AWWA ACE58131

The Environmental Protection Agency will propose Cryptosporidium CT Tables for the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). Preliminary indications show that the required CT values will be higher than originally thought for Cryptosporidium inactivation. Several water utilities would be impacted by higher CT-values with respect to ozone operations and bromate control strategies. The Southern Nevada Water Authority (SNWA) is currently implementing 900 MGD of ozonation between two treatment facilities. The design of these facilities was based on initial Cryptosporidium inactivation research to achieve a 2.0-log inactivation. Substantial pilot plant testing has already been performed with respect to ozone operations and bromate mitigation strategies. Previous testing indicated that a combination of 0.1 mg/L ammonia and 0.5 mg/L chlorine could be used to maintain bromate levels below the 10 ppb Maximum Contaminant Level (MCL) while achieving a 2.0-log Cryptosporidium inactivation. This combination was evaluated with three other previously determined optimal strategies at seven different CT values. The results were compiled into operational matrices showing the impact on ozone dose, ozone residual quenching dose, and bromate control strategies. Overall, the results showed substantial increases in bromate formation, along with significant revisions to the current bromate control strategies. Includes 3 references, table, figures.