Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2007
Publication Date: 3/22/2007
Citation: Poach, M.E., Hunt, P.G., Reddy, G.B., Stone, K.C., Johnson, M.H., Grubbs, A. 2007. Effect of intermittent drainage on swine wastewater treatment by marsh-pond-marsh constructed wetlands. Ecological Engineering 30:43-50. Interpretive Summary: Ammonia emissions can occur from constructed wetlands treating liquid animal waste. This is of particular concern in the pond sections of marsh-pond-marsh constructed wetlands. Our previous studies on continuously loaded marsh-pond-marsh constructed wetlands indicated that the pond sections did release more ammonia than the marsh sections at high loading rates. In an effort to reduce the ammonia emissions from the pond section of the wetlands, a project was initiated to determine if pulsing wastewater flow into the marsh-pond-marsh wetlands at different rates would increase oxygen and thereby reduce ammonia. One wetland was loaded for two weeks then no application the next week. The other wetlands were loaded for either three or four weeks with no application the following week. We found that the pulsing of the flow into the wetlands did not reduce the ammonia emissions. Ammonia emissions were about the same as without pulsing. However, we did determine that pulsing of flow into the wetlands did significantly increase the overall treatment efficiency of the marsh-pond-marsh wetland over continuous flow into the wetlands.
Technical Abstract: The research objective was to investigate the effect of pulsed wastewater flow on swine wastewater treatment by marsh-pond-marsh (m-p-m) constructed wetlands. From June to October of 2004, each of four, m-p-m wetlands in Greensboro, North Carolina, USA, received a different application of swine wastewater. The four application schemes were as follows: 1) continuous application; 2) four weeks of application followed by one week of no application; 3) three weeks of application followed by one week of no application; and 4) two weeks of application followed by one week of no application. The effect of pulsed wastewater application was determined by comparing each system's soil oxidation, wastewater constituent removal, and ammonia volatilization. Soil oxidation was increased during drainage periods of the two highest aeration treatments. While the removal of total suspended solids, chemical oxygen demand, and total phosphorus were not affected by pulsed wastewater application, the efficiency of total nitrogen removal significantly increased with increased frequency of drainage. For drainage frequencies of 0, 19, 25, and 31%, the total nitrogen removal efficiencies were 57, 64, 70, and 67%, respectively. Drainage frequency did not reduce ammonia volatilization from either marsh or pond sections.