Treatment technology for remediation of wood preserving sites: Overview

This is the first in a series of five articles describing the applicability, performance, and cost of technologies for the remediation of contaminated soil and water at wood preserving sites. Site‐specific treatability studies conducted under the supervision of the United States Environmental Protection Agency (US EPA), National Risk Management Research Laboratory (NRMRL), from 1995 through 1997 constitute much of the basis for the evaluations presented, although data from other treatability studies, literature sources, and actual site remediations have also been included to provide a more comprehensive evaluation of remediation technologies. This article provides an overview of the wood preserving sites studied, including contaminant levels, and a summary of the performance of the technologies evaluated. The subsequent articles discuss the performance of each technology in more detail. Three articles discuss technologies for the treatment of soils, including solidification/stabilization, biological treatment, solvent extraction and soil washing. One article discusses technologies for the treatment of liquids, water and nonaqueous phase liquids (NAPLS), including biological treatment, carbon adsorption, photolytic oxidation, and hydraulic containment. The reader should be aware that other technologies including, but not limited to, incineration, thermal desorption, and base catalyzed dehalogenation, also have application for treating contaminants on wood preserving sites. They are not discussed in these five articles since the focus was to evaluate lesser known and hopefully lower cost approaches. However, the reader should include consideration of these other technologies as part of any evaluation or screening of technologies applicable to remediation of wood preserving sites.     

Methodology and model for performance and cost comparison of innovative treatment technologies at wood preserving sites

Wood preserving facilities have used a variety of compounds, including pentachlorophenol (PCP), creosote, and certain metals, to extend the useful life of wood products. Past operations and waste management practices resulted in soil and water contamination at a portion of the more than 700 wood preserving sites in the United States (EPA, 1997). Many of these sites are currently being addressed under federal, state, or voluntary cleanup programs. The U.S. Environmental Protection Agency (EPA) National Risk Management Research Laboratory (NRMRL) has responded to the need for information aimed at facilitating remediation of wood preserving sites by conducting treatability studies, issuing guidance, and preparing reports. This article presents a practical methodology and computer model for screening the performances and comparing the costs of seven innovative technologies that could be used for the treatment of contaminated soils at user‐specified wood preserving sites. The model incorporates a technology screening function and a cost‐estimating function developed from literature searches and vendor information solicited for this study. This article also provides background information on the derivation of various assumptions and default values used in the model, common contaminants at wood preserving sites, and recent trends in the cleanup of such sites. © 2001 John Wiley & Sons, Inc.     

Review of in situ remediation technologies for lead,zinc, and cadmium in soil

This article presents a review of in situ technologies for the remediation of soils contaminated with lead, zinc, and/or cadmium. The objective of this review is to assess the developmental status of the available in situ technologies and provide a general summary of typical applications and limitations of these technologies. The literature review identified seven in situ remediation technologies—solidification/stabilization, vitrification, electrokinetic remediation, soil flushing, phytoextraction, phytostabilization, and chemical stabilization. These technologies were considered for their ability to meet a specific set of remediation objectives under a range of conditions. Each of these technologies has both strengths and weaknesses for addressing particular remedial situations discussed in the article for each of the technologies. A general summary of which technologies are most applicable to common remedial scenarios is also provided. © 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.     

Optimization of cement-based stabilization/solidification of organic-containing industrial wastes using organophilic clays

The treatment of organically contaminated industrial wastes by cement-based stabilization/solidification has, in the past, been restricted by the detrimental effect of organic compounds on cement hydration. This work investigates the use of organophilic clays as adsorbents for the organic components of industrial wastes prior to conventional cement-based solidification. Three industrial wastes containing between 2–12% organic carbon and trace heavy metal contamination were treated with a quaternary ammonium salt exchanged clay. The organic component of all three wastes was well adsorbed by the clay. Solidification of the waste/clay mixes produced a monolithic mass with adequate strength and very low leaching of either the organic compounds or the metals. This study has shown that organophilic clays can act as successful adsorbents for the organic contaminants of industrial wastes and enable them to be treated by cement-based solidification.     

Use of open-path FTIR spectroscopy to address air monitoring needs during site remediations

Although open-path Fourier-transform infrared (FTIR) spectroscopy has been an Environmental Protection Agency (EPA) Toxic Organic Compendium Method since 1996, it has been underutilized as a means to assess exposure to gaseous contaminants during the remediation of hazardous waste sites. This might be considered surprising in light of the many benefits that proper application of this technology can offer. In this article, we provide an overview of the technology and the principle of operation, describe the nature of the data generated, discuss the benefits associated with the technology's use in site clean-up, present emission-rate estimation techniques, and examine the reasons why it has not gained more support over the years. Finally, we present a case study in which the technology was used to drive an 11-month emergency removal action under the direction of the U.S. Environmental Protection Agency.     

Geochemical evaluation of metals in groundwater at long‐term monitoring sites and active remediation sites

At many sites, long‐term monitoring (LTM) programs include metals as chemicals of concern, although they may not be site‐related contaminants and their detected concentrations may be natural. At other sites, active remediation of organic contaminants in groundwater results in changes to local geochemical conditions that affect metal concentrations. Metals should be carefully considered at both types of sites, even if they are not primary contaminants of concern. Geochemical evaluation can be performed at LTM sites to determine if the monitored metals reflect naturally high background and, hence, can be removed from the analytical program. Geochemical evaluation can also be performed pre‐ and post‐treatment at active remediation sites to document the effects of organics remediation on metals and identify the processes controlling metal concentrations. Examples from both types of sites are presented in this article. © 2008 Wiley Periodicals, Inc.     

Yardsticks to Integrate Risk Assessment,Risk Management,and Groundwater Remediation

Remediation of contaminated sites has focused largely on restoration of groundwater aquifers. Often the stated remedial goal is to achieve conditions allowing unrestricted use and unrestricted exposure. Such total groundwater cleanup has occurred at some sites, but is the exception rather than the rule. At the same time, significant effort occurs to perform risk assessments for potential exposure to contaminants in groundwater at sites, both before and after remediation. The logical synergy between risk assessment and remediation is for risk management to seek opportunities for optimal use of groundwater based upon realistic expectations of cleanup technologies and the relevant acceptable residual (postremediation) levels of contaminants. This article explores an approach to improve this synergistic relationship between risk assessment, risk management, and remediation for groundwater cleanups. ©2015 Wiley Periodicals, Inc.     

Evaluating a Site for Natural Attenuation: EPA Region IV's New Guidance

Natural attenuation has recently been recognized by the U.S. Environmental Protection Agency (EPA) as an appropriate remedy for sites contaminated with chlorinated solvents. Because natural attenuation does not require active remediation, it is considerably less expensive than other groundwater remedies. However, as laid out in EPA's recently released guidance, careful, systematic evaluation of natural attenuation must be conducted to ensure that the remedial approach is appropriate for a given site. The guidance requires that data be collected to demonstrate that natural attenuation is occurring and a fate-and-transport model must be conducted to estimate the extent to which a contaminated plume will ultimately migrate. Finally, the proponent of natural attenuation must be prepared to conduct long-term groundwater monitoring to verify that natural attenuation is controlling plume migration and that human health and the environment are not adversely affected.     

Solidification and stabilization of hazardous wastes using geopolymers as sustainable binders

Journal of Material Cycles and Waste Management - Solidification/stabilization (S/S) of hazardous waste using cement for immobilization of contaminants has been recognized as Best Demonstrated...     

Accessing EPA's hazardous waste remediation technology information

Hazardous waste remediation technologies are rapidly evolving, and it is a challenge for environmental consultants and those working in the government and public sectors to remain current with those technologies. Fortunately, the U.S. Environmental Protection Agency (EPA), through a variety of programs and initiatives, has been a leader in providing information on hazardous waste remediation technologies. This article provides an overview of EPA remediation programs and guides the reader through valuable EPA information sources including publications, databases, and on-line services.     

Cement-based solidification/stabilization of lead-contaminated soil at a utah highway construction site

This article describes portland cement-based solidification/stabilization (S/S) treatment of heavy metal-contaminated soil. The soil was discovered during highway construction in West Jordan, Utah. Environmental Chemical Corporation (ECC) performed an emergency response to remediate the soil under contract with the EPA and the United States Bureau of Reclamation (USBR). The soil was treated by S/S. Treatment of the soil, contaminated with lead and arsenic, involved: (1) excavation, (2) size segregation, (3) reduction of oversized particles, (4) addition and mixture of portland cement and cement kiln dust, and (5) beneficial reuse of the treated soil as a subbase. S/S treatment successfully reduced Toxicity Characteristic Leaching Procedure (TCLP) concentrations of the contaminants to below regulatory levels.     

Comparing PFAS to other groundwater contaminants: Implications for remediation

Established groundwater contaminants such as chlorinated solvents and hydrocarbons have impacted groundwater at hundreds of thousands of sites around the United States and have been responsible for multibillion dollar remediation expenditures. An important question is whether groundwater remediation for the emerging contaminant class comprised of per‐ and polyfluoroalkyl substances (PFAS) will be a smaller, similar, or a larger‐scale problem than the established groundwater contaminants. A two‐pronged approach was used to evaluate this question in this paper. First, nine quantitative scale‐of‐remediation metrics were used to compare PFAS to four established contaminants: chlorinated solvents, benzene, 1,4‐dioxane, and methyl tert‐butyl ether. These metrics reflected the prevalence of the contaminants in the U.S., attenuation potential, remediation difficulty, and research intensity. Second, several key challenges identified with PFAS remediation were evaluated to see similar situations (qualitative analogs) that have been addressed by the remediation field in the past. The results of the analysis show that four out of nine of the evaluated quantitative metrics (production, number of potential sites, detection frequency, required destruction/removal efficiency) indicate that the scale of PFAS groundwater remediation may be smaller compared to the current scale of remediation for conventional groundwater contaminants. One attenuation metric, median plume length, suggests that overall PFAS remediation could pose a greater challenge compared to hydrocarbon sites, but only slightly larger than chlorinated volatile organic compounds sites. The second attenuation metric, hydrophobic sorption, was not definitive regarding the potential scale of PFAS remediation. The final three metrics (regulatory criteria, in‐situ remediation capability, and research intensity) all indicate that PFAS remediation might end up being a larger scale problem than the established contaminants. An assessment of the evolution of groundwater remediation capabilities for established contaminants identified five qualitative analogs for key PFAS groundwater remediation issues: (a) low‐level detection analytical capabilities; (b) methods to assess the risk of complex chemical mixtures; (c) nonaqueous phase dissolution as an analog for partitioning, precursors, and back diffusion at PFAS sites; (d) predictions of long plume lengths for emerging contaminants; and (e) monitored natural attenuation protocols for other non‐degrading groundwater contaminants. Overall the evaluation of these five analogs provided some comfort that, while remediating the potential universe of PFAS sites will be extremely challenging, the groundwater community has relevant past experience that may prove useful. The quantitative metrics and the qualitative analogs suggest a different combination of remediation approaches may be needed to deal with PFAS sites and may include source control, natural attenuation, in‐situ sequestration, containment, and point‐of‐use treatment. However, as with many chlorinated solvent sites, while complete restoration of PFAS sites may be uncommon, it should be possible to prevent excessive exposure of PFAS to human and ecological receptors.     

Look at groundwater quality to set VOC cleanup levels

In 1981, the Arizona Department of Health Services (ADHS) discovered groundwater contamination by solvents and chromium at the Phoenix Goodyear Airport (PGA), just outside the city of Phoenix. ADHS and the U.S. EPA sampled the site for the next two years, finding that eighteen of their wells were contaminated with trichloroethene (TCE), six exceeding ADHS's action level of five micrograms per liter (μg/l). In 1983, the PGA site was added to the National Priorities List, and, in 1984, EPA began a $3 million remedial investigation, focusing on soils and groundwater. This article discusses how that investigation inspired the authors to develop a stream-lined evaluation method for PGA's volatile organic compounds (VOCs), the process for establishing VOC cleanup levels, and the $26 million of remediation work needed to be done at the site. The heart of this effort is a computer program called VLEACH, loosely standing for VOC-LEACHing, which anticipates the influence of VOCs on PGA's groundwater, even as remediation proceeds.     

Progress toward remediation of the Sydney Tar Ponds: A major Canadian PCB/PAH “superfund” site

The Muggah Creek estuary in Sydney, Nova Scotia, received liquid and solid wastes from a steel mill and its associated coke ovens for approximately 100 years. This resulted in pollution of soils and sediments with polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), heavy metals, and other pollutants, including those in untreated domestic wastewaters. The Canadian federal and Nova Scotia provincial governments organized the Sydney Tar Ponds Agency (STPA) to develop a remediation approach for the Coke Ovens site soils and Sydney Tar Ponds sediments. The STPA developed a remediation approach for the Sydney Tar Ponds sediments, involving solidification/stabilization (S/S) through mixing cement and other materials into the sediments, and then capping them as a waste pile. High‐density polyethylene (HDPE) plastic sheeting vertical barriers are proposed to be used to divert groundwater and surface water from entering into the S/S‐treated sediments and to collect any water and associated pollutants released from the S/S‐treated sediments. The Coke Ovens site soils are proposed to be landfarmed to reduce some of the PAHs and other pollutants and then capped with a layer of soil. This remediation program is estimated to cost on the order of $400 million (CAN). This article presents a review of the significant potential problems with the STPA proposed remediation strategy of the Sydney Tar Ponds sediments and Coke Ovens site soils. © 2006 Wiley Periodicals, Inc.     

The State of the Practice: Characterizing and Remediating Contaminated Groundwater at Fractured Rock Sites

Characterizing and remediating contaminated groundwater in fractured rock are often the most difficult challenges facing environmental professionals. The U.S. Environmental Protection Agency (EPA), other U.S. federal agencies, and the Ontario Ministry of Environment recently supported a workshop, held an international conference, and developed a Web site to promote the understanding of the state of the practice. Field practitioners and researchers were surveyed and questioned concerning their experiences. This article summarizes the results of these efforts and provides an overview of the use of characterization methods and remediation technologies at fractured rock sites. © 2002 Wiley Periodicals, Inc.     

Net impact of remediation

Following years of progress in designing and executing cleanups of contaminants at waste sites, the U.S. Air Force, state regulatory groups, and others are crafting methods to evaluate broader considerations of risk in remedial decisions. Integrating worker and climate risks into remediation efforts may confer significant benefits, but challenges exist to identifying, assessing, and accounting for them in the remedial process. For sites where future risk posed by contamination far exceeds the risk posed to workers who may be exposed to the contaminants during the remedial process, limiting the range of decision inputs to those presented by the site conditions made sense and provided a net benefit to human health and the environment. There are other sites, however, where future risk posed by the in situ contamination are at levels comparable to the real risks posed to workers, ecology, and even emerging concerns about climate change. For these sites, a net risk reduction cannot be assumed to be a result of remedial action, challenging the remedial community to develop new approaches to ensure positive results. © 2009 Wiley Periodicals, Inc.     

Coupling surfactants/cosolvents with oxidants for enhanced DNAPL removal: A review

Surfactants and cosolvents are useful for enhancing the apparent solubility of dense nonaqueous‐phase liquid (DNAPL) compounds during surfactant‐enhanced aquifer remediation (SEAR). In situ chemical oxidation (ISCO) with permanganate, persulfate, and catalyzed hydrogen peroxide has proven to be a cost‐effective and viable remediation technology for the treatment of a wide range of organic contaminants. Coupling compatible remedial technologies either concurrently or sequentially in a treatment train is an emerging concept for more effective cleanup of DNAPL‐contaminated sites. Surfactants are effective for DNAPL mass removal but not useful for dissolved plume treatment. ISCO is effective for plume control and treatment but can be less effective in areas where large masses of DNAPL are present. Therefore, coupling SEAR with ISCO is a logical next step for source‐zone treatment. This article provides a critical review of peer‐reviewed scientific literature, nonreviewed professional journals, and conference proceedings where surfactants/cosolvents and oxidants have been utilized, either concurrently or sequentially, for DNAPL mass removal. © 2010 Wiley Periodicals, Inc.     

Rocky Flats,plutonium, and controversy: Citizen activists provide institutional memory

The U.S. Atomic Energy Commission (AEC) selected Rocky Flats, east of the Rocky Mountains, as the site to fabricate “plutonium pits,” triggers for H‐bombs, and operations began in 1952. Press reports revealed the plant's connection to atomic weapons in 1956. Denver is downwind and “downslope” by about 16 miles. As western suburbs moved closer to Rocky Flats over time, plant accidents sent plutonium and other contaminants offsite. In 1989, armed agents of the U.S. Environmental Protection Agency (EPA) and Federal Bureau of Investigation raided the facility, and the plant operator, Rockwell International, subsequently pleaded guilty to criminal environmental violations. By this time, the U.S. Department of Energy had inherited responsibility for Rocky Flats and atomic weapons production. In 1993, the primary mission at Rocky Flats became cleanup of contamination from plutonium and other hazardous substances. Under Energy's “Accelerated Cleanup” plan, remediation was certified complete in 2005 by the Department's cleanup regulators, EPA, and the Colorado Department of Public Health. But planned uses for the “buffer zone” around the facility's central industrial area, and for off‐site areas continued to generate public controversy. This article examines the controversy and reports on general “stewardship” concepts for long‐term waste management.     

Developing Effective Decision Support for the Application of “Gentle” Remediation Options: The GREENLAND Project

Gentle remediation options (GRO) are risk management strategies/technologies that result in a net gain (or at least no gross reduction) in soil function as well as risk management. They encompass a number of technologies, including the use of plant (phyto‐), fungi (myco‐), and/or bacteria‐based methods, with or without chemical soil additives or amendments, for reducing contaminant transfer to local receptors by in situ stabilization, or extraction, transformation, or degradation of contaminants. Despite offering strong benefits in terms of risk management, deployment costs, and sustainability for a range of site problems, the application of GRO as practical on‐site remedial solutions is still in its relative infancy, particularly for metal(loid)‐contaminated sites. A key barrier to wider adoption of GRO relates to general uncertainties and lack of stakeholder confidence in (and indeed knowledge of) the feasibility or reliability of GRO as practical risk management solutions. The GREENLAND project has therefore developed a simple and transparent decision support framework for promoting the appropriate use of gentle remediation options and encouraging participation of stakeholders, supplemented by a set of specific design aids for use when GRO appear to be a viable option. The framework is presented as a three phased model or Decision Support Tool (DST), in the form of a Microsoft Excel‐based workbook, designed to inform decision‐making and options appraisal during the selection of remedial approaches for contaminated sites. The DST acts as a simple decision support and stakeholder engagement tool for the application of GRO, providing a context for GRO application (particularly where soft end‐use of remediated land is envisaged), quick reference tables (including an economic cost calculator), and supporting information and technical guidance drawing on practical examples of effective GRO application at trace metal(loid) contaminated sites across Europe. This article introduces the decision support framework. ©2015 Wiley Periodicals, Inc.