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Appl. Environ. Microbiol. doi:10.1128/AEM.01422-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Bacterial population dynamics in dairy waste during aerobic and anaerobic treatment and subsequent storage

Foodborne Contaminants Research Unit and Produce Safety Microbiology Research Unit U.S. Department of Agriculture, Agricultural Research Service, Albany, CA. Department of Biological and Agricultural Engineering and Department of Animal Science, University of California, Davis, CA

^* To whom correspondence should be addressed. Email: McGarvey{at}pw.usda.gov,

	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.