Universal scaling of consolidation in batch settling

The characteristics of the settled bed in gravitational sedimentation have been studied by many researchers. The settled bed, often composed of flocculated or aggregated particles, is formed from a process of freesettling, followed by consolidation, subjected to compression. Although the free-settling of the particles is well understood, there is scope for advancing our knowledge to explain and predict the characteristics of the consolidation. The aim of this research was to develop a universal description of the bed consolidation, limited to incompressible systems that do not yield. A series of batch settling tests was conducted using a model experimental system to generate a broad range of data. Hence the initial volume fraction of the particles ranged from 0.28 to 0.55. Spherical, low density, particles were used in the batch tests. These model particles exhibited some features similar to flocculated particles. The new theoretical model is used to calculate the quantity of water expressed from each layer of sediment. The water expressed in a time period scales directly with the quantity of expressible water in the layer, and inversely with the lapse time squared. The batch settling test results, defined in terms of the height of the settled solids versus time, were used to validate the theoretical model. Excellent agreement across the full range of solids concentrations was obtained.