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Soil clean-up by bioremediation

Soil clean-up by bioremediation. Prof. dr. ir. W. Verstraete Dr. ir. N. Boon ir. W. Ossieur (wendy.ossieur@avecom.be) Laboratory of Microbial Ecology and Technology (LabMET) Faculty of Bioengineering Ghent University LabMET.Ugent.be. Topics of discussion. General considerations

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Soil clean-up by bioremediation

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  1. Soil clean-up by bioremediation Prof. dr. ir. W. Verstraete Dr. ir. N. Boon ir. W. Ossieur (wendy.ossieur@avecom.be) Laboratory of Microbial Ecology and Technology (LabMET) Faculty of Bioengineering Ghent University LabMET.Ugent.be 1Laboratory of Microbial Ecology and Technology

  2. Topics of discussion General considerations Ex situ clean-up by micro-organisms In situ clean-up by micro-organisms Future perspectives 2Laboratory of Microbial Ecology and Technology

  3. Topics of discussion General considerations Ex situ clean-up by micro-organisms In situ clean-up by micro-organisms Future perspectives 3Laboratory of Microbial Ecology and Technology

  4. General Considerations • The 33 synthetic organic contaminants reported to be most frequently found in drinking water wells(Rittman et al., 1994) 4Laboratory of Microbial Ecology and Technology

  5. General considerations Many of these toxic compounds serve as food to some types of microbes. Microbes can eliminate or neutralize many toxic compounds in the environment 5Laboratory of Microbial Ecology and Technology

  6. General considerations • The application of micro-organisms to clean-up contaminated sites is considered to be a sustainable solution because it is based on: • the natural degradation capacity of the environment • a minimal impact on the environment • Firms and environmental consulting are the interestedparties for this application 6Laboratory of Microbial Ecology and Technology

  7. General Considerations • The application of micro-organisms to realize the clean-up of contaminated soils can be done by 3 strategies: • Natural Attenuation • Biostimulation • Bioaugmentation 7Laboratory of Microbial Ecology and Technology

  8. General Considerations • Monitored Natural Attenuation (MNA): • In situ degradation by ‘indigenous’ bacteria under natural conditions without intervention of human actions • Actions: Monitoring of the degradation products produced by the indigenous populations • Example: Perchloroethylene  ethene, Dover (VS), Dehalobacter and Desulfitobacterium, Davis et al. (2002) Journal of Contaminant Hydrology, 57, 41-59. 8Laboratory of Microbial Ecology and Technology

  9. General Considerations Principal criteria for the use of MNA • There must be solid indications that clean-up can be achieved in a reasonable time-span (< 30 years); • The processes must be aimed at the protection of the site and its surroundings; • There must be transparent agreements on financial responsibilities over long-term periods, also if certain goals are not reached or unforeseen events occur; • There must be proper geohydrological monitoring 9Laboratory of Microbial Ecology and Technology

  10. General Considerations • Biostimulation: • Accelerated natural attenuation by human intervention • Actions: in situ supplementation of nutrients to the soil + monitoring of the degradation products produced by the stimulated indigenous population • Example:Oil, Houston (VS), + inorganic nutrients and alternative electron acceptor, Mills et al. (2004) Marine Pollution Bulletin, 49, 425-435 10Laboratory of Microbial Ecology and Technology

  11. General Considerations • Bioaugmentation: • The inoculation of bacteria into the soil to improve the specific biological activity • If the degradation by indigenous populations delivers harmful products ordemands too much time • Actions: in situsupplementation of bacteria and nutrients in the soil + monitoring of the degradation products of the inoculated and stimulated indigenous bacteria • Example:Tetrachloromethane, Schoolcraft (VS), Pseudomonas stutzeri KC + acetate and nutrients, Dybas et al., (2002) Environmental Science and Technology, 36, 3635-3644. 11Laboratory of Microbial Ecology and Technology

  12. Topics of discussion General considerations Ex situ clean-up by micro-organisms In situ clean-up by micro-organisms Future perspectives 12Laboratory of Microbial Ecology and Technology

  13. Ex situ clean-up by m.o. 13Laboratory of Microbial Ecology and Technology

  14. Ex situ clean-up by m.o. • Griftpark (Utrecht, 1996) • 10 ha, surrounded by bentonite clay wall down to 50m into the clay layer • Time scale : 1-3 centuries! • Pump 10 m3/h water (~netto precipitation) to 1) Activated sludge 2) Decantor 3) Sandfilters 4) Activated carbon filter + biofilter 14Laboratory of Microbial Ecology and Technology

  15. Ex situ clean-up by m.o. • Griftpark (Utrecht, 1996) • Time scale : 1-3 centuries! • Price : • Investment: 150 x 106 EUR or 15 x 106 EUR/ha • Operation: 0,5 EUR/M3 water or 4000 EUR/ha.yr 15Laboratory of Microbial Ecology and Technology

  16. Ex situ clean-up by m.o. • Membrane-aerated biofilm reactor • No undesired coagulation of iron oxides • No stripping of 1,2 dichloroethane (DCA) (Hage et al., AMB 64, 718-725, 2004) 16Laboratory of Microbial Ecology and Technology

  17. Ex situ clean-up by m.o. Example: Pd-PCB Biopalladium byShewanella oneidensis MR-1 17Laboratory of Microbial Ecology and Technology

  18. Ex situ clean-up by m.o. • Catalytic activity in solution? PCB 21 PCB 173 Intermediates Biphenyl 18Laboratory of Microbial Ecology and Technology

  19. Ex situ clean-up by m.o. Catalytic activity in solution 19Laboratory of Microbial Ecology and Technology

  20. Ex situ clean-up by m.o. • Example: Budelco • Groundwater containing:several mg Zn2+/Lup to 1g SO42-/L Groundwater to discharge Biopaq – UASB reactor Aerobic reactor with limited oxygen supply 20Laboratory of Microbial Ecology and Technology

  21. Topics of discussion General considerations Ex situ clean-up by micro-organisms In situ clean-up by micro-organisms Future perspectives 21Laboratory of Microbial Ecology and Technology

  22. In situ clean-up by m.o. • Severalin situ bioremediation strategies (MNA, biostimulation, bioaugmentation), and several concepts to reach clean-up goals • None of them will be the solution for the total clean-up of a contaminated site (source versus plume) • None of them is the only answer for the problem 22Laboratory of Microbial Ecology and Technology

  23. Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl In situ clean-up by m.o. FAST DEGRADATION UNDER ANAEROBIC CONDITIONS SLOW DEGRADATION UDNER ANAEROBIC CONDITIONS Ox. Degree C +ll +l 0 -1/2 -l -3/2 -ll Ethenes PCE TCE cis-1,2-DCE VC etheen Ethanes 1,1,2-TCA 1,2-DCA Propanes 1,2-DCP propeen resistance against reductive degradation 23Laboratory of Microbial Ecology and Technology

  24. In situ clean-up by m.o. • Challenges for the anaerobic remediation of chlorinated ethenes in groundwater • DNAPL formation (inaccessibility) • Microbial degradation mechanism: reductive dehydrochlorination, but • Accumulation of recalcitrant and carcinogenic intermediates: cis-DCE and VC due to: • Oxidation degree of the intermediates • Competition for hydrogen • Complete degradation from PCE to ethene seems to be attainable if Dehalococcoides species are present, but it is not a guarantee! 24Laboratory of Microbial Ecology and Technology

  25. In situ clean-up by m.o. • Challenges for the anaerobic remediation of chlorinated ethenes in groundwater (competition for H2) (required hydrogen pressure) 25Laboratory of Microbial Ecology and Technology

  26. In situ clean-up by m.o. • The biodegradation of 1,2-dichloroethane by the anaerobic halorespiring bacteria:Desulfitobacterium dichloroeliminans strain DCA1 • The anaerobic strain respires 1,2-DCA and this process delivers energy! • Complete and fast degradationof high concentrations • No toxic intermediates like VC 26Laboratory of Microbial Ecology and Technology

  27. In situ clean-up by m.o. In situ pilot test in contaminated aquifer inoculum 27Laboratory of Microbial Ecology and Technology

  28. inoculum Wolk StamDCA1 28Laboratory of Microbial Ecology and Technology

  29. In situ clean-up by m.o. In situ pilot test in contaminated aquifer 29Laboratory of Microbial Ecology and Technology

  30. In situ clean-up by m.o. • Intensive monitoring of: • Physico-chemical parameters:pH, T, redox potential, D.O., conductivity • Chemical parameters:decrease 1,2-DCA and increase etheneno detection of VC and CH4 • Molecular parameters:concentration strain DCA1 through specific molecular techniques • Goal: in situ biodegradation and to obtain data for the simulation of the transport and the activity of strain DCA1 with MOCBAC-3D 30Laboratory of Microbial Ecology and Technology

  31. In situ clean-up by m.o. • Molecular confirmation of the transport of strain DCA1 from the injection well towards the monitoring well • Activity of the robust strain DCA1 in the injection well and monitoring well confirmed by: • Strong decrease in the 1,2-DCA concentration (e.g. from 1142 to 1µM in a time interval of 36 days) • Increase ETHENE concentration • NO production of vinyl chloride and CH4 • Excellent biodegradation capacity of strain DCA1 in reduced groundwater conditions 31Laboratory of Microbial Ecology and Technology

  32. In situ clean-up by m.o. • The degradation of carbon tetrachloride (CT): field evaluation of a full-scale bioaugmentation technique in a CT- and nitrate impacted aquifer (MI) • Inoculation of Pseudomonas stutzeri KC, a denitrifying bacterium that co-metabolically degrades CT without producing chloroform (CF) • Goal: to establish and maintain a “biocurtain” for CT degradation through • the intermittent addition of base to create favorable pH conditions; • inoculation strain KC; • weekly addition of acetate (electron donor), alkali, and phosphorus. 32Laboratory of Microbial Ecology and Technology

  33. In situ clean-up by m.o. 33Laboratory of Microbial Ecology and Technology

  34. In situ clean-up by m.o. • The degradation of CT: • High CT removal efficiencies (median of 98-99.9%) • Uniform removal efficiencies over a significant vertical depth (15 m), despite significant variability in hydraulic conductivity • Similar levels of strain KC colonization(>105 strain KC/g) • Sustained and efficient (98%) removal of CT has been observed over 4 yr • Low levels of CF (<20 ppb) and H2S (<2 ppm) 34Laboratory of Microbial Ecology and Technology

  35. In situ clean-up by m.o. • Approximately 18,600 m3 of contaminated groundwater was treated during the project • Closely spaced wells and intermittent substrateaddition were effective means of delivering organisms and substrates to subsurface environments. • Dybas et al. (2002) Environ. Sci. Technol. 3635-3644 35Laboratory of Microbial Ecology and Technology

  36. In situ clean-up by m.o. • Exxon Valdez (March 1989): spill of33.000 tons of crude oil in Alaska • 3500-5500 sea otters out of a total population in the region of approximately 35.000 • 300000-675000 seabirds perished 36Laboratory of Microbial Ecology and Technology

  37. In situ clean-up by m.o. • Oil degraders: • A lot of bacteria can degrade environmental pollutants such as oil • Three modes of microbial uptake: • Utilization of solubilized organic compound • Direct contact of cells (e.g. fimbrae) • Direct contact with fine substrate droplets • Enhanced uptake by the production of biosurfactans 37Laboratory of Microbial Ecology and Technology

  38. In situ clean-up by m.o. No biosurfactans => cells do not clump and do not stick to oil droplets oil 38Laboratory of Microbial Ecology and Technology

  39. In situ clean-up by m.o. Biosurfactans  cells stick to oil droplets 39Laboratory of Microbial Ecology and Technology

  40. Topics of discussion General considerations Ex situ clean-up by micro-organisms In situ clean-up by micro-organisms Future perspectives 40Laboratory of Microbial Ecology and Technology

  41. Future Perspectives • A wide variety of bioremediation strategies can be offered, based on the great diversity of ‘genetic capacity’ and ‘biological know-how’ present in the microbial ecosystem in the soil • These sustainable techniques can and will be applied in the future if: • They are proven to be safe • They are proven to offer protection to the environment over a long-term periods (monitoring) • They are studied by interdisciplinary research • They are integrated with other clean-up strategies to achieve a complete answer to the problem 41Laboratory of Microbial Ecology and Technology

  42. Take-home message • Microbial communities bring about a wide variety of powerfull processes. • We are able to use a number of these processes for soil clean-up purposes and to develop sustainabale and safe biotechnology-techniques. 42Laboratory of Microbial Ecology and Technology

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