Biodegradation of RDX-contaminated wastes in a nitrogen-deficient environment

A feasible biological treatment process for RDX-contaminated wastes was dem onstrated in a bench-scale system, using real wastewater of a munitions fac tory. The wastewater mixture tested included the nitramine RDX together wit h high levels of nitrate and various organic solvents such as cyclohexanone and acetone. The purpose of the study was to remove both RDX and nitrate i n order to prevent groundwater contamination. A two-stage reactor system in cluding an anoxic stage followed by an aerobic one was tested. The anoxic s tage was aimed at removing nitrate by denitrification, using available carb on sources present in the waste mixture. Additional supply of carbon source (acetone) was required to support complete removal of nitrate. Further rem oval of residual organic was achieved in the aerobic stage together with to tal mineralization of RDX. Complete removal of nitrate in the anoxic stage was found to be crucial to RDX mineralization in the aerobic stage, since R DX was used solely as a nitrogen source. Additional carbon source (cyclohex anone) was also required in the aerobic stage to assure complete removal of RDX. The treatment scheme tested may be a cost-effective alternative to ph ysico-chemical treatments such as carbon adsorption and UV destruction, com monly applied for explosives-contaminated wastes. (C) 1998 Published by Els evier Science Ltd. All rights reserved.