TECHNICAL ASSISTANCE PROJECT
AT THE
ST. ANDREI'S WASTEWATER TREATMENT PLANTS
ST. ANDREWS, SOUTH CAROLINA
ENVIRONMENTAL PROTECTION AGENCY
SURVEILLANCE AND ANALYSIS DIVISION
ATHENS, GEORGIA
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EPA 904/9-77-033
TECHNICAL ASSISTANCE PROJECT
AT THE
ST. ANDREWS WASTEWATER TREATMENT PLANTS
ST. ANDREWS, SOUTH CAROLINA
W-v"\ ปv ฆ
, .... . .. -j.
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TABLE OF CONTENTS
Introduction
Summary
Recommendations
Pierpont Wastewater Treatment Plant
Treatment Facility
Personnel
Study Results and Observations
Flew
Waste Characteristics and Removal Efficiencies
Aeration Basins
Clarifiers
Chlorination
Aerobic Digester
Laboratory
Savage Road Wastewater Treatment Plant
Treatment Facility
Personnel
Study Results and Observations
Flow .....
Waste Characteristics and Removal Efficiencies
Aeration Basins
Clarifiers
Chlorination
Sludge Handling
preferences
1
3
4
6
6
6
6
6
9
10
13
14
14
16
18
18
18
18
18
18
21
23
24
24
27
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Appendices
A. Laboratory Data
B. Aeration Basins Dissolved Oxygen
C. General Study Methods
D. Project Personnel
E. Oxygen Uptake Procedure
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LIST OF TABLES
I. Design Data. . . . 8
II. Waste Characteristics and Removal Efficiencies - Pierpont WTP. ... 9
HI. Activated Sludge Operational Parameters - Pierpont WTP 10
IV. Secondary Clarifier Operational Parameters - Pierpont WTP 13
V. Depth of Sludge Blanket 13
"I. Waste Characteristics and Removal Efficiencies - Savage Road WTP . . 20
VII. Activated Sludge Operational Parameters - Savage Road WTP 21
'.'III. Secondary Clarifier Operational Parameters - Savage Road WTP .... 29
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LIST OF FIGURES
1. Pierpont WTP 7
2. Activated Sludge Settleability - Pierpont WTP 12
3. Clarifier Dye Study - Pierpont WTP 15
4. Savage Road WTP 19
5. Activated Sludge Settleability - Savage Road WTP 22
6. Clarifier Dye Study - Savage Road WTP 25
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INTRODUCTION
A technical assistance study of operation and maintenance problems at the
Pierpont and Savage Road Wastewater Treatment Plants, St. Andrews, South Carolina
was conducted July 25 through 29, 1977 by the Region IV, Surveillance and Analysis
Division, U. 3. Environmental Protection Agency. Operation and maintenance tech-
nical assistance studies are designed to assist wastewater treatment plant personnel
in maximizing treatment efficiencies, as well as assisting with special operational
problems.
The selection of these plants was based on a request from the South Carolina
Department of Health and Environmental Control (SC-DHEC). The study was coordinated
with the US-EPA Enforcement and Water Divisions and the SC-DHEC. The specific study
objectives were:
(1) To optimize treatment through control testing and recommended operation
and maintenance modifications;
(2) To introduce and instruct plant personnel in new operation control
techniques;
(3) To determine influent and effluent wastewater characteristics;
(4) To assist laboratory personnel with any possible laboratory procedure
problems; and
(5) To compare design and current loading data.
A follow-up assessment of plant operation and maintenance practices will be
accomplished through utilization of data generated by plant personnel. If necessary,
subsequent visits to the facility will be made. The followup assessment will
determine if recommendations were successful in improving plant operations and if
further assistance is required.
1
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The cooperation of the South Carolina Department of Health and
Environmental Control is gratefully acknowledged. The technical assistance
team is also especially appreciative for the cooperation and assistance
received from personnel of St. Andrews Public Service District.
2
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SUMMARY
The Pierpont and Savage Road Wastewater Treatment Plants (WTPs) were designed
as 1.5 mgd activated sludge facilities. During the study the average flows at
the two plants were 0.56 mgd and 0.8 mgd, respectively. The average BOD^ and T3S
removal efficiencies were 90 and 83 percent at the Pierpont WTP, and 90 and 86
percent at the Savage Road OTP.
Major observations made during the study are:
1. The food to microorganism ratio was much too low at both plants. This
condition resulted from excessive solids being retained in the system
and low hydraulic and organic loadings.
2. The average effluent quality of the Pierpont WTP was BOD,- - 16 mg/1 and
TSS - 30 mg/1. The Savage Road WTP average effluent quality was B0D5 -
15 mg/1 and TSS - 49 mg/1. The effluent at Pierpont met NPDES permit
limits. The effluent TSS concentration at the Savage Road facility slightly
exceeded the 45 mg/1 permit limit.
3. Both plants had a highly nitrified effluent.
4. Dissolved oxygen concentrations in the aeration basins were below good
operational levels.
5. Large quantities of solids were being lost over the final clarifier
effluent weir.
6. There was a thick floating mat of solids on the surface of the clarifiers
and chlorine contact chamber.
7. There was no means of measuring return sludge and waste sludge rates.
8. Effluent flow measuring and recording equipment had been out of order
for some time and were being repaired.
9. Plants were attended for only one eight hour period each day and One half
day per weekend.
3
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RECOMMENDATIONS
FIERPONT AND SAVAGE ROAD WASTEWATER TREATMENT PLANTS
Based on observations and data collected during the study, it is recommended
that the following measures be taken to improve wastewater treatment plant opera-
tions. Trend charts and operational testing will assist in determining optimum
control.
1. A regular sludge wasting schedule should be established. Increased
sludge wasting would eliminate the major problem of too many solids.
2. The food to microorganism ratio (F/M) should be maintained consistently
within the range of 0.2 to 0.4. At the present organic loadings the
MLVSS concentration should be gradually lowered to approximately 1,000
to 1,500 mg/1. Along with the lower MLVSS the F/M should be monitored
and adjusted as required.
3. The air flow rate to the air lift pump on the sludge thickener should
be adjusted so that a continuous sludge wasting schedule can be- maintained.
4. The dissolved oxygen (DO) concentrations in the contact and stabilization
tanks should be monitored and maintained at 1.0 to 2.0 mg/1. The maintenance
of solids at 1,000 - 1,500 mg/1 should reduce the oxygen demand and assist
in increasing DO.
5. Settlometer test as well as TSS and VSS should be run on the aeration tank
effluent. Waste sludge and return sludge should also be analyzed for TSS
and VSS.
6. The back titration procedure given in Standard Methods should be used by
plant personnel for residual chlorine determination.
7. Data from recommendations 5 through 7 should be incorporated into trend
charts. Trend charts should be plotted and posted in order to assess
responses to operation changes. Suggested trend chart parameters are
4
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F/M, clarifier effluent turbidity, return sludge flo'.', waste sludge
flow, plant effluent flow, sludge blanket depth, settlometer, (especially
the 5 and 60 minute reading), return sludge concentrations, settled
sludge concentration, aeration basin dissolved oxygen, !"TLSS, as well as
influent and effluent BOD^, TSS, and COD.
S. Consideration should be given to increasing the number of hours per day
that the plants are manned.
5
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PIERPONT WASTEWATER TREATMENT PLANT
TREATMENT FACILITY
A diagram of the 1.5 mgd Pierpont WTP is presented in Figure 1 and
design data are listed in Table 1. The influent wastewater is primarily from
domestic sources.
Pre-aerated return sludge was mixed with raw wastewater in the aeration
basin. Solids were separated in the final clarifiers and the clarified effluent
was chlorinated and discharged to the receiving stream. Waste solids were condi-
tioned in the aerobic digester, dewatered on sand drying beds and hauled to a
landfill for disposal. Air was supplied by three 60 HP compressors and distributed
by diffusers located along one wall of each basin.
PERSONNEL
Both the Pierpont and Savage WTPs are manned for an eight hour period five
days per week and four hours on Saturdays and/or Sundays. Staffing at the
facilities consisted of a class-B superintendant, one class-B operator, one
class-C operator, one class-D operator and one operator trainee. The staff
is divided between the two facilities. Another individual who has a class-D
certificate performs maintenance and substitutes in the laboratory, which serves
both plants.
STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and general study methods are
presented in the Appendices." Significant results and observations made during
the study are discussed in the following sections.
Flow
Plant flow was measured by a Sparling propeller flow meter located at the
effluent end of the chlorine contact chamber. The meter was coupled to a recorder
6
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FIGURE "I
Pierpont WTP
St. Andrews PSD
EFFLUENT ^
CHLORINATION
RETURN
SLUDGE
PUMPS
COMMINUTOR a
RAW SEWAGE LIFT
SLUDGE TO
DRYING BED
Sampling Stations
7
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TABLE I
DESIGN DATA
FLOW MEASUREMENT
Design Flow
Effluent
Return Sludge
Waste Sludge
AERATION BASIN
Dimensions
Volume
Aeration
RE-AERATION BASIN
Dimensions
Volume
Aeration
FINAL CLARIFIERS
Number
Dimensions
Total Surface Area
Total Volume
CHLORINE CONTACT CHAMBER
Dimensions
Volume
AEROBIC DIGESTER
1.5 mgd
Propeller flow meter
None
None
91 X 30 X 17 ft.
46,400 cu. ft. (0.35 m.gal.
Diffused Air
30 X 30 X 17 ft.
15,300 cu.ft. (0.11 m.gal.)
Diffused air
91 X 12 X 10.5 ft.
2,184 sq.ft.
22,932 cu.ft. (0.17 m.gal.)
5.5 X 80 X 10.5 ft.
4,620 cu.ft. (0.03 m.gal.)
Dimensions
Volume
Aeration
59.75 X 30 X 17 ft.
30,470 cu.ft. (0.23 m.gal.)
Diffused Air
PUMPS
Return Sludge
AERATION
2 - 7.5 hp variable speed
Compressors
DRYING BEDS
3 - 60 hp
Number
Dimensions
Total Area
80 X 35 ft,
8,400 sq.ft.
8
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and totalizer, however, the recorder was out of service for repairs during the
study. A Stevens stage recorder was installed by EPA personnel and used in
conjunction with the 5 foot rectangular weir at the effluent end of the chlorine
contact chamber. The average flow was 0.56 tagd and ranged from 0.12 to 0.81
mgd during the study.
Excessive inflow and infiltration is a problem during spring and summer wet
weather periods. Flows often reach 3 mgd with subsequent plant washout during
these periods.
Waste Characteristics and Removal Efficiencies
A chemical description of the WTP influent and effluent wastewaters with
calculated treatment reductions are presented in Table XI, Analyses were con-
ducted on 24-hour, flow proportional, composite samples; except for chlorine
residual and oil and grease, which were based on grab samples. The percent re-
ductions were calculated from the averaged results.
TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
PSD PIERPONT WTP
PARAMETER
INFLUENT
(mg/1)
EFFLUENT
(mg/1)
REDUCTION
%
BOD 5
COD
TOC
TS
TVS
TSS
VSS
TKN-N
NH3-N
N03-N02-N
Total Phosphorus
Lead
Chromium
Cadmium
Copper
Zinc
CI2 Residual*
Chlorides
Oil and Grease*
165
341
60
502
267
180
132
16
44
11
453
174
30
22
90
87
82
10
35
83
83
87
90
27
25
3.6
2.6
9.5
7.7
0.05
0.08
0.01
0.032
0.076
1.25
<0.01
9.7
<0.05
<0.08
<0.01
0,082
0.120
61
37
21
96.4
4.0
134
*Analysis conducted on grab samples.
9
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The average influent BOD5 (165 mg/1), and TSS (180 mg/1) concentrations are
indicative of a medium strength domestic waste (5). The average effluent BOD^
(16 mg/1) and TSS (30 mg/1) concentrations met the NPDES weekly limitations of
36 and 45 mg/1, respectively. The wastewater treatment process was attaining
a high degree (90 percent) of nitrification.
The conditions within the WTP were conducive to nitrification as indicated
by the change in the nitrogen concentrations. The TKN-N and NH^-N concentrations
were reduced by 87 and 90 percent, respectively, while the NO2-NO3-N concentrations
increased from <0.01 in the influent to 9.5 mg/1 in the effluent. Nitrification
was probably the cause of the dH change from the influent to the effluent of
7.0 to 5.8 since 7.15 mg of alkalinity as CaC03 is destroyed per mg of ammonia
nitrogen oxidized (9).
Aeration Basins
Grab samples were collected daily from the aeration basin and analyzed for
TSS, VSS and percent solids as determined by the centrifuge. Settleability of
the activated sludge was determined -by the settlometer. Presented in Table III
are various activated sludge operational parameters based on data collected during
the study and the corresponding recommended values for the conventional activated
sludge process.
TABLE III
ACTIVATED SLUDGE OPERATIONAL PARAMETERS
PIERPONT OTP
Measured Recommended(2)(5)(7)
MLSS (mg/1) 9,800 1,000 - 4,500
MLVSS (mg/1) 4,500
Lbs BODr/day/lb MLVSS (F/M) 0.03 0.2 - 0.4
Lbs COD/day/lb MLVSS 0.07 0.5 - 1.0
Lbs BOD/day/1,000 cu.ft. aeration basin 12.5 20 - 40
Sludge Age 65 3.5 - 10
It is evident from the measured parameters (Table III) that there were too
many solids in the system. To maintain an F/M within the recommended limits, the
10
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MLVSS concentration should be maintained in the range of 1,000 to 1,500
mg/1 at the present BOD loading (165 mg/1).
Dissolved oxygen (D9) concentrations measured in the aeration and reaeration
basins are presented in Appendix B. The DO concentrations ranged from 0.3 - 1.4
m^/1 at the surface and 0.3 - 1.0 mg/1 at the five foot depth. It is recommended
that DO concentration for the activated sludge process be maintained in the 1-2
mg/1 range.
Activated sludge settleability was determined by the settlometer test. The
results are presented in Figure 2. Settling characteristics varied significantly,
however, the supernatant remained clear in all cases. Settling was hanraered by
excessive solids.
Activated sludge quality was determined by measuring the oxygen uptake rate
of the sludge by the procedure presented in Appendix C. The sludge activity
may be measured by mixing return activated sludge with influent (fed) and non-
chlorinated effluent (unfed) wastewater and determining the uptake rate-, from
which the load ratio (LR) may be calculated.
LR = ADO (mg/l/min) fed sludge
ADO (mg/l/min) unfed sludge
The LR reflects the conditions at the beginning and at the end of aeration.
Generally, a large LR signifies an abundant, acceptable feed under favorable
conditions. A small LR (<2) may mean dilute feed, sick sludge, poorly acceptable
feed, or other unfavorable conditions. Load ratios less than 1.0 indicates that
a wastewater constituent has shocked or poisoned the "bugs."
Assuming a 50 percent return sludge flow, the LR was determined to be 4.0.
A LR in the range of 2 to 5 indicates an acceptable sludge.
A microscopic examination of the WTP mixed liquor, return sludge, and scum
layer revealed an abundant growth of bacterial filaments. Filaments are normal
11
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100
90
80
70
60
50
40
30
20
10
FIGURE 2
Activated Sludge Settleability
Pierpont WTP
July 26
July 27
July 28
J i ป l I I I I I
5 10 15 20 25 30 40 50 60
TIME (MIN)
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inhabitants of wastewater treatment systems, but are generally found in low
concentrations. Heavy growth of these organisms may result from lov? DO, old
sludge, high mean cell residence time and/or nutrient imbalance.
The protozoan uopulaticn was limited to stationary or slow moving low energy
using ciliaties and rotifers. These organisms in combination are generally associated
with good stable sludges which give a low BOD5 effluent.
Clarifiers
Measured, designed and recommended operating parameters for secondary clarifiers
following the conventional activated sludge process are presented in Table IV.
TABLE IV
SECONDARY CLARIFIER OPERATIONAL PARAMETERS
PIERPONT WTP
Measured Designed Recommended(3)(4)(7)
Hydraulic Loading (gpd/sq.ft.) 256 687 400 - 800
Solids Loading (lbs/day/sq.ft.) 19 29 12 - 30
Hydraulic Detention Time (hrs.) 5* {1.3} 1.37 1-25
Weir Overflow Rate (gpd/lin.ft.) 2,300 5,210 <15,000
^Calculated as volume/flow assuming 50% return sludge flow.
{ } Measured by dye.
It can be seen from this information that the solids loading falls within
the recommended range while the hydraulic loading is only a fraction of design
loading.
Results of the clarifier dye study are presented in Figure 3. The hydraulic
detention time, determined as the centroid of the curve, was 76 minutes.
The depth of the sludge blanket below the clarifier water surface was measured
routinely. The results are shown in Table V.
TABLE V
DEPTH TO SLUDGE BLANKET
Date Clarifier
Julv 1977
Time
#1 (ft)
it 2 (1
26
10:30 a.m.
8.5
4-0
26
3:25 p.m.
9.5
4.5
27
10:00 a.m.
6.5
>7
27
4:30 p.m.
>7
7
28
8:10 a.m.
>7
>7
13
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These data indicate an uneven inflow into the clarifiers or an uneven return
sludge flow on July 26. This was corrected on the 27th and 28th by shifting more
flew into #1 clarifiar. There was no means available to measure the return sludge
flow.
Chlorinat ion
Effluent from the final clarifiers was disinfected in the chlorine contact
chamber (CGC). The hydraulic detention time was 77 minutes at the average flow
of 0.56 mgd.
On July 26 the effluent chlorine residual was 2.65 mg/1 based on the amper-
ometric back titration method as compared to 0.35 mg/1 measured by the orthotolidine
color comparator normally used at the WTP. Chlorine usage was reduced on July 27
and 28 and the subsequent average residual was 0.55 mg/1. Use of the amperometric
back titration method to measure chlorine residual could reduce chlorine usage,
resulting in a substantial monetary savings.
Aerobic Digester
Waste activated sludge was conditioned in the aerobic digester prior to
dewatering on the sludge drying beds. The average dissolved oxygen in the digester
was 6.6 mg/1 (Appendix B). The TSS and VSS concentrations were 19,717 and 8,417
mg/1, respectively, and the pH in the digester was 4.0.
Built into the digester is a small square compartment equipped with an air
lift pump. This compartment was designed to serve as a sludge thickener with the
pump utilized to deliver the thickened sludge back to the digester. Clear super-
natant should flow to the final clarifier, permitting space for continuous wasting
to the digester. The thickener has never worked, resulting in periodic wasting
of large amounts of sludge rather than wasting on a continuous basis. It appears
that excessive velocity in the thickener prevents proper settling of the sludge.
The velocity could probably be reduced by adjusting the air flow rate to the pump.
14
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FIGURE 3
Clarifier Dye Study
TIME (MIN)
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Laboratory
The laboratory for the St. Andrews PSD Pierpont and Savage Pvoad WTPs is
located in the main control building of the Pierpont WTP. The chief operator
for both WTPs conducts the routine analyses which include: BOD5, TSS, fecal
coliforrn, DO, chlorine residual, pH, and temperature. He also conducts the
control tests which are listed below. The laboratory appeared to be adequately
maintained.
While at the WTP various analytical procedures were discussed, however, the
following observations were specifically noted:
1. Although effluent BOD5 samples were collected before chlorination,
the dechlorination procedure was demonstrated, and the advantage of
collecting BGD5 samples after chlorination was discussed.
2. The DO meter was being standardized incorrectly, therefore, the winkler
standardization procedure was demonstrated.
3. The orthotolidine method was used in determining chlorine residual.
The determination of residual chlorine in samples containing organic
matter present special problems, therefore, Standard Methods (8)
recommends a back titration procedure for determining residual chlorine
in wastewater.
A quality control program (OC) is desirable in all laboratories. A good QC
program would include setting up duplicates on approximately 20 percent of the
samples, and analyzing standards, if available, approximately 10 percent of the
time. This would help the analyst in determining the precision and accuracy of
his data.
The in-plant control testing program included influent BOD5, and TSS; and
aeration basin TSS, VSS, SVI, and DO (surface). It was suggested that the
following tests also be included in their program: (1) settlometer instead of
the 1,000 ml graduated cylinder since the settlometer better represents clarlfier
16
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conditions; (2) clarifier sludge blanket depth; (3) aeration basin DO at
various depths and (4) centrifuge. The centrifuge tests give a quick indi-
cation as to the solids content in the aeration basin. It was further
suggested that trend charts be established and maintained. Useful parameters
for plotting include MLSS, sludge settleability, significant influent and
effluent waste characteristics, flow (plant, return sludge, waste sludge),
depth of clarifier sludge blanket, and F/M. Experience will dictate which
of these parameters are necessary for successful plant operation. These
suggested parameters should serve only as a guide and are intended to establish
trends so that gradual changes in plant conditions can be noticed prior to
deterioration in effluent quality.
17
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SAVAGE ROAD WASTEWATER TREAT'.EOT PLANT
TREAT! IE NT FACILITY
A diagram of the 1.5 mgd Savage Road WTP is presented in Figure 4. The
design data and unit processes are the same as that for the Pierpont WTP (Table
I).
PERSONNEL
See the discussion under Pierpont Section of the report.
STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and general study methods are
presented in the Appendices. Significant results and observations made during
the study are discussed in the following sections.
Flow
Plant flow was measured by a Sparling propeller flow meter located at the
effluent end of the chlorine contact chamber. The meter was coupled to a recorder
and totalizer, however, the recorder was out of service for repairs during the
study. A Stevens stage recorder was installed by EPA personnel and used in conjunction
with the 5 foot rectangular weir at the effluent end of the chlorine contact chamber.
The average flow was 0.80 mgd and ranged from about 0.3 to 1.1 mgd. There were no
metering or flow devices for measuring return sludge or waste sludge flows.
Waste Characteristics and Removal Efficiencies
Table VI presents a chemical description of the influent and effluent waste-
water streams with calculated treatment reductions. Removal efficiencies were
calculated using average data from three consecutive 24-hour, flow proportional,
composite samples except for chlorine residual and oil and grease, which were
based on grab samples. The percent reductions were calculated from the average
results.
18
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FIGURE 4
Savage Road WTP
St. Andrews PSD
CHLORINATION
EFFLUENT |
I
RETURN , I
SLUDGEL_n
PUMPS^ i |
INFLUENT
1
i
~
I
t
ฃ
ISE^IE
scv
SC2
CLARIFIER
SRS
(Sl
REAERATION
L
\
SAD SSN<^
AEROBIC DIGESTER
1
AERATION TANK
4 SI
-II iT'
SCB<
1
I
I
hM
I
I
I
I
I
I
\
r
OVERFLOW
~ I
|O
o
FORCE MAIN
I
*
t
COMMINUTOR 8
RAW SEWAGE LIFT
SLUDGE TO
DRYING BED
Sampling Stations
19
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TABLE VI
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
SAVAGE ROAD OTP
IMFLUEIIT EFFLUENT REDUCTION
PARAMETER (mg/1) (mg/l) %
BOD 155 15 90
COD 481 87 82
TS 1.A16 1,095 23
TVS 359 230 36
Xss 362 49 86
TVSS 216 28 87
TKN 24.5 4.3 82
NH o-N 22 3.8 83
N02_NO,-N <0.01 9.2
Chlorides 579 471 19
Total Phosphorus 9 12
Oil and Grease* 25
Chlorine Residual*
Turbidity (MTU's)* " 19
Lead <0.055 <0.05
<0.08 <0.08
Chromium
Copper
Cadmium
Zlnc 0.192 0.054 72
0.099 0.024 76
<0.01 <0.01
^Average results of grab samples taken on three different days.
During the study/the V7T? effluent exceeded the NPDES average weekly permit
limits for T3S. The average weekly NPDES limits for BOD5 and TSS are 45 mg/l.
As shown in Table VI the WTP was achieving high treatment efficiencies for
most permit parameters. The infiltration of salt water as evidenced by the high
chloride (579 mg/l) concentration in the influent accounted for approximately
41 percent of the TS concentration and 55 percent of the soluble TS fraction.
Thw WTP was attaining a high rate of nitrification. Organic nitrogen (NH3-N)
and TKN were significantly reduced within the activated sludge process by 83 and 82
percent, respectively. The increase in N02-N03~N of 9.2 mg/l was only 50 percent
of the 18 mg/l of NH3-N reduced, which indicates that the remaining 50 percent
was being assimilated within the process or was given off as nitrogen gas.
Inorganic nitrogen data show that denitrification was also being accomplished
at a significant rate. All metals concentrations were low.
20
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Aeration Basins
Grab samples were collected daily from the aeration basin and analyzed for
T3S, VSS and percent solids as determined by the centrifuge. Settleability of
the activated sludge was determined by the settlometer. Presented in Table VII
are various activated sludge operational parameters based on data collected
during the study and the corresponding recommended values for the conventional
activated sludge process.
TABLE VII
ACTIVATED SLUDGE OPERATIONAL PARAMETERS
SAVAGE ROAD OTP
Measured Recommended(2)(5)(7)
MLSS (mg/1) 8,700 1,000 - 4,500
MLVSS (mg/1) 4,300
Lbs B0D5/day/lb MLVSS (F/M) 0.06' 0.2-0.4
Lbs COD/day'/lb MLVSS 0.19 0.5-1.0
Lbs BOD5/day/l,000 cu.ft. aeration basin 16.76 20 - 40
Sludge Age (days) 18.0 3.5 - 10.0
These data demonstrate that the MLSS concentration was too high for the organic
waste load received. The sludge was too old. The volatile content of the mixed liquor
was also too low (49 percent) indicating an over-oxidized sludge and/or excessive
inert solids.
Dissolved oxygen concentrations measured in the aeration and reaeration basins
ranged from 0.0 to 0.45 mg/1 (Appendix C). These DO concentrations were too low for
satisfactory operation. The low DO concentrations are possibly the result of the
high suspended solids concentrations. The removal of the excessive solids from the
system should result in a corresponding increase in DO.
The unfed sludge activity was stable at 0.5 mg 02/l/min. The fed sludge activity
increased to an average uptake rate of 1.09 mg 02/l/min and the resultant, LR, was
2.10. Conventional activated sludge WTPs commonly operate within the LR range of
2 to 5.
21
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100
o5 90
w ~
s 80
Z>
O 70
>
LiJ 60
CD
|o O _
^ 3 50
_1
^ 40
Q
y 30
I
20
LlI
CO
10
FIGURE 5
Activated Sludge Settleability
Savage Road WTP
-ฉ
July 26
July 27
July 28
J I I I I I I I I
5 10 15 20 25 30 40 50 60
TIME (MIN)
-------
Activated sludge settleability was determined by the settlometer test.
The results ara presented in Figure 5. Observations and results of the
settlometer show that the sludge settled to a minimum volume within half an
hour. On one occasion the settled sludge started to rise during the second
half hour. On each day of testing the settled sludge rose to the surface
within 50-80 minutes. This demonstrates that sludge should not remain in
the final clarifier beyond 50 minutes.
A microscopic examination of MLSS, aeration basin foam, clarifier floating
scum and effluent suspended solids revealed an abundance of small filamentous
organism. Filaments are commonly found in many wastewater treatment systems,
but in very limited concentrations. An increase of these organisms may result
from low DO, high mean cell residence time, old sludge and/or a nutrient imbalance.
The predominant protozoan organisms in the activated sludge process were the low
energy requiring crawling dilates, rotifers and stalked ciliates. These organisms
in combination are generally associated with .a sludge rendering a good low BOD5
ef fluent.
Clarif ier
Observation of the final clarifiers included the presence of a thick floating
mat of solids on the first section of the clarifier, a continuous loss of fine
particulates over the weir from the intermediate sections and turbulance accompanied
by solids washout in the last section. On several occasions large clumps of solids
were observed rising to the surface and dispersing into smaller clumps ultimately
flowing over the effluent weir.
Measured designed and recommended operating parameters for the secondary
clarifiers are presented in Table VIII.
23
-------
TABLE VIII
SECONDARY CLARIFIES. OPERATIONAL PARAiMETERS
SAVAGE ROAD OTP
Measured
Designed Recommended(3) (4)(7)
Hydraulic Loading (gpd/sq.ft.)
Hydraulic Detention Time (hrs.)
Solids Loading (lbs/dav/sq.ft.)
Weir Overflow Rate (gpd/lin.ft.)
366
3.4* {0.72}
18
3,300
687
1.37
28.5
5,210
400 - 800
1 - 2.5
12 - 30
<15,000
* Calculated as volume/flow assuming 50^ return sludge.
{ } Measured by dye study.
The clarifiers were operating within recommended design criteria except for
the detention time as measured by the dye study.
Results of the dye study are presented in Figure 6. The detention time for
the dye through the clarifiers was 42 minutes. Dye sampling of the overflow from
the forward section of the clarifiers demonstrated a detention time of 43 minutes.
During the study average turbidity following final clarification were 19 NTU's.
After 60 minutes of settling the same samples measured 4 NTU's. These results
indicate some short-circuiting, which is a common condition in many clarifiers, and
that the solids would settle if provided adequate detention tine.
Chlorination
Effluent from the final clarifiers was disinfected in the chlorine contact
chamber (CCC) . The calculated hydraulic detention time was approximately 54 minutes
at the average flow of 0.80 mgd.
The chlorine residual during the study ranged from 0.15 to 1.5 mg/1, as measured
by the amperometric back titration procedure. The chlorine residual measured by
ฆJTP personnel using the orthotolidine color comparator was approximately one third
of the amperometric measurement. The use of the amperometric back titration method
to measure chlorine residual could reduce chlorine usage.
Sludge Handling
Waste activated sludge was conditioned in the aerobic digestor. The average
dissolved oxygen concentration in the digester was 6.3 mg/1 (Appendix B). The
24
-------
100 r
K>
Ui
FIGURE 6
Clarifier Dye Study
Savage Road WTP
Centroid-43 Min.
200 300 400
TIME (MIN)
500
600
-------
TSS and TVS3 concentrations were 12,000 and 4,000 mg/1, respectively, and the
pil in the digester was 4.6.
On July 1977 the digester content was settled and the supernatant was
drained to the clarifiers. The BOD5 and TSS concentrations for the supernatant
was 12 and 96 mg/1, respectively.
Digested sludge is dewatered on three sand filled drying beds. According
to OTP personnel sludge is wasted to the beds once or twice per month depending
on weather conditions. Solids from the activated sludge process are wasted to
the digester as space is available. This WTP has a sludge thickening unit iden-
tical to the one at the Pierpont WTP.
26
-------
1
2
3
4
5
6
7
8
9
10
11
12
13
14
REFERENCES
McKinney, R.oss E. and Gram, Andrew. "Protozoa and Activated Sludge,"
Sewage and Industrial Waste 28 (1956): 1219-1231.
US-EPA, Operation of Wastewater Treatment Plants, A Field Study Training
Program, Technical Training Grant No-5TTlWP1603, 1970.
US-EPA Technology Transfer, Process Design Manual fer Suspended Solids
Removal, January 1975.
American Society of Civil Engineers, Sewage Treatment Plant Design,
Manual of Engineering Practice No. 36, 1959.
Metcalf and Eddy, Inc., Wastewater Engineering, 1972.
West, Alfred W., Operational Control Procedures for the Activated Sludge
Process. Part I., Observations, EPA-330/9-74-001-a, April 1973.
Great Lakes - Upper Mississippi River Board of State Sanitary Enginers,
Recommended Standards for Sewage Works, Revised Edition, 1971.
American Public Health Association, Standard Methods for the Examination
of Water and Wastewater, 13th Edition, 1971.
US-EPA Technology Transfer, Process Design Manual for Upgrading Existing
Wastewater Treatment Plants, October 1974.
Black and Veatch, Estimating Costs and Manpower Requirements for Conventional
Wastewater Treatment Facilities, October 1974.
Homer W. Parker, Wastewater SySfeems Engineering. 1975.
From Script for slide tape XI-43, "Dissolved Oxygen Analysis - Activated
Sludge Control Testing," prepared by F. J. Ludzack, NWTL, Cincinnati.
Alfred W. West, Operational Control Procedures for the Activated Sludge
Process, Appendix, March 1974.
Steel, E. W. , Water Supply and Sewerage, Fourth Edition, 1960.
27
-------
APPENDIX A
LABORATORY DATA
-------
APPENDIX A
LABORATORY DATA"
ST. ANDREWS PSD PIERPONT AND SAVAGE ROAD WTPs
CHARLESTON, S. C,'
INFLUENT AND EFFLUENT
0 VM
s.i o
sr.it: c.v
H
7S-
j <5
c
O
iU
Q
>*
*/ฆ*/ฆ*/ฃ
/ & / . / ^ / . N
/
ป.*/ / / / / 7% / /
"t/&?/*/ s/f/ wUJ.
Hso i fir ! 7 | A.
77
! /5"3a
-
" r~\' - f j~j~r
-; i -
-
-
- 1 - I
^~0 1 j 1
i 9oi
3oL
/7Z
//V
2S.3
2^./ 7
77
/3a 7
_
/fi/
*/
7
%
77
J/, ft.
Ce/nf-
/S"i
iof
70''
5ฅ/
pie
/70
J?*3
2C
<0.01
?.z
to.oS
0
232.
2t-C
n
-
?ฆ?
V.oS7
iii1
%?
77
ฅ*ฃ/ป.. 1 JtT
y<*
To
(,96a
in
ybr
2/.Z
d./ysi 1 i
: 1
_ซ 1
ฆ
i
'i
_J .1
!li!
1
1
i
.
i;
I I i 1
! 1 I 1
-------
APPENDIX A
, LABORATORY DATA
ST. ANDREWS PSD'PIERPONT AND SAVAGE ROAD UTl'ts
fHARlFQTHM S.C.
PLANT AND CLARIFIER EFFLUENT AND AEROBIC DIGESTER SUPERNATANT
-------
APPENDIX A
. LABORATORY 'DATA ,
ST. ANDREWS PSD PIERPONT AND SAVAGE ROAD OTPS
CHARLESTOWN, S'.C.
CONTACT AND REAERATION BASINS, RETURN SLUDGE, AND AEROBIC DIGESTOR
MitL
if if
/903, * t, '..7 at 77 ^92^ฃฃ....Z
-------
APPENDIX B
DISSOLVED OXYGEN DATA
-------
APPENDIX B
DISSOLVED 0XYG3N CONCENTRATIONS
PIERPONT WTP
Influent
1 9* "
*12
9
Reaer. 13
I
- Aerator
11
1
LO
00
Digester
#4
14
10
5 6ป
Date
Temp
DO (mg/1)
DO (mg/1)
:ation
July 1977
(ฐc)
1-ft.
5-ft.
1
26
29
0.5
0.4
2
26
29
0.3
0.3
3
26
29
0.5
0.5
4
26
29
0.6
0.6
5
26
29
0.9
0.9
PI
26
29
1.7
6
26
29
1.4
1.0
7
26
29
0.9
0.7
8
26
29
0.7
0.4
9
26
29
0.7
0.4
10
26
30
6.7
6.6
11
26
30
6.8
6.8
12
26
29
0.8
0.4
13
26
30
0.4
0.3
14
26
30
6.5
6.5
PRS
26
29
0.6
PE
26
29
3.3
Clarifier
26
0.0
-------
1
2
3
4
5
6
7
8
9
12
13
14
SI
APPENDIX B
DISSOLVED OXYGEN CONCENTRATIONS*
SAVAGE ROAD WTP
Temp DO (mg/1) DO (mg/1) DO (mg/1)
(QC) 1-ft. 3-ft. 5-f-t.
28 0.0
28 2.6
28 0.2 0.2 0.15
28 0.3 0.2 0.2
28 0.3 0.25 0.2
28 0.4 0.25 0.2
28 0.2 o.l 0.0
28 0.35 0.2 0.1
28 0.2 0.15 0.1
28 0.0
28 0.0
31.5 6.3 6.3 6.3
31.5 6.4
31.5 6.3
27 0.0
on July 27, 1977 between 2:30 and 3:30 p.m.
-------
APPENDIX C
GENERAL STUDY METHODS
-------
APPENDIX C
GENERAL STUDY METHODS
Methods used to accomplish the stated objectives included extensive
sampling, physical measurements and daily observations. ISCO model 1392-X
automatic samplers were installed on the influent and final effluent wastewater
streams. Samples were collected for three consecutive 24-hour periods. Aliquots
of sample were pumped at hourly intervals into individual refrigerated glass
bottles which were composited proportional to flow at the end of each sampling
period. An influent grab sample for oil and grease was collected.
All flows were measured from plant recorders and totalizers. All
dissolved oxygen measurements were determined using the YSI model 57 dissolved
oxygen meter. Temperatures and pH were measured at various stations throughout
the WTP with a thermometer and portable pH meter. Depth of the secondary
clarifier sludge blankets were determined daily using equipment suggested by
Alfred W. West, EPA, Cincinnati (13). Sludge activity was determined by the
oxygen uptake procedure presented in Appendix F.
A series of standard operational control tests were run daily:
(1) Settleability of mixed liquor suspended solids (MLSS) as determined
by the settlometer test;
(2) Percent solids of the mixed liquor and return sludge determined by
centrifuge;
(3) Suspended solids and volatile suspended solids analysis on the
aeration basin mixed liquor and return sludge and
(4) Turbidity of each final clarifier effluent.
Daily effluent total chlorine residual concentrations were determined
using an amperometric titrator (Fischer and Porter Model 1771010).
The procedure for the BOD^ determination deviated from Standard Methods
(8). Samples were set up and returned to Athens, Georgia in an incubator where
the analyses were completed.
Visual observations of individual unit processes were recorded.
Mention of trade names or commercial products does not constitute endorse-
ment or recommendation for use by the Environmental Protection Agency.
-------
APPENDIX D
PROJECT PERSONNEL
-------
Charles Sweatt
Ronald Barrow
Herb Barden
Lavon Revells
Tom Sack
Eddie Shollenberger
Richard Rehm
Bill Cosgrove
APPENDIX D
PROJECT PERSONNEL
Sanitary Engineer
Sanitary Engineer
Microbiologist
Chemist
Technician
Technician
Student Trainee
Student Trainee
-------
APPENDIX E
OXYGEN UPTAKE PROCEDURE
-------
appendix e
OXYGEN UPTAKE PROCEDURE 1/
Apparatus
1. Electronic DO analyzer and bottle probe
2. Magnetic stirrer
3. Standard BOD bottles (3 or more)
4. Three wide mouth sampling containers (approx 1 litpr 0 u
5. DO titration assembly for instrument calibration }
6. Graduated cylinder (250 ml)
7. Adapter for connecting two BOD bottles
Procedure
1. Collect samples of return sludge, aerator ifluent and fl
> M ^ ฐve r; f" the r"Urฐ SlUdge sa""Ple Pซปptlv.
2. Mix the return sludge and measure that quantity *or I
300 ml BOD bottle that corresponds to the return *1 a 3
of the plant aerator, i.e. for a 4
-------
APPENDIX (Continued)
The load factor (LF) , a derived figure, is helpful in evaluating
sludge activity. It is calculated by dividing the DO/min of fed sludge
by the DO/min of the unfed return sludge. The load ratio reflects the
conditions at the beginning and end of aeration. Generally, a large
factor means abundant, acceptable feed under favorable conditions. A
small LF means dilute feed, incipient toxicity, or unfavorable conditions.
A negative LR indicates that something in the wastewater shocked or
poisoned the "bugs".
1/ Taken from "Dissolved Oxygen Testing Procedure,: F.J. Ludzack and
script for slide tape XT-43 (Dissolved Oxygen Analysis - Activated Sludge
Control Testing) prepared by F.J. Ludzack, NERC, Cincinnati.
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