Manganese and Chromium Leaching from High Carbon Fly Ash Amended Embankments

Abstract

Most of the electricity consumed in the US is supplied by Coal Power Plants. During the coal combustion process approximately 75 million tons of fly ashes are produced as a result of burning coal annually, yet only 50% of these fly ashes are currently reused. The majority of the remaining landfilled or stockpiled fly ashes are high carbon fly ashes (HCFAs). Recycling of these HCFAs is tremendously important for reducing the waste material, saving valuable land space and money. Highway constructions such as embankments have great potential to dispose of these stockpiled fly ashes. However, one key issue that precludes amendment of fly ashes into the embankment constructions is the potential for groundwater and other environmental impacts caused by heavy metals in the fly ash. To evaluate the environmental suitability, a series of column leach tests (CLTs) were conducted to determine the leaching potential of chromium and manganese from fly ashes. In addition, computer modeling program (WiscLeach) was used to predict the metal concentrations in the field. Results from CLTs showed that an increase in fly ash content increased the pH of the effluent concentrations and increased Cr concentrations. All metals exhibited first flush leaching pattern.