Perfluorinated alkyl substances: Sewage treatment and implications for receiving waters.

Area of Science:

• Environmental Chemistry
• Water Quality Assessment
• Environmental Engineering

Background:

• Per- and polyfluoroalkyl substances (PFAS), including PFOS and PFOA, are persistent organic pollutants found globally.
• Wastewater treatment works (WwTW) are potential sources of PFAS entering aquatic environments.
• Regulatory frameworks, such as the Water Framework Directive, set environmental quality standards (EQS) for specific contaminants like PFOS.

Purpose of the Study:

• To analyze the effectiveness of WwTW in removing PFOS and PFOA.
• To assess compliance with PFOS EQS in receiving waters downstream of WwTW discharges.
• To investigate the sources and implications of upstream PFAS concentrations.

Main Methods:

• Analysis of effluent, upstream, and downstream water samples from over 600 WwTW.
• Comparison of measured PFOS and PFOA concentrations against established EQS.
• Evaluation of the impact of WwTW discharges on receiving water quality.

Main Results:

• PFOS concentrations in effluents exceeded the annual average EQS by 1.1- to 40-fold.
• PFOA concentrations in effluents exceeded EQS by 2- to 22-fold.
• Between 25% and 33% of WwTW reduced fluorocarbon concentrations downstream due to upstream inputs.

Conclusions:

• PFAS contamination in aquatic environments is ubiquitous, originating from diffuse sources.
• Current WwTW are often ineffective at meeting stringent PFOS EQS.
• A biota-derived quality standard may offer a more realistic environmental risk assessment than freshwater EQS for PFOS.