Demand for water is increasing due to rapid population growth and increased industrial activities. Membranetechnologies have attracted most attention as a promising advanced technology for the supply of sustainable water resources.Chemical and structural properties of polyamide membranes, one of the most widely used membranes in water treatmentplant, has been reported to be affected by residual chlorine dissolved in water after chlorine disinfection. This paper focuseson the chlorine speciation at various solution pHs and change of surface properties/performance of polyamide membranesdue to the chlorine exposure.