MICROBIAL QUALITY IN WATER SOURCES USED FOR DRINKING WATER IN THE PHOENIX METROPOLITAN AREA

The Phoenix metropolitan area, one of the fastest growing urban areas in the United States, relies on the Verde River, the Salt River, Central Arizona Project (CAP) canal water, and groundwater for its drinking water. The main objective of this study was to investigate microbial water quality of surface waters as sources of drinking water. Water samples from five sampling locations in this area were analyzed for Cryptosporidium oocysts, Giardia cysts, and indicator microorganisms including male specific coliphages, somatic coliphages, total coliforms, fecal coliforms, and heterotrophic plate count (HPC) bacteria. The recovery efficiency of oocysts and cysts from seeded surface waters using immunomagnetic separation followed by an immunoflurescence assay (IMS-IFA) averaged at 81.6% and 30.9%, respectively. The results of oocyst recovery using IMSIFA and an integrated cell culture-polymerase chain reaction assay (ICC-PCR) were comparable. According to the comparison study of IMS and flotation percoll-sucrose gradient methods, the IMS method seems to be a better technique to process environmental samples for the detection of (oo)cysts. No oocyst was detected in any of the samples by IFA or ICC-PCR, whereas cysts were detected in 9.4% (3/32) of the samples. Based on the level of bacteria and coliphages detected in source waters, three surface waters were ranked for the level of fecal pollution: the Verde River > the Salt River > CAP water. Relatively high numbers of male specific coliphages in the samples from the South drinking water treatment plant (WTP) suggest probability of anthropogenic sources of contamination as the water passes through urban areas.