The pollution can be controlled by the following ways:
1. Municipal sewage :
Municipal sewage has got many organic and inorganic substances and human excreta with many pathogenic bacteria. All sewage discharge of a city or town should be in a river which has past the town. If there is no river near a town then the sewage may be discharged in a nearby lake or pond. This type of arrangement usually decrease oxygen contents of water due to which fishes and vegetation of rivers may die. Hence it is required that sewage purification is made before its contents enter a river, lake or pool.
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This is done as follows:
a) First the sewage is passed through special filters (process called—straining), then the impurities are allowed to settle down (process called – settling). By these many inorganic and organic substances are separated but some organic substances remain in the suspended state.
b) The next step is mineralization of these substances due to which these organic substances are converted to inorganic form. This is done through oxidation. This oxidation is done by artificially adding oxygen or green algae are added in oxidation tanks which produce oxygen in photosynthesis. Dirty water contains all mineral elements essential for the healthy growth and development of algae e.g., nitrogen, phosphorus, sulphur and potassium, but in dirty water these are present as compounds of organic substances. To be utilized by algae these substances must be oxidised to CO2, NH3, SO4, NO3, PO3. This is done by algae and bacteria. Algae produce oxygen for bacteria and bacteria oxidise these complex organic components to inorganic form. This type of purification take place in oxidation ponds or stabliza-tion ponds. Sewage enters these ponds at a specific pond and outlet of water is at the other end of the pond.
2. Household detergents :
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Household detergents should also be allowed to fall in rivers on their lower level side after the town. In the same way effluents from industries should not be allowed to go into fields and water reservoirs where fish population is present. The tank that are used for supply of drinking water (by man and his animals) should not be used for washing. Similarly the water from fields in which weedicides or pesticides were sprayed should be kept away from water reservoir. Also water from factories should be kept away from drinking water reservoirs.
3. Atomic blasts
Atomic blasts should be reduced and stopped entirely. The disposal of radioactive wastes is also an important problem and sea is thought to be best dumping place for such wastes.
4. Residential localities
Residential localities should be situated away from roads so as to reduce the possibility of smoke from automobiles and noise pollution.
5. House dung
House dung should be collected in compost pits outside the villages, so that it does not become a breeding place for flies and it may not emit foul smell and also good manure may be produced from this dung. Dung should be used to produce “gobargas” through “gobargas plants.”
6. Dead animals and other household wastes
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Dead animals and other household wastes should be buried in pits away from residence and should be covered by soil. Engineers of Central Public Health Engineering Research Institute after a survey of methods of control for water, air and soil pollution have suggested various methods for the control of pollution. They have suggested use of different types of filters. They have also recommended several other important processes.