EPA, 9Q4/9-77-025
TECHNICAL ASSISTANCE PROJECT
AT THE
FORT LAUDERDALE WASTEWATER TREATMENT PLANTS
FORT LAUDERDALE, FLORIDA
ENVIRONMENTAL PROTECTION AGENCY
SURVEILLANCE AND ANALSIS DIVISION
ATHENS, GEORGIA
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EPA 9QA/9rv77-025
TECHNICAL ASSISTANCE PROJECT
AT THE
FORT LAUDERDALE WASTEWATER TREATMENT PLANTS
FORT LAUDERDALE, FLORIDA
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TABLE OF CONTENTS
Page No.
Introduction ^
3
Summary
Recommendations
Sixth Street "A" Wastewater Treatment Plant ^
Treatment Process ^
Study Results and Observations ^
Flow 7
Waste Characteristics and Removal Efficiencies I2
Primary Sedimentation 13
Aeration Basins 13
Secondary Clarifiers 15
Coral Ridge "B" Wastewater Treatment Plant .-^9
Treatment Process 19
Study Results and Observations 19
Flow 19
Waste Characteristics and Removal Efficiencies 21
Primary Clarifiers 22
Aeration Basins 22
Secondary Clarifiers 23
Executive Airport "E" Wastewater Treatment Plant 2^
Treatment Process ^6
Study Results and Observations
Flow 26
Waste Characteristics and Removal Efficiencies 26
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Page No.
Contact Tank 31
Clarifier 33
Laboratory 33
References 36
Appendices
A. Laboratory Data 38
B. Dissolved Oxygen Concentrations 43
C. Oxygen Uptake Procedures 47
D. General Study Methods 50
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LIST OF FIGURES
Page No.
1. Sixth Street "A" WTP 8
2. Effluent Flows - Sixth Street "A" WTP 11
3. Average Sfettlometer Results - Sixth Street "A" WTP 16
4. Ideal Settlometer Results. 17
5. Coral Ridge "B" WTP 20
6. Average Settlometer Results - Coral Ridge "B" WTP 24
7. Executive Airport "E" WTP 27
8. Effluent Flows - Executive Airport "E" WTP 30
9. Average Settlometer Results - Executive Airport "E" WTP 34
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LIST OF TABLES
Page No.
I. Design Data- Sixth Street "A" WTP 9
II. Waste Characteristics and Removal Efficiencies - Sixth Street
"A" WTP 12
III. Activated Sludge Operational Parameters - Sixth Street "A" WTP .... 13
IV. Secondary Clarifier Operational Parameters - Sixth Street "A" WTP. . . 18
V. Waste Characteristics and Removal Efficiencies - Coral Ridge "B"
WTP 21
VI. Activated Sludge Operational Parameters - Coral Ridge "B" WTP 22
VII. Secondary Clarifier Operational Parameters - Coral Ridge "B" WTP ... 23
VIII. Design Data - Executive Airport "E" WTP 28
IX. Waste Characteristics atld Removal Efficiencies - Executive Airport
"E" WTP 31
X. Contact and Stabilization Basin Operational Parameter - Executive
Airport "E" WTP 32
XI. Secondary Clarifiet Operational Parameters - Executive Airport "E"
WTP 33
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INTRODUCTION
A technical assistance study of operation and maintenance problems of
three Fort Lauderdale, Florida municipal wastewater treatment plants (Sixth
Street "A", Coral Ridge "B" and Executive Airport "E") was conducted April
2 through 7, 1977 by the United States Environmental Protection Agency (US-EPA),
Region IV, Surveillance and Analysis Division. These studies are designed
to assist wastewater treatment plant operators in maximizing treatment effi-
ciencies. Municipal wastewater treatment plants are selected for technical
assistance studies after consultation with state pollution control authorities.
Visits are made to each prospective plant prior to the study to determine if
assistance is desired and if study efforts would be productive.
The Coral Ridge WTP was selected at the request of EPA Enforcement Division,
and after a reconnaissance visit the "A" and "E" WTPs were selected. A request
was made by the Florida Department of Environmental Regulation and City of
Fort Lauderdale personnel to present an activated sludge operational control
course. The specific study objectives were to:
o Present, in a combined classroom - WTP environment, a course for
trouble shooting activated sludge WTP's to the area operators. The
course emphasized new operational control techniques;
o Optimize treatment of the three Fort Lauderdale WTP's through control
testing and operation and maintenance modifications;
o Determine influent and effluent wastewater characteristics.
Since one of the primary objectives in this study was to provide classroom
instructions for operators in new operational control testing and trouble
shooting, less time than normal was spent in evaluating the operation of
the WTP's. This has resulted in a less detailed report containing fewer
specific recommendations. It is hoped that the individual operators will
1
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be better able to recognize problems at their own plant as a result of
the course.
The cooperation of the Florida Department of Environmental Regulation
is gratefully acknowledged. The technical assistance team is especially
appreciative of the cooperation and assistance received from personnel of
the Fort Lauderdale Utilities Department.
2
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SUMMARY
SIXTH STREET "A" WASTEWATER TREATMENT PLANT
The sixth street "A" Wastewater Treatment Plant (WTP) was designed as
a 8.25 mgd conventional activated sludge system. The average wastewater flow
diring the study was 7.19 mgd and ranged from 6.96 to 7.43 mgd. The average
BOD5 and TSS reductions during the study were 87 and 44 percent, respectively.
Major observations made during the study were:
1. Dissolved oxygen concentrations throughout the activated sludge process
ranged from 0.05 to 1.3 mg/1.
2. Settleability of the mixed liquor was poor.
3. There were dense growths of filamentous organisms in the return sludge
and mixed liquor.
4. The sludge age and mean cell residence times were excessive.
5. There was heavy greasy appearing tan foam covering the aeration
basin.
6. A dense scum mat was observed on the surface of the final clarifiers.
7. The influent wastewater had an unusually low suspended solids
concentration.
8. The plant effluent was not meeting NPDES requirements.
CORAL RIDGE "B" WASTEWATER TREATMENT PLANT
The Coral Ridge "B" Wastewater Treatment Plant was designed as a 7 mgd
conventional activated sludge system. Average wastewater flow during the study
was 6.96 mgd with a maximum flow of 12 mgd. Flow through the Cantex Unit which
was designed for 1 mgd; averaged 0.8 mgd. The average BOD^ and TSS reductions
during the study were 86 and 83 percent, respectively.
3
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Major observations made during the study were:
1. The plant is hydraulically overloaded during the tourist season.
Flows peaked at 12 mgd or greater for extended period of time.
2. Dissolved oxygen concentrations in the Cantex unit were too low.
3. The plant effluent did not meet NPDES permit requirements for TSS.
EXECUTIVE AIRPORT "E" WASTEWATER TREATMENT PLANT
The Executive Airport "E" Wastewater Treatment Plant was designed as
a 0.5 mgd contact stabilization activated sludge system. The average waste-
water flow during the study was 0.24 mgd with a range of 0.058 to 0.49 mgd.
The average B0D5 and TSS reductions during the study were 81 and 68 percent.
Major observations made during the study were:
1. The timing cycle of aerators resulted in septic conditions in the
aeration basin much of the time.
2. Solids concentrations in the contact tank were excessive.
3. The sludge age and mean cell residence time were too high.
4. Sludge wasting was irregular and limited.
5. The plant effluent did not meet NPDES permit requirements.
4
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RECOMMENDATIONS
Based on observations and data collected during the study, it is
recommended that the following measures be taken to improve wastewater
treatment and plant operations. Trend Charts and operational testing will
assist in determining optimum control. It is recognized that hydraulics
and other restraints may hamper complete implementation of these recommen-
dations .
SIXTH STREET "A" WASTEWATER TREATMENT PLANT
1. The dissolved oxygen concentration throughout the aeration basin should
be monitored regularly with an electronic DO meter and maintained in the
1.0 and 2.0 mg/1 range.
2. The mean cell residence time and sludge age should be decreased gradually
to increase sludge settleability. This operational change should help
to eliminate the filamentous bacteria.
3. An in-plant control testing schedule should be initiated, and trend
charts established and maintained.
4. The use of oxidants in treating return sludge should be used as an interim
solution to the poor settlability problem rather than as a permanent solution.
Better regulation of the MLSS inventory and monitoring of the D.O. levels
should provide the long term solution.
CORAL RIDGE "B" WASTEWATER TREATMENT PLANT
1. An in-plant control testing program should be initiated and trend charts
established and maintained.
2. The dissolved oxygen concentrations in the Cantex Unit should be monitored
regularly and maintained in the 1.0 to 2.0 mg/1 range.
3. Consideration should be given to utilization of the abandoned trickling
filter to relieve peak loads.
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EXECUTIVE AIRPORT "E" WASTEWATER TREATMENT PLANT
1. A regular sludge wasting schedule should be established. Increased sludge
wasting would eliminate the major problem of too many solids.
2. An in-plant control testing schedule should be initiated and trend charts
established and maintained.
3. The dissolved oxygen concentration in the contact and stabilization tank
should be monitored and maintained at 1.0 - 2.0 mg/1.
4. The minimum aerator shut-down time should be determined by measuring
the DO depletion rate, and the timing clocks should be adjusted to
maintain the DO range stated above.
5. The chlorine concentration in the final effluent should be decreased
to maintain a 0.5 - 1.0 mg/1 concentration following a 30 minutes detention
time.
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SIXTH STREET "A" WASTEWATER TREATMENT PLANT
Treatment Process
A schematic diagram of the 8.25 mgd conventional activated sludge waste-
water treatment plant (WTP) is shown in Figure 1 and design data are enumerated
in Table 1.
Raw wastewater was passed through a comminutor to primary clarifiers. The
primary clarifiers and sludge thickeners are enclosed in a building with air
recirculation and scrubbers for odor control. Effluent from the primary
sedimentation tanks flow by gravity to parallel aeration basins. Slow speed
mechanical aerators are utilized in the twin aeration basins. The plant has
two final clarifiers and a chlorine contact basin. Chlorine is added to the
return sludge for odot control and to control filamentous growths.
Sludge from the system is treated via the Zimpro process.
Study Results and Observations
A complete listing of all analytical data and general study methods are
presented in the Appendices. Significant results and observations made during
the study are discussed in the following sections.
Flow
Wastewater flow was measured with a Parshall flume installed on the effluent
which was equipped with a recorder and totalizer. The flume was checked and
found to be accurate.
Average effluent flow during the study period was 7.19 mgd and ranged
from 6.96 to 7.43 mgd. Hourly WTP flows during the study period are illus-
trated in Figure 2.
Return sludge flow (RSF) was measured with magnetic flow meters equipped
with recorders and totalizers. Return sludge flow during the study period
was approximately 2.84 mgd or 39 percent of the average WTP flow.
7
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Ki't 'ir--. Slviu^v
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TABLE I
DESIGN DATA
SIXTH STREET WASTEWATER TREATMENT PLANT
FORT LAUDERDALE, FLORIDA
I. General Design
Designed Flow
Design Loadings
BOD
Suspended Solids
II. Flow Measurement
Effluent
Return Sludge
Waste Sludge
III. Preliminary Treatment
8.25 mgd
14,000 lbs/day
17,000 lbs/day
Parshall Flume
Magnetic Flow Meter
Magnetic Flow Meter
Bar Screen
Comminutor
Chlorination
By-passed
IV. Primary Treatment
Primary Clarifiers
Number
Area (each)
Volume
Surface Loading
Weir Overflow Rate
V. Contact Basins
5,600 sq. ft.
71,000
540,000 gals
730 gpd/sq. ft.
14,000 gpd/ft.
Number
Design Loading (BOD)
Average MLSS
Return Sludge Rate
Volume (each)
BOD Loading per 1,000 cu. ft.
Detention Time
13,000 lbs/day
2,500 mg/1
100 %
118,000 cu. ft.
890,000 gals
55 lbs.
5.15 hrs.
9
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TABLE 1 (CONTINUED)
VI. Secondary Clarifier
Number
Area (each)
Surface Loading
Volume
Detention Time
Weir Overflow Rate
VII. Chlorine Contact
Volume
Detention Time
VIII. Sludge Handling
2
5,700 sq. ft.
720 gpd/sq. ft.
74,000 cu. ft.
560,000 gals
3.29 hrs.
15,000 gpd/ft.
11,000 cu. ft.
81,000 gals.
0.24 hrs.
Sludge Thickener
Number
Area (each)
Volume
Solids Loading
Wet Air System - Zimpro
2
1,600 sq. ft.
22,000 cu. ft.
162,000 gals.
6.3 lbs/day/sq. ft.
10
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11 .
8 f
7 -
6 —
April 4-5, 1977
FIGURE 2
EFFLUEiJT FLOWS
SIXTH STREET "A" WTP
FT. LAUDERDALE, FLA.
TIME (hrs) April 3-6,1977
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Waste sludge flow (WSF) was measured with a magnetic flow meter. The
average WSF during the study period was 0.103 mgd.
Waste Characteristics and Removal Efficiencies
Table II presents a chemical description of the influent and effluent
wastewater with calculated treatment reductions. Removal efficiencies
were calculated using average data from two consecutive 24-hour, flow pro-
portional composite samples. The weekly average NPDES permit limits are
24 mg/1 and 45 mg/1, respectively, for BOD5 and TSS.
TABLE II
WASTE CHARACTERISTIC AND REMOVAL EFFICIENCIES
SIXTH STREET "A" WTP
PARAMETER
INFLUENT EFFLUENT % REDUCTION
1qq 26 87
BOD (mg/1) f l 103 71
C0D (®8/« 941 896 5
TS (mg/1) lit 192 21
TVS (mg/1) 2f 53 44
TSS (mg/1) " 40 52
TVSS (mg/1) I3 27.6 6
TKN (mg/1) 29.4
NH3-N (mg/1) l1-' 0.03
N02-N03-N (mg/1) 5>6 6.7
Total Phosphorus (mg/1)
Oil and grease* (mg/1) ^ 2 2
Cl2 Residual* (mg/1) <0~059 <0^050
? °-159 <0.123
Cr V^g/1) 0 nog 0.063 36
cu (vg/1) 4;^ <0.010
Cd (yg/1) 0 17o 0.115 32
Zn (ug/1) * 18
Turbidity* (NTU)
*Average results of grab samples taken on two different days.
The average composite BOD5 (199 mg/1) and COD (374 mg/1) concentrations
were typical of domestic wastewater, however, the suspended solids (95 mg/1)
were lower than normal.
As shown in Table II. nitrification was not achieved in the treatment
system. To the contrary ammonia
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location. These side streams were not sampled during the study due to the
limited time spent oh e&ch plant.
Primary Sedimentatloh
Primary sedimtetitation at the WTP consisted of two 540,00.0 gallon circular
center-fed, rim take-off tanks. Concentrations of B0D5 and COD entering the
prioary settling tank average 199 and 374 mg/1, respectively. The same para-
meters leaving the primary settling tank were increased to 213 and 384 mg/1.
The increase in B(% arid COD can be attributed to side streams which discharge
just prior to the pritttdry system. Total suspended and volatile suspended
solids were reducdd in the primary portion of the plant by 56 and 53 percent,
respectively.
Aeration Basins
Grab samples W0*e taken from the aeration basins (Figure 1, stations AA-1,
AA-2) and analyzed £ot total suspended solids (TSS), volatile suspended solids
(VSS), percent solidfl by centrifuge, and settleability as determined by the
settlometer. Presented in Table III are various calculated activated sludge
operational parametete using study data and corresponding recommended values
for the conventional activated sludge process.
TABLE III
ACTIVATED SLUDGE OPERATIONAL PA^AMfiTfeRS
SIXTH STREET "A" WTP
MEASURED
2,776
2,483
4.19
14
8.28
0.34
0.62
RECOMMENDED(1).(4).(6),(8)
MLSS (mg/1)
ML VSS (mg/1)
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/1,000 cu.ft. Aeration Basin
Return Sludge (% of Average Plant Flow)
Waste Sludge (% of Average Plant Flow)
54
39
1,000 - 4,500
750 - 3,600
4-8
5-15
3.5 - 7.0
0.2 - 0.5
0.5 - 1.0
20 - 40
15 - 75
1.37
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As shown in Table III the calculated sludge age was greater than recommended
limits and mean cell residence time was just within the upper limit. The
organic loading of 54 lbs BOD/day/1,000 cu.ft. was greater than the recommended
limit for the conventional activated sludge process but within the design limit
of 55 lbs/day/1,000 cu.ft. (Table I).
A greasy tan colored foam was observed floating on the surface of the
aeration basins. On examination of the -mixed liquor and the foam by microscope,
filamentous organisms were found to be the predominate form. The filaments
were very small in diameter and short with the appearance of much branching.
Indications from observations and cell characteristic tentatively identified
the organisms as Actinomycetes. Predominate protozoan organisms in the return
sludge were rotifers and crawling ciliates. The rotifers are normally present
in high numbers when the sludge has reached a high degree of stability and is
approaching the upper limits on sludge age as calculated in Table III. Crawling
ciliates appear and increase in numbers as the sludge ages beyond desirable
limits.
The oxygen uptake rate is helpful in evaluating sludge activity. This
activity is measured by mixing return activated sludge with influent (fed)
and nonchlorinated effluent (unfed) wastewater and determining the uptake
rate, then calculating the load ratio (LR).
Load Ratio - no frne/1/min) fed sludge
DO (mg/l/min) unfed sludge
The detailed procedure for this test is contained in Appendix C. The
load ratio reflects the conditions at the beginning and end of aeration.
Generally, a large increase signifies an abundant, acceptable feed under
favorable conditions. A small LR (<2) may mean dilute feed, sick sludge,
poorly acceptable feed, or other unfavorable conditions. A LR less than
1.0 indicates that a wastewater constituent shocked or poisoned the "bugs."
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The oxygen uptake rate for the fed sludge averaged 2.7 mg/l/min. over a
two minute period, reading the rate of uptake every 30 seconds. The calculated
load ratio for the sludge before and after feeding was 3.60. Load ratios in the
2 to 4 range are commonly found in activated sludge plants. The 3.6 factor observed
at this plant indicates a rather active sludge with an acceptable feed.
The results of the settlometer tests are presented in Appendix A and
illustrated in Figure 3. Sludge settleability was significantly different
for three consecutive days in each of the two basins. On April 4, 1977
the 6Q-minute settling volume was only 38 and 45 percent for aeration basin
1 and 2, respectively. Settling solids in basin 2 separated about mid-column
after 10 minutes and half the solids mass floated while the other half settled
to the bottom. On April 5, 1977 the same phenomena occurred after 15 minutes
of settling in both settlometers. On April 6, 1977 the settling rate for the
two basins reversed and the settled sludge volume was 43 and 38 percent for
basin 1 and 2, respectively. These phenomena cannot be fully explained, but
the characteristic settleability of the sludge was far from desirable. A more
ideal settling curve for a stable sludge which yields a good quality effluent
is depicted in Figure 4.
Dissolved oxygen (DO) concentrations measured in the aeration basins are
presented in Appendix B. Dissolved oxygen concentrations throughout the basins
ranged from 0.05 to 1.3 mg/1. Measurable DO ranges at the one, five, and ten
foot depths were, 0.3 to 1.3 mg/1, 0.1 to 1.0 mg/1 and 0.05 to 0.85 mg/1,
respectively. These DO concentrations were measured with all aerators in
operation. From these data it is readily apparent that DO concentrations
were well below recommended levels of 2.0 mg/1.
Secondary Clarifiers
Measured and recommended operating parameters for secondary clarifiers
following the conventional activated sludge process are presented in Table
IV. All calculated and -measured parameters were within recommended limits.
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FIGURE 3
AVERAGE SETTLOMETER RESULTS FOR EACH AERATION BASIN
SIXTH STREET "A" WTP
TIME (min.)
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FIGURE 4
IDEAL SETTLOHETER RESULTS FOR AERATION BASINS
TIME (min.)
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The major observation on the final clarifier was that the surface was
covered with a thick greasy looking mat of scum. As the skimmer passed over
the scum box some of the scum spilled over into the effluent trough. This
was most apparent in clarifier number two. Depth of the sludge blanket
was maintained at greater than six feet below the water surface during the
Solids and sludge settleability, as discussed under the aeration basin
section show that compaction was very poor. One settlometer showed that under
quiescent conditions the sludge solids column was prone to split and rise to
the surface. This was probably the reason for the heavy scum layer on the
clarifier surfaces. The filamentous organisms may be reduced to manageable
levels by insuring that adequate DO is provided in the aeration basins. A
reduction in the MLSS concentration may be necessary.
study.
TABLE IV
SECONDARY CLARIFIER OPERATIONAL PARAMETERS
SIXTH STREET "A" WTP
MEASURED
RECOMMENDED (1).(2).(4),(6)
300 - 1,200
Hydraulic Loading (gpd/sq.ft.)
Hydraulic Detention Time (hrs.)
Solids Loading (lbs/day/sq.ft.)
Weir Overflow Rate (gpd/ft.)
631
2.6
2-3
12 - 30
Depth "SWD" (ft.)
20.7
13,460
12
5,000 - 20,000
>8 - 15
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CORAL RIDGE "B" WASTEWATER TREATMENT PLANT
Treatment Process
A schematic diagram of the 7 mgd conventional activated sludge wastewater
treatment plant is presented in Figure 5. The primary system consists of two
vacuum flotation units pperated in parallel. Twin aeration basins are aerated
with slow speed mechanical aerators followed by two centerfeed rim take-off
circular clarifiers.
Sludge is digested in anaerobic digesters and dewatered by vacuum filtration.
Hydrogen peroxide was used for increased oxygen and odor control in the influent.
Plant "B" has a 1 mgd contact stabilization unit (Cantex) which increases the
total plant capacity to 8 mgd. The old original trickling filter unit is located
on site but is not in service.
Study Results and Observations
A complete listing of all analytical data and general study methods are
presented in the Appendices. Significant results and observations made during
the study are discussed in the following sections.
Flow
Plant flow was measured with a Parshall flume located on the plant effluent.
The flume was checked and found to be accurate. This unit measured the combined
plant flow which included the Cantex unit. During the study period flow through
the main plant average 7 mgd with a maximum of 12 mgd. Flow through the Cantex
unit averaged 0.8 mgd.
Excessive flows are a major problem at plant "B" during the tourist season.
Plant flows typically peak at 12 mgd or greater around 8:00 a.m. and continue
at that level unit 2:00 p.m. This produces a heavy, extended hydraulic loading
on all units.
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FlC-l'RE S
CORAL RIDGE 'V VTP
FT. LAUDERDALE, FLA.
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Waste Characteristics and Removal Efficiencies
Table V presents a chemical description of the WTP influent and effluent
wastewaters with calculated treatment reductions. Analyses were made on two
24-hour, flow proportional, composite samples collected on April 4-5 and April
5-6. Percent reductions were calculated from averaged values. Plant data was
used for reported BOD5 and solids values in Table V since EPA Station BI
received some waste secondary sludge. Thus EPA data for Station BI {Appendix
A) is not representative of the raw plant influent, however, it is a measure
of the wastewater flowing into the vacuum flotation primary units.
TABLE V
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
CORAL RIDGE "B" WTP
INFLUENT
EFFLUENT
% REDUl
282*
39*
86
572
91
84
1,616*
1,292*
20
432*
73*
83
28.3
5.8
80
23
3.5
85
0.03
2.95
10.25
4.9
52
—
4.25
<0.07
<0.05
——
<0.08
<0.08
0.16
0.03
81
<0.01
<0.01
0.24
0.05
79
PARAMETER
BOD5 (mg/1)
COD (mg/1)
Total Solids (mg/1)
TSS (mg/1)
TKN (mg/1)
NH3-N (mg/1)
N02-N03-N (mg/1)
Total Phosphorus (mg/1)
Cl2 Residual (mg/1)**
Pb (ug/1)
Ci? (ug/1)
Cu (Mg/1)
Cd (yg/1)
Zn (ug/1)
* Plant data.
**Averaged results of gsab sample.
The influent BOD5 (282 mg/1) and TSS (432 mg/1) concentrations for the two
day period were somewhat above average since according to plant data the typical
average BOD5 and TSS concentrations for the month of April are 196 mg/1 and 352 mg/1,
respectively. This rather strong waste should be expected however, since this
plant serves a highly developed affluent area consisting of single family homes,
condominiums, and tourist facilities such as motels, restaurants, etc. Consequently
the waste reflects the popularity of garbage disposals and grease from food
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preparation establishments. The weekly average NPDES permit limits are
45-mg/l for B0D5 and TSS.
Removal efficiencies of 86 and 85 percent for BQD5 and TSS, respectively,
were below typical plant data averages for the month of April which were 87.3
and 90 percent, respectively.
Primary Clarifiers
The suspended solids removal in the vacuum air flotation units during the two
day study averaged 12 percent. The average removal rate for the month of April
was 25 percent. Some waste activated sludge was recirculated back to these
units in order to improve their efficiency. It has been found that the biological
solids trap air bubbles facilitating better removal rate.
Aeration Basins
Grab samples were collected daily from each of the two aeration basins
(not from the Cantex plant). These 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 VI
are various activated sludge operational parameters based on data collected
during the study and the corresponding recommended values for the conventional
activated sludge process.
TABLE VI
ACTIVATED SLUDGE OPERATIONAL PARAMETERS
CORAL RIDGE "B" WTP
MEASURED
HUM 0.8/1) 2.0X0-.eS171
MLVSS (mg/1) 1»bJ^
Detention Time (hrs) 3.7
Mean Cell Residence Time (days) 8.^
Lbs. BOD/day/lb MLVSS (F/M) .53
Lbs. COD/day/lb MLVSS
Lbs. BOD/day/1,000 cu.ft. of Aeration Basin 91
Return Sludge Rate (% of Average Plant Flow) 53
*Plant Data
RECOMMENDED
1,000 - 4,500
750 - 3,600
4-8
5-15
0.2 - 0.5
0.5 - 1.0
20 - 40
15 - 75
22
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Calculated parameters in Table VI show that the plant was overloaded
organically, however, BOD5 data for the two day sampling period (280 mg/1)
was considerably above the average for the month of April (196 mg/1) according
to plant records. The average for the month of March was 187 mg/1. These
lower values indicate that the plant is operating well within the recommended
ranges. These data illustrate the problem associated with making a comparison
based on calculations using one or two days data. A better method would be
to calculate the values based on a 7 day moving average.
Dissolved oxygen (DO) was measured throughout the aeration basins and
the results are presented in Appendix B. DO levels were generally found to
be in the 1 to 2.5 mg/1 range in the main plant with the exception of the
twelve foot depth. The DO level in the Cantex unit was too low, ranging from
0 to „75 mg/1.
The results of the settlometer test are presented in the Appendices and
illustrated in Figure 6. Figure 5 shows the settleability curves for basin
number 1, during the two day study. The settling curve for basin number 2
was very similar and should be identical except for the slight difference in
MLSS. These curves indicate a good settling sludge with good compaction.
Secondary Clarifiers
The measured and recommended operating parameters for secondary clarifiers
following the conventional activated sludge process are presented in Table
VII. The measured values are based on the average flow during the study of
6.96 mgd.
TABLE VII
SECONDARY CLARIF1ER OPERATIONAL PARAMETERS
/is\r>«T OTnpD "U" TJTT>
RECOMMENDED (1,2,4,6)
300 - 1,200
12 - 30
2 - 3.0
5,000 - 20,000
(JUKAL o viir
MEASURED
788
Hydraulic Loading (gpd/sq. f t.),
Solids Loading (lbs/day/sq.ft.) 16.5
Hydraulic Detention (hrs) 2.05
Weir Overflow Rate (gpd/ft,) 14,777
23
-------
FIGURE 6
AVERAGE SETTLOMETER RESULTS FOR AERATION BASINS
CORAL RIDGE "B" WTP
100
o
6-8
W
X
3
hJ
O
>
w
ci
o
3
w
o
w
ij
H
H
W
CO
O O 4 /' 4/76
¦ / 5 / 7 6
4/6/76
30
TIME (min.)
-------
The clarifiers were operating within recommended design criteria at
average design flows, however, plant flows peak at 12 to 13 tngd during the
tourist season. At 12 mgd the hydraulic loading is 1,360 gpd/sq.ft. and the
weir overflow rate is 25,500 gpd/ft. At these higher loadings, solids carry
over, due to clarifier turbulance, does occur.
25
-------
EXECUTIVE AIRPORT "E" WASTEWATER TREATMENT PLANT
Treatment Process
A schematic diagram of the 0.5 mgd contact stabilization activated
sludge wastewater treatment plant is presented in Figure 7 and design data
are presented in Table VIII. Sludge is digested in an aerobic digester and
is trucked to the disposal site. Each basin and the digester was aerated
by a single slow speed mechanical aerator. Chlorine was added to the final
effluent for disinfection*
Study Result and Observations
A complete listiiig of all analytical data and general study methods
are pressed in the sfrpehdices. Significant results and observations
made during the stud* ate discussed in the following sections.
Flow
Effluent wastewater wbs measured with a Parshall flume equipped with
a recorder and totalizer. Average effluent wastewater flow during the study
was 0.24 mgd with maxitnunl and minimum flows of 0.49 and 0.058 mgd, respectively.
Hourly effluent wastewater flows during the study are presented in Figure 8.
Return sludge arid warite sludge flow was measured with magnetic flowmeters
equipped with a reedier and totalizer. Average return sludge flow during
the study was 0.19 agd <39 percent of the WTP flow).
A volume of 13,5^0 gallons of sludge was wasted to the digester during
the study.
Waste CharrfP.ristics and Removal Efficiencies
A chemical description of the influent and effluent wastewater with
calculated treatment reductions are presented in Table IX. Removal efficiencies
were calculated using average data from two separate 24-hour, flow proporational
composite samples. Effluent residual chlorine concentrations averaged 6.87
mg/1 during the study.
26
-------
FIGURE 7
EXECUTIVE AIRPORT "E" WTP
FT. LAUDERDALE, FLA.
TO
DISPOSAL
I
-------
TABLE VIII
EXECUTIVE AIRPORT "E" WTP
FORT LAUDERDALE, FLORIDA
I• General Design
Design Flow
Maximum Flow
Average Flow
II. Flow Measurement
Effluent
Return Sludge
Waste Sludge
III. Preliminary Treatment
Comminutor
IV. Contact Basin
Length
Width
Depth
Area
Volume
Aeration
V• Stabilization Basin
Length
Width
Depth
Area
Volume
Aeration
Detention Time
VI. Digester
Length
Width
Depth
Area
Volume
Aeration
0.5 mgd
0.85 mgd
0.20 mgd
Parshall flume
Magnetic flow meter
Magnetic flow meter
24 ft.
24 ft.
10 ft.
576 sq. ft.
5,760 cu. ft\
43,000 gals.
1-10 hp; fixed surface aerator,
rated @ 25.2 lbs
02/hr
41 ft.
41 ft.
10 ft.
1,680 sq.
16,800 cu.
ft.
ft.
126,000 gals.
1-15 hp; fixed surface aerator
rated @ 50.8 lbs.
6.04 hrs.
02hr
34 ft.
34 ft.
11 ft.
1,156 sq. ft.
12,700 cu. ft.
95,000 gals.
1-15 hp; fixed surface aerator,
rated @ 47.2 lbs 02hr.
28
-------
table viii (Continued)
VII. Final Clarifier
Diameter
Depth
Area
Volume
Weir Length
Weir overflow rate
Detention Time
VIII. Chlorine Contact Basin
Length
Width
Depth
Area
Volume
Detention Time
30 ft.
11.5 ft.
707 sq. ft.
8,125 cu. ft.
61,000 gals.
94 ft.
5,319 gal/lin. ft.
2.92 hrs
20 ft.
8 ft.
11 ft.
160 sq. ft.
1,120 cu. ft.
8,380 gals.
15 min.
29
-------
FIGURE 8
EFFLUENT FLOWS
EXECUTIVE AIRPORT "E" WTP
FT. LAUDERDALE, FLA.
4/4 - 4/5/77 4/6 - 4/7/77
TIME (hrs.)
-------
TABLE IX
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
EXECUTIVE AIRPORT "E" WTP
PARAMETER
INFLUENT
EFFLUENT
% REDUCTION
223
43
81
463
117
75
623
469
25
269
138
49
139
45
68
99
35
32.8
25.2
23
30
24
20
<0.01
0.025
8.15
2.95
64
6.87
20
<0.05
<0.05
<0.08
<0.08
—
0.049
0.029
41
<0.01
<0.01
—
0.109
0.035
68
BOD (mg/1)
COD (mg/1)
TS (mg/1)
TVS (mg/1)
TSS (mg/1)
TVSS (mg/1)
TKN (mg/1)
NH3-N(mg/1)
NO -NO -N (mg/1)
Total Phosphorus (mg/1)
Chlorine Residual* (mg/1)
Turbidity* (NTU)
Pb (yg/1)
Cr (yg/i)
Cu (vig/1)
Cd (ug/1)
Zn (ng/1)
•Grab samples analyzed individual and the results averaged.
The average influent B0D5 (223 mg/1) and COD (463 mg/1) were typical of
wa8 very little nitrification occurring in the
domestic wastewaters. There was
i a nnf- have been expected since DO concentrations
process. Nitrification would not nave v
Observed during the study «ere very low. The weekly average WDES permit limits
are 13 mg/1 and 20 mg/1 for BOD, and TSS, respectively.
Contact Tank
, the contact and stabilization tanks and
Grab samples were taken from the contac
a.a anlids. volatile suspended solids, and percent
analyzed for total suspended solias,
o u aa*mles from the contact taAk were analyzed for
solids by centrifuge. Grab samples rru»
settleability as determined by the settlometer.
Aeration and mixing of the contact and stabilization tank were accomplished
by a 10 and 15 hp fixed mechanical aerator, respectively.
concentrations in the contact tank ranged from 0.4
Dissolved oxygen (DO; concen
to 0.8 mg/1 on the surface. At the same time the DO concentration in the stabili-
sation tank was 0.0 mg/1. The DO concentration in the stabilization tank waa
31
-------
measured during a cycle when the aerator was off. The aerators in the
stabilization tank and digester were on a timer, during which the off cycles
lasted from 15 to 30 minutes. DO was again measured at Q.O mg/1 within
five minutes after the aerator cycled. This operational mode permitted the
mixed liquor to remain in a septic condition much of the time.
Presented in Table X are various calculated stabilization activated sludge
operational parameters, using EPA and WTP laboratory data and corresponding
recommended values.
TABLE X
CONTACT AND STABILIZATION BASIN OPERATIONAL PARAMETERS
CONTACT AND blA AIRP0RT "E" WTP
(1), (4),
MEASURED RECOMMENDED(6).(8)
, 11\ ^ 6,140* (3,588) 1,000 - 3,000
MLSS (mg/1) (Contact) (9,450) 4,000 - 10,000
(Stabilization) 4,851**(2,830) 750 - 2,400
MLVSS (mg/1) (Contact) ccq\
(Stabilization) 2.4' 0.5-1.0
Detention Time (hrs) (Contact) 54 3-6
(Stabilization) 42 9 (35.9) 5-15
Mean Cell Residence Time (days) ^ ^ ^ q
Sludge Age (days) 0<25 (0.43) 0.2 - 0.6
Lbs BODs/day/lb MLVSS (F/M) _ __
Lbs BODr/day/1,000 cu. ft. (Contac ^ ^ (0.91) 0.5 - 1.0
Lbs COD/day/lb MLVSS
Return Sludge Concentration (mg/ ) »
Return Sludge Rate (% of PI®' Flow) 79 150
( ) - EPA data measured after one week of holding tine.
" I ^iir^^ntrrJISILd^ing 79 percent volume of volatile,
to"on-™UtileS in EPA's measurement.
Solids concentrations in the contact tank were excessive. This resulted
x,4„v, mprt and sludge age. The weight to concentration
in a low F/M ratio and a high M.uu 8110 81 » 6
ratio (WCR) of the sludge was 1,042 and 1,208 which is indicative of an old
sludge. A good healthy desirable sludge would have a WCR of 700 to 800.
-
-------
the volatiles solids over the period of one week, were degraded and/or utilized
by the floe. For this reason the WTP solids data was used in calculating
loading parameters.
It is concluded from these data that the most feasihle way to control
the solids level in the contact tank would be by maintaining an F/M of between
°-2 and 0.6, a WCR of approximately 800, and initiating a regular sludge wasting
schedule.
Clarifier
Presented in Table XI are various measured and recommended clarifier
parameters following the contact stabilization activated sludge process
TABLE XI
SECONDARY CLARIFIER OPERATIONAL PARAMETERS
EXECUTIVE AIRPORT "E" WTP
„ . MEASURED RECOMMENDRTU^' ^'
Hydraulic Loading (gpd/sq.ft.) 339 j(ju _ ji 200
Solids Loading (lbs/day/sq.ft.) 31.4 22 - 30
Hydraulic Detention (hrs) 3.4 2-3
Depth (ft.) 11.5 10 - 15
Weir Overflow Rate (gpd/ft.) 2,553 5,000 - 20,000
All parameters measured were within or better than the recommended ranges
except for solids loading. The calculated solids loading was 31.1 lbs/day/
ft. if the solids concentrations were maintained at the 3,500 mg/1 the
solids loading to the clarifier would have been only 17.75 lbs/day/sq.ft.
Results of the settlometer test and observation of the settling character
of the mixed liquor solids are presented in the Appendices and Figure 9.
LABORATORY
A chemical and biological laboratory was located at the Coral Ridge "B"
WTP and served as the main environmental laboratory for the Fort Lauderdale
area. Analyses are conducted for all of five wastewater treatment facilities
33
-------
FIGURE 9
AVERAGE SETTLOMETER RESULTS FOR THE CONTACT BASIN
EXECUTIVE AIRPORT "E" WTP
TIME (min.)
-------
and the areawide sanitation department. Staffing at the laboratory consisted
of a chemist, a hiologist, five technicians and an assistant. Laboratory space
and equipment was considered adequate for the work load and general house
keeping was commendable.
While at the laboratory various analytical procedures were discussed.
A Federal Register approved method was followed for each test except for the
chlorine residual determination. The orthotoludine method was used for this
test, however, the Standard Method's DPD procedure is to be used in the
future.
The in-plant control testing program included aeration basin TSS, VSS,
BOD5 (influent), and DO (Surface-analyzed by operators); anaerobic digester
volatile acids and alkalinity; and effluent chlorine residual. It was suggested
that the following tests also be Included In their program; (1) One hour
settlometer; (2) clarlfler sludge blanket depth; (3) aeration basin DO at
various depths; (4) centrifuge.
The centrifuge test gives a quick Indication as to the solids content
in the aeration basins and whether or not the basins are receiving equal solids
loading. It was further suggested that trend charts be established and maintained.
Useful parameters for plotting Include MLSS, sludge settleability, significant
influent and effluent waste characterise, flow (plant, return sludge, waste
sludge), depth of clarlfler sludge blanket, and MCRT. Experience will dictate
are necessary for successful plant operations. These
which of these parameters are necea 3
. J aerve only as a guide and are intended to establish
suggested parameters should serve omy
. , ^ances in plant conditions can be noticed prior to
trends so that gradual changes in
deterioration in effluent quality.
35
-------
REFERENCES
1. "Operation of Wastewater Treatment Plants," A Field Study Training
Program, US-EPA, Technical Training Grant No-5TTl-WP-16-Q3, 1970.
2. "Process Design Manual for Suspended Solids Removal," US-EPA Technology
Transfer, January 1975.
3. "Sewage Treatment Plant Design," American Society of Civil Engineers,
Manual of Engineering Practice No. 36, 1959.
4. "Wastewater Engineering," Metcalf and Eddy, Inc. 1972.
5. West, Alfred W., Operational Control Procedures for the Activated
Sludge Process. Part I., Observations, EPA-330/9-74-001-a, April 1973.
6. "Recommended Standards for Sewage Works," Great Lakes - Upper
Mississippi River Board of State Sanitary Engineers, Revised Edition,
1971.
7. "Standard Methods for the Examination of Water and Wastewater,"
13th Edition, 1971.
8. "Process Design Manual for Upgrading Existing Wastewater Treatment
Plants," US-EPA Technology Transfer, October 1974.
36
-------
APPENDICES
-------
APPENDIX AI
LABORATORY DA^A
SIXTH STREET/ CORAL RIDGE, AND!EXECUTIVE AIRPORT WTP
FT. LAUDERDALE-, FLORIDA
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APPENDIX A
LABORATORY DATA|
SIXTH STREET, CORAL RIDGE, AND I&EGUTIVE AIRPORT HTP
FT. LAUDERDALE;'FLORIDA
INFLUENT, PRIMARY EFFLUENT, PLANT EFFLUENT
-------
APPENDIX ^
•LABORATORY D#TA
SIXTH street; CORAL RIDGE, ant! EXECUTIVE AIRPORT WTP
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APPENDIX A I
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APPENDIX A
LABORATORY DATAi
SIXTH STREET, CORAL RIDGE, AND EXECUTIVE AIRPORT WTP
FT. LAUDERDALE,• FLORIDA
RETURN SLUDGE, WASTE SLUDGE, AEROBIQ DIGESTER
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APPENDIX B
DISSOLVED OXYGEN CONCENTRATIONS
SIXTH STREET *A» WTP
STATION DATE
AA-1 BASIN
3 770406
4 770406
5 770406
AA-2 BASIN
7 770406
8 770406
9 770406
AC-I CLARIFIER 770406
AC-2 CLARIFIER 770406
AI INFLUENT 770406
TEMP
C
28
28
28
DO-MG/L
1FT
0.7
1.3
1.2
0.75
0.30
0.60
0.10
0.10
0.05
DO-MG/L
5FT
0.6
1.0
0.95
0.40
0.30
0.45
DO-MG/L
10FT
0.05
0.7
0.85
0.35
0.05
0.20
DO-MG-L
14FT
0.8
0.95
0.40
AERATION BASINS
DO PROFILE STATIONS
SIXTH STREE "A" WTP
AA-1
L
r\
D C
5
•
3. .
•
EFFLUENT
AA -2
43
-------
APPENDIX B
DISSOLVED OXYGEN CONCENTRATIONS
CORAL RIDGE «B* WTP
TEMP
DO-MG/L
DO-MG/L
DO-MG/L
DO-MG-
STATION
DATE
C
1FT
5FT
10FT
12FT
BA-1 basin
Ba-A
/70405
27
2.2
0.7
0.15
ba-b
770405
27
2.6
1.4
0.2
&A-C
770405
27
2.0
1.4
0.05
Ba-0
770405
27
2.4
1.8
1.8
0.2
Ba-E
770405
27
2.1
2.05
1.7
0.1
ba-f
770405
27
2.1
1.8
1.5
0.4
Ba-G
770405
27
2.2
1.6
0.9
0.25
Ra-h
770405
27
1.8
1.75
1.4
1.4
BA-I
770405
27
2.3
1.7
1.4
1.4
Ba-j
770405
27
2.1
1.75
1.3
0.75
ba-k
770405
27
2.1
2.0
0.2
0.2
Ba-L
770405
27
1.0
0.4
0.7
0.5
SA-i? BASIN
Ba-m
770405
1.5
0.25
0.05
Ba-o
770405
2.1
2.2
0.15
0.05
Ba-o
770405
2.55
1.8
1.05
0.4
Ba-S
770405
1.7
1.75
1.6
1.5
Ba-U
770405
1.8
1.3
0.85
0.5
Ba—v
770405
2.6
0.3
0.1
Ba-w
770405
0.7
0.6
0.7
0.9
BC-1 CANTEX WTP
BCC-1
0.05
Contact tank
770405
BCr-2
keaeration tank
770405
0.75
BCS-3
settling tank
770405
0.0
BCD-*
0.25
1)IGESTER
770405
44
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AERATION BASINS
DO PROFILE STATIONS
CORAL RIDGE "B" WTP
w
N
Effluent
06666
BA-2
W
A.
0
JL
M
, Influent
6 6 6 6 6
L
H
D
JL
BA-l
CANTEX UNIT
45
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APPENDIX B
DISSOLVED OXYGEN CONCENTRATIONS
EXECUTIVE AIRPORT *E• WTP
TEMP DO-MG/L DO-MG/L DO-MG/L
STATION DATE C 1FT 5FT 10FT
EI 770406 27 0.6
EAT
AERATION TANK 770406 0.4 0.8
EST
STABILIZATION TANK770406 0.0 AERATOR OFF
0.0 5 MIN. AFTER AERATOR
EAD
AEROBIC DIGESTER 770406 0.0
EC CLARIFER 770406 0.0
EE EFFLUENT 770406 27 2.25
46
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APPENDIX C
OXYGEN UPTAKE PROCEDURE 1/
Apparatus
1. Electronic DO analyzer and hottle probe
2. Magnetic stirrer
3. Standard BOD bottles (3 or more)
4. Three wide mouth sampling containers (approximately 1 liter each)
5. DO titration assembly for instrument calibration
6. Graduated cylinder (250 ml)
7. Adapter for connecting two BOD bottles
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 _
1.0 + .4 IA 86 ml '
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
47
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APPENDIX (Continued)
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 DO.
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=) . Read and record
the DO again at 1 minute intervals until at least three consistent
readings for the change in DO per minute are obtained (^DO/min).
Check for the final sample temperature. This approximates sludge
activity in terms of oxygen use after stabilisation of the sludge
during aeration (unfed sludge activity).
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 aDO/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 t"he 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, accept-
able feed under favorable conditions. A small LF means dilute feed, incipient
48
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APPENDIX (Continued)
toxicity, or unfavdtibife conditions. A negative LR indicates that something
in the wastewater tjkbbkrid or poisoned the "bugs."
1/ Taken from "DisitllVifl Oxygen Testing Procedure," fr.j. Ludzack and script
for slide tape XT-4i (faissolved Oxygen Analysis - Afctivated Sludge Control
Testing) prepared by Ludzack, NERC, Cincinnati.
49
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APPENDIX D
GENERAL STUDY METHODS
Methods used to accomplish the stated objectives included extensive
sampling, physical measurements and daily observation. ISCO Model 1392-X
automatic samplers were installed at plants "A," "B," and "E" to sample
influent and/or effluent streams. Additional samplers were installed to
sample aeration basin influent and Cantex unit effluent at the Coral Ridge
Plant "B". The aeration basins influent was also sampled at the Sixth Street
Plant "A". These samplers operated two consecutive 24-hour periods, pumping
individual hourly aliquots of sample into separate refrigerated glass bottles
which were composited proportional to flow at the end of each sampling period.
Special grab samples taken included influent, effluent, return sludge, wasted
sludge and digester supernatant for PCB analysis plus influent samples for
oil and grease.
Flows were determined from plant totalizers and recording charts. All
dissolved oxygen measurements were determined using the YSI Model 57 dissolved
oxygen meter. An Analytical Measurements Model 30 WP cordless pH recorder
was installed to monitor influent pH throughout the sampling periods. Tempera-
tures and pH were determined at other stations with thermometer and portable pH
meter. Depth of the secondary clarifier sludge blankets were determined daily
using equipment suggested by Alfred W. West, EPA, NFIC, Cincinnati (Appendix E).
Sludge activity was determined by the oxygen uptake procedure presented in
Appendix C.
A series of standard operational control tests were run daily:
(1) Settleability of mixed liquor suspended solids (MLSS)
as determined by the settlometer test;
50
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(2) Percent solids of the mixed liquor and return sludge
determined by centrifuge;
(3) Suspended solids and volatile suspended solids analysis
on the aeration basin mixed liquor and return sludge and
(4) Turbidity of each final clarifier effluent.
Daily effluent total chlorine residual concentrations were determined
using an amperometric titrator (Fischer and Porter Model 1771010).
The procedure for the BOD,, determination deviated from Standard Methods.
Samples were set up and returned to Athens, Georgia in an incubator where the
analyses were completed.
Visual observations of individual unit processes were recorded.
Mention of trade names or commercial products does not constitute endorse-
ment or recommendation for use by the Environmental Protection Agency.
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