Community water systems are required to deliver safe and reliable drinking water to their consumers.

If the water supply becomes contaminated, consumers can become seriously ill. Drinking water suppliers should take many steps to ensure safe drinking water. One of the most important steps is to regularly test the water for coliform bacteria.

Although access to safe drinking water is a fundamental requirement for good health, recently drinking water supplies of Kathmandu Valley have been found to be contaminated with coliform bacteria.

Coliform bacteria include a large groups of bacteria that occur throughout the environment. They are common in the soil and surface water and may even occur on your skin.

A large number of certain kinds of coliform bacteria can also be found in wastes from humans and animals. Most coliform bacteria are harmless to humans, but some can cause mild illnesses and a few can lead to serious waterborne diseases.

Coliform bacteria are often referred to as “indicator organisms” because they indicate the potential presence of disease causing bacteria in water. The presence of coliform bacteria indicates that a contamination pathway exists between a source of bacteria and the water supply.

Disease-causing bacteria may use this pathway to enter the water supply.

Fecal coliform bacteria are specific to the intestinal tracts of animals including human representing fecal contamination in water. E. coli is a fecal coliform commonly found in the intestines of humans. A positive E. coli result in water indicates that human or animal waste is entering the water supply which may produce powerful toxins and cause severe illness and death.

If disease-causing bacteria are present, the most common symptoms are gastrointestinal and general flu-like symptoms such as fever, abdominal cramps and diarrhea. Symptoms are most likely in children and the elderly.

Household residents may acquire immunity to waterborne bacteria that are common in their drinking water but visitors who have not acquired immunity may become ill after drinking such kind of water.

Most coliform bacteria do not cause disease but greater their number greater the likelihood that disease-causing bacteria may be present.

Since coliform bacteria usually persists in water longer than most disease-causing organisms, the absence of coliform bacteria leads to the assumption that the water supply is microbiologically safe to drink.