Environmental Impact and Physicochemical Assessment of Pond Ash for its Potential Application as a Fill Material

Abstract

Thermal power plants (TPPs) produce a large quantity of coal ash, whose disposal is a big environmental issue. A major portion of coal ash is dumped as pond ash in ash pond near TPPs. Properties of pond ash vary from TPP to TPP and also within the same ash pond at inflow and outflow point. To assess the feasibility of pond ash as a fill material, pond ash samples were collected from inflow and outflow points of three TPPs in Haryana. This paper presents a detailed characterization study on the physico-chemical, mineralogical and morphological properties of pond ash samples. Leaching study was also carried out to assess the potential contamination of ground water from coal ash fills. Results reveal that all inflow and outflow pond ashes have low specific gravity (2.03–2.27) as compared to soil (2.6–2.7), i.e. natural fill material, low amount of unburned carbon content (1.79–3.49 %) and the values of maximum dry density and optimum moisture content are within the permissible limits as per design standards of embankment construction. The results of leaching study indicate that concentration of lead (Pb) and chromium (Cr) are quite high from standard land disposal limit, prescribed by Ministry of Environment and Forest in all pond ash samples. So it can be effectively used as construction fill materials for low-lying areas and as embankment materials etc., with caution to protect ground water from contamination due to the high concentration of lead (Pb) and chromium (Cr).