Our researchers determined the triggers of taste and odour problems affecting the water supply, enabling more proactive reservoir management strategies and creating significant financial savings for UK water companies.

Certain species of filamentous cyanobacteria, blue-green algae, which are found in almost every aquatic environment, are known to produce the metabolites 2-Methyl-Isoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin). These compounds produce taste and odour issues in drinking water, even in miniscule quantities (as little as 5 ng per litre).

Although cyanobacteria are known to produce 2-MIB and geosmin, the triggers for their production went unrecognised for decades, until researchers from the School of Earth and Environmental Sciences discovered how varying nutrient levels from water catchment areas were triggering the production of cyanobacteria metabolites.

This discovery enabled more proactive and less invasive reservoir management strategies and led to Welsh Water redefining its strategy for reservoir water treatment, creating significant financial savings. It also resulted in improved industry best practice and policy which led to economic savings for UK water companies, and influenced water companies across the world.

Finding the triggers for cyanobacteria

In collaboration with Welsh Water, Dr Rupert Perkins analysed the Plas Uchaf and Dolwen reservoir system in North Wales. His research found that the critical trigger for cyanobacteria was fine scale changes in nutrient ratios, specifically the amount of ammonium relative to nitrate and phosphate. This occurs as a result of catchment processes, such as farming, that cause significant pulses of ammonium. Changes in farming activities with ammonium-rich slurries, specifically at times when nitrate availability was low, but phosphate supply was high, stimulated cyanobacteria to produce 2-MIB and geosmin.

Through several Welsh Water-funded projects, Dr Perkins designed a new water sampling strategy for Welsh Water and improved laboratory analysis methods to detect changes in nutrient levels. This yielded further data from over seven additional reservoir systems in Wales, allowing Dr Perkins to test the prevalence of the nutrient ratio trigger. The findings suggested that there was a widespread problem with control of taste and odour.

Together with Wessex Water and Bristol Water, Cardiff researchers found causal links to taste and odour causing cyanobacteria at additional testing sites across the UK. These studies fully corroborated the initial findings demonstrating that nutrient ratio triggers of ammonium, nitrate and phosphate produce 2-MIB and geosmin, which results in taste and odour problems.