Environmental Evaluation on Leaching of Trace Elements from Coalashes from Thermal Power Stations of Eastern India

摘要

On the basis of the study of the leaching of trace elements from coal ashes, following conclusions can be drawn: 1. In the study period of about three (3) years there was practically no leaching of thirteen elements namely, chromium, nickel, cobalt, cadmium, selenium, aluminium, silver, arsenic, boron, barium, vanadium, antimony and molybdenum from all the ash samples. 2. Out of the nine elements found in the leachates only calcium and magnesium were found to be leaching in the entire period. The leaching of other seven elements namely, iron, lead copper, zinc, manganese, sodium and potassium was intermittent The leaching of sodium and potassium practically stopped after 35 and 40 days, respectively. 3. The concentration of the elements in the leachates was invariably well below the permissible limits for discharge of effluents as per IS:2490 and also for drinking water as per IS: 10500. Overall, the coal ashes evaluated in this study were found to be environmentally benign and can be engineered for their bulk utilization particularly for mined out areas reclamation and for soil amendment for good vegetation. The Centre of Mining Environment at ISM Dhanbad is currently engaged in evolving low technology high volume field demonstration to show that coal ash particularly fly ash can be disposed and utilized as fill material in an environmentally acceptable way in reclamation of abandoned mines (Bradley C. Paul, Gurdep Singh et al. 1995, 1998). Use of fly ash as backfill material for reclamation of mined out sites provide benefits such as easy availability, cheaper to transport because empty coal carriers returning from the power plant can "back haul" it to the mine site. From the standpoint of the power plant, this is essentially a waste material which requires large costs of handling and a disposal to comply with environmental regulations. From the environmental point, this waste material will go back to the same place where it was mined and use of this material serves as extra benefit to power plants. Studies are also in progress to use fly ash for agriculture development.