All surface water supplies are at some degree of risk for Cryptosporidium . Unfiltered supplies are especially vulnerable to an outbreak if contamination occurs. Therefore, protective measures must be in place to prevent the organism from entering the source water or the distribution system. Traditional measures of water purity do not apply to crypto. Coliform analysis cannot accurately predict protozoan contamination, so negative bacteriological analysis results are no guarantee of the absence of Cryptosporidium .
Chlorine is virtually ineffective on crypto at levels typically used for disinfection.
While ozone is the most effective disinfectant against the oocyst, its use is not widespread at this time. Turbidity, which is generally accepted as an accurate measure of filter performance, is a poor indicator of oocyst removal, especially in low- turbidity source water. While all this might sound discouraging, optimizing water treatment can minimize the risk presented by Cryptosporidium . Strive to achieve 0.1 to 0.2 ntu or less in finished water. Use particle analysis to enhance filter performance.