混凝剂品种对混凝-超滤联合工艺膜污染的影响

本实验以工业化学合成聚合硫酸铁混凝剂和自制生物聚合硫酸铁为例,考察了铁系混凝剂品种对地表水浊度、TOC和UV254的去除效果,混凝剂品种对混凝-超滤联合工艺处理地表水过程中超滤膜污染的影响。混凝实验结果表明,在10 mg/L(以Fe3+计)最佳投加量下,两类混凝剂对浊度、TOC和UV254的去除率基本相同。超滤膜污染实验结果表明,生物聚合铁预处理水样通量衰减速度略大于化学聚合铁预处理水样;膜污染阻力分析结果显示,随着循环次数的增加,工业化学合成聚合铁预处理水样造成的不可逆污染阻力逐渐增加,而生物聚合铁预处理水样造成的不可逆污染阻力却略有下降;膜污染机理分析表明,2组过滤过程的膜污染类型基本相似,由最初的膜孔堵塞过渡到最终的滤饼层污染。SEM分析表明,生物聚合铁预处理水样的膜污染较为严重。

Effect of different coagulants on performance of membrane fouling during coagulation-ultrafiltration hybrid process

The lab scale coagulation-ultrafiltration hybrid process for surface water treatment was investigated using two different polymeric ferric sulfate (PFS) coagulants, one synthesized by a chemical method (PFS) and the other synthesized with bacteria (BPFS). As the pretreatment process of ultrafiltration, coagulation was carried out to investigate the removal rate of turbidity, TOC, UV₂₅₄ and membrane fouling. The result of the coagulation experiment demonstrated that both PFS and BPFS had the same efficiency for turbidity, TOC, UV₂₅₄ absorption removal at optimal coagulant dose of 10 mg/L (Fe³⁺). Dead-end ultrafiltration experiment demonstrated that, the flux decrease filtrated by the BPFS pretreated water sample is more serious than that by PFS. Resistance analysis showed that the total resistance increased with the filtration cycles. And with the increased filtration cycles, the irreversible resistance caused by the PFS pretreated water was increasing, however, that caused by the BPFS pretreated water was slightly decreasing. Membrane fouling mechanism was almost supposed as the same. The membrane pores were blocked at the initial stage, then translated into cake layer. SEM picture also showed that the fouling caused by BPFS pretreated water was more serious.