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 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 show that these wastewater treatment and reuse systems can be integrated in different community projects, demonstrating their broader applicability beyond site-specific contexts. Local phosphorus fertilizer demand can be fully covered, as well as a considerable proportion of the nitrogen fertilizer demand (up to 90% demand coverage rate). At Cambium, the reclaimed water of the green wall system can nearly supply all water demands, achieving up to 90% coverage by utilizing only 20% of the available wastewater, with the limitation being to prevent overfertilization due to the high nutrient content in reclaimed water. For larger areas, combining it with rainwater harvesting is recommended to fully address water needs. 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. Integrating anaerobic digestion further enhances nutrient recovery and supports sustainable energy generation. Overall, green wall treatment systems can effectively close local water and nutrient cycles, enhancing resilience and sustainability in local food production. • Green wall treatment systems enable effective water and nutrient reuse • On-site water reuse offers high nutrient coverage across different crops • Local water and nutrient demand can be met in different geographical contexts • On-site wastewater treatment has advantages over rainwater and composting • Mass flow analysis supports sustainable management of treated wastewater