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The goal of this project is to compare dairy waste treatment methodologies, especially varying levels of aerobic and anaerobic treatment, as well as wastewater lagoon circulation, aeration and covering for the reduction of pathogens and volatile compound emission. <P>These studies will provide greater understanding of how pathogens persist or are destroyed under various conditions and simultaneously elucidate the type of volatile organic compounds that are emitted during treatment. The studies will involve lab scale aerobic and anaerobic digesters, as well as on site dairy waste lagoon experiments conducted at an operating dairy, and thus real world conditions. The results of these studies will have impact on the way diary waste is treated for both human health and environmental considerations.
Approach: Dairy waste treatment methodologies are of concern because of human illnesses caused by pathogens within manure and because of volatile organic gas emissions which cause poor air quality in and around dairy operations. Pathogens such as E. coli O157:H7. Salmonella spp., Campylobacter spp. etc. have caused outbreaks associated with improper diary waste treatment. In addition, improper treatment of diary waste can emit volatile chemicals into the atmosphere, including volatile fatty acids (VFAs), volatile organic compounds (VOCs), and ammonia. Furthermore, improper application of diary waste to crop fields can result in the accumulation of sodium chloride, phosphate, nitrate and nitrite. These chemicals not only impact crop production, but also leach into ground water making it unsuitable for human or animal consumption. To better understand how dairy waste can be treated to eliminate pathogens, and decrease air emissions and unwanted groundwater leaching, we will initiate bench scale aerobic and anaerobic digester experiments. We will feed raw diary waste (manure and urine) into aerobic and anaerobic reactors under different parameters such as temperature, amount of dissolved oxygen, redox potential, retention time, etc. and analyze the starting material and effluent for microbial content. We will also collect gasses emitted from the waste treatment systems and analyze their chemical composition using GC/MS. We will conduct experiments with manure that has been spiked with known amounts of pathogenic bacteria including Salmonella, E. coli O157:H7, Mycobacterium avium subsp. paratuberculosis, etc. to determine the effect these methodologies have on pathogen growth and survival. Lastly we will conduct experiments on a working 800-cow dairy farm. This farm is uniquely suited for experiments on waste treatment methodologies because it has two waste lagoons that receive waste from the same source, but are run independently of each other, thus providing an experimental treatment lagoon and a control lagoon. We will treat one lagoon under conditions found to be ideal for the reduction of pathogen and volatile organic compound emission, and chemical changes as they evolve. This work will not only provide proof of principal in lab experiments but will show how these concepts correlate to real world conditions on a working dairy.