State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
Water Res. 2022 May 15;215:118263. doi: 10.1016/j.watres.2022.118263. Epub 2022 Mar 9.
Nanofiltration (NF) is utilized in water treatment for controlling disinfection by-products formation potential (DBPFP) and disinfection by-products (DBPs). Attention regarding NF-based technology has been paid on membrane fouling of NF and the rejection efficiency of contaminants by NF membranes. Natural organic matter (NOM) presenting in surface waters is one main removal target in drinking water treatment by NF-based technology, and is thereby a contributor to the membrane fouling of NF. In application, pretreatments of other membrane filtration (e.g., microfiltration (MF) and ultrafiltration (UF)) has been taken prior to NF, resulting in the separation of NOM of specific molecular weight. Meanwhile, it is well known that NOM is composed of organic compounds of different molecular weights. However, the effect of NOM of specific molecular weight has been seldom investigated from the aspects of membrane fouling and the resulting DBPFP after membrane filtration. By using combinations of MF and UF (molecular weight cut-off of 100K or 20K) as pretreatment prior to NF, the NOM of various molecular weight on DBPFP and DBPs in the NF-treated water were investigated. The experiments were conducted with two real-world surface water samples and one tap water sample. It was found that medium molecular weight NOM, defined as NOM that passed UF100K but did not pass UF20K in this study, reduced fouling of the NF membrane. This is supported by the excitation and emission matrix (EEM) fluorescence spectra, size exclusion chromatography (SEC) and flux analysis. In addition, the medium molecular weight NOM also reduced the DBPFP in the NF treated water and eventually the DBPs by participating in forming a protective layer on the NF surface, blocking the transfer of small molecular weight NOM into the NF filtrate, thereby reducing the DBPFP of the NF filtrate since small molecular weight NOM was the major contributor to DBPFP in this study.
纳滤（NF）被用于水处理中，以控制消毒副产物生成潜力（DBPFP）和消毒副产物（DBPs）。NF 基技术的关注点在于 NF 的膜污染和 NF 膜对污染物的截留效率。地表水中存在的天然有机物（NOM）是 NF 基技术进行饮用水处理的主要去除目标之一，因此也是 NF 膜污染的一个促成因素。在应用中，NF 之前通常会进行其他膜过滤（例如微滤（MF）和超滤（UF））的预处理，从而分离特定分子量的 NOM。同时，众所周知，NOM 由不同分子量的有机化合物组成。然而，从膜污染和膜过滤后产生的 DBPFP 方面，很少有研究关注特定分子量的 NOM 的影响。通过使用 MF 和 UF（分子量截止值为 100K 或 20K）的组合作为 NF 的预处理，研究了不同分子量的 NOM 对 NF 处理水中 DBPFP 和 DBPs 的影响。实验采用了两个实际地表水样本和一个自来水样本。结果发现，中等分子量 NOM（在本研究中，定义为 UF100K 透过但 UF20K 截留的 NOM）减少了 NF 膜的污染。这一结果得到了激发和发射矩阵（EEM）荧光光谱、尺寸排阻色谱（SEC）和通量分析的支持。此外，中等分子量 NOM 还减少了 NF 处理水中的 DBPFP，最终减少了 NF 处理水中的 DBPs，因为在本研究中，中等分子量 NOM 参与在 NF 表面形成保护层，阻止小分子 NOM 进入 NF 滤液，从而降低 NF 滤液中的 DBPFP，因为小分子 NOM 是 DBPFP 的主要贡献者。
