Answer:
- Eutrophication is that process whose beginning starts with an increase in the amount of nutrients (especially nitrogen and phosphorus) in water bodies—such as ponds, lakes, rivers, or wetlands. Due to these excessive nutrients, uncontrolled growth of algae and micro-plants occurs in the water. Ultimately, as a result of this, massive loss of aquatic biodiversity happens and the decay (death) of the concerned water body takes place. Although this is a slow geological process of the natural aging/filling of lakes, due to anthropogenic (human) activities its rate has become extremely rapid, which is called 'Cultural Eutrophication'.
Mechanism of Eutrophication:
- The process of eutrophication in water bodies is completed in sequential stages:
- Entry of Nutrients: Through agricultural runoff (running water from fields), domestic waste, sewage, and industrial effluents, nitrogen and phosphorus in large quantities enter water bodies.
- Algal Bloom: Due to the abundance of nutrients in ponds and lakes, extremely rapid growth of algae begins, which is called 'Algal Bloom'.
- Blockage of Sunlight: A dense green layer of algae spreads over the upper surface of the water. Because of this, sunlight is unable to reach the aquatic plants present below, due to which their photosynthesis stops and they begin to die.
- Increase in BOD and Depletion of DO: To decompose the dead algae and plants, bacteria consume excessive amounts of dissolved oxygen (DO) in the water. Consequently, the Biochemical Oxygen Demand (BOD) of the water increases rapidly and the level of dissolved oxygen becomes extremely low.
- Formation of Dead Zones: Due to the level of dissolved oxygen in the water becoming extremely low (Hypoxia), fish and other aquatic organisms begin to die of suffocation, and that water body turns into a lifeless "dead zone".
Primary Causes of Eutrophication:
Its primary causes are divided into two categories:
Anthropogenic Factors:
- Excessive Use of Chemical Fertilizers: Nitrogen- and phosphorus-rich fertilizers (Urea, DAP, etc.) used in agricultural fields reach water bodies along with rainwater runoff.
- Domestic Waste and Detergents: Disposal of untreated sewage water and phosphate-containing detergents into water bodies.
- Animal Husbandry and Industrial Effluents: Direct discharge of animal husbandry wastes and industrial wastewater into rivers and lakes.
Natural Factors:
- Due to heavy rainfall, landslides, and soil erosion, minerals and nutrients from surrounding land naturally get integrated into reservoirs.
Adverse Impacts on Aquatic Ecosystem and Human Life:
- It completely destroys the crucial resources of water bodies—such as food (fish), medicines, fodder, etc.
- As soon as the level of Dissolved Oxygen (DO) falls below 4 mg/L, the survival of aquatic organisms comes under threat, causing severe damage to aquatic biodiversity.
- Toxins released by cyanobacteria (blue-green algae) render drinking water poisonous, which can lead to serious diseases related to the liver and nervous system in animals and humans.
- Due to the foul odor, turbidity, and unpleasant taste in the water, the natural aesthetic beauty of reservoirs is destroyed, bringing tourism activities to a standstill.
- Due to the continuous settling of organic debris in the sediments, water bodies progressively become shallow and eventually turn into marshes, losing their economic and ecological significance.
Measures for Effective Control and Mitigation of Eutrophication:
- Organic and natural farming should be encouraged around agricultural fields and water sources, and the use of chemical fertilizers should be limited.
- Green belts (Riparian Buffer Zones) should be created along the banks of water bodies so that tree and plant roots can absorb runoff nutrients beforehand.
- Industrial effluents must compulsorily be treated by Effluent Treatment Plants (ETPs) before discharging them into water bodies.
- Instead of directly dumping domestic waste and sewage water into ponds or rivers, it should be treated up to the tertiary level (Tertiary Treatment) in Sewage Treatment Plants (STPs) to separate nitrogen and phosphorus.
- Regulatory bans should be imposed on the use of phosphates in detergents and soaps.
- Dredging (cleaning of silt and sediment) of reservoirs should be undertaken periodically, and oxygen levels should be improved through artificial aeration of the water.
Conclusion:
- Eutrophication is a grave threat to water security and the environment. To overcome this complex challenge, there is a necessity to undertake stringent regulatory efforts collectively, strengthen sewage infrastructure, and lay special emphasis on sanitation and water conservation.