Wang Jin, Wang Xiao-chang
Department of Municipal and Environmental Engineering, Beijing Jiaotong University, Beijing 100044, China.
J Environ Sci (China). 2006;18(5):880-4. doi: 10.1016/s1001-0742(06)60008-9.
Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration (UF) with in-line coagulation. The results showed dissolved organic carbon (DOC) and UV254 removals by the UF with in-line coagulation at pH 7 were increased from 28% to 53% and 40% to 78% in comparison with direct UF treatment respectively. At the same time, the analysis of high performance liquid chromatography showed that UF with coagulation had significant improvement of removal of humic acid with molecular weights less than 6000 Da in particular. Compared to direct UF, the in-line coagulation UF also kept more constant permeate flux and very slight increase of transmembrane pressure during a filtration circle. Two typical membrane fouling models were used by inducing two coefficients Kc and Kp corresponding to cake filtration model and pore narrowing model respectively. It was found that membrane fouling by pore-narrowing effect was effectively alleviated and that by cake-filtration was much decreased by in-line coagulation. Under the condition of coagulation prior to ultrafiltration at pH 7, the cake layer formed on the membrane surface became thicker, but the membrane filtration resistance was lower than that at pH 5 with the extension of operation time.
对采用在线混凝的超滤（UF）去除天然腐殖酸及膜污染进行了实验和理论分析。结果表明，与直接超滤处理相比，在pH值为7时采用在线混凝的超滤对溶解有机碳（DOC）和UV254的去除率分别从28%提高到53%和从40%提高到78%。同时，高效液相色谱分析表明，混凝超滤对分子量小于6000 Da的腐殖酸的去除有显著改善。与直接超滤相比，在线混凝超滤在一个过滤周期内也能保持更稳定的渗透通量，跨膜压力增加非常小。通过引入分别对应于滤饼过滤模型和孔径缩小模型的两个系数Kc和Kp，使用了两种典型的膜污染模型。结果发现，在线混凝有效地减轻了孔径缩小效应导致的膜污染，滤饼过滤导致的膜污染也大大减少。在pH值为7时超滤前进行混凝的条件下，随着运行时间的延长，膜表面形成的滤饼层变厚，但膜过滤阻力低于pH值为5时的情况。
