Ito Yui, Hafuka Akira, Kimura Katsuki
Division of Environmental Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060-8628, Japan.
Division of Environmental Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060-8628, Japan.
Water Res. 2025 Nov 1;286:124195. doi: 10.1016/j.watres.2025.124195. Epub 2025 Jul 9.
Ammonia in municipal wastewater, which is commonly treated by energy-intensive biological nitrification/denitrification systems, should be recovered in terms of energy efficiency, resource utilization and mitigation of global warming (prevention of emission of NO). The use of a membrane contactor (MC) seems to be effective for recovery of ammonia in municipal wastewater. However, fouling of the membrane in the MC is a potential problem. The effectiveness of direct membrane filtration (DMF) as a pretreatment for controlling the fouling in an MC was investigated in this study. Although DMF can efficiently capture the carbon in municipal wastewater, it cannot remove or capture ammonia in municipal wastewater. Therefore, it was thought that the combination of the use of an MC and DMF would compensate each other. Experiments were carried out by using both synthetic wastewater and municipal wastewater under a high alkaline condition (pH of 11) and a moderate alkaline condition (pH of 9.2). For municipal wastewater, the effluent from primary sedimentation and the permeate from DMF using microfiltration (pore size: 0.1 µm) were examined. It was shown that pretreatment by DMF significantly mitigated the fouling in the MC, leading to maintenance of efficient mass transfer of ammonia in the MC. Ammonia in municipal wastewater could almost completely be recovered by the MC within 6 h regardless of pH. Thus, it was shown that the integration of DMF and an MC could recover 70-80 % of carbon and almost 100 % of ammonia from municipal wastewater. Long-term operations of the proposed system with multiple replacements of the feed wastewater demonstrated that concentration of ammonia nitrogen in the recovery solution (sulfuric acid) could be increased to >350 mg/L. In the long-term operations, due to strict removal of particles/colloids by DMF, the performance of an MC operated at pH of 9.2 was comparable to that operated at pH of 11. This justifies the operation of an MC under a moderate alkaline condition rather than a high alkaline condition, for enhancing the feasibility of the use of an MC for recovery of ammonia from municipal wastewater.
城市废水中的氨通常由能源密集型生物硝化/反硝化系统处理，从能源效率、资源利用和缓解全球变暖（防止一氧化氮排放）的角度来看，氨应该被回收利用。使用膜接触器（MC）似乎对回收城市废水中的氨有效。然而，膜接触器中的膜污染是一个潜在问题。本研究考察了直接膜过滤（DMF）作为控制膜接触器中膜污染预处理方法的有效性。虽然DMF可以有效地捕集城市废水中的碳，但它不能去除或捕集城市废水中的氨。因此，人们认为将膜接触器与DMF结合使用可以相互补充。在高碱性条件（pH值为11）和中等碱性条件（pH值为9.2）下，使用合成废水和城市废水进行了实验。对于城市废水，研究了初次沉淀池的出水以及使用微滤（孔径：0.1µm）的DMF渗透液。结果表明，DMF预处理显著减轻了膜接触器中的膜污染，从而维持了膜接触器中氨的高效传质。无论pH值如何，城市废水中的氨几乎可以在6小时内被膜接触器完全回收。因此，结果表明，DMF与膜接触器的结合可以从城市废水中回收70-80%的碳和几乎100%的氨。对所提出的系统进行多次更换进水废水的长期运行表明，回收溶液（硫酸）中的氨氮浓度可以提高到>350mg/L。在长期运行中，由于DMF严格去除颗粒/胶体，在pH值为9.2下运行的膜接触器的性能与在pH值为11下运行的膜接触器相当。这证明了在中等碱性条件而非高碱性条件下运行膜接触器的合理性，以提高使用膜接触器从城市废水中回收氨的可行性。
