The impact of a Wastewater Treatment Works in Southern Gauteng, South Africa on efavirenz and nevirapine discharges into the aquatic environment

There has been growing concern regarding the pollution of the aquatic environment with synthetic organic chemicals.Antiretroviral drugs,such as efavirenz and nevirapine,are pharmaceutical drugs and are referred to as emerging contaminants.Such drugs can be environmentally persistent and may be expected to pose potential risks to drinking water supplies.Sources of pharmaceutical drugs include effluents from Wastewater Treatment Works(WWTPs),hospital and pharmaceutical production facilities and the incorrect disposal of unused and expired medicines.Currently there are no monitoring programs and legislative guidelines for their regulations in South Africa.The aims of this study were firstly to develop a semi-quantitative method to extract and analyse efavirenz and nevirapine in the primary settling tank sludge.Secondly to use that method,and an existing method for liquid wastewater samples,to monitor the concentrations of efavirenz and nevirapine as the wastewater passes through the different stages of purification(anoxic;aerobic;pre and post chlorination)in the WWTP.This was repeated weekly over a period of 4 weeks.Thirdly,to determine if binding of efavirenz and nevirapine to the solids in the WWTP played a role in the removal of these compounds from the WWTP liquid phase.No references to the analysis of ARVDs in WWTP sludge were found in the literature.Grab samples of wastewater and sludge samples were collected from a WWTP(activated sludge treatment process)weekly for 4 weeks.Liquid samples were extracted solid phase extraction,solid samples were extracted using sonication followed by a QuEChERs clean-up.Sample extracts were then subjected to gas chromatography-time of flight mass spectrometry for analyte determination.Efavirenz concentrations entering the WWTP ranged between 5500 to almost 14000 ng/L.The removal of efavirenz by the WWTP ranged between 27 and 71%.The largest removal occurred in the anoxic zone,smaller amounts were removed in the aerators.Slight increases in efavirenz concentrations were found after chlorination and the final effluent into the river post maturation ponds again were slightly lower.Solids were found to contain efavirenz at concentrations between 17 and 43 mg/kg dried primary settling tank sludge and it is proposed that this binding to the solids is the main mechanism of removal of efavirenz from the wastewater stream as it passes through the WWTP.Although an order of magnitude lower nevirapine concentrations displayed the opposite behaviour and gradually increased through the various stages of purification in the WWTP.Minor fluctuations occurred but the concentrations of nevirapine were higher at the effluent(between 92 and 473 ng/L)than those entering the WWTP.No nevirapine was detected in the PST sludge.The increase in nevirapine concentrations are likely to be the result of the de-conjugation of the hydroxylated metabolites of nevirapine in the WWTP,its resistance to degradation and the lack of binding of the nevirapine to the PST sludge.

Seasonal variations and the influence of geomembrane liners on the levels of PBDEs in landfill leachates,sediment and groundwater in Gauteng Province,South Africa

In the present study,the seasonal concentrations of polybrominated diphenyl ethers(PBDEs)in leachate and sediment samples,and the influence of geomembrane liners on PBDE levels and the extent of their infiltration into groundwater on selected landfill sites in Gauteng Province,South Africa were determined.Leachate and sediment samples were collected from seven operational landfill sites namely:Goudkoppies,Robinson Deep,Marie Louis,Soshanguve,Onderstepoort,Hatherly and Garankuwa from Johannesburg and Pretoria,in winter and summer.Groundwater samples were collected from monitoring boreholes from two landfill sites.Liquid-liquid and Soxhlet extraction techniques were employed for the extraction of leachate and groundwater,and sediment respectively using dichloromethane.The extracted samples were subjected to column clean up and,thereafter,analysed using gas chromatographyemass spectroscopy(GC-MS).PBDEs selected for the study were:BDE-17,-28,-47,-100,-99,-153,-154,-183 and-209.The P9PBDE concentrations in leachate samples for winter and summer ranged from 0.316e1.36 ng L-1 and 0.560e1.08 ng L-1 respectively.The P9 PBDE concentrations obtained for sediment in winter and summer were 3.00e4.91 ng g-1 and 2.50e3.71 ng g-1 respectively.Winter samples exhibited higher(p<0.05)concentrations for both leachate and sediment samples compared to summer samples.This trend was attributed to high precipitation rate in summer which may have infiltrated into the landfills,subsequently diluting the leachate and sediment samples.In contrast,the winter period is generally dry and PBDEs are,therefore,more likely to be concentrated.The concentrations of PBDEs in leachate and sediment samples were higher in landfill sites with geomembrane liners compared to those without liners.Groundwater samples taken from the vicinity of selected landfill sites without geomembrane liners exhibited high concentrations of P9PBDEs,indicating possible migration of PBDEs from landfill site into groundwater.Pearson correlation(r)and statistical significant t-test(p)for the PBDE congeners versus dissolved organic carbon(DOC)resulted in positive moderate interactions with a statistical significance for most congeners.Suggesting that there is a possible influence of organic carbon on the levels of PBDEs.

Batch equilibrium studies on the adsorptive capacity of powdered and pelleted maize tassel to remove PFOA and PFOS from aqueous medium

This study was aimed at evaluating the potential of raw maize tassel powder and pellets to remove PFOA and PFOS from water.Batch experiments were first conducted using ultrapure water to investigate the effects of pH,adsorbent dosage,initial PFASs concentration,contact time and temperature in adsorption efficiency of powdered and pelleted maize tassel.The optimum conditions for the removal of PFOA/PFOS observed for both maize tassel powder and pellets were as follows:pH 2.0,adsorbate initial concentrations of 20 mg g1,adsorbent dosage of 0.5 g(20 pellets),1 h contact time,all at 25℃.These optimum conditions were,thereafter,applied to surface water samples from Apies River in Pretoria,spiked with 20 mg L^(-1)PFOS/PFOA.Shimadzu LC-MS/MS was employed in analysis and the Langmuir and Freundlich isotherm models were used to determine the types of adsorption mechanism.High percentage removal 91.3%and 89.7%for PFOA and PFOS respectively using both MT powder and pellets were achieved.The maximum adsorption capacities identified for the monolayer of the Langmuir isotherm model was found to be between 41.6 mg g^(-1)and 58.82 mg g^(-1)for PFOA using powder and pellets respectively;and between 42.37 mg g^(-1)and 176.5 mg g^(-1)for PFOS for the same adsorbents respectively.These results showed very insignificant conformity to the Langmuir model;therefore it can be assumed that the Langmuir model was not obeyed.However,the experiments proved to be primarily consistent with the Freundlich model,with high correlation coefficient(R2)values ranging from 0.900 to 0.998 for both PFOA and PFOS.Maximum adsorption capacities of 142.8 mg g^(-1)and 78.57 mg g^(-1)for PFOA and 107.4 mg g^(-1)and 85.7 mg g^(-1)for PFOS at 25℃using both powder and pellets respectively were obtained suggesting that adsorption took place on heterogeneous layers for both targeted PFASs.