城市污水回用系统中反渗透膜的膜污染及清洗机理研究

The high concern for severe water shortages and desire for protection of the aquatic environment in water scarcity regions throughout the world have led to the evolution of wastewater reclamation technologies. In recent decades, the maturation of membrane technology contributed to its increasing recognition as a reliable technology for cost effective production of high quality effluents in wastewater reclamation. MBR-RO systems, combining membrane bioreactors and reverse osmosis membranes have been identified as strong candidates for reuse of municipal wastewater. However, membrane fouling has greatly restricted the popularization and application of MBR-RO systems. In the case of fouling, the consumption of cleaning agents can be significantly reduced if the fouling characteristics can be linked to the layer removal mechanisms and more effective cleaning protocols will be developed. In this study, the physical-chemical interactions between the fouling (original from MBR-RO systems) and cleaning agents will be detected by QCM-D. In our previous study, the crosslinked aromatic amide membrane has been successfully synthesized on the surface of quartz crystal, which accurately simulated the surface properties of reverse osmosis membrane. The data for frequency and dissipation energy change of the quartz crystal during the adsorption and cleaning of the fouling will be collected and the Voigt visco-elastic model equation will be used to calculate the mass, thickness, viscosity, elasticity of the fouling layer before or after cleaning. We will predict and measure the RO membrane fouling potential and cleaning efficiency by comparing QCM-D results to the flux change in a lab-scale RO filtration unit. QCM-D provides the possibility of real time monitoring the fouling potential and cleaning efficiency, the relation between permeate flux change and frequency shift values analyzed in QCM-D may open new avenue on quantitative relation of fouling rate and reduced membrane performance as well as cleaning efficiency.

随着膜技术在城市污水再生利用中应用规模的增大,膜污染及清洗问题更为突出。分析膜污染及清洗机理，从而找出防止或减缓反渗透膜污染的有效方法，提高膜的清洗效果已成为当今膜技术的研究热点和前沿。该项目利用耗散型石英晶体天平这一新型研究手段，深入探究双膜法污水回用系统中膜污垢与不同类型清洗剂之间的物理化学交互作用。在前期工作中，已成功在石英晶体表面合成交联的芳酰胺膜，精确模拟了反渗透膜表面性质。本研究将根据在膜污垢吸附及清洗过程中的石英晶体频率及耗散能量的变化，利用Voigt粘弹性模型方程估算清洗前后膜污垢的质量、厚度、粘度和弹性等信息，分析构建合理的吸附及清洗机理，并结合微型反渗透膜过滤装置中清洗前后膜通量，膜污垢层形态及成分变化，揭示膜污染及清洗机理，预测膜污染状况，建立清洗模型，以从理论上指导膜污染的预防和及时清除。

随着膜技术在城市污水再生利用中应用规模的增大，膜污染及清洗问题更为突出。分析膜污染及清洗机理，从而找出防止或减缓反渗透膜污染的有效方法，提高膜的清洗效果已成为当今膜技术的研究热点和前沿。本项目是针对污水处理系统中反渗透膜的膜污染及清洗机理的研究。主要利用耗散型石英晶体微天平（QCM-D）频率及耗散能量的变化研究出水有机物(EfOM)和细菌胞外聚合物(EPS)等膜污垢在石英晶体聚酰胺涂层上的吸附及清洗特性，并据此建立起一套针对反渗透膜抗污性能(结污特性和清洗效率)的快速定量评估体系。同时，还将其结果与实际反渗透系统中得到的膜抗污性能指标(膜通量衰减和膜通量恢复)进行比较，验证该抗污性能评估体系的有效性。除此之外，由QCM-D可以通过监测石英基传感器材料共振频率的变化，快速、灵敏地测量振荡表面沉积层的厚度和物理性质。本研究还结合其他表征手段从分子和分子力学水平上来分析模式及真实膜污垢在反渗透膜结污及清洗过程中，膜与污垢，膜污垢之间，污垢与清洗剂之间内聚力与吸附力的变化，以及膜污垢层本身在清洗前后的构象变化；明确了EPS和EfOM等真实污垢中会导致膜通量显著下降的具体组分，同时还深入揭示了清洗剂对不同膜污垢清洗效率及清洗偏好的相关作用机制。拓展研究的部分包括：1. 基于氧化石墨烯的新型纳米复合膜 (TFN) 的研制，及其表征和性能研究。所研制的氧化石墨烯TFN膜在低温等离子体处理后呈现出了包括高膜通量、较高的盐截留率、抗氯性，抗污性及抑菌性等优良特性。2. 抗污抑菌型膜改良材料的研究：主要包括石墨烯微管，石墨烯气凝胶等基于氧化石墨烯的光催化细菌灭活材料等。这类新材料可快速高效低成本地灭活几乎所有细菌并降解90%以上燃料类污染物，从而从源头上减少膜污染，可作为反渗透膜前处理手段。另外，基于三维石墨烯微管的宏观形貌和较好的机械强度，此类材料也可考虑作为膜改性材料，摻杂膜内，以达到污染物降解及持续抑菌目的，抑制膜污垢的生成。