BIOTRANSFORMATION OF EXPLOSIVE-GRADE NITROCELLULOSE UNDER NITRATE-REDUCING CONDITIONS

Waste nitrocellulose (NC) is regulated as a hazardous material. The objective of this study was to determine if NC exposed to denitrifying conditions would undergo sufficient removal of the nitro groups to yield a material that is no longer explosive. Enrichment cultures were established with activated sludge inoculum and methanol as the electron donor, and stoichiometric conversion of nitrate to nitrogen gas was observed. NC was added to the cultures at 10 g/L. A statistically significant decrease in the nitrogen (N) content of NC occurred, from approximately 13.1-13.2% in virgin NC to 12.2-12.4%. The presence of methanol was necessary to affect this change; NC itself did not serve as an electron donor. In cultures that were carrying out denitrification but were then depleted of nitrate, with methanol still present, a slightly greater removal of nitro groups from NC occurred along with additional formation of nitrogen gas. NC did not have an inhibitory affect on the denitrification process. Fourier Transform Infrared Spectroscopy (FTIR) results indicated that NC exposed to denitrifying conditions contained hydroxyl groups, confirming removal of some of the nitro groups by hydrolysis of the nitrate esters. NC exposed to denitrification and virgin NC were also compared based on their explosive properties using a small-scale burning test. No significant difference was observed. Thus, the %N, N2, and FTIR results demonstrated that NC does undergo biotransformation during denitrification, but the extent of nitro group removal does not appear to be adequate to yield a nonhazardous product.