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.     

Phytoremediation of a Petroleum‐Hydrocarbon Contaminated Shallow Aquifer in Elizabeth City,North Carolina,USA

A former bulk fuel terminal in North Carolina is a groundwater phytoremediation demonstration site where 3,250 hybrid poplars, willows, and pine trees were planted from 2006 to 2008 over approximately 579,000 L of residual gasoline, diesel, and jet fuel. Since 2011, the groundwater altitude is lower in the area with trees than outside the planted area. Soil‐gas analyses showed a 95 percent mass loss for total petroleum hydrocarbons (TPH) and a 99 percent mass loss for benzene, toluene, ethylbenzene, and xylenes (BTEX). BTEX and methyl tert‐butyl ether concentrations have decreased in groundwater. Interpolations of free‐phase, fuel product gauging data show reduced thicknesses across the site and pooling of fuel product where poplar biomass is greatest. Isolated clusters of tree mortalities have persisted in areas with high TPH and BTEX mass. Toxicity assays showed impaired water use for willows and poplars exposed to the site's fuel product, but Populus survival was higher than the willows or pines on‐site, even in a noncontaminated control area. All four Populus clones survived well at the site. © 2014 Wiley Periodicals, Inc.*     

Determination of suitable TPH remediation approach via MANOVA and inferential statistics assessment

Soil contamination resulting from petroleum hydrocarbon contaminants poses a fairly substantial hazard to human health and the environment. Phytoremediation, land farming, and chemico–biological stabilization were used to treat total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) at a crude oil polluted soil site in Nigeria. A field pilot study was conducted by preparing nine cells with subcells attached to each serving as a control with an overall area of 1.53 m². A complete block design method was used for the study. The prepared soil sample cells were divided into three groups with each group having approximately 300 kg of soil and delineated as low, medium, and high test plots. The low samples were spiked with 6.1 kg of crude oil, the medium samples were spiked with 12.2 kg of crudeoil, and the high samples were spiked with 18.3 kg of crude oil. Each row containing three cells with low, medium, and high concentrations were treated separately using the three treatment methods. The ratio of the soil sample to the organic amendment for the treatments was 2:1. The results showed over 90% degradation in the initial concentration of TPH and PAHs across different contaminant levels except in the control subcells where only 30% of degradation was recorded. Multivariate analysis of variance was employed to assess the significant difference in each treatment group while inferential statistics using a mean performance plot was used to ascertain the optimum treatment method. Land farming, chemico–biological stabilization, and phytoremediation ranked 1, 2, and 3, respectively. In conclusion, the three treatment methods employed all degraded the contaminants (TPH and PAHs) with land farming emerging as the best method.     

Carbon isotope forensics for methane source identification

Methane (CH₄) in ecosystems originates from ancient petroleum formed deep within the earth and/or via microbial fermentation of organic carbon and subsequent reduction of carbon dioxide (CO₂). Given the complexity of different ecosystems, origins of CH₄ present can be difficult to determine. This issue was realized in a situation where an antimethanogenic in situ chemical reduction (ISCR) remedial amendment containing organic carbon plus zero‐valent iron was applied to treat chlorinated solvents in groundwater at a former dry cleaner facility. The technology rapidly and effectively reduced the concentration of tetrachloroethene in groundwater thus meeting project goals without the stoichiometric accumulation of catabolites such as trichloroethene (TCE), cis‐1,2‐dichloroethene, or vinyl chloride and without excessive methanogenesis (e.g., <2 mg/L) in the treated area. However, approximately 9 months after treatment, increased levels of CH₄ (from 5 to 10 mg/L) were observed downgradient from the treated area. The applied remedial amendment contained approximately 60% (weight basis) fermentation organic carbon and was therefore a potential source of this CH₄. However, there was <500 mg/L total organic carbon in groundwater emanating from the upgradient treatment area which was unlikely sufficient to produce that much CH₄. Moreover, the soil gas also contained benzene, toluene, ethylbenzene, and xylenes and other gasoline constituents. These data suggested that the presence of three gasoline/diesel underground storage tanks that were previously closed in place with no active remediation performed could be the source of elevated CH₄. Thirdly, there were sewer lines, utilities, multiple gasoline stations, and industrial activities in the immediate area. With an initial assumption that CH₄ source(s) could include the ISCR amendment over stimulation of production, gasoline sourced CH₄ from nearby leaking lines, or sewage from local fractured pipes, carbon isotope analyses—radiocarbon (Δ¹⁴C) and stable carbon (δ¹³C)—were coupled with CH₄ and CO₂ concentration data from groundwater samples to determine the origin of respired carbon. The δ¹³C range for carbon sources respired in the process would be approximately ?26.5‰ to ?33.0‰ for the ISCR amendment and total petroleum hydrocarbons (TPH) residuals, respectively. Δ¹⁴C is approximately 0‰ and ?999‰ for the ISCR amendment (young carbon) and TPH (old carbon), respectively. The isotopic signature of respired gasses confirmed that elevated CH₄ downgradient of the treated area originated primarily from sewer gasses (or fermentation of liquids released from sewer lines). This study provides an overview of the capability to apply carbon isotope geochemistry to confirmation of remedial protocols and sources of anthropogenic carbon pools that conclusively identify the origin of CH₄ in a complex ecosystem undergoing a remedial action.     

Alternative method of groundwater sparging for petroleum hydrocarbon remediation

An alternative method of in-situ groundwater sparging, termed density-driven convection (patent pending), is presented. This method has been successfully used to remediate eight underground storage tank releases involving a wide distillation range of petroleum hydrocarbons (gasoline to waste oil) and in a variety of site soils (clay to sandy gravel). Application of the density-driven convection method is detailed in a case study. The system, installed to remediate a gasoline and diesel release from an underground storage tank, was operated and monitored for a period of one year. Monitoring data indicate reductions in total petroleum hydrocarbon concentrations in groundwater and in soil. Concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylenes, and naphthalene) also decreased in both media. Stimulation of natural biodegradation, the primary mechanism of removal, occurred rapidly. Natural biological activity gradually declined over the subsequent 150 days. After one year of operation, the sparging system has achieved or is rapidly approaching the regulatory cleanup goals for both soil and groundwater, including reduction of dissolved concentrations below maximum contaminant levels established under the Safe Drinking Water Act.     

Managing bioremediation of a creosote‐contaminated superfund site by optimizing moisture and temperature in a biopile

Soil moisture content and temperature in a contaminated soil biopile equipped with immobilized microbe bioreactors (IMBRs) were optimized during ex situ bioremediation at a creosote‐contaminated Superfund site. Efficiency of remediation during warm summer months without soil‐temperature and moisture optimization was compared with that of cold winter months when corrective measures were applied. Significant reduction (35 percent) in total polycyclic aromatic hydrocarbons (PAHs) was observed, compared to 3.97 percent without corrective measures (p < 0.05). Kinetic rates (KRs) for total PAH removal were significantly enhanced from 3.93 to 50.95 mg/kg/day. KRs for removal of high molecular mass four‐to‐six‐ring PAHs were also significantly enhanced from 70.29 mg/kg/day to 97.45 mg/kg/day ( p < 0.05). Bioremediation of two‐ and three‐ring PAHs increased significantly from 15 percent to 40 percent. Benzo[a]pyrene toxicity equivalent mass (BaP_equiv) was significantly reduced by 48 percent with KR of 0.47 mg/kg/day as compared to 22 percent with KR of 0.14 mg/kg/day (p < 0.05). Soil moisture content was enhanced from 15.7 percent to 41.4 percent. © 2007 Wiley Periodicals, Inc.     

Sustainable wind‐driven bioventing at a petroleum hydrocarbon–impacted site

Bioventing—the injection of air into the vadose zone to increase microbial activity—is a commonly used, proven technology for remediating volatile organic compounds present in the vadose zone. Passive systems driven by wind or solar power are both more cost‐effective and sustainable than conventional systems. Such a passive system is being applied successfully to remediate a site impacted with total petroleum hydrocarbons (TPH) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in soil. Bioventing technology was approved by the regulatory agency as an interim remedial action to remove chemicals of concern (COCs) in the vadose zone. A bioventing pilot study was conducted to evaluate the effectiveness of COC removal and collect parameters for full‐scale design and implementation. To evaluate the potential to use wind‐driven bioventing technology, two mobile weather stations were installed at the site and monitored for one month for a wind speed study. Based on the pilot‐test data and wind speed research, 12‐inch diameter funnel/vane 360‐degree wind collectors were designed as passive wind‐driven air‐injection devices and connected to existing monitoring wells. The measured air velocity ranged from 20 to 110 feet per minute during the start‐up and the first three months of operation and maintenance. Monitoring indicated a 20 percent oxygen delivery and greater than 90 percent reduction in COC concentrations, demonstrating a successful sustainable remediation with no power requirement and minimal operation and maintenance. © 2012 Wiley Periodicals, Inc.     

Chemical oxidation using stabilized hydrogen peroxide in high temperature,saline groundwater impacted with hydrocarbons and MTBE

In situ chemical oxidation (ISCO) of petroleum hydrocarbons (PHCs) within groundwater is considered a proven approach to addressing PHC‐impacted groundwater in nonsaline environments. One of the most common oxidants used for oxidation of PHCs in groundwater is hydrogen peroxide (H₂O₂). Due to its highly reactive nature, H₂O₂ is often stabilized to aid in increasing its reactivity lifespan. Limited research and application of ISCO has been completed in warm, saline groundwater environments. Furthermore, even fewer studies have been completed in these environments for ISCO using stabilized H₂O₂. In this research, stabilized H₂O₂ was examined to determine its effectiveness in the treatment of PHCs and the additive methyl tert‐butyl ether (MTBE). Three stabilizers (citrate, phytate, silica [SiO₂]) were tested to determine if the stabilizers could enhance and extend the treatment life of H₂O₂ within saline groundwater. To determine the effect of salinity on the three stabilizers, groundwater and aquifer samples were collected from two saline locations that had different salinity (total dissolved solids of about 7,000 mg/L and 18,000 mg/L). Specific target chemicals for treatment were water soluble, mobile components of gasoline including benzene, toluene, ethylbenzene, xylenes, (BTEX) and MTBE. Previous studies using unactivated persulfate indicated that the PHCs within the groundwater could be oxidized, however, only limited oxidation of the MTBE could be affected. The results of the laboratory tests indicated that greater than 95 percent of the target hydrocarbons were removed within 7 days of treatment. Microcosms with citrate‐stabilized H₂O₂ demonstrated a significantly faster and greater decline with most hydrocarbon concentrations reaching < 5 μg/L. The exceptions were ethylbenzene and m‐xylene, which were slightly decreased to about 30 and 20 μg/L, respectively. Initial mean concentrations of the BTEX compounds within the citrate‐stabilized microcosms were 10,554 μg/L, 9,318 μg/L, 6,859 μg/L, and 14,435 μg/L, respectively. The silicate‐stabilized H₂O₂ microcosms showed no significant benefit over the unstabilized control microcosms. The better performance of citrate‐stabilized microcosms was confirmed by increasing δ13C values of remaining hydrocarbons. MTBE declined from > 400 mg/L to < 100 mg/L in all microcosms, again with the best removal (> 90 percent) being measured in the citrate‐stabilized microcosms. Unfortunately, H₂O₂ oxidation in the microcosms also resulted in production of up to 40 mg/L TBA or approximately 10 percent of the MTBE oxidized.     

Passive to active tie‐in for soil gas surveys: Improved technique for source‐area,spatial variability,remediation‐monitoring,and vapor‐intrusion assessment

The mass‐to‐concentration tie‐in (MtoC Tie‐In) correlates passive soil gas (PSG) data in mass to active soil gas data in concentration determined by the US EPA Method TO‐17 or TO‐15. Passive soil gas surveys consist of rapid deployment of hydrophobic sorbents (dozens to several hundred locations typically installed in one day) to a depth of six inches to three feet in a grid pattern with exposure in the field from three days to two weeks to target a wide variety of organic compounds. A power function is used on a compound‐to‐compound basis to correlate spatially varying mass (nanograms) from selected locations within a passive soil gas survey to concentration (µg/m³) at those same locations. The correlation from selected PSG locations is applied to the remainder of the PSG grid. The MtoC Tie‐In correlations provide added value to a PSG survey, with the PSG data then used to estimate risk throughout the limits of the investigation for quantitative assessment. The results from a site in northern California show the MtoC Tie‐In correlations for both benzene and total petroleum hydrocarbons (TPH). The correlations are applied on a compound‐to‐compound basis to the remaining locations in the PSG grid to provide an estimate of concentration that can be used for comparison to risk/screening levels or fate‐and‐transport diagnostic tools (partitioning equations, solubility laws, etc.). An example of how the correlations are applied is presented in tabular form. The results from a chlorinated solvent survey show the MtoC Tie‐In correlation from a site in Maryland for tetrachloroethene (PCE). In this instance, there was a near‐perfect relationship between the PSG mass and the active soil gas concentration (R² value of 1). The concentration estimated throughout a PSG grid enables a vast new realm of interpretive power at sites. Several other sites are discussed, including an example application for groundwater. © 2009 Wiley Periodicals, Inc.     

Chemical Oxidation Performance in High Temperature,Saline Groundwater Impacted With Hydrocarbons

A series of laboratory microcosm experiments and a field pilot test were performed to evaluate the potential for in situ chemical oxidation (ISCO) of aromatic hydrocarbons and methyl tertiary butyl ether (MTBE), a common oxygenate additive in gasoline, in saline, high temperature (more than 30 °C) groundwater. Groundwater samples from a site in Saudi Arabia were amended in the laboratory portion of the study with the chemical oxidants, sodium persulfate (Na₂S₂O₈) and sodium percarbonate (Na₂(CO₃)₂), to evaluate the changes in select hydrocarbon and MTBE concentrations with time. Almost complete degradation of the aromatic hydrocarbons, naphthalene and trimethylbenzenes (TMBs), was found in the groundwater sample amended with persulfate, whereas the percarbonate‐amended sample showed little to no degradation of the target hydrocarbon compounds in the laboratory. Isotopic analyses of the persulfate‐amended samples suggested that C‐isotope fractionation for xylenes occurred after approximately 30 percent reduction in concentration with a decline of about 1 percent in the δ¹³C values of xylenes. Based on the laboratory results, pilot‐scale testing at the Saudi Arabian field site was carried out to evaluate the effectiveness of chemical oxidation using nonactivated persulfate on a high temperature, saline petroleum hydrocarbon plume. Approximately 1,750 kg of Na₂S₂O₈ was delivered to the subsurface using a series of injection wells over three injection events. Results obtained from the pilot test indicated that all the target compounds decreased with removal percentages varying between 86 percent for naphthalene and more than 99 percent for the MTBE and TMBs. The benzene, toluene, ethylbenzene, and xylene compounds decreased to 98 percent on average. Examination of the microbial population upgradient and downgradient of the ISCO reactive zone suggested that a bacteria population was present following the ISCO injections with sulfate‐reducing bacteria (SRB) being the dominant bacteria present. Measurements of inorganic parameters during injection and postinjection indicated that the pH of the groundwater remained neutral following injections, whereas the oxidation–reduction potential remained anaerobic throughout the injection zone with time. Nitrate concentrations decreased within the injection zone, suggesting that the nitrate may have been consumed by denitrification reactions, whereas sulfate concentrations increased as expected within the reactive zone, suggesting that the persulfate produced sulfate. Overall, the injection of the oxidant persulfate was shown to be an effective approach to treat dissolved aromatic and associated hydrocarbons within the groundwater. In addition, the generation of sulfate as a byproduct was an added benefit, as the sulfate could be utilized by SRBs present within the subsurface to further biodegrade any remaining hydrocarbons. ©2015 Wiley Periodicals, Inc.     

Evaluation of in situ steam‐injection processes for reduction of petroleum compounds within an abandoned canal

A conceptual approach of a novel application of in‐situ thermal processes that would either use a steam injection process or a steam/surfactant injection process was considered to remediate petroleum contaminated sediment residing in an abandoned canal. Laboratory tests were conducted in an attempt to volatilize or mobilize contaminants of concern (selected polycyclic aromatic hydrocarbons [PAHs]) from the contaminated sediment into a phase that could be physically removed. The processes were operated above ambient temperature and pressure in an attempt to increase the removal of the contaminants of concern from the sediment. The ability of both the steam injection process and the steam/surfactant process to remove PAHs from the sediment was considered ineffective; as only two of the seventeen selected PAHs (naphthalene and C1 naphthalene) were associated with a percentage mass reduction greater than 34% for both treatments (four trials). The steam/surfactant injection process generally resulted in higher reductions than the steam injection process, but had larger variances within the two trials using the treatment type. This preliminary evaluation suggests that steam‐based injection processes for removing petroleum contamination from this canal sediment, using the surfactants selected, equipment set‐up, and operating conditions studied, would be considered ineffective. © 2010 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.

     

Fenton氧化—微生物法降解土壤中石油烃

以长期被苯系物污染的活性污泥为菌源,采用液相“诱导物-中间产物-目标污染物”驯化模式驯化出专性混合石油降解菌群,并将其用于Fenton氧化—微生物法处理模拟石油污染土壤。高通量测序结果表明,产黄杆菌属（Rhodanobacter）、分支杆菌属（Mycobacterium）和根瘤菌属（Rhizobiales）为主导菌属。实验结果表明：接种混合菌群后降解50 d,土样的总石油烃（TPH）去除率较土著菌提高了13.4~20.5百分点;对于TPH含量（w）分别为4%,8%,11%的土样,Fenton氧化的最佳H₂O₂加入量分别为3,4,4 mol/L（Fe²⁺加入量0.04 mol/L）,TPH总去除率分别可达88.8%,65.0%,47.7%,较单独Fenton氧化或单独微生物法均有很大程度的提高,且缩短了降解时间,增加了土壤有机质。     

Lysinibacillus sphaericus and Geobacillus sp Biodegradation of Petroleum Hydrocarbons and Biosurfactant Production

Petroleum oil is a major driver of worldwide economic activity, but it has also created contamination problems during the storage and refining process. Also, unconventional resources are natural resources, which require greater than industry‐standard levels of technology or investment to exploit. In the case of unconventional hydrocarbon resources, additional technology, energy, and capital have to be applied to extract the gas or oil. Bioremediation of petroleum spill is considered of great importance due to the contaminating effects on human health and the environment. For this reason, it is important to reduce total petroleum hydrocarbons (TPH) in contaminated soil. In addition, biosurfactant production is a desirable property of hydrocarbon‐degrading microorganisms. Seven strains belonging to Lysinibacillus sphaericus and Geobacillus sp were selected to evaluate their ability to biodegrade TPH in the presence of toxic metals, their potential to produce biosurfactants, and their ability to improve the biodegradation rate. The seven bacterial strains examined in this study were able to utilize crude petroleum‐oil hydrocarbons as the sole source of carbon and energy. In addition, their ability to degrade crude oil was not affected by the presence of toxic metals such as chromium and arsenic. At the same time, the strains were able to reduce toxic metals concentration through biosorption processes. Biosurfactant production was determined using the drop‐collapsed method for all strains, and they were characterized as both anionic and cationic biosurfactants. Biosurfactants showed an increase in biodegradation efficiency both in liquid minimal salt medium and landfarming treatments. The final results in field tests showed an efficiency of 93 percent reduction in crude oil concentration by the selected consortium compared to soil without consortium. The authors propose L. sphaericus and Geobacillus sp consortium as an optimum treatment for contaminated soils. In addition, production of biosurfactants could have an application in the extraction of crude oil from unconventional hydrocarbon resources. © 2014 Wiley Periodicals, Inc.     

Remedial Process Optimization and Ozone Sparging for Petroleum Hydrocarbon‐Impacted Groundwater

A former natural gas processing station is impacted with total petroleum hydrocarbons (TPH) and benzene. Remedial process optimization (RPO) was conducted to evaluate the effectiveness of the historical air sparging/soil vapor extraction (AS/SVE) system and the current groundwater extraction and treatment system. The RPO indicated that both remedial activities offered no further benefit in meeting remediation goals. Instead, an in situ chemical oxidation (ISCO) system was recommended. Ozone was selected, and the results of a bench test indicated that the ozone demand was 8 to 12 mg ozone/mg TPH and that secondary by‐products would include hexavalent chromium and bromate. A capture zone analysis was conducted through groundwater flow modeling (MODFLOW) to ensure containment of the injected oxidant using the existing groundwater extraction system. Results of a pilot study indicated that the optimum frequency of ozone sparging is 60 minutes in order to reach a maximum radius of influence of 20 feet. TPH concentrations within the treatment zone decreased by 97 percent over two months of ozone sparging. Concentrations of hexavalent chromium and bromate increased from nondetect to 44 and 110 mg/L, respectively, during the ozone sparging but attenuated to nondetectable concentrations within three months of system shut down. ©2016 Wiley Periodicals, Inc.     

Enhanced land treatment of petroleum-contaminated soils using solid peroxygen materials

A pilot field study evaluated whether adding solid peroxygen materials during land treatment could cost effectively accelerate cleanup at a site contaminated with petroleum-related compounds. Five test cells were constructed containing approximately five cubic yards of soil contaminated with 300–400 mg/kg of total petroleum hydrocarbons (TPH). Three cells received treatment with solid peroxygen materials (either MgO₂ or CaO₂), while the other two cells served as controls (no peroxygen amendment). Adding solid peroxygen compounds effectively reduced the hydrocarbon contamination in the soils and decreased the treatment time. During this time, the concentration of TPH in soil in the three treatment cells decreased. In contrast, there was little loss of TPH from the two control cells simulating traditional land treatment. Adding the solid peroxygen materials reduced the total site remediation time, thereby reducing the overall costs.     

Determination of BTEX by GC–MS in Air of Offset Printing Plants: Comparison between Conventional and Ecological Inks

The use of inks containing organic solvents by the offset printing process implies in the release of volatile organic compounds to the work environment. Many of these compounds such as benzene, toluene, ethylbenzene, and the xylene isomers (well known by the acronym BTEX) are extremely toxic. In this study, the BTEX concentrations were determined in two different printing plants that use distinct types of inks: the conventional and the so-called ecological, which is manufactured based on vegetal oil. Concentration ranges were 43–84, 15–3,480, 2–133, 5–459, and 2–236 μg m^?3 for benzene, toluene, ethylbenzene, m?+?p-xylene, and o-xylene, respectively, for the conventional printing plant. At the ecological printing plant, concentration ranges were below limit of detection (<LD)-31, <LD-618, <LD-1,690, <LD-10,500, <LD-3,360 μg m^?3 for benzene, toluene, ethylbenzene, m?+?p-xylene, and o-xylene, respectively. BTEX concentrations are lower at the ecological printing environment than in the conventional, where mineral oil-based inks are used. However, the worker who cleans the printing matrices is exposed to high concentrations of ethylbenzene and xylenes, due probably to the cleaning product’s composition (containing high amounts of BTEX). Although the BTEX concentrations found in both printing work environments were below the limits considered by the Brazilian Law for Activities and Unhealthy Operations (NR-15), the exposure to such vapors characterizes risk to the workers’ health for some of the evaluated samples, mainly the personal ones.     

Evaluation of algal phytoremediation of light extractable petroleum hydrocarbons in subarctic climates

The presence of an organic mat in a hydrocarbon‐impacted creek in Whitehorse, Yukon Territory, Canada was examined for contributions to in situ remediation of petroleum‐contaminated water. This article investigates the role of algae, found in the organic mat, in the remediation of light extractable petroleum hydrocarbons (LEPHs) at the site and in the laboratory. During the study, LEPH concentrations were reduced by 16.8 percent in the presence of algae alone (algal solution) and 30.4 percent in the combined organic mat solution containing microbial consortia. The study results indicate that algal species at the site did not directly phytoremediate hydrocarbons. Rather, they were part of the total biological degradation taking place. © 2009 Wiley Periodicals, Inc.     

The Use of Oxygen Release Compound for the Accelerated Bioremediation of Aerobically Degradable Contaminants: The Advent of Time-Release Electron Acceptors

Oxygen Release Compound (ORC®) is a patented formulation of intercalated magnesium peroxide that releases oxygen slowly when hydrated. ORC treatment represents a “low intensity” approach to site remediation. It provides a simple, passive, low-cost and long-term acceleration of aerobic natural attenuation and has been shown to cost-effectively reduce time to site closure. ORC is now a proven technology as evidenced by its five years of use on over 5,000 sites in 50 states and 11 countries, and the existence of a full body of independent, peer reviewed literature on its performance. The first applications of ORC were for the treatment of benzene, toulene, ethylbenzene, and xylene (BTEX) and other light petroleum hydrocarbon fractions. Use has now expanded to the treatment of heavier fractions such as heating oil and some of the Polycyclic aromatic hydrocarbons (PAHs). More recently. ORC has been used to bioremediate the highly mobile and problematic gasoline oxygenate methyl tertiary butyl ether (MTBE) and has been applied to sites impacted with nitroaromatics, chloroaromatics, and some of the lower-order chlorinated hydrocarbons that can be treated aerobically—most notably vinyl chloride. Since ORC is an insoluble powder, it can be packaged in material composed of a specially designed filter fabric. These “filter socks” are then contacted with contaminated groundwater via an array of wells or trenches. ORC can also be mixed directly with water to form a slurry for permanent injection applications in the saturated zone or dispersed in powdered form for the in-situ or ex-situ treatment of soil. A broad array of treatment points, in which ORC slurry is backfilled or injected, can be implemented with low-cost, small-bore push-point technologies to directly treat dissolved phase plumes and moderate levels of sorbed contaminants. Powder or slurry is traditionally used in the remediation of residual contamination at the bottom of contaminated soil excavations. © 1999 John Wiley & Sons, Inc.     

Evaluation of white‐rot fungi for the remediation of creosote‐contaminated soil

Application of fungal‐based bioaugmentation was evaluated for the remediation of creosote‐contaminated soil at a wood‐preserving site in West Virginia. Soil at the site contained creosote‐range polycyclic aromatic hydrocarbons (PAHs) at concentrations in some areas that exceed industrial risk‐based levels. Two white‐rot fungi (Pleurotus ostreatus and Irpex lacteus) were evaluated for remediation effectiveness in a two‐month bench‐scale treatability test. Both fungi produced similar results, with up to 67.3 percent degradation of total PAHs in 56 days. Pilot‐scale testing was performed at the site using Pleurotus ostreatus grown on two local substrate mixtures. During the 276‐day field trial, total PAHs were degraded by up to 93.2 percent, with all individual PAHs except one achieving industrial risk‐based concentrations. It was recommended that fungal‐based remediation be applied to all contaminated soil at the site. © 2002 Wiley Periodicals, Inc.     

Treating contaminated groundwater using a fluidized-bed reactor

Both biological treatment and carbon adsorption have inherent advantages for remediation of groundwater contaminated with compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX). Biological treatment destroys the contaminants and is extremely cost-effective. Carbon adsorption is a positive removal mechanism that ensures a product water of high quality, but the process is relatively expensive and requires frequent carbon replacement and/or regeneration. Coupling the two processes realizes the inherent advantages of both approaches. An additional benefit of combining these removal mechanisms in a biological fluidizedbed reactor (FBR) system is that no loss of BTEX from volatilization occurs, since predissolution of oxygen is used in place of conventional aeration for the fluidized-bed process. This article summarizes preliminary performance data from a laboratory, pilot-scale biological FBR, using granulated activated carbon (GAC) as the support media (GAC-FBR), operated at various BTEX concentrations and organic loading rates. Greater than 99-percent degradation of total BTEX was achieved at an organic loading rate of 3.0 kg COD/m³-day or less and an empty bed hydraulic retention time of 5.0 minutes. System performance was extremely robust, easily handling a tenfold step increase in loading due to the combined adsorptive capability of the biofilm-coated GAC and ability to subsequently bioregenerate the GAC. Monitoring verified that no off-gas was produced during treatment.