Cryptosporidium parvum, a parasite found in surface waters worldwide, has become a major
concern for drinking water suppliers over the past 15 years. Dozens of outbreaks have occurred in
developed countries where sanitation and water treatment practices are sophisticated and in
widespread use. Cryptosporidium oocysts are extremely resistant to physical and chemical
stresses and can survive for long periods of time, particularly in water. The oocysts can pass
through conventional water treatment plants under some circumstances and are highly resistant to
chlorine disinfection. Cryptosporidium causes a moderate to severe gastrointestinal illness for
which there is no medical treatment. For most individuals, the disease is self-limiting (like the
common cold, it runs its course), but for certain immunocompromised individuals, the disease can
be fatal. The parasite is found in fecal material from mammals, therefore runoff from agricultural
operations and sewage are potentially significant sources of surface water contamination. To
address this issue, the Water Environment Research Foundation (WERF) funded a study to
develop 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 municipal
sewage. An additional goal of the study was to incorporate cell culture techniques into the
method so that the infectivity of oocysts could be assessed.
Three methods were developed for analysis of wastewater samples, each based on Method 1622
for Cryptosporidium in source water. These variations are needed to account for the variety of
matrices found in the wastewater treatment process. The performance of the wastewater
Cryptosporidium method is similar to that seen with source water samples. The method is
sensitive (can detect low concentrations of oocysts), but is more variable in overall recovery. To
address the higher level of variability, an internal positive Cryptosporidium control, ColorSeed£
is added to each sample prior to analysis. The methods have been used over the last 16 months to
develop a database of Cryptosporidium occurrence across the wastewater treatment processes at
ten publicly-owned treatment works (POTWs) across the US. Cryptosporidium oocysts have been
consistently recovered in all nine plants and in all matrices (raw, primary and secondary effluent)
except the tertiary effluents. Includes 3 references, tables.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 230 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 4 |
| Published : | 11/02/2003 |
