United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
September 1980
Research and Development
International Seminar on
Control of Nutrients in
Municipal Wastewater
Effluents
OOOR80016
Proceedings
Volume I: Phosphorus
Hotel del Coronado
(San Diego)Coronado, California 92118
September 9, 10, and 11, 1980
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CONTROL OF NUTRIENTS
IN MUNICIPAL WASTEWATER EFFLUENTS
VOLUME I: PHOSPHORUS
Proceedings of an International Seminar
San Diego, California
September 9-11, 1980
Seminar Convener:
E. F. Barth
Wastewater Research Division
Municipal Environmental Research Laboratory
Speakers:
Dr. N. W. Schmidtke, Burlington, Canada
Dr. J. V. DePinto, Potsdam, New York
Mr. W. L. Morley, Gladstone, Michigan
Dr. B. G. Hultman, Stockholm, Sweden
Mr. T. Annaka, Tokyo, Japan
Mrs. D. VanDam, Grand Haven, Michigan
Mr. C. Heim, Tonawanda, New York
Municipal Environmental Research Laboratory
and
Center for Environmental Research Information
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
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AGENDA FOR
INTERNATIONAL SEMINAR
ON
CONTROL OF NUTRIENTS IN WASTEWATER EFFLUENTS
SEPTEMBER 8, 1980
7:30 to 9:00 p.m. RECEPTION/EARLY REGISTRATION
VOLUME I Page
SEPTEMBER 9, 1980 PHOSPHORUS CONTROL TECHNOLOGY
7:30 to 9:00 a.m. REGISTRATION
9:00 to 9:15 WELCOME AND INTRODUCTION TO PROGRAM
Mr. Edwin Barth
Chief, Biological Treatment Section
Wastewater Treatment Division
U.S. EPA/MERL
9:15 to 10:05 NUTRIENT REMOVAL TECHNOLOGY - THE CANADIAN 1
CONNECTION
A presentation of the rationale for nutrient
control; the development of an R&D, legislative,
and technology transfer program; implementation
of low cost technology at existing municipal
plants; and impact and current status of control
technology.
Speaker: Dr. Norbert W. Schmidtke, Director
Wastewater Technology Centre
Environmental Protection Service
Environment Canada
Burlington, Ontario, Canada
10:05 to 10:20 COFFEE BREAK
10:20 to 11:10 PHOSPHORUS REMOVAL IN LOWER GREAT. LAKES MUNICIPAL 39
TREATMENT PLANTS
A survey of phosphorus removal processes of
various types, with statistical summary of lower
lakes facilities, histograms of performance and
loadings, and a discussion on phosphorus
availability in relation to treatment processes.
Speaker: Dr. Joseph DePinto
Department of Civil and Environmental
Engi neeri ng
Clarkson College, Potsdam, New York
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VOLUME I (Continued) Page
11:10 to 12:00 EXPERIENCES AT GLADSTONE, MICHIGAN UTILIZING 91
ROTATING BIOLOGICAL CONTACTORS FOR BOD,
PHOSPHORUS AND AMMONIA CONTROL
A rotating biological contactor facility with
summary data on effluent residuals, key daily
operational points, actual cost data, and
recommendations on future facility design from an
operational standpoint.
Speaker: Mr. Willard Lee Morley, Superintendent
Water and Wastewater Treatment
City of Gladstone, Michigan
12:00 to 1:00 LUNCH
1:00 to 1:50 CONTROL TECHNOLOGY FOR NUTRIENTS IN MUNICIPAL 113
WASTEWATER TREATMENT IN SWEDEN
Necessity for nutrient control in Sweden,
techniques to translate basic nutrient research
into full-scale facilities, and extent of
implementation of nutrient control in municipal
facilities in Sweden.
Speaker: Dr. Bengt Gunnar Hultman
Swedish Water and Wastewater
Works Association
Stockholm, Sweden
1:50 to 2:40 RESEARCH ON PHOSPHORUS CONTROL IN JAPAN (separate
The type of research on phosphorus control being manuscript)
conducted in Japan, the reasons why phosphorus
control is necessary, and views of operating
facilities that utilize phosphorus removal
processes.
Speaker: Mr. T. Annaka
Department of Sewage and Serage
Purification
Ministry of Construction
Japan
2:40 to 3:30 ECONOMICAL AND EFFICIENT PHOSPHORUS REMOVAL AT A 139
DOMESTIC-INDUSTRIAL WASTEWATER PLANT
The combination of industrial and domestic waste
characteristics considered in the design of the
facility, a summary of several years of plant
efficiency, and the low-cost experience of
phosphorus control.
Speaker: Mrs. Doris Van Dam, Superintendent
Wastewater Treatment Plant
Grand Haven, Michigan
iv
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VOLUME I (Continued) Page
3:30 to 3:45 COFFEE BREAK
3:45 to 4:35 THE PHOSTRIP PROCESS FOR PHOSPHORUS REMOVAL 159
The PhoStrip process is discussed with emphasis
on efficiency, cost, and reliability in relation
to original design approaches.
Speaker: Mr. Carl J. Heim
Assistant Staff Engineer
Union Carbide Corporation
Linde Division
Tonawanda, New York
4:35 to 5:00 DISCUSSION ON PHOSPHORUS CONTROL TECHNOLOGY
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VOLUME II Page
SEPTEMBER 10, 1980 NITROGEN CONTROL TECHNOLOGY
8:00 to 8:50 EMERGING STRATEGY FOR NITROGEN CONTROL BASED ON 1
RECEIVING WATER QUALITY CONSIDERATIONS
Emerging nitrogen strategies and the need for
nitrification will be discussed, along with
research needs for nitrification to suit European
situations.
Speaker: Dr. Willi Gujer
Swiss Federal Institute for Water
Pollution Control
Dubendorf, Switzerland
8:50 to 9:40 FULL-SCALE CARBON OXIDATION/NITRIFICATION STUDIES 43
AT THE METROPOLITAN SANITARY DISTRICT OF GREATER
CHICAGO
Large-scale plant manipulations to accomplish
single-stage nitrification, with operational
control techniques related to nitrification
kinetics and to implications of control and costs
for a 1,300 MGD facility.
Speaker: Dr. Cecil Lue-Hing, Laboratory Director
Metropolitan Sanitary District of
Greater Chicago
Chicago, Illinois
9:40 to 10:30 PHOSPHORUS REMOVAL WITH IRON SALTS AT BLUE PLAINS 98
Data from the world's largest nutrient control
plant on mineral addition for phosphorus control.
Discussion of costs, alternate chemical
selection, and sludge production, plus what it
takes to put a plant of this size on-line,.
Speaker: Mr. Ed Jones, Chief Process Engineer
Wastewater Treatment Plant
Washington, D.C.
10:30 to 10:45 COFFEE BREAK
10:45 to 11:45 NITRIFICATION AT LIMA, OHIO 129
Design of second-stage plastic media for
nitrification, summarizing several years of
efficiency data, operational control, and costs,
and relating these to design changes of second
generation designs.
Speaker: Mr. Felix Sampayo
Jones and Henry Engineers, Ltd.
Toledo, Ohio
vi
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VOLUME II (Continued) Page
11:45 to 1:30 LUNCH
Speaker: Dr. Henry Heimlich, Professor of
Advanced Clinical Studies
Xavier University
Cincinnati, Ohio
Author of the Heimlich Maneuver
1:30 to 2:20 OPERATING EXPERIENCE WITH A 30 MGD TWO-STAGE 153
BIOLOGICAL NITRIFICATION PLANT
A summary of efficiency data, control-loops,
operational modifications, and costs for the John
Eagan Plant.
Speaker: Mr. Earl W. Knight
Assistant Chief Engineer
Metropolitan Sanitary District
of Greater Chicago
Chicago, Illinois
2:20 to 3:10 NITRIFICATION-DENITRIFICATION IN FULL-SCALE 170
TREATMENT PLANTS IN AUSTRIA
Single stage nitrification/denitrification, plus
status of nitrification control in Austria and
the need for this technology.
Speaker: Dr. Norbert F. Matsche
Assistant Professor
Technical University, Vienna, Austria
3:10 to 3:25 COFFEE BREAK
3:25 to 4:15 SINGLE STAGE NITRIFICATION-DENITRIFICATION AT 194
OWEGO, NEW YORK
Second generation design for single-stage
nitrification/denitrifi cation systems, and a
real-world perspective on reliability, efficiency
demands, cost, and operation.
Speaker: Mr. Donald E. Schwinn, P.E.
Stearns and Wheler
Civil and Sanitary Engineers
Cazenovia, New York
4:15 to 5:00 DISCUSSION ON NITROGEN CONTROL TECHNOLOGY
vi 1
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VOLUME III
SEPTEMBER 11, 1980 COMBINED PHOSPHORUS AND NITROGEN CONTROL
TECHNOLOGY
8:15 to 9:05 DESIGN AND OPERATION OF NITROGEN CONTROL
FACILITIES AT TAMPA AND THE NSSD
Three-step nitrogen control at Tampa and two-step
nitrogen control at the North Shore Sanitary
District in Illinois. A summary of the design,
operation, and use of the unusual flexibility
buillt into these plants.
Speaker: Mr. Thomas E. Wilson
Principal Engineer
Greely and Hansen
Chicago, Illinois
9:05 to 9:55 PERFORMANCE OF FIRST U.S. FULL-SCALE BARDENPHO 34
FACILITY
A managed biological system for nitrogen and
phosphorus control.
Speaker: Dr. H. David Stensel, Manager
Sanitary Engineering Technology
Development, EIMCO PMD
Salt Lake City, Utah
9:55 to 10:10 COFFEE BREAK
10:10 to 11:00 DENITRIFICATION IN CONTINUOUS-FLOW SEQUENTIALLY 74
AERATED ACTIVATED SLUDGE SYSTEMS AND BATCH
PROCESSES
Present developments on batch systems controlled
by time-clocked valves and evolution into a
microprocessor-controlled municipal facility.
Speakers: Dr. Mervyn C. Goronszy
Senior Investigating Engineer
State Pollution Control Commission
Sidney, Australia
and
Dr. Robert L. Irvine, P.E.
Deptartment of Civil Engineering
University of Notre Dame
Notre Dame, Indiana
vi i i
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VOLUME III (Continued) Page
11:00 to 12:00 NITROGEN AND PHOSPHORUS REDUCTION FROM LAND 118
APPLICATIONS AT THE DISNEY WORLD RESORT COMPLEX
Several approaches to attaining defined effluent
residuals and accumulating large amounts of
analytical data for this entertainment complex,
with data on phosphorus control in the activated
sludge system, overland flow, spray, and
perculation basins.
Speaker: Mr. Robert Kohl, Director
Reedy Creek Utilities Company, Inc.
Walt Disney World
Lake Buena Vista, Florida
12:00 to 1:00 LUNCH
1:00 to 1:50 EXPERIENCE WITH AMMONIA REMOVAL BY SELECTIVE ION 137
EXCHANGE AND CLOSED-CYCLE AIR STRIPPING
REGENERANT RENEWAL
A discussion of the Tahoe-Truckee Sanitation
Agency and the Upper Occoquan facility in
Virginia, covering a closed-cycle stripping
process in relation to efficiency and effluent
residuals, operational considerations, and cost
data.
Speaker: Mr. L. Gene Shur
Vice President and Director
CH2M-Hill Consultants
Corvallis, Oregon
1:50 to 2:40 NITRIFICATION AND PHOSPHORUS REMOVAL IN A 35 MGD 185
ADVANCED WASTE TREATMENT PLANT AT ROANOKE, VA
Design parameters related to operational results
for control of nitrification and phosphorus
residuals.
Speaker: Mr. Donald E. Eckmann
Alvord, Burdick, and Howson Engineers
Chicago, Illinois
and
Mr. Harold S. Zimmerman, Plant Manager
Waste Treatment Plant
Roanoke, Virginia
2:40 to 3:30 FULL-SCALE EXPERIENCE WITH TWO-STAGE 214
NITRIFICATION AND PHOSPHORUS REMOVAL
Accumulated efficiency and cost data from two
facilities, a summary of efficiency data, as
frequency distribution, overall costs, and
operational modifications necessary for enhanced
second generation design.
Speaker: Mr. Winfield A. Peterson, Chief
Plant Operating Group N.E.
Metcalf and Eddy, Inc.
Boston, Massachusetts
ix
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NUTRIENT REMOVAL TECHNOLOGY - THE CANADIAN CONNECTION
N.W. Schmidtke, Ph.D., P. Eng.
Director, Wastewater Technology Centre
Environmental Protection Service, Environment Canada
INTRODUCTION
Man-initiated acceleration of eutrophication of large and small
bodies of water has received attention from the public because of
dramatic and rapid, visible changes in water quality. This not
only results in undesirable changes in water use patterns such as
restricted use of pleasure craft, swimming, fishing, but also
more subtle effects such as clogging of water intakes, increased
turbidity, taste and odor problems and general interferences with
water treatment processes. These effects are caused by algae blooms
which in most instances are a manifestation of a biological re-
sponse to excessive nutrient input to the water column.
Even though Canada has 1/3 of the world's fresh water, deteriora-
tion in water quality such as previously noted exists. More speci-
fically 4 major areas (Figure 1) where significant evidence of
water quality impairment has been identified are:
1. The Okanagan Basin - British Columbia
2. The Qu'Appelle River Basin - Saskatchewan
3. The Saint John River Basin - New Brunswick
4. The Great Lakes Basin - Ontario
Phosphorus has been implicated as a limiting or key nutrient in
the eutrophication of many natural or man-made bodies of water
throughout the industrialized world (1).
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FIGURE 1, MAJOR AREAS OF WATER QUALITY CONCERN ,
Detergents, human waste, agricultural run-off, atmospheric
transport and industrial activities are all major sources of
phosphorus being discharged to receiving bodies of water. An
additional phosphorus reservoir exists in the bottom sediments
of lakes and rivers.
An obvious solution to the problem consists of reducing the input
of phosphorus to the environment. This is a relatively simple
problem if dealing with point sources. One of the main point
sources of phosphorus is the effluent from municipal waste treat-
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ment plants. Removal of phosphorus contained in domestic and
industrial wastewaters is recognized as an essential step in
decelerating and eventually reversing the extent of eutrophication
in receiving waters.
The water management studies (2) conducted in the Okanagan Basin,
the Qu'Appelle River Basin and the Saint John River Basin all con-
firm that reduction in nutrient inputs, especially phosphorus,
will result in a decrease in the rate of water quality deteriora-
tion and will ultimately lead to improvement of existing water
quality. In these three areas,activities related to the construc-
tion of new treatment plants and installation of phosphorus removal
facilities are in progress.
This paper will provide an overview of the numerous activities
undertaken by the Canadian government and the Province of Ontario
in a concerted effort to control nutrient inputs (phosphorus) to
the Great Lakes.
A POINT SOURCE PHOSPHORUS CONTROL STRATEGY
The International Joint Commission (IJC) Report (3) completed in
1969 after a six year study of pollution in the Lower Great Lakes
drainage basin, recommended that all phosphorus discharges to the
Lower Great Lakes be reduced to the lowest practical level, call-
ing for an effluent objective of 1.0 mg.L"1 total phosphorus.
To meet this challenge, Canada opted for a double-pronged attack on
eutrophication, relying on legislative as well as technical means
to reduce phosphorus concentrations in wastewater discharges.
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Thus, the Canadian Government, under the provisions of the Canada
Water Act (1970), legislated a policy calling for a staged reduc-
tion in the phosphorus content of detergents to a limit - by
weight as P205 - of 20% by August 1970 and 5% by December 31, 1972.
Establishment and support of the framework for developing the
technical means to reduce the nutrient content of municipcil waste-
water discharges to the Great Lakes system was recognized to be
a joint Federal-Provincial responsibility.
A FEDERAL-PROVINCIAL ACCORD
As a prelude to the Canada-United States Agreement which was signed
between the United States and Canada in 1972, the Governments of
Canada and Ontario signed an Agreement (4) in August 1971, to im-
plement and accelerate programs of pollution control in the Lower
Great Lakes to meet the recommendations of the IJC. The Agreement
secured funding for a $250 million capital works program aimed at
upgrading sewage collection systems and treatment works. This
included the installation of phosphorus removal equipment at an
estimated cost of $40 million. An additional $6 million over the
5 year term of the Agreement was provided for related research
studies. Phosphorus removal technology and treatability studies
were given top priority in the research program.
The $6 million research fund was jointly shared and administered
by the Governments of Canada and Ontario. The Agreement was sub-
sequently extended for an additional 2 year period with a further
$1 million allocation of research funding.
Largely as a result of this research funding, a program of integrat-
-------
ing chemical treatment with existing plant processes was
designed. This program consisted of jar testing followed by
treatability studies at each plant. The success of this strategy
is evident in that the deadlines for implementation of phosphorus
removal at existing plants as established by Ontario in 1970 were
largely met. Figure 2 illustrates the Ontario phosphorus removal
program with scheduled compliance dates.
kT ONTA«.b '
LEGEND
Dec. 31.1973
Dec 31.1973
Dec.31.1975
Future
Plants larger than
1mgd or where
local problems
demonstrated.
Planta larger
than t m.g d
n Studies required
to determine need
FIGURE 2, PROVINCE OF ONTARIO-SOUTHERN SECTION
PHOSPHORUS REMOVAL PROGRAM SCHEDULED
COMPLIANCE DATES, (8)
Even though the emphasis of phosphorus removal has been placed on
point-source reduction at municipal treatment plants, other sources
are not ignored. Specifically:
1. Ontario poticy calLt> faon. an e^&ieitt objective,
pkoAphotuiA dLf>c.haAge.A ofa 1 mg.L~l maximum tataJt
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2. Uiban Viainage. Sub -Committee. o{> the, Canada-Ontasiio Ag-t.ee-
me.nt in thojji PtLOpoAe.d Model Policies {.ofi Unban
Management (5) AuggeAtA that *e.ach municipality AhaH
late. and implejne.nt a comptLe.he.nAi.ve. pollution cont/iol
At>iate.gy /Lzlate.d to iti> own pasiticula/L land aie, drainage.
and fiun-o^ chaAacte.suAtia>."
3. The. ?fw\)i.nc. &ummany tizpotit to the. IJC (7) no.comne.ndA that
pho&phoiuA tie.du.ction through non-point 06 well OA point
AOLLtice. control piogiamA be. implejme.nte.d . ThiA would include.
control o& Aoil e.tu>Aion, Atn.e.ngthe.nj,ng ofi the. oA.e.aA oft
ne.duci.ng wate.fi. pollution p*.oblejnA ^om animal manuAe-A, and
improving fieAtiLize.*. application ptiacti.c.&A .
EFFECT OF DETERGENT PHOSPHORUS CONTROL
Before the Canadian Government imposed controls on detergent phos-
phorus levels, the phosphorus content of laundry detergents aver-
aged approximately 25% (as P205) . Influents to municipal sewage treatment
plants had typical phosphorus concentrations of around 10 mg.L"1.
Following the introduction of the first control regulations in
August 1970 (limiting the laundry detergent phosphorus concentra-
tions to 20% as PzOs) the raw sewage phosphorus concentration
decreased to around 8.8 mg.L 1.
Further legislative controls imposed December 1972 (laundry deter-
gent phosphorus concentration to 5% as P20s) saw influent phosphor-
us concentration decrease to approximatly 7 mg.L"1.
The phosphorus concentration continued to decrease through 1974
to a low value of about 5.6 mg.L"1 but has since increased to the
current level of about 6.8 mg.L"1 (9). Figure 3 illustrates the
phosphorus influent concentrations over the period 1967 to 1977
for the province of Ontario.
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10
_, 9
* >
5 7
£^
S 6
y 5
—»« '
STEP 1 (AUG. 1970)
•20Z CRITERIA
67 68 69 70 71 72 73 74 75 76 77
YEAR
FIGURE 3, PHOSPHORUS CONCENTRATIONS IN RAW SEWAGE, (11)
The impact of legislated phosphorus detergent reductions was best
illustrated in a ten-month long full-scale study of the activated
sludge plant at the Canadian Forces Base in Uplands (10).
Figures 4 and 5 highlight these effects. Figure 4 illustrates the
average diurnal variations of influent phosphorus for the 1972-
1973 period, before and after reformulation. Each data point in
Figure 4 is the mean of hourly samples collected on at least
seven different days.
Figure 5 shows the average weekly data for total phosphorus and
plant flow and clearly indicates that the reduction in total phos-
phorus concentration was not due to dilution by increased flows.
The data show that influent phosphorus loadings dropped from an
average of 126 kg.d"1 in 1972 to an average of 55 kg.d~J in 1973;
a 56% reduction.
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1»m 4
FIGURE 4,
12pm
DIURNAL VARIATION OF TOTAL
PHOSPHORUS IN RAW WASTE-
WATER AT C.F.B, UPLANDS, QQ)
07
•••
I.:
KWAOE FLAKT MXUENT FLOW
TOTAL
«UB KP OCT MOV KC.MN FB MAR AMI MAY JUH ML AUC HP
MONTW
FIGURE 5.
INFLUENT TOTAL PHOSPHORUS AND
FLOW TRENDS DURING DEMONSTRATION
STUDY AT C , F ,B , UPLANDS , (10)
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In another study (12) available Ontario phosphorus influent data
were summarized over the bre-ban and post-ban periods. The data,
based on approximately 35 plants, showed that the influent total
phosphorus concentration had decreased from approximatly 7.1 mg.L~1
to 5.7 mg.L"1. This represents a 20% reduction in wastewater phos-
phorus loading directly attributable to laundry detergent reformu-
lation (Table 1).
TABLE 1, IMPACT OF DETERGENT REFORMULATION ON WASTE-
WATER PHOSPHORUS LEVELS (J2)
Raw wastewater
total phosphorus
(mg/lasP)
Secondary effluent
total phosphorus
(mg/1 as P)
"Average value.
b . , .
Before
Reformulation
(Prior to
January 1973)*
7.1
•
(n° = 38)
4.5
(n = 31)
tftf
After
Reformulation
(1973 to Date)'
5.7
(n « 35)
3.4
(n = 25)
Percent
Reduction
20
24
When using iron or aluminum salts for phosphorus precipitation, a
very stronc[_correlation between chemical dosage and influent phos-
ph^us__conceritration -exists. Figure 6, for example, illustrates
the quantity of aluminum required to attain an effluent phosphorus
concentration of 1 mg.L"1 as a function of the influent phosphorus
concentration. Clearly then, reduced total phosphorus influent
concentrations will lead to reduced coagulant dosages, which is
an operating cost saving. As well, the resulting smaller increases
in sludge quantity represent additional reductions in plant opera-
tional costs.
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DOSE - -3.2 + 2.5 (P)
(X
E
24-,
22-
20-
18-
16-
14-
12-
10-
8-
6-
4-
2-
• RAW SEWAGE
_SECONDARY
EFFLUENT
T"
8
T—
10
0 2 4 6 8 10 12
INITIAL PHOSPHORUS CONCENTRATION (mg/l)
FIGURE 6, RELATIONSHIP BETWEEN ALUM DOSE
REQ D FOR iMGA RESIDUAL P AND
INITIAL PHOSPHORUS, (13)
Jar test data for coagulant dosage selection at Ontario treatment
plants as summarized in Table 2 show dramatic reductions in
coagulant dosage requirements between pre- and post- detergent
legislation dates. By correcting the jar test dosages to full
scale dosage requirements using the relationship developed in
another investigation (13), it can be calculated that the reductions
in chemical dosage requirements to achieve a 1 mg.L"1 total phos-
phorus effluent are 7.6 mg.L"1 as Fe3+ and 5.1 mg.L~l as A13+
respectively.
Using chemical costs (1980) of $0.558 kg"1 for FeCl3 and $0.134
kg"1 for alum it can be calculated that the saving in chemical cost
10
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TABLE 2, AVERAGE JAR TEST DOSAGES OF ALUM OR FERRIC
CHLORIDE REQUIRED TO ACHIEVE A 1 MG,I>
TOTAL PHOSPHORUS RESIDUAL PRIOR TO 1973 (J2)
Raw Wastewatei Addition Mixed Liquor Addition
Reduction Reduction
Chemical Pre-1973 1973-Present (%) rVc-1973 1973-Present (%)
Ferric 30.5 17.2 44 21.5 12.8 41
chloride
(mg/l)a» (na = 37) (n = 36) (n = 31) (n=26)
Alum 19.4 13.1 32 12.8 6.9 46
(mg/las (n=38) (n=36) (n=31) (n = 27)
A13+
'n » number of observations.
alone amounts to $2.96 capita^yr""1 for FeCl3 and $1.82 capita'^r"1
for alum. In addition, available data permits one to calculate that
if the laundry detergents had not been reformulated, sludge volumes
would be approximatly 26% greater.
IMPLEMENTATION OF LOW COST TECHNOLOGY AT EXISTING PLANTS
A major component of the research program under the Canada-Ontario
Agreement addressed the subject of treatability studies as a pre-
lude to installing full-scale phosphorus removal facilities.
Ontario's successful experience in implementing the phosphorus
removal program was to a large measure due to the two-phase approach
used: initial jar testing studies followed by fairly long term full-
scale studies. The data base thus developed and correlations
obtained between jar test and full-scale data coupled with experience
have given us sufficient confidence so that full-scale studies no
longer need be conducted. At the initiation of the program the two-
11
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phase approach gave us not only information on chemical and
dosage selection but optimum point of chemical application and
compatibility with the existing wastetreatment process type and
operation.
Figure 7 is a summary of the Ontario treatability data when com
paring jar test to full scale performance data. As shown, the
30
28-
26
24
|_20-
8 w-
M
oT 16-
***
14-
12-
I 10-
6-
4'
ofe3*
Jar Test _115
FullScate '
0 24 6 810121416182022242628
Full Scale Dosage (mg/l as Al~or Fe~)
FIGURE 7, COMPARISON OF JAR TEST DOSAGES (FOR 1
p 50% OF THE TIME) TO FULL SCALE DOSAGES
(FOR 1 MGA P AVERAGE) AT PLANTS ADDING
ALUM OR FERRIC CHLORIDE TO THE MIXED LIQUOR, (32)
jar tests tended to overestimate the full-scale dosage require-
ments by about 15%. In one study (12) the Ontario treatability
data was standardized and regression analyses were carried out to
develop predictive equations for chemical phosphorus removal.
The equations so developed were capable of predicting chemical
12
-------
dosages for a particular wastewater to -30%. The implication of
this is that in future treatability programs the scope of the jar
testing phase can be reduced. Some consultants have already used
this approach successfully (14). An attempt was also made (15) to
refine the predictive capability of the equations by including
parameters additional to influent phosphorus concentrations, such
as hardness, alkalinity, conductivity, etc. Even though the re-
sultant equations now allowed one to predict chemical dosage
requirements to within -20% as opposed to the earlier -30%, it was
concluded, that based on this marginal degree of improvement, the
extra time and expense required cannot be justified.
Jar test and full-scale treatability cost data are summarized
in Tables 3 and 4 respectively (11). The cost is not only a
TABLE 3, JAR TESTING TREATABILITY COSTS (11)
($) 1974
Type of Facility Hurt Staff Outside Contractor
Primary 964 5020
Secondary 817 5877
Lagoons 588
function of the type of waste treatment facility but more impor-
tantly whether the study was contracted out or conducted by the
plant operations staff. Chemical costs are excluded. The wide
TABLE 4, FULL-SCALE TEMPORARY STUDY COSTS (11)
Type of Facility
Primary
Secondary
Lagoons
Maximum
62,000
83,000
8,000
Cost($) 1974
Minimum
7.000
1,000
800
Average
19.100
13,100
4,100
13
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variations shown in the full-scale treatability costs reflect
whether chemical feed equipment had to be purchased or whether it
was available on loan from the Ontario Ministry of the Environment.
The numerous phosphorus removal studies conducted at Ontario
treatment plants have resulted in the development of a massive
data base. Figure 8 is another example showing correlations for
the molar effectiveness of FeCl3 or alum on the removal of
soluble phosphorus. As shown, the molar effectiveness is similar
2;
*'
O.B
0.7
0.6
0.6
0.4
0.2
01-
(Uptands)
M«FE OR ALUM
4 ft 6
MOLES M ADDED
MOLE MTMI. TOTAL SOLUBLE PHOSPHORUS
FIGURE 8, COMPARISON OF THE MOLAR EFFECTIVENESS
OF FE CL3 AND ALUM AT C.F.B, UPLANDS, (10)
for each chemical and agrees with the relationship reported by
others (16) for alum addition to the secondary clarifier,, What
this means, is that if both chemicals were compared under identi-
cal total soluble phosphorus conditions, their performance on a
molar basis would be similar.
14
-------
CLARIFIER HYDRAULIC LOADING
Hydraulic overloading of secondary clarifiers is one cause of
poor effluent total phosphorus quality which is associated with
suspended solids carryover. Data from the one study (10) illus-
trates the effluent total phosphorus/suspended solids dependence
(Figure 9). The effect of plant flow and thus overflow rate
O PHASE 7
D PHASE 8
4-
I
3-
2-
1 -
20
40 60 60
SUSPENDED SOLIDS (mg/l)
100
120
FIGURE 9, CORRELATION BETWEEN EFFLUENT TOTAL.-P AND
SUSPENDED SOLIDS, (10)
(OR) of the secondary clarifier on total phosphorus removal is
illustrated in Figure 10 which shows data during the alum addition
phases of a long term study.. A trend line has been drawn using
the average total phosphorus removals and flow rates for the
various addition phases. The trend line shows that phosphorus re-
movals in excess of 80% were obtained when plant flows were at or
below the design flow or OR of less than 1.4 mh~1. There was a
15
-------
SECONDARY CLARIFIER SOR (mh~1)
12 14 16 t8
2D
80
60
20 H
Trend toe
•Plant design
How
O Experimental study
o Results obtained after study period
rRange of values
I
10
i
2.0
I
3.0
ZO " 2& " 3D
PLANT FLOW (WOO* m3d-1)
3.5
FIGURE 10, EFFECT OF PLANT FLOW AND SOR ON TOTAL PHOSPHORUS
REMOVAL DURING ALUM ADDITION, (10)
decided increase in the variability of the effluent phosphorus
concentration above the design flow.
Figure 11 also illustrates the effect of hydraulic load on second-
ary clarifier performance (17). Once the hydraulic load increased
beyond 1.5 mh"1 effluent quality steadily deteriorated. In all
cases chemicals were added to the aeration tank discharge.
Experience has shown that phosphorus removal efficiency is very
closely related to solids removal efficiency. No matter how much
chemical is added, unless the suspended solids level can be
16
-------
50-
40-
OT 30-
u 20-
u_
u. 10'
LLl
0.8
1.2 1.6 2.0
HYDRAULIC LOAD (mh-1)
i
2.4
FIGURE 11, EFFECT OF HYDRAULIC LOAD OF SECONDARY CLARIFIER
CHEMICAL ADDITION TO AERATION SECTION, (17)
reduced to less than 15 mg.L"1, it will be impossible to achieve an
effluent total phosphorus concentration of less than 1 mg.L"1, even
though the soluble phosphorus may be as low as 0.1 mg.L"1.
Extremely low levels of effluent total phosphorus of <0.3 mg.L"1
are only attainable through tertiary filtration.
PHOSPHORUS REMOVAL FROM LAGOONS
The requirement of phosphorus removal from some 80 lagoons in
Ontario is dependent upon location and/or size of facility. It
has been Ontario's experience that high levels of phosphorus re-
moval can be attained at all types of lagoons. The approach to
implementing a phosphorus removal scheme depends considerably upon
the lagoon type.
AERATED LAGOONS
Sewage pumping stations are ideal locations for adding alum or
ferric chloride to the influent of aerated cells. A high degree of
mixing prior to reaching the lagoon is ensured. As with activated
17
-------
sludge plants the successful and quick implementation of
phosphorus control depends on following the typical jar test
procedures.
While several aerated lagoons are successfully removing phosphorus
using alum and ferric chloride, Ontario's experience has been that
lime is not effective (18,19).
CONVENTIONAL STABILIZATION PONDS
Phosphorus removal is achieved by the continuous addition of alum
or ferric chloride to the influent (18). Jar testing, excluding
lime, should be conducted to determine optimum chemical and approxi-
mate dosage requirements. Unless there is concern over inadequate
mixing, full-scale tests are unnecessary.
SEASONAL RETENTION PONDS
Ontario's experience in phosphorus removal from seasonal retention
ponds favors batch treatment prior to discharge (20). Jar tests
again provide valuable information but the dosage selected should be
the one which reduced the phosphorus concentration to approximately
0.5 mg.L"1. Batch treatment should be carried out by having the
chemical in its liquid state contained in a 600-700 i plastic tank
mounted amidships in a 5 m, 70 HP outboard motorboat. Chemical
dispersal occurs through a 50 mm siphon discharging into the prop
wash while traversing the lagoon. Even, rapid chemical distribution
and good mixing are prerequisites. This type of treatment has been
extremely successful.
Effluent quality after treatment is usually less than 10 mg.L"1
BOD and 20 mg.L~l SS with total phosphorus generally less than 0.5
18
-------
mg.lT1. It is desirable to complete the discharge of the lagoon
contents within an 8-10 day period after treatment, otherwise a
slight deterioration in effluent quality is experienced after about
2 weeks (20).
SLUDGE GENERATION AND HANDLING
The topic of sludge generation, handling and disposal at phosphorus
control facilities was recently presented at the Cornell 1979
Conference (21). A few summary highlights have been extracted.
Figures 12 and 13 illustrate the increase in sludge volume and mass
for primary and secondary plants using metal salt addition.
Figure 12 shows a 60% increase in sludge volume when metal salts are
added to the primary plant to meet the 1 mg.L"1 effluent total
9.000
•.000
T.OOO-
6.000-
5.000-
4.000-
3.000-
1000-
1.000-
(1)
/
/ <1> e-e BEFORE CHEMCAL MXXTON
/ (gal/MG wastewater treated)
(2)o-o AFTER CHEMICAL ADDITION
(gal/MG waslewaler treated)
(3) •—» BEFORE CHEMICAL ADDITION
(t> dry aohds/MG wastewater treated)
(4) »—. AFTER CHEMICAL ADDITION
(to dry io>ds/MG wastewater treated)
(4)
MG-K>6gal
2 S K> 20304050607080 9OOS 8699 086999
% of observations equal to or less than stated value
(Ibs. dry solids/MGH 10 = kg/1000
m
FIGURE 12, PROBABILITY DISTRIBUTION FOR SLUDGE PRODUCED
AT PRIMARY PLANTS WITH ADDITION OF METAL SALTS, (22)
19
-------
phosphorus target. The sludge mass increased by 40%. Similarly,
sludge volume and mass increased by 35% and 26% respectively for
activated sludge plants where metal salts had been added to the
aeration tanks (Figure 13).
•.000-
•.000
*000
3000-
t.ooo- •
1000
ID •—• BETOflE OCMCM. *DOITlON(o*/k«G ntWMMt kMMd)
(2) 0—0 If Iff OCMCAl ADDITION (gil/VlG MlWMUr ItuMdl
(J) • • BEFORE OCMCAL ADDITION IB »> toMS/MG MMwmr IrMltd)
(4) • • AFTER CHEMCAL ADOITON (b »y «o*M
-------
TABLE 5, SLUDGE PRODUCT I ON -SUGGESTED DESIGN
DATA (22)
System
g capita" 'd '
Conventional Primary 77
Upgraded Primary 109
b
Conventional A.S. ll"i
Upgraded A.S.b US
Sludge
Volume
* of
Influent
0.20
0.32
0.38
0.51
Quantity
kg d.s./lOV
120
170
173
218
'Based on Q - 658 I capita" d" .
Primary + waste activated.
d.s.
dry sol ids.
SLUDGE DIGESTION
Before sludges can be disposed of in Ontario, they are digested.
In general, sludges from Ontario phosphorus removal facilities
have been found to be readily digestible in both existing aerobic
and anaerobic digesters. Initial problems which were experienced
could be related to the increase in sludge loading rather than the
nature of the sludge itself. This increased digester loading
has resulted in inadequate heat exchanger capacity which led to
operational problems caused by reduced digester temperature. Di-
gester (primary) foaming due to increased volatile solids loading
and inadequate gas/liquid separation has in some cases led to
further operational problems.
Inhibitive effects due to accumulated metal salts have never been
experienced. In one case (23), digester operation was completely
disrupted due to erratic lime dosing for phosphorus removal during
start-up. This resulted in periodic massive doses of high pH
21
-------
sludge being pumped to the digester until the digesters' buffer-
ing capacity was exceeded.
Later, under continuous operation, the digester was found to oper-
ate very effectively provided a sludge blanket of 0.3-0.5 m was
maintained in the clarifier. This partially neutralized the raw
sludge to a pH of 8.5-9.0.
Phosphorus resolubilization within the digester has been found to
be insignificant in relation to the total plant loading, regard-
less of the chemical used.
SLUDGE UTILIZATION AND DISPOSAL
As shown in Table 6, the most common method of sewage sludge dis-
posal in Ontario is land application of liquid digested sludge to
agricultural lands. The application of sludge to agricultural
lands is governed by Provincial Guidelines (6). Every effort is
made to dispose and at the same time utilize the sludge for its
TABLE 6, SLUDGE DISPOSAL METHODS PRACTICED IN
ONTARIO(22)
Method of Disposal
Application to
Agricultural Lands
Incineration
Landfill Application
Dumpsite
Stoiage Lagoon
Drying Beds
TOTAL
No. of
Plants
98
3
17
14
7
16
155
Percent of
Total Plants
63.2
2.0
11.0
9.0
4.5
10.3
100
Wt of Sludge
(dry tons/yr)
52,900
62,000
35,000
5,800
155,700
Percent of
Total Wt
34.0
39.8
22.5
3.7
100
potential nutrient value and soil builder characteristics. The
Guidelines take cognizance of this potential nutrient value but
at the same time ensure that no appreciable metal build-up in the
22
-------
soil will occur. Details concerning Ontario's experience have
been reported on elsewhere (21).
FULL SCALE PHOSPHORUS REMOVAL COSTS
The costs depicted in Figures 14 and 15, are capital and operating
cost data from 64 Ontario plants which had been practising phos-
12
•o" 10
I •'
1°:
CAPITAL COSTS
(1975 Dollars)
LtCAR REGRESSION &
95% CONFCENCE BAND
1 mad-4546 m'/d
0 2 4 6 81012141618202224
CAPACITY (mgd)
FIGURE 14, PHOSPHORUS REMOVAL EQUIPMENT-CAPITAL
COSTS, (24)
12
10
.*. 6
cc
4-
2-
0
OPERATIONAL COSTS*
(l975Dolars)
UNEAR REGRESSION &
95% CONFDENCE BAND
1 mgd-4546 m'/d
2 4 6 8 10 12 14 16 18 20 22 24
CAPACITY (mgd)
*Costs Exclude Chemical Costs
FIGURE 15, PHOSPHORUS REMOVAL-OPERATIONAL COSTS, (24)
23
-------
phorus removal for 3-6 years prior to the survey (24). The cost
data can be adjusted to 1979 dollars by using a multiplication
factor of 1.38. This is based on the Marshall and Swift index of
451 for 1975 and 621 for 1979. The operational costs shown in
Figure 15 exclude the cost of chemicals.
Chemical costs represent invariably the largest fraction of the
total operating cost of the phosphorus removal facility component.
Table 7 shows a percentage breakdown of the total annual costs for
a 4500 m3d~J P-removal facility.
TABLE 7, TOTAL ANNUAL COSTS FOR A 4500 MV1
P-REMDVAL FACILITY (25)
Percentage of Total Annual Coat
Maintenance
LiM Primary 19 40 41
Metallic aalt 19 70 11
Llae Tertiary 31 24 45
Actual chemical costs (1976) for operating facilities have ranged
from $0.55 to $17. per 1000 m3 of sewage treated in the plants
surveyed. The average being $5. per 1000 m3 treated.
CURRENT PICTURE
The initial and current distribution of chemical usage at Ontario
phosphorus removal facilities is summarized in Table 8 (26). As
TABLE 8, CHEMICAL USAGE DISTRIBUTION (26)
Chemical
Aluminum Sulfate
lion Salts
Lime
None
Initial
(%)
32
60
5
3
1976
(*>)
25
64
6
5
1979
W
26
70
2
2
24
-------
shown, the type of chemical used for phosphorus removal has changed
little over the years. It should be noted, however, that the
number of plants using lime has decreased dramatically. This in
part is attributable to the fact that plant operators do not like
lime and their bad experiences with lime feeding equipment.
Figure 16 summarizes the current status of phosphorus removal
technology for Ontario's primary and secondary treatment plants.
Since 1973 the total number of plants practicing phosphorus
removal has increased from 111 to 272 in 1979, out of a total of
340 plants. This represents 87% of the total hydraulic plant capac-
ity in Ontario.
COAGULANT
ftffLUENT
BOO 136
SS 208
TP 81
Vb< tnciMM
OO-j
"i
*soJ n«>
»i
EFFLUENT
BODj 45
SS 37
TP 20
VMSTE SLUDGE CHARACTERISTICS
Dri
WOO
woo-
*~
wt
.—,1700
PttOO 0«MC»LS
* OCMCALS
SLUDGE
PRIMARY PLANT
IM if** in mg/L iftttu nauM
COAGULANT DOSE (Ange)
»IFLUENT |
[ UME 70 mg/L
COAGULANT DOSE (Avge)
Fe*3 11
or
ALUM 65
EFFLUENT
BODS 13
SS 20
TP 12
-V*STE SLUDGE CHARACTERISTICS
Dry W1
VWSTE SLUDGE
1000'
,7175
CHEMICALS
OL
SECONDARY PLANT
AH IVMS art mg/L urtmt ffChc*t«d oltwrw«c
#1975 data
FIGURE 16, TYPICAL PHOSPHORUS REMOVAL PROCESSES, (27)
25
-------
Having removed all this phosphorus over the years, the obvious ques-
tion is raised: "Are we seeing any response by improved lake
water quality?" Data summarized (28) recently as shown in Figure
17 does indeed show an encouraging decreasing trend in both total
26
24
22-
20-
«-
I
r
£ 10)-
8-
6-
707274 767880826486
|26
SMOOTHED TREND OF
TOTAL I
\
SMOOTHED TREND OF SOLUBLE E
REACTIVE PHOSPHORUS
-24
22
-20
-18
-16
-14
12
PROPOSED TOTAL
P GOAL
PROPOSED
SRPGOAL
687072747678806284 66
YEAR
FIGURE 17, LAKE ONTARIO PHOSPHORUS IN SPRING 1969 TO 1979. (28)
and soluble reactive phosphorus in the offshore waters of Lake
Ontario.
This paper paper has focused on phosphorus control even though nitro-
gen has in some cases been found to be nutrient limiting.
In Ontario several municipal and industrial treatment plants
26
-------
nitrify their effluents. In these instances local water quality
requirements dictate that nitrification be practiced. In general
though, nitrogen removal is not required in Ontario.
FUTURE DIRECTIONS
The new Canada-United States Agreement signed in 1978 reaffirms
among other things the objectives outlined in the 1972 Agreement.
As far as nutrients are concerned lower targets of 0.5 mg.L"1 for
point-discharges from municipal plants in the Lower Great Lakes
are advocated.
Before embarking on this course of action the question of other
phosphorus management strategies to meet the loading targets for
the various Great Lakes has to be examined. The IJC Task Force on
Phosphorus Management Strategies has recently addressed this aspect
and has now (July 1980) delivered its final report to the IJC's
Great Lakes Water Quality Board and Great Lakes Science Advisory
Board.
It would seem reasonable though that regardless of any other new
phosphorus management strategy or strategies, every effort be made
that the initial target of 1.0 mg.L"1 total effluent phosphorus
concentration be met. Larger plants may also be in a position to
produce effluents with lower than 1.0 mg.L"1 total phosphorus con-
centration at little extra expense.
The question of phosphorus availability, its significance vis-a-vis
waste treatment processes and impact on phosphorus management
strategies remains to be resolved.
27
-------
Promising new technologies which require no or reduced amounts of
chemical precipitants for phosphorus are under development and
demonstration, which, once proven will be implemented.
SUMMARY
This paper outlined the phosphorus control program embarked on by
Canada and specifically identified the highly successful joint
venture between the Governments of Canada and the Province of
Ontario in this regard.
Some technical points of significance which should be of interest
to others are:
1 . Re.du.cU.onA in laundfty dzte.tiQe.nt phoAphotuA conc.e.ntAati.on&
tieAu.tte,d in at le.at>t 201 towe.fi infiluznt phot>phofuuA
ce.ntnationA to tn.aatme.nt plants*, hence loweA. pfie.cJipit.ant
clie.mical dotage. ne.quAtieme.ntt>, and leA& kludge. volume. Qe.ne.fi-
ate.d.
2. A pfioQfiam o£ tA.e.atability Atudie.A i& a, ptieAe.quiAite. to
-6ucce4-6jjo£ low-co&t imple.me.ntation oft clie.mical pn.e.cipitation
technology &oft pho&photwA sizmovat at e.XAAting wa&te.wateM.
tfie.atme.nt ptantb.
3. The. me.ta£ &attt> o& JUion and aluminum one. e.qu.a££y paputan a&
a. choice, oft pfie-dpitant not a. poputafi choice. o£ pfie,cipitant-
5. Simuttane.ou& pfie.cipitation at e.Xsit>ting activated Atudge.
ptantb ha& been fioiwd to be. the. mo&t e.^e.cti\)e. tow-co&t
&o£ution faon the. tiemovaJi ofa pho&phofuuA.
6. The. application o/J chemicat pfie.cipitation te.chno&iyy to
typeA o& lagoon tsi.e.atme.nt pfioceAt>eA did not pneAe.nt
any
7. SecondoAw cHa^ii^ie.fif> mutt be. deAign&d fan. oveAfitou} fiate,
asie. that an
objective, oft .1.0 mg.L'1 can be. achie.ve.d.
8. Sludge, volumes incn.e.aAe, by 60% and 351 (Jot pnimany and
&e.condaft.y plant* Uimu.Jttane.out> precipitation) tonen adding
metal AoltA to acliie.ve. an e.^lue.nt obje.ztiv£ o& .1.0 \ng L~l
total
9. Sludge. dige.6tion problem* [ae.nobic o>t anaeAobic]
not encountered.
28
-------
ACKNOWLEDGEMENTS
The author is indebted to a number of his colleagues,especially
Mr. S.A. Black, Ontario Ministry of the Environment and Dr. E.E.
Shannon, Canviro Consultants,for making some of the information
presented herein, available.
REFERENCES
1. O.E.C.D., "Eutrophication in Large Lakes and Impoundments."
(Proceedings of a Symposium held at Uppsala, Sweden, May 1968)
2. Canada Water Year Book, Environmental Management Service,
Fisheries and Environment Canada, 1976.
3. International Joint Commission, "Pollution of Lake Erie, Lake
Ontario and the International Section of the St. Lawrence
River," Vol. 1, Summary (1969).
4. "Canada-Ontario Agreement on the Lower Great Lakes Water
Quality." (August 1971.)
5. Urban Drainage Subcommittee of the Canada-Ontario Agreement
on Great Lakes Water Quality, "Manual of Practice on Urban
Drainage."
6. Ontario Ministry of Agriculture and Food - Ontario Ministry of
the Environment, "Guidelines for Sewage Sludge Utilization on
Agricultural Lands," (April, 1978).
7. International Reference Group on Great Lakes Pollution from
Land Use Activities (PLUARG), "Environmental Management
Strategy for the Great Lakes System." Final Report to the
International Joint Commission (July 1978) .
29
-------
8. Van Fleet, G.L., "Phosphorus Removal in Ontario," Phosphorus
Design Seminar, Canada-Ontario Agreement Conference Proceedings
No. 1, (1973).
9. Ministry of the Environment, "Operating Summary - Water Pollu-
tion Control Projects," (1978).
10. Stepko, W.E. and E.E. Shannon, "Phosphorus Removal Demonstra-
tion Study Using Ferric Chloride and Alum at C.F.B. Uplands,"
Environment Canada, Environmental Protection Service Report
EPS 4-WP-74-5.
11. Black, S.A., "Experience with Phosphorus Removal at Existing
Ontario Municipal Wastewater Treatment Plants," Chapter 13,
Phosphorus Management Strategies for Lakes, Loehr, Martin and
Rast, editorsjAnn Arbor Science, publishers (1980).
12. Prested, B.P., et al., "Development of Prediction Models for
Chemical Phosphorus Removal, Volume 1," Canada-Ontario Agree-
ment Research Report No. 68 (1977) .
13. Shannon, E.E. and R.J. Rush, "Phosphorus Removal Treatability
Studies at C.F.B. Borden, Petawawa, Trenton and Uplands,"
Environment Canada, Environmental Protection Service Report
EPS 4-WP-73-5.
14. Shannon, E.E. "Physical-Chemical Phosphorus Removal Processes,"
presented at the Nutrient Control Seminar, Calgary, Alberta
(February, 1980).
15. Prested, B.P., E.E. Shann and R.J. Rush, "Development of Pre-
diction Models for Chemical Phosphorus Removal, Volume II,"
Canada-Ontario Agreement Research Report No. 78, (1978).
30
-------
16. Black and Veatch, Consulting Engineers, "Process Design
Manual for Phosphorus Removal," Report to U.S. Environmental
Protection Agency, Program #170.0GNP (1971).
17. Boyko, B.I. and J.W.G. Rupke, "Phosphorus Removal Within Exist-
ing Wastewater Treatment Facilities," Canada-Ontario Agreement
Research Report No. 44 (1976).
18. Graham, H.J. and R.B. Hunsinger, "Phosphorus Reduction from
Continuous Overflow Lagoons by Addition of Coagulants to
Influent Sewage," Canada-Ontario Agreement Research Report No.
65, (1977) .
19. Ahlberg, N.R., "Phosphorus Removal in a Facultative Aerated
Lagoon - Grimsby WPCP," Ontario Ministry of the Environment,
Research Branch, (July 1973).
20. Graham, H.J. and R.B. Hunsinger, "Phosphorus Removal in Sea-
sonal Retention Lagoons by Batch Chemical Precipitation,"
Canada-Ontario Agreement Research Report No. 13, (1971).
21. Schmidtke, N.W., "Sludge Generation, Handling and Disposal
at Phosphorus Control Facilities," Chapter 15, Phosphorus
Management Strategies for Lakes, Loehr, Martin and Rast, editors;
Ann Arbor Science, publishers, (1980).
22. Antonic, M., M.F. Hamoda, D.B. Cohen and N.W. Schmidtke, "A
Survey of Ontario Sludge Disposal Practices", Project No.
74-3-19, Canada-Ontario Agreement Research Report (in press).
23. Black, S.A., "Anaerobic Digestion of Lime Sewage Sludge,"
Canada-Ontario Agreement Research Report No. 50, (1976).
24. Archer, J., "Summary Report on Phosphorus Removal", Canada-
Ontario Agreement Research Report No. 83, (1978).
31
-------
25. Schmidtke, N.W. , "Coagulation and P-Removal," Lecture presented
at the IAWPR Post-Conference Continuing Education Course,
University of Melbourne, Australia,(October 23-26, 1976).
26. Rupke, J.W.G., "Operational Experience in Phosphorus Removal,"
Chapter 14, Phosphorus Management Strategies for Lakes, Loehr,
Martin and Rast, editors; Ann Arbor Science, publishers,
(1980).
27. Schmidtke, N.W. and D.B. Cohen, "Municipal Sludge Disposal
on Land, A Down-to-Earth Solution," presented at. the 29th
Annual Convention of the Western Canada Water and Sewage
Conference, Edmonton, Alberta, September 29-30, 1977.
28. Dobson, H., "Observed Phosphorus in Lake Ontario," Great Lakes
Focus on Water Quality, 6(1), April 1980. International
Joint Commission, Windsor, Ontario.
Appendix A to this paper summarizes the many phosphorus related
studies conducted in Ontario, over the past 8 years.
Appendix B identifies nitrogen conversion/removal studies con-
ducted under the Canada-Ontario Agreement.
32
-------
APPENDIX A
PHOSPHORUS RELATED STUDIES
Project Title
Report Number*
TOPIC - 1. Phosphorus Removal - Primary and Secondary Treatment Plants
Phosphorus Removal at the Sarnia Water Pollution
Control Plant
The Use of Lime in the Treatment of Municipal
Wastewaters
Phosphorus Removal Treatability Studies at CFB Borden,
Petawawa, Trenton and Uplands
Full Scale Phosphorus Removal at CFB Petawawa
(Primary Plant)
Phosphorus Removal Demonstration Study Using Ferric
Chloride and Alum at CFB Uplands
Phosphorus Removal Within Existing Wastewater Treatment
Facilities
Phosphorus Removal Demonstration Studies at CFB Trenton
Phase I
Phase II
Phosphorus Removal Demonstration Studies Using Lime,
Alum and Ferric Chloride at CFB Borden
Phosphorus Removal Design Seminar, Toronto, 1973
Integration of Physi co-Chemical and Biological
Wastewater Treatment Processes
14
21
EPS 4-WP-73-5
EPS 4-WP-74-3
EPS 4-WP-74-5
44
EPS 4-WP-74-9
EPS 4-WP-76-4
EPS 4-WP-78-2
1 (Conf. Proc.)
7
TOPIC - 2. Phosphorus Removal - Lagoons
Nutrient Control in Sewage Lagoons
Volume I
Volume II
Phosphorus Removal in Seasonal Retention Lagoons by
Batch Chemical Precipitation
Spray Runoff Disposal of Waste Stabilization Pond
Effluent
Phosphorus Reduction from Continuous Overflow Lagoons
by Addition of Coagulants to Influent Sewage
8
23
13
22
65
TOPIC - 3. Process Control
Chemical Control for Phosphorus Removal
Individual numbers refer to reports published in the Canada-Ontario
Agreement Research Report and Conference Proceedings (Conf. Proc.)
Series.
EPS numbers are reports published in the Environmental Protection
Service, Environment Canada, Report Series.
33
-------
PHOSPHORUS RELATED STUDIES (CONT'D.)
Project Title
TOPIC - 4. Prediction Models
Development of Prediction Models for Chemical
Phosphorus Removal
Volume I
Volume II
TOPIC 5. Sources of Chemicals
Use and Production of Iron Salts for Phosphorus Removal
Utilization of Industrial Wastes and Waste By-products
for Phosphorus Removal: An Inventory and Assessment
Utilization of Aluminized Red Mud Solids (ARMS) for
Phosphorus Removal
TOPIC 6. Chemical Aids
Assessment of Polyelectrolytes for Phosphorus Removal
TOPIC 7. Process Studies
Design and Performance Criteria for Settling Tanks for
the Removal of Physical Chemical Floes
Volume I
Volume II
TOPIC 8. Polishing Processes
Effluent Polishing by Filtration Through Activated
Alumina
Volume I
Volume II
Tertiary Phosphorus Removal and Limiting Nutrient
Studies at CFS Lac St. Denis
The Welland Canal Water Quality Experiments
Report Number*
68
78
5
6
EPS 4-WP-75-2
37
10
56
39
40
EPS 4-WP-74-1
EPS 4-WP-74-10
* Individual numbers refer to reports published in the Canada-Ontario
Agreement Research Report and Conference Proceedings (Conf. Proc.)
Series.
EPS numbers are reports published in the Environmental Protection
Service, Environment Canada, Report Series.
34
-------
PHOSPHORUS RELATED STUDIES (CONT'D.)
Project Title
Report Number*
TOPIC - 9. Detergent Substitution Studies
Effect of Citrate and Carbonate Based Detergents on
Wastewater Characteristics and Treatment
A Study of NTA Degradation in a Receiving Stream
Detergent Substitution Studies at CFS Gloucester
Impact of Nitrilotriacetic Acid (NTA) on an Activated
Sludge Plant
Activated Sludge Degradation of Nitrilotriactic Acid
(NTA) - Metal Complexes
61
EPS 4-WP-74-7
EPS 4-WP-73-3
91
EPS 4-WP-78-5
TOPIC 10. Sludges
a) Dewateringy Conditioning
Sludge Dewatering Design Manual
b) Digestion Processes
Aerobic Digestion of Organic Sludges Containing
Inorganic Phosphorus Precipitates
Phase I
Volume I
Anaerobic Digestion of Lime Sewage Sludge
c) Application to Land
Land Application of Sewage Sludge
Heavy Metals in Agricultural Lands Receiving
Chemical Sewage Sludges
Volume I
Volume II
Volume III
Volume IV
Land Disposal of Sewage Sludge (Field Studies)
Volume I
Volume II
Volume III
Volume IV
Volume V
Volume VI
Volume VII
Land Application of Digested Sludge Under Adverse
Conditions
Air-Dried Chemical Sewage Sludge Disposal on Agricultur-
al Land
Volume I
Phosphate Fertilizer and Sewage Sludge Use on Agricultur
al Land - The Potential for Cadmium Uptake by Crops
72
3
58
50
9
25
30
51
16
24
35
60
73
90
98
53
EPS 4-WP-78-3
EPS 4-WP-79-2
Chemical Sewage Sludge Disposal on Land (Lysimeter Studies)
Volume I 67
Volume II 79
*Individual numbers refer to reports published in the CanadarOntario
Agreement Research Report and Conference Proceedings (Conf.Proc.) Series
EPS numbers are reports published in the Environmental Protection
Service, Environment Canada, Report Series.
35
-------
PHOSPHORUS RELATED STUDIES (CONT'D.)
Project Title
d)
e)
f)
8)
h)
i)
Heat Processes
Wet Air Oxidation of Chemical sludges
Evaluation of the Barber-Coleman Wetox Process for
Sewage Sludge Disposal
Sludge Incineration and Precipitant Recovery
Vo lume I
Volume II
Volume III
Recovery of Materials from Process Residuals
Recycling of Incinerator Ash
Removal of Phosphates and Metals from Sewage Sludge
The Removal and Recovery of Metals from Sludge and
Sludge Incinerator Ash
Reuse of Waste S02 and Phosphate Sewage Sludge by
Solidification with Lime and Fly Ash
Health Hazards
Examination of Sewage and Sewage Sludge for
En terovi ruses
Vo lume I
Volume II
Computer-aided Planning of Regional Sludge Disposal
Systems
Analysis
The Analysis of Chemical Digester Sludges for Metals
by Several Laboratory Groups
Development of an Efficient Sampling Strategy
to Characterize Digested Sludges
Sludge Handling and Disposal Seminar, Toronto,
1974 and 1978
Report Number"
12
20
31
74
75
19
28
33
69
27
52
46
EPS 4-WP-78-1
71
2 & 6
(Conf .Proc. '.
* Individual numbers refer to reports published in the Canada-Ontario
Agreement Research Report and Conference Proceedings (Conf. Proc.)
Series.
EPS numbers are reports published in the Environmental Protection
Service, Environment Canada, Report Series.
36
-------
APPENDIX B
NITROGEN RELATED STUDIES
Project Title
Report Number*
TOPIC - 1. Nitrification
Reliability of Nitrification Systems with Integrated
Phosphorus Precipitation
64
TOPIC - 2. Denitrification
Continuous Biological Denitrification of
Wastewater
Evaluation of Industrial Waste Carbon Sources
for Biological Denitrification
EPS 4-WP-74-6
EPS 4-WP-79-9
TOPIC - 3. Nitrification-Denitrification
Nitrogen Removal from Municipal Wastewater
Nitrification-Denitrification of Wastewater
Using a Single Sludge System
Volume I
Volume II
Single Sludge Nitrogen Removal
Systems
17
86
96
88
* Individual numbers refer to reports published in the Canada-Ontario
Agreement Research Report and Conference Proceedings (Conf. Proc.)
Series.
EPS numbers are reports published in the Environmental Protection
Service, Environment Canada, Report Series.
37
-------
PHOSPHORUS REMOVAL IN LOWER GREAT LAKES
MUNICIPAL TREATMENT PLANTS
Joseph V. DePinto
Michael S. Switzenbaum
Thomas C. Young
James K. Edzwald
Department of Civil and Environmental Engineering
Clarkson College of Technology
INTRODUCTION
The North American Great Lakes contain approximately 20 percent
of the world's supply of surface freshwater and, as such, are
indispensible resources worthy of every effort possible to
protect and preserve their quality. With respect to eutrophi-
cation control, it has been determined that reducing and
restricting phosphorus inputs is the best approach for the Great
Lakes. The International Joint Commission (IJC) of Canada and
the United States recognized the need for phosphorus control in
its 1978 Great Lakes Water Quality Agreement. This agreement
called for, among other things, the achievement by all plants
discharging more than one million gallons per day of "effluent
concentrations of 1.0 milligram per litre total phosphorus
maximum for plants in the basins of Lakes Superior, Michigan,
and Huron, and 0.5 milligram per litre total phosphorus maximum
for plants in the basins of Lakes Ontario and Erie." (IJC,1978).
The 1978 Agreement also provided for an eighteen month review
to confirm the cited phosphorus load limitation, followed by the
39
-------
establishment of load allocations and compliance schedules.
The purpose of this study was to provide information that might
be useful in making recommendations regarding phosphorus load
reduction requirements for municipal treatment plants in the
lower Great Lakes basins.
There are several questions related to the efficacy and desira-
bility of a 0.5 mg/L lower lakes municipal effuent phosphorus
standard which were addressed in this study. The current
status of municipal treatment plant activities in the lower
lakes with respect to phosphorus removal has been evaluated.
Such questions as "what are the prevalent approaches being taken
to reduce phosphorus effluent concentrations to 1.0 mg/L" and
"what technological needs would the treatment plants have to
reduce total phosphorus effluent levels to 0.5 mg/L or any point
below 1.0 mg/L" have been addressed. Also, there is a need to
know the reliability with which full scale treatment operation ^
can operate at the various phosphorus reduction performance
levels.
In addition to the technological aspect of establishing a phos-
phorus treatment regulation for the lower lakes treatment
plants, prudent use of the taxpayer's money requires systematic /
evaluation of the relationship between costs incurred and phos-
phorus effluent performance. These costs could then be weighed
against the economic and environmental benefits of various
phosphorus effluent limitations below 1.0 mg/L. This type of
40
-------
cost analysis at the individual treatment plant level is
examined in this study. Costs data gathered in this study can
provide crucial information and confirmation of assumptions
necessary to make basin-wide cost projections for various munici-
pal phosphorus management programs.
In order to address the questions posed in the above discussion,
this study contained the following three-phase approach:
• A survey was made of all municipal treatment plants in
the lower Great Lakes basins with effluent flows
greater than 1 MGD. The purpose of the survey was to
evaluate the phosphorus treatment approaches and plant
performance and to confirm municipal phosphorus loads.
• A detailed field operation monitoring program was
conducted at four treatment plants practicing phos-
phorus removal processes representative of lower Great
Lakes basin plants. The performance of these plants
was evaluated in terms of removal of various phosphorus
fractions and the overall effluent quality as a
function of the phosphorus removal process employed.
• A detailed analysis of costs incurred at the four
selected treatment plants was made for the existing
level of treatment. With these data as a base,
estimates were made for costs associated with
phosphorus removal.
SURVEY METHODS
In order to meet the objectives of the project, it was felt that
several important pieces of information had to be gathered on
every treatment plant in the Lake Erie and Lake Ontario basins
with a discharge flow greater than 1 MGD. It was, therefore,
determined that the following information be obtained for the
plants in question:
Identification of the location of treatment plant in
terms of lake basin, regulatory unit, county, city and
receiving water body.
41
-------
• Identification of type of treatment plant (eg.
conventional activated sludge, extended aeration,
trickling filter, primary treatment only, etc.)
• Identification of method of phosphorus removal,
including point of chemical additions and any tertiary
processes associated with P removal (such as filtration,
sedimentation, etc.).
• Identification of annual average daily flow and design
flow as well as total P concentrations in the raw
sewage and plant effluent.
It was determined that there are 229 municipal treatment plants
in the lower Great Lakes basins with a discharge greater than 1
MGD (3785 m /d). The above information was obtained for these
plants primarily from a questionnaire, which elicited a 66 per-
cent response. Although not all of the above information was
obtained from every plant, a flow and effluent phosphorus
concentration has been assigned to each of the 229 plants,
either from the questionnaire data or from an independent IJC
survey (IJC, 1979).
TREATMENT PLANT MONITORING PROCEDURES
Four different treatment plants were intensively monitored
during the field study phase of this project, which was
performed during July and August, 1979. Each of the four treat-
ment plants was visited for a two-week period, during which time
12 to 15 eight-hour composite samples (24 hour composites at the
Frank Van Lare plant) were collected from three key locations
within each plant. The sampling points for each plant were
selected in an effort to isolate the effect of the phosphorus
removal procedure. Presented in Table 1 is a listing of the
sampling locations which were used at each plant.
42
-------
TABLE 1. SAMPLING LOCATIONS WITHIN MONITORED TREATMENT PLANTS
Plant Name
Sampling Location Name Location Characteristics
Gates-Chili-Ogden
Frank Van Lare
Big Sister Creek
Ely
Raw Influent
Primary Effluent
Secondary Effluent
Raw Influent
Alum Effluent
Biological Effluent
Raw Influent
Secondary Effluent
Filtered Effluent
Raw Effluent
Secondary Effluent
Filtered Effluent
Sample taken from aerated grit
chamber
Sample taken from weir of
primary clarifier
Sample taken from weir of
final clarifier
Sample taken from aerated grit
chamber
Sample taken from weir of
primary clarifier after alum
treatment
Sample taken from weir of
final clarifier
Sample taken from post-
screening wet we!1
Sample taken from weir of
secondary clarifier
Sample taken from sand
filter effluent channel
Sample taken from aerated grit
chamber
Sample taken from weir of
secondary clarifier
Sample taken from dual media
filter effluent channel
43
-------
A flow chart of the analyses performed on the composite samples
is presented in Figure 1. Each composite sample was analyzed
on-site for chemical oxygen demand (COD), suspended solids (SS),
pH, alkalinity, soluble reactive phosphorus (SRP), total phos-
phorus (TP), total particulate phosphorus (TPP), and "available
phosphorus" (AP) as defined by NaOH extraction. Less frequently,
on-site analyses were performed to determine total Kjelclahl
nitrogen (TKN), nitrate and nitrite nitrogen (NO ), and five-day
A,
biochemical oxygen demand (BOD,.) . Phosphorus precipitation
cations (Al and Fe ) were measured off-site on sub-samples
taken in connection with the less frequent series of on-site
analyses.
For the most part the analytical methods used in this study were
according to Standard Methods (APHA, 1975) and/or recommended by
EPA (1976) . Additionally, the determination of the total NaOH-
extractable fraction of particulate phosphorus was made by an
extraction method similar to that of Sagher, et al. (1975).
Inasmuch as the particulates of interest in this investigation
were from municipal wastewaters and, thus, contained relatively
labile organic phosphorus, it was decided to measure the total
phosphorus in the extracts (rather than inorganic P only) for
comparison with bioassay tests of particulate phosphorus bio-
availability to algae.
As a verification of the chemical analysis of phosphorus avail-
ability in the wastewaters, a bioassay of algal-available
soluble and particulate phosphorus was conducted on selected
44
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samples from each plant (see Figure 1). While it is generally
accepted that only a bioassay can be used to measure truly
available phosphorus, the details of the experimental pro-
cedures vary widely (DePinto, 1978a). We have selected an
approach which employs a direct measurement of phosphorus taken
up by a test algal species, thus overcoming the problems
associated with indirect estimates relating algal growth to
phosphorus uptake. Furthermore, our approach provides for the
separation of the assay algae from the particulate material in
the plant effluent, which is a prerequisite for direct measure-
ment of algal phosphorus.
Given the above considerations it was determined a dual culture
approach similar to that currently being used in our laboratory
(DePinto, 1978b) would circumvent many of the problems
associated with bioassay determination of available phosphorus
from particulates. The apparatus employed (hereafter referred
to as a Dual Culture Diffusion Apparatus - DCDA) allows a
suspension of particulate matter from a wastewater sample to be
placed in one culture vessel (regeneration vessel) and the
placement of a unialgal assay culture (with a known P content)
in a separate assay vessel. The two vessels would be clamped
together but the contents would be separated by a 0.4 ym
membrane filter. This set-up permits repeated, routine sampling
of the algae in the assay vessel without disturbing the
particle-water system in the regeneration vessel. The membrane
between the two vessels would prevent cross-contamination of
46
-------
particulates but would allow cross-diffusion of soluble material
(including P released from the particle-water suspension). Any
available phosphorus released by the material in the regener-
ation vessel will have a tendency to diffuse across the membrane
to the assay vessel where it will be rapidly immobilized by the
P-starved algae. By periodically sampling the phosphorus
content of the assay vessel and performing a mass balance on the
system one can determine the extent to which phosphorus is being
released by the particulates. Details of DCDA operation and data
analysis can be found in McKosky (1978).
In addition to the above analysis on the suspended solids in a
sample, a bioassay of algal available P was performed on the
soluble fraction. To bioassay the fraction of total soluble
(less than 0.45 ym) phosphorus in these samples that is
available for algal uptake, a simple sequential batch uptake
experiment was performed. A filtered wastewater sample was
inoculated with algae of a known phosphorus content and subse-
quently harvested after a 3-5 day growth period to measure the
phosphorus taken up by the algae. This procedure was repeated
until no further uptake occurred. The cumulative algal-uptake
of phosphorus represented that portion of the total soluble
phosphorus that was bioavailable.
WASTEWATER TREATMENT PLANT DESCRIPTIONS
Given below are general descriptions of the treatment methods
employed at the four wastewater plants which were studied
47
-------
intensively on-site during this investigation. Included in the
descriptions are the approaches used for preliminary, primary,
secondary, and tertiary wastewater treatment, and sludge treat-
ment and disposal.
GATES-CHILI-OGDEN
At the Gates-Chili-Ogden facility, a 20 MGD plant located near
Rochester, NY, raw municipal wastewater was given preliminary
and primary treatment prior to biological treatment, by a con-
ventional activated sludge process. To remove phosphorus, alum
was added in liquid form to the effluent of the aeration basin,
upstream from the final clarifiers as illustrated in the process
schematic (Figure 2). The secondary sludge, which consisted of
biological and aluminum-phosphorus solids, was partially
recycled to the aeration basin and partially wasted. By recy-
cling alum with the return activated sludge, the contact period
between alum and phosphorus in the wastewater was increased,
which would permit kinetically-limited precipitation reactions
to approach equilibrium more closely than could occur without
alum recycle. Waste secondary sludge was conditioned for
flotation thickening with a polymer and combined after thicken-
ing with primary sludge. The combined sludges were dewatered by
vacuum filtration and incinerated or composted on-site.
FRANK VAN LARE
The Frank Van Lare wastewater treatment plant is located in
Rochester, NY. It has an average daily flow of approximately
100 MGD. During the monitoring studies, treatment consisted of
48
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two main streams, as shown in the process schematic (Figure 3).
Raw wastewater received preliminary screening and degritting and
was then split for primary sedimentation and further treatment.
To 20 percent of the total flow, liquid alum and a polymer were
added just upstream from the primary clarifiers to enhance phos-
phorus removal during primary sedimentation. The remainder of
the flow was given primary treatment, without alum addition, and
biological treatment by conventional activated sludge. The
clarified secondary effluent and alum-treated primary effluent
were combined for chlorination prior to discharge. The primary
sludges from both treatment streams were combined with wasted
biological sludge for treatment by gravity thickening, vacuum
filtration, and incineration.
BIG SISTER CREEK
The Big Sister Creek wastewater treatment plant, a 3.1 MDG plant
located near Angola, NY, was upgraded in 1978 from a primary
treatment facility to a tertiary treatment system. As shown in
the process schematic for the Big Sister Creek plant (Figure 4),
screened and degritted raw wastewater was sent without primary
sedimentation to an aeration basin for biological treatment by
an extended aeration activated sludge process. Effluent from
the aeration basin is clarified by sedimentation and 70 percent
of this flow was dosed with ferric chloride and a polymer for
phosphorus removal in a solids contact clarifier. Effluent from
the solids contact clarifier was applied to a sand filter, after
which the filtrate was chlorinated for discharge. A portion of
50
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the iron-phosphorus sludge from the solids contact clarifier was
recycled back to the clarifier influent. The sludge recycle
provides an increased contact period between iron and wastewater
phosphorus, which permits a closer approach to precipitation
equilibrium, than would occur in the absence of solids recycle.
Both secondary and iron-phosphorus sludges were thickened by
flotation and combined for storage in an aerobic digester.
Centrifugation and sand bed drying were employed for sludge de-
watering. Dewatered sludge was trucked to an adjacent land fill
for disposal.
ELY
As illustrated in the process schematic for the Ely, MN waste-
water treatment plant (Figure 5), screened and degritted raw
wastewater was given primary settling before biological treat-
ment, which consisted of a single-stage trickling filter.
Liquid alum and a polymer were added to the trickling filter
effluent to enhance phosphorus removal during secondary
clarification. All biological solids and alum-phosphate sludge
which collected in the final clarifiers were recycled to the
influent of the primary sedimentation tanks, which served to
increase the time of contact between the alum, wastewater solids,
and phosphorus. The secondary effluent was chlorinated, held
briefly in non-functional solids contact tanks, and passed
through a dual media filter prior to discharge from the plant.
Sludge from the primary clarifier was thickened by gravity and
conditioned with lime prior to vacuum filtration. A landfill
53
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54
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was used for disposal of the vacuum filter cake.
SURVEY RESULTS
The distribution of municipal treatment plants in the lower
Great Lakes basins by state and Canadian province is presented
in Table 2. Note that for the Lake Ontario basin the distribu-
tion of plants is relatively equal between U.S. and Canada;
however, 77 percent of the Lake Erie basin plants are located in
the U.S. These 229 plants range in annual phosphorus discharge
from 0.6 to 2000 metric__tons/yr, with effluent total phosphorus
concentrations ranging from 0.3 to 17.5 mgP/L.
PHOSPHORUS REMOVAL APPROACHES
Based on the results of the questionnaire, an estimate of the
relative distribution of treatment approaches for phosphorus
removal at wastewater plants in the lower Great Lakes vicinity
can be made. Of the 154 plants responding to the questionnaire,
104 indicated that phosphorus removal was being practiced while
30 were not practicing phosphorus removal. An additional 20
plants were eliminated from those who responded since they were
later determined to be located outside the lower lakes basins or
abandoned. Thus, from the questionnaire responses approximately
80 percent of the plants in the survey practiced phosphorus
removal.
A summary of the major chemicals used for phosphorus removal and
their point of addition in the treatment process (i.e. primary,
secondary or tertiary) is shown in Table 3. Of the 104 plants
55
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TABLE 2. NUMBER OF PLANTS IN SURVEY
Lake Ontario
New York
Ontario
48
43
91
U.S. 48
Canada 43
Lake Erie
New York
Pennsylvania
Indiana
Michigan
Ohio
Ontario
10
1
3
23
69
32
138
U.S. 106
Canada 32
Totals: U.S. 154
Canada 75
229
56
-------
practicing phosphorus removal, 53 used an iron salt (one more
than shown in Table 6 as one respondent listed iron but did not
specify where), 49 used an aluminum salt, and only two used
lime. One plant used both iron and alum. The frequency of use
of the precipitation cations (aluminum or iron) is compared by
country in Table 4. In comparison, Fe or Al are used with about
the same frequency. Lime is now seldom used, based on our
survey.
In regard to the point in the treatment scheme where the majority
of phosphorus removal takes place, the data are summarized in
Table 5. At this point in time a relatively small percentage of
the plants are actually using a tertiary process to accomplish
phosphorus removal. A summary of the data suggests that
approaches for phosphorus removal include aluminum addition to
the secondary process, iron addition to primary, and iron addi-
tion to the secondary process, in order of decreasing frequency
of use.
PHOSPHORUS REMOVAL ACCOMPLISHMENTS
In spite of the fact that very few truly tertiary processes are
employed in the lower lakes area, those plants practicing phos-
phorus removal appear to be consistently achieving a 1.0 mgP/L
effluent total phosphorus goal. A frequency distribution,
developed for 30-day average effluent phosphorus concentrations,
is presented in Figure 6. Note that more plants (112) are
achieving a 1.0 mgP/L standard than the number which indicated
that they were practicing phosphorus removal (104). Of the
57
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TABLE 3 TREATMENT APPROACHES BY CHEMICAL
(PRECIPITATION CATION) AND LOCATION
Number of Plants
Primary
Secondary
Tertiary
Total
Al
1
26
2
29
U.S
Fe
16
6
2
24
Canada
Total
17
32
4
53
Al
2
17
1
20
Fe
20
8
0
28
Total
22
25
1
48
Al
3
43
3
49
Total
Fe
36
14
2
52
Total
39
57
5
101
TABLE 4. FREQUENCY OF PRECIPITATION CATION USAGE
Metal
Al
Fe
Lime
U.S.
54
44
2
Percent
Canada
41
57
2
Total
48
50
2
TABLE 5. SUMMARY OF LOCATION OF PHOSPHORUS REMOVAL TREATMENT
IN THE TREATMENT PLANT PROCESS
Process
Location
U.S.
Percent
Canada
Total
Primary
Secondary
Tertiary
32
60
8
46
52
2
39
56
5
58
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EFFLUENT PHOSPHORUS CONCENTRATION ( mg/
8O OOOOOO OoO
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plants for which effluent P data were available, 9 percent have
an effluent total phosphorus concentration £ 0.5 mgP/L and 52
percent are discharging <_ 1.0 mgP/L. These accomplishments are
summarized by plant size and basin in Table 6.
Whether required or not, there are _]^9__p_laiv^s_J.n^ jthe_JDa£>ins
currently meeting^ a 0 .5. jngP/L^standard-.. We received a
questionnaire response, and therefore have treatment approach
information, on 14 of these 19 plants. It is especially
interesting to note that only 2 of_the J__4_plants are currently
employing any tertiary treatment processes. Seven of the plants
use Fed (some also use a polymer) or pickle liquor at some
point in the treatment process; three of the plants use jilum; and
three plants claim to achieve 0.5 mgP/L_with no chemical addition
simply because the influent phosphorus is so low (1-2 mgP/L).
In order to get some feel for what percentage removals are
currently needed to meet today's effluent phosphorus standards,
a frequency distribution of removal percentage was prepared from
our questionnaire data (Figure 7). It should be pointed out
that only 117 plants made up the sample for this distribution,
since both influent and effluent data were necessary to compile
removal percentages. Recall that approximately 80 percent of
the respondents to the survey were practicing phosphorus removal,
yet only 63 percent_.g,f_t.hgse reporting influent and effluent
phosphorus levels were achieving 80 percent removal of total
phosphorus through the plant.. Virtually all (96 percent) of the
60
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TABLE 6. DISTRIBUTION OF PLANTS BY SIZE AND BASIN REACHING
1.0 and 0.5 mg P/L TOTAL PHOSPHORUS EFFLUENT
CONCENTRATIONS
Plant Size No. of Plants
(mgd)* in Size Range**
<1 12
1-<10 94
10-<50 18
50-<100 5
>100 2
Total 131
1 5
1-<10 60
10-<50 11
50-<100 4
>100 3
Total 83
Plants Meeting
1 .0 mg P/L Standard
Lake Erie
6
47
14
1
1
69
Lake Ontario
3
29
8
1
2
43
Plants Meeting
0.5 mg P/L Standard
0
8
3
0
0
11
2
5
1
0
0
8
* 1.0 mgd = 3,785 m3/d
** Phosphorus effluent data were not available for 7 plants in the Erie
basin and 8 plants in the Ontario basin
61
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plants which reported removal of 80 percent or more were using
iron or aluminum for precipitation during treatment. Conversely,
only 68 percent of all the plants which employed chemicals for
phsophorus removal were achieving removal of 80 percent or
better.
The above data suggest two possibilities: either the treatment
plants do not generally have to remove 80 percent of the phos-
phorus to meet 1.0 mgP/L effluent concentration, or there is
room for improvement in many plants as far as phosphorus removal
efficiency is concerned. For two reasons it seems likely that
the latter case is most prevalent. First, 47 percent of the
lower lakes plants are failing to meet a_l.0 mgP/L standard.
Also, according to our questionnaire the mean influent phos-
phorus concentration to plants in the lower lakes is 6.3 mgP/L.
This means that on the average 84 percent TP reduction through
plant would be necessary to achieve a 1.0 mgP/L effluent standard
and 92 percent TP reduction would be necessary to achieve a 0.5
mgP/L effluent concentration.
FIELD MONITORING RESULTS
OVERALL TREATMENT PERFORMANCE
In order to evaluate the performance of the four intensively
monitored plants with respect to phosphorus removal, it was
deemed necessary to also monitor the plant performance with
respect to the more conventional wastewater parameters. A
summary of the overall performance data during the monitoring
period for each plant is presented in Table 7.
63
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The G-C-O, Big Sister Creek and Ely plants were all performing
quite well with respect to secondary treatment. On the order of
90 percent or greater removal of BOD5 and suspended solids was
being accomplished during the monitoring periods. In these
plants, therefore, adequate phosphorus removal was not being
hampered by an inefficient secondary treatment system.
On the other hand, the Frank Van Lare plant, during our monitor-
ing period, was less efficient than the other plants at removing
conventional wastewater pollutants. The biological treatment
stream was adequately removing BOD-; however, the effluent
suspended solids from the final clarifiers was erratic and
averaged 53 mg/£ during the two-week monitoring. It should be
pointed out that one of the final clarifiers and several primary
sedimentation tanks were out of service at this time. As a
result, the suspended solids removal facilities in the biological
treatment stream were often overloaded. Phosphorus removal on
this portion of the flow was as good as could be expected under
the circumstances.
As might be expected, the BOD- removal was not good in the 20
percent of the flow receiving only the alum-enhanced primary
sedimentation. The suspended solids removal in this process was
slightly better than might be anticipated in a conventional
primary sedimentation process, no doubt due to the use of alum
in the system. However, it will become evident in later
discussions that solids separation problems were the cause of
lower total phosphorus removal efficiencies at the Van Lare plant,
66
-------
PHOSPHORUS REMOVAL PERFORMANCE
Presented in Table 8 is a summary of data collected on phos-
phorus during the field monitoring studies. These data are
listed by plant and sampling location within each plant and
include the average values of total phosphorus as well as several
fractions of the total phosphorus in the wastewater.
Gates-Chili-Ogden
At the Gates-Chili-Ogden plant, the addition of alum to the
aeration tank effluent resulted in an excellent reduction of all
fractions of phosphorus analyzed (Figure 8). Soluble phosphorus
removal or conversion to particulate P was slightly more
efficient than particulate phosphorus removal, thus causing a
decrease in the relative total soluble P from 62 percent of the
total P in the raw influent to 45 percent of the total P in the
secondary effluent. As shown in Table 8, only a slight
reduction in particulate phosphorus (about 30 percent) occurred
during primary treatment, and virtually no change in soluble
phosphorus took place.
It was also noted that the relative contribution of the NaOH-
extractable phosphorus (EXP) to the total particulate P increased
through the plant. Particulate phosphorus which is formed during
alum precipitation would be likely to contribute directly to the
NaOH-extractable fraction, which probably explains the observa-
tion.
67
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GATES-CHILI-OGDEN
TP TPP EXP TSP SRP
RAW INFLUENT
TP TPP EXP TSP SRP
FINAL EFFLUF.NT
Figure 8. Mean Concentrations of Phosphorus and Phosphorus
Fractions at the Gates-Chili-Ogden Plant. Error
Bars Signify +_ One Standard Deviation for the 12
Samples Analyzed.
70
-------
Frank Van Lare
Reduction of total phosphorus at this plant was similar in both
the biological treatment stream (60 percent) and the alum-
primary settling stream (66 percent) (Figure 9). In both cases
soluble P reduction was sufficient, but particulate phosphorus
reduction was not effective enought to achieve a total P
standard of 1.0 mgP/L. The phosphorus removal in the biological
stream was typical for this treatment scheme. However,
relatively ineffective solids separation in the alum-primary
settling process accounted for a lower removal percentage than
might be expected. This ineffective capture of aluminum-
phosphorus precipitation solids resulted in a relatively large
fraction of the effluent particulate P from this process being
NaOH-extractable (91 percent).
Big Sister Creek
The performance of the Big Sister Creek plant for phosphorus
removal is illustrated in Figure 10. Figure 10 shows a near 70
percent reduction in total raw wastewater phosphorus from
biological treatment alone, due almost exclusively to removal of
particulate phosphorus. The effluent from the secondary
clarifier averaged 0.17 mgP/L of total particulate phosphorus,
compared with 4.40 mgP/L in the raw wastewater, while the total
soluble phosphorus concentration averaged 2.13 and 2.15 mgP/L on
samples taken from the two locations. The unusually low
particulate P in the secondary clarifier effluent was the result
of excellent solids separation in this phase of treatment.
71
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73
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The data indicate that iron precipitation reduced the total
soluble phosphorus from 2.13 mgP/L in the secondary effluent to
0.16 mgP/L in the solids contact clarifier effluent. Sand
filtration was really unnecessary for phosphorus removal at this
plant. The increased concentration of phosphorus observed in
the filtered effluent, after iron precipitation, was due to
routing of a portion of the secondary effluent around the solids
contact clarifier for mixing with the iron treated effluent
downstream from the clarifier and application to the sand
filters.
ELY
Very good phosphorus removal was being accomplished at the Ely
plant (Figure 11), with the filtered effluent very close to
meeting a 0.5 mgP/L standard. The Ely plant has a permit
requiring a 0.4 mg/L total phosphorus effluent level. Excellent
reduction of soluble phosphorus was accomplished by alum
addition to the trickling filter effluent; however, high
suspended solids in the secondary clarifier effluent was again
responsible for only a 33 percent reduction of particulate P to
that point. Through the dual media filter, the extremely low
concentrations of soluble phosphorus did not change, while the
total particulate fraction was reduced to 20 percent of the raw
wastewater particulate phosphorus.
An examination of the distribution of fractions of total phos-
phorus through the plant shows the approach to treatment at Ely
favored removal of phosphorus from the soluble fraction to the
74
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75
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extent that over 90 percent of the total phosphorus which
remained in the wastewater after alum treatment or filtration
occurred as particulate phosphorus (Table 8). Additionally, the
NaOH extractable fraction of the total particulate phosphorus
was an increasingly predominant component of that fraction,
relative to the total phosphorus that remained in the wastewater
at the stages of treatment which were sampled.
PHOSPHORUS BIOAVAILABILITY RESULTS
Algal bioassays were conducted on 22 samples of wastewater, taken
from various locations in each of four wastewater treatment
plants, to determine the availability of phosphorus, both soluble
and particulate, to aquatic organisms; and, to determine the
extent of relationship, if any, between analytically-defined
chemical fractions and bioassay-defined available phosphorus.
The results of these experiments are presented in Figures 12
through 15 for each of the four plants in our field study. A
comparison of available phosphorus fractions at the different
sampling points in each wastewater plant indicated that, at the
wastewater plants selected for study, the methods of treatment
had no major effect on the biologically available fraction of
either soluble or particulate phosphorus relative to the total
phosphorus content of those fractions (Table 9). Thus, with the
exception of the Van Lare plant, reductions of available phos-
phorus fractions through the plants corresponded quite closely
with the reductions in the analytically-defined chemical
fractions. Among the three plants behaving in this way, the
76
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TABLE 9. PERCENTAGES OF BIOLOGICALLY AVAILABLE PHOSPHORUS AND
REDUCTION IN BIOLOGICALLY AVAILABLE PHOSPHORUS AT
MONITORED WASTEWATER PLANTS
Percent
Biologically Available
Phosphorus
Plant Name and
Sampling Location*
Gates-Chili-Ogden
Raw Influent (1 )
Primary Effluent (
Secondary Effluent
Frank Van Lare
Raw Influent (2)
Alum Effluent (2)
1)
(2)
Biological Effluent (2)
Big Sister Creek
Raw Influent (2)
Secondary Effluent
Filtered Effluent
Ely
Raw Influent (2)
Secondary Effluent
Filtered Effluent
(2)
(2)
(2)
(2)
TBAP
TP
60
60
58
72
68
73
80
88
76
71
66
64
BAPP
TPP
62
68
74
44
52
62
40
48
40
59
63
62
BASP
TSP
59
57
40
88
86
82
94
91
79
82
92
86
Reduction of Biologically
Available Phosphorus
Compared to Raw Influent
TBAP
-
-
88
-
51
26
-
58
85
-
64
83
BAPP
-
-
79
-
12
38
-
90
96
-
21
62
BASP
-
-
94
-
59
41
-
53
83
-
92
96
Number of samples assayed is given in parentheses.
81
-------
percentage removals of total phosphorus ranged from 85 to 88
percent (Table 8), while total available phosphorus (BAP)
removal ranged from 83 to 88 percent (Table 9).
The results of these experiments could be summarized by noting
that biologically available phosphorus averaged 72 percent of
the total phosphorus. the available particulate fraction
averaged 55 percent of the total particulate phosphorus, and the
available soluble fraction averaged 82 percent of the total
soluble phosphorus concentration in the wastewater samples. It
should be noted that these fractions are based on relatively
short-term (approximately 2 weeks) incubations; and, although
accumulation of phosphorus by the DCDA assay cultures was slow
towards the end of the incubation, a larger availability
likely would have been measured with longer-term incubations.
Attempts to correlate biologically available phosphorus with
various chemically-defined measures in the 22 samples assayed
yielded several quite good correlations. Among the best was
simply a correlation between total phosphorus and total bio-
available phosphorus. This correlation is illustrated in Figure
16. The fact that the slope of the line in Figure 16 is
identical to the average BAP/TP ratio for all the samples
reflects the narrow range of values for that proportion among
the treatment plants as well as between sampling locations with-
in a plant.
82
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83
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COSTS FOR PHOSPHORUS REMOVAL
The proper evaluation of a given phosphorus effuent standard
requires the costs incurred as well as the benefits obteiined.
As was stated previously, one of the goals of this study was to
analyze the costs incurred at the four selected treatment plants
associated with phosphorus removal. A summary of these costs is
presented in Table 10, comparing these costs to the total
operation and maintenance costs (O&M) at each of the four plants.
The data indicate a wide variation in both total and phosphorus
associated O&M costs for the four plants. On a $/1000 gallons
basis, the two plants with tertiary treatment had much higher
costs for phosphorus removal. The ratio of associated phos-
phorus removal costs to total O&M costs also varied widely
among the four plants.
A more detailed breakdown of the various fractions of the O&M
costs associated with phosphorus removal is presented in Table
11. In general the most sensitive item was chemical costs.
Labor and power costs were more significant at the plants with
tertiary treatment (Ely and Big Sister Creek) than those with
only secondary treatment (GCO and Van Lare). Sludge costs were
in general substantial but it should be pointed out that the
sludge production associated with phosphorus removal is generally
only a small fraction of the total sludge generated at these
treatment plants. This is shown in Table 12. It should be
pointed out, however, that the sludge generated from phosphorus
removal is more difficult to handle and process than typical
84
-------
TABLE 10. TOTAL O&M COSTS AND O&M COSTS ASSOCIATED
WITH PHOSPHORUS REMOVAL AT FOUR
MONITORED TREATMENT PLANTS
Treatment
Gates-Chil
El/
Big Sister
Frank Van
Plant
2
i-Ogden
Creek3
Lare4
106
1
0
0
9
Total
$/Year
.035
.301
.569
.015
O&M
$/l
0
0
0
0
Costs
000 gal
.214
.916
.482
.243
O&M
106
0
0
0
0
Costs
$/Year
.141
.035
.121
.407
for P
$/l
0
0
0
0
Removal
000 gal
.030
.107
.109
.011
% Total O&M
for P Removal
14.0
11.7
22.6
4.5
Base Period: Nov. '78-April '79
2
Base Period: Summer '79; excluding sludge costs, which were unavailable because
of recent changeover to alum treatment approach
3Base Period: 1978
4Base Period: Feb. '79-June '79
85
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TABLE 11. BREAKDOWN OF ASSOCIATED O&M COSTS
Item
Labor
Power
Chemical
Sludge
Disposal
Item
Labor
Power
Chemical
Sludge
Disposal
GCO1
Unit Cost $71000
$7.00/hr <0.
$0.031/Kw-hr <0.
$0.059/lb 0.
liquid alum
$71.40/ton 0.
dry solids
Big Sister Creek
Unit Cost $/l
$7.00/hr
Unavailable
FeCla $0.0895/lb
Polymer $1.40/lb
$223/ton
dry solids
gallons
001
001
025
004
000 gallons
0.081
0.004
0.011
0.013
Elj
Unit Cost
$6.00/hr
$0.06/Kw-hr
Unavailable
Unavailable
Frank Van
Unit Cost
$7.00/hr
$0.029/Kw-hr
Alum $0. 059/1 b
Polymer $1.32/lb
$158/ton
dry solids
2
$/1000 gallons
0.038
0.019
0.050
-
La re4
$71000 gallons
0.0001
0.0001
0.0007
0.004
1
Base Period:
>
"Base Period:
Base Period:
Base Period:
Nov. '79-April '79
Summer 1979
1978
Feb. '79-June '79
86
-------
TABLE 12. SLUDGE PRODUCTION AT THE FOUR
MONITORED TREATMENT PLANTS
GCO
Ely
Big Sister Creek
Frank Van Lare
Total Sludge
lbs/106 gallons
1387
3415
990
1529
P Sludge
lbs/106 gallons
120
82
116
252
87
-------
primary and secondary sludges generated at wastewater treatment
plants. The costs shown in Table 11 for sludge disposal were
calculated from stoichiometric relationships and then assigning
that fraction of the unit cost to the phosphorus sludge. There-
fore, they are probably on the liberal side.
CONCLUSION
The survey and field studies of phosphorus removal performance
at municipal wastewater treatment plants in the lower Great
Lakes basins were quite useful in revealing the current trends
in full-scale phosphorus removal practice and the kejys to
successful phosphorus removal. Our survey showed that the basic
approach most frequently employed to comply with present phos-
phorus effluent restrictions amounted to ^he addition of iron or
aluminum to the wastewater at some point in a conventional
secondary treatment system. Furthermore, both the survey and
the field studies indicated that average final effluent total
phosphorus concentrations of less than 1.0 mgP/L could be
reliably attained without resorting to filtration.
Based on the field studies, achieving a low concentration and
less available phosphorus effluent via chemical treatment could
best be accomplished by converting as much of the wastewater
phosphorus to a particulate form, followed by conservative design
and operation of clarification facilities. In the four plants
studied, phosphorus removal problems were the result of over-
loaded settling tanks. On the other hand, the G-C-0 plant total
phosphorus effluent averaged 0.75 mgP/L while operating the final
88
-------
2
clarifier at overflow rates of 300-450 gpd/ft , conservative
2
operation compared to the design rate of 650 gpd/ft . At Big
Sister Creek, a tertiary plant, an effluent level of 0.5 mgP/L
was consistently met by operating the solids contact clarifier
for the iron + polymer treated secondary effluent at overflow
2
rates ranging from 380-550 gpd/ft . The filtration step,
although reducing the average particulate P solids contact
clarifier effluent from 0.19 mgP/L to 0.06 mgP/L in the sand
filter effluent, proved to be unnecessary for achieving a 0.5
mgP/L standard.
Consequently, in planning and designing for phosphorus removal
at municipal facilities careful evaluation of less costly,
alternative treatment approaches should be performed before
resorting to a more expensive filtration process. Furthermore,
more full-scale studies should be undertaken to optimize
chemical addition at some point in a conventional secondary
treatment system as a phosphorus removal alternative. Optimi-
zation of such operational parameters as point of chemical
addition and dosage, clarifier overflow rates, and solids
retention times should be the focus of these studies.
-------
REFERENCES
1. APHA, Standard Methods. 1975. 14th Edition, American
Public Health Association, Washington, D.C.
2. DePinto, J.V. 1978a. Phosphorus Availability of Aquatic
Sediment Material: A Review. Environmental Engineering
Technical Report. Clarkson College of Technology,
Potsdam, N.Y. 24 pp.
3. DePinto, J.V. 1978b. Annual Progress Report of EPA Grant
No. R-804937. November 1, 1976 - October 31, 1977.
4. IJC. 1978. Great Lakes Water Quality Agreement of 1978.
5. IJC. 1979. Inventory of Major Municipal and Industrial
Point Source Dischargers in the Great Lakes Basin. Great
Lakes Water Quality Board Remedial Programs Subcommittee.
6. McKosky, P.M. 1978. Laboratory Study of the Kinetics of
Phytoplankton Decomposition and Subsequent Phosphorus
Regeneration. M.S. Thesis. Clarkson College of Technology,
Potsdam, N.Y. 99 pp.
7. Sagher, A., R.F. Harris, and D.E. Armstrong. 1975.
Availability of sediment phosphorus to microorganisms.
Technical Report WISWRC-75-01. Water Resources Center,
University of Wisconsin, Madison.
8. USEPA. 1976. Methods for Chemical Analysis of Water and
Wastes. U.S.E.P.A. Office of Technology Transfer,
Cincinnati, Ohio.
90
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EXPERIENCES AT GLADSTONE, MICHIGAN
UTILIZING ROTATING BIOLOGICAL CONTACTORS
FOR BOD-5, PHOSPHORUS, AND AMMONIA CONTROL
Willard Morley
Superintendent
Water & Wastewater Treatment
Gladstone, Michigan
INTRODUCTION
In March of 1974, the first federally funded municipal waste-
water treatment plant utilizing Rotating Biological Contactors
(RBC) was placed in operation in Gladstone, Michigan. The plant
was designed by Williams & Works of Grand Rapids, Michigan to
replace an existing primary treatment plant at the same site.
Because, in many respects, this plant was the first of its kind
in the United States, the performance of the system in a mod-
erately severe northern climate has received a relatively high
degree of scrutiny by engineers and manufacturers engaged in the
design of other RBC installations. The design considerations
for this plant, operating data for four years of operation, and
some general observations about RBC installations based on the
Gladstone experience will be presented in this paper.
DESIGN CONSIDERATIONS
Gladstone, Michigan is a predominantly residential community of
about 5,000 people located in the southern part of Michigan's
Upper Peninsula, on the shore of Lake Michigan, approximately 10
miles north of Escanaba. The climate in the area is character-
ized by cool, dry summers and cold, snowy winters. The mean
91
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annual temperature is 42°F (5.5°C). Gladstone derives its water
supply from Lake Michigan and wastewater temperatures are
frequently in the mid 40's (°F) during winter months.
The 1.0 mgd (3,785 cu m/day) RBC plant was designed to provide
secondary treatment and phosphorus removal on the site of an
existing primary treatment plant. A system incorporating housed
rotating biological contactors was selected on the basis of
aesthetics, operational advantages, and data from successful
pilot plant testing. The general design parameters are listed
in Table 1.
Table 1
General Design Parameters
Population 10,000
BOD-5 1,670 Ib/day (9758 kg/day)
TSS 2,000 Ib/day (908 kg/day)
Average Daily Flow 1.0 mgd (3,785 cu m/day)
Peak Flow 2.88 mgd (10,000 cu m/day)
Effluent Quality Limitations:
BOD-5 30 mg/1 (30-day average)
Total Suspended Solids 30 mg/1 (30-day average)
Total Phosphorus (TP.) 20% of influent TP
General pilot plant tests of the RBC process were conducted at
the University of Michigan in Ann Arbor in 1968-1969 under the
supervision of Professor J.A. Borchardt. The pilot plant
consisted of three stages in series, each with fifty, 4-foot
92
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(1.22 m) diameter, 0.5-inch (1.27 cm) thick disks, with 0.75-in.
(1.90 cm) spacings between the disks. The pilot plant was
operated for approximately one year using raw wastewater and
primary effluent from the Ann Arbor municipal treatment plant.
Some results of the pilot plant tests are summarized in Table 2.
In general, this jpilot plant expeerience offered the following
design considerations:
Primary treatment is necessary to prevent accumulations of
debris on RBC shafts and to increase overall BOD-5
removals.
The RBC shafts must be rotated at a speed sufficient to
entrain sloughings and mixed liquor solids. At low speeds,
solids accumulations within the RBC tankage caused the
depletion of dissolved oxygen and created odor nuisances.
An average of 80 to 93 percent overall BOD-5 removals were
consistently achieved at hydraulic loadings of 1 to 4 gpd
per sq. ft. and at temperatures ranging from 48° to 63°F.
At similar hydraulic loadings, BOD-5 reductions through the
RBC process dropped about 1% for each 1°C drop in
wastewater temperature.
A schematic flow diagram of the treatment facility is shown in
Figure 1. The design parameters of the unit processes and
appurtenant equipment are summarized in Table 3. Raw wastewater
is screened and pumped to two grit chambers, then it is
comminuted and settled in a single, rectangular primary
clarifier, salvaged from the old plant. Primary clarifier
effluent is split to two parallel RBC paths, each with three
shafts and six stages. Mixed liquor within the RBC tanks flows
through 2-foot (0.61 m) diameter submerged openings to
subsequent stages. RBC efluent is dosed with liquid alum for
phosphorus precipitation prior to pumping to twin rectangular
93
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INFLUENT
LANDFILL
SLUDGE
DRYING
BEDS
SECONDARY
DIGESTER
PRIMARY
DIGESTER
BAR SCREEN
RAW SEWAGE PUMPS
GRIT CHAMBERS
PARSHALL FLUME
COMMINUTOR
PRIMARY CLARIFIER
ROTATING
BIOLOGICAL
CONTACTORS
(LIQUID ALUM FEED)
SECONDARY PUMPS
•{POLYMER FEED)
FINAL CLARIFIERS
TO LAKE MICHIGAN
CHLORINE
CONTACT
CHAMBER
Figure 1. Wastewater Treatment System
Gladstone, Michigan
94
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Table 3
Unit Process and Equipment Data
Equipment
Raw Sewage Pumps
Primary Clarifier
RBC Units
RBC Effluent Pumps
Secondary Clarifiers
Chlorine Contact
Primary Digester
Secondary Digester
Tank Truck
Drying Beds
Liquid Alum Storage
Design Data
3@ 1,400 gpm (88.3 I/sec), 2
variable speed, 1 constant speed
lag pump
1 rectangular 70,000 gallon (265
cu in) capacity with 1.5 hr.
detention and 895 gpd/sq ft
(36.5 cu m/day/sq m) overflow
rate
Bio-Surf by Autotrol. Two
parallel paths with three shafts
and six stages in each, 515,500
ft2 (47,890 sq m) of media,
90 minutes retention and 1.94
gpd/sq ft (0.097) cu m/day/sq m)
hydraulic loading rate
Same as raw sewage pumps
2 rectangular, 2.75 hr detention
and 620 gpd/sq ft (25.3 cu
m/day/m2) overflow rate
2 baffled tanks, 35 min reten-
tion
1 fixed cover, 100,000 gal
(378.5 cu m) capacity with 15.5
days detention at design
loading, heated, mixed by gas
recirculation
1 floating cover, 100,000 gallon
(378.5 cu m) capacity with
supernatant discharge to raw
wastewater wet well
1 2,500 gallon
capacity
(9.4 m3)
Adjoining sanitary landfill
site, 600' x 200' (183 m x 61
without underdrains
m)
2 tanks, each 2,600
cu m) capacity
gallons (9.8
96
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clarifiers. Secondary effluent is chlorinated prior to
discharge to Lake Michigan.
Grit is manually cleaned from the grit chambers and disposed of
at a sanitary landfill. Settled primary and secondary sludges
are pumped to a primary anaerobic digester that is heated and
equipped with gas recirculation and mixing apparatus. Settled,
digested sludge from the secondary digester is withdrawn by tank
truck to sludge drying beds off-site. Dried sludge is disposed
of in a sanitary landfill. Supernatant from the secondary
digester is drained by gravity to the raw wastewater wet well.
INITIAL OPERATING EXPERIENCE
The operation of the plant was begun on March 1, 1974. At the
same time, an 18-month testing and shakedown program was begun
to monitor the performance of the plant and to make operational
improvements where necessary. During this period, wastewater
flows averaged 0.755 mgd (2,875 cu m/day) and were influenced
occasionally by sewer infiltration and inflows. At start-up,
wastewater temperatures averaged 45°F (7.2°C), then gradually
increased to the low 60's (°F) by mid-summer.
Influent BOD-5 concentrations ranged from 129 to 219 mg/1 and
influent total suspended solids concentrations ranged from 101
mg/1 to 168 mg/1. The average influent BOD-5 and total
suspended solids concentrations for the test period were 164
mg/1 and 132 mg/1, respectively.
97
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The results of the initial 18-month test period are summarized
as follows:
Because the influent wastewater temperatures were quite
cold at start-up, it took 18 days before heavy sloughings
of biomass were observed and several months to achieve a
steady state operation.
During the last 12 months of the testing period (September
1974 through September 1975) with the addition of 70 mg/1
of alum and 0.8 mg/1 of polymer, effluent BOD-5's were
generally less than 10 mg/1; effluent suspended solids
averaged 15 mg/1; and effluent total phosphorus con-
centrations were less than 1.6 mg/1.
In January 1975, design flow conditions were simulated for
two weeks by shutting down one of the parallel RBC paths
and one of the final clarifiers. The effluent BOD--5 for
this two-week test period averaged 19 mg/1, while the
average wastewater temperature was 47°F (8.3°C).
Because of low hydraulic loadings (1.0 to 2.1
nitrification occurred; 50% to 60% reductions in ammonia
nitrogen occurred during the winter months and 85% to 95%
reductions occurred during summer months.
After one of the RBC paths was restarted in February 1975,
after being shut down for full scale tests, nitrifiers did
not re-establish dominant cultures on latter stages until
June, when wastewater temperatures approached 60°F
Excellent BOD-5, suspended solids and ammonia nitrogen
removals permitted reductions in effluent chlorine doses,
from 6-7 mg/1 to 2-3 mg/1.
Recycling of secondary sludge through the primary clarifier
was required to thicken the combined sludges from 2% - 3%
solids to 4% - 5% solids content.
Slug releases of digester supernatant to the head end of
the plant were detrimental to overall nitrification
results. Controlled release of digester supernatant is
considered essential to achieve consistent ammonia
nitrogen reduction.
No significant differences were noticed in the digesti-
bility of sludges with or without alum addition. Phos-
phorus release, volatile solids reduction, or gas
production were not significantly affected by alum
addition. The average total sludge production was 0.83 Ib
of total solids per pound of BOD-5 removed. This figure
takes into account chemical sludge production.
98
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The measured power usage by the rotating biological
contactor shafts ranged from 5.6 hp to 3.5 hp. The average
running horsepower per shaft was 4.2 hp.
PLANT PERFORMANCE (1976-1979)
The overall performance of the plant, subsequent to the 18-month
test program, is summarized in Table 4. The data covers the
period from January 1976 through December 1979. Table 5 shows a
comparison of plant performance under summer and winter con-
ditions. Data for these tables was obtained from the monthly
operating reports prepared by the plant operators.
This data shows that the plant is consistently removing over 90%
of influent BOD-5 even under winter conditions and at hydraulic
loading rates of between 1.0 and 1.4 gpd/ft^. Wastewater
strength is affected by increased infiltration and inflow during
warm weather months. During winter months, effluent BOD-5
concentrations increase as wastewater temperatures decrease to
lows of 45°F. Effluent dissolved oxygen concentrations are
consistently above 7 mg/1.
Effluent total suspended solids concentrations remained fairly
consistent throughout the period at an average of about 16 mg/1.
The hydraulic profile of the plant is such that secondary solids
are pumped twice prior to removal with settled primary solids.
The addition of polymer assists secondary sedimentation, and
lower suspended solids concentrations could probably be obtained
in the final effluent if flocculants were not disturbed by the
centrifugal pumps.
99
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Table 4
Performance Summary
Parameter 1976
Flow (mgd) .635
Hyd. Loading (gpd/sq.ft.) 1.23
BOD-5 (mg/1)
-Influent 182
-Effluent 6
-% Removed 97%
TSS (mg/1)
-Influent 135
-Effluent 15
VSS (mg/1)
-Influent 111
-Effluent 8
Total Phosphorus (mg/1)
-Influent 7.8
-Effluent 1.4
-% Removed 82%
Ammonia-N (mg/1)
-Influent
-Effluent
-% Removed
Eff. Dissolved Oxygen (mg/1) 7.3
Raw Sludge Pumped (Ib VSS/day) 576
Digester Gas Prod, (cu.ft./day) 4,307
Chemicals Used (Ib/day)
-Chlorine 13
-Alum 435
-Polymer 1.5
- — rtllllUctJ. ttVti L cty fcib. ____ _ _
1977 1978 1979
.725 .612 .712
1.41 1.19 1.38
143 155 129
7 7 12
95% 95% 91%
122 139 118
16 17 16
95 112 92
789
6.3 4.7 3.5
1.1 0.9 0.9
83% 81% 74%
15.5 17.4 15.9
3.5 2.1 2.0
77% 88% 87%
7.6 7.6 8.2
544 512 544
3,981 3,954 3,718
19 12 12
485 365 262
1.7 1.5 1.4
100
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Table 5
Comparative Performance Summary
Winter vs Summer Operation
Average Winter Average Summer
Values I/ Values 2/
Flow (mgd) 0.530 0.726
Hydraulic Loading (gpd/sq.ft.) 1.03 1.41
Waste Temperature (°F) 46 64
BOD-5 (mg/1)
-Influent 181 128
-Effluent 10 9
-% Removed 94 93
TSS (mg/1)
-Influent 140 130
-Effluent 16 16
Total Phosphorus (mg/1)
-Influent 5.8 4.7
-Effluent 0.8 1.0
-% Removed 86 79
Ammonia-N (mg/1)
-Influent 20.0 15.1
-Effluent 4.9 1.0
-% Removed 76 93
Effluent Dissolved Oxygen (mg/1) 8.1 7.3
I/ From January, February, iMarch, 1977 through 1979 reported data.
2/ From July, August, September, 1977 through 1979 reported data.
101
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More than 80% of influent total phosphorus concentrations are
removed by the addition of alum (hydrated aluminum sulfate).
Plant operators attempt to maintain a liquid alum dosage rate
sufficient to provide 1.5 moles of aluminum to 1.0 mole of
influent total phosphorus.
The plant was not designed to accomplish nitrification.
However, because it is currently operated at hydraulic loadings
of less than 2 gpd/ft2, nitrification does occur. Ammonia
analyses show that average influent ammonia concentrations of 16
mg/1 to 18 mg/1 are reduced to 2 mg/1 to 4 mg/1 through the
plant. As might be expected, less nitrification occurs during
winter months.
In 1979, an average of 710 pounds per day of sludge was pumped
to the primary digester with an average solids content of 3.7%
by weight. The volatile content of the sludge averaged 74% by
weight. Total sludge production, including chemical sludges,
averaged 1.14 pounds per pound of BOD-5 removed, or approxi-
mately 1,000 pounds per million gallons treated. Approximately
262 pounds per day of alum was added to remove an average of 2.6
mg/1 of total phosphorus.
OVERALL OPERATIONS AND MAINTENANCE
The Gladstone plant is staffed by one superintendent and three
shift operators. The plant is manned 16 hours per day, five
days a week; eight hours per day on week-ends and holidays. The
superintendent also has the responsibility of the water
filtration plant, staffed by two operators. Most of the
102
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operators are cross-trained to provide flexibility. All opera-
tors are state certified and operate shifts on a rotational
basis.
All laboratory tests are conducted according to "Standard
Methods", 14th edition.
Flows are measured weekly at the Parshall flume to check the
flow meter. The chlorinator, sampler, alum and polymer feeders
are regulated by the flow meter.
Secondary sludge is returned at least five times per day to the
primary clarifier to thicken the combined sludges from 2%-3% to
4%-5% solids content. The combined sludge is then pumped to the
primary anaerobic digester. Digesting sludges are monitored
weekly for volatile acid/alkalinity relationships and volatile
content. When the volatile percentage is less than 50% and the
supernatant shows excessive solids, sludge is hauled by tanker
to the drying beds. The digesters are cleaned and inspected at
three year intervals.
The RBC units are greased at the main bearings twice per week
with 5 to 6 shots of grease. The oil in the chain casings and
speed reducers is changed yearly or more often if the oil should
become diluted with water. The walkways and the area around the
disks are scrubbed weekly. The tanks are drained and flushed
yearly for a general inspection. Very little accumulation has
ever been found. The three V-belts on the drive units are
replaced about yearly upon breakage. One main shaft bearing
failed in the six years of operation.
103
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The plant staff also maintains the six lift stations throughout
the 22 miles (35.4 km) of the collection system, which ranges in
size from 4 inches (10.2 cm) to 30 inches (76.2 cm). Most of
the collection system was installed during the 1920's and
1930's, and was a combined system until new storm sewers were
installed in the late 1950's. This contributes at times, to
excessive infiltration and inflow during snow melts, severe
rains and high lake levels. Step I studies are presently being
conducted to locate the problem areas of the system.
Maintenance of the collection system other than the lift
stations is performed by the Public Works Department.
PROBLEMS THAT DEVELOPED
During the first years of operation a few problems developed and
were solved by the operators. These included changes in alum
feed points, sampling equipment, digester piping, and sludge
handling. The problems as well as the solutions we employed are
explained below.
ALUM APPLICATION POINTS
It was found that during low flows the alum dosages needed to be
increased considerably to remove the required amounts. Also,
with low flows, concentrations of phosphorus increased, creating
the need for an increase in alum application.
Feed points at the secondary wet well did not provide enough
turbulance for proper mixing, so a temporary feed line was
installed to the sixth stage of each RBC path. This provided
enough dispersion for coagulation and flocculation, but after
104
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passing over a weir, through the wet well, and being pumped to
the secondary clarifier, the floe was broken up. By adding alum
to the primary wet well, dosages could be reduced at times, but
results were not consistent.
Temporary lines were installed in 1979 to the discharge side of
the primary pumps. A 30% reduction in the feed rate was found
to achieve the same results. Permanent feed lines were then
installed to each of the primary pumps. This has proven
effective during both low and high flows.
METHANE GAS UTILIZATION
The heating system of the building and the primary anaerobic
digester was designed to use both methane and natural gas.
Methane gas has a content of about 650 BTU per cubic foot, and
the boiler needed a rate of 5090 cubic feet per hour. The gas
pressure in the digester would raise a column of water 10 inches
(25.4 cm). A 2-inch (5.1 cm) gas pipe had been installed from
both digesters. The floating cover of the secondary digester
can hold about 4,000 cubic feet of gas. A sufficient gas rate
was not available to sustain the gas boiler, since the piping
extends some 70 feet (21.5 m), plus the meter, check valve,
flame arrester, and etc. By reducing the orifices of the
burner, some gas could be burned at times.
With the cleaning of the digesters in 1977, the portion of
2-inch (5.1 cm) pipe inside the secondary digester was changed
to 4-inch (10.2 cm) with the intent of changing all the piping
to this larger size.
105
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After temporarily connecting to clean the primary digester and
to burn off the gas, we found the boiler would operate at all
times. The remainder of the pipe has never been changed.
SLUDGE ODORS
Sludge, especially when controlling ammonia, must be removed at
intervals of 2 to 3 hours to eliminate bulking and its odors.
Sludge remaining at the bottom of the clarifiers will soon
become anaerobic and de-nitrify. Higher temperatures will also
accelerate bulking.
Secondary sludge must be removed manually. When the plant is
not manned on week-ends and holidays, we occasionally experience
rising sludge. An automatic sludge removal system would be
advantageous, as these clarifiers are uncovered and the odors
are readily noticed by our neighbors.
Combined sludges are pumped to the anaerobic digesters at two to
three hour intervals to assure proper utilization of digester
capacity and functions.
DIGESTER UPSET
In the six years of operations, only once were the digesters
upset. This happened in 1976, when gas production ceased and
the digesters went "sour". The nitrifiers on the RBC units were
disrupted as well.
The supernatant from the primary digester contained small
.cellophane-type pieces of irregular shapes, somewhat resembling
bleached potato peelings. The volatile acid/alkalinity ratio
rose above 1.0 and the pH was dropping below 6.4.
106
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To correct the problem, heat was maintained at 90°F in the
digester and continuous mixing was was employed. About 300
pounds of soda ash were added over a 10-day period to hold the
pH near 7.0. Within two weeks the digesters were back
functioning normally.
The only explanation as to the cause of the upset was that the
city fire department floor had been stripped of several layers
of paint using paint remover which was flushed to the sanitary
sewers.
SAMPLING EQUIPMENT INADEQUACIES
The original sampling equipment supplied with the plant did not
provide representative samples. The three samples required were
raw wastewater, primary effluent, and final effluent. Only the
final effluent samples could be collected continuously.
The samplers had a small opening about the size of the lead in a
pencil, and the raw and primary effluent samples soon clogged
the orifice. The pumps for raw and primary effluent had 1
1/2-inch (3.8 cm) suction piping but only 1-inch (2.54 cm)
discharges. The primary effluent would pass easily enough,
however, the raw pump would plug at the 1-inch opening almost
immediately.
In 1975, a dipper type three-stage sampler with refrigeration
was purchased from "Sonford Products" of Minneapolis, Minnesota
and installed by the plant operators. All piping to the sampler
was increased to 1 1/2-inch (3.8 cm) with provisions provided
107
-------
for backflushing with final effluent. A submersible raw sample
pump was installed directly behind the bar screen. The pump
delivers 15 gallons per minute to the sampler and seldom causes
any problems. The new sampling system works well with very
little maintenance and we are assured of representative samples.
ENERGY AND CHEMICAL COSTS
The energy and chemical uses and costs associated with the plant
operation for 1978 are summarized in Table 6. The costs shown
per million gallons reflect actual prices Gladstone paid for the
respective commodities in 1978.
Electricity consumption is of primary interest and the table
shows electrical power consumption in terms of raw sewage
pumping, secondary (RBC) treatment, and anaerobic digestion.
The power consumption for the RBC units actually includes power
consumption by clarifier drives, intermediate pumps, lights,
ventilating equipment, etc., and computes to an average of
approximately 38 running horsepower at any given time. Of this,
approximately 80 percent (30 hp), including power draw by the
RBC units, could be considered independent of actual flows.
Based on measured power consumptions by the six RBC drive units
in 1975, the RBC system draws an average of 25-26 horsepower at
any given time.
TOTAL FACILITY BUDGET
Table 7 begins with the total facility budget and is followed by
some of the major operating expenses. The remainder of the
budget incorporates items such as the collection system, audit,
administration, engineering, insurances, and etc.
108
-------
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Table 7
1979 Fiscal Year Budget
Total Facility Budget $178,000.00
Power
Lift Stations 32,607 KWH
Plant 313,627 KWH
Total Power Costs 14,781.97
Natural Gas 1,185,490 cu ft 2,861,87
Chlorine 4,550 Ibs 827.25
Aluminum Sulfate 95,648 Ibs 4,497.96
Polymer 501 Ibs 1,005.52
Labor 7,136 man-hours 57,088.00
Plant Maintenance 3,000.00
Parts, Supplies, Miscellaneous 4,000.00
Equipment Rentals 3,000.00
110
-------
REVENUE TO OPERATE
In 1972, water meters were installed in every home. The water
plant staff maintains these meters. All meters larger than
1-inch are checked at three year intervals. Small household
meters are checked to assure accuracy as needed. Ten percent of
the meters have registered 1 million gallons since 1972 and a
routine maintenance program is being initiated.
The water distribution system originally began in 1889 and at
the present, approximately 72% of the water produced can be
accounted for.. 63% of the water treated at the wastewater plant
comes from inflow and infiltration.
Prior to 1969, no wastewater charges were collected, with the
system operating solely on taxes. Water charges prior to 1970
averaged $1.00 per month. Today, with the new water filtration
plant and the upgraded wastewater facility, the average house-
hold using 5,000 gallons of water pays $11.65 for water and
$10.49 for wastewater per month.
SUMMARY
We believe the RBC treatment system is an ideal treatment
process for the city of Gladstone, Michigan. Excellent
treatment results are being obtained and plant effluent quality
is well within design limits. Consistent nitrification at
loading below 2 gpd/sq ft is being achieved as an added bonus
toward high quality treatment.
Ill
-------
The system has been very consistent in achieving wastewater
treatment and permitting stable solids handling procedures. Few
problems have occurred with the day-to-day operation of our RBC
secondary treatment system.
ACKNOWLEDGEMENTS
The author wishes to thank Williams & Works of Grand Rapids,
Michigan for their cooperation in the preparation of this paper.
112
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CONTROL TECHNOLOGY FOR NUTRIENTS IN
MUNICIPAL WASTEWATER TREATMENT IN SWEDEN
Bengt G. Hultman
Research Engineer
Swedish Water and Waste Water Works Association
Regeringsgatan 86
S-lll 39 STOCKHOLM
Sweden
NEED FOR NUTRIENTS CONTROL
Sweden is comparatively rich in lakes with more than 20,000 ex-
ceeding 0.1 sq. km in area. Most of them are fairly shallow. In
their natural states the lakes and coastal areas are deficient in
nutrients. This means that the lakes and coastal areas will react
to artificial supply of nutrients from for instance urban areas.
At the end of the 1950's limnologists began to warn about the
deterioration of the water quality in lakes and coastal areas
due to the increased rate of the growth of algae and other vege-
tation. Rodhe (1958) pointed out that the phosphorus in sewage
could increase the productivity in natural waters as much as com-
mersial fertilisers applied on land. Different investigations on
lakes indicated a significant rise in the water's content of
phosphorus and biomass.
During two weeks in August 19-72 an extensive lake survey was car-
ried out by the National Swedish Environment Protection Board and
the County Administrations (Johansson and Karlgren, 1974). A to-
tal of 1250 minor and medium-sized lakes were examined. Although
not being the primary aim of the study, an attempt was made to
estimate the degree of nutritional influence on the lakes resul-
113
-------
ting from human activities. It was found that the inorganic phos-
phate content in water showed similar regional variations as that
of total phosphorus and of total nitrogen with low concentrations
in the low-productive lakes in northern Sweden and parts of south-
ern Sweden and high concentrations in the high-productive lakes
of the plains.
Based on the lake survey and complementary studies Hannerz and
Forsberg (1975) estimated that less than 10 % of the Swedish la-
kes were eutrophic. In south Sweden about 10 to 20 % of the lakes
were eutrophic and the percentage of eutrophic lakes in the Stock-
holm county amounted to about 50 %.
Several substances such as phosphorus, nitrogen, carbon dioxide,
iron and vitamins can stimulate algal growth. Of these substances
only phosphorus and nitrogen have been considered as main factors
for stimulating eutrophication. A strong emphasis has been laid
on phosphorus removal as the method for control of eutrophication
especially from the National Swedish Environment Protection Board,
while nitrogen has been considered to be of minor importance. The
reasons for this view seem to be:
Phosphorus seems to be rate limiting for algal growth
in most Swedish lakes based on values of the weight pro-
portion of nitrogen to phosphorus, which is about 25:1
for natural or low polluted lakes.
A large fraction of phosphorus comes from point sources
which may be more easily controlled than diffusive sour-
ces.
Algae have the possibility of taking up nitrogen from the
atmosphere if nitrogen is a limiting growth factor.
114
-------
In the end of the 1960's phosphorus removal was a much
more wellknown technique than nitrogen removal in Sweden.
For a total of about 900 samples from surface water from 20 waste
affected lakes in Sweden during August-October 1972 Forsberg et
al. (1975) found phosphorus to be the growth limiting nutrient
in waters having total-P values less than 0.05 mg/1. Above 0.1
mg P/l nitrogen played the principal role. Between these values
the growth was primarily limited by phosphorus or nitrogen or
chelating agents.
Nitrogen seems to be the primarily rate limiting factor for algal
growth in case of eutrophic lakes (Forsberg, 1977) and in some
coastal waters as the Stockholm archipelago (Lindahl and Melin,
1973). In this case the policy of the National Swedish Environ-
ment Protection Board has been to try to reduce the phosphorus
supply to the water body as much as possible in order to make
phosphorus the growth limiting substance (Anonymous, 1971).
IMPLEMENTATION OF NUTRIENTS CONTROL
LEGISLATION AND ADMINISTRATION
Legislation concerning discharge of waste water into lakes and
rivers has been in existence in Sweden since the end of the
1930's. A new law, the Environment Protection Act, came into for-
ce in July 1969 and tightened up regulations considerably.
The Environment Protection Act applies to what are termed pollu-
ting activities, i.e. the discharge of effluent, solids or gas
115
-------
from land, a building or an installation or the use of such pro-
perty in a manner liable to cause water pollution, atmospheric
pollution, noise, vibration, the emission of light etc., if the
nuisance thus caused is more than temporary (National Swedish
Environment Protection Board, 1979a).
The chief principle of the act is to prevent environmental dis-
turbances as far as possible. The precautionary measures, such
as effective methods of wastewater treatment, shall be "economi-
cally feasible" and "technically practible".
Sewage from locations with more than 200 inhabitants must not be
emitted without a permit. A special board, the Franchise Board
for Protection of the Environment, holds the responsibility for
the granting of permits. The obligation to apply for a permit is
however not compulsory. The National Swedish Environment Protection
Board may after due examination exempt an applicant from the need
to apply to the Franchise Board for a permit. In exemption cases,
the Board attempts through negotiations to come to an agreement
with the applicant as to the conditions to be applied to the ac-
tivity. An exemption granted lacks formal legal validity - as
opposed to a permit - and may be withdrawn (National Swedish En-
vironment Protection Board, 1979a).
SOURCE CONTROL
The synthetic detergents which were introduced in Sweden during
the 1950"s have greatly improved laundry cleaning efficiency. Po-
lyphosphates were totally dominating as complexing agents in the
116
-------
detergents. In the end of the 1960's the average phosphate con-
centration was about 35 % in cleaning agents and in some special
products the phosphate concentration could amount to more than
60 % (Kjellman, 1975) .
In the middle of the 1960"s municipal sewage from urban areas
contained phosphorus corresponding to about 4 g P per person and
day. Approximately half of this amount originated from detergents
(Ahl et al., 1967). The general opinion that phosphorus was the
main agent causing eutrophication lead to investigations of dif-
ferent methods to reduce the phosphate concentration in detergents,
In order to comply with authorities different manufacturers dimi-
nished the amount of phosphates in their detergents. As can be
seen from Table 1 the use of phosphate in detergents diminished
from about 3.9«106 kg in year 1968 to about 2.65'106 kg in 1972,
corresponding to a decrease of 32 %. Due to the decrease of phos-
phate in detergents the phosphorus content in sewage diminished
to about 3.3 g P per person and day of which about 30 % originated
from detergents (Kjellman, 1975). The use of phosphorus in deter-
gents has increased a little after 1972.
The trisodium salt of NTA may be used as a partial substitute for
or a complement to sodium tripolyphosphate as builder in house-
hold detergents. NTA was introduced on the market at the end of
the 1960's (see Table 1). Several studies were performed in order
to evaluate the biodegradability of NTA (Forsberg and Lindquist,
1967, Bouveng et al., 1968 and 1970, and Bjorndal et al., 1972).
117
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The results obtained showed that aerobic biological processes
are capable of degrading NTA fairly efficient under normal con-
ditions of operation. However, different foreign reports, for
instance the Epstein report, raised some doubts that NTA could
be safely used without negative consequences on the environment.
These doubts lead to a decreased interest in using NTA. in deter-
gents (National Swedish Environment Protection Board, 1970) and
the use of NTA in detergents has decreased during the 1970~s.
CHOICE OF PROCESS TECHNOLOGY FOR NUTRIENTS CONTROL
The first sewage works with chemical precipitation was built in
1961 in Aker, a small municipality with about 2,000 persons con-
nected to the sewage works. The treatment plant was equipped for
primary sedimentation with subsequent chemical precipitation whe-
re the floes were separated in a flotation unit. The chemical
precipitation agent was aluminium sulphate.
The sewage works in Aker was built before any significant research
had started in chemical precipitation. In the middle of the 1960's
several research projects started on combined biological and che-
mical treatment of sewage. At that time the two processes which
were considered were simultaneous precipitation and post-precipi-
tation. Studies were performed in a laboratory scale, pilot plant
scale and as full scale experiments.
Early studies on the simultaneous precipitation process gave rat-
her high effluent values of total phosphorus. Pilot plant studies
with simultaneous precipitation with aluminium sulphate gave eff-
118
-------
luent values of total phosphorus of about 2 mg P/l (Balme'r et
al., 1968). Full scale tests at Eolshalls sewage works in Stock-
holm during a short test period showed effluent values of total
phosphorus of about 1-1.5 mg P/l. Addition of aluminium sulphate
caused a lower reduction of the BOD-values due to separation
problems in the final sedimentation basin (Cronholm, 1968). Ulm-
gren (1969) reports other full scale tests in which simultaneous
precipitation were studied giving high effluent values of total
phosphorus. Laboratory studies of the simultaneous precipitation
process, however, showed that it was possible to reach effluent
values of total phosphorus below 1 mg P/l (Ericsson, 1967).
Laboratory experiments with post-precipitation showed that an
effluent value could be reached of total phosphorus below 1 mg P/l
(Ericsson, 1967, and Weijman-Hane, 1968). Similar results were
obtained in evaluation of the first built sewage works with post-
precipitation (National Swedish Environment Protection Board,
1969) .
Based on the rather few experimental studies performed in Sweden
concerning chemical precipitation and foreign experiences for
instance in Switzerland the National Swedish Environment Protec-
tion Board strongly recommended post-precipitation instead of si-
multaneous precipitation as the removal method of phosphorus. In
1968 the expansion period began with chemical treatment plants
with the purpose of reducing as much as possible of the phospho-
rus content in wastewaters.
119
-------
No significant interest was laid on nitrogen removal. However,
some research started in the middle of the 1960"s concerning
nitrogen removal, especially by use of biological methods
(Hultman, 1973, and Ericsson, 1975).
DESIGN GUIDELINES
To guide those who prepare or scrutinize proposals for treatment
plants the National Swedish Environment Protection Board (1971)
prepared "Guidelines for design of sewage treatment plants". In
the guidelines the following are given: design values for sludge
loads on the activated sludge process, BOD loads on trickling
filters, detention time in flocculating units, surface loads in
sedimentation basins etc (Ulmgren, 1975a).
EMISSION CONTROL
Instructions for emission control in Sweden have been issued by
the National Swedish Environment Protection Board (1973). The
sampling frequency in relation to the required parameters total
BOD_, total COD and total phosphorus is given in Table 2. In ad-
dition local authorities may demand more extensive emission cont-
rol and programs for recipient control.
STATE GRANTS
State grants are since 1st of July 1968 payable on certain con-
ditions for the construction, enlargement or alteration of sewage
purification plants, outfalls and, in some cases, intercepting
mains as well (National Swedish Environment Protection Board,
1968) .
120
-------
TABLE 1. YEARLY CONSUMPTION OF RAW MATERIALS FOR WASHING,
DISH-WASHING AND OTHER CLEANING MATERIALS USED IN
HOUSEHOLDS IN SWEDEN 1968-1972 (The consumption
figures are given in thousand kilograms; 1 kg =
2.205 Ib) (Kjallman, 1965).
Raw material
Soap
Synthetic tensides
Phosphates
NTA
Other organic com-
plexing agents
1968
1377
7500
3920
111
116
1969
2037
7704
3644
1019
115
Year
1970
2624
7450
2855
1711
226
1971
2597
7443
2797
1525
330
1972
2766
8483
2650
1373
492
TABLE 2. FREQUENCY OF SAMPLING IN EMISSION CONTROL
(National Swedish Environment Protection Board/ 1970)
Parameter
Person
equivalents (p.e.) connected to treatment plant
200-2000 2000-5000
CODU)
BOD20000
4 /month
1 /month
4 /month
121
-------
Grants are gauged according to degree of purification and are
payable at rates between 30 and 50 per cent of approved con-
struction costs (see Table 3). During the fiscal years 1971/72-
1973/74 grants were payable 25 per cent in excess of those rates
given in Table 3. This formed a part of a programme to create
jobs (National Swedish Environment Protection Board, 1979a).
Grants given for different types of treatment are exemplified
in Table 4 based on rates in Table 3.
PRESENT SITUATION
The general policies for implementation of the Environment Pro-
tection Act on sewage treatment as developed in the end of the
1960's has essentially been maintained. Thus, a combined biologi-
cal and chemical treatment of municipal wastewater is normally
prescribed. In certain relatively few cases, only biological or
only chemical treatment may be allowed. In localities with poor
recipient conditions in relation to the discharge complementary
treatment (mainly post-filtration) is prescribed in addition to
biological and chemical treatment. Recently, requirements of nit-
rification has been prescribed for a sewage works in the Stock-
holm area. The main reason for this requirement is to diminish
the oxygen demand of the wastewater which may give rise to oxygen
deficit at the bottom of certain parts of the Stockholm archipe-
lago and thereby cause leakage of phosphorus from the bottom se-
diments. Thus, the requirement of nitrification is to prevent
phosphorus leakage and thereby according to the general view
decrease algal growth.
122
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TABLE 3. STATE GRANTS FOR MUNICIPAL WASTEWATER WORKS
(National Swedish Environment Protection Board, 1968)
Percentage BOD_ pu- Percentage phosphorus purifica-
rification effect tion effect
<50 50-89 >90
Percentage grant:
60-74 30 35 40
75-89 30 35 45
>90 35 40 50
TABLE 4. PERCENTAGE GRANTS FOR DIFFERENT PROCESS COMBINATIONS
(National Swedish Environment Protection Board/ 1969)
Process combination Percentage grant
Simultaneous precipitation 35
Direct precipitation 40
Post-precipitation 45-50
123
-------
Sewage purification facilities in Sweden have expanded very
quickly during the last decade (see Figure 1). In the beginning
of 1979 about 640 municipal wastewater treatment plants were ope-
rated with combined biological and chemical treatment correspon-
ding to about 72 % of the total amount of wastewater from urban
areas.
The dominating process combination is post-precipitation with a
share of more than 80 % calculated on the number of treatment
plants with chemical precipitation (see Table 5). However, some
of the largest sewage works, for instance in the Stockholm region,
use pre-precipitation or simultaneous precipitation.
Aluminium sulphate has been the dominating precipitation agent.
During the last years especially larger sewage works have changed
to iron salts (see Table 6). This depends on that the production
of ferric chloride from waste products has considerably lowered
the price of the chemical. Besides there are some benificial ef-
fects on the sludge properties in the use of iron salts compared
with aluminium sulphate.
EVALUATION OF NUTRIENTS CONTROL MEASURES
OPERATIONAL RESULTS
Several papers have been written on experiences of full scale
operations of chemical precipitation in Sweden (Eklund, 1974,
Gronqvist et al., 1978, Hultman, 1978, Isgard and Ericsson, 1976,
and 1978, and Ulmgren, 1975a and 1975b). These papers discuss
124
-------
Percent of the population in urban areas!localities)
1979-01-01
100
1970
1975
Chemical
treatment
Biologica!-
71%| chemical
treatment
Complementary
1,5%| treatment
(filtration etc.)
1980
Type of sewage treatment
No treatment
Sedimentation
Biological treatment
Chemical treatment
Bio. chemical treatment
Complementary treatment
Number of
treatment plants
156 (-34)
380 (-37)
141 (+ 3)
625 (+18)
18 (+ 2)
Number of persons
served
7 000 (- 1 000)
181 000 (- 21 000)
1 398000 (-110000)
324000 (+ 22000)
4833000 (+106000)
107000 (+ 7000)
1 320 (-48)
The figures in brackets refer to the change since January 1 st, 1978
6 850 000
Figure L. Sewage Treatment in Sweden .Iy&S~iy79
12 ^
-------
TABLE 5. DIFFERENT TYPES OF SEWAGE WORKS WITH CHEMICAL PRECIPI-
TATION IN SWEDEN IN THE BEGINNING OF 1978
(National Swedish Environment Protection Board, 1979b)
PROCESS COMBINATION:
Direct precipitation
Pre-precipitation
Simultaneous precipitation
Post-precipitation
NUMBER OF PLANTS
138
17
35
554
Post-precipitation systems:
Trickling filters
Activated sludge
Separation of chemical floes
by contact filtration
Polishing by deep-bed filters
49
505
11
16
TABLE 6. USE OF DIFFERENT PRECIPITATION AGENTS AT MUNICIPAL SE-
WAGE WORKS IN SWEDEN IN THE BEGINNING OF 1977 AND 1979
(National Swedish Environment Protection Board, 1979b)
TYPE OF CHEMICAL PRECIPITATION AGENT:
Aluminium Ferric &
sulphate ferrous
iron
Lime Iron Aluminium
salts & sulphate &
lime iron salts
Number of
plants
Percentage of
connected po-
pulation
600 (578) 92 (60) 60 (48) 26 (22) 4 (3)
49 (69) 42 (23) 5 (3) 2 (3) 2 (2)
Numbers from the beginning of 1977 are within brackets.
126
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different process configurations, the influence of different ope-
rational parameters such as dosage, pH-value in the flocculation
step and type of chemical precipitation agent and the influence
of separation methods.
Data from the emission control at municipal sewage works shall be
sent to the National Swedish Environment Protection Board once a
year. Compilations of such data have been published by the Natio-
nal Swedish Environment Protection Board (1977 and 1979b). Obtai-
ned results for different treatment systems are shown in Table 7.
The results are compared in the table with expected results from
treatment plants with a good operation and no significant distur-
bances based on results reported by Gronqvist et al. (1978).
A large fraction of the Swedish municipal sewage works do not
operate reliably. Investigations of post-precipitation plants in-
dicate that effluent values of BOD7 are not below 15 mg/1 (requi-
red limit) for about 30 % of the plants and effluent values of
total phosphorus are not below 0.5 mg P/l (required limit) for
about 40 % of the plants (National Swedish Environment Protection
Board, 1977).
Full scale experiences of simultaneous precipitation plants in
the Nordic countries have been put together by Gronqvist and
Arvin (1979). It was shown that much better results could be ob-
tained for the treatment plants than results shown in Table 7.
The average concentration of total phosphorus from five simulta-
t
neous precipitation plants in the Stockholm area was 0.6 mg P/l.
127
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TABLE 7. OPERATIONAL RESULTS BY USE OF DIFFERENT CHEMICAL PRECI-
PITATION METHODS
PROCESS COMBINATION
Direct precipitation
Pre-precipitation
Simultaneous preci-
pitation
Post-precipitation
OPERATIONAL RESULTS
IN 1977
T-J /-~V 1-^
13(Jlj -J
mg/1
39
35
28
10
(1)
P
tot
mg/1
0.70
0.98
1.48
0.53
EXPECTED RESULTS
FOR PLANTS
SIGNIFICANT
BANCES (2)
Ptot' mg
-
0.5-0.
0.5-0.
0.5-1.
WITH NO
DISTUR-
/l
8
8
2 (3)
Post-precipitation
followed by deep-
bed filtration
0.22
0.2-0.4 (4)
0.15-0.3 (5)
Notes: (1) Average values from different plants. Data from
National Swedish Environment Protection Board (1979b)
(2) According to Gronquist et al. (1978).
(3) Post-precipitation with aluminium sulphate at pH
6.5-7.2 or lime in single stage at normal loaded
plants.
(4) Post-precipitation with aluminium sulphate at pH
5.5-6.4, with ferric chloride and recirculation of
sludge to the aeration basin or with lime in single
stage at low loaded plants.
(5) Post-precipitation with aluminium sulphate at pH
5.5-6.4.
128
-------
In order to elucidate the reasons of the unsatisfactory removal
efficiencies of certain sewage works an enquiry was sent in spring
1979 to the County Councils. These were requested to give their
opinion of the reasons for the unsatisfactory results of sewage
works with effluent values of BOD and total phosphorus above 15
mg/1 and 0.5 mg P/l, respectively. Several explanations were gi-
ven such as hydraulic problems, difficult industrial wastes and
unreliable machinery equipment. The percentage distribution of
reasons to unsatisfactory results is given in Table 8.
COSTS OF POST-PRECIPITATION PLANTS
The costs for post-precipitation plants based on average values
from different Swedish reports are put together in Table 9. The
capital costs are somewhat higher than the operating costs. Due
to increasing treatment costs for diminishing sizes of the sewage
works there is a tendency to centralize the wastewater treatment.
The grant system has promoted this development. The use of comple-
mentary treatment by deep-bed filtration will increase the total
costs for a post-precipitation plant 15-20 %. Different cost
factors for the operating costs are shown in Table 10.
EFFECTS ON RECIPIENTS
In order to elucidate the effects of biological and chemical
treatment on the water quality in the recipient the National Swe-
dish Environment Protection Board started a program in 1972 for
analyzing the conditions in a number of different recipient lakes
(Forsberg et al., 1975).
129
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TABLE 8. CAUSES OF UNSATISFACTORY REMOVAL EFFICIENCIES OF POST-
PRECIPITATION PLANTS (Carlsson and Nordstrom, 1979)
CAUSE
Hydraulic problems
Industrial wastes
Machinary equipment
Process technology
Maintenance
Repairs, reconstruction
Unreliable analysis (1)
Unknown causes
PERCENTAGE DISTRIBUTION,
18
12
19
17
2
4
17
12
Note: (1) Probably depending on significant nitrification in
BOD-bottles during the BOD-.-measurement.
130
-------
TABLE 9. APPROXIMATE COSTS FOR SEWAGE TREATMENT (1978).
Number of per-
son equivalents
(p.e.)
Costs for post-preci-
pitation plants (inclu-
ding sludge treatment)
Additional costs
for deep-bed filt-
ration
2,000
5,000
20,000
50,000
Capital
costs
Skr
p.e. -year
130
100
60
45
Operating
costs
Skr
p.e. -year
100
70
50
40
Capital
costs
Skr
p.e. -year
—
25
10
7
Operating
costs
Skr
p.e. -year
-
8
4
3
Notes: 1 Skr = 0.24 US dollars
In calculation of capital costs the annuity used is 10 %
and 13 % for post-precipitation plants and deep-bed fil-
ters, respectively.
Average municipal water consumption is about 400 1 per
person and day in Sweden.
TABLE 10. OPERATING COSTS FOR POST-PRECIPITATION PLANTS (INCLU-
DING SLUDGE TREATMENT) (1978)
COST FACTOR
Labour and administration
Chemicals
For chemical precipitation
For sludge conditioning
Energy
Sludge transportation
Other costs factors
PERCENTAL COSTS, %
30
25
(15)
(10)
20
10
15
TM
131
-------
From the experiences of phosphorus removal positive responses
have been reported from some water bodies. In other lakes delayed
recovery has been observed after nutrient reduction. In some la-
kes, where the phosphorus load was reduced by 30-40 %, no marked
improvements were noted. The results available indicate that a
comparatively great change in phosphorus load must occur in or-
der to get significant improvement in water clarity in the lakes.
As the phosphorus load from treatment plants is often the domi-
nant phosphorus source, reduction of phosphorus by advanced treat-
ment seems to be a good tool for controlling eutrophication in
many lakes (Ryding, 1978a and 1978b).
TRENDS IN IMPROVEMENT OF CONTROL OF NUTRIENTS
The operating costs have steadily increased at Swedish sewage
works. Therefore great interest has been directed towcirds biolo-
gical-chemical treatment methods which can reduce the operating
costs and which are more efficient. Such methods include the use
of counterflow of precipitated sludges, two-step precipitation,
regulation of the alkalinity and automatic control.
For a constant value of the suspended solids in the effluent it
is advantageous to have a low fraction of phosphorus in the sus-
pended solids in order to obtain low effluent values of phospho-
rus. If the effluent concentration of suspended solids is 10 mg/1
and the fraction of phosphorus in the suspended solids 6 % and 2
% the effluent concentration of suspended phosphorus will be 0.6
and 0.2 mg P/l, respectively.
132
-------
A suitable way to diminish the fraction of phosphorus in the sus-
pended solids is to decrease the influent phosphorus concentration
before the precipitation step. This technique has been tried in
full scale at several sewage works in Sweden. Different examples
are:
Two-step precipitation at Balinge sewage works (Holm-
strom, 1977) by use of the combination of simultaneous
precipitation and contact filtration in which process
combination the principal part of phosphorus removal
occurs in the simultaneous precipitation step after
which still more phosphorus is removed by the addition
of low concentrations of ferric iron before a deep-bed
filter.
Two-step precipitation at Kappala (Isgard and Ericsson,
1978) and Bankeryd sewage works in which simultaneous
precipitation is followed by post-precipitation.
Recirculation of post-precipitated sludge to the aera-
tion basin of the activated sludge process (Gronqvist
et al., 1978). The phosphorus reduction in the biologi-
cal step is hereby improved and the phosphorus concent-
ration before the post-precipitation step will be much
lower than if no recirculation takes place. Some preli-
minary results indicate, however, that nitrification
may be inhibited by recirculation of aluminium contai-
ning post-precipitated sludges.
Use of biological phosphorus reduction at Kristianstad
sewage works by use of an anaerobic zone in the first
part of the aeration basin. In this way the phosphorus
concentration is diminished before the post-precipita-
tion step.
These operational modifications of an existing post-precipitation
plant have shown very promising results including better removal
efficiencies of total phosphorus, lower total amount of chemical
precipitation agents and better sludge properties. It therefore
seems probable that a large fraction of the Swedish post-precipi-
tation plants will change to a modified operating scheme.
133
-------
The alkalinity of the effluent from a biological step is mainly
determined by the influent alkalinity and the degree of nitrifi-
cation and denitrification. In nitrification the produced amount
of hydrogen ions reduces the alkalinity of the wastewater. This
reduction often leads to reduced requirements of aluminium sulp-
hate or lime in post-precipitation and several treatment plants
are operated in this way in Sweden (Ericsson et al., 1976, and
Gronqvist et al., 1978). Promising results have been shown by
regulation of the alkalinity of the effluent from an activated
sludge process by regulation of the degree of nitrification and
denitrification by the supply of oxygen (Olsson, 1980).
SUMMARY
During the 1950~s observations were made and the conclusion drawn
that the water quality in some lakes and coastal waters had dete-
rioted. Different recipient studies indicated that phosphorus was
the main factor which caused this deterioration. Some efforts were
made to decrease the phosphate concentrations in the synthetic de-
tergents and approximately a 30 % reduction of the phosphate
amount in synthetic detergents was obtained between 1968 and 1972.
In 1968 the expansion period began with chemical treatment plants
and in the beginning of 1979 about 640 municipal wastewater treat-
ment plants were operated with combined biological and chemical
treatment corresponding to about 72 % of the total amount of
wastewater from urban areas. At present a large interest has been
directed towards modified operating schemes in order to get bet-
ter removal efficiencies and savings in operating costs.
134
-------
REFERENCES
Ahl, T., Karlgren, L., Olsson, E. and Tullander, V. (1967): Hus-
hallsavloppsvattnet. Vatten, 23, 3, pp 178-204 (in
Swedish).
Anonymous (1971): Eutrofieringsproblemet. Vatten, 27, 4, pp 463-
465 (in Swedish).
Balme'r, P., Blomquist, M. and Lindholm, M. (1968): Simultanfall-
ning i en hogbelastad aktivslamprocess. Vatten, 24, 2,
pp 112-116 (in Swedish).
Bjorndal, H., Bouveng, H.O., Solyom, P. and Werner, J. (1972):
NTA in sewage treatment. Part 3. Biochemical stability
of some metal chelates. Vatten, 28, 1, pp 5-16.
Bouveng, H.O., Davidsson, G. and Steinberg, E.-M. (1968): NTA in
sewage treatment. Vatten, 24, 4, pp 348-359.
Bouveng, H.O., Solyom, P. and Werner, J. (1970): NTA in sewage
treatment. Part 2. Degradation of NTA in a trickling
filter and an oxidation pond. Vatten, 26, 4, pp 389-402.
Carlsson, A. and Nordstrom, B. (1979): Orsaker till otillfreds-
stallande reningsresultat vid kommunala avloppsrenings-
verk. National Swedish Environment Protection Board,
SNV PM 1248 (in Swedish).
Cronholm, M. (1968): Fosforreduktion medelst aluminiumsulfat vid
Eolshalls reningsverk, Stockholm. Vatten, 24, 2, pp 117-
124 (in Swedish).
Eklund, L. (1974): Bearbetning av resultat fran driftundersoknin-
gar vid kommunala reningsverk. National Swedish Environ-
ment Protection Board, SNV PM 556 (in Swedish).
Ericsson, B. (1967): Narsaltreduktion vid avloppsverk. Vatten, 23,
2, pp 92-102 (in Swedish).
Ericsson, B. (1975): Nitrogen removal in a pilot plant. J. Water
Pollution Control Federation, 47, 4, pp 727-740.
Ericsson, B., Mard, G. and Akesson, M. (1976): Drifterfarenheter
med biologisk nitrifikation vid Srebro reningsverk.
Vatten, 32, 3, pp 301-310 (in Swedish with an English
summary).
Forsberg, C. (1977): Nitrogen as a growth factor in fresh water.
Prog. Wat. Tech., Vol 8, Nos 4/5, pp 275-290.
135
-------
Forsberg, C. and Lindqvist, G. (1967): Experimental studies on
bacterial degradation of nitrilotriacetate, NTA. Vatten,
23, 4, pp 265-277.
Forsberg, C., Ryding, S.-O. and Claesson, A. (1975): Recovery of
polluted lakes. A Swedish research program on the effects
of advanced waste water treatment and sewage diversion.
Water Research, 9, 1, pp 51-59.
Gronqvist, S. and Arvin, E. (1979) : Simultanfalining - erfaren-
heter och FoU-behov. Nordforsk-prosjektet: Drift av
renseanlegg, rapport 5 (in Swedish).
Gronqvist, S., Holmstrom, H., Hultman, B. and Reinius, L.-G. (1978):
Experiences and process development in biological-che-
mical treatment of municipal wastewaters in Sweden.
Prog. Wat. Tech., Vol 10, Nos 5/6, pp 701-713.
Hannerz, L. and Forsberg, C. (1975): Eutrofieringssituationen i
Sverige. Tionde nordiska symposiet om vattenforskning.
Nordforsk, Miljovardssekretariatet, Publ. 1975:1 (in
Swedish).
Holmstrom, H. (1977) : Simultanfallning och kontaktfiltrering vid
Balinge reningsverk. Swedish Water and Waste Water Works
Association, Rapport 1/77 (in Swedish with an English
summary).
Hultman, B. (1973) : Biological nitrogen reduction studied as a ge-
neral microbiological engineering process. In "Environ-
mental Engineering." G. Lindner and K. Nyberg (Eds.),
D. Reidel Publ. Co., Dordrecht, Netherlands, pp 264-275.
Hultman, B. (1978): Chemical precipitation in Sweden - Present
situation and trends in process improvement and cost
reduction. Paper presented at 2nd International Congress
of the Environment 4-8 Dec. 1978, Palais de Congres,
Paris, France.
Isgard, E. and Ericsson, B. (1976): Chemical and biologiceil sewage
treatment in Sweden. Effluent and Water Treatment Con-
vention, Manchester 1976.
Isgard, E. and Ericsson, B. (1978) : A review of the Swedish situa-
tion in combined wastewater treatment. Paper presented
at "Colloque International 16-19 mai 1978, Traitement
combing des eaux usees domestiques et industrielles."
Universite de Liege - Section d'Environnement.
Johansson, K. and Karlgren, L. (1974): Tusen sjoar. Rapport fran
en inventering. National Swedish Environment Protection
Board, Publ. 1974:11 (in Swedish),
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Kjallman, A. (1975): Tvatt- och diskmedel som narsaltkalla. Tion-
de nordiska symposiet om vattenforskning. Nordforsk,
Miljovardssekretariatet, Publ. 1975:1 (in Swedish).
Lindahl, P.E.B. and Melin, R. (1973): Algal assays of archipelago
waters. Quantitative aspects. OIKOS, 24, pp 171-178.
National Swedish Environment Protection Board (1968): Statsbidrag
till avloppsreningsverk. Meddelande V 5 (in Swedish).
National Swedish Environment Protection Board (1969): Experience
of chemical purification. Publ. 1969:10 E.
National Swedish Environment Protection Board (1970): Tvattmedel
som miljoproblem. Publ. 1970:4 (in Swedish).
National Swedish Environment Protection Board (1971): Dimensione-
ring av kommunala reningsverk (in Swedish).
National Swedish Environment Protection Board (1973): Utslapps-
kontroll vid kommunala avloppsanlaggningar. Publ. 1973:
16 (in Swedish).
National Swedish Environment Protection Board (1977): Sewage treat-
ment in built up areas in Sweden as at 1st January 1977.
SNV PM 911 E.
National Swedish Environment Protection Board (1979a): Water Pro-
tection in Sweden. Bulletin, SNV PM 1153 E.
National Swedish Environment Protection Board (1979b): Avlopps-
rening - tatorternas avloppsforhallande den 1 januari
1979. Meddelande 4/1979 (in Swedish).
Olsson, G. (1980): Automatic control in wastewater treatment
plants. Trib. Cebedeau, Vol 33, N 436, pp 121-130.
Rodhe, W. (1978): Aktuella problem inom limnologin. Svensk Natur-
vetenskap, pp 55-107 (in Swedish).
Ryding, S.-O. (1978a): The significance of sewage effluent for the
hydraulic and nutrient loads on lakes. Prog. Wat. Tech.,
Vol 10, Nos 5/6, pp 907-916.
Ryding, S.-O. (1978b): Research on recovery of polluted lakes.
Loading, water quality and responses to nutrient reduc-
tion. Acta Universitas Upsaliensis, Abstracts of Uppsala
Dissertations from the Faculty of Science, 459.
Ulmgren, L. (1969): Drifterfarenheter fran nagra reningsverk for
narsaltreduktion. Vatten, 25, 2, pp 140-145 (in Swedish).
137
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Ulmgren, L. (1975a): Experiences and results from chemical pre-
cipitation of domestic waste water in full-scale
plants. Prog. Wat. Tech., Vol 7, Nos 3/4, pp 409-416.
Ulmgren, L. (1975b): Swedish experiences in chemical treatment
of wastewater. J. Water Pollution Control Federation,
47, 4, pp 696-703.
Weijman-Hane, G. (1968): Narsaltreduktion. Vatten, 24, 2, pp 106-
111 (in Swedish).
138
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ECONOMICAL AND EFFICIENT PHOSPHORUS CONTROL
AT A DOMESTIC-INDUSTRIAL WASTEWATER PLANT
Doris Van Dam
Wastewater Treatment Plant Superintendent
Grand Haven - Spring Lake, Michigan Sewer Authority
INTRODUCTION
In 1968, the Michigan Water Resources Commission (MWRC) issued
orders for phosphorus and other pollutant reductions to commun-
ities and industries whose wastes were being discharged to the
waters or tributaries of the Great Lakes by December 1972. The
MWRC adopted its standard from the Federal State Conference on
the pollution of Lake Michigan and its tributary basin held in
Chicago, Illinois in March 1968.
The response at Grand Haven and Spring Lake, Michigan, located
on the sandy coast where the Grand River enters Lake Michigan,
was to form a combined sewer authority and build a new central
treatment plant. The plant was designed not only to process
domestic wastes, but also to receive a substantial contribution
from the Eagle Ottawa Leather Co., a chrome and vegetable tan-
ner of 12,000 hides per week and a principal employer in the
Grand Haven - Spring Lake area. (Figure 1).
It is the purpose of this paper to discuss the special challen-
ges the merged waste flow posed to design and subsequent opera-
tion of the treatment plant. How concentrated side streams,
such as heat treatment supernatants, must be considered in over-
all plant efficiency is discussed. The techniques used to control
139
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phosphorus at a very low cost are presented. A summary of sev-
eral years of plant efficiency and cost figures accompany the text.
BACKGROUND
The MWRC requirements called for an 80 percent removal of phos-
phorus for Grand Haven, Spring Lake, and the Eagle Ottawa Leather
Co., as well as combined maximums from all three sources of 1,126
pounds per day (511.2 kg) of BOD, and 30 mg/1 of suspended solids.
At the time, Grand Haven, population 10,500, was served by an out-
dated primary treatment plant, Spring Lake, population 3,034, em-
ployed an overloaded Imhoff tank, and Eagle Ottawa Tannery efflu-
ent was simply screened before discharge to the Grand River.
To meet the requirements, the newly-formed joint district construct-
ed a single 5.0 mgd (18,925 cu m/day) activated sludge plant. The
plant went on line in November, 1973, and 1978-1979 average con-
tributions from the three sources were 2.1 mgd (7,759 cu m/day)
from Grand Haven, 0.4 mgd (1,476 cu m/day) from Spring Lake, and
0.8 mgd (3,179 cu m/day) from Eagle Ottawa (Figure 2 ).
Although tannery wastes have amounted to just 26 percent of treat-
ment plant flow, they represent 81 percent of total influent BOD,
and 80 percent of influent suspended solids. The tannery waste
contains in mg/1 60 sulfides, 34 chromium, 57 ammonia, 2911 COD,
and a total nitrogen as N of 106 (Figure 2 ).
The treatment plant employs grit removal, phosphorus removal, pri-
mary clarification, activated sludge and chlorine contact; solids
are conditioned thermally prior to vacuum filtration (Figures).
141
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All domestic flow is comminuted prior to reaching the grit tank.
Eagle Ottawa wastes are screened at the tannery. Grit collected
on the bottom of a square, aerated-type grit collector is removed
by means of an air lift pump from the hoppered end of the tank.
Grit is washed by means of a mechanical inclined screw mechanism.
Ferrous sulfate for phosphorus removal is added to the total flow
in the rapid mix tank located in the grit building.
Air flocculcation is provided in the primary clarifiers for poly-
mer flocculation.
The plant includes three 60-foot (18.29 m) diameter, primary clari-
fiers, 200,000 gallon (757 cu m) capacity each. The three aeration
tanks have a total capacity of 1,700,000 gallons (6,434.5 cu m), and
and are equipped with duo-spargers and coarse bubble diffusion.
The aeration tanks are arranged so that the activated sludge pro-
cess can be operated in one of four modes: conventional, complete
mix, step aeration, or contact stabilization. Air is provided by
four centrifugal blowers, each having a capacity of 5,200 cubic
feet (145.6 cu m) per minute.
The three final clarifiers are the same size as the primaries, and
are equipped with suction-type sludge removal mechanisms. The chlo-
rine contact tank has been constructed to provide two separated tanks
with gates so that either tank may be isolated for cleaning.
Effluent water is used for lawn sprinkling, the incinerator scrubber,
filter belt wash, foam suppression, line flushing, thickener, and
chlorinators.
144
-------
Return sludge pumps are 20 hp (14.914 kw) , and can provide 100
percent return sludge capacity. Sludge from primary clarifiers
is drawn off from a sump at the center of the clarifier by means
of positive displacement pumps, and pumped directly to two 45-
foot (13.716 m) diameter, 20-foot (6.096 m) deep covered thicken-
ing tanks, with total capacity of 1,000,000 gallons (3,785 cu m),
or 28,000 pounds (12,712 kg) per day of solids.
After thickening, sludge is processed through a wet oxidation unit
where it is thermally conditioned at a rate of 68 gallons (257.38
liters) per minute. Sludge is first ground in one of two grinders
which are piped in parallel to insure operation if one is out of
service.
Air is supplied by a 50 hp (37.29 kw), 134 scfm (3.75 cu m/min)
@ 500 spig (35.15 kg/sq cm) compressor, and the sludge-air mix-
ture is pumped to reactor pressure of 306 psig (21.51 kg/sq cm) by
a high pressure positive displacement ram-type pump. The material
is fed through stainless steel heat exchangers to a stainless steel-
clad reactor. A steam boiler maintains reactor temperature at 385°F
(195.9°C). A standby boiler, and a second high pressure pump, pro-
vide backup capability.
Oxidized sludge is decanted in a separate tank and dewatered on
one of two cloth-covered, 370 square foot (34.37 sq m) vacuum fil-
ters. When the incinerator is bypassed, sludge cake is hauled to
landfill or used on agricultural land.
Plant performance has averaged 96 percent BOD removal, 76 percent
COD removal, 96 percent suspended solids reduction, 88 percent
145
-------
phosphorus removal, and chromium reduction of 96 percent (Figure 4 )
SPECIAL PROBLEMS - LOCATION/ODORS
Inclusion of tannery wastes in the new treatment plant created con-
ditions which required special consideration from the very first.
Because the hair, lime and grease in tannery wastes tend to clog
sewer lines unless there is adequate sewer dilution or primary
treatment prior to discharge into sewers, plant siting became a
crucial decision. To minimize the anticipated difficulties in
moving tannery effluent over longer distances, the new treatment
plant was situated within the city limits of Grand Haven, immed-
iately sputh of the Eagle Ottawa plant. The location is in a semi-
residential neighborhood, and special provisions for odor control
have had to be implemented.
In the original scheme, all usual odor-producing areas (grit and
screening building, decant tank, thickeners, vacuum filters) were
covered. The areas are vented and odors drawn off to the inlet
of the aeration blowers and solubilized in the mixed liquor.
Because of equipment failures and the tannery contribution, how-
ever, odor problems unforeseen originally have required extraord-
inary odor control techniques.
TREATABILITY
Treatability of the tannery-domestic waste mixture was a second
important question. Pilot studies verified the effectiveness of
the activated sludge method, provided the chromium content of pri-
mary effluent could be reduced to approximately 5 mg/1 to avoid
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toxicity in the biological phase. This was achieved by blending
lime from the tannery's beamhouse to aid in the precipitation of
chromium hydroxide. The addition of sodium hydroxide to the tan-
nery waste prior to its combination with the domestic flow is also
possible. This has rarely been necessary, however, except for a
period during a strike when the tannery was operating with limited
staff and not using the beamhouse to full capacity.
Since the tannery wastes are discharged on a batch basis, with pH
ranging from 3 to 12, an equalization tank was incorporated into
the system to hold tannery efflyent and create an acceptable pH
level of 8.5 to 9.0.
In addition, the system is designed so that all tannery wastes
can be taken into one primary tank, exclusive of domestic wastes,
and treated separately, should that become necessary.
SIDESTREAM RECYCLE
A great deal has been said about the supernatant decant liquor
which is returned from thermally conditioned sludge to the treat-
ment plant. Sidestream treatment should be studied in light of
purpose and design of the total solids handling system and the
fate of solids throughout.
Let us deal with solids first. While thermal conditioning is high-
ly successful in making the difficult-to dewater sludge easily de-
waterable, it also solubilizes a portion of the raw suspended sol-
ids. At the same time, a relatively small amount, approximately 5
percent, of oxidation of volatile solids occurs, due to the addi-
tion of air in the thermal conditioning system.
148
-------
Supernatant recycle, of course/ is another concern. After condi-
tioning, the oxidized sludge flow enters the decant tank, where it
thickens before it is sent to the vacuum filter for dewatering.
The decant supernatant, a relatively clear liquid resulting from
the thickening process, is decanted and returned to the aeration
tanks for treatment. While its suspended solids concentration is
only, 2460 mg/1, its COD, 8005, and P concentrations are 22, 320
mg/1, 9370 mg/1 and 45 mg/1 respectively, due to the solubilized
dissolved volatile solids. It constitutes the major biological
solids handling sidestream load on the plant. It also has some
phosphorus load. Additional capacity and operational flexibility
were designed into our secondary system to allow for adequate
treatment of the solids handling recycle streams.
PHOSPHOROUS REMOVAL
A chemical mixing, feeding and distribution system was provided to
provide chemical removal of phosphorous in the wastewater stream.
It was planned that the chemicals used for phosphorous removal
would include ferric chloride and polymer.
Ferric chloride would be delivered by truck and transferred to two
10,000 gallon (37,850 1) storage tanks located adjacent to the chem-
ical feed room underground outside the control building.
Because the concentrations of ferric chloride delivered to the
plant would vary from 38 percent to 45 percent during winter and
summer months respectively, the operator had flexibility as to how
to store and feed the ferric chloride. A dilution system was in-
stalled so that a constant dilution could be fed throughout the
149
-------
year if desired. Non-potable water could be added to the storage
tank along with air mixing from the bubbler system to provide the
desired diluted concentration. Should the operator not desire to
dilute the concentration, as is the case with waste pickle liquor
currently used, the solution can be fed directly from the storage
tanks to the plant.
A bubbler system was incorporated in the design to measure the
level in both ferric chloride tanks.
Positive displacement metering pumps were provided to meter the
iron solution to the various feed points which consisted of the
rapid mix tank, inlet and outlet of primaries and aeration tanks,
and inlet of the final settling tanks. Metering pumps were elec-
tronically paced from the main plant master flow meter. A stand-
by iron solution pump was also included. The solution from the
pumps flows to a rotameter distribution panel where it can be
distributed throughout the plant.
It was designed for polymer to be delivered to the plant in dry
form. An automatic mixer and dispenser were provided to meter the
polymer solution to the various feed points. As in the case of
the iron solution, the feed pumps were paced from an SCR controller
which in turn was paced from the main plant master flow meter. The
rotameter panel for polymer was also provided for distribution
throughout the plant. This panel would split only the diluted poly-
mer.
Numerous programs of varying chemical concentration and feed points
for phosphorous removal were conducted (Figure 5). In March 1974
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ferric chloride was applied to the rapid mix tank, and polymer to
the final sedimentation tank influent. Ferric chloride in the a™
mount of 8.01 mg/1 as Fe and polymer in the amount of 0.21 mg/1
was applied at a cost of $1,181. Influent phosphorous was 5.5 mg/1
and the final effluent 1.2 mg/1.
In April the polymer was again used in the influent to final sed-
imentation only/ with the ferric chloride split, adding 60 percent
to the rapid mix tank and 40 percent to the final sedimentation
influent with no apparent improvement in phosphorus removal. Ferric
chloride in the amount of 8.63 mg/1 as Fe and polymer in the amount
of 0.17 mg/1 was applied at a cost of $1,271. Influent phosphorous
was 5.2 mg/1 and final effluent 1.3 mg/1.
This mode of operation was continued in May and again with no ap-
parent improvement in phosphorus removal.
In June both the polymer and ferric chloride were split with two-
thirds of the chemicals added to the rapid mix and one-third to the
influent to final sedimentation. Although the final effluent phos-
phorous concentration was lower at 0.7 mg/1, it should be noted
that the influent phosphorus was also lower at 3.8 mg/1. The a-
mount of ferric chloride used was 8.38 mg/1 as Fe and polymer ap-
plied was 0.21 for a total chemicals cost of $1,989. The diluted
phosphorous concentration in the influent was due to heavy precip-
itaion and river water backflow. This condition was corrected
shortly thereafter. Perhaps the impact of the tannery coming on
line May 28, 1974 may also have helped in phosphorus removal. How-
ever, the tannery was on limited operation at that time and were
152
-------
buying some of the hides in the blue, which reduced beamhouse lime
waste.
It was apparent that neither split feed, nor chemicals added to the
final sedimentation influent were as effective as adding the total
iron solution to the rapid mix tank prior to primary sedimentation.
Removals were excellent either with or without polymer addition.
It would follow that polymer use was discontinued and the iron
solution added to the rapid mix tank.
After several months of operation with ferric chloride we were con-
tacted by several companies who were contracted to remove waste
pickle liquor from the steel mills in Gary, Indiana. We were able
to purchase the waste pickle liquor for less than the cost of com-
mercial ferric chloride. This has been used for over five years
to date. It has been equally as effective in phosphorus removal
as was ferric chloride.
Also shown on the lower portion of Figure 5 is 1975 data for the
same months as reported in 1974 for comparison. In March 1975
ferrous sulfate in the amount of 4.1 mg/1 as Fe at a cost of $381
was applied to the influent containing 4.6 mg/1 of phosphorus and
resulted in a final effluent phosphorus content of 0.9 mg/1.
In April $352 was spent to apply 4.3 mg/1 of ferrous sulfate as
Fe to an influent containing 5.2 mg/1 of phosphorous which resulted
in a final effluent containing 0.9 mg/1 of phosphorus.
In May $402 spent for 4.8 mg/1 of Fe applied to an influent con-
taining 5.8 mg/1 of phosphorus resulted in a final effluent of 1.1
mg/1 of phosphorus.
153
-------
In June $542 was spent for 6.4 mg/1 of Fe applied to an influent
containing 6.1 mg/1 of phosphorus resulting in an effluent con-
taining 0.9 mg/1 of phosphorus.
It would appear from the data shown in Figure 6 , which shows the
iron used for phosphorus removal, that waste pickle liquor was
actually more effective than ferric chloride in that the amount
applied in milligrams per liter went from 9.3 in 1974-1975 to 6.6
in 1975-1976. We would propose/ however, that the increasing load
from the Eagle Ottawa Leather Co. resulted in much more lime from
their beamhouse operations being discharged to the treatment plant,
which aided in the decrease in the amount of iron required for phos-
phorus removal.
To support that theory, Figure 7 shows the amount of flow from
the tannery and the amount of iron applied for phosphorus removal
for the same period of time. As the amount of tannery waste in-
creased, the amount of iron necessary to control phosphorus removal
decreased. The tannery flow went form 190 mg (719,150 cu m) in
1974-1975 to 307 mg (1,161,995 cu m) in 1978-1979. The iron ap-
plied to the total plant flow decreased from 9.3 mg/1 to 1.6 mg/1.
On May 18, 1978 the tannery discontinued the use of the million
gallon equalization tank that had been in use prior to that time
for equalizing the flow to the wastewater treatment plant. Follow-
ing this, the tannery added more lime to their discharge; during
periods of dump from the tanhouse portion of their operation. In
the tanhouse operation, a pickling process brings the hides to an
acid condition in preparation for tanning. This waste has a low pH,
154
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Further documentation in regard to the relationship between volume
of tannery flow and phosphorous removal at the treatment plant for
January and February of 1979 as compared to 1980 is as follows: In
January 1979 the tannery flow was 24.65 mg and 2.21 mg/1 of Fe was
fed resulting in final effluent phosphorus of 0.6 mg/1. To compare,
in January 1980 the tannery flow was only 13.857 and 6.65 mg/1 of
Fe resulted in final effluent phosphorus being 0.6 mg/1. In Feb-
ruary 1979 the tannery flow was 27.424 mg, no Fe feed was required,
and the final effluent phosphorus was 0.5 mg/1. However, in Feb-
reary 1980 the tannery flow was only 18.494 mg and 4.89 mg/1 of
Fe was applied which resulted in final effluent phosphorus concen-
tration of 0.7 mg/1.
SUMMARY
This domestic-industrial activated sludge wastewater plant with
approximately 18 percent of the total flow emanating from a chrome
tanner and 80 percent of the suspended solids and BOD, has achieved
excellent purification. Suspended solids and BOD removals have con-
sistently been above 90 percent. The final effluent phosphorus con-
centration has been under 1.0 mg/1 with removal over 80 percent.
This excellent phosphorus purification has been accomplished with
pickle liquor, all added prior to primary sedimentation, and without
a flocculating aid. Although phosphorus removal was successful with
limited amounts of iron application when the tannery waste was pre-
sent in considerable amount, it was necessary to add much larger a-
mounts of iron solution when the tannery waste was limited or off
entirely. Simple laboratory control has been practiced with analyses
made on the daily composite sewage samples, and iron feed adjusted
based on the prior day's operating results.
157
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158
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THE PHOSTRIP PROCESS FOR PHOSPHORUS REMOVAL
By
Mr. Carl J. Heim
Assistant Staff Engineer
Union Carbide Corporation
Linde Division
Tonawanda, New York
INTRODUCTION
The PhoStrip process is a combined biological-chemical process for the
removal of phosphorus from wastewater. The process works by concentrating
the phosphorus in the wastewater through biological means into a small sub-
stream, to which chemicals are added for precipitation of the concentrated
phosphorus. Normally lime is used for phosphorus precipitation because the
quantity of lime required is proportional to the flow being treated rather than
the phosphorus concentration in that flow. Thus, if the phosphorus in the
wastewater is concentrated into a substream that is 15% of the entering waste-
water flow, the amount of lime required would be only 15% of the lime required
to treat the entire wastewater flow.
In addition to drastically reducing the chemical requirement for phosphorus
removal, the PhoStrip process also produces relatively small quantities of
chemical sludge. Phosphorus is precipitated in a separate reactor in the
process and the resulting chemical sludge does not contain.significant bio-
logical solids. This sludge is inert and stabilization (such as digestion) is
not required prior to disposal. When lime is used for phosphorus precipitation,
a very easily dewatered sludge is produced. The net results are very substantial
savings in both chemical costs and sludge disposal costs.
159
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DESCRIPTION OF THE PHOSTRIP PROCESS
A flow schematic of the PhoStrip process is shown in Figure 1. In the
process, return sludge is mixed with plant influent and aerated exactly as in
a conventional activated sludge system. While under aeration, the micro-
organisms have the capability of removing essentially all of the soluble phos-
phorus from the wastewater because of special conditioning received in the
PhoStrip process. The phosphorus removed in the aeration basin is incorporated
into the sludge in the form of stored polyphosphates. The phosphorus content
of the sludge leaving the aeration basin can be more than twice that of sludge
from a conventional system. Removals of biological oxygen demand and sus-
pended solids in the aeration system are unaffected by PhoStrip.
The phosphorus-laden sludge is separated from the phosphorus-free effluent in
the secondary clarifier. The sludge withdrawn with the clarifier underflow is then
either sent directly back to the aeration basin, wasted from the system (excess
biological sludge quantities are not affected by the PhoStrip process) or sent to
a stripper tank, where it is held under anoxic conditions for several hours.
While under anoxic conditions, the microorganisms release their stored phospho-
rus in soluble form. The released phosphorus is "washed" from the sludge blanket
by an elutriation stream and withdrawn as a supernatant from the stripper tank.
This supernatant stream is then fed to a reactor-clarifier where the phosphorus
is precipitated with lime. Typically, the supernatant flow is 10-20% of the influent
flow. Therefore, as explained previously, lime requirements are reduced by
160
-------
Influent
Aeration
Basin
Direct Recycle
Reactor-
Clarifier
Supernatant
Effluent
\
Waste
Sludge
Stripper Feed
Anoxic
Stripper
Tank
Elutriation Stream
Waste Chemical Sludge
Stripper Underflow
Figure 1. Phostrip System Flow Schematic
161
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80-90% and chemical sludge quantities are also reduced. The inert chemical
sludge is withdrawn from the bottom of the reactor-ciarifier. The overflow
from the reactor-ciarifier, which has a relatively low phosphorus concentration,
is used as the elutriation stream.
Sludge is withdrawn from the bottom of the anoxic stripper tank at the same
rate as it is fed to the tank to avoid solids buildup. This sludge is returned
to the aeration basin where phosphorus uptake is resumed.
The PhoStrip process typically produces an effluent with a total phosphorus
concentration of 0.5-1.0 mg/1. The effluent soluble phosphorus concentration
normally ranges from 0.1-0.5 mg/1. The PhoStrip process operates over the
normal range of activated sludge system operating conditions and can be used
with either air or oxygen activated sludge systems.
THEORY
Biochemical Aspects
The biochemical phenomemon responsible for the PhoStrip process has not
been fully defined. Results of experimental work have led .to the formulation
of the following mechanisms for the observed phenomenon.
Organisms containing high intracellular phosphate concentrations have
been isolated from wastewater treatment systems exhibiting high phosphorus
removal rates. Typical of these isolates are organisms of the genus Acineto-
bacter. The organisms of this genus have demonstrated the ability to take
162
-------
up and release phosphorus as a function of the aerobic-anoxic cycle, while
in pure culture form. The interior of the cells have been characterized as
containing very large volutin (polyphosphate) granules while under aerobic
conditions. The size of these granules diminished as the culture was main-
tained in an anoxic environment. This indicates a transfer of phosphorus
from the voiutin granules into solution. These particular organisms are so
abundant in activated sludge systems that the Water Research Centre Labora-
tory at Stevenage, England, has utilized pure cultures to simulate activated
sludge systems. These organisms are also obligate aerboes preferring Krebs
cycle intermediates and acetates as substrates for metabolism.
It is believed that the anoxic period of the PhoStrip process forces these
strict aerobes to undertake a sequential series of reactions which result in
their forming polyphosphate granules while in the aerobic period. This results
in a set of aerobic organisms that can compete more effectively with facultative
organisms in a cyclic aerobic-anoxic environment. The polyphosphate granules
within the cell may provide phosphorus and energy to convert ADP to ATP during
(2 3)
the anoxic period through the catalysis of the polyphosphokinase enzyme . '
Substitution of polyphosphate for ATP in biochemical reactions during anaero-
(4)
biosis is also possible. (A third potential pathway of phosphorus release
utilizing the phosphatese enzyme has not yet been delineated.)
In the first mechanism, conversion of ATP to ADP during the anoxic period
results in the release of phosphorus from the cell as well as providing a source
of energy. This energy is utilized by the obligate aerobes to continue some of
their metabolic functions. The fact that the addition of acetates increases the
163
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rate of phosphorus release suggests an interaction between these organisms
and the facultative microbes present in activated sludge. Under anoxic condi-
tions, the facultative aerobes produce acetates which enhance the rate of phos-
phorus release by the oligate aerobes. When the sludge leaves the anoxic
environment and enters aerobic conditions, the ATP content within the cell
is low because the reaction of ATP—^ADP + P is a high rate reaction relative
to the formation of ATP from polyphosphates.
In the second, direct substitution mechanism, the energy of the poly-
phosphate-phosphorus bond is utilized in place of the ATP bond energy. The
phosphorus would be directly released to solution from the polyphosphate
molecule. If direct substitution is the major means of phosphorus release,
the above ATP to ADP reaction would also occur producing a low ATP/ABP
ratio in the ceil.
Under aerobic conditions, the strict aerobes' oxidize stored metabolites
and other substrates to provide energy to increase the ATP content of the cell.
After a very short time, the ATP/ADP ratio in the cell becomes high enough
to trigger the formation of polyphosphate via the reversible polyphosphokinase
enzyme. This results in the formation of polyphosphate granules which are
stable storage products in an aerobic environment.
The performance of the PhoStrip process is consistent with the theory.
The theory implies a temperature dependency. In fact, an Arrhenius type
relationship has been established. This theory also indicates that the rate
of phosphorus release per unit mass of organisms is a function of the duration
164
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of the anoxic period, as well as the quantity and activity of facultative
organisms. The activity of the facultative bacteria can be related to the
Food-to-Microorganism ratio (F/M) of the activated sludge system, while
quantity is related to the concentration of sludge in the stripper tank. Since
strict aerobes are implicated in the above theory, too long an anoxic period
relative to the aerobic period could cause the organisms to cease phosphorus
uptake. Experimentally determined operating limits for such a response do
exist. However, there is a broad spectrum of conditions under which good
performance has been established.
The finite capacity of these organisms for phosphorus storage results
in a loading requirement which must not be exceeded if a high degree of
phosphorus removal is to be achieved. Different activated sludge systems
have exhibited different maximum levels of phosphorus per unit mass of
MLVSS. This maximum P/VSS ratio has been observed to be a function
of the viable organism content of the volatile suspended solids. The P/
VSS ratio observed in efficiently operating PhoStrip Systems depends on the
phosphorus available in the feed, the maximum P/VSS ratio attainable,
and the environmental conditions presented earlier.
Ideally, all the phosphorus in the feed would be incorporated into the
cell mass and wasted from the system as biological sludge. This mode of
operation would eliminate the need for chemical precipitation facilities and
significantly reduce the operating cost of the process. However, there are
factors which prevent this from being realized in all but a few instances.
165
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First, effluent quality is a function of the soluble and particulate phosphorus
content. Even if an effluent soluble PQ^ level of ^^.01 nig/1 were achieved,
a 20 mg/1 VSS in the effluent would limit the phosphorus to VSS ratio to <"0.05
in order to achieve an effluent <^ 1.0 mg PO.-P/l. Second, for a given P/
VSS level, a specific quantity of sludge must be wasted as dictated by phos-
phorus mass balances in order to remove enough phosphorus to achieve the
desired effluent. The amount wasted generally depends on the F/M (SRT) of
the system. In most cases a high degree of phosphorus removal could only be
achieved at very high F/M (low SRT) values because of the low P /VSS levels
necessary to satisfy effluent criteria as presented above. Third, bio-chemical
sludges tend to release phosphorus when digested. If high P /VSS levels
are employed for phosphorus removal, large quantities of phosphorus could
return to the head end of the plant. This level of phosphorus return would
require a significant increase in sludge wasting unless some method of chemi-
cal precipitation were employed.
The PhoStrip System is normally designed for a phosphorus content of
0.03-0.04 Ib. P/lb. VSS in the sludge in order to achieve effluents of less
than 1.0 mg PO.-P/l.- The phosphorus that is not removed through wasting is
precipitated from the supernatant stream leaving the stripper tank. The
relative amounts of phosphorus removed through sludge wasting and precipi-
tation depend on the F/M (SRT) of the activated sludge system and the BODS /P
level in the wastewater. The ratio of phosphorus removal by precipitation to
166
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the overall phosphorus removal can range from 0 to 0.9+. Each wastewater
will result in different values of this ratio depending on the design conditions
of the activated sludge system and the method of waste sludge disposal.
Chemical Precipitation of Phosphorus
Lime was chosen as the precipitant because of its pH functionality.
Unlike alum and ferric chloride, the gross quantity of lime required for pre-
cipitation of phosphorus in water is dependent only on the amount and alkalinity
of the water not the concentration of phosphorus. Further reduction in chemical
requirements can be achieved by precipitating phosphorus at lower pH levels
(8.5-9.0). At these pH levels, the stripper supernatant after lime addition
may typically contain 2-5 mg soluble PO.-P/l. A lower phwillalso result in sub-
stantially less chemical sludge to be handled because less calcium carbonate
and no magnesium hydroxide are formed. The chemical sludge production will
be typically less than 50 percent of that produced at a pH = 10.5. This material
could be used as an agricultural fertilizer because of its high phosphate content.
FULL SCALE PERFORMANCE
The PhoStrip system has been demonstrated at two localities under full
scale conditions and 9 pilot plant locations. These two full scale plants
were Seneca Falls, NY and Reno/Sparks, Reno, Nevada.
167
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SENECA FALLS, NY
The wastewater treatment facility at Seneca Fall, NY is an activated
sludge treatment plant with two trains and a total capacity of 3 .5 MGD
3
(13,247 m /day). The plant consists of a bar screen, comminutor, two cir-
cular primary clarifiers, two completely mixed aeration basins with mechanical
aerators, two rectangular secondary clarifiers and a chlorine contact chamber. The
The wastewater is largely domestic in character with a BOD of approximately
160 mg/1; total dissolved solids of 680 mg/1 and total phosphorus of 6.3 mg/1.
Conversion of the plant to the PhoStrip process was facilitated by the
3
fact that, at the time of the study, the raw wastewater flow was only 3800 m /6
(1 mgd). This enabled the plant to handle the full plant flow through one of
the two reactor trains, thus freeing a primary clarifier to provide the anoxic
environment required for the return sludge to release excess phosphorus.
The tank providing this anoxic zone has been labelled the "stripper tank".
The use of a single train to treat the entire wastewater flow also permitted
the test to be run on a system that was much nearer the design hydraulic loading
for the Seneca Falls plant. The use of the primary clarifier as the stripper tank
was expeditious; however, it was significantly oversized relative to the waste-
flow entering the aeration basins. Table 1 presents a concise summary
of the data obtained during the first thirty days of operation at Seneca Falls.
It is evident from this table that substantial savings have been demonstrated.
The amount of lime has been greatly reduced since the supernatant from the
168
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Table 1. Results of Phosphorus Removal Test
at Seneca Falls, N.Y.
Plant Flow, m3/d (mgd) 3400 (0.9)
Return Flows, percent of raw flow:
Sludge to Stripper 24
Sludge to .Aeration from Stripper 10
Supernatant to Primary Clarifier 14
Total Suspended Solids, mg/1:
Mixed Liquor 1,440
Sludge to Stripper 7,840
Sludge to Aeration from Stripper 15,910
Influent, mg/1:
BOD5 158
Total Phosphorus 6.3
Effluent, mg/1:
BOD5 ^4
Total Phosphorus .6
Plant Performance:
BODr Removal, percent 98
«J
Total Phosphorus Removal, percent 91
Lime Dose, Stripper Supernatant, mg/1 of supernatant 170
(as CaO)
Lime Dose, prorated to mg/1 of raw flow (as CaO) 24
169
-------
PhoStrip stripper is only fourteen percent of the incoming flow. Calculated on
the basis of the incoming flow, the lime dose would be 24 mg/1 as CaO.
When compared to conventional lime requirements of 300-660 mg/1 for post
precipitation to obtain the same total phosphorus effluent concentration of
less than 1 ppm (0.6 ppm), the savings are quite apparent. This represents
the period of operation during which the performance of the process was inten-
sively monitored. -The recycle flow rates presented are typical of a system
utilizing sludge thickening in the stripper tank to produce the phosphate-
enriched supernatant. The data on plant performance indicates that very high
removals of both BODS and phosphorus were achieved. The lime dosage is
reflective of the chemical requirements anticipated for many full scale systems.
RENO/SPARKS. RENO, NEVADA
The Reno/Sparks facility is designed to process an average flow of
3
76,000 m /d (20 mgd) and discharges into the Truckee River. The system con-
sists of an aerated grit chamber, three primary clarifiers, three activated sludge
trains and three secondary clarifiers. The PhoStrip System initially operated
by Kennedy Engineers, San Francisco, California, on one third of the total av-
3
erage plant flow (25,000 m /d) by using the sludge recycle option of operation
(Figure 2). In this option, the stripper is operated in a thickening mode and a
portion of the stripper underflow is recycled back to the stripper feed. The rea-
son for recycling the underflow is to increase the supernatant phosphorus by mix-
ing high P/low P streams. (This mode of operation produced an elutriation effi-
ciency of approximately 38%, where elutriation efficiency, E, is defined as the
170
-------
Wastewater
Primary
Clarifier
Lime
Reactor
Clarified
Waste
Sludge
Chemical
Aeration
Secondary
Clarifier
Effluent
Direct Recycle
Stripper
Supernatant
Stripper
Stripper
Feed
Stripper Return
Waste
Sludge
Sludge
Recycle
Figure 2. Sludge Recycle Option
171
-------
amount of phosphorus removed by the stripper overflow per day divided by the
amount of phosphorus released in the stripper per day. )
On June 25, 1975, Union Carbide Corporation began its evaluation of the
PhoStrip process on the full scale plant at Reno/Sparks, Nevada. A set of
conditions was established on the full scale (Table 2) and the system was
allowed to come to steady state. After steady operating conditions were
achieved, a period of intensive evaluation followed. Table 3 presents the
results of analyses performed at Reno/Sparks during this phase. Figures 3 &
4 present the influent and effluent phosphorus levels during the testing period
and their variation with the flow to the plant. The system demonstrated excel-
lent effluent quality in all respects, and as evident in the figures, total phos-
phorus levels were consistently 1 mg/1 or less.
In an effort to improve the elutriation efficiency a low phosphorus elutria-
tion (LPE) modification was employed. The cross sectional area requirement
for the stripper as dictated by the limiting-flux theory is reduced relative to the
sludge recycle system. Since the primary clarifier (stripper tank) at the Reno/
Sparks plant had a fixed cross-sectional area,the solids flux considerations
3
indicated that two-thirds of the plant flow (50,000 m /d) could be treated
with the available area. As a result, the system was modified according to
Figure 1, which was referred to earlier. Table 4 presents the operating condi-
tions for this two week test period (Jan. 18-30, 1977) and Figure 5 graphically
displays the influent and effluent phosphorus concentration. Again, the efflu-
ent total phosphorus levels were usually 1.0 mg/1 of phosphorus or under.
172
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Table 2. Operating Conditions for the Phostrip
Sludge Recycle System - Full Scale Testing
at Reno/Sparks, Nevada (9/13/75-9/27/75)
Parameter
•5
Flow Rates (m°/day)
Feed, (Q)
Recycle to Stripper (R^)
Stripper Underflow (R,3)
Stripper Supernatant "*
Recirculation Rate (R2)
Waste Sludge Rate
Aeration Time, Hr. (based on Q)
Anoxic Period, Hr. (based on R3)
MLSS, mg/1
MLVSS, mg/1
RjSS, mg/1
RiVSS, mg/1
R3SS, mg/1
R3VSS, mg/1
•TSS Stripper Supernatant, mg/1
VSS Stripper Supernatant, mg/1
D.O., End of Aeration, mg/1
D.O. , Rj, mg/1
\ D.O. , R3, mg/1
pH, End of Aeration Basin
PH, R,
pH, R^J
pH, Stripper Supernatant
Temperature, °C
F/Ma (kg COD/day/kg MLVSS)
Clarifier Overflow Rate, m/day
Clarifier Blanket Level, rru
Minimum
14,690
5,180
2,330
2,850
4,230
639
10.2
16.
—
-
3,060
2,480
9,620
7,700
65
50
_
0.4
0.3
—
6.8
6.4
6.6
23
-
22.4
0.08
Time
Weighted
Maximum Mean
25,060
7,340
4,150
3,200
2,420
639
6.0
9.4
_
-
4,620
3,740
9,120
7,300
90
69
1.5 (0.7-2.2)
0.7
0.3
7.0
6.8
6.4
6.5
23
-
38.2
0.09
22,460
6,830
3,630
3,110
2,850
639
7.1
11.0
1,150
900
4,230
3,420
9,250
7,340
84
64
_
0.6
0.3
_
-
-
-
23
0.96
34.3
0.09
173
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Table 3. Analytical Results for the Phostrip
Sludge Recycle System Full Scale Testing
at Reno/Sparks, Nevada (9/13/75-9/27/75)
Parameter
COD, mg/1
Influent
Effluent
Total Suspended Solids, mg/1
Influent
Effluent
Effluent Volatile Suspended Solids, mg/1
Total Phosphorus, mg P/l
Influent
Effluent (ortho)
Stripper Supernatant
Stripper Underflow
Filtered Stripper Underflow
Filtered Aeration Effluent (ortho)
Secondary Clarifier Underflow
P/VSS
Secondary Clarifier Underflow
Stripper Underflow
Minimum
187
40
-
19
13
9.6
1.0 (.3)
44
257
67
-
104
0.042
0.025
Maximum
266
37
-
13
10
9.1
0.8 (.4)
41
240
55
- (.04)
161
0.043
0.025
Flow
Weighted
Mean
253
37
113
13
10
9.2
0.8 (.4)
42
247
58
-
113
0.043
0.025
174
-------
en
CO
z>
tr
o
X
Q_
CO
O
22 -
20 -
8 —
2 -
0 -
8 -
6 -
4 ->
ii -i
0
INFLUENT TOTAL =A
EFFLUENT TOTAL= D
EFFLUENT ORTHO= O
I I i I I I 1 I I I I I I I I I
12 13 14 15 16 17 18 192021 222324252627
SEPTEMBER, 1975
Figure 3. Reno/Sparks Full Scale Phosphorus Data Obtained
during Minimum Flow Period (16% of the Total
Volume Treated by the Phostrip System)
175
-------
22-
20-
8 -I
e -i
CO
ID
CE
O
m
o_
CO
O
^L
Q_
4 -
2 -
1 0 -
8 -
INFLUENT TOTAL »
6 -
2 H
EFFLUENT TOTAL =D
EFFLUENT ORTHO =O
ill i 1 I t I J I I
i r
2 13 14 15 16 17 IS 19 20 21 22 23 24 25 26 27
SEPTEMBER, 1975
Figure 4. Reno/Sparks Full Scale Phosphorus Data Obtained
during Maximum Flow Period (84% of the Total
Volume Treated by the Phostrip System)
176
-------
12-,
IOH
C/5
ID
a- 5-
CO
O
X
a
4-1
3-J
INFLUENT = A
EFFLUENT*!
EFFLUENT*2
O
O
18 19 20 21 22 23 24 25 26 27 28 29 30
JANUARY, 1977
Figure 5. Reno/Sparks Full Scale Phosphorus Data for LPE System
177
-------
A comparison between the LPE and sludge recycle system indicates that the
LPE System was capable of producing the same quality effluent while utilizing
the same stripper, but handling twice the flow.
The main reason for this is an improvement in elutriation efficiency with
the LPE System ( £ = 0.59 vs. £ = 0.38). This improvement translates to a
decrease in the initial capital cost due to the decrease in tankage.
178
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ECONOMIC EVALUATION
COMPARISON OF OPERATING COSTS FOR PHOSPHORUS REMOVAL SYSTEMS
Table 4 shows a comparison of operating costs for various phosphorus
removal systems. Included in the comparison are conventional chemical pre-
cipitation with lime, alum, ferric chloride and pickle liquor, as well as the
PhoStrip process with lime or pickle liquor addition. The costs are based on
an alkalinity of 250 mg/1, and an influent phosphorus concentration of 1 mg/1.
Chemical requirements and costs for the conventional phosphorus removal
systems were taken from the EPA Process Design Manual for Phosphorus
Removal (1976) and have been adjusted to 1st quarter 1980. Chemical sludge
disposal costs were assumed to be $100/ton of dry solids.
It is apparent from inspection of Table 5 that the use of the PhoStrip process
drastically reduces the operating costs for phosphorus removal. For the example
case shown, operating costs are reduced by approximately 40-55% compared
to a conventional system using pickle liquor, which has the lowest operating
cost of the conventional systems.
CASE STUDY
The following economic study has been taken verbatim from the EPA Bio-
logical-Chemical Process for Removing Phosphorus at Reno/Sparks, NV
publication, and is for illustrative purposes only.
179
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Table 4. Operating Conditions for Pull Scale
Testing at Reno/Sparks, Nevada
Phostrip LPE System (January 18-30, 1977)
PARAMETER
MINIMUM
TRAIN I/TRAIN 2
MAXIMUM*
TRAIN I/TRAIN 2
FLOW
WEIGHTED MEAN
TRAIN 1/TRAIN 2
Flow Rates, m /day
Feed Q, (each train)
Recycle to Stripper, Rj
Stripper Underflow, Rj
Stripper Supernatant, S
Elutriation, EL
Total Aerobic Recycle, R\ + Rdirect
Sludge Wasting
Aeration Time, Hrs. (based on Q)
Anoxlc Period, Hrs. (based on Rj)
MLSS, mg/1
VSS/TSS
RlSS, mg/1
VSS/TSS
R3SS, mg/1
R3VSS, mg/1
TSS Stripper Supernatant, mg/1
VSS Stripper Supernatant, mg/1
17280/17280
1987/2160
1210/1470
6570
5270
-
-
9.0/9.0
11.6
1230/1280
0.8
5750/5460
0.78
8930
7360
-
-
29380/29380
3200/3370
2250/2250
7000
5620
-
-
5.1/5.1
7.0
1110/1140
0.8
6770/6720
0.78
8310
6590
-
-
22460/22460
2510/2680
1640/1810
6740
5440
4490/5530
331/418
6.8/6.8
9.5
1170/1220
0.8
6210/6030
0.78
8650
7010
59
54
pH, Mixed Liquor, mg/1
Temperature (Influent). *C
F/Ma Qcg BOD5/dayAg MLVSS)
7.1/7.0
13
0.45
Secondary Clarifier Overflow Rate,m/lay 26.4/26.4
Clarifier Blanket Level, m.
7.0/7.0
13
0.88
44.8/44.8
13
0.62
34.3/34.3
<0.2
* duration at max. flow y 11 hrs/day
180
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EPA Recommended Dose
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PhoStrio System with Li
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181
-------
ADRIAN. MICHIGAN
The proposed Adrian WWTP design is for a two-stage activated sludge
system. The first stage will be used for carbonaceous removal and the second
stage will convert ammonia to nitrate. The PhoStrip process will be operated
in conjunction with the first stage aeration system. The main advantage of
the PhoStrip System is dosing only 10-15% of the sewage flow with chemicals
as compared to the conventional method of chemical treatment which uses
addition of chemical to the entire flow of sewage. Most of the operating ex-
penses of phosphorus removal is the chemical cost and the PhoStrip System
significantly reduces this cost. (Tables 6 & 7)
An economic evaluation was made comparing PhoStrip against the traditional
chemical addition methods using ferric chloride and alum. The cost-effective
analysis included initial installment cost and total annual costs which includes
capital cost amortized over 20 years at 6.125%interest; chemical cost; operating
labor; maintenance and repair costs; and sludge disposal costs.
The PhoStrip costs were based on (chemical) treatment of 15% of the maximum plant
flow of 7 mgd , or 1.0 mgd. The cost of the two traditional chemical processes
were based on total plant flow of 7 mgd. The bench scale lime dosage test
conducted during the pilot plant operation established a lime dosage of 250 mg/1
to produce the desired treatment. The dosage required for treatment with the
traditional chemicals were: 90 mg/1 of ferric chloride and 135 mg/1 of alum.
182
-------
Table 6. Cost Comparison between Phostrip and
Chemical Addition for Phosphorus Removal
at Adrian, Michigan
Design Flow = 7 mgd
Influent P = 10 mgd
Effluent P = 1 mg/1
Item PhoStrip Ferric Chloride Alum
A. Installed Investment1 $520,000 $ 60,000 $ 65,000
B. Annual Costs
1. Amortized Investment2 (A x 0.08897) 46,265 5,338 5,783
2. Chemical Costs
a. Lime3 20,000
b. Ferric Chloride4 105,500
c. Alum5 — 115,000
3. Operating Labor, Maintenance
& Repair 8,006 3,000 3,500
4. Sludge Disposal Cost O&M at 800T/yr at835 T/yr at 525 T/yr
a. Anaerobic Digestion at $5/ton 4,000 4,175 2,625
b. Transport of Liquid Sludge by
Tank Truck at $15/Ton 12,000 12,525 7,875
TOTAL ANNUAL COST 90,265 130,538 134,783
$/mg $33.50 $51,10 $52.75
See Table 7 for cost breakdown.
2
Assumes a 20-year equipment life and 6-1/8% capital cost.
3
Based on a 250 mg/1 lime dosage, 15% Qt supernate flow, and a lime
cost of $50/ton delivered, (where Qt is the total influent flow to the plant.)
4
Based on a 90 mg/1 FeCU dosage, 7 mgd flow, and a FeCl3 cost of
$110/ton delivered.
Based on a 135 mg/1 alum dosage, 7 mgd flow, and an alum cost of
$80/ton delivered.-'
183
-------
Table 7. PhoStrip Cost Comparison
Equipment Cost '(PhoStrip) Cost
1 . Stripper Tank
a. Concrete 65-ft. dia. at 20-ft. SWD $150,000
b. Mechanism & Warranty (supplied by Union Carbide) 245,000
2. Lime-Mix Tank
a. Concrete 9-sq. ft. at 12-ft. SWD 57,500
b. Mixer 2,500
3. Pumps
a. Stripper supernatant Pumps 2,000
b. Anaerobic RAS Pumps 2,000
c. Stripper Waste Pumps 1,000
4. Lime Feed Equipment* (50 ton Bin, Feeder, Slaker) 60,000
Total Installed Cost $520,000
* Cost taken from EPA Manual "Phosphorus Removal", p. 10-32
ENR = 77— - = 1.53
1643(1971)
Equipment Cost (Ferric Chloride)
1. Bulk Storage 2/8000 gal. tanks $ 25,000
2. Pumps
Transfer 15,000
Feed
3. Dilution and Feed Tanks, Agitation, Piping 20,000
Total Installed Cost $ 60,000
Equipment Cost (Alum)
1. Bulk Storage 4/8000 gal. tanks $ 50,000
2. Pumps
Transfer 15,000
Feed
Metering
Total Installed Cost $ 65,000
184
-------
The estimated total annual cost of increasing the capacity of the existing
plant and adding the capability for phosphorus removal are: $85,565 per year
using the PhoStrip process; $129,163 per year using the ferric chloride process;
and $136,183 per year using the alum process.
185
-------
REFERENCES
1) Fuhs/ G. W., and Min Chen, "Microbiological Basis of Phosphate in
Activated Sludge Process for Treatment of Wastewater, " Microbial
Ecology, 1976.
2) Kornberg, S. R., "Adhenosine Triphosphate Synthesis from Polyphosphate
by an Enzyme from Eschericia Coli", Biochimica et Biophysica, Acta, 26,
294, 1957.
3) Buller, L., "A Suggested Approach to ATP Regeneration for Enzyme Tech-
nology Applications", Biotechnology and Bioengineering, 19, 591, 1977.
4) Fox, J. L., "Pyrophosphate Drives Biochemical Reaction", Chemical &
Engineering News, 22, April 25, 1977.
186 * U S GOVERNMENT PRINTING OFFICE 1980-657-165/0077
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U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604 ;
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