WATER POLLUTION CONTROL RESEARCH SERIES
17050 EJB 11/70
FULL-SCALE RAW WASTEWATER
FLOCCULATION WITH POLYMERS
U.S. ENVIRONMENTAL PROTECTION AGENCY
-------
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe
the results and progress in the control and abatement
of pollution in our Nation's waters. They provide a
central source of information on the research, develop-
ment, and demonstration activities in the Environmental
Protection Agency, through inhouse research and grants
and contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications
Branch (Water), Research Information Division, R&M,
Environmental Protection Agency, Washington, D. C. 20460.
-------
PULL-SCALE RAW WASTEWATER PLOCCULATION WITH POLYMERS
by
Paul V. Freese
Edward Hicks
Department of Sanitary Engineering
District of Columbia
Washington, D.C. 20004
for the
Office of Research and Monitoring
ENVIRONMENTAL PROTECTION AGENCY
Program #17050 EJB
Grant #WPRD 53-01-6?
November, 1970
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402- Price 60 cents
-------
EPA Review Notice
This report has been reviewed by the
Environmental Protection Agency and ap-
proved for publication. Approval does
not signify that the contents necessarily
reflect the views and policies of the
Environmental Protection Agency, nor does
mention of trade names or commercial
products constitute endorsement or recom-
mendation for use.
ii
-------
ABSTRACT
A21-M (90% anionic A21, 10% cationic C31) at an average dose of
0.74 mg/1 increased the removal of suspended solids from 50% to 63%
and BOD removal from 36% to 45% from the raw wastewater and recycled
thickener overflow in the primary settlers. With recycle of the
plant's elutriate into the primary settlers, 1.14 mg/1 of A21-M
increased the solids removal from 43% without polymer treatment to
64%. Cationic Reten 210 at a dose of 0.089 mg/1 did not improve
the sedimentation of solids or BOD removal from the raw wastewater
or recycled thickener overflow. With the recycle of solids in the
elutriate into the primary basins, a dose of 0.124 mg/1 of Reten 210
increased the solids removal from 43% to 51%. Addition of an
average of 0.294 mg/1 of anionic ST 269 with 2.54 mg/1 of clay
builder did not improve primary sedimentation of the wastewater or
recycled thickener overflow. During the last half of the elutriate
recycle test and with reduced ST 269 doses of 0.197 mg/1, the
primary sedimentation of solids increased from 387o without polymer
treatment to 54%, and indicated a probable polymer overdose in
the earlier portions of the ST 269 test.
Without elutriate recycle, improved primary sedimentation with
effective flocculation (A21-M treatment) decreased the waste activated
sludge production by 25%, increased the accumulated BOD removal
through secondary treatment from 73.6 to 78.3%, but did not increase
the accumulated solids removal. The polymers did not improve solids
capture in elutriation, and, with recycle of the elutriate to the
primary basins, the solids in the elutriate accumulated in the plant's
solids handling system. As in previous operations without polymer
treatment, the accumulating solids would have prevented continuous
recycle of the elutriate. Thus, without an independent solution to
the problem of pollutants in the plant's elutriate, polymer treatment
in the primaries was not practical for reducing the pollutants
discharged from the District of Columbia Water Pollution Control Plant.
This report was submitted in fulfillment of Grant No. WPRD 53-01-67,
Program No. 17050 EJB, between the Federal Water Quality Administration
and the District of Columbia, Department of Sanitary Engineering.
Key words:
raw wastewater flocculation
polymer treatment
primary sedimentation
111
-------
TABLE OF CONTENTS
Page No.
RECOMMENDATIONS 1
INTRODUCTION 3
PLAN OF OPERATION 5
Polymer Selection; Preparation, and Dosing
Analytical and Sampling Program
PRIMARY SETTLER PERFORMANCE 13
PRODUCTION OF PRIMARY AND WASTE ACTIVATED SLUDGE 23
PRIMARY-SECONDARY PLANT PERFORMANCE 2?
SOLIDS HANDLING 37
CHEMICAL COST ^5
CONCLUSIONS Vf
REFERENCES ^9
-------
List of Figures
Page
Figure 1: Schematic Flow Diagram of the District of Columbia
Water Pollution Control Plant Showing the Locations
of the Sampling Stations k
Figure 2: Quantity of Sludge Produced Using A21-M 38
Figure 3: Quantity of Sludge Produced Using Reten 210 39
Figure 4: Quantity of Sludge Produced Using ST 269 1*0
Figure 5: Quantity of Sludge Produced Using No Polymer ^1
VI
-------
List of Tables
Table 1
Table 2: Analytical Program
Table 3: Primary Settler Material Balance
Table 4: Suspended Solids and Primary Settling
Table 5: BOD and Primary Settling
Table 6: TOG and Primary Settling
Table 7: Total Phosphates and Primary Settling
Table 8: Total Nitrogen and Primary Settling
Table 9: Ratio of Primary to Secondary Sludge
Table 10: Plant Suspended Solids Removal
Table 11: Plant BOD Removal
Table 12: Plant TOG Removal
Table 13: Plant Phosphorus Removal
Table 14: Plant Nitrogen Removal
Table 15: Plant Solids Production
Table 16: Chemical Costs
Page
6
9
11
1A
15
16
IT
18
2k
28
29
30
31
32
^3
46
VI1
-------
RECOMMENDATIONS
Polymer treatment in the primary basins should not be adopted for
the District of Columbia plant because of problems in the recycling
of solids lost in elutriation and of hydraulic overload in the
plant's secondary settlers.
Polymer treatment should be re-evalutated at a small scale by
observing overall effects on the performance of a plant without
a problem with elutriate recycle.
Polymer treatment in the primary basins should be evaluated in a
plant which is overloaded with respect to pollutants but is not
overloaded hydraulically.
-------
INTRODUCTION
High molecular-weight organic polyelectrolytes (polymers) have
been used successfully to flocculate raw wastewater and to increase
the removal of pollutants from the wastewater during primary
sedimentation' '. At present, however, a satisfactory method for
predicting the effectiveness of a particular polymer for flocculating
solids in a specific wastewater is not available. In general,
laboratory and full-scale experimental studies are required to
evaluate the effectiveness of the flocculation and to determine
the optimum doses of the polymer.
Often the laboratory investigations conducted under controlled
environments are promising, but results are difficult to reproduce
in normal plant operation. Thus, a full-scale study of raw waste-
water flocculation with high molecular-weight organic polymers was
conducted at the District of Columbia Water Pollution Control Plant
(figure 1).
The District of Columbia Plant is a 240 mgd modified activated
sludge plant comprised of primary settling, two hour aeration, and
final clarification. The aeration tanks operate with 400-500 mg/1
of mixed liquor suspended solids and employ approximately 0.6 cubic
feet of air per gallon of wastewater. The sludge treatment system
includes thickening, digestion, elutriation, chemical conditioning,
and vacuum filtration. The overflows from the thickening processes
are recycled to the plant influent. Recycle of the elutriate,
produced by washing the digested sludge, has in the past overloaded
the Plant's solids handling system and prevented satisfactory
operation. Thus, the elutriate was normally discharged directly in-
to the Potomac River and contributed significantly to the total
load of pollutants discharged from the plant into the River.
The research objectives of the "Raw Wastewater Flocculation Study"
in the District of Columbia Water Pollution Control Plant were to:
(1) determine and optimize the improvement in solids capture
produced by polymer flocculation of solids in the primary
settlers,
(2) determine the effects of the polymer and of any increased
solids capture in the primary settlers on the operational
efficiency of all other processes in the plant,
(3) reduce the solids and BOD load to the aerators and permit
recycle of the elutriate to the plant influent,
(4) evaluate various polymers.
-------
Effluent
Sludge
Figure 1: Schematic Flow Diagram of the District of Columbia Water Pollution Control Plant
Showing the Locations of the Sampling Stations
-------
PLAN OF OPERATION
General
Since the plant hydraulics does not permit dual train operation,
of the primary tanks the general procedure for evaluating the
polymers on the full scale plant consisted of:
(1) determining plant "baseline" data before addition of
polymer,
(2) adding polymer to the inlet flows to the primary settlers
for a period of about 30 days with the plant operating
normally (i.e. elutriate and filtrate discharge to the
river) to acclimate the plant to the polymer,
(3) continuing polymer addition for a period of about 50 days
with elutriate and filtrate recycled to the plant influent,
(4) redetermining the "baseline" data between polymers to
remove the preceding polymer and to indicate seasonal
variations.
The baseline periods, periods of polymer addition for plant
acclimation, periods of polymer addition with elutriate recycle
for each of the various polymers, and the corresponding overflow
rates in the plant's settlers during these periods are summarized
in Table 1. The average overflow rates of 1626 to 1839 gallons
per day per square foot in the primary settlers and 972 to 1273
gallons per day per square foot in the final settlers were higher
than usually recommended by the Ten State Standards' ' and thus
stressed the sedimentation processes. The final period (XI) was
operated as a "baseline" in which the elutriate was recycled to
the plant influent without polymer treatment. In addition, a
summary of the plant operation on suspended solids for the year
preceding the polymer study was prepared. Several periods were
also divided into sub-periods a and b to reveal time related
changes in plant performance.
Polymer Selection, Preparation, and Dosing
Laboratory evaluations of the polyelectrolytes were performed to
measure their effectiveness in the District of Columbia wastewater
and to select the polymers for full-scale testing. All polymers
and polymer systems were evaluated using the manufacturers'
suggested methods of solution preparation, mixing, and addition
to the wastewater. Varying concentrations were used on raw
wastewater alone, raw wastewater with 57= thickener overflow, and
-------
TABLE 1
OVERFLOW RATES
gpd/ft2
Secondary
7
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI
Via
VIb
ST 269
+ CA-25
4/66-3/67 217
4/3-4/30/67 224.1 0.0
5/1-6/5 235.7 0.743
6/7-7/20 241.7 1.137
6/7-6/30 237.2 1.125
7/1-7/20 247.2 1.151
7/21-9/26 244.1 0.0
9/27-10/29 219.2 0.039
10/30-12/16 217.7 0.124
10/30-11/24 207.7 0.137
11/25-12/16 229.5 0.110
No 1626 1777 984 1122
No 1684 1942 1095 1262
Yes 1799 1957 1169 1272
Yes --
Yes
No 1822 2096 1173 1322
No 1644 1816 1018 11.46
Yes 1628 2092 972 1246
Yes -
Yes
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
12/17/67-
1/28/68
2/5-3/5
3/7-4/24
3/7-4/2
4/3-4/24
5/1-5/27
5/28-7/16
5/28-6/21
6/22-7/16
225.6
212.4
239.7
243.7
234.8
0.0
0.284
0.239
0.270
0.197
0.0
2.94
2.64
3.11
2.05
229.4
254.0
252.6 --
255.4 ---
No
No
Yes
Yes
Yes
1648
1569
1783
1975
1784
2209
983 1177
1023 1159
1273 1579
No 1666 1948 1141 1303
Yes 1839 2213 1110 1320
Yes
Yes -
-------
raw waste-water with 5% thickener overflow and 1% elutriation
overflow. The percentages of the added materials were selected
to correspond to average plant conditions.
In selecting a laboratory procedure for the evaluation of the
polymers, the hydraulic conditions in the District of Columbia
Plant suggested the selection of a rapid mixing ( 100 rpm) period
of one minute, four minutes for flocculation, and ninety minutes
for settling. However, in preliminary tests, settling times from
two to sixty minutes under dynamic mixing conditions (5-10 rmp)
in a conventional jar test apparatus indicated that a five minute
dynamic settling time was necessary to maximize the differential
laboratory settling rate between the polymer treated samples and
an untreated control. Longer settling times in the small laboratory
apparatus showed decreasing differences in solids removal with and
without polymer and prevented effective laboratory evaluation.
The final laboratory procedure used was:
1. Each polymer was prepared in accordance with the manufacturer's
directions. Usually a 17o stock solution was prepared and was
stable for at least a 2-week period. From the stock
solution a suitable working solution of 0.1, 0.05, or 0.01%
was prepared each day.
2. Liter samples of fresh raw wastewater were arranged in a jar
test apparatus with one sample as a control. Rapid mixing
( 100 rpm) of the samples was initiated before polymer
addition. Polymers were added at various concentrations.
After polymer addition, the system was rapidly mixed for
one minute.
3. Mixing was then slowed to a flocculation speed of 30 rpm and
flocculated for four minutes.
4. After flocculation, the mixing was slowed to 5-10 rpm for a
dynamic settling period, and settled for five minutes.
Samples were then removed with a large tip syringe for
analysis of suspended solids and TOG. Pertinent observations
such as size and type of floe, and of their settling
characteristics were recorded.
The three polymers selected from the laboratory studies for the
full-scale tests were Dow Chemical Company's A21-M, Hercules Inc.'s
Reten 210, and Calgon Inc.'s ST 269 with coagulant aid No. 25.
A21-M and ST 269, both basically anionic polymers, were effective
in the laboratory in increasing the rate of sedimentation of the
solids in the raw wastewater. Reten 210, a cationic polymer, was
effective on the solids in the elutriate.
-------
Each manufacturer was responsible for furnishing full-scale
equipment to feed his own polymer. The manufacturer, in
cooperation with the District, selected the feed points and the
dosages. Brief descriptions of each polymer and dosing system are:
Polymer A21-M
Polymer A21-M consists of a pre-mixed combination of PURIFLOC A-21
and PURIFLOC C-31 in an approximate 10;1 weight ratio of A-21 to
C-31. PURIFLOC A-21 is a granular anionic sodium polystyrene
sulfonate with molecular weight greater than five million. PURIFLOC
C-31 is a liquid cationic polyamine with a molecular weight greater
than 30,000.
The polymer mixture was prepared as a stock solution of 1.570
concentration based on total content of A-21 and C-31. The stock
solution of combined polymers was mixed in equipment specially
designed by Dow. The 1.5% concentrate was then pumped to an
eductor and further diluted with about 70 GPM of service water.
After studying several dosing points, the dosing location finally
selected was at the Plant's grit chamber elevators.
Polymer Reten 210
Reten 210 is a powdered, strongly-cationic, high-molecular weight,
synthetic polymer. It was prepared as a 0.5% solution using an
automated feeder-mixing system developed for the trial by Hercules.
The 0.5% solution was further diluted with from 5 to 10 parts of
dilution water prior to introduction into the wastewater. The
point of application was varied several times during the course
of the trial. Multiple individual dosing locations at the inlet
to each primary basin were finally selected.
Polymer ST 269 and Coagulant Aid No. 25
Sludge Conditioner ST 269 is an anionic hydrolyzed polyacrylamide
with a molecular weight in excess of two million. Coagulant
Aid No. 25 is a clay-base inorganic material of the montmorillonite
class. In the test, the chemicals were fed from two dry feeders
into mixing tanks, and were added as pre-mixed and separate
solutions. The pre-mixed or separate solutions were introduced to
the effluent leaving the grit chamber.
Analytical and Sampling Program
The analytical program established to compare the plant's
operation before and during polymer addition (table 2) employed
procedures from Standard liethods' ' except for TOG (total organic
carbon) and total phosphate analyses. The TOG analysis included
-------
TABLE 2
ANALYTICAL PROGRAM
Sample Location
Analyses
Station 1
Station 2
Station 5,
17, 20
Station 11
Station 14,
14
Station 16
Raw Wastewater
Primary Effluent
Secondary Effluent
Thickener Overflow
Elutriate
Filtrate
SS, BOD, TOG, P, NH3, TKN,
TS, TVS
Station 7
Station 8
Station 12
Station 13
Station 15
Waste Secondary
Raw Primary Sludge
Thickened Sludge
Digested Sludge
Elutriated Sludge
TS, TVS, TOG, P; TKN
Station 18 Filtercake
Tons wet cake, 70 moisture
Notes
1. Sample stations are shown on figure 1.
2. All samples are 24-hour composites proportioned to flow.
Key:
BOD 5-day Biochemical Oxygen Demand, mg/1
NH Ammonia Nitrogen, mg/1 as N
P Total Phosphorus as P04, mg/1
SS Suspended Solids mg/1
TKN Total Xjeldahl Nitrogen, mg/1
TOG Total Organic Carbon, mg/1
TS Total Solids, mg 1
TVS Total Volatile Solids, mg/1
-------
acidification, blending, and nitrogen stripping before organic
carbon determination with a Beckman Carbonaceous Analyzer^5'
The total phosphate method^ ' used the digestion of the sample with
sulfuric acid-potassium persulfate before phosphate analysis.
The various sampling points in the plant are indicated in Figure 1.
Initially, twenty-four hour samples of the raw wastewater (point 1),
primary effluent (point 2), and secondary effluent (point 5) were
automatically proportioned to flow and composited by the plant's
Chicago Pump Automatic Samplers. All other twenty-four hour
composite samples were collected manually, usually at 30 minute
intervals, and were manually composited pro-rated to flow.
Material balances were computed around the primary settlers (table 3)
for suspended solids, total organic carbon (TOG), total phosphate,
and total Kejdhal nitrogen (TKN) to verify flow measurement,
analytical, and sampling techniques. BOD balances could not be
computed since the BOD of the underflow (primary sludge) was not
measurable. The computations on the first two months of data
(periods I and II) revealed negative unbalances of approximately
35% for suspended solids and 20% for TOC. The computations for
total phosphates and TKN, which in the District of Columbia raw
wastewater were mainly soluble components, produced satisfactory
balances within 9%. Subsequent review of the previous year's
suspending solids analyses also revealed the same unbalance and
indicated more solids leaving the settlers than entering. Discussions
with District of Columbia plant personnel concerning gas production
and solids handling confirmed that more solids were entering the
plant than were being measured.
Laboratory grab samples, composited manually over twenty-four
hours on raw wastewater, revealed raw wastewater suspended solids
nearly double that in the samples from the automatic sampler. In
contrast, laboratory grab samples on the primary and secondary
effluents (point 2 and 5) showed that the automatic samples at these
points were operating satisfactorily. Thus, a flow proportioned
grab sampling schedule on the raw wastewater was added to the
overall analytical program to eliminate the incorrect automatic
sampling of the raw wastewater.
With the grab sample schedule on the raw wastewater, material
balances on suspended solids and TOC based on the grab samples
of the raw wastewater were usually within 10% for any period and
averaged 1.97. and 6.5% respectively for the entire test period.
Material balances for the phosphates and TKN average 0.6% and 6.0%
respectively. These balances support the flow measurement,
analytical, and sampling techniques. For the first two months of
the test (periods I and II) and for all plant data before the test,
the amounts of suspended solids, TOC, total phosphate, and TKN in
10
-------
PERIOD
St 269 + CA-25
VII
VIII
IX
No Polymer
X
XI
TABLE 3
PRIMARY SETTLER MATERIAL BALANCE
SS
-7.1
-10.3
I DIFFERENCE
TOG PQ/.
0
13,2
-7.1
12.6
9.7
2.8
8.0
14.7
10 % Difference =
2. Automatic Samples
Input - Output
Input
0.4
(100)
TKN
4/66-3 '67
A21-M
I
II
III
Reten 210
IV
V
VI
-39.9^
-33. 52
-38. 52
-41. 32
2.0
-4.9
-0.7
2.7
>
-19. 92
-29 .42
-17. O2
2.9
4.7
-6.8
7.0
0.72
-8.42
-2.42
4.7
4.1
-2.7
-7.0
-2.32
0.82
3.72
5.2
11
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the raw wastewater were calculated by material balance from the
recycle, underflow, and overflow measurements on the primary
settlers.
Since the BOD of the underflow (primary sludge) could not be
determined satisfactorily, the amounts of BOD in the raw wastewater
could not be calculated and the BOD content for periods I and II had
to be estimated by multiplying the BOD concentration obtained from
the automatic raw wastewater sampler by 1.22, which was the average
ratio of BOD in the grab samples to the BOD in corresponding
automatic samples from 9 months of data. The results from the
periods III-XI are based completely upon measured values.
12
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PRIMARY SETTLER PERFORMANCE
The performance of the plant's primary settlers in removing
pollutants, especially suspended solids, from the raw wastewater
and the recycled streams entering the settlers is the most important
factor in evaluating polymer induced flocculation and settling. In
the polymer tests, the recycled streams included thickener overflow
alone, and thickener overflow and elutriate. Thus, the performance
of the settler was best characterized by the percent removal of a
pollutant based upon the total amount of the pollutant in the
influent to the settlers (raw wastewater and recycle). The con-
ventional removal efficiencies based upon the amount of pollutant in
the raw wastewater and the amounts of the pollutants in the primary
effluent are presented in the tabulated results (tables 4-8).
Before discussing polymer treatment, the baseline settler performance
with and without elutriate recycled must be reviewed. For the year
preceding the polymer study, the primary settlers removed an average
of 47.87 of the suspended solids based upon the total influent
(thickener overflow solids and raw solids) to the settlers. During
the baseline periods (I, IV, VII, and X) without elutriate recycle,
the solids removals by the settlers varied between 46.7% and 52.47o
of the solids in the total influent (table 4). The average removals
of BOD by the primary settlers from the total influent during the
same baseline operations (periods I, IV, VII, and X) varied from
23.97 to 36.07,; the average removals of TOG, from 39.47, to 45.57,;
the average removals of total phosphorus, from 7.77, to 11.37,; and
the average removal of TKN for period I (TKN measurements were
discontinued at the end of period III), 11.57, (tables 5, 6, 7, and 8).
In the baseline elutriate recycle without polymers (period XI), the
recycled elutriate added digested solids to the recycled solids and
increased the solids loading on the settlers to an average of 299
tons per day compared to the normal 202-233 tons per day for
baseline operation without elutriate recycle. During the addition
of the digested solids, the 43.27, removal of the total influent
solids in primary settlers represented a decrease of approximately
187, in the 52.47, removal of the preceding baseline without elutriate
recycle (period X). The solids in the recycled elutriate caused the
solids in the primary effluent to increase from the normal 102-116
tons per day without elutriate recycle to an average of 169.9 tons
per day.
Both the primary effluent quality and the solids removal percentages,
as shown by sub-periods XIa and Xlb in Table 4, progressively
deteriorated as the elutriate recycle proceeded. For the last half
of the recycle baseline (period Xlb), the primary effluent contained
an average of 184.3 tons per day of solids, and the settlers removed
13
-------
TABLE 4 SUSPENDED SOLIDS AND PRIMARY SETTLING
/ SUSPENDED SOLIDS - TONS/DAY /7. REMOVAL /
°>
4/66-3/67
A21-M
I
II
III
Ilia
Illb
Reten_210
IV
V
VI
Via
VIb
ST 269 + CA-25
177. 4
25.8
97.2
106.0 47.8 40.2
0
0.743
1.137
1.125
1.151
177 X
199.0
214.3
214.5
213.8
25.4
23.1
74. 15
63. 55
86. 35
101.3
140.2
178.0
161.5
197.5
101.9
81.9
104.7
103.9
105.6
49.9
63.1
63.9
62.6
64.8
42.7
58.8
51.1
51.6
50.6
0
0.089
0.124
0.137
0.110
189.0
191.4
178.9
177.4
179.7
28.0
32.9
8 7. 15
71. 95
306.35
112.0
106.7
129.2
124.2
135.2
115.7
119.2
129.7
120.4
141.1
46.7
46.9
51.2
51.7
50.7
38.8
37.7
27.5
32.1
21.5
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
0.294
0.239
0.27
0.197
_ ._
_ _ ~
186.0
179.4
192 . 2
139.1
195.8
200.7
200.4
209.4
191.2
40.2
39.6
111.85
89. 35
143. 75
33.0 '
98. 95
90.. 95
107. I5
118.0
89.6
168.3
143.9
197.2
139.2
160.2
160.5
159.9
108.6
100.4
157.2
159.4
154.6
111.2
169.9
155.1
184.?
52.0
54.2
48.3
42.7
54.5
52.4
43.2
48.4
38.2
41.6
44.0
18.2
15.7
21.0
44.6
15.2
25.9
3.6
= Mn or Mdi + 14 + 16)
2. % Removal = (Ml + MRE - M2)
( M{"+ Hm )
3. % Removal = (Ml - M2)
( MI ) (100)
4. Calculated Mj_ = M2 + MS - M
5. Elutriate Recycled
(100)
-------
TABLE 5 BOD AND PRIMARY SETTLING
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI
Via
VIb
ST 269 + CA-25
VII
VIII
IX
IXa
1Kb
No Polymer
X
XI
XIa
Xlb
Footnotes:
0
0.743
1.137
1.125
1.151
151.57
153.3
153.3
153.2
153.4
23.3
21.6
32. 85
35. 45
29. 45
0
0.089
0.124
0.137
0.110
148.7
150.5
143.7
148.2
137.0
20.6
27.3
47.9^
47.9^
48. 05
0
0.294
0.239
0.270
0.197
151.5
149.9
184.9
153.8
221.5
156.3
149.8
153.6
145.8
34.0
31.1
52.3^
49.85
56.15
2909
42.95
39.15
47.15
or M
(ii + 14 + 16)
2. 7o Removal = (Ml + MRE - M2) (100)
+
112.0
96.6
110.4
108.9
112.0
128.9
131.6
129.2
128.5
129.4
120.3
120.0
121.7
118.3
36.0
44.8
40.6
42.3
38.7
23.9
26.0
32.6
34.5
30.1
35.4
37.7
36.9
38.7
26.1
37.0
28.0
28.9
27.0
13.3
12.6
10.1
13.3
5.6
124.2
120.6
138.2
137.4
139.0
33.1
33.4
41.8
32.5
49.9
18.0
'19.5
25.3
10.7
37.2
23.0
19.9
20.8
18.9
3. % Removal = (Ml - M2) (100)
4. Estimated Grab =1.22 Auto M]_
5. Elutriate Recycled
6. BOD of Underflow not used.
-------
TABLE 6 TOC AND PRIMARY SETTLING
TOC IN TONS /DAY
/ 7. REMOVAL /
A21-M
I
II
III
Ilia
Illb
0.
1.
1.
1.
0
743
137
125
151
94.
105.
85.
87.
83.
7?
34
7
3
7
13
11
29
31
26
.3
.5^
.2\
.6
.4
42
59
49
57
38
.5
.0
.2
.8
.9
65.5
57.8
62.4
66.5
57.4
39.4
50.5
45.7
44.0
47.9
30.8
45.1
27.2
23.8
31.4
0 88.9
0.089 109.7
0.124 107.2
0.137 105.1
0.110 109.3
0 98.4
0.294 100.1
0.239 107.3
0.270 105.3
0.197 110.7
Reten 210
IV
V
VI
Via
VIb
St 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
XI b
Footnotes:
1. MRE = Mll or M(ll + 14 + 16)
2. 7. Removal = (Ml + MRE - M2) (100)
3. 7. Removal = (Ml - M2) (100)
4. Calculated MI = M2 + Mg - MRF
5. Elutruate Recycled
23.5
22.7
35. 55
32.9
38. 65
40.4
68.4
54.0
58.5
48.7
66.7
73.0
78.7
75.5
82.6
40.7
44.9
44.9
45.3
44.2
25.0
33.5
26.6
28.2
24.4
21.1
19.6
39. 15
33. 65
46. 65
39.2
42.2
52.8
44.0
63.5
65.2
65.9
90.0
88.8
91.5
45.5
44.9
38.7
36.1
41.9
33.7
34.2
16.5
15.7
17.3
108.4
107.0
113.5
99.9
18.4
32.3^
30. 65
34. 25
42.6
37.6
35.9
39.2
74.0
81.2
79.3
83.1
41.6
41.7
45.0
38.0
31.7
24.1
30.2
16.8
16
-------
TABLE 7 TOTAL PHOSPHATES AND PRIMARY SETTLING
TOTAL P04 - TONS/DAY
/
7» REMOVAI
7
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI
Via
VIb
ST 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
Footnotes:
0,
1,
1
1
0
0
0
0
0
0
0
0
0
.743
.137
.125
.151
0
.089
.124
.137
.110
0
.294
.239
.270
.197
_-.-
_ « «
24. 84
28. 64
26.9
26.5
27.3
25.2
25.7
25.0
25.2
24.5
24.7
26.3
27.2
26.8
27.6
26.9
26.2
26.8
25.6
3.
3.
7.
7.
7.
4.
3.
7.
7.
8.
3.
4.
9.
8.
12.
4,
8.
7,
5
2,
3^
55
O5
1
9
85
l5
85
8
5
1\
^
,05
.1
4**
_
.9?
2
ij
4
4
4
2
2
4
4
5
2
-
-
.4
.3
.5
.2
.9
.1
.8
.7
.2
.3
.3
__
,_-
--
._=-
8.9^
25.9
26.5
28.1
28.3
27.8
26.0
27.6
30.4
30.0
30.6
26.1
27.9
33.2
32.7
33.8
28 06
31.8
31.0
32.5
8.5
16.7
17.9
17.0
19.0
11.3
6.8
7.3
7.1
8.1
8.6
9.3
9.9
6.2
14.4
7.7
8.1
10o5
5.7
-4.
+7.
-14.
-15.
-13.
-3.
-7.
-21.
-19.
-24.
-5.
-6.
-22.
2
3
5
5
0
2
4
6
0
9
7
1
1
-22.0
-22.5
/- o
-0.3
-21.4
-15.7
-27.0
1. MRE = Mll or M (11 + 14 + 16)
2. % Removal = (Ml + MRE - M2) (100)
3.
Removal =
(100)
4. Calculated ₯LI = M£ +
5. Elutriate Recycled
17
-------
TABLE 8 TOTAL NITROGEN AND PRIMARY SETTLING
/ TOTAL NITROGEN - TONS/DAY / 7, REMOVAL /
A21-M
I
II
III
Ilia
Illb
0
0.743
1 . 137
1.125
1.151
24. 9*
23. 14
23.8
23.3
24.3
3.8
3.3
9.25
9.65
8.85
3.3
4.3
5.3
5.1
5.5
25.4
22.1
25.7
26.3
25.1
11.5
16.3
22.0
20.2
24.3
-2.0
44.3
-8.0
-12.9
-3.2
Footnotes:
1. MRE = Mll or M(ll + 14 + 16)
2. 7. Removal = (Ml + MRE - M2) (100)
3.
4.
5.
% Removal = (Ml - M2) (100)
( MI )
Calculated MI = M2 + Mg -
Elutriate Recycled
18
-------
only 38.2% of the total solids entering the settlers. In the past
operation of the plant, this progressive deterioration in the
removals of suspended solids by the primary settlers and the
progressive increase in recycled solids when the elutriate was
returned to the plant influent eventually forced the discharge
of the elutriate into the river.
The amounts of BOD, TOG, and total phosphate in the elutriate
compared to the amounts in the raw wastewater were lower relative
to the same comparison for solids. Recycle of the elutriate with-
out polymer addition did not significantly alter the settler removal
efficiencies for these pollutants (periods X and XI; tables 5, 6,
and 7), but did increase the amounts of these pollutants entering
and leaving the primary settlers.
Since each polymer test was divided into two periods, polymer
treatment with the elutriate discharged into the river and polymer
treatment with the elutriate recycled to the plant, the effects
of each polymer on the different solids in primary settlers for
these two operating variations were considered separately. With
the elutriate discharged into the river the addition of the first
polymer, A21-M, at an average dose of 0.743 mg/1 increased the
average solids capture of the combined raw and thickener overflow
solids from the preceding baseline removal (period I) of 49.9% by
26% to 63.1% removal of the solids in the total influent (table 4).
The actual solids in the primary effluent correspondingly decreased
during the A21-M treatment by approximately 20% from over 100 tons
per day to 81.9 tons per day.
For the same periods, the average BOD removal efficiency with
A21-M addition increased by 24% from a baseline of 36% to 44.8%
removal, and the average BOD in the primary effluent decreased
by 14% from 112 tons per day to 96.6 tons per day (table 5).
Similarly the TOC removal efficiency increased by 28% from a
baseline 39.4% to 50.5% (table 6). The total phosphate removal
efficiency increased from a baseline 8.5% to 16.7% (table 7);
and the total nitrogen removal, from 11.5% to 16.3% (table 8).
The average overflow rate in the primary settlers (table 1) during
the baseline (period I) was 3.5% lower than during A21-M treatment
(period II). This small increase in overflow rate during polymer
treatment should, if any effect occurred, decrease the settler
performance when compared to baseline. The above primary settler
performance, during A21-M treatment with the elutriate discharged in-
to the river, not only exceeded the settler performance during
the preceding baseline, but was also markedly superior to all base-
line performances. Thus A21-M was an efficient flocculant of the
raw solids and the solids in the thickener overflow.
After approximately 30 days of A21-M treatment, the elutriate was
recycled to the influent of the primary settlers. The digested
19
-------
solids in the elutriate increased the solids in the recycle streams
from about 25 tons per day to an average of 74 tons per day. The
average solids loading (period III) to the primary settlers of
288 tons per day represented a 42% increase in solids compared to
the preceding baseline (period I), and was similar to the 299 tons
per day of solids in the influent to the primary settlers during
elutriate recycle without polymer treatment. The 63.9% capture of
solids, however, with similar solids loading represented a 48%
improvement over the 43.2% capture during elutriate recycle without
polymer treatment (period XI). The removal percentage was essentially
the same as that achieved during A21-M treatment without elutriate re-
cycle (period II).
The solids in the elutriate entering the primary settlers increased
the average required dose of A21-M from 0.743 mg/1 without elutriate
recycle to 1.137 mg/1. The additional loading to the settlers also
increased the solids in the primary effluent to 104.7 tons per day
compared to the 81.9 tons per day for A21-M treatment without
elutriate recycle. The primary effluent with 104.7 tons per day of
solids had approximately the same solids content as the primary effluent
without elutriate recycle and without polymer treatment, and contained
65.2 fewer tons of solids than the effluent during the baseline elutriate
recycle. While the solids in the primary effluent did not increase as
elutriate recycle continued, the amount of solids in the recycle stream
to the settlers gradually increased. This increase in solids in the
recycle stream represented an unstable plant operation.
Recycle of the elutriate in period III reduced the removal efficien-
cies of BOD and TOC (tables 5 and 6) compared to A21-M treatment without
elutriate recycle, but maintained or improved the removal efficiencies
and the primary effluent quality compared to the baseline (period I).
The total phosphorus and TKN removals in the settlers (tables 7 and 8)
actually increased with elutriate recycle and A21-M treatment to 18
and 22% respectively. Thus, A21-M was an effective flocculant to all
solids entering the plant's primary settlers and either maintained or
improved the primary effluent quality for all pollutants during the
entire A21-M test.
In the Reten 210 test without elutriate recycle (period V), the solids
capture of 46.9% (table 4) with an average dose of 0.089 mg/1 of
Reten 210 remained unchanged compared to the 46.7% capture of the
preceding baseline. The average removals of BOD and TOC slightly
exceeded the removals of the preceding baseline (tables 5 and 6),
but the increases were marginal as they did not exceed the average
removals occurring in the most efficient baseline period. The
removals of phosphates (table 7; period V) actually decreased com-
pared to the baseline removal (period IV).
The overflow rate (table 1) in the primary settlers during Reten 210
addition (period V) was approximately 10% lower than the baseline
20
-------
(period IV). When compared to the baseline, this lower overflow rate
during polymer treatment should have improved settler performance
during polymer treatment. 'However, for operation without elutriate
recycle, Reten 210 did not improve the capture of the raw and
thickener recycle solids in the primary settlers, and did not improve
the overall performance of the settlers.
With the recycle of the elutriate, the solids removal of 51.2% during
an average Reten 210 dose of .124 mg/1 represented a 19% improvement
over the 43.4% removal for baseline elutriate recycle, but the
solids in the primary effluent increased from 120.4 tons per day for
the first half of elutriate recycle test (period Via) to 141.1 tons
per day for the second half (period VIb). Thus, although the solids
capture increased and the solids in the primary effluent were less
than those of the baseline elutriate recycle (period XI), Reten 210
did not prevent a gradual increase in the solids content of the
primary effluent. In addition, the removals of BOD, TOG, and total
phosphorus during elutriate recycle with Reten 210 addition (tables 5,
6, and 7; period VI) were not significantly different from those
during elutriate recycle without polymer treatment. Hence, although
Reten 210 produced some improvement in solids capture during elutriate
recycle, the polymer, as applied, was not generally an effective
flocculant in the District of Columbia primary settlers and with
recycle of the elutriate did not prevent gradual deterioration in
the primary effluent.
In the ST 269 test, an average of 0.294 mg/1 of ST 269 and 2.94 mg/1
of clay builder did not produce significant changes in the primary
settler performance with the elutriate discharged into the river. The
average overflow rate (table 1) in the primary settlers during ST 269
addition (period VIII) was 4.8% lower than the preceding baseline
(period VII) and should have slightly improved settler performance.
The solids capture (table 4) marginally increased from 52.0% to
54.2%; BOD, TOG, and total phosphate removals (tables 5, 6, and 7)
remained essentially unchanged at 33%, 45%, and 970, respectively.
The recycle of the elutriate immediately increased the solids in the
primary effluent from an approximately 100 tons per day to 157 tons
per day. In fact, in the first portion of elutriate recycle with
ST 269 addition (period IX), the solids capture of 42.7% was less than
that during the elutriate recycle baseline (period XI). However,
in spite of a solids loading which increased from 27804 tons per
day in period IXa to 339.5 tons per day in period IXb, the overall
solids capture increased during the last half of the test (period IXb)
to 54.57= and indicated a significant reversal in polymer performance.
The 54.5% overall solids capture at the highest solids loading
rate encountered with or without polymers in the entire Study repre-
sented 44% improvement over the 38.2% capture for the corresponding
elutriate recycle without polymer addition (period Xlb). Indeed,
the solids in the primary effluent actually decreased in period IXb
21
-------
compared to period IXa even though the solids entering the settlers
increased.
The pin point floe produced by ST 269 was difficult to capture in
the settlers, especially early in the test. The reduction in the
average polymer dose from 0.270 mg/1 of ST 269 and 3.11 mg'1 of
clay to 0.197 mg/1 of ST 269 and 2.05 mg/1 of clay along with the
increased solids loading apparently improved the solids capture in
the settlers, and indicated initial improper dosing with ST 269.
Similarly, ST 269 with its clay builder did not initially produce
improvements in removals of BOD, TOC, or total phosphate (table 5,
6, and 7) during the first half of elutriate recycle (period IXa).
The removals actually decreased compared to those of the elutriate
recycle baseline (period XIa). In the last half of elutriate
recycle (period IXb), however, the average overall BOD removal
(table 5) increased to 49.9%; the overall total phosphate removal
(table 7) increased to 14.4700 Both removals sharply exceeded those
of the elutriate recycle baseline. In the same period (IXb), the
overall TOC removals of 41.9% (table 6) slightly exceeded that of
the elutriate recycle baseline (period Xlb).
The very high removals of BOD occurred with an unusually high BOD
content of 221.5 tons per day in the raw wastewater compared to the
normal 150-180 tons per day. The phosphate content in the recycle
to the primary settlers was also unusually high averaging 12.0 tons
per day compared to 8-9 tons per day normally occurring during
elutriate recycle. Thus the wastewater and plant operation during
period IXb was not typical of the District of Columbia Plant, and its
uncertainty in the test prevented clear evaluation of ST 269 in the
primary settlers.
22
-------
PRODUCTION OF PRIMARY AND WASTE ACTIVATED SLUDGE
The primary sludge and the secondary sludge in the District of
Columbia Plant are combined, thickened, digested, elutriated, and
finally dewatered by vacuum filtration. The ratio of the amounts
of primary to waste activated sludge in the combined sludges must
increase sharply with efficient polymer flocculation because the
ratio reflects changes in the relative amounts of primary and
waste activated sludge.
For baseline operation (periods I, IV; VII, and X), the average
ratios of primary to waste activated sludge (table 9) varied between
1.48 and 1.91. During elutriate recycle without polymer addition
(period XI), the ratio averaged 1.43 and indicated that significant
portions of the digested solids recycled in the elutriate were
recaptured in the plant's final settlers rather than in the primary
settlers. In fact, during elutriate recycle without polymer addition,
the primary sludge (table 9) actually increased by only 21 tons per
day over that of the preceding baseline (period X), while the waste
activated sludge increased by 39 tons per day.
In the A21-M test, the ratio of primary to waste activated sludge
increased to 2.74 without elutriate recycle (period II) and to 2.88
with elutriate recycle (period III). During polymer treatment with-
out elutriate recycle, the waste activated sludge production with
A21-M treatment decreased by 25% from a baseline average of 68.5
tons per day to only 51.1 tons per day. Even with the digested
solids and BOD recycled in the elutriate, the waste activated sludge
averaged only 61.7 tons per day for A21-M treatment.
The waste activated sludge production in the last half of the
elutriate recycle (period Illb) averaged only 55.8 tons per day
compared to a baseline of 117.9 tons per day in period Xlb. The
ratio of primary to waste activated sludge in the period Illb
increased to 3.54, compared to the baseline 1.36 even with the increas-
ing amounts of digested solids in the elutriate recycled to the primary
settlers. These results clearly confirmed the improved performance
of the primary settlers during A21-M treatment.
In the Reten 210 test, the ratio of primary to waste activated
sludge (table 9) of 1.55 without elutriate recycle (period V) and
1.38 with elutriate recycle (period VI) were slightly lower than
the corresponding baseline ratios, and thus confirmed the lack of
improvement in the performance of the primary settlers during Reten
210 treatment.
23
-------
TABLE 9 RATIO OF PRIMARY TO SECONDARY SLUDGE
PERIOD
TOTAL SOLIDS (TONS/DAY)
Primary
Secondary
Combined
RATIO
Primary
Secondary
4/66-3/67
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI
Via
VIb
ST 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XI a
XI b
97.2
101.3
140.2
178.0
161.5
197.5
112.0
106.7
129.2
124.2
135.2
118.0
89.6
168.3
143.9
197.2
139.2
160.2
160.5
159.9
84.1
68.5
51.1
61.7
65.3
55.8
60.8
69.0
93.9
81.8
108.9
78.1
69.9
141.5
160.0
119.0
72.8
111.9
105.2
117.9
181.3
1.16
169.8
191.3
239.7
226.8
253.3
1.48
2.74
2.88
2.47
3.54
172.8
175.7
223.1
206.0
244.1
1.84
1.55
1.38
1.52
1.24
196.1
159.5
309.8
303.9
316.2
212.0
272.1
265.7
277.8
1.51
1.28
1.19
0.90
1.66
1.91
1.43
1.53
1.36
-------
In the ST 269 test, during the period of polymer addition without
elutriate recycle (period VIII) the average overflow rate in the
primary settlers decreased 4.8% and in the secondary settlers
increased 4.4% from the baseline period VII; the suspended solids
concentration in the primary influent during this period increased
less than 1% from the baseline. However, contrary to these favorable
conditions for improved primary performance relative to secondary,
the ratio of primary to waste activated sludge decreased from 1.51
to 1.28. This decrease in ratio indicated that the 0.294 mg/1
dosage of polymer had actually dispersed the solids while in the
primary settlers. Indeed, the change from a very low ratio of
0.90 during the first half of the elutriate recycle (period IXa)
to a ratio 1.66 in last half (period IXb) and the decrease in pro-
duction of waste activated sludge from 160 to 119 tons per day in
the same intervals occurred with increasing amounts of recycled
digested solids and with decreased polymer dosage. This sudden
increase in ratio of primary to waste activated sludge strongly
supported the suspected polymer overdoses during the initial portions
of ST 269 test.
-------
PRIMARY-SECONDARY PLANT PERFORMANCE
In the District of Columbia Plant, the plant pollutant removal
efficiencies and the pollutants discharged into the river varied not
only with the pollutants in the secondary effluent, but also with
those in the elutriate when it was discharged directly into the
river. In addition, the pollutants in the elutriate fluctuated
widely and independently of primary and secondary treatment.
Suspended solids in the elutriate especially were a significant
portion of the solids entering the river. As examples, for the
year preceding the polymer study, the solids discharged into the
river (table 10) averaged 55.9 tons per day of which 27.1 tons
per day or 48.5% of the total was in the elutriate. In the baseline
periods (I, IV, VII, and X), the solids in the elutriate varied
from 11.4 to 31.2 tons per day and averaged 39.7% of the solids
discharged into the river. The overall solids removals for the same
periods with the solids in the elutriate included in the calculation
varied from 65.6 to 75.9%. In contrast, the solids removal effi-
ciencies for primary-secondary treatment, excluding the effect of
the elutriate, exhibited only a 2% variation from 80.3 to 82.3% for
the four baseline periods, and thus revealed the marked variability
produced in overall plant solids removal efficiency by the solids in
the elutriate. In fact, if the elutriate could have been continuously
recycled without loss of primary-secondary treatment efficiency, the
80% efficiency in primary-secondary treatment would have represented
an 8 to 24% improvement in overall plant solids removal during the
baseline periods.
The elutriate did not produce as marked variability in the plant
removals of BOD, TOC, total phosphorus and TKN. The overall BOD
removal efficiencies (table 11) for the baseline with the elutriate
included in the calculation varied from 68.1 to 69.7%; TOC removals
(table 12), from 48.4 to 63.3%; and the total phosphorus removals
(table 13), from 4.4 to 8.9%. The overall TKN removal (table 14)
for the first baseline (period I) was 6.4%. Plant BOD removal
efficiencies based only upon the amounts of BOD in the secondary
effluent varied from 73.6 to 75.4%; TOC removal efficiencies, from
64 to 70.5%; and total phosphorus removal efficiencies, from 12.3 to
19.0%. Plant TKN removal efficiency based upon the secondary
effluent was 20.9% for the first baseline. Nevertheless, the amounts
of BOD, TOC and total phosphorus in the elutriate during the four
baseline periods average 17, 24.2, and 11.4% respectively, of their
totals entering the river. Thus, elimination of the discharge of the
elutriate by recycling it to the plant influent without decreases
in secondary effluent quality, would have represented significant
improvements in removal of all pollutants.
27
-------
TABLE 10 PLANT SUSPENDED SOLIDS REMOVAL
VERAGE SUSPENDED SOLIDS IN
TONS /DAY
/% REMOVAL /
4/66-3/67
A21-M
I
II
III
Ilia
Illb
Re ten 210
IV
V
VI
Via
VIb
0
0
0.743
1.137
1.125
1.151
0
0.089
0.124
0.137
0.110
177. 45
c
177. 8D
199. O5
214.3
214.5
213.8
189.0
191.4
178.9
177 A
179.7
28.8
31.4
32.4
37.7
40.7
34.2
37.2
42.8
42.9
44.4
40.7
27.1
11.4
13.8
52. 46
50. 06
55. 66
28.7
26.1
39. 36
26. 26
56. 06
55.9
42.8
46.3
37.7
40.7
34.2
66.1
69.3
42.9
44.4
40.7
83.8
82.3
83.7
82.5
81.0
84.0
80.3
77.6
76.0
75.0
77 .4
68.5
75.9
76.7
82.5
81.0
84.0
65.0
63.8
76.0
75.0
77.4
ST 269 -1- CA-25
VII
VIII
IX
IXa
IXb
0.
0.
0.
0.
0
294
239
270
197
186.0
179.4
192.2
139.1
195.8
33.2
38.1
39.9
40.1
39.6
25
19
62
41
92
.3
.7
2<
.26
.6^
58
57
39
40
39
.6
.9
.9
.1
.6
82
78
79
78
79
.2
.8
.2
.8
.8
68.5
67.7
79.2
78.8
79.8
No Polymer
X
XI
XIa
Xlb
Footnotes:
200.7
200.4
209.4
191.2
37.8
44.8
46.5
43.1
31.2
52.76
46. 66
59. 16
69.1
44.8
46.5
43.1
81.2
77.6
77.8
77.5
65.6
77.6
77.8
77.5
M5 - M17 - M20 (Figure 1)
2. MR=M
3. J, Removal =
+ M + M (no elutriate recycle)
-J* 14 16
(100)
4. 7. Removal = M1 - M_ (100)
5. Calculated Mj (Tabl-3 4)
6. Elutriate Recycled
28
-------
TABLE 11 PLANT BOD REMOVAL
Z/A, / AVERAGE BOD IN TONS /DAY
/ 'y
/ 7« REMOVAL /
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI
Via
VIb
ST 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
Footnotes:
0
0.743
1.137
1.125
1.151
0
0.089
0.124
0.137
0.110
0
0.294
0.239
0.270
0.197
__-
___
151.5^
153. 35
153.3
153.2
153.4
148^7
150.5
143.7
148.2
137.0
151.5
149.9
184.9
153.8
221.5
156.3
149.8
153.6
145.8
40.1
33.2
35.9
36.9
34.7
38.7
48.7
44.7
44.5
44.7
37.2
44.7
48.9
48.6
49.3
39.6
41.7
44.3
39.1
5.7
6.6
ll.S^
12 a6
10. 16
7.4
12.1
10.96
9.36
12.96
10.5
6.8
13. 26
8.36
19. 56
8.4
12.96
10. 65
15. 56
45.8
39.8
35.9
36.9
34.7
46.2
61.0
44.7
44.5
44.7
47.8
51.5
48.9
48.6
49.3
48.1
41.7
44.3
39.1
73.6
78.3
76.6
75.9
77.4
74.0
67.6
68.9
70.0
67.4
75.4
70.2
73.6
68.4
77.7
74.7
72.2
71.2
73.2
69.7
74.0
76.6
75.9
77.4
68.9
59.5
68.9
70.0
67.4
68.1
65.6
73.6
68.4
77.7
69.2
72.2
71.2
73.2
1. M5* = M5- - M17 - M2Q
2. M_ = M5^ + M14 -t- M16 (No elutriate recycle)
3.
Removal =
- M (100)
4. % Removal = M.J_ - MR
-
5. Estiroated Grab M-^ = 1.22 Auto
6. Elutriate Recycled
29
-------
TABLE 12 PLANT TOG REMOVAL
Zf ^ / AVERAGE TOG IN TONS /'DAY
/ 7. REMOVAL /
'
A21-M
I
II
III
Ilia
I lib
Reten 210
IV
V
VI
Via
VIb
0
0.743
1.137
1.125
1.151
0
0.089
0.124
0.137
0.110
94. 75
105. 35
85.7
87.3
83.7
88.9
109.7
107.2
105.1
109 . 3
29.2
29.6
32.4
33.1
31.5
32.0
34.6
35.9
35.7
36.0
5.5
6.5
14.36
15. 06
13. 46
13.8
8.6
14.9
13.2
17.0
34.7
36.1
32.4
33.1
31.5
45.9
43.3
35.9
35.7
36.0
69.2
71.9
62.2
62.3
62.2
64.0
68.5
66.5
66.0
67.1
63.3
65.7
62.2
62.3
62.2
48.4
60.5
66.5
66.0
67.1
ST 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
Footnotes:
1. M5*=M5
2. MR = M*
M = M^
R 5*
0
0.294
0.239
0.270
0.197
__-.
,
_ ._
- M1? - M20
. + M14 + M ,
(Elutriate
98.4
100.1
107.8
105.3
110.7
108.4
107.0
113.6
99.9
29.2
32.1
38.8
39.0
38.5
32.0
41.7
49.9
33.6
(No elutriate
recycled)
9.1
11.3
17.3°
12. 86
23. 76
12.1,
14.3°
12. 26
16. 76
recycle)
38.3
43.4
38.8
39.0
38.5
44.1
41.7
49.9
33.6
70.3
67.9
64.0
63.0
65.2
70.5
61.0
56.1
66.4
61.1
56.6
64.0
63.0
65.2
59.3
61.0
56.1
66.4
3. 7. Removal = M - M (100)
1 5*
4. 7. Removal = ^ - MR (100)
MY~
5. Calculated MI (Table 6)
6. Elutriate Recycled
30
-------
TABLE 13 PLANT PHOSPHORUS REMOVAL
// / AVERAGE PHOSPHORUS AS P0£.
/ A> / TONS /DAY
/
A21-M
I
II
III
Ilia
Illb
Reten 210
IV
V
VI.
Via
VIb
ST 269 + CA-25
VII
VIII
IX
IXa
IXb
No Polymer
X
XI
XIa
Xlb
Footnotes:
1. M5* = M5 .-
/ *V J
/ £&
0
0.743
1.137
1.125
1.151
0
0.089
0.124
0.137
0.110
0
0.294
0.239
0.270
0.197
__-
mm - ft
M17 - M2Q
2. MR = M5* + M14 + M16
MB = M,-- (Elutriate
K J7*
3. % Removal
4. % Removal
= MX - M
= M! - MR
7&
24. 85
28. 65
26.9
26.5
27.3
25.2.
25.7
25.0
25.2
24.5
24.7
26.3
27.2
26.8
27.6
26.9
26.2
26.8
25.6
'»//
21.3
22.1
22.2
23.0
21.3
20.7
21.9
22.3
22.4
22.1
20.0
22.5
23.9
23.4
24.6
21.3
21.8
22.2
21.5
(No elutriate
Recycle)
(100)
(100)
"v /
1.9
1'56
3.66
3.86
3.46
3.3
2'66
3. 16
2.46
4.16
2.5
2.0,
/ i- D
A. S
3!26
6.36
3.1
4.1
3.76
4.66
recycle)
, /
V / r^
23.3
23.6
22.2
23.0
21.3
24.1
24.6
22.3
22.4
22.1
22.5
24.5
23.9
23.4
24.6
24.5
21.8
22.2
21.5
i/.
12.3
22.7
17.4
13.2
22.1
17.9
14.8
10.8
11.1
9.8
19.0
14.4
12.1
12.7
10.9
17.1
16.8
17.2
16.0
/% REMOVAL /
'////
6.0
17.5
17.4
13.2
22.1
4.4
4.3
10.8
11.1
9.8
8.9
6.8
12.1
12.7
10.9
8.9
16.8
17.2
16.0
5. Calculated ^ (Table 1)
6. Elutriate Recycled
31
-------
TABIJ5 14 PLANT NITROGEN REMOVAL
/AVERAGE NITROGEN REMOVAL (TKN) 7Z WMnw4T /
/ AS N. TONS/DAY / 7, REMOVAL /
0
0.743
1.137
1.125
1.151
24. 95
23. 15
23.8
23.3
24.3
19.7
18.1
21.3
21.4
21.2
3.7
5.6
5.2
23.3
21.5
21.3
21.4
21.2
20.9
21.6
10.4
3.7
12.9
6.4
6.9
10.4
3.7
12.9
Footnotes:
1- M5* = M(5 _ 20 - 17)
2. M = M + Mj4 + M.., (No elutriate recycle)
MT = Mr* (Elutriate recycled)
3. % Removal = M - M (100)
4. % Removal = M - MR (100)
5. Calculated Mj^ (Table 6)
6. Elutriate Recycled
-------
In the 50 day elutriate recycle baseline (period XI), recycle of the
elutriate without polymer treatment, in general, produced improvements
compared to the baseline (period X) in the overall plant removals
for all pollutants (tables 10-13). The most important improvement
occurred in the overall solids removal efficiency (table 10) which
increased from 65.6 to 77.6% and represented a 35% reduction in the
solids entering the river.
The additional loading from the recycled elutriate, however, produced
for all pollutants a small but consistent decrease in the plant
removal efficiencies based upon the secondary effluent. As examples,
the solids removals for primary-secondary treatment decreased from
the baseline efficiencies (periods I, IV, VII) of 80.3-82.3% without
elutriate recycle to 77.6% with elutriate recycle, and the BOD removals,
from the efficiencies of 73.6-75.4% without elutriate recycle to 72.2%
with elutriate recycle. In the overall plant operation, useful polymer
treatment should improve the plant removal efficiencies of the particulates
(solids and BOD) based upon the secondary effluent when the elutriate is
discharged into the river, and at least prevent the observed consistent
decrease in the same efficiencies when the elutriate is recycled to the
p1ant influent.
In the A21-M test with the elutriate discharged into the river
(period II), the plant removal efficiencies based upon the secondary
effuent of 83.7% for suspended solids (table 10), 71.9% for TOG
(table 12), and 21.6% for TKN (table 14), remained essentially
unchanged from the preceding baseline removals of 82.3, 69.2, and
20.9% respectively. The amounts of these three pollutants entering
the river in the secondary effluent either remained unchanged or
increased slightly with increased plant loading. The BOD removal
(table 11), however, increased from 73.6%, to 78.3% and the phosphorus
(table 13) from 12.3% to 22.7%. The BOD in the secondary effluent
actually decreased by 13%. Thus, in the 30 day test without elutriate
recycle, the A21-M treatment, which reduced the loadings to the
aerators by 20% for solids and by 14% for BOD, produced corresponding
improvements in the primary-secondary efficiencies for BOD removal
but not for solids removal. However, with the available plant
aeration controls, the air used in aeration at the lower BOD and
solids loading during A21-M treatment was not less than the preceding
baseline.
With the recycle of the elutriate (period III), the plant removal
efficiencies of 82.5% for solids and 76.6% for BOD represented an
increase of approximately 6% over the efficiencies (76.67, and 72.2%
respectively, for solids and BOD) of the elutriate recycle without
polymer addition (period XI). This modest increase in overall
efficiencies would reduce the solids entering the river by 22% and
the BOD by 17% if applied to the baseline (period XI). In contrast,
33
-------
the TOG and phosphorus removal efficiencies during elutriate
recycle with and without A21-M addition were essentially identical.
With a 207= lower plant loading, the TOG discharged into the river
in the elutriate recycle trial with the A21-M treatment was 227,
lower than that in the elutriate recycle without A21-M; with the
same plant loading, with and without polymer treatment, the phosphorus
entering the river was unchanged.
The solids removal efficiency of 84% and the BOD removal efficiency
of 77.47. in the last half of the elutriate recycle with A21-M
treatment (period lllb) represented the best performance of the plant
during the entire study. This performance, however, occurred with
ferric chloride addition in elutriation, and thus could not be
attributed solely to the polymer. With only an 80 day trial, the
A21-M treatment could not be fully assessed, but it prevented decreases
in the important primary-secondary removal efficiencies for suspended
solids and BOD which occurred when the elutriate was recycled without
polymer treatment.
In the Reten 210 treatment with the elutriate discharged into the
river (period V), the primary-secondary removal efficiencies based
upon the secondary effluent of 77.6% for suspended solids (table 10),
67.6% for BOD (table 11), and 14.8% for total phosphorus (table 13)
were from 2 to 17% lower than the corresponding baseline efficiency
(period IV). The TOC removal (table 12) of 68.5% represented a 7% in-
crease over the 64% efficiency of the baseline. The 64% baseline
efficiency, however, was unusually low as the other three baseline
efficiencies varied between 69.2 and 70.5%. The amount of TOC in the
secondary effluent during the baseline was actually lower than that
during the Reten 210 trial. Clearly, Reten 210 treatment with the
elutriate discharged into the river did not produce improvements in
the primary-secondary system.
When the elutriate was recycled (period VI), the removal efficiencies
of 76.0% for suspended solids (table 10), 68.9% for BOD (table 11),
and 10.8% for total phosphorus (table 13) were lower than similar
efficiencies during elutriate recycle without polymer treatment
(period XI). The TOC removal efficiency (table 12) of 66.5%, however,
was 9% higher than that of the elutriate recycle baseline. Even
with the increase in TOC removal efficiency, the decrease in the
removal efficiencies for solids, BOD and total phosphorus indicated
that Reten 210 during elutriate recycle did not improve the primary-
secondary treatment system.
In the ST 269 test, the primary-secondary removal efficiencies
(period VIII) of 78.8% for suspended solids (table 10), 70.2% for
BOD (table 11), and 67.9% for TOC (table 12) were 3 to 7/. lower
than the corresponding baseline efficiencies (period VII). The
total phosphorus removal efficiency (table 13) of 14.4% was also
-------
lower than that of the baseline. With the elutriate recycle (period IX),
the removal efficiencies of 79.2% for solids and 73.6% for BOD were
only 2% higher than those of the baseline elutriate recycle (period XI).
The TOG removal of 64% was 5% higher than that of the baseline while
the phosphorus removal of 12.1% was 28% lower. In general, ST 269 treat-
ment, as applied, did not produce significant or consistent changes in
the performance of the primary-secondary system during either the
periods with the elutriate discharged into the river or recycled to
the plant influent.,
35
-------
SOLIDS HANDLING
In normal operation, the plant's digested sludge could not be
directly dewatered by vacuum filtration, and required elutriation
to reduce the alkalinity and the fine solids in the sludge before
dewatering by chemical conditioning and vacuum filtration. The
digested solids during elutriation did not separate efficiently from
the washwater and the overflow (elutriate) returning to the plant
influent repeatedly recycled more than 50% of these solids back into
the primary settlers and subsequently into the solids handling system.
In 1962 the plant's increasing solids loading finally overloaded
the solids handling and disposal system, produced unstable plant
operation, and forced the direct discharge of the elutriate into the
Potomac River. Thus, the effects of the polymers on the various
sludge handling processes, especially elutriation and vacuum filtration,
were an important factor in the evaluation of the polymers.
The most important variable in solids handling was the amount of
solids within the various sludge handling processes. In normal
operation without elutriate recycle or polymer treatment, the combined
primary and secondary solids (table 9) for the four baseline periods
varied from 170 tons per day for period I to 212 tons per day for
period X.
For the 30 days of polymer treatment without elutriate recycle, the
total amount of solids fed to the solids handling system did not change
significantly from the baselines. Even with the increased capture of
solids in the primary settlers during A21-M treatment^ the increased
primary solids were off set by decreases in the waste activated sludge,
and the combined sludges averaged approximately 190 tons per day
(table 9) compared to the 170 tons of the preceding baseline (period I).
Since the plant solids loading increased by 21 tons per day from the
baseline to the period with A21-M addition, the increase of 20 tons
per day in combined sludges was not significant. Thus, the solids in
the handling system with the plant's elutriate discharged into the
river were not increased by polymer treatment.
With the elutriate recycle, the amount of solids in the thickened
sludge, in the digested sludge to elutriation, and in the elutriate
began increasing (figure 2-5), with or without polymer treatment. The
solids content in these streams generally increased as the period of
the elutriate recycle continued. The larger amounts of solids in the
elutriate in the second half of each polymer test with elutriate
recycle (table 10; periods lib, VIb, and 1Kb) indicated unstable
increasing amounts of solids in the solids handling system. In
general, similar increases in the last half of each elutriate recycle
test also occurred for the BOD, TOG, total phosphate, and TKN (tables 11,
12, 13, 14).
37
-------
CD
en
Q
g
500
400
300
200
100
A21-M
Recycle
April | May | June | July
iFigure 2: Quantity of Sludge Produced Using A21-M
-------
oo
1
CO
Q
M
iJ
O
en
Pi
500
400
300
200
100
Reten 210
Recycle
Thickened Sludge
Elutriate
July I
August
1 September
October
I November
December
Figure 3: Quantity of Sludge Produced Using Reten 210
-------
CO
§
H
CO
Q
500
ST 269
400
300
200
100
thickened Sludge
December | January | February | March
Recycle
April
Figure 4: Quantity of Sludge Produced Using ST 269
-------
500
400
H P
H
hJ
O
CO
300
200
100
Thickened Sludge
Recycle
May
June
I July
Figure 5: Quantity of Sludge Produced Using No Polymer
-------
Although most of the solids in the recycled elutriate were recaptured
either in the primary settlers or in the secondary settlers, and
returned into the sludge handling system, the increased amounts of
digested solids did not settle in elutriation. The production of
dewatered sludge (filter cake) by the vacuum filters did not increase
regardless of the polymer used in the primary settlers (table 15).
Under the operating conditions in the plant, the accumulating solids
in the sludge handling system would have eventually exceeded the
system's capacity, and as in the past, forced discharge of the
elutriate directly into the Potomac River. For A21-M treatment, attempts
to increase filter cake production by increasing feed rates to elutri-
ation during elutriate recycle were unsuccessful. The increased solids
loading in elutriation increased the solids in the elutriate but not
the filterability and production of the elutriated sludge.
For A21-M with its efficient capture of solids in the primary settlers,
the accumulation of solids in the plant became immediately evident.
Thus, FeClo was added at a rate equivalent to 12.8 pounds per million
gallons of raw wastewater to elutriation to increase production of
dewatered sludge. Although in the short 80 days test with A21-M
equilibrim in the solids handling system was not completely achieved,
the filter cake production averaged 69 tons per day with peaks over
80 tons per day for FeCl3 treatment compared to the normal 40-50 tons
per day (table 15). The FeCl, treatment in elutriation removed excess
solids and eventually should have stabilized solids handling system.
During elutriate recycle, solids gradually accumulated within the
plant's solids handling system especially in the digesters, regardless
of polymer treatment. After discontinuing all polymer addition, the
solids capture in elutriation and the filterability of the accumulated
solids improved. With the increased filterability, the solids
production increased to 82.5 tons per day without elutriate recycle
(period X). With the elutriate recycled (period XI), the plant's
solids production increased from the normal 30-50 tons per day for
elutriate recycle with polymer treatment to an average of 103.2 tons
per day (table 15). The cause for these high filter yields during
these two periods was not determined, and the high yields have not
been repeated. These filter yields, however, were not possible
during the polymer treatment. Thus it should be emphasized that
polymer treatment alone did not stablize solids handling nor permit
continuous elutriate recycle, and that chemical treatment such as
FeCl3 addition was necessary to remove solids accumulating within the
plant during elutriate recycle.
-------
TABLE 15 PLANT SOLIDS PRODUCTION
PERIOD
4/66-3/67
A21-M
I
II
HI3,
Ilia3
7/1-7/163
Illb3
Reten 210
IV
V
VI3
Via3
VIb4
ST 269 +
VII
VIII
IX3
IXa3
IXb
POLYMER DOSE
mg/1
0.74
1.137
1.25
1.21
1.15
_ ?_ _
0.089
0.124
0.137
0.110
CA-25
«
0.294
0.239
0.270
0.197
POLYMER USED FeCl
Ibs/day Ibs/
1460
2280
2240 2040
2460 3140
2362
» -_
162.1
225.0
236.5
211.4
- _ -, -
520.8
477.8
548.8
385.8
3 FILTERED SOLIDS
day Tons /day
44.8
58.0
51.1
55.1
1 49.6
2 69.0
61.7
49.7
32.4
40.7
42.4
38.7
36.0
30.9
32.4
36.4
27.6
No Polymer
X
XI3
XIa3
Xlb3
......
_r.
« _ -.
« D
:._- ...
~. »,_. -. -.
«H^
82.9
103.2
95.1
111.3
1. Average Ibs/day for 8 days (6/14-6/21) in elutriation
2. Average Ibs/day for 16 days (7/1-7/16) in elutriation
3. Elutriate Recycled
-------
CHEMICAL COSTS
The costs for each polymer employed in the trials are summarized
in Table 16. If FeCl3, added in elutriation, was included at
$0.05 per pound for a dose rate equivalent to 12.8 pounds per million
gallons of raw wastewater, the chemical costs increased by $0.64 per
million gallons. Thus for A21-M treatment with ferric chloride
in elutriation the combined chemical cost with the elutriate recycled
(period III) was $9.53 per million gallons.
Since polymer treatment of the raw wastewater did not produce
satisfactory performance of the elutriation process, chemical treat-
ment (either FeCl^ or polymers) in elutriation must be applied
independently of raw wastewater flocculation, and the costs of the
chemical treatment in elutriation appropriately should be separated
from those for raw wastewater flocculation. If chemical treatment
is successfully (907=, capture of solids) employed in elutriation,
however, the solids in the elutriate would not significantly increase
the solids loading in the primary settlers. Thus the chemical
requirements and costs of raw wastewater flocculation alone, assuming
an independent solution to the elutriate problem, would be closer to
the dosages and costs in the polymer trials with the elutriate discharged
into the river (periods II, V, and VIII).
Since Reten 210 and ST 269, as applied, did not produce significant
overall plant improvement during their trials with the elutriate dis-
charged into the river, the costs of these polymers can not be related
to pollutant removals. In the A21-M test (period II), the chemical
cost for the 17% reduction in the BOD in the secondary effluent was
approximately $5.90 per million gallons. Since with the aeration
controls in the District of Columbia Plant the reduced BOD and solids
loadings to the aerators during the A21-M test did not produce
observable decreases in plant air requirements, the cost of the
polymers were not offset by reduced plant operating costs. Further
studies with the elutriate problem independently solved are needed
before complete costs for the raw wastewater flocculation can be
obtained for the District of Columbia wastewater.
-------
TABLE 16 CHEMICAL COSTS
PERIOD POLYMER DOSE
Ib/mg
1
ADDITIVE
Ib/mg
POLYMER
COST $/mg
ADDITIVE
TOTAL
A-21
C-31
II
III
5.76
8.66
.44
.82
5.76
8.66
.14
.25
5.90
8.91
Re tan 210
V
VI
VIII
IX
0.742
1.035
ST-269
2.45
2.08
CA-25
24.5
22.0
1.08
1.50
3.55
3.02
2.02
1.82
1.08
1.50
5.57
4.84
A-21 $1.00 per Ib. C-31 $0.31 per Ib.
Reten 210 $1.45 per Ib.
ST-269 $1.45 per Ib. CA-25 $0.0825 per Ib.
All cost FOB manufacturer
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CONCLUSIONS
Flocculation of solids in the raw wastewater and in the recycled
thickener overflow by A21-M (anionic A21 modified with cationic C31)
improved the efficiency of primary sedimentation by approximately 26%
from a normal 50% solids removal to 63%. With the recycle of the
solids in the elutriate to the influent of the primary settlers, the
A21-M treatment increased the sedimentation efficiency by 48% from
the 43% removal during elutriate recycle without polymer treatment
to 63%.
Cationic Reten 210, at the doses employed, did not improve primary
sedimentation of the solids in the raw wastewater and the recycled
thickener overflow. With the recycle of the solids in the elutriate
to the primary basins, Reten 210 increased the primary sedimentation
efficiency by 19% from the 43% removal without polymer treatment
to 51%.
Anionic ST 269 with its clay builder did not substantially improve
primary sedimentation of the solids in the raw wastewater and the
recycled thickener. During the last half of the elutriate recycle
and with reduced ST 269 doses, the primary sedimentation efficiency
increased by 43% from the 38% removal without polymer treatment to 54%.
This reversal in treatment performance indicated a probable overdose
of ST 269 in the beginning of the ST 269 test.
Before elutriate recycle, the improved primary sedimentation with
A21-M reduced the solids entering aeration by 20% and the BOD by 14%,
and decreased the amounts of waste activated sludge by 25%,. The
benefits of the improved primary sedimentation, however, did not
produce completely parallel improvements in the secondary effluent,
and with the available aeration controls did not reduce the plant
air requirements. The high average rise rates of 1,000 to 1,300
gallons per day per square foot of clarification area washed solids
out of the final settlers relatively independently of the solids and
BOD load to the aeration tanks. Thus with the elutriate discharged
into the river, the average removals through secondary treatment of
solids, TOG, and TKN remained unchanged with or without polymer improved
primary sedimentation. The decreased BOD load to aeration during A21-M
treatment, however, increased the average BOD removals through secondary
treatment from 73.6% to 78.3%, and represented a 13% decrease in BOD in
secondary effluent.
With the recycle of the elutriate, none of the three polymers added
in the primary basins increased the capture of the digested solids in
elutriation. As with elutriate recycle without polymer treatment,
the unsettled solids in the elutriate gradually accumulated during
elutriate recycle in the plant's solids handling system. Although the
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addition of FeCl3 in elutriation during the last portion of the A21-M
test increased the solids capture of the digested solids and may have
eventually stablized the plant, polymer addition in the primaries,
including A21-M, did not prevent the accumulation of solids in the solids
handling system. As in the past, these accumulating solids would have
forced the discharge of the elutriate into the Potomac River.
In summary, while an appropriately applied polymer significantly improved
primary sedimentation in the District of Columbia Plant, the improved
primary sedimentation did not reduce solids discharge in the secondary
effluent, only modestly decreased (13%) BOD discharge, and did not permit
recycle of the elutriate to the plant influent. Since the test of each
polymer was not long enough to achieve plant equilibrium, it is still
undetermined whether efficient polymer flocculation of solids in primary
sedimentation at the District may produce overall plant improvement if
independent chemical treatment in elutriation is first developed to
eliminate accumulation of solids in the elutriate.
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REFERENCES
1. City of Cleveland, Ohio, "The Use of Organic Polyelectrolyte for
Operational Improvement of Waste Treatment Processes." FWPCA
Grant No. WPRD 102-01-68, May 1969.
2. Gales, M. E., Julian, E. C., and Kroner, R.C., "Methods for
Quantitative Determination of Total Phosphorus in Water", JAWWA
58, 1363 (1966).
3. Recommended Standards foe Sewage Works, Adopted by the Great
Lakes-Upper Mississippi River Board of State Sanitary Engineers,
May 10, 1960.
4. Standard Methods for the Examination of Water and Wastewatar, 12 ed,,
APHA, AWWA, and WP-F, New York (1965).
5. Van Hall, C. E. Safranco, J», Stenger, V«A., "Rapid Combustion
Method for Determination of Organic Substances in Aqueous Solutions",
Analytical Chemistry, 3_5, 315 (1963).
* U. S. GOVERNMENT PRINTING OFFICE :1972484-486/245
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1
Accession Number
w
5
Organization
2
District of
Subject Field & Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Columbia
Department of Sanitary Engineering
Washington, D.C.
Title
"FULL SCALE RAW WASTEWATER FLOCCULATION WITH POLYMERS"
10
Authors)
Freese, Paul V.
Hicks, Edward
Bishop, Dolloff F.
Griggs, Samuel H.
16
Project Designation
1T050 EJB
21
Note
22
Citation
23
Descriptors (Starred First)
*Flocculation
*Sedimentation
*Sludge Disposal
*Secondary Treatment
Wastewater Treatment
Filtration
Biochemical Oxygen Demand
25
Identifiers (Starred First)
*Raw Wastewater Flocculation
*Anionic Polymer
*Cationic Polymer
*Suspended Solids
Elutriation
27
Abstract
Three polymers, Dow's anionic A-21 modified with cationic C-31, Hercules
cationic Reten 210, and Calgon's anionic ST 269 with a clay builder, were added to the
District of Columbia's raw wastewater in 240 MGD tests of raw wastewater flocculation.
The objectives of polymer flocculation of the raw wastewater were to increase solid
capture in the primary tanks, reduce the BOD load to aeration, and permit recycle of
the elutriate to the plant's influent.
A-21 increased the amounts of raw and thickener overflow solids captured
within the primary basins by 25%. With recycle of the solids in the elutriate, the
amount of captured solids increased by 50%, compared to elutriate recycled without
polymer treatment. ST 269 did not increase the capture of the raw and thickener overflow
solids. Later, with reduced ST 269 dosage and recycled elutriate, the solids captured
increased by 40% compared to the elutriate recycle without polymer treatment. Reten 210
increased amounts of the captured solids (by 19%) only when the elutriate solids were
recycled.
Polymer treatment of raw wastewater did not improve the solids capture in
elutriation or permit continuous elutriate recycle.
The best polymer treatment in the primary basins increased the plant BOD
removal from 74% to 78%. (Bishop-FWQA)
Abstractor
Dolloff F. Bishop
Institution
Federal Water Quality Administration
WR:I02 (REV. JULY 1969)
WRSIC
SEND, WITH COPY OF DOCUMENT, TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 20240
* OPO: 1970-389-930
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