T0745
.588
1978
c.l
OOOR79105
Symposium on
Advanced Treatment
of Biologically Treated
Effluents Including
Nutrients Removal
U.S.A. U.S.S.R.
Working Group
on the Prevention of
Water Pollution
Industrial Sources
November 12 13, 1978
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Symposium on
Advanced Treatment
of Biologically Treated
Effluents Including
Nutrients Removal
U.S.A.-U.S.S.R.
Working Group
on the Prevention of
Water Pollution
from Municipal and
Industrial Sources
November 12-13, 1978
U.S. Environmental Protection Agency
Reg:on V, Library
230 South Dearborn Street
Ch^?°o, Illinois 60604
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Preface
The seventh cooperative US/USSR symposium on the
"Advanced Treatment of Biologically Treated Effluents,
Including Nutrients Removal" was held in the Soviet
Union at the Moscow headquarters of Gosstroy on
November 12th and 13th, 1978. This symposium was con-
ducted in accord with the sixth session of the Joint
USA/USSR Commission held in Moscow, USSR from
November 14 through 18, 1977.
This symposium was sponsored under the auspices of
the Working Group on the Prevention of Water Pollu-
tion from Municipal and Industrial Sources. The co-
chairmen of the Working Group are H. P. Cahill, Jr. of
the United States Environmental Protection Agency and
S. V. Yakovlev of the Department of Vodgeo in the
Soviet Union.
The United States delegation was led by Harold P.
Cahill, Jr., Director Municipal Construction Division,
U.S. Environmental Protection Agency.
The twelve papers that were presented at the sym-
posium (six US and six USSR) are reprinted in English
in this volume in accord with the protocol signed by the
delegation leaders on November 24, 1978.
U,S. Environmental Protection Agency
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Index
Papers Presented at the USA/USSR Symposium
Jorling, Thomas C., Thomas, Richard E., (US EPA),
Land Treatment: Achieving Nutrient Removal by Recy-
cling Resources
Gyunter, L. I., Razumovsky, C., (USSR), Works for
Final Purification of Municipal Wastes
Cahill, Harold P., O'Farrell, Thomas P., (US EPA),
Operation of 5 MGD Model at the Advanced
Wastewater Treatment in Piscataway, Maryland
Sebastian, Frank P., Lachtman, Dennis S., (Envirotech,
USA), Granular Carbon and Other Tertiary Treatment
Process
11 .
Kirichenko, A. G., (USSR), Aerated Filters for Tertiary
Treatment oj Secondary Effluents 21
25
loakimis, E. G., Yusupov, E. A., (USSR), Aftertreat-
ment of Biochemically Treated Wasiewaters Before Their
Reuse 33
Lacy, William J., (US EPA), Facilities for the Treatment
of Biologically Treated Effluents from Industrial and
Municipal Sources by Ozone 39
Golovenkov, Yu. N., Kravtsova, N. V., Slavinsky,
A. S., Charirov, R. S., (USSR) Investigation of the
Loading Regeneration of the Mixed-Media Filter with
the Descending Particle Seize Distribution for the Ad-
vanced Wastewater Treatment
45.
Stanley, Richard H., Wallace, Douglas A., (Stanley
Consultants, USA), Municipal Wastewater Treatment by
Land Application in Minneapolis, St. Paul, Minnesota
Area 47
Stadnik, A. M.( (USSR), The Mathematical Model of
the Adsorption of Organic Impurities from Water Solu-
tions with Microporous Adsorbents 69
Butterfield, Ossian R., (Tahoe-Truckee, USA), Tahoe-
Truckee Sanitation Agency Water Reclamation Plant
73
Latyshev, Yu. M., Zavarzin, V. I., (USSR), Tertiary
Treatment of Biologically Purified Waste Waters Aimed
at their Recycling in the Production Processes 93
Protocol
Appendix 1 Participants at Symposium 97
Appendix 2 Papers Presented 97
Appendix 3 Future Program 98
in
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Land Treatment:
Achieving Nutrient Removal by
Recycling Resources
Thomas C. J or ling
Assistant Administrator, EPA
Office of Water and Waste Management
Richard E. Thomas
Physical Scientist, EPA
Office of Water and Waste Management
Office of Water Program Operations
Introduction
As it is throughout much of the world, land treatment is
an established methodology for treatment and reuse of
wastewaters in the United States. A discussion of land
treatment for recycling loses meaning without a common
understanding of background, terminology, and present
concepts. Land treatment as we know it today represents
a substantial advancement of technology over that of
even a few decades ago. This advancement of technology
includes many changes in terminology beginning with the
term sewage farming and shifting to more specific terms
describing alternative land treatment processes.
Background
A strong beginning for sewage farming in the United
States was followed by a period of popularity and exten-
sive use which continued into the first part of the twen-
tieth century. This early concept of land treatment for
recycling was based on farming with settled sewage as
the source of nutrients and water. Use of raw sewage for
farming was reasonably successful although there were
odor problems and occasional transmission of disease to
farm animals or humans. In the third decade of the
twentieth century there was a definite shift away from
sewage farming to inplant treatment of sewage with
discharge of the partially treated wastewater directly to
streams and lakes. This treatment and discharge ap-
proach to handling of sewage gained quick popularity.
Most of the new sewage treatment systems built in the
United States between 1930 and 1970 adopted the non-
recycle alternative of inplant treatment and discharge.
Pollution of streams and lakes increased dramatically
during this period. It quickly became apparent that
discharge of partially treated sewage and the plant
nutrients it contained intu streams and lakes was unsatis-
factory. By 1960 there was a strong movement to either
provide more nutrient removal through inplant processes
or to reconsider nutrient recycling through processes
such as sewage farming. A concerted effort was initiated
to advance the state-of-the-art for both of these alter-
natives. Others are covering several aspects of improving
inplant treatment to remove nutrients. I will address
nutrient recycling by land treatment. I use the term land
treatment instead of sewage farming because the ad-
vances in technology have made it possible to select from
several land treatment alternatives.
Terminology
These recent advances in technology have been accom-
panied by coinage of many terms to describe land treat-
ment alternatives. The United States Environmental Pro-
tection Agency (US EPA) has adopted three terms from
the many available. I shall describe each of these to
avoid confusion while covering the nutrient recycling
aspects of land treatment systems. The terms to be
described are "slow rate," "rapid infiltration" and
"overland -flow.''
Slow Rate: Slow rate land treatment is often referred
to as irrigation. The term slow rate land treatment is
used to focus attention on wastewater treatment rather
than on irrigation of crops. However, in slow rate
systems, vegetation is a critical component for managing
water and nutrients. The applied wastewater is treated as
it flows through the soil matrix, and a portion of the
flow percolates to the groundwater. Surface runoff of
the applied water is generally not allowed. When the
primary objective of the slow rate process is treatment,
the hydraulic loading is limited either by the infiltration
capacity of the soil or the nitrogen removal capacity of
the soil-vegetation complex. If the hydraulic capacity of
the site is limited by a relatively impermeable subsurface
layer or by a high groundwater table, underdrains can be
installed to increase the allowable loading. Grasses are
usually chosen for the vegetation because of their high
nitrogen uptake capacities.
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When the crop yields and economic returns from slow
rate systems are emphasized, crops of higher values than
grasses are usually selected. In the West, application
rates are generally between 1 and 3 inches/wk (2.5 to 7.6
cm/wk), which reflect the consumptive use of crops.
Consumptive use rates are those required to replace the
water lost to evaporation, plant transpiration, and stored
in plant tissue. In areas where water does not limit plant
growth, the nitrogen and phosphorous in wastewater can
be recycled in crops. These nutrients can increase yields
of corn, grain sorghum, and similar crops while pro-
viding an economic return.
Slow rate treatment is generally capable of producing
the best results of all the land treatment systems. The
quality values shown in Table 1 can be expected for
most well designed and well operated slow rate systems.
Rapid Infiltration: In rapid infiltration land treatment
(frequently referred to as infiltration-percolation), all of
the applied wastewater percolates through the soil, and
the treated effluent eventually reaches the groundwater
unless intercepted by drains or recovery wells. The
wastewater is applied to rapidly permeable soils, such as
sands and loamy sands, by spreading in basins or by
sprinkling, and is treated as it travels through the soil
matrix. Vegetation is not usually used, but there are
some exceptions. Removals of wastewater constituents
by the filtering and straining action of the soil are ex-
cellent. Suspended solids, BOD and fecal coliforms are
almost completely removed in most cases as shown in
Table 1. The nitrogen content of the reclaimed water is a
nutrient s6urce which can be recycled when the water is
recovered through drains or wells for use as an alternate
source of irrigation water.
Overland Flow: In overland flow land treatment,
wastewater is applied over the upper reaches of sloped
terraces and allowed to flow across the vegetated surface
to runoff collection ditches. The wastewater is renovated
by physical, chemical, and biological means as it flows
in a thin film down the relatively impermeable slope.
Biological oxidation, sedimentation, and grass filtration
are the primary removal mechanisms for organics and
suspended solids. Biological nitrification/denitrification
is a major mechanism for achieving the nitrogen removal
shown in Table 1. Overland flow is a relatively new
treatment process for municipal wastewater in the United
States. As of August 1976, only three relatively small,
full-scale municipal systems have been constructed.
These are located in Oklahoma, Mississippi, and South
Carolina.
Present US EPA Concepts
A changing attitude toward conservation and recycling in
the United States also includes emphasis on management
of nutrients in wastewaters. The concept of recycling the
nutrients in sewage is gaining in popularity as opposed
to expending energy and using resources to provide more
nutrient removal without use of the nutrients. The three
land treatment options which were described in the
previous section offer varying capabilities to recycle
nutrients while reducing energy requirements for treat-
ment. Slow rate systems which emphasize crop produc-
tion provide the greatest opportunity for recycling
nutrients. Tailoring the preapplication treatment to con-
serve the nutrients while eliminating pathogenic
organisms is a key to effective design of these slow rate
systems. Rapid infiltration systems provide for less
recycling opportunity because the emphasis is on use of
minimum land areas to reclaim the wastewater. The op-
portunity to recycle nitrogen comes if the reclaimed
water is recovered and used as an alternate source of
irrigation water. Overland flow provides for partial
recycle of nutrients while emphasizing reclamation of
wastewater with discharge to a surface water. Although
the reclaimed water could be recovered for a secondary
use such as irrigation, it would be a comparatively poor
source of nutrients. The attractiveness of overland flow
is its simplicity, low cost, and suitability for use on low
permeability soils.
The US EPA sees this concept of three types of land
treatment systems (slow rate, rapid infiltration, and
overland flow) as complimentary technologies which fur-
nish land treatment alternatives suited to most site condi-
tions regardless of the dominant soils at the site. This
ability to select alternatives provides flexibility for tailor-
ing nutrient recycling and wastewater reclamation to site
conditions and a variety of project purposes.
Recycling With Slow Rate Systems
Slow rate systems offer a direct pathway for recycling of
the plant nutrients contained in wastewaters. Although
there are several options for the design of a project, the
basic premise is to use wastewater to provide the major
nutrients and the supplemental water, if needed, to grow
a crop. We use the term slow rate because the emphasis
is on maximum recycling rather than providing sup-
plemental water. Slow rate systems are usually designed
with the amount of wastewater applied or the amount of
nitrogen applied as the limiting factor. It is only recently
that consideration of the amount of nitrogen applied
became an important design factor. All of the older
systems were designed on the basis of the amount of
wastewater applied as the limiting factor.
Designing and operating slow rate systems on the basis
of applied wastewater alone has been very successful for
producing crop yields equalling or exceeding yields ob-
tained by using commercial fertilizers and well or surface
waters for irrigation. Such practices have provided
economical wastewater treatment while recycling sub-
stantial quantities of plant nutrients. Many examples of
operating slow rate systems in the United States are
described in a recent US EPA survey of land treatment
systems^). Some of these systems have been studied in
detail over the last decade to determine long term results
for crop production, changes in soil properties, and
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changes in groundwater quality under the site.
Systems at Bakersfield, California, and Lubbock,
Texas, are typical examples of systems that have pro-
duced consistently high yields for a variety of crops for
up to 50 years. Approximately 1,000 hectares is being
irrigated at each of these locations. Recent investi-
gations(2) at these sites have confirmed that consistently
high yields are still being harvested after many decades
of operation. There have been no adverse affects on the
soil properties that would reduce crop yields or harm the
quality of the crops. While crop yields are excellent and
soil properties remain good, there has been considerable
loss of nitrate nitrogen to the local groundwater. This
has been a consequence of failing to consider the
amount of nitrogen applied as an important and perhaps
a limiting design factor.
A similar slow rate system at Roswell, New Mexico,
has operated over a comparable period of time. The
amount of wastewater applied at this site has been
substantially less than that at Bakersfield, California, or
at Lubbock, Texas. The crops have used virtually all of
the nitrogen applied over the 30 plus years of continuous
wastewater irrigation. Consequently, there has not been
a comparable loss of nitrate nitrogen to the shallow
groundwater under the irrigated fields.
Newer slow rate systems in the United States are being
designed on the basis of nitrogen applied as well as the
amount of wastewater being applied to the crops. A
large system of about 2100 hectares at Muskegon,
Michigan, is a good example of this approach to the
design of a system. While still early in its operating life,
the Muskegon system is providing valuable quantitative
information on nutrient recycling(3). This system,
designed to serve a population equivalent to 430,000
people, recycles water and fertilizer nutrients to grow
corn. Operating at a population equivalent of 300,000
people in 1976 the 2,200 ha farm produced 144,000 hi
(400,000 bu) of corn. Revenues from the sale of the crop
offset much of the costs to operate all components of
the wastewater management system. About 90 metric
tons of phosphorus, 230 metric tons of nitrogen, and
250 metric tons of potassium were recycled by crop
uptake or stored in the soil as the wastewater was
reclaimed.
In addition to the obvious project benefits from the
recovery and recycling of nutrients through crop produc-
tion and crop sales to help offset the system's overall
operating costs, there are important water quality
benefits provided by this wastewater treatment system.
Improvements have already been observed in the water
quality of the lakes that had been receiving the waste-
water discharges now passing through the land treatment
system. This marriage of water quality improvement and
wastewater treatment with nutrient recovery and recy-
cling has been achieved without adverse effects on the
groundwater underlying the project site or surface waters
into which the renovated water is discharged.
These examples of nutrient recycling with slow rate
systems offer a cross-section of operating systems in the
United States. They depict the flexibility available for
design and operation of slow rate systems and many new
systems are being planned or constructed at the present
time. The concept of multiple use projects is gaining
popularity in water short areas of the country where
some projects include recreational use as well as nutrient
recycling for crop production. Forest irrigation is an ap-
proach which is also receiving much attention as a means
for maintaining native vegetation. The future of nutrient
recycling by slow rate systems is very optimistic in the
United States at the present time.
Recycling by Rapid Infiltration
Rapid infiltration seldom offers a direct pathway for
recycling of plant nutrients contained in wastewaters.
The major purpose of rapid infiltration is to reclaim
wastewater and, by so doing, condition the wastewater
for other uses. Recycling of nutrients by using the
reclaimed water as an irrigation source is one of the
practical uses of the reclaimed wastewater. If there is no
need to make direct use of the reclaimed wastewater it is
usually released to surface waters. A system at Phoenix,
Arizona, is a good example of using the reclaimed water
for irrigation and a system at Lake George, New York,
is a good example of releasing the reclaimed wastewater
to surface waters.
Phoenix, Arizona, is located in the southwestern part
of the United States where water is in short supply.
There is a need to make direct use of wastewaters to ex-
tend the limited water supply. Soil and geologic condi-
tions are favorable for using rapid infiltration to reclaim
wastewater by providing advanced treatment of a con-
ventional treatment plant effluent and storing it
underground where it can be recovered as needed for
crop irrigation. Research conducted at Phoenix,
Arizona, shows the renovated water following rapid in-
filtration to contain less than 2 mg/1 of suspended solids
and BOD, 7.5 mg/1 of total nitrogen, 0.2 mg/1 of
phosphate phosphorus, and 6 fecal coliforms per 100 ml.
After the rapid infiltration process has removed the SS,
BOD, and fecal coliforms the reclaimed water is suitable
for irrigation of crops including those which may be
eaten raw. This rapid infiltration approach is an
economical process with a low energy demand because it
relies on natural processes in the soil to reclaim
wastewater for subsequent use for many uses including
crop irrigation.
Lake George, New York, is located in the northeastern
part of the United States where surface waters are
plentiful. The need to reuse wastewaters is low yet it is
necessary to eliminate pollution of surface waters by
discharging conventional treatment plant effluents and
the nutrients they contain into these surface waters. The
rapid infiltration system at Lake George was designed to
prevent discharge of wastewater (even after treatment)
into clear and beautiful Lake George. The reclaimed
water which discharges into the lake through springs
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after rapid infiltration is of very high quality(5).
Suspended solids, biochemical oxygen demand, and fecal
bacteria are completely removed by filtration through
the soil. Phosphorus has been reduced to a concentration
of less than 0.1 mg/1 and the nitrogen concentration is
about 7 mg/1. The reclaimed water discharge which
averages 4.3 I/sec is so pure that it has no adverse af-
ffects on the quality of water in a small brook into which
the reclaimed water is discharged by the springs. With
no specific need to recycle the nutrients by direct reuse
of the wastewater, the rapid infiltration system provides
low cost and energy conserving use of natural processes
to reclaim wastewater and prevent the pollution of a
clean lake.
These examples of operating rapid infiltration systems
under radically different climatic conditions and for
substantially different objectives show the utility of this
technique. In water short Phoenix, Arizona, the em-
phasis is on conservation of a water resource for subse-
quent reuse including the recycling of nutrients. In Lake
George, New York, where high quality water is plentiful,
the emphasis is on preventing the direct discharge of
pollutants into the lake. The situation and site conditions
at Lake George are not conducive for recycling nutrients
while the situation and conditions at Phoenix are ideal
ft>r nutrient recycle and multiple use of reclaimed
wastewater.
Nutrient Recycling by Overland Flow
The overland flow process provides a land treatment
alternative suited to locations with low permeability
soils. Such sites are unacceptable for rapid infiltration
and unacceptable to marginally acceptable for slow rate
systems. Overland flow systems must be vegetated with
selected species of grasses. Nutrient recycling into a hay
crop is an integral part of system operation although the
fraction of the applied nutrients removed in the vegeta-
tion is a small fraction of that applied in the wastewater.
Use of overland flow for treatment of domestic
wastewaters is a little used but rapidly developing
technology in the United States. The principal use in the
United States has been for treatment of high strength
food processing wastewaters as described in a research
study of an operating system at Paris, Texas (6).
Research on treatment of domestic wastewaters by
overland flow has been conducted at a US EPA
laboratory in Ada, Oklahoma, since 1971. The results of
these studies (7)(8) show that overland flow can provide
simple and low cost treatment of raw sewage as well as
serving as a process for providing advanced treatment
following either primary or secondary treatment ( ). As a
process for treatment of raw sewage overland flow
eliminates the generation and consequent handling of
sludges while producing an excellent quality effluent.
Using a land area of one hectare per 600 persons to treat
raw wastewater the overland flow process produces an
effluent containing less than 10 mg/1 of SS and BOD,
and about 5 mg/1 of total nitrogen and total
phosphorus. It is these aspects of the overland flow
process for land treafment which make it very attractive
as an energy saving and low cost alternative for reclaim-
ing wastewater where treatment and discharge is of
greater importance than direct recycling of nutrients.
Removal of nitrogen is attributed to natural nitrifica-
tion/denitrification. The dual step of nitrification/
denitrification in a system open to the atmosphere is
achieved by having a double layer effect in the water
flowing as a sheet down the slope. Nitrogen balances
show that 1150 kg/ha of nitrogen are applied yearly. Of
this amount 100 kg are discharged in the system effluent
and 150 kg are removed by harvesting the crop. This
leaves about 900 kg/ha which is converted to gaseous
nitrogen and released to the atmosphere. This represents
a substantial loss of a resource which could be recycled
as a plant nutrient but it is achieved by natural processes
without an input of additional energy. The future is
bright for use of overland flow as a wastewater reclama-
tion alternative for year round operation in geographic
regions with mild to warm climates or for seasonal
operation in colder regions.
Summary
Nutrient removal by land application furnishes many op-
tions to the user. Slow rate systems offer the best oppor-
tunity for direct recycling of the nutrients for crop pro-
duction as the nutrients are stripped from the waste-
water. After preapplication treatment which reduces
fecal organisms to desired levels while conserving plant
nutrients the wastewater is used directly for irrigation of
selected crops. Rapid infiltration offers the best oppor-
tunity to reclaim water while using the least amount of
land area so opportunities for direct recycling are
minimal. The opportunity for combining nutrient recy-
cling with rapid infiltration comes through recovery of
the reclaimed water for subsequent reuse as an irrigation
water. The purpose of using rapid infiltration is to make
the reclaimed wastewater suitable for irrigation of all
types of crops as well as providing temporary under-
ground storage. Overland flow offers a limited oppor-
tunity to recycle nutrients while providing a low cost and
energy saving option for reclaiming wastewater. It is
especially suited for low permeability soils which make
rapid infiltration impossible and slow rate systems im-
practicable. This combination of complimentary ap-
proaches makes nutrient removal, or more appropriately
nutrient management by land treatment, an attractive
alternative to removal of nutrients by using additional
inputs of chemicals or energy to conventional inplant
treatment. The future is very promising for nutrient
management and recycling by land treatment in the
United States.
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Table 1
Expected Quality of Treated Water From Land Treatment Processes
mg/L
Slow rale* Infiltration1* Overland flowc
Constituent Average Maximum Average Maximum Average Maximum
Biochemical Oxygen demand
(BOD) 25 25 10 15
Suspended solids (SS) 15 25 10 20
Ammonia nitrogen as N 0.5 2 0.5 2 0.8 2
Total nitrogen as N 38 10 20 35
Total phosphorus as P 0.1 0.3 15 4 6
a. Percolation of primary or secondary effluent through 5 ft. (1 5m) of soil.
b. Percolation of primary or secondary effluent through 15 ft. (4.5m) of soil.
c. Runoff of comminuted municipal wastewater over about 150 ft. (45m) of slope.
References
1. Survey of Facilities Using Land Application of Wastewater, July
1973. US Environmental Protection Agency. No. EPA 430/9-73-006,
377p.
2. Hinesly, T.D., R.E. Thomas, and R.G. Stevens. "Environmental
Change from Long-term Land Application of Effluents," US EPA No.
MCD-26, March 1978.
3. Muskegon report: Wastewater: Is Muskegon County's Solution
Your Solution? US EPA No. 905/2-76-004, September 1976, 5p.
4. Bouwer, H. "Renovating Secondary Effluent by Groundwater
Recharge with Infiltration Basins.", In: Recycling Treated Municipal
Wastewater and Sludge through Forest and Cropland Sopper, W.E.,
and L.T. Kardos (ed.) Univ. Park, Penn State Univ. Press, 1973.
p. 164-175.
5. Aulenbach, Donald, Fresh Water Institute at Lake George, "Thirty-
Five Years of Use of A Natural Sand Bed For Polishing A Secondary
Treated Effluent", FWI Report #73-15.
6. Law, J.P., R.E. Thomas, and L.H. Myers. Cannery Wastewater
Treatment by High-Rate Spray on Grassland Journal WPCF.
42:1621-1631, September 1970.
7. Thomas, R.E., K. Jackson, and L. Penrod. Feasibility of Overland
Flow for Treatment of Raw Domestic Wastewater. Robert S. Kerr
Environmental Research Laboratory. EPA Series No. 660/2-74-087.
July 1974. 31p.
8. Thomas, R.E., B. Bledsoe, and K. Jacksdn. Overland Flow Treat-
ment of Raw Wastewater with Enhanced Phosphorus Removal, U.S.
Environmental Protection Agency. EPA- 600/2-76-131, June 1976.
36 p.
9. Thomas, R.E., Preapplication Treatment for Overland Flow, R.E.
Thomas EPA-OWPO-MCD for presentation at International Sym-
posium on Land Treatment of Wastewater, August 20-25, 1978,
Hanover, New Hampshire, USA.
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Works for Final
Purification of
Municipal Wastes
L.I. Gyunter, D. Techn. Sc.,
and
E. S. Razumovsky, C. Techn. Sc.
The necessity of final purification of municipal wastes
has arisen as a result of continuously increasing water
consumption and population growth reaching a point
where waste effluent, even after a complete biological
treatment characterized by a decrease of the biologically
permissible concentration and suspended matter to 10-15
mg/1 and by the beginning of the process of nitrifica-
tion, can no longer ensure that a required quality of the
water is maintained at the place of water consumption.
A long-term forecast shows that if complete biological
treatment plants are constructed and effectively exploited
in every town, the pollution of water reservoirs will in-
crease. Therefore one of the directions of the develop-
ment of research and techniques of waste treatment is
the development of works for additional removal of
pollutants from biologically treated municipal effluent.
The most pressing problem now is the general reduc-
tion of pollutants in discharged waste waters in terms of
the content of suspended matter and biologically per-
missible concentration.
At present the most sophisticated method for their
removal is by filtering through gauze devices and
granular materials allowing water of different quality to
be produced by using devices of different construction.
Investigations carried out using filters consisting of
granular materials have shown that the suspended matter
of biologically treated effluent is characterized by strong
forces of cohesion with the filtering medium, i.e. by
capacity for forming aggregates on the surface of grains
in the medium and for accumulating in the initial layers
of the medium. Because of this, filters used for final
purification of biologically treated effluent are charac-
terized by a curvilinear (parabolic) increase in the loss of
head in contrast to a rectilinear one for filters in water
treatment plants. These peculiarities of suspended matter
lead to the necessity of filtering the water in the direc-
tion of the decreasing size of the filtering material and
of using water-air washing. This can be achieved by
employing double- or multi-layer filters and upflow
gravel-sand filters.
Double-bed anthracite-sand filters are exploited at the
Zelyonograd Aeration Plant of the City of Moscow. For
a filtering rate of 5 m/hr there is a decrease in the
suspended matter on the filters from 10-12.5 to 1.3-2.9
mg/1 and that of biologically permissible concentration
from 5.8-6.8 to 2 mg/1.
However, it is better, in our opinion, to use upflow
gravel-sand filters for final effluent purification, since
they have a greater mud capacity and the loss of head
increases most slowly along a comparatively flat curve.
The utilization of the upflow filtration principle has
allowed the filter mud capacity to be increased by a
factor of up to 2 or 2.5 as compared with conventional
fast filters and the filtering rate to be increased up to
12-13 m/hr under normal conditions and up to 14-15
m/hr under forced conditions. For water with a sus-
pended matter content of up to 20 mg/1 the duration of
a filtration cycle was over 24 hr. With an increase in the
content of the suspended matter to 30 or 40 mg/1 the
filters worked steadily, the duration of the filtration
cycle remaining sufficiently large, up to 12 hours.
The latter circumstance allows one to reduce, when
utilizing upflow filters, not only the area of the filters
themselves but also the volumes of the aerator tanks.
The fact is that in the Soviet Union it is customary to
calculate the volumes of secondary precipitation tanks
for the staying of sewage during two hours from a max-
imal hourly inflow. This restricts the amount of acti-
vated sludge in the aerator tanks to 1.8-2.5 g/1, with a
permissible removal of the suspended matter from the
secondary settling tanks reaching 10 to 15 mg/1 (in the
absence of works for final effluent purification). If
upflow filters are used, it is possible to increase the per-
missible removal from the secondary tanks to 30 or 40
mg/1, which makes it possible to increase the amount of
the activated sludge in the aerator tanks to 3 or 4 g/1,
without changing the volumes of the secondary precipita-
tion tanks, and to reduce the volumes of the aerator
tanks.
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Upflow filters ensure a stable removal of impurities
with a short-term increase in the content of the sus-
pended matter to 60 or 80 mg/1, which insignificantly
affects the quality of the filtrate with a duration of the
filtration cycle of not less than eight hours.
A three-stage water-air washing is recommended. The
volume of water required for one washing is 1.5-2 per
cent of the volume of water to be treated.
Under the above working conditions upflow filters en-
sure a decrease in the content of the suspended matter of
up to 80 or 90 per cent, of the biologically permissible
concentration of up to 60 to 70 per cent and of the
chemically permissible concentration of up to 25 or 45
per cent.
The application of 40 to 70-mu gauze microfilters for
the final purification of effluent can ensure a decrease in
the content of the suspended matter by 50 or 60 per cent
and that of the biologically permissible concentration by
20 or 30 per cent with a filtering rate of 20 to 30 m/hr.
Unlike granular material filters, there is no decrease in
the dissolved oxygen.
It can be seen from the above data that microfilters
ate less effective in the removal of pollutants than filters
with a granular material, especially in reducing the
biologically permissible concentration. In view of their
low cost, however, microfilters will find application in
those places in the Soviet Union where a decrease in the
suspended matter is of primary concern. It is also pos-
sible to use microfilters at water treatment plants with
biological ponds as independent works or final purifica-
tion works.
There are biological ponds for final effluent purifica-
tion with both natural and artificial aeration in the
Soviet Union. The advantages of biological ponds
thorough results of treatment for the biologically
permissible concentration (up to 5 or 6 mg/1 with a
simultaneous decrease in the nitrogen and phosphorus
compounds by 90 per cent), the simplicity of
maintenance and relatively low cost of construction
lead to their application even at water treatment plants
of major cities, such as Gorki and Kuibyshev, each with
a population of more than a million. The lack of unoc-
cupied areas and the severe climatic conditions in the
greater part of the Soviet Union prevent them from
being practiced on a larger scale. Among the disadvan-
tages of biological ponds one should mention a high
content of suspended matter (mainly phytoplankton) in
the emerging effluent, which can be successfully retained
by microfilters.
If there are surface-active materials (or detergent) in
the effluent, one can use froth flotation for the final
purification of the water from the surface-active
materials and general pollution. The degree of final puri-
fication of the effluent by froth flotation depends on the
kind of surface-active materials used, on their froth-
forming capacity. It is of stable character in towns,
however, 70 to 90 per cent of the surface-active materials
and 50 to 60 per cent of the content of the suspended
concentrations being removed. The intensity of bar-
botage is 35 m3/(m2hr) for a process lasting 30 min. The
collected froth is damped down and moved on to be
treated together with the precipitate.
Froth flotation is the cheapest method, the effect of
the treatment in terms of the common pollutants is inter-
mediate with respect to those for filters with a granular
material and microfilters, but its obvious advantage is a
decrease in the surface-active materials. As to its disad-
vantage it is that froth flotation can be applied only if
there are surface-active materials (not less than 2-3 mg/1)
in the biologically treated water.
In recent years many scientists have been giving their
attention to the removal of biogenous elements from
biologically treated effluent when the latter is discharged
into closed water reservoirs or reservoirs with slightly
flowing water. For the Soviet Union this problem is also
becoming an urgent one since it has more than 150 big
reservoirs alone, the volume of each exceeding 100 mill.
m . The total volume of the artificial reservoirs reaches
500 km3, almost 10 per cent of the total annual runoff
of the country or 22 per cent of the volume of all reser-
voirs in the world.
By the present time, reagent methods for the removal
of phosphorus have been studied in the Soviet Union,
such as simultaneous precipitation and reagent filtration.
For this purpose one can use traditional mineral
coagulants, viz. aluminum and iron salts, lime, etc. It
has been established that the best results for the removal
of phosphorus using simultaneous precipitation are ob-
tained with 20 mg/1 batches of coagulant (Fe2O3) the
residual phosphate content having amounted to less than
0.5 mg/1. However, increasing the coagulant batch led to
the oppression of the activated sludge which was mani-
fested by a decrease in its dehydrogenation activity. It
has been established that iron coagulant exerts toxic
effect when introduced in amounts exceeding 5 mg per 1
g of the ashless- material of the sludge, the effect becom-
ing aggravated with sludge loads exceeding 500 mg of
biologically permissible concentration per 1 g of ashless
material.
In the case of simultaneous precipitation the sludge
index was observed to decrease to 50 cm/g, which makes
it possible to increase the sludge batch in the aerator
tanks to 6 or 7 g/1. In the above process the growth of
activated sludge increases by 25 or 35 per cent. When
salts of divalent iron are used, the blast intensity should
be increased by a factor of 1.4.
Upflow filters can be used to reduce the total amount
of pollutants after the simultaneous precipitation, the
technological parameters being the same as for non-
reagent filtration.
When using filters it is possible to introduce reagents
before the filters (reagent filtration). Then the coagulant
batch is reduced to 5 or 8 mg/1 (for Fe2O3) as compared
with simultaneous precipitation. But even these amounts
of coagulant increase the sludge load on the filter, which
leads to the necessity of decreasing the filtering rate to 5
or 7 m/hr and the duration of a cycle of filtration to 8
or 12 hr. The effect of the treatment is 80 to 90 per cent
8
-------
for phosphorus, 70 to 90 per cent for the suspended
matter, 70 to 90 per cent for the biologically permissible
concentration and 35 to 50 per cent for the chemically
permissible concentration.
The last method is the most expensive in terms of
capital costs but attains the greatest effect in removing
pollutants.
Investigations are in progress in the Soviet Union into
the removal of nitrogen compounds from biologically
treated effluent by physiochemical and biological
methods, but they have not been completed vet
The high requirements for the quality of efiluent treat-
ment for water reservoirs make it economically advisable
to use thoroughly treated municipal wastes in industrial
water systems. At present, because of the lack of reliable
data for a sanitary-hygienic estimation of thoroughly
treated effluent, it appears advisable not to use it in
food, meat and milk or pharmaceutical industries.
In most water-consuming industries (power engineer-
ing, non-ferrous and ferrous metallurgy, oil industry,
etc.) the greatest amount of water is needed for uc: as
heat-carrier, for which purpose municipal effluent can be
used to advantage after proper treatment with due
regard for precautions excluding any contact of the
operating staff with the water.
The current lack of scientifically based requirements
for the quality of water used in various industries
restrains the utilization of treated municipal effluent as
industrial water.
-------
OPERATION OF 5
MGD MODEL AT
THE ADVANCED
WASTEWATER
TREATMENT IN
PISCATAWAY,
MARYLAND
Harold P. Cahill, Jr.
Director
Municipal Construction Division
U.S. Environmental Protection Agency
Thomas P. O'Farrell
Sanitary Engineer
Municipal Construction Division
U.S. Environmental Protection Agency
Objective
The project objectives were to operate a 5 mgd tertiary
wastewater treatment plant to demonstrate high effi-
ciency removal of phosphates, organic carbon and sus-
pended solids. The process train included lime clarifica-
tion, filtration and granular carbon absorption.
Abstract
A 5 mgd tertiary wastewater treatment plant was con-
structed to demonstrate treatment of effluent from a 5
mgd step aeration activated sludge plant. The two-stage
high lime process with intermediate recarbonation, filtra-
tion and activated carbon adsorption operated con-
tinuously at the design rate for 36 days. A single-stage
low lime process with filtration and activated carbon
adsorption operated for 89 days. The combined second-
ary and tertiary treatment removed 97% of BOD, TSS
and P in the raw waste-water. Capital cost of the 5 mgd
tertiary treatment system was 4.7 million dollars and
operating costs were estimated as 36 cents per 100
gallons of wastewater.
Detailed Description of Secondary Treatment Facility
The primary and secondary treatment facilities at
Piscataway consist of two parallel systems (capacity = 5
and 25 mgd) with a common solids handling system.
Raw wastewater is presently pumped to the plant from
four pumping stations with the total capacity of 75 mgd.
Although the total feed system has the capacity to feed
75 mgd, neither the sewer taps nor the plant have the
capacity to collect or treat this volume of wastewater.
A schematic diagram of the liquid treatment facilities
is shown in Figure 1. Although the entire secondary
plant is presented, only those unit processes associated
with the 5 mgd system feeding the Model Plant will be
discussed. The 5 mgd secondary system as operated dur-
ing the grant is shown in Figure 2.
The raw sewage is manually split and fed to the three
grit chambers. The effluent from the single grit chamber
for the 5 mgd system passes through two 3/8" bar-
minutors equipped with automatic rotating cutters. Four
centrifugal pumps, each rated at 1750 gpm, are piped to
the open channel following the barminutors to provide a
constant flow of 5 mgd through the 5 mgd secondary
section into the Model Plant. Since the three chambers
are interconnected, all flow in excess of 5 mgd is
diverted to the two grit chambers in the 25 mgd system.
The degritted effluent is split at the primary inlet well
and fed to two parallel primary settling tanks. The
primary solids are wasted by gravity to the primary
solids collection well. At the collection well, the primary
solids are combined with the scum from the surface
skimmers and flow bv gravity to the sludge thickener.
Primary effluents from tne two claritiers are combined
and flow by gravity to the step aeration basins. Settled
solids from the secondary clarifiers are recycled to the
11
-------
RAW WASTE WATER
I
PLANT RECYCL
25m9d SYSTEM ^
1 1 *
GRIT
1 k. d 1
1 >
f DISTRIBUTIO
| ^ 5mgd SI
CHAMBERS 131
N STRUCTURE
I1 STEM
~~|
O LIFT PUMPS 141
1
i
T
.4 i b..
PRIMARY CLARIFIERS (41
AERATION BASINS 14)
w
Q/6 ^-
Q/6 *
Q/6 *-
r
* Q/6
* Q/6
-> Q/6
SECONDARY CLARIFIERS 14)
>C*-
I,
^
I*
PONDS
i
1
MODEL PLANT
CHLORINATION BASIN
PISCATAWAY BAY
Figure 1. Flow schematic of the Piscataway secondary plant.
RAW WASTE WATER
I*
THICKENER OVERFLOW AND FILTRATE RETURN
TO PISCATAWAY BAY
Figure 2. Schematic of the S mgd system of the Piscataway plant
secondary plant.
head of the two reactors to maintain an average MLSS
concentration of 2000 mg/1. Normally, the recycle flow
was maintained at 33% of total with 4.5 hours deten-
tion. Normal operation called for control of the DO at
approximately 2.5 mg/1 O2.
The mixed liquor flows by gravity to the secondary
settler inlet structure where the flow is split and fed to
two settlers. At a flow of 2.5 mgd/settler, the units pro-
vide 2.75 hours of detention time at a surface loading of
650 gpd/sq. ft. Centrifugal pumps return the settled
solids to the reactors. Excess flow not reporting to the
Model Plant is diverted through a Parshall flume to the
polishing ponds which were installed at the plant as an
interim upgrading step pending completion of the 25
mgd system.
The waste solids from both the primary and secondary
settlers flow by gravity to the thickeners' inlet structure
from which the flow is directed to four gravity
thickeners; two basins 35 ft in diameter and two basins
55 ft in diameter.
The underflow from the thickeners was pumped to
two anaerobic digesters. The capacity of the digesters
was the controlling factor in the solids handling system.
Overflow from the thickeners are recycled to the head of
the plant. Because of the limited capacity of the digester
this overflow was high in suspended solids which
effected the operation of the primary settlers.
Following anaerobic digestion the under flow is
vacuum filtered. The cake is trucked to a farm for
spreading. Because of health requirements, only stabi-
lized sludge can be vacuum filtered and disposed of on
the land.
Tertiary Treatment
Operation of the tertiary treatment plant consisted of
treating the secondary effluent from the 5 mgd step aera-
tion system by lime clarification, dual-media filtration
and granular activated carbon adsorption. The solids
12
-------
from the chemical clarification system were gravity
thickened and dewatered by solid bowl centrifuges. The
dewatered cake was recalcined in a multiple hearth fur-
nace. The exhausted granular activated carbon was ther-
mally regenerated in another multiple hearth furnace.
Lime Treatment
In lime clarification of relatively low alkalinity waste-
waters, two options are available: two-stage high lime
with intermediate recarbonation or single-stage low lime.
Since the alkalinity of the Piscataway wastewater is less
than 150 mg/1 as CaCO3 and adequate flexibility was in-
corporated into the design of the plant, both the single
and two stage systems were evaluated.
In the two-stage high system shown in Figure 3, lime
slurry, wastewater and recycled settled solids are mixed
in the rapid mix zone of the first clarifier to reach pH
11.5. At pH 11.5 nearly all of the magnesium is preci-
pitated as magnesium bycloride which serves as an excel-
lent coagulent aid. Settled solids are recycled to increase
the rate of precipitation and size of the precipitated
solids. As a result of the high lime dose, excess calcium
ions are present in the effluent from the first clarifier.
Carbon dioxide is added in the two stage recarbonation
unit to reduce the pH to approximately 9.5. Carbon
dioxide was supplied by the recalcination of calcium car-
bonate which produces calcium oxide (CaO) and carbon
dioxide (CO2). This allows the excess calcium ions to be
precipitated as calcium carbonate. These solids are cap-
tured in the second clarifier with the aid of a small dose
(18/I/for FeC13 of ferric chloride).
In this single stage lime system, shown in Figure 4, the
pH of the wastewater is increased to 10.5 by the addition
of lime in the rapid mix zone of the first clarifier. Most
of the phosphorus is precipitated along with the
available carbonate. However, without the precipitation
of magnesium hydroxide, good clarification does not
occur and a coagulant aid is required. Ferric chloride is
added for this purpose to the rapid mix zone of the
single clarifier. The concentration of excess calcium ions
in the effluent from the single-stage is approximately 50
to 60 mg/1 as Ca and recovery by the addition of carbon
dioxide is not economically feasible.
SECONDARY EFFLUENT
FIRST REACTOR CLARIFIER
RECARBONATION BASIN
SECOND REACTOR CLARIFIER
FILTER INLET WELL
5 3 I?
DUAL
MEDIA
FILTERS
STABILIZATION BASIN
ADSORBERS
POLISHING PONDS
*
CHLORINE CONTACT
RISC AT AW AY BAY
Figure 3. Two-stage high lime tertiary process.
Dual Media Filter
In the two stage lime system effluent from the second
clarifier (ph 9.0) was reduced to pH 8 in the filter inlet
well and fed directly to the dual media filter. Care must
be taken to combat the pH since excessive calcium ions
will produce cementation of the filter media as calcium
carbonate. In the single storage system, the recombus-
tion basin is used to reduce the pH to 8 thus converting
the insoluble calcium carbonate to the soluble ion forms.
The effluents were fed to the dual media gravity filter
for removal of paniculate materials including phospho-
rus and organics. It was felt that reduction of the pH
below 8 would result in insolubilization of the
phosphorus thus allowing it to pass through the filter.
The filter media consists of 18 inches anthrocite coal (ef-
fective size 0.85 to 0.95 mm) over 6 inches of fine sand
(effective size 0.40 to 0.45 mm). The backwash water
from both the filter and carbon calcium is stored and
returned to the head of the plant at a controlled rate.
The filter effluent is reduced to pH 7.5 in the water
stabilization tank by the addition of carbon dioxide. The
reduction in pH is necessary to meet stern discharge
standards and optimize activated carbon absorption.
13
-------
SECONDARY EFFLUENT
REACTOR CLARIFIER
RECARBONATION BASIN
FILTER INLET WELL
DUAL
MEDIA
FILTERS
1
1
1
^
r
I
1
STABILIZATION BASIN
I
1
1
CARBON
ADSORBERS
POLISHING PONDS
I
CHLORINE CONTACT
PISCATAWAY BAY
Figure 4. Single stage low lime tertiary process.
Activated Carbon Adsorption
The final unit process in the tertiary treatment scheme is
activated carbon adsorption. The carbon adsorption
system consists of six downflow pressurized vessels
arranged in sets of two to provide three parallel trains of
two columns each. A depth of 16 ft of activated carbon
provides 18 minutes of Empty Bed Contact Time
(EVCT) per column. The effluent from the stabilization
tank is pumped at a rate of 6.5 gpm/sq ft through a
packed granular activated carbon bed which absorbs
soluble organic materials from the wastewater. The ad-
sorbed organics serve as a food source for bacteria
which multiply on the carbon to produce biological
slimes. The biological activity, if controlled, can substan-
tially increase the life of the activated carbon. To control
the activity and to prevent excessive pressure losses
through the packed carbon beds, backwash and surface
wash of the carbon columns are necessary. The
backwash rate is 15 gpm/sq ft. The effluents from the
three carbon systems are collected in a common line and
flow to the polishing ponds. The effluent from the
ponds receiving carbon effluents is combined with the
effluents from the ponds containing Piscataway second-
ary effluent, chlorinated and discharged to Piscataway
Bay.
Carbon Regeneration
Following exhaustion of the activated carbon, the carbon
is removed from the column for thermal regeneration.
The carbon regeneration system is shown in Fig. 5. The
exhausted carbon is removed from the activated carbon
column through the four funnels located in the under-
drain of each column (Fig. 6) and hydraulically carried
to the exhausted carbon storage tank. It is transferred,
at a controlled rate, into a multiple hearth furnace where
the regeneration takes place in 4 stages:
CARBON ADSORBERS
T
+
SPENT CARBON
STORAGE TANK
MULTIPLE HEARTH
REGENERATION FURNACE
NZ.
QUENCH TANK
REGENERATED CARBON
STORAGE TANK
Figure 5. Flow schematic for carbon regeneration.
14
-------
15ft. O.D.
Secondary Operation
PROCESS EFFLUENT
4- Carbon draw-off hoppers used to transfer carbon
from the adsorbers to the spent storage tank
Figure 6. Cross section of carbon adsorber underdrain.
1. The wet carbon is dried by simple evaporation at
temperatures above 200°F.
2. Upon application of heat to the carbon grains at
temperature above 600°F, the high molecular weight
impurities on the carbon will crack to produce gaseous
hydrocarbons, hydrogen and water vapor.
3. The final regeneration step is the gasification of the
residue from the pores of the carbon grains. This is
accomplished using steam (approximately 1 Ib steam/lb
dry carbon) at temperatures between 1700 and 1850°F.
The gaseous products of the reactions are carbon mon-
oxide and hydrogen.
4. The regenerated carbon is finally cooled rapidly to
ambient temperatures by water sprays.
Lime Handling and Recovery
The chemical solids from the lime clarification system
must be either recovered for reuse or subjected to
ultimate disposal. Laboratory tests and material balance
calculations show that at Piscataway in the single-stage
system, the solids production is approximately 2 lb/1000
gal with a calcium carbonate concentration of 50%. The
two-stage system will produce approximately 4 lb/1000
gal with a 75% calcium carbonate concentration. One of
the objectives of this study was to determine the cost of
solids handling and calcination both with and without
recovery of the calcium carbonate.
Results of Two-Stage High Lime Evaluation
The operation of the two-stage high lime system was sus-
tained at the design flow rate for 36 days in October and
November, 1973.
The operation of the step aeration activated sludge sys-
tem described in Table 1 corresponds to the 36 days of
operation of the tertiary facility and was typical of that
achieved during the two years of the grant period. The
mixed liquor suspended solids concentration of 2133
mg/1 is an average of samples taken at the quarter points
along the reactor. As seen by the average decrease in
alkalinity from 135 to 97 mgl/1 as CaCo33, the activated
sludge system was nitrifying. The reduction in alkalinity
is a result of the production of nitric acid during
nitrification. The variations in alkalinity and TKN in the
secondary effluent is shown in Figure 7. The SRT of 6.6
days is based on the average wasting rate for the 36
operating period. The average concentrations of BOD
and suspended solids for the raw wastewater, primary ef-
fluent and secondary effluent are presented in Tables 2
and 3. The effect of the recycle of solids from the solu-
ble handling system to the grit chamber is reflected in
the high values for these parameters in the primary ef-
fluent.
Table 1
Operating Conditions of the Piscataway Secondary Plant
During the High Lime Process Evaluation
Daily Flow, mgd 5.675
Detention Time, hr 4.4
MLSS, mg/1 2133
Recycle Rate, % 37
Solids in Recycle, mg/1 7970
Waste Rate, 1000 gal/day 38.1
SVI, ml/gm 96
SRT, days 6.6
F/M, Ib BOD5/lb MLVSS 0.41
Raw Wastewater pH 7.2
Secondary Effluent pH 7.4
Raw Wastewater Temperature, °F 65
Raw Wastewater Alkalinity, mg/1 CaCo3 135
Secondary Effluent Alkalinity, mg/1 CaCO3 97
140
n
O
!
100
< 60
X
12
Z
8
8!
z'
8
32
16 24
DAYS
Figure 7 Comparison of Alkalinity and TKN of Secondary Effluent.
15
-------
Table 2
Table 5
Removal of Biochemical Oxygen Demand (BOD 5 Day)
During the High Lime Process Evaluation
Removal of Nitrogen* Compounds During Evaluation
of the High Lime Process
Raw
Primary
Secondary
Lime clarified
Filtered
Carbon Adsorption
mg/l
141.0
145.0
16.5
5.9
5.7
4.0
Removal
88.3
95.8
96.0
97.2
Note: Secondary Plant recycle enters between the raw sample point and the
primary Clarifier.
Table 3
Removal of Suspended Solids During Evaluation
of the High Lime Process
Raw
Primary
Secondary
Lime Clarified
Filtered
Carbon Adsorption
Note: Secondary Plant recycle enters between the raw sample point and the
primary clarifier.
Table 4
Removal of Total Phosphorus (AS P) During Evaluation
of the High Lime Process
mg/l
121
183
27.5
21
6
2.5
% Removal
77.3
82.6
95.0
97.9
Raw
Primary
Secondary
Lime Clarified
Filtered
Carbon Adsorption
Note: Secondary Plant recycle enters between the raw sample point and the
primary clarifier.
mg/l
7.90
9.60
3.50
0.26
0.20
0.10
Removal
55.7
96.7
97.5
98.7
The phosphorus concentrations are given in Table 4.
During the evaluation period for the tertiary lime treat-
ment systems, 80 mg/l alum was being added to the
aeration tanks of the 25 mgd activated sludge system to
improve removals of phosphorus and suspended solids.
Return streams to the head of the plant containing high
concentrations of alum sludge and precipitated
phosphate entered the 5 mgd secondary system and pro-
duced high phosphorus concentrations in the primary
effluent. The overall effect of the return stream was in
increase in phosphorus removal through the old 5 mgd
secondary plant. During the 36 days of operation, the
secondary plant removed 55.7% of the incoming phos-
phorus. The average nitrogen concentrations are given in
Table 5, but do not reflect the variability as seen in
Fig. 7.
13.1
TKN
16.2
NO,
No2 Total N
1.1 0.1 17.4
4.5
5.4
4.1
2.9
5.2
6.0
3.3
6.7
6.4
5.9
8.3
.4
.3
.1
12.3
12.7
11.5
Raw
Primary
Secondary
Lime Clarified
Filtered
Carbon Adsorption
*A11 values mg/l as N
Tertiary Treatment
During the 36 days of continuous operation the influent
flow to the Model Tertiary Plant averaged 4.589 mgd.
The hydraulic loadings to the unit processes based on in-
fluent flow plus recycle are presented in Table 6. The
recycled plant water was 11.3% of the total flow. A
summary of the plant recycle flows is presented in Table
11. The chemical usage during the operation of the
system is presented in Table 8. As seen, the calcined lime
accounted for 75% of the lime added and 67% of the
available calcium oxide. Carbon dioxide was supplied by
the recalcination furnace 22 of the 36 days. Liquid car-
bon dioxide was supplemented for a portion of 14 days.
Three methods were used to determine the material
balances around the clarification and solids handling sys-
tem using the following data:
1. Chemical analyses of the liquid streams and measured
daily influent flow rates.
2. Chemical analyses of the sludge streams and mea-
sured sludge flows.
Table 6
Loading Rates During Evaluation of the High Lime Process
Secondary Plant
Flow 5.7 mgd
Primary Clarifiers 2-60 ft dia.
Secondary Clarifiers 2-70
Model AWT Plant
External Flow and Recycle = Total Flow
4.586 mgd + 0.588 mgd = 5.174 mgd
First Stage Reactor Clarifier 1-80 ft dia
Second Stage Reactor Clarifier 1-70 ft dia.
Dual Media Filtration (5 units) 242 sq ft/unit
Carbon Adsorption
Column Set #1 Avg. Flow 2.063 mgd
Column Set #2 Avg. Flow 1.420 mgd
Column Set #3 Avg. Flow 1.309 mgd
1008 gpd/sq ft
741 gpd/sq ft
1029 gpd/sq ft
1344 gpd/sq ft
4276 gpd/sq ft
or
2.97 gpm/sq ft
8.1 gpm/sq ft
5.6 gpm/sq ft
5.1 gpm/sq ft
All loadings are based on an average flow of 5.174 mga.
16
-------
Table 7
Plant Recycle Flows During High Lime Evaluation
Total Gallons/Day % of Flow
232,320 4.49
96,068 1.86
236,160 4.56
Sources
1. Filter Backwash
38,720 gal x 6 filters/day
2. Carbon Column Backwash
24,017 gal x 4 columns/day
3. Recalcination Furnace
164 gal/minx 1440 min/day
4. Misc. (centrate, pump sealing
water, flushing & wash water)
Total
23,452
588,000
0.45
11.36
All percentages are based on an average flow of 5.174 mgd.
Table 8
Chemical Usage in the High Lime Process
Lime
Total Virgin Pounds
Average Available Lime Index (ALL), %
Available CaO, Ib
Average Daily Usage, Ib
Average Daily Dose, mg/1
Total Recalcined Pounds
Average Available Lime Index (ALL), %
Available CaO, Ib
Average Daily Usage, Ib
Average Daily Dose, mg/1
Ferric Chloride (FeClj)
Total Pounds Added to Clarifier, Ib
Average Daily Usage, Ib
Average Daily Dose, mg/1
Polymer Usage (Centrifuge Only)
Total Pounds Used
Average Daily Usage, Ib
Pounds Polymer/Ton of Dry Sludge
1 37,079
87
119,259
3,138
87
426,618
60
#5,971
6,73 1
170
23,496
618
17.8
568.3
15.0
0.25
3. Total solids concentrations and measured sludge
flows.
The dual media filters were not effective in removing
additional materials with the exception of suspended
solids. The calculated removal of suspended solids in the
filteis was 15 mg/1. However, since the suspended solids
in the influent to the filter system consists mainly of pre-
cipitated calcium carbonate, a portion of which is solubi-
lized in the filter inlet well, an accurate efficiency of the
filters alone cannot be determined. However, if one
assumes that 15 mg/1 of suspended solids is captured in
one 24-hour run at 1 mgd, an estimate of the efficiency
of the filters can be determined. A total of 125 Ibs of
solids would be captured in each filter for a loading of
0.52 Ib/sq ft/cycle. By using a termination headless of 8
ft, then the loading can be expressed as 0.065 Ib/sq ft/ft
of headloss. These loadings are quite reasonable con-
sidering that the units contain 24 inches of filter media
compared to 36 inches of media in most designs.
Cost Analysis
The major purpose of this project as conceived by EPA
and WSSC was to gather reliable data with regard to
operating costs and operational problems. Accomplished
on a small pilot scale and the purpose of the Piscataway
Model Plant project was to build and evaluate a larger
system. The costs for the Model Plant were high for the
following reasons:
1. Data are based on the startup period where equip-
ment was being modified and adjusted.
2. Operators were unfamiliar with the plant. The major-
ity of the staff had little training in the wastewater field
or prior experience in treating wastewater.
3. Processes were not operated within optimum ranges
of efficiency.
Capital Expenditures
The engineer estimated the cost of the 5 MGD model
plant at 3.2 million dollars. As shown in Table 10, the
final cost of the Model Plant was 4.68 million dollars.
Table 11 shows a more detailed breakdown of the costs
in which the EPA's final share was 3.1 million dollars,
the State of Maryland paid 0.3 million and WSSC paid
1.1 million dollars. Table 12 includes the cost of engi-
neering services. Included in Table 13, 14 and 15, unit
process and equipment costs have been detailed. Note in
Table 13, that an attempt was made to determine capital
cost of the low line system. Also in Table 13, note that
the engineering services have been included as complete
plant costs and are not broken down for the individual
processes.
Table 9
Removals of Chemicals Oxygen Demand (COD) and
Total Organic Carbon (TOC) During Evaluation
of the High Lime Process
Raw
Primary
Secondary
Clarified
Filtered
Carbon Adsorption
COD
mg/1
34.8
24.7
13.4
TOC
mg/1 as C
12.3
13.4
7.5
1.8
17
-------
Table 10
Table 13
Capital Costs of the Model Plant
General Contractor (Main Contract) $3,037,100
Change Orders 210,338
Furnace Contractor 529,000
Activated Carbon 148,356
Centrifuges 66,480
Electric Substation 153,800
Sub Total $4,145,074
Engineering Services 535,243
Total $4,680,317
Capital Costs for the Model Plant Unit Processes
Process
Lime Clarification
Filtration & Carbon Adsorption
Solids Handling
Carbon Regeneration
Sub Total
Electrical Substation
Engineering Services
Total
High Lime Cost
$1,340,190
1,150,354
1,099,247
401,483
$3,991,274
153,800
535,243
$4,680,317
Low Lime Cost*
$ 991,000
1,150,354
291,930
401,483
$2,834,767
** 109,198
** 380,022
$3,323,987
Low lime cost is based on a calculated estimate.
"Both of these numbers are proportional to the sub totals.
Table 14
Breakdown on Capital Costs for the Model Plant Unit Processes
Clarification
Table 11
Distribution of Capital Costs of the Model Plant
U.S. Environmental Protection Agency
Under Project 17080DZY
Research and Development
$3,200,000 x .75
Under Project WPC - MD - 233
Additional Facilities
55% EPA's share
$1,320,453 x .55
25% State of Md. share
$1,320,453 x .25
Washington Suburban Sanitary Commission
Main Contract $ 800,000
Additional Facilities $ 264,090
$1,064,090
EPA's share 75%
= $2,400,000
$1,320,453
= $ 726,249
= $ 330,113
Table 12
Costs of Engineering Services for the Model Plant
Preliminary Engineering Design and Report $ 28,449
Study of Advanced Treatment 7,281
Preparation of Plans and Specifications 288,511
Construction Services 190,095
Preparation of Operations Manual 20,907
Total $535,243
Filtration
Excavation
Concrete Work
Mechanical Work
Electrical Work
Painting
Other Work
Steel Shelves
Underdrains
Filter Media
Mechanical Work
Piping and Valves
Painting
Electrical Work
Other
Steel Tanks and Supports
Filter Bottom
Mechanical Work
Piping and Valves
Electrical Work
Painting
Other Work
Operations Building
Centrifuge Area & Cake Handling System
(excluding centrifuge)
Lime Handling System
Fed and Polymer System
Motor Control Center and Power Distribution
Instrumentation
Miscellaneous Equipment, Steel and Clean-up
Carbon Adsorbers
$ 52,700
187,400
237,000
28,000
10,000
20,300
$ 535,400
$ 118,000
35,000
8,000
29,500
32,000
3,000
600
7,100
$ 232,200
$ 232,000
28,000
26,000
75,000
6,000
7,900
1,800
$ 367,700
$1,076,900
33,800
100,200
43,200
105,500
308,800
226,337
$3 f" '
18
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Table 15
Conclusions
Capital Cost Breakdown for the Model Plant Equipment
General Contract Cost
Reactor Clarifier $ 294,000
Recarbonation Basin & Associated Tanks 92,400
Lime Pumping Stations 81,000
Thickener & Pumping Station 68,000
Operations Building 1,076,900
Dual Media Filters 194,000
Backwash Tanks 78,4000
Stabilization Tank 50,500
Activated Carbon Adsorbers 247,500
(excluding carbon)
Carbon Storage Tanks 30,500
Lime Bins 31,500
Lime Slaker System 25,700
Assorted Lime Handling Systems 43,000
Lime Cake Handling Systems 33,800
Miscellaneous Plant Equipment 61,600
Chemical Feed System 42,200
(Ferric & Polymer)
Steam Generator 13,500
Platform & Structures 69,200
Motor Control Center & Power 105,500
Distribution
Instrumentation 308,800
Sitework & Piping 88,100
Sub Total
Change Orders
Furnace Contracts
Activated Carbon
Centrifuges
Total
$3,037,100
210,338
529,000
148,356
66,480
$3,991,274
Date of
Completion
October 72
October 72
October 72
October 72
April 72
April 72
April 72
April 72
April 72
April 72
May 72
February 73
February 73
October 72
April 72
October 72
April 72
April 72
March 72
February 73
April 72
February 73
March 73
October 72
July 72
This report covers results from the operation of a 5 mgd
tertiary wastewater treatment plant used to upgrade the
quality of effluent from a conventional secondary plant
using step aeration activated sludge. The tertiary plant
used either two-stage high lime or single-stage low lime
followed by dual-media filtration and granular activated
carbon adsorption. Major conclusions from the demon-
stration project are as follows:
1. The high lime process using an average dosage of 257
mg/1 CaO and 18 mg/1 FeCl3 significantly reduced resid-
uals of BOD, TSS and P in the secondary effluent. BOD
was reduced from 16.5 mg/1 to 4.0 mg/1; TSS was
reduced from 27.5 mg/1 to 2.5 mg/1 and P was reduced
from 3.50 mg/1 to 0.10 mg/1.
2. The low lime process using an average dosage of 113
mg/1 CaO and 25 mg/1 FeCl3 produced removals of
BOD, TSS and P comparable to those obtained with the
high lime process.
3. Tertiary treatment did not significantly affect total N
residuals in the secondary effluent.
4. Carbon losses from regeneration of three columns
under less than optimum conditions were estimated as
8-10%.
4. Operating costs for tertiary treatment in this demon-
stration plant were in the range of 29-36 cents" per 1000
gallons. These are considered to be unusually high
because data are based on the startup period when the
plant was not at optimum efficiency and operators were
not familiar with the plant.
6. A highly competent, well trained, technical staff is re-
quired to successfully operate a complex tertiary waste-
water treatment plant. Extra efforts must be made to
select, train and retain personnel.
19
-------
Aerated Filters for Tertiary
Treatment of
Secondary Effluents
A.G. Kirichenko
Cand. Techn. Sc.
(Kharkov Department of VNIIVODGEO)
Aerotanks of various modifications are the most popular
units for removal of organics from municipal and indus-
trial waste waters where their concentration is expressed
as biochemical oxygen demand (BOD) value.
Theoretically aerotanks are able to reduce BOD value
down to 2-3 mg/1, but in our country from the econom-
ical point of view it is recommended to treat effluents
down to BOD value 15 mg/1, and in some countries the
standard degree of effluents treatment in aerotanks is
even lower.
When biologically treated effluents are being dis-
charged into streams of low rate of flow in comparison
with this discharge, or into water bodies used for fish
propagation, etc., the degree of treatment on aerotanks
does not satisfy rules of discharge, and water inspec-
torate authorities demand in designs provision for a ter-
tiary treatment installation.
For some years economically developed regions are
experiencing shortage of service water for industrial
needs. The water shortage can be alleviated by usage of
treated municipal effluents for some industrial processes,
for example for equipment and apparatus cooling,
mountain waste and cinder hydraulic transportation, gas
cleaning, etc. In such cases tertiary treatment of efflu-
ents is also necessary.
Thus the necessity of tertiary treatment of secondary
effluents is caused not only by hygienic demands to
improve quality of the effluents, but also by the ration-
ality of usage of treated effluents for industrial water
supply.
In connection with this in our country and elsewhere
for some years investigations are being conducted with
aim to develop new methods and designs of units for ter-
tiary treatment of effluents. As concentration of sus-
pended solids in biologically treated effluents is low - -
usually within 15-50 mg/1 they can be removed by
filters with an inert medium, such as quartz sand,
granite rubble, etc. Such filters have been very popular
for potable water treatment for a long time. But biologi-
cally treated effluents contain not only suspended pol-
lutants but also colloidal and dissolved organics which
are more dangerous from the sanitary point of view.
Their concentration is also expressed by BOD value.
Also they contain biogenic elements, in particular nitro-
gen and phosphorus. Such pollutants practically are not
removable by treatment of effluents on conventional
filters with a granular medium. Moreover, dissolved oxy-
gen of aerobically treated effluents is completely
absorbed by such filters. As dissolved oxygen concentra-
tion in secondary sedimentation tank effluents usually is
not higher than 2 - 3 mg/1, the oxygen is absorbed by an
upper layer of the filtering medium. Therefore in this
layer, conditions appropriate for aerobic microorganisms
and for biological processes are being created and these
cause a partial reduction of BOD value. As the lower
layers of the medium are deprived of oxygen, their
anaerobic conditions are substituted for aerobic ones,
captured suspended matter starts to decay, and by the
end of filtration cycle the effluents acquire unpleasant
putrescent odour and contain no dissolved oxygen.
Effluents treated in conventional filters have to be satu-
rated with oxygen before discharge into receiving waters.
At the Kharkov Department of VNIIVODGEO we
have designed a granular filter for tertiary treatment of
biologically treated effluents. Here filtration process is
designed with due regard for peculiarities of such ef-
fluents and thus it obviates to a considerable extent
shortcomings inherent to conventional filters.
It is known that the process of tertiary treatment of
effluents in granular filters depends not only on
physical-chemical and hydraulic factors, but also on con-
current biochemical factors as the bioflocculation phe-
nomenon considerably influences the mechanisms of
filtration. Some types of microorganisms are barely
tolerant to turbulence occurring in aerotanks, but they
can form a biological film on surfaces of solid bodies
and this film very efficiently absorbs colloid and dis-
solved organics from effluents, provided the dissolved
oxygen concentration is sufficient for their biological
development.
Investigations of physical fundamentals of filtration
processes of a low-concentration suspension of activated
21
-------
sludge, i.e. effluents of secondary sedimentation tanks
after aerotanks, give justification to the idea that the
granular filter supplied with air or oxygen would be suit-
able for biochemical processes throughout the depth of
filtering medium, and thereby it would be possible to en-
sure tertiary removal not only of suspended solids but
also of dissolved and colloidal organics. Concentrations
of these substances are expressed as BOD value.
It is recommended to conduct tertiary treatment of
effluents in two stages: preliminary sedimentation of
activated sludge particles in the unaerated layer of the
filter followed by filtering through the aerated layer.
We have developed for this purpose units of various
designs. One of them (Fig. 1) is a two-tier filter. It con-
sists of the tank 1 separated into two tiers (lower 2 and
upper 4) by the perforated plate 3. Effluents of a
secondary sedimentation tank are delivered by the pipe-
line 8 into the lower unaerated layer of the filtering
medium where suspended particles are retained. The
effluents from the lower tier are passing through the per-
forated plate of a special design 3 into the filtering
medium of the upper tier 4 supplied with air or oxygen
through the pipeline 6 when the filter is in operation.
The treated water is collected and discharged by channels
5. The filtering medium of both tiers can be washed
either jointly or separately. At separate washing the
wash water of the lower tier is discharged through the
pipeline 7.
When filtering, introduction of oxygen and nutrients
in the form of residual organics remaining in the second-
ary effluents induces formation of a biological film on
granular particles of the medium. The film consists of
microorganisms intensively adsorbing and mineralizing
pollutants. The tertiary treatment in a short time is en-
sured by a large area of the interphase contact (about 50
times larger than in rubble filters), by intensive forms of
microorganisms, and by aerobic conditions.
Experimental investigations have been conducted in
laboratory and pilot scale on effluents of the Kharkov
aeration plant with aim to establish design, construction,
and technology parameters. The effluents delivered for
tertiary treatment contained 15-25 mg/1 suspended
solids, 15-20 mg/1 BOD, 90-120 mg/1 COD, 2-3 mg/1
DO. The filters were charged with quartz sand of 1.0-1.8
mm grains diameter, depth of the charge layers were
1000 mm for each layer. The hydraulic load amounted
from 5 to 13 m per m/hr.
Treatment and analysis of experimental data have
demonstrated that at filtration rate 6-7 m/hr and dura-
tion of filtering cycles 24-30 hrs, content of suspended
solids was reduced by 85% in the lower tier of the filter.
At the same rate of filtering through the aerated tier of
the filter and at rates of air supply for upward filtering
1 m per m /hr and for downward filtering 2.5 m per
m2/hr, total BOD was reduced by 75-80%. At the same
time the treated water was saturated with oxygen up to
7-8 mg/1.
Hydrobioiogical analyses have demonstrated that
microorganisms-populating the biofilm on the grains
22
were active throughout the whole depth of the aerated
medium.
Investigations of kinetics of BODtotal values reduction
by different layers of the medium of the lower and
upper tiers of the filter have demonstrated that introduc-
tion of air into the medium ensured aerobic conditions
for biochemical processes and caused additional con-
sumption of oxygen and reduction of BODtota] from
15-20 mg/1 down to 4-5 mg/1. In unaerated layers of the
filter biochemical consumption of oxygen, due to its
shortage, was observed only in first layers of the
medium when looking in direction of filtering (Fig. 2).
In the process of tertiary treatment in aerated filters
the acid-base reaction of water was shifted by 0.3 units
to the alkaline zone (in unaerated filters this shift
amounted to 0.1 unit). This also indicates to biochemical
activity of the microorganisms.
For investigation of influence of various factors on ef-
fluent treatment efficiency and for obtaining compara-
tive characteristics of operation of aerated filters, pilot
scale experiments were conducted on filters of various
designs: two-tier aerated and unaerated filters, conven-
tional grit filters with upward and downward delivery of
effluents, reaerated filters, aerated filters with the micro-
filter.
Factors of operation of the units are given in the
table. It is readily seen that the aerated granular filters
provided the highest reduction of concentrations of the
main kinds of pollutants.
On the basis of these investigations the main construc-
tion, design and technological parameters have been
determined: filtering rate 7 m/hr, charge of the quartz
sand of 1-1.8 mm coarseness; depth of medium layers
1000 mm for each layer; aeration intensity in downward
filtering 2.5 m3 per m2/hr, in upward filtering 1 m3 per
m /hr; filtering cycle duration 24-28 hrs; washing inten-
sity 16-17 1 per s/m2 at 6-8 min. duration; supporting
layers, distribution, collection and discharge of water
have to be designed in accordance with the construction
standards and guidelines CHHII 11-31-74.
When conducting experiments, concentrations of dis-
solved oxygen in the water were also determined. Water
samples were taken from various points throughout the
filter depth. The results of oxygen regime investigations
are given on the diagram (Fig. 3). The diagram indicates
that filtering through the lower unaerated layer of the
medium reduced the dissolved oxygen concentration
from 2-3 mg/1 to 0.8-1.2 mg/1. In the upper aerated
layer the treated effluents were saturated with oxygen up
to 7-8 mg/1, thus the necessity of construction of special
units for water aeration was eliminated.
Application of aerated filters for tertiary treatment of
secondary effluents instead of conventional filters or bio-
lagoons and aerating channels at a station of 25000 m
per- day throughput would give an annual economic
effect of 74 thousand roubles. But the main result con-
sists in ensuring a steady high degree of treatment of
effluents which can be discharged into a receiving water
body of any type, or can be used for industrial water
supply.
-------
Fig. 1. Diagram of the two-tier aerated filter
1. tank, 2. lower tier, 3. perforated plate, 4. upper tier,
5. collecting channel for filtrate and washing water, 6. air inflow,
7. pipeline for filtrate and washing water, 8. inflow of effluents and
washing water.
a
£ ,
0 400 800 1200 1600 2000 2400 2800 3200
Filter depth, mm
Fig. 2. BOD|0|I| value variation through the filter depth at filtering rate
7 m/hr
1. two-tier aerated filter
2. two-tier unaerated filter
a. lower tier, b. upper tier
Upper Her
" 400 800 1200 1600 2000 2400 2800 3200
Filter depth null
Fig. 3. Variation of DO concentration through the filter depth
at filtering rate 7 m/hr
1. two-tier aerated filter
2. two-tier unaerated filter
3. aerated filter with the microfilter
a. lower -tier, b. upper tier
23
-------
Granular Carbon and Other
Tertiary Treatment Processes
Uy
Frank P. Sebastian
Senior Vice President
Envirotech Corporation
Menlo Park, California
and
Dennis S. Lachtman
Environmental and Occupational
Health Analyst
Envirotech Corporation
Menlo Park, California
Introduction
Previous papers (1,2,3) have discussed the need for and
benefits of wastewater reclamation. The quality of many
domestic water supplies throughout the world is inferior
in comparison to many effluents from selected advanced
wastewater treatment plants. It was discussed that, in the
United States, although reclaimed sewage is not allowed
for use as water supply, 145 of 155 cities having popula-
tions above 25,000 were found to have 17% to 18.5%
sewage constituents by volume in their potable water
supplies (4). At the 1977 Moscow symposium (1) various
examples of advanced wastewater treatment facilities and
their flowsheets were mentioned (see Table I).
Increased attention on toxic elements contained in
water supplies has raised questions about the public
health risks associated with the domestic water supplies
of the U.S. According to Harris (5), communities deriv-
ing their water supplies from the southern portions of
the Mississippi river had carcinogens in their potable
water supplies. Accordingly, the question of the effec-
tiveness of some systems for removal of trace toxic
substances, including carcinogens, from wastewater prior
to reuse needs careful consideration.
This paper will review two unit processes: carbon
adsorption and lime treatment, and how their respective
methods remove various elements posing health concerns
to water reuse.
Health Considerations
Although economics may be attractive for water reuse,
many would argue that countless examples of non-
intentional water reuse in various communities are
insufficient criteria to justify commitments to water
reclamation plants. Problems such as health risks and
esthetic considerations are crucial determinants for plan-
ning water reclamation facilities.
Many examples illustrate the existence of communities
having water supply qualities that are less than ideal. For
instance, a U.S. survey from 3,500 U.S. communities
revealed that the water supplies consumed by 41% of
these municipal systems had potable water of a poorer
quality than the effluent from advanced wastewater
treatment (6). Projected nationally, this is equal to 50
million people in the U.S. drinking tap water of a qual-
ity lower than the effluent from an advanced wastewater
treatment plant. These communities do not appear to
have any acute public health problems associated with
consumption of drinking water that fails to meet the
United Nations World Health Organization, WHO
drinking water standards. WHO standards are shown in
Table II. However, recent U.S. research indicates a
health risk associated with drinking water containing low
level residuals of trihalomethanes resulting from chlori-
nation of natural and organic residuals. Where tri-
halomethane levels indicate synthetic organic chemical
levels exceeding the recommended levels, granular activ-
ated carbon filtering of drinking water is required (7).
Reclaimed water for non-potable uses such as cooling
water make-up and industrial processes often allow even
less stringent treatment levels than WHO standards.
The agents of public health concern found in waste-
water can be divided into two categories: biological
(infectious) and chemical compounds.
Infectious agents could include entities of bacterial,
viral, or parasitic origins (8). The most important patho-
gens, including members of the genera Salmonella and
Shigella, cause frequent outbreaks, but are controllable
by adequate secondary treatment methods and are easily
detected by standardized monitoring techniques. Viruses
are not accurately monitored and present a more serious
25
-------
Table 1
Examples of Advanced Wastewater Treatment Technology
Windhoek Biological-algae- WHO Standard Tap water
South West Africa physical-chemical
Lake Tahoe Biological-physical- WHO Standard Trout lake,
California chemical swimming,
irrigation
Colorado Springs Biological-physical- BOD 11 ppm* Industrial cooling
Colorado chemical SS 1.5 ppm water
Rye Meads Extended-biological BOD 10-5 ppm Up to 20% of
U.K. SS 10-5 ppm London tap water
Central Contra Lime plus biological BOD 2.0 ppm Industrial cooling
Costa Sewage SS 1.0 ppm and processing
Treatment Plant
* parts per million
Table 2
World Organization Requirements
World Health Organization Drinking Water Standards
Chemical Substances that
Serve as Criteria for
Potability
Total solids
Color
Turbidity
Taste
Odor
Iron (Fe)
Manganese (Mn)
Copper (Cu)
Zinc (Zn)
Calcium (Ca)
Magnesium (Mg)
Sulphate (SO )
Chloride (Cl)
pH range
Maximum Acceptable
Concentration
500.0 mg/1
5 units*
5 unitst
Unobjectionable
Unobjectionable
0.3 mg/1
0.1 mg/1
1.0 mg/1
5.0 mg/1
75.0 mg/1
50.0 mg/1
200.0 mg/1
200.0 mg/1
7.0-8.5
Maximum Allowable
Concentration
1,500.0 mg/1
50 units*
25 unitst
1.0
0.5
1.5
15.0
200.0
150.0
400.0
600.0
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
less than 6.5 or
greater than 9.2
1,000.0 mg/1
Magnesium + Sodium 500.0 mg/1
Sulphate
Phenolic substances 0.001 mg/1 0.002 mg/1
(as phenol)
Carbon chloroform extract 0.02 mg/1 0.5 mg/lt
(CCE: organic pollutants)
Alkyl benzyl sulfonates 0.5 mg/1 1.0 mg/1
(ABS: surfactants)
Health Hazards
Nitrate as NO 45.0 mg/1
Fluoride 1.5 mg/1
Toxicity
Phenolic substances
Arsenic 0.05 mg/1
Cadmium 0.01 mg/1
Chromium (Cr hexavalent) 0.05 mg/1
Cyanide 0.2 mg/1
Lead 0.05 mg/1
Selenium 0.01 mg/1
Platinum-cobalt scale.
(Turbidity units.
tConcentrations greater than 0.2 mg/1 indicate the necessity for further analysis
to determine the causative agent.
concern. The viral components of major health concern
include:
1. enteroviruses (polio, coxsackie, Echo);
2. adenoviruses;
3. reoviruses; and
4. the agent of infectious hepatitus.
The second category of health-aftecting agents
includes the organic and inorganic chemicals. Many
organic chemicals are those identified as problematic
factors causing increased cancer risks. Table HI is a list
of organic chemicals identified by Cooper (8) in U.S.
drinking water. Inorganic chemicals include the metallic
ions. Table IV is adapted from Cooper (8) and is a list
of toxic ions and their recommended concentration limits
for safe drinking water as derived from available toxicol-
ogy data and established dose tolerance levels.
The following discussion will analyze both carbon
adsorption and lime treatment in respect to their indi-
vidual and collective removal capabilities for these
defined health hazards. Combinations of both unit pro-
cesses have been shown to have the capability to remove
most, if not all, of these agents from wastewater
effluents.
Table 3
A Selected List of Potentially Toxic Chemical Agents Found in
Drinking Water and Recommended Limit Concentrations
Chemical
Agent
Arsenic
Barium
Cadmium
Chromium
Cyanide
Lead
Mercury
Nitrate
Nitrite
Selenium
*mg Nitrate or Nitrite-Nitrogen
Source: (8)
Recommended
Maximum
Standard mg/1
0.05
1.0
1.01
0.05
0.20
0.05
0.002
10.0*
1.0*
0.01
Trace Metals
Since many trace metals form insoluble hydroxides at
pH 11, lime treatment eliminates these metallic consti-
tuents through coagulation or precipitation. Table V
summarizes the lime removal efficiencies as condensed
from the available literature (9). Filtration methods used
to remove the residuals from lime coagulation will result
in additional incremental removal of heavy metals. A
full-scale example of an advanced water reclamation
plant using lime treatment without carbon adsorption
processes is the 113,500 mVday (30 million gallon/day)
26
-------
Table 4
Table 5
Organic Compounds Identified from Finished Drinking Water
Removal of Heavy Metals by Lime Coagulation and Recarbonation
Acetone Chloro Hydroxy Benzophenone Methyl Benzothiazole
Acetophenone Bis-Chloroisopropyl Ether Methyl Biphenyl
Acetylene Dichlonde Chloromethyl Ether Methyl Chloride
Benzene Chloronitro Benzene Nitroanisole
Benzo Thiazole Chloropyndme Nitrobenzene
Bromo Benzene Chloromethylethy! Ether Octane
Bromo Chlorobenzene Dibromo Benzene Pentane
Bromo Dichloromethane Dichloroethane Propylbenzene
Bromoform Dichloroethyl Ether Tetrachloroethylene
Bromo Phenyl Phenyl Ether Dimethoxy Benzene Toluene
Butyl Benzene Hexachloro Benzene Tnchloroethane
Camphanol Hexachloro Ethane Triglycodichlonde
Camphor Hydroxy Adiponitnle Thiomethylbenzothiazole
Caprolactam Isoborneol Vinyl Benzene
Carbon Tetrachlonde Isocyanic Actd Dimethyl Naphthalene
Chloro Benzene Isopropanyl Isopropyl Benzene Dimethyl Sulfoxtde
Chloro Dibromo Methane Isopropyl Benzene Dimtrotoluene
Chloro Ethoxy Ether p-menth-l-en-8-pl Ethyl Benzene
Chloro Ethyl Ether o-methoxy Phenol Ethylene Dichlonde
Chloroform 2-Methoxy Biphenyl Exo-2-Camphanol
Source: (8)
Central Contra Costa Sanitation District (CCCSD)
Water Reclamation Plant in Concord, California. The
plant flowsheet, as shown in Figure 1, is designed for a
possible expansion to handle up to 445,000 m3/day (120
million gallon/day) (10, 1, 11). The influent characteris-
tics are expected to average 220 mg/1 BOD, 240 mg/1
suspended solids, 30 mg/1 nitrogen N, 11 mg/1 total
phosphorus as P. After treatment, the effluent values
will be 3.5 mg/1, 6.0 mg/1, 2.0 mg/1 and 0.5 mg/1,
respectively (10). The effluent will be used by the fol-
lowing five industries: Phillips Petroleum, Shell Oil,
Stauffer Chemical, Monsanto and the Pacific Gas and
Electric power station. Although no data are available
for heavy metal removal, it is expected to equal or
exceed those high removal values as shown in Table IV.
A study at the University of Colorado (12) demon-
strated that four trace elements (cadmium, chromium,
selenium and silver) having particularly low allowable
levels by USPHS drinking water standards were removed
by lime coagulation from secondary effluent by 97% for
the silver and 94% for cadmium ions. Using a combina-
tion of lime for coagulation and settling, sand filtration,
activated carbon adsorption and an anion-cation ex-
change sequence demonstrated that (see Tables VI and
VII) extremely high removal efficiencies (more than
98.6%) were achieved by the combination of these pro-
cesses for selenium, chromium, silver, and cadmium
ions. With only sand filtration and carbon adsorption,
chromium, cadmium and silver were removed by at least
98.5% efficiency, with selenium having a 44.7% removal
efficiency. This clearly suggests that using lime plus car-
bon adsorption will effectively remove toxic metals. The
use of sand filtration and lime will help keep the carbon
column from overloading with organics and trace metals
for a longer time period before regeneration is necessary.
Metal Concentration Concentration Final %
Before Treatment After Treatment pH Removal
mg/1 mg/1
Antimony3 1 1 90
Arsenic8 11 <10
23 23 9.5 0
Barium" ~1.3(sol)b 11
. Bismuth" .0002 (sol) 1 1
Cadmium Trace 11 ~ 50
0.0137 0.00075 >11 94.5
Chromium ( + 6) 0.056 0.050 >11 11
Chromium ( + 3) 7,400 2.7 8.7 99.9 +
15 0.4 9.5 97
Copper 15,700 0.79 8.7 99.9 +
7 1 8 86
7 .05 9.5 93
302 Trace 9.1 99 +
15 0.6 9.5 97
Gold" <.001 (sol) 11 90 +
Iron 13 2.4 9.1 82
17 0.1 10.8 99*
2.0 1.2C 10.5 40
Lead" <.001 (sol)b 11 90 +
15 0.5 9.5 97
Manganese 2.3 <0.1 10.8 96
2.0 l.lc 10.5 -45.
21.0 0.05 9.5 95
Mercury" Oxide soluble < 10
Molybden&m Trace 8.2 ~10
11 9 9.5 18
Nickel 160 0.08 8.7 99.9 +
5 0.5 8.0 90
5 0.5 9.5 90
100 1.5 10.0 99
16 1.4 9.5 91
Selenium 0.0123 0.0103 >11 16.2
Silver 0.0546 0.0164 >11 97
TelluriumM (< 0.001?) 11 (?90+)
Titanium"ld (< 0.001?) 11 (?90+)
Uranium* ? ?
Zinc .007 (sol) 11 90 +
17 0.3 9.5 98
"The potential removal of these metals was estimated from solubility data.
Barium and lead reductions and solubilities are based upon the carbonate.
cThese data were from experiments using iron and manganese in the organic
form.
Titanium and tellurium solubility and stability data made the potential reduction
estimates unsure.
eUranium forms complexes with carbonate ion. Quantitative data were unavail-
able to allow determination of this effect.
South Lake Tahoe, which we have previously dis-
cussed numerous times, is a facility where physical-
chemical treatment was added to conventional or second-
ary treatment. This water has been used to form Indian
Creek Reservoir, a trout lake, for swimming and for
grazing areas. This biological plus physical-chemical
advanced wastewater treatment flowsheet is shown in
Figure 1. This facility, which benefits from using a com-
bination of lime treatment and carbon adsorption, pro-
duces an effluent that easily meets both United States
Public Health Service and World Health Organization
(WHO) drinking water standards (9). Table VII lists data
of this effluent showing the concentrations of heavy
metals.
-------
RAW SEWAGE
PRECHLORINATION
WASTE
BIOLOGICAL >
SLUDGES
NITROGEN GAS
TO A
ATMOSPHERET
TABIUZATION 1
POSTAERATIO
POSTCHLORIN*
SCREENING
^
INFLUENT PUMPING
1
1
LLIME REACTOR
AND PREARATION
*
PRIMARY
SEDIMENTATION
^ POLYMER
^ and/or F.CI3 RECLAIMED LIME
SLUDGE ^ SOLIDS ASH TO
* PROCESSING ""*" DISPOSAL
^ STEAM
t PRIMARY EFFLUENT
PUMPING
1
AERATION
NITRIFICATION
I
[SECONDARY
SEDIMENTATION
TURBINE 1
BLOWERS
AIR
n RETURN
SLUDGE
^ WASTFSLUnr.F
TO PREAERATION
\4 METHANOL
DENITRIFICAT1ON
REACTOR
AERATED
STABILIZATION
^
FINAL
SEDIMENTATION
N AIR -i -fr.
4 . MIXING
RETURN
SLUDGE
w WASTE SLUDGE
TO PREAERATION
^ EFFLUENT TO
FINAL EFFLUENT
PUMPING
TILTnATION
CHLORINATION ^-i
[INDUSTRIAL SYSTEM
PUMPING
RECLAIMED WATER
TO INDUSTRY
Figure 1. Central Contra Costa Sewage Liquid Process Flow Sheet
Treatment Plant, Concord, CA.
Table 6
Removals of Trace Metals in Lime Coagulation-Settling Process
Trace Metal Removal
Ag(Ag + )
Cd(Cd + 2)
Cr(Cr207-2)
Se(SeO3-2)
97.0
94.5
9.3
16.2
Source (12)
Table 7
Removals of Trace Elements in Sand Filtration, Activated Carbon,
Cation Exchange, and Anion Exchange
Cumulative Removal After
Given Process
Trace Metal
Ag(Ag + )
Cd(Cd + 2)
Cr(Cr2072)
Se(Se03-2)
Source (12)
Sand
Filtra-
tion
11.6
6.2
2.5
9.5
Acti-
vated
Carbon
97.1
98.8
96.6
43.2
Cation
Ex-
change
98.8
98.5
98.5
44.7
Anion
Ex-
change
99.4
99.1
98.6
99.9
Although the Tahoe facility was designed and built
during a low energy cost era, it could be retrofitted and
made less energy intensive through methods previously
reported in this forum (1, 11). The energy recovery
methods to which we are referring are improved
dewatering, heat recovery, and pyrolysis, or co-disposal.
The latter option appears particularly attractive as,
according to California and Nevada state law, all refuse
solid waste must be transported out of the Tahoe Valley.
Thus, the transportation savings would further augment
the inherent energy recovery economics of pyrolysis.
Organic Compounds
Most of those organic constituents identified in Table II
are adsorbed on carbon. Generally, the chemical nature
of carbonaceous compounds is of relatively minor signif-
icance for the adsorption of these compounds by the
activated carbon medium, as activated carbon has a pre-
ference for adsorbing organic compounds. Carbon filtra-
tion is particularly effective in removing trace organic
substances associated with chronic health problems, in
addition to eliminating odor and taste problems (9).
Essentially, carbon adsorption in combination with other
processes including pre- or post-chlorination and ozone
treatment including pre-ozonation of carbon filter media
and ozonation of water (13, 14) will eliminate organic
residues. The success of the Tahoe process is qualita-
tively demonstrated at Tahoe where a rainbow trout
fishery has been maintained for more than nine years
using this effluent at Indian Creek Reservoir. Since trout
fingerlings are extremely sensitive to chloro-organic com-
pounds, one has a high degree of confidence that trace
organics are effectively removed.
The effectiveness of carbon adsorption in removing
trace organics is recognized by the U.S. Environmental
Protection Agency (EPA) drinking water standards,
which require carbon adsorption to insure the absence of
these organic compounds which include many identified
carcinogens (7). Since the cost of activated carbon can
be quite expensive, carbon regeneration and reuse are
most attractive. Numerous installations of carbon regen-
eration furnaces exist for carbon used in wastewater
treatment, industrial processing and for potable water
supplies. Table VIII is a list of the carbon regeneration
facilities of one equipment manufacturer. The process
utilizes a multiple hearth furnace (MHF) which raises the
activated carbon to 1500°F., driving off the adsorbed
carbon constituents into a gaseous phase. Water is used
to quench the carbon prior to its being returned to the
carbon filter. A loss rate of 5%-7% per regeneration
cycle can be maintained. Cost estimates for virgin acti-
vated carbon were reported at approximately $.30 per
pound (.46R/kg) while using this same price index would
render the cost of regenerating activated carbon by MHF
methods at $.04 per pound (.06R/kg) (9). As previously
discussed, where levels of trace synthetic organic chem-
icals exceed baseline levels, activated granular carbon is
required to remove these constituents (7).
28
-------
Table 8A
Table B
Municipal Carbon Regeneration Furnace List
Industrial Carbon Regeneration Furnace List
1963 6'0" O
1969 4'0" 0
1972 6'0" O
1974 7'9" O
1974 12'9" 0
1975 5'6" O
1976 16'9" O
1976 12'9" O
1976 (3) 10'9" O
1977 10'9" O
D. x 6H South Lake Tahoe, Ca.
D. x 6H Colorado Springs, Co.
D. x 8H Rocky River, Ohio
D. x 5H Derry Township, Pa
D. x 6H Vallejo, Calif.
D. x 6H Palo Alto, Santa Clara, Ca.
D. x 6H Tahoe-Truckee, Calif.
D. x 6H North Tonawanda, N.Y.
D. x 6H Alexandria, Va.
D. x 5H Nassau Co., N.Y.
Source: Envirotech Corporation
Table 8B
Industrial Carbon Regeneration Furnace List
Date of
Date of
User Installation Size AppUcatkn
Cargill, Inc., 1974 8'-6 x 7H Corn Syrup
Memphis, Tenn. Refining
Corn Sweeteners 1974 13'-6" x 6H Corn Syrup
Refining
Onisa, Mexico 1974 7'-0" OD x 6H Cane Sugar
Regeneration
Republic Steel Corp. 1974 16' -0 x 8H + OH Wastewater
Corn Sweeteners 1975 13'-6" x 6H Corn Syrup
Refining
Imperial Sugar Co., 1975 12'-9" x 5H + OH Cane Sugar Refining
Sugar Land, Tx.
American Maize Products, 1975 12"-9" x 6H Corn Syrup
Decatur, Al. Refining
Clinton Corn, 1975 I4'-3" x 6H Corn Syrup
Montezuma, N.Y. Refining
Cargill, Inc., 1975 8'-6" x 6 + OH Corn Syrup
Dayton, Ohio Refining
Corn Sweeteners, 1976 13'-6" OD x 8H Corn Syrup
Cedar Rapids Refining
User Installation Size Application
Spreckles Sugar, Salinas
Accent international,
San Jose
Spreckles Sugar, Mendota
Spreckles Sugar, Woodland
Holly Sugar Co., Calif.
Everglades Sugar, Florida
Florida Sugar, Florida
Supreme Sugar, Louisiana
Spreckles Sugar, Arizona
Spreckles Sugar, Manteca
Corn Sweeteners
Industrial Sugar, Missouri
Spreckles Sugar, Maryland
West Virginia WW, Nitro,
W. Va.
Penick & Ford Ltd., Iowa
The Upjohn Co.,
Michigan
Cargill Inc., Iowa
Dow Badische, Texas
Dimmit Wheat Growers,
Texas
Holleytex Carpet Mills,
Pa.
Rhodia Inc., Oregon
C.P.C. International,
Yonkers, N.Y.
(Refined Syrups)
Penick & Ford, Iowa
St. Lawrence Starch,
Canada
BP Oil, New Jersey
Eli Lilly
FMC Corp., Wyoming
Pfizer Chemical,
Connecticut
Stepan Chemical Co. ,
N.J.
Hercules, Mississippi
Reichhold Chemicals,
Alabama
South Coast Corp.,
Amerada Hess,
New Jersey
American Aniline,
Pennsylvania
Anheuser Busch
Esso Research
St. Lawrence Starch,
Canada
American Maize Products
Cargill Inc., Dayton, Ohio
1961 8'-6 x 8H Beet Sugar Refining
1962 10' x 8H Monosodium
Glutamate
1962 8'-6 x 8H Beet Sugar Refining
1962 8'-6 x 8H Beet Sugar Refining
1963 8'-6 x 8H Beet Sugar Refining
1964 8'-6 x 6H Bone Char
1964 6' x 6H Cane Sugar Refining
1964 9'-3 x 6H Cane Sugar Refining
1965 8'-6 x 8H Beet Sugar Refining
1965 8'-6 x 6H Beet Sugar Refining
1966 7' x 8H Corn Syrup
Refining
1966 6' x 8H Cane Sugar Refining
1966 6' x 8H Cane Sugar Refining
1966 6' x 8H Water Purification
1967 30" x 6H Corn Syrup
Refining
1967 6' x 8H Pharmaceuticals
1968 7' x 8H Glucose
1968 30" x 6H Acetic Acid
1969 7' x 6H Corn Syrup
Refining
1969 30" x 6H Dye Wastewater
1969 6' x 6H Chlorinated Phenols
1970 10' x 8H Cane Sugar Refining
1970 12' x 6H Corn Syrup
Refining
1970 6' x 5H Corn Syrup
Refining
1971 6' x 6H Wastewater
1971 6' x 6H Pharmaceuticals
1971 7' x 6H Soda Ash
1971 8'-6 x 6H Citric Acid
1971 6' x 6H Wastewater
1972 12' x 6H Wastewater
1972 13'-6 x 6H Wastewater
1972 10' x 6H Cane Sugar Refining
1973 8'-6 x 6H Wastewater
1973 6' x 6H Wastewater
1973 10' x 6H Corn Syrup
Refining
1973 30" x 4H Wastewater
1973 6' x 4H Corn Syrup
Refining
1974 10' x 6H + OH Corn Syrup
Refining
1974 8'-6 x 7H Corn Syrup
Refining
Viral Removal
While viral inactivation is well documented with chlori-
nation usage, lime treatment of secondary sand-filtered
effluents has been shown to virtually eliminate viral
problems. Figure 2 shows that with lime treatment ap-
plied to a secondary effluent to arrive at a pH of 11.1,
inactivation of polio virus was virtually complete within
90 minutes. Table IX contains data from a 1969 sample
for South Lake Tahoe effluent, illustrating removal of
viral components. The one exception that occurred was
eliminated after the effluent passed through the carbon
adsorption and chlorination steps whereby the final
effluent was found to be free of all remaining viruses.
100 g"«-^. >L^ , | ! ( ^
"~ ^^ * * ~~ ~
\
<
-
\
10 r \ -E
x - \ -
O*1 ^ M
5 = ^V :
| - \
1 ~ \
-------
Table 9
Virus Sampling, 1969, at the South Tahoe Public Utility District Water
Reclamation Plant
Viruses Recovered (Plaque Forming Units)
Carbon Column Chlorinated
May 29
June 5
June 12
Aug. 20
Aug. 27
Sept. 11
Sept. 18
Sept. 25
Oct. 2
Primary
Effluent
3
3
179
NRD
207
Secondary
Effluent
0
18
14
430
320
Unchlorinated
Effluent
1
0
0
NRD*
NRD*
0
9
0
0
Final
Effluent
0
0
0
0
0
0
0
0
0
It turns out that extensive testing has shown that
viruses were removed from the effluent (16). During
1976, studies at Daspoort also confirmed the Windhoek
sampling data. The data demonstrated that viruses and
bacteriological contaminants were present in treatment
plant influent, but absent from the treated effluent.
Epidemiologic studies analyzing the long-term health
consequences of trace organics and other trace residuals
in the tertiary treated wastewater of the Windhoek
municipal population were unable to detect any change
in disease or morbidity patterns that could be associated
with the consumption of tertiary wastewater. While more
epidemiologic data in the U.S. and other countries are
needed to provide better assurances of safety, the Wind-
hoek work is an initial positive data point indicating a
probable lack of adverse chronic health effects associ-
ated with consumption of high quality reclaimed
wastewater.
No reliable data.
Human Health Data
As previously discussed, the problems of trace organics,
toxic metals and viral impurities are virtually eliminated
in advanced wastewater treatment facilities that utilize
carbon filters and lime treatment. The addition of
chlorination can be utilized effectively to enhance
removal of these constituents in addition to being an
excellent unit process to eliminate bacterial pathogens.
Tertiary quality treatment systems deliver wastewater
effluents that are equal to or surpass the quality of many
current water supplies in the U.S. However, such treated
effluents often have some trace impurities (organics,
metals, etc.) as do fresh potable water sources. How
important or critical from a health standpoint are these
substances? Although we do not presently know the
answer to this question, some research on this subject is
underway.
It is useful to evaluate human experience as an addi-
tional assurance of safe drinking water quality. Data of
this nature are scarce. We can look to Windhoek for
further information on the health implication of drink-
ing reclaimed water. Direct use of reclaimed drinking
water has occurred in the Windhoek, Namibia, waste-
water treatment plant which is the only advanced
wastewater treatment installation in the world that
directly integrates purified wastewater into the city's
domestic water supply on a continual basis. The facility
played a vital role in alleviating the water shortages dur-
ing the acute drought of 1969-1971. This installation
consists of a conventional wastewater treatment plant
which had algae lagoon and physical-chemical treatment
stages added. The effluent met the United Nations
World Health Organization (WHO) drinking water stan-
dards and was used to supplement up to 50% of the tap
water for this community of approximately 70,000 peo-
ple (3, 15).
Summary
The parameters of greatest health concern with direct
reuse of reclaimed water are vectors of a viral, organic
chemical and inorganic chemical or trace metallic nature.
The biological or infectious agents are effectively
eliminated by modern advanced sewage treatment
methods. The combination of lime treatment and carbon
adsorption have been shown to effectively eliminate
organic compounds, toxic metals and viruses from
advanced wastewater effluents. Unit processes such as
ozonation, carbon regeneration, chlorination plus many
others can reduce costs and improve pollutant removal.
Human experience is scarce, but the information avail-
able suggests that modern technology for wastewater
reuse is acceptable in terms of public health.
30
-------
References
1) Sebastian, Frank P. and D. Lachtman. "Municipal and Industrial
Wastewater Treatment and Reuse," Symposium Recycling Water Sup-
ply Systems and Reuse of Treated Wastewater at Industrial Plants,
USSR/USA Environmental Agreement, September 1977, (Moscow).
2) Sebastian, Frank P. and Sumitomo Jukikai. "Reclamation and Use
of Wastewater at Tahoe, Windhoek and Colorado Springs and Recent
Advances in Physical Chemical Treatment," Environmental Seminar
U.S. Department of Commerce, December 1971.
3) Sebastian, Frank P. "Purified Wastewater The Untapped Water
Resource," JWPCF, V46(2), February 1974.
4) "Studies Relating to Market Projections for Advanced Waste
Treatment." FWPCA Publ. WP-20 AWTR-17, U.S. Department of
the Interior, Washington, D.C., 1966.
5) The Implications of Cancer Causing Substances In Mississippi
River Water, Environmental Defense Fund, November 1974.
6) "Community Water Supply StudyAnalysis of National Survey
Findings." USPHS, HEW July 1970.
7) "Interim Primary Drinking Water Regulations." Environmental
Protection Agency, Federal Register Part II, p 5756, February 9, 1978.
8) Water Reuse Highlights. AWWA Research Foundation, January
1978, p 34.
9) Culp, G.L. and Culp, R.L. New Concepts in Water Purification,
VanNostrand Reinhold Company, New York 1974.
10) Eisenhower, D.L., Sieger, R.P., Parker, D.S. "Design of Inte-
grated Approach to Nutrient Removal," Journal of the Environmental
Engineering Division.
11) Sebastian, Frank P. and D. Lachtman. "Pyrolysis Applications for
Industrial and Municipal Treatment," Symposium Physical/Mechanical
Treatment of Wastewater, USSR/USA Environmental Agreement,
April 1977, (Cincinnati, Ohio).
12) Linstedt, K.D., et al. "Trace Element Removals in Advanced
Wastewater Treatment Process," Journal Water Pollution Control
Fed., 1971, p43, 1507.
13) "Ozone Gives Waste Water The Treatment," Chemical Week,
June 21, 1978.
14) Rice, R.G., Cornelia, C. and Miller, G.W. "Rouen, France Water-
Treatment Plant; Good Organics and Ammonia Removal With No
Need to Regenerate Carbon Beds," Civil Engineering, May, 1978.
15) Middletown, F.M. "Planned Wastewater Reuse," News of Envi-
ronmental Research in Cincinnati, USEPA, July 1977.
16) Hanaway. "Water Research Commission Annual Report,"
Republic of South Africa, 31 December 1976.
31
-------
Aftertreatment of
Biochemically Treated
Wastewaters before
Their Reuse
E.G. loakimis and E. A. Yusupov
Bashkirian Scientific Research Institute
of Petroleum Refining (BashNII NP)
(USSR)
A method for biochemical treatment of industrial and
storm refinery wastewaters returned to the circulating
cooling water systems has been widely applied over the
recent years. To biochemically treat these wastewaters,
one-stage complete-mix activated sludge systems pro-
viding for 6 to 8-hr aeration are largely used. Quality of
wastewaters before and after biochemical treatment is
shown in Table 1.
Table 1
Quality of Wastewaters Before and After Biological Treatment
No.
1 .
2.
3.
4-
5.
6.
7.
8.
9.
Analysis
Oil Products (extract-
able with hexane)
COD
BOD
Before
treatment
mg/1
After
treatment
mg/1
Sulfides
Phenol
Ammonium nitrogen
Suspended solids
pH
up to 25
-"- 400
-"- 150
-"- 250
-"- 20
-"- 10
-"- 30
-"- 50
6-8
3-5
70-100
10-15
15-20
abs.
0.1
4-8
10-90
6-8
As is seen from the Table, biochemically treated
wastewaters are essentially free from contaminants.
Their chemical composition is in full accordance with
quality standards for make-up water with the exception
of suspended solids.
The wastage of activated sludge from activated sludge
clarifiers remains larger and in some cases (technological
regime deviations) may be in excess of 100 mg/1. The
activated sludge together with the activated sludge
effluent goes to coolers where it settles on cooling sur-
faces and reduces the heat transfer factor. In the case of
1-mm deposits on tubes, the heat transfer factor is
reduced by 10 to 30%.
Thus, the main task is to remove suspended solids
from biochemically treated wastewaters before their
return to a circulating system.
One of the promising treatment methods is filtration.
The applicability of granular and pressure screen
filters has been tested. Quartz sand of a 0.5 to 2mm size
(equivalent diameter 1.25 mm) and coke of a 1.5 to 3.5
mm size (equivalent diameter 2,3 mm) have been tested
as a granular bed. The filter bed height is 1 m. Accord-
ing to the USSR standards, filtering media should meet
the following requirements for mechanical strength:
grindability max. 4%, attrition max. 0.5%. Quartz
sand used in filters has a grindability of 3.6% and an
attrition of 0.14%. Petroleum delayed coke used as filter
bed has a grindability of 1.14% and an attrition of
0.4%, which shows its applicability.
Tests were performed on pilot filters with an efficiency
as high as 100 1/hr. Sand was used in one filter, coke
in the other and then both filters were operated in paral-
lel with the same influent. The average test results are
presented in Table 2. One can see from the reported data
that the best treatment quality and the best filter run
duration are achieved at an average filtration rate of
8 m/hr.
Such a difference in filter run duration is attributed to
the filter bed size composition. Coarse grained filters
which provide optimum filter performance are needed
for aftertreatment of biochemically treated wastewaters.
It should be noted that when operating pilot filters,
their regeneration was due to the achievement of maxi-
mum pressure loss, which was indicative of a strong
adherence of the retained activated sludge to the filter
medium, the filtrate quality remaining good.
Therefore, while regenerating filters, a prior air
loosening-up of the filter bed is used, which results in
the destruction of contaminant clots due to the intense
intermixing of filter bed and the removal of contami-
nants from the surface of particles. Air for loosening-up
is supplied by an air blower. It is fed to a separate air
distribution system located in the lower filter part.
Before feeding air into the distribution system the water
33
-------
Table 2
Performance of Granular Filters
No.
1.
2.
3.
4.
5.
6.
7.
Average
filtration
rate,
m/hr
7.9
8.1
8.8
8.1
8.0
7.2
7.3
Pressure loss, mm Hg
initial final
Pilot filter
35 650
40 650
17 657
19 650
Industrial filter
45 620
48 600
52 600
Filter Run
duration, hr
12
10
18
22
9
11
10
Suspended solids, mg/l
influent
62
81
118
79
35
38
44
filtrate
3.3
4.0
5.2
4.7
6.5
6.0
8.0
Filter bed
Sand, 0.5-2.0mm
» >
Coke, 1.5-3.5mm
» »
Sand, 0.5-2.Omm
level in the filter is lowered by 0.3 to 0.5 m in order to
prevent the filter medium wastage. Air blowing is carried
out during 5 minutes with an intensity of 13 to 15
1/sec-m2. After completing the air blowing a conven-
tional back washing of filter bed is performed. Water is
fed to a drain distribution system located under the air
system. Washing intensity is 18 1/sec-m2, washing dura-
tion is 10 minutes. Washings are sent to aerotanks.
Washing water consumption amounts to 2-3% of the
quantity of filtered water.
It should be noted that in spite of the use of air for
filter regeneration the filter bed is loaded with time by
very dense residual contaminants. They are essentially
presented by biogrowths that strongly adhere to the filter
bed, which necessitates a periodic treatment of filter bed
with biocides.
Chlorine water containing 100 to 200 mg/l of active
chlorine is recommended as biocide. To prepare chlorine
water, typical chlorinators are used. Filtering media are
treated after the achievement of a residual pressure loss
of 0.3 to 0.5 m for pressure filters and 0.2 to 0.3 m for
open filters. Before treating filter with chlorine water
conventional washing is performed. Water is then fully
drained from the filter and the latter is filled with
chlorine water. After a 1-day contact of chlorine water
with filter bed the former is drained to a separate vessel
where, if necessary, it is neutralized by sodium thiosul-
fate and sodium carbonate.
After the drainage of chlorine water the filter under-
goes a conventional washing during 2 to 3 minutes, the
first portions of washings being discharged to sludge
tanks.
The averaged data obtained on industrial filter with
quartz sand filter bed of a 0.5 to 2.0 mm size composi-
tion are presented in Table 2. One can see from the data
that at a filtration rate of 7.2 to 8 m/hr the filter pro-
vides a sufficiently high quality of wastewater treatment
at a level of 6 to 8 mg/l. Water of this quality is in full
accordance with the requirements for water returned to a
circulating cooling water system.
Highly efficient self-cleaning VSF type ("VSF" means
"filter with a high filtration rate") filters of a serial pro-
duction are destined for mechanical water treatment on
screens to remove suspended matter. The filters are
applied in chemical, food, paper, metallurgical, and
other industries.
Filtration of biochemically treated wastewaters has
been tested under industrial and laboratory conditions
using these filters. VSF-2000 filter (Fig. 1) comprises the
following main parts:
cylindrical shell;
two filtering elements;
washing device;
drive.
The filter is completed with a control board.
Maximum filter efficiency, m3/hr 2000
Electric power consumption, kwh 0.5
Installed capacity of electric motor, kw 1.7
Overall dimensions mm
diameter 2032
Weight, kg 3000
Water treatment is performed at a pressure of 10
kgf/cm2 (1.0 M Pa). The washing device is switched on
automatically, washing is carried out simultaneously with
filtration and, depending on the quality of water to be
treated, is performed continuously or periodically. This
provides for a continuous filter performance.
The filter laboratory model (Fig. 2) 0 150 mm is a part
of the filtering element of industrial filter. Investigations
on filtration of biochemically treated wastewaters were
performed at a pressure of 10 kgf/cm2, at a filtration
rate of 150 to 600 m/hr. Back washing was carried out
"using river and filtered water.
Based on the laboratory filter model, pressure loss and
filter run duration versus filtration rate as well as screen
cleaning quality versus washing intensity and duration
were studied.
Pressure loss is plotted against filtration duration in
Fig. 3,4. As is seen from the curves the filter run dura-
tion is 7 to 24 hours for PO-0.25 -2 screens packet (mesh
34
-------
tn
Fig. 1.
VSF-2000
size of 200 to 250 micrometers) and 10 to 80 minuie!> for
S -200 dense screen, its value being decreased with in-
creasing filtration rate. The curves convexity may
evidence the carry-over of contaminants from screens.
Activated sludge settled on the screens has a density of
1.12 -r- i'.15 and an ash content of about 25%. The
deposit can be considered to be compressible. Pres-
surized particles or their aggregates are deformed, which
leads to an increase in the deposit resistance with in-
creasing pressure difference during the filtration process.
The back washing efficiency of screens for the purpose
of their cleaning was evaluated by initial pressure drop
and filtration run duration subsequent to the washing.
The obtained data are presented in Fig. 5. As is seen
from Fig. 5, an increase in washing intensity up to 400
l/m2>sec. leads to a decrease in initial pressure drop on
the screen and accordingly to an increase in filter run
duration. A further increase in intensity does not
improve the screen cleaning degree. The removal of
residual contaminants requires a prior treatment of
screens to lessen the forces of adhesion of activated
sludge to the screen.
1 Shell
2 Filtering medium
3 Upper grid
4 Lower grid
5 Support
6 Manometer boss
Fig. 2.
VSF filter model
As with filtration using granular filter beds, the forces
of sludge adhesion to the screen are lessened under the
action of biocides. A one-day treatment of screens using
chlorine water with a concentration (based on active
chlorine) as high as 200 mg/1 makes it possible to clean
screens by a subsequent back washing. This is confirmed
by an experience of operating VSF-2000 industrial filter
in one of the petroleum refineries.
Washing time variations over the range of 5 to 30
seconds did not affect the washing quality. This time
seems to exceed the required one; the time necessary for
washing one section of VSF filter is 1 to 2 sec.
In the performed experiments, the average effect of
purifying biochemically treated wastewaters was not
more than 10 to 15%; for a number of samples the con-
tent of suspended solids in filtrate was higher than that
in influent, especially at high filtration rates such as 400
to 600 m/hr, which is attributable to the carry-over of
contaminants from filter screens under these conditions.
Along with tests on the filter model, the VSF-200
industrial filter (used for aftertreatment of biochemically
treated wastewaters before their return to the circulating
system) has been studied. The filter has been mounted
on the open site and operated automatically. The filter
flow diagram is presented in Fig. 6.
Effluents from activated sludge clarifiers are partially
passed through the filter and fed as make-up water to
circulating systems of the refinery. The filter washing
water is pumped to aerotanks.
During the initial operating period the filter run dura-
tion amounted to 3 hours. It is gradually diminished
with time to 20-30 minutes. The filter is switched off.
35
-------
I.U
.08
CM .06
I
s
fe* t
.04 <
O2 t
(
jy
W&^~^^Q
IL
W
T
I
£
0/Af'!
M/
?
£
k* i
t
-0-,
A C
V 1
0 [
^
:iltration rate
(clean sere
:iltration rate
(contamined
>o 82.5m/hr
3o 300m/hr
>o 600m/hr
>~ '-
150m/hr
ens)
1 50m/hr
screens)
) 20 40 60 80 10
T, min.
Fig. 3.
Pressure drop versus filtration time (S-200 screen)
VSF-2000
1. Filtered wastewater to UOV*-1
2. Filtered wastewater to UOV-8
3. Washing water from granular filters
4. Effluents from the 1-st stage of biochem.
treatment to the 2-nd one
5. Effluents from the 1-st stage of biochem.
treatment to biological filters
6. Effluents from the 1-st stage of biochem.
treatment
7. Washings to aerotanks
*UOV means "unit of circulating cooling
water system"
300-400m3/hr
200-300m3/h
O
6 800m3/hf
^
Fig. 6.
Flow diagram of VSF-2000
Fig. 4.
Pressure drop versus filtration time (PO - 025 + 02 packet)
r
, min
20
16
12
ht ir
kgf/
0.5
0.4
0.3
0.2
0.1
0
itial
cm2
X
^'
_»-
0
I
I
-------
filters shows that in spite of compactness and high water
filtration rates in the case of screen filters, granular
filters provide a higher aftertreatment quality of waste-
waters because of their higher efficiency.
Table 3
Performance of VSF-2000 Filters
(averaged data)
Ranges of initial contamination
mg/l
10-25 26-50 51-100 101-105
Initial content of sus-
pended matters, mg/l 21.7 38.2 56.2 117.4
Residual content of sus-
pended matters, mg/l 18.0 31.7 42 85.5
Purification effect, % 17.7 17 25 27
37
-------
Facilities for the Treatment of
Biologically Treated Effluents
from Industrial and Municipal
Sources by Ozone**
by
William J. Lacy, P.E.*
Background
Ozone is a colorless gas naturally occurring in the atmo-
sphere. It is a particularly active form of, and in fact is
produced from, and decomposes to, the element oxygen.
Its molecule contains three oxygen atoms, whereas the
more common form, which comprises about a fifth of
the air we breathe, has only two oxygen atoms per
molecule. Ozone result's from exposing oxygen to energy
such as from electrical discharge or irradiation. Its activ-
ity results from the release of this energy as the mole-
cules resume their original state. This decomposition
takes place rather rapidly, so that the energy may be
harnessed for a number of useful purposes. Because of
this, ozone is frequently called "activated oxygen."
It exists naturally at relatively high concentrations in
the atmosphere at an altitute of about 20,000 to 30,000
meters. This ozone layer in the upper atmosphere is cru-
cial to terrestrial life because it shields the earth from
harmful ultraviolet light radiations.
At the earth's surface, the concentration of ozone is
greatly reduced. Terrestrial ozone occurs naturally as a
result of reactions in the atmosphere and that which may
filter down from the upper levels. It is not, as are many
air pollutants, present as a result of synthetic products
from chemical sources. The slightly pungent traces of
odor in the air during and following a thunderstorm are
due to ozone.
Ozone is one of the most powerful oxidants available
to man. It is an effective bleach. It is a powerful steri-
lant, killing bacteria and fungi more rapidly than
chlorine. It also attacks viruses and carcinogenic mate-
rials that are not attacked by those chemicals most often
used in treating water. It deodorizes by destroying odor-
causing substances rather than by masking the odor.
Principal Engineering Science Advisor, Office of Research and Development,
U.S. Environmental Protection Agency, Washington, D.C. 20460
"Presentation by Mr. Harold P. Cahill, Director, Municipal Construction Divi-
sion, EPA, at the US/USSR "Facilities for Tertiary Treatment of Biologically
Treated Effluents" Symposium in VODGEO, Moscow, USSR,
November 13-15, 1978.
The commercial use of ozone for purifying drinking
water is over seventy years old. Its major application has
been in regions where raw water supplies are of generally
poor quality and a method of advanced treatment of
drinking water, such as ozonization, is required to pro-
duce economically an esthetically pleasing supply free of
pathogens.
As problems of pollution, safety, and rising costs in
all the industrial areas concerned with treatment of
water, wastes and air become more difficult to handle,
ozone is providing an answer from both technological
and economical considerations.
Ozone must be generated on-site near its point of use.
Ozone cannot be stored so only the amount being gener-
ated at any instant might be accidentally released. This
eliminates all of those safety problems associated with
transportation and storage of chemicals. Because of its
unique nature it is easily identified, and generation may
be immediately ceased on detection of its presence. At
higher, potentially toxic levels, it rapidly degrades into
oxygen.
Ozone is not an environmental panacea, but the con-
tinuous development of its valuable attributes as a viri-
cide, general disinfectant and pollution-free oxidant
should be utilized by informed scientists and engineers.
Introduction
Historically, sewage treatment plant effluents in the
United States have been disinfected with chlorine. Dur-
ing the late 1960's it began to be apparent that dis-
charges of chlorinated sewage treatment plant effluents
to rivers, lakes and streams were sometimes causing
severe environmentally detrimental effects upon the
aquatic lives in these receiving bodies of water.
In November, 1974, EPA made public results showing
that treating drinking water supplies with chlorine pro-
duced many halogenated compounds, some of which
39
-------
might be responsible for causing liver carcinomas. The
U.S. Environmental Protection Agency, Office of
Research & Development, funded a grant to the Inter-
national Ozone Institute to conduct a state-of-the-art
review of the published literature dealing with the use of
ozone. About 240 published articles have been reviewed.
Abstracts of each article appear in the final report. (1)
The discharge of industrial wastewaters is being regu-
lated by EPA by the Water Pollution Control Act
Amendments of 1972. The objective of WPCA is to halt
the promiscuous discharge of pollutants by applying
wastewater treatment techniques commercially available
in 1977, and even more advanced technologies to pro-
duce effluents of improved quality by 1983.
Progressively, the quality of industrial.discharges will
improve. Industry is encouraged to recycle and/or reuse
as much of its wastewater as posssible and many
manufacturers presently are studying the use of ozone, a
powerful oxidant, to destroy pollutants and to otherise
purify certain wastewater.
An EPA demonstratioin grant was awarded to the city
of Wyoming, Michigan, to compare the toxicities of
sewage treatment plant effluents on certain species of
fish. Side-by-side comparisons of the effects of chlori-
nation, chlorination/dechlorination, ozonation, bromine
chloride and no disinfection were conducted on two ef-
fluentsone largely municipal sewage and the second
containing about 50% industrial wastes.
Results of this demonstrated program (2) reveal that
ozone is effective as a disinfectant, although at higher
cost than gaseous chlorination. In addition, ozonated ef-
fluents are not toxic to indigenous aquatic life.
Several cities in the USA have been considering chang-
ing to ozonation for some time, and the first operational
plant to install ozone for this purpose was at Indian-
town, Florida (3). This is about 2,000 cu. meters/day
sewage treatment plant which incorporates an Imhoff
tank, trickling filter, chemical coagulation, and set-
tlings of solids, followed by ozonation. The plant has
been fully operational since November, 1975, and the
city of Indiantown is pleased with the results. See Figure
1.
Municipal Wastewater Treatment
I. Disinfection
A. EPA Policy
In the United States, until recently disinfection of
sewage treatment plant effluents has been required by
the EPA. The original concept was to disinfect to pro-
tect the public health.
The continued discharge of tons/day of chlorine into
the environment has been shown to cause massive fish
kills, as well as to produce chlorinated organic materials
which can progress up the food chain. EPA has recently
(1) enunciated a policy that disinfection (currently
synonymous with chlorinationin the United States)
need only be practiced where known to be necessary to
protect the public health. Estimates equate this to mean
that at least 80% of current municipal effluents will con-
tinue to have to be disinfected. All plants will have to
have standby disinfection facilities, in case of
emergenices.
EPA's role is to protect the public healthfirst by in-
suring that disinfection is practiced where it is needed
and, secondly, by demonstrating to states, local munici-
palities and their consulting engineers the benefits,
drawbacks and economics of methods which are viable
alternatives to chlorination.
Two types of ozone contactors were evaluated with
respect to performance, coliform reduction and ozone
efficiency. The two systems included a packed column
filled with ceramic media and a jet scrubber unit. It ap-
pears that a single-stage jet scruber is not a feasible gas-
liquid contactor for effluent coliform reductiion with
ozone. The addition of one or more jet scrubbers in
series would probably improve coliform reduction and
utilization, but the needed repressurization costs would
likely offset any savings in increased efficiency.
Figure 1
U.S.A. Sewage Treatment Plants Using Ozone (1978)
Location
Woodlands, TX
Indiantown, FL
Estes Park, CO
Springfield, MO
Orange County, NY
Santa Clara, CA
Under Construction
Meander Creek, OH
Chino Basin, CA
Potomac Heights, MD
Concord, NC
Pensacola, FL
Murphreesboro, TN
Frankfort, KY
Madisonville, KY
Under Design
Cleveland, OH
Size
(mgd)
0.6
0.5
3
35*
2
4
Purpose
Disinfection
Disinfection
Disinfection
Disinfection
Disinfection +
Dissolved
Oxygen
Disinfection +
Organics
Startup
Date
1975
1976
1977
1977
1977
1977
5*
3
0.2
30*
24*
10*
9
4.5*
Disinfection
Susp. Solids
Disinfection
Disinfection
Disinfection
Disinfection
Disinfection
Disinfection
2/78
early 1978
early 1978
late 1978
late 1978
9/78
bid 12/77
bid 12/77
50-100*
1980
Organics +
Disinfection
Indianapolis, IN 2 x 125* Disinfection bid late 1978
at least 15 others known, 12 oxygen activated sludge
Oxygen Activated Sludge Process
"Ozone before and after activated carbon
Woodlands, Texas (2,300 cu. meters/day) and Estes
Park, Colorado (11,400 cu. meters/day) have recently
begun operation, and ozonation for disinfection is incor-
porated in these plants. During 1977, six additional U.S.
cities began operation of sewage treatment plants using
40
-------
ozone for disinfection. Three other plants have been bid
and at least 15 other plants are known to be in the
design stages at this time. The growth of ozone use as an
effluent disinfectant was recently discussed in the May
11, 1978 issue of Engineering News Record (7).
B. Oxygen Activated Sludge Process
Ozone technologists recognize that about half the elec-
trical energy is required to generate a given weight of
ozone from oxygen than from air. These favorable
economics can be coupled with sewage treatment pro-
cesses which employ oxygen activated sludge processes.
See Figure 2. After generating ozone from oxygen (and
producing 2% ozone in oxygen) then disinfecting the
activated-sludge effluent, the contactor off-gases (still
very rich in oxygen) can be sent to the biological reactor.
Then most of the oxygen originally taken for ozone
generation can be utilized in the treatment process. The
only oxygen "lost" will be that which actually dissolves
in the disinfected effluent.
WASTE G'AS VENT
1 OXYGEN STREAM
WASTEWATER
| I
ACTIVATED
SLUDGE
REACTOR
*
SECONDARY
CLARIFICATION
-*
FILTRATION
h*
OZONE
GENERATOR
-ti
OZONATION &
SUPER
OXYGENATION
t
I
TO OUTFALL
Figure 2
The Oxygen Activated Sludge Process
Even this "lost" oxygen is utilized, because it serves
to increase the dissolved oxygen content of the receiving
body of water, which is beneficial to the local aquatic
life.
The first USA sewage treatment plant to couple ozone
generation from oxygen with the oxygen activated sludge
process was a 22,800 cu. meters/day plant at Meander
Creek (near Youngstown, Ohio). (5), (6). This plant is
now in the early stages of start-up. One other oxygen ac-
tivated sludge plant using ozone disinfectant is opera-
tional. The March, 1978 Water and Wastes Engineering
describes the ozonation expanded wastewater plant in
Springfield, Missouri (8).
II. Suspended Solids Removal
The State of California has adopted very stringent
discharge standards, particularly with respect total col-
iforms, viruses and dissolved solids. For example, disin-
fection standards for the more water-rich areas of the
USA are normallly 200 fecal coliforms/100 ml (most
probable number); however, the standard in California is
2.2 total coliforms/100 ml.
Chino Basin, California is constructing about 12,000
cu. meters/day activated sludge sewage treatment plant.
To meet the suspended solids standard by standard treat-
ment techniques requires the addition of a chemical floc-
culent (alum) followed by filtration. Since flocculents are
soluble chemicals, their use will result in increased levels
of dissolved solids in the effluents, such that the Califor-
nia Total Dissolved Solid (TDS) standard now would ex-
ceed. Filtration of chemically flocculated effluents is
relatively slow, and the chemical sludge must be disposed
of. To reduce TDS to an acceptable level would require
additional effluent processing, thereby adding costs. .
Engineers for Chino Basin (4) discovered that by ap-
plying 10 mg/1 of ozone directly to "the secondary ef-
fluent the suspended solids are coagulated, filtration is
rapid, the TDS remains below the level required, and
there is no chemical sludge to be disposed of.
This novel application for ozone in sewage treatment
was incorporated into the plant design, construction is in
its later stages, and the plant is expected to begin full-
scale operation this year.
Industrial Wastewater Treatment
I. Cyanides
Destruction of cyanides by means of ozone takes place
in two discrete steps, the first being rapid oxidation to
cyanate, followed by the much slower oxidation hydro-
lysis of cyanate to carbon dioxide and nitrogen.
Iron cyanide complexes are very stable to destruction
with ozone alone, the cyanide portion being only slowly
decomposed. However, in combination with ultraviolet
radiation, destruction of the complex and of the cyanide
is very rapid. In effecting a more rapid destruction of
such stable complexes, the ozone/ultraviolet combination
conserves energy, since otherwise very long treatment
times would have to be employed.
Laboratory studies of cyanide containing simulated
gold mining wastewaters were conducted by the Cana-
dian Department of Energy and Mines, using the Film
Layer Purifying Chamber (a spray tower type of ozone
contactor). In this contacting apparatus, cyanides ap-
parently were converted totally to carbon dioxide and
nitrogen in a contact time of about 30 seconds. Neither
cyanide nor cyanate were detected in the ozonized ef-
fluent (9).
Since the mid-1950's, ozone has been used by the Boe-
ing Company, Wichita, Kansas, to remove cyanides
from their metal finishing wastes (10), (11). Combined
wastewater streams from various metal finishing baths
are ozoned prior to discharge into a local receiving lake.
This plant has met all applicable discharge standards for
cyanide consistently over the past 20 years. Recently, the
company announced that it will expand and upgrade the
capabilities of its ozonation treatment system.
41
-------
EPA has funded a demonstration of ozonation to
reduce cyanides in metal finishing wastewaters at Sealec-
tro Corporation, Mamaroneck, New York (12). This
plant has been operating successfully since early 1974,
and all applicable local discharge standards are being
met.
Since late 1976, Hughes Tool Company, Houston,
Texas, has been treating its metal finishing wastewaters
with ozone in synergistic combination with ultraviolet
radiation. Wastewater flows of up to 80 liters/minute
are treated first with ozone (to remove simple cyanides)
and then with ozone/UV to remove otherwise stable iron
complexes and heavy metals levels of 30-100 mg/1. This
treatment system reduces total cyanide and heavy metals
to levels of 0.1 mg/1 (13).
Photoprocessing Wastes
A novel use for ozone in the photoprocessing industry-
has been developed recently, which is the oxidative
regeneration of bleaching compositions. Iron ferri-
cyanide is used as the photoprocessing bleach, and in so
bleaching, the ferric (trivalent) iron is reduced to the fer-
rous (divalent) state. Both iron cyanides complexes are
so stable to ozonation that the ferrous iron is merely
converted back to the ferric form upon ozonation,
without degradation of cyanide moieties or destroying
the complexes themselves.
This ability to regenerate iron cyanide complexes is be-
ing exploited commercially by a small U.S. company
who manufactures an integrated ozonation treatment
system specifically for regenerating spent photoprocess-
ing laboratory wastes, the spent bleach being subjected
to ozonation. During the night shift, however, when no
bleach is being generated, the ozone generator is auto-
matically programmed to treat the other more readily
oxidizable components in photographic processing baths.
Thiosulfate is converted to sulfate, hydroquinone and
other organic compounds are destroyed. Thus the ozona-
tion system is programmed to regenerate spent
photographic processing bleach during the hours of
laboratory operation, then it is programmed to treat
other oxidizable components of the processing wastes at
night (14).
Figure 3
Ozonization of Iron Cyanides
NC CN
\ / +3
NC FE CN
NC CN
OZONE/UV
-3
NC
\ /
NC FE
S \
NC
CN
CN
CN
OZONE
C02 N2
A
CO2+N2+CNO-+FE+3
FE(OH) 3
OZONE/UV
In this manner, the pollutional load of photoprocess-
ing wastewaters can be reduced. It is claimed that the in-
tegrated ozone treatment system can pay for itself, on
the basis of bleach recovered alone, within a period of
3-5 years, depending upon the size of the installation.
An EPA supported demonstration of the efficacy of
ozone regeneration of spent photoprocessing bleach was
successfully completed at Berkey Photo, Needham,
Massachusetts, in 1974 (15) and this company, as well as
many others throughout the United States, Japan, and in
some countries in Europe, are using this treatment
technique.
Polychlorinated Biphenyls (PCB's)
PCB's are quite toxic in very small quantities and are
very stable to oxidation. In addition, they are not com-
pletely adsorbed onto activated carbon. They have been
defined as toxic substances, pose very great public health
hazards, and hence methods of assuring their absence in
wastewater discharges from certain electrical motor
manufacturing plants must be found.
Recent EPA sponsored studies 1977+ (16) with the
Versar Company of Springfield, Virginia, have shown
that the combination of ozone with ultraviolet radiation
(UV) can reduce the levels of PCB's in industrial
wastewaters to less than 0.01 microgram/liters, and in
many cases to below detectable limits. Activated carbon
adsorption can only reduce PCB level to 0.1 microg/1.
Having compared treatment costs, efficiencies and com-
mercial availability of ozone/UV systems, EPA has pro-
posed that existing sources and new sources of PCB
discharges be required to meet a standard of 0.01
microg/1 which can be attained by ozone/UV systems.
Thus, the combination of ozone/UV has been
specified as "Best Practicable Control Technology"
(BPCT) currently available for the PCB's (as well as for
photoprocessing wastewaters).
Phenols
In Sarnia, Ontario, The BP Oil Refinery discharges
itswastewaters, after treatment, into Lake Ontario. A
rather complex biological treatment scheme has been
practiced for the past 20 years, the final step of which is
ozonation to remove phenolic compounds and trace
amounts of other organics which are not removed by
earlier treatment process steps (17), (18).
Power Plant Cooling Waters
Biological growth in power plant condensers reduces the
efficiency of heat exchange. Present techniques of com-
bating this, and in cleaning biofouled surfaces and struc-
tures, include the addition of rather high concentrations
of :hlorine to the intake and cooling waters. Because of
42
-------
the massive amounts of water currently used in once-
through cooling systems, many tons of chlorine are
being discharged hourly into the environment, with
detrimental effects on aquatic life.
The Electric Power Research Institute has recently
funded the Public Service Electric and Gas Company of
New Jersey (PSEG/NJ) to conduct demonstrations of
the efficacy of ozone in side-by-side comparisons with
chlorine. These successful demonstrations were con-
ducted during the sumer of 1977 at two PSEG/NJ power
plants in New Jersey.
Associated Treatment Considerations
I. Organic Oxidation Products
One uncertainty currently delaying more rapid accep-
tance of ozonation are questions of what oxidation prod-
ucts are formed when organic materials in water are
ozonized and what are the toxicities of these materials to
man and to the environment. Although considerable
research now is being conducted to answer these signifi-
cant questions, it will be years before quantitative
answers are obtained for all compounds which might be
formed in all cases.
This general subject was discussed in detail at the
November, 1976, Workshop on Ozone/Chlorine Dioxide
Oxidation Products of Organic Materials, sponsored by
the International Ozone Institute and EPA, in Cin-
cinnati, Ohio. It was the consensus of those present that
(a) ozonation of organic compounds produces organic
oxidation products which generally are more bio-
degradable than their precursors, (b) there are some
compounds formed upon ozonization which exhibit
mutagenic activities, (c) chlorination of the same starting
organic compounds produces oxidized and halogenated
products, (d) a greater number of biologically active
compounds are produced upon chlorination than upon
ozonation. (19).
Electric Power Requirements
One other point that should be mentioned is the electric
power requirements per 500 grams of ozone. Figure 5
shows the figures as based on ozone equipment already
available on the market today (20).
At this point on our learning curve, intelligent water
and wastewater treatment technologists must conclude
that any chemical oxidant (chlorine, ozone, chlorine
dioxide, bromine chloride, permanganate, etc.) should be
employed with caution, and with as much knowledge
about the composition of the system to be treated as
possible.
Figure 4
Industrial Categories Reporting Use of Ozone*
No. of Articles Found
Category
Aquaculture
Breweries
Electroplating
Food & Kindred Products
Hospital Wastes
Iron & Steel
Leather Tanneries
Mining
Organic Chemicals
Paint & Varnish
Petroleum Refineries
Photoprocessing
Plastics & Synthetics
Pulp & Paper
Soaps & Detergents
Textiles
Cyanide-Containing Wastes
Phenolic-Containing Wastes
Totals
*1978
Figure 5
Power Requirements per 500 gram/Ozone*
Ozone generator with 2% ozone concentration from 8.20 kwh
pre-dried air
Oil-less compressor 1.67
Meatless air dryer 0.125
Ozone turbine contactors 0.550
Control, relays, timers, etc. .001
Closed loop cooling waters .001
TOTAL POWER REQUIREMENTS 10.557
OR ABOUT 10.6 kwh
(The above figures are based on commercially available ozone
equipment).
Stopka, K. "Ozone Plant Improves Efficiency and Economy of Wastewater
Treatment" Water and Sewage Works, April 1978
Actual Wastes
1
0
7
4
0
7
0
4
10
2
8
4
1
7
2
14
77
Total
6
8
17
5
2
12
4
5
51
2
16
7
2
24
5
17
13
26
232
Conclusion
Ozone is not an environmental panacea but the con-
tinuous development of its valuable attributes as a
viricide, general disinfectant, and pollution-free oxidant
should be utilized and enhanced by informed scientists
and engineers.
43
-------
References
1. A. Hais, "An EPA Overview of the Disinfection Requirements for
Municipal Wastewater Treatment Plants", in E. Fochtman, R. G. Rice
& M. E. Browning, Editors, Forum on Ozone Disinfection, Intl. Ozone
Inst., pp. 31-35, Syracuse, N.Y* (1977). Also, "Disinfection of Waste-
water, Task Force Report", U.S. Environmental Protection Agency
Report, EPA-430-9-75-012 (March 1976); Federal Register 41 (144), p.
30786 (July 26, 1976).
2. R.W. Ward, R.D. Giffin, G.M. DeGraeve & R.A. Stone,
"Disinfection Efficiency and Residual Toxicity of Several Wastewater
Disinfectants." Volume IGrandville, Michigan, EPA Report No.
EPA-600/2-76-156 (Oct. 1976).
3. F-. Novak & A. Henderson, "Municipal Disinfection with Ozone
and Without Filtration", in E. Fochtman, R.G. Rice & M.E. Brown-
ing, Editors, Forum on Ozone Disinfection, Intl. Ozone Inst., pp.
98-107, Syracuse, N.Y. (1977).
4. R. Trussell, T. Nowak, C. Tate, S. Lo & F. Ismail, "Ozone
Pretreatment for Coagulation/Filtration of Secondary Effluents", in
R.G. Rice, P. Pichet & M.A. Vincent, Editors, Proc. Second Intl.
Symposium on Ozone Technology, Intl. Ozone Inst., pp. 586-610,
Syracuse, N.Y. (1976).
5. W. Guirguis, T. Cooper, J. Harris & A. Ungar, "Improved Per-
formance of Activated Carbon by Pre-ozonization", presented at
Water Pollution Control Federation Meeting, Minneapolis, Minnesota,
October, 1976.
6. W. Guirguis, R. Prober, Y. Hanna, T. Meister & P. Srivastava,
"Reactions of Non-sorbable Organic Materials in Sewage by Activated
Carbon and Ozone", presented at Workshop on Ozone/Chlorine Dioxide
Oxidation Products of Organic Materials, Cincinnati, Ohio, November,
1976.
7. "The Growth of Ozone Use as an Effluent Disinfectant", Engineer-
ing News Record, May 11, 1978.
8. Water and Wastes Engineering, pp. 50-53, March 1978.
9. G.I. Mathieu, "Application of Film Layer Purifying Chamber Pro-
cess to Cyanide DestructionA Progress Report", in R.G. Rice & M.E.
Browning, Editors, Ozone for Water & Wastewater Treatment, Intl.
Ozone Inst., pp. 533-550, Syracuse, N.Y. (1975).
10. R. P. Selm, "Ozone Oxidation of Aqueous Cyanide Waste Solutions
in Stirred Batch Reactors and Packed Towers", in ACS Advances in
Chemistry Series, Vol. 21, pp. 66-77, Am. Chem. Soc., Washington,
D.C. (1957).
11. G. Klingsick, "Application of Ozone at the Boeing Company,
Wichita, Kansas", in R.G. Rice & M.E. Browning, Editors, Ozone for
Water & Wastewater Treatment, Intl. Ozone Inst., pp. 587-590,
Syracuse, N.Y. (1975).
12. L.J. Bollyky, C. Balint & B. Siegel, "Ozone Treatment of Cyanide
and Plating Waste on a Plant Scale", in R.G. Rice, P. Pichet & M.A.
Vincent, Proc. Second Intl. Symposium on Ozone Technology, Intl.
Ozone Inst., pp. 393-420, Syracuse, N.Y. (1976).
13. R. Legan (Houston Research Inc.), Private Communication (to
R.G. Rice), March, 1977.
14. T.N. Hendrickson, "Economical Application of Ozone for
Chemical Recovery and Pollution Control in the Photographic Film
Processing Industry", in R.G. Rice & M.E. Browning, Editors, Ozone
for Water & Wastewater Treatment Intl. Ozone Inst., pp. 578-586,
Syracuse, N.Y. (1975).
15. T.N. Hendrickson & L.G. Daignault, "Treatment of Complex
Cyanide Compounds for Reuse or Disposal", U.S. Environmental Pro-
tection Agency Report No. EPA-R2-73-269 (June, 1973).
16. Versar, Inc., "PCB's in the United States: Industrial Use and
Distribution", Natl. Tech. Info. Service, Springfield, Va., PB 252,
402/3WP, Feb. 1976, pp. 173, 177; Versar, Inc., "Assessment of
Wastewater Management, Treatment Technology and Associated Costs
for Abatement of PCB Concentrations in Industrial Effluents", Feb.
1976; Versar, Inc., "Refinement of Alternative Technologies and
Estimated Costs for Reduction of PCB's in Industrial Wastewaters
from the Capacitor and Transformer Manufacturing Categories", Jan.
1977; Federal Register 42, 6531 (Feb. 2, 1977).
17. W.T. McPhee & A.R. Smith, "From Refinery Wastes to Pure
Water", Engr. Bull., Purdue Univ. Engr. Ext. Service 109, pp. 311-326
(1962).
18. T.W. Hoffman, D.R. Woods, K.L. Murphy & J.D. Norman,
"Simulation of a Petroleum Refinery Waste Treatment Process", J.
Water Poll. Control Fed. 45(11), pp. 2321-2334 (1973).
19. W.J. Blogoslawski, C. Brown, E.W. Rhodes & M. Broadhurst,
"Ozone Disinfection of a Seawater Supply System", in R.G. Rice &
M.E. Browning, Editors, Ozone for Water & Wastewater Treatment,
Intl. Ozone Inst., pp. 674-687, Syracuse, N.Y. (1975).
20. K. Stopka "Ozone Plant Improves Efficiency and Economy of
Wastewater Treatment", Water and Sewage Works, April 1978.
44
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Investigation of the Loading
Regeneration of the
Mixed-Media Filter with the
Descending Particle Seize
Distribution for the Advanced
Wastewater Treatment.
Golovenkov Yu.N.
Kravtsova N.V.
Slavinsky A.S.
Chabirov R.S.
One of the most widely used methods of the advanced
treatment of the biologically treated wastewaters is the
filtration on quick filters. At present at the stage of deep
wastewater treatment various structures of filters are
used. The most perspective are the structures which have
realized the principle of the filtration with the descend-
ing particle seize distribution and in which the appropri-
ate conditions for the intensive washing are created. The
multi-media filters and filters with the ascending water
flow meet the first requirement, the structures which
make it possible to create the intensive regime of the
water-air washing meet the second requirement.
Out of the great experience of the VNII VODGEO it
is clear that the mixed-media filter, developed in the
VODGEO, meets the above mentioned requirements to
the full. The mixed-media filter has 3 layers of loading:
gravel-support, sand-gravel, gravel-frame. The frame
gravel fraction is 40-60 mm, the quartz sand fraction is
0,8-1,0 mm, the general height of loading including the
supporting layers is 2,3 m (1).
Table 1 shows the efficiency of the advanced waste-
water treatment on the mixed-media filters, quartz and
two-layer filters when the concentration of suspended
substances in the given water variates from 10 to 50
mg/1 and BOD total variates from 10 to 25 mg/1.
Table 1
The effect of the advanced wastewater treatment on the quartz,
two-layer and mixed-media filters.
Type of filter
The reduction of the
suspended substances
in the filtrate, %
The reduction of
the BOD total, %
Quartz 92,0 80,0-72,0
Two-layer 84,9 80,0-70,0
Mixed-media 89,0 79,0-72,0
The effect of the advanced treatment is practically the
same but the length of the interregeneration period of
the mixed-media filter is 1,5 times as much as of the
two-layer filters and two times as much as of the quartz
filters.
Mixed-media filters do not react to the variations of
the wastewater quantity and to the variations of the
wastewater pollution concentration. As a rule they work
in the regime of the nonfilm filtration. The largely
dispersed suspended substance of the activated sludge re-
mains in the upper gravel layers of the filter, small-
dispersed suspended substance remains in the low layers
of the sand media.
Thus, mixed-media filter provides high efficiency of
the advanced treatment of the biologically treated waste-
water and to the full meets the requirement of the filtra-
tion with the descending particle seize.
To evaluate the conditions of the regeneration of the
filter loading the investigations were carried out on the
pilot plant mounted at the treatment facilities of the
Salarskaya aeration station in Tashkent. There were 3
stages of the loading regeneration: I stage air feeding,
II stage air and water feeding, III stage water
feeding. In the process of regeneration sand suspension
occurs in the interpore gravel space and in the limited
conditions of the ascending flow gravel and sand pollu-
tion is removed. The floaks of the washed sludge are
transported by the washing water through the troughs,
which are 200 mm higher than the loading surface.
Pic. 1 shows the principle scheme of the experimental
mixed-media filter. The diameter is 1200 mm,
height4,8 m, capacity250-300 mVday. In the course
of the investigation isotope Au-198 was used. The
definite volume of sand with fractions of 0,8-1,0 mm d
= 0,9 mm was put into the isotope solution, then it was
loaded to the filter on the surface of the sand media.
The coordination net-work was marked on the outside
surface of the filter to determine the trajectory of the
sand particle displacement in the process of washing.
The absciss axis was located on the upper boundary of
the sand layer. The points of the radioactivity measure-
ment were marked at the net-work. As a result of the
investigation the diagrams of isolines were obtained.
They characterize the change of the radioactivity back-
ground before washing, in the process of washing and
45
-------
1 Pipe-line, feeding influent and draining polluted washing water;
2 Pipes for the feeding of the washing water and draining of the
filtrate;
3 Pipe-line, feeding air for washing;
4 Overflow pipe-line.
Pic. 1
Principal scheme of the pilot mixed-media filter
after washing when the expenditure of water and air was
different.
Pic. 2 shows two such diagrams, one for water wash-
ing, another for water-air washing. In both cases the
suspension of the sand media was provided by 100%. By
the water washing the sand particles moved mostly in the
vertical direction and after the water feeding ceased they
occupied practically the primary position. By the water
and air feeding thanks to the circulation flows the more
intensive sand mixing and its displacement in the hori-
zontal and vertical directions in the frame pores took
place. After washing the marked sand, as a rule, moved
to the deeper media. Providing in the mixed-media filter
the intensive mixing conditions during the water-air
washing doesn't create the danger of the gravel-support
layer displacement, as the frame itself remains fixed. The
trajectory of the sand movement during washing corre-
sponds to the form of the isolines. The analysis of the
diagrams shows that the conditions of the limited settle-
ment created by the frame do not prevent the intensive
mixing of the sand media. More than that, thanks to the
limited space the speed of the ascending flow consider-
ably increases. And because of this the possibility of the
clash of the loading particles among each other and with
the frame grains increases.
Before washinq
In the process of washing
fie. 2
Distribution of isolines of the radioactivity of the labeled loading in the
course of washing
The investigations showed that the calculation inten-
sity of the water feeding in case of water washing should
amount to 20-24 I/sec m .
In case of water-air washing at the first stage air with
the intensity of 14-16 I/sec m is fed, at the second stage
air with the intensity of 14-16 I/sec m2 and water with
the intensity of 5-6 I/sec at the third stage water with
the intensity of 14-15 I/sec m2.
The loading regeneration in such regime makes it
possible to fulfil the washing in 8-9 minutes.
The diagrams on Pic. 3 show the quantity of the
removed loading pollution using the recommended
intensities.
i i i i
1 - After the filtration cycle with V f =IO m/hour
A \ 2 - After the filtration cycle with V f = 8 m/hour
Length of washing, min.
Pic. 3
Washing of the pollution from the loading of the mixed-media filter
The mam pollution mass is removed from filters at the
1 and 2 stages of washing. The low outlet of the washing
water through troughs placed at the height of 200 mm
above the loading level makes the transportation of the
washed sludge floaks of every seize possible.
The resulted of the carried out investigations on
loading regeneration of the mixed-media filter showed
that these filters make it possible to use the intensive
regime of the water-air washing, which provides the
reliable removal of pollution.
Mixed-media filters are one of the most perspective
structures for the advanced treatment of the biologically
treated wastewater.
46
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Municipal Wastewater
Treatment by Land Application
in the Minneapolis-St. Paul,
Minnesota Area
by
Richard H. Stanely, P.E.
President
and
Douglas A. Wallace, Ph.D., P.E.
Associate Chief Environmental Engineer
Introduction
General
The Metropolitan Council of the Twin Cities is respon-
sible for the preparation and adoption of a 20-year
wastewater management plan for the Minneapolis-St.
Paul Metropolitan Area, Minnesota. This plan is being
prepared and funded under the auspices of Section 208
of the Federal Water Pollution Control Act (PL 92-500).
The Metropolitan Council is the regional planning
agency for a 7-county area including and surrounding
the cities of Minneapolis and St. Paul.
This paper is based on a study by Stanley Consultants,
Inc., conducted for the Metropolitan Council to evaluate
the potential for land application systems for treatment
of municipal wastewater. The Administrator of the U.S.
Environmental Protection Agency has recently empha-
sized utilization of land application systems (1). Land
application systems can achieve a high degree of waste-
water treatment and are most likely to be cost-effective
where stream water quality standards require tertiary
treatment of biologically treated effluents. If land appli-
cation systems appear cost-effective for certain areas
they will be investigated in more detail during Facility
Planning studies conducted under Section 201 of the
Federal Water Pollution Control Act.
Objectives
The purpose of this study was to develop the tools neces-
sary to evaluate the potential for land application
systems in the study area. Specific work tasks required
to complete the evaluation include:
1. Development of criteria for the preliminary design
and costing of land application systems in the study
area.
2. Development of construction and operation and
maintenance costs for land application systems under
analysis. In addition, costs for transmission of
wastewater to the land application site are developed.
3. Assessment of climatological, land use, soils, and
topographic data pertinent to land treatment of
wastewater in the study area.
4. Identification of potential sites for land application
in the study area.
Study Area
The study area consists of a 7-county area surrounding
the cities of Minneapolis and St. Paul (Figure 1). The
1976 study area population is estimated to be about
1,993,000, which is the 14th largest urban area in the
USA. Minnesota is one of the most northern states with
Minneapolis-St. Paul located along latitude 45°. Winters
are rather severe with an average of 160 days where the
minimum daily temperature is equal to or below 32°F
(0°C). Average yearly snowfall is about 42 in. (107 cm)
and the growing season is about 120 days.
The majority of the wastewater transmission and treat-
ment systems in the study area are owned and operated
by the Metropolitan Waste Control Commission
(MWCC). The MWCC is the designated 201 Agency for
preparation of more detailed facility plans. The existing
system consists of 20 treatment plants, 400 miles (644
km) of interceptor sewers and 40 lift stations. The
system served 100 communities and approximately 1.8
million persons in 1976. Wastewater treatment facilities
range in size from the 200 mgd (757,000 m3/d) Metro-
politan Plant to facilities <1 mgd (<3,785 nr/d).
The study area has a large number of lakes and three
major river systems which receive most of the waste-
water treatment plant discharges. These rivers are the
Mississippi, Minnesota, and St. Croix. Although all of
the final effluent standards for the wastewater treatment
facilities are not yet fully established, certain stream seg-
ments are water quality limited and some effluent stand-
ards may be more stringent than secondary treatment (30
47
-------
mg/1 BOD5 and 30 mg/1 TSS). Phosphorus removal to 1
mg/1 is required for facilities discharging to the St.
Croix River. It is the smaller communities, outlying
Minneapolis-St. Paul, where land application of waste-
water appears to have the most promise for being cost-
effective.
Land Treatment Processes
General
There are three principal processes used for land applica-
tion of municipal wastewaters which were considered for
use in this study area. These three processes are:
1. Slow rate.
2. Rapid infiltration.
3. Overland flow.
A fourth lesser-used process in which wastewater is
applied to peatland for renovation was also briefly inves-
tigated since there are many peat deposits in the study
area. Although peat soils have been used to treat second-
ary effluent at several campgrounds in Minnesota with
good results (2, 3), the use of peat for larger scale
systems appears to have limitations because of extensive
and expensive site preparation requirements. This,
coupled with no actual operating experience with large
scale land treatment systems using peat soils, preclude
further consideration of these sites for land treatment in
the study area.
Slow Rate
In the slow rate land treatment process, sometimes
referred to as irrigation, wastewater is treated as it flows
through the soil system. Vegetative cover removes nitro-
gen from the wastewater while helping to keep the infil-
tration capacity of the soil at an acceptable rate to
receive the volume of applied wastewater. Wastewater is
applied using either surface or sprinkler application tech-
niques. The wastewater applied either evapotranspirates
or percolates to the groundwater. The hydraulic loading
rate for this process is limited by either the infiltration
capacity of the soil or the nitrogen removal capacity of
the soil-vegetation system. This treatment system pro-
vides the highest level of treatment and the most reliabil-
ity of the three treatment processes under consideration.
Rapid Infiltration
The rapid infiltration treatment process, sometimes
referred to as infiltration-percolation, applies large
volumes of wastewater to the land for treatment. The
soils must be rapidly permeable, and vegetation is not
usually required. The applied wastewater percolates
through the soil and reaches the groundwater unless
recovered by the use of underdrains or recovery wells.
The wastewater may be applied by spreading in basins or
by sprinkling.
This method of land treatment uses the filtering and
straining action of the soil as well as biological activity
to remove suspended solids, BOD, and fecal coliform.
Although this method of treatment results in a highly
nitrified effluent, overall nitrogen removal is generally
poor. Phosphorus removal varies with the type of soil
and travel distance of the wastewater through the soil,
but expected quality after treatment is still in the 1 to 5
mg/1 range (4).
Overland Flow
Wastewater is applied to the upper portions of sloping,
relatively impermeable soil in the overland flow process.
The wastewater is treated as it flows down the slope, and
a large portion of the water applied appears as run-off
at the bottom of the slope. This method has not been
widely used for municipal wastewater treatment and does
48
-------
not provide as great a degree of removal of BOD, sus-
pended solids, and fecal coliform as the two previously
discussed methods of treatment.
Table 2
Comparison of General Site Characteristics for Land Treatment
Processes
Land Treatment Process Comparisons
Design features for slow rate, rapid infiltration, and
overland flow land treatment processes are compared in
Table 1. Table 2 compares site characteristics, while
Table 3 shows the expected quality of treated wastewater
from the various land treatment processes.
Table 1
Comparison of General Design Features for Land Treatment Processes
Feature
Application
techniques
Annual
application
rate, ft6
Slow Rate
Sprinkler or
surface'
2 to 20
Processes
Rapid Infiltration Overland Flow
Usually
surface
20 to 560
Field area 56 to 560 2 to 56
required, acres2-7
Typical weekly 0.5 to 4
application rate,
a
in.8
4 to 120
Minimum pre- Primary Primary
application treat- sedimentation5 sedimentation
ment provided in
United States
Disposition of EVapotranspira- Mainly
applied waste- tion and percolation
water percolation
Need for
vegetation
Required
Optional
Sprinkler or
surface
10 to 70
16 to 110
2.5 to 63
6 to 164
Screening and
grit removal
Surface runoff
and evapotrans-
piration with
some percolation
Required
Notes: 'includes ndge-and-furrow and border strip.
2n-..u (na) not mdudjng buffer area, roads, or ditches for 1
2Field area in acres
mgd flow.
^Range for application of screened wastewater.
4Range for application of lagoon and secondary effluent.
'Depends on the use of the effluent and the type of crop
61 ft = 0.3048 m
71 acre -= 0.40469 ha
81 in = 2.54 cm
Land Treatment Design Criteria
General
There are a number of local factors which must be con-
sidered in selection of potential land treatment systems
Characteristics Slow Rate
Slope
Processes
Rapid Infiltration Overland Flow
Less than 20%
on cultivated
land; less than
40% on non-
cultivated land
Not critical;
excessive slopes
require much
earthwork
Finish
8%
slopes 2 to
Soil Pre-
meability
Depth to
Moderately slew Rapid (sands,
to moderately loamy sands)
rapid
Slow (clays, silts,
and soils with
impermeable
barriers)
2 to 3 ft
(minimum)
(0.61 to 0.91 m)
10 ft (3.05 m) Not critical
(lesser depths are
acceptable where
underdrainage is
provided
Climatic
Restrictions
Storage often None (possibly Storage often
needed for cold modify operation needed for cold
weather and in cold weather) weather
precipitation
Source: Reference (4)
and development of design criteria for the systems
selected. This section presents the local factors that must
be taken into consideration, identifies land treatment
processes which appear to have potential for use in the
study area, and evaluates design criteria for the selected
land treatment systems.
Local Factors
Raw Wastewater Characteristics Typical raw waste-
water characteristics for municipal wastewater in the
study area were developed in a previous study (5). These
characteristics are as follows:
BOD5 (5-day biochemical
oxygen demand) 225 mg/I
TSS (total suspended solids) 250 mg/1
NH?-N (ammonia nitrogen) 20 mg/1
Organic-N (organic nitrogen) 11 mg/1
P (phosphorus) 9 mg/1
It has been assumed for this study that concentrations
of heavy metals in the predominantly municipal waste-
water are not significant enough to affect application of
wastewater at the annual hydraulic loading rates dis-
cussed in this report. Industries contributing wastewater
to the municipal wastewater collection systems would be
required to pretreat their discharges to the degree where
heavy metal interference with land application would not
occur.
49
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Table 3
Expected Quality of Treated Water from Land Treatment Processes
mg/1
Slow Rate1
Constituent
BOD
Suspended Solids
Ammonia Nitrogen as N
Total Nitrogen as N
Total Phosphorus as P
Average
<2
<1
<0.5
3
Maximum
<5
<5
<2
<8
<0.3
Note: 'Percolation of primary or secondary effluent through 5 ft (1.52 m) of soil.
^Percolation of primary or secondary effluent through 15 ft (4.57 m) of soil.
^Runoff of comminuted municipal wastewater over about 150 ft (45.7 m) of slope.
Source: Reference (4).
Rapid
Infiltration2
Average
2
5
0.5
10
1
Maximum
<5
<10
<2
<20
<5
Overland Flow-5
Average
10
20
0.8
3
4
Maximum
<2
<5
<6
This study also assumes that raw wastewater will be
transmitted to the land application site where the neces-
sary pretreatment takes place. At a minimum, primary
.clarification is required prior to land application to pre-
vent plugging of distribution systems and soil clogging.
In certain cases secondary treatment may be desirable.
This study does not address the cost-effectiveness of
utilizing existing wastewater treatment facilities for pre-
treatment prior to transmitting the wastewater to the
land application site.
Climate Climatic information is based primarily on
data collected at the U.S. Weather Bureau station at the
Minneapolis-St. Paul airport. Climatological data are
used in the calculation of water balances, wastewater
application rates and periods, and storage requirements.
Table 4 presents climatic data for the study area.
Soils Soil characteristics are important factors to be
considered when evaluating land treatment alternatives.
Soil properties affect the choice of process and applica-
tion method, thereby greatly influencing the land area
requirements. Soil characteristics evaluated during this
study included soil depth, texture (root zone and sub-
stratum), permeability, and slopes. Evaluation of soil
characteristics was conducted based on general condi-
tions occurring over a broad area versus specific site
evaluations. No actual field testing or analysis of site
specific field data was conducted.
Sources of information utilized in evaluating soil
characteristics included USGS quadrangle maps; publica-
tions and maps of the Soil Conservation Service, USDA;
and the Agricultural Extension Service and Agricultural
Experiment Station, at the University of Minnesota (11,
12, 13, 14, 15, 16, 17).
* Groundwater Table The depth of the groundwater
table determines the depth of unsaturated soil in which
renovation will occur and, therefore, the degree of treat-
ment which will take place in the soil. Groundwater
depth was determined from USGS quadrangle maps in
combination with an areawide water table elevation con-
tour map (18) and references listed in the preceding soils
subsection of this report.
A portion of the wastewater applied to the soil by
land treatment systems will eventually percolate to the
groundwater if not intercepted by underdrains or
recovery wells. The treated wastewater must not raise
groundwater constituent concentrations to levels exceed-
ing EPA Interim Primary Drinking Water Standards if
the groundwater is being used or could be used as a
source of drinking water supply.
Land Use Land use information was based on
USGS quadrangle maps, exclusion maps compiled by the
Minnesota Land Management Information Center com-
puter system, and projected growth of urban areas
through the year 2000 from the Metropolitan Council.
Land Treatment Process Selection
Based on analysis of local factors discussed previously
and data from numerous references (4, 19, 20, 21, 22,
23, 24, 25), slow rate and rapid infiltration systems are
considered to be feasible land treatment systems for use
in the study area. Overland flow systems were ruled out
due to their lower level of treatment and the lack of
extensive areas having soils with the proper permeability
and slope relationships for use with this treatment
process.
Slow rate systems proposed in this study are based on
the treatment of wastewater, rather than the maximiza-
tion of crop yields as is sometimes considered for crop-
land irrigation systems. This choice was made because
application of wastewater solely to supplement natural
rainfall consumed by crops requires much larger land
areas since the wastewater cannot be applied at as high a
rate or for as long a period as when grasses are grown.
Grasses take up more nutrients than do crops such as
corn, allowing higher nutrient and hydraulic loadings.
Although there is a larger economic return from corn or
other crops as opposed to grasses, slow rate systems
which maximize wastewater treatment are considered
50
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Table 4
Climatic Data for the Twin Cities Metropolitan Area
Temperature. °F (°C)
Mean Number of Days
Precipitation (Pr)
Prevailing Direction
Month
January
February
March
April
May
June
July
August
September
October
November
December
Mean
12
16
28
45
58
67
73
71
61
48
31
18
Mean
Daily
Minimum
3
5
18
33
46
56
61
59
49
37
21
9
Maximum
32" (0°) 0
Below
24
19
11
<05
0
0
0
0
0
0
6
22
Minimum
32° (0°)&
Below
31
28
27
12
2
0
0
0
1
7
22
30
Average
Annual
On)4
0.73
084
1 68
204
3 37
3.94
3 69
305
2 73
1 78
1.20
089
Wettest1 Mean Number
Year in of Days with
10 Pr 05 In4
(m.)4
1.05
1 12
1.96
2.71
4 44
5 27
457
4.12
3 79
265
1 73
1 20
1
2
4
4
4
7
4
4
6
4
2
1
(ET)3
Evapolrans-
piration
On )4
1 32
3 32
508
5 87
487
3 15
1 69
_
Monthly Net
Water Excess
Pr-ET
On)4
105
1 12
1 96
1 39
1 12
019
-1 30
-075
065
096
1 73
1 20
and Mean Speed of Wi
Direction
Wind From Mean Sp
(miles/hr)5
NW
NW
NW
NW
SE
SE
S
SE
S
SE
NW
NW
11
II
12
13
12
n
9
9
10
II
12
11
82
160
25 94
34.61
43
25.30
9 3!
Notes. 'The design annual precipitation was determined on the basis of a frequency analysis tor the wettest year in 10 utilizing data from the period 1934-1973 The monthly totals are based on
the average percentage of the annual precipitation that occurs in each month
2Based on eleven (II) years of records, 1964-1974
Based on Thornthwaite method for period 1931-1969
"1 in
2 54cm
51 mile/hr = 1.609 km/h
Source References (6, 7. 8, 9, 10, 26) and U S Weather Bureau Data, Minneapolis-St Paul, Minnesota
more practical for the study area. The length of time
over which wastewater can be applied during the year is
.ather short, even with grasses, due to local climatic
conditions.
Slow rate systems will provide sufficient treatment to
the wastewater so that the percolate can discharge to the
groundwater without causing adverse effects. Only one
hydraulic loading rate and set of application criteria
have been developed for the slow rate system, since most
soils in the study area which are best suited for slow rate
land treatment have a similar permeability range.
There are soils in the study area which have permea-
bilities allowing use of rapid infiltration systems. Rapid
infiltration systems require much less land area than do
slow rate systems, but the degree of treatment provided
by this method is not as great as that for the slow rate
process. The degree of effluent quality required prior to
release of percolate to the groundwater is based on cur-
rent or potential aquifer usage. If the aquifer is presently
or could potentially be used as a source of drinking
water supply, groundwater quality must meet U.S. EPA
Interim Primary Drinking Water Standards. Within the
study area, there are bedrock aquifers 100 to 300 ft (30.8
to 92.5,m) below the surface which are used primarily
for drinking water. In general, these aquifers are sealed
from overlying aquifers, but there is no way of assuring
that water percolating downward will not reach the deep
aquifers. Therefore, rapid infiltration systems would
require collection of the percolate for discharge to sur-
face waters so that nitrate nitrogen standards «10
mg/1) would not be exceeded in the groundwater.
Rapid infiltration systems may not remove phosphorus
to a level <1 mg/1, so that discharge of the recovered
percolate would be limited to streams or rivers which do
not have a phosphorus limitation. This means that rapid
infiltration system effluent could not be discharged to
the St. Croix River or area lakes. Since two distinct
ranges of soil permeabilities are availble for use with
rapid infiltration systems in the study area, two different
design criteria have been developed for rapid infiltration
treatment. No special crops are grown on the infiltration
basins where the wastewater is applied, although it is
anticipated that a grass cover would be maintained.
Design Criteria Usage
The design criteria proposed in this study are based on
climatological, groundwater table, and land use data in
combination with general soil physical, hydraulic, and
chemical properties. The data base was determined from
references listed in the preceding "Local Factors"
subsection. This information was used in conjunction
with listed references and discussions with researchers at
the USDA Agricultural Research Service concerning their
findings at a wastewater land application test site in
Apple Valley, Minnesota, to establish the proposed land
treatment design criteria. While the design criteria and
cost information developed for this study are adequate
for preliminary planning purposes, it must be empha-
sized that detailed and site specific analyses must be con-
51
-------
ducted to assure that a given site is suitable for land
treatment. Field testing of soil properties, analysis of
groundwater quality and location, and evaluation of site
topography and vegetation are required to establish final
land treatment process design criteria.
Hydraulic Loading
Slow Rate The allowable hydraulic loading of
wastewater for slow rate systems is affected by soil per-
meability, climate, and crop selection. The permeability
of soils in the study area which are considered most suit-
able for slow rate land treatment fall within the 0.6 to 2
in./hr (1.5 to 5.1 cm/h) category, which is described by
the SCS as "moderate" permeability. Figure 2 presents
application rates which are suitable for this range of soil
permeability.
Using water balance and climatic data and Figure 2,
an annual wastewater loading rate of 55 in./yr (140
cm/y) has been selected for slow rate systems in the
study area. This loading rate is based on the use of reed
canarygrass as a cover crop and application over a
26-week period per year. Application of 55 in. (140 cm)
over a 26-week period results in an average weekly appli-
cation rate of 2.11 in (5.36 cm). Since mean annual
evapotranspiration and precipitation in the study area
nearly balance, the 2.11 in./wk (5.36 cm/wk) average
application rate falls near the middle of application rates
shown on Figure 2 used in practice for moderate per-
meability soils.
Table 5 shows weekly application rates proposed for
use throughout the application period. Wastewater
would generally be applied at a rate of approximately
0.25 in./hr (0.64 cm/h) for a period of 4 to 16 hr one
day per week, with no wastewater application the follow-
ing 6 days. If soil conditions or management practices
dictated, the application time could be halved and twice
weekly application could be utilized.
Reed canarygrass was selected as the forage crop for
slow rate systems due to its good water tolerance, its
maintenance of high surface infiltration rates, and its
high nutrient uptake (23). It is assumed that the reed
canarygrass would be harvested three times per year in
order to maximize nutrient uptake and crop quality. The
harvests would occur approximately the first week in
June, the last week in July, and the latter part of Sep-
tember. The Minnesota Department of Agriculture
estimates that the value of the harvested reed canary-
grass is about $50 per ton as a forage crop for domestic
animals and that the annual yield would be about 2.5
tons/acre (918 kg/ha) for a total crop value of about
$125 per acre ($51/ha).
Reed canarygrass generally requires a year to become
established. Therefore, another grass such as orchard or
ryegrass should be planted simultaneously with the reed
canarygrass to provide a crop the first year of waste-
water application.
Hydraulic loading rates proposed in this study exceed
Table 5
Proposed Application Periods and Rate!
for Slow Rate Land Treatment Systems
Approximate Dates
23 April-14 May
15 May-22 June2
23 June-September2
2 September-
30 September2
1 October-15 October
Application Amount Total During Period
(in./acre/wk)3 (in.)4
36.
6
55
Notes: 'Application amounts and dates shown should be modified in
actual operation to reflect current temperature, moisture, crop
requirements, and overall management objectives.
Indicates no wastewater application during one week of this
period for purposes of crop harvest.
31 in./acre/wk = 6.276 cm/ha/wk.
41 in. = .54 cm
Source: Stanley Consultants, Inc.
guidelines established by the Minnesota Pollution Con-
trol Agency. PCA regulations allow a spray irrigation
season of only 18 weeks and an overall maximum
hydraulic loading of 52 in./acre/yr (326 cm/ha/y). For
purposes of determining land requirements, the max-
imum application allowable by the PCA regulations is 36
in./acre/yr (226 cm/ha/y).
Rapid Infiltration As mentioned previously, two
different rapid infiltration application rates are pro-
posed. The first application rate is based on applying 15
in./wk (38.1 cm/wk) for 8 months of each year. This
amounts to 520 in./yr (1,321 cm/y), or 43 ft/yr )13.1
m/y). This hydraulic loading rate would be used with
those soils having permeabilities in the range of 4 to 6
in./hr (10.2 to 15.2 cm/h). The second hydraulic loading
rate is associated with sites where permeabilities of 12 to
14 in./hr (30.5 to 35.6 cm/h) are available. For this high
permeability, an application rate of 28 in./wk (71.1
cm/wk) could be used on an 8-month/yr basis, resulting
in a total application of 960 in./yr (2,438 cm/y), or 80
ft/y (24.4 m/y). The application cycle for these systems
would be approximately 2 weeks, with wastewater
applied to an infiltration basin for 1 to 4 days and a
resting period of 10 to 14 days before additional applica-
tion of wastewater would be allowed.
Land Area Requirements
Land is required for preapplication treatment lagoons,
storage lagoons, wastewater application areas, buffer
zones for spray application systems, buildings, service
roads, and other miscellaneous items. The area actually
receiving direct wastewater application is termed the
"wetted area" and is related directly to the total annual
wastewater application.
52
-------
1000
J
c
ae
Q.
o
Q-
O
z
o
QC
jc.
O
H-
<
o.
0_
PROBABLE RANGE OF
LONG TERM INFILTRATION
FOR WASTEWATER
RAPID
INFILTRATION
RANGE OF APPLICATION
RATES IN PRACTICI
ARBITRARY DIVISION
BETWEEN SLOW RATE
AND RAPID INFILTRATION
SYSTEMS
PERMEABILITY RATES OF MOST RESTRICTIVE LAYER IN SOIL PROFILE, m./hr.'
PERMEABILITY*. SOIL CONSERVATION SERVICE DESCRIPTIVE TERMS
VERY SLOW
< 0.06
SLOW
0.06-0.20
MODERATE-
LY SLOW
0.20-0.60
MODERATE
0.60-2.0
MODERATE-
LY RAPID
2.0-6.0
RAPID
6.0-20.0
VERY RAPID
> 20.0
' MEASURED WITH CLEAR WATER
1 I in./wk. = 2.5U cm./wk.
2 I in./hr. = 2.5t cm./hr.
SOURCE: REFERENCE
Figure 2
Soil Permeability Versus Ranges of Application Rates for Slow Rate
and Rapid Infiltration Treatment
53
-------
Slow Rate This land treatment system requires 244
"wet acres" per mgd (0.026 ha/m3/d). Total land area
for this system would be approximately 350 acres/mgd
(0.037 ha/m3/d) (4). These land area requirements may
be considered sufficiently accurate for planning pur-
poses, but there may be additional quantities of land for
certain treatment sites which are not readily usable for
wastewater application. Sites containing tracts of small
hilltops and valleys, steep slopes, or unsuitable soils will
add to the overall land area required at a given site per
mgd (m3/d) of wastewater treated.
Buffer zones of approximately 200 ft (61 m) in width
will be provided around the perimeter of all spray appli-
cation areas. These buffer areas increase the overall land
requirements for the slow rate system, but are considered
necessary to help prevent carryover of aerosols resulting
from the spray application system.
Rapid Infiltration The lower rate rapid infiltration
system would require a "wet acreage" of 26 acres per
mgd (0.0028 ha/m3/d), while the higher rate rapid in-
filtration system would require only 14 "wet acres" per
mgd (0.0015 ha/m3/d). Total land area for the rapid
infiltration systems is based on land for preapplication
treatment, storage, wastewater application areas,
buildings, roads, etc, but does not include buffer zones,
as were required for spray application systems in the
slow rate land treatment process. Total land area for the
first rapid infiltration system is approximately 52
acres/mgd (0.0056 ha/m3/d), while total land area for
the second rapid infiltration system is approximately 35
acres/mgd (0.0037 ha/m3/d).
Land Acquisition The outright purchase of land for
land treatment is usually considered to be the best land
acquisition method (4). Direct purchase of the land
allows more control over application site management
and allows the controlling agency a greater degree of
freedom in terms of long-range planning. Financing of
land to be used in the treatment process is generally
eligible for PL 92500 construction grant funding.
Long-term leases may also be eligible for construction
grant funding if they can be shown to be more cost-
effective than outright purchase of the land.
Constituent Loadings
Nitrogen The nitrogen balance for slow rate
systems is a function of the nitrogen applied, the
nitrogen removed by crop uptake, nitrogen lost by
devitrification and volatilization, and nitrogen lost to the
groundwater. The percolate to the groundwater must
contain < 10 mg/1 of nitrate nitrogen in order to meet
requirements for discharge to groundwaters that are
presently or could potentially be used as a source of
drinking water supply.
Reed canarygrass, proposed for use on slow rate land
treatment application areas, can be assumed to uptake
approximately 300 Ib/acre/yr (336 kg/ha/y) of nitrogen
with the rate of application of nitrogen to the soil and
the number of harvests. Three harvests have been
assumed over the application season in the study area.
Denitrification in slow rate systems can be assumed to
range from approximtely 15 to 25 percent of the applied
nitrogen (4). For purposes of the nitrogen balance com-
putations, denitrification was estimated at 15 percent of
the applied nitrogen, since denitrification rates are lowest
for uniform soils with moderate to rapid permeabilities
(24).
Table 6 presents the nitrogen balance calculations for
the slow rate system proposed for use in the study area.
Nitrate nitrogen concentrations are very low, thereby
assuring that 55 in./yr (140 cm/y) of wastewater could
be applied without exceeding nitrogen limitations. The
nitrogen balance indicates that 293 Ib (113 kg) of nitro-
gen would be applied per year with application of 55 in.
(140 cm) of wastewater containing 23.5 mg/1 of nitrogen
which is the estimated total nitrogen in the effluent from
the pretreatment facilities (total nitrogen in the typical
raw wastewater for the study area is 31 mg/1). To assure
maximum crop yield, the nitrogen balance indicates that
it might be necessary to apply a small amount of sup-
plemental nitrogen during the early part of the growing
season. It is doubtful that additional fertilizer would be
added, but rather a slightly lower crop yield would pro-
bably be accepted. It becomes apparent that if soil tests
at a specific site indicate a higher annual application rate
could be utilized from a hydraulic standpoint, nitrogen
limitations will not preclude use of application rates in
excess of 55 in./yr (140 cm/y). Experimental work con-
ducted by USDA Agricultural Research Service and
University of Minnesota researchers at an Apple Valley
land application test site indicated that application of up
to 95 in./yr (241 cm/y) of secondary wastewater effluent
[365 Ib N/acre (409 kg N/ha)7 on reed canarygrass did
not result in unacceptable nitrate concentrations in the
percolate (23). This application rate would be impossible
to achieve on a full-scale operation due to problems with
groundwater mounding and maintenance of a farming
operation, but illustrates that nitrogen limitations should
not be a problem with the use of three harvests of reed
canarygrass and practical wastewater application rates.
Rapid infiltration systems rely on nitrification, denitri-
fication, and ammonium absorption for nitrogen
removal. Rapid infiltration systems do not utilize a crop
in the application area, so nitrogen removal by crop up-
take is minor. Generally, rapid infiltration systems will
produce a highly nitrified effluent, but total nitrogen
removal is usually not great enough to allow percolation
of the effluent to the groundwater in cases where the
groundwater is or can be used for drinking water supply.
Therefore, recovery of the applied wastewater by use of
underdrains or recovery wells is proposed in this study,
with discharge of the percolate to surface waters.
Phosphorus Most of the phosphorus applied to the
soil in the slow rate system is utilized by crops or
retained in the soil by means of adsorption and chemical
precipitation reactions. Harvest of reed canarygrass in
the study area could be assumed to remove approximate-
ly 40 Ib/acre/yr (45 kg/ha/y) of phosphorus. Most of
54
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Table 6
Slow Rale S>slem
Monlhlv Nitrogen Balance
Month
January
February
March
April
May
June
July
August
September
October
November
December
Pr-KT.1
Net
MonlhK
Kxcesi
Water
(in )6
.05
.12
.96
.39
.12
0.19
-1.30
-0.75
0.64
0.96
1.73
1.20
Nines 'l rom I able
55.0
Maximum4
l.w.
Applied
Waslewater
(in )6
0
0
0
1.0
6.0
8.0
16.0
16.0
6.0
2.0
0
0
l.n.2
Waslewaler
Nitrogen
Loading
(Ib/acre)7
0
0
0
5.33
32.01
42.68
85.35
85.35
32.01
10.67
0
0
l),3
Denilrificalion
(Ib/acre)7
0
0
0
0.80
4.80
6.40
12.80
12.80
4.80
1.60
0
0
Potential
Crop
Nitrogen
Update
(Ib/acre)7
0
0
0
15.65
39.37
60.24
69.60
57.75
37.35
20.04
0
0
Wp,
Percolate
Water
(lb/acre)7(m.)6
2.39
7.12
8.19
14.7
15.25
6.64
2.96
Pn,
Percolate
Nitrogen
(Ib/acre)7
05
05
05
2.95
14.80
05
05
Cp.
Percolate
Nitrogen
Concentration
(mg/l)
0.88
4.28
293.40
44.0
300.0
^Assutn
Assuiii
^Assum
lion tut
-sll i ho
s applied
s deininh
d nuiMiiu
annual c
Milt
ant
n i
a pi
gen L
11 equ
ed ca
ians|
in
il
la
n
etmaiion ol 2^ 5 ing 1
15 poison! i>l niiuuioii applied
sgiass uptake it adequate niiiogen is a\ailable MomhK upiake is assumed 10 tonespoiid \\nti taiio ol nionihh e\apotianspita-
tion
I in 2 54 un
7I Ib/auc I 12 kg/h.i
SIHIKC KdiTi'iKi1 (4) anil Sianlc\ C onsiilunK. IIK
the remainder of the applied phosphorus will remain in
the soil and will result in the phosphorus adsorption
capacity being reached after a number of years. The
actual life of an application site can be computed once
the phosphorus adsorption capacity of the soil is
analyzed by means of laboratory testing of field samples.
Rapid infiltration systems do not utilize a crop, so
phosphorus removal by crop uptake is minor. Rapid
infiltration systems also use coarse*, textured, more per-
meable soils than do the slow rate systems, resulting in
less retention of phosphorus in the soil matrix than soils
associated with slow rate systems. Actual removal of
phosphorus by rapid infiltration soils depends on soil pH
and the levels of free iron oxides, calcium, and alumi-
num. It has been assumed in this analysis that rapid
infiltration systems will not reliably produce an effluent
with a phosphorus concentratipn < 1 mg/l. Therefore,
percolate from rapid infiltration treatment cannot be
discharged to phosphorus limited rivers and lakes in the
study area.
Biochemical Oxygen Demand and Suspended Solids
Slow rate and rapid infiltration systems both provide a
high percentage of BOD and SS removal. Table 3 shows
expected quality for these parameters following land
treatment by these two processes.
Preapplication Treatment
Slow Rate Systems Although reduction of organic
and suspended solids material in the wastewater is not
necessry from a soil treatment standpoint, preapplication
treatment is necessary to reduce these parameters so that
a reliable distribution system may be maintained. It is
also advantageous to reduce organic and suspended
solids so that storage of wastewater does not create
nuisance conditions, soil clogging is reduced, and health
risks due to spray of aerosols are minimized. For these
reasons, preapplication systems proposed for slow rate
systems consisting of aerated lagoons providing 6 days
detention. Treatment in the aerated lagoons and further
treatment in the storage lagoons, coupled with use of
200-ft (61 m) buffer zones and fencing of the entire site,
should allow spray application to be conducted without
prior disinfection. Aerated lagoons are assumed to have
an average working depth of approximately 15 feet (4.6
m), and will use surface floating aerators to meet the
oxygen demand of the wastewater.
Rapid Infiltration These land treatment systems will
also require preapplication treatment consisting of
aerating lagoons providing 6 days detention. The aerated
lagoons remove settleable solids that could cause clog-
55
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Table 7
Slow Rale System Storage Determination (In. of Waler)'
Month
January
February
March
April
May
June
July
August
September
October
November
December
Precipitalion^
(1)
1.05
1.12
1.96
2.71
4.44
5.27
4.57
4.12
3.79
2.65
1.73
1.20
Kllluenl
Applied
(2)
0
0
0
1.0
6.0
8.0
16.0
16.0
6.0
2.0
0
0
Kvapotrans-
piration-'
0)
1.32
3.32
5.08
5.87
4.87
3.15
1.69
Required
Percolation
(it: ')
(4)
1.05
1.12
1.96
2.39
7.12
8.19
14.70
15.25
6.64
2.96
1.73
1.20
Kffluenl
Available
(5)
4.66
4.36
4.66
4.51
4.66
4.51
4.66
4.66
4.51
4.66
4.51
4.66
Change in
Storage
(5 2)
(f>)
4.66
4.36
4.66
3.51
-1.34
-3.49
-11.34
-11.34
-1.49
2.66
4.51
4.66
Total4
Storage
(V)
16.49
20.85
25.51
29.02
27.68
24.19
12.85
1.51
0.02
2.66
7.17
11.83
34.61
55.0
25.3
57.25-
55.0
Note
' 1 in - 2 54 uu
2[ rom Table 5. based on wettest \cai in 10
M-rom Table 5
^Storage reservoir empty at the end ol September
^Does not inelude pteupiiauon in November, December, lanuaiv, lebruaiv, 01 \tateh
Source Stanley Consultants, Ine
ging of the soil at the high loading rates applied in rapid
infiltration systems. In addition, the aerated lagoons will
help to minimize nuisance conditions associated with
storage of the wastewater during winter periods. Design
criteria similar to those discussed previously for slow
rate systems will be utilized.
Storage Requirements
Slow Rate Slow rate land treatment systems require
storage to hold the wastewater flow which cannot be
applied during periods of inclement weather. Based on
the application schedule in Table 5, the maximum
storage volume for the slow rate system can be calcu-
lated. Table 7 illustrates the quantity of storage required,
based on a mass balance between wastewater applied and
wastewater available. A total quantity of 29.02 in. (73.7
cm) of wastewater must be stored, translating to a stor-
age volume of 592.5 acre-ft/mgd (193 mVmVd). This
volume represents the equivalent of 193 days flow. The
maximum storage occurs in April when the application
season is just starting. Applying a safety factor for stor-
age of an additional 2 weeks flow in the case of an
exceptionally late or wet spring, or incomplete emptying
of the lagoon at the end of the previous application
season, results in a proposed storage lagoon requirement
of 207 days flow, or 635.5 acre-ft/mgd (207 mVmVd).
Rapid Infiltration Although several references (4,
19, 20) indicate that rapid infiltration land treatment
systems can often be operated on a continuous year-
round basis, review of literature on systems located in
severe northern climates similar to that experienced in
the study area indicates that these systems apply warm
wastewater to infiltration basins located immediately ad-
jacent and following mechanical treatment facilities.
Therefore, the temperature of the applied wastewater is
still high enough to allow the wastewater to percolate
through the permeable soil without causing freezing
problems. Sometimes ice forms on the infiltration
basins, but the warm wastewater is reported to float the
ice and infiltrate through the soil underneath. In systems
proposed in the study area, however, the wastewater will
be transmitted from the community collection systems
through transmission lines to the aerated lagoon where it
is held for 6 days. Although the aerators should keep the
wastewater mixed enough to prevent total freezing, the
temperture of the applied wastewater is going to be near
32°F (0°C) in extremely cold weather. Application of
this near freezing wastewater to the infiltration basin
would probably result in freezing of the surface and
water in the soil pores, resulting in extreme operational
difficulties. Therefore, it has been assumed that those
periods of extreme climatic conditions (December,
January, February, and March) will not be conducive to
continuous wastewater application. A storage lagoon of
adequate size to hold the volume of wastewater
generated during this period is proposed. The volume of
the lagoon would be sufficient to hold 120 days flow or
require 368.3 acre-ft/mgd (120 mVmVd) of wastewater
56
-------
to be treated.
Design Criteria Storage lagoons for both slow rate
and rapid infiltration systems are assumed to have an
operating depth of 12 feet (3.7 m). A lining of asphaltic
material is proposed for the entire inside area of the
reservoir to prevent percolation of the wastewater
through the bottom of the storage lagoon into the
ground water prior to land application. Lagoons also will
require riprap on the inside slope of the dikes in order to
prevent erosion of the embankment by wind-created
wave action, a 3-foot (0.91 m) freeboard is assumed
above high water level. Large storage reservoirs are
assumed to be divided into multiple cells.
Application Systems
Slow Rate Wastewater may be applied using either
surface or sprinkler techniques for slow rate systems.
Surface application, however, requires relatively flat land
in order to minimize the amount of earthwork necessary
to prepare the application sites for wastewater distribu-
tion. Sprinkler distribution is less dependent on slope
considerations. Sprinkler distribution may be accom-
plished by either fixed, solid set permanent sprinklers or
hand or mechanically moved sprinkling systems. Due to
the somewhat rolling terrain found in the study area,
and savings on labor over hand-moved systems, center
pivot mechanically moved irrigation systems have been
proposed for use for most application sites. Center pivot
systems will work well in large open areas, but solid set
systems may be used to advantage in smaller, odd
shaped fields, even though solid set systems hamper the
planting and harvesting of crops in the field area. Costs
presented later in this report are based on the use of
center pivot spray systems.
Rapid Infiltration Application of wastewater for
rapid infiltration systems usually consists of surface
flooding of infiltration basins which are constructed on
near-level ground and surrounded by dikes. The basins
should generally be flat in order to allow uniform
distribution of the applied wastewater over the surface.
In order to minimize the amount of earthwork required
in construction, infiltration basins are best located in
relatively flat areas. It is possible to contract basins by
terracing into the side slopes of steeper areas, but appli-
cation of wastewater in an upper basin may adversely
effect application in lower basins further down the slope.
Multiple basins are generally required to provide flexibil-
ity in operation of the system and to insure adequate
drying time between application periods. Vegetation is
not required on the surface of the basin, but a grass or
other vegetative cover generally helps to maintain the
infiltration rate of the soil surface.
Subsurface Drainage
Slow Rate The ground water table must be con-
trolled at level that will provide sufficient soil detention
time and travel distance to insure that the required
degree of treatment is achieved. For slow rate systems, it
is necessary to maintain a groundwater table approxi-
mately 5 ft (1.52 m) below the ground surface. The addi-
tion of percolated wastewater will tend to raise the
natural ground water level. Areas of the application site
which already have or develop on a high groundwater
table will require artificial drainage to maintain the
groundwater table at the desired depth.
Application sites selected in the study area will
generally not require subsurface drainage over the entire
area, but natural drainageways and lower portions of
natural sloping areas may require underdrains to main-
tain proper groundwater depths. Treated wastewater col-
lected in the underdrains from these areas will be .
discharged to adjacent surface streams.
Costs for slow rate systems do not include the cost of
underdrains, since this is a site specific requirement. For
planning purposes, however, construction of underdrain
systems can be assumed to add approximately $1,000 per
underdrain acre ($405/ha /based on spacing of 250 ft (76
m)y, and have annual operating costs of approximately
$150/acre/yr ($61/ha/y) for an underdrained area of 25
acres (10.1 ha) to approximately $40/acre/yr ($16/ha/yr)
for an underdrained area of 2,500 acres (1,012 ha).
Rapid Infiltration Rapid infiltration systems require
that soils be adequately drained to maintain desired
infiltration rates. Subsurface drainage will insure that the
soil is unsaturated and has adequate resting periods
between applications for renovation. In addition, it is
necessary to collect the percolate for discharge to surface
waters, since groundwater quality standards would be
violated by rapid infiltration system effluent.
Percolate can be collected by either underdrain sys-
tems or recovery wells. It is necessary that underdrains
be located below the water table in sandy soils so that
they will collect the percolating water. In those cases
where the water table is deep and the soils where the
water table is located are permeable enough, the per-
colate would be recovered by pumped withdrawal rather
than underdrains.
It has been assumed that pumped withdrawal will be
the most suitable method of recovering the rapid infiltra-
tion land treatment percolate in the study area. Costs for
rapid infiltration systems include the cost of recovery
wells for percolate collection and discharge. In those
cases where underdrains may be suitable, a spacing of
400 ft (122 m) at 6 to 8 ft (1.8 to 2.4 m) depth may be
assumed for planning purposes.
Stormwater Run-off Control
Slow rate land treatment systems must usually provide
some method of control of stormwater run-off to pre-
vent erosion. Sediment control may be achieved by use
of sediment control basins, or control measures such as
terracing of steep slopes, grass border strips, and stream
57
-------
huffier zones. Since the slow rate systems proposed for
the study area utilize a grass forage crop, rather than
crops requiring plowing and exposure of the soil to the
elements, it is felt that sediment control will not be a
great problem. Since wastewater application is not
allowed during times when storm run-off might occur,
recirculation of the storm run-off for further treatment
is not considered necessary (4).
Due to the relatively flat slopes and the high permea-
bilities of soils used for rapid infiltration .land treatment,
surface run-off is not considered to be a problem.
System Monitoring
Slow Rate Monitoring facilities will be required to
determine groundwater quality both before wastewater
application begins (base line data) and during wastewater
application by the slow rate treatment process. Sampling
wells around the perimeter of the application site and
within the application site itself, will be required to
determine the performance of the land treatment pro-
cess. The wastewater being applied to the soil must be
monitored, as well as any percolate collected for
discharge to area streams. The surface water discharge
must be monitored to insure compliance with water qual-
ity standards and NPDES permit requirements. Typical
monitoring requirements can be obtained from Reference
(4).
Rapid Infiltration Since the effluent from the rapid
infiltration land treatment system will be collected and
discharged as a point source to surface waters, NPDES
permit requirements must be satisfied. It may also be
necessary to disinfect this effluent prior to discharge to
the surface water. Costs for rapid infiltration systems
presented in a later section include disinfection. Monitor-
ing requirements for rapid infiltration systems include
analysis of the wastewater prior to application, as well as
effluent analysis. Sampling wells are generally also re-
quired to insure that the percolate is being collected by
the underdrain or recovery well system, and that ground-
water quality is not being degraded.
Land Treatment System Costs
General
Costs for construction and operation and maintenance
of land treatment systems proposed for use in the study
area have been developed. These costs are presented in
the cost curves on Figures 3 and 4. In addition, cost
information for transmission of wastewater to the land
treatment sites has been developed.
Cost Curve Development
Construction and operation and maintenance (O&M)
costs were developed for each component of the land
treatment systems. The costs for the individual compo-
nents were then aggregated by system to arrive at the
total land treatment system cost curves presented on
Figure 3. Most of the unit costs for individual com-
ponents were based on Reference (27). The time base for
all curves is June 30, 1977. Indices and unit costs utilized
in cost curve development are as follows:
EPA Sewage Treatment Plant Construc-
tion Cost Index (LCAT), Minneapolis,
Second Quarter, 1977 127.0
EPA Sewer Construction Cost Index
(CUSS)/Minneapolis, Second
Quarter, 1977 133.0
Wholesale Price Index, Industrial
Commodities, June 30, 1977 194.6
ENR Construction Cost Index,
Minneapolis, June 30, 1977 2575.8
Treatment System Operation and
Maintenance Labor $9.50/hr
Electricity 2.59 kWh
FLOW, (mgd)
SLOW RATE
LAND TREATMENT
COSTS BASED ON: COSTS INCLUDE:
Loading rate of 55 in./yr. Preapplication treatment, field
(139.7 cm) preparation, storage lagoons, distribution
207-day storage pumping, center pivot spray irrigation
system, monitoring wells, administration
and laboratory facilities, service roads
and fencing
-------
(52q'Vyr>
(960"/yrl| ; i
J 4 » T««
FLOW, (mgd)
RAPID INFILTRATION.
LAND TREATMENT
COSTS BASED ON: COSTS INCLUDE:
120-day storage, loading Preapplication treatment. Held
rates as shown preparation, storage lagoons, distribution
pumping, infiltration basins recovery
wells, effluent disinfection, monitoring
Figure 3 wells, administration and laboratory
Cost Curves facilities, service roads and fencing
GRAVITY INTERCEPTOR
COSTS BASED ON:
Trench depths of 6'-28',
average depth ol 17'
Minimum velocity - 2.5 feet
per second at design flow
Manholes spaced at 350' (8"-60")
and 500' (-> 60')
Peaking factors vary from 3,0
@ 1 mgd Mow to 2.0 @ flows
<-. |0 mgd
COSTS INCLUDE:
Material, lay back trenching, labor
FORCE MAIN - PUMPING STATION
WASTEWATER TRANSMISSION SYSTE,
COSTS BASED ON:
6-foot depth of cover over
pipe crown
Average velocity approximately
5 feet per second
Total pumping head = 200 feet
Peaking factors vary from 3.0
@ 1 mgd flow to 2.0 @ flows
> to mgd
COSTS INCLUDE:
Force mam - material.
layback trenching, labor
Pumping station - valves, controls,
wet well, dry well, and
enclosing structure
Figure 4
Cost Curves
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Slow Rate Treatment Cost Curves
Items.for which costs for construction and operation and
maintenance were figured individually to form the com-
posite cost curve for the slow rate land treatment system
are presented on the following page.
1. Preapplication treatment consisting of preliminary
treatment (screening, grit removal, and metering)
and an aerated lagoon of 6 days detention.
2. Storage lagoon of adequate volume to hold 207
days flow.
3. Site clearing of the land treatment site. Costs based
on an area of mostly brush with a few trees, and
clearing using bulldozer-type equipment.
4. Heavy-duty electrically driven center pivot spray rig
for wastewater application.
5. Distribution pumping consisting of a pumping
system providing 250 ft (76.2 m) of head. Capital
costs are related to the peak flow supplied to the
distribution system while O&M costs are based on
average flow.
6. Administrative and laboratory facilities.
7. Monitoring wells.
8. Service roads and fencing.
9. Planting, cultivation, and harvesting costs based on
reed canarygrass crop.
The cost curves do not include:
1. The cost of land.
2. Costs of transmitting the wastewater from the col-
lection system to the land treatment site.
3. Costs for relocation of residents who are living in
the proposed land application area.
4. Benefits (negative costs) due to the harvest of reed
canarygrass crop.
5. Engineering, legal, administrative fees, interest dur-
ing construction, or contingencies.
Rapid Infiltration Treatment Cost Curves
Items included in the cost curves for rapid infiltration
systems are as follows:
1. Preapplication treatment (same as for slow rate
system).
2. Storage lagoons of sufficient volume to hold 120
days flow.
3. Site clearing of area with brush and a few trees
using bulldozer-type equipment.
4. Multiple-unit infiltration basins with 4 ft (1.2m)
dikes.
5. Distribution pumping system with pumping head
of 50 ft (15.2 m) to pump from the treatment or
storage lagoons to the infiltration basins.
6. Recovery wells using vertical turbine pumps with
associated electrical work and shelter.
7. Chlorination of rapid infiltration treatment
effluent prior to discharge to surface waters.
8. Administrative and laboratory facilities.
9. Monitoring wells and effluent sampling systems.
10.Service roads and fencing.
The cost curves do not include:
1. The cost of land.
2. Costs of transmitting the wastewater from the col-
lection system to the land treatment site, or of
transmitting the effluent from the recovery wells to
the point of discharge to surface waters.
3. Costs for relocation of residents living in the pro-
posed land application area.
4. Engineering, legal, administrative fees, interest dur-
ing construction, or contingencies.
Transmission System Costs
Costs for typical transmission systems, both gravity and
force main, have been developed for various quantities
of flow. Construction and O&M cost curves for trans-
mission systems are shown on Figure 4.
Gravity Pipelines Gravity transmission system cost
curves are based on the following design critera:
1. Trench depths range from 6 to 28 ft (1.8 m to 8.5
m), average depth of 17 feet (5.2 m).
2. Minimum velocity at the design flow is 2.5 ft/sec
(0.76 m/s).
3. Manning's roughness coefficient is assumed at n =
0.013.
4. Manholes are spaced at 350 ft (107 m) for 8 to 60
in. (20.3 to 152.4 cm) while lines >60 in. (> 152.4
cm) in diameter have manholes spaced 500 ft (152
m). The average depth of manholes is 17 ft (5.2 m).
5. Pipe slope varies from 0.05 ft/100 ft to 0.25 ft/100
ft.
Force Mains Typical design criteria used for costing
of force mains are as follows:
1. The depth of cover over the crown of the pipe is 6
ft (1.8m).
2. Minimum velocity in the force main is 2 ft/sec
(0.61 m/s), with a maximum velocity of 8 ft/sec
(2.44 m/s).
3. Pumping total dynamic head is 200 ft (61 m).
4. The Hazen-Williams coefficient is C = 120.
Costs for the force main system include force main
piping and a pumping station with wet well, dry well,
valving, site work, and standby equipment.
Construction Costs Neither gravity nor force main
construction cost curves include contingencies, engineer-
ing and legal fees, administrative costs, or interest during
construction.
Both gravity and force main systems are sized to
handle the peak flow, utilizing peaking factors common
to the area (5). Costs associated with both force main
and gravity sewer transmission line construction include
allowances for clearing and grubbing, roadway repair
and surface restoration, as well as normal dewatering
costs. Special construction techniques or requirements
due to specific problems encountered in the field (cross-
ing major roadways, crossing major rivers or streams,
very deep pipelines requiring extensive excavation or tun-
60
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neling, rock excavation, extensive dewatering, etc.)
would require special cost calculations.
Operation and Maintenance Costs O&M costs for
both gravity and force main systems include the cost of
periodic cleaning by a contractor, while force main
systems also include the costs associated with pumping
station operation and maintenance (power, labor for
operation and repair, and replacement parts).
Cost Curve Usage
Capital Cost Determination The capital, or con-
struction cost, of a proposed land treatment system may
be calculated by summing the following four cost items.
Costs thus calculated should be used for preliminary
planning purposes only. Actual total capital costs will
vary from site to site and require a more detailed site
specific cost analysis. For preliminary planning purposes
and comparison of land treatment alternatives, however,
the cost methodology proposed herein should be suffi-
ciently accurate.
1. Based on the flow projected at the end of the plan-
ning period, the construction costs for the land treat-
ment system components can be calculated by entering
the appropriate land treatment system composite con-
struction cost curve, Figure 3, and obtaining the cor-
responding construction cost. This cost should be
multiplied by a service and interest factor of 1.27 to
include costs of engineering, legal, administration, con-
tingencies, and interest during construction.
2. Again, based on the flow to be treated at the end of
the planning period (or whatever ultimate flow is con-
sidered appropriate for pursuit of land acquisition), the
total land area required for the land treatment system
can be determined. Based on knowledge of land cost in
the area of the proposed treatment site, the total land
acquisition costs may be determined by multiplying the
number of acres (ha) needed by the $/acre ($/ha). Total
land requirements for the various systems in relationship
to flows were presented under "LAND TREATMENT
DESIGN CRITERIA."
3. The cost of transmission systems to convey the flow
from the existing municipal collection system to the land
treatment site may be calculated using the transmission
system cost curves presented on Figure 4. Use of USGS
maps will allow general determinations to be made of
whether force main or gravity transmission lines are
required, and the approximate length needed. Based on
this data, the approximate costs for transmission of
wastewater to the land treatment site may be obtained.
Land treatment systems discharging to surface waters
(rapid infiltration systems and slow rate systems where
groundwater mounding is a problem) will also require
transmission systems to convey the flow to the ultimate
point of discharge. Again, USGS maps may be utilized
to make preliminary decisions regarding length and type
of transmission system required. Construction costs of
transmission systems from the cost curves must also be
multiplied by the 1.27 service and interest factor, as
discussed under Item 1.
4. Costs must be evaluated and included for relocation
of families living in the proposed land treatment system
site. Local agencies such as the Minnesota Highway
Commission and the St. Paul District, U.S. Army Corps
of Engineers, may be able to provide additional informa-
tion regarding these costs.
Operation and Maintenance Costs The yearly cost
for operation and maintenance of land treatment systems
may be calculated by addition of the following factors:
1. Operation and maintenance costs for the land treat-
ment components may be calculated by entering the
appropriate composite land treatment system cost curve
and obtaining the O&M cost in $/mil gal ($/m3) for the
appropriate flow being treated in the year under" con-
sideration. This cost fS/mil gaj ($/m3)7 is then multiplied
by 365 times the flow in mgd (m3/d) to obtain a total
annual cost.
2. Operation and maintenance of transmission systems
are associated with O&M costs for pipelines and pump-
ing stations. Again, from the transmission system cost
curves on Figure 4, an annual cost for transmission
system O&M can be calculated by multiplying the length
of the transmission system in miles (km) by the annual
$/mile ($/km) from the appropriate cost curve.
3. Slow rate systems will harvest reed canarygrass
three times during the application season. This grass can
probably be sold, resulting in a total dollar value that
should be subtracted from the annual cost for operation
and maintenance obtained in Items 1 and 2.
Comparison of Alternatives
Comparison of land treatment alternatives to determine
the most cost-effective alternative for wastewater
management should be done in accordance with EPA
cost-effectiveness analysis procedures contained in 40
CFR 35. The interest rate to use in this analysis is deter-
mined by the Water Resources Council, and is currently
valued at 6 5/8 percent. Either the present worth or
equivalent annual cost method of analysis may be used
to place alternatives on a common basis for evaluation.
Assuming the present worth method of analysis is
utilized, it is necessary to determine constructin costs for
proposed land treatment systems and transmission
system components, as well as the value of the remaining
economic life of the systems at the end of the planning
period (salvage). Land is assumed, per the cost-
effectiveness guidelines, to have a value at the end of the
planning period equal to its current market value at the
time of purchase. Gravity pipes and force mains are
assumed to have economic lives of 50 years, while pump-
ing stations can be assumed to have a life of 25 years.
Individual components of the land treatment systems
have varying service lives, but an overall composite ser-
vice life for the complete land treatment system of 30
years may be utilized for preliminary planning purposes
61
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(28). Relocation costs are a one-time cost at the start of
the study period. By knowing the times when cash ex-
penditures for the various items are made and the
remaining economic life and salvage values of land,
treatment systems, and transmission systems, it is pos-
sible to arrive at the present worth cost of construction
for the proposed system.
Yearly operation and maintenance costs (less crop
harvest value) may be calculated as described in the
previous subsections. These costs may be discounted
back to the base year by application of the appropriate
factors.
The total present worth value of an alternative is equal
to the total present worth construction cost plus the total
present worth of operation and maintenance.
Land Treatment Site Screening Methodology
General
Identification of potential sites for land treatment in the
study area required analysis of land use (existing and
future), soils, slopes and surface and groundwater condi-
tions. Criteria were established for each of these param-
eters and the study area was evaluated on the basis of
each parameter in turn. If an area was considered
unacceptable on the basis of one of the parameters, it
was ruled out and not evaluated for suitability of
remaining parameters.
The result of the screening is presented on the Figure 5
map. Those areas shown on the map as potential land
treatment sites are based on the site screening
methodology used in this study. Field investigations will
be required to positively confirm that a specific site has
all the necessary characteristics required for the desired
type of system and to confirm specific design
requirements.
Land Use
Land use screening was conducted to exclude those areas
deemed unsuitable for land treatment processes. Com-
puter generated maps based on the Minnesota Land
Management Information System (MLMIS) were used as
an aid to screening. The MLMIS divides land use into
nine distinct classifications: forested, cultivated, water,
marsh, urban residential, extractive, pasture/open space,
urban/non- or mixed residential, and transportation. In
addition to the MLMIS maps, USGS maps and maps
prepared for other studies were used (16, 17).
The initial screening process was performed using map
overlays with the MLMIS map to exclude urban residen-
tial, urban/non- or mixed residential and extractive land
uses. Subsequent screening using USGS maps identified
additional areas encompassing these land use classifica-
tions that were excluded. Using man.; orovided bv the
Metropolitan Council, urban expansion to the year 2000
was delineated as shown on the final map presented on
Figure. 5.
Many areas shown on the Figure 5 map are designated
as existing built-up areas but are outside the year 2000
Metropolitan Urban Service Area (MUSA) boundary.
These areas generally consist of residential or mixed
residential land uses bordering the MUSA, but also in-
clude free standing growth areas and small
developments.
Identifiable parks, wildlife preserves, and recreation
areas were excluded as a part of this use classification.
Within the areas classified as suitable for land treat-
ment are areas of scattered forest. It may be necessary to
clear some of these forested areas or design around them
when specific land treatment sites are planned. Also,
within the areas classified as suitable, there are transpor-
tation facilities such as roads, highways, and railroads.
These facilities will require consideration when siting
specific land treatment systems.
Soils
The physical characteristics of the soil directly influence
the suitability of an area for land application. Soil prop-
erties requiring evaluation include texture and structure,
infiltration rate and permeability, moisture-holding
capacity, and soil depth. The position of the soil in the
landscape can also be a significant factor in determining
its suitability for land treatment.
The soil infiltration rate and permeability depend on
the texture and structure of the soil. Medium-textured
(loamy) soils are best for slow rate systems while coarse-
textured (sandy) soils are best for infiltration-percolation
systems. Well structured soils are desirable because the
large pores readily conduct air and water within the soil.
The infiltration rate must be sufficiently high to
minimize the occurrence of effluent ponding and the
associated run-off hazard. The permeability of the most
restrictive soil layer in the upper 5 ft (1.5 m) of the soil
profile should equal or exceed the infiltration rate to
facilitate downward movement of applied effluent in
order to prevent the root zone soil from becoming satu-
rated for long periods.
Soil moisture-holding capacity is an indication of the
soil's textural class. Fine-textured soils have high
moisture-holding capacity and are not readily drained.
Such soils are generally unsuited to land application.
Soil depth is an important factor in land application.
Plant growth, available soil moisture, and treatment time
in the soil are all functions of soil depth. Where shallow
soil depth is underlain with fractured or crevassed rock,
the applied effluent may be short-circuited to the under-
lying groundwater before it has been adequately treated
in the soil.
Soils information was obtained from Soil Conserva-
tion Service county soil surveys and other studies (11,
12, 13, 14, 15, 16, 17). Table 8 presents those soil char-
acteristics considered most desirable for the potential
62
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Twin Cltiofl Metropolitan Aren
Figure 5
Potential Land Treatment Sites in the Twin Cities Metropolitan Area,
Minnesota
land treatment processes evaluated herein.
Table 9 presents soil characteristics and classifications
deemed unsuitable for use in a land treatment system.
Although alluvial soils subject to flooding were
screened out in this analysis, it might be possible to
locate wastewater application areas /"wet acres (ha)'V in
the flood plain. Rapid infiltration systems are probably
best suited to the soils found in these areas and do not
require mechanical center pivot spray rigs which might
be damaged by flooding. The final decision as to suit-
ability of these areas is dependent on the frequency and
severity of flooding and can only be determined by a
detailed analysis of specific sites. It would be required
that storage facilities, office and lab areas, and preappli-
cation treatment systems be located out of the area sub-
ject to flooding. Storage lagoons must be adequate to
store the volume of wastewater received at the site dur-
ing times when the application area was flooded and
whatever time was required after flood subsidence before
wastewater application could be resumed.
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Table 8
Desirable Soil Characteristics for Land Treatment
Land Treatment Process
Soil Characteristic Slow Rate Rapid Infiltration
Minimum Depty
Texture
5ftJ
5ft3
Permeability
medium moderately coarse
(loam to silt loam) (sandy loam)
to coarse
(loamy sand)
moderate moderately rapid
(0.60-2.0 in./hr)4 (2.0-6.0 in./hr)4
to rapid
(6.0-20 in/hr)
Depth to
Ground water
Slope
5 ft
1,3
10ft
1,3
<5%2
Notes: 'Shallower depths are acceptable where underdrainage is provided.
^Steeper slopes will require progressively greater earthwork operations
during construction. If infiltration basins are terraced into slopes, lateral
movement of water from upper basins may affect percolation rates in
lower basins
31 ft = 0.3048 m
4l'in./hr = 2.54 cm/h.
Source: Stanley Consultants, Inc
Table 9
Soil Characteristics and Classification Unsuitable for Land Treatment
Rock (R) Shallow depth to bedrock, possible inadequate soil
depth. May result in groundwater mounding or
may short circuit aphed effluent to groundwater
aquifers without adequate treatment if rock is ex-
tensively fractured.
Peat (P) Organic soils formed in low, wet areas. Unsuitable
due to wetness in its natural state.
Marsh (M) Unsuitable due to wetness in its natural state.
Alluvium (A) Soils along stream channels susceptible to
flooding.
Poorly Drained (D) Soils with permeability rates unsuitable for use in
land treatment systems.
Wet Soil Conditions
There are a large number of lakes and wet depressions
associated with the broad physiographic moraine areas in"
the metropolitan counties. Many of the depressions in
these moraine areas are subject to periodic inundation
due to the seasonal high water table. Often these depres-
sions are closed; i.e., the drainage system is not
integrated and the depressions cannot be easily drained.
Land treatment of wastewater effluent is predicated on
the fact that the soil and cover crop act as a treatment
medium. A soil depth of 3 to 5 ft (0.9 to 1.5 m) is
necessary to provide adequate treatment before the per-
colating effluent reaches the groundwater table. The
screening process attempted to eliminate those areas
where the groundwater table was near the surface.
Screening was accomplished using USGS maps, a water
table elevation contour map (18), and maps prepared for
other studies (16, 17, 26).
It should be noted that scattered areas deemed unsuit-
able as a result of areawide screening may be found
suitable when evaluated on a site specific basis. Such
areas may be made suitable through installation of
underdrains or recovery wells. This is particularly true in
the Anoka Sand Plain geomorphic region.
Slopes
Within the study area there are a wide variety of topo-
graphic conditions ranging from nearly level to gently
rolling to steeply sloped. Steep slopes are more suscep-
tible to erosion hazards and are likely to produce run-off
conditions. For this study, areas with slopes in excess of
15 percent are considered unsuitable for land applica-
tion. Screening on an areawide basis was conducted to
identify and eliminate significant areas where unsuitable
slope combinations are present. Screening was accom-
plished using USGS quadrangle maps and Soil Conserva-
tion Service Soil Survey books (11, 12, 13, 14, 15).
Within the areas designated as being generally suitable
for land application there may occur small tracts with
slopes greater than 15 percent which are difficult to
locate in areawide screening. These small areas will have
to be identified and dealt with when a land treatment
facility is being considered for a specific site.
Land Treatment Site Selection and Costing Example
General
This section presents a preliminary analysis of a poten-
tial site and present worth cost of land treatment for
approximately two-thirds of the flow from the Lake
Elmo (Tri-Lakes and Old Town) area. The projected
flow to be treated, the location of the sources of
wastewater input to interceptor systems for transmittal
to the land treatment site, and general location of a site
were furnished by the Metropolitan Council. This basic
input was used to locate and layout a potential site to
handle the projected flow in the year 2000 and do a pre-
liminary design of the wastewater transmission system
required to carry the flow from the service area to the
site. Construction costs and O&M costs for the land
treatment process have been calculated and are presented
on a present worth basis.
64
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Flow projections for the area to be served by land
treatment are as follows:
1980: 0.24 mgd (908 m3/d)
1990: 0.30 mgd (1,136 m3/d)
2000: 0.73 mgd (2,763 m3/d)
2020: 1.24 mgd (4,693 m3/d)
Treatment Process Design
The slow rate process has been selected for land treat-
ment of the Lake Elmo flow. Soils in the area of the
proposed site have general permeabilities in the range of
0.6 to 2.0 in./hr (1.5 to 5.1 cm/h), with slopes generally
13 percent or less. Soil series contained in the application
site are shown in Table 10.
General design criteria proposed in earlier sections of
the report for slow rate systems are utilized for this
system and are presented on the following page.
1. Apply 55 in. (140 cm) of wastewater per year over a
26-week period, starting in late April and continuing
through the middle of October. Weekly application rates
would be similar to those shown in Table 5.
2. Reed canarygrass would be grown on the applica-
tion site, with harvest three times per season.
3. Preapplication treatment would consist of prelimi-
nary treatment and 6 days detection in an aerated
lagoon.
4. A storage lagoon of sufficient volume to hold 207
days flow would be required.
5. Wastewater application would be accomplished by
center pivot spray irrigation rigs.
6. Percolate will discharge to the groundwater. No ad-
ditional cost for subsurface drainage is included.
7. Approximately 8 monitoring wells have been
assumed. These wells would be located both on-site and
adjacent to the land treatment site.
8. Buffer zones of 200 ft (61 m) are provided adjacent
to roads or other areas where people might be found.
Some areas abutting on the airport property do not
require a full 200 ft (61 m) buffer width. The entire land
treatment site would be fenced.
Land Area Requirements
Application of 55 in. (140 cm) of wastewater per year
requires 244 "wet acres (ha)" per mgd (0.026 ha/m3/d)
of wastewater. Assuming that the site will be designed to
handle the year 2000 flow of 0.73 mgd (2,763 m3/d), the
"wet acres (ha)" required is approximately 180 acres (73
ha).
The aerated lagoon, based on a 15 ft (4.6 m) depth
and 3 to 1 side slopes, will occupy approximately 1.6
acres (0.65 ha). The storage lagoon with a 12-ft (3.7 m)
depth, 3 to 1 side slopes, and two cells with require an
additional 45 acres (18.2 ha).
The actual layout of the system is shown on Figure 6.
The total area required for the land treatment site is
greater than the 350 acres/mgd (0.037 ha/m3/d) pro-
posed for planning purposes due to the roadways and
other constraints inherent in the general location
originally set forth for siting analysis. Total area
required for the site is 400 acres (162 ha).
Figure 6 shows tentative locations of the treatment
and storage lagoons, as well as a possible configuration
for deployment of center pivot spray rigs.
Wastewater Transmission System Design
Wastewater transmission systems were designed to
handle the 2020 flow. This flow was utilized to be con-
sistent with transmission system costs developed for
mechanical wastewater treatment facility alternatives
developed in a previous study (5). Land treatment of the
Lake Elmo flow was one of the alternatives originally
delineated for analysis in that study. In addition, some
land is available in the vicinity of the proposed site
which might be used for expansion of the process after
the year 2000. The wastewater transmission system could
be extended at that time to serve an adjacent site.
The flow from the Tri-Lakes area (one-half of pro-
jected flow in "General" subsection) would be pumped
through a 12,500 ft (3,810 m) long, 10 in. (25.4 cm)
diameter force main to a point where it would be com-
bined with the flow from the Old Town area (remaining
one-half of projected flow). The Old Town area flow
would also require a pumping station to convey its flow
through the 2,500 ft (762 m) long, 14 in. (35.6 cm)
diameter force main carrying the total combined flow
from the point of addition to the proposed land treat-
ment site. Force main systems were selected due to the
great pipe depths needed for gravity flow. Gravity flow
would have required special "open cut" construction
through many areas where normal trenching machinery
would not provide adequate pipe depth. Proposed pump-
ing station and pipe locations are shown on Figure 6.
Land Treatment System Costs
On-Site Land Treatment System The construction
cost of the components of the on-site land treatment
system may be obtained from Figure 3. For a flow of
0.73 mgd (2,763 m3/d), the approximate construction
cost is $1.87 million. Multiplying by the service and
interest factor of 1.27, the capital cost of the land treat-
ment system at the time of construction in 1979 would
be approximately $2.37 million. The value of the remain-
ing economic life (salvage) at the end of the study period
(year 2000), based on straight-line depreciation over a
30-year economic life, is $0.79 million in the year 2000.
Discounting both the construction cost in 1979 and the
value of the remaining economic life in the year 2000
back to the base year of 1977 using a 6 5/8 percent in-
terest factor results in a total present worth of construc-
tion (construction present worth less salvage present
65
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- *'^>'-V-?" v- : 5f *J '
;._.:.. .A ^-J'; ;;ArtiJ -,
, 'S:\''
Q
Z
U3
O
I
z
UJ
O
CO
Figure 6
Proposed Lake Elmo Land Treatment Facility
66
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Table 10
Soil Types and Physical Properties for Potential Lake Klmo Land Treatment Site
Most O'omon
Texture and Thickness In of
deoniorpliic' Significant |lt(m)| High Water Slope
County Region Soil Scries Rool Zone Substratum fable (It)'
Washington Mississippi Waukegon Silt Loam Sand &
Valley (2-3) Ciravel
Oulwash
Dakota Sandy Loam Sand
(2-3)
Dakota
Loam
(30
Notes: 'From Reference (16)
^Permeability ot mosl restrictive layer in upper 5 ieel
31 ft = 0 3048 m
4I in = 2.54cm
5I in./hr = 2 54 cm/h
Sources: References (16, 17, 18) and Sianley ( onsullants, Inc
Sand
Judson Silt Loam Silt Loam
(3)
>5
>6
>5
4-6
Range
(Percent)
0-8
x-n
3-8
0-3
Moisture Relationships
Available
Water Drainage
to 5 It4 Class Permeability^
(in /hr)5
7-9 Well 0.6-2.0
6-9
7-9
Well
Well
0.6-2.0
20-6.0
8-1" Well to 06-2.0
Moderately
Well
worth) of $1.90 million.
Operation and maintenance costs will vary each year
of the study period as the flow increases. O&M present
worth costs are most easily calculated by assuming a
straight-line increase in flow between dates for which
flow is calculated and use of annual and gradient series
to arrive at present worth costs. The O&M costs (annual
costs) for the land treatment system components for
years 1980, 1990, and 2000 would be approximately
$0.087, $0.101, and $0.2 million, respectively. The total
present worth cost of O&M of the treatment system for
the study period of 1980 to 2000 (base year of present
worth analysis is 1977) is $0.97 million.
Wastewater Transmission System Cost The total
cost for constructing the wastewater transmission line
and pumping stations (including service and interest
factor) in 1979 has been estimated at a cost of $1.17
million. This cost is based on a layout of the pipe rout-
ing on USGS maps and cost estimation based on pipe
length utilizing cost data developed in a previous study
(5). Pumping station costs include cost of a wet well/dry
well structure, pumping equipment, internal piping and
valves, controls, and electrical work.
The present worth of the construction cost of the
force main and pumping stations is $1.03 million.
Assuming economic lives of 50 years for the pipe and 25
years for the lift stations results in a total present worth
of construction (initial cost less salvage) of $0.93 million
for the transmission system.
Operation and maintenance costs for the transmission
system will vary yearly with flow. The present worth of
O&M for this sytem, based on transmission pumping
O&M costs developed in a previous study (5), is $0.054
million.
Total Present Worth Cost Summing up the total
present worth costs of construction and O&M for the
on-site land treatment system and wastewater transmis-
sion system results in a total present worth value of
$3.85 million. This cost does not include the present
worth of land acquisition (initial purchase less salvage),
the one-time cost of family relocation, or any benefits
resulting from marketing of the teed canarygrass crop.
The total present worth value of $3.85 million for a
land application system should be compared to alternate
mechanical wastewater treatment systems that achieve
equivalent effluent standards to determine if land appli-
cation is cost-effective for the Lake Elmo area.
Summary
Criteria for preliminary design and costing of slow rate
and rapid infiltration land application systems in the
Minneapolis-St. Paul, Minnesota area have been
developed. Using these criteria, typical construction and
operation and maintenance costs for land application
systems have also been determined. Climatological, land
use, soils, and topographic data has been used to iden-
67
-------
tify potential land application sites in the study area. An
example of how this information can be used to prelimi-
narily design and cost a land application system was
presented.
The Metropolitan Council of the Twin Cities has used
the information and methodology presented in this paper
to investigate a variety of potential land application
systems in the Minneapolis-St. Paul area. At this time,
several land application systems in the study area appear
to be potentially cost-effective. These potential systems
are for smaller sized communities on the outskirts of the
metropolitan area and appear to be cost-effective when
tertiary wastewater treatment is required. They will be
investigated in greater detail during the 201 Facility
Planning Studies that are currently under way.
References
1. Memo to Assistant and Regional Administrators (Regions I-X)
from Administrator, U.S. Environmental Protection Agency, regarding
EPA Policy on Land Treatment of Municipal Wastewater, October 3,
1977.
2. Farnham, R.S., and Boelter, D.H., "Minnesota's Peat Resources:
Their Characteristics and Use in Sewage Treatment, Agriculture, and
Energy," in Freshwater Wetlands and Sewage Effluent Disposal, Pro-
ceedings of Symposium, University of Michigan, Ann Arbor,
Michigan, 1976.
3. Stanlick, H.T., "Treatment of Secondary Effluent Using a Peat
Bed," in Freshwater Wetlands and Sewage Effluent Disposal, Pro-
ceedings of Syjnposiurri, University of Michigan, Ann Arbor,
Michigan, 1976.
4. Metcalf and Eddy, Inc., for the U.S. Environmental Protection
Agency, U.S. Army Corps of Engineers, and U.S. Department of
Agriculture, Process Design Manual for Land Treatment of Municipal
Wastewater, October, 1977.
5. Stanley Consultants, Inc., for the Metropolitan Council of the
Twin Cities Area, Wastewater Treatment Facility Alternative Costs,
January, 1978.
6. Baker, D.G., and Strub, J.H., Jr., "Probability of Occurrence in
the Spring and Fall of Selected Low Temperatures," in Climate of
Minnesota, Part I, Tech. Bulletin 243, Minnesota Agricultural
Experiment Station, March 1963.
7. Baker, D.G., and Swan, J.B., "Spring Soil Temperatures," in
Climate of Minnesota, Part IV, Minnesota Agricultural Experiment
Station, November 1965.
8. Baker, D.G., Haines, D.A., and Strub, J.H., Jr.,-"Precipitation
Facts, Normals, and Extremes," in Climate of Minnesota, Part V,
Technical Bulletin 254, Minnesota Agricultural Experiment Station,
1967.
9. Climates of the States, Volume II Western States, 1974, Water
Information Center, Inc., Water Research Building, Manhasset Isle,
Port Washington, New York 11050.
10. Climatic Atlas of the United States, U.S. Department of Com-
merce, Environmental Science Services Administration, Environmental
Data Service, June 1968. Reprinted by the National Oceanic and
Atmospheric Administration, 1974.
11. Soil Survey, Dakota County, Minnesota, Series 1955, Number 10,
Soil Conservation Service, USDA, in cooperation with Minnesota
Agricultural Experiment Station, August, 1960.
\2~. Soil Survey, Scott County, Minnesota, Series 1955, Number 4, Soil
Conservation Service, USDA, in cooperation with Minnesota
Agricultural Experiment Station, October, 1959.
13. Soil Survey, Carver County, Minnesota, Soil Conservation Service,
USDA, in cooperation with Minnesota Agricultural Experiment Sta-
tion, November, 1968.
14. So/7 Survey, Hennepin County, Minnesota, Soil Conservation Ser-
vice, USDA, in cooperation with Minnesota Agricultural Experiment
Station, April, 1974.
15. Soil Survey, Anoka County, Minnesota, Soil Conservation Service,
USDA, in cooperation with Minnesota Agricultural Experiment Sta-
tion, September, 1977.
16. Soil Landscapes and Geomorphic Regions, Twin Cities
Metropolitan Area Sheet, Miscellaneous Report 130-1975, Minnesota
Agricultural Experiment Station, 1975.
17. Interpretations of Soil Landscapes and Geomorphic Regions, Twin
Cities Metropolitan Area Sheet, Extension Bulletin 320-1976,
Agricultural Extension Service, University of Minnesota, 1976.
18. Water Table Elevation (contour map), in "Configuration of the
Water Table and Distribution of Downward Leakage to the Prairie du
Chien-Jordan Aquifer in the Minneapolis-St. Paul Metro Area,"
USGS/Metro-Council Study, USGS open file report 75-342.
19. Metcalf and Eddy, Inc., for the U.S. Environmental Protection
Agency, Evaluation of Land Application Systems, EPA-430/9-75-001,
March, 1975.
20. Land Treatment of Municipal Wastewater Effluents, Design Fac-
tors -1, U.S. Environmental Protection Agency Technology Transfer,
January 1976.
21. Land Treatment of Municipal Wastewater Effluents Design Factors
- II, U.S. Environmental Protection Agency Technology Transfer,
January, 1976.
22. Land Treatment of Municipal Wastewater Effluents, Case
Histories, U.S. Environmental Protection Agency Technology
Transfer, January, 1976.
23. Clapp, et. al., "Nitrogen Removal From Municipal Wastewater Ef-
fluent by a Crop Irrigation System," in Land as a Waste Management
Alternative, Proceedings of the 1976 Cornell Agricultural Waste
Management Conference, edited by R. C. Loehr, Ann Arbor Science,
1977.
24. Stanley Consultants, Inc., for the Metropolitan Atlanta Water
Resources Study Group, Wastewater Treatment Unit Processes Design
and Cost Estimating Data, January, 1975.
25. Stanley Consultants, Inc., for the U.S. Army Corps of Engineers,
New Orleans District, New Orleans-Baton Rouge Metropolitan Area,
Louisiana, Wastewater Treatment by Land and Marsh Application
Work Report, June, 1977.
26. Nowitch, R.F., Ross, T.G., and Brietkrietz, A., U.S.G.S., for the
Metropolitan Council of the Twin Cities, Water Resources Outlook for
the Minneapolis-St. Paul Metropolitan Area, Minnesota, 1973.
27. Metcalf and Eddy, Inc., for the U.S. Environmental Protection
Agency, Costs of Wastewater Treatment by Land Application,
EPA-430/9-75-003, June, 1975.
28. U.S. Environmental Protection Agency, Areawide Assessment Pro-
cedures Manual, EPA-600/9-76-014, July, 1976.
68
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The Mathematical Model of the
Adsorption of Organic
Impurities from Water
Solutions with
Microporous Adsorbents
by
A. M. Stadnik
All-Union Scientific Research
Institute "VODGEO"
Moscow, USSR
The analysis of the Soviet and foreign literature shows
that the adsorption technology is the most perspective
and economically expedient for the deep purification of
natural and waste waters from dissolved organic
pollutants. In this connection the practical problems of
design and optimization of the adsorption treatment of
water as well as the construction of the highly effective
sorption equipment demands the appropriate develop-
ment of the theory of solutes adsorption. However, both
the choice of sorbents for these purposes and the design
of sorption units were mainly based up to now upon the
purely empiric approach using empiric constants, the
changes of which while passing from one system to
another couldn't be predicted. This necessitated carrying
out numerous experiments in every concrete case first in
a laboratory and then on a pilot plant.
The attempts to create the formalized mathematical
models of the adsorption treatment of wastewaters also
do not seem to be a solution of the problem since such
models again use empiric constants.
The aim of our investigations was the development of
the theoretical basis for a mathematical model of ad-
sorption of organics (partly soluble in water) from water
solutions with microporous adsorbents under static and
dynamic conditions (for a stationary adsorbent bed). We
mean such a mathematical model, which is based on the
adequate reflection of physico-chemical processes taking
place when organic substances are adsorbed and which
permits to carry out the design of adsorption units for
water treatment, to choose the most effective sorbent for
given conditions and to evaluate the technical and
economic efficiency of the process, the experimental data
being minimal.
The description of the process of adsorption from
solutions under equilibrium and non-equilibrium condi-
tions is the basis of the suggested model. Let us begin
with the description of the adsorption equilibrium. Ac-
cording to the theory of the volumetric filling of
micropores, developed by M. M. Dubinin and L. V.
Radushkevich /1 / the equation of the characteristic
adsorption curve may be presented in the form:
W = WQexp -Ke2
(1)
This Equation expresses the distribution of the filled
volumes of the adsorption space W along the differential
molar works of adsorption e . WQ is the maximum
volume of the adsorption space, characterizing the
volume of the adsorbent's micropores; K is the con-
stant, characterizing the adsorption system. This Equa-
tion was obtained for the case of vapours adsorption on
microporous activated carbons. In our work 121 we sug-
gested that this Equation should be applied to the case
of adsorption from solutions on the ground that the
function of the adsorbent pores distribution in principle
must not depend on whether adsorption occurs from
gaseous or liquid phase.
On the basis of the thermodynamics of the maximum
diluted solutions (such are solutions of many organic
substances partly soluble in water) it is shown that the
differential molar work of adsorption may be expressed
in this case as:
e = RTln Cs/Cp
(2)
where Cs is the concentration of a solute, corresponding
to the saturated solution;
C the equilibrium concentration of a solute in the
solution;
R gas constant;
T absolute temperature.
After substitution of Equation 2 into Equation 1 and
some transformations we obtain the Equation of the ad-
sorption isotherm:
W0 Cs 2 BT2
logPp = lg - 2.303(lg-)2--ry-
m p
69
-------
Where I\, specific equilibrium adsorption;
Vm^- molar volume of the adsorbate;
B structural-energetic constant,
characterizing the adsorbent;
j3 affinity factor expressed by the
relative molar work of adsorption of
the given solute at a selected standard
substance.
The relation between constants K and B is expressed as:
B = KR202 (4)
It is obvious that if the experimental adsorption
isotherm satisfies Equation 3, then in logarithmic coor-
dinates Ig Fp; (lgCs/C J2 it must be the straight line
with the angle of inclination tangent tg
-------
sorbate concentration change in the solution:
I C°
C = C exp | In exp (-« . T)
(12)
tions are interrelated by the following Equation (for the
same value of
a = a*
C0rp'inc0/cp
(17)
where the initial, running and equilibrium concentrations
of the adsorbate in solutions are designated through C0,
C and C respectively. If we know the value of the runn-
ing concentration C at some moment of time 7 , from
this Equation we can determine the kinetic parameter of
adsorption under the static conditions expressed by oc*:
(13)
In order to obtain the correspondent integral equation of
the adsorption kinetics for the constant and limited
volume of solution (under so-called static conditions) it
is sufficient to solve Equation 12 jointly with the known
expression for Gibbs adsorption:
(C0-C)-V
m
(14)
where F running adsorption;
V volume of the solution;
m the mass of the adsorbent.
Where C = Cp, T = Tp. In this case the dependence
of the relative adsorption on the phases contact time will
be expressed by the Equation:
7* =
C0 - Cp exp (in C0/Cp exp (-cc*T)}
(15)
If we mathematically direct V > oo(or equivalently m
> O) then we shall come to the case of such adsorp-
tion when the constant concentration of the sorbate is
maintained around the adsorbent's grain at the interface
(adsorption under the continuous-flow conditions). In
order to obtain the specific expression of the adsorption
kinetics equation for this particular case, it is necessary
to turn to the limit in Equation 15 at C > C :
(16)
y = linry* =1 -jexp -
-------
adsorption space filling 0 at C = CQ. One can
show that:
e =
0Rj3
(20)
In Equations (19-20) R is the gas constant. Equations
(17-20) express the relationship between the kinetic and
equilibrium characteristics of the adsorption process and
permit to theoretically calculate the adsorption kinetics
both under static and dynamic conditions on the basis of
the equilibrium data. They reflect the dependence of the
kinetic parameters upon the structural characteristics of
the adsorbent and upon the adsorbate nature.
For a number of reasons the exact solution of the
adsorption dynamics problem obtained for some par-
ticular cases cannot be directly used for calculation of
full-scale adsorption units. In connection with this one
should note that it is not obligatory to know the whole
breakthrough curve of adsorption dynamics. It is quite
I sufficient to be able to calculate the operating period of
the filter before the breakthrough of impurities ( 7 )
occurs, the period from the breakthrough to the total ex-
haustion of the sorbent's bed (AT) and the length of
the mass-transfer zone (LQ) depending on various factors
affecting the, adsorption process under dynamic condi-
tions, and in the first place, on such parameters as the
height of the sorbent's bed in the filter (L), the specific
filtering velocity (U), the initial concentration of the ad-
sorbate in the feed solution (CQ), the size and the
geometric shape of the sorbent's grains, porosity of the
filter bed ( \f/ ) etc. On the ground of the use of the ad-
sorption dynamics stationary front and the described
model of the kinetics of adsorption from solutions, the
authors in work / 5 / suggested the method of calculation
of main dynamic parameters of the sorption filter opera-
tion, which may be presented by the following Equa-
tions:
La
Q
nP UCr
AT =
2Ran
(21)
(22)
where dH bulk density of an adsorbent (g/1)
The given model is true when the adsorption isotherm
is convex, L ^ LQ and the adsorption kinetics is limited
by the internal diffusion. The latter condition may be
realized at U > 1.8 m/h, as was shown by a number of
investigators. It should be noted that the adsorption
treatment of natural and waste waters is carried on at
higher filtering velocities, that is under such conditions
when the adsorption process is surely limited by the
intradiffusive transfer.
With the account of the above-stated it is clear that
Equations 21-23 express the relation of dynamic para-
meters both with the conditions of the treatment process
and the structural characteristics of the adsorbent and
the nature of the adsorbate.
The mathematical model given in this paper can be
assumed as the basis of the method of calculation of an
adsorption unit for treatment of multi-component mix-
tures, in particular wastewaters. In this case the values
of concentration and adsorption of organic impurities
must be expressed in terms of the generalized index of
wastewater pollution, for example by TOC and COD
values.
L0
2R
(23)
In these Equations a0 the adsorbate concentration in the
solid phase, corresponding to the substance concentra-
tion C0 in the feed solution and expressed per unit of the
adsorbent bed volume (in the same units as C0). It is
related to the correspondent value of the equilibrium ad-
sorption expressed per one gram of the sorbent by the
expression:
ao = ro
(24)
72
-------
Tahoe-Truckee Sanitation
Agency Water
Reclamation Plant
by
Ossian R. Butterfield
General Manager/Chief Engineer
Tahoe-Truckee Sanitation Agency
The Tahoe-Truckee Sanitation Agency was formed on 1
May 1972 to carry out the mandate of the Porter
Cologne Water Quality Act, a California law requiring
exportation of all sewage from the Lake Tahoe Basin.
Upon its formation, the Agency immediately embarked
on a program to plan, program, design and construct a
regional system which would transport all sewage from
an area encompassing the California north shore of Lake
Tahoe and Truckee to a regional plant. Construction of
this new facility would result in the replacement of the
existing interim treatment facilities operated by the
Agency's five member entities: the Tahoe City Public
Utility District, the North Tahoe Public Utility District,
the Alpine Springs County Water District, the Squaw
Valley County Water District and the Truckee Sanitary
District. The Tahoe-Truckee Sanitation Agency (T-TSA)
is governed by a Board of Directors comprised of five
appointed directors, one from each member district.
Since it was mandatory that effluent be disposed of
outside the Lake Tahoe Basin and in a manner that
would protect the quality of any receiving waters and all
potable water sources possibly affected by its disposal,
the following alternative plans were identified by T-TSA
as being worthy of study:
1) Exportation of treated wastewater to Long Valley,
Sierraville or Loyalton for use as irrigation water on
farmland.
2) Discharge of highly treated wastewaters to the
Truckee River, either in Martis Valley or after the trans-
portation of either treated or untreated wastewater to the
Reno/Sparks treatment plant located in Nevada.
3) Land disposal of treated wastewater in the Truckee or
Carson JRiver Basins.
4) Upgrading existing treatment facilities in each of the
member districts.
Retention of the effluent in the Truckee River Basin
was decided to be of prime importance in order that the
quality of water available to downstream users would
not be diminished by this project. It was also determined
that treatment of the wastewater to a high degree at a
location near Truckee was the most economical solution
and that this plan had the least adverse impact on the
environment. Third, the existing high water quality
standards required of the Truckee River could not be
adhered to by upgrading of the existing treatment plants.
The State of California's rigid waste discharge require-
ments necessitated the implementation of the most
sophisticated treatment available
The project finally selected as the most advisable
required the construction of an interceptor line from
Tahoe City to Truckee, California, the construction of a
4.83 MOD regional sewage treatment plant in Martis
Valley, and the installation of an underground disposal
system that would allow the effluent to percolate into
the permeable glacial outwash soil near the plant. Full
tertiary treatment, including maximum removals of
nitrogen and phosphorus, was deemed necessary to pro-
tect the quality of the Truckee River into which the
effluent would ultimately find its way and to ensure the
safety and integrity of this primary water source for
Reno, Nevada, a major city downstream.
Studies of the background concentration of pollutants
in the Truckee River revealed that the critical pollutants
were total nitrogen and total phosphorus. These were
determined to be the most difficult standards to meet;
other pollutants could easily be removed by proven pro-
cesses. The primary goal of process design was to ensure
that the treated effluent, when mixed with background
concentrations existing in the river, would not violate the
river standards even if discharged directly into the river.
Percolation into the Martis Valley soils would provide an
additional treatment factor wherein a residence time in
the soil of about 150 days is experienced. The effluents's
mixing with surface water percolating into the soil would
result in additional dilution of its pollutants.
73
-------
T-TSA's regional facilities became operational in
February 1978. The reclamation plant was designed to
produce the effluent quality shown in Table I. Treatment
processes selected for the project are shown in Table II.
Figure 1 depicts the process flow diagram illustrating
the general arrangement of these processes.
Treatment Processes
After thorough review of the requirements for effluent
quality, it was concluded that only a combination of bio-
logical and physical-chemical treatment could meet the
applicable criteria.
Primary Treatment
Primary treatment removes a large portion of the settle-
able organic and inorganic solids entering the plant.
Primary treatment facilities consist of the headworks,
grit removal chamber, primary clarifiers and primary
sludge pump station.
Headworks
Raw sewage enters the headworks flow distribution
channel and normally passes through one of two com-
minutors. The comminutors shred the coarse solids in
the sewage into smaller particles. This reduces the possi-
bility of large organic solids settling in the grit removal
system or continuing through the plant and clogging
pumps and sludge lines.
Grit Removal
The grit removal system removes heavy inorganic solid
materials such as sand and gravel, thus protecting mov-
ing mechanical equipment within the plant from abrasive
wear and preventing grit accumulation in basins and
digesters.
The comminuted sewage is distributed across the entire
grit chamber so that the velocities are reduced to about
one foot per second which allows the heavy materials to
settle and be removed.
Settled grit is pumped to the grit cyclone where most
of the inorganics are separated from the lighter organics.
The grit washer removes the remaining organics, and the
grit is discharged to a bin for disposal.
Primary Clarifiers
The primary clarifiers provide relatively quiescent condi-
tions which allow settleable solids to be removed, and
thus reduce the organic loading on the subsequent treat-
ment processes. Supernatant from the clarifiers flows to
the biological treatment process. The settled solids
(primary sludge) are pumped to the digester by pumps
located in the primary sludge pump station.
Table 1
Design Criteria kffluent Quality
5:day BOD
COD
Suspended solids
MBAS
Turbidity
Total nitrogen
Total Phosphorus
Coliform organisms
2 mg/1 or less
10 mg/1 or less
1 mg/1 or less
. 1 mg/1 or less
1 JTU or less
2 mg/1 or less
. 1 mg/1 or less
less than 2.2 mpn/100 ml
Table 2
Primary Treatment
Comminution
Flow metering
Grit removal
Primary sedimentation (clarification)
Biological Treatment
Pure oxygen activated sludge
Chemical Treatment
Rapid mix and flocculation with lime
Chemical clarification
First stage recarbonation
Recarbonation clarification
Second stage recarbonation
Advanced Waste Treatment
Dual media filters
Activated carbon adsorption
Ammonia removal using clinoptilolite (ion exchange)
Disinfectin Using Chlorine
Solids Handling and Side Stream Systems
Anaerobic digestion of organic sludge
Filter press dewatering of chemical and digested
sludges
Land disposal of sludge
Ammonia removal and recovery from regenerant
Activated carbon regeneration
Biological Treatment
Biological treatment removes most of the soluble and
finely suspended organic matter in sewage. The biolog-
ical treatment system utilizes a pure oxygen-activated
sludge process and consists of oxygenation basins, car-
bon dioxide stripping, secondary clarifiers, and the
return and waste activated sludge pump station.
Oxygenation ^Basins
Primary effluent is mixed with return activated sludge
and some plant return flows in a common mixing
74
-------
Figure 1
Plant Process Diagram
75
-------
chamber prior to entering the oxygenation basins. The
flow then enters the flow distribution channel where it
passes through submerged gates to the first stage of the
oxygenation basin trains in service. Actual flow division
between basins is determined by overflow weirs at the
outlet of the basins.
Each oxygenation basin train consists of three separate
covered stages in series. Pure oxygen is supplied at a
controlled rate to the first stage. Each stage is equipped
with a mechanical aerator for transferring the oxygen to
the liquid and for keeping the basin contents completely
mixed. The liquid (mixed liquor) and gas flow through
ports to the second stage. The gas space is vented to the
atmosphere at a controlled rate at the end of the second
stage, and the mixed liquor flows to the third stage
through a submerged port.
The third stage is used to strip carbon dioxide gas
from the mixed liquor and gas space, in addition to pro-
viding additional biological treatment to the wastewater.
One end of the third stage is vented to the atmosphere
while a CO2 compressor pulls gas from the other end,
stripping CO2 with the air flow. The stripped air con-
taining a relatively high concentration of carbon dioxide
(±3 percent) is drawn from the third stage, compressed,
and used in the recarbonation basins along with the
combustion gases from the boilers.
Secondary Clarifiers
The secondary clarifiers provide a quiescent condition
that permits the biological solids in the mixed liquor to
settle and form a sludge. The clarified wastewater, now
low in organics, overflows from the secondary clarifiers
to the chemical treatment process. Settled sludge is
removed from the secondary clarifier through sludge suc-
tion lines that are attached to the lower rotating clarifier
mechanism.
Oxygen Generation
High purity oxygen is generated by an on-site PSA
(pressure swing adsorption) generator. Compressed air is
fed to the generator, and it separates the nitrogen and
other impurities from the air producing a relatively high
purity oxygen. A backup liquid oxygen (Driox) storage
tank and vaporizer provide oxygen to the oxygenation
basin when the PSA generator is out of service or cannot
meet the demand.
Chemical Treatment
In the chemical treatment process, lime is added to
secondary effluent to precipitate phosphorus as calcium
hydroxyapatite, Ca10(OH)2(PO4)6, which is then
removed by settling in the chemical clarifier. In addition
to forming calcium hydroxyapatite, the lime also precipi-
tates calcium carbonate, CaCO3, and magnesium
hydroxide, MgOH2, which is similar to the lime soften-
ing process in water treatment. Although the primary
purpose of the lime treatment process is to remove phos-
phorus, it also reduces the suspended solids which are
carried over from the secondary clarifiers by trapping
the solids in the chemical precipitates (floe). Since these
organic solids contain C.O.D. and viruses, removal of
these impurities is enhanced.
The chemical treatment system consists of the rapid
mix basins, flocculation basins, chemical clarifiers and
chemical sludge pump station.
Rapid Mix Basins
Secondary effluent enters the rapid mix basin inlet
chamber along with chemical sludge thickener overflow
and chemical sludge recycle (if practiced). Lime is added
at the inlet to the rapid mix basins to raise the pH to
about 11.2. Each of the rapid mix basins contains a
mechanical mixer which rapidly disperses the lime slurry
throughout the secondary effluent. Secondary effluent
can be bypassed to the emergency storage pond from the
rapid mix inlet chamber if necessary because of a process
failure.
Flocculation Basins
The high pH wastewater flows from the rapid mix basins
into parallel flocculation basins. The purpose of the floc-
culation basins is to gently mix and agglomerate the
coagulated precipitates into large floe particles for better
settling in the chemical clarifiers.
Each flocculation basin is equipped with two vertical
adjustable-speed paddle mixers. Polymer can be added at
the influent and effluent end of both basins as an aid to
flocculation and settling.
Chemical Clarifiers
Flocculated wastewater flows from the flocculation
basins to two chemical clarifiers where the solids are
allowed to settle. Overflow from the clarifiers, which is
now low in phosphorus and at a high pH, moves on to
the recarbonation process. Chemical solids that settle to
the bottom of the clarifiers are scraped to a sludge sump
by the clarifier scraper mechanism.
Chemical Feeding
Lime is stored in two bins and is fed to two detention-
type slakers. Lime slurry is continuously pumped from
the slurry tank to a pipe loop around the plant and back
to the slurry tank in order to keep the lime is suspen-
sion. A slurry is prepared and fed to a lime slurry receiv-
ing tank on demand. Lime slurry is bled off the pipe
loop to the rapid mix basins where it is injected and con-
trolled by a pH feed back control loop.
Polymer solution, prepared automatically from dry
polymer, is pumped to a distribution panel in the
chemical sludge pump station where it can be distributed
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to feed points at the flocculation basins and first-stage
recarbonation.
to pH control loops. The recarbonated effluent flows by
gravity to the ballast ponds.
Recarbonation
The primary purpose of the recarbonation system is to
inject carbon dioxide (CO2) gas into the wastewater to
lower the high pH resulting from lime treatment. The
two-stage system with intermediate settling also provides
for maximum removal of calcium carbonate which
reduces the calcium and total dissolved solids (TDS) con-
tent of the water below that which would result from the
same pH reduction in a single stage. The intermediate
settling step also provides an additional minor reduction
of phosphorus.
The three sources of carbon dioxide for the recarbona-
tion system are (1) compressed stack gas from the boilers
in the digester building, (2) stripped gas from the oxy-
genation basins, and (3) an auxiliary 31-ton liquid car-
bon dioxide storage facility that supplements the first
two CO2 sources.
First Stage Recarbonation
The pH is reduced to approximately 10 in the first stage
recarbonation basin. This pH reduction occurs as a
result of the reaction of the carbon dioxide with the
hydroxyl alkalinity remaining from the lime treatment.
This reaction causes carbonates to be formed which react
with calcium ions forming a settleable precipitate,
calcium carbonate.
Effluent from the chemical clarifiers enters the first-
stage recarbonation basins through slide gates at the inlet
distribution box. Carbon dioxide is injected through
distribution headers in the basins and is controlled by
motorized valves positioned in response to pH control
loops. Polymer can also be added at the discharge end
of these basins to aid in conditioning the sludge for
settling.
Clarification
Effluent from first-stage recarbonation flows to the
recarbonation clarifiers. Calcium carbonate sludge settles
to the bottom of the clarifiers and is mechanically
scraped to the center hoppers and removed by the recar-
bonation sludge pumps located in the chemical sludge
pump station. Sludge is pumped to the chemical sludge
thickener with a portion recycled to the distribution box
of the first-stage recarbonation basins. The recarbona-
tion clarifiers are identical to the chemical clarifiers.
Second-Stage Recarbonation
The pH isNreduced to the normal range of 7 to 7.5 in
second-stage recarbonation. Carbon dioxide is
automatically applied to distribution headers in the
basins through motorized valves positioned in response
Filtration
It is the purpose of the filtration system to provide the
maximum water clarity achievable for several reasons:
(1) the discharge requirements specify that the mean
effluent turbidity shall not exceed 2 NTU; (2) filtration
ahead of carbon adsorption reduces the load of organics,
suspended solids, and colloidal matter reaching the car-
bon which increases carbqn efficiency and reduces car-
bon fouling; and (3) the effectiveness of disinfection by
chlorination is significantly improved by removing par-
ticulate matter containing entrapped viruses, bacteria,
and other chlorine-demanding materials.
Activated Carbon Adsorption
The filtered effluent flows directly to the granular
activated carbon columns. In biological treatment of
wastewater, dissolved organic materials are removed
including most of those measured by the BOD (bio-
chemical oxygen demand) test. However, biological pro-
cesses do not remove all of the undesirable organic
materials, as measured by the COD (chemical oxygen
demand) test. These materials include MBAS (methylene
blue active substancesprimarily from detergents),
herbicides, pesticides, tannins, lignins, ethers, proteina-
ceous substances, and other color and odor producing
organics. It is the purpose of the activated carbon
adsorption process to remove the organic materials
which are not adequately removed in the biological pro-
cess. Activated carbon adsorption also has the ability to
provide some removal of trace inorganics such as cad-
mium, chromium and silver. Activated carbon is
especially effective in eliminating taste, odor, and color
as a result of the above-described removal of organic
materials.
Removal of soluble organics is important for several
reasons: (1) the discharge requirements specify that the
mean COD shall not exceed 15 mg/1, and the mean
MBAS shall not exceed 0.15 mg/1; (2) the organic con-
tent of the reclaimed water should be minimized to
eliminate taste, odor and foam; and (3) the removal of
organics reduces the chlorine demand of the wastewater,
reducing the cost for effective disinfection.
Ammonia Removal
The carbon treated effluent flows to the clinoptilolite ion
exchange beds for ammonia removal. Clinoptilolite is a
naturally occurring mineral (zeolite) found in such areas
as Hector, California and Yuma, Arizona. The mineral
is mined and then crushed to a 20 x 50 mesh size
(similar to fine sand). Consequently, the clino beds
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located at the end of the waste treatment process serve
as polishing filters and remove carbon fines which would
otherwise pass out with the effluent reducing effluent
suspended solids and COD.
Four horizontal pressurized clino beds operate in
parallel. These beds are very similar to the filters. Nor-
mally, three beds are on line and the fourth is under-
going regeneration. The ion exchange beds operate in
two basic cycles: (1) service cycle which captures the am-
monium ions on the beds, and (2) regeneration cycle
which elutriates the captured ammonium ions from the
beds to a regenerant solution. During the service cycle,
the beds are "on line" and are part of the treatment
process. During regeneration, the beds are completely
disassociated from the main treatment process and are
part of the ion exchange bed regeneration system
(described in a following section). During the service
cycle, flow passes downflow through the beds. In
regenerating, the flow is reversed to an upflow direction.
All of the flow passing through the carbon columns
must pass through the clino beds during the service
cycle. The rate of flow or flow balance through the clino
beds is manually adjusted, if necessary, by the clino bed
effluent valves. Flow indication is provided at each clino
bed for balancing or adjusting flow rates.
Service cycle duration is determined by the number of
bed volumes treated and the ammonium ion concentra-
tion. The service cycle is considered to end when the
ammonia-nitrogen concentration in the effluent reaches a
"breakthrough" concentration of 2 mg/1.
Chlorination
Chlorine may be applied to the wastewater at four points
in the treatment process. These points are (1) plant head-
works, (2) effluent from the oxygenation basin (mixed
liquor), (3) C&CT effluent (prior to the ballast ponds),
and (4) final AWT effluent.
Chlorination at the headworks is a standby process for
odor control. Normal odor control is achieved by the
addition of hydrogen peroxide.
A chlorine feed point is provided to the oxygenation
basin mixed liquor lines to help control filamentous
growths and nitrification if needed.
Chlorination of the C&CT effluent is for control of
growths in the ballast ponds and filters and is used only
if necessary.
* AWT effluent Chlorination provides final disinfection
and reduces ammonia nitrogen concentration if necessary
to comply with waste discharge requirements. Chlorine
solution is injected into the 30-inch pipeline to the
disposal fields. Theoretical detention time at design flow
is 15 minutes.
There is one continuous chlorine residual analyzer. A
residual sample is taken from the plant effluent line
approximately 30 seconds from the point of chlorine
injection. The primary chlorinator receives a dosage
signal from this residual analyzer which also varies the
chlorine feed rate to maintain the set point residual.
Effluent Disposal Field
The plant effluent, still under pressXire, flows through a
30-inch pipeline to eight disposal fields located about
1,500 feet south of the treatment plant. These eight sub-
surface disposal fields are sized for an initial design flow
of 4.83 MGD under normal operation which includes at
least a 50-percent "resting" cycle. Treatment plant
operators determine the number of fields in operation by
referring to an application rate chart, manually selecting
the fields for operation, and setting a time which alter-
nates the fields from service to rest mode. Fields are nor-
mally alternated every 12 hours.
Organic Sludge Thickening
Waste activated sludge is pumped to the organic sludge
thickener for thickening prior to being fed to the
digesters. This allows the digesters to be operated with
longer hydraulic detention times which produces a more
stable digested sludge than would be experienced with
the less concentrated waste activated sludge.
The sludge will normally thicken to a 4 to 5 percent
solids. Thickened sludge is pumped from the thickener
to the digesters by two thickened WAS pumps. Superna-
tant overflows the thickener and discharges to the oxy-
genation basin.
Organic Sludge Digestion
Organic sludge digestion reduces the total mass of vola-
tile sludge by over 55% with most of the degraded
organic material being converted to methane and carbon
dioxide gas. The digesters handle organic sludges from
two major sources: (1) the settleable solids contained in
the raw sewage (primary sludge), and (2) the waste
activated sludge from the oxygen-activated sludge pro-
cess.
Thickened organic sludge enters the primary digesters
through eductors in the sludge recirculation lines. The
organic sludge includes thickened WAS, primary sludge
and primary scum. Each of the primary digesters is com-
pletely independent with a sludge recirculation system,
heat exchanger and gas mixing system. Normally one
primary digester will be maintained in an empty-standby
mode to be used for storage in the event of a filter press
outage.
Sludge flows by gravity from the primary digesters to
the secondary digester where the solids settle and
thicken, along with some additional solids breakdown.
The secondary digester has a floating cover for gas
storage. The thickened sludge is drawn off the bottom of
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the secondary digester and pumped to sludge dewatering
facilities, and the supernatant is drawn off and returned
to the plant headworks. Digester gas is used to fire
boilersthe flue gases of which are rich in CO2 and are
used in the recarbonation process.
Chemical Sludge Conditioning
Chemical sludges are thickened by gravity settling to
remove excess liquid prior to dewatering. The thickeners
also provide storage of chemical sludges.
Chemical sludge is produced at three points in the
treatment process: chemical clarifiers, recarbonation
clarifiers and regenerant clarifiers that are part of the
regenerant recovery system in the AWT building. These
sludges are pumped to the chemical sludge distribution
box and divided between the two thickeners. The sludge
will normally thicken to 10-12 percent solids. Thickened
sludge is drawn from the thickeners by the filter press
feed pumps.
Dewatering
A filter press system is used to dewater digested organic
and chemical sludge prior to land disposal. Digested
sludge is dewatered to about 45 percent solids. Chemical
sludge is dewatered to about 55 percent solids.
Digested sludge is drawn from the ready tank and
pumped to the filter press for dewatering by selected
filter feed pumps. At design flow, approximately 5 hours
of filter press operation daily is required for dewatering
digested sludge. Chemical sludge is drawn from both
chemical sludge thickeners by any filter feed pump.
Approximately three hours of filter press operation daily
is required for dewatering chemical sludge at design
flow.
The filter press consists of eighty 64-inch by 1.18 inch
thick chambers. Other pieces of equipment in the system
include: (1) a filtrate storage tank, (2) a filtrate measur-
ing weir, (3) a control panel, and (4) an acid storage and
wash tank.
The filter press system operates semiautomatically.
The control panel features allow for control of the com-
plete dewatering cycle in accordance with four subcycles:
Subcycle 1 (organic sludge supply cycle) low ready
tank level starts the sludge transfer pumping.
Subcycle 2 (organic sludge conditioning) the chemical
feeders and reaction tank mixer start when the sludge
transfer pumps are started.
Subcycle 3 (filtration) the filtration cycle is automatic
but is initiated manually by the filter press operator.
Subcycle 4 (discharge) filtration cycle is stopped auto-
matically and the operator initiates the discharge of the
cakes.
Upon manual initiation by the operator, all sludge
cakes are discharged and the unit is ready for another
cycle.
Filtrate from the dewatering process flows through a
weir box and into a filtrate tank, and then returns to the
rapid mix or oxygenation basins. The flow is measured.
When it reaches a preset low flow, the filtration cycle is
stopped and the operator is alerted.
Calcium carbonate buildup in the filter press must be
removed periodically by washing with dilute acid. _
Muriatic acid from the acid storage tank is diluted and
pumped through the filter press? The acid solution is
returned to the dilute acid tank for reuse.
Activated Carbon Regeneration
Granular activated carbon removes detergents, insecti-
cides, herbicides and various organic substances which
contribute to the taste, odor and color of the waste-
water. The carbon increases in weight and with con-
tinued use eventually becomes saturated and loses its
ability to further adsorb organic materials. The carbon
nearest to the inlet (bottom) of the carbon column
becomes saturated or exhausted first. As this occurs, the
exhausted carbon is removed for regeneration and is
regenerated. Previously regenerated or fresh carbon is
added to the top of the column to return the carbon bed
to its original depth.
The regeneration process restores the adsorptive
capacity of the granular carbon. Regeneration is accom-
plished by heating the carbon to temperatures in excess
of 1,700°F. The heat vaporizes, drives off and oxidizes
the impurities which have been adsorbed on the
carbonultimately restoring the carbon very nearly to
its original activity.
As the carbon in the bottom of a carbon column
becomes saturated with impurities and loses its capacity
to adsorb organics from the incoming wastewater,
approximately 10 percent of the carbon in one column is
withdrawn and discharged to a dewatering bin. Carbon
is transferred from one container to another in slurry
form. About one gallon of water per pound of carbon is
required to form a suitable slurry.
The dewatering bins are epoxy-coated to protect the
steel against the corrosive action of partially dewatered
carbon. It requires about 10 minutes for the free water
to drain from the carbon through the screened drains.
Because of the fine pore structure of the carbon, it still
retains 40-45 percent moisture after draining, which is
about optimum moisture content for thermal regenera-
tion. The partially dewatered carbon is transferred from
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one of the two dewatering tanks to the carbon regenera-
tion furnace inlet at the top of the furnace by means of
a variable speed, stainless steel screw conveyor at rates
which can be varied from 80-500 pounds per hour (dry
basis).
The carbon regeneration furnace is a gas-fired, six-
hearth unit rated at 3,825 pounds per day of dry carbon.
There are six burners, two each on Hearths 4, 5 and 6.
Temperatures on these hearths are independently con-
trolled within 10°F by an automatic temperature
controller. All hearth temperatures are recorded. Propor-
tional flowmeters on the burner air-gas mixture lines
ensure a constant percentage of excess oxygen. The oxy-
gen content of the furnace atmosphere must be limited
to avoid everburning of the carbon. Each burner may be
adjusted to maintain 0.5 percent oxygen by volume. In
addition, steam can be added to Hearths 4 and 6 to give
more uniform distribution of temperatures throughout
the furnace.
The carbon is moved across the hearths by four
rotating stainless steel rabble teeth which are oriented
vertically. The rabble arms are driven by a central shaft.
Cooling air is blown through the hollow rabble arms and
central drive column shaft. The exhausted cooling air is
ducted into the main exhaust stack. Furnace gases pass
from the top of the furnace through an afterburner and
enter the precooler and scrubber which eliminates odors
and dust from the exhaust.
The regenerated carbon is discharged from the bottom
of the furnace into a quench tank for cooling. There are
several pressure water jets" strategically located to keep
the carbon moving in the quench tank and pump suction
lines. The carbon slurry is pumped from the quench tank
by eductors to either of two transfer and de-fining tanks.
The carbon is washed in the de-fining tanks to remove
fines and then is ready for transfer back to the columns
for reuse.
Clinoptilolite Bed Regeneration
Clinoptilolite bed regeneration removes the ammonium
ions from the exchange sites on the Clinoptilolite media.
With periodic regeneration, the clino beds will effectively
and continuously remove ammonia nitrogen from the
wastewater. The ammonium ions are removed and
recovered from the spent regenerant so that the regener-
ant solution can be reused.
When the clino bed effluent ammonia-nitrogen con-
centration exceeds 2.0 mg/1, breakthrough has occurred,
and the bed must be regenerated. The regeneration cycle
.. is initiated manually or automatically. Automatic cycle
initiation is normally determined by the total flow pass-
ing through the bed since the last regeneration cycle. The
regeneration cycle involves over 30 completely automated
steps which must take place in the proper sequence.
Basically, the following steps occur during a regeneration
cycle: (1) surface wash, (2) backwash, (3) purge liquid
bed content to waste with regenerant, (4) ammonion
elutriation cycle, (5) purge regenerant solution to basins
with influent, (6) rinse bed to waste, and (7) return bed
to "on line" position or service cycle. The pressure
vessels which contain the clino beds are divided into two
compartments to reduce backwash flow requirements.
Only one-half of the vessel is backwashed at a time.
During elutriation, regenerant solution is passed
upflow through the bed in four phases. In each phase,
10 bed volumes of regenerant solution are passed
through the bed. The four phases of regeneration are
staged so as to initially produce a spent regenerant solu-
tion with a high ammonia concentration for later
recovery processes, and save the highest quality
regenerant solution for the last 10 bed volumes which
ensures maximum regeneration of the clino media. By
concentrating the ammonia-nitrogenin the spent
regenerant during the early phases of elutriation. The
total amount of regenerant solution passing through the
regenerant recovery system is significantly reduced.
The purge steps reduce the loss and/or dilution of
regenerant solution. The surface wash, backwash and
rinse steps serve the same function as for the filters.
Regenerant Clarification Process
Spent regenerant from elutriation is pumped from the
basin with the highest ammonia concentration, basin 4,
to the constant head box. Sodium hydroxide is added as
the spent regenerant leaves the constant head box to
raise the pH to approximately 11.4 in order to convert
the ammonium ions to ammonia gas.
Magnesium ions are also removed by the ion exchange
bed and are therefore present in the regenerant. The
regenerant solution must be clarified to remove the
magnesium hydroxide precipitate so that subsequent
clogging of (he clino media does not occur.
Flow from the constant head box is split equally to
two regenerant clarifiers. Magnesium hydroxide sludge
settles in the clarifiers, is allowed to thicken as much as
possible and is periodically blown down to the chemical
sludge thickener automatically. High pH clarified spent
regenerant flows from the clarifiers to the stripper
supply pumped from the wet well. The regenerant is
pumped from the wet well to the ARRP modules.
Ammonia Removal and Recovery Process
The Ammonia Removal and Recovery Process (ARRP)
is a closed-air-cycle system which strips dissolved am-
monia gas from the spent regenerant and reabsorbs the
ammonia gas in a sulfuric acid solution. Spent regener-
ant passes vertically down through the stripping tower
while a countercurrent closed loop air stream flows
upward. The ammonia-gas-laden airstream leaves the top
of the stripping tower and enters the bottom of the
absorber tower where the acidic absorber solution scrubs
the ammonia gas from the air stream, which returns to
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the bottom of the stripping tower for the next pass
through that tower.
The absorbed ammonia gas combines with sulfuric
acid in the absorber solution to form ammonium sulfate,
a common chemical fertilizer. A portion of this solution
is automatically pumped to the ammonium sulfate
storage tank when the ammonium sulfate reaches a
strength of about 40 percent. As the ammonium sulfate
is being blown down to the storage tank, 50 percent
strength sodium hydroxide is added to adjust the solu-
tion to near neutral pH.
Spent regenerant, after passing through the ARRP, is
then capable of being reused for elutriating ammonium
ions from exhausted clino beds. The recovered
regenerant that passes through the ARRP is low in am-
monia, approximately 30 mg/1, and is discharged into
Regenerant Storage Basin 1. This represents the highest
quality regenerant solution in the basins and is the regen-
erant solution pumped through the clino beds during the
last 10-bed volumes of that 40-bed volume regeneration
cycle. Sodium chloride brine is added to the regenerant
solution to make up for salt losses which occur during
the purge cycles and magnesium hydroxide sludge
blowdown.
Energy Consumption
During the evaluation of the various treatment processes,
much consideration was given to the efficient use of
energy and to the possible recycling of various consti-
tuents in the sewage.
In the case of the ammonia removal and recovery
system, ammonium sulfate is produced and is period-
ically removed from the plant by truck for use as a ferti-
lizer. It is also anticipated that a program will be
developed for use of the chemical sludge produced in the
lime treatment step on agricultural lands, although
agricultural lands are a considerable distance from the
plant. In this manner, the calcium carbonate and
calcium phosphate compounds which can have value to
certain agricultural soils will be returned to the land in
an environmentally aesthetic program.
The plant utilizes anaerobic digestion for the accu-
mulated organic solids. The methane gas byproduct of
this process is used for plant heating and may eventually
be used for reducing the plant electrical load require-
ment. Carbon dioxide produced from the burning of the
methane gas is used for the recarbonation processes
following lime treatment. The stabilized organic solids
will also be returned to agricultural lands if a market can
be found.
Comparisons were made of energy consumption for
the following processes:
Oxygen vs. air for biological treatment;
Ozone vs. chlorine for disinfection;
Chemical vs. electrolytic processes for the ammonia
stripping-recovery process; and
Incineration vs. land disposal for both organic and
chemical sludge.
On-site incineration and calcining were eliminated
from the plant as a result of these energy analyses.
Perhaps the most interesting of the various processes
used in the plant is the use of clinoptilolite, a natural
zeolite, and its regenerant recovery. Before the selective
ion exchange process was chosen, detailed consideration
was given to three other possible treatment processes for
nitrogen removal: biological nitrogen removal, break-
point chlorination, and ammonia stripping.
Considering the Truckee area climate, where winter
temperatures have dropped as low as -40°F, and the
anticipated loading variations, the ion exchange process
using clinoptilolite appeared to be the only process which
could reliably meet the 2 mg/1 total nitrogen discharge
standard. The key to the use of the ion exchange process
lies in the processing necessary for recovery of the spent
regenerant solution. The process is generally of little
value unless this solution can be recovered by removal of
the accumulated ammonium ions. Coincident with the
nitrogen removal study, the firm of CH2M Hill, of
Redding, California, designers of the T-TSA facility,
were in the process of the development of an ammonia
removal and recovery process (ARRP) which appeared
to fulfill this need. Pilot studies subsequently confirmed
that this new process complemented the ion exchange
process and offered numerous advantages over the other
three alternatives which had been previously considered
for recovery of the regenerant solution: air stripping,
electrolytic cells and steam stripping. Air stripping had
the significant disadvantages of freezing and low
temperature problems, calcium carbonate scaling and
discharge of ammonia into the atmosphere. Electrolytic
cells used to accomplish ammonia removal by breakpoint
chlorination had the significant disadvantages of high
electrical energy demand, high operating costs and
potential scaling of the electrodes. The steam stripping
process also had three major disadvantages: high energy
demand, use of high pH regenerant and associated
media clogging and attrition problems, and recovery of
only a very dilute ammonia fertilizer.
The new ARRP process appears to overcome these
disadvantages. Advantages include:
1) No freezing or air temperature limitations.
2) Scaling reduced to a minor maintenance item.
3) No discharge of ammonia or other waste product into
the atmosphere.
4) Low energy consumptionequivalent to normal ferti-
lizer production.
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5) Recovery of a valuable, concentrated, conventional
chemical fertilizerammonium sulfate.
6) Use of a 9-11 pH regene/ant with no media fouling or
measurable attrition.
Although the process requires the addition of caustic
soda (NaOH), and some makeup salt (NaCl), the offsite
energy and environmental effects were also considered to
be a positive factor. Caustic production requires consid-
erable offsite electrical consumption, but this offsite
energy consumption together with the internal plant
energy consumption attributable to ammonia removal is
still less than the amount necessary for equivalent
nitrogen fertilizer production using normal industry
methods. The process is also much less energy intensive
than other nitrogen removal processes.
Another rather unusual and interesting feature of the
T-TSA water reclamation plant is that even though the
.plant effluent is of very high quality, with virtually all
contaminants removed, current regulations still prohibit
it from being directly discharged into the receiving
waters of the Truckee River Basin. This requirement
came about because of the pristine quality of the
Truckee River in this vicinity and because it is the
primary source of the Reno, Nevada water supply. Con-
sequently, as a further precautionary measure, the
effluent is discharged into an underground disposal
system near the plant.
The combination of advanced waste treatment pro-
cesses and the underground disposal system is believed to
provide the best assurance possible of the protection and
preservation of this environmentally sensitive and
pristine receiving water.
Another unique teature in this treatment facility is the
use of a combination piping, electrical conduit, pedes-
trian and light-vehicle corridor which runs through the
center of the plant. This corridor was deemed necessary
to ease the operators' burden of maintaining and operat-
ing the numerous chemical feed lines during extreme
weather conditions. It also allows flexibility in the areas
of additions of future facilities. Two-way electrical light
vehicles facilitate the operators' movement through the
corridor from one end of the plant to the other, a
distance of nearly one half mile.
Architecturally, the plant was designed with the idea
of low maintenance, as first priority, coupled with an
environmentaly attractive appearance. Architectural
features include a combination of split face masonry
block, Corr-ten (self-rusting steel) on an extended man-
zard frame, and translucent panels in the larger
buildings.
As would be expected, an advance waste treatment
facility utilizing all of the previously described processes
and located in an extremely varied climate is expensive.
The construction bid for the plant was $19.2 million,
and the total project cost including the effluent disposal
system, a regional interceptor sewer, and other indirect
costs amounted to about $32 million. Current sewer use
charges for maintenance and operation of the regional
facilities for each dwelling unit are $7.50 a month, which
is minimal considering the high degree of wastewater
treatment and the protection afforded the surrounding
environment.
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Startup and Operation of the
Tahoe-Truckee Sanitation
Agency Advanced Wastewater
Treatment Plant
Thomas J. Kennedy, Plant Manager
Ossian R. Butterfield,
General Manager/Chief Engineer
Craig F. Woods, Operations Engineer
Introduction
The Tahoe-Truckee Sanitation Agency began operation
of its 18,300 cu m/day (4.83 MGD) advanced waste
treatment facility on February 1, 1978, and has com-
pleted the startup phase of plant operation. This report
details operations, problems, and plant performance dur-
ing startup. Because of the plant's overall complexity a
thorough discussion of its design features and design
parameters is beyond the scope of this presentation.
Briefly, the major sewage treatment processes
employed are as follows: Primary clarification; pure
oxygen activated sludge (Pressure Swing Adsorption);
lime treatment and chemical clarification for phosphorus
removal; two stage recarbonation with intermediate
calcium carbonate settling; mixed media filtration; acti-
vated carbon adsorption; ion exchange ammonia
removal using clinoptilolite; and disinfection. Sidestream
processes include sludge thickening; anaerobic digestion
of organic sludges; sludge dewatering using high pressure
filtration of chemical and organic sludges; thermal
regeneration of activated carbon; clinoptilolite regener-
ant recovery using chemical clarification and ammonia
stripping. The process flow diagram is presented in
Figure 1.
Sewage originates from the communities on the North
and West Shores of Lake Tahoe and along the Truckee
River Corridor from Lake Tahoe to Truckee, California.
The area's major industry is tourism which has two
primary seasons: the winter ski season and the summer
season. Heavy influx of tourists results in extremes of
sewage flows and loadings over holidays, weekends and
seasonal peaks.
Effluent from the plant is indirectly discharged to the
pristine receiving waters of the Truckee River and conse-
quently, the discharge limits (Table 1.) imposed upon the
Agency by the State Water Resources Control Board are
stringent, necessitating a very high degree of treatment.
Historical
The Tahoe-Truckee Sanitation Agency was formed on
1 May 1972 to carry out the mandate of the Porter
Cologne Water Quality Control Act, a California law
requiring the exportation of all sewage from the Lake
Tahoe Basin. The newly formed Agency's initial task
was to consider the design and construction of a regional
wastewater treatment facility that would result in the
replacement of existing interim facilities operated by its
member entities: the Tahoe City Public Utility District,
the North Tahoe Public Utility District (both located in
the Lake Tahoe drainage basin), the Alpine Springs
County Water District, the Squaw Valley County Water
District and the Truckee Sanitary District which are
located in the Truckee River drainage basin (Figure 2.).
The Agency is governed by a Board of Directors com-
prised of five appointed directors, one from each
member district.
Retention of the effluent in tne Truckee River Basin
was decided to be of primary importance in order that
the quantity of water available to downstream users not
be diminished by this project. It was also determined
that treatment of the wastewater to a high degree at a
plant near Truckee was the most economical solution
and that this plan had the least adverse impact on the
environment. Thirdly, the existing high water quality
standards required of the Truckee River could not be
adhered to by simply upgrading the existing treatment
plants. The State of California's rigid waste discharge
requirements necessitated the implementation of the
most highly sophisticated treatment available.
The project which was finally selected from many
alternatives studied required the construction of an inter-
ceptor line from Tahoe City to Truckee, California, the
construction of a 4.83 MGD advanced waste treatment
plant in Martis Valley near Truckee, California, and the
installation of an underground effluent disposal system
83
-------
84
-------
Table 1.
T-TSA Discharge Requirements
Constituent Units
COD mg/1
Suspended solids mg/1
Turbidity ntu
Total Nitrogen mg/1
Total phosphorus mg/1
MBAS mg/1
Total dissolved solids mg/1
Chloride mg/1
Total coliform organisms mpn/100 ml
10-Sample Daily
Average
15
2.0
2.0
2.0
0.15
0.15
440
110
Maximum
40
4.0
8.0
4.0
0.4
0.4
23
TRUCKEE
SANITARY DISTRICT
TTSA WATER
RECLAMATION PLANT
Dollar Point
NORTH TAHOE
P.U.D.
Figure 2
T-TSA Service Area
at a total cost of $32 million. Full tertiary treatment,
including maximum removals of nitrogen and
phosphorus, was deemed necessary to protect the quality
of the Truckee River into which the effluent would
ultimately find its way after percolation into the per-
meable glacial out wash soil near the plant. This would
ensure the safety and integrity of this primary water
source for Reno, Nevada, a major city 48 km (30 miles)
downstream.
Studies of the background concentration of pollutants
in the Truckee River revealed that the critical pollutants
were total nitrogen and total phosphorus. These were
determined to be the most difficult contaminants to
remove; other pollutants could easily be removed by
proven processes. The primary goal of process design
was to ensure that the treated effluent, when mixed with
background concentrations existing in the river, would
not violate the river standards even if discharged directly
into the river. Percolation into the Martis Valley soils
would provide an additional treatment factor where a
residence time in the soil of about 150 days would be
experienced, and the effluent's mixing with natural
groundwater moving through the soil would result in
additional dilution of its residential pollutants.
Startup
The facility was accepted for operation on February 1,
1978, with several major incomplete, faulty or untested
systems including the secondary digester, the filter press
and the ion exchange system. Sewage was accepted at
that time on a limited basis from an interceptor connec-
tion from the Truckee Sanitary District in order to deter-
mine if the plant could be operated on a sustained basis.
Flow from the one source was estimated to average 190
cu m/day (0.5 MOD).
Seed activated sludge was trucked from a nearby
facility in Nevada operated by the Incline Village
General Improvement District. A two-foot snow storm
following the first day of sludge hauling prevented fur-
ther addition of seed sludge to desired levels. Never-
theless, activated sludge did develop rapidly and reached
an acceptable mixed liquor suspended solids concentra-
tion after two weeks of operation, even with the influent
sewage temperature being in the range of 4 to 6°C.
Empty clarifiers during startup detained the passage of
partially treated sewage through the plant. Use of the
emergency retention basin (ERB), which has a capacity
of 57,000 cu m (15 MG), further delayed startup of the
advanced waste treatment (AWT) facilities and the pro-
cessing of sewage through them for over three weeks.
Potable water remaining in the plant from the contrac-
tor's systems checkout was processed through AWT
prior to the passage of sewage and provided additional
systems testing experience.
All sewage was comminuted and degritted and sent to
aeration after primary clarification. All primary sludge
was pumped to the oxygenation basins during the first
-------
several weeks in order to build up the activated sludge
solids as fast as possible. Anticipated problems from the
primary sludge were encountered but were offset by the
advantage of the rapid buildup of activated sludge
solids.
The partially treated sewage from the secondary
system was given full chemical treatment with lime and
recarbonation and pumpedjo the. emergency retention
basin to be reprocessed after the biological population
had developed in the secondary system.
During the beginning of March an unexpected prob-
lem was encountereda severe algae bloom in the emer-
gency retention basin. Reprocessing of this water
resulted in the only period of operation to date during
which"the final effluent suspended solids concentrations
and turbidities were above discharge limits. No further
bypasses to the ERB were permitted until it could be
fully drained and dried. Subsequent use of the ERB has
been restricted to bypassing only during major process
failures or outages which have been infrequent.
Additional sewage flows from the remaining member
districts were permitted into the plant beginning
February 17. By March 1, the plant was accepting flow
from all scheduled sources. Severe infiltration problems
from snowmelt were detected during the latter part of
February and continued through April as evidenced by
high sewage flows (Figure 3.) and low sewage strengths.
During Easter week, flows in excess of the design capac-
ity of the plant were encountered with a peak seven day
average flow of 18,000 cu m/day (4.8 MGD). This week,
traditionally the last major ski week of the season, was
unseasonably warm and resulted in coincident peak
flows from the large tourist population and from heavy
infiltration. Infiltration is a local district problem which
each district must individually correct. Because of flow
limits allocated by the State Water Resources Control
Board to each district which must include accounting for
infiltration, the two major districts located in the Tahoe
Basin have enacted self-imposed building moratoriums
on their districts until their infiltration problems can be
substantially reduced
5.0
Flow (MGD)
3 -» M W t
3 b b b e
<
(
)
i
t
DESIGN FLOW= 4.83
I
' 1
* \ '
1 '
Feb Mar Apr May Jun Jul Aug
Month
Figure 3
T-TSA Monthly Average Flow
Conventional Treatment
Following the development of a healthy activated sludge
population, the secondary treatment system as well as
the entire conventional treatment process have achieved
their design objectives with the exception of two brief
periods.
The first period occurred as the ski-tourist season
ended and raw sewage loadings diminished. With all
four oxygenation trains in service, aerator loadings
reduced to less than 0.2 kg BOD/day/kg MLVSS (0.2
Ibs. BOD/day/lbs/MLVSS) and resulted in over-
aeration, frothing and secondary clarifier solids losses to
a maximum of 57 mg/1. Removal of two oxygenation
basin trains from service had the problem under control
in less than one week. No nitrification was observed dur-
ing the period nor during any period to date. Chemical
treatment and advanced waste treatment effectively con-
trolled the problems associated with the secondary solids
carryover maintaining final effluent suspended solids and
COD within discharge limits.
The second period was of slightly longer duration and
resulted from a more severe problem. Failure of the
filter press to dewater adequate quantities of anaero-
bically digested sludge caused massive recycling of
digested solids to the primary clarifiers and at one point
virtually eliminated the ability to waste activated sludge.
Carryover of the digested sludge from the primary tanks
with their high sludge blankets to the activated sludge
system together with large quantities of solids in the
secondary system saw the secondary effluent quality
gradually deteriorate. A concerted effort was made to
rectify the filter press problems and to operate the filter
press dewatering digested sludge all available hours.
Outstanding dewatering performance by the filter
press following repairs rapidly reduced the solids inven-
tory in the conventional treatment system and enabled
the process to once again achieve its design objectives.
Also during this period, chemical treatment and
advanced waste treatment processes were able to reduce
the final effluent SS and COD below discharge limits.
Average performance of the conventional treatment
process in terms of several major pollutants can be
ascertained from Table 2. Secondary effluent nitrite and
nitrate concentrations have never exceeded 0.1 mg/1.
Activated sludge settling characteristics as measured by
sludge volume index (SVI) typically have been in the
range of 70 to 100 with a maximum SVI of 140 and a
minimum of 60 being observed.
Incorporated into the design of the pure oxygen
activated sludge process was a feature in which pure
oxygen is added only in the first two stages of the three
stage aeration system. In the third stage, atmospheric air
is drawn in to allow carbon dioxide dissolved in the
mixed liquor to.be stripped and captured for utilization
in the subsequent recarbonation processes. Experience to
date has shown that during periods of low organic
loading, bicarbonate alkalinity will increase or only show
a slight reduction across the third stage. Only during the
86
-------
Table 2
Plant Performance (6 month averages;
Process
Stream
Raw
Primary eff.
Secondary eff.
Chem. clar. eff.
Filter eff.
Car. col. eff.
Final eff.
Discharge
Requirement
Overall
Removal (%)
Table 3.
Chemical Treatment Relationships (summer)
ss
(mg/l)
156
120
16
17
2.8
2.8
1.3
COD
(mg/l)
338
57
26
15
12
T.N.
(mg/l)
32
34
28
25
3.7
T.P.
(mg/l)
10.5
8.7
4.9
0.7
0.3
2.0 15 2.0 0.15
99.2 96.4 88.4 97.1
pH Alkalinity Calcium Total P Ortho P
(mg/l) (mg/l) (mg/l) (mg/l)
6.8
7.2
7.0
11.1
10.3
7.3
351
240
216
305
223
191
38
85
51
31
___
6.35
0.80
0.64
0.24
5.78
0.05
0.53
0.21
Process
Stream
Mixed liquor
2nd stage
Effluent channel
Secondary Effluent
Chem. clar. eff.
Recarb. clar. eff.
Final eff.
height of the summer tourist season did significant alka-
linity reductions of 100 mg/l or more occur (Table 3).
Carbon dioxide analysis of the off-gases supported this
finding. Because of the low carbon dioxide concentra-
tions, the off-gases from this process have not been
routinely utilized in recarbonation. Perhaps as sewage
loadings increase in the future, this feature may become
practical.
With respect to the Pressure Swing Adsorption (PSA)
pure oxygen generation system, there have been no signi-
ficant operation or maintenance problems.
Chemical Treatment
A wide range of lime dosages as controlled by pH set
points from 10.8 to 12.0 and a variety of organic
polymers have been tried in the plant as well as in exten-
sive laboratory tests. Experience has indicated that
removals of phosphorus (P) to a level below 0.2 mg/l as
P in the chemical clarifiers is virtually impossible at any
lime dosage, polymer concentration, or polymer type
except at very low clarifier overflow rates, whereas pH
set points of 11.0 to 11.2 consistently yield chemical
clarifier effluent phosphorus concentrations of 1.0 mg/l
or below, even at the highest overflow rates experienced
with one of the two clarifiers out of service. This
residual can readily be removed by 5-15 mg/l of alum
applied ahead of the mixed media filters provided the
pH of the water to the filter can be kept below 7.5.
Presently, this mode of operation with a lime dosage pH
set point of 11.0 to 11.2 is used along with alum
treatment.
A pH set point of 10.8 or above has been found to be
very effective in removing soluble ortho P. However,
turbidity in the chemical clarifier effluent contains
chemically precipitated phosphorus which readily reverts
to soluble ortho P in recarbonation as the pH of the
water is lowered (Table 3.). Increasing the pH set point
above 10.8 results in less and less turbidity carryover
with sparkling clear effluents produced above a pH set
point of 11.4. As the pH set point is raised, however,
more lime is used, more soluble* calcium is carried over
to recarbonation, and more turbidity is created through
recarbonation. For the slight amount of additional
phosphorus removal at a higher pH set point, the
accelerated requirements for lime do not prove cost
effective.
A variety of pH set points have been tried for control
of the first stage recarbonation process. Reduction of
soluble calcium (Ca) to a level of 40 mg/l as Ca has
been the lowest achievable on a consistent basis. A pH
set point of 10.1 to 1.04 has been required for this.
Reduction of the pH set point below 10.0 has resulted in
higher calcium concentrations as the result of the forma-
tion of soluble calcium bicarbonate.
The first stage recarbonation reaction which forms cal-
cium carbonate appears to be time dependent. It has
been consistently observed in the recarbonation clarifiers
that the water in and near the clarifier center ring is
clear and that a cloud of turbidity develops toward the
outer periphery of the clarifiers. Consequently, polymer
treatment in the recarbonation clarifier has been ineffec-
tive and has been abandoned.
Because of the formation of turbidity in the outer
reaches of the clarifiers, considerable turbidity is carried
over the weirs during high flow periods. Operation of
the lime treatment system at pH set points of 11.0 to
11.2 minimizes the soluble calcium entering the recar-
bonation system, and, hence, minimizes the effects of
turbidity losses from the recarbonation clarifiers.
Control of the pH in and following second stage
recarbonation has been the plant's foremost problem.
Addition of carbon dioxide in excess of several times the
stoichiometric amounts during numerous peak flow
periods has failed to reduce the effluent pH below 8.0.
Several possible reasons postulated for this phenomenon
relate to the low atmospheric pressure at the 5900 foot
elevation of the plant; poor transfer efficiency in the
basins; carbon dioxide stripping resulting from the high
volumes of dilute boiler off-gases having 6-12% carbon
dioxide content which are used; and to the low efficiency
of the second disassociated hydrogen ion of carbonic
acid.
-------
Temporary facilities for adding concentrated sulfuric
acid to the ballast ponds to reduce the AWT influent pH
to 7.5 or below were installed during the middle of
August. A permanent facility has been designed and will
be installed in the near future. Since mineral acid addi-
tion was implemented and pH control to AWT attained,
the effluent from the plant (for a continuous period of
over 30 days at this writing) has not exceeded its
discharge limits for SS, COD, Total P or Total N.
The importance of pH control to AWT is apparent
when the following facts are considered:
The effectiveness of alum in removing phosphorus is
diminished considerably as the pH exceeds 7.5.
The effectiveness of carbon adsorption in removing
COD decreases with increasing pH.
As pH increases more and more ammonium ion
reverts to non-ionized ammonia which passes through
the cation exchange media to the effluent unchanged.
Additional ammonium ion previously taken up by the
media can also be reverted to the non-ionized form and
be rejected from the media.
The chemical treatment system as a whole has unques-
tionably been the most troublesome with respect to
maintenance. Major problems have included:
Frequent blockages in transfer lines in the dry lime
system from lime fines or coarse rejects resulting in
intermittent periods of failure to dose lime.
Inefficient lime slaking requiring excess quantities (up
to 50%) of lime to be dosed.
Ineffective removal of grit from slakers causing severe
abrasion of piping, valving and pumps and requiring
replacement of valving, rotors and stators after less than
6 months operation; also forming deposits in clarifiers
and thickeners which cause tank mechanisms to trip out
from over-torque and which result in frequent blockages
of sludge withdrawal lines.
Formation of calcium carbonate scaling on clarifier
launders and sludge pump impellers, and deposits of
chemical sludge in connecting structures, recarbonation
basins and ballast ponds.
Insufficient pH control with carbon dioxide during
peak flows.
High costs due to large quantities of lime and liquid
carbon dioxide required and to excessive maintenance
problems.
Solids Handling System
Anaerobic Digesters. Since primary sludge solids were
recycled to the aeration tanks during the first three
weeks of startup, the startup of the digester system was
initially delayed. Furthermore, as activated sludge solids
built up, additional aeration trains were put on line
delaying considerably the time before any waste
activated sludge was available to be pumped to the diges-
tion system.
One primary digester filled with water and heated to
32° C was put on line when primary sludge was first
wasted. Intermittent feeding was used so that the con-
tents could be recirculated after being continously fed
for a period of time but allowed to settle before re-
feeding. Extensive rework to the floating cover of the
secondary digester by the contractor prevented its use.
Overflow from the primary digester was returned to the
plant headworks. As the waste solids quantities
increased, the second primary digester was put in service.
Each digester was alternately fed.
Within several weeks, gas was being generated and
flared. Shortly thereafter, the secondary digester became
available and was put into service. Extensive problems
with rag accumulations in the heat exchangers and with
insufficient steam supply to the heat exchangers caused
erratic temperature control and consequently intermittent
periods of foaming and low pH. At one point lime addi-
tion for over one week was required before pH control
could be regained.
Gas production and volatile solids reduction to date
have been good.
Filter Press. The filter press was plagued by startup
problems resulting almost entirely from the feed pump-
ing system. Feed pump rotors and stators were found to
be frozen to each other and were destroyed during initial
testing. Problems were also encountered with the
hydraulic drive system for the pumps. Chemical sludge
dewatering was given priority whenever the filter press
was usable as the chemical sludge would form an
umpumpable paste if allowed to settle for any extended
period of time. One problem followed another until
three months after startup when the plant had a reliable
system. Minimal amounts of digested sludge had been
dewatered, and digested and raw sludges accumulated
within the plant.
A further complication to removing dewatered solids
from the plant was the fact that the solids were removed
by a scavenger to a local landfill, precluding night
pickup and seven day per week operation.
Recently, the filter press has worked quite well as
indicated by the performance data presented in Table 4.
Initial poor experiences with improperly conditioned
digested sludge, necessitating time-consuming manual
cleaning of the filter media, prompted the operators to
devise a scheme to reduce this problem. Their present
practice is to precoat the media with chemical sludge
which dewaters readily without conditioning and then
add the conditioned digested sludge. Even if the digested
sludge is improperly conditioned, the cake will release
and require little if any medial cleaning.
88
-------
Table 4.
Table 5.
Filter Press Performance
Feed solids
Range (%)
Dewatered solids
Range (%)
Average (%)
Design (%)
Chemical
Sludge
6-20
52-66
58
55
Digested Combined
Sludge Sludge
2.8-3.6
39-52
46
35
43-54
49
Advanced Waste Treatment
Mixed Media Filtration. Removals of suspended material
across the mixed media filters has been consistently
good. Neither addition of alum nor polyelectrolyte to the
filter influent have proven effective in either increasing
the length of filter runs or in reducing filter effluent tur-
bidity. Addition of either chemicals alone or in combina-
tion typically results in increased filter head loss and
consequent shorter filter runs between backwash. Addi-
tion of alum has been required, however, for supple-
mental phosphorus removal. Average filter effluent SS
and COD are presented in Table 2. Higher than expected
SS concentrations have resulted from alum treatment of
high pH water and from high alum dosages.
Activated Carbon Adsorption. The activated carbon
adsorption column operation has been troublefree, and
the removal process has worked consistently well in
removing COD and MBAS. Indications of COD
breakthrough were initially diagnosed as being attri-
butable to exhausted carbon and the regeneration pro-
cedure initiated three times to date. During each
regeneration procedure, 20% of the carbon in each car-
bon column was removed, regenerated and replaced.
This was done contrary to the design recommendation of
10% carbon withdrawal because of problems in furnace
operation during the first two regenerations which
extended the regeneration process over long periods.
During the third regeneration procedure, 20% carbon
regeneration was again undertaken as the peak summer
tourist season was approaching and because the
regeneration process was performing so well.
In retrospect, it is now felt that the preliminary indica-
tions of COD breakthrough in carbon column operation
were attributable to high pH water reducing carbon
removal efficiency rather than to completely exhausted
carbon columns.
Because of the low frequency of regeneration, the
scant data accumulated to date regarding carbon
removal efficiency and carbon attrition, as presented in
Table 5, are susceptible to considerable errors, especially
when considering that twice as much carbon as recom-
mended was regenerated each cycle and that the actual
Activated Carbon Adsorption, System Performance
Average C.O.D. Carbon Usage Performance
Contact Final Overall fk. ron «mov«H
Exhaustion Time Eff. Removal (kg COD removed)
Cycle (min.) (mg/l) (mg/l) (mg/l) (Ibs/mg) (kg carbon spent)
47 11.3 13.2 52
#2
#3
45
11.3
13.1
14.0 57
431
473
0.26
0.25
state of exhaustion was unknown prior to regeneration.
Extensive carbon makeup during the first regeneration
procedure due to unknown losses associated with the
defining of the original carbon; the bedding of the fur-
nace; and significant burning of carbon during the initial
regenerations prevents use of preliminary data.
Average COD removals through the carbon columns
for the first six months of operation are presented in
Table 2. Location of the ion exchange beds with their
fine-mesh media following the carbon columns has
proven effective in reducing losses of carbon fines. Fines
which represent both SS and COD are continuously
washed out of the carbon colunmns in low concentra-
tions and are washed out in high concentrations during
the regeneration procedures.
Ion Exchange. In terms of achieving design objectives
and in meeting effluent discharge requirements, the ion
exchange system was the poorest performing system dur-
ing the first five months of startup. The type of system
employed has never been tried on a full scale, so con-
siderable startup problems were anticipated. Addition-
ally, this system was in the least-constructed state of the
main stream process when the plant began operation,
and further compounding the problem were the higher
than anticipated ammonia loadings during the peak
summer season and the pH control problems previously
described.
Unquestionably, the ion exchange beds have been
effective in removing ammonium ion to desired concen-
tration levels as well as carbon fines. Recent data (Table
6), however, suggests that the exchange capacity is either
below design requirements or has substantially
deteriorated. This matter is presently under thorough
examination. Had regeneration been able to keep pace
with exhaustion, effluent standards could easily have
been met with respect to total nitrogen
Realizing mat the removal capacity of the ion
exchange system was below actual loadings, supple-
mental ammonia removal in the form of breakpoint
chlorination was employed beginning in mid summer. As
the chlorine system was limited to a maximum dosage of
454 kg/day (1,000 Ibs./day), the breakpoint chlorination
procedure was used only when operator analysis of the
clino bed effluent ammonia nitrogen showed chlorine
requirements for total breakpoint chlorination to be
within the limit of the system. Careful control of the
clino system, coupled with extensive monitoring by
89
-------
Table 6.
Tabte 7.
Ion Exchange Bed Performance (summer)
Design Actual
Flow to Exhaustion
cu m/bed 6100 3000
(mil. gal./bed) (1.62) (0.8)
Time to regenerate
hours/bed 6.95 7.8
Regeneration capability
beds/day 3.45 3.0
Inf. NH3-N
mg/1 24.0 30.2
NH3-N loading
Kg/bed/cycle 127 91
(Ib./bed/cycle) (280) (201)
Design flow loading
Kg NH3-N/day 439 552
(Ib. fcIH3-N/day (966) (1217)
Removal capability with all
available beds
Kg NH3-N/day 439 281
(Ib. NH3-N/day) (966) (619)
Removal capability at design flow
% NH3-N removed 100 50.9
operators, has enabled the combination of ion exchange
and breakpoint chlorination to reduce total nitrogen to
within discharge limits. Recent low ammonia loadings on
the clino system hve reduced the need for supplemental
breakpoint chlorination.
Studies related to shortening regeneration cycles and
multiple bed regeneration are presently underway to
determine if the existing system can be modified to pro-
vide removal of design loadings without substantial
capital improvements.
Problems limited to the exchange beds themselves have
been few but significant. Butterfly valves which failed to
properly seat in the high pressure system have caused
either brine leakage to the effluent or process water
leakage to the brine basins necessitating blowdown from
the basins to restore proper levels. Inefficient purging of
the brfne from the beds following regeneration also has
caused excessive brine losses.
Brine loss to the final effluent has been found to be
related to frequency of regeneration rather than process
flow. Since the required frequency of regeneration
exceeds the design capacity of the system, regeneration is
continuous, and brine loss is fairly consistent on a day
to day basis. Consequently, as flow decreases, final
effluent total dissolved solids (TDS) increases. A labora-
tory study using week long composite samples of raw
sewage and final effluent during a period in which the
sewage flow to the plant averaged 8,300 cum/day (2.2
MOD) showed that the TDS increases of final effluent
Ion Analysis to Determine Extraneous TDS Sources.
(samples composited over a period of one week during which sewage
flow averaged 8300 cu m/day (2.2 mgd)
Raw Final
(mg/1) (mg/l)
Cations
Ammonium (as NH4+) 27 .3
Calcium
Magnesium
Potassium
Sodium
Total cations
Anions
Bicarbonate (as HCO3-)
Chloride
Phosphate (as PO4-3)
Sulfate (as SO4-2)
Total anions
Sum of cations/anions
Tot. dis. solids
27
25
3
11
50
116
178
50
8
25
261
377
205
37
2
11
278
328
290
252
0.08
55
597
925
725
over raw sewage result mainly from sodium, chloride,
and bicarbonate ions (Table 7.).
No abnormal scale deposits have been found within
the beds on structures or on the media. However, accu-
mulations of scale have been found in the backwash line
which also carries the final rinse waters after most of the
brine has been purged.
The presence of high calcium concentrations and high
pH in the brine and the presence of high bicarbonate
alkalinity in the process water are conducive to calcium
carbonate formation at any point where brine and pro-
cess water interface.
The ammonia removal and regenerant recovery system
has been plagued by bizarre problems, most noteworthy
of which has been calcium carbonate formation in pipe-
lines, pumps, spray nozzles and stripping media. Scale
formation during the first few months was extremely
severe and rapid, necessitating nozzle and pump
impleller cleaning in hydrochloric acid as frequently as at
two week intervals. Reducing free fall from the regener-
ant clarifier weirs by addition of standpipes in the
discharge pipe and sealing of the regenerant clarifiers'
coverplates to reduce absorption of carbon dioxide from
the air have considerably reduced the scale problem. The
effect of temperature on the solubility of calcium car-
bonate, however, has not yet been ruled out as a major
factor in scale formation.
Most of the scale deposits on the media in the strip-
ping towers occurred on the top few inches of the media.
Twice the top few inches of media were removed for
acid cleaning. On July 11, a temporary acid feed and
recirculatin system was set up to acid clean the entire
stripping systempiping, pumps, nozzles and media.
Approximately 1,000 gallons of concentrated
90
-------
hydrochloric acid were added to the system before the
neutralization reaction slowed down. A permanent acid
wash system has been designed and will be installed in
the near future.
A second significant but less complicated problem has
also occurred in the absorber system. In the absorber
system ammonia laden air from the stripping tower is
blown through media being sprayed with an acidic solu-
tion, sulfuric acid in the solution is to absorb the
ammonia as well as moisture to form an acidic solution
of ammonium sulfate having a concentration below its
saturation value. However, the absorption rate of water
has been less than predicted resulting in severe crystaliza-
tion of ammonium sulfate within the media, piping and
pumps, reducing the efficiency of air flow or absorber
recirculation and, hence, reducing overall removal of
ammonia. Pursuant to discovery of this problem,
operators have been instructed to monitor the specific
gravity of the solution daily and to add dilution water
when necessary to keep the solution slightly below satu-
ration.
Table 8.
Regenerant Brine Characteristics (after 6 months operation)
Cesium
Rubidium
Potassium
Sodium
Calcium
Aluminum
Magnesium
Concentration
(mg/1) (meq/1)
0.004 neg.
0.005 neg.
1400 36
9250 402
4000 200
1.5 0.2
9.2 0.8
Brine Strength 2.3% as sodium chloride
Table 9.
Chemical Costs (6 month averages)
Process
Product
Dosage Treatment Cost
(mg/l) C/cu m C/1,000 gal.
Boilers
Phosphorus
Removal
($5.37/lb.
P-removed)
Ammonia
Removal
($0.95/lb.
N-removed)
Fuels
Lime
Liquid CO2
Alum
Polymer
Total
Salt
Caustic soda
Sulfuric acid
Liq. chlorine
Total
449
192
24
1.4
153
153
91
12.5
2.5
3.3
1.0
0.3
0.8
5.4
0.6
3.1
.5
.3
4.5
9.4
12.7
4.0
1.0
2.9
20.6
2.4
11.7
1.8
1.1
17.0
A recent analysis of the brine solution to determine
the concentrations of impurities which build up after
prolonged recycling is presented in Table 8. The cations
are listed in the table in order of exchange preference by
the clinoptilolite. The low concentrations of cesium and
rubidium which are preferentially selected by clinop-
tilolite are indicative of their relative absence in the
sewage. Buildup of calcium to high levels has been anti-
cipated. Removal of calcium could be accomplished
simply, but at considerable expense, so it is not
practiced. The overall effects of the high calcium con-
centrations will, however, have to be studied in much
greater detail.
Costs
Operation and maintenance costs for each unit process
have not been determined because of the overall com-
plexity of the treatment plant and the limited metering
equipment from which to base cost. Additionally, the
startup phase of operation required considerable experi-
mentation which would not prove cost effective on a sus-
tained basis.
Since the use of chemicals in the plant is so extensive
and a major portion of the annual budget, average usage
and resulting treatment costs of the high-use chemicals
have been summarized in Table 9 with respect to
phosphorus and ammonia removal. Boiler fuel costs
have been included, since all flue gas is used as a source
of carbon dioxide in the recarbonation process. Boilers
are used only to supply heat and air conditioning for
buildings and for maintaining mesophilic temperatures in
the anaerobic digesters.
The dosages presented are average and probably con-
siderably higher than optimum. As operation of the
various chemical treatment processes as well as all other
processes stabilizers, more meaningful costs will be
generated.
91
-------
Table 10. Summary
Plant Performance (last 30 days) The Tahoe.Truckee Sanitation Agency's advanced waste
Flow ss COD T.N T.P treatment plant has completed its startup phase of opera-
(mVd) (mgd) (mg/i) (mg/1) (mg/l) (mg/i) tion. Many operational problems were encountered and
Raw sewage 10,200 2.69 199 435 39.2 10,5 solved while others, which are more complex, are under
Final effluent 05 88 08 012 study. Major problems affecting overall plant perform-
rysch e ance in meeting all discharge standards with the excep-
10 inn A a-* *, n ,* n -, n nic l^on °f T°S and chlorides due to brine losses are
requirement 18,300 4.83 2.0 15.0 2.0 0.15 ,,.,,,, , , ,
believed to have been brought under control. Recent
Ovcrsll
plant performance (Table 10) has been exceptionally
removal W - - 99.8 98.0 98.0 98.9 goodi and it is anticipated that future performance will
continue to be good and provide a product water
exceeding the quality required by the plant's discharge
requirements.
92
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Tertiary Treatment of
Biologically Purified Waste
Waters Aimed at Their
Recycling in the
Production Processes.
Yu. M; Latyshev, V.I. Zavarzin
Moscow, "NIOPIK"
(Scientific Research Institute for
Organic Intermediates and Dyestuffs).
Rapidly developing branches of the USSR chemical
industry resulting in the increasing amounts of waste
waters polluted with different chemical products as well
as the water quality standards getting more rigid and
strict with every coming day make it necessary to take to
various and new treatment techniques, some of which
permit to reuse the treated waters in the production
water cycle.
This paper describes the tertiary waste water treatment
system at the "Pigment" enterprise in the city of Tam-
bov. The waste waters are biologically pretreated. The
authors present optimal after-treatment parameters; the
treated waters can be recycled in the closed water supply
system of the enterprise.
The tertiary waste water treatment at this enterprise
comprises the following technological stages:
1) filtration,
2) desalination,
3) ozonization.
The total amount of waste waters including those
from the shops already used today as well as those to be
commissioned in the nearest future, all of them subject
to biological treatment, will come to 5000 m3/day.
All biologically pretreated waste waters, with their ter-
tiary purification completed, can be recycled to the
production processes.
The tertiary treatment system receives waters from
biological treatment facilities. These waters meet the
following requirements:
Actual Data "VNIIVODGEO" Standards
Temperature, °C
Suspended
matter, mg/1
Oils and resin-
formers, mg/1
Odour, in balls
pH
Hardness
Total salt
content, mg/1
Chlorides, mg/1
Sulphates, mg/1
Permanganate
oxidation,
mg O2/l
BOD,,
up to 25
35-40
up to 3
7.5-8.5
6.9
up to 1500
105
468
48-52
15-20
25-40
up to 20-30
up to 10-20
up to 3
7.2-8.5
7
up to 1300
150-300
350-500
10-15
up to 15-20
It is obvious that after their biological treatment these
waste waters do not meet the standards in the following
parameters:
suspended matter,
total salt content,
permanganate oxidation.
To provide these waters with the qualities required by
the official standards the enterprise uses the tertiary
treatment system, including filtration, desalination and
ozonization, upon which they are recycled to the produc-
tion processes.
93
-------
The flow diagram of this tertiary treatment system is
shown in Fig. 1.
Filtration of Waste Waters Before Their Desalination
From the secondary biological treatment facilities the
waste waters are pumped (following Scheme la, b) into a
tank* (Scheme 2) wherefrom they go to cartridge filters
(following Schemes 3a, b and 4a, b), the filters are of
the type PAP 80-248; they work on some auxiliary
material such as filterperlite. Lavsan sleeve cloth of the
type TG-519 is used as the filter partition. The filterper-
lite suspension is prepared upon the offered scheme (7).
The volume of the suspenzator is 159% larger than that
of the pipeline and the filter body. To make one layer of
filterperlite for one operation it is necessary to take 40
kg of perlite as 0.5% suspension. Filtration is accom-
plished with a perlite as 0.5% suspension. Filtration is
accomplished with a perlite feed of 100 g/m3 of waste
waters. The filtration efficiency is 500 l/m2/h; the time
necessary to make one layer is 0.5 h; the working cycle is
5 hours; residue disposal and filter regeneration take half
an hour.
Perlite is fed to the suspendator pneumatically. The
filterperlite suspension is directed to the filters by pumps
(Scheme 5a, b). We use a 2% suspension prepared as
described in Scheme 8 and pump it to the filter (Scheme
6a, b). After each cycle the filter is washed with hot
water (70-80°C), about 3 m3 per each cycle.
The sludge suspension from the residue disposal and
filter regeneration is collected in a special collector
(Scheme 9) wherefrom it is pumped to the sludge pond
(Scheme 10).
The filtrate containing up to 5 mg/1 suspended matter
with particles of 1 mkm enters the filtrate tank (Scheme
II).
Desalination
After filtration the waste waters containing up to 1.5 g/1
salts are pumped to a dialyzer (Schemes 12a, b and 13).
The electrodialyzer is made of equal numbers of
deionization and concentration chambers which make a
sequence of packets bait-tightened with one another. The
upper and lower parts of the packets contain electrodes
through which some direct current voltage is supplied.
Heterogenic membranes MK-40 and MA-40 have been
used. Their characteristics is as follows:
MK-40 MA-40
Swelling capacity, %
in thickness 134.4 127.7
in area 121.1 121.0
S.V.C. mg-equi/g, dry membrane 3.03 3.56
Volume resistivity, ohm/cm 210.3 258.8
Selectivity 0.9 0.82
Tensile strength, kg/cm
183.5 195.2
The waste waters enter the electrodialyzer by three
independent tracts, one of them is for washing the elec-
trode chambers (of cathode and of anode), the second is
for desalted water; here the waters are purified from
ions which, following their own charge, are directed
either to the cathode or to the anode; the third one is for
concentration; here the solution is saturated with ions.
The desalted waters contain up to 0.5 g/1 of salts
which corresponds to the total salt content in river
waters used for water-rotation cycle. These waters enter
a tank for storage (Scheme 28).
The solution contains up to 2.5 g/1 of salts when
entering the tank (Scheme 14) from which it is pumped
(Scheme 15a, b) to the electrodialyzer (Scheme 16). The
desalted waters contain up to 0.5 g/1 of salts and enter
tank N28. The liquid from Device N16 contains up to
4.5 g/1 of salts when it goes to the tank (Scheme 17)
wherefrom it is pumped to the electrodialyzer (Scheme
19). Leaving this device, the water contains up to 0.5 g/1
of salts and goes to tank N28 while the solution with
about 8 g/1 of salts enters tank N20 from where (Scheme
21 a, b) it is disposed into deep well-isolated horizons; in
total, some 12.5% of all waters are disposed of in this
way after desalination.
In all the described electrodialyzers (Schemes 13, 16,
19) during desalination the electrodes are washed in a
closed cycle. The filtered waters from the tank (Scheme
11) are pumped (Scheme 12a, b) for washing the elec-
trodes of the dialyzer (Scheme 13), after which the elec-
trode chambers of dialyzers NN 16 and 19 are washed
one by one. Then the washing waters are collected in
tank N22 and pumped back to tank Nil (Scheme 23a,
b).
The membrane life in the electrodialyzers is about 5
years on the average. With this time expired, the mem-
branes are either partially or completely replaced.
-------
Ozonization
Legend to Fig. 1. Tertiary Waste Water Treatment
Upon filtration and desalination, the waters from tank
N28 are pumped (Scheme 29a, b) to the mixing chamber
of the contacting device (N31a, b) which is a rectangular
horizontal tank with a vertical plate-like sectional
column.
Before their ozonization the waste waters had the
following main parameters: 1) suspended matter,
mg/1 up to 0.5
2) total salt content,
g/1 up to 0.5
3) permanganate oxidation,
mg O2/l up to 48-52
4) colourity, in grades
900.
To obtain ozon an ozon generator was used (OP-121)
(Scheme 30) with efficiency of 1.6 kg/h (Scheme 30).
The air coming to the ozonator after the frying device of
the type UOVB-0.5M (Scheme 2)) has the dew point
equal to -50°C.
The ozon-air mixture with 15 g/m3 of ozon is supplied
to the mixing chamber of the contacting device (Scheme
3 la, b) where simultaneously come the waste'waters
from device N28. The unreacted ozon from the contact-
ing device (3la, b) enters the degasator (Scheme 32)
filled with a catalyst and equipped with an electric air
heater. Upon degasation, the ozon-free air is discharged
in the atmosphere. After ozonization the waste waters
overflow into a tank (Scheme 33a, b) and therefrom are
pumped (Scheme 34a, b, c, d) back into the water rota-
tion cycle.
Upon ozonization, the waste waters meet the following
basic requirements:
1) suspended matter, mg/1 up to 5
2) total salt content, g/1 up to 0.5
3) permanganate oxidation, mg O2/l up to 15
4) colourity, in grades up to 80.
la, b) pump to supply the waste waters; 2) tank for storing the waste
waters; 3a, b) pump to feed the waste waters to the filter; 4) cartridge
filter, type PAP 80-248; 5a, b) pump to supply the filterperlite;
6a, b) proportioning pump; 7) suspenzator to supply the perlite;
9) sludge collector; 10) pump to supply the sludge; 11) tank for the
filtrate; I2a, b) pump to feed the filtered waste waters;
13) electric dialyzer, type EXO-5000x 200; 14) receiving tank; 15) cen-
trifugal pump; 16) electric dialyzer EDU-l-400x4; 17) receiving tank;
18a, b) centrifugal pump; 19) electric dialyzer EDU-l-400x4; 20)
receiving tank; 21a, b) centrifugal pump; 22) receiving lank;
23a, b) centrifugal pump; 27) air drying device, type UOVB-9.5M; 28)
tank; 29) centrifugal pump; 30) ozonalor, type OP-12 B 1; 31a, b) con-
tacting device; 32) degasator; 33a, b) tank for treated waste waters;
34a, b, c, d) centrifugal pump.
Conclusions *
The authors show that the waste waters from the "Pig-
ment" enterprise in Tambov were biologically purified
and after-treated on a tertiary treatment system working
on the following technological scheme: filtration, desali-
nation, ozonization; upon such treatment the waste
waters were in complete agreement with the standards set
up for water recycling. The desalinized waters, free of
suspended matter and organics, return to the closed
water rotation cycle of the enterprise.
The pickle containing up to 8 g?l of salts is disposed
of into deep, safely isolated horizons; in total, about 10
to 12% of the total water amount entering the tertiary
treatment system are disposed of in this way.
-------
Protocol
3.
Protocol of the 7th Meeting of the USA and USSR
delegations on the problem of Prevention of Water
Pollution from Industrial and Municipal Sources
(Moscow, USSR, November 12-23, 1978).
In accordance with the Memorandum of the Meeting
of the Joint USA-USSR Commission on Coorperation in
the field of Environmental Protection (Moscow, Novem-
ber, 1976) the USA and USSR delegations held a
meeting on problems of wastewater treatment in Moscow
between November 12-23, 1978.
The American.delegation was headed by Mr. Harold
P. Cahill, Jr., Director of the Municipal Construction
Division, U.S. Environmental Protection Agency.
The Soviet Delegation was headed by Prof. S. V.
Yakovlev, Director of VNII VODGEO, Gosstroy USSR.
The list of participants is attached in Appendix I.
In the course of the meeting the following was accom-
plished:
1. A Symposium was held on the subject of "Ad-
vanced Treatment of Biologically Treated Effluents, In-
cluding Nutrients Removal".
2. The accomplishments of the 1978 Program of
Cooperation were discussed.
3. The Working Program for 1979 was coordinated.
In the course of the Symposium 12 professional papers
were delivered: 6 papers from the US side and 6 papers
from the Soviet side. The titles of these papers are at-
tached in Appendix II.
Of particular interest were the papers of American ex-
perts of ozone treatment and advanced treatment
facilities, including those operating in the area of Lake
Tahoe and papers of Soviet specialists on wastewater
treatment on sand filters.
The delegations have agreed that each side will publish
all reports in the necessary number of copies in its own
language prior to Februray 1, 1979, and will distribute
them to interested organizations. The sides will exchange
10 copies each of the published Proceedings of the Sym-
posium.
2.
In the course of the meeting the specialists discussed
the results of current research carried out in accordance
with the Program of Cooperation and exchange scientific
and technical literature. The delegations expressed their
satisfaction that a 30-day exchange of specialists in the
field of wastewater treatment and sludge handling was
accomplished in 1978. Two American environmental
engineers visited the USSR in July and two Soviet
specialists visited the USA in November.
The exchange of specialists was of great scientific and
practical importance. The sides noted the value of such
exchanges for the future.
The delegations agreed that in January 1979 they will
exchange lists of selected projects for advanced treat-
ment of waste waters. During 1979 the sides will ex-
change detailed design plans and specifications for these
projects. This exchange will involve no cost to either
sides.
The delegations defined and coordinated the Program
of Cooperation for 1979 (Appendix III).
The sides have agreed that a Symposium on subject of
"Treatment of Oil-Containing Wastewaters and also
summary of experience in operating facilities for
biological treatment of wastewaters using pure oxygen"
will be held in the USA between April 8-20, 1979.
The following has been agreed upon for the prepara-
tion of the forthcoming Symposium:
each side will present 5 professional papers for the
Symposium;
both sides will exchange the titles of papers to be
delivered by February 1, 1979;
both side will exchange the texts of the papers, both in
Russian and English, at the beginning of the Sym-
posium.
In the course of the Meeting in the USSR (Moscow,
August 12-24, 1979) the delegations will continue to
discuss and coordinate the details of the projects of ex-
perimental units for wastewater treatment and sludge
handling.
In the course of the meeting the delegations will hear
professional papers on the methods of wastewater treat-
ment, facilities, units and equipment for experimental
treatment plants.
The American delegation during this visit to the USSR
was given a briefing on the operation of municipal and
industrial waste waters treatment plants in Moscow,
Novopolotsk, Togliati and visited a number of research
organizations in Tallin, Leningrad, Moscow.
The sides expresssed their satisfication that the Meet-
ing was held on a high scientific and technical level in an
atmosphere of friendship and mutual understanding thus
contributing to further development and strengthening of
cooperation in the field of environmental protection.
This Protocol was signed on November 24, 1978, in
two copies, in Russian and English, both texts being
equally authentic.
From the US Side
Harold P. Cahill, Jr.
Head of Delegation
From the Soviet Side
S.V. Yakovlev
Head of Delegation
96
-------
Appendix 1
Appendix 2
List Of Participants at the Symposium "Advanced
Treatment of Biologically Treated Effluents, Including
Nutrients Removal"
From the American Side
Harold P. Cahill, Jr.
Andrew Paretti
Frank P. Sebastian
Delegation Leader
Director, Municipal Con-
struction Division, US
EPA
Consultant, US EPA
Senior Vice President,
ENVIROTECH
Menlo Park, California,
USA
General Manager and
Chief Engineer,
Tahoe-Truckee Sanitary
Agency
Prof. Alexey N. Malyshev Interpreter,
US Department of State
Ossian R. Butterfield
From the Soviet Side
S.V. Yakovlev
R.F. Slavolyubov
V.N. Shvetsov
I.N. Myasnikov
N.V. Pisanko
E.A. Lobacheva
Delegation Leader
Director, VNII VODGEO,
Gosstroy USSR
Department Chief of Main
Administration, Gosstroi
USSR
Deputy Director,
VNII VODGEO, Gosstroi
USSR
Laboratory Head, VNII
VODGEO, Gosstroi,
USSR
Chief Engineer, State Proj-
ect Institute "Ukrvodo-
kanal Project", Gosstroi
USSR
Senior Interpreter,
VNII VODGEO, Gosstroi
USSR
List Of Papers Presented at the Symposium "Advanced
Treatment of Biologically Treated Effluents, Including
Nutrients Removal"
From the American Side
1. Land Treatment: Achieving Nutrient Removal by Re-
cycling Resources Thomas C. Jorling and Richard
E. Thomas
2. Operation of a 5 MGD Model Advanced Wastewater
Treatment Plant at Piscataway, Maryland Harold
P. Cahill, Jr. and Thomas P. O'Farrell
3 Granular Carbon and Other Tertiary Treatment Pro-
cesses Frank Sebastian and Dennis Lachtman
4. Facilities for the Treatment of Biologically Treated
Effluents from Industrial and Municipal Source by
Ozone William Lacy.
5. Municipal Wastewater Treatment by Land Applica-
tion in the Minneapolis St. Paul, Minnesota Area
Richard Stanley and Douglas Wallace, Stanley
Consultants Inc.
6. Tahoe-Truckee Water Reclamation Plant Ossian
Butterfield
From the Soviet Side
1. Works for Final Purification of Municipal Wastes
L.I. Gyunte and E.S. Razumovsky
2. Aerated Filters for Tertiary Treatment of Secondary
Effluents A.G. Kirichenko
3. After treatment of Biochemically Treated Waste-
waters Before Their Reuse E.G. loakimis and E.A.
Yusupov
4. Investigation of the Lading Regeneration of the
Mixed-Media Filter with the Descending Particle Seize
Distribution for the Advanced Wastewater Treatment
Yu.N. Golovenkov, N.V. Kravtsova, A.S. Slavin-
sky, R.S. Chabirov
5. The Mathematical Model of the Adsorption of
Organic Impurities from Water Solutions with
Microporous Adsorbents A.M. Stadnik
6. Tertiary Treatment of Biologically Purified Waste
Waters Aimed at Their Recycling in the Production
Processes Yu.M. Latyshev and V.I. Zavarzin
97
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USA-USSR Cooperation of Working Group on Prevention of Water Pollution from Industrial and Municipal Sources for 1979
NO TITLES
2.
3.
Modernization of existing and
development of new combined
facilities with high efficiency for
wastewater treatment, including
hydrocyclones, multistage settlers,
flotators, investigation of usage of
flocculants and coagulants
Development of hydrocyclones
and pressure flotation units
Development of tubular
and plate settlers
Development of open aeration
tanks^jf "Marox" type with the
usage of technical oxygen
Development of closed combined
aeration tanks of "Oxitank" type
with the usage of oxygen.
Development of multimedia filters
with gradually descending particle
size distribution
Development of multimedia filters
and facilities with continuous
washing.
Intensification of wastewater
treatment processes in petro-
chemical, chemical petroleum
refining and pulp and paper
industries
Intensification of wastewater
treatment processes in petroleum
refining industry
Development of highly efficient
methods and facilities for munic-
ipal sewage treatment with
removal of biogenous elements;
usage of treated effluents in re-
cycling systems at industrial
enterprises.
Development of methods and
facilities for nitrates and nitrites
removal.
Development of optimal schemes
of facilities for nutrients removal
FORM OF WORK
Joint development of themes,
scientific information and special-
ists delegation exchange.
Symposium of: "Treatment of
Oil-Containing Wastewaters and
also summary of experience in
operating facilities for biological
treatment of wastewaters using
pure oxygen" (USA, April 8-20,
1979)
Visit of 6 Soviet specialists to the
USA
Visit of 6 American experts to the
USSR, August 12-24, 1979
RESPONSIBLE FOR TIME EXPECTED RESULTS
From the From the
USSR USA
4 5 67
VNIIVODGEO EPA 1980 Improvement of the efficiency of
existing and development of new
treatment facilities, reduction of
reagents and cost of wastewater
treatment.
VNII VODGEO 1980 Recommendations for designing
Gosstroy USSR hydrocyclones and pressure flota-
tion units.
EPA 1980 Recommendations for use of
settlers for wastewater treatment.
EPA 1979 Development of open aeration
tank with the usage of technical
oxygen.
EPA 1979 Development of closed aeration
tanks with the usage of technical
oxygen.
VNII VODGEO 1979 Recommendations for designing
Gosstroy USSR filters for treatment and final
treatment of wastewaters.
EPA 1979 Recommendations for construc-
tion of multimedia filters.
Information and delegation
exchange
Joint development of themes,
information and delegation
exchange
VNII VODGEO EPA
Gosstroy USSR
VNII VODGEO
VNII VODGEO EPA
1979 Increasing of wastewater treat-
ment efficiency of existing treat-
ment plants, introduction of new
treatment schemes, maximum
usage of treated effluents in recir-
culating systems.
1979 Development of treatment scheme
of a petroleum refining plant
using mechanical, physical and
biochemical methods.
1980 Development of new treatment
facilities for prevention of water
basing eutrophication; develop-
ment of new treatment systems
with maximum usage of treated
effluents in recycling systems at
industrial enterprises.
VNII VODGEO Recommendations for designing
units.
EPA Recommendations for designing
facilities
98
-------
USA-USSR Cooperation of Working Group on Prevention of Water Pollution from Industrial and Municipal Source* for 1979
NO TITLES
1 2
4. Wastewater sludge handling
Wastewater sludge stabilization
and dewatering processes
Methods and facilities for sludge
heat treatment and utilization
FORM OF WORK
Information and delegations
exchange
RESPONSIBLE FOR TIME EXPECTED RESULTS
From the From the
USSR USA
4 5
VNII VODGEO EPA
VNII VODOEO
EPA
6
1980
Reduction of cost of wastewater
sludge handling, improvement of
the efficiency of operation of
sludge handling facilities.
Recommendations for designing
facilities for sludge stabilization
and dewatering
Recommendations for designing
sludge heat treatment and utiliza-
tion facilities.
99
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100
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