Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2007
Publication Date: 5/1/2007
Citation: Mcgarvey, J.A., Miller, W.G., Zhang, R., Ma, Y., Mitloehner, F. Bacterial population dynamics in diary waste during aerobic and anaerobic treatment and subsequent storage. Applied and Environmental Microbiology. 73:193-202 Interpretive Summary: Two types of digesters were evaluated for their ability to treat dairy cow waste (manure and urine). One pumps atmospheric air through the waste so that it contains dissolved oxygen in it and the other does not. Both methods were found to be effective at reducing the levels of total solids (59-68%), BOD5 (85-90%), sulfate (56-65%) and aerobic (83-95%), anaerobic (80-90%) and coliform (>99%) bacteria. However the first method was more efficient at reducing the levels of ammonia, and the second treatment was more effective at reducing total sulfur and sulfate. We also looked at the type of bacteria present and how these populations changed during treatment. The treatment method involving oxygen resulted in the greatest amount of bacterial change and the other method altered the bacterial populations to a lesser degree.
Technical Abstract: The objective of this study was to model a typical dairy waste stream and monitor the chemical and bacterial population dynamics that occur during aerobic or anaerobic treatment and subsequent storage in a simulated lagoon, and compare them to waste held without treatment in a simulated lagoon. Both aerobic and anaerobic treatment methods followed by storage effectively reduced the levels of total solids (59-68%), BOD5 (85-90%), sulfate (56-65%) and aerobic (83-95%), anaerobic (80-90%) and coliform (>99%) bacteria. However, only aerobic treatment reduced the levels of ammonia, and anaerobic treatment was more effective at reducing total sulfur and sulfate. The bacterial population structure of waste before and after treatment was monitored using 16S rDNA sequence libraries. Both treatments had unique effects on the bacterial population structure of waste. Aerobic treatment resulted in the greatest change in the type of bacteria present with the levels of 8 out of 9 phyla being significantly altered. The most notable differences were the >16-fold increase in the phylum Proteobacteria and the approximately 8-fold decrease in the phylum Firmicutes. Anaerobic treatment resulted in fewer alterations, but significant decreases in the phyla Actinobacteria, Bacteroidetes and increases in the phyla Planctomycetes, Spirochetes, and TM7 were observed.