Elevated PFAS Precursors in Septage and Residential Pump Stations

Area of Science:

• Environmental Chemistry
• Environmental Science
• Wastewater Engineering

Background:

• Residential wastewater is an underrecognized source of per- and polyfluoroalkyl substances (PFAS).
• Decentralized systems like septic tanks and pump stations are critical points for PFAS management.
• Understanding PFAS behavior in these systems is vital for environmental protection.

Purpose of the Study:

• To compare per- and polyfluoroalkyl substance (PFAS) concentrations and precursors in septage versus pump station wastewater.
• To evaluate the effectiveness of the total oxidizable precursor (TOP) assay in assessing PFAS contamination in residential wastewater.
• To identify the role of septic systems and pump stations in PFAS transport and potential groundwater contamination.

Main Methods:

• Analysis of 70 per- and polyfluoroalkyl substances (PFAS) and their precursors.
• Application of the total oxidizable precursor (TOP) assay to assess oxidizable PFAS.
• Direct comparison of PFAS levels in septage from septic systems and wastewater from pump stations.

Main Results:

• Septage showed significantly higher median post-TOP PFAS concentrations (687.5 ng/L) compared to pump stations (84.2 ng/L).
• Full oxidation of FTCAs and incomplete oxidation of diPAPs were observed, influenced by organic loads.
• Septic systems act as PFAS reservoirs, increasing groundwater contamination risks, while pump stations cause episodic PFAS spikes.

Conclusions:

• Septic systems and pump stations play distinct roles in the fate and transport of PFAS in residential wastewater.
• Precursor analysis is essential for accurate risk assessment, as it reveals significant underestimation by targeted PFAS measurements alone.
• Tailored analytical methods and pretreatment technologies are needed to manage PFAS risks in both decentralized and centralized wastewater systems.