Investigating the influence of geologic bombs and reservoir management on biogeochemical cycling of trace metals and resultant water quality.

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The main aim of this project is to further contribute to the scientific knowledge base of the geologic sources and biogeochemical pathways of manganese concentrations within drinking water reservoirs and their catchments. Manganese (Mn) is a naturally occurring trace metal which in high concentrations can cause health problems in humans. Although manganese is an essential trace element for human health, manganism (or manganese poisoning) is a toxic condition that can result from sustained exposure to high levels of manganese in the environment, for example from manganese in the air or in drinking water. Therefore, there is a need to monitor and manage manganese levels in drinking water from a human health perspective. As well as having an effect on human health, manganese can also cause aesthetic issues with drinking water odour, taste and appearance, and physical blockages in water distribution systems due to manganese precipitation in pipe networks. Manganese is one of the primary causes of taste and odour problems that UK drinking utilities must deal with, resulting in £millions of fines annually in customer complaints. This has led to almost all UK water utilities currently managing their drinking water reservoirs by pumping oxygen into the hypolimnion of the reservoir to promote the oxygenation and sedimentation of reduced manganese forms, and its subsequent removal from the water column. There is a current general lack of understanding, however, of how these engineered aeration systems affect the biogeochemical controls on water quality (Bristol Water, pers. comm.). With increased pressure on water resources worldwide created by a rising population, combined with environmental pressures such as climate change, it will become more important to utilise new, more sustainable water resources that may be of lower quality, and to utilise existing water resources in a more efficient way. Therefore, there is a precedent for understanding the cycling of manganese and other trace metals in these environments that influence the quality of our water supplies.To further elucidate manganese geochemical cycling from a water quality standpoint, this project focuses on characterising the catchment sources and biogeochemical pathways of manganese that can be better targeted for improved management. This work will be carried out at Blagdon Lake - a drinking water reservoir managed by Bristol Water; research results will directly contribute to water utilities' and general scientific understanding of manganese dynamics in a drinking water reservoir.Two primary lines of research will be investigated:1) The novel use of voltammetric electrodes to further understand oxygen-manganese dynamics at the sediment-water interface, including spatial and temporal differences in the reservoir.2) The influence of local (catchment) geology on reservoir water quality, with focus on manganese formations linked to riparian runoff.Results will ultimately be incorporated into a catchment-reservoir model, building upon current Blagdon-focused research by WISE student Jack Waterhouse, which would be used to better manage manganese levels in the future and alleviate existing UK water-supply issues with taste and odour.