Roof runoff quality in view of its utilization and discharge : the effect of material leaching and treatment possibilities

An increasing water demand, in combination with a decreasing amount of qualitative fresh water, is a major driving force in the search for alternative water sources. Rainwater, and more specifically roof runoff, is one of these alternatives. Although rainwater runoff is generally presumed to be a relatively clean source of water in terms of physicochemical quality, an extensive literature review in the scope of this doctoral research revealed that roof runoff could be potentially contaminated by a wide range of organic as well as inorganic contaminants. In the same literature review, both atmospheric deposition and material leaching were identified as important contaminant sources. Nevertheless, for many materials, information on leaching was scarce. Therefore, this doctoral research aimed to contribute to the knowledge in this field by using laboratory leaching tests, which allowed to identify contaminants, benchmark materials and identify the dominant leaching mechanisms. In addition, also the leaching behavior under real outdoor conditions was studied. This allowed to identify the effect of external factors such as the preceding meteorological conditions. In order to study these outdoor conditions, a pilot scale set-up consisting of different small roofs equipped with different roofing materials was used. As also atmospheric deposition was considered here, roof runoff quality from different roofing materials was evaluated in view of its utilization and discharge. Next to the identification of contaminants and contaminant sources, this doctoral research also investigated the potential to produce water fit-for-use from roof runoff by applying conventional treatment and disinfection techniques