Biochar-driven fouling mitigation in sustainable microalgal-bacterial membrane bioreactors

Microalgal-bacterial membrane bioreactor (MB-MBR) have emerged as a crucial technology for sustainable wastewater treatment. However, membrane fouling caused by free microalgae remains a major obstacle to their cost-effective operation. This study investigated the impact of biochar addition on membrane fouling in MBMBR. The findings indicated that biochar significantly reduced membrane fouling, primarily due to the enlargement of floc size and the reduction of soluble microbial products (SMP). Detailed analyses suggested that biochar's adsorptive properties and its effect on decreasing the abundance of algae and bacteria species, such as Proteobacteria and Leptolyngbya, which promote fouling, are key factors. This alteration enhanced specific amino acid metabolic pathways, thereby reducing SMP production and fouling potential. Consequently, adhesion interaction energy of the flocs and membrane fouling were both diminished. This study demonstrated that biochar addition is an effective strategy for mitigating membrane fouling in MB-MBR systems, providing a theoretical foundation for their stable and sustainable operation.