Which process during wastewater treatment helps in killing germs?

The correct option is D

Chlorination

Sewage treatment is the process of removing contaminants from wastewater, primarily from household sewage. It includes primary or physical, secondary or biological, secondary sedimentation processes to remove the contaminants and produce environmentally safe treated wastewater (or treated effluent).
1. Primary treatment - Large and small particles are removed physically by the process of filteration and sedimentation.
2. Biological process - Organic compounds are removed from the effluent of the primary treatment by using microbial flocs (masses of aerobic bacteria associated with fungi forming a mesh-like strucutures) in an aeration tank.
3.Secondary sedimentation process - The effluent from biological process is settled in a settling tank where the bacterial flocs are allowed to sediment.
After the secondary sedimentation process the effluent is chlorinated by adding chlorine (Cl2) or hypochlorite to water. This method is used to kill certain bacteria and other microbes before it is released as treated effluent. In particular, chlorination is used to prevent the spread of waterborne disease.