Study of Inhibitory Effects on Aerobic Biomass: Interaction Between Per-/Polyfluoroalkyl Substances (PFAS) and Traditional Toxic Compounds

This work aims to investigate the inhibitory effects of PFAS on activated sludge biomass and compare them to the impact of conventional toxic substances that may be found in wastewater, such as phenol, trichlorophenol, and copper sulphate. Respirometric assays, i.e., batch and continuous oxygen uptake (OUR) tests, were used to evaluate the response of aerobic biomass to various aqueous wastes containing PFAS and traditional inhibitory compounds. The study is divided into many phases, assessing the inhibitory effects of tested pollutants over different time scales: short-term exposure (10 min contact time in batch tests) and medium-term exposure (several hours in continuous tests). The results highlight that while PFAS did not cause acute or medium-term chronic toxicity on biomass (OUR values between 6 and 8 mgDO (gSSV·h)−1), copper sulphate (at a concentration of 166.7 mg L−1) involved irreversible inhibition beyond critical exposure time. Furthermore, the biodegradability of the studied substrates was impacted by the interaction between PFAS and conventional toxic substances, with certain mixtures showing the capacity to lessen inhibitory effects (OUR values between 5 and 20 mgDO (gSSV·h)−1). This study provides new knowledge on the potential inhibitory mechanisms of PFAS and underlines the importance of considering the combined effects of these pollutants with other contaminants. The findings support the development of more effective treatment approaches for PFAS-contaminated wastewater and help in improving the operational strategies of wastewater treatment plants.