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| Water Pollution |
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| Water pollution is a major problem associated with the developing countries. It severely affects the lives of people. There is an entire village in Karnataka that has been affected by excess of fluoride in the ground water. It causes deformities of the bone. In order to effectively control the pollution, the causes or the sources must be identified and understood. |
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| Sewage that includes organic matter, animal and human excreta-one of the major pollutants of water in the urban and rural areas is the sewage. The sewage most often contains the organic matter that encourages the growth of microorganisms. These organisms besides spreading diseases also consume the oxygen present in water. This is called oxygen depletion. The aquatic organisms like the fish cannot then survive in such waters. This creates an imbalance in the aquatic ecosystems. |
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| Industries |
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| The industries are mostly situated along the riverbanks for easy availability of water and also disposal of the wastes. But these wastes include various acids, alkalis, dyes and other chemicals. They change the pH of water. There are also detergents that create a mass of white foam in the river waters. All these chemicals are quite harmful or even fatally toxic to fish and other aquatic populations. |
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| The industrial wastes include toxic metals like lead, mercury, cadmium, etc, and other chemicals like the fluorides, ammonia, etc. |
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| Certain industries such as power plants, refineries, nuclear reactors release a lot of hot water from their cooling plants. This hot water is let into the water bodies without the temperature being reduced. This results in heating up of the water and thereby killing the aquatic life. The oxygen content of water also becomes less due to increase in the temperature. This is called thermal pollution. |
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| Agriculture |
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| Modern methods of agriculture have resulted in use of fertilisers and pesticides to increase the yield of the crops. Most of them are synthetic and chemicals-based. They are collectively called agro-chemicals. These chemicals enter into the water bodies with the rain water flow and the ground water by seepage. The chemicals remain in the environment for a long time and can enter the food chain. They cause a number of problems in the animals. |
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| Oil |
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| Oil spill is a major problem in the oceans and seas. The oil tankers and offshore petroleum refineries cause oil leakage into the waters. This pollutes the waters. Oil floats on the water surface and prevents the atmospheric oxygen from mixing in the water. The oil enters the body of the organisms. It also coats the body of the aquatic animals and birds which may also kill them. |
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| Eutrophication |
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| Water bodies are being constantly polluted by dumping of sewage which includes organic matter and by the runoff from the agricultural fields that contains fertilisers. Pollutants like sewage, organic wastes and fertilisers contain good amount of inorganic nutrients like nitrates and phosphates. |
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| These nutrients enrich the water promoting the growth of algae. The water turns green. This is called algal bloom. Rich algal growth leads to great increase in the number of the decomposers. All these life forms-decomposers, algae, other plants, fishes and other aquatic animals, use the oxygen in the water for respiration. This causes great demand for oxygen and results in depletion of oxygen. |
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| Pollution is measured by knowing the biological oxygen demand (BOD). Low BOD means little pollution and high BOD means higher pollution. |
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| Eutrophication also results in overgrowth of plants like Eicchornia that covers the entire surface of water. This reduces the light reaching the lower layers in water. |
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| Thus, enrichment of water with inorganic nutrients like nitrates and phosphates is called eutrophication. |
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| There are many pollutants like the DDT that are not bio-degradable. These accumulate in the organisms and cause serious health problems. The contamination of water with these pollutants results in their entry into the microscopic plants and animals. These organisms are fed upon by higher aquatic life like the fish. The fish in turn are fed upon by the land animals including man. |
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| Thus, the pollutant reaches the body of man. At each step in the food chain, the contaminant increases in quantity. This is because a fish feeds on large quantity of smaller plants and man eats fish. These contaminants like DDT remain in the fats and are not degraded in the body. Over the years the amount of DDT increases in the body. This is called biomagnification. |
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| Bio-magnification |
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| Pollutants like DDT also reach the human body through milk if the cattle are exposed to DDT sprayed grass or contaminated water. This causes serious blood and nervous disorders in man and other animals. |
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| Epidemics |
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| Pollution of water by organic wastes is a major cause for occurrence of epidemics like cholera, gastroenteritis in India. The microorganisms causing these diseases enter the water bodies through the organic wastes and then into the bodies of healthy persons causing diseases. In fact, a good indication of pollution of water is the presence of bacteria E. coli that lives in the human intestines. |
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| Acid Rain |
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| As discussed under air pollution, acid rain occurs due to the pollution of atmosphere and the pollutants coming down get mixed with water during rain. These waters also run into the water bodies where they cause a lot of damage due to the presence of acids. They cause change in pH of water and damage the aquatic life. |
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| Sewage Treatment |
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| The sewage before being let into the water bodies must be purified. |
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| This is done in three steps as follows: |
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 Primary treatment |
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Secondary treatment |
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Tertiary treatment |
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Effluent treatment |
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| Primary Treatment |
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| The water is sieved through coarse sieves and made to stand in sedimentation tanks. This makes the heavy suspended matter settle down. It is then passed through a bed of rocks. |
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| Secondary Treatment |
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| The organic materials that are biodegradable are treated with the help of decomposers and oxygen. Then, the water is also chlorinated to remove the germs. |
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| Tertiary Treatment |
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| This step removes the inorganic pollutants like the nitrates, phosphates, detergents, metal ions, etc. by passing the water through activated charcoal that acts as a filter. |
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| Effluent Treatment |
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| The industrial wastes should be treated before being let into the water bodies. The toxic materials should be removed, the metallic compounds should be precipitated, the acids and alkalis should be neutralized and the temperature of the hot waters should be reduced. |
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| Public Awareness |
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| The public should be made aware of the dangers of water pollution. This will ensure that the water bodies are not contaminated and are maintained clean. |
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