ABSTRACT
The survival of potentially infectious enteropathogens in digestate from two-phase mesophilic anaerobic digestion (Two-phase MAD) technique raises concern on handling and application of the resulting digestate as far as hunan health and environment safety is concerned. In this research, temperature validation and hygienization potential of Two-phase MAD operated as a completely stirred-tank reactor with semi-continuous feeding was investigated. High enteropathogens survival up to 6.4 log E. coli and 6.1 log Salmonella Senftenberg was observed in digestate resulted from anaerobic digestion of potato peels artificially spiked with 8.7 log Salmonella Senftenberg and 8.8log E. coli simulating extra high pathogens contamination in biowaste used as feedstock. Even though an average decrease in pH by 2.3 units from the original value of 6.5 observed in hydrolysis reactor created unfavorable environment on the survival of both E. coli and Salmonella Senftenberg causing a 3.6 log and 3.8 log reduction, yet the alkaline condition in the methanation reactor pH 7.7 boosted the surviving rate by 1.3 log in E. coli and 1.2 log in Salmonella Senftenberg confirming the inefficiency of Two-phase MAD set-up at providing a completely hygienized digestate. This renders the biosafety of the resulting final digestate questionable and limit the possibility of farmapplication for nutrients recycling due to the involving environmental threat and health risks in case the digestate is to be used. Temperature-time combination at 65 °C for 30min was confirmed sufficient at completely elimination of E. coli and effecting >1 log cycle die-off equivalent to 90% die-off in Salmonella Senftenberg with z-Value of 11 ºC validating the temperature-time
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