BIOLOGICAL DENITRIFICATION OF HIGH EXPLOSIVES PROCESSING WASTEWATERS

Previous work in our laboratory over the past four years has shown tha t the high explosives hexahydro-1,3,5,-trinitro-1, 3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) can be read ily destroyed by alkaline hydrolysis. The hydrolysis process produces large quantities of concentrated but conventional wastewaters, contain ing acetate, formaldehyde, formate, ammonia and nitrite. To treat thes e wastewaters, a denitrifying (anoxic) biological process was develope d that converts the hydrolysates to harmless endproducts, such as N-2 and CO2. The nitrite is produced during the hydrolysis process as the electron acceptor, but additional nitrite is required to completely ox idize the carbon compounds. Over 90 percent of each organic carbon sou rce can be removed in a packed-bed, upflow reactor in 3 hours hydrauli c retention time. Formaldehyde and acetate are first degraded at appro ximately the same rate, and formate is degraded more slowly. Results c losely match the stoichiometry predicted by the empirical redox equati ons describing the process. (C) 1997 IAWQ. Published by Elsevier Scien ce Ltd.