This study shows a possibility of using sewage sludge after thermal treatment (at 1050°C for 3h) in the production of a building material. The use of dehydrated sewage sludge as a component in building materials, like in the sludge-clay mixture employed in the manufacture of bricks, tiles and cements, has been frequently done around the world. During sludge-clay mixture firing, which was done by controlled heating at a temperature above of 1000°C for 3h, organic substances of the sludge were completely eliminated. After thermal treatment, the micropores formed due to the released expansive gases, are responsible for the acoustic and thermal isolation properties of the resulting material. A problem found in the ashes was the high concentration of toxic compounds like Zn, Ni, Cr, Cu, Al oxides. The aim of the present work was to observe through scanning electron microscopy (SEM), X-ray fluorescence (XRF) and inductively coupled plasma optical emission spectrometer (ICP-OES) the integration of these oxides into the sintered ceramic matrix of sludge. Oxide integration is an important factor in brick manufacturing used as building materials.