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<p>Low molecular weight organic acids possess considerable potential for modulating microbial nitrogen metabolism. However, existing studies have largely been confined to their application in pure bacterial cultures, leaving their roles in enhancing nitrogen removal performance and underlying mechanisms within activated sludge systems insufficiently understood. In this study, citric acid (CA), oxalic acid (OA), and tartaric acid (TA) were systematically introduced into an activated sludge system to elucidate their effects on nitrogen removal via microbial community restructuring. The results revealed that TA at dosages of 0.05–0.10&#xa0;g/g SS, sustained nitrate removal above 80%, whereas ammonia removal declined to ~ 40% at 0.10&#xa0;g/g SS. In contrast, OA caused irreversible damage to the microbial system, while CA enhanced nitrogen removal performance but simultaneously promoted the secretion of extracellular polymeric substances (EPS) and increased sludge floc size. Notably, TA imposed a non-destructive stress on microbial cells, leading to a reduction of EPS, reconfiguration of sludge floc architecture, and sustained high-efficiency nitrogen removal. Concurrently, synergistic pressures arising from environmental acidification and EPS structural modulation reshaped the microbial community, facilitating the targeted enrichment of acid-tolerant denitrifiers, such as <i>Thermomonas</i> and <i>Thauera</i>, thereby enhancing nitrogen removal under low carbon to nitrogen ratio conditions. Overall, the addition of organic acids provides a controllable and effective strategy for inducing EPS reorganization and microbial community optimization in activated sludge systems, offering a robust theoretical foundation for their practical application in wastewater treatment engineering.</p>

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Exogenous Organic Acid–Induced Reconfiguration of Extracellular Polymeric Substances Enhances Biological Nitrogen Removal

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Chuchu Wang,
  • Ao Xu,
  • Shangbin Ma,
  • Dawen Gao,
  • Xiaofei Gong,
  • Tiantian Li,
  • Zheng Huang,
  • Yanyu An

摘要

Low molecular weight organic acids possess considerable potential for modulating microbial nitrogen metabolism. However, existing studies have largely been confined to their application in pure bacterial cultures, leaving their roles in enhancing nitrogen removal performance and underlying mechanisms within activated sludge systems insufficiently understood. In this study, citric acid (CA), oxalic acid (OA), and tartaric acid (TA) were systematically introduced into an activated sludge system to elucidate their effects on nitrogen removal via microbial community restructuring. The results revealed that TA at dosages of 0.05–0.10 g/g SS, sustained nitrate removal above 80%, whereas ammonia removal declined to ~ 40% at 0.10 g/g SS. In contrast, OA caused irreversible damage to the microbial system, while CA enhanced nitrogen removal performance but simultaneously promoted the secretion of extracellular polymeric substances (EPS) and increased sludge floc size. Notably, TA imposed a non-destructive stress on microbial cells, leading to a reduction of EPS, reconfiguration of sludge floc architecture, and sustained high-efficiency nitrogen removal. Concurrently, synergistic pressures arising from environmental acidification and EPS structural modulation reshaped the microbial community, facilitating the targeted enrichment of acid-tolerant denitrifiers, such as Thermomonas and Thauera, thereby enhancing nitrogen removal under low carbon to nitrogen ratio conditions. Overall, the addition of organic acids provides a controllable and effective strategy for inducing EPS reorganization and microbial community optimization in activated sludge systems, offering a robust theoretical foundation for their practical application in wastewater treatment engineering.