Bacterial responses to temperature during aeration of pig slurry

The temperature effect on total anaerobic and aerobic bacterial growth in pig slurry was studied using low level batch aeration treatments. Five bioreactors were built using Plexiglas tubes to perform five temperature treatments (5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C). An airflow rate of 0.129 L/min/L manure was used to aerate manure contained in all reactors. Data showed that temperature had a profound impact on the aerobic counts in pig slurry during the aeration process. When the temperature increased from 15 degrees C to 25 degrees C, the average oxidation-reduction potential decreased from +40 mV to -60 mV, accompanied by a 75% reduction of aerobic bacteria in the manure. At 25 degrees C, the anaerobic counts were consistently higher than aerobic counts for most of days. A quadratic relationship was observed between the aerobic counts and the oxidation-reduction potential with a correlation coefficient of 0.8374. To reduce odor generation potential, the oxidation-reduction potential in the manure should be maintained at +35 mV or higher.