DECONTAMINATION AND BENEFICIAL REUSE OF DREDGED ESTUARINE SEDIMENT:
THE WESTINGHOUSE PLASMA VITRIFICATION PROCESS
The operation of the New York/New Jersey harbor (Harbor) requires regular dredging. The offshore dumping facility has been closed due to regulations on ocean dumping of contaminated sediments, forcing the Harbor to consider alternative treatment and disposal options. The current report describes development of the plasma vitrification process for decontamination and beneficial reuse of contaminated sediments. Phase I bench testing characterized the sediment and provided verification that good quality glass could be prepared with addition of less than 15% fluxing agents. Kilogram quantities were prepared, and tested for decontamination efficiency; organics were destroyed to 99.9999% efficiency, and the product passed the TCLP leaching test for all heavy metals by several orders of magnitude.
Phase II pilot testing followed, including large-scale sediment pretreatment (screening, dewatering, and blending). Four metric tons of pretreated Harbor sediment were melted at approximately 0.8 Mg/hour in a full-sized plasma melting reactor powered by a Westinghouse Marc-11 plasma torch. Processing characteristics were evaluated, and detailed heat and material balances were prepared, including off gas and wastewater characterization. All gaseous and liquid effluents met discharge requirements.
Pilot plant data were then used to prepare preliminary plant designs for a 76,000 cubic meter per year demonstration plant (100,000 yd3/yr) and a 380,000 cubic meter per year full-scale facility. This study included material handling, pretreatment, vitrification, offgas treatment, and pollution control systems, and predicts an overall 99% reduction in waste volume compared to the original sediment. Preliminary costs were developed for the integrated sediment processing (including amortized capital), with a range between $90 and $120/Mg depending on the cost of electricity.
Finally, Phase III testing demonstrated conversion of an additional 1.4 Mg of vitrified sediment into commercial architectural tile, using technology developed by Futuristic Tile of Allenton WI. This tile represents a high-value product with a large potential demand, sale of which could more than offset all of the cost of sediment decontamination, even before credit is taken for a tipping fee.
Further details are available in the recently published paper at the following link