Status of nanoremediation and its potential for future deployment: Risk‐benefit and benchmarking appraisals

NanoRem (Taking Nanotechnological Remediation Processes from Lab Scale to End User Applications for the Restoration of a Clean Environment) was a research project, funded through the European Commission's Seventh Framework Programme, which focuses on facilitating practical, safe, economic, and exploitable nanotechnology for in situ remediation of polluted soil and groundwater, which closed in January 2017. This article describes the status of the nanoremediation implementation and future opportunities for deployment based on risk‐benefit appraisal and benchmarking undertaken in the NanoRem Project. As of November 2016, NanoRem identified 100 deployments of nanoremediation in the field. While the majority of these are pilot‐scale deployments, there are a number of large scale deployments over the last five to 10 years. Most applications have been for plume control (i.e., pathway management in groundwater), but a number of source control measures appear to have taken place. Nanoremediation has been most frequently applied to problems of chlorinated solvents and metals (such as chromium VI). The perception of risk‐benefit balance for nanoremediation has shifted as the NanoRem Project has proceeded. Niche benefits are now more strongly recognized, and some (if not most) of the concerns, for example, relating to environmental risks of nanoremediation deployment, prevalent when the project was proposed and initiated, have been addressed. Indeed, these now appear overstated. However, it appears to remain the case that in some jurisdictions the use of nanoparticles remains less attractive owing to regulatory concerns and/or a lack of awareness, meaning that regulators may demand additional verification measures compared to technologies with which they have a greater level of comfort.     

A Preliminary Risk Assessment Protocol for Renegade Nanoparticles Deployed During Nanoremediation

The NanoRem European research project aims to support and develop the appropriate use of nanotechnology for contaminated land remediation by facilitating practical, economic, and exploitable nanotechnology for in situ remediation. This can only be achieved in parallel with a comprehensive understanding of the environmental risk‐benefit balance for the use of the nanoparticles (NPs) being investigated. While the NanoRem NPs could have a significant toxicity this is likely to be less potent than NPs currently being released into the environment, such as those from a variety of antibacterial products. The NanoRem NPs are likely to interact with the aquifer matrix, each other, and groundwater chemistry to rapidly cease to be mobile and are unlikely to penetrate into the aquifer more than a few meters from the point of injection. In terms of the source‐pathway‐receptor paradigm, the NanoRem NPs are cautiously presumed to represent a hazard (i.e., source). At least one receptor, in the form of not yet polluted groundwater, is present at all the NanoRem case study sites. While there are considerable uncertainties particularly with regards to the transport of NanoRem NPs, the ability of NPs to penetrate far into the formation is likely to be very limited. The relatively short travel distances reported in the literature for a variety of NP types and geological conditions suggest that the pathways are at best very limited in extent. Overall, this means that in many cases the level of risk renegade NPs can pose to the environment or human health is at most minimal. A qualitative protocol developed for the NanoRem field trials can demonstrate that injecting NanoRem NPs into contaminated groundwater poses a minimal level of risk due to the reduced pathway. ©2016 Wiley Periodicals, Inc.     

Selectivity of Nano Zerovalent Iron in In Situ Chemical Reduction: Challenges and Improvements

Nano zerovalent iron (nZVI) is a promising remediation technology utilizing in situ chemical reduction (ISCR) to clean up contaminated groundwater at hazardous waste sites. The small particle size and large surface area of nZVI result in high reactivity and rapid destruction of contaminants. Over the past 20 years, a great deal of research has advanced the nZVI technology from bench‐scale tests to field‐scale applications. However, to date, the overall number of well‐characterized nZVI field deployments is still small compared to other alternative remedies that are more widely applied. Apart from the relatively high material cost of nZVI and questions regarding possible nanotoxicological side effects, one of the major obstacles to the widespread utilization of nZVI in the field is its short persistence in the environment due to natural reductant demand (NRD). The NRD for nZVI is predominantly due to reduction of water, but other reactions with naturally present oxidants (e.g., oxygen) occur, resulting in situ conditions that are reducing (high in ferrous iron phases and H₂) but with little or no Fe(0). This article reviews the main biogeochemical processes that determine the selectivity and longevity of nZVI, summarizes data from prior (laboratory and field) studies on the longevity of various common types of nZVI, and describes modifications of nZVI that could improve its selectivity and longevity for full‐scale applications of ISCR. © 2016 Wiley Periodicals, Inc.     

Quantitative Environmental Footprints and Sustainability Evaluation of Contaminated Land Remediation Alternatives for Two Case Studies

Since the US Environmental Protection Agency (US EPA) launched its “green remediation” program and EU member states began to reassess their national regulations for environmental remediation in order to reach a Europe‐wide consensus on policy and standards, the need and interest for sustainable remediation of contaminants from brownfields has grown considerably. Concomitantly, the ability to calculate and assess the suitability as well as the environmental footprints and associated risks of a growing number of remediation techniques has become a priority. The authors quantitatively evaluate the differences between various remediation techniques, and for this purpose, a number of ex situ and in situ remediation techniques are adapted to model 21 remediation scenarios for two contaminated sites in the Gothenburg region of Sweden: the Bohus Varv site on the Göta älv river bank and the Hexion site in Mölndal. A wide range of quantitative results for these models are presented, compared, and analyzed. Based on the results from both projects, it is concluded that: (1) remediation techniques requiring long distance residual transportation have significant footprints, except the transportation of contaminated residuals by train due to Swedish energy production conditions; (2) residual transportation by ship results in much higher SO_x, NO_x, and particle releases compared to the other alternatives; and (3) residual transporation by truck results in high accident risks. Finally, activities powered by electricity result in a reduced footprint compared to activities powered by fossil fuels, considering Swedish energy production conditions. The authors conducted a cross‐benefit analysis of SiteWise^TM applications which recognizes its potential as a tool for presenting life cycle assessment analyses with appropriate system boundary definitions and an easy inventory analysis process. Results from this tool provide valuable support to decision makers aiming at more sustainable remediation. © 2013 Wiley Periodicals, Inc.     

Applying sustainable development principles to contaminated land management using the SuRF‐UK framework

In the past decade, management of historically contaminated land has largely been based on prevention of unacceptable risks to human health and the environment, to ensure a site is “fit for use.” More recently, interest has been shown in including sustainability as a decision‐making criterion. Sustainability concerns include the environmental, social, and economic consequences of risk management activities themselves, and also the opportunities for wider benefit beyond achievement of risk‐reduction goals alone. In the United Kingdom, this interest has led to the formation of a multistakeholder initiative, the UK Sustainable Remediation Forum (SuRF‐UK). This article presents a framework for assessing “sustainable remediation”; describes how it links with the relevant regulatory guidance; reviews the factors considered in sustainability; and looks at the appraisal tools that have been applied to evaluate the wider benefits and impacts of land remediation. The article also describes how the framework relates to recent international developments, including emerging European Union legislation and policy. A large part of this debate has taken place in the “grey” literature, which we review. It is proposed that a practical approach to integrating sustainability within risk‐based contaminated land management offers the possibility of a substantial step forward for the remediation industry, and a new opportunity for international consensus. © 2011 Wiley Periodicals, Inc.     

A cost study for enhanced sludge washing of high-level radioactive waste at the U.S. Department of energy Hanford Site

Enhanced Sludge Washing (ESW) with caustic has the potential to significantly reduce the amount of sludge-based underground storage tank (UST) high-level radioactive waste at the Hanford Site. The alternative to ESW is a simple sludge wash, a process that does not take advantege of recent dissolution development efforts. During the past several years, studies have been conducted to determine the remediation cost savings derived from the development and deployment of ESW. The tank waste inventory and ESW process performance continues to be revised as waste characterization, and ESW development efforts advance. This study provides a new cost savings estimate based upon the most recent waste inventory and ESW process performance revisions, an estimate of the associated cost savings uncertainty, and an estimate of the rate of return (ROR) on the investment in technology development. The revised remediation cost savings estimate due to ESW of all UST waste at Hanford is $4.8 billion ± $0.7 billion within 95 percent confidence in 1998 dollars. The ROR on investment was estimated to range from 100 percent to 130 percent. A sensitivity analysis indicated that it would be difficult to imagine a remediation scenario for which ESW did not yield a significant remediation cost savings and ROR.     

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.     

Injecting remediation compounds—How you inject is equally as important as what you inject

The injection of remediation compounds has rapidly become a widely accepted approach for addressing contaminated sites. One of the most fundamental questions surrounding the use of in situ remediation has been “What compound are you injecting at your site?” With the advances in the industry's understanding and acceptance of the in situ remediation process remediation professionals are now asking a follow‐up question that has become equally important to the success of a project: “How are you injecting a compound at your site?” This article discusses advances in field applications for in situ remediation and injecting remediation compounds. © 2003 Wiley Periodicals, Inc.     

Risk communication as a key component of a successful remediation project

Decisions made during the course of investigating and remediating a contaminated site, as well as the technology used, are most often driven exclusively by physical, technical, and health-based concerns. Additionally, in both determining and managing the potential risks posed by a remediation project, the focus tends to be placed primarily on health risks. However, a contaminated site and its remediation are neither static over time nor do they exist in a vacuum. Other elements of risk associated with the site and remedial activities include continuing regulatory oversight and compliance, public and agency relations, remedial technology costs, current and future land-use issues, and future technological/regulatory risks. Agencies, consultants, contractors, and facility management must consider these other non-health-related elements of risk. Additionally, efforts made to communicate a project's decisions, technologies, and risks are often made in a defensive or reactive posture, resulting in ineffective communication and an alienated, angry, or distrustful public. Proactive risk communication, as well as public involvement in the remedial process, are critical to the success of any remedial activity.     

Climate-influenced hydrobiogeochemistry and groundwater remedy design: A review

The process of designing a remedy for contaminated groundwater historically has not commonly included climate-future, hydrologic, and biogeochemical aquifer characteristics. From experience, the remedy design process also has not consistently nor directly integrated or projected future hydrologic and biogeochemical effects of the human-induced or developed environment—aka the anthropogenic influence—on potential remedy performance. The apparent practice of (1) not regularly assessing anthro-influenced hydrological (termed here as anthrohydrology) or biogeochemical characteristics (collectively hydrobiogeochemistry) of a site and (2) rarely accounting for future climatic shifts as design factors in remedy design may be due, in part, to the general practice-level view that groundwater remediation systems (whether in situ or ex situ) have seldom been anticipated to last more than a few years (or one or two decades at the most). Second, methods to reliably and quantitatively estimate site-specific, climate-future shifts in groundwater conditions using global and/or regional climate models and the resultant impacts on contaminant plume characteristics have not been readily available. The authors here suggest that while the concept of remedy design resilience and durability, within an envelope of climate change and anthropogenic influence, has been discussed in some technical circles as a component of “sustainable remediation,” we have found that direct application of these technical concepts in quantifiable terms remains rare. By incorporating the potential influence of future hydrobiogeochemical scenarios into remedy design, however, the design process could account for reasonable climate-induced influence on the groundwater system for a given site. These scenarios could then be applied within the remedy selection process to assess performance durability under potentially changing hydrologic, biological, and chemical conditions.     

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.     

Economic Project Risk Assessment in Remediation Projects Prior to Construction: Methodology Development and Case Study Application

Probabilistic economic analysis, including uncertainty of probabilities and consequences of project risks, is not widely used in remediation projects. This article presents a project risk assessment (PRA) method to identify, quantify, and analyze risks in remediation projects. The suggested method is probabilistic and includes uncertainty analysis of input variables based on expert judgment. It was originally developed as a part of a sustainability assessment tool, but is viable as a stand‐alone tool for remediation projects. The method is applied to a case study: a former paint factory that is being redeveloped into a residential area. The PRA method is used for analyzing and comparing the project risks associated with four remediation options, all including excavation but with different degrees of onsite treatment. The result of the case study application shows which alternative has the lowest mean risk cost, the highest probability to have the lowest risk cost, and how the risk costs are distributed, but also, importantly, helps the user to prioritize between risk‐reduction measures. ©2015 Wiley Periodicals     

Groundwater geochemistry diagnostics during in situ ERH remediation

In situ remediation represents a series of challenges in interpreting the monitoring data on remedial progress. Among these challenges are problems in determining the progress of the remediation and the mechanisms responsible, so that the process can be optimized. The release of organic pollutants to groundwater systems and in situ remediation technologies alter the groundwater chemistry, but outside of natural attenuation studies using inorganic chemical analyses as indicators of intrinsic biodegradation, typically little attention has been paid to the changes in inorganic groundwater chemistry. Smith (2008) noted that during an electrical resistance heating remediation that took place at a confidential site in Chicago, a two‐orders‐of‐magnitude increase in chloride concentrations occurred during the remediation. This increase in chloride resulted in a corresponding increase in calcium as a result of what is known as the common ion effect. Carbon dioxide is the gas found in highest concentrations in natural groundwater (Stumm & Morgan, 1981), and its fugacity (partial pressure) corresponds directly with calcium concentrations. Carbon dioxide at supersaturation in groundwater is capable of dissolving organic compounds, such as trichloroethene, facilitating removal of nonaqueous‐phase liquids at temperatures below the boiling point of water. One means of diagnosing these reactions is through the use of compound‐specific isotopic analysis, which is capable of distinguishing between evaporation, biodegradation, and differences in sources. The appropriate diagnosis has the potential to optimize the benefits from these reactions, lower energy costs for removal of nonaqueous‐phase liquids, and direct treatment where it is needed most. © 2010 Wiley Periodicals, Inc.     

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.     

A European approach to increase innovative soil and groundwater remediation technology applications

The European Commission (EC) has recognized a need for strengthening innovation of environmental technologies in order to increase competitiveness of European technologies on a global market and to achieve a more sustainable development in Europe. In the area of soil and groundwater remediation, innovative technologies are principally available and have proven applicability and performance on demonstration scales, but market uptake is disappointing. Consequently, initiatives have been launched in order to promote application of these technologies and to investigate on the harmonization of applications. The European Co‐ordination Action for Demonstration of Efficient Soil and Groundwater Remediation (EURODEMO), an EC‐funded project, is one strategic initiative for supporting these goals. This article summarizes results obtained so far regarding the investigation of the European situation and some undertaken and envisaged measures to achieve better market uptake. The results of this research project may serve as prerequisites for a European Environmental Technologies Verification (ETV) process. © 2006 Wiley Periodicals, Inc.     

An evaluation of permeable reactive barrier projects in California

Permeable reactive barriers made of zero‐valent iron (ZVI PRBs) have become a prominent remediation technology in addressing groundwater contamination by chlorinated solvents. Many ZVI PRBs have been installed across the United States, some as research projects, some at the pilot scale, and many at full scale. As a passive and in situ remediation technology, ZVI PRBs have many attractive features and advantages over other approaches to groundwater remediation. Ten ZVI PRBs installed in California were evaluated for their performance. Of those ten, three are discussed in greater detail to illustrate the complexities that arise when quantifying the performance of ZVI PRBs, and to provide comment on the national debate concerning the downgradient effects of source‐zone removal or treatment on plumes of contaminated groundwater. © 2009 Wiley Periodicals, Inc.     

Centrifugal Bioreactors and Their Application in Remediation

A new approach to the maintenance of large microbial populations for bioremediation purposes has been developed in which a centrifugal bioreactor is used to immobilize microbial populations at extremely high density. The cells are ordered into a three‐dimensional array through which wastewater or groundwater volumes may be flowed, unimpeded by frits or screens. The process methodology is independent of the type, shape, or viability of the individual cells immobilized and, thus, may be adapted to many different bioremediation needs. The utilization of this new process has been explored for three different types of remediation: the removal of heavy metals from wastewater, the aerobic degradation of methyl‐tert‐butyl ether (MTBE), and the anaerobic reduction of nitrate to nitrogen gas. This article discusses the use of centrifugal bioreactors and their application in remediation. © 2001 John Wiley & Sons, Inc.     

Combined thermal and zero‐valent iron In Situ soil mixing remediation technology

Thermal remediation of contaminated soils and groundwater by injection of hot air and steam using large‐diameter auger in situ soil mixing effectively remediates volatile and semivolatile organic compounds. This technology removes large amounts of contamination during the early treatment stages, but extended treatment times are needed to achieve high removal percentages. Combining thermal treatment with another technology that can be injected and mixed into the soil, and that continues to operate after removal of the drilling equipment, improves removal efficiency, and reduces cost. Using field‐determined pseudo first‐order removal rates, the cost of the combined remediation of chlorinated volatile organic compounds (CVOCs) by thermal treatment followed by reductive dechlorination by iron powder has been estimated as 57 percent of the cost of thermal treatment alone. This analysis was applied to a case‐study remediation of 48,455 cubic yards, which confirmed the cost estimate of the combined approach and showed over 99.8 percent removal of trichloroethene and other chlorinated VOCs. © 2010 Wiley Periodicals, Inc.