Occurrence and prevalence of antibiotics in wastewater treatment plants and effluent receiving rivers in South Africa using UHPLC-MS determination.

The increased usage of antibiotics over the recent years has led to an increased interest in monitoring their presence in wastewater all over the world. In this study the occurrence of sixteen (16) selected antibiotics (amoxicillin, ampicillin, azithromycin, ciprofloxacin, doxycycline, erythromycin, gentamicin, metronidazole, norfloxacin, ofloxacin, penicillin, sulfamethoxazole, sulfapyridine, sulfamethizole, tetracycline and trimethoprim) were determined in two wastewater treatment plants and two effluent receiving rivers in Northern part of Pretoria, South Africa. Targeted screening and identification of antibiotics was done using ultra high-performance liquid chromatography coupled with mass spectrometry after sample clean-up and pre-concentration using solid phase extraction. The concentrations of the targeted antibiotics detected in influent samples ranged between 0.78 and 96.8 ng mL-1 and those in effluent were between 0.12 and 9.89 ng mL-1. The highest recorded concentrations in all samples were those of doxycycline (30.9-120 ng mL-1) and sulfamethoxazole (2.52-96.8 ng mL-1) in effluent and influent samples, respectively. The concentrations of antibiotics in the rivers receiving effluents were between 0.03 and 72.8 ng mL-1 in upstream samples and 0.008-76.8 ng mL-1 in downstream samples, indicating that there is other source of contaminate to these rivers other than the treatment plants. Risk assessment using the hazard quotients ranged between 0.24 and 889 indicating that the presence of these antibiotics and antibiotic mixtures posed higher ecological risks to aquatic organisms. From the study, it could be concluded that wastewater treatment plants were releasing antibiotics to the environment and posing a risk to the aquatic ecosystem and public health. Therefore, there is a need to research into developing more efficient conventional wastewater treatment technologies that can completely remove antibiotics from wastewater.

Determination of antibiotics during treatment of hospital wastewater using automated solid-phase extraction followed by UHPLC-MS: occurrence, removal and environmental risks.

The extent of removal of pharmaceuticals by African-based wastewater treatment plants (WWTPs) is relatively unknown with various studies observing high concentrations in effluents. This is mainly due to WWTPs still utilising the traditional treatment methods which are known to be less effective. In this study, 15 selected antibiotics (amoxicillin, ampicillin, azithromycin, ciprofloxacin, doxycycline, erythromycin, gentamicin, metronidazole, norfloxacin, ofloxacin, penicillin, sulfamethoxazole, sulfapyridine, tetracycline and trimethoprim) were monitored in wastewater as it goes through sedimentation (primary and secondary), aeration and chlorination stages of a WWTP. Analytical method involved solid-phase extraction followed by liquid chromatographic determination. Removal efficiencies during sedimentation were generally positive with doxycycline achieving 80-95.8%, while negative removal efficiencies were observed for penicillin V (-46.4 to -17.1%) and trimethoprim (-26.2 to -18.9%). The aeration and agitation stage resulted in concentration enhancement for several antibiotics with seven of them ranging between -273 and -15.5%. This stage was responsible for the relatively low overall removal efficiencies in which only 4 antibiotics (doxycycline, tetracycline, ciprofloxacin, and erythromycin) experienced overall removal efficiencies above 50%. The recorded effluent concentrations ranging between 0.0130 and 0.383 ng/mL were translated to low potential for development of antibiotic resistance genes in the receiving environments while ecotoxicity risk was high for only amoxicillin, ampicillin and sulfapyridine. The study has provided an overview of the performance of common wastewater treatment processes in South Africa and hopes that more monitoring and environmental risk data can be made available towards drafting of antibiotic priority lists that cater for Africa.