Investigation of Environmental-Concern Trace Elements in Coal and Their Combustion Residues from Thermal Power Plants in Eastern India

The bituminous-to-sub-bituminous quality feed coals of thermal power plants contain several environmental-concern trace elements (As, Se, Ni, Cr, Zn, Pb, Cu, Cd, Co and Mn). During combustion, these elements are enriched or depleted in the major coal combustion residues (CCR, fly and bottom ash). The analyzed elements are classified into three different groups according to the estimated enrichment ratio and relative enrichment index. Class I contains the volatile elements As, Se, both of which are depleted in fly and bottom ash. Class II contains the semi-volatile elements Zn, Cu, Ni, Cr, Cd and Pb, which are more enriched in finer fly ash than coarse bottom ash. In contrast, the less volatile Class III elements Co and Mn are equally enriched in fly and bottom ash. The major CCR containing heavy load of these elements (about 1826 t/year) are gradually exposed to the different segments of environment such as air, water and soil. These elements may have a possibility to be bioavailable in the food chain, which may give harmful influence to the ecological receptors. As per risk assessment code, the analyzed elements As, Se, Cr and Ni have low-risk character, while rest of the elements Cd, Cu, Pb, Zn, Co and Mn are safe for the environment. Laboratory water leaching experiment of elements in fly ash and bottom ash shows that these combustion residues are non-hazardous and may be used in various sectors such as construction field, land filled materials, mine reclamation and also in agriculture field. An understanding of regular monitoring and skillful management for the disposal practice as well as environmentally safe utilization of combustion residues generated from thermal power plants is a crucial issue from public health viewpoint.