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.

• Alternative Disinfectants and Oxidants Guidance Manual (PDF)(328 pp, 17000 K, About PDF) EPA 815-R-99-014, April 1999 This manual provieds technical data and engineering information on disinfectants and oxidants that are not as widely used as chlorine.

• Microbial Disinfectant Byproduct Rules Simultaneous Compliance Manual (PDF)(148 pp, 413 K, About PDF) EPA 815-R-99-015, August 1999 This manual describes many of the potential conflicts that may arise as systems comply with the rules currently being developed by the EPA, known collectively as the Microbial and Disinfection Byproduct (M-DBP) cluster of rules.

• Guidance Manual for Conducting Sanitary Surveys of Public Water Systems; Surface Water and Ground Water Under the Direct Influence (GWUDI) (PDF)(432 pp, 21000 K, About PDF) EPA 815-R-99-016, April 1999 This manual provides guidance on how to conduct a sanitary survey of surface water and ground water under the direct influence of surface water systems.

• Uncovered Finished Water Reservoirs Guidance Manual (PDF)(92 pp, 385 K, About PDF) EPA 815-R-99-011, April 1999 This manual provides a basic understanding of the potential sources of external contamination in uncovered finished water reservoirs and provides guidance to water treatment operators for evaluation and maintaining water quality in these reservoirs.

• Optimizing Water Treatment Plant Performance Using the Composite Correction Program (PDF)(268 pp, 2000 K, About PDF) EPA 625-6-91-027, August 1998 This handbook provides detailed information on Comprehensive Performance Evaluations (CPEs)

• Surface Water Treatment Rules: What do they mean to you? (PDF)(87pp, 1314 K, About PDF) EPA 816-R-20-006, June 2020 The purpose of this guidance is to detail the regulatory requirements of the interim enhanced surface water treatment rule.

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