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A potential remediation technique for groundwater contaminated by bromate has been investigated, utilising biological bromate reduction to bromide by augmentation of indigenous microbial populations. This technique, involving addition of a carbon source to contaminated groundwater, is being developed as an ex-situ methodology analogous to commercial denitrification systems, but may also have in-situ applications. Trials have focussed on a laboratory-scale anaerobic suspended growth chemostat system, investigating glucose addition to real groundwater supplies. Steady states for a range of glucose and bromate concentrations demonstrated bromate reduction up to 700 microgl(-1) (50% of 1400 microgl(-1) influent) with glucose excess (above 52 mgl(-1)), but specific reduction rates (up to 2.83 micromol Br.g dry wt(-1) hr(-1) for 1400 microgl(-1) bromate influent) were low compared to denitrification (up to 305 micromol N g dry wt(-1) hr(-1)). More recent enrichment trials have demonstrated reduction of 32 mgl(-1) bromate within a 40 hour residence time with specific reduction rates of up to 160.48 micromol Br.g dry wt(-1) hr(-1), suggesting the presence of high rate bromate reducing bacterial strains.

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In this paper the results of a sampling programme, undertaken as part of the EU MicroRisk project, are described. This project was undertaken to ascertain the occurrence of pathogens and indicators in the River Thames and their subsequent removal through a treatment works. Appropriate physico-chemical surrogates, as determined by statistical correlation are proposed for the microorganisms identified in the raw water. This study shows that under normal raw water conditions the treatment works is able to remove microbial contamination with a significant margin of safety.