Project

HARM: High Attenuation Recycling Materials as sustainable barriers for waste disposal sites

Goal: The need to minimize the amount and foster the safe treatment of waste, and thereby reduce the risk of contamination; emphasises the importance of promoting technologies which are environmentally sound with products suitable for re-use/recycling. This project establishes an experimental method to determine the performance of contaminant barriers built with natural clay and construction waste or biomass ash. The aim is to (1) evaluate the attenuation and containment capacities by these mixtures of contaminants in the long term, (2) develop design guidelines to construct barriers for waste facilities and similar applications, and (3) interpret their performance using numerical modelling tools. Landfill leachate and CO2 gas are passed through different waste:clay mixtures in a geotechnical centrifuge which simulates realistic times, pressures and temperatures of landfill field. The geochemistry of the pore water barriers after permeation are examined to deduce pollutant removal and retention processes. The exposure effects of these barriers to an aggressive acid, rainfall or groundwater are studied too. Results are aimed at recycling industrial residues and conserving natural resources (clay) by constructing contaminant barriers. It will also provide an effective and more environmentally sustainable basis to control landfill pollution risks.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 743880. This work reflects only the author’s view, exempting the community from any liability.

Date: 13 March 2018 - 12 March 2020

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Mercedes Regadío
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Globalmente, el 70% de los residuos (≈1,4×10 9 toneladas) son depositados en alguna forma de vertedero (Kaza, et al., 2018). Los vertederos son una gran fuente de contaminación y enfermedad, directamente relacionados con la degradación de la tierra y la contaminación del agua. Para evitar estos problemas, se instalan barreras alrededor de los residuos que evitan que el líquido contaminante producido se escape. Las barreras geológicas naturales que se usan en vertederos son arcillas compactadas, las cuales pueden agrietarse al sufrir cambios de volumen debido a la hidratación/deshidratación, lo que provoca problemas de ingeniería. Este trabajo presenta un nuevo diseño de barreras en vertederos que combina (1) arcillas con (2) materiales no expansivos ni cohesivos procedentes de residuos industriales. Así, al mismo tiempo que se estudia prevenir la contaminación de vertederos, se pretende minimizar la producción de un tipo de residuos. Los residuos industriales utilizados son: áridos finos mixtos de la construcción y cenizas de fondo en plantas de biomasa. Para saber si se podrían usar dichos residuos sin perjuicio ambiental, se realizaron ensayos de conformidad en las que se lixiviaron con agua. Los ensayos demostraron que los residuos son inertes y no peligrosos, ya que las cantidades de metales movilizadas del residuo al medio acuoso estaban por debajo de los valores límite legislados (Tabla 1). Ambos residuos se usaron como aditivos a tres arcillas naturales de distintas características: (1) London clay: rica en esmectita y arcilla de muy alta plasticidad, (2) Oxford clay: rica en illita, fósiles y materia orgánica, arcilla de alta plasticidad y capacidad tampón de pH (carbonatos) y (3) Coal measures clay: rica en caolinita, arcilla de plasticidad intermedia y ácida. London clay es el material que mejores características de atenuación y contención presentaba, por su mayor capacidad de sorción y su menor conductividad hidráulica, respectivamente. Sin embargo, es el que tenía mayor susceptibilidad a contraerse excesivamente (su índice de plasticidad es 50, el doble del óptimo para barreras de vertedero arcillosas) y facilidad para alterar sus minerales arcillosos (Regadío, et al., 2020). Para estudiar la eficacia a largo plazo de estos materiales como barreras, se realizaron experimentos de permeabilidad con un lixiviado de vertedero real en una centrífuga geotécnica. La rotación de la centrífuga (300 rpm, 2 m radio del rotor) hace que los tiempos de estudio se reduzcan significativamente, ya que 19 días de modelo experimental equivalen a 33 años de prototipo. Barreras hechas por compactación Proctor británica con London clay y aditivos de áridos finos (20%) mostraron una conductividad hidráulica de 0.81×10-9 m/s durante 33 años (por debajo del máximo legal de 1×10-9 m/s). En cuanto a la capacidad de estas mezclas aditivo-XXVII Reunión de la Sociedad Española de Arcillas 55
Mercedes Regadío
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You can now read the results in brief of #HARM_MSCAIF.
This short article is available in different languages (DE, EN, ES, FR, IT, PL...).
 
Mercedes Regadío
added a research item
Engineered synthetic liners on their own cannot protect the environment and human health against landfill leachate pollution. Despite their initial impermeability, they are susceptible to failure during and after installation and have no attenuation properties. Conversely, natural clay liners can attenuate leachate pollutants by sorption, redox transformations, biodegradation, precipitation, and filtration, decreasing the pollutant flux. Depending on the clay, significant differences exist in their shrinkage potential, sorption capacity, erosion resistance and permeability to fluids, which affects the suitability and performance of the potential clay liner. Here, the physico-chemical, mineralogical and geotechnical characteristics of four natural clayey substrata were compared to discuss their feasibility as landfill liners. To study their chemical compatibility with leachate and rainwater, hydraulic conductivities were measured every ≈2 days spread over 7 weeks of centrifugation at 25 gravities. At field-scale, this is equivalent to every 3.4 yrs spread over 80 yrs. All the clayey substrata had favourable properties for the attenuation of leachate pollutants, although different management options should be applied for each one. London Clay (smectite-rich) is the best material based on the sorption capacity, hydraulic conductivity and low erodibility, but has the greatest susceptibility to excessive shrinkage and alterable clay minerals that partially collapse to illitic structures. Oxford Clay (illite rich) is the best material for buffering acid leachates and supporting degradation of organic compounds. The Coal Measures Clays (kaoline-rich) have the lowest sorption capacity, but also the lowest plasticity and have the most resistant clay minerals to alteration by leachate exposure.
Mercedes Regadío
added an update
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 743880. This work reflects only the author’s view, exempting the community from any liability.
 
Mercedes Regadío
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Clayey barrier construction in a modern, controlled landfill (USA).
1 Breaking the in-situ clay.
2 Piling up the clay.
3 Loading the track.
4 Transport the clay to the area of interest.
5 Water adjustment to optimum conditions for the barrier.
6 Compaction of the barrier.
 
Mercedes Regadío
added an update
The HARM project succeeded in representing pollutant transport through compacted liners tested in self-designed experiments to mimic real landfills. This experimental set-up allowed to extrapolate the results from a test of weeks with a sample of centimetres, to a real scenario of years and meters, i.e. the prototype. The (1) centrifuge set-up (gas and fluids tubing, sensors, valves, connections), (2) the test cells (sample liner aluminium container, bottom collector for effluents, overhead fluid chamber, air/fluid release valves) and (3) instructions on how to run tests to avoid experimental errors (homogenization of flow, size-mass-time relationships), calculations of gravity (or revolutions per minute) – induced flow, and collection-analysis-interpretation of data to link the experimental data to the corresponding prototype, and represent the experimental resolution accurately in real landfill scenarios. A selection of long-term liners with constant low permeability (0.2–0.4·10-9 m/s) and compatible under landfill leachate (pollution source) and rainwater (reversibility risk scenario) exposures (over 100 years) was delivered.
 
Mercedes Regadío
added an update
The main research was focused on constructing innovative landfill liners to avoid contamination to land, water and living beings. To assess their performance, both their low permeability (traditional approach) and attenuation (innovative approach) characteristics were studied. Low permeability was required to comply with the landfill legislation and attenuation is important to reduce the pollutant load over time. Liners cannot be impermeable in perpetuity and will eventually release pollutants to the environment. Thus, the importance being able to predict the attenuation capacity, which is still not well-implemented in liners design, is emphasised to ensure environmental security.
The HARM project has implemented the enhanced pollutant attenuation approach within the conventional liner construction. The developed liners minimize leachate migration by their impermeability (slow transport) and attenuation (leachate self-cleaning) capacities and may readily be transferred to other pollution management issues, such as mine drainage management or contaminated stormwater runoff.
 
Mercedes Regadío
added an update
The landfill leachate liners were built with readily available natural clays and industrial by-products without any value (i.e. residues with no current application).
The HARM project has characterized and identified the most relevant properties of waste and natural materials for liner design to be geotechnical stable and effective in pollutant attenuation, over long periods of time (mineralogy, shrink/swell potential, attenuation capacity, dispersive/erosion behaviour and fluid permeability variation).
 
Mercedes Regadío
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Summary of the project and your own contribution to the problem.
 
Mercedes Regadío
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The project has redesigned (in line with the zero-waste hierarchy) a new application for industrial by-products (currently with no other beneficial/marketable use) which has no risk of leachability of their own constituents to fresh water or soils. This decreases the waste generation by avoiding their landfilling.
Adding the by-products (residues) decreased the (very) high plasticity of clays and therefore their associated risk of shrinkage. It is important to avoid shrinking as it can induce instability and cracks with a consequent increase of fluid leakage and contaminant transport through liners.
Overall, the redesigned (sustainable and competitive) liners will benefit the society’s health from the protection of leachate pollution and the EU's economy from the decrease of industrial waste.
 
Mercedes Regadío
added a research item
In a world where circular economy and zero waste are taking over, exploring the potentialities to transform a residue into a marketable product is essential. Industrial process residues are very abundant in part due to the fourth industrial revolution currently evolving. The reuse of industrial residues would save natural resources, avoid the cost of landfill permits, reduce land reclamation and provide economic benefits from their sale. Hence the importance of studying their feasibility for beneficial use (or recycling) with zero risk to human health. The potential risk is assessed by the leachability of contaminants (e.g., heavy metals) to ground water, fresh water or soils, above harmful concentrations. These contaminants (constituents released from the residues by dissolution/percolation with water) can accumulate in plants and pass into the food chain. Here, we compare different standard methods and discuss the differences in the risk estimation.
Mercedes Regadío
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HARM project Logo
 
Mercedes Regadío
added 2 research items
A new approach in landfill liner design which combines hydraulic containment of leachate with contaminant attenuation to improve the performance of these environmental control systems at landfills is described. The idea is to re-use readily available industrial waste residues (construction and biomass waste) as additives for natural clay liners, wherein the additives have specific properties which enhance the attenuation of contaminants by the mixture. The aim is to (1) evaluate the contaminant attenuation capacity of these mixtures, (2) develop design guidelines to construct liners for waste containment systems and similar applications, and (3) interpret their performance using numerical modelling. This is evaluated in permeation studies using a geotechnical centrifuge, which enables the performance of liner compositions to be tested for representive time-scales (100 years), pressures and temperatures at realistic experimental time-scales of days-weeks in the laboratory. The permeation experiments include liner compositions flushed with leachate to deduce contaminant transport and attenuation mechanisms, followed by rainwater to assess the potential for release of attenuated contaminants. This experimental methodology is illustrated with depth profiles from permeation studies conducted on different clay-additive compositions. The concept will be applicable for liner design at other waste disposal facilities and is a timely improvement which addresses the problem of managing large quantities of industrial residues. Instead of disposal these can be recycled as an additive in host clay to construct these liners, thus conserving natural resources (clay) and reducing construction costs. It also provides an effective and more environmentally sustainable basis to reduce risks from leachate leakage.
Engineered synthetic liners on their own are not the ideal solution to protect land, water and living beings against landfill leachate pollution. Despite their impermeability, engineered liners are susceptible to fail during installation and after a few years of landfill operation, and have no attenuation properties. Conversely, natural clay liners can attenuate leachate pollutants by reactions of sorption, dilution, redox, biodegradation, precipitation and filtration; resulting in a decrease of the pollution load over time. Depending on the clay, significant differences exist in the shrinkage potential, sorption capacity, erosion resistance and permeability to fluids; which would affect the suitability and performance of the potential clay liner. Here, the physical, chemical, mineralogical and geotechnical characteristics of four natural clayey substrata were compared to discuss their feasibility as landfill liners. All the studied clayey substrata had favourable properties for attenuation of leachate pollutants, although different management options should be applied for each one. London clay (smectite-rich) is the best material based on the sorption capacity, hydraulic conductivity and low erodibility, but has the greatest susceptibility to excessive shrinkage and easily alterable clay minerals that partially collapse to illitic structures. Oxford clay (illite rich) is the best material for buffering acid leachates and degrading organic compounds. The Coal Measures Clays (kaoline-rich) have the lowest sorption capacity, but on the plus side they have the lowest plasticity and most resistant clay minerals to alteration by leachate exposure
Mercedes Regadío
added 2 research items
Landfills produce a toxic, dark and smelly liquid that can pollute the surrounding areas; representing a groundwater risk. For that reason, landfill barriers that stop the migration of leachate pollutants are required. Compacted clays are normally used for the attenuation of landfill leachates. However, clays suffer from volume changes due to hydration (engineering problems). If mixing clays with non-hazardous industrial process residues, one could (1) stabilize clayey barriers, (2) improve the attenuation of landfill leachates, (3) save natural resources and (4) add value to a product with currently no market value. Here, the characterization of four natural clays is discussed to choose the ones to be mixed with non-hazardous recycled additives.
Mercedes Regadío
added a project goal
The need to minimize the amount and foster the safe treatment of waste, and thereby reduce the risk of contamination; emphasises the importance of promoting technologies which are environmentally sound with products suitable for re-use/recycling. This project establishes an experimental method to determine the performance of contaminant barriers built with natural clay and construction waste or biomass ash. The aim is to (1) evaluate the attenuation and containment capacities by these mixtures of contaminants in the long term, (2) develop design guidelines to construct barriers for waste facilities and similar applications, and (3) interpret their performance using numerical modelling tools. Landfill leachate and CO2 gas are passed through different waste:clay mixtures in a geotechnical centrifuge which simulates realistic times, pressures and temperatures of landfill field. The geochemistry of the pore water barriers after permeation are examined to deduce pollutant removal and retention processes. The exposure effects of these barriers to an aggressive acid, rainfall or groundwater are studied too. Results are aimed at recycling industrial residues and conserving natural resources (clay) by constructing contaminant barriers. It will also provide an effective and more environmentally sustainable basis to control landfill pollution risks.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 743880. This work reflects only the author’s view, exempting the community from any liability.