522 bioremediation

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Information about 522 bioremediation
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Published on January 19, 2008

Author: Penelope

Source: authorstream.com

Biodegradation (Biooxidation):  Biodegradation (Biooxidation) The biochemical transformation of an organic chemical to another form as a result of highly complex chain of events interacted between the specific compound, microorganism, and the environmental conditions. Operational Categories:  Operational Categories Primary biodegradation Minimal amount of change Ultimate biodegradation Conversion into CO , H O, CH , and inorganic substances 2 4 2 Acceptable biodegradation Change to a non-toxic compound Acclimated Culture:  Acclimated Culture • Selection of populations by controlling environmental factors to encourage only the desired species. • An increase in the biodegradation rate of a chemical after exposure of the microbial community to the chemical for some period of time. Example of Acclimation:  Example of Acclimation Mutated Pure Culture:  Mutated Pure Culture Selection of highly efficient pure mutant cultures in breaking down a particular type of waste. Bioengineered Bacteria:  Bioengineered Bacteria Alteration of the DNA code of the existing species or development of new bacteria through gene splicing techniques of molecular biology. Persistent Compound:  Persistent Compound A chemical that fails to undergo biodegradation under a specific set of conditions. A chemical may be inherently biodegradable yet persist in the environment. PCBs in Hudson River Aroclor 1254 Aerobic Anaerobic Minimal degradation Extensive transformation Recalcitrant Compound:  Recalcitrant Compound A chemical that has an inherent resistance to any degree of biodegradation. e.g., toxaphene, dieldrin, endrin Biogenic Compounds:  Biogenic Compounds Naturally occurring compounds that have been present for millions of years. Thus, there are organisms somewhere in the biosphere that can initiate their biodegradation. Xenobiotic Compounds:  Xenobiotic Compounds Compounds that are foreign to the biosphere, having been present for only an instant on the evolutionary time scale. May or may not be biodegradable. Bioremediation/Biotreatment:  Bioremediation/Biotreatment The manipulation of living systems to bring about desired chemical and physical changes in a confined and regulated environment. Gratuitous Metabolism:  Gratuitous Metabolism Reactions involving enzymes having high substrate specificity with respect to catalytic function but low specificity with respect to substrate binding. Relationship between Enzyme Action and Gratuitous metabolism:  Relationship between Enzyme Action and Gratuitous metabolism Cometabolism/Cooxidation:  Cometabolism/Cooxidation The transformation of a non-growth substrate in the obligate presence of a growth substrate or another transform- able compound. Distinction between Surface and Subsurface Remediation:  Distinction between Surface and Subsurface Remediation Surface treatment Dominant electron acceptor is oxygen supplied directly from the atmosphere. Subsurface treatment Electron acceptor is supplied by perfusing the contaminated material with water or air. Treatability Protocols Properties Assessed:  Treatability Protocols Properties Assessed • Biodegradability of contaminants - aerobic - anaerobic • Effectiveness of nutrient amendments - inorganic supplements (N, P, S) - electron acceptors - organic supplements Slide17:  Treatability Protocols Properties Assessed - continued • Effectiveness of inocular - cultures of natural organisms - specific degraders • Nondegradative losses - volatilization - sorption - leaching • Genotoxicity of the waste Protocol Components:  Protocol Components • Scope and approach • Summary and method • Collection and sampling of site materials Sample selection Sample collection Sample characterization Sample transportation Sample preservation Sample holding times Slide19:  Protocol Components (continued) • Apparatus and materials Reactor components Reactor design • Procedures Reactor setup Reactor operation Analysis of reactor contents Reactor configurations Minimal treatment Intermediate treatments Complete treatment Slide20:  • Data recording and analysis Data to be reported Determination of degradation rates • References General Chemical analysis Sampling Protocol Components (continued) Treatability Protocols Soils - Aerobic:  Treatability Protocols Soils - Aerobic Interim Protocol for Determining the Aerobic Degradation Potential of Hazardous Organics in Soil, Biosystems Technology Development Program, U.S. EPA, September 1988. Uses four reactor configurations No tillage Periodic tillage Forced aeration Soil slurry Measures loss of target chemicals Corrects for volatile losses Requires psuedo-mass balance Slide22:  Pesticide assessment guidelines subdivision N Chemistry: Environmental Fate, Office of Pesticides and Toxic Substances, U.S. EPA, Washington, D.C., October 1982. Uses waterlogged soils (30 days) One reactor design Measures loss of product Strict anaerobic conditions optional Treatability Protocols Soils – Aerobic - continued Slide23:  Not available Treatability Protocols Suboils – Aerobic - continued Slide24:  Treatability Protocols Subsurface - Anaerobic • Anaerobic Microbiological Transformation Rate Data for Chemicals in the Subsurface Environment, Federal Register, Vol. 53, No. 115, pp. 22320-22323, June 1988. • Methanogenic • Sulfate reducing • Serum bottles for reaction vessels • Requires strict anaerobic technique • Designed for subsurface materials • Uses 20% (w/v) slurries • Could be modified for denitrifying conditions • Measures loss of target chemicals Slide25:  Treatability Protocols Sediments - Aerobic Under development Slide26:  Treatability Protocols Sediments - Anaerobic • Anaerobic Microbiological Transformation Rate Data for Chemicals in the Subsurface Environment, Federal Register, Vol. 53, No. 115, pp. 22320-22323, June 1988. • Methanogenic • Sulfate reducing • Serum bottles for reaction vessels • Requires strict anaerobic technique • Designed for subsurface materials • Uses 20% (w/v) slurries • Could be modified for denitrifying conditions • Measures loss of target chemicals Slide27:  Treatability Protocols Water - Aerobic Under development Slide28:  Treatability Protocols Water - Anaerobic • Shelton, D. R. and Tiedje, J. M. 1984. General Method for Determining Anaerobic Biodegradation Potential, Applied Environ. Microbiol. Vol. 47, pp. 850-857. • Methanogenic • Sulfate reducing • Serum bottles for reaction vessels • Requires strict anaerobic technique • Designed for subsurface materials • Uses 20% (w/v) slurries • Could be modified for denitrifying conditions Slide29:  29 Slide30:  Control Intermediate Maximal Time Compound loss Data Analysis Experimental Design:  Experimental Design • Controls: sterile, no treatment, field background, number? • Replicates: duplicate or triplicate? all time points? all controls? • Treatment: what are the questions you want answered? • How are you going to optimize the degradation process? Slide32:  Experimental Design (continued) • Treatment time: how long should the study be performed? • Types of analysis: bulk measurement? waste specific? • Data reduction: raw data? massaged data? QC/QA? • Cost considerations: how will it limit scope of test? Summary:  Summary • Clearly define the scope of work • Look for well controlled studies • Look for statistically valid experimental design • Always look at the raw data and formulate your own opinion • Beware of the limitations of standard methodologies • Always seek expert opinion and independent evaluation Bioremediation Limiting Factors:  Bioremediation Limiting Factors Distribution of the waste which may limit microorganism access to the waste Supply of nutrients required for metabolism Toxicity of the waste due to concentration and/or type of constituents present Formation and accumulation of toxic byproducts (1) (2) (3) (4) Slide35:  Bioremediation Limiting Factors - continued Inadequate population(s) of requisite microorganisms Non-competitiveness of non-survivability of inoculated cultures Inadequate management of the system (5) (6) (7) Enhancement of Soil/Site Assimilative Capacity:  Enhancement of Soil/Site Assimilative Capacity (1) Soil mixing (2) Aeration of the soil (3) Addition of nutrients (4) Addition of carbon and energy sources (5) Water addition (irrigation) (6) Drainage (7) Runon and runoff controls (8) pH adjustment Ways to Maximize Available Soil Oxygen:  Ways to Maximize Available Soil Oxygen • Prevent water saturation • Presence of sand, loam (not heavy clay) • Moderate tilling • Avoid compaction • Controlled waste loading Effect of Manure and pH Amendments on PAHs Degradation in a Complex Waste Incorporated into Soil:  Effect of Manure and pH Amendments on PAHs Degradation in a Complex Waste Incorporated into Soil PAH compound Half-life in waste:soil mixture (days) Without amendments With amendments Acenaphthylene Anthracene Phenanthrene Fluoranthene Benz(a)anthracene Benz(a)pyrene Dibenz(a,h)anthracene 78 28 69 104 123 91 179 14 17 23 29 52 69 70 38 Effect of Soil Moisture on PAHs Degradation:  Effect of Soil Moisture on PAHs Degradation Moisture (field capacity) 20 - 40 60 - 80 Anthracene 43 37 Phenanthrene 61 54 Fluoranthene 559 231 Half-life (days) Formulation of Nutrient Mix:  Formulation of Nutrient Mix • Usually determined empirically • Not related to C:N:P:S ratios Use high concentrations to project significant concentrations into the aquifer • Should formulations be related to C:N:P:S ratios? Properties of Molecular Oxygen:  Properties of Molecular Oxygen Advantages • Low toxicity to acclimated organisms • Supports biodegradation of many organic chemicals • Inexpensive Disadvantages • Low solubility in water • Will precipitate iron hydroxide Slide42:  Properties of Hydrogen Peroxide Advantages • Miscible in water • Supports biodegradation of many organic chemicals • Chemically oxidizes many organic and inorganic contaminants Disadvantages • Toxic at  500 mg/L • Will precipitate iron hydroxide • Relatively expensive Slide43:  Properties of Nitrate Advantages • Very soluble in water • Low toxicity to microorganisms • No precipitation of iron hydroxide • Inexpensive Disadvantages • A regulated substance • Potential for accumulation of nitrite • Only aromatics are removed Cost Comparison of Electron Acceptors:  Cost Comparison of Electron Acceptors Electron acceptors Sodium nitrate Liquid oxygen Hydrogen peroxide Bulk cost (per kg) $0.66 $1.46 $1.54 Electrons accepted (moles/kg) 58.8 125.0 58.8 Real cost (per moles of electrons accepted) $1.12 $1.17 $2.62 Advantages of Pulsing Amendments:  Advantages of Pulsing Amendments If more than one amendment is required to promote subsurface bioremediation, they can be injected in alternating pulses. This prevents undue production of biomass near the injection system, which would otherwise plug the system. High concentrations of hydrogen peroxide (> 100,000 mg/L) can remove biofouling and restore the efficiency in injection wells or injection galleries. Pulses of hydrogen peroxide at high concentration can sterilize the aquifer and destroy catalase activity, preventing premature decomposition of the peroxide. Sampling Frequency:  Sampling Frequency The frequency of sampling should be related to the time expected for significant changes to occur along the most contaminated flow path. Important considerations • Time required for water to move from injection wells to the monitoring wells • Seasonal variations in water-table elevation or hydraulic gradient • Changes in the concentration of electron acceptor • Cost of monitoring compared to day-to-day cost of operation Factors Controlling the Rate and Extent of Bioremediation at Field Scale:  Factors Controlling the Rate and Extent of Bioremediation at Field Scale • Rate of supply of essential nutrients, usually the electron acceptor • Spatial variability in flow velocity • Seclusion of the waste from the microorganisms Interpretation of Treatability Studies:  Interpretation of Treatability Studies A good treatability study determines whether bioremediation is possible and whether there are any biological barriers to attaining the goal for clean-up. It can also provide an estimate on the rate of remediation that can be attained if the organisms are not limited by the rate of supply of some nutrient. Performance Evaluation - Monitoring:  Performance Evaluation - Monitoring • Soil cores • Soil-pore liquid • Groundwater • Runoff water • Air Slide50:  Hydrogen peroxide injected 7 ft from injection wells Oxygen injected 7 ft from injection wells 31 ft from injection wells 50 ft from injection wells mg O /L day 60 20 8.1 7.3 Rates of Oxygen Consumption in the Most Contaminated Flow Path at Traverse City 2 50 Bioremediation Study Costs:  Bioremediation Study Costs Laboratory treatability study 50,000-100,000 Pilot-scale study 150,000-200,000 Full-scale study 400,000 + Scope Current dollars Field Implementation Costs:  Field Implementation Costs • Land area requirements • Site preparation • Amendments • Equipment • Maintenance • Monitoring Subsurface Remediation:  Subsurface Remediation Hazardous wastes that occur as a discrete oily-phase act as source areas for plumes of contamination in groundwater. They also contaminate the soil air with hazardous fumes. The primary emphasis in subsurface bioremediation has been the source areas. Subsurface bioremediation of the plumes is often technically feasible, but it is usually easier to pump then out and treat them on the surface. Rate of Bioremediation:  Rate of Bioremediation If the supply of mineral nutrients is adequate, the rate of bioremediation is the rate of supply of electron acceptor. As a result, the rate of remediation is directly proportional to the concentration of electron acceptor in the injected water and the flow velocity of water through the source area. Time Required for the Most Contaminated Area Clean-up:  Time Required for the Most Contaminated Area Clean-up Time required to clean most contaminated flow path Length of path through source area Concentration of contaminant along flow path Seepage velocity along the most contaminated flow path  × Control of Hydrology on the Rate of Remediation:  Control of Hydrology on the Rate of Remediation Seepage velocity  Hydraulic permeability × Hydraulic gradient Hydraulic permeability is an intrinsic property of the subsurface. It is difficult or impossible to improve it, but it is easily degraded. The hydraulic gradient is controlled by the amount of water available for pumping, and by the difference in elevation between the source area and the land surface. Bioremediation:  Bioremediation 57 Problems with Wells As Monitoring Tools:  Problems with Wells As Monitoring Tools Treatment can occur in the well itself. The water in the well may not be representative of the water in the aquifer. A conventional monitoring well produces a composited water sample. Water from the most contaminated flow path is diluted by water from many other flow paths that are less contaminated. A water sample from a well tells nothing about the amount of hazardous material that is sorbed to aquifer solids or is trapped as an oily phase. Co-distribution of Contamination and Hydraulic Permeability in an Aquifer Contaminated by a Fuel Spill :  Co-distribution of Contamination and Hydraulic Permeability in an Aquifer Contaminated by a Fuel Spill Depth interval (ft below surface interval cored or screened interval) Fuel hydrocarbons (mg/kg aquifer) Seepage velocity (ft/day) 15.1 - 15.5 15.5 - 15.8 15.8 - 16.2 16.2 - 16.5 16.5 - 17.2 17.2 - 17.5 18.0 - 18.3 19.4 - 19.6 20.9 - 21.4 < 11 39 2370 8400 624 < 13 < 13 7.2 9.0 15.6 19.7 59 Slide60:  The migration of a plume away from its source area can often be prevented by capturing the plume with a purge well. The well must pump hard enough to overcome regional flow in the aquifer. The flow from purge wells that is necessary to capture a plume depends on the hydraulic permeability of the aquifer, the regional hydraulic gradient, and the size of the source area. Hydraulic Containment In Situ Bioremediation:  In Situ Bioremediation Water table Infiltration gallery Control building To carbon filter Contaminated area Mineral nutrients Nitrate solution 61

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