STABILIZATION OF A MIXED WASTE SLUDGE FOR LAND DISPOSAL

A solidification and stabilization technique was developed for a chemi cally complex mixed waste sludge containing nitrate processing wastes, sewage sludge and electroplating wastewaters, among other wastes. The sludge is originally from a solar evaporation pond and has high conce ntrations of nitrate salts; cadmium, chromium, and nickel concentratio ns of concern; and low levels of organic constituents and alpha and be ta emitters; Sulfide reduction of nitrate and precipitation of metalli c species, followed by evaporation to dryness and solidification of th e dry sludge in recycled high density polyethylene with added lime was determined to be a satisfactory preparation for land disposal in a mi xed waste repository. The application of post-consumer polyethylene ha s the added benefit of utilizing another problem-causing waste product . A modified Toxicity Characteristic Leaching Procedure was used to de termine required treatment chemical dosages and treatment effectivenes s. The waste complexity prohibited use of standard chemical equilibriu m methods for prediction of reaction products during treatment. Waste characterization followed by determination of thermodynamic feasibilit y of oxidation and reduction reactions allowed estimation of reactants required and possible reaction products. These calculations were show n to be accurate in laboratory testing.