In a world where climate change and water scarcity threaten the security of millions of people, the metropolitan region of Barcelona clearly reflects this challenge: rising demand and conventional sources unable to sustain the future. The drought of 2022–2024 showed that losing water is not just a technical failure, but a failure of vision. This project proposes a bold response: to transform the El Prat de Llobregat Water Reclamation Plant into a Water Positive asset through Advanced Reverse Osmosis Optimization (AWC) and the strategic expansion of reuse and recharge, capable of transforming the relationship between city, industry, and water resources. The goal is to produce more useful water with less freshwater extraction, accelerate the recovery of the aquifer, and generate traceable volumes under VWBA 2.0, ensuring credibility with auditors and offtakers.
The market situation in Barcelona shows structural water stress: although the El Prat de Llobregat Water Reclamation Plant already regenerates up to 50 hm³ per year, equivalent to the consumption of more than one million people, it is still insufficient to meet rising demand. The European Union warns that 40% of its territory could suffer severe water stress in the coming decades, underlining the urgency of local solutions.
In this context, the project sets a clear strategic objective: to transform existing infrastructure into a benchmark of water circularity, able to reduce freshwater extractions, increase reuse and recharge volumes, and generate verifiable volumetric benefits that support corporate and community resilience goals.
At the heart of the initiative is the El Prat de Llobregat Water Reclamation Plant, located in the delta of the Llobregat River in Barcelona, Spain. In an environment marked by recurrent saline intrusion and strong urban-industrial pressure, improving reverse osmosis efficiency and expanding reuse destinations is the fastest and most cost-efficient way to ensure future availability and comply with European reuse regulations (EU Regulation 2020/741).
The initiative involves the metropolitan water operator, the Catalan Water Agency, the City of Barcelona and neighboring municipalities, technology partners specialized in AWC, membranes and sensors, a financial structurer, and external compliance verifiers (AWS, VWBA, auditors). This governance architecture guarantees physical and digital traceability of results and alignment with international commitments.
The link with the Water Positive strategy is direct: efficiency improvements generate additional volumes (additionality), the measurement and recording system ensures traceability, and explicit substitution and recharge agreements demonstrate intentionality. Thus, the project is fully integrated into the regional roadmap and into corporate goals aligned with SBTN Water.
The market supports this transformation: the EU demands efficiency, circularity, and quality (EU Regulation 2020/741), while standards such as AWS, ISO 14046 (water footprint), and ISO 46001 (water efficiency management) already set the benchmark. Corporate commitments such as Science-Based Targets for Water require reducing extractions and increasing replenishment in stressed basins. In this context, the plant is projected as a platform of volumetric benefits: each point of RO recovery gained equals the annual consumption of thousands of households, each cubic meter of permeate substituted or recharged represents tangible water security. The opportunity is immediate: decoupling urban and industrial growth from freshwater consumption, strengthening the resilience of the Llobregat, and positioning investors as leaders of an unavoidable European water transition.
The El Prat de Llobregat Water Reclamation Plant is located in a delta historically dependent on freshwater, with recurrent saline intrusion, metropolitan demand pressure, and recurring droughts. The baseline shows operational inefficiencies typical of reverse osmosis trains, moderate recoveries, non-optimized cleanings, pretreatment losses, and an underutilized potential of reclaimed water for industrial uses and recharge. The opportunity lies in implementing AWC (membrane, chemical, hydraulic and control optimization) to increase RO recovery, reduce specific energy, losses and CIP frequency, and reconfigure permeate allocation toward substitution of freshwater in municipal and industrial uses and managed aquifer recharge.
The project modernizes the MBR/UF/RO trains with AWC practices (dosing, antiscalant/antifouling, smart flushing, fouling control, condition-based cleaning), adds advanced instrumentation and analytics (flow, conductivity, SDI, ΔP, water balance) and a digital twin, formalizes substitution agreements with large consumers, and expands/optimizes recharge points with quality control and traceability. This shift represents freshwater savings and additional recharge volumes that can be measured and reported under VWBA.
Direct and tangible benefits include annual cubic meters of avoided freshwater extraction, volumes recharged, improved delivery quality, lower specific energy per cubic meter, and a low-CAPEX optimization scheme. At the same time, the strategic return translates into ESG compliance, operational resilience, reduced regulatory risk, and VWBA assets marketable to corporate offtakers.
This transformation is made possible by the metropolitan operator of the plant, the Catalan Water Authority, the City of Barcelona and industrial zones, AWC technology partners (membranes, chemicals, sensors), external auditors (VWBA/AWS), and corporate VWB buyers.
The model is replicable in any large reclamation facility with reverse osmosis trains: its key is to act now, in a context of recurrent droughts and increasing regulatory requirements. Companies in water, energy, food, or retail sectors with ambitious ESG commitments will find here not only technical compliance but also a story of leadership and competitive differentiation aligned with new regulations and the transition toward a Water Positive future.
Implementation is conceived as a structured sequence combining technology, governance, and climate resilience. In the first stage, AWC optimization is deployed on existing RO trains, focused on the dosing of specialized products that improve reverse osmosis efficiency and enable higher recoveries with less frequent cleanings and lower energy consumption. Operation is reinforced with condition-based CIP defined by ΔP thresholds and flow normalization, oscillatory flushing and adaptive dosing of antiscalants, while train-by-train recovery management balances fouling loads. At the same time, a digital twin connected to SCADA/IoT predicts fouling, normalizes flows, and triggers preventive alarms. Alternatives such as new RO modules or artificial wetlands were evaluated, but this solution was chosen for its higher benefit-cost ratio, train-by-train scalability, and ability to simultaneously improve performance and quality in a context of severe water stress. The operational capacity is estimated in tens of thousands of cubic meters per day, potentially benefiting more than one million end users, configured as a hybrid solution combining gray infrastructure with digital intelligence.
The project addresses a critical technical and environmental problem: losses and low efficiency in RO trains that force greater freshwater extractions, aggravated by saline intrusion in the delta and climate variability. The choice of AWC is justified because it reduces energy consumption, improves permeate quality, and ensures traceability, complying with European regulations and international standards. The criteria for its selection included operational efficiency, cost, environmental and social impact, replicability, and compatibility with the Water Positive roadmap and VWBA principles, ensuring additionality, traceability, and intentionality in each generated volume.
Expected benefits are quantifiable: annual cubic meters of water saved and reused, volumes infiltrated into the aquifer, improvements in quality parameters such as conductivity, nitrates and TOC, emission reductions thanks to lower energy use, decreased chemical consumption, recovery of ecosystem resilience in the delta, and strengthening of public health and regional water security. Economically, optimization reduces operating costs, enables certifications, and enhances ESG reputation for participating companies.
Operational risks include biofouling, scaling and technological failures; environmental risks include hydrological variability and social acceptance of recharge. Mitigation measures integrate redundant systems, operational buffers, contingency plans, recharge protocols under EU Regulation 2020/741, transparent communication with communities, and shared governance with the basin authority. Long-term resilience to climate change is ensured through continuous monitoring, VWBA alarms and reports, preventive and predictive maintenance, and protocols to prevent critical failures such as contamination, supply shortages, or saline intrusion.
Finally, the model’s scalability is high: it can be replicated in reclamation and desalination plants in other Mediterranean basins or urban regions under water stress, provided that reuse regulatory frameworks, public-private governance capacity, and industrial or municipal users willing to substitute freshwater exist. Its competitiveness is measured in a favorable cost/benefit ratio compared to more CAPEX-intensive alternatives, and in the strength of technological and community alliances that enable its expansion nationally and internationally.
Implementation is conceived as an integral, phased process designed to maximize technical efficiency and ensure traceability and resilience over time. An adaptive and staged approach is adopted, so each phase builds on the previous one and allows adjustments according to results and external conditions.
The first phase, with a horizon of 0 to 3 months, focuses on diagnosis and baseline construction. RO train data are normalized, including membrane flows, ΔP, salinity, SDI, and CIP frequency. A comprehensive water balance from intake to reject is established, energy and chemical consumption is characterized, and current destinations are documented. At the same time, instruments are audited and the measurement plan is defined under VWBA methods (A-2 and A-4), ensuring future comparability with a without-project scenario.
The second phase, between months 3 and 9, corresponds to the execution of AWC optimization. Specialized product dosing is implemented to increase RO train recovery and reduce cleaning frequency, critical sensors of flow, conductivity, SDI and ΔP are installed, control logics for condition-based CIP and smart flushing are configured, and a digital twin is integrated with SCADA/IoT to model real-time operation. During this stage, high-recovery train pilots, hydraulic stress tests and freshwater substitution agreements with key users are carried out, in addition to managed recharge protocols with quality and flow control.
The third phase, from months 9 to 12, includes validation and technical closure. It covers independent verification of annual volumetric benefits, reporting under VWBA 2.0, AWS and applicable ISO standards, and the formalization of Water Positive claims and contracts with offtakers. External validation and data audit protocols are established, ensuring that each generated volume meets additionality, traceability, and intentionality criteria.
Performance indicators include reduction of freshwater withdrawal and consumption (VWB A-2), managed net recharge (VWB A-4), RO recovery, fouling loss, specific energy, chemicals per cubic meter, and permeate quality parameters under EU Regulation 2020/741. Certified flow meters at intake, feed and permeate, online probes, dataloggers and laboratory sampling are used. Data collection frequency ranges from continuous in sensors to monthly or quarterly consolidated reports.
Physical traceability is ensured by instrumentation of each point of the water cycle and digital traceability by SCADA platforms with optional DLT registry. The system generates automatic alarms for deviations in recovery, energy, quality or flows, and monthly VWBA reports reviewed quarterly and externally verified annually.
Governance involves the plant’s technical operator, the basin authority, industrial and municipal beneficiaries, technology partners and external verifiers. Each actor assumes clear roles in operation, maintenance, monitoring and validation, and agreements are established on the allocation and destination of saved or regenerated volumes. The maintenance plan combines preventive and predictive routines: fouling trending, periodic sensor calibration, pump inspections and optimized CIP protocols with critical spare parts inventory.
The monitoring system ensures reporting compatible with VWBA/WQBA, comparing results with the without-project scenario. Continuous improvement is implemented through data feedback, dosing adjustments, and technological updates according to regulatory and climate evolution. This guarantees the permanence of benefits over time, with a project able to adapt to scenarios of greater water stress or climate variability.
The project transforms the El Prat ERA into a hub of circular and resilient water through the implementation of Advanced Reverse Osmosis Optimization (AWC). The main intervention consists of increasing the efficiency of reverse osmosis by dosing specialized products that raise recovery rates, lower energy consumption, and reduce chemical use. Technically, the process integrates pretreatment, ultrafiltration, and optimized RO trains, supported by sensors, flow meters, SDI probes, and a digital twin connected to SCADA for real‑time monitoring. The permeate is directed both to industrial and municipal uses that substitute freshwater and to managed aquifer recharge, under strict compliance with EU Regulation 2020/741, AWS v2.0, ISO 14046, ISO 46001, Spanish and Catalan legislation, and SBTN Water principles.
This solution is relevant because it addresses structural challenges of the Llobregat delta: overexploitation of the aquifer, saline intrusion, and rising demand from urban and industrial users. Compared to the baseline, where inefficiencies forced higher withdrawals and frequent cleanings, the optimized process delivers more permeate with fewer resources and measurable volumetric benefits. It is technically and socially appropriate because it enhances water security, restores aquifer conditions, and aligns with regulatory and community expectations.
Expected results include annual cubic meters of water saved, reused, or replenished, reductions in conductivity, nitrates and TOC in recharged water, lower kWh/m³ and reduced chemical dosing, and co‑benefits such as emission reductions, biodiversity protection in the delta, improved public health and enhanced food security through reliable supply.
Strategically, the project strengthens the Water Positive roadmap, creating verifiable and tradable VWBA assets that support ESG commitments and global frameworks such as SBTi, NPWI, the SDGs, and ESRS E3. It offers tangible ESG benefits: social license to operate, strengthened reputation, competitive differentiation, and regulatory compliance.
The model is modular and scalable, suitable for replication in other Mediterranean basins, reclamation plants, or industrial sectors under water stress, provided enabling technical and social conditions exist. Partnerships with operators, communities, governments, and companies are key to its expansion.
The final impact is to improve the basin’s water balance and resilience to climate change, while generating social benefits such as employment, secure access to water, and stronger communities. For investors, clients, and society, it delivers a powerful message: this is not only a technical upgrade but a step toward a regenerative water economy where each cubic meter regenerated becomes an asset of resilience and shared prosperity.
