页岩气压裂返排液处理技术的研究进展

页岩气是一种重要的天然气资源,在其水力压裂开采过程中加入了多种有机添加剂,产生了大量具有高黏度、高COD、高含盐量特性的压裂返排液,常规处理技术难以实现其达标排放或回用。分析了页岩气压裂返排液的组分和特点,归纳总结了成熟的传统处理技术和新型处理技术的特点,提出了优化压裂返排液处理工艺、加强环境信息公开、研发节能环保的新型页岩气压裂技术的未来发展方向,为页岩气压裂返排液无害化、资源化处理技术的研发提供了思路和参考。     

中美页岩气开发环境管理制度的分析与建议

随着页岩气开发技术的突破与发展,我国已成为继美国、加拿大之后第三个实现页岩气工业化生产的国家。而由页岩气开发伴随的地下水污染、生态破坏等环境问题亦不可忽视。本文通过分析中美页岩气开发过程中的环境管理政策、管理模式,提出加快完善我国页岩气开发环境管理体系及环境监管的建议：1）形成页岩气开发全过程环境管理体系;2）强化页岩气开发的区块规划环评,落实生态保护红线和资源利用上线要求;3）规范项目环境影响评价,提高页岩气环境管理要求;4）在制定页岩气开发污染控制相关标准时纳入开采工艺过程的环保管理要求。     

1,4‐Dioxane Treatment Technologies

The chlorinated solvent stabilizer 1,4‐dioxane (DX) has become an unexpected and recalcitrant groundwater contaminant at many sites across the United States. Chemical characteristics of DX, such as miscibility and low sorption potential, enable it to migrate at least as far as the chlorinated solvent from which it often originates. This mobility and recalcitrance has challenged remediation professionals to redesign existing treatment systems and monitoring networks to accommodate widespread contamination. Furthermore, remediation technologies commonly applied to chlorinated solvent co‐contaminants, such as extraction and air stripping or in situ enhanced reductive dechlorination, are relatively ineffective on DX removal. These difficulties in treatment have required the industry to identify, develop, and demonstrate new and innovative technologies and approaches for both ex situ and in situ treatment of this emerging contaminant. Great strides have been made over the past decade in the development and testing of remediation technologies for removal or destruction of DX in groundwater. This article briefly summarizes the fate and transport characteristics of DX that make it difficult to treat, and presents technologies that have been demonstrated to be applicable to groundwater treatment at the field scale.  ©2016 Wiley Periodicals, Inc.     

Sustainable soil remediation by refrigerated condensation at sites with “high‐concentration” recalcitrant compounds and NAPL: Two case studies

Remediation of recalcitrant compounds at sites with high concentrations of volatile organic compounds (VOCs) or nonaqueous‐phase liquids (NAPLs) can present significant technical and financial (long‐term) risk for stakeholders. Until recently, however, sustainability has not been included as a significant factor to be considered in the feasibility and risk evaluation for remediation technologies. The authors present a framework for which sustainability can be incorporated into the remediation selection criteria focusing specifically on off‐gas treatment selection for soil vapor extraction (SVE) remediation technology. SVE is generally considered an old and standard approach to in situ remediation of soils at a contaminated site. The focus on off‐gas treatment technology selection in this article allows for more in‐depth analysis of the feasibility evaluation process and how sustainable practices might influence the process. SVE is more commonly employed for recovery of VOCs from soils than other technologies and generally employs granular activated carbon (GAC), catalytic, or thermal oxidation, or an emerging alternative technology known as cryogenic‐compression and condensation combined with regenerative adsorption (C3–Technology). Of particular challenge to the off‐gas treatment selection process is the potential variety of chemical constituents and concentrations changing over time. Guidance is available regarding selection of off‐gas treatment technology (Air Force Center for Environmental Excellence, 1996; U.S. Environmental Protection Agency, 2006). However, there are common shortcomings of off‐gas treatment technology guidance and applications; practitioners have rarely considered sustainability and environmental impact of off‐gas treatment technology selection. This evaluation includes consideration of environmental sustainability in the selection of off‐gas treatment technologies and a region‐specific (Los Angeles, California) cost per pound and time of remediation comparisons between GAC, thermal oxidation, and C3–Technology. © 2008 Wiley Periodicals, Inc.     

Life‐cycle assessment of in situ thermal remediation

A detailed cradle‐to‐grave life‐cycle assessment (LCA) of an in situ thermal treatment remedy for a chlorinated‐solvent‐contaminated site was performed using process LCA. The major materials and activities necessary to install, operate, monitor, and deconstruct the remedy were included in the analysis. The analysis was based on an actual site remedy design and implementation to determine the potential environmental impacts, pinpoint major contributors to impacts, and identify opportunities for improvements during future implementation. The Electro‐Thermal Dynamic Stripping Process (ET‐DSP?) in situ thermal technology coupled with a dual‐phase extraction and treatment system was evaluated for the remediation of 4,400 yd³ of tetrachloroethene‐ and trichloroethene‐impacted soil, groundwater, and bedrock. The analysis was based on an actual site with an estimated source mass of 2,200 lbs of chlorinated solvents. The remedy was separated into four stages: remedy installation, remedy operation, monitoring, and remedy deconstruction. Environmental impacts were assessed using Sima Pro software, the ecoinvent database, and the ReCiPe midpoint and endpoint methods. The operation stage of the remedy dominated the environmental impacts across all categories due to the large amount of electricity required by the thermal treatment technology. Alternate sources of electricity could significantly reduce the environmental impacts of the remedy across all impact categories. Other large impacts were observed in the installation stage resulting from the large amount of diesel fuel, steel, activated carbon, and asphalt materials required to implement the technology. These impacts suggest where opportunities for footprint reductions can be found through best management practices such as increased materials reuse, increased recycled‐content materials use, and clean fuels and emission control technologies. Smaller impacts were observed in the monitoring and deconstruction stages. Normalized results show the largest environmental burdens to fossil depletion, human toxicity, particulate matter formation, and climate‐change categories resulting from activities associated with mining of fossil fuels for use in electricity production. In situ thermal treatment can reliably remediate contaminated source areas with contaminants located in low‐permeability zones, providing complete destruction of contaminants in a short amount of time, quick return of the site to productive use, and minimized quantities of hazardous materials stored in landfills for future generations to remediate. However, this remediation strategy can also result in significant emissions over a short period of time. It is difficult to quantify the overall value of short‐term cleanups with intense treatment emissions against longer‐term cleanups with lower treatment emissions because of the environmental, social, and economic trade‐offs that need to be considered and understood. LCA is a robust, quantitative tool to help inform stakeholder discussions related to the remedy selection process, trade‐off considerations, and environmental footprint‐reduction opportunities, and to complement a broader toolbox for the evaluation of sustainable remediation strategies. © 2012 Wiley Periodicals, Inc.     

Characterizing In Situ Methane‐Enhanced Biostimulation Potential for 1,4‐Dioxane Biodegradation in Groundwater

This study characterizes the 1,4‐dioxane biodegradation potential for an in situ methane‐enhanced biostimulation field pilot study conducted at Air Force Plant 44, located south of the Tucson International Airport in Arizona. In this study, the use of methane as the primary substrate in aerobic cometabolic biodegradation of 1,4‐dioxane is evaluated using environmental molecular diagnostic tools. The findings are compared to an adjacent pilot study, wherein methane was generated via enhanced reductive dechlorination and where methane monooxygenase and methane‐oxidizing bacteria were also found to be abundant. This article also presents the use of ¹³C and ²H isotopic ratio enrichment, a more recent tool, to support the understanding of 1,4‐dioxane biodegradation in situ. This study is the first of its kind, although alkane gas‐enhanced biodegradation of 1,4‐dioxane has been evaluated extensively in microcosm studies and propane‐enhanced biodegradation of 1,4‐dioxane has been previously studied in the field. ©2016 Wiley Periodicals, Inc.     

California's Low‐Threat LUFT Site Closure Policy: Looking Forward

California's regulatory agencies have historically been at the forefront of national efforts to address environmental concerns. In 2012, California's agency for addressing leaking underground fuel tanks (LUFTs) adopted a policy that identifies low‐threat conditions warranting closure of an LUFT case. That development clearly fulfills the role of risk management in the risk assessment–risk management paradigm inherent in environmental remediation. It also encourages identification of additional categories of sites and other circumstances that are “low threat” to develop similar guidance on closure to apply to those sites. ©2015 Wiley Periodicals, Inc.     

Full‐scale bioremediation of a dilute 50‐acre plume

Enhanced anaerobic dechlorination is being conducted to remediate a 50‐acre groundwater area impacted with chlorinated volatile organic compounds (CVOCs). The plume, which is over 3,000 feet (ft) long, initially contained tetrachloroethene and breakdown products at concentrations of 2 to 3 milligrams per liter. The site's high groundwater flow velocity (greater than 1,000 ft per year) was incorporated into the design to help with amendment distribution. Bioaugmentation was conducted using a mixed culture containing Dehalococcoides ethenogenes. There is evidence that it has migrated to distances exceeding 600 ft. The major benefit of the high groundwater flow velocity is greater areal coverage by the remediation system, but the downside is the difficulty in delivering sufficient donor to create the required anaerobic conditions. Overall performance has been excellent with total CVOC reductions and conversion to ethene of 98 percent within a 25‐acre area downgradient of the treatment transect that has operated the longest. © 2011 Wiley Periodicals, Inc.     

Characterization and pilot‐scale studies for chemical oxidation remediation of fractured shale

The distribution of volatile organic compounds (VOCs) in fractured shale overlain by thin (< 10 feet) overburden at the Watervliet Arsenal near Albany, New York, was initially determined by sampling water from the fracture network using packer systems in boreholes and also using conventional monitoring wells. Furthermore, short‐term pumping and injection tests were conducted and the boreholes were logged using a variety of geophysical and hydrophysical tools. Tetrachloroethene is the dominant VOC in the groundwater, with lesser concentrations of trichloroethene and degradation products (cis‐1,2‐dichloroethene, trans‐1,2‐dichloroethene, and vinyl chloride). The vertical VOC distributions in the rock matrix were obtained from continuous‐cored holes from which small rock samples, collected at many depths between 18 and 150 feet below ground surface, were analyzed. The rock core VOC concentrations were determined by methanol extraction of crushed rock followed by direct methanol injection onto a gas chromatograph and subsequent estimation of rock porewater VOC concentrations. The rock core data support the concept that diffusion‐driven mass transfer has caused nearly all the VOC mass initially present in the fractures to now reside in the rock matrix, which has a porosity three or four orders of magnitude larger than the bulk fracture porosity. The results of the site characterization indicate that an effective site investigation strategy in fractured shale must include characterization of both the fracture and matrix contaminant distribution. These results also indicate that the most favorable remediation technologies for this fractured shale are those that will destroy VOCs in the rock matrix, particularly contaminants in the sorbed phase, and also destroy the VOC mass in the fractures including both dissolved and immiscible phases. The site characterization resulted in the selection of potassium permanganate for an in situ chemical oxidation pilot study. © 2004 Wiley Periodicals, Inc.     

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.     

In Situ Remediation of 1,4‐Dioxane Using Electrical Resistance Heating

Recent regulatory changes need more challenging treatment goals for 1,4‐dioxane. However, significant treatment limitations exist in part due to the high solubility and low Henry's law constant of 1,4‐dioxane. Two case studies are reported with substantial 1,4‐dioxane concentration reductions through in situ thermal remediation via electrical resistance heating (ERH). Concentration reductions greater than 99.8 percent of 1,4‐dioxane have been observed in the field using ERH. Concentrations of 1,4‐dioxane in air and steam extracted by an ERH vapor recovery system have also been evaluated. Laboratory studies were conducted to further understand the mechanisms that enable ERH remediation of 1,4‐dioxane. Vapor liquid equilibrium studies in water and soil were conducted and utilized to develop an ERH treatment cost model for 1,4‐dioxane. Existing field data were correlated to the 1,4‐dioxane treatment cost model. Field observations and laboratory testing indicate steam stripping that occurs through ERH remediation is an effective treatment method for 1,4‐dioxane. ©2015 Wiley Periodicals, Inc.     

Steady‐state field‐scale gas permeability estimation and pore‐gas velocity calculation in a domain open to the atmosphere

Field‐scale estimation of gas permeability and subsequent computation of pore‐gas velocity profiles are critical elements of sound soil venting design. It has been our experience, however, in U.S. Environmental Protection Agency's (EPA's) technical assistance program, provided by the Office of Research and Development in support EPA regional offices, that many venting practitioners are unaware of equations and data interpretation methods appropriate for gas permeability estimation and pore‐gas velocity computation. To ameliorate this situation, we use data collected at a U.S. Coast Guard Station in Traverse City, Michigan, to demonstrate gets permeability estimation and pore‐gas velocity calculation for steady‐state, axisymmetric, two‐dimensional gas flow in a domain open to the atmosphere. For gas permeability estimation, we use random guesses constrained with decreasing intervals of radial and vertical permeabilityand analysis of root mean square errors to ensure attainment of a global versus local minimum. We demonstrate confidence in permeability estimation by providing plots of observed versus simulated pressure response. Finally, we illustrate how plots of pore‐gas velocity as a function of distance and flow rate can be helpful in venting design.     

Monitored natural attenuation forum: State of the practice—Highlights from a breakfast discussion

The Monitored Natural Attenuation (MNA) Forum is published as a column in each issue of Remediation. The format typically includes one or two questions related to MNA with responses from several MNA Panel members. This column highlights MNA topics discussed at a breakfast held in support of the MNA Forum. It includes thoughts from various MNA Panel members and other environmental professionals who attended the breakfast on the “state of the practice.” © 2005 Wiley Periodicals, Inc.     

Resilience: A New Consideration for Environmental Remediation in an Era of Climate Change

There has been a growing movement within the environmental industry to develop more sustainable approaches in environmental remediation. These have generally included carbon footprint analysis, life cycle assessment, and best management practices to reduce the overall net environmental, social, and economic impacts of investigation and remediation activities. One of the foundational reasons net environmental impacts are currently evaluated is to identify and, subsequently, reduce contributions to climate change, primarily greenhouse gas emissions. While this trend toward sustainability and reduction in impact to the global environment is both important and admirable, the approach to remediation design and long‐term planning now needs to evolve further to better incorporate climate resilience into sustainable remediation design and implementation: designing remediation solutions that account for the projected impacts of climate change, as well as have the capacity to adapt to changing conditions. As a global population, we are now beyond the point of being able to prevent climate change and instead need to plan for adapting to it. In remediation, the effects of climate change create both risks and opportunities which should be considered during remedial design and long‐term planning. Responsible parties may see the push for—and management of—these considerations through their internal corporate risk management. The authors of this paper propose a simple framework for climate adaptation and resilience evaluations and plan development for remediation projects. ©2015 Wiley Periodicals, Inc.     

Easing the Pain for Disputants: Fundamentals of Environmental Mediation

“If we don't change the way we are going, we will end up where we are headed,” the saying goes. Well, with respect to environmental disputes, we are changing the way we are going, and we are doing it primarily through mediation. We are reaching for and finding cooperative, collaborative, and less expensive ways of solving problems. We are using mediation to eliminate or minimize the side effects of environmental issues and problematic sites. We are avoiding or dramatically reducing the “transactional” costs that have devastated so many persons and businesses involved in environmental problems. And we are finding ways to utilize collective intelligence and minimize collective damage through mediation. It's definitely good business.     

Successful full‐scale enhanced anaerobic dechlorination at a NAPL strength 1,1,1‐TCA source area

Bioremediation of 1,1,1‐trichloroethane (TCA) is more challenging than bioremediation of other chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE). TCA transformation often occurs under methanogenic and sulfate‐reducing conditions and is mediated by Dehalobacter. The source area at the project site contains moderately permeable medium sand with a low hydraulic gradient and is approximately 0.5 acre. TCA contamination generally extended to 35 feet, with the highest concentrations at approximately 20 feet. The concentrations then decreased with depth; several wells contained 300 to 600 mg/L of TCA prior to bioremediation. The area of treatment also contained 2 to 30 mg/L of TCE from an upgradient source. Initial site groundwater conditions indicated minimal biotic dechlorination and the presence of up to 20 mg/L of nitrate and 90 mg/L of sulfate. Microcosm testing indicated that TCA dechlorination was inhibited by the site's relatively low pH (5 to 5.5) and high TCA concentration. After the pH was adjusted and TCA concentrations were reduced to less than 35 mg/L (by dilution with site water), dechlorination proceeded rapidly using whey (or slower with sodium lactate) as an electron donor. Throughout the remediation program, increased resistance to TCA inhibition (from 35 to 200 mg/L) was observed as the microbes adapted to the elevated TCA concentrations. The article presents the results of a full‐scale enhanced anaerobic dechlorination recirculation system and the successful efforts to eliminate TCA‐ and pH‐related inhibition. © 2012 Wiley Periodicals, Inc.     

Synthetic Media: A Promising New Treatment Technology for 1,4‐Dioxane

1,4‐Dioxane (14DX) is classified as a probable human carcinogen by the US Environmental Protection Agency (EPA), and it has toxic effects on the kidney and liver. EPA's Health Advisory Level (HAL) for 14DX is 0.35 micrograms per liter (μg/L). Accordingly, several states have lowered their drinking water advisory levels and site cleanup levels. The widespread occurrence of 14DX in contaminated groundwater has contributed to a growing demand for remediation services. Treating 14DX is a challenge due to its very low Henry's law constant, low sorption potential, and strong ether linkages. The primary solution for 14DX remediation has been various forms of advanced oxidation processes (AOP), namely pump and treat followed by ex situ treatment with catalyzed ultraviolet light oxidation or ozone‐peroxidation. Many of the available advanced oxidation systems are complex, requiring careful monitoring and maintenance to adjust for variable source water and operating conditions. Synthetic media is a relatively new 14DX treatment technology that overcomes many of the operating challenges faced by existing technologies. AMBERSORB? 560 (AMBERSORB) has recently demonstrated the effective removal of 14DX over a wide range of concentrations and operating conditions, including those created by in situ thermal remediation. Consistent and reliable treatment down to sub‐0.3 μg/L levels differentiates synthetic media technology from other 14DX treatment technologies. AMBERSORB provides a solution to the problem of “stranded capital” by offering a 14DX treatment system capable of meeting regulatory standards today and in the foreseeable future. © 2014 Wiley Periodicals, Inc.     

Crop‐based systems for sustainable risk‐based land management for economically marginal damaged land

The increasing need for biomass for energy and feedstocks, along with the need to divert organic methane generating wastes from landfills, may provide the economic leverage necessary to return this type of marginal land to functional and economic use and is strongly supported by policy at the European Union (EU) level. The use of land to produce biomass for energy production or feedstocks for manufacturing processes (such as plastics and biofuels) has, however, become increasingly contentious, with a number of environmental, economic, and social concerns raised. The REJUVENATE project has developed a decision support framework to help land managers and other decision makers identify potential concerns related to sustainability and what types of biomass reuse for marginal land might be possible, given their particular circumstances. The decision‐making framework takes a holistic approach to decision making rather than viewing biomass production simply as an adjunct of a planned phytoremediation project. The framework is serviceable in Germany, Sweden, and the United Kingdom. These countries have substantive differences in their land and biomass reuse circumstances. However, all can make use of the set of common principles of crop, site, value, and project risk management set out by REJUVENATE. This implies that the framework should have wider applicability across the EU. This article introduces the decision support framework. © 2011 Wiley Periodicals, Inc.     

Off‐gas treatment carbon footprint calculator: Form and function

The quantification of greenhouse gas (GHG) emissions can be a powerful sustainability measurement indicator for assessing environmental impacts of various operations, which can include remediation of chemically impacted media or construction projects. A carbon footprint calculator was developed and is presented in this article as one tool for applying sustainable practices to environmental remediation—specifically to assess the GHG footprint for remediation projects. The calculator is constructed from a compilation of published metrics and “standards.” © 2008 Wiley Periodicals, Inc.     

Insights from years of performance that are shaping injection‐based remediation systems

Research and field experience from the past 15 years has allowed remediation professionals to purposefully design injection‐based remediation systems with a high potential for success. Industry professionals can now claim a number of achievements that were unthinkable just a few years ago: (1) we have demonstrated that maximum contaminant levels (MCLs) can be achieved for multiple contaminants; (2) we have successfully targeted dense nonaqueous‐phase liquid (DNAPL) source zones; (3) we have expanded our understanding of injection hydraulics to treat large plumes; and (4) we have collected sufficient data on rates of treatment to be more predictive regarding outcomes. The next decade will continue to evolve the design and execution of these types of systems for application to more complex problems. At this point on the timeline, questions regarding the mechanisms of treatment have largely been addressed, allowing a shift in focus to operational enhancements. Specific operational insights arising from the body of work to date that arguably will continue to shape and influence the design and execution of injection‐based remediation systems include: (1) the fact that delivery does not always equal distribution, (2) treatment optimization requires aquifer tuning, and (3) life‐cycle costs can be reduced with remedy‐optimized investigation. The number of examples that support these concepts and their ramifications to future technology refinement is already increasing, demonstrating how the refinements that can be made around these areas of focus will enhance our ability to effectively tackle larger and more complicated plumes, and do so with maximum efficiency. © 2011 Wiley Periodicals, Inc.