Environmentally responsible disposal and reuse of MSW incineration bottom ash: assessment from two Indian plants

The efforts to encourage sustainable development have brought to attention the use of secondary materials in civil engineering applications. Global experimental data suggest that municipal solid waste (MSW) incineration bottom ash (IBA) can potentially replace natural aggregates in field applications. However, IBA is currently disposed in open dumps or sanitary landfills in India. Assessing contaminant leaching from IBA is crucial to ascertain its options for disposal or reuse. The current study analyzes the mineralogy, chemical constituents, organic content, and leaching of contaminants from IBA collected from two incineration plants in Delhi. The study takes into consideration the effect of particle size, liquid-to-solid (L/S) ratio, and pH on contaminant leaching. The experimental results revealed that the leaching concentration of contaminants and organic content of IBA decreases with an increase in particle size. A considerable influence of pH was noted on the leaching of all contaminants except chlorides, sulfates, and antimony. The results further indicate that IBA is suitable for disposal in non-hazardous waste landfills regardless of particle size at its intrinsic pH. However, it is recommended to dispose IBA in monofils as co-disposal with MSW in sanitary landfills can cause the pH of IBA to shift toward the acidic range, which may exacerbate the contaminant leaching from IBA. The comparison of leaching test results with international regulatory standards for reuse demonstrates that using IBA in unbound applications is feasible in paved roads and earthworks subjected to minimal infiltration of water.