Question

Study the graph. Explain how is oxygen concentration affected in the river when sewage is discharged in it.

Answer 1

In a water body, as the organic wastes or domestic sewage are introduced, microbes involved in its degradation start consuming a lot of oxygen resulting in a decline in the amount of dissolved oxygen in the water body. However, as the organic content reduces in concentration, the amount of oxygen required by the microorganisms reduces and the dissolved oxygen is thus seen increasing in concentration for the same water body.