TECHNICAL ASSISTANCE PROJECT
AT THE
OMUSSEE WASTEWATER TREATMENT PLANT
DOTHAN, ALABAMA
January, 1976
Environmental Protection Agency
Region IV
Surveillance end Analysis Division
Athens, Georgia
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TECHNICAL ASSISTANCE PROJECT
AT THE
OMUSSEE WASTEWATER TREATMENT PLANT
DOTHAN, ALABAMA
January, 1976
M?
:*,£p
Environmental Protection Agency-
Region IV
Surveillance and Analysis Division
Athens, Georgia
-------
CONTENTS
Page
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 . 8
DISSOLVED OXYGEN 10
GRIT CHAMBER 12
AERATION BASINS 12
CLARIFIERS 13
CHLORINE CONTACT CHAMBER 16
AEROBIC DIGESTER AND DRYING BEDS 16
OXYGEN UPTAKE RATES 17
LABORATORY 18
REFERENCES 19
APPENDICES
A - CHEMICAL LABORATORY DATA 20
B - DISSOLVED OXYGEN 23
C - GENERAL STUDY METHODS 24
D - ACTIVATED SLUDGE FORMULAE USED FOR
GENERAL CALCULATIONS 26
E - OXYGEN UPTAKE PROCEDURE 28
FIGURES
1. OMUSSEE WTP 5
2. FLOW AND pH 9
3. AERATION BASIN DISSOLVED OXYGEN 11
4. SETTLOMETER TEST 15
TABLES
I. DESIGN DATA 6
II. WASTE CHARACTERISTICS AND REMOVAL
EFFICIENCIES 10
III. ACTUAL AND RECOMMENDED PARAMETERS FOR THE
CONVENTIONAL ACTIVATED SLUDGE PROCESS .... 13
IV. ACTUAL AND RECOMMENDED PARAMETERS
FOR SECONDARY CLARIFIERS 14
V. OXYGEN UPTAKE RATES 17
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INTRODUCTION
A technical assistance study of operation and maintenance
problems at the Omussee Wastewater Treatment Plant (WTP) serv-
ing Dothan, Alabama was conducted January 12-16, 1976 by the
Region IV, Surveillance and Analysis Division, U. S. Environ-
mental Protection Agency. 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 pla-nts 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.
This plant was selected because of difficulty in achiev-
ing design treatment efficiencies. In addition, excessive
solids are frequently lost in the effluent. The specific study
objectives were to:
© Optimize treatment through control testing and
recommended operation a.nd maintenance modifications,
e Determine influent and effluent wastewater character-
istics ,
© 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 made at a later date. This will be accom-
plished 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 Alabama Water Improvement Commision
is gratefully acknowledged. The technical assistance team is
especially appreciative of the cooperation and assistance
received from personnel of the Omussee WTP.
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SUMMARY
The Ornussee vVTP was designed as a 3 mgd activated sludge
facility with flexibility to operate in either the conventional,
tapered aeration, st6p feed or contact stabilization modes.
The plant serves a population of about 30,000 and industrial
sources, primarily slaughterhouses, which account for approxi-
mately 30 percent of the plant flow.
The dissolved oxygen concentrations were critically low
in the aeration basins and excessively high in the aerobic
digester. Large air leaks were observed in the air line to
the diffusers. Presently, air is supplied uniformly to all
basins. These low dissolved oxygen concentrations contributed
to reduced treatment efficiencies.
Sludge is wasted to the aerobic digester on a batch rather
than continuous basis. Conditioned digester sludge is pumped
to the drying beds on an infrequent schedule controlled by
available drying bed space. The digester is refilled with
waste sludge which is batch conditioned until drying bed space
again becomes available and this process results in the follow-
ing problems.
Although 100 percent of the settled sludge is returned
to the aeration basins, settleability tests and visual obser-
vations indicated a young, poor settling sludge. The young
sludge resulted from excessive solids lost in the final
effluent. The poor settleability of the sludge results in
reduced treatment efficiency.
The plant has recently obtained sophisticated analytical
equipment which will necessitate additional training for the
quantity and type of analytical work to be performed.
-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 and plant operation:
o The leak in the air line to the diffusers should
be repaired immediately.
© Dissolved oxygen should be monitored throughout the
aeration basin and aerobic digester.
© Air supplied to the aeration basins and aerobic
digester should be regulated such that a uniform
dissolved oxygen concentration of approximately
2 mg/1 is maintained in both units.
© Sludge should be wasted to the aerobic digester on
a continuous schedule.
g The scum decant unit should be modified with a
baffle across part of the basin to prevent short
circuiting and around the supernatant discharge pipe
to prevent scum discharge.
© The sludge age should be increased to improve
settleability. This could be accomplished by
the addition of polymers to reduce solids lost in
the effluent and/or pumping of digester sludge back
to the aeration basin.
© Clarifier effluent weirs should be kept clean.
© A chlorine residual must be maintained in the final
effluent.
© Sludge should be pumped out of the chlorine contact
chamber as often as necessary to prohibit anaerobic
conditions and excessive chlorine demands.
© Laboratory personnel need additional training in
laboratory procedures and techniques.
e Trend charts of key parameters should be maintained.
Contingent on the success of the above recommendations,
additional long range suggestions include:
-3-
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o Additional sludge drying beds should be constructed.
o Blocking off the outside clarifier effluent weir
may improve settling in the clarifier.
TREATMENT FACILITY
TREATMENT PROCESSES
A schematic diagram of the 3 mgd Omussee WTP is presented
in Figure 1. Design data are enumerated in Table I. The
activated sludge WTP began operation in February, 1971,
serving an approximate population of 30,000 and industrial
sources, primarily slaughterhouses, which account for approxi-
mately 30 percent of the plant flow. Design of the plant is
flexible with the capability of operating in a number of
activated sludge operational modes, e.g., conventional,
tapered aeration, step feed, and contact stabilization.
All influent wastewater enters the plant by gravity,
flows through a comminutor and bar screen and then is pumped
to the aerated grit chamber by three 40 hp, variable speed
pumps. Wastewater flows through the remainder of the plant
by gravity.
The aeration basin was operated as a conventional (plug
flow) activated sludge system during the study. Diffused
air is supplied to the aeration basins and aerobic digester
by three 200 hp blowers, one of which was out of service at
the time of the study. Return sludge is pumped back to the
head of the plant and mixed with raw wastewater in the aeration
basin influent channel.
Waste sludge is conditioned in an aerobic digester prior
to discharge to sludge drying beds. Filtrate from the sludge
drying bed flows back to the influent line and mixes with the
raw influent wastewater.
Clarifier effluent is chlorinated in the chlorine contact
chamber. Chlorinated effluent flows over a three foot rec-
tangular weir and through a pipe for approximately 200 yards
to where it is discharged to a swampy area adjacent to Omussee
Creek.
PERSONNEL
The plant staff consists of 12 persons including 2 operators,
2 laboratory technicians, 3 assistant operators, and 4 helpers.
Four of the operators are certified; two are Class IV and two
are Class III. The plant is manned 24 hours per day, 7 days
per week.
-4-
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FIGURE 1
OMUSSEE WASTEWATER TREATMENT PLANT
DOTHAN, ALABAMA
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TABLE I
DESIGN DATA
OMUSSEE WTP
DOTHAN, ALABAMA
FLOW MEASUREMENT
Type Rectangular weir, recorder, totalizer
Size 36-in.
AERATED GRIT CHAMBER
Length 18 ft.
Width 18 ft.
Depth 9 ft.
Aerator Diffused aeration
AERATION BASINS
Number 3
Length 100 ft.
Width 41 ft.
Depth (water) 18 ft.
Volume 73,800 cu. ft. (.552 m.g.)
CLARIFIERS
Number 2
Diameter 60 ft.
Depth (mean) 11 ft.
Area 2,827 sq. ft.
Volume 31,102 cu. ft. (.233 m.g.)
Weir Length 342 ft.
CHLORINE CONTACT CHAMBER
Area
Depth (water)
Volume
Contact time at design
flow
1650 sq. ft
6 ft.
9900 cu. ft.
35 min.
(.074 m.g.)
AEROBIC DIGESTER
Basins
(1) Volume
(2) Volume
Depth (water)
45,000 cu. ft.
37,800 cu. ft.
18 ft.
(.337 m.g.)
(.283 m.g.)
-6-
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SLUDGE DECANT UNIT
Basins
Volume
Depth (water)
1
4,920 cu. ft.
12.3 ft.
(.037 m.g.)
DRYING BEDS
Number
Length
Width
Depth
6
100 ft.
50 ft.
18 in.
-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
general calculations are enumerated in Appendix D. Signifi-
cant results and observations made during the study are dis-
cussed in the following sections.
FLOW
Plant flow was measured with a 36 inch, sharp crested,
rectangular weir with end contractions which was equipped
with a totalizer and recorder. The weir, installed at the
effluent of the chlorine contact chamber, was level and the
totalizer and recorder were recording accurately.
Average hourly flow from the plant during the study
period is presented in Figure 2. The average flow was
2.94 mgd with mean hourly flows varying from a low of 1.5 mgd
to a maximum of 4.0 mgd. Plant personnel stated that wet
weather flows exceed 6.5 mgd because of infiltration. When
wet weather flows exceed 6.5 mgd they are bypassed. The
annual average daily flow during 1975 was 3.03 mgd.
Approximately 30 percent of the total plant flow was
industrial wastewater, primarily from slaughterhouses, which
operate 5 days a week.
Flow from the aeration basin was split and discharged
into two clarifiers. A magnetic flow meter, with recorder
and totalizer, monitored the individual influent flows.
Activated sludge from the final clarifiers was returned
to the head of the plant at an average rate of approximately
3.1 mgd and was measured with a magnetic flow meter, recorder,
and totalizer.
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Table II presents a chemical description of the influent
and effluent with calculated percent reductions. Analyses
were made on 24-hour composite samples. Presented is an
average of all data during the study.
-8-
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J/IJ/70
A.M.
1/15/76
AM
l/lj/70
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TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Parameter
Influent
Ef fluent
% Reduct
B0D5 (mg/1)
245
52
79
COD (mg/1)
320
222
31
Suspended Solids (mg/1)
250
132
47
Total Solids (mg/1)
620
381
38
NH3-N (mg/1)
15.3
15.8
--
NO3-NO9-N (mg/1)
*< . 01
< .01
--
Total Phosphorus (mg/1)
7.1
6.0
15
Pb (ug/1)
<50
< 50
--
Cr (ug/1)
**<80
< 80
--
Cd (ug/1)
<20
< 20
--
Cu (ug/1)
67
35
48
Zn (ug/1)
426
164
62
* Was .09 mg/1 one day
** Was 95 ug/1 one day
DISSOLVED OXYGEN
A complete listing of dissolved oxygen (DO) concentrations
throughout the plant is presented in Appendix B. On January
14, the following DO concentrations were observed.
Raw Influent Wastewater 0.2 mg/1
Aerated Grit Chamber 0.7 mg/1
Aeration Basin (mean) 0.1 mg/1
Final Clarifiers (mean) 0.1 gm/1
Final Effluent 7.5 mg/1
Aerobic Digester 10.2 mg/1
Dissolved oxygen concentrations measured throughout the plant
were critically low except in the effluent following the
chlorine contact chamber. Higher DO concentrations were
measured in the effluent due to aeration in the pipe line
from the clarifiers to the chlorine contact basin. The DO
in all three aeration basins ranged from 0.0 to 0.3 mg/1 and
was uniform with depth (see Figure 3).
On January 15, the air supplied to the aeration basins
was increased, and the resulting mean DO concentrations in
Basins 1, 2, and 3 increased to 2.9, 0.5, and 0.2 mg/1,
respectively. The greatest oxygen demand was exerted in
Basin #3 where the raw, incoming flow entered. A lesser
demand in the following basins resulted in increased DO
concentrations (see Figure 3). A more efficient method of
aeration would be to taper the air supplied to the aeration
basins by increasing air to Basin #3 and gradually decreasing
air in successive basins.
-10-
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FIGURE 3
AERATION BASIN DISSOLVED OXYGEN
1
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( 0° 2)
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(0.2)
BEFORE INCREASING AIR
1
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(0.5)
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to
AFTER INCREASING AIR
Dissolved oxygen concentration in mg/1
-II-
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The DO concentration measured in the aerobic digester
was always greater than 8 mg/1 throughout the study period.
This condition resulted from both excessive air supplied to
the digester and the oxidised condition of the sludge. Air
supplied to the digester should be adjusted to maintain
approximately 2 mg/1 throughout.
Air was furnished to the aeration basins and aerobic
digester by two 200 hp blowers; the third 200 hp blower was
out of service during the study. The total average air flow
during the study was 10,132 cubic feet/minute (cfm); however,
a large air leak reduced the amount actually reaching the
basins.
These results indicate a poor balance of air distribu-
tion in the aerobic digester and aeration basins. Adjustment
of the diffusers to maintain an approximate DO concentration
of 2 mg/1 is critical to efficient plant operation.
GRIT CHAMBER
Aeration is accomplished by air diffusers. The hydraulic
detention time is approximately 10 minutes at the average
design flow of 3 mgd.
According to plant personnel, the only problem with
the grit chamber is insufficient bottom slope to efficiently
collect and remove grit. Consequently, significant quantities
of grit enters the aeration basin.
AERATION BASINS
Grab samples were taken at the point of discharge from
the aeration basin (Station Al-7) and at an intermediate point
in the aeration basin (Station A3-1). Samples 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 III are various activated sludge
operational parameters calculated during the study period
and the corresponding recommended values for the conventional
activated sludge process. The true sludge age was less than
the calculated value of 5.8 days due to the significant loss
of solids in the effluent. The activated sludge appeared
to be young based on visual observations and sludge settlea-
bility. Temporary recycling of digester sludge back to the
aeration basin could improve sludge settleability by increas-
ing sludge age.
-12-
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The excessive return sludge flows observed during the
study should have resulted in increased MLSS and sludge age
However, this was not the case, the average TSS of return
sludge was 4,880 mg/1 (7.5% by centrifuge) of which 82 per-
cent were volatile SS. The return sludge flow rate is main-
tained fairly constant.
The aeration basin diffusers have a tendency to become
clogged with undesirable materials not removed by the bar
screen.
TABLE III
ACTUAL AND RECOMMENDED PARAMETERS FOR THE CONVENTIONAL
ACTIVATED SLUDGE PROCESS
Hydraulic Retention Time
(hours)
Mean Cell Residence Time
(days)
Sludge Age (days)
Lbs B0D5/day/lb MLVSS (F/M)
Lbs COD/day/lb MLVSS
Lbs BOD5/day/1000 cu. ft.
MLSS
Return Sludge Rate (% of
average design flow)
Average Flow (mgd)
Actual Recommended (5)(6)
6. 6
4-8
6.7
5-15
5.8
3.5-10
0. 21
0.2-0.4
0. 27
0.5-1.0
28
20-40
2, 598
1,500-3,000
100
15-75
3.0
3.0 (Design)
CLARIFIERS
The primary problem in the final clarifier was frequent
solids carryover. The average turbidity of the effluent from
both clarifiers was 8.2 standard turbidity units (STU) based
on four grab samples. Observation of individual hourly
samples indicated a high concentration of solids in the
effluent from approximately 9 p.m. until 4 a.m. On the
evening of January 12, an extremely high concentration of
solids were discharged from the clarifiers. According to
plant personnel, this excessive discharge of solids occurred
two or three times weekly.
Significant quantities of grease balls and algal growths
were clogging the V-notch effluent weirs. According to plant
personnel, these weirs are usually cleaned daily; however,
foul weather occurring prior to the study had hampered the
routine.
-13-
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The addition of a dye to the influent of both clarifiers
on three different occasions indicated non uniform flow
distribution and short circuiting. Concentrated slugs
of dye were observed passing over sections of the weirs in
as short a time as 25 minutes.
The actual and recommended hydraulic loading, solids
loading and weir overflow rates for final clarifiers follow-
ing conventional activated sludge wastewater treatment are
presented in Table IV.
ACTUAL AND RECOMMENDED PARAMETERS FOR SECONDARY CLARIFIERS
Calculations in Table IV are based on an average flow
of 3 mgd. However, from observations of Figure 2, the maximum
sustained flow was approximately 4 mgd. Based-on a flow of
4 mgd, the hydraulic loading on the clarifier is 708 gpd/sq. ft.
during significant periods of the day.
The settlometer test was performed daily on grab samples
from stations A3-1 and Al-7 in the aeration basins. Poor
settling characteristics were observed from both stations.
The sludge settled slowly, was fluffy in appearance, and
light brown in color. These are all indications of a young,
underoxidized sludge. The settleability of the activated
sludge is shown graphically in Figure 4.
Calculated values in Table IV illustrate adequate hydraulic
sizing of the clarifiers. Sludge quality and age could be
improved by increased aeration in the aeration basin and
control of solids carrying over the clarifier weirs. Temporarily
adding polymers would help minimize solids lost in the effluent
and increase sludge age. As the sludge age increases,
settleability should improve allowing regular sludge wasting
to the aerobic digester. Polymer addition would then be
required only during upsets.
TABLE IV
Actual Recommended (2)(3)(6)
Hydraulic Loading (gpd/sq. ft.) 531
Solids Loading (3bs/day/sq. ft.) 23
Weir Overflow Rate (gpd/lin. ft.) 4,386
Hydraulic Detention Time (hrs.) 3.7
400-800
20-30
<15,000
2-3
-14-
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FIGURE 4
SETTLOMETER TEST
Station A3-1
Station Al-7
SETTLING TIME (MINUTES)
-------
CHLORINE CONTACT CHAMBER
Detention time in the contact chamber was approximately
35 minutes at an average flow of 3 mgd. Chlorine was applied
to the influent at the rate of 120 lbs/day. This application
rate was not sufficient to produce a chlorine residual in
the effluent during the study.
Solids accumulation in the chlorine contact chamber ranged
from approximately 0.5 feet at the influent to 1.5 feet near
the effluent weir. Bubbling, which is indicative of septic
sludge conditions, was also observed in the chamber. Sludge
should be pumped from the contact chamber as often as necessary
to reduce the chlorine demand.
The dissolved oxygen level throughout the chamber was
approximately 7.5 mg/1. Elevation differences between the
final clarifier weirs and contact chamber resulted in aerating
the wastewater as it flowed to the chamber. This aeration
produced a white foam which covered approximately 1/3 of
chamber surface.
AEROBIC DIGESTER AND DRYING BEDS
Waste sludge is batch conditioned in the aerobic digester.
When space is available on the sludge drying beds, the
aerators are turned off, the digester contents allowed to
settle and then pumped to the drying beds. To refill the
digester a large portion of return sludge is routed to the
decant unit for additional thickening and thence to the
aerobic digester. The contents of the digester are then
aerated until space again becomes available on the drying
beds. Plant records revealed that no sludge was wasted from
November 1 - December 11, 1975 and December 13, 1975 -
January 14, 1976 indicating retention times of 30+ days. De-
sign cirteria for aerobic digesters (5) recommend hydraulic
detention times of 16 to 18 days at 20°C.
The average volatile solids content during the study was
69 percent. The high DO (>8 mg/1) in the basins and length
of time under aeration (30 days) demonstrated that the cell
tissue had been oxidized as far as possible. More efficient
use of the digester would be accomplished by continuously
wasting the sludge, thereby maintaining a constant oxidation
rate.
-16-
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Continuous wasting would require slight modification of
the decant unit. Sludge wasted into the digester would dis-
place supernatant from the decant unit. An existing adjustable
pipe should be modified with a collar/baffle to hold back
scum but allow supernatant to discharge back to the aeration
basin. A section of 10 inch pipe welded to the existing pipe
should work satisfactorily. In addition, a baffle across
a portion of the unit would be required to prohibit short
circuiting.
Discharging sludge to the drying beds is limited by
available bed space. Additional drying beds would allow
additional solids control in the entire treatment system
and subsequent improved overall treatment efficiency. Land
is available for additional bed construction.
OXYGEN UPTAKE RATES
General activity of an activated sludge can be determined
by comparing oxygen uptake rates (in mg/] per minute) of a
return sludge mixed with raw influent (fed) to a return
sludge mixed with non chlorinated effluent (unfed). A load
ratio can be calculated from this relationship as follows:
Load Ratio = iDO/min. of fed sludge
ADO/min. of unfed sludge
The procedure and significance of this test are presented
in Appendix E.
Presented in Table V is a listing of the oxygen uptake
data with a calculated load ratio.
TABLE V
OXYGEN
UPTAKE
RATES
1/
2/
3/
Date
Time
%RS
FRS
UFRS
Load Ratio
1/13/76
1600
45
1.30
0.55
2.36
1/14/76
1400
45
1.55
0.60
2. 58
1/15/76
1400
45
1.46
0.30
4.50
1/ %RS = percent return sludge volume to volume mixed with
influent and effluent
2/ FRS = fed return sludge
3/ UFRS = unfed return sludge
-17-
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The calculated load ratios indicate a readily biodegradable
waste and a well acclimated sludge.
LABORATORY
At the time of this study the Ornussee WTP laboratory was
being expanded to increase analytical capabilities. New
equipment had been recently purchased which included such
instrumentation as a total organic carbon analyzer and an
atomic absorption spectrophotometer. Future plans are for
the facility to become a regional laboratory, performing
environmental analyses on samples from other sources in the
area.
The facility had a control testing routine, however,
monitoring of DO in the aeration basins was not included. DO
levels in the aeration basins need to be closely monitored
to be certain aerobic conditions are maintained. These
measurements are best determined by an electronic meter and
probe. The WTP has a portable meter with laboratory and
field probes; however, there had been some difficulty with
the field probe. EPA and plant personnel checked the DO
measuring apparatus and found it to be working satisfactorily.
The plotting of control data on a graph is extremely
helpful to an operator. These graphs or trend charts
reveal increases or decreases of a particular parameter with
time. This helps the operator anticipate changing conditions
in his plant and make necessary adjustments before a critical
situation develops.
Observations of laboratory operations revealed a con-
scientious attitude of the personnel involved and, in general,
techniques were good. Due to the planned expansion of
analytical responsibilities, however, it is suggested that
training in laboratory instrumentation and procedures be
obtained.
-18-
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REFERENCES
1. "Process Design Manual for Suspended Solids Removal",
US-EPA Technology Transfer, January 197 5.
2. "Process Design Manual for Upgrading Existing Wastewater
Treatment Plants", US-EPA Technology Transfer, October
1974.
3. "Sewage Treatment Plant Design", American Society of
Civil Engineers, Manual of Engineering Practice No. 36,
1959.
4. "Standards for Sewage Works", Upper Mississippi River
Board of State Sanitary Engineers, Revised Edition,
1971.
5. "Wastewater Engineering", Metcalf and Eddy, Inc., 1972.
6. "Operation of Wastewater Treatment Plants", A Field
Study Training Program, US-EPA, Technical Training Grant
No. 5TT1-WP-16-03, 1970.
7. "Standard Methods for the Examination of Water and
Wastewater", 13th Edition, 1971.
-19-
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INFLUENT & EFFLUENT
APPENDIX A
CHEMICAL LABORATORY DATA
OMUSSEE WASTEWATER TREATMENT PLANT
DOTHAN. ALABAMA
A/
STATION
MONTH
DAY
03
<
W
>
TIME
°/?c° / 7 ^> / / 7 OZ
IV to
.01
7.4-
/
:
/sti n.*
<.01
6.9
-------
APPENDIX A (cont'd)
CHEMICAL LABORATORY DATA
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AERATION BASIN
APPENDIX A (cont'd)
CHEMICAL LABORATORY DATA
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-------
APPENDIX B
DISSOLVED OXYGEN A/
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APPENDIX C
GENERAL STUDY METHODS
To accomplish the stated objectives, the study included
extensive sampling, physical measurements and daily observa-
tions. Plant influent and effluent sample stations 1-1 and
E-l, respectively, were sampled for two consecutive 24-hour
periods 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 each sampling period.
Dissolved oxygen was determined initially at all stations
throughout the plant and thence daily at stations in the
aeration basins and aerobic digester 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. Individual samples of the two 24-hour
compositing periods were used to determine hourly influent
pH variation.
Depth of the secondary clarifier sludge blankets were
determined daily using equipment suggested by Alfred W. West,
EPA, NFIC Cincinnati.
Sludge activity was determined by the oxygen uptake
procedure presented in Appendix E.
Samples of sludge discharged to the drying beds were
analyzed for suspended solids and volatile suspended solids.
A series of standard operational control tests were run
daily:
© Settleability of mixed liquor suspended solids (MLSS)
as determined by the settlometer test;
© Percent solids of the mixed liquor and return sludge
determined by centrifuge;
© Suspended Solids and Volatile Suspended Solids analy-
sis on the aeration basin mixed liquor and return
sludge;
© Turbidity of each final clarifier effluent.
-24-
-------
An amperometric titrator (Fischer & Porter Model 17T1010)
was used to determine effluent chlorine concentrations.
The procedure for the BOD5 determination deviated from
standard methods (7). Samples were set up and carried in an
incubator back to Athens, Georgia for completion of the
analyses.
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.
-25-
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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
(BOD or COD) x flow x 8.34 = lbs. BOD or 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. BODg conc. (f^g. 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.
^m5§^°nC;^ X(Pvaf (8'34) = lbs. BOD/lb. MLVSS
(MLVSS) x (Basin Vol.) x 8.34
-26-
-------
XCOD conc.) x (plant flow) x (8.34)
(MLVSS) x (Basin Vol.) x (S.34) ibs> 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
(Waste activated sludge conc.) x (waste flow) x 8.34 + ~ days
(Plant effl. TSS x plant flow x 8.34)
Clarifier
1. Detention time = hours
Plant flow to each clarifier = gals/day
Individual clarifier vol. = gals.
(clarifier Vol. (each) x 24 _ ^ours
Plant flow to each clarifier
2. Surface loading rate = gal./day/sq. ft.
Surface area/clarifier = sq. ft.
plant flow to clarifier = gal./day
Plant flow to clarifier
Clarifier surface area
= gal./day/sq. ft.
Weir Overflow Rate (gal./day/lin. ft.)
Weir Length = ft.
Plant flow to clarifier = gal./day
Plant flow .. . ,
Weir length = Bal./day/lm. ft.
-27-
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APPENDIX E
OXYGEN UPTAKE PROCEDURE3
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)
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 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).
-28-
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APPENDIX E (ConL)
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 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."
(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.
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