Bioremediation: Treatment of Contaminated Sites PDF

1 Bioremediation: Treatment of Contaminated Sites Environmental Bioremediation 1  Biological Remediation or “Bioremediation” Application of microbial processes to remove or reduce the concentration of hazardous chemicals in contaminated groundw...

1 Bioremediation: Treatment of Contaminated Sites Environmental Bioremediation 1  Biological Remediation or “Bioremediation” Application of microbial processes to remove or reduce the concentration of hazardous chemicals in contaminated groundwater, soil and sediments to levels that are below the established environmental standards Accelerate natural biodegradation processes Environmental Bioremediation 2  Contaminant Removal by Indigenous Microorganisms Degradation of soil and groundwater contaminants including: – Industrial solvents – Aromatic and aliphatic hydrocarbons – Alcohols – Wood preservatives such as PCBs – Explosives such as TNT and agrochemicals Sequestration of metals and radionuclides: – Reduction of concentrations and mobility in the subsurface Bioremediation is especially effective for the removal of residual contamination Environmental Bioremediation 3  Site Zones Vadose zone or unsaturated zone: – Geological formation between the land surface and the saturation zone – Contains both water and air in pore spaces Saturated zone: – Geological formation below the water table – All open spaces are filled with water Capillary fringe: – Zone of soil immediately above the water table – Contains water in small pores that act like capillary tubes United States Geological Survey: http://geology.er.usgs.gov/eespteam/brass/ground/art/fig1 0_6.gif Environmental Bioremediation 4  Contaminated Site: Historical Facts Nearly 250,000 sites are contaminated worldwide and need to be remediated In Canada, according to the Federal Contaminated Sites Inventory (FCSI) (2023): 5,337 active contaminated sites exist 2,355 suspected sites are identified 17,059 sites are closed and require no further action Environmental Bioremediation 5  Municipal Farm and Industrial activities Agro Industry activities Waste streams; Solid wastes; Discharges, etc Mining Tailings Fertilizers, Transportation herbicides, insecticides Acid mine etc. drainage fuel VADOSE ZONE AQUIFER Environmental Bioremediation 6 Leaking Underground Storage Tank From Barlow and Philp, published in Atlas and Philp, 2005 Environmental Bioremediation 7 Leaking Underground Storage Tank: Remediation Example Environmental Health - Toxic Substances Hydrology Program, USGS, 2018 Methyl tert-butyl ether (MTBE) has often been added to gasoline as an octane enhancer and stabilizer Environmental Bioremediation 8 Example of Soil and Groundwater Contamination Storage tank https://oneclass.com/ Environmental Bioremediation 9  Bioremediation Mechanism Microorganisms destroy organic contaminants by using the chemicals/contaminants for their growth and reproduction – Organic chemicals provide: source of carbon, source of electrons, source of energy – Microbial cells catalyze oxidation of organic chemicals (electron donors), causing transfer of electrons from organic chemicals to an electron acceptor Environmental Bioremediation 10  Factors Controlling Site Bioremediation Nature and concentration of contaminants: toxicity, recalcitrance, chemical properties, e.g. vapor pressure, adsorption Type of microorganisms present at the site and their activities: e.g. indigeneous microorganisms Environmental conditions: pH, temperature, availability of terminal electron acceptors (TEAs), nutrients, etc. Geological characteristics of the site: stratigraphy, geochemistry, bedrock properties, soil permeability etc. Hydrogeological characteristics: depth to groundwater, type of aquifer, hydraulic parameters (conductivity, porosity, etc.) Contaminant bioavailability Environmental Bioremediation 11 Microbial Biodegradation Environmental Bioremediation 12  What is Biodegradation? Breakdown of organic compounds by microorganisms through metabolic processes Extent and rate of biodegradation depend on: – Type of the microorganisms involved in the process – Type of contaminants – Environmental conditions Environmental Bioremediation 13 Persistence of Hazardous Compounds in the Environment Hazardous compounds persist in the environment because: – Recalcitrance – Toxicity – Lack of bioavailability – Unfavorable environmental conditions Environmental Bioremediation 14 Site Remediation Methods Environmental Bioremediation 15  Unsaturated Zone Remediation Methods Physical-chemical methods (In situ or Ex situ): – Soil washing – Thermal desorption – Incineration – Solidification and stabilization – Soil vapor extraction – In situ soil flushing Bioremediation methods (In situ or Ex situ): – Bioventing – Natural attenuation – Slurry bioreactors – Biopile – Landfarming Environmental Bioremediation 16  Saturated Zone Remediation Ex situ: – Pump and treat: Physical-chemical or biological methods In situ: – Air stripping – Surfactant introduction – Chemical oxidation (ISCO) – In situ bioremediation Environmental Bioremediation 17  Pump and Treat Operation: Ex Situ Treatment of Groundwater EPA/600/8-90/003 Environmental Bioremediation 18  Decontamination of Groundwater by In Situ Chemical Oxidation (ISCO) ISCO involves the injection of chemical oxidants, e.g. permanganate, persulfate, and hydrogen peroxide into the subsurface https://www.frtr.gov/matrix/In-Situ-Chemical-Oxidation/ Environmental Bioremediation 19  In Situ Remediation: In Situ Treatment of Groundwater in situ groundwater redox manipulation http://oceanworld.tamu.edu/resources/environment-book/groundwaterremediation.html Environmental Bioremediation 20 Bioremediation Environmental Bioremediation 21  Advantages/Benefits of Bioremediation Lower cost compared to physical-chemical techniques Destruction of hazardous chemicals Relatively inexpensive inputs requirement, e.g. nutrients No residuals in situ possibility Environmental Bioremediation 22  Removal of Metals or Metal Toxicity from Contaminated Sites during Bioremediation Stabilization of metals by promoting their precipitation as hydroxides, carbonates, phosphates and sulfides, for example: – Biological sulfate reduction by sulfate reducing bacteria (SRB), whereby redox reactions lead to precipitation of metals as sulfide Toxicity reduction, e.g. chromium toxicity decreases upon reduction from Cr(VI) into Cr(III) Uptake, accumulation, and concentration of metals: Biosorption Bioaccumulation Environmental Bioremediation 23  Limitations of Bioremediation Lack of removal of chemicals toxic to microorganisms Low efficiency under adverse environmental conditions Limited capacity in the remediation of heavy metals, particularly those that are not readily absorbed or captured (bioaccumulated) by microorganisms, such as lead Environmental Bioremediation 24 Bioremediation Technologies Environmental Bioremediation 25  Classification of Bioremediation Technologies Classification of bioremediation: – In situ – Ex situ In situ bioremediation: Treatment at the site without excavation of soil or withdrawal of groundwater. Examples: – Natural attenuation, bioventing, air sparging, in situ landfarming, bioaugmentation and biostimulation Ex situ bioremediation: Removal of contaminated material, i.e. soil, groundwater or sediment, and treatment above-ground. Examples: – Surface reactors, biopile and ex situ landfarming Environmental Bioremediation 26  In Situ Bioremediation http://library.thinkquest.org/03oct/01840/types_of_bioremediation.htm Environmental Bioremediation 27  Ex-Situ Bioremediation Pumping of the groundwater or excavation of contaminated soil, including the following processes: ▪ Liquid phase ▪ Slurry-phase ▪ Solid-phase Environmental Bioremediation 28 Advantages of In Situ Bioremediation Compared to Ex Situ Bioremediation More cost effective than ex situ technologies: Lack of excavation or extraction and transportation of contaminated material Can be employed in areas that are inaccessible: Example: Upstream introduction of electron acceptor or electron donor amendment without the need for excavation of soil or extraction of groundwater Environmental Bioremediation 29 In Situ Bioremediation Technologies Environmental Bioremediation 30  Types of In Situ Bioremediation Technologies Examples of in situ bioremediation technologies include: – Biobarrier – Intrinsic bioremediation or natural attenuation – Biostimulation – Bioaugmentation – Bioventing – Air sparging – Landfarming Environmental Bioremediation 31  Biobarrier Technology: Permeable Reactive Barriers (PRBs) A bioreactive zone that removes the contaminants by biological degradation processes http://www.powellassociates.com/sciserv/3dflow.html Environmental Bioremediation 32  Intrinsic Bioremediation/ Natural Attenuation Relies on natural processes to clean up or attenuate contaminants in soil and groundwater Occurs to various degrees at most contaminated sites: requires right environmental conditions Commonly observed in petroleum contamination sites such as old gas stations with leaky underground oil tanks Monitored natural attenuation or MNA Environmental Bioremediation 33  Natural Attenuation http://www.eas.slu.edu/People/DJCrossley/scomm/images/fig1.jpg Environmental Bioremediation 34  Bioventing An in situ process used predominantly for the treatment of unsaturated zone (soil) contaminated with petroleum products Involves the venting of oxygen through soil, to stimulate the growth and activity of indigenous microorganisms for biodegradation of organic constituents Uses low air flow rates to minimize volatilization of contaminants All aerobically biodegradable constituents can be treated by bioventing Environmental Bioremediation 35  Typical Bioventing Operation http://enviro.nfesc.navy.mil/erb/erb_a/restoration/technologies/remed/bio/pres_biovent.pdf Environmental Bioremediation 36  Air Sparging An in situ process that involves injecting air directly into the saturated zone (groundwater) Air sparging remediates groundwater by two processes: volatilization and biodegradation Volatilization, often followed by a soil vapor extraction (SVE) system to remove the vapors from the unsaturated zone (soil) Biodegradation takes place by the naturally-occurring (indigenous) consortium of microorganisms Environmental Bioremediation 37  Typical Air Sparging Operation http://www.epa.gov/OUST/pubs/tum_ch7.pdf Environmental Bioremediation 38 Ex Situ Bioremediation Technologies Environmental Bioremediation 39  Ex Situ Bioremediation Technologies Examples of ex situ bioremediation technologies include: – Surface Bioreactors – Biopile – Landfarming Environmental Bioremediation 40  Surface Bioreactors Treatment of contaminated groundwater, soil or sludge under controlled environmental conditions Used when in situ decontamination techniques are ineffective, requiring the excavation of soil or extraction of groundwater Culture reactor or “enricher reactors” are usually used to propagate specific types of microorganisms with the desired capabilities for bioaugmentation in the reactors Environmental Bioremediation 41  Full-Scale Decontamination of Groundwater by Bioreactors Bioreactor Nutrients http://ewr.cee.vt.edu/environmental/teach/gwprimer/bioreact/bior.html Environmental Bioremediation 42  Biopile Technology This ex situ process involves: – Mixing contaminated soil with amendments – Incubating the entire mixture under controlled environmental conditions – Monitoring and maintenance of environmental conditions Environmental Bioremediation 43  Biopile Technology http://www.nodump.ca/filestore/Biopile.jpg Environmental Bioremediation 44  Landfarming Landfarming or land treatment or land application: Treatment of contaminated soil and sediment Required steps: Excavation of soil, mixing with soil amendments such as soil bulking agents and nutrients, spreading in a thin layer on the ground surface, tilling into the earth Increasing the activity of indigenous aerobic microbial consortium within the soil through aeration and/or the addition of nutrients and moisture and enhanced by periodical tilling Can be carried out in situ or ex situ depending on the depth of contamination Environmental Bioremediation 45  Landfarming hat Operation Contaminated soil Groundwater Tilling for soil monitoring well aeration Leachate collection http://www.epa.gov/OUST/pubs/tum_ch5.pdf Environmental Bioremediation 46  References 1. Bioremediation: A Critical Review Head, I. M., Singleton, I. and Milner, M.G., 2003 2. Bioremediation: Applied Microbial Solutions for Real-World Environmental Cleanup Atlas R. M. and Philp, J., ASM Press, 2005 3. Environmental Biotreatment: Technologies for Air, Water, Soil, and Waste Mulligan, C. N., 2002 4. Manual of Environmental Microbiology Hurst, C. J. et al., ASM Press, 2002 Environmental Bioremediation 47