Which of the following is NOT a method of water treatment?

Evaporation is not classified as a method of water treatment because it is primarily a natural process where water is transformed into vapor due to heat. While evaporation does play a role in the water cycle and can concentrate certain substances, it does not actively remove contaminants or improve water quality in the manner that the other methods do.

Chlorination involves adding chlorine to water to disinfect it by killing pathogens, making it an effective treatment method for ensuring safe drinking water. Filtration removes suspended solids and some bacteria from water by passing it through filters of various materials, thus improving its clarity and safety. Desalination is the process of removing salt and other impurities from seawater to produce fresh water, which is essential in areas lacking natural freshwater sources. Each of these methods directly contributes to treating water to make it safe and suitable for consumption, which distinguishes them from evaporation.