预处理对东江原水超滤过程中膜污染的控制作用

Control Effect of Pretreatment on Membrane Fouling during Ultrafiltration of Dongjiang River Raw Water

以珠江流域东江水作为原水,研究不同预处理(混凝、吸附、氧化)及其组合对水体中有机污染物的去除效果及对超滤膜污染的控制作用。试验结果表明,针对东江原水中天然有机物的去除,聚合氯化铝(PACl)、粉末活性炭(PAC)和高锰酸钾(KMnO4)的最佳投加量分别为20、30、0. 1 mg/L;三种单一预处理方法能够在一定程度上缓解膜通量衰减,而两两组合预处理则能够进一步提高膜运行通量;对于聚偏氟乙烯膜,PACl+PAC组合预处理对膜污染的控制作用最好。对于UV254和蛋白质,PACl和KMn O4对其去除效果优于PAC;对于多糖,三种预处理方法对其去除效果均不佳(<40%),其中PAC略好于PACl和KMn O4。此外,三种单一预处理方法对腐殖酸类荧光物质的去除效果高于蛋白质类荧光物质,而组合预处理能够更加显著地降低这两类荧光物质的响应强度,其中PACl+PAC组合预处理对有机物各荧光组分的去除效果最佳。通过对膜污染物成分的识别分析可知,东江原水中造成超滤膜污染的物质有腐殖酸类、多糖类和蛋白质类物质,而化学不可逆污染物主要为多糖类物质及少量的腐殖酸类物质,化学可逆污染物主要为蛋白质类物质及部分腐殖酸类物质。

Effects of different pretreatment processes( coagulation,adsorption and oxidation) and their combinations on removal of organic pollutants in raw water of Dongjiang River in Pearl River Basin and control of ultrafiltration membrane fouling were explored. For removal of natural organic matter in raw water of Dongjiang River,the optimal dosages of coagulant( polyaluminum),adsorbent( powdered activated carbon) and oxidant( KMn O4) were 20 mg/L,30 mg/L and 0. 1 mg/L,respectively. Three single pretreatment process could effectively alleviate membrane flux attenuation,while pairwise combined pretreatment processes could further alleviate membrane fouling. The combined pretreatment of polyaluminum and powdered activated carbon exhibited the best control effect on fouling of the polyvinylidene fluoride membrane. Polyaluminum and KMnO4 had better removal efficiency of UV254 and protein compared with that of powdered activated carbon. However,the three pretreatment processes had poor removal efficiency of polysaccharides( < 40%),among which,powdered activated carbon was slightly better than polyaluminum and KMnO4. In addition,the three single pretreatment processes were more effective in removing humic-like fluorescent substances than protein-based fluorescent substances,while combined pretreatment processes could significantly reduce the response intensity of these two types of fluorescent substances. Among them, the combined pretreatment process of polyaluminum and powdered activated carbon had the best removal effect on each fluorescent component of organic matter.Through the identification and analysis of membrane fouling components,it was showed that the main fouling substances during ultrafiltration of Dongjiang River raw water included humic acids,polysaccharides and proteins. Among them,chemically irreversible foulants were polysaccharides and a small amount of humic acids,whereas the chemically reversible foulants were proteins and some humic acids.