A pilot-plant membrane bioreactor (MBR) and two pilot-plant hybrid moving bed biofilm reactor-membrane bioreactors (MBBR-MBRs), divided into three aerobic and one anoxic chambers, were started up for the treatment of salinity-amended urban wastewater. The MBBR-MBR systems worked with and without carriers in the anoxic zone (MBBR-MBRanox and MBBR-MBRn/anox, respectively). The systems were operated from start-up to stabilization, showing high removal of organic matter-a maximum of 90% chemical oxygen demand and 98% biochemical oxygen demand on the fifth day for MBBR-MBRn/anox in the stabilization phase-but low nitrogen elimination-30% maximum for MBBR-MBRn/anox in the stabilization phase. Biofilm attached to carriers reached less than 50 mg L-1 in the hybrid system. MBR showed faster kinetics than the two MBBR-MBR systems during start-up, but the opposite occurred during stabilization. Maximum specific growth rates for heterotrophic and autotrophic biomass were 0.0500 and 0.0059 h(-1) for MBBR-MBRn/anox in the stabilization phase. (C) 2017 American Institute of Chemical Engineers