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1.
Water Res ; 207: 117834, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34763281

RESUMO

Effluents of conventional wastewater treatment systems contain antibiotic residues at concentrations below the minimal inhibitory concentrations (MIC), which nevertheless could still select for antibiotic-resistant bacteria. This work focuses on evaluating the changes of antibiotic resistance genes (ARGs) and bacterial communities in a planted advanced biological wastewater treatment system (ABWWTS) under long-term exposure to sub-MIC tetracycline. In the ABWWTS, the removal rates of tetracycline ranged from 97.9% to 99.9%, and a 17.2% decrease in the average removal rates of NH4+-N was observed after the addition of tetracycline. Although the background of ABWWTS contributed to the ARGs in effluents, the concentration of 283 targeted ARGs (ΣARGs) was 83.5% lower in effluents than in influents after sub-MIC tetracycline exposure, and the concentrations of ΣARGs in the ABWWTS were, on average, 30.0% lower than those in an unplanted biological wastewater treatment system (UBWWTS) after a performance of 130 days. The relative abundance of tetracycline resistance genes increased within ABWWTS and UBWWTS under tetracycline exposure. After tetracycline exposure, bacterial diversity in ABWWTS and UBWWTS increased on average by 36.2% and 42.7%, respectively, and the abundances of Nitrosomonas and Nitrospira in the aerobic zone were more than 10-times higher in the ABWWTS than in the UBWWTS. Sub-MIC tetracycline concentrations were linearly correlated with the relative abundance of tetracycline resistance genes in Escherichia coli (E. coli). Long-term exposure to tetracycline at the same concentration increased abundances of the same ARGs (i.e., tetR-02 and tetM-01) in E. coli and the microflora of the ABWWTS, revealing that sub-MIC tetracycline could increase the abundance of ARGs in the ABWWTS by facilitating the vertical transfer of tetracycline resistance genes. These findings demonstrated that planted ABWWTS played a positive role in removing ARGs under low antibiotic selective pressure, which was in accompany with increasing levels of corresponding ARGs within the system.


Assuntos
Antibacterianos , Purificação da Água , Antibacterianos/farmacologia , Bactérias/genética , Resistência Microbiana a Medicamentos/genética , Escherichia coli/genética , Genes Bacterianos/genética , Tetraciclina , Águas Residuárias/análise
2.
Artigo em Inglês | MEDLINE | ID: mdl-32151776

RESUMO

Chromium is toxic to marine animals and can cause damage to many of their organs, including the liver. To test the toxicity of chromium on marine organisms, we exposed the liver of the marine medaka (Oryzias melastigma) with hexavalent chromium [Cr(VI)]. Our results show that Cr enrichment in the liver demonstrates a positive correlation to the exposure concentration. With the increase of Cr(VI) concentration, pathological changes including nuclear migration, cell vacuolization, blurred intercellular gap, nuclear condensation, become noticeable. To further study changes in gene expression in the liver after Cr(VI) exposure, we used RNA-seq to compare expression profiles before and after Cr(VI) exposure. After acute Cr(VI) exposure (2.61 mg/l) for 96 h, 5862 transcripts significantly changed. It is the first time that the PPAR pathway was found to respond sensitively to Cr(VI) exposure in fish. Finally, combined with other published study, we found that there may be some difference between Cr(VI) toxicity in seawater fish and freshwater fish, due to degree of oxidative stress, distribution patterns and detailed Cr(VI) toxicological mechanisms. Not only does our study explore the mechanisms of Cr(VI) toxicity on the livers of marine medaka, it also points out different Cr(VI) toxicity levels and potential mechanisms between seawater fish and freshwater fish.


Assuntos
Cromo/toxicidade , Fígado/efeitos dos fármacos , Oryzias , Poluentes Químicos da Água/toxicidade , Animais , Estresse Oxidativo , RNA-Seq , Transcriptoma
3.
RSC Adv ; 10(35): 20691-20700, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-35517748

RESUMO

In recent years, rural sewage treatment facilities have grown rapidly in China, and yet the water quality of the effluent has not been well monitored. The detection of chemical oxygen demand (COD) via ultraviolet-visible (UV-Vis) spectroscopy is an emerging technology with advantages of low cost and easy maintenance, which make it appropriate for the on-line monitoring of effluents from rural sewage treatment facilities. Because there are numerous sewage treatment devices in rural regions and as their locations are usually very scattered, it is difficult to calibrate the COD estimation model for each monitoring site. Hence, a COD estimation model with global calibration is a specific problem for application in rural regions. However, little research was performed on real rural sewage, yet much is desired in terms of the model accuracy and robustness. Consequently, a practical COD detection method with UV-Vis spectroscopy was established in this study. The COD estimation model was globally calibrated with effluents from rural sewage treatment devices. In order to avoid misleading data for evaluating the model performance caused by the differences in the COD concentration range of training sets, two new criteria, namely the Root Mean Square Relative Error (RMSRE) and Relative Error Variance (REV), were proposed to evaluate the model accuracy and robustness. Differences in the organic composition as characterized by excitation-emission matrix (EEM) fluorescence spectroscopy were shown to significantly affect the accuracy of the global calibration model. Through comparison among the methods of the partial least squares (PLS), support vector machine (SVM), and back-propagation neural network, PLS was verified to be able to attain sufficient accuracy and to be suitable for applying to the modeling with global calibration. A simplified modeling method was proposed to replace the absorption spectra at the full wavelength band with the absorbance at some specific wavelengths that were selected by interval partial least-squares regression (iPLSR) and synergy interval partial least-squares regression (siPLSR). In this study, the simplified model was proven to be reliable with three specific wavelengths: 251, 356, and 363 nm. An on-line COD monitor utilizing UV-Vis spectroscopy was thus developed for combining with the global calibration model.

4.
Environ Int ; 131: 105026, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31351383

RESUMO

Antibiotic resistance genes (ARGs) have been considered as emerging contaminants of concern nowadays. There are no special technologies designed to directly remove ARGs in wastewater treatment plants (WWTPs). In order to reduce the risk of ARGs, it is vital to understand the efficiency of advanced treatment technologies in removing antibiotic resistance genes in WWTPs. This review highlights the application and efficiency of tertiary treatment technologies on the elimination of ARGs, s, based on an understanding of their occurrence and fate in WWTPs. These technologies include chemical-based processes such as chlorination, ozonation, ultraviolet, and advanced oxidation technology, as well as physical separation processes, biological processes such as constructed wetland and membrane bioreactor, and soil aquifer treatment. The merits, limitations and ameliorative measures of these processes are discussed, with the view to optimizing future treatment strategies and identifying new research directions.


Assuntos
Resistência Microbiana a Medicamentos/genética , Genes Bacterianos , Águas Residuárias , Poluentes da Água/isolamento & purificação , Purificação da Água/métodos , Reatores Biológicos , DNA , Oxirredução , Instalações de Eliminação de Resíduos , Águas Residuárias/análise
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