Characterization of alum sludge for reuse and disposal

Abstract

The properties of spent drinking water treatment sludge (WTS) were investigated to determine its physical and chemical properties. WTS was obtained from the Semanggar Water Treatment Plant, Kota Tinggi, Johore, Malaysia. Bulk density, particle density, porosity, surface area, particle size, moisture content, ash content, chemical composition, leachability of heavy metals, pH and the total organic carbon (TOC) were determined. Surface and other physicochemical properties were also studied using the scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), TGA, FTIR, BET single point surface area analyzer, and TOC analyzer. Results showed that the particle size, bulk density and particle density of WTS were 2-5 μm, 0.831 ± 0.061 g/cm3 and 2.66 ± 0.029 g/cm3, respectively. The porosity was 68-69% with surface of 38.92 m2/g and ash content of 67%, reflecting the high TOC of 1440.37±14.71. The sludge contained 29% moisture and showed a pH value of 4.28 in solution. Analysis of acid digest indicated a high content of Al and Fe. The WTS were shown to leach very low levels of selected heavy metals.