Feasibility of effluent reclamation for the Futian municipal WWTP in Taichung Taiwan was evaluated using an “SF‐UF‐RO” pilot plant. The optimal parameters of each unit were obtained during the pilot plant test. The pilot plant started the operation in late October 2008 and operated until January 2011. The reverse osmosis (RO) system produces 75 m3 water daily, and the produced water quality was comparable to the city water in Taichung. Chlorine dosed in the sand filtration (SF) inlet and ultrafiltration (UF) backwash had the most significant effect on the stability of system performance. When the chlorine was underdosed, biofilm clogged the bag filter (prefilter of UF) and led to the flow rate decay of the UF. The prefilter needed replacement every 1 or 2 weeks resulting in increased process cost. On the other hand, when the chlorine dosage was increased to mitigate the biofilm growth, the residual chlorine not only reacted with TOC and derived trihalomethanes (THMs) in the RO product water (more than 20 µg/L), but it also damaged the RO membrane. After trial and error, the chlorine concentration was optimized as 0.7 mg/L in SF inlet to prevent growth of biofilm as well as to control the residual chlorine in the RO inlet and THMs in the RO product water. It is suggested that cautiously adjusting chlorine dosage is essential for stably operating such a hybrid membrane system to reclaim the municipal wastewater.