NC0026441_Efluent Toxicity testing results memo_20190415

Division of Water Resources
April 15, 2019
MEMORANDUM
To: Rick Bolich
Water Quality Regional Operations, RRO
Through: Cindy A. Moore ou-
Supervisor, Aquatic Toxicology Branch (ATB)
From: Carol Hollenkamp T
Quality Assurance icer, Aquatic Toxicology Branch (ATB)
Subject: Whole effluent toxicity test results
Siler City WWTP
NPDES Permit# NC0026441/001
Chatham County
The aquatic toxicity test using flow-proportional composite samples of effluent discharged from
the Siler City WWTP has been completed. Siler City WWTP has a permitted effluent discharge of
4.0 million gallons per day(MGD) entering Loves Creek(7Q10 of 0.25 CFS). Whole effluent
samples were collected on March 12 and March 14 by Cheng Zhang for use in a chronic
Ceriodaphnia dubia pass-fail toxicity test. The test passed. Toxicity test information follows.
Test Type 3-Brood Ceriodaphnia dubia chronic pass-fail
Test Result Pass
Test Concentration 90%
Control Survival 91.7%
Control Mean Reproduction 30.7 neonates
Test Treatment Survival 91.7%
Treatment Mean Reproduction 28.2 neonates
First Sample pH 7.66 SU
First Sample Conductivity 654 micromhos/cm
First Sample Total Residual Chlorine <0.1 mg/L
Second Sample pH 7.93 SU
Second Sample Conductivity 793 micromhos/cm
Second Sample Total Residual Chlorine <0.1 mg/L
Test results for the above samples indicate that the effluent would not be predicted to have
water quality impacts. Please contact us if you have any questions or if further effluent toxicity
monitoring is desired. We may be reached at(919)743-8401.
Basin: Cape Fear
cc: Cheng Zhang(RRO)