Application of in-situ bioremediation to a gasoline spill in fractured bedrock

After achieving remediation goals during only thirty-two months of operation, the first full-scale in-situ bioremediation (ISB) system in the state of Missouri was shut down in 1990. In addition to ISB, the system included a combination of soil venting and air stripping to remediate subsurface gasoline contamination at a large manufacturing facility. More than 84,000 pounds of gasoline were degraded or removed from the fractured limestone bedrock aquifer and overburden materials. The successful application of ISB in this complex geologic environment and the fact that this was the first such system to complete remediation in Missouri make this system unique.     

A systematic approach to in situ bioremediation in groundwater

In situ bioremediation (ISB) melds an understanding of microbiology, chemistry, hydrogeology, and engineering into a strategy for planned and controlled microbial degradation of specific contaminants. ISB creates subsurface environmental conditions, typically through reduction oxidation manipulation, which induce the degradation of contaminants via microbial catalyzed biochemical reactions. In turn, the microbes produce enzymes that are utilized to derive energy and that are instrumental in the degradation of target chemicals. To accomplish this chain of events, the type of microorganisms, contaminant, and the geological conditions at the site must be considered. Since in situ conditions are manipulated by engineered means, the most important consideration is the ability to transmit and mix liquids in the subsurface. The Interstate Technology Regulatory Council (ITRC)–ISB Team has recently completed a guidance document that describes a systematic approach to ISB in groundwater. ITRC is a state‐led coalition of more than 40 states working together with industry and stakeholders to achieve regulatory acceptance of environmental technologies. © 2003 Wiley Periodicals, Inc.     

In situ bioremediation of a hydrocarbon polluted site with cyclodextrin as a coadjuvant to increase bioavailability

Bioavailability is one main factor that influences the extent of biodegradation of hydrocarbons. They are very poorly soluble in water and easily adsorbed to clay or humus fractions, so they pass very slowly to the aqueous phase where they are metabolised by microorganisms. Cyclodextrins are natural compounds that form soluble inclusion complexes with hydrophobic molecules and increase degradation rate of hydrocarbons in vitro. In the perspective of an in situ application, we previously checked that -cyclodextrin does not increase eluviation of hydrocarbons through the soil and consequently does not increase the risk of groundwater pollution. The results of an in situ application of -cyclodextrin for bioremediation of a hydrocarbon polluted site are presented. We stated that the combination of bioaugmentation and enhanced bioavailability due to -cyclodextrin was effective for a full degradation.     

DOE genomics: Applications to in situ subsurface bioremediation

Microbial communities can greatly affect the mobility and fate of subsurface contaminants, yet relatively little is known about the functioning of microorganisms in subsurface environments. Major advances in DNA sequencing capability and the advent of genome‐enabled studies have produced key insights into how microorganisms adapt to environmental conditions and/or biotransform subsurface contaminants starting from analyses of genome content. These techniques enable the researcher to detect how an organism responds to its environment and, potentially, to devise better methods to promote specific microbial activity in subsurface environments. The U.S. Department of Energy sponsors genome research through the Genomics:GTL program. One of the applications of this research is to better understand and control biological processes influencing the mobility of contaminants of concern to DOE such as metals and radionuclides. Genome and gene expression techniques have led to new insights into the functioning of subsurface microbial communities, but the true potential of these techniques is still to be revealed. As genome‐enabled science progresses, techniques for evaluating gene expression patterns of whole communities will advance the understanding and development of optimized in situ bioremediation and more realistic simulations of microbial contaminant biotransformation. © 2006 Wiley Periodicals, Inc.*     

Case study of ex situ remediation and conversion to a combined in situ/ex situ bioremediation approach at an oxygenated gasoline release site

In response to an oxygenated gasoline release at a gas station site in New Hampshire, a temporary treatment system consisting of a single bedrock extraction well, a product recovery pump, an air stripper, and carbon polishing units was installed. However, this system was ineffective at removing tertiary butyl alcohol from groundwater. The subsequent remedial system design featured multiple bedrock extraction wells and an ex situ treatment system that included an air stripper, a fluidized bed bioreactor, and carbon polishing units. Treated effluent was initially discharged to surface water. Periodic evaluation of the remediation system performance led to system modifications, which included installing an additional extraction well to draw contaminated groundwater away from an on‐site water supply well, adding an iron and manganese pretreatment system, and discharge of treated effluent to an on‐site drywell. Later, the air stripper and carbon units were eliminated, and an infiltration gallery was installed to receive treated, oxygenated effluent in order to promote flushing of the smear zone and in situ bioremediation in the source area. This article discusses the design, operation, performance, and modifications to the remediation system over time, and provides recommendations for similar sites. © 2007 Wiley Periodicals, Inc.     

Slurry phase bioremediation of PAHs in industrial landfill samples at laboratory scale

The effect of Tween 80 and selected bacteria additions on the bioremediation of PAH contaminated landfill soil (70.38mgkg(-1)) was evaluated in a slurry phase bioreactor. A phenanthrene-degrading consortium was selected by enrichment cultures and used as autochthonous inoculum. The Tween 80 addition increased the aqueous concentration of both high and low molecular weight PAHs. In the experiment with Tween 80 and inoculum addition, added microorganisms improved (>90%) the biodegradation of two- and three-ring PAHs as well as of the four-ring PAHs pyrene and fluoranthene. Biodegradation of the higher molecular weight PAHs was about 30% in experiments with Tween 80 addition, with and without inoculum addition.     

Evolution of predictive tools for in situ bioremediation and natural attenuation evaluations

Proving the viability of in situ bioremediation technologies and gathering data for its full‐scale implementation typically involves collecting multiple rounds of data and often completing microcosm studies. Collecting these data is cumbersome, time‐consuming, costly, and typically difficult to scale. A new method of completing microcosm studies in situ using an amendable sampling device deployed and incubated in groundwater monitoring wells provides actionable data to expedite site cleanup. The device, referred to as a Bio‐Trap® sampler, is designed to collect actively colonizing microbes and dissolved organic compounds from groundwater for analysis using conventional analytical techniques and advanced diagnostic tools that can answer very specific design and viability questions relating to bioremediation. Key data that can be provided by in situ microcosm studies using Bio‐Trap® samplers include definitively demonstrating contaminant destruction by using compound‐specific isotope analysis and providing data on the mechanism of the degradation by identifying the responsible microbes. Three case studies are presented that demonstrate the combined flexibility of Bio‐Trap® samplers and advanced site diagnostics. The applications include demonstrating natural attenuation of dissolved chlorinated solvents, demonstrating natural attenuation of dissolved petroleum compounds, and using multiple Bio‐Trap® samplers to comparatively assess the viability of bioaugmentation at a chlorinated solvent release site. At each of these sites, the in situ microcosm studies quickly and cost‐effectively answered key design and viability questions, allowing for regulatory approval and successful full‐scale implementation. © 2010 Wiley Periodicals, Inc.     

Real time oil spill forecasting during an experimental oil spill in the arctic ice

The oil spill trajectory and weathering model OILMAP was used to forecast spill trajectories for an experimental oil spill in the Barents Sea marginal ice zone. The model includes capabilities to enter graphically and display environmental data governing oil behavior: ice fields, tidal and background current fields, and wind time series, as well as geographical map information. Forecasts can also be updated from observations such as airplane overflights. The model performed well when wind was ‘off-ice’ and speeds were relatively low (3–7 m s⁻¹), with ice cover between 60 and 90%. Errors in forecasting the trajectory could be directly attributed to errors in the wind forecasts. Appropriate drift parameters for oil and ice were about 25% of the wind speed, with an Ekman veering angle of 35° to the right. Ice sheets were typically 1 m thick. When the wind became ‘on-ice’, wind speeds increased to about 10 m s⁻¹ and trajectory simulations began to diverge from the observations, with observed drift parameters being 1.5% of the wind speed, with a 60° veering angle. Although simple assumptions for the large scale movement of oil in dense ice fields appear appropriate, the importance of good wind forecasts as a basis for reliable trajectory prognoses cannot be overstated.     

A universal design approach for in situ bioremediation developed from multiple project sites

This article describes a design approach that has been developed for bioremediation of chlorinated volatile organic compound–impacted groundwater that is based upon experience gained during the past 17 years. The projects described in the article generally involve large‐scale enhanced anaerobic dechlorination (EAD) and combined aerobic/anaerobic bioremediation techniques. Our design approach is based on three primary objectives: (1) selecting and distributing the proper additives (including bioaugmentation) within the targeted treatment zone; (2) maintaining a neutral pH (and adding alkalinity when needed); and (3) sustaining the desired conditions for a sufficient period of time for the bioremediation process to be fully completed. This design approach can be applied to both anaerobic and aerobic bioremediation systems. Site‐specific conditions of hydraulic permeability, groundwater velocity, contaminant type and concentrations, and regulatory constraints will dictate the best remedial approach and design parameters for in situ bioremediation at each site. The biggest challenges to implementing anaerobic bioremediation processes are generally the selection and delivery of a suitable electron donor and the proper distribution of the donor throughout the targeted treatment zone. For aerobic bioremediation processes, complete distribution of adequate concentrations of a suitable electron acceptor, typically oxygen or oxygen‐yielding compounds such as hydrogen peroxide, is critical. These design approaches were developed based on understanding the biological processes involved and the mechanics of groundwater flow. They have evolved based on actual applications and results from numerous sites. An EAD treatment system, based on our current design approach, typically uses alcohol as a substrate, employs groundwater recirculation to distribute additives, and has an operational period of two to four years. An aerobic in situ treatment system based on our current design approach typically uses pure oxygen or hydrogen peroxide as an electron acceptor, may involve enhancements to groundwater flow for better distribution, and generally has an operational period of one to four years. These design concepts and specific project examples are presented for 17 sites. © 2012 Wiley Periodicals, Inc.     

In situ treatment of a dilute chlorinated solvent plume in an acidic aerobic aquifer

In situ bioremediation was selected in the Record of Decision (ROD) as the remedial technology for a 29‐acre dilute, acidic and aerobic, chlorinated solvent plume (principally trichloroethylene [TCE] and 1,1‐dichloroethylene) for a Superfund site located in central New Jersey. Implementation of the remedy at full‐scale began in late 2010, using reductive dechlorination and bioaugmentation, and treatment has continued steadily over the last 9 years. The amendments injected include electron donor and alkaline (bicarbonate) buffer solution and, once anaerobic aquifer conditions became established, a bioaugmentation culture. Amendment injections occurred in multilevel injection wells (IWs), to maintain control over the vertical interval of amendment delivery. The areal coverage of the plume has been reduced by 59% based on the 10 µg/L TCE isocontour and the contaminant mass has been reduced by 79% through the 9 years of treatment. Lessons learned from this project include the need for bioaugmentation in the acidic aquifer and an efficient and effective manner of well construction and amendment injection using multiscreen single casing IWs and packer systems. Additional lessons learned include differences in longevity of the electron donor amendment versus the bicarbonate neutralization additive, and the need for varied amendment delivery techniques (IWs, direct injection, horizontal well installation) in selected lower permeable zones to attain treatment.     

Pilot‐scale evaluation of in situ cometabolic bioremediation of TCE in groundwater using PHOSter® technology

A study was conducted to evaluate the efficacy of PHOSter® technology for treating groundwater contaminated with trichloroethene (TCE) at Edwards Air Force Base, California. The technology consists of injecting a gaseous mixture of air, methane, and nutrients into groundwater with the objective of stimulating the growth of methanotrophs, a naturally occurring microbial group that is capable of catalyzing the aerobic degradation of chlorinated solvents into nontoxic products. Injection operations were performed at one well for a period of three months. Six monitoring wells were utilized for groundwater and wellhead vapor monitoring and for groundwater and microbial sampling. In the five monitoring wells located within 44 feet of the injection well, the following results were observed: dissolved oxygen concentrations increased to a range between 6 and 8 milligrams per liter (μg/L); the biomass of target microbial groups increased by one to five orders of magnitude; and TCE concentrations decreased by an average of 92 percent, and to below the California primary maximum contaminant level (MCL; 5 micrograms per liter [µg/L]) in the well closest to the injection well. © 2008 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

     

Enhanced intrinsic bioremediation of hydrocarbons using an oxygen-releasing compound

An “oxygen barrier” was formed by depositing an oxygen-releasing compound in a series of wells that were placed perpendicular to the direction of groundwater flow at a site in Belen, New Mexico. The objective was to enhance the intrinsic bioremediation of dissolved phase BTEX contamination in the aquifer and to quantify the results. The oxygen was supplied by a controlled release formulation of magnesium peroxide called Oxygen Release Compound (ORC®), a virtually insoluble powder that is packaged in polyester filter socks. The areal distributions of the initial concentrations of dissolved oxygen and BTEX were measured and compared to the concentration changes at various times in the first 93 days of system operation. The concomitant reduction in BTEX can be seen in a series of contour plots. In 93 days, dissolved oxygen had dispersed at least 20-feet downgradient from the ORC source wells based on the pattern of decreasing BTEX concentrations.     

In situ remediation of arsenic in contaminated soils

In situ chemical fixation represents a promising and potentially cost‐effective treatment alternative for metal‐contaminated soils. This article presents the findings of the use of iron‐bearing soil amendments to reduce the leachability and bioaccessibility of arsenic in soils impacted by stack fallout from a zinc smelter. The focus of this investigation was to reduce the lead bioaccessibility of the soils through addition with phosphorus‐bearing amendments. However, as phosphorus addition was expected to increase arsenic mobility, the fixation strategy also incorporated use of iron‐bearing amendments to offset or reverse these effects. The findings of this investigation demonstrated that inclusion of iron‐bearing chemicals in the amendment formulation reduced arsenic leachability and bioaccessibility without compromising amendment effectiveness for reducing lead bioaccessibility. These results suggest that in situ chemical fixation has the potential to be an effective strategy for treatment of the impacted soils. © 2003 Wiley Periodicals, Inc.     

In-situ bioremediation of an aquifer contaminated with 1,2-dichloroethane

This article describes the application of in-situ bioremediation for the treatment of an aquifer contaminated with 1,2-dichloroethane (DCA). The first step in the process was to properly delineate the contamination and to contain the contaminated groundwater using a pumping well. The second step was to isolate in the groundwater microorganisms able to degrade DCA and to demonstrate the possibility of increasing their efficiency by injecting in-situ nutrients and hydrogen peroxide (H₂O₂) solution. In the third step, after the characterization of the hydrogeology of the aquifer with tracing experiments, the in-situ bioremediation of the groundwater was conducted. The analyses show that 95 percent of DCA was destroyed by this treatment, leading to a DCA concentration around the pumping well of about 0.2 mg/l.     

In situ ammonia removal in bioreactor landfill leachate

Although bioreactor landfills have many advantages associated with them, challenges remain, including the persistence of NH(3)-N in the leachate. Because NH(3)-N is both persistent and toxic, it will likely influence when the landfill is biologically stable and when post-closure monitoring may end. An in situ nitrogen removal technique would be advantageous. Recent studies have shown the efficacy of such processes; however, they are lacking the data required to enable adequate implementation at field-scale bioreactor landfills. Research was conducted to evaluate the kinetics of in situ ammonia removal in both acclimated and unacclimated wastes to aid in developing guidance for field-scale implementation. Results demonstrate that in situ nitrification is feasible in an aerated solid waste environment and that the potential for simultaneous nitrification and denitrification (even under low biodegradable C:N conditions) in field-scale bioreactor landfills is significant due to the presence of both aerobic and anoxic areas. All rate data fit well to Monod kinetics, with specific rates of removal of 0.196 and 0.117 mgN/day-g dry waste and half-saturation constants of 59.6 and 147 mgN/L for acclimated and unacclimated wastes, respectively. Although specific rates of ammonia removal in the unacclimated waste are lower than in the acclimated waste, a relatively quick start-up of ammonia removal was observed in the unacclimated waste. Using the removal rate expressions developed will allow for estimation of the treatment times and volumes necessary to remove NH(3)-N from recirculated landfill leachate.     

In situ remediation of MTBE utilizing ozone

There has been a great deal of focus on methyl tertiary butyl ether (MTBE) over the past few years by local, state, and federal government, industry, public stakeholders, the environmental services market, and educational institutions. This focus is, in large part, the result of the widespread detection of MTBE in groundwater and surface waters across the United States. The presence of MTBE in groundwater has been attributed primarily to the release from underground storage tank (UST) systems at gasoline service stations. MTBE's physical and chemical properties are different than other constituents of gasoline that have traditionally been cause for concern [benzene, toluene, ethylbenzene, and xylenes (BTEX)]. This difference in properties is why MTBE migrates differently in the subsurface environment and exhibits different constraints relative to mitigation and remediation of MTBE once it has been released to subsurface soils and groundwater. Resource Control Corporation (RCC) has accomplished the remediation of MTBE from subsurface soil and groundwater at multiple sites using ozone. RCC has successfully applied ozone at several sites with different lithologies, geochemistry, and concentrations of constituents of concern. This article presents results from several projects utilizing in situ chemical oxidation with ozone. On these projects MTBE concentrations in groundwater were reduced to remedial objectives usually sooner than anticipated. © 2002 Wiley Periodicals, Inc.     

In situ Remediation of Metals Comes of Age

Since the early 1970s, technologies for remediating organic contamination in soils and groundwater have evolved through three stages with primary emphasis on (1) gross removal processes, (2) active in situ treatment, and (3) risk-based closure and natural attentuation. Technologies for treating metals contamination are evolving through similar stages. In the late 1990s, metals remediation has arrived at the second stage in which a wide range of in situ technologies are available either to extract metals directly from the subsurface or to render them immobile and harmless. In situ geochemical fixation is an example of a commercial technology capable of addressing a wide range of metals contamination sites. Four case histories demonstrate the versatility of this approach. Other promising technologies for treating metals contamination are also emerging. These include geokinetics, biocatalytic precipitation processes, phytoremediation, and artificial wetlands. As our knowledge continues to grow, the most elegant solutions to metals contamination will rely more and more heavily on the soil's natural capacity to stabilize and immobilize metals over time.     

In situ burning of emulsions R&D in Norway

SINTEF Applied Chemistry has been working in the field of in situ burning since 1988, beginning with the first open water testing of the 3M fire proof boom which took place on Spitsbergen. In recent years, the focus of SINTEF's research activities in this area has been on the burning of emulsions. An experimental programme was initiated by NOFO in 1990 to study the in situ burning of water-in-oil (w/o) emulsions, as part of a wider NOFO programme ‘Oil spill contingency in Northern and Arctic waters’ (ONA). The research conducted under this programme has addressed many areas of in situ burning including:

• •• study of processes governing burning emulsions
• •• development of ignition techniques for emulsions
• •• effect of environmental conditions on burning
• •• burning crude oil and emulsions in broken ice
• •• uncontained burning of crude oil and emulsions.

     

Use of lignin degrading fungi in bioremediation

The use of lignin degrading fungi for decomposition of a wide variety of xenobiotics has become an area of intensive research. One distinct advantage of lignin degrading fungi over bacteria is that they do not require preconditioning to a particular pollutant prior to transformation. This degradative ability has been attributed to a nonspecific and nonstereoselective extracellular lignin-degrading enzymatic system (ligninase) which is induced by the fungi under nitrogen or carbon-limiting conditions (Reid, 1979). Ligninases (lignin-peroxidases) are responsible for the initial oxidative attack on lignin and other complex molecules via formation of a free radical thereby leading to depolymerization of complex molecular structures. Potential degradative ability of peroxidases may extend to include (1) sorbed contaminants, (2) high molecular-weight, hydrophobic contaminants, and (3) complex mixtures of chemicals typical of a contaminated site.