Legacy and Emerging Poly and Perfluoroalkyl Substances (PFAS) in Surface Water, Sediments, and Treated Effluent: A Case Study in Pretoria (South Africa)

Abstract

Polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative, and toxic compounds that pose significant environmental and health risks. Although PFAS contamination has been extensively studied in high-income countries, there is limited data on its occurrence and impact in low and middle-income countries, particularly in Africa. This study addresses the lack of comprehensive data on PFAS in wastewater treatment plants (WWTP), surface water, and sediments in Pretoria (South Africa), to inform pollution control strategies and health risk assessments. The Apies River in Pretoria, which receives treated effluent from nearby WWTPs, was selected for investigation due to its importance to local communities and potential exposure to PFAS. Samples were collected during the dry season weekly on days 1, 7, 14, and 21, to investigate temporal variations in PFAS concentrations in treated effluent, sediment, and surface water, and analysed for legacy and emerging PFAS. Sampling during the dry season provides an opportunity to detect and quantify PFAS more effectively as they are less likely to be diluted by rainfall. PFAS were recovered from the samples using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry. The results showed that the ΣPFAS concentrations were consistently higher in treated effluent samples over 21 days. Long-chain PFAS concentrations were significantly different (p < 0.05) between upstream and downstream locations. Perfluorocarboxylic acids were consistently found at higher concentrations in treated effluent, surface water, and sediment samples, with surface water (downstream) showing the highest concentration (62.98%). Sediment samples upstream (31.44%) and downstream (29.24%) showed a higher percentage of perfluorosulfonic acids, indicating stronger sediment adsorption. The findings of this study will drive future research and policy development focused on protecting water resources in South Africa’s waterways.