Spatial occurrence and distribution of micropollutants (pharmaceuticals and personal care products) in the eThekwini catchment, South Africa

This study presents, for the first time, the spatial and short-term temporal occurrence of forty-two multiclass pharmaceuticals, their metabolites, and personal care products in wastewater across a catchment area with and without rivers connected to wastewater treatment plants (WWTPs) in the eThekwini Metropolitan Municipality of South Africa. Four major WWTPs were studied, each with different wastewater treatment technologies and their receiving water bodies, over a week. This study compared the efficiency of the treatment plants and found that the removal efficiency depends on the treatment process employed. Wastewater treatment plants that employed activated sludge consistently achieve higher removal efficiencies for pharmaceuticals and personal care products (PPCPs) than plants that rely solely on screening and sedimentation. Most detected PPCPs increased downstream, indicating contributions from WWTP effluent; however, for some compounds, lower concentrations in the effluent relative to upstream concentrations led to dilution after mixing, demonstrating the combined influence of effluent inputs and hydrological mixing on river water quality. There is also concern about synergistic effects from the combination of these PPCPs, which may be detrimental despite their presence at trace levels. Among the PPCPs monitored, 26 were detected in the influent and effluent, with the most detected PPCPs in both being benzophenone-3, metformin, gliclazide, atenolol, carbamazepine, carbamazepine-10,11-epoxide, 10,11-dihydro-10-hydroxycarbamazepine, nicotine, caffeine, 1,7-dimethylxanthine, N-desmethyltramadol, and O-desmethyltramadol. The weekday-weekend concentrations of some PPCPs (citalopram, 1,7-dimethylxanthine, nicotine, metformin, atenolol, cimetidine, benzophenone-3, gliclazide, quetiapine, and 10,11-dihydro-10-hydroxycarbamazepine) were significantly different across the various plants, indicating variation in the consumption habits of the people these plants serve. The highest concentrations in the influents and effluents were observed for 1,7-dimethylxanthine (a metabolite of caffeine), with mean concentrations of 723 668.4 ± 180 002.5 ng L−1 and 409 405.7 ± 173 761.3 ng L−1, respectively. Except for acetaminophen, desvenlafaxine, carbamazepine-10,11-epoxide, nicotine, caffeine, and 1,7-dimethylxanthine in one or two treatment plants, the majority of the PPCPs in the effluent showed an insignificant to medium aquatic risk (this level of risk is similar for the studied surface water), based on an ecotoxicological risk assessment. Given that these PPCPs are present as complex mixtures with diverse physicochemical properties and varying capacities to influence a range of molecular and cellular processes in organisms, a better understanding of their ecological risk is needed to promote environmental health.