超滤组合工艺在线加氯化学清洗中试研究

试验采用次氯酸钠对组合工艺之超滤膜组件进行在线化学清洗,旨在研究膜污染状况与特点。试验结果表明,水力清洗可有效恢复膜通量,反洗水加氯可有效延缓膜污染。在水力清洗废水中,相对分子质量大于1 k的有机物占有机物总量的87.3%,表明膜截留的大分子有机物可通过水力清洗使其从膜表明剥离;而在化学清洗废水中,相对分子质量小于1 k的有机物含量是水力清洗废水的2.6倍,故小分子有机物需要进行化学清洗方可恢复膜运行通量。化学清洗废水中的中性亲水和极性亲水组分分别占总溶解性有机物的44.9%和40.8%,水力清洗废水中的强疏水和弱疏水组分分别占总溶解性有机物的50.9%和23.6%,表明亲水性组分是造成膜不可逆污染的主要因素,而膜截留的疏水性物质可通过水力清洗将其从膜表面清除。

EXPERIMENTAL RESEARCH ON A PILOT-SCALE ULTRAFILTRATION COMBINED PROCESS WITH CHEMICAL CLEANING OF CHLORINATION

In order to study characteristic of membrane fouling,sodium hypochlorite was added into backwashing water to clean ultrafiltration membrane.The results showed that membrane flux could be recovered by hydraulic washing,and backwashing-chlorination could delay membrane fouling effectively.The proportion of organics with molecular weight beyond 1 k in hydraulic cleaning water was 87.3%,and the proportion of organics with molecular weight below 1 k in chemical cleaning water was 2.6 times of that in hydraulic cleaning water.So organics with high molecular weight could be removed from membrane,while membrane flux could be recovered only when organics with low molecular weight were removed by chemical cleaning.The neutral hydrophilic fraction and strong hydrophilic fraction in chemical cleaning water were 44.9% and 40.8% of the total dissolved organic carbon.In addition,strong hydrophoblic fraction and weak hydrophoblic fraction in hydraulic cleaning water were 50.9% and 23.6% of the total dissolved organic carbon,which showed that hydrophilic fraction was the main reason of the irreversible membrane fouling,and hydrophoblic fraction on the membrane surface could be removed by hydraulic cleaning.