Solids & Colour in Roof-water Preventing its Reuse and Technologies to Remove Them

Increased urbanisation throughout the world has led to an increase in the likelihood of flooding. Therefore, stormwater management has become an important issue. In the context of Auckland, New Zealand, stormwater is managed mainly to prevent nuisance and damage to other properties downstream. The installation of a detention tank is a common means to manage the stormwater flow from site. A dual purpose tank is also common especially in Stormwater Management Control Area, where the receiving network/watercourse is particularly sensitive to discharge. A dual purpose tank detains stormwater before slowly releasing it downstream, thus reducing peak flow issues. Retention volume is captured for the purpose of reuse, e.g., for laundry and toilet flushing. However, the question has been raised whether these stormwater tanks do serve their designed purposes. We have found several cases in which the tank owners were reluctant to use stormwater for toilet flushing and laundry. This reluctance was due to aesthetic reasons, specifically the dissolved colour present in the water that cannot easily be removed. They therefore turn off the tap once the Producer statement (PS4) has been signed off. In this work, case studies of how dissolved colour in water preventing the utilization of the harvested water will be presented. Furthermore, a detailed investigation on removal of colour from the water is demonstrated using ozonation and adsorption filters. Following the test, a pilot scale setup for rainwater reuse was installed in a building to monitor long term performance. The results will be shown during the presentation and are not included in this paper. It is the aim of this work to improve the quality of water and gain a better understanding of people’s perceptions toward reusing the harvested rainwater.