Title 07-Pollution of air & water.pdf ✅

Oil spill ➢ EFFECT OF WATER POLLUTION (1) The polluted water contains a number of disease-causing pathogens like bacteria, protozoa and virus which cause water borne diseases. (2) The acids and alkalis present in industrial wastes kill those microorganisms which are the natural cleaning agents of water. (3) The sewage and fertilisers present in polluted water are rich in nutrients. This leads to an excessive growth of algae (algal bloom) which cover the whole surface of the waterbody. This process is called eutrophication. (4) The industrial wastes of industries like paper, paint, pesticide, metal, etc. Contain toxic chemicals like mercury, lead, copper, cadmium, etc. When polluted water is used, these toxic substances can enter the human body through food chains and affect their health. ➢ PREVENTION OF WATER POLLUTION Water pollution can be prevented or minimised by adopting following measures - (1) The toxic industrial wastes should be treated chemically to neutralise the harmful substances present in it before discharging into rivers and lakes. (2) The sewage should not be dumped into rivers. It should first be treated at the sewage treatment plant to remove the organic matter from it in the form of manure. (3) The use of excessive fertilisers and pesticides should be avoided. (4) The use of synthetic detergent should be minimised or biodegradable detergents should be used. (5) Dead bodies of human beings and animals should not be thrown into rivers. (6) The excreta and other garbage should be treated in a biogas plant to get fuel as well as manure. (7) The water of rivers, streams, ponds and lakes should be purified or cleaned. This can be done both by the industries and the government. One such example is the Ganga Action Plan launched by the Indian government. (8) Trees and shrubs should be planted along the banks of the rivers. (9) There should be general awareness among the masses regarding the harmful effects of water pollution and the ways of preventing it. (10)Waste paper, plastics, waste food materials, and rotten food and vegetables should not be thrown into open drains. ➢ POTABLE WATER Water which is suitable for drinking by human being is called potable water. ➢ PURIFICATION OF WATER People in big cities get purified river or lake water through a network of water pipe lines. The three main processes that water undergoes during purification are sedimentation, filtration, and chlorination. Let us study about these processes. Sedimentation : Water is pumped from a river into a large tank and allowed to stand for some time. The heavy suspended particles settle down at the bottom of the tank as sediments. This process is called sedimentation. The upper layer of water is then sent for filtration. Filtration : After sedimentation, the water is filtered through thick layers of sand and gravel. In this process the remaining suspended impurities are removed. Chlorination : The filtered water is chlorinated by adding chlorine or bleaching powder. Chlorine kills all the harmful germs. This process of adding chlorine to filtered water to kill germs is known as chlorination. The purified and chlorinated water is then supplied for human use through a network of pipes.