Breaking the Forever PFAS Cycle: Recycle Stream Treatment to Reduce PFAS Loading to WRRF Influent and Biosolids

The main objective of this project is to reduce per- and polyfluoroalkyl substances (PFAS) stemming from recycled process flows from solids handling by treating recycle streams prior to recycling back to the head of the plant.

Recycle streams as applied in this context refers to all liquid streams from biosolids processing (i.e., thickener decant, filtrate, centrate, etc.). All these streams are hereby referred to as recycle streams that are returned to the head of the wastewater treatment process and thereby “recycled.”

If recycle stream treatment can reduce PFAS loading by a measurable amount (5%‐10%), a secondary objective is to determine what can be done to maximize the effectiveness of treatment.

Specific benefits of the project include:

• Increased understanding of recycle stream contributions to PFAS loads in water resource recovery facilities (WRRFs), including precursor impacts, of potential importance for both effluent (especially considering expected surface water regulations) and biosolids quality (with some biosolids thresholds in place and more likely on the way).
• Potential identification of pragmatic approaches to:
  • Lower PFAS loading to WRRF headworks attributed to solids processing recycle flows – and potentially reduced WRRF effluent and biosolids PFAS concentrations through low‐cost, readily implementable technologies.
  • Reduce the water‐associated fraction of total PFAS in biosolids, potentially reducing leaching potential and plant uptake from land‐applied biosolids.
  • Decrease uncertainties for future pilot studies by defining suitability factors (for example, recycle stream characteristics) for each approach and potentially achievable PFAS reduction performance.