The Long Term 2 Enhanced Surface Water Treatment Rule specifies that UV disinfection must provide at least what level of log removal for Cryptosporidium?

The Long Term 2 Enhanced Surface Water Treatment Rule specifies that UV disinfection must provide at least what level of log removal for Cryptosporidium?

• A. Two-point-zero-log removal inactivation for Cryptosporidium
• B. One-point-five-log removal inactivation for Giardia
• C. Two-point-zero-log removal inactivation for Giardia
• D. One-point-five-log removal inactivation for Cryptosporidium

Answer: (A)

UV disinfection performance is measured in log removal to show how much of a pathogen is inactivated. The LT2 rule sets a specific requirement for Cryptosporidium because it is highly resistant to disinfection. Under this rule, UV disinfection must achieve at least a 2.0-log removal (about a 99% reduction) of Cryptosporidium to ensure a meaningful level of protection for drinking water. This is the reason the correct option specifies two-point-zero-log removal for Cryptosporidium. The other options mix in Giardia or use the wrong log value for Cryptosporidium, which doesn’t meet the regulation. Giardia may have different susceptibilities, but the rule’s UV criterion for Cryptosporidium is the 2.0-log threshold, making that the best answer.

UV disinfection performance is measured in log removal to show how much of a pathogen is inactivated. The LT2 rule sets a specific requirement for Cryptosporidium because it is highly resistant to disinfection. Under this rule, UV disinfection must achieve at least a 2.0-log removal (about a 99% reduction) of Cryptosporidium to ensure a meaningful level of protection for drinking water. This is the reason the correct option specifies two-point-zero-log removal for Cryptosporidium.

The other options mix in Giardia or use the wrong log value for Cryptosporidium, which doesn’t meet the regulation. Giardia may have different susceptibilities, but the rule’s UV criterion for Cryptosporidium is the 2.0-log threshold, making that the best answer.