Odour management in drinking water systems fed by mixed water supplies

Abstract

Algae-derived odour events in water supplies have been increasing with eutrophication and climate change. It is important to engage in proactive management of odourants to retain consumer confidence in the safety of their drinking water. In this study, historical monitoring data were analysed to provide a holistic understanding of source-to-tap odour risks at a large drinking water filtration plant, supplied via pipeline and open canal from reservoirs in protected catchments, as well as a supplementary reservoir located adjacent to the water filtration plant. The occurrence of odourant chemicals, odour descriptors and potential odour-producing algae were analysed during periods of variable supply from the supplementary reservoir. Fishy odour was more likely to occur in mixed raw water during periods of high supply from the supplementary reservoir. High cell densities of potential odour-producing algae, including the Cyclotella, Cryptomonas, Dinobryon and Synedra and Asterionella genera, were detected in the supplementary reservoir. Interestingly, more odour complaints were received from consumers when the supplementary reservoir was offline or in limited use, and they were primarily described as ‘earthy/musty’ and ‘chemical’ odours, or as a general ‘bad smell’. This research identified the need for improved monitoring of odourants in source and raw water as well as the development of publicly available resources for odour identification.