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The Surface Water Analytical Tool (SWAT) has been used to evaluate future drinking water regulatory options during the Stage 2 Disinfectants/Disinfection By-Products Rule and Long Term 2 Enhanced Surface Water Treatment Rule negotiations. In this process, national projections of the likely impact of these regulatory scenarios were necessary to inform the negotiating committee. SWAT provided the means to predict national estimates of compliance technologies and disinfection byproduct (DBP) exposure. SWAT utilizes the predictive US Environmental Protection Agency Water Treatment Plant Model (WTP Model) and observed Information Collection Rule (ICR) data to forecast what treatment technologies are needed to comply with a given regulatory option. This prediction of treatment selection, specifically the proportion of plants predicted to select various technologies to meet a given regulatory scenario, is known as a compliance forecast. In forecasting compliance technologies, SWAT also utilizes the WTP Model to assess DBP exposure. A comprehensive description of the Surface Water Analytical Tool is presented in this paper. Future regulatory options were evaluated using SWAT during the negotiation process. These options varied TTHM, HAA5, and bromate MCL values, spatial and temporal aggregation of distribution system DBPs, and microbial inactivation requirements. Given the requirements of evaluating a wide array of regulatory options, SWAT performance had to be assessed to determine and correct, if possible, predictive limitations. A comprehensive validation process using observed ICR data characterized and improved SWAT predictive limitations. The results of this validation process are presented in this paper. SWAT is a valuable tool in understanding the future picture of drinking water compliance. Sensitivities in DBP exposure when considering microbial control requirements are well illustrated by SWAT predictions. SWAT also gives insight to the feasibility of treatment technologies given regulatory constraints. Results from SWAT predictions for regulatory options are presented in this paper. Trends in compliance forecasts and DBP exposures will also be discussed. These trends will explore responses to regulatory requirements. Includes 3 references, table, figures.

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Edition: Vol. - No. Published: 06/01/2001 Number of Pages: 18File Size: 1 file , 440 KB