Change of particle structure of sewage sludges during mechanical and biological processes with regard to the dewatering result

Abstract

Particle size seems to be the most important parameter, to describe the dewatering behaviour and result of sludges. But there are many other parameters, which can influence the dewatering result. The dewatering result of a sludge depends on the type of sludge, the mechanical and biological process. Out of the numerous parameters to characterize wastewater sludges five were selected, which describe the properties of the particulate matter. These parameters are the suspended solids (SS), the volatile suspended solids (VSS), the density of the particles (ρ), the fraction of small particles (fines) and a new parameter, called φ-value, which is the ratio of the mass of waste activated sludge to the total mass of sludge. The tested sludges were analysed for the Zeta Potential, but there could not be found a correlation between this parameter and the dewatering result.

Combining the parameters in a model led to an overall sludge parameter, the so-called “Integral Property Parameter, f_E”. A correlation between the f_E-values and the dewatering results of municipal sludges (n = 49) can be found. A proposal was made to transfer the experimental results to a full scale dewatering process with high performance centrifuges.