Evaluating the effects of pasteurization temperature and treatment duration on pathogen inactivation in separated liquid dairy manure

Abstract

<abstract> Abstract. Mesophilic anaerobic digestion is used to treat organic wastes like dairy manure to recovery energy (biogas) and reduce the negative environmental impacts associated with manure, including high chemical oxygen demand, odors, and greenhouse gas emissions (GHG). However, recent research has indicated that MAD does not significantly decrease pathogen concentrations, particularly E. coli, Salmonella, and fecal coliform bacteria. Insufficiently treated manure has the potential to contaminate food and water supplies when land applied, posing a threat to human and environmental health. The objective of this study was to (i) determine the effective combination of pasteurization temperature and treatment duration for reducing fecal coliform, E.coli, and Salmonella concentrations in separated liquid dairy manure to the minimum levels required for use as organic fertilizer in human food production; and (ii) determine the minimum pasteurization temperature and treatment duration required to achieve sufficient pathogen inactivation. Three pasteurization temperatures (70, 75, or 80 degrees C) and nine treatment durations (0, 15, 30, 45, 60, 75, 90, 105, and 120 minutes) were evaluated in the lab. The results showed reductions in fecal coliform concentrations of 85 to 95%, E.coli reductions of 87 to 96%, and 100% reductions in Salmonella. No significant differences in pathogen concentration reductions were detected due to the duration of pasteurization. Over 85% of inactivation was achieved during the period when the manure temperature was raised to the desired pasteurization temperature. All treatments met the minimum requirement for use in organic food production. This study contributed greater understanding about pathogen inactivation response in dairy manure.