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EPA ORD/EPA REGION 2/PITTSBURGH WSA COOPERATIVE EFFORT: EVALUATING CRYPTOSPORIDIUM AND GIARDIA IN COMBINED SEWER OVERFLOW AS A THREAT TO DRINKING WATER SUPPLIES
Arnone*, R D., J. F. Walling, AND M Borst*. EPA ORD/EPA REGION 2/PITTSBURGH WSA COOPERATIVE EFFORT: EVALUATING CRYPTOSPORIDIUM AND GIARDIA IN COMBINED SEWER OVERFLOW AS A THREAT TO DRINKING WATER SUPPLIES. Presented at WSWRD Peer Review, Cincinnati, OH, September 26 - 29, 2004.
To inform the public.
Since the first identified Cryptosporidium outbreak in the United Kingdom in 1983, emerging protozoa pathogens Cryptosporidium and Giardia have become the subject of growing local, state, and national concerns. Both organisms have been the causative agent of many gastrointestinal illnesses linked to the consumption of contaminated surface or ground water. Cryptosporidium and Giardia are found in streams, rivers, ground water, and soil.
This study focuses on the combined sewer overflow (CSO) contribution. CSOs are discharges of untreated sewage and stormwater released directly into receiving waters during heavy rainfall, when the combined flow in the sewer system exceeds the system's hydraulic capacity. Limited comprehensive data are available assessing the CSO discharge contribution as a source of these two pathogens.
This cooperative effort determined the detection frequency and concentration of Cryptosporidium and Giardia in CSO. These data are useful to drinking water treatment plants located downstream of where CSOs occur during times of wet weather. This is crucial in determining the potential concentration of these parasites in treatment plant intake. Using a modified version of EPA Method 1623, this project also assesses method variability and cyst/oocyst recoveries among the three laboratories participating in this joint effort, and within an individual laboratory. Six indicator organisms (total coliform, fecal coliform, E. coli, Enterococcus, fecal streptococcus, endospores) and several physical and chemical parameters are being analyzed in unison to further describe the sample.
CSO from urban areas was not found to be a contributor of Cryptosporidium, but CSO was found to be a source of Giardia. Because Cryptosporidium was not frequently found, a meaningful relationship could not be tested with bacterial indicators or endospore concentrations. Bacterial indicators and endospore concentrations were not well correlated with Giardia. The best correlated indicator was Enterococcus (R2 = 0.4526). Recognizing the limited data set (N=12), strong correlations were not expected.