Liu Qiushan, Zhou Tong, Liu Yuru, Wu Wenjun, Wang Yufei, Liu Guohan, Wei Na, Yin Guangshuo, Guo Jin
National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Beijing University of Technology, Ping Leyuan No. 100, Beijing 100124, China.
Membranes (Basel). 2024 Oct 7;14(10):214. doi: 10.3390/membranes14100214.
There is limited research on the relationship between membrane fouling and microbial metabolites in the nitrogen removal process coupled with membrane bioreactors (MBRs). In this study, we compared anoxic-oxic (AO) and partial nitritation-anammox (PNA), which were selected as representative heterotrophic and autotrophic biological nitrogen removal-coupled MBR processes for their fouling behavior. At the same nitrogen loading rate of 100 mg/L and mixed liquor suspended solids (MLSS) concentration of 4000 mg/L, PNA-MBR exhibited more severe membrane fouling compared to AO-MBR, as evidenced by monitoring changes in transmembrane pressure (TMP). In the autotrophic nitrogen removal process, without added organic carbon, the supernatant of PNA-MBR had higher concentrations of protein, polysaccharides, and low-molecular-weight humic substances, leading to a rapid flux decline. Extracellular polymeric substances (EPS) extracted from suspended sludge and cake sludge in PNA-MBR also contributed to more severe membrane fouling than in AO-MBR. The EPS subfractions of PNA-MBR exhibited looser secondary structures in protein and stronger surface hydrophobicity, particularly in the cake sludge, which contained higher contents of humic substances with lower molecular weights. The higher abundances of Brocadia and in PNA-MBR could lead to the production of more hydrophobic organics and humic substances. Hydrophobic metabolism products as well as anammox bacteria were deposited on the hydrophobic membrane surface and formed serious fouling. Therefore, hydrophilic membrane modification is more urgently needed to mitigate membrane fouling when running PNA-MBR than AO-MBR.
关于膜生物反应器（MBR）脱氮过程中膜污染与微生物代谢产物之间的关系，相关研究有限。在本研究中，我们比较了缺氧-好氧（AO）和部分亚硝化-厌氧氨氧化（PNA）这两种作为代表性的异养和自养生物脱氮耦合MBR工艺的膜污染行为。在相同的100 mg/L氮负荷率和4000 mg/L混合液悬浮固体（MLSS）浓度下，通过监测跨膜压力（TMP）的变化证明，与AO-MBR相比，PNA-MBR表现出更严重的膜污染。在自养脱氮过程中，不添加有机碳时，PNA-MBR的上清液中蛋白质、多糖和低分子量腐殖物质的浓度较高，导致通量迅速下降。从PNA-MBR的悬浮污泥和滤饼污泥中提取的胞外聚合物（EPS）也比AO-MBR导致更严重的膜污染。PNA-MBR的EPS亚组分在蛋白质中表现出更松散的二级结构和更强的表面疏水性，特别是在滤饼污泥中，其中含有较高含量的低分子量腐殖物质。PNA-MBR中较高丰度的布罗卡德氏菌可能导致产生更多的疏水性有机物和腐殖物质。疏水性代谢产物以及厌氧氨氧化细菌沉积在疏水膜表面并形成严重污染。因此，运行PNA-MBR时比AO-MBR更迫切需要进行亲水性膜改性以减轻膜污染。
