SoW & FloW – Green Walls that Filter Wastewater

Living walls are increasingly becoming tools for green climate adaptation in the urban context, but distribution efforts are dampened by high investment and operational costs. Those costs are derived mainly from designing and manufacturing unique equipment for such new projects. A system using wastewater could relieve some of these costs by decreasing their irrigation and fertigation needs. Muuras is developing helophyte filters integrated into living wall systems that can readily be attached to any wall surface, with the ultimate purpose of local water recycling. Additionally, based on the fact that Muuras is a pre-engineered company, their product is modular, which means that a considerable advantage is recognized regarding the decreased capital cost. To realize scalable implementation of such a system, research with regards to the purification capabilities of lightweight substrates and small wetland plant species is imperative. In SoW & FloW, the NHL Stenden Water Technology Professorship proposes a collaboration between two SME’s (Muuras, Greenwave Systems) and a company (DeSaH), to evaluate a selection of substrates and endemic plant species based on their capability to use domestic wastewater as an irrigation source.

Eindrapportage

Sow & Flow project aimed to determine the feasibility of implementing vertically constructed wetland as a
decentralized and circular wastewater treatment solution.
The project could meet relevant water quality standards for reuse and/or disposal into surface water. The
experimental setup was built and it worked as intended, showing that the objective of constructing a system
that is, at the same time, a green wall and a vertical wetland is feasible. The results of the greywater treatment
provided a better understanding of the efficiency of this type of system.
Furthermore, with all the auxiliary tests, the system’s hydraulics and biological strength were also better
understood. Each one of the substrates was efficient in pathogens and physicochemical pollutants removal.
The reuse application of the treated greywater was evaluated for each parameter, and it provided a clear vision
of how close a Green wall/vertical wetland system can get to any of the proposed reuse applications. Some of
the measured parameters fitted the reuse standards, and other were at least close to the required values, so
the common pre- or post-treatment techniques used with greywater can be applied as a tool to enhance the
system‘s efficiency or a bigger system.
Lastly, the implementation of the system studied on a real building facade was assessed and it showed that it
is feasible to connect it to a building if it is greywater ready. Depending on the scale it is necessary to add
more greywater to lower modules to prevent nutrient deficiency. The amount of greywater needed in the study
case was only a part of the building’s greywater production. Adding a vertical wetland on the facade can have
an effect on the building climate, as it improves the microclimate and functions as thermal and noise insulation.