Generally if coliform bacteria are present, other harmful bacteria are likely to be present. Most of the harmful bacteria cause diarrhea, abdominal cramps, nausea, low-grade fever, and vomiting. Coliform samples are carefully collected in sterilized bottles. A certain portion of each sample is mixed with a nutrient medium and incubated for twenty-four hours. A color change or the production of gas indicates the presence of coliform bacteria.
Chlorine is the most widely used drinking water disinfectant in North America.
Chlorine is added to drinking water as a solution. When the level of chlorine is above 0.5 parts per million, most people can smell chlorine in the water. State regulations require at least 0.2 parts per million of chlorine throughout the distribution system. Chlorine is measured in the field using a portable instrument. One way to reduce TTHM levels has been to change from chlorine disinfection to chloramine disinfection.