The polluted river stretches have increased in India

The polluted river stretches have increased in India

Kamaraj IAS Academy | The polluted river stretches have increased in India
  • September 17, 2018, 3:21 pm

In News

The number of polluted stretches in India’s rivers has increased to 351 from 302 two years ago, and the number of critically polluted stretches — where water quality indicators are the poorest — has gone up to 45 from 34, according to an assessment by the Central Pollution Control Board (CPCB).

The most significant stretches of pollution highlighted by the CPCB assessment (which is yet to be published) include the Mithi river — from Powai to Dharavi — with a BOD (Biochemical Oxygen Demand) of 250 mg/l, the Godavari — from Someshwar to Rahed — with a BOD of 5.0-80 mg/l; the Sabarmati — Kheroj to Vautha — with a BOD from 4.0-147 mg/l; and the Hindon — Saharanpur to Ghaziabad — with a BOD of 48-120 mg/l.

Graded scale

The CPCB, since the 1990s, has a programme to monitor the quality of rivers primarily by measuring BOD, which is a proxy for organic pollution — the higher it is, the worse the river. The health of a river and the efficacy of water treatment measures by the States and municipal bodies are classified depending on BOD, with a BOD greater than or equal to 30 mg/l termed ‘priority 1,’ while that between 3.1-6 mg/l is ‘priority 5.’

The CPCB considers a BOD less than 3 mg/l an indicator of a healthy river.

Biochemical oxygen demand (BOD)

Biochemical oxygen demand (BOD), the amount of dissolved oxygen used by microorganisms in the biological process of metabolizing organic matter in water. The more organic matter there is (e.g., in sewage and polluted bodies of water), the greater the BOD; and the greater the BOD, the lower the amount of dissolved oxygen available for higher animals such as fishes. The BOD is therefore a reliable gauge of the organic pollution of a body of water. One of the main reasons for treating wastewater prior to its discharge into a water resource is to lower its BOD—i.e., reduce its need of oxygen and thereby lessen its demand from the streams, lakes, rivers, or estuaries into which it is released.


  1. Sewage and Waste Water: Sewage, garbage and liquid waste of households, agricultural lands and factories are discharged into lakes and rivers. These wastes contain harmful chemicals and toxins which make the water poisonous for aquatic animals and plants.
  2. Dumping: Dumping of solid wastes and litters in water bodies causes huge problems. Litters include glass, plastic, aluminum, styrofoam etc. Different things take different amount of time to degrade in water. They affect aquatic plants and animals.
  3. Industrial Waste: Industrial waste contains pollutants like asbestos, lead, mercury and petrochemicals which are extremely harmful to both people and environment. Industrial waste is discharged into lakes and rivers by using fresh water making the water contaminated.
  4. Oil Pollution: Sea water gets polluted due to oil spilled from ships and tankers while traveling. The spilled oil does not dissolve in water and forms a thick sludge polluting the water.
  5. Acid Rain: Acid rain is pollution of water caused by air pollution. When the acidic particles caused by air pollution in the atmosphere mix with water vapor, it results in acid rain.
  6. Global Warming: Due to global warming, there is an increase in water temperature. This increase in temperature results in death of aquatic plants and animals. This also results in bleaching of coral reefs in water.
  7. Eutrophication: Eutrophication is an increased level of nutrients in water bodies. This results in bloom of algae in water. It also depletes the oxygen in water, which negatively affects fish and other aquatic animal population.
  8. Agricultural Run-Off:The use of land for agriculture and the practices followed in cultivation greatly affect the quality of groundwater.Intensive cultivation of crops causes chemicals from fertilizers (e.g., nitrate) and pesticides to seep into the groundwater, through the process of leaching. Routine applications of fertilizers and pesticides for agriculture and indiscriminate disposal of industrial and domestic wastes are increasingly being recognized as significant sources of water pollution.


It is very important to prevent the polluting of water bodies and remove existing contaminants or reducing the concentration of these contaminants so as to make it fit for desired use. Following are some of the ways of treating polluted water:

Industrial Treatment: The raw sewage is needed to be treated correctly in a water treatment plant before it can be safely released into the environment. To reduce the amount and toxicity of waste, it is passed through a number of chambers and chemical processes in water treatment plant.

  • Conversion of nitrates in gas is called Denitrification. It is an ecological approach to prevent leaching of nitrates in soil. It stops ground water from getting contaminated.

Ozone Waste Water Treatment: Ozone waste water treatment method is becoming very popular. In this method, the pollutants in water are broken down by an ozone generator. Ozone oxidizes bacteria, molds, organic material and other pollutants in water.

Septic Tanks: Septic tanks are used to treat sewage at the place of location instead of treating it in any plant or sewage system. This system is used at the individual building level.The sewage is separated into solid and liquid components and treated separately.


The steps taken by the Government to address the issues of water pollution include the following:-

i.Preparation of action plan for sewage management and restoration of water quality in aquatic resources by State Governments;

ii.Installation of Online Effluent Monitoring System to check the discharge of effluent directly into the rivers and water bodies;

iii.Setting up of monitoring network for assessment of water quality;

iv.Action to comply with effluent standards is taken by SPCBs / PCCs to improve the water quality of the rivers;

v.Financial assistance for installation of Common Effluent Treatment Plants for cluster of Small Scale Industrial units;

vi.Issuance of directions for implementation of Zero Liquid Discharge;

viii.Implementation of National Lake Conservation Plan (NLCP) and National Wetland Conservation Programme (NWCP) for conservation and management of identified lakes and wetlands in the country which have been merged into an integrated scheme of National Plan for Conservation of Aquatic Eco-systems (NPCA) to undertake various conservation activities including interception, diversion and treatment of waste water, pollution abatement, lake beautification, biodiversity conservation, education and awareness creation, community participation etc.