有机物分子尺度对纳滤膜污染的影响研究

Effects of Molecular Weight Distribution of Organic Matter on Nanofiltration Membrane Fouling

以市政污水处理厂的MBR出水作为纳滤进水，从有机物分子尺度分布的微观角度分析进水中有机物分布特征与纳滤膜污染的相关性，研究含不同分子质量的有机物水样对纳滤膜通量衰减、脱盐率以及膜表面污染的影响规律。结果表明，随着进水中溶解性有机物分子质量的减小，膜比通量衰减幅度不断增加，特别是分子质量〈1ku的溶解性有机物引起膜通量衰减幅度最大，连续运行28h后膜比通量下降了85．2％。电镜扫描分析进一步表明，进水中分子质量〈1ku的有机物是造成膜有机污染的主要成分。此外，水中有机物在纳滤膜表面的累积会使纳滤膜的脱盐率有所增加。当进水中有机物分子质量在1ku以下时，纳滤膜的初始脱盐率在94％左右，经28h连续运行后脱盐率上升了3．5％～4％；进水中有机物分子质量在100ku以下时，纳滤膜的初始脱盐率为91％～92％，经28h连续运行后脱盐率上升4％～4．5％。

The relationship between molecular weight distribution of organic matter and nanofiltration membrane （NF） fouling was analyzed using the effluent from membrane bioreactor （MBR） in a municipal wastewater treatment plant. The effects of wastewater samples containing different molecular weight fractions of organic matter on membrane flux decline, desalinization efficiency and membrane surface fouling were investigated. The results showed that the attenuation of membrane specific flux continuously increased with decreasing molecular weight of dissolved organic matter in influent, especially when below 1 ku. After continuous operation for 28 h, the membrane specific flux decreased by 85.2%. Electron microscope scanning of membrane surface further suggested that dissolved organic matter with molecular weight below 1 ku was the dominant component to cause membrane fouling. Accumulation of organic matter on the membrane surface could result in an increase of desalinization efficiency. When the molecular weight of organic matter in influent was below 1 ku, the initial desalinization efficiency of NF was a- bout 94% , and after continuous operation for 28 h, the desalinization rate increased by 3.5% to 4%. When the molecular weight of organic matter in influent was below 100 ku, the initial desalinization of NF was about 91% to 92%, and after continuous operation for 28 h, the desalinization efficiency increased by 4% to 4.5%.