Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2004
Publication Date: 12/1/2004
Citation: Poach, M.E., Hunt, P.G., Reddy, G.B., Stone, K.C., Johnson, M.H., Grubbs, A. 2004. Swine wastewater treatment by marsh-pond-marsh constructed wetlands under varying nitrogen loads. Ecological Engineering. 23:165-175. Interpretive Summary: Animal operations with limited land area can avoid the need for offsite waste disposal if management options that increase the farm's capacity to treat wastewater are adopted. One promising option is the use of constructed wetlands to reduce wastewater pollutants prior to land application. Treatment wetlands generally have one of two designs, either continuous marsh or marsh-pond-marsh. While swine wastewater treatment by continuous marsh wetlands has been studied extensively, treatment by marsh-pond-marsh wetlands has not. We investigated the ability of marsh-pond-marsh wetlands to reduce pollutants in swine wastewater. It was expected that the pond section would help the marsh-pond-marsh wetland remove more wastewater nitrogen than continuous marsh wetlands. Investigations were performed on a swine farm in North Carolina that had six marsh-pond-marsh wetlands. The marsh-pond-marsh wetlands were able to reduce wastewater pollutant levels, and they removed more nitrogen than an equal area of crop or pastureland. Therefore, marsh-pond-marsh constructed wetlands can be used to increase a farm's capacity to treat wastewater nitrogen. Marsh-pond-marsh wetlands did not remove more nitrogen than previously studied continuous marsh wetlands.
Technical Abstract: The objective of the present research was to investigate the ability of marsh-pond-marsh (m-p-m) constructed wetlands to treat wastewater from a confined swine operation over varying N loads. From September 2000 to September 2001, swine wastewater was applied at N loads between 2 and 50 kg N/hectare/day to six, m-p-m wetlands at a swine farm in Greensboro, North Carolina, USA. The efficiency of each wetland system to remove total suspended solids (TSS), chemical oxygen demand (COD), nitrogen (N), and phosphorus (P) was determined on a monthly basis using constituent wastewater concentration and wastewater flow measured at the wetland inlet and outlet. On a mass basis, the wetlands removed an average of 30 to 58% of wastewater TSS, 24 to 49% of wastewater COD, 34 to 55% of wastewater N, and 14 to 37% of wastewater P. Freezing temperatures and high rainfall events tended to reduce wetland treatment efficiency. The wetlands removed more nitrogen than an equal area of land used for wastewater treatment, but they tended to remove less when compared to continuous marsh wetlands. Results indicated that these m-p-m wetlands were not superior in their ability to nitrify swine wastewater than previously studied continuous marsh systems.