Department of Integrated Science and Engineering for Sustainable Society, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Division of Built Environment, Graduate School of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
Water Res. 2014 May 1;54:123-36. doi: 10.1016/j.watres.2014.01.024. Epub 2014 Feb 6.
Although membrane filtration is a promising technology in the field of drinking water treatment, persistent membrane fouling remains a major disadvantage. For more efficient operation, causative agents of membrane fouling need to be identified. Membrane fouling can be classified into physically reversible and irreversible fouling on basis of the removability of the foulants by physical cleaning. Four types of natural organic matter (NOM) in river water used as a source of drinking water were fractionated into hydrophobic and hydrophilic fractions, and their potential to develop irreversible membrane fouling was evaluated by a bench-scale filtration experiment together with spectroscopic and chromatographic analyses. In this study, only dissolved NOM was investigated without consideration of interactions of NOM fractions with particulate matter. Results demonstrated that despite identical total organic carbon (TOC), fouling development trends were significantly different between hydrophilic and hydrophobic fractions. The hydrophobic fractions did not increase membrane resistance, while the hydrophilic fractions caused severe loss of membrane permeability. These results were identical with the case when the calcium was added to hydrophobic and hydrophilic fractions. The largest difference in NOM characteristics between hydrophobic and hydrophilic fractions was the presence or absence of macromolecules; the primary constituent causing irreversible fouling was inferred to be "biopolymers", including carbohydrates and proteins. In addition, the results demonstrated that the extent of irreversible fouling was considerably different depending on the combination of membrane materials and NOM characteristics. Despite identical nominal pore size (0.1 μm), a polyvinylidene fluoride (PVDF) membrane was found to be more rapidly fouled than a PE membrane. This is probably explained by the generation of strong hydrogen bonding between hydroxyl groups of biopolymers and fluorine of the PVDF membrane. On the basis of these findings, it was suggested that the higher fouling potential of the hydrophilic fraction of the dissolved NOMs from various natural water sources are mainly attributed to macromolecules, or biopolymers.
虽然膜过滤是饮用水处理领域很有前途的技术，但持续的膜污染仍然是一个主要缺点。为了更有效地运行，需要确定膜污染的原因。根据污染物通过物理清洗的可去除性，膜污染可分为物理可逆和不可逆污染。将用作饮用水源的河水中原位天然有机物（NOM）分为疏水性和亲水性两部分，通过中试规模过滤实验以及光谱和色谱分析，评估了它们形成不可逆膜污染的潜力。在本研究中，仅研究了溶解的 NOM，而没有考虑 NOM 部分与颗粒物的相互作用。结果表明，尽管总有机碳（TOC）相同，但亲水性和疏水性部分的污染发展趋势有很大差异。疏水性部分不会增加膜阻力，而亲水性部分会导致膜渗透性严重损失。当将钙添加到疏水性和亲水性部分时，结果是相同的。疏水性和亲水性部分之间 NOM 特征的最大差异是是否存在大分子；推断引起不可逆污染的主要成分是“生物聚合物”，包括碳水化合物和蛋白质。此外，结果表明，不可逆污染的程度取决于膜材料和 NOM 特征的组合而有很大差异。尽管名义孔径（0.1 μm）相同，但发现聚偏二氟乙烯（PVDF）膜比 PE 膜更容易受到污染。这可能是由于生物聚合物的羟基与 PVDF 膜的氟之间产生了强烈的氢键。基于这些发现，建议各种天然水源中溶解 NOM 的亲水性部分具有较高的污染潜力，主要归因于大分子或生物聚合物。
