Abstract:

A laboratory-scale membrane bioreactor（MBR）was operated for 100 days with complete sludge retention in order to investigate the filterability of mixed liquor. Soluble microbial products（SMP），molecular weight（M_w）distributions of SMP，proteins and carbohydrates in the extracellular polymeric substances（EPS）were periodically monitored. A modified fouling index（MFI）was used to investigate the filterability of mixed sludge. It is closely related to the mixed liquor suspended solids（MLSS），SMP and EPS. The results showed that the MFI increased rapidly after 30 days of operation，which indicated that the long term operation of a MBR with no sludge discharge had a negative influence on the filterability of mixed sludge. The concentration of SMP，especially the SMP with M_w>10 kDa，was positively correlated to the filterability of mixed sludge. MLSS concentration had a complex interaction with the filterability of mixed sludge in MBR，and the existence of a threshold above which the MLSS concentration had a influence on the filterability of mixed sludge were also found. The protein fractions in the EPS were biodegradable and available for microorganism metabolism after about 60 days. Test results demonstrated that carbohydrates in the EPS had a negative effect on the filterability of mixed sludge.

摘要：

膜生物反应器（MBR）在无排泥条件下运行100 d，定期对溶解性微生物产物（SMP）、SMP分子量分布、胞外聚合物（EPS）中的蛋白质和多糖进行监测，应用修正的污染指数（MFI）考察污泥混合液可滤性的变化。实验表明：长时间无排泥运行模式下将导致污泥混合液可滤性的恶化；污泥混合液上清液中分子量（M_w）大于10 kDa 的SMP浓度对污泥混合液的可滤性产生强烈的负面影响；污泥浓度（MLSS）与混合液可滤性之间关系复杂，MLSS对污泥可滤性的影响存在一个临界值；EPS中的蛋白质60 d后发现可被微生物迅速降解，多糖类物质对污泥混合液可滤性有较强的负面影响。