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Toxicity Identification Evaluation/Toxicity Reduction Evaluation

A TRE is a site-specific multidisciplinary program aimed at bringing a facility back into compliance with whole effluent toxicity (WET) permit requirements. A TRE is a step-wise logical program that consists of: evaluation of site-specific information, identification of the cause or source of toxicity (referred to as toxicity identification evaluation [TIE]), selection and implementation of an appropriate toxicity control strategy/technology, and confirmation of the reduction or elimination of effluent toxicity. A TRE relies on “weight of evidence” reasoning, and it is critical to maintain flexibility (schedule, strategy, and budget) throughout the program.

The objective of the TIE procedure is to identify the specific chemical(s) or categories of chemical(s) that may be contributing to WET. The U.S. Environmental Protection Agency’s (EPA’s) Phase I TIE methods (EPA 1991) characterize the physical and chemical nature of the toxicants. Phase II TIE methods (EPA 1993a) are intended to further characterize and identify the cause(s) of toxicity in effluents, and Phase III methods (EPA 1993b) are designed to confirm that the suspected toxicants are indeed the cause(s) of the measured toxicity.

EA brings a consulting approach to TIE/TREs, assisting our clients in the process of meeting compliance requirements. The methods for TIE/TREs apply to effluents, sediment pore water, sediment elutriates, hazardous waste leachates, and sediments (EPA 2007). The scientists at EA can custom design a study to meet each facility’s needs.

EA scientists have been instrumental in the development and refinement of TIE/TRE methods and strategies since their inception in 1985. EA’s experience and involvement in the TIE/TRE arena is highlighted by the following:

  • EA co-authored the first and second editions of EPA’s TRE Guidance for Municipal Wastewater Treatment Plants (EPA 600/2 88/062 and EPA/833/B-99/002). The second edition (1999) includes guidance on state-of-the-science procedures such as toxicity tracking methods (e.g., Refractory Toxicity Assessment Protocol).
  • EA co-authored EPA’s Generalized Methodology for Conducting Industrial TREs (EPA/600/2-88/070).
  • EA performed the first and largest EPA TRE case study (1986-1987), which was a cooperative EPA/City of Baltimore municipal TRE program conducted at the Patapsco Wastewater Treatment Plant.

TIE/TRE Methodology

EPA. 1991. Methods for Aquatic Toxicity Identification Evaluations: Phase I Toxicity Characterization Procedures. EPA-600-6-91-003. February.

EPA. 1993a. Methods for Aquatic Toxicity Identification Evaluations: Phase II Toxicity Identification Procedures for Samples Exhibiting Acute and Chronic Toxicity. EPA-600-6-91-003. September.

EPA. 1993b. Methods for Aquatic Toxicity Identification Evaluations: Phase III Toxicity Confirmation Procedures for Samples Exhibiting Acute and Chronic Toxicity. EPA-600-6-91-003. September.

EPA. 2007. Sediment Toxicity Identification Evaluation: Phases I, II, and III Guidance Document. EPA 600-R-07-080. September.


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