TECHNICAL ASSISTANCE PROJECT
AT THE
INDUSTRIAL WASTEWATER TREATMENT PLANT
MOORESVILLEV NORTH CAROLINA
February, 1976
Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
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TECHNICAL ASSISTANCE PROJECT
AT THE
INDUSTRIAL WASTEWATER TREATMENT PLANT
MOORESVILLE, NORTH CAROLINA
February, 1976
Environmental Protection Agency
Region IV
Surveillance and Analysis Division
Athens, Georgia
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CONTENTS
Page
INTRODUCTION 1
SUMMARY 2
RECOMMENDATIONS 3
TREATMENT FACILITY 4
TREATMENT PROCESSES 4
PERSONNEL 4
STUDY RESULTS AND OBSERVATIONS 8
FLOW 8
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES. . 8
AERATION BASINS 10
CLARIFIERS 12
CHLORINE CONTACT CHAMBER 12
AEROBIC DIGESTER 12
LABORATORY 13
REFERENCES 14
APPENDICES
A - LABORATORY DATA 15
B - GENERAL STUDY METHODS 16
C - ACTIVATED SLUDGE FORMULAE USED FOR
GENERAL CALCULATIONS 17
D - INFLUENT FLOW . 19
FIGURES
1. MOORESVILLE IWTP 5
2. SETTLOMETER TEST 11
TABLES
I. DESIGN DATA 6
II. WASTE CHARACTERISTICS AND REMOVAL
EFFICIENCIES 9
III. MEASURED AND RECOMMENDED PARAMETERS FOR THE
EXTENDED AERATION ACTIVATED SLUDGE
PROCESS 10
IV. MEASURED AND RECOMMENDED PARAMETERS FOR
CLARIFIERS FOLLOWING EXTENDED AERATION
ACTIVATED SLUDGE TREATMENT 12
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INTRODUCTION
A technical assistance study of operation and maintenance
problems at the Industrial Wastewater Treatment Plant (IWTP)
serving primarily industrial waste sources in Mooresville, NC
was conducted February 18-19, 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 maxjmi^inp- °ffip.ipnf.ipR as well
as assisting with special operational problems. Municipal
wastewater treatment plants are selected for technical assis-
tance studies after consultation with state pollution control
authorities. Visits are made to each prospective plant prior
to the study to determine if assistance is desired and if
study efforts would be productive.
This plant was selected ^ecause of nnw-np agcpggmpn^ 0f plant operation and maintenance
practices will be made at a later date— This will be accom-
plished by utilizingdata generated by plant personnel and,
if necessary, subsequent visits to the facility will be made.
The follow-up assessment will determine if recommendations
were successful in improving plant operations and if further
assistance is required.
The cooperation of the North Carolina Department of Natural
and Economic Resources is gratefully acknowledged. The technical
assistance team is especially appreciative of the cooperation
and assistance received from Mr. Troy Scoggins, Sr., Director
of Public Works.
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SUMMARY
The Mooresville, NC industrial wastewater treatment plant
(IWTP) was designed as a 4 million gallon per day (mgd) extended
aeration activated sludge facility; however, the average flow
during the study was 2.65 mgd. Approximately 96 percent of
the influent flow is from industrial sources, primarily textile
mills. Waste sludge from the IWTP is discharged to the
Mooresville municipal wastewater treatment plant for condition-
ing and disposal.
1 A few weeks nrior to the technical assistance (TA) study.
conditions at the IWTP were extremely nnnr Two weeks of
intensive clean-up and repair prior to the study significantly
improved overall operation and treatment efficiency. Improve-
ments included removing sludge accumulated in the clarifier and
chlorine contact chamber and cleaning clogged influent ports
along the clarifier rim-feed canal.
Lack of tra-jn^ p^-»-g:r>nngi wag a major problem at the time
of the study. The city has subsequently hired a new operator
and is actively training treatment plant personnel. During the
TA study^no in-plant control testing was performed; however,
subsequent phone conversations indicate that control testing
has been initiated.
Tremendous improvements have been made in improving
treatment efficiency and plant operations during the past few
months. (Consistently high treatment efficiency can be achieved
through continued effort by properly trained personnel.\
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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 operation:
1. An in-plant control testing schedule should be
initiated and trend charts established and maintained.
2. Operator and laboratory training should be emphasized
and encouraged.
3. Additional personnel should be hired to provide daily
operation and maintenance of the plant.
4. Influent bar screens need to be cleaned on a regular
basis.
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TREATMENT FACILITY
TREATMENT PROCESSES
A schematic diagram of the 4 mgd industrial wastewater
treatment plant (IWTP) serving Mooresville, North Carolina
is presented in Figure 1. Design data are enumerated in
Table 1. The plant began operation in 1961 and was upgraded
in 1973 to the existing extended aeration activated sludge
facility.
PERSONNEL
Lack of trained pmplovppc; t.n nppi-atp. thp plnn| and
perform routine control testing is a major problem. As of
March 18, 1976, the city had employed a new chief operator
and was sending eight employees to an operator's training
course.
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FIGURE I
MOORESVILLE IWTP
MOORESViLLE, N.C.
o
SAMPLING LOCATIONS
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TABLE I
DESIGN DATA
INDUSTRIAL WASTEWATER TREATMENT PLANT
MOORESVILLE, NC
FLOW MEASUREMENT
Type
Size
Location
Design Flow
Avg.
Max.
Parshall flume, recorder, totalizer
18 in.
Influent
4.0 mgd
8.0 mgd
AERATION BASINS
Number
Volume (each)
Length
Width
Depth (water)
Detention
Aerators
Number
Size (each)
267,380 cu. ft. (2 m.g.)
260 ft.
120 ft.
12 ft. (with side slope)
24 hrs.
4
75 hp
CLARIFIER
Diameter
Sidewater Depth
Volume
Detention
Overflow rate
Sludge recycle
Number pumps
Capacity (each)
AEROBIC DIGESTER
86 ft.
12 ft.
69,600 cu. ft. (.52 m.g.)
3 hrs.
700 gal/day/sf
2800 gpm
Volume
Length
Width
Depth (water)
Aerators
Number
Size (each)
24,500 cu. ft. (0.18 m.g.)
120 ft.
84 ft.
11 ft (with side slopes)
2
25 hp
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CHLORINATION FACILITIES
Chlorine Contact Tank
Volume 16,500 cu. ft. (0.12 m.g.)
Length 120 ft.
Width 84 ft.
Depth (water) 9.5 ft.
Detention 45 min.
Chlorinators
Number 2
Capacity 500 lbs/day
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STUDY RESULTS AND OBSERVATIONS
A complete listing of all analytical data and study
methods are presented in Appendices A and B. Formulae used
ior general calculations are enumerated in Appendix C.
Significant results and observations made during the study
are discussed in the following sections.
FLOW
Plant flow is measured with an 18-inch Parshall flume,
recorder and totalizer. The flume was checked and found to
be installed properly. The recorder and totalizer were
determined to be recording accurately.
The average hourly flow into the plant during the study
period was 2.65 mgd. The flow record for February 9-16, 1976
is presented in Appendix D. Typical weekday flows vary from
approximately 6 mgd to 0.4 mgd. An estimated 96 percent of
the influent wastewater is from industrial sources, primarily|-^u" ^ tA
textile mills.
The return sludge is not metered, however, practically
all sludge is returned to the aeration basins.
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Table II presents a chemical description of the influent
and effluent with calculated percent treatment reductions
shown for all parameters. Analyses were made on 24-hour
composite samples.
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TABLE II
WASTE CHARACTERISTICS AND REMOVAL EFFICIENCIES
Influent
Parameter (mg/1)
BOD5 133
COD 537
Total Suspended Solids 92
Volatile Suspended Solids 76
Total Solids 1,204
NH3-N 2.75
N03-N02-N <.01
TKN-N 11.6
Total Phosphorus 9.0
Lead <.08
Chromium <.08
Cadmium <.02
Copper .23
Zinc .160
Effluent
(mg/1) % Reduction
8 94
122 77 - ^
12 87 "*""°
11 86 I7
960 20-
.20 93.
^ 3Q sv- Yeduflir,'
2.92 75
7.7 14
<.08
<.08
<.02 — ,
.08 65— "
.275 0
The influent BOD^/COD ratio of 0.25 and relatively low
influent BOD5 concentration reflects the primarily inorganic
industrial nature of the influent wastewater. Hourly pH
measurements ranged from 6.9 to 7.6 during the 24-hour
composite sampling period.
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AERATION BASINS
Grab samples were taken from each aeration basin at
sampling locations designated AB-N and AB-S.- Samples were
analyzed for total suspended solids (TSS), volatile suspended
solids (VSS), percent solids by centrifuge, and settleability
as determined by the settlometer.
Dissolved oxygen (DO) concentrations were measured at two
sampling stations in each aeration basin at one and ten foot
depths. Concentrations ranged from 2.0 to 3.1 mg/1 and did
not vary significantly with depth.
The results of the settlometer test are presented in
Figure 2. The settled sludge volume after 60 minutes of
settling was 69 percent. Although the activated sludge did
not settle and concentrate as well as would be desired, the
supernatant was free of suspended material.
Presented in Table III are various activated sludge
operational parameters calculated during the study period and
the corresponding recommended values for the extended aeration
activated sludge process.
The food to microorganism (F/M) ratio was low due to
the low BODg concentration of the influent wastewater. The
average mixed liquor suspended solids (MLSS) and mixed liquor
volatile suspended solids (MLVSS) for the two aeration basins
were 2412 and 1812 mg/1, respectively. The MLSS has been
reduced to approximately 1900 mg/1 since the TA study with no
improvement in settleability.
TABLE III
MEASURED AND RECOMMENDED PARAMETERS FOR THE EXTENDED
AERATION ACTIVATED SLUDGE PROCESS
Hydraulic Detention Time (hrs)
Sludge Age (days)
Lbs BODc/day/lb MLVSS (F/M)
Lbs COD/day/lb MLVSS
Lbs BOD^/day/lOOO cu. ft. of
aeration basin
Return sludge rate (% of
average flow)
Measured Recommended (3)(4)
16 18-36
40 >10
.05 .05-.15
0.2 <0.2
5.5 10-25
1/
nown .75-150
1/ - Return sludge could be estimated from the capacity of
the 2800 gpm return sludge pump and a visual estimate
of the waste sludge flow.
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FIGURE 2
5 10 15 20 25 30 35 40 45 50 55 60
SETTLING TIME (MINUTES)
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CLARIFIERS
The circular secondary clarifier has a rim feed, rim
take-off flow configuration. On November 10, 1975 an O&M
inspection revealed zero percent reduction in TSS and
flooding of the influent rim-feed trough directly into the
effluent trough due to the clogged influent ports. During
the two weeks prior to the technical assistance study the
clarifier was completely cleaned resulting in an immediate
improvement in operation, as shown in Table I.
The measured and recommended parameters for a secondary
clarifier following extended aeration activated sludge waste-
sater treatment are presented in Table IV. Measured values
in Table IV were calculated using the average flow (2.65 mgd)
during the study and indicate adequate clarifier capacity.
The hydraulic loading at design flow is high for a clarifier.
following extended aeration treatment.
TABLE IV
MEASURED AND RECOMMENDED PARAMETERS FOR CLARIFIERS
FOLLOWING EXTENDED AERATION ACTIVATED SLUDGE TREATMENT
Measured* Recommended (1)
Hydraulic Loading (gpd/sq. ft.) 456(688) 200-400
Solids Loading (lbs/day/sq. ft.) 9.2(14) 20-30
Hydraulic Detention (hrs.) 4.7(3.1) 2-3
Depth (ft.) 12 12-15
* () indicate values assuming the design flow of 4 mgd.
CHLORINE CONTACT CHAMBER
A few weeks prior to the TA study an excessive quantity
of sludge had collected in the chlorine contact chamber result-
ing in anaerobic conditions and a tremendous chlorine demand.
However, the chlorine contact chamber was subsequently cleaned
out and was operating properly during the study.
AEROBIC DIGESTER
Waste activated sludge is conditioned in the aerobic
digester and then discharged to the head of the municipal
wastewater treatment plant. Dissolved oxygen in the digester
was measured at the 1 and 14 foot depths and found to be 6.2 and
5.2 mg/1, respectively.
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LABORATORY
Laboratory support for the IWTP is accomplished at the
Mooresville Municipal WTP. The physical facilities are
adequate; however, only limited testing is performed. An
in-plant control testing schedule should be initiated
immediately to include chemical and physical measurements,
e.g. settlometer, clarifier sludge blanket depth and aeration
basin TSS, VSS and DO. Trend charts should be established
and maintained to include MLSS, settlometer, influent and
effluent waste characteristics, flow, aeration basin DO,
depth of clarifier sludge blanket and F/M ratios. These
parameters should serve only as a guide and are intended to
establish trends such that gradual changes in plant conditions
can be noticed prior to a deterioration in effluent quality.
All plant changes should be done one at a time and maintained
for approximately two weeks to allow the plant to reach
equilibrium.
Assistance in laboratory operations will be provided
by the O&M technical assistance team upon request.
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REFERENCES
1. "Process Design Manual for Suspended Solids Removal",
US-EPA Technology Transfer, January 1975.
2. "Sewage Treatment Plant Design", American Society of
Civil Engineers, Manual of Engineering Practice No. 36,
1959.
3. "Wastewater Engineering", Metcalf and Eddy, Inc., 1972.
4. "Operation of Wastewater Treatment Plants", A Field Study
Training Program, US-EPA, Technical Training Grant
No. 5TT1-WP-16-03, 1970.
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APPENDIX A
LA30RAT0RY DATA
INDUSTRIAL WASTEWATER TREATMENT PLANT
MOORESVILLE, NORTH CAROLINA
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APPENDIX B
GENERAL STUDY METHODS
To accomplish;the stated objectives, the study included
sampling, physical measurements and observations. Plant
influent and effluent sample stations 1-1 and E-l, respectively,
were sampled for 24 hours with ISCO Model I392-X automatic
samplers. Aliquots of sample were pumped at hourly intervals
into individual refrigerated glass bottles which were composited
proportional to flow at the end of the sampling period.
Dissolved oxygen was determined in the aeration basins
and aerobic digester using a YSI model 51A dissolved oxygen
meter.
The plant flow totalizer was used to determine total
daily flow and the recorder was used for hourly flows.
Accuracy of the plant flow recorder and totalizer was checked
with instantaneous readings from the parshall flume.
Water temperature was recorded while measuring the
dissolved oxygen concentration. Individual samples from the
24-hour composite samples were used to determine hourly in-
fluent pH variation.
A series of standard operational control tests were run:
© Settleability of mixed liquor suspended solids (MLSS)
as determined by the settlometer test;
e Percent solids of the mixed liquor and return sludge
determined by centrifuge;
e Suspended Solids and Volatile Suspended Solids analy-
sis on the aeration basin mixed liquor and return
sludge.
Visual observations of individual unit processes were
recorded.
Mention of trade names or commercial product does not
constitute endorsement or recommendation for use by the
Environmental Protection Agency.
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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 cone) x (Basin vol.) x 8.34 = lbs. of solids
2. Aeration basin loading (lbs. BOD or COD/day)
Inf. flow to aeration basin = mgd
Inf. BOD or COD = mg/1
(BOD or COD) x flow x 8.34 = lbs. BOD or COD/day
3. Sludge Age (days)
MLSS conc. (avg. of daily values) = mg/1
Aeration Basin Vol. = m.g.
TSS, Primary Eff. or Basin Inf. conc. = mg/1
Plant Flow = mgd
(MLSS) x (Basin Vol.) x (8.34)
(TSS) x (Flow) x 8.34
4. Sludge Vol. Index (SVI)
30 min. settleable solids (avg. of daily values) = %
MLSS conc. = mg/1
(%, 30 min. set, solids) x (10,000)
MLSS
5. Sludge Density Index (SDI)
SVI Value 100
SVI
6. Detention time (hours)
Volume of basins = gal.
Plant flow = gal./day
Return sludge flow = gal./day
Basin volume x 24
(Flow) + (Return sludge flow)
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.
X-(Pva?VlQ^ (8'34) - ^S. BOD/lb. MLVSS
(MLVSS) x (Basin Vol.) x 8.34 '
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X.COD cone.) x (plant flow) x (8.34) COD/]b MI VSS
(MLVSS) x (Basin Vol.) x (8.34) lbs' LUD/Jb-
8. Mean cell residence time (MCRT) = days
MLSS cone. (avg. or daily value) = mg/1
Basin vol. = m.g.
Clarifier vol. = nr. g.
Waste activated sludge cone. = mg/1
Waste activated sludge flow rate=mgd
Plant effl. T-SS = mg/1
Plant flow = ingd
(MLSS) x (Basin vol. + Clarifier vol.) x 8.34 _
(Waste activated sludge conc.) x (waste flow) x 8.34 + ~ days
(Plant effl. TSS x plant flow x 8.34)
Clarifier
1. Detention time = hours
Plant flow to each clarifier = gals/day
Individual clarifier vol. = gals.
(clarifier Vol. (each) x 24 _ hours
Plant flow to each clarifier
2. Surface loading rate = gal./day/sq. ft.
Surface area/clarifier = sq. ft.
plant flow to clarifier = gal./day
Plant flow to clarifier _ /flo
TPs j gal./day/sq. ft.
Clarifier surface area.
3. Weir Overflow Hate (gal./day/lin. ft.)
Weir Length = ft.
Plant flow to clarifier = gal./day
Plant flow n , , ... .
Weir length = 8*1./day/lin. «.
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