Emissions and transport of pharmaceutical residues from three wastewater treatment plants in Saudi Arabia and the associated risk for the aquatic environment

Pharmaceuticals are inadequately removed by wastewater treatment plants (WWTPs), allowing their residues to contaminate the environment and pose potential risks. This study investigates the occurrence, removal efficiency, and environmental risks of 16 pharmaceuticals in three WWTPs in Riyadh, Saudi Arabia. Seasonal variations and the leaching behavior of these compounds when wastewater is applied to soil were also examined using laboratory soil column experiments.A total of 144 wastewater samples over 12 months and 80 soil column samples were collected and analyzed. Wastewater samples were processed using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), while soil samples were analyzed using ultrasound-assisted extraction (UAE) with LC-MS/MS. Of the 16 pharmaceuticals, 10 were detected in WWTP influents and 5 in effluents. Caffeine and acetaminophen were the most abundant (>1000 µg/L), followed by ciprofloxacin, metformin, and others (