Preliminary research on the effect of lime addition on the rheology of sludge

Samples of excess sludge from wastewater treatment plants were investigated in order to determine the dependence of rheological parameters of sewage sludge on lime addition. Hydration of the sludge is one of its main features which determine sludge management and waste disposal cost. The rheological behavior of sludge is a key characteristic, since it determines the treatment processes. This research has evaluated the use of rheological properties for characterization and control of sludge and lime mixture flow behaviour. A laboratory investigation was conducted using rotating coaxial cylinder and several different gravimetric oncentrations of the investigated sludge. In order to describe the rheological characteristics, the 3-parameter Herschel-Bulkley model was applied. Rheological characterization is of great importance in sludge management, both in terms of biomass dewatering and stabilizing properties, and in terms of design parameters for sludge handling operations.