Treatment of heterogeneous mixed wastes: Enzyme degradation of cellulosic materials contaminated with hazardous organics and toxic and radioactive metals

The redirection and downsizing of the U.S. Department of Energy's nuclear w eapons complex requires that many facilities be decontaminated and decommis sioned (D&D). At Los Alamos National Laboratory, much of the low-level radi oactive, mixed, and hazardous/chemical waste volume handled by waste manage ment operations was produced by D&D and environmental restoration activitie s. A combination of technologies-air stripping and biodegradation of volati le organics, enzymatic digestion of cellulosics, and metal ion extraction-w as effective in treating a radiologically contaminated heterogeneous paint- stripping waste. Treatment of VOCs using a modified bioreactor avoided radi oactive contamination of byproduct biomass and inhibition of biodegradation by toxic metal ions in the waste. Cellulase digestion of bulk cellulose mi nimized the final solid waste volume by 80%. Moreover, the residue passed T CLP for RCRA metals. Hazardous metals and radioactivity in byproduct sugar solutions were removed using polymer filtration, which employs a combinatio n of water-soluble chelating polymers and ultrafiltration to separate and c oncentrate metal contaminants. Polymer filtration was used to concentrate R CRA metals and radioactivity into <5% of the original wastewater volume. Pe rmeate solutions had no detectable radioactivity and were below RCRA-allowa ble discharge limits for Pb and Cr.