The Use of Thermal Inactivation of Male-Specific Coliphages as Potential Indicators of Pathogen Reductions in Thermophilic Anaerobic Digestion

Male-specific (F+) coliphages were investigated as indicators of virus inactivation during thermophilic digestion and other thermal processes. Because pathogen monitoring in sludge is difficult, costly, and impractical, microbial indicators are needed to predict pathogen reductions in Class A biosolids. F+ coliphages are a promising candidate indicator of fecal contamination and a surrogate for virus reduction in waste treatment processes. F+ RNA group I, F+ RNA group III, and F+ DNA phages were isolated from municipal sludge. In laboratory studies the kinetics and extent of inactivation of groups I and III F+ RNA, and F+ DNA coliphages were quantified and compared at 53°C, a temperature used in thermophilic anaerobic digestion. Isolates of groups I and III F+ RNA and F+ DNA coliphages were exposed to 53°C in an automated, thermoregulated heat block and titered after 0, 5 and 60 minutes. After 60 minutes at 53°C, F+ RNA group III coliphages were inactivated significantly greater (P < .0001) than the F+ RNA group I and F+ DNA coliphages. The inactivation kinetics of group III F+ RNA coliphages resemble those of some enteric viruses and some other pathogens. The results of this study elucidate the thermal properties of the male-specific coliphage subgroups and facilitate the development of time and temperature relationships that predict enteric virus and other pathogen reductions in thermal and thermophilic processes used to meet Class A biosolids requirements.Master of Science in Public Healt