PFAS Removal During Pyrolysis of Biosolids Is Affected by Initial PFAS Concentration and Pyrolysis Efficiency

Area of Science:

• Environmental Science
• Chemical Engineering
• Waste Management

Background:

• Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants of concern in biosolids.
• Current regulations are driving the need for advanced biosolids treatment technologies.
• Thermal processes, like pyrolysis, show promise for PFAS removal from biosolids.

Purpose of the Study:

• To investigate the fate of PFAS during biosolids pyrolysis.
• To compare PFAS removal efficiency in non-industrially and industrially impacted biosolids.
• To analyze PFAS distribution in biochar, py-liquid, and py-gas phases.

Main Methods:

• Bench-scale pyrolysis experiments were conducted at 500°C and 800°C.
• Triplicate experiments were performed using non-industrially and industrially impacted biosolids.
• PFAS concentrations were quantified in biochar, py-liquid, and py-gas.

Main Results:

• PFAS removal exceeded 95% at 800°C for both biosolids types.
• At 500°C, PFAS removal ranged from 24%-88% for industrially impacted biosolids.
• Approximately 50% of influent PFAS mass was found in effluent liquid and gas for non-industrially impacted biosolids.

Conclusions:

• Pyrolysis is effective for PFAS removal from biosolids, especially at higher temperatures.
• Industrially impacted biosolids may require different pyrolysis conditions for optimal PFAS removal.
• Effluent streams from pyrolysis require further treatment to achieve complete PFAS remediation.