Microalgae-based membrane bioreactor for wastewater treatment, biogas production, and sustainable energy: a review

Managing wastewater and using renewable energy sources are challenges in achieving Sustainable Development Goals. This study provides an overview of the factors influencing the performance of algae-based membrane bioreactors (AMBRs) for contaminant removal from wastewater and biogas. This review highlights that the performance of AMBRs in removing total phosphorus (TP) and nitrogen (N) from wastewater can reach up to 93% and 97%, depending on parameters such as pH, hydraulic retention time (HRT), and algae concentration. Besides, the removal of H₂S from biogas substantially depends on the type of bioreactor used. Furthermore, algal biomass has proven to be a good option for biogas production and CO₂ sequestration, contributing to the achievement of carbon neutrality. This review also underscores that microalgae are a valuable feedstock, either alone or in combination with other raw materials, for biogas production. To sum up, this review outlines that maximizing the performance of bioreactors and the efficiency of microalgae used for biogas production and wastewater treatment requires careful control of parameters, such as HRT, solid retention time, pH, and temperature. Additionally, pH and the carbon-to-nitrogen ratio (C:N) are among the factors influencing CH₄ yield based on microalgae anaerobic digestion (AD). Further research is needed to assess the operational costs of AMBRs used for wastewater treatment and to compare the biogas produced by different types of bioreactors under similar conditions, including the same feedstock.