Green walls for water purification

Title of the research project

SUPERGREEN - SUstainable Purification of wastewatER with GREEN walls

Scientific area 

Water treatment, Circular Economy, Nature-Based Solutions

Project coordinator

Fulvio Boano


Wastewater treatment represents a big challenge for sustainability, because conventional technologies have a high cost, both in economics and energy consumption terms.  The Supergreen project investigated the possibility to reuse diluted greywater, treated in green walls, as nutrient-rich irrigation source or for local recycling.

Description of the research project 

Approximately 70% of domestic wastewater sent to treatment is actually made up of diluted greywater, which is discharged from showers, bathtubs, washing machines, and hand washing sinks and whose contaminant content is much lower than in blackwater from toilets. Separating different types of wastewater would make possible to locally treat greywater that could provide a local source of reusable water available for other purposes, such as toilet washing or irrigation, which would otherwise employ clean water. This reuse would so turn greywater from a waste product into a resource, in a circular economy perspective.  

SUPERGREEN  investigated the possible use of green walls, which are vegetated vertical elements that exploit unused building surfaces,  for diluted graywater treatment. Additional benefits would be greening, improved aesthetics, and shading. SUPERGREEN  analyzed different mixtures of conventional and innovative materials as growing media, to identify the most efficient green wall configuration.

Impact on society 

SUPERGREEN contributed to a relevant technology advancement about  wastewater treatment, by splitting the treatment of graywater at the building or block level and the treatment of blackwater in conventional plants. Urban development strategy planners could therefore optimize the global wastewater management.

SUPERGREEN's socio-economic impacts concern:

  • the generation of workplaces created by the implementation of the proposed technology on full-scale; 
  • an overall reduction of wastewater treatment environmental and economic costs and
  • the reuse of reclaimed greywater and consequently a reduction of tap water consumption.

Research results

The project was organized into two phases: (1) Testing ans selection of optimal plants and materials to build the green wall; (2) building a pilot plant in an open space at Politecnico di Torino and realize experimental tests.

Results showed an excellent capacity of the green wall to remove organic matter due to the use of detergents but also bacteria such as Escherichia Coli.

We highlight, among the main scientific and socio-economic impacts:

·       Presentation of the project to 6 international conferences

·       Publication of 4 scientific papers, with a review paper about nature-based solutions for water treatment

·       New collaboration with Royal Military College of Canada

·       Supergreen presentation to the Italian television RAI programme Memex Galileo

Short CV of project coordinator 

Fulvio Boano, Master degree in Environmental Engineering and  Ph.D. in Hydraulic Engineering at Politecnico di Torino is Associate Professor in Hydraulics at the Department of Environment, Land, and Infrastructure Engineering of Politecnico di Torino. He has been visiting student at Northwestern University, IL (USA). He is author of more that 40 papers in international peer-reviewed ISI journals.  In 2011 he has won the Excellence award for young researchers from Politecnico di Torino.

 His main research interest is to understand how natural processes such as self-depuration can be harnessed to improve water quality and reduce anthropic impact on the environment. 

Gruppo di lavoro @Polito

Silvia Fiore, Professor

Luca Ridolfi, Professor

Alice Caruso, Research fellow

Elisa Costamagna, PhD student

Marco Chiappero, PhD student


Academic partner: Instituto Superior Técnico, Universidade de Lisboa, Portugal

Non-academic partner: Iridra, Italy

  • Budget: 141.463 euro
  • Start date: 15/09/2017
  • End date: 14/09/2019