Experimental investigation on sludge dewatering using granulated blast furnace slag as skeleton material

The highly compressible nature of sludge and the presence of colloidal particles cause difficulties in sludge dewatering. Reducing the moisture content in secondary sludge is a key factor in reducing the capital costs, operational costs, and transportation costs in wastewater management. This investigation concerned the combined utilization of quicklime and granulated blast furnace slag (GBFS) to improve sludge dewatering. The experimental work included the initial characterization of the sludge and granulated blast furnace slag and evaluation of the dewatering ability of the treated sludge (CST, moisture content, turbidity, zeta potential, and heavy metal and biopolymer contents). Optimization using the Box-Behnken design (BBD) was carried out with various operational parameters, and the best performance was found to be at a pH of 10.2, a dose of 0.34 g/g DS, and a contact time of 14 min. A characterization study was carried out by scanning electron microscopy (SEM) in conjunction with EDS, X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR) to confirm the structural features (dense), elemental composition, and the presence of different functional groups. Hence, this study concluded that the use of quicklime with granulated blast furnace slag is suitable for conditioning during sludge dewatering. Graphical abstract.