Properties and performance of clay brick containing water treatment sludge (WTS)

Every year, a large quantity of water treatment sludge (WTS) is produced from water treatment plant in Malaysia. Sanitary landfill disposal of sludge at authorized site is the common practice in Malaysia. However, searching the suitable site for landfill is the major problem as the sludge produced keeps on increasing. Reuse of the sludge could be an alternative to disposal. This study investigated the reusability of WTS as brick making material. The performance of clay-WTS bricks produced by mixing clay with different percentages of WTS with an increment of 20% from 0% up to 100% by weight was investigated. Each molded brick with optimum moisture content was pressed under constant pressure, oven-dried at 100˚C for 24 hours and heated up to 1050˚C for 5 hours. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis were used to characterize clay, WTS and clay- WTS bricks. The performance of the bricks were evaluated with firing shrinkage, loss on ignition (LOI), water absorption, bulk density, and compressive strength tests. Increasing the sludge content results in an increase of brick shrinkage and water absorption. The results revealed that the brick with 100% by weight of sludge could generate the highest compressive strength of 15.6 N/mm2. The optimum amount of sludge that could be mixed with clay to produce good bonding of clay–WTS bricks was found to be 40% by weight and comply with the British Standard 3921:1985, which can fulfil the requirement for general usage of clay bricks.