EPA 904/9/75/002
TECHNICAL ASSISTANCE PROJECT
AT THE
CALHOUN, GEORGIA
WASTEWATER TREATMENT PLANT
JULY ~ AUGUST 1975
,^S*V
PRC
Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
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TABLE OF CONTENTS
PAGE
INTRODUCTION . 1
SUMMARY OF STUDY FINDINGS 2
RECOMMENDATIONS 3
STUDY OBJECTIVES AND METHODS s. 5
TREATMENT FACILITIES 8
DISCUSSION OF OPERATION AND MAINTENANCE PROBLEMS 10
STUDY RESULTS AND OBSERVATIONS 12
FLOW 12
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES .... 12
DISSOLVED OXYGEN PROFILES 14
OXYGEN UPTAKE 14
MIXED LIQUOR IN AERATION BASIN 17
SLUDGE BLANKET IN CLARIFIERS 18
RETURN SLUDGE 19
DIGESTER, THICKENER AND DRYING BEDS 19
DAILY FECAL COLIFORM DENSITIES 19
BACTERIAL CHARACTERISTICS OF ACTIVATED SLUDGE 20
CHLORINE CONTACT TANK BY-PASS 20
USE OF CHLORINATED EFFLUENT FOR FOAM CONTROL 21
GENERAL OBSERVATIONS 21
OTHER PARAMETERS . . . . . 23
APPENDICES
A. PLANT DESIGN DATA 24
B. CHEMICAL LABORATORY DATA 26
C. DISSOLVED OXYGEN CONCENTRATION IN THE AERATION
BASINS 36
D. OXYGEN UPTAKE PROCEDURE 37
E. INFLUENT pH AND CONDUCTIVITY LEVELS 39
FIGURES
1. CALHOUN SEWAGE TREATMENT PLANT 6
2. RAW WASTE FLOW 13
3. DISSOLVED OXYGEN PROFILES - AERATION BASIN #1 . . . 15
4. DISSOLVED OXYGEN PROFILES - AERATION BASIN #2 . . . 16
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INTRODUCTION
A technical assistance study of operation and maintenance problems
at the wastewater treatment plant serving Calhoun, Georgia was conducted
during July 28 - August 3, 1975. This was the first in a series of
studies to be conducted by the U.S. Environmental Protection Agency,
Region IV, Technical Assistance Team. The purposes of the study are to
assist local wastewater treatment plant operators in maximizing treatment
efficiencies and in solving special operational problems.
The activated sludge plant, serving approximately 4,700 residents
of the City of Calhoun and several tufted carpet mills, has been in oper-
ation for about three years. Industrial wastes constitute approximately
80 to 90 percent of the total plant flow. During September 1974, an
efficiency study showed the plant to be in a poor state of repair with
removal efficiencies similar to those of a primary plant. Under new
plant supervision and a city ordinance requiring_pretreatment, operation
and maintenance has greatly improved; however, treatment efficiencies
can be further improved by the elimination of some existing operational
problems which this study addresses.
The cooperation and active participation of the Georgia Environmental
Protection Division in planning and conducting the study is gratefully
acknowledged. The team is especially appreciative of the cooperation
and assistance received from Calhoun City officials and plant personnel.
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SUMMARY OF STUDY FINDINGS
The 7.0 mgd activated sludge plant serving the city of Calhoun was
operating at the hydraulic design capacity during weekdays, however,
organic loadings and weekend hydraulic loadings were well below design
capacities. A major problem since start-up of the facility has been an
abundance of lint from the carpet industries served by the system. Although
there are still significant amounts of lint throughout the system, the
problem is improving because of a city ordinance now in affect which
requires fine screening of wastewaters by the industries prior to discharge
into the municipal sewerage system. Maintenance problems noted during
a September 1974, efficiency study of plant operation have been corrected.
Another major problem at the start-up of the facility was the
inability to produce a healthy activated sludge. In an effort to
increase the mixed liquor suspended solids, a minimum amount of sludge
has been wasted resulting in an old, overoxidized sludge. Increased
wasting of sludge has been initiated in an effort to produce a healthier,
younger sludge.
Screens on pumps located in the chlorine contact chamber, used to
recirculate water for foam control in the aeration basins, must be
cleaned periodically. Cleaning requires the chlorine contact chamber
to be by-passed and drained, a process which should be performed on
the weekend during low flow.
Dissolved oxygen profiles throughout the aeration basins were
determined under each major flow condition and aerator usage configura-
tion. These data indicated the need to use all aerators during normal
weekday flows. Half of the aerators can be shut off during nightly and
weekend low flow periods without causing serious dissolved oxygen defi-
ciencies. When only half of the aerators are working, good, mixing is
not presently attained due to the high settling velocity of the mixed
liquor solids. However, the mixed liquor solids should become less
dense with the increased wasting program.
A portion of the chlorinated effluent is pumped back and sprayed onto
the aeration basins for foam control. An oxygen uptake study indicated
that the recirculated effluent should be limited to less than 20 percent
of the plant flow to prevent reductions in treatment efficiencies.
- Observations of laboratory procedures indicated some necessary modi-
fications in the BOD5 and COD analyses. Past laboratory data indicated
significant fluctuations of BOD^ values on the influent. This occasionally
caused oxygen depletions in the BOD5 test outside the 40-70% range recom-
mended by the procedure. Recommendations were made related to standardi-
zation of laboratory procedures.
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 treatment
efficiencies and plant operation:
1. An increased volume of solids should be wasted daily from the
system. Settling characteristics and volatile solids concen-
tration of the mixed liquor should be closely monitored. Mixed
liquor volatile suspended solids in the 2,200 to 2,500 mg/1
range are suggested under present loading conditions.
2. All aerators should be operated during periods when influent
flow exceeds 5 mgd. During low flow periods, at night and
on weekends, half the aerators may be shutdown to conserve
energy.
3. All aerators should not be shutoff simultaneously for servic-
ing, unless it presents a safety hazard. At least two aerators
should be operated in each basin at all times.
4. A fire hose may be used in breaking up the floating fiber and
sludge mat in the return sludge pits before pumping to the
digester.
5. The sand drying bed surface should be worked before pumping
sludge.
6. The chlorine contact chamber recirculating pump screens should
be cleaned during the weekend at low flow periods.
7. Recirculated chlorinated e.ffluent for foam control should be
limited to less than 20 percent of the plant flow.
8. Maintenance schedules and activities should be posted for
the employees information and/or instructions.
The following laboratory procedures should be initiated to improve
the quality of data from the BOD and COD analysis:
1. The sodium thiosulfate should be standardized against primary
standard potassium biniodate at a minimum of twice weekly.
2. Blanks of the formula C dilution water should be run daily.
3
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3. Ac least two dilutions of influent BOD5 samples should be made
in order to consistently obtain oxygen depletion within the AO
to 7C percent range recommended by the procedure.
4. Ferrous ammonium sulfate titrant used in the COD test should
be standardized daily against primary standard potassium Hi-
chromate.
A
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STUDY OBJECTIVES AND METHODS
Municipal wastewater treatment plants are selected for possible
technical assistance 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 the study
efforts will result in improved operational efficiencies.
At the Calhoun, Georgia Wastewater Treatment Plant, two specific
questions by plant personnel were addressed. The first was to determine
if the use of relatively large amounts of chlorinated effluent (1 tngd)
for foam control in the aeration basins had a detrimental effect on
microbial activity. This was accomplished by observing oxygen uptake
rates using varying amounts of chlorinated effluent and mixed liquor.
The other question was to determine if the 500 foot discharge line
provided adequate contact time for chlorine disinfection when by-pass-
ing the contact chamber. This procedure is occasionally necessary when
cleaning the two recirculating pump screens mounted on the bottom of
the chlorine contact chamber. This situation was assessed by by-passing
the chamber and making coliform MFN determinations. Dye was used to
determine retention time in the by-pass line.
Influent and effluent sample stations, 1-1 and E-3 respectively,
(Figure 1) were sampled for five 24-hour periods with ISCO model 1392-X
automatic samplers. The samplers were set to pump aliquots of sample
_at hourly intervals into individual glass bottles packed in ice.
Individual aliquots were composited proportional to flows at the end of
each 24-hour sampling period. The samples were used to characterize
the influent and to determine overall plant efficiency. An additional
ISCO model 1392-X automatic sampler was installed at station 1-1 and the
individual hourly samples were analyzed for pH and conductivity.
Daily dissolved oxygen profiles were obtained throughout the two
aeration basins employing a YSI model 51A dissolved oxygen meter.
Profile locations were selected in order to represent expected low DO
areas. These areas varied depending on the number of aerators operating.
Sludge activity was determined by the oxygen uptake procedure
presented in Appendix D. The rate of oxygen uptake for fed and unfed
sludge was determined and a load factor was calculated. The load factor
is a ratio which is a function of microorganism acclimation and the
biodegradability of the waste.
A series of standard operational control tests were run twice daily;
once in the morning and once in the afternoon for five days. The control
tests consisted of:
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FIGURE I
CALHOUN SEWAGE TREATMENT PLANT
CALHOUN, GA.
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o Settleability of the mixed liquor suspended solids as determined
by the 60 minute settlometer test;
® percent solids by centrifuge on the mixed liquor and return
sludge;
© complete solids analysis on mixed liquor, digester and return
sludge;
© depth of clarifier sludge blanket in final clarifiers, and
e turbidity of the effluent from both final clarifiers.
Physical observations of individual unit processes and flow meter
readings were recorded during each test sampling period.
A follow-up assessment of plant operations and maintenance will be
made at a later date. This will be accomplished by utilizing control
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.
7
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TREATMENT FACILITIES
The wastewater treatment plant is an activated sludge facility
with a hydraulic design capacity of 7.0 mgd. Construction of the
$2,600,000 facility was started in 1969 and completed in the fall of
1972.
Unit processes include bar screens, an aerated grit chamber,
aeration basins, final clarifiers, aerobic digester, chlorine contact
tank, gravity sludge thickener, and sludge drying beds (Figure 1).
Wastewaters flow to the plant by gravity along two major interceptor
lines. One is located along the Oostanaula River on the north side of
the city and the other along Oothcaloga Creek on the south. The raw
waste flows into a deep wetwell in the primary lift station where it is
lifted by three spiralift pumps to ground level.
Wastewater flows into the treatment plant through two parallel
mechanically cleaned bar screens and Parshall flumes, and an aerated
grit chamber. From this point, the waste is again lifted by spiralift
pumps to the aeration basins.
Wastewater then flows through a splitter flume into two parallel
aeration basins. Air is supplied by four 100 hp electric motor driven
brush aerators. After a 10 to 30 hoar retention time, depending on
plant inflow and recirculated sludge rate, mixed liquor flows from the
bottom of each basin through separate pipes to two clarifiers. Each,
pipe is equipped with a Venturi meter for flow measurement and a
hydraulically operated (water pressure) butterfly valve which controls
the water level in each aeration basin. Regulation of each valve is
controlled by a water level sensor in each basin.
Waste from the aeration basins flows to the two center feed,
circular clarifiers for final settling. Overflow from the clarifiers
flows into a discharge sewer where chlorine gas is applied for disin-
fection. The treated wastewater then flows through a baffled rectangular
chlorine contact chamber with subsequent discharge into the Oostanaula
River. Return activated sludge flows via gravity from the clarifiers
to the raw waste secondary lift station. Waste sludge is pumped from
the sludge pit at the clarifiers to the aerobic digester.
The digester is a rectangular basin with rounded ends similar
in geometry and operation to the aeration basins. Sludge is circulated
and aerated with two brush aerators turning in opposite directions on
each side of the basin, forcing a counterclockwise circulation pattern.
As sludge is pumped into the digester, overflow from the digester flows
8
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into a gravity thickener. Sludge can be recycled from the thickener
to the digester when dischaige to the drying beds is not required.
Digested sludge is pumped from the thickener to one of twelve
uncovered sand drying beds. The beds are filled from a single stand
pipe located in one corner of each bed.
Design criteria for the wastewater treatment plant are enumerated
in Appendix A.
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DISCUSSION OF OPERATION AND MAINTENANCE PROBLEMS
Effective start-up of the plant has been extremely slow due to
numerous problems. One of the major problems has been excessive lint
entering the plant from the area carpet mills. This resulted in
plugging of all moving parts and unmanageable floating masses of fiber
and sludge. Fins were broken off the brush aerators by accumulated
lint resulting in greatly reduced efficiency. Butterfly valves on
each of the aeration basin discharge and return sludge lines presented
continual problems. Motors and brush aerator bearings were inoperative
due to lint accumulation, fluctuating water levels in the aeration basin
and inadequate servicing. The follox-ying is an excerpt from the Organic
Characterization Study, Coosa River Basin - Northwest Georgia, September 30-
Oc.tober 3, 1974, prepared by the U.S. Environmental Protection Agency,
Surveillance and Analysis Division, Athens, Georgia, and describes oper-
ations as they existed:
Removal efficiencies are:
o Five-day Biochemical Oxygen Demand (BOD5) - 38 percent
o Total Suspended Solids (TSS) - 20 percent
o Chemical Oxygen Demand (COD) - 13 percent
Another evidence of ineffective treatment is the low level
of sludge produced.
Operation and maintenance is almost nonexistent. The operation
of the plant and upkeep of existing equipment have been victims
of neglect. Only two of 16 aerators were working at most; and
on one day, none were operating. Several fins had been broken
off the aerators. The overall appearance of the plant was poor.
Lint was piled up at the side-of the aeration basin and the
grass needed cutting.
In the past year, city officials have made a determined effort to
repair equipment and get the plant into satisfactory operation. This
effort has shown significant results. In the recent study period
(July 28 - August 3, 1975), removal efficiencies were:
o BOD5 - 91 percent
o TSS - 77 percent
o COD - 72 percent
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Steps taken by city officials have included:
«> Hiring a new engineer who has devoted essentially all
of his time to maintenance and operational problems at
the wastewater treatment plant. Activated sludge was
hauled from the wastewater treatment plant at Dalton,
Georgia, for seed and all aerators were repaired and
placed in operation.
o The passing and enforcement of a new city ordinance
requiring industries to fine screen wastes before
discharge into the city sewerage system.
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STUDY RESULTS AND OBSERVATIONS
FLOW
Raw wastewater flow into the plant is determined by a two-foot
Parshall flume, totalizer and recorder. The flume was checked for
proper calibration and was found to be accurate.
The raw waste flow during the study period is presented in Figure
2. Weekday influent flow averaged 6.2 mgd and varied from approximately
9 mgd during the day to about 4 mgd at night. The average weekend flow,
determined during a 24 hour period beginning 9:00 AM Saturday and ending
8:00 AM Sunday, was 2.1 mgd. The -minimum weekend flow was approximately
1.2 mgd.
Return sludge flow (RSF) from the final clarifiers back to the
aeration basins varied from zero to about 4 mgd during the study period.
During the weekend, the RSF was greater than the raw waste flow entering
the plant.
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
A chemical description of the influent, effluent and percent reduction
through the plant is listed below.
PARAMETER INFLUENT EFFLUENT % REDUCTION
BOD^ (Avg. of 3 Days)
142 mg/l
13 mg/l
91
COD (Avg. of 5 Days)
496 mg/l
140 mg/l
72
Total Suspended Solids
(Avg. of 5 Days)
70 mg/l
16 mg/l
77
TKN (Avg. of 5 Days)
8.38 mg/l
2.80 mg/l
67
NH3 (Avg. of 5 Days)
1.92 mg/l
0.19 mg/l
91
NO3 - NO2 (Avg. of 5 Days)
0.20 mg/l
1.75 mg/l
-
Total Nitrogen
(Avg. of 5 Days)
8.58 mg/l
4.55 mg/l
47
Total-P (Avg. of 5 Days)
10.2 mg/l
8.7 mg/l
15
Pb (Avg. of 3 Days)
<80 yg/1
<80 pg/1
-
Cd (Avg. of 3 days)
<80 pg/l
<80 pg/1
-
12
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7/28 7/2P 7/30 7/31 8/1 8/2 8/3
TIME
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PARAMETER
INFLUENT
EFFLUENT
% REDUCTION
Cu (Avg. of 3 Days)
Cr (Avg. of 3 Days)
<80 yg/1 <80 pg/1
36 yg/l 18.6 )jg/l
48
Zn (Avg. of 3 Days)
Temp, range (°C)
1368 yg/1 856 jjg/1
37
34-42
29-32
pH range
6.0-7.5
6.4-6.8
Conductivity range
(ymhos cm' )
573-2290
A complete listing of all laboratory data is presented in Appendix B.
DISSOLVED OXYGEN PROFILES
A profile of dissolved oxygen concentrations at various locations
within the aeration basins was determined under each major flow condition
and aerator usage configuration (Appendix C and Figures 3 and 4).
During normal weekday flows, a minimum DO concentration of 3 mg/1
was maintained in both basins with all aerators in use; however, when
operating only half the aerators under these flow conditions extremely
low DO concentrations occurred. Dissolved oxygen, during low flow periods,
remained at a satisfactory level with only half the aerators in use.
These data indicate the need to use all aerators during weekday
normal flow. Half of the aerators can be shut off during nightlv and
weekend low flow periods without encountering low dissolved oxygen levels.
However, with only half of the aerators operating, solids deposition
may be expected, as evidenced from the settlometer test data and samples
collected from the basin bottom. These solids are resuspended when all
aerators are turned back on.
OXYGEN UPTAKE
General sludge activity can be measured by determining the difference
in oxygen uptake rates of the sludge before and after introduction of the
raw waste. The ratio of these two variables or "load ratio" is calculated
as follows:
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FIGURE 3
DISSOLVED OXYGEN PROFILES
AERATION BASIN j
Aerators
4.0
3.0
2.0
I. 0
0.0
3.0
2.0
1.0
0.0
4.0 r-
on
I I I
All Aeration Units On (Flow-8mgd)
off
i
I
I
Aeration Units On ( Flow-7.6 mgd )
I
on
I
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FIGURE 4
DISSOLVED OXYGEN PROFILES
AERATION BASIN 2
5.0
n 4.0
s 3.0
§ 2.0
1 1.0
ro
2 0.0
C7>
o
ci
10
o
t
o
K)
s
3.0
m
2.0
ig
CJ
1.0
tn
IO
0.0
3.0
2.0
1.0
0.0
4.0
3.0
2.0
1.0
0.0
Aerators
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Load ratio =
A DO/min of fed sludge
A DO/min of unfed sludge
OXYGEN UPTAKE RATES
DATE
TIME
% RS
Avg. O2 Uptake
(ppTa/min)
URS 1/
Avg. 02 Uptake
(ppm/min)
FRS 2/
LOAD RATIO
FRS/URS
7/29
-
38.5
0.45
1.6
3.55
7/30
-
40.0
0.60
1.4
2.33
7/31
1100
37.5
0.70
1.8
2.57
7/31
1430
7.0
0.25
0.5
2.0
8/1
-
27.8
0.70
2.35
3.4
8/1
1530
77.6
0.90
2.10
2.3
1/ ~
URS
- Unfed
Return Sludge
2/ -
FRS
- Fed Return Sludge
The step by step procedures and
Appendix D.
significance of
the test are presented in
Calculated load factors indicate a well acclimated sludge with a good
supply of acceptable food under favorable conditions. It has been stated
by Ludzack, et al that extended aeration plants normally perform best at
a load ratio of less than two; however, each plant will have its own
optimum operation range. The load ratios in the table reflect conditions
typical of conventional activated sludge plants.
MIXED LIQUOR IN AERATION BASIN
Samples were taken from each basin at the point of discharge to
the clarifiers (sample stations A-3, A-6 Figure 1). Settleability was
determined using the 60 min. settleometer test with both basins exhibiting
similar settling characteristics. Near maximum compaction was attained
in about two minutes. The average five minute reading was 12 percent with
an average final reading of eight percent by volume. A slow settling
straggler pen floe was left in the supernatant. The samples were allowed
to sit undisturbed to see if the sludge would swell (denitrification) and
float to the surface as would be expected; however, no change was observed
after 24 hours. Suspended solids, volatile suspended solids and percent
17
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solids by the centrifuge test were run on these samples to further
determine the amount and condition of the solids in the aeration basin.
The centrifuge values for percent solids ranged from 1.0% to 3.0%
in Basin #1 (Station A-3) and from 0.8 to 3.9% in Basin it 2 (Station A-6) .
The suspended solids concentrations ranged from about 1100 mg/1 up to
3500 mg/1. The fast settling characteristics of the solids led to
difficulty in obtaining a representative sample. The amount of solids
in suspension at the five foot depth, where the samples were taken, was
dependent upon the amount of mixing in each aeration basin. During
periods when half of the aerators were off, some of the mixed liquor
solids settled to the bottom producing much lower TSS concentrations than
when all aerators were running. (Based on past plant data and data
collected during periods of good mixing, the actual TSS values were 3500
mg/1 or greater).
Calculated sludge volume index (SVI) values ranged from 17 to 83.
The median value was 36 reflecting the very dense compact nature of the
settled sludge.
Sludge age calculations using a MLSS concentration of 3500 mg/1,
an influent TSS of 70 mg/1 and an average flow rate of 5.0 mgd indicated
a value of 51 days. This value appears to be much too high and indicates
the need to remove solids from the system.
Current BOD^ and COD loading parameters were calculated by using
a MLTSS value of 3500 cg/1 with 65 percent volatile. The BOD5 loading
was .06 lbs BOD5 per day/lb of MLVSS with the recommended range falling
between .05 to 0.10. COD loadings averaged .21 lbs COD per day/lb of
MLVSS. The recommended range for COD is less than 0.2. These loading
factors appear to be at or near the recommended loadings for uhe extended
aeration process; however, the sludge is very old and over oxidized.
SLUDGE BLANKET IN CLARIFIERS
The sludge blanket depth in each clarifier was measured on several
occasions during the study by using an optical viewer constructed from
aluminum pipe and equipped with a lense and light on the bottom. This
procedure enables the operator to observe clarifier operating conditions
below the surface and to obtain advance warning when operational problems
such as bulking, etc. may be imminent.
Because of the high rate of sludge return and the dense nature of
the sludge at the Calhoun plant, the sludge blanket was less than 2 feet
thick on all occasions. On several occasions, there was essentially no
blanket.
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RETURN SLUDGE
Return sludge from each clarifier flows through telescoping valves
into separate sludge pits and thence into a common manhole where it
flows by gravity into the secondary raw waste lift station. Each return
line was constructed with a Venturi meter and butterfly valve. Excessive
clogging of one of the valves with lint caused plant personnel to remove
the valve. Lint also caused continual problems in the sludge sumps by
plugging the telescoping valves and also by forming thick mats on the
sludge surface. Plant personnel are currently removing lint from the
sumps by hand which is a difficult and time-consuming task.
As a result of valve clogging problems and in an effort to prevent
clogging by increasing flow rate, the rate of return sludge is highly
variable. As shown in Appendix B, TSS concentrations vary from 6,000 to
42,000 mg/1 with a corresponding variable flow rate of from near zero to
4 mgd. An increased hydraulic loading is placed on the aeration basins
by returning excessive water with the sludge.
DIGESTER, THICKENER AND DRYING BEDS
During the initial years of plant operations, the sludge handling
facilities were not used due to the lack of sludge production. After
repairs were made and the plant reseeded, operators concentrated on
retaining the mgxixmtrn pmount of solids in the system in order to build
MLSS up to the 3000 to 3500 mg/1 level. When the predetermined level
of solids was reached, a gradual wasting program was started and the
sludge handling system is now in full operation. At the conclusion of
the study digested sludge had been pumped to two drying beds. One bed
was pumped during the survey and the other bed was pumped about three
weeks before. The first bed had cracked to a depth of two to three
inches and appeared to be drying rather slowly; however, drying condi-
tions had been poor. Considerable quantities of carpet fibers could
be seen in the partially dried surface layer,
A sample was collected for solids determination as the sludge was
pumped onto the second bed. The solids content was 8% by weight and
58% volatile.
Samples collected from the digester contained a volatile fraction
of 62%. Although the volatile contents are somewhat higher than would
normally be expected, the sludge appeared to be well stabilized and there
were no offensive odors from either drying bed.
FECAL C0LIF0RH DENSITIES
Fecal coliform densities in the wastewater treatment plant effluent
(Station E-3) were 50/100 ®1 (MPN) or less for all samples as shown
below:
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STATION DATE TIME
FC/100 ml
RESIDUAL CHLORINE nig/I
E-3 7/29 1015
1330
20
20
1.20
0.27
7/30 0825
1215
7/31 0845
20
50
50
1.40
1.38
0.35
BACTERIAL CHARACTERISTICS OF ACTIVATED SLUDGE
Microscopic slide examinations were made on both return sludge and
mixed liquor samples. Return sludge slides showed a dark sediment with
limited observable microbial activity. Protozoans were in mixed popula-
tion, with ciliates being the predominant organisms. Mixed liquor from
the aeration basins contained numerous fibers and chaining bacterial
cells. In each examination stalked ciliates were observed, but in lesser
numbers than free swimming rotifiers and nematodes. The majority of the
bacteria cells were non-motile, with little flock formation, and few new
cell formations on established floes. Total bacteria analysis showed
the following densities in the aeration basins:
STATION
DATE
TIME
TOTAL BACTERIA/100 ml
A-l
7/30
1545
23,000,000
A-2
7/30
1600
23,000,000
A-3
7/30
1552
33,000,000
CHLORINE CONTACT TANK BY-PASS
Samples were collected from the plant effluent while the chlorine
contact chamber was by-passed. Dye was used to determine the retention
time in the 500 foot outfall line. The dye was poured into the No.' 2
clarifier discharge and reached the river in four minutes. Chlorine
gas is injected into the outfall line a short distance downstream of
the clarifiers. Grab samples were collected from the plant effluent
and analyzed for fecal coliform concentrations with the following results:
CHLORINE
TIME
FC/100 ml (MPN)
CONTACT TIME
PLANT FLOW
RESIDUAL (mg/1)
1600
192,000
4 min.
8 mgd
0.22
1605
17,200
4 min.
8 mgd
-
1610
22,100
4 min.
8 mgd
20
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The study shows that during normal weekday flow conditions proper
disinfection cannot be attained while by-passing the chlorine contact
tank. It would be advisable, therefore, to by-pass the tank only on
weekends when the flow rate is at a minimum. This would in effect give
a longer contact time and should provide more efficient disinfection.
USE OF CHLORINATED EFFLUENT FOR FOAM CONTROL
Chlorinated effluent is sprayed on the aeration basins for foam
control. The effect of this procedure on microbial activity was determined
using the oxygen uptake procedure.
An experimental return sludge to raw waste ratio was determined
using the following data:
Varying volumes of chlorinated effluent containing 1.4 mg/1
residual chlorine were mixed with a constant volume of the experi-
mental mixed liquor. The following data show the amount of chlorinated
effluent (as percent of total volume) and the corresponding oxygen
uptake rate.
These data indicate that effluent waters containing 1.4 mg/1
residual chlorine can be used for foam control without inhibiting
biological activity, as long as the amount used is limited to 20 percent
of plant influent.
GENERAL OBSERVATIONS
The following are general observations related to the operation
and maintenance of the plant:
o One problem with brush aerators is the water spray and wind
drift which causes a very dangerous film of sludge to accumulate on
walkways near the aerators. This problem exists at the Calhoun
Wastewater Treatment Plant. However, plant personnel are in the process
of installing a water system to permit periodic hose washdown of the
aerators and digester. This action will greatly improve safety condi-
tions and the general appearance of the basins.
Assume: One mgd chlorinated effluent for foam control
Six mgd raw waste influent to plant
Two mgd returned sludge to aerators.
% Chlorinated
Effluent
Average
0? Uptake Rate (mg/l/min)
0.5
1.0
10.0
20.0
60.0
1.05
0.92
1.00
0.88
0.36
21
-------
o As plant influent flow rates build up during the day to the
eight or nine mgd rate, fluffy 1/4 inch sludge particles can be
observed rising to the surface near the clarifier walls and flowing
over the weirs. On one occasion when flow to the clarifiers was
in the 12 to 14 mgd range, the problem was particularly noticeable.
This carry over is caused by scouring on the clarifier bottom at
the walls as the flow direction turns upward.
o All aerators in each basin are normally shut off once per
week for one hour periods for servicing aerator and motor bearing.
This permits most of the mixed liquor solids to settle and oxygen
levels to be depleted.
© A fire hose was used to break up the lint mat in the sludge
sumps to permit pumping of the sump contents to the digester. A
large portion of the lint goes through the sludge handling system and
is pumped to the drying beds.
o Butterfly valves control the water level in each aeration
basin. Proper operation of the valves is absolutely critical to plant
operation. If the valves open too much, the clarifiers flood causing
washout of solids with a resulting drop in water level in the aeration
basins. A drop of a few inches results in loss of ability to aerate
and mix the contents of the basin. Conversely, improper restriction
in the valve results in a water level rise in the aeration basin, which
overloads the aerators causing reduced oxygen transfer, poor mixing
and possible mechanical failure.
© Laboratory facilities at the Calhoun Wastewater Treatment
Plant were very well equipped and maintained. The equipment was
neatly arranged and evidenced conscientious care. General lab tech-
niques of the operators were good. Data generated by the operators
were well organized for easy reference.
e For quality control purposes, total suspended solids samples
from Basin No. 1 and No. 2 were split and analyzed by plant personnel
and EPA. The results are as follows:
EPA PLANT
Basin No. 1 4,500 4,100
Basin No. 2 5,770 5,710
Duplication was obviously very good.
22
-------
Other Parameters
Hourly variation of influent pH and conductivity is presented
in Appendix E. The pH varied from 6.0 to 7.4 and the conductivity
ranged from 5 73 to 2290 umhos/cm .
Influent and effluent samples were analyzed for chlorides.
Chloride concentrations varied from 220-292 rng/1 in influent samples
(1-1) and 215-270 mg/1 in effluent samples (E-3).
23
-------
Appendix A
Treatment Facilities
Calhoun S.T.P., Calhoun, GA
I. Plant Design Capacities
a. Design Flow - 7.0 mgd average daily
b. Population Equivalent (Solids) - 30,000
c. Population Equivalent (BOD) - 66,000
II. Treatment Units
a. Primary Lift Station
3 spiralift pumps with a rated capacity of 10 mgd each.
Lift - 29.5 ft.
b. Mechanically Cleaned Bar Screens
85° Industrial, 2 units, 20 mgd capacity each, 1" spacing.
c. Two parallel Parshall Flumes
Influent throat width 2 feet. Only one flume normally in use.
d. Grit Tank
1 unit, mechanically cleaned, aerated (diffused air)
surface loading at design flow 15,800 gpd/sf
detention period - 60 sec.
disposal of grit - burial
e. Secondary Lift Station
3 units, spiral pump, 15 mgd each, Lift - 12 ft.
f. Aeration Tanks
number - 2 units
type - rectangular with rounded ends
dimensions, rectangular area - 343' length
84' width
circular area - A3' radius
surface area - 34,620 sq. ft. each
volume - 340,000 cu. ft. each
detention time - 8.75 hours including 100% returned sludge
17.5 hours at no return sludge
24
-------
Appendix A (Cont)
g. Aeration Equipment
number aerators per basin (100 HP) - 4
lineal feet, aerators (brush, area) - 296 feet per basin
type - constant speed surface-brush
theoretical capacity - 2960 lbs. oxygen/hour or
7 lbs 02/lb. BOD/day
provision for foam control—spray (treated effluent)
h. Secondary Clarifiers
number - 2 (circular) center-fed
dimensions - 86 ft. diameter
8 feet depth (outside)
13.A" depth (center)
surface area - 5,809 sq. ft. each
design loading
Detention Surface Overflow Rate
Flow MGD Period, hours Loading gpd/sf gpd/ft weir
Min.
3.5
6.0
300
6,500
Design
7.0
3.0
600
13,000
Peak
21.0
1.0
1,800
39,000
sludge removal - mechanical - gravity flow
i. Waste Sludge Pumps (to aerobic digester)
number - 2
capacity of each - 350 gpm
j. Return Sludge
gravity flow controlled by telescoping valves
sludge returned to secondary lift station, 14 MGD max. return
rate
k. Aerobic Digester
number - 1
volume - 92,000 cu ft.
aeration, brush aerators, 48 linear feet capacity - 240 lbs.
oxygen/hr.
25
-------
Appendix A (Cont)
Sludge Thickener
number - 1
size - 25* diameter
491 sq. ft.
15' 9" depth
mechanically mixed
Sludge Beds
number - 12
size - 96' x 26'
total area of 12 beds - 30,000 sq. ft.
sludge drying bed area/capita - 1 sq. ft.
underflow - returned to influent
Chlorine Contact Chamber
size - 19,500 cu. ft.
detention time (avg. flow) - 30 min.
type - gas
max. capacity - 68 ppm (based on design flow)
Flow Measuring Devices
Location & Method:
influent - Parshall flume 2 ft. throat
mixed liquor - two Venturi meters
waste sludge - Venturi meter
return sludge - two Venturi meters
26
-------
Appendix B
Chemical Laboratory Data
Calhoun," Georgia
*,— ifrirwn-cin.-i.
-------
Appendix B (Cont)
Chemical Laboratory Data Calhoun, Georgia
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makes data'suspect
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i
-------
Appendix B (Cont)
Chemical Laboratory Data Calhoun, Georgia
///////$/*/ /$///// / / / / /
/ / s/.y.w /&//$'/£./&/ $/£ / /.V /*/*/$/<,/ /
STATION
S3
1
1
TIME
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//7 7 /?7S/ 7 //// //
1-1
7
28/
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75
24 hr.
corrtPj
427 ! 220
1
28 I 2.5
154
70
58
932
285
83
31
8.35
2.45
0.21
8.0
1 1
<80 |<80 ! 33 1 <10
1351
—
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29/!
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| 24 hr.
! comp.
i 24 hr.
comp.
291 1 240
1.0
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1
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1
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24 hr.
24 hr.
comp.
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1
-------
Appendix S (Cant)
Chemical Labotatoty Data Calhoun, deafgia
i
•
' ///$/////// / / / / / / /
/ / /J" // / // // / // // / / //
./ / /An/A / // // / // // / / / / ,
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YEAR
TIME
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-------
Appendix B (Cont)
Chemical Laboratory Data Calhoun, Georgia
>
STATION
MONTH
DAY
YEAR
TIME
/ / 41/?
/ '•v /? / *y S
/ / ^ ? / a'/O
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1 A / / / / / / / / /
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-------
Appendix B (Cont)
Chemical Laboratory Data Calhoun, Georgia
-------
Appendix B (Cont)
Chemical Laboratory Data Calhoun, Georgia
/ /' /// /«/ /////////// /
/ JiJh i/ J J J ////////.
i
MONTH
DAY
YEAR
/ # y/ ^ g/ / '
7
! 31
1400
1 !
11.0 |12020 i7160
__l __
| |
D-2 Sludge i
ro Tlrv Rprl i 7 1 31
*
*
1430
! i ! '
64.0 ! — I — I 92
58
1 j
i
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^Sludge collected |>y |
'plant perS0T?np1 fur mc'l-nl «
3152
6480
160
252.4(
0
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i ' 1
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-------
Appendix B (Corit)
Chemieal Laboratory Data Calhoun, Georgia
-------
PbfSRrtPjf}: pPRFgt*
S fi^HSRF S3ffpf-&^ f»F pfl 3^4
FSiaRe^EHTP -
/ / / / /' / ///"/"/ 7 / / / / / /
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j
»
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! 1 1
-------
Appendix C
DISSOLVED OXYGEN CONCENTRATION IN Tht AERATION BASINS
CALHOUN, GA. STP. JULY 29 - AUGUST 2, 1975
1/
7/29
1030
1130
A-l
34
3.7
3.5
3.5
3.3
/
1030
1130
A-S
34
4.6
4.1
3.3
2.7
<1.0
A-3
34
4 . 1
3.2
2.4
1.7
<1.0
A-l 0
34
3.2
3.3
3.0
3.0
A-7
34
2.7
2.7
2.5
2.6
A-ll
34
3.7
3.6
3.6
3.6
3.6
A-8
34
2.9
2.8
2.5
2.2
A-9
34
2.5
2.0
2.0
1.9
7/3l/
1045
1130
A-l
33 . 5
2.4
2.2
2.3
2.4
2,5
1135
1223
A-4
34
2.2
2.3
2.1
2.1
33.5
0.9
0,7
0,4
0.2
4-6
34
1,0
0.6
0.4
0.1
A-7
33. 5
0.8
0.6
0.4
0.4
A-10
34
0.7
0.6
0.4
0.4
A-8
33. 5
1. 3
0.7
0.3
0.0
A-ll
34
0.8
0.7
0.7
0.7
A-9
33. 5
'0.7
0.2
0.1
0.1
A-14
34
0.7
0.5
0.4
0.2
A-12
33.5
0.7
0.5
0. 3
0.2
A-13
33.5
0.1
0.0
0.0
0.0
3
8/1-
0630
0800
A-l
33
3.8
3.8
3.9
3.8
§188
A-6
33
2,7
2,5
2.3
2.0
A-3
33
3.1
2.7
2.7
2.5
A-ll
33
2.8
2.6
2.7
2.7
A-7
33
2.8
2.7
2.7
2.7
A-14
33
3,1
?,,7
2.5
2.3
A-9
33
2.9
2.9
2.6
2.0
A-16
33
2.2
1.9
2.2
1.8
A-15
33
2.7
2.5
2.3
2.1
3,
8/2
1000
1100
A-l
32
3.2
3.1
3.0
3.0
1000
1100
A-5
32
4.0
3.9
3.6
3.6
A-3
32
3.2
2.4
2.3
2.0
A-ll
32
3.3
3.0
3.0
2.9
A-9
32
3.2
3. 0
2.8
2.7
A-14
32
2.9
2.6
2.4
1.9
A-15
32
2.5
2.3
1.8
1.6
A-20
32
2.7
2.4
2.0
0.0
1/ - All four aeration units operating in each basin
2/ - Only two aeration units per basin 1 & 3 Basin #1, 5 & 7 Basin #2 In operation
~Z/ - Only two aeration units per basin 1 & 4 Basin #1, 5 & 8 Basin #2 in operation
4/ - No thermal stratification was observed - Temperature was constant throughout each basin.
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APPENDIX D
¦>
Oxygen Uptake Procedure
A. Apparatus
1. Electronic DO analyzer and bottle probe
2. Magnetic stirrer
3. Standard BOD bottles (3 or more)
4. Three vide mouth sampling containers (apprcx. 1 liter each)
5. DO titration assembly for instrument calibration
6. Graduated cylinder (250 ml)
7. 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 ' --,e
return sludge proportion of the plant aerator, i.e. for
a AO % return sludge percentn.^e in the plant the ai
added to the test j'OD bottle is:
300 x .4 = 120 - 86 ml
1.0 + .4 1.4
3. Carefully add final clarifier overflow to ."ill 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 novr be well mixed and have a high
D. 0,
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 (A DO/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).
37
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Appendix D (Cont)
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 DO/minute
series reflects sludge activity after mixing with the new
feed. The test results indicate the degree of sludge
stabilization and the effects 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 load factor means abundant, acceptable feed under
favorable conditions. A small LF means dilute feed, sick sludge,
poorly acceptable feed, incipient toxicity, or .unfavorable
conditions. A negative LR indicates that something in the wastewater
shocked or poisoned the "bugs."
(3) 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.
38
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Appendix E
Influent pH ana Conductivity Levels
Calhoun. OA STP
0100
3.45
6.15
6.95
6.55
766
0200
3.7
6. 15
6.7
6.9
573
0300
3.9
6. 55
6.8
7.2 |
668
0400
3.8
6.95
7.2
7.45
668
0500
3. 55
6.5
7.5
6.7
2290
0600
7. 15
6.2
7.2
6.95
945
1
0700
3. 75
6.5
7.0
7.1
831
0800
7.0
6.65
7.05
6.85
888
0900
3.6
6.65
6.8
6.0
973
1590
:
1000
1
1
6.75
6.7
6.5
1671
|
1100
Is. 75
6.7
6.5
i376
j
1200
3.8
6.8
6.8
1573
1300
[3.7
6.8
6.8
L671
1
1400
[>. 75
6.8
6.7
1365
1
1
1500
6.5 Is.9
6.7
6.7
876
i
!
i
1600
6.7 |6.6
6.5
6.75
1460
1700
6.6 jo. 5
6.8
6.75
1168
! 1800
7.1
6.75
6. 85
6.6
L362
1900
6.5
6.5
7.1
6.5
1411
2000
6.8
6.4
6.85
6.8
973
2100
6.9
6.75
6.7
6.95
778
1
2200
6.6
6.0
6.8
6.9
632
2300
6.7
6.2
6.5
6.65
867
2400
6.4
6.4
6.7
6.5
1156
: to
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