Geo-characterisation of lime water treatment sludge

In-situ and laboratory tests were performed on lime sludge generated from a drinking water-softening process and disposed of in a sedimentation lagoon. The sludge consists predominantly of calcite. It is poorly graded, low-plasticity silt with in-situ w c around 70%, γ t around 15 kN/m3 and e between 1·5 and 2·5. The optimum w c for standard and modified Proctor compaction is 30% and the maximum γ d values are 12 and 13·5 kN/m3 respectively. The C c and C r for undisturbed sludge specimens are 0·54–0·68 and 0·021–0·046. C v and k decrease with increasing vertical stress. The disposed sludge is sensitive and the in-situ S u,max varies with depth. Stratification of the sludge is evident by the varying values of in-situ S u,max, S u,r and S t with depth and V s profiles. Potential engineering reuse options for the sludge are buffer for acidic soil and low-permeability fill for landfills and brownfields, as well as engineering fill. The properties of lime sludge are different from those of coagulation sludge,...