lluted water originating from household sinks, basins and showers. This differs from heavily polluted sewerage water, that is generated from sources such as toilets and washing machines. Common pollutants found in greywater include surfactants from soaps and oils and skin cells from humans.

Several studies have looked at the effectiveness of green walls in laboratory environments, using synthetic greywater (artificially preparing greywater using soap, oil, etc). However, the green wall erected at WRL is one of the first research-based green walls in Australia to use real greywater. The greywater is supplied from the hand washing basins and shower, located in the main amenities block of WRL’s administration building, which involved diverting existing plumbing from the bathroom to the exterior of the building, collecting the greywater in a pit (reservoir), and then being pumped to the irrigation system for the plants.

It is hoped that the pollutants from the greywater can be removed by, and serve as a nutrient source for, the growing plants. Absorbance onto the media will also have an impact on removal.

A recent study conducted by PhD student, Hafiz Muhammad Abd-Ur-Rehman shows that with the selection of right media, green wall systems are able to remove xenobiotic organic compounds that are of health concern and commonly found in greywater.  

Pollutant remediation via this ‘green’ passive method is an example of a Nature Based Solution (NBS), a growing field of study and engineering aimed at improving the sustainability and appearance of urbanised areas. Such solutions should have a better environmental impact compared to industrial remediation at a water treatment facility. They cool the surrounding area via transpiration of the plants, and the growth of aesthetically pleasing greenery on an otherwise bare concrete/brick/etc façade is another advantage.  

This green wall presents the first showcase technology of a planned Research Innovation Showcase Precinct (RISP), built and maintained at the Water Research Laboratory on UNSW Sydney’s Manly Vale campus. RISP will highlight implementations of novel technologies, e.g., water treating green walls, stormwater rain gardens, micro-hydro turbines, etc. This space will evolve over time and adopt new technologies as UNSW research progresses. It will provide the opportunity for industry and government to experience first-hand how novel technology functions, what the benefits are and how UNSW research can be translated into real working systems. Every technology will be accompanied with a detailed explanation of system’s design, monitoring and maintenance needs. RISP will further provide a space for open discussion and project planning.

Many thanks to our team: Hafiz Muhammad Abd-Ur-RehmanDr Aaron ColussoDr Veljko Prodanovic and Dr Kefeng Zhang.

Further reading

Abd-ur Rehman, HM, Deletic, A, Zhang, K and Prodanovic, V (2022) "The comparative performance of lightweight green wall media for the removal of xenobiotic organic compounds from domestic greywater" Water Research, Volume 221, 118774, ISSN 0043-1354. https://doi.org/10.1016/j.watres.2022.118774.

Prodanovic, V, Hatt, B, McCarthy, D and Deletic, A (2020) "Green wall height and design optimisation for effective greywater pollution treatment and reuse" Journal of Environmental Management, Volume 261, 110173, ISSN 0301-4797. https://doi.org/10.1016/j.jenvman.2020.110173.

Prodanovic, V, Wang, A and Deletic, A (2019) "Assessing water retention and correlation to climate conditions of five plant species in greywater treating green walls" Water Research, Volume 167, 115092, ISSN 0043-1354. https://doi.org/10.1016/j.watres.2019.115092.