Treatment of Heterogeneous Mixed Wastes: Enzyme Degradation of Cellulosic Materials Contaminated with Hazardous Organics and Toxic and Radioactive Metals

Abstract

The redirection and downsizing of the U.S. Department of Energy's nuclear weapons complex requires that many facilities be decontaminated and decommissioned (D&D). At Los Alamos National Laboratory, much of the low-level radioactive, mixed, and hazardous/chemical waste volume handled by waste management operations was produced by D&D and environmental restoration activities. A combination of technologiesair stripping and biodegradation of volatile organics, enzymatic digestion of cellulosics, and metal ion extractionwas effective in treating a radiologically contaminated heterogeneous paint-stripping waste. Treatment of VOCs using a modified bioreactor avoided radioactive contamination of byproduct biomass and inhibition of biodegradation by toxic metal ions in the waste. Cellulase digestion of bulk cellulose minimized the final solid waste volume by 80%. Moreover, the residue passed TCLP for RCRA metals. Hazardous metals and radioactivity in byproduct sugar solutions were removed using polymer filtration, which employs a combination of water-soluble chelating polymers and ultrafiltration to separate and concentrate metal contaminants. Polymer filtration was used to concentrate RCRA metals and radioactivity into <5% of the original wastewater volume. Permeate solutions had no detectable radioactivity and were below RCRA-allowable discharge limits for Pb and Cr.