Abstract：
A biofilm has a significant effect on water treatment processes. Currently, there is a lack of knowledge about the effect of temperature on the biofilm structure in water treatment processes. In this study, a gravity-driven membrane ultrafiltration system was operated with river feedwater at two temperatures (\"low\", 4 °C; \"high\", 25 °C) to explore the biofilm structure and transformation mechanism. The results showed that the difference in dissolved oxygen concentration might be one of the main factors regulating the structural components of the biofilm. A denser biofilm formation and reduced flux were observed at the lower temperature. The linoleic acid metabolism was significantly inhibited at low temperature, resulting in enhanced pyrimidine metabolism by Na+ accumulation. In addition, the biofilm at low temperature had a higher proportion of the metabolites of lipids and lipid-like molecules (11.25%), organic acids and derivatives (10.83%), nucleosides, nucleotides, and analogues (7.083%), and organoheterocyclic compounds (6.66%). These small molecules secrete more polysaccharides having C═O and O═C-O functional groups, which intensified the resistance of the biofilm. Furthermore, the upregulation pathway of pyrimidine metabolism also increased the risk of urea accumulation at low temperature. Limnohabitans, Deinococcus, Diaphorobacter, Flavobacterium, and Pseudomonas were identified as the principal microorganisms involved in this metabolic transformation.
摘要：
生物膜对水处理过程具有显著影响。目前,缺乏关于水处理过程中温度对生物膜结构的影响的知识。在这项研究中,重力驱动膜超滤系统在两种温度下用河流给水运行(“低”，4°C；“高”，25°C）以探索生物膜的结构和转化机理。结果表明，溶解氧浓度的差异可能是调节生物膜结构成分的主要因素之一。在较低温度下观察到更致密的生物膜形成和降低的通量。低温下亚油酸代谢受到显著抑制,通过Na+积累导致嘧啶代谢增强。此外,低温生物被膜中脂质和类脂分子的代谢产物比例较高(11.25%),有机酸及其衍生物(10.83%)，核苷，核苷酸,和类似物（7.083％），和有机杂环化合物(6.66%)。这些小分子分泌更多具有C=O和O=C-O官能团的多糖，这增强了生物膜的抵抗力。此外，嘧啶代谢的上调途径也增加了低温下尿素积累的风险。Limnohabitans,异常球菌,血透杆菌,黄杆菌,和假单胞菌被鉴定为参与这种代谢转化的主要微生物。
