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Soil Testing and Analysis

Published: 10th Sep 2011 in OSA Magazine

Introduction

Dealing with contaminated land has long been one of the more challenging elements of brownfield land projects, with remediation requirements needing to be balanced against increasingly complex regulation and, in more recent years, set against a difficult financial outlook.

Given these constraints, there is an obvious need for a remediation technology that can deliver a relatively rapid solution to soil and groundwater contamination, and fit within the frameworks being developed for sustainable remediation, including economic considerations. As a result, ‘green’ and ‘sustainable’ remediation are becoming frequently heard phrases within the contaminated land sector, with ‘nanotechnology’ something of an associated buzzword.

This article explores nanotechnology, its potential as a sustainable remediation technology, and its potential role in groundwater remediation projects in the UK.

Where we are now

At the moment most remediation work carried out in the UK is triggered by the planning process; that is, the management of environmental risks during redevelopment, and by transactional drivers. The previous UK government developed policies to encourage the reuse of brownfield land, including development targets such as 60% of new homes to be built on brownfield land (1998).

However, the current government’s Localism Bill and its ongoing review of planning and environmental legislation looks set for a significant change in approach, with the potential for varying degrees of ’sustainable development’ across regions.

To ensure that this redevelopment maintains a truly sustainable approach - of which the redevelopment of brownfield land plays a critical part - the potential environmental impacts of remediation need to be balanced against the inherent impact of the contamination on the environment.

Often the most significant factors that affect the sustainability of a remediation scheme are the generation of waste and carbon emissions associated with energy intensive technologies, which may need to be implemented over long timeframes. As a result there is a real need for rapid and cost effective solutions to remediating contaminated land and bringing brownfield land back into sustainable use.

In recent years the principles and benefits of sustainable development have been increasingly recognised and incorporated into the decision making process associated with brownfield redevelopment. Major drivers for this are the principles and approaches adopted by the Sustainable Remediation Forum (SuRF), represented in the UK by SuRF UK. The approach championed by SuRF is designed to ensure greater consideration of the environmental, social and economic impacts of remediation in order to maximise the benefits of the same. Such an approach feeds into other schemes which aim to benchmark the sustainability of a development such as BREEAM, CEEQUAL and LEED.

Established remediation techniques

In the UK there has been a move away from historical dig and dump practices to more cost effective and sustainable remediation techniques such as bioremediation, stabilisation and solidification. This is particularly true since the introduction of legislation designed to implement the Waste Framework Directives, and the removal of exemption from landfill tax for contaminated soils by the 2008 budget.

These techniques can be carried out either in situ or ex situ, but are limited by a number of factors including soil type, contamination type and the time required for successful treatment versus scheduling of a redevelopment.

The latter consideration is often the determining factor, meaning that in situ remediation is often discounted in favour of ex situ treatment. When this treatment is used, the contaminated material may have to be removed from the site (depending on its size) and taken to an off-site treatment centre and replaced with clean material to use in the development. This has obvious financial implications as well as reducing the sustainability credentials of the development.

Although effective, established groundwater remediation techniques, for example ‘pump and treat’ or ‘multi-phase extraction’, involve installation and maintenance of groundwater wells and pumps, installation and maintenance of surface treatment plants and require an energy source throughout the treatment period.

In reality, these techniques can often be limited by site-specific factors, including the lateral extent of the contamination plume versus the presence of on-site and neighbouring buildings, underground services, zone of influence of the remediation technique and site security. The presence of remediation equipment on-site during its marketing and sale is an obvious limiting factor in terms of the perception of potential purchasers.

Introducing nanotechnology

Nanotechnology was first described in 1959 by Nobel physicist Richard Feynman and is an area that has since grown rapidly, with Science magazine declaring nanotechnology as the “breakthrough of the year” in 2001. In 2008, the United States Nanotechnology Initiative defined nanotechnology as:

“The understanding and control of matter at dimensions between approximately 1 and 100 nanometers where unique phenomena enable novel applications.”

To put this into context, a human hair is approximately 80,000 and a red blood cell approximately 7,000 nanometers wide, thus nanotechnology gives us the resources to enable engineering at particulate level that was not previously possible.

There are three categories of nanoscale materials:
• Natural (e.g. some clay particles)
• Incidental (e.g. nanoscale particles resulting from an activity, such as burning diesel)
• Engineered (e.g. those materials designed with specific properties and released into the environment through industrial or environmental applications)

Nanotechnology as a remediation tool uses engineered nanoscale materials, the most common of which is the application of nanoscale zero valent metals, particularly iron (nZVI).

Nanoparticles such as nZVI are three dimensional, thus have a large reactive surface compared to larger particles. Their small size and the ability to add surface coatings to the nanoparticles has been recognised as giving them the potential to penetrate small, subsurface spaces and to remain suspended in groundwater - both important properties for effective in situ treatment of chemicals in the soil and groundwater environment.

Nanotechnology as a remediation technology

The use of iron in chemical reactions with common environmental contaminants, including recalcitrant pollutants such as chlorinated solvents, has been extensively investigated and used at the micrometer scale in permeable reactive barriers. This existing understanding of how iron induces the dechlorination process can be extended to the understanding of iron at the nanoscale, albeit via injection into the groundwater rather than containment within a permeable barrier system.

Research and application carried out since the 1990s has found that nZVI is effective in the detoxification (via reduction) of a number of common contaminants including chlorinated solvents, polychlorinated biphenyls and organochlorine pesticides. Existing field evidence suggests that nanoscale zero valent metals may have significant advantages over more established in situ technologies. For example:
• They can remain active in soil and groundwater for up to eight weeks after injection
• They can migrate within groundwater for distances greater than 20m
• They can be used to treat non aqueous phase liquids as well as those dissolved within the groundwater column
• Depending on the coating applied, some nanoscale particles will remain suspended in the groundwater column for varying periods, while others will bind to soil particles and remain in the source zone, continuing to treat the groundwater
• Their small size means easier injection at varying depths to enable treatment of source zones occupied by buildings
• Different types of contamination can be treated by varying the coating applied, including inorganics such as arsenic

As with any remediation technique, the effectiveness of nanotechnology to a specific site will be governed by the conceptual site model, including soil type, geology, groundwater chemistry and aquifer properties. However, its application as a remediation technology has been growing over the last ten years.

To date, the majority of remediation projects using nanotechnology have been carried out in the United States, for example4:
• Emulsified nZVI has been used at a manufacturing site in Florida with trichloroethene (TCE) concentrations in groundwater of 150,000µg/l, reducing the concentrations to 3,580µg/l over a period of five years
• An aluminium processing plant in Alabama with TCE contaminated soil and groundwater at concentrations of 1,655ppb reduced to 72ppb after 29 days (field injection and monitoring, one year for the total project including preparation) using carboxymethyl cellulose stabilised nZVI

However, the technology is not only restricted to the United States and published examples of remediation using nanotechnology in Europe include:
• A site in the Czech Republic with tetrachloroethene (PCE), TCE and dichloroethene (DCE) contaminated groundwater where concentrations were reduced by an order of magnitude in one month using nZVI
• A site in Italy where 20-50% reductions in TCE and DCE concentrations were achieved in the groundwater within one month using nZVI

As the majority of projects are privately funded, the amount of published information, especially relating to cost is limited. However, assuming all sites with contaminated groundwater in the United States were treated using nanotechnology, estimates published in 2009 determined potential savings of between $87 and $98 billion6, predominantly associated with the comparative speed of the treatment process.

Considerations

The small size of nanoscale particles poses unique problems associated with their use in the environment. The actual structure and reactivity of the particles is more likely to be the influencing factor in determining their potential toxicity. This is at odds with the current approach to regulating releases of substances into the environment (based on concentration and volume) and is a significant factor for consideration when applying nanotechnology as a remediation technique and assessing related environmental issues.

Naturally occurring nanoscale iron oxide particles that are bound with copper have been found many kilometres downstream of mining sites, proving their ability to travel potentially significant distances in surface water courses. Depending on the hydrogeological conditions, similar migration within groundwater has been identified with the potential for engineered nanoparticles to form stable nanoclusters incorporating sorbed contaminants. Differences in the chemical reactivity and kinetic relationships may mean that the nanoparticles have no toxic properties, but the bound contaminants may.

Manufactured nanoparticles may also have toxic properties that their naturally occurring counterparts do not possess. This is a potential result of manufactured nanoscale particles being engineered to behave in a specific manner.

Laboratory studies have proven the uptake of manufactured nanoparticles by aquatic organisms. Similarly, laboratory studies have indicated the potential for adverse health effects from iron oxide nanoparticle uptake by mammalian cells.

As nanotechnology is a relatively recent development, studies into toxic properties associated with nanoscale particles are in their relative infancy and little is known of the potential for bioaccumulation of nanoscale particles in the food chain and related affects.

To date, the use of nZVI has raised little concern as it is fully oxidised following reaction with the contaminant and is typically present as ‘rusted’ iron particles within the treated media. Additionally, the nanoscale iron particles have not been found to behave significantly differently (from a toxicity perspective) compared to microscale sized iron particles. However, the application of coatings to enhance specific properties of nZVI and other nanometals could alter the toxicity of nanoparticles used in remediation projects.

In 2004, the level of uncertainty surrounding the behaviour and related risks of nanoparticles in the environment caused the UK’s Royal Society and The Royal Academy of Engineering to recommend that the use of free nanoparticles (those not fixed to or incorporated into a material) be prohibited from use as a remediation technology until more is known about their environmental fate.

Other reviews of nanotechnology and its potential have been more positive. Also in 2004, the European Commission (EC) adopted ‘Communication towards a

European Strategy for Nanotechnology’, which promotes a safe, integrated and responsible strategy for developing nanotechnology, including assessing and addressing environmental concerns.

This strategy is supported by the European Economic and Social Committee and has resulted in the adoption of an action plan. This action plan encourages industry to take into account the economic, social and environmental impacts of commercial activities associated with nanotechnology, e.g. to develop the technology referencing the principles of sustainable development. The action plan also encourages adoption of a risk based approach throughout the life cycle of nanotechnology products, and integration with REACH when appropriate.

The Community Research and Development Information Service (CORDIS) coordinates the EC funded nanotechnology projects, researching the development and use of nanotechnology as well as assessing the associated implications and their management.

The majority of applications of nanotechnology as a remediation device have been in the United States and the comparative lack of experience in Europe and the need for technology transfer from the United States has been identified as a key barrier to commercialisation by the Europe-based Observatory Nano project. The need for international collaboration for the development of nanotechnology and research into the associated environmental risks is therefore encouraged via the action plan.

The future of nanotechnology as a remediation technology

Nanotechnology is already proven to be effective for in situ remediation as it can significantly reduce a range of common, normally recalcitrant contaminants encountered on brownfield sites. As it can be used to treat contaminated soil and groundwater in situ, it has a potential to be promoted as a green remediation technology because it removes the need for energy consuming, carbon producing activities associated with ex situ treatments.

The comparative speed by which nanotechnology can reduce contaminant concentrations means it has the potential to significantly reduce the costs associated with remediation of contaminated sites. This and the short treatment period will appeal to developers and landowners and could play an influential role in the sustainable development of contaminated land.

However, there are a number of significant unknown factors relating to the release of nanoscale particles into the environment, not least surrounding their fate, transport and related toxicity. The need for further research into these areas is already recognised and encouraged at national and international levels and numerous projects have been and are underway. These studies will take time and further research and development of analytical techniques to measure nanoscale particles in the environment is required in tandem with the study of fate and transport.

All this information is critical to informing decisions as to safe levels of nanoscale particles and in order to enable effective, science-based regulation either by adopting existing legislation or developing new, nanotechnology specific regulatory tools.

The current factors limiting the international community’s full embracing of nanotechnology for remediation are not specific to our field - nanotechnology is already widely applied in the drug and cosmetic industries where similar concerns about fate, transport and toxicity apply - but by using nanotechnology in remediation, we are causing a direct release into the environment.

If the industry does want nanotechnology to form part of the solution to contaminated soil and groundwater and to increase available groundwater resources, we need more certainty over the wider environmental and toxicological implications, and for this, greater and more effective international collaboration is vital. 

Authors

Catherine Leaf MIEMA CEnv, ENVIRON, Edinburgh

Catherine is a Senior Consultant and Chartered Environmentalist in ENVIRON’s Edinburgh office. Catherine’s role focuses on the management of contaminated land investigations and remediation projects on behalf of developers and industrial clients across the UK.
Catherine has particular expertise in waste management and minimisation associated with brownfield redevelopment, including the development of site waste and material management plans. She is a certified Qualified Person under the CL:AIRE Definition of Waste: Development Code of Practice, providing independent third party review of the reuse of materials on brownfield sites.

Andy Goddard BSc FGS, ENVIRON, Bath

Andy Goddard is a Senior Manager based in ENVIRON’s Bath office. Andy supports a wide range of clients to address contaminated land liabilities, through investigation, risk assessment and remediation throughout the UK and Europe. He advises international clients in a range of sectors, including telecommunications, manufacturing, petroleum and development.
Andy has particular expertise in the assessment of contaminated land liabilities associated with merger and acquisitions, property investment portfolios and environmental permitting. He is currently directing a number of soil and groundwater remediation projects associated with site closures and corporate risk management programmes.

For more information visit www.environcorp.com

www.osedirectory.com/environmental.php

Published: 10th Sep 2011 in OSA Magazine

Author


Catherine Leaf & Andy Goddard


Catherine Leaf MIEMA CEnv, ENVIRON, Edinburgh
Catherine is a Senior Consultant and Chartered Environmentalist in ENVIRON’s Edinburgh office. Catherine’s role focuses on the management of contaminated land investigations and remediation projects on behalf of developers and industrial clients across the UK.
Catherine has particular expertise in waste management and minimisation associated with brownfield redevelopment, including the development of site waste and material management plans. She is a certified Qualified Person under the CL:AIRE Definition of Waste: Development Code of Practice, providing independent third party review of the reuse of materials on brownfield sites.
Andy Goddard BSc FGS, ENVIRON, Bath
Andy Goddard is a Senior Manager based in ENVIRON’s Bath office. Andy supports a wide range of clients to address contaminated land liabilities, through investigation, risk assessment and remediation throughout the UK and Europe. He advises international clients in a range of sectors, including telecommunications, manufacturing, petroleum and development.
Andy has particular expertise in the assessment of contaminated land liabilities associated with merger and acquisitions, property investment portfolios and environmental permitting. He is currently directing a number of soil and groundwater remediation projects associated with site closures and corporate risk management programmes.
For more information visit www.environcorp.com


Catherine Leaf & Andy Goddard

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