Occurrence and seasonal variation of contaminants of emerging concern (CECs) in influent and effluent of four Australian wastewater treatment plants (WWTPs)

This study investigates the occurrence, seasonal trends, and mass fluxes of 19 contaminants of emerging concern (CECs) in influents and effluents from four wastewater treatment plants (WWTPs) in Australia. A total of 352 triplicate 24-h composite samples were collected over seven days during autumn (May 2023) and spring (November 2023) and analysed using solid-phase extraction and LC-MS/MS. All CECs were detected in influents with >73 % frequency, while detection in effluents was lower, indicating partial removal. Acetaminophen (1,610-26,600 ng/L) and caffeine (716-9,720 ng/L) were the most abundant in influent, irrespective of WWTP or season. Spatial and seasonal variations were evident; analgesics (codeine) and antibiotics (ofloxacin, sulfamethoxazole, trimethoprim) were higher in autumn, while psychiatric drugs (citalopram, desvenlafaxine) and DEET peaked in spring. Weekly trends revealed significant fluctuations (p < 0.05) in ten compounds, with caffeine peaking midweek, while pharmaceuticals (fluoxetine, venlafaxine, sulfamethoxazole), pesticides (atrazine, piperonyl butoxide), and industrial chemicals (BBP, TCEP) peaked on Sundays. Removal efficiencies (RE) varied widely, from complete removal to elevated effluent levels for certain herbicides and psychiatric drugs. One WWTP consistently achieved >85 % RE for most CECs. Risk Quotient assessment indicated low acute risks to algae and invertebrates, but moderate to high chronic risks to fish from venlafaxine, fluoxetine, citalopram, and carbamazepine (90th percentile). Median concentrations showed reduced risks, except for carbamazepine at W2. Invertebrates faced moderate chronic risks from acetaminophen and sulfamethoxazole. This assessment did not account for dilution in receiving waters and considered both peak and typical exposure levels.