State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology, 73 Huanghe Road, Nangang District, Harbin, 150090, PR China.
Department of Chemical & Environmental Engineering, University of Arizona, Tucson, AZ 85721, United States.
Water Res. 2017 Nov 15;125:42-51. doi: 10.1016/j.watres.2017.08.030. Epub 2017 Aug 13.
Wastewater reclamation has increasingly become popular to secure potable water supply. Low-pressure membrane processes such as microfiltration (MF) and ultrafiltration (UF) play imperative roles as a barrier of macromolecules for such purpose, but are often limited by membrane fouling. Effluent organic matter (EfOM), including biopolymers and particulates, in secondary wastewater effluents have been known to be major foulants in low-pressure membrane processes. Hence, the primary aim of this study was to investigate the effects of pre-ozonation as a pre-treatment for UF on the membrane fouling caused by EfOM in secondary wastewater effluents for hydrophilic regenerated cellulose (RC) and hydrophobic polyethersulfone (PES) UF membranes. It was found that greater fouling reduction was achieved by pre-ozonation for the hydrophilic RC membrane than the hydrophobic PES membrane at increasing ozone doses. In addition, the physicochemical property changes of EfOM, including biopolymer fractions, by pre-ozonation were systemically investigated. The classical pore blocking model and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theories were employed to scrutinize the fouling alleviation mechanism by pre-ozonation. As a result, the overarching mechanisms of fouling reduction were attributed to the following key reasons: (1) Ozone degraded macromolecules such as biopolymers like proteins and polysaccharides into smaller fractions, thereby increasing free energy of cohesion of EfOM and rendering them more hydrophilic and stable; (2) pre-ozonation augmented the interfacial free energy of adhesion between foulants and the RC/PES membranes, leading to the increase of repulsions and/or the decrease of attractions; and (3) pre-ozonation prolonged the transition from pore blocking to cake filtration that was a dominant fouling mechanism, thereby reducing fouling.
污水再生已成为保障饮用水供应的一种流行方式。作为大分子物质的屏障，低压膜工艺（如微滤（MF）和超滤（UF））在这方面发挥着重要作用，但常常受到膜污染的限制。二级废水处理厂中的出水中的有机物（EfOM），包括生物聚合物和颗粒物质，已被公认为低压膜过程中的主要污染物。因此，本研究的主要目的是研究预臭氧化作为超滤预处理对二级废水处理厂 EfOM 引起的亲水性再生纤维素（RC）和疏水性聚醚砜（PES）UF 膜污染的影响。结果发现，随着臭氧剂量的增加，预臭氧化对亲水性 RC 膜的污染减轻效果大于疏水性 PES 膜。此外，还系统研究了 EfOM 的物理化学性质变化，包括生物聚合物部分，通过预臭氧化。采用经典的孔阻塞模型和扩展的德加古因-兰德au-Verwey-Overbeek（XDLVO）理论来仔细研究预臭氧化的减轻污染机制。结果表明，减少污染的总体机制归因于以下几个关键原因：（1）臭氧将大分子物质（如蛋白质和多糖等生物聚合物）降解成较小的片段，从而增加 EfOM 的内聚自由能，使它们更亲水和稳定；（2）预臭氧化增加了污染物与 RC/PES 膜之间的界面粘附自由能，导致排斥力增加和/或吸引力降低；（3）预臭氧化延长了从孔阻塞到主要污染机制滤饼过滤的转变，从而减少了污染。
