在线周期反冲洗超滤膜污染过程研究

采用切割分子量105Da的中空纤维超滤膜,对污水厂二沉池出水进行了不同频度周期反冲洗超滤试验,试验结果与膜污染过程的理论分析相一致.过滤膜阻与反冲洗次数或过滤时间的关系曲线可分为两段:起初的增长段为不可逆滤饼层的累积阶段,直线的斜率为各次反冲洗不可逆膜阻增量;后期的水平段为滤饼层累积与剥离达到相对平衡的阶段.增加在线反冲洗频度降低了不可逆膜阻增量,有效提高了净产水速率.扫描电镜分析结果表明,水力反冲洗去除了部分膜表面污染物,将滤饼层变得松散,一定程度上减轻了膜污染,经化学清洗后,膜表面的滤饼层基本被去除.

Study on the Membrane Fouling Process of Ultrafiltration with Periodic Backwashing on Line

Membrane fouling during periodic filtration and back flush on line is studied theoretically and experimentally to treat secondary effluent from sewage treatment plant using hollow fiber ultrafiltration membrane with 10~5 Da molecular weight cut_offs. The experimental results are in good agreement with theoretical analysis. It shows that the curve of membrane filtration resistance with back flush frequency n or filtration time t can be divided into two sections: the initial section represents the accumulation stage of undetachable cake layer, and the final section represents the equilibrium stage of accumulation and detachment of cake layer. Increasing the back flush frequency reduces the irreversible membrane resistance increment, slows down the flux decline and improves the velocity of net water production greatly. The scanning electronic microscopy(SEM) analysis show that hydraulic cleaning can only remove a portion of the membrane pollutant, however, the cake layer is much loosened so that membrane resistance is reduced. The pollutants on the membrane surface can be almost completely eliminated by chemical cleaning and thus results in an effective recovery of permeate flux.