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Green walls: water consumption & quantity and quality of drain water.

Nowadays, more and more buildings with green walls appear in the street scene. To allow plants to grow on a wall, essentially two different system types are used. Within the soilbound system, the so-called Green Facades, plants root in het open ground at the base of the wall and grow on it whether or not supported by a climbing aid. Within wall-bound systems, so called Living Wall Systems, plants root in a substrate that is maintained on the wall in one way or another (flower box, geotextile, module,...). Most often, plants in living wall systems depend on an irrigation and fertilization system for their water and nutritional elements. Although many manufactures are active on the market, each with their own system, still many questions remain on the actual successful and durable implementation of these systems. One of these questions is about their real water consumption and the amount and quality of drain water (excess of irrigation water coming out of the system) and what can still be done with it. To answer this question, a test setup, consisting of nine different living wall systems available on the market, was built. It was equipped with an irrigation and fertigation system allowing an individual program for each wall. A flow logger allowed us to monitor the water consumption of each wall individually. Also, the drain water coming from each wall was collected for quantification and quality analysis. Within this analysis part, several parameters were looked at which each have their importance for either storage, reuse or evacuation to the sewer system of this drain water. Within this paper, the results of a first monitoring campaign will be presented.