Chemical pollutants may affect our health not only directly but also indirectly by accumulating in aquatic life such as fish that are consumed by humans. Though pollution seems to be an inevitable consequence of modern industrial technology, the challenge is to determine the level of pollution that permits economic and social development without causing hazards to health. Free of chemical substances such as chlorides, hardness, free and saline ammonia, albuminoid ammonia, nitrites and nitrates, oxygen, and dissolved oxygen. Toxic substances such as arsenic, cadmium, cyanide, lead, mercury, and selenium etc. indicate chemical contamination of water. Free of bacteria such as E. coli, and faecal streptococcus, clostridium perfringens, which indicate faecal pollution.
Purification of water is of great importance.
Despite this process, water gets polluted when it is piped to users due to various factors specific to India. Therefore, further purification at home becomes necessary. This is an easy, time tested and a satisfactory method of purification in households. Water must be brought to a rolling boil for five to ten minutes. It kills bacteria, spores, ova, cysts and sterilizes water.