Managing Ammonia On Hog Farms To Improve Environmental Quality.

Anaerobic lagoons are widely used across the southeastern U.S. to store and treat wastewater generated from confined swine production operations. During lagoon treatment, gaseous losses of nitrogen (N) in the form of ammonia occur as a result of mineralization of organic N compounds and subsequent ammonia volatilization. Extensive use of anaerobic lagoons followed by application of their effluents on spray fields can contribute to air pollution. Thus, there is major public interest to develop and demonstrate best control technologies that can lessen or eliminate the environmental and health problems caused by ammonia gas emissions from confined animal production. In a 15-month pilot-scale study, the effect of influent pre-treatment was evaluated for water quality improvement and reduction of nitrogen (N) losses from anaerobic lagoons using: 1) enhanced solid-liquid separation with polymers (Solid Separation), and 2) the same solid-liquid separation plus biological N treatment using nitrification-denitrification (SS+NDN). A typical anaerobic lagoon was included in the study as a control. The total Kjeldahl N (TKN), total ammoniacal N (TAN), and nitrate concentrations and volumes of both lagoon liquid and sludge were used to estimate N mass flows. At the end of the study, water quality improvement was moderate with Solid-Separation alone with TKN and TAN concentrations 35% and 37% lower than the control, respectively. However, water quality improvement was highly significant with the Solid-Nitrification pre-treatment with TKN and TAN concentrations 97% and 99% lower than the control, respectively. The N mass flow revealed that Solid-Separation reduced total N inflow by 30% and Solid-Nitrification by 82% with respect to the control. Both pre-treatments halted the accumulation of total N in the lagoon sludge. Lowering N concentrations with the Solid-Nitrification pre-treatment substantially reduced ammonia loss by 50% with respect to the control in the first six months; ammonia loss was reduced to 86% with respect to the control in the last nine months of the study. Overall, these results demonstrate that influent pre-treatment using a new wastewater technology that combines solid-liquid separation with biological N can dramatically improve water quality in lagoon liquid and significantly reduce N gas losses into the atmosphere.