FACULTY OF SCIENCE
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Item Analysis, occurrence and ecological risk assessment of diclofenac and ibuprofen residues in wastewater from three wastewater treatment plants in South-Western Nigeria.(World Bank-assisted National Agricultural Research Programme, 2021) Ajibola, A. S.; Adebiyi, A. O.; Nwaeke, D. O.; Ajibola, F. O.; Adewuyi, G. O.Despite the frequent detection of non-steroidal anti-inflammatory drugs (NSAIDs) worldwide in the aquatic environment, there is currently a paucity of studies from Africa, including Nigeria, on the occurrence and potential ecological risks of two commonly used NSAIDs diclofenac and ibuprofen in wastewater and effluent receiving water. In this work, diclofenac and ibuprofen were determined in wastewater from three wastewater treatment plants (WWTPs) and effluent receiving water in South-Western Nigeria. Instrumental analysis was performed by high-performance liquid chromatography. Ecological risk was assessed for four trophic levels: fish, daphnia, algae and bacteria. The method quality parameters were satisfactory for the accurate determination of target NSAIDs in wastewater and effluent receiving water. Maximum concentrations of diclofenac and ibuprofen in wastewater were 166.1 µg L-1 (UCH influent) and 62.0 µg L-1 (Ijaiye effluent), respectively. Ibuprofen posed high risk to fish in all effluent and effluent receiving water samples. Bacteria were the most sensitive organisms to the presence of diclofenac while fish was the most sensitive to ibuprofen. To the best of our knowledge, this is the first report on the occurrence and ecological risk assessment of diclofenac and ibuprofen residues in wastewater from Nigerian municipal and hospital WWTPs. More efficient wastewater treatment processes and technologies are recommended for the investigated WWTPs to reduce the discharge of target NSAIDs and other pharmaceuticals into the Nigerian aquatic environment.Item Diclofenac and ibuprofen determination in sewage sludge using a QuEChERS approach: Occurrence and ecological risk assessment in three Nigerian wastewater treatment plants.(Springer Nature, 2021) Ajibola, A. S.; Fawole, S. T.; Ajibola, F. O.; Adewuyi, G. O.A quick, easy, cheap, effective, rugged and safe (QuEChERS) method was optimized for the extraction of non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac and ibuprofen from sewage sludge. Dispersive-solid phase extraction (d-SPE) was employed for sample clean-up. Instrumental analysis was performed by high-performance liquid chromatography. Ecological risk was assessed for four trophic levels: fsh, daphnia, algae and bacteria. The method limits of quantification for diclofenac and ibuprofen were 0.43 µg g−1 and 0.45 µg g−1, respectively. Correlation coefficients were above 0.999. Extraction recoveries ranged from 70 to 118% and satisfactory inter-day reproducibility (% RSD) of <18% was obtained. Diclofenac and ibuprofen were measured up to 1.02 µg g−1 and 6.6 µg g−1, respectively in sewage sludge from three Nigerian wastewater treatment plants (WWTPs). Ibuprofen posed high risk to fish, daphnia, algae and bacteria. This work presents the first report on the ecological risk assessment of diclofenac and ibuprofen in sewage sludge from Nigerian WWTPs.Item QuEChERS approach for the analysis of three fluoroquinolone antibiotics in wastewater: Concentration profiles and ecological risk in two Nigerian hospital wastewater treatment plants.(Springer Nature, 2021) Ajibola, A. S.; Amoniyan, O. A.; Ekoja, F. O.; Ajibola, F. O.Hospital wastewater is regarded as a primary and very important source of antibiotics in the aquatic environment. Studies on the analysis, occurrence, and ecological risk assessment of fluoroquinolone antibiotics in wastewater are still limited in Africa. A quick, easy, cheap, effective, rugged, and safe extraction method was optimized and applied for determination of three fluoroquinolone antibiotics (ciprofloxacin, norfloxacin, and ofloxacin) in wastewater from two Nigerian hospital wastewater treatment plants (WWTPs) and effluent receiving water. Separation, detection, and quantification of target fluoroquinolone antibiotics were performed by high-performance liquid chromatography. Ecological risk of the three fluoroquinolone antibiotics was evaluated for three trophic levels: fish, daphnid, and algae. The method LODs were 4.1 µg L−1, 7.0 µg L−1, and 18.5 µg L−1 for ciprofloxacin, norfloxacin, and ofloxacin, respectively. Satisfactory recoveries and precisions were achieved, in addition to the correlation coefficients of greater than 0.993. Target fluoroquinolones were quantified in influents up to 228 µg L−1 (UCH influent) for ciprofloxacin, 561 µg L−1 (Ijaiye influent) for norfloxacin, and 198 µg L−1 (UCH influent) for ofloxacin. Norfloxacin had the highest concentration (386 µg L−1) in effluent receiving water. All three fluoroquinolones posed low risk to fish, whereas ciprofloxacin and norfloxacin presented moderate risk to daphnid and algae. To the best of our knowledge, this work presents the first data on the occurrence and risk assessment of the target fluoroquinolones in wastewater from Nigerian hospital WWTPs. The findings revealed the importance of developing local and nationwide surveys of fluoroquinolone antibiotics in the Nigerian aquatic environment.Item Simultaneous determination of multiclass antibiotics in sewage sludge based on QuEChERS extraction and liquid chromatography tandem mass spectrometry(Royal Society of Chemistry, 2020) Ajibola, A. S.; Tislera, S.; Zwiener, C.A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) based methodology with a dispersive solid-phase extraction (d-SPE) clean-up followed by liquid chromatography-triple quadrupole mass spectrometry analysis was developed and validated for simultaneous determination of seventeen multiclass antibiotics in sewage sludge. The target antibiotics included four sulfonamides, three fluoroquinolones, three macrolides, two tetracyclines, three b-lactams, trimethoprim and thiamphenicol. Extraction solvents, buffer salts and d-SPE sorbents were optimized. Chromatographic separation of target antibiotics was performed on a Poroshell EC-C18 column while detection and quantification were achieved with a triple quadrupole mass spectrometer using electrospray ionization in both positive and negative modes by fast polarity switching. The method limits of detection ranged from 0.003 ng g 1 dw (trimethoprim) to 120 ng g 1 dw (oxytetracycline). Intra-day precision of less than 18% (% RSD) was achieved. The applied d-SPE clean-up was effective for reducing matrix effects due to co-extracted components. The method was successfully applied for measurements of target antibiotics in sewage sludge samples from three wastewater treatment plants (WWTPs) in Nigeria. Except for b-lactam antibiotics which were not recovered during the method development, most target antibiotics were detected in the sludge samples. The highest concentrations were found for tetracyclines (up to 4689 ng g 1 dw for oxytetracycline) and fluoroquinolones (up to 1201 ng g 1 dw for ciprofloxacin). This work expands our knowledge on the applicability of QuEChERS method for the extraction of antibiotic residues from sewage sludge. The findings revealed the ubiquitous presence of the majority of the target antibiotics in the investigated Nigerian WWTPs.Item Leachate quality characteristics and groundwater contamination around closed and active landfills in Lagos, Nigeria(International Institute for Science, Technology and Education (IISTE), 2017) Ajibola, A. S.Landfilling is widely applied as a disposal method for solid wastes in most developed and developing countries. However, in many developing nations many landfills are not properly managed, and pose a serious threat to the environment due to leachate run-off. The risk of groundwater contamination by leachate is considered a significant environmental concern associated with landfilling. This study evaluated the quality characteristics of leachates from four landfills (two closed and two active landfills) in Lagos, Nigeria. The quality characteristics of groundwater samples near the landfills were also assessed. Leachate and groundwater samples were analyzed for some physicochemical properties, trace and major elements. The obtained results revealed that the total hardness in the leachates from all the landfills exceeded the regulatory limits in Nigeria. COD values in all the leachates were above the limit set by the Lagos State Environmental Protection Agency (LASEPA) which is an indication of gross organic pollution of the leachates. Generally, the concentrations of trace and major elements in the leachates were low. The presence of high concentrations of Pb in raw leachates of Abule-Egba (1.037 mg/L) and Olusoshun (1.680 mg/L) is a matter of concern because Pb is known to be one of the highly toxic environmental pollutants. Moreover, the total hardness level in groundwater near Soluos 3 landfill (190 mg/L) exceeded the limits by the Nigerian Standard for Drinking Water Quality (NSDWQ) and World Health Organization (WHO). Trace metals concentrations in the groundwater samples were generally low. Finally, the leachate quality characteristics of the closed and active landfills in this study and the associated groundwater quality characteristics did not follow any specific pattern but might have been largely influenced by the composition and type of solid wastes disposed at each of the landfill sites.Item Assessment of trace and major elements contamination in waste soils: Leaching potential from active and closed landfills in Lagos, Nigeria(International Institute for Science, Technology and Education (IISTE), 2016) Ajibola, A. S.Lagos with a population of about 21 million people is the commercial capital of Nigeria. About nine million metric tonnes of wastes were deposited into various landfill sites in Lagos in 2014. Many existing and abandoned landfills pose serious detrimental health impacts to the environment. This study evaluates the trace and major elements (Zn, Pb, Ni, Cd, Cu, Mn, Fe, Ca, K and Na) composition of waste soils from five landfills (three closed and two active landfills) in Lagos and the leaching potential of these elements from waste soils with a view to assessing the potential contamination of the groundwater resources near the landfill sites. The US EPA Toxicity Characteristics Leaching Procedure (TCLP) was employed as the leaching test method. The concentrations of trace and major elements in waste soils were determined. TCLP extracts were also analyzed for the selected trace and major elements. The concentrations of Zn in all the landfill sites (closed and active) exceeded the LASEPA regulatory limit for soil. Worthy of note was the high concentration of Pb in waste soils from Abule-Egba (closed landfill). The concentrations of the analyzed metals in TCLP extracts were found to be lower than the allowable concentrations (especially Cd, Pb and Ni) based on the TCLP standard. With the exception of Zn and Ni in Abule–Egba landfill where a leaching rate of about 24% was observed the leaching rate of trace metals were higher in active landfill sites than the closed landfills. Considering the high leaching rate of Zn and Ni in Abule-Egba landfill and the considerable leaching potential of other trace metals, it is recommended that Abule-Egba landfill, despite its current closure to waste disposal activities, should be more closely monitored in order to prevent possible contamination of groundwater resources around the landfill.Item Benzosulfonamides in wastewater: Method development, occurrence and removal efficiencies(Elsevier Ltd., 2015) Ajibola, A.; Gago-Ferrero, P.; Borova, V. L.; Dasenaki, M. E.; Bletsou, A. A.; Thomaidis, N. S.Benzosulfonamides (BeSAs) are a family of compounds with a broad application as industrial chemicals: plasticizers, intermediates for pesticides and drugs or used in the production of artificial sweeteners, among others. BeSAs constitute a class of organic compounds of emerging environmental concern. However, analytical methodologies for their determination in the environment are scarce as well as there is a lack of environmental occurrence data for these substances. An analytical methodology based on pseudo-SRM liquid chromatography–tandem mass spectrometry (LC–(ESI–)MS/MS) was developed and optimized for the determination of three BeSAs (benzenesulfonamide (BSA), o-toluenesulfonamide (o-TSA) and p-toluenesulfonamide (p-TSA)) in wastewater. The solid phase extraction protocol was also carefully optimized. The method provided recoveries in the range 83–118% (three different fortification levels). Good precision (<10.2% (intra-day) and <13.6% (inter-day)) and limits of detection achieved (11–89 ng L1) allow a reliable quantification of these compounds in both effluent and influent wastewaters. The presence of BeSAs has been evaluated during seven consecutive days in influent and effluent samples from the wastewater treatment plant of Athens, Greece. o-TSA and p-TSA were detected in 100% of the samples, while BSA was detected in all the influents and in 43% of the effluents. All three compounds were determined in relevant concentrations (up to 1.4 lg L1 in the case of p-TSA), constituting the first evidence of the presence of these compounds in Greece, and contributing to the scarce occurrence data. Removal efficiencies of BeSAs during wastewater treatment was also assessed and discussed. In this regard, different behaviors were observed: while BSA and p-TSA were removed in different rates, o-TSA was formed during wastewater treatment. A daily load of 0.48 kg of o-TSA and 0.47 kg of p-TSA was discarded in the receiving Saronikos Gulf.Item Contribution of primary and secondary treatment on the removal of benzothiazoles, benzotriazoles, endocrine disruptors, pharmaceuticals and perfluorinated compounds in a sewage treatment plant.(Elsevier B.V., 2013) Stasinakis, A. S.; Thomaidis, N. S.; Arvaniti, O. S.; Asimakopoulos, A. G.; Samaras, V. G.; Ajibola, A.; Mamais, D.; Lekkas, T. D.The occurrence and fate of 36 emerging contaminants, belonging to five different classes, (benzotriazoles, BTRs; benzothiazoles, BTHs; perfluorinated compounds, PFCs; non-steroidal anti-inflammatory drugs, NSAIDs and endocrine disruptors, EDCs) were investigated in raw, treated wastewater (both particulate and dissolved phases), and in sludge from a sewage treatment plant (STP) in Athens, Greece. The average concentrations of BTRs, BTHs, NSAIDs and EDCs in raw wastewater ranged between 11 ng L−1 and 7.27 μg L−1 , while PFCs did not exceed 100 ng L−1 . In dewatered sludge, the average concentrations ranged between 0.8 ng g−1 dw (perfluorohexanoic acid, PFHxA) and 3895 ng g−1 dw (nonylphenol, NP). The distribution of emerging contaminants between particulate and dissolved phase was different among the compounds. BTRs and BTHs showed lower solid–liquid distri bution coefficients (Kd) than all other compounds. For 9 over the 27 compounds detected in influents, the removal efficiency was higher than 70%, while the others either were removed to a lesser extent or detected at higher concentrations in effluents. Based on this, advanced treatment processes should be applied in the future for achieving adequate emerging contaminants removal in STPs. Regarding removal mechanisms, almost 60% of BTRs and 30 to 75% of BTHs were removed in bioreactors, while the contribution of primary and secondary clarifiers was of minor importance. Sorption to primary sludge was a significant mechanism affecting EDCs fate in STP.Item Occurrence and removal efficiencies of benzotriazoles and benzothiazoles in a wastewater treatment plant in Greece.(Elsevier B.V., 2013) Asimakopoulos, A. G.; Ajibola, A.; Kannan, K.; Thomaidis, N. S.Despite the widespread use of benzotriazoles and benzothiazoles and the occurrence of these compounds in wastewater treatment plants (WWTPs), no earlier study has comprehensively examined their fate in WWTPs. In this study, an integrated liquid chromatography–tandem mass spectrometry (LC–ESI(+)MS/MS) method was developed and validated for simultaneous determination of four benzotriazoles and four benzothiazoles in dissolved and particulate phases of wastewater (raw and treated), and in dewatered sewage sludge. The target benzotriazoles (BTRs) were 1H-benzotriazole, 1-hydroxy-benzotriazole, tolyltriazole, and xylyltriazole (or 5,6-dimethyl-1H-benzotriazole), and the target benzothiazoles (BTHs) were benzothiazole, 2-hydroxy-benzothiazole, 2-methylthio-benzothiazole, and 2-amino-benzothiazole. The limits of detection ranged from 0.08 (2-methylthio-benzothiazole) to 17 ng/L (benzothiazole) for dissolved phase samples, and from 0.04 (2-methylthio-benzothiazole) to 13 ng/g dry weight (dw) (benzothiazole) for particular matter and sludge samples. The method was applied in the analysis of wastewater and sludge samples from the WWTP in Athens, Greece. All target chemicals were detected in wastewater samples, and in some cases the concentrations were significant, on the order of a few μg/L. In sludge samples, benzothiazole and tolyltriazole were present at the highest concentrations (174 and 116 ng/g dw, respectively). For benzotriazole and tolyltriazole, the removal efficiency was below 68%, and for benzothiazoles, the removal efficiency was greater than 64% in the activated sludge treatment process. Both BTRs and BTHs showed low solid–liquid distribution coefficients.Item Benzil and benzoin: General spray reagents for the visualization of organic compounds on thin layer chromatograms(Vieweg & Sohn Verlag/GWV Fachverlage GmbH, 2007) Dare, E. O. || Ajibola, A. S.Benzil and Benzoin spray reagents have been adopted to detect some organic compounds on thin layer chromatograms (TLC). These reagents were found to visualize sugars, amino acids, dicarboxylic acids and some natural products on thin layer plates. Colors produced with these reagents were shades of the spectrum and characteristic of individual or class of the organic and natural products.