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Cryptosporidium parvum, a parasite found in surface waters worldwide, has become a majorconcern for drinking water suppliers over the past 15 years. Dozens of outbreaks have occurred indeveloped countries where sanitation and water treatment practices are sophisticated and inwidespread use. Cryptosporidium oocysts are extremely resistant to physical and chemicalstresses and can survive for long periods of time, particularly in water. The oocysts can passthrough conventional water treatment plants under some circumstances and are highly resistant tochlorine disinfection. Cryptosporidium causes a moderate to severe gastrointestinal illness forwhich there is no medical treatment. For most individuals, the disease is self-limiting (like thecommon cold, it runs its course), but for certain immunocompromised individuals, the disease canbe fatal. The parasite is found in fecal material from mammals, therefore runoff from agriculturaloperations and sewage are potentially significant sources of surface water contamination. Toaddress this issue, the Water Environment Research Foundation (WERF) funded a study todevelop and validate methods for recovery and identification of Cryptosporidium in wastewater,and to use these methods in a national survey to assess the levels of this parasite in municipalsewage. An additional goal of the study was to incorporate cell culture techniques into themethod so that the infectivity of oocysts could be assessed.Three methods were developed for analysis of wastewater samples, each based on Method 1622for Cryptosporidium in source water. These variations are needed to account for the variety ofmatrices found in the wastewater treatment process. The performance of the wastewaterCryptosporidium method is similar to that seen with source water samples. The method issensitive (can detect low concentrations of oocysts), but is more variable in overall recovery. Toaddress the higher level of variability, an internal positive Cryptosporidium control, ColorSeedis added to each sample prior to analysis. The methods have been used over the last 16 months todevelop a database of Cryptosporidium occurrence across the wastewater treatment processes atten publicly-owned treatment works (POTWs) across the US. Cryptosporidium oocysts have beenconsistently recovered in all nine plants and in all matrices (raw, primary and secondary effluent)except the tertiary effluents. Includes 3 references, tables.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 4File Size: 1 file , 230 KB