Spreadsheet‐Based Design Tool for In Situ Anaerobic Bioremediation Using Soluble Substrate

A Microsoft Excel spreadsheet‐based design tool has been developed to assist remediation professionals in the design of injection systems for distributing soluble substrate (SS) to enhance in situ anaerobic bioremediation. The user provides site data, design parameters, and unit‐cost information to generate estimates of remediation‐system cost and steady‐state contact efficiency (CE_SS) for various designs. CE_SS is estimated from a nonlinear regression equation that includes terms for the SS injection concentration (C_I), minimum substrate concentration (C_MIN), groundwater travel time between rows of injection wells (T_T), SS half‐life (T_H), substrate reinjection time interval (T_R), and pore volumes of substrate solution injected (PV). With this tool, users can quickly compare the relative costs and performance of different injection alternatives and identify the best design for their specific site conditions. The design process embodied in the tool includes: (1) entering injection‐well configuration and unit costs for well installation, injection, and substrate; (2) determining treatment‐zone dimension; (3) selecting trial injection‐well spacing, time period between substrate reinjection, and injection pore volume; and (4) estimating contact efficiency and capital and life‐cycle costs. This process is then repeated until a final design is selected. In most cases, injection costs increase with increasing CE_SS. However, the best (highest) ratio of CE_SS to injection cost typically occurs for CE_SS in the range of 70 to 80 percent. © 2013 Wiley Periodicals, Inc.     

Innovative use of a pressure‐pulse injection tool to increase transmissivity in a collection trench

Pressure‐pulse injection tools are widely used in the oil and gas extraction industry to increase well production yields; however, they have been sparingly used in the environmental industry. These injection tools work by applying a pressure pulse to the subsurface that can open subsurface pore throats in unconsolidated material, increasing yields or increasing a radius of influence from a substrate injection. Collection trenches at an industrial site were installed to increase recovery of No. 2 fuel oil in the subsurface and maintain hydraulic control of the contaminant plume. However, after operating for seven years, significant reduction in recovery was observed. Diminished recovery was attributed to biofouling, iron fouling, and/or excessive scaling. A pilot test was conducted in 2009 to determine if a pressure‐pulse injection tool could be used to inject an antifouling agent and rehabilitate two of the site collection trenches. The pilot test was successful in increasing the transmissivity of both trenches, with an order‐of‐magnitude increase in groundwater recovery at Collection Trench 1 and a 50 percent increase in recovery at Collection Trench 2. The trench rehabilitation using the pressure‐pulse injection tool was conducted at two other site collection trenches in 2010 with similar success and is now proposed as part of regular maintenance of the trenches on an as‐needed basis. © 2011 Wiley Periodicals, Inc.     

Norwegian Testing of Emulsion Properties at Sea--The Importance of Oil Type and Release Conditions

This paper is a review of the major findings from laboratory studies and field trials conducted in Norway in recent years on the emulsification of oils spilled at sea. Controlled bench-scale and meso-scale basin experiments using a wide spectrum of oils have revealed that both the physico-chemical properties of the oils and the release conditions are fundamental determinants of the rate of emulsion formation, for the rheological properties of the emulsion formed and for the rate of natural dispersion at sea.During the last decade, several series of full-scale field trials with experimental releases of various crude oils have been undertaken in the North Sea and the Norwegian Sea. These have involved both sea surface releases, underwater pipeline leak simulations (release of oil under low pressure and no gas) and underwater blowout simulations (pressurized oil with gas) from 100 and 850 m depth. The field trials have been performed in co-operation with NOFO (Norwegian Clean Seas Association for Operating Companies), individual oil companies, the Norwegian Pollution Control Authority (SFT) and Minerals Management Services (MMS). SINTEF has been responsible for the scientific design and monitoring during these field experiments. The main objectives of the trials have been to study the behaviour of different crude oils spilled under various conditions and to identify the operational and logistical factors associated with different countermeasure techniques.The paper gives examples of data obtained on the emulsification of spilled oil during these field experiments. The empirical data generated from the experimental field trials have been invaluable for the validation and development of numerical models at SINTEF for predicting the spreading, weathering and behaviour of oil released under various conditions. These models are extensively used in contingency planning and contingency analysis of spill scenarios and as operational tools during spill situations and combat operations.     

The technology windows-of-opportunity for marine oil spill response as related to oil weathering and operations

This paper identifies and estimates time periods as ‘windows-of-opportunity’ where specific response methods, technologies, equipment, or products are more effective in clean-up operations for several oils. These windows have been estimated utilizing oil weathering and technology performance data as tools to optimize effectiveness in marine oil spill response decision-making. The windows will also provide data for action or no-action alternatives. Crude oils and oil products differ greatly in physical and chemical properties, and these properties tend to change significantly during and after a spill with oil aging (weathering). Such properties have a direct bearing on oil recovery operations, influencing the selection of response methods and technologies applicable for clean up, including their effectiveness and capacity, which can influence the time and cost of operations and the effects on natural resources.The changes and variations in physical and chemical properties over time can be modeled using data from weathering studies of specific oils. When combined with performance data for various equipment and materials, tested over a range of weathering stages of oils, windows-of-opportunity can be estimated for spill response decision-making. Under experimental conditions discussed in this paper, windows-of-opportunity have been identified and estimated for four oils (for which data are available) under a given set of representative environmental conditions. These ‘generic’ windows have been delineated for the general categories of spill response namely: (1) dispersants, (2) in situ burning, (3) booms, (4) skimmers, (5) sorbents, and (6) oil-water separators. To estimate windows-of-opportunity for the above technologies (except booms), the IKU Oil Weathering Model was utilized to predict relationships—with 5 m s⁻¹ wind speed and seawater temperatures of 15°C.The window-of-opportunity for the dispersant (Corexit 9527^®) with Alaska North Slope (ANS) oil was estimated from laboratory data to be the first 26 h. A period of ‘reduced’ dispersibility, was estimated to last from 26–120 h. The oil was considered to be no longer dispersible if treated for the first time after 120 h. The most effective time window for dispersing Bonnic Light was 0–2 h, the time period of reduced dispersibility was 2–4 h, and after 4 h the oil was estimated to be no longer dispersible. These windows-of-opportunity are based on the most effective use of a dispersant estimated from laboratory dispersant effectiveness studies using fresh and weathered oils. Laboratory dispersant effectiveness data cannot be directly utilized to predict dispersant performance during spill response, however, laboratory results are of value for estimating viscosity and pour point limitations and for guiding the selection of an appropriate product during contingency planning and response. In addition, the window of opportunity for a dispersant may be lengthened if the dispersant contains an emulsion breaking agent or multiple applications of dispersant are utilized. Therefore, a long-term emulsion breaking effect may increase the effectiveness of a dispersant and lengthen the window-of-opportunity.The window-of-opportunity of in situ burning (based upon time required for an oil to form an emulsion with 50% water content) was estimated to be approximately 0–36 h for ANS oil and 0–1 h for Bonnie Light oil after being spilled. The estimation of windows-of-opportunity for offshore booms is constrained by the fact that many booms available on the market undergo submergence at speeds of less than 2 knots. The data suggest that booms with buoyancy to weight ratios less than 8:1 may submerge at speeds within the envelope in which they could be expected to operate. This submergence is an indication of poor wave conformance, caused by reduction of freeboard and reserve net buoyancy within the range of operation. The windows-of-opportunity for two selected skimming principles (disk and brush), were estimated using modeled oil viscosity data for BCF 17 and BCF 24 in combination with experimental performance data developed as a function of viscosity. These windows were estimated to be within 3–10 h (disk skimmer) and after 10 h (brush skimmer) for BCF 17. Whereas for BCF 24, it is within 2–3 d (disk skimmer) and after 3 d (brush skimmer).For sorbents, an upper viscosity limit for an effective and practical use has in studies been found to be approximately 15,000 cP, which is the viscosity range of some Bunker C oils. Using viscosity data for the relative heavy oils, BCF 17 and BCF 24 (API gravity 17 and 24), the time windows for a sorbent (polyamine flakes) was estimated to be 0–4 and 0–10 d, respectively. With BCF 24, the effectiveness of polyamine flakes, was reduced to 50% after 36 h, although it continued to adsorb for up to 10 d. For BCF 17, the effectiveness of polyamine flakes was reduced to 50% after 12 h, although it continued to adsorb for up to 4 d. The windows-of-opportunity for several centrifuged separators based upon the time period to close the density gap between weathered oils and seawater to less than 0.025 g ml⁻¹ (which is expected to be an end-point for effective use of centrifugal separation technology), were estimated to be 0–18 (ANS) and 0–24 h (Bonnie Light) after the spill. Utilizing the windows-of-opportunity concept, the combined information from a dynamic oil weathering model and a performance technology data base can become a decision-making tool; identifying and defining the windows of effectiveness of different response methods and equipment under given environmental conditions. Specific research and development needs are identified as related to further delineation of windows-of-opportunity.     

Determination of the Burning Characteristics of a Slick of Oil on Water

The burning rate of a slick of oil on a water bed is characterized by three distinct processes, ignition, flame spread and burning rate. Although all three processes are important, ignition and burning rate are critical. The former, because it defines the potential to burn and the latter because of the inherent possibility of boilover. Burning rate is calculated by a simple expression derived from a one-dimensional heat conduction equation. Heat feedback from the flame to the surface is assumed to be a constant fraction of the total energy released by the combustion reaction. The constant fraction (χ) is named the burning efficiency and represents an important tool in assessing the potential of in situ burning as a counter-measure to an oil spill. By matching the characteristic thermal penetration length scale for the fuel/water system and an equivalent single layer system, a combined thermal diffusivity can be calculated and used to obtain an analytical solution for the burning rate. Theoretical expressions were correlated with crude oil and heating oil, for a number of pool diameters and initial fuel layer thickness. Experiments were also conducted with emulsified and weathered crude oil. The simple analytical expression describes well the effects of pool diameter and initial fuel layer thickness permitting a better observation of the effects of weathering, emulsification and net heat feedback to the fuel surface. Experiments showed that only a small fraction of the heat released by the flame is retained by the fuel layer and water bed (of the order of 1%). Ignition has been studied to provide a tool that will serve to assess a fuels ease to ignite under conditions that are representative of oil spills. Two different techniques are used, piloted ignition when the fuel is exposed to a radiant heat flux and flash point as measured by the ASTM D56 Tag Closed Cup Test. Two different crude oils were used for these experiments, ANS and Cook Inlet. Crude oils were tested in their natural state and at different levels of weathering, showing that piloted ignition and flash point are strong functions of weathering level.     

Effect of the water–oil ratio on brine/surfactant/alcohol/oil systems optimized for soil remediation

The optimum middle-phase microemulsion used for remediation of oily contaminated soils is often obtained by mixing a certain amount of a surfactant/alcohol mixture with oil and adjusting the salinity concentrations at a constant water–oil ratio. Upon introduction to the subsurface, however, the system may not be in the optimum state throughout the remediation process owing to the change in the water–oil ratio. This research has attempted to investigate the effect of the water–oil ratio on the phase behavior of systems containing brine, anionic surfactant, alcohols, and different oils. By systematically changing the water–oil ratio, while keeping the others variables constant, the systems exhibited different phase behavior. The results revealed that the effect of the water–oil ratio on system behavior was significant, and analogous to that of salinity. Increasing the water–oil ratio led the system change from winsor I → winsor III → winsor II. The greater the water–oil ratio the lower the salinity required to produce the middle-phase microemulsion, but the narrower the salinity range of the three-phase region. An empirical correlation has been developed in order to predict the changes in phase behavior with the changes in water–oil ratio. This provides a useful tool for designing optimum formulations suitable for soil remediation. Received: October 5, 1999 / Accepted: March 27, 2000     

Novel Polymeric Materials from Biological Oils

A variety of novel polymeric materials ranging from elastomers to tough, rigid plastics have been prepared by the cationic copolymerization of regular soybean oil, low-saturation soybean oil, or conjugated low-saturation soybean oil with various alkene commonomers. Using appropriate compositions and reaction conditions, 70–100% of the soybean oil is covalently incorporated into the cross-linked polymer networks, contributing significantly to cross-linking during copolymerization. The resulting thermosets exhibit thermophysical and mechanical properties that are competitive with those of their petroleum-based counterparts. In addition, good damping and shape memory properties have been obtained by controlling the degree of cross-linking and the rigidity of the polymer backbone. New materials with similar characteristics have also been produced from other biological oils, including tung, and fish oils using the same technique. The new, more valuable properties of these bioplastics suggest numerous promising applications of these novel polymeric materials.     

Enhanced anaerobic bioremediation of chlorinated solvents utilizing vegetable oil emulsions

The use of vegetable oil as an electron donor to enhance the reductive dechlorination of chlori‐nated solvents as an in situ remediation technology is gaining significant traction. Vegetable oil is a cost‐effective slow‐release electron donor with greater hydrogen‐release efficiency than other electron‐donor products. However, neat vegetable oil can inhibit distribution in aquifers due to the oil droplets blocking the flow of groundwater through the smaller pore spaces in the aquifer materials. This issue has been partially overcome by applying the vegetable oil as an oil‐water emulsion, which typically is created in the field. However, the field preparation results in a mixture of droplet sizes, including larger droplets that can make the emulsions unstable and reduce the soil permeability by blocking soil‐pore throats with oil. RNAS, Inc., has developed a kinetically sta‐ble soybean oil emulsion (“Newman Zone”) consisting of submicron droplets with less droplet‐size variation than field‐prepared emulsions. This product is composed of a blend of fast‐release (sodium lactate) and slow‐release (soybean oil) electron donors. The emulsion is produced in a stable factory environment in which it is pasteurized and packaged in sterile packaging. This ma‐terial can be utilized as an electron donor without further treatments or amendments in the field. This article discusses factors associated with selecting electron donors and the development of vegetable oil–based products. A case study of an application of Newman Zone at a former adhe‐sives manufacturing facility is then presented. The case study demonstrates the effect of Newman Zone in reducing chlorinated solvent concentrations in groundwater by both rapidly stimulating initial microbial activity and supporting long‐term reductive dechlorination with a slow‐release electron donor. © 2006 Wiley Periodicals, Inc.     

Use of a novel biomarker,botryococcane, to monitor biodegradation of two lacustrine‐sourced crude oils

Bioremediation is a proven alternative for remediating petroleum‐impacted soils at exploration and production (E&P) sites. Monitoring remediation performance can involve detection and quantification of biodegradation resistant compounds such as C₃₀17α(H),21β(H)‐hopane, which requires the use of gas chromatography with mass spectrometry detection (GC/MS). Due to the remoteness of many E&P sites, this technology is not always available, and alternative methods are needed to provide reliable quantitative measurements of petroleum remediation efficiency. This study provides a detailed chemical characterization of lacustrine‐sourced crude oils and a technical basis for measuring the effectiveness of bioremediation efforts for soil impacted by those crudes. We show that the novel isoprenoid hydrocarbon botryococcane is relatively stable in lacustrine‐sourced crude oils compared with C₃₀17α(H),21β(H)‐hopane under moderate biodegradation conditions generally observed in field samples. We have also demonstrated that, due to the stability and relatively elevated concentration of botryococcane in lacustrine oils, it can be reliably measured using the more cost‐effective and available GC/FID methodology, and thereby be used to monitor the progress of ongoing soil bioremediation activities at remote sites.     

Control of Biofouling: Lessons Learned From a Decade of Carbon Injection System Operation and Maintenance

Over the past decade, we have learned a number of critical lessons surrounding carbon substrate handling while operating and maintaining hundreds of enhanced in situ biological remedies. The same qualities that make these substrates effective can also cause biofouling of the mixing system, piping infrastructure, and remediation wells. Managing biofouling is a key piece of a successful remedy and requires a unique set of design principles. Small decreases in injection rates can have considerable impacts to life‐cycle costs and performance caused by decreased substrate distribution and longer injection time frames, resulting in the need for system cleaning, well rehabilitation, and even well replacement. Biofouling can impair performance in any size system, but effects are often magnified by large injection volumes and extended time frames. Design should be considered in all stages of the anaerobic enhanced in situ bioremediation life cycle, particularly related to reagent mixing, storage, and residence time within the system. By understanding the fundamental mechanisms of biofouling, practitioners can make operational adjustments to enhance remedy performance by considering potential biofouling controls in the design; balancing site‐specific strategy and diagnostics; and proactively adjusting and fine tuning control/prevention technology and methodology. Ultimately, a combination of chemical and physical methods may be required to operate a carbon handling system over the long term; however, the operational costs can be greatly reduced and delivery efficiency increased if these methods are understood during the design phase. © 2013 Wiley Periodicals, Inc.     

Storage stability of biocrude oils from fast pyrolysis of poultry litter

The unstable nature of biocrude oils produced from conventional pyrolysis of biomass is one of the properties that limits its application. In the disposal of poultry litter via pyrolysis technology, the biocrude oil produced as a value-added product can be used for on farm applications. In this study, we investigated the influence of bedding material (wood shavings) on the storage stability of biocrude oils produced from the fast pyrolysis of poultry litter. The biocrude oils produced from manure, wood (pine and oak), and mixtures of manure and wood in proportions (75:25 50:50, and 25:75 w/w%) were stored under ambient conditions in sealed glass vials for a period of 6 months and their stability were monitored by measuring the changes in viscosity over time. The manure oil had the lowest rate of viscosity change and thus was relatively the most stable and the oils from the 50:50 w/w% litter mixtures were the least stable. The rate of viscosity change of the manure biocrude oil was 1.33 cP/day and that of the 50/50 litter mixture was 7.6 cP/day for pine and 4.17 cP/day for oak.The spectrometric analyses of the biocrude oils showed that the presence of highly reactive oxygenated functionalities in the oil were responsible for the instability characteristic of the litter biocrude oils. The poor stability of the biocrude oil from the 50:50 w/w% litter mixtures was attributed to reactions between nitrogenous compounds (amides) from protein degradation and oxygenated compounds from the decomposition of polysaccharides and lignin. The addition of 10% methanol and 10% ethanol to the oil from 50% manure and 50% pine reduced the initial viscosity of the oil and was also beneficial in slowing down the rate of viscosity change during storage.     

Application of Ultraviolet Fluorescence Spectroscopy to Monitor Oil–Mineral Aggregate Formation

At an excitation wavelength of 320 nm, the ultraviolet fluorescence (UVF) spectra emitted by reference oils dispersed in seawater with mineral fines yielded two important results:

• (1)Resuspended negatively-buoyant oil–mineral aggregates (OMAs) exhibited maximum fluorescence at an emission wavelength of 450 nm and,
• (2)the hydrocarbons dispersed and/or dissolved in the seawater that remained after the aggregates had settled out exhibited maximum fluorescence at 355 nm.

Data from UVF analysis (450 nm emission) and microscopical observations of seven reference oils suggest that higher-viscosity oils are less likely to form aggregates with mineral fines. This decline in OMA formation with increased oil viscosity could be predicted from a decrease in the ratio of emission at 450–355 nm. The data suggest that direct UVF spectroscopy of dispersed/dissolved oil and OMAs in seawater can be used to predict and verify the extent of OMA formation.     

Biodiesel from lignocellulosic biomass – Prospects and challenges

Biodiesel can be a potential alternative to petroleum diesel, but its high production cost has impeded its commercialization in most parts of the world. One of the main drivers for the generation and use of biodiesel is energy security, because this fuel can be produced from locally available resources, thereby reducing the dependence on imported oil. Many countries are now trying to produce biodiesel from plant or vegetable oils. However, the consumption of large amounts of vegetable oils for biodiesel production could result in a shortage in edible oils and cause food prices to soar. Alternatively, the use of animal fat, used frying oils, and waste oils from restaurants as feedstock could be a good strategy to reduce the cost. However, these limited resources might not meet the increasing demand for clean, renewable fuels. Therefore, recent research has been focused the use of residual materials as renewable feedstock in order to lower the cost of producing biodiesel. Microbial oils or single cell oils (SCOs), produced by oleaginous microorganisms have been studied as promising alternatives to vegetable or seed oils. Various types of agro-industrial residues have been suggested as prospective nutritional sources for microbial cultures. Since the most abundant residue from agricultural crops is lignocellulosic biomass (LCB), this byproduct has been given top-priority consideration as a source of biomass for producing biodiesel. But the biological transformation of lignocellulosic materials is complicated due to their crystalline structure. So, pretreatment is required before they can be converted into fermentable sugar. This article compares and scrutinizes the extent to which various microbes can accumulate high levels of lipids as functions of the starting materials and the fermentation conditions. Also, the obstacles associated with the use of LCB are described, along with a potentially viable approach for overcoming the obstacles that currently preclude the commercial production of biodiesel from agricultural biomass.     

The Significance of Oil Spill Dispersants

There is growing acceptance worldwide that use of dispersants to counter the effects of an oil spill offers many advantages and can often result in a net environmental benefit when considered in relation to other response options. A major reason for this growing support and increased reliance on dispersants is the advent of improved dispersant products that are low in toxicity to marine life and more effective at dispersing heavy and weathered oils – oils previously believed to be undispersible. This capability has been demonstrated through extensive laboratory testing, field trials, and dispersant application on actual spills. This paper summarizes recent advances in dispersant R&D and reviews the implications of technology advances.     

Development of a procedure for sustainable in situ aquifer denitrification

Denitrification experiments have provided data showing the pitfalls and successes in developing a sustainable injection/extraction system in a sand and gravel aquifer. Experiments increase in complexity from continuous injection at one well to automated‐pulsed eight well injections. In both continuous and pulsed injection of organic carbon, 40 mg NO_3‐N l^?1 was reduced below the detection limit of < 0.1 mg NO_3‐N l^?1 in the denitrification zones. Under continuous injection, accumulation of bacterial exudates in the vicinity of the injection well resulted in injection well clogging within ten days. Periodic cleaning of the injection well and the adjacent gravel matrix was accomplished by using a tool developed to circulate a cleaning solution composed of 5 percent H₂O₂ and 0.02 percent NaOCl; but, biofouling could not be eliminated. In the later experiments, acetate became the carbon amendment because ethanol promoted more biomass development. A specialized pulse injection procedure was developed to separate nitrate from acetate‐C and was successful in alleviating the proliferation of bacterial exudates without affecting the performance of the denitrification system. Using pulsed injection, a maximum of 72 percent nitrate reduction was accomplished in the extraction well water, and denitrification was sustained for three months without clogging. © 2003 Wiley Periodicals, Inc.     

Field Performance of Point Velocity Probes at a Tidally Influenced Site

Conventional methods to estimate groundwater velocity that rely on Darcy's Law and average hydrogeologic parameter values are insensitive to local‐scale heterogeneities and anisotropy that control advective flow velocity and direction. Furthermore, at sites that are tidally influenced or have extraction wells with variable pumping schedules, infrequent water‐level measurements may not adequately characterize the range and significance of transient hydraulic conditions. The point velocity probe (PVP) is a recently developed instrument capable of directly measuring local‐scale groundwater flow velocity and direction. In particular, PVPs may offer distinct advantages for sites with complex groundwater–surface water interactions and/or with spatially and temporally variable groundwater flow conditions. The PVP utilizes a small volume of saline tracer and inexpensive sensors to directly measure groundwater flow direction and velocity in situ at the centimeter‐scale and discrete times. The probes are installed in conventional direct‐push borings, rather than in wells, thus minimizing the changes and biases in the local flow field caused by well installation and construction. Six PVPs were installed at a tidally influenced site in North Carolina to evaluate their implementability, performance, and potential value as a new site characterization tool. For this study, a new PVP prototype was developed using a rapid prototyping machine (i.e., a “three‐dimensional printer'') and included both horizontally and vertically oriented tracer detectors. A site‐specific testing protocol was developed to account for the spatially and temporally variable hydraulic conditions and groundwater salinity. The PVPs were tested multiple times, and the results were compared to the results of several different groundwater flux and velocity estimation tools and methods, including a heat‐pulse flowmeter, passive flux meters, single‐well tracer tests, and high‐resolution hydraulic gradient analysis. Overall, the results confirmed that the PVP concept is valid and demonstrated that reliable estimates of groundwater velocity and direction can be obtained in simple settings. Also, PVPs can be successfully installed by conventional methods at sites where the formation consists primarily of noncohesive soils and the water table is relatively shallow. Although some PVP tests yielded consistent and reliable results, several tests did not. This is likely due to the highly transient flow conditions and limitations associated with the PVP design and testing procedures. PVPs offer particular advantages over, and can effectively complement, other groundwater flow characterization techniques for certain conditions, and objectives may be useful for characterizing complex flow patterns under steady conditions; however, this study suggests that PVPs are best suited for conditions where the flow hydraulics are not highly transient. For sites where the hydraulic conditions are highly transient, the most reliable approach for understanding groundwater flow behavior and groundwater–surface water interactions would generally involve both a high‐resolution hydraulic gradient analysis and another local‐scale method, such as tracer testing. This study also highlighted some aspects of the current PVP design and testing protocol that can be improved upon, including a more robust connection between the PVP and injection line and further assessment of tracer solution density effects on vertical flow. © 2013 Wiley Periodicals, Inc.     

Influence of Salinity on Petroleum Accommodation by Dispersants

The effect of receiving water salinity on the effectiveness of two oil dispersants, Corexits^® 9527 and 9500, was investigated using a recently implemented modified version of the Swirling Flask efficacy test. The dispersants were tested with ten different oils, representing a wide range of physical–chemical properties. Test salinities ranged from 0 to 35 ppt, with temperature held constant at 15°C. Results showed Corexit 9500 to be generally more effective on most of the dispersible oils at most salinities, but performance of both products was significantly affected by salinity. Both dispersants performed best at salinities above 25 ppt, with Corexit 9500 maintaining its effectiveness over a fairly wide range of salinities. Correlations between dispersant effectiveness and various oil physical/chemical properties were highly variable.     

Successful unsaturated zone treatment of PCE with sodium permanganate

In situ chemical oxidation (ISCO) with permanganate has been widely used for soil and groundwater treatment in the saturated zone. Due to the challenges associated with achieving effective distribution and retention in the unsaturated zone, there is a great interest in developing alternative injection technologies that increase the success of vadose‐zone treatment. The subject site is an active dry cleaner located in Topeka, Kansas. A relatively small area of residual contamination adjacent to the active facility building has been identified as the source of a large sitewide groundwater contamination plume with off‐site receptors. The Kansas Department of Health and Environment (KDHE) currently manages site remedial efforts and chose to pilot‐test ISCO with permanganate for the reduction of perchloroethene (PCE) soil concentrations within the source area. KDHE subsequently contracted Burns & McDonnell to design and implement an ISCO pilot test. A treatability study was performed by Carus Corporation to determine permanganate‐soil‐oxidant‐demand (PSOD) and the required oxidant dosing for the site. The pilot‐test design included an ISCO injection approach that consisted of injecting aqueous sodium permanganate using direct‐push technology with a sealed borehole. During the pilot test, approximately 12,500 pounds of sodium permanganate were injected at a concentration of approximately 3 percent (by weight) using the methods described above. Confirmation soil sampling conducted after the injection event indicated PCE reductions ranging from approximately 79 to more than 99 percent. A follow‐up treatment, consisting of the injection of an additional 6,200 pounds of sodium permanganate, was implemented to address residual soil impacts remaining in the soil source zone. Confirmation soil sampling conducted after the treatment indicated a PCE reduction of greater than 90 percent at the most heavily impacted sample location and additional reductions in four of the six samples collected. © 2009 Wiley Periodicals, Inc.     

Enhanced oil biodegradation with mineral fine interaction

During recent oil spill clean-up operations, residual oils stranded in the intertidal environment were successfully dispersed into the sea by physically accelerating the natural interaction between oil and mineral fines. Oil-mineral fine interaction reduces the adhesion of oil to solid surfaces and promotes the formation of stable micron-sized oil droplets in the water column. By increasing the oil-in-water interface, i.e. the oil becomes more accessible to nutrients, oxygen and bacteria, this interaction becomes a key factor in enhancing oil biodegradation. There is, however, concern that this technique merely transports the oil from one compartment of the environment to another. In our study, controlled laboratory shaker-flask experiments showed that oil-mineral fine interactions stimulates microbial activity by enhancing both the rate and extent of oil degradation by stimulating microbial activity. These results support the application of shoreline oil spill clean-up techniques based on the acceleration of oil-mineral fine interactions.