Finding PFOA and PFOS in your wastewater residuals or biosolids?  Do you question what concentrations are acceptable for land application?
There are means to determine acceptable concentrations.  Most residuals and biosolids meet US EPA soil screening levels for contact, inhalation, and ingestion.  However, determining the acceptable concentrations to protect the groundwater resource can be a challenge because these compounds are not retained very well in mineral soil. 
Natural Resource Solutions LLC has devised management options that should protect groundwater and allow land application of residuals and biosolids containing PFOA and PFOS.  Here is what we do.  
Natural Resource Solutions LLC utilizes the US EPA Standardized Reasonable Maximum Exposure Equation to determine acceptable PFOA and PFOS concentrations in residuals and biosolids.  This equation takes into account the organic carbon in a substrate.  This is critical because PFOA and PFOS have a strong affinity to organic carbon, which is abundant in residuals and biosolids.  A key factor to the proper use of organic carbon data is to adjust it's content to reflect long-term decomposition.  Natural Resource Solutions LLC is capable of doing this utilizing the same lab procedures and modeling employed in it's nitrogen mineralization studies.  This is a unique approach that may be limited to us.
If you want to know more, or have Natural Resource Solutions LLC evaluate your residuals or biosolids, please contact us.