## 1 Introduction
\begin{table}
\begin{tabular}{c l l l} \hline
**Process** & & **Description** & **Stoichiometric Equation** & **Equation** \\ \hline \multicolumn{4}{c}{**Description**} \\ \hline \multicolumn{4}{c}{**Description**} \\ \hline \multicolumn{4}{c}{**-complex organic matters are broken into simple molecules, such as sugars i.e., glucose} \\ \multicolumn{4}{c}{(C\({}_{\mathrm{H}}\)H\({}_{2}\)O\({}_{\mathrm{0}}\)), amino acids, and fatty acids} \\ \multicolumn{4}{c}{hydrolysis} \\ \multicolumn{4}{c}{**-** reaction catalyzed by acids} \\ \multicolumn{4}{c}{**-** phase relatively slow considered a rate-limiting step in the anaerobic digestion} \\ \multicolumn{4}{c}{**-** exemplary microorganisms. _Bacteristics, Clostritia, Bifidobacterium, Struggococcal, Entroducteria_} \\ \multicolumn{4}{c}{**-** known as the fermentation stage} \\ \multicolumn{4}{c}{**-** compounds formed during the hydrolysis are degraded into hydrogen (H\({}_{2}\)), alcohols, carbon} \\ \multicolumn{4}{c}{**-** flexible (CO\({}_{2}\)), carbon acids, and ammonia} \\ \multicolumn{4}{c}{**-** for pH 5 volatile fatty acid production is favored, meanwhile for pH + 5 ethanol} \\ \multicolumn{4}{c}{**acidogenesis**} \\ \multicolumn{4}{c}{**-** produced aortic acid (CH\({}_{3}\)COOH) and buvtor acid (CH\({}_{5}\)CH\({}_{5}\)COOH) are the preferred} \\ \multicolumn{4}{c}{**-** precursors for CH\({}_{4}\) production} \\ \multicolumn{4}{c}{**-** exemplary microorganisms. _Srupticoccus, Staphylococcus, Escherichia, Bacillus,_} \\ \multicolumn{4}{c}{**-** _Sarcia, Dos/equiro_} \\ \multicolumn{4}{c}{**-** conversion of acidogenesis products into CO\({}_{2}\) H\({}_{2}\), and CH\({}_{3}\)COOH} \\ \multicolumn{4}{c}{**-** phase reflecting the biogas production efficiency} \\ \multicolumn{4}{c}{**-** exemplary microorganisms. _Desai/equiro, Syntrophulucar utilini, Syntrophumans_} \\ \multicolumn{4}{c}{**-** the most crucial stage in biogas production} \\ \multicolumn{4}{c}{**-** production of CH\({}_{4}\) from acetate by methanogens (nearly 70\%) and via reaction of CO\({}_{2}\) and H\({}_{2}\)} \\ \multicolumn{4}{c}{**-** formation of CH\({}_{4}\) by decarboxylation of ethanol} \\ \multicolumn{4}{c}{**-** the CH\({}_{4}\) production rate depends on both the availability of substrate and methane formers} \\ \multicolumn{4}{c}{**-** exemplary microorganisms. _Methenobacterium fomicicum, Methanowberi bacterium_} \\ \hline \end{tabular}
\end{table} 
Table 1: Subsequent steps in the anaerobic digestion process. Based on [3,10,15,20,23,24,25]. Recent advances in chemical engineering have opened up the possibility of overcoming the above-mentioned limitations by application of anaerobic membrane bioreactor (AnMBR) technology. AnMBRs combine conventional anaerobic digestion with a membrane separation unit that retains high molecular-mass substances and prevents the washout of methane-forming microorganisms. For this purpose, mainly the low-pressure membrane processes: microfiltration (MF) and ultrafiltration (UF) are applied. Consequently, as was indicated in [47], the amount of biogas produced in AnMBRs is more significant than that obtained via conventional processes of the wastewater treatment. The undeniable advantages of AnMBRs technology have been presented in a significant number of review papers [26; 38; 48; 49; 50; 51; 52; 53; 54; 55]. According to the above-mentioned studies, the most important benefits of the AnMBRs application are high biomass concentration and enhanced biogas yield, effluent with excellent quality without suspended solids, small footprint, low sludge production, and high treatment capacity. It should be pointed out that in our recently published review article [48], it was demonstrated that the AnMBRs are energy-efficient technology. Indeed, through detailed studies, it was concluded that the net energy demand of submerged AnMBRs used for the treatment of sulfate-rich municipal wastewater is significantly lower than that noted for WWTPs.