Characterization and Thermal Behavior of a Drinking Water Treatment Sludge

In Morocco, as a result of the coagulation flocculation process used for drinking water treatment, large quantities of sludge are produced each year. The goal of this work is to characterize the sludge produced at the Khemiss Zemamra DWTP in El Jadida City, Morocco, and evaluate its thermal behavior. This involves the chemical, mineralogical, structural, and microstructural characterization of the raw sludge and the study of the effect of thermal treatment on these characteristics. This was accomplished by using XRF, XRD, FTIR, TGA, and SEM analysis techniques. The chemical composition of the raw sludge identified by XRF is in good agreement with XRD and SEM analysis, which revealed that the main mineral phases in the XRD pattern are Quartz, Muscovite, Calcite, Nacrite, and showed that the raw sludge has a badly defined morphology imprisoning Calcite aggregates, Quartz grains, and Muscovite platelets. The thermal behavior of the sludge is observed between 200 and 1000 °C. The sludge phase transitions are significantly influenced by calcination, a temperature of 700 °C is sufficient to improve the overall dehydroxylation of Nacrite and its transformation to an amorphous reactive phase, but it is not enough to completely disintegrate Muscovite.