Rheological characterization of digested sludge by solid sphere impact

• Published in: Bioresource technology Vol. 218; pp. 301 - 306
• Main Authors: Jiang, Jiankai, Wu, Jing, Poncin, Souhila, Li, Huai Z.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2016; Elsevier
• Subjects: Chemical and Process Engineering; Crater; Digested sludge; Elastic Modulus; Engineering Sciences; Environmental Engineering; Environmental Sciences; Fluids mechanics; High-speed camera; Impact method; Mechanics; Models, Theoretical; Rheological characterization; Rheology - methods; Sewage - chemistry; Stress, Mechanical; Viscosity; Digested sludge; Rheological characterization; Impact method; Crater; High-speed camera
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2016.06.101

Impact process captured at 45° overhead leaned position (glass sphere diameter 4mm; free falling height 500mm). [Display omitted] •Impact method was applied to high-solids digested sludge.•Crater diameter and depth depend on sphere diameter and fall height.•Impact viscosity and elasticity were evaluated through a simplified force model.•Elastic modulus and viscosity are in agreement with results of classical methods. An impact method was applied to investigate the rheological characteristics of digested sludge and reveal its transient dynamics. A high-speed camera allowed visualizing the dynamic impact process and observing interaction between impacting sphere and targeted sludge. A damping oscillation was observed after the impact. The crater diameter followed an exponential function, while the crater depth varied as a logarithmic function of both sphere diameter and free fall height. Furthermore, the viscosity and elasticity of digested sludge were evaluated by establishing a simplified impact drag force model. The impact elastic modulus was consistent with the Young’s modulus measured by a penetrometer. The impact viscosity was reasonable as the estimated impact shear stress was greater than the yield stress of digested sludge resulting in the formation of crater. The impact method offers an alternative way to reveal the viscoelasticity of digested sludge through a dynamic process.