Remediation of Trapped Free‐Phase LNAPL

Free‐phase light nonaqueous phase liquids (LNAPLs) may be trapped in certain stratigraphic and structural features near or at contaminated sites due to seasonal or other variations in the water table elevation. The purpose of this article is to point out particular subsurface conditions that are conducive to trapping of free‐phase LNAPLs and to suggest approaches to remediating LNAPL‐contaminated sites exhibiting similar subsurface geometry and stratigraphy. To trap free‐phase LNAPL, a structure must have, in addition to closed contours, an upper boundary with pores small enough so that the LNAPL will not enter them. This boundary usually consists of clay‐rich sediments. The Lower Mississippi River Valley contains thousands of these potential traps associated with the geomorphic surfaces mapped as outwash or braided stream terraces, which are covered with thin layers of backswamp clays. These traps may have closure heights ranging from about 1 to 7.5 meters or more and have variable lateral extents. Based on surface geomorphic analysis, the potential LNAPL traps in the Lower Mississippi River Valley range in size from about 0.06 by 0.02 km to 4.19 by 0.69 km. The apparent best remediation strategy for LNAPL sites located on these geomorphic surfaces, which contain these trapping structures, is to first determine if free‐phase is present. If it is present, and is contained in one of the stratigraphic traps, the free‐phase can be removed through an extraction well or wells located at the trap apex. Geomorphic analysis and geophysical surveys may be necessary to accurately locate the trap apex. The remaining residual hydrocarbons might best be remediated using an air sparging system, although it may be necessary to install air vents through the clay cap by backfilling augured holes with washed sand. If it is determined that, due to geometry, the dissolved LNAPL plume cannot be adequately remediated using an air sparging system, then groundwater circulation wells or monitored natural attenuation may be alternative technologies. © 2002 Wiley Periodicals, Inc.     

Immobilizing a light,nonaqueous phase liquid

A new technique has been developed to immobilize organic chemicals at a Superfund site. In the course of predesign studies in preparing the Remedial Design for the Pioneer Sand Superfund site in Pensacola, Florida, a light, nonaqueous phase liquid (LNAPL) was discovered floating on the groundwater within the on-site landfill. The liquid, with a viscosity similar to SAE 20 motor oil, was made up of heavy organic chemicals and volatile organic chemicals (VOCs), but no pesticides or polychlorinated biphenyls (PCBs). The volatiles present included toluene, ethylbenzene, and xylenes. Regulatory agencies expressed concern over the possibility of LNAPL migration and asked that a method of LNAPL immobilization be devised.     

In situ chemical oxidation of residual LNAPL and dissolved‐phase fuel hydrocarbons and chlorinated alkenes in groundwater using activated persulfate

A treatablity study (TS) was conducted to evaluate the efficacy of in situ chemical oxidation (ISCO) using activated persulfate, alone and in combination with air sparging (AS), for treating a source area contaminated with residual light nonaqueous‐phase liquid (LNAPL), dissolved‐phase fuel hydrocarbons (HCs), and dissolved‐phase chlorinated alkenes at Edwards Air Force Base (AFB), California. The TS was implemented in two phases. Phase I included injecting a solution of sodium persulfate and sodium hydroxide (NaOH) into groundwater via an existing well where residual LNAPL and dissolved‐phase contaminants were present. Because the results of Phase I indicated a limited distribution of the activated persulfate, Phase II was performed to assess whether AS could enhance the distribution of the sodium persulfate. Each phase was followed by groundwater monitoring and sampling at the injection well and at three monitoring wells, located 20 to 44 feet from the injection well. Results from Phases I and II of the TS indicated that (1) alkaline‐activated persulfate was effective in promoting the dissolution of LNAPL and the degradation of dissolved‐phase contaminants, but only at the injection well; (2) the addition of AS was effective in enhancing the radius of persulfate distribution from less than 20 feet to greater than 44 feet, and (3) persulfate alone (i.e., not in an activated state) was effective in reducing the concentrations of dissolved‐phase fuel HC and chlorinated alkenes. © 2009 Wiley Periodicals, Inc.     

Solar‐powered in situ soil washing with surfactant to collect LNAPL

This article presents the findings of a sustainable, surfactant‐enhanced, product recovery pilot‐scale study (PSS) completed between January 2010 and May 2010 at the Hydrocarbon Burn Facility located at the John F. Kennedy Space Center in Florida. The goal of this study was to implement a unique, simple, and sustainable light nonaqueous‐phase liquid (LNAPL) recovery process and evaluate site‐specific volumes and rates of LNAPL that could be collected and the degree of soil and groundwater cleanup that could be achieved. The recovery process was a combination of groundwater recirculation at a rate of approximately 2.9 gallons per minute (11.0 liters per minute), soil washing via LNAPL mobilization, and collection of LNAPL via a hydrophobic LNAPL skimmer. A biodegradable surfactant, ECOSURF^TM SA‐15, was added to the recirculation line to lower the interfacial tension and facilitate LNAPL recovery via mobilization. All equipment (submersible pump, LNAPL skimmer, surfactant feed pump, controls, and various other equipment) used was powered by a solar panel array. Approximately 60 gallons (227 liters) or 429 pounds (195 kilograms) of LNAPL were collected at the recirculation site over approximately three months during the PSS. The data suggest that surfactant amendments greatly enhanced free product collection. The maximum rate of free product collection was approximately 1 gallon (3.8 liters) per day. © 2012 Wiley Periodicals, Inc.     

Transmissivity as a Primary Metric for LNAPL Recovery—Case Study Comparison of Short‐Term vs. Long‐Term Methods

This article presents a case study and comparative analysis of light nonaqueous phase liquid (LNAPL) transmissivity estimated using short‐ and long‐term test methods at an active petroleum refinery. LNAPL transmissivity (Tn) is a recognized direct indicator of LNAPL recoverability with increasing acceptance by regulatory agencies. Historical releases at a refinery resulted in widespread LNAPL accumulations across the site and, as such, a focused approach is being implemented to enhance recovery, shorten remedial timeframes, and prioritize areas for recovery. Groundwater pumping systems operate continuously to maintain hydraulic containment of impacts, along with 12 LNAPL recovery systems. Transmissivity has been established as a primary metric and management tool for LNAPL recovery at the refinery. In this case study, estimated transmissivity values from short‐term data (baildown testing) and long‐term data (LNAPL skimming operations) from the same locations are analyzed and compared. Overall results are presented with respect to variations in transmissivities between the short‐ and long‐term tests, significance of data collection and quality, and consideration factors affecting transmissivity including fluid properties, soil types, hydrogeology, saturation levels, tidal effects, migration rates, and receptor risks. Additionally, the application of transmissivity as a metric for monitoring progress toward LNAPL recovery endpoints as part of the LNAPL remediation program development is discussed. ©2015 Wiley Periodicals, Inc.     

Superfund site remediation by landfilling—overview of landfill design,operation, closure,and postclosure issues

This article discusses the appropriateness of using landfills as part of remediating hazardous chemical and Superfund sites, with particular emphasis on providing for true long‐term public health and environmental protection from the wastes and contaminated soils that are placed in the landfills. On‐site landfilling or capping of existing wastes is typically the least expensive approach for gaining some remediation of existing hazardous chemical/Superfund sites. The issues of the deficiencies in US EPA and state landfilling approaches discussed herein are also applicable to the landfilling of municipal and industrial solid “nonhazardous” wastes. These deficiencies were presented in part as “Problems with Landfills for Superfund Site Remediation” at the US EPA National Superfund Technical Assistance Grant Workshop held in Albuquerque, New Mexico, in February 2003. They are based on the author's experience in investigating the properties of landfill liners and the characteristics of today's landfills, relative to their ability to prevent groundwater pollution and to cause other environmental impacts. Discussed are issues related to both solid and hazardous waste landfills and approaches for improving the ability of landfills to contain wastes and monitor for leachate escape from the landfill for as long as the wastes in the landfill will be a threat. © 2004 Wiley Periodicals, Inc.     

In‐Canal Stabilization/Solidification of NAPL‐Impacted Sediments

In situ solidification (ISS) has been used with increasing frequency as a remedial technology for source area treatment at upland sites impacted with a variety of organic contaminants, including coal tar, creosote, and other nonaqueous phase liquids (NAPLs). With several large, complex, urban water ways and rivers impacted with NAPLs, ISS is more recently being considered as a technology of choice to help reduce remedial costs, minimize short‐ and long‐term impacts of mobile NAPL, and lower the carbon footprint. This article presents the results of a successful pilot study of ISS at the Gowanus Canal Superfund site in Brooklyn, New York. This represents the first major sediment ISS field demonstration project in a saline environment and the first project to evaluate large‐scale implementation of ISS from a barge and through overlaying sediment. ©2016 Wiley Periodicals, Inc.     

Thermal desorption of PCB-contaminated waste at the waukegan harbor superfund site

In June 1992, SoilTech ATP Systems, Inc., completed the soil treatment phase of the Waukegan Harbor Superfund Project in Waukegan, Illinois, after approximately five months of operation. SoilTech successfully treated 12,700 tons of sediment contaminated with polychlorinated hiphenyls (PCBs) using a transportable SoilTech anaerobic thermal processor (ATP) system nominally rated at ten tons per hour throughput capacity. The SoilTech ATP technology anaerobically desorbs contaminants such as PCBs from solids and sludges at temperatures over 1,000° F. Principal products of the process are clean, treated solids and an oil condensate containing the hydrocarbon contaminants. At the Waukegan Harbor Superfund site, PCB concentrations in the sediments excavated and dredged from a ditch, lagoon, and harbor slip averaged 10,400 parts per million (ppm) (1.04 percent) and were as high as 23,000 ppm (2.3 percent). Treated soil was backfilled in an on-site containment cell. The removal efficiency of PCBs from the soil averaged 99.98 percent, relative to the project performance specification of 97 percent, and treated soil PCB concentrations were measured below 2 ppm. Approximately 30,000 gallons of PCB oil, desorbed from the feed material, were returned to the owner for subsequent off-site disposal. After modifications to the emissions control equipment, compliance with the 99.9999 percent destruction and removal efficiency (DRE) for PCBs in stack emissions required by the U.S. Environmental Protection Agency was achieved.     

Sand Cap Placement and Cap Thickness Monitoring: A Case Study at a Confined Disposal Facility

Thin sediment capping is a commonly used technique to prevent mobilization of contaminants from sediments into the environment. A 70‐m‐deep subaqueous confined disposal facility (CDF, 350,000 m²) at Malmøykalven, Oslofjord, which received dredged contaminated sediments from Oslo Harbor, was capped with 148,900 m³ of sand in 2009. This research serves as a case study regarding some of the key considerations involved with the cap placement and monitoring of the cap layer. Uncertainty is included in all the cap thickness monitoring methods and a combined use of them provided a better understanding of the cap coverage and structure at the site. An open water disposal model (STFATE) was used to simulate the behavior of the barge‐released cap material. The modeling results were consistent with field observations regarding the material spread, and the results provided insight into the relatively high material losses calculated. Better knowledge obtained of material settling resulted in cap properties and cap monitoring methods that are useful when planning similar operations. ©2015 Wiley Periodicals, Inc.     

Full‐scale in‐situ biobarrier demonstration for containment and treatment of MTBE

The Naval Facilities Engineering Service Center (NFESC), Arizona State University, and Equilon Enterprises LLC are partners in an innovative Environmental Security Technology Certification Program cleanup technology demonstration designed to contain dissolved MTBE groundwater plumes. This full‐scale demonstration is being performed to test the use of an oxygenated biobarrier at Naval Base Ventura County, in Port Hueneme, California. Surprisingly, few cost‐effective in‐situ remedies are known for the cleanup of MTBE‐impacted aquifers, and remediation by engineered in‐situ biodegradation was thought to be an unlikely candidate just a few years ago. This project demonstrates that MTBE‐impacted groundwater can be remediated in‐situ through engineered aerobic biodegradation under natural‐flow conditions. With respect to economics, the installation and operation costs associated with this innovative biobarrier system are at least 50 percent lower than those of a conventional pump and treat system. Furthermore, although it has been suggested that aerobic MTBE biodegradation will not occur in mixed MTBE‐BTEX dissolved plumes, this project demonstrates otherwise. The biobarrier system discussed in this article is the largest of its kind ever implemented, spanning a dissolved MTBE plume that is over 500 feet wide. This biobarrier system has achieved an in‐situ treatment efficiency of greater than 99.9 percent for dissolved MTBE and BTEX concentrations. Perhaps of greater importance is the fact that extensive performance data has been collected, which is being used to generate best‐practice design and cost information for this biobarrier technology. © 2001 John Wiley & Sons, Inc.     

Phytoremediation of dissolved phase organic compounds: Optimal site considerations relative to field case studies

The United States Environmental Protection Agency/Environmental Response Team (EPA/ERT) has been supporting and implementing the use of phytoremediation to remediate dissolved phase organic compounds at Superfund sites since March 1996. Since then, ERT has applied phytoremediation field plots, both pilot and full scale, to a variety of field conditions. These active sites vary considerably as to depth to groundwater, groundwater transmissivity, contaminant concentrations, contaminant hydrophobicity, climate, planting design, plant selection, planting technique, and type of monitoring. Here we compare the literature and discuss lessons learned at five Superfund sites. Current maintenance and monitoring techniques at these sites are also discussed with recommendations for the maintenance and monitoring of similar sites in the future. © 2003 Wiley Periodicals, Inc.     

Evaluation of a vertical frozen soil barrier at oak ridge national laboratory

Arctic Foundations, Inc. (AFI), of Anchorage, Alaska, has developed a freeze barrier system designed to hydraulically isolate a contaminant source area. The system can be used for long‐term or temporary containment of groundwater until appropriate remediation techniques can be applied. The technology was evaluated under the United States Environmental Protection Agency's (EPA's) Superfund Innovative Technology Evaluation (SITE) program at the United States Department of Energy's (DOE's) Oak Ridge National Laboratory (ORNL) facility in Oak Ridge, Tennessee. For the demonstration, an array of freeze pipes called “thermoprobes” was installed to a depth of 30 feet below ground surface around a former waste collection pond and keyed into bedrock. The system was used to establish an impermeable frozen soil barrier to hydraulically isolate the pond. Demonstration personnel collected independent data to evaluate the technology's performance. A variety of evaluation tools were used—including a groundwater dye tracing investigation, groundwater elevation measurements, and subsurface soil temperature data—to determine the effectiveness of the freeze barrier system in preventing horizontal groundwater flow beyond the limits of the frozen soil barrier. Data collected during the demonstration provided evidence that the frozen soil barrier was effective in hydraulically isolating the pond.     

Update to the light nonaqueous phase liquid infiltration conceptual model

The 1970s oil spill model described the infiltration of oil (light nonaqueous phase liquid or LNAPL) into the subsurface, resulting in an oil pancake depressing the water table within the capillary fringe. An update to the 1970s model is needed because, according to the discussion by Lenhard et al. on the work of Lenhard and Parker and Farr et al., “A key concept of their efforts was that LNAPL-saturated ‘pancakes’ do not exist.” Lenhard and Parker and Farr et al. showed that the distribution of water, LNAPL, and air in the subsurface was a function of the LNAPL, water, and air pressures; fluid properties; and the pore-size distribution of the porous medium, and that the fluid saturations can be calculated from fluid levels in a monitoring well. The 1970s oil spill infiltration model described that spilled LNAPL migrates downward through the vadose zone under the force of gravity with some lateral spreading. The vadose zone, where all of the liquid pressures are less than atmospheric pressure, becomes a three-fluid zone consisting of variable saturations of air, water, and LNAPL, which together fully saturate the pore spaces. One important update to the 1970s model is that instead of the infiltrating LNAPL stopping at and depressing the water table, LNAPL penetrates the water table to a depth consistent with the gravitational and capillary forces experienced during LNAPL infiltration and creates a two-fluid zone below the water table where LNAPL and water pressures are greater than atmospheric pressure. After the LNAPL release stops, LNAPL infiltration and migration will cease after reaching equilibrium. The updated LNAPL infiltration conceptual model, like the 1970s model, describes the situation where the LNAPL release has stopped and LNAPL infiltration and migration have ceased after reaching equilibrium. The volume of LNAPL released is also assumed to be sufficient to pass through the vadose zone and enter the saturated zone.     

Challenges of soil mixing using catalyzed hydrogen peroxide with rotating dual axis blending technology

Although known to be one of the most effective oxidants for treatment of organic contaminants, catalyzed hydrogen peroxide (CHP) is typically not used for soil mixing applications because of health and safety concerns related to vapor generation and very rapid rates of reaction in open excavations. In likely the first large‐scale in situ CHP soil mixing application, an enhanced CHP, modified Fenton's reagent (MFR), was applied during soil mixing at the Kearsarge Metallurgical Superfund Site in New Hampshire. An innovative rotating dual‐axis blender (DAB) technology was used to safely mix the MFR into low‐plasticity silt and clay soils to remediate residual 1,1,1‐trichloroethane (111TCA); 1,1‐dichloroethene (11DCE); and 1,4‐dioxane (14D). It was expected that the aggressive treatment approach using relatively “greener” hydrogen peroxide (HP) chemistry would effectively treat Site contaminants without significant byproduct impacts to groundwater or the adjacent pond. The remediation program was designed to treat approximately 3,000 cubic yards of residual source area soil in situ by aggressively mixing MFR into the soils. The subsurface interval treated was from 7 to 15 feet below ground surface. To accurately track the soil mixing process and MFR addition, the Site was divided into 109 10‐foot square treatment cells that were precisely located, dosed, and mixed using the DAB equipped with an on‐board GPS system. The use of stabilizing agents along with careful calculation of the peroxide dose helped to ensure vapor‐free conditions in the vicinity of the soil mixing operation. Real‐time sampling and monitoring were critical in identifying any posttreatment exceedences of the cleanup goals. This allowed retreatment and supplemental testing to occur without impacting the soil mixing/in situ chemical oxidation (ISCO) schedule. Posttreatment 24‐hr soil samples were collected from 56 random locations after ensuring that the HP had been completely consumed. The posttreatment test results showed that 111TCA and 11DCE concentrations were reduced to nondetect (ND) or below the cleanup goals of 150 μg/kg for 111TCA and 60 μg/kg for 11DCE. Supplemental posttreatment soil samples, collected six months after treatment, showed 100 percent compliance with the soil treatment goals. Groundwater samples collected one year after the MFR soil mixing treatment program showed either ND or low concentrations for 111TCA, 11DCE, and 14D. Successful stabilization and site restoration was performed after overcoming considerable challenges associated with loss of soil structure, high liquid content, and reduced bearing capacity of the blended soils.     

Nanotechnology for site remediation

As a remediation tool, nanotechnology holds promise for cleaning up hazardous waste sites cost‐effectively and addressing challenging site conditions, such as the presence of dense nonaqueous phase liquids (DNAPLs). Some nanoparticles, such as nanoscale zero‐valent iron (nZVI) are already in use in full‐scale projects with encouraging success. Ongoing research at the bench and pilot scale is investigating particles such as self‐assembled monolayers on mesoporous supports (SAMMS™), dendrimers, carbon nanotubes, and metalloporphyrinogens to determine how to apply their unique chemical and physical properties for full‐scale remediation. There are many unanswered questions regarding nanotechnology. Further research is needed to understand the fate and transport of free nanoparticles in the environment, whether they are persistent, and whether they have toxicological effects on biological systems. In October 2008, the U.S. Environmental Protection Agency's Office of Superfund Remediation and Technology Innovation (OSRTI) prepared a fact sheet entitled “Nanotechnology for Site Remediation,” and an accompanying list of contaminated sites where nanotechnology has been tested. The fact sheet contains information that may assist site project managers in understanding the potential applications of this group of technologies. This article provides a synopsis of the US EPA fact sheet, available at http://clu‐in.org/542F08009 , and includes background information on nanotechnology; its use in site remediation; issues related to fate, transport, and toxicity; and a discussion of performance and cost data for field tests. The site list is available at http://clu‐in.org/products/nanozvi . © 2008 Wiley Periodicals, Inc.     

Evaluation of a Slag and Portland Cement Mix to Simulate Treatment of Acidic Waste via Solidification/Stabilization in a Deep Soil Mix Application

Site investigations at an oil and gas facility identified a highly acidic waste referred to as residual acid tar that resulted in the transport of dissolved nickel toward the point of compliance at concentrations that exceeded site environmental screening levels. Solidification/stabilization (S/S) via deep soil mixing was selected as the remedial approach and a mixture of ground granulated blast furnace slag cement and Portland cement was subjected to treatability testing to evaluate the reagent mix's ability to achieve treatment objectives. Results from the treatability test showed a cement mix dose of 21 percent was sufficient to raise the pH above the target of 6.0 and reduce dissolved nickel concentrations to below site screening levels in leachate from treated samples of residual acid tar and material impacted by residual acid tar. Cement mix doses of 21 percent or greater were sufficient to achieve target strengths in the unimpacted shallow overburden. However, none of the doses tested were able to achieve target strengths in the residual acid tar or peaty material impacted by the residual acid tar. Results showed soil strengths increased significantly when the pH in leachate from the treated samples approached 12, suggesting the presence of organic acids related to the peaty soils may interfere with the cement set. Recommendations from the study include additional treatability testing to evaluate pre‐treatment with hydrated lime to satisfy acid neutralization requirements prior to dosing with the cement mix. ©2016 Wiley Periodicals, Inc.     

Pilot‐scale demonstration of in situ capping of PCB‐containing sediments in the lower Grasse River

A fish‐consumption advisory is currently in effect in a seven‐mile stretch of the Grasse River in Massena, New York, due to elevated levels of PCBs in fish tissue. One remedial approach that is being evaluated to reduce the PCB levels in fish from the river is in situ capping. An in‐river pilot study was conducted in the summer of 2001 to assess the feasibility of capping PCB‐containing sediments of the river. The study consisted of the construction of a subaqueous cap in a seven‐acre portion of the river using various combinations of capping materials and placement techniques. Optimal results were achieved with a 1:1 sand/topsoil mix released from a clamshell bucket either just above or several feet below the water surface. A longer‐term monitoring program of the capped area commenced in 2002. Results of this monitoring indicated: 1) the in‐place cap has remained intact since installation; 2) no evidence of PCB migration into and through the cap; 3) groundwater advection through the cap is not an important PCB transport mechanism; and 4) macroinvertebrate colonization of the in‐place cap is continuing. Additional follow‐up monitoring in the spring of 2003 indicated that a significant portion of the cap and, in some cases, the underlying sediments had been disturbed in the period following the conclusion of the 2002 monitoring work. An analysis of river conditions in the spring of 2003 indicated that a significant ice jam had formed in the river directly over the capping pilot study area, and that the resulting increase in river velocities and turbulence in the area resulted in the movement of both cap materials and the underlying sediments. The pilot cap was not designed to address ice jam–related forces on the cap, as the occurrence of ice jams in this section of the river had not been known prior to the observations conducted in the spring of 2003. These findings will preclude implementation of the longer‐term monitoring program that had been envisioned for the pilot study. The data collected immediately after cap construction in 2001 and through the first year of monitoring in 2002 serve as the basis for the conclusions presented in this article. It should be recognized that, based on the observation made in the spring of 2003, some of these conclusions are no longer valid for the pilot study area.The occurrence of ice jams in the lower Grasse River and their importance on sediments and PCBs within the system are currently under investigation. © 2003 Wiley Periodicals, Inc.     

In Situ Solidification (ISS) of River Sediments: Pilot Demonstration and Discussion of ISS as a Remedial Alternative to Dredging and Capping

In situ solidification (ISS) is a proven technology for remediation of upland site soils, but has not been thoroughly demonstrated for use in impacted underwater sediments. This article describes the first successful use of ISS techniques to solidify underwater sediments containing manufactured gas plant non‐aqueous‐phase liquid (NAPL). The techniques consisted of mixing cementitious grout with the sediments in situ to create a monolith that immobilized the contaminants, significantly decreased the hydraulic conductivity, and also vastly decreased contaminant leaching potential of the sediments. The success of this pilot demonstration project suggests that ISS may be a viable alternative for: sites requiring deep dredging; large volume projects on urban waterways where staging and amending areas are limited; sites with NAPL impacts that cannot be controlled during dredging; and sites where eventual NAPL breakthrough is anticipated if reactive caps are employed. The potential economic, environmental, and operational benefits of this technology will be discussed. This article focuses on the primary objectives of the pilot demonstration: to meet quantitative performance criteria for strength and hydraulic conductivity; to assess the leach performance of the solidified sediments; and to satisfy water quality parameters for turbidity, pH, and sheen. Approach/activities: The pilot study utilized a customized marine platform (modular floats, tug boats, etc.) and full‐scale ISS equipment (auger rig, silos, etc.) and varied operational parameters to provide a range of data to assist in evaluating the feasibility and efficacy of the technology for use in similar environments and in planning future ISS projects on the water. Water quality controls and monitoring were implemented during the operation, and the study documented and evaluated the environmental disruption (short‐term impacts) and costs of the application of the ISS process to contaminated aquatic sediments. ©2016 Wiley Periodicals, Inc.     

Microbially Mediated In Situ Desorption Accelerates Remediation of Large Gasoline Product Plume

Remediation of a large separate‐phase hydrocarbon product and associated dissolved‐phase gasoline plume was accelerated by coupling multiphase extraction with in situ microbial stimulation. At the beginning of remediation activities, the separate‐phase hydrocarbon plume extended an estimated seven acres with product thickness measuring up to 2.1 feet thick. Within 18 months after beginning extraction, reduction of gasoline constituents in groundwater became asymptotic and measureable product disappeared from the upgradient source area. At that time, the remediation team initiated a program of limited in situ anaerobic bioremediation with the goal of stimulating production of natural surfactants from native microbes to release petroleum from the soil matrix. Groundwater concentrations of gasoline constituents increased gradually over the next three years, improving recovery without biofouling the pump‐and‐treat infrastructure. Using this approach, the groundwater component of the remedy was completed in less than five years, substantially less than the 10 years to 15 years predicted by modeling. This strategy demonstrated a more sustainable approach to remediation, reducing electrical usage by an estimated 800 megawatt hours, reducing infrastructure requirements, and preserving an estimated 150 million gallons of groundwater for this arid agricultural area. © 2014 Wiley Periodicals, Inc.     

CytoSol – Cleaning Oiled Shorelines with a Vegetable Oil Biosolvent

A cleanup process has been developed to aid in the removal of crude or fuel oil from shorelines using CytoSol “biosolvent” formulation based on vegetable oil methyl esters in combination with bioremediation enhancers. The CytoSol biosolvent dissolves and floats the oil, the oil/biosolvent mixture is rinsed off with ambient temperature water for collection as a consolidated layer with skimmers. The collected oil mixture can be recycled as a burner fuel. Nutrient enhancers in the formulation then stimulate the natural biodegradation of the remaining residual hydrocarbons. This new approach minimizes physical and chemical impacts to marine organisms, cleans oiled surfaces effectively, and allows the oiled ecosystem to recover with less mortality than conventional methods involving hot water, detergents or other chemical cleaners. CytoSol is ideally suited for port facilities and waterfronts dealing with occasional small oil spills and has undergone extensive laboratory testing for the US EPA. In 1997, the CytoSol biosolvent was licensed in the state of California as a shoreline cleaner and set up for commercial distribution.CytoSol biosolvent can extract heavy petroleum (crude, fuel oils) off shoreline habitats, mussel-encrusted breakwaters or pilings, and estuary vegetation. The viscosity of the product tends to limit the penetration of the CytoSol/oil mixture into sand and gravel beaches, allowing more of the dissolved oil to be removed from the shoreline by washing. The product has a low specific gravity (0.87), tends to consolidate oil, and is practically immiscible with water, so it facilitates the recovery of spilled oil with conventional skimming and absorbent boom technologies. Since it is non-volatile and non-flammable, there is little danger of explosion or fire when spraying it inside confined spaces.