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lecture12 - LECTURE 12 BIOREMEDIATION Bioremediation...

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Unformatted text preview: LECTURE 12 BIOREMEDIATION Bioremediation Bioremediation is the use of microorganisms to destroy or immobilize waste materials Microorganisms include: Bacteria (aerobic and anaerobic) Fungi Actinomycetes (filamentous bacteria) Bioremediation mechanism Microorganisms destroy organic contaminants in the course of using the chemicals for their own growth and reproduction Organic chemicals provide: carbon, source of cell building material electrons, source of energy Cells catalyze oxidation of organic chemicals (electron donors), causing transfer of electrons from organic chemicals to some electron acceptor Electron acceptors Electron acceptors: In aerobic oxidation, acceptor is oxygen In anaerobic, acceptor is (with decreasing efficiency): nitrate manganese iron sulfate Microorganisms also need essential nutrients such as nitrogen and phosphorus pE-10-5 +5 +10 +15 AEROBIC RESPIRATION IRON REDUCTION SULFATE REDUCTION NITRATE REDUCTION MANGANESE REDUCTION METHANE FERMENTATION DENITRIFICATION Image adapted from: Wiedemeier, T., J. T. Wilson, D. H. Kampbell, R. N. Miller, and J. E. Hansen, 1995. Technical Protocol for Implementing Intrinsic Remediation with Long-Term Monitoring for Natural Attenuation of Fuel Contamination in Groundwater. Air Force Center for Environmental Excellence, San Antonio, Texas. November 11, 1995. Figure B.5.4, Pg. B5-14. Bacterial growth Typically very rapid if food (carbon source) is present: population doubles every 45 minutes Pristine soils contain 100 to 1000 aerobic bacteria per gram of soil Increases to 10 5 within one week if carbon source is introduced Limitations to biodegradation Adequate bacterial concentrations (although populations generally increase if there is food present) Electron acceptors Nutrients (e.g., nitrogen and phosphorus) Non-toxic conditions (NAPL pools are likely to be toxic) Minimum carbon source (which may exceed regulatory limits for toxic chemicals) Note that rapid growth may be limited by diffusive or advective transport of any of the above History of bioremediation 1972 - First commercial application: Sun Oil pipeline spill in Ambler, Pennsylvania 1970s - Continuing bioremediation projects by Richard Raymond of Sun Oil mid-1980s - emphasis on bioengineering organisms for bioremediation. This technology did not live up to its initial promise 1990s - emphasis switched to greater reliance on natural microorganisms and techniques to enhance their performance Relative biodegradability Simple hydrocarbons and petroleum fuels degradability decreases as molecular weight and degree of branching increase Aromatic hydrocarbons one or two ring compounds degrade readily, higher molecular weight compounds less readily Alcohols, esters Nitrobenzenes and ethers degrade slowly Chlorinated hydrocarbons decreasing degradability within increasing chlorine substitution highly chlorinated compounds like PCBs and chlorinated solvents do not appreciably degrade aerobically Pesticides are not readily degraded Increasing biodegradability Bioremediation technologies for soil...
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This note was uploaded on 12/06/2011 for the course ESD 1.34 taught by Professor Petershanahan during the Spring '04 term at MIT.

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lecture12 - LECTURE 12 BIOREMEDIATION Bioremediation...

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