Performance of a pond aeration system for treating anaerobic swine lagoon effluent

The waste treatment system presented in this article is one of the alternative waste management systems that have been evaluated for swine farms in North Carolina. The treatment system was designed and installed on a commercial hog farm by International Ecological Systems and Services (IESS), Inc. The objectives of the treatment system were to reduce odor and ammonia emissions and nitrogen to be land applied. The treatment system consisted of an aeration pond with bacterial augmentation and was designed to treat 190 m(3/)d (50,000 gal/d) of swine anaerobic lagoon effluent. System performance was evaluated continuously over a 27-month period (Nov. 2000 to Jan. 2003). Nitrification, based on increased nitrite and nitrate concentrations in the aeration pond, varied with temperature. Dissolved oxygen (D.O.) concentrations during the last 18 months of monitoring were usually 2 to 3 mg/L. Low D.O. sometimes occurred because of increased loading or loss of aeration due to broken belts on the blower or severed aeration lines. Based on the inflow and oufflow concentrations of the aeration pond, total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN) reductions during the last 18 months of monitoring were 93% and 95%, respectively. The nitrate + nitrite nitrogen concentrations and the nitrite concentrations increased from near zero in inflow to the aeration pond to averages of 224 and 25 mg/L, respectively, in outflow during the last 18 months of monitoring. The treatment system experienced some operational and maintenance problems during the evaluation period, mainly with the bacteria delivery system, the blower the flush tank plunger valves, and flushing controls. Effluent from the aeration pond had low odor intensity, usually low total ammonia nitrogen, variable amount of nitrate/nitrite nitrogen, and lower concentrations of phosphorus, copper and zinc compared to the anaerobic lagoon effluent.