In the context of growing urban population and demand for gradually depleting resources, coupled with environmental crisis, a shift towards circular and more efficient management of water, food and energy in cities is a necessity. REUCITY delivers knowledge, tools and practical approaches in this direction. It provides options for restructuring and/or decentralizing the urban water infrastructure to facilitate the extraction of water, nutrients and energy from wastewater and enable their reuse in food and energy systems on site. Thus, on one hand the resources can be used for increasing the urban resilience and on the other hand this management assists the existing infrastructure by reducing the waste load.

In short, REUCITY proposes closedloop management of resources in cities, which comprises variety of concepts with the same goal. Grey water separation (all wastewater except the one from toilets) and reuse is one of those management concepts, which aims to close one part of the water cycle. REUCITY presents a greywater (GW) reuse concept based on membrane bioreactor (MBR) technology. The concept: GW separation-treatment-disinfection-storage-reuse is evaluated for hotels in densely urbanised areas. The results show good performance, economic feasibility and positive environmental impacts.

In spite of the clear benefits of closedloop concepts, there are quite a few obstacles that need to be overcome for their wider implementation. A decision support system called LoopAdvisor aims to assist the decision-making process for implementing the REUCITY vision, i.e. closedloop concepts for resources management in cities. It is composed of a database including information about technologies, economics, legislation, products and stakeholders, and combined with tools and engines capable of intelligent search for information in the database guided by selected stakeholders’ requirements. The goal is to propose and rank several alternatives for achieving the objectives related to closing water and nutrient cycle at building and neighborhood spatial scale.