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Drinking Water Requirements for States and Public Water Systems

Interim Enhanced Surface Water Treatment Rule Documents

The Interim Enhanced Surface Water Treatment Rule (IESWTR) builds on the requirements of the Surface Water Treatment Rule. IESWTR specifies treatment requirements to address Cryptosporidium and other microbial contaminants in public water systems serving 10,000 or more persons.

The rule balances the need for treatment with potential increases in disinfection by-products. The materials found on this page are intended to assist public water systems and state in the implementation of the IESWTR.

For more information, please see the Surface Water Treatment Rules page.