title: Mixing characteristics of sludge simulant in a model anaerobic digester.
abstract: This study aims to investigate the mixing characteristics of a transparent sludge simulant in a mechanically agitated model digester using flow visualisation technique. Video images of the flow patterns were obtained by recording the progress of an acid-base reaction and analysed to determine the active and inactive volumes as a function of time. The doughnut-shaped inactive region formed above and below the impeller in low concentration simulant decreases in size with time and disappears finally. The 'cavern' shaped active mixing region formed around the impeller in simulant solutions with higher concentrations increases with increasing agitation time and reaches a steady state equilibrium size, which is a function of specific power input. These results indicate that the active volume is jointly determined by simulant rheology and specific power input. A mathematical correlation is proposed to estimate the active volume as a function of simulant concentration in terms of yield Reynolds number.
authors.affiliation: School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, VIC, 3001, Australia.
authors.forename: Siew Cheng
authors.initials: SC
authors.lastname: Low
authors.affiliation: School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, VIC, 3001, Australia.
authors.forename: Nicky
authors.initials: N
authors.lastname: Eshtiaghi
authors.affiliation: ATC Williams, 1141 Hay St, West Perth, WA, 6005, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Slatter
authors.affiliation: Irstea, UR TSCF, 03150, Montoldre, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Baudez
authors.affiliation: School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, VIC, 3001, Australia. rchrp@rmit.edu.au.
authors.forename: Rajarathinam
authors.identifier: http://orcid.org/0000-0003-3337-8678
authors.initials: R
authors.lastname: Parthasarathy
mesh_terms: D008956:Models, Chemical; D012722:Sewage / Q000737:chemistry*
chemical_list: D012722:Sewage
keywords: Active volume; Anaerobic digester; Mechanical mixing; Sludge simulant