Fundamental dewatering properties of wastewater treatment sludges from filtration and sedimentation testing

The prediction and optimisation of the performance of dewatering devices such as filters and thickeners requires the laboratory measurement of fundamental material characteristics. This work presents the application of recently developed methods for the extraction of meaningful phenomenological properties from filtration and sedimentation testing of wastewater sludges, which has previously been limited due to theoretical and experimental constraints. The results for a sample of digested wastewater treatment sludge described a material with weak network strength that was quite permeable at low solids concentrations and the gel point was about 1 v/v%. The sample compressed to high solids concentrations at moderate pressures (up to 40 v/v% at 400 kPa) but became extremely impermeable at these high concentrations. The solids concentration dependencies of the material characteristics had a form that was expected for highly compressible materials such as wastewater sludges, but had not been reported previously. The extracted material characteristics were then used to predict the test results to show that the characterisation was valid.