Human and environmental health risks and benefits associated with urban stormwater

For stormwater harvesting to achieve its full potential in mitigating water scarcity problems and restoring stream health, it is necessary to evaluate the human and environmental health risks and benefits associated with it. Stormwater harbors large amounts of pollutants and has traditionally been viewed as a leading cause of water-quality degradation of receiving waters. Harvesting stormwater for household use raises questions of human exposure to pollutants, especially human pathogens, which have the potential to cause large-scale disease outbreaks. These issues are compounded by uncertainties relating to the performance of stormwater treatment technologies in pathogen removal. Quantitative microbial risk assessment provides an objective risk estimate based on scientific data and the best assumptions, which can be used to educate and instil confidence in stakeholders of the practice. Although limited, human health risk studies have positively supported the use of minimally treated rainwater and stormwater for some non-potable applications. In addition to the well-known benefit of preserving the stream hydrology and ecology, wetlands used for harvesting stormwater can also provide new habitats for wildlife that benefit environmental health. A fundamental change from viewing stormwater as waste to resource requires the coordinated efforts in research, education, and effective communication.