絮凝剂投加对MBR工艺膜污染及污泥混合液性能的影响

Effects of Flocculant Dosing on Membrane Fouling and Mixed Liquor Property for MBR Process

采用FeCl_3、聚合硫酸铁(PFS)及聚合氯化铝(PAC)作为絮凝剂,考察其对AO-MBR混合液性质及膜污染的影响。投加絮凝剂对COD及氮的去除影响较小,而TP的去除效果有所提高,其中投加PAC的反应器出水TP浓度最低;投加絮凝剂能有效缓解膜污染,且膜污染延缓作用的大小依次为:PAC>PFS>FeCl_3;投加絮凝剂对反应器溶解性微生物产物(SMP)及胞外聚合物(EPS)中的多糖及蛋白质均有一定的去除作用,且多糖的去除率高于蛋白质;由分子量分布的分析结果可知,投加无机絮凝剂能够吸附反应器中的溶解性大分子类物质,将其转化到固相体系中,并通过絮凝作用使反应器中的小颗粒物质脱稳聚集形成大颗粒物质,从而缓解膜污染。

Impact of three flocculants, namely, Feel3, polymer ferric sulfate （PFS） and poly aluminium chlorid （PAC）, on membrane fouling and properties of sludge mixed liquor in the long-term running of AO-MBR are determined. Results show that flocculants have no impact on the removal of COD and nitrogen,while the removal efficiency of total phosphorus （TP） is improved,and TP in the effluent of MBR added with PAC is of the lowest level. All tested flocculants can reduce fouling rate, among them PAC exhibits the best performance and PFS takes the second place. It is also found that all flocculants can reduce the concentrations of polysaccharides and protein in soluble microbial products （SMP） and extracellular polymeric substances （EPS）, and the removal rate of polysaccharide is higher than that of protein. Based on the analysis of molecular weight distribution, macromolecular organics in the supernatant can be absorbed and transformed to solid phase by additon of flocculants,which is supposed to be one of the reasons for fouling mitigation. Furthermore, the enlargement of floc size is expected to be another reason for the reduction of membrane fouling.