The leachability of heavy metals from fly ash, bottom ash, dumping site ash, cement, and brick samples admixtured with fly ash in the area of a thermal power plant were compared. During these studies, extraction and leaching of various heavy metals like Zn, Ni, Cu, Fe, Pb, Mn, Mg, and Cd was carried out by applying batch leach test and toxicity characteristic leaching procedure (TCLP) to check the possibility of ground water contamination. The ground water samples in the vicinity of ash dumping sites were also analyzed for heavy metal concentrations and results obtained were compared with Indian and WHO permissible limits.
Mg, Mn, and Fe were leached to a larger Zn, Cu, and Pb to moderate, and Ni to a smaller extent, from the ash and admixtured samples. Cd was not leached at all from any sample in batch leach as well as TCLP tests. The concentrations of Zn, Fe, Mn, Mg, and Cd in groundwater samples were below the permissible limits of WHO and Indian standards. The concentrations of Ni and Pb were slightly higher than WHO permissible limits but below the Indian standards. The concentration of Cu was within the WHO permissible limits but slightly higher than Indian Standards. The admixturing of thermal power plant fly ash in cement and bricks seems to be an eco-friendly practice as far as leaching of heavy metals in groundwater is concerned.