CURRENT STATUS
OF ADVANCED WASTE-TREATMENT
PROCESSES
JULY 1, 1970
ADVANCED WASTE-TREATMENT RESEARCH LABORATORY
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CURRENT STATUS OF ADVANCED
WASTE TREATMENT PROCESSES
TABLE OF CONTENTS
Municipal Pollution Control Technology-Sewered Wastes
Non-Sewered Municipal Wastes
Virology
Dissolved Nutrient Removal
Dissolved Refractory Organics
Suspended and Colloidal Solids Removal
Dissolved Inorganic Removal
Dissolved Biodegradable Organics Removal
Microorganisms Removal
Ultimate Disposal
Wastewater Renovation and Reuse
Waste Treatment Optimization
Scientific Bases of Waste Treatment Processes
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FOREWORD
Waste treatment technology is moving rapidly nowadays.
A huge impetus has been given to this field by the substantial
sums of money made available for research by the Congress and
administered by the Research and Development Office of the
Federal Water Quality Administration, The Advanced Waste
Treatment Research Laboratory (AWTRL) in Cincinnati, Ohio is
a key element in conducting treatment research for FWQA„
This status report is current as of July 1, 1970„ It
reports the programs of the Advanced Waste Treatment Research
Laboratory but mentions other pertinent work as well, It is
not, however, a comprehensive review of the field. The pur-
pose of the report is to inform Federal Water Quality Adminis-
tration operating and managing officials of the state of the
art of treatment,, It is expected others will find it useful-
If the details of the scientific investigations are desired,
they are available in various reports named in the text.
F. M. Middleton
Director of Research
Advanced Waste Treatment
Research Laboratory
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
Cincinnati, Ohio
CURRENT STATUS OF ADVANCED
WASTE TREATMENT PROCESSES
July 1, 1970
PPB 1101 & 1105 Municipal Pollution Control
PPB 1700 Waste Treatment and Ultimate
Disposal Technology
PPB 1603 (Biological Identification of
Pollutants1) Virus Studies
DIVISION OF PROCESS RESEARCH & DEVELOPMENT
FEDERAL WATER QUALITY ADMINISTRATION
U. S. DEPARTMENT OF THE INTERIOR
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MUNICIPAL POLLUTION CONTROL TECHNOLOGY
PPB - 1101 - SEWERED WASTES
APPLICATION OF ADVANCED WASTE TREATMENT PROCESSES
TO THE TREATMENT OF MUNICIPAL WASTEWATER
Transfer of advanced waste treatment technology from laboratory
scale or experimental pilot plant scale is taking place through the
continuing evaluation and development of specific processes and treat-
ment systems in large-scale pilot plants and full-scale demonstration
plants. The following discussion covers specialized treatment processes
that have achieved full-scale application. Comments are made as to the
general effectiveness and limitations or disadvantages of such processes
under actual use conditions.
PURE OXYGEN IN ACTIVATED SLUDGE PROCESS
Promising results were obtained from a study recently completed
at Batavia, New York in which the use of pure oxygen was compared with
air in the activated sludge process. The test plant has two identical
and separate 1.25 mgd trains. Each treatment train has separ»t-e aeration
tanks, final sedimentation tanks, and return sludge facilities. Primary
sedimentation is not provided. One train was covered and converted to
use of pure oxygen and operated in parallel with the air system. With
recent developments in oxygen production and dissolution technology, under
the conditions of the Batavia test, pure oxygen was shown to be competi-
tive with air. The oxygen can be produced economically on site.
Under test conditions the pure oxygen train achieved 90 percent or
more BOD removal at detention times of 1 to 1,5 hours. With 3 hours
detention time BOD removal averaged 85 percent for the air train and 93
percent for the oxygen train. Another significant difference in per-
formance was quantity of waste activated sludge. Although confirming
data are needed, preliminary results indicate a reduction of 30-40
percent. Further information will be obtained during a continuation
of the study.
Based on the Batavia data, cost estimates projected for new plants
indicate the possibility of lower capital investment and operating costs
for the pure oxygen treatment. The major factor contributing to the cost
reduction is the ability to carry higher MLSS and thereby reduce aeration
tank capacity to 40 or 50 percent of that required for the conventional
systems. Additional savings are indicated for sludge handling and dis-
posal.
Results of the study are being published as an FWQA research report
titled "An Investigation of the Use of High Purity Oxygen Aeration in the
Conventional Activated Sludge Process." Copies of the report, expected
to be ready by September 15, 1970, may be obtained by writing Planning
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and Resources Office, Office of Research and Development, FWQA,
Department of Interior, Washington, D. C. 20242.
Further evaluation and development of the pure oxygen process
will be accomplished under terms of an FWQA R&D Grant recently awarded
to New York City. A 20 mgd train at the Newtown Creek treatment plant
will be converted to the use of pure oxygen and operated for at least
12 months.
The use of pure oxygen for the treatment of municipal waste
waters is being aggressively promoted by Linde Division of Union
Carbide Corporation who was contractor for FWQA on the Batavia study.
GRANULAR ACTIVATED CARBON
The use of granular activated carbon for removal of nonbiode-
gradable organics, color and residual BOD has been demonstrated in
full-scale plants and is felt to be sufficiently developed to be used
on full-scale applications wherever conditions warrant such treatment.
Because suspended solids are partially removed on the carbon, the
solids load and need for pretreatment must be considered when designing
a carbon adsorption system. In order for the carbon treatment system
to be economical, the used carbon must be regenerated and reused.
Large-scale plants currently using and regenerating granular activated
carbon include the 7.5 mgd plant at Lake Tahoe and the 0.5 mgd plant
at Nassau County, New York. A number of articles have been published
covering the Tahoe plant. One appeared in the June, 1969 issue of
Civil Engineering entitled "Wastewater Reclamation and Export at South
Tahoe." A few copies are available from the Cincinnati Laboratory.
At the 300,000 gpd Pomona, California Pilot Plant secondary
effluent is applied directly to the carbon columns without requiring
excessive backwashing. This is only possible, however, because of
exceptionally high quality secondary effluent at this location.
Results of this study will appear in a 1970 issue of the Chemical
Engineering Progress Symposium Series.
Full-scale evaluation of granular carbon adsorption as a replace-
ment for biological treatment will be obtained on a 10 mgd plant at
Rocky River, Ohio. This is an R&D Grant project which involves chemical
pretreatment of raw sewage in an improved primary treatment ahead of the
carbon columns. Construction of this plant is scheduled for completion
by fall of 1971. Further details regarding design and operating condi-
tions scheduled for this plant may be obtained from Mr. A. N. Masse,
Cincinnati, Ohio.
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PHOSPHORUS REMOVAL
Phosphorus removal from wastewater on plant scale has been
carried out for a number of years at certain locations where the
water was needed for industrial reuse purposes. It has been rela-
tively recent, however, that phosphorus removal has been considered
necessary as a pollution control measure.
Although purely biological methods of phosphorus removal have
been proposed, it appears that addition of chemicals to the water to
precipitate the phosphorus is the only dependable method. Chemicals
that can be used are iron salts, aluminum salts, and lime. The simplest
method for carrying out chemical precipitation is to add the chemicals
at some point in a conventional activated sludge plant. The point of
addition can range from before primary treatment to near the exit of
the aerators. Iron salts and aluminum salts are preferable to lime.
A number of R&D Grant projects have been sponsored by FWQA including
Grand Rapids, Michigan at 45 mgd. Contact Mr. E. F. Barth, Cincinnati,
Ohio for additional information.
An alternative method for carrying out precipitation of phosphorus
is by using a clarifier-settler combination either for treating screened
raw sewage or as a tertiary treatment. Lime presently appe^s most
appropriate for this method of removal. Excellent phosphorus removal
can be obtained along with a high degree of solids removal, especially
if the settler is followed by a filter. Probably the best known example
of tertiary chemical clarification is the 7.5 mgd plant at Lake Tahoe.
Reference has been made to this plant in connection with carbon treat-
ment. Other FWQA supported projects include plants at Colorado Springs
and Nassau County. When chemical clarification is used for treatment of
raw sewage, it can serve as the first stage of a purely physical-chemical
treatment system. Under an R&D Grant, a 5 mgd plant will be constructed
and operated at Painesville, Ohio that utilizes chemical clarification
followed by carbon treatment. There is increasing interest in this type
of treatment system. Additional plants are likely to be constructed in
the near future.
AMMONIA STRIPPING
Up to 95 percent of the ammonia in wastewater can be air-stripped
from solution using about 400 ft^ of air per gallon of water treated.
Effective ammonia removal requires a pH of 11. A nitrified secondary
effluent cannot be treated by this method.
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A 3h mgd ammonia stripping tower has been operated at South Lake
Tahoe to treat one-half of the total flow at that location. This is
part of a two-stage lime precipitation process. Lime is added in the
first stage to raise the pH to 11. This step removes most of the
suspended solids, phosphates, and carbonate compounds. Effluent from
the first-stage clarifier is then subjected to countercurrent air
contacting to remove ammonia; effluent from the stripping tower is
recarbonated with CO2 to precipitate excess calcium as CaCOo in the
second-stage clarifier; at this point the pH is dropped to 9.5.
Although the process has been quite effective in reducing the
ammonia content of the wastewater, operational problems raise questions
as to the desirability of promoting the widespread use of ammonia
stripping towers. The process is subject to freezing problems in cold
climates and reduction of the ammonia removal efficiency at low tempera-
tures. Lime deposits on the slats and superstructure of the tower
create serious maintenance problems. At this time, use of stripping
totters will most likely be restricted to more temperate locations where
freezing is not a problem or areas where high percentage removal is not
required during winter months.
POLYMER ADDITION TO PRIMARY SEDIMENTATION
The addition of polymers to raw sewage to improve sedimentation
of suspended solids was studied at the District of Columbia Water
Pollution Control Plant. The study was carried out at full scale on
this 240 mgd plant. The test involved three separate phases in which
each of three polymer suppliers carried out extended studies with his
own most effective polymer. Best results were obtained with anionic
polymers used in doses of less than 1 mg/1. The amount of solids
removed by sedimentation increased by as much as 25 percent. Because
of hydraulic overload at the plant, which affected operation of the
final settlers, the improved primary treatment did not improve overall
treatment significantly. For plants having only primary treatment,
however, use of polymers could increase effectiveness of treatment
significantly. Use of polymers to improve primary treatment may also
improve secondary treatment where organic load to the aerators is very
high. Additional results of the study will be reported in an FWQA
research report entitled "Raw Wastewater Flocculation with Polymers
at the District of Columbia Water Pollution Control Plant." Copies
are expected to be available from FWQA's Research Division by October
1, 1970.
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COMBINATION CONVENTIONAL-AWT TREATMENT
The treatment plant at South Tahoe, California is probably the
best known advanced treatment plant in the country. Reference has
already been made to the plant several times. It is of 7.5 mgd capacity
and includes conventional primary treatment and activated sludge treat-
ment followed by tertiary processes including two-stage lime clarifica-
tion with ammonia stripping between stages, pressure multimedia filtra-
tion and granular carbon treatment. The effluent from the plant is of
high clarity and contains only traces of phosphorus and organic materials.
The water is presently exported to Nevada for eventual use in irrigation
of crops after prior holding in a recreational lake, Indian Creek
Reservoir, The take can be used for all types of water recreation
including contact sports. Use has been restricted, however, by a lack
of facilities. Because of the high quality of the water, algae are not
a significant problem.
Since biological treatment is included in the Tahoe system, the
system is a hybrid between conventional and purely physical-chemical
advanced treatment. There is increasing interest in pure physical-
chemical systems. These have the advantage of not being affected by
toxic materials that can upset the operation of biological processes
for long periods. They also require less land area. Where only organic
and phosphorus removal is required, chemical clarification followed by
carbon treatment are the processes considered most reliable at this time.
R&D Grants at Rocky River and Painesville, Ohio utilize variations of
these processes. The effluents from these plants will not be of as high
a quality as that from the Tahoe plant. The effluents are expected to
be the equivalent of secondary effluent. Where nitrogen removal is
required, ammonia stripping or selective ion exchange are most likely
candidates. Stripping is less expensive but is subject to several
operating problems. More work is needed to develop a completely satis-
factory physical-chemical nitrogen removal system.
DESIGN MANUALS FOR ADVANCED WASTE TREATMENT PROCESSES
We have recognized the need for improved methods of disseminating
results from research and development programs and we are currently
making arrangements for a series of treatment process design manuals.
These manuals will supplement technical seminars and publications
covering results of the Advanced Waste Treatment Laboratory inhouse
and extramural projects.
The information needed by consulting engineers for design of
advanced waste treatment plants is now available for some processes.
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However, the data are contained in numerous segmented publications,
reports and manufacturers' literature. The purpose of the manuals
will be to compile available information in a form which can be readily
utilized, and provide detailed information on hardware selection and
system design.
Contracts are being negotiated for preparation of the following
design manuals:
1. Activated carbon adsorption, primarily for the treatment of
secondary effluent or an equivalent waste stream.
2. Phosphorus removal by chemical treatment and solids separation.
3. Suspended solids removal including such techniques as micro-
screening, filtration, tube settlers, etc.
4. Upgrading of existing plants through the application of such
techniques as pure oxygen treatment, flow equalization, etc.
Target date for completing the first manuals is March, 1971. At
that time the manuals should be ready for general distribution to con-
sulting engineers and other treatment plant design interests.
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PPB - 1101 - SEWERED WASTES
Flow Reduction From Individual Homes and
Alternative Waste Collection Systems
FLOW REDUCTION
A study on state-of-the-art of methods for flow reduction has
been completed by Electric Boat Division of General Dynamics Corporation.
This study concluded that use of modified plumbing fixtures for flow
reduction is economically feasible and would result in cost savings in
many cases. There are many household functions in which water is used
wastefully. Water usage could be reduced up to 35 percent by use of
presently available devices and technology. Feasible devices are
shallow trap toilets, toilets with separate flush cycles for urine and
feces, flow control showers, and faucet aerators. Treatment and reuse
of wastewater in individual homes is not economically feasible, except
for filtration and reuse of wash waters or aerobic unit effluent for
toilet flushing in water-short areas.
A study is planned for demonstration of flow reduction devices
and technology for 8 homes. Present water usage will be monitored prior
to installation of modified plumbing fixtures. The program will include:
4 homes with flow control showers and shallow trap-dual cycle
toilets
2 homes with flow control showers and with recycled (filtered)
wash water reused in normal trap-dual cycle toilets
2 homes with shallow trap-dual cycle toilets and flow control
showers, and with recycled (filtered) wash water used for
lawn watering
PRESSURE SEWER SYSTEMS
Collection and treatment of wastewater at a central point should
be utilized where feasible in lieu of individual home systems. However,
it is not always practical to install conventional gravity sewer systems
because of rough terrain and necessity for rock excavation. One possible
solution is use of a pressure system, which is being studied under an
R&D Grant at Grandview Lake, Indiana.
The Grandview Lake system will serve about 60 homes initially.
Individual grinders and pumps will be installed at some homes. Septic
tank effluent will be pumped directly without grinding at others.
Three and one-fourth inch PVC pipe will be used for the pressure sewer
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with 1-inch connections from homes. Wastes will be treated by a combined
anaerobic and aerobic lagoon. Lagoon effluent will be utilized for
irrigation of a hay field.
The individual home pump and grinder unit was designed using
commercially available home garbage grinders, pumps, and check valves.
Unit cost without installation is $450 to $500.
VACUUM SEWER SYSTEMS
One of the most interesting developments in water closets and
waste collection is the Liljendahl vacuum system. This system uses air
rather than water as the major transport system for a vacuum toilet.
A vacuum toilet requires only one-half gallon per flush compared to 4
to 6 gallons for conventional toilets. The vacuum system can also be
utilized for waste collection from groups of homes in lieu of conven-
tional gravity sewers.
The Sanivac Division of National Homes Corporation is marketing
the Liljendahl vacuum system. This system has been used in Europe, the
Bahamas, and in Latin America. A grant project is being developed for
demonstration of the vacuum system in an area now served by septic tanks.
Connections with house sewers will be made at lot lines. Another grant
is planned for demonstration of the vacuum toilet system.
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
MUNICIPAL POLLUTION CONTROL TECHNOLOGY
NON - SEWERED WASTES
PPB 1105
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
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PPB - 1105 - NON-SEWERED MUNICIPAL WASTES
INTRODUCTION
A study on state-of-the-art of individual home waste treatment
systems has been completed by Electric Boat Division of General Dynamics
Corporation (Report 11050 FKE, "Flow Reduction and Treatment of Waste
Water from Households," available September, 1970). In addition, an
inhouse survey of proprietary equipment developed by industry but not
now commercially available has been conducted.
SEPTIC TANK SYSTEMS
At the present time, there are approximately 15 to 17 million
septic tanks in use. 1,4 million new systems have been installed since
1960. In many cases, operation of septic tank systems has not been
satisfactory and has resulted in health hazards. This is due to poor
soils which do not readily accept effluent. Lack of maintenance by
homeowners is also a contributing problem. Regulatory agencies now
require large lots in areas with low soil permeability. This has
prohibited housing developments in many areas. However, in areas, with
high soil permeability and low population density, septic tanks usually
perform satisfactorily and will continue to be an acceptable disposal
method.
Septic tank costs are upwards from $120 and installation from
$250. Tile field costs vary from $200 to $2400 depending on type of
soil and regulatory requirements.
ACTIVATED SLUDGE PACKAGE PLANTS
Individual home aerobic package plants have been marketed since
about 1955. It is estimated that there are 20,000 to 30,000 units now
in operation. Initially, State health departments allowed discharge to
natural waterways. Because of periodic discharge of suspended solids,
subsurface disposal is now required by most regulatory agencies. Unit
costs vary from about $800 to $1600 installed. If filtration and dis-
infection are required, costs are increased by $300 to $800.
DEVELOPMENT OF IMPROVED SYSTEMS
If an acceptable individual home treatment unit to replace septic
tanks could be developed, a multimillion dollar market would exist.
This potential market has induced industries to expend funds for R&D.
From results of the inhouse survey, there are 5 companies that have
conducted studies on unit development. In several cases, system
components and total systems are now ready for field evaluation.
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The basic problem in unit development is acceptable capital and
operating costs. The Electric Boat study has concluded that use of
advanced treatment processes, including distillation, reverse osmosis,
electrodialysis, chemical treatment, and activated carbon adsorption,
is not economically feasible at this time.
The basic problem area is solids disposal, as is the case for
large-scale conventional treatment. Capital and maintenance costs for
incineration are expected to be high. Another problem area is air
pollution potential of incineration. Solids could be stored in the
unit and disposed of similarly to sediment from septic tanks. However,
this may not be aesthetically acceptable to all homeowners.
Fail-safe design is necessary. Homeowners tend to ignore operating
and maintenance requirements for presently available package plants. There
have been cases where power to units has been shut off. Policing of a
large number of units by regulatory agencies is difficult. A possible
solution to maintenance requirements is a permanent service contract with
the manufacturer.
FUTURE STUDIES
In view of effort expended by industry on development of new
equipment and approaches to individual home treatment, support of basic
research on new systems or hardware development is not planned at this
time. Planned studies include demonstration of commercially available
hardware and modifications to improve treatment, and new proprietary
equipment developed by industry. Studies on the relative absorption
rates of effluent from package plants as compared to septic tanks will
be conducted.
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July I, 19TO
VIROLOGY
PPB 1603 - 1706
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
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Virology Section
Robert A. Taft Water Research Center
Cincinnati, Ohio
1603-1706
Introduction
Large quantities of viruses of human origin are present in sewage,
sewage effluents, and in rivers and streams. Viruses of animal, plant
and bacterial origin must also abound in these waters, but their presence
is not as well documented, and their importance to the human animal is
largely unknown.
The viruses of human origin are small in numbers compared with the
numbers of bacteria that are excreted. Moreover, viruses do not multiply
outside of living susceptible cells, and these numbers decrease even in
that most nutritional environment constituted by domestic waste. The
great importance of viruses in water, however, lies not Just in their
numbers, but in their great capacity to infect their hosts. The smallest
amount of virus capable of infecting the most highly susceptible cells
in cultures, our most sensitive indicators of infection, is usually
capable of producing infection in man.
The clear capability of minimal quantities of viruses for producing
infection in man is sufficient justification for seeking the total
removal of viruses from any waters which man might consume. The
permissible level for viruses in such waters should be none.
Epidemiology
Small amounts of viruses ejected into rivers and streams with
partially treated wastewater become a potential hazard to downstream
recreationalists and to those in downstream communities who must consume
these waters. Even 19 PFU per 50 gallons of river water, an amount we
have recovered with an inefficient technic even in cold months, constitutes
a considerable hazard, for what this means in terms of the amounts of
viruses that may enter the intakes of any community every day is readily
calculable.
Unfortunately, small amounts of waterborne viruses may infect swimmers
and consumers and not be readily detected by the effect they produce.
This is so because small amounts of ingested viruses are likely to produce
infection, but not disease. Infection Is the state whereby the virus
enters and multiplies within susceptible cells. It is a disease state
with no overt signs. Overt disease exists when sufficient damage has
been done to bring about systemic malfunctions. Thus, Individuals
Infected with small amounts of virus may show no signs; yet, they may
excrete large amounts of virus, their contacts may be infected with
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large amounts and recognizable illness may result* Hie spread of infection
and disease in this fashion will appear to be by the personal contact
route with no indication that the original source was water. Die frustration
of epidemiological studies intended to demonstrate a water source of trans-
mission may be the result of using clinical illness and not index infection
rates as criteria. In bathing water and similar studies, the disease rates
in secondary contacts might well be a much better indicator of source than
the disease rates in bathers themselves. "Dais same principle may hold for
bacterial infection and disease, for the main thrust of efforts in this
area has always been in the direction of disease and not infection.
Recovery of Small Quantities of Viruses from Large Volumes of Water
Several years ago, we set a tentative standard for ourselves of less
than 1 FFU of virus per 100 gallons of water. This standard was based on
our assessment that detection of one PFU of virus in 100 gallons of water
would be feasible within five years of that time, and not on any conviction
that water with less than that amount of virus would be safe. It was our
intent to raise our sights if developing technology allowed, and to lower
them should a more modest limit need to be imposed upon us.
Clearly, the recovery of 1 PFU of virus from one-hundred gallons of
water or more requires exquisite concentration procedures, and many are
under study. It is not yet clear which of the several systems presently
under investigation will prove the most efficient and utilitarian if, in
fact, any one does become universal in all of the several applications
for which such methodology is needed. Viruses must be recovered from
waters of qualities ranging from raw sewage to completely renovated.
Except in the unusual situation where raw sewage or primary effluents
need to be pasteurized or sterilized, only small volumes of such waters
need to be tested for viruses because relatively large amounts of viruses
are usually present. This is generally true of secondary effluents as
well, and in these situations, effective technics, not adaptable to large
volume efforts, are already available. Hie A1(oh)j adsorption procedure
is reportedly capable of recovering 100# of several enteroviruses
experimentally added to sewage effluents, but the method leaves most
of the large reoviruses and adenoviruses behind. England (16030 DWW)
recently reported efficient recovery of experimentally added reoviruses
and adenoviruses from effluents by precipitation with protamine sulfate
which leaves most of the smaller picorna viruses behind. England uses
both methods for maximum recovery of all of these viruses. Protamine
precipitation of the larger viruses from Al(OH)o-adsorbed effluents is
an important approach today to the effective recovery of viruses from
heavily contaminated waters.
The phase separation technic suffers same disadvantage from an
overnight time requirement for completion. It has also been reported
recently that the method is not efficient with all viruses.
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Both the Al(OH)^-protamine sulfate and the phase separation procedures
are limited by the volumes they can accommodate, this the result of the
large quantities of chemicals required for each unit volume of water
tested. When only a few liters or gallons need to be tested, these
technics may be considered. When a hundred gallons or more must be
tested, other methods must be looked to.
To accommodate large volumes of water, a filtration system seems
the best approach. This technic consists of filtering water through
O.J+5 (i cellulose nitrate membrane filters to which viruses adsorb and
from which they can be eluted. For some time now, we have consistently
obtained quantitative recovery of enteroviruses and about 80$ recovery
of reovirus 1. Most of our studies were done with 1-liter samples, but
we achieved complete recovery of viruses from 25 gallon quantities as
well. With larger quantities of water, recovery has so far been less
efficient. In most of these experiments, less than 100 FFU of virus
were added to the total volume studied. Most of these experiments were
done in distilled water, but several were done in tap water from which
we could not always recover viruses quantitatively. As others have
reported, certain substances, presumedly organics, apparently can react
with the adsorptive sites on the membranes and make them unavailable
to the virus. Thus, our immediate goal is to apply the technic to
renovated and other clean waters, but it may be necessary to pretreat
even such relatively clean waters to remove interfering substances
before the membrane filter method can be effectively used for quantitative
recovery of viruses. Whether waters of poorer quality can be sufficiently
purified without removing or destroying viruses so that such waters can
be tested with this technic is still conjecture. However, there is
another filtration approach currently in a state of reincarnation that
offers promise for quantitative recovery of viruses from water—the ion
exchange resin, more voguishly, the insoluble polyelectrolyte. This
method consists of filtering water through two Millipore AP 20 fiberglass
prefliters between which a Monsanto insoluble polyelectrolyte designated
PE 60 is sandwiched. The virus is eluted with 10$ fetal calf serum in
borate saline at pH $.0. In our hands, when small amounts of viruses in
1-liter volumes of distilled water were passed through such filters,
relatively poor recoveries resulted. Poliovirus 1 recovery in experiments
sometimes ranged over 80$, but echovirus J recoveries were sometimes
somewhat lower than 30$ and reovirus 1 recoveries were sometimes lower
than 20$. The extent to which the ion exchange resin is affected by
water quality is not clear, but apparently, it is less affected than the
cellulose nitrate filter.
Nonetheless, we have repeatedly used the technic for virus recovery
studies from 50-gallon samples of river water, and repeatedly obtained
recoveries. As much as 19 PFU of virus have been recovered from samples
taken long distances from outfalls along a large fast-flowing river
during the winter months. Thus, despite its low and erratic efficiency
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at present, the technic appears to be the most sensitive presently
available. Since the numbers of different ion exchange resins that
can be produced is vast, these substances clearly warrant the rein-
carnation they now experience.
Other technics including osmotic ultrafiltration and electro-
osmosis are also under study, but it is not yet clear what their final
contribution to the developing technology will be. Nor is it clear
at present whether we will eventually achieve a universal recovery
system that can be utilised efficiently with waters of all qualities,
or whether we will have to tailor the recovery system to the water
under study.
Gerald Berg, Ph.D.
July 7, 1970
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July I, 1970
DISSOLVED NUTRIENT REMOVAL FROM WASTEWATER
PPB 1701
Division of Process Research & Development
Federal Water Quality Administration
U.S. Department of the Interior
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NITROGEN REMOVAL - GENERAL
Municipal wastewaters have nitrogen contents in the 15-25 mg/1 range in
untreated and primary settled wastes; the nitrogen is divided between
organic compounds, which are mostly insoluble, and ammonia. In general,
we can depend on conventional biological processes to transform almost
all nitrogenous components in wastewater into ammonia and biological
sludge. Once this has been accomplished, we can design systems to
remove ammonia by air-stripping„ Ammonia stripping at high pH in cooling
towers following lime treatment is effective but cannot be used during
freezing weather and may suffer from serious scale problems.
Under favorable conditions, biological processes may also oxidize ammonia
to nitrates by a tvio-step sequence called nitrification. It would be
beneficial if waste treatment plants were required to produce nitrified
effluent. Ammonia nitrogen in effluents has several undesirable features:
(1) Ammonia consumes dissolved oxygen in the receiving water;
(2) Ammonia reacts with chlorine to form chloramines which are
less effective disinfectants than free chlorine;
(3) Ammonia is toxic to fish life;
(4) Ammonia is corrosive to copper fittings;
(5) Ammonia increases the chlorine demand at waterworks downstream.
A nitrified effluent, free of substantial concentrations of ammonia, offers
several advantages:
(1) Nitrates will provide oxygen to sludge beds and prevent the
formation of septic odors;
(2) Nitrified effluents are more effectively and efficiently
disinfected by chlorine treatment;
(3) A nitrified effluent contains less soluble organic matter
than the same effluent before nitrification.
A nitrified effluent is far preferable to one containing substantial
ammonia. However, ammonia and nitrate are interchangeable nitrogenous
nutrients for green plants and algae, as well as bacteria. If the
nitrate level is too high and is helping to stimulate undesirable aquatic
growths, the effluent can be further treated by biological action to
convert the nitrates to nitrogen gas. This process is called denitrifi-
cation. The best developed method at this time for control of nitrogen
compounds is biological oxidation to nitrates followed by denitrification
with the aid of methanol.
22
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Selective ion exchange of ammonia with lime regeneration may be practical
but the process is still in the pilot stage. Several other processes
are being studied including selective ion exchange of nitrate and chlori-
nation of ammonia to liberate nitrogen gas.
NITROGEN REMOVAL BY BIOLOGICAL SUSPENDED GROWTH REACTORS
Success in providing a high efficiency for nitrogen removal by biological
denitrification requires that the biological transformation of ammonia
nitrogen to nitrate nitrogen be under good process control. Any reduced
nitrogen compounds introduced into the denitrification stage will pass
through the process unaltered and impair overall nitrogen removal efficiency.
Complex factors are involved in maintaining nitrification with a conven-
tional activated sludge system. If nitrification occurs at all, it may
be due only to an unintentional accident of design. A three sludge
variation of the activated sludge process, developed at the Robert A.
Taft Water Research Center, greatly simplifies the process control
problems associated with maintaining nitrification.
The three sludge system allows management of the separate biological
transformations which are necessary for successful denitrification. The
three sludge systems are staged in sequence, with flow passing from one
stage to the next. The first stage is a high-rate sludge system, the
second stage a nitrification sludge system, and the third a denitrification
sludge system., The high-rate system handles the bulk of the carbonaceous
removal and at this station the waste activated sludge is removed. Thus,
the nitrification stage receives a predominantly ammonia nitrogen feed
and an enriched culture develops because each sludge system has its own
sludge recycle. This process design also has other desirable features.
The high rate system protects subsequent nitrification stages from toxic
chemicals. Since this is a staged system there can be no direct short
circuiting of materials from the influent to the effluent. Temperature
effects on the enriched culture of the nitrification stage are not as
extreme as with a single sludge system which contains only a marginal
population of nitrifying organisms.
Once controlled nitrification has been established, the biological
denitrification process can be optimized. The nitrified effluent flows
to a slowly stirred anaerobic reactor where methyl alcohol is added in
proportion to the nitrate nitrogen concentration. The organisms in this
stage use the oxygen component of the nitrate radical to oxidize the
organic carbon of methyl alcohol. The end products of this metabolism
are elemental inert nitrogen gas and carbon dioxide, which are liberated
to the atmosphere.
The stage approach to nitrification has been investigated in work at the
Robert A. Taft Water Research Center (1) and in large pilot plant operations
at the University of Notre Dame (2) and Manassas, Virginia (3). The
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process has also been evaluated on a 1 mgd scale at Hazel Crest,
Illinois. A summation of these studies show that biological denitri-
fication is a controllable process if the reaction is forced with an
organic supplement, such as methyl alcohol. Total nitrogen in an
effluent can be reliably reduced to about 2 mg/1. The cost of the
methyl alcohol for 20 mg/1 of nitrate nitrogen is estimated to be about
2f/1000 gallons treated. For more information contact:
Mr. E. F. Barth
U. S. Dept. of the Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
References:
(1) Barth, E. F., et al.,_ "Chemical-Biological Control of Nitrogen and
Phosphorus in Wastewater Effluent," Jour. Water Pollution Control
Federation, December 1968.
(2) Echelberger, W. F. and Tenny, M. W., "Control of Organic and
Eutrophying Pollutants by Combined Chemical and Biological Wastewater
Treatment," Division of Water, Air and Waste Chemistry, American
Chemical Society, Minneapolis, Minnesota, 1969.
(3) Mulbarger, M. C., et al., "Manassas, Virginia, Adds Nutrient Removal
to Waste Treatment," Water and Wastes Engineering, April 1969,
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NITROGEN REMOVAL FROM WASTEWATERS BY COLUMN REACTORS
Columnar nitrate reduction represents a second alternative to the suspended
growth systems as a means of biochemically reducing the nitrate ion to
elemental nitrogen. In a packed column, the cell residence time of the
surface bound slime is much greater than the hydraulic detention time.
This, combined with a large contact surface and short diffusion dis-
tances afforded by small media such as sand, provides an efficient system
for rapid denitrification of an applied feed.
Work at the FWQA Lebanon, Ohio Pilot Plant (J. M. Smith, 1970, Unpublished)
has shown that the smaller media systems (sand to 3/4 inch diameter
stone) are effective when operated downflow at surface loading rates of
7.0 gpm/ft and at actual contact times of 50 to 30 minutes. Daily back-
washing is required to relieve pressure drop due to the accumulation of
suspended solids in the upper portion of the column. The denitrifying
slime is firmly attached to the media surface, and is not removed during
the backwash operation. Greater than 90 percent nitrate reduction can
be achieved within these columns at contact times of 10 minutes for sand
and 30 minutes for the 3/4 inch stone. The effluent normally contains
less than 2.0 mg/1 of nitrate nitrogen with effluent turbidities less
than 3 JTU, indicating little solids contribution from the attached
organisms.
Larger media varying in size from 1 inch to 2 inch aggregate have been
successfully employed to denitrify agriculture subsurface drainage at
Firebaugh, California (Tamblyn, T.A., and Sword, B.R., "The Anaerobic
Filter for the Denitrification of Agricultural Subsurface Drainage,"
24th Purdue Industrial Waste Conference, 1969.) The larger media permits
upflow operation without backwashing at the expense of longer contact
times and increased effluent suspended solids. Nitrate reduction of
greater than 90 percent were achieved in contact times of 1 hour for
the 1 inch aggregate and 2 hours for the 2 inch aggregate at temperatures
above 12°C. The 2 inch columns have been operated continuously for
over six months on agriculture subsurface drainage without the loss of
efficiency or solids accumulation.
As with suspended growth denitrification, methyl alcohol is used as the
supplemental organic carbon source of choice for columnar denitrification
because of its low cost, blodegradability and ease of handling. Approxi-
mately 3 mg of methyl alcohol are required per mg of nitrate nitrogen
removed including the requirement for deoxygenating the nitrified feed.
The chemical cost for removing 20 mg/1 of nitrate nitrogen in the presence
of 5 mg/1 of dissolved oxygen is estimates to be about 2c/1000 gallons
treated. For additional information, contact:
Mr. John M. Smith
U. S. Department of Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
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AMMONIA NITROGEN REMOVAL BY STRIPPING WITH AIR
Ammonia can be removed from a wastewater effluent by raising the pH to
convert ammonium ion to dissolved ammonia and then contacting the effluent
with a sufficient quantity of ammonia-free air. This physical process
is called desorption or, more commonly, "stripping."
If the contacting is done in a packed tower, the pressure drop across the
tower is about 1.0 psi or 28 inches of water„ Since the volume of air
required per unit volume of wastewater effluent is very high, about 400
cubic feet per gallon in a countercurrent operation, the cost for power
to overcome even this relatively low pressure drop is prohibitive.
The problem of high power cost was solved by investigators at the South
Lake Tahoe Public Utility District (Slechta, A. F. and Culp, G. L.,
"Water Reclamation Studies at the South Tahoe Public Utility District,"
Jour. Water Pollution Control Federation, May 1967).who used a slat-
filled tower such as is used for cooling water to contact water and air.
The pressure drop across such a device is very low, about 1/2 inch of
water, so power costs are reduced to reasonable levels. Removal effi-
ciencies as high as 90 percent were obtained in a 24-foot high tower
ift which wastewater effluent and gas were contacted in a nearly counter-
current fashion. On the basis of this experience, a full-seal* stripping
tower was constructed at South Lake Tahoe. The tower was designed to
remove 90 percent of the ammonia from 3-1/2 MGD of Tahoe's removated
wastewater. The air flow is not countercurrent to the liquid but flows
across the tower (cross-flow), while the wastewater drips downward
through the packing.
Initial operation of Tahoe's stripping tower was in the winter and
immediately revealed a limitation of ammonia stripping. When air temp-
erature fell below 0°C,freezing of water occurred at the air inlets,
making the tower inoperable. Also, since ammonia solubility is higher
in cold water than in warmer water, more air is required to remove it
(800 cubic feet per gallon at 0°C). The Tahoe tower was designed for
400 cubic feet per gallon; therefore, removal was much lower than 907..
Another problem which developed at Tahoe is the formation of scale in
the tower. The scale is chiefly calcium carbonate. It forms because the
previously lime-treated effluent is supersaturated with respect to
calcium carbonate. In the case of the tower at Tahoe, the sludge can be
flushed from the tower except from inaccessible areas which cannot be
reached with a water jet. A pilot scale ammonia stripping tower at
FWQA's Blue Plains, Washington, D. C. Pilot Plant, has had similar
scaling problems, except the scale is hard and adheres to the tower
fill. The causes of the differences in the nature and amount of scale
in various locations has not been resolved. Studies are in progress to
see if the scale can be prevented from forming, or if it can be made
nonadherent.
26
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The cost of ammonia stripping has been estimated for the South Lake
Tahoe facility to be about 2.9C pet 1000 gallons of wastewater treated.
This does not include the cost of the lime and facilities to raise the
pH to about 11. These costs have been charged to phosphorus removal
because this is the direct objective of the lime addition. If 90%
removal of ammonia nitrogen is required even in cold weather, these costs
should be increased by about 50% to provide for a higher air-to-water
ratio.
Ammonia stripping is feasible when the temperature is above freezing
but there is danger of serious fouling by scale. The best approach for
minimizing scale and its effects appears to be to use a pH of about
10.5, countercurrent operation rather than cross-flow, and an open fill
to allow for easy flushing of accumulated solids. For more information
contact:
Dr. J. B. Farrell
U. S. Dept. of the Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
NITROGEN REMOVAL BY CHEMICAL METHODS
A. Removal of Ammonia by Selective Ion Exchange
Conventional water softening ion exchange resins which are selective
for calcium and magnesium do a relatively poor job of removing ammonium
from dLlute solutions. Total deionization by mixed bed ion exchange
resins will, of course, remove ammonium ions along with other cations
but this process is too costly for wastewater treatment.
Certain zeolites show unusual selectivity for the ammonium ion. A
number of these hava been investigated by the Atomic Energy Commission
because they also show selectivity for cesium and potassium ions. A
demonstration project at the Battelle Memorial Institute - Pacific
Northwest (Hanford) Laboratories, 1969 (Mercer, B. W., et al., "Ammonia
Removal from Secondary Effluents by Selective Ion Exchange," Jour. Water
Pollution Control Federation, Research Supplement, February, 1970) showed
that certain zeolites, including the naturally occurring mineral clinop-
tilolite, had a high selectivity for ammonium in natural and wastewaters.
A trailer mounted demonstration plant with a capacity of 100,000 gallons
per day was built as a cooperative demonstration project between the FWQA
and Battelle-Northwest. This trailer is now operated under contract to
the FWQA to demonstrate selective ion exchange removal of ammonium ions
from solution. ,
Clarified secondary effluent is passed downward through columns
containing clinoptilolite. When a column becomes loaded with ammonia, it
is regenerated with limewater containing sodium chloride to speed up
the rate of regeneration. The high pH of the limewater converts the
27
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ammonium ion to unionized ammonia gas in solution. The ammonia laden
limewater is then pumped through a packed column through which heated
air is blown to remove the ammonia.
Pilot studies at Battelle-Northwest indicated a cost approaching
10c/1000 gallons for their Zeolite method. At Lake Tahoe, where winters
are severe and the area is not readily accessible for chemical deliveries,
a cost of 15C/1000 gallons has been estimated for a 7-1/2 mgd plant.
More reliable cost estimates will be available at the conclusion of the
present contract with Battelle-Northwest.
B. Ion Exchange for Nitrate Removal
Several attempts have been made to develop selective ion-exchange
processes for nitrate removal. Dow Chemical Company is presently under
contract to FWQA (Contract No. 14-12-808) to develop a nitrate removal
process based on the use of a porous solid absorbent containing a nitrate-
selective water-immiscible extractant. The process has the advantages of
liquid ion-exchange technology and the ease of operation of the granular
bed resin systems.
Selective nitrate removal by ion exchange will not be feasible until
new resins are synthesized with a high selectivity for nitrate over other
anions present in the water. In addition, a suitable process for treating
the nitrate laden regenerants must be developed.
C. Chlorination of Ammonia
Ammonia can be oxidized to nitrogen gas by chlorinating to the break-
point with either chlorine gas or sodium hypochlorite. Four moles of
chlorine or hypochlorite per mole of nitrogen gas liberated are required.
Hypochlorite is more expensive than chlorine gas, but it is much safer
to transport and handle.
Breakpoint chlorination, of course, also disinfects the wastewater
as well as oxidizing ammonia. However, the addition of 200-300 mg/1 of
chloride ion would not be acceptable for many inland waters.
Assuming 20 parts of ammonia nitrogen in a secondary effluent, 200
parts of chlorine would be required for breakpoint chlorination. This
is equivalent to 1.5 lbs of chlorine per 1000 gallons or about 6<:/1000
gallons. To this must be added the cost of handling the corrosive hydro-
chloric acid produced. Sodium hypochlorite may cost twice as much as
chlorine but associated costs are greatly reduced.
For more information on ammonia removal by selective ion exchange or break-
point chlorination, contact:
Dr. R. B. Dean
U. S. Dept. of the Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
For additional information on selective nitrate removal, contact Mr. R. A.
Dobbs at the same address.
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PHOSPHORUS REMOVAL - GENERAL
Phosphorus is considered by many investigators to be the key nutrient
in breaking the eutrophication cycle, However, conventional secondary
plants are not efficient in phosphorus removal. Phosphorus enters a
plant in the highest oxidized form. But, no common biological systems,
reduce phosphorus; therefore, it cannot be liberated in a gaseous form
as nitrogen, carbon, and sulfur are. Removal by biological means, then,
is limited to cell metabolic needs and whatever excess phosphorus can be
encouraged to be taken by and stored by the cells. The quantity stored
above the 1% required for maximum growth is usually classified as "luxury
uptake."
A few plants have reported efficient phosphorus uptake on a sustained
basis, including the San Antonio Rilling Plant and the Baltimore,
Maryland Plant. These results cannot be readily duplicated at other
plants by manipulation of operating conditions. We have not learned
enough about thephenomenon to take advantage of it. The removal of
phosphorus by biological synthesis and "luxury uptake" is not a
controllable process at this time.
If we are to reliably remove phosphorus from wastewaters on a sustained
basis, we must choose the chemical or the chemical-biological methods.
Strict chemical methods precipitate phosphorus either in the primary
settler or in a tertiary clarifier. The chemical-biological method
employs direct chemical dosing to the aerator of an activated sludge
plant. The chemically-bound precipitated phosphorus is removed with
the sludge and is not resolubilized during sludge disposal unless the
pH is substantially lowered. Effluent phosphorus concentrations of
1-2 mg/l as P can be regularly achieved if the precipitation is accom-
plished in the primary or secondary portions of the plant. Tertiary
lime clarification followed by filtration will lower the concentration
to less than 0.5 mg/l.
BIOLOGICAL PHOSPHORUS REMOVAL
The literature indicates that several factors exert an inrluence on
biological phosphorus removal. The rate of aeration and the aeration
time have been indicated by most investigators as the most important
criteria, the rate of air supply probably being the more critical of
the two. Aeration rates in the order of 3 to 7 cfm/gal and detention
times of 4 to 6 hours appear to be desirable.
There is some disagreement in the literature with respect to optimum
concentration of mixed liquor suspended solids (MLSS). Apparently,
increased uptake has been attained at both low and high MLSS from 500 mg/l
up to 4300 mg/l. At the San Antonio, Texas treatment plants, the optimum
appeared to be 1000 mg/l or slightly higher (1). It was also found that
the maximum overall phosphorus removal occurred at organic loadings of
45 to 55 pounds of BOD/day/100 pounds of MLSS under aeration.
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It also appears essential from the literature that a dissolved oxygen.
(DO) level of at least 2 mg/1 should be maintained in the last half of
the aeration tank to insure that phosphorus will not be released in the
secondary clarifier. It is possible that a still higher DO level of
3 to 5 mg/1 may be advantageous to maintain a minimum DO concentration
of 1.5 mg/1 in the sludge until it is through the secondary clarifier.
Phosphorus leakage or resolubilization will occur in the secondary clar-
ifier when the sludge consumes available dissolved oxygen. It has been
suggested that solids detention time in final clarifiers should be less
than 30 minutes.
These key design criteria and operational parameters have not been suffi-
ciently isolated and identified to effectively predict and implement con-
trolled phosphorus removal by the solely metabolic mechanism. As more
data have been collected, an alternative chemical explanation has been
advanced (2). Simply stated this theory indicates, especially in hard
water areas, that phosphorus can be precipitated within the biological
floe as calcium phosphate at the end of the aeration period, where carbon
dioxide is scrubbed from the water by aeration and a substantial increase
in pH occurs. This amount of precipitated calcium phosphate and the pre-
cipitation of additional phosphorus by traces of iron, aluminum,and mag-
nesium normally present in wastewater would produce an efficient overall
removal.
The calcium phosphate theory has been tested at several treatment plants
with erratic results. Operating a segment of the Hyperion, California
Plant according to the guidelines outlined by the theory has greatly in-
creased the efficiency of phosphorus removal. At Baltimore, Maryland
where efficient phosphorus removal occurs routinely, observations show
no major increase in pH during operation. Studies at Texas City, Texas
where attempts were made to deliberately force calcium phosphate pre-
cipitation by the addition of 200 mg/1 of lime to the aerator have not
shown efficient removal.
The preliminary data reported from these full-scale treatment plants
are still not complete or detailed enough at this date to confirm either
the metabolic or calcium phosphate precipitation theory. For further
information contact:
Dr. C. H, Connell
The University of Texas Medical Branch
Department of Preventive Medicine and
Community Health
Galveston, Texas 77550
or
Dr. R. L. Bunch or Mr. E. F. Barth
U. S. Dept. of the Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
/
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References
(1) Vacker, D., et al., "Phosphate Removal Through Municipal Wastewater
Treatment at San Antonio, Texas," Jour. Water Pollution Control
Federation, May 1967.
(2) Jenkins, D. and Menar, A. B., "The Fate of Phosphorus on Waste
Treatment processes: the Enhanced Removal of Phosphate by
Activated Sludge," Proceedings of the 24th Purdue Industrial
Waste Conference, 1969.
PHOSPHORUS REMOVAL BY MINERAL ADDITION TO THE PRIMARY OR SECONDARY
Mineral addition is out of the research stage and into the application
stage. Field experience on full-scale and large demonstration pilot
plants shows that ferrous, ferric, and aluminum salts can be equally
effective as phosphorus precipitants in wastewater. Plants can accomplish
80 to 90 percent phosphorus removal with a minor investment in capital
equipment for chemical storage tanks, chemical pumps, and control equip-
ment (Barth, E. F. and Ettinger, M. B., "Mineral Controlled Phosphorus
Removal in the Activated Sludge Process," Jour. Water Pollution Control
Federation, August, 1967).
For trickling filter plants, the chemical precipitation should be
accomplished in the primary tank. Direct dosing of chemicals to the
trickling filter has not proven highly effective. A small dose of
polymer is needed to flocculate and settle the phosphorus which is
insolubilized by the mineral addition. Subsequent passage through the
trickling filter to satisfy metabolic needs serves as a polishing step.
Dow Chemical has conducted several studies of iron-polymer precipitation
in the primary at Midland, Lake Odessa, Grayling, and Benton Harbor,
Michigan. FWQA sponsored projects include Grand Rapids, Michigan (45 mgd)
and Richardson, Texas (1.5 mgd). For further information contact:
Mr. Ronald F. Wukasch
The Dow Chemical Company
2020 Abbott Road Center
Midland, Michigan 48640
Phone: 517-636-2634
With an activated sludge plant, it makes very little difference where
the point of addition of themetal ion is. Efficient removals have been
obtained when dosing raw wastewater before primary settling, after primary
settling, in the aeration tank, or near the mixed liquor exit point. Phy-
sical constraints of a particular plant may favor one point of addition
over another. However, the key factor in this approach is that no matter
where the metal ion insolubilizes the phosphorus, the overall plant effi-
ciency is dependent upon the ability of the biological floe to collect
31
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these dispersed precipitates and remove them from the final plant effluent.
Polymer addition in the primary is not necessary for an activated sludge
plant as the naturally occurring polymeric materials in the mixed liquor
will serve the same purpose. FWQA sponsored projects of phosphorus pre-
cipitation in an activated sludge plant include Penn State University (2 mgd),
Texas City, Texas (0.75 mgd), University of Notre Dame (50,000 gpd), Man-
assas, Virginia (1 mgd), Xenia, Ohio (1 mgd), and Detroit, Michigan (7,000 gpd).
For more Information contact:
Mr. E. F. Barth
U. S. Dept. of the Interior, FWQA
4676 Columbia Parkway
Cincinnati, Ohio 45226
Phone: 513-871-1820
Dosages of 1.5 to 2.0, on a molar basis, of metal ion to phosphorus can
produce effluents with a residual total phosphorus of 1 milligram per
liter or less consistently on full-scale application. As is true with
other parameters such as BOD, COD, and suspended solids, if very low re-
siduals are desired, filtration of the effluent would be required. If
commercial aluminum and iron minerals are used, the chemical cost will
vary from 2-5
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Currently, lime precipitation is also being considered as the first
step in a chemical-physical treatment sequence for raw wastewater that
does not include a biological unit. Subsequent units in the sequence
include lime recovery, filtration, carbon adsorption and possibly ammonia
stripping.
The above sequence is similar to the tertiary sequence demonstrated for
several years at Lake Tahoe's 7.5 mgd Water Reclamation Plant. The Lake
Tahoe Plant utilizes secondary effluent as feed water. Phosphorus removal
costs at Tahoe vary monthly from 6-8
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT1 STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
DISSOLVED REFRACTORY ORGANICS
PPB 1702
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
35
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DISSOLVED REFRACTORY ORGANICS
PPB 1702
PROCESSES FOR ORGANICS REMOVAL
I. Introduction
Most liquid wastes, both domestic and industrial, contain a complement
of organics which must be removed or altered before discharge. The
classical approach and the method now most widely used has been biologi-
cal oxidationo Decades of research have produced a great variety of
processes, all dependent on biological activity, to consume organics for
energy and for cell protoplasm. Biological oxidation has limitations:
some organics are not degradeable, toxic materials must be avoided and
low temperatures slow biological activity„ Recognition of these limita-
tions plus the need to produce increasingly higher quality effluents for
discharge or for reuse, led AWT to search for alternatives to biological
treatment.
Several processes for removal of organics from both domestic and indus-
trial waste streams are in varying stages of development. These are:
1. Granular activated carbon
2. Powdered activated carbon
3. Adsorbent resins
4» Oxidation processes
II. Granular Activated Carbon
Activated carbon is an adsorbent medium characterized by an extensive
system of internal pores which provide it with a very large surface area
per unit of weight. This large area plus the variety of functional groups
(acidic, basic, oxygenated, etc.) attached to the surface give activated
carbon a significant adsorptive capacity for most dissolved organics in
wastewater. The carbon, when exhausted^ can be reused after regeneration
by heating to high temperature (ca 1700 F).
The method of application is primarily determined by the particle size
of the carbon to be used. Granular carbon, in the mesh size range from
8 x 30 to 40 x 60, is generally contacted with the wastewater in a fixed
36
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or fluidized bed of carbon. Originally, carbon adsorption was con-
sidered as a tertiary treatment to supplement biological processes to
produce a high quality product of reuseable quality. More recently,
the main thrust of research has shifted from the treatment of biologi-
cal secondary effluent to treatment of clarified raw sewage. Success
in the latter effort will provide the sanitary engineer an alternative
to biological treatment.
One of the first large-scale applications of granular carbon to waste-
water treatment was the South Tahoe Wastewater Reclamation Plant.
This 7.5 mgd granular activated carbon plant treats secondary effluent
after clarification by lime and mixed media filters. The carbon
effectively reduces an influent BOD from 5-20 mg/l to 2-5 mg/lj COD
from 20-30 mg/l to 2-10 mg/l; and color from 20-50 to less than 5 units.
The average dosage of carbon to accomplish this treatment has been
300 lb/million gallons of treated wastewater.
Large-scale studies at Pomona have substantially confirmed the results
obtained at Tahoe. Carbon dosage, however, was found to average about
350 lbs/million gallons. Here, too, effluent quality has been good.
Total COD was reduced from 47 mg/l to 9'5 mg/l; color from 30 units to
3 units and turbidity from 10 JTU to 1.6. Significantly the CCE, which
has been used as a measure of water quality for drinking water supplies,
was 0.014 mg/l> substantially below the recommended 0.2 mg/l.
These two large-scale studies plus bench investigations firmly estab-
lished that activated carbon can produce effluents with low organic
contents and at a cost that is reasonable. To make the process economic
it was recognized very early that multiple use of the carbon, in contrast
to the single use practiced in water treatment, was necessary. Current
regeneration techniques using temperatures of 1600-1700°F plus steam have
been able to recover 92-95$ of the carbon. Some losses, both physical and
chemical, do occur during regeneration. Attempts to regenerate carbon in
situ with chemical oxidants or caustic washes have not been successful.
The manner in which the carbon is contacted with the wastewater has been the
subject of considerable investigation. The wastewater can be upflow or
downflowj the carbon can be static or moved continuously or in slugs; or
a fluidized bed can be used. In most of these applications pressure has
been used to maintain flows. Simple gravity flow contactors (using lower
flow rates) have been suggested as economic. Recent estimates by Swindell-
Dressier show that the gravity flow system is less expensive by about
2^/1000 gallons in spite of the smaller flow rate. Flow rates in pressure
systems have ranged 6-10 gpm/ft2 while gravity flow will range 2-4 gpm/ft2.
-------
The most thorough estimate of the cost of treating secondary effluent by
carbon adsorption was prepared by Swindell-Dressier. Various systems were
subjected to side-by-side economic analyses, using data then available in
the literature. Total costs have ranged from as little as 8.5^/1000 gallons
for the gravity system to as much as 12.5^/1000 gallons for a 10 mgd plant.
These studies and others have clearly established that activated carbon
can produce good quality effluents from secondary effluent at some reason-
able and predictable cost.
A more recent concept in the use of activated carbon is replacement of the
biological secondary treatment process in conventional treatment. The
process sequence consists of chemical clarification of raw sewage by either
organic flocculants or by metal coagulants, when phosphate removal is desired,
followed by carbon adsorption. To date, technical feasibility has been
demonstrated only at small scale, but full-scale application will be demon-
strated within the next two years.
Some impressive information has already been developed on this process
which could replace biological treatment by a purely physical-chemical
process. Calgon's studies of the treatment sequence (clarification-carbon)
has shown the following removals are obtainable when contact time with the
carbon is 24 minutes; suspended solids 93%; BOD 93$; COD 81% and T0C 75%.
When metal coagulants are used in the clarification step, phosphate removals
in excess of 90% can be obtained.
Pilot scetle investigations at the Lebanon Pilot Plant of AWTRL have shown
that lime clarification followed by carbon adsorption of primary effluent
can consistently produce an effluent equal or better in quality than
secondary biological treatment. Over five million gallons of primary
effluent were processed to produce an average effluent product containing
10 mg/l T0C and BOD with a range of 2-23 mg/1. Effluent turbidity averaged
less than 2 JTU and phosphate removals were consistently 90% or better.
Some advantages that can be cited for a physical-chemical process are:
1. Substantially less land would be required. Calgon claims as
little as l/lO.
2. Capital costs for conventional plants may be 30-40% greater than
that for the P-C plant.
3. P-C process should be less influenced by shock loads, low
temperature and by substances which would be toxic to a
biological system.
38
/
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4. The plant should be easy to operate and could be readily-
adjusted to produce a ranging quality of effluent as desired.
5. Odor problems should be minimal.
6. Significantly, much less sludge will need to be handled. For
example, a conventional 10 mgd activated sludge plant will
produce about 150,000 gpd of sludge, about 70$ of which, or
105,000 gpd, is secondary sludge. The P-C plant could very
well reduce the volume to about one-half of the to tail, depending
on the flocculant used, and this sludge should be readily
filterable.
A major disadvantage of the P-C process is that ammonia nitrogen
will be unaffected. Substantial reductions of organic nitrogen can be
expected through solids removal both by the clarification step as well
as by the filtering function of the carbon beds.
The plant which will probably be the first to demonstrate the P-C
process sequence is located at Rocky River, Ohio. While the original
process envisions polymer flocculation, phosphate removal and clarification
is being studied for possible use. The carbon adsorption plant will consist
of eight pressure contactors, 25 feet high (15 feet of carbon bed) and 16
feet in diameter, and will process a peak flow of 20 mgd (nominal flow of
10 mgd). Flow rate will be 4.-3 gpm/ft2 with a peak rate of 8.6 gpm/ft2.
Carbon will be.thermally regenerated at an anticipated rate of 300-500
lbs/day/million gallons. Loss on regeneration is expected to be no more
than 5%' Effluent quality objectives are 15 mg/l BOD and 10 mg/l suspended
solids, but actual quality may exceed these.
Another plant at Painesville, Ohio, will be designed for a flow of 5.0 mgd,
part of which (up to one-half) consists of oil and chemical wastes.
Fluctuations of pH from 2-11 and the presence of high concentrations
of phenol and chlorine would make biological treatment difficult if not
impossible.
Preliminary studies have shown that the wastewater can be effectively
clarified (and phosphate precipitated) by ferric chloride. Initial plans
call for clarification, roughing sand filters and gravity-flow carbon
contactors. The latter will be 15 feet deep, containing 8 x 30 mesh carbon
in columns operated in parallel at 2 gpm/ft*. Effluent quality objectives
are, BOD, 20 mg/l; COD, 30 mg/lj phosphates 80$ removal and suspended solids
10 mg/l.
39
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Status Summary
The technical feasibility of adsorption of organics by activated carbon
has been well established. Regeneration of exhausted granular carbon can
be considered to be operational. It remains for the two P-C demonstration
plants discussed above to provide operational and cost information. If
cost of P-C treatment is comparable to conventional biological secondary
and for comparable effluent quality, then increasing numbers of these plants
will be used. Reliability of the effluent quality, the smaller land
requirements, the freedom from toxic influences, the lack of odor nuisance
in areas of population, are some of the reasons why P-C plants will find
increasing use.
III. Powdered Activated Carbon
Powdered carbon has developed into a rival of granular carbon. Its finer
grain size increases the kinetics of adsorption such that 90# of its
adsorption equilibrium is attained in less than 10 minutes. Powdered
carbon is dosed in slurry form, after which it is separated by sedimenta-
tion following polymer flocculation. Other methods of separation are
being investigated. Powdered carbon has the advantage over granular in
that its cost is about l/3 as great. Unit cost and the possibility to
control the dosage applied are two of the advantages over granular.
Powdered carbon can be applied to either primary or secondary effluent
and is being tested on both feeds. Determination of the technical and
economic feasibility must await the results of contracts with Eimco Corp.
and Infilco. In contrast to granular carbon regeneration, recovery of
spent powdered carbon has been accomplished only in small prototype
furnaces. Larger scale regeneration will have to be done before the
powdered carbon process is a practical alternative to granular carbon.
IV. Other Methods for Organic Removal
At the present "time, powdered and granular carbon provide the reagents
of choice for removal of organics. Other methods, however, are being
investigated as alternatives to carbon or for specialized applications.
Adsorbent synthetic resins are available and newer ones are being
developed which have the ability to sorb organics without any substantial
inorganic exchange capacity. At this point of development, sorbent resins
are not likely to replace carbon but the search for better ones is
continuing.
A variety of chemical oxidation methods have been investigated such as
chlorine catalyzed by U-V light, metal catalyzed photo-oxidation and
ozone. Of these, only ozone appears to be promising. Technical
AO
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feasibility was established in the laboratory by Airco, Inc., which is
currently constructing a 50,000 gpd plant to establish economic
feasibility. Because of the cost of ozone itself and the rather large
doses, up to 100 mg/l, required for oxidation, application is likely
to be limited to treatment of low organic content feeds, such as carbon
effluents which need further organic reduction. A valuable benefit of
ozonation is its disinfection of the waste stream.
41
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Recent Publications and Reports
Oxidation and Adsorption in Water Treatment Theory and Application. The
University of Michigan Dept. of Civil Engineering, Division of
Sanitary and Water Resources Engineering, February 1965.
Bishop, D. F., et al., "Studies on Activated Carbon Treatment". Jour. WPCF,
February 1967.
Removal of Organic Contaminants. Sorption of Organics by Synthetic Resins
and Activated Carbon. Sanitary Engineering Research Laboratory,
College of Engineering and School of Public Health, University of
California, Berkeley, SERL Report No. 67-9, December 1967.
Masse, Arthur N., "Removal of Organics by Activated Carbon". Robert A.
Taft Water Research Laboratory, August 1968. (mimeo)
A Comparison of Expanded-Bed and Pack-Bed Adsorption Systems. Robert A.
Taft Water Research Center Report No. TWRC-2. December 1968.
Ozone Treatment of Secondary Effluents from Wastewater Treatment Plants.
Robert A. Taft Water Research Center Report No. TWRC-4-. April 9, 1969.
Nutrient Removal and Advanced Waste Treatment. Robert A. Taft Water
Research Laboratory. Symposium on April 29-30, 1969, at Stouffer's
Inn, Cincinnati, Ohio.
42
i
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Appraisal of Granular Carbon Contacting. Phase I Evaluation of the Literature
on the Use of Granular Carbon for Tertiary Waste Water Treatment.
Phase II Economic Effect of Design Variables. Robert A. Taft Water
Research Center Report No. TWRC-11. May 1969-
Appraisal of Granular Carbon Contacting. Phase III Engineering Design and
Cost Estimate of Granular Carbon Tertiary Waste Water Treatment Plant.
Robert A. Taft Water Research Center Report No. TWRC-12. May 1969.
Rizzo, J. L., and R. E. Schade, "Secondary Treatment with Granular Activated
Carbon". Water & Sewage Works, August 1969.
Hager, D. G., and P. B. Reilly, "Clarification-Adsorption in the Treatment
of Municipal and Industrial Wastewater". Presented at the 4.2nd Annual
Conference of the Water Pollution Control Federation Meeting in Dallas,
Texas, October 5-10, 1969.
Weber, W. J., Jr., C. B. Hopkins, H. Bloom, Jr., "Physicochemical Treatment
of Primary Effluents". Prepared for the 42nd Annual Conference of the
Water Pollution Control Federation Research Symposiun Session, October 7,
1969, Dallas, Texas.
Knopp, P. V., and W. B. Gitchel, "Wastewater Treatment with Powdered
Activated Carbon Regenerated by Wet Air Oxidation". Presented at the
25th Purdue Industrial Waste Conference, May 5-7, 1970.
43
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Sources of Information
Much of the research on processes for removal of organics from
wastewaters is conducted at or out of the Advanced Waste Treatment Research
Laboratory. The address of the laboratory and the principal investigators
are given below:
1. Francis M. Middleton Director Research
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
, Cincinnati, Ohio 45226
(513)871-1820, X-225
2. Arthur N. Masse Chief, Municipal Treatment Research Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513)871-1820, X-416
3. Jesse M. Cohen Chief, Physical & Chemical Treatment Research
Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513)871-1820, X-230
44
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
JULY 1, 1970
SUSPENDED AND COLLOIDAL SOLIDS REMOVAL
PPB 1703
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
45
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SUSPENDED AND COLLOIDAL SOLIDS REMOVAL
PPB 1703
PROCESSES FOR SOLIDS REMOVAL
I. Introduction
Removal of suspended or colloidal solids from domestic and industrial
wastewater is of major importance in any treatment system- Evidence of
its importance is the great variety of methods and devices which have
been developed for this task,, This brief review can only discuss the
more widely used processes and describe the newer, more promising tech-
niques now being developed„ The subject material can be considered in
two parts; the physical aspects which relate to the equipment and the
physical methods of solids-liquid separation, and the chemical aspects
which involve chemical modifications to facilitate or improve the
separation of solids. The principal unit processes employed for solids
removal include:
1. Sedimentation
2. Flotation
3. Filtration
4. Microscreening
5. Coagulation-flocculation
6. Miscellaneous processes which include: moving bed filter,
ultrafiltration, magnetic separation, ultrasonic flocculation,
etc.
II. Physical Processes
A„ Sedimentation
The time-honored method for separation of solids involves sedimentation
by gravity. In the conventional horizontal flow sedimentation tank, de-
tention periods of 2 to 4 hours are used to enable suspended particles
to settle by gravity. It is the simplest of the processes to remove
solids, and it is also the least efficients Colloidal particles settle
at such a slow rate that they are not effectively removed. Some degree
of short circuiting always occurs leading to lesser detention times for
portions of the flow. Because of the inefficiencies of this process
many attempts have been made to improve on the separation, still using
gravity as the driving force.
One such improvement is the tube settler developed in this country and the
Lamella separator developed in Sweden. Both processes achieve separation
46
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by causing the particles to settle only inches rather than the several
feet as in the conventional settler. This is accomplished by conducting the
wastewater upward thru inclined tubes or plates, the solids move toward the
lower end of the tubes while the water passes out of the tops. The tube
settler has been rather widely used for separation of floe in chemically
treated river water. It is also finding application for removal of solids
from chemically treated wastewater. There is sufficient information to
indicate that this device does separate particles, but insufficient
evidence is at hand to conclude that the increased capital investment over
conventional sedimentation alone is warranted.
B. Flotation
Another process which separates particles by gravity is flotation.
Separation is achieved by attachment of air bubbles, which effectively
reduces the specific gravity of the particles to less than that of water.
Flotation lias found application for clarification of a number of industrial
wastes, however, the process is little used at the present time for clarifi-
cation of domestic wastewater. Its widest application in wastewater treat-
ment is for sludge thickening operations. With additional development, air
flotation may find wider application to raw sewage clarification following
flocculation by chemical additives.
Air flotation has some attractive potential advantages over sedimentation:
1) a more positive control over the separation rate by controlling process
variables such as air/solids ratio or chemical addition; 2) a lower initial
capital cost owing to higher separation rates and shorter detention times;
3) reduction of septicity and associated odors owing to aeration of feed
and shorter detention times; 4) greater sludge density allowing use of
smaller equipment for dewatering; and 5) multiple use of a single treatment
unit for removal of heavy grit, suspended solids and oil or grease. These
advantages are gained with the following disadvantages: 1) higher operation
costs, and 2) greater operational skill is required. The process clearly
needs additional research to define in more detail the above advantages and
disadvantages.
C. Filtration
Whenever a high degree of clarification is required, then in-depth filtration
after chemical treatment is the process of choice. Rapid sand filtration has
been practiced for decades by water treatment plants but only recently for
wastewater application. In this process, the wastewater passes through a
bed of granular media which captures the particles within the filter. When
the capacity to store particles is reached, the filter is restored by back-
washing. In an ideal filter for downflow operation, the media is uniformly
graded from coarse to fine from top to bottom. The usual sand filter does
47
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not meet this ideal requirement, hence mixtures of media have been
employed to approach the ideal filter. The most common is a two
component filter of coal on top of sand. A tri-media filter contains
coal, sand and garnet.
One of the difficulties with filters is that the upper layers of the bed
become clogged with solids well before storage capacity is reached in the
remainder of the filter. Several approaches have been taken to overcome
this problem. The filter can be operated upflow in which case the flow
proceeds from coarse to fine media approaching the ideal. Some filters
have been designed to introduce the feed into the middle of the filter
with flow in two directions.
One of the more promising techniques developed by Johns Manville is
described as a moving bed filter. The object here is to renew the sand
bed surface either continuously or intermittently to avoid surface plugging.
This process has been tested at pilot scale and a full scale installation
is being made in Manville, New Jersey. Yet another approach has been pro-
posed by the Research Triangle Institute in which a lightweight media floats
to form a packed bed. Wastewater is filtered upflow. As the media becomes
clogged, it is removed from the bed, washed, and then reintroduced with the
wastewater. The concept is sound but feasibility remains to be tested.
D. Microscreening
Microscreening involves straining of wastewater through a woven metal fabric
having openings ranging upwards from 23 microns. The screen is continuously
cleaned by pressure sprays. Only larger suspended particles are removed
since straining is limited to particle sizes greater than the mesh size.
These devices have thus far found their greatest application in treatment
of river waters. More recently, application to removal of suspended solids
from secondary effluents has been tested. Chicago's Hanover Treatment Plant
has successfully operated a microstrainer to reduce suspended solids in
secondary effluent to less than 5 mg/l. Since about one-half of the
residual BOD of secondary effluent is attributable to the suspended solids
content, removal of the solids effects a reduction of the BOD as well as
suspended solids.
Ill. Chemical Processes
A. Metal Coagulants
The colloidal components of wastewater cannot be removed by any of the
physical processes described above. To remove these solids, the particles
must be coagulated and flocculated to larger size before physical methods
can be effective. In conventional secondary treatment the colloids are
48
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flocculated by organic polymers produced during the biological oxidation.
Coagulation and flocculation can also be achieved by chemical additives.
Chemical coagulation and flocculation were first proposed some thirty years
ago but was never widely employed. Today, chemical flocculation is the
essential first step in physical-chemical treatment. The use of chemical
additives has gained impetus from the need to remove phosphates from
wastewater, All metal coagulants now being used for phosphate removal
also accomplish clarification.
A wide variety of metal coagulants are suitable for clarification (also
phosphate removal). These include: aluminum salts, such as aluminum
sulfate, and sodium aluminate; iron salts, such as ferric or ferrous
chloride or sulfate, pickling liquor which is an iron-containing waste
stream from the steel industry; and lime. Which one of the several
coagulants to Use in any specific instance cannot be predicted beforehand.
All metal coagulants are effective and the choice of one from the many has
to be made for any application. The choice for any particular application
is generally based on relative dosage, the cost of the coagulant and the
chemical composition of the wastewater. It is well to remember that to
obtain clarification and phosphate removal in wastewater will require
substantial dosages of coagulant which in turn will produce chemical
sludges which must find disposal. The range of dosages for iron or
aluminum salts range 100 to 300 mg/l while for lime the range is 300 to
600 mg/l or more.
In addition to being the first step in physical-chemical treatment, chemical
clarification may have some other benefits in solids removal in the primary
prior to biological treatment. This concept is being tested at Grand Rapids,
Michigan, at full scale. Some of the advantages that may emerge from this
are: decreased air requirement in activated sludge resulting from the
increased solids capture in the primary; less difficult-to-filter sludge
from the secondary while producing more but filterable solids in the primary.
And, of course, phosphates will be removed. One of the advantages of lime
is that the sludge can be calcined to recover reuseable lime. This has
been demonstrated at Tahoe for lime used in secondary effluent and will be
applied to lime sludge from raw sewage precipitation at Rocky River, Ohio.
One of the interesting developments of recent years has been the synthesis
of a wide variety of organic polymers. Use of organic polymers or poly-
electrolytes as sole coagulants or as aids to the inorganic coagulants has
added a new dimension to clarification. Very low dosages of polymer may
improve efficiency of solids removal, permit reduction of inorganic coagulant
dosages and increase settling rates, thus allowing operation of existing
equipment at higher flow rates. Dosages range from fractions of a mg/l to
several mg/l. Thus, in contrast to inorganic coagulants, sludge volume is
49
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not increased. But organic polymers are not a total panacea. They do
not remove phosphates, they are all expensive ranging$l-$2/lb for the
100$ product, and their behavior for any particular application is
unpredictable. The plant operator is faced with selecting a single
polymer from the .literally hundreds available and even then he cannot
be sure that his choice will be effective all of the time. Polymer
clarification of raw sewage has been tried at Cleveland's Easterly
Plant and at Grand Rapids.
Whether primarily for clarification or for phosphate removal, chemical
addition to wastewater is a growing practice. The resulting chemical
sludges will pose problems for their disposal.
IV. Miscellaneous Processes
A number of other processes for solids separation are in varying stages
of development. One of these is ultrafiltration which is a process akin
to reverse osmosis except that inorganic minerals are not removed. The
process involves application of wastewater under pressure to a porous
membrane. The process cannot compete economically with other solids
removal processes for treatment of large volumes of wastewater. But
there are special applications for small volume filtration where ultrafiltration
may have application. For example thickening of organic sludges or powdered
carbon sludge has been investigated.
Another membrane process, called "cross-flow" filtration by the inventor
at Oak Ridge, may be useful for solids separation. In this process a
membrane is formed on a support and solids separation is obtained under
pressures of 30-50 psi.
V. Assessment for the Future
Research of the last decade has provided the consulting engineer with an
arsenal of processes for removal of solids. This development comes at a
time when, more than ever, better and cheaper ways of solids removal are
required. Phosphate precipitation, improved clarification of raw or
secondary effluent, and higher quality effluents for tertiary processes
have increased the need for separation processes which are more effective
and sophisticated than the simple gravity sedimentation now so widely used.
Of the processes discussed here, media filtration, microstraining and
chemical coagulation and flocculation are the processes which are now
being used. The other processes will be applied as this technology is
improved.
50
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Recent Publications and Reports
Rimer, Alan E.
"Filtration Through a Trimedia Filter"
Jour. San.Engng. Div., ASCE, SA 3 (June 1968).
Miller, D. G.
"Rapid Filtration Following Coagulation, Including
the Use of Multi-Layer Beds"
Proc. of The Society for Water Treatment & Examination,
Vol. 16, Part 3, 1967.
Culp, Gordon
"Secondary Plant Effluent Polishing, Part 1"
Water & Sewage Works, 145 (April 1968).
Ives, K. J., and Gregory, J.
"Basic Concepts of Filtration"
Proc. of The Society for Water Treatment & Examination,
Vol. 16, Part 3, 1967.
Diaper, E. W. J.
"Tertiary Treatment by Microstraining"
Water & Sewage Works, 202 (June 1969).
Packham, R. F.
"Polyelectrolytes in Water Clarification"
Proc. The Society for Water Treatment & Examination,
Vol. 16, Part 2, 1967.
Smith, R. M.
"The Use of Synthetic Organic Flocculants in the Treatment
of Industrial Water and Wastewater"
Proc. International Water Conf., Pittsburgh, Pa., Oct. 1965.
Culp, Gordon
"Chemical Treatment of Raw Sewage, Part 1 and 2"
Water & Wastes Engineering, July 1967 and October 1967.
O'Melia, Charles R.
"A Review of the Coagulation Process"
Public Works, 87 (May 1969).
"Nutrient Removal and Advanced Waste Treatment"
Technical Symposium, Cincinnati, Ohio, April 29-30, 1969
Published by U.S.D I., Federal Water Quality Adm.
51
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Sources of Information
Much of the research on processes for removal of suspended and colloidal
solids from wastewater is conducted at or out of the Advanced Waste Treat-
ment Research Laboratory. The address of the laboratory and the principal
investigators are given below:
1. Francis M. Middleton Director of Research
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 225
2. Jesse M. Cohen Chief, Physical & Chemical Treatment
Research Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 230
3. Sidney A. Hannah Supervisory Research Chemist
Physical & Chemical Treatment Research Prog,
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 309
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
DISSOLVED INORGANIC REMOVAL
PPB 1704
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
53
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DISSOLVED INORGANIC REMOVAL
PPB 1704
PROCESSES FOR REMOVAL OF MINERALS
I. Introduction
During domestic and most industrial uses of water there is added an
increment of dissolved inorganic minerals which must be removed if
water quality is to be maintained. If recycle of wastewater will be
practiced in the future, then almost surely methods will be required
to remove inorganic salts„ Soluble inorganics are even now a signi-
ficant problem for many municipalities» For example, a recent survey
has shown that of the 20,215 municipal water supplies in the 50 states
and 5 provinces in the United States and Canada, 1066 had raw water
supplies with a total dissolved solids (TDS) of 1000-3000 mg/1; there
were an additional 31 supplies that had a TDS of 300-10,000 mg/1,,
The rising salinity of many water supplies and the increasing cost of
developing alternate sources of better quality make it difficult or
uneconomic in many locations to meet the USPHS recommended limit of
500 mg/1 TDS for potable water. These factors justify the support for
research to develop inorganic removal processes.
Several processes are currently being investigated for reducing the
mineral content of municipal wastewater to an acceptable level. These
include: (a) ion exchange, (b) reverse osmosis, (c) distillation,
(d) electrodialysis, (e) freezing and (f) electrochemical treatment.
These processes are in varying stages of development and only the first
four mentioned are currently being given serious consideration as
practical processes for demineralization.
All demineralization processes produce a brine solution. The disposal
of this brine represents a major technical problem in the development
of demineralization technology. In coastal areas it may be feasible
to discharge brines to the ocean. Solar evaporation in lined lagoons
can be employed where climatic conditions are favorable. However,
inland areas with limited potential for solar evaporation will require
the development of more sophisticated techniques for brine disposal.
54
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II. Ion Exchange
Ion exchangers are materials containing ions that can be replaced by
other ions from solution. The replaceable ion carried by the exchanger
is known as the counter ion. Carriers of exchangeable cations are
called cation exchangers, and carriers of exchangeable anions, anion
exchangers. Once all the counter ions are replaced the exchanger is
exhausted and must be restored by regeneration with a solution con-
taining the original counter ion.
Ion exchange will almost certainly be an economic process for deminerali-
zation of wastewater, if the mineral solids do not exceed 1000-1500 mg/1.
This development derives from the commercial availability of new anion
resins which have 1) high selectivity for chloride ion, 2) require less
regenerant and rinse water, yielding a more favorable ratio of product to
feed. But most important has been the discovery that these anion resins
do not become "fouled" by organics - the single most important deterrent
to ion exchange with the older resins. Up to 50-60% of the COD is re-
moved from secondary effluent with no detectable loss of exchange capacity.
The COD is eluted with the regenerant.
Research at AWTRL has confirmed that COD is removed and that fouling does
not occur. Studies at the Pomona Pilot Plant facility demonstrated that
an effluent containing about 50 mg/1 of TDS can be produced from a feed
of about 800 mg/1 TDS. The bulk of the residual TDS was silica which is
not removed by a weak anion resin. Total costs for the process were
estimated to be 24
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The authors also concluded that ion exchange was applicable to feeds up
to 3000 mg/1 TDS - a level that we had not generally considered competi-
tive for ion exchange. Of the four methods being considered for de-
mineralization of wastewater, ion exchange will most likely be applied
earliest to full scale. The technology is well-developed and the costs
appear to be reasonable.
III. Reverse Osmosis
Reverse osmosis is a membrane process in which water is forced to flow
from a solution of high salts concentration to one of lower concentration.
In natural osmosis, water flows in the opposite direction. Pressures of
600-800 psi are required to obtain this reversal of flow. The earliest
applications of reverse osmosis were in the fields of chemical purifi-
cation and brackish water desalination. The discovery of the cellulose
acetate membrane was, perhaps, the single biggest advance in the appli-
cation of reverse osmosis to desalination.
Membranes are defined as imperfect barriers which "retain" or "reject"
molecules of a certain minimum size and will "pass" smaller molecules.
The membranes can be tailored to almost any degree of porosity. Several
types of materials have been identified as having membrane forming prop-
erties suitable for reverse osmosis. Research is continuing on develop-
ment of more useful membranes.
Cellulose acetate membranes developed for brackish water desalination are
relatively tight (i.e., low water permeability) and can reject over 99%
of most mineral species. The water flux through these membranes is very
low ( - 10 gal/day/ft^ ) and are not economic for wastewater deminerali-
zation. Moreover, in treating wastewater, the membranes become "fouled"
by dissolved and colloidal organic material leading to drastic reduction
in flux. These problems have led FWQA to a membrane development program
pointed specifically toward wastewater treatment. Most of the effort to
date has been in new membrane development and in methods to control flux
decline. The most attractive membranes appear to be modified cellulose
acetate types. Current judgment is that the optimum membrane will reject
50-75% of the inorganics and 90% of the organics with fluxes of 50-100 gfd.
At the same time substantial effort is being directed toward alleviating
the fouling problem. Essentially two approaches are being taken:
(a) prevention of fouling by pretreatment procedures or by changes in the
hydraulics of the system and (b) cleaning methods once the membrane has
become fouled. A promising method for the latter is periodic rinsing
of the membrane surface with an enzyme solution. Interestingly, the
most effective enzyme solutions have been the common commercial detergent
pre-soak mixtures such as Biz.
56
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In addition to membranes an extremely important aspect of reverse osmosis
is the hardware. Current modules are of several types and configurations:
(a) tubular, (b) spiral wound and (c) hollow fiber. Each of these con-
figurations has its advantages as well as disadvantages, and at this point
in development no single choice can be made. All are being investigated
concurrently. A recent projection of the economics of RO by Kaiser
Engineers compared the configuration as follows:
sq ft membrane flux productivity
cu ft equipment gpd/sf gpd/cf
Tubular
20
32
640
Spiral wound
250
32
8000
Hollow fiber
(nylon)
5400
1
5400
Hollow fiber
(CA)
2500
10
25000
From this comparison, it would seem that the follow fiber configurations
are superior but in practice hydraulic inadequacies may be a serious
drawback.
Another approach to reverse osmosis has been entitled "dynamically formed"
membranes. In this development, the membrane is formed either from the
constituents of the wastewater or from small additions of a variety of
additives. The advantage of these homemade membranes is that they can
be destroyed and re-formed whenever the membrane becomes fouled. This
work is still in the early stages of development.
Reverse osmosis has enormous potential for wastewater treatment.
Theoretically, it is conceivable that most components of wastewater can
be removed to a high degree in a single unit process. Typical removals
that have been obtained are shown in the following table:
Typical Removals from Secondary Effluent
(CA membrane, 450 psi, ~ 8 gfd)
% rejection
TOC
TDS
Turbidity
Alkalinity
Chloride
90
93
99+
90
80-85
Phosphate 94
Nitrate 65
Ammonia 85
Organic Nitrogen 86
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The practical achievement of the above theoretical capability must await
the solution of some serious problems, among which are: membrane foul-
ing 5 membrane cost, greater (and therefore economic) fluxes, and reduction
of operating costs. On the latter, the best estimate is on the order
of 40
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Assessment for the Future
Almost surely, increasing parts of this country and the world, will look
to their wastewater as an additional source of water resources. And
just as surely, some form of demineralization will have to be applied to
reduce mineral salts„ At this time, no single process, of the several
being studied, is ready for full-scale application and no single process
has a clear and obvious advantage over the others. However, ion-exchange,
because of its highly developed technology in other fields, appears to
be the process which will find earliest application'. A modest breakthrough
in reverse osmosis could find this process applied, particularly to certain
industrial waste streams. It bears repetition that a suitable method has
to be found for disposal of the brine concentrates from any demineralization
process.
Recent Publications and Reports
Eliassen, R., Wyckoff, B„ M«> and Tonkin, C. D.
"Ion Exchange for Reclamation of Reusable Supplies"
JAWWA, 57, 1113 (Sept. 1965)
Sturia, Piero (Rome, Italy)
"Pilot Plant Studies of the Kunin Process"
Paper presented at International Water Conf., of The Engineer's Society of
Western Pennsylvania, September 30, 1964, Pittsburgh, Pa.
Pollio, F. X», and Kunin, R0
"Tertiary Treatment of Municipal Sewage Effluents"
Environmental Science & Technology, 2t 54 (Jan. 1968)
Parkhurst, J, D., Chen, C., Carry, C. W., and Masse, A. N.
"Demineralization of Wastewater by Ion Exchange"
Paper to be presented at 5th International Conf. on Water Pollution Research,
August 1970, San Francisco, California.
Kraus, K. A., Shor, A. J., and Johnson, J. S. Jr.
"Hyperfiltration Studies X. Hyperfiltration with Dynamically-Formed Membranes"
Desalination, 2,, 243 (1967)
Hindin, E., and Bennett, P. J.
"Water Reclamation by Reverse Osmosis", Water and Sewage Works, 66 (February 1969)
"Study and Experiments in Waste Water Reclamation by Reverse Osmosis"
Final Report - Gulf General Atomic - Contract 14-12-181 prepared by
L Nusbaum, J. H. Sleigh, Jr., and S, S, Kremen
"Engineering & Economic Evaluation Study of Reverse Osmosis", F. L. Harris,
Kaiser Engineers, Presented at Office of Saline Water 2nd Symposium on
Reverse Osmosis, (April 1969)
Merten, U., and Bray, D. T„, "Reverse Osmosis for Water Reclamation"
Presented at 3rd International Conf. on Water Poll. Research, Paper
No. 15 (1966).
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Cooke, W. P.
"Hollow Fiber Permeators in Industrial Waste Stream Separations"
Desalination, 7^31 (1969/70)
Brunner, C. A.
"Pilot-Plant Experiences in Demineralization of Secondary Effluent
using Electrodialysis"
JWPCF, 39, Rl (October 1967)
O'Connor, B., Dobbs, R. A., Villiers, R. V., and Dean, R. B.
"Laboratory Distillation of Municipal Waste Effluents"
JWPCF, 39, R25 (October 1967)
Sources of Information
Much of the research on processes for removal of minerals from wastewater
is conducted at or out of the Advanced Waste Treatment Research Laboratory.
The address of the laboratory and the principal investigators are given
felow:
1. Francis M. Middleton Director of Research
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research *>nter
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 225
Chief, Physical & Chemical Treatment
Research Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 230
Research Chemist, Physical & Chemical
Treatment Research Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 362
Sanitary Engineer,
Municipal Treatment Research Program
Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
Cincinnati, Ohio 45226
(513) 871-1820, Ext. 262
2. Jesse M. Cohen
3. Richard A. Dobbs
4. John M. Smith
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
DISSOLVED BIODEGRADABLE ORGANICS REMOVAL
FROM WASTEWATER
PPB 1705
Division of Process Research & Development
Federal Water Quality Administration
U. S, Department of the Interior
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PURE OXYGEN AERATION OF ACTIVATED SLUDGE
Linde Division of Union Carbide, under contract to FWQA, has completed a
comparison of pure oxygen aeration and air aeration in the conventional
activated sludge process. The study was carried out in identical parallel
trains at the 2.5 mgd Batavia, New York plant. Inefficient utilization of
costly pure oxygen has discouraged similar full-scale operation in the past.
The covered-staged oxygen injection and dissolution concepts developed by
Linde overcome this obstacle and 90-95% utilization of the input oxygen
was achieved.
The oxygenation system used employed sealed covers on the aeration tanks
and intertank baffles to form a series of staged compartments. Each com-
partment or stage is equipped with a submerged turbine-rotating sparger
unit and a recirculating gas compressor located on the top of the tank
cover.
The three points demonstrated by this study with the greatest potential
for reducing the cost of waste treatment are:
1. The substantial reduction in aeration volume possible with oxygen
aeration while maintaining efficient carbon and solids removal.
The oxygen train achieved better treatment in 1-1/2 hours aeration
detention time than the air train at 3 hours.
2. The high solid content of the waste activated sludge achieved by
the oxygen system; thereby, possibly eliminating the need for a
separate thickener operation. Oxygenated sludge had a Sludge
Volume Index of 40 and concentrated to about 37. in the final
clarifier underflow.
3. The reduced quantity of waste sludge produced with oxygen.
Significant reduction in the quantity of waste activated sludge
produced by the oxygen system was noted. The best estimates at
this time are that the reduction, by weight was 30-407.. Better
data on the exact amount will be obtained this summer.
The economic substitution of pure oxygen for air may eventually prove to
be one of the most significant breakthroughs in the history of the activated
sludge process. The pure oxygen process, in addition to offering potential
reduction in new plant construction, is also applicable to many existing
high-rate or overload plants which are performing poorly.
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For more information, see report "Investigation of the Use of High Purity
Oxygen Aeration in the Conventional Activated Sludge Process" "by Linde
Division of Union Carbide Corporation, Contract No. 14-12-465, or contact:
Mr. Richard C. Brenner
Advanced Waste Treatment Research Laboratory
(Alio Basin Region
Cincinnati, Ohio 45226
TRICKLING FIHTERS
There has been no major breakthrough in the past two years. This process
is capable of producing a good quality effluent having a BOD5 of less than
20 mg/l if lightly loaded. In the United States, the tendency is to load
the filter at a much higher rate than is done in England. Thus, we find
today many installations that will have difficulty in meeting the more
stringent water quality standards.
It is not enough to just look for completely new processes, but attention
and action must be given immediately to applying known technology to up-
grading present treatment plants. All the needed new plants and plant
expansion cannot be built in a short time. Substantial amounts of pollu-
tion can be prevented from reaching our surface waters by upgrading present
plants. There are several ways of achieving higher removals. There is
probably no one solution that will work at all Installations, for each
plant is different. If a plant is not getting good removal and the impair-
ment is not due to toxic or grossly atypical waste, then It Is usually due
to either hydraulic overload, organic overload, or poor final liquid-solids
separation. The following are suggested ways of alleviating these conditions.
Easing hydraulic overload
1. Find and reduce needless sources. Infiltration, downspouts, arid
cross connection can contribute greatly to the flow.
2. Use large interceptors as holding tanks. Many towns use their
main Interceptor to the plant to back-up the flow during the day
and treat it at night when the flow is low.
3. Construct an equalizing or surge tank to smooth out the high peak
flows. An equalization tank will mix and dilute toxic wastes,
giving better downstream settling and lessen load fluctuations.
Aiding organic overloaded plants
Most organically overloaded plants can be aided by the same methods
suggested for hydraulic overloads since they commonly occur con-
currently. Additional methods are:
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1. Have industry program the load for slow release. In smaller towns,
most industries are willing to program extremely high organic waste
flows.
2. Have industry treat at source using a roughing filter or other
appropriate means to relieve part of the load.
3. Treat digester supernatant return "by alternate methods or program
return load to time of low load.
Remove more material in the primary tank by using iron or aluminum
salts and polymers in the incoming waste. This will also remove
phosphorus.
Lessen final solids discharge
One of the greatest improvements that can be made in secondary treat-
ment is reliable solid removal from effluents. For efficient overall
removal, the final settler must remove better than 98$ of the solids.
If overflow weirs are submerged several Inches with the present flow,
then there is no recourse except to increase settler capacity. For
less hopeless cases, the following can be tried.
1. Chemical flocculation or precipitation in process or ixnal effluent
treatment.
2. Improve inlet and/or overflow design.
3. Install a microscreener.
4. Install mixed media filters.
5. Install tube settlers.
If a town has a trickling filter that is water tight or can be made so, the
filter unit can be simply converted to an aeration tank. This can be done
by removing the filter media and installing a surface aerator. The existing
primary and final clariflers can be utilized with minimal structural and
piping changes. This type of conversion will usually increase the capacity
of the plant twofold for a fraction of the cost of a completely new plant.
All the methods discussed are not new, but are well-proven processes. Thus,
there are answers to the question on how a town can meet the nev vater quality
standards. All that is needed is an awareness of the fundamentals involved
and a willingness to pay for and use all the technology that is known.
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ROTATING BIOLOGICAL DISCS
The rotating biological disc method of treating waste has been used In
Europe for at least the last five years. The system basically consists
of closely spaced rotating discs alternately submerged In wastewater and
exposed to air. Wastewater continuously flows parallel to the discs. The
waste level is slightly less than half the disc diameter. The units are
usually arranged in series or stages.
The discs are molded of low-density expanded polystyrene. The entire
downward load is offset by the buoyancy of the discs. Thus, the only power
required to rotate the discs is that needed to overcome bearing friction.
Microorganisms attach themselves to the discs and perfonn the same function
as in a trickling filter. The biamass sloughed off the discs is removed in
a final clarifier. In short, the rotating biological disc method is a modern
version of the "Immersion Filter" developed by Buswell in the middle twenties.
JVQA has funded a grant (1701 EB4) with Rutgers University to assess the
degree of treatment and to obtain operating data on this method of treatment.
The pilot plant used in this study is a ten-staged unit with a design flow
of 8 gjm. This gives a detention period of 5 minutes per stage or a 50-
mlnute overall detention time for the disc unit. The plant has been in oper-
ation for about one year at the Jamaica Treatment Plant in New York City near
the Kennedy International Airport. Data obtained thus far show that the unit
is oxidizing about 93$ of the biodegradable carbonaceous matter and 80% of
the ammoniacal nitrogen in the primary effluent being treated. A report on
the work is not available at this tine.
A demonstration grant (11010 EBX) has been awarded to the Village of Pewaukee,
Wisconsin to evaluate the effectiveness and efficiency of the rotating bio-
logical disc method for treating municipal wastes on a full-scale community
level. The perfoxnance of the unit will be compared directly with an existing
trickling filter under Identical conditions. The design flow of the disc unit
Is 0.146 mgd. The unit Is scheduled to be on-stream the latter part of this
year.
The rotating disc system has an advantage over a trickling filter unit in
that recycle Is not necessary at night to keep the biological mass wet be-
cause the trough always contains liquid. It seems quite possible that the
method can produce an effluent In quality some place between that of a trick-
ling filter and an activated sludge unit. It is conceivable that the system
would find application at seme of our Federal installations, such as small
parks or rest stations where there is a wide variation in the flows. There
Is a small two-stage unit available that handles population equivalents of
12 to 200 persons.
The main disadvantages of the method are that It must be housed to protect
it from storms, hall, etc. and the large disc surface area required, for
90£ removal, the unit load is 2.7 gal/day/ft2 of disc surface area. Kormally
the discs are ten feet in diameter and the disc spacing is 0,Bk6 inches.
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INSTRUMENTATION OF WASTE TREATMENT HANTS
Instrumentation and control have not yet caught up with the basic require-
ments of wastewater plants. There are several reasons for the limited use
of continuous automatic analysis and control. Some of these are the absence
of sensors to measure seme of the most important factors directly, the fairly
high cost of instruments available, and the willingness of those in the waste
treatment field to decide that automatic operation is necessary and to take
all the steps required to bring it to fruition. In the past, the cost of
instrumentation has eliminated them from consideration by managers of small
and medium-sized plants.
Recent emphasis on water quality standards is bringing about a natural in-
crease in the extent of automatic control. This is especially evident in
newer facilities where instrumentation is no longer an "afterthoughtbut
an integrated part of plant design. Unfortunately, some engineers engaged
in designing new plants have not kept up with the Improved processing tech-
niques . The design of a modern plant for treatment of wastewater requires
a considerably broader knowledge of treatment and control techniques than
in the past.
Many sensors cannot be used in treating wastewater because they beccme fouled
by the gross solids, greases, oil, and aquatic growths. Despite the encum-
brances inherent in the physical makeup of raw wastewater and sludge drawoff,
measuring devices and instrumentation are now available that can monitor and
control most of the secondary plant flow systems. The real problem in auto-
mating the various flow regimes is not a lack of flow controlling equipment,
but the inability to rapidly measure biological activity or "state-of-health"
of the system. For Instance, wasting of activated sludge could logically
be based on the active mass of microorganisms in the system. However, the
closest we can came now to determining active mass is mixed liquor volatile
suspended solids and this has been estimated to represent 50 to 100 percent
more active solids than are actually present. Thus, the difficulty in con-
trolling the treatment plant is directly attributable to the inability to
model constantly changing life processes.
It would appear that the best index for understanding and controlling the
activated sludge process would be the amount of living cells in the aeration
tank. No method now exists which permits determination of the microbial
activity in a manner useful to process control. Adenoslnetrlphosphate (ATP)
is present in and essential to all living cells. Measurement of ATP would
be a rapid and unequivocal method for active microbial mass. Blospherlcs
Incorporated Is under contract (14-12-149) to design and fabricate an in-
strument for use in the ATP assay. In addition, they will adapt the fire-
fly biolumlneBcent method to determine the ATP of activated sludge which is
directly proportional to the blomass. E.I. DuPont is now producing commer-
cially the reagents needed for the test; therefore, there will not be any
difficulty in obtaining the reagents if the method becomes a reality. This
method probably can be automated. The time to perform the tests should be
about 15 minutes if done manually.
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Biological process efficiency is now measured by various laboratory analytical
techniques. The time required to collect, transfer samples, and perform the
analyses may take anywhere from three hours to five days. The time Involved
in obtaining data seriously hinders rapid and effective process control. On-
line instrumentation designed to yield reliable, useful information In tents
of minutes instead, of hours would contribute significantly to improving plant
operation. Contracts are now being let to develop an on-line instrument to
measure the organic strength of influent and effluent streams at a waste treat-
ment plant. The instrument will be capable of analyzing both filtered and un-
filtered samples. This will entail developing an on-line macerating device
as well as an on-line filter. Within the next year, it is hopeful that a
full automatic on-line COD and TOC analyzer will be available to treatment
plants.
A wastewater treatment plant can have too much instrumentation and auto-
mation or it cannot have enough. Most wastewater treatment plants now have
too little instrumentation to give adequate control. The new pilot plant
at AWTRL In Cincinnati will test new process control equipment and instru-
ments in the coning year. Hie aim here is to operate them under controlled
conditions to detezmlne durability, performance, and limitation. This in-
formation will then be made available to construction grants people and con-
sultants so that new plants can be operated more efficiently.
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
MICROORGANISMS REMOVAL FROM WASTEWATER
PPB 1706
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
69
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Introduction
In this first annual report covering the status of disinfection of wastewater
and AWT treatment plant effluents, it is believed that a look at where we
stand now and what is planned for the future should provide a better under-
standing of what may be expected from this subprogram.
Present Status of Chlorlnation
The most desirable objective is to be able to say that application of a
specified dose of chlorine would provide safe disinfection of all effluents.
The collform test should be considered the primary standard; the chlorine
residual can only be considered as a secondary standard and it is only valid
to the extent confirmed by the results obtained in the coliform test. The
conclusions of Browning and McLaren (Jour. Water Poll. Control Fed., August
1967) indicate the problems of operating on a basis of a specified combination
of chlorine residual and contact time. They state '^Generally speaking, a
correlation exists between chlorine residual and coliform density (coliform
densities decrease with increased chlorine residuals) but the individualities
of waste treatment plants and their effluents make it difficult to apply a
correlation determined from one plant to other plants." Each plant must
develop its own data for correlating chlorine dosage, residual, and contact
time to yield predictably the desired reduction in coliform count.
The most highly clarified and oxidized effluents are the easiest to disinfect.
If good control of microorganism content is to be attained by chlorlnation,
good secondary waste treatment should be the minimum. Chlorlnation of pri-
mary effluents should not be considered an acceptable practice in most sit-
uations except as an Interim process until secondary treatment facilities
can be constructed.
Same concern has been expressed regarding the fact that numerous viruses
are more resistant to chlorine than the coliform bacteria. Methods of using
viruses as an indicator of chlorlnation efficiency have not reached the stage
where practical tests for routine use are available. The coliform test still
remains an effective criterion for disinfection of drinking water. Except
for hepatitis, clearly defined outbreaks of virus diseases traceable to
drinking water have not been reported (Clarke, Berg, et al., Adv. Water Pol.
Control Research, Pergamnon Press, McMillan Company, New York, Vol. 1, 1964).
Epidemics of hepatitis originating in chlorinated water supplies judged satis-
factory by the coliform test have not been reported except In instances where
obvious deficiencies in chlorlnation were shown or suspected. It is not,
therefore, considered likely that effluents disinfected to satisfactoay coliform
70
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destruction levels are much of a health hazard. JWQA. has funded a grant
(69-G385) to Investigate the possibility of locating a new bacterial indi-
cator that is sufficiently more resistant than coliform organisms to pro-
vide a safety factor for virus destruction. The emphasis is on the dis-
covery of an organism that can be enumerated by simple plate count or MF
procedures.
Status of Research
Because of personnel limitations and other problems, research in the dis-
infection program had been limited in scope thus far. The outlook for the
future is Improving and a marked increase in the number and variety of
grant and contract projects is anticipated in FY 1971.
In-House:
There have been numerous reports in the literature of a major synergistic
effect of gamma radiation on the disinfecting action of chlorine, but the
vork reported has not been adequately controlled. An investigation to de-
termine whether gamma radiation exerts a synergistic effect on the dis-
infecting action of chlorine is now in progress. This work is being done
under very carefully controlled conditions. Present progress indicates
that this project will be completed in FT 1971, and it is anticipated that
definitive data will be produced to either support or negate the existence
of a synergistic effect.
Grants:
Grantee
Illinois State Water
Survey, University of
Illinois, Urbana,
Illinois.
Subject
Disinfection of
Sewage Effluents
with Chlorine and
Bromine.
Project Director
Expected Corop. Date
Dr. F. W. Sollo
9/30/T0
City of St. Michaels
St. Michaels, Maryland.
(Clow Waste Treatment
Division Aer-o-Flo
Yecmans, Melrose
Park, Illinois En-
gineering Operator for
Grantee)
University of Illinois
Urbana, Illinois
Controlled Treatment
system-Ultraviolet
Disinfection.
New Microbial Indi-
cators of Wastewater
Disinfection.
John A. Roeber
7/9/TO
Dr. R. S. Engelbrecht
9/30/71
Much of our research in disinfection of wastewater deals with problems re-
lated to the use of chlorine. Chlorine, however, Is not necessarily the
answer to all of our disinfection problems, and little Information Is avail-
able regarding the use of other disinfectants for the destruction of micro-
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organisms in wastewater. Other disinfectants are, therefore, being in-
vestigated. The program is planned to develop, as rapidly as possible,
methods for the use of a variety of disinfectants and provide guidelines
for their practical application. The rationale for this approach is to
make available to the sanitary engineer a spectrum of proven disinfection
processes from vhich he can select the one most applicable to a specific
waste treatment disinfection problem.
Research Statements of Need
The extent to which the Disinfection Subprogram can satisfy the needs of
the respective Regional Programs depends upon how well we can identify
those needs and formulate work programs to satisfy them. Satisfaction
of those needs can best be expedited by good liaison with the Region.
It would be most helpful if the Regions would submit statements of re-
search needa to cover specific problems in need of solution. The devel-
opment of an adequate research work plan to satisfy a particular need,
however, depends upon the content of the need submitted. This can best be
accomplished through a preliminary discussion of the proposed need by the
Program Chief and the proponent.
The Commercial Telephone Number: (513)-871-1820, ext. 202
The ITS Telephone Number: (513)-871-l£20, ext. 202
For further information contact:
Cecil W. Chambers
Robert A. Taft Research Center
Advanced Waste Treatment Research Laboratory
Ohio Basin Region
Cincinnati, Ohio 45226
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
ULTIMATE DISPOSAL
PPB 1707
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
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THE UI/HMATE DISPOSAL RESEARCH PROGRAM
at the
Robert A. Taft Water Research Center
Cincinnati, Ohio
The Ultimate Disposal Research Program is responsible for finding places
to put the pollutants which have "been extracted from waters "by conventional
and Advanced Waste Treatments. Disposal of residues must of course he done
in ways that will not cause pollution and ideally the residues should he
reused to the maximum extent possible. Our responsibilities cover disposal to
the air, waters, and to the land, as well as reuse and recycling of constituents.
Control of pollution of underground waters is a specific assignment of the
Robert S. Kerr Water Research Center, but general considerations of deep-
well disposal are also reviewed here. Deep-well disposal is not a generally
applicable method and should be used only where the local geological forma-
tions are particularly favorable and there are no acceptable alternative
methods for disposal.
Disposal of wastes is the most frequently neglected part of our modem
industrial civilization, and is directly responsible for our polluted planet.
Attention to unit operations, with little regard for the fate of by-products
which are no longer interesting and are frequently embarassing, has produced
the present situation. In an attempt to focus attention on disposal problems,
and to reduce some forms of pollution at their sources, a number of papers
have been published calling attention to valid and invalid disposal methods
(see Bibliography).
Disposal of organic sludge from conventional wastewater treatment
plants accounts for up to 50# of the total costs of treatment. Disposal of
sludge requires removal of the water content which accounts for 95 to 99*5#
of the weight, followed by storage of oxidation of the organic matter.
Since activated sludge has a much lower solid content than primary sludge,
the addition of secondary treatment greatly increases the sludge disposal
problems of the plant. Equipment which was effective for primary sludge
frequently proves to be inadequate when waste activated sludge is added. The
current FWQA policy, requiring secondary treatment for most large plants
discharging to inland waters, will greatly magnify the sludge disposal pro-
blems in this country.
Incineration can be accomplished in modern equipment without producing
pollution of the air or water. An outstanding example of pollution-free
incineration may be seen at the South Lake Tahoe Advanced Waste Treatment
Plant (see "Product Recovery" in attached list of contracts). At Lake Tahoe,
organic sludge and lime sludge are separately incinerated in two incinerators
which produce absolutely no plume or odor. It is impossible to tell from
outside the plant whether the incinerators are working or not.
The coBt of incinerating sludge is directly dependent on the water
content; therefore, efficient dewatering is the key to efficient incineration.
Present dewatering techniques include sedimentation, vacuum filtration,
pressure filtration, and centrifuging. All of these techniques are being
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examined In full-scale equipment under demonstration grants. There are a
number of chemicals vhich aid dewatering, including lime and salts of iron
and aluminum, as veil as synthetic polymeric flocculants. A limited amount
of laboratory work is devoted to evaluation of available products, but it
is recognized that field experience provides the most usefuly information.
Radiation, freezing, pressure cooking, treatment vith enzymes and the
addition of sludge ash have all been proposed as useful aids to devaterlng.
Both radiation and freezing have turned out to be too expensive for the
benefits achieved. Pressure cooking vith or without the addition of oxygen
is being evaluated at Colorado Springs, Painesville, Ohio and Santee Cali-
fornia. Pressure filtration vith ash is being evaluated at Cedar Rapids,
Iowa, and vacuum filtration has been studied in the laboratory. A contract
for the development of enzymes to thicken sludge has been underway at
Aerojet-General.
Land disposal of sludge without previous devaterlng is particularly
attractive, since it uses a low cost filter, the earth, and low temperature
oxidation by microorganisms. Although larger quantities have to be trans-
ported when the sludge is not first dewatered, the transportation can be
done economically by pipeline. A recent contract with Bechtel, Inc.
appraises the cost of pipeline transport of sludges for the case of Cleveland,
Ohio, but can be applied to many other situations. Land disposal of sludge
if properly operated is true conservation of resources and recycles essen-
tial elements to the biosphere. On low grade land, sludge improves
fertility and enhances the value of the environment. Political objection
to other people's "sludge" and a natural aversion to old fashioned smelly
sewage farms has held back rational utilization of the land for sludge
disposal even though its cost may be as low as one fourth of that for drying
and incineration. Papers have been published and talks given to point out
the advantages of land disposal. Greenhouse and field plot studies are
underway, both in-house and under grants, to improve our knowledge of land
disposal. A recent workshop at Chicago reviewed the state of the art of
land disposal and an excellent summary has appeared in the May l6, 1970
issue of the Prairie Farmer.
There are valid objections to land disposal of sludges, particularly
if they are improperly applied. Excessive loadings of sludge can contaminate
ground water and in some situations it may be necessary to collect and treat
water from underdrains as it is date in major irrigation projects. Nitrates
are apt to be the principal pollutant, just as they are with irrigation.
There is little evidence that the soil will be poisoned by excessive
quantities of organic matter or by heavy metals in the sludge, if proper
care is taken. Pathogens can be controlled by pasteurization if necessary,
or by long holding periods in lagoons. Even without these protective
measures there have been no reports of sludge born disease since 1919,
despite widespread application of sludge to farm lands in this country and
in Europe. Studies of pathogen survival in soil are underway.
Sludge can not be stored without some form of stabilisation to prevent
putrefaction and the development of objectionable odors. Anaerobic digestion
is a reasonably veil -understood process that causes a great deal of difficulty,
particularly when practiced on a small scale. Aerobic stabilization is poten-
tially capable of destroying nitrogen compounds and appears to be an ideal
pretreatment for land disposal. The process is poorly understood, and the
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costs of aeration are high. Seme in-house vork on aerobic stabilization
has been carried out and ve are looking for a suitable contractor to investi-
gate this process further. Treatment with lime is an attractive alternative
to digestion preceding land disposal.
Petroleum wastes represent an Interesting application of land
disposal. Despite common knowledge that oil "kills the soil11, well-oxidized
soil will destroy up to 12 inches of petroleum by-products in a year under
favorable conditions of temperature and humidity, provided that the soil
is kept well-aerated (Dotson, et al., 1970).
Industrial sludges frequently consist of soil minerals such as calcium,
carbonate and sulfate and oxides of iron and aluminum. There minerals can
be incorporated into the soil in substantial quantities without destroying
the agricultural value of the land. In all applications of wastes to the
land it is necessary to have good farm management, and not to treat the
land as a dump.
The lend treatment of sewage is of Interest far small communities.
This process is frequently referred to as the "living filter". Extensive
work on this application has been done at Pennsylvania State University and
by several food processes. We have recently received a number of proposals
for grants to use the "living filter" treatment for phosphate removal In
the Great Lakes area.
Disposal to the atmosphere should be limited to gases which are naturally
present. In addition to nitrogen, oxygen. i»ter vapor, and carbon dioxide
these Include ammonia, nitrous oxide (NgO), and products of combustion such
as higher oxides of nitrogen and sulfur. The last two groups are well-
recognized air pollutants, but are contributed in insignificant quantities
by well-operated incinerators. Nitrous oxide Is remarkably inert and is
probably not an air pollutant. Ammonia is rapidly absorbed by moisture and
vegetation and reacts with the oxides of sulfur, preventing formation of
sulfuric acid. It could be an objectionable nutrient if released upwind
of a large body of water, but it could reduce air pollution in sons
industrial areas. Ve are studying the removal and destruction of ammonia
under a contract with Battelle-Northwest.
Conversion of nitrates to nitrogen gas by dilute solution reduction has
been the subject of another contract which is being brought to a close. The
process does not appear to be practical for municipal effluents but may be
useful for certain industrial wastes.
Brine disposal can contribute a significant part of the cost of water
renovation in inland areas. The problem of brine disposal at three major
western cities is being evaluated under a contract with Burns and Roe. If
salt water lakes or playas are not available, it may be necessary to evapo-
rate the bulk of the water and transport the remaining slurry to a salt-
water area. Evaporation ponds appear to be the best solution in arid areas
where desalting is most necessary. A small evaporation pond study la being
carried out as a part of our cooperative research program with IACSD at
Pomona* We are currently regotiating a contract to evaluate the potential
of cooling towers for evaporating bring solutions, particularly In high
rainfall areas,
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Recovery and reuse of the chemical values In sludge is esthetically
attractive, "but only in rare cases are sludges attractive sources of rav
materials for other operations. Utilization of sludge to increase the agri-
cultural value of land is, of course, one form of reuse which is economically
attractive. At the other end of the scale, although sludge is a good source
of Vitamin B-12, extraction of this substance does not significantly reduce
the problem of sludge disposal. The sale of dried sludge for agricultural
purposes at Chicago defrays only a quarter of the cost of drying sludge.
Recovery of chemicals used to treat sewage or sludge is seldom able to pay
the cost of recovery. Lime recovery at Lake Tahoe is probably no better
than a break-even proposition; however, it reduces the sludge disposal pro-
blem significantly. We are Investigating under contract possible markets for
the phosphate-rich fraction of the recovered lime which would otherwise be
disposed of in a land-fill. In-house studies of aluminum recovery from
sludges containing aluminum that was used to remove phosphates indicate
that in most situations the recovered aluminum salt would cost more than
new chemical; however, the recovery process greatly improves the dewatering
qualities of the sludge and may be economical from that point of view. We
have also found that recovered lime is superior to fresh lime on a calcium
hydroxide basis when used for phosphate removal. The recovered lime pro-
duces sludges which are easier to filter and centrifuge because of the
presence of Inert filter aids formed by the ash.
A small contract has studied the recovery of amino acid values from
sludge and their utilization as animal feed. Activated sludge is essentially
a form of single-cell protein containing, unfortunately, substantial quanti-
ties of undigestlble matter. If the nutritive amino acids and sugars can
be economically separated from the undigestlble fraction, It should be
possible to make a valuable feed supplement (Dean and Bouthllet, 1970).
Attached is a list of references to pertinent publications from the
Ultimate Disposal Program and a list of contracts dealing with significant
aspects of our work.
For further information contact:
Robert B. Dean
Robert A. Taft Water Research Center
Advanced Waste Treatment Research Lab.
Ohio Basin Region
Cincinnati, Ohio 1+5226
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PUBLICATIONS
Ames, L. L., Jr., and Dean, R. B., May 1970. "The Use of Alumina Columns
for Phosphorus Removal from Secondary Sewage Effluents," J. Water
Pollution Control Federation 42(5)# l6l-172
Dean, R. B., December 1968. "Ultimate Disposal of Waste Water Concentrates
to the Environment," Environmental Science & Technology 2(12). 1079-1086.
Dean, R. B., March 1969. "Ultimate Disposal of Advanced Waste Treatment
Residues," TAPPI 52(3), 457-461
Dean, R. B., June 1970. "Wastes from Membrane Processes," Environmental
Science & Technology 4(6), 453.
Dean, R. B., 1969. "Ultimate Disposal of Waste Water: A Philosophical Viev,"
Water - 1969"# Chemical Engineering Progress Symposium Series 65(97). 1-4.
Dean, R. B., September 1969. "Colloids Complicate Treatment Processes,"
Environmental Science & Technology. 3(9)> 820-824.
Dean, R. B. and Bouthilet, R., July 1970. "Hydrolysis of Activated Sludge,"
to "be presented at the Fifth International Conference on Water Pollution
Research, San Francisco, California.
Dotson, G. K., Dean, R. B., Ketiner, B. A., and Cooke, W. B., July 1970.
"Land Spreading, A Conserving and Non-Polluting Method of Disposing of
Oily Wastes," for presentation at the Fifth International Conference
on Water Pollution Research, San Francisco, California.
Evans, J. 0., February 1968. "They Spread 'Black Gold1 on Their Fields,"
Pennsylvania Farmer 178(3). 36.
Evans, J. 0., June 1969. "Ultimate Sludge Disposal and Soil Improvement,"
Water & Wastes Engineering 6(6). 45-I<8.
Farrell, J. E., Salotto, B. V., Dean, R. B., and Tolliver, W. E., 1968.
"Removal of Phosphate from Wastewater by Aluminum Salts and Subsequent
Aluminum Recovery," "Water - 1968", Chemical Engineering Progress
Symposium Series 64(90), 232-239.
Mercer, B. W#, Ames. L. L., Touhill, C. J., Van Slyke, W. J., and Dean, R. B.,
February 1970. Ammonia Removal from Secondary Effluents by Selective
Ion Exchange," J. Water Pollution Control Federation 42(2), R95-R107.
Mulbarger, M. C., Grossman, E., Ill, Dean, R. B«, and Grant, 0. L., December
1969. "Lime Clarification, Recovery, Reuse, and Sludge Devatering
Characteristics," J. Water Pollution Control Federation 4l(l2),
2070-2085.
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CONTRACTORS' REPORTS
TWRC-1 (1^-12-52), October 1968. "Dilute Solution Reactions of the Nitrate
Ion as Applied to Water Reclamation", Rocketdyne Division of North
American Rockwell Corporation.
TWRC-5 (VTPRD 26-01), March 1969, "Ammonia Removal from Agricultural Runoff
and Secondary Effluents "by Selected Ion Exchange", Battelle-Northwest.
TWRC-8 (1^-12-^13), March 1969. "Evaluation of Operating Parameters of
Alumina Columns for the Selective Removal of Phosphorus from Wastewaters
and the Ultimate Disposal of Phosphorus as Calcium Phosphate", Battelle-
Northwest.
TWRC-10 (14-12-1+15), September, 1969. "Mathematical Model of Sewage Sludge
Fluidized Bed Incinerator Capacities and Costs", General American Trans-
portation Corporation.
WPRC 17070 DJW (1^-12-^95), November 1969. "State of the Art Review on
Product Recovery", Resource Engineering Associates,
WP-20-4 (PH 86-66-32), May 1968. "A Study of Sludge Handling and Disposal",
R. S. Burd, Dow Chemical Company.
lU-12-171# January 1970. "Ultimate Disposal of Phosphate from Waste Water
By Recovery as Fertilizer", W. R. Grace & Company, Dearborn Chemical
Division.
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
WASTEWATER RENOVATION AND REUSE
PPB 1708
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
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1970 STATUS OF WASTEWATER RENOVATION AND REUSE
PPB - 1708
Reuse applicationsof wastewater include irrigation, formation of
recreational lakes, industrial uses, groundwater recharge for a
variety of reuses, and direct domestic reuse. Some of the applications
can now be considered well established. Others are only beginning to
be considered. There is, however, some activity in each area at this
time.
IRRIGATION
Use of biologically treated wastewater for irrigation of non-edible
crops and for parks and golf courses has become fairly widespread.
With the technical feasibility of this application no longer in doubt,
it should become more common in the future. Use of wastewater has the
benefit of supplying significant amounts of plant nutrients, thus
reducing fertilizer requirements. R&D Grant projects at Colorado Springs,
Antelope Valley near Los Angeles, Irvine Ranch, California, and South
Lake Tahoe, California include production of water for irrigation. An
area in which wastewater is not used is for irrigation of food crops.
Studies are needed to define better the water quality for this application.
RECREATIONAL LAKES
Filling of recreational lakes with renovated wastewater was begun at
Santee, California in 1961. The success of that project has resulted
in the establishment of several other lakes and many more are now being
planned. To use wastewater for this application requires at least
biological treatment and phosphorus removal. At Santee, phosphorus removal
was first accomplished by passing biologically treated water through
natural gravel beds. This method will probably be replaced by chemical
precipitation using lime. Work at the site is being supported by an R&D
Grant.
At Antelope Valley, California filling of a recreational lake with
renovated wastewater was begun early this year. Treatment of the water
at this location includes oxidation ponds and chemical clarification with
alum. Development of the treatment system was partly supported by FWQA.
The full scale project is being supported by an R&D Grant.
Another recreational lake project is that at South Tahoe. Indian Creek
reservoir receives very high quality water from the Tahoe advanced waste
treatment plant. The water is secondary effluent that has been clarified
using lime and carbon treated.
The use of wastewater for recreational lakes can often be combined with
irrigation. The lake merely serves as a reservoir for the irrigation
water. The Tahoe site is an example of this dual purpose reuse.
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INDUSTRIAL REUSE
Industrial reuse of wastewater represents a very large potential application.
The largest single industrial use of water is for cooling water with an
estimated annual volume of 57,000 billion gal. Two other important uses
are for process water and boiler water feed.
The only major industrial reuse of wastewater up to this time has been
for cooling water. For a number of years the Bethlehem Steel Company
plant near Baltimore has been using secondary effluent for this purpose.
Generally, it has been found that phosphorus removal is required for the
water to be acceptable. At Baltimore the peculiar composition of the
water allows phosphorus removal to occur during biological treatment.
At other locations, such as at Las Vegas where the Nevada Power Company
uses wastewater in their condensers, tertiary phosphorus removal is
required. Lime treatment is used at the latter site.
FWQA did not support the early work on reusing wastewater for cooling
purposes. Presently, however, Colorado Springs is receiving R&D Grant
support for work in this area. A recently funded R&D Grant to Contra
Costa County, California also includes reclamation of wastewater for
cooling.
There is a need to investigate the use of wastewater for other industrial
applications. The recent R&D Grant to Contra Costa County includes study
of wastewater for boiler water feed. Work at that location may be
extended to other industrial uses. More projects of this nature appear
justified.
GROUNDWATER RECHARGE
An increasingly serious problem in water short areas is the lowering of
the groundwater level. This occurs because water is pumped out but is
not replaced. In coastal areas the result can be intrusion of seawater
into aquifers making them unusable. In other locations brackish water
may eventually replace the water removed.
It has been recognized that renovation of wastewater and recharge of
this water may be a practical method for overcoming the problem.
Recharge may be carried out by surface spreading of the water or injection
into a well. In the Los Angeles area, surface spreading is being practiced.
Recharge was begun in 1962 of the effluent from the Whittier Narrows Plant.
This plant, operated by the Los Angeles County Sanitation Districts, pro-
duces a very high quality secondary effluent. Because of the porous
nature of the spreading surface, no further treatment has been found
necessary. Additional biological oxidation and nitrification of the
effluent do take place during percolation through the soil. The quality
of the renovated water is further improved by dilution with the natural
groundwater.
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In locations where the percolation rate is low or where spreading
areas are not available, well injection would be necessary. Care
must be taken in these cases to assure that the water is of proper
quality to be compatible with the strata of the aquifer, i.e., will
not form precipitates which clog the area around the well. Further-
more, the water must not contain suspended matter that will cause
clogging. Orange County, California has experimented with injection
of wastewater to decrease seawater intrusion. Treatment of the
wastewater consisted of oxidation in a trickling filter followed by
alum clarification. Nassau County, Long Island is studying injection
for prevention of seawater intrusion and for other uses. This work is
being supported by an R&D Grant. Treatment of the wastewater at this
location consists of activated sludge, alum clarification, and granu-
lar carbon treatment. Nitrogen removal is also being considered.
DOMESTIC REUSE
Reuse of wastewater for domestic purposes involves both non-potable and
potable applications. Non-potable use is not new and is no longer rare.
Since 1925 treated wastewater has been used for flushing and other pur-
poses at the Grand Canyon. Treatment consists of activated sludge, coal
filtration, and chlorination. Similar systems are being used in other
water-short resort areas. A biological treatment unit followed by
membrane filtration is being tested at Pikes Peak. This work is being
supported by an R&D Grant. It produces water of high clarity.
Instances of indirect potable use of renovated wastewater, such as occurs
when a municipality practices water recharge, are increasing. In these
cases there is usually a large amount of dilution water. The situation
is similar to that occurring in many cities where river water containing
effluents from cities upstream is used for the water supply.
The concept of direct reuse of wastewater for potable water has been
discussed at length by many authorities in the water field for a decade
or more. Essentially no direct reuse was actually carried out, however,
until 1969 when a renovation plant at Windhoek, Southwest Africa began
operation. For more than a year this plant has been supplying about
one-third of the total water supply. The treatment system includes
biological oxidation by trickling filter, further oxidation in
maturation ponds,algae separation by alum flotation, foam fractionation
for removal of foaming contaminants, filtration, carbon treatment for
removal of remaining organic materials, and breakpoint chlorination for
removal of any residual ammonia and for disinfection. This pioneering
operation will have an important bearing on the growth of direct waste-
water reuse. Other African communities are very much interested in
similar projects. Continued success at this location should contribute
significantly to the acceptance of this reuse concept.
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OTHER SOURCES OF INFORMATION
Many articles have been written recently about reuse of wastewater. While
these have dealt at length with the philosophy of reuse and possible
treatment systems, they have not often reported actual reuse results.
Much practical information on reuse has, undoubtedly, never been published.
This information is of great importance to municipalities and to potential
reuse customers in making decisions. There is a strong need to collect
and analyze existing reuse results and to make them available in unified
form.
A number of reuse articles have been collected in "Water Reuse", Chemical
Engineering Progress Symposium Series No. 78, Vol. 63, 1967. Reading of
this publication is recommended.
For additional information contact Robert A. Taft Water Research Center,
4676 Columbia Parkway, Cincinnati, Ohio 45226.» Attention: Francis M.
Middleton or Carl A. Brunner.
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
WASTE TREATMENT OPTIMIZATION
PFB 1709
Division of Process Research & Development
Federal Water Quality Administration
U. S. Department of the Interior
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Waste Treatment Optimization
PPBS Category 1709
The four principal areas of activity for PPBS Category 1709, Waste
Treatment Optimization are shown in Figure 1. A list of in-house
reports completed is shown in Table I.
Design and performance technology is principally concerned with
finding quantitative expressions for performance and cost of waste-
water treatment processes as a function of the nature of the waste-
water to be treated and the decision variables associated with the
individual processes. These quantitative relationships take the
form of mass bcl-'nce relationships for all of the elementary chemical
and physical constituents of contamii at present in the water, rate
of reaction equations, and equations expressing the separation
efficiency between liquid, particulate, and gaseous phases. Normally,
a group of equations is required to express the performance of the
process operating over the full gamut of operating modes and design
decisions. This group of equations is often referred to as a
mathematical model for the process. Mathematical models can be
steady-state, quasi-steady-state, or time-dependent. Time-dependent
models are of interest when the quality of the effluent stream from
the process as a function of time is important or when the effective-
ness of various kinds of control schemes is being considered. The
computational procedure for solving all of the quantitative equations
simultaneously is usually too laborious to be accomplished by hand
calculation. The digital computer is, therefore, used in most cases.
Expressing the models as computer programs has the additional advantage
of packaging the information in succinct form readily usable by design
engineers and planners.
A list of reports produced as a result of in-house activity is shown
in Table I. A list of reports which have been completed as a result
of contracting activity is shown in Table II. Only three of these
contractor reports are now available for distribution. Other
contracts in force will produce models for multiple hearth incinera-
tion of sewage sludges and microscreening. Contracts in force will
also produce capital and operating and maintenance cost data for all
of the conventional processes as well as a cost estimating guidelines
manual and a staffing guidelines manual.
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TREATMENT OPTIMIZATION RESEARCH PROGRAM
I. DESIGN AND PERFORMANCE PREDICTION TECHNOLOGY
1. Develop quasi-steady-state and time-dependent models
for preliminary design and simulation
2. Validate design and simulation models by comparison
with detailed measurements on operating plants
3. Develop quasi-steady-state models into a recognized
standard of performance for use by governmental
agencies for regulation and administration of grant-
in-aid programs
II. OPERATION, MAINTENANCE, AND PLANT MANAGEMENT TECHNOLOGY
1. Plant performance standards and effluent quality
control methods
2. Plant management, training, and staffing criteria
and methods
3. State, County, or Regional systems for management
and regulation
III. AUTOMATIC CONTROL FOR PLANTS
1. Study feasibility of proposed control loops with
time-dependent models to solve transient problems
2. Study cost-effectiveness trade-off between automation
and additional or better trained staff or better
managerial surveillance
3. Demonstrate and evaluate control schemes on a loop-
by -loop basis
4. Demonstrate interprocess control of complete plants
IV. COST-EFFECTIVENESS STUDIES
1. Selection of processes and design policies for least
cost
2. Collection and organization of basic cost information
3. Develop recommended cost guidelines for cost estimation
89
FIGURE 1
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TABLE I
PRINCIPAL REPORTS PRODUCED BY
TREATMENT OPTIMIZATION RESEARCH PROGRAM
1. Smith, Robert, "Preliminary Design and Simulation of Conventional
Wastewater Renovation Systems Using the Digital Computer",
FWPCA Publication No. WP-20-9 (March, 1968).
2. Smith, Robert, "Cost of Conventional and Advanced Treatment of
Wastewater", FWPCA Publication (July, 1968).
3. Smith, Robert, Eilers, Richard G. and Hall, Ella D., "Executive
Digital Computer Program for Preliminary Design of Wastewater
Treatment Systems", FWPCA Publication No, WP-20-14 (August, 1968).
4. Roesler, Joseph F. and Smith, Robert, "A Mathematical Model for
a Trickling Filter", FWPCA Publication No. W69-2 (February, 1969).
5. Smith, Robert and McMichael, Walter F#, "Cost and Performance
Estimates for Tertiary Wastewater Treating Processes", FWPCA
Publication (June, 1969), TWRC-9 Released January 15, 1970.
6. Roesler, Joseph F., "Preliminary Design of Surface Filtration
Units (Microscreening)", FWPCA Publication (June, 1969).
7. Smith, Robert and Eilers, Richard G., "A Generalized Computer
Model for Steady-State Performance of the Activated Sludge
Process", FWPCA Publication (October, 1969).
8. Smith, Robert, "Factors to be Considered in Developing a Data
Gathering and Analysis Plan Leading to Improvement of the
Operational Effectiveness of Conventional Wastewater Treatment
Plants", FWPCA Publication (December, 1969)o
9. Roesler, J. F., Smith, R. and Eilers, R. G., "Mathematical
Simulation of Ammonia Stripping Towers for Wastewater Treatment",
In-House Report.
10. Smith, Robert and Eilers, Richard G», "Simulation of the Time-
Dependent Performance of the Activated Sludge Process Using the
Digital Computer", In-House Report 90% Complete.
11. Smith, Robert and Eilers, Richard G., "Cost to the Consumer of
Collecting and Treating Wastewater in the United States", In-
House Report (July, 1970).
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TABLE II
1. "Cost of Wastewater Treatment Processes", 1WRC-6, Dorr-Oliver,
Inc.
2« "Mathematical Model of Tertiary Treatment by Lime Addition",
TWRC-14, General American Research Division/General American
Transportation Corp.
3. "Mathematical Model of Sewage Sludge Fluidized Bed Incinerator
Capacities and Costs", TWRC-10, General American Research
Division/General American Transportation Corp*
4. "Mathematical Model of the Electrodialysis Process", Process
Research, Inc.
5. "A Mathematical Model of a Final Clarifier for the Activated
Sludge Process", Rex Chainbelt Inc.
6. "Ammonia Stripping Mathematical Model for Wastewater Treatment",
IIT Research Institute.
7. "Mathematical Model of Recalcination of Lime Sludge with Fluidized
Bed Reactors", General American Research Division/General American
Transportation Corp.
8. "Mathematical Model for Wastewater Treatment by Ion Exchange",
IIT Research Institute.
9. "Methodology for Economic Evaluation of Municipal Water Supply/
Wastewater Disposal Including Considerations of Seawater
Distillation and Wastewater Renovation", Bechtel Corp.
10. "Mathematical Model for the Reverse Osmosis Process", Aerojet-
General Corp.
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As a result of the work reported in the first report in Table I,
it was realized that a tool was needed which would allow the process
designer to select the group of processes and the piping arrangement
to be used and then calculate the performance and cost of the
system as a whole. To meet this need an Executive Program was
developed as described in the third report of Table I.
By iterative techniques the Executive Program calls each process
subroutine in turn and recomputes all recycle streams until the
correct solution for the system is found. Performance and cost
for each process and for the system as a whole is printed. This
program is simple in concept and requires a digital computer with
a core memory of about 16K words.
Every quasi-steady-state model developed will ultimately be included
in the Executive Program. A list of the individual processes to
be included in the Executive Program are shown in Table III with
the status of each model. No advanced processes are included in
the Executive Program at the present time although several sub-
routines have been developed.
Preferred advanced or tertiary wastewater treatment systems are
shown in the fifth report of Table I (TWRC-9). Estimated removal
efficiency for all significant contaminants are given together
with capital and operating and maintenance cost.
A generalized model for the activated sludge process has been
developed and has been shown to fit data from a wide range of
process modifications from the short detention time, low mixed
liquor suspended solids, "modified process" to the "extended
aeration process". This model is described in the seventh report
listed in Table I. The most significant discovery associated with
this work was that the maximum rate constant for synthesis is not a
true constant but varies significantly with the loading on the process.
A time-dependent model for the activated sludge process has also been
completed and the report on this model is about 90% complete. Three
classes of active solids are considered; heterotrophs which convert
biodegradable carbon to new cells, Nitrosomonas which converts
ammonia nitrogen to new cells and nitrite, and Nitrobacter which
converts nitrite to new cells and nitrate. This model has been used
to investigate a number of schemes for automatic control of the acti-
vated sludge process. The most practical of the schemes involve
sludge storage in the stabilization tank.
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Another model for which a report has recently been completed is
the model for ammonia stripping and cooling towers. The ammonia
stripping portion of the program is embedded in the cooling tower
calculation in order that the variation of Henry's Law constant
with water temperature can be taken into account. The program can
be used to calculate either ammonia stripping tower performance or
cooling tower performance. Both crosscurrent and countercurrent
towers are simulated. A numerical integration technique is used
in which the tower is divided into cubical elements. Performance
from various sources is being used to find the height of a transfer
unit as a function of the type of packing and design decisions.
Experimental data received from the Marley Co. for a particular
packing have been analyzed to find the relationship between height
of a transfer unit and the liquid and gas loading, (lb/hr/sq ft).
The height of a transfer unit was found to depend on the ratio of
gas to liquid loading as follows;
1 257
Height of Transfer Unit, ft = 4.1272 (Gas loading/liquid loading)
Various in-house and contract activities are underway to develop
operation, maintenance, and plant management policies and methods
which can be used to assure that a level of performance commensurate
with the capability of the installed treatment works will be con-
sistently achieved. The eighth report listed in Table I deals with
these problems. Various contracts are either funded or being
considered for funding.
The State of Minnesota has shown an interest in developing and
demonstrating a computerized system for surveillance and regulation
of treatment works within the State. The system would make use of
all design and simulation relationships known to be valid for treat-
ment processes. The physical characteristics of each particular
treatment plant would be stored in the computer program. Design and
simulation relationships would be used to compute the expected
performance of each plant as a function of the measured influent
stream. The transient nature of the feed stream and the stochastic
aspects of performance relationships would be used to compute a range
of expected performance. Monthly performance reports submitted by
individual plants would be analyzed and evaluated in a matter of
minutes. If deficiencies are detected some sort of remedial action
could then be initiated.
Our approach to automatic control of plants is to study the cost and
effectiveness of each individual control loop. Performance must be
measured and documented with and without the control loop installed.
Time-dependent mathematical models will be used to study the
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feasibility of untried control loops and to study the significance
of time-dependent measurements made on individual processes. The
tenth report in Table I deals with a time-dependent model for the
activated sludge process.
Various cost-effectiveness studies are undertaken to show the cost
contribution of various process system components and to study the
cost-effectiveness trade-offs for competing process systems. The
influence of size of community and the contribution of ancillary
elements such as Customer Services and Accounting or General and
Administrative Expense are studied to show the general cost
perspective. A recent report shown as number eleven in Table I
deals with these ancillary costs. Three selected figures from this
seventy page report are shown in Figures 2, 3, and 4.
94
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TABLE III
PROCESS SUBROUTINES TO BE INCLUDED IN THE EXECUTIVE PROGRAM
CONVENTIONAL PROCESSES
I. Physical Processes
1. Conveyance for Ultimate Disposal
a# Pipelines
b. Truck and Rail Transportation RFP (1/15/70)
c# Ocean Outfalls
2a Sewage Pumping Facilities (In-house Task)
3. Pretreatment
aa Bar Screens
b. Comminution (In-house Task)
Ca Grit Removal
4. Primary Sedimentation (Completed)
5a Sludge Drying Beds (In-house Task)
6a Post and Pre Aeration (In-house Task)
II, Biological Processes
1. Activated Sludge Process (Completed)
2a Trickling Filter Process (Completed)
3a Waste Stabilization Ponds
a* Aerated Lagoons
b. Facultative Ponds RFP (1/15/70) + (In-house Task)
Ca Oxidation Ditches
4a Anaerobic Digestion (Completed)
5. Aerobic Digestion RFP (1/15/70)
III. Physical-Chemical Processes
Gravity
1. Thickening of Organic Sludges RFP (1/15/70)
2a Centrifugation of Organic Sludges (Contract 515 Underway)
3* Flotation Thickening of Organic Sludges (Proposal Recommended)
4a Vacuum Filtration of Organic Sludges RFP (1/15/70)
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5. Use of Chemicals to Promote Sedimentation (No Plar.s)
6. Elutriation of Organic Sludge (No Plans)
7. Multiple Hearth Incineration of Sludges (Contract 547 Underway)
8. Fluidized Bed Incineration of Organic Sludge (Completed)
9. Wet Oxidation of Organic Sludge (No Plans)
ADVANCED PROCESSES
I. Physical Processes
1. Cooling Towers (Completed)
2. Microscreening (Contract 819 Underway)
3. Rough Filtration of Secondary Effluent RFP (1/15/70)
4. Dual Media Filtration RFP (1/15/70)
II* Biological
1. Disinfection
a* Chlorine
b« Iodine (No Plans)
c« Ozone
2, Denitrification in Columns RFP (1/15/70)
III. Physical-Chemical Processes
1. Lime Clarification (Completed)
a* Recalcination of Lime Sludge (Fluidised Bed Complete)
b# Recarbonation using C02 (In-house Task)
2« Ammonia Stripping Towers
a* Countercurrent (Completed)
b« Crosscurrent (Completed)
c. Aeration (In-house Task)
ds Biological Activity (In-house Task)
e. Scaling (In-house Task)
96
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3. Granular Carbon Adsorption RFP (1/15/70)
4. Powdered Carbon Adsorption (No Plans)
5. Electrodialysis (Conpleted)
6. Reverse Osmosis (Completed)
7» Ion Exchange (Model Complete - In-house Task Req'd)
97
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280
260
240
220
200
180
160
140
120
lOO'
80
60
40
20
0
>50
1990
rATUS OF MUNICIPAL WASTEWATER TREATMENT FACILITIES
IN THE UNITED STATES /
98
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Type of Treatment
w « o u o
W H *H Ct, *H
Activated
Sludge
i
Interceptor
and Outfall^
Trickling
Filter
Primary
Sediraentati'
Upgrading F:
Primary to
Activated
Sludge
Stabili2ati
Ponds
Total Sewered
Population
28,95
29. a 8
29.46
17,71
17,49 5,23
Activated Sludge
and Extended
Aeration
25*53
29,49
Trickling
Filter
45,14
i
Primary
Sedimentation
16,04
;
15,10 |
Stabilization
Ponds
1
21,42
r
i
NATIONWIDE AVERAGE CONSTRUCTION COST, DOLLARS PER CAPITA (1968 DOLLARS)
Source: cost data - R# L. Michel, Construction Grants and Engineering Branch, FWfW
population distributions - 1968 Inventory of Municipal Waste Facilities in the U.
FIGURE 3
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FIGURE 4
TOTAL COST OF SEWAGE COLLECTION AND TREATMENT IN 1968
ON A CONTINUOUS CASH FLOW BASIS
1968 dollars/capita/year
Amortization Cost
House Connection $ 1.38
Municipal Sewers $ 8.64
Interceptors and Outfalls $ 2.46
Treatment Plants $ 2.83
Total Amortization Cost $15.31
Current Expenses
Municipal Sewer Maintenance $0.86
Treatment Operation and
Maintenance $1*55
Customer Service and Accounting $0,71
General and Administrative $1.37
Total Current Expenses $4*4?
Total Cost of Municipal Collection $19.80
and Treatment
Imputed Cost of Industrial $ 5.05
Wastewater Treatment
Total $24.85
For additional information contact:
Robert Smith
Robert A. Taft Research Center
Advanced Waste Treatment Research Laboratory
Ohio Basin Region
Cincinnati, Ohio 45226
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ADVANCED WASTE TREATMENT RESEARCH LABORATORY
CINCINNATI, OHIO
CURRENT STATUS OF ADVANCED WASTE TREATMENT PROCESSES
July 1, 1970
SCIENTIFIC BASES OF WASTE TREATMENT PROCESSES
PPB 1700
Division of Process Research & Development
Federal Water Quality Administration
U.S. Department of the Interior
101
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Status of Research on
Scientific Bases of Waste Treatment Processes
Waste treatment is a chemical process industry. Its function is to
treat a starting material (sewage) of some chemical composition by
optimum processes to convert it to another material of higher economic
value/lower nuisance effect (treated effluent). Optimum processing
requires adequate knowledge of the chemistry, physics, and biology of
the raw material, treatment agents, and final product.
The major research effort has been on composition of wastes and its
changes. Though sewage has been analyzed for nearly a century, our
background knowledge is slight and expressed in quite general terras.
An intensive analytical program has begun only now, both in-house and
by contracts and grants. A first effort has been to determine how to
sample effluents and transport samples to the laboratory. Freeze-
concentration, though highly praised, is unsuitable. Vacuum concentra-
tion is the only practical means available so far. Though a systematic
analytical program is evolving, we have leapfrogged to some more
specific approaches. One of these, just begun by contract, consists of
liquid chromatography of primary and secondary sewages, yielding finger-
print chromatograms. First trials show some 50 - 75 separated organic
components, with conspicuous differences developing during biological
treatment. Another of these leaps involves developing specific analyses
for contaminants of special significance in sewage. Methods were
developed for residual polymeric coagulant in treated sewage and for
nitrilotriacetic acid in sewage receiving proposed new detergent formu-
lations.
The molecular weight of sewage components is an important property for
two reasons: (1) It controls the fractionation of organic components
necessary to achieve ultimate isolation and identification of each,
and (2) it has been claimed to be the controlling parameter in physical
waste treatment processes. Molecular weight studies, both contract and
in-house, are employing three techniques: membrane ultrafiltration, gel
permeation chromatography, and osmometry. Comparison of the methods
shows unexpected discrepancies in the apparent molecular weight values,
also evidence of these fractions being complexed with metals. Early
results indicate that the major part of secondary effluent organics
average below 500 in molecular weight.
Of the treatment agents susceptible of elucidation by fundamental
scientific research, activated carbon is the most important economi-
cally and also is most productive of useful information to guide processes,
which have been largely empirical until now. The efficiency of activated
carbon was found to depend on its basic characteristics, surface area,
pore volume and dimensions, and surface functional groups, as predicted
by theory. Other fundamental properties, not yet isolated, appear to be
related to these. Apparently for the first time, meaningful information
is being obtained about used and exhausted carbons, relating basic parame-
ters to the performance of these carbons and their behavior on reactiva-
tion. In a different but related approach, thermal analysis has begun to
/
102
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be explored as a means of characterizing both the activated carbon
and the adsorbed sewage components, as well as being used to predict
reactivation behavior. These theoretical studies are aimed at
establishing a sound scientific basis for carbon treatment processes
now conducted with inadequate understanding.
One of the favorable characteristics of sewage, namely, that it supports
well the bacterial population effecting biological treatment, is also a
disadvantage, in that it makes sewage a hospitable medium for disease-
producing bacteria. An intensive research program has been started to
pass far beyond today's fixation on indicator organisms. Methods for
assaying important pathogens in sewage — Salmonella, Pseudomonas,
Shigellae, among others — are being developed and applied as criteria
to measure the effectiveness of treatment processes in removing or
destroying these organisms. Information about pathogens and indicator
organisms has been assembled systematically to demonstrate the pollutional
effect of primary effluent, even where BOD is not an issue.
If bacteria produce biological treatment, they can also interfere with
other forms of treatment, especially physical methods, and with ultimate
disposal of waste concentrates. Adverse bacterial effects have been
characterized in carbon treatment (growth of pathogens) membrane processes
(fouling organisms), and sludge disposal (persistence of bacteria).
The above research areas are fundamental and relatively long-term con-
tributions to the efficiency of waste treatment processes. Since the
bulk of treatment research, by other components, is immediate and neces-
sarily empirical, this research must be guided by extensive analytical
surveillance. To take advantage of the intrinsic efficiencies of
specialization and centralization of advanced instruments, most of the
required analyses are provided by a central analytical service labora-
tory, supplying about 3,000 analyses per month, distributed among some
35 methods. This support is also supplied to research contractors and
grantees, including assistance in setting up and standardizing their
laboratories.
To supply these services requires a constant program to select appro-
priate analytical methods, adapt them to labor-saving systems and
instruments, develop new methods and systems for this purpose, and to
shake down and calibrate these instrumental adaptations.
If the initial premise of this review is reprised -- that effective
processes require adequate knowledge of the composition of starting and
final materials and the way specific processes affect these compositions —
then it is apparent that the concept applies as well to full-scale treat-
ment plants. The objective of automated control of treatment plants is
accepted; such control can be accomplished only if equally automated
methods of sensing composition changes can be developed. The automated
instrumentation developed for volume work in the analytical laboratory
is also the most promising approach to plant control instrumentation. A
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research effort in this direction, necessarily limited by meagre
resources, has attained initial success in controlling a denitrifica-
tion pilot plant by on-line analysis of nitrogen compounds and of
denitrifying reagent feed# The extension of automated chemical
instrumentation to full-scale treatment plant automation is a major
program objective.
For additional information contact:
Dr. A. A. Rosen
Robert A. Taft Water Research Center
Advanced Waste Treatment Research Laboratory
Ohio Basin Region
Cincinnati, Ohio 45226
104
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