DEQ-CFW_00061767

__see REV. 12-79
aUPONT
ESTASUSNFD 180.
E. I. DU PONT DE NEMOURS & COMPANY
1MCORroRAT[0
P. O. DRAWER Z
FAYETTEVILLE, N. C. 28302
POLYMER PRODUCTS DEPARTMENT
Arthur C. Mouberry, Permit Branch Head
Division of Environmental Management
Department of Natural Resources and
Community Development
P.O. Box 27687
Raleigh, NC 27611-7687
Dear Mr. Mouberry:
March 2. 1988
n;
MAR 4 .198E
PERMITS & ENGINEERINC
The purpose of this letter is to submit to you plans and
specifications for a wastewater treatment plant modification in
accordance with the Part III B requirement of our NPDES Permit,
NC0003573 for Fayetteville Works of E.I. du Pont de Nemours & Co.. Inc.
These modifications are required to adequately handle
expansion for the existing Butacite® manufacturing operations. In
addition, the aeration tank erected with these modifications frees up
a basin which will be converted to an aerobic sludge digester to be
used in conjunction with an independent landfarm sludge disposal
project for later permit submission.
At this time, no change in permit limits are being
requested. However, the expansion impacts are currently being
reviewed with respect to industry guidelines which could result in a
full permit application for relief at a later time. Therefore, this
submission is strictly to gain approval for the construction of the
aeration tank and associated modifications.
The facility modifications have been designed by the Du Pont
Engineering Department in Wilmington, Delaware, who designed the
original plant and all subsequent modifications. Attached as a design
package are:
1. A summary memorandum describing the design basis and
parameters.
2. Two equipment and piping arrangement blueprints — W388407 and
W993519.
3. Two piping and instrument diagrams on the aeration tank,
sludge digester (converted aeration basin), and existing
clarifiers — W945772 and 992699.
BETTER THINGS FOR BETTER LIVING
DEQ-CFW 00061767

9
MARCH 2. 1988
=' j�(tTHUR C . MOUBERRY
ns from your office, I have attached two cspcosY f the
Per instackago
design package to this letter and one set to Mr. Nolan
We are desirous of initiating this work ruction activities
as soon as e
in order to efficiently dovetail with other const
and shutdowns and thus are willing to provide
whatever assistanceyouis
necessary to expedite approval. gladly
engineering review personnel in Raleigh at your convenience if this
will speed the review process.
In case of any questions
or
absencena3ohnneed.
Holianase at Ext. 274
at [phone] Ext. 155 or, y
or John Nagle at Ext. 280.
Sincerely
0 1014
Thomas W. Olcott
Environmental Control Coordinator
TWO: mn
2105M
CC: M.J. Noland. Regional Supervisor
Fayetteville, NC
DEQ-CFW 00061768

ATTACHMENT A
DESCRIPTION AND DESIGN BASIS OF
EXPANDED WASTEWATER TREATMENT FACILITIES
s DU PONT FAYETTEVILLE WORKS
BLADEN COUNTY, NC
Background
PERMITS & ENGINEERING
The Du Pont Company's Fayetteville Works manufactures ButaciteA
polyvinylbutyral sheeting, DymetrolA elastomeric tapes, TRXA
toughener, NafionA.fluorocarbon membrane, and nylon strapping.
A major expansion in production planned in the Butacitek area
will increase the wastewater flow and organic load. The existing
wastewater treatment facilities must be expanded to handle this
increase. The treatment system expansion has been designed and
is described below, along with an explanation of the design
basis.
Existing Facilities and Capacity
The existing wastewater treatment system at the Fayetteville
Works employs activated sludge treatment and consists of the
following units:
o Emergency retention tank - 180,000 gallons
o Equalization tank - 250,000 gallons
o Aeration basin - 745,000 gallons
o Surface aerators -,six 40 hp floating units in aeration basin
o Two secondary clarifiers - one 45 ft and one 55 ft diameter
Wastewater is collected in a sump in the wastewater treatment
area and is pumped into the above -ground equalization tank.
Wastewater flows by gravity from the equalization tank to the
aeration basin to the clarifiers. Combined clarifier overflow is
monitored for flow and sampled at Outfall 001. -Clarifier
underflow sludge is returned to the aeration basin by pumping.
Excess sludge is currently disposed in lagoons on plant property.
However, Du Pont has agreed to eliminate this practice. A
separate project,'.independent of the wastewater treatment
expansion,is underway to dewater - the waste activated sludge by
belt press and spread the dewatered sludge on plant property to
grow a Bermuda grass crop.
Expanded Svstem
The expanded system will utilize the major existing facilities
listed above. However, a new aeration tank will be installed to
replace the function of the aeration basin. The aeration basin
will be converted to use as an aerobic digester. The important
features of the aeration tank and associated appurtenances are
listed below:
rt,,, ...:
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Carbon steel tank, 112 ft diameter x 20 ft liquid depth plus 4
ft freeboard. This provides a liquid volume of 1.5 million
gallons.
Two 4000 scfm blowers to deliver diffused air in the tank.
Air distribution laterals spaced at 5 ft 7 in intervals, with
"stations" spaced at 5 ft 7 in intervals along the bottom of
each lateral. There are a total of approximately 315
"stations" in the tank. Each "station" is a set of. two 7/16".
orifices.
System Design Parameters
Studies have shown the wastewater to have the following
oxygenation characteristics:
o Alpha: 0.80
o Beta: 0.98
This means that at a minimum dissolved oxygen content of 1.5
mg/l, the ratio of field oxygen transfer to standard transfer
(ie, N/No) is between 0.65 and 0.66 for temperatures between 100C
and 30° C.
With full blower capability (8000 scfm), the air delivery for
each of the 315 stations is 25 scfm/station. Clean water studies
with diffused air through open orifices has shown that the
transfer efficiency at 20 ft water depth at 25 scfm per station
is 3.8 lbs/hr per station at standard conditions (clean water,
20°C). The maximum standard transfer in the tank is therefore:
315 x 3.8 = 1200 lbs Oz/hr or 28,700 lbs.Oz/day.
The transfer efficiency under the waste conditions is:
0.65 x 28,700 = 18,700 lbs 0Z/day.
Studies at Fayetteville have shown that oxygen utilization and
BOD removal is related by the factor 1.34 lbs 02/lb BOD5 removed.
The BOD5 capacity of the system is therefore:
18,700/1.34 = 13,900 lbs BOD5 removed/day.
At Fayetteville the'peak (95th percentile) raw wasteload BOD5 is
historically 2.0 times the long-term average, expressed as
lbs/day.. Thus a peak BOD5 of 13,900 lbs/day relates to a long-
term average of about 7000 lbs/day. For proper operation the
Fayetteville site must operate at an FJM ratio of no more than
about 0.2 lbs BOD5/lb MLVSS-day on a long-term average basis.
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At an average load of 7000 lbs/day BODS with an MLVSS
concentration of 3000 mg/l in the 1.5 million gallon aeration
tank, the F/M would be:
7000/(3000 x 1.5 x 8.34) = 0.19 lbs BODS/lb MLVSS-day.
With the MLVSS held at 3000 mg/l, and a ratio of VSS/TSS of 0.85
giving a total MLSS concentration of 3500 mg/l, optimum settling
characteristics are achieved. The clarifiers at the Fayetteville
Works have a combined surface area of 3964 sq ft. GLUMRB
Standards recommend a peak overflow rate of 700 gpd/sq ft (Great
Lakes -Upper Mississippi River Board of State Sanitary Engineers,
Recommended Standards for Sewage Works, 1971). This would
suggest a peak flow capacity of 2.7 million gpd at the
Fayetteville Works. liowever, ,the industrial activated sludge at
Fayetteville cannot be expected to perform as well. It is
recommended that a peak overflow rate of only 500 gpd/sq ft be
applied. This gives a peak capacity of 2.0 million gpd.
Historically, peak (95th percentile) flow has been 1.30 times the
long-term average. Therefore, the average flow capability of the
clarification system at Fayetteville is 1.5 million gpd.
Sludge production at Fayetteville is 0.225 lbs TSS/lb BODS
removed, based on average loadings. At an average of 7000
lbs/day BODS, 1575 lbs/day of sludge would be produced. This
sludge would be pumped to the aeration basin, which will be
converted to an aerobic digester. Periodically the sludge will
be settled and decanted to a concentration of 2% solids (20,000
mg/1) in the basin. The detention of the 745,000 gallon basin
will be:
745,000 x 0.02 x 8.34/1575 = 79 days.
This is more than adequate detention for complete aerobic
digestion and stabilitzation.
In summary, the expanded treatment system will have the following
capacities:
BOD5
Peak: 13,900 lbs/day
Average: 7,0O0 lbs/day
Flow:
Peak: 2.0 million gpd
Average: 1.5 million gpd
It is recognized that these capacity values are applicable for
the major equipment items, including the aeration tank, blowers,
air distribution system and clarifiers. Modifications in pumping
and piping would have to be made in order to fully accommodate
the increased flow and increased sludge recycle requirements.
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Anticipated Wasteload After Expansion -
The current ButaciteA expansion is expected to result in the
following raw waste load characteristics:
BOD5
Peak: 10,000 lbs/day
Average: 5,000 lbs/day
Flow:
Peak: 1.45 million gpd
Average: 1.1 million gpd
The character of the waste will be unchanged from the present
since the manufacturing processes are intended to be essentially
similar to current. Comparing the expected loadings to the
expanded system capacity, it is obvious that the expanded system
will be fully capable of handling the ButaciteA expansion.
DEQ-CFW 00061772