The following documents include additional supporting information for the Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rule's economic analysis.
This report documents the development of empirically-based models used for predicting trihalomethanes, haloacetic acids, chloral hydrate, and bromate. The models can be used to assess the impact of changing water quality conditions on disinfection byproduct products (DBP) formation or to evaluate the impact of treatment modifications and were used in part in the Water Treatment Plant (WTP) Model v2.0 and Surface Water Analysis Tool (SWAT) v1.1.You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.
Surface Water Treatment Analytical Tool (SWAT) (PDF)(48 pp, 611 K,
This document describes the background and assumptions of the Surface Water Analytical Tool (SWAT) and provides guidance on its usage. The SWAT was prepared to assist USEPA in developing the Stage 2 Disinfectants/Disinfection By-Products (D/DBP) Rule and was used to estimate changes in technology and trihalomethane concentrations in drinking water predicted to occur when utilities complied with the Stage 1 and Stage 2 DBP Rules.
Water Treatment Plan (WTP) Manual (PDF)(126 pp, 794 K,
May 18, 2001)
The Water Treatment Plant (WTP) Model predicts treated drinking water quality given source water quality conditions, water treatment plant configuration and operation. It consists of a series of algorithms that predict levels of DBP precursors (e.g., bromide, Total Organic Carbon [TOC] and UVA254), pH values, disinfectant decay, and cumulative concentrations of DBPs formed from reactions of chlorine and chloramine with the aforementioned precursors. The WTP was a component of SWAT.