TECHNICAL ASSISTANCE PROJECT
AT THE
AUGUSTA WASTEWATER TREATMENT PLANT
AUGUSTA, GEORGIA
JUKE - JULY, 1976
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Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
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TECHNICAL ASSISTANCE PROJECT
AT THE
AUGUSTA WASTEWATER TREATMENT PLANT
AUGUSTA, GEORGIA
JUNE - JULY, 1976
Library Region IV
D4 Epvsrosiaiestai Protedioi Ageacy
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A'iSai£'5ap Geoirgsa 303SS
Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
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CONTENTS
Page
No.
INTRODUCTION 1
SUMMARY 2
RECOMMENDATIONS 3
TREATMENT FACILITY 4
TREATMENT PROCESSES 4
PERSONNEL 4
STUDY RESULTS AND OBSERVATIONS 8
FLOWS 8
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES 8
PRIMARY SEDIMENTATION 11
AERATION BASINS 11
FINAL CLARIFIERS 18
CHLORINE CONTACT CHAMBER 19
AEROBIC DIGESTER 19
ANAEROBIC DIGESTERS 19
LABORATORY 22
REFERENCES 24
APPENDICES
A - LABORATORY DATA 25
B - DISSOLVED OXYGEN PROFILES 30
C - GENERAL STUDY METHODS 31
D - ACTIVATED SLUDGE FORMULAE USED
FOR GENERAL CALCULATIONS 33
E - OXYGEN UPTAKE PROCEDURE 35
FIGURES
1. AUGUSTA WASTEWATER TREATMENT PLANT 5
2. INFLUENT AND RETURN SLUDGE FLOW 9
3. SETTLOMETER TEST 15
4. AERATION BASIN DISSOLVED OXYGEN 17
TABLES
I. DESIGN DATA 6
II. WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES .... 10
III. WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
FOR THE PRIMARY SEDIMENTATION BASINS 12
IV. MEASURED AND RECOMMENDED PARAMETERS FOR THE
COMPLETE-MIX ACTIVATED SLUDGE PROCESS "... 13
V. OXYGEN UPTAKE RATES 16
VI. MEASURED AND RECOMMENDED PARAMETERS
FOR SECONDARY CLARIFIERS 18
VII. ANAEROBIC DIGESTERS 20
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INTRODUCTION
A technical assistance study of operation and maintenance problems
at the Wastewater Treatment Plant (WTP) serving Augusta, Georgia was
conducted June 28 - July 1, 1976 by the Region IV, Surveillance and
Analysis Division, U. S. Environmental Protection Agency. On August 11,
1976, additional sampling was conducted on the anaerobic digesters to
clarify discrepancies in data collected during the initial study.
Operation and Maintenance technical assistance studies are designed
to assist wastewater treatment plant operators in maximizing treatment
efficiencies as well as assisting with special operational problems.
Municipal wastewater treatment plants are selected for technical assis-
tance studies after consultation with state pollution control authorities.
Visits are made to each prospective plant prior to the study to determine
if assistance is desired and if study efforts would be productive.
The Augusta WTP was selected because of difficulty in achieving
design treatment efficiencies. The specific study objectives for the
WTP were to:
© Optimize treatment through control testing and recommended
operation and maintenance modifications,
• Introduce and instruct plant personnel in new operational
control techniques,
9 Determine influent and effluent wastewater characteristics,
e Assist laboratory personnel with any possible laboratory
procedure problems, and
« Compare design and current loadings.
A follow-up assessment of plant operation and maintenance practices
will be conducted by October 197*6. This will be accomplished by utilizing
data generated by plant personnel and, if necessary, subsequent visits
to the facility will be made. The follow-up assessment will determine
if recommendations were successful in improving plant operations and if
further assistance is required.
The cooperation of the Georgia Environmental Protection Division is
gratefully acknowledged. The technical assistance team is especially
appreciative of the cooperation and assistance received from Mr. Mark
Boner (Zimmerman, Evans & Leopold Consulting Engineers), the City of
Augusta engineering department, and the wastewater treatment personnel
in Augusta, Georgia.
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SUMMARY
The Augusta Wastewater Treatment Plant (WTP) was designed as a
30 mgd activated sludge system. The hydraulic load at the WTP was
about 23.9 mgd (average three day flow) during the technical assistance
(TA) study. The average BOD5 and TSS reduction during the TA study was
83 and 59 percent, respectively.
The major problems observed during the study were as follows:
• The activated sludge appeared old, inactive, and settled
extremely fast leaving a significant amount of colloidal
material in the supernatant.
• The food to microorganism ratio was higher than recommended
values.
• Dissolved oxygen concentrations in the aeration basins and
aerobic digester were, in general, too low for optimum treat-
ment efficiency.
o The aeration basins were organically overloaded due to low
BOD^ removal in the primary treatment units and an influent
waste stronger than anticipated.
s The return activated sludge was inactive and had an immediate
oxygen demand. This situation was caused by low dissolved
oxygen concentrations throughout the secondary system.
• Prior to this TA study, sludge wasting to the aerobic digester
was not monitored or controlled on a regular schedule.
• The anaerobic digesters and related mixing, gas collection, and
monitoring systems had not been in full efficient operation for
some time.
9 Most of the automatic monitoring and control metering equipment
was out of service for various reasons including repair, cali-
bration, or lack of knowledge on operation.
-2-
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RECOMMENDATIONS
Based on observations and data collected during the study, it is
recommended that the following measures be taken to improve wastewater
treatment and plant operation.
1. Sludge wasting should be controlled to maintain a mean cell residence
time (MCRT) of about 8 days. This will provide a baseline of data
on which to make additional operational changes.
2. Dissolved oxygen in the aeration basins and aerobic digester should
be increased to about 2 mg/1. The depth of submergence of the brush
aerators should be increased to transfer more oxygen.
3. As the old 9ludge is removed, the MLSS should be increased to about
3,000 mg/1, if adequate DO can be maintained.
4. Final clarifier effluent weirs should be checked closely and leveled
where necessary.
5. The return sludge flow rate should be reduced as the settleability
of the activated sludge improves. Aerobic conditions in the clari-
fier must be maintained and this will dictate the minimum return
sludge flow.
6. The mixing system in the primary anaerobic digesters should be
checked closely and repaired, if necessary, to insure adequate
mixing.
7. Automatic monitoring and control equipment throughout the plant
should be repaired, calibrated and placed in operation.
8. An in-plant control testing schedule should be initiated and trend
charts established and maintained.
9. Standardization of titrants should be incorporated as a routine
laboratory procedure.
10. Sulfuric acid (10%) or hydrochloric acid (10%) should be used to
clean BOD glassware instead of chromerge.
-3-
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TREATMENT FACILITY
TREATMENT PROCESSES
A schematic diagram of the 30 mgd activated sludge wastewater treat-
ment plant (WTP) serving Augusta, Georgia is presented in Figure 1. Design
data are enumerated in Table I. The original primary plant began operation
in March 1969 and was expanded to the existing secondary system in March
1975.
After passing through a grit chamber and mechanically cleaned bar
screens, the influent wastewater is split into four parallel primary sedi-
mentation basins. Sludge from the primary sedimentation basins is pumped
to the anaerobic digesters.
Wastewater from the primary units flows to two activated sludge aera-
tion basins operated in parallel. The aeration basins are operated in an
oxidation ditch type flow scheme with oxygen supplied by rotating brush
aerators. The wastewater then flows through two parallel secondary
clarifiers, is chlorinated and discharged to the Savannah River via
Butler Creek.
Sludge from the secondary clarifier is pumped to an aerobic digester.
After concentration in a sludge thickener, this sludge is usually pumped
directly to the vacuum filters. During the study, one filter was down for
repair; consequently, thickened aerobic digester sludge was pumped to
the number 3 (secondary) anaerobic digester and then to the filter.
Sludge from the vacuum filters is used as a soil conditioner by the City
of Augusta.
Supernatant from the anaerobic digesters and sludge thickener, filtrate
from the vacuum filters and scum from the primary sedimentation basins is
discharged into the Butler Creek sewer, which flows back to the head of
the plant.
PERSONNEL
The City of Augusta WTP is staffed by thirty-four persons. Of the
thirty-four, twelve hold the following certifications: 1-Class I, 1-
Class II, 7-Class III, and 3-Class IV.
-4-
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FIGURE 1
CITY OF AUGUSTA
WASTEWATER TREATMENT PLANT
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TABLE I
DESIGN DATA
AUGUSTA WASTEWATER TREATMENT PLANT
AUGUSTA, GA
GENERAL DESIGN
Design Year
Population
Industrial Equivalent Population
Total Equivalent Population
Average Flow
Peak Flow
BOD
1995
203,000
20,000
223,000
30 mgd
42 mgd
37,200 lbs/day
II. FLOW MEASUREMENTS
Influent
Effluent
Primary Effluent
Return Sludge
Waste Sludge
(Anaerobic Digester)
(Aerobic Digester)
Aerobic Digester Recycle
Waste Sludge
(Thickener)
111• PRELIMINARY TREATMENT
Bar Screen (1)
Aerated Grit Chamber (2)
IV. PRIMARY SEDIMENTATION BASINS
5 ft. Parshall flume, recorder,
totalizer
5 ft. Parshall flume, indicator,
totalizer
Venturi meter - 48 in. pipe line
Venturi meter - 30 In. pipe line
Venturi meter - 8 in. pipe line
Venturi meter - 8 in. pipe line
Venturi meter - 8 in. pipe line
Venturi meter - 6 in. pipe line
1 3/8 in. spacing, mechanically
cleaned
mechanically cleaned
V.
Number
Volume (each)
Design Detention
Settling Rate
Total Effluent Weir Length
AERATION BASINS
700,000 gal.
2.24 hrs.
850 gal/sq. ft./day
1,440 lin. ft.
Number
Volume
Aeration (each basin)
2.16 M Gal.
6 Rotating Brush Aerators
-6-
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VI.
FINAL CLARIFIERS
Number
Diameter
Area (each)
Volume (each)
Detention Time
Weir Length (each)
Depth
VII. CHLORINATION
Capacity
Detention
VIII. AEROBIC DIGESTION
Number Basins
Volume
Aeration
IX. SLUDGE THICKENER
Type
Surface Area (effective)
Diameter
X. ANAEROBIC DIGESTION
Number Units
Total Volume
XI. SLUDGE DRYING
Type
Number Units
Total Filter Area
2
160 ft.
20,106 sq. ft.
1.87 M. Gal.
3 hrs.
967 lin. ft.
13 ft.
4,020 lbs/day
30 min.
1
2.16 M. Gal.
6 Rotating Brush Aerators
Circular
1,385 sq. ft.
42 ft.
3 (2 heated and mixed)
659,200 cu. ft.
Vacuum Filters
2
500 sq. ft.
-7-
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STUDY RESULTS AM) OBSERVATIONS
A complete listing of all analytical data and study methods are
presented in Appendices A, B, and C. Formulae used for general cal-
culations are enumerated in Appendix D. Significant results and obser-
vations made during the study are discussed in the following sections.
FLOWS
Plant flow was measured with a 5 foot Parshall flume, equipped with
a recorder and totalizer. Average hourly influent flows during the study
are depicted in Figure 2. The average influent flow was 23.9 mgd; the
minimum flow was 16 mgd and the maximum flow was greater than 50 mgd, which
occurred during a heavy rain. Part of the wastewater collection system
is combined, thereby causing a tremendous inflow problem.
Approximately 6 mgd of the influent wastewater flow was from industrial
sources, comprised of wastewaters from baking, textile and paper product
operations.
Return sludge flow rates were manually controlled at about 70 percent
of the total plant inflow. A Venturi meter with recorder and totalizer
in a 30 inch pipe line, normally used to automatically control return
flow, was out of service for repairs. The average return sludge flow
during the study was approximately 16.7 mgd.
Waste sludge flow rates were not monitored until the week prior to
the O&M technical assistance (TA) study. For the week prior to the
study, wasting was arbitrarily controlled at 0.216 mgd (150 gpm). On
June 29, 1976, after reviewing preliminary study findings and on recommen-
dation of the TA team, waste sludge flow was doubled to 0.432 mgd (300 gpm).
Total flows from the anaerobic digester supernatant overflow, filtrate
from the vacuum filters, and overflow from the primary sedimentation scum
troughs were measured using a portable Manning flow meter. The average
24-hour flow from these contributing sources was 0.33 mgd.
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Table II presents a chemical description of the WTP influent and
effluent with calculated average percent reductions. The removal
efficiencies were calculated using data from stations 1-1 and E-l,
which were collected on a 24-hour proportional to flow composite basis
for the first two consecutive sampling periods (June 28 - July 1, 1976).
-8-
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FIGURE 2
INFLUENT 8 RETURN SLUDGE FLOW
AUGUSTA, GA WTP
6/28 6/29 6/30 7/1
TIME
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TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
PARAMETER
INFLUENT—''
EFFLUENT
% REDUCTION
B0D5 (mg/1)
168
28.5
83
Total Solids (mg/1)
627
422
33
TVS (mg/1)
266
94
65
TSS (mg/1)
126
52
59
TVSS (mg/1)
75
42
44
2/
Settleable Solids (ml/1)
3.0
<0.1
>97
COD (mg/1)
401
131
67
TK.N-N (mg/1)
29.5
26.5
10
NH3-N (mg/1)
20.6
23.6
-14
N03-N02-N (mg/1)
<0.01
<0.01
—
Total Phosphorus (mg/1)
6.4
6.1
5
Pb (yg/1)
100
<50
>50
Cr (yg/1)
102
<55
>46
Cd (yg/1)
<10
<10
—
Cu (yg/1)
108
50
54
Zn (yg/1)
210
75
64
Oil & Grease (mg/1)
34
<5.5
>84
1/ The supernatant from the anaerobic digester is included in the influent
'waste characteristics.
2/ Analysis conducted on June 28-29 sampling period only.
-10-
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The removal efficiency calculation for oil and grease was the only
exception. It was based on data from three grab samples taken during
the period (June 28 - July 1).
According to the data in Table II, nitrification was not being
achieved in the treatment system. This is probably due to the short
aeration period, low dissolved oxygen and the poor quality activated
sludge.
PRIMARY SEDIMENTATION
Table III presents a general description of the influent and effluent
from each primary sedimentation basin, with calculated percent reductions
shown for all parameters. Analyses were made on 24-hour composite samples
collected on three consecutive days (June 28 - July 1) except for sampling
station PE-1. Because of an inoperative sampler, no sample was taken from
basin //I during the June 30 - July 1 sampling period, therefore, only a
two-day average is given for this basin.
The average detention time in the primary sedimentation basins was
about 1.7 hours, which is within recommended detention times of 1-2 hours
(4). The extremely low influent settleable solids raises two questions;
the necessity of the primary sedimentation basins and removal of enough
primary solids to effectively operate both primary anaerobic digesters.
AERATION BASINS
Grab samples taken from the discharge end of both aeration basins
(Stations A-l and A-3) were analyzed for total suspended solids (TSS),
volatile suspended solids (VSS), percent solids by centrifuge, and
settleability as determined by the settlometer.
Presented in Table IV are various activated sludge operational
parameters calculated during the study period and the corresponding
recommended values for the complete mix activated sludge process. The
actual design parameters for the Augusta OTP are slightly different than
those recommended in Table IV. The plant was designed as a modified
(high-rate) version of the conventional step-feed activated sludge
process and approaches completely mixed conditions.
-11-
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TABLE III
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
FOR THE PRIMARY SEDIMENTATION BASINS
PE-2 PE-3 PE-4 3j
Influent / % ^ ^ 1 Average
Cone. Cone.- Cone. Reduction Cone. Reduction Cone. Reduction Cone. Reduction % Reduction
BOD (mg/1)
185
(168)
149
11
167
10
144
22
158
14
14
COD (mg/1)
487
(401)
304
24
366
25
351
28
387
20
24
TSS (mg/1)
204
(126)
51
60
66
68
91
55
103
50
58
VSS (mg/1)
123
(75)
45
40
56
54
69
44
84
32
42
Settleable / Solids
(ml/l)-£
<0.1
—
<0.1
—
A
O
—
<0.1
—
<0.1
—
—
Pb (ug/1)
133
(100)
80
20
93
30
77
42
93
30
30
Cr (ug/1)
130
(102)
100
2
8b
32
92
29
94
28
23
Cd (ug/1)
<10
(<10)
<10
—
<10
—
<10
—
<10
—
—
i Cu (ug/l)
152
(108)
65
40
83
45
83
45
142
6
34
m Zn (ug/1)
313
(210)
130
38
172
45
148
53
252
19
39
' TKN-N (mg/1)
31.1
(29.5)
28.9
2
31.2
-0.3
31.1
0
32.6
-4.8
-0.8
NH3-N (mg/1)
23.4
(20.6)
28.2
-37
27.5
-18
26.5
-13
26.2
-12
-20
NO3-NO2-N (mg/1)
<0.02
(<0.01)
<0.01
—
<0.03
—
<0.01
—
<0.05
—
—
Total Phosphrous
(mg/1)
7.2
(6.4)
6.4
0
6.4
11
6.5
9.7
9.6
-33
-3.1
1_/ Average based on data for the first two days of sampling.
2/ Analysis conducted on 2nd day composite sample.
3/ Based on average percent reductions from each individual basin.
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TABLE IV
MEASURED AND RECOMMENDED PARAMETERS FOR THE
COMPLETE-MIX ACTIVATED SLUDGE PROCESS
Measured Recommended (1)(7)
Hydraulic Retention Time (hrs.)
2.5
3-5
Mean Cell Residence Time (days)
A
5-15
Sludge Age (days)
4.2
3.5-7.0
Lbs. BODc/day/lb. MLVSS (F/M)
0.7
.2-.6
Lbs. COD/day/lb. MLVSS
1.6
.5-1.0
Lbs. BOD^/day/1000 cu. ft.
aeration basin
53
50-120
MLSS (mg/1)
1,855
3,000-6,000
Return sludge rate (% of average
flow)
70
25-100
* - Waste sludge flow rate had not been measured prior to study;
consequently, MCRT could not be calculated.
Data collected during the study indicate that the aeration basins
were organically overloaded by approximately 20 percent. The basins
were designed to treat 26,000 lbs. of BOD,-/day, but were receiving about
30,900 lbs/day during the study. Since the plant was operating at only
80% of the hydraulic design capacity, the organic overload was due to
less than anticipated removal in the primary treatment and a slightly
stronger than anticipated influent waste strength. In design of the
plant, it was assumed that primary treatment would remove 30 percent of
the influent BOD^; however, only 14 percent was removed during the study.
The raw influent BOD- was .168 mg/1 during the study versus 148 mg/1 assumed
in design. These two factors resulted in a wastewater flow into the
aeration basins with a BOD^ concentration of 155 mg/1 as opposed to
104 mg/1 assumed in design. This plant was designed for a loading rate
(45 lbs. BOD^/1,000 cu. ft.), somewhat above conventional activated
sludge loadings (20-40 lbs. BOD^/ljOOO cu. ft.), and for a rather weak
influent waste. These two design criteria have resulted in minimum
sized basins. This results in a short hydraulic detention time of 2.5
hours using average plant flow and return sludge rates observed during
the study. Consequently, there is very little reserve capacity to
handle an organic or hydraulic overload.
-13-
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The P/M ratio is much too high. In order to maintain an F/M of
about 0.4, the MLSS concentration should be approximately 3,000 mg/1.
The sludge age of 4.2 days (Table IV) is not a true representa-
tion of sludge in the system. Settleability and visual observation
of the mixed liquor activated sludge indicate an old, inactive sludge.
The total suspended solids in the final effluent were about 82 percent
volatile. This implies that the young, biologically active solids were
being lost in the effluent while the older, heavier, less biologically
active solids were being retained in the secondary system.
The activated sludge settleability for both aeration basins was
the same. The average settleability during the study period is presented
in Figure 3. The activated sludge was too old and settled too rapidly,
leaving a considerable amount of suspended solids in the supernatant.
A slower rate of settling would remove most of these solids, leaving
a clearer supernatant. A settled sludge volume of about 20 percent
after 60 minutes of settling should approach optimum and can be achieved
with a younger activated sludge.
The condition of an activated sludge process can be assessed by
several means. One of these is sludge activity by microscopic examination.
A combination of select protozoa types in a given activated sludge at a
given aeration time is the barometer by which the observation is based.
A very active sludge will accommodate a wide variety of protozoan organisms,
depending on the abundance of biodegradable food. As the sludge approaches
stability or reaches its optimum age, the selection of protozoan types
becomes more restrictive. The organisms most commonly observed at optimum
age are stalked ciliates, free-swimming ciliates, and rotifers. When
the sludge gets too old, the balance shifts; free bacterial cells
become limited, and free-swimming ciliates and rotifers decrease or desist.
With this die-off, another group of floc-eating organisms, including
crawling ciliates, mites, and nematodes, becomes prevalent.
Examination of the Augusta OTP mixed liquor demonstrated a very
limited and selective population of stalked ciliates, crawling ciliates,
and flagellates. Protozoan populations of this type are generally
associated with old activated sludges. The observation of individual
sludge particles revealed the settled solids to be small, separate, dense
granules without bacterial floe.
The oxygen uptake procedure is another indicator of sludge condition.
General sludge activity using this procedure can be determined by utiliz-
ing the difference in oxygen uptake rates before and after introduction
of the raw waste. The ratio of these two variables or "load ratio" is
calculated as follows:
Load ratio = DO/min. of fed sludge
DO/mm. of unfed sludge
-14-
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100
FIGURE 3
SETTLOMETER TEST
AUGUSTA,GA
90
80
Z* 70 -
60 -
30 -
20 -
10 -
10
15
20
25
30
40
50
60
TIME (MIN)
-------
The calculated load ratios presented in Table V indicate that the
Augusta OTP activated sludge (A/S) was inactive. These data indicate
that the sludge is not of high quality or the incoming waste is toxic
or not readily biodegradable, A conventional A/S process commonly per-
forms best in the load ratio range of 2-4. On the initial aerated samples
dissolved oxygen was depleted very rapidly. This rapid oxygen utiliza-
tion was characteristic of a very active A/S or an oxygen demand that
was non-biological. After several reaerations of the samples, a biological
demand was measured as shown (Average C>2 uptake) in Table V. From the
calculated load ratio and the microscopic examination, it was concluded
that the inactivity of the sludge was due to the low dissolved oxygen
conditions which existed. Mixed liquor dissolved oxygen (DO) was normally
less than 0.5 mg/1, resulting in a septic sludge in the clarifier. This
septic condition tends to deactivate the sludge and produces an immediate
oxygen demand.
TABLE V
OXYGEN UPTAKE RATES
Average 0? Uptake
Date
Time
RS^/
PPM/Mini/
URS
PPM/Min.—/
FRS
Load Ratio
FRS/URS
6/30
6/30
9:15 a.m.
12:15 p.m.
70
70
1.5
1.42
1.7
1.47
1.13
1.03
1/ RS - Return Activated Sludge
2/ URS - Unfed Return Sludge
3/ FRS - Fed Return Sludge
Results of the dissolved oxygen (DO) measurements in the aeration
basins are presented in Figure 4 and Appendix B. Except for surface
(1.0 foot depth) measurements at points between the aerators, dissolved
oxygen concentrations were too low. The submergence on the aerators
was about seven inches. Oxygen in the aeration basins can be increased
by increasing the aerator submergence.
Activated sludge mixed liquor solids must be wasted at a controlled
rate to remove the old, inactive sludge presently in the system. Maintain-
ing constant conditions will allow operational control parameters to be
evaluated and then subsequent operational changes can be made more
efficiently and accurately. Based on a mean cell residence time (MCRT)
of eight days and plant conditions at the time of the TA study, the waste
sludge flow should be maintained at about 230 gpm. The waste sludge
rate should be calculated at least once weekly, based on the previous
5-7 days' data, and the appropriate changes made. A subsequent gradual
buildup of a younger, more active, slower settling sludge should
improve treatment but will require close operational control. Initially,
the MLSS level should be built up to around 3,000 mg/1, A younger sludge
-16-
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FIGURE 4
AERATION BASIN D. 0.
BASIN #1
BASIN #2
-17-
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will probably increase the oxygen demand in the aeration basins; conse-
quently, aeration capacity may dictate the maximum MLSS concentration
that can be maintained. Sludge settleability and aeration basin DO
must be monitored closely in order to maintain optimum treatment efficiency,
FINAL CLARIFIERS
The two final clarifiers are circular with center feed and rim
take-off. The effluent weir trough consists of two parallel weirs
around the periphery of the clarifier.
Observation of unequal flow over the effluent weirs indicated that
the weirs were not level. The weirs were checked with an engineer's
level and found to vary 0.15 feet (1,8 inches) and 0.11 feet (1.3 inches)
in elevation in clarifiers #1 and //2, respectively.
Suspended solids appear to flow over the outside effluent weir more
frequently than the inner-most weir. This is a common occurrence when
weirs are placed along the tank wall. The density of the activated
sludge mixed liquor is much greater than that of the liquid in the
clarifier. Consequently, it flows along the bottom until hitting the
wall, then flows up and over the weir.
The depth of the 6ludge blanket below the water surface was measured
daily. No sludge blanket existed during the study period. This was due
to the high return sludge rate, which was maintained at about 70 percent
of the plant influent flow. The return sludge total suspended solids
concentrations (sampling Station RS), on two days of grab samples, were
4,300 and 6,400 mg/1. These concentrations of solids were due to the
extremely fast settleability of the activated sludge. A lower return
sludge rate will be necessary to allow better concentration of solids
as a younger sludge is developed. Monitoring the depth of the sludge
blanket and watching for signs of denitrification are critical in
secondary clarifier operation and will dictate the return sludge flow
rate.
Measured and recommended parameters for final clarifiers following
activated sludge wastewater treatment are presented in Table VI.
TABLE VI
MEASURED AND RECOMMENDED PARAMETERS FOR
SECONDARY CLARIFIERS
Recommended
Measured (1)(3)(4)
Hydraulic Loading (gpd/sq. ft.)
Solids Loading (lbs./day/sq. ft.)
Weir Overflow Rate (gpd/lin. ft.)
Hydraulic Detention Time (hrs.)
600
15.7
12,400
2.2
400-800
20-30
<15,000
2-3
-18-
-------
The weir overflow rate approaches the maximum recommended value
by ASCE (A), The existing placement of the weirs does not develop
the entire surface area of the clarifier and results in high up-flow
velocities along the periphery of the basins.
CHLORINE CONTACT CHAMBER
The primary concern with a chlorine contact chamber (CCC) is the
detention of OTP effluent flow to allow adequate time for disinfection.
At the Augusta WTP, chlorine was added to the wastewater stream just prior
to the CCC. Detention time in the CCC was approximately 30 minutes at
design flow. According to WTP personnel, the chlorine gas feed rate
is manually controlled at 2,000 lbs./day. This dosage rate resulted
in the chlorine residual varying from 2 mg/1 to less than 0.1 mg/1.
AEROBIC DIGESTER
Digestion and conditioning of waste activated sludge is accomplished
in an aerobic digester. The aerobic digester is similar to the aeration
basins except for 30-hp brush aerators, only one inlet port, and no
automatic effluent valve or level control. Prior to the TA study, waste
activated sludge flow to the aerobic digester was not monitored. This
lack of control sometimes resulted in overfilling, thereby overloading
the motors and causing motor malfunctions and repairs. During the
study, two of the six brush aerators in the aerobic digester were
inoperable, needing repairs.
A DO profile in the aerobic digester demonstrated consistently low
DO concentrations (Appendix B).
Conditioned sludge from the aerobic digester flows to a sludge
thickener. Overflow from the thickener was returned to the WTP influent;
thickened sludge was being temporarily pumped to the secondary anaerobic
digester due to breakdown of one of the vacuum filters.
The average total suspended solids concentration in the aerobic
digester was 17,525 mg/1. The solids were concentrated to 27,000 mg/1
(2.7 percent) by the sludge thickener,
ANAEROBIC DIGESTERS
Primary sludge is treated by three anaerobic digesters. The two
primary digesters (#1 and §2), operated in parallel, are heated and mixed.
The secondary digester (/'3) is operated as a holding and solids separation
basin prior to pumping to the vacuum filters. Mixing is accomplished by
recirculating sludge through the heat exchangers and by the Perth gas
mixing system. Gas measuring equipment was inoperative during the study,
and all gas produced was burned by the waste gas burner. Observation of
the orange flame indicated poor methane production.
-19-
-------
Analytical results of anaerobic digester sampling during the TA study
are presented in Table VII. Volatile acids results in both primary
digesters were exceptionally high and not compatible with previous WTP
volatile acid data. Consequently, samples were collected again on August 11
for volatile acids analysis.
TABLE VII
ANAEROBIC DIGESTERS
Total Solids (mg/1)
Total Volatile Solids (mg/1)
Alkalinity (mg/1 as CaCO^)
Volatile Acids (mg/1)
pH
Temperature (°F)
Lead (yg/1)
Copper (yg/1)
Chromium (yg/1)
Cadmium (yg/1)
Zinc (yg/1)
Primary
//I
Primary
// 2
Secondary
Combined
Supernat,
3,588
49,132
51,132
7,904
2,040
30,534
29,904
4,496
1,830
1,350
2,250
—
2,232
2,620
1,344
—
6.6
6.0
6.2
—
93
91
86
—
1,250
22,800
—
3,260
1,230
24,150
—
3,275
550
8,230
—
1,460
<100
720
—
100
3,430
72,000
—
7,450
Analytical data (Table VII) reveal significant concentrations of
heavy metals in the digesters. However, a consulting engineer (9),
experienced with anaerobic digester operation, stated that properly
operated anaerobic digesters can function efficiently with the concen-
tration of metals listed in Table VII.
According to plant personnel and operating records, the two primary
digesters had been fed raw primary sludge equally. However, total
solids data (Table VII) indicate that this is not the case. Assuming
efficient mixing and equal raw sludge feed to each digester, these
differences are unexplainable. Consequently, additional digester sampling
was performed on August 11, 1976. Samples were collected from an unused
supernatant line located in the top portion of the digester and from the
recirculation line located at about mid-depth. Samples were split with
WTP laboratory personnel. These results are presented in Appendix A.
The average total solids (TS) concentration in the #1 and //2 digesters
were 4,260 and 3,212 mg/1, respectively. Review of recent data obtained
by WTP personnel indicate variation in TS concentrations of 0.3 to 7
percent solids. These data suggest poor mixing in both primary digesters,
with most of the digester solids settling below the mid-depth level. Two
possible causes are insufficient gas production and a malfunction in the
gas mixing system.
-20-
-------
Alkalinity, volatile acids, arid pH were within acceptable ranges;
however, the quantity and quality of methane production was unknown.
A Fischer Gas Partitioner, coupled directly to the digesters, has never
operated properly. In order to effectively run equipment using digester
gas (methane), the quantity and quality of gas must be monitored.
The following anaerobic digester sampling schedule (1) should be
initiated and the data continually plotted on trend charts.
A. Daily
1. Temperature
B. Twice Per Week (Minimum)
1. Recirculated sludge.
a. Volatile Acids
b. Alkalinity
c. Calculate Volatile Acid/Alkalinity Relationship
C. Weekly
1. Raw sludge
a. pH .
b. Total Solids— .
c. Volatile Solids-'
2. Recirculated sludge
a. pH
b. Total Solids
c. Volatile Solids
3. Supernatant
a. pH
b. Total Solids
c. Volatile Solids
1/ Collect raw sludge samples daily at the start, middle, and end of
the pumping cycle. Once a week prepare a composite sample by mixing
the daily samples together and run total and volatile solids tests.
-21-
-------
D. Monthly to Quarterly
1. Sound digester by sampling from bottom up at five-foot
intervals and test for:
a. Total Solids
b. Volatile Solids
2. Use sample results from (D.l.) to determine:
a. Sludge concentrations at various levels in the digester.
b. Depth of grit accumulation at bottom of digester. (A
gradual build-up of grit will occur, and plant personnel
should estimate the date when the digester will have to
be cleaned.)
c. Presence of scum blanket and its thickness.
d. The effectiveness of digester mixing equipment in mixed
primary digesters.
LABORATORY
The laboratory is located within the main control building and has
a staff of two chemical technicians. Observations revealed an adequate
records system; however, some changes in routine laboratory operations
would be of benefit in assuring quality data and increase laboratory
efficiencies.
At the time of the study, standardization of some titrants was not
a routine procedure. To be confident of data generated in analyses
involving titrations, standardization of the titrant against a primary
standard is necessary.
The laboratory had a dissolved oxygen (DO) meter with laboratory
and field probes. Laboratory personnel stated that they had experienced
problems with the instrument. The meter and laboratory probe was checked
by EPA personnel, standardized, and found to be working satisfactorily.
At the conclusion of the study, laboratory personnel were using the
instrument for DO determinations in the BOD5 test.
The DO meter with field probe could be of great benefit in deter-
mining dissolved oxygen levels in the aeration basins. The meter gives
valuable data since profiles throughout the basins can be determined
and areas of low DO revealed.
-22-
-------
Routine control testing was limited at the time of the study.
The use of the settlometer and centrifuge tests was explained to
WTP personnel, and at the conclusion of the study, these analyses were
implemented on a routine basis.
All data that is generated is best utilized when plotted on graphs
or trend charts. These trend charts reveal changing conditions in a
plant, and process changes can be initiated, as necessary, to correct
impending problems.
-23-
-------
REFERENCES
1. "Operation of Wastewater Treatment Plants", A Field Study Training
Program, US-EPA, Technical Training Grant No. 5TT1-WP-16-03, 1970.
2. "Process Design Manual for Suspended Solids Removal", US-EPA
Technology Transfer, January, 1975.
3. "Process Design Manual for Upgrading Existing Wastewater Treatment
Plants", US-EPA Technology Transfer, October, 1974.
4. "Sewage Treatment Plant Design", American Society of Civil Engineers,
Manual of Engineering Practice No. 36, 1959.
5. "Standard Methods for the Examination of Water and Wastewater",
13th Edition, 1971.
6. "Standards for Sewage Works", Upper Mississippi River Board of
State Sanitary Engineers, Revised Edition, 1971.
7. "Wastewater Engineering", Metcalf and Eddy, Inc., 1972.
8. Alfred W. West. Operational Control Procedures for the Activated
Sludge Process. Part I, Observations, April, 1973: Pages 7, 8.
9. Personal Communication, T. M. Reagan, Consulting Engineer, Lexington,
KY, August 2, 1976.
10. "Operations Manual - Anaerobic Sludge Digestion", U. S. Environmental
Protection Agency, EPA 430/9-76-001, February, 1976.
-24-
-------
Influent and Effluent
APPENDIX A
Laboratory Data
Augusta, GA WTP
1
STATION
MONTH
>
<
a
YEAR
TIME
/#
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^ /
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/ / Pl
' ,y / / /
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f / /
/ Ci / Cd / Cu
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—
-
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76
ay *r.
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-
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-------
appendix a
Laboratory Data
Augusta, Georgia WTF
-------
APPENDIX A
Laboratory Data
-------
Effluent, Supernatant, and Overflow
APPENDIX A
Laboratory Data
Augusta, GA WTP
-------
Digesters
APPENDIX A
Laboratory Data
Augusta WTP
Alignsca. GA
#
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1
-------
APPENDIX B
DISSOLVED OXYGEN PROFILES
AUGUSTA, GEORGIA
DATE TIME STA DEPTH D.O. TEMP
DATE TIME STA DEPTH D.O. TEMP
DATE
TIME STA DEPTH D.O. TEWP
6-29 1330 A-4
1430
0.3
27
1515
1530
3
0.2
27
5
0.1
27
11
0.1
27
A-9
1
1.8
27
3
1.1
27
5
0.6
27
8
0.2
27
11
0.3
27
A-ll
1
3.2
27
3
1.5
27
5
1.0
27
8
1.5
27
11
L. 3
27
A-12
1
2.8
27
3
1.9
27
5
3.0
27
8
0.3
27
11
0.6
27
A-10
1
2.9
27
3
1.6
27
5
0.6
27
8
0.4
27
U
0.9
27
A-3
1
0.4
27
3
0.2
27
5
0.2
27
11
0.2
27
A-l
1
0.2
27
5
0.1
27
11
0.2
27
A-8
1
1.3
27
3
1.0
27
5
0.6
27
8
0.2
27
11
0.2
27
A-5
1
0.9
27
3
0.4
27
8
0.4
27
11
0.2
27
A-2
1
0.4
27
5
0.2
27
11
0.2
27
5-29 1545 D-l
D-2
D-3
D-6
6-30 1030 A-l
A-8
A-6
A-7
A-5
1100 A-4
A-9
1
0.2
27
5
0.1
27
11
0.1
27
1
0.3
26
5
0.2
26
11
0.1
26
1
0.2
26
5
0.1
26
11
0.1
26
1
0.2
26
5
0.1
26
8
0.1
26
1
0.2
26
5
0.2
26
11
0.2
26
1
2.8
26
3
2.3
26
5
1.6
26
8
0.4
26
11
0.2
26
1
1.3
26
3
0.5
26
5
0.4
26
8
0.3
26
11
0.4
26
1
1.0
26
3
0.4
26
5
0.3
26
8
0.3
26
11
0.2
26
1
0.8
26
3
0.4
26
5
0.2
26
8
0.2
26
11
0.2
26
1
0.5
26
5
0.2
26
11
0.5
26
1
3.0
26
3
2.0
26
5
1.0
26
8
0.3
26
11
0.1
26
6-30
A-ll
A-10
A-12
A-3
1300 D-l
D-l*
D-6
2.8
0.8
0.4
0.3
0.1
2.6
1.4
0.7
0.5
0.3
3.0
2.2
0.7
0.2
0.2
0.2
O.A
0.4
0.2
0.4
0.2
0.2
0.2
0.2
0.2
0.2
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
J >C, I 6
Ail I A|1 |
'
*Inside turning wall.
-30-
-------
APPENDIX C
GENERAL STUDY METHODS
To accomplish the stated objectives, the study included extensive
sampling, physical measurements, daily observations, and consultations.
Plant influent, three of four primary effluents, and the plant effluent
sample stations were sampled for three consecutive 24-hour periods
with ISCO Model 1392-X automatic samplers. The fourth primary effluent,
sample station (PE-4), was sampled using a SERCO automatic sampler for
three consecutive 24-hour periods.
Aliquots of sample were drawn at hourly intervals into individual
refrigerated glass bottles, which were composited proportional to flow
at the end of each sampling period, at all composite sampling stations.
Dissolved oxygen concentrations were measured at stations throughout
the WTP aeration basins and aerobic digester using a YSI Model 51A
dissolved oxygen meter.
The WTP flow totalizer was used to determine total daily influent
flow, and the recorder was used for hourly flows, A combined flow of
anaerobic digester supernatant, scum trough overflow and vacuum filter
filtrate was determined with a Manning flow recording meter.
Temperature was measured while determining dissolved oxygen concen-
trations. Individual samples over two 24-hour compositing periods were
used to determine hourly influent and effluent pH variations.
Depth of the secondary clarifier sludge blankets were determined
daily using equipment suggested by Alfred W. West, EPA, NFIC, Cincinnati (8).
Sludge activity was determined by the oxygen uptake procedure
presented in Appendix E.
A series of standard operational control tests were run daily:
o Settleability of mixed liquor suspended solids (MLSS) as
determined by the settlometer test,
o Percent solids of the mixed liquor and return sludge determined
by centrifuge,
• Suspended solids and volatile suspended solids analysis on the
aeration basin mixed liquor and return sludge,
• Turbidity of each final clarifier effluent.
-31-
-------
An amperometric titrator (Fischer & Porter Model 17TT010) was used
to determine effluent chlorine concentrations.
The procedure for the BOD5 determination deviated from standard
methods (5). Samples were set up and carried in an incubator back to
Athens, GA for completion of the analyses.
Visual observations of individual unit processes were recorded.
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the Environmental Protection
Agency,
-32-
-------
APPENDIX D
Activated Sludge
Formulae Used tor General Calculations
Aeration Basin
1. lbs. of solids in aeration basin
Basin volume ¦= m.g.; MLSS (eonc.) = mg/1
(MLSS conc.) x (Basin vol.) x 8.34 = lbs. of solids
2. Aeration basin loading (lbs. BOD or COD/day)
Inf. flow to aeration basin = mgd
Inf. BOD or COD = mg/1
(BOD or COD) x flow x 8.34 = lbs. BOD of COD/day
3. Sludge Age (days)
MLSS conc. (avg. of daily values) = mg/1
Aeration Basin Vol. = m.g.
TSS, Primary Eff. or Basin Inf. conc. = mg/1
Plant Flow = mgd
(MLSS) x (Basin Vol.) x (8.34)
(TSS) x (Flow) x 8.34
4. Sludge Vol. Index (SVI)
30 min. settleable solids (avg. of daily values) = %
MLSS conc. = mg/1
(%, 30 min. set, solids) x (10,000)
MLSS
5. Sludge Density "Index (SDI)
SVI Value 100
SVI
6. Detention time (hours)
Volume of basins = gal.
Plant flow = gal./day
Return sludge flow = gal./day
Basin volume x 24
(Flow) + (Return sludge flow)
F/M Ratio (Food/Microorganism) BOD or COD
Basins Inf. EOD5 conc. (avg. or daily value) = mg/1
Basins Inf. COD conc. (avg. or daily value) = mg/1
Plant Flow = mgd
MLVSS conc. (avg. or daily value, note Volatile SS) = mg/1
Basin Vol. = m.g.
(BOD^ conc.) x (plant flow) x (8.34) = lby_ B0D/lb. MLVSS
(MLVSS) x (Basin Vol.) x 8.34
-33-
-------
^Trf'r-OJ4r^f-3— =lbs- C0D/lb- ,,LVSS
(MLVbS) x (Basin Vol.) x (8.34)
8. Mean cell residence time (MCRT) = days
MLSS c.onc. (avg. or daily value) = mg/1
Basin vol. = m.g.
Clarifier vol. = m.g.
Waste activated sludge conc. = mg/1
Waste activated sludge flow rate = mgd
Plant effl. TSS = mg/1
Plant flow = mgd
(MLSS) x (Basin vol. + Clarifier vol.) x 8.34 dayg
(Waste activated sludge conc.) x (waste flow) x 8.34 +
(Plant effl. TSS x plant flow x 8.34)
Clarifier
1. Detention time = hours
Plant flow to each clarifier = gals./day
Individual clarifier vol. = ga]s.
(clarifier Vol. (each) x 24 = hours
Plant flow + Return Sludge Flow
2. Surface loading rate = gal./day/sq. ft.
Surface area/clarifier = sq. ft.
plant flow to clarifier = gal./day
Plant flow to clarifier = gai./day/sq. ft.
Clarifier surface area
3. Weir Overflow Rate (gal./day/lin. ft.)
Weir Length = ft.
Plant flow to clarifier = gal./day
Plant flow = gai./day/lin. ft.
Weir length
-34-
-------
APPENDIX E
OXYGEN UPTAKE PROCEDURE U
A. 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 liter each)
5. DO titration assembly for instrument calibration
6. Graduated cylinder (250 ml)
Adapter for connecting two BOD bottles
B. Procedure
1. Collect samples of return sludge, aerator influent and final
clarifier overflow. Aerate the return sludge sample promptly.
2. Mix the return sludge and measure that quantity for addition
to a 300 ml BOD bottle that corresponds to the return sludge
proportion of the plant aerator, i.e. for a 40% return sludge
percentage in the plant the amount added to the test BOD
bottle is:
300 X .4 = 120 = 86 ml
1.0 + • .4 1.4
3. Carefully add final clarifier overflow to fill the BOD bottle
and to dilute the return sludge to the plant aerator mixed
liquor solids concentration.
4. Connect the filled bottle and an empty BOD bottle with the
BOD bottle adapter. Invert the combination and shake vigorously
while transferring the contents. Re-invert and shake again
while returning the sample to the original test bottle. The
sample should now be well mixed and have a high D.O.
5. Insert a magnetic stirrer bar and the previously calibrated
DO probe. Place on a magnetic stirrer and adjust agitation
to maintain a good solids suspension.
6. Read sample temperature and DO at test time t=0. Read and
record the DO again at 1 minute intervals until at least 3
consistent readings for the change in DO per minute are
obtained (ADO/min). Check the final sample temperature.
This approximates sludge activity in terms of oxygen use
after stabilization of the sludge during aeration (unfed
sludge activity).
-35-
-------
Appendix E (cont'd.)
7. Repeat steps 2 through 6 on a replicate sample of return
sludge that has been diluted with aerator influent (fed
mixture) rather than final effluent. This A T)0/minute
series reflects sludge activity after mixing with the new
feed. The test results indicate the degree of sludge
stabilization and the effect of the influent waste upon
that sludge.
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.
------- |