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I.V. Suresh: Disaster Management Institute (DMI), Paryavaran Parisar, Bhopal, India
C. Padmakar: Regional Research Laboratory (CSIR), Bhopal, India
Prabha Padmakaran: Regional Research Laboratory (CSIR), Bhopal, India
M.V.R.L. Murthy: Regional Research Laboratory (CSIR), Bhopal, India
C.B. Raju: Regional Research Laboratory (CSIR), Bhopal, India
R.N. Yadava: Regional Research Laboratory (CSIR), Bhopal, India
K. Venkata Rao: Vijayawada Thermal Power Station (VTPS), Ibrahimpatnam, India
Introduction
Fly ash is produced as a result of coal combustion in thermal power plants and discharged in ash ponds. In thermal power plant boilers, the inorganic mineral content of coal is converted into amorphous glassy material due to combustion of coal at 1,300-1,350[degrees]C and devitrified as a result of high viscosity. Currently, more than 60 million tonnes of ash per annum are produced from different thermal power stations in India, which will touch the figure of 100 million tonnes by the next century. The predominant methods for fly ash disposal in developing countries are ash settling tanks, dumping or direct disposal in local waterways. These pond waters contain many soluble cations/ anions that are released from the glass matrix of the ash. After settling, water with its higher quantity of total dissolved solids (TDS) may either enter into river or stream or partly seep into the ground water.
It has been reported by Malek et al. (1983) that fly ash contains higher concentrations of B, Co, Cr, Cd, Mo, Ni, As, and Se thannormally found in soils. The most environmental concern comes from the above aforesaid heavy metals in fly ash. The leaching potential of these heavy metals from an open system (fly ash ponds) is expected to be greater due to diurnal and seasonal variations in temperature, moisture content, and other parameters.
Since all the metals of fly ash are in the priority pollutants list (USEPA, 1993), their suitability and leaching potentials will be expected to be high. It has been determined by Russel (1981) that longterm leaching of fly ash using low pH water released substantial amounts of Na, K, Al, S, As, Mo, Se, and V into the solution phase. Other studies by Natusch et al. (1975) indicate that Na, S0[sub]4, As, Se, Mo, Cr, and Pb levels were higher in fly ash affected ground water than in samples from unaffected...