NC0001121_NOV2014PC0045

DENR-FRO
MAR 1 9 2094
DWG
cIYD.:A'A.HER
SPECIALTY PRODUCTS.
2100 West Broad Street
Elizabethtown, NC 28337
March 17, 2013 CERTIFIED MAIL
Ms. Belinda Hinson
Fayetteville Regional Supervisor
Division of Water Resources
NC DENR
225 Green Street Suite 714
Fayetteville, NC 28301
Re: NOTICE OF VIOLATION FOR FAILURE OF WHOLE EFFLUENT TOXICITY
DURING COMPLIANCE BIOMONITORING INSPECTION NOV-2014-PC-0045
Danaher Controls WWTP
NPDES Permit No. NC0001121
Bladen County
Dear Ms. Hinson,
The cause of a low recorded pH and the subsequent failure of the toxicity test are
predicated on understanding the combined flow make-up of the 004 discharge which
includes:
1. The treated process water flow from either the batch chrome treatment or the
batch cyanide treatment as they occur and pass through the final clarifier. The pH
adjustment during these batch treatments is monitored continuously and is critical
to effective use of polymer use and solids settling. The desired pH of the process
tank prior the addition of the polymer is 8.5 to 8.8.
2. The groundwater remediation process flow which passes through an aeration
tank for the removal of VOC. The pH of the recovered groundwater from three
recovery wells is between 4.0 and 4.5.
3. The wet well flow from the plating department is a non -contact cooling water and
rinse water that bypasses the batch treatment tanks. The pH of this city water is
7.9.
The daily proportion of each of these flows is not consistent. When a batch treatment
occurs, this volume will pass through the final clarifier over about a 4 hour period. The
groundwater flow is a fairly stable well pumping rate. The wet well flow varies with
production activity.

The effluent sampling point manhole has sufficient mixing of these flows to presume a
representative sample. In the past, the pH of the combined flow has not been a concern,
as evidenced in a record of compliance for the grab sample taken each week. During the
past eight quarterly sample months, the minimum pH was 6.9 and the maximum pH was
7.4 as taken by grab. During the same time frame, the laboratory performing the acute
toxicity test, recorded a minimum pH of 6.48 and a maximum of 7.15 at the start of the
tests.
Our records indicate that a batch chrome treatment was performed on February 11th.
The final pH recorded for that batch was 8.3. We have since evaluated the pH probe and
have concluded that its calibration was off by as much as 1 std. pH unit. Given this
information low pH water in the clarifier from that batch would have significantly
lowered the 24-hr composite sample pH.
As a result of our investigation and findings we have calibrated and installed a new pH
probe for this treatment process. We are therefore going to begin daily pH measurements
at both the intake and outlet ends of the clarifier to identify slugs of low pH water that
may occur going forward.
We have already implemented the recommended sample equipment cleaning procedures
for aquatic toxicity testing.
Results for the other monitoring parameters during February 18th sampling event have
been received and are in compliance.
Sincerely,
Rodney H. Lan'g
EHS Engineer, ORC
910-862-5453