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Bioremediation of Explosive Contaminants Matt Mahler Introduction In the late 19th century many nitramine compounds were created through the process of nitration. During WW I and WW II their application for industrial and military purposes was investigated. By 1945 an estimated 1.2 million tons of soil surrounding production plants had been contaminated. (Lewes et.al, 2004) Introduction Cont’d Enter the environment through wastewater from production plants. Many bioremediation techniques are currently being investigated. Compounds Discussed: TNT, RDX, HMX and CL-20 (Lewes et.al, 2004) Bioremediation of RDX Readily degradable in a variety of environments. Aerobic and Anaerobic Mechanisms Two-Electron Reductive Pathway and Denitration (Crocker et. al, 2006) RDX - Two Electron Reductive Pathway Mechanism Bacteria Invlolved Intermediates End Products Mechanism I Enterobacteria, E. Coli Mono, Di and Tri-nitroso-RDX Ethanol and Formaldehyde Mechanism II or McCormick's Pathway Clostridium Acetylbutilecum MNX, hydroxyl amino, 1,3,5triamino-1,3,5-triazine Ethanol and Formaldehyde Mechanism III Aspirgillus Niger MNX Ammonium, Nitrous Oxide, Formaldehyde RDX - Two Electron Reductive Pathway Cont’d Special Notes Mechanism II: No Ring Cleavage Mechanism III: Uses Oxireductase Still Disagreement Among Researchers RDX - Denitration Believed to be the most common method of RDX Degradation. Occurs aerobically and anaerobically RDX - Denitration Cont’d Pathway Bacteria Invlolved Intermediates End Products Aerobic Rhodococcus rhodochrous, Williamsia and Gordonia - NDAB, nitrous oxide, ammonium, formaldehyde and carbon dioxide Anaerobic K. pneumonia, C. bifermentans MNX Water, Nitrous Oxide and Formaldehyde RDX - Denitration Cont’d Special Notes Aerobic: NDAB is Readily Degraded by Many Organisms In the anaerobic denitration process two electrons are added prior to ring cleavage. Bioremediation of HMX Most methods that degrade RDX have also been shown to degrade HMX. Also involves aerobic and anaerobic processes. Bioremediation of HMX Aerobic Methylobacterium Cometabolize HMX with Carbon Dioxide Anaerobic Some process as RDX , however McCormick’s Pathway not aplicable. Bioremediation of CL-20 Recently Developed Nitramine 20% More Powerful Than HMX Degradation Mechanisms Similar To Those of RDX and HMX. Bioremediation of CL-20 Anaerobic Degradation Cloistridium Utilizes CL-20 for Cell Growth Catalyzed by Dehydrogenase End Products: Acetic Acid, Glyoxal, Nitrous Oxide and Nitrogen Dioxide Bioremediation of CL-20 Aerobic Degradation While possible, CL-20 most occur in high concentrations for process to take place. In environments that support fungal growth, white-rot fungi is responsible for aerbic mineralization of CL-20. Enhancing Anaerobic Nitramine Treatment Anaerobic Treatment of HMX, RDX and TNT Current Limiting Step in Process is the Availability of Substrate. Historically Starch Has Been Used Enhancing Anaerobic Nitramine Treatment Anaerobic Treatment of HMX, RDX and TNT Recent Research Introduced Propylene Glycol and Ethanol to Cultures Consumption of these Molecules Produces Hydrogen Gas Enhancing Anaerobic Nitramine Treatment Enhancing Anaerobic Nitramine Treatment Conclusion Addition of Propylene Glycol and Ethanol Did Increase Rate of Degradation Not Necessary for TNT and RDX Degradation. Enhancing Nitramine Treatment Enhancing Treatment CL-20 Added Sucrose, Pyruvate, Yeast, Acetate, Glucose and Starch to act as Carbon Sources Enhancing Ntramine Treatment Conclusions The addition of these substrates does increase the rate of CL-20 Degradation. Process is independent of microbial cell growth. Over half randomly selected microbes could degrade CL-20. Aerobic Degradation of CL-20 Researchers investigated the use of P. Chrysosporium for its use as a CL-20 degrading molecule. At the end of the 8 day experiment concentrations of CL-20 were virtually non-existant. Growth of fungi was observed. Case Study Louisiana Army Ammunition Plant Currently disposes of waste through dumping and incineration. Experiment performed to analyze the potential use of land farming and soil slurry as potential methods of waste treatment Case Study Results Soil Slurry showed 99% removal of TNT and near complete removal of HMX and RDX at the end of the 182 day experiment Land Farming showed 82% removal of TNT and little to know RDX and HMX removal after same amount of time. Conclusion The production of nitramines is only expected to increase. More efficient and economical degradation mechanisms must be found. Conclusion Molecule Name of Degradation Me thod Bacteria Involved RDX Two-Electron Reductive Pathway Enterobacteira, E. Coli, Clostridium Acetylbutilecum, Aspirgillus Nige r RDX Anaerobic Denitration K. pneumonia, C. bifermentans RDX Aerobic Denitration Rhod ococcus rhodochrous, Williamsia and Gordonia HMX Aerobic Degradation Methylobacterium HMX Anaerobic Denitration K. pneumonia, C. bifermentans CL-20 CL-20 Aerobic Degradation Anaerobic Degradation P. Chrysosporium Clostridium QUESTIONS?
