|Bullard, Gary - CA DAIRY CAMPAIGN|
Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2009
Publication Date: October 1, 2009
Citation: Mcgarvey, J.A., Miller, W.G., Lathrop, J.R., Silva, C.J., Bullard, G. 2009. Induction of Purple Sulfur Bacterial Growth in Dairy Wastewater Lagoons by Circulation. Letters in Applied Microbiology. 49:427-433. Interpretive Summary: The purple sulfur bacteria (PSB) are a group of bacteria that are able to degrade volatile organic chemicals such as short chain fatty acids, alcohols and hydrogen sulfide; all of which are volatilized from dairy wastewater lagoons and cause poor air quality in dairy farming regions. If we can induce the growth of these bacteria within dairy wastewater lagoons we can limit the amount of these chemicals emitted from the lagoons and increase the air quality in dairy farming regions. We have previously reported that the PSB are found in higher numbers in wastewaters that are circulated than those that are stagnant. In this study we show that circulation induces the growth of PSB within wastewater lagoons.
Technical Abstract: Aims: To determine if circulation of diary wastewater induces the growth of phototrophic purple sulfur bacteria (PSB). Methods and Results: Two dairy wastewater lagoons that were similar in size, geographic location, number and type of cattle loading the lagoons were chosen. The only obvious difference between them was that one was stagnant and contained undetectable levels of purple sulfur bacteria (PSB) and extractable carotenoid pigments (ECP) (Farm 1) and the other was circulated and was known to contain PSB and ECP (Farm 2). Both wastewaters were sampled monthly for 3 months and assayed for PSB and ECP. After this point, circulators were placed in the wastewater lagoon on Farm 1 and samples were taken monthly for 9 months and assayed for PSB and ECP. Before the installation of circulators, no PSB-like 16S rRNA sequences or ECP were observed in the wastewater from Farm 1; however, both were observed in the wastewater from Farm 2. After the installation of circulators statistically greater levels of PSB and extractable carotenoid pigments were observed in the wastewater from Farm 1. Conclusions: Circulation enhances the growth of PSB in dairy wastewater. Significance and Impact of this Study: Because PSB utilize H2S and volatile organic acids (VOA) as an electron source for photosynthesis and VOA and alcohols as a carbon source for growth, the increase in these bacteria should reduce H2S, VOC, and alcohol emissions from the lagoons, enhancing the air quality in dairy farming areas.