Subramani Arun, Huang Xiaofei, Hoek Eric M V
University of California, Los Angeles Civil & Environmental Engineering Department and Water Technology Research Center, 5732-G Boelter Hall, P.O. Box 951593, Los Angeles, CA 90095-1593, USA.
J Colloid Interface Sci. 2009 Aug 1;336(1):13-20. doi: 10.1016/j.jcis.2009.03.063. Epub 2009 Apr 7.
Nanofiltration (NF) and reverse osmosis (RO) membranes are commonly applied to produce highly purified water from municipal wastewater effluents. In these applications, biofouling limits overall process performance and increases the cost of operation. Initial bacteria adhesion onto a membrane surface is a critical early step in the overall process of membrane biofouling. However, adsorption of effluent organic matter onto the membrane may precede bacterial deposition and change membrane surface properties. Herein we employed direct microscopic observation to elucidate mechanisms governing bacterial cell deposition onto clean and organic-fouled NF and RO membranes. Bovine serum albumin (BSA) and alginic acid (AA) were used as models for protein and polysaccharide rich organic matter in secondary wastewater effluents. In all experiments, organic fouling increased membrane hydraulic resistance and salt rejection, in addition to interfacial hydrophilicity and roughness. Even though surface hydrophilicity increased, the rougher surfaces presented by organic-fouled membranes produced nano-scale features that promoted localized bacterial deposition. An extended DLVO analysis of bacterial cells and membrane surface properties suggested that bacterial deposition correlated most strongly with the Lewis acid-base free energy of adhesion and root mean square (RMS) roughness, whereas van der Waals and electrostatic free energies were weakly correlated. This was true for both clean and organic-fouled membranes. Bacterial deposition rates were clearly influenced by an antagonistic interplay between macroscopic surface hydrophilicity and nano-scale surface roughness.
纳滤（NF）膜和反渗透（RO）膜通常用于从城市污水厂二级出水制取高纯水。在这些应用中，生物污染会限制整个工艺的性能，并增加运行成本。细菌最初附着在膜表面是膜生物污染整个过程中的一个关键早期步骤。然而，污水中的有机物在膜上的吸附可能先于细菌沉积，并改变膜的表面性质。在此，我们采用直接显微镜观察来阐明控制细菌细胞在清洁的和有机污染的纳滤膜及反渗透膜上沉积的机制。牛血清白蛋白（BSA）和海藻酸（AA）被用作二级污水中富含蛋白质和多糖的有机物的模型。在所有实验中，除了界面亲水性和粗糙度外，有机污染还增加了膜的水力阻力和脱盐率。尽管表面亲水性增加，但有机污染膜呈现出的更粗糙表面产生了促进局部细菌沉积的纳米级特征。对细菌细胞和膜表面性质进行的扩展DLVO分析表明，细菌沉积与路易斯酸碱粘附自由能和均方根（RMS）粗糙度的相关性最强，而范德华力和静电自由能的相关性较弱。清洁膜和有机污染膜都是如此。细菌沉积速率明显受到宏观表面亲水性和纳米级表面粗糙度之间的拮抗相互作用的影响。
