Reuse of alum sludge in clay brick manufacturing

When alum is used as a coagulant in a water treatment plant (WTP), a large volume of sludge is generated. The characteristics of the sludge depend strongly on the water source and the quality and quantity of the chemicals used for processing. For a plant with total suspended solids (TSS)/turbidity unit (TU) factor of 1.7, the weight of the alum sludge produced at an average alum dose of 28.2 mg/L is approximately 25 kg/MLD. Disposal of sludge in a way that is economically and environmentally sustainable is a major challenge faced by WTPs around the globe. In this study, the alum sludge generated during water treatment was used as a partial substitute for clay in a clay brick manufacturing process. Alum sludge and commercial local clay were blended in various proportions and sintered at different temperatures to produce clay-sludge bricks. In this paper, the physical and mechanical properties of clay-sludge bricks, such as loss on ignition (LOI), water absorption, and compressive strength, are investigated. The results from this study indicate that alum sludge could be used as a partial substitute in commercial clay bricks to a maximum of 20% without compromising the strength of the bricks.