Understanding Coal Combustion Residues Leaching Chemistry Under Disposal Environment

The present study is focused on leaching characteristics of coal combustion residues under the disposal environment. The coal combustion residues collected from a thermal power station of Eastern India were used for the study purpose. Leaching study using open column percolation experiment were carried out for almost three years to understand the long-term effects of disposal of such solid wastes in the disposal environment. Potentiometric parameters, like pH, conductivity and total dissolved solids (TDS) of the samples were studied and was found within the permissible limits for effluent discharge in the inland surface water bodies and on land for irrigation (IS:2490). The leachates pH reflected that coal combustion residues (CCRs) are slighltly acidic to alkaline but overall on the long-term basis, these are alkaline in nature. The leachates were also analyzed for 23 elements. The study revealed the elements, like Ca, Mg, Na and K were at a higher concentration as compared to other elements. These elements were found to be leaching throughout the study period although their concentrations reduced considerably with time. The most volatile elements, like B, Hg, Se and others, such as Cr, Ni, Cd, Al, Ag, As, Ba, V, Sb, Mo were reported at BDL level. Elements, like Fe, Mn, Ci and Zn showed intermittent leaching. These were found to leach at significant concentration levels for some time but found to be absent on a long-term basis. Thus, the leaching study conducted on five samples of Burnpur Thermal station clearly shows that coal combustion residue is safe with respect to trace and/or heavy metals leaching in the disposal environment when used as a fill material in bulk