Encapsulation of fluoride sludge in stabilised mud blocks

Non-engineered disposal of hazardous sludge can contaminate surface water and groundwater sources. Defluoridation of water using magnesium oxide (MgO) is being implemented in a village in Karnataka, India. Defluoridation of water by the MgO method produces fluoride-contaminated magnesium oxide sludge (FCMOS). This paper examines the impact of encapsulating FCMOS on the engineering and environmental integrity of the host matrix. Encapsulation of the sludge is accomplished by using the FCMOS as a constituent of stabilised mud blocks (SMBs). SMBs are an alternative to burnt bricks and are produced by cement stabilisation of densely compacted soil mass. Experimental results indicate that incorporation of FCMOS as a constituent of SMBs does not impact their compressive strength, linear expansion or durability. Furthermore, the fluoride release potential of SMB specimens is not increased.