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Defining Critical Process Elements To Achieve Economical Class A Biosolids Through High-Temperature Anaerobic Digestion Systems
Author: Perry L. Schafer, Steve Krugel, John Willis, Gary Newman, Joseph B. Farrell
Date: 10/98
Prepublication copy for presentation at WEFTEC'98, The '71st Annual Program for Technical Professional Development, Orlando, Florida, October 3-7, 1998

Several high-temperature anaerobic digestion process options are potentially available to meet US EPA Class A pathogen standards. Some of these options have been investigated at full-scale and some have been investigated at bench or pilot scale. The work here concentrates on continuous or nearly-continuous flow systems using complete mix reactors. Fecal coliform data from full-scale work at the Greater Vancouver Regional District in Vancouver, Canada are compared with bench-scale work at Iowa State University to begin to evaluate process potential to meet Class A requirements. Several important process variables are discussed with ramifications to meeting Class A needs. This assessment shows high reliability in fecal coliform reduction for multiple stage thermophilic systems. Actual pathogen dieoff testing results for the options discussed are limited, and this factor leads to slow EPA determination of these as Class A processes.