PAC-Impregnated Sludge Flocs for PFAS Wastewater Removal

The patent combines powdered activated carbon (PAC) with biological flocs to create a hybrid treatment system. The PAC is mixed with the activated sludge biomass, allowing simultaneous adsorption of PFAS onto carbon particles and biological degradation of organic contaminants. This merged approach integrates physical adsorption and biological treatment mechanisms within a single process train, achieving effective PFAS removal without requiring separate dedicated treatment units.

The invention utilizes composite material formation by combining PAC particles with biological flocs. The resulting mixed liquor contains a composite structure where hydrophobic PAC surfaces provide adsorption sites for PFAS compounds, while the biological matrix provides enzymatic degradation capacity. This composite approach leverages the complementary strengths of both materials to address the limitations of conventional single-mechanism systems.

The system is designed to automatically manage PAC dosing and integration with the activated sludge process. The PAC is fed into the aeration basins where it becomes incorporated into the biological flocs through natural mixing and flocculation processes. This self-service approach eliminates the need for manual PAC application and complex control systems, allowing the process to regulate itself through inherent hydrodynamic and biological mechanisms.

The PAC is introduced into the system before the secondary clarification stage, allowing sufficient time for adsorption equilibrium to be established and for PAC-floc complexes to form. This preliminary action ensures that PFAS removal occurs during the aeration and settling phases, with the treated effluent already containing adsorbed PFAS on the solid phase, ready for separation in the clarifier.

The PAC particles become nested within the biological floc structure during the mixing and flocculation process. Smaller PAC particles are incorporated into the larger floc matrix, creating a nested configuration where the floc acts as a carrier. This nesting allows fine PAC particles with high adsorption capacity to be effectively transported and settled with the biomass in the secondary clarifier, overcoming the separation difficulty associated with fine particle sizes.

The system allows different regions of the treatment process to have different PAC particle size characteristics. In the aeration basins, finer PAC particles provide maximum adsorption surface area. In the secondary clarifier, the PAC particles are embedded within larger floc structures that facilitate settling. This local quality variation optimizes both adsorption capacity in the treatment zone and separation efficiency in the clarification zone.