Pathogen Reduction

The second parameter in determining biosolids quality is the presence or absence of pathogens such as Salmonella bacteria, enteric viruses, and viable helminth ova. Biosolids are classified as class A or B based on the level of pathogen present. Biosolids meet class A designation if pathogens are practically below detectable levels. All biosolids that are sold or given away in a bag or other container for application to land, lawns, or home gardens must meet class A status. Part 503 lists six alternatives for treating sludge to meet class A requirements. These alternatives are summarized in Table 1.6. One of the alternatives is to treat sludge in one of the processes to further reduce pathogens (PFRP), which are described in Table 1.8.

Biosolids are designated class B if pathogens have been reduced to levels that do not pose a threat to public health and the environment as long as actions are taken to prevent exposure to the biosolids after their use or disposal. Alternatives for meeting class B pathogen requirements, including processes to significantly reduce pathogens (PSRP), are described in Tables 1.9 and 1.10.

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