4.2.1. Water Treatment Technology and Regulations

During the CALFED years, two clusters of USEPA drinking water regulations were promulgated: the Enhanced SWTRs [44,51,52] and the DBP Rule [44,45]. In response to these rules, the CALFED program established targets for providing safe, reliable, and affordable drinking water as either: (i) average bromide concentrations of 50 μg/L and 3.0 mg/L TOC concentrations at southern and central Delta drinking water intakes or (ii) an equivalent level of public health protection using a cost-effective combination of alternative source waters, source control, and treatment technologies [77]. The CALFED targets were predicated, in part, on data and information developed through the MWQI program.

Because the CALFED targets could not be feasibly achieved in the short time frame required to comply with the promulgated rules, water agencies participating in the MWQI program generally adopted advanced treatment technologies during this era that went beyond the best available technologies outlined in response to the new USEPA drinking water regulations. Typical advanced treatment technologies included GAC adsorption with chlorine as the primary and secondary disinfectant or ozone and chloramines as the primary and secondary disinfectants, respectively. By the end of 2005, more than 70 percent of the combined treatment capacity of the agencies employed ozonation (Figure 2), including Metropolitan's 326 million gallon per day (mgd) Mills plant and 750 mgd Jensen plant, which treat Delta water from the east and west branches of the California Aqueduct, respectively. Nonetheless, continued efforts to develop a Delta "fix" were made to address a possible future tightening of the USEPA regulations and/or to reduce the costs of operating the advanced treatment technologies in place.
