Optimization of Nitrogen Removal Efficiency in eAnMBR-PN/A Integrated Process:Model Development and Microbial Interaction Mechanisms

YAN Zhang; ZENG Wuqiang; TANG Yi; PAN Jianxin; CHEN Jinfeng; JIANG Zhuwu

doi:10.20078/j.eep.20250702

Abstract：The study investigates the optimization of nitrogen removal efficiency in an enhanced anaerobic membrane bioreactor coupled with a partial nitrification/anammox(eAnMBR-PN/A)integrated process.Simulation results demonstrate that the surface oxygen loading rate significantly influences system performance.When maintained between 0.12 and 0.14 g/(m d),the system achieves a peak total nitrogen(TN)removal efficiency of 64.45％,which corresponds to the highest relative abundance of anaerobic ammonium-oxidizing bacteria(AnAOB)in the biofilm.However,at rates exceeding 0.16 g/(m d),elevated dissolved oxygen concentrations inhibit AnAOB activity while promoting the growth of nitrite-oxidizing bacteria(NOB),resulting in nitrate accumulation and reduced TN removal efficiency.The carbon-to-nitrogen(C/N)ratio also plays a crucial role in regulating system performance.At low influent NH4-N concentrations(＜35 g/m3),increasing the C/N ratio enhances TN removal by stimulating the denitrification activity of heterotrophic bacteria(HB).In contrast,at high NH+-N concentrations(≥ 35 g/m3),maintaining a low C/N ratio(＜2.0)is essential to prevent HB from competitively competitively inhibiting AnAOB functionality.The findings indicate that the eAnMBR-PN/A process can effectively remove nitrogen from municipal wastewater with low C/N ratios by optimizing oxygen transfer and substrate distribution.This provides valuable theoretical insights and a technical pathway for the low-carbon transformation of wastewater treatment plants.The study highlights the importance of balancing the surface oxygen loading rate to avoid suppression of ammonia-oxidizing bacteria(AOB)activity at low oxygen levels and inhibition of AnAOB at high oxygen levels.Additionally,when the influent NH4+-N concentration is low,increasing the influent chemical oxygen demand(COD)can enhance TN removal,albeit at the cost of higher operational expenses.Conversely,under high NH+4-N concentrations,maintaining a lower influent COD facilitates AnAOB activity,thereby reduce costs.Microbial community analysis reveals that at oxygen loading rate of 0.12 g/(m3·d),a stable symbiotic biofilm community of AnAOB,AOB,and HB is established.As the oxygen loading rate increases to 0.16 g/(m3·d)and above,AnAOB abundance initially increases and subsequently decreases due to high dissolved oxygen inhibition.In conclusion,the eAnMBR-PN/A integrated process offers an effective solution for nitrogen removal from municipal wastewater with low C/N ratios.By optimizing the oxygen loading rate and C/N ratio,the system can achieve high nitrogen removal efficiency while reducing operational costs.This study advances the understanding of nitrogen removal mechanisms and underscores the potential of the eAnMBR-PN/A process in promoting the enrichment of functional microbial communities for efficient treatment.