Adsorption, inhibition, and biotransformation of ciprofloxacin under aerobic conditions

Biodegradation of ciprofloxacin using machine learning tools: Kinetics and modelling

Recently, the rampant administration of antibiotics and their synthetic organic constitutes have exacerbated adverse effects on ecosystems, affecting the health of animals, plants, and humans by promoting the emergence of extreme multidrug-resistant bacteria (XDR), antibiotic resistance bacterial variants (ARB), and genes (ARGs). The constraints, such as high costs, by-product formation, etc., associated with the physico-chemical treatment process limit their efficacy in achieving efficient wastewater remediation. Biodegradation is a cost-effective, energy-saving, sustainable alternative for removing emerging organic pollutants from environmental matrices. In view of the same, the current study aims to explore the biodegradation of ciprofloxacin using microbial consortia via metabolic pathways. The optimal parameters for biodegradation were assessed by employing machine learning tools, viz. Artificial Neural Network (ANN) and statistical optimization tool (Response Surface Methodology, RSM) using the Box-Behnken design (BBD). Under optimal culture conditions, the designed bacterial consortia degraded ciprofloxacin with 95.5% efficiency, aligning with model prediction results, i.e., 95.20% (RSM) and 94.53% (ANN), respectively. Thus, befitting amendments to the biodegradation process can augment efficiency and lead to a greener solution for antibiotic degradation from aqueous media.

Effects of operating conditions on iron (hydr)oxides evolution and ciprofloxacin degradation in potassium ferrate-ozone stepwise oxidation system

In this study, a stepwise oxidation system of potassium ferrate (K2FeO4) combined with ozone (O3) was used to degrade ciprofloxacin (CIP). The effects of pH and pre-oxidation time of K2FeO4 on the evolution of K2FeO4 reduction products (iron (hydr)oxides) and CIP degradation were investigated. It was found that in addition to its own oxidation capacity, K2FeO4 can also influence the treatment effect of CIP by changing the catalyst content. The presence of iron (hydr)oxides effectively enhanced the mineralization rate of CIP by catalyzing ozonation. The pH value can influence the content and types of the components with catalytic ozonation effect in iron (hydr)oxides. The K2FeO4 pre-oxidation stage can produce more iron (hydr)oxides with catalytic components for subsequent ozonation, but the evolution of iron (hydr)oxides components was influenced by O3 treatment. It can also avoid the waste of oxidation capacity owing to the oxidation of iron (hydr)oxides by O3 and free radicals. The intermediate degradation products were identified by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Besides, the degradation pathways were proposed. Among the degradation products of CIP, the product with broken quinolone ring structure only appeared in the stepwise oxidation system.

Enhanced biodegradation of fluoroquinolones and the changes of bacterial communities and antibiotic-resistant genes under intermittent electrical stimulation

In this study, an anaerobic-aerobic coupling system under intermittent electrical stimulation was used to improve the biodegradation of synthetic wastewater containing fluoroquinolones (FQs). The effect of electrical stimulation on FQ removal performance is more pronounced with appropriate voltage and hydraulic retention time. In addition, the combination of anaerobic-anodic and aerobic-cathodic chambers is more conducive to improving the removal efficiency of FQs. Under 0.9 V, the removal efficiencies of ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin were significantly improved in the anaerobic-anodic and aerobic-cathodic system. The contribution of the anaerobic/aerobic anodic chambers to FQ removal was greater than that of the anaerobic/aerobic cathodic chambers. Electrical stimulation selectively enriched electroactive bacteria related to biodegradation (Desulfovibrio and Terrimonas), antibiotic-resistant bacteria (Atopobium and Neochlamydia), and nitrifying bacteria (SM1A02 and Reyranella). This study indicated the potential effectiveness of intermittent electrical stimulation in treating fluoroquinolone-containing wastewater in a biofilm reactor. However, electrical stimulation led to an increase in mobile genetic elements , induced horizontal gene transfer and enriched resistant bacteria, which accelerated the spread of antibiotic-resistant genes (ARGs) in the system, indicating that the diffusion of ARGs remains a challenge.

Effects of ciprofloxacin, trimethoprim, and amoxicillin on microbial structure and growth as emerging pollutants reaching crop soils

The presence of emerging pollutants, and specifically antibiotics, in agricultural soils has increased notably in recent decades, causing growing concern as regards potential environmental and health issues. With this in mind, the current study focuses on evaluating the toxicity exerted by three antibiotics (amoxicillin, trimethoprim, and ciprofloxacin) on the growth of soil bacterial communities, when these pollutants are present at different doses, and considered in the short, medium, and long terms (1, 8 and 42 days of incubation). Specifically, the research was carried out in 12 agricultural soils having different physicochemical characteristics and was performed by means of the leucine (³H) incorporation method. In addition, changes in the structure of soil microbial communities at 8 and 42 days were studied in four of these soils, using the phospholipids of fatty acids method for this. The main results indicate that the most toxic antibiotic was amoxicillin, followed by trimethoprim and ciprofloxacin. The results also show that the toxicity of amoxicillin decreases with time, with values of Log IC₅₀ ranging from 0.07 ± 0.05 to 3.43 ± 0.08 for day 1, from 0.95 ± 0.07 to 3.97 ± 0.15 for day 8, and from 2.05 ± 0.03 to 3.18 ± 0.04 for day 42, during the incubation period. Regarding trimethoprim, 3 different behaviors were observed: for some soils the growth of soil bacterial communities was not affected, for a second group of soils trimethoprim toxicity showed dose-response effects that remained persistent over time, and, finally, for a third group of soils the toxicity of trimethoprim increased over time, being greater for longer incubation times (42 days). As regards ciprofloxacin, this antibiotic did not show a toxicity effect on the growth of soil bacterial communities for any of the soils or incubation times studied. Furthermore, the principal component analysis performed with the phospholipids of fatty acids results demonstrated that the microbial community structure of these agricultural soils, which persisted after 42 days of incubation, depended mainly on soil characteristics and, to a lesser extent, on the dose and type of antibiotic (amoxicillin, trimethoprim or ciprofloxacin). In addition, it was found that, in this research, the application of the three antibiotics to soils usually favored the presence of fungi and Gram-positive bacteria.

Effects of different carbon sources on the removal of ciprofloxacin and pollutants by activated sludge: Mechanism and biodegradation

This research investigated the effects of ciprofloxacin (CIP) (0.5, 5, and 20 mg/L) on SBR systems under different carbon source conditions. Microbial community abundance and structure were determined by quantitative PCR and high-throughput sequencing, respectively. The biodegradation production of CIP and possible degradation mechanism were also studied. Results showed that CIP had adverse effects on the nutrient removal from wastewater. Compared with sodium acetate, glucose could be more effectively used by microorganisms, thus eliminating the negative effects of CIP. Glucose stimulated the microbial abundance and increased the removal rate of CIP by 18%-24%. The mechanism research indicated that Proteobacteria and Acidobacteria had a high tolerance for CIP. With sodium acetate as a carbon source, the abundance of nitrite-oxidizing bacterial communities decreased under CIP, resulting in the accumulation of nitrite and nitrate. Rhodanobacter and Microbacterium played a major role in nitrification and denitrification when using sodium acetate and glucose as carbon sources. Dyella and Microbacterium played positive roles in the degradation process of CIP and eliminated the negative effect of CIP on SBR, which was consistent with the improved removal efficiency of pollutants.

Potential biotransformation pathways and efficiencies of ciprofloxacin and norfloxacin by an activated sludge consortium

Fluoroquinolones (FQs), such as ciprofloxacin (CIP) and norfloxacin (NOR), are types of emerging trace pollutants that have attracted great attention. In this study, an activated sludge (AS) consortium with high bio-removal capability to CIP and NOR was obtained by acclimating with CIP and NOR for 10 d. Meanwhile, a CIP- and NOR- transforming bacterial strain (S5), which is highly homologous to the 16S rRNA gene sequence of Enterobacter sp., was isolated from the acclimated AS. The bio-removal efficiency of CIP under the acclimated AS consortium was better than that under the pure culture of Enterobacter sp. S5 (93.1% vs. 89.3%), while the bio-removal efficiency of NOR under the acclimated AS consortium was lower than that under the pure culture of Enterobacter sp. S5 (83.9% vs. 89.8%). The biotransformation and bio-adsorption were two main ways to bio-remove CIP and NOR. However, the CIP and NOR biotransformation efficiencies of the acclimated AS were higher than under the pure culture of Enterobacter sp. S5, while the CIP and NOR adsorption of acclimated AS were lower than that under the pure culture of Enterobacter sp. S5. The N-acetylciprofloxacin and N-acetylnorfloxacin were the main biotransformation products of CIP and NOR. It is possible that acetyltransferase may be involved in the biotransformation process. Whether under the pure culture or AS consortium, the cytotoxicity of CIP and NOR transformation products to gram-negative bacteria was alleviated. Therefore, the acclimated AS and Enterobacter sp. S5 might provide a new strategy for removing contaminants and alleviating of FQs resistance.

Anaerobic biodegradation of levofloxacin by enriched microbial consortia: Effect of electron acceptors and carbon source

For improving the understanding of anaerobic degradation mechanism of fluoroquinolone antibiotics (FQs), the degradation of a representative FQs, levofloxacin (LEV), by six enriched anaerobic consortia were explored in this study. The effect of sulfate and nitrate as the electron acceptor and glucose as the carbon source on LEV anaerobic degradation were investigated. Addition of glucose and nitrate alone deteriorated LEV removal from 36.5% to 32.7% and 29.1%, respectively. Addition of sulfate slightly improved LEV removal to 39.6%, while simultaneous addition of glucose and sulfate significantly enhanced LEV removal to 53.1%. Twelve biodegradation intermediates were identified, which indicated that cleavage of piperazine ring is prior to that of quinolone ring, and hydroxylation, defluorination, demethylation, and decarboxylation were the primary steps of LEV anaerobic degradation. Lactobacillus, unclassified _f_Enterobacteriaceae, and Bacillus were enriched by simultaneous addition of glucose and sulfate, with relative abundance of 63.5%, 32.7%, and 3.3%, respectively. The predicted high gene abundance of xenobiotics biodegradation & metabolism, carbohydrate metabolism, and assimilatory sulfate reduction in the consortium, indicated a co-metabolism between carbohydrate metabolism, sulfate metabolism, and LEV degradation under glucose and sulfate added condition. The study revealed that simultaneous addition of glucose and sulfate is the favorable condition for LEV anaerobic degradation.

Stress-responses of microbial population and activity in activated sludge under long-term ciprofloxacin exposure

In this study, the effects of ciprofloxacin on activated sludge were evaluated based on the microbial community and metabolic characteristics. The results indicated that the metabolism of chemical oxygen demand (COD) and nitrogen were inhibited with ciprofloxacin at mg/L level compared to the control experiment, and the concentration of ciprofloxacin was slightly decreased. High-throughput sequencing (HTS) results showed that ciprofloxacin greatly shaped the microbial communities in activated sludge, especially for the Nitrospirae phylum and Nitrospira genus. High concentrations of ciprofloxacin stimulated the enrichment of Zoogloea, thus reducing the stability of the activated sludge. Moreover, quinolone resistance proteins in Aeromonas were enriched, which demonstrates their competitive advantage in these enrichment incubations. Finally, the functional profiles were predicted through Tax4Fun, which revealed the adaption to microbes in activated sludge to the ciprofloxacin selective pressure. This work demonstrates the influence of ciprofloxacin on the activated sludge process, and can provide a useful reference for the assessment of the ecological security of ciprofloxacin.

Effect of the C/N Ratio on Biodegradation of Ciprofloxacin and Denitrification from Low C/N Wastewater as Assessed by a Novel 3D-BER System

Emerging pollutants in the form of pharmaceuticals have drawn international attention during the past few decades. Ciprofloxacin (CIP) is a common drug widely found in effluents from hospitals, industrial and different wastewater treatment plants, as well as rivers. In this work, the lab-scale 3D-BER system was established, and more than 90% of the antibiotic CIP was removed from Low C/N wastewater. The best results were obtained with the current intensity being taken into account, and a different C/N ratio significantly improved the removal of CIP and nitrates when the ideal conditions were C/N = 1.5–3.5, pH = 7.0–7.5 and I = 60 mA. The highest removal efficiency occurred when CIP = 94.2%, NO3−-N = 95.5% and total nitrogen (TN) = 84.3%, respectively. In this novel system, the autotrophic-heterotrophic denitrifying bacteria played a vital role in the removal of CIP and an enhanced denitrification process. Thus, autotrophic denitrifying bacteria uses CO2 and H2 as carbon sources to reduce nitrates to N2. This system has the assortment and prosperous community revealed at the current intensity of 60 mA, and the analysis of bacterial community structure in effluent samples fluctuates under different conditions of C/N ratios. Based on the results of LC-MS/MS analysis, the intermediate products were proposed after efficient biodegradation of CIP. The microbial community on biodegrading was mostly found at phylum, and the class level was dominantly responsible for the NO3−-N and biodegradation of CIP. This work can provide some new insights towards the biodegradation of CIP and the efficient removal of nitrates from low C/N wastewater treatment through the novel 3D-BER system.

Variable surface charge of humic acid-ferrihydrite composite: Influence of electrolytes on ciprofloxacin adsorption

Antimicrobial compounds are found in a range of environments as pollutants. Here, we evaluated the influence of two common anions, NO₃^- and PO₄^3-, on ciprofloxacin adsorption on humic acid/ferrihydrite composite (HA-DIG/Fh), synthetic ferrihydrite (Fh), and humic acid (HA-DIG) under controlled pH (7.0), ionic strength (0.1 M) and temperature (25 °C). All materials were characterized by isoelectric point (IEP), while the composite and the iron oxide were characterized by Mössbauer spectroscopy. Kinetic and isotherm adsorption studies were carried out using cyclic voltammetry (in KH₂PO₄) and square wave voltammetry (in KNO₃). The application of kinetic models for both anions revealed Fh to fit to a pseudo second order model (R² = 0.941); while HA-DIG (R² = 0.950) and HA-DIG/Fh (R² = 0.993) were fitted to pseudo first order models. The adsorption results showed a high dependency electrolyte, especially in Fh, where different shape curves (H-type in KNO₃ and C-type in KH₂PO₄) and maximum experimental adsorbed amount C_m were observed. This finding is supported by the distinct IEP values and change in sign of surface charge between the two ions. Finally, results suggest that HA-DIG could be potentially used in environmental remediation to remove antibiotics from natural matrices, though the risk of antibiotic transportation increased with depth in the soil profile.

Simple, fast and environmentally friendly method to determine ciprofloxacin in wastewater samples based on an impedimetric immunosensor

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater. To achieve this, an anti-ciprofloxacin antibody was immobilized on the surface of a printed carbon electrode. Then, the developed immunosensor was applied in wastewater samples from Université Laval residences (Québec, Canada) through the load transfer resistance (R_ct) using [Fe(CN)₆]^3−/4− as a redox probe, and the average CIP concentration was found to be 2.90 × 10⁻⁴ μg mL⁻¹. The observed R_ct changes presented a linear relationship from CIP concentrations of 10⁻⁵ to 1.0 μg mL⁻¹, with detection and quantification limits of 2.50 × 10⁻⁶ and 7.90 × 10⁻⁶ μg mL⁻¹, respectively. The immunosensor presented high selectivity and repeatability, as well as a good recovery rate in wastewater samples (97%). Significant interference with other compounds was not observed. The proposed method requires only 30 μL of sample without the use of organic solvents or preceding sample preparation and/or extraction techniques. Moreover, the method is fast: only 20 min of incubation followed by 2 min of analysis time was sufficient to obtain the CIP concentration. The method's estimated cost is U$ 2.00 per sample.

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater samples.

Stress-responses of activated sludge and anaerobic sulfate-reducing bacteria sludge under long-term ciprofloxacin exposure

The activated sludge (AS) and sulfate-reducing bacteria (SRB) sludge systems were continuously operated for 200 days in laboratory to investigate the stress-responses of these two sludge systems under ciprofloxacin (CIP) exposure. It was found that CIP was effectively removed by SRB sludge via adsorption and biodegradation, but little biodegradation in AS system. The CIP biodegradation by SRB sludge made the SRB sludge system more sustainable and tolerant to long-term CIP exposure than AS system with significant (p < 0.05) CIP desorption and decrease of CIP removal. CIP shaped the microbial communities in AS and SRB sludge, and significantly (p < 0.05) inhibited the family Nitrosomonadaceae (ammonia-oxidizing bacteria (AOB)) and genus Nitrospira (nitrite-oxidizing bacteria (NOB)/complete ammonia oxidizer(comammox)) and the nitrogen removal in AS system. Moreover, CIP posed the increase of genus Zoogloea-like organisms and the non-filamentous bulking of AS, e.g. 313 ± 12 mL/g of sludge volume index (SVI) at phase V (influent CIP = 5000 μg/L). The genus Desulfobacter was enriched in SRB sludge system under long-term CIP exposure, and stimulated chemical oxygen demand (COD) removal and sulfate reduction. The increase of genera Zoogloea, Acinetobacter and Flavobacterium in AS, and Zoogloea and Acinetobacter in SRB sludge systems under CIP exposure promoted extracellular polymeric substances (EPS) production and CIP adsorption for self-protection of microbes against CIP toxicity. The functional groups of N-H, O-H, C-O-C and C=O in EPS of AS and SRB sludge provided adsorption sites for CIP and impeded CIP impact on microbial cells. The findings of this study provide an insight into the stress-responses of AS and SRB sludge under long-term CIP exposure, and exhibit the great potential of treating CIP-laden wastewater by SRB sludge system.

Fate and removal of Ciprofloxacin in an anaerobic membrane bioreactor (AnMBR)

This study examined the removal of varying concentrations of the antibiotic Ciprofloxacin (CIP) over the long-term (120 days) in an anaerobic membrane bioreactor (AnMBR). The results showed that 50-76% CIP was removed with 0.5-1.5 mg CIP/L in the feed, although at 4.7 mg/L its removal efficiency decreased to <20%. It was found that biological degradation was the main mechanism for removing CIP, while adsorption onto the sludge only contributed a small fraction, and an even smaller fraction was due to the waste sludge discharged. CIP was biodegraded to some degree in the AnMBR, with some intermediate compounds detected using LC-MS/MS and GC-MS. This work showed the effectiveness of an AnMBR in removing CIP at low concentrations of <1.5 mg/L, and hence may be an effective treatment for removing other antibiotics from wastewater.

Insights into the Fate and Removal of Antibiotics in Engineered Biological Treatment Systems: A Critical Review

Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical-chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48-77%) in the removal of antibiotics. In this review, we systematically summarize the behavior and removal of different antibiotics in various biological treatment systems with discussion on their removal efficiency, removal mechanisms, critical bioreactor operating conditions affecting antibiotics removal, and recent innovative advancements. Besides, relevant background information including antibiotics classification, physical-chemical properties, and their occurrence in the environment from different sources is also briefly covered. This review aims to advance our understanding of the fate of various classes of antibiotics in engineered biological wastewater treatment systems and outlines future research directions.

Effect of ciprofloxacin dosages on the performance of sponge membrane bioreactor treating hospital wastewater

This study aimed to evaluate treatment performance and membrane fouling of a lab-scale Sponge-MBR under the added ciprofloxacin (CIP) dosages (20; 50; 100 and 200 µg L^-1) treating hospital wastewater. The results showed that Sponge-MBR exhibited effective removal of COD (94-98%) during the operation period despite increment of CIP concentrations from 20 to 200 µg L^-1. The applied CIP dosage of 200 µg L^-1 caused an inhibition of microorganisms in sponges, i.e. significant reduction of the attached biomass and a decrease in the size of suspended flocs. Moreover, this led to deteriorating the denitrification rate to 3-12% compared to 35% at the other lower CIP dosages. Importantly, Sponge-MBR reinforced the stability of CIP removal at various added CIP dosages (permeate of below 13 µg L^-1). Additionally, the fouling rate at CIP dosage of 200 µg L^-1 was 30.6 times lower compared to the control condition (no added CIP dosage).

Effect of ciprofloxacin on methane production and anaerobic microbial community

This study investigated the effects and fate of CIP on anaerobic sludge over a wide range of concentrations (0.05-50 mg/L), and 0.5-50 mg/L significantly inhibited organic removal and methanogenic activity, increased volatile fatty acids accumulation and low molecular weight soluble microbial products (SMPs), including p-cresol and nitrogen-containing compounds. Although microbial communities exposed to CIP did not differ significantly from the control in species diversity indices, Syntrophobacter and Methanothrix associated with acetogenesis and acetoclastic methanogenesis, respectively, were underrepresented in the CIP-exposed communities. Our study advances understanding of how environmentally relevant concentrations of CIP disrupts anaerobic digestion, which has important implications for anaerobic engineered systems treating CIP-bearing waste streams.

Study of ciprofloxacin biodegradation by a Thermus sp. isolated from pharmaceutical sludge

Ciprofloxacin (CIP) is an antibiotic drug frequently detected in manure compost and is difficult to decompose at high temperatures, resulting in a potential threat to the environment. Microbial degradation is an effective and environmentally friendly method to degrade CIP. In this study, a thermophilic bacterium that can degrade CIP was isolated from sludge sampled from an antibiotics pharmaceutical factory. This strain is closely related to Thermus thermophilus based on 16S rRNA gene sequence analysis and is designated C419. The optimal temperature and pH values for CIP degradation are 70°C and 6.5, respectively, and an appropriate sodium acetate concentration promotes CIP degradation. Seven major biodegradation metabolites were identified by an ultra-performance liquid chromatography tandem mass spectrometry analysis. In addition, strain C419 degraded other fluoroquinolones, including ofloxacin, norfloxacin and enrofloxacin. The supernatant from the C419 culture grown in fluoroquinolone-containing media showed attenuated antibacterial activity. These results indicate that strain C419 might be a new auxiliary bacterial resource for the biodegradation of fluoroquinolone residue in thermal environments.

Analysis of extracellular polymeric substances (EPS) and ciprofloxacin-degrading microbial community in the combined Fe-C micro-electrolysis-UBAF process for the elimination of high-level ciprofloxacin

Extracellular polymeric substances (EPS) and ciprofloxacin-degrading microbial community in the combined Fe-C micro-electrolysis and up-flow biological aerated filter (UBAF) process for the treatment of high-level ciprofloxacin (CIP) were analyzed. The research demonstrated a great potential of Fe-C micro-electrolysis-UBAF for the elimination of high-level CIP. Above 90% of CIP removal was achieved through the combined process at 100 mg L^-1 of CIP loading. In UBAF, the pollutants were mainly removed at 0-70 cm heights. Three-dimensional fluorescence spectrum (3D-EEM) was used to characterize the chemical structural of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) extracted from biofilm sample in UBAF. The results showed that the protein-like substances in LB-EPS and TB-EPS had no clear change in the study. Nevertheless, an obvious release of polysaccharides in EPSs was observed during long-term exposure to CIP, which was considered as a protective response of microbial to CIP toxic. The high-throughput sequencing results revealed that the biodiversity of bacteria community became increasingly rich with gradual ciprofloxacin biodegradation in UBAF. The ciprofloxacin-degrading microbial community was mainly dominated by Proteobacteria and Bacteroidetes. Microorganisms from genera Dechloromonas, Brevundimonas, Flavobacterium, Sphingopyxis and Bosea might take a major role in ciprofloxacin degradation. This study provides deep theoretical guidance for real CIP wastewater treatment.

Enhanced adsorption of ciprofloxacin by KOH modified biochar derived from potato stems and leaves

Potato stems and leaves biochar (PB) was prepared by pyrolysis at a temperature of 500°C under anoxic conditions. In order to strengthen the adsorption capacity, biochar was modified with alkaline solution (alkali modified biochar, APB). Two kinds of biochars were adopted as adsorbents to remove ciprofloxacin (CIP) from aqueous solution. The adsorption behavior of CIP onto biochar before and after alkali modified including adsorption kinetics and isotherms were investigated. The effects of different factors (equilibrium time, pH, temperature and initial concentration) during the adsorption process were also investigated. Biochar samples were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherm. The results showed that the alkali treated biochar possessed more mesopores than raw biochar, and accordingly exhibited a more excellent adsorption performance (23.36 mg·g^-1) than raw biochar. Hydrophobic interaction, hydrogen-bonding interaction, electrostatic interaction, and π - π interaction were the adsorption mechanisms for CIP uptake onto the two adsorbents.

Enhanced phosphorus and ciprofloxacin removal in a modified BAF system by configuring Fe-C micro electrolysis: Investigation on pollutants removal and degradation mechanisms

A modified biological aerated filter (BAF) system configured Fe-C micro electrolysis was applied to enhance phosphorus and ciprofloxacin (CIP) removal. A novel sludge ceramic and sintering ferric-carbon ceramic (SFC) were separately packed into a lab-scale BAF and Fe-C micro electrolysis reactor. The BAF and Fe-C micro electrolysis coupled system was operated about 230days. The enhancement of phosphorus and ciprofloxacin removals by Fe-C micro electrolysis, the degradation mechanisms of CIP and the variations of microbial population were investigated. The removal efficiencies of chemical oxygen demand (COD_cr), ammonia (NH₄-N), total phosphorus (TP) and CIP reached about 95%, 95%, 80% and 85% in the combined process, respectively. Configuring Fe-C micro electrolysis significantly enhanced phosphorus and CIP removal, whereas had no promotion on N removal. Four main degradation pathways were proposed according to the LC-MS analysis. More than 12 degradation products were detected through the treatment of Fe-C micro electrolysis and only 3 biodegraded products with low concentration were identified in BAF effluent. The high-throughput sequencing analysis showed that the microbial community changed a lot under CIP pressure. The relative abundance of Sphingomonadaceae, Xanthomonadaceae, Bradyrhizobium, Helicobacter and Pseudomonas increased with CIP influent. This study provides a promising process in CIP wastewater treatment.

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.

Sulfamethoxazole degradation in anaerobic sulfate-reducing bacteria sludge system

Sulfamethoxazole (SMX) is one of the most commonly used antibiotics. SMX degradation in sulfate-reducing bacteria (SRB) sludge systems has not been reported so far. This research investigated the SMX degradation using SRB sludge in a sulfate-reducing up-flow sludge bed reactor. Moreover, the mechanisms and kinetics of SMX removal were also investigated using SRB sludge via a series of batch experiments. The results showed that SMX removal was characterized by a rapid sorption onto SRB sludge, and desorption from SRB sludge to aqueous phase until achieving equilibrium, and then followed by slow biodegradation. Biodegradation was the dominant route for SMX removal. The sorption process conformed well to a pseudo-second-order kinetic model, meaning that the sorption occurred primarily via a chemical sorption process. The removal of SMX followed the pseudo-zero-order kinetic model with a specific removal rate of 13.2 ± 0.1 μg/L/d at initial SMX concentration 100 μg/L in batch tests. Based on the analysis of metabolites, most of the SMX biotransformation products' structures altered in the isoxazole ring, which were significantly different from that produced by aerobic and anaerobic sludge systems. Thus, SRB sludge system could play an important role in SMX biodegradation, especially in Sulfate-reduction Autotrophic denitrification and Nitrification Integrated (SANI) process for sewage treatment.

Degradation kinetics of pharmaceuticals and personal care products in surface waters: photolysis vs biodegradation

Poor removal of many pharmaceuticals and personal care products (PPCPs) in sewage treatment leads to their discharge into the receiving waters, where they may cause negative effects. Their elimination from the water column depends of several processes, including photochemical and biological degradation. We have focused this research on comparing the degradation kinetics of a wide number (n=33) of frequently detected PPCPs considering different types of water, pH and solar irradiation. For those compounds that were susceptible of photodegradation, their rates (k) varied from 0.02 to 30.48h^-1 at pH7, with the lowest values for antihypertensive and psychiatric drugs (t_1/2>1000h). Modification of the pH turned into faster disappearance of most of the PPCPs (e.g., k=0.072 and 0.066h^-1 for atenolol and carbamazepine at pH4, respectively). On the other hand, biodegradation was enhanced by marine bacteria in many cases, for example for mefenamic acid, caffeine and triclosan (k=0.019, 0.01 and 0.04h^-1, respectively), and was faster for anionic surfactants. Comparing photodegradation and biodegradation processes, hydrochlorothiazide and diclofenac, both not biodegradable, were eliminated exclusively by irradiation (t_1/2=0.15-0.43h and t_1/2=0.14-0.17h, respectively). Salicylic acid and phenylbutazone were efficiently photo (t_1/2<3h) and biodegraded (t_1/2=116-158h), whereas some compounds such as ibuprofen, carbamazepine and atenolol had low degradation rates by any of the processes tested (t_1/2=23-2310h), making then susceptible to persist in the aquatic media.

Sorption mechanism of enrofloxacin on humic acids extracted from Brazilian soils

Veterinary antimicrobials are emerging environmental contaminants of concern. In this study, the sorption of enrofloxacin (ENR) onto humic acids (HAs) extracted from three Brazilian soils was evaluated. HAs were characterized by elemental analysis and solid ¹³C nuclear magnetic resonance spectroscopy. The sorption of ENR onto HAs was at least 20-fold higher than onto the soils from which they were separated. Ionic and cation bridging are the primary interactions involved. The interactions driven by cation exchange are predominant on HAs, which appear to have abundant carboxylic groups and a relatively high proportion of H-bond donor moieties with carbohydrate-like structures. Interactions explained by cation bridging and/or surface complexation on HAs are facilitated by moieties containing conjugated ligands, significant content of oxygen-containing functional groups, such as phenolic-OH or lignin-like structures. HAs containing electron-donating phenolic moieties and carboxylic acid ligand groups exhibit a sorption mechanism that is primarily driven by strong metal binding, favoring the formation of ternary complexes between functional groups of the organic matter and drugs.

Remobilization Dynamics of Caffeine, Ciprofloxacin, and Propranolol following Evaporation-Induced Immobilization in Porous Media

Changing weather conditions can cause cycles of wetting and drying in the unsaturated zone. When porewater evaporates, any nonvolatile solutes present in the pores will be driven to adsorb and ultimately precipitate on solid surfaces. When media are subsequently resaturated through rainfall infiltration, the remobilization of solutes likely depends on both the hydraulics of resaturation and the dynamics of dissolution processes. The focus of this work was to study the dynamics of remobilization of three different emerging contaminants (caffeine, ciprofloxacin, and propranolol) and two model compounds (fluorescein and sulforhodamine B) from porous media following evaporation of porewater. Remobilization column experiments were conducted to study this phenomenon and were evaluated using a finite difference model developed to simulate the adsorption-desorption dynamics during resaturation and elution. Results indicate that dissolution dynamics become increasingly important with increasing adsorption affinity for solid surfaces. Trends in observed elution behavior are not well-predicted from chemical properties, such as solubility. One of the most significant observations of the work is the presence of spikes in elution concentrations well above initial porewater concentration, resulting from the hydraulics of the resaturation process. The effect is most significant in highly mobile compounds that exhibit low adsorption affinity for solid surfaces.

An insight into the removal of fluoroquinolones in activated sludge process: Sorption and biodegradation characteristics

The detailed sorption steps and biodegradation characteristics of fluoroquinolones (FQs) including ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin were investigated through batch experiments. The results indicate that FQs at a total concentration of 500μg/L caused little inhibition of sludge bioactivity. Sorption was the primary removal pathway of FQs in the activated sludge process, followed by biodegradation, while hydrolysis and volatilization were negligible. FQ sorption on activated sludge was a reversible process governed by surface reaction. Henry and Freundlich models could describe the FQ sorption isotherms well in the concentration range of 100-300μg/L. Thermodynamic parameters revealed that FQ sorption on activated sludge is spontaneous, exothermic, and enthalpy-driven. Hydrophobicity-independent mechanisms determined the FQ sorption affinity with activated sludge. The zwitterion of FQs had the strongest sorption affinity, followed by cation and anion, and aerobic condition facilitated FQ sorption. FQs were slowly biodegradable, with long half-lives (>100hr). FQ biodegradation was enhanced with increasing temperature and under aerobic condition, and thus was possibly achieved through co-metabolism during nitrification. This study provides an insight into the removal kinetics and mechanism of FQs in the activated sludge process, but also helps assess the environmental risks of FQs resulting from sludge disposal.

Comparison of biological and advanced treatment processes for ciprofloxacin removal in a raw hospital wastewater

The treatability of ciprofloxacin (CIP) antibiotic was investigated using a single aerobic, a single anaerobic, an anaerobic/aerobic sequential reactor system, a sonicator and a photocatalytic reactor with TiO2 nanoparticles in a raw hospital wastewater in Izmir, Turkey. The effects of increasing organic loading on the performance of all biological systems were investigated, while the effects of power and time on the yields of sonication and photocatalysis were determined. The maximum COD and CIP yields were 95% and 83% in anaerobic/aerobic sequential reactor system at an HRT of 10 days and at an OLR of 0.19 g COD/L × day after 50 days of incubation, respectively. The maximum CH4 gas production was 580 mL day(-1) at an HRT of 6.7 days. The maximum COD and CIP yields were 95% and 81% after 45 min sonication time at a power of 640 W and a frequency of 35 kHz while the maximum yield of COD and CIP were 98% and 88% after 45 min UV irradiation time with a UV power of 210 W using 0.5 g L(-1) TiO2. Among the aforementioned treatment processes, it was found that the highest treatment yields for COD (98%) and CIP (88%) pollutants were obtained with the photocatalytic process due to high OH((●)) radical productions.

Biodegradation of antibiotic ciprofloxacin: pathways, influential factors, and bacterial community structure

Antibiotic ciprofloxacin is ubiquitous in the environment. However, little is known about ciprofloxacin dissipation by microbial community. The present study investigated the biodegradation potential of ciprofloxacin by mixed culture and the influential factors and depicted the structure of ciprofloxacin-degrading microbial community. Both the original microbiota from drinking water biofilter and the microbiota previously acclimated to high levels of ciprofloxacin could utilize ciprofloxacin as sole carbon and nitrogen sources, while the acclimated microbiota had a much stronger removal capacity. Temperature rise and the presence of carbon or nitrogen sources favored ciprofloxacin biodegradation. Many novel biotransformation products were identified, and four different metabolic pathways for ciprofloxacin were proposed. Bacterial community structure illustrated a profound shift with ciprofloxacin biodegradation. The ciprofloxacin-degrading bacterial community was mainly composed of classes Gammaproteobacteria, Bacteroidia, and Betaproteobacteria. Microorganisms from genera Pseudoxanthomonas, Stenotrophomonas, Phenylobacterium, and Leucobacter might have links with the dissipation of ciprofloxacin. This work can provide some new insights towards ciprofloxacin biodegradation.

Optimized removal of antibiotic drugs from aqueous solutions using single, double and multi-walled carbon nanotubes

In this study, experiments were carried out to investigate the use of as-synthesized single-walled (SWCNT), double-walled (DWCNT) and multi-walled carbon nanotubes (MWCNT) agglomerates for the removal of two antibiotics, Oxytetracycline (OXY) and Ciprofloxacin (CIP) from aqueous solution. The variations of key operating parameters on the removal process were assessed in order to find out the optimum conditions. It includes exposure time, solution pH, temperature, ultrasound assistance and desorption assays. The experimental results revealed that a moderate increase in adsorption was registered between pH 3 and 7 for both antibiotics. The application of ultrasound helped enhancing the removal capacities of OXY for all tested CNTs. For the case of MWCNTs, 1h of ultrasonication increased the adsorption capacity by 44.6%. As for CIP, the ultrasonic treatment did not enhance the overall adsorption, especially for the case of DWCNTS. The Brouers-Sotolongo equation was the best fitting isotherm model. The highest removal capacities were registered using SWCNTS for both antibiotics (724 mg/g for CIP and 554 mg/g for OXY). In addition, ethanol was the solvent that induced the highest desorption percent for the case of CIP (52% for MWCNTs). However, the desorption of OXY was negligible for all solvents (maximum 3.3% for DWCNTs using ethanol).

Biotransformation of the Antibiotic Danofloxacin by Xylaria longipes Leads to an Efficient Reduction of Its Antibacterial Activity

Fluoroquinolones are considered as critically important antibiotics. However, they are used in appreciable quantities in veterinary medicine. Liquid manure and feces can contain substantial amounts of unmetabolized antibiotics and, thus, antibiotics can enter the environment if manure is used for soil fertilization. In this study, the microbial biotransformation of the synthetic veterinary fluoroquinolone danofloxacin by the ascomycete Xylaria longipes was investigated. Fungal submerged cultures led to a regioselective and almost quantitative formation of a single metabolite within 3 days. The metabolite was unequivocally identified as danofloxacin N-oxide by high-resolution mass spectrometry and one- and two-dimensional nuclear magnetic resonance spectroscopic techniques. An oxidation of the terminal nitrogen of the substituted piperazine moiety of the substance led to a remarkable reduction of 80% of the initial antibacterial activity. Thus, fungal enzymes involved in the biotransformation process might possess the potential to reduce the entrance of antibiotics via biotransformation of these compounds.

Inhibitory effects and biotransformation potential of ciprofloxacin under anoxic/anaerobic conditions

The inhibitory effects and biotransformation potential of the fluoroquinolone antibiotic ciprofloxacin (CIP) under anoxic (i.e., nitrate reducing) and anaerobic (i.e., sulfate reducing and methanogenic) conditions were investigated. Fermentation and sulfate reduction was inhibited in 10-80 mg/L CIP-amended sulfate-reducing cultures but recovered with prolonged incubation. Methanogenesis in the mixed culture was significantly inhibited at 80-100 mg CIP/L. No significant decrease of CIP concentration was observed under both sulfate-reducing and methanogenic conditions. However, a low degree of CIP biotransformation was observed in a fed-batch denitrifying culture after a lag time even though the microbial, denitrifying activity was gradually inhibited at 24-40 mg CIP/L. Furthermore, the degradation of CIP was accelerated with a CIP reamendment of the denitrifying culture. Two CIP biotransformation products in the denitrifying culture were detected and their proposed chemical structures suggest that the antibiotic quinolone moiety of CIP was intact.