title: The influence of additives (Ca2+, Al3+, and Fe3+) on the interaction energy and loosely bound extracellular polymeric substances (EPS) of activated sludge and their flocculation mechanisms.
abstract: The activated sludge (AS) flocculability markedly improved after the addition of Al(3+) and Fe(3+) compared to Ca(2+) at a concentration of 2 mEq/L. Though the energy barrier decreased about 30% when Ca(2+) was added, the AS flocculability did not improve substantially. This indicates that extended DLVO theory can explain AS flocculation with Al(3+) and Fe(3+) as additives but is not appropriate for Ca(2+). In addition, no matter which cation was added, the AS flocculability was highly correlated to the loosely bound extracellular polymeric substances (LB-EPS) content. The majority of added Ca(2+) remained in the bulk solution (about 92%), whereas almost all of the Al(3+) and Fe(3+) added was found in the pellet (about 98%). The cation' ability to bind to the AS is closely related to the energy barrier and LB-EPS contents, therefore it is the core reason behind the AS flocculation changes observed upon the addition of multivalent cations.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Haisong
authors.initials: H
authors.lastname: Li
authors.forename: Yue
authors.initials: Y
authors.lastname: Wen
authors.forename: Asheng
authors.initials: A
authors.lastname: Cao
authors.forename: Jingshui
authors.initials: J
authors.lastname: Huang
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhou
authors.forename: Ponisseril
authors.initials: P
authors.lastname: Somasundaran
mesh_terms: D001704:Biopolymers / Q000737:chemistry* / Q000378:metabolism*; D004735:Energy Transfer; D045604:Extracellular Fluid / Q000737:chemistry* / Q000378:metabolism*; D005427:Flocculation; D008670:Metals / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*
chemical_list: D001704:Biopolymers; D008670:Metals; D012722:Sewage