(Environment & Ecology)General Studies Paper 3
Question:- 80. What is Eutrophication? Discuss the challenges faced by the global cities in dealing with eutrophication. Also, mention the scientific solutions available in this regard. Answer in 250 words.
Oct 01, 2022


Eutrophication is the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.) The nutrients can be introduced via leaching from soil by rainfall or released
as part of sewage. Eutrophication is common around agricultural lands where the use of artificial fertilisers are prevalent. An increase in nutrient supply within waterways will result in several ecological consequences:



1. A rapid growth in algal populations will occur (algal blooms) as a result of the increased availability of nutrients
2. As the algae die, there will be a subsequent spike in the numbers of saprotrophic microbes (decomposers)
3. The high rate of decomposition will result in an increased biochemical oxygen demand (BOD) by saprotrophic bacteria
4. The saprotrophs will consume available quantities of dissolved oxygen, leading to deoxygenation of the water supply
5. Eutrophication will also increase the turbidity of the water, which will reduce oxygen production by photosynthetic seaweeds. This will stress the survival of marine organisms, potentially leading to a
reduction in biodiversity within the ecosystem.

In the recent times Eutrophication cases have  surfaced in various cities such as Chandigarh, Bengaluru, Kolkata, etc.


BODY PARAGRAPH-2 -Solutions to Eutrophication:

1. Sewage Treatment – Trickle Filter Beds
The aerobic conditions required for the saprotrophic decomposition of liquid effluent can be maintained by trickle filter beds.  Trickling filter systems continually recirculate the effluent by spraying it over a bed of stones to maintain dissolved O2  levels. A biofilm of saprotrophic bacteria is situated in the stone bed and feed on the
organic matter within the sewage. Clean water filters out the bottom into another tank, whereby bacteria are removed and water is further treated (chlorination).

2. Bacterial Destruction by Bacteriophages
Bacteriophages are viruses that specifically target bacteria, and are commonly used in the disinfection of water systems. Bacteriophages may quickly spread through all bacterial cells and disrupt the coordinated maintenance of the biofilm. The virus will propagate within the bacterial cell and cause it to lyse as part of its viral life cycle.

3. Bioremediation: Bioremediation is the process by which microorganisms are used to return a polluted environment to its natural state. Microorganisms may produce specific enzymes and undergo certain chemical processes that can break down contaminants. Bioremediation is often supported by physical and chemical procedures that help filter the contaminant out of the environment

4. Physical:  Detergents and dispersal agents may be deployed on oil spills to prevent the contaminants from aggregating.

5. Chemical:  Contaminants can alternatively be burnt, removed by dissolving or destroyed by chemical oxidation.