NC0032719_Correspondence_20111028

Division of Water Quality
October 28, 2011
MEMORANDUM
To: Al Hodge
Surface Water Protection, WaRO
.Through: Cindy A. Moore WN
Supervisor,Aquatic Toxicology Unit
From: Carol Hollenkamp
1�
Quality Assurance Officer,Aquatic Toxicology Unit
Subject: Whole effluent toxicity test results
Chowan Co. Valhalla WTP
NPDES Permit 4 NCO032719/001
Chowan County
The Aquatic Toxicology Unit(ATU)conducted a time-variable chronic Ceriodaphnia dubia multiple dilution
toxicity test(non-standard test)from 10/19/11-10/26/11 using effluent discharged from Chowan Co. Valhalla
WTP. Valhalla WTP has an effluent discharge permitted that is 0.6 million gallons per day(MGD)entering the
UT Pollack Swamp (7Q10 of 0 CFS). A whole effluent grab sample was collected on October 17 by Robbie
Bullock and Tom Bulls for use in this test.
This was a non-standard test utilizing a time-variable approach. The time-variable approach exposes organisms
to a sample for a length of time that approximates the exposure time of the organism in the environment. The
estimated time of exposure(estimated time of plant discharge)is 3 hrs per day for the Valhalla WTP. For this
test, one sample was used for the 7-day chronic test. The organisms were exposed to this sample for a 3-hr
period on 10/19, 10/21, and 10/24. After each test exposure period,the organisms were transferred to control
(dilution)water.
Test results for this sample indicate that the effluent would be predicted to have water quality impacts on the .
receiving water. This test resulted in a Chronic Value(ChV)of 35.4%which is considered a fail because it is
less than the 90%monitoring limit for this facility. For the five effluent concentrations tested, statistically
significant effects were observed at 50%, 75%,90%,and 100% effluent. Test results are presented in the
attachment. It should be noted that the significant effects at these concentrations were due to very low
reproduction numbers for the third brood neonates. On day 7 of the test,the adult test organisms appeared
healthy and were developing fourth brood eggs.
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: CH004
cc: Central Files
Robbie Bullock, WaRO
Kristin Jarmin, WaRO
Attachment: "Test Results for Chowan Co. Valhalla WTP,NC0032719/001"
Aquatic Toxicology Unit Environmental Sciences Section

Test Results for Chowan Co.Valhalla WTP, NCO0327191001
Test Type Time-Variable 3-Brood Ceriodaphnia dubia chronic multiple
dilution (non-standard test)
Test Result Fail
ChV=-35.4%which is less than 90% monitoring limit
Test Concentrations T 0, 25, 50, 75, 90, 100%sample
Test Endpoints ChV7=35.4%
NOECZ=25%
LOEC3= 50%
1C254= 50.5%
Control Survival 100%
Control Mean Reproduction 28.2 neonates
Test Treatment Survival y 100%at all concentrations
Treatment Mean Reproduction 28.0 at 25%
21.5 at 50% (significant effect)
15.8 at 75% (significant effect)
14.8 at 90% (significant effect)
12.1 at 100%(significant effect)
Sample pH 7.78 SU
Sample Conductivity 6.43 mS/cm
Sample Total Residual Chlorine <0.1 mg/L
IChV=Chronic Value. The Chronic Value is the geometric mean of the No Observed Effect Concentration and the
Lowest Observed Effect Concentration. For standard North Carolina multi-concentration chronic WET tests,a ChV lower
than the permit limit for the facility is considered a"Fail".
2NOEC=No Observed Effect Concentration. In this test,this is the highest effluent concentration tested at which there is
no significant reduction in reproduction from the control.
3LOEC=Lowest Observed Effect Concentration. In this test,this is the lowest effluent concentration tested that shows a
significant reduction in reproduction from the control.
4IC25=Inhibition Concentration(1C25). The IC25 is a calculated point estimate of the effluent concentration that would
cause a 25%reduction in reproduction.
Aquatic Toxicology Unit Environmental Sciences Section