MULTISOURCE D1.3 - Pilot Evaluation, including ENTS Pilot Factsheets

This Deliverable 1.3, “Pilot Evaluation, including ENTS Pilot Factsheets” presents a comprehensiveassessment of the seven nature-based solution (NBS) pilots implemented under the MULTISOURCEproject. Moving beyond the monitoring focus of Deliverable 1.2, this report synthesizes insights fromacross the pilot sites to reflect on design performance, treatment outcomes, co-benefits, challenges, andlessons learned for future implementations. The evaluation integrates findings from several workpackages (WP1–WP5), providing a multi-dimensional perspective on the pilots’ technical, environmental,and social impacts: hydraulic and treatment performance data (WP1), risk assessments (WP2), businessmodel analyses (WP3), and life cycle and co-benefit assessments (WP4). The report combines bothquantitative and qualitative findings and is structured around cross-cutting discussion sectionsaccompanied by individual pilot factsheets. Each pilot is examined through a harmonized factsheet andanalyzed in relation to system typology, pollutant removal, risk reduction, and reuse readiness. Whilesystems differ in influent type and local objectives, common themes emerged, such as the value ofmodular designs, stakeholder engagement, and monitoring technologies.The accompanying pilot factsheets are intended for a broad audience, from researchers and waterprofessionals to planners and citizens. They summarize each system’s design and performance,supporting replication and knowledge transfer. Datasets will be made available via Zenodo, and scientificpublications are underway to extend the project’s legacy beyond its formal end.All pilots were operational for at least one year, and most of them for over two years, allowing for theobservation of seasonal variations and a range of operational conditions. The evaluation confirms thatthe pilots generally met their primary treatment objectives, whether for greywater reuse, stormwatercontrol, or combined sewer overflow (CSO) mitigation, while also delivering significant co-benefits suchas biodiversity enhancement, climate adaptation, and public engagement.Key findings include:• High treatment efficiency for conventional pollutants (TSS, BOD, COD), with several pilotsachieving over 90% removal.• Variable but promising performance on nutrients (nitrogen and phosphorus), heavy metals,organic micropollutants, and microplastics, with systems showing adaptability throughhybridization or post-treatment additions (e.g. ozonation).• Demonstrated pathogen reduction in multiple pilots, supporting safe water reuse for toiletflushing and irrigation.• Measurable co-benefits including educational outreach, temperature mitigation, increased greencover, and stakeholder engagement, essential to urban acceptance and NBS mainstreaming.• Operational robustness in both temperate and cold climates, with strategic design adaptationssuch as effluent recirculation, modular configurations, and smart aeration.Challenges encountered include infrastructure constraints, stakeholder dependency for monitoring,limited reuse infrastructure, and regulatory misalignment, particularly for decentralized reuse schemes.Lessons learned emphasize the need for flexible design, clear ownership models, and co-designedimplementation strategies with local actors.This deliverable contributes to the formulation of design and replication guidance (linked to WP4Nat4Wat tool and book), supporting the wider uptake of NBS in European and international contexts. Theaccompanying pilot factsheets provide accessible, transferable knowledge for practitioners, planners,citizens and policymakers, facilitating technology sharing and cross-fertilization within and beyond theMULTISOURCE network.