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Development of Indicators and Surrogate for Chemical Contaminant

Project: 03-14
Product: Report
Year: 2008

Program: Principal
Funding Partner: Water Environment Research Foundation, Bureau of Reclamation, California State Water Resources Control
Total Investment: $290,245.28 (Cash)

Principal Investigator: Jörg E. Drewes, Ph.D., Colorado School of Mines


The recent detection of a variety of chemicals in municipal wastewater effluent has raised concerns about the potential presence of wastewater-derived chemical contaminants in water produced by indirect potable reuse systems. Regulatory agencies and utilities have struggled with this issue because the wastewater-derived chemicals often are present at extremely low concentrations and because no standardized analytical methods are available.

Goals and Objective

The project identifies surrogate parameters and indicator compounds for wastewater-derived chemical contaminants that might be useful in the assessment of indirect potable reuse systems, identifies and assesses the performance of analytical methods for the chosen surrogates and indicators, and validates the ability of chosen surrogates and indicators to predict the occurrence and removal of wastewater-derived contaminants in indirect potable reuse systems.

Research Approach

The approach for monitoring wastewater-derived contaminants developed in this study is utilizing a combination of surrogate parameters and indicator compounds tailored to monitor the removal efficiency of individual unit processes comprising an overall treatment train. An indicator compound is an individual chemical occurring at quantifiable level, which represents certain physicochemical and biodegradable characteristics of a family of trace constituents that are relevant to fate and transport during treatment, providing a conservative assessment of removal. A surrogate parameter is a quantifiable change of a bulk parameter that can serve as a performance measure of individual unit processes or operations regarding their removal of trace compounds. Selecting multiple indicators representing a broad range of properties will allow accounting for compounds currently not identified (“unknowns”) and new compounds synthesized and entering the environment in the future (i.e., new pharmaceuticals) provided they fall within the range of properties covered. The underlying concept is that absence or removal of an indicator compound during a treatment process would also assure absence or removal of unidentified compounds with similar properties.

Findings and Conclusions

For each treatment process, a master list of indicator compounds was provided by recruiting compounds, for which analytical methods existed, from a final list of viable indicator compounds present in secondary or tertiary treated wastewater effluents. The developed treatment removal categories for indicator compounds for each treatment process of interest (i.e., SAT, ozone, advanced oxidation, chlorination, carbon adsorption, and reverse osmosis) was validated through laboratory-, pilot-, and full-scale experiments. Findings of these studies confirmed the classification of indicator compounds into the different removal categories. As expected, results of these efforts also revealed that surrogate parameters are not strongly correlated with the removal of indicator compounds occurring at ng/L-level concentrations. Partial or complete change of select surrogate parameters, however, can demonstrate the proper operation of a unit operation or treatment train. Thus, to fully access the performance of unit operations regarding the removal of wastewater-derived contaminants, a combination of appropriate surrogate parameters and indicator compounds should be used. This framework is a conservative approach designed to detect failures in system performance regarding occurrence of wastewater-derived contaminants. Adopting the treatment categories framework can also assist in more properly tailor multiple-barriers of treatment processes with a demonstrated ability of remove wastewater-derived contaminants in indirect potable reuse applications.

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