Occurrence of antibiotics and antibiotic resistance genes in the Fuxian Lake and antibiotic source analysis based on principal component analysis-multiple linear regression model

In recent years, the dramatic increase in antibiotic use has led to the evolution of antibiotic resistant genes (ARGs), posing a potential risk to human and aquatic ecological safety. In this study, source contribution and correlations between twelve antibiotics and their corresponding ARGs were firstly investigated in surface water in the Fuxian Lake. The results showed that sulfamethoxazole (SMX) (0.98-14.32 ng L^-1) and ofloxacin (OFL) (0.77-7.3 ng L^-1) were the dominant antibiotics in surface water, whereas erythromycin-H₂O (EM-H₂O), SMX and OFL posed the medium risk to aquatic organisms. Meanwhile, the mean concentrations of MLs in inflowing rivers were 5.6 times more than those in the lake, which was related to dilution and degradation. Moreover, the facter1 (co-sources L (Living quarters), M (Mining area), A (Agricultural district) and T (tourist area)) contributed 78% of antibiotic concentrations, and the source L was predominant. The results also revealed the prevalence of intL1, sul1 and sul2 in all the sampling sites, and that the abundance of ARGs in the lake was significantly lower (P < 0.01) than that in inflowing rives. Additionally, significant correlations (p < 0.0001) between intL1 and sulfanilamide resistance genes (sul1, sul2) were detected, indicating that intL1 promoted the propagation and they originated from the same anthropogenic sources. Overall, our findings revealed the presence of antibiotics and ARGs and their inconsistent correlations in the Fuxian Lake, which provides a foundation to support further exploration of the occurrence and transmission mechanisms of antibiotics and ARGs.

Occurrence, sources and risk assessment of fluoroquinolones in dumpsite soil and sewage sludge from Chennai, India

Soil and sludge are major reservoirs of organic compounds such as fluoroquinolones (FQs) which are broad-spectrum antibacterial agents. Hence, we monitored three major FQs, namely, ciprofloxacin (CIP), norfloxacin (NOR), and ofloxacin (OFL), in surface soil from two major dumpsites and dry and wet sludge from sewage treatment plants in Chennai city. The mean concentration of FQs in soil and sludge samples were 20 μg/g and 26 μg/g, respectively. Nearly 50% of the total FQs in dumpsite soil was contributed by CIP followed by NOR (32%) and OFL (13%). Similarly, CIP was the major contributor in sludge samples followed by NOR and OFL. The concentration of FQs was two folds higher in wet sludge than dry sludge most likely indicating that water solubility of these compounds might play an important role for elevated level of FQs in wet sludge. Solid waste from pharmaceutical industries, households, and sludge from wastewater treatment plants were expected to be the major source of FQs in dumpsite soil. Predicted risk assessment using soil to water migration concentrations via surface run off indicated high risk to aquatic organisms. However, risk quotient (RQ) was found less to earthworm in most of the soil samples. The findings from this study might help in future policies on disposal of household antibiotics in the solid waste stream.

Mechanistic insight into ultrasound-induced enhancement of electrochemical oxidation of ofloxacin: Multi-response optimization and cost analysis

In this paper, a hybrid advanced oxidation process of sonoelectrochemical, in which ultrasound and electrochemical are applied simultaneously, has been used for the degradation of ofloxacin (bio-recalcitrant pharmaceutical pollutant). Response surface methodology based central composite design was applied to understand the parametric effects of ultrasonic power, current density, initial pH, and electrolyte dose. Enhanced ofloxacin degradation was obtained using sonoelectrochemical (≈95%) process in comparison to the electrochemical (≈60.6%) and sonolysis alone (≈7.2%) after 120 min treatment time. Multi-response optimization was used so as to maximize COD removal (70.12%) and minimize specific energy consumption (11.92 kWh (g COD removed)^-1)at the optimized parametric condition of pH = 6.3 (natural pH), ultrasonic power = 54 W, current density = 213 A m^-2, and Na₂SO₄ electrolyte dose = 2.0 g L^-1. It was revealed that ^•OH radicals contribute major to the ofloxacin degradation reaction among the other oxidizing agents. Degradation of the ofloxacin followed pseudo-first-order kinetics with a higher reaction rate, which confirmed the synergistic effect of 34% between ultrasound and electrochemical approaches. The degradation pathway of ofloxacin removal was elucidated at optimum condition by the temporal evolution of the intermediate compounds and final products using gas chromatography coupled with mass spectroscopy (GC-MS), liquid chromatography-mass spectroscopy (LC-MS), high-resolution mass spectroscopy (HR-MS), and Fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) and field emission scanning electron microscope (FE-SEM) coupled with energy dispersed X-ray (EDX) were used to determine the morphology of electrodes. Operational cost analysis was done based on the reactor employed in the present study.

A time-resolved luminescence aptasensor of ofloxacin based on rolling circle amplification and magnetic separation

A novel sensitive, competitive, and time-resolved luminescence sensor for the detection of ofloxacin (OFL) was developed in this study. The sensor used OFL-specific aptamer as a recognition molecule and rolling circle amplification (RCA) as a signal amplification tool. In this way, the time-resolved luminescence can not only avoid background noise from sample, but also provide robust luminescence for detection. Besides, the separation and enrichment of target veterinary drug can be conducted assisted by magnetic treatment. Under optimal conditions, the logarithmic correlation between the concentration of OFL and the luminescence intensity was found to be linear in the range of 5 × 10^-11-5 × 10^-8 mol L^-1 (R² = 0.9988), with a detection limit (LOD) of 32.1 pmol L^-1. Furthermore, this method was applied to the determination of OFL in chicken and pork samples, exhibiting good recovery (72.5-100%) and repeatability (RSD < 10.0%). These results confirm that this novel established method has good application potential for the detection of OFL in food samples.

Fluorescent aptasensor for ofloxacin detection based on the aggregation of gold nanoparticles and its effect on quenching the fluorescence of Rhodamine B

This paper proposes the idea of building a fluorescent biosensor for ofloxacin (OFL) determination in aqueous and milk samples by label-free OFL-specific aptamer, gold nanoparticles (AuNPs) and Rhodamine B (RB). In the absence of OFL, AuNPs are coated with OFL aptamer and maintain dispersed in the high concentration of NaCl. The dispersed AuNPs could reduce the strong fluorescence intensity of RB efficiently. By contrast, in the presence of OFL, OFL is combined with aptamer to form stable compounds, causing the aptamers separated from the surface of AuNPs, thus AuNPs would be exposed in the solution. And the aggregated AuNPs will not quench the fluorescence intensity of RB. Through the distinction of the fluorescence intensity, the concentration of OFL could be detected in aqueous and milk samples quantitatively. The convenient and specific fluorescent assay for OFL is established with a linear range (R = 0.9907) from 20 to 300 nM and a detection limit of 1.66 nM in aqueous solution, and a linear range (R = 0.9963) from 20 to 300 nM and a detection limit of 4.61 nM (1.66 μg/L) in milk samples. With the good sensitivity and selectivity, this biosensor has good application potential to detect OFL in food and environmental samples.

Influence of organic carbon fractions of freshwater biofilms on the sorption for phenanthrene and ofloxacin: The important role of aliphatic carbons

Sorption to biofilms is thought to be a crucial process controlling the fate of trace organic contaminants in aquatic systems. The organic composition of biofilms is regarded as the determining factor in the sorption mechanism of biofilm organic carbon fractions; however, its role is not well known. Here, the sorption of phenanthrene and ofloxacin was modeled with classic and emerging organic contaminants, respectively, by comparatively investigating nine type of freshwater biofilms cultured in a river, lake, and reservoir in spring, summer, and autumn. The chemical features of the nine biofilms were analyzed using elemental analysis, infrared spectroscopy, X-ray photoelectron spectroscopy, and carbon-13 nuclear magnetic resonance. Results showed that the freshwater biofilms were aliphatic-rich natural amorphous solid substances with O-containing functional groups, and their surface polarity was significantly lower than their bulk polarity. All the isotherms of phenanthrene and ofloxacin sorption by the biofilms were linear. The organic carbon-normalized partition coefficient values for phenanthrene and ofloxacin on the nine biofilms ranged from 91.9 to 364.2 L g^-1 and 3.2 to 43.2 L g^-1, respectively. The van der Waals interaction between a majority of aliphatic carbon (73.4%-83.9%) in biofilms and the two sorbates was much stronger than π-π interactions between a minority of aromatic carbon (12.7%-21.7%) and sorbates. The surface polarity of the biofilms regulated polar interactions including the hydrogen bonding and electron donor-acceptor interactions. Both the aliphatic carbon and surface polarity in the biofilms enhanced the sorption of phenanthrene and ofloxacin. The sorption characteristics and mechanisms of polycyclic aromatic hydrocarbons and antibiotics on biofilms shown in our present and previous studies are different from those of other ubiquitous natural solid materials such as soils and sediments. This study provides insight into the importance of aliphatic carbon fractions of freshwater biofilms for the sorption of classic and emerging organic contaminants.

Phytotoxicity and degradation of antibiotic ofloxacin in duckweed (Spirodela polyrhiza) system

The phytotoxicity and degradation of ofloxacin (OFX) in duckweed Spirodela polyrhiza based system was estimated in this study. For that, OFX was added in an environmentally relevant range (0.01-1.0 mg L^-1) in medium (Hoagland nutrient) and toxicity biomarkers, i.e. changes in plant biomass, relative growth rate (RGR), photopigment (Chl-a, Chl-b and carotenoids), protein content, antioxidative enzymes (catalase, CAT; superoxide dismutase, SOD; and ascorbate peroxidases, APX) in fronds were estimated. The batch-scale setups (250 ml) was prepared in triplicate for each concentration of OFX and reared in growth chambers (Algae Tron AG 230) for 7 d. Results suggested that the high concentrations of OFX caused a reduction in biomass (4.8-41.3%), relative root growth (RGR), protein (4.16-11.28%) and photopigment contents. The fronds in OFX spiked setups showed an increased level of antioxidative enzymes: CAT (0.230-0.338 mmol_H2O2 mg^-1 protein), APX (0.043-0.074 mmol_ascorbate mg^-1 protein), and SOD (0.267-0.317 U mg^-1 protein) than control. At the end (7 d), the residual OFX content in the medium was also estimated, and results suggested a significant (p < 0.05) reduction (93.73-98.36%) in OFX content than control setup (54.76-75.53%) at the end of the experimentation. The trend of residual OFX suggested phytodegradation as a significant mechanism of antibiotic degradation other than hydrolysis and photodegradation processes. This study indicates that duckweed can be an effective bio-tool for the removal of environmental relevant concentration of the antibiotics from the wastewater.

Effects of dissolved humic acid on fluoroquinolones sorption and retention to kaolinite

Fluoroquinolones (FQs) are widely used in human and veterinary medicaments, and as such are ubiquitous environmental contaminants. Dissolved organic matter (DOM) is widely distributed in natural water and sediment and dissolved humic acid (DHA) is a major component of DOM. The coexistence of DHA might influence the sorption, migration and transformation of FQs, thus determining their environmental fate. In this study, the interaction of DHA and ofloxacin (OFL)/flumequine (FLU) was evaluated using dialysis-bag assays. The sorption of OFL and FLU to kaolinite in the presence of DHA under different pH conditions was investigated. The results revealed that the binding affinities of FQs to DHA were weakened with increasing pH from 4.0 to 10.0 due to the increased negative charge of DHA and subsequent electrostatic repulsion. Sorption experiments indicated that co-precipitation was an important mechanism for OFL/FLU removal from the aqueous phase under acidic conditions. At pH 7.0, the affinity of OFL-DHA/FLU-DHA to kaolinite was weaker than that of OFL/FLU thus suppressed its sorption. At pH 9.5, the affinity of OFL-DHA to kaolinite was stronger than that of OFL and consequently promoted its sorption, but there was no observed effect of DHA on FLU sorption. During desorption, DHA could bind to OFL/FLU and promote its desorption from kaolinite at neutral pH. In binary solute systems of OFL and FLU, OFL was a more effective competitor for the sorption sites of kaolinite than FLU.

Size-dependent adsorption of antibiotics onto nanoparticles in a field-scale wastewater treatment plant

This work present aims to evaluate the effect of a conventional wastewater treatment process on the number of nanoparticles, and the role of nanoparticles as a carrier of antibiotics. A set of methods based on asymmetrical flow field flow fractionation coupled with multi-angle light scattering to separate and quantify nanoparticles in real wastewater was established. The characterization of nanoparticles was conducted by transmission electron microscopy, energy dispersive spectrometer, UV-visible spectrophotometer and three-dimensional excitation-emission matrix fluorescence spectroscopy. The adsorption of different sizes of nanoparticles separated from the real wastewater for four targeted antibiotics (sulfadiazine, ofloxacin, tylosin and tetracycline) was studied. The results show that the number of nanoparticles were increased in the wastewater treatment process and the size range between 60 and 80 nm was predominant in wastewater samples. The nanoparticles were mainly composed of O, Si, Al and Ca elements and organic components were in the size range of 0-10 nm. Targeted antibiotics were dominantly adsorbed onto nanoparticles with 60-80 nm size range at each stage. The concentrations of tetracycline adsorbed on nanoparticles were surprisingly increased in the end of the treatment process, while ofloxacin and tylosin had the completely opposite phenomenon to tetracycline. The pH and ionic strength definitely affected the aggregation of nanoparticles and interaction with the antibiotics. It is of great significance to give insights into nanoparticle-antibiotic assemblages for the effective treatment and avoiding the water risks due to nanoparticles' ubiquitous and their risks of carrying antibiotics.

Effects of antibiotics on nitrogen uptake of four wetland plant species grown under hydroponic culture

To investigate the effects of antibiotics on nitrogen removal and uptake by wetland plants, four typical macrophyte species, Cyperus alternifolius L., Typha angustifolia L., Lythrum salicaria L., and Acorus calamus L., were grown in hydroponic cultivation systems and fed wastewater polluted with 10 μg L^-1 Ofloxacin (OFL) and Tetracycline (TET). Biomass production, nitrogen mass concentration, chlorophyll content, root exudates, and nitrogen removal efficiency of hydroponic cultivation were investigated. The results indicated that in all hydroponic systems, NH₄⁺-N was entirely removed from the hydroponic substrate within 1 day and plant nitrogen accumulation was the main role of the removed NO₃^-. OFL and TET stimulated the accumulation of biomass and nitrogen of A. calamus but significantly inhibited the NO₃^--N removal ability of L. salicaria (98.6 to 76.2%) and T. augustifolia (84.3 to 40.2%). This indicates that A. calamus may be a good choice for nitrogen uptake in wetlands contaminated with antibiotics. OFL and TET improved the concentrations of total organic carbon (TOC), total nitrogen (TN), organic acid, and soluble sugars in root exudates, especially for oxalic acid. Considering the significant correlation between TOC of root exudates and nitrogen removal efficiency, the TOC of root exudates may be an important index for choosing macrophytes to maintain nitrogen removal ability in wetlands contaminated with antibiotics.

Heterogeneous fenton-like degradation of ofloxacin over sludge derived carbon as catalysts: Mechanism and performance

In this study, heterogeneous Fenton-like degradation of ofloxacin (OFX) was investigated by sludge derived carbon (SC). The effects of SC catalyst, temperature and pH on the efficiency of ofloxacin degradation were investigated. SC treated with sulfuric acid (SC-H₂SO₄) performed high catalytic activity, indicating that sulfate group produced low pH of the surface and was beneficial for heterogeneous Fenton-like degradation. The removal of ofloxacin and TOC was 91.5% and 62.3%, respectively, after 180 min adsorption and 540 min oxidation, at pH 6 and a dosage of 138 mg L^-1 H₂O₂. It was found that OFX conversion increased with the decrease of pH and OFX was degraded under the wide range of pH (3-6) by SC-H₂SO₄. These promising results clearly demonstrate the potential of the heterogeneous Fenton-like process for the effective degradation of ofloxacin by SC-H₂SO₄. Based on intermediated products identified by gas chromatography-mass spectrometry, a possible OFX oxidation pathway in Fenton-like reaction was proposed.

Comparison of chlorination behaviors between norfloxacin and ofloxacin: Reaction kinetics, oxidation products and reaction pathways

Fluoroquinolones (FQs) are very ubiquitous in water environment in China. The commonly application of free available chlorine (FAC) during water treatment stimulated the focus on the transformation of FQs during chlorination. Among these FQs, norfloxacin (NOR) and ofloxacin (OFL) are the representatives of secondary amine FQs and tertiary amine FQs, respectively. To better understand the difference between secondary amine FQs and tertiary amine FQs during chlorination, reaction kinetics, products and mechanisms were determined. The maximum k_app of NOR were four orders of magnitude higher than that of OFL. Moreover, eleven products of NOR and twelve products of OFL were obtained by LC-MS/MS analysis. For the two FQs, the common reactive sites were three nitrogen atoms, benzene ring, carboxyl group and double bond by chlorination. For OFL, the ether ring was also active in aqueous system. The formation mechanisms of these products were presented in this study. The main reaction pathways were electrophilic addition to nitrogen, nucleophilic substitution to benzene ring, halodecarboxylation of carboxyl group and hydrolysis of ether ring. Na₂S₂O₃ as a reducing agent had large effect on the chlorination of secondary amine FQ, but no effect on tertiary amine FQ. Be different to secondary amine FQ, the opening of quinolone ring happened in tertiary amine FQ after halodecarboxylation of carboxyl group.

Electro-oxidation of Ofloxacin antibiotic by dimensionally stable Ti/RuO2 anode: Evaluation and mechanistic approach

Present study investigates the potential of Ti/RuO₂ electrode for degradation and mineralization of Ofloxacin (OFLX) antibiotic from synthetic wastewater by electro-oxidation (EO) method, not reported earlier. Effects of various EO parameters such as applied current (I), initial pH, initial OFLX concentration (C₀) and supporting electrolyte concentration on %OFLX removal efficiency and %TOC removal efficiency were systematically studied and reported. Decay kinetics of OFLX by varying C₀ and applied I were also studied. Additionally, mineralization current efficiency and specific energy consumption of OFLX mineralization were evaluated. Moreover, mode of oxidation method involved (direct and/or indirect oxidation) was also explored. Major OFLX transformation products during EO were identified using UPLC-Q-TOF-MS, and possible degradation reaction mechanism was proposed. Furthermore, operating cost analysis was performed to check the economic feasibility of the EO process. The optimum pH and current (I) were found to be ≈6.8 (natural pH of OFLX wastewater) and 1 A, respectively. Mineralization current efficiency decreased from 7.8% to 4.9% with increase in I value from 0.25 to 1 A. ≈80% of OFLX removal in 30 min of electrolysis and 46.3% TOC removal in 240 min of electrolysis at I = 1 A were observed. Pseudo-first-order kinetic model best fitted the experimental data showing R² value ≈ 0.99 for all the C_o and applied I studied.

Reuse and recovery of raw hospital wastewater containing ofloxacin after photocatalytic treatment with nano graphene oxide magnetite

Inadequate treatment of hospital wastewater could result in considerable risks to public health due to its macro- and micropollutant content. In order to eliminate this problem, a new nanoparticle composite was produced under laboratory conditions and a photocatalytic degradation approach was used. Chemical oxygen demand (COD), biological oxygen demand (BOD₅), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP) (macro) and oflaxin (micro) pollutant removal were investigated with the nano graphene oxide magnetite (Nano-GO/M) particles by two different processes, namely adsorption and photodegradation. Low removal efficiencies (21-60%) were obtained in the adsorption process for the parameters given above, after 90 min contact time at a pH of 7.8 with 5 g/L Nano-GO/M composite. Using the photodegradation process, higher removal efficiencies were obtained with 2 g/L Nano-GO/M composite for COD (88%), TSS (82%), TKN (95%) and oflaxin (97%), at pH 7.8 after 60 min irradiation time at a UV power of 300 W. The synthesized nanoparticle was reused for two sequential treatments of pharmaceutical wastewater with no significant losses of removal efficiencies (for oflaxin 97%-90%). The quality of the treated hospital wastewater was first class according to the Turkish Water Pollution Control Regulations criteria. This water could also be used for irrigation purposes.

Oil shale powders and their interactions with ciprofloxacin, ofloxacin, and oxytetracycline antibiotics

The interaction of oil shale, as a widespread sedimentary rock, with common antibiotics ofloxacine, oxytetracycline, and ciprofloxacine was studied. The selected Moroccan deposit and its thermally treated forms were fully characterized from a chemical and structural point of view, indicating the prevalence of quartz as a mineral component together with aluminum- and iron-rich phase that are converted into Al-doped iron oxide phases upon heating. The presence of 4 wt% organics was also detected, which was removed at 550 °C without significant loss of specific surface area. The pseudo-second-order kinetic model and Langmuir equation were found the most adequate to reproduce the kinetics and isothermal sorption experiments. These analyses enlighten the contribution of the organic matter on antibiotic retention as well as the key role of hydrophobic interactions on the molecule-mineral surface interactions. Our results emphasize the possible contribution of raw oil shale in the accumulation of antibiotics in soils and suggest that thermally treated oil shell powders can constitute cheap mineral sorbents for environmental cleaning.

Co-contaminant effects on ofloxacin adsorption onto activated carbon, graphite, and humic acid

Given their voluminous application, significant amounts of fluoroquinolones are discharged into the environment through wastewater effluent. Adsorption has been shown to be a critical process controlling the environmental behaviors of fluoroquinolones. Competition between ofloxacin (OFL) and naphthalene (NAP)/bisphenol A (BPA) and their adsorption on activated carbon (AC), graphite (GP), and humic acid (HA) were investigated. The suppressed adsorption of OFL was observed on AC and GP, but not on HA, by NAP or BPA. Moreover, for AC, the competition by NAP was slightly stronger than that by BPA. However, for GP, the competition with BPA was higher than that with NAP. These observations indicate that competitive adsorption of OFL with respect to NAP/BPA depends on the degree of overlap of adsorption sites, as interpreted by the following: (i) AC can provide overlapping adsorption sites for OFL, BPA, and NAP, which include non-specific adsorption sites, such as hydrophobic sites, π-π interactions, and micropore filling; (ii) π-π interactions and hydrogen bonding might be responsible for the strong competitive adsorption between BPA and OFL on GP; and (iii) OFL adsorbs on HA through specific adsorption force-electrostatic attraction, with which NAP and BPA cannot compete.

Simultaneous Estimation of Ofloxacin, Clotrimazole, and Lignocaine Hydrochloride in Their Combined Ear-Drop Formulation by Two Spectrophotometric Methods

Two sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the simultaneous estimation of ofloxacin (OFX), clotrimazole (CLZ), and lignocaine hydrochloride (LGN) in their combined dosage form (ear drops) without prior separation. The derivative ratio spectra method (method 1) includes the measurement of OFX and CLZ at zero-crossing points (ZCPs) of each other obtained from the ratio derivative spectra using standard LGN as a divisor, whereas the measurement of LGN at the ZCP of CLZ is obtained from the ratio derivative spectra using standard OFX as a divisor. The double divisor-ratio derivative method (method 2) includes the measurement of each drug at its amplitude in the double divisor-ratio spectra obtained using a standard mixture of the other two drugs as the divisor. Both methods were found to be linear (correlation coefficients of >0.996) over the ranges of 3-15, 10-50, and 20-100 μg/mL for OFX, CLZ, and LGN, respectively; precise (RSD of <2%); and accurate (recovery of >98%) for the estimation of each drug. The developed methods were successfully applied for the estimation of these drugs in a marketed ear-drop formulation. Excipients and other ingredients did not interfere with the estimation of these drugs. Both methods were statistically compared using the t-test.

Risk assessment of three fluoroquinolone antibiotics in the groundwater recharge system

Three fluoroquinolone antibiotics agents (FQs) in groundwater and reclaimed water have been investigated in Changzhou and Beijing, China. The occurrence of ofloxacin (OFL), enrofloxacin (ENR) and norfloxacin (NOR) is in nanograms per liter and has 100% frequency. The concentration order of FQs in reclaimed water is NOR>OFL>ENR, whilst the order in groundwater is NOR>ENR>OFL. And then the single and mixture adsorption-desorption have been studied and showed that (i) silty clay loam has higher sorption capacity than loamy sand, (ii) competitive adsorption exists when the three selected FQs coexist, (iii) ENR has a significantly priority sorption to NOR, whilst OFL has a least sorption among the mixture, (iv) there is no significant difference between the desorption results of mixture and the indivdual compound in relatively low concentration, (v) the formed chemical bonds and the irreversible combination of adsorption point are the significant influential factors for explaining desorption hysteresis of the selected FQs. Based on the above study, transport model and risk quotient have been performed, and the calculated risk quotient reveals that: (i) the selected FQs risk order in reclaimed water is OFL>ENR>NOR, (ii) in groundwater, OFL and ENR pose a higher risk than NOR no matter whether considering the long time groundwater recharge. This study will help policy makers to decide which FQs need to be covered in the priority substance lists defined in legislative frameworks.

Occurrence, fate and interrelation of selected antibiotics in sewage treatment plants and their receiving surface water

The occurrence and fate of 12 commonly used antibiotics, two fluoroquinolones (FQs), three sulfonamides (SAs), three macrolides (MLs), two β-lactams and two tetracyclines (TCs), were studied in four sewage treatment plants (STPs) and their receiving water, the Huangpu River, Shanghai. The levels of selected antibiotics in the STPs ranged from ngL(-1) to μgL(-1), while ofloxacin (OFL) was predominant (reach up to 2936.94ngL(-1)). The highest and lowest proportions were of FQs (STP 1, STP 2 and STP 3) and TCs (in four STPs) respectively in both influents and effluents. And the second-highest proportion was of FQs in STP 4 (only 2% lower than the highest). What could be inferred was that the usage of TCs were extremely low while the usage of FQs were larger than other antibiotics in our study area. The elimination of antibiotics through these STPs was incomplete and a wide range of removal efficiencies (-442.8% to 100%) during the treatment was observed. Based on the mass loadings as well as the per-capita mass loadings of target antibiotics in four STPs, OFL was considered the primary contaminant herein. In the Huangpu River, 3 antibiotics were not detected in any water samples, while the detection frequencies of 4 antibiotics were 100%. The highest concentration detected in the river was 53.91ngL(-1) of sulfapyridine (SD). The Spearman correlation analysis of antibiotics in STPs and the nearby water samples suggests that the antibiotics discharged from some STPs might influence the receiving water to some extent. Moreover, most of the hazard quotient (HQ) values in STP effluents were one order magnitude higher than those in their receiving water. However, there is no imminent significant ecotoxicological risk caused by any single compound in the effluents and receiving waters.

Distribution, fate, and risk assessment of antibiotics in five wastewater treatment plants in Shanghai, China

The project studied the occurrence, fate, and seasonal variation of 14 antibiotics, from five wastewater treatment plants (WWTPs) in Shanghai. The results indicated that ofloxacin, sulfamethoxazole, and oxytetracycline were the predominant antibiotics, with maximum concentrations of 1208.20, 959.13, and 564.30 ng/L in influents, while 916.88, 106.60, and 337.81 ng/L in effluents, respectively. The level of antibiotics in WWTPs obviously varied with seasonal changes, and higher detectable frequencies and concentrations were found in winter. The daily mass loads per capita of amoxicillin, enrofloxacin, and oxytetracycline in the study were all higher than those in other regions/countries, such as Hong Kong, Australia, and Italy. The elimination of antibiotics through these WWTPs was incomplete, and a wide range of removal efficiencies during the different treatment process and seasons were observed (-500.56 to 100 % in winter and -124.24 to 94.21 % in summer). Sulfonamides were relatively easy to be removed in WWTPs and the ultraviolet (UV) process can effectively improve the removal efficiency. Risk assessment of antibiotics in effluents was estimated. Only AMOX's hazard quotient (HQ) was higher than 0.01. Even though the environmental risks in the study were estimated to be low, the potential negative effects on aquatic ecosystems should call our attention as continually discharge in the long term.

Heterogeneous Fenton oxidation of ofloxacin drug by iron alginate support

A new catalytic wet peroxide oxidation of ofloxacin antibiotic is presented in this work. The removal was achieved using a biodegradable sodium alginate-iron material. Several parameters were studied such as iron content, drying duration of the catalytic support, temperature, solid amount and initial drug concentration. The process showed a strong oxidative ability; at optimum conditions, a nearly complete removal of the drug (around 98%) has been reached after three h of treatment. A relatively low decrease of support activity (around 10%) has been observed after three successive oxidation runs and a low iron leaching has been detected (1.2% of the incorporated quantity). The removal of the substrate has been also examined in the absence of hydrogen peroxide in order to discriminate between the contributions of simple adsorption and oxidation processes in the drug disappearance. We also discussed the influence of the studied experimental parameters on the removal kinetic.

Removal of ofloxacin antibiotic using heterogeneous Fenton process over modified alginate beads

The aim of this work is to study the heterogeneous oxidative degradation of ofloxacin antibiotic using a composite material prepared from sodium alginate and cyclohexane dinitrilo tetraacetic acid (CDTA). The characterization tests indicated the successful incorporation of metal chelator and iron. It was also demonstrated that the synthesized beads are mesoporous. The influence of several experimental parameters (i.e.: H2O2 dose, working temperature, beads loading and initial drug concentration) on the process performances was evaluated. The reaction temperature significantly affects the drug conversion efficiency. It was also observed that the synthesized material was efficient toward the target antibiotic degradation in the presence of small quantities of hydrogen peroxide. Under optimum conditions (0.05 g of granules, initial drug concentration=10mg/L, 25μL of 10mmol/L H2O2), conducted in a batch reaction, 94% degradation of ofloxacin was reached. The results also indicate that the composite material showed a reasonable stability; a relatively low decrease of activity after four successive runs (only 9%) and a negligible iron leaching (0.8%) have been observed. The synthesized composite material offered interesting advantages in terms of simplicity, good stability, ease of recovery from the liquid medium after use and its efficiency in the presence of low quantities of oxidant. It constitutes a good candidate in the water treatment area.

[Development of Determination Method of Fluoroquinolone Antibiotics in Sludge Based on Solid Phase Extraction and HPLC-Fluorescence Detection Analysis]

Fluoroquinolone antibiotics (FQs), as the common pharmaceuticals and personal care products (PPCPs), are widespread in the environment. FQs contained in wastewater would be ultimately enriched in sludge, posing a potential threat to the consequent sludge utilization. To optimize the analytical method applicable to the determination of FQs in sludge, the authors selected ofloxacin (OFL), norfioxacin (NOR), ciprofloxacin (CIP) and lomefloxacin (LOM) as the target FQs, and established a method which was based on cell lysis, FQs extraction with triethylamine/methanol/water solution, Solid Phase Extraction (SPE) and HPLC-Fluorescence Detection (FLD) determination. After the investigation, phosphoric acid-triethylamine was decided to be the buffer salt, and methanol was chosen as the organic mobile phase. The gradient fluorescence scanning strategy was proved to be necessary for the optimal detection as well. Furthermore, by the designed orthogonal experiments, the effects of the extraction materials, pH, and the eluents on the efficiency of SPE extraction were evaluated, by which the optimal extraction conditions were determined. As a result, FQs in liquid samples could be analyzed by utilizing HLB extraction cartridge, and the recovery rates of the four FQs were in the range of 82%-103%. As for solid samples, the recovery rates of the four FQs contained reached up to 71%-101%. Finally, the adsorptivity of the sludge from the different tanks ( anaerobic, anoxic and oxic tanks) was investigated, showing gradual decrease in the adsorption capacity, but all adsorbed over 90% of the EQs. This conclusion also confirmed that 50% removal of FQs in the domestic wastewater treatment plant was realized by sludge adsorption.

Occurrence and risk assessment of antibiotics in river water in Hong Kong

The occurrence and distribution of six typical antibiotics in the main rivers of Hong Kong were investigated using high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ES-MS/MS). The results revealed that the antibiotics were widely distributed in the area studied. Of the target antibiotics, ofloxacin was the most frequently detected in the rivers, with a detection rate of 69.6% and a median concentration of 0.7ng/L. Sulfadimidine (n.d-580.4ng/L) and doxycycline (n.d-82.2ng/L), with detection frequencies of 65.2% and 30.4%, respectively, were found at the same level as in rivers in North America, Spain, France, Australia, and in the Yangtze and Pearl Rivers of China, while the other target antibiotics were found at lower levels. According to the ratios of the measured environmental concentration to the predicted no-effect concentration, ofloxacin and doxycycline could present a medium to low ecological risk to algae, while sulfonamides posed no obvious ecological risk to the relevant aquatic organisms (algae, Daphnia magna, and fish). A high detection rate of antibiotics occurred in densely populated areas, revealing that population activities might be greatly contributing to the increasing levels of antibiotics in the area. Thus, the residues of antibiotics present in the waters of Hong Kong need to be closely monitored.

Levels of six antibiotics used in China estimated by means of wastewater-based epidemiology

Due to lack of proper regulation, information about antibiotics consumption in many countries such as China is difficult to obtain. In this study, a simple method based on wastewater-based epidemiology was adopted to estimate their usage in four megacities of China. Six antibiotics (norfloxacin, ofloxacin, sulfamethoxazole, trimethoprim, erythromycin and roxithromycin), which are the most frequently consumed antibiotics in China, were selected as the targets. Based on our results, Chongqing had the largest total annual consumption of the selected six antibiotics among the four megacities, followed by Guangzhou, then Hong Kong, with Beijing having the least, with values of 4.4 g/y/P, 4.0 g/y/P, 1.6 g/y/P, and 1.3 g/y/P, respectively. Compared with the daily consumption per capita in Italy, the estimated consumption levels of the selected six antibiotics in four cities of China were 12-41 times those of Italy. Our results suggested that the consumption of antibiotics in China was excessive.