17 th International Conference on Environmental Science and Technology Athens, Greece, 1 to 4 September 2021 CEST2021_00811 Green walls for greywater treatment and reuse in Mediterranean countries MARTINUZZI N. 1 , RIVAI K. 1 , RIZZO A. 1,* , MASI F. 1 , SARNARI B. 2 and BOUSSELMI L. 3 1 IRIDRA Srl, via La Marmora 51, 50121 Florence, Italy 2 EuroMediterranean Center for the Sustainable Development (SVI.MED.), via Teocrito 6A Ragusa Italy 97100 3 Wastewater and Environment Laboratory, Center of Researches and Water Technologies of Borj-Cedria (CERTE) Tourist Route of Soliman, Nabeul, PO-Box No. 273, 8020, Soliman, Tunisia *corresponding author: e-mail: rizzo@iridra.com Abstract This paper describes four case studies in which two types of green walls are implemented for greywa ter treatment and reuse in Mediterranean countries, Living walls and Green façade. Green walls are vertical vegetated systems that can be integrated into urban environments, providing various benefits. The green walls described in this paper were implemented as part of the NAWAMED project in Mediterranean countries in public facilities with the aim of demonstrating the potential of Nature Based Solutions and reducing the use of potable water by reusing treated greywater. The pilot projects are located in Italy, Jordan, Lebanon and Tunisia, and the treated greywater is mainly reused for irriga tion and toilet flushing. In addition, technical indications a re provided to foster future implementations of green walls for this specific application and to disseminate sustainable water management schemes. Keywords: Greywater; Sustainable Water Management; Green Walls; Nature-Based Solutions. 1. Introduction Green Walls (GWs) are vertical vegetated systems, generally built along the walls of buildings, obtaining multiple benefits, such as thermal insulation, noise reduction or aesthetic improvement. Recently, these systems are starting to be investigated to also implement the additional purpose of treating greywater produced by the facility for reuse. The NAWAMED project aims at demonstrating the technical and economic feasibility of nature-based and low-cost solutions, to treat non-conventional water resources in schools, universities, and public facilities. To this aim, it was planned to implement real scale pilot installations for greywater/rainwater treatment and reuse in each participating country (Italy, Tunisia, Jordan a nd Lebanon), recovered greywater will be reused for different purposes, including toilet flushing and irrigation, therefore, reducing the consumption of potable water f or domestic uses. There are different types of GWs: they can consist of climbing plants planted in trenches along the walls, structures anchored to the walls with planted pots, or planted on the roofs and pending along the façade. Two types of GWs are implemented in the projects, Green façades (GFs) and Living walls (LWs), accordin g to the classification given by Bustami et al (2018) for greenery systems: Green façades are planted with orna mental a nd climbing plants; Living wa lls a re modular tray containers with pots filled with filling medium in which the vegetation grows. This paper wants to share the part of the preliminary experience of the NAWAMED project in designing GWs for the particular application of greywater treatment and reuse. This use of GWs is still at an infant stage of the technology, and it was principally studied in a few pilot research studies (e.g. Masi et al. 2016), as also recently reviewed by Boano et al. (2020). Therefore, NAWAMED also aims to push the technological readiness level of this solution with real full-scale demonstration sites, helping to address significant engineering challenges at full sca le that still needs to be answered. 2. Case studies 2.1. Ferla, Italy Coordinates: 37°07'06.6"N 14°56'12.0"E The Living Wall implemented in Ferla treats greywater (from sinks) produced by the middle school Istituto Comprensivo Statale “Valle dell'Anapo”, in Sicily, Ita ly, with a total of about 190 students. The system was designed considering to treat a greywater flow rate of 1.3 m 3 /d, about 260 m 3 /year, corresponding to 23% of the school’s water demand for toilet flushing. The LW covers an area of about 30 square meters (Figure 1), and is divided into 3 façades (north-west, north-east, south-east). The treated greywater is accumulated in an underground deposit a nd reused for toilet flushing and irrigation.