Biofilm-mediated algal-bacterial consortia for enhanced nitrogen removal: Exploring the dynamics of symbiotic interactions in membrane aerated reactors

A novel algal-bacterial membrane aerated biofilm reactor (AB-MABR), integrating algal-bacterial systems with membrane aeration, was proposed for enhanced nitrogen removal in low C/N wastewater. Compared to conventional MABR (B-MABR), the AB-MABR system achieved improved nitrogen removal efficiencies across all C/ N ratios tested (2, 4, and 6), with the most significant enhancement observed at a C/N ratio of 4. Kinetic of ammonia removal analysis revealed that algal assimilation was a significant factor in nitrogen removal, contributing approximately 50 % to the overall process across the three low C/N ratios studied. The increased microbial biomass concentration and improved microbial biological activity (SOUR and SOGR) were the primary factors contributing to enhanced nitrogen removal in AB-MABR. This was particularly evident at a C/N ratio of 4, where algae and bacteria achieved optimal growth balance. Further analysis suggested that the microbial diversity and community structure were enhanced in the AB-MABR, with an enrichment of bacteria associated with nitrogen removal and algal growth within the algal-bacterial biofilm. Additionally, the community structure exhibited greater stability. Moreover, functional prediction indicated that the introduction of algae led to a higher relative abundance of genes involved in nitrogen transfer pathways. Consequently, both physiological properties and community characteristics contributed to the synergistic interaction between algae and bacteria, leading to improved nitrogen removal in AB-MABR at low C/N ratios. Our findings highlight the potential of ABMABRs for efficient and sustainable wastewater treatment, offering valuable insights into membrane-based bioreactor design.