Use of Vertical Greenery Systems for the domestic scale treatment of greywaters for fit-for-purpose reuse. Applicability and future prospects.

Abstract Only less than 1% of the Earth’s water is fit for human activities. Domestic consumption accounts for roughly 20% of all uses of water, adding pressure to the increasing water scarcity stress. Water intakes of residential buildings for all everyday uses are constituted by a high-quality resource, which is either costly to produce or conspicuous in amounts to withdraw from natural sources. The present proposal aims to test the feasibility of the application of decentralized greywater treatment strategies, based on the use of vertical greenery systems integrated into residential buildings to assess both the optimal scale of application in residential settlements and a comparative analysis on reclaimed water resource savings. The aim is to promote the circular use of water resources by allowing for fit-for-purpose employment, thus reducing the overall intake due to the residential sector. The methodology hereby proposed has been developed using as a case study the most widespread residential typologies in the Southern Italian context, such as single detachment, row houses, low and medium-rise apartment buildings. The result is the proposition for each residential typology of a retrofitting strategy that employs the integration of a green infrastructure inside the residential spaces. Until now, the Mediterranean context has been characterized by limited use of strategies directed towards the efficient employment of water resources, since the mild climatic conditions have always provided for an adequate amount of freshwater. Therefore, limited studies have been carried out on the application of those strategies in Mediterranean landscapes. However, the rapid shift in precipitation patterns due to climate change has defined the need to quickly embrace new strategies, systems, and technical solutions for improving water use efficiency and promoting reuse.