Recently published reports indicate that some wastewater treatment plants using anaerobic digestion and certain dewatering processes have experienced increases in fecal coliform concentrations immediately after dewatering and/or conveyance. The mechanisms behind the phenomena of fecal coliform density increases are still being studied and researchers are trying to understand why this has been observed at some facilities but not at others using similar processes. This document presents a summary of the current body of knowledge on this issue and a preview of ongoing research. It gives an overview of related regulatory issues for biosolids stabilization and testing protocols for fecal coliforms. Recommendations for communication strategies on this issue are provided. Finally, a description of currently known methodologies to address sudden increase/reactivation/regrowth phenomena is presented. This document is an update of the August 2006 Technical Practice Update (TPU) and includes more recent information since the original TPU was published.
Keywords: Technical Practice Update, sludge, biosolids, fecal coliform, pathogen, reactivation, regrowth, viable but nonculturable, digestion, stabilization, E. coli, thermophilic, mesophilic, WERF