Uptake of 15N by macrophytes in subsurface-flow wetlands treating domestic wastewater
R W Weaver1, J J Lane, M J Johns
1Department of Soil & Crop Sciences, Texas A&M University, College Station 77843-2474, USA.
Abstract:
Constructed subsurface-flow wetlands are becoming more common for on-site treatment of domestic wastewater to provide secondary quality effluent. Macrophytes are generally added to wetlands to increase treatment efficiency but their role in reducing N content is controversial. Our investigation utilized two subsurface-flow wetlands to determine the efficiency of different macrophytes in uptake of 15N labeled ammonium sulfate. Macrophytes in Wetland 1 recovered 35% of the added N in their shoots but only 5% of the added N was recovered in the shoots and roots in Wetland 2. A major difference for the two wetlands was N and hydraulic loadings. Wetland 1 received 7.5 Kg N ha(-1)d(-1) and Wetland 2 received 16.9 Kg N ha(-1)d(-1). Retention time for Wetland 1 based on pore volumes was 2.9 d and for Wetland 2 it was 1.2 d. The retardation factor for NH4+ was approximately 2.5 for both wetlands and the breakthrough curves indicated lack of plug flow. The importance of macrophytes in taking up NH4 appeared to dependent on N and hydraulic loadings.
Related Concept Videos
Bioremediation
Overview of Nitrogen Metabolism
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
Environmental Applications of Microorganisms
Microbial Bioremediation of Uranium
Microbial Wastewater Treatment
Biological Treatment of Effluent and Waste Water


