Inactivation of Cryptosporidium parvum oocysts and faecal indicator bacteria in cattle slurry by addition of ammonia

Aims: To determine inactivation of Cryptosporidium parvum oocysts and reduction of Escherichia coli and enterococci in cattle slurry added aqueous ammonia.
Methods and Results: Escherichia coli, enterococci and non-viable C. parvum oocysts (DAPI+ PI+) were enumerated every second day for two weeks in cattle slurry amended with 60 mmol l-1 aq. ammonia and compared with untreated slurry at three temperatures. Regardless of temperature, the proportion of non-viable C. parvum oocysts increased significantly faster over time in slurry with added ammonia than raw slurry (p=0.021) corresponding to 62.0% higher inactivation (P=0.001) at day 14. Additionally, 91.8% fewer E. coli and 27.3% fewer enterococci was observed slurry added ammonia at day 14 compared raw slurry.
Conclusion: The addition of aqueous ammonia to raw slurry significantly reduced the viability of C. parvum oocysts and numbers of bacterial indicators. Hence, ammonia is usable to lower pathogen concentrations in slurry prior before application to agricultural land.
Significance and Impact of Study: Livestock waste is a valuable source of plant nutrients and organic matter, but may contain high concentrations of pathogens like Escherichia coli and Cryptosporidium spp. that can be spread in the environment, and cause disease outbreaks. However, die-off rates of pathogens in organic waste can increase following increasing ammonia concentrations.