Analysis of targeted pharmaceuticals and metabolites at a wastewater treatment plant in KwaZulu-Natal, South Africa.

Abstract

Globally, surface water bodies are shown to be severely contaminated by chemical compounds as a result of human activity. Some of these compounds are inclusive of pharmaceuticals and their metabolites which are classified as emerging contaminants (ECs). A major contributor to this pollution event is treated wastewater effluent. This is an area of growing concern, particularly for emerging economies, due to an increase in demand for clean and potable water arising from rapid urbanisation and significant population growth. In South Africa, there is limited information outlining concentrations of various pharmaceuticals in treated wastewater effluent and surface water bodies and there is currently no legislation indicating maximum concentrations to be allowed in wastewater effluent. This research study aimed to identify and quantify concentrations of selected pharmaceuticals and metabolites present at various stages within the Wastewater Treatment Plant (WWTP). Additionally, the study aimed to determine seasonal pharmaceutical trends in relation to SARS-CoV-2 (COVID-19) and influenza infections, removal efficiencies and undertake an environmental risk assessment (ERA). The pharmaceuticals that were analysed included metformin, caffeine, sulfamethoxazole hydroxylamine, sulfamethoxazole, nevirapine, prednisolone, valsartan, rifampicin, 17α ethinylestradiol (EE2) and ivermectin, all of which being pharmaceuticals that are commonly prescribed for the treatment of medical conditions that are prevalent in South Africa and for the treatment and prevention of COVID-19. Analyte concentrations were assessed in wastewater samples taken from the inlet, balancing tank, secondary effluent, and maturation river over three sampling seasons. Analytes were extracted using a solid phase extraction (SPE) method and extracts were analysed using liquid chromatography – mass spectrometry (LC – MS). Method percentage recoveries ranged from 73.53 – 100.70% while limit of detection (LOD) and limit of quantification (LOQ) overall ranged from 0.0330 – 0.886 mg L-1 and 0.0990 – 2.68 mg L-1, respectively. Analyte concentrations quantified in inlet samples ranged from 0.007587 – 1.243 mg L-1 while balancing tank concentrations ranged from 0.007599 – 1.042 mg L-1. Secondary effluent and maturation river concentrations ranged from 0.0005244 – 0.9483 mg L-1 and 0.0002507 – 0.9286 mg L-1, respectively. Non-detection of certain analytes in some samples could imply the possibility that the pharmaceutical converted into transformation products and thus evaded detection. Influent pharmaceutical concentrations showed distinct seasonal variation, and this was statistically shown using a one-way ANOVA analysis. P-values were recorded as < 0.05 for caffeine, sulfamethoxazole hydroxylamine, sulfamethoxazole, EE2 and ivermectin, thus implying that significant differences were observed between seasonal levels of pharmaceutical compounds and in relation to the COVID-19 and influenza infection peaks. Analyte removal efficiencies based on the plant treatment processes ranged from 7.70 – > 99.99 %. The ERA performed indicated ratios within the range of 0.0863 and 10.5x 108, which is of significant concern as values greater than 1 would severely impact the health of aquatic organisms and ecosystems within the receiving surface water body.