A novel application of anaerobic bio-entrapped membrane reactor for the treatment of chemical synthesis-based pharmaceutical wastewater

Pharmaceutical wastewaters are mainly generated by chemical-synthetic industries and usually contain high chemical oxygen demand (COD) and toxicity. A novel lab-scale anaerobic bio-entrapped membrane reactor (AnBEMR) packed with bio-ball carriers was constructed and compared with an anaerobic membrane bioreactor (AnMBR). The aims of this study are to investigate the treatment performances and evaluate the stability of the membrane filtration of the AnBEMR and AnMBR under the conditions of a high organic loading rate (OLR), ranging from 8.0 to 36.7 kgCOD/m3 d, and high total dissolved solids (TDS), ranging from 18,411 to 25,925 mg/L, in the treatment of chemical synthetic-based pharmaceutical wastewater. Four different hydraulic retention times (HRTs) of 10.6, 14.1, 21.3, and 42.6 h were studied. Total COD (TCOD) removal efficiency of the AnBEMR ranged from 36.7% to 50.8% at an OLR of 8.7 ± 0.7 kgCOD/m3 d, while the highest OLR (34.0 ± 2.7 kgCOD/m3 d) only led to TCOD removal efficiency of 10.1-20.7%. The AnBEMR achieved approximately 5-10% higher TCOD removal efficiency than the AnMBR. The influences of HRT and TDS (salinity) were also studied. The results show an increase of trans-membrane pressure (TMP) with decreasing HRT in both MBRs, where extracellular polymeric substances (EPS), soluble microbial products (SMP) and suspended biomass concentration were significantly higher at the shortest HRT of 10.6 h, resulting in faster membrane fouling. Membrane fouling was improved in the AnBEMR (i.e., longer membrane filtration operating periods) due to the production of lower concentrations of EPS and SMP (protein and carbohydrate contents). Proteins, rather than carbohydrates, were the major component of EPS and SMP in both reactors. The study concludes that the application of the AnBEMR could achieve better treatment performance and reduced membrane fouling by producing lesser EPS, SMP, and suspended biomass concentration.