Living green wall - Wall2Water
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The “Living green wall” is an innovative system designed to collect, treat and reuse the greywater of the Istituto Comprensivo Statale Valle dell’Anapo in the Municipality of Ferla, in Sicily and the greywater of the student house “Les Jardins” in Tunis; it is constructed at the "Sustainable Water Management House- SWM House", pilot station of the Centre for Water Research and Technologies-CERTE located within the National Agricultural Institute of Tunisia (INAT) , in Tunis, Tunisia.
The green wall has been designed by IRIDRA and built in the Municipalities of Ferla and Tunis by SVIMED and CERTE, in the framework of the International project “Nature Based Solutions for Domestic Water Reuse in Mediterranean Countries” (NAWAMED).
Unlike the more common green facades that can be found in several cities today, the system treats the greywater from the school washbasins (Sicily) and the showers (Tunisia) and makes it reusable for toilet flushing, and for irrigation of fruit trees using jars at the edible garden (Tunisia). thus reducing the consumption of high-quality drinking water, .
Why is the system special?
In recent years, research and experiments have grown to allow the reuse of greywater, treating it with natural techniques, with solutions that use normally unused surfaces, such as walls and roofs, thus saving space on the ground. However, only a few cases have gone beyond the laboratory scale. Ferla and Tunis' Wall2Water are among the first non-experimental, but real-scale installations: new “green infrastructure” that offers multiple ecosystem services and aesthetic functions in urban areas by integrating a nature-based solution in a public building, in a place with a Mediterranean climate
How the treatment takes place
From a functional point of view, the system provides for the collection of water – mainly from the sinks (Ferla) or the showers (Tunis) – in a small tank from which it is pumped to feed the green wall, after pretreatment (Tunisian case). The water percolates inside the pots, where it undergoes a treatment process and, from here, is collected in a tank for subsequent reuse. The living green wall is composed of modules hanging from the wall made up of pots whose filling material favours the development of bacterial biofilm, the main agent of the treatment processes. The plant species hosted by the pots favour bacterial biodiversity and allow the water to be distributed uniformly in the pots, guaranteeing an effective treatment and an aesthetic and refreshing function. Before being sent to the toilet for flushing and resue, the treated water is disinfected with an ultraviolet lamp.
What are the system numbers in Ferla?
The green wall in Ferla covers an area of about 30 square meters, designed to maximize treatment capacity, facilitating maintenance by municipal technicians, thus reducing management costs. Approximately 1300 litres of water per day feed the system, producing treated water which is reused for flushing the toilets to replace precious drinking water. The estimate is about 1,000 litres of drinking water saved per year for each student (about 200).
The Istituto Comprensivo Statale Valle dell’Anapo is divided over two floors (upper floor about 120 students, ground floor about 70 students).The bathrooms of interest are a single block and is specular between the ground floor and first floor and the external wall of this block from the north-west, although not very exposed to the sun during the day and not very visible from the entrance, is the easiest wall to be managed for a retrofitting intervention for the treatment and recovery of greywater.
What are the system figures in Tunis?
The “Living Green wall for circular water” is designed to treat 2.2m3/day and covers a surface of 70m 2 around the SWM house. It delimits a relaxation area for students. The treated greywater is used for toilet flushing at SWM house after disinfection or to irrigate an edible garden nearby. A rainwater is collected in small tank to ensure the irrigation of the LGW during the summer period when students are in holidays and the greywater production is interrupted. Therefore, the operation of the wall will be adapted to the available water resource. The monitoring of the variation of LGW efficiencies in term of quantities and qualities will be conducted for long period by CERTE in order to include in this assessment all operation scenarios. Technical visits and training sessions are organized for technical transfer, multiplication and upscaling to technical water actors and national stakeholders.
What advantages does the system bring in Ferla?
The reuse of the greywater in the toilet flushing allows a saving of the drinking water supply equal to about 260 cubic meters per year, making it possible to cover about 25% of the water needs for the toilet flushing of the entire school.Discharges into the public sewer are greatly reduced by the amount of greywater recovered, i.e. reducing the volume of water discharged into the sewer daily by about 10%.
More than 100 professionals were involved in the implementation of the activities. Courses and technical visits have been organized to help professional and public authorities to replicate this experience; the green wall at the Ferla school has been monitored for more than a year to provide consistent data and the monitoring will continue for the next 5 years thanks to a Horizon Europe project (CARDIMED).
Fields of application
Treatment and reuse of NCW at urban level
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 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 scale that still needs to be answered.Target
Researchers, architects, water agencies, decision makers, professionals and water supply companies
Quantity of greywater produced by the building and possible reuse, according to the national legislationPreliminary knowledge required (if any)
Nature Based solution concept and types for the treatment of water as well as general operation/function principles
Decentralized and sustainable water system components
UV disinfection process
References/Online resources
https://www.enicbcmed.eu/projects/nawamed
https://www.pareteverdeferla.it/
https://bpinventory.com/best-practice/wall2water
https://bpinventory.com/best-practice/living-green-wall-circular-water
Boano, F., Caruso, A., Costamagna, E., Ridolfi, L., Fiore, S., Demichelis, F., Galvão, A., Pisoeiro, J., Rizzo, A. and Masi, F., 2020 (a). A review of nature-based solutions for greywater treatment: Applications, hydraulic design, and environmental benefits. Science of the total environment, 711, p.134731.
Boano, F., Caruso, A., Costamagna, E., Fiore, S., Demichelis, F., Galvão, A., Pisoeiro, J., Rizzo, A. and Masi, F., 2020 (b). Assessment of the Treatment Performance of an Open-Air Green Wall Fed with Graywater under Winter Conditions. ACS ES&T Water.
Masi, F., Bresciani, R., Rizzo, A., Edathoot, A., Patwardhan, N., Panse, D. and Langergraber, G., 2016. Green walls for greywater treatment and recycling in dense urban areas: a case-study in Pune. Journal of Water, Sanitation and Hygiene for Development, 6(2), pp.342-347.
Paul, U., Karpf, C. and Schalk, T., 2018. Hydraulic simulation of perforated pipe systems feeding vertical flow constructed wetlands. Water Science and Technology, 77(5), pp.1431-1440.
Contacts
Italy - Barbara Sarnari: 📧 b.sarnari@svimed.eu
Tunisia - Latifa Bousselmi: 📧 latifa.bousselmi.certe@gmail.com