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We investigated the occurrence and the environmental risk of eight contaminants of emerging concern (CECs; acetaminophen, naproxen, diclofenac, methylparaben, 17ß-estradiol, sulfathiazole, sulfadimethoxine, and sulfamethazine) in three Brazilian water bodies, namely, the Monjolinho River Basin (São Paulo State), the Mogi Guaçu River (São Paulo State), and the Itapecuru River (Maranhão State) in three sampling campaigns. The CECs were only quantified in surface water samples collected at the Monjolinho River Basin. Acetaminophen, naproxen, and methylparaben were detected in the range of <200 to 575.9 ng L-1, <200 to 224.7 ng L-1, and <200 to 303.6 ng L-1, respectively. The detection frequencies of the three measured compounds were between 33% and 67%. The highest concentrations of CECs were associated with intense urbanization and untreated sewage discharge. Furthermore, CEC concentrations were significantly correlated with total organic carbon, electrical conductivity, and dissolved oxygen levels, suggesting that domestic pollution from urban areas is an important source in the distribution of CECs in the Monjolinho River Basin. The environmental risk assessment indicated a high risk for acetaminophen (risk quotient [RQ] values between 2.1 and 5.8), a medium risk for naproxen (RQs between 0.6 and 0.7), and a low risk for methylparaben (RQs < 0.1) to the freshwater biota of the Monjolinho River Basin. Our findings show potential threats of CECs in Brazilian water bodies, especially in vulnerable areas, and reinforce the need for improvements in environmental regulations to include monitoring and control of these compounds in aquatic systems. Environ Toxicol Chem 2024;00:1-12. © 2024 SETAC.

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Antimicrobial Photodynamic Inactivation (a-PDI) is based on the oxidative destruction of biological molecules by reactive oxygen species generated by the photo-excitation of a photosensitive molecule. When a-PDT is performed with the use of mathematical models, the optimal conditions for maximum inactivation are found. Experimental designs allow a multivariate analysis of the experimental parameters. This is usually made using a univariate approach, which demands a large number of experiments, being time and money consuming. This paper presents the use of the response surface methodology for improving the search for the best conditions to reduce E. coli survival levels by a-PDT using methylene blue (MB) and toluidine blue (TB) as photosensitizers and white light. The goal was achieved by analyzing the effects and interactions of the three main parameters involved in the process: incubation time (IT), photosensitizer concentration (CPS), and light dose (LD). The optimization procedure began with a full 23 factorial design, followed by a central composite one, in which the optimal conditions were estimated. For MB, CPS was the most important parameter followed by LD and IT whereas, for TB, the main parameter was LD followed by CPS and IT. Using the estimated optimal conditions for inactivation, MB was able to inactivate 99.999999% CFU mL-1 of E. coli with IT of 28 min, LD of 31 J cm-2, and CPS of 32 µmol L-1, while TB required 18 min, 39 J cm-2, and 37 µmol L-1. The feasibility of using the response surface methodology with a-PDT was demonstrated, enabling enhanced photoinactivation efficiency and fast results with a minimal number of experiments.

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Petrochemical industries generate wastewaters containing pollutants that can severely impact the biological treatment systems. Some streams from specific production units may contain nonbiodegradable or toxic compounds that impair the performance of the wastewater treatment plant and should be segregated and treated by specific techniques. In this work, the utilization of chemical oxidation (H2O2/UV) was investigated for removing 4-vinylcyclohexene (VCH) from a liquid stream coming from the production of hydroxylated liquid polybutadiene (HLPB). Besides VCH, this stream also contains ethanol, hydrogen peroxide, and many other organic compounds. Experiments were carried out in a small-scale photochemical reactor (0.7 L) using a 25-W low-pressure mercury vapor lamp. The photochemical reactor was operated in batch, and the reaction times were comprised between 10 and 60 min. Assays were also performed with a synthetic medium containing VCH, H2O2, and ethanol to investigate the removal of these substances in a less complex aqueous matrix. By-products formed in the reaction were identified by gas chromatography and mass spectroscopy (GC-MS). VCH was significantly removed by the oxidation process, in most assays to undetectable levels. Ethanol removal varied from 16 to 23 % depending on the reaction conditions. Acetic acid, acetaldehyde, and diols were detected as by-products of the industrial wastewater stream oxidation. A drop on the toxicity of the industrial stream was also observed in assays using the organism Artemia salina.

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This review assesses microwaves (MW) coupled to advanced oxidation processes (AOPs) for pollutants degradation, as well as the basic theory and mechanisms of MW dielectric heating. We addressed the following couplings: MW/H2O2, MW/UV/H2O2, MW/Fenton, MW/US, and MW/UV/TiO2, as well as few studies that tested alternative oxidants and catalysts. Microwave Discharge Electrodeless Lamps (MDELs) are being extensively used with great advantages over ballasts. In their degradation studies, researchers generally employed domestic ovens with minor adaptations. Non-thermal effects and synergies between UV and MW radiation play an important role in the processes. Published papers so far report degradation enhancements between 30 and 1,300%. Unfortunately, how microwaves enhance pollutants is still obscure and real wastewaters scarcely studied. Based on the results surveyed in the literature, MW/AOPs are promising alternatives for treating/remediating environmental pollutants, whenever one considers high degradation yields, short reaction times, and small costs.

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