STABILIZATION OF A MIXED WASTE SLUDGE SURROGATE CONTAINING MORE THAN 260 PPM MERCURY

In an earlier demonstration of an innovative mercury stabilization technology for the Department of Energy, ATG's full-scale process stabilized mercury in soils that initially contained more than 260 ppm of mercury of unknown speciation. The treated waste satisfied the leaching standards for mercury that qualify wastes containing less than 260 ppm for land disposal. This paper describes the extension of that work to demonstrate a full-scale process for the stabilization of a representative sludge that contained more than 260 ppm of Hg of several mercury species. RCRA (Resource Conservation and Recovery Act) regulations now require the recovery of mercury from any waste containing more than 260 ppm of mercury, usually with thermal retorts. The results of this work with a surrogate sludge, and of the previous work with an actual soil, support a proposal now before the U.S. EPA (Environmental Protection Agency) to allow such wastes to be stabilized without retorting. The full-scale demonstration with a sulfide reagent reduced the mercury concentrations in extracts of treated sludge below the relevant leaching standard, a Universal Treatment Standard (UTS) limit of 0.025 mg mercury per liter of leachate generated by the Toxicity Characteristic Leaching Procedure (TCLP). The sulfide formulation reduced the concentration to about onehalf the UTS limit