Effect of Anaerobic Digestion and Application Method on the Presence and Survivability of E. coli and Fecal Coliforms in Dairy Waste Applied to Soil Olivia Saunders & Joe Harrison & Ann Marie Fortuna & Elizabeth Whitefield & Andy Bary Received: 23 April 2011 /Accepted: 5 August 2011 /Published online: 24 August 2011 # Springer Science+Business Media B.V. 2011 Abstract Animal wastes are commonly used in a sustainable manner to fertilize crops. However, manures contain numerous pathogenic bacteria that can impact animal and human health. Treatment of animal waste by anaerobic digestion has the potential to reduce pathogen loading to land. This study was conducted to determine the fate of bacteria applied in raw and anaerobically digested dairy slurries that were broadcast and subsurface applied in a field of forage grasses. Digested slurry had significantly fewer indicator bacteria, Escherichia coli and fecal coliform at time of application. Anaerobic digestion did not increase the survivability of indicator bacteria. Waste treatment and application method did not affect the rate of bacteria die-off. There were fewer E. coli and fecal coliform at the end of each trial in the soils that received digested slurry. Anaerobic digestion of dairy waste has the potential to reduce pathogenic bacteria loading to cropland. Keywords Anaerobic digestion . Dairy manure . Fecal coliform . E. coli . Bacteria decline 1 Introduction As livestock facilities become larger in scale and size, management of pathogens concentrated in animal manure will become a greater challenge (Cole et al. 1999; Venglovsky et al. 2009). Untreated livestock manures contain over 150 pathogens, or disease- causing microorganisms, which pose a risk to human health (Strauch and Ballarini 1994; USEPA 2003). Application of dairy manure to land presents a risk to both humans and grazing animals as pathogens applied in manure can be found in the soil long after application and have the potential to be transported to surface waters via runoff (Avery et al. 2004; Nicholson et al. 2005). Bacteria are regulated only if a nearby water body exceeds the Total Maximum Daily Load (TMDL) of bacteria set by the U.S. Clean Water Act (USEPA 2010a). In a grazing system, animal pathogens deposited on land can re-cycle and re-infect a herd (Avery et al. 2004). Raw and treated manures applied at low pathogen concentration still pose a threat as some pathogens multiply in the environment (Crane and Moore 1986). A number of pathogens including enterococci, E. coli, fecal streptococci and Salmonella Water Air Soil Pollut (2012) 223:1055–1063 DOI 10.1007/s11270-011-0923-5 O. Saunders : A. M. Fortuna Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA J. Harrison (*) : E. Whitefield Department of Animal Sciences, Washington State University, 2606 West Pioneer, Puyallup, WA 98371, USA e-mail: jhharrison@wsu.edu A. Bary Department of Crop and Soil Sciences, Washington State University, Puyallup, WA 98371, USA