## 1 Introduction
Furthermore, results obtained in the above-mentioned work indicated that the AnMBRs technology used for the treatment of low-sulfate municipal wastewater has the potential to be a net energy producer. Due to the above-presented advantages, the AnMBRs technology is a highly appreciated opportunity for biogas production via municipal and domestic treatment. The application of AnMBR technology for biogas production is frequently investigated in scientific research. Indeed, ScienceDirect contains 5946 records related to the presented subject which have been published between 2003 and 2022. Moreover, the performed analysis demonstrated that the number of articles focused on biogas and AnMBRs increased significantly, especially in the last decade (Figure 3). Undoubtedly, this finding confirms the importance of the research topic presented in the current study. It is recognized that the large-scale implementation of AnMBR technology is a great challenge mainly due to the fouling which is caused by the matter attached to the membrane surface or trapped inside its pores. This issue is of critical importance since it leads to a reduction in the system performance and thus, an increase in the operation cost. In terms of the treatment of municipal and domestic wastewater, fouling is a very complex phenomenon. It is due to the fact that the above-mentioned types of wastewater contain a  
Figure 3: The number of articles focused on biogas production in membrane bioreactors according to ScienceDirect. Keywords: ‘anaerobic membrane bioreactor + biogas’. Data retrieved: 29 March 2023.  
huge number of various compounds, such as organic matters, nutrients, heavy metals, and organic micropollutants [56; 57; 58]. Moreover, the wastewater composition may vary with the seasons and location [59; 60; 61] which additionally hinders the estimation of the process performance and efficiency. Worthy of note, anaerobic sludge may produce granules leading to more severe membrane contamination [50]. A more detailed overview on the membranes fouling in the AnMBRs can be found for example in [54; 62; 63; 64; 65; 66]. It has been recognized that the successful long-term performance of AnMBRs depends on the effectiveness of membrane cleaning. Indeed, it is a key procedure that aims to maintain the membrane performance and separation properties as well as to prevent contamination of the installation with microorganisms. In AnMBRs technology, the fouling mitigation strategy is of crucial importance since it accounts for more than 70% of the energy consumption [67]. In brief, the methods of membrane cleaning are categorized into three groups: chemical, physical, and physio-chemical. It should be emphasized that physical cleaning is adopted to remove reversible fouling while chemical cleaning to remove irreversible fouling [26; 68; 69]. To the best of the authors' knowledge, the review articles focused on biogas performance in AnMBRs applied for the treatment of municipal and domestic wastewater are very limited. Consequently, the impact of the process parameters on biogas yield has been poorly described so far. The present paper is a continuation and complement of our recently published study [48] wherein it was clearly documented that the AnMBRs are an energy-efficient technology. Accordingly, the current work aimed at comprehensively evaluating and discussing the impact of the process parameters, such as temperature and hydraulic retention time, on biogas production yield in AnMBRs via the treatment of municipal and domestic wastewater. Analysis reported so far in the literature have been conducted with the use of submerged and external AnMBRs equipped with both polymeric and ceramic membranes. Moreover, the possibilities of applying various fouling mitigation strategies have been discussed in detail.