Biodegradation of high explosive production effluent containing RDX and HMX by denitrifying bacteria

Abstract

The biodegradation of high explosive production effluent containing RDX (royal demolition explosive) and HMX (high melting-point explosive) in the presence of denitrifying bacterial isolates was investigated. The effluent collected from HMX production plant containing acetic acid, ammonium nitrate and explosive residue with water and other organic nitro bodies was used. The diluted and neutralized effluent was subjected to biodegradation using Pseudomonas (HPB1) and two Bacillus (HPB2, HPB3) denitrifying bacterial isolates. Samples were analysed by HPLC for qualitative and quantitative analysis of remaining RDX and HMX. The results indicate that the HMX and RDX was biodegraded under denitrifying conditions. The isolate Pseudomonas (HPB1) was found to be an efficient biodegrading strain for HMX. However, the isolate Pseudomonas (HPB1) was found to have lower biodegradation activity for RDX as compared to the denitrifying strain Bacillus (HPB2). Denitrifying bacteria Bacillus (HPB2) was found to be the most efficient strain for the biodegradation of RDX and HMX containing effluent neutralized with sodium bicarbonate. The biotransformation activity for HMX and RDX was lower for the isolate Bacillus (HPB2) in the effluent neutralized with ammonia. Removal of nitrate from the effluent containing HMX and RDX by the three denitrifying bacteria was also studied. Denitrifying bacteria Pseudomonas (HPB1) showed the maximum nitrate reduction in the presence of both the neutralizing agents- sodium bicarbonate and ammonia.