Managed Aquifer Recharge and Water Quality
Managed aquifer recharge (MAR)—intentionally infiltrating surface water or treated wastewater into aquifers for storage and later recovery—is a water management strategy increasingly used to address water scarcity. MAR introduces PFAS from surface water sources into aquifers, with implications for recovered water quality and treatment needs.
PFAS Attenuation During Soil Passage
Soil passage during infiltration can attenuate some PFAS through sorption to soil organic matter and mineral surfaces. Long-chain PFAS show moderate attenuation during soil aquifer treatment (SAT), while short-chain PFAS move largely unimpeded through soil passage. Studies of MAR facilities show significant attenuation of PFOA and PFOS but minimal reduction of PFBS and PFHxA during subsurface passage—replicating the chain-length limitation of conventional treatment in the natural system.
Aquifer PFAS Accumulation
PFAS not attenuated during soil passage accumulate in the receiving aquifer, potentially affecting the quality of recovered water and nearby private wells. MAR programs using surface water containing regulated PFAS should evaluate the long-term implications of aquifer PFAS accumulation, including effects on private well owners in the recharge area and the treatment requirements for recovered water.
Regulatory and Design Implications
Water agencies planning MAR projects should conduct PFAS source water characterization and soil column testing before full-scale implementation. MAR wells in PFAS-contaminated areas may require pre-treatment of recharge water to prevent aquifer contamination. Recovered water treatment should be designed accounting for the PFAS compounds that pass through soil without attenuation