Simulating the effects of mesophilic anaerobic and aerobic digestions, lagoon system, and composting on pathogen inactivation

Abstract

To improve understanding of pathogen inactivation in flushed dairy manure during anaerobic digestion, lagoon systems, and mesophilic composting, we assessed pathogen inactivation in batch-scale anaerobic digesters, aerobic lagoons, and manure piles. Further, we assessed the impact of air injection in lagoon systems on pathogen inactivation. The inactivation of Salmonella and E. coli was studied for more than 70days. The change in pH, total solids, total carbon, and total nitrogen during manure treatment was determined. The results showed that the lagoon system with air injection to be more effective in pathogen removal compared to the lagoon system with no air injection, anaerobic digestion, and mesophilic composting. Both types of lagoon systems (with and without air injection) were found to be more effective in eliminating pathogens than anaerobic digester systems. Mesophilic manure pile extended the survival of both Salmonella and E. coli. In the anaerobic system, E. coli was detected beyond 60days of incubation, while in the aerobic system; it was eliminated in 30–35days. In anaerobic system, Salmonella reached to non-detectable level in 30–35days, while in aerobic system it took 4–12days. In the mesophilic manure pile, however, E. coli survival was extended beyond 78days. Less than one log reduction was obtained in 78days of mesophilic composting. Salmonella survival was also extended in mesophilic composting pile.