Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Water Res. 2015 Dec 15;87:282-91. doi: 10.1016/j.watres.2015.09.037. Epub 2015 Sep 25.
Periodic chemical cleaning is an essential step to maintain nanofiltration (NF) membrane performance and mitigate biofouling, a major impediment in high-quality water reclamation from wastewater effluent. To target the important issue of how to clean and control biofouling more efficiently, this study developed surface-enhanced Raman spectroscopy (SERS) as a layer-by-layer tool to interrogate the chemical variations during both biofouling and cleaning processes. The fact that SERS only reveals information on the surface composition of biofouling directly exposed to cleaning reagents makes it ideal for evaluating cleaning processes and efficiency. SERS features were highly distinct and consistent with different biofouling stages (bacterial adhesion, rapid growth, mature and aged biofilm). Cleaning was performed on two levels of biofouling after 18 h (rapid growth of biofilm) and 48 h (aged biofilm) development. An opposing profile of SERS bands between biofouling and cleaning was observed and this suggests a layer-by-layer cleaning mode. In addition, further dynamic biochemical and infrastructural changes were demonstrated to occur in the more severe 48-h biofouling, resulting in the easier removal of sessile cells from the NF membrane. Biofouling substance-dependent cleaning efficiency was also evaluated using the surfactant sodium dodecyl sulfate (SDS). SDS appeared more efficient in cleaning lipid than polysaccharide and DNA. Protein and DNA were the predominant residual substances (irreversible fouling) on NF membrane leading to permanent flux loss. The chemical information revealed by layer-by-layer SERS will lend new insights into the optimization of cleaning reagents and protocols for practical membrane processes.
周期性化学清洗是维护纳滤（NF）膜性能和减轻生物污染的重要步骤，生物污染是从废水处理中回收高质量水的主要障碍。为了针对如何更有效地清洁和控制生物污染这一重要问题，本研究开发了表面增强拉曼光谱（SERS）作为一种逐层工具，以检测生物污染和清洁过程中的化学变化。SERS 仅揭示了直接暴露于清洁试剂的生物污染表面成分的信息，这使其成为评估清洁过程和效率的理想选择。SERS 特征在不同的生物污染阶段（细菌附着、快速生长、成熟和老化生物膜）之间具有高度的独特性和一致性。在 18 小时（生物膜快速生长）和 48 小时（老化生物膜）后，对两个水平的生物污染进行了清洁。观察到生物污染和清洁之间 SERS 带的相反分布，这表明存在逐层清洁模式。此外，还证明了在更严重的 48 小时生物污染中发生了进一步的动态生化和基础设施变化，导致更易于从 NF 膜上去除固着细胞。还使用表面活性剂十二烷基硫酸钠（SDS）评估了生物污染物质依赖性的清洁效率。SDS 在清洁脂质方面比多糖和 DNA 更有效。蛋白质和 DNA 是 NF 膜上主要的残留物质（不可逆污染），导致通量永久性损失。通过逐层 SERS 揭示的化学信息将为优化清洁试剂和实际膜过程的协议提供新的见解。
