NERC Priortiy Area - WATER - Predicting the natural attenuation of ethyl-tertiary-butyl-ether (ETBE) in groundwater

Ether oxygenate compounds have been used as additives in unleaded gasoline since the 1980s to enhance combustion and reduce emissions. In Europe the ether oxygenate compound ethyl-tertiary-butyl-ether (ETBE) is now being introduced for this purpose. Although ETBE is believed to have a similar environmental hazard profile to other ether oxygenates that have previously been used in unleaded gasoline, there is insufficient information on the fate of ETBE in the subsurface environment. This is needed to evaluate the environmental risk from a release of ETBE-amended gasoline to groundwater, and to devise appropriate management and remediation strategies. Previous research suggests that new synthetic chemicals (of which ETBE is one) that are released into the environment can persist because microorganisms lack the metabolic potential to biodegrade them. However there is evidence that over time, biodegradation pathways can develop naturally to metabolise such chemicals. This seems to occur through complex interactions between different populations of microorganisms in communities and mechanisms which allow transfer of genes between species to support such biodegradation. It is necessary to understand these relationships to identify conditions when biodegradation of ETBE will occur in groundwater and to qualify the environmental risk of using ETBE-amended gasoline in the UK and Europe. This project will provide scientific evidence to help address these issues. It will deduce the microbiological controls on the biodegradation potential of ETBE in groundwater under different environmental conditions. This will help identify conditions in groundwater where ETBE biodegradation may occur and whether natural attenuation can be an effective risk management strategy for groundwater contaminated by gasoline containing ETBE. Laboratory studies will be used to assess the effect of different environmental factors on ETBE biodegradation rates in groundwater under representative controlled conditions. These factors will include (i) the availability of different electron acceptors for biodegradation, (ii) ETBE concentration required to support biodegradation or that which may inhibit it, (iii) nutrient limitations, (iv) interaction of ETBE with other organic compounds and potential carbon sources in gasoline which may control biodegradation, and (v) the presence and metabolic function of microorganisms responsible for such biodegradation. Groundwater and aquifer sediment samples from uncontaminated and ETBE-contaminated sites will be used in these experiments, which will be manipulated as the biodegradation behaviour evolves to explore interactions between the microbial communities, for detailed interpretation. Novel microbiological techniques, which include state-of-the-art molecular analysis, will be used to investigate the microbiological processes and relationships between different populations of microorganisms responsible for ETBE biodegradation under the range of conditions examined. The project will be carried out in the Groundwater Protection and Restoration Group at the University of Sheffield, as a CASE studentship sponsored by CONCAWE, the European Oil Industry Association for the Environment and Health, which has responsibility to advise its membership and policy makers on the safety and environmental performance of the industry. It will be linked with a new EU Marie Curie Initial Training Network ('ADVOCATE'), which will be established at Sheffield in 2011 to provide scientific and practical research training to young scientists in the field of sustainable in situ remediation for contaminated land and groundwater.