ET-4B1A (2/8/05 version)
Pathogens in Surface Waters: Why is This a
Drinking Water Problem?
The protozoan parasite Cryptosporidium is a potential contaminant that is
particularly threatening to surface water sources of drinking water. This was
demonstrated in 1993 when the City of Milwaukee public water supply became
contaminated with Cryptosporidium, leading to several deaths and hospitalizing
thousands more. The Milwaukee water treatment plant filters were unable to
remove the tiny microorganisms and chlorine could not destroy them. There are
many potential sources of Cryptosporidium in watersheds, including septic
system discharges and nonpoint sources associated with animal feces.
Therefore, the Enhanced Surface Water Treatment Rules (ESWTR)
will require public water systems to provide additional treatment to protect
against Cryptosporidium and allow for the development of a watershed control
program that reduces the water supply risk of contamination from
Cryptosporidium and other pathogens.