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National Pollutant Discharge Elimination System (NPDES) |  |
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Whole Effluent ToxicityWhole Effluent Toxicity (WET) is a term used to describe the aggregate toxic effect of an aqueous sample (e.g., whole effluent wastewater discharge) as measured by an organism's response upon exposure to the sample (e.g., lethality, impaired growth or reproduction). WET tests replicate the total effect and actual environmental exposure of aquatic life to toxic pollutants in an effluent without requiring the identification of the specific pollutants. WET testing is a vital component of the water quality standards implementation through the NPDES permitting process.
WET Requirements
WET tests are designed to predict the impact and toxicity of effluents discharges from point sources into waters of the U.S. WET limits, developed by permitting authorities, are included in NPDES permits to ensure that state or tribal water quality criteria for toxicity are met. WET monitoring requirements are included in NPDES permits to generate data for use in assessing whether a WET limit has been exceeded or to assess if a WET limit is needed. Key ReferencesDraft National Whole Effluent Toxicity (WET) Implementation Guidance (PDF) (109 pp, 1.1MB) Freshwater Series Videos - WET test and organism culturing videos, produced by EPA beginning in 1988, serve as an important training tool for EPA Regions, states and private laboratories. Due to the recognized need for WET training, EPA has now revised the original videos to incorporate the 2002 WET test methods technical updates and has added new features to enhance the training benefits. Three training videos are available for download: NOTE: These MP4 files consist of both audio and video and can be viewed on portable MP3 and iPod devices. If your device is not video compatible this file can still be downloaded for just the audio. These training videos range from about ten to twenty minutes in duration. These files are very large and will take a long time to download.
To order copies of the Freshwater Series package, which include electronic copies of supplemental reports that provide additional instruction on conducting Freshwater WET tests, contact the National Service Center for Environmental Publications (NSCEP) at (800) 490-9198 or nscep@bps-lmit.com. Reference publication number EPA-833-C-06-001 in your inquiry. For further information or questions, contact Laura Phillips.
EPA document developed by the Office of Wastewater Management/Water Permits Division to provide additional clarification on conducting toxicity reduction evaluations and toxicity identification evaluations with respect to whole effluent toxicity (WET) testing. The document clarifies for National Pollutant Discharge Elimination System (NPDES) permit writers and permittees a number of common issues such as: when and under what circumstances a permittee should conduct a TRE and/or a TIE; technical limitations on the TIE process; consideration of persistence and magnitude of toxicity events; ionic imbalances of effluents; the applicability of compliance schedules; and inconclusive TREs/TIEs. The document supplements existing EPA guidance and policies on WET and TREs/TIEs but does not change current policy or legal authority. Date Published: 03/27/2001
Technical guidance on how to identify the cause of whole effluent toxicity. Part three of a three part set (EPA-600-R-92-081). Date Published: 09/01/1993 Technical guidance on how to identify the cause of whole effluent toxicity. Part two of a three part set (EPA-600-R-92-080). Date Published: 09/01/1993 Aid in conducting aquatic organism Toxicity Identification Evaluations. Part one of a three part set (EPA-600-R-91-003). Date Published: 02/01/1991 Guidance for the performance of Toxicity Reduction Evaluations (TREs) at industrial facilities. This document presents a generalized methodology for designing and conducting a TRE and 10 supporting case studies which illustrate various approaches that have been used in the performance of TREs to date (EPA-600-2-88-070). Date Published: 04/01/1989 Procedures and rationale for toxics control. Date Published: 07/24/1985 EPA Regional and State WET Coordinators (PDF) (8 pp, 60K) |
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EPA's promulgated 
