Conditioning of alum sludge with polymer and gypsum

In this study, gypsum was introduced into alum sludge as a skeleton builder in combination with a polymer. The selection of gypsum lies in its common use as an amendment for ameliorating alkaline soils and may enhance the potential disposal of alum sludge to land. Preliminary work describes the impact of gypsum on the net sludge solids yield (YN), a factor which is used to express sludge filterability. Experiments demonstrated that gypsum could be used in association with a polymer to improve sludge filterability. The purpose of the skeleton builder is to form a permeable and rigid lattice structure that can remain porous under high pressure. By examining the polymer residual in the bulk solution and comparing data between the cases of gypsum and glass-microsphere (as a non-shrinking skeletal material) it was evident that the gypsum possesses a polymer demand indicating an interaction between them.