Several goals can be considered when optimizing blends from multiple water resources for urban water supplies. Concentration-response relationships from the literature indicate that a changed water quality can cause impacts on health, lifetime of consumer goods and use of water additives like softeners. This paper describes potential economic consequences of diluting Copenhagen's drinking water with desalinated water. With a mineral content at 50% of current levels, dental caries and cardiovascular diseases are expected to increase by 51 and 23% respectively. Meanwhile, the number of dish and clothes washer replacements is expected to decrease by 14%. In economic terms these changes are equal to 24–85% of water production costs in 2005. Our calculations further indicate that the economic impact from changing the water quality can be at least as significant as the change in operating costs going from fresh water based to desalinated water supply. Large uncertainties prevent the current results from being used for or against desalination as an option for Copenhagen's water supply. In the future, more impacts and an uncertainty analysis will be added to the assessment.

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