Australian Centre for Water and Environmental Biotechnology (ACWEB, Formerly AWMC), The University of Queensland, St. Lucia, QLD 4072, Australia.
Australian Centre for Water and Environmental Biotechnology (ACWEB, Formerly AWMC), The University of Queensland, St. Lucia, QLD 4072, Australia.
Water Res. 2023 Dec 1;247:120754. doi: 10.1016/j.watres.2023.120754. Epub 2023 Oct 18.
Membrane aerated biofilm reactor (MABR) and shortcut nitrogen removal are two types of solutions to reduce energy consumption in wastewater treatment, with the former improving the aeration efficiency and the latter reducing the oxygen demand. However, integrating these two solutions, i.e., achieving shortcut nitrogen removal in MABR, is challenging due to the difficulty in suppressing nitrite-oxidizing bacteria (NOB). In this study, four MABRs were established to demonstrate the feasibility of initiating, maintaining, and restoring NOB suppression using low dissolved oxygen (DO) control, in the presence and absence of anammox bacteria, respectively. Long-term results revealed that the strict low DO (< 0.1 mg/L) in MABR could initiate and maintain stable NOB suppression for more than five months with nitrite accumulation ratio above 90 %, but it was unable to re-suppress NOB once they prevailed. Moreover, the presence of anammox bacteria increased the threshold of DO level to maintain NOB suppression in MABRs, but it was still incapable to restore the deteriorated NOB suppression in conjunction with low DO control. Mathematical modelling confirmed the experimental results and further explored the differences of NOB suppression in conventional biofilms and MABR biofilms. Simulation results showed that it is more challenging to maintain stable NOB suppression in MABRs compared to conventional biofilms, regardless of biofilm thickness or influent nitrogen concentration. Kinetic mechanisms for NOB suppression in different types of biofilms were proposed, suggesting that it is difficult to wash out NOB developed in the innermost layer of MABR biofilms because of the high oxygen level and low sludge wasting rate. In summary, this study systematically demonstrated the challenges of NOB suppression in MABRs through both experiments and mathematical modelling. These findings provide valuable insights into the applications of MABRs and call for more studies in developing effective strategies to achieve stable shortcut nitrogen removal in this energy-efficient configuration.
膜曝气生物膜反应器（MABR）和短程硝化反硝化是两种降低污水处理能耗的解决方案，前者提高曝气效率，后者降低氧需求。然而，将这两种解决方案集成，即在 MABR 中实现短程硝化反硝化，具有挑战性，因为难以抑制亚硝酸盐氧化菌（NOB）。本研究建立了四个 MABR，分别在有和没有厌氧氨氧化菌的情况下，展示了通过低溶解氧（DO）控制启动、维持和恢复 NOB 抑制的可行性。长期结果表明，MABR 中严格的低 DO（<0.1mg/L）可以启动并维持超过五个月的稳定 NOB 抑制，亚硝酸盐积累比超过 90%，但一旦 NOB 占优势，就无法再次抑制。此外，厌氧氨氧化菌的存在增加了维持 MABR 中 NOB 抑制的 DO 水平阈值，但它仍然无法在与低 DO 控制结合时恢复恶化的 NOB 抑制。数学模型证实了实验结果，并进一步探讨了常规生物膜和 MABR 生物膜中 NOB 抑制的差异。模拟结果表明，与常规生物膜相比，在 MABR 中维持稳定的 NOB 抑制更加具有挑战性，而不管生物膜厚度或进水氮浓度如何。提出了不同类型生物膜中 NOB 抑制的动力学机制，表明由于高氧水平和低污泥流失率，难以冲洗掉 MABR 生物膜内层中形成的 NOB。总之，本研究通过实验和数学模型系统地证明了 MABR 中 NOB 抑制的挑战。这些发现为 MABR 的应用提供了有价值的见解，并呼吁开展更多研究，以开发在这种节能配置中实现稳定短程硝化反硝化的有效策略。
