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Update on the WET method errata and data questions for whole effluent toxicity test methods
Citation:
Norberg-King, T. Update on the WET method errata and data questions for whole effluent toxicity test methods. SETAC North America, Sacramento, CA, November 04 - 08, 2018.
Impact/Purpose:
Clean Water Act (CWA) implementation starts with the development of water quality criteria to protect uses, such as aquatic life.implementation of EPA’s WET test methods under the NPDES permit program completes an integrated strategy for water quality-based toxics control that fulfills the Clean Water Act’s goals to protect aquatic life and prohibit the discharge of toxic pollutants in toxic amounts. As aquatic life are exposed to innumerable chemical mixtures in the nation’s waters, whole effluent toxicity (WET) methods are used to assess whether chemical mixtures of effluents and ambient waters are causing toxicity to aquatic life, thereby filling a key role in meeting the CWA goal of “no toxics in toxic amounts.” the WET refers to the aggregate toxic effect to aquatic organisms from all pollutants contained in a facility's wastewater (effluent). These WET test methods measure the aggregate acute and short-term chronic toxicity of an effluent using standardized freshwater, marine, and estuarine plants, invertebrates, and vertebrates. EPA promulgated the WET test method guidance document in 1995 and ratified most of the methods in the EPA manuals in 2002. EPA’s WET test methods have been successfully implemented for both wastewater effluent and ambient receiving water testing. EPA has one acute testing manual and two short-term chronic WET test methods manuals for assessing not only the aggregate toxic effect of pollutants to aquatic organisms but also the aggregate effect of receiving waters to freshwater organisms.. Over the years, continued toxicity testing method modifications, increased training, and technical resources have abounded for toxicity tests while EPA’s promulgated methods have widespread use. Errata have been periodically published and a summary of the errata will be presented.In whole effluent testing, the use of the toxicity test has become a valuable component of most water quality monitoring programs, and the use of standardized acute and sublethal freshwater and marine methods specify test acceptability criteria (TAC) for survival, growth, reproduction and provide specific testing procedures. Acute toxicity of effluents appears to have decreased since WET test has been required. Data reviews of test results have shown laboratories interpret the required procedures differently. Additional interpretation guidance is needed for these technical method issues and by strengthening the knowledge exchange with practicing laboratories, more consistent interpretations should be able to be made. Additional species are needed for effluent assessments, and methods are being assessed for two sensitive species, e.g., mayflies and mussels. This presentation will discuss the progress that has been made in the conduct and application of these tests and changes made in EPAs errata, along with recommendations to improve the quality and utility these tests, including suggestions for laboratory proficiency guidelines.
Description:
The Clean Water Act sets the goal of maintaining the chemical, physical, and biological integrity of the Nation's waters and the national policy, and with that goal, the discharge of toxic pollutants in toxic amounts is prohibited. The use of aquatic toxicity testing, such as whole effluent toxicity (WET), under the National Pollutant Discharge Elimination System (NPDES) permits program, is an important component of the Environmental Protection Agency’s integrated approach to water quality-based toxics control, along with aquatic life chemical-specific criteria and biological assessments. Over the years, continued toxicity testing method modifications, laboratory accreditation, increased training, and technical resources have abounded for toxicity tests with the widespread use of the promulgated methods. Errata have been periodically published, and a summary of the errata will be presented.In whole effluent testing, the use of the toxicity test has become a valuable component of most water quality monitoring programs, and the use of standardized acute and sublethal freshwater and marine methods specify test acceptability criteria (TAC) for survival, growth, reproduction and provide specific testing procedures. Acute toxicity of effluents appears to have decreased since the WET testing has been required. Data reviews of test results have shown laboratories interpret the required procedures differently. For example, while the time frame to end the chronic Ceriodaphnia dubia test is when 60% of the controls have three broods, some labs do not terminate until 80% have the third brood. Interpretation guidance is needed for these types of issues, and by strengthening the knowledge exchange between practicing laboratories, more consistent interpretations should be able to be made. Additional species are needed for effluent assessments, and methods are being assessed for two sensitive species, e.g., mayflies and mussels. This presentation will discuss the progress that has been made in the conduct and application of these tests and changes made in EPAs errata, along with recommendations to improve the quality and utility these tests, including suggestions for laboratory proficiency guidelines. This abstract does not necessarily represent the position or policy of the U.S. EPA.