Occurrence and treatment of contaminants of emerging concern in the African aquatic environment: Literature review and a look ahead

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 μg L^-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.

Influence of cosubstrate and hydraulic retention time on the removal of drugs and hygiene products in sanitary sewage in an anaerobic Expanded Granular Sludge Bed reactor

Diclofenac (DCF), ibuprofen (IBU), propranolol (PRO), triclosan (TCS) and linear alkylbenzene sulfonate (LAS) can be recalcitrant in Wastewater Treatment Plants (WWTP). The removal of these compounds was investigated in scale-up (69 L) Expanded Granular Sludge Bed (EGSB) reactor, fed with sanitary sewage from the São Carlos-SP (Brazil) WWTP and 200 mg L^-1 of ethanol. The EGSB was operated in three phases: (I) hydraulic retention time (HRT) of 36±4 h; (II) HRT of 20±2 h and (III) HRT of 20±2 h with ethanol. Phases I and II showed no significant difference in the removal of LAS (63 ± 11-65 ± 12 %), DCF (37 ± 18-35 ± 11 %), IBU (43 ± 18-44 ± 16 %) and PRO (46 ± 25-51 ± 23 %) for 13±2-15 ± 2 mg L^-1, 106 ± 32-462 ± 294 μg L^-1, 166 ± 55-462 ± 213 μg L^-1 and 201 ± 113-250 ± 141 μg L^-1 influent, respectively. Higher TCS removal was obtained in phase I (72 ± 17 % for 127 ± 120 μg L^-1 influent) when compared to phase II (51 ± 13 % for 135 ± 119 μg L^-1 influent). This was due to its greater adsorption (40 %) in the initial phase. Phase III had higher removal of DCF (42 ± 10 % for 107 ± 26 μg L^-1 influent), IBU (50 ± 15 % for 164 ± 47 μg L^-1 influent) and TCS (85 ± 15 % for 185 ± 148 μg L^-1 influent) and lower removal of LAS (35 ± 14 % for 12 ± 3 mg L^-1 influent) and PRO (-142 ± 177 % for 188 ± 88 μg L^-1 influent). Bacteria similar to Syntrophobacter, Smithella, Macellibacteroides, Syntrophus, Blvii28_wastewater-sludge_group and Bacteroides were identified in phase I with relative abundance of 3.1 %-4.7 %. Syntrophobacter was more abundant (15.4 %) in phase II, while in phase III, it was Smithella (12.7 %) and Caldisericum (15.1 %). Regarding the Archaea Domain, Methanosaeta was more abundant in phases I (84 %) and II (67 %), while in phase III it was Methanobacterium (86 %).

Electrooxidation of amoxicillin in aqueous solution with graphite electrodes: Optimization of degradation and deciphering of byproducts using HRMS

Contaminants of emerging concern (CECs) such as antibiotics have become a matter of worry in aquatic environments worldwide. Their presence in the environment has been increasing due to the inability of conventional wastewater and water treatments to annihilate them. Hence, attempts have been made to remove CECs using electrochemical oxidation (EO). Present study employed the low cost, active carbon based graphite sheet electrodes as anode and cathode to oxidize and degrade Amoxicillin (AMOX)- a β-lactum thiazolidine antibiotic. Optimization studies found pH 9, 45 mA cm-2, 81 cm2 electrode surface area, 6 mM electrolyte concentration and 60 min treatment time to be optimal for AMOX removal. Studies with varying concentrations of AMOX (20 mg L-1, 30 mg L-1 and 40 mg L-1) found that increase in concentrations of AMOX require higher current densities and treatment time for better TOC removal. High performance liquid chromatography photo diode array (HPLC-PDA) studies found 94% removal for 40 mg L-1 of AMOX at optimal conditions with 90% COD and 46% TOC removal. High resolution mass spectrometry (HRMS) studies using Ultra performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-ToF-MS) identified major degradation mechanisms to be hydroxylation, β-lactum ring cleavage, breakage of thiazolidine ring chain from the aromatic ring and piperazinyl ring formation. The final byproducts of AMOX oxidation were carboxylic acids.

Environmental impact and source-controlled approaches for emerging micropollutants: Current status and future prospects

Emerging micropollutants, originating from diverse sources, including pharmaceutical, pesticides, and industrial effluents, are a serious environmental concern. Their presence in natural water bodies has negative effects on ecosystems and human health. To address this issue, the importance of a source-controlled approach has grown, highlighting the use of advanced technologies such as oxidation processes, membrane filtration, and adsorption to prevent micropollutants from entering the environment. Therefore, this review provides a comprehensive overview of emerging micropollutants, their analytical detection methods, and their environmental impacts, with a focus on aquatic ecosystems, human health, and terrestrial environments. It also highlights the importance of using a source-controlled approach and provides insights into the benefits and drawbacks of this strategy. The primary micropollutants identified in this review were erythromycin, ibuprofen, and triclocarban, originating from the pharmaceutical industries for their use as antibiotics, analgesic, and antibacterial drugs. The primary analytical methods used for detection involved hybrid techniques that integrate chromatography with spectroscopy. Thus, this review emphasizes the source-controlled approach's benefits and drawbacks, focusing on emerging micropollutants, their detection, and impacts on ecosystems and health.