NC0000892_Correspondence_20240520

May 16, 2024
North Carolina Department of Environmental Quality
Raleigh Regional Office — Division of Water Resources
Attn: Donald Smith
3800 Barrett Drive
Raleigh, NC 27609
Re: WWTP —April 10, 2024 Visit Follow Up
Arclin USA, LLC; Permit NC0000892
790 Corinth Rd.
Moncure, North Carolina 27559
RE: Summary of Response Activities to Upset Condition
Dear Mr. Smith,
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MAY 2 0 2024
This is a follow-up to your May 8, 2024 email requesting the summary of activities and sampling plan
implemented in response to the waste water treatment plant (WWTP) upset as discussed during April
10, 2024, site visit and initial agency communication. The upset was noted upon exceedances of the
phenol and BOD parameters for sampling events conducted on February 2024 and March 2024,
respectively.
The corrective measures implemented have proved effective in gradually re-establishing normal
operating conditions. Results of weekly sampling for regulated parameters for April 2024 were in
compliance with permit limits. Note that these do not include phenol, which will be included in the May
2024 priority pollutants sampling. There has also been a considerable increase in dissolved oxygen (DO)
uptake, along with mixed liquor suspended solids (MLSS) increase which is expected to increase phenol
removal substantially.
The following is a discussion of the activities we implemented and are continuing to monitor to
understand the cause of the upset condition to prevent reoccurrence:
1 Initially walked the site looking for spills or discharges which could have reached the treatment
plant. No discharges were identified which could have increased the phenol to the concentrations
observed in the effluent.
2 Met with and interviewed plant personnel as to any unusual discharges which may have been
occurred. No discharges were identified which could have increased the phenol to the concentrations
observed in the effluent.

3 Locked out all the sumps such that a visual assessment may be made prior to discharge and a
key is required to open valves prior to discharge to WWTP. To date, nothing unusual has been observed
in these sumps.
4 Additional measures implemented at site are detailed in letter to NCDEQ on March 26, 2024.
5 We typically monitor the Equalization Basin and the Aeration Basin for pH, temperature,
dissolved oxygen concentration and level as routine process parameters. After the upset event, since
February 2024, we increased in-house process monitoring of our wastewater treatment plant to include
monitoring for variations in TSS, oxygen uptake rate, and ammonia and their impact on removal of
phenol. This has allowed us to better track relative phenol concentrations which dropped substantially.
Site plan is to continue monitoring the above parameters until our effluent phenol meets the regulatory
requirements.
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For example, the chart below presents in-house sampling results for increased monitoring data from our
Equalization Basin of relative phenol concentrations versus temperature. The temperature rising to near
15 C from the lows below 7 C correlates the temperature increase to the phenol concentration
decrease.
EQ Basin
Temperature Vs Phenol Conc.
25
23
21
19
17
°c
E 15
m
m
a
13
NO
71
9
7
5
1/29/2024
2/18/2024 3/9/2024 3/29/2024 4/18/2024 5/8/2024 5/28/2024
♦ Temperature ■ Phenol Conc —Poly. (Temperature)
Figure 1 — in-house Phenol measurements & Temperature over Time
6 We are working with a contract laboratory to determine sample collection requirements to
analyze for a suite of metals, as recommended during site visit. Unsettled and settled samples are being
analyzed to better determine what metals are in solution and what metals have been taken up by the
bacteria. We will compare the metals concentration to known inhibition and toxicity values to see if
they are impacting WWTP.
We are continuing to monitor the system as described above as part of our investigation as to what
caused the upset, and work to develop any additional preventive measures based on findings.

Feel free to contact me if you would like to discuss further at [phone] or Sam Littlejohn at (919)
545-5742.
&.. :. Regards, NC Beet of Erviromr:e;�ral Q aljf,/
Ja es Gard MAY 2 0 2024
Plant Manager
Arclin
Moncure, NC