混凝处理防止膜污染的作用与机理

The effect and mechanisms of coagulation on preventing membrane from fouling

通过膜过滤混凝上清液的方法 ,并比较膜进水和透过水中有机物相对分子质量分布的变化 ,探讨了混凝防止膜污染的作用和机理 .结果表明 ,相对分子质量大于 10 0 0的有机物是造成膜污染的主要因素 ,而相对分子质量小于 10 0 0的有机物对膜污染的影响较小 .尽管混凝能有效地去除相对分子质量较大的有机物 ,但混凝防止膜污染的效果与其投加量有密切的关系 .较低的混凝投加量 (2 5mg·L- 1 )防止膜污染的效果较差 ,较大的投加量 (>5 0mg·L- 1 )防止膜污染的效果较好 .UV2 54能更好地反映有机物对膜污染的影响程度 ,如何有效地去除这类有机物是防止膜污染的关键 .混凝防止膜污染的效果与去除相对分子质量大于 10 0 0的UV2 54的程度密切相关 .试验结果表明 ,混凝去除这类有机物的效果达到 5 0 %时 。

By means of filtration of coagulated supernatant and comparison of the distribution of organic molecular weight for the feed and permeated water, the mechanisms and the effects of coagulation as pretreatment for membrane were studied. The experimental results showed that the key factor responsible for membrane fouling was organics of molecular weight(MW)greater than 1000, and the effect of organics MW smaller than 1000 on membrane fouling was minor. Although coagulation could remove greater MW organics effectively, the effect of coagulation on preventing membrane from fouling was closely related to coagulant dosages. The effect of coagulation treatment with relatively low dosages(25mg·L^(-1))was poor, and good effect could be achieved by relatively high dosages(>50mg·L^(-1)).UV_(254) was a good parameter for understanding influence of organics on fouling, so how to remove UV_(254) organics effectively was critical for preventing fouling. The effect of coagulation on preventing membrane fouling is closely related to the amounts of UV_(254) with MW greater than 1000 removed by coagulation.The result obtained from this study demonstrated that whem UV_(254) with MW greater than 1000 was removed by 50% by coagulation,the fouling could be prevented effectively.