Immobilization of heavy metals in fly ash from thermal treatment of municipal sewage sludge

Authors:

• Łukasz Szarek

Abstract

The growing number of municipal sewage treatment plants in Poland, desirable from an ecological point of view, raises the problem of managing more and more sewage sludge. The thermal treatment of municipal sewage sludge (TTMSS) method, by greatly reducing the waste volume, increases the heavy metal concentration in fly ash (primary, end product of the treatment process), which may constitute a risk factor when attempting to utilize them economically e.g. in the construction industry, where coal combustion by-products are successfully used. Heavy metal leaching primarily depends on the internal properties of the material (e.g. porosity, hydraulic permeability) and the operating conditions of a given material (material form, operating environment, contact with aggressive media, pH). The study focused on determining the level of immobilization of selected heavy metals (Zn, Cu, Pb, Cd, Cr) in TTMSS subject to testing with the percolation test (basic characterization test) and batch test (compliance test).