Evaluation of a Field-Scale Surface Aeration System in an Anaerobic Poultry Lagoon

Abstract

Odor from animal feeding operations (AFOs) is a leading public nuisance that livestock and poultry producers face frequently. The objective of this study was to evaluate a field-scale surface aeration system to minimize odor from an anaerobic poultry lagoon in Texas. The aeration module consisted of three aerators, each aerator contained two venturi air injectors arranged in parallel and connected to a perforated PVC pipe network that aerated a site of 23 m 23 m. The pipe network in the aeration system was placed 0.30 m below the liquid surface for aerating the lagoon. To compare the effect of aeration on lagoon odors and other parameters, a non-aerated (control) site was established about 30 m away from the aerated site to minimize treatment interference. Automatic samplers were used to collect effluent samples from each site at a depth of 0.30 m below the liquid surface once a week for 14 weeks. The samples were analyzed for changes in biochemical oxygen demand (BOD5), volatile fatty acids (VFAs), solids, and nutrients concentrations. Real-time dissolved oxygen and water temperature were also monitored by deploying sensors at the same depth. Six air samples (three each from aerated and non-aerated sites) were collected once a week in 10-L Tedlar bags and were analyzed for odors (dilution to threshold, DT), ammonia (NH3), and hydrogen sulfide (H2S) concentrations. Average DO and NH3 concentrations from aerated liquid were significantly (p<0.05) higher (62% and 27%, respectively) than the non-aerated liquid. On the other hand, DT value in the aerated site was significantly lower (50%) than the non-aerated site. Average H2S and BOD5 concentrations in the aerated site were about 16% and 13% lower, respectively, than the non-aerated site for the liquid and air samples collected three days after flushing, although these concentrations between the two sites were not significantly different (p>0.05). There were no significant differences in solids and nutrient concentrations between aerated and non-aerated site. These results demonstrated that surface aeration is effectively reducing odor and H2S concentrations and increasing NH3 concentrations in the aerated site as compared to the non-aerated. Struvite build-up in the lagoon liquid circulation pump, venturi injectors and the PVC pipe network, and clogging of strainers and PVC pipe aeration holes with lagoon surface scum and egg-shells required frequent cleaning and maintenance of the aeration system.