Point‐of‐use treatment and the revised arsenic MCL

Abstract

Community water systems (CWSs) may comply with the US Environmental Protection Agency's new 10‐μg/L arsenic (As) standard using point‐of‐use (POU) treatment by reverse osmosis; however, current regulations do not specify exactly how a CWS should implement POU treatment. This article describes three scenarios for implementing a POU program and provides cost estimates for each scenario. These costs vary significantly depending on the amount of monitoring and maintenance assistance provided for each POU unit. The scenario with less‐frequent (triannual) As monitoring and annual maintenance assistance to the customer could be substantially less expensive than centralized treatment for many small CWSs. The triannual As monitoring is supplemented by more frequent conductivity measurements to ensure proper operation of the individual POU treatment units. The higher‐cost scenario, which includes a quarterly As monitoring schedule more typical of recent POU applications, is likely to be more expensive than centralized treatment for most CWSs. Although most CWSs would probably not adopt POU treatment as the preferred method of compliance with a stricter As standard under the current regulations, a POU treatment program may be a less‐costly variance option for CWSs for which centralized treatment is not economically feasible.