Microbiological parameters supply unique information on water and wastewater quality and public health risks from waterborne diseases. Microbiological monitoring of drinking water has been practiced in the United States and other countries since the beginning of the century. The most effective microbiological monitoring of water sources is the simple, rapid, and inexpensive determination of the presence of indicator bacteria. Standards on microbiological quality were based previously on the detection and enumeration of the coliform group and were related to enteropathogens such as cholera and typhoid bacilli. Chlorination for microbiological disinfection was introduced at the beginning of this century. Since 1925, most public water supplies were equipped with some form of treatment. In 1985, the proposed rule of the National Primary Drinking Water Regulations, the Environmental Protection Agency (EPA) proposed a recommended Maximum Contaminant Level (MCL) of zero for total coliform. Turbidity regulation was coupled with the microbiological parameters setting a recommended limit of 0.1 Nephelometric Turbidity Unit (NTU).