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Whole Effluent Toxicity (WET) Testing

Introduction | WET Testing Documents | WET Coordinator | EPA Vessel General Permit

Introduction

The chemical analysis of an effluent (a municipal or industrial wastewater) cannot by itself predict its potential toxic effect. Many toxic pollutants cannot be detected by commonly available chemical analysis methods. The toxicity of many chemicals is unknown even when they can be detected. Different chemicals combined together in the same effluent can have unknown additive effects even when the toxicity of each individual chemical is well-known.

WET tests are required in some wastewater discharge permits in order to measure the potential toxicity of effluents to the rivers, lakes, bays, and ocean waters of the state. WET testing is sometimes called "biomonitoring" or "bioassay testing."

The WET Coordinator for the Department of Ecology reviews all WET tests to see that the test method was correctly followed and that the results can be used to reliably evaluate effluent toxicity. The WET Coordinator begins the review with the raw data to check for entry errors and arithmetic mistakes. Data errors are the most common mistakes currently being made by labs.

Sample handling and test conditions such as temperature and test organism age are checked and occasional problems are also found. Another purpose for WET test review is the identification of test results where adverse effects on test organisms do not have a concentration-response relationship and may not be due to effluent toxicity.

Only toxicity tends to produce a concentration-response relationship where an adverse effect increases as the concentration of effluent (along with the toxic chemicals it contains) increases. Factors other than toxicity such as disease or contaminated glassware sometimes produce adverse effects on test organisms, but these effects do not usually increase with effluent concentration. Excluding tests without a good concentration-response relationship makes WET testing more fair and enforceable.

Courtesy of: Massimo Lorenzoni.
Università di Perugia (University of Perugia). Italy.
(http://www.bio.unipg.it/staff/massimo.html). Further use requires his permission.

WET Testing Documents

The Canary Book: The document linked here is the "Canary Book" or Laboratory Guidance and Whole Effluent Toxicity Test Review Criteria, which describes our WET test evaluations. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file. The Canary Book is Ecology publication #WQ-R-95-80 and will be updated every year or so.

There is a Responsiveness Summary for the June 2005 version of the Canary Book. Ecology has a database which contains around 6,000 WET test results from 216 NPDES permittees. We believe that our database is the most extensive in the nation. The database allows us to provide a valuable service to both Ecology staff and permit holders either of whom can request a summary table of WET test results.

The Whole Effluent Toxicity Program Evaluation Summary: The Washington State Department of Ecology planned from the beginning to evaluate the implementation of the state's regulation on WET based on our experience and the contents of the database. Ecology prepared the Whole Effluent Toxicity Program Evaluation Summary (publication #98-16) to summarize the state's experience with WET testing and effluent toxicity. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file. In addition, it presents Ecology's analysis on the interaction of regulation and science in controlling toxicity in the state's waters.

The Whole Effluent Toxicity Program Evaluation: Ecology prepared the summary from a longer and more detailed version, the Whole Effluent Toxicity Program Evaluation (publication # 98-03). It is in Adobe Acrobat (.PDF file) format. See below for information on using the file. The first three sections of the evaluation provide background and a description of the WET program. The fourth section discusses improvements to the implementation of the WET program and offers new strategies. The fifth section considers various scientific issues involved in WET testing. The last section evaluates the relationship between science and regulation and presents our regulatory philosophy for WET.

Statistics and Management of WET Tests: This document discusses different statistical approaches for analyzing WET tests and describes how to choose an approach in order to effectively manage a regulatory program for monitoring effluents. A slightly different version of this article appeared in the September 1996 SETAC NEWS. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file.

Does WET Testing Need To Be Predictive?: This document discusses conflicts inherent in the regulatory use of WET testing and offers a common sense perspective. A slightly different version of this article appeared in the September 1997 SETAC NEWS. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file.

A State’s Perspective on WET Methods: This document gives an overview of the WA State perspective on WET. It is based on a presentation given at the EPA 22nd Annual Conference On Analysis Of Pollutants In The Environment. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file. Use of the Washington State WET Database to Demonstrate Inadequate Monitoring Frequencies and Cost-effectiveness: This document discusses WET monitoring frequency as it relates to environmental protection and cost-effectiveness. It is based on a poster presentation at the November 1998 SETAC conference. It is in Adobe Acrobat (.PDF file) format. See below for information on using the file.

Whole Effluent Toxicity Testing And Limits (Chapter 173-205 WAC)

Final Report on Pacific Herring (Clupea pallasi) Test Development and Validation with an Appendix on Herring Embryo Temperature Tolerance Comparisons between West Coast Stocks: Because of the serious and ongoing decline in the population of the state′s once largest herring stock, the Department of Ecology and Western Washington University have been developing and validating herring toxicity tests since the 2000 spawning season. The herring test development effort has produced methods for a 96-hour acute survival test, an embryo survival & development test, and a larval 7-day survival & growth test. The report describes the test development and validation results.