David Sedlak

The creation of treatment systems capable of removing contaminants from water has been one of the most impactful achievements of environmental engineers. Because regulations usually assume uniform temporal performance and water infrastructure tends to be built in places where space is limited, the technologies used in modern treatment plants usually consist of mechanical devices (i.e., unit processes) for which conditions are rigorously controlled. In contrast, nature-based treatment systems employ physical, chemical and biological processes to improve water quality in larger spaces. They also exhibit temporal fluctuations in performance. If environmental engineers can develop the ability to predict, manipulate and enhance the performance of nature-based treatment systems, it may be possible to reduce the costs of this approach while simultaneously providing co-benefits that are increasingly important to decision makers and members of the public. To illustrate the potential for making nature-based treatment systems a more attractive option, this talk examines the treatment of effluent-dominated surface waters and reverse osmosis concentrate from water recycling projects with two new types of constructed wetlands. By understanding the mechanisms of contaminant removal, quantifying co-benefits and realistically articulating the tradeoffs associated with these systems, environmental engineers may be able to address some of the world's greatest water challenges.