Large volumes of wastewater from confined pig production are stored in anaerobic lagoons. Control methods are needed to reduce air pollution by foul odors released from these lagoons. In a pilot-scale experiment, we evaluated the effect of pig wastewater pre-treatment on reducing the concentration of selected malodor compounds in lagoons receiving liquid from: (1) flocculant enhanced solid-liquid separation (SS), and (2) solid-liquid separation plus biological N treatment using nitrification-denitrification (SS+NDN). A conventional anaerobic lagoon was included as a control. Concentrations of five selected malodorous compounds (phenol, p-cresol, 4-ethylphenol, indole, and skatole) and water quality parameters (ammonia-nitrogen and chemical oxygen demand) were determined in lagoon effluents. The SS+NDN pretreatment was more efficient than the SS in reducing odorous compounds in the lagoon liquid. The SS+NDN reduced by about 99% the liquid concentrations of all selected compounds. An odor panel test revealed that SS was ineffective to reduce the human sense of malodor with respect to the control. Whereas the SS+NDN had the significant lowest odor intensity and unpleasantness. These results are supported by the strong correlations found between the sum of odorous compound concentration with odor panel results and concentrations of both ammonium-nitrogen and chemical oxygen demand in lagoon liquid samples.
Keywords: Swine; ammonium; chemical oxygen demand; malodor; wastewater treatment.