title: Influence of operational conditions on the stability of aerobic granules from the perspective of quorum sensing.
abstract: Integrated aerobic granules were first cultivated in two sequencing batch reactors (SBRs) (A1 and A2). Then, A1's influent organic loading rate (OLR) was changed from alternating to constant (cycling time was still 6 h), while A2's cycling time varied from 6 to 4 h (influent OLR strategy remained alternating). After 30-day operation since the manipulative alternations, granule breakage happened in two reactors at different operational stages, along with the decrease of granule intensity. Granule diameter in A1 declined from the original 0.84 to 0.32 cm during the whole operation, while granules in A2 dwindled to 0.31 cm on day 22 with similar size to A1. Both the amount of total extracellular polymeric substances (EPSs) and the protein were declining throughout the operation, and the large molecular weight of protein was considered closely related to the stability of aerobic granules. The relative AI-2 level decreased at the same time, and influent OLR strategy might had more evident impact on quorum sensing (QS) ability of sludge compared with starvation period. Combined with microbial results, the decline of total EPS amount in two reactors could be concluded as follows: During the reactor operation, some functional bacteria gradually lost their dominance and were eliminated from the reactors, which finally caused granule disintegration. In summary, the results further confirmed that alternating OLR and proper starvation period were two major factors in effective cultivation and stability of aerobic granules from the perspective of QS.
authors.affiliation: Shanghai Municipal Engineering Design General Institute, Shanghai, 200092, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, China.
authors.forename: Supu
authors.initials: S
authors.lastname: Sun
authors.affiliation: Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, China. liuxiang@fudan.eu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, China. hitwan@163.com.
authors.forename: Chunli
authors.initials: C
authors.lastname: Wan
authors.affiliation: Department of Chemical Engineering, National Taiwan University, Taipei, 106, Taiwan.
authors.forename: Duu-Jong
authors.initials: DJ
authors.lastname: Lee
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000378:metabolism; D001704:Biopolymers / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology; D053038:Quorum Sensing; D012722:Sewage / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D001704:Biopolymers; D012722:Sewage
keywords: Aerobic granules; Autoinducer-2 (AI-2); Extracellular polymeric substance (EPS); Organic loading rate (OLR); Stability; Starvation period