Correct Answer - Option 2 : Dilution
Explanation:
Disposal of sewage effluent:
Disposal of sewage effluent can be done either by dilution or on land.
Disposal by dilution:
It is the process in which sewage effluent is disposed of in the large water body which either static or running. After which it undergoes the process of self-purification.
When the sewage effluent is disposed of in a river stream it undergoes the process of self-purification by the following natural mechanism;
- Dilution & dispersion
- sedimentation
- Sunlight
- Oxidation & Reduction
