Reduction of ammonia emissions from treated anaerobic swine lagoons

There is a need for treatment technologies that can effectively address environmental concerns associated with manure in confined animal production, including accurate assessment of their environmental benefit. These technologies must be able to capture nutrients, kill pathogens, and reduce emissions of ammonia (NH3) and nuisance odors from manure. To meet these needs, a wastewater treatment plant was demonstrated at full-scale in one of two 4,360-pig production units on a finishing farm in Duplin County, North Carolina. The treatment system installed in the first production unit combined new treatment technologies consisting of solid-liquid separation with removal of nitrogen and phosphorus from the liquid phase. The second production unit was used as a control to evaluate emission improvements using traditional anaerobic lagoon technology. Both production units had similar production management and lagoons with similar surface area (about 0.9 ha each) and wastewater design. As the treatment system recovered the manure solids and replaced the anaerobic lagoon liquid with cleaner water, it converted the anaerobic lagoon into a treated water pond. Our objective was to study changes in NH3 emissions as a result of improved water quality. The study was done one year after lagoon conversion into aerated pond as a result of manure treatment and included cold and warm weather conditions. Passive flux samplers were used to measure NH3 gas fluxes from both lagoon systems. Average total ammoniacal N (TAN) concentrations in lagoon liquid were 31 and 388 mg/L for the treated and traditional systems, respectively. We found that free NH3 (FA) concentration, which integrates TAN, temperature, and pH into a single factor, explained 90% of the variation in NH3 emissions from these lagoon systems. Lower N concentrations in the converted lagoon substantially reduced annual NH3 emissions by 90% with respect to those found in the traditional anaerobic lagoon. Ammonia emissions from the converted lagoon totaled 1,210 kg N/lagoon/year (or 1,311 kg N/ha/year). This annual rate compares with NH3 emissions of 12,540 kg N/lagoon/year (13,633 kg N/ha/year) from the traditional lagoon. Overall, these results demonstrate that production of clean water using new wastewater technologies can accelerate lagoon cleanup and substantially reduce ammonia emissions from confined animal production.