Citation:

Lazorchak, Jim, T. Norberg-King, A. Biales, V. Wilson, L. Phillips, AND J. Clark. Overview of existing and next generation whole effluent toxicity testing methods for assessing wastewater toxicity. XENOWAC II, Limasol, CYPRUS, October 10 - 12, 2018.

Impact/Purpose:

This presentation will overview the current WET and TIE programs in EPA as well as in vitro and molecular, protein and metabolomics methods that can be used to detect and assess treatment effectiveness of CEC removal in wastewater being discharged or reused.

Description:

Whole Effluent Toxicity (WET) refers to the aggregate toxic effect to aquatic organisms from all pollutants contained in a facility's wastewater (effluent). It is one way we implement the Clean Water Act's prohibition of the discharge of toxic pollutants in toxic amounts. For over 30 years, beginning as early as 1983 when the U.S. Environmental Protection Agency (EPA) published its first WET test method guidance documents to later when the methods were promulgated in 1995 and then ratified in 2002, EPA’s WET test methods have been successfully implemented for both wastewater effluent and ambient receiving water testing. This presentation will include an brief overview of the trend in the reporting data for acute toxicity measured by major municipal dischargers. EPA currently requires the use of these WET test methods for its National Pollutant Discharge Elimination System (NPDES) permits program testing of wastewater effluent samples nationwide for permits issued by 47 NPDES authorized states and ten EPA Regions for the remaining unauthorized states and Indian Tribes. 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. The 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. EPA has two freshwater 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. The acute manual describes test procedures for effluents and receiving waters and includes guidelines on test species selection and mobile toxicity test laboratory design. The test duration ranges from 24 to 96 hours. The freshwater short-term chronic test manuals describes four-to seven-day methods for estimating the short-term chronic toxicity of effluents and receiving waters to three surrogate WET method test species.These methods will be overviewed in the presentation including their applications in the NPDES program. When toxicity is measured, the next step is to use the Toxicity Identification Evaluation (TIE) process to identify and reduce the toxicity. The TIE is a three-phase process that characterizes, identifies, and confirms the cause or causes of toxicity. Once the identification/isolation process has confirmed the potential cause of toxicity, the next step is to determine what needs to be done to reduce or treat the chemical or chemicals causing toxicity in the effluent. Some suggested adaptations of the WET procedures using in vitro, molecular, metabolomics, or protein endpoints will be presented to illustrate how to use next generation testing to detect and assess removal efficiency of treated effluents that are discharged or reused for Contaminants of Emerging Concern (CECs). In vitro assays are being used to screen water samples for the presence of compounds that activate specific cellular pathways (e.g. activating an estrogen-dependent pathway) or that target a particular cell type (e.g. bladder). Omics endpoints, measured in exposed organisms, represent the immediate and early response that underlie the development of adverse outcomes. Existing experimental platforms allows the interrogation of the entire complement of expressed genes, proteins or metabolites, which can number in the 100s to 10000s. The sheer size of these data sets, that their expression is tightly regulated and that they are often crucial components of cellular pathways that lead to disease states, suggests they can be used to establish signatures of activated Mode of Action (MOAs). Signatures from these new

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