Explanation:

- Decantation: This is a method of separating liquids from solids or other immiscible liquids by gravity. It is not typically used for purifying water on a large scale.

- Chlorination: This is the correct answer. Chlorination involves adding chlorine to water to kill bacteria, viruses, and other microbes, making it safe for public consumption.

- Distillation: This process involves boiling water and condensing the steam back into a liquid to remove impurities and is not used widely for municipal water supply due to high energy costs.

- Filtration: This process removes particles and impurities through a physical barrier, and while important, it may not remove all pathogens on its own.