Leaching of milled asphalt pavement amended with waste to energy ash

Abstract

The environmental suitability of using Waste-to-Energy (WTE) ash as a partial substitute for aggregate in hot-mix asphalt concrete was investigated using a series of leaching lysimeters. Eight samples of processed asphalt concrete manufactured with 25% by weight WTE ash as aggregate were leached using stainless steel lysimeters. A ninth lysimeter contained asphalt without WTE ash. Simulated rainfall was passed through the processed asphalt concrete to simulate pollutant leaching that might occur from stockpiled or disposed milled asphalt. Leachate samples were collected every five days for 75 days and analysed for lead, Total Dissolved Solids (TDS), aluminium, and chloride. Polychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans, and polycyclic aromatic hydrocarbons were analysed in the first flush leachates but were not detected. Although previous batch leaching studies found lead, chloride, TDS, and aluminium to present possible risk to groundwater, the lysimeter leachates found only aluminium concentrations to remain above water quality standards throughout the experiment. Lead was detected only sporadically, and TDS and chloride diminished to below water quality thresholds early in the experiment. The source of the aluminium was the WTE ash.