General Atomics Electromagnetic Systems (GA-EMS) conducted live demonstrations of its industrial Supercritical Water Oxidation (iSCWO) system for destroying PFAS chemicals before a delegation of government, remediation, and waste management company representatives on 29 August.

It appeared to demonstrate the successful destruction of PFAS using an Aqueous Film Forming Foam (AFFF) waste feed in a series of back-to-back demonstrations of GA-EMS’ iSCWO system at the company’s dedicated, full-scale system test facility located in San Diego.

A variety of oxidation and other technologies are currently being explored in relation to the disposal of PFAS in substrates such as landfill leachate.

“PFAS chemicals have been used in products since the 1940s and communities today are grappling with the environmental and human health consequences caused by decades of exposure to these forever chemicals,” said Scott Forney, president of GA-EMS. “It’s time to end the cycle of PFAS contamination for good. We invited legislative and waste industry representatives to witness first-hand iSCWO’s effectiveness in eliminating PFAS, using our commercial technology that has been out of the lab and operational in the field for more than a decade.”

GA-EMS’ iSCWO system processes organic waste with water in an extremely high temperature (650°C) and high pressure (4000 psi) environment to efficiently destroy PFAS and PFAS waste containing other organic co-contaminants. The system is described as being safe to operate, environmentally sound, and cost-effective. There is no post-treatment required, no gas or liquid emissions to deal with, and no hazardous by-products to store, transport, or dispose of.

“We are working with remediation companies to develop plans to integrate our proven iSCWO systems into their waste treatment infrastructures and begin the process of eliminating PFAS from a wide range of waste sources, including landfill leachate, wastewater, biosolids, soils, and water filtration by-products,” continued Forney. “To date, our iSCWO systems have destroyed over 6 million gallons of hazardous and non-hazardous waste with a greater than 99.99% destruction efficiency.”

The EPA issued a detailed report documenting the first-ever test and verification of PFAS destruction efficiency greater than 99.99% using GA-EMS’ industrial-scale SCWO technology. In addition, GA-EMS’ iSCWO system has been successfully tested to destroy more than 200 different types of hazardous and non-hazardous liquids, solids, and slurry waste streams with the same 99.99% plus destruction results.

Envirotec struggles to find solid takeaways in the literature about PFAS contamination in landfills, and what might be done about it. As regulations tighten, the topic seems to be growing more urgent.

A contaminant whose importance appears to have grown significantly in recent years, poly- and perfluoroalkyl substances (PFAS) present a challenge to pollution management given their apparent toxicity – although a clear picture is still emerging – and persistence. The tag “forever chemicals” is clearly very appropriate for a class of synthetic compounds whose unusual molecular structure, including the carbon-fluorine (C-F) bond (considered one of the strongest found in organic chemistry), appears to offer little scope for any thermal or other degradation at all, so they endure permanently.

They make ideal surfactants, given their water- and oil-resistance, although this also contributes to their extreme mobility – problematic for those who might seek to constrain them.

These and other properties have made them an all-but-indispensable ingredient in a wide range of consumer and industrial products, and they have been used since the 1940s with applications including textiles and clothing, electroplating, fire-fighting foam, and ammunition.

And there are many of them (more than 4,000 on the global market). Most of the health studies and legislation have focused on the “long chain” PFAS compounds – whose molecular structure tends to feature 7 or more carbon atoms – and includes things like perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).

These compounds are known to accrete in human tissues, through consumption of contaminated food or water, and are not readily excreted. Efforts to phase out PFOS began in the US and Europe in the early 2000s, and these long-chain PFAS have gradually been substituted with short-chain replacement compounds, offering some of the same properties but presumed less toxic – an appraisal that seems to have been premature as these compounds are believed to raise similar health concerns.

The short-chain PFAS tend to feature 4 to 6 carbon atoms in their molecular structure, and include materials like perfluorobutanoic acid (PFBA) and GenX.

With their wide deployment and persistence, it’s no surprise PFAS collect in landfills – one of a number of acute pressure points in the environment where there is an elevated risk of their finding their way into soil, water and air. Numerous studies attest to their presence in landfills large and small, young and old, across diverse geographies and using different modes of operation. And they seem to appear in diverse landfill media, including solid waste, leachate, and the air at these sites.

Reliance on landfill is diminishing but it has served as the destination for more than 50% of the municipal solid wastes in the US, for example.¹

A January 2023 paper, appearing in the journal Waste Management, attempted to draw conclusions from the studies completed to date, looking at things like the occurrence and transformation of PFAS at these sites, factors affecting PFAS compounds’ release from waste, its effect on the liner system, and potential treatment technologies.²

Immediate weaknesses are apparent in the extant literature, however, and the authors, Zhang et al note that “the majority of current studies have targeted only a small fraction of PFAS (<200 out of > 4000 on the global market), which can lead to serious underestimation.”

Based on what’s been researched, a few nuggets of insight appear forthcoming about the types of PFAS prevalent at these sites. Shorter chain C4-C7 PFCAs, for example, appear the most abundant in landfill leachate in the US, Europe and Asia. Longer-chain PFAS such as PFOS and PFOS-precursors seem to dominate in landfill sediment.

With leachate, the short-chain predominance might be attributed to things like their higher solubility in water, the shift in global production towards these compounds in recent decades, and potential transformation mechanisms at landfill sites (where long chain compounds degrade into shorter chain ones).

“Mercurial” might be the term best applied to substances whose manifestations appear numerous and whose behaviour eludes easy categorisation.

Maybe the recent studies are the most trustworthy, as researchers get a better idea of what’s happening. A 2021 study by Liu et al, for example, seems to find PFAA precursors make up most of the “fresh liquid from waste collection vehicles”, while the leachate from the landfill where the same waste was left seems to be dominated by PFAAs, suggesting that a transformation is occurring at the landfill site.³

There has been lots of work attempting to correlate PFAS occurrence at landfills with factors like the type of waste, the age of the landfill, how it is operated and so on. No clear correlation with waste types seems apparent at this stage, but then only a small number of the most dominant PFAS have been studied. One study notes a higher prevalence of PFHxS in C&D leachate, likely due to its use in sealants and other building materials.

PFAS concentrations seem lower in older landfill sites, although this effect diminishes with those which closed more recently than 1993, and the growing prevalence of short-chain replacements like PFNA and PFBS over time reflects their greater usage as legislation changed. But PFAS might be expected to deplete over time in landfills because of things like desorption, leaching and decomposition.

Biological processes such as methanogenesis seem to encourage PFAS to release into leachate, and studies of bioreactor-style landfills seem to show more PFAS here than dry-tomb landfills.

These materials appear to be subject to a dizzying range of effects and dependencies over time, as landfill material passes through different phases of decomposition for example, and these in turn affect chemical properties like pH, which in turn affects things like adsorption and desorption. Zhang et al conclude that the release of PFAS from waste could be influenced by things like pH, dissolved organic matter (DOM) and electrical conductivity.

Do PFAS leak through landfill liners and geomembranes? Zhang et al conclude that “there is very limited data published to date” on the matter. One study of PFOA and PFOS onto a plastic geomembrane (LLDPE) seems to show that these PFAS have partitioning coefficients “at least two orders of magnitude lower than” other common hydrophobic (water repellent) compounds found in leachate (like benzene and PCBs). In other words, showing a greater propensity to leak. However, after 202 days of testing at different temperatures, the concentrations of these two PFAS remained below the detection limits in the receptor cells. So, no obvious leakage then.

Existing removal methods
When it comes to removing PFAS from leachate, there is a lot of data appraising activated carbon adsorption, ion exchange, biological treatment, and membrane separation.
Activated carbon has been more effective with longer-chain than short-chain compounds – a finding also apparent with groundwater, say Zhang et al. Its effectiveness depends on the adsorption rate of PFAS, which will be lower when it has to compete with other solutes in the leachate.

However, it doesn’t destroy PFAS, and disposing of the PFAS-laden media is costly as it involves expensive solvents like methanol (and subsequent disposal and handling) – and so very often this spent media is sent for incineration, which again is costly given the high temperature (over 900ºC) required to destroy PFAS.

Ion exchange removes PFAS, but like AC it doesn’t destroy them, presenting a need for costly regeneration or disposal of media.

Membrane separation methods like ultrafiltration and reverse osmosis (RO) have also been used to treat landfill leachate for many years, although ultrafiltration is ineffective. RO is “one of the most promising technologies” that has been used for leachate treatment but is energy-intensive, subject to membrane fouling if other materials or suspended solids are present, and – again – it doesn’t destroy PFAS so the RO concentrate has to be dealt with using methods that are all quite costly.

Emerging techniques to treat PFAS from leachate include foam fractionation, whereby gas bubbles are introduced, which are able to concentrate PFAS at the gas-liquid interface of the bubbles. Like RO, this concentrates PFAS in a form ready for removal and destruction.

In discussion of PFAS treatment and clean-up generally, Ian Ross – co-author of The Contaminant Handbook – has suggested solutions are likely to comprise “multiple technologies working in tandem”, and seems to anticipate a two-step process, where one of the aforementioned methods is used to remove PFAS from liquid media or water, and then this concentrated form is worked on by a destructive technology.⁴

Destructive methods
Hopes for a biological approach to remediate media such as soil and water have been suggested as “unlikely” by Ian Ross in a 2021 article.⁵ The somewhat alien chemistry of PFAS seems an obstacle, and he describes it as “a true xenobiotic” whose arrival on Earth, as it were, is a recent event.

Emerging chemical and physical possibilities for removal and destruction of PFAS in leachate include electrochemical oxidation, photocatalytic oxidation, and plasma-based treatment.

With electrochemical oxidation, Zhang et al cite a 2021 study demonstrating an average removal efficiency of 80% and 78% for PFOA and PFOS at a current density of 75 mA/cm2 after eight hours. And this could be increased to 100% with a higher current density, but with the formation of shorter chain PFAS. The method can also produce toxic halogens like perchlorate, presenting additional treatment demands. It seems expensive at present, with this study using boron-doped diamond (BDD) electrodes. There is also a high potential for electrode fouling when using real waste streams, suggest Zhang et al.

Photocatalytic oxidation, on the other hand, has successfully removed large proportions of PFAS from leachate relatively quickly (> 95% of 13 PFAS within 2 hours) in a 2021 study. It employs a novel electrode system (Fe-doped carbon-supported titanate nanotubes) to bind the PFAS prior to its destruction using UV light. However, this seems to lead to the creation of PFBA and PFPeA.

Plasma-based treatment also offers a way to destroy PFAS in leachate (or water). A 2021 study demonstrates a very high degree of PFAS removal after only 10 minutes (90% of PFOA and PFOS, >99.9 % of long-chain PFAAs, and 10–99.9 % of short-chain PFAAs). Problems so far include the generation of toxic halogen chemicals like chlorite, and challenges with scaling up – for example, making the plasma technology practical with a high flow rate of material.

Certainly, the need for reliable methods of treatment grows increasingly urgent. March 2023 saw a notable legislative landmark with the US EPA announcing the first enforceable drinking water limits for six PFAS with adverse health effects: PFOA, PFOS, and mixtures containing the shorter-chain compounds PFBS, PFHxS, PFNA, and GenX. Compliance will require monitoring down to miniscule levels, including 4ng/L for both PFOA and PFOS. As Ian Ross points out on the website of US firm CDM Smith, “Some studies have shown that rainfall in parts of the US has exceeded these levels.”

References
[1] “Poly- and Perfluoroalkyl Substances (PFAS) in Landfills: Occurrence,
Transformation and Treatment”, Zhang et al, Waste Management 155 (2023) 162-178.
[2] ibid
[3] ibid
[4] “An enduring threat to water”, Envirotec magazine, May 2021

Petroleum hydrocarbons in soil continues to be an area of interest for scientists as they are the most common contaminants that are toxic to human and environmental receptors. These contaminants include various molecules that are grouped into aliphatic and aromatic hydrocarbons. Generally, initial field-based soil analysis is non-specific and, while useful, the results are normally supplemented with those of more accurate and precise lab-based techniques. Here Paul Vanden Branden, director and product manager at laboratory equipment supplier SciMed, discusses the performance of field-based non-dispersive infra-red spectroscopy (NDIRS) technology for petroleum hydrocarbon determination compared to traditional lab-based methods.

Typically, the analysis of oil-contaminated soils during site investigation and remediation involves a range of non-specific field-based screening techniques and specific lab-based fingerprint techniques completed off-site by commercial laboratories using certified analytical methods.

Typical non-specific field-based techniques include NDIRS, portable gas chromatography coupled with mass spectroscopy (GC-MS), ultra-violet fluorescence spectroscopy (UVFS), visible-near infrared (vis-NIR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and photo-ionisation detection (PID). These are used to screen total petroleum hydrocarbons (TPH), quantify aliphatic and aromatic hydrocarbons during site investigation, identify potential hydrocarbon concentration hotspots and compare TPH concentrations in the environmental.

Generally, the lab-based fingerprint techniques used are either GC-MS or high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). These provide in-depth data into aliphatic and aromatic hydrocarbon speciation, qualitative and quantitative hydrocarbon degradation due to weathering or engineered remediation, and have high sensitivity and accuracy for risk indicator compounds, which is required to meet regulatory requirements.

While the lab-based fingerprint techniques offer high accuracy and precision, the procedures involved are often time-consuming and expensive. Therefore, they are not seen as cost-effective methods for decision making needed during site investigation, remediation monitoring and validation.

Over the past decade, various field-based analytical technologies have been developed, expediting hydrocarbon determination on site and increasing the number of soil samples that can be analysed at lower cost. However, more data is needed before these can be widely adopted, such as their performance and accuracy for different soil types, different levels of contamination and different fuel types. Furthermore, comparison of their ability to quantify different hydrocarbon groups for risk assessment purposes and evaluation of whether they can offer a good alternative to lab-based technologies for remediation monitoring and validation is still limited.

Field-based NDIRS
In analytical chemistry, extraction procedures aim to separate the analyte quickly, quantitatively and using as little solvent as possible. A recent report by Concawe outlined how solvent-based extraction field technologies, including NDIRS, performed well for the detection and quantification of TPH between 100 and 10,000 mg kg-1, independent of soil type and fuel type. The NDIRS instrument used in Concawe’s study was the Infracal 2 ATR-SP TPH analyser, which can perform TPH determination of hydrocarbons in five to ten minutes, significantly faster than lab-based GC-MS.

For the experiments covered in Concawe’s report, scientists used a hexane extraction method, adding 1% v/w to soil samples and shaking them for two minutes. This extract was cleaned using activated silica gel and Whatman no. 40 filter paper. For level three spiked soils, the extracts were further diluted five times in accordance with the Infracal 2’s detection range. Before each measurement, the attenuated total reflectance (ATR) crystal was cleaned with 99.9% isopropanol and zeroed every hour. To measure a sample, 60 μL was deposited into the ATR crystal, and the solvent was given time to evaporate before the measurement was taken.

The report concluded that the NDIRS field test provides GC-MS comparable TPH recoveries and meets the performance requirements for many regulatory standards. This means scientists can use the Infracal 2, which SciMed supplies, to conduct cost-effective petroleum hydrocarbon analysis on-site, without outsourcing to commercial analytical labs.

To speak to one of SciMed’s team about how the Infracal can help you in your application, fill out an enquiry form on the company’s website.

Trials have been undertaken by two independent institutions, using a next generation PFAS adsorbent media developed by Puraffinity, the London based science materials company.

These show that Puraffinity’s new material performs better by lasting longer and treating three times the amount of GenX contaminants compared with current ion exchange and activated carbon technologies.

“Our adsorbent material binds the GenX contaminants like lego blocks as the water flows past,” explained Puraffinity CEO Henrik Hagemann. “And, once all the Puraffinity material is filled up with GenX, the material is engineered to unclick the bound GenX using a safe regeneration step. The Puraffinity material can then be re-used for industrial or environmental remediation, enabling a circular economy for the future of water filtration materials.”

GenX chemicals are found in products such as food packaging, clothes and firefighting foam (pictured) and a recent study identified them across 200 different use categories.
“We are excited by third party results demonstrating that our next generation adsorbent performs strongly and can deal with these pollutants to avoid serious negative situations,” said Mr Hagemann. “The adsorbent material can operate in both Brita type cartridge applications, where GenX chemicals can be removed at the smallest pitcher type scale as well as in large steel tanks or vessels for industrial applications.”

www.puraffinity.com

They are the salt-tolerant shrubs that thrive in the toughest of conditions, but according to new research, mangroves are also avid coastal protectors, capable of surviving in heavy metal contaminated environments.

A group researchers – from University of South Australia (UniSA) – seems to have found that grey mangroves (Avicennia marina) can tolerate high lead, zinc, arsenic, cadmium and copper in contaminated sediment – without sustaining adverse health impacts themselves.

The study tested the health of grey mangroves living around a smelter in Port Pirie, near Adelaide, South Australia. Using leaf chlorophyll content as a proxy to plant health, mangroves were found to be unaffected by metallic contaminants, despite lead and zinc levels being 60 and 151-fold higher than regulatory guidance values.

The findings highlight the vital role of mangroves in stabilising polluted regions, and the importance of protecting these ‘coastal guardians’ around the world.

The study also coincides with a $3 million Australian federal government initiative to restore mangrove forests in Adelaide’s north.

Dr Farzana Kastury from UniSA’s Future Industries Institute said the ability of mangroves to withstand high metal concentrations make them invaluable in managing polluted environments.

“Mangroves are the ideal eco-defender: they protect our coastlines from erosion and sustain biodiversity, but they also have an incredible ability to trap toxic contaminants in their sediments,” he said.

“Grey mangroves are known for their tolerance of potentially toxic elements, but until now, little has been known about the health of these plants in the Upper Spencer Gulf.

“Our research found that grey mangroves were able to adapt and survive exposure to very high levels of lead and zinc – without adverse health effects in their chlorophyll content – demonstrating how valuable they are to coastal ecosystems.”

Other, ongoing work being done at Port Pirie by UniSA’s Associate Professor Craig Styan suggests there may be 4-7 times more metals stored in the sediments in mangroves than in adjacent unvegetated mudflats. Assoc Prof Styan said that, generally, a greater concentration of metals found in sediments means greater contamination risk for the animals and plants living on/in them.

“The levels of bioavailable metals we measured in the surface sediments in mangrove stands are the same as adjacent mudflats, meaning that although mangroves storing significantly more metals this doesn’t appear to increase the risk of contamination for the many animals that use mangrove habitats,” Prof Styan says.

“People should nonetheless still refer to the SA Department of Health’s advice if they are considering eating fish caught near the smelter.”

Mangroves (along with tidal marshes and seagrasses) are part of the blue carbon ecosystem; when protected or restored, they sequester and store carbon, but when degraded or destroyed, they emit stored carbon into the atmosphere as greenhouse gases.

Dr Kastury said understanding the role of mangrove forests in safely stabilising metallic contaminants in highly polluted areas is imperative – not only for South Australian communities, but also around the world.

“Globally, over a third of mangrove forests have disappeared, mostly due to human impact such as reclaiming land for agriculture and industrial development and infrastructure projects,” Dr Kastury says.

“We must protect our mangrove forests so that they can continue their job in protecting our environment.”

Phytoremediation is the use of plants to extract and store contaminants from soil. As a first step to determine if candidate plants had phytoremediation abilities, the team examined samples of them for levels of heavy metals and metalloids. The detection of a high concentration suggested an ability to absorb the pollutants.

The study team say they discovered that there are existing tropical plants which could potentially play a role in the remediation of contaminated lands. The plants examined are widely available and include species native or naturalised to Singapore. The team suggested they could be introduced and removed from plots of land with minimal impact to ecosystems providing a sustainable way of managing contaminants in soil.

The findings were published in the peer-reviewed journal Environmental Pollution in February.

Land remediation is a particular priority in countries where available land is scarce, as Professor Lam Yeng Ming explained. The study set out to uncover how to better make use of tropical plants to do phytoremediation.

Such an approach is also cost effective, simple to manage, aesthetic, and sustainable over the long-term. “The strategy prevents erosion and metal leaching by stabilising or accumulating heavy metals, so that helps reduce the risk of contaminant spread,” said Lam Yeng Ming.

The team conducted a field survey and collected soil and plant samples between March 2019 and January 2020. A total of 46 plant species were studied as potential candidates for phytoremediation.

An ability to accumulate several types of heavy metals and metalloids was observed in 12 plant species, including the commonly seen Cow Grass (Axonopus compressus), as well as “hyperaccumulators” like the Brake Fern (Pteris vittata) and the Indian Pennywort (Centella asiatica).

The metals

The elements investigated in the study were heavy metals and metalloids that are potentially toxic to humans and animals, such as cadmium, arsenic, lead, and chromium.

They occur naturally in soils, but rarely at toxic levels. However, they can accumulate and reach higher levels over a long period of time, as heavy metal particles from air pollution (e.g. vehicle emissions, construction activities) tend to accumulate and remain in the top layers of soil.

Other factors that could result in high levels of heavy metals in soil include the use of synthetic products such as pesticides, paints, batteries, industrial waste, and land application of industrial or domestic sludge.

To assess whether the levels of heavy metal were dangerous, the team used the Dutch Standard, which provides values for the acceptable threshold of environmental pollutants in soils. This mode of assessment has also been adopted by Singapore’s government agencies.

Associate Professor Tan Swee Ngin, from the Academic Group of Natural Sciences and Science Education at NTU’s National Institute of Education, who was the study’s co-author, said: “Our results revealed there were regions where levels of heavy metals and metalloids were relatively high and could affect the environment and the health of flora and fauna in Singapore. This would call for preventive actions, such as our method of using plants to remove these toxic materials, to be employed to minimise heavy metal contamination.”

How does it measure up to classic remediation?

Phytoremediation could serve as a more environmentally friendly alternative to existing industrial options to remove the heavy metals from polluted soil, which include methods such as soil washing and acid leaching. These methods can be costly and may employ harsh chemicals to remove pollutants from soil.

Heavy machinery to conduct excavation and transportation of soil is also usually required in such processes and these procedures may negatively affect the environment by affecting soil health and fertility. These methods also run a high risk of exposing humans or animals to the heavy metals.

However, phytoremediation is a slow and long-term commitment and requires prudent management in the removal and disposal of the contaminated plant samples. Using different types of efficient plants to carry out phytoremediation in polluted soils, and with enough growth cycles through repeated planting, can ultimately lead to reductions in the level of heavy metals and metalloids in the soil.

The joint research team is currently testing the plants on plots of land in Singapore that have high concentrations of heavy metals to better determine the effectiveness of the plants in an urban setting.

They are also testing the usage of other inorganic particles that are incorporated into plants and that can both help in the plant growth and improve the uptake of these contaminants by the plants. This will reduce the time taken for the absorption of the heavy metals and hence speed up the remediation time.

Dunton Environmental “challenges traditional thinking in the construction industry and continuously develop new ideas to solve complex environmental ground and contamination problems to deliver their clients real programme and cost benefits.” Services include remediation contracting, waste management, Japanese knotweed treatment, soil and water treatment as well as contaminated land assessments.

Challenge

To efficiently and safely accelerate the reduction in TPH levels of hydrocarbon-contaminated soils onsite in order to enable their future use. The soil is initially screened to remove any builder’s rubble and deleterious materials. It is then treated according to the chemical nature of the soils, either by way of accelerated bioremediation to degrade any residual organic pollutants such as TPH and PAH (including benzo(a)pyrene); or by the addition of Dunton’s chemical oxidation compounds which induce chemical reduction.

OSE II solution

The Dunton team were interested to understand how effective the product Oil Spill Eater II (OSE II) could be at accelerating the bioremediation of hydrocarbons and ran an evaluation on an initial small quantity of contaminated soil. The accelerated reduction in TPH values met Dunton’s requirements and they agreed to implement the use of OSE II on larger-scale bioremediation of hydrocarbon contaminated ex-situ soil stockpiles.

Application: Chemical pollutants

Hydrocarbon contaminants are common on most brownfield developments, often the result of former works, in ground tanks or similar. Dunton has developed a rapid treatment technology for a wide variety of chemical pollutants in soils.

Application method

Using a combination of OSE II with natural water, this is then sprayed towards soils that are being aerated to improve the oxygen levels within them. Along with OSE II, this improves the conditions for microorganisms to naturally grow within them. This increase in microbial activity within the soils accelerates the biodegradation of hydrocarbons with the end products being only CO2 and water.

The geology of Cornwall is unique, with today’s landscape a relic of both geological and human processes. Heavy metal contamination is present across much of the country, with Arsenic levels varying in accordance with geological formations and their subsequent exploitation in the 19th and 20th Centuries. Although Arsenic has historically been extracted for use in paint, weedkillers and insecticides (most notably at Botallack in the late 19th Century), it was generally a by-product of tin and copper processing. Arsenic and other unwanted heavy metals were often deposited in mine waste tips close to the mine from which they were extracted.

In 2013 the British Geological Survey collected data on the spatial distribution of heavy metals across the Southwest, as part of the TellusSW Project. The extract below illustrates Arsenic distribution across the Southwest region; (Contains British Geological Survey materials © UKRI 2021).

In assessing the risk from Arsenic to sensitive receptors (e.g. humans), a Category 4 Screening Level (C4SL) of 37 mg/kg is used. This is a generic assessment criterion for Arsenic in residential soils in England. As can be seen above, much of the Southwest is above the 37 mg/kg threshold. In fact, a study by R. S. Middleton et al [2017] found that 69% of soils in Cornwall exceed the C4SL for Arsenic under the “Residential with Homegrown Produce” setting.

Most residential developments in Cornwall are now required to be assessed under the LCRM model, starting with a Phase 1 Desk Study. Bioaccessibility testing is a relatively inexpensive test that can help prevent costly remediation. This laboratory test essentially simulates the conditions inside the human digestive system, to determine the percentage of total Arsenic absorbed by the body. An average of 20% Bioaccessibility is generally accepted across Cornwall in naturally occurring soils. In certain circumstances, this figure can be assumed at the Phase 1 stage to prevent unnecessary and costly physical testing.

groundconsultants.co.uk

Is a remediated site a clean site? Amy Jones, Associate Director with environmental engineering firm Idom Merebrook, considers the challenges of meeting zero waste targets when recycling land for development.

The race to zero waste is on, and the challenge is perhaps greatest in the construction industry, which is one of the UK’s largest producers of waste.

To help preserve our green spaces the UK is committed to developing brownfield sites as a priority. However, dealing with the regeneration and repurposing of brownfield land ready for development can be problematic and costly.

Most brownfield sites have physical health hazards, such as uncovered holes and unsafe structures. And, with former industrial sites there can also be a risk of chemical contamination and polluted ground water.

According to Amy Jones, leading environmental engineer at Idom Merebrook one of the most challenging aspects of land remediation is waste management, she commented:

“Urban planners and developers typically inherit a land legacy of old industrial plants, factories, power stations, gas works and petrochemical sites. Before any development can be considered the land must be made safe and fit for purpose through remediation.

On brownfield sites being redeveloped the disposal of waste soils often amounts to significant costs, which are often not fully accounted for during the preconstruction phase

An efficient materials management strategy can be a silver bullet in reducing the amount and cost of waste – and the earlier that focus begins the better.”

Identification and management of contaminated waste on brownfield sites, can save construction projects both time and money as well as mitigating environmental impact.

Early consultation and understanding of the contractor risks from both a legal and commercial standpoint will help reduce the risks associated with ground works during the construction phase.

Understanding the quality of the site investigation and identifying weaknesses within a report can mitigate program delays and the impact of costs associated with disposal by preferentially removing lower rate materials.

Amy identified three areas of focus for ground engineers working on brownfield sites; the first consideration is what are the proposed remediation solutions? We need to consider the physical removal of old structures, utilizing a clean cover system and ensuring gas protection and treatment; we also need to consider whether these measures satisfy the local authority stipulations.

The second are of focus is waste assessment – have soils been considered within their waste category? Basic classification determines the type of waste and Waste Acceptance Criteria determines whether it can be accepted into specific waste facilities. This should be considered before planning submission therefore reducing the amount of materials to be removed within legal parameters.

Lastly, proper consideration needs to be given to health and safety requirements for the public, site operatives and end-users; this may include checking for asbestos in soil, general site contamination and ground gases.

Amy continued:

“Zero waste on site is something of a holy grail…and a remediated site does not necessarily mean it is a clean site or that the material on site is inert, with regards to waste categories.

It means that it is fit for purpose and that materials can be left in-situ with a hard standing or clean cover system in place, which breaks the exposure pathway to the end user, depending on the assessment criteria used (residential, public open space or commercial) the material could still be classed as hazardous waste.

A common misunderstanding with contaminated land is that soils cannot be reused and must be disposed of as hazardous waste. This, however, is not the case as it is often possible for soil to be reengineered and reused – even if there is contamination present.

One of the main goals for any developer is reducing the volume materials being removed from site. This can be achieved by either following the waste hierarchy of reduce, reuse, recycle, repurpose and disposal as a last resort – assessing material to determine if it is inert, non-hazardous or hazardous for appropriate handling and disposal.

Amy added:

“At Idom Merebrook we are increasingly asked to assess, plan and manage the redevelopment of brownfield sites, which offers an opportunity to both enhance the surroundings, preserve green spaces and boost the local economy.

For the developer a sustainable waste management strategy is key to unlocking the benefits of best practice. These include income generation through collection of materials for reuse, reduced waste disposal costs at landfill, reduced costs through purchasing fewer materials, less accidents on-site through correct materials storage and regulatory compliance with duty of care requirements.”

A new “greenfield surcharge” is among a series of practical proposals to encourage future brownfield development, according to a new report from member-funded group the Environmental Industries Commission (EIC).

The proposals for the greenfield surcharge, which would be added to the infrastructure levy proposed in recent planning changes, would see the funds earmarked by local authorities for infrastructure spending to help mitigate the higher development costs often associated with brownfield.

The group, which represents the companies large and small working in the environmental technologies and services sector, argues that brownfield development can help meet ambitions around levelling up, but in order to do so further planning reforms, as well as new tax reliefs and development incentives, are required.

The research points out that in 2014, 40% of new residential projects in England was on land that had already been developed, and that this proportion has dropped to 20% in 2018 with economies of scale, technical complexities and additional costs and uncertainties, all contributing factors.

Commenting on Brownfield First, Matthew Farrow, director of policy at EIC, says: “Our analysis shows that developers are making significantly less use of brownfield, yet there is huge potential for it to deliver ambitions around levelling up. Not only can it help find the space for 300,000 homes a year, but it can also funnel new investment to those traditionally underfunded post-industrial towns, cities and communities.

“Our practical, common-sense proposal around a greenfield surcharge would revitalise brownfield development, help to deliver homes, and ensure that we are making the most of this chronically underused asset.”

Bob Blackman MP, chairman of the All Party Parliamentary Group (APPG) on Building Communities, which brings together politicians and the industry to encourage placemaking, also commented: “With more than 20,000 brownfield sites across the country, there is a huge opportunity to drive levelling-up and revitalise communities wherever they are based. The report’s proposals present a series of common sense recommendations which could help us realise brownfield’s potential.”

As well as the introduction of a “greenfield surcharge”, it also calls for the adoption of the Construction Leadership Council’s (CLC)’s recommendations for longer-term regeneration zones to support redevelopment on complex sites.

In addition, it seeks improvements to the economic viability of marginal brownfield projects by increasing land remediation tax relief on sites with fewer than 25 units, and to update the definition of derelict land to incorporate all sites that have been abandoned for more than a decade.

Finally, it argues that new funding earmarked for levelling-up, either through the new National Infrastructure Bank or the Levelling Up Fund, should specifically favour brownfield proposals over greenfield ones.

Peter Atchison is chair of the EIC contaminated land working group, and director at PAGeoTechnical. He says: “Despite inspiring high-profile examples of brownfield development, such as the former Olympic Park in the East End of London, developers are making less use of brownfield than before. Our recommendations aim to revitalise this sector and place it as the realistic alternative to building on greenfield sites, as well as a key driver for levelling up.”