title: Effect of solids retention time on structure and characteristics of sludge flocs in sequencing batch reactors.
abstract: The effect of solids retention time (SRT) (4-20 d) on sludge floc structure, size distribution and morphology in laboratory-scale sequencing batch reactors receiving a glucose-based synthetic wastewater was studied using image analysis in a long-term experiment over one year. Floc size distribution (>10 microm) could be characterized by a log-normal model for no bulking situations, but a bi-modal distribution of floc size was observed for modest bulking situations. In each operating cycle of the SBRs, the variation in food /microorganisms ratio (0.03-1.0) had no significant influence on floc size distribution and morphology. The results from a long-term study over one year showed that no clear relationship existed between SRT and median floc size based on frequency. However, sludge flocs at the lower SRTs (4-9 d) were much more irregular and more variable in size with time than those at higher SRTs (16 and 20 d). The level of effluent-suspended solids at lower SRTs was higher than that at higher SRTs.
authors.affiliation: Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON, Canada P7B 5E1. baoqing.liao@lakeheadu.ca
authors.forename: B Q
authors.initials: BQ
authors.lastname: Liao
authors.forename: I G
authors.initials: IG
authors.lastname: Droppo
authors.forename: G G
authors.initials: GG
authors.lastname: Leppard
authors.forename: S N
authors.initials: SN
authors.lastname: Liss
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D048430:Cell Shape / Q000502:physiology; D048429:Cell Size; D005427:Flocculation; D010316:Particle Size; D012037:Refuse Disposal; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods; D014866:Waste Products / Q000032:analysis*
chemical_list: D012722:Sewage; D014866:Waste Products