The results of the US Environmental Protection Agency, Office of Drinking Water, sampling and analysis of volatile organic compounds (VOCs) in finished water supplies that use groundwater sources are discussed. Concentrations of 29 VOCs in addition to five trihalomethanes and total organic carbon from 945 water supplies were measured. The five most frequently found compounds other than trihalomethanes were trichloroethylene, 1,1,1‐trichloroethane, tetrachloroethylene, cis‐ and/or trans‐1,2‐dichloroethylene, and 1,1‐dichloroethane. Approximately half of the samples were taken from a random list of water systems, which were subdivided into two sets of systems—those serving fewer than 10 000 persons and those serving more than 10 000 persons. The nonrandom samples were taken from systems selected by the states, using groundwater sources that were likely to show VOCs in drinking water. Large systems in the random sample had a significantly higher frequency of occurrence of VOC contamination than small systems and were also more likely to have higher levels of contamination.

Larger systems with high TOC concentrations are likely to be required by the ICR to conduct bench or pilot studies of granular activated carbon or membranes for the control of DBP precursors. The Information Collection Rule (ICR) will require surface water systems serving ≥100,000 people with raw‐water total organic carbon (TOC) levels of >4.0 mg/L and groundwater systems serving ≥50,000 people with finished‐water TOC levels of >2.0 mg/L to conduct bench or pilot studies of granular activated carbon or membranes for the control of disinfection by‐product (DBP) precursors. The US Environmental Protection Agency has developed and is considering an approach to ensure that adequate data are obtained and that the resources for performing these studies are appropriately distributed. Also, the AWWA Disinfectants/DBP Technical Advisory Workgroup has developed a database on the geographic and temporal distribution of TOC in the United States.

Utilities are currently evaluating membranes and GAC for DBP precursor removal. Under the treatment study requirement of the Information Collection Rule, 493 treatment plants were required to monitor total organic carbon (TOC) concentrations in their influent or finished water to determine whether studies evaluating granular activated carbon or membranes would be required. These TOC results were aggregated and analyzed by source water type, treatment type, disinfection practices, and geographic location. Seventy‐eight percent of these plants met the criteria to avoid the treatment study requirement. The remaining plants will be required to conduct new treatment studies, submit data from previous studies, or contribute funds to a cooperative research effort. Under the treatment study requirement, 62 granular activated carbon studies and 37 membranes studies will be conducted.

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