Submitted to: International Conference on Wetland Systems for Water Pollution Control
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2008
Publication Date: November 1, 2008
Citation: Ro, K.S., Hunt, P.G., Johnson, M.H., Matheny, T.A., Reddy, G.B. 2008. Trace gas exchanges of marsh-pond-marsh constructed wetlands treating swine wastewater [abstract]. In: Proceedings of the 11th International Conference on Wetland Systems for Water Pollution Control, November 2-7, 2008, Indore, India. Technical Abstract: Marsh-pond-marsh (MPM) constructed wetlands have been used effectively to treat wastewater from swine anaerobic lagoons. However, at high N loading rates, a significant portion of ammonia in the wastewater could be volatilized into the atmosphere. To mitigate ammonia emission, ponds can be covered with floating wetlands. Constructed wetlands may also be a significant emission source for greenhouse gases such as CH4, CO2, and N2O due to prevailing anaerobic/anoxic conditions. This paper reports on the ammonia and greenhouse gas emissions and oxygen transfer efficiencies of the MPM constructed wetlands with or without floating wetlands. Two of four MPM constructed wetlands were covered with floating wetlands consisted of recycled rubber mat on which American bulrush (Schoenoplectus americanus) was planted. Ammonia and greenhouse gas emissions were measured using a wind tunnel and a static chamber with a photoacoustic multigas analyzer. Oxygen transfer efficiencies of the aerated ponds, both open and covered, were estimated by conducting the ASCE standard oxygen transfer tests in a 400L tank with or without the recycled rubber mat. Water quality parameters such as alkalinity, TSS, COD, TKN, pH, DO, NH3, NOx, and TP were also measured. Nitrous oxide emission was negligible while ammonia volatilization rates ranged from 0.01 to 7.7 kg-N/ha/d. Carbon dioxide emission rates varied from 109 to 569 kg/ha/d. Diffused oxygen transfer in the ponds with floating wetlands were as efficient as that of open ponds with significantly reduced ammonia emission from ponds with floating wetlands.