Groundwater systems at high risk for fecal contamination must provide a 4.0-log inactivation of viruses.

Groundwater systems at high risk for fecal contamination must provide a 4.0-log inactivation of viruses.

• A. 3.0-log, Cryptosporidium
• B. 4.0-log, Cryptosporidium
• C. 3.0-log, viruses
• D. 4.0-log, viruses

Answer: (D)

High-risk groundwater must be disinfected to inactivate viruses at a very high level because viruses are fecal contaminants that can travel with groundwater and cause illness. Inactivation means rendering viruses nonviable, and a four-log reduction indicates the virus count is decreased by a factor of ten thousand, leaving very few viable viruses remaining. This is specifically about viruses, not protozoa like Cryptosporidium. Different pathogens require different treatment credits, and the standard for high-risk groundwater is four-log inactivation of viruses to ensure strong protection. Therefore, the correct requirement is four-log inactivation of viruses.

High-risk groundwater must be disinfected to inactivate viruses at a very high level because viruses are fecal contaminants that can travel with groundwater and cause illness. Inactivation means rendering viruses nonviable, and a four-log reduction indicates the virus count is decreased by a factor of ten thousand, leaving very few viable viruses remaining.

This is specifically about viruses, not protozoa like Cryptosporidium. Different pathogens require different treatment credits, and the standard for high-risk groundwater is four-log inactivation of viruses to ensure strong protection. Therefore, the correct requirement is four-log inactivation of viruses.