Understanding climate change-related increases in dissolved Mn, Fe, OM in drinking water systems: identifying future risks and facilitating fit-for-pu

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Many drinking water sources in Scotland and worldwide are experiencing seasonal fluctuations in dissolved Mn, Fe, OM concentrations. Over prolonged periods during summer and autumn, dissolved Mn concentrations are now approaching the WHO guideline value of 400 g L-1, above which there may be potential negative human health impacts. Dissolved Fe concentrations are typically higher and, although there is no similar health-based limit for Fe in drinking water, concentrations of >200 g L-1 can impair taste, cause staining of laundry and result in coatings/precipitates within drinking water distribution systems. Evidence suggests that the increasing dissolved concentrations are linked to climate change, specifically the increased frequency of extended dry periods interspersed by intensified storm events. Indeed, in 2021, many UK drinking water reservoir levels were at their lowest for ~160 years. There is now an urgent need for water providers to invest in fit-for-purpose water management systems; e.g. source water aeration, oxygenation and artificial destratification, specific raw water treatment processes, e.g. ozonation, chemical contactors, and/or flushing of distribution systems. Such mitigation measures are expensive and recent studies indicate that they are inefficient in treating organic-rich waters and in maintaining Mn/Fe concentrations below the levels which impact on the water distribution systems.