&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/2-79-010
January 1979
Research and Development
Survey of Biological
Treatment in the Iron
and Steel Industry
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NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
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EPA-600/2-79-010
January 1979
Survey of Biological Treatment
in the Iron and Steel Industry
by
D.F. Finn and J.D. Stockham
IIT Research Institute
lOWest 35th Street
Chicago, Illinois 60616
Contract No. 68-02-2617
Task No.2-5
Program Element No. 1BB610
EPA Project Officer: John S. Ruppersberger
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute, endorsement or
recommendation for use.
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ABSTRACT
This study was conducted with the objective of surveying the current
uses of biological methods of treatment for wastewaters produced by the U.S.
iron and steel industry.
Topics considered in this survey included identification and charac-
terization of wastestreams receiving treatment on a pollutant component
basis, capabilities of biological treatment, advantages and disadvantages of
various biological systems, nitrification and denitrification,i-ear-rent -.utiliza-
tion of biological treatment by the industry and possible options to standard
biological methods.
Results of the survey indicate that coke plant wastewaters, particu-
larly waste ammonia liquor, containing phenol, ammonia, cyanide, thiocyanate,
carbonate, sulfide, oil, suspended solids and dissolved solids are the pri-
mary wastewater source for biological treatment units. Advantages of biolo-
gical treatment include the capability of meeting the 1983 BATEA guidelines
for phenol removal and providing reduced levels of ammonia, cyanide and thio-
cyanate. Disadvantages include susceptibility of the system to upset due to
increases in influent temperature or component concentrations, and in some
cases, cost.
Biological treatment of wastewater is capable of attaining as high as
99% removal of phenolic constituents. Increased retention times, in con-
junction with other operational parameters, will allow for increased removal
of ammonia, cyanide and thiocyanate. Where nitrification and denitrification
units are provided, as much as 90% of influent ammonia may be oxidized.
Current use of biological treatment in the iron and steel industry for
coke plant wastewaters is limited. Where it is utilized, interest is cen-
tered upon phenol removal. Suspended growth systems are the biological
methods employed, with little attention paid to fixed growth, either for pri-
mary treatment, roughing or polishing.
Options to standard biological treatment include physical/chemical
treatment and variations of the activated sludge process. Pilot studies
have shown some methods to be competitive with biological treatment.
This report was submitted in fulfillment of Contract No. 68-02-2617 by
IIT Research Institute under the sponsorship of the U.S. Environmental Pro-
tection Agency. This report covers the period August 31, 1977, to January 31,
1978, and work was completed as of September 29, 1978.
iii
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CONTENTS
Abstract
Tables iv
1. Introduction 1
2. Conclusions 2
3. Recommendations 4
4. The Coking Process and Wastewater Sources 5
5. Biological Oxidation of Coke Plant Wastewaters 6
6. Current Utilization of Biological Treatment Processes 13
7. Possible Options to Standard Biological Treatment 18
Bibliography 21
TABLES
Number
1983 Effluent Limitations for Byproduct Coke Operations
Based on (340 £/tonne) Discharge Volume 5
Concentration Ranges of Coke Plant Wastewater Constituents . . 8
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SECTION 1
INTRODUCTION
The American iron and steel industry comprises approximately 400 plants.
Of this number, however, only 63 are classified as integrated mills, that is,
a steel plant which has facilities for coking, iron, and steel making, and
for rolling and finishing. Steel production from such a plant requires bet-
ween 84,500 to 135,200 H of water per tonne (metric ton) of steel produced.
Of this amount of water, 20-40 percent comes into direct contact with pro-
cess gas or product. Major water-using operations are coke plants, sintering,
blast furnace, steelmaking, hot forming, pickling, cold rolling, and coat-
ings.1 Of these operations, the wastewater most commonly treated by biolo-
gical processes is the waste ammonia.liquor from*coke byproduct plants.
During the 1920s production from byproduct coke ovens surpassed that of
beehive ovens. This resulted from three advantages of the byproduct process:
1) improved coke quality, 2) the chemical recovery made possible by the pro-
cess, and 3) the fact that the byproduct process produced significantly less
air pollution.
Since the mid-1960s, coke production has remained constant at 54-63 mil-
lion tonnes per year. Chemical recovery, however, has grown progressively
less economical. Concurrent with this change, and particularly since the ad-
vent of the Federal Water Pollution Control Act Amendment of 1972 (PL 92-500),
attention has been directed toward a fourth difference between the coking
operations. That difference is the water pollution problems which are a
direct result of chemical recovery processes.
The present study has focused on wastewaters treated by biological
methods, problems associated with these methods, and preventive measures to
avoid these problems.
1Kwasnoski D. Water Pollution Control in an Integrated Steelplant.
International Metallurgical Reviews, Vol. 20, 1975, pp.137-145.
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SECTION 2
CONCLUSIONS
1. Biological methods of treating coke plant wastewaters are capable of
meeting the 1983 Best Available Technology Economically Achievable
(BATEA) guidelines for phenolics and possibly ammonia.
2. Although biological oxidation of wastewaters is an accepted treatment
method, it is utilized by less than 20 percent of the integrated steel
plants in the United States. Where biological treatment units are op-
erating, they are utilized essentially for phenol removal, with little
attention given to other pollutants.
3. The variable nature of coke plant wastewater will produce system shock
and upset. Methods utilized to avert upset conditions are 2 to 7 day
equalization capacity, auxiliary basins, and dilution.
4. After a system is upset, recovery times will vary from 24 hours to 2 or
more weeks. Recovery time varies with the type of loading in the waste
stream (e.g., high organic concentration) and its effect upon resident
microorganisms.
5. Single-stage activated sludge systems will remove more than 99 percent of
the phenolic compounds with a retention time of approximately 24 hours.
Increased retention times and proper hydraulic loadings will provide
greater levels of ammonia, cyanide, and thiocyanate removal.
6. A multi-stage activated sludge unit with carbonaceous, nitrification, and
denitrification tanks will provide high levels of phenolic and ammonia
degradation. These units are, however, difficult to operate and maintain
due to the susceptibility of the microorganisms involved to fluctuations
in temperature and component concentrations in the effluent.
7. Coke oven wastewaters are deficient in certain nutrients required by the
resident microorganisms. In single-stage activated sludge systems phos-
phate is provided as phosphoric acid.
8. Polishing steps in conjunction with biological treatment are not utilized
due to expense. Where polishing is necessary, a physical/chemical treat-
ment system may be selected rather than biological.
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9. The applicability of rotating biological contactors and trickling filters
in the treatment of coke plant wastes has received little attention be-
cause of wastewater composition and limited treatment capacity.
10. Real estate requirements are a function of the volume of wastewater and
the levels to which it is to be treated.
11. There is question as to whether biological treatment will remain com-
petitive with physical/chemical processes. As additional waste streams
are added or levels of treatment increased, the size and therefore cost
of the system increases.
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SECTION 3
RECOMMENDATIONS
1. The economic feasibility of biological treatment vs. physical/chemical
treatment must be studied in terms of what compounds are removed and in
what quantities, and the treatment of additional wastewaters.
2. Economic and operational studies are necessary to determine the feasi-
bility of the use of trickling filters and rotating biological contac-
tors as roughing or polishing steps in conjunction with activated sludge.
3. More investigations of multi-stage and parallel treatment systems are
necessary. All operating problems and solutions must be defined and
system economics evaluated.
4. Methods to decrease "down time" following system upset must be developed.
Such materials as dried biological matter should be considered.
5. Automatic on-stream analyzers should be utilized. Such units would
detect wastewater variations before reaching the treatment system and
automatically shunt the "loaded" wastewater to an auxiliary basin from
where it could be added to the treatment system at a controlled hy-
draulic rate.
6. Research is necessary to clarify methods which will reduce retention
times.
7. Cooperative pilot plant studies and demonstration projects are necessary
for the elucidation of process problems and solutions in various bio-
logical and physical/chemical treatment processes. Favorable results
and reliable operation would probably result in an increased interest
on the part of industry.
8. Possible uses of treated coke plant wastewater should be determined.
9. Studies should be conducted to identify treatment methods used by other
industries, and their possible application to the iron and steel
industry. Such studies will require detailed evaluations of operating
characteristics, treatment potential, and economics.
10. Multi-media effects of various operations such as stripping should be
investigated with regard to air pollution.
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SECTION 4
THE COKING PROCESS AND WASTEWATER SOURCES
The coking process involves heating coal (average charge, 14-18 tonnes)
in the absence of air for 16-20 hours at temperatures between 870°-1260°C.
Organic compounds within the coal are released as gases and drawn off through
exhaust pipes for processing and recovery. Wastewaters orginate from these
prime sources: moisture within the coal during decomposition, and gas treat-
ment/chemical recovery (process water). The largest wastewater fraction is
process water and may account for 60-85 percent of the total flow of 400-
1000 £/tonne of coal. Process waters may be grouped into six categories:2
1. tar still wastewater
2. waste ammonia liquor
3. ammonia absorber and crystalyzer blowdown
4. final cooler wastewater blowdown
5. benzol plant wastewater
6. desulfurizer and cyanide stripper wastewater
Wastewaters from coke plants are saline and contain a variety of pollu-
tants such as ammonia, phenols, cyanide, thiocyanate, sulfides, oil and
grease, and suspended solids. In PL 92-500, the E.P.A. has indicated the
maximum allowable concentration of these constituents by 1983, as shown in
Table 1.
TABLE 1. 1983 EFFLUENT LIMITATIONS FOR BYPRODUCT COKE OPERATIONS
BASED ON (340 &/tonne) DISCHARGE VOLUME
Pollutant Parameter Concentration, mg/£
Cyanide 0.25
Phenol 0.5
Ammonia as N 10
Sulfide 0.3
Oil and grease 10
Suspended solids 10
pH 6.0-9.0
2Dunlap, R.W., and F.C. McMichael. Treatment Technology is Suggested for
Reducing Coke Plant Effluent. Environmental Science and Technology, 10(7):
654-657, 1976.
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SECTION 5
BIOLOGICAL OXIDATION OF COKE PLANT WASTEWATERS
Biological oxidation of coke plant wastewaters can best be understood in
terms of certain fundamentals of the oxidative process involved. These in-
clude the fact that the microorganisms involved are ubiquitous, require an
organic or inorganic carbon source, nutrients, controlled pH and temperature,
and in most organisms, require molecular oxygen. Based on these needs, micro-
organisms will multiply according to species predominance and diversity.
Organisms that require molecular oxygen, either dissolved in water or
from the air, are known as aerobic microoganisms. Those which exist in the
absence of molecular oxygen are anaerobic microorganisms. A number of
anaerobic species may obtain oxygen from radicals such as nitrate (NOs) or
sulfate (SOi,), and are termed denitrifiers or sulfate reducers. In the
development of most biological wastewater treatment units, however, aerobic
microorganisms are of the greatest interest.
BIOLOGICAL TREATMENT SYSTEM DESIGN
Biological wastewater treatment systems fall into two categories: sus-
pended growth (activated sludge) and fixed growth (trickling filters and
rotating biological contactors).
Suspended Growth Systems
Of the various types of activated sludge systems, two of the most com-
mon are the completely-mixed and contact-stabilization versions. The flexi-
bility of the former in allowing adjustments in wasteload variations, makes
it a very popular treatment process for wastewaters containing a relatively
high organic concentration. It has seen some success in the treatment of
industrial wastes with a high concentration of suspended and colloidal or-
ganics. During the contact stabilization process, biological solids are
brought into contact with the wastewater for a short time period. They are
then separated and reaerated in order to degrade sorbed organics.
Activated sludge plant design should consider four major aspects:
1. influent composition stability
2. mixing and aeration
3. nutrient addition
4. retention time
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Influent Composition Stability—
Batch or intermittent wastewater operations are often included in the
waste to be treated. The fluctuating composition of the waste must be min-
imized if effluent of consistent quality is to be produced. A holding tank
may be utilized to off set such fluctuations, but the addition of the contents
of the holding tank to the unit must be carefully monitored.
Mixing and Aeration—
Concentrations of components which are toxic to the microorganisms
occurring in activated sludge units must be reduced to low levels throughout
the aeration tank. Rapid dispersion of the influent stream through the ves-
sel by a completely mixed system will provide the most favorable environment
for efficient treatment.
Aeration provides the oxygen levels required by the microorganisms for
respiration and also allows the sludge to make contact with the components
to be treated.
Nutrient Addition—
The amount of nutrient addition necessary varies from wastewater to
wastewater. Generally, only phosphate is necessary and is added as phos-
phoric acid.
Retention Time—
Retention time has a great influence on the size and cost of a treat-
ment unit, therefore this parameter should be minimized as much as possible,
though a sufficient margin of safety should be built in to handle overloads.
The retention time has a direct effect on effluent quality. However, theo-
retical retention times for given wastewater component concentrations may
have to be increased due to organic and inorganic inhibitors or dilution.
Another process capable of equaling the organic removal of activated
sludge systems is the aerated lagoon. These lagoons, however, are less
desirable options. They are sensitve to temperature fluctuation and need
much more real estate due to the longer hydraulic retention time required
for a given degree of treatment, as measured in days rather than hours.
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Fixed Growth Systems
Trickling filter systems generally utilize a rock or synthetic substrate
upon which a biological film will grow. As the wastewater passes over this
medium, soluble organics are extracted and degraded. Only the top 1-2 mm
of the film is completely aerobic. As depth increases the microorganisms
found are facultative anaerobes and finally obligate anaerobes which do not
perform as the system is intended. As a result there is a build-up of in-
active biological material. This process has seen use as a roughing or
pretreatment process for wastewaters due to its inability to produce con-
sistently high-quality effluent? Trickling filters are used at some plants
for treatment of in-plant sewage and in at least one case, the effluent is
recycled to other water using operations."*
The rotating biological contactor is another type of fixed growth system
which has received attention in recent years. In this process a thin, large
diameter disc provides the substrate upon which the biological film grows.
Many discs are placed closely together on a rotating shaft. Approximately
1/3 of the rotating disc is immersed in a trough through which the wastewater
flows. Aeration occurs when the disc is brought through the water and into
the air.
The rotating disc system provides certain advantages over both the
trickling filter system and activated sludge process. In particular, the
rotating disc provides a shearing force which prevents the build-up of in-
active biological material seen in the trickling filter and provides the
spread of oxygen through the biological film at all times. The unit also
requires less energy for operation than activated sludge systems, and may do
without sludge recirculation, which reduces sludge handling problems.5 The
rotating disc does, however, have a disadvantage. In order to treat waste-
waters containing high concentrations of organics, it requires many discs,
which leads to a high capital cost. Additionally, if the organics are re-
fractory, long contact periods are required and it is possible that less than
optimal reduction will be attained.
Ford, D.L., and L.F. Tischler. Biological System Developments. Chemical
Engineering, 84(17):131-135, 1977.
^Hydrotechnic Corporation. Integrated Steel Plant Pollution Study for Zero
Water and Minimum Air Discharge. Progress Report, EPA Contract 68-02-2626,
July 7, 1977.
5The British Carbonization Research Association. The Biological Treatment of
Coke Oven Effluents: Laboratory Studies Using the Rotating Disc Process.
Carbonization Research Report No.23, December 1975„
8
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TREATMENT OF COKE PLANT WASTEWATER CONSTITUENTS
Constituents of coke plant wastewaters which are of concern to regula-
tory authorities and are at the same time amenable to biological treatment
are phenol, ammonia, cyanide, thiocyanate, and sulfide. Typical concentra-
tion ranges are shown in Table 2.
TABLE 2. CONCENTRATION RANGES OF COKE PLANT WASTEWATER CONSTITUENTS6
Constituents Range (mg/£)
Phenolics 300-4000
Free Ammonia, as NH3 1300-2000
Fixed Ammonia, as NH3 2600-4000
Carbonate, as C03 2300-2600
Cyanide, as CN , 10-100
Thiocyanate, as SCN 50-500
Oils and Tars 20-40
Suspended Solids 80-120
Total Dissolved Solids 4000-13,000
Phenol Oxidation
A number of miroorganisms capable of oxidizing phenolic compounds have
been identified. Among these microogranisms are representatives of the genera
Pseudomonas, Bacillus, Achromobacter, and Micrococcus. Certain strains have
been reported to tolerate phenol in concentrations above 10,000 mg/£.
Many phenolic compounds, such as cresol, resorcinol, benzene, and cate-
chol, etc., which are believed to be present in coke plant wastewater, have
also been biologically oxidized.
6Jablin, R., and G.P. Chariko. A New Process for Total Treatment of Coke Plant
Waste Liquor. AICHE Symposium Series-Water, 70(136):713-722, 1973-
7DeFalco, A.J. Biological Treatment of Coke Plant Wastewaters. Iron and
Steel Engineer, 52(6):39-41, 1975-
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It is not uncommon to read of reported phenol removals of 99.8-99.9
percent.8 These levels, however, are regulated by wastewater temperature,
pH, and the tolerance of the microorganisms involved to other wastewater com-
ponents such as ammonia, cyanide, and thiocyanate.
Cyanide Oxidation
Cyanide is produced during the cooling operation due to the formation of
hydrogen cyanide. The hydrogen cyanide is highly soluble in water and there-
fore the gas cooling water will absorb the compound.
Cyanide removals of 10-87 percent have been reported in pilot plant op-
erations. There has been some question whether the removal process is bio-
logical or air stripping.8 The former, however, has been shown to be the
case more than 99 percent of the time.9
Cyanide has also been shown to exert an inhibitory effect upon thiocya-
nate removal and nitrification. Free cyanide above 3 mg/& completely inhib-
its thiocyanate removal, while nitrification does not commence until cyanide
is reduced to levels below 0.5 mg/£.9
Other researchers have shown that cyanide can be biologically treated
when retention times are directly proportional to influent cyanide concen-
trations.10 For high cyanide concentrations, however, this observation may
be academic because of the capital costs which would be incurred in con-
structing a treatment unit with an adequate retention time.
Thiocyanate Oxidation
The oxidation of thiocyanate is considered the rate-controlling step in
the biological oxidation of coke oven wastewater.11
8Barker, J.E., and R.J. Thompson. Biological Oxidation of Coke Plant Waste.
Paper presented at AISI Regional Technical Meeting, Chicago, 1971.
9Wong-Chong, G.M., and S.C. Caruso. Biological Oxidation of Coke Plant
Wastewaters for the Control of Nitrogen Compounds in a Single-stage Reactor.
Report prepared for American Iron and Steel Institute.
30The British Coke Research Association. New Advances in the Biochemical Oxi-
dation of Liquid Effluents. Coke Research Report No.64, March 1971,
%earce A.S., and S.E. Punt. Biological Treatment of Liquid Toxic Wastes,
Part II. Effluent and Water Treatment Journal, 15(l):87-95, 1975.
10
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Thiocyanate oxidation does not commence until most of the phenolic constit-
uents of the waste liquor have been removed, and, as stated above, until cya-
nides have been reduced to 3 mg/£. Thiocyanate also exerts an inhibitory
effect upon nitrification, though not as extensively as cyanide.
It has been reported that thiocyanate removal may be obtained and re-
tention times decreased by the addition of para-aminobenzoic acid.10 Other
researchers have indicated that reduced wastewater strength will lead to an
increase in thiocyanate degradation.8
Ammonia Control
Biological control of ammonia is achieved through the process of nitri-
fication-denitrification. This process is accomplished primarily by two
specialized genera of bacteria, Nitrobacter and Nitrosomonas. The nitrifi-
cation stage is oxidative when ammoniacal nitrogen is oxidized to nitrite by
bacteria of the genus Nitrosomonas and the subsequent nitrite to nitrate
oxidation is controlled by the genus Nitrobacter. Denitrification consists
of reduction of oxidized nitrogen compounds to gaseous nitrogen. The pro-
cess is controlled by many organisms (e.g., Thiobacillis denitrificans).
Coke oven wastewater frequently contains ammonia in concentrations as
high as 2000 mg/.i. Biological organisms are not capable of existing in such
an environment, thereby necessitating a means for ammonia reduction to levels
amenable to biological treatment. This is generally accomplished with the
use of an ammonia still which, if operating efficiently, will produce an ef-
fluent containing approximately 200 mg/& free ammonia. If a still is not
utilized, dilution water must be provided. This will increase the hydraulic
load, giving increased Detention times and either increased overflow or a
larger and more expensive facility.
The oxidation of ammoniacal nitrogen to nitrite produces acid, with the
resultant decrease in pH. Nitrification has been reported to be most effi-
cient in the pH range of 7.8 to 8.3, which may be adjusted with sodium
hydroxide.12
12Adams, C.E., and W.W. Eckenfelder, Jr. Nitrification Design Approach for
High Strength Ammonia Wastewaters. Journal of the Water Pollution Control
Federation, 49(3):413-421, 1977.
11
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Nitrifiers also require an inorganic carbon source for the synthesis of
organic compounds necessary for metabolism. To a limited extent this inor-
ganic carbon may be obtained from the wastewaster itself, but generally a
material such as sodium carbonate must be added. Pilot plant studies indi-
cate that a near optimum alkalinity concentration is approximately 100 mg/H,
which may be difficult to maintain.8 This is due to conversion of alkalinity
to carbon dioxide as pH is reduced by acid formation. Also, if lime is used
for pH control in place of sodium hydroxide, calcium carbonate may be precip-
itated with the concomitant reduction in inorganic carbon, thereby limiting
the system.
The requirements for denitrification are significantly different from
those of nitrification. Denitrification proceeds anaerobically and also re-
quires the addition of an organic, rather than inorganic carbon source.
Among the carbon sources which have received attention are methanol, sucrose,
methylethylketone, formaldehyde, acetone, glucose, and molasses, with methanol
being frequently recommended.
Temperature, pH, and alkalinity are not as critical to denitrification
as to nitrification; however, acid addition may be required if pH rises too
high.
Ammonia control through nitrification and denitrification is extremely
complicated. Many variables exist, any one of which can halt the treatment
process. In pilot and laboratory studies, however, ammonia removals have
been reported to exceed 90 percent.
12
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SECTION 6
CURRENT UTILIZATION OF BIOLOGICAL TREATMENT PROCESSES
Of the 63 integrated steel plants in the United States, fewer than 20
percent are currently operating a biological treatment unit for wastewaters
other than sanitary sewage.
TREATMENT METHOD SELECTION
The decision to construct a biological treatment system is based upon
such criteria as cost, treatment potential, real estate availability, poten-
tial for upset and recovery, and prior experience with such units. This
decision may be precipitated by the construction of new coke ovens, or noti-
fication by the local municipal district that it can no longer accept a
plant's wastewater for treatment.
The construction of a biological treatment plant is a significant capi-
tal investment for any mill. It has been reported that a single-stage treat-
ment unit with a capacity of 250 gpm costs approximately $6 million for all
components (clarifiers, stream stripper, chemical tanks, etc.). This does
not include operation costs or real estate acquisition, if necessary. Of
this amount, approximately 40 percent is attributable to the biological com-
ponents. The total expenditure will vary with the size and capabilities of
a new treatment unit, but the 40 percent biological component is expected to
remain relatively constant. If stepped or multi-stage units are constructed,
however, both the total expenditure and percent contribution of the biologi-
cal components will increase. Costs also increase if polishing steps are re-
quired to meet a given effluent quality standard.
An advantage of biological treatment methods is their abilitiy to meet
the 1983 effluent limitations for phenolics and possibly ammonia; however,
the degree of treatment attained is dependent upon the characteristics of the
wastewater. It is for this reason that many of the presently operational
systems have been constructed.
Conversely, a decision may be made against construction of a biological
treatment unit in view of the fact that such systems may be upset by varia-
tions in wastewater temperature or component concentrations. If a treatment
system is upset, a long period of time may elapse (often more than two weeks)
before the unit is operating efficiently again. During this time any dis-
charge of coke oven wastewaters would put the plant out of compliance with
effluent limitations. Therefore, the avoidance of such a situation appears
13
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highly desirable in the eyes of the industry. Another, and much more basic,
reason for non-selection of biological treatment systems is the fact that the
industry is not extremely knowledgeable about biological treatment processes.
It has not invested the money, as have other industries, to attain the work-
ing knowledge necessary to apply the process to coke oven wastewaters.
Other treatment methods are better known and understood, and therefore stand
a better chance of selection.
Operation
Currently operating biological treatment systems are generally single
stage activated sludge units. The capacities of these systems are highly
variable, but certain parameters are common to all systems. Temperatures in
the treatment units are between 24-36 C. Influent suspended solids are in
the range of 30-100 mg/£, mixed liquor suspended solids are 2,000-12,000 mg/£,
and the final effluent is usually between 75-100 mg/£. Currently operating
systems and those under construction are not achieving oxidation of all com-
pounds. Most systems are treating specifically for phenolics, reducing in-
fluent concentrations of 1100-1400 mg/£ by approximately 99 percent- Less
attention is given to cyanide, thiocyanate, and ammonia in these units, with
removals of 20-50 percent being reported for cyanide and thiocyanate and al-
most no removal of ammonia. Retention times in the aeration basin sometimes
exceed 35 hours, with 24 hours being common. An approximately two day
equalization capacity is generally maintained, but, depending on the design
of the system, as much as a seven day capacity may-be recommended. Sludge
wasteage rates are extremely variable as is sludge disposal. If sludge
wasteage occurs infrequently, the sludge may be disposed of in the blast fur-
nace. Otherwise it is either dewatered or combined with lime to achieve a
12-15 percent solids content, and is then hauled to a landfill. As the waste-
water is deficient in phosphate, all operating or planned units provide for
the addition of phosphoric acid. No units are reported to respond adversely
to changes in ambient temperatures, but, as mentioned earlier, changes in
influent wastewater temperature may shock the system. There are also no known
plans for variations on the activated sludge process (e.g., Zurn-Attisholz
process), stepped or multi-stage treatment, or roughing and polishing steps,
the latter being due to excessive cost.
SYSTEM UPSETS
A number of factors can lead to the shut-down of a biological treatment
system or to its operation at reduced efficiencies: increased wastewater
temperature, transient loadings of wastewater constituents such as cyanide
and ammonia, and mechanical failure. Depending upon the event or combination
of events which lead to upset conditions, recovery time can vary greatly. In
14
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some cases, improvement may be seen in 24 hours where no curative steps have
been taken other than to return the wastewater stream to its normal composi-
tion. In others, a period of two or more weeks may be required to obtain and
acclimate a "starter" culture and return the system to efficient operation.
A "starter" culture is activated sludge trucked"**^ municipal sewage
treatment plant already treating industrial wastewater to the coke plant
wastewater treatment facility. Some operators also add soil taken from the
areas proximal to the coke ovens, in the belief that the organisms inhabiting
that soil are the same organisms which function in biological treatment
units.
OPTIMIZATION OF BIOLOGICAL TREATMENT UNITS
As stated earlier, the oxidative process which occurs in the biological
treatment of wastewaters is an extremely complex one, and is highly sensitive
to any local changes in its environment. Therefore, maximum attention must
be given to providing for the needs of the microorganisms which carry out the
treatment process. A number of steps may be taken to prevent upset condi-
tions and optimize the treatment process. These are discussed in the follow-
ing sections.
Equalization
Auxiliary basins collect wastewaters containing abnormally high concen-
trations of one or more pollutants. The water is stored in these basins and
then delivered to the biological treatment system at a controlled rate. When
such basins are used, the diversion of abnormal wastewaters is accomplished
by the use of an automatic on-stream analyzer.
Dilution
Heavily loaded waste streams are sometimes diluted with water containing
lower pollutant concentrations where it is know that the undiluted influent
stream will shock or upset the treatment system. Treatment will continue
even at these somewhat reduced food/microorganism ratios because the oxida-
tive mechanism is more sensitive to toxic or inhibitory compound concentra-
tion than to substrate concentration. Surface or ground water, once-through
cooling water, or blowdown from the in-plant utilities provide sources of
dilution water.
Stripping
The reduction of high organic and inorganic loads and the sequestering
of wastewater variations can be achieved through steam or solvent stripping.
15
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The resulting wastewater is then much more amenable to biological treatment.
Recently however, attention has been given to the multi-media effects of
such stripping practices, notably the potential problem of air pollution.
Increased Sludge Inventory
An increased sludge inventory in the biological treatment unit provides
a greater number of active microorganisms per unit area, thereby reducing any
deleterious effects which are exerted by influent variations. Sludge inven-
tory may be increased by reducing sludge wasteage and/or increasing the sludge
recycle ratio.
Sludge inventory is related to food/microorganism ratio, F/M. At in-
creased F/M ratios, the microorganisms approach their maximum growth rate.
The type of "food," or substrate available, however, is very important. If
the substrate is a complex organic compound, it must first be reduced to sim-
ple substrates before it can be utilized by the microorganisms. This will
provide a reduced growth rate, although the F/M ratio is high.
Sludge Age
Sludge age is defined as the average contact time between the microor-
ganisms and substrate. The optimum sludge age for treatment of coke oven
wastewaters is dependent upon the complexity and concentrations of the in-
fluent components and the aeration basin temperature. Other parameters of
importance include retention time in the aeration basin and food/microorgan-
ism ratio.
Enhancement of Nitrification
Nitrification provides a means to keep ammonia levels within discharge
limits. The nitrifying microorganisms, however, are highly sensitive to in-
fluent variations and temperature. The two-stage activated sludge process
is capable of providing nitrification, although it is much more expensive
than conventional activated sludge units. The first stage removes the car-
bonaceous oxygen demand from the wastewater, which then flows to the second
stage for nitrification. Nitrification can also be achieved in extended aer-
ation single-stage units which are operated for the purpose, and by the ro-
tating biological disc.
16
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Activated Carbon Treatment
The use of activated carbon in conjunction with biological oxidation has
apparently received little attention from the iron and steel industry. It
has been suggested as a polishing step before discharge or reuse for the re-
moval of any remaining organic compounds, certain toxic constituents, and re-
sidual color. The primary drawback of this combined method is the total cost
of the treatment operation.
Studies have been conducted, however, using activated carbon as part of
a physical/chemical treatment process for coke plant wastewaters.13 Results
indicate that nearly complete organic, color, and suspended solids removal
can be achieved. Free cyanide is then removed by catalytic oxidation on the
granular carbon.
13Van Stone, G. R. Treatment of Coke Plant Waste Effluent. Iron and Steel
Engineer, 49(4):63-66, 1972
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SECTION 7
POSSIBLE TREATMENT OPTIONS TO STANDARD BIOLOGICAL TREATMENT
Treatment options to the standard biological treatment techniques in-
clude the use of nitrification-denitrification systems, physical/chemical
treatment schemes and variations on the activated sludge process, such as the
Zurn-Attisholz process.
NITRIFICATION-DENITRIFICATION
Difficulties encountered in operating biological nitrification-denitri-
fication units and their increased cost have been among the reasons for the
limited use of these systems in treating coke plant wastewaters. Pilot and
laboratory studies have shown, however, that such systems can reduce the
levels of certain compounds (e.g., phenol, ammonia) which meet stringent dis-
charge limitations, while achieving a reduction in concentrations of cyanide
and thiocyanate. 9' 1 "*
Nitrification-denitrification treatment systems require three stages for
operation. The first stage is the carbon removal unit:, followed by nitri-
fication, and then devitrification.
Wastewater enters the carbon removal unit where phenolic compounds are
degraded. Temperatures are maintained between 27-38°C with a retention time
of approximately 24 hours. Phosphate addition occurs in this unit. Phenolic
removals in this unit may exceed 99 percent. Some cyanide and thiocyanate
removal may be observed.
Effluent from the carbon removal system flows to the nitrification unit.
Inorganic carbon addition and pH control are necessary to aid in ammonia "de-
gradation. Studies indicate that under proper conditions, 90 percent of in-
fluent ammonia can be oxidized.
Wastewater then flows from the nitrification unit to the denitrification
unit where oxidized nitrogen is converted to nitrogen gas under anaerobic
llfBarker, J.E., and R.J. Thompson. Biological Removal of Carbon and Nitrogen
Compounds from Coke Plant Wastes. EBA-R2-73-167, U.S. Environmental Pro-
tection Agency, Ada, Oklahoma, 1973*
18
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conditions. With controlled rates of addition, approximately 95 percent of
the oxidized nitrogen can be converted.
PHYSICAL/CHEMICAL TREATMENT OF COKE PLANT WASTEWATERS
Many components of coke plant wastewater are removable by physical/chem-
ical treatment methods. Organics are frequently removed through the use of
activated carbon or dephenolizers with ammonia removal accomplished by steam
stripping. Cyanides are removed by catalytic oxidation or precipitation dur-
ing the clarification process.13' l5
A pilot study has shown that activated carbon is capable of removing or-
ganics from barometric condenser water1.5 However, problems arise with the
addition of other coke plant wastewater sources to the activated carbon, no^-
fcably waste ammonia liquor. The phenol content of ammonia liquor is as much
as 50 time greater than other wastewaters. The increased load on the acti-
vated carbon makes frequent carbon regeneration necessary, contributing to
increased operating costs. The study determined that ammonia liquor can be
treated in an economic manner by passing it through virgin activated carbon
or reducing phenol levels through the use of dephenolizer before activated
carbon treatment.
Ammonia removal is achieved through steam stripping of highly loaded
wastewaters. Removal is pH dependent and does not occur below pH 7, neces-
sitating the addition of alkaline materials such as lime or caustic soda.
The latter has been recommended for its ability to eliminate or reduce dis-
advantages associated with lime addition.15
Wastewater clarification is a third major operation in physical/chemical
treatment of coke plant wastewater. To avoid coating the activated carbon,
oils (free and emulsified) must be first removed. One method of accomplishing
this is agglomeration of oil on an iron precipitate, produced by adding spent
pickle liquor and caustic soda to the wastewater.15 Upon removal of the
agglomerated oil, the wastewater is ready for treatment of other contaminants.
The economics of activated carbon treatment for industrial wastewaters
compares favorably with other treatment options, owing primarily to the re-
activation capabilities of the carbon.13 However, physical/chemical treat-
ment of coke oven wastewater does not exhibit a vast superiority over other
1SJ.W. Schroeder, and A.C. Naso. A New Method of Treating Coke Plant Waste
Water. Iron and Steel Engineer, 53(12):60-66, 1976.
19
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treatment options. Therefore, the selection of the type of treatment which
will provide the desired pollutant reduction most economically will have to
be made on an individual coke plant basis.
ZURN-ATTISHOLZ PROCESS
The Zurn-Attisholz process has achieved greatest utility in Europe, where
more than 50 installations are operating. In the United States, 11 Zurn-
Attisholz installations are in operation, the majority treating the waste-
waters of the pulp and paper industry.
The Zurn-Attisholz process is a two-stage high-rate system marked by a
high sludge recycle rate and sludge age. In operation, the first stage main-
tains a 6,000-8,000 mg/£ mixed liquor suspended solids (MLSS) concentration,
0.1-0.5 mg/5, dissolved oxygen and a 200 percent sludge recycle. Characteris-
tics of the second stage are approximately 2,000 mg/& MLSS, 2.0 ppm dissolved
oxygen and 150 percent sludge recycle. Suspended solids and biochemical
oxygen demand removals exceed 98 percent with retention times of 2.5 hours
per stage.
The applicability of this process to coke oven wastewaters has not been
adequately investigated. The second stage of the system can be designed for
ammonia removal; however, the levels of removal which may be achieved are not
known. The problem of cyanide and thiocyanate removal, with respect to the
Zurn-Attisholz process, has not been adequately researched. The Zurn-Atti-
sholz process for the biological treatment of wastewaters has, where imple-
mented, been highly successful. No Zurn-Attisholz systems are known to be
treating coke plant wastes, but there is no indication that studies have not
been carried out on the applicability of the process to such wastes. Due to
the impressive results of this process with wastewaters from other industries,
investigations (economic and operational) should be conducted on its appli-
cability to coke plant wastes and other wastewater streams.
20
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BIBLIOGRAPHY
Antill, J.F., and R.L. Cooper. Design Aspects of Mixing and Aeration in the
Biological Treatment of Toxic Wastes. Institute of Chemical Engineers
Symposium Series No.41, 1975. 13 pp.
Ashmore, A.G., J..R. Catchpole, and R.L. Cooper. The Biological Treatment of
Coke Oven Effluents by the Packed Tower Process. Coke Oven Managers
Association Yearbook, 1970, pp.103-122.
Borne, B.J. Industrial Effluent Treatment: Physicochemical and Biochemical
Options. Effluent and Water Treatment Journal 16(10):523-530, 1976.
Cooper, R.L., and J.R. Catchpole. The Biological Treatment of Coke Oven
Effluents. Coke Oven Managers Association Yearbook, 1967, 35 pp.
Davis, E.M., J.K. Petros and E.L. Powers. Organic Biodegradation in Hyper-
saline Wastewater. Industrial Wastes, January/February 1977, pp.22-25.
Dehnert, J.F. and E. Weisberg. Biological Surfaces plus Carbon Upgrade Plant
Water Treatment. The Oil and Gas Journal, January:1978. pp.87-90.
Eisenhaur H.R. Oxidation of Phenolic Wastes. Journal Water Pollution Con-
trol Federation, 36:1116-1128, 1964.
Kincannon, D.F. Some Effects of High Salt Concentrations on Activated Sludge.
Journal Water Pollution Control Federation, 38(7):1148-1159, 1966.
Little, A.D. Inc. Environmental Considerations of Selected Energy Conserving
Manufacturing Process Options. Vol III. Iron and Steel Industry Report.
EPA-600/7-76-034C, U.S. Environmental Protection Agency, Cincinnati, OH.
1976, 88 pp.
Ludzack, F.J., W.A. Moore, H.L. Krieger, and C.C. Ruchhoft. Effect of Cya-
nide on Biochemical Oxidation in Sewage and Polluted Water. Sewage and
Industrial Wastes, 23(10):1298-1307, 1951.
Ludzack, F.J., and R.B. Schaffer. Activated Sludge Treatment of Cyanide,
Cyanate, and Thiocyanate. Journal Water Pollution Control Federation,
34(4):320-341, 1962.
Malaney, G.W., and R.E. McKinney. Oxidative Abilities of Benzene-Acclimated
Activated Sludge. Water and Sewage Works, August:1966. pp.802-809.
21
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Nelbosine, R., and I. Pouschine, Jr. Federal Water Pollution Control Bill
and the Steel Industry. Iron and Steel Engineer, December:1972.
pp.89-91.
Parsons, T. Industrial Process Profiles for Environmental Use: Chapter 24 The
Iron and Steel Industry. EPA 600/2-77-023X, U.S. Environmental Protec-
tion Agency, Research Triangle Park, N.C., 1977 202 pp.
Schmidt, R.K. How to Meet Water Cleanup Deadlines. Environmental Science
and Technology. 10(2):140-143,1976.
The British Coke Research Association. Further Improvements in the Biochem-
ical Oxidation of Liquid Effluents. Coke Research Report No.80. August
1973. 14 pp.
The British Carbonization Research Association. Mixing and Aeration in
Biological Treatment Plants: A Study of Six Designs of the Surface-
Aerated System. Carbonization Research Report No. 1, March 1974, 13 pp.
The British Carbonization Research Association. The Principles of Biologi-
cal Treatment and their Application to the Design and Operation of
Effluent - Treatment Plant. Special Publication 15. March, 1975, 11 pp.
The British Carbonization Research Association. The Treatment of Carboni-
zation Effluents: A study of some Post-Biological Treatment Processes.
Carbonization Research Report No. 24, December 1975, 13 pp.
The British Carbonization Research Association. Mixing and Aeration in
Biological - Treatment Plants: Examination of Existing Surface Aeration
System Designs. Carbonization Research Report No. 37, March 1977, 32 pp.
U.S. Environmental Protection Agency. Polish/U.S. Symposium on Wastewater
Treatment and Sludge Disposal. EPA 600/9-76-021, U.S. Environmental
Protection Agency, Cincinnati, OH, 1976, 156 pp.
Walton, G.L. Effluent Treatment in Steel Works. Metal Finishing Journal,
September, 1972. pp.276-279.
22
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TECHNICAL REPORT DATA , . ,
(Please read Instructions on the reverse before completing)
1. REPORT NO ~ ~
EPA-600/2-79-010
2.
3. RECIPIENT'S ACCESSION1 NO.
4. TITLE AND SUBTITLE
Survey of Biological Treatment in the Iron and Steel
Industry
S. REPORT DATE
January 1979
6. PERFORMING ORGANIZATION CODE
!. AUTHOR(S)
D.F. Finn and J. D. Stockham
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
ITT Research Institute
10 West 35th Street
Chicago, Illinois 60616
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
68-02-2617, Task 2-5
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
ND PERIOD COVERED
13. TYPE OF REPORT AND PERIOD C
Task Final; 8/77 - 1/78
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES IERL-RTP project officer is John S. Ruppersberger, Mail Drop
62, 919/541-2733.
16. ABSTRACT
repOrt gives results of 2i survey of current uses of biological treatmen'
methods for U.S. iron and steel industry wastewater. It includes identification and
characterization, on a pollutant component basis, of waste streams receiving treat-
ment; capabilities of biological treatment; advantages and disadvantages of various
biological systems; nitrification and denitrification; current utilization of biological
treatment by the industry; and possible alternatives to current biological methods.
The coke plant, particularly its waste ammonia liquor, is the major wastewater
source for biological treatment. The liquor contains phenol, ammonia, cyanide,
thiocyanate, carbonate, sulfide, oil, suspended solids , and dissolved solids. Bio-
logical treatment of wastewater can remove 99% of its phenolic constituents. Adjus-
ting operational parameters, including increasing retention time, increases removal
of ammonia, cyanide, and thiocyanate. Ammonia reduction exceeding 90% is achie-
vable in nitrification and denitrification units; however, biological systems are sus-
ceptible to upsets due to fluctuations in temperature or waste loading. Current use
of biological treatment is limited, with interest centered on phenol removal. Pilot
studies have shown some physical/chemical methods to be competitive with biologi-
cal treatment.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Coking
Iron and Steel Industry
Biology Ammonia
Waste Water Phenols
Water Treatment
Nitrification
Pollution Control
Stationary Sources
Biological Treatment
Denitrification
13B
11F
06C
07C
13H
07B
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
28
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
23
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