Comparison of single and mixed microalgae in microalgae-bacteria MB-MBR:From efficiency of wastewater treatment, bioactivity and membrane fouling

In this study, two microalgae-bacterial moving bed membrane bioreactors (MB-MBRs) were constructed for co-culture of L1 (Scenedesmus obliquus) and L2 (Chlorella pyrenoidosa and Scenedesmus obliquus) with activated sludge. Nutrient removal efficiency, biological activity and membrane fouling of two microalgae-bacterial MB-MBRs were evaluated. Both reactors demonstrated robust performance, with L2 exhibiting superior functionality. near-complete ammonia nitrogen removal (99.33 ± 1.11 %), total organic carbon (TOC) removal of 73.72 ± 4.83 %, chemical oxygen demand (COD) removal of 92.93 ± 3.23 %, and dehydrogenase activity (DHA) peaked at 10 μg TF/(mL·h). L2 sludge flocs displayed a more compact circular morphology compared to those of L1. It was found that proteins in the extracellular polymeric substance (EPS) were the key to initial biofilm attachment, while polysaccharides facilitated biofilm maturation. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy demonstrated that tryptophan and aromatic proteins played critical roles in biofilm formation and membrane fouling. According to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, ΔG^AB was the main factor influencing membrane fouling. These results demonstrate that hybrid microalgae-bacterial systems with biofilm carriers synergistically enhance wastewater treatment efficiency, increase biological activity, and alleviate membrane fouling, offering a sustainable strategy for wastewater treatment.