Review of leaching behavior of municipal solid waste incineration (MSWI) ash

Incineration is widely adopted in modern waste management because it provides an effective way to minimize municipal solid waste that needs to be disposed of in landfills. The ash residue is often disposed by landfilling. Alternatively, the incineration ash may be recycled and reused for various applications. The crucial issues, however, are the leaching of harmful elements during the use and the end-of-life phases. This review summarizes extensive studies on leaching behavior of municipal solid waste incineration ash. Specifically, pollutants generated through leaching, factors governing leaching, methodologies to study leaching, leaching mechanisms, and treatments to reduce leaching. Many types of pollutants are generated through leaching from municipal solid waste incineration ash, in which heavy metals and organic contaminants are the most toxic and concerned. Ash properties, pH and liquid to solid ratio are the main factors governing municipal solid waste incineration ash leaching. Leaching behavior of municipal solid waste incineration ash is complicated and existing methods to evaluate leaching may not be able to represent the field conditions. Solubility and sorption are the two major leaching mechanisms. Many treatment methods have been proposed. However, not all methods are effective and some approaches are associated with high energy and high cost, which makes them less economically feasible and attractive.