• The Central Pollution Control Board (CPCB) in 2018 identified 351 polluted river stretches in India.
  • CPCB study reveals that discharge of untreated wastewater is one of the main causes of river pollution.
  • The assessment of water quality for identification of polluted river stretches found that 31 states and Union territories (UT) had rivers and streams that did not meet the water quality criteria.

Important points:

  • Concentration of Polluted River Stretches: Almost 60% of polluted river stretches exist in eight states: Maharashtra, Assam, Madhya Pradesh, Kerala, Gujarat, Odisha, West Bengal and Karnataka.
  • Maharashtra has the maximum number of polluted river stretches in the country.
  • Disproportionate Sewage Treatment: The National Green Tribunal (NGT) in 2019 directed that 100% treatment of sewage needed to be ensured before 31st March, 2020.
  • However, these states have sewage treatment capacity disproportionate to the sewage generated.
  • According to the CPCB report National inventory of sewage treatment plants 2021, about 72,368 million litres per day (MLD) of sewage was generated against which operational treatment capacity was only 26,869 MLD in 2021.
  • Increasing Biological Oxygen Demand: This huge amount of sewage is left untreated/partially treated and discharged directly into rivers and pollutes rivers by increasing the biological oxygen demand.

Biological Oxygen Demand

  • Biological Oxygen Demand is the amount of dissolved oxygen needed by microorganisms to decompose organic matter (waste or pollutants) under aerobic reaction (in the presence of oxygen).
  • The more organic matter there is (e.g., in sewage and polluted bodies of water), the greater is the BOD.
  • Greater 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 water body.
  • One of the main reasons for treating wastewater prior to its discharge into a water resource is to lower its BOD i.e. to reduce its need of oxygen and thereby lessen its demand from the streams, lakes, rivers, or estuaries into which it is released.

Dissolved Oxygen

  • It is the amount of dissolved oxygen present in the water which is needed for aquatic life to survive. The quality of water increases with an increase in DO levels.
  • A DO level of 5 mg/l or above is the recommended level for bathing in a river.

Government Initiatives:

  • Recently, the National Green Tribunal (NGT) directed the Ministry of Jal Shakti to devise an appropriate National River Rejuvenation Mechanism for effective monitoring of steps to curb pollution and for rejuvenation of all polluted river stretches across the country.
  • It aims to take cognizance of the existing situation, to propose a framework for creation of a system of laws and institutions and for a plan of action with a unified national perspective.
  • Started by the Ministry of Water Resources, it highlights the importance of water for human existence as well as for economic development related activities.
  • It suggests frameworks to conserve water resources through optimal, economical, sustainable and equitable means.

Way Forward

  • To maintain and restore the wholesomeness of the river (Aquatic ecosystem), there is a need to maintain the minimum flow.
  • Minimum flow of the river is also important to discharge treated sewage.
  • There is a need for a comprehensive waste management policy that stresses the need for decentralised garbage disposal practices as this will incentivise private players to participate.
  • It is important that Bioremediation (i.e. use of microbes to clean up contaminated soil and water) is made compulsory for areas wherever they can be applied.
  • To overhaul the waste management sector and induce the necessary behavioural change, citizen participation and engagement is the key.


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