How does chlorination treat drinking water, and what is a potential concern related to disinfection byproducts?

• A. Chlorination adds chlorine to water to kill pathogens.
• B. Chlorination increases water salinity.
• C. Chlorination sterilizes water by killing pathogens; a concern is disinfection byproducts like trihalomethanes formed with organic matter.
• D. Chlorination neutralizes all pollutants by oxidation.

Answer: (C)

Chlorination treats drinking water by adding chlorine, which acts as a disinfectant to kill or inactivate pathogens, making the water safer to drink. A key point to understand is that while this kills germs, chlorine can also react with natural organic matter and other substances in the water to form disinfection byproducts, such as trihalomethanes. These byproducts can pose health risks if consumed, so water systems aim to balance effective disinfection with minimizing byproduct formation. The other ideas aren’t accurate: chlorination doesn’t raise salinity, it doesn’t literally sterilize all components of water, and it doesn’t remove every pollutant through oxidation.