Research Project Summary: Survey of Surface Source Waters for Giardia and Cryptosporidium and Water Treatment Efficiency Evaluation

Giardia and Cryptosporidium (shortened to "Crypto") parasites are among the leading identified causes of waterborne disease in the United States. Giardia cysts and Crypto oocysts have been identified in many surface waters throughout the country, but the concentrations in most of New Jersey's (NJ) surface waters, many of which are used as source waters for drinking water treatment plants, are unknown. To provide safe drinking water, treatment plants need to remove Giardia and Crypto from untreated water or reduce their concentrations to safe levels. Peak parasite levels, together with adverse water treatment factors, such as low water temperature, determine the maximum risk of human infection. However, parasite testing is not required by law and is not routinely performed by water treatment plants or regulatory personnel because the methods available are difficult, expensive, time-consuming, and have other drawbacks. In this project, 15 sites (. 45% of NJ's surface source waters) were selected to represent the full anticipated range of water quality and potential parasite impact in the state. Each site was sampled 10 times over a one year period at varying turbidity levels (final n=147). Parasites were isolated and partially purified from 100 gallon samples and examined microscopically. Giardia and Crypto were detected in 23% and 20% of the samples at average concentrations of 2.1 cysts/liter (range 0.4-6.3) and 2.0 oocysts/liter (range 0.3 - 9.8), respectively. These concentrations were similar to those found in an earlier national study. No individual location had unusually high parasite concentrations. Parasite levels did not correlate with any other, more easily measured water quality parameter such as turbidity or coliform bacteria. The treatment effectiveness of two of the treatment facilities was monitored on 9 parasite sampling days by measuring particle count reductions and determining disinfectant (chlorine) concentration and contact time (C x t) inactivation values for Giardia. Source water Giardia levels were reduced following treatment to a health risk-based goal of 0.0007 organisms per 100 liters on all but one occasion when pre-disinfection C x t values were included with the post-disinfection values. There is currently insufficient health-risk and "field" disinfection data to perform similar treatment efficiency calculations for Crypto