What process describes chlorine being released to the water as gas?

The process of releasing chlorine gas into water is aptly described as chlorination. This term refers specifically to the addition of chlorine, whether in gas, liquid, or solid form, to water in order to disinfect it and kill harmful bacteria and pathogens.

In this context, the term 'chlorine feeder system' refers to the equipment used to introduce chlorine into the water supply, but it does not define the act of adding chlorine itself. Chlorine generation, on the other hand, pertains to the production of chlorine from precursors, while chlorine filtration would involve the removal of chlorine or its by-products from water, which does not relate to the release of chlorine gas into the water. Therefore, the precise term for the process of adding chlorine to water is chlorination, making it the most accurate choice for this question.