At the time, finding the culprit was a serious challenge for public health officials. Cryptosporidium is a protozoan that can sometimes be found in drinking water even after the water has been treated to make it presumably potable. Another protozoan that is often found in rivers and can persist in drinking water is Giardia . At the time of the Milwaukee crisis, Cryptosporidium was a microbe we knew little about. The problem is that we know a great deal more about chemical contamination of drinking water than about biological contamination.
Chemicals are relatively easy to identify and quantify.
We have chromatographs to separate one species from another and spectrometers to identify them. That is not the case with biological contamination. Many biological methods are basically visual, requiring a specially trained biologist to grow a colony of bacteria for inspection or to look through a microscope to identify the protozoa. One might at first think that the solu tion to microbiological contamination would be to treat water with disinfection chemicals such as chlorine or ozone, irrespective of whether the microbes are present. The problem is that the cure can cause more problems than the microbe it potentially removes.