Occurrence, Removal and Risk Assessment of Priority Pharmaceuticals and Selected Pesticides in Wastewater in Lebanon

Abstract

The prevalence of pharmaceutical residues and pesticides in wastewater and sludge has emerged as a pressing environmental issue, attributed to their extensive usage and potential implications in affecting human health and aquatic ecosystems. Within the Lebanese context, characterized by elevated pharmaceutical consumption rates, this matter assumes notable significance. This study investigates the occurrence and seasonal variation of pharmaceuticals and pesticides in wastewater across Lebanon and evaluates their removal efficiency in wastewater treatment plants operating under different schemes and conditions. Twenty-seven pharmaceuticals and four pesticides were targeted and were selected based on their common use in Lebanon, their widely reported occurrence in wastewaters, and recognized environmental impacts. The methodological framework involved the collection of wastewater influents, effluents and sludge samples, and their subsequent extraction and analysis employing advanced analytical techniques (QToF). The results revealed significant concentrations of various pharmaceuticals, with caffeine, valsartan, ibuprofen, and acetaminophen being the most prominent in all influents. The presence of these pharmaceuticals in Lebanon's WWTPs is consistent with global patterns, highlighting the widespread nature of these contaminants. The study identified Tebnine WWTP, which receives wastewater from livestock farms and hospitals, as a hotspot for elevated pharmaceutical concentrations, highlighting the impact of diverse wastewater sources on contamination levels. Sixteen pharmaceuticals and three pesticides were also detected in the sludge samples, amplifying the concerns. The removal efficiencies varied across different compounds and WWTPs, emphasizing the complexity of treatment mechanisms. Significant amounts of pharmaceuticals and pesticides were found to persist in the treated effluents. The study also revealed significant variations in the removal efficiencies of the targeted compounds across the treatment stages. Primary treatment results indicated limited removal through adsorption for most compounds, with some instances of desorption and accumulation. Secondary treatment, dominated by biodegradation, showed higher removal efficiencies for compounds like acetaminophen, ketoprofen, and certain antibiotics, though variability persisted among different WWTPs. Disinfection methods, including chlorination and UV light, further contributed to the removal of residual compounds, with differential effectiveness based on the chemical characteristics of each compound. The ecotoxicological risk assessment revealed that caffeine and clarithromycin posed the highest risk, particularly against algae, with varying risk levels observed in different WWTPs. Diclofenac, caffeine, clarithromycin, sulfamethoxazole, and diazinon also exhibited significant risks against various aquatic species. The human risk assessment unveiled varying risk levels associated with different compounds across varying age groups. Diazinon stood out with the highest human risk quotient (HRQ), in both influent and effluent samples, while clarithromycin, acetamiprid and carbamazepine also demonstrated notable risks, with effluent samples from certain WWTPs still posing potential threat to human health. This study contributes to the understanding of pharmaceutical contamination in wastewater in Lebanon, its spatial distribution across the country, its response to seasonal variations, and the efficiency of its removal using conventional treatment processes. Such insights are paramount for evaluating potential risks to human health and the environment and formulating efficacious strategies for mitigating such contamination in the environment.