Development of Surrogates to Determine the Efficacy of Groundwater Recharge Systems for the Removal of Trace Organic Chemicals
Year Released: 2011
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board, Southwest Florida Water Management District
Total Investment: $413,000 (Cash: $200,000, In-Kind: $213,000)
Principal Investigator: Jörg E. Drewes, Ph.D., Colorado School of Mines
An increasing number of water utilities are using drinking water sources influenced by wastewater discharge and others are planning for or implementing indirect potable reuse via groundwater recharge systems. The use of water sources influenced by wastewater has raised public concerns because of the presence of trace organic contaminants.
Goals and Objectives
The project identifies potential surrogates and indicators for the removal of wastewater-derived chemical contaminants in groundwater recharge projects employing soil-aquifer treatment after surface spreading and membrane treatment ahead of direct injection projects, validates the ability of chosen surrogates and indicators to predict the removal of wastewater-derived contaminants in groundwater recharge projects, and develops recommendations for the water industry regarding suitable surrogates for groundwater recharge systems using reclaimed water.
The approach for monitoring trace organic chemicals for groundwater recharge operations developed in this study utilizes a combination of surrogate parameters and indicator chemicals. In the context of this study, an indicator chemical is an individual chemical occurring at a quantifiable level, which represents certain physicochemical and biodegradable characteristics of a family of trace constituents that are relevant to fate and transport during treatment, and thus provides a conservative assessment of removal. A surrogate parameter is a quantifiable change of a bulk parameter that can serve as a measure of individual unit processes or operations’ performance in removing trace compounds. This approach utilizes only a limited set of analytes for the evaluation of proper performance of soil-aquifer treatment and high-pressure membrane treatment systems and may be a reasonable way to circumvent the significant costs associated with analysis of a wide range of chemicals of concern.
Findings and Conclusions
Based on findings derived from conducting field monitoring efforts at five different field sites, redox conditions and feed water types did not seem to impact the removal of indicator chemicals during SAT. The results indicate that removals for biodegradable indicator chemicals are similar across sites for similar travel times despite differences in the extent of vadose zones, which supports the robustness and reliability of SAT operations regarding the removal of biodegradable trace organic chemicals. Removal of indicator chemicals was correlated with removal of surrogate parameters, such as TOC, TOX and UVA. In general, select indicator chemicals, with the exception of benzophenone, exhibited a significant correlation with both TOC and TOX.