title: Characterization of anaerobic granular sludge using a rheological approach.
abstract: High-rate anaerobic granular sludge reactors have been developed and are widely used for wastewater treatment. An accurate estimate of sludge rheological properties is required for the design and efficient operation of the digestion process. The present work determined the rheological behavior of anaerobic granular sludge obtained from a full-scale bioreactor at different solid concentrations, operation temperatures and particle sizes, and highlighted common features in flow and dynamic measurements. The granular sludge showed a shear-thinning behavior with a yield stress under flow measurements and a viscoelastic property in dynamic measurements. The structure of granules was nearly temperature-independent in the range of operational temperature (20-70 °C), but the total solid concentration and particle size had significant effects on not only the rheological properties, but also the operation of the bioreactors. In addition, anaerobic granular sludge could cross over from the strong-link regime to the weak-link regime as the solid concentration increased. Furthermore, we adopted a Wagner-type constitutive model to describe the time-dependent and non-linear viscoelastic behaviors of anaerobic granular sludge, and then evaluated its validity and limitation.
authors.affiliation: CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, China.
authors.forename: Hou-Feng
authors.initials: HF
authors.lastname: Wang
authors.affiliation: CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Hai-Yang
authors.initials: HY
authors.lastname: Yang
authors.affiliation: CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, China. Electronic address: rzeng@ustc.edu.cn.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Zeng
mesh_terms: D001421:Bacteria, Anaerobic; D019149:Bioreactors; D012212:Rheology; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage
keywords: Anaerobic granular sludge; Particle size; Rheological behavior; Solid concentration; Temperature; Wagner-type model