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Reactivation of Fecal Coliform Bacteria    

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A report entitled “Examination of Reactivation and Regrowth of Fecal Coliforms in Centrifuge Dewatered Anaerobically Digested Sludges” was published in June 2006 by the Water Environment Research Foundation (WERF).  The document describes the findings of a study of fecal coliform levels in biosolids from a small sampling of treatment plants, all of which used anaerobic digestion followed with high-solids centrifugation.  The researchers hypothesized that the centrifugation process reactivated bacteria that had entered a “viable but non-culturable” state.  The study also compared test results using standard culturing methods with those using an alternative testing method. Click here for a fact sheet providing more information on Phase I of the research study.  Phase II of the project includes a survey of additional facilities; mechanistic studies to examine methods to grow viable but nonculturable bacteria; and two laboratory-scale, digestion time–temperature experiments. 

Background Information
Click here for additional “plain English” background information on the WERF Study.  
Click here for a set of questions and answers on the study.
Click here to read a copy of the US EPA’s fact sheet on the study.

Technical Practice Update
The WEF Technical Practice Committee formed a task force to provide a summary of the state of knowledge on this issue and produce a Technical Practice Update. The mechanisms behind the phenomena of fecal coliform reactivation and regrowth are still being studied and researchers are trying to understand why this has been observed at some facilities but not at others utilizing similar processes. The Technical Practice Update 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 reactivation/regrowth phenomena is presented. Click here to be directed to the WEF Marketplace to download the document.