Rheological Characterization Of Thermal Hydrolysed Waste Activated Sludge

Hii, K, Farno, E, Baroutian, S, Parthasarathy, R and Eshtiaghi, N 2019, 'Rheological Characterization Of Thermal Hydrolysed Waste Activated Sludge', Water Research, vol. 156, pp. 445-455.


Document type: Journal Article
Collection: Journal Articles

Title Rheological Characterization Of Thermal Hydrolysed Waste Activated Sludge
Author(s) Hii, K
Farno, E
Baroutian, S
Parthasarathy, R
Eshtiaghi, N
Year 2019
Journal name Water Research
Volume number 156
Start page 445
End page 455
Total pages 11
Publisher I W A Publishing
Abstract Rheological properties are important in the design and operation of sludge-handling process. Despite this, the rheology of sludge in thermal hydrolysis processes (TH) is not well described. In-situ measurements were performed to characterize the flow behaviour of various concentrations (7-13 wt%) of waste activated sludge (WAS) at TH conditions. Equations were presented for predicting in situ rheological parameters (high-shear viscosity, eta(infinity,i), consistency index, k(i), and yield stress, sigma(c,i)) under various treatment conditions, which are useful for design of process units. The equations enable convenient estimation of in-situ properties based on ambient rheological measurements. Results suggested that the proportion of sludge solubilization and its rate were unaffected by varying sludge concentration. Thermally treated sludge still exhibited gel-like, viscoelastic characteristics similar to untreated sludge; however, the storage (G') and loss (G '') moduli decreased with higher treatment temperatures. Frequency and creep responses were described by a fractional derivatives Kelvin-Voigt (FKV) model, which showed increasing viscous characteristics of treated sludge. These equations can be utilised in CFD models. Results obtained from oscillatory measurements can also approximate steady-shear behaviour by comparing dynamic viscosity, eta'(omega), and steady-shear viscosity, eta(gamma'), whose values were very similar. This enables convenient estimation of steady-shear behaviour of sludge from oscillatory measurements, which is found to be a non-destructive technique for measuring flow behaviour of highly concentrated sludge. Yield stress can also be predicted from the product of modified Cox-Merz shift factors and storage modulus (G'). Practical engineering implications of the rheological observations were discussed.
Subject Rheology
Wastewater Treatment Processes
DOI - identifier 10.1016/j.watres.2019.03.039
Copyright notice © 2019 Elsevier Ltd. All rights reserved.
ISSN 0043-1354
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