PHOSPHATE REMOVAL BY ACTIVATED SLUDGE
Amenability Studies at
Pontiac, Michigan
by
F. M. Pfeffer, M. R. Scalf, B. L. DePrater,
L. D. Lively, J. L. Witherow, and C. P. Priesing*
*The authors are, respectively, Research Chemist, Research Sanitary
Engineer, Supervisory Chemist, Research Chemist, Research Sanitary
Engineer, and Acting Chief, Treatment and Control Research Program,
Robert S. Kerr Water Research Center, Federal Water Pollution Control
Administration, U. S. Department of the Interior, Ada, Oklahoma.
-------
TABLE OF CONTENTS
Item Page
ABSTRACT ill
INTRODUCTION 1
Plant Investigation 2
Aeration Jug Studies 2
RESULTS AND DISCUSSIONS 4
Plant Characteristics 4
Dye Tracer Studies 6
Plant Performance 8
Aeration Jug Studies 17
Sewage Characterization 31
Microbiological Studies 31
SUMMARY . ' 33
CONCLUSIONS 34
RECOMMENDATIONS 35
APPENDIX 36
Analytical Procedures 36
REFERENCES 40
ACKNOWLEDGEMENT 41
GLOSSARY 42
TABLES
1. Plant Monitoring Summary - Orthophosphate 12
2. Plant Monitoring Summary 13
3. Components of Aeration Jugs 18
4. Suspended Solids Variation 20
5. BOD Variation 24
6. Chemical Addition 26
7. Orthophosphate Variation 29
-------
11
TABLE OF CONTENTS (Cont'd)
Item
FIGURES
1.
2.
3.
4.
5.
6.
7.
8.
9.
East Boulevard Plant Design
Dye Detention in Aeration Tanks
Dye Detention in Final Clarifiers
Dye Detention in Return Sludge
Suspended Solids Variation
Solids Variation - Removal vs. Solids
BOD Variation .
Chemical Addition
Orthophosphate Variation
Page
5
7
9
10
19
21
25
27
30
-------
ill
ABSTRACT
Phosphate removal by activated sludge was investigated at pilot
and plant levels in the East Boulevard Sewage Treatment Plant, Pontiac,
Michigan. These studies revealed erratic and low level soluble
phosphorus removal, although plant design was similar to that found
advantageous at the Rilling Plant in San Antonio, Texas^' and the
Back River activated sludge plant in Baltimore, Maryland.- Pilot-
scale investigations of the amenability of waste and activated sludge
to orthophosphate removal demonstrated that increasing the dissolved
oxygen and suspended solids concentrations in the mixed liquor above
existing plant conditions resulted in high levels of phosphate uptake.
In contrast, test variations of orthophosphate, biochemical oxygen
demand, and hardness loading on a pilot scale had less significant
effects.
Considering amenability, design, and operation, the East
Boulevard Plant has potential for soluble phosphate removal. With
minor design and operational changes, it is suitable for full-scale
demonstration of orthophosphate removal.
-------
INTRODUCTION
The research summarized in this report was conducted at the
East Boulevard Sewage Treatment Plant, Pontiac, Michigan and
represents a continuation of a program investigating the removal of
soluble phosphorus from sewage by conventional activated sludge
treatment. Field research conducted at San Antonio, Texas^' demon-
strated high removals of orthophosphate in the aeration tanks from
the liquid phase to the mixed liquor suspended solids. The removal
efficiency at San Antonio was controlled by the following design
and operational parameters: dissolved oxygen and suspended solids
concentrations in the mixed liquor, displacement times in the
aeration tanks and final clarifiers, rapid solids-liquid separation
with minimum sludge blanket depth, biochemical oxygen demand (BOD)
and phosphate load, and no return of waste activated sludge to the
process.
The purposes of the phosphorus removal studies conducted at
Pontiac, Michigan were:
1. To determine if this facility contained waste and sludge
amenable to biological removal of phosphorus, both on a plant and
pilot scale.
2. To verify the controlling parameters of phosphorus removal
identified at San Antonio by collecting data from an area of different
geographic, population, and sewage characteristics.
3. To identify any additional parameters controlling phosphate
removal.
4. To determine the expediency of this facility for plant-scale
demonstration, wherein phosphorus removal will be monitored over a
sustained period under desired operational conditions.
Aerated jugs of mixed liquor simulate the aeration tank process.
This method was selected for testing the amenability of waste and
activated sludge to phosphorus removal. Aerated jug tests circumvent
many operational problems in activated sludge plants, in that aeration
capacity, detention time, suspended solids concentration, and phospho-
rus and BOD load may be controlled easily. Sludge solids and sewage
samples from various points in the secondary system may be studied
conveniently. Detention time of the mixed liquor in the various unit
processes may be controlled.
-------
By deliberately varying operational parameters, the conditions
for sludge response and maximum removal can be established. Test
results may indicate necessary operational or design changes, or the
period of acclimation required to achieve a process capable of high
phosphate removal. Optimal operation can only be defined when plant
limitations are considered in conjunction with aerated jug findings.
Plant Investigation
The plant was studied to determine pertinent design and opera-
tional characteristics. Plant sampling and tracer work together with
jug studies defined plant performance.
Plant records were examined for type and frequency of sewage flow,
BOD loading, suspended solids and orthophosphate (0-PO^) concentrations,
additional chemical and physical data, and performance characteristics.
Plant personnel were questioned about sampling practices, analytical
procedures, waste anomalies, and peculiarities of operational control.
The wasting schedules of raw sewage and activated sludge were determined.
Disposal methods for waste activated sludge, primary sludge, digester
contents, and other waste streams were studied in anticipation of
auxiliary, inhibitory, or latent effects on the phosphate removal process.
Tracer studies were conducted using Rhodamine WT dye on aeration
tanks and final clarifiers to determine hydraulic characteristics such
as displacement, short circuiting, and degree of longitudinal mixing.
Grab samples were collected throughout the plant to determine the
phosphate concentrations and removal. These samples were analyzed for
concentrations of orthophosphate and, occasionally, total phosphate
(T-POA) and suspended solids. Chemically-fixed samples were transported
to the Robert S. Kerr Water Research Center for total phosphate deter-
mination. The sample sources were raw sewage, primary effluent (PE) ,
return sludge (RS), aeration tank influent, aeration tank (one-half
point), aeration tank effluent, and final effluent. Dissolved oxygen
(DO) measurements were made throughout the plant in conjunction with
the sampling program.
Aeration Jug Studies
An aeration jug study usually consisted of six jugs. The quality
of mixed liquor in each jug was unique.
Total suspended solids (TSS) concentrations were obtained for
plant return sludge and mixed liquor as initial information for jug
synthesis.
-------
Return sludge, as such, or concentrated by flotation,* was mixed
with primary and/or final effluent to obtain the desired range of
suspended solids concentration. The mixture was placed in a 5-gallon
polyethylene jug for subsequent aeration. Mixed liquor suspended
solids (MLSS) concentrations were then measured.
A portable air compressor supplied air, which was delivered via
plastic tubing to the jugs through a manifold containing individual
needle valves and rotometers. Plastic tee fittings served as diffusers.
Air flow throughout the experiment was regulated and maintained at
15 liters per minute per 15 liters of jug content.
The dissolved oxygen content and the temperature of the mixed
liquor were monitored several times during each run.
Samples were withdrawn from the jugs usually at half-hour or
hourly intervals. To purge the withdrawal tube, approximately 100 ml
of mixed liquor was siphoned off and returned to the jug of origin.
Thereafter, 100 ml was taken for orthophosphate analysis and 250 ml
when more tests were planned. Samples were processed immediately to
prevent orthophosphate release.
*A pilot flotation device was designed specifically for amenability
studies to provide a sufficient volume of concentrated return sludge
to synthesize six jugs of mixed liquor of varying suspended solids
concentrations. That volume of pure water representing 300 percent
of the quantity of sludge to be concentrated was pressurized to
40 psi in a separate tank. Plant return sludge was placed in a
50-gallon drum serving as a flotation cell. The supersaturated
water was rapidly released to atmospheric pressure beneath the
sludge at the bottom of the flotation cell. Air bubbles were
created by the pressure differential in such a turbulent fashion
that the sludge and water were rapidly and completely mixed. In
the cell, these bubbles rose to the surface carrying suspended
matter with them in the form of a suspended float. Withdrawal of
the subnatant liquid left behind a concentrated return sludge.
The process effectively concentrated return sludge from 0.25 to
0.5 percent to 1 to 3 percent solids. Thickened sludge was stored
under aeration until use in jug synthesis.
-------
RESULTS AND DISCUSSIONS
Plant Characteristics*
The East Boulevard Sewage Treatment Plant in Pontiac, Michigan
consists of one primary clarifier and two parallel activated sludge
systems. The activated sludge systems contain two aeration tanks and
two final clarifiers each and are operated independently with no
intermixing of return sludge. A plant schematic is found in Figure 1.
Digested primary sludge and raw sewage in excess of 9.4 million
gallons per day (mgd) is pumped to the Auburn Sewage Treatment Plant.
In addition, waste activated sludge may be pumped to the Auburn Plant.
An average of 5.8 mgd of raw waste is treated at the East Boulevard
Plant. Treatment consists of preliminary screening and degritting
followed by primary clarification in one 0.5 million gallon circular
tank. Primary effluent averages 58 mg/1 BOD and 40 mg/1 TSS. Waste
activated sludge is recycled to the head of the primary clarifier.
The average loading to the activated sludge process is 6 Ibs. BOD/
100 Ibs. MLSS/day.
Venturi meters measure and valves control primary effluent, return
sludge, and air to the aeration tanks. Each end-around tank has a
volume of 590,000 gallons and a total length to width ratio of 18:1.
Tapered aeration is used. Three tanks employ Pacific Flush Tank
diffusers while the fourth uses Walker Process "Sparjar" diffusers.
Standby blower capacity is available. Each aeration tank receives
air at the rate of 2.1 million ft-^/day or 1.4 ft^ of air per gallon
of sewage.
There are two return sludge pumps in each half of the activated
sludge process having respective ratings of 1,000 gallons per minute
(gpm) and 600 gpm. The 600 gpm pumps are held in reserve. The 1,000 gpm
pumps operate continuously, returning sludge at the rate of 1.4 mgd and
maintaining MLSS levels near 2,000 mg/1. For each 200 mg/1 increment in
excess of 2,000 mg/1 TSS, activated sludge is wasted for one hour at the
rate of 200 gpm.
*Conditions described in this section are those experienced during
the two-week study and do not necessarily reflect yearly averages.
-------
K
g
.8
cc
X
o
o
CL
o:
o
LJ
O
<
LJ
cn
Q
o:
^
LJ
O
CO
CO
LU
I
LU
CC
-------
Metal plating processes are the major sources of toxic metals
found in the plant influent. Concentrations of free cyanide and
hexavalent chromium are determined every hour. Concentrations rarely
reach 0.5 mg/1 and are normally ^0.2 mg/1.
Dye Tracer Studies
Tracer studies were conducted on aeration tanks and final
clarifiers on July 21 and July 29, 1967, respectively. Rhodamine WT
dye* served as a tracer for determining hydraulic characteristics
including displacement time, degree of mixing, and short circuiting.
1. Aeration Tanks
The theoretical displacement time for each tank was 6 hours.
One and five tenths (1.5) liters of 20 percent Rhodamine WT was
introduced at the influent end (beyond the point of entry of primary
effluent and return sludge) of each aeration tank at 7:30 a.m. on
July 21, 1967. Dye concentrations were monitored at the half-way and
effluent points. Mixed liquor flow during the 8-hour period averaged
8.4 mgd.
Figure 2 represents dye dispersion curves of the four tanks
obtained from effluent dye concentrations. These curves were not
corrected for dye recycled by return sludge because this effect was
insignificant within six hours after dye injection. Eighty-six percent
of the dye introduced was recovered during eight hours of monitoring.
A percent flow- through curve averaged from the areas under the four
dye curves is shown in Figure 2 .
The mode, median, t^o, an^ tgg (10 and 90 percent flow- through
times) are 3.8, 4.0, 2.5, and 5.9 hours, respectively. The dispersion
index (tgQ/t^o) i-s 2.5, and the modal detention time is equal to 63 per-
cent of the theoretical displacement time. The Pontiac aeration tanks
have somewhat greater longitudinal mixing and less plug flow than the
aeration tanks of the Rilling Plant^' in San Antonio, Texas.
Based on Figure 2, 10 percent of the mixed liquor receives
less than 2.5 hours aeration and 30 percent less than 3.5 hours. Such
flow-through characteristics appear to be satisfactory for high phosphate
(?80 percent) removal. Reducing hydraulic loading and adjustment of
other operating parameters could increase phosphate removal.
*LBS Rhodamine WT Solution (20%), E. I. DuPont de Nemours Company,
Organic Chemicals Department, Dye and Chemical Division, de Nemours
Building, Wilmington, Delaware 19898.
-------
HOnOHHl MCTIJ %
CD
X.
z:
<
UJ
o
UJ
h-
UJ
Q
UJ
>-
Q
i
CM
UJ
(T
13
-QNOO 3AQ
-------
The following data are presented for comparison with two plants
experiencing ^80 percent phosphate removal, namely, the Baltimore, Maryland
Back River activated sludge plant2/ and the San Antonio, Texas Rilling
Sewage Treatment Plant.-'
Aeration Tank Pontiac Baltimore San Antonio
Length:Width 18:1 25:1 20:1
Volume (mg) 0.6 2.6 1.9
Type 2-pass 2-pass 2-pass
Theoretical
Displacement (hrs) 6.3 4.6 8.6
Modal/Theoretical 0.6 1.0 0.9
Dispersion Index 2.5 2.4 3.5
2. Final Clarifiers
At 10:00 a.m. on July 29, 1967, 725 ml of 20 percent Rhodamine
WT dye was injected at each influent of Final Clarifiers No. 1 and 3.
Dye concentration was monitored in return sludge samples from both wet
wells, the effluents from Final Clarifiers No. 1 and 3, and the combined
final effluent at the head of the chlorine contact tank.
Based on primary flow and combined clarifiers (No. 1-4) volume,
the theoretical detention time for final clarification was 2.8 hours.
Figure 3 presents dye displacement curves for the two clarifiers studied.
Superimposed on this graph is the percent flow-through curve averaged
from dye curves of Clarifiers No. 1 and 3. Figure 4 presents dye
detention curves for return sludge.
Figure 3 reveals that about 40 percent flow-through takes
place in the first hour, and approximately 90 percent occurs at the
time of theoretical displacement. The modal time is 27 percent of
the theoretical detention time. Significant short circuiting of mixed
liquor is evident in Figure 4.
Plant Performance
Erratic removal of soluble phosphorus occurred during the two-
week study of the East Boulevard activated sludge process. Eight
samples which allowed for displacement time indicated that Aeration
Tanks No. 1 and 3 removed 10 percent from influent to effluent.
Performance ranged from 40 percent removal to 30 percent release.
Four samples taken with plug-flow consideration showed 3 percent
-------
250
200
150
o.
Q.
O
z
UJ
100
80
60
40
20
0
-t_L
100
90
80
x
o
70 o
(E
60 ^
o
50 H1
40 UJ
o
cr
LU
30 Q.
20
10
ITHEORETICAL DETENTION TIME'
TIME, Mrs.
FIGURE 3 - DYE DETENTION IN FINAL CLARIFIERS
-------
10
250
200
150
O.
a.
O
0 100
80
60
'Return Sludge (Tanks I &2)
Sludge(Tanks4&3)
l__
I
TIME, Hrs.
FIGURE 4 - DYE DETENTION IN RETURN SLUDGE
-------
11
release of soluble phosphorus in Final Clarifiers No. 1 and 3.
Clarifier performance ranged from no removal to 10 percent release.
Plant orthophosphate results for the two-week study are shown in
Table 1.
The plant analytical data obtained during this period are
presented in Table 2. Several parameters have been abbreviated
including total suspended solids (TSS), nonvolatile organic carbon
(NVOC), soluble nonvolatile organic carbon (SNVOC), and total oxygen
demand (TOD).
The average theoretical orthophosphate concentration in aeration
tank mixed liquor at the influent end was 4.1 mg/1 P. This value was
based on soluble phosphorus content and relative volumes of primary
effluent and return sludge. Mixed liquor influent averaged 4.8 mg/1 P
for two weeks of monitoring. Release of soluble phosphorus when
primary effluent and return sludge mix was considered insignificant.
The four aeration tanks averaged 0.5 mg/1 dissolved oxygen at
the influent end and 0.8 mg/1 at the effluent. Unchlorinated final
effluent, primary effluent, and return sludge averaged 0.3 mg/1.
Two previously investigated activated sludge plants showed higher
concentrations of dissolved oxygen in the mixed liquor effluent using
an air supply similar in quantity to that at Pontiac and having higher
primary effluent BOD concentrations:
Air Supply Avg. BOD DO Range in ML
Plant (ft?/gal waste) of PE (mg/1) Effluent (mg/1)
East Boulevard, 1.4 58 0.1-3.8
Pontiac, Michigan
Rilling, . 1.6 180 2.0-5.0
San Antonio, Texas-
Back River Activated 1.1 200 2.5-7.0
Sludge Plant, 2/
Baltimore, Maryland-
These data indicate that the Pontiac plant experiences air transfer
in the aeration tanks inadequate for high phosphate removal.
Phosphate (mg/1 P) measured as follows in the raw sewage, primary
effluent, and final effluent:
-------
12
Table 1
PONTIAC EAST BOULEVARD PLANT
Plant Monitoring Summary
July 21-29, 1967
Orthophosphate (mg/1 P)
Di
ite - Time
Raw
PE
A»l
in out
AT#2
in out
AT#3
in out
AT#4
in out
FE
*1
FE
#2
FE
#3
FE
#4
AT in
comp
AT out FE
corap comp
RS
1&2
RS RS
3&4 comp
7/21 -11:45 am 2.8 2.8 4.3 3.4 4.3 3.6 3.8 3.6 4.0 4.0 - ... - . 4.2 5.5 5.0
7/22 -12:00 N-3.2-- ------ - ... . - 3.6 4.2 - -
7/24 - 9:45 am - 4.0 -- ------ - --- - - --..
11:00 am- --- ------ - --- - . - 6.0 - -
11:30 am- --- ------ - --- - . 4.1 - . -
2:30 pm 4.8 4.7 - - - - - - -
3:00 pm - - 8.1 3.8 8.3 5.1 6.9 4.5 7.2 5.8 - - - - - . 4.0 - - 6.7
7/25 -10:00 am- --- ------ . --- - . _ 4.0 - -
10:30 am -2.8-- ------ - --- . . ....
11:30 am- --- ------ - --- - .4.3-..
7/26 - 6:00 am 1.7--- ------ - --- . . ....
7:00 am 2.0--- ...... . ... . . ....
8:30 am - 2.9 3.6 - 3.9 - - - - - 3.7 - - 6.5 5.4 -
9:30 am - 3.2 3.6 - - - 4.2 - - - - - - - 3.8 - - 5.0 5.8
12:30 pm - 2.2 - - - 3.6 - - . - . 2.8
1:30 pm - - - 2.2 - - - 3.4 5.1 3.4 ----- 2.9 -
7/26 - 2:00 pm 2.4 - 3.8 - - - 2.8
3:00 pm - - - - ------ 2.6 - 4.0 - - - 3.4. - - -
7/27 8:15 am- - -.- - - - 6.9 - -
9:00 am -3.3-- ------ - ... - - .---
5:00 pm - - 7.6 4.8 7.6 5.6 6.0 5.4 6.0 5.4 - - - - - - - - -
7/28 -12:00 N2.9--- ------ - ... - - ----
1:00 pm 2.7 2.6 3.9 - 3.8 - - - - 4.0 - - - - 5.5
2:00 pm - 2.8 4.9 - 4.2 - - - - - 4.3 - - - - 4.8
5:00 pm- --4.1---5.0-- - --- - 49 .---
6:00 pm - - - 3.8 - - - 4.6 - - - ... - 4.6 _ - - -
6:30 pm 4.1 - 5.1 - - - 5.1
7:30 pm 3.4 - 4.6 - - - 4.4
7/29 -10:00 am 1.7 2.9 3.8 3.9 4.0 4.3 3.5 4.9 3.7 5.4 4.5 5.5 5.7 5.3 -
2:00 pm 3.3 2.6 5.0 2.8 5.3 2.7 3.9 3.8 4.3 3.9 3.0 3.2 4.6 4.3 -
-------
Table 2
Plant Monitoring Summary
July 21-29, 1967
13
AT#1 (In)
ATM (1/2)
Date
7/21
7/24
7/26
7/28
7/29
7/21
7/22
7/24
7/25
7/26
7/27
7/28
7/29
7/21
7/24
7/26
7/27
7/28
7/29
7/21
7/26
7/28
Time
10:20 am
11:45 am
3:00 pm
2:30 pm
6:00 am
7:00 am
12:00 N
1:00 pm
10:00 am
2:00 pm
11:45 am
3:00 pm
12:00 N
9:45 am
2:30 pm
10:30 am
8:30 am
9'30 am
9:00 am
1:00 pm
2:00 pm
10:00 am
2:00 pm
9:55 am
11:45 am
3:00 pm
8-30 a»
9:30 am
5:00 pm
1:00 pm
2:00 pm
10:00 am
2:00 pm
10:00 am
10:30 am
11:30 am
3:00 pm
4:00 pm
TSS
(Sg7l)
_
422
-
-
74'
-
-i;
-
_
-
252
-
48
124
-
116
7*!'
18
SOI'
-
-
-
_
-
-
1744I/
-
-
- i /
1595-='
-
1110
-
.
-
_
-
Ortho
P
(mg/1)
_
2.8
-
4.8
1.7
2.0
2.9
2.7
1.7
3.3
2.8
-
3.2
4.0
4.7
2.8
2.9
3.2
3.3
2.6
2.8
2.9
2.6
_
4.3
8.1
3.6
3.6
7.6
3.9
_
4.9
3.8
5.0
.
2.5
2.5
4.5
5.4
Carbon TOD Total Total Total
Temp DO NVOC SNVOC Whole Filt. P Hardness Plate Count
("C> (mg/1) (mg/1 C) (mg/1 C) (mg/1 CO) (mg/1 OD) (mg/l)(ng/l CaC<>3) (count/ml)
21.0 2.2 - - - - - - - ,
8.8 - 4.2 x W
280
-
20.0 3.5 - I/ - I/ 'I/ * - 11 - ' ,
21. 01 17. o!' 821' - 2.4' - 5.4 x 104 I/
20.0 3.4 - -
22.5 2.8 -l/ -l/ 324 - 7.9 - 3.1 X 104
22.5 2.6 - -
_
-
5.5 - 5.5 x 105
275
85 71 105 70 5.0
36.0 31.5 108 100 4.6
-
36 32 142 70 3.4
20.0 0.3 - - ., - - - - 1.0 x 104
40. Oi' 29.5-=' lOOi/ - 3.6i' -
20.0 0.3 - -
4
26 24.5 86 70 3.6 - 1.7 X 10
22.0 0.5 - - -ll - - lf - 2.4 X 104
------ --
-_-_. - -
-
20.5 0.7-- -- -- -,
2.7 x 10
24.0 0.6 - -
20.5 0.3 - - - - - 3.4 x 105
15. oi' - ...
21.0 0.2 - -
22.0 0.2 - -
21.5 0.5 - - 1720 - 45 4.4 x 105
______ - -
22.0 0.4 - -
20.5 0.3 - -
-
20.5 1.0 - - - - - 1.1 x 106
21.0 0.4 - - - - - - 1.1 x 105
21.0 0.6 - -
22.5 0.3 - - - - - - 1.2 X 105
21.5 0.3 - -
^/Composite figure of times sampled.
-------
14
Table 2 (Cont'd.)
Sample
AMI (out)
AT»2 (in)
AT02 (out)
AT*3 (.n)
AT« (1/2)
Date
7/21
7/24
7/26
7/27
7/28
7/29
7/21
7/24
7/27
7/29
7/21
7/24
7/27
7/29
7/21
7/24
7/26
7/27
7/28
7/29
7/21
7/26
7/28
Time TSS
9:50 am
11:45 am 1852
3:00 pm
12:30 pm -
162
-------
15
Table 2 (Cont'd.)
Sample
AT*3 (out)
AT*4 (In)
AT04 (out)
AT comp (in)
AT comp (out)
FE01
ra#2
Date
7/21
7/24
7/26
7/27
7/28
7/29
7/21
7/24
7/26
7/27
7/29
7/21
7/24
7/26
7/27
7/29
7/26
7/28
7/26
7/28
7/24
7/26
7/28
7/29
7/24
7/29
Time TSS
9:35 am
11:45 am 1892
3:00 pm
12:30 pm
1:30 pm
5:00 pm
5:00 pm
1770!/
6:00 pm
10:00 am
1:00 pm
2:00 pm
9:30 am
11:45 am
3:00 pm
1:30 pm
5:00 pm
10:00 am
2:00 pm
9:30 am
11:45 am 1348
3:00 pm
1:30 pm
5:00 pm
10:00 am
1:00 pm
2:00 pm
8:30 am - .,
1540-
9:30 am
1:00 pm - .
165o!'
2:00 pm
12:30 pm - i /
1740+
1 : 30 pm
5:00 pm -
169oi
6:00 pm
3:00 pm
2:00 pm
3:00 pm
6:30 pm
7:30 pm
10:00 am
2:00 pm
3:00 pm
10:00 am
2:00 pm
nrtho Carbon TOD Total Total
(mg/1) 7"c) (mg/1) (ng/1 C) (mg/1 C) (mg/1 OD)(mg/l OD) (mg/1) (mg/1 CaC(
21.0 0.4 - - - - - -
3.6 - - - -
4.5 22.0 0.1 - - - - - -
3.6 21.0 1.0 - - - - - -
3.4 21.0 0.5 - - - - - -
5.4 22.0 0.5 - - - - - -
5.0 22.0 0.6 - - - - - -
. . - - -- - -
4.6 22.0 0.4 - - - - - -
4.9 21.0 0.5 - - - - - -
21.5 0.8 - - - - - -
3.8 - - - -
20.5 0.4 - - - - - -
4.0---- -- --
7.2 22.0 0.1 - - - - -
5.1 - - - -
6.0 22.0 0.4 - - - - - -
3.7 21.0 0.5 - - - - - -
4.3.--- -- --
20.5 0.4 - - - - - -
4.0---- -- --
5.8 22.0 0.1 - - - - - -
3.4 .... . - -
5.4 22.0 1.8 - - - - - -
5.4 21.0 3.3 - - - - - -
22.5 3.8 - - - -
3.9---- -- --
3.7 - - - - - - - -
27. Oi' - - 38. &i' -
3.8 - - -
4.0---- -- ..
30!' - - 30!' -
4.3---- -- --
2.8 - - - - - - - -
33.6^ -
2.9---- -. -.
4.9---- -- .-
46!' -
4.6---- -- ..
22.0 0.5 - - - -
2.4 21.0 0.4 - - - _
2.6 21.0 0.5 - - - - - -
4.1 22.5 0.3 24 - 36 - 3.4
3.4---- -- --
4.5---- -- ..
3.0 - -
22.0 0.3 - - - - .
5.5 - -
3.2---- -. ..
Total
>JT (count /ml)
f.
1.5 x 10°
-
1.7 x 105
-
-
3.5 x 105
-
-
-
"
-
"
-
-
-
-
-
-
-
-
-
.
_
-
_
_
-
8.2 x 105
-
.
_
-
8.9 x 105
-
-
8.0 x 104
4
2.4 x 10
-
-
-
.
^./Composite figure of time a sampled.
-------
16
Table 2 (Cont'd.)
FE04
FE comp
RS 16.2
RS 3&4
RS (coop)
7/24
7/26
7/28
7/29
7/24
7/29
7/21
7/22
7/24
7/25
7/26
7/28
7/21
7/22
7/24
7/25
7/26
7/27
7/28
7/29
7/21
7/26
7/29
7/24
7/28
3:00
2:00
3:00
6:30
7:30
10:00
2:00
3:00
10:00
2:00
9:15
11:45
12:00
11:30
3:00
11:30
2:00
3:00
6:30
7:30
11:45
12:00
9:20
11:00
10:00
8:30
9:30
8:15
1:00
2:00
10:00
2:00
11:45
8:30
9:30
10:00
2:00
3:00
1:00
2:00
pm
pm
p«
p.
pm
am
pm
pm
am
pm
am
am
N
am
pm
am
pm
pm
pm
pm
am
N
am
am
am
am
am
am
pm
pm
am
pm
am
am
am
am
pm
pm
pm
pm
(ng7l)
.
-
_
-
_
-
-
.
-
_
20
54
-
87
~jl/
-
.
ii/
-
3795
2880
5120
5950
6610
455fli'
3920
.
-
_
-
4635
.
462C>i
-
_
-
-
678(>i'
-
Ortho Carbon TOD Total Total
(mg/1) (UC) (mg/1) (mg/1 C) (mg/1 C) (mg/1 OD) (mg/1 OD) (mg/1) (mg/1 CaCO^
22.0 0.2 - - - - - -
3.8 21.0 0.2 - - - - -
4.0 21.0 0.2 - - - '
5.1 22.5 0.4 - - - - - -
4.6---- -- -"
5.7..-- -- --
4.6---- -- - -
22.0 0.2 - - - - - -
5.3---- -- --
4.3.--- -- --
- 21.0 ----- -
4.2 - - 4.0 -
3.6 - - 28.5 28.0 5 5 3.7
4.1 - - 19 16 49 40 3.3
4.0---- -- --
4.8 - - 19.5 19.5 42 42 4.8
18. »i' 13. si' 3&i' - 2.si' -
3.4..-- -- --
5.1 - - -I/ -,, -I/ - - ,, -
- 18~ 16^ 40" 4.6-
4.4 .--- -- - -
5.5.--- -- --
4.2 - 96.0
__.- -- - -
6.0 - - 120
4.0 129
6.5 20.5 0.3 - i; - . -^ - -,,
- - 20.5- 15. Oi' 4440- - 97-
5.0 21.0 0.2 - - - - -
6.9 - - - - 4640 - 99.5 -
22.0 0.3 - - - - -
21.5 0.3 - - - - - -
8.1---- -- --
7.1-.-- -- --
5.0 ._.- -- - -
5.4 20.5 0.3 - - - - -
94.51' -
5.8 21.0 0.1 - - - - - -
5.8---- -- - -
5.4 - ... - - - -
6.7 -- - - - - - -
!:! I '- '- 2?i' 41601' : mi' :
4.8---- -- --
Total
4
3.0 x 10
2.5 x 10*
_
"
-
_
-
3
1.6 x 10
-
.
-
-
-
-
-
-
-
-
-
_
-
.
6.7 x 105
3.2 x 105
1.8 x 105
-
_
-
-
5.2 * 105
-
-
-
-
.
^/Composite figure of times sampled.
-------
17
Ortho Total
Source Min Max Min Max Avg. (Ortho/Total)
Raw Waste 1.7 4.8 2.4 8.8 0.4
Pri. Effl. 2.6 4.7 3.4 6.4 0.7
Final Effl. 2.8 5.1 2.8 4.8 1.0
Orthophosphate loading was 0.4 Ib. P/day/100 Ibs. MLSS.
Temperatures in the aeration tanks averaged 21.5 C at both the
influent and effluent ends. The average total bacterial plate count
was 1.5 x 10^ per ml for primary effluent, 3.8 x 10-> per ml for aeration
tank influent, 8.5 x 105 per ml for aeration tank effluent, and 3.3 x 10
per ml for unchlorinated final effluent.
Aeration Jug Studies
1. Suspended Solids Variation
Seven 5-gallon polyethylene aeration jugs were set up at
12:30 p.m. on July 22, 1967, to determine the effect of mixed liquor
suspended solids concentrations on soluble phosphorus removal. Jug
synthetic components are shown in Table 3. Jug No. 4 contained
mixed liquor composited from the influent of each aeration tank.
Suspended solids concentrations ranged from about 700 to
6,000 mg/1. Initial soluble phosphorus concentrations showed minor
variations with no apparent relationship to mixed liquor suspended
solids (MLSS). Insignificant release of soluble phosphorus during
mixed liquor preparation was attributed to preaeration of concentrated
return sludge.
Soluble phosphorus removal after 4 hours aeration ranged
from zero percent in the jug containing the low solids concentration
to a maximum of 64 percent in the jug containing the high solids
concentration. The jugs with ^3,840 mg/1 suspended solids concen-
trations removed 10 to 40 percent more than plant mixed liquor and
other jugs containing lower suspended solids concentrations. Figure 5
is a plot of orthophosphate concentration versus aeration time for
each jug. Analytical results are found in Table 4.
Percent phosphate removal versus suspended solids concentra-
tion is shown in Figure 6. This curve indicates that the optimum
solids concentration for subsequent pilot studies is about 6,000 mg/1.
-------
18
Table 3
Components of Aeration Jugs
Suspended Solids Variation
Components 1 2 3 4 5 (
PE (liters)
RS (liters) _a/
RS (liters) b_/
ML (liters)
FE (liters)
Avg. TSS (mg/1)
BOD Variation
PE (liters)
RS (liters) b_/
FE (liters)
Metrecal (ml) cj
ML (liters)
Chemical Addition
PE (liters)
PE (liters) d/
RS (liters) b/
FE (liters)
City Water (liters)
Metrecal (ml)
FeSOi (final cone, of
Fe^2 in mg/1)
Al2(S04)-j (final cone.
of Al+3 in mg/1)
Orthophosphate Variation
PE (liters)
RS' (liters) b/
City Water (liters)
K2HP04 (final cone, of
P in mg/1)
a/Return sludge from wet well (Tanks No. 1 and 2).
b_/Concentrated return sludge - 60 liters from wet well (Tanks No. 1 and 2)
concentrated to approximately 20 liters.
_c/BOD of Metrecal is 290 mg/ml.
d/Prim. effl. free of all hardness (normally total hardness - 280 mg/1 CaCO^
_e/Jugs No. 3, 4, and 5 had same make-up, and composite sample of these three
jugs was considered the experimental control.
10.0
1.5
3.5
670
7.0
3.7
4.3
5.0
4.0
1.0
f\ o
u u
^-
>n
5.
4.
_
10.0
3.0
2.0
1385
10.0
3.7
1.3
10.0
4.0
1.0
11.
4.
8.3
10.0
4.4
0.6
2360
10.0
3.7
1.3
1.5
~
10.0
4.0
1.0
25.
ne/
4.
__
15.0
3130
10.0
3.7
1.3
3.8
~
10.0
4.0
1.0
25.
11.
4.
10.0
2.5
2.5
3840
10.0
3.7
1.3
6.3
~
4.6
5.4
4.0
1.0
11.
4.
_
10.0
3.5
1.5
4660
15.0
0.5
9.5
4.0
1.0
10.0
4.5
0.5
6170
"
10.0
4.0
1.0
_.
Ortho
Phosphate TSS
(mg/l-P) (mg/1)
3.2
4.2
3.4
3.6
4.0
2.4
4.1
2.8
2.8
2.8
4.8
3.3
2.5
60
4005
16090
50
124
12260
54
116
12230
87
18
10910
-------
19
JUG
I
2
3
4
5
6
7
TSS(mg / I)
670
1385
2360
3f30
3840
4660
6170
E
UJ
O
I
Q.
O
I
t-
cr
o
TIME, Hrs.
FIGURE 5-SUSPENDED SOLIDS VARIATION
-------
20
Table 4
Suspended Solids Variation
Ortho ""^
Sample
Jug I
Settled
Supernatant
-;pu-l9d
Sludgp
jug 2
Settled
Supernatant
Settled
Sludie
Jug 3
Settled
Supernatant
Settled
Sludge
Jug i
Settled
Supernatant
Settled
Sludge
Jug 5
S"ttled
Supernatant
Settled
SJudgt
Jug 6
Settle'.'
I'uper i.itoi.t
Settled
V ludge
Jug 7
Srttleil
c pern.o*-a.-it
Settled
Time
12:30
1:30
2:30
3:30
4:30
5:00
'. 00
12:30
1:30
2:30
3:30
4:30
5:00
5:00
J2-30
1:30
2:30
3:30
4:30
5:00
5:00
12:30
1:30
2:30
i:30
4:30
5:00
5:00
12:30
1 :30
2:30
i:30
;:30
5:00
5:00
12:30
1:30
2:30
3:30
4:30
5:00
5:00
12.30
1:30
2:30
3:30
4.30
5:00
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pin
pm
pm
pm
pm
P'H
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
pm
ntn
PUI
pm
pm
pr.
pm
pm
pm
pn
pm
TSS
(mg/1)
_
-
670
-
-
252
-
1480
-
1290
-
-
228
-
2250
-
2470
-
-
302
-
2800
-
3460
-
-
252
-
3680
-
.'000
-
-
203
-
4550
-
4780
-
-
13:
-
6070
6270
-
-
82
P
(mg/1)
3.
3.
3.
3.
3.
3.
4,
3.
3.
3.
3.
3.
3.
4.
3.
3.
J .
3.
3.
3.
/,.
3.
3.
3.
3.
3.
'
4.
3.
2.
2.
9.
2.
2.
4.
).
2
2 .
J
1.
8
6
8
6
8
5
q
3
2
4
4
2
2
8
j,
2
4
1
0
c
8
1
4
2
1
0
0
7
3
4
.2
0
2
,2
/,
Q
7
0
c
,8
l.t
3.0
3.9
1.6
1.4
1.4
.^
1.5
PO
(mg/I)
11.6
10.8
11.4
11.2
11.6
10.9
15.0
10.0
10.0
10.2
10.2
9.6
9.c.
14.8
in. c
4.8
10.2
9.5
1.2
9.:
14.8
11.9
10.2
9.9
9.5
9 2
9.3
14.4
10. i
.',3
5.7
6.1
6.7
6.8
' 3 , j
11.1
5 9
6.0
'. .7
5-7
5.8
9.2
1 !.«
Temp
To
24
27
30
32
32
25
27
29
12
33
:\
25
26
28
29
-
-
23
24
25
27
28
-
-
24
25
26
28
29
-
-
2t
25
26
27
29
-
-
24
.5
.0
.0
.0
.0
-
-
.5
.5
.0
.0
.0
-
-
.0
.0
.5
.5
.0
.0
.0
.5
.5
.0
.0
.0
.5
.0
.n
.0
t >;
.5
.5
,0
.5
5.0 27.0
4.3
4.1
4. i
'.(
28,
?9,
,0
,5
jo.o
-
" ' Carbon TOD
DO NVOC SNVOC Whole Flit.
(mg/1) (mg/1 c) (mg/1 cl (mg/1 OD) (mg/1 OD)
5
5
5
6
5
6
6
6
6
6
5
5
6
6
5
-
-
5
5
6
6
6
-
-
4
4
^
5
4
-
-
4
'i
4
4
3
-
-
j
2
2
2
.0 - - -
.8 -
.4 - -
.1 -
.6 -
23.5 20.0 50.0 47.r-
-
.3 - -
.3 -
.7 -
.6 -
.6 -
21.5 20.0 45.0 35.0
- -
.a - - - .
.3
.3 -
.1
.8 - - -
23.0 18.5 42.5 42.5
- -
.6 -
.2
.7 - - -
.1
.1 -
19.0 19,0 37.5 35.0
-
.5 -
.9 - -
.2 - - - -
.2 - - -
.8 - - -
22.0 17.0 27.5 25.0
- -
.& - - -
.7 _
.5
.2 -
.3
19.0 K,.o IV .5 T> 5
-
.5
.2 - -
.8
.6
2.6 -
-
27.0 25.0 2?. 5 22.5
Total Plate
Count
(Count/ml)
?.S x 10*
-
4.0 x 10
_
6.6 x 105
-
-
_
_
-
.
-
-
-
_
_
_
-
-
4./ x ]05
_
2.5 x 105
_
1.2 x 106
-
-
_
-
-
-
-
-
-
-
-
-
-
-
7.1 x 10^
9.2 t. \f
2.3 y. Kj6
-
5:00 pm
-------
21
60
_J 50
LJ
K
Ul
X
a.
M
O
x 30
Q.
20
10
I
L
I
I
t
/
/
TOTAL SUSPENDED SOLIDS (mg/l x I0~3)
FIGURE 6-SOLIDS VARIATION - REMOVAL VS. SOLIDS
-------
22
Due to limitations in plant return sludge pumping capacity, 3,500 mg/1
MLSS was chosen for subsequent studies so that test results would be of
practical value in plant selection and operation.
A marked increase in phosphate removal in Jugs No. 5 through
7 is evident in Figure 5. This elevated performance, disproportionate
to the increased solids levels found in these jugs, requires explanation.
These jugs were synthesized with thickened return sludge while Jugs
No. 1 through 3 contained unconcentrated plant return sludge. The
authors can only speculate about the enhanced capabilities of concen-
trated sludge by pointing out the differences between the two sources
of jug solids:
a. Activated sludge taken from the secondary system averaged
^1 mg/1 DO. During sludge thickening by air flotation, suspended solids
contact water supersaturated with air. The resulting solids might be
considered preaerated return sludge in contrast to plant return sludge
which was essentially anaerobic at the time of jug synthesis.
b. Plant activated sludge contains dissolved interstitial
substances, some of which might have a toxic influence in jug
phosphate removal. Air flotation using city water undoubtedly
removed a portion of these interstitial materials by elutriation.
c. Thickened sludge contained 20 percent less orthophosphate
and 10 percent less total phosphate, per unit suspended solids, than
unadulterated plant return sludge. This might account for its greater
affinity for soluble phosphorus.
2. BOD Variation
Six jugs were set up on July 24, 1967, to determine the effect
of BOD load on soluble phosphorus removal. Aeration commenced at 11:30 a.m.
According to plant records, the average BOD concentration for
primary and final effluent during the two-week study was 90 and 7 mg/1,
respectively. These figures were used in estimating jug BOD loadings in
this experiment.
Each jug contained suspended solids (3.7 liters of concentrated
sludge diluted with 1.3 liters of final effluent) and a BOD source which
will be termed substrate in order to distinguish it from plant primary
effluent. The substrate volume was 10 liters for each jug.
Jug No. 2 contained 10 liters of plant primary effluent as
substrate and represented the synthetic control. It is termed the
100 percent substrate jug, in reference to the 10-liter substrate
-------
23
volume containing a BOD concentration equal to 100 percent of the
primary effluent value. Substrate BOD was reduced to about 75 percent
in Jug No. 1 by diluting primary effluent with final effluent (Table 3).
Approximately 175, 300, and 400 percent substrate BOD concentrations
were established in Jugs No. 3, 4, and 5, respectively, by the addition
of a BOD supplement (Metrecal). Jug No. 6 contained mixed liquor
composited from the influent ends of the aeration tanks and served
as a control.
Suspended solids concentrations were about 3,500 mg/1 for
all jugs except Jug No. 6 (2,500 mg/1 TSS). Experimental results are
found in Table 5. The results of four hours aeration are presented
in Figure 7.
Initial phosphate values.were higher for those jugs having
substrate BOD concentrations greater than 75 percent of the average
primary effluent figure. The initial orthophosphate concentrations
for all jugs, based on phosphate content of all jug constituents,
were 20 to 30 percent below the observed concentrations. Similar
results were observed in the suspended solids variation study.
The low BOD jug (75 percent of the primary effluent) showed
68 percent removal while synthetic jugs with higher BOD loading gave
slightly higher results (72-78 percent). The mixed liquor control
showed 29 percent removal of soluble phosphorus.
The similar removals observed with increasing BOD concentra-
tions indicate that little could be gained by such practice at this
facility on a plant scale. Accordingly, all future studies were
performed with substrate BOD concentrations similar to that of plant
primary effluent.
3. Chemical Addition
A set of jugs was prepared on July 25, 1968, to determine the
effects of iron and aluminum salts, hardness, and low phosphate load
on soluble phosphorus removal. Jug constituents are given in Table 3.
The experimental results are summarized in Table 6 and shown graphically
in Figure 8.
Theoretically, Jug No. 1 contained one-half the normal
phosphate load contributed by primary effluent (Metrecal was added
to this jug to restore the BOD lost by addition of final effluent
and city water). High initial phosphate concentrations were found
in Jugs No. 1, 2, 5, 6, and 7. Each was 50 percent greater than the
-------
24
Table 5
BOD Variation
July 24, 1967
Ortho
Sample
Jug 1
Settled
Supernatant
Settled
Sludge
Jug 2
Settled
Supernatant
Settled
Sludge
Jug 3
Settled
Supernatant
Settled
Sludge
Jug 4
Settled
Supernatant
Settled
Sludge
Jug 5
Settled
Supernatant
Settled
Sludge
Jug 6
Settled
Supernatant
Settled
Sludge
Time
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
11:30 am
12:30 pm
1:30 pm
2:30 pm
3:30 pm
4:00 pm
4:00 pm
TSS
(mg/1)
3530
-
-
3600
-
226
-
3470
-
-
3750
-
270
-
3490
-
-
3580
-
212
-
3440
-
-
3860
-
238
-
3230
-
-
3270
-
220
-
2470
-
-
2580
-
218
-
P
(mg/1)
4.4
1.9
1.4
1.3
1.4
1.5
3.2
5.0
2.0
1.5
1.4
1.4
1.4
2.2
5.3
2.0
1.3
1.2
1.2
0.7
2.0
5.1
1.8
1.2
1.1
1.1
1.1
1.8
5.1
2.1
1.3
1.1
1.1
1.1
1.9
4.8
3.5
3.4
3.5
3.4
3.4
4.7
PO/,
(mg/1)
13.5
5.8
4.2
4.0
4.3
4.5
9.9
15.3
6.1
4.5
4.2
4.3
4.3
6.7
16.2
6.3
4.0
3.5
3.6
2.3
6.1
15.6
5.6
3.7
3.4
3.5
3.5
5.6
15.6
6.4
4.0
3.4
3.3
3.4
5.8
14.7
10.8
10.5
10.7
10.4
10.1
14.4
Temp
(°C)
23.5
25.5
28.0
29.5
-
-
-
24.0
25.5
27.0
28.0
-
-
-
23.5
25.0
27.0
27.5
-
-
-
23.5
25.0
27.0
27.5
-
-
-
23.5
25.0
26.5
28.0
-
-
-
23.5
25.0
27.0
28.0
~
-
-
Carbon TOD
DO NVOC SNVOC Whole Flit.
(mg/1) (mg/1 c)(mg/l c) (mg/1 OD)(mg/l OD)
0.6 - -
4.4 -
3.5 - - - -
3.9 - - - -
- -
23.0 21.0 25.0 22.5
_ -
0.2 - - -
4.5 - - - -
4.2 - -
4.5 - -
- _
19.5 15.0 11.0 11.0
- - - - -
0.1 - -
4.2 - -
4.4 - - - -
4.6 -
_ _
15.0 15.0 17.5 15.0
_ _
0.1 - - - -
4.2 - - - -
4.5 - - -
4.7 - -
- _
16.0 15.5 11.0 11.0
- - - -
0.1 -
3.7 -
4.1 - - - -
4.4 - -
_ _
18.0 18.0 11.0 11.0
- -
3.2 - -
5.8 - -
5.8 - -
5:8 - - - -
_ _
15.0 12.0 27.5 27.5
- _
Total Plate
Count
(Count /ml)
3.3 x 105
~ r;
7.0 x 10
L
6.7 x 10
-
-
1.4 x 106
6
6.2 x 10
f.
1.1 x 10
-
-
_
-
-
-
-
-
-
.
-
-
-
-
-
-
3.7 x 105
~ c.
2.4 x 10
~ e;
3.3 x 10
-
-
2.1 x 106
s
6.5 x 10
~ R
6.6 x 10
-
-
-------
JUG TSS(mg/l)
25
ESTIMATED SUBSTRATE
BOD (% of PE)
1
2
3
4
5
6
3565
3610
3535
3650
3250
2525
75
100
175
300
400
ui
CO
o
0-
I
o
H
CE
O
1.0 -
TIME, Hrf.
FIGURE 7-BOD VARIATION
-------
26
Table 6
Chemical Addition
July 25, 1967
Sample
Jug 1
Settled
Supernatant
Settled
Sludge
Settled
Supernatant
Settled
Sludge
Jug 3
Settled
Supernatant
Settled
Sludge
Jug 4
Settled
Supernatant
Settled
Sludge
Jug 5
Settled
Supernatant
Settled
Sludge
Jug 6
Settled
Supernatant
Settled
Sludge
Jug 7
Settled
Supernatant
Settled
Sludge
Ortho
Time
12:15 pm
1:15 pm
2:15 pm
3:15 pm
3:45 pm
3:45 pm
12:15 pm
1:15 pm
2:15 pm
3:15 pm
4:15 pm
4:45 pm
4:45 pm
12:00 N!/
12:15 pm-'
1:15 pm
2:15 pm
2:45 pm
2:45 pm
12:00 ^
12:15 pur1'
1:15 pm
2:15 pm
2:50 pm
2:50 pm
12:15 pm
1:15 pm
2:15 pm
3:15 pm
4 : 15 pm
4:45 pm
4:45 pm
12:15 pm
1:15 pm
2:15 pm
3:15 pm
4:15 pm
4:45 pm
4:45 pm
12:15 pm
1:15 pm
2:15 pm
3:15 pm
4:15 pm
4 : 45 pm
4:45 pm
TSS
(mg/1)
4250
-
3940
~
30
-
3600
-
3540
-
~
34
-
3750
-
3670
30
-
3850
-
3510
14
-
3890
-
3530
-
-
22
-
3730
-
3620
-
~
48
-
3700
_
3550
-
-
-
-
p
(mg/1)
4.0
0.4
0.2
0.3
0.4
0.9
4.8
1.4
0.6
0.3
0.6
0.6
1.1
2.9
0.7
0.2
<0.1
<0.1
0.2
2.9
0.3
0.2
«J.l
<0.1
0.1
4.1
1.5
0.7
0.4
0.2
0.4
1.3
4.6
1.9
1.0
0.3
0.2
0.7
1.5
4.5
1.3
0.6
0.2
<0.1
0.4
1.1
2°4
(mg/1)
12.3
1.2
0.5
0.8
1.1
2.7
14.8
4.4
1.8
1.0
1.7
1.7
3.4
8.8
2.3
0.6
0.2
0.2
0.6
8.8
1.7
0.5
0.2
0.2
0.3
12.7
4.6
2.3
1.2
0.6
1.3
4.0
14.0
5.8
3.0
1.0
0.6
2.1
4.5
13.7
4.3
1.8
0.7
0.2
1.1
3.3
Carbon TOD
Temp DO NVOC SNVOC Whole Filt.
( C) (mg/1) (mg/1 c)(mg/l c) (mg/1 OD) (mg/1 OD)
24.0 0.3 - - -
25.0 2.2 - -
27.0 2.0 - - - -
29.5 4.4 - - - -
- - - 24.0 24.0
-
24.0 0.3 - -
25.0 3.8 - - - -
26,5 3.9 -
28.5 4.2 - - - -
27.5 4.2 - - - -
20.0 19.0 22.0 16.0
-
24.0 0.7 - -
25.0 4.1 - - - -
26.0 4.1 - -
- - - - 28.0 28.0
-
24.0 0.9 - - - -
25.5 4.1 -
26.0 4.1 - - - -
42.0 32.0
.
25.0 0.7 - -
26.0 3.9 - - - -
26.0 5.6 - - - -
27.5 4.5 - -
27.0 4.2 - -
21.0 21.0 16.0 16.0
-
25.0 0.3 - - - -
26.0 3.1 - - - -
26.0 3.9 - -
27.0 4.2 - - - -
27.0 3.9 - - - -
32.0 32.0 20.0 16.0
-
25.0 0.3 - -
26.0 2.2 - - - -
26.0 3.9 - -
27.0 4.2 - - - -
27.0 3.5 - - - -
-
_ - -
Total Plate
Count
(Count /ml)
4.1 x 105
-
2.4 x 105
-
-
-
5.6 x 105
-
7.1 x 105
-
3.7 x 105
-
-
1.9 x 106
-
6.8 x 10
-
-
5.1 x 105
~ c
6.0 x 10
-
-
6.6 x 105
5
7.4 x 103
A
1.0 x 10
-
-
-
-
-
-
-
-
5.4 x 106
- ,
2.9 x 10
fi
4.5 x 10
-
-
jVBefore metals addition.
2/After metals addition.
-------
27
C/5
o
X
Q.
I
O
I-
tr
o
1/2 P04 Load
Control
Fe+2
AI+3
I70mg/l T-Hard
85mg/l T-Hard
Control
TIME, Mrs.
FIGURE 8-CHEMICAL ADDITION
-------
28
theoretical value based on phosphate content of the jug components.
The increase was attributed to release from the return sludge used in
jug synthesis. Jugs No. 2 and 7 were used as controls.
After three hours aeration, Jugs No. 1, 2, and 7 showed
greater than 90 percent soluble phosphorus removal. Jug No. 1 showed
90 percent removal within the first hour of aeration.
Jugs No. 5 and 6, synthesized with primary effluent deionized
with respect to cations, contained less total hardness than was normal
for raw waste (290 mg/1 CaCO^). These jugs, one with 170 mg/1 hardness
and the other with 85 mg/1, removed over 90 percent of the soluble
phosphorus within 3 hours aeration. There was, however, no significant
difference in phosphate removal between these and the control jugs.
4-9 +3
Jugs No. 3 and 4 contained 25 mg/1 Fe and Al , respectively.
Each removed essentially 100 percent of the soluble phosphorus within
one hour of metals addition. Apparently, the removal was by chemical
precipitation before aeration commenced.
This experiment demonstrated that the hardness range studied
had no effect on phosphate removal. The effect of decreased phosphate
load on percent removal was not discernible, partly because initial
phosphate concentrations were higher than anticipated. Addition of
iron and aluminum salts brought about immediate reduction and
essentially complete removal of soluble phosphorus within one hour.
4. Orthophosphate Variation
A set of jugs was prepared on July 27, 1967, to determine the
effect of phosphate loading on orthophosphate removal. Jug No. 1
contained half the primary effluent of the control jugs. Phosphate-
free city water served to dilute this jug to volume. Control Jugs
No. 3 through 5 contained phosphate concentrations typical of the
primary effluent. Samples from these jugs were composited since
their constituents were identical. Jug No. 2 contained twice the
normal phosphate load. Solids concentrations in all jugs were about
3,200 mg/1 TSS. Jug constituents are seen in Table 3, and experimental
results are found in Table 7.
Jug performances are seen in Figure 9. After three hours
aeration, the jug having low phosphate concentration showed 82 percent
removal, the control jugs 73 percent, and the jug with high phosphate
concentration 50 percent removal. The data show that phosphate
loading increases the magnitude of removal but decreases the percent
removal under these test conditions.
-------
P-i C
cd o
o
H
O
m v£>
O O
rH rH
K I X
in rH
in co
in i-H C
0) ~
cu 4J r^
i 1 Cfl CN
9 -^ *.
cfl CX >,
J 0
D rH
> -«. 1 1 1 1 m l 1
3 00 rH
0 s5
o
J O
D i-H
> ~s. i i i l m l l
Z 00 iH
1
|
1 1
1 1
O
in
rH
0
o
CN
l
l
0
m l
rH
1 1
1
|
o
sr
rH
|
1
0
m
i i
^^ co|co|co|
rH CN rH
/^N
rH rH v£) ST CN 00
2 ~* 1 1
^ 00 sf \D xD \O CN
E
^^
xj m m m o o
r^.
m
in
HcflrH cut) rHrHi-HCO 1 |i-HrH
0 3 E
CX
0
4-1
)H
O
C
c
o
^2
4J
J-J
o
c
c.
L
t
t
H| CM CM CM CM CM
sTi i o co in in rH ^o co
3|~
l-i 00 OOCNrHi 1 i-H srm
,5 CM
^-^
i i oo oo m LA <» info
""i*. *
L<00 CNOOO O rHOO
£
/ s.
0 rH O CN O
n -^ in VD
H 00 rH 1 | | 1 CM
E co co
^-^
!J ESEE B BE
3 COcflCXCX CX CXCO
H
H inininm in mm
rH rH rH rH Sf Sf rH
O i-l CM rH rH rH O
CM
o>
sr
rH
CM
LO
|
§
m
rH
rH
co r*~
\o m
m m
rH CM
CM CM
r- in
sr CM
rH rH
00 rH
sr sr
l i
e E
m m
rH rH
..
CN rH
|
|
OO
CO
rH
in
sf
CM
CX
m
sf
it
l
l
co
m
rH
O
m
l
E
CX
m
sf
rH
0 0
-H -H
CO i-H
CO vD
CMl
6 o
rH rH
CM CN
m o
CM m
rH
rH ^£>
ST rH
m
rH
CO 1
CO
cfl CO
in in
rH rH
0 rH
0
-H
co
vO
in
rH
CN
o
sr
CO
rH
1
§.
m
rH
CN
^
"3" 1
i-H
VO
m
CM
CM
CO
CO
rH
rH
1
e
CX
in
rH
1 I
l
l m
-a
c
cfl
fl
sr
0
co
sr
m en
oo
0 3
ro (0
c
rH -H
sr
cu
*« P
co co
en
CO
00 C
3 co
1 UH co
O cu
}_i
CU 3
4-1 4-1
H CO
E en »H
cx o cu
Oj O-i
m 6E
sr o cu
OH
rH «-^ -~^
m
T3
pj
CO
n
sr
^
CO
co
00
3
>->
UH
O
O
R
cu
00
cfl
fr 0
Q)
>
<
CO
00
1-3
MH
O
CU
rJ
3
00
H
MH
0
R
|csl|co|-3-|
CU
rH
o
B
cfl
u.
rH
M
3
*~>
a
cu
rH
4-1
4-1
CU
C/3
4J
Cfl
4-1
Cfl
13
cu
CX
3
a
cu cu
rH 00
4J TJ
(UrH
C/5C/3
CM
00
3
a
0)
rH
4-1
4J
01
C/)
4-1
13
cfl
4J
Cfl
C
cu
a
3
C/3
T3
cu cu
rH 00
4J T3
4J 3
CU rH
CO W
in
sr
*
co
00
3
rrj
CU
i-H
4-1
4-1
CU
C/3
4J
Cfl
4J
Cfl
C
VJ
CU
CX
3
-------
30
o>
E
UJ
X
o.
CO
o
I
Q.
I
O
I
8
ESTIMATED
ORTHO-P
JUG (% of PE)
I 50
2 100
3,4,5 200
I 2
TIME, Mrs.
FIGURE 9 - ORTHOPHOSPHATE VARIATION
-------
31
Sewage Characterization
A related purpose of the amenability program was to characterize
samples collected at low and high flow from the various unit processes
of activated sludge plants with regard to selected chemical paremeters.
Additional samples from an aeration jug study were included in the
characterization scheme. These samples were taken from a jug study
whose operation and constituents were those which resulted in
maximum phosphate removal. Primarily, the intention was to search
for trends or correlatable functions within or between various
chemical parameters which would be useful in defining the phosphate
removal process. Frequently, phosphate removal realized from jug
aeration was higher than that occurring in the aeration tanks.
During such instances the probability of identifying gross differences
of possible significance was greatly enhanced.
The samples were analyzed with and without solids to differentiate
between the quantity of each respective chemical parameter associated
with the solids and that associated with the liquid. Solids separation
was accomplished by first decanting, then subjecting the resulting
supernatant to further solids removal using a Sharpies Ultra centrifuge.
Samples resulting from such treatment are referred to as centrates of
the original sample.
The significance of the results will not be discussed in this
report since the basic purpose was for comparison with similar data
from other plants studied. A separate report has been prepared-^/
Microbiological Studies
Microbiological studies conducted in conjunction with chemical
and physical measurements were divided into two phases. Phase one
consisted of bacterial isolation by the membrane filter technique and
enumeration as total plate count. By this method, correlation was
sought between bacterial population and both phosphate removal and
mixed liquor suspended solids. The second phase involved selection
of predominate colonial types isolated in phase one, transfer of the
same to agar slants, and shipment to the Ada laboratory for identi-
fication. The final portion of this phase is under way. Results of
the Pontiac study and all other amenability studies are reported under
separate cover.-'
Data from the plate count determinations are recorded in Tables 2
and 4 through 7. There is no apparent relationship between total
suspended solids concentrations and bacterial counts. Microbial
-------
32
populations remain essentially constant throughout the aeration tanks.
In Jug Experiment No. 1 dealing with mixed liquor solids variation,
total plate count increased with increasing solids and increasing time
of aeration. Subsequent jug experiments revealed no trends in
bacterial populations during the runs. From these data, it was
concluded that bacterial counts and phosphate removal, if related,
were not demonstrated by these measurement techniques.
-------
33
SUMMARY
Studies at the East Boulevard Sewage Treatment Plant, Pontiac,
Michigan, from July 21 through 29, 1967, showed inconsistent ortho-
phosphate removals averaging 5 percent from aeration tank influents
to final effluents.
Aeration tanks have a length to width ratio of 18:1 and employ
tapered aeration. Dissolved oxygen concentrations average less than
1.0 mg/1 in the activated sludge process. BOD loading was 6 Ibs. BOD/
100 Ibs. MLSS/day. Mixed liquor suspended solids concentrations
average 2,000 mg/1. Dye tracer studies point to short circuiting
in the aeration tanks and final clarifiers. Modal detention times
of about four hours for the aeration tanks were 60 percent of the
theoretical. The dispersion index (t_ /t.. ) was 2.5.
The effects of MLSS, phosphate, iron, and aluminum concentrations
on phosphate removal were determined by pilot studies using aerated
jugs. The optimum MLSS for satisfactory removal was 5,000 to 6,000 mg/1
TSS. In considering MLSS versus phosphate removal, a figure of 3,500 mg/1
TSS is practical for reasons of return sludge pumping capacity. Near
this suspended solids level, variations in BOD and hardness caused
little or no increase in percent phosphate removed. At the same concen-
tration of suspended solids, increased levels of initial soluble
phosphate effect a greater milligram uptake while decreasing the
percent phosphorus removed. Addition of metals (aluminum and iron
salts) brought about nearly complete removal of soluble phosphorus.
With sufficient dissolved oxygen concentrations in the mixed
liquor, pilot studies pointed to mixed liquor suspended solids con-
centration as the significant factor limiting the amenability of
Pontiac waste and sludge to satisfactory phosphate removal.
-------
CONCLUSIONS
1. Plant removal of soluble phosphorus was limited to the level
considered necessary for metabolic requirements.
2. Soluble phosphorus removal showed wide fluctuation within the
aeration tanks during the study period as a result of present operation.
3. Displacement times within the aeration tanks are satisfactory
for high orthophosphate removal based on observations at other plants.
4. Low levels of mixed liquor dissolved oxygen, when considered
in light of a sufficient air supply and a low primary effluent BOD
concentration, point to inefficient air transfer which may require
modification if high orthophosphate uptake is to be obtained.
5. Pontiac waste and sludge demonstrated 30 to 90 percent ortho-
phosphate removal in pilot studies at optimum MLSS concentrations.
6. Orthophosphate removal increased with increasing concentrations
of total suspended solids.
7. Orthophosphate removal is independent of hardness concentrations
within the range studied.
8. Within the range studied, increasing orthophosphate in the
mixed liquor results in a greater quantity of phosphate removed and
a decreased percentage uptake.
9. With adequate suspended solids concentrations in the system
and a surplus of air supplied, increasing BOD concentrations in the
mixed liquor increases phosphorus removal, but not significantly.
10. High phosphate removal resulting from metal ion addition to , ~ ,
the mixed liquor concurred with results from studies at other plants.*
-------
35
RECOMMENDATIONS
This plant is recommended for use as a research demonstration
plant, provided:
1. The concentrations of mixed liquor suspended solids are
adjusted, and at least 2 mg/1 dissolved oxygen is established by
remedying the air transfer system. Both changes should coincide
with controlled flow and detention.
2. The effects on phosphorus removal of recycling waste
activated sludge and digester supernatant to the main flow, thereby
designing an effective treatment for handling recycle streams, should
be considered in the demonstration.
3. The demonstration should cover a 12-month period to evaluate
seasonal temperature influences.
-------
36
APPENDIX
ANALYTICAL PROCEDURES
Sample Preparation
Samples collected for analyses in the field were processed as
outlined in the respective analytical test procedures.
Samples sent to the Robert S. Kerr Water Research Center are
referred to as whole, centrate, whole fixed, and centrate fixed.
The following table lists the treatment each type received
preceding shipment to Ada.
Sample Treatment
1. Whole Shipped as is with no treatment.
2. Whole fixed Shipped as is plus 1 ml cone, sulfuric
acid per liter.
3. Centrate The sample was passed through a
Sharpies motor driven, laboratory
model continuous centrifuge, equipped
with a clarifier bowl, at 23,000 rpm.
The sample was delivered to the
centrifuge by a peristaltic pump
at a feed rate of 150 ml/min. The
bowl was cleaned and rinsed with
distilled water after each sample.
4. Centrate fixed The centrate sample plus 1 ml cone.
sulfuric acid per liter.
All samples were shipped in either 250 ml plastic bottles or
1,000 ml cubetainers. *
*Hedwin Corporation, 1600 Roland Heights Avenue, Baltimore, Maryland 21211.
-------
37
Chemical Tests
1. Orthophosphate
In the field, initial samples for orthophosphate were
filtered immediately using Schleicher and Schuell No. 588 paper.
Subsequent handling by the stannous chloride procedure in Standard
Methods^/ included the use of a spectrophotometer (Bausch and Lomb
Spectronic 20) at 690 my.
A continuous automatic sampling device, built specifically
to support jug-study phosphate analyses, supplied whole samples to a
Technicon AutoAnalyzer platformed after Gales and Julian.-' The
manifold and reagents were modified to more closely approximate
Standard Methods.5/ The arrangement, in order of sequence, was as
follows:
a. A six-port peristaltic pump circulating jug mixed
liquor continuously.
b. An open-shut solenoid valve regulating flow from a
T-connection in each circulating jug line.
c. A stepping relay alternately activating one of six
jug sample solenoids and one solenoid to a distilled water supply.
d. A master timer regulating the stepping relay over
two-minute intervals.
e. A Technicon proportioning pump providing the flow of
samples and distilled water to a Technicon continuous filter. This
pump also diluted filtered samples with distilled water in the ratio
of 1:40, respectively.
No significant orthophosphate. bleedback occurred in unfiltered
samples over a 30-minute period. Whole plant samples were run on the
Technicon AutoAnalyzer using a Technicon Sampler II and continuous
filter with samples reaching the filter within 30 minutes.
2. Total Phosphate
Fixed whole samples were analyzed at the Ada laboratory
within 15 days of sample collection. Initially whole samples were
blended for 3 to 5 minutes in a Waring Blendor and then analyzed
by the persulfate procedure of Gales and Julian.-' The procedure
was modified to more closely approximate the procedure of Standard
-------
38
Methods- for orthophosphate in that the samples were neutralized after
digestion. Also the manifold design and reagents for the AutoAnalyzer
were adjusted to deliver approximately the amount of reagents per sample
outlined by Standard Methods.-*'
3. Carbon
Instrumentation and procedure for carbon analysis in the field
followed that of Van Hall et al.12-' Preliminary homogenization in a
Waring Blendor provided representative syringe sampling of whole samples.
Two acidified and purged aliquots of each sample were injected into the
Beckman Carbonaceous Analyzera whole homogenate and an homogenized
filtrate.* Both results are nonvolatile organic carbon (NVOC). Whereas
carbon figures for a S&S No. 588 filtrate and a 0.45 y Millipore filtrate
do not differ significantly, the carbon value for the S&S filtrate was
reported as soluble nonvolatile organic carbon (SNVOC). Acetic acid
standards provided instrument calibration.
4. Total Oxygen Demand
97
Samples were run by the method of Stenger and Van Hall- using
the instrument and techniques described therein. Analysis of whole
samples included preliminary homogenization. A homogenized portion
of each sample received S&S No. 588 filtration before TOD analysis
and was reported as "filtered TOD." Sodium acetate standards were
used.
5. Total Hardness
In the field, hardness was performed by EDTA titrimetry
according to Standard Methods^-/ (Method B, pages 147-152).
Physical Tests
1. Solids
Tests for total suspended and total volatile suspended solids
were conducted according to Standard Methods^/ (Methods C and D, pages
424-425). Reeve Angel 2.4 cm glass fiber filters, grade 934AH, were
used in lieu of asbestos mats. Gooch crucibles were fired at 600°C,
cooled, the filter mats placed in the crucibles and dried at 103°C for
at least 1 hour before initial weighing. At intervals crucibles with
*Schleicher and Schuell filter paper, No. 588.
-------
39
filters were subjected to 600 C furnace temperatures to check for
weight loss due to the filter. Total and total volatile solids
were determined according to Standard Methods5-/ (Methods A and B,
pages 423-424).
2. Dissolved Oxygen
Measurements were made in situ with a YSI Model 51 oxygen
meter equipped with a Model 5103 oxygen/temperature probe. The
meter was calibrated against the Azide Modification of the Winkler
Method described in Standard Methods5-/ (Method A, pages 406-410).
The meter was also calibrated against saturated air at the temperature
of the test medium.
3. Hydrogen Ion Concentration
All pH measurements were made using a line current Beckman
Zeromatic II equipped with a glass/calomel electrode system. Meas-
urements were made on whole-untreated samples.
4. Temperature
Temperature measurements were made with a battery powered
thermistor-thermometer.
5. Specific Conductance
Whole samples were measured using an Industrial Instruments
Model RC 16B2 wheatstone bridge with cathode ray null indicator
equipped with platinum electrode (cell constant 1). Resistance
measurements at a constant temperature for both samples and a KC1
standard gave specific conductances in ymhos/cm by calculation.
Mention of products and manufacturers is for identification only
and does not imply endorsement by the Federal Water Pollution
Control Administration or the U. S. Department of the Interior.
-------
40
REFERENCES
1. Priesing, C. P. et al., "Phosphate Removal by Activated Sludge
Plant Research," Presented October 11, 1967, New York Water Pollution
Control Federation Meeting, New York, USDI, FWPCA, Robert S. Kerr
Water Research Center, Ada, Oklahoma.
2. Scalf, M. R. et al., "Phosphate Removal by Activated Sludge,
Amenability Studies at Baltimore, Maryland," Internal Report,
USDI, FWPCA, Robert S. Kerr Water Research Center, Ada, Oklahoma.
1968.
3. Lively, L. D. et al., "Phosphate Removal by Activated Sludge,
Waste Characterization," Internal Report, USDI, FWPCA, Robert S.
Kerr Water Research Center, Ada, Oklahoma. 1968.
4. Moyer, J. E. et al., "Survey of Activated Sludge Treatment Plants
for Predominant Bacterial Types," Internal Report, USDI, FWPCA,
Robert S. Kerr Water Research Center, Ada, Oklahoma. 1968.
5. Standard Methods for the Examination of Water and Wastewater,
12th Edition. 1965.
6. Gales, M. E. and Julian, E. C., "Determination of Inorganic
Phosphate or Total Phosphate in Water by Automatic Analysis."
Presented at the 1966 Technicon Symposium on Automation in
Analytical Chemistry.
7. Van Hall, C. E. et al., "Rapid Combusion Method for the
Determination of Organic Substances in Aqueous Solutions,"
Analytical Chemistry 35:3, 315. 1963.
8. Van Hall, C. E. et al., "Elimination of Carbonates from Aqueous
Solutions Prior to Organic Carbon Determination," Analytical
Chemistry 37:6, 769. 1965.
9. Stenger, V. A. and Van Hall, C. E., "Rapid Method for
Determination of Chemical Oxygen Demand," Analytical
Chemistry 39:2, 207. 1967.
-------
41
ACKNOWLEDGEMENT
Gratitude is expressed for the generous participation of many
individuals which contributed to this study. The field work was
made possible by the cooperation of the city of Pontiac, Michigan.
Special recognition is given to Mr. John Hennessey, Plant Superin-
tendent. Staff members of the Robert S. Kerr Water Research Center
are acknowledged as follows: Messrs. M. L. Cook and J. F. McNabb
for analytical support in the field; Messrs. R. L. Cosby, K. F.
Jackson, and B. D. Newport for analytical support at the Center;
and Mr. Tommy Redman for drawing of the figures.
-------
42
GLOSSARY
AT Aeration Tank
BOD Five-Day Biochemical Oxygen Demand
Comp. Composite
DO Dissolved Oxygen
FE Final Effluent
ft. Cubic Feet
gal. Gallon(s)
gpm Gallons Per Minute
1 Liter(s)
mg Million Gallons
mgd Million Gallons Per Day
mg/1 Milligrams Per Liter
min. Minutes
ml Milliliter(s)
ML Mixed Liquor
MLSS Mixed Liquor Suspended Solids
my Millimicrons
mv Millivolt(s)
NVOC Nonvolatile Organic Carbon (Whole Sample)
PE Primary Effluent
ppb Parts Per Billion = Micrograms Per Liter
psi Pounds Per Square Inch
-------
43
rpm Revolutions Per Minute
RS Return Sludge
SNVOC Soluble Nonvolatile Organic Carbon (Filtered Sample)
TOD Total Oxygen Demand
TS Total Solids (Dissolved Plus Suspended)
TSS Total Suspended Solids
------- |