Protozoan monitoring: from the ICR to the ESWTR

The proposed Information Collection Rule may require utilities to monitor source and finished waters for Giardia and Cryptosporidium and to use the data for compliance with treatment requirements imposed by the Enhanced Surface Water Treatment Rule. Variations in sample collection and analytical methods, water quality, weather conditions, and proposed averaging methods could result in widely varying detection limits; in certain cases detection limits could easily be inaccurately pushed beyond 100 organisms/100 L. The optimal balance between sample cost and laboratory analysis is achieved by examination of 1-3 membrane filters, depending on source water turbidity. Improved monitoring results and detection limits may prevent decisions to institute unnecessary and possibly expensive treatment.