The sulfentrazone dechlorination using bimetallic nanoparticles of Fe/Ni was studied. Different variables that could influence the sulfentrazone conversion were investigated, such as nitrogen atmosphere, pH and dosage of the nanoparticles and initial concentration of sulfentrazone. The best results were obtained using controlled pH (pH 4.0) and 1.0 g L⁻¹ of nanomaterials, resulting in 100 % conversion in only 30 min. Kinetic studies were also conducted, evaluating the influence of different nanoparticle dosages (1.0 to 4.0 g L⁻¹), system temperatures (20 to 35 °C) and nickel levels in the composition of the nanomaterials (0.025 to 0.10 gNi/gFe). The mechanism of sulfentrazone conversion has changed due a direct reduction on the catalytic activity sites and indirect reduction by atomic hydrogen. Both mechanisms have followed pseudo-first order models. The conversion rate improved when the dosage of the nanomaterials, system temperature and nickel content in the composition of the nanocomposites were increased. Finally, the conversion products were elucidated by mass spectrometry and toxicity assays were performed using Daphnia Similis. The results showed that the dechlorination product is less toxic than sulfentrazone.

Metformin (MET) is among the most consumed pharmaceuticals worldwide. This compound has been frequently detected in fresh surface water. However, ecotoxicological information for MET is still too limited, particularly regarding chronic and behavioral data. This study aimed to help filling these knowledge gaps, by carrying out both acute and chronic studies with four different test organisms from three different trophic levels. We assessed different endpoints, including the swimming behavior of Danio rerio larvae. We also derived both short-term and long-term environmental quality standards (EQS) for the protection of freshwater pelagic biota towards MET adverse effects. A risk quotient (RQ) was calculated for MET in fresh surface water, considering a worst-case scenario. Daphnia similis was by far the most sensitive species evaluated. An EC₁₀ of 4.4 mg L⁻¹ was obtained from the reproduction test with D. similis. A long-term EQS of 88 μg L⁻¹ was derived and a RQ of 0.38 was obtained. An ecological risk is not expected for the chronic exposure of pelagic freshwater species to MET, considering the endpoints and the standard bioassays usually recommended in standard protocols. However, endocrine disruptive effects and potential interactive effects of MET with other co-occurring contaminants cannot be ruled out. To the best of our knowledge, this study presents the first data related with MET effects on population endpoints of D. similis and Hydra attenuata, as well as on the locomotor activity of D. rerio.

In firefighting of class B, fire suppression agents (FSA), such as aqueous film-forming foams (AFFF) and encapsulating agents (EA), have been used to cool, suppress, and remove the burning surface. However, several studies pointed out the aquatic environment as the destination of perfluorinated compounds and their degradation products. The toxicity of per- and polyfluoroalkyl compounds (PFASs), especially the FSAs, raises environmental health concerns. In this study, the reproduction and body length of the aquatic microcrustaceans Daphnia similis were analyzed through the organisms’ exposure to two FSAs (Cold Fire® Suppressant Agent and Liovac®) in the following dilutions: 0.000093%, 0.0001875%, 0.000375%, 0.00075%, 0.0015%, 0.0003125%, 0.000625%, 0.01025%, 0.025%, and 0.005%, respectively. Our results showed that exposure to FSA caused inhibitory effects on the reproduction of Daphnia similis. The LOEC and NOEC of Cold Fire® were respectively 0.0001875% and 0.000093%, and significant chronic toxicity (p < 0.05) was observed at 0.0015 to 0.0001875% concentrations. The mean body lengths of surviving organisms exposed to all dilutions of Cold Fire® were significantly lower (p < 0.05) than the control organisms. For Liovac®, the respective LOEC and NOEC were 0.005% and 0.0025%. No significant differences were observed (p < 0.05) in the length of the organisms exposed to the Liovac®, compared to the control. The adverse effects on D. similis were observed at concentrations lower than those recommended by the manufacturers. Our results show that FSAs may cause chronic toxicity to freshwater aquatic organisms, posing risk in a real environmental scenario.

Wastewater and effluent discharges are the main causes of receiving water body pollution and important challenges in water quality management. Among the emerging contaminants, pharmaceuticals have increasingly drawn attention due to their incomplete removal during conventional biological treatment, inducing potential and actual risks to living organisms following residue discharges in river effluent. Electron beam irradiation (EBI) is a clean process technology for organic compound degradation and mineralization, as well as persistent pollutant detoxification. This study aimed to evaluate EBI effects on the degradation and toxicity removal of anti-inflammatory aspirin (ASA) in a single solution and in a fluoxetine (FLX) mixture. Results indicate that 98% of the single aspirin was degraded at 5.0 kGy. Aspirin toxicity to Daphnia similis, however, increased with increasing absorbed dose (1.0 to 5.0 kGy), possibly as a result of the presence of H₂O₂ and other byproducts formed during the oxidation process. Regarding the irradiated mixture, complete degradation was achieved for both pharmaceuticals. Toxicity removals for the mixture were of 56.2 ± 0.9% and 58.8 ± 5.4% for 1.0 and 2.5 kGy, respectively. These findings demonstrate that EBI can be an interesting alternative process to be applied as a pre-treatment followed by biological treatment.

Full-scale application of heterogeneous photocatalysis for industrial wastewater treatment remains a challenge because of the complex nature of these matrices and the potential to form toxic by-products during treatment. A recent unsuccessful attempt to find adequate conditions for TiO₂/UV treatment of a cotton dyeing textile mill led to this study on the treatability of mixtures of the dyes used in the greatest amounts at the mill and therefore most likely to be present in mill effluent. Four reactive and three vat dyes were mixed in different combinations and treated (10 mg/L of each dye, 0.5 mg/L TiO₂, pH 4) to evaluate the influence of the different dyes on ADMI color, chemical oxygen demand (COD), and acute toxicity. While ADMI color removal was similar in all dye mixtures, COD removal was higher when vat dyes were absent. When treated individually, vat dyes exhibited greater recalcitrance, with no ADMI color removal and COD removals of less than 30%. Toxicity to Daphnia similis was decreased or eliminated from dye mixtures that exhibited the highest COD removals and corresponded to those in which reactive dyes were partially degraded. For raw textile mill effluent, photocatalysis reduced but did not eliminate treated effluent toxicity (EC50 = 26.8%).

Algal organic matter (AOM) in water reservoirs is a worldwide concern for drinking water treatment; once it is one of the main precursors for disinfection by-products formation (DBPs). In this context, this study investigated the ecotoxicity of DBPs from chlorination of AOM to Ceriodaphnia silvestrii and Daphnia similis (Crustacea, Cladocera). The bioassays evaluated three scenarios, including the AOM extracted from Chlorella sorokiniana, the quenching condition used in the tests, and the DBPs formed after the chlorination of the two test waters with AOM (with and without bromide presence). The results showed that AOM has no toxic effects for the tested species under typical environmental concentration (5 mg∙L⁻¹). However, since AOM is a potential precursor of DBPs, the toxicity of two test waters (TW-1 and TW-2) after the chlorination process (25 mg Cl₂·L⁻¹, for 7 days, at 20 °C) was tested. The sample with higher toxicity to the tested species was TW-1, in which chloroform and chloral hydrate were quantified (615 and 267 µg∙L⁻¹, respectively). However, TW-2 showed lower concentration of chloroform and chloral hydrate (260 and 157 µg∙L⁻¹, respectively), although bromodichloromethane, dibromochloromethane, and bromoform were also detected (464, 366, and 141 µg∙L⁻¹, respectively). Although free chlorine is highly toxic to the tested species, the quenching conditions also affected the organisms’ survival due to the use of ascorbic acid and the presence of reaction intermediates. Nonetheless, both species were more affected by TW-1 and TW-2 than the quenching condition. These results endorse the importance of removing the AOM before the disinfection process to avoid the formation of DBPs. In addition, ecotoxicological analyses could provide a more comprehensive assessment of water quality, especially considering the challenges of quantifying DBPs and other emerging contaminants.

Organophosphate esters (OPEs) are substances globally used as flame retardants and plasticizers that have been detected in all environmental compartments. This study aimed to evaluate the occurrence and sources of ten OPEs in the Piracicaba River Basin (Brazil). Twelve sampling sites were selected in five rivers with different pollution sources; six sampling campaigns were performed encompassing dry and wet seasons. ΣOPEs ranged from 0.12 to 6.2 μg L⁻¹; the levels in urban areas were higher than in rural and non-urban areas, but no overall tendency concerning the seasonal effect on OPEs concentrations was observed. Tris(2-butoxyethyl) phosphate (TBOEP), tris(2-chloroisopropyl) phosphate (TCIPP), and tris(1,3-dichloroisopropyl) phosphate (TDCIPP) were the most abundant and frequently detected compounds. Nine OPEs were detected at higher concentrations in a site affected by effluents from textile industries. An acute toxicity test using Daphnia similis was performed for tris(2-ethylhexyl) phosphate (TEHP) for the calculation of a preliminary predicted no effect concentration (PNEC). The risk quotient (RQ) approach was applied and risk to aquatic environment related to TEHP levels was observed in areas adjacent to textile industries, but more toxicity studies are required for the determination of a more reliable PNEC.

The use of aqueous film-forming foams (AFFFs) have been related to environmental contamination due to handling, storage, and use in the firefighting against class B fire. Studies have associated the use of AFFFs with toxic effects from its perfluorinated compounds (PFCs) to the aquatic ecosystem, which led the Stockholm Convention to restrict their use. In Brazil, despite the large-scale use, there is no data on employment or annual commercialization of these products. This study evaluated the toxicity of seven brands of AFFFs used in the firefighting of the petrochemical’s terminal of fuel storage in Port of Santos (Santos, São Paulo, Brazil) which occurred in 2015, in which more than 61,000 L of AFFFs drained into the adjacent aquatic ecosystems. The toxicity evaluation was performed by means of the acute bioassay using the freshwater microcrustacean Daphnia similis. The AFFF brands tested were considered toxic to D. similis, including at much lower dilutions than those recommended by the manufacturers. The brand that showed the lowest toxicity was Kidde Sintex® 3% × 6%, followed by Kidde Sintex® 1% × 3%, Argus Prime®, Cold Fire®, Ageofoam®, and Liovac®, and the one with the highest toxicity was F-500 fire®. These results provide valuable information for the development of public policies aimed at managing the AFFF discharge in freshwater ecosystems.

Ivermectin (IVM) is a broad-spectrum antiparasitic drug that is regularly employed in veterinary medicine. In this work, the sorption and desorption of IVM in two Brazilian soils (N1-sand and S2-clay) as well as its leaching capacity, dissipation under aerobic conditions, and degradation in aqueous solution by photocatalysis with TiO₂ in suspension were evaluated. The kinetic sorption curves of IVM were adjusted to a pseudo-second-order model. The sorption and desorption data were well fitted with the Freundlich isotherms in the log form (r > 0.96). The Freundlich sorption coefficient (K F ᵃᵈˢ) and the Freundlich desorption coefficient (K F ᵈᵉˢ) were 77.7 and 120 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹ and 74.5 and 138 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹, for soils N1 and S2, respectively. A greater leaching capacity of IVM was observed for the sandy soil N1 than for the clay soil S2. Under aerobic conditions, the dissipation (DT₅₀) at 19.3 °C was 15.5 days (soil N1) and 11.5 days (soil S2). Photocatalysis with UVC and TiO₂ in suspension resulted in the degradation of 98 % of IVM (500 μg L⁻¹) in water in 600 s. The toxicity (Daphnia similis) of the solutions submitted to the photocatalytic process was completely eliminated after 10 min.

There has been increased interest in the use of natural dyes for textile coloration as alternatives to synthetic dyes, due to the general belief that natural dyes are more environmentally friendly. However, natural dyes have poor affinity for textiles, which can lead to high dye levels in the resultant wastewater. While chlorine treatment has proven to be effective for dye wastewater disinfection and decolorization, this process can also lead to the formation of more toxic degradation products for certain synthetic dyes. On the other hand, little information is available regarding the ecotoxicity of natural dyes and their chlorination products. To advance knowledge in this area, madder was selected due to its historical importance and wide application in the textile industry. Specifically, we sought to characterize the chlorine-induced degradation products of an aqueous madder solution and to assess their ecotoxicity. The main component of the present madder sample was Alizarin (89.8%). Chlorination led to complete decolorization, and 2-hydroxynaphthalene-1,4-dione and phthalic anhydride were identified as key degradation products. Chlorination of madder decreased toxicity to Daphnia similis (microcrustacean) 10-fold and removed the toxicity to Raphidocellis subcapitata (algae), when compared to the parent dye.