Associate Professor, Civil and Environmental Engineering Department, Washington State University, Pullman, Washington, USA
Enhancing Ammonia Removal in Constructed Treatment Wetlands
The presentation will begin with an overview of the nitrogen cycle and a discussion of nitrate removal in a constructed treatment wetland in Washington's Yakima Valley that treats row crop irrigation runoff. The presentation will then discuss results of a laboratory experiment to enhance ammonia removal via oxygen addition to surface-flow wetland mesocosms. While constructed treatment wetlands are efficient at removing nitrate from wastewaters, they are much less effective at removing ammonia. Oxygen addition was expected to alleviate this limitation. Oxygen addition increased ammonia removal rates by an order of magnitude. Oxygen addition also lead to a significant increase in ammonia oxidation potential in wetland sediment, with levels in oxygenated wetland sediments 2–3 orders of magnitude higher than those reported in the literature. Phylogenic analysis of sediment revealed substantial differences in microbial diversity in oxygenated and non-oxygenated wetlands, including the presence of ammonia-oxidizing bacteria (Nitrosomonas oligotropha) and denitrifying bacteria only in oxygenated wetland sediment. Results show that oxygen-activated nitrification wetlands, a hybrid of conventional oxygenation technology and wetland ecotechnology, hold promise in economically enhancing rates of ammonia removal and shrinking the wetland area needed to polish ammonia-dominated secondary effluent. The presentation will end with a brief discussion of a proposed field study to assess greenhouse gas emissions from a large constructed treatment wetland in southern California that treats nitrate-rich river water prior to percolation into a groundwater basin used for drinking water.
Marc Beutel is an associate professor in the Civil and Environmental Engineering Department at Washington State University, in Pullman, Washington, USA. He earned a B.S. degree in Civil Engineering from the University of California, Los Angeles, and a M.S. and Ph.D. in Civil and Environmental Engineering from the University of California, Berkeley. He has also worked as a staff engineer at a large water utility and as a senior engineer at a national water resources consulting firm. Dr. Beutel's research focuses on the control of dilute pollutants in surface waters, including mercury in lakes and reservoirs. He has published over two-dozen peer reviewed articles and has performed research funded by multiple agencies including the National Science Foundation. He can be contacted at email@example.com.