Survival of Enteric Bacteria and Viruses in Biosolids

Abstract

In the developed world most of domestic sewage is treated by the activated sludge process, which results in large volumes of sludge or biosolids being produced. This results in millions of tons of biosolids produced each year in the United States, which must either be disposed of or recycled in some manner. Land application is seen as the most economical and beneficial way of handling biosolids. Although the United States Environmental Protection Agency supports and regulates the land application of biosolids, more research is needed to ensure its safe.The Appendix study A assessed the potential of Salmonella regrowth in Class A biosolids pellets and compost after land application. No Salmonella growth occurred in any of the soil/biosolids mixtures regardless of inoculum size or moisture content. While regrowth of Salmonella in biosolids may occur under saturated conditions it does not occur after Class A biosolid land application at typical agronomic rates. The Appendix B study evaluated the sensitivity of BGM and PLC/PRF/5 cell lines for detection of viruses as well as the occurrence and concentration of adenoviruses. The PLC/PRF/5 cell line was more sensitive for the detection of adenovirus and other enteroviruses in raw and Class B biosolids. The Appendix C study determined the potential of regrowth of Salmonella typhimurium in vermicompost and Class A biosolids alone and after addition to soil. In summary, no regrowth of Salmonella was observed, and the die-off of Salmonella was not different in soil, biosolids or vermicompost.