The reuse of treated effluents represents a key strategy to increase the availability of water resources, especially in contexts where conventional sources are under pressure. With industrial production consuming nearly 90% of the global freshwater supply, the natural hydrological cycle has been overwhelmed, a situation worsened by the effects of climate change. The United Nations has characterized this scenario as one of “too much water, too little water, and polluted water.” Madrid is no exception: the city faces increasing urban and industrial demand, extreme weather events, and persistent water quality challenges. In this context, wastewater reuse becomes an essential tool for bridging water availability gaps and enhancing water resilience.
Aligned with this need, the current project is being developed at the Wastewater Treatment Plant (WWTP) Arroyo Culebro Cuenca Media Alta, located in the municipality of Pinto (Community of Madrid, Spain) and operated by Acciona. This urban wastewater treatment plant is equipped with an advanced tertiary treatment system that feeds three reverse osmosis (RO) trains, currently operating at a recovery efficiency of 70%, a figure that represents the global industry standard. This presents an excellent opportunity to innovate in efficiency enhancement and set a new market benchmark.
To further increase recovery, American Water Chemicals (AWC), a company specializing in optimizing complex water chemistry to maximize water recovery, has proposed a strategic partnership with Acciona. This collaboration aims to implement advanced solutions that reduce chemical consumption, increase the production of high-quality treated water, and minimize the volume of liquid waste. These technical improvements translate into a net increase in the volume of reused water, which can be quantified as an additional water benefit under the VWBA 2.0 framework. Therefore, the project’s strategic goal is to transform operational improvement into a verifiable and reportable environmental impact, aligned with international water sustainability frameworks.
Wastewater Pollution: A Global Threat, A Local Opportunity
Every day, 80% of the world’s wastewater is discharged into the environment completely untreated, jeopardizing nature and public health. The consequences are systemic: weakened climate resilience, disrupted aquatic ecosystems, and growing threats to food and water security. Wastewater introduces a toxic cocktail of pathogens, pharmaceuticals, microplastics, heavy metals, and endocrine disruptors, polluting the very resources we depend on.
Our current systems have allowed us to “flush it and forget it,” evading the complex and uncomfortable truth of water pollution. But the impacts are catching up with us. Algal blooms suffocating aquatic life, fisheries collapsing, and coastal zones closing due to contamination. The problem is not isolated. Wastewater pollution is everywhere.
And yet, within this crisis lies an untapped opportunity. Spain, long regarded as a water-stressed country, is now awakening as a potential global leader in water reuse. In 2020, Spain reused only 325 hm³, representing less than 6% of its estimated technical potential. But projections show that with the right regulatory and technical conditions, this figure could rise to 1,800 hm³ per year. The gap is enormous, and so is the opportunity.
Today, industrial leaders like AWC and Acciona are deploying advanced reuse technologies under a Water Stewardship framework. These are not just technology providers. They are market catalysts. When the industrial sector leads, others follow. Spain’s “sleeping giant” is stirring not through obligation but through strategic foresight.
The barriers are not just technical. They are psychological. Reuse still suffers from outdated perceptions and poor communication. The shift happens when projects are framed as regenerative, traceable, safe, and resilience-driven. This is where the Water Positive narrative plays a critical role. We’re not treating wastewater. We’re recovering value.
Regulation, once seen as a bottleneck, is now becoming an innovation platform. EU Regulation 2020/741 introduced new quality standards for agricultural reuse. Initially perceived as restrictive, it is now reframed as a springboard for innovation. Real-time validation, digital twins, and traceable certifications are turning compliance into a competitive advantage.
Governance, historically fragmented, is being reshaped by market pressure and private investment. The entry of global corporations, EU recovery funds, and demand for measurable water benefits is forcing institutional adaptation. Governance will not evolve by decree. It will be pulled forward by impact.
This is more than infrastructure. It is a paradigm shift. Turning wastewater from liability into asset is not only possible. It is already happening. And Spain, through industrial leadership and a Water Positive lens, is proving that reuse is not the future. It is the strategy.
The 30% recovery gap primarily consists of water that can be reclaimed without major complexity, thanks to innovative solutions developed in laboratories like those of American Water Chemicals (AWC), an American firm headquartered in Spain. Unlike traditional reverse osmosis systems, tertiary reuse systems involve complex water chemistry. This project represents a unique opportunity for water savings and the generation of new, high-quality freshwater in a decentralized manner across the globe, where thousands of facilities are already involved in water reuse.
Each year, an estimated 365 km³ of treated and untreated wastewater is discarded worldwide—an amount that could play a key role in repairing the broken water cycle. Increasing the recovery rates of these systems is not only feasible but highly replicable globally. This effort also offers a powerful educational opportunity to teach future generations to classify water by its quality rather than its source. Reuse must be given a real chance, and this project can serve as a model and educational platform for corporations looking for tangible water-saving opportunities.
It is increasingly evident that the natural water cycle alone is no longer sufficient to meet growing global demands. This application, by recovering high-quality water from existing effluents, offers a practical and scalable way to complement and reinforce the natural hydrological system. It contributes not only to balancing supply and demand, but also to restoring the integrity of the water cycle that has been critically strained by human activity and climate change.
The project is located in the upper-middle basin of the Manzanares River, within the Culebro stream sub-basin, an area under intense urban pressure due to the population density of municipalities like Pinto, Getafe, and Fuenlabrada. This urban concentration, combined with the discharge of treated wastewater and limited natural water availability, creates a fragile scenario for both water quantity and quality. In this setting, implementing innovative reuse solutions is not only relevant, it is essential.
The roadmap for implementation unfolds in three key stages, each designed to ensure that technological innovation is both effective and verifiable.
Stage 1: Simulating the Future
The journey begins with a robust technical simulation. Using advanced digital modeling tools, the project team recreates the complex environment in which the reuse system will operate. Real water quality data—such as pH, temperature, and concentrations of metals and salts—are input to simulate performance under new operating conditions. The goal is to push the system to an 80% recovery rate, anticipating how the membranes will behave, what risks of fouling may arise, and whether the solution will truly improve system efficiency. These simulations help define clear operating protocols and confirm that the approach aligns with membrane manufacturer guidelines.
Stage 2: Testing the Innovation
Once the digital proof is established, it’s time to bring the model into the real world. One full train of reverse osmosis at the plant is operated using the proposed solution. Real-time sensors monitor flow, pressure, conductivity, and other critical variables, while lab samples confirm improvements in water quality and operational stability. The pilot tests not only demonstrate technical gains like lower cleaning frequency and reduced chemical use, but also validate that a higher recovery rate is sustainable under real-world conditions.
Stage 3: Scaling with Confidence
With strong results in hand, the solution is extended to the full system. All RO trains are upgraded, and operational settings are adjusted accordingly. A smart monitoring framework is put in place, complete with automated alerts and performance dashboards. Standard operating procedures are updated, and predictive maintenance routines are introduced to preserve performance over time.
A key innovation at this stage is the integration between Acciona’s operational monitoring platform and Aqua Positive’s additionality reporting system. This connection ensures that all performance data—such as flow recovery, chemical consumption, and cleaning cycles—feeds directly into a centralized platform that quantifies the environmental benefit generated. On an annual basis, this system produces a verified report that is shared with the corporate entity seeking to compensate its water footprint through this reuse initiative. This step guarantees full traceability, transparency, and alignment with global water stewardship frameworks.
This project addresses a critical opportunity to generate positive impact on water resources and produce additionality under a verified framework. It is being implemented at the Arroyo Culebro Cuenca Media Alta Wastewater Treatment Plant (WWTP), located in Pinto, Madrid, and operated by Acciona. The facility treats urban wastewater and is equipped with a tertiary treatment system feeding three reverse osmosis (RO) trains, currently operating at 70% recovery.
To improve recovery and performance, American Water Chemicals (AWC) and Acciona joined forces to implement a targeted antiscalant solution tailored for complex tertiary effluents. The goal is to raise recovery to 80%, while reducing chemical usage, membrane cleaning needs, and liquid waste generation. These optimizations lead to a net increase in reused water and enable the declaration of Volumetric Water Benefits under the VWBA 2.0 framework, creating a pathway for companies to compensate their water footprint in Madrid through a traceable and measurable reuse initiative.
A central innovation is the integration of operational data from Acciona’s system with Aqua Positive’s platform, which calculates the water benefit generated. This enables automatic reporting of water savings—volume recovered, chemicals reduced, cleanings avoided—resulting in a verified annual impact statement.
The WWTP serves the Culebro stream sub-basin in the upper-middle Manzanares River, a zone under pressure from urban growth and water scarcity. In this vulnerable context, the project strengthens climate resilience and helps restore the regional water cycle.
By transforming internal process improvements into environmental benefits, the initiative showcases a scalable, replicable model for other reuse facilities worldwide. With over 365 km³ of wastewater discarded each year, boosting tertiary recovery offers a powerful solution to rebalance global water systems through innovation, accountability, and regeneration.
