This project proposes a comprehensive strategy for the reuse of treated effluent from the Wastewater Treatment Plant aiming to transform it into a safe, traceable, high-sanitary-quality regenerated water resource suitable for two primary applications: advanced agricultural irrigation in nearby irrigated zones and irrigation of urban green areas. The intervention is framed under the Volumetric Water Benefit Accounting (VWBA 2.0) methodology, applying Appendix A-4 to account for water benefits generated through the replacement of conventional sources with safe alternative sources.
The Waste Water Treatment Plant is one of the most significant treatment facilities in Aragón in terms of volume and currently discharges its secondary effluent into the receiving water body without productive use. This represents a substantial loss of a resource that, with adequate tertiary treatment, could meet key seasonal water demands in a context of increasing scarcity and growing pressure on local aquifers.
The initiative aims to articulate a dual-use model: on one hand, part of the flow will be directed to irrigation communities near the Flumen Canal for agricultural purposes; on the other, a separate network will be established to supply municipal green spaces, sports facilities, and non-potable urban uses such as street cleaning. System traceability will be ensured through inline sensors, SCADA platforms, and external validation, guaranteeing continuous compliance with quality standards defined by Spanish regulation.
This project addresses a concrete territorial need for water efficiency, incorporating strong circular economy principles by reintegrating treated water into both the agricultural and urban cycles, generating environmental, social, and operational benefits.
The Waste Water Treatment Plant treats a significant daily volume of urban wastewater from the city and its metropolitan area, including domestic and municipal service inputs. Despite having effective secondary treatment, the effluent is discharged directly into the Isuela River without being valorized, representing a strategic loss in a context marked by water stress.
At the same time, local agricultural irrigation systems rely on conventional sources such as the Flumen Canal or groundwater withdrawals, which face restrictions due to reduced flows, recurring droughts, and regulatory pressures. In parallel, the City Council of Huesca uses potable water to irrigate parks, gardens, and public facilities, increasing operational costs and intensifying pressure on the potable supply network.
This fragmented model results in structural inefficiencies, dependence on vulnerable sources, and a lack of integration between urban and agricultural water cycles. The absence of a reuse system prevents the local water cycle from closing and limits territorial climate adaptation capacity.
The project includes the installation of a full tertiary treatment line designed to ensure the production of Class A sanitary quality regenerated water, as per the standards set by Spanish regulations (Royal Decree 1620/2007 and its update RD 1085/2024). The treatment train consists of a membrane ultrafiltration unit with a molecular cut-off below 0.1 microns, enabling efficient removal of suspended solids, pathogens, viruses, and colloidal compounds. This is followed by a high-intensity ultraviolet disinfection stage to ensure microbiological inactivation, and an inline automated chlorination system as a secondary safety barrier to maintain residual disinfectant during water transport.
The regenerated water will be conveyed to an intermediate storage system equipped with level, quality, and temperature sensors, from which it will be distributed on demand through two independent hydraulic networks: one connected to advanced agricultural irrigation systems in nearby plots, and another designated for non-potable urban uses such as green area irrigation, sports fields, and street cleaning.
All operations will be controlled through a next-generation SCADA platform that integrates data from inline sensors at critical system points: turbidity, free chlorine, UV transmittance, flow, and pressure. This platform will enable real-time monitoring, alert generation, and historical parameter logging, ensuring traceability, continuous quality control, and regulatory compliance.
Furthermore, the project formalizes operational agreements with irrigation communities near the Flumen Canal and with the City of Huesca, both acting as end users of the regenerated resource. Traceability will be reinforced through quarterly external validation by accredited laboratories, guaranteeing that the benefits generated are additional (compared to the baseline without reuse), permanent over time, and verifiable under the methodological principles of VWBA 2.0 and certification frameworks such as Aqua Positive or CDP Water.
Project implementation is organized into three technical phases that progressively coordinate diagnostics, infrastructure, and monitored system operation, ensuring traceability, additionality, and permanence of water benefits.
Stage 1: Technical Diagnosis and System Engineering (Months 0–6) This phase includes comprehensive characterization of secondary effluent from the Huesca WWTP using automatic sampling equipment and laboratory analysis for physicochemical parameters (pH, conductivity, total suspended solids, BOD₅, COD) and microbiological indicators (total coliforms, E. coli). Based on this data, the hydraulic design of the tertiary system, sizing of ultrafiltration and UV units, and selection of materials and equipment are defined.
Simultaneously, documentation for the required administrative permits is prepared, including reuse authorization from the Ebro River Basin Authority and the Aragon health authority. Planning for the dual distribution system (agricultural and urban) is also carried out, identifying connection points with existing networks.
Stage 2: Construction and Technology Installation (Months 6–12) This stage includes civil works for tertiary system installation: foundations, channels, technical chambers, and storage tanks. Membrane ultrafiltration units (cut-off < 0.1 µm), UV disinfection systems, inline chlorination, and inline sensors for turbidity, free chlorine, UV transmittance, flow, and pressure are installed.
The SCADA digital monitoring platform is configured and launched, integrating all sensors in real time. Leak tests, instrument calibration, hydraulic load tests, and dry-run validation are conducted. System outlets are connected to agricultural networks and municipal cisterns through check valves, pumping stations, and pressurized pipelines.
Stage 3: Continuous Operation and Validated Monitoring (From Month 12) Stable production of Class A regenerated water begins. Key parameters are continuously monitored by SCADA-integrated sensors, with alerts triggered for any deviation. Preventive maintenance routines and in-situ cleaning protocols (CIP) for membranes are implemented.
Delivered volumes are recorded using electromagnetic flow meters, and quarterly validation of microbiological and physicochemical quality is performed by accredited laboratories. All records are stored in auditable databases, and reports are issued for external verification under VWBA 2.0. This stage ensures continuous benefit generation, traceability, and regulatory-compliant, efficient, and resilient system operation.
This project proposes a structural transformation of treated effluent management at the Wastewater Treatment Plant (WWTP) by converting it into a safe and traceable regenerated water resource suitable for advanced agricultural irrigation and non-potable urban uses. Located in the Isuela River sub-basin within the Ebro River Basin, the WWTP currently discharges effluent into the receiving body without reuse, in a regional context of growing water stress due to pressure on conventional sources, recurrent droughts, and intensive agricultural and urban demands.
The initiative follows the Volumetric Water Benefit Accounting (VWBA 2.0) framework using Appendix A-4 to quantify verifiable benefits generated by replacing potable or surface water withdrawals with regenerated water. The intervention includes the installation of a tertiary treatment line consisting of membrane ultrafiltration, UV disinfection, and residual chlorination, capable of producing Class A sanitary quality water in accordance with Royal Decree 1620/2007 and its update RD 1085/2024.
The treated water will serve two differentiated uses: (1) distribution to agricultural irrigation networks connected to the Flumen Canal area, and (2) supply to urban green areas, municipal facilities, and street cleaning through an independent network. All operations will be monitored via a SCADA platform integrating quality sensors (turbidity, chlorine, UV) and flow meters, allowing full traceability and external data validation.
Implementation is structured in three phases: first, technical diagnostics and the design of the hydraulic and sanitary system; second, infrastructure construction, equipment installation, and digital monitoring setup; and third, continuous system operation and validated control. Quarterly external audits will be conducted to ensure regulatory compliance, permanence of water benefits, and verifiability under VWBA 2.0 and platforms such as Aqua Positive.
The project directly contributes to restoring hydrological balance in the Isuela River sub-basin by reducing discharges and pressure on aquifers, while strengthening agricultural and urban resilience to climate change. Through a replicable technological solution, institutional cooperation, and collaborative water governance, the intervention consolidates a circular water economy model that delivers long-term environmental, social, and operational benefits.
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