Construction of a Heterotrophic Nitrification–Aerobic Denitrification Composite Microbial Consortium and Its Bioaugmentation Role in Wastewater Treatment

Nitrogen pollution in wastewater remains a pressing environmental concern, prompting the need for efficient and sustainable treatment technologies. This study constructs an HN-AD microbial consortium using three pre-screened strains (<i>Delftia tsuruhatensis</i> SDU2, <i>Pseudomonas stutzeri</i> SDU10, <i>Alcaligenes faecalis</i> SDU20) and evaluates its bioaugmentation effects in sequencing batch reactors (SBRs). An orthogonal test optimized the inoculation ratio as 2:3:3 (SDU2:SDU10:SDU20), achieving the highest ammonium removal efficiency of 96.02% in vitro. In SBR experiments, the bioaugmented reactor (SBR1) demonstrated superior nitrogen and organic matter removal compared to the control (SBR2). By day 40 of the enhancement phase, SBR1 achieved 88.9% ammonium removal and 93.7% COD removal, representing improvements of 20.5% and 17.9% over SBR2, respectively. Microbial community analysis revealed that bioaugmentation enriched Proteobacteria and Bacteroidota phyla, promoting functional guilds like <i>Alcaligenes</i>, <i>Pseudomonas</i>, and <i>Paracoccus</i>, which synergized with indigenous microbiota to enhance metabolic efficiency. This study highlights the potential of HN-AD consortia to overcome limitations of conventional nitrogen removal systems, offering a promising strategy for optimizing wastewater treatment processes.