DEQ-CFW_00062559

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NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
FAYETTEVILLE REGIONAL OFFICE
DIVISION OF WATER QUALITY
May 5, 1999
Mr. Michael Johnson
Environmental Coordinator
DuPont Fluoroproducts
22828 NC 87 Hwy West
Fayetteville, NC 28306
SUBJECT: Installation of "Biomixer"
DuPont WWTP
NPDES Permit No. NC0003573
Bladen County
Dear Mr. Johnson:
This letter is follow-up to several conversations held with David Goodrich,
Supervisor NPDES Unit, and myself concerning the installation of a `Biomixer"
to enhance aeration in the main activated sludge aeration tank. Based on those
conversations and a review of the information provided, you may proceed with
the installation and operation of the unit described.
Please be advised that all NPDES permit conditions and limitations must
be met during and after the installation of this unit.
If you have questions or comments concerning this matter, please do not:
hesitate to contact me at 910-486-1541.
Sincerely,
Paul E. Rawls
Water Quality Regional Supervisor
PER/bs
cc: David Goodrich, NPDES Unit
DWQ Central Files
FRO File, DuPont
225 GREEN STREET, SUITE 714, FAYETTEVILLE, NORTH CAROLINA 28301-5043
PHONE [phone] FAX [phone]
AN EQUAL OPPORTUNITY / AFFIRMATIVE ACTION EMPLOYER - 50% RECYCLED/109o' POST -CONSUMER PAPER
DEQ-CFW 00062559

aUPONT� `�'
DuPont Fluoroproducts
Mr. David Goodrich
NC DENR
Division of Water Quality
Permits & Engineering Unit
P. O. Box 29535
Raleigh, NC 27626-0535
RE: NPDES Permit No. NC0003573
Dear Mr. Goodrich:
REE 4'
APR 3 0 1999
FAYETTEVILLE
REG. OFFICE
DuPont Fluoroproducts
22828 NC 87 HWY W.
FAYETTEVILLE, NC 28306
April 21, 1999
This letter is to inform you of a planned change to the DuPont — Fayetteville Works
Wastewater Treatment Plant (WWTP), which will enhance the WWTP's performance by adding
additional oxygen and mixing to our main activated sludge Aeration Tank.
DuPont does not believe that this change requires any approval or authorization by the
Division of Water Quality prior to beginning construction for the following reasons:
1. The referenced NPDES Permit states in Part II Section E(2) that notice must be given to
the Director of any planned alteration if the alteration is a new source, if it could
significantly change the nature or increase the quantity of pollutants, or if it results in a
significant change in the sludge use or disposal practices. The proposed alteration is not,
nor does, any of the above.
2. The referenced NPDES Permit states in Part III Section A that no construction of
wastewater treatment facilities or additions to add to the plant's capacity can begin until
written approval is received from the Department. The proposed alteration does not
constitute a wastewater treatment facility, nor is the capacity of the WWTP being
increased.
However, in case NCDENR believes that your approval is needed prior to DuPont proceeding
with this enhancement, DuPont is providing information about this planned change for your
review.
Currently the DuPont WWTP Aeration Tank uses a diffused air system to oxygenate the
wastewater for the aerobic biodegradation using activated sludge. The planned enhancement is
to install an air injection and mixing device (Biomixer) into the existing Aeration Tank.
Attachment 1 is a drawing of the Biomixer, which shows it to be a floating platform with an
adjustable submerged rotator assembly that diffuses the air.
To improve the efficiency of the WWTP, DuPont plans on installing the Biomixer in the
front half of the Aeration Tank where it will inject compressed air through rotating, submerged
rotors. This action provides additional dissolved oxygen for the wastewater's activated sludge in
a region of the tank that has a measurable oxygen deficiency, and also mixes the contents of the
tank to ensure a more homogenous mixture.
E. I. du Pont de Nemours and Company ® Printed on Recycled Paper
FL-4
DEQ-CFW 00062560

Mr. David Goodrich
NCDENR Division of Water Quality
April 21, 1999
The Biomixer will be flotation mounted inside the Aeration Tank, and will be fixed in one
location via a floating walkway and mooring cables. Attachment 2 is a "bird's eye view" of the
equipment layout and shows the location of the Biomixer inside the Aeration Tank. Attachment
3 is a side view of the Biomixer and the floating walkway.
The Biomixer's rotation provides not only mixing of the incoming wastewater, but also
creates ultra -fine air bubbles by shearing off emerging bubbles as they are forming on the rotating
diffusers. These extremely small bubbles increase the oxygen transfer rate. Additionally, the
shearing force also reduces biological growth and build-up that can foul the diffuser.
The depth of the Biomixer's diffusion rotors is adjustable, and allows for variable power
input by adjusting the submergence depth of the diffusers. The greatest submergence depth
requires the greatest power to the air blower to realize the maximum air delivery. Also, the
greater the submergence depth results in a higher dissolved oxygen transfer rate since the
individual air bubbles are in the water for a longer time.
Attachment 4 gives some of the general specifications of the Biomixer (model 400-85-15),
including the 85 horsepower motor, the air injection rate of 1,691 CFM, and the fourteen blades
of the rotating section. It should be noted that 75 HP of the 85 HP motor will be used to drive
the air blower of the Biomixer, and the remaining 10 HP will be utilized to rotate the blades
underwater.
Attachment 5 shows the DuPont Specifications for the Biomixer, with the specifics of the
piece of equipment to be used in this enhancement.
Hopefully this information is adequate for NCDENR's needs. Should you require additional
information, or if you have any questions, please contact me at [phone].
Michael E. Johnson
Environmental Coordinator
Attachments
cc: Mr. Paul Rawls, NCDENR Division of Water Quality, Fayetteville
DEQ-CFW 00062561

• THIS DRAWING CONTAINS PROPRIETARY INFORMATION AND DESIGNES CAT—FEFS.DWG
OWNED BY BIOMIXER CORPORATION. ALL DESIGNES, MANUFACTURING,
REPRODUCTION, USE. PATENT RIGHTS, AND SALES RIGHTS REGARDING SCALE 1 " 5'
THE SAME ARE EXPRESSLY RESERVED BY BIOMIXER CORPORATION
MODEL 400-85-15 U.S. PATENT NO. 5681509 FOREIGN PATENTS APPLIED FOR CSPEC #1231
ATTACHMENT 1
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PROJECT No. " faTION WER—EAL: OMIXER -GENERAL VIEW of. CHECKED:
05.08.98 WEICHT: 9500 LOS
DEQ-CFW 00062562

INLET CAP
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OWNED BY BIOMIXER CORPORATION. ALL DESIGN$, MANUFACTURING.
REPRODUCTION. USE. PATENT RIGHTS, AND SALES RIGHTS REGARDING
THE SAME ARE EXPRESSLY RESERVED BY BKAIIXER COMbORATION
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DEQ-CFW 00062565

ATTACHMENT 4
BIOMIXER CORPORATION
400 Series Standard Submergence Floating Aeration, Mixing and Control System .
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Model No.
400 - 85 -15
120315
Horsepower
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85
429-
Blower Size
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7L
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CFM
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1,691
-2,488
Number of Blades
-8-
14
48-
Max. Submergence - Ft.
15
Voltage
230/460
Amperage
189.4/94.7�-
Min. Blade Diameter - Ft.
448-
18
48-
Max. Blade Diameter - Ft.
-26- �
25
Weight - Lbs.
-40,GN-
10,900
-42,400-
Dimensions - W x L x H
38' - 6" x 40' - 5" x 28' - 6-
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ATTACHMENT 5
DUPOKI
ST &A epparnCAMNS
I. PRODUCT
A. AERATION-MI(ING SYSTEM
i. Aerator shall be a Biomixer Aeration -Mixing and Control System Model 400-85-15.
B. SERVICE CONDITIONS
1. Aerator will be utilized to provide aeration for the activated sludge system.
Anticipated mixed liquor suspended solids In the aeration basin concentration is in
the range of 1,500 to 3,500 mg/I. The power density in the aeration basin will be in
the range of 35 to 75 hp per million gallons.
C. PERFORMANCE CHARACTERISTICS
1. The aerator shall have the following characteristics:
a) Nominal Horsepower (total)
b) Operating Depth (maximum)
c) Minimum Mixing Diameter
d) Minimum 02 Dispersion Diameter
e) Minimum Transfer Rate in Domestic Wastewater
D. AERATOR CONSTRUCTION AND MATERIALS DETAILS
85 hp
15ft
130 ft
400 ft
2.6 lb. 02/hp/hr @
D.O. = 0.5 mg/I.
1. General:
a) The 85 hp Biomixer 400-85-15 Aeration -Mixing and Control Unit will be
equipped with:
DuPont Contract specs
(1) A floating frame structure.
PAGE 1
12j1i96
DEQ-CFW 00062567

ATTACHMENT 5
(2) Power Module. (continued)
(3) Control System.
(4) Rotation System.
(5) Automatic diffuser retraction system capable of 15 ft. maximum
submergence.
(6) One set of composite fine pore diffuser blades.
2. Structure:
a) The floating frame structure shall consist of four (4) galvanized truss
weldments and galvanized central attachment frame. Trusses and frame
shall be supported by two (2) dosed cell foam filled polyethylene floats and
one (1) power module float. Mounted to the central attachment frame shall
be the air shaft, air shaft rotation system, the air shaft retraction system, and
the air delivery system.
3. Mechanical:
a) Rotation drive shall consist of one (1) Sumitomo cyclo-helical gearmotor,
vertical down solid output shaft, 62.1 nominal ratio, 1750 RPM, 9.40
mechanical horsepower rating, 19,000-inch lbs. output torque rating, with 5
HP, 1750 RPM, 3/60/230/460 volt, TEFC integrally mounted motor, grease
filled gearbox, with weatherproof option.
b) Retraction drive shall consist of one (1) Sumitomo worm drive gearbox and
motor with corrosion resistant drive chain. Bushings are self -lubricated
bronze with polished stainless steel shaft.
4. Diffuser Blades:
a) One set of dynamic fine pore diffuser blades shall be included for the unit.
Each blade is a composite structure consisting of a stainless steel spar,
urethane outer structure and a polyethylene fine pore diffuser material.
Included are all required seals and mounting hardware.
5. Blower:
a) Blower will be a Gardner Denver/Sutorbilt positive displacement rotary lobe
type contained within an enclosed structure called the power module.
Included in this structure will be the blower motor, an Inlet air filter, an Inlet
silencer and discharge silencer.
DuPont contract Specs PAGE 2 12/7/98
DEQ-CFW 00062568

ATTACHMENT 5
(continued)
6. Motors:
a) The blower motor shall be a General Electric premium efficiency 75 hp,
230/460 3 phase 60 Hz with TEFL enclosure.
b) The retraction drive motor shall be a General Electric, 2 hp, 230/460 3 phase
60 Hz.
c) The power required for the system is 3 phase 460 volts/95 amps. 230
volts/190 amps power is available as an option.
7. Operator interface:
a) Operator interface for the system consists of a digital operator interface with
extended temperature liquid crystal display and elastomeric keypad.
included for operator interface is a NEMA-4 control potentiometer which
allows manual and automatic selection of dissolved oxygen (DO) production
levels (horsepower), without requiring the use of the keypad and menu
structure.
8. Electric Monitoring and Control:
a) Included with the Biomixer unit shall be one (1) Biomixer Model C-400-85
control package built to NEC standards by Cutler -Hammer. The control
system to be furnished shall be installed in a NEMA-4 panel. In the NEMA-4
panel are all electrical components required for normal operation of the
Biomixer unit and include:
(1) Main breaker and disconnect handle.
(2) Programmable logic controller.
(3) Electrical cable from the Biomixer control panel to the floating
Biomixer unit up to 50 feet. Cable over 50 feet available as an option.
(4) Power distribution blocks.
(5) Blower motor reduced voltage starter.
(6) Variable speed rotation drive.
(7) Retraction drive breaker and reversing motor starter.
(8) Control transformer and breaker blower motor starter.
DuPont contract specs
PAGE 3 12/7/98
DEQ-CFW 00062569

(9) Interposing control relays.
(10) Cooling fan.
(11) 24V DC power supply and breaker.
9. Sensor Package:
ATTACHMENT 5
(continued)
a) Included with each Biomixer shall be one (1) Biomixer Model SD-400-85
sensor package. Each sensor package shall include:
(1) Linear transducer to monitor diffuser depth.
(2) Pressure transducer to measure system Pressure-
(3) Rotation drive power.
(4) Rotation drive gearbox temperature-
(s) Blower gearbox oil temperature-
(6) Filter vacuum restriction.
(7) Retraction limit switch for both the upper and lower positions.
(8) Sensor cable from the Biomixer
over 50 feet available as an option.Biomixer
unit up to 50 feet. Cab
10. Coatings:
a) All fabricated steel parts shall be 304InASTM sbeel or hot -dip nda d specification Ai23d-
steel after fabrication, in accordance with
89a.
DOOM Cm"d Specs
b) All motors, gearboxes, blowers, silencers and similar items shall be standard
finish as provided by the original manufacturer.
PAGE 4
Y
DEQ-CFW 00062570

ATTACHMENT 5
(continued)
11. Power Cables:
a) Buyer will furnish sufficient 4 AWG four conductor UL approved electrical
cable to the Biomixer Control Panel. Biomixer shall furnish the water
submersible cable from the Biomixer Control Panel to the Biomixer Systems
motors up to 50 feet. Optional lengths over 50 feet are available. The
electrical cable shall be one piece of continuous length. No splices will be
permitted. Only flexible type copper stranded cable with four individually
jacketed conductors bound together with a non -wicking filler and sheathed In
a PVC, neoprene, or equal over jacket shall be used. The jacketed cable shall
be Impervious to sunlight, fungus, oil and grease, gasoline and kerosene.
Buyer to advise Seller of any other substances not included above.
12. Fasteners:
a) All fasteners shall be hot -dip galvanized.
13. Mooring Cables:
The aerator -mixing and control system shall be moored by the walkway
attachment and two cables, one attached to each of the auxiliary trusses.
Anchor cables shall be of 304 stainless steel of 1/4 inch minimum diameter 7 x 19
strand. Ali mooring hardware shall be of 304 stainless steel. All mooring cables
and hardware are provided by Buyer.
II. EXECUTION
A. Blomixer's Representative Services
1. A Biomixer representative shall supervise Installation of the aerator and the electrical
connections in the field. Biomixer is also responsible for instructing the Buyer's
personnel in the operation and maintenance of the equipment. Biomixer shall certify
the correctness of the installation. A minimum of five (5) days of a Biomixer
representative's time shall be provided at Buyer's expense. Travel and living
expenses for Biomixer representative shall be paid by Buyer.
DuPont Contract specs
PAGE 5
12/7/ 8
.l —
DEQ-CFW 00062571

= NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
FAYETTEVILLE REGIONAL OFFICE
FAX COVER SHEET
FAYETTEVILLE REGIONAL OFFICE
DATE: ✓�
TO: rr-
FAX #: 9) O (0 28 i 4 -�
FROM: �� i�
Number of pages, including cover:
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225 GREEN STREET, SUITE 714, FAYETTEVILLE, NORTH CAROLINA 28301-5043
PHONE [phone] FAX [phone]
AN EQUAL OPPORTUNITY /AFFIRMATIVE ACTION EMPLOYER - 50% RECYCLED/10% POST -CONSUMER PAPER
DEQ-CFW 00062572