NC0026051_correspondence_19790831

CITY OF DURHAM
NORTH CAROLINA
Division of Water Resources
OFFICE OF
THE DIRECTOR
Mr. Neil S. Grigg
Acting Director
Division of Environmental Management
Department of Natural Resources and
Community Development
Post Office Box 27687
Raleigh, North Carolina 27611
Dear Mr. Grigg:
Subject:
SEP 10 1979
PER;1I S AND
ENGIITEERING
August 31, 1979
Durham County Wastewater Treatment Plant
NPDES #NC0026051
Draft Permit
The City of Durham operates the Durham County Wastewater Treatment
Plant (WWTP) through a contractual agreement with Durham County. For
this reason the City of Durham would like to provide the following comments
in response to the "Public Notice" of intent to issue a new National
Pollutant Discharge Elimination System (NPDES) permit for this plant.
The existing plant should be able to meet the proposed permit limits on
a year-round basis at current wastewater flows. However since the
existing plant was not designed to meet these limits; i. e., not designed
for nitrification, some problems may be experienced during winter months
as the plant flow approaches the design flow of 3.0 million gallons per
day (mgd) . The effluent ammonia limit of 2 milligrams per liter (mg/1) on
a monthly average has already been violated during February, 1978, (see
enclosed data.) The proposed monthly average Biological Oxygen Demand
(BOD) of 9 mg/1 may also be violated during winter months as the flow
increases. During February, 1978, with an average flow of only 0.595 mgd,
the average effluent BOD was 9 mg/1.
Based on actual operating data for the Durham County WWTP, we would
request that a "seasonal variation" for BOD and ammonia be included in
this permit in accordance with Environmental Management regulation
1 SNCAC 2B. 0404. No adverse effect on the receiving stream should occur
AN EQUAL OPPORTUNITY EMPLOYER

' Department of Water Resources
PAGE 2 OF A LETTER TO Mr. Neil S. Grigg
DATE August 31, 1979
during the winter months as a result of granting this variation. By
granting this variance the added cost of providing nitirfication on a
year-round basis may be avoided.
The Environmental Management Commission should be congratulated for
providing a more reasonable regulation that recognizes the seasonal
variation of the impact of oxygen consuming wastes on the receiving
stream. This kind of regulation reflects the "real world" conditions and
is a more realistic approach to the goal of protecting the receiving stream
water quality.
Your favorable consideration of this request will be greatly appreciated.
Very truly yours,
DIVISION OF WATER RESOURCES
A. . Rolan, Assistant Director
ATR:hvl
Enclosures

Dirision rAf Water Resources
• WASTEWATER TREAT;:ENT DATA
1978
MONTH
AVE.
FLOW SUSPENDED SOLIDS B.O.D. pH
MG DO INF. EFF. % RED. INF. EFF. 7. RED. INF. EFF.
RESEARCH TRIANGLE PLANT
January 0.74 10.0 270 13 95 224 7 97 7.9 6.7
February 0.595 9.93 203 14 93 205 9 97 7.8 6.7
March 0.69 8.95 185 8 96 129 5 96 7.2 6.6
April 0.702 7.76 145 3 98 153 6 96 7.6 6.8
May 0.60 7.3 345 8 98 289 3 99 7.5 6.6
June 0.492 6.57 631 5 99 167 4 98 7.5 6.6
July 0.436 7.0 240 5 98 165 6 96 7.8 7.2
August 0.704 6.9 365 3 99 371 3 99 7.8 7.1
September 0.657 7.1 210 5 98 362 3 99 8.1 7.1
October 0.692 8.2 215 3 99 199 2 99 8.2 6.8
November 0.75 8.2 128 3 98 111 2 98 8.1 7.1
December 0.753 8.8 114 7 94 111 5 95 7.5 7.2
Total 7.811 96.71 3051 77 1165 2486 55 11691 93.0 82.5
Average 0.651 8.1 254 6 97 207 5 97 7.8 6.9
WASTE TREATMENT PLANT NUTRIENT DATA FOR 1978
,< <� NO2 mg/1 NO3 mg/1
TKN mg/1 as "N" NHI mg/1 as N as `N as "N" P mg/1 as "P"
DATE/PLANT INF. EFF. INF. EFF. EFF. EFF. INF. EFF.
7,:r
DURHAM COUNTY
January 27.7 5.1 9.27 1.70 0.06 8.5 2.9 1.2
February 18.8 5.2 7.56 2.04 0.05 6.5 3.2 2.1
March 18.7 1.8 6.80 0.60 0.10 13.7 1.2 1.0
April 16.5 0.7 8.40 0.10 0.04 16.8 1.6 0.8
May 26.1 1.3 7.96 0.09 0.02 9.3 3.3 0.9
3une 18.6 2.1 6.47 1.61 1.13 12.1 1.8 0.8
July 21.0 1.9 9.17 0.09 0.03 13.1 2.9 1.0
August 28.1 1.5 7.95 0.09 0.13 13.89 3.5 1.6
September 30.1 1.9 5.49 0.37 0.02 13.5 4.0 0.4
October 30.9 1.0 2.93 0.33 0.20 13.8 4.0 0.4
November 16.9 0.8 6.05 0.18 0.06 13.7 3.7 1.2
December 16.9 1.3 13.80 0.16 0.03 11.7 2.9 2.6
AVERAGE 22.5 2.1 7.65 0.64 0.15 12.2 2.9 1.2

T
Di.'ision'pf Walc r h esuur,
MONTH
WASTEWATER TREATMENT DATA
1978
AVE.
FLOW SUSPENDED SOLIDS B.O.D. pH
MG DO INF. EFF. % RED. INF. EFF. 7. RED. INF. EFF.
RESEARCH TRIANGLE PLANT
January 0.74 10.0 270 13 95 224 7 97 7.9 6.7
February 0.595 9.93 203 14 93 205 9 97 7.8 6.7
March 0.69 8.95 185 8 96 129 5 96 7.2 6.6
April 0.702 7.76 145 3 98 153 6 96 7.6 6.8
May 0.60 7.3 345 8 98 289 3 99 7.5 6.6
June 0.492 6.57 631 5 99 167 4 98 7.5 6.6
July 0.436 7.0 240 5 98 165 6 96 7.8 7.2
August 0.704 6.9 365 3 99 371 3 99 7.8 7.1
September 0.657 7.1 210 5 98 362 3 99 8.1 7.1
October 0.692 8.2 215 3 99 199 2 99 8.2 6.8
November 0.75 8.2 128 3 98 111 2 98 8.1 7.1
December 0.753 8.8 114 7 94 111 5 95 7.5 7.2
Total 7.811 96.71 3051 77 1165 2486 55 1169 93.0 82.5
Average 0.651 8.1 254 6 97 207 5 97 7.8 6.9
WASTE TREATMENT PLANT NUTRIENT DATA FOR 1978
NO2 mg/ 1 NO3 mg/ 1
TKN mg/1 as `N�� NHI mg/1 as `N�� as `N as "N" P mg/1 as P"
DATE/PLANT INF. EFF. INF. EFF. EFF. EFF. INF. EFF.
DURHAM COUNTY
January 27.7 5.1 9.27 1.70 0.06 8.5 2.9 1.2
February 18.8 5.2 7.56 2.04 0.05 6.5 3.2 2.1
March 18.7 1.8 6.80 0.60 0.10 13.7 1.2 1.0
April 16.5 0.7 8.40 0.10 0.04 16.8 1.6 0.8
May 26.1 1.3 7.96 0.09 0.02 9.3 3.3 0.9
June 18.6 2.1 6.47 1.61 1.13 12.1 1.8 0.8
July 21.0 1.9 9.17 0.09 0.03 13.1 2.9 1.0
August 28.1 1.5 7.95 0.09 0.13 £3.89 3.5 1.6
September 30.1 1.9 5.49 0.37 0.02 13.5 4.0 0.4
October 30.9 1.0 2.93 0.33 0.20 13.8 4.0 0.4
November 16.9 0.8 6.05 0.18 0.06 13.7 3.7 1.2
December 16.9 1.3 13.80 0.16 0.03 11.7 2.9 2.6
AVERAGE 22.5 2.1 7.65 0.64 0.15 12.2 2.9 1.2