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Water reuse in the Municipality of Cascais

In order to cope with the growing demand for water, Positive Benefits in partnership with P Water supported the Municipality of Cascais to study the potential reuse of water is an alternative source, contributing to the sustainable use of water resources and its preservation for future uses, safeguarding the present use, in line with the principles of the circular economy.

Wastewater is one of the most under-exploited resources we have. Water from industrial or domestic use contains energy, water reuse, organics, phosphates, nitrogen, cellulose, rare earths, and other resources. Globally, the reuse of water has expanded from agricultural irrigation or green spaces and restricted urban uses to potable uses (indirect and direct), and treated waste water is seen as a new source of water, additional and/or alternative for multiple purposes.

Agriculture is, in almost all countries, the sector that consumes more water, accounting for 70% of water consumption worldwide [Asano et al., 2007]. The reuse of wastewater for irrigation in agriculture is widely practiced in the U.S. [US EPA, 2004].

Also, the reuse of treated waste water can be a important measure of adaptation to climate change and a good practice of water management, in particular to cope with the increased frequency and intensity of periods of droughts and water scarcity, enabling the resilience of systems to be increased by including the measures provided for in the Climate Change Adaptation Action Programme (P-3AC).


In the municipality of Cascais most of the drinking water used comes from the Castelo de Bode Reservoir, which is about 200 km from the municipality's headquarters. So, the existence of alternative local sources of water production for less demanding use will be a strategic safety measure for the preparation and projection of the future needs. The reuse of treated waste water and the desalination of seawater are two of the potential alternative local water sources.

In June 2015, in the middle of a dry year, Cascais Ambiente used treated waste water to wash the streets of the municipality. The volumes of treated waste water consumed by Cascais Ambiente where approximately 5.500 to 6.600 m3/year, which corresponds to less than 2% of the total waste water treated in the Guia waste water treatment plant ( capacity to treat 9.000 m3/day of waste water with adequate quality for reuse for various purposes).

The implementation of the cascais municipalitiy wastewater reuse system is associated with additional positive added value, that will increased the resilience of urban water services. This will improve the water sources resilience and safety of climate uncertainty, and will contribute to the SDG6 (UN and to the conservation of ecosystems), and also, contribute to promote the conservation and reuse of nutrients (N and P) as fertilizers in the irrigation of green spaces.


Positive Benefits is committed to incorporate this powerful tool in every project we work on, identifying which of the 17 goals can the project relate to and creating specific solutions to achieve them.

The Sustainable Development Goals (SDGs), also known as the Global Goals, were adopted by the United Nations in 2015 as a universal call to action to end poverty, protect the planet, and ensure that by 2030 all people enjoy peace and prosperity.

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