An Accelerated, On-Site Bottom Ash Aging and Washing Treatment and Its Effect for Long-Term Leaching

Abstract

Ash stabilization is important for realizing safe and reliable disposal sites and promoting MSW bottom ash (BA) recycling. An on-site technology that uses a modified detachable container and stabilizes BA with sprinkling water (watering) and flowing 100% CO2 through the ash layer (carbonation) was developed. Experimental verification of this technology was undertaken (Treatment condition: L/S = 0.6–0.7, 24 h duration, 2.2 t/time). Two treatment methods were investigated using unsieved BA: (1) sprinkling water only (2) sprinkling water combined with carbonation. In the verification test, the chlorine (Cl) content of the BA decreased by up to 72% after the watering treatment. The BA treated by watering and carbonation showed reduction in solubility of Pb by up to 90%. An exothermic reaction due to carbonation was also confirmed. In the lysimeter test (column size: o104 × 400 mmH) conducted to evaluate the long-term leaching performance of the BA treated to promote stabilization, leachate data was acquired over 400 days from both treated and untreated BA. It was confirmed that the leachate of BA treated with watering showed lower EC, cumulative Cl and TOC than untreated BA. The leachate of BA treated with watering and carbonation showed lower pH, Pb concentration and higher cumulative Cl, Ca after 400 days than the one treated with watering alone.