An anaerobic/anoxic/oxic (A²O) reactor was applied to simultaneously remove organics and nutrients, particularly nitrogen and phosphorus compounds from wastewater. The effect of chloride on biological nutrient removal from wastewater was investigated, using synthetic and real wastewaters. The internal recycle flowrate and the solids retention time were varied to determine the optimal operational conditions for the reactor using synthetic wastewater. The chloride concentrations of both synthetic and real wastewaters were increased to simulate the wastewater during salinity period. During the first phase, the chloride concentrations of synthetic wastewater were varied from 150 to 5,000 mg L^-1 and the real wastewater obtained from the Taipa wastewater treatment plant in Macau SAR, China was tested during the second phase with the chloride concentrations varied from 500 to 2,500mg L^-1. Results showed that the removal of ammonia nitrogen was not significantly affected by the chlorde concentration for both synthetic and real wastwaters. The phosphorus removal efficiency, however,was decreased from 94% at 150 mg L^-1 chloride to 74% at 1,500 mg L^-1 chloride for the synthetic wastewater and from 86% at 500 mg L^-1 chloride to 58% at 1,000 mg L^-1 for the real wastewater, respectively. The phosphorus removal was completely inhibited when the chloride concentration was higher than 2,500 mg L^-1 for both synthetic and real wastewaters. The removal efficiency for soluble chemical oxygen demand was also negatively affected by higher chloride concentrations.