A lake with an inflow of domestic sewage rich in organic waste may result in

A lake with an inflow of domestic sewage rich in organic waste may result in
  1. drying of the lake very soon due to algal bloom
  2. an increased production of fish due to lot of nutrients
  3. death of fish due to lack of oxygen
  4. increased population of aquatic food web organisms .

Solution

Domestic sewage rich in organic waste will exert a very high demand of oxygen in order to get biodegraded. Thus depleting the dissolved oxygen below critical level necessary to support aquatic life. Especially fish, which is very sensitive to the dissolved oxygen available in water, starts dying if the level goes below $4 \mathrm{mg} / \mathrm{L}$.

Asked in: NEET 2008 (Mains)

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