Ammonia Volatilization from Constructed Wetlands That Treat Swine Wastewater

Increasingly, large–scale animal production occurs in confinement where large per–unit–area quantities of waste are generated. With the increased scale of production, new environment–friendly technologies are needed to deal with the waste. Constructed wetlands are considered an alternative treatment, but it is not known if volatilization of free ammonia (NH3) governs nitrogen removal in these systems. The objective of this research was to quantify the NH3 volatilization from constructed wetlands that treat swine wastewater. In May and July of 2000, a specially designed enclosure was used to measure NH3 volatilization from constructed wetlands receiving swine wastewater. Laboratory and field calibration tests indicated that the enclosure was effective at measuring NH3 volatilization. Wetland tests indicated that NH3 volatilization was occurring. From average hourly rates, it was estimated that 7% to 16% of the nitrogen load to the wetlands was removed through NH3 volatilization. Although NH3 losses should not be ignored, results indicated that NH3 volatilization was not responsible for removing the majority of nitrogen from the swine wastewater.