Degradation of oxytetracycline (OTC), a primary member of antibiotics in water, was performed by a gas phase dielectric barrier discharge (GPDBD) plasma reactor. The influences of operation ...conditions including applied voltages, air bubbling rates, initial OTC concentrations and initial pH values on OTC abatement were investigated respectively. The results showed that the decontamination process can be fitted by first order kinetics, and the removal ratio and rate were affected obviously by those parameters. After 20 min of discharge treatment, approximately 93.4% of OTC was removed under the experimental conditions: applied voltage of 7.5 kV, air flow rate of 1.0 L/min, initial OTC concentration of 100 mg/L, and initial pH of 5.0. In addition, TOC and COD removal efficiency reached 43.0% and 73.7% at the original pH 9.3, respectively. Furthermore, the amounts of hydrogen peroxide and ozone in aqueous were quantitatively measured to evaluate their roles during antibiotic removal, and the main function of hydroxyl radicals was demonstrated by the radicals scavenger test. At last, the analyses of UV–Vis spectra and HPLC-MS were employed to study the OTC elimination mechanism, and the possible decomposition pathway was proposed based on the speculated intermediates.
This Figure illustrates the main process of oxytetracycline (OTC) removal by a gas phase dielectric barrier discharge (GPDBD) plasma system. The production of OH, H2O2, and O3 by discharge plasma is the critical step during OTC degradation process, and the OH radicals play a dominative role in organic compounds removal. HPLC-MS is employed to study the mechanism of OTC degradation. The results show that OTC would firstly be oxidized to some big molecule intermediates, and gradually be decomposed to a few of small molecule compounds and organic acids, even mineralized to CO2, H2O, NH4+ and NO3− ultimately. Display omitted
•Oxytetracycline was degraded effectively by a gas phase DBD system.•H2O2 and O3 generated during discharge process were determined quantitatively.•Radicals scavenger addition proved that OH played a vital role in removal process.•Oxytetracycline degradation mechanism was proposed based on HPLC-MS analysis.
In the work, Bi
WO
/C-TiO
photocatalyst was successfully synthesized for the first time by loading narrow bandgap semiconductor Bi
WO
on MOF-derived carboxyl modified TiO
. The phase structure, ...morphology, photoelectric properties, surface chemical states and photocatalytic performance of the prepared photocatalysts were systematically investigated using various characterization tools. The degradation efficiency of oxytetracycline by 6BT Z-scheme heterojunction photocatalyst under visible light could reach 93.6 % within 100 min, which was related to the high light harvesting and effective separation and transfer of photo-generated carriers. Furthermore, the effects of various environmental factors in actual wastewater were further investigated, and the results showed that 6BT exhibited good adaptability, durability and resistance to interference. Unlike most works, the degradation system with a different single active species were designed and constructed based on their formation mechanism. In addition, for the first time, a positive study was conducted on the priority attack sites, intermediate products, and degradation pathways for the photocatalytic degradation of oxytetracycline by a single active species through HPLC-MS and Fukui index calculations. The toxicity changes of intermediate products produced in three different single active species oxidation systems were evaluated using toxicity assessment software tools (T.E.S.T.), Escherichia coli growth experiments, and wheat growth experiments. Among them, the intermediate products formed through O
oxidation had the lowest toxicity and the main active sites it attacked were the 20C, 38O, 18C, 41O, and 55O atoms with high f
values in the oxytetracycline molecular structure. This work provided the insight into the role of each active species in the degradation of antibiotics and offered new ideas for the design and synthesis of efficient and eco-friendly photocatalysts.
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•The pathogenicity gene is similar for biofloc and clear seawater.•The oxytetracycline resistance genes are also similar.•In biofloc, vibriosis can be controlled by Shewanella sp.•Use ...of oxytetracycline to treat vibriosis in clear seawater is inefficient.
In May and June 2015, moderate and severe lesions were observed in Litopenaeus vannamei reared in clear seawater while, at the same time, lesions in shrimp reared in biofloc were considerably fewer. The signs of disease included anorexia, lethargy, melanization, expanded chromatophores, luminescence and necrotic areas in the uropods, suggesting a possible vibriosis. However, lesions observed in shrimp reared in biofloc disappeared after a certain time and without mortality in tanks, whereas mortality and severe signs continued to be observed in shrimp reared in clear seawater. To treat the possible vibriosis, oxytetracycline was administered only in clear seawater tanks, but the results were not successful. Bacterial cultures from hepatopancreas tissues of shrimp from both rearing systems confirmed a vibriosis outbreak only in the clear seawater system. Subsequently, Vibrio harveyi, Vibrio rotiferianus, Photobacterium sp. and Photobacterium damselae were identified from bacterial culture previously isolated for both rearing systems by molecular methods. Shewanella sp. was isolated and identified only in biofloc. To understand the possible pathogenicity and resistance mechanisms of the Vibiro strains for both rearing systems, pathogenicity (toxR) and oxytetracycline resistance-related genes (tet(B), tet(D), tet(G)) were determined. Although these genes were expressed for both rearing systems, biofloc proved to have the ability to control the development of the disease, in comparison to clear water, where the vibriosis was evident regardless of the administration of oxytetracycline as a treatment.
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A series of Ag3PO4-GO-X (X = 1, 2 and 3) photocatalysts, with different graphene oxide (GO) content, were successfully prepared by chemical precipitation. Oxytetracycline ...hydrochloride (OTC) was selected as target compound to assess the photocatalytic efficiency of the Ag3PO4-GO -X composites. The characteristics of the photocatalysts were studied by SEM, TEM, XRD, XPS, UV–vis DRS, Raman spectroscopy and photoelectrochemical measurements. The enhanced photocatalytic mechanism of Ag3PO4-GO composite was proposed. Results indicated that Ag3PO4 was successfully integrated with GO. The visible light absorption range of Ag3PO4-GO composites effectively was expanded more than pure Ag3PO4. The adsorption capacity of the catalyst for OTC was also greatly enhanced. 99.24 % of OTC was removed in 60 min visible light irradiation, as the content of GO was 6% in the composite. After being reused five times, the photocatalytic degradation efficiency still reached 94.77 %. Reactive species of h+ were the main participants in oxidizing OTC, meanwhile •O2− and OH• contributed to the degradation process. This work provided a simple and effective approach to prepare Ag3PO4-GO composites. The results suggested that the addition of GO increased the electron-hole pairs separation efficiency of Ag3PO4 and improved the photocatalytic degradation activity of Ag3PO4 The as-prepared Ag3PO4-GO composites displayed promising effects in the photocatalytic removal of refractory organic pollutants as a visible light-responsive photocatalyst.
Atypical Aeromonas salmonicida causes furunculosis infections of non‐salmonid fish, which requires antibiotic therapy. However, antibiotics may induce biofilm in some bacteria, which protects them ...against hostile conditions while allowing them to persist on surfaces, thus forming a reservoir for infection. The aim of this study was to determine whether atypical isolates of A. salmonicida increased biofilm in the presence of two antibiotics, florfenicol and oxytetracycline. A microtitre plate assay was used to quantify biofilm in the presence and absence of each antibiotic. Fifteen of 28 isolates formed biofilms under control conditions, while 23 of 28 isolates increased biofilm formation in the presence of at least one concentration of at least one antibiotic. For oxytetracycline, the most effective concentration causing biofilm to increase was one‐quarter of that preventing visible bacterial growth, whereas for florfenicol it was one‐half of this value. This is the first study to demonstrate that a bacterial pathogen of fish increases biofilm in response to antibiotics. Biofilm formation may increase the risk of re‐infection in culture systems and this lifestyle favours the transmission of genetic material, which has implications for the dissemination of antibiotic‐resistance genes and demonstrates the need for enhanced disease prevention measures against atypical A. salmonicida.
Highlights
•A facile hydrothermal method was used for the synthesis of binary and ternary metal hydroxide.•The removal of oxytetracycline (OTC) antibiotic using prepared metal hydroxide was ...studied.•Electrostatic interaction and anion exchange were mainly responsible for the removal of the OTC.•The adsorption of OTC was endothermic in nature and maximum adsorption capacity was found to be 250.07 mg/g.
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Pharmaceuticals are emerging pollutants present mainly in industrial and municipal wastewater. Herein, structurally variable binary and ternary metal hydroxides based on copper, manganese, and aluminum were used for the adsorptive scavenging of the oxytetracycline (OTC) antibiotic. A facile hydrothermal method was used for the synthesis of binary CuAl-hydroxide, MnAl-hydroxide, and ternary CuMnAl-hydroxide. Structural and morphological characteristics of the metal hydroxides (MHs) were studied by X-ray diffraction (XRD), Fourier transformed infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM) analysis. The adsorptive removal for OTC was found in the order CuMnAl-hydroxide > CuAl-hydroxide > MnAl-hydroxide. The highest removal of OTC by CuMnAl-hydroxide and CuAl-hydroxide was observed at pH 7 while MnAl-hydroxide showed the optimum adsorption at pH 9. All three materials showed different saturation time and equilibrium concentration for OTC adsorption. The mechanism investigation found that strong electrostatic attraction, hydrogen bonding, and anion exchange were mainly responsible for the removal of the OTC and adsorption process followed the pseudo-second-order kinetic model and equilibrium data was best fitted to the Langmuir isotherm model. The adsorption of OTC was influenced by the presence of Cu (II) and Cr (VI) ions in the aqueous solution due to the competitive adsorption of co-ions. Moreover, the adsorption of OTC was endothermic in nature, and maximum adsorption capacity was found to be 250.07 mg/g at 50 °C.
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•Effect of oxytetracycline (OTC) on pesticide removal was assayed in a biomixture.•Biomixture respiration was mostly stimulated with the application of OTC.•Chlorpyrifos ...mineralization improved at low OTC doses, resembling a hormetic effect.•The biomixture was able to remove three herbicides simultaneously.•During herbicide removal, OTC co-application only increased the half-life of ametryn.
Biopurification systems (BPS) are design to remove pesticides from agricultural wastewater. This work assays for the first time the potential effect of an antibiotic of agricultural use (oxytetracycline, OTC) on the performance of a biomixture (biologically active core of BPS), considering that antibiotic-containing wastewaters are also produced in agricultural labors. The respiration of the biomixture was stimulated in the presence of increasing doses of OTC (≥100mgkg−1), and only slightly increased with lower doses (≤10mgkg−1). When co-applied during the removal of chlorpyrifos, OTC increased chlorpyrifos mineralization rates at low doses, resembling a hormetic effect. The biomixture was also able to remove three herbicides (atrazine, ametryn and linuron) with half-lives of 24.3 d, 43.9 d and 30.7 d; during co-application of OTC at a biomixture-relevant concentration, only the removal of ametryn was significantly inhibited, increasing its half-life to 92.4 d. Ecotoxicological assays revealed that detoxification takes place in the biomixture during the removal of herbicides in the presence of OTC. Overall results suggest that co-application of OTC in a biomixture does not negatively affect the performance of the matrix in every case; moreover, the co-application of this antibiotic could improve the mineralization of some pesticides.
Aquaculture wastewater contained a high remnant of oxytetracycline (OTC) and nitrate. In this study, OTC co-metabolized with denitrification/desulfurization was investigated in terms of kinetic ...analysis, pathway, microbial communities and produces analysis in sulfate-reducing bacteria (SRB) mediated system. Long-term acclimatization with sulfate (300 mg-S/L) could markedly accelerate the removed rate of OTC from 0.9 to 1.4 mg/g-SS/d, with the kinetic constants increasing from 0.2760 to 0.5232 d−1, mainly via enzymes including adenosine-5′-phos-phosulfate reductase and cytochrome P450, and non-enzymatic process related to intermediates (adenosine-5′-phos-phosulfate and S0). Furthermore, OTC was likely detoxified by SRB enriched sludge mainly via hydrolysis, dehydration, oxidation and reduction. The denitrification process would postpone the OTC degradation via outcompeting electron donors with the desulfurization process. Redundancy analysis suggested that sulfur-oxidizing bacteria (Acidithiobacillus, Ochrobactrum) were highly related to OTC degradation processes. This study provides deep insight and a new opportunity for the treatment of aquaculture wastewater containing OTC, sulfate and nitrate by SRB sludge.
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•Oxytetracycline co-metabolism with sulfate/nitrate in SRB mediated system.•OTC could be biodegraded via CYP450 and APSR in the SRB sludge system.•Internal oxidation is involved in OTC degradation via CYP450, APS and S0.•Sulfonation and internal oxidation lead to lower ecology toxicity.
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•ZnFe-LDH loaded on MBC was prepared by co-precipitation method.•The composite exhibited outstanding adsorption capacity for OTC at 426.61 mg/g.•Multiple physical and chemical ...mechanisms were involved in OTC adsorption.•Plant invasion control and pollutants removal was accomplished simultaneously.
Antibiotic contamination in water has been an increasing global concern, and how to effectively remove antibiotics (e.g., oxytetracycline OTC hydrochloride) from wastewater becomes imperative. In this study, the biochar derived from an invasive plant (Mikania micrantha Kunth) was synthesized with Zn/Fe- layered double hydroxide (LDH) by co-precipitation method (ZnFe-LDH/MBC) to remove OTC from water. ZnFe-LDH/MBC posed the highest OTC removal performance of 426.61 mg/g. ZnFe-LDH/MBC exhibited stability and efficiency in OTC adsorption at different pH levels and under interfering conditions with co-existing ions, as well as outstanding regeneration capabilities during adsorption–desorption cycles. Furthermore, the removal of OTC by ZnFe-LDH/MBC was mediated by several processes including pore filling, hydrogen bonding force, electrostatic interaction, π-π interaction, as well as complexation. Consequently, ZnFe-LDH/MBC has excellent potential for the purification of OTC pollutants that is low-cost, efficient, and environmentally friendly.
•Hydrothermal pretreatment obviously affected bacterial diversity and composition.•ARGs inevitably elevated during the composting process of OFR.•Hydrothermal pretreatment efficiently reduced the ...enrichment of ARGs.
Hydrothermal pretreatment can efficiently remove the residual antibiotics in oxytetracycline fermentation residue (OFR), but its effect on antibiotic resistance genes (ARGs) during composting remains unclear. This study compared the shifts in bacterial community and evolutions in ARGs and integrons during different composting processes of OFRs with and without hydrothermal pretreatment. The results demonstrated that hydrothermal pretreatment increased the bacterial alpha diversity at the initial phase, and increased the relative abundances of Proteobacteria and Actinobacteria but decreased that of Bacteroidetes at the final phase by inactivating mycelia and removing residual oxytetracycline. Composting process inevitably elevated the abundance and relative abundance of ARGs. However, the increase in ARGs was significantly reduced by hydrothermal pretreatment, because the removal of oxytetracycline decreased their potential host bacteria and inhibited their horizontal gene transfer. The results demonstrated that hydrothermal pretreatment is an efficient strategy to reduce the enrichment of ARGs during the OFR composting.
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