Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2006
Publication Date: N/A
Technical Abstract: The dairy industry in California produced over 100 million pounds of waste (manure and urine) in 2005, most of which was spread onto crop fields as a soil fertilizer/conditioner with little or no treatment. This practice is of concern for multiple reasons including: volatile compound emission into the atmosphere, nutrient runoff and leaching into surface and ground waters and the contamination of crop plants by pathogenic bacteria. One way to reduce these risks is to treat the waste before land application. In this study aerobic and anaerobic digestion techniques were used to treat dairy waste before storage in simulated holding lagoons. The microbial population dynamics of the waste stream was monitored using small-subunit ribosomal rRNA gene (16S rDNA) sequence libraries derived from DNA extracted from the waste, the aerobic and anaerobic digester effluent, and the simulated wastewater holding lagoons. The results showed that aerobic digestion altered the bacterial population structure the greatest, with the levels of 8 out of 9 phyla being significantly different. The most notable differences are the >16-fold increase in the phylum Proteobacteria and the approximately 8-fold decrease in the phylum Firmicutes. Other significant differences included the phyla Actinobacteria, Thermus, Planctomycetes, Spirochetes, TM7, and Verrucomicrobia. Storage of the aerobic digester effluent in a simulated wastewater holding lagoon resulted in increases in the phyla Firmicutes, Planctomycetes, Spirochetes, and a decrease in the phylum TM7. Anaerobic digestion resulted in fewer differences, with statistically significant decreases observed in the phyla Actinobacteria and Bacteriodetes and significant increases in the phyla Planctomycetes, Spirochetes, and TM7. Subsequent storage of this effluent in a simulated wastewater holding lagoon resulted in a significant increase in the phylum Thermus, all other phyla in the library remained unchanged. Storage of the waste without treatment resulted in the least amount of change with only the phylum Spirochetes showing a significant increase. Statistical analysis of the libraries revealed that the waste contained the greatest amount of microbial diversity and that anaerobic treatment resulted in the greatest amount of diversity loss followed by no treatment and aerobic treatment.