Viscous behaviour of sludge centrate in response to polymer conditioning

This note outlines an analysis of the centrate viscosity in response to polymer conditioning of an alum sludge. Recognising the complexity of the controls on viscosity, an analytical scheme is described in which the centrate viscosity (at low contaminant concentrations) can be regarded as the linear sum of component terms. As the polymer dose is increased from zero, the centrate viscosity decreases initially, passes through a minimum and then increases. The interaction of viscosity contributions arising from the turbidity and residual polymer in the centrate appear to control the polymer dosage at which the minimum occurs, whereas the solvent viscosity, together with an electrolytic component contribute towards the overall viscosity. Associated analysis indicates that the minimum in the viscosity-dose trend coincides with the onset of adsorption saturation of a nonionic polymer. (C) 1999 Elsevier Science Ltd. All rights reserved.