Treatments using ozone for filter backwash water (FBW) and calcium oxide for floated residue (FR) were evaluated adopting bench-scale testing for the inactivation of Giardia spp. cysts and Cryptosporidium parvum oocysts. The protocol chosen for protozoa detection involved following the concentration step by direct centrifugation (adding ICN 7X cleaning solution at 1.0%) and purification by immunomagnetic separation (IMS). The FR treatment with calcium oxide (dosage of 23 mg CaO 100 mL⁻¹ and 3-day contact time at 25 °C) proved to be efficient, as no parasites were detected after the treatment. The reduction of calcium oxide dosage (16 mg CaO 100 mL⁻¹ and 3-day contact time at 25 °C) was insufficient to inactivate the protozoa, since potentially viable organisms were identified using propidium iodide (PI). Concerning the disinfection conditions with ozone (5-min and 10-min contact time and dosage of 10 mg O₃ L⁻¹ and 7.5 mg O₃ L⁻¹, respectively), there was complete removal of the target organisms, as no protozoa were detected after the FBW treatment. From the results obtained, the tested treatments can be considered promising alternatives for water treatment plants (WTPs). However, the costs incurred from these treatments have to be considered.

Large areas of soils in China are contaminated with Cd and are deficient in Se. Therefore, here, we aimed to reduce Cd accumulation while increasing Se content in rice grain, and to elucidate the mechanisms associated. A greenhouse pot experiment was conducted to determine grain concentrations of Se and Cd upon foliar spraying of Se combined with the application of horse manure and/or fly ash to different contaminated soils containing Cd 0.51 (T1), 1.46 (T2), and 4.59 mg Cd kg⁻¹ (T3). The amount of Fe, Si, and Cd in root iron plaque, and concentrations of Cd and Si in rice tissues were also determined. Foliar spray of Se increased Se concentration in brown rice from approximately 0.04 to 0.15 mg kg⁻¹. Fly ash significantly reduced Cd concentration in brown rice from 0.07 to 0.05, 0.15 to 0.09, and 1.00 to 0.55 mg kg⁻¹ at the T1, T2, and T3 treatment levels, respectively, and soil Cd bioavailability (by at least 33.3%), while it increased Si content in rice roots and shoots by at least 34%. The increase of Si concentration in rice tissues inhibited Cd translocation to brown rice by at least 17%. Horse manure increased the formation of root Fe plaque by approximately 2.3-fold, which resulted in the significant reduction of Cd accumulation in brown rice, shoots, and roots by 36–56%. Thus, foliar spray of Se in combination with the application of fly ash and horse manure proved an effective method to produce Cd-low and Se-rich rice.

The naproxen adsorption capacity enhancement of activated carbon prepared from the Indian gooseberry seed-shells by manufacturing a composite blended with the surface-modified graphite powder and silver nanoparticles was studied in the present context. The composite of the nano-sized materials was prepared in dimethylformamide solution and characterized by employing XRD, Raman, EDS and FT-IR spectroscopy, FETEM, and FESEM microscopy. The pseudo-first-order, pseudo-second-order, and Elovich models were applied to test the removal kinetics. Preliminary results were also fitted to the Langmuir, Freundlich, Temkin, and Dubinine-Radushkevich (D-R) adsorption isotherm models to determine the specific parameters of each model. The effects of the initial pH of the solution, naproxen concentration, and contact time on the process were optimized. The maximum adsorption capacity was obtained as 154.98 mg g⁻¹ (61.99%) with an increment of 25.31% by the addition of surface-modified graphite powder and silver nanoparticles at the optimized experimental conditions.

This study aimed to evaluate histological changes in targeted tilapia organs exposed to sublethal concentrations of carbofuran. Fishes with an average weight of 67.5 ± 2.0 g were exposed to sublethal concentrations (0.0044, 0.0088, 0.0440, and 0.0880 mg L⁻¹) of carbofuran for 7 days. In the end of the experiment, the gill, the liver, and the kidney samples were collected for histological evaluation. In gills exposed to 0.0044 mg L⁻¹ of carbofuran, an increase in interlayer epithelium and disruption of the secondary lamella was observed, while in other concentrations (0.0088, 0.0440, and 0.0880 mg L⁻¹), only blood congestion in the secondary lamellae occurred. In the liver samples of exposed tilapias, all carbofuran concentrations caused hepatocyte hypertrophy with the nuclei displaced to the cell periphery, stasis within the sinusoid capillaries, and necrosis points. All sublethal concentrations tested caused detachment of the glomerular capsule, necrosis in the proximal and distal tubules, and absence of intercellular space in the kidney of exposed tilapia. The presence of carbofuran in aquatic environments at concentrations from 0.0044 mg L⁻¹ and exposure periods longer than 7 days alters the gill, the liver, and the kidney histology and consequently compromising the fish’s health.

In the proposed model, the estrogen activity values and thyroid hormone activity values of PAEs molecules were normalized using the TOPSIS method by eliminating the dimension coefficients, and the comprehensive activity values of estrogen and thyroid hormone were obtained by analyzing the activity of each hormone and assigning the corresponding weight. The five pharmacophore models of hormone combined activity were constructed using the comprehensive activity values. Hypol 1 was the optimal pharmacophore model, showing good predictive power and significance. Then, the DBP, DNOP, and DMP molecules in environmental priority control pollutants were selected as the target molecules to perform common substitution reactions of hydrogen bond donor. Eleven PAEs derivative molecules with significantly reduced combined activity and single activity were screened. In analysis of the differences before and after modification of the docking parameters and amino acid residues before and after modification of PAEs and their derivatives, the reduced closeness between ligand and receptor leads to the decrease of thyroid hormones and estrogen activities. Moreover, the establishment of the models, not only shows that the PAEs hormone activity has certain linear relationships with the physical parameters of molecules but also shows that thyroid hormone activity and estrogen activity of PAEs is consistent with the hormone combined activity. The results confirmed the feasibility of the modified PAEs modification scheme with reduced combined activities of hormones, providing an important theoretical method for the construction of the pharmacophore model of combined activities of hormones and the study of PAEs derivative molecules.

Algae are widely distributed in the aquatic environment. In the analyzed algae from the Black Sea, metals like cadmium, iron, zinc, copper, lead, and thallium were present. From all of the analyzed elements in the algae, iron was present at the highest concentrations. The presented study confirmed that thallium is accumulated in relatively large quantities (1.60–2.12 μg g⁻¹) by all the studied algae. Cadmium and copper were accumulated at the same level (1.98 μg g⁻¹), which was lower in comparison to the average concentrations determined in the analyzed plant material. The average amounts of zinc were at 0.21 μg g⁻¹ for Ulva. High possibility of accumulation of metals by Ulva and Cystoseira allows to use them as a natural indicator of environmental cleanliness.

Hydroxyl radical (•OH)-based advanced oxidation technologies (AOTs) is an effective and clean way to remove sulfonamide antibiotics in water at ambient temperature and pressure. In this study, we systematically investigated the degradation kinetics of sulfamethazine (SMT) by •OH with a combination of experimental and theoretical approaches. The second-order rate constant (k) of SMT with •OH was experimentally determined to be 5.27 ± 0.06 × 10⁹ M⁻¹ s⁻¹ at pH 4.5. We also calculated the thermodynamic and kinetic behaviors for the reactions by density functional theory (DFT) using the B3LYP/6-31G*. The results revealed that •OH addition pathways at the methylene (C4) site on the pyridine ring and the ortho sites (C12 and C14) of the amino group on the benzene ring dominate the reaction, especially C14 site on the benzene ring accounted for 43.95% of SMT degradation kinetics. The theoretical k value which was calculated by conventional transition state theory is 3.96 × 10⁹ M⁻¹ s⁻¹, indicating that experimental observation (5.27 ± 0.06 × 10⁹) is correct. These results could further help AOTs design in treating sulfonamide during wastewater treatment processes.

Metal oxide nanoparticles have wide applications, which have elevated serious alarms about their impacts on the environment. Therefore, we investigated the potential adsorptive capacity of rice husk toward Fe₂O₃ and Al₂O₃ nanoparticles to reduce their genotoxic effects. Fish were subjected to 10 mg/l of Fe₂O₃ and Al₂O₃ nanoparticles in single and combined doses with and without rice husk water treatment for 7 days. The genotoxic effects were evaluated using the micronucleus test in the peripheral blood and comet assay in liver tissues. Significant elevation of micronuclei induction in addition to eight nuclear and cytoplasmic abnormalities (P < 0.05) was observed in all fish groups compared to the control groups. Fish that exposed to Fe₂O₃ nanoparticle showed the maximum induction of all recorded anomalies. Moreover, two indices of DNA damage were evaluated by the comet assay (comet score and % tail DNA) in liver tissues. The scoring of comet cells indicated that the highest frequencies of stage 0 (undamaged DNA) were in control and Al₂O₃ exposed groups, while stage 4 (extensive DNA damage) was significantly elevated in Fe₂O₃ exposed fish. The % of DNA damage was maximized in the Fe₂O₃ nanoparticles exposed fish and minimized in Al₂O₃ nanoparticles exposed fish. Based on the frequencies of nuclear anomalies, degree, and percentage of DNA damage, all rice husk treated groups showed a marked reduction in the genotoxic damage compared with untreated groups. Finally, both nanoparticles showed genotoxic potential and the rice husk had an efficient absorptive capacity for both of them individually or combined.

Anaerobic digestion (AD) is an effective technology to dispose antibiotic mycelial residues, but biogas production is influenced by hydrolysis rates and antibiotic residue. Herein, the effects of thermal hydrolysis pretreatment for AD of spectinomycin mycelial residues (SMRs) were investigated. The results showed that the removal ratio of spectinomycin was increased while the temperature of pretreatment was escalating. Meanwhile, thermal hydrolysis facilitated the dissolution of organic matters. However, non-biodegradable substances measured by fluorescence excitation–emission matrix accumulated and thus had an adverse influence on biogas production. Based on batch assays, the optimal pretreatment temperature for SMRs was 120 °C. The removal of spectinomycin was benefit for biogas production (increasing by 7.6%), and the overall biogas production increased by 27.6% compared with 289.90 mL gVS⁻¹ of untreated SMRs. The microbial community analysis revealed that spectinomycin (265 mg L⁻¹) might influence bacteria in the early stage of AD (first 5 days), while redundancy analysis showed that spectinomycin had a non-significant influence on community succession over the 32 days of fermentation.

Rivers play an irreplaceable role in nature and human society but are the most vulnerable ecosystem in the world to multiple environmental stressors. However, the global-scale research status and the distribution patterns of major stressors in large rivers remain unclear. This study analysed research publications (12,807 documents from 1900 to 2019) related to six large rivers with continental representativeness to tackle these knowledge gaps. The results showed that the total outputs have grown rapidly over the study period, particularly since the 1990s. Consistent with the varied environmental characteristics and problems among the rivers, the research outputs and focuses demonstrated clear differences, which could further be attributed to geographical location, journal preferences and the economic strength of the country in which the river is located. Overall, climate change was the most frequently and widely considered environmental stressor in large rivers. Regardless of climate change, species diversity and hydropower development were widely addressed in the Amazon, Congo and Mekong river basins. Water pollution was the main stressor studied in the Rhine River and Mississippi River, while agricultural irrigation and drought were the most frequently addressed research subjects in the Murray-Darling River. This study provides a comprehensive understanding of the research status and stressor distribution in large global rivers, highlighting the relationship between river research and geographical regions, pointing out future research directions and providing management guidance for large rivers.