Assessment of Emerging Contaminants in Wastewater Treatment Plants and Receiving Surface Waters from Uruguay

Emerging contaminants (ECs) are increasingly detected in aquatic environments worldwide, yet integrated assessments combining occurrence, mixture risk, and suspect screening remain scarce in South America. This study investigated the occurrence, distribution, and ecological risks of ECs in four wastewater treatment plants (WWTPs) in Uruguay, representing a technological gradient, including effluent and surface waters. Target and suspect screening were applied to effluents and receiving waters using liquid chromatography–high-resolution mass spectrometry (LC-HRMS), complemented by mixture-based ecological risk assessment. Twenty-one target compounds were found, with Caffeine (57.1 μg L–1) and theobromine (46.1 μg L–1) showing the highest concentrations, followed by trimethoprim (11.0 μg L–1) and carbamazepine (10.6 μg L–1). Distinct WWTP-specific chemical fingerprints were observed, with Castillos and Santa Lucı́a exhibiting the highest contaminant loads. Suspect screening tentatively identified 35 additional compounds, including cocaine, benzoylecgonine, losartan, and sildenafil. Ecological risk assessment showed that 62% of detected compounds exceeded predicted no-effect concentrations (PNEC), with metolachlor presenting the highest risk quotient (RQ = 150,064). Mixture risk quotients ranged from 97 in surface waters to 31,911 in WWTP effluents, indicating substantial cumulative ecological risk. These findings highlight the importance of integrating analytical and risk-based approaches to support water quality management in Uruguay and similar regions.