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

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 set up at BGS looking at clay-microbe-steel interactions in compacted bentonite.

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.

CASE or Collaborative Partner
The student will spend 3-4 months at BGS working in the geomicrobiology laboratory alongside two staff members and one PhD student, in addition to the BGS supervisor.

Training
The student will receive training in aerobic and anaerobic microbiology, including enrichment, isolation and characterization of microorganisms, and viable count estimates (most-probable-number series). Metabolic investigations will involve analysis by high-pressure liquid chromatography, gas chromatography, light and fluorescence microscopy and spectrophotometry. Molecular techniques will be used for identification of microorganisms in pure and enrichment cultures based (16S rRNA and functional genes).

How to apply:

You should submit an application for postgraduate study via the Cardiff University Online Application Service, including:

an upload of your CV
a personal statement/covering letter
two references (applicants are recommended to have a third academic referee, if the two academic referees are within the same department/school)
current academic transcripts.

You should apply to the Doctor of Philosophy in Earth and Ocean Sciences with a start date of October 2020.

In the research proposal section of your application, please specify the project title and supervisors of this project and copy the project description in the text box provided. In the funding section, please select ’I will be applying for a scholarship/grant’ and specify that you are applying for advertised funding from NERC GW4+ DTP.

If you wish to apply for more than one project please email [Email Address Removed].

The deadline for applications is 16:00 on 6 January 2020.

Shortlisting for interview will be conducted by 31 January 2020.

Shortlisted candidates will then be invited to an institutional interview. Interviews will be held in Cardiff University between 10 February and 21 February 2020.