Sequential anaerobic–aerobic treatment of pharmaceutical wastewater with high salinity

•A sequential anaerobic–aerobic treatment of pharmaceutical wastewater conducted.•COD removal of 41.3±2.2% was achieved by anaerobic process – UASB.•Adverse effect of salinity on the anaerobic phase found with TDS above 14.92g/L.•UASB+MBR and UASB+SBR systems achieved excellent organic removal and nitrification. In this study, pharmaceutical wastewater with high total dissolved solids (TDSs) and chemical oxygen demand (COD) content was treated through a sequential anaerobic–aerobic treatment process. For the anaerobic process, an up-flow anaerobic sludge blanket (UASB) was applied, and a COD removal efficiency of 41.3±2.2% was achieved with an organic loading rate of 8.11±0.31gCOD/L/d and a hydraulic retention time of 48h. To evaluate the salinity effect on the anaerobic process, salts in the wastewater were removed by ion exchange resin, and adverse effect of salinity was observed with a TDS concentration above 14.92g/L. To improve the anaerobic effluent quality, the UASB effluent was further treated by a membrane bioreactor (MBR) and a sequencing batch reactor (SBR). Both the UASB+MBR and UASB+SBR systems achieved excellent organic removal efficiency, with respective COD removal of 94.7% and 91.8%. The UASB+MBR system showed better performance in both organic removal and nitrification.