Municipal wastewater effluent is becoming increasingly important both as a potable water supply and a habitat for aquatic organisms. However, recent reports linking chemical contaminants in wastewater effluent with adverse impacts to fish as well as decreased confidence of the public in the safety of potable water supplies has led to a need to remove trace concentrations of organic compounds from effluent. While advanced treatment systems, such as reverse osmosis membranes, can remove many contaminants, high costs, energy consumption and production of wastes are likely to limit their future application. Despite a lack of knowledge about their design or efficacy, treatment wetlands are being installed worldwide as an alternative means of removing trace concentrations of organic contaminants from wastewater effluent. The principal objective of this project is to develop an understanding of the mechanisms of contaminant removal in treatment wetlands that will allow engineers to predict treatment efficiency and to optimize the removal of specific contaminants.
The intellectual merits of the project are related primarily to efforts to test hypotheses about mechanisms of contaminant removal. Through the use of a custom-built treatment wetland system and a suite of probe compounds that can be used to discriminate between different removal mechanisms, we will advance the state of science in treatment wetland design and operation. Experiments will be conducted to assess the role of macrophytes that serve as substrates for microorganisms in the biotransformation of wastewater-derived contaminants. By manipulating the types of plants and the rates at which carbon is delivered to the wetland, we hypothesize that it will be possible to enhance the attenuation of chemical contaminants. Experiments also will be conducted to assess the potential for operating shallow wetlands in a manner that enhances the removal of contaminants through photochemical reactions. By coupling wetland cells that rely upon different attenuation mechanisms, it will lead to the development of a low maintenance, inexpensive treatment system that effectively removes a broad suite of compounds.
The broader impacts of the project are related to two aspects of the research. First, the project will engage the community where the field experiments are being conducted by enlisting volunteers as research participants and as partners in communicating our findings to the public. If the research shows that effective treatment wetlands can be built, the town is likely to build a full-scale treatment wetland that will serve as a model for communities interested in sustainable solutions to challenges posed by wastewater-derived contaminants. The second way in which the project contributes to NSF's broader impacts objective involves the training of students from traditionally underrepresented groups, by including undergraduates in an innovative program that provides mentorship and support to enable students to pursue advanced degrees.
