title: Compressional rheology: A tool for understanding compressibility effects in sludge dewatering.
abstract: Water and wastewater treatment sludges exhibit compressible behaviour due to flocculation and aggregation. At a critical solids concentration called the gel point, which is as low as 1-2 v/v%, a continuous interconnected network of particles is formed that can resist an applied load. The applied load (mechanical filtration pressure or buoyancy in settling for example) must exceed the network strength in order to consolidate the network. The network strength increases with solids concentration such that the equilibrium extent of consolidation is a function of the applied load. Improved understanding of the nature of compressible suspensions can have a significant impact through optimising design and operation of sludge handling and dewatering processes. This work gives an overview of compressional rheology, which has proven to be a useful tool for describing the solid-liquid separation of compressible systems. This is followed by three examples where compressibility effects must be taken into account, namely the extraction of material properties for extremely compressible materials, consolidation and crust formation during constant rate evaporation, and the effect of bed height in thickening.
authors: Particulate Fluids Processing Centre, Department of Chemical and Biomolecular Engineering, The University of Melbourne, 3010, Australia. Electronic address: stad@unimelb.edu.au.
authors: Anthony D
authors: AD
authors: Stickland
mesh_terms: D005374:Filtration; D005427:Flocculation; D011312:Pressure; D012212:Rheology; D012722:Sewage; D013535:Suspensions; D014865:Waste Disposal, Fluid / Q000379:methods; D014867:Water / Q000737:chemistry; D018508:Water Purification / Q000379:methods
chemical_list: D012722:Sewage; D013535:Suspensions; D014867:Water
keywords: Compressibility; Compressive yield stress; Gel point; Solid–liquid separation; Wastewater treatment sludge