Question

Discuss the effects of sewage discharge on a river.

Answer 1

1. Oxygen depletion: Microorganisms involved in the biodegradation of organic matter present in sewage consume a large amount of dissolved oxygen (DO) in the river. This leads to a sharp decline in DO downstream from the sewage discharge point, causing oxygen deficiency.
2. Mortality of aquatic life: The decrease in dissolved oxygen results in the death of fish and other aquatic animals due to suffocation.
3. Pathogenic contamination: Sewage contains several pathogens that can cause waterborne diseases and contribute to pollution.
4. Unpleasant conditions: Putrescible materials in sewage create obnoxious and foul conditions, making the water filthy and odorous.
5. Eutrophication: The nutrients in sewage promote excessive growth of planktonic algae (algal blooms), which further depletes oxygen when they die and decompose, worsening oxygen deficiency.
6. Growth of aquatic weeds: Eutrophic conditions favor the growth of invasive aquatic weeds like Eichhornia crassipes (water hyacinth), which disrupt the ecological balance of the water body.
7. Irreparable environmental damage: Overall, sewage discharge causes serious pollution, leading to degradation of water quality and damage to the aquatic ecosystem.