An adsorption tower must be installed to after treatment of excess hypochlorous acid which is used to remove ammonia and protein in the water. In this work. the dechlorination pretreatment method was mentioned that extend the changing time of the active carbon when high concentration of residual chlorine flowed in adsorption tower. At the pretreatment stripping tower installation for removing residual chlorine, the removal efficiencies of residual chlorine by using aquacell media were researched. When media is used, removal efficiency is extent 80%. When media and aeration were used at the same time, removal efficiency is over 10% in 10min.