NC0024911_Pretreatment_HWA_Letter_20190710

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Sent via email ([e-mail])
Mr. Chad Ledford
Pretreatment Supervisor
MSD Buncombe
2028 Riverside Drive
Asheville, NC 28804
NORTH CAROLINA
Environmental Quality
July 10, 2019
Subject: Pretreatment Review of Headworks Analysis (HWA)
Metropolitan Sewerage District (MSD) of Buncombe County
NPDES# NCO024911
Dear Mr. Ledford:
The Pretreatment, Emergency Response, and Collection Systems (PERCS) Unit of the Division of
Water Resources has reviewed the Headworks Analysis (HWA) for the Metropolitan Sewerage
District (MSD) of Buncombe County. This HWA was received by the Division on March 27, 2019.
Additional information was requested and was received on May 29, 2019 and June 14, 2019.
The Division concurs with the HWA calculations for all pollutants of concern with comments and
observations discussed below. These approved Maximum Allowable Headworks Loadings
(MAHLs), and the basis for these values are found on the last page of the HWA spreadsheet and
also on the last page of the allocation table.
The following corrections were made during the HWA review. All changes were highlighted in the
attached HWA sheet.
1) Flow information: uncontrollable flow was updated to 19.89 MGD to match the
uncontrollable mass balance sheet. 7Q10 stream flow was updated to 301.04 MGD.
2) Pass through loading calculations:
a) Plant Removal Rates were updated for copper and zinc to match the removal rates sheet.
b) Dissolved metal stream standards for cadmium, nickel and zinc were updated to match
the dissolved metal calculator.
c) The detection level for arsenic specified in the LTMP was 0.005 mg/L, while the data
indicated a detection level of 0.01 mg/L. Please make sure the future samples are tested
using the detection levels in the approved LTMP.
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
Noana GwauNn �
919.707.9000

3) Sludge Incinerator: PERCS appreciates your submittal of information regarding compliance
with your Sludge Incinerator permit. We have obtained similar information for the other
sludge incinerator POTWs. PERCS continues to study this issue and may request additional
information in the future. Any possibility of establishing Pretreatment Program related
requirements or recommendations for Pretreatment POTWs with sludge incinerators will be
discussed thoroughly with all applicable POTWs well in advance.
a) Sludge loadings were input into the column J to reflect the calculations for sludge POCs.
4) LTMP: The LTMP was received on April 30, 2019.
a) Total Phenols should be added to the LTMP POC list as it is limited in GF laminar permit.
Toluene should also be added as it is limited in Day International permit. They both have
NC stream standards. Both pollutants were added to the HWA with literature removal
rates, please start sampling them and update the site specific removal rates for beryllium,
total phenols and toluene by August 31, 2020.
b) Significant Industrial User should be sampled for all LTMP POCs at least once per year.
Please refer to the state model/ notes in attached LTMP for suggested wording.
c) It is recommended to sample plant influent and effluent quarterly.
d) The recommended detection levels for copper is 0.002 mg/L and for silver is 0.001 mg/L.
e) PERCS has a copy of the WWTP diagram in the 2005 submission. Please submit an updated
version if available.
f) Please submit an updated LTMP before August 31, 2019.
5) Allocation table:
a) It is highly recommended to use state's model and link the allocation table with the HWA.
b) CBOD: The MAHL for CBOD of 70,391 lb/day was used in the allocation table instead of
the design criteria loading of 80,731 lb/day for BOD as CBOD was limited in the NPDES
permit. The POTW may assign SIUs CBOD limits so the samples do not account for
nitrogenous oxygen demand (NBOD) and potentially free up some CBOD availability.
c) NH3: Although there is no NPDES permit limit for ammonia, a MAHL could be developed
based on the literature inhibition value to protect the microorganisms in the WWTP. It is
recommended to add ammonia to the allocation table and start to evaluate the ammonia
levels in SIUs, considering a future NPDES limit would be assigned.
d) Silver over allocation: The SIUs discharge only 0.0036 lb/day and uncontrollable
discharges 0.4307 lb/day. It appears that the SIUs discharge below their silver limits and
there are other sources for silver. Please respond by August 31, 2019 with a strategy to
resolve the over allocation (e.g. IUP revisions, apply the lower detection level for both the
plant and SIU samplings) and to pinpoint the source of unaccounted for silver (e.g. more
accurate mass balance, truck line sampling).
e) Total Phenols and Toluene: should be added to the allocation table.
6) Next HWA Due Date: The HWA was based primarily on 2014-2018 data. Unless conditions
at the POTW change significantly and thus warrant an earlier submittal, the POTW must
submit an updated HWA on or before April 1, 2024.

Thank you for your continued support of the Pretreatment Program. If you have any questions
or comments, please contact me at [phone] [email: [e-mail]] or
Deborah Gore, Unit Supervisor at [phone] [email: Debora [e-mail]].
Sincerely,
Ii
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Linda Wiggs, ARO
Shannon Bergeron, MSD
Central Files (Laserfiche)