Soil Vapor Extraction and Bioventing - Engineering and Design
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The present study aimed to illustrate how an intended air-injection bioventing technology can be transformed into a soil vapour extraction effort when the air flow rates are pushed to a stripping mode, thus leading to the treatment of the off-gas resulting from volatilisation. As such, a combination of an air-injection bioventing system and a biotrickling filter was applied for the treatment of contaminated soil, the latter aiming at the treatment of the emissions resulting from the bioventing process.
A biotrickling filter was simultaneously used to treat the outlet gas emissions, which presented average removal efficiencies of ca. The proposed combination of biotechnologies proved to be an efficient solution for the decontamination process, when an excessive air flow rate was applied, reducing both the soil contamination and the outlet gas emissions, whilst being able to reduce the treatment time required by bioventing only. The characteristics of the site included clayey-sand soils and nonfuel organic contamination such as acetone, toluene, and naphthalene in the vadose zone.
Based on the results of an In situ bioventing at a natural gas dehydrator site: Field demonstration. The chemicals of interest are benzene, toluene, ethylbenzene, and xylenes BTEX and alkanes.
Soil sampling indicated that the capillary fringe and saturated zones were heavily contaminated, but that the unsaturated zone was relatively free of the contaminants. Three different air sparging operating modes were tested to determine an optimal process configuration for site remediation. These operational modes were compared through in situ respirometry studies.
Respirometry measurements were used to estimate biodegradation rates. Dissolved oxygen and carbon dioxide were monitored in the groundwater. Three different air sparging operational modes pulsed, continuous, and offgas recycle were tested to determine the optimum process configuration for site remediation. Biodegradation was also evaluated. Operational mode performance was evaluated by situ conducting in situ respirometry studies. Depletion of oxygen and hydrocarbons and production of carbon dioxide were used to calculated biodegradation rates in the vadose and saturated zones.
The mass of hydrocarbons biologically degraded was estimated based on these biokinetic rates. In addition, biodegradation was also estimated based on contaminant removal shown by analytical sampling of soil and groundwater and based on other losses attributed to pump and treat and soil vapor extraction systems. In addition, an engineering evaluation of the operating modes is presented. This report describes the formulation, numerical development, and use of a multiphase, multicomponent, biodegradation model designed to simulate physical, chemical, and biological interactions occurring primarily in field scale soil vapor extraction SVE and bioventing B Monitoring biodegradation of diesel fuel in bioventing processes using in situ respiration rate.
An in situ measuring system of respiration rate was applied for monitoring biodegradation of diesel fuel in a bioventing process for bioremediation of diesel contaminated soil. On-line O2 and CO2 gas measuring system was applied to measure O2 utilisation and CO2 production during biodegradation of diesel for 5 months. Biodegradation rate of TPH was calculated from respiration rate measured by the on-line gas measuring system. There were no apparent differences between calculated biodegradation rates from two columns with different venting modes. These results suggested that the on-line measuring system of respiration rate would be applied to monitoring biodegradation rate and to determine the potential applicability of bioventing process for bioremediation of oil contaminated soil.
Soil vapor extraction SVE and bioventing BV are proven strategies for remediation of unsaturated zone soils. Mathematical models are powerful tools that can be used to integrate and quantify the interaction of physical, chemical, and biological processes occurring in field sc Phase 1 remediation of jet fuel contaminated soil and groundwater at JFK International Airport using dual phase extraction and bioventing. The total area remediated by the DPE wells is estimated to be 4. After 6 months of remediation, approximately 5, lbs.
Of these three mechanisms, the rate of petroleum hydrocarbon removal was the highest for biological oxidation in one area and by groundwater extraction in another area. Pilot-scale studies of soil vapor extraction and bioventing for remediation of a gasoline spill at Cameron Station, Alexandria, Virginia. Because the base is to be closed and turned over to the city of Alexandria in , the Army sought the most rapid and cost-effective means of spill remediation.
A commercial vapor-extraction machine was used to remove nearly gal of gasoline from Argonne-installed horizontal wells. Argonne staff also determined that bioventing stimulated indigenous bacteria to bioremediate the gasoline spin. Performance and Cost Summary. Atlas , Ronald M, and Richard Bartha. Microbial Ecology : Fundamentals and The most notable success of steam injection for remediation has been the Southern California Edison wood treating site in Visalia Removal efficiencies using ISTD are typically very high, and since this technology relies on conduction of heat through the soil Soil vapor extraction and bioventing : Applications, limitations, and future research directions.
Soil vapor extraction SVE has evolved over the past decade as an attractive in situ remediation method for unsaturated soils contaminated with volatile organic compounds VOCs. SVE involves the generation of air flow through the pores of the contaminated soil to induce transfer of VOCs to the air stream. Air flow is established by pumping from vadose zone wells through which contaminant vapors are collected and transported above ground where they are treated, if required, and discharged to the atmosphere. The popularity of SVE technologies stems from their proven effectiveness for removing large quantities of VOCs from the soil, their cost competitiveness, and their relatively simple non-intrusive implementation.
Widespread field application of SVE has occurred following the success of early laboratory and field scale feasibility studies [Texas Research Institute, , ; Thornton and Wootan, ; Marley and Hoag, ; Crow et al. Hutzler et al. Microbial destruction of highly chlorinated organic compounds must be initiated by anaerobic followed by aerobic dechlorination.
In-situ dechlorination of vadose zone soil contaminated with these compounds requires, among other factors, the establishment of highly reductive anaer Chlorinated solvents such as tetrachloroethylene, trichloroethylene, carbon tetrachloride, chloroform, 1,2-dichloroethane, and dichloromethane methylene chloride can exist in contaminated subsurface material as 1 the neat oil, 2 a component of a mixed oily waste, 3 a solu In an underground transfer pipeline fracture was discovered after a spill exceeding , gallons occurred.
The hydrogeology is fresh water at less than ten feet down overlying more dense salt It is common to use bioventing as a polishing step for soil vapor extraction. It was originally planned to use soil vapor extraction and bioventing at a former landfill site in Delaware but laboratory scale biodegradation studies indicated that most of the volatile organic compou Frequently both the subsurface vadose zone and underlying aquifer at Air Force Base spill locations are contaminated with fuel hydrocarbons such as benzene and degreasing solvents such as trichloroethene.
In many instances these concentrations exceed regulatory limits mandated by Bioremediation encompasses a collection of technologies which use microbes to degrade or transform contaminants. Three technologies have an established track record of acceptable performance: aerobic bioventing for fuels; enhanced reductive dechlorination for chlorinated solvent The bioremediation of petroleum hydrocarbons has evolved into a number of different processes.
These processes include in-situ aquifer bioremediation, bioventing , biosparging, passive bioremediation with oxygen release compounds, and intrinsic bioremediation. Although often viewe Laboratory biotreatability studies evaluated the use of bioventing and biosparging plus groundwater circulation UVB technology for their potential abililty to treat soil and groundwater containing creosote and pentachlorophenol.
Soils from two former wood-treatment facilities w Dissolved chlorinated aliphatic hydrocarbons CAHs also are present in the shallow Biotreatability studies conducted in our laboratory used soils from two former wood-treatment facilities to evaluate the use of in situ bioventing and biosparging applications for their potential ability to remediate soil and groundwater containing creosote. The combination of ph Rhizosphere-enhanced remediation is a developing technology.
It is a subset of phytoremediation —a term often used in a broad sense and sometimes The operative process in phytoremediation depends largely on.
Hydro Geo Chem -- Environmental Consulting and Remediation Engineering
It is a subset of phytoremediation —a term that is often used in a broad sense, and sometimes used The operative process in phytoremediation depends largely on the. Atlas , Ronald M. Microbial Ecology : Fundamentals and Applications. In cold climates, in situ bioremediation is limited to the summer when soil temperatures are sufficient to support microbial Microbial respiration Preliminary studies found evidence of hydrocarbon contamination extending from 10 feet below ground surface bgs down to the shallow water table, at 20 to 25 feet bgs.
In June of , Kelly AFB authorized the installation and evaluation of a bioventing system at this site to aid in the cleanup of the hydrocarbon contaminated soils. Augmenting oxygen to the indigenous soil microorganisms promotes the aerobic metabolism of fuel hydrocarbons in the soil. Air flow across a site is thus a key aspect, but soil moisture and subsurface heterogeneity i. In some situations, such as enhancement of monitored natural attenuation, a passive SVE system that relies on barometric pumping may be employed  .
SVE has several advantages as a vadose zone remediation technology. The system can be implemented with standard wells and off-the-shelf equipment blowers, instrumentation, vapor treatment, etc. SVE can also be implemented with a minimum of site disturbance, primarily involving well installation and minimal aboveground equipment. Depending on the nature of the contamination and the subsurface geology, SVE has the potential to treat large soil volumes at reasonable costs. The soil gas vapor that is extracted by the SVE system generally requires treatment prior to discharge back into the environment.
The aboveground treatment is primarily for a gas stream, although condensation of liquid must be managed and in some cases may specifically be desired. A variety of treatment techniques are available for aboveground treatment  and include thermal destruction e. The most commonly applied aboveground treatment technologies are thermal oxidation and granular activated carbon adsorption. The selection of a particular aboveground treatment technology depends on the contaminant, concentrations in the offgas, throughput, and economic considerations.
The effectiveness of SVE, that is, the rate and degree of mass removal, depends on a number of factors that influence the transfer of contaminant mass into the gas phase. The effectiveness of SVE is a function of the contaminant properties e. As an example, a residual quantity of a highly volatile contaminant such as trichloroethene in a homogeneous sand with high permeability and low carbon content i.
Soil Vapor Extraction
SVE effectiveness issues include tailing and rebound, which result from contaminated zones with lower air flow i. Recent work at U.
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Department of Energy sites has investigated layering and low permeability zones in the subsurface and how they affect SVE operations  . Enhancements for improving the effectiveness of SVE can include directional drilling , pneumatic and hydraulic fracturing , and thermal enhancement e. Directional drilling and fracturing enhancements are generally intended to improve the gas flow through the subsurface, especially in lower permeability zones.
Soil Vapor Extraction System Optimization, Transition, and Closure Guidance
Thermal enhancements such as hot air or steam injection increase the subsurface soil temperature, thereby improving the volatility of the contamination. In addition, injection of hot dry air can remove soil moisture and thus improve the gas permeability of the soil. On selection as a remedy, implementation of SVE involves the following elements: system design, operation, optimization, performance assessment, and closure.
Several guidance documents provide information on these implementation aspects. EPA and U. As time goes on, it is typical for a SVE system to exhibit a diminishing rate of contaminant extraction due to mass transfer limitations or removal of contaminant mass. Performance assessment is a key aspect to provide input for decisions about whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE.