Validation of a Framework for Evaluating the Potential Effects and Risks of Trace Organic

Validation of a Framework for Evaluating the Potential Effects and Risks of Trace Organic Compounds (TOrCs) to Aquatic Life

Carrie Turner Senior Project Engineer LimnoTech (734) 332-1200

Thousands of trace organic compounds (TOrCs), such as pharmaceuticals, personal care products, plasticizers, pesticides, flame retardants, and other organics, are regularly released into the aquatic environment. Targeted studies have suggested that TOrC exposures may cause reproductive, neurological, and/or other effects on the aquatic community. Because of uncertainty concerning potential risks, management actions might focus on the wrong sites, and/or the wrong compounds, and might not yield the expected improvement of water quality and ecological integrity. These uncertainties make it challenging to regulate the discharge of TOrCs to surface waters, and for wastewater utilities to manage downstream risks to aquatic life. It is therefore critical that the characterization of potential risk due to TOrCs be assessed in a holistic manner within the context of each site’s unique features, aquatic community composition, and stressors. WERF researchers, led by LimnoTech, have recently completed a project to refine and validate site screening tools that can assist water quality managers in evaluating the potential for adverse ecological effects associated with exposure to TOrCs discharged in treated wastewater.

WERF researchers, led by LimnoTech, have recently completed a project to develop site screening tools that support management decision-making. The benefits of this research include providing water quality manager with easy-to-use tools and a management-oriented framework that enable them to 1) evaluate the potential for adverse ecological effects associated with exposure to TOrCs discharged in treated wastewater; 2) understand what data are needed so that sampling programs can be designed for smart data collection; and, 3) support more informed and reliable management decisions.

The site screening approach developed by the research team focuses on receiving waters below wastewater treatment plants (WWTPs) where there are documented aquatic life impairments. The approach takes full account of relationships between those impairments and other possible stressors, and it also distinguishes to the extent possible any relationships between TOrC exposures and observed effects. The research project was conducted by refining the site- screening tools, then designing and executing a sampling program for a more complete weight of evidence (WoE) analysis, and validating the WoE tools in the final year of the project.

The refined site-screening tool (Figure 1) uses a tiered risk approach that reflects the potential risk to the aquatic ecosystem from TOrCs and other stressors, as well as the degree of uncertainty related to that potential risk:

 Tier 1 (Possible Concern): Sites where the effects of TOrC exposures cannot be characterized with high probability.  Tier 2 (Lower Concern): Sites with no observed aquatic life impairment and/or low observed or predicted TOrC exposures, suggesting a high probability that TOrCs do not cause impairment.

 Tier 3 (Moderate Concern): Sites where aquatic life impairment and/or TOrC exposure data suggest a high probability of a low-level effect of TOrCs on aquatic life that can be distinguished from the effects of other stressors.

 Tier 4 (High Concern): Sites where aquatic life impairment and/or TOrC exposure data suggest a high probability of a moderate or high-level effect of TOrCs on aquatic life that can be distinguished from the effects of other stressors.

The site screening tools were tested with data from six sites and validated with additional field studies at three sites. Data from the three validation sites have yielded differences in observed effects (Figure 2) and exposures. The project outcome demonstrated the benefits of using a weight-of-evidence approach as a decision-making framework to determine whether TOrCs are contributing to existing beneficial use impairments below municipal WRRF outfalls.

This paper will present the results of this WERF research project, including descriptions of the site screening tools, their application to the field sites and lessons learned so that interested IWEA members can apply the framework to their site. Figure 1. Overview of WERF TOrC Site Screening Process. Figure 2. Example of Observed Effects from Caged Fish Studies at Three Field Sites and Scoring in the Weight of Evidence Approach.