超滤膜在处理农药废水过程中的膜污染行为分析

Membrane fouling during the ultrafiltration process for pesticide wastewater treatment

由于高级氧化后的农药废水中含有大量小分子有机物,纳滤膜被应用于农药废水处理,但是,纳滤膜对进水水质有一定的要求,需要采用混凝-超滤法对高级氧化后的农药废水进行预处理.本文考察了混凝剂种类和用量对混凝效果的影响,并对3种孔径的聚偏氟乙烯(PVDF)中空纤维超滤膜在不同压力下的抗污染性能和临界操作条件进行了研究.结果表明,当聚合氯化铝(PAC)投放量为800mg/L,三氯化铁(FeCl_3·6H_2O)投放量为500mg/L,聚丙烯酰胺(PAM)投放量为10mg/L时,混凝-超滤组合工艺对废水中化学需氧量(COD_(Cr))、总磷(TP)、浊度、色度的去除率分别达到58.0%~59.1%、88.8%~89.7%、99.8%~99.9%、84%.平均孔径为20nm的PVDF超滤膜比平均孔径为11nm和40nm的PVDF超滤膜具有更高的临界通量和渗透性能.对膜污染、通量衰减模型的考察结果显示,孔内堵塞是导致孔径减小和通量衰减的主要原因.通过优化超滤膜孔径,能够显著降低膜孔堵塞现象,获得较高的运行通量.

Nanofiltration is used in pesticide wastewater treatment to remove the low-molecule organic matters following advanced oxidation.It is necessary to pretreat the wastewater before nanofiltration by coagulation-ultrafiltration （UF） process to meet the feed requirement of nanofiltration membrane system.The effects of coagulant type and dosage were investigated,and the anti-fouling performance and the critical operation condition of the three kinds of ultrafiltration membranes under different pressures were studied.The optimized concentrations of polyaluminium chloride （PAC）,ferric chloride （FeCl3 under which conditions,the removal rates of CODCr,total phosphorus,turbidity,chromaticity by the hybrid process were 58.0％～59.1％,88.8％～89.7％,99.8％～99.9％,84％,respectively.PVDF UF membrane with mean pore size of 20 nm exhibited higher critical flux and permeability compared with the membranes with pore size of 11 nm and 40 nm.Membrane fouling induced the reduction of membrane pore size,and a higher permeate flux can be obtained by optimizing the membrane pore size to reduce membrane fouling.