Whole Effluent Toxicity Testing
The Whole Effluent Toxicity (WET) program is managed by the Surface Water Permits Branch of the Division of Water. Staff provide technical review of all self-monitoring reports conducted by the regulated community for compliance, as well as Toxicity Reduction Evaluations (TREs).
In 1988 the Department for Environmental Protection adopted a strategy to control toxic discharges into waters of the Commonwealth. This toxics control strategy was implemented by including both chemical-specific and WET limits in Kentucky Pollutant Discharge Elimination System (KPDES) permits issued to major industrial dischargers and major municipal wastewater treatment plants (WWTPs) as well as minor WWTPs with an approved pretreatment program. In 2014, WET testing was added to coal facilities. The WET limits include both acute and chronic levels based on the instream waste concentration. Acute Wet tests are conducted using the water flea (Ceriodaphnia dubia, Daphnia magna or Daphnia pulex) and the fathead minnow (Pimephales promelas). Chronic WET tests are conducted using the water flea (Ceriodaphnia dubia) and the fathead minnow (Pimephales promelas).
The toxics control strategy consists of a two-tiered approach of chemical-specific and WET limits that are implemented through the KPDES program. The chemical-specific tier is generally well known. The WET tier was added by the agency because it directly measures toxicity and takes into account the aggregate toxicity in complex effluents and the chemical and physical interactions that can occur.
The DOW currently has approximately 800 industrial facilities, municipal facilities and coal facilities whose permit includes the WET limit. All these facilities are required to perform self-monitoring for the WET permit condition (usually performed by a consulting laboratory). Our staff reviews all toxicity data reported on
discharge monitoring reports (DMRs). Our job is to verify the quality of the data, ensure proper methods were followed, track compliance and determine enforcement for noncompliance. The staff has reviewed more than 11,000 toxicity test reports since 1988. We now average approximately 800 reports per calendar quarter.
When submitting WET reports, please use the following naming convention:
FacilityName_KPDESPermitNumber_Date
Example: SmithWWTP_KY8675309_11-18-15
WET Testing Labs
A list of approved laboratories that currently perform WET testing for discharge operations under a Kentucky Pollution Discharge Elimination System (KPDES) permit can be found by emailing
DOWLabCertification@ky.gov and requesting the information.
Approval by the state includes certain requirements that must be met including submittal of standard operating procedures and results of tests performed on aquatic organisms. For more information, contact program staff.
This list does not constitute an endorsement for services by the Commonwealth of Kentucky. The list is provided for information only.
WET Permits
Whole Effluent Toxicity (WET) limits have been added to
Kentucky Pollutant Discharge Elimination System (KPDES) permits since 1988, with the exception of coal which was added in 2014. The program has grown to the point that now approximately 800 facilities have WET as a permit condition requiring self-monitoring. In the permit, the limit is expressed on the limits page as a toxicity unit (TU), either acute or chronic.
Almost all major discharge facilities are required to perform WET, as well as some minor industries or municipalities with pretreatment requirements. Both acute and chronic limits based on stream flow versus volume of discharge are used for testing.
When a KPDES permit is issued, the facility is required to test using both the fathead minnow, Pimephales promelas, and the water flea (Ceriodaphnia dubia, Daphnia magna or Daphnia pulex) Most facilities begin with quarterly WET testing. A permittee may request a reduction in frequency from quarterly to annual upon demonstration that no test failures, incomplete tests, or invalid tests occurred during the following specified timeframes:
1) Existing facilities: four (4) consecutive quarters
2) New or expanded facilities: eight (8) consecutive quarters.
A permittee may request a reduction in species after at least six (6) consecutive passing toxicity tests using both the water flea and the fathead minnow.
Upon permit renewal, the facility is required to return to testing both species for four tests to re-establish the most sensitive species. If the facility is currently testing monthly, then both species may be tested monthly. If quarterly testing was in effect at renewal, both species are tested quarterly.
The most recent minor modifications were made to the generic permit language for biomonitoring in Kentucky in 1999. The changes cleared up confusion that had arisen over the years concerning interpreting specific language. To get a copy of a specific permit, please submit a written Freedom of Information request to the Surface Water Permits Branch, email to
swpbsupport@kygov.