This document is an instructional module package prepared in objective form for use by an instructor familiar with chlorine, the reasons for chlorination and safe operation and maintenance of gas chlorine, dry calcium hypochlorite and liquid sodium hypochlorite chlorination systems for water supply and wastewater treatment facilities. Included are objectives, instructor guides, student handouts and transparency masters. The module considers purposes of chlorination, properties of chlorine, methods of chlorination, safety, maintenance of chlorination units and interpretation of test results. (Author/RH)