Redox-Active Fe-Bearing Clay-Coated Sand for Groundwater Remediation

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None of the industrialized or developing countries has adequately protected its aquifers against domestic, agricultural and industrial contaminants and groundwater pollution is at an all time high in many parts of the world. In the UK, the quality of almost half of the groundwater used for public supply is estimated to be compromised, resulting in high capital and operating costs and increasing water charges for the consumer. The scale and urgency of the problem is largely recognised and managing authorities in the UK and across the EU are continuously revising their approach to pollution control or abatement. The EC Water Framework Directive now requires that surface, coastal and underground waters meet 'good status' within all the member states by 2015. With only 9 years to go, initiatives to develop and implement cost-effective and sustainable water remediation technologies are crucially needed.The proposed project aims to develop and demonstrate the efficiency and durability of a novel reactive material to be used in the design of permeable reactive barriers for the remediation of contaminated groundwater. The proposed research is cutting-edge in that, for the first time ever, it will take advantage of the unique ability of some polymers in efficiently binding clay particles to the surface of sand grains and will exploit the now well recognised ability of reduced Fe-bearing smectites in promoting the degradation of various organic compounds.The new Fe-bearing clay-coated sands are expected to efficiently immobilize and/or remediate a wide range of inorganic and organic contaminants, including nitroaromatics and chlorinated compounds, and may therefore be self-sufficient for the treatment of certain complex groundwater plumes. They are also expected to be a more sustainable and possibly a more cost-effective alternative than other reactive materials commonly used in PRBs, including zero valent iron.The proposed project will be completed in 2 years and will involve bench-scale experiments simulating field-conditions and will be conducted using state-of-the-art facilities and a multi-disciplinary approach, associating clay science, rock/soil mechanics, and organic geochemistry. The first 16 months of the project will allow identifying adequate procedures for making clay-coated sands of required permeability for use in PRBs and will help evaluate their stability and hydraulic properties as a function of pH changes and iron-reduction. The last 8 months will allow assessing the remediation performance of the porous materials under laboratory simulated PRB conditions using nitrobenzene as model contaminant. The estimated cost-effectiveness of the clay-coated sands will be compared with data available in the literature for other reactive materials commonly used in PRBs.The results of the project are crucially needed to inform the scientific community, policymakers, managers and stakeholders on the relevance of the new clay-based reactive material. The fundamental understanding to be gained will be used to attract industrial partners in the UK and advocate the deployment of a pilot-scale PRB technology for the remediation of contaminated groundwater using a Fe-bearing clay-coated sand of adequate permeability.