Performance of a felt based living wall with greywater irrigation using different indoor ornamental species

Vertical greening systems are becoming popular nature-based solutions for including vegetation in the built environment. However, one of the main concerns regards to their water requirements. The use of greywater for their irrigation can be a solution. While several studies have proven that using living walls as a biofilter can improve the quality of the greywater applied for their irrigation, the effects on the vegetation of continuous irrigation with greywater are still unknown. The main objective of this work is the assessment of the vegetation performance using different plant species in indoor living walls exclusively irrigated with greywater. For that, three species (Philodendron hederaceum, Spathiphyllum wallisii and Nephrolepis exaltata) planted on felt-based living wall modules were tested for 30 weeks. Information regarding the main water quality parameters (pH, electrical conductivity (EC), concentration of major cation and anions, chemical oxygen demand (COD) and biological oxygen demand for an incubation period of 5 days (BOD₅) were obtained and the development of the vegetation was monitored. The three species adapted well to the continuous irrigation with greywater, though S. wallisii showed a slight decrease in green cover at the end of the study. As the greywater was recirculated, EC increased with time, but no clear effects on growth and appearance were observed in the plants. This suggests the need of periodically replacing the greywater used for irrigation or including irrigation events with freshwater.