EPA 904/9-76-026
TECHNICAL ASSISTANCE PROJECT
AT THE
PASCAGCULA WASTEWATER TREATMENT PLANTS
PASCAGOULA, MISSISSIPPI
July, 1976
$ \
I 9
Enviroiimentnl Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
-------
TECHNICAL ASSISTANCE PROJECT
AT THE
PASCAGOULA WASTEWATER TREATMENT PLANTS
PASCAGOULA, MISSISSIPPI
July, 1976
Library Regioa IV
US EsvirsBsaesial Praledsca
345 Cc^iiiemd Ske#
Maata, Georgia 41'
Environmental Protection Agency-
Region IV
Surveillance and Analysis Division
Athens, Georgia
-------
TABLE OF CONTENTS
Page
INTRODUCTION 1
SUMMARY 2
RECOMMENDATIONS 5
FOSTER STREET WASTEWATER TREATMENT PLANT 8
TREATMENT FACILITY 8
Treatment Processes 8
Personnel 8
STUDY RESULTS AND OBSERVATIONS 12
Flow 12
Waste Characteristics and Removal Efficiencies ..... 12
Aeration Basins 14
Clarifiers 18
Chlorine Contact Chamber 20
Aerobic Digesters 22
Laboratory 22
BAYOU CASOTTE WASTEWATER TREATMENT PLANT 24
TREATMENT FACILITY 24
Treatment Processes 24
Personnel 24
STUDY RESULTS AND OBSERVATIONS 24
Flow 24
Waste Characteristics and Removal Efficiencies 29
Aeration Basins 29
Clarifiers 32
Chlorine Contact Chamber 35
Aerobic Digesters 35
EAST SIDE WASTEWATER TREATMENT PLANT 37
TREATMENT FACILITY 37
Treatment Processes 37
Personnel 37
STUDY RESULTS AND OBSERVATIONS 37
Flow 37
Waste Characteristics and Removal Efficiencies 39
Aeration Basins 40
Clarifier 41
Aerobic Digester 41
APPENDICES
A. Laboratory Data 43
B. General Study Methods 48
C. Activated Sludge Formula Used for General Calculations . . . 49
D. Dissolved Oxygen 51
E. Oxygen Uptake Procedure 53
F. Supernatant Selector 55
REFERENCES 56
-------
TABLES
Page
I. Design Data—Foster Street WTP 10
II. Waste Characteristics and Removal Efficiencies -
Foster Street WTP 14
III. Activated Sludge Operational Parameters - Foster St. WTP . 15
IV. Secondary Clarifier Operational Parameters -
Foster Street WTP 18
V. Design Data - Bayou Casotte WTP 26
VI. Waste Characteristics and Removal Efficiencies -
Bayou Casotte WTP 29
VII. Activated Sludge Operational Parameters -
Bayou Casotte WTP 30
VIII. Secondary Clarifier Operational Parameters -
Bayou Casotte WTP 33
IX. Design Data - East Side WTP 39
X. Waste Characteristics and Removal Efficiencies -
East Side WTP 40
-------
FIGURES
Page
1. Foster Street WTP 9
2. Plant Flow—Foster Street WTP 13
3. Modified Influent Flow Distribution 17
4. Settlometer Test—Foster Street WTP 19
5. Clarifier Dye Tracer Study—Foster Street WTP .... 21
6. Bayou Casotte WTP 25
7. Plant Flow—Bayou Casotte WTP 28
8. Settlometer Test—Bayou Casotte WTP 31
9. Clarifier Dye Tracer Study—Bayou Casotte WTP 34
10. East Side WTP 38
11. Settlometer Test—East Side WTP 42
-------
INTRODUCTION
A technical assistance study of operation and maintenance problems
at the Poster Street, Bayou Casotte, and East Side Wastewater Treatment
Plants (WTP), Pascagoula, Mississippi was conducted July 19-24, 1976
by the Region IV Surveillance and Analysis Division, U. S. Environmental
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 plants are selected for tech-
nical 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 study efforts would
be productive.
These plants were selected based upon the recommendation of the
¦Mississippi Air and Water Pollution Control Commission and an EPA re-
connaissance visit to the plants. The specific study objectives were to:
• Optimize treatment through control testing and recommended
operation and maintenance modifications;
o Introduce and instruct plant personnel in new operational
control techniques;
o Determine influent and effluent wastewater characteristics;
« Assist laboratory personnel with any possible laboratory pro-
cedure problems and
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, making subsequent
visits to the facilities. The follow-up assessment will determine if
recommendations were successful in improving plant operations and if
further assistance is required. In order to relate preliminary study
findings and stay abreast of process changes and results, contact has been
maintained with plant personnel since the study was conducted. Many of
the recommendations in this report have been implemented since the study,
and recent reports have shown significant improvements in removal effi-
ciencies .
The cooperation of the Mississippi Air and Water Pollution Control
Commission is greatefully acknowledged. The technical assistance team
is especially appreciative of the cooperation and assistance received
from personnel of the Foster Street, Bayou Casotte, and East Side Waste-
water Treatment Plants.
-------
SUMMARY
FOSTER STRiCKT WASTKWATKR TRKATMKNT PLANT
The Foster Street Wastewater Treatment Plant (WTP) was designed
as a 4.25 mgd actLvated sludge system. The WTP was handling an ap-
proximate flow of 1.65 mgd. The average 1501),- and TSS reductions during
the study were 92 and 80 percent, respectively.
Helow are the major problems observed during the study:
1. The grit chamber was In need of repair and was not in operation.
2. The MLSS concentration was too high (5,81.2 mg/1) .
3. The dissolved oxygen (DO) concentrations in the aeraLion basins
were too low; the average DO concentration was 0.14 mg/1 over
two days of sampling.
4. Grease and scum collected from the clarLflcrs were recycled back
to the raw influent, which caused a build-up In the treatment
system. The major source of grease In the influent was the
Quaker Oats Company.
5. The activated sludge settled and compacted poorly in the final
clarifiers. F.xcessive grease and filamentous organisms In the
treatment system were suspected as a major cause.
6. KxcessLve solids were accumulating and denitrifying in the
chlorLne contact chamber. Sludge was periodically floating
to the surface and flowing over the effluent weir.
7. Kffective operation of the aerobic digesters was hindered by
thin waste sludge and inability to effectively decant super-
natant .
8. The WTP was manned 16 hours/day and often the morning shift
spent time recovering from problems which occurred during the
time the WTP was not staffed.
9. The effluent flow measuring equipment was out of calibration.
10. The flow splitting arrangement to the five aeration basins will
not perform satisfactorily under varying plant flows.
• Minimum operational control testine was performed.
2
-------
BAYOU CASOTTE WASTEWATER TREATMENT PLANT
The Bayou Casotte WTP serving southeast Pascagoula, Mississippi
was designed as a 1.6 mgd conventional activated sludge system. Re-
portedly the WTP receives an average daily flow of 1.5 mgd with peaks of
3-4 mgd. During the study OTP influent flow averaged 1.36 mgd with a peak
flow of 2.7 mgd. Average BOD^ and TSS reductions during the study period
were 74 and 55 percent, respectively. The activated sludge was dark in
color and settled slowly with minimal compaction, resulting in a turbid
effluent.
Below are major problems observed during the study:
1. The organic loading to the aeration basins exceeded recommended
levels.
2. At the BOD loadings during the study, oxygen supplied to the
aeration basins was marginal; this allowed no excess aeration
capacity for equipment breakdown or increased loads.
3. Solid deposits were found on the bottom and in the corners of the
aeration basins.
4. The clarifier weir was not level.
5. The waste sludge line from the east digester and supernatant
line from the west digester were clogged.
6. The maintenance of the aerobic digesters was hampered due to
poor structural conditions.
7. The return sludge flow rate was excessive.
8. Grit removal equipment was inoperable.
9. The plant was operated by one uncertified operator.
10. There was no in-plant control testing.
11. The effluent flow measuring equipment was inoperable.
3
-------
EAST SIDE WASTEWATER TREATMENT PLANT
The East Side WTP was designed as a 0.4 mgd activated sludge system
and was operating at about design flow. The average BOD5 and TSS reduc-
tion during the study was 93 and 96 percent, respectively.
Below are major problems observed during the study:
1. The activated sludge settled slowly and compacted poorly; the
sludge blanket was within three feet of the clarifier water surface.
2. Volatile content of the mixed liquor suspended solids was only
47 percent.
3. The mixed liquor suspended solids concentration bordered on
maximum recommended limits.
4. Dissolved oxygen was depleted within five minutes after aerators
were turned off.
5. Influent metal concentrations were above generally observed values
for purely domestic wastes.
6. The effluent flow recorder and totalizer were inoperative.
4
-------
RECOMMENDATIONS
Based on observations and data collected during the study, it is
recommended that the following measures be taken to improve wastewater
treatment and plant operation. Some of the items listed below have
been discussed with WTP personnel and have already been implemented.
FOSTER STREET WASTEWATER TREATMENT PLANT
1. The MLSS should be reduced to about 3,000 mg/1 (2,100 mg/1 MLVSS),
which will produce an F/M ratio of approximately 0.2, based on current
plant loadings. Activated sludge settleability and effluent quality
will dictate the optimum MLSS, F/M and MCRT.
2. Sludge should be wasted on a regular schedule. After the MLSS have
been reduced, the optimum MLSS and MCRT will determine the appropri-
ate wasting rate.
3. Grease and scum collected from the secondary clarifier should be
removed to a sanitary landfill, if acceptable, instead of recircu-
lated to the plant influent. An alternate, but less desirable,
solution would be discharge to the aerobic digesters.
A. If recommendation 3 does not improve activated sludge settleability
and compaction, then the use of a polymer should be investigated.
However, polymers should not be considered a long term treatment
solution. Better inplant operational control and grease control at
the source and within the treatment system is the key to improved
treatment.
5. The dissolved oxygen concentration in the aeration basins should
be maintained in the 1.0 to 2.0 mg/1 range, and monitored in each
basin regularly with a DO meter and field probe. Reduction of the
MLSS should help in maintaining adequate DO.
6. The return sludge flow should be gradually decreased as the MLSS is
reduced. Aerobic conditions in the clarifier must be maintained,
and this will dictate the minimum return sludge flow.
7. The supernatant withdrawal piping for the aerobic digesters should
be modified to allow either selective withdrawal from several levels
or at least withdrawal from a higher level.
8. The aerators should be checked to see that they are delivering maximum
efficiency. This can be done by checking the amperage pulled and depth
of submergence.
9. The chlorine contact chamber should be equipped with a drain or
pump to facilitate sludge removal.
5
-------
10. The two-Inch drain line from Lhe thickener (supernal ant) surge Lank
hIhhiIcI bo Increased Lo at leasL four Inches.
1.1. The WTI' hIiouUI hi1 man nod 24 bourn/day. Additional staffing Lh necessary
to efficiently operate tho plant.
12. The Quaker Oats discharge should be monitored regularly and the
sewer ordinance strlc-Lly enforced.
13. The grit chamber should be repaired and placed back in operation.
14. An In-plant" control testing schedule should be Immediately InLtiated
and trend charts established and maintained aL all three wastewater
treatment plants.
HAYOU C.ASOTTI1'. WASTKWATKK TKKATMKNT PLANT
I
1. The feasibility of diverting a portion of the flow from the Iiayou
flasotte WIT to the Foster SLreet WTI' should be Investigated.
2. The clurlfler weir should be replaced and/or leveled.
'}. The waste sludge line from the east digester and supernatant line
from the west digester should be reopened.
4. The MI.SS concentration should be maintained at about 2,500 mg/1
and a regular sludge wasting schedule should be established. Mixed
liquor se11Ieab11 Ity and aeration basin dissolved oxygen will dic-
tate ithe optimum MLSS concentration.
5. The aerators should be checked to see that they are del. Ivering
maximum efficiency. This can be done by checking the amperage
pulled and depth of submergence.
f
6. The aeration basins should be sounded to determine the extent of
solLds accumulation and If necessary, these solids should be pumped
out.
7. The grit removal equipment should be repaired and placed back in
operation.
8. The fiow meter, recorder, and totalizer should be repaired, calibra-
ted, and placed back in operation.
, \
9. The chlorine metering equipment should be repaired and placed back
Ln operation.
10. The WTP should be staffed 16 hours/day and routinely checked during
the remaining 8 hours.
6
-------
EAST SIDE WASTEWATER TREATMENT PLANT
1. The aerators should remain ON at all times.
2. The MLSS concentration should be reduced to about 3,400 mg/1.
Monitoring sludge blanket depth, sludge settleability and effluent
quality will help determine the optimum MLSS concentration.
7
-------
FOSTER STREET WASTEWATER TREATMENT PLANT
TREATMENT FACILITY
Treatment Processes
A schematic diagram of the 4.25 mgd Foster Street Wastewater
Treatment Plant (WTP) is presented in Figure 1. Design data are
enumerated in Table I. According to the WTP O&M manual, the WTP was
designed for tapered aeration. However, each aeration basin has four
mechanical aerators, all of equal size and equal spacing. Therefore,
the plant should be considered as a conventional activated sludge process.
The WTP began operation in March 1975 and serves an approximate population
of 15,500. Roughly 10 percent of the influent plant flow was from indus-
trial sources, primarily the Quaker Oats dog and cat food plant.
Preliminary treatment consisted of a bar screen, grit chamber, and
three comminutors. The grit chamber was out of service during the study.
After preliminary treatment, raw wastewater and return sludge flowed into
a long channel which distributed the flow into five parallel aeration
basins.
Aeration basin mixed liquor was settled in two secondary clarifiers.
The overflow was chlorinated and discharged into the Pascagoula River.
Sludge from the clarifiers was either returned to the aeration basins or
wasted to the aerobic digesters.
The sludge handling facilities included three aerobic digesters,
sludge thickener and a vacuum filter. Sludge from the filter, grit, and
screenings were trucked to a sanitary landfill.
Personnel
The three wastewater treatment plants were staffed by 13 men with
the following classifications: 1-1, 2-II and l-III. All laboratory,
maintenance, and other support personnel were stationed at the Foster
Street WTP. Of a total of six operators, four operated the Foster Street
WTP, which is staffed 16 hours per day.
8
-------
Sludge
condition-
ing and
dewaterinp
jfc, to sanitary landfill
FIGURE 1
FOSTER STREET WTP
PASCAGOULA, MS
Outfal- to Pascapoula River
-------
TABLE I
DESIGN DATA - FOSTER ST. WTP
PASCAGOULA, MS
FLOW MEASUREMENT
Final Effluent
Return Sludge Flow
Design Flow
Average Flow
AERATION BASINS
Number 5
Basin #1
Length 127 ft.
Width 29 ft.
Water Depth 9 ft.
Area 3,683 sq. ft.
Volume 33,147 cu. ft. (0.25 m.g.)
Basins //2, 3, 4
Length 127 ft.
Width 23 ft.
Depth 12 ft.
Area 2,921 sq. ft.
Volume 35,052 cu. ft. (0.26 m.g.)
Basin #5
Length 127 ft.
Width 33 ft.
Depth 10.9 ft.
Area 4,191 sq. ft.
Volume 45,682 cu. ft. (0.34 m.g.)
Aeration 4-7.5 hp mechanical aerators per basin
CLARIFIERS
Number 2
Diameter 68 ft.
Side Water Depth 8.5 ft.
Area 3,630 sq. ft.
Volume 34,279 cu. ft. (0.26 m.g.)
Weir Length 214 ft.
6 ft. Rectangular Weir (with end
contractions)
2.5 mgd (study period average)
4.25 mgd
1.65 mgd (study period average)
10
-------
TABLE I
DESIGN DATA - FOSTER ST. WTP
PASCAGOULA, MS (continued)
CHLORINE CONTACT CHAMBER
Length
Width
Water Depth
Volume
Detention (at design flow)
AEROBIC DIGESTERS
Number
Diameter
Side Water Depth
Volume
Aeration
PUMPS
Return sludge
Waste sludge
41 ft.
60 ft.
6 ft.
14,760 cu. ft.(0.11 m.g.)
30 min.
3
No. 1-40 ft.
No. 2, 3, - 38 ft.
23 ft.
No. 1 - 30,144 cu. ft.(0.225 m.g.)
No. 2, 3 - 27,579 cu. ft.(0.21 m.g.)
40 hp mechanical(i/tank)
2 (+1 standby) 550-1,100 gpm
variable speed
2 150-200 gpm variable speed
11
-------
STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and general study methods
are presented in Appendices A and B. Formulae used for general calcula-
tions are enumerated in Appendix C. Significant results and observations
made during the study are discussed in the following sections.
Flow
Plant flow was measured by an EPA installed Stevens stage recorder
on a 6-foot rectangular weir at the effluent from the chlorine contact
chamber. The WTP recorder and totalizer were out of calibration. Conse-
quently, they were not used for flow measurements during the study. The
TA team installed a staff gage in the chlorine contact chamber and fur-
nished WTP personnel with hydraulic tables so that instantaneous flows
could be accurately determined to check permanently installed flow record-
ing equipment. Return sludge flow was determined by a flume, recorder,
and totalizer.
Average hourly flows from the plant during the study period are
presented in Figure 2. Average flow during the study was 1.65 mgd and
varied from 0.3 to 3.2 mgd. According to plant personnel, the Quaker
Oats dog and cat food plant accounts for about .182 mgd of the WTP
influent flow.
The return sludge flow was maintained fairly constant during the
study at about 2.5 mgd, which was about 150 percent of the influent
plant flow.
Waste Characteristics and Removal Efficiencies
Table II presents a chemical description of the WTP influent and
effluent wastewaters with calculated treatment reductions. Analyses
were made on 24-hour, flow proportional, composite samples, collected
on three consecutive days and percent reductions calculated from averaged
values.
The influent BOD^ (347 mg/1) and total solids (1,257 mg/1) concen-
trations represent a rather strong waste. These high concentrations
were the result of the Quaker Oats Company discharge, which had BOD^
concentrations of 1,400 and 1,067 mg/1 and total solids concentrations
of 2,398 and 2,108 mg/1, based on grab samples taken on two different
days.
Although the BODj. reduction was good (92%), total suspended solids
removal was less impressive (80%). Very little nitrification was accom-
plished in the treatment system.
12
-------
3.0
2.5
2.0
Q
O
S
3
O
OJ
L. 5
1.0
0.5 -
11
9 N 3 6 9 M 3 6
7/20
FIGURE 2
PLANT FLOW - FOSTER STREET WTP
PASCAGOULA, MS
Return Sludge Flow (approx.)
J I I I I I ... I I I I I I I I I I
9N369M369N369M36
7/21 7/22
TIME
-------
TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
FOSTER ST. WTP
Parameter
Influent
Effluent
% Reduction
BOD5 (mg/1)
347
26
92
COD (mg/1)
583
92
84
Total Solids (mg/1)
1,257
980
22
TVS (mg/1)
408
168
59
TSS (mg/1)
205
40
80
TVSS (mg/1)
165
25
85
iSettleable Solids (ml/1)
6.7
<0.13
>98
TKN (mg/1)
46
33
28
NH3-N (mg/1)
34
32
6
N02-N03-N (mg/1)
<0.01
0.03
—
Total Phosphorus (mg/1)
9.2
13
—
Chloride (mg/1)
273
278
—
Oil and Grease (mg/1)*
52.2
<5.0
>90
CI2 Residual (mg/1)*
—
2.9
—
Pb (pg/1)
<80
<80
—
Cr (Mg/1)
<80
<80
—
Cu (yg/1)
93
18
81
Cd (yg/1)
<20
<20
—
Zn (yg/1)
285
49
83
* Averaged results of grab
samples taken
on three different
days.
The analytical results
of two grab
samples collected from the Quak'
Oats wastewater discharge (sample station 01) are presented in Appendix A.
Based on an approximate flow of 182,000 gpd, suggested by a City official,
the Quaker Oats discharge contributed about 1,870 pounds/day of BOD5 and
158 pounds/day of grease to the WTP. The city sewer ordinance restricts
the Quaker Oats BOD5 and grease discharge to 1,589 and 70 pounds/day at a
maximum flow of 300,000 gpd.
Aeration Basins
Grab samples were collected daily from each of the five aeration
basins and in the discharge channel after the effluent from all basins
had mixed. These samples were analyzed for total suspended solids (TSS),
volatile suspended solids (VSS), percent solids by centrifuge, and settle-
ability 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.
14
-------
TABLE III
ACTIVATED SLUDGE OPERATIONAL PARAMETERS
FOSTER ST. WTP
MLSS (mg/1)
MLVSS (mg/1)
Hydraulic Detention Time (hrs.)
Mean Cell Residence Time (days)
Sludge Age (days)
Lbs. BOD/day/lb MLVSS (F/M)
Lbs. COD/day/lb MLVSS
Lbs. BOD/day/lOOO cu. ft.
of aeration basin
Return sludge rate (% of
average plant flow)
Measured Recommended (2) (5) (7)*
5,812 1,500-3,000
3,846
7.96 4-8
26** 5-15
23.6 3.5-7.0
0.11 0.2-0.4
0.18 0.5-1.0
26 20-40
150 (2.5 mgd)
* References 1-12 appear on page 56.
** Based on wasting schedule setup after the TA study.
25-50
Dissolved oxygen (DO) was measured throughout the aeration basins
and the results are presented in Appendix D. The DO concentrations
ranged from zero to 0.8 mg/1; the average DO concentration over a two-day
period was 0.14 mg/1. These concentrations are much too low and result
in a number of conditions causing poor settleability and/or treatment
efficiencies. Attempts should be made to maintain DO concentrations in
the 1.0-2.0 mg/1 range in the aeration basins.
Prior to the TA study, sludge was not wasted to the aerobic digesters
on a regular schedule. However, since the TA study, a regular wasting
schedule has been instituted. The long MCRT and low food/microorganism
(F/M) ratio was due to the high MLSS concentration. These operational
parameters should approach recommended ranges as regular sludge wasting
continues and the MLSS concentration is reduced. Close monitoring of the
sludge settleability and MLSS must be maintained so that the MLSS is not
reduced too much.
Assuming an F/M ratio of about 0.2, the MLSS should be reduced to
about 3,000 mg/1 (MLVSS = 2,100 mg/1); sludge settleability and effluent
quality will determine the optimum F/M and MCRT.
The method of introducing raw wastewater and return sludge was un-
desirable and resulted in several bad effects. The influent raw waste
and return sludge entered at one end of a long distribution channel di-
rectly in front of the opening to the #1 aeration basin. Foam and scum
were much denser in the first two basins (#1 and //2) than in the final
three (//3, #4, and //5) basins. The supernatant in the settlometer test
was cloudy for aeration basins //1, //2, and //3 and relatively clear for
basins //4 and #5.
15
-------
The flow split to each aeration basin was controlled by the elevation
and length of the effluent weir in each basin. Each weir had a length
proportional to the volume of the respective basin so that theoretically
the detention time was the same in each basin. This is not an effective
method of splitting the flow. Head losses to each basin vary due to
roughness in the entrance channel and abrupt changes in the direction
of flow. These losses change with the rate of plant flow so that the
relative amount of waste to each basin varies at a given weir elevation.
Normally in this type flow configuration the first basins get a dispro-
portionally high portion of the total waste flow. Even though no flow
measurements were made, there was evidence of an uneven flow split observed
in the amount of grease and foam on each basin.
, AI more effective method of flow distribution could be accomplished
by installing adjustable weirs or orifices in the entrance to each basin
(see sketch in Figure 3). This would increase the water surface elevation
in the entrance flume by 6 inches to a foot, producing a head loss into
the basins. This procedure would permit regulation and measurement of the
flow to each basin. The additional backwater in the entrance flume may
cause some deposition of solids and the weirs will have to be cleaned
periodically. Weirs could be cut in sheet metal gates (preferably alumi-
num) to be installed in the existing basin openings. This would permit
lifting of the gates periodically to flush the entrance flume.
An alternative method to the use of weirs would be a rectangular
orifice formed by installing a sheet metal gate in the rectangular basin
opening and adjusting the gate so that it is not completely sealed. This
would permit flow through the opening under the gate. Bolts with nuts
welded to the bottom of the gate could be used to adjust the size of the
opening. This method may cause fewer problems with deposition of solids
in the entrance flume but would not provide the degree of accuracy in
flow measurement and splitting provided by the weirs.
A microscopic examination of mixed liquor and return sludge demon-
strated a dense sludge which supported in high densities the entire
spectrum of protozoan organisms from a young sludge to an old sludge.
Also observed was a dense concentration of very small filamentous organisms.
The presence of all major protozoans indicate an activated sludge that
would give characteristics of a young sludge if the solids level was
decreased. The filamentous growth|was of high enough concentration to
cause floating of the newly formed biological sludge, resulting in an
effluent with a high volatile solid content.
Another indicator of sludge quality is the oxygen uptake rate of the
return sludge. The oxygen uptake rate is a measure of the difference in
sludge activity before and after introduction of the raw waste. The
ratio of these two variables or "load ratio" is calculated as follows:
Load ratio = DO/™in of fed sludge
DO/min of unfed sludge
The procedure is presented in Appendix E.
16
-------
FIGURE 3
MODIFIED INFLUENT FLOW DISTRIBUTION
-------
The return sludge was septic and could be quickly aerated to a DO
concentration of only 3.0 mg/1 which was depleted in one minute. After
satisfying the septic sludge demand, an unfed uptake of 1.5 and a fed
rate of 2.1 was measured.
A calculated ratio for these two rates was 1.4. A conventional
activated sludge process generally operates within a load range of 2 to
4. This ratio of 1.4 is indicative of a sludge of low activity with an
acceptable feed. The rapid depletion of oxygen was the result of septic
conditions.
Clarifiers
Both circular clarifiers have a center feed, rim take-off flow
configuration with a short center baffle to distribute incoming flow.
Activated sludge settleability as determined by the settlometer test
is presented in Figure 4. Settleability in each aeration basin did not
vary appreciably from that of the combined aeration basin effluents.
The activated sludge settled and concentrated poorly, probably due to
the buildup of grease in the treatment system.
-The depth of the sludge blanket (DOB) below the water surface
varied between 2 and 3.5 feet. This would be expected due to the poor
settleability of the sludge. Many factors including flow and tempera-
ture can cause solids to carry over the weirs when the sludge blanket
is this close to the water surface. This is a dangerous zone of opera-
tion and usually results in excessively high solids in the effluent.
The measured and recommended operating parameters for secondary
clarifiers following the conventional activated sludge process are
presented in Table IV.
TABLE IV
SECONDARY CLARIFIER OPERATIONAL PARAMETERS
FOSTER ST. WTP
Measured
Recommended (3)(4)
Hydraulic Loading (gpd/sq. ft.)
Solids Loading (lbs/day/sq. ft.)
Hydraulic Detention (hrs.)
227
28
400-800
20-30
2-2.5
Clarifier #1
3.0+(1.2)*
3.0t(1.5)*
3,855
Clarifier #2
Weir Overflow Rate (gpd/lin. ft.)
15,000
+ = calculated as volume/flow
* = measured by dye study
18
-------
Fic;^: m
SETTLOMKTER TEST
FOSTER STREET Wl'P
LOO
90
80
70
z:
3
J
O
>
60
50
E-
F-
U
AO
30
20
1C
10
15
20
30
TIME(MIX)
;o
50
60
-------
The results of the clarifier dye tracer study are presented in
Figure 5. The area under the two curves (Figure 5) are an indication
of the flow split to the two clarifiers which was 53 and 47 percent to
the #1 and //2 clarifiers, respectively. The hydraulic detention time
was determined as the centroid of the respective curves (Figure 5) and
are presented in Table IV.
The return sludge flow was kept constant at about 2.5 mgd, which
was approximately 150 percent of the influent plant flow. This rate
of return sludge was exceptionally high, but necessary, in order to
contain the sludge blanket in the clarifiers and to maintain aerobic
conditions. As sludge settleability improves, the return sludge flow
should be reduced to a rate which maintains good clarifier operation.
Septic conditions, excessive sludge blanket, black color, sludge float-
ing to the surface, and bubbles are indicators that the return sludge
flow has been reduced too much.
The solids loading (Table IV) approached the maximum recommended
loading, even though the WTP was operating at less than half the design
flow. This was due to the extremely high MLSS concentration.
Grease removed from the final clarifiers can be pumped to the
digesters or flow to the head of the plant. During the study, grease
flowed to the head of the plant, which was the least desirable alter-
native of handling excessive grease. Preferably, grease removed from
the final clarifiers should be disposed at the sanitary landfill rather
than re-introduced to the liquid flow.
Effective sludge wasting to the aerobic digesters will be diffi-
cult due to the poor activated sludge settleability and compaction in
the final clarifiers. The use of polymers may improve sludge settle-
ability and compaction resulting in improved effluent quality and sludge
control in the treatment system. However, the influent grease concen-
tration should be controlled at the source and recycling grease in the
treatment system should be stopped immediately.
Chlorine Contact Chamber
The hydraulic detention time in the chlorine contact chamber (CCC)
at existing flows (1.65 mgd), was about 96 minutes. The average chlo-
rine residual during the study period was 2.5 mg/1 and ranged between
1.3 and 3.5 mg/1. Chlorine was fed at the rate of about 140 pounds/day.
Sludge had accumulated in the CCC as evidenced by periodic boiling
up of black solids. Plant design does not include any means of draining
the CCC and no portable pump was available for sludge removal. A drain
or pump should be provided to facilitate draining and sludge removal.
20
-------
F . C»L h. 5
s"i_A•X (VIN)
-------
Aerobic Digesters
Sludge is treated in three aerobic digesters, a gravity sludge
thickener and a vacuum filter. Sludge from the aerobic digester may
be thickened in a sludge thickener prior to the vacuum filter if desired.
Effective operation of the aerobic digesters was hampered by certain de-
sign flaws. According to plant personnel, the supernatant draw-off line
is located too low to decant clarified liquid; consequently, the super-
natant piping cannot be used. In order to decant from the digesters a
small portable pump must be used, which requires about 25-30 hours to
pump clarified supernatant. Extending the supernatant draw-off pipe
vertically in either a fixed or movable position (Appendix F) by using
a swivel joint would allow use of existing piping and valves to more
effectively decant clarified digester supernatant.
The O&M manual for the Foster Street WTP states that, "The three
digesters are so designed and valved that the sludge may be transferred
from tank 1 to tank 2 to tank 3 under normal operation". According to
WTP personnel, however, existing piping does not allow this flexibility.
Reduction of the high solids in the aeration basins will require
increased wasting to the aerobic digesters. Poor sludge compactability
in the final clarifiers will complicate the wasting/digestion process.
Aerobic digesters should not be shut off for more than 1-4 hours to
decant and/or pump solids to the vacuum filter. In order to accomplish
this, the supernatant piping arrangement must be modified.
Supernatant from the sludge thickener flows into the supernatant
surge tank. This tank was designed with an exceptionally small (about
2 inch) drain line which continually plugs. This small line should be
replaced with a larger line at least 4 inches in diameter.
Laboratory
The laboratory for all three plants is located at the Foster Street
WTP. It is manned by two laboratory technicians who conduct all chemical
analyses for the three plants plus conduct chlorine residual tests and a
fecal coliform sampling program for the City of Pascagoula Water Department.
The laboratory was adequate in size for the analyses performed.
During the study the following observations and suggestions were made:
1. Sodium thiosulfate which was obtained from a private laboratory
and used in the BOD^ and DO determinations was not standardized
by laboratory personnel. The procedure and importance of stan-
dardizing was discussed. After returning to the EPA laboratory,
a bottle of 0.0375 N potassium biniodate and standardized 0.0375
sodium thiosulfate was sent to the laboratory personnel as a
check for their sodium thiosulfate. It was suggested that a
portable DO meter with a field and laboratory probe would save
time and effort.
22
-------
2. DO was determined in the effluent, after chlorination, without
using the correct dechlorination procedure. The proper proce-
dure was discussed.
3. Routine tests conducted by the lab personnel for all three
plants included BOD^ (influent and effluent before chlorination),
TSS (influent, effluent, mixed liquor, return sludge and sludge
before dewatering), CI2 residual, fecal coliform, pH (influent
and effluent), DO (influent, effluent, and aeration basins),
settleable solids (influent and effluent), and 30-minute settling
test (SVI). It was suggested that they replace the SVI test with
the settlometer test and include the centrifuge test. The pro-
cedure and the importance of these two tests were discussed.
Because of an inoperative muffle furnace, no volatile solids tests
were being conducted. The importance of these results in loading
calculations and operation of aeration basins was also discussed.
A. Trend charts were not being used. The procedure and importance
of these were discussed.
It was suggested that an in-plant control testing program be initiated
immediately, including the following chemical and physical parameters:
settlometer, clarifier sludge blanket depth, and aeration basin TSS, VSS,
and DO. It was further suggested that dissolved oxygen measurements be
made throughout the aeration basins at various depths and trend charts be
established and maintained. Useful parameters for plotting include MLSS,
sludge settleability, significant influent and effluent waste character-
istics, flow (plant, return sludge, waste sludge), depth of clarifier
sludge blanket, MCRT, and F/M ratios. Experience will dictate which of
these parameters are necessary for successful plant operation. These
suggested parameters should serve only as a guide and are intended to
establish trends so that gradual changes in plant conditions can be noticed
prior to a deterioration in effluent quality. It is advisable that plant
changes be made one at a time and maintained for approximately two weeks
to allow the plant to reach equilibrium.
23
-------
BAYOU CASOTTE WASTEWATER TREATMENT PLANT
TREATMENT FACILITY
Treatment Processes
A schematic diagram of the 1.6 mgd Bayou Casotte OTP is presented in
Figure 6. Design data are enumerated in Table V. The plant began opera-
tion in 1965 and serves a population of approximately 11,000. No industrial
wastes are received at the WTP.
The WTP is operated in the conventional activated sludge (A/S) mode.
Return sludge is pumped from the clarifier back to the aeration basins.
Waste sludge is pumped to the aerobic digesters, after which it is dis-
charged onto sludge drying beds.
The grit removal system was not operational. The final effluent is
chlorinated and discharged into Bayou Chico.
The WTP is staffed by one non-certified operator eight hours per day.
STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and general study methods
are presented in Appendices A and B. Formulae used for general calcula-
tions are enumerated in Appendix C. Significant results and observations
made during the study are discussed in the following sections.
Flow rate prior to the study was determined by measuring the head
with a yard stick over a 2 foot rectangular contracted weir. A recorder
and totalizer were not calibrated properly. During the study, flows were
determined with an EPA installed Stevens stage recorder and staff gage.
Since there was no flow measuring device on the return sludge, an approxi-
mated flow was calculated utilizing simplified mixing formulae.
The average hourly WTP flow during the study is illustrated in Figure
7. The flow range was from 0.603 to 2.73 mgd, the average having been
1.36 mgd. A staff gage was installed by EPA personnel to facilitate
daily operation and data reporting.
Return sludge flow for one return pump operating at maximum capacity
is 400 gpm (0.576 mgd). On July 20, 1976 the return sludge rate was cal-
culated at 0.468 mgd or 36 percent of the average daily flow.^^) During
July 21-22, 1976, two pumps were in operation for 8 hours each day. Return
sludge flows were calculated for the indicated days as follows:
Personnel
Flow
July 20, 1976
July 21, 1976
July 22, 1976
0.468 mgd
0.812 mgd
0.695 mgd
24
-------
FIGURE b
BAVCL' CASOTTE l.ASTEU'ATER TR£AT:iE\l PLAI.T
PASCaCOULA, MS
SL'JDGF, DRYING BEDS
L
SUPERNATANT RETURN
J
-------
TABLE V
DESIGN DATA - BAYOU CASOTTE WTP
PASCAGOULA, MS
Flow Measurement
Type
Design flow
Aeration Basin
Number
Dimensions
Surface
Length
Width
Bottom
Length
Width
Water Depth
Surface Area/basin
Volume/basin
Aeration
Clarifier (Final)
Number
Diameter
Depth (SWD)
Center
Hopper Depth
Surface Area
Volume
Weir Length
Chlorine Contact Chamber
2 ft. rectangular weir
1.6 mgd
80 ft.
52 ft.
56 ft.
28 ft.
12.0 ft.
4,160 sq. ft.
32,640 cu. ft. (244,150 gals.)
2-15 h.p. aerators/basin
1 (circular)
52 ft. (ID)
7.4 ft.
9.58 ft.
2.2 ft.
2,123 sq. ft.
17,300 cu. ft. (129,000 gals.)
163 ft.
Dimensions
Surface (WL)
Length
Width
Bottom
Length
Width
Water Depth
Surface Area
Volume
62 ft.
22.5 ft.
50 ft.
10.5 ft.
6 ft.
1,395 sq. ft.
5,544 cu. ft. (41,470 gals.)
26
-------
TABLE V (Cont.)
Aerobic Digesters
Number
Dimensions
Surface (W.L)
Length
Width
Bottom
Length
Width
Water Depth
Surface Area/basin
Volume/basin
Aeration/basin
52 ft.
52 ft.
28 ft.
28 ft.
12 ft.
2,704 sq. ft.
19,200 cu. ft. ((143,620 gals.)
1-15 h.p. aerator
Sludge Drying Beds
Number
Length
Width
Area
7
59.2 ft.
20 ft.
8,284 sq. ft.
27
-------
3
N>
OO
T3
OO
a
7/20
FIGURE 7
PLANT FLOW
BAYOU CASOTTE WTP
PASCAGOULA, MS
1 ¦ ¦ * 11 ' '
N6M6N6M6
7/21
7/22
7/23
-------
The average return sludge flow rate for the study period was 0.658
mgd or 48 percent of the average daily flow.
When only one pump was operational, sludge wasting to the digesters
was accomplished by closing off the return sludge valves and then opening
valves to the digesters. When the second pump was repaired and in opera-
tion, flow could be maintained in the return and waste lines, thus elimi-
nating the closing of the valves. Sludge was wasted only once during the
study (July 22)„
Waste Characteristics and Removal Efficiencies
Table VI presents a chemical description of the influent and effluent
waste water with calculated treatment reductions. Removal efficiencies
were calculated using averaged data from three consecutive 24-hour, flow
proportional composite samples.
TABLE VI
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
BAYOU CASOTTE WTP
Parameter
Influent
Effluent
% Reduction
BOD (mg/1) 253
COD (mg/1) 432
TS (mg/1) 1,097
TVS (mg/1) 342
TSS (mg/1) 108
TVSS (mg/1) 80
TKN (mg/1) 28.7
NH3-N (mg/1) 23.8
N02-N03-N (mg/1) <0.01
Total Phosphorus (mg/1) 19.3
Chloride (mg/1) 247
Oil and Grease (mg/1)* 43.2
CI2 Residual (mg/1)*
Pb (yg/1) <80
Cr (yg/1) <80
Cu (yg/1) 120
Cd (yg/1) <20
Zn (yg/1) 278
Settleable Solids (ml/1) 14
,1
,5
67
206
971
183
49
40
24.
18.
0.03
6.5
267
5.1
<80
<80
80
<20
182
<0.8
74
52
11
46
55
50
16
22
66
33
35
>94
*Averaged results of grab samples taken on three different days.
These influent data are indicative of a typical domestic wastewater
with an organic content somewhat higher than the normal 200 mg/1 BOD^.
The Bayou Casotte WTP was accomplishing poor treatment efficiency.
Aeration Basins
Grab samples were taken from the aeration basins (Stations BA1-1,
BA2-1) and analyzed for total suspended solids (TSS), volatile suspended
solids (VSS), percent solids by centrifuge, and settleability as deter-
mined by the settlometer. Presented in Table VII are various activated
29
-------
sludge operational parameters calculated during the study period and
the corresponding recommended values for the conventional plug flow
process.
TABLE VII
ACTIVATED SLUDGE
OPERATIONAL PARAMETERS
BAYOU CASOTTE WTP
Measured Recommended (5)(7)(9)
MLSS (mg/1) 2,537 1,500-3,000
MLVSS (mg/1) 1,778
Hydraulic Detention Time (hrs.) 5.8 4-8
Mean Cell Residence Time (days) 8.8 5-15
Sludge Age (days) 8.4 3.5-10
Lbs. BOD/day/lb MLVSS (F/M) 0.39 0.2-0.4
Lbs. COD/day/lb MLVSS 0.67 0.5-1.0
Lbs. BOD/day/l,000 cu. ft. of
aeration basin 44 20-40
Return Sludge Rate (% of average 15-75
plant flow) 48
Oxygen requirement (lbs 02/lb
BOD removed) 1.2* 0.8-1.1
(lbs. 02/lb BOD under aeration) 0.9*
Based on an effective transfer rate of 1.8 lb. 02/h.p. - hr.
(9)
The aeration basins contained a dark grey-black mixed liquor and
return sludge, with foam accumulations in the corners of the aeration
basins. These observations were indicative of an inadequate air supply
to the aeration basin for the organic load received.
The results of the settlometer tests are presented in Appendix A
and illustrated in Figure 8. Sludge settleability was slow, leaving
a turbid supernatant. A microscopic examination of the suspended par-
ticles in the supernatant demonstrated small fluffy particles of bacteria
cells attached to short filamentous (bacteria) agglomerates. A further
examination of mixed liquor solids and return sludge revealed heavy con-
centrations of stalked ciliates and filamentous bacteria. These data
indicate an under-oxidized sludge.
The oxygen uptake rate of the return sludge is another means of
measuring sludge quality. An oxygen uptake rate or load ratio was cal-
culated using the oxygen depletion rate before and after introduction
of the raw waste.
T , . DO/min fed sludge
Load ratio = —; —:—-®—
DO/min unfed sludge
The oxygen uptake procedure is presented in Appendix E.
30
-------
z
~J
o
in
100
90
80
70
60
50
30
20
10
10
15
20
FIGURE 8
SETTLOMETER TEST
BAYOU CASOTTE WTP
-------
The calculated load ratio for the Bayou Casotte WTP was 2.0. Generally,
a conventional activated sludge plant should operate in a load range of 2-4.
A load ratio of 2.0 is indicative of an acceptable feed, but conditions and
sludge quality probably need to be improved. What is not shown here is the
high rate at which oxygen was depleted from the aerated return sludge sample.
A sludge that leaves the aeration basin having less than 0.5 mg/1 of DO
will become septic in the clarifier and exert an immediate demand upon the
air supply system.
Dissolved oxygen (DO) concentrations measured in the aeration basins
are presented in Appendix D. Dissolved oxygen concentrations throughout
the aeration basins ranged from 0 to 0.2 mg/1. To calculate the amount of
oxygen supplied to the aeration basins, an oxygen transfer rate of 1.8
lbs. 02/hp-hr was used. ^ ' From this calculation, 2,592 lbs/day of oxygen
can be supplied by the four 15 hp aerators. Assuming an influent BOD5 con-
centration of 253 mg/1 (Table VI), an influent flow of 1.36 mgd, and an
effluent BOD5 concentration of 30 mg/1, the existing aeration equipment
can supply about 1.0 lbs. C^/lb. BOD^ removed. This is within recommended
values.(9)
A qualitative sounding of the aeration basins demonstrated that there
were solid accumulations on the outer areas of the aeration zones. Solid
deposition may be the result of poor mixing, high specific gravity solids
(sand) in the influent, and/or deposition during periods of aerator mal-
function. The buildup of sludge banks within the aeration basins may
significantly reduce the effective volume. Also, solids accumulated on
the bottom and in the corners exert an increased oxygen demand upon the
system, further stressing the limited oxygen supply.
It can be concluded from the above data that the aeration basins
received a heavy organic loading and the aeration capacity was marginal.
Under the present organic loading, aerobic conditions cannot be maintained
in the system with one aerator out of service, or an increase in the organic
or hydraulic load. Past experience has shown that one of the four aerators
was frequently out of service. During about 6 continuous hours/day, the
plant flow exceeds 1.6 mgd (Figure 7). The obvious solution to this
problem is to reduce the load on the plant and/or provide standby aerators
and replacement parts for existing equipment.
Clarifiers
The circular clarifier has a center feed, rim take-off flow configura-
tion. Measured and recommended operating parameters for secondary clarifiers
following the conventional activated sludge process are presented in Table
VIII.
32
-------
TABLE VIII
SECONDARY CLARIFIER OPERATIONAL PARAMETERS
BAYOU CASOTTE WTP
Measured
Recommended (5)(7)
Hydraulic Detention Time (hrs.) 1.25* (1.4)
Hydraulic Loading (gpd/sq. ft.) 641
Solids Loading (lb/day/sq. ft.) 13.4
Weir Overflow Rate (gpd/lin. ft.) 8,344
<15,000
12-15**
2-3
400-800
20-30
Depth (SWD) (ft.)
7.4
* Calculated as volume/flow
() Indicate detention time as determined from the dye study.
**Ten State Standards, ( 'section 54.12 recommends that final clarifiers
following activated sludge should not be less than eight feet deep.
The clarifier side water depth was less than recommended by Ten State
Standards. The shallow depth causes difficulty in holding the sludge
blanket in the clarifier.
The clarifier weir was found to be out of level. The elevation
of the weir varied 0.08 feet (.96 inch) around the clarifier and the
flow around the weir was observed to vary significantly.
The results of the clarifier dye tracer study are presented in
Figure 9. Location of the centroid of the dye concentration curve is a
measure of the clarifier detention time (DT) which was 83 minutes (1.4
hours). A calculated detention time using plant flow and return sludge
flow during the period of the dye tracer study was 1.25 hours. The longer
DT during the dye study compared to the calculated DT was due to a 30-
minute dramatic drop in flow, from about 1.6 to .59 mgd. This drop in
flow rate is not shown in Figure 7, due to the short duration. The cal-
culated detention time using average study flow and return sludge flow
was 1.5 hours. In all cases, detention times were less than the recom-
mended 2 hours.
Solids washout was documented as a recurring problem attributed to
rainfall and heavy infiltration. On July 20, 1976, there was a brief
solids washout between 10 and 12 a.m. Influent wastewater flow at this
time was recorded at 2.7 mgd. Influent plus return sludge flow was ap-
proximately 3.2 mgd. The clarifier DT during this period was only 0.97
hours.
Sludge blanket depth, measured 2 hours following the washout, was
3.7 feet. Only one return sludge pump was being operated at full capa-
city. Sludge blanket depths of 4-5 feet were measured on the remaining
days of the study. These depths were observed when both return sludge
pumps were pumping, one full capacity, the other 1/3 capacity.
It can be summarized from the above data and observations that the
clarifier is hydraulically overloaded during many hours of the day, and
especially when both return sludge pumps are operating.
33
-------
FIGURE 9
CLARIFIER DYE STUDY
BAYOU CASSOTTE WTP
TIME (MIN.)
-------
The clarifier was designed with a detention time of 2 hours. Calcu-
lations show that this design (2 hours DT) corresponds to a flow of 1 mgd,
allowing 50 percent return flow rather than 1.6 maximum influent flow. To
avoid solids washout and efficiently operate this clarifier, it will be
necessary to divert a portion of the plant flow to the Foster Street WTP.
Return sludge pumping should be limited to one pump at 1/2 to 3/4 capacity
running continuously with the other pump as standby and during times of
sludge wasting.
Chlorine Contact Chamber
The 0.41 mg chlorine contact chamber (CCC) has a theoretical deten-
tion time at design flow of 40 minutes. At the average influent flow
during the study, the calculated detention time was 44 minutes.
Chlorine usage, according to WTP personnel, was manually adjusted at
45 lbs. of CI2 per day to the effluent. Using the cylinder weight scale,
the following daily chlorine rates were determined:
July 20, 1976 July 21, 1976 July 22, 1976
65 lbs. 88 lbs. 67 lbs.
The effluent chlorine residual ranged from 1.4 to 8.4 mg/1. This
heavy usage of chlorine was unnecessary to disinfect the wastewater ef-
fluent. It is generally recommended that a 0.5 mg/1 residual with a
CCC detention time of 30 minutes is adequate for WTP effluent disinfection.
Aerobic Digesters
The Bayou Casotte WTP digesters have serious structural defects.
There are large visible cracks in the walls which, according to opera-
ting personnel, extend to the bottom of the digesters. Due to a plugged
withdrawal line, digested sludge could not be wasted from the east di-
gester (BAD1) directly to the drying beds. Supernatant cannot be pumped
from the west digester (BAD2) to the OTP headworks because of a plugged
line. Supernatant from the west digester had to be pumped via a portable
pump to the east digester supernant line and then to the WTP headworks.
Sludge withdrawal from the east digester had been accomplished by
pumping (portable pump) sludge to the west digester and then to the
drying beds. The pump suction line only extends about 3 feet below the
surface, so the heavily concentrated sludge on the bottom was not removed.
The inadequacy of this pumping procedure can be readily demonstrated by
the solids levels and the DO concentrations of the two basins. The average
TSS concentration in the east and west digesters were 7,900 and 2,725 mg/1,
respectively, and DO concentrations ranged from 0.2-0.5 and 3.9-4.3 mg/1,
respectively. On July 19 and July 22, all digested sludge was pumped from
the west digester. The solids concentration of the 27,000 gals, of sludge
pumped to the drying beds on July 19 was such that the cake remaining from
10 inches of sludge did not require removal before refilling. On July 22,
18,000 gals, of digested sludge was pumped to the drying bed. This di-
gested sludge had a TSS concentration of 13,250 mg/1 (2,000 lbs.).
35
-------
During the study, the pH on the west digester ranged from 5.2 on
July 20 to 3.8 on July 22. The low pH cannot be adequately dealt with
at this time for lack of information; however, it was probably due to
septic sludge in the bottom of the digester. Balancing the solids levels,
maintaining adequate air, and pumping from both digesters to the sludge
drying beds should eliminate these low pH values.
In conclusion, the solids levels in the two digesters need to be
balanced to enhance digester operation and to increase DO levels. To
accomplish this, the waste line from the east digester and the supernate
line from the west digester will need to be opened and cleaned. An alter-
native to cleaning the plugged lines would be the use of a portable sludge
pump to maintain a solids balance in the two digesters. Both digesters
appear to be structurally unsound.
36
-------
EAST SIDE WASTEWATER TREATMENT PLANT
TREATMENT FACILITY
Treatment Processes
A schematic diagram of the 0.4 mgd completely mixed activated sludge
wastewater treatment plant (WTP), serving east Pascagoula, is presented
in Figure 10. Design data are enumerated in Table IX. The WTP began
operation in January 1970 and serves an estimated population of 5,000.
The WTP influent is pumped to the elevated grit chamber and then
flows by gravity through the subsequent treatment units. Aeration in
the aeration tanks and aerobic digester is supplied by a single 15-hp
mechanical aerator in each tank. After clarification and chlorinating,
the plant effluent flows into Lake Avenue via a canal.
Return sludge is pumped to the head of the plant and waste sludge is
pumped to the aerobic digester. Four sludge drying beds are available
to dewater digested sludge.
Personnel
The plant is staffed by a single operator, 8 hours per day.
STUDY RESULTS AND OBSERVATIONS
A complete listing of analytical data and study methods are presented
in Appendices A, B, and D. Formulae used for general calculations are
presented in Appendix C. Significant results and observations are dis-
cussed in the following sections.
Flow
Wastewater Treatment Plant (WTP) flows were measured using a 90°
V-notched weir, located at the effluent of the chlorine contact tank.
A recorder and totalizer were available but inoperative during the study.
Plant flow, determined from an EPA-installed Stevens Stage Recorder, dur-
ing the study was 0.138 mgd. This flow was significantly lower than
design flow and the reported average daily flow of 0.4 mgd. Since the TA
study, the plant flow meter has been repaired and calibrated. The average
daily flow is reported by WTP personnel to still be about 0.4 mgd.
Return sludge flow was reported to be 35 percent (0.14 mgd) of design
flow. This rate was based on the capacity of the two return sludge pumps;
one pump operating at any given time.
Activated sludge was wasted from the digester to drying beds three
times per week. Waste volumes were not available during the study.
37
-------
FIGURE 10
EAST SIDi: WTH
PASCACOULA, MS
38
-------
TABLE IX
DESIGN DATA - EAST SIDE WTP
PASCAGOULA, MS
Flow Measurement
Type
Design Flow
Aeration Basins
Number
Diameter
Depth (water)
Area
Volume
Aeration
Clarifier
Number
Diameter
Depth (water)
Area
Volume
Weir length
Aerobic Digestor
Number
Diameter
Depth (water)
Volume
90° V-notch weir, recorder
totalizer
0.4 mgd
2 (circular)
28 ft.
14 ft.
615 sq. ft.
8,616 cu. ft. (0.064 m.g.)/basin
1-15 hp mechanical aerator
1 (circular)
28 ft.
14 ft.
615 sq. ft.
8,616 cu. ft. (.064 m.g.)
88 ft. (approximate)
1 (circular)
28 ft.
14 ft.
8,616 cu. ft. (0.064 m.g.)
Waste Characteristics and Removal Efficiencies
Table X presents a chemical description of the influent and effluent
wastewater with calculated treatment reductions. Analyses were made on a
single 24 hour, flow proportional, composite sample collected from the
influent and effluent during the period July 22-23, 1976.
39
-------
TABLE X
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
EAST SIDE WTP
Parameter
Influent
Effluent
% Reduction
B0D5 (mg/1)
380
27
93
COD (mg/1)
816
76
91
TS (mg/1)
1,638
748
54
TVS (mg/1)
742
154
79
TSS (mg/1)
805
32
96
TVSS (mg/1)
485
16
97
TKN (mg/1)
26.5
2.55
90
NH3-N (mg/1)
15
0.8
95
N02-N03-N (mg/1)
<0.01
0.10
Total Phosphorus (mg/1)
17.5
2.6
85
Chloride (mg/1)
175
165
6
Oil and Grease (mg/1)*
41.6
<5.0
>88
Pb (yg/1)
1,060
80
92
Cr (yg/1)
3,990
205
95
Cu (yg/1)
600
55
91
Cd (yg/1)
<20
<20
Zn (yg/1)
1,440
165
89
Settleable Solids (ml/1)
38
0.5
99
* Grab sample
The influent wastewater was much stronger than a typical domestic
wastewater. The concentrations of lead, chromium, copper, and zinc were
significantly high. According to plant personnel, there are no industrial
connections, except the hospital, into the East Side WTP.
The decrease in NH3-N concentration demonstrated that extremely good
nitrification was occurring. However, the resulting small increase in
NC^-NO^-N indicates denitrification was also occurring. Low DO concen-
trations in the aeration basins, after the aerators shut off, would
account for this phenomenon.
Aeration Basins
Grab samples were taken from the aeration basins and analyzed for
TSS, VSS, percent solids by centrifuge, and settleability as determined
by settlometer.
Dissolved oxygen concentrations were measured while the aerators
were running at the 1, 5, and 8 foot depths in the aeration basins. DO
concentrations at the 1, 5, and 8 foot depths in basin EA1 were 1.2,
0.6, and 0.2 mg/1, respectively. In basin EA2, DO concentrations were 1.0,
0.5, and 0.3 mg/1, at 1, 5, and 8 foot depths, respectively. The aerators
were reported to be operating on a 45 ON - 15 minute OFF time cycle. During
a 15 minute OFF cycle, a DO depletion rate was determined. A DO concen-
tration of 1.0 mg/1 in EA 1 was completely depleted within 5 minutes, and
AO
-------
a DO concentration of 1.0 mg/l in EA 2 was completely depleted within
1.5 minutes.
The results of the settlometer tests are presented in Figure 11.
The sludge in EA1 settled faster than EA2; however, neither sludge com-
pacted well. Total suspended solids levels in the aeration basins are
presented in Appendix A. There is no significant difference between the
solids levels in EA1 and EA2, 6,020 and 5,320 mg/l, respectively. The
slow settleability of the sludge can be attributed to interference from
the excessive solids concentration. Most activated sludge mixed liquor
solids fall into a range of 70-80% volatile content. The volatile solids
content of the MLSS during the study was 47 percent. This is unusually
low and indicates retention of excessive inert solids.
Clarifier
Results of the settlometer test and observation of the settling
character of the sludge revealed that settling and compaction of the
activated sludge was poor (Figure 11). Supernatant in the settlometer
test was clear with floating scum on the surface. Settling characteris-
tics in the clarifier were similar to the settlometer test except for
flow turbulence and solids carryover.
The hydraulic detention time calculated for the average daily flow
of 0.40 mgd and a 35 percent return sludge flow was 2.8 hours. The
sludge blanket depth was less than three feet below the water surface
and effluent turbidity was 36 NTU's.
Sludge was returned from the clarifier at a 0.14 mgd rate. The
return sludge concentration was 11,967 mg/l. These data indicate that
solids carryover was caused by the high sludge blanket in the clarifier.
This condition may be corrected by wasting activated sludge down to a
level to maintain an F/M ratio of about 0.4. As sludge is wasted, the
volatile content of the MLSS should increase to about 75 percent.
Based on average daily flow (0.4 mgd) and study organic loadings, a
MLSS of 3400 mg/l would be recommended.
Aerobic Digester
During the study, DO concentrations at the 1, 5, and 8 feet depths
were 3.6, 3.4, and 3.3 mg/l, respectively. Solids (TSS, TVSS) concen-
trations were 23,500 and 9,700 mg/l, respectively. Volatile content in
the digester was comparable with the aeration basin at 41 percent.
41
-------
100
ro
90
80
70
60
50
AO
30 -
20
FIGURE 11
SETTLOMETER
EAST SIDE WTP
-o
-9 EAl-l
-O EA2-1
25
30
50
60
TIME (MIN)
-------
APPEfTOIX A
LABORATORY DATA
FOSTER ST., BAYOU CASOTTE AND EAST SIDE WTP
PASCAGOULA. MISSISSIPPI
Influent & Effluent
-O
LO
-------
APPENblX A
LABORATbRY DATA
FOSTER. ST., BAYOU CASbTTE AND EAST SIDE UTP
PASCAGOULA, MISSISSIPPI
Influent., Frfiuent jpc1 Supernatant
:
S'10
nUr
*- /.//
1092 8Z
7 i 2! 1 7t, I /UO
I |
1 f
1
"¦ "
r ;
1013
( 1 7 122 1 7<6 S - i - 1 -
iO 79 ! 1
7 \3'/ip\ 7h \z/o\uS7\l!kl
3 7V
/bo
//$ '
10
7f, 1
21 s"
20.0/
10.0
HO
*30 \j&0
1 —1
2 '
/JTTH0O
2S5 1 — 1
tt>S0
7 \*%,\76
•??£
la/a
2./0
(Pi
£7
(•.$
f>0
^20
7UO
_
C-rab
f t.
ZtP
— j
use
V
7
1%
76
9ffi
(9b
7t?
2(t
2* 7
/F-1
a./i2
$-1?
^¥0
60
/((?
Crf*b
U-0
<
/D99
FLZ
7
77!
jjj$ .1 —
/103 ! ^
l2//
7 ! /«
76
f/6
//>!«
7k I
$P1
(ft*
26-1
(9(>
£0.6/
(7,1
/0W
if./TO,
6
*20
7 600
77 f
— 1
7(0* \ E £
7
76
z^-Co?
7srTHfl
27
76
y^g
J 5a
li
(ft
0-5
0 70
?s
77,0
76 <;
1 :
i
7 1.2 a
76
//J 5
-
/029
RSa/
7 I2/7
76
/D10
—
—
.
(ff
| 1
*1.0 1 !
IPt/
7 j 2/
7b
e>9^-^
__
/(TP
KM
(96
77
(?
__
7,7/7
((¦0
(?e
2.2
+?(?
TF
10
—
_
jCJ.0 j 1
/ Ofti ' i ]
7 >22 .
76
DV30
/fir
4\7
__
i_
_
—
ZAP
A/-0 ' ... '
1102. ' *
7
76
C,-yU>
Cerrtj#.
,
324-
110
/?|2
2?
22
_
'/34
U-5
3A
/.V0
If
2.20
7?0
—
1X0
IfiUl
7
iu"
76
RStP
5710
ZS0P
\
f-f I
J£kL..\
t '
7
21
J2£_
/V7u0
_ _.
_
t?77-
ft?
701
$0
h
i '
(
I
¦ \
1 1
1
4>
-O-
-------
APPENDIX A
LABORATORY DATA
FOSTER ST., BAYOU CASCfTTE AND EAST SIDE WTP
PASCAGOULA, MISSISSIPPI
Aeration Basins
0 i M
SRD
&
iO/7 \FA-/-/ 17 \20 76 fl?(7P ItWIOM 7,5
-------
APPE?WlX A
LABORATORY DATA
FOSTER St., BAYOO CASCjTTE AND EAST SIDE OTP
PASCAGOULA, MISSISSIPPI
Aeration Basins & P.eturn Sludge
C J ^
SR D
STATIC
1012 \sAt-{
.. 7 Utf j 76
mo \2Me\m0
ss
$5
6 J
Iff
97
41
Ifl
*to
J7 1 2h
SutafiiAtfii*
f 1/OJ-I
105* !
7 i ¦?/ ! 76
Of IS \2Ubo\l7M
f-fi
—
$P
£7
?/x
47
ut>
6* '
??
3o
¦SzwU
—"V
^ 1 !
10 f?*
7 \l2
7*
Oie* Ls^y
t76S
S7
97
se
7t7
43
40
1?
2b
Turtot'd Su
1 !
i GAZ-I
7 \20
76
10 30 Vnw
/fW
W
—.
7^
St
kl
Ut
2U
1 ^
(
i
7
*<
76
nt27 \l920
2QVQ
S.n
—
1$
$3
ff
-A;ji f,
f
1
i
/tlS.
tfAT
7
20
76
/OLS \rs7/
(6*1
r,i?
MfS
\
7
m
76
a20
2?0p
4-9
—
6?
4?
7tf
4/
If
7 f
73
It
<>r <
/cj9*-
i !
/Q9s
EA2-J
7
76
U69
f?2C
JfflW
.f,f
/2V?
13
fTT-
7?
l7J
£7
62
f ?
iff
&s
Y*sJ A
r? f
•
/B/S
Fas-T
7
ic>
76
a?
C,3ob
is.fi
—
/
- ! I
/a it i
I
7
21
76
OllW
7767
M7
/£¦(>
J£3/
7
76
/33a
%67
76 0
-! i
10 2(, '
BRS
7
20
76
/nss
rtai
7U
/C57
7
2/
lb
-------
appeJtdix a
LABORATORY DATA
FOSTER ST., BAYOU CASpTTE AND EAST SIDE WTP
PASCAGOULA,' MISSISSIPPI
Aerobic Digestors
"7
01
SFtO
STVTIOX
r-
o
1
1
I5
c
C.J-
>«
TI>£
¦ / ^ \f $ &/S7 W /////////// / / /
/$¦&/# */^g/ >/ / // // // // // //
i / 1^ ** / / / // // // // // // /
» A ^NbAcV &//////// / / // // /
! / 7 v/c y/t?.»/ / // / / / / / // / / / / /
| / "V / J? ,.0 / o/ / / / / / / / / / / / / / / /
J A, ys- / // / / / / / // // // //
/ /' /
!/).7*
FM -/
7
2 [
7tf
o e/o
1*7/27
(iihff
i i
101,1,
ir
7
32
7(?
0750 \mn
7fT/7
if-e
i i
Mil
FAO-1
7
2/
7t>
aim 1 g"?
frf
«>o
—
l
l
i j
/0(lLt
I
7
22
76
0 750
?«7
ffirp
n
-------
APPENDIX A
LABORATORY DATA
FOSTER ST., BAYOU CAS6TTE AND EAST SIDE WTP
PASCAGOULA- MISSISSIPPI
'J ljTj i iers
j
! J
0 ¦ >i 1 c-'-rr ¦
son ,
! 3 jf
i
LJ
JL.
±V.\&
ion, . fa-2
7 \zo
7(> i $9ot) \?,g\ I
,
'
1 l~
i
1
I i
/Ms ! (
7
Zt
76 \as0c 17o I
i
I i i
Ja y
7 i 32
7£ 0735 \$.0
i
1 1 !
10/U
Fa- 2
7
i
zp
7i \ Otero \9.S
!
i i .
JdbL (
i
7
2/
76
s9os i ?.o
tOM
\
7
22
7f
/>73S 1 ?./>
i
1 ;
i.
/CiO ,
73C-2.
7
?e
76
//«5 i /7
/Afa
(
7
3/
76
A9/S- \lc
i
i
i i
i
709/ ! ^
7
72
7
^4
-------
APPENDIX B
GENERAL STUDY METHODS
To accomplish the stated objectives, the study included extensive
sampling, physical measurements and daily observations. Foster Street
and Bayou Casotte plant influent-effluent stations were sampled for
three consecutive 24-hour periods and East Side influent-effluent sta-
tions were sampled for one 24-hour period with ISCO Model 1392-X automa-
tic 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.
Stevens Type F water level recorders were installed on all plant
effluents to record gage height of the individual flow devices through
the 24-hour compositing periods. These gage heights were converted to
daily total flow (mgd).
Dissolved oxygen was determined at stations throughout the plants
and in the aeration basins using a YSI Model 51A dissolved oxygen meter.
Temperature and pH levels were determined at specified stations
throughout the plants. Individual samples of the 24-hour compositing
period were used to determine hourly influent pH variations.
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 pre-
sented in Appendix E.
A series of standard operational control tests were run daily:
(1) Settleability of mixed liquor suspended solids (MLSS) as
determined by the settlometer test;
(2) Percent solids of the mixed liquor and return sludge deter-
mined by centrifuge;
(3) Suspended Solids and Volatile Suspended Solids analysis on
the aeration basin mixed liquor and return sludge;
(4) Turbidity of each final clarifier effluent.
An amperometric titrator (Fischer & Porter Model 17T1010) was used
to determine effluent chlorine concentrations.
The procedure for BOD^ determinations deviated from Standard Methods.
Samples were set up and returned in an incubator to Athens, GA for com-
pletion.
Visual observations of individual unit processes were recorded.
48
-------
APPENDIX C
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 conc.) x (Basin vol.) x 8.34 = lbs. of solids
2. Aeration basin loading (lbs. BOD or COD/day)
Inf. flow to aeration basin = mgd
Inf. BOD or COD = mg/1
(BOD or COD) x flow x 8.34 = lbs. BOD of COD/day
3. Sludge Age (days)
MLSS conc. (avg. of daily values) = mg/1
Aeration Basin Vol. = m.g.
TSS, Primary Eff. or Basin Inf. conc. = mg/1
Plant Flow = mgd
(MLSS) x (Basin Vol.) x (8.34)
(TSS) x (Flow) x 8.34
4. Sludge Vol. Index (SVI)
30 min. settleable solids (avg. of daily values) = %
MLSS conc. = mg/1
(%, 30 min. set, solids) x (10,000)
MLSS
5. Sludge Density Index (SDI)
SVI Value 100
SVI
6. Detention time (hours)
Volume of basins = gal.
Plant flow = gal./day
Return sludge flow = gal./day
Basin volume x 24
(Flow) + (Return sludge flow)
7. F/M Ratio (Food/Microorganism) BOD or COD
Basins Inf. BOD^ 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.
(8'34? = BOD/Xb. MLVSS
(MLVSS) x (Basin Vol.) x 8.34
49
-------
(COD conc.) x (plant flow) x (8.34)
(MLVSS) x (Basin Vol.) x (8.34) " bs* C0D/lb- ^VSS
8. Mean cell residence time (MCRT) = days
MLSS conc. (avg. or daily value) = mg/1
Basin vol. = m.g.
Clarifier vol. = m.g.
Waste activated sludge conc. = mg/1
Waste activated sludge flow rate = mgd
Plant effl. TSS = mg/1
Plant flow = mgd
(MLSS) x (Basin vol. + Clarifier vol.) x 8.34 _
(Waste activated sludge conc.) x (waste flow) x 8.34 +
(Plant effl. TSS x plant flow x 8.34)
Clarifier
1. Detention time = hours
Plant flow to each clarifier = gals./day
Individual clarifier vol. = gals.
(clarifier Vol. (each) x 24 _ hours
Plant flow + Return Sludge Flow
2. Surface loading rate = gal./day/sq. ft.
Surface area/clarifier = sq. ft.
plant flow to clarifier = gal./day
Plant flow to clarifier = gai./day/Sq, ft.
Clarifier surface area
3. Weir Overflow Rate (gal./day/lin. ft.)
Weir Length = ft.
Plant flow to clarifier = gal./day
Plant flow _ gal./day/lin. ft.
Weir length
50
-------
APPENDIX D
DISSOLVED OXYGEN DATA
FOSTER ST. WTP
DATE
TIME STA,
7/20/76 1330 FA1-5
FA2-5
FA3-5
PA4-5
FA5-5
FA1-3
FA2-3
FA 3-3
FA4-3
FA5-3
FA1-1
FA2-1
FA 3-1
FA4-1
FA5-1
DEPTH
(ft.)
1
3
5
8
B
1
5
9
1
5
9
1
5
9
1
5
9
1
5
9
1
5
9
1
5
9
1
5
9
1
5
9
1
5
8
1
5
9
1
5
9
I
5
9
1
5
9
D.O. TEMP.
(rag/1) (°C)
0.2
0.25
0.5
0.3
0.0
0.2
0.2
0.1
0.1
0.0
0.0
0.2
0.0
0.0
0.2
0.1
0.1
0.2
0.1
0.1
0.2
0.1
0.1
0.2
0.1
0.0
0.25
0.2
29
DATE
7/21/76
TIME STA.
FA 1-5
DEPTH D.O. TEMP,
(ft.) (mg/1) (°C)
1
2
1
2
2
2
1
2
0.1
0.0
0.2
0.1
0.0
0.2
0.1
0.0
0.2
0.1
0.0
FA2-5
FA 3-5
FA4-5
FA5-5
FA 1-3
FA2-3
FA3-3
FA4-3
FA5-3
FA1-1
FA2-1
FA3-1
FA4-1
FA5-1
10
1
1
10
10
10
10
10
10
0.3
0.2
0.1
0.1
0.0
0.0
0.2
0.1
0.0
0.6
0.1
0.1
0.8
0.2
0.1
0.2
0.1
<0.1
0.2
<0.1
0.0
0.2
0.1
0.2
<0.1
<0.1
0.3
0.2
0.1
0.3
0.2
-------
APPENDIX D
AERATION AND DIGESTER BASIN DISSOLVED OXYGEN
BAYOU CASSOTE, MS
Date 7/20/76
7/21/76
BAI - 1
1400
29
0.0
1130
28
0. 1
0.1
BA1 - 2
0.2
0.1
BAI - 3
0.2
0.1
<
CO
0.2
0.0
28.5
0.2
0.1
BAI - 5
0.2
0.1
0.1
O.J
BAI - 6
0.2
0.1
BAI - 7
0.2
0.1
BA2 - 1
0.1
0.0
29
0 2
0.1
BA2 - 2
0. 1
0.0
BA2 - 3
0.2
0.0
BA2 -
0.0
0,0
0.1
0.1
BA2 - 5
0.0
0.0
BA2 - h
0.2
0.1
*
BA2 - 7
*
0.2
0.1
ba2 - a
0. 1
0.0
0.2
0.1 |
1
badi - l ]
27.5
0 4
0.2 | 0.2
[ BADI - 2 i
1 i
0.5
0.4
BADI - 3
0.5
0.4
1200
27
0 4
0.2
BADI - 4
0.5
0.3
0 5
0 u
BADI - ^
27.0
0.4
0.3
0.5
0.2
u 0
BAD2 - 1
2(. 5
L . 2
4. 2
•'.,0
i
1
1 26. 5
4 'i
h 3
BADi - 2
1
4.0 i
4 V
1
1
! I l i
ISAD2 - 3
|4.2
1
i ! ! 4 1
52
-------
APPENDIX E
OXYGEN UPTAKE PROCEDURE U
A. Apparatus
1. Electronic DO analyzer and bottle probe
2. Magnetic stirrer
3. Standard BOD bottles (3 or more)
4. Three wide mouth sampling containers (approx. 1 liter each)
5. DO titration assembly for instrument calibration
6. Graduated cylinder (250 ml")
Adapter for connecting two BOD bottles
B. Procedure
1. Collect samples of return sludge, aerator influent and final
clarifier overflow. Aerate the return sludge sample promptly.
2. Mix the return sludge and measure that quantity for addition
to a 300 ml BOD bottle that corresponds to the return sludge
proportion of the plant aerator, i.e. for a 40% return sludge
percentage in the plant the amount added to the test BOD
bottle is:
300 X .4 = 120 = 86 ml
1.0 + . .4 1.4
3. Carefully add final clarifier overflow to fill the BOD bottle
and to dilute the return sludge to the plant aerator mixed
liquor solids concentration.
4. Connect the filled bottle and an empty BOD bottle with the
BOD bottle adapter. Invert the combination and shake vigorously
while transferring the contents. Re-invert and shake again
while returning the sample to the original test bottle. The
sample should now be well mixed and have a high D.O.
5. Insert a magnetic stirrer bar and the previously calibrated
DO probe. Place on a magnetic stirrer and adjust agitation
to maintain a good solids suspension.
6. Read sample temperature and DO at test time t=0. Read and
record the DO again at 1 minute intervals until at least 3
consistent readings for the change in DO per minute are
obtained (ADO/min). Check the final sample temperature.
This approximates sludge activity in terms of oxygen use
after stabilization of the sludge during aeration (unfed
sludge activity).
53
-------
Appendix E (cont'd.)
7. Repeat steps 2 through 6 on a replicate sample of return
sludge that has been diluted with aerator influent (fed
mixture) rather than final effluent. This A 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".
1/ Taken from "Dissolved Oxygen Testing Procedure," F. J. Ludzack
and script for slide tape XT-43 (Dissolved Oxygen Analysis - Activated
Sludge Control Testing) prepared by F. J. Ludzack, NERC, Cincinnati.
54
-------
APPENDIX F
SUPERNATANT SELECTOR (-1)
SUPERNATANT SELECTOR—An "operator-made" device was installed in an existing digester
while it was down for repairs that helped draw the best possible supernatant even though liquid
level varied.
A hoist was mounted on the tank wall and %" plastic coated boat control cable was attached to a
section of movable supernatant pipe. A swivel joint composed of an ell and street ell allowed the
draw-off point to be changed by operation of the hoist.
Hoist
55
-------
1,
2,
3
4
5
6
7
8
9
10
11
12
REFERENCES
McKinney, Ross E. and Gram, Andrew. "Protozoa and Activated Sludge",
Sewage and Industrial Waste 28 (1956):1219-1231.
"Operation of Wastewater Treatment Plants", A Field Study Training
Program, US-EPA, Technical Training Grant No-5TTl-WP-16-03, 1970.
"Process Design Manual for Suspended Solids Removal", US-EPA Tech-
nology Transfer, January 1975.
"Sewage Treatment Plant Design", American Society of Civil Engineers,
Manual of Engineering Practice No. 36, 1959.
"Wastewater Engineering", Metcalf and Eddy, Inc. 197 2.
West, Alfred W., Operational Control Procedures for the Activated
Sludge Process. Part I., Observations, EPA-330/9-74-001-a, April 1973.
"Recommended Standards for Sewage Works", Great Lakes - Upper
Mississippi River Board of State Sanitary Engineers, Revised Edition,
1971.
"Standard Methods for the Examination of Water and Wastewater", 13th
Edition, 1971.
"Process Design Manual for Upgrading Existing Wastewater Treatment
Plants", US-EPA Technology Transfer, October 1974.
West, Alfred W., Operational Control Procedures for the Activated
Sludge Process. Part IIIA, Calculation Procedures, EPA-330/9-74-001-C,
December 1973.
"Operations Manual - Anaerobic Sludge Digestion", US-EPA, EPA 430/9-
76-001, February 1976.
Operation and Maintenance Manual for Wastewater Treatment Facilities
Foster Street Plant, Pascagoula, Mississippi, Barth and Associates,
Inc., 1975.
56
------- |