Heavy metals in a municipal solid waste deposition cell

The physical and chemical changes of a waste mixture consisting of municipal solid waste (MSW) and sewage sludge were investigated during the anaerobic waste stablilization phases of the mixture. The emphasis of this study was the behavior of heavy metals. The waste was deposited in a test cell in 1973. It was found that the waste mass decreased by about 30% (wt) during the years 1973 to 1993 and yielded gas and leachate during the stabilization phase. Most of the leachate constituents increased rapidly shortly after deposition and a stable methanogenic phase prevailed by the end of the second decade. Approximately 30% of the total amount of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) in the waste have been identified as available reactive solid forms. However, the proportion was found to be different for each. Most of the remaining 70% of the heavy metals are believed to he less available as they are bound into lattice structures, such as metal and polymer items.