Flexi Says: Bleaches contain various compounds such as sodium hypochlorite (NaClO), which release oxygen that oxidizes stains. Water suppliers add chlorine or another disinfectant to kill bacteria and germs in the water. To kill remaining harmful bacteria and other pathogens in the processed wastewater, chlorine and other chemicals are added in a disinfection tank. The chlorine can be harmful if added in excess quantities. (You may have noticed the smell of chlorine or have had irritated eyes when you were exposed to chlorine in a swimming pool.) Therefore, in some cases, the chlorine must be neutralized with other chemicals after it has killed the bacteria to protect marine organisms.