effluent.
As the laboratory investigations and the operation
experience have shown, the treatment efficiency of two-step
facilities is by 10 to 15% better in comparison to that of
single-step facilities, in terms of both BOD and oil
removals. The operation of two-step facilities creates
conditions stimulating adaptation of the second-step
activated sludge microorganisms for uptake of difficult-to-
oxidize substances. Therefore, most petroleum refineries use
a two-step biochemical treatment. The treatment efficiency
of these facilities for oil-containing wastewater is as follows:
BOD removal 93 to 98%
oil removal 77 to 86%
phenols removal 99 to 100%
The same result can be achieved in single-step activated
sludge units by increasing the total aeration duration by 30
to 35%.
Special investigations have shown that only about 20% of
ether-soluble substances contained in a biochemical
treatment effluent are hydrocarbons originated from
petroleum, the remaining substances being decomposition
and oxidation products which do not undergo complete
biodegradation.
Thus, petroleum hydrocarbons account for 2 to 3 mg/1
out of 8 to 12 mg/1 of ether-soluble substances in a refinery
biochemical treatment effluent.
The operation data has shown that when using two-step
biochemical treatment of refinery wastewater in activated
sludge units and an advanced treatment in oxidation ponds
the following composition of the final effluent is obtained:
COD, mg Q2/1
BODS, mg Q2/1
Ether-solubles
Oil
Phenols
60 to 80
2 to 8
4 to 8
1 to 2
0.0 to 0.002
Thus, the use of a complete biochemical treatment of re-
finery wastewater followed by its advanced treatment makes
it possible to minimize the amounts of pollutants to be
30
-------
discharged to receiving waters. However, a long-term
wastewater treatment in activated sludge units, big volumes
of facilities and a high electric energy consumption
stimulate the search of intensification ways for lessening this
process capital and operation costs. Therefore, investiga-
tions are carried out in the USSR to intensify the
biochemical wastewater treatment process in activated
sludge units, to reduce their aeration duration, and to
diminish the facilities sizes and treatment costs.
The intensification of biochemical treatment of oil-
containing wastes is possible by raising the activated sludge
and dissolved oxygen concentrations as well as by the
facilities hydrodynamics improvement.
For a process with high sludge doses most suitable are
integrated facilities (aero-accelerator type) which are
equipped with pneumatic mechanic aeration systems and
are combined with a settler. The combined construction of
facilities makes it possible to achieve maximum treatment
efficiency with low space requirements. The oxygen quantity
fed into the facility can be changed by changing automati-
cally the aerator rotation rate. The use of flotators instead
of secondary settlers makes it possible to increase the sludge
dose in an activated sludge unit. Thus, at a petroleum
refinery a two-step plant for biochemical treatment has been
tested, with a flotator provided for the first step sludge
separation. Due to the flotator it is possible to maintain a
higher activated sludge dose in the activated sludge unit.
However, during aeration using air the intensified biochemi-
cal oxidation at high activated sludge doses can give rise to
anaerobic conditions in the activated sludge unit, which
adversely affects the treatment process.
The aeration using technical oxygen instead of air is a
promising method to intensify the process of wastewater
biochemical treatment. The performed investigations have
shown the replacing of air with technical oxygen to be
capable of shortening the aeration duration when treating
oil-containing wastewater by a factor of 4 to 6 and to lessen
accordingly the volume of activated sludge units in
comparison to conventional air aeration or to increase their
capacity. The replacing of air with technical oxygen
dramatically raises the dissolved oxygen concentration in a
facility. Good oxygen regime in an activated sludge unit
makes it possible to increase the activated sludge dose.
Changing from air to oxygen for aeration results in
considerably better properties of the activated sludge: little
or no thread bacteria, no swelling, and improved settleabili-
ty. Therefore, suspended solids in a secondary clarifier
effluent do not increase in spite of increasing sludge
concentration. Also, the use of technical oxygen contributes
to nitrogen and phosphorus removals.
The substitution of technical oxygen for air requires
special design reactors: tight, with mechanical mixing of
sludge liquor and oxygen reuse.
Two types of facilities destined to using technical oxygen
have been developed in the USSR: countercurrent aerotank
- a clarifier with airlift circulation and oxytank - a tight
aerotank with mechanical aeration, combined with sludge
separator. In the oxytank the efficiency of oxygen
utilization achieves 95%. New design biooxydizers are
adapted for operating with high sludge doses of 10 to 15
g/1, which, along with increasing oxygen concentration up
to 8 to 10 mg/1, raises the oxytank oxydation capacity up to
5 to 10 kg BOD'otai/m' day. The oxytank was tested for
chemical plant wastewater under semicommercial condi-
tions.
Technical and economical calculations have verified the
profitability of using oxygen for wastewater biochemical
treatment. The use of oxytanks for industrial wastewater
treatment is most profitable when oxygen is supplied by air
fractionation departments of industrial plants.
The wastewater biochemical treatment equipment is
persistently improved to enable an advantageous use of
oxygen even in those cases when it is to be produced
specially for wastewater treatment.
In recent years, much emphasis has been placed on the
hydrodynamics improvement of aeration facilities.
In the Soviet Union and abroad various types of activated
sludge units are widely used. Their basic types include
completely mixed and plug flow systems as well as
intermediate types.
According to the theory of chemical reactors and the
theoretical analysis of kinetic models used now for organics
biochemical oxidation in activated sludge units, the
oxidation degree of starting materials in a completely mixed
activated sludge systems (for a zero order reaction) is above
that in a plug flow activated sludge system at equal facility
volumes. However, the practice of treating wastewater has
shown the completely mixed activated sludge system to be
superior to other systems in many respects, for the most
part in that it contributes to a fail-free performance at an
immediate concentrated wastewater influent. Therefore, the
completely-mixed activated sludge system as well as that
with a many point wastewater feed (intermediate type) have
found wide application for petroleum refining wastewater
treatment.
Large-scale flow studies in various types of activated
sludge systems have shown the flow conditions of even long
conventional plug flow activated sludge systems to
approach those of complete mixing. Thus, various types of
large-scale activated sludge systems achieve essentially the
same efficiency.
Laboratory and pilot data have shown a specially
designed activated sludge system to perform more efficient-
ly than a conventional one, which allows a 1.5 to 2-fold
reduction in the facility volume.
Thus, the use of combined facilities with high sludge
doses, specially designed activated sludge systems, and
technical oxygen instead of air makes it possible to
considerably intensify the biochemical treatment process for
petroleum refining wastewater- and to reduce capital and
operating costs.
Quality requirements for waste discharge into receiving
waters are now stringent both in the Soviet Union and
abroad. This makes it reasonable to subject biochemically
treated petroleum refinery wastewater to an advanced
(tertiary) treatment such as filtration; treatment improve-
ment, the use of such methods for a biochemical treatment
effluent leads to diminishing sizes of biochemical treatment
facilities.
31
-------
Biological Methods for
Control of Nitrogen in
Municipal Wastewaters
William A. Rosenkranz*
* Director, Waste Management Division
Office of Research and Development
Environmental Protection Agency
Washington, D.C. 20460USA
Various compounds containing the element nitrogen are
becoming increasingly important in wastewater manage-
ment due to the many effects that nitrogenous materials in
wastewater can have on the environment. Nitrogen, in
various forms, can deplete dissolved oxygen levels in
receiving waters, stimulate aquatic growth, exhibit toxicity
toward aquatic life, affect disinfection efficiency, present a
public health hazard and affect the suitability of wastewater
for reuse.
Biological and chemical processes which occur in
wastewater treatment plants and in the natural environment
can change the chemical form in which nitrogen exists. Such
changes may eliminate a deleterious effect of nitrogen, while
producing, or leaving unchanged, another effect. For
example, by converting ammonia in raw wastewater to
nitrate, the oxygen-depleting and toxic effects of ammonia
are eliminated, but the biostimulatory effects may not be
changed significantly.
Most of the nitrogen in raw municipal wastewater is
usually in the ammonia form, although 30 percent to SO
percent is normally associated with organic matter.
Nitrogen is removed in various ways in wastewater
treatment facilities. A large portion of the organic nitrogen
is removed by primary sedimentation, while additional
amounts of organic nitrogen may be biologically converted
to ammonia when the wastewater is subjected to secondary
treatment such as activated sludge. Nitrates and nitrites
usually absent in raw wastewater, may be present following
a highly efficient secondary treatment process and the
presence of signigicant numbers of nitrifying bacteria.
Effective methods of wastewater treatment which will
remove nitrogen are increasingly needed in many locations
where critical water quality conditions exist. Governmental
agencies have promulgated effluent standards relating to
water quality in an attempt to relieve or prevent the
symptoms of nitrogen pollution in such locations. Scientists
and engineers have devoted considerable research and
development effort toward developing both biological and
physical-chemical methods for nitrogen removal in order to
produce effluents which can be discharged into streams
which require such action for achieving acceptable water
quality.
Physical-chemical methods which have been shown to be
effective depending on effluent quality requirements in-
clude:
1. Breakpoint Chlorination—Addition of chlorine to
wastewaters for the purpose of oxidizing the ammoni-
um ion to end products composed predominately of
nitrogen gas.
2. Selective Ion Exchange for Ammonia Removal—Use
of an ion-exchange resin which is selective for
ammonium. A natural zeolite, clinoptilolite, occurring
in the Western United States has been found effective
for this purpose.
3. Air Stripping of Ammonia—Countercurrent circula-
tion of large volumes of air and effluent through a
stripping tower after the treated effluent has been
adjusted to high pH.
Biological methods of removing nitrogen, the subject of
this paper, consist of two wastewater treatment phases:
nitrification and denitrification. The processes which have
been used for this purpose utilize several configurations, but
all involve first the nitrification step, followed by a
denitrifaction step. Certain controlling factors form the
basis of configuration selection. Nitrification by autotropic
bacteria (Nitrosomes and Nitrobacter) achieves a maximum
rate in the activated sludge process at dissolved oxygen
concentration of about 2 mg/1 or above. The rate decreases
to zero as the dissolved oxygen concentration decreases to
zero. While denitrification by facultative bacteria occurs in
both anoxic and slightly aerobic systems, the most rapid
denitrification occurs with dissolved oxygen concentration
of zero. Ample sources of readily acceptable organic carbon
to serve as an energy supply for the bacterial reduction of
the nitrate and nitrite are required.
In biological treatment of wastewaters, oxidation of
carbonaceous material, nitrification, and denitrification all
occur within a single process if sufficient bacterial solids
retention time is provided for development of the nitrifying
and denitrifying organisms. Optimum process operating
conditions for oxidation and for subsequent denitrification
are thermodynamically antagonistic. The presence of the
more powerful oxidant oxygen (electric acceptor) sup-
presses the use of NOa (electron acceptor) in the biological
oxidation of the carbonaceous material in the wastewater.
In conventionally aerated biological systems, efficient
oxidation of the carbonaceous and nitrogenous materials,
in either a single or two-stage process, is achieved under
aerobic reactor conditions. The aerobic conditions produce
the nitrate product, but also remove the organic materials
which act as readily available electron donors for denitrifi-
cation. In addition, the dissolved oxygen in the water
significantly suppresses or minimizes the biological reduc-
tion of the nitrate or nitrite as they are produced.
Although the biological potential exists in municipal
wastewaters for both nitrification and denitrification
without supplemental organic carbon sources, the operating
conditions usually employed in aerobic biological processes
produce efficient carbonaceous removal and nitrification
but not efficient denitrification. Thus, the operating
conditions for the activated sludge process must be selected
which will produce efficient nitrification and denitrification
with the indigenous carbonaceous material in the waste-
water acting as the electron donor during denitrification.
Research to accomplish this objective was undertaken at
the EPA Pilot Plant at Washington, D.C. The approach to
achieving nitrification—denitrification in a single, activated
sludge reactor-clarifier with the wastewater organic carbon
used for denitrification consisted of providing alternate
periods of aerobic and anaerobic conditions within the
reactor and operating the reactor at sufficiently low food-to-
32
-------
microorganism ratios (high solids retention times) to ensure
a nitrifying population within the mixed liquor culture. To
provide the alternating aerobic-anaerobic conditions while
continuously operating the air compressor, the activated
sludge reactor was divided into two equal basins operating
in series. Each basin, with a water depth of 3.35 m(ll ft.),
provided a detention time of 3.55 hr., at a process flow of
189 cu m/day (50,000 gpd). Air was supplied alternately to
each basin; first to one basin and then to the other on a 30-
minute cycle. The dissolved oxygen in the basins was
manually controlled at between 2 and 3 mg/1 during
aeration and rapidly decreased to zero during the anaerobic
period.
Mechanical mixers in each basin, operated at 30 rpm,
suspended the mixed liquor solids without any significant
surface aeration of the wastewater. Figure I illustrates the
pilot plant configuration.
Nine months of test data are shown in Table I. During 9
months of operation, the pilot plant operated at a F/M
(food-to-mass ratio) of approximately 0.1 Ib BODs/lb.
MLVSS/day (0.1 g/g/day) expressed on the basis of the
total inventory in the reactor. This F/ M was sufficiently low
to permit the development of a mixed culture of organisms
for carbon oxidation, nitrification and denitrification. Total
nitrogen removal efficiencies were highest at the higher
COD/TKN ratios.
Nitrogen removals during the study varied from 54 to 84
percent. As in other alternating aerobic/ anoxic studies, it
was found that a severe filamentous bulking condition
developed in the sludge, limiting wintertime clarifier
overflow rates to about 12.24 cu m/day/sq m (300 gpd/sf).
Bulking sludge had been observed during operation of this
pilot study at low temperatures and at low F/M operation
here and at other plants. It appeared that clarifier would
limit operation of this aerobic/anoxic system as it will other
similar systems.
On March 1, 1975, the Office of Research and Develop-
ment funded a full-scale plant evaluation project of the
above described process at Owego, New York. The plant
operates over a range of wastewater temperature of 5°C to
20°C. The objective of the project was to maximize nitrogen
removal by simple changes in operational techniques.
The plant is designed for 7,570 cu m/day (2 mgd) at the
design date of 1990. Present flow averages 1,514 cu m/day
(0.4 mgd), with a maximum dry weather flow of 2,271 cu
m/day (0.6 mgd) and a minimum of 1,135 cu m/day (0.3
mgd). The plant does experience the impact of infiltration
since high flows of 3,406 cu m/day (0.9 mgd) have been
recorded. Facilities consist of dual primary settlers and
aerators (Figure II). Each reactor has two compartments
and each compartment has one surface aerator. The
compartments are sized for contact stabilization; with the
larger units having 15 horsepower and the smaller 10
horsepower surface aerators. Dual final clarifiers are fitted
with chain drags and scum baffles. Sludge is digested in a
two-stage anaerobic digester. Sludge is hauled to nearby
farms and disked into the soil.
In line with our findings at the Blue Plains pilot single
stage system that a rather high BOD/TUN ratio is needed
for denitrification, the Owego primary clarifiers were taken
off line. The aerators received raw wastewater with a BODs
of approximately 200 mg/1 and a total nitrogen content of
approximately 40 mg/1.
D.C. RAW WASTEWATER
PRIMARY
VL
AIR ,
i-'fc, i
NITRIFICATION DENTRIFICATION
REACTOR
WASTE,
RETURN SLUDGE >v
SECONDARY
FINAL EFFLUENT
Figure 1 Blue Plains Alternating AnoxloAerobic System
I
*
FINAL
SETTLING
•4—
em n«i^>*^ ^
CONTACT +f
•- •*-•
' J
AERATION TANKS
SOUTH 1
Figure 2
Extended Aeration
Water Pollution Control Plant
Town of Owego, New York
33
-------
MONTH
1973
JAN
FEB
MARCH
APRIL
MAY
JUNE
JULY
AUGUST
SEPT
F M MISS
DET. l.B BOD APPLIED MG 1 SVI. COD
TIME I.BMI.VSS DAY <9j Ml. TKN
HR OR C G DAY VOLATILE) O RATIO
12.3
12.3
123
12.4
10.5
8.8
6.8
6.6
8.7
0.072
0.066
0.10
0.081
0.089
0.105
0.093
0.089
0.11
3510
(74)
3980
(73)
2950
(73)
3540
(67)
4170
(69)
4010
(69)
3040
(64)
3200
(57)
3700
(65)
245
250
330
277
227
188
133
134
_
9.6
9.9
10.5
10.6
10.0
10.3
7,9
7.5
10.0
INFLUENT QUALITY MG
TEMP..
C
14.0
14.2
15.5
--
—
23.0
25.0
25.5
26.0
BOD;
96.5
99
110
98.8
115
107
51
44.2
99
TOTAL
KJELDAHI.
SS NITROGEN
MO
108
128
120
109
112
153
197
110
25.7
. 23.2
24.8
21.7
23.3
24.0
15.0
14.9
22.6
1
BODi
20.4
14.0
6.5h
5.3"
3.3"
3.2"
3.8"
2.6"
7.2"
EFFLUENT QUALITY M« 1.
SS
15.4
14.3
15.0
13.0
11.8
7.8
9.0
10.0
16.0
TOTAL
KJELDAHI. NO)
NITROGEN NO:-N
2.28
1.52
4.20
5.20
1.36
1.51
2.14
1.23
I0.2C
3.99
4.41
2.30
6.03
8.25
2.3
2.72
3.74
0.22
REMOVALS.
BOD'
79
86
94"
95"
97*
,7b
93"
94"
93"
PLKtTM
TOTAL
SS NITROGEN
85
87
88
89
89
93
94
95
83
7*
75
74
49
39
84
68
67
54
,PRIOR TO FILTRATION
t NITRIFICATION INHIBITED
cAMMONIA LEVEL WAS 9.4 MG/L AS N (SEE TEXT)
Table 1 Summary of operation and performance for the Blue
Plains Alternating Aerobic/Anoxic System (Reference 60)
After a brief start-up period, it was determined that the
plant was operating well and that conditions were suitable
for pulsing the surface aerators to encourage denitrification.
Again, on the basis of Blue Plains experience, a 50 percent
cycle was set for the initial period of study. The aerators
would be on for 30 minutes and off for 30 minutes. The
project included plans to collect data during warm and cold
weather. The warm weather data was collected up to
September of 1975. The cold weather data collection period
was scheduled to begin in January of 1976.
Performance of the Owego plant has been very good. For
the period through September of 1975, BOD' and
suspended solids removals were better than 90 percent, nitrification
was complete, and total nitrogen removals were in excess of 80
percent without the addition of an organic supplement. At times
total nitrogen removal approached 95 percent efficiency.
This project is nearly complete. The cold weather data is
undergoing analysis. Based on the on-site experiences, the process
appears to be relatively easy to operate. It has been observed that
Nocardia growths have not appeared during the report period. We
expect that the process could be made to operate automatically
with the proper sensors to monitor the effluent for the degree of
nitrification and/or denitrification required.
As mentioned earlier, there are several processes or process
configurations that can be used for nitrogen removal. The Pasveer
ditch, or endless channel system can be effective in removing
nitrogen. Removals of 90 percent have been reported. This system
is illustrated in Figure III.
EPA funded an evaluation project of this type of system at
Dawson, Minnesota. The Dawson plant is designed to treat 984 cu
m/day (0.26 mgd) having a strength of 230 mg/1 BOD5 and 200
rug/1 suspended solids. One of the objectives of the study
was to determine the feasibility of nitrifying and denitrifying
the wastewater without the addition of an alternate carbon
source (for denitrification).
Nitrification-denitrification efficiency is linked to the
concentration of dissolved oxygen in the channel. In the
zone that experiences a D.O. of greater than 0.5 to 1.0
mg/1, nitrification will occur. In the zone where D.O. is less
than 0.5 mg/1, denitrification will take place without the
addition of an alternate carbon source such as methanol.
Instead, the raw BOD acts as the carbon source.
Denitrification is limited by the ratio of BOD (or COD) to
TKN. The higher the ratio the more efficient"the process.
Even though the plant was not operated in the most
optimum mode, removals ranged from approximately 50 to
80 percent. As stated earlier, the Dutch and others have
reported removal of nitrogen in excess of 90 percent.
.RAW WASTEWATER
ROTOR OR OTHER
AERATION SYSTEM
EFFLUENT
Figure 3 Pasveer ditch or Endless Channel System for nitrogen
removal
Figure IV shows two additional systems, one of which
utilizes methanol as a carbon source.
The advantages and disadvantages of the several
biological nitrogen removal systems are summarized in
Table II.
34
-------
INFLUENT
WASTEWATER
INFLUENT
WASTEWATER
I RETURN SLUDGE
ANOXIC*
DENITRIFICATION
TANK (4 HR)
AEROBIC
COMBINED CARBON
OXIDATION-
NITRIFICATION
TANK
(18 HR)
ANOXIC
DENITRIFICATION
TANK (5 HRl
I
AEROBIC TANK 12 HR)
SEDIMENTATION
TANK
(I HRl
COMBINED CARBON
OXIDATION-
NITRIFICATION
TANK
(10 MR)
INTERMEDIATE
SEDIMENTATION
TANK (4 HRl
OENITRIFICATION
TANK (2 HR)
1
AEROBIC TANK (1 HRl
FINAL
SEDIMENTATION
TANK (4 HRl
4—
DENITRIFIED
EFFLUENT
A. BAROENrHOfROCESSRIHRI
DENITRIFIED
EFFLUENT
B. ALTERNATIVE METHANOL
BASEO SYSTEM 121 HR)
Figure 4 Comparison of Denitrification Systems
SYSTEM TYPE
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NtTRIMIHSAGAIHIT TORICAMrl
BIHICUirTOOrHMIHHIllllMCAllOII
MDDINItMIHtAIIDIIimilUtlV
Table 2. Comparison of Denitrification Alternatives
References
Bishop, D.F., et al, Single Stage Nitrification-
Denitrification, Environmental Protection Series, EPA
670/2-75-051, June 1975
Grounds, Harry C, Draft Final Report Dawson, Minneso-
ta Demonstration Project, U.S. EPA Grant No. 803067-
01-1, December 1975
Personal Communication w Donald E. Schwinn (Stearns
and Wheler Civil and Sanitary Engineers), May 6,1975 in
reference to Owego, New York/EPA Demonstration
Project: Full-Scale Operation of a Single-Stage Nitrifica-
tion-Denitrification Plant
Schwinn, Donald E., Quarterly Report on Single-Stage
Nitrification Denitrification Full-Scale Study at Owego,
New York, EPA Project S-803618-01, July 1975
Process Design Manual for Nitrogen Control U.S.
Environmental Protection Agency, Technology Transfer,
October 1975
35
-------
Operation Experience of
Oxytanks
Skirdov, I.V., Shvetzov, V.N., Bondarev,
A.A., Lurje, B.J., Bereykina, N.G., Katchko-
va, S.E.
The Institute VODGEO has developed a construction and
a system design method for carrying out the biological
wastewater treatment process of high intensity by using both
pure oxygen and high concentrations of activated sludge.
The system is termed "an oxytank".
The oxytank system affords achieving a high efficiency in
supplied oxygen utilization, a significant reduction in total
structural volume due to a combined action of biological
oxidation process and mixed liquor separation in the same
structural volume as well as it enables to promote the
automatically controlled system for oxygen supply propor-
tional to quantity and quality of influent wastewater.
The oxytank (Fig. 1) involves a cylindrical container inside
of which a hermetically sealed reactor is positioned. (2) The
reactor is provided with the surface tyrbo-aerator (5) driven
in rotation by an electric motor located on the cover. The
rotary hydraulic valve enables the aerator shaft to be
hermetical. In the annular space between the reactor and the
outside wall of the container a sludge separation tank (3) is
installed where activated sludge - treated water separation
has taken place. The middle part of the partition separating
the reactor is equipped with ports with directed tangential
nozzles (7) and with gates for mixed liquor delivery to the
sludge separation tank from the reactor. The activated sludge
is returned to the reactor via the annular aperture (8) in the
lower part of the partition.
Thus in order to promote the intensification of sludge
separation and to prevent the unwanted sludge deposits
settling at the bottom of the sludge separation tank the
mixing device is mounted in the form of grid with rods of 30-
50 mm in diameter. The scrapers (6) are hinged in the lower
part of grids. The wastewater is passed to the reactor through
the pipe (I) and it is mixed with activated sludge by means of
the aerator (5) then the mixed liquor is saturated with gas
that is under the reactor cover. The oxygen is fed to the
reactor through the pipe (9) equipped with automatic valve
actuated by a pressure sensor. (12) The treated wastewater is
introduced simultaneously with activated sludge to the
sludge separation tank via the nozzles under the action of
speed head developed by the aerator. The clarified liquor is
withdrawn through the annular collecting gutter (4). The
settled activated sludge is" returned to the reactor through the
annular aperature (8).
The given concentration of dissolved oxygen in the
reaction chamber is maintained automatically. As the
oxygen is being consumed by the mixed liquor the pressure of
gaseous mixture in the reactor over the liquid surface
decreases,
At that moment the pressure sensor (12) gives a signal for
opening the valve located on the pipe (9) through which the
oxygen is fed. The oxygen starts to be introduced into the
system. When the gaseous mixture pressure in the reactor
achieves the set level the valve automatically closes.
Gradually accumulated respirated carbon dioxide formed
during the biochemical oxidation process as well as nitrogen
stripped from the wastewater and also inert gases being
supplied simultaneously with pure oxygen have changed
gaseous mixture composition in the reactor. In this case the
partial pressure of oxygen reduces while that of carbon
dioxide and of other components increases. The decrease of
oxygen partial pressure results in the oxygen concentration
reduction in the mixed liquor and hence for the stabilization
of gaseous mixture composition in the reactor it is necessary
periodically to remove the accumulated gases by blowing
the oxveen throueh thp sv«tpm
As the partial pressure of oxygen in gaseous mixture
drops below the set level the dissolved oxygen concentration
sensor (11) gives a signal for opening the automatic valve
(10). The gaseous mixture from the working chamber
is released into atmosphere. The oxygen is fed to the reactor
through the pipe (9) instead of being withdrawn from the
gaseous mixture. As the set level of dissolved oxygen
concentration in mixed liquor is achieved the valve (11)
closes,
On the basis of pilot plant investigations in oxytank it the
method has been developed for estimation of the above type
of treatment works capable to operate in a regime of reactor
with complete mixing.
The wastewater retention time in oxytank reactor may be
determined by the following equation
t= Lo ' Lt
KozKseCsc (1)
where t - average retention time for wastewater in
oxytank reactor, hrs;
Lo - influent wastewater BOD fed to oxytank,
mg/1;
Lt - effluent wastewater BOD, mg/1;
-specific oxygenation rate at Cu = 3 g/1 and at
oxygen concentration of 2 mg/1.
Koz - coefficient with regard for the effect of
dissolved oxygen concentration on specific
oxygenation rate;
K sludge - coefficient with regard for the effect of
activated sludge concentration on specific
oxygenation rate;
'Csludge - activated sludge concentration, g/1. ,
The value of coefficients of both Ko2 and Ksiudge were
experimentally defined and Figs 2 and 3 yield the
corresponding curves.
The sludge separation tank design is based on determina-
tion of ultimate hydraulic load. In the course of investiga-
tions performed at the Institute VODGEO it was defined that
the effect of the assumed hydraulic load on the sludge
separation tank as a function of dimensionless criterion of
1C.
where I - sludge index value, sm2/g;
C - activated sludge concentration in solution, g/cm3.
The curve in Fig. 4 represents this relationship. To
improve the treated water quality the sludge separation tank
is designed to be operated in a regime of settling tank by use
of suspended solids. Special means in oxytanks allow the
depth of suspended solids beds to be stabilized and ensure its
exchange.
One of the oxytank features is a high oxygen concentra-
36
-------
tion in the mixed liquor supplied to the sludge separation
tank from the reactor. Significant store of dissolved oxygen
in recycling zone of sludge separation tank combined with
favourable hydrodyanamic operating conditions create
provisions for intensive biochemical process in the zone.
The total volume of oxytank may be divided into several
zones depending on performed functions (Fig. 5).
Figure 1. - Scheme of oxytank
\
* cona»atrttloa (/I
Figure 2. - Coefficient Ku VS activated sludee concentration
».-
fi
'
16
<
10
<\i
A
I
/
^r
o • e; «
^
^^
**~ \
\
t *o. a* i
.
dissolved oxygen concentration, ng/1
Figure 3. - Coefficient Km VS dissolved oxygen concentration
If
o.»
v__
0,6
'hi
*t
i
\
!
;
V
\
O
>
\
0 0
—
0 oo
» <
\
-
•*
l 0
o
>
' ^^*>
>J
•* -.
0,5 0,4 ,£W tf> 0,7 Qf O,S $0
3C
Figure 4. - Hydraulic load acting on sludge separation tank of
oxytanks VS dimensionless parameter 1C.
Figure 5. - Scheme of oxytank divided into the following process
zones:
I. Reactor - biochemical oxidation and mixed liquor saturation by
oxygen.
2. Recycle zone of Sludge separation tank - biological oxidation
and mixed liquor separation.
3. Zone of suspended solids filler water treatment by filtering and
oxidizing the organic compounds.
4. Protective zone.
37
-------
The given scheme shows that the largest part of sludge
separation tank volume in oxytank fulfils two functions
such as thickening of mixed liquor and biochemical
oxydation. The total structural volume is considerably
reduced due to this fact.
The experimental oxytanks at wastewater treatment
works of Schekinsk Combine "Azot" have been constructed
and were put into operation in 1974. VNII VODGEO has
recommended the oxytanks be designed on the basis of
investigation of a pilot plant with a capacity of 150-200
m3/day.
The oxytanks of volume 270 m3 a 9.6 m in diameter each
have been built at Schekinsk Combine "Azot". The following
values of estimated parameters for oxytanks are presented
below:
1. Oxygenation capacity (OC), BODcompi. - 2.04
kg/m3/day Oxygenation capacity (OC), COD - 2.73
kg/m3/day
2. Wastewater flow rate - 59 m3/hr (at influent waste-
water BOD of 300 mg/1)
3. Effluent BOD compi. - 15 mg/1
4. Effluent suspended solids - 15-20 mg/1
In order to define the actual technologic data and the
sanitary efficiency of oxytank operation the Institute
VODGEO in cooperation with the laboratory of treatment
at Schekinsk Combine "Azot" as well as with Tula regional
and Schekinsk sanitary-epidemologic stations have consist-
ently observed these treatment works.
The average compared data of both oxytank and aeration
tank operation through a long period of service are
summarized in Table I.
As shown in the given results, the oxytank generation
capacity was close to that estimated and exceeded 3.5 times
the Oxygenation capacity of full-scale aeration tanks
operating in parallel at Schekinsk Combing "Azot". In this
case the removal efficiency of main components from
wastewater was in accordance with the complete biological
treatment.
The oxytank operating efficiency doesn't practically vary
at its long overload evaluated by organic impurities. So
through the period of operation from March 1, to March 6,
1976 with average duration of flow retention time of 3.9
hours in reaction zone the oxytank oxygenation capacity
was equal to 3720 g COD m3/day. Over this period of time
the oxytank ensured the wastewater biological treatment to
be complete. Effluent BODcompi. was not higher than 15
mg/1, COD averaged 77 mg/1 and suspended solids were
maintained in amounts of 22 mg/1. With a nitrogen initial
content stripped from ammoniated salts at a dose of 73
mg/1 in effluent ammoniated nitrogen observed in amounts
of 29.8 mg/1 on average.
It should be noted that oxytank short overloads that are
1.6-1.9 times as much as the estimated loads have no
adverse effect on the effluent quality.
As evidenced by the oxytank operation data which show
that at the same extent of treatment the sludge index value
in oxytank can be decreased 1.4-1.6 times compared to that
in aeration tank.
The efficiency of oxygen usage that is supplied to
oxytanks was not below 80% and averaged 93-96%.
Attention was attracted to a high concentration of
ammoniated nitrogen in oxytank effluent as a result of
insufficient process has taken place.
Both efficient and economical advantages of oxytanks
usage may be illustrated as an example for wastewater
treatment at plants of nitrogenous industry.
For economical comparison the treatment works have
been taken in the following combination:
Example I - Aeration tanks with air supply by compressors.
Example II- Combined hermetical aeration tanks (oxy-
tanks) with oxygen supply from air separation installa-
tion at the industrial plant.
The mechanical wastewater treatment works and sludge
disposal plants in the given examples were accepted to be the
same and because of this they are neglected in calculations.
The examples are compared by using the biological
treatment plant efficiencies in the of 50,000-300,000 m3/day.
The treatment works are designed so that complete
biological treatment is ensured.
To determine the estimated parameters of aeration tanks
for wastewater treatment the following performance data are
used:
Influent BOD - 300 mg/1
Effluent BOD 15 mg/1
Aeration time - 16 hrs
Sludge dose - 1.5 - 3 gr/1
Aeration intensity - 4-5 m3/m2/hr
In oxytank calculations the retention time adopted to be
3 hours (including retention time in sludge separation tank
of half an hour). An increase in oxytank capacity is caused
by rise of both sludge dose up to 10-12 gr/1 and dissolved
oxygen concentration up to 12-14 m/1.
Technologic data from the above are considered that the
compared examples are summarized in Table II.
insert table
By determining the capital expenditures for oxytank at
wastewater treatment the oxygen accepted to be supplied
from air separation installation. In this case the capital
investment have been denned by specific investment based
on cryogranic plant cost that amounted to 303 rou-
bles/m3/hr.
By estimating energy consumption using mechanical type
aerators in oxytank the specific rate accepted to be equal
0.32kw.hr
kg(02)
with regard for an increase in aerator capacity and a
decrease in energy cost respectively, therewith the oxygen
was dissolved due to partial pressure elevation of this gas.
Technical-economical calculation results are summarized
in Table III.
Conclusions
1. The oxytank construction is manufactured on reactor
complete mixing principle and most applying to the
wastewater treatment. The considered system is character-
ized by a high efficiency of oxygen utilization, by reducing
the construction size associated with this fact that three
processes such as settling, filtering through activated sludge
38
-------
suspended solid bed and biochemical oxydation are
combined in a sludge separation tank, as well as by
automatic control system for oxygen supply that is
proportional to organic impurities quantity fed with
wastewater.
2. Full-scale plant studies showed that the technologic
data related to oxytank performance agreed with the
estimated results. In this case oxytank oxygenation capacity
is 3.5 times higher compared to that for aeration tank at
complete biochemical treatment of wastewater as concerns
of the basic components.
3. The pure oxygen utilization affords the activated
sludge concentration in oxytank to be maintained in 6-10
g/1 range at high dissolved oxygen concentration of 10-12
mg/1. In so doing the settling properties of activated sludge
are improved.
4. Oxytank system provided for a high quality of treated
water at short overloads by 1.6-1.9 times and at long ones
by 1.3-1.4 times.
Table I
Average Month
Parameters
1. Estimated aeration
time, hrs
2, Activated sludge
concentration, g/1
3. Dissolved oxygen,
mg/1
4. Sludge index, sm3/g
5. Removed BOD, %
6. Oxygenation capaci-
ty, g COD/ m3/ day
7. Load effect on
sludge, g COD/g day
Wastewater
8. COD, mg/1
9. BODcompi. mg/1
10. Ammoniated nitrogen
11. Nitrite nitrogen, mg/1
12. Nitrate nitrogen, mg/1
13. pH
Treated water
14. COD, mg/1
15. BODcompi., mg/1
16. Ammoniated nitrogen,
mg/1
17. Nitrite nitrogen, mg/1
18. Nitrate nitrogen, mg/1
19. Suspended solids, mg/1
Data
Aeration
tank
20
2.5
3-4
90
97.4
743
298
663
487
45
13
20
Table II Technologic data
Example Capacity Removed
BOD
1000
m3 t/day t/day
50 18.8
I 100 37.6
200 75.2
300 113.8
SO 18.8
II 100 37.6
200 75.2
300 1 13.8
Duration
Aeration Settling
hr hr
16 1.5
16 1.5
16 1.5
16 1.5
3.0 1.5
3.0 1.5
3.0 1.5
3.0 1.5
Oxytank
5.5
7.8
12
66
97.4
2610
335
663
497
65
13
18
taken from
-
Average Week
Data
Aeration
tank Oxytank
20 3.9
2.5 7.4
3-4 12
73
965 3720
302 503
686 686
512 512
48 78
13 13
29.8
20 22
the examples I and II
Volume Gas rate
Aeration Settling Air Oxygen
tank
1000
mj
45.0
90.0
180.0
270.0
8.4
16.8
33.6
50.0
tank
1000
m3 m3/hr m3/hr
4.2 70,000
8.4 140,000
16.8 280,000
25.2 420,000
4.2 - 708
8.4 - 1416
16.8 - 2832
25.0 - 4248
39
-------
S. The distinguishing feature of oxytanks is elimination of
wastewater volatile components discharged into the atmos-
phere that prevents it from being polluted by harmful
substances. At the same time if ammonium nitrogen is
present in wastewater influent in large amounts because of
lack of stripping the ammonia, the ammonium nitrogen
content in oxytank effluent was higher than in aeration tank
one.
6. Technical-economical evaluation obtained for the case
of wastewater treatment of nitrogenous industry showed
that the oxygen utilization in oxytanks proved to be
advantageous from an economic point of view. Therewith
capital investment for biological treatment works are
reduced by 1.5-2 times, operating expenditures are decreased
by 1.4-1.6 times and economical effect for plants with
capacity of 50,000-300,000 m3 of wastewater per day was
177,000-625,000 m'/year respectively.
Table HI
Examples
I
Aeration
tanks
II
Oxytanks
Capacity of
treatment
plant
1000 m3/day
50
100
200
300
50
100
200
300
Volume
of aeration
tanks or
oxytanks
1000m3
45.0
90
180
270
8.4
16.8
33.6
50.0
Air or
oxygen
rate
1000 m'/hr
70
140
280
420
0.71
1.42
2.73
4.25
Capital
Aeration tanks or
oxytanks
Unit
roubles/ m3
20.4
15.9
14.1
13.0
31.0
21.5
21.5
21.5
Total
1000
roubles
920
1430
2530
3510
260
362
723
1120
cost
Air flowing and
oxygen
Unit
roubles/
m'/hr
-
-
-
-
303
303
303
303
plants
. Total
1000
roubles
150
190
240
260
215
430
860
1290
General
K
1000
roubles
1070
1620
2770
3770
575
792
1583
2490
Operating costs
Amortization charges
Energy cost
Construction Equipment
3.9% 5.
Total Unit Per year General
Biochemical Compared Economical
treatment expenditures effect
1000
roubles
per year
36.0
55.7
98.5
137.0
10.1
14.3
28.2
43.7
1000
roubles
per year
7.9
10.1
12.7
13.8
11.4
22.8
45.6
78.4
1000
roubles
43.9
55.8
111.2
150.8
21.5
37.1
73.8
122.1
roubles
1000m3
-
-
-
-
16.9
16.9
16.9
16.9
1000
roubles
per year
257
512
1024
1540
178
356
712
1070
1000
roubles
per year
300.9
567.8
1135.2
1690.8
199.5
393.1
785.8
1192.1
roubles
1000m3
16.5
15.6
15.5
15.5
6.1
5.9
5.9
5.9
1000
roubles
per year
464
784
1505
2183
280
703
981
1540
1000
roubles
per year
.
-
-
-
177
266
475
625
40
-------
Improvements for Kraft Pulp
and Municipal Treatment
Processes
Frank P. Sebastian
Senior Vice President
Envirotech Corporation
Menlo Park, California
Dennis S. Lachtman
Assistant to the Senior Vice President
Envirotech Corporation
Menlo Park, California
Introduction
The opportunity to reappear before such a distinguished
group of Soviet and American scientists is indeed an honor.
As the title suggests, my comments will be directed to
process improvements in bleached kraft pulp mills, and in
the municipal sector to solids processing and water
monitoring. While I am not a paper expert, I am pleased to
have this opportunity to present this development.
The pulp and paper industry, which has been a major
contributor to both water and environmental degradation,
now has some new developments that promise to reverse
this trend. The Salt Recovery Process in conjunction with
the closed-cycle bleached kraft mill, which will subsequently
be discussed in depth, can serve as either a modification of
existing facilities or an entirely new flowsheet for new or
existing facilities. The closed-cycle bleached kraft mill
avoids the cost of both secondary and tertiary treatment
processes because it recycles materials and eliminates the
need for treatment while both saving the costs of new
materials and reducing water consumption.
In the municipal process area, but certainly not limited to
such applications, the Hi-solids filter and control systems
based on the TOC analyzer represent modifications that
both enhance treatment efficiency and reduce expense.
The Hi-solids filter increases sewage sludge solids content
which allows for greater energy recovery while maximizing
furnace handling capability.
The TOC analyzer is a proven useful resource for quick
effluent and influent monitoring and has been used to
increase plant performance through a strategy of feedfor-
ward and feedback control. Where previous carbon
analyzer technology was susceptable to fouling or shut-
downs, new developments have all but eliminated these
maladies.
Closed-Cycle Mill
One of the industries traditionally having problems with
effluent streams has been the pulp and paper industry,
which in the United States has recently experienced some
costly and difficult years dealing with environmental
control. According to Chemical Weekd), the paper and pulp
industry paid an unprecedented $1 billion (0.756 billion
Rubles) for pollution control last year. As the pulp and
paper industry effluent streams approach zero discharge
requirements in the United States, these costs promise to
escalate further under present technology. Regardless of
which country, be it the USSR or the USA, such large kinds
of expenditures put a strain on production capacity.
Fortunately, there is a new and emerging process for the
kraft pulp industry that promises to eliminate both
contaminated effluents and the needs for external advanced
waste treatment facilities. This process also reduces the cost
of raw chemicals. The processes I am referring to are called
the closed-cycle mill and salt control processes and were
first developed by W.H. Rapson and D.W. Reeve in their
research efforts at the University of Toronto<2,3). Erco-
Envirotech, a joint venture of American and Canadian
business interests, continued the development of the closed-
cycle concept for commercial applications.
The closed-cycle mill combines a number of innovative
procedures providing a process design that eliminates
effluent discharges through internal recycling. The system
also recovers fibers, chemicals, organics and heat normally
lost to external treatment systems in conventional kraft
mills.
Recognizing the obvious merits of this system a Canadian
firm, Great Lakes Paper Company, has installed the first
closed-cycle bleached kraft pulp mill in Thunder Bay,
Ontario, Canada<4). The plant will enjoy the economic
benefits to be had from eliminating waste treatment
facilities, yet it will be the world's first pulp mill not to
discharge contaminated effluents. The only effluent from the
plant will be clean cooling water. Among the advantages
that the Great Lakes Paper Company's mill will have are <5>:
1. water consumption will only be 1/6 of previous levels;
2, substantial energy savings associated with heat recycle
and water use reduction;
3. lower raw chemical consumption;
4. improved pulp yield, strength and brightness; and
5. elimination of need for external treatment.
Kraft Pulping and Bleaching
Before proceeding to discuss the closed-cycle kraft mill
with the Salt Recovery Process, I would like to digress a
moment to review the basic concepts inherent to kraft
pulping.
Kraft or sulfate pulping is a process that treats wood
chips with a strong alkali solution during cooking, as shown
in Figure 1. The alkali solution penetrates the wood and
dissolves the lignin. After cooking and washing, the end
product is pulp.
The afkali solution, called white liquor, consists of
sodium sulfide (NazS) and sodium hydroxide (NaOH). The
sodium sulfide (Na2S) serves to both speed the reaction and
strengthen the pulp. Toward the end of the cook, the
physical integrity of wood chips is weakened and they can
be blown from the digester under pressure. The fibers are
easily blown apart by steam expansion and the resultant
dark-colored product is a very strong pulp, hereafter
referred to as unbleached kraft pulp. The liquid fraction
remaining after the cook is black and it contains more than
half the original wood content in addition to spent
chemicalstj).
The kraft process must recover this black liquor to be
economically efficient. The box marked "Black Liquor
Evaporator" in Figure 1 is where the black liquor, after
41
-------
being washed from the brown pulp in the preceding box
marked "Brown Stock Washing" is concentrated via
evaporation. The concentrated black liquor is burned in a
furnace and the remaining smelt is dissolved in water. This
solution contains sodium carbonate (NaaCOa), and sodium
sulfide (NazS) and is referred to as green liquor. The sodium
carbonate (NazCOj) is then causticized with lime. This last
step is schematically shown in Figure 1 as occurring in the
box marked "Liquor Preparation." The resultant solution,
which is clear and called white liquor, is reused for pulping.
The kraft mill is not a major pollutant process, as 95% of
the chemicals are continuously reused in the described
flowsheet. However, the brown-colored pulp is not as
desirable nor does it command as high a price as bleached
pulp.
Early attempts to bleach brown pulp with chlorine (Ch)
and caustic soda led to substantial strength losses. However,
bleaching with chlorine dioxide (ChO), chlorine (Ch) and
sodium hydroxide (NaOH) make it possible to get pulp
brightness of 88-92% G.E. without losing pulp strength.
This development which was also pioneered by Dr. Rapson,
led to a large worldwide expansion of kraft pulp produc-
tion<5).
The bleaching plant contributes the major pollutant
burden from bleached kraft mills. Bleaching dissolves
another 7-10% of the pulp which in combination with spent
chemicals and toxic compounds like chlorophenols com-
prise the bleaching plant effluent. Since this effluent can be
very toxic, the closed-cycle bleached kraft mill concept is a
significant development, both economically and environ-
mentally. I will be discussing the detailed economic
advantages of the closed-cycle mill in a following section.
The Process at Great Lakes Paper Company
Thunder Bay, Ontario, Canada
The plant scheduled to start up late this year will produce
250,000 tons (227,000 metric tons) per year of bleached
market grade pulp. Many of the process techniques for this
plant have either been demonstrated or are being used in
mills throughout the world today. Those process techniques
already used elsewhere and contained in the Thunder Bay
flowsheet are the following^:
1. Countercurrent washing in the bleachery:
2. high chlorine dioxide substitution for chlorine in the
first bleaching stage;
3. steam stripping of contaminated condensate; and
4. a closed screen room; and
5. spill tanks to accommodate temporary process upsets
and allow subsequent recycle.
The unique aspect of the Thunder Bay flowsheet is the
total recycle of bleachery effluent, as shown in Figure 2, to
the unbleached portion of the mill. Normally, the problem
with such a recycle procedure would be the build-up or
introduction of sodium chloride, which must be removed at
the same rate it is introduced. To remedy the situation, the
Erco-Envirotech SRP (Salt Control Process) System will be
used.
Salt Control Process
The SRP System is schematically represented in Figure 3.
Basically, the process uses white liquor from the liquor
preparation section of the mill and treats it in a two-stage
evaporization and crystallization procedure where sodium
chloride is purified for reuse and sodium carbonate
(NazCCb) and sodium sulfate (NaSO,») are recycled back to
recovery and recausticizing.
The white liquor fed into stage one is 2-3% by weight
sodium chloride (NaCl) and 10-11% by weight consists of
sodium hydroxide (NaOH) and sodium sulfide (Na2S). As
shown in Figure 4, a triple set of evaporators using
backward feed concentrate the liquor to approximately 26%
by weight sodium hydroxide (NaOH) plus sodium sulfide
(Na2S). All three evaporators are forced-circulation units
having external heat exchangers. The final liquor tempera-
ture is between 250 and 260°F(6).
In the evaporators, sodium carbonate (NaCOj) and the
double salt burkeite (NazCOs^NaiSCh) will crystallize out
of solution. A clarifier removes these crystals and a rotary
vacuum drum-filter further dewaters these crystals. Most of
these crystals are recycled to the liquor preparation or
recausticizing section and a small quantity is sent, as needed,
to the furnace for the purpose of reducing sulfates (SO4) to
sodium sulfide (Na2S). The filtrate from the rotary vacuum
drum filter is recycled back to the first evaporator.
The concentrated liquid leaving the clarifier in step 1
enters an evaporator-crystallizer in step 2 and is further
concentrated to approximately 36% by weight sodium
hydroxide (NaOH) and sodium sulfide (Na:S). At this point
most of the sodium chloride crystallizes out of solution.
The sodium chloride (NaCl) crystal slurry enters another
clarifier unit where a concentrated white liquor is removed.
This white liquor contains only trace quantities of sodium
chloride (NaCl), sodium carbonate (NasCOs) and sodium
sulfate (NazSOij, but has all the active alkali for pulping.
The stage 2 clarifier underflow is pumped to another rotary
vacuum drum filter for crystal dewatering. These crystals
are further purified via an agitated leach tank, where
residual amounts of sodium carbonate (Na2COa) and
burkeite (Na2CO3-2Na2SO*) are dissolved. The slurry is fed
to a horizontal vacuum belt-filter, where a countercurrent
washing process yields a better than 99% pure sodium
chloride (NaCl) cake. As will be mentioned later, the pure
sodium chloride (NaCl) cake can serve as a raw material for
the manufacture of chlorine dioxide (ClOa) in the bleaching
process or it may be used as a resource having an average
selling price of 0.64
-------
I. Salt Control Process:
2. counter current washing;
3. high substitution of chlorine dioxide (CIO:) for
chlorine in the first stage of the bleachery;
4. steam stripping of condensate; and
5. closed screen room and spill tanks that accommodate
process upsets; and
6. recycle of all bleachery effluent within the mill.
The total savings from operating costs which are in excess
of $5,000,000 (3,785,000 Rubles) are approximately one-
half the capital costs. Additionally, these statistics exclude
such factors as the value of salt (NaCl) recovered or the
potential value of heat that could be recovered from the
clean cooling water make-up. The value of the salt (NaCl)
for a 900 TPD (818 metric tons/day) plant would be
$224,000 per year (169,344 Rubles/year). The value of heat
recovery would vary depending on the climate, but would
be of greatest value in colder climates like those characteris-
tically found in many parts of Russia, where such thermally
enriched waters can be used for building heat. Appendix 1
contains the detailed analyses for the cost savings statistics
as contained in Figure 5.
Recent statistics for the Thunder Bay installation show
that the 250,000 ton per year (227,000 metric tons/year)
facility (Figure 6) will save approximately $4,000,000
(3,024,000 Rubles) annually(g). This saving originates from
modifications that improve its performance over a conven-
tional mill in the following areas:
I. Reduction of fresh water usage from 25,000 (95 cubic
meters/1000 kg) to 4,000 gallons per ton (64 cubic
meters /1000 kg) of pulp,
2. net energy savings of 5,000 Ibs. (2500 kg) of steam per
ton (1000 kg) of pulp, and
3. savings from reduced consumption of raw chemicals.
Since the differential cost of this closed-cycle and that of a
conventional mill is $8,000,000 (6,048,000 Rubles), the
payback or break even period is approximately two years.
Whereas conventional primary, secondary and tertiary
wastewater treatment facilities do not normally bring in a
return of economic benefit to the plant, the closed-cycle mill
with the SRP System, which is less costly than these
external waste treatment systems, has the advantage of
paying for itself within a remarkably short time period.
According to the Environmental Protection Agency
(EPA>9), the 1975 U.S. production capacity for all kinds of
pulp was 96,000 metric tons per day. The largest single pulp
process used is the kraft process, which produced 72,379
metric tons per day or 75.4% of the U.S. pulp supply in
1975. The EPA reports that kraft pulp mills will need to
spend $895,000,000 (677 million Rubles) to meet best
practical technology (BPT) and $732,000,000 (553 million
Rubles) for best available technology (BAT) effluent
guidelines as required by the EPA
-------
TOC Analyzer
Another innovation that, can be used for improving
municipal treatment efficiency is the total organic carbon
(TOC) analyzer. The importance of this instrument has
increased in the United States since recognition of the link
between trace organics and cancer in humans. Accordingly,
sewage treatment facilities are starting to place more
emphasis on reducing organic and trace organic effluent
streams loadings.
Whereas BODs has been and should remain a useful
indicator of water quality, the TOC measurement gives a
more detailed and rapid assessment of organic loadings that
can be used to modify and optimize treatment efficiency.
While BODs measurements take five days to complete, TOC
data is ready in a matter of minutes. Measurement of total
organic carbon at various points in a treatment plant can
provide timely and valuable operating information. This is
especially true when operating activated sludge processes.
Optimization of Sludge Treatment
The TOC analyzer is an effective test for controlling
activated sludge processes. The TOC can be used to
implement two popularly used design approaches for
activated sludge systems. The first uses a food to
microorganism (F/M) ratio and relies on the observation
that the amount of biodegradable organics applied to
biological systems affect the microorganism metabolic
rate. In their
technique, SRT is the inverse of the biological growth rate.
The SRT is espoused as a comprehensive basis for
biological design because all process variables can be related
to it. The SRT process is controlled by sludge wasting.
While opinions may vary as to the efficiency of using
either or both the F/M ratio or the SRT process control
strategy, TOC measurements apply to both process control
strategies.
TOC measurement might be taken in the activated sludge
process at various stages (see Figure 12). For example, using
the TOC values from raw sewage and comparing this to
TOC values after primary treatment can be used to evaluate
the effectiveness of the primary settling process.
The collecting of samples at either of the above two
points poses problems in regard to representative or truly
random sampling. To alleviate these difficulties, laboratory
models use blenders and homogenizers. For treatment
plants using on-line measurements, commercial grade
grinding pumps homogenize the sample particles before
analysis. In either case, good TOC analyzers are specifically
designed to handle such samples.
The mechanisms for TOC feedforward and feedback
control strategies would be implemented after making
various changes depending on the design characteristics
being followed.
For example, F/M ratio control can be effected by
measuring TOC for primary effluent, TOCpRi, and for
return activated sludge, TOCRAs. The F/M ratio can then
be calculated as follows:
F_
M
Primary Flow (Vol/Time x
TOX PR1 (Wt/Vol)
RAS FLOW (Vol/Time x
TOCRAS (Wt/Vol)
= Wt. of Primary Organics
Wt. of RAS Organics
Adjustment of RAS flow can be applied to maintain a
constant F/ M ratio. Sludge retention time can be controlled
by regulating the sludge inventory of the plant since,
SRT =
Biological Mass in System
Biological Mass wasted/time
TOC measurement of mixed liquor leaving the aerator,
TOC MO and TOC RAS can be used in combination with plant
volumetric data to calculate the organic mass in the system.
This data can then be utilized to adjust the plant wasting
rate.
Alternately, TOCpRi - TOCsEc (TOC of secondary or
final effluent) can be used to calculate the quantity of new
sludge made. This data can be used to adjust the plant
wasting rate and thus utilize SRT control. This technique
assumes that (k) is constant in the following relationship:
New Sludge = k (TOCpRi - TOC SEC)
Finally, TOCsnccan be employed as a final indication of
plant effectiveness. While the quality of effluent water from
a waste treatment plant is usually evaluated by the BODs,
TOC values are an equally useful monitoring tool. If the
effluent TOC values are maintained as low as are
economically feasible, the BODs values will also be as low
as are economically feasible.
The Hillsboro Story
Although many sewage treatment plants use TOC
analyzers to monitor and aid in optimizing their treatment
efficiency, one case stands out above the rest as an
illustrative testimony for the TOC analyzer. This example
involves the Hillsboro, Oregon Waste Treatment Facility
that was put on line in March 197 luj). Due to high and
varying organic loadings from the local food industry, the
Hillsboro plant was operating below the effluent standards
set forth by Oregon's Department of Environmental Quality
(see Figure 13). At times the wastes from local industries
comprised 75% of the plant's organic loading. Organic
loadings have and will vary up to 50%.
In July of 1973, a new strategy was initiated which relied
upon fast measurement and control of key plant variables.
The following measurements routinely measure and
controlled for were the following:
1. F/M ratio,
2. respiration rate of aeration tank effluent,
3. 5-minute settling of aeration tank effluent, and
4. dissolved oxygen in aeration tank.
The adjusted parameters to improve performance efficiency
were:
1. returned sludge flow,
44
-------
2. waste sludge flow,
3. sludge conditioning time, and
4. aerator air flow.
The results of this new strategy have proven extremely
successful. Figure 14 shows that the Oregon plant had
BODs average from 20-90mg/ liter prior to adoption of the
new strategy. Following institution of the new strategy, the
plant was able to consistently meet the Oregon effluent
standards as the BODs dropped to between 10 and 15
mg/ liter on a monthly average (see Figure 14).
This is one working example of the TOC analyzer and its
useful application for controlling efficiency in municipal
waste treatment processing plants. Many other applications
for the TOC analyzer are employed as it is widely used by
American industry, which has traditionally accounted for
the largest sector of the TOC analyzer production output.
Whether the TOC analyzer be used as a laboratory or
continuous in-line device, the results and application
potentials remain the same; only the means of sampling
changes.
Summary
In conclusion, I have discussed three treatment modifica-
tions that have the advantages of improving treatment
efficiency and reducing costs.
The closed-cycle mill, which can be a modification of
existing kraft pulp plants, totally eliminates contaminated
effluents while saving enough through operating expenses to
recover its initial capital expenditures in a two year period.
After the two years of operation, the closed-cycle mill
continues to generate these savings as revenue - a prospect
that external waste treatment facilities cannot offer.
The high-solids filter has application for both municipal
and industrial sludge processing. This new development is a
modification in sludge processing that promises to reduce
energy consumption and increase energy recovery in sludge
thermal systems.
The TOC analyzer also has applications for both
industrial and municipal treatment processes. Although no
examples of industrial uses were given, the product is most
widely purchased for industrial applications. The TOC
analyzer has the advantage of being a reliable and quick
measurement tool that has found application in improving
waste treatment efficiency through a network of feedfor-
ward and feedback control strategies in addition to its
general application as a monitoring device.
Bibliography
1. Papermakers Face More Pollution Woes, Chemical
Week, p 35, May 5, 1976.
2. TAPP1 Medalist, Tappi, 58:12, p 3, December 1975.
3. Stevens, F., First Pollution Free Bleached Kraft Mill
Gets Green Light, Pulp and Paper Canada, 76:10, p 27,
October 1975.
4. Rapping With Rapson, Pulp and Paper, October 1973,
5. Emmerson, D. W., The Long Hard Road To The
Effluent-Free Mill, Chemistry In Canada, p 11, April
1976.
6. Cornell, C.F., Salt Recovery Process Allows Reuse of
Pulp-Bleaching Effluent, Chemical Engineering, p 136,
November 10, 1975.
7. Rowlandson, G., Economic Advantages of Closed-Cycle
Mill, Erco-Envirotech Study, December 15, 1975.
8. "Zero Pollution From A Paper Pulp Process," Business
Week, p 48, December 22, 1975.
9. Development Document for Interim Final and Proposed
Effluent Limitations Guidelines and Proposed New
Source Performance Standards for the Bleached Kraft,
Groundwood, Sulfite, Soda, Deink and Non-Integrated
Paper Mills, (Vol. I) Segment of the Pulp, Paper and
Paperboard Point Source Category, United States
Environmental Protection Agency, p 31, January 1976
(EPA 440/ 1-76/047-a).
10. Economic Analysis of Proposed and Interim Final
Effluent Guidelines for the Bleached Kraft, Groundwood,
Sulfite, Soda, Deinked and Non-Integrated Paper
Sectors of the Pulp and Paper Industry, United States
Environmental Protection Agency, p 12, January 1976,
(EPA-230/2-76-045).
11. State of the Art Review on Sludge Incineration Practice,
U.S. Department of Interior 17070 Div. 04/70.
12. Stensel, H. D., Shell, G. L., Two Methods of Biological
Treatment Design, JWPCF \(s(2), p 271, February 1974.
13. Joyce, R. J., Ortman, C., and Zickefoose, C.,
Optimization of An Activated Sludge Plant Using TOC,
Dissolved Oxygen, Respiration Rate and Sludge Settling
Volume Data, Presentation before WWEMA Industrial
Water and Pollution Conference, Detroit, Michigan,
April 1, 1974.
WHITE LIQUOR
DIGESTER
COOKING
BROWN STOCK
HASHING
WOOD
BROWN PULP,
BLACK LIQUOR
EVAPORATOR
PURGE ATMOSPHERE)
FURNACE
PURGE .
DREGS «-
GRITS
Figure 1
LIQUOR PREPARATIOt!
45
-------
Purge.
(Dfffli)
(Gths)
Purgt
CO.& H,0
M,0
N_
\_
L'rjuor
Preparation
*»-
A
Bl«c» Liquor
r
Condcnijlt
While Liqu
Cooking *
1 " Stripp
/
H,0
Pulping
Chemical J
NaCH
Nt.S
.'
Bit ching
Ch -nical t
M*nu'aetur«
CI6,
Cl, y
NaOH ^
I Bl»ching "*" H,0 *
-». Bleached .
Pulp '
Figure 2
EVAPORATOR"
CBYUM.LUEI
>ITI ,_] STAGE 1
MOT U.AIII FUR
lAORjAjSjNAjCOj
(UCl JA2SO(,
PHA
IE
SEPARATION
UNREG!
CHEMIC
A
i
Figure 3
BLEACH PLANT
SHITE
EVAPOHATOR:-
CRVSTALLIIEM
STAOE 1!
PHASE
SEPARATION
fRATED
LtdUQR
NE RATED PuiriK
KLS TO BLACK LiauoR
6o.c»
®\
NAtL
PURIFICATION
PHASE
SEPARATION
RECYCLE I
2 * RECOVERED
SODIUM
'RATED
ouoa
iESIEH
Estimated Annual Operating Cost Savings Closed-Cycle Mill Salt
Recovery Process
(Calculated l<> Nearest Tliousand)
1. Heat Savings
A. Decreased Steam Consumption
B. Additional Steam Production
from Reclaimed Organics
2. Fiber Savings
3. Yield Increase
4. Chemical Savings
5. Water Savings
6. Savings in Effluent Treatment Cost
Dollars
$ 839,000
$ 271,000
$ 776,000
$ 636,000
$1,189,000
$ 68,000
$1,584,000
Rubles
634,284
204.876
586,656
480,816
898,884
51,408
1,197,504
$5,363,000 4,054,428
Basis: 900 TPA (409,0001 day) Coniferous Pulp - KAPPA No. 32
Bleached Pulp Brightness - 90 (G.'E.)
Figure 5
Capital and Operating Costs
Mill Capacity
White Liquor Use
Active Alkali
Sodium Chloride Recovered
Capital Cost
Utilities
Steam
Power
Water
Raw Materials:
700 A.D. tons per day
(636,000 kg per day)
130 ft' per ton pulp
793 Ibs Na20 per ton pulp
(324 kg per 1,000 kg pulp)
120 to 200 Ibs NaCl per ton pulp
(54.5 to 90.9 1,000 kg)
$8,000,000
(6,048,000 Rubles)
96,000 Ibs per hour (43,636 kg/ per hour)
875 H.P.
6,000 G.P.M (surface condenser)
None
Figure 6
PC. . process
SC . s'eam co^dcnsate
HE... fient enchangc
Figure 4
46
-------
DESIGN CONDITIONS
GAS EXIT TEMP.-
EXCESS AIR
FBF
150(fF
202
HHF*
800* F
FLUIDIZED BED
FURNACE
WITHOUT HEAT
RECOVERY
FBF
FLUIDIZED BED
FURNACE
WITH HEAT
RECOVERY AND
PREHEAT AIR TO
1000' F
X TOTAL SOLIDS IN SLUDGE
@ 75% VOL AND 9500 BTU/LB. VOLATILE
* Multiple Hearth Furnace - 22' dia.; 6 hearths
Source: (11) and Dnvirotecli data
Effect of moisture content on the cost of sludge combustion
systems with and without heat recovery
Figure 7
Performance summary
Hatfield, Pennsylvania
Filter
Type
Drum
Hi-solids
Production
(Kg DS/hr-sq m)
6.8
9.1
Filter Cake
DS-% Kg H20/Kg DS
20.2 3.95
32.8 2.05
Figure 8
Incineration Fuel Comparison
Dry sludge solids
Per year; metric tons
Cake; % ds
Gross Heat required;
Billions BTU per year
Fuel cost 2.0 U.S.
Dollars per million BTU:
U.S. dollars per year
Rubles per year
Vacuum
niter
5000
20
108
216,000
Hi-solids
niter
5000
27
73.0
146,000
163,296 110,396
32% FUEL SAVINGS
Figure 9
Sewage treatment plant locations with sludge energy recovery
systems
(United Stales)
1. Central Contra Costa Sanitation District, California
2. Jacksonville, Florida
3. Granite City, Illinois
4, Western Branch Facility, Prince Georges County, Maryland
5. Atlantic County, New Jersey
6. Trinity River Authority, Texas
7. Hatfield. Pennsylvania
8. Chesapeake-Elizabeth-Hampton Roads Sanitation District
Virginia,
9. Hopewell, Virginia
10. Green Bay, Wisconsin
Figure 10
Hi-solids filter capability
Sludge
type
Raw Primary
Waste activated
Raw primary plus
waste activated
(50:50 by weight)
Raw primary plus
humus (50:50 by
weight)
Heat treated raw
primary plus waste
activated
PCT (lime)
Production
(Kg DS/hr-sq m)
25-50
7-10
10-15
15-20
15-25
10-20
Filter cake
DS-% KG H20/
KgDS
30-40 1.5-2.3
18-20 4.0-4.6
24-28 2.6-3.2
25-27 2.7-3.0
45-55 0.82-1.2
30-35 1.9-2.3
Figure 11
TO^IAM ^Ml ^HL TQ^IIC
1 1 1 1
I i i i
I
imiuutr
NIHMV
IfTTllM
ID
|
1 .
. hut
|
1 .
SECONDAftV
SETTLIM
(uii T
*ll
TOCM,
|
SrrflOH*Bt *
FINAL
EFFLUENT
WAS = waste sludge flow
RAS = return sludge flow
TOC RAW = TOC of raw influent
TOC PRI = TOC of primary effluent
TOC ML = TOC of mixed liquor leaving aerator
TOC SEC = TOC of secondary of final effluent
TOC RAS = TOC of return activated sludge
Figure 12
47
-------
100-
— 80-
o
S 60-
40
20-
o
•a
Hillsboro plant performance
Estimated annual operating cost savings closed-cycle mill salt
recovery process
(Calculated to Nearest Thousand)
I. Heat Savings
A. Decreased Steam Consumption
B. Additional Steam Production from
Reclaimed Organics
2. Fiber Savings
3. Yield Increase
4. Chemical Savings
5. Water Savings
6. Savings in Effluent Treatment Cost
S 839,000
1972
1973
$ 271,000
$ 776,000
$ 636,000
$1,189,000
$ 68,000
SI.584,000
$5,363,000
500
400
I 300
O 200
| 100-
O
final effluent
new operating
strategy
Figure 13
— 250
£ 200
fea«
§ 150-
n
s 1CO
2 50
§
E 0-
1972
primary
effluent
."•XA
1973
» '
1972
1973
150
f 125
a
a.
w 100
i1 75
> 50
| 25
0-
Figure 14
new operating
strategy
i i primary
»' */' ! effluent
t
i
i
i
i
i
final effluent
1972
1973
C
6.5%
0
0
0
0
6.5%(130#)
E
0
4.50%
0.20%
0.50%
0.05%
5.25% (105#)
D
0
0
1.0%
0
0.5%
1.5%(30#)
BASIS: 900 TPD Coniferous Pulp - KAPPA No. 32
Bleached Pulp Brightness - 90 (G.E.)
CONIFEROUS PULP—900 T/D - 345 D/YR
—310,500 T/YR
(1) Bleacher} Sequences C-E 1-D i-E z-D 1
Stage
1
2
3
4
5
Chemical Balance:
1# Chlorine Requires 1.I3# NaOH
1# Chlorine Dioxide requires 0.60# of NaOH
.'.Checking Cl- and Na+
Chloride (Caustic)
1st Stage C = 6.5% = 130#/T = 130 x 1.13 = 146.9
3rd Stage Di = 1.0% = 20#/T = 20 x 0.6 = 12.0
5th Stage D 2 = 0.5% = 10#/T = 10 x 0.6 = 6.0
Total caustic required (for "balance") = 164.9#/T
NOTE: All units are U.S., i.e. tons are short tons (2000 Ibs).
Sodium
2nd Stage (E i) = 4.50% = 90.0# (1st extraction)
3rd Stage = 0.20% = 4.0# (buffer-pH control)
4th Stage (E 2) = 0.50% - 10.0# (2nd extraction)
5th Stage = 0.05% = 1.0# (pH control)
Caustic added in bleach plant - 105#
.'.additional caustic to "balance": 164.9 - 105 = 59.9#/T. This
amount must be added to the mixed nitrate for link-up of Cl- and
Na+ (as NaCl) and need for pH adjustment.
Sodium Chloride Load:
Stage
1
3
5
Chlorine
130.0
0
0
130.0
Chlorine
Dioxide
0
10.5
5.2
15.7
Appendix 1(7)
Total chloride = 145.7
.'.Total sodium chloride load (as NaCl)
= 145.7 x 58.5 = 240#/T
35.5
48
-------
Total dioxide needed - 1.5 x 900 = 13.5 T/D
100
(2) Bleachery Sequence D/C-Ei-Di-Ei-D2
(Based on 70% substitution with chlorine dioxide in the first stage)
—30% as C12 = 1.95% - 39.0#/T
Chloride Load - 39.0#/T
—70% of total Cl2 demand as dioxide
C102 as CI2 - 0.7 x 6.5 - 4.55%
as C102 = 4.55= 1.73% = 34.6#/T
2.63
Chloride load = 34.6 x 35.5 = 17.9#/T
67.5
Total chloride (C1-) load = 39.0 + 17.9 + 105 (Di)
+ 5.2 (D2) = 72.6
Sodium chloride (NaCl) load
= 72.6 x 58.5 - I20#/T
35.5
Balancing Cl- and Na + (actual NaOH = 81#/T)
Caustic Requirement:
Stage
1
2
3
4
5
Chlorine
(as NaOH)
39.0 x 1.13 = 44.10 —
44.10
Dioxide
Caustic
—
64
6
10
3
83#
(as NaOH)
34.6
20
10
x 0.6
xO.6
xO.6
= 20.76
= 12.00
= 6.00
38.76
Caustic requirement = 44.10 + 38.76 = 82.86#/T
.'.Cl- and Na+ are balanced (NaCl)
Total dioxide needed
= [1.73% + 1.0% + 0.5%] x 900
100
+3.23_x 900 = 29.07 T/D
100
(3) Basic Data
(a) Costs
Chlorine
Caustic Soda
Chlorine Dioxide
Wood
Unbleached Fiber
Fiber in process
Pulp "semibleached"
Bleached Pulp
Steam
Water
Effluent and
Emmissions
6.5t/lb.
7.0c/lb.
24.0c/lb (R3)
$40/cord (2.25 cords/T)
$ ISO/Ton
$195/Ton
$250/Ton
$360/Ton
S2.25/M Ibs. (Total Cost)
2c/M Gals (Incl power,
labor & treatment)
$7/Ton (OECD, Ekono)
(For primary & secondary)
tions of bleach solutions, etc., is approximately
130,000#/Hr. The steam required to concentrate the mill
white liquor in the SRP in order to remove the salt load is
approximately 85,000#/HR (quadruple effect).
.'. Differential 130,000 - 85,000 = 45,000#/Hr
Savings = 45,000 x 2.25 x 24 x 345 = $839,000/yr.
1,000
(B) Steam Production (Higher Organlcs S4T/D)
Bleachery shrinkage 6% overall—recovery boiler (steam)
efficiency 65% [decreased inorganics—sodium carbonate,
sodium sulfate (as well as make-up salt cake) considering
salt input] recovered organic solids heating value 5,000 +
B.T.U./lb.
Savings = 0.06 x 310.500 x 2,000 x 5,000 x 2.25 x .65
1,000,000
= $271,000/yr.
(C) Fiber Loss Decreased ("average" pulp price $250/Ton as
fiber not completely processed—bleached nor dried)
Elimination of fiber loss from dryer, bleachery, screening
and washing departments means an "average" fiber gain of
1.00 x 900 = 9.0 T/D. This pick-up increases pulp
100 .
production—decreases chemical usage—or mill may
choose depending on boiler capacity, etc., to decrease
amount of wood cooked (lower overall and organic load
to the recovery boiler).
Savings = 9.0 x 250 x 345 = $776,000/yr ("Increase Income")
(D) Yield
Due to the high substitution (70%) with chlorine dioxide
in the first stage (since it will be operated "HOT") there is
a yield improvement of at least one (1) percentage point
when compared to a hot chlorination sequence. This
enhancement due mainly to the protection of the hemi-
celluloses will coincidentally decrease other associated
processing charges so that an overall cost advantage of at
least S2.05/T may be realized.
Savings = 2.05 x 310,500 = $636,000/yr.
(E) Bleaching Costs
** (i) For the sequence C-Ei-Di-Ez-D2 the chemical
consumptions are:
Chlorine =
Caustic Soda =
Chlorine Dioxide =
130#/Tat6.5c/lb = $ 8.45
163#/Tat7.0c/lb = $11.55
30#/Tat 24t/lb = $ 7.20
Total Chemical: $27.20
(b) Operating days per year 345
(c) Bleachery Chemical shrinkage 6%
(Minimum of one (1) percentage point yield gain due to high
substitution with C1O2 for Cl2 in the 1st stage.)
(d) Bleachery fiber loss l%(average-withconventional"C"and
"El" filtrates sewered)
(4) Estimated Savings ** Per year (D/C-Ei-Di-Ei-DJ)
(A) Steam Consumption
The decreased amount of steam due to: lower water volume
used, countercurrent reuse of filtrates, modified concentra-
(F)
(ii) For the sequence D/C-Ei-Dt-E2-D2 the chemical
consumptions are:
Chlorine = 39ft/T at 6.5c/lb =
Caustic Soda = 83#/T at 7.0/lb =
Chlorine Dioxide = 62.6#/T at 24c/lb =
Total Chemicals =
Differential = 27.20 - 23.37 = S3.83/T
Savings = 310,500 x 3.83 = $l,189,000/yr,
Effluent and Emissions - Treatment
(a) Based on independent cost data, the treatment cost
(primary and secondary only) amounts to approxi-
mately $7/Ton (Including power, oil, gas, labor,
steam, air, chemicals, lime, phosphate, ammonia.
49
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sulfuric, special reagents).
(b) Selective reuse is made of separated and steam - (high
percentage) stripped contaminated condensates
within the mill. Cost incurred amounts to $ 1.90/ Ton.
Annual cost = 1.90 x 310,500 = $590,000/yr
(c) Annual savings is the differential for these treatments;
namely, 310,500 ($7- $1.90) = $1,584,000
(G) Water Consumption
"Average" water quantity - 35,000 gpt (total)
"New" water quantity = 4,000 gpt (bleachery countercur-
rent use, etc.,)
= 20,000 gpt * (surface condensers,
utilities, cooling)
'Thermally enriched water which can be discharged
directly through the sewers or to the river or lake without
effluent treatment. It may be reused in some locations
(northern climates) or for associated mills. At millsites
where temperature levels are of concern, cooling towers
(as are now in use) are installed.
Overall decrease in water requirements = 35,000 -
24,000= 11,000 gpt
Savings = 11,000 x 2_x_310,500 = $68,000
1,000 100
Total Annual Savings = $5,363,000/yr.
**(i) The estimated amounts of the major savings
(accounting for the "extra" steam consumed for the
evaporation-crystallization phases of the SRP flowsheet)
are tabulated herein based on various cost assumptions
(listed for reference) which are considered quite conserva-
tive as compared to actual forecast or even present values.
(ii) If the conventional sequence C-E1-D1-E2-D2 is
practiced and there is no reclamation of bleachery filtrate
back through the unbleached pulp washing, there is no
need "within" the mill to add extra balancing caustic (it
would then dictate, however, installation and operation of
external effluent treatment and use of additional lime to
adjust effluent pH). Then the bleachery chemical cost
would be $23.00/Ton.
NOTE: You may wish to consider partial recovery of effluent in
some instances with evaporation of commensurate volume of white
liquor to control the salt load.
(iii) No credit has been taken for the salt (NaCl) removed
and purified in the SRP flowsheet. Average salt (basic
price) cost is approximately 0.64t/lb. Said sodium
chloride may be reused for generation of bleachery
agents—for roads or otherwise disposed of. If consumed,
the savings = 120 x 310,500 x 0.6 = $224,000
100
(iv) No credit has been taken for the ("low level") large heat
quantity available from the thermally enriched water
which may be of considerable economic use by associated
facilities (surface condenser waters, etc.).
The term SRP as used in this comparison is a trademark of Erco
Envirotech Ltd.
Biological Waste Water
Treatment in the Presence of
Steroid Compounds
S.V. Yakplev
T.A. Karjukhina
The principle possibility of stimulating the process of
biological oxidation in aerobic conditions by means of
addition of steroid compounds to the water to be treated
was investigated.
As a basis for carrying out investigations, a known fact
was taken which established experimentally that steroid
compounds added to the culture medium have various
effects on pure cultures of microorganisms.
Effects of three major types have been defined: steroids
are growth factors; they would stimulate or inhibit
metabolic processes in the cell; and would protect
microorganisms against the action of toxic substances.
It is supposed, that some of the steroids would be toxic to
the cell, and therefore, the transformation of steroids inside
the cell, leading to formation of non-toxic substances, is a
sort of protection of the microorganism. The action of four
steroid hormonal preparations, produced on commercial
scale, was investigated.
These are: methyltestosterone (I), testosteronepropionate
(II), progesterone (III), pregnine (IV).
The first part of the investigations has been carried out
using synthetic waste water (SWW), which included such
components as peptone, buffer ammonium salts and
dipotassium hydrogen phosphate (KaHPCM).
The first part of the investigations consists of three sets of
experiments:
1. Oxidation in Warburg apparatus;
2. SWW treatment in mixing aeration tank models;
3. Aerobic mineralization of activated sludge (in models).
The conditions for carrying out the experiments and the
results, which have been obtained for the sets of experi-
ments, are briefly described below.
1. Oxidation in Warburg Apparatus.
Conditions of experiments:
—temperature of mixture - 25° C,
—concentration of activated sludge, adapted to SWW and
to the appropriate steroid, is about 1 g/1,
—incubation time - 5 hours, Teachings taken every half an
hour.
The investigated substances are insoluble in water,
therefore they were added to SWW in the form of alcoholic
solution. The same amount of alcohol, but without any
steroid, was added to the control flask.
The results of the first sets, averaged from many tests are
shown in Table I.
50
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Table I. Oxygen demand for Sh incubation % tng/1
Steroid Steroid Concentration
1
11
III
IV
0
100
100
100
100
1
141
161
127
144
2
115
142
113
139
5
105
136
107
95
10
113
112
104
46
15
89
116
103
60
20
92
116
100
63
25
_
100
104
66
30
44
103
99
67
Note: Oxygen demand in the control flasks, taken as 100%, for
experiments with substance I was 137 mg/1 substance 11-249 mg/1,
substance 111 • 176 mg/l and substance IV - 158 mg/l.
Conclusions:
a) Addition of steroids has a marked effect on the
activated sludge oxygen demand in the process of
peptone oxidation.
b) The action of the four compounds is of similar
nature, while the degree of influence is different.
Maximum increase in oxygen demand was
observed at steroid concentration of 1 mg/l.
Further increase in steroid concentration resulted
in decrease of oxygen demand. Within the
concentrations investigated two substances, I and
IV, had an inhibitory effect, this being expected for
substances II and III at concentrations above 20
mg/l.
c) Results of this set of experiments have confirmed,
that it would be advisable to carry out investiga-
tions in aeration tank models with continuous
cultivating of microorganisms.
2. S\VW Treatment in Mixing Aeration
Tank Models.
Experiment conditions: capacity of aeration tank model -
10 1, settling tank - from 1.5 1 to 2.0 1. Time of each cycle -
not less than 20 days (to obtain stable results) and not more,
than 43 days. 5 cycles in total have been studied with
aeration duration 12, 9, 6, 3 and 2 hours.
Table 2 shows basic results, averaged from 5 to 10 tests.
Discussion of the results obtained: The fact that BODs of
SWW with the steroid added is higher, than BODs of the
control sample is of interest. Increase in BODs for the four
preparations is different. The average increase in BODs with
the addition of substance I is 8%, substance II - 15%,
substance III - 40% and substance IV - 68%. In three of the
five cycles with aeration duration of 12,9 and 6 hours tertiary
treatment took place in all models. BODs removal was
actually the same for all aeration tanks, variations in effluent
BODs value being relatively small. Differences in effluent
COD were observed, the COD of the water from the
experimental models being somewhat lower, than that from
the control models.
In 3 and 2 h cycles the treatment was incomplete.
According to average results effluent BODs was more, than
25 mg/l, and for individual samples up to 150 mg/l.
Supposedly, there was no time for pregnine (IV) to be
metabolized during such a short period of treatment, as
effluent BODs was higher than COD value.
Because of high sludge loadings, deficiency of dissolved
oxygen was felt in some cycles that would partly limit the
oxydation rates. The sludge of the first three cycles was
swelled and rich in various Protozoa. In two last cycles the
sludge index was very high. The sludge biocenasis of these
cycles was noticeably poorer than in the first three sets.
Estimates of the amount of sludge growth have shown that
under conditions of tertiary water treatment (in 12 and 9 h
cycles) the growth in experimental aeration tanks was higher
than in the control one, in 6 h cycle-approximately the same,
and in 3 and 2 cycles lower than in the control unit.
As a result of comparison of relative effluent BODs values
and oxidation rates, it is possible to state that the presence of
steroids makes the treatment of water more rapid and more
effective. The latter is fixed by lower values of effluent COD
in the experimental models (in the first three cycles); this
means that substances, which are difficult to oxidize, have
been implicated in the treatment processes.
Conclusions
a) The stimulating action of the steroids on the oxidation
Table 2. Performance of aeration link model with the steroid substance added to waste water it concentration of 1 mg/l
Aeration duration (h)
12 9
Nos Parameter Control
2
3
4
5
6
7
Influent BODs
(mg/l)
Effluent BODs
(mg/l)
Effluent COD
(mg/l)
Sludge dosage
(g/D
02
-------
processes have been observed in activated sludge during
synthetic waste water treatment, prepared on the basis of
peptone at steroid concentration of the treated water 1
mg/1.
b) Biological treatment of water will be more rapid and more
effective in the presence of steroids. Substances, almost
not available for activated sludge microorganisms under
normal conditions, will be implicated in the oxidation
processes.
c) The effect of the four substances studied was not specific;
that allowed to considerable extend the sphere of search
for most effective stimulators among the lots of steroid
compounds.
3. Aerobic Mineralization of Activated
Sludge.
Experiment conditions: capacity of mineralizer -51.
Steroid concentration in each model 0.2 mg/1. Experimet
duration - 20 to 26 days. Activated sludge, adapted to the
appropriate steroid (as from aeration tank models), was
investigated, as well unadapted sludge, which was taken from
the operating treatment plants of the city of Moscow.
Temperature is 20° C.
The degree of activated sludge mineralization was
estimated only as ash content.
Conclusions
a) Addition of steroids at concentration of 0.2 mg/1 will
stimulate processes of aerobic mineralization of sludge.
b) The effect of steroids will show in two ways and will result
in reaching the required degree of mineralization for a
shorter period of time or will ensure a higher degree of
mineralization for the same time of treatment.
c) The effect of the steroids is not specific. Only the degree of
influence of the steroid will be different.
The second part of the investigations has been carried out
on municipal sewage, fed to the operating treatment plant of
the city of Moscow. The second part consists of some sets of
experiments for BODs measurement by the dilution method.
The following problems have been investigated:
1) Effect of steroids on BODs value of the clarified water,
supplied to the biological treatment plant;
2) Effect of steroids on BODs value of the effluent water
from the aeration tanks of the plant.
3) Action of steroids, when an inhibitor of the biological
treatment process, such as cuprous sulphate, was added to
the waste water.
Some of the results obtained are described below.
1) Effect of steroids on BODs of clarified
water
Experiment conditions: steroid in the form of alcoholic
solution was added to the diluting water, used for BOD
measurement by the dilution method. The same quantity of
the alcoholic solution was added to the control bottle, but
without any steroid.
Results obtained and conclusions: some hundred of
individual measurements have been carried out, both on
single waste Water samples and daily average ones. The
addition of steroid varied within 0.1 mg/1 and 2.0 mg/1.
Substances I, III and IV were investigated.
The addition of alcohol resulted in sharp rise of BODs
value. During the investigations BODs of the clarified water
varied within 70 mg/1 and 140 mg/1.
According to the quantity of alcohol added, BODs of the
control sample increased up to 202 mg/1 to 1780 mg/1. This
being so, it was found possible to show the effect of steroids
only after a great number of experiments. Table 3 shows, as
an example, the results obtained with progesterone (111).
Table 3
Concentration
of
substance
III(mg/l)
1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.1
1.3
1.5
1.7
1.9
BODs
initial
2
100
97
104
95
137
139
93
71
110
96
122
86
88
92
of waste water
with alcohol
3
202
308
429
528
712
745
997
872
1265
1405
1540
1170
1460
1780
(mg/l)
with alcohol
and HI
4
208
320
437
561
671
799
948
992
1225
1360
1350
1118
1288
1620
Similar results have been obtained with other substances.
Data in Table 3 show, that at progesterone concentrations
of 0.1 mg/1 to 0.8 mg/1, a small increase in oxygen demand
will occur, while at concentrations above 0.8 mg/1 there will
be a decrease in oxygen demand, as compared with the
control. Since in reality the addition of steroids in the form
of alcoholic solutions is not advisable, subsequent experi-
ments were carried out with the addition of investigated
substances in the form of dry powders.
This version of the experiment gave a pronounced
increase in BODs, and for progesterone, for example, the
value was quite impressive - from 69% to 279% (see Table
7).
Conclusions
a) Addition of steroids will have a marked effect on BODs
value of the waste water, measured by the dilution
method
b) The action of steroids will depend on the concentration
of steroids.
c) Direct addition of the steroids in the form of dry powder
will result in sharp stimulating of biological oxidation
processes, when the dilution method is used for BOD
measurement.
2) Effect of steroids on BOD s value of
effluent water from the aeration tanks of
the plant
Experiment conditions: steroids were added in the form
of alcoholic solutions and dry powders.
52
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The results, averaged from many tests, are shown in
Tables 4, 5 and 6.
Table 4
Table 7
Concentration
of substance
HI
(mg/l)
0.2
0.3
0.5
0.7
Effluent
initial with
9.6
8.1
6.5
6.5
BODs(mg/l)
alcohol with alcohol
and III
202 181
241 301
509 520
635 621
Table 5
Concentration of
substance
(mg/l)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Effluent BODs(mg/l)
initial
10.5
12.0
10.9
9.9
10.9
10.9
11.4
13.8
with powder
12.4
13.0
12.0
13.5
11.5
13.6
13.4
15.6
Table 6
Concentration of
substance
HI (mg/l)
0.5 - 2.0
Effluent
initial
3.5 - 16.4")
9x1)
BODs(mg/l)
with powder III
20.0-78.1*)
57**;
Note: x) Variation limits
xx) Average BODs value
Conclusions
a) Steroids will have a much more pronounced effect when
added in the form of powder.
b) The degree of influence of various steroids will be
noticeably different.
3) Effect of steroids with addition of
inhibitor to waste water
Experiment conditions: Progesterone (III) was added to
the clarified water in the form of dry powder. Cuprous
sulphate and cuprous sulfate with progesterone were added
to the parallel samples.
The results of the experiment are shown in Table 7.
BODs of clarified waste water
(mg/1)
with cuprous
Initial with powder sulfate-
108 208
110 186
76 288
62 215
76 208
65
75
34
87
53
with cuprous
sulfate and II
105
118
206
184
132
Conclusions
a) Steroids would be used as measure for protection of
activated sludge microorganisms against the action of
toxic substances.
Some of the results, obtained for the effect of steroids on
waste water treatment processes, briefly described here,
allow to make the following general conclusions:
1. The group of steroid hormones is biologically active
and will stimulate (or inhibit) treatment processes with
complex activated sludge biocenosis.
2. Steroid substances will stimulate processes at low
concentrations (up to 1 mg/l) and will inhibit them at high
concentrations. Stimulation will manifest itself in implicat-
ing in processes organic substances, both exogenous and
endogenous, which are difficult to oxidize and also in
accelerating the processes.
3. The effect of the steroid hormones studied was not
specific, while the degree of influence on the process was
different, which will allow to extend the sphere of search for
the most available, inexpensive and effective preparations.
4, In the processes of biological treatment of waste water
in aeration tanks, many organic substances remain in the
effluent water which would be oxidized if steroid stimulators
were added to the water.
5. Investigations of technological aspects of the effect of
steroid stimulators should be supplemented with biochemi-
cal investigations to elucidate the mechanism of action of
the substances.
S3
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A Comparison of
Conventional Activated
Sludge Process and Pure
Oxygen Activated Sludge
Process for a 75-MGD
Secondary Treatment Facility
Fred A. Harper,
General Manager
Orange County Sanitation Districts
California
This paper will discuss the process by which a pure oxygen
system was selected over a conventional air system for a 75
mgd facility to adequately and economically produce the
required effluent to meet State and Federal discharge
requirements. Included in this discussion is a description of
a pure oxygen wastewater treatment system for open tanks.
The Orange County Sanitation Districts provide for the
collection,treatment and disposal of domestic and industrial
liquid wastes for a service area of 320 square miles in
Southern California, on the West Coast of the United
States. The area has a population of 1 !/2 million people in 23
communities, including the internationally known tourist
attraction, Disneyland.
The agency operates two primary treatment facilities
which are presently being upgraded to comply with State
and Federal secondary treatment requirements. At Plant
No. 1, which is a 50 million gallons per day (mgd) facility,
an air activated sludge process plant is being constructed
and is scheduled to be operational in January, 1977. Plant
No. 2 is essentially a primary treatment facility, having a
present rated capacity of 130 mgd average flow with a
hydraulic maximum of 230 mgd.
Existing treatment comprises screening, pumping, grit
removal, primary sedimentation, and chlorination when
necessary. The effluent is pumped into the ocean five miles
offshore through an outfall diffusion system some 6000 feet
long. Sludge collected in the primary sedimentation basins
is anaerobically digested and then dewatered by centrifuga-
tion. The dewatered sludge is sold to a soil supplement
manufacturer.
A 1974 report investigated alternative wastewater
treatment and disposal projects for meeting the State and
Federal secondary treatment water quality goals and
included the analysis for 16 candidate systems and an
implementation schedule for improved treatment. This
program called for staged additions totaling 175 mgd of
secondary treatment at Plant No. 2. The first stage is a 75
mgd addition.
Four alternative systems were selected for final evaluation
from the 16 candidate systems:
A. Air activated sludge
B. Pure oxygen activated sludge
C. Roughing filter and activated sludge
D. Roughing filter and pure oxygen activated sludge
The following preliminary design criteria and physical
characteristics for the four alternatives for the 75 mgd
facility were developed for the purpose of determining the
necessary land requirements, energy demand, sludge
production and over-all costs.
Primary effluent BODs is assumed to be 225 mg/1,
suspended solids 142 mg/1 and grease 35 mg/1.
Aeration and oxidation facilities are sized based on a
sustained 10-hour daily flow of 1.2 times the average flow. A
sustained (peak month) primary effluent BODs of 1.25 times
the annual average BODs and a sustained daily primary
effluent BODs of 1.20 times the daily average BOD5are also
used as a basis for biological facility design. The over-all
removal is assumed to meet the Federal effluent standards as
follows:
BOD = 30 mg/1 -Monthly Average
SS = 30 mg/1 -Monthly Average
The wastewater flows entering the existing treatment
facilities have shown peaks of nearly two times the average
flow. These peaks lasted 8-10 hours and occurred when
influent flow was actually restricted because of surcharged
influent sewer lines. These conditions necessitate a peak
design flow two times the average flow.
The following is a general comparison of normal
operating and design parameters for pure oxygen and air
activated sludge processes:
Normal operating and design parameters based
on typical municipal sewage
Conventional Air
Activated Sludge Parameter Pure Oxygen
3-8 Oxygenation Detention Time,
Mrs. 1.0-2.5
2500-4000 Mixed Liquor Suspended Solids
(MLSS), MG/L 3000-7000
2000-3200 Mixed Liquor Volatile Suspend-
ed Solids (MLVSS), MG/L 2500-6000
0.5-2 Mixed Liquor D.O., MG/L 2-6
30-75 Organic Loading, #BOD/1000 CF 100-250
0.15-0.40 Food to Mass Ratio (F/M),
#BOD/#MLVSS 0.4-1.0
5000-15000 Return Sludge Concentration,
MG/L 10000-30000
50-125 Return Sludge Rate, %Q 30-50
75-150 Sludge Volume Index, SV1 50-100
1.1-1.5 Oxygen Requirements, #O2/
#BOD5 0.9-1.3
4-10 Oxygen Utilization, %O2 Sup-
plied 85-90
54
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Alternative A —Air activated sludge
physical characteristics
Item
Design Value
Secondary Lift Station
Aeration Basin Pumps
Horsepower installed 1,200
Horsepower utilized 350
Blowers
Aeration mode diffused air
Air requirements, cfm (average) 142,000
Horsepower installed 9,200
Horsepower utilized 5,600
Aeration Basins
Basin type rectangular
Number basins 13
Length, feet 355
Width, feet . 50
Sidewater depth, feet 15
Volume each, MG 2
Total volume, MG 26
Detention time, hours 8.3
Secondary clarifiers
Basin type rectangular
Number basins 22
Length, feet 150
Width, feet 40
Sidewater depth, feet 10
„ Surface area, each, ft2 6,000
Waste activated sludge flotation thickeners
Basin Type circular
Number basins 4
Diameter, feet 40
Roughing Filter Concept
Use of roughing filters in a two-stage biological treatment
scheme in conjunction with the activated sludge process has
been found to have the following advantages: Reduction in
applied aerator biochemical oxygen demand and consequent
reduction in aerator volume; biological buffer for the
activated sludge and subsequent prevention of aeration basin
upset due to toxic loads; reduction in sludge volume;
dampening of diurnal biochemical oxygen demand variation
on the aeration basin; and the imparting of dissolved oxygen
to the waste prior to aeration.
The literature contains numerous articles regarding plastic
media niters and the roughing niter concept. Manufacturers
have published data and extensive literature on the plastic
media roughing filter. These data predict biochemical
oxygen demand removals as high as 60 percent. Operating
experience at other locales, though limited, verifies the
roughing filter and air activated sludge process designs.
Effective five-day BOD removal is estimated to be 40
percent. If roughing filters are used in conjunction with
intermediate clarifiers, it is estimated that BOD removals
would be from 50 to 55 percent. Due to possible operational
problems with pure oxygen and filamentous organisms, the
roughing filter/pure oxygen activated alternative is analyzed
herein with intermediate clarifiers. The conventional
aeration alternative with roughing filters does not incorpo-
rate intermediate clarifiers.
The following illustrates the physical characteristics
utilizing roughing filters for both the air activated sludge and
pure oxygen activated sludge systems.
.Alternative B—Pure oxygen activated sludge
physical characteristics
Item Design Value
Secondary lift station
Aeration Basin Pumps
Horsepower installed 1,200
Horsepower utilized 350
Oxygen generation and storage
Oxygen absorption efficiency, percent 85-90
Installed oxygen supply, tons per day' 150
Oxygen demand, average daily
flow and average month
BODs, tons per day 91
Oxygen demand, average daily flow and
maximum month BODs, tons per day 110
Oxygen standby storage, tons 480
Horsepower installed 6,000
Horsepower utilized 2,000
Oxygenation tanks
Mode surface aeration
Basin type rectangular
Sidewater depth, feet 17
Total volume, MG 8.4
Detention time, hours 2.7
Horsepower installed 2,400
Horsepower utilized 2,000
Secondary clarifiers
Basin type rectangular
Number basins 22
Length, feet 150
Width, feet 40
Sidewater depth, feet 12-14
Surface area, each, ft2 6,000
Waste activated sludge flotation thickeners
Basin Type circular
Number basins 4
Diameter, feet 40_
Air Activated Sludge
The air activated sludge process is well known and
therefore will not be discussed in any detail. The costs
associated with the enumerated physical characteristics for
the air activated sludge facility include provisions for plug
flow, step feed, and complete mix. In addition, costs for
covering the aeration basins and scrubbing the foul air for
odor control are included.
Pure Oxygen Wastewater Treatment in
Closed Tanks
The use of pure oxygen in waste treatment is becoming
popular in the United States and many installations are
being constructed utilizing pure oxygen in closed tanks. The
process is commonly known as the Unox System, developed
by the Union Carbide Company.
This alternate system involves the production of oxygen
gas followed by oxygen dissolution in closed tanks generally
constructed with substantial freeboard. Oxygen dissolution
in the mixed liquor will be accomplished by the use of high
speed surface aerators in the closed tanks which achieve 85*
90 percent utilization of the oxygen. The ability of the
oxygen to be dissolved in the mixed liquor efficiently
reduces the oxygenation detention time considerably over a
conventional air activated sludge plant. This allows for
oxygenation tanks to be smaller in size or greater flows can
55
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be treated in the same volume of tanks. The pure oxygen
systems handle higher shock loads with less effect on the
mixed liquor basin and over-all plant. This occurs because
of the higher dissolved oxygen level which is maintained in
the tanks.
Alternative C—Roughing (liter and air activated
sludge physical characteristics
Item
Design Value
Secondary lift station
Roughing Filter Pumps
Horsepower installed 1,660
Horsepower utilized 1,000
Aeration Basin Pumps
Horsepower installed 1,200
Horsepower utilized 350
Roughing filters
Basin type circular
Number basins 2
Diameter, feet 145
Media depth, feet 20
Total volume, ft3 660,000
Blowers
Aeration mode diffused air
Air requirements, cfm (average) 80,000
Horsepower installed 5,200
Horsepower utilized 3,100
Aeration tanks
Basin type rectangular
Number basins 9
Length, feet 355
Width, feet 50
Sidewater depth, feet 15
Volume, each, MG 2
Total volume MG 18
Detention time, hours 5.8
Secondary clarifiers
Basin type rectangular
Number basins 22
Length, feet 150
Width, feet 40
Sidewater depth, feet 10
Surface area, each, ft3 6,000
Waste activated sludge flotation thickeners
Basin type circular
Number basins 4
Diameter, feet 40
Alternative D—Roughing filter and
pure oxygen activated sludge
physical characteristics
Item
Design Value
Secondary life station
Roughing Filter Pumps
Horsepower installed 1,660
Horsepower utilized 1,000
Aeration Basin Pumps
Horsepower installed 1,200
Horsepower utilized 350
Roughing filters
Basin type Circular
Number basins 2
Diameter, feet 145
Media depth, feet 20
Total volume, ft5 660,000
Roughing filter clarifiers
Basin type Rectangular
Number basins 16
Length, feet 150
Width, feet 40
Sidewater depth, feet 10
Surface area, each, ft2 6,000
Flow capacity, each, MOD 4.7
Oxygen generation and storage
Oxygen absorption efficiency, percent 85-90
Installed oxygen supply, tons per day 75
Oxygen demand, average daily flow and average
month BODj, tons per day 60
Oxygen demand, average daily flow and maximum
month BODs, tons per day 75
Oxygen standby storage, tons 240
Horsepower, installed 3,000
Horsepower, utilized 1.000
Alternative D—Roughing filter and
pure oxygen activated sludge
physical characteristics
(continued)
Item
Design Value
Oxygenation tanks
Mode Surface aeration
Basin type Rectangular
Sidewater depth, feet 17
Total volume, MG 4.3
Detention time, hours 1.4
Horsepower, installed 1,200
Horsepower, utilized 1,000
Secondary clarifiers
Basin type Rectangular
Number basins 22
Length, feet 150
Width, feet 40
Sidewater depth, feet 12-14
Surface area, each, ft2 6,000
Row capacity, each, MGD 3.4
Waste activated sludge flotation thickeners
Basin type Circular
Number basins 4
Diameter, feet 40
56
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Rotating Active Diffusers (RAD)
Each diffuser unit is a 7'/4 hp motor driven disc-shaped
diffusion device having a porous ceramic medium installed
in the anular space near the disc edge. As the RAD rotates
at a constant speed of 76-82 rpm in the mixed liquor
approximately 2 feet off the tank floor, the hydraulic sheer
reduces the gas bubbles being diffused by the porous
medium to 50 microns. Oxygen gas is transmitted through
the hollow drive shaft to the diffuser disc at the bottom,
then radially outward to the diffuser medium.
The typical process schematic shows the mixing action of
the diffusers which are rated at 1500#O2perday with a 90%
transfer to the mixed liquor. The tank mixing is achieved by
curved radial vanes on the top and bottom surfaces of the
diffusers. This action prevents the settling of the solids on
the tank bottom and provides adequate contact between the
mixed liquor and the diffused oxygen. The unique design of
the disc prevents any buildup of scum or grease on the
diffuser. A disc unit was removed after 7 months of
continuous operation and flow tests determined that no
plugging of the medium had occurred; there was only a
slight discoloration to the ceramic medium.
Pure oxygen wastewater treatment in open tanks
MAROX-Pure Oxygen System
Typical process schematic
This method, utilizing fine bubble diffusion, is capable of
reacting extremely fast to changes in demand as oxygen,
instantaneously sensed and indicated through the use of
dissolved oxygen probes and analyzers, is fed directly into
the diffuser and then directly into the mixed liquor. The
time elapsed from a change in oxygen demand in the tank
until a change in oxygen diffused by the dissolution
equipment is only a matter of seconds.
Operational Performance
Typical performance of the MAROX System applied to
municipal wastes is shown in the accompanying data.* The
municipal plant data was observed in full-scale pilot and
demonstration plants treating primarily domestic waste
during 1973 through 1975. ('Supplied by MAROX manu-
facturer.)
Detention Time, Hours
Biomass Loading, F/M, Ib BODs/
day/lb MLVSS
Organic Loading, Ib BODs/day/
HOOOcf
Mixed Liquor TSS, mg/1
Mixed Liquor VSS, mg/1
Recycle TSS RAS, mg/1
Water Temperature, °C
SV1
SRT, days
Clarifier Overflow, GPDPSF
Oxygen Usage, Ibs O: supp/lb
BODr
installations
ABC
1.1 2.0 1.9
D
2.3
1.02 0.71 0.56 0.59
244
4,743
3,886
133
3,730
3,060
141
4,859
4,217
12,221 11,39013,461
19.0 15.6 15.7
67.8
6.2
617
79
3.5
577
78
7.5
614
110
3,846
3,110
9,870
16.0
84
6.8
523
0.92 1.12 1.11 1.37
COUM.IUIIII
Schematic flow diagram cryogenic oxygen plant plant no. 2
Pure oxygen waste treatment in enclosed tanks
Pure Oxygen Wastewater Treatment in
Open Tanks
While most pure oxygen wastewater treatment installa-
tions currently being constructed utilize the closed tank
concept, another pure oxygen dissolution technique has
been evolving in the United States. It is a diffuser system
which generates very fine pure oxygen bubbles deep in the
mixed liquor, achieving 90% or greater oxygen transfer. The
process, known as the MAROX System, has been
developed by the FMC Company of Chicago, Illinois.
Covered tanks are not needed because of the efficient
transfer of oxygen in the mixed liquor and since there is
little surface agitation, no more than two feet of freeboard is
necessary.
MAROX System
The system is comprised of three major components :
1. A source of pure oxygen gas such as on-site cryogenic
oxygen supply system. The cryogenic process has been
in wide use for many years in the United States with
57
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thousands of existing industrial installations.
2. An oxygen dissolution system utilizing "Rotating
Active Diffusers" (RAD). Pure oxygen gas, in the
form of minute (50 micron) bubbles, is simultaneously
introduced deep into mixed liquor via RAD to
accomplish the mass oxygen transfer.
3. The system is controlled by an automatic dissolved
oxygen control system that accurately monitors and
controls the DO level. DO sensors are strategically
located in the mixed liquor to automatically regulate
oxygen flow to the diffusers. Mixed liquor is
constantly monitored and consistently maintained
within 1.0 mg/1 even through diurnal flow variations.
Upgrading Existing Air Diffuser Systems
The MAROX system is appropriate for upgrading
treatment facilities. Most existing aeration tanks can be
utilized by the addition of the diffuser equipment and a
source of oxygen gas. With minimal modifications to the
tanks, the capacity of the mixed liquor basins can be
increased several fold. A recent conversion at a treatment
facility in Colorado was completed in 6 weeks after
fabrication of the diffusers. The tank was upgraded from a 3
mgd air diffuser system to a 10 mgd MAROX system.
Thirteen RAD diffusers replaced 21 air diffusers in a
basin 210 feet long, 25 feet wide and 17 feet deep. Six RAD
diffusers were paired at 21-foot intervals at the inlet end of
the tank and monitored by a DO probe.
A second DO probe monitored the next four diffusers
which were mounted singly at 21-foot intervals in the center
of the basin.
A third probe monitored the remaining three diffusers
which were spaced uniformly at the outlet end of the tank.
Observations of the MAROX System
I. The system appears to be very simple to operate since
the oxygen feed rate to the diffuser system is
automated to the dissolved oxygen of the mixed
liquor.
2. Open tank construction with minimal freeboard
means savings in capital construction costs compared
to closed tank systems.
3. This system appears ideal in pre-aeration or pre-
treatment modes because each diffuser unit is
complete in itself, the spacing can be arranged to put
the greatest oxygen supply in areas of greatest
demand.
4. Existing aeration tanks can be upgraded with minimal
modifications in a short period of time.
5. The danger of explosive mixtures associated with pure
oxygen is minimized with the open tank system when
compared to the closed tank system.
Conclusions
Land Requirements
Like many waste treatment facilities in highly urbanized
areas, the agency's two treatment facilities, which comprise
approximately 100 acres each, are surrounded by residential
and industrial development. Because of this, it is important
to conserve all usable land space when expanding for
projected flows of 320 mgd in the year 2000, by employing
processes which can concentrate treatment in compact
facilities. In addition, we must provide odor abatement
facilities and incorporate these features into new construc-
tion whenever possible. The pure oxygen activated sludge
process utilizes the least amount of land.
Land requirements
Alternate Acres
A 13.1
B 10.7
C 13.9
D 11.5
Acres for
Structures
8.6
6.2
9.4
7.0
Secondary Sludge Generation
While it would appear that Alternate D generates the
least amount of sludge, there is no difference between
Alternates D and C, since the intermediate clarifier sludge
returns as primary sludge. The difference in secondary
sludge generation is not significant in the selection of the
alternate process.
SECONDARY SLUDGE GENERATION • 75 MGD
(pounds dry solids per day)
Secondary Sludge Generation
Alternate
A
B
C
D
Raw
(dry ft/day)
96,000
96,000
77,000
71,000
Digested
(dry #/day)
54,000
54,000
46,000
42,000
Digested*
(cubic yards/day)
142
142
121
110
'Assumes 20% solids with 90% solids capture from centrifuges
Energy Requirements
The projects analyzed require significant amounts of
energy to operate; much of the energy will be available on
site in the form of digester (methane gas from biological
treatment alternatives.
In the analysis, equipment (installed) horsepower is
estimated to exceed the horsepower utilized daily. This is
normal practice to insure sufficient power and equipment in
cases of equipment failure, maintenance work, and peak
load periods. Much of the utilized horsepower needs may be
met by use of digester gas for fueling engines, boilers,
incinerators, and other equipment for the biological
treatment alternatives. Not all equipment can be operated
on this fuel, and alternative power sources are needed to
ensure continuous, uninterrupted treatment and pumping
processes during normal circumstances, during emergen-
cies, and during natural disasters.
Energy requirements
Installed Utilized
Alternate Horsepower Horsepower
A 12,609 8,406
B 8,745 5,830
C 9,889 6,593
D 7,500 5,000
Horsepower
from
Digester Gas
2,923
2,423
1,943
2,796
Purchased
Horsepower
5,483
3,407
4,650
2,204
58
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Cost Analysis
A detailed cost analysis was performed on each of the
alternatives set forth herein. All costs are based on the same
construction cost index. Capital costs were developed from
the construction bid for the SO mgd activated sludge plant
currently under construction at Plant No. 1, from
manufacturers' quotes, and from other similar construction
jobs. The costs are estimated for a 75 mgd increment of
secondary treatment. They include a secondary pump
station, secondary treatment basins and clarifiers, roughing
filter and aeration basin covering for odor control, air or
oxygen supply facilities, sludge thickeners, yard work,
instrumentation, construction of an electrical service
entrance, and emergency power generation. Oxygen
generation facilities considered are cryogenic units, which
are more economical than other oxygen generating facilities
for quantities necessary herein.
Capital Cost
The total project capital cost was determined by
estimating the construction cost and then adding 43 percent
to cover contingencies, engineering, legal and administra-
tive costs, and interest during construction in conformance
with Federal guidelines.
Definitions:
BOD;—Biochemical oxygen demand - 5 day
SS—Suspended solids
F/M—Food to microorganisms
MG/L (mg/1)—Milligrams per liter
MLSS—Mixed liquor suspended solids
DO—Dissolved oxygen
MG—Million gallons
MGD (mgd)—Million gallons per day
ft2—Square feet
ft'—Cubic feet
Recommended Project
On the basis of the analysis presented, an evaluation of
alternatives has shown the pure oxygen activated sludge
process to be the most cost-effective for secondary treat-
ment.
Pure oxygen activated sludge offers an 18 percent savings
in project cost over the next cost-effective alternative. The
recommended alternative provides a degree of treatment
which will meet secondary treatment effluent quality limits
and will provide a cost savings for maintenance, operation,
and power over the conventional aeration secondary
treatment alternatives. Digester gas generated from the 75
million gallons per day treatment scheme will provide 5,830
horsepower. This recommended alternative also provides a
savings in land utilization over other alternatives.
The costs enumerated for the pure oxygen activated
sludge process are based on the closed tank system. For
construction competition purposes, relatively few addition-
al drawings are needed when both the closed tank and open
tank oxygen systems are under consideration. Only the
oxygenation tanks and associated electrical requirements
are different, while the oxygen gas production and the final
clarification systems are similar. For example, only 8
additional design sheets were required to determine
competitive costs recently for a proposed 20 mgd oxygen
treatment facility.
Monetary cost of alternatives
Alternate A
Air Activated
Sludge
Alternate B
Oxygen
Activated
Sludge
Alternate C
Roughing
Filter
and
Air Activated
Sludge
Alternate D
Roughing
Filter
and Oxygen
Activated
Sludge
Construction cost
Annual costs
Capital Recovery
Maintenance
Operation
Power
Chemicals
Interim Sludge
Disposal
Total annual cost
$/MG
$/MG
$/MG
$/MG
$/MG
$/MG
$/MG
$49,705,000
233
29
9
43
34
349
42,193,000
203
25
9
24
I
34
296
49,682,000
233
29
10
33
32
338
51,369,000
244
30
10
23
I
32
340
59
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Studies of Artificial Aeration
in the Lithuanian SSR.
Skirckiavichus A.L.
The Kaunas Polytechnic
Institute of Snechkus A.
All our efforts to treat wastewaters result in pure water
and rivers useful for beneficial purposes. Therefore further
treatment of effluents discharged from treatment plants may
be necessary. The effluent residual BOD presents considera-
ble loading for receiving waters, especially if they are not
large.
For example an average industrial town (on the
Lithuanian SSR scale) produces 50,000 cu.m. of waste-
waters having a BOD5 700 mg/1 or 35 T. BOD5 per day.
This BOD value is typical for wastewaters discharged by
our towns having food-processing industry. At 95 percent
treatment efficiency residual BODs will be 1,75 T. per day
and equal to load produced by 32,000 inhabitants.
Attention should be given to river pollution caused by
urban storm waters, drainage waters and effluents from
small agricultural areas, where chemicals and fertilizers are
widely used their load may be significant.
Biological treatment process also takes place in rivers
where all these pollutants go into with natural waters or
sewage and therefore it should be subjected to adequate
control.
During the dry summer period at high temperatures or
the winter period when ice cover inhibits natural surface
aeration temporary bad river conditions may bring to
naught all attempts and expenditures spent on wastewaters
treatment.
Artificial aeration is a method which prevents anaerobic
in the river and promotes destruction of contaminants. The
studies of artificial aeration have been conducted by the
Kaunas Polytechnic Institute and the Ministry of Municipal
Economy since 1971.
The investigations were conducted at the Nevejis River
polluted by insufficiently treated wastewaters of Panevejis-
town. For these purposes the experimental unit "NEVEJIS-
1" with mechanical C-16 type aerators developed by Vitols
O. and Resinsh was established at the river. The capacity of
an aerator is 2.2 kw. They were mounted from 4 to 9 in
number on metal frame which was fixed to supporting
pontoons. The river width in this region is 16-20 m, frame
length is 12 m. So the cross-section of the river was wholly
included into aeration zone.
The DO concentrations have been measured by electro-
chemical DO analyzer of UT-6803 type developed by Tartu
State University.
Special studies were conducted to select DO sampling
point at cross-sections, to determine reiteration of measure-
ments and to choose upstream and downstream cross-
sections for sampling.
Detailed measurements of DO were made in a number of
cross-sections at 5-10 m. distance downstream and
upstream from aerators when they were in operation and
out of operation. Variation-static method was used to work
up data and to estimate accuracy of measurements.
Downstream cross-section for sampling has been selected
in such a way that the DO concentration variation
coefficient didn't exceed the value of the coefficient for the
same cross-section under natural conditions (aerators are
turned off).
On the basis of analysis of static characteristics it has
been found that samples to be taken at the depth of 0.3 m;
reiteration of measurement should be more than 5; the
duration of five time measurement shouldn't exceed 4-5
min., downstream sampling point should be at 50m.
distance from an aerator. Upstream sampling point is
assumed to be at the same distance from an aerator
proceeding from convenience in sampling and calculations.
Measurements were made at cross-sections taking into
account the flow time between sampling points.
For comparison of results obtained from particular tests
under different conditions data have been converted to
standard conditions (river temperature is 20°C, 0 percent
DO saturations, pure water, 760 mm Hg pressure).
If rotor is submerged at 1,0 m depth and aerators are
mounted at 3m distance from each other average oxygena-
tion capacity at standard conditions is 1,14 kgOz/kwh. This
value is lower than those obtained according to data which
were reported by American (1,34 kgO2/kwh) and Ger-
man (1,37 kgO/kwh) investigators. It is evident that the
difference is negligible. It can be attributed to low flow rate,
as it has been found efficiency of artificial aeration increases
with increasing flow rate.
In practice this efficiency was obtained during tests on
turbine suction aerators having a capacity of 30kw.
DO saturation should be better under actual river
conditions in comparison with that in tanks under steady-
state conditions, due to a new dosage of water with high
saturation deficit of DO which reaches aerator all the time.
But oxygenation capacity of aerators of all types is lower
than that achieved under non-flow conditions. Similar
results have been reported by foreign scientists Huntre J.V.
Whipple W. et al. Probably it may be explained by the fact
that there is no standard method for evaluation of aerator's
efficiency. Of course reasons will be further investigated, but
at present while designing this fact should be considered and
aerator efficiency index which is about 0,33-0,4 should be
introduced into coefficient..
Studies of barbotage aeration also were conducted at the
experimental unit. Aerators- plastic corrugate drainage
pipes with a diameter of 50mm and a length of 2,20m- were
put on branch pipes welded to a steel pipeline which was
laid across the river. 1080 openings with a diameter of
1,5mm were made at each meter along aerator's length.
Total openings area on one running meter of the pipe is
0,00191 sg.m. Air was provided by air blower approximate-
ly 60 cu.m. in hour per one aerator. Efficiency of oxygen
consumption is 2.2 percent. Average air rate at outlets is
4m/sec. Oxygenation capacity of barbotage aeration at
standard conditions is 0,99kg O2/kwh or 13 percents lower
than that of mechanical aeration.
Barbotage aeration has such shortcoming as the noise
which is produced by air blowers. This disadvantage limits
its application in densely populated areas of the Lithuanian
SSR. The construction of special buildings for air blowers
increases the construction cost of artificial aeration unit.
As a result of DO tests carried out at weirs it was
concluded that weirs for artificial aeration should be
constructed with a height of to 1,0 m. Weir should be with a
free-spilling jet and reaches conjugated according to
60
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submerged hydraulic jump.
Studies of artificial aeration were conducted at PpK 70-
BO-100 Kruosta hydraulic turbine. Air was supplied
through pipes in upper cap of a turbine which connect zone
of discharging with atmosphere.
In the course of aeration the DOconcentration varied in
the range from 0,55 to 1,70 mg/1. The loss of a unit capacity
was ranging from 4,8 to 8,7 percent during artificial
aeration.
Average oxygenation capacity under standard conditions
is 2,58kgCh/kwh. The efficiency of artificial aeration by
hydraulic turbine is higher than those obtained by other
methods.
Investigations showed that above mentioned value of
capacity loss was conventional. Discharge which doesn't
pass through hydraulic turbine due to artificial aeration,
remains in head race and naturally conserves its potential
energy. So when not all of the turbines are in operation and
there is no dummy discharge saved flow rate passes through
another hydraulic turbine. Thus amount of energy generat-
ed by hydropower station as a whole decreases slightly.
Only amortization of units increases due to their operation
together for longer time than that without aeration.
Therefore aeration efficiency of the hydropower station
estimated by this method is up to 12,94kgO2/kwh or 17,86
kgO2/kwh under standard conditions.
The results of the studies conducted to determine the
effect of artificial aeration on self-purification properties of
the receiving waters didn't show improvement in self-
purification properties. Variations in BOD and COD values
were nearly the same during artificial aeration as well as
without it and didn't indicate an obvious relationship.
The same results were achieved during microbiological
tests. Only number of anaerobic bacteria decreased slightly.
Index of testing on glander ranged equally with aerators in
operation as well as out of operation: ranging from 2,6-3,0
in the region in front of aerators to 2,2-2,75 at the 5km
potion behind cross-section of artificial aeration.
As a result of analysis of data taking account of literary
data the following conclusion can be drawn: under aerobic
conditions the increase in the DO concentration doesn't
intensify self-purification process significantly.
It conforms to Phelpth-Striter theory. According to it the
rate of BOD removal is directly proportional to BOD value
and is independent of DO content in water. Of course it may
exist until anaerobic conditions will occur which inhibit self-
purification process. According to Velner CH A, Melder
Ch.A. and Laene A.A. maximum rate of aeration is
determined at DO concentration ranging from 1,5 to 2,5
mg/1. Probably the DO concentration shouldn't be less than
above given values below the place of wastewater discharge
under extreme conditions (low flow rate, high temperatures,
ice cover etc.)
If anaerobic conditions exist in front of artificial aeration
zone, aeration promotes self-purification process. Some-
times it requires a certain time depending on the degree of
anaerobics in the region in front of the cross-section of
reaeration. Of course during artificial aeration the process
restores more rapidly than that under natural conditions.
The effect of artificial aeration on oxygen regime in the
river is estimated by comparison of slopes of oxygen curves
(mgO2/ I/km) prior to and after artificial aeration.
The definition "slope of oxygen curve" (mgO2/l/km) in
our view reflects fully the dissolved oxygen saturation
process in conjunction with reaeration.
As a result of investigations it has been found that the
slope of oxygen curve increases slightly (7-11%) if artificial
aeration unit is located in the descending potion of oxygen
curve. It may be attributed not to increase in the rate of self-
purification process and oxygen consumption but to
decrease in the rate of natural surface reaeration due to
increased saturation of water with oxygen.
Artificial aeration is graphically shown in Figure 1
considering all above mentioned conclusions.
Prior to wastewater discharge to receiving waters (point
1) BOD value is normal and DO concentration's high and
near saturation value. Pollutant concentration increases
during wastewater discharge. Intensive self-purification
process starts below the point of discharge. BOD concentra-
tion reduces and natural surface reaeration can't supply
sufficient amount of oxygen. The oxygen curve descends
rapidly and intersects line of desired minimum concentration
(1,5-2.0 mgO/1) at point 2. Normal aeration process is
broken, fish is killed, self-purification process is inhibited
considerably.
At point 3— oxygen supply is exhausted, anaerobic
digestion process occurs. BOD concentration doesn't reduce
and even increases due to secondary pollution.
At a certain distance at point 4 air supply again exceeds
oxygen consumption its concentration restores and reaches
level of desired minimum concentration at point 5, above
which self-purification process takes place under normal
conditions. Thus under natural conditions normal process
of self-purification doesn't occur in the river potion with L
length, between points 2 and 5.
If artificial aeration is applied at point 2, DO concen-
tration increases BOD removal goes on. If it is necessary
artificial aeration is applied at several cross-sections (e.g. at
point 3, 4) until oxygen curve reaches point 5. Self-
purification process goes on all the time under normal
aerobic conditions and ends somewhere at point 6, which is
located nearer than that under the same conditions without
artificial aeration.
Of course pollutants concentration exceeds normal value
in the region between points 2 and 6, it isn't so dangerous
due to presence of oxygen. If we must select either "dead
stream" that is with zero. DO concentration of "alive river"
although it doesn't meet water quality standards, the latter
should be chosen. As we have already seen such alternative
may arise with any small stream, even if we have good
wastewater treatment plants.
Wastewater treatment plants can't be replaced by
artificial aeration and therefore we shouldn't exaggerate its
possibilities. However more attention should be paid to
artificial aeration as an economical and effective method of
a partial solution to river DO problems at present day
growth of pollution.
The Kaunas Polytechnic Institute continues studies of
artificial aeration. The design of powerful summer unit of
artificial aeration has been performed and it should prevent
formation of regions with anaerobic conditions in the
Nevejis River until wastewaters discharged by Kedainiay
town will receive sufficient treatment. Unit's capacity is
600kw. Oxygenation capacity is approximately 7000kg
DO/day. At present the possibility of constructing the
aeration unit in 1977 is being considered.
61
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a.
Ml/A
Fig. 1. Self-purification process in overloaded river.
a. River aeration;
b. Artificial aeration;
1. DO concentration;
II. BOD concentration;
III. Desired minimum DO concentration.
Wastewater Treatment
Concerns of the Organic
Chemicals Industry in the
United States
Carl E. Adams, Jr., Ph.D., P.E.
President
Associated Water & Air
Resources Engineers, Inc.
Nashville, Tennessee
Billy T. Sunnier, P.E.
Immediate Past President
American Consulting Engineers Council
Vice President
Barge, Waggoner, Sumner and Cannon
Nashville, Tennessee
July 1976
I. Introduction
The organic chemicals industry is the most complex and
diversified industry in the United States. It not only
generates thousands of different products, but even
produces at different plants identical chemicals by different
processes.
Synthetic organic chemicals are products derived from
naturally-occurring raw materials—primarily from petrole-
um, natural gas, and coal—that have undergone at least one
chemical conversion. Originally, coal was the primary raw
material for the organic chemicals industry, but in the last
20 years, it has been replaced by petroleum-based
feedstocks because, even though the price of coal is less than
one-half that of most fluid feedstocks, the handling and
processing of fluids is more economical. Moreover, the
mining of coal is far more labor-intensive than the
extraction of fluid fuels from the earth. The term
"petrochemical" is commonly used to refer to all organic
chemical products derived from petroleum fractions and by-
products or from natural gas constituents.
Within the last 10 years, there has been an extraordinary
simplification of numerous organic syntheses, chiefly
because of unique developments in catalysis and automatic
control. This, combined with the construction of larger and
larger production facilities, has resulted in a drop in the
price of organic chemicals that would not have been
thought possible a few years ago.
This trend toward lowering production costs is counter-
balanced by a rapidly developing crisis in the organic
chemicals industry: the diminishing availability of economi-
cal raw materials. The chemical manufacturers are now
paying more and more for crude oil and natural gas—a
situation that is expected to become more severe. In
addition to this economic problem, the industry is
confronted with the cost of complying with the pollution
62
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abatement goals established by the federal government.
II. Categorization of the Organic Chemicals
Industry
There has been an effort in the United States to establish
effluent discharge limitations for each major industrial
product. For some industries, such as pulp and paper,
relatively broad effluent guidelines that apply to certain
segments of these industries can be established. However,
this is impossible for the organic chemicals industry in
which increasingly complex technologies produce a diversi-
ty of interrelated chemicals by a variety of processes. The
water usage and subsequent discharges of wastewater are
directly related to this mixture of products and processes.
Therefore, the federal government has prepared effluent
limitations for the organic chemicals industry as a whole
with subcategories that are related to the manufacturing
process and the extent of water usage within the process.
There are four major subcategories:
Subcategory A: Nonaqueous Processes
This subcategory is limited to processes in which there is
minimal contact between water and the reactants or
products; water is not required as a reactant or diluent and
is not generated as a reaction product. The water usage in
this category would result only from necessary washes or
catalyst hydration.
Subcategory B: Process Water Contact as Steam Diluent or
Adsorbent
This subcategory is limited to processes in which water is
utilized in the form of dilution steam, direct product
quench, or adsorbent for effluent gases in reactions that are
all vapor-phase over a solid catalyst. Most processes in this
subcategory utilize an adsorbent combined with steam
stripping of chemicals for purification and recycling.
Subcategory C: Aqueous Liquid-Phase Reaction Systems
This subcategory includes processes in which the
reactions are liquid-phase with the catalyst in an aqueous
medium. Continuous regeneration of the catalyst requires
extensive water usage and in some cases substantial removal
of inorganic by-products. This subcategory also includes
processes in which water is involved in the final purification
or neutralization of products.
Subcategory D: Batch and Semicontinuous Processes
This subcategory includes the processes in which the
reactions are liquid-phase with aqueous catalyst systems; in
which very rapid cooling makes it necessary to add contact
quench water or ice; or in which the reactants and products
are transferred through the various processes by gravity
flow, pumping, or pressurization. This subcategory also
includes processes in which much of the materials handling
is manual; in which solids-liquid separations are common
and employ filter presses and centrifuges; or in which air or
vacuum ovens are used for drying products: a major source
of wastewater results from cleaning the noncontinuous
production equipment.
All effluent limitations and treatment technologies for the
organic chemicals industry were defined on the basis of
these four subcategories. In addition, Subcategories B and
C were further subdivided according to raw waste loads by
groups—B-l, B-2, C-l, C-2, C-3 and C-4—that consist of
product/process segments with similar ra.w waste load
characteristics for the major pollutant parameter, bio-
chemical oxygen demand (BOD).
III. WASTEWATER CHARACTERISTICS FOR THE
ORGANIC CHEMICALS INDUSTRY
Because of the diversity of the organic chemicals
manufacturing processes, practically every significant
pollution parameter exists at one plant or another. Some
waste streams may contain only two or three significant
parameters, whereas others may contain as many as 50 or 60
significant constituents. After extensive literature review
and numerous field surveys, the federal government
concluded that there are only 27 that significantly affect the
quality of surface waters (see Table 1). Of course, the
effluent limitations include the usual pollution indicators:
biochemicals oxygen demand (BOD), chemical oxygen
demand (COD), total suspended solids (TSS), etc. In
addition, there are other limitations that, for the most part,
pertain to dissolved organic pollutants in process wastewa-
ter. No specific limitations were proposed for pollutants
associated with non-contact wastewater like boiler and
cooling-tower blowdown because these waste streams
primarily contain inorganic materials and it is difficult to
allocate such wastes to specific processes in multi-product
plants.
Other parameters considered include total organic
carbon, ammonia, cyanide, extractable oils and grease, and
various heavy metals. These were generally found to be in
concentrations substantially lower than those that would
require specialized end-of-pipe treatment, i.e., treatment
that is not an integral part of the industrial process.
Summaries of the amount of flow, BOD and COD for
Subcategories A, B, and C are shown in Tables 2, 3, and 4,
respectively. There is insufficient data at this time from
Subcategory D processes; however, Table 5 does show some
data from a batch organic chemical plant producing azo
dyes.
Table 1
Significant pollutant parameters for the organic chemicals industry
General Parameters
1. Biochemicals Oxygen
Demand (BOD)
2. Chemical Oxygen Demand
(COD)
3. Total Suspended (Nonfilter-
able)
Solids (TSS)
4. Total Dissolved (Filterable)
Solids (TDS)
5. pH
6. Acidity
7. Alkalinity
8. Hardness - Total
9. Calcium - Total
10. Magnesium - Total
11. Chloride
12. Sulfate
13. Color
14. Oil and Grease
Organic Pollutants and Nutrients
15. Totals Organic Carbon (TOC)
16. Ammonia Nitrogen
17. Total Kjeldahl Nitrogen (TKN)
18. Phenols
19. Cyanide - Total
20. Phosphorus - Total
Metals
21. Zinc-Total
22. Copper-Total
23. Iron - Total
24. Chromium - Total
25. Cadmium - Total
26. Cobalt - Total
27. Lead - Total
-------
Table 2
Summary of raw waste load data
Subcategory A - nonaqueous processes
Product/Process
BTX Aromatics
(Hydrotreatment)
BTX Aromatics
(Solvent Extractin)
Cyclohexane
Vinyl Chloride
Mean Value
Flow
liters 1 1000 kg
114.0
504.0
No Discharge
2,004.0
873.0
gal 1 1000 Ib
13.6
60.4
240
105.0
BOD
kg /1000kg
0.10
-
.
0.10
COD
(IbllOOO Ib)
0.31
-
0.12
0.22
Table 3
Summary of raw waste load data by Subcategory group
Subcategory B - processes with process water contact as steam diluent or adsorbent
B-l Product/Process
Ethyl benzene
Ethylene and Propylene
Butadiene (from ethylene)
Methanol
Acetone
Vinyl Acetate
Formaldehyde
Ethylene Oxide
Ethylene Dichloride
Vinyl Chloride (from
ethylene dichloride)
Methyl Amines
B-l Mean Value
Flow
liters 11 000 kg
317
2,961
1,693
417
1,460
234
1,093
617
800
2,802
3,661
1,460
gall 1000 Ib
38
355
203
50
175
28
131
74
96
336
439
175
BOD
kg /1 000 kg
0.13
0.35
0.63
0.49
0.26
0.04
-
0.7
-
-
0.48
0.38
COD
Ob /WOO Ib)
1.86
2.36
2.04
0.94
1.10
0.13
-
6.48
4.84
7.66
12.8
4.0
B-2 Product/Process
Acetaldehyde (from
ethanol) 13,344 1,600 1.12 2.48
Butadiene (from
n - butane) 9,674 1,160 2.96 3.23
Acetylene 4,679 561 1.92 5.95
Styrene 14,453 1,733 1.00 3.74
B-2 Mean Value 10,541 1,264 1.75 3.85
64
-------
Table 4
Summary of raw waste load data by subcategory group
Subcategory C - aqueous liquid phase reaction systems
C-l Product/ Process
Coal Tar (pitch forming
Acetic Acid
Acrylic Acid
Ethylene Glycol
Terephthalic Acid
C-l Mean Value
C-2 Product/ Process
Acetaldehyde (ethylene and
oxygen)
Phenol and Acetane
(cumene process)*
OXO Chemicals
Coal Tar (distillation)
Caprolactam
C-2 Mean Value
C-3 Product/Process
Acetaldehyde (ethylene and
air)
Anilene
Bisphenol A*
Dimethyl Terephthalate
C-3 Mean Value
C-4 Product/ Process
Acrylates
P - Cresol*
Methyl Methacrylate
Terephthalic Acid (nitric
acid process)
Tetraethyl Lead
C-4 Mean Value
* Phenols raw waste load - 10
Flow
liters /WOO kg
1,043
4,170
3,962
4,871
1,551
3,119
509
2,335
3,503
3,336
10,842
4,103
751
1,585
559
2,252
1,284
23,819
10,767
1,668
5,496
100,000
28,366
kg/ 1000 kg (lb/1000 Ib)
gall 1000 Ib
125
500
475
584
186
374
61
280
420
400
1,300
492
90
190
67
270
154
2,856
1,291
200
659
12,000
3,401
BOD
kg/1000 kg
0.35
0.74
0.34
0.82
0.56
1.9
5.6
3.2
2.8
1.6
3.03
26.6
.
..
24.4
25.5
47
123
45
59
-
68.5
COD
(lb/1000 Ib)
0.06
0.78
1.64
8.76
1.72
2.59
5.8
11.0
4.25
8.7
4.0
6.75
44
21.2
17.1
38.2
30.1
118
256
386
104
110
195
Table 5
Summary of raw waste load data
Subcategory D—batch and semi-continuous processes
Product/Process
Azo Dye (Batch)
@ 50% occurrence
Mean Value
liters 11000 kg
793,826
114,395
175,768
361,329
Flow
gall 1000 Ib
(95,069)
(13,700)
(21,050)
(43,273)
BOD COD TOC
kg/1000 kg (lb/1000 Ib)
79
220
59
119
1,850
1,075
175
1,033
790
450
60
433
65
-------
IV. Wastewater Control and Treatment
Technology
Three distinct levels of technology are being utilized to
reduce the concentrations of various pollutants to the levels
required by law and are defined as follows:
1. Best Practical Control TecKnology Currently Availa-
ble (BPCTCA), which represents the quality that must
be achieved no later than July 1, 1977.
2. Best Available Technology Economically Achievable
(BATEA), which is more stringent than BPCTCA and
will be required by July 1, 1977, in those situations in
which water quality has deteriorated so much that
improvements beyond BPCTCA are necessary. This
technology will be required for all treatment facilities
by 1983.
3. Best Available Demonstrated Control Technology
(BADCT), which is an improvement over BPCTCA
that is required for all new industrial plants generating
an effluent for the first time.
Effluent limitations for 1977 and new source performance
standards (BPCTCA and BADCT, respectively) were based
upon three significant pollutant indicators: BOD, TSS, and
phenols. The effluent limitations for phenolic compounds
were applicable only to the cumene process (bis-phenol A
and p-cresol manufacturing). In addition, the 1983
performance standard (BATEA) specified COD as well.
The 1977 standard (BPCTCA) specifies that a biological
process (activated sludge, trickling filter, aerated lagoon, or
anaerobic lagoon) be used to provide end-of-pipe treatment.
With any of these processes, there must be appropriate
pretreatment for pH control, equalization, oil and grease
removal, etc., in order to limit various waste loads and
remove materials that might interfere with the performance
of the biological system. In some instances, however, a
combination of physical and chemical processes, (for
example, activated carbon, ammonia stripping, chemical
oxidation, ion exchange, and reverse osmosis) is allowed;
or, if waste loads are adequately reduced as part of the
industrial process, then biological treatment is not required.
The 1983 standard (BATEA) requires the addition of an
activated carbon process following the biological system in
order to remove those refractory dissolved organics that
have passed through the biological system as well as to
remove some biodegradable pollutants that have not been
adequately removed in the biological system. Effluent
suspended-solids reduction utilizing filtration or coagula-
tion may be required between the biological and carbon
systems. Even though the activated carbon process is
utilized, it may also be necessary to have the industrial
process include certain controls to reduce pollutants: for
example,
1. Substitution of noncontact heat exchangers or direct
contact water cooling;
2. Use of nonaqueous quench media as a substitute for
water where direct contact quench is required;
3. Recycling of process water;
4. Reuse of process water (after appropriate treatment)
as makeup to evaporative cooling towers where
noncontact cooling water is circulated;
5. Use of process water to generate low-pressure steam
by noncontact heat exchangers in reflux condensers of
distillation columns;
6. Recovery of spent acids or caustic solutions for reuse;
7. Recovery and reuse of spent catalyst solutions; and
8. The use of nonaqueous solvents for extraction of
products.
The end-of-pipe technology for new source standards
(BADCT) has been defined as the use of biological
treatment followed by suspended-solids removal by clarifi-
cation sedimentation or by granular media filtration.
Exemplary in-plant controls such as the above are assumed
to be applicable as well. This is particularly important if
constituents are present-that might be toxic to the biological
system.
V. General Considerations for End-of-pipe
Treatment Technology .
The technologies which are now utilized in the organic
chemicals industry in the United States and the achievable
treatment level which have been proposed by the federal
government are as follows:
Biological Treatment Performance
The biological treatment techniques most commonly used
by the organic chemicals industry are activated sludge and
aerated lagoons. In developing its guidelines for the organic
chemicals industry, the federal government relied on the
performance records of a number of treatment plants (see
Table 6). Data from those judged to be exemplary are
summarized below:
Exemplary Single-
Stage and Multiple-
Stage Treatment
Plants
Exemplary Single-
stage Treatment
Plants
COD BOD TOC Effluent
Removal Removal Removal TSS
percent percent percent mg/Iiler
74
69
93
92
79
60
134
65
Some additional sampling was performed at these plants;
the results, which are summarized in Table 7, agree very
well with the long-term historical data shown in Table 6.
Table 7 also indicates the impact of total dissolved solids
and oil on the level of suspended solids. Data from
exemplary plants are summarized below:
Exemplary Treatment
Plants
COD BOD TOC
Removal Removal Removal
percent percent percent
72
87
58
There is growing evidence that high concentrations of
total dissolved salts or high levels of oils and greases
entering a biological plant contribute to high TSS levels.
The effect of salts on a biological treatment system,
especially on an activated sludge process, are summarized1 in
Table 8.
66
-------
Table 6
Historic treatment plant performance 50% probability of occurrence
COD
Plant Treatment %
No. System4 Category Removal
I4 AL
2' 2 AS-AL
31 AS
41 AS
5' 2 TF-AS
6 AL
7 AL
8' AL
9i AS
10' AS
II12 AS-AL
12 AS
13 AS
14 AS
15 AL
16' AS
17' AS
18 AS
19' AS
20' AS
Exemplary Plant
Exemplary Single
Plants - Average
D
C
D
B
B
B-C
C
B
C
B
C
A-B
B
B
D
D
D
D
C
Average
Stage
75
96.4
63
64.2
73.5
74.5
.
85
.
_
.
.
67
25.4
-
74
69
BOD
TOC SS
Effluent % Effluent %
Mg/liter Removal Mg/liter Removal
320
470
200
120
83
165
75
80
-
97
610
.
226
.
1,760
1,520
296
378
97
93.5
83
90.1
99.7
-
.
73
-
82.5
.
63.6
97.6
98.8
93
92
10
16
15
291
9.9
23.5
152
20
20
59
294
410
63
362
.
303
157
46.9
82.2
60
.
97
-
-
42
-
-
.
.
-
-
79
60
Effluent % Effluent
Mg/liter Removal Mg/liter
170
.
100 -370
-
295
780
-
-
.
.
-
-
135
-
163
55
665
81
24.3
130
.
145
-
189
280
-
289
.
480
-
-
134
65'
Data Base
Duration Performance
(months) Period
6(Sept-Feb) daily average
12 daily average
12 monthly average
14 monthly average
14 monthly average
12 weekly average
12 monthly average
12 monthly average
7(Aug-Feb) daily average
12 weekly average
12 daily average
12 monthly average
14 monthly average
14 monthly average
6(July-Dec) weekly average
8(Aug-Mar) monthly average
6(June-Oct) daily average
12 weekly average
S(June-Sept) montly average
S(June-Sept) weekly average
1 Plants considered to be exemplary in performance.
2 Multiple-stage biological treatment
3 Plant 16 is not included in average
Table 7
Treatment plant survey data1
COD
Total BOD
TOC
TSS
TDS
AS - activated sludge
TF - trickling filter
Oil & Grease
Plant Treatment % Effluent % Effluent % Effluent %
No. System6 Category Removal Mg/liter Removal Mg/liter Removal Mg/liter Removal
22 AS-AL C 64 2,300 90
y AS D 71 284 73
42 AS B 57 214 82
52 TF-AS B 59 133 92
6 AL B-C 66 980 73
8J AL B 69 92 84
9 AS C 75 595 92
IP AS-AL C 94 337 99
13 AS B-C 65 940 90
I6Z AS D 54.8 1,650 82.1
172 AS D 60 1,400 81.4
77.3 1,000 90
18 AS D 22.1 2,680 16.7
192 AS D 59.5 5,100 69.8
202 AS C 96.2 317 99.5
21 AL C 62 600 78
22 AS B 16.1 1,370 47.5
23 AS B 95.4 147 92.6
Average5 72 87
1 Based on 24 hours composit samples.
2 Plants considered to be exemplary in performance
427
74
13
12
235
6
75
16
177
300
240
310
650
1,800
19
27
210
4!
32
71
35
43
11
26
69
27
64
80.8
63.4
76.8
-
55.8
96.6
66
8.3
95.4
58
based on historical
2,710
132
80
61
573
52
242
343
470
280
410
360
1,025
1,700
114
47
550
35
data.
Negative
Negative
40
97
Negative
99
Negative
Negative
120
43.6
Negative
42.9
Negative
Negative
89
53.4
Negative
Effluent
Mg/liter
4,700
62
14
44
362
3
50
145
338
552
1,300
732
1,170
2,500-
100
30
82
37
Effluent
Mg/liter
2,300
3,100
2,900
1,430
3,000
690
3,810
2,690
1,520
10,990
3,750
4,060
2,050
8,360
1,950
9,800
15,400
580
Effluent
Mg/liter
.
P
43
2-1
II-1
-
12'
P
63
226"
24"
22"
106"
-
)94
-
<.034
21"
3 Oil and grease are reported as carbon letrochloride extractables.
4 Oil and grease and reported as Freon extractables.
5 Includes exemplary plants as well as Plant 23.
* AL - aerated lagoon
67
-------
Granular Media Filtration
The present use of granular media filters is very limited in
the organic chemicals industry. However, many industries
are in the process of installing these niters in order to meet
effluent limits for TSS. The selection of media types and the
addition of chemicals can substantially influence the quality
of the final effluent, and it is generally assumed that effluent
suspended solids can be reduced to a range of 5 to 30
mg/ liter (50 to 90 percent removal) through the use of these
filters. Some samples collected from organic chemical plants
were tested for suspended solids removal. The results,
shown in Table 9, indicate that filtration removed an
average of 20% COD, 17% BOD, and 20% TOC.
Activated Carbon Adsorption
Granular activated carbon technology has been exten-
sively studied in the United States for several years.
Although it seems feasible on a small scale, many problems
develop in full-scale situations. For example, there are high
attrition losses of carbon due to mechanical grinding and
other materials handling problems. Moreover, precise and
dependable methods of operating the regeneration furnace
have yet to be developed. Another problem is that many low
molecular weight compounds are not amenable to adsorp-
tion on activated carbon. The clogging and substantial
increases in head loss across the carbon column, which are
caused by TSS of more than 50 mg/liter and by more than
10 mg/liter of oils and greases applied directly to carbon
beds, are also matters of concern.
Table 8
Effects of total dissolved inorganic solids on biological system
performance
Salt Concentration
Effects on Biological System
500 - 2,500 Optimum Activity
2,500 - 5,000 Slight Increase in Effluent
Suspended Solids
5,000 - 8,000 Suspended Solids in Effluent
Settleability Decreases Slightly
8,000 - 12,000 Significant Effluent Suspended
Solids Settleability Poor
12,000 - 15,000 High Concentrations of Effluent
Suspended Solids. Difficult
to Operate Activated Sludge.
Effluent Soluble BOD
Increases Settleability Very Poor
15,000 Severely Toxic
Table 9
Removal by
Filtration
(Performed on Biological Treatment
Plant
3
15
15
14
9
9
13
4
24
12
21
16
25
20
35
26
27
18
17
19
Average1
% COD
9
87
85
24
11
10
32
8
21
3
84.3
39.3
8.5
51.4
26.2
—
86.8
88.4
33.3
20
Plant Effluent)
% BOD
4
56
.
28
36
2
__
57.8
17.2
71.4
12.5
72.1
55.6
—
17
% TOC
3
78
82
14
5
17
8
20
7
8
75.9
39.4
33.0
27.7
41.2
25.0
90.6
91.6
66.0
20
1 Average does not include plants 15, 16, 17, 18, and 26, since these
plants have excessively high effluent TSS and would bias the results
The results of a survey at six activated carbon plants
treating raw organic chemical wastewaters are shown in
Table 10. Based on these data and on small-scale laboratory
studies, the average performance for activated carbon
systems was determined to be as follows:
Parameter
COD
BOD
TOC
Carbon Exhaustion
Rate Ib. Removed/Ib.
Carbon
0.41
0.03
0.06
Soluble Removal
%
69
20
87
VI. Effluent Limitations From the Various
Technologies
In reviewing the above data, the federal government
arrived at percentage removal factors and minimum
concentrations that could be achieved through the applica-
tion of the technologies discussed above. These levels are
summarized below.
BPCTCA Treatment Systems - 1977 Standard
The following pollutant reduction factors are considered
achievable with BPCTCA treatment technology:
BOD'
COD
TSS
'Controlling Parameter
2Annual Average
'Monthly Average
Reduction Factors
Range Average
83-99% 93%2
. 63_-96% 74%2
reduced to 65 mg/liter*
Best Achievable
Under Worst
Conditions
mg/liter1
20
30
68
-------
Table 10
Activated carbon plants treating raw wastewaters
Removal Efficiencies •
Hydraulic
Loading
Flows-gpd gpm/sq. ft. Contact Time-minutes Carbon Exhaustion Rate
Plant Pretreatment Design Present Design Present Design Present Design Present Design Isotherm
28 Solids Removal and
Equalization 9-hr.
detention time — Polyol-11 100,000 55,000 5.6 3.0 22
40 0.4 Ib. polyol
Ib. carbon
29 Equalization 150-
day detention time TOC-94 TOC-89 20,000 7,000 0.49 0.17 540 1,550 0.07 Ib. TOC 0.19 Ib. TOC
Ib. carbon Ib. carbon
30 Equalization, Neu-
tralization and
solids removal Phenol-89 Phenol-94 750,000 500,000 4.6 3.1
31 Equalization and
Neutralization —
TOC-91
30,000 20,000
32 Equalization and
Neutralization Phenol-99.9Phenol-95 72,000 22,000 2.0 0.6 215
33 Equalization, Neu-
tralization and
solids removal Color-90
800,000 — 7.7
60 104 .028 Ib. phenol
Ib. carbon
660 912 -
75 —
27 — 5.4 Ibs. color
Ib. carbon
Federal permits for BPCTC A have generally been granted
on the basis of a plant's achieving 93 percent removal of
BOD on an annual basis. This allows, under worst winter
conditions, a monthly average of 2.1 times the annual
average and a maximum daily discharge of 3.9 times the
annual average. Although this approach works well in many
cases, in others—for example, multi-product, batch-
operated, and campaign-scheduling industries—it is not
satisfactory, and generalized approaches have not proven to
be successful.
BATEA Treatment Systems - 1983 Standard
Based on previous performance data for multiple-stage
biological treatment plants, existing carbon treatment
plants, and laboratory carbon data, waste reduction factors
were formulated by the federal government for BATEA as
follows:
Reduction
Applied to
BPCTCA
Effluent
Limitations
90%'
60%'
reduced to 15 mg/ liter2
Best Achievable
Under Worst
Conditions
mg/ liter2
10
50
10
Parameter
BOD
COD
TSS
* Annual Average
2 Monthly A verage
The affected industries do not agree with the limitations,
claiming that there is not yet enough known about carbon
technology.
BADTC Treatment Systems - New Sources
Based merely on filtration test data, the federal govern-
ment proposed the following reductions for BADTC
technology:
Parameter
BOD
COD
TSS
Reduction Factors
Applied to BPCTCA
Effluent Limitations
17%'
20%'
reduced to 10 mg/liter2
Best Achievable
Under Worst Conditions
mg/liler2
10
10
Annual Average
2Monthly Average
VII. Summary
Since all of the above recommendations were made by the
federal government primarily on the basis of its own studies,
many questions still remain within the organic chemicals
industry regarding final effluent limitations. Since the
industry cannot be standardized, it is unrealistic to attempt
to establish guideline limitations that are applicable to every
industrial plant within each subcategory. Because of this
complexity, each permit is generally evaluated on a case-by-
case basis using the guidelines as a starting point. One key
factor not considered by any of the guideline studies is the
incorporation of effluent variability into the permits. For
the organic chemicals industry, in which most of the
biodegradable materials are soluble, many operational
constraints and environmental conditions influence the
variability of the final effluent. For example, during cold
weather, the effluent will deteriorate because the biological
organisms cannot perform as they do in warm weather.
Therefore, the permits must be based on worst conditions,
i.e., worst winter situations anticipated during the life of the
69
-------
permit. This is a subject currently under discussion between
industry and the government. In addition, because small
industrial plants do not have the capability to reduce
waste-water flows on the same level as the larger plants, they
have been penalized more severely. Industrial plants that
are multi-product in nature and employ batch processes
have much higher variability in raw waste characteristics;
consequently, their treatment facilities are subject to
varying wastestreams, which results in much more variable
effluents than those of continuously operated industries.
Finally, those industries that manufacture products as
orders come in are subject to campaign scheduling in order
to meet requests from their customers; such campaign
scheduling can cause significant variability in the quality of
the raw waste and therefore of the treated effluent.
Because of the above considerations and the difficulties
encountered in attempting to secure workable yet controlla-
ble permits, many problems have arisen with respect to the
organic chemicals industry's efforts to comply with
pollution abatement goals. There is no doubt that the
technology will eventually develop to allow industry to
construct economically feasible treatment systems that are
capable of upgrading the water quality in the United States
and of being monitored satisfactorily by the government.
Acknowledgements
The majority of the information contained in this paper
was taken from the April, 1974, publication, "Development
Document for Effluent Limitations Guidelines and New
Source Performance Standards for the MAJOR ORGAN-
IC PRODUCTS Segment of the Organic Chemicals
Manufacturing, Point Source Category," based on a study
conducted by Roy F. Weston Company for the U.S.
Environmental Protection Agency. The purpose of the
study was "to establish effluent limitations guidelines for
existing point source discharges and standards of perform-
ance and pretreatment standards for new sources."
All of the tables except Table 8 were taken from the
above referenced publication.
Biochemical Treatment of
Highly Concentrated
Wastewaters from Wool-
Scouring Operations
Skirdov I.V., Shvetzov V.N.,
Morosova K.M., Gubina L.A.
The problems associated with highly concentrated
wastewater treatment are becoming more noticeable today.
A typical example of a given type of wastewaters is a highly
concentrated wastewater generated from wool scouring
plants. The wastewaters contain substantial amounts of wool
grease, wool, various impurities, dissolved organic and
inorganic matter. The concentration of suspended solids is
up to 20 g/1, organic concentration varies ranging from 10 to
35 g/1. COD and from 5,0 to 20 g/1 total BOD. At present
mechanical, chemical, physical-chemical and biological
treatment processes are being used to treat wool scouring
operation wastewaters. In spite of a variety of treatment
methods, these wastewaters present certain treatment
problems. Chemical treatment process requires the use of
expensive chemicals, careful control of the process and
accurate dosing of reagents, resulting in large production of
waste sludge. At the same time the area for application of
anaerobic Biological treatment in digesters is broadening due
to ease of operation, reduced production of sludge and
efficiency. The BOD limit in treated effluent from digesters
varies ranging from 800 to 1000 mg/1, therefore effluent
requires final treatment. It should be noted that digestion
detention period of 20 days is needed to produce an effluent
with a total BOD of 8000 to 1000 mg/1. In practice, existing
digesters are designed with detention period of 8-10 days,
resulting in effluent with a total BOD of 1500 to 2000 mg/1,
then effluent should be treated in municipal biological
treatment plants (Fig 1, Scheme 1).
However in most cases the treatment capacity of
municipal treatment plants doesn't meet existing standards
and isn't sufficient to handle wool-scouring wastewaters
without additional dilution after pretreatment in digesters.
It makes us seek ways of final wastewater treatment prior to
their discharge into municipal sewerage system or to
receiving waters.
The institute VODGEO has carried out studies on the
feasibility of wool-scouring wastewaters treatment in
digesters followed by final treatment in aeration tanks
without dilution as well as complete biological treatment
under aerobic conditions. Studies were conducted on
natural wastewaters generated from worsted factory where
they are treated by using soap and soda.
Experiments were carried out on laboratory scale
continuous flow models of digesters and complete mixing
aeration tanks. The facilities performance was monitored by
analyses of COD and total BOD, pH, volatile fat acids
concentrations, the N and P content, concentration of
ether-soluble material, anaerobic and aerobic activated
sludge concentrations, quantity and composition of gas
produced from digesters. In order to obtain the criterion for
adequate evaluation of digesters performance as well as for
quantitative evaluation of biodegradable substrate in
70
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digesters determinations of influent and effluent BOD from
digesters have been conducted according to special proce-
dure.
As digesters are completely mixed biological reactors.
oxidation rate is determined on the basis of effluent
substrate concentration. The relationships between oxida-
tion capacity of digester and specific oxidation rate and
effluent organic concentration were found experimentally;
oxidation capacity and specific oxidation rate increase with
decreasing the degree of treatment. It has been found that
the effect of effluent organic concentration and volatile fat
acid concentration on specific oxidation rate is expressed by
hyperbolic function (Fig. 2) and may be described by
Michaelis-Menten expression for fermentation reactions.
r.ai BCD anaerobic
~T< £ ViS ir. flour
D ~~fK> I* Kn, 2° 35-
£ -^ jgj gg£00 ,'ggg /KM '/jcc/jfCc'ialMLa fat aciJi =j/l
Figure 2. Specific oxidation rate versus organic concentration (on
BOD basis) and volatile fat acids concentration in effluent
I to r.n:iicipal
;rfiatra'Mit plant;";
to nunicipol
treatment planto;
to receiving.
Figure 1. Biological treatment schemes for wool-scouring operation
wastewaten
1. Primary settling tanks;
2. Digestion tanks;
3. Final setting tanks;
4. - first-stage aeration tank;
5. - second-stage aeration tank;
.
— ?
^
^
.
.
x'
X
'
"o«-/«r
^
mg BOD anaerobic
= 35.; g VSS in hour
r y,W> "s/i
LJ .
2 / r. "• .! 3
-------
5 = Vmax[S2]
Kmt[S2]
where: ^ — specific oxidation rate; mg BOD anaerobic per
g VSS in hour
S2 - substrate concentration, mg BOD anaerobic/1
or mg volatile fat acids 1/1.
Vmax - maximum reaction rate, mg BOD anaer-
ob per g VSS in hour.
Km - Michaelis-Menten constant expressed as
substrate concentration at which reaction
rate is equal to half the maximum rate.
Method of binary reciprocal values was used to define
Vmax and Km. It can be seen from Fig. 3, that maximum
specific oxidation rate of wool scouring wastewaters in
digesters is 33.3 Mg BOD • h, km is 16700 mg/1.
gVSS
As the value of constant Km is dependent on its nature
rather than substrate concentration, high value of Km
obtained for treated effluent from digesters indicates the
complexity of wool-scouring wastewater composition. The
effect of anaerobic activated sludge concentration on basic
technological parameters has been investigated for the
purpose of improving digester performance. Oxidation
capacity of digesters and the degree of treatment considera-
bly increase with increasing activated sludge dosage while
specific rate decreases. However it decreases slower than
increases activated sludge concentration due to overall
oxidation rate increases. The decrease in specific oxidation
rate with increasing sludge dosage appears to be accounted
for changes in prebacterial film under hydrodynamic
conditions that in turn prevents feeding of substrate to
microorganisms and inhibits metabolism.
In order to define the relationship between anaerobic
activated sludge concentration and specific oxidation rate
coefficient Ksiudge have been suggested.
Coefficient Ksiudge is equal to the ratio of specific rate at a
given sludge concentration to rate at sludge concentration
of 5 g VSS/1.
It has been proven that coefficient Ksiudge doesn't depend
on substrate concentration, but depends only on anaerobic
activated sludge concentration (Fig. 4).
Taking into account specific oxidation rate and coeffi-
cient Ksiudge technological parameters of digesters treating
highly concentrated wastewaters should be calculated by
using the equation:
T=.
where: T
So
St
5
Ksiudge =
So-St
detention period in digesters, days.
organic concentration in influent, mg/1
total BOD.
effluent organic concentration mg/1
total BOD.
specific oxidation rate at sludge con-
centration on VSS 5 g/1, mg total BOD
per g VSS.
ash content in sludge, parts/unity.
coefficient considering effect of sludge
concentration on its activity, deter-
mined experimentally.
The studies on the final treatment of wool scouring
wastewaters have shown that treated effluent from
digesters with unoxidized organic material content of 3000
mg/1 on a total BOD basis, can be treated successfully
without dilution in complete mixing aeration tanks,
operating according to a two-stage scheme.
It is evident from Fig. 5 that oxidation kinetics of wool-
scouring wastewaters in complete mixing aeration tanks can
be described by Michaelis-Menten expressions for fermen-
tation kinetics.
The values of kinetic constants (Fig. 6,7) have been found
experimentally and may be used to calculate basic
technological parameters of aeration tank performance.
With reference to Fig. 6, 7, it can be seen that maximum
specific oxidation rate in a first-stage aeration tank is 55.5
mg BOD hour and in a second-stage aeration tank is
g VSS hour
mgBOD
g VSS h
The value of constant Km for the first-stage aeration tank
is higher than that for the second-stage aeration tank and is
equal to 83.5 mg/1 and 13.8 mg/1, respectively. From data
obtained, it can be concluded that high oxidation rate
occurs in the first stage aeration tank because activated
sludge is under conditions of excess substrate. At the second
stage the required degree of treatment is achieved at lower
oxidation rate due to lack of sufficient amount of substrate.
At each stage in aeration tank the development of specific
microorganisms takes place due to autoselection of
microorganisms acclimitized to given conditions and
mutant changes in the culture. In its turn it affects both
physical properties of activated sludge (in particular, its
settling properties) and kinetics of biochemical treatment
process. In the first stage if amount of substrate isn't limited,
autoselection of microorganisms takes place promoting
increase in maximum oxidation rate, and at the second
stage if amount of substrate is limited the development of
the culture encourages reduction in K m value and more full
substrate utilization. So the division of the process into two
stages improves process efficiency at the first stage and
provides more full oxidation of organic matter at the second
stage.
wool-scouring waste
water without pretreat-
ment in digesters.
wool-scouring waste-
water treated in digester
Figure S. Relationship between specific oxidation rate in first-stage
and second-stage aeration tanks and effluent organic concentra-
tion.
-------
9J
-------
eliminated, thus enhancing effectiveness and efficiency of
the treatment process as a whole
Table I. Technical-economic comparison of biological treatment
schemes for wool-scouring operation wastewaters
Scheme
I
II
III
IV
V
Digestion
Treatment unit tank
15000
4000
-
4000
-
First-stage
aeration
tank
Volume (cu m)
_
1230
2700
1560
7700
Second-stage
aeration
tank
_
900
3560
1200
1200
Municipal
treatment
plants
3800
630
630
_
-
volume
(cu m)
18800
6760
6900
6760
8900
Analytical and Process
Improvements in Biological
Treatment of Municipal
Waste Waters
William J. Love
The operation of biological wastewater treatment plants
is a complicated process requiring the blending of inter-
disciplinary professions, skills and experience. To managers
responsible for the operation of wastewater treatment
programs, the biological treatment process appears to be an
all too delicate, sensitive and often elusive process. Yet, the
biological treatment process still remains today, sixty years
after its innovation, as the most economical and widely used
type of secondary treatment for large municipalities. This
continued popularity has resulted from the biological
process' ability to consistently produce good quality
effluents when properly operated and controlled. The
emphasis here is on operation and control; the key to
successful operation of a biological treatment plant is
extensive analytical and process control. The analytical
investigations must completely characterize all wastewater
parameters and also each step of the biological treatment
process. The process control must incorporate the analytical
results into an operational program based on the biological-
chemical-physical principles of microorganisms metabolism
and liquid-solids separation. The analytical and process
control programs must be flexible to meet the ever changing
conditions within a plant, and must be continually
reevaluated and revised to meet the increasing growth of
wastewater flows.
The intent of this presentation is to discuss my
organization's experience in operating biological treatment
plants, to outline our analytical and process control
programs, and to discuss the role of analytical and process
control in solving some of the peculiar problems which have
occurred in our biological treatment plants.
Process Control Program
A process control program in a biological treatment plant
involves the collection and analysis of representative
samples of waste and process flow throughout the plant;
monitoring and controlling critical process functions and
variables according to established principles; recording and
evaluating historical data for use in predicting trends and
process modification requirements; and conducting experi-
mental investigations with process modifications, and even
with entirely new processes for solving treatment problems.
Our own process control program can best be explained by
example using one of our biological plants treating a high
strength industrial waste.
This plant is a 10 MOD activated sludge plant which
treats a brewery waste having a 1000 mg/1 BOD concentra-
tion and comprising 75% of the total influent plant loading.
The plant has screening, grit removal, primary gravity
clarification, large 13 hour detention complete mix aeration
tanks, final gravity clarification with low surface loading
rates of 360 gpd/square foot, and chlorine disinfection.
Sludge handling is by gravity thickening, centrifugal
dewatering and multiple hearth incineration. Although the
plant's BOD removals have been excellent, the activated
sludge process produces a very light sludge floe which is
difficult to separate in the final clarifiers and which results in
the plant's not meeting expectations. A tremendous amount
of analytical, process control and experimental work has
been performed attempting to improve the settling
characteristics of this activated sludge system.
Daily samples of the individual brewery, domestic and
combined plant influent wastes are composited proportion-
al to flow and analyzed for such parameters as TSS, SS,
VSS, BOD, COD, TOC, TKN, NHs-N, ortho PO
-------
control. This data is also used to routinely prepare solids
balances around the activated sludge system for controlling
the return and waste activated sludge flow rates from the
final clarifier and the overall sludge handling requirements
of the plant.
In addition to the complex analytical work performed in
the laboratory, the plant operators periodically perform
simpler tests to closely monitor several critical functions in
the plant. These tests include conducting dissolved oxygen
profiles of the aeration tanks to insure that there is sufficient
oxygen present; measuring oxygen uptake rates of the
activated sludge biomass as an indicator of changing
conditions such as influent shock loading or toxic wastes,
monitoring aeration tank and return sludge concentrations
using laboratory centrifuges; performing settleometer tests
of the aeration tank effluent to measure the activated
sludge's settling characteristics; and measuring the depth of
clear water in the final clarifiers to the sludge blanket to
indicate the overall settleability and solids balance in the
system. All of the above tests are performed every two hours
to four hours and provide an accurate picture of existing
plant conditions. These simple tests often serve as early
warning indicators of impending process upsets and allow
the plant personnel to take corrective actions before the
final effluent deteriorates.
This plant has had continued difficulty in producing a
satisfactoy settling activated sludge floe in spite of all the
close attention to monitoring and controlling the biological
process. Therefore, the plant's process control program was
expanded to try several process modifications. One of the
first was the addition of inorganic salts and organic poly-
electrolyites to the aeration tank effluent in an attempt
to weight down the sludge floe in the final clarifiers. This
proved to be not only far too expensive, but also not too
effective for this industrial waste. Alum addition to the
primary clarifiers at a feed dosage of 100 mg/1 produced an
extremely clear primary effluent and resulted in overall
primary removals of 80% SS and 40% BOD, but there were
no benefits observed in the activated sludge system.
Chlorine and hydrogen peroxide addition to the return
activated sludge were tested for controlling filamentous
microorganisms, but this proved to have no beneficial
effect. The final clarifiers were modified with the addition of
mechanical mixers and picketts to promote better floccula-
tion of the activated sludge floe, but this did not produce
better settling. One of the more recent process control
modifications has been the conversion of the complete mix
aeration system to a plug flow aeration system in an attempt
to influence the biological metabolism rate and shift the
microorganism predominance away from the filamentous
and lower microorganisms. Consideration is now being
given to a further conversion of the aeration tanks so that a
sludge reaeration system can be evaluated. Nutrient
addition in the form of nitrogen, phosphorous, and trace
metal supplements have been evaluated due to the industrial
waste's natural deficiency in these substances, and this
investigation is continuing. Each of the above process
modifications requires months for conducting a complete
research investigation and full scale plant trial. This work
requires considerable additional laboratory analytical work
and operational monitoring for a thorough evaluation of
the testing program.
In addition to the full scale plant process modifications
discussed above, our process control program has also
included a considerable amount of pilot scale testing and
bench scale experimental work. Several fong term scale
model pilot reactors have been operated to investigate all
aspects of aerobic biological treatment of this brewery-
domestic waste. This pilot Work has investigated the effects
of aeration detention time, biomass concentration, sludge
age, chemical and nutrient additions, oxygen and mixing
intensities, pH adjustment and shock loading susceptibility.
Pilot work was also performed using ultra sonic sound
generation in an attempt to alter the activated sludge floe
structure, causing it to degasify and thereby improving its
settleability. In this work, which showed no overall benefit,
lower frequencies tended to improve the initial settling rates
while higher frequencies tended to mix the sludge and
completely prevent settling. Several solids separation
processes have been piloted' to be used either as an
alternative or in conjunction with gravity clarification of the
activated sludge. One of the processes piloted, floatation
separation, proved to be a fairly successful method of
activated sludge solids separation but proved to be
unfeasible due to the large area requirements needed. Also,
this method would have required an additional solids
removal step such as microscreening to meet the effluent
requirements. Another piloted process, mixed media
filtration, was rejected because it required more backwash
water than the total plant influent. Still another piloted
process, dilution of the final clarifier influent mixed liquor
suspended solids by an intermediary Sweco centrifugal
solids separator, has proven to be both feasible and to
improve the settling characteristics of the diluted sludge in
the final clarifiers. The centrifugal solids separator appears
to selectively classify the biological solids so that the
filamentous microorganism count in the final clarifiers is
reduced. Our process control investigations at this plant are
continuing with both full scale and pilot testing.
Another problem caused by septic sewage is that it does
not respond to treatment by the activated sludge process as
rapidly as fresh sewage. This condition required a major
deviation at our 24 MOD contact stabilization activated
sludge plant from conventionally established process
control for contact stabilization plants. The septic sewage at
this plant receives no primary clarification and would turn
the influent ends of the contact aeration tanks black. We
were unsuccessful in developing a viable biomass in the
aeration system as long as we attempted to operate the plant
around conventional parameters of fifteen to forty-five
minutes detention time in the contact zone. Laboratory
pilot scale and full plant testing indicated that a considera-
bly longer contact time was required to allow the
microorganisms to assimilate the septic waste. The
treatment process was modified to provide a minimum of
two hours detention time in the contact aeration tanks, and
immediately a viable biomass developed. This resulted in
good treatment performance and a good effluent. Higher air
supply rates are required to maintain adequate dissolved
oxygen in the contact aeration tanks, and a longer
proportion of the aeration system must be devoted to
contact aeration rather than stabilization aeration than was
originally designed.
The second process control problem caused by our force
main system is that the plants experience a severe diurnal
flow pattern. In a force main system flow is immediately
75
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received at the plant when outlying pump stations are
operating. This eliminates any flow lags and dampening
such as are experienced in gravity collection systems. We
receive very high flows during the daytime and virtually no
flow at night, and the switch from high flows to low flows
occurs rapidly within an hour as people go to bed and get
up. Using our 24 MGD contact stabilization plant as an
example, the present average daily flow is 16 MOD, but the
daytime flow rate from 6:00 A.M. to midnight is 20 MGD
and the nighttime flow rate from midnight to 6:00 A.M. is
only 4 MGD. Process control problems arise in trying to
maintain a constant solids balance around the aeration
system. If the return sludge flow rates are not carefully
adjusted to match the widely varying influent flow rates, the
solids concentration in the contact aeration tanks will
significantly increase during early morning—low flow
periods. Later, the high flow surges occurring at 6:00 A.M.
wash out the contact aeration tanks and exceed the solids
loading capacity of the final clarifiers. More poundage of
solids are put into the final clarifiers in a short period of
time than can be removed by, the return sludge flow,
resulting in the final clarifiers filling up with solids and
dumping. Adjustment of the final clarifier return sludge
flow rates to compensate for the varying influent flows is
difficult due to the wide variation in the liquid hydraulic
levels in the siphon suction drawoff type final clarifiers.
Process control to prevent solids dumping at this plant
requires attention to clarifier sludge blanket depths and
influent and return sludge flow rates. In order to expand the
usable capacity of the plant and to remedy some of the
hydraulic variation effects, we are considering the installa-
tion of additional final clarifiers to handle above average
daytime flows and also upstream holding tanks to help
equalize the flow between daytime and nighttime.
Foaming
A problem which recently developed at one of our
activated sludge plants is the production of a heavy,
voluminous foam in the aeration tanks. The foam is dark
and greasy and cannot be dissipated with the usual spray
water. The foam, containing considerable solids, will
overflow the aeration tanks and literally spread across the
plant site if unchecked, causing nuisance and odor
conditions. The foam causes a thick greasy scum to form on
the final clarifier surfaces which often spill over into the
effluent. The foaming material is incorporated into the
mixed liquor and lessens its density, thus decreasing the
sludge's normal settleability. The anaerobic digesters have
also experienced a severe foaming problem during this time.
It was initially believed that the foaming was due to the
activated sludge system's sludge age, but exhaustive process
control proved this not to be so. Attention was then
diverted to the possibility of influent synthetic detergents or
other industrial wastes, and an extensive analytical waste
monitoring program was initiated to identify the causative
agent and locate its source. The analytical tests included oil,
grease, ionic, nonionic, and cationic detergent determina-
tions for the plant flows and selected industrial contribu-
tors. After considerable research effort, we have concluded
that it is not a single factor such as oil or grease causing the
foaming problem, J>ut more likely a combination of factors.
After several exasperating months of having foam and
sludge moving around the plant grounds, we found a fairly
economical commercial defoaming agent. This defoamer
reduces the foam level in the aeration tanks to an acceptable
level and prevents its overflowing. However, we've felt that
this is only treating the symptoms and is not a corrective
process control measure. Some interesting recent outside
research indicates that a particular foam producing
bacteria, actinomycetes, may proliferate in activated sludge
systems where there is no anaerobic digester supernatant
returned to the activated sludge system. This research
indicates that anaerobic digestors produce a toxic agent
which prevents actinomycetes growth and foam production
in most plants. As a possible coincidence, we had
discontinued returning anaerobic digestor supernatant to
the activated sludge system at this plant two months before
the foaming first occurred. We have now reinstituted a
program of limited digestor supernatant return to the
aeration system, but since the plant's own anaerobic
digestors are themselves foaming, the test supernatant is
being trucked in from another plant.
Capacity Upgrading
The need arose at another of our activated sludge plants
to double the existing treatment capacity before construc-
tion of the expansion facilities could be completed. The
original facility treating domestic wastewater had a 5 MGD
capacity and utilized a conventional plug flow activated
sludge system with both primary and final gravity clarifiers.
The plant was required to produce a 20 mg/1 SS and BOD
effluent. Considerable bench and full scale pilot work was
undertaken to investigate alternatives for increasing the
plant's capacity. The method selected for increasing the
capacity was to institute a process modification and to exert
close process control over the entire plant operation. The
aeration system was changed from the plug flow mode to a
contact-stabilization system. Incidentally, this change
resulted with our having an empty aeration tank left over.
Alum and polyelectrolyte feed facilities were installed, and
alum was added to the contact aeration tank at a point
providing fifteen minutes detention in the tank. The mixing
in the contact aeration tank provided excellent flocculation
with an alum feed dosage of only 25 mg/1., and a small,
densely compacted activated sludge-alum floe was pro-
duced. An organic polymer at a dosage of 1 mg/1 was added
to the contact aeration tank effluent at a manhole just prior
to its entering the final clarifiers. The flow's gentle roll in the
manhole and clarifier influent structures provided adequate
flocculation of the activated sludge-alum-polymer floe. The
result was a large dense floe which rapidly settled in the
overloaded final clarifiers, then being operated at a surface
loading rate of 1100 GPD/square foot. The small alum
dosage used did not create a measurable increase in sludge
production, and the overloaded anaerobic digestors were
able to handle the sludge without any adverse effects.
Overall, the process was very stable and reliable but
required close control of the solids inventory as higher
solids levels tended to be washed out by heavy rains. The
extra treatment capacity was obtained with a relatively
small cost expenditure for the chemical feed equipment and
a low $ 170 per day increment of operating cost for alum and
polymer. The success of the temporary process control
technique has led us to consider it for a permanent further
76
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expansion of this plant.
Force Main System
Most of our service area is extremely flat with elevations
ranging from only five to fifteen feet above sea level. The
majority of the wastewater flows are pumped long distances
from outlying neighborhoods to our plants through force
mains. The distances pumped through the force mains
approach twenty miles and the detention time in the force
mains approach twenty-four hours. Such a collection
system as this presents two difficult process control
problems in the treatment plants—a highly septic plant
influent sewage and a very marked diurnal flow pattern.
Sewage arrives at two of our activated sludge plants in a
very septic condition. The dissolved oxygen of the domestic
sewage is zero, its hydrogen sulfide content approximately
10 to 12 mg/1, and the color is dark black. This septic
sewage causes several problems with the biological
processes. First, a severe odor problem is created within the
plant and extending to adjacent neighborhoods and
industrialized areas. This rotten egg odor is highly
objectionable to the people working and living in the area.
Various methods have been tested to eliminate or reduce the
odor levels. One of the early attempts was to return
activated sludge to the plant headwords to freshen the raw
influent sewage. Chlorination of the raw influent flow was
tested both at low and at massive dosage levels. Chlorina-
tion at low dosages of 20 to 30 mg/1 just prior to the
headworks was completely ineffective. Massive chlorination
of the septic sewage was tested at our 24 MGD contact
stabilization plant having no primary clarification. Chlorine
dosages of 50 to 60 mg/1 applied approximately thirty
minutes upstream of the plant proved to be effective in
reducing the hydrogen sulfide and odor levels at the plant's
headworks. However, the heavy chlorination tended to
"sterilize" the influent wastewater, and chlorine residuals of
1 to 2 mg/1 were carried though the plant's preliminary
treatment works and into the aeration system. This chlorine
residual carried into the aeration tanks knocked out the
contact stabilization activated sludge process and complete-
ly prevented an active biomass from reforming during the
entire six month project. Although successful from an odor
control standpoint, the project had to be discontinued. We
have also tested air stripping, masking agents, nitrous oxide
and hydrogen peroxide as odor control measures. Of these,
only hydrogen peroxide has proven successful in reducing
odor levels. Hydrogen peroxide is applied at dosages of IS
to 20 mg/1 at a point approximately fifteen minutes
upstream of the plant's headworks. The peroxide oxidizes
the sewage organics and the sewage has a bleached color
when it reaches the plant. Although the hydrogen peroxide
is effective, its daily operating cost of $700 per day is too
expensive and we are presently pursuing other methods. A
side benefit claimed for the hydrogen peroxide treatment is
that influent BOD levels are reduced by about 5%.
Sludge Handling
From the standpoint of our own experience, we would
say that the single most critical factor in process control of
biological treatment systems is sludge handling. It is a futile
and disheartening experience to attempt process control
over a biological process when its related sludge handling
facilities are either inoperative, inadequate or incompatable.
It is impossible to maintain process control over biological
systems where waste sludge cannot be effectively removed
when and in the quantities required. We have found
ourselves in severe problems over the past few years when
the construction of our sludge handling facilities was
delayed up to several years behind the upgrading and
expansion of our sewage treatment plants. Under these
situations, we have had to utilize innovative techniques to
stretch our existing sludge handling capabilities. Although
sludge handling may not generally be thought of as a
biological process control measure, the overall operation of
a sludge handling system is indispensible to process control
of other biological treatment systems and therefore merits
mention here.
Most of our older plants utilize anaerobic digestion for
sludge disposal. In almost every instance, the original
digestion facilities consisted of primary and secondary low
rate digestion. These systems became too overloaded to
function properly when the plant flows and sludge
production increased. With imminent failure of the
anaerobic digestors threatening to upset the biological
processes, the secondary digestors were converted to
primary digestors, and the sludge feed was increased to
operate all digestors at higher rates. Digestor supernatant,
which was formerly separated in the secondary digestors
and returned to the plant flow, was either piped or trucked
to sludge holding lagoons. This modification greatly
increased the sludge digestion capacity of the plants and
allowed their continued successful operation. Due to land
limitations at one plant preventing construction of sludge
lagoons, a solid bowl scroll centrifuge was installed to
dewater the combined primary digestor transfer sludge. The
cake was then landfilled in a much smaller area than would
have been required for the liquid sludge.
Another activated sludge plant went on line four years
prior to the completion of its centrifugal dewatering/ incin-
eration sludge handling facilities. In the interim, sludge
handling was accomplished by converting two spare
aeration tanks into aerobic digestors providing twenty days
detention. The unthickened aerobically digested sludge was
then pumped three miles and applied to unused open farm
land. The digested sludge was spray irrigated for the first
two years onto a planted grass cover crop. During a later
project, the digested sludge was pumped through a 600 foot
flexible hose dragged by a tractor and directly injected
beneath the soil surface. The soil could be walked over
immediately after injection and there was no surface runoff
from this system. The system's major advantages were its
lack of nuisance conditions and its soil enrichment
potential.
Pilot Studies
Our organization has conducted extensive large scale
pilot work over the past few years for purposes of either
prototype design, interim plant upgrading, or process
control. We have tested a varied assortment of proposed
processes; we have either considerably altered or altogether
abandoned many of the projects.
A four month pilot study was undertaken of a proposed
lime clarification-biological nitrification advanced waste-
77
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water treatment process. This 100 gallon per minute pilot
unit utilized a high purity oxygen activated sludge system.
As a result of the study, we concluded that the proposed
process would work and could produce the desired effluent,
but that the biological nitrification system was too sensitive
to pH and shock loading caused by upsets in the lime
clarification system, and therefore the proposed system was
not practical from a process control standpoint.
Over a year's pilot work was performed on all types of
centrifugal dewatering devices for all types of sludges—
primary, waste activated, digested, alum and lime sludges.
The information gathered here was used for the design of
six large centrifugal dewatering facilities. A Porteous Heat
Treatment Process was piloted for three months to test its
dewatering capabilities on a high strength industrial waste
activated sludge. We concluded from the study that
resolubilization of the sludge would create too high a return
loading on the activated sludge process and would further
complicate an already difficult biological process control
problem. A Purifax Sludge Treatment Process was piloted
at several of our plants, and one unit was installed for
handling excess undigested sludge. Also tested was a flash
dryer in which undigested sludge was quickly accelerated to
high speeds and completely dried within a few seconds. The
end product would be pelletized and used as fertilizer.
Personnel Development
One last item directly related to process control of
treatment operations is personnel qualifications. It is most
important to staff the wastewater treatment plants with
personnel who understand and are fully qualified to control
the treatment processes. We are operating sophisticated
treatment plants which are designed and operated based on
complex biochemical engineering principles, and it is
unreasonable to expect untrained personnel to grasp the
complexities of these processes and successfully operate the
plants. Our organization is strongly emphasizing the need
and the requirement for operators to have secondary school
and advanced education. We promote and sponsor
operator's attendance at training schools for wastewater
treatment plant operation, and we have conducted our own
school for wastewater operators for several years in
addition to the on-the-job training given each operator.
Also, it is just as necessary to maintain a competent staff of
trained engineeres, biologists and chemists to provide the
supervision and assistance required in the operation of these
complex treatment facilities.
Development and
Improvement of the
Municipal Sewage Biological
Treatment Facilities.
Yershov A., Kyghel M., Zemlyak M.,
candidates of sciences
The paper describes aeration tank types of new designs
used for municipal sewage biochemical treatment, deve-
loped by the Scientific Research Institute for Municipal
Economy. The paper provides technological basis of this
equipment designing.
A conclusion of the necessity for choosing a certain
aeration tank depending on conditions and special features
of the sewage system is given.
The achievements of chemical engineering are the ground
for modification of equipment arfd technology in the field of
biochemical sewage treatment, particularly, the activated -
sludge process.
There are three types of aeration tanks used in biological
oxidation of contaminations by activated-sludge process:
plug-flow, mixing tanks and combined systems.
Of all these types the mixing tanks are every more wide
spread on a large scale that have been used lately only for
high concentrated wastewater treatment. More profound
research of kinetics and the pattern of sewage activated
sludge biological oxidation allowed to modify this process,
in particular, the methods of rapid removal of low
concentrated wastewater, prevailing in suspended and
colloidal form. The rapid removal process is due to the
phenomena the kinetics of which is similar to adsorption
process kinetics that is why such modification is called on
condition as "biosorption". In municipal sewage treatment
the rapid removal process in some cases is characterized by
zero order equations that is over the range of low
concentrated contaminations the process rate does not
depend upon concentration; sewage retention time in the
aeration tanks generally is determined by reactors type, that
is by the hydrodynamic conditions in the aeration tank.
Thus, municipal sewage with low concentrated impurities
(BOD up to 200 g/m3) can be treated in a complete mixing
system because under these conditions the activated sludge
biosorption capacity is used. Municipal sewage with an
average concentrated impurities (BOD from 250 to 350
g/m3) can be treated in the plug flow reactors because
complete oxidation organic matters process with active
mass growth must take place. However, taking into
consideration that municipal sewage impurities are mainly
in the form of small dispersed suspended solids colloid
matters, complete mixing aeration tanks or combined tanks
can be used, under economical grounds and rational
installation design. High concentrated municipal sewage
(BOD from 400 to 600-800 g/m3) can be treated in the
multistage plants as activated sludge is adapted properly to
changed load at every step depending on concentration
changes of organic matters during the process. On the other
hand the step sludge process gives the possibility to decrease
sludge growth and to increase general rate and degree of
process proceeding. Due to these factors, step-sludge
78
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process can be used for treatment of a low concentrated
municipal sewage. On account of these conditions the
various models of aeration tanks were designed: mixing
systems equipped with mechanical aerators and different
modifications of aeration tanks-clarifiers with activated
sludge fluidized bed; multistage basins with successive
compartments or fluidized beds are used as plug-flow
reactors.
For treating the low concentrated municipal sewage the
main part of which consists of unevenly flowing biodegrable
industrial wastes contact stabilization aeration tanks
equipped with turbine aerators were developed, (fig. 1).
For average concentrated municipal sewage treatment
aeration tanks-clarifiers and settling tanks with sedimenta-
tion zone equipped with pneumatic and mechanical aerators
begin to be used together with conventional long-form plug
flow aeration tanks. These facilities provide the impurities
removal (oxydation) and separation of sludge mixed liquor
in one and the same technological unit. The main advantage
of combined facilities is simultaneous usage of the whole
activated sludge mass in sewage purification process. In
view of sludge mixture increased recirculation between
aeration and clarification zones there it is set practically
uniform oxygenation regime and uniform activated sludge
load. The above mentioned factors provide oxygenation
process practically through the whole volume.
As a variety of combined aeration tanks with settling
zone aeroacclerators used for a low and average concentrat-
ed municipal sewage treatment with the capacity over the
range from 5000 to 50000 m3/d can be applied.
Aeration tanks - clarifiers are rectangular basins divided
baffle plate into aeration and clarification zones (fig. 2).
Raw wastewater is distributed into aeration zone where it is
mixed with activated sludge, and mixed liquor flows
through the openings into the degazation zones and then to
the clarification zones.
Aeration tanks-clarifiers include contrary to aeration
settling tanks the system of baffle plates providing directed
circulation of mixed liquor as a result of which downtake
flow rate increases in clarification zones and activated
sludge fluid-fluidized bed is formed. The presence of stable
fluidized bed is due to the increased recirculation of mixed
liquor on one hand, and on the other hand it promotes
increased recirculation that is intensification of mass
exchange between aeration and clarification zones.
In practice under the rational structural design these
factors permit to transfer the impurities oxydation process
to activated sludge fluidized bed that is to use it as a reactor.
Increasing process removal rate in fluidized bed is explained
by intensity of mass transfer under nitration mixing
condition. This stage is proved by the experiments as it is
shown on the fig. 3.
The curve 1 shows the process in aeration tank-clarifier
with oxydation of impurities mainly in fluidized bed (ratio
of fluidized bed and aeration zone volumns is 4:1); the
curve 2 - depicts the process with partial transference into
fluidized bed (ratio of volumes is respectively 1:0,7); the
curve 3 characterizes the process in aeration settling tanks
(Municipal Economy Academy types, USSR) and "Degre-
mont" oxycontact, French firm (the data are approximat-
ed).
Hydraulic loading on activated sludge fluidized bed
depended on MLSS concentration is the main factor
limiting aeration tanks-clarifiers capacity. This relation is
shown on the fig. 4. Optimum sludge concentration is
determined in its turn, by sewage impurities concentration
• that is by organic matters load on the facilities. For
municipal sewage the range of activated sludge concentra-
tion in aeration tanks-clarifiers is within the limits of 2 - 5
g/1 that corresponds to a hydraulic loading in values 1 - 2,5
m3/m2 • h(0,3 - 0,7 mm/s).
Two typesizes aeration tanks-clarifiers are design for
municipal sewage treatment stations of the capacity 17000 -
160000 m3/d. Besides, aeration tanks-clarifiers designing
principle is a base of long-form aeration tanks intensifica-
tion by means of their reconstruction into aeration tank-
clarifiers. Although aeration zone volume is too high, there
is necessity to use secondary settling tanks and total
biological treatment complex capacity increases. There is
also some possibility of increasing activated sludge
operational concentration. The calculations for reconstruc-
tion of present long-form aeration tanks into aeration
tanks-clarifiers at the municipal sewage station, the
Ukraine, have given the following results: according to
11-32-74 total sewage retention time in aeration tanks
and secondary settling tanks accounts for 13 h. at the
oxydation rate in aeration tanks equal to 22,6 mg BODs/g.
of sludge after the reconstruction sewage retention time in
aeration tanks-clarifiers has become 7,73 h at oxydation
rate 25,2 mg BODs/g of sludge/h. The secondary settling
tanks can now be used for intensification of the other
aeration tanks.
The hydraulic principle of aeration tanks-clarifiers
desining was used to developed various technological
modifications of small and average plants equipped with
mechanical aerators in order to form fluidized bed.
Two compartment aeration settling tanks use step-sludge
sewage treatment process at a low oxydation rate securing
sludge stabilization (total oxydation process).
Aeration zone is divided into successively operating
compartments. The first compartment (stage) accepts high
loads levelling their changes, securing the concentration of a
considerable part of impurities on the activated sludge floes.
A certain part of MLSS from the first stage compartment
with the flow that is equal to the sewage flow outlets into the
second stage where organic matters and the sludge grown in
the first stage are mineralized by the sludge adapted to a low
oxydation rate. Clarification zone and the second stage
compartment have common inner recirculating flow
creating activated sludge fluidized bed in this zone as in
aeration tanks-clarifiers.
The first stage of two compartment aeration settling tanks
is equipped with cylindrical or impeller rotor aerators; the
second stage is equipped with longitudinal rotation axis
cylindrical rotor aerators.
Hydrodynamic scheme of the combined aeration unit
with cylindrical rotor aerator is characterized by flow lines
on one plane and thus simplifying its calculation and
maintenance.
The further development and modification of aeration
tank-clarifiers tends to the facilities design with spread
activated sludge fluidized bed surface without volume
increasing and with intensified vortical circulation within
the beds. This provides high hydraulic capacity of the
aeration tanks-clarifiers, decreases' sewage retention time
and increases sewage treatment quality.
79
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Together with combined aeration facilities CMAS-
aeration tanks with secondary settling tanks are widely
used; they are stable to load changes during the day. These
facilities are used at small communities, towns and
municipal sewage treatment plants designed for the capacity
up to 7000 m3/d with food industry wastes of high
concentrated impurities, flowing from the enterprises
located there. Radial type aeration basins APT and
circulation oxydation ditches UOK. were developed for
these purposes. Both facilities are equipped with mechanical
longitudinal rotation axis rotor aerators.
APT is a cylindrical basin (fig. 5) with concentrically
installed secondary settling tank. The ring space is used as
an aeration compartment equipped with rotor aerators.
UOK. is a circular ditch (aeration tank) with rotor
aerators; secondary settling tank is situated apart from the
ditch (fig. 6). The secondary settling tank is of a vertical type
(fig. 7). It has intensified hydrodynamic scheme permitting
to increase considerably its capacity in comparison with
"orthodox" type.
The calculations of the process rates and other kinetic
parameters for described new aeration facilities are based
on the unified method of the USSR BUILDING STAND-
ARDS and regulations H-32-74, however, the
calculations have some peculiarities in any single case due to
facilities hydrodynamic characteristics.
Practical application of the facilities is secured with a set
of experimental and standard designs and unified aeration
equipment.
Legend to figure 1
Contact stabilization aeration tank.
1 - sewage inlet
2 - turbine aerators
3 - return sludge inlet from secondary settling tanks
4 - discharge lines
5 - outlet of mixed liquor to secondary settling tanks
6 - contact basin
7 - stabilization basin
Legend to Figure 2
Aeration tank - clarifier
1 - clarification zone
2 - gates
3 - aeration zone
4 - overflow trough
5 • degazation zone
6 - cap
7 - trough for treated water collecting and discharging
8 - surplus sludge outlet
9 - opening
10 - aerators
11 - sewage inlet
12 - "tooth"
13 - baffle plate
Legend to figure 3
Isotherms of impurities removal in combined aeration facilities
(Explanations are given in the text).
Legend to Figure 4
Activated sludge fluidized bed calculated hydraulic load dependan-
cy on its MLSS concentration.
Legend to Figure 5
Radial type aeration basin.
1 - aeration compartment
2 - secondary settling tank
3 - rotor aerators
4 - treated water outlet
5 - MLSS outlet to recirculating pump
6 - surplus sludge outlet
7 - return sludge inlet by means of recirculating pump
Legend to figure 6
Circulating oxydation ditch
1 - shelter
2 - UOK
3 - recirculating sludge pump
4 - secondary settling tank
5 - rotor aeration tanks
Legend to figure 7
UOK secondary vertical settling tank
I - sewage inlet
2 - distributing compartment
3 - Roatting matters outlet
4 - collecting funnel
5 - toothed weir
6 - baffle plate
7 - distributing trough
8 - trough for treated water collecting and draining
9 - discharge pipe
10 -cylindrical baffle
11 - sludge outlet
Protocol
of the third Meeting of the USA and USSR delegations on
the problem of Prevention of Water Pollution from
Industrial and Municipal Sources (Moscow, USSR, August
22 - September 5, 1976)
In accordance with the Memorandum of the third
Meeting of Joint USA-USSR Commission on Cooperation
in the field of Environmental Protection (Washington,
October 1975) the USA and the USSR delegations Meeting
on the problems of Waste Water Treatment was held in
Moscow, August 22 - September 5, 1976.
The Soviet delegation was headed by Prof. S.V.
Yakovlev, Director of the Scientific Research Institute
VODGEO, Honoured Scientist of the RSFSR.
The American delegation was led by Mr. J.T. Rhett,
Deputy Assistant Administrator, Water Program Opera-
tions, EPA.
The list of participants is attached in Appendix I.
In the course of the Meeting the following was accomp-
lished:
I. The Symposium "Intensification of Bio-Chemical
Treatment of Waste Waters".
2. The accomplishments of the 1976 Program of
cooperation were discussed.
3. Coordination of the Working program for 1977 was
agreed upon.
80
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1
At the Symposium 15 reports were delivered: 8 reports
were delivered from the Soviet Side and 7 reports from the
American Side.
The list of reports delivered is attached as Appendix II.
Of particular interest were reports delivered by the Soviet
specialists on technical oxygen usage for industrial waste
water treatment and bio-chemical treatment of highly
concentrated waste waters as well as the reports delivered by
American specialists on combined physical-chemical and
bio-chemical treatment processes and on designing of bio-
chemical treatment systems with the use of oxygen.
The delegations have agreed that each side will publish all
reports in the necessary number of copies in its own
language prior to February 1, 1977 and will distribute them
among interested organizations. The sides will exchange 10
copies each of the published Proceedings of the Symposi-
um.
In the course of the Meeting the specialists discussed the
results of current researches carried out in accordance with
the Program of cooperation and exchanged scientific and
technical literature.
The delegations determined and coordinated the program
of cooperation for 1977 (Appendix III).
The sides have agreed that the Symposium "Physical-
Mechanical Waste Water Treatment Facilities" will be held
in the USA, April 3-17, 1977.
The following has been agreed about the preparation of
the forthcoming Symposium:
—each side will present 5-7 reports at the Symposium;
—the sides will exchange the report titles by February 1,
1977.
—the texts of the reports will be exchanged in Russian
and in English prior to March 1, 1977.
Organizational Work for carrying out the Symposium
"Recycling Water Supply Systems and Reuse of Treated
Effluents at Industrial Enterprises" to be held in the USSR,
September 18 - October 2, 1977 will be considered in the
course of the delegation meeting in April 1977.
In 1977 an exchange of specialists will be carried out:
—of Soviet specialists in the USA on the problems of
waste water treatment, and
—of American specialists in the USSR on the problem of
waste water treatment and reuse.
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 USSR the American
delegation visited industrial and municipal wastewater
treatment plants in Ufa, Leningrad, Shekino, Baikalsk and
Tashkent, and a number of scientific research and project
institutes in Moscow, Leningrad and Tashkent.
Both sides expressed their satisfaction that the Meeting
was conducted in an atmosphere of friendship and mutual
understanding thus contributing to the further development
and strengthening of cooperation in the field of environ-
mental protection.
This protocol was signed on September 4, 1976 in two
copies, in Russian and English, both texts being equally
authentic.
From the Soviet Side
S.V. Yakovlev
Chief of Delegation
From the American Side
John T. Rhett
Chief of Delegation
Appendix I
List of Participants from the Soviet Side
S. Yakovlev
Director, VNII VODGEO, Prof. Chairman of the USSR
Delegation
D. Slavolyubov
Chief of the Department, Glavpromstroyproekt.
GOSSTROY USSR
I. Skirdov
Head of the laboratory, VNII VODGEO cand. techn. sci.
V. Ponomarev
Head of the laboratory, VNII VODGEO cand. techn. sci.
P. Kandsas
Head of the laboratory, VNII VODGEO cand. techn. sci.
I. Myasnikov
Head of the Sector, VNII VODGEO cand. techn. sci.
V, Shvetzov
Head of the Sector, VNII VODGEO cand. techn. sci.
A. Nechaev
Senior Researcher, VNII VODGEO cand. techn. sci.
M. Voronina
Senior Engineer, VNII VODGEO
N. Nelubina
Interpreter
GOSSTROY USSR
List of Participants from the
American Side
J. Rhett
Chairman of the US Delegation Deputy Assistant Adminis-
trator for Water Program Operations, EPA.
A. Paretti
Consultant, Water Program Operations.
A. Cywin
Senior Science Advisor, Office of Water & Hazardous
Materials.
81
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W. Lacy
Senior Engineering Advisor, Office of Research & Develop-
ment.
W. Rosenkranz
Director, Waste Management Div.
F. Sebastian
President, Waste Water Equipment Manufactures Associa-
tion.
F. Harper
General Superintendent, Orange County Sanitation Dis-
trict.
W. Love
General Superintendent
Hampton Roads Sanitation District.
B. Sumner
President, U.S. Council of Consulting Engineers.
A. Malyshev
Interpreter, Colorado College.
Appendix II
Reports
of reports presented at the USSR-USA Symposium
"Intensification of Bio-Chemical Treatment of Waste
Waters"
From the Soviet Side
1. Yakovlev S.V., Skirdov I.V., Shvetzov V.N., Rogovs-
kaya C.I. (VNII VODGEO) "Kinetics of Biochemical
Oxidation".
2. Skirdov I.V., Shvetzov V.N., Bondarev A.A., Lurie
B.I., Bereyskina I.G., Katkova S.E. (VNII VODGEO,
Complex "ASOT" in Shekino) "Operation Experience
of Oxytanks".
3. Shvetzov V.N., Morosova K.M., Gubina L.A. (VNII
VODGEO) "Biochemical Treatment of Wastewaters
from W001-Scouring Operations".
4. Yakovlev S.V., Karjuhina T.A. (MISI) "Biological
Waste Water Treatment in the Presence of Steroid
Compounds".
5. Shifrin S.M., Mishookov B.C., Ivanov G.V., Goloo-
bovskaya E.K. (LISI) "The Trends in Intensification in
Biochemical Treatment of High Density Wastewater".
6. Gerber V.Y. (Bash. Nil NP) "Facilities Improvement
for Biochemical Treatment of Petroleum Refinery
Wastewaters".
7. Skirckyavichus R.L. (The Ministry of Municipal
Economy of the Lithuanian SSR) "Studies of
Artificial Aeration in the Lithuanian SSR".
8. Yershov A., Kyghel M., Zemlyak M. (NIKTI GH)
"Development and Improvement of the Municipal
Sewage Biological Treatment Facilities".
From the American Side
1. A. Cywin (EPA) Enchancement of Biological Waste
Water Treatment'by Chemical Addition in the Petro-
chemical Industry.
2. W. Lacy (EPA) "Steel Industry Waste Water Treat-
ment Using Biological-Chemical Technology".
3. W. Rosenkranz (EPA) "Biological Methods for
Control of Nitrogen in Municipal Waste Waters".
4. F. Sebastian (EPA) "Improvements for Pulp and
Paper and Municipal Treatment Processes".
5. F. Harper (EPA) "A Comparison of Conventional
Activated Sludge Process and Pure Oxygen Activated
Sludge Process for a 75 MGD Secondary Treatment
Facility".
6. B. Sumner (EPA) "Report on the State of the Art of
Biological Waste Treatment in the Organic Chemical
Industry in the United States".
7. W. Love (EPA) "Analytical and Process Improve-
ments in Municipal Bio-Chemical Wastewater Treat-
ment".
Appendix III
Program
USA-USSR Cooperation of Working Group on Prevention of Water Pollution from
Industrial and Municipal Sources
No. Title
I. Modernization of existing and de-
velopment of new combined facili-
ties with high efficiency for waste-
water treatment, including hydrocy-
clones, multistage settlers, Rotators,
facilities with utilization of technical
oxygen, investigation of usage of
flocculants and coagulants.
Form of Work
Joint development
of themes, scientific
information and spe-
cialists delegation
exchange.
Responsible for
from the from the
USSR USA
VNII VODGEO EPA
Gosstroy
USSR
Time Expected Results
1978 Improvement of the efficiency
of existing and development o
new treatment facilities, reduc-
tion of space for location, re-
duction of reagents and cost
price of waste water treatment
Development of hydrocyclones and
flotation facilities; schemes of usage
of coagulants.
Symposium on
"Physical-Mechani-
cal Waste Water
Treatment Facilities"
(USA, Cincinnati,
April 3-17, 15 days,
8 specialists)
VNII VODGEO
82
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No.
2.
3.
Title
Development of tubular and plate
settlers and facilities with utilization
of technical oxygen; schemes of
usage of flocculants.
Intensification of wastewater treat-
ment process in petrochemical,
chemical, petroleum refining, pulp
and paper industries, and metallur-
gical industry.
Intensification of wastewater treat-
ment process in petroleum refining
industries, and metallurgical indus-
try.
Intensification of wastewater treat-
ment process in petrochemical and
pulp and paper industries.
Development of highly efficient me-
thods and facilities for removal of
nutrients and treatment of municipal
wastewaters; usage of treated efflu-
ents in recycling systems at indus-
trial enterprises.
Development of methods and facili-
ties for removal of nutrients and
treatment of municipal wastewaters.
Usage of treated effluent in recycling
systems at industrial enterprises.
4. Treatment of wastewater sludges.
Stabilization and dewatcring of was-
tewater sludges.
Technology and facilities for utiliza-
tion and treatment of wastewater
sludges.
5. Exchange of two Soviet specialists
for 2 months in US on the problem
of usage of technical oxygen at
biological waste water treatment
plants.
Exchange of two American special-
ists for 2 months in the USSR on
the problems of wastewater treat-
ment and reuse.
Form of Work
Symposium on
theme: "Recycling
water supply systems
and reuse of treated
effluent at industrial
enterprises" (USSR,
Moscow, Septem-
ber 18-October 2,
1977, 15 days, 8 spe-
cialists).
Information and
delegation exchange
Joint development
of themes, informa-
tion and delegation
exchange
Information and
delegation exchange
Study of research
work of American
'companies and or-
ganizations, partici-
pation in scientific
studies.
Acquaintance with
research work of the
Soviet organizations
and institutes, par-
ticipation in scientif-
ic studies.
Responsible for
from the from the
ISSR
I:SA
EPA and
appropriate
industries
Time
VNI1 VODCEO
Gosstroy
USSR
VN1I VODGEO
EPA
1978
VNll VODGEO
Gosstroy
USSR
VNH VODGEO
EPA and
appropriate
industries
EPA
1977
VNll VODGEO
Gosstroy
USSR
VNII VODGEO
EPA and
appropriate
industries
EPA
1977
EPA and
appropriate
industries
Expected Results
Increasing of wastewater treat-
ment efficiency of existing
treatment plants, introduction
of new treatment schemes,
maximum usage of treated ef-
fluents in recirculation.
Development of new treatment
facilities for prevention of wa-
ter basin eutrofication and de-
velopment of new treatment
systems with maximum usage
of treated effluents in recycling
systems at industrial enter-
prises.
Reduction of cost price of
waste water sludge treatment,
increasing of treatment facili-
ties efficiency.
VNll VODGEO
Gosstroy
USSR
EPA
HI Quarter Studying of the USA expe-
1977 rience in the field of waste
water treatment.
Ill Quarter Studying of the USSR expe-
1977 rience in the field of waste
water treatment.
NOTE: Companies to be involved in carrying out the joint activities on the American Side will be named at the 4-th meeting of
specialists, April 1977. in the USA.
83
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Appendix IV
Itinerary
for the US-Delegation Stay in the USSR at the US-USSR
Symposium" Intensification of Bio-Chemical Treatment of
Waste Waters".
Sunday, August 22
Flight CY-242 Arrival at the airport. Putting
19:10 up at the hotel.
9:00
9:15
9:45
10:25
11:05
11:20-11:35
11:35
12:15
12:55
13:10
14:10
14:50
15:30
15:45
Monday, August 23
Discussion on the program for the
US-Delegation stay in the USSR.
Opening ceremonies of the
symposium
Yakovlev S.V., Skirdov I.V., Shvet-
zov V.N., Rogovskaya C.I. (VN1I
VODGEO), "Kinetics of Biochemi-
cal Oxidation."
Cywin A. (EPA) "Enhancement of
Biological Waste Water Treatment
by Chemical Addition in the Petro-
chemical Industry."
Discussion.
Break.
Shifrin S.M., Mishookov B.G.,
Ivanov G.V., Goloobovskaya E.K.
(LICI)" The Trends in Intensifica-
tion in Biochemical Treatment of
High Density Wastewater."
Lacy W.J. (EPA) "Steel Industry
Waste Water Treatment Using
Biological-Chemical Technology."
Discussion.
Break.
Gerber V.Y. (Bash. Nil NP) "Facili-
ties Improvement for Biochemical
Treatment of Petroleum Refinery
Wastewaters".
Rosenkranz S. (EPA)" Biological
Methods for Control of Nitrogen in
Municipal Waste Waters."
Discussion.
Skirdov I.V., Shvetzov V.N., Bon-
darev A.A., Lurie B.I., Bereyskina
I.G., Katckova S.E. (VNII VOD-
GEO, SHekinsky Complex
"ASOT") "Operation Experience of
Oxytanks".
16:25
9:00
9:40
10:20
10:35
10:50
11:30
12:10
12:25-13:25
13:25
14:05
14:45
15:00
15:40
16:00
10:00
Flight N 341
14:55
Discussion.
Tuesday, August 24
Sebastian P.P. (EPA) "Improve-
ments for Pulp and Paper and Mu-
nicipal Treatment Processes".
Yakovlev S.V., Karjukhina T.A.
(MISI) "Biological Waste Water
Treatment in the Presence of Ste-
roid Compounds.)
Discussion.
Break.
Harper F. (EPA) "A Comparison of
Conventional Activated Sludge Pro-
cess and Pure Oxygen Activated
Sludge Process for a 75 MOD Se-
condary Treatment Facility".
Skirckyavichus A.L. (The Ministry
of Municipal Economy of the Li-
thuanian SSR, KPI) "Studies of
Artificial Aeration in the Lithuanian
SSR;"
Discussion.
Break.
Sumner B. (EPA) "Report on the
State of the Art Biological Waste
Treatment in the Organic Chemical
Industry in the United States
Shvetzov V.N., Morosova K.M.,
Gubina L.A. (VNII VODGEO)
"Biochemical Treatment of
Wastewaters from Wool-Scouring
Operations".
Discussion.
Love B(EPA) "Analytical and Pro-
cess Improvements in Municipal
Bio-Chemical Wastewater Treat-
ment."
Discussion.
Adjournment.
Wednesday, August 25
Visit to the Scientific Research Insti-
tute of Municipal Water Supply and
Wastewater Treatment.
Leaving for Upha.
18:40 Arrival in Upha. Putting up
(16:40 Moscow time) at a hotel. Rest.
84
-------
10:00
Flight 340
20:05
20:00
23:55
8:25
11:00
z!5:00
23:55
8:25
12:00
Flight 121
19:59
8:05
10:00
14:00
17:00
Flight 3719
15:35.
20:05
Thursday, August 26
Acquaintance with Treatment Facil-
ities of Petroleum Refinery Plant in
Upha.
Leaving for Moscow.
Arrival in Moscow.
Leaving for Leningrad by train.
Friday, August 27
Arrival in Leningrad, putting up at
a hotel.
Visit to the Leningrad Department
of the Institute "Sojusvodocanalpro-
ject".
Acquaintance with Experimental
Pulp and Paper Complex in Kras-
nogorsk, VNPO BYMPROM.
Saturday, August 21
Sightseeing excursions around
Leningrad.
Sunday, August 29
Sightseeing excursions around
Leningrad.
Departure for Moscow by train
"Red Arrow"
Monday, August 30
Arrival in Moscow.
Visit to Shekino, visit to treatment
facilities of the Complex "ASOT.
Leaving for Irkutsk.
Tuesday, August 31
Arrival in Irkutsk, putting up at a
hotel.
Departure for Baikalsk by buses.
Visit to the treatment facilities of
Pulp and Paper Complex.
Leaving for Irkutsk by buses.
Wednesday, September 1
Leaving for Tashkent.
'Arrival in Tashkent, putting up at a
hotel.
10:00
15:00
Flight 5087
8:00
8:55
Flight 688
20:24
22:44
10:00
17:00
Thursday, September 2
Visit to the department of VNII
VODGEO.
Acquaintance with the Salar Aera-
tion Plant.
Friday, September 3
Leaving for Samarkand.
Arrival in Samarkand. Sightseeing
excursions around Samarkand.
Departure for Moscow.
Arrival in Moscow, putting up at a
hotel.
Saturday, September 4
Excursion to Archangelskoye.
Signing the protocol. Final Meeting.
Sunday, September 5
Departure.
as
-------
References
lerusalimskii, N.K., 1967, Academy of Science, USSR,
Series of Biology, No. 3,339.
Michaelis L., Menten M.L., 1913, Biochem 7,49,333.
Monod J. Annual Review of Microbiology, 1949, 3,371.
Hinshelwood, C.N., The Chemical Activities of Bacteral
Cee. Clarendon Press. Oxford, 1946.
Harbert D., 1961, Sonety of Chemical Ind. Monogr., N
12,25-5.
Dawning, A.Z., Wheatliand A.B., Paper Press to Mid.
Pranch. of Inst. of Chem. Eng. 1960.
Benedek, P., 1967, VITUK1 Report, N 20, Budapest.
Gyunter, L.I., Zaprudskiy, V.S., 1971, Collection Microbi-
ological Industry, No. 5.
Garrett, T.M., Sawejer, C.N., 1961, Ind. Waste Contr. Fed.
N 33, 800-816.
Eckenfelder, W.W., 1966, Ind. Water Poll. Contr. New-
York, Toronto, London.
McGabe, B.I., Eckenfelder, W.W., 1961, J. Wat. Poll.
Contr. Fed. 33,3,258.
Zhukov, A.I., Karelin Ya, A., Kolobanov, S.K., Yakovlev,
S.V., Sewerage System "Stroyizdat," Moscow, 1969.
Wuhrman, K., e.a. 1959, Schweiz, Ztschr. Hydrol., 20,284.
Yeilevich, M.A., Korovin, L.N., Shvytov, I.A., Inf. Biol II,
All Union School on Mathematical Modeling in Biology.
USSR Academy of Science, Pushchino, 1975.
Repin, V.N., Materials of the Scientific-Methodological
Conference of Aspirante MISI. Collection of Works, No.
62, Third Edition, Moscow, 1969.
Karelin, Ya. A., Zhukov, D.D., Rozanov, V.L., Research
on Waste-Water Treatment, Collection of Works, MISI,
No. 66, Moscow, 1970.
Smith, D.B., Sex. and Ind. Wastes, 24, 9 Sept., 1952.
Okun, D.A., Lynn, W.R., Biol. Treatment of Sw. and Ind.
Was'es. I. Aerobic Oxidation. R.P.C. New-York, 1956.
Bennet, G.F., Kempe, L.L., Chem. Geng. Poc. Symposium
Series, 1967, 63, N 78.
Joung, H.L., J. Bacterial, 1969, 97, N 3.
Goftlieb, S.F., J. Bacterial, 1969, 92, N 4.
Okun, D.A., Sewage Works Journal, 21, 1949.
McKinney, R.E., Pfeffer, S.T., Water and Sewage Works,
October, 1965.
Kariuskiy, A.A., Laskov, Yu.M., 1958, News of Higher
Institutes of Learning Construction and Architecture, 10.
Gilsderman, Yu.I., 1969, Mathematization of Biology,
Moscow, "Znaniya"
lyervsalimskiy, N.D., Neronova, N.M., 1965, DAN USSR
161, No. 6, 1437.
Vestali, D. 1972, Ferentative Catalyst, Moscow, "MIR"
Muzchenko, L.A., Gubin, V.A. Kautere, V.M., 1973,
Collection of Mathematical Modeling of Microbiological
Processes, Pushchino on the Oka.
86
-------
Table I
Operation data of counter-flow aeration tanks with air and oxygen supply and acetone as a substrate
Lest
Number
Oxygen Supply
1
2
3
4
5
6
7
8
9
10
11
12
Air Supply
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MLVSS
g/l
2.81
3.01
3.27
3.83
3.41
2.46
331
4.10
2.9
3.29
2.5
3.6
mean:
2.6
2.95
3.0
3.1
3.4
3.47
3.1
5.73
5.81
6.57
2.75
2.92
3.21
3.05
D.O.
Concentration
mg/l
11
7.3
17
10
10
14
7.3
14
14
16.5
13
13.8
12.7
2.5
2.5
2.4
2.3
3.1
2.7
3.2
3.3
3.6
3.2
3.0
3.0
3.4
3.2
Wastewater
COD
Influent
3962
4906
4610
4264
4850
3468
4667
5781
4089
4638
3525
5076
1070
1280
1026
1345
1475
1505
1007
2508
2257
2851
1193
1898
2808
2318
mg OV1
Effluent
132
154
174
99
61
71
174
102
125
166
94
981
69
54
84
76
84
307
125
55
120
104
31
23
61
46
Organic
Matter
COD
m'/day
7544
9333
8692
8223
9417
6727
11023
9034
7795
8819
6768
9307
8558
2402
2452
3982
2538
2782
2486
1760
1920
4280
5502
2397
3731
5037
1502
Specific
Oxidation
Rate
mg COD
g/hour
111.6
129.1
110.2
87.0
114
114
141.6
91.6
111.6
111.6
112.5
107.9
111.9
38.5
31.6
42.5
34.1
34.1
28.0
23.0
38.4
30.0
34.8
34.8
40.3
65.4
61.2
mean:
2.98
3400
39.4
iiiiiimry J.
Substrates
,
Desig-
nation
on
ri.ure
2
Flhyl alcohol I
Propyl alcnhol 3. 5
Ihupropyl alcohol 6
Butyl alcohol 4
Propyonic aldehyde?
Prapionic acid 8
Propylen glycoj 9
Benfalcohol 10
Ben/aldehyde 1 1
Ken/oic acid 12
Pyrocatechol 12
Rciorcipol 1 3
Hydrouuinone
Acelone
heptanol
lactic acid
acetylfornic acid
onho-creiot
meta-creaol
pira-crciol
14
15
16
17
18
Molecu-
Chemical lar
I 4
t'HtOH 3204
ClHiCH 46.05
OH'OH 6009
(CH)ICHOH 6009
CJ MO 12
UP"
(CHiHCO 5808
CHKCHlBCHlOH 11621
CHiCHOH CO:H 9008
CHJCO COlH 8806
CHH*OH 10814
CHiCiHOH 108 14
CHJC.IH4OH 10814
organic
carhon
rug m|!
mailer
5
0,37
0,52
ait
059
0.65
062
0.48
048
0.78
O.H
0.69
0.65
0.65
0-65
062
0.72
0,39
041
0,77
077
0.77
Water
My
1 I
6
90
200
40
33
30
451
2290
59
09
245
235
194
ton
m«O
mg
substance
7
156
184
23-24
2.22
240
220
151
157
2.51
241
2.0
1,9
189
1 86
217
2,7
1.07
091
2.31
245
245
BOD
maO
mj
substance
8
102-12
1)8
162
1 54
1 60
120
1 19
1 20
204
21
1.67
146
1.5
015
1,68
1.8
0.93
064
1 78
184
1.84
Kaho
BOD
COD
9
68-80
75
70
69.0
660
65
79
76.5
81
87.5
13.5
78.5
79)
8
77.4
7003
75
Diffe-
rence
COD-BOD
10
036
046
072
08
08
10
032
0.35
047
0)1
033
0.43
039
043
049
0.27
Oxidation
specific
rale
mg BOH
g il hour
II
2>-54»
I6.6<
141-215
167
16.6k
M.5
221
24.3
)5-3»
26
293
163-157
160
8-10
59-1)8
496
V™,,
m»O;
g • hour
12
•30
670
200
17
260
7J
45
125
158
202
3937
57)
415
K.
mjBOD COD-BOD
1
13
167
15
143
160
3.9
29
16
IS*
9.6
314
2163
12.3
0.786
COD
14
026
025
032
0.33
0.57
0.45
0.21
024
0.19
0 14
023
019
062
0.23
15
0022
0055
0.007
0.038
0.106
0.040
0 101
0.143
0069
(> D h\
V.irhurg
Sludge mm
increase m^ %, . ho|1I
* *
Id 17
Oil II
0..12 7
OSS 8
0,25 10.
016 II
031 28
024 240
062 17
193 21
108 19
IXiA IIMA
my si h\
summers
IK
13 5
125
I6X
98
150
184
143
235
158
Ihc number ..1
mid.Hii'n t drs skiduo
14
.' .10"
3 1(1"
,t III' '
4 10"
5 10-
3 10"
1 10"
.1 10'
1 10"'
3 10'"
3 10"
5 10'"
87
------- |