Biosolids Sample Update


Biosolids Sample Update:

In response to a request from WDNR on 8-27-2018, the Marinette Wastewater Utility initiated a second sampling of the biosolids holding tank to confirm the presence and concentration of PFAS compounds. In this request, the WDNR put wastewater utility staff in contact with Merit Laboratories-East Lansing Michigan to preform analysis using a different ASTM method because it was considered more accurate than the Modified EPA Method 537.

The sample was collected on 9-25-2018 from the mixed biosolids holding tank and sent to the lab for analysis. During communications with Merit Laboratories it was understood that the ASTM method for samples greater than 2.0% solids was still under development but should be completed shortly. In talks with Merit Laboratories we agreed to allow our sample to be run with the understanding that the method ASTM D7968 for PFC's in soil, sediment, and sludge was very new.

Through the process of analysis and quality control recovery, Merit Labs were not able to properly recover the necessary spike concentrations as well as internal and surrogate standards to guarantee the validity of the concentrations present in the sample. Merit Laboratories has worked diligently to try and come up with verifiable results using this new ASTM method, but have not been able to generate results that they would feel comfortable saying are accurate.

In a letter dated on March 1, 2019 to the Marinette Wastewater Utility from the WDNR, a request was made that Marinette explore a different method of disposal for the municipal biosolids generated by the utility, which may be incineration or landfilling. This request was made to allow time for the regulatory agency to develop a protective standard for PFOA and PFOS that would be protective of surface water and groundwater. Due to the need for dewatering for the two options of disposal, a new sample would need to be analyzed for accurate data on the concentration of PFOA and PFOS in the dewatered biosolids. Because of the need for a new sample to be analyzed, the pending results from the 9-25-2018 sampling would not be necessary due to the resampling needed for the different method of disposal requested by WDNR.

PFAS Sampling