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In the last years, increasing attention has been paid on the presence of antibiotics in aqueous environments due to their ecological damage and potential adverse effects on organisms. Membrane biofilm reactors (MBfR) have been gained a significant popularity as an advanced wastewater treatment technology in removing of organic micro-pollutants. In this study, the performance of H 2 -MBfR for simultaneous removal of nitrate and chlortetracycline, formation of transformation products and community analysis of the biofilm grown on the gas permeable hollow fiber membranes was evaluated by considering effect of the hydraulic retention time, surface loadings of target pollutants and H 2 pressure. The results showed that the simultaneous chlortetracycline (96%) and nitrate removal (99%) took placed successfully under the conditions of 5 h HRT and 2 psi H 2 pressure. It has been determined that the main elimination process was biodegradation and Betaproteobacteria species was responsible for chlortetracycline degradation. [ABSTRACT FROM AUTHOR]

Microbial degradation of chlortetracycline (CTC) is an effective bioremediation method. In the present study, an enrichment technique was used to isolate a Bacillus cereus LZ01 strain capable of effectively degrading CTC from cattle manure. Response surface methodology was used to identify optimized conditions under which strain LZ01 was able to achieve maximal CTC removal (83.58%): temperature of 35.77 °C, solution pH of 7.59, CTC concentration of 57.72 mg/L and microbial inoculum of 0.98%. The antibacterial effect of CTC degradation products on Escherichia coli was investigated by the disk diffusion test, revealing that the products by LZ01 degradation of CTC exhibited lower toxicity than parent compound. Shake flask batch experiments showed that the biodegradation of CTC was a synergistic effect of intracellular and extracellular enzymes, and intracellular enzyme had a better degradation effect on CTC (77.56%). Whole genome sequencing revealed that genes associated with ring-opening hydrolysis, demethylation, deamination and dehydrogenation in strain LZ01 may be involved in the biodegradation of CTC. Subsequent seven possible biodegradation products were identified by LC-MS analyses, and the biodegradation pathways were proposed. Overall, this study provides a theoretical foundation for the characterization and mechanism of CTC degradation in the environment by Bacillus cereus LZ01. [Display omitted] • A Bacillus cereus strain capable of biodegrading CTC was isolated. • The degradation conditions of CTC by strain LZ01 were evaluated and optimized by RSM. • The product of LZ01 degradation of CTC exhibited low toxicity. • The products of CTC and possible degradation pathways were proposed. • Genomics revealed functional genes associated with CTC biodegradation. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) pharmaceutical residue with strong acidity and in high CTC concentration is a hazardous solid waste. There is a huge attention but few studies on whether and how the CTC raw residue (CRR) can be degraded in microbiological way. In this study, three self-screened fungi, LJ245, LJ302 and LJ318, were used and thoroughly investigated to remove CTC, strong acidity and biotoxicity in CRR. The result disclosed that the concentration of CTC decreased rapidly in the first seven days and declined slowly subsequently, and the decreasing curve was similar to "L" shape. the corresponding degradation ratios of three strains were 95.73%, 98.53% and 98.07%, respectively. Meanwhile, numerous intermediates in degradation appeared in early days and gradually reduced, and eventually disappeared once the degradation time was long enough, among which eleven intermediates from CTC were identified. Moreover, the strong acidity of CRR declined dramatically using this biological method along with the CTC being metabolized, the pH value increased from 2.30 to 8.32 in the first 7 days. The toxicity of CRR was significantly reduced by LJ302 with inhibition rate from 96.02% to no inhibition effect to Micrococcus luteus. Therefore, CTC, strong acidity and biotoxicity of CRR could be effectively removed simultaneously through a biodegradation process driven with proposed strains. [Display omitted] • CRR with high-content CTC and strong acidity is categorized as a hazardous waste. • CTC in CRR was significantly degraded by fungi with degrading ratio of 95.7~98.5%. • Strong acidity of CRR was transformed driven by fungi with the pH from 2.30 to 8.32. • Some intermediate products from CTC were identified. • CTC, acidity and toxicity of CRR could be removed simultaneously by biological way. [ABSTRACT FROM AUTHOR]

Ionic antibiotics and metals generally coexist, and their interaction can affect their sorption behaviors onto soil minerals, therefore determining their environmental hazards. This study investigated the sorption and cosorption of Zn(II) and chlortetracycline (CTC) onto montmorillonite at different solution pH (3−10) using batch experiments and extended X-ray absorption fine structure (EXAFS) analysis. The Langmuir model could reproduce well the sorption isotherms of Zn(II) and CTC. The presence of CTC/Zn(II) could promote the maximum sorption capacity (Q m) of Zn(II)/CTC, based on site energy distribution (SED) theory. Generally, Zn(II) sorption increased with pH increasing. Comparatively, CTC sorption decreased as pH increased till approximately pH 5.0, then increased continuously with pH increasing. Both CTC and Zn(II) co-existence enhanced their individual sorption in both acidic and neutral environments. The processes behind CTC and Zn(II) sorption mainly included cation exchange and surface complexation. The EXAFS data evidenced that the presence of CTC could alter the species of Zn(II) on montmorillonite via surface complexation at pH 4.5 and 7.5, with Zn-CTC complexes being the predominant species on montmorillonite at pH 7.5. At pH 9.5, Zn(II) may exist onto montmorillonite in precipitated form similar to Zn-Al hydrotalcite-like compound (HTlc) regardless of CTC presence. [Display omitted] • Coexistence of pollutants increased their individual sorption on montmorillonite. • The increase of sorption sites was confirmed by site energy distribution theory. • Chlortetracycline mainly complexed with zinc in solutions at pH 7.0–9.0. • The species of zinc on montmorillonite were characterized by EXAFS. [ABSTRACT FROM AUTHOR]

Ionic antibiotics and metals generally coexist, and their interaction can affect their sorption behaviors onto soil minerals, therefore determining their environmental hazards. This study investigated the sorption and cosorption of Zn(II) and chlortetracycline (CTC) onto montmorillonite at different solution pH (3−10) using batch experiments and extended X-ray absorption fine structure (EXAFS) analysis. The Langmuir model could reproduce well the sorption isotherms of Zn(II) and CTC. The presence of CTC/Zn(II) could promote the maximum sorption capacity (Q m) of Zn(II)/CTC, based on site energy distribution (SED) theory. Generally, Zn(II) sorption increased with pH increasing. Comparatively, CTC sorption decreased as pH increased till approximately pH 5.0, then increased continuously with pH increasing. Both CTC and Zn(II) co-existence enhanced their individual sorption in both acidic and neutral environments. The processes behind CTC and Zn(II) sorption mainly included cation exchange and surface complexation. The EXAFS data evidenced that the presence of CTC could alter the species of Zn(II) on montmorillonite via surface complexation at pH 4.5 and 7.5, with Zn-CTC complexes being the predominant species on montmorillonite at pH 7.5. At pH 9.5, Zn(II) may exist onto montmorillonite in precipitated form similar to Zn-Al hydrotalcite-like compound (HTlc) regardless of CTC presence. [Display omitted] • Coexistence of pollutants increased their individual sorption on montmorillonite. • The increase of sorption sites was confirmed by site energy distribution theory. • Chlortetracycline mainly complexed with zinc in solutions at pH 7.0–9.0. • The species of zinc on montmorillonite were characterized by EXAFS. [ABSTRACT FROM AUTHOR]

The abuse of antibiotics has triggered the rise of drug-resistance bacteria, which has seriously threatened public health globally. As a result, carrying out efficient and accurate antibiotic and bacteria identification are quite significant but challenge. Herein, an unprecedented Cd-MOF-based sensor, [CdL] n [ 1 , H 2 L = 4-(2-methyl-1H-benzo[ d ]imidazol-1-yl) isophthalic acid] with multiple fluorescence response behaviours towards antibiotics and bacteria was developed. Single-crystal X-ray diffraction revealed that 1 is a mesomeric 2D bilayer, which is comprised of two opposite chiral mono-layers, each assembled by left-handed or right-handed helixes. More interestingly, 1 represented multiplex detection capability towards antibiotics and bacteria through two detection behaviors: toward nitro-antibiotics and chlortetracycline (CTC) via fluorescent quenching, while toward Staphylococcus albus (S. albus) via fluorescent enhancement. Remarkably, 1 showed a low limit of detection (LOD, 47 CFU/mL) accompanied with specificity in the detection of S. albus compared to other bacteria, such as Staphylococcus aureus , Acinetobacter baumannii , Klebsiella pneumonia , Pseudomonas aeruginosa and Escherichia coli. In addition, the LOD could reach to ppm level for nitro-antibiotics and CTC. Moreover, the practical application of 1 was further reinforced through the detection of nitro-antibiotics and CTC, as well as S. albus in fetal calf serum and river water. [Display omitted] • An unprecedented highly stable Cd-MOF multiple fluorescence sensor was reported. • This sensor can rapidly and efficiently identify antibiotics or bacteria. • It can be as "turn-off" sensor towards nitro antibiotics and chlortetracycline. • It can be as "emission enhancement" sensor towards Staphylococcus albus. [ABSTRACT FROM AUTHOR]

Abstract: Recently, the occurrence of antibiotics in sewage treatment plant effluent, as well as drinking water, has raised concern about their potential impacts on the environment and public health. Antibiotics are found in surface and ground waters, which indicate their ineffective removal by conventional wastewater treatment processes. Therefore, advanced oxidation processes (AOPs) have received considerable attention for the removal of antibiotics. This study was conducted to evaluate the degradation and mineralization of antibiotics (sulfamethoxazole and chlortetracycline) using an electron beam, ozone and UV, and the change of toxicity. Also, the electrical energy consumption based on the EE/O parameter (the electrical energy required per order of pollutants removal in 1m3 wastewater) was used to quantify the energy cost associated with the different AOPs (electron beam, ozone and UV) for the degradation of antibiotics. The results showed that an electron beam effective for the removals of both sulfamethoxazole and chlortetracycline in aqueous solutions. However, degradation of the target compounds by ozone and UV showed different trends. The oxidation efficiency of each organic compound was very dependent upon the AOP used. Algal toxicity was significantly reduced after each treatment. However, based on the electrical energy, the electron beam was more efficient than ozone and UV. Electron beam treatment could be an effective and safe method for the removal of antibiotic compounds. [Copyright &y& Elsevier]

Abstract: This study investigated the abiotic transformation kinetics of chlortetracycline (CTC) by synthesized δ-MnO2 under conditions of different solutions. CTC was rapidly oxidized by δ-MnO2, with the generation of Mn2+. The measured CTC transformation rate increased considerably with an increase in initial δ-MnO2 concentration but it decreased as the initial CTC concentration increased. Both the measured CTC transformation rate and the amount of Mn2+ generated decreased with increasing pH. The CTC transformation rate rose with an increase in temperature. The apparent activation energy (45±14kJmol−1) was consistent with a surface-controlled reaction. Dissolved Mn2+ and Zn2+, as background cations, and substituted phenols, as co-solutes, remarkably decreased the transformation rate of CTC. Liquid chromatography–tandem mass spectrometry (LC–MS-MS) was used to identify oxidation products, which include iso-CTC, 4-epi-CTC, anhydro-CTC and 4-epi-anhydro-CTC, keto-CTC, 4-epi-keto-CTC, N-demethyl-CTC, 4-epi-N-demethyl-CTC, N-didemethyl-CTC and 4-epi-N-didemethyl-CTC. Product identification together with Fourier transform-infrared (FTIR) spectra suggested that the hydroxyl groups at C6 and C12 and the dimethylamine group of CTC reacted with the Mn–OH groups on the δ-MnO2 surface. Thus, δ-MnO2 in the soils most probably plays an important role in the abiotic transformation of tetracycline antibiotics. [Copyright &y& Elsevier]

Chlortetracycline (CTC) is one of only ten antibiotics licensed in the U.S.A. for use as growth promoters for livestock. The widespread use and persistence of CTC may contribute in development of antibiotic-resistant bacteria. The objective of this study was to determine the effect of composting on the fate of CTC residues found in manure from medicated animals. The effect of CTC residues on composting was also investigated. Five beef calves were medicated for 5 days with 22mg/kg/day of CTC. Manure samples collected from calves prior to and after medication were mixed with straw and woodchips, and aliquots of the subsequent mixtures were treated in laboratory composters for 30 days. In addition, aliquots of the CTC-containing mixture were incubated at 25°C or sterilized followed by incubation at 25°C and 55°C (composting temperature). The presence of CTC did not appear to affect the composting process. Concentrations of CTC/ECTC (the summed concentrations of CTC and its epimer ECTC) in the composted mixture (CM) and sterilized mixture incubated at 55°C (SM55) decreased 99% and 98% (from 113μg/g dry weight (DW) to 0.7μg/g DW and 2.0μg/g DW), respectively, in 30 days. In contrast, levels of CTC/ECTC in room temperature incubated (RTIM) and sterilized mixture incubated at 25°C (SM25) decreased 49% and 40% (to 58μg/g DW and 68μg/g DW), respectively, after 30 days. Concentrations of the CTC metabolite, iso-chlortetracycline (ICTC), in CM and SM55 decreased more than 99% (from 12μg/g DW to below quantitation limit of 0.3μg/g DW) in 30 days. ICTC levels in RTIM and SM25 decreased 80% (to 4μg/g DW) in 30 days. These results confirm and extend those from previous studies that show the increased loss of extractable CTC residues with increased time and incubation temperature. In addition, our results using sterile and non-sterile samples suggest that the decrease in concentrations of extractable CTC/ECTC at 25°C and 55°C (composting temperature) is due to abiotic processes. [Copyright &y& Elsevier]

Abstract: The fate of antibiotic residues in the manure of treated animals is of considerable concern because of the potential development of antibiotic-resistant bacteria in the environment. The objective of this study was to determine the fate of chlortetracycline (CTC) during the anaerobic digestion of manure from medicated calves. Five beef calves were medicated for 5 days with 22mg/kg/day of CTC. Manure samples collected from calves after medication were diluted 5-fold with water, loaded into triplicate 1L anaerobic digesters and incubated at 35°C. The CTC concentration decreased approximately 75% (from 5.9 to 1.4ppm) during the 33 days digestion period, yielding a half-life of about 18 days. The concentration of the CTC epimer, 4-epi-chlortetracycline (ECTC), declined roughly 33% (from 4.1 to 2.5mg/L) during anaerobic digestion. However, the concentration of the CTC metabolite, iso-chlortetracycline (ICTC), increased 2-fold (from 2.3 to 4.6mg/L) during the digestion period. Although the water-soluble concentration of CTC decreased 84% (from 0.3 to 0.04mg/L), the water-soluble concentrations of ECTC and ICTC increased roughly 2-fold during digestion (from 0.5 to 0.93, and 1.0 to 2.7mg/L, respectively). Since ECTC and ICTC are more water-soluble than the parent tetracycline CTC, it is more likely that these compounds present in digested manure slurry will be detected in water monitoring samples. [Copyright &y& Elsevier]

Finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concerns. Herein, we investigated the co-adsorption behaviors of chlortetracycline (CTC) and Pb (II) onto struvite loaded diatomite (SD) in aqueous solution, and their interface interactions mechanism was investigated using crystal and microstructure analysis combined with density functional theory (DFT) calculations. The adsorption capacity at equilibrium of CTC increased from 44.28 to 87.58 mmol/kg with the presence of Pb (II), but the adsorption capacity at equilibrium of Pb (II) decreased from 4289.70 to 3559.9 mmol/kg with the presence of CTC. Besides, the effect of environmental factors (solution pH and humic acid) was also evaluated. Microstructure analysis for recovered products demonstrated that the interface interactions brought by the surface Pb(II) of Pb 5 (PO 4) 3 OH and carbonyl-O of CTC could facilitate the removal of CTC but inhibit the removal of Pb(II) by suppressing the crystal growth of Pb 5 (PO 4) 3 OH, especially the orientation growth of (0 0 1) crystal plane. DFT calculations gave theoretical support for the interface interactions between Pb 5 (PO 4) 3 OH and CTC. Struvite loaded diatomite (SD) was used for simultaneously removing CTC and Pb (II). This work provides a new perspective for the study of the co-adsorption behaviors of CTC and Pb (II) onto SD. It indicates that the interface interactions brought by the surface Pb (II) of Pb 5 (PO 4) 3 OH and carbonyl-O of CTC facilitated the removal of CTC but inhibited the removal of Pb (II) by suppressing the crystal growth of Pb 5 (PO 4) 3 OH, especially the orientation growth of (001) crystal plane. DFT calculations gave theoretical support for the interface interactions between Pb 5 (PO 4) 3 OH and CTC. ga1 • Struvite loaded diatomite was used for simultaneous removal of CTC and Pb (II). • Microstructure analysis and DFT calculations were applied for mechanism study. • The presence of Pb (II) enhanced the adsorption of CTC onto SD. • Adhesion of CTC to the surface of Pb 5 (PO 4) 3 OH suppressed the removal of Pb (II). • Effect of humic acid on the co-adsorption of CTC and Pb (II) onto SD was studied. [ABSTRACT FROM AUTHOR]

• GO/PAA-CdS was prepared by facile polymerization-precipitation method. • GO/PAA-CdS showed excellent photocatalytic activity to CTC under visible light. • The polymer network favored the size control and distribution of CdS nanoparticles. • DFT calculation helped to predict reactive sites and degradation pathways of CTC. Here a CdS embedded poly acrylic acid (PAA)/graphene oxide (GO) polymeric composite was prepared for the efficient degradation of chlortetracycline (CTC) driven by visible light irradiation. The structure-activity relationship of GO/PAA-CdS was confirmed through the photocatalytic evaluation of a series of samples prepared by varying GO concentration, molar ratio of Cd:S and the amount of crosslinking agent. Through the composition, morphology, photoelectrochemical characterizations and degradation kinetic studies, it could be confirmed that the enhanced photocatalytic activity is attributed to the controlled growth of CdS nanoparticles by polymer net structure and effective electron transfer along GO nanosheets. The photodegradation of CTC was confirmed to be mainly governed by O 2 − and OH radicals generated from GO/PAA-CdS. The degradation intermediates of CTC were confirmed by LC–MS, and possible degradation pathways were proposed based on the prediction of radical attacking sites according to Fukui function values obtained through Density Functional Theory (DFT). Moreover, it was found that the catalytic activity of the photocatalyst was maintained after several cycles confirming the enhanced anti-photocorrosion of GO/PAA-CdS. This research provided an efficient approach by a novel photocatalyst for the removal of CTC from wastewater. [ABSTRACT FROM AUTHOR]

• Fate of chlortetracycline (CTC) during anaerobic degradation was investigated. • CTC degradation was explained by the first-order incomplete decay model. • Substantial amounts of epimer- CTC, and isomer- CTC was transformed from CTC. • Most of CTC, epimer, and isomer-CTC existed in the solid phase of digestate. • CTC degradation could be inhibited by co-metabolization by substrate. As veterinary antibiotics (VAs) cause adverse effects on nature, anaerobic digestion (AD) of livestock manure has been receiving attention as an exposure route of VAs. This research evaluated the anaerobic degradation and phase distribution of chlortetracycline (CTC) with its epimer (4-epi-CTC, ECTC) and isomer (Iso-CTC, ICTC). In addition, whether CTC can inhibit not only AD of a substrate but also the degradation of CTC was assessed. Anaerobic batch assays were performed with cattle manure for 30 days by varying the initial concentration of CTC; 0, 10, 25, 50, and 100 mg/L. Approximately 25–43 % (w/w) of CTC was primarily degraded while 18–25 % and 20–26 % of CTC was transformed into ECTC and ICTC, respectively. Up to 88 % (w/w) of the remaining CTC, ECTC, and ICTC was present in the solid phase. In addition, CTC inhibited not only the mineralization of the cattle manure but also the degradation of CTC due to co-metabolism. In conclusion, significant quantities of CTC, ECTC, and ICTC can be exposed to nature by solid phase of anaerobic digestate. The inhibition on AD can reduce the degradation of CTC, ECTC, and ICTC during the AD. [ABSTRACT FROM AUTHOR]

• Toxicity of 3 sewage sludge-derived micropollutants to soil nematoda were tested. • LFIA was used to asses effect of chlortetracycline, HHCB and BDE-99 to C. elegans feeding activity. • HHBC inhibited nematode feeding at high concentrations and showed medium risk quotient. • Environmentally relevant concentration of micropollutants showed no harmful effect. Sewage sludge application to soil is of great interest, due to required organic matter and the wide spectra of nutrients it provides. However, the presence of unpredictable content of emerging contaminants may turn this valuable raw material into a hazardous substance. In this study, three selected sewage sludges derived micropollutants from different origins; that is, one each under persistent organic pollutants (POPs), pharmaceuticals and personal care products (PPCPs) were considered. The effect of each micropollutant on the feeding activity of free-living soil nematode Caenorhabditis elegans was analysed. The analysis was performed in model soil solution using a larval feeding inhibition assay. The results showed no significant effects from selected POP—2,2′,4,4′,5-pentabromodiphenyl either and pharmaceutical—chlortetracycline on the feeding activity of tested nematodes. On the contrary, feeding activity was inhibited by PPCP—galaxolide (HHCB) with an effective concentration of 12.2 ± 2.2 mg.l-1. The calculated risk quotient for galaxolide (RQ = 0.14) demonstrated a medium ecological risk to the nematodes. Based on our findings, concentrations of micropollutants in sewage sludge treated soil pose negligible risk to feeding activity of soil nematode. However, the potential impact of musk compounds on free-living soil biota requires detailed evaluation in further research. [ABSTRACT FROM AUTHOR]