NC0025453_Authorization to operate_20031231

SUPPORTING CALCULATIONS
FOR
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March 18, 2003
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Prepared by:
AUTHORIZATION TO OPERATE THE EXPANDED 2.5 MGD LCWRF
CLAYTON, NORTH CAROLINA
THE WOOTEN COMPANY
Engineers • Architects • Planners
120 North Boylan Avenue
Raleigh, North Carolina 27609
: JO. S E A I
= 8089
Coinin'''
Shankar R. Mistry, P.E., Ph.D.
SUPPORTING CALCULATIONS
FORI
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March 18, 2003
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Prepared by:
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1
AUTHORIZATION TO OPERATE THE EXPANDED 2.5 MGD LCWRF
CLAYTON, NORTH CAROLINA
THE WOOTEN COMPANY
Engineers • Architects • Planners
120 North Boylan Avenue
Raleigh, North Carolina 27609
pl Ukl yr (2. .
Shankar R. Mistry, P.E., Ph.D.
8089
XX’r'XX"
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TABLE OF CONTENTS
PAGE
1 11.0 Design Influent Wastewater Characteristics
Effluent Limitations (given in draft NPDES Permit No. N0025453)12.0
13.0 Compliance with Annual Limits for Total Nitrogen
74.0 Evaluation of the LCWRF Unit Operations/Processes
74.1 Mechanical Screen/By-Pass Manual Screen
I 104.2 Grit Removal System
129-Inch Parshall Flume4.3
124.4 Influent Pumps
12Activated Sludge (Oxidation Ditch Type) SystemI4.5
Evaluation of Alkalinity Requirement and Chemical Feed Facilities 204.6
4.7 Alum Feed System (For Chemical Phosphorus Removal, Polishing)22
264.8 Polymer Feed System (For Flocculation and Improved Clarification)
264.9 Tertiary Filtration
274.10 Effluent DisinfectionI
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1.
2.
3.
4.
5.
29
29
30
31
32
32
4.11 Evaluatiohn of Sludge Handling Facilities
Estimate of Sludge Quantity
Rotary Drum Sludge Thickenng
Sludge Stabilization/Storage Tanks
Sludge Drying Beds
Sludge Disposal
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1.0 Design Influent Wastewater Characteristics
2.5
I 5.0
6.25
2301215
35125
7
135
6.8-7.0
I Winter = 12; Summer = 27
2.0 Effluent Limitations (given in draft NPDES Permit No. N0025453)
Limits Monitoring RequirementsEffluent Characteristics
Sample Location*Monthly Average
Influent or Effluent2.5 MGD Continuous RecordingFlow
I Composite Influent or Effluent7.5 mg/1 Daily5.0 mg/1
Composite Influent or Effluent10.0 mg/1 15.0 mg/I Daily
Total Suspended Residue2 Influent or EffluentComposite30.0 mg/1 45.0 mg/1 Daily
I Composite Effluent3.0 mg/1 Daily1.0 mg/1
Composite Effluent6.0 mg/1 Daily2.0 mg/1I
EffluentGrabDaily
I Grab3/WeekDissolved Oxygen
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NH3 as N (November
1-March 31)
Average daily flow, mgd
Maximum daily flow, mgd
Peak daily flow, mgd
BOD5, mg/L
TSS, mg/L
TKN, mg/L
NH3-N, mg/L
Total Phosphorus as P, mg/L
Total Alkalinity as CaCOs, mg/L
pH, Standard Units
Temperature, °C
NOTE: The reported year 2000 average BOD? and NHj-N concentration were 210
mg/L and 22 mg/L, respectively.
SUPPORTING CALCULATIONS
FOR
AUTHORIZATION TO OPERATE THE EXPANDED 2.5 MGD LCWRF
Weekly
Average
Daily
Maximum
Measurement
Frequency
Sample
Type
Upstream &
Downstream
BOD. 5 day (2(TC)2
(April 1 - October 31)
BOD, 5 day (20:C)2
(November 1 - March 31)
NH3 as N (April - October
31)
Dissolved Oxygen3
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Monitoring RequirementsEffluent Characteristics Limits
Sample Location1Monthly Average
Grab EffluentDaily400/100 ml
3/Week Grab
Total Residue Chlorine4 EffluentDailyGrab28 pg/1
EffluentCompositeMonitor & Report WeeklyTKN (mg/1)
I Composite EffluentWeeklyN02-N -r N03-N (mg/1)Monitor & Report
Composite EffluentMonitor & Report Weekly
I Calculated EffluentWeeklyMonitor & Report
TN Load6 Effluent Effluent
EffluentWeeklyComposite2.0 mg/L (Quarterly Average)
Grab EffluentDaily
Grab3/Week
Grab EffluentDailyConductivity
Grab3/weekConductivity
Composite EffluentQuarterly
Composite EffluentMonthlyCopper
I EffluentMonthlyCompositeZinc
Composite EffluentMonthlySilver
pH10 EffluentGrab6-9 Daily
Footnotes:
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Fecal Coliform
(geometric mean)
Fecal Coliform
(geometric mean)
Per 15A NCAC 2B .0505(c)(4), stream sampling (as well as influent/effluent sampling) may
be discontinued when flow conditions could result in injury or death of the person(s)
collecting the samples. In such cases, on each day that sampling is discontinued, written
justification shall be specified in the monitoring report for the month in which the event
Monitor & Report (Ib/month)
21.400 Ib/year (Annual Mass Loading)7
Weekly
Average
Daily
Maximum
Measurement
Frequency
Monthly
Weekly
Calculated
Calculated
Sample
Type
Upstream &
Downstream
Upstream &
Downstream
Upstream &
Downstream
Total Monthly Flow
(MG)
200/100 ml
TN (mg/1)5
Chronic Toxicity9
1. Sample locations: E - Effluent, I - Influent, U - Upstream at NCSR 1700, D - Downstream at
(1) NC Highway 42 and (2) NCSR 1908. Stream samples shall be grab samples and shall
be collected 3/Week during June - September and 1/Week during the remaining months of
the year. Instream monitoring is provisionally waived in light of the permittee’s
participation in the Lower Neuse Basin Association. Instream monitoring shall be
conducted as stated in this permit should the permittee end its participation in the
Association.
Total Phosphorus 8
Temperature (- C)
Temperature (-C)
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I 3.0 Compliance with Annual Limits for Total Nitrogen
The compliance requirements with the annual limits for Total Nitrogen, as given in the draft
I NPDES Permit are listed as follows:
1.I
(b)
2.
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(b) The Division must receive notification no later than August 31 for changes
proposed for the following calendar year.
occurred.
2. The monthly average effluent BOD5 and Total Suspended Residue concentrations shall not
exceed 15% of the respective influent value (85% removal).
3. The daily average dissolved oxygen effluent concentration shall not be less than 6.0 mg/1.
4. Total residual chlorine is required only if chlorine is used as a disinfectant (or elsewhere in
the process).
5. TN means Total Nitrogen. For a given wastewater sample, TN is the sum of Total Kjeldahl
Nitrogen and Nitrate-Nitrite Nitrogen: TN = TKN + NO2-N + NO3-N.
6. TN load is the mass load of TN discharged by the Permittee in a period of time. See Special
Condition A.(3.), Calculation of TN loads.
7. The annual TN load limit shall become effective with the calendar year beginning on January
1, 2003. Compliance with this limit shall be determined in accordance with Special A.(4).
Compliance with Annual Limits for Total Nitrogen.
8. The quarterly average for total phosphorus shall be the average of composite samples
collected weekly during the calendar quarter (January-March, April-June, July-September,
October-December).
9. Chronic Toxicity (Ceriodaphnia dubia) P/F at 1.6%: March, June, September, and December
[see Special Condition A.(6)]. Toxicity monitoring shall coincide with metals monitoring.
10. The pH shall not be less than 6.0 standard units nor greater than 9.0 standard units and shall
be monitored daily at the effluent by grab sample.
the Permittee is a Member of a group compliance association and a Co-Permittee
to that association’s group NPDES permit, in which case the Permittee’s TN
discharge is governed primarily by the association’s permit.
If the Permittee elects to become a Co-Permittee Member of a group compliance
association or if it withdraws or otherwise loses its Co-Permittee Member standing in an
association, it must notify the Division in writing of the proposed change.
(a) Notification shall be sent to:
NCDWQ / NPDES Unit
Attn: Neuse River Basin Coordinator
1617 Mail Service Center
Raleigh, NC 27699-1617
For any given calendar year, the Permittee shall be in compliance with the annual TN
load limit in this permit if:
(a) The Permittee’s annual TN Load is less than or equal to said limit, or
3.
I (b) Such changes become effective on January 1st following permit modification.
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The Town of Clayton will comply with the annual limit for Total Nitrogen by becoming a
member of the Neuse River Compliance Association (the “Association”) and a co-permittee to the
Association’s group NPDES Permit. Articles of Incorporation forming the Neuse River
Compliance Association (the “Association”) have been filed, establishing the Association as a
non-profit corporation. The Town has submitted the required resolution of intent to join the
Association in form acceptable to the Association. See the attached copy of the letter from the
Association confirming the formation of Association. A copy of the Town’s resolution of intent to
join the Association is also attached hereto.
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(a) Changes in an association’s membership become effective only through
modification of its NPDES permit.
For the purpose of Condition (l)(b) above, an association’s Co-Permittee Members in
any calendar year shall be as defined in its group NPDES permit.
(c) Beginning on January 1st of each year, the association’s membership is fixed for
the remainder of the calendar year.
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September 27, 2002
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Re:Town of Clayton - Membership in the Neuse River Compliance Association
Dear Mr. Reid:
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Sincerely,
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Cc:
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Timothy L. Donnelly, PE
Chairman
Lower Neuse Basin Association
And Neuse River Compliance Association
Town of Clayton
The Wooten Co.
P. O. Box 590 Raleigh, North Carolina 27602
[phone]
If you have any questions regarding this matter, don’t hesitate to contact me at
[phone].
J. William Reid, Supervisor
Point Source Branch
Division of Water Quality
NC Dept, of Environment and Natural Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
This letter is being sent at the request at the Town of Clayton in response to your
letter of June 10, 2002 concerning their application for a modification of NPDES Permit
No. NC0025453. Articles of Incorporation forming the Neuse River Compliance
Association (the “Association”) have been filed, establishing the Association as a
nonprofit corporation. Furthermore, the Town of Clayton has submitted the required
resolution of intent to join the Association in a form acceptable to the Association. The
final Association membership roster and operational parameters will be completed upon
approval of the operational agreement by the Division of Water Quality and
Environmental Management Commission.
Lower Neuse Basin Association, Inc.
Raleigh, North Carolina
9195531918 TOWNOFCLAYTO: N
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RALE1GH/0I50I 7-001/337231 v.J
' AND WHEREAS, in addition to such ongoing cooperative surface water monitoring
activity and other joint efforts, the LNBA and DWQ jointly support other additional strategies to
ensure overall Total Nitrogen reduction at the mouth of the Neuse River in the Pamlico Sound as
required by the wastewater discharge requirements of the Neuse River Basin Nutrient Sensitive
Waters Management Strategy.
WHEREAS, the Lower Neuse Basin Association (LNBA), formerly the Neuse Basin
Association was created in 1994 to establish a formal, voluntary' agreement between itself and
the North Carolina Division of Water Quality (DWQ), by which the LNBA is responsible for
surface water monitoring, reporting, and other cooperative efforts by NPDES dischargers within
the Lower Neuse River Basin to obtain water quality information in the basin.
Town of Clayton
Resolution to Join the Neuse River
Compliance Association
Attest:
\!AA Crf
Ken Reed
Town Clerk
AND WHEREAS, the formation of another body, the Neuse River Compliance
Association (Association) is necessary to obtain a group NPDES permit for Total Nitrogen, as an
alternative framework in which interested point source dischargers in the lower Neuse River
Basin can work cooperatively to reduce their individual and collective discharge of that nutrient
pollutant and comply with applicable limits. '
08/13/2002 14:27 PAGE 02
THEREFORE, the Town of Clayton agrees with the overall intent of the cooperative
arrangements set out in the By-Laws of the Neuse River Compliance Association and, at this
time, intends to join the Association and to participate according to said By-Laws.irf)
Douglas O&cCoimac'^-
Mayor
4.0 Evaluation of the LCWRF Unit Operations/Processes
The Unit Operations/Processes, incorporated in LCWRF are evaluated as follows for
adequacy of hydraulic capacity and overall LCWRF compliance with the effluent limits for 2.5 mgd
flow.
4.1 Mechanical Screen/By-Pass Manual Screen
The plant includes one (1) mechanical screen and one (1) by-pass manual screen for
screening of the influent wastewater at the plant.
The mechanical screen unit (HYCOR HELISIEVE UNIT, MODEL HLS500XL) consists of
I a spiral assembly, screen basket, transfer tube, press zone assembly, discharge section, drive system,
pivot stand, and controls. The design description of the screen is summarized as follows:
Number of unit, Hycor Helisieve Model HLS500XL 1
Peak hydraulic capacity, mgd 5.9
Screen opening, inch 0.25
24Channel width, inch
99Channel width, inch
35Screen installation angle, degree
3Drive horsepower, hp
Electrical service 230/460 Volts, 3 Phase, 60 Hz
Accessories: Level controls and timer for operation of the screen and screenings container
Based upon the attached manufacturer’s Hydraulic Performance Chart of the Helisieve HLS
500 XL Screen Unit with 1/4-inch diameter screen openings, it can be seen that the screen is
capable of handling up to 6.5 MGD peak flow. The design peak flow is 6.25 MGD which indicatesIthat the mechanical screen is more than adequate to handle the design peak flow at the plant.
Considering 23.28 inches downstream water level in the screen channel, controlled by a 9-
inch Parshall Flume, and using the attached screen hydraulic performance chart, the headloss
through the screen at 6.25 MGD peak flow is estimated to be 8.5 inches. Accordingly, the upstream
I -7-
water depth in the screen channel will be equal to 23.28” + 8.5” = 31.78 inches. The screen basket
height from the screen channel bottom is 32.01 inches which indicates the screen is adequate to
handle the 6.25 MGD peak flow.
The design description of the by-pass manual screen is summarized as follows:
Number of units 1
Unit capacity, mgd 5.9
Screen opening, inch 1
1 '/4Bar spacing, inch
Channel width, inches 24
Channel height, inches 99IScreen installation angle, degree 45
Method of cleaning Manual
The screen is designed for stand-by service and considering the screen openings and
associated head loss, when compared with the 1/4 inch mechanical screen opening, the manual by­
pass screen should be adequate to handle 6.25 MGD peak flow.
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HLS500XL Hydraulic Performance
Sieve with 1/4" Diameter Perforations
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10 15 20 25
Downstream Water Level [Inch]
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;6.5 MOD
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4.5 MpD
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4.2 Grit Removal System
I The plant includes a Vortex type grit removal system, manufactured by Jones and Atwood.
The system consists of a rotating impeller mechanism housed within a specifically designed tank to
I give sufficient retention to allow efficient grit collection, grit pump, grit concentrator, grit dewatering
screen and grit storage container. The design description of the grit removal system is summarizedIas follows:
Number of units, Jeta Vortex Type (By Jones and Atwood)1
Unit capacity, mgd 4
Percent grit removal of grit size greater than 100 mesh (0.15 mm) %60
Grit chamber diameter, ft.8
Grit chamber depth, ft.6
Grit chamber volume, gal.2,255
grit storage zone diameter, ft.3.25
Grit hopper depth, ft.3
Grit storage volume, cu. Ft.25
Propeller drive horsepower, hp.1
Grit pump capacity, gpm 200
Grit pump drive, horsepower, hp 3
Electrical service 460 Volt, 3 Phase, 60 Hertz
Accessories: Grit concentrator, grit dewatering screen, grit container and controls for grit
paddle and manual and time based operation of the grit pump.
Evaluation of the Grit Removal System for 6.25 MGD Peak Flow:
1. Check Inlet Velocity to Grit Chamber
Peak Flow, mgd (cfs)6.25 (9.670)
Inlet channel invert level, ft.228.92
Maximum water level in inlet channel 230.86
-10-
J/
Width of inlet channel, ft.1.5
Velocity in inlet channel at 6.25 MGD Peak Flow, ft. /sec.
3.32 ft./sec.
Velocity in inlet channel at 80% of Peak Flow, ft./sec.
I = 2.65 ft./sec.
As per the WEF Manual of Practice No. 8 - Design of Municipal Wastewater Treatment
Plant, the ideal velocity (at flows 40 to 80 percent of peak flow) in the influent channel
should be in the range of 2 to 3 ft./sec. The manufacturer of Vortex grit removal system
recommends that the influent channel velocity should not exceed 3.5 ft./sec. This indicates
that the existing grit removal system is within the acceptable velocity range of the inlet
channel at the design peak flow of 6.25 MGD.
2. Check for Hydraulic Retention Time
6.25Peak FlowI 2,255Grit Chamber Volume, gal.
Hydraulic Retention Time, SecondsI
X X
= 31.17 seconds
As per the WEF Map 8, typical hydraulic retention times for the Vortex grit removal
system at peak flow are in the range of 20 to 30 seconds. This also indicates that the
existing grit removal system will provide more than adequate hydraulic retention time at a
peak flow of 6.25 mgd.
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1,440 mn.
day
60 sec.
min.
2,255 gal
6,250,000 gal/day
9.67 cfs x 0.8
(230.86 - 228.92) x 1.5
9.67 cfs
(230.86-228.92) x 1.5
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4.3 9-Inch Parshall Flume
The influent flow to the LCWRF is continuously monitored by a 9-inch Parshall Flume. The
design description of the Parshall Flume is summarized as follows:
Parshall Flume size (throat width), inch 9
Flume capacity, mgd 0.058 - 5.73
Accessories:Ultrasonic level sensor, flow transmitter, indicator and totalizer
Evaluation of the Parshall Flume at 6.25 MGD peak flow indicated that maximum water depth
in the Flume will be 2 feet, 1.3 inches. The total Flume height is 4 feet, 2 inches which indicates the
existing Flume should be adequate to handle the peak flow.
4.4 Influent Pumps
The influent pump station includes three (3) 2,170 gpm capacity dry pit submersible pumps
and one 1,200 gpm capacity dry pit submersible pump. The drive horsepower for the 2,170 gpm
pumps is 75 hp, each and the drive horsepower for the 1,200 gpm pump is 40 hp. Two of the 2,170
gpm pumps are designed to operate with the float level control Variable Frequency Drives. The
controlled remaining 2,170 gpm and 1,200 gpm pumps are operated at constant speed by float level
controls. Operation of the two 2,170 gpm pumps will pump 6.25 mgd which is more than adequate
for handling peak flow at the plant. The other two pumps will be used for stand-by mode operation.
4.5 Activated Sludge (Oxidation Ditch Type) System
The plant includes the extended aeration (Carrousel Oxidation Ditch) type activated sludge
system. The design description of the system is summarized as follows:
Aeration Tanks (Carrousel Oxidation Ditches)
Total aeration tank volume, mil gal.1.90
1 Hydraulic retention time, hr., at 2.5 mgd avg. Daily flow 18.24
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Number of units: 0.75 MG capacity
1.15 MG capacity
1
1
1
1
Number of aerators in 0.75 MG tank, 25 hp
50 hp
200Total aeration horsepower, hp
105.26Aeration horsepower capacity, hp/mil. Gal
Aeration capacity of the aerator, lb 02/hp/hr at stand. Condition 3.5
Total aeration capacity, lb 02/hr 700
4,000Operating MLSS concentration, mg/L
16Sludge retention time, days
0.8MLVSS/MLSS ratio
F/M ratio, lb BODs/lb MLVSS/day 0.094
0.75Net sludge yield, lb solids/lb BODs removal
100Sludge recycle ratio, percent
I Clarifiers:
Number of clarifiers,
Clarifier volume, gal.
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Surface area, sq ft
277.53Surface overflow rate, gpd/sq ft at 2.5 mgd flow
Weir length, ft
4,304
18.52
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Weir overflow rate, gpd/lin ft
Solids loading rate, lb solids/sq ft/day,
including sludge recirculation flow, 2.5 mgd
BODs loading, lb BODs/day
lb BODs/1000 cu. Ft./day
55 ft diam clarifier
65 ft diam clarifiers
Total
55 ft diam clarifier
65 ft diam clarifiers
Total
55 ft diam clarifier
65 ft diam clarifiers
Total
55 ft diam x 12ft. SWD
65 ft diam x 14 ft. SWD
213,146
694,634
907,780
2,375
6,633
9,008
4,795.5
18.87
172.7
408.2
580.9
1
1
1
2
Number of aerators in 1.15 MG tank, 50 hp
75 hp
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Evaluation Of The Oxidation Ditch System For BODs Removal And Nitrification
1. Design Considerations
Average daily flow
BODs: Influent 230mg/L; Effluent 5.0 mg/L
TSS: Influent 230 mg/L; Effluent 10.0 mg/L
3.0 mg/LTKN: Influent 35 mg/L; Effluent
NHs-N: Influent 25 mg/L; Effluent 1.0 mg/L
I NOs-N: Influent 0 mg/L;Effluent 2.0 mg/L
28° CTemperature:
4,000 mg/LOperating MLSS Concentration
16 daysSludge retention time
Net Sludge Yield, Yn, lb solids/lb BODs removed 0.75
Oxygen Requirements, lb 02/lb BOD removed 1.5
4.6lb 02/lb NHs-N removed
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Sludge Recirculation/Waste Pumps
Number of recirculation pumps, 800 gpm capacity
1,100 gpm capacity
1,700 gpm capacity
Number of waste sludge pumps, 250 gpm capacity
Drive horsepower, hp, 800 gpm pump
1,100 gpm pump
1,700 gpm pump
250 gpm pump
2.5 mgd (Influent flow to 0.75 MG ditch = 0.987 mgd and
Influent flow to 1.15 MG ditch = 1.513 mgd)
1
1
1
1
15
25
40
5
NOTE: The sludge piping design also allows sludge wasting from the sludge recirculation
line.
NOTE: The reported year 2000 average BODS and NH3-N concentrations were
210 mg/L and 22 mg/L, respectively.
Winter = 12° C; Summer
2. Required Oxidation Ditch Volume
The required oxidation ditch volume is determined using the following equation:
Volume, mil. gal. =
Where BODrI
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MLSS
Volume, mil. gal.
I 3. Aeration Requirement for 0.75 MG Carrousel Ditch
Oxygen Requirements for BODs Removala.
= (230-5) mg/L BODs x 8.34 x 0.987 mgd x 1.5 = 2778 lb 02/day
b.Oxygen Requirement for Nitrification (NHs-N Removal)
35 -230 x
= 852 lb OVday
-15-
Considering influent flow to 0.75 MG ditch = 0.987 mgd, 5 mg/L nitrogen
requirement for each 100 mg/L BODs for cell synthesis, influent TKN = 35 mg/L,
effluent NHs-N = 1.0 mg/L and oxygen requirement for nitrification = 4.6 lb
O2/NH3-N nitrified, the total oxygen requirement for nitrification is:
Considering influent flow to 0.75 MG ditch = 0.987 mgd, influent BODs = 230 mg/L,
effluent BODs = 5.0 mg/L and oxygen requirement for BODs = 1.5 lb Oi/lb BODs
removed, the total oxygen requirement for BODs removal is:
Yn
SRT
(230 - 5) mg/L BODs x 8.34 x 2.5 mgd
4691 lb BOD/day
Net sludge yield = 0.75 lb solids/lb BODr
Sludge retention time required for complete nitrification = 16
days
Operating mixed liquor suspended solids concentration
4,000 mg/L
BOER xYnx SRT
MLSS x 8.34
5
100
4691 x 0.75 x 16
4000 x 8.34
= 1.687 mil. gallon
The available volume in the existing carrousel oxidation ditches = 0.75 MG +1.15 MG
= 1.90 MG which is more than adequate for the required ditch volume of 1.687 MG.
-1 mg/L NH^-N x 8.34 x 0.987 mgd x 4.6
I c.
SOR = AOR
(P
Co
a
T
e
SOR = 151.25
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Total Oxygen Requirement
= 2778 + 852
= 3630 lb 02/day
= 151.251b 02/hr.
d. Aeration Horsepower Requirement
The total required horsepower for the platform mounted mechanical aeration is
estimated as follows:
1375
5.195
C
sw
p =
Csw =
= 264.7 lb 02/hr
Considering 3.5 lb 02/hp/hr standard oxygen transfer rate of the EIMCO platform
mounted aerator, the required horsepower is:
405.68 LB 07 hr
3.5 lb 0^/hp/hr
= 75.63 hp
C
s
- C jeAT-20 xa
Where: AOR = Actual oxygen requirement = 231.8 lb 02/hr
Cs = Oxygen saturation value of clean water at standard conditions = 9.092
mg/L
Ratio of oxygen saturation value of waste to that of clean water = 0.95
Oxygen Saturation value of clean water for the site conditions of
Temperature = 28° C and actual barometric pressure (Pa = 14.575 psia) =
7.76 mg/L.
Residual concentration of dissolved oxygen desired during normal
operation = 2.0 mg/L.
Ratio of oxygen transfer in waste to that of clean water at the same
temperature = 0.8
Design temperature = 28° C
Temperature correction constant = 1.024
______________9.092______________
(0.95 x7.76 - 2.0) (1.024 j28"20 x 0.8
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4.
a.
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35 -230 x
I c.
SOR = AORI x a
P
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The existing 0.75 MG ditch is equipped with one (1) - 25 hp aerator and one (1) -50 hp
aerator. This will provide the total aeration horsepower of 75 hp. The required aeration
horsepower without the denitrification oxygen credit is 75.63 hp. In the oxidation ditch
some denitrification will occur that should supplement the oxygen need for BODs removal.
Accordingly, the current aeration capacity should be adequate to handle the expanded 2.5
mgd flow.
5
100
(PC
= 1306 lb OVday
Total Oxygen Requirement
= 4258 + 1306
= 5564 lb 02/day
= 231.8 lb Oz/hr.
d. Aeration Horsepower Requirement
The total required horsepower for the platform mounted mechanical aeration is
estimated as follows:
Aeration Requirement for 1.15 MG Carrousel Ditch
Oxygen Requirements for BODs Removal
Considering influent flow to 1.15 MG ditch = 1.513 mgd, influent BODs = 230 mg/L,
effluent BODs = 5.0 mg/L and oxygen requirement for BODs = 1.5 lb 02/lb BODs
removed, the total oxygen requirement for BODs removal is:
= (230-5) mg/L BODs x 8.34 x 1.513 mgd x 1.5 = 4258 lb 02/day
b. Oxygen Requirement for Nitrification (NHs-N Removal)
Considering influent flow to 1.15 MG ditch = 1.513 mgd, 5 mg/L nitrogen
requirement for each 100 mg/L BODs for cell synthesis, influent TKN = 35 mg/L,
effluent NHs-N = 1.0 mg/L and oxygen requirement for nitrification = 4.6 lb
O2/NH3-N nitrified, the total oxygen requirement for nitrification is:
-1 mg/L NH3-Nx 8.34 x 1.513 mgd x 4.6
e7’20
Where: AOR = Actual oxygen requirement = 231.8 lb 02/hr
SOR = Oxygen transfer rate, lb 02/hr at standard conditions = 3.5 lb 02/hp/hr
Cs = Oxygen saturation value of clean water at standard conditions = 9.092 mg/L
= Ratio of oxygen saturation value of waste to that of clean water = 0.95
Csw = Oxygen Saturation value of clean water for the site conditions of Temperature
= 28° C and actual barometric pressure (Pa = 14.575 psia) = 7.76 mg/L.
C
s
- c )
sw o /
Co
a
T
0
SOR = 231.8
x 0.8
Evaluation of Clarifiers:
1. Check for Surface Overflow Rates
Design average flow, mgd 2.5
Total surface area of the clarifiers, sq ft 9008
Surface Overflow Rate, gpd/sq ft
277.53 gpd/sq ft
The surface overflow rate at 5.8 mgd peak flow is 644 gpd/sq ft
-18-
2107.5
5.195
22)00,000 gpd
9008 sq ft
= Residual concentration of dissolved oxygen desired during normal operation
= 2.0 mg/L.
= Ratio of oxygen transfer in waste to that of clean water at the same
temperature = 0.8
= Design temperature = 28° C
= Temperature correction constant = 1.024
The existing 1.15 MG ditch is equipped with one (1) - 50 hp aerators and one 75 hp
aerator. This will provide the total aeration horsepower of 125 hp. The required
aeration horsepower without the denitrification oxygen credit is 116 hp. Accordingly,
the current aeration capacity should be adequate to handle the expanded 2.5 mgd flow.
______________9.092_________
(0.95 x7.76 - 2.0) (1.O24)28"20
= 405.68 lb OVhr
Considering 3.5 lb 02/hr/hp standard oxygen transfer rate of the EIMCO platform
mounted aerator, the required horsepower is:
405.68 IbO /hr
3.5 lb O^/hp/hr
= 115.9hp
= 116 hp
I
2. Check for Solids Loading Rate
Design average daily flow, mgd 2.5
I Sludge recirculation flow, mgd 2.5
Operating MLSS concentration, mg/L 4,000
Total surface area of the clarifiers, sq ft 9,008
Solids Loading Rate, gpd/sq ft
18.52 lb solids/sq ft/day
Evaluation of Sludge Recirculation Pumps
I 1. Check for Required Sludge Recirculation (hydraulic) Capacity
I
-19-
The sludge recirculation pumps are designed to operate one - 1,700 gpm pump to provide
2.5 mgd, i.e. 100 percent sludge recirculation pump capacity. The one - 800 gpm and one
- 1,000 gpm pump are used together to provide standby capacity and alternate pumps
operation flexibility to maintain even wear of the pumps. As per the WEF MOP 8, the
design sludge recirculation capacities are in the range of 75 to 150 percent of the average
daily influent flow. This indicates that the pump’s capacities are adequate for the sludge
recirculation needs, including standby capability.
As per the WEF MOP 8, the allowable maximum solids loading rate for efficient
secondary clarifier operation is in the range of 20 - 30 lb solids/sq ft/day. This indicates
that the existing clarifiers are more than adequate to handle the anticipated solids loading
at 2.5 mgd influent flow with 100 percent recirculation flow.
As per the WEF MOP 8, the average and peak allowable clarifier surface overflow rates
for secondary clarifiers are 560 gpd/sq ft and 644 gpd/sq ft, respectively .This indicates
that the existing clarifiers are more than adequate to handle the hydraulic loadings at the
plant.
4,000 mg/L x 8.34 x (2.5 + 2.5) mgd
9,008 sq ft
Sludge recirculation pumps: One - 800 gpm capacity
One - 1,000 gpm capacity
One - 1,700 gpm capacity
Evaluation of Waste Sludge Pumps
1. Check for Required Sludge Wasting Need
Waste sludge quantity Ib/day, at design 2.5 mgd flow = 3,882
Waste sludge quantity, gal/day, at design 2.5 mgd flow = 57,000*
Waste Sludge pump capacity, gpm = 250I
4.6 Evaluation of Alkalinity Requirement and Chemical Feed Facilities
a. Design Considerations
Average daily flow 2.5 mgd
TKN: Influent 35 mg/L; Effluent = 2.0 mg/L
NHa-N: Influent 25 mg/L; Effluent = 1.0 mg/L
NOs-N: Influent 0.0 mg/L; Effluent = 0.5 mg/L
BODs: Influent 230 mg/L; Effluent = 5 mg/L
Total Alkalinity 130 mg/L; Effluent = 50 mg/L
Total Nitrogen requirement for cell synthesis = 5 mg/L N/100 mg/L BODsIAlkalinity requirement for nitrification = 7.14 mg/L alkalinity/mg/L of NH3-N
Alkalinity recovery in denitrification = 3 mg/L alk/mg/L NOs denitrified
b. Amount of Nitrogen Nitrified
I
= 35 - 2.0
I = 21.5 mg/L NHa-N
-20-
I
Considering most of the organic nitrogen portion of TKN will be mineralized to NHs-N,
5 mg/L N/100 mg/L BODs nitrogen requirement for cell synthesis and effluent TKN =
2.0 mg/L, the total amount of nitrogen nitrified is:
Considering 57,000 gal/day waste sludge production and 250 gpm waste sludge pumping
capacity, the required sludge pumping can be accomplished in 3.80 hours/day. This
indicates that the waste sludge pumping capacity is adequate for sludge wasting needs.
The design of sludge recirculation and waste piping also allows for sludge wasting from
the recirculation line.
5 x 230
100
* Sludge quantity at 1.02 specific gravity of sludge and 0.8 % waste sludge solids
concentration.
I
- Nx
= 153.51 mg/L alkalinity
- Nx
= 52.5 mg/L alkalinity
I = 130 - 153.51 + 52.5
I = 28.99 mg/L
I
= 50 - 28.99I= 21.01 mg/L
1 d. Alkali (Magnesium Hydroxide) Feed System
1. Magnesium Hydroxide Dose:
= 21.01 mg/L alkalinity x 0.60 mg/L Mg (OH)?
= 12.6 mg/L Mg (OH)?
2. Magnesium Hydroxide Feed Rate
-21-
I
Considering the effluent residual alkalinity requirement of 50 mg/L for nitrification
process stability and improved sludge settling characteristics, the supplemental alkalinity
additional requirement is:
Considering the influent alkalinity of 130 mg/L, alkalinity loss of 178.5 mg/L in
nitrification and alkalinity gain of 75 mg/L in denitrification, the effluent alkalinity will be:
Considering the alkalinity requirement of 7.4 mg/L alkalinity/mg/L NH3-N nitrified, the
alkalinity loss during the nitrification process is:
Considering the plant average daily flow of 2.5 mgd, liquid Mg (OH)? slurry
concentration of 53% and Mg (OH)? bulk density of 12.3 lb/gal., the amount of liquid
Considering approximately 0.60 mg/L magnesium hydroxide is required to raise 1.0
mg/L alkalinity, the magnesium hydroxide dose requirement is:
3.0 mg/L alkalinity
mg/L N0^ - N
7.14 mg /L alkalinity
mg/LNH3-N
Considering all the NHs-N got converted to nitrate, 4.0 mg/L effluent NOs-N
concentration and the alkalinity recovery of 3.0 mg alk/mg NO3-N denitrified, the recovery
of alkalinity during the denitrification process is:
= 21.5 mg/L NH^
= (21.5 - 4.0) mg/L N03
c. Alkalinity Addition Requirement
I
I Ma(0H)2 required is:
I
= 40.32 gal/day
3. Bulk Storage Requirement
= 3,800 gal. X 1.5
= 5,700 gallon
4. Magnesium Hydroxide Feed Pumps
= 40.32 gal/day x 2.0 xI
= 3.36 gal/hr
I 4.7 Alum Feed System (For Chemical Phosphorus Removal, Polishing)
needed basis for compliance with the Total Phosphorus limit of 2.0 mg/L, on quarterly average
basis. The design description of the alum feed system is summarized as follows:
Number of 7,500 gal. Bulk storage tanks 1
I Number of 500 gal day tanks 1
Number of metering pumps 2
I Metering pump capacity, gal/hr 0-20
Feed points: Effluent weir boxes of the oxidation and/or distribution box to the clarifiers.
I -22-
The existing 6,000 gallon bulk storage tank at the plant is adequate for the bulk
storage need.
The existing two feed pumps are designed for 0 - 10 gal/hr, each, which are more than
adequate for feeding the required magnesium hydroxide.
12.6 mg/L x 8.34 x 2.5 mgd
12.3 Ib/galx 0.53
day
24 hr
The alum feed system at the plant is designed for chemical phosphorus removal on an as
Considering the Mg(OH)2 feed rate of 40.32 gal/day and applying peak to average
volumetric ratio of 2.0, the required size of the feed pump is:
Considering the Mg (OH)? is delivered as 3,800 gallon/truck load and providing bulk
storage of 1.5 times the truck load volume, the total Ma(OH)2 bulk storage required is:
I Evaluation of Alum Feed System for Phosphorus Removal:
Design Considerations1.
2.5Average daily flow, mgd
2.0
Liquid AlumChemical(s) considered for P removal:
2.0:1Design mole ratio of Al :PI 27Atomic weight of Al
31Atomic weight of P
122Atomic weight of A1 P04
78Atomic weight of Al (OH)3
11.1 Ib/galLiquid alum data:Bulk density = 1.33 g/cc
49Percent Ab (S04)3 14 H2O
8.3Percent AI2O3
4.37Percent Al
Feed Points:
Alum Requirement and Feed Rate2.
Chemically Removable Phosphorus as Pa.
I = 2.0 mg/L P x 8.34 x 2.5 mgd
= 41.7 IbP/day
I
= 1.345 lb mole P/day
-23-
Target phosphorus concentration to be removed chemically
during the biological process upset, mg/L
= 41.7 lb P/day
31
Effluent weir boxes of the oxidation ditches and/or distribution box to
the clarifiers
b.Alum Requirement
= 1.345
I = 2.69 x
I = 2.69 x
= 72.63 x
I
= 149.73 gallon liquid alum/day
Alum Dosec.
= 79.71 mg/L liquid alum
Bulk Storage Requirementd.
= 6,000 gallon
-24-
Considering the liquid alum is delivered in 4,000 gallon/truck load and providing
bulk storage of 1.5 times the truck load volume, the total liquid alum bulk storage
requirement is:
Considering the 149.73 gal/day liquid alum requirement, 11.1 Ib/gal bulk density
of liquid alum and design average daily flow of 2.5 mgd, the liquid alum dose for
chemical phosphorus removal is:
Considering liquid alum having 4.37 percent Al (8.3% as AI2O3 or 49% as A2I
(S0j)3 • 14 H2O) and density of liquid alum of 11.1 Ib/gal, the total quantity of
liquid alum required is:
Considering the design A1:P mole ratio of 2.0:1, the total Ib-mole of Al required
is :
149.73 gal/day x 11.1 Ib/gal
8.34 Ib/gal x 2.5 mgd
lb mole P
day
lb mole Al
day
lb mole A1
day
72.63 lb Al/day
11.1 Ib/gal x 0.0437
2.0 lb mole Al
1.0 lb mole Al
27 lb Al
1.0 lb mole Al
4,000 gal x j 5
truck load
lb mole P----------- xday
I
= 50 days
Alum Feed Pumpse.
= 149.73 x 2.5
I = 15.60 gal/hr
f.Sludge Production Due to Chemical P Removal
= 0.129 mmole/L Al added
A1P04 Sludge
-25-
The existing two alum feed pumps are designed for 0-20 gal/hr, each, which are
adequate for alum feed needs for chemical phosphorus removal.
Considering the liquid alum feed rate of 149.73 gal/day and applying peak to
average volumetric requirement ratio of 2.5, the required size of the alum feed
pump is:
The existing liquid alum bulk storage tank capacity is approximately 7,500 gallon
which is more than adequate for the bulk storage need. Using the liquid alum feed
rate of 149.73 gal/day, the total number of days of alum supply available from the
existing bulk storage tank is:
gal
day
7500 gal
149.73 gal/day
day
24 hr
= 0.0645 mmole/L x 122
= 7.869 mg/L AlPO4
Al (OH)s sludge = 0.0645 mmole/L x 78
= 5.031 mg/L Al (OH)s
Total Chemical Sludge Produced
= 7.869 + 5.031
= 12.9 mg/L
= 0.0645 mmol added / L AlPO^ produced
Stoichiometry of Sludge Production:
Al + PO4 = A1PO4
Al + 3 OH = Al (OH)3
2.0 mg/LP
31
(2.0 mg/ LPx 2.0x27/31
27
0.129 - 0.0645 = 0.0645 mmole in excess as Al (OH)3
= 12.9 mg/Lx 1.35
= 17.415 mg/L sludge
= 17.415 mg/L x 8.34 x 2.5 mgd
= 363 lb sludge/day
4.8 Polymer Feed System (for flocculation and improved clarification)
The polymer feed system at the plant is provided for flocculation and improved clarification to
enhance quality of the effluent discharge. The design description of the polymer feed system is
summarized as follows:
Number of 1,250 gal mix tank with mixer 1
Number of polymer solution transfer pumps 2
25Transfer pump capacity, gpm
3Number of 500 gal polymer solution storage tanks
Number of polymer feed pumps 1
25Polymer feed pump capacity, gal/hr
1Polymer blending system 0-24 gallon of neat polymer per day
Based upon the polymer dose of 0.25 to 0.5 mg/L at 0.5% solution strength, used at the plant.
the polymer feed rate for improved clarification is estimated to be 10.4 to 20.8 gal/hour. This
indicates that the polymer feed system is more than adequate to handle the clarification need, if1required, at the plant. It should be noted that the polymer feed system is used only during the time
of process upset or bulking situations experienced at the plant.
4.9 Tertiary Filtration
The tertiary filtration system at the plant consists of two shallow bed traveling bridge filters
-26-
with integral backwash pumps, indexing, backwash hood and piping. The design description of the
Considering the reported sludge production to be higher than the calculated sludge
production by use of stoichiometry it has been recommended that the calculated
sludge production value be increased by 35 percent. Accordingly, the chemical
sludge production is estimated to be:
filters is summarized as follows:
Number of filters (48’-8” x 12’-6”, each) DAVCO traveling bridge type 2
Filter area, sq ft, each 608.33
1,216.66Total filter area, sq ft
Filter Media:
I
As per the WEF MOP 8, the filtration rate normally used in design of the gravity filters are in
the range of 2 to 6 gpm/sq ft. As per the Ten State Standards for Wastewater Treatment Facilities,
the design filtration rate at peak flow should not exceed 5.0 gpm/sq ft. Considering the design
filtration rate of the existing filter system and the acceptable design hydraulic loading rates for
tertiary filtration system it is evident that the existing filter system is more than adequate to handle
the design average and peak daily flows at the plant.
4.10 Effluent Disinfection
The effluent disinfection at the plant consists of UV disinfection and back-up chlorineIdisinfection with dechlorination. The design description of the effluent disinfection system is
summarized as follows:
UV Disinfection (Trojan UV 3000 System)
4.75Peak daily flow, mgd
65UV Transmission, percent
30Filter effluent TSS, mg/L
1Number of UV ChannelsI
-Tl-
Material
Course Sand
Silica Sand
Anthracite
Depth
9 inches
5 inches
6 inches
1.42
2.85
3.56
7.13
Effective Size
0.80 to 1.20 mm
0.55 to 0.65 mm
1.00 to 1.10 mm
Filtration rate, gpm/sq ft, at avg. Daily flow - both filters online
one filter online
at peak daily flow - both filters online
one filter online
Accessories: Filter backwash pumps, traveling bridges, controls, and filter backwash waste
recycle pumps.
Number of UV banks 2
Number of UV modules per bank 13
Total number of UV modules 26
Number of UV lamps per module 8
Total number of lamps 208IAccessories:
Chlorine Disinfection System (Back-up Only)
Chlorine Contact Tanks
Number of tanks 2
I Tank volume, gal, each 39,000
Total tank volume, gal 78,000
Hydraulic retention time, min, at 2.5 mgd flow 44.92
Chlorine (Sodium Hypochlorite) Feed System
Number of hypochlorite feed pumps 2
Feed pump capacity, gal/hr 7.5
Number of 55 gallon hypochlorite storage container 4
Dechlorination System (Back-up Only)
Number of sodium bisulfite feed pumps 2
Feed pump capacity, gal/day 50
Number of 55 gallon sodium bisulfite containerI 1
Note:
Evaluation of the existing UV 3000 system by Trojan Technologies, Inc. indicated that the
existing UV 3000 system was designed using the UV lamps that decayed from 100% to 65%
output after one year. The system was installed in year 1995 and all the UV lamps have been
replaced with the new UV lamps that decay from 100% to 80% output after one (1) year. As per
-28-
The plant is also equipped with gas chlorine and sulfur dioxide feed equipment for
chlorination and dechlorination, respectively.
Control and instrumentation panel, automatic level controller and portable
cleaning tank.
the Trojan Technologies, Inc. evaluation, the UV system with new lamps will disinfect the peak
flow of 6.25 mgd. It should be noted that the system was designed using the 65% UV
transmission and 30 mg/L TSS concentration in the filter effluent. The filter effluent at the plant
has a UV transmission in the range of 70 to 75 percent and an average TSS concentration of <5.0
mg/L which indicates that the UV disinfection system will be more than adequate to disinfect the
peak flow at the plant.
The chlorine disinfection and dechlorination facilities are provided at the plant for standby and
emergency use only and are more than adequate to provide disinfection and dechlorination needs
of the effluent discharge.
4.11 Evaluation of Sludge Handling Facilities
Estimate of Sludge Quantity1.
Design Considerationsa.
2.5 mgdAverage daily flow
230 mg/L; Effluent = 5.0 mg/LBOD5:Influent
0.75 lb solids/lb BODrSludge produced in activated sludge system
17.415 mg/LSludge produced in Chemical P removal
0.8 percentPercent solids in waste sludge
1.02Specific gravity of the waste activated sludge
I b. Waste Sludge Production
1.
= (230 -5) mg/L BOD5 x 8.34 x 2.5 mgd x
= 3518 lb solids/day
I
I -29-
2. Chemical Phosphorus Removal (Polishing) Sludge
Chemical sludge quantity, Ib/day
= 17.415 mg/L x 8.34 x 2.5 mgd
Waste Activated Sludge
Sludge quantity, Ib/day:
0.75 lb solids
lb BOD R
I
= 57,000 gal/day
Percent Volatile Solids Content in Waste Sludgec.
I
% volatile solids =
= 72.98
“ 73%
Rotary Drum Sludge Thickening2.
I The waste activated sludge at the plant is thickened by a rotary sludge thickener
manufactured by Parkson Corporation. The design description of the sludge thickener is
summarized as follows:
Number of thickeners 1
Thickener capacity, gpm, at 0.7 to 1.0 percent feed solids 75 to 95
I Thickened solids concentration, percent 3.5 to 5.0
Accessories: polymer feed system, flocculation tank, wash water supply and controls.
I Evaluation of the Rotary Drum Sludge Thickening
Design Considerationsa.
Sludge Quantity
I
-30-
Operation Schedule
Polymer Dose
Considering that waste activated sludge contain 80% volatile solids and the chemical
phosphorus removal sludge contain 80% volatile solids and the chemical
phosphorus removal sludge contain 5% volatile solids, the percent volatile solids, the
percent volatile solids in the combined sludge is:
3,881 Ib/day
57,000 gal/day at 0.8% solids
8 hrs/day, 5 days/wk
6 to 8 lb polymer/dry ton of solids
= 363 lb solids/day
3. Total Sludge Production, Ib/day
= 3518 + 363
= 3881 lb solids/day
4. Total Sludge Volume, gal/day
3881 Ib/day
" 8.34 x 1.02 x 0.008
(80 x3512) + (5 x 363)
3518 + 363
Thickened solids concentration 4.0 Percent
I
Sludge Loading, gpm =
= 166 gpm
Required Rotary Drum Thickener Sizec.
Thickener operation, hr/day =
= 14.3 hours/day
3. Sludge Stabilization/Storage Tanks
-31-
i
The existing rotary drum sludge thickener has a design capacity of 75 gpm at 1.0
percent feed solids concentration. The solids loading capacity is 375 lb dry
solids/hr. The equivalent thickener capacity at 0.8 percent solids is approximately 93
gpm. This indicates that for 8 hrs/day, 5 days/wk operation schedule, additional
rotary drum thickener capacity of 166 - 93 = 73 gpm will be required to handle the
design sludge thickening need.
If no addition to the thickener capacity is considered, then the existing 93 capacity
thickener will be required to operate at the following hours/day on 5 days/wk basis:
Considering 57,000 gal/day sludge production and thickener operating schedule of
8 hrs/day, 5 days/wk, the sludge loading to the rotary drum thickener is:
From the above, it can be seen that by extending the operating hours of the sludge
thickening operation, no additional thickener capacity is required to handle the
sludge production at a design average flow of 2.5 mgd. It should be noted that the
waste activated sludge can also be discharged directly to the existing sludge
stabilization/holding tanks. The Town is also planning to provide one additional 250
gpm thickener for which the plans and specifications for submittal to the State are
being prepared at the present time.
57,000 gal / day x 7 day / wk
8 hr/day x 5 day/wk x 60 min/hr
57000 gal / day x 7 day / wk
93 gpm x 5 day / wk x 60 min / hr
The plant includes one 90,000 gallon capacity and another 360,000 gallon capacity
sludge stabilization/storage tank. The 90,000 gallon tank is equipped with a 5 hp floating
mixer and a 220 SCFM diffused aeration system. The 360,000 gallon tank is equipped
with a 30 hp floating mixer and 1,100 diffused aeration capacity. Considering a
discharge of 11,295 gal/day thickened (4%) sludge from the thickener to the sludge
stabilization/storage tanks the total hydraulic sludge retention time provided by the tanks
is 39.84 days which is more than adequate to meet the 30-day storage requirement by the
State regulations for land application of residuals. Please note that the Town is also in the
process of providing one additional 360,000 gallon capacity sludge stabilization/storage
tank for which plans and specifications are being prepared for submittal to the State.
b. Sludge Loading to Rotary Drum Thickener
4. Sludge Drying Beds
Sludge Disposal5.I
I
I
I
I
-32-
Vector Attraction Reduction: Compliance with the Vector Attraction Reduction for
land application of sludge is achieved by using one of the following options: Option 1 -
Reduction of Volatile Solids Content [503.33 (b) (1)], Option 3 - additional Digestion of
Aerobically Digested Sludge [503.33 (b) (1)], Option 5 - Aerobic Processes
(composting) at greater than 40 °C 503.33 (b) (5)], Option 6 - Additional of Alkali
[503.33 (b) (6)] , Option 9 - Injection [503.33 (b) (9)], or Option 10 -Incorporation of
Sludge into Soil [503.33 (b) (10)]. The Town has primarily used Option 5, Option 6,
Option 9 and Option 10 for compliance with the vector attraction reduction requirements.
Class A Pathogen Reduction: Compliance with Class A pathogen reduction is
achieved by using Alternative 5 - Use of composting PFRP [503.22 (a) (7)]. It should be
noted that McGill Environmental Service, one of the Town’s sludge disposal contractors
use Alternative 5 for complying with Class A Pathogen reduction requirements.
For disposal of sludge by application, the Town will comply with the Pollutant Limits,
Pathogen Reduction, Vector Attraction Reduction, General Requirements and
Management Practices, and frequency of monitoring, record keeping, and reporting
requirements contained in the EPA 503 sludge regulations and the Non-Discharge
Permits for land application of sludge.
The current practices of sludge disposal by the Town include: (1) land application of
stabilized sludge using private contractors (East Coast Resources - Permit No.
WQ0000506 and Granville Farms - Permit No. WQ0004801) in accordance with
requirements set forth in the State and EPA 503 sludge regulations and the Non­
Discharge Permits, (2) sludge dewatering, composting and disposal using McGill
Environmental Services, (Permit No. WQ0006816) and (3) dewatering and disposal at
Johnston County’s and Waste Industries Sampson County landfills, using private
contractors(s).
The plant includes nine (9) - 97’ x 20’, each , sludge drying beds providing total bed
area of 17,460 sq. ft. The beds are used only in emergencies when sludge disposal needs
warrant the use of the sludge drying beds for dewatering. The dewatered sludge from the
beds is normally disposed of at Johnston County’s landfill and Waste Industries
Sampson County landfill.
Class B Pathogen Reduction: Compliance with the Class B pathogen reduction is
achieved by using one of the following alternatives: Alternative 1 - Monitoring of Fecal
Coliform [503.32 9b) (2)] or Alternative 2 - Use of Lime Stabilization PSRPS [503.32
(b) (3)].