Enterobacterial and viral decay experimental models for anaerobic digestion of piggery waste

Summary A laboratory study was conducted to determine effects of the continuous mesophilic anaerobic digestion of raw pig manure in two types of enteropathogenic microorganisms, bacterial and viral. Faecal coliforms (indigenous to pig manure) and coliphage f2 (ATCC 15766 B1) were used as a model for some indigenous enteropathogenic microorganisms. The study was completed with laboratory survival experiments in lagoon stabilization of raw pig manure, for both models. Experiments for f2 survival in cell-free synthetic medium were also carried out. The results show that the anaerobic digestion process is more effective in eliminating viral than bacterial particles. Some parameters related to the ultimate biogas yield and kinetics were also determined. Lagoon stabilization of raw pig manure provides a more suitable environment for the removal of faecal coliforms than does anaerobic digestion. Finally, it was concluded that volatile fatty acids appeared to be responsible for the elimination of faecal coliforms. The agent that causes f2 inactivation is not well identified, although in some cases it could be NH₃ that seems to act as a vircidal agent.Correspondence to: J. Mata-Alvarez