ENVIRONMENTAL TRIGGERS FOR GEOSMIN PRODUCTION IN FRESHWATER ECOSYSTEMS

This project will determine the triggers initiating cyanobacterial production of taste and odour problem metabolite, 1,10-dimethyl-trans-9-decalol (geosmin). Geosmin is a metabolite produced in drinking water supply reservoirs primarily by cyanobacteria. It is a natural compound that results in an unpleasant earthy and/or musty taste to drinking water, resulting in customer product rejection and complaints. To prevent this, final treated water undergoes costly removal of these compounds using activated carbon filtration, at a cost of up to £1,500 per day per water treatment works. Taste and odour issues are estimated to cost the UK Water industry over £200 million per annum (Drinking Water Inspectorate, DWI). This project will deliver a mechanistic model of the triggers for geosmin production that will drive evidence based management of lakes and reservoirs. Geosmin is produced by cyanobacteria in the mevalonate (MV) and 2-methylerythritol-4-phosphate isoprenoid (MEP) metabolic pathways. It is a precursor for a range of important cellular compounds in cyanobacteria, including photosynthetic pigments. Recent work by the PI within Welsh Water has determined that geosmin production is the result of periods of rapid growth phase by cyanobacteria when exposed to reducing or low concentrations of nitrate and increasing or high concentrations of ammonium. This can be explained as ammonium is the most biologically available nitrogen (N) fraction, being the most reduced form in aquatic systems. This project will use three test sites to determine nutrient triggers for geosmin synthesis by cyanobacteria: Pentwyn and Pontsticill reservoirs and Llwyn-Onn reservoir have been studied by the PI and are known sites with geosmin production and cyanobacteria taxa recorded include Dolichospermum and Oscillatoria, both known geosmin producers. The water chemistry at each site has been studied as part of a taste and odour investigation by the PI and Welsh Water. The test sites therefore provide ideal sources for samples to test for a mechanistic pathway between nutrient supply and geosmin synthetase activity and hence geosmin production.