Synergistic strategies for optimizing microalgae-based wastewater treatment: a comprehensive review

Microalgae-based wastewater treatment (MBWT) addresses significant environmental challenges posed by traditional wastewater treatment (WWT), which is often limited in pollutant removal, nutrient recovery, and bioactive compound production. This review presents a comprehensive analysis of recent advancements in MBWT, emphasizing the synergistic integration of microalgae cultivation for both wastewater treatment and the production of valuable bioactive compounds. It highlights the feasibility and scalability of vertical photobioreactors (PBRs) and open raceway ponds as optimal systems for MBWT due to their operational efficiency and cost-effectiveness. The review also emphasizes the importance of introducing microalgae during secondary treatment, where nutrient levels are favorable and pretreatment has removed large debris. In addition, we propose that harvested biomass can be further valorized to produce value-added bioactive compounds like fertilizer, biofuel, and antioxidants, supporting a circular economy approach. Furthermore, underexplored microalgal strains (e.g., Haematococcus pluvialis) show significant promise due to their dual role in efficiently treating wastewater and producing high-value antioxidants like astaxanthin. Further research is needed to optimize the simultaneous production of bioactive compounds and wastewater treatment in integrated microalgal systems. •Recent progress in microalgae-based wastewater treatment (MBWT) is introduced.•Co-culturing microalgae strains may improve wastewater treatment efficiency.•Different designs of photobioreactors for specific MBWT conditions are illustrated.•H. pluvialis and C. zofingiensis are used in MBWT which produces bioactive compounds.•Integration of microalgae into MBWT requires further comprehensive investigation.