Chlorate Challenges for Water Systems

Chlorate, currently included in the US Environmental Protection Agency's monitoring of unregulated contaminants and on the contaminant candidate list, could potentially receive a regulatory determination in the near future. This article, using available literature along with past and current monitoring data, assesses the presence of chlorate in drinking water and the potential impact of its regulation. The article gives specific attention to the variety of threshold concentrations that appear most often in the literature—210, 700, and 840 μg/L—and evaluates the effect a regulatory requirement at each of these values would have on utilities. The research indicated that potential regulatory thresholds > 700 μg/L would be violated by only < 10% of utilities. The effects of regional conditions and type of disinfection used depend greatly on the adopted thresholds. Utilities in the southern region of the United States and those using chloramination are most at risk if a low maximum contaminant level is adopted.