Bacteria are naturally present everywhere in the environment, including raw water sources. As part of the treatment process, all water treatment plants disinfect the water prior to distribution. In Attleboro, we use sodium hypochlorite as a disinfectant. The residual chlorine concentration is maintained at a level sufficient to keep all harmful bacteria out of the system.
To ensure that the disinfection process is effective throughout all parts of the City, we test the water weekly from between 15 to 18 sample points, including the most remote parts of the City. We check for the presence of coliform. The coliform serve as an indicator of the presence of other more harmful bacteria. Should coliform be detected, steps would be taken immediately to identify the source and remedy the situation, usually with further disinfection.
While the detection of coliform in Attleboro's drinking water is a rare occurrence, should more than 5% of samples drawn in any given month indicate their presence, the public would be notified as to what steps should be taken. Most often, the situation would require that the water be boiled before consumption.