Biotransformation routes of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine by municipal anaerobic sludge

Recently we demonstrated that hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) , a trimer of methylene nitramine (CH2=N-NO2) undergoes spontaneous decompo sition following an initial microbial attack using a mixed microbial cultur e at pH 7 in the presence of glucose as carbon source. The present study de scribes whether the second cyclic nitramine octahydro-1,3,5,7-tetranitro-1, 3,5,7-tetrazocine (HMX), a more strained tetramer of CH2=N-NO2, degrades si milarly using sludge of the same source. Part of HMX biotransformed to give products that are tentatively identified as the nitroso derivatives octahy dro-1 -nitroso-3,5,7-trinitro-1,3,5,7-tetrazocine (mNs-HMX) and octahydro-1 ,3-dinitroso-5,7-dinitro-1,3,5,7-tetrazocine and its isomer octahydro-1,5-d initroso-3,7-dinitro-1,3,5,7-tetrazocine (dNs-HMX). Another fraction of HMX biotransformed, apparently via ring cleavage, to produce products that a r e tentatively identified as methylenedinitramine (O2NNHCH2-NHNO2) and bis(h ydroxymethyl)nitramine ((HOCH2)(2)-NNO2). None of the above intermediates a ccumulated indefinitely; they disappeared to predominantly form nitrous oxi de (N2O) and formaldehyde (HCHO). Formaldehyde biotransformed further to ev entually produce carbon dioxide ((CO2)-C-14). Nitrous oxide persisted in HM X microcosms containing glucose but denitrified rapidly to nitrogen in the absence of glucose. The presence of nitrous oxide was accompanied by the pr esence of appreciable amounts of hydrogen sulfide, a known inhibitor of den itrification.