Solidification as a process of treatment of post-coagulation sludge from the water treatment plant

Post-coagulation sludge is a mixture of pollutants removed from water and coagulants, which was added to the water. It has a hydrophilic and colloidal character. It is important to search processes whereby this sludge could be reused or eventually disposed of. The studies of solidification of post-coagulation sludge were carried out. The solidification process consists in the appropriate and rapid mixing the sludge with the material used for solidification in order to ensure the adequate homogenization conditions. The reagent used in solidification absorbs water contained in the sludge as a result of rapid homogenization with the sludge due to hydration, in a strongly exothermic process. The excess water evaporates form the sludge. This reduces the mass and volume of the sludge and leads to the formation of granules. During the tests, quicklime and cement Gorkal 40, Gorkal 50 and Gorkal 70 were used as a solidifying material, in doses of 0.7; 1.4; 2.1; 2.8; 3.5 g/kg TS. During the maturing process of the lime-sludge and cement-sludge mixtures, changes in the total solids concentrations were checked. The obtained test results show that increasing the solidification material dose and extending the maturation time results in a significant increase in the total solids concentration of the mixtures. Changing the structure and consistency of the sludge from plastic to solid gives the possibility to use sludge as a building material, for the reclamation of dumps, hardening roadsides or creating slopes and embankments.