AEROBIC PROCESSES (chart) (with oxygen) or anaerobic processes (without oxygen) occur naturally in the subsurface. Enhanced bioremediation uses an understanding of site specific geochemistry and naturally occurring microbial processes to optimize site conditions. Enhanced bioremediation improves the environmental conditions for the microbial degradation of specific contaminants by adding an electron acceptor such as oxygen, which is frequently the limiting factor of the natural process.
GAS SOLUBILITIES - Different gases have different solubilities, depending on pressure (of the well column). According to Henry’s law, the higher the pressure on a gas, the more soluble a gas. Consequently, a monitoring well with 5 feet of head above an iSOC infusion tool will allow oxygen to remain at 42 mg/L, but 50 feet of well head pressure on the infusion tool will allow for up to 111 mg/L dissolved oxygen (in solution). Movement of the highly concentrated dissolved oxygen will move through the well screen and into the aquifer according to Fick’s Second Law of Diffusion, which can be observed in movies when someone exhales cigar smoke, and the smoke diffuses or spreads out in the room along a concentration gradient.
EBS performs biological and chemical laboratory bench biofeasibility evaluations for all contaminants and microcosm studies (growing the microbes on a particular substrate) for many projects, but not normally for petroleum hydrocarbon sites. These planning activities are highly recommended before starting any in-situ enhanced bioremediation program. A good hydrogeology primer is the USGS Basic Hydrogeology (Water-Supply Paper 2220 by Ralph Heath). For in-situ remediation of chlorinated solvents, the U.S. EPA document provides background information.
Enhanced Anaerobic Bioremediation
Hydrogen and Fermentable Carbon Substrates
The anaerobic fermentation process (SEE ATTACHED PDF) can be used for dehalogenation of chlorinated solvents as well as lowering the redox potential of the aquifer to encourage the precipitation of heavy metals. This approach is a well understood and documented method to remediate many chlorinated solvents (such as PCE and TCE), perchlorate, nitrate, TNT and some heavy metals, such as chromium in soil and groundwater. The EBS works in the laboratory and in the field with a variety of rapid, immediately bioavailable (hydrogen gas) to moderate (lactate) to slow and long-lasting electron donors (edible soybean oils) for a full range of carbon substrates to encourage microbial degradation and abiotic reduction processes to degrade a variety of chlorinated solvents, heavy metals, perchlorate, nitrates and other pesticides/herbicides. Edible soybean oils can be made into a micro-emulsion, which allows for better migration through the pore throat openings of the aquifer. As documented on a site in New Mexico, combining fermentable edible oils with hydrogen infusion using the gPRO (or HiSOC), chlorinated solvent dehalogenation results were up to 50% greater than just the use of fermentable oils alone. The dehalogenation process is shown below.
EBS also performs microcosm studies and works with various microbe laboratories to culture specific bacteria for PCE, TCE degradation (SDC-9 Cultures) dehalococcoides sp.(DHC) or TCA-20, dehalobacter sp. Strain TCA1 (EBS works with Shaw Environmental who supplies these specific microbial cultures).
SWI allowed for controlled mobilization of the NAPL ganglia into the water table for collection using dual phase extraction. SWI technology relies on water which is supersaturated with carbon dioxide, a highly soluble gas, in providing a mass transfer system. Carbon dioxide saturated water is injected under high pressure into the former tank pit where the carbon dioxide bubbles nucleate at the targeted area of the aquifer. The rising carbon dioxide bubbles contact with the submerged NAPL the saturated zone and cause volatilization of the free product into the vapor phase and mobilization of NAPL trapped in the pores.
Several extraction wells and dozens of small-diameter reinjection probe-rod ports were used to recirculate the carbon dioxide saturated water and provide a closely-spaced delivery and extraction system. The carbon dioxide is distributed by flowing water resulting in effective carbon dioxide distribution followed by heterogeneous bubble nucleation and continuous growth of gas bubbles in situ. A gas saturation front developed which expanded laterally and vertically towards the water table in the former underground tank pit. The NAPL mobilizes to soil gas and is extracted with a dual phase extraction system.
FIGURE 2 - Direct pore-scale evidence of volatilization by the SWI process of a drop of TCE (photo-micrograph courtesy of inVentures Technologies, Inc.)
TECHNOLOGY FOCUS: SATURATED WATER INFUSION PROCESS
Saturated water infusion (SWI) process equipment from inVentures Technologies, Inc. has been used for removing both LNAPLs and DNAPLS. The equipment can be enclosed and secured in a trailer-mounted system. The carbon dioxide enhances the saturated water infusion process since carbon dioxide is highly soluble in water, and the bubbles of carbon dioxide will volatilize liquid droplets of contaminants (such as PCE, TCE, and petroleum hydrocarbons) into the bubbles of carbon dioxide. A two phase extraction system is used to remove the carbon dioxide and contaminant vapors from the vadose zone as long as the mass of TCE in vapors and groundwater continues to decline.
The saturated water infusion process is an example of a cost-effective method for extraction and infusion for rapid removal of non-aqueous phase liquids (NAPLs) of hydrocarbons and chlorinated solvents. The SWI process is especially effective with NAPLs that are trapped in pore spaces as ganglia. The removal of free product from pore spaces was modeled recently. In the study, Soltrol, a nonvolatile hydrocarbon, was modeled by Leif Nelson below (Figure 1).
FIGURE 1 – Conceptual model of NAPL ganglia removal by SWI by Leif Nelson (Jacobs et al, 2008).
Enhanced Bioremediation Using Gases and Liquids
Although bioremediation is generally a slow process, taking a few months to start to see results, it can be an effective and low cost remediation strategy, usually in the residual remediation management zone (Zone 2). If the source of contamination has been removed using excavation, two-phase extraction (or soil vapor extraction for the soil source zone), chemical oxidation (ozone, perozone, Fenton’s Reagent, persulfate, etc.) or other method, enhanced bioremediation is a good choice to reduce the residual concentrations of petroleum hydrocarbons to levels that will allow case closure.
Enhanced bioremediation can be used to treat some source areas, particularly for chlorinated solvents, when using anaerobic processes (hydrogen infusion with lactate compounds and edible soybean oils), and off-site migration even in low permeability materials. This technology can also enhance existing pump and treat systems, reducing remediation time significantly. EBS recommends gas infusion technologies, a delivery method for electron acceptors, such as oxygen, for aerobic systems. Different gases such as propane, butane, ethene, methane or others can be used for anaerobic systems. A successful passive gas mass-transfer device is the iSOC diffusion tool, which provides up to 1.5 cubic feet of oxygen per day per well on a continuous basis. The iSOC does not contain moving parts or use electricity, but rather, uses the pressure in the oxygen tank to provide the power for oxygen infusion into the aquifer.
AEROBIC BIOREMEDIATION (photo of oil and microbes in petri dish) = microbes (subsurface) + food (hydrocarbons) + electron acceptor (oxygen). The oxygen accepts the electron as part of the microbial cellular respiration process. The photo above shows crude oil being degraded by aerobic microbes in a laboratory cell culture dish.
[Pseudomonas (microbe)] Enhanced bioremediation relies on general availability of naturally occurring microbes to consume contaminants as a food source (petroleum hydrocarbons in aerobic processes) or as an electron acceptor (chlorinated solvents). In addition to microbes being present, in order to be successful, these processes require nutrients (Carbon: Nitrogen: Phosphorus equals 100:10:2 or 100:10:1). EBS evaluates geochemical and redox conditions in aquifers as well as microbial counts for biofeasibility studies (aerobic, anaerobic, and co-metabolic). EBS will perform nutrient calculations as well as provide the design and liquids for site-specific nutrient mixes. Sometimes, the microbes necessary to provide exude the proper enzymes are not present in volumes capable of reasonable degradation rates. In those cases, EBS works with laboratories to develop microbe cultures for specific contaminants, such as MTBE, PCE, TCE and other compounds.
The trapped TCE droplet in a pore space opening is shown above (see FIGURE 2). Using the saturated water infusion technology, the A carbon dioxide bubble nucleates (above) by mass transfer from the injected supersaturated aqueous phase carbon dioxide into water. Upon contact with the carbon dioxide bubble, the NAPL, in this case, a drop of TCE, spontaneously spreads over water and the volatile components of the NAPL are readily transferred into the carbon dioxide bubble. The carbon dioxide bubble migrates to the top of the groundwater surface, where it is extracted using dual phase extraction and the TCE is treated using above ground methods, such as a thermal oxidizer.
At the point the SWI process has removed as much of the DNAPL and TCE as possible, the SWI process is changed from using dissolved carbon dioxide to dissolved hydrogen. Dissolved hydrogen enhances anaerobic treatment in the source remediation management zone (RMZ 1) and the residual remediation management zone (RMZ 2). Using the infused hydrogen to maintain a highly reducing environment, the addition of fermentable oils from JRW Bioremediation LLC (WilClear®, Accelerite®, and LactOil®) provide the short and long-term (up to 24 months) carbon substrate for anaerobic degradation of TCE. Recent studies in New Mexico with tetrachloroethylene (PCE) have shown that chlorinated solvent degradation rates can be increased by 50% when the fermentable oil is enhanced with solubilized hydrogen gas (Sheldon et al., 2008). If the microbial counts for anaerobic microbes are low based on the anaerobic biofeasibility studies, dehalogenating bacteria can be added to the subsurface to enhance the TCE degradation process.
Jacobs, J., and Brewer, R., 2009, Workshop 7: RBCA Grows Up: Introduction to Environmental Hazard Evaluation and Advanced Approaches for Site Investigation, The Nineteenth Annual AEHS Meeting and West Coast Conference on Soils, Sediments, and Water, March 12, 2009, Mission Valley Marriott, San Diego, California.
Jacobs, J., Nelson, L., and Begley, J., 2008, Two Rapid Enhanced Flushing NAPL Recovery Methods, Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Battelle Memorial Conference, Monterey, California, May 19-22, Abstracts.
Sheldon, J., Fogel, S. and Begley, J.F., 2008, Results of Field Testing Hydrogen Gas Infusion for PCE Bioremediation, Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Battelle Memorial Conference, Monterey, California, May 19-22, Abstracts.
Jim Jacobs, P.G., C.H.G., is a hydrogeologist with 25+ years of experience. He has a bachelors and graduate degree in geology and is a Fulbright scholar in environmental science/engineering with three awards. He has co-authored two books and more than 100 articles. He is active in the Groundwater Resources Association, American Institute of Professional Geologists, The California Council of Geoscience Organizations and the Consultants-Owners-Regulators-Envirovendors (CORE) Foundation. He can be reached at (tel: 415-381-5195) or firstname.lastname@example.org
Laboratory Bench Scale Services
Commonly overlooked, bench testing provides some of the most important site-specific information about the likelihood of success or failure of an in situ remediation project. EBS performed dozens of bench tests for in situ chemical oxidation (ISCO) (bench tests for Fenton's Reagent, permanganate, persulfate, ozone, and others), enhanced bioremediation (microbiological feasibility studies and microcosm studies) and metals stabilization for numerous consulting companies. These tests are a way to optimize reactant chemistry in the laboratory rather than in the field. In addition, EBS provides bench tests for process treatments for environmental equipment to verify successful results and proper designs. Below are some of the treatment compounds that can be bench tested in the laboratory and that are used in soil and water treatments. Due to patents, some of the technologies are only allowed in above ground treatments. The treatments are listed by the type of process:
• Bench Testing
• Natural Attenuation Lab Studies
• iSOC Testing Parameters
• Microbiological Lab Analyses
• EBS Spectrophotometry Field Laboratory
• List of Field Parameters
In-Situ Chemical Oxidation
EBS designs and implements a variety of in situ chemical oxidation (ISCO) processes for soil and groundwater remediation. EBS designs and provides field oversight for the high-pressure injection of liquid or solid chemical oxidants such as the hydroxyl radical (Fenton's Reagent), hydrogen peroxide, persulfate, potassium, sodium and calcium permanganate, percarbonate, and persulfate to greatly accelerate the complete destruction of petroleum hydrocarbons, chlorinated solvents, MTBE, BTEX, PCBs, PCPs and other organic chemicals. Delivery pressures for liquid oxidants include well and filter gallery trenches (30 to 40 psi), moderate pressure injection rods (200 to 600 psi) to high pressure (3,000 to 5,000 psi) lances. Ozone, a gas, is also used for in-situ remediation in a variety of delivery systems. EBS oversees the installation of the oxidants with proprietary injection and pumping technologies in specialized sparge points or treatment trenches. Ozone can be injected at low pressure (less than 15 psi) or higher line pressures (40 to 75 psi) for in situ applications. Safety design is an important element of any EBS-designed injection project.
• Groundwater Modeling services
• Design Considerations For In-Situ Chemical Oxidation Using High Pressure Jetting
• In-Situ Chemical Oxidation Using Jetting Delivery
• List of organisms destroyed by Chemical Oxidation
Ozone Treatment Packages
Ozone (O3) is a powerful gas phase oxidizer that can be used to treat volatile organic compounds. Ozone must be generated on-site and the gas cannot be stored; therefore all the ozone gas that is generated must be injected into the subsurface or destroyed using an ozone destruction unit on the ozone generator. The ozone gas can be bubbled into closely spaced injection ports that release the bubbles into the aquifer for remediation. The smaller the bubbles, the more surface area and the faster they can travel through small pore spaces. Pumping the ozone gas through specially designed ozone diffusers can produce micro-bubbles. Advanced oxidation processes refer to when ozone is catalyzed or enhanced by ultra violet light, hydrogen peroxide or other oxidizers, to increase the power of the ozone by producing more hydroxyl radicals. Treatability testing in the laboratory can evaluate the cost benefit of the different ozone enhancements prior to mobilizing into the field.
EBS has performed ozone and perozone (the addition of hydrogen peroxide to catalyze the ozone) bench tests. In addition, EBS has designed complete and competitive ozone packages (equipment provided by Remediation Shop www.remediationshop.com for in-situ and surface treatment of water, including wells, well points, sparge points, and trenches. EBS installation oversight is available. Please call for custom services (electronic controllers, other project requirements). With ozone compatible compressors, line pressures from the ozone unit to the sparge points can range from about 40 to 75 psi. Please note: the higher the line pressure, the lower the stability and concentration of the ozone being delivered to an aquifer or vadose zone. Safety design is an important element of any EBS injection project.
In-Situ Metals Geochemical Fixation or Stabilization
EBS designs and injects liquid and gas reducing agents to immobilize toxic soluble metals such as lead, arsenic, chromium (VI) also called “hexavalent chromium”, cadmium, nickel and other metals using geochemical fixation. The treated metals become insoluble in the process, reducing the need for expensive excavation and disposal. EBS uses sulfur dioxide (gas) as well as the following liquids: calcium polysulfide, sodium metabisulfite and ferrous sulfate in a proprietary jetting technology. Safety design is an important element of any EBS designed injection project.
• Metals Stabilization Using Geochemical Fixation
• PowerPoint - Hexavalent Chromium Remediation (click screen to advance presentation)
• Chromium (VI) Handbook
• Chromium (VI) Attenuation Study
EBS does not sell remediation equipment, except for the inVentures Technologies, Inc. gas infusion equipment. Other companies, such as Remediation Shop www.remediationshop.com sell a variety of remedial equipment and license remedial processes. For more information, please contact: Kevin Pope, 800-794-1789). Remediation Shop installs and distributes a variety of groundwater and treatment water and soil remedial equipment such as ozone generators, thermal oxidizers, oil water separators, emulsion-splitting plants, evaporators, equipment and chemical storage, sewer treatment discharge plants, car/truck wash systems, industrial wash wastewater recycling systems, advanced oxidation systems, fluidized bed bioreactors, and grease treatment systems.
EBS works with consultants who work with small wineries (<30,000 cases per year) and larger ones who are required to meet water treatment goals for waste water used in the wine making process and equipment washing process. Until relatively recently, this segment of industry has not seen much regulatory oversight, however, water regulators are now focusing on wineries. This water typically has 3,000 to 5,000 mg/L biological oxygen demand (BOD). EBS has developed a modular approach that is flexible for wineries as well as cost effective for discharge to land through irrigation or discharge to a sanitary sewer. Typical waste discharge requirements for discharges of winery waste are available in the link below.
• Winery Discharge Requirements
EBS provides bench testing, field testing as well as the designs and oversight for the field implementation by others of a variety of remedial processes.
• Cold Mix Asphalt Process for soils and sludges (for metals, hydrocarbons, solvents and pesticides)
• High Pressure Biosolvent Flushing Process for Groundwater (for heavy oils, diesel, motor oil, crude oil,
• hydraulic oil, PCBs, PAHs)
• CO2 Saturated Water Injection Process for Groundwater Free Product (LNAPL and DNAPL)
Soil and Sludge Recycling Process
Cold mix asphalt (CMA) is a remedial process that recycles sludges and soils contaminated with petroleum hydrocarbons, heavy metals, chlorinated solvents and pesticides/herbicides into a useful product: asphalt. The asphalt can be stored for 6 months or more, and can be used for parking lots, bike paths, hiking trails, berms and other uses.
COLD MIX ASPHALT
Free Product Removal Technologies
EBS has developed or worked with two in-situ free product removal processes that are performed by others, in which EBS provides technical oversight. These include the High Pressure Biosolvent Flushing Process and the CO2 Saturated Water Injection Process.
High Pressure Biosolvent Flushing Process
In the laboratory, an environmental-friendly biosolvent for the removal of heavy to moderate weight petroleum hydrocarbons, such as diesel, motor oil, hydraulic oil, PCBs and crude oil has been developed. It has been approved by the US EPA for use in off-shore and river oil spills. EBS uses environmentally friendly, naturally occurring surfactants for acceleration of in-situ remediation of free product (both hydrocarbon and chlorinated solvents). By generating micro-droplets, the free product is broken down from one large liquid area into billions of micro-droplets. This transformation increases in surface area, allowing for more rapid degradation by both chemical oxidation and enhanced bioremediation.
CO2 Saturated Water Injection Process
The CO2 Saturated Water Injection Process (SWI) was developed by inVentures Technologies, Inc. for the removal of LNAPLs and DNAPLs in groundwater. The process uses two phase extraction equipment and above ground processing as part of the process.
Since 1989, EBS has served hundreds of small to large environmental consulting and engineering contracting companies, in the following industries or settings:
• EBS projects are brought in by consultants, working on a variety of settings, including many industries, including the refining and distribution of petroleum and oils, dry cleaners, transportation, marine transportation companies and rental companies as well as public sector owners such as cities, counties, the Federal government, including the military.
• Types of Properties: EBS has worked on projects on Manufacturing, Industrial and Commercial properties, for consultants whose clients represent both the private and public sector.
PRICING FOR CONSULTANTS - FIXED FEE PRICING
Many of the EBS projects (bench testing, for example) use a fixed fee basis.
EMERGENCY AND WEEKEND / NIGHT WORK
In an effort to be responsive to consultant’s needs for rapid response or low disruption remediation on site, EBS will provide services that do not occur during the normal business day. Emergency or weekend/night work will have a $25/hour surcharge added to the field staff rate.
EBS will work with selected projects on a wait-and-pay basis for consultants working with A and B category claimants in the California Underground Storage Tank Cleanup Fund (USTCF).