The Madrid City Council is promoting a structural transformation in urban water management through the progressive implementation of an irrigation system based on reclaimed water for public parks and gardens, replacing the use of potable water from the municipal network. This decision is based on the recognition that urban green spaces represent a key opportunity to introduce circular water economy solutions that reduce the consumption of conventional water resources and optimize the use of treated effluents with sanitary safety criteria.
To ensure the safety of the water used, advanced microbiological regeneration technologies are employed, which do not use added chemicals and eliminate pathogens through physical processes such as hydrodynamic cavitation, advanced oxidation, or atmospheric plasma. These systems not only comply with the requirements of Royal Decree 1620/2007 for urban uses but exceed them, ensuring quality levels equivalent to potable water in terms of their application in exposed public environments.
This model allows the Madrid City Council to reduce pressure on aquifers and reservoirs that supply the city, decrease the institutional water footprint, and improve the efficiency of public spending on green space irrigation. Likewise, by promoting the closure of local water cycles and reducing dependency on conventional sources, the city advances toward more resilient and climate-adaptive resource management. Expected benefits include the mitigation of water stress, improved financial sustainability of municipal services, reduced indirect emissions associated with the pumping of potable water, and improved citizen perception of the municipality’s environmental commitment.
Madrid faces a dual structural challenge in water management. On the one hand, the city heavily depends on the potable water supply from the Canal de Isabel II, whose flow is subject to high demand and a progressive reduction in availability, especially during the summer months. According to data from the Canal itself, potable water consumption in the municipality of Madrid exceeds 400 million m³ annually, a significant percentage of which is used for non-priority purposes such as the irrigation of green areas. This resource-intensive practice not only increases municipal operational costs but also compromises the hydrological balance of the Tagus River basin.
On the other hand, the Wastewater Treatment Plants (WWTPs) of La Gavia, Rejas, and Viveros produce hundreds of thousands of cubic meters of treated water each year that is largely discharged into the environment without further use. This water, with complementary tertiary treatment, could fully meet the reuse criteria established by Royal Decree 1620/2007 and EU Regulation 2020/741, becoming a safe alternative source for urban uses such as garden irrigation, street cleaning, or road washing.
Furthermore, the climate change context projects for Madrid a reduction in rainfall and an increase in the frequency and intensity of heatwaves, which raises the risk of prolonged droughts and urban water stress. Added to this is the growing citizen demand for sustainable, resilient public policies that optimize resource use. In this context, maintaining park irrigation with potable water represents not only an economic inefficiency but also a reputational and environmental risk for the city.
Consequently, the lack of utilization of regenerated effluents, combined with the intensive use of potable water for secondary uses, generates an unsustainable scenario that must be addressed through robust and socially acceptable water circularity solutions.
The intervention consists of establishing a safe and efficient reclaimed water reuse system for urban irrigation, leveraging existing infrastructure and expanding its reach through advanced technologies. The main lines of action include:
This modular and scalable system allows adaptation to different demand conditions, locations, and water pressure, with the possibility of replication in other municipalities of the Community of Madrid. Additionally, by integrating the principles of circular economy, climate resilience, and environmental health, it represents a cutting-edge solution to face 21st-century challenges in densely populated cities like Madrid.
Applied Technologies: The project integrates advanced physical-chemical treatment technologies to ensure high microbiological quality of reclaimed water, without the use of chemicals. Processes such as advanced oxidation, which eliminates pathogens through highly oxidative reactions; hydrodynamic cavitation, which breaks cell structures through pressure changes; atmospheric plasma, which generates reactive species that disinfect water; and membrane ultrafiltration, which acts as a physical barrier to viruses and bacteria, are used. These technologies are complementary and ensure that the reclaimed water meets the required standards for urban uses such as public space irrigation
Monitoring Plan: It is structured over a digital network of online sensors and control points. It includes spectrophotometric equipment for E. coli and enterococci, amperometric probes for free residual chlorine, multiparameter sensors for physical-chemical quality (pH, turbidity, conductivity), and pressure and flow meters to ensure hydraulic integrity. These data are managed from a SCADA platform with smart irrigation algorithms based on meteorological conditions, evapotranspiration, and type of vegetation (Kc).
Partnerships: The project is structured around an inter-institutional collaboration network.
Participants include the General Directorate of Green Areas and Urban Trees of the Madrid City Council as the local operator; Canal de Isabel II as the reclaimed water supplier and technical support; companies specialized in non-chemical regeneration technologies (such as Geodesic and others with CE validation); and the Aqua Positive platform as traceability, validation, and volumetric water benefits (VWBs) accounting support. Integration with local universities is also considered for co-benefit evaluation and independent monitoring.
The project also includes a collaborative governance model, based on a technical-administrative consortium that regulates operational responsibilities, sanitary emergency protocols, and predictive maintenance. Regular training for operators, water quality validation protocols before point of use, and citizen awareness campaigns are established to strengthen public confidence. A pilot phase is planned in large parks such as Juan Carlos I or Valdebebas, where system performance will be validated, followed by progressive expansion to other districts such as Fuencarral-El Pardo, San Blas, or Usera.
The objective of this project is to transform water management in the urban green spaces of the municipality of Madrid through the safe reuse of reclaimed water from the city’s main wastewater treatment plants. This strategic intervention will replace the use of potable water for the irrigation of public parks with treated water that meets the microbiological and physicochemical requirements established by current regulations. The proposal is based on a circular model, integrating advanced regeneration technologies without the use of chlorine and a dedicated separate distribution network, ensuring traceability and sanitary safety at all times.
With an initial phase focused on large-scale parks and high-use density areas, the project is scalable and replicable across the entire municipal territory. Its implementation will reduce pressure on conventional water supply sources, contribute to the water balance of the Tagus River basin, decrease municipal operating costs, and strengthen public perception of the City Council’s commitment to sustainability and climate resilience. The project is fully aligned with the commitments of the European Green Deal, the objectives of Madrid’s Climate Change Adaptation Plan, and international water sustainability standards such as the AWS Standard and the principles of the CEO Water Mandate.
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