Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, PR China.
Kurita Water Industries Ltd., Nakano-ku, Tokyo 164-0001, Japan.
Sci Total Environ. 2018 Dec 10;644:486-493. doi: 10.1016/j.scitotenv.2018.06.286. Epub 2018 Jul 11.
Biofouling represents the "Achilles' heel" for reverse osmosis (RO) processes due to the growth of bacteria and their production of extracellular polymeric substances (EPSs). Although the microbial community structure on the RO membrane has been analysed previously, the bacterial species with a high potential of causing RO membrane fouling have not yet been identified clearly. The key components in EPSs causing RO membrane fouling have not been revealed either. In this study, seven different bacterial species were isolated from fouled RO membranes, and their EPSs were analysed in terms of the content of polysaccharides and proteins, fluorescence characteristics and molecular weight (MW) distributions. The membrane fouling potentials of these bacterial species and EPSs were evaluated based on normalized flux decline. Generally, under the same growth conditions, bacterial species with higher EPS concentrations, rather than higher cell numbers, resulted in more severe flux decline. The flux decline showed an apparent positive correlation with the EPS concentration, indicating that the concentration of EPS rather than the bacterial number mainly contributed to biofouling. Furthermore, it was found that the MW distribution was the key factor affecting the RO membrane fouling potential of EPSs from different bacterial species. With the increase in the percentage of the high-MW fraction (>10 kDa) in the EPSs from 12.6% to 74.4%, the normalized flux decline increased from 0.4 to 0.59. The components in EPSs with a MW over 10 kDa were also separated by the ultrafiltration membrane and were proven to have a higher membrane fouling potential.
生物污损是反渗透（RO）过程的“阿喀琉斯之踵”，因为细菌的生长及其产生的胞外聚合物（EPS）。虽然之前已经分析了 RO 膜上的微生物群落结构，但尚未明确具有高致 RO 膜污损潜力的细菌种类。EPS 中导致 RO 膜污损的关键成分也尚未揭示。在这项研究中，从污损的 RO 膜中分离出了七种不同的细菌，分析了它们的 EPS 在多糖和蛋白质含量、荧光特性和分子量（MW）分布方面的情况。根据归一化通量衰减评估了这些细菌和 EPS 的膜污染潜力。一般来说，在相同的生长条件下，EPS 浓度较高的细菌种类，而不是细胞数量较高的细菌种类，会导致更严重的通量衰减。通量衰减与 EPS 浓度呈明显正相关，表明 EPS 浓度而不是细菌数量主要导致生物污损。此外，还发现 MW 分布是影响不同细菌 EPS 的 RO 膜污损潜力的关键因素。随着 EPS 中高 MW 部分（>10 kDa）的百分比从 12.6%增加到 74.4%，归一化通量衰减从 0.4 增加到 0.59。MW 超过 10 kDa 的 EPS 中的成分也通过超滤膜进行了分离，并被证明具有更高的膜污染潜力。
