WQ0039473_NOV-2024-LV-0061 & NOV-2024-LM-0003_20240205

February 5, 2024

Mr. Andrew Wheeler
Atkinson Milling Company, Inc.
95 Atkinson Mill Road
Selma, NC 27576

Re: Atkinson Milling Process Water Treatment

Dear Mr. Wheeler,

The Atkinson Milling operation expansion involved adding a permitted wastewater system as
required by the state. The wastewater system involved a series of settling tanks, an anaerobic-
up-flow reactor, and a storage/distribution tank equipped with a pump to dose a spray
irrigation system. This system was reviewed and permitted by the NC DEQ DWR.

Following the bench-scale testing proposed previously, it is apparent additional BOD reductions
in the final effluent are possible through a combination of filtration and aeration.

The last samples from the wastewater treatment system had parameters that were out of the
regulatory range for fecal coliform, TSS, and BOD. Of these, the BOD and fecal coliform are the
most concerning. The TSS is over the monthly average by 4.8 ppm and is of less concern.

The most immediate issue is the source of the fecal coliform contamination. The wastewater
source is food processing wash down. Given that hot water and detergents are used, as well as
the sanitary procedures in place for the food processing, it is presumed that the source of the
fecal coliform is likely to be post-waste generation, in other words, somewhere intermediate to
the treatment process. After a review of the system and the installed components to isolate
potential sources, a possibility of some introduced flow from the closed portions of the old
treatment system seems a likely candidate.

To isolate the source of the contamination, a series of samples will be collected at several
points in the wastewater stream. These will be at the source (the inflow pipe from the floor
drain inside the plant) and then at the outflow of each of the following system treatment units.
These are the settling tank, the initial Biomicrobics tank, the secondary Biomicrobics tank, and
the irrigation storage tank (the current sampling location). This series of sampling locations will
be analyzed for each parameter above the regulatory threshold. Taking samples at these points

should isolate the source of the fecal contamination and provide information to evaluate the
parameter reduction provided by each treatment component.

Remediation

Once the samples are evaluated, remediation procedures can be initiated. The first is to cut off
the source of the fecal coliform introduction. This would include removing or capping any line
connections to the old system if this is the source. Because the treatment unit is a biological
system, the fecal bacteria is likely well established in all downstream units from the point of
introduction. It will probably be necessary to kill off all the resident bacterial populations and
reintroduce the beneficial bacteria. The simplest method is utilizing a hypochlorite solution.

During this process, modifying the existing system with additional treatment capability may be
decided to bring all the parameters within regulatory limits.

The goal is to eliminate the source of the fecal coliform, so treatment beyond the elimination of
the existing population is not envisioned.

While out of range, the TSS is close to being in range. Depending on the sampling results, some
filtration or other enhanced solids removal processes will be considered. These are most
efficiently installed near the process's front end. Removing more of the TSS should also have
the additional effect of removing BOD.

The BOD reduction will likely require aeration to be added to the system. The results of the
sampling would dictate the location of the aeration. The most efficient location for aeration is
as far downstream in the system as possible. This allows the bacteria upstream to reduce the
BOD as much as possible before using the aeration.

Schedule

The comprehensive sampling of the system is tentatively scheduled for the week of Feb 12th.

Let’s discuss the next steps as we implement the action plan for the bench scale testing. Please
get in touch with us if you have any questions. Thank you.

Respectfully Submitted,

A.R. Rubin, Scott J. Frederick, NCLSS Stephen Crawford, PE
Professor Emeritus,
NCSU-BAE