Two-Phase Anaerobic Digestion of Municipal Sewage Sludge Optimization of the Pathogen Destruction

摘要

The Two-Phase Thermo-Meso Anaerobic Digestion of municipal sewage sludge has gathered a lotrnattention in recent years for its capability to produce Class A biosolids. During 1997 and 1998 Suezrnand Ondeo Degremont, Inc. ran a pilot study of the Two-Phase Thermo-Meso Feed-SequencingrnAnaerobic Digestion at the Belmont AWT facility in Indianapolis, Indiana. Consistent productionrnof Class A biosolids as well as 3-log and 2-log reduction of enteric virus and viable helminth ovarnrespectively were documented. Most of the pathogen destruction occurred in the first phase of thernprocess. Data from the literature was carefully reviewed in an attempt to find the cause of suchrnextensive pathogen reduction. The use of a well-mixed “draw and fill” digester, a thermophilicrntemperature, the presence of free ammonia and volatile fatty acids (VFA) were all found to berngermicidal. A combination of all these factors in the first phase of the process is believed to be atrnthe source of the pathogen destruction observed. The pilot test results can be reasonablyrnextrapolated to full-scale systems as long as proper operation of the thermophilic phase is ensuredrnand sufficient mixing is provided with the industrial size digesters. The Two-Phase Thermo-MesornFeed-Sequencing Anaerobic Digestion process (2PADTM) has currently a site-specific PFRPrnequivalency recommendation. However, this recommendation is in the process to be changed overrnto a “conditional” national PFRP equivalency recommendation.