Carla Campbell, a doctoral candidate in civil engineering, will defend their dissertation titled “Nutrient Fate, Mass Balance, Species Selection, and Plant Management Strategies with Floating Treatment Wetlands.” Their advisor, Dr. Mark Fitch, is an emeritus professor in the civil, architectural and environmental engineering department. Their co-advisor, Dr. Dev Niyogi, is  a professor in the biological sciences department. The dissertation abstract is provided below.

Excess nutrients in shallow urban ponds can lead to harmful algal blooms, low dissolved  oxygen, and internal phosphorus cycling. These effects can compromise municipal water  supplies and cause negative impacts on fisheries and recreation. Floating treatment  wetlands (FTWs) show promise to mitigate surface water nutrient pollution. However,  despite recent research, many aspects of FTWs remain poorly characterized. The  contribution of FTW components to nutrient removal, local species selection, and plant  management strategies were the focus of this dissertation. Mesocosm experiments  revealed that the combination of plants and coir fiber growth media in FTWs appeared to  positively affect plant biomass gain and nutrient removal from water over controls  containing only floating mats. In species-specific nutrient removal experiments,  pickerelweed, softstem bulrush, and southern blueflag iris reduced nutrient  concentrations to a greater degree than controls. While plant biomass gain was not  significantly different than controls, there was significant total phosphorus (TP) and total  nitrogen (TN) gain for pickerelweed, and TN gain for bulrush compared to controls.  Bulrush also showed greater total dissolved nitrogen removal compared to controls. Results of a plant management study performing aerial harvest, whole-plant harvest, and  passive management of FTW macrophytes suggested harvesting may not benefit FTWs in the short term. Simple passive management of mesocosms led to very low nutrient  concentrations through mid-December. TP mass in settled detritus in controls suggested that algae and bacteria played a significant role in reducing TP in those controls while  plants had greater influence on TP reduction in planted FTWs.