Water contamination can be defined as alteration in physical, chemical or biological characteristics of water, making it unsuitable for designated use in its natural state. World Health Organisation has defined water contamination as, any foreign material either from natural or other sources that may pollute the water supply and make it harmful to life.
Contamination of water leads to reduction of normal oxygen level of water, causes aesthetically unpalatable effects and spread of epidemic diseases.
Water gets polluted in fresh water bodies due to domestic, industrial and agricultural effluents. Saline water in the oceans also get affected by thermal pollution and other waste pollutants such as oil slicks and nuclear waste.
Contamination of water affects man, aquatic animals as well as the environment. Most of the waste waters especially sewage contain pathogenic and non-pathogenic micro-organisms and many viruses. Polluted water is responsible for causing several water=borne diseases like cholera, typhoid, diarrhoea, dysentery, hepatitis, polio and jaundice.
Pollutants such as heavy metals, pesticides, cyanides and many other organic and inorganic compounds are harmful to all organisms.
Some heavy metals like lead, mercury and cadium cause various types of that contains toxic substances ultimately affects human health.
Mercury dumped into water is transformed into water soluable methyl mercury by bacterial action. Methyl mercury accumulates in fish. In 1953, people in Japan suffered from numbness of body parts, vision and hearing problems and abnormal mental behaviour. This disease called Minamata disease occured due to consumption of methyl mercury contaminated fish caught from Minamata Bay in Japan. Pollution by the heavy metal, cadium caused the disease called Itai-itai among the people of Japan.
Algae which is responsible for imparting a peculiar taste and odor to the water supplies, due to pollution causes gastro enteritis. Agal poison usually act on the central nervous system and skin. It is reported to be capable of producing cirrhosis of the liver.
Tips and comments:
In order to control water contamination from point sources, treatment of waste water is essential before it is being discharged. There must be strict regulations for the discharge of domestic, sewage and industrial effluents. These must not be discharged into water bodies. Industries should develop its own effluent treatment plant.
All types of waste and effluents should be treated before they are released into water bodies. The pollutants should be detoxified before being dumped. The sewage should be fully treated before releasing it into rivers or fields.