The characterisation of slurry dewatering

The dewatering of flocculated suspensions presents a significant challenge to water and waste water processing operations world-wide. Traditionally th e dewatering process is enhanced through the use of flocculants or a surfac e chemical modifier to draw together fine particles and increase settling r ates and sediment permeabilities, however, present methods of gauging chemi cal performance are somewhat empirical. Recently, Landman and White develop ed a theory of suspension filtration which incorporates the compressibility and permeability of a sediment into a filtration diffusivity, D(phi). D(ph i) is a material properly used to calculate the time scale of a dewatering process from first principles for a given set of process conditions i.e. fi nal desired solids concentration, applied pressure, initial sediment height . A model alumina system and an alum water treatment sludge have been used to show the effect of flocculation conditions on compressibility, permeabil ity (determined from filtration experiments) and the diffusivity, D(phi).