Chlorine gas can kill harmful bacteria and germs present in water. So, it is used to disinfect drinking water.
Water consists of harmful germs and bacteria which have to be killed so that the water becomes fit for human consumption.
So, a naturally occurring gas called chlorine is added to the water.
Chlorine inactivates the microorganisms present in water by disrupting their cell membrane.
After disrupting the cell membrane chlorine enters the cell and disrupts cellular respiration and DNA activity which are the two vital processes for cell survival.