The Potential of Wastewater Reuse and the Role of Economic Valuation in the Pursuit of Sustainability: The Case of the Canal de Isabel II

Abstract

Wastewater reuse is an activity that reduces pollution from discharges while increasing the available water resources. However, the high financial costs of this activity affect the viability of projects, either because of low water productivity or because of the presence of a cheaper alternative, such as natural water sources. The existence of environmental or social benefits makes reuse a positive option for society for its environmental and social benefits. This leaves the public sector to decide whether the benefit obtained justifies its participation in the development of reuse programs, for which it is necessary to use a tool such as cost-benefit analysis, which combines diverse costs and benefits. This article studies the potential for water reuse in Spain and the importance of informed decision-making, based on information regarding water stress, wastewater reuse, and the case study of the Canal de Isabel II (Madrid). The results confirm the potential of wastewater reuse; agriculture has a water productivity below EUR 1 per cubic meter and industry and services need their own sources of water, but financial constraints prevent the greater use of reclaimed water in all economic sectors and public intervention is necessary to obtain the optimum scenario for society. The case study from Madrid that we have analyzed in this paper shows the importance of considering all factors, since the results of prioritizing the financial criterion would have been detrimental to society, in the form of EUR 200 million in environmental damage, while EUR 740 million of non-financial benefits would make wastewater reuse an advantageous alternative for society, thus justifying the public investment.