正常污泥和膨胀污泥中EPS膜污染特性及其与膜表面作用能分析

胞外聚合物(Extracellular polymeric substance,EPS)是导致膜污染的重要物质,且不同形态污泥的EPS具有不同的性质,研究正常污泥和膨胀污泥的EPS膜污染特性具有重要意义.因此,实验考察了正常污泥和膨胀污泥的膜污染速率.结果表明,膨胀污泥膜污染速率远高于正常污泥,膨胀污泥EPS(Bulking sludge-EPS,BS-EPS)浓度((172.9±10.4) mg·g-1)明显高于正常污泥EPS(Normal sludge-EPS,NS-EPS)浓度((95.9±6 6) mg·g-1),且膨胀污泥的蛋白质/多糖(Protein/Carbohydrate,P/C)值(2.26)高于正常污泥的P/C值(1 97)此外,通过序批式吸附实验研究了正常污泥和膨胀污泥的EPS膜污染差异,并基于Derjaguine-Landaue-Verweye-Overbeek (XDLVO)理论计算了EPS与PVDF膜表面之间的作用能结果表明,EPS-膜系统的总界面能为负值,即EPS-膜系统之间会发生自吸附行为,而膜与BS-EPS的总界面能(-63.943mJ.m2)较膜与NS-EPS(-56.366 mJ·m2)具有较高的能量,因此,BS-EPS与膜的吸附力较强;NS-EPS和BS-EPS主要能量壁垒分别为8.89 kT和7.51 kT,表明NS-EPS与膜之间的排斥力更强,因而BS-EPS更容易造成膜污染

Fouling property and interaction energy with EPS membrane in normal sludge and bulking sludge

Extracellular polymeric substances (EPS) are the major substances leading to membrane fouling, and the EPS collected from different sludges have different characteristics. Therefore, characterization of the fouling property of EPS in normal sludge and bulking sludge (NS-EPS and BS-EPS) is important. Results from this study showed that the fouling rate of bulking sludge was much higher than that of normal sludge, and the EPS concentration and the ratio of protein/carbohydrate (P/C) of bulking sludge ((172.9±10.4) mg·g^-1 and 2.26, respectively) were also higher than the counterpart of normal sludge ((95.9±6.6) mg·g^-1 and 1.97, respectively). In addition, adsorptive fouling experiment was carried out to identify different EPS fouling properties between normal sludge and bulking sludge, and the interaction energy between the membrane and EPS was calculated based on the extended Derjaguine-Landaue-Verweye-Overbeek (XDLVO) theory. The result indicated that the membrane with EPS had a negative total energy, indicating self-adsorption as EPS approached the membrane. The energy between BS-EPS and membrane (-63.943 mJ·m²) was higher than that between NS-EPS and membrane (-56.366 mJ·m²), indicating stronger adsorption of BS-EPS than NS-EPS. The energy barrier of NS-EPS and BS-EPS were 8.89 kT and 7.51 kT, respectively, which showed that the NS-EPS had a strong repulsion force than BS-EPS, and BS-EPS was easier to attach to the membrane and led to membrane fouling.