Sequential batch membrane bio-reactor for wastewater treatment: The effect of increased salinity

•A SB-MBR pilot plant treating wastewater subject to salinity increase was investigated.•Salinity increase influenced the biological contribution of COD removal efficiency.•Salinity increase did not exert a significant stress on heterotrophic bacteria.•Significant reduction of the respiration rates of autotrophic species due to salt.•The irreversible cake deposition was the predominant membrane fouling mechanism. In this work, a sequential batch membrane bioreactor pilot plant is investigated to analyze the effect of a gradual increase in salinity on carbon and nutrient removal, membrane fouling and biomass kinetic parameters. The salinity was increased by 2gNaClL−1 per week up to 10gNaClL−1. The total COD removal efficiency was quite high (93%) throughout the experiment. A gradual biomass acclimation to the salinity level was observed during the experiment, highlighting the good recovery capabilities of the system. Nitrification was also influenced by the increase in salinity, with a slight decrease in nitrification efficiency (the lowest value was obtained at 10gNaClL−1 due to lower nitrifier activity). Irreversible cake deposition was the predominant fouling mechanism observed during the experiment. Respirometric tests exhibited a stress effect due to salinity, with a reduction in the respiration rates observed (from 8.85mgO2L−1h−1 to 4mgO2L−1h−1).