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Microbial survival and activity in bentonite clay: relevance to the safety case for geological disposal of radioactive waste

  • Full or part time
  • Application Deadline
    Monday, January 07, 2019
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

Project Background
The disposal of radioactive waste in geological disposal facilities (GDF) deep underground is being planned by several countries including the UK. Considerable effort continues to be put into research to inform the safety case for this process. One ongoing area of research is into the potential for microbial activity to affect the GDF. Microbial activity has been implicated in several processes in and around the GDF, including corrosion of metals, gas generation and the alteration of clay barriers. The presence of methanogens in a repository environment could have important implications for 14C transport, gas volume and metal corrosion. The limits to methanogenesis (e.g. pH, temperature, compaction density) remain to be fully detailed and are important for understanding the potential for methanogenic activity to impact the GDF and the safety case. In addition to methanogens, the limits on growth of a number of other microbial groups are important to predict processes such as metal corrosion and degradation of bentonite.

Project Aims and Methods
•To confirm the assumption that methanogens cannot be isolated from a range of commercially available bentonites and then to investigate the conditions under which methanogens transported in groundwater can establish and become active in bentonites.
•To establish the extent to which commercial bentonites contain other key microbial groups of interest (e.g. sulphate reducers, acetogens and metal reducers)
•To understand how environmental variables (e.g. pH, temperature, compaction and groundwater composition) affect microbial survival and activity. The primary focus will be on methanogens, but other anaerobic microbial groups will also be investigated in this project.

Laboratory experiments will be set up to establish the limits of microbial processes in bentonite under a range of conditions. Facilities for this include a thermal gradient and pressure incubation systems (Cardiff University) and facilities for the preparation of compacted bentonite samples (BGS). Epifluorescence microscopy and culture-based assays (e.g. MPN) will be combined with chemical analysis (e.g. ion chromatography and gas chromatography) to assess microbial survival and activity. Molecular methods (PCR and sequencing) will be used where appropriate to further characterise the microbial community. The focus of the PhD will be on methanogens but other microbiological characterisation will be carried out to give an insight into other linked microbial processes such as fermentation of organic carbon compounds, acetogenesis and sulphate reduction. The student will also have access to samples from long term experiments running for several years that were set up at BGS looking at clay-microbe-steel interactions in compacted bentonite. The student will also benefit from the mineralogical, petrological and physical properties and fluid processes expertise of the BGS team involved in those long term experiments.

Candidate Requirements
2.1 or better undergraduate degree in a science subject, such as biology, environmental or Earth sciences. A relevant MSc would also be desirable.

Evidence of an interest in environmental microbiology e.g. in the form of a relevant dissertation project and any experience of working in a laboratory outside of formal education would be very welcome.


Humphreys, P.N., West, J.M. and Metcalfe, R. (2010). Microbial Effects on Repository
Performance. Quintessa Report QRS-1378Q-1 for the NDA-RWMD.

How good is research at Cardiff University in Earth Systems and Environmental Sciences?

FTE Category A staff submitted: 14.99

Research output data provided by the Research Excellence Framework (REF)

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