Compartments for the Management of Municipal Solid Waste

Abstract

Despite technological developments and improved liner-material applications, heavy metals in landfill leachate still penetrate the soil profile, polluting the soil and ground-water. An alternative approach therefore must be explored to reduce heavy-metal migration in soil-bentonite landfill liners. By considering the interaction of different heavy metals and their synergetic and antagonistics behaviors, such an approach could be developed. Low mobility metals such as Cu2+, and Pb2+ inhibit the adsorption of Cd2+ which is a moderate-mobility metal and Cu2+ sorption is decreased by the presence of Zn2+ and Cd2+. Therefore, Zn2+, a low-mobility metal, cannot be grouped with Cu2+. This way, four compatible metal groups have been identified: (1) low mobility: Pb2+, Cu2+, and Ag, (2) low mobility: Zn2+ and Cr3+; (3) moderate mobility: As2+, Fe2+, and Ni2+; (4) high mobility: Cd2+ and Hg2+. Cd2+ with a moderate mobility pattern is synergetic to Fe2+ and is more mobile with Ni2+. Therefore, Cd2+ is separated from the moderate-mobility group and is consigned with Hg, a high-mobility metal. The liner materials suitable for Hg2+ are assumed to be suitable for Cd2+ as well. Based on this concept, and to reduce heavy metal mobility, wastes should be segregated on compatibility basis according to their heavy metal contents before being disposed in different individual compartments. For wastes containing several incompatible heavy metals, sorting should be based on the heavy-metal with the highest concentration. Another solution is the manufacturing of products using compatible heavy metal combinations and then labeling them accordingly. Such waste segregation and landfill compartmentalization lowers risks of groundwater contamination and liner cost.