Studies on potential of Portland cement mortar for binding of waterworks sludge to reduce heavy metal leaching

The investigation of heavy metal leaching and physicochemical properties of cement-solidified waterworks sludge (CMWWS) formed by incorporating waterworks sludge (WWS) into cement mortar was carried out. The chemical composition, compressive strength and other physicochemical properties of the CMWWS cube specimens were determined using field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD) and Fourier transform-infrared spectroscopy (FTIR). The major type of chemical components present in CMWWS was found to be Al and Fe. The increasing amount of WWS added to cement mortar resulted in the increasing of organic matter, urchin-like morphology and clear peak intensity. At the end of 28 days of curing, the soaking solution became strongly basic and CMWWS cube specimens leached out higher amount of heavy metals. The compressive strength of CMWWS increased up to a WWS percentage of 10%, and basic (pH > 7) curing solution was found to be better than water for curing purposes. It is concluded that solidification–stabilisation (S/S) technique is able to effectively reduce the leaching of heavy metals from the WWS and CMWWS containing up to 10% WWS can be used as construction material.