Faculty of Applied Sciences
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Item Optimization of extraction techniques for the isolation and pre-concentration of pharmaceuticals in aquatic environments(2021) Sigonya, Sisonke; Mdluli, Phumlane Selby; Chimuka, LukeThe occurrence of pharmaceuticals in South African aquatic environments has been reported in several studies. However, most of these reports focused on the occurrence of organic compounds in wastewater and surface water. There are very few studies reporting the presence and concentration of these compounds in seawater and coastal areas. Further, most studies have looked at only on one season. This study focussed on the optimisation of a SPE extraction method using Bond Elut Plexa cartridges for the identification and quantification three nonsteroidal anti-inflammatory drugs (NSAIDs), three antiretroviral drugs (ARVs) and a lipid regulator in coastal area of Durban city, South Africa covering four seasons. The optimised SPE conditions were as follows: 500 mL sample volume and at pH 5.8, 5 and 5 mL as conditioning and elution volumes, respectively. The flow rate ranging from 5 to 10 mL/min 10 and 5 mL/min as sample and elution flow rates. The extracted compounds were qualitatively and quantitatively detected by a high-performance liquid phase chromatographic instrument coupled to a photodiode array detector (HPLC-PDA). The recoveries ranged from 62 -102% with RSD values of 0.56 to 4.68% respectively for the determination of emtricitabine, tenofovir, naproxen, diclofenac, ibuprofen, efavirenz, and gemfibrozil. The analytical method was validated by spiking estuarine water samples with 5 µg L-1 of a mixture containing the target pharmaceuticals and the matrix detection limits (MDL) were established to be 0.62- 1.78 µg L-1 for the target compounds. The optimized method was applied to seasonal monitoring of pharmaceuticals at chosen study sites from winter and spring of 2019 and summer and autumn of 2020.The sum of emerging pollutants (ƩEP) were calculated based on each study site. The influent of the Kingsburgh WWTP (EFK) had the highest ƩEP of 144.88 µg L-1 in winter between the two wastewater treatment plants area in this study. The Northern WWTP influent (INN) had a total ƩEP of 117.11 µg L-1 in autumn, the Kingsburgh WWTP effluent (EFK) had a concentration 63.8 µg L-1 in autumn and a concentration 63.8 µg L-1 in summer and the Northern (EFN) had a total ƩEP of 43.97 µg L-1 in winter. A comparison between UMgeni (UR) and Kingsburgh river (KR) showed that the KR had the highest concentration of total ƩEP of 22.66 µg L-1 and UR with the total ƩEP of 18.3 µg L-1 both in winter and spring, respectively. The seawater EPs Blue Lagoon (BL) had the highest ƩEP of 46.75 µg L-1 in spring, subsequently Warner Beach bottom (WBB), Glen Ashley (GA) and Warner Beach top (WBT) with concentrations of 24.96 µg L-1 in summer, 13.29 µg L-1 in spring and 6.94 µg L-1 in autumn, respectively. Estuarine EPs had concentrations of 37.9 µg L-1 and 20.97 µg L-1 for Warner beach estuary (WE) and UMgeni estuary (UE) in winter. WBE having the highest concentration between the two. This showed a significant variation on the presence of these pharmaceuticals in different season.Item Synthesis and characterization of membrane with molecularly imprinted polymers for selective adsorption of triclosan(2019) Mntambo, Siyabonga Aubrey; Mdluli, Phumlane S.; Mahlambi, Mphilisi MciniseliAmongst many tenacious emerging traces of lethal organic pollutants in wastewater, triclosan (TCS) is typically the often-encountered compound. This pollutant has been reported in the water circle, including surface water, wastewater treatment plants, groundwater, aquatic sediments and aquatic organisms and, to a lesser extent, drinking water, at levels in the nanograms to low micrograms per litre range. Triclosan mainly find its way into the human system through its extensive use in pharmaceutical industries over the recent years. Excessive exposure to this water pollutant may result in adverse conditions like hematological disorders such as blood cancer. Despite the variety of its negative effects, triclosan is still used as a preservative in many pharmaceutical personal care products (PPCPs), e.g. toothpaste, disinfectants, hand wash, cosmetics, soaps and medication. In light of the aforementioned applications, it is imperative to remove triclosan to accepted levels and find more efficient, low-cost and less energy consuming methods of its removal in order to counter the challenges of water scarcity in the country and its wastewater channels. In this study, a “fractionated approach” was used, as it accounts for the synthesis of selective polymeric membranes using a phase inversion by immersion precipitation technique. Hence, the quest to address these water challenges was through the application of polyvinylidene fluoride (PVDF) polymeric membranes for the removal of triclosan in effluent treatment plant (ETP) water. This was carried out by fabricating this polymer with selective micro composite particles called molecularly imprinted polymers (MIPs). This improved the mechanical behaviour and strength of the membrane. The MIPs were synthesised using a two-step bulk polymerisation process. The synthesized MIPs possess specific binding cavities within its structure. The PVDF membrane were functionalised with MIPs and were characterised using Scanning Electron Microscopy (SEM), for their morphological properties. Thermogravimetric analysis (TGA) was used to study their thermal behaviour and the Fourier transform infrared coupled with universal attenuated total reflectance (FTIR- ATR) was utilized to determine the functional groups present in the membrane. The dynamic mechanical analysis (DMA) was used to study the mechanical behaviour and strength of the membranes. The SEM images showed the equal distribution of micro particles on the membrane surface. The TGA analysis revealed that all the studied polymeric membranes were thermally stable up to an average temperature of 502°C. The FTIR-ATR analysis showed new absorption peaks that were brought by the functionalisation and revealed that the PVDF membrane does not interfere with the MIP chemical integrity despite being infused within the polymeric membrane. DMA revealed an improved stability and behaviour once the concentration of the additives was increased. Moreover, the water and porosity content percentage of the MIP infused PVDF membranes increased as the concentration of the adsorbent was increased. Wastewater samples were collected from an effluent treatment plant (ETP)and pre- treated before analysis. Experimental parameters such as sample size, contact time, stirring speed were optimised. The synthesised PVDF/MIP membranes had an adsorption efficiency of 97% TCS in membranes compared to PVDF/NIP and PVDF bare membrane which had 92%, 88%, respectively. This might be due to the effect of the binding sites of the additives. The analytical method had limits of detection (LOD) and limits of quantification (LOQ) of 0.22, 0.71 µgL-1 in wastewater effluent, respectively. The percentage recovery for the effluent samples was 68 %. The results obtained therefore shows that MIPs have the potential modifier for the development and continuous progress in PVDF membranes.Item Prevalence and fate of antibiotics and its derivatives in sewage treatment in Durban and the receiving environment(2019) Faleye, Adekunle Christopher; Stenström, Thor-Axel; Ramluckan, Krishan; Adegoke, Anthony Ayodeji; Bux, FaizalAntibiotics are released to the environment either directly in an unchanged form or partially metabolized. The discharge is usually through untreated waste or through wastewater treatment effluents. The stable antibiotics in reduced amounts persist through the wastewater treatment processes and end up in receiving waters, where they may impact crops through irrigation or affect drinking water intakes. Antibiotics in the waste and sludge fractions may similarly impact crops and arable land through their use as fertilizers. Conventional wastewater treatment plants are not designed for the removal of antibiotics but may to a varying extent reduce their concentrations. Their quantitative occurrence within the water matrices depends on the frequency and quantities of use for therapeutic purposes or as growth promoters in animal production. Additional inputs may emanate from individual waste discharges. Antibiotics present in sub-inhibitory concentrations may predicate for resistance among the resident bacteria in the water matrix, biofilms or in humans and animals. In South Africa antibiotics are extensively used both in human therapy and in animal husbandry without clearly followed regulations and are sometimes readily available. The available studies have focused on the presence of antibiotic resistant bacteria in wastewater influent and effluent but there is a paucity of information relating to these antibiotics as emerging contaminants in South Africa wastewater. In this thesis a rapid and sensitive analytical methodology was initially assessed and applied, based on the use of HPLC/diode array UV detector for six antibiotics (ethionamide (ETI), metronidazole (MET), trimethoprim (TRI), ciprofloxacin (CIP), sulfisoxazole (SUF) and albendazole (ALB). Validation of the method was performed by screening assessment in selected wastewater treatment plants (WWTPs) with the aim of determining the sensitivity of the equipment (Shimadzu 2020), assess the limit of detection, optimize the extraction procedure (solid phase extraction) and screen for the most prevalent antibiotics. The percentage recovery for the optimized method using wastewater sample was above 65 % for all antibiotics of interest. The limit of detection, which ranges from 0.03 to 0.48 mg L-1, enables the determination of a range of concentration of antibiotics in polluted sample such as the wastewater influent sample. Furthermore in this thesis, a more advanced, online solid phase extraction – high performance liquid chromatography mass spectrometry (SPE-HPLC-MS) method, was applied to measure the concentration of these and an additional seven antibiotics, norfloxacin (NOR), ofloxacin (OFL), clindamycin (CLI), sulfamethoxazole (SUL), erythromycin (ERY), clarithromycin (CLA), azithromycin (AZI) and roxithromycin (ROX) in ng L-1 concentrations. The quantity and occurrence of the selected antibiotics was assessed in untreated wastewater in four wastewater treatment plants in Durban, KwaZulu-Natal (KZN), at different treatment stages and in the effluent and recipient surface water environment. In the influent the additive concentration of the antibiotics associated to the separated sediment fraction through centrifugation and in the supernatant of samples collected were accounted for and analyzed. The limit of detection (LOD) and the limit of quantification (LOQ), ranged from 0.07 – 0.33 ng L-1 and 0.23 – 1.09 ng L-1, respectively for the 13 assessed antibiotics and the percentage recovery were in the range of 51 to 111 %. The percentage of antibiotics recovered from the sediment (centrifuged) samples, which would have been lost to filtration if not analyzed in parallel, were in the range of 2.6% – 97% (n = 32), while the frequency of detection in the influent samples for the sampling period ranges from 62.5 – 100 % (n = 32). All the studied antibiotics were detected in the influent of each WWTP and the concentration was in the rage of 1.3 ng L-1 (AZI) – 81748 ng L-1 (CIP). The antibiotics with the highest concentrations (median) detected in the receiving water (downstream) for each of the four WWTPs in KZN, were TRI (217 ng L-1), SUL (239 ng L-1), CIP (708 ng L-1) and ALB (325 ng L-1) respectively. The overall percentage removal efficiency for the four WWTPs ranged from 21 % - 100 %. The most effective treatment steps were assessed with the focus on activated sludge filter and trickling filter. Within these, it was actually the sedimentation treatment stages (secondary clarifier), after these steps that played the most vital role in the reduction of antibiotics where > 70 % of the antibiotics was removed. Finally, the impact of post chlorination was analyzed for the effluent of the WWTPs. The presence of transformation product as a result of post chlorination was examined in a parallel study using a controlled experiment and full scale analysis. The efficiency of chlorine in the reduction of antibiotics was more of transformation of antibiotics than degradation. The oxidative ability of chlorine enhances its reaction with antibiotics thereby transforming the antibiotics. The percentage reduction of antibiotics in relation to chlorination was >85 % (pilot experiment) and ranged between 14 % - 97 % in the field experiments. Likewise, UV was effective in the degradation of antibiotics, with longer exposure time producing higher degradation. Future research should focus on determining the toxicological impact of these transformation products. The concentration of the antibiotics in the downstream samples were generally low when compared to their influent concentrations.