## 2 MBR Types and Configuration
### Anaerobic MBR (AnMBR) for OMPs Removal
\begin{tabular}{c} Synthetic \\ wastewater \\ \end{tabular}  & \ \begin{tabular}{c} Hollow-fiber \\ ceramic UF \\ membrane module \\ (PURON® \\ (PURON® \\ (Valencia, \\ Spain), \\ \end{tabular}  &
\begin{tabular}{c} 1 \\ 2-1 \\ 2-2 \\  
As reviewed by [PERSON] et al. (2015) in an anaerobic process too low removal was achieved for an OMP such 17a-ethinylestradiol. Other OMPs--octyl phenol and nonylphenols--were also showed poor degradation [87]. In contrast, other researchers accomplished 20% removal for 17a-ethinylestradiol [89]. Those contradictory findings could be related to the wide variety of anaerobic microbes responsible for OMPs biodegradation. Though methanogenic archaea are major community for anaerobic degradation other electron acceptors such as sulfate-reducing, iron-reducing and nitrate-reducing microbial communities also plays significant role in OMP removal [87]. [PERSON] et al. (2019) report that AnMBR improved up to 80% removal for 15 OMPs. In addition, they distinguished refractory compounds to biodegradation such as carbamazepine, diazepam and diclofenac. Further, naproxen, sulfamethoxazole, trimethoprim and fluoxetine were easily biodegradable compounds under anaerobic conditions. The authors further report that certain compounds were removed with combined UASB and the post-treatment reactor such as \(\beta\)-estradiol E2, \(\alpha\)-ethinylestradiol EE2, erythromycincin and erythromycincin [80]. Salt accumulation, membrane module integrity, fouling of membrane and presence of refractory compounds are considered as major bottleneck for evolution of AnMBR in micropollutants removal during sewage treatment [81]. [PERSON] et al. (2015) have evaluated fate of 27 OMPs in AnMBR. They deduced that removal of OMPs can be correlated to their hydrophobicity and molecular structures. In particular, hydrophobic OMPs could be easily adsorbed on to the sludge and more than 70% removal for such OMPs had been reported. On the other hand electron donating hydrophilic OMPs such as sulfamethoxazole, carbamazepine, linuron, omeprazole and atrazine having hydroxyl and amine bearing nitrogen atoms in their structure shown high removal [87]. Another report by [PERSON] et al. (2011) also confirmed improved process performance in anoxic process compared to aerobic process with regard to carbamazepine removal [91]. On the contrary, halogenated compounds such as chlorine molecule and amide like hydrophilics with EWGs had shown recalcitrant behavior in AnMBR process [80]. [PERSON] et al. (2014) evaluated OMP removal in AnMBR process and deduced that 50-90% removal were accomplished. However, nine OMPs showed over 90% removal. They also postulate OMP removal mechanism by AnMBR in detail, such as the impact of biodegradation, sorption and physicochemical properties (hydrophobicity, presence of EDG and EWG). As can be seen in Figure 3, easily biodegradable OMPs show better removal in AnMBR. Certain OMPs such as etriol, primidone, 17a-ethynylestradiol, 17a-estradiol, 17b-estradiol and rosterone and testosterone showed higher attachment onto the sludge having an overall 69 ng OMPs/g total solids (TS) sludge sorption capacity for OMPs. Nevertheless, analysis of variance (ANOVA) revealed a non-linear correlation for OMPs sludge sorption and Kow and the Log D values. Furthermore, authors noticed that AnMBR process showed better removal for EWDG containing compounds having higher Log D values as compared to too low removal (<21.4%) for OMPs bearing strong EWG [89]. [PERSON] et al. (2015) evaluated OMP removal in their work and deduced that more than 27% removal could be accomplished for the entire set of hydrophobic compounds. The authors co-related the removal of OMPs by AnMBR to their physicochemical properties, particularly hydrophobicity and molecular structure. Their results showed that all hydrophobic compounds out of 27 OMPs were removed by>70%. On the other hand, hydrophilic OMPs having strong electron withdrawing groups in their structure were found recalcitrant to the biodegradation.