The proposed Geological Disposal Facility (GDF), conceptually designed for the management of the United Kingdom’s (UK) radioactive waste inventory, will isolate nuclear waste in chambers and vaults 200m-1000m below the grounds surface. Eventually, groundwater is expected to re-saturate a GDF by gradually seeping through the multibarrier system, where interactions with cementitious materials will result in alkaline, anoxic conditions. Under these conditions it is anticipated that the cellulosic materials present within the waste will hydrolyse, resulting in the formation of a range of microbially available substrates. Sulphate and chloride are present within UK groundwaters and would therefore, be expected to influence microbial metabolism in a GDF. There has been limited consideration of the impact of sulphate and chloride on microbial processes such as methanogenesis and sulphate reduction in a GDF simulated environment.The development of microcosms to simulate geological disposal conditions, under a range of sulphate and salinity concentrations, allowed for an in-depth analysis of the microbial processes that could occur post-closure of GDF. This study demonstrated for the first time that hydrolysed cellulose comprised predominantly of the alpha and beta forms of isosaccharinic acid (ISA) degraded into hydrogen, carbon dioxide and acetic acid in high salinity and high sulphate concentrations. Methanogenesis was shown in high sulphate and high salinity conditions, but competition between sulphate reduction and methanogens was observed, as was the sensitivity of methanogens to salinity. Sulphate reduction was observed with increased rates coinciding with increased sulphate concentrations. This study also showed the microbial communities capable of growth in high sulphate and high salinity concentrations, and a thorough assessment of the metabolic pathways of Metagenomic Assembled Genomes (MAGs) was achieved through metagenomics to identify the MAGs responsible for fermentation, methanogenesis and sulphate reduction.
| Date of Award | 10 Jun 2026 |
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| Original language | English |
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| Sponsors | Engineering and Physical Sciences Research Council |
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| Supervisor | Martin Carr (Main Supervisor) |
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