Removal of PFAS from synthetic wastewater using aerobic granular sludge

Abstract

The project assesses the performance of the aerobic granular sludge (AGS) to remove poly- and per-fluoroalkyl substances (PFAS) and conventional nutrients like carbon, nitrogen, and phosphorus from synthetic wastewater in a sequencing batch reactor (SBR). AGS is an emerging wastewater treatment biofilm that may be effective in reducing the PFAS concentration in wastewater via sorption. PFAS are a class of man-made chemicals used as surfactants, fire retardants, and coating materials. PFAS compounds are very persistent in the environment and can lead to adverse health outcomes in humans. PFAS can migrate from consumer products and enter the influent of wastewater treatment plant (WWTP). PFAS compounds are poorly removed by conventional wastewater treatment methods making effluent from WWTP a significant source of PFAS in the environment. The project uses two specific PFAS which are perfluorooctanoic acid (PFOA) and perfluoro octane sulfonate acid (PFOS). Other objectives of this project are to monitor how PFAS influences the treatment of conventional wastewater constituents and the granules' structure and morphology. Two SBRs were started with floccular sludge from seed granules and continued for 402 days. Some standard laboratory analytical methods for nitrogen, phosphorus, and organic carbon were used to monitor the removal efficiencies of the granules. Solid phase extraction (SPE) and liquid chromatography with mass spectrometry (UPLC with ESI Q-TOF-MS) were used to assess the removal of PFOA and PFOS both from liquid and sludge phases. Maximum removal of 33% for PFOS and 28% for PFOA was achieved by AGS in the test SBR. PFOS/PFOA exposure affected the granule's physical properties, and the properties recovered within approximately 34 days of dosing. PFOS/PFOA contamination produced no significant effect on conventional nutrient removal except nitrification. Thus, the treatment of PFAS by AGS is economical, since AGS can treat several pollutants simultaneously in a single reactor. More research should be done on the disposal of PFAS-contaminated sludge and to increase the treatment efficiency.