Effect of variable salinity wastewater on performance and kinetics of membrane‐based bioreactors

BACKGROUND A membrane bioreactor and two hybrid moving bed biofilm reactor‐membrane bioreactor systems were operated in parallel for the treatment of variable‐salinity wastewater. Influent salinity was changed according to tidal‐like cycles: 6 h of maximum salinity (4.5 or 8.5 mS cm −1 ) followed by 6 h of regular wastewater salinity (around 1 mS cm −1 ). RESULTS For the two salinity scenarios, the bioprocesses operated under different conditions of mixed liquor total suspended solids (2500 and 3500 mg L −1 ), and hydraulic retention time (6, 9.5 and 12 h). The results showed that the bioprocesses had better performance under 4.5 mS cm −1 than under 8.5 mS cm −1 in terms of removal of biological oxygen demand at day 5 (BOD 5 ) (+6.07%), ammonium cation (NH 4 + ) (+41.29%) and total nitrogen (+37.64%), the heterotrophic and autotrophic yield coefficients (+0.02777 mgVSS mgCOD −1 and +0.13990 mgVSS mgN −1 ), and the autotrophic rate of substrate utilization (+3.39559 mgN L −1 h −1 ). CONCLUSIONS The results obtained would become of help for the modeling of membrane‐based systems treating variable saline wastewater. © 2019 Society of Chemical Industry