Rainwater harvesting from roofs for non-potable reuse

The use of harvested rainwater is one approach for freeing up potable water for more essential applications such as drinking water. Roofs are a readily available surface area that can easily be adapted for rainwater collection; however, some surface materials are not benign and may be more likely to leach contaminants than others. For this study, several commonly available roofing materials were evaluated for runoff water quality for approximately a year and a half. The runoff samples were analyzed for zinc, copper, pH, total phosphorus, total nitrogen, and conductivity. Data from this study showed that traditional roofing materials such as uncoated galvanized metal and treated woods are more likely to leach heavy metals, nitrates, and ammonia than other materials such as green roofs and coated metal roofs. Currently, the water quality data is being compared to recorded storm data and inter-event times to determine what factors affect the quality of the runoff.