Analysis of Material Flows and Resource Potential of Decentralized Water Management: On-Site Water and Nutrient Reuse in an Austrian Eco-Village and its Upscaling to Urban Environments

Urban water scarcity and growing agricultural water demands underscore the urgent need for advanced sustainable strategies in water and nutrient management. This study examines the potential of green wall treatment systems for on-site agricultural water and nutrient reuse to create local circular food systems. Two case studies are evaluated: Cambium eco-village (rural area of Styria, Austria) and Zukunftshof urban farm (city of Vienna, Austria), with scenarios involving green wall treatment systems as well as rainwater and compost use. A material flow analysis approach is used to investigate the efficiency of these scenarios in meeting agricultural water and nutrient demands. The findings demonstrate that treatment systems can effectively be integrated in both very different community projects to address agricultural water and nutrient needs, establishing their broader applicability beyond site-specific contexts. The phosphorus demand of local agriculture can be fully covered, as well as a considerable proportion of the nitrogen demand. For smaller agricultural areas like Cambium, the green wall system can nearly meet all water demands. For larger areas, combining it with rainwater harvesting is recommended to fully address water needs. In general, the use of reclaimed wastewater offers advantages over rainwater collection as source of water and composting as source of nutrients due to consistent availability and reduced storage requirements. Combining treatment systems with anaerobic digestion further enhances nutrient recovery and facilitates sustainable energy generation. Overall, green wall treatment systems have the potential to effectively close local water and nutrient cycles and support more resilient and sustainable local food production.