## 3 Fouling Mitigation Strategies  
It is a well-accepted fact that the membrane fouling phenomenon can be controlled by various methods. Table 3 shows literature reports on fouling mitigation strategies in submerged and external AnMBRs applied for biogas production via the treatment of municipal and domestic wastewater. Overall, the strategies can be categorized into the following methods: (i) physical cleaning, such as biogas sparging, manual cleaning, relaxation, and ultrasonication as well as (ii) physio-chemical cleaning, including chemically enhanced backwashing, and (iii) chemical cleaning. It is fundamental to note that in most of the studies, a combination of several methods of membrane cleaning has been applied. This can be explained by the fact that some compounds of wastewater form irreversible fouling, the removal of which requires various cleaning methods, including chemical cleaning.  
\begin{table}
\begin{tabular}{l l l l l l l l l l l l l l l} \hline \multicolumn{3}{c}{**AnMBR**} & \multicolumn{3}{c}{**Membrane Characteristics**} & \multicolumn{5}{c}{**Foupling Mitigation Strategy**} \\ \multicolumn{3}{c}{**Scale**} & \multicolumn{1}{c}{**Configuration**} & \multicolumn{1}{c}{**Type**} & \multicolumn{1}{c}{**Material**} & \multicolumn{1}{c}{**Configuration**} & \multicolumn{1}{c}{**Biggs**} & \multicolumn{1}{c}{**Manual**} & \multicolumn{1}{c}{**Relaxation**} & \multicolumn{1}{c}{**Ultrasonic**} & \multicolumn{1}{c}{**Enhanced**} & \multicolumn{1}{c}{**Channel**} & \multicolumn{1}{c}{**Channel**} & \multicolumn{1}{c}{**Cleaning/**} & \multicolumn{1}{c}{**Uosed Agents**} & \multicolumn{1}{c}{**Ref.**} \\ \hline pilot & sch submerged & UF & NI & hollow fiber & + & – & + & – & + & – & + & NoGO & [72] \\ pilot & submerged & UF & NI & hollow fiber & + & – & + & – & + & – & + & – & - & [73] \\ pilot & submerged & UF & PES & flat sheet & + & – & + & – & + & – & + & – & [74] \\ pilot & submerged & UF & PES & flat sheet & + & – & + & – & + & – & – & [75] \\ pilot & submerged & UF & PES & flat sheet & – & – & + & – & + & – & + & – & [76] \\ pilot & submerged & UF & NI & hollow fiber & – & – & – & – & + & + & & NoGO & [76] \\ pilot & submerged & UF & NI & hollow fiber & + & – & + & – & – & – & – & [78] \\ pilot & submerged & MF & PVOF & hollow fiber & + & – & + & – & + & – & – & NoGO & [77] \\ pilot & submerged & MF & PVOF & hollow fiber & + & – & + & – & – & – & – & [78] \\ pilot & submerged & MF & PVDF & hollow fiber & + & – & – & – & + & & [79] \\ pilot & external & UF & NI & hollow fiber & – & – & – & – & – & + & [78] \\ pilot & external & UF & NI & hollow fiber & – & – & + & – & – & + & [78] \\ pilot & external & UF & NI & hollow fiber & – & – & + & – & + & – & [78] \\ pilot & subengred & MF & PVDF & flat sheet & – & – & – & – & + & – & [78] \\ bench & sch submerged & MF & PES & plate and frame & – & – & – & – & – & + & NoGO & [88] \\ bench & schmed & VF & emulic & NI & + & – & – & – & + & – & [78] \\ laboratory & submerged & MF & N & rectangular & + & – & – & + & – & – & [78] \\ laboratory & submerged & MF & ocular & + & – & – & – & + & – & – & [78] \\ laboratory & submerged & MF & PT & hollow fiber & – & + & – & – & – & [78] \\ laboratory & submerged & MF & FE & flat sheet & – & + & – & – & + & NoGO & [79] \\ laboratory & submerged & MF & ceramic & flat sheet & – & + & – & – & + & NoGO and time cold & [79] \\ laboratory & submerged & MF & counter & hole fiber & – & – & – & + & [78] & \\ laboratory & submerged & MF & N & NI & – & + & – & – & + & NoGO and time cold & [79] \\ laboratory & external & MF & PTFE & nullbar & – & – & – & + & [78] & \\ laboratory & external & UF & PVOF & flat sheet & – & + & – & – & + & NoGO and time cold & [79] \\ laboratory & external & MF & organic & NI & – & – & – & – & + & NoGO and time cold & [79] \\ \hline \end{tabular}
\end{table}
Table 3: Fouling mitigation strategies in AnMBRs technology applied for the treatment of municipal and domestic wastewater: Literature review.