Recent research indicated reactivation and regrowth of fecal coliforms in dewatered biosolids, which drew concerns on biosolids quality as well as their impacts to subsequent residual management programs. However, since fecal coliforms are only indicator organisms, it is, therefore
important to verify whether similar phenomena are occurring on actual pathogens. Side-by-side analyses of 4 facilities with various thermophilic anaerobic processes showed that though reactivation and/or regrowth occurred on fecal coliforms, no reactivation or regrowth occurred on Salmonella.
One mesophilic facility was also tested, which showed regrowth on both fecal coliforms and Salmonella. The results showed that thermophilic digestions can achieve complete Salmonella destruction, despite the observed regrowth and/or reactivation. For Class B mesophilic biosolids,
Salmonella are expected to be further removed upon land-application and protected from the public through required site-restriction. Overall, the results showed that the current EPA regulations provides suitable protection to the public health.
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