Abstract
Our investigation focuses on in-depth characterization of seasonal sludges and ashes from the incineration of sewage sludge from the wastewater treatment plant in the city of Mila, Algeria, for their valorization in the manufacture of construction materials. Numerous analyses have been carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), hydrogen potential (pH), volatile matter (VM), electrical conductivity (EC), principal component analysis, real and apparent volumetric mass ( \({{\rho }_{{{\text{real}}}}}\) , \({{\rho }_{{{\text{app}}}}}\) ), and porosity ( \(\varepsilon \) ). The physicochemical characterization of sludge from the treatment plant of Mila City exhibited structural stability, whatever the seasonal variations. This stability was confirmed by statistical analysis. Thermal treatment of the sludge was performed by incineration at temperatures stretching from 550°C up to 1100°C. The chemical analysis using X-ray fluorescence demonstrated that the sludges’ ashes are rich with the oxides such as CaO, SiO2, Fe2O3, and Al2O3, which represent about \(95\% \) of the clinker’s compounds, which are responsible for cement hardening. On the other side, the X-ray diffraction analysis revealed that the mineral matrix contained in the ashes is mostly composed of calcite, quartz, hatrurite, and hedenbergite. The obtained phases from 750°C by calcination are the most important in the construction materials, and this is the key finding of this study. The most important mass loss during the thermal treatment was observed at 550°C owing to the organic matter decomposition at this temperature. The rise of the basic character with raising the c temperature is owing to the formation of basic metal oxides. The soluble ions in the calcined sludges are sensitive to the increase of temperature.
