The purpose of this research was to evaluate and compare various thermophilic anaerobic digestion processes for meeting U.S. EPA biosolids Class A pathogen standards. The project was split into three phases. Phase 1 screened three bench-scale thermophilic anaerobic process configurations at three different thermophilic temperatures based on their fecal coliform destruction efficiency. All three of the thermophilic process configurations tested were capable of achieving the Class A fecal coliform standard and were included in Phase 2. In Phase 2, bench-scale anaerobic digesters were fed...

Successful operation of the activated sludge process relies heavily on the ability to effectively separate mixed liquor into return activated sludge (RAS) and a high quality final effluent. Solids separation efficiency is dictated in large part by the relative population of floc-forming and filamentous microorganisms present in the activated sludge. During normal operation, mixed liquor will be composed primarily of floc-formers with relatively low levels of filamentous organisms. Some population of filamentous organisms is necessary to promote the formation of larger flocs and prevent...