Submitted to: Proceedings Of International Animal Waste Conference
Publication Type: Proceedings
Publication Acceptance Date: 9/28/1998
Publication Date: N/A
Technical Abstract: Swine production is a major enterprise in the USA that has problems related to confined, high density production, flushing of waste to anaerobic lagoons, and the subsequent land application of wastewater. One of the alternative treatment methods is the use of constructed wetlands. Our research had two objectives: to better understand the function of constructed wetlands in a total swine waste management system and to asses the ability of wetlands to remove nitrogen and thereby decrease the required land application area. Three systems comprised of two wetlands connected in series were evaluated. One set of two contained rush and bulrushes, and another set contained bur-reed and cattails. The third set contained soybean grown in saturated-soil culture connected to a wetland with flooded rice. During the growing season with N loading <10 kg/ha/day, nitrogen reduction rates were similar between wetland plants and agronomic crops. At the low loading rate, 94% of the nitrogen was removed, but at the higher loading rates, 80 to 90% was removed. The mean above-ground dry matter production by wetland plants was 21 Mg/ha/yr. The redox conditions of the wetland soils were highly reducing. Denitrification enzyme assays indicated that nitrate was the limiting factor for denitrification. Additionally, results of a microcosms study indicated that removal rates could likely be increased at least two-fold by pre-wetland nitrification of wastewater.