Hazardous metal wastes : landfill alternatives
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This study was proposed to find technologically available processes which could be used as economically feasible alternatives to land disposal of hazardous wastes. The scope of the study was limited to heavy metal contaminated hazardous wastes generated in Missouri. Data on 95 such waste streams were taken from the Missouri Department of Natural Resources’ Hazardous Waste Generator Registration Files. Economic criteria reduced the number of streams under consideration to twelve. Two streams, an electric arc furnace flue dust and an electroplating wastewater treatment sludge, were chosen for detailed study. An electrothermic reduction roast process called the Plasmazinc process was proposed to recover iron, lead and zinc from the electric arc furnace flue dust. In this process, an electrically generated plasma is used to supply heat to a low shaft furnace which contains the dust and an excess of coke. A reducing atmosphere of carbon monoxide and hydrogen is maintained throughout the process so that lead and zinc can be collected as metals in a splash condenser. Iron is tapped from the bottom of the furnace. This process was developed by SKF Steel of Sweden. A profitability analysis for a Plasmazinc plant capable of processing 91,000 kkg of dust annually suggested that the dust would have to be delivered to the plant free of charge for it to be feasible. The discounted cash flow rate of return for this case was found to be 15.1%. A reverse osmosis unit integrated into the rinsing system was proposed to recycle nickel plating salts currently contaminating the electroplating wastewater sludge. As suggested by the generator, the 99.97. reduction of nickel in the sludge which would result could be sufficient to induce the EPA to grant a regulatory exclusion for the waste. The estimated savings in disposal and plating chemicals' costs would effect a projected discounted cash flow rate of return of 15.8%. Elimination of these two streams would reduce the amount of hazardous waste generated in Missouri and disposed of on or in the land by 10%.
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