Processes for Treatment of Heavy Metals in Ash from Municipal Solid Waste Incinerators

Modem municipal waste combustors (MWC's) process approximately 100 million tons of refuse each year in the United States, Europe and Japan, producing 30 million tons of ash. The incineration process has the effect of concentrating the toxic heavy metals normally present in municipal refuse. As a result, the ash may require treatment to reduce the quantity or the mobility of heavy metals within the ash. Four treatment categories are discussed: stabilization, extraction, vitrification and solidification. Within each category a variety of treatment processes are reviewed. Numerous methods have been shown to be successful in laboratory-scale tests and full­ scale trials. Several processes have been in continuous, full-scale use for several years including: stabilization using cement; stabilization using phosphate; stabilization by lime addition; and vitrification processes.