||Destruction of Enteric Bacteria and Viruses during Two-Phase Digestion.
Lee, K. M. ;
Brunner, C. A. ;
Farrell, J. B. ;
Eralp, A. E. ;
||Environmental Protection Agency, Cincinnati, OH. Risk Reduction Engineering Lab. ;Cincinnati Univ., OH. Dept. of Civil and Environmental Engineering.
Escherichia coli ;
Water microbiology ;
Microbial colony count ;
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The pathogenic microorganism destruction obtained during two-phase anaerobic digestion was compared to that for a conventional single-stage digester using municipal wastewater treatment sludge. Operation was draw-and-fill. Total digester residence times of 10 days and 20 days were evaluated. Evaluations were carried out at 35 and 53 C. Microorganisms measured included fecal coliforms, Escherichia coli, fecal streptococci, and enterovirus. Pathogen reductions were compared to those calculated from a kinetic relationship developed specifically for draw-and-fill operation. Ascaris were added to digested sludge and held at 53 C for up to 8 hours to observe their decline with time under thermophilic conditions. Common digester operating parameters were also measured. At the thermophilic temperature of 53 C essentially all the microorganisms measured were reduced to undetectable levels. At 35 C, two-phase digestion achieved from 0.48 to 0.91 greater log reduction of bacterial indicators, but essentially the same reduction in virus.