TECHNICAL ASSISTANCE PROJECT
AT THE
HOLLY HILL WASTEWATER TREATiW PLMF
HOLLY HILL/ FL
March, 1975
Environmental Protection Agency
Region IV
Surveillance ard Analysis Division
Athens, ua 30601
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TECHNICAL ASSISTANCE PROJECT
AT TO
HOULY HILL WASTEWATER TREATfOT PLANT
HDLLY HILL/ FL
March, 1976
Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, GA 30601
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CONTENTS
INTRODUCTION 1
SUMMARY 2
RECOMMENDATIONS 3
TREATMENT FACILITY 4
TREATMENT PROCESSES 4
PERSONNEL 4
STUDY RESULTS AND OBSERVATIONS 8
FLOW 8
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES. ... 10
AERATION BASINS 11
CLARIFIERS 13
CHLORINE CONTACT CHAMBER 14
ANAEROBIC DIGESTER 14
LABORATORY 16
REFERENCES 17
APPENDICES
A - LABORATORY DATA 18
B - AERATION BASIN DISSOLVED OXYGEN 19
C - GENERAL STUDY METHODS 20
D - ACTIVATED SLUDGE FORMULAE USED FOR
GENERAL CALCULATIONS 22
FIGURES
1. HOLLY HILL WASTEWATER TREATMENT PLANT 5
2. EFFLUENT AND RETURN SLUDGE FLOW 9
3. SETTLOMETER TEST 12
4. CLARIFIER DYE TRACER STUDY 15
TABLES
I. DESIGN DATA 6
II. WASTE CHARACTERISTICS AND REMOVAL
EFFICIENCIES 10
III. MEASURED AND RECOMMENDED PARAMETERS FOR THE
CONVENTIONAL ACTIVATED SLUDGE PROCESS 11
IV. MEASURED AND RECOMMENDED PARAMETERS FOR
SECONDARY CLARIFIERS 14
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INTRODUCTION
A technical assistance study of operation and maintenance
problems at the Holly Hill Wastewater Treatment Plant (WTP)
serving Holly Hill, FL, was conducted March 3-4, 1976, by
the Region IV, Surveillance and Analysis Division, U. S.
Environmental Protection Agency. Operation and maintenance
technical assistance studies are designed to assist waste-
water treatment plant operators in maximizing treatment
efficiencies as well as assisting with special operational
problems. Municipal wastewater treatment plants are selected
for technical assistance studies after consultation with state
pollution control authorities. Visits are made to each pros-
pective plant prior to the study to determine if assistance
is desired and if study efforts would be productive.
This plant was selected for study because of difficulty
in achieving design treatment efficiencies. In addition,
excessive solids are frequently lost in the effluent. The
specific study objectives were to:
a Optimize treatment through control testing and
recommended operation and maintenance modification.
9 Determine influent and effluent wastewater character-
istics .
© Assist laboratory personnel with any possible laboratory
procedure problems.
e Compare design and current loadings.
A follow-up assessment of plant operation and maintenance
practices will be made at a later date. 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 Florida Department of Environmental
Regulation (FL-DER) is gratefully acknowledged. The technical
assistance team is especially appreciative of the cooperation
and assistance received from personnel of the Holly Hill WTP.
1
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SUMMARY
The Holly Hill Wastewater Treatment Plant (WTP) was designed
as a 1.2 mgd conventional activated sludge facility with the flexi-
bility to operate in the contact stabilization mode. The approxi-
mate influent flow during the study was 1.01 mgd.
Specific problems encountered at the WTP are straggler floe
and severe activated sludge bulking due to filamentous growths,
excessive foam and scum on the secondary clarifier, as well as
inadequate sludge conditioning in the anaerobic digester. For
13 days prior to the study, return sludge was chlorinated result-
ing in extremely rapid settling of the mixed liquor suspended
solids and elimination of the foam and scum problems. The effect
of chlorinating the return sludge was evident during this study.
The percent BOD5 and TSS reduction during the study period was
90 and 88 percent, respectively. However, two weeks after stop-
ping the return sludge chlorination, the initial problems had
recurred.
The dissolved oxygen (DO) concentrations in the aeration
basins were low (1.7-0 mg/1), especially below the 5- to 7-foot
depths, indicating poor mixing and insufficient aeration. Aerators
are operated on timers and the DO was observed to rapidly decrease
when the aerators shut off.
The plant receives approximately 100,000 gpd of laundry
wastewater, most of which is discharged to the WTP between 8:00
a.m. and 4:00 p.m. During these hours, the laundry wastewater
accounts for approximately 15-25 percent of the plant inflow
and may be a significant contributor to treatment problems
encountered at the WTP.
2
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RECOMMENDATIONS
Based on observations and data collected during this study,
it is recommended that the following measures be taken to improve
wastewater treatment and plant operation:
1. Dissolved oxygen must be maintained at about 2 mg/l(3)
throughout the aeration basins at all depths. This will
probably require all aerators to remain on at all times.
2. Dissolved oxygen profiles should be made regularly to
insure that sufficient dissolved oxygen is being main-
tained throughout both aeration basins.
3. An in-plant control testing schedule should be
initiated and trend charts established and maintained.
A. Chlorination of the return sludge should be a temporary
control measure only and will require metering of
chlorine feed.
5. A secondary anaerobic digester will be necessary to
efficiently condition waste sludge. This should be
considered in the event that hauling of waste sludge
must be discontinued.
3
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TREATMENT FACILITY
TREATMENT PROCESSES
A schematic diagram of the 1.2 mgd conventional activated
sludge wastewater treatment plant (WTP) serving Holly Hill, FL,
is presented in Figure 1. Design data are enumerated in Table 1.
The WTP began operating in 1965 and presently serves an approxi-
mate population of 9,300.
After passing through the bar screen and comminutor, the
influent wastewater is split into the two parallel aeration
basins. Approximately 25 feet from the discharge of each aera-
tion basin, a wall is located with three openings (Figure 1)
which restricts mixing with the remainder of the basin. The
wall allows flexibility to operate the WTP in the contact stabili-
zation activated sludge mode if desired; however, the WTP has never
been operated in this mode. After clarification and chlorination,
the effluent is pumped to a canal which flows into the Halifax
River.
Waste sludge is pumped into an anaerobic digester. Condi-
tioned sludge from the digester is either trucked away to a
land disposal site or dried on sludge drying beds.
PERSONNEL
The plant staff consists of six persons responsible for
the WTP and the collection system, including one Class-B lead
operator and three Class-C operators. The plant is manned
sixteen hours per day.
4
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FIGURE »
WASTEWATER TREATMENT PLANT
HOLLY HILL, FLORIDA
Return Sludge
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TABLE I
DESIGN DATA
HOLLY HILL WTP
HOLLY HILL, FLORIDA
FLOW MEASUREMENT
Type
Design Flow (avg.)
AERATION BASINS
Number
Length
Width
Depth (water)
Volume
Aeration
CLARIFIERS
Number
Length
Width
Depth (water)
Surface Area
Volume
Weir Length
Return sludge pumps
Waste sludge pumps
CHLORINE CONTACT CHAMBER
Length
Width
Depth (water)
Volume
Contact time at design
ANAEROBIC DIGESTER
90° V-notch weir, recorder,
totalizer
1.2 mgd
2
72 ft.
24 ft.
12 ft.
20,736 cu. ft. (0.155 m.g.)
3-7.5 hp mechanical
2 (rectangular)
65 ft.
16 ft.
9 ft.
1,040 sq. ft.
9,360 cu. ft.(0.07 m.g.)
120 ft.
2-250 gpm (plus one stand-by)
600 gpm (variable speed)
45 ft.
12 ft.
8 ft.
4>320 cu.
38 min.
ft.(0.032 m.g.)
Number 1
Diameter 50 ft.
Depth (side water depth) 25.5 ft.
Volume L963 cu.
ft.(0.015 m.g.)
6
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SLUDGE DRYING BEDS
Number
Length
Width
14
40 ft.
32 ft.
7
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STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and study methods
are presented in Appendices A, B, and C. Formulae used for
common calculations are presented in Appendix D. Significant
results and observations made during the study are discussed
in the following sections.
FLOW
Plant flow was measured with a 90° V-notch weir, located
at the effluent end of the chlorine contact chamber, equipped
with a recorder and totalizer. The recorder and totalizer were
found to be recording accurately.
Average hourly effluent and return sludge flows from
February 26-March 4, 1976, are presented in Figure 2. The
average effluent and return sludge flow during the study period
was 1.01 and 0.31 mgd, respectively.
The plant receives approximately 100,000 gallons per day
(gpd) of laundry wastewater, most of which is discharged to
the WTP between 8:00 a.m. and 4:00 p.m. This accounted for
approximately 30 percent of the total wastewater flow to the
WTP during this eight-hour period.
Return sludge is pumped by either of two 250 gpm sludge
pumps. Approximately ]2,000 gallons of waste sludge is pumped
daily to the digester by a 600-gpm, variable speed pun?).
8
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FIGURE 2
HOLLY HtLL WTP FLOW
HOLLY HILL, FLORIDA
2 0
*
O
IMIutnl Plant Flow
J I l I l_J I I l I l l I 1
J I .1
J 1 I i_u I I
2/26
Thur.
2/27
ft I
2/28
Sat.
2/29
Sun.
3/1
Mon.
3/2
Tu»»
3/J
Wid.
3/4
Thur.
I 0
e
-os
>
o
Rtlurn ! ludg* Flow
Pumping C|
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WASTE CHARACTERISTICS MP REMOVAL EFFICIENCIES
Table II presents a chemical description of the WTP influent and
effluent along with treatment efficiencies. Analyses were made on
one 24-hour composite sample.
TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Parameter
Influent
(mg/1)
Effluent
(mg/1)
% Removal
BOD5
170
17
90
COD
496
92
81
Total Suspended Solids
98
12
88
Volatile Suspended Solids
94
12
87
Total Solids
784
620
21
Spttleable Solids (ml/1)
8.5
<0.1
>98
TKN-N
33.1
26
21
NH3-N
21
13
38
no3-no2-n
<.01
.54
—
Total Phosphorus
6.3
5.8
8
Lead
<.08
<.08
—
Chromium
<.08
CO
0
•
V
—
Cadmium
<.02
<.02
—
Copper
.04
.02
50
Zinc
.173
.03
82
10
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AERATION BASINS
Grab samples taken from the discharge of the north (station HABN)
and south (station HAB5) aeration basins were analyzed for total
suspended solids (TSS), volatile suspended solids (VSS)s percent solids
by centrifuge, and settleability as determined by the settlometer.
Presented in Table III are various activated sludge operational
parameters calculated during the study period and the corresponding
recommended values for the conventional activated sludge process.
TABLE III
MEASURED AND RECOMMENDED PARAMETERS FOR THE CONVENTIONAL
ACTIVATED SLUDGE PROCESS
Measured Recommended (1)(7)
Hydraulic Retention Time (hours) 6.5 4-8
Mean Cell Residence Time (days) 6.2 5-15
Sludge Age (days) 5.3 3.5-10
Lbs BODc/day/lb MLVSS (F/M) 0.35 0.2-0.4
Lbs COD/day/lb MLVSS 1.0 0.5-1.0
Lbs BOD5/day/1000 cu. ft.
aeration basin 34.4 20-40
MLSS (mg/1) 1,695 1,500-3,000
Return Sludge Rate (% of Average
Flow) 31 15-75
The average settleability of the activated sludge from the north
and south aeration basins is presented in Figure 3. The rate of settling
was faster than desired during the first five minutes of settling. This
early rapid settling left a visible quantity of suspended colloidal
material in the supernatant which was present in the final effluent.
A slower settling rate would remove some of these solids resulting in
a clearer supernatant, A settled sludge volume of 20 percent after 60
minutes of settling should be optimum.
Results of dissolved oxygen (DO) measurements in the aeration
basins are presented in Appendix B. The DO profile in both aeration
basins indicated either poor mixing or rapid DO uptake as evidenced by
a rapid DO drop below the five- to seven-foot depth. All DO measure-
ments below the five-foot depth were 0.5 mg/l or less. The number 6
and 3 aerators remain on at all times while the remaining aerators
were operated by timers. Dissolved oxygen was measured before and
after the number 1 and 3 aerators were manually turned off for the test.
These data demonstrated a rapid DO drop after the aerators were shut
off. The DO dropped to 0.4 mg/1 or less, near both aerators, three
minutes after the aerator was shut off.
11
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00
90
80
70
60
50
40
30
20
10
0
FIGURE 3
SETTLOMETER -TEST
HOLLY HILL, FLORIDA
-O-
10 15 20 25 30
TIME '( MIN )
40
50
60
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Several days after this study, the MLSS concentration increased
to 2,500 mg/1 with extremely poor settling. The WTP operators are
trying to decrease the MLSS to approximately 1,700 mg/1 and have
already observed improved settling.
CLARIFIERS
The primary problems encountered with the secondary clarifiers
were light solids carryover, severe bulking, foam, and scum. The
sludge bulking was caused by a prolific growth of filamentous bacteria.
At the recommendation of the FL-DER, return sludge was chlorinated
during February 19-March 2, 1976, resulting in rapid settling, reduced
bulking, and minimized foam and scum. The plant presently has no
means to adequately control and measure the quantity of chlorine dis-
charged into the return sludge. The return sludge chlorination was
killing the filamentous bacteria but not correcting the conditions which
favor its growth. Adequate DO in the aeration basins should help
control the filamentous growth. When the practice of return sludge
chlorination was terminated, the sludge bulking, foam, and scum
problems reappeared. Scum removed from the clarifiers is discharged
to the sludge drying beds.
The results of a clarifier dye tracer study are presented in Fig. 4. The
effluent dye concentration was measured in the combined clarifier flow.
The hydraulic retention time of the clarifiers may be equated to the
centroid of the dye plume which passed over the clarifier weirs in
approximately 78 minutes (1.3 hours). However, of more significance
is the shape of the dye concentration curve and visual observations
during the test. After entering the influent to each clarifier, no
trace of the dye was observed for approximately 15 minutes until it
exploded over the weirs as shown by the spike on Figure 4. These
data and visual observations indicated that short-circuiting was
taking place along the clarifier bottom. The short-circuited flow
apparently hit the end wall of the basins and flowed up the end walls
and over the weirs. Plant personnel stated that bulking occurs and
solids flow over the weirs at a point against the end wall first. This
agrees with observations made during the dye tracer study. This type
of short-circuiting can be expected in rectangular clarifiers due to
density currents. The density of the mixed liquor is much greater
than that of the liquid in the clarifier. Consequently, it flows
along the bottom until hitting the end wall where it surges up and
over the weirs.
Measured and recommended parameters for final clarifiers following
conventional activated sludge wastewater treatment are presented in
Table IV.
13
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TABLE IV
MEASURED AND RECOMMENDED PARAMETERS FOR SECONDARY CLARIFIERS
Measured Recommended (1)(3)(4)
Hydraulic Loading (gpd/sq. ft.)
486
400-800
Solids Loading (lbs/day/sq. ft.)
9
20-30
Weir Overflow Rate (gpd/lin. ft.)
8,420
<15,000
Hydraulic Detention Time (hrs.)
, -1/
3.3^ . or
2/
1.3-
2-3
1/ - Calculated as volume/flow.
2/ - Actual hydraulic detention time as measured by addition of dye.
As shown in Table IV, the sizing of the clarifiers is adequate;
however, undesirable flow velocities and patterns exist which adversely
affect treatment efficiency. The effluent weirs were found to be level
and in good repair.
CHLORINE CONTACT CHAMBER
Theoretical detention time in the chlorine contact chamber (CCC)
is approximately 38 minutes at design flow. However, observation of
dye flowing through the CCC indicated the actual detention time was
only a few minutes and well defined short-circuiting was observed.
This phenomenon is not uncommon and is probably due to the size of
the opening between the baffle and tank wall and the roughness of
the concrete. The primary concern with a CCC is bacterial kill which
was adequate according to WTP records.
ANAEROBIC DIGESTER
Waste sludge is conditioned in a single anaerobic digester and
then trucked to a land disposal site or spread on sludge drying beds.
According to WTP personnel, the digester is not heated due to the
inadequate size of the heat exchanger. The waste gas flame was yellow
indicating poor methane production. The digester temperature was
approximately 70°F, much less than the optimum mesophilic range of
85° to 100°F (7). The pH in the digester was 6.4 which is slightly
lower than the recommended range of 6.6 to 7.6 (7).
Anaerobic sludge digestion could be better accomplished with two
digesters; a heated and mixed primary digester and a secondary digester
for solids separation. However, as long as land is available for sludge
disposal, digester construction is not necessary.
14
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1,200
1,000
J3
Q.
Q.
<
tr
h-
Z
UJ
o
800
600
O
° 400
200
FIGURE 4
CLARIFIER DYE TRACER STUDY
HOLLY HILL, FLORIDA
KEY
¦ Dye Concentrations
Projected Concentrations
Centroid
T -4--
200
250 300
TIME ( MlN)
350
400
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LABORATORY
The physical facilities are adequate; however, only limited
in-plant control testing is performed. An in-plant control testing
program should be initiated immediately. This program should include
the following chemical and physical parameters: settlometer, clari-
fier sludge blanket depth, and aeration basin TSS, VSS, and DO.
Dissolved oxygen measurements should be made throughout the aeration
basins at various depths. Trend charts should be established and
maintained. These charts should include MLSS, sludge settleability,
significant influent and effluent waste characteristics, flow,
aeration basin DO, depth of clarifier sludge blanket, and F/M ratios.
These suggested parameters should serve only as a guide and are
intended to establish trends so that gradual changes in plant condi-
tions can be noticed prior to a deterioration in effluent quality.
All plant changes should be made one at a time and maintained for
approximately two weeks to allow the plant to reach equilibrium.
Additional laboratory equipment that would enhance plant opera-
tion—although not absolutely necessary—includes a new analytical
balance, centrifuge, COD apparatus, and microscope.
16
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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. Ross E. McKinney and Andrew Gram. "Protozoan and
Activated Sludge," Sewage and Industrial Wastes, 28 (1956):
1219-1231.
9. Alfred W. West. Operational Control Procedures for the
Activated Sludge Process. Part I, Observations, April
1973: pages 7, 8.
17
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Ai'i'iaiDrc A
IABOKATOTY DATA
HOLLY HILL, FL - WTP
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APPENDIX B
AERATION BASIN DISSOLVED OXYGEN
HOLLY HILL, FLORIDA
ABS-]
/ "v
3/3
1400
25.5
0.6*
0*
0*
0*
ABS-2
26
1.0
1.0
0.6
0.3
--
ABS-3
26
1. 0
1.1
1.1
0.5
--
ABN-1
26
1.5
1.5
1.0
0.5
0.3
AB\'-2
26
1.2
0.6
0.1
0.2
—
ABN-3
26
1.3
1. 3
1.0
0.4
——
ABS-3
3/3
1430
—
1.0**
ABS-3
1431
—
0.5**
ABS-3
1432
—
0.4**
0
ABS-3
1433
—
—
—
—~"
ABS-1
3/3
1435
2 . Of
ABS-1
1436
i. o
ABS-1
14 37
0.4 -
/N ^
ABN-1
3/4
1300
25. 5
1.6
—
i.i.
0.6
ABN-4
26
0.8
--
0.6 '
0. 3
ABM-5
26
0.6
—
0.5 •
0.3
ABS-1
25.5
1.7
—
0.9
1.0
ABS-4
26
1.1
—
1.1 "
0.9
ABS-5
26
1.4
—
1.0
— — '
0.6
AERATION BASIN SAMPLING STATIONS
influent
ABN-5
•
6© 5®
ABN-3 ABN-4 ABN-2
• • O
ABN-1 —
pr •
• • •
ABS-3 ABS-4 ABS-2
3© 4©
A^-5
e
ABS-1 "
effluent
* #1 Aerator turned off just prior to DO check
** #3 Aerator turned off a.t 1430
t #1 Aerator turned off at 1435
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APPENDIX C
GENERAL STUDY METHODS
To accomplish the stated objectives, the study included
sampling, physical measurements and observations. Plant
influent and effluent sample stations HI and HE, respectively,
were sampled for a 24-hour period with ISCO Model 1392-X
automatic samplers. Aliquots of sample were pumped at hourly
intervals into individual refrigerated glass bottles which
were composited proportional to flow at the end of the sampling
period.
Dissolved oxygen was determined in the aeration basins
using a YSI model 51A dissolved oxygen meter.
The plant flow totalizer was used to determine total
daily flow and the recorder was used for hourly flows. Accuracy
of the plant flow recorder and totalizer was checked with
instantaneous readings from the effluent weir.
Temperature was recorded while measuring the dissolved
oxygen concentration.
Depth of the secondary clarifier sludge blankets were
determined daily using equipment suggested by Alfred W. West,
EPA, NFIC Cincinnati.
A series of standard operational control tests were run
as follows:
e 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;
o Suspended Solids and Volatile Suspended Solids analy-
sis on the aeration basin mixed liquor and return
sludge;
• Turbidity of each final clarifier effluent.
An amperometric titrator (Fischer & Porter Model 17T1010)
was used to determine effluent chlorine concentrations.
20
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BODg samples were set up by EPA personnel and the final
dissolved oxygen concentrations were determined by laboratory
personnel at the Titusville, Florida Wastewater Treatment Plant.
Visual observations of individual unit processes were
recorded.
Mention of trade names or commercial product does not
constitute endorsement or recommendation for use by the
Environmental Protection Agency.
21
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APPENDIX D
Activated Sludge
Formulae Used For General Calculations
Aeration Basin
1. lbs. of solids in aeration basin
Basin volume = m.g.; MLSS (conc.) = mg/1
(MLSS cone) 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
(BUD or (JUL); x now x 8.34 = ids. aujj or uuu/aay
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. BODg 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.
!i*>Pg°°nC;> X-(P,1,a?\fl°»)^ (8'34) - lbs. BOD/lb. MLVSS
(MLVSS) x (Basin Vol.) x 8.34
22
-------
(COD conc.) x (plant flow) x (8.34)
(MLVSS) x (Basin Vol.) x (8.34) lbs> C0D/1^- MLVbb
8. Mean cell residence time (MCRT) = days
MLSS conc. (avg. or daily value) = mg/1
Basin vol. = m.g.
Clarifier vol. = nr.'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
/ TIT _ —_ X. _ - — T » J ^ « r» \ -«r ^ ttrA <-»4- A -p "I N ' v O O A _L. ^
y 11 Ui kJ O V V-/ O -L. V C4 «/ V- C4 W X L4S4^ W ** « J V" **•-' w ^ ^
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