Regulatory impact analysis of the disinfectants-disinfection by-products rule

As part of the rule-making process, regulatory impact analyses (RIAs) are performed to determine the potential effects of implementing different regulatory options. An RIA was prepared for the Disinfectants/Disinfection By-Products (D/DBP) Rule. DBPs can be controlled by using either precursor removal technologies or alternative disinfectants. In the RIA, total organic carbon (TOC) was used as a surrogate for DBP precursors. To represent the occurrence and control of chlorination by-products, trihalomethanes (THMs) and haloacetic acids (HAAs) were evaluated. It was predicted that reductions in DBPs would parallel the TOC reductions anticipated for the precursor removal strategies. In addition, it was predicted that ozone/chloramines would produce THM levels as low as those produced by granular activated carbon and HAA levels comparable to those produced by optimized coagulation. The RIAs were used during the rule-making process to evaluate the efficacy of various technologies in controlling DBPs and to develop the nationwide and household casts of different regulatory scenarios.