Water pollution:

Water pollution is contamination of streams, lakes, underground water, bays or ocean by substances harmful to living things. Water is necessary to life on earth. Plants and animals require water that is moderately pure, and they cannot survive if their water is loaded with toxic chemicals or harmful microorganisms.

Oxygen demanding waste in water pollution:

Oxygen demanding wastes are organic compounds, such as sewage and agriculture runoff, which decompose through microbial action in water.

Oil and chemicals derived from oil are used for fuel, lubrication, plastics manufacturing and many other purposes. These petroleum products get into water mainly by means of accidental spills, from ships, tanker trucks, pipelines and leaky underground storage tanks.

Pesticides and Herbicidesare chemicals used to kill unwanted animals and plants. These chemicals may be collected by rainwater and carried into streams.

Heavy metals such as copper, lea, mercury, and selenium get into water from many sources, including industries, automobiles exhaust, mines and even natural soil. Heavy metals can be immediately poisonous or can result in long-term health problems similar to those caused by pesticides and herbicides.

Fertilizersand other nutrients used to promote paint growth on farms and in gardens may find their way into water.

Sewage from shipsand food waste discarded from ships on the open sea do little harm, but plastic thrown overboard can kill birds or marine animals by entrapping them, choking them or blocking their digestive tracts if swallowed.

Water pollution can also be caused by other types of pollution. The polluted air mixes with atmospheric moisture to produce airborne sulphuric acid, which falls to the earth as acid rain. In turn, the acid rain can be carried into a stream or lake, becoming a form of water pollution that can harm or even eliminatewildlife.

Prevent Water Pollution:

Water pollution can be controlled by adopting certain measures.

1. Water treatment plants should be established to treat industrial effluents before they are released to water bodies.
2. Reuse of treated water for non-drinking purposes should be promoted.
3. Use of sewage and city waste water for irrigation to agriculture and horticultural crops should be promoted.
4. Ban and imposition of fines on industries not following pollution control methods.
5. Ban on dumping of industrial wastes in unsafe ways.
6. Recycling and composting of the city wastes.
7. Safe handling of sanitary wastes by internal drainage system.