Shear and solid-liquid separation behaviour of anaerobic digested sludge across a broad range of solids concentrations

Tanmoy Das; Shane P Usher; Damien J Batstone; Catherine A Rees; Anthony D Stickland; Nicky Eshtiaghi

doi:10.1016/j.watres.2022.118903

Shear and solid-liquid separation behaviour of anaerobic digested sludge across a broad range of solids concentrations

Water Res. 2022 Aug 15:222:118903. doi: 10.1016/j.watres.2022.118903. Epub 2022 Jul 25.

Authors

Tanmoy Das¹, Shane P Usher², Damien J Batstone³, Catherine A Rees⁴, Anthony D Stickland⁵, Nicky Eshtiaghi⁶

Affiliations

¹ Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC 3001, Australia; Department of Chemical Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia.
² Department of Chemical Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia.
³ Advanced Water Management Centre, The University of Queensland, St. Lucia, Queensland 4072, Australia.
⁴ Melbourne Water Corporation, 990 La Trobe Street, Docklands, Victoria 3008, Australia.
⁵ Department of Chemical Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: stad@unimelb.edu.au.
⁶ Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC 3001, Australia. Electronic address: nicky.eshtiaghi@rmit.edu.au.

PMID: 35940153
DOI: 10.1016/j.watres.2022.118903

Abstract

Due to the non-homogeneous and multiphase nature of anaerobic lagoon constituents, CFD modelling for process optimisation requires continuous functions for shear and solid-liquid separation properties across a large range of solids concentrations. Unfortunately, measurement of existing material properties of anaerobic sludges is limited to only shear or solid-liquid separation, or to a limited solids concentration. In this work, the shear properties of an anaerobic sludge were measured from 0.4 to 12.5 vol%, which corresponds to the solids concentrations seen in lagoons. The sludge showed Newtonian behaviour at 0.4 vol% and Herschel-Bulkley yield stress fluid behaviour for higher concentrations ranging from 0.5 to 12 vol%. We compared multiple approaches to determine relationships between the model fitting parameters of consistency, k, flow index, n, and shear yield stress, τ_y with solids volume fraction ϕ.The solid-liquid separation properties were measured from sedimentation and filtration experiments to obtain compressibility and permeability properties across all the above-mentioned concentrations, enabling development of hindered velocity sedimentation curves. Comparison to full-scale anaerobic digestate identified that the pilot lagoon sludge had faster sedimentation at a given solids concentration in comparison to the digestate. This is the first study on simultaneous rheological characterisation and solid-liquid separation behaviour of an anaerobic sludge across a wide range of concentrations, thus enabling CFD modelling of the hydrodynamics and performance of anaerobic lagoons.

Keywords: Lagoon anaerobic digested sludge; Parameter estimation; Shear rheology; Solid-liquid separation.

MeSH terms

Anaerobiosis
Hydrodynamics*
Rheology
Sewage*
Viscosity

Substances

Sewage