Why in news? According to a report from the CPCB number of polluted stretches in India’s rivers has fallen from 351 in 2018 to 311 in 2022, though the number of most polluted stretches is practically unchanged

Highlights

• The CPCB network monitors water quality at 4,484 locations across the country
• Two or more polluted locations identified on a river in a continuous sequence are considered as a “polluted river stretch.

• Gujarat and Uttar Pradesh had the highest number of “Priority 1” river stretches
• Maharashtra had the most polluted river stretches of followed by Madhya Pradesh , Bihar , Kerala , Karnataka and Uttar Pradesh.
• National Green Tribunal passed orders that the CPCB and the Jal Shakti Ministry monitor river pollution and every State to ensure that at least one river stretch was “restored” to at least be fit for bathing.

Classification according to pollution

Biochemical oxygen demand (BOD):

• More than 3 mg/l – identified as polluted locations.
• Less than 3 mg/l – Fit for “outdoor bathing.”
• “Priority 1” (P1): Exceeding 30 mg/l- Most polluted and need the urgent remediation.
• “Priority 2” (P2) : BOD of 20-30 mg/l
• “Priority 5” (P5) : 3-6 mg/l.

Central Pollution Control Board

• Nature: Statutory organization
• Parent Ministry: Ministry of Environment, Forest and Climate Change
• Origin : Water (Prevention and Control of pollution) Act, 1974.
• Powers and functions : Air (Prevention and Control of Pollution) Act, 1981.
• Serves as a field formation and also provides technical services to the MoEFCC under Environment (Protection) Act, 1986.
• Co-ordinates the activities of the State Pollution Control Boards by providing technical assistance and guidance and also resolves disputes among them.
• Apex organization in country in the field of pollution control as a technical wing of MoEFCC.
• The board is led by its Chairperson appointed by the Appointments Committee of the Cabinet of the Government of India.
• Chairman: Shri Tanmay Kumar
• Zonal Office : Located at Bengaluru, Kolkata, Shillong, Bhopal, Lucknow, Vadodara, Chandigarh, Pune and a Project Office at Agra

WHAT IS BOD

• It is the amount of dissolved oxygen (DO) needed by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period
• Higher BOD indicates more oxygen is required, signifying lower water quality.
• Low BOD means less oxygen is being removed from water, water is usually more pure.