BACKGROUNDThe integrated free-floating biofilm and activated sludge (IFFAS) process is an ideal candidate for simultaneous nitrification and denitrification (SND). However, traditional carriers have their inherent drawbacks, such as the weak hydrophilicity and negative charges on the surface. In this study, novel carriers with favorable hydrophilicity and electrophilicity were prepared and implemented in an IFFAS-based SND reactor. RESULTSCompared with traditional carriers, the water contact angle of the novel carriers dropped to 60.2 degrees and positive charges on the surface (+11.7 mV, pH 7.0) were acquired. Through accurate control of dissolved oxygen (DO), it took only 30 days to start SND, with a total nitrogen (TN) removal efficiency of 80.2%. In contrast, the start-up period was 42 days with weaker TN removal capacity in a control reactor filled with traditional carriers. Novel carriers provided a favorable niche for more types of bacteria to survive, of which Nitrosomonadales and Nitrospirale were identified as nitrifiers while anoxic denitrifiers, aerobic denitrifiers and anammox bacteria also co-existed in the system, contributing to TN removal. CONCLUSIONNovel carriers with favorable hydrophilicity and electrophilicity were successfully prepared through a relatively facile approach, and a novel carriers-based SND process enabled a shorter start-up period, higher biomass and better TN removal efficiency. (c) 2017 Society of Chemical Industry