Uptake of 15N by macrophytes in subsurface-flow wetlands treating domestic wastewater.
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.
Weaver
R W
RW
Department of Soil & Crop Sciences, Texas A&M University, College Station 77843-2474, USA.
Lane
J J
JJ
Johns
M J
MJ
Lesikar
B J
BJ
D017753:Ecosystem; D005068:Eutrophication; D009584:Nitrogen / Q000378:metabolism / Q000493:pharmacokinetics*; D009587:Nitrogen Isotopes / Q000493:pharmacokinetics; D010944:Plants; D014865:Waste Disposal, Fluid; D014872:Water Movements
D009587:Nitrogen Isotopes; D009584:Nitrogen