Survival of Infectious Prions During Anaerobic Digestion of Municipal Sewage Sludge and Lime Stabilization of Class B Biosolids

摘要

The objective of this study was to evaluate the fate of infectious prions during various stages of municipal waste treatment. Specifically mesophilic (35°C) and thermophilic (50°C) anaerobic digestion of sewage sludge (biosolids) and lime stabilization of Class B biosolids were evaluated. Standard scrapie cell assay which includes the ELISPOT (Enzyme Linked Immuno-Spot) reaction was utilized to quantitatively determine prion infectivity. A 4.2-log10 decrease was observed under mesophilic conditions after 21 days of digestion, while thermophilic digestion resulted in a 4.7-log10 decrease. When Class B mesophilically digested biosolids were treated with lime, a 2.9-log10 reduction of infectious prions was observed within the first two hours. Overall these results suggest that infectious prions are reduced significantly by either anaerobic digestion and/or lime treatment, and subsequent land application of biosolids is not a viable route of human exposure to prions.