Picard, Christian R. (2004) Nutrient removal in treatment wetlands at two different scales. MSc thesis, University of Akron, Ohio. (Fraser)

Abstract:

            Eutrophication is a worldwide water quality problem. Wetlands are known to naturally remove nutrients from inflow sources through their unique characteristics and biogeochemical processes. Treatment wetlands are constructed systems designed specifically for the purpose of treating wastewater. These systems have been designated as a possible solution to issues concerning eutrophication. It is evident that plant composition and temperature play important roles in the nutrient removal efficiency of these wetlands. However, the interactions between these variables are not well understood. This project investigates the seasonal efficiency of treatment wetlands using microcosms. Each microcosm contains one of six vegetation treatments. The vegetation treatments are as follows: unplanted, planted with one of four species in monoculture or planted with an equal abundance of all four species. The species of wetland plants being used are Carex lacustris, Scirpus validus, Phalaris arundinacea and Typha latifolia. Microcosms are also being subjected to two temperature treatments. These treatments include insulated microcosms and exposed microcosms. A constant nutrient solution containing 56 mg/L N and 31 mg/L P is being added to all microcosms three times a week. Water samples are analyzed monthly for total nitrogen and total phosphorous. Microcosms exhibited a typical pattern of seasonal nutrient removal with higher removal rates in the growing season and lower rates in the winter months. In general, planted microcosms outperformed unplanted microcosms. However, unplanted microcosms also removed large amounts of nutrients. Consequently, plants probably play a supplemental role in nutrient removal and act primarily as ecosystem engineers by promoting microbial activity. Among the plant treatments, Carex lacustris was the least efficient. Insulated microcosms often were more efficient in the winter and early spring months. Although a seasonal pattern of nutrient removal was observed, this variation can be minimized through planting and insulation of wetlands. 

Full Thesis on file at UA.