Synthesis, characterization and performance of microorganism-embedded biocomposites of LDH-modified PVA/SA hydrogel beads for enhanced biological nitrogen removal process

In this study, to improve the biological treatment of nitrogenous wastewater, a series of hybrid embedding materials were synthesized and applied in microbial immobilization to form novel biocomposites, which utilize MgAl-LDH as additives to modify the polyvinyl alcohol/sodium alginate (PVA/SA) beads. As proved by several characterizations, the synthesized PVA/SA/LDH biocomposites formed well in quality and possessed suitable features, such as the dense surface morphology and three-dimensional internal network structure. By regulating the addition amount of LDHs, a better cross-linking reinforcing effect of PVA/SA/LDH biocomposite was achieved. Among the different synthesized materials, PS0.6LDH (0.6 g addition in each synthesis process) exhibited improved mechanical strength and stability, thereby providing a protected environment for the proliferation of embedded microorganisms. Based on this, a significant treatment performance was observed in the biological process of PS0.6LDH, and the removal efficiencies of TN and COD reached above 90% in the periodic experiments. Microbial community analysis indicated that the dominant microorganisms of the genera Acinetobacter, Chryseobacterium, and unclassified-Enterobacteriaceae contribute to the biological nitrogen removal, and the heterotrophic nitrification-aerobic denitrification and assimilation were the main pathways. This study would be a valuable reference for the development of microbial immobilization technology in the practical applications of wastewater treatment.