Water pollution is deterioration of quality of land water (rivers, lakes and ground water) or sea water as a result of various human activities. Water pollution is a global problem that can adversely affect organisms. It occurs due to any physical or chemical change in water.
The major water pollutants are
· Domestic sewage, animal manure and industrial wastes
· Disease causing elements like bacteria, viruses and parasites
· Inorganic chemicals
· Sediments (soils, silts)
· Organic chemicals like pesticides, plastics, detergents etc.
· Heat from industrial and power plant cooling towers
· Radioactive substances
Out of the above sediment is the major water pollutant. The water pollutants can be classified as degradable or non-degradable.
Sources of water pollution
In today’s world clean water has become a precious commodity and its quality is degraded by several sources of pollution such as
Industrial effluents: The industrial discharged into drains, rivers or water bodies contains a lot of toxic chemicals like cyanides, amines, toxic acids, oils, greases, dyes, biocides, suspended solids and thermal pollutants from numerous industries. These effluents pose several pollution problems.
Fertilizers: Today’s agriculture relies a lot on artificial fertilizers. These fertilizers enhance the vegetation but on the other side they disrupt the entire natural aquatic ecosystem. Excessive use of these fertilizers on land has also created an adverse ecological effect on aquatic ecosystem because some of them are washed off land into rivers and lakes through irrigation, rain or drainage.
Sewage and domestic wastes: About 75% of water pollution is caused by sewage and domestic wastes. It includes human excreta, soap, metals, glass, garden waste and sewage sludge. The water bodies are not able to recycle them and lose their self regulating capacity.
Detergents: Household detergents contain several polluting agents which adversely affect the water bodies. They contribute to phosphates of sodium, sodium sulphates etc.
Thermal pollutants: As the temperature of water rises, there is more demand for dissolved oxygen because of less oxygen in water. The hot water discharged into water bodies adversely affects the aquatic environment.
Siltation: Silt contains dirt and dust particles carried from land to water. It is the most widespread and damaging pollutant. The soil particles create turbulence in water which hinders the free movement of aquatic organisms, growth of fishes and their productivity.
Radioactive substances: Radioactive pollutants enter the water bodies from nuclear power plants, nuclear reactors and fusion products etc. It produces a set of syndrome characterized by nausea, vomiting, diarrhoea and general sickness known as radiation sickness. The human body become less resistant towards a variety of diseases.