Nitrate, coliforms, and Cryptosporidium spp. as indicators of stream water quality in western Pennsylvania.

Surface-water treatment plants provide water to approximately 67 percent of the residents of Pennsylvania. Industrial activities and agricultural practices significantly contribute to the chemical and microbiological load of surface-water systems. For the study reported here, surface water from three sites along Two Lick Creek in Indiana County in Pennsylvania were sampled and analyzed for nitrate, iron, total and fecal coliforms, and Cryptosporidium oocysts. Mean nitrate concentrations were 2.88, 3.15, and 3.83 mg/L for Site 1, Site 2, and Site 3, respectively, while mean total-coliform counts ranged from 6.89 x 10(2) to 22.40 x 10(2) CFUs per 100 mL, and fecal coliform counts ranged from 0.30 x 10(2) to 11.1 x 10(2) CFUs per 100 mL. Cryptosporidium oocysts ranged from a low of <46 to a high of 91 per 100 L depending on sample turbidity. The recovery rates of oocysts from spiked samples ranged from 22 percent (low-turbidity samples) to a low of 0.76 percent (high-turbidity samples). This paper discusses the impact of environmental factors on nitrate concentration, coliforms, and Cryptosporidium, as well as the health significance of these water quality indicators.