Successful solid-phase bioremediation of petroleum-contaminated soil

Biological processes have been used to remediate petroleum hydrocarbons, pesticides, chlorinated solvents, and halogenated aromatic hydrocarbons. Biological treatment of contaminated soils may involve solid-phase, slurry-phase, or in situ treatment techniques. This article will review the general principle of solid-phase bioremediation and discuss the application of this technique for the cleanup of total petroleum hydrocarbons on two sites. These remedial programs will reduce total petroleum hydrocarbon contamination from the mean concentration of 2,660 ppm to under the 200-ppm cleanup criteria for soil and under the 15-ppm cleanup criteria for groundwater. Over 32,000 yards of soil have been treated by solid-phase treatment to date. The in situ system operation is effectively producing biodegradation in the subsurface. The project is approximately one-third complete.     

The treatment of contaminated water at remedial wood preserving sites

Contaminated groundwater and surface water have posed a great challenge in restoring wood preserving sites to beneficial use. Often contaminated groundwater plumes extend far beyond the legal property limits, adversely impacting drinking water supplies and crop lands. To contain, treat, and/or remediate these valuable resources is an important part of restoring these impacted sites. Various options are available for remediating the groundwater and other affected media at these sites. Frequently, pump and treat technologies have been used that can provide well‐head treatment at installed extraction wells. This approach has shown to be costly and excessively time consuming. Some of the technologies used for pump and treat are granular activated carbon (GAC), biotreatment, and chemical oxidation. Other approaches use in‐situ treatment applications that include enhanced bioremediation, monitored natural attenuation (biotic and abiotic), and chemical reduction/fixation. Ultimately, it may only be feasible, economically or practicably, to use hydraulic containment systems. Depending upon site‐specific conditions, these treatment approaches can be used in various combinations to offer the best remedial action. A comparison of water treatment system costs extrapolated from the treatability studies performed on contaminated groundwater from the McCormick/Baxter Superfund site in Stockton, California, yielded operation and maintenance costs of $1.19/1,000 gal. for carbon treatment and $7.53/1,000 gal. for ultraviolet (UV) peroxidation, respectively.     

Field trial experiment: Phytoremediation with Salix sp. on a dredged sediment disposal site in Flanders,Belgium

Remediation of heavy metal contamination in soil is a widespread environmental issue. Conventional remediation techniques are invasive and often too expensive, particularly if large areas of soil are contaminated. Phytoremediation is the use of plants to remediate soil and groundwater. Phytoremediation of inorganic comtaminants such as metals can be further catagorized into phytostabilization and phytoextraction. These techniques have gained an increasing amount of attention and research over the last ten years. Phytoextraction of heavy metals and periodical removal of harvestable plant parts results in a gradual decrease of pollutant levels in the top soil. Woody species such as Salix sp. (willow) do not represent the fastest phytoextraction procedure compared to uptake by herbaceous species; however, they offer the added advantage of possible reuse of the produced biomass (wood) for the production of renewable energy. Here we present the results of a field experiment conducted to evaluate the use of Salix to remediate soil contaminated with cadmium and zinc at a dredged sediment disposal site in Flanders, Belgium. © 2003 Wiley Periodicals, Inc.     

In situ thermal remediation of DNAPL and LNAPL using electrical resistance heating

Electrical resistance heating (ERH) is an in situ treatment for soil and groundwater remediation that can reduce the time to clean up volatile organic compounds (VOCs) from years to months. The technology is now mature enough to provide site owners with both performance and financial certainty in their site‐closure process. The ability of the technology to remediate soil and groundwater impacted by chlorinated solvents and petroleum hydrocarbons regardless of lithology proves to be beneficial over conventional in situ technologies that are dependent on advective flow. These conventional technologies include: soil vapor recovery, air sparging, and pumpand‐treat, or the delivery of fluids to the subsurface such as chemical oxidization and bioremediation. The technology is very tolerant of subsurface heterogeneities and actually performs as well in low‐permeability silts and clay as in higher‐ permeability sands and gravels. ERH is often implemented around and under buildings and public access areas without upsetting normal business operations. ERH may also be combined with other treatment technologies to optimize and enhance their performance. This article describes how the technology was developed, how it works, and provides two case studies where ERH was used to remediate complex lithologies. © 2005 Wiley Periodicals, Inc.     

Survey: Bioremediation contractors guarantee performance

Experience with bioremediation technology has enabled bioremediation contractors to offer performance-based contracts for many types of bioremediation projects. This development is significant because it alleviates the previous concern with the technology regarding its lack of success at certain sites. Environmental Strategies Corporation, an independent environmental consulting firm with no financial interest in bioremediation technology, conducted an independent survey to identify bioremediation contractors that are willing to enter into performance-based bioremediation contracts. This article discusses the background of treating contaminated soil and groundwater using bioremediation and describes how a performance-based contract can be structured. The survey's format and results are then presented and analyzed. Finally, several case studies of successful bioremediation projects are presented.     

Hydrogen Release Compound: A Cost‐Effective Alternative to PCE Remediation at Dry Cleaning Facilities

Tetrachloroethylene, also known as perchloroethylene or PCE, is one of the most difficult to treat chlorinated solvents when present in groundwater. Unfortunately, this elusive and recalcitrant compound is also the most commonly used dry cleaning solvent. As a result, releases of PCE at dry cleaning sites are somewhat common. Regenesis Bioremediation Products, of San Clemente, California, has developed Hydrogen Release Compound (HRC), which has been successfully used to promote bioremediation of PCE in groundwater. This product is directly injected into contaminated groundwater to speed up the natural attenuation of PCE through an anaerobic, natural process known as reductive dechlorination. A key benefit of HRC is its ability to slowly release hydrogen over extended periods of time. Reductive dechlorination relies on a steady source and readily available supply of electron donors as part of the degradation process. Hydrogen is one of the best electron donors available, and thus, the application of HRC significantly enhances the rate of PCE degradation. For dry cleaners, this technology can substantially reduce major design, capital, and operating costs, allowing the implementation of a low‐impact application and remediation solution. This article discusses the use of the HRC to remediate PCE contamination and presents the results of two specific HRC‐treated dry cleaner sites. © 2002 Wiley Periodicals, Inc.     

Coupling Flow Analysis With Geochemical and Microbiological Analyses to Assess the Bioremediation Feasibility of a Contaminated Aquifer

An integrated approach combining classic and molecular microbiological methods, “in vitro” bioremediation assays and groundwater numerical modeling, has been established to identify optimized solutions for remediating aquifers contaminated with organic pollutants. Bacteria have been isolated from an aquifer contaminated with toluene and methyl tert‐butyl ether (MTBE), selected for their growth with contaminants as a sole carbon source and identified through 16S rDNA partial sequencing. Successive biodegradation laboratory tests have been performed to determine which chemical conditions were more appropriate for the isolated bacteria to more efficiently oxidize toluene and MTBE. A groundwater model was created using FEFLOW code first to determine the movement of the plume front and second to simulate the impact of the biodegradation processes along the groundwater flow directions based on the bioremediation rates obtained in the laboratory. The results show that this innovative and interdisciplinary model can be used to assist in developing monitoring and remediation plans for cleaning up complex contaminated groundwater sites. This approach successfully combines the identification of the optimum biogeochemical conditions for bacterial biodegradation to occur with the predictability of the development of the process over time, ensuring decisive support in the management of contaminated sites. ©2016 Wiley Periodicals, Inc.     

ART in‐well technology proves effective in treating 1,4‐dioxane contamination

A common industrial solvent additive is 1,4‐dioxane. Contamination of dissolved 1,4‐dioxane in groundwater has been found to be recalcitrant to removal by conventional, low‐cost remedial technologies. Only costly labor and energy‐intensive pump‐and‐treat remedial options have been shown to be effective remedies. However, the capital and extended operation and maintenance costs render pump‐and‐treat technologies economically unfeasible at many sites. Furthermore, pump‐and‐treat approaches at remediation sites have frequently been proven over time to merely achieve containment rather than site closure. A major manufacturer in North Carolina was faced with the challenge of cleaning up 1,4‐dioxane and volatile organic compound–impacted soil and groundwater at its site. Significant costs associated with the application of conventional approaches to treating 1,4‐dioxane in groundwater led to an alternative analysis of emerging technologies. As a result of the success of the Accelerated Remediation Technologies, LLC (ART) In‐Well Technology at other sites impacted with recalcitrant compounds such as methyl tertiarybutyl ether, and the demonstrated success of efficient mass removal, an ART pilot test was conducted. The ART Technology combines in situ air stripping, air sparging, soil vapor extraction, enhanced bioremediation/oxidation, and dynamic subsurface groundwater circulation. Monitoring results from the pilot test show that 1,4‐dioxane concentrations were reduced by up to 90 percent in monitoring wells within 90 days. The removal rate of chlorinated compounds from one ART well exceeded the removal achieved by the multipoint soil vapor extraction/air sparging system by more than 80 times. © 2005 Wiley Periodicals, Inc.     

Effectiveness of Capture Zones Generated by Intermittent Pumping of a PV‐Powered Pump‐and‐Treat System Without Energy Storage

A common technology to remediate and/or contain contaminated groundwater is pump‐and‐treat remediation (P&T). Traditionally, P&T systems have been designed to operate continuously to achieve steady‐state capture zones, for which large amounts of energy are required. Green and sustainable remediation (GSR) is emerging as a viable method to minimize the adverse effects of remediation on the environment. One of the challenges associated with photovoltaic‐ (PV‐) powered P&T systems is the assessment of their performance given the intermittent nature of the power availability. This article characterizes the hydraulic containment effectiveness of a PV‐powered P&T system without energy storage using data collected at two different remediation sites, a Dry‐Cleaning Environmental Response Trust Fund site in Rolla, Missouri, and the Former Nebraska Ordnance Plant near Mead, Nebraska. Additionally, a method to estimate the effectiveness of the hydraulic containment as a function of the total volume of groundwater expected to be extracted is being proposed. Two transient and a continuously pumped capture zones were modeled using Visual MODFLOW^® 2012.1 along with MODPATH and compared. The study shows that smaller capture zones will be generated from intermittent pumping when compared to continuous pumping. © 2013 Wiley Periodicals, Inc.     

In situ bioremediation of an aniline spill in an industrial setting

In situ remediation of aniline from soils and groundwater using biological and physical treatments was conducted at the BASF Corporation facility in Geismar, Louisiana. To mitigate the migration of aniline, remediate contaminated soil and groundwater, and determine concentrations, 24 immobilized microbe bioreactors were fixed in the subsoil, and a horizontal recovery well and 7 monitoring wells were installed. Soil and monitoring wells were sampled quarterly to assess bioplug impact on the aniline concentrations. The recovery well was sampled monthly to estimate the pounds of aniline removed from groundwater. Soil pH, composition, and microbial counts were used to estimate the fate and transport. Aniline levels were lowered significantly after remediation and total cancer risk was below levels for industrial sites, as established by State of Louisiana Risk Evaluation/Corrective Action Program guidelines. © 2010 Wiley Periodicals, Inc.     

石油烃污染地下水原位修复技术研究进展

概述了石油烃污染地下水原位修复技术的进展，包括原位化学氧化、原位电动修复、渗透反应格栅、冲洗、土壤气抽出、地下水曝气、生物修复，并对今后的研究发展趋势进行了展望。     

Multiphase extraction radius of influence: Evaluation of design and operational parameters

A common remedial technology for properties with subsurface soil and groundwater contamination is multiphase extraction (MPE). MPE involves the extraction of contaminated groundwater, free‐floating product, and contaminated soil vapor from the subsurface. A network of recovery wells conveys fluids to a vacuum pump and to the treatment system for the contaminated groundwater and soil vapor. This article describes a study of MPE operational data from nine similar remediation projects to determine the most important design parameters. Design equations from guidance manuals were used to estimate the expected radius of influence (ROI) based on measured field data. ROIs were calculated for the vapor flow rate through the subsurface and for the groundwater drawdown caused by the MPE remediation activities. The calculated ROIs were compared to the measured ROIs to corroborate the assumptions made in the calculations. Once it was established that the calculated and field‐measured ROIs were comparable, a sensitivity analysis determined ranges of different design and operational parameters that most affected the ROIs. © 2012 Wiley Periodicals, Inc.     

In-situ biological treatment of vinyl acetate-contaminated soil: An emergency response action

In-situ biological solid-phase (or land) treatment was cost-effectively used to remediate 1,500 cubic yards (1,100 m³) of contaminated soil within three months of field operation following spillage of an estimated 12,000 gallons (45,000 L) of vinyl acetate from a railroad tank car onto surface soil. The vinyl acetate rapidly hydrolyzed to acetate and acetaldehyde with concentrations ranging up to 22,000 and 3,000 mg/kg, respectively. Ethanol, a metabolic intermediate, was found to accumulate in soil to concentrations as high as 280 mg/kg. The estimate for excavation, transportation, and disposal of the contaminated soil as a special waste, and for backfilling of the excavated area, was $850,000. The cost for biological remediation of the contaminated soil was $400,000, which was less than half the cost of excavation. In-situ biological treatments have been used to readily remove contaminants, such as acrylonitrile, styrene, butylcellosolve, ethylacrylate, and n-butylacrylate, at other sites involving railroad incidents.     

An Improved Technique for Determining Abundance of Polycyclic Aromatic Hydrocarbon Degrading Microbial Populations

The current study describes an improved method for estimating the abundance of polycyclic aramatic hydrocarbon (PAH) degraders in contaminated soil and groundwater. Since the method is a simple incremental improvement to a commonly used approach, it can be easily introduced into the remediation practitioner's testing protocols by simply changing growth indicator dyes. The procedure described is relatively easy to conduct and provides an important addition to laboratories that are using conventional, nonmolecular techniques for microbial enumeration in their bioremediation programs. © 1999 John Wiley & Sons, Inc.     

Remediation of sites contaminated with TCE

Widespread use of trichloroethylene (TCE) in the U.S. has resulted in its frequent detection in soil and groundwater. TCE can become a health hazard after being processed in the human liver; or reductive dehalogenation in the environment may result in production of vinyl chloride, a known carcinogen. This has generated a high degree of interest in efficient and cost-effective technologies that can be used to remediate soil and ground-water contaminated with TCE. The purpose of this paper is to present and discuss relevant physicochemical properties and reactive mechanisms of TCE, and to delineate and discuss promising remediation methodologies that have been proposed and/or demonstrated for restoring contaminated subsurface environments. The information in this article has been funded wholly or in part by the U.S. EPA under contract No. 68–C8–0058 to Dynamac Corporation; it has been subjected to the Agency's peer and administrative review process and approved for publication.     

Integrated bioremediation of soil and groundwater at a superfund site

The soil and two aquifers under an active lumber mill in Libby, Montana, had been contaminated from 1946 to 1969 by uncontrolled releases of creosote and pentachlorophenol (PCP). In 1983, because the contaminated surface soil and the shallower aquifer posed immediate risks to human health and the natural environment, the U.S. Environmental Protection Agency placed the site on its National Priorities List. Feasibility studies in 1987 and 1988 determined that in situ bioremediation would help clean up this aquifer and that biological treatment would help clean up the contaminated soils. This article outlines the studies that led to a 1988 EPA record of decision and details the EPA-approved remedial plan implemented starting in 1989; EPA estimates a total cost of about $15 million (in 1988 dollars). The plan involves extensive excavation and biological treatment of shallow contaminated soils in two lined and bermed land treatment units, extraction of heavily contaminated groundwater, an aboveground bioreactor treatment system, and injection of oxygenated water to the contaminant source area, as well as to other on-site areas affected by the shallower aquifer's contaminant plume.     

The use of enhanced bioremediation at the Savannah River Site to remediate pesticides and PCBs

Enhanced bioremediation is quickly developing into an economical and viable technology for the remediation of contaminated soils. Until recently, chlorinated organic compounds have proven difficult to bioremediate. Environmentally recalcitrant compounds, such as polychlorinated biphenyls (PCBs) and persistent organic pesticides (POPs) such as dichlorodiphenyl trichloroethane (DDT) have shown to be especially arduous to bioremediate. Recent advances in field‐scale bioremedial applications have indicated that biodegradation of these compounds may be possible. Engineers and scientists at the Savannah River Site (SRS), a major DOE installation near Aiken, South Carolina, are using enhanced bioremediation to remediate soils contaminated with pesticides (DDT and its metabolites, heptachlor epoxide, dieldrin, and endrin) and PCBs. This article reviews the ongoing remediation occurring at the Chemicals, Metals, and Pesticides (CMP) Pits using windrow turners to facilitate microbial degradation of certain pesticides and PCBs. © 2003 Wiley Periodicals, Inc.     

Operation of a 27‐m3 biopile for the treatment of petroleum‐contaminated soil

Soil and groundwater contamination due to petroleum hydrocarbon spills is a frequent problem worldwide. In Mexico, even when programs oriented to the diminution of these undesirable events exist, in 2000, a total of 1,518 petroleum spills were reported. Exploration zones, refineries, and oil distribution and storage stations frequently are contaminated with total petroleum hydrocarbons (TPH); diesel fraction; gasoline fraction; benzene, toluene, ethyl benzene, and xylenes (BTEX); and polycyclic aromatic hydrocarbons (PAHs). Among the many methodologies available for the treatment of this kind of contaminated soil, bioremediation is the most favorable, because it is an efficient/low‐cost option that is environmentally friendly. This article discusses the capability of using a biopile to treat soils contaminated with about 40,000 mg/kg of TPH. Design and operation of a 27‐m³ biopile is described in this work, including microbiological and respirometric aspects. Parameters such as TPH, diesel fraction, BTEX, and PAHs considered by the U.S. Environmental Protection Agency were measured in biopile samples at 0, 2, 4, 6, 8, 10, and 22 weeks. A final average TPH concentration of 7,300 mg/kg was achieved in 22 weeks, a removal efficiency of 80 percent. © 2007 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.     

A bench scale PVD remediation system experiment

Prefabricated vertical drains (PVDs) have been used for decades for soil improvement. Recent research has shown that PVDs can also be used to remediate contaminated fine-grained soils. A research program was undertaken at The University of Texas at Austin to study the use of PVDs in soil flushing (pump and treat). This research program included both analytical and experimental studies. The focus of this paper is the experimental part of the research effort. The design and results of two experiments are presented. These results provided insight into the operation and design of PVD remediation systems and exposed areas that need additional research. The laboratory results support prior research that indicate that PVD remediation systems can be an effective means of remediating contaminated fine-grained soils. In addition, the importance of keeping the injection and extraction rates similar to minimize consolidation was highlighted. The measured heads did not indicate that a significant amount of drawdown occurred over the course of the experiment. More research needs to be done on maintaining a consistent extraction rate and additional post experiment concentration measurements would be required if determining the tracer mass balance is the focus of any future experiments.