AWWA JAW41508

The concentration of microbiota and total particulates in raw and finished water samples from 55 conventional treatment plants was compared. Analyses included: enumeration and identification of the microbiota; direct measurement of the pellet volume of total particulates after laboratory centrifugation; total particle counts; and, Giardia and Cryptosporidium detection. Organism reduction based on microscopic particulate analysis in the raw and finished waters ranged from -0.8 to 6.0 log. There was a significant correlation between reduction values generated by organism counts, centrifugate pellet measurements, and particle counts. However, only organism reduction values remained consistent regardless of influent turbidity or flocculent material present in the effluent. Because of low concentrations and intermittent occurrence, counts of Giardia and Cryptosporidium did not accurately reflect treatment plant performance. Includes 42 references, table, figures.