Context: Recently, the Forest and Environment Minister of Karnataka, revealed that 16 rivers in Karnataka are polluted.
Rivers in Karnataka Highly Polluted
- Major rivers in Karnataka, including Arkavati, Lakshmana Tirtha, Tungabhadra, Bhadra, Tunga, Kaveri, Kabini, Kagina, Krishna, Shinsha, Bhima and Netravati had found their names on the list of polluted water bodies.
- The concentration of biochemical oxygen demand (BOD) in River Arkavati had soared to more than 30 milligrammes per litre, making it the most polluted river in the state.
- Tungabhadra, Bhadra, and Shinsha rivers, grappling with BOD concentrations of 6-10 mg per litre, were also distressingly contaminated.
- The remaining eight rivers had relatively lower BOD levels in the 3-6 mg per litre range.
Biological Oxygen Demand:
- Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present) conditions at a specified temperature.
- Indicator of Organic Pollution: BOD is used to gauge the level of organic pollutants in rivers, lakes, and streams. High levels of BOD indicate a high concentration of biodegradable material, often due to pollution.
- Significance for Ecosystem Health: Low levels of BOD are usually an indicator of good water quality, suggesting the water body can support a healthy ecosystem. High BOD levels deplete oxygen, leading to anoxic conditions harmful to aquatic life.
- Application in Wastewater Treatment: BOD analysis is crucial in wastewater treatment processes. It helps in assessing the effectiveness of treatment methods in removing organic waste.
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River Pollution: Causes
- Sewage and Discharge:
- Industrial Discharge: Factories and industrial plants often discharge chemicals and toxic waste directly into rivers.
- Urban Runoff: Urban areas contribute pollutants such as oils, grease, heavy metals, and other chemicals through stormwater runoff.
- Agricultural Runoff: Fertilizers, pesticides, and herbicides used in agriculture can run off into rivers, especially during rainfall. This runoff can increase nutrient levels in the water, leading to eutrophication.
- Deforestation: Removing trees along riverbanks can increase erosion rates, leading to more sediments and pollutants entering rivers.
- Airborne Pollutants: Pollutants from the air can settle in rivers. This includes particulate matter from vehicles, industries, and natural sources like volcanic ash.
Way Forward
- Establishment of Sewage Treatment Plants: The Karnataka government established 24 Sewage Treatment Plants (STP) strategically placed to purify the contaminated water.
- Citizen Participation and Coordinated effort: Need for sustained public awareness, community involvement and stricter enforcement of environmental laws.
- Enhancing Underground Drainage Systems: The underground drainage systems require significant enhancements to improve efficiency and effectiveness.
- For Example: the Karnataka State Pollution Control Board (KSPCB) emphasized enhancement for municipalities and panchayats to actively engage in the establishment of robust underground drainage systems and STPs.
News Source: Down to Earth
December 15, 2023