Sewage treatment removes the vast majority of protozoa

An analysis of raw sewage and treated wastewater at six sewage plants in three states showed that standard sewage treatment processes get rid of 98% of cryptosporidium oocysts and 97% of giardia cysts.

Cryptosporidium measured in oocysts per liter; giardia measured in cysts per liter.
Chart: The Conversation, CC-BY-NDSource: Rose, 2007.Get the data Download image