Partial nitrification-denitrification strategies with different sludge sources and their impact on membrane fouling...

Biological nitrogen removal under low C/N conditions presents significant challenges in wastewater treatment. Although shortcut nitrogen removal processes have attracted research interest due to their energy-saving advantages, current studies primarily focus on enriching ammonia-oxidizing bacteria (AOB) while suppressing nitrite-oxidizing bacteria (NOB), paying insufficient attention to microbial community diversity and ecological stability. This study successfully established a stable simultaneous partial nitrification-denitrification (PND) system using contaminated sediment from rare earth mining areas as inoculum. After 35 days of acclimation, the system achieved efficient nitrite accumulation (NAR: 88.38 ± 3.53%) and demonstrated superior microbial diversity, with the relative Nitrosomonas (AOB) and Rhodobacter (DNB) being approximately 10 and 23 times those in the municipal sludge system, respectively. Metabolic pathway analysis revealed significant upregulation of ammonia oxidation genes (amoC, Hao) and denitrification genes (nirK, norQ), coupled with marked downregulation of nitrite oxidation genes (nxrA/B), indicating enhanced simultaneous PND performance. The increased protein and polysaccharide content in tightly bound extracellular polymeric substances (TB-EPS) promoted floc structure stability and alleviated membrane fouling. These findings provide valuable insights for shortcut nitrogen removal strategies and establish a theoretical foundation for efficient treatment of low C/N wastewater from rare earth mining operations.