Water is an irreplaceable natural resource on this earth which comprises marine, estuarine, fresh water (river and lakes), ground water across coastal and inland areas. Even though there is huge water resource in this world, about 97% of water is salt water (marine) only 3% is fresh water. And in this small fraction of fresh water a major part is in the form of ice in polar region. So just 0.003% is in the form of ground water and surface water which we can use.
Fresh water is a limited resource in many parts of the world. And this will become more dearth due to increasing in population, urbanization and climate change. The major fact for this paucity of fresh water is not only due to demand for water but also due to pollution in freshwater ecosystem. Due to the pollution created by human beings in this ecosystem, the usable water has decreased drastically and the cost of purifying the water has increased dramatically. The main sources of water pollution are point source and non point source. Point sources include pipeline discharge of pollutants such as domestic sewage discharge industrial waste effluents from factories or plants, to receiving waters. In contrast, non-point pollution results from storm runoff, which transports polluting materials diffusely over land.
Water pollutants are of different types such as oxygen demanding wastes, disease causing agents, synthetic organic compounds, plant nutrients, inorganic chemicals and minerals, oils, thermal discharge and radioactive wastes. Of all these water pollutants, heavy metals and synthetic organic compounds cause majority of water pollution. Industries like paper and pulp, tanneries, textiles and coke ovens, pharmaceutical, food processing, meat packing, pickling, dye-stuff and fertilizer discharge these pollutants into natural water bodies. Heavy metals and synthetic organic compounds are non-biodegradable and they can be accumulated living tissues causing various diseases and cause a great damage to human habitation. So these impurities and wastes shall be removed and water shall be purified before we use. Oil spillage from ships in sea leads to pollution of beaches. And also oil spillage from oil bores in deepwater’s of sea causes a major pollution to the ecosystem. Some wastes from pharmaceuticals and petrochemical industries contain phenols which are toxic to the natural life of flora and fauna.
Liquid effluents from industries manufacturing drugs, dye stuffs, pesticides and detergents can also be toxic. Colour in the liquid effluents can also decrease the capacity of plants in...