Several efforts have been made to prevent river water pollution because rivers have special importance for human beings. The Government of India passed an Act in 1974 for prevention and control of water pollution. In 1985, Central Ganga Tribunal was established to make the Ganga water pollution free. Under the ‘Yamuna Conservation Programme’ (1993), programmes were run in 21 towns in the country situated on the banks of the Yamuna to make the river free from polluted water. The Gomati River Conservation Programme was begun by the Government of India in 1993 with the financial assistance of the UK. The Damodar River Conservation Plan was begun in 1996 by Government of India. It is to be noted that the Damodar river has become a ‘biological desert’ between Giridih and Durgapur (300 km). The waste products coming from factories and cities have so much polluted this river that the existence of any living being is not possible.
Water Pollution can be classified on the basis of the source, mainly in the following way:
The waste products coming out of industries are chief sources of water pollution. The chemical pollutants (e.g. chlorides, sulphides, carbonates, ammonium nitrates, nitrites etc.), heavy metallic pollutants (e.g. mercury, lead, zinc, cadmium) and other pollutants coming out of industries pollute aquatic ecosystem.
The chemicals and fertilizers dissolved in the soil flow with water and reach rivers and oceans to pollute them.
Water Pollution from city waste
City wastes are disposed of through drains directly to rivers and oceans without being treated this makes the river water poisonous.
Water Pollution due to oil leakage
The river and ocean get polluted due to leakage of oil from oil tankers. The Cuyahoga river and drains into Erie lake after passing through Cleveland is badly affected by oil pollution. Once the river had caught fire because of oil leakage.
Note: Super Bug is a bacterium prepared with the help of genetic engineering which eats out oil spread on the surface of water very rapidly. It may solve oil spill problem to some extent.
Pollution due to Natural Elements
For Example, pollution created by volcanic ash, dust, erosion, landslide etc.
When sewage without being treated mixed in the river water, the number of saprophytes and pathogenic elements gets increased. It is known as biotic pollution. This polluted water gives birth to a disease called Schistosomiasis which is caused by blood fluke worm.
Indicators of Water Pollution
Biological Oxygen Demand (BOD)
The aquatic animals use oxygen dissolved in water for their respiration. If the quantity of this dissolved oxygen in water comes down to 16 percent the aquatic animals begin to feel problem in respiration. This kind of water is kept in the category of polluted water.
Chemical Oxygen Demand (COD)
The impurity of water is measured by it using chemicals. The sample of polluted water is heated with potassium dichromate. Potassium dichromate is an oxidising agent. When it is heated with polluted water, it is hydrogenized. The ratio between the quantity of oxygen in the water and the impurities is found out by the titration of hydrogenized potassium dichromate.
E. Coli Method
According to the World Health Organization (WHO), if the number of E. Coli is more than 10 in 100 ml water. it will be considered polluted. The increase in the number of E. Coli in water increased the level of water pollution gradually.
The purity of water is measured on the basis of the quantity of oxygen dissolved in water by ‘Winkler method‘. BOD and COD methods come under it.
Several times, the quantity of nitrate in underground water or wells increases too much because of the use of nitrogenized fertilizer urea. If the quantity of nitrate is more than 10 mg/l, it causes a disease called ‘Methemoglobinemia‘ (the blue blood disease) in children if they drink this water.
Endosulfan: Endosulfan is an insecticide which caused cancer in the people around the cashew nut plantations in the district of Kasaragod (Kerala). It is to be noted that this insecticide is totally banned in several developed nations whereas, in India, it has been kept in the ‘medium dangerous’ category.
Eutrophication: The gradual accumulation of nutrients in water results in the excess growth of algae and other aquatic plants. These plants begin to utilize oxygen dissolved in water in a large quantity. This creates the lack of oxygen for aquatic animals and they begin to die. This phenomenon is called eutrophication.
The sudden increase in the quantity of algae in water is called ‘algal boom’.
The increase in the number of water hyacinth increases the process of eutrophication. On one hand, it uses the oxygen dissolved in water whereas, on the other hand, it prevents the connection between water and atmosphere, the diffusion of atmospheric oxygen in water does not occur.