What are Processes to Further Reduce Pathogens (PFRPs) and Processes to Significantly Reduce Pathogens (PSRPs)?
A process to further reduce pathogens (PFRP) (PDF) (7 pp, 642 KB) is a treatment process that is able to consistently reduce sewage sludge pathogens to below detectable levels. A PFRP must reduce enteric viruses to below 1 plaque forming unit (PFU) per 4 grams of total solids (dry weight basis) and reduce the density of viable helminth ova to below 1 per 4 grams of total solids (dry weight basis). PFRP processes and PFRP equivalent processes, when paired with an appropriate vector attraction reduction (PDF) (7 pp, 615 KB) option, meet the requirements for Class A (PDF) (10 pp, 170 KB) sewage sludge. All Class A alternatives require that either the density of fecal coliforms in the sewage sludge be less than 1,000 MPN per gram total solids (dry weight basis) or the density of Salmonella spp. bacteria in the sewage be less than 3 MPN per 4 grams of the total solids (dry weight basis) at the time the treated sludge is used or disposed. A process to significantly reduce pathogens (PSRP) (P
