Sewage sludge that must meet the Class A pathogen requirements includes sewage sludge that is sold or given away in a bag or other container for application to land and bulk sewage sludge that is applied to a lawn or home garden. Part 503 Subpart D establishes six alternatives for demonstrating that sewage sludge meets Class A pathogen reduction requirements. The rule requires that the density of fecal coliforms be less than 1,000 Most Probable Number (MPN) per grams total solids (dry weight) or that Salmonella sp. bacteria be less than 3 per 4 grams total solids. This requirement must be met at one of the following times: a) when the sewage sludge is used or dispose; b) when the sewage sludge is prepared for sale or give-away in a bag or other container for land application; or c) when the sewage sludge or derived materials is prepared to meet the Part 503 requirements in 503.10 (b), (c), (e), or (f). Pathogen reduction must take place before or at the same time as vector attraction reduction, except when the pH adjustment or percent solids vector attraction reductions options are met, or if vector attraction reduction is accomplished through injection or incorporation.

Bulk sewage sludge that is applied to agricultural land, forest, public contact sites, or reclamation sites must meet the Class B pathogen requirements if it does not meet Class A pathogen requirements. Part 503 Subpart D establishes three alternatives for demonstrating that sewage sludge meets Class B pathogen requirements. The rule's implicit objectives for all three approaches is to ensure that pathogenic bacteria and enteric viruses are reduced in density, as demonstrated by a Fecal Coliform density in the treated sewage sludge of 2 million MPN dry weight.