EPA’s Standards for the Use or Disposal of Sewage Sludge (40 CFR Part 503) contain the requirements that protect public health and the environment when biosolids are applied to the land. Included in the requirements are pollutant limits, pathogen reduction requirements, and vector attraction reduction requirements.

Land-applied biosolids must meet both ceiling and pollutant concentration limits for metals. Metals concentrations in all samples of biosolids must meet the land application ceiling concentration limits. In addition, the average of the concentrations of a metal in all biosolids samples analyzed in a month (i.e., monthly average concentration) must meet the pollutant concentration limit for the metal.

The Part 503 regulation contains requirements for Class A and Class B biosolids with respect to pathogens. There can be immediate exposure to Class A biosolids because Part 503 requires that pathogen densities in Class A biosolids be reduced to below detectable levels through treatment. Pathogen densities in Class B biosolids also are reduced through treatment, but not to below detectable levels. For this reason, restrictions are placed on the sites where Class B biosolids are applied to allow the environment time to reduce the pathogens to below detectable levels.

The Part 503 regulation also requires that the attractiveness of vectors (e.g., flies and mosquitoes) to land-applied biosolids be reduced. This is done by either treating the biosolids or by placing a barrier between the biosolids and vectors after the biosolids are land-applied.

The MagnaGro™ Process is used to treat biosolids to meet either the Class A or Class B pathogen reduction requirements. Vector attraction reduction also can be achieved in the MagnaGro™ Process by raising the pH of the biosolids to a specified value and keeping the pH of the biosolids at a specified value for a period of time (i.e., the pH adjustment vector attraction reduction option).