Occurrence and fate of quinolone and fluoroquinolone antibiotics in a municipal sewage treatment plant

Tetracycline Removal by Activating Persulfate with Diatomite Loading of Fe and Ce

Persulfate (PS)-based oxidation technology is efficient in removing refractory organics from water. A novel diatomite (DIA) support Fe and Ce composite (Fe-Ce/DIA) was prepared for activating persulfate to degrade tetracycline in water. The Fe and Ce were uniformly loaded on DIA, and the total pore size of Fe-Ce/DIA was 6.99 × 10⁻² cm³/g, and the average pore size was 12.06 nm. Fe-Ce/DIA presented a good catalytic activity and 80% tetracycline was removed under the persulfate system. The Fe-Ce/DIA also had photocatalytic activity, and the corresponding tetracycline removal efficiency was 86% under UV irradiation. Fe-Ce/DIA exhibited less iron dissolution rate compared with Fe-DIA. The tetracycline degradation rate was enhanced when the temperature increased. The optimal tetracycline removal efficiency was obtained when the conditions were of persulfate 10 mM, Fe-Ce/DIA dosage 0.02 g/L, and tetracycline concentration 50 mg/L. In addition, Fe-Ce/DIA showed a wide pH application and good reusability and stability.

Occurrence and fate of antibiotics, antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in municipal wastewater treatment plant: An overview

The occurrence and fate of antibiotics and antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in Municipal Wastewater Treatment Plants (WWTPs) worldwide were reviewed. The prevalence of antibiotics in WWTPs among different periods (1999-2009 and 2010-2019) and geographical areas (Europe, America, Asia and Africa) was summarized, analyzed and evaluated. The classes of macrolides (clarithromycin, erythromycin/erythromycin-H₂O, azithromycin, roxithromycin), sulfonamides (sulfamethoxazole), trimethoprim, quinolones (ofloxacin, ciprofloxacin, norfloxacin) and tetracyclines (tetracycline) were the antibiotics most frequently detected, while bla (bla_CTXM, bla_TEM), sul (sul1, sul2), tet (tetO, tetQ, tetW) and ermB genes were the ARGs commonly reported in WWTPs. There was a positive correlation between antibiotics and ARGs commonly detected in WWTPs, except for β-lactam antibiotics and bla genes. The genes bla were found frequently, despite β-lactam antibiotics were seldom detected owing to the hydrolysis. Most of antibiotics had lower levels in the period 2010-2019 in Asian countries than that in period 1999-2009 in North American and European countries. In the effluent of secondary treatment, the concentration of trimethoprim was the highest (138 ng/L in median) and the concentration of other antibiotics remained at lower than 80 ng/L, while the relative abundance of ARGs ranged 2.9-4.6 logs (copies/mL, in median). Future researches on the development of effective antibiotic removal technologies, such as advanced oxidation processes, are suggested to focus on antibiotics frequently detected and their corresponding ARGs in WWTPs.

Recognition of typical antibiotic residues in environmental media related to groundwater in China (2009-2019)

The potential adverse environmental and health-related impacts of antibiotics are becoming more and more concerning. China is globally the largest antibiotic producer and consumer, possibly resulting in the ubiquity and high detection levels of antibiotics in environmental compartments. Clear status on the concentration levels and spatial distribution of antibiotic contamination in China's environment is necessary to gain insight into the establishment of legal and regulatory frameworks. This study collects information from over 170 papers reporting the occurrence and distribution of antibiotics in China's environment. A total of 110 antibiotics were detected, and 28 priority antibiotics were ubiquitous in China in almost all compartments of the environment, excluding the atmosphere. Seven dominant antibiotics in all environment compartments were identified by cluster analysis, including tetracycline, oxytetracycline, chlortetracycline, ofloxacin, enrofloxacin, norfloxacin, and ciprofloxacin. Meanwhile, sulfamethoxazole, sulfadiazine, and sulfamethazine were also frequently found in aqueous phases. Among the main basins where antibiotics were detected, the Haihe River Basin had higher median antibiotic concentrations in surface water compared to other basins, while the Huaihe River Basin had higher median concentrations in sediment. The median values of antibiotic concentrations in the sources were as follows: animal manure, 39 μg/kg (microgram per kilogram); WWTP (wastewater treatment plant) sludge, 39 μg/kg; animal wastewater, 156 ng/L (nanogram per liter); WWTP effluent: 15 ng/L. These concentrations are 1 - 2 orders of magnitude higher than that of the receptors (soil, 2.1 μg/kg; sediment, 4.7 μg/kg; surface water, 8.1 ng/L; groundwater, 2.9 ng/L), whether in solid or aqueous phases. Based on the number of detected antibiotics in various environmental compartments, animal farms and WWTPs are the main sources of antibiotics, and surface water and sediment are the main receptors of antibiotics. Hierarchical clustering identified the two main pathways of antibiotic transfer in various environmental compartments, which are from animal wastewater/WWTP effluent to surface water/sediment and from animal manure/WWTP sludge to soil/groundwater.

Oxygen vacancy enhancing Fenton-like catalytic oxidation of norfloxacin over prussian blue modified CeO2: Performance and mechanism

To develop an efficient heterogeneous Fenton-like catalyst is of great importance for degrading organic pollutants. CeO₂ was selected as the catalyst carrier. Prussian blue (PB) was chose as the iron resource for its sensitivity to H₂O₂ and low toxicity. PB modified CeO₂ composite was successfully fabricated and used for Fenton-like oxidation of norfloxacin (NOR) in this study. The characteristics of the catalysts demonstrated that the doping of PB distorted the lattice locally and increased the surface area of CeO₂ obviously. The XPS analysis also indicated that chemically supported catalysts PB/CeO₂ with more Ce³⁺ was beneficial to Fenton-like catalytic reaction. The degradation tests showed that the PB/CeO₂ significantly enhanced the removal of NOR which indicated a synergistic effect between PB and CeO₂. The reason should be mainly attributed to the synergetic catalysis of H₂O₂ by Fe³⁺/Fe²⁺ and Ce³⁺/Ce⁴⁺ redox couples. At the same time, PB/CeO₂ composite showed well reusability and wide pH value range of 2-9 with fairly low concentration of iron ions. The reaction mechanisms were identified to be OH oxidation and improvement of oxygen vacancies (OVs).

Fate of antibiotics and antibiotic resistance genes during conventional and additional treatment technologies in wastewater treatment plants

Information on the removal of antibiotics and ARGs in full-scale WWTPs (with or without additional treatment technology) is limited. However, it is important to understand the efficiency of full-scale treatment technologies in removing antibiotics and ARGs under a variety of conditions relevant for practice to reduce their environmental spreading. Therefore, this study was performed to evaluate the removal of antibiotics and ARGs in a conventional wastewater treatment plant (WWTP A) and two full-scale combined with additional treatment technologies. WWTP B, a conventional activated sludge treatment followed by an activated carbon filtration step (1-STEP® filter) as a final treatment step. WWTP C, a treatment plant using aerobic granular sludge (NEREDA®) as an alternative to activated sludge treatment. Water and sludge were collected and analysed for 52 antibiotics from four target antibiotic groups (macrolides, sulfonamides, quinolones, tetracyclines) and four target ARGs (ermB, sul 1, sul 2 and tetW) and integrase gene class 1 (intI1). Despite the high removal percentages (79-88%) of the total load of antibiotics in all WWTPs, some antibiotics were detected in the various effluents. Additional treatment technology (WWTP C) showed antibiotics removal up to 99% (tetracyclines). For ARGs, WWTP C reduced 2.3 log followed by WWTP A with 2.0 log, and WWTP B with 1.3 log. This shows that full-scale WWTP with an additional treatment technology are promising solutions for reducing emissions of antibiotics and ARGs from wastewater treatment plants. However, total removal of the antibiotics and ARGS cannot be achieved for all types of antibiotics and ARGs. In addition, the ARGs were more abundant in the sludge compared to the wastewater effluent suggesting that sludge is an important reservoir representing a source for later ARG emissions upon reuse, i.e. as fertilizer in agriculture or as resource for bioplastics or bioflocculants. These aspects require further research.

Monitoring of Water Quality, Antibiotic Residues, and Antibiotic-Resistant Escherichia coli in the Kshipra River in India over a 3-Year Period

The emergence of antibiotic resistance is a major global and environmental health issue, yet the presence of antibiotic residues and resistance in the water and sediment of a river subjected to excessive anthropogenic activities and their relationship with water quality of the river are not well studied. The objectives of the present study were a) to investigate the occurrence of antibiotic residues and antibiotic-resistant Escherichia coli (E. coli) in the water and sediment of the Kshipra river in India at seven selected sites during different seasons of the years 2014, 2015, and 2016 and b) to investigate the association between antibiotic residues and antibiotic-resistant E. coli in water and sediment and measured water quality parameters of the river. Antibiotic residues and resistant E. coli were present in the water and sediment and were associated with the measured water quality parameters. Sulfamethoxazole was the most frequently detected antibiotic in water at the highest concentration of 4.66 µg/L and was positively correlated with the water quality parameters. Significant (p < 0.05) seasonal and spatial variations of antibiotic-resistant E. coli in water and sediment were found. The resistance of E. coli to antibiotics (e.g., sulfamethiazole, norfloxacin, ciprofloxacine, cefotaxime, co-trimoxazole, ceftazidime, meropenem, ampicillin, amikacin, metronidazole, tetracycline, and tigecycline) had varying associations with the measured water and sediment quality parameters. Based on the results of this study, it is suggested that regular monitoring and surveillance of water quality, including antibiotic residues and antibiotic resistance, of all rivers should be taken up as a key priority, in national and Global Action Plans as these can have implications for the buildup of antibiotic resistance.

Occurrence and risk assessment of fluoroquinolone antibiotics in reclaimed water and receiving groundwater with different replenishment pathways

Artificial recharge to groundwater with reclaimed water is considered a promising method to alleviate groundwater depletion and over-exploitation. However, the occurrence of fluoroquinolone antibiotics (FQs) was ubiquitous in wastewater, surface water, groundwater and even drinking water threating human health and ecology. In this study, the occurrence of six selected FQs in reclaimed water effluent and their removal by tertiary treatment units were investigated. The overall removal efficiencies in average of the tertiary treatment processes in Beijing and Changzhou were ranging from 21.2% to 55.2%. Activated carbon exhibited better performance for FQs removal than ozone and biological treatment such as membrane bioreactor, anaerobic-anoxic-oxic and biofilter. The results of two pilot study showed that the impact of reclaimed water to groundwater quality in terms of FQs concentration by direct injection in GBD was stronger than surface spreading in Changzhou, which might be due to the recharge strategy and the physical and chemical characteristics of sediment and aquifer soil. The hazard quotient (HQ) values of ofloxacin (OFL) in reclaimed water was up to 12.54, indicating the extreme eco-toxicological risk, while enrofloxacin (ENR) exhibited medium risk. After recharge with reclaimed water, the HQ values of OFL and ENR in groundwater ranged from low to medium ecological risk to the environment. Thus, the FQs in reclaimed water need to be paid more attention during their reuse for groundwater recharge, especially by direct injection. It is suggested that FQs should be considered in the priority substances lists in standards and guidelines of reclaimed water reuse for groundwater recharge to ensure the safety of groundwater.

Sonophotocatalytic degradation of sodium diclofenac using low power ultrasound and micro sized TiO2

The nonsteroidal anti-inflammatory drug sodium diclofenac (DC) is an emerging water pollutant which resists conventional wastewater treatments. Here the sonophotocatalytic degradation of DC was carried out using micrometric TiO₂ (both pristine and Ag-decorated), UV-A irradiation and 20 kHz pulsed ultrasound. Sonophotocatalytic tests were compared with photolysis, sonolysis, sonophotolysis, sonocatalysis and photocatalysis data performed in the same conditions. A synergy index of over 2 was determined for tests with pristine TiO₂, while values close to 1.3 were observed for Ag-TiO₂. Reaction intermediates were studied by HPLC-MS, showing degradation mechanisms activated by hydroxyl radicals. Similar pathways were identified for photocatalytic and sonophotocatalytic tests, although the latter led to more oxidized compounds. Different reactor configurations (static and dynamic set ups) were studied. Sequential and simultaneous application of UV light and ultrasound led to similar performance. The role of water matrix was investigated using ultrapure and drinking water, showing marked detrimental effects of electrolytes on the DC degradation. Overall, the combined treatment proved more efficient than photocatalysis alone especially in demanding working conditions, like in drinking water matrices.

Municipal Solid Waste Landfills: An Underestimated Source of Pharmaceutical and Personal Care Products in the Water Environment

Pharmaceutical and personal care products (PPCPs) have been the focus of increasing concern in recent decades due to their ubiquity in the environment and potential risks. Out-of-date PPCPs are usually discharged into municipal solid wastes (MSWs), enter the leachates in MSW landfills, and have serious adverse effects on the surrounding water environment. However, the occurrence and removal of PPCPs from landfill leachates have rarely been examined to date. This lack of knowledge makes the landfill an underestimated source of PPCPs in the environment. In this review, we collected the relevant publications of PPCPs in landfill leachates, systematically summarized the occurrence of PPCPs in landfill leachates globally, evaluated the removal performances for various PPCPs by different types of on-site full-scale leachate treatment processes, and assessed the impacts of landfill leachates on PPCPs in the adjacent groundwater. In particular, influencing factors for PPCPs in landfill leachates, including the physicochemical properties of PPCPs, climate conditions, and characteristics of landfill sites (i.e., landfill ages) as well as sociological factors (i.e., economic development), were extensively discussed to understand their occurrence patterns. Future perspectives were also proposed in light of the identified knowledge gaps. To the best of our knowledge, this is the first review regarding the occurrence and removal of PPCPs from landfill leachates worldwide.

Sorption of fluoroquinolones to nanoplastics as affected by surface functionalization and solution chemistry

Microplastics have attracted much attention in recent years as they can interact with pollutants in water environment. However, nanoplastics (NPs) with or without the surface functionalization modification have not been thoroughly explored. Here, the sorption behaviors of two fluoroquinolones (FQs), including norfloxacin (NOR) and levofloxacin (LEV) on polystyrene NPs (nano-PS) and carboxyl-functionalized polystyrene NPs (nano-PS-COOH) were investigated. The results showed that sorption isotherms were nonlinear and well fitted by Langmuir model. The sorption capacities of NOR and LEV on nano-PS-COOH were higher than those on nano-PS, and their physical interactions, including polar interaction, electrostatic interaction and hydrogen bonding may be the dominant mechanisms. Moreover, the increase of pH firstly increased the sorption of two FQs on NPs and then decreased because NOR and LEV had a reverse charge at different pH values. Salinity and dissolved organic matter both inhibited the sorption process. These findings show that NPs with or without the surface functionalization modification have different sorption behaviors for environmental pollutants, which deserve our further concern.

A review of emerging organic contaminants (EOCs), antibiotic resistant bacteria (ARB), and antibiotic resistance genes (ARGs) in the environment: Increasing removal with wetlands and reducing environmental impacts

Emerging organic contaminants (EOCs) include a diverse group of chemical compounds, such as pharmaceuticals and personal care products (PPCPs), pesticides, hormones, surfactants, flame retardants and plasticizers. Many of these compounds are not significantly removed in conventional wastewater treatment plants and are discharged to the environment, presenting an increasing threat to both humans and natural ecosystems. Recently, antibiotics have received considerable attention due to growing microbial antibiotic-resistance in the environment. Constructed wetlands (CWs) have proven effective in removing many EOCs, including different antibiotics, before discharge of treated wastewater into the environment. Wastewater treatment systems that couple conventional treatment plants with constructed and natural wetlands offer a strategy to remove EOCs and reduce antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) far more efficiently than conventional treatment alone. This review presents as overview of the current knowledge on the efficiency of different wetland systems in reducing EOCs and antibiotic resistance.

Ciprofloxacin removal via sequential electro-oxidation and enzymatic oxidation

The combination of electro-oxidation and enzymatic oxidation was tested to evaluate the potency of this system to remove ciprofloxacin (CIP), a fluoroquinolone antibiotic, from water. For the electro-oxidation boron-doped diamond (BDD) and mixed metal oxides anodes were tested, at three current densities (4.42, 17.7 and 35.4 A/cm²). BDD anode at 35.4 A/cm² exhibited the highest removal efficiency in the shortest time (>90 % removal in 6 min). For the enzymatic oxidation, laccase from Trametes versicolor was chosen. Laccase alone was not able to remove CIP; hence the influence of redox mediators was investigated. The addition of syringaldehyde (SA) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) resulted in enhanced CIP transformation. About 48.9±4.0 % of CIP remained after 4 h of treatment when SA-mediated laccase was applied and 87.8±6.6 % in the case of ABTS-mediated laccase. The coupling of enzymatic oxidation followed by electro-oxidation led to 73 % removal of the antibiotic. Additionally, the antimicrobial activity increased up to its original efficiency after the treatment. The combination of electro-oxidation followed by enzymatic oxidation led to 97-99 % removal of CIP. There was no antimicrobial activity of the solution after the treatment. The tests with wastewater confirmed the efficacy of the system to remove CIP from the complex matrix.

Fabrication of sustainable manganese ferrite modified biochar from vinasse for enhanced adsorption of fluoroquinolone antibiotics: Effects and mechanisms

An effective adsorbent towards fluoroquinolone antibiotics was synthesized via a facile two-step approach, the co-precipitation of Fe, Mn with vinasse wastes and then pyrolysis under controlled conditions which denoted as FMB. Its adsorption behavior was examined based on a batch adsorption experiment of fluoroquinolone antibiotics pefloxacin (PEF) and ciprofloxacin (CIP). Experimental factors, such as pH, adsorbent dose, ionic strength, contact time and temperature have done a great deal to influence the adsorption of PEF and CIP. The FMB demonstrated excellent performance in reusability tests towards to both PEF and CIP, which showed that the recycling efficiency of PEF and CIP could remain ~55% and ~80% after five recycle cycles, respectively. The dominated adsorption mechanisms included pore filling effect, π-π stacking interaction, π-π EDA, hydrogen bonding and hydrophobicity. Overall, this work presented FMB was recognized as an effective, environmental-friendly and magnetically separable adsorbent for alleviating fluoroquinolone antibiotics contamination from water.

Shifts of bacterial community and molecular ecological network at the presence of fluoroquinolones in a constructed wetland system

Fluoroquinolones (FQs) has caused increasing concerns regarding its potential environmental risks. However, their effects on bacterial community and microbial interactions in wetland system remains unclear. To verify these issues, a lab-scale constructed wetland exposed to low concentration FQs mixture was carried out for two months. The results showed that the removal efficiencies of COD and TP were negatively affected. FQs significantly increased the bacterial diversity and altered the overall bacterial community structure. Proteobacteria significantly decreased while Firmicutes exhibited opposite tendency (P < 0.05). Dechloromonas and Delftia, involved in phosphorus removal, decreased significantly (P < 0.05). Molecular ecological network analysis suggested that FQs promoted the network complexity and microbial interactions. A super module emerged at FQs and among-module connections were weakened obviously. Additionally, Nodes of Betaproteobacteria lost most interactions while Clostridia acquired more interactions at the presence of FQs. This study provided insights into how the bacterial community and their molecular ecological network respond to FQs in constructed wetland system.

Occurrence of quinotone antibiotics and their impacts on aquatic environment in typical river-estuary system of Jiaozhou Bay, China

There is a data gap on occurrence and transport of antibiotics in river-estuary system, with limited understanding of their impact on aquatic environment. To gain insight into the antibiotic pollution in river-estuary system, 22 surface sediments and 5 wetland plants from Yang River and its estuary in Jiaozhou Bay were selected to explore the occurrence and transport of eight quinotone antibiotics (QNs), and their impacts on aquatic environment. Our results indicated that QNs were widely present in the sediments from Yang River and its estuary, with a range of 1.34-8.69 ng/g (average 4.46 ng/g) in Yang River and 0.99-10.86 ng/g (average 3.92 ng/g) in its estuary, respectively. No obvious correlations were observed between QNs values and TOC contents in sediments from our study area, due to low detective concentrations and frequencies of QNs. The mass loading of individual antibiotic from Yang River to its estuary was from 11.73 to 391.59 g/year, far below those from the other estuarine regions all over the world. QNs were observed in all five wetland plants, demonstrating that QNs contaminants could be taken up by wetland plants and providing the evidence that phytoremediation could be a feasible way to remove contaminants. Negative partial coefficients between individual antibiotic and brassicasterol biomarker suggested the presence of QNs inhibited the phytoplankton growth. Evaluation of ecological risk based on the values of risk quotients (RQs) showed that OFL in Yang River displayed medium risk for algae, and CIP and OFL in its estuary also displayed medium risk value for plant and algae. The results could provide powerful basis on controlling river antibiotics pollution to enhance rivers-estuary security in similar regions.

A slurry microcosm study on the interaction between antibiotics and soil bacterial community

Antibiotics released in the environment have attracted great attention. The environmental emission control of antibiotics should be based on the degree of their negative impacts on the environment and ecology. Here, we conducted a series of soil slurry microcosm experiments to investigate the interactions between antibiotics and the soil bacterial community. In the soil slurry, distinctive behaviors were observed for different antibiotics. Beta-lactams (ampicillin and ceftriaxone) experienced fast biodegradation. Kanamycin was adsorbed on soil particles soon after its addition. Nalidixic acid was stable throughout the experimental period (164 h). The main inactivation mechanism of tetracycline was deduced to be hydrolysis. Bacterial communities in slurries with or without antibiotic-treatment were profiled via high-throughput Illumina sequencing of the 16S rRNA gene. Unstable (ceftriaxone) and adsorbed (kanamycin) antibiotics show minor or negligible influences on the soil bacterial community. Stable antibiotics (nalidixic acid and tetracycline) have significantly affected the structure of the bacterial community. Most of enriched bacterial genera by various antibiotics belong to the same phylum, Proteobacteria. Inhibited bacterial phyla by nalidixic acid are Firmicutes and Bacteroidetes, while those inhibited by tetracycline are Firmicutes, Bacteroidetes and Cyanobacteria. According to the PICRUSt prediction of metagenome, influence of antibiotics on overall metabolic function of the bacterial community is rather limited. This study has provided valuable information, from a phylogenetic viewpoint, about the influence of high concentration of antibiotics on soil bacterial community.

Understanding effect of interaction of nanoparticles and antibiotics on bacteria survival under aquatic conditions: Knowns and unknowns

The review provides a comprehensive overview of the available state-of-the-art of nanoparticles (NPs) and antibiotics (ABs) occurrence and their fate in the natural aquatic settings by addressing different research questions and the challenges faced while addressing those questions. Firstly, understand the interaction of NPs and ABs with themselves in addition to other matrix components (presence of natural organic matter, bacteria, biofilms, other anthropogenic pollutants and metals from natural sources). Secondly, summarize the bactericidal activity of NP and AB due to reactive oxygen species (ROS) production. The complete information was gathered from database and analysed as per the conjectured questions under laboratory versus environmental-relevant conditions (1. Fate of NPs and ABs, and 2. Will the presence of NPs and ABs alone and their mixtures influence the ROS concentration and antibacterial activity), and proposed six reactions to describe the fate of NP and AB in natural aquatic settings. However, laboratory-based studies revealed that NP and AB fate largely depend on the ionic strength, organic matter content and pH of the matrix whereas field based information is missing about this. The former was performed at sterile conditions using sophisticated instruments and standard protocol as compared to latter and can't be replicated under natural aquatic settings due to lack of: (i) accurate environmental concentration of NPs and ABs, (ii) knowledge of bacterial type and their concentration, (iii) optimized protocol and tracking systems. The author's recommendation is to verify the proposed reactions experimentally by using the frequently found pairs of NPs and ABs in the natural aquatic settings. Further, ranked them on their decreasing order of toxicity and informed regulatory bodies for further action. Overall research is needed in the suggested directions to reduce uncertainty behind the impacts of NPs and ABs on the aquatic settings and their role in bactericidal activity.

Ciprofloxacin transformation in aqueous environments: Mechanism, kinetics, and toxicity assessment during •OH-mediated oxidation

The initial reactions of organics with ^•OH are important to understand their transformations and fates in advanced oxidation processes in aqueous phase. Herein, the kinetics and mechanism of ^•OH-initiated degradation of ciprofloxacin (CIP), an antibiotic of fluoroquinolone class, are obtained using density functional and computational kinetics methods. All feasible mechanisms are considered, including H-abstraction, ^•OH-addition, and sequential electron proton transfer. Results showed that the H-abstraction is the dominant reaction pathway, and the product radicals P7H, P9H, and P10H are the dominating intermediates. The aqueous phase rate coefficients for the ^•OH-triggered reaction of ciprofloxacin are calculated from 273 K to 323 K to examine the temperature dependent effect, and the theoretical value of 6.07 × 10⁹ M^-1 s^-1 at 298 K is close to the corresponding experimental data. Moreover, the intermediates P7H, P9H, and P10H could easily transform to several stable products in the presence of O₂, HO₂^•, and ^•OH. The peroxy radical, which is generated from the incorporation of H-abstraction product radicals (P7H, P9H, and P10H) with O₂, prefers to produce HO₂^• into the surrounding through direct concerted elimination rather than the indirect mechanism. In addition, the peroxy radical could react with HO₂^• via triplet and singlet routes, and the former is more favorable due to its smaller barrier compared with the latter. The hydroxyl-substituted CIP has higher activity than its parent compound in their reactions with ^•OH due to its lower barrier and faster rate. In addition, the -NHC(O)-containing compound IM3-P10-H-4 is harmful to aquatic fish and is the primary product in the ^•OH-rich environment according to the ecotoxicity assessment computations. This study can improve our comprehension on CIP transformation in complex water environments.

Mineralization Enhancement of Pharmaceutical Contaminants by Radical-Based Oxidation Promoted by Oxide-Bound Metal Ions

While the use of transition metal oxides in catalyzing advanced oxidation reactions has been widely investigated, very few reports have focused on how the preliminary contact of oxides with target compounds may affect the succession of reaction. In this study, we examined the adsorption and electron transfer reactions of two fluoroquinolones, flumequine (FLU), and norfloxacin (NOR), with goethite (α-FeOOH) or manganese (Mn) oxide, and their impact on the subsequent mineralization of target compounds using H₂O₂ or S₂O₈^2- under UVA irradiation. Intriguingly, higher total organic carbon (TOC) removal was achieved when antibiotics and metal oxides were allowed for preequilibration before starting the oxidation reaction. The rate and extent of TOC removal are strongly dependent on the molecule structure and the redox-active mineral used, and much less on the preequilibration time. This high efficiency can be ascribed to the presence of reduced metal ions, chemically or photochemically generated during the first stage, onto oxide minerals. Oxide-bound Mn^II plays a crucial role in catalyzing oxidant decomposition and then producing greater amounts of radical species through a photoassisted redox cycle, regardless of the underlying surface, Mn^IVO₂ or Mn^IIIOOH. This finding will be of fundamental and practical significance to Mn-based oxidation reactions and wastewater treatment processes.

Highly efficient and selective removal of low-concentration antibiotics from aqueous solution by regenerable Mg(OH)2

The prevalent presence of fluoroquinolone antibiotics in aquatic environments has attracted considerable attention because of their harmful effects on humans and the ecological environment. Magnesium hydroxide nanocrystals were found to act as a simple and effective adsorbent to remove low-concentration ciprofloxacin (CIP) in aqueous solution. The as-prepared Mg(OH)₂ nanocrystals exhibited excellent CIP adsorption performance and high selectivity toward CIP molecules compared with other antibiotics or aromatics, e.g., norfloxacin (NOR) and eosin B (EB). The adsorbent showed pH-dependent adsorption, indicating that the adsorption process is probably dominated by an electrostatic interaction mechanism. In addition, structural analysis of the adsorbent indicated that coordination and hydrogen bonding between CIP and Mg(OH)₂ nanocrystal might also be involved in the adsorption process. Moreover, the adsorbent could be easily recovered by pyrolysis and hydration without significant reduction of adsorption capacity. The superior adsorption behavior of Mg(OH)₂ nanocrystal indicates that it may serve as a potential adsorbent material candidate for the selective removal of CIP from aquatic environments.

Comparison of ciprofloxacin degradation in reclaimed water by UV/chlorine and UV/persulfate advanced oxidation processes

This study analyzed the ciprofloxacin (CIP) degradation in real reclaimed water through UV/chlorine and UV/persulfate (UV/PS) advanced oxidation processes. The influence of oxidant dosage, pH, inorganic anions, and humic acid (HA) on the oxidation capacity and performances of various UV-based processes was investigated. The results revealed that the CIP degradation rate constants in the UV/chlorine and UV/PS processes were higher than that in UV/H₂ O₂ , direct-UV, NaClO, and K₂ S₂ O₈ processes. The removal rate peaked at 0.1 mM oxidant dosage for 1 μM CIP, while the rate constant was highest at pH 5 (UV/chlorine) and pH 7 (UV/PS). The presence of Cl^- , HCO₃ ^- , and HA inhibited CIP removal in both processes. The degradation rate observed in reclaimed water was high, but still lower than that in laboratory water by 9.2 (UV/chlorine) and 9 (UV/PS) times. The UV/chlorine and UV/PS processes were found to be more cost-effective and hence more feasible in removing refractory compounds in reclaimed water. PRACTITIONER POINTS: The addition of oxidant and UV irradiation together had a pronounced promotion in the degradation of CIP. Cl^· and SO₄ ^·- had potential importance for enhancing CIP degradation in UV/chlorine and UV/PS process, respectively. UV/chlorine and UV/PS processes exhibited effective removal capability to CIP in real reclaimed water.

Oxidation of flumequine in aqueous solution by UV-activated peroxymonosulfate: Kinetics, water matrix effects, degradation products and reaction pathways

The degradation of flumequine (FLU) in aqueous solution by ultraviolet (UV)-activated peroxymonosulfate (PMS) was investigated in this work. Under the conditions of [PMS]₀:[FLU]₀ = 1:1, T = 25 ± 2 °C, pH = 7.0 ± 0.1, nearly complete removal of FLU was achieved after 60 min. The effects of various operating parameters, including oxidant doses, pH, the presence of typical ions (NH₄⁺、Mg²⁺、Fe³⁺、Cl^-、NO₃^-、HCO₃^-) and humic acid were evaluated. It was found that the pseudo-first-order rate constants of FLU degradation increased with increasing PMS dosage and decreasing solution pH. The presence of Mg²⁺ could accelerate FLU removal, while Fe³⁺, HCO₃^-, NO₃^- and HA inhibited the reaction. Moreover, the degradation of FLU in different water matrices were also explored, and the removal followed the order of Tap water > Ultrapure water > River water > Secondary clarifier effluent. According to the control and radical quenching experiment results, direct photolysis and reactive radicals (SO₄^- and HO) contributed mainly to FLU degradation in the UV/PMS system. Initial FLU molecule underwent reactions such as hydroxylation, hydroxyl substitution, demethylation, decarboxylation/decarbonylation and ring opening, leading to the formation of nineteen oxidation products. The effective degradation by UV/PMS suggests a feasible technology for treating FLU in waters and wastewaters.

A sustainable ferromanganese biochar adsorbent for effective levofloxacin removal from aqueous medium

This present study reported the synthesis and characterization of a low-cost, environment friendly and high efficient biochar, ferromanganese modified biochar (Fe/Mn-BC) for the removal of levofloxacin (LEV) from aqueous medium. Fe/Mn-BC was synthesized through the facile co-precipitation of Fe, Mn with vinasse wastes and then pyrolysis under controlled conditions. The characterization of Fe/MnBC was analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction patterns (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman. Some influencing factors (e.g., pH, Fe/Mn-BC dosage, initial LEV concentration, ionic strength, contact time and temperature) were comprehensively investigated. The results manifested that the adsorption process of LEV onto Fe/Mn-BC was high pH dependence and the maximum adsorption capacity was achieved at pH 5. Moreover, the adsorption capacity of LEV was increased with increasing ionic strength. To gain a clearer perspective on the adsorption behavior of LEV onto Fe/Mn-BC, the adsorption kinetics and isotherms were also performed, revealing pseudo-second-order and Freundlich model had a better fitting effect. Reusability experiments indicated that Fe/Mn-BC could maintain a certain adsorption capacity for LEV after 5 recycles. Overall, this work showed that Fe/Mn-BC was an effective and promising adsorbent for eliminating LEV from aqueous medium.

Responses of antibiotics, antibiotic resistance genes, and mobile genetic elements in sewage sludge to thermal hydrolysis pre-treatment and various anaerobic digestion conditions

Sewage sludge from wastewater treatment plants (WWTPs) harbours large amounts of antibiotics, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs), the variation and fate of these emerging pollutants during sludge treatment processes must be thoroughly studied to reduce their potential risks to human health. In this study, 7 pilot-scale CSTR anaerobic digesters were established with the same seed sludge and fed with the same thermal hydrolysis pre-treated sewage sludge, while operating under different conditions. High-throughput quantitative PCR, UPLC-MS/MS and Illumina Hiseq-sequencing were used to systematically evaluate the responses of antibiotics, ARGs, and MGEs in sewage sludge to thermal hydrolysis pre-treatment and various anaerobic digestion (AD) conditions. The results showed that thermal hydrolysis effectively reduced the abundance (>94%) of almost all subtypes of ARGs and MGEs, and it was a powerful technology for reducing tetracyclines, macrolides, and lincosamides. Besides, the abundance of ARGs and MGEs in thermophilic digesters was lower than that in mesophilic digesters, suggesting that thermophilic digesters could be used to avoid the ARGs rebounding. In addition, the thermophilic system further reduced the concentrations of quinolones. For the digesters operated under the mesophilic conditions, a longer hydraulic retention time (HRT) facilitated the removal of antibiotics, ARGs, and MGEs. Furthermore, the microbial community and MGEs had important effects on the persistence and proliferation of ARGs in AD process. The findings of this study provide effective clues for controlling the spread of antibiotic resistance and suggest the optimal operating conditions of digesters.

Prevalence of Antibiotic Resistance Genes and Their Association with Antibiotics in a Wastewater Treatment Plant: Process Distribution and Analysis

Effluents from wastewater treatment plants has been identified as a main point-source of antibiotics and antibiotic resistance genes in natural water environments. In this study, a typical municipal sewage treatment system in south China was taken as the research object to investigate the effects of each treatment unit on eight target antibiotics (sulfamethoxazole, sulfamethazine, tetracycline hydrochloride, oxytetracycline dihydrate, norfloxacin, ofloxacin, clarithromycin, roxithromycin), 17 antibiotic resistance genes (ARGs) and class 1 integron genes in the system using Accelerated Solvent Extraction-Solid phase extraction-Ultra high Performance Liquid Chromatography-Tandem mass spectrometry (ASE-SPE-UPLC-MS/MS) and real-time fluorescent quantitative PCR (qPCR) and the correlation between them. Seven antibiotics (mainly sulfonamides and tetracyclines, 4.19–141.97 ng·L−1) were detected in the influent, while only sulfamethoxazole, sulfamethazine, ofloxacin, and clarithromycin were detected in the effluent (3.11–16.61 ng·L−1). The tetracycline antibiotics in the wastewater treatment plant (WWTP) were transferred to the sludge phase by adsorption, in which tetracycline hydrochloride and oxytetracycline dihydrate were mostly removed in the aerobic and anaerobic stages, while sulfamethoxazole was mainly removed through biological transformation. Sul I was the most abundant resistance gene, but the WWTP had no obvious effect on its removal. Anaerobic treatment was found to play an important role in tetA, tetQ, and tetX removal. Moreover, correlation analysis revealed that the relative abundance of tetX was significantly correlated with clarithromycin (p = 0.039) and ofloxacin (p = 0.028), while that of tetQ was significantly correlated with sulfamethazine (p = 0.007) and sulfamethoxazole (p = 0.001), and that of tetC was significantly correlated with the class 1 integron gene (p = 0.014). Overall, the results presented herein provide a reference for improving the antibiotics and ARGs removal efficiency of WWTPs in south China.

The cardiovascular toxicity induced by high doses of gatifloxacin and ciprofloxacin in zebrafish

As a new type of pollutant, fluoroquinolones (FQs) antibiotics are ubiquitous in environment and have some threat to human health and ecological environment. Their ecological toxicity to the environment urgently need to be assessed. Therefore, we firstly explored the toxic effects and possible mechanism of cardiovascular toxicity induced by gatifloxacin (GTFX) and ciprofloxacin (CPFX) using zebrafish model. After 24 h exposure, the zebrafish treated with GTFX showed pericardial edema which was further investigated by histopathological examination, while CPFX exposure did not induce morphological abnormalities. However, both of them induced cardiac dysfunction, such as decreased heart rate and cardiac output which was showed a positive correlation with the concentration. To better understand the possible molecular mechanisms underlying cardiovascular toxicity in zebrafish, we investigated the transcriptional level of genes related to calcium signaling pathway and cardiac muscle contraction. The results indicated that the expression of ATPase (atp2a1l) and cardiac troponin C (tnnc1a) genes were significantly inhibited, the expression of calcium channel (cacna1ab) gene showed slight promoted trend after CPFX exposure. For zebrafish treated with GTFX, the expression of atp2a1l genes was also significantly inhibited, while the expression of tnnc1a genes was slightly inhibited and cacna1ab genes expression had no obvious effect. The present study firstly revealed that GTFX exposure can induce morphological and functional abnormalities on the cardiovascular system of zebrafish. Though CPFX exposure did not induce morphological abnormalities, the function of cardiovascular system was still damaged. Mechanistically, this toxicity might result from the pressure of down-regulation of genes associated with calcium signaling pathway and cardiac muscle contraction. The results of this study can provide a valuable theoretical basis for the establishment of FQs environmental quality standards in water environment, environmental drug regulation and risk management.

A review on removing antibiotics and antibiotic resistance genes from wastewater by constructed wetlands: Performance and microbial response

Pollution caused by antibiotics has been highlighted in recent decades as a worldwide environmental and health concern. Compared to traditional physical, chemical and biological treatments, constructed wetlands (CWs) have been suggested to be a cost-efficient and ecological technology for the remediation of various kinds of contaminated waters. In this review, 39 antibiotics removal-related studies conducted on 106 treatment systems from China, Spain, Canada, Portugal, etc. were summarized. Overall, the removal efficiency of CWs for antibiotics showed good performance (average value = over 50%), especially vertical flow constructed wetlands (VFCWs) (average value = 80.44%). The removal efficiencies of sulfonamide and macrolide antibiotics were lower than those of tetracycline and quinolone antibiotics. In addition, the relationship between the removal efficiency of antibiotics and chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH₃-N) concentrations showed an inverted U-shaped curve with turning points of 300 mg L^-1, 57.4 mg L^-1, 40 mg L^-1, 3.2 mg L^-1 and 48 mg L^-1, respectively. The coexistence of antibiotics with nitrogen and phosphorus slightly reduced the removal efficiency of nitrogen and phosphorus in CWs. The removal effect of horizontal subsurface flow constructed wetlands for antibiotic resistance genes (ARGs) had better performance (over 50%) than that of vertical wetlands, especially for sulfonamide resistance genes. Microorganisms are highly sensitive to antibiotics. In fact, microorganisms are one of the main responsible for antibiotic removal. Moreover, due to the selective pressure induced by antibiotics and drug-resistant gene transfer from resistant bacteria to other sensitive strains through their own genetic transfer elements, decreased microbial diversity and increased resistance in sewage have been consistently reported. This review promotes further research on the removal mechanism of antibiotics and ARGs in CWs.

Cetylpyridinium bromide assisted micellar-enhanced ultrafiltration for treating enrofloxacin-laden water

The presence of a fluoroquinolone base veterinary antibacterial drug enrofloxacin in aqueous media poses a major threat due to its ecotoxicity on aquatic microbiota. Hence, for the first time, an attempt was made to remove enrofloxacin (ENX) from its aqueous solution by employing micellar-enhanced ultrafiltration (MEUF) where cetylpyridinium bromide (CPB), a cationic surfactant was used for micellization. Response surface methodology (RSM) with central composite design (CCD) approach was applied to design the experiment, and to optimize the process parameters, namely, ENX concentration (3-15 mg/L), transmembrane pressure (2-6 kg_f/cm²), recirculation flow rate (5.5-7.5 L/min) and CPB concentration (1.4-4.2 mM). The objective of this study was to maximize the permeate flux and rejection coefficient and to find out the optimal process condition for the removal of enrofloxacin from aqueous solution. Though maximum 68.23 L/m² h of permeate flux and 94.20% of rejection coefficient were achieved at different process conditions, the optimization study reveals that the predicted optimal values of permeate flux and rejection coefficient are 67.53 L/m² h and 89.67% respectively. Modelling was also carried out with the aid of artificial neural network (ANN) to validate the prediction of RSM. The predictability of the model by RSM and ANN was compared statistically by evaluating root-mean-square error (RMSE), absolute average deviation (AAD) and mean absolute error (MAE), where ANN exhibited better predictability. The following set of parameters was proposed for industrial scale up: ENX concentration of 8.4 mg/L, TMP of 5 kg_f/cm², recirculation flow rate of 6 L/min and CPB concentration of 2.1 mM.

Molecular Modification of Fluoroquinolone-Biodegrading Enzymes Based on Molecular Docking and Homology Modelling

To improve the biodegradation efficiency of fluoroquinolone antibiotics during sewage treatment, fluoroquinolone aerobic, anaerobic and facultative degrading enzymes for fluoroquinolone degradation were modified by molecular docking and homology modelling. First, amino acid residues of the binding sites of degrading enzymes for the target fluoroquinolones ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL) were analysed by the molecular docking method. The hydrophobic amino acid residues within 5 Å of the target fluoroquinolone molecules were selected as the modification sites. The hydrophobic amino acid residues at the modified sites were replaced by the hydrophilic amino acid residues, and 150 amino acid sequence modification schemes of the degrading enzymes were designed. Subsequently, a reconstruction scheme of the degrading enzyme amino acid sequence reconstruction scheme was submitted to the SWISS-MODEL server and a selected homology modelling method was used to build a new structure of the degrading enzyme. At the same time, the binding affinities between the novel degrading enzymes and the target fluoroquinolones (represented by the docking scoring function) were evaluated by the molecular docking method. It was found that the novel enzymes can simultaneously improve the binding affinities for the three target fluoroquinolones, and the degradation ability of the six modification schemes was increased by more than 50% at the same time. Among the novel enzymes, the affinity effect of the novel anaerobic enzyme (6-1) with CIP, NOR and OFL was significantly increased, with increases of 129.24%, 165.06% and 169.59%, respectively, followed by the facultative enzyme and aerobic enzyme. In addition, the designed degrading enzymes had certain selectivity for the degradation of the target quinolone. Among the novel enzymes, the binding affinities of the novel anaerobic enzyme (6-3) and CIP, the novel aerobic enzyme (3-6) and NOR, and the novel facultative enzyme (13-6) and OFL were increased by 149.71%, 178.57% and 297.12% respectively. Calculations using the Gaussian09 software revealed that the degradation reaction barrier of the novel degrading enzyme (7-1) and CIP NOR and OFL decreased by 37.65 kcal·mol-1, 6.28 kcal·mol-1 and 6.28 kcal·mol-1, respectively, which would result in efficient degradation of the target fluoroquinolone molecules. By analysing the binding affinity of the degrading enzymes before and after the modification with methanol, it was further speculated that the degradation effect of the modified aerobic degrading enzymes on organic matter was lower than that before the modification, and the increase or decrease in the degradation effect was less than 10%. The mechanism analysis found that the interaction between the modified amino acid residues of the degrading enzymes and the fluoroquinolone molecules increased. The average distance between the amino acid residues and the fluoroquinolone molecules represented a comprehensive affinity effect, and its value was positively correlated with the degradation effect of the novel degrading enzymes.

Translating antibiotic prescribing into antibiotic resistance in the environment: A hazard characterisation case study

The environment receives antibiotics through a combination of direct application (e.g., aquaculture and fruit production), as well as indirect release through pharmaceutical manufacturing, sewage and animal manure. Antibiotic concentrations in many sewage-impacted rivers are thought to be sufficient to select for antibiotic resistance genes. Yet, because antibiotics are nearly always found associated with antibiotic-resistant faecal bacteria in wastewater, it is difficult to distinguish the selective role of effluent antibiotics within a 'sea' of gut-derived resistance genes. Here we examine the potential for macrolide and fluoroquinolone prescribing in England to select for resistance in the River Thames catchment, England. We show that 64% and 74% of the length of the modelled catchment is chronically exposed to putative resistance-selecting concentrations (PNEC) of macrolides and fluoroquinolones, respectively. Under current macrolide usage, 115 km of the modelled River Thames catchment (8% of total length) exceeds the PNEC by 5-fold. Similarly, under current fluoroquinolone usage, 223 km of the modelled River Thames catchment (16% of total length) exceeds the PNEC by 5-fold. Our results reveal that if reduced prescribing was the sole mitigating measure, that macrolide and fluoroquinolone prescribing would need to decline by 77% and 85%, respectively, to limit resistance selection in the catchment. Significant reductions in antibiotic prescribing are feasible, but innovation in sewage-treatment will be necessary for achieving substantially-reduced antibiotic loads and inactivation of DNA-pollution from resistant bacteria. Greater confidence is needed in current risk-based targets for antibiotics, particularly in mixtures, to better inform environmental risk assessments and mitigation.

Water Flow Variability Affects Adsorption and Oxidation of Ciprofloxacin onto Hematite

The mobility of pharmaceuticals in environmental systems is under great scrutiny in the scientific literature and in the press. Still, very few reports have focused on redox-driven transformations when these compounds are bound to mineral surfaces, and how their transport is affected under flow-through conditions. In this study, we examined the adsorption and electron transfer reactions of ciprofloxacin (CIP) in a dynamic column containing nanosized hematite (α-Fe₂O₃). CIP binding and the subsequent redox transformation were strongly dependent on inflow pH and residence time. These reactions could be predicted using transport models that account for adsorption and transformation kinetics. Our results show that flow interruption over a 16 h period triggers oxidation of hematite-bound CIP into byproducts. These reactions are likely facilitated by inner-sphere iron-CIP complexes formed via the sluggish conversion from outer-sphere complexes during interrupted flow. When intermittent flow/no-flow conditions were applied sequentially, a second byproduct was detected in the column effluent. This work sheds light on a much overseen aspect of redox transformations of antibiotics under flow-through conditions. It has important implications in adequately predicting transport, and in developing risk assessments of these emerging compounds in the environment.

Hospital wastewater treatment by sponge membrane bioreactor coupled with ozonation process

Herein, a sponge membrane bioreactor (Sponge-MBR) combined with ozonation process was performed to remove the antibiotics which frequently existed in the hospital wastewater. Whilst seven antibiotics i.e., norfloxacin, ciprofloxacin, ofloxacin, sulfamethoxazole, erythromycin, tetracycline and trimethoprim were widely used in medications, this integration was applied for the evaluation of treatment performance under different fluxes. As the results, whilst the antibiotics were eliminated about 45-93%, the tetracycline was completely removed (100%) using Sponge-MBR operated at the flux of 10 LMH. For enhancement of antibiotics removal, the ozonation process was introduced to treat the membrane permeate. Overall efficiencies were 97 ± 2% (trimethoprim), 92 ± 4% (norfloxacin), 90 ± 1% (erythromycin), 88 ± 4% (ofloxacin), 83 ± 7 (ciprofloxacin) and 66 ± 1% (sulfamethoxazole). These results demonstrated Sponge-MBR coupled with ozonation could be a prospective technology for the hospital wastewater treatment.

Occurrence and distribution of selected antibiotics in the surface waters and ecological risk assessment based on the theory of natural disaster

With increasing population growth and resource depletion, ecological health is a hotspot and urgent topic. Our study investigated the occurrence and distribution of five antibiotics, i.e., metronidazole (MET), sulfamethoxazole (SMZ), ciprofloxacin (CFX), norfloxacin (NFX), and enrofloxacin (EFX), in the surface water from Erlong Lake, China. With the seasonal and spatial variations of antibiotics, this study developed an interdisciplinary approach for the ecological risk of antibiotics considering the natural, human, and socioeconomic elements of watershed based on the risk theory of natural disaster. This approach integrates the geographic information system (GIS) spatial analysis tool, natural disaster theory, "driving force"-"pressure"-"state"-"impact"-"response" (DPSIR) model, and ordered weighted averaging (OWA) operators in terms of various environmental factors, representing a new ecological risk paradigm for environmental managers or decision-makers to identify environmental change. A total of 69 samples were collected in wet, dry, and normal seasons from 2017 to 2018, and laboratory analyses revealed that four antibiotics (MET, SMZ, CFX, and NFX) were widely detected in the lake. The mean concentrations decreased in the order of MET (1041.7 ng L^-1) > SMZ (771.4 ng L^-1) > CFX (646.4 ng L^-1) > NFX (179.0 ng L^-1) > EFX (15.3 ng L^-1), with their levels in natural surface waters higher than those in other studies. Antibiotic concentrations were higher in dry seasons than in other seasons, and the concentrations were strongly correlated with EC (electrical conductivity), pH, DOC (dissolved organic carbon), and TP (total phosphorus) according to redundancy analysis (RDA). Significant seasonal variations were found in CFX and EFX (ANOVA, p < 0.001). For the whole watershed, the ecological extremely and heavily vulnerable levels were concentrated in the central and northwest regions of the watershed, i.e., Changling county and Lishu county. Hence, the ecological distributions of extreme risk and heavy risk posed by the five selected antibiotics were assessed by using the mixture hazard quotient methods and DPSIR model which were also located in these counties in different seasons. The antibiotic results of ecosystem risk assessment can support decision-makers in identifying and prioritizing the necessary taking of specific measures and different risk attitudes to preserve the quality of ecological health for a city or multiple counties.

Adsorption behavior of diclofenac-containing wastewater on three kinds of sewage sludge

Diclofenac (DCF) is one of the most frequently detected non-steroidal anti-inflammatory drugs (NSAIDs) in the water environment. One of the main removal routes of DCF in wastewater is sludge adsorption, and the mechanisms need to be investigated. In this study, the effects of adsorption time, temperature, pH value, and ionic strength on the adsorption of DCF on suspended particles (SP), secondary sedimentation tank sludge (SSTS) and concentrated sludge (CS) were investigated. The results showed that most of the adsorption of DCF by the three matrices was conducted in the first 4 h and equilibrium was achieved at 8 h. The adsorption kinetics were well fitted with the pseudo-second-order model and the rate constants were 0.29-0.88 mg·(μg·min)^-1, with chemical adsorption as the dominant one. Adsorption isotherm conformed to Freundlich, Langmuir and Linear adsorption isotherm models. The order of adsorption capacity was: CS > SSTS > SP, which was proportional to the organic matter content and specific surface area of the adsorbents. The decrease of the pH value and the increase of ionic strength promoted the adsorption of DCF. The results can provide data support for the removal of DCF from different treatment unit types in wastewater treatment plants.

Chlorination of enoxacin (ENO) in the drinking water distribution system: Degradation, byproducts, and toxicity

Chlorine is widely used as a drinking water disinfectant to ensure water security. However, the transformation mechanisms of its degradation of emerging pollutants within the water distribution system (WDS) is insufficiently understood. Thus, the kinetics, degradation byproducts, and toxicity of the chlorination of enoxacin (ENO, a type of emerging pollutant) were explored in a pilot-scale WDS for the first time. It was found that the chlorination rate of ENO was higher in deionized water (DW) than in the pilot-scale WDS, and the degradation followed second-order kinetics in DW. The degradation efficiency was found to be sensitive to pH, and was highest at a pH of 7.4. The chlorination rate of ENO increased with increasing temperature in both DW and WDS. For different pipe materials, the relative performance of ENO chlorination efficiency followed the order of steel pipe > ductile iron pipe > polyethylene (PE) pipe. Seven intermediates were identified during ENO chlorination, and the primary oxidation reaction involved the cleavage of the piperazine group. Finally, it was found that the potential for chlorine toxicity in treated drinking water in the presence of ENO is higher than it is without this pollutant.

Simultaneous removal of antibiotics and antibiotic resistance genes from pharmaceutical wastewater using the combinations of up-flow anaerobic sludge bed, anoxic-oxic tank, and advanced oxidation technologies

Pharmaceutical wastewater often contains high levels of antibiotic residues and serves as an important reservoir for antibiotic resistance genes (ARGs). However, the current pharmaceutical wastewater treatment plants (PWWTPs) were not sufficiently effective in removing antibiotics and ARGs. Here, we designed a lab-scale simulation reactor, including up-flow anaerobic sludge bed (UASB), anoxic-oxic tank (A/O), and four separate advanced oxidation processes (AOPs) i.e., UV, Ozonation, Fenton, and Fenton/UV, to simultaneously remove 18 antibiotics and 10 ARGs from a real pharmaceutical wastewater. The results showed that all antibiotics were fully eliminated through the reactor during 180 d-operation. Among all treatment units, UASB provided the greatest contribution (85.8 ± 16.1%) for the removal of 18 antibiotics. The mass balance results manifested that degradation was a predominant mechanism for the removal of tetracyclines, sulfamethoxazole, and ampicillin (62.5-80.9%), while sorption to sludge (73.9%) was predominant for enrofloxacin removal in UASB. Meanwhile, the substantial decrease of ARG absolute abundance (log reduction by 0.1-3.1 fold) through the whole reactor was observed although the existence of the partial enrichment (1.2-3.8 log units) from the influent to the A/O unit. Fenton/UV combination was the most effective AOP for the removal of ARGs. Finally, the optimum operating conditions for the removal of ARGs using Fenton was also proposed considering the relatively lower cost and high ARG elimination. Overall, this study provides feasible suggestions for the design of real PWWTPs for simultaneous removal of antibiotics and ARGs.

Removal and dissipation pathway of typical fluoroquinolones in sewage sludge during aerobic composting

To observe the effect of aeration strategies on the dissipation of fluoroquinolones (FQs) during aerobic composting and explore their dissipation pathways, 60-L composting and 0.5-L incubation experiments were carried out in this study. Three aeration strategies (windrow, static aeration, feedback aeration) were applied to remove two typical FQs (Norfloxacin (NOR) and Ofloxacin (OFL)) during the 60-L composting of sewage sludge with 5 mg kg^-1 of FQs added. Then, three 0.5 L-sample groups were taken during the three phases of the 60-L composting matrixes without FQs under static aeration, and were inoculated separately at 35 °C, 55 °C and 40 °C after being added with 5 mg kg^-1 of FQs. In each group, incubation was carried out for three treatments (sterilization + no aeration, sterilization + aeration, and no sterilization + aeration). The FQs in the sewage sludge were mainly removed in the mesophilic and thermophilic phases in all the aeration strategies. The removal efficiencies were high for the whole process: 89.6-95.4% for NOR and 87.2-95.4% for OFL. The order of removal efficiency of FQs was static aeration > feedback aeration > windrow. The combination of composting phases facilitated to the rapid dissipation of FQs, which reduced the half-life to about 1/6 to 1/5 of the values in each phase. In the mesophilic and thermophilic compost, biodegradation was the main pathway for the dissipation of FQs followed by irreversible adsorption. Irreversible adsorption and biodegradation provided similar removal efficiencies for the curing compost. The volatilization of FQs was non-negligible in all phases.

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.

Fate of antibiotics in three distinct sludge treatment wetlands under different operating conditions

Sludge treatment wetlands (STWs) have recently been used to treat surplus sludge. However, the distribution of antibiotics involved in the process has not been comprehensively investigated. This study aimed to evaluate the fate of two antibiotics, i.e., ciprofloxacin (CIP) and azithromycin (AZM) in STWs during the treatment of surplus sludge. Three pilot-scale STWs units-S1 with aeration tubes, S2 with aeration tubes and reed planting, and S3 with reed planting-were constructed and operated under feeding followed by resting periods. The results showed that antibiotic content in residual sludge decreased over time and unit S2 performed the best in terms of antibiotic removal. Planting reed considerably improved the antibiotic removal performance of the STWs. Biodegradation and absorption resulted in removal of most of the antibiotics in the test units. Less than 2% of the antibiotics was taken up by plants, whereas <5% of the influent antibiotics left the STW units through the drainage discharge. Overall, STW units contributed to effectively decrease CIP and AZM to 41-72% and 49-84%, respectively.

Water depollution using metal-organic frameworks-catalyzed advanced oxidation processes: A review

This paper presents a review on the environmental applications of metal-organic frameworks (MOFs), which are inorganic-organic hybrid highly porous crystalline materials, prepared from metal ion/clusters and multidentate organic ligands. The emphases are made on the enhancement of the performance of advanced oxidation processes (AOPs) (photocatalysis, Fenton reaction methods, and sulfate radical (SO₄^-)-mediated oxidations) using MOFs materials. MOFs act as adsorption and light absorbers, leading to superior performance of photocatalytic processes. More recent examples of photocatalytic degradation of dyes are presented. Additionally, it is commonly shown that Fe-based MOFs exhibited excellent catalytic performance on the Fenton-based and SO₄^•--mediated oxidations of organic pollutants (e.g., dyes, phenol and pharmaceuticals). The significantly enhanced generation of reactive species such as OH and/or SO₄^- by both homogeneous and heterogeneous catalysis was proposed as the possible mechanism for water depollution. Based on the existing literature, the challenge and future perspectives in MOF-based AOPs are addressed.

Seasonal dynamics of bacterial communities associated with antibiotic removal and sludge stabilization in three different sludge treatment wetlands

In this study, antibiotics removal, sludge stabilization and the change in the bacterial community in sludge treatment wetlands (STWs) were investigated in different seasons. Pilot-scale STWs were characterized for sludge stabilization and the fate of antibiotics in surplus sludge applied during different seasons in three different configurations. The three configurations were unit S1 with ventilation, unit S2 with ventilation and reed plantings and unit S3 with reed plantings. The antibiotics used were ciprofloxacin, azithromycin and oxytetracycline and their degradation, degree of sludge stabilization and bacterial community dynamics were monitored. The results showed that the removal of antibiotics and reduction in the amount of organics in the planted units S2 and S3 were higher than those in the unplanted unit S1, especially in summer. The antibiotic removal efficiency in the planted unit S2, which was equipped with aeration tubes, was the highest over the entire test period. Bacterial community was analyzed by IlluminaMiSeq sequencing of the 16SrRNA gene, showed that the presence of plants in STWs enhanced microbial diversity and richness which promote the removal of antibiotics and sludge stabilization. Proteobacteria, Bacteroidetes and Firmicutes were dominant in the bacterial communities, with Thiobacillus, Dechloromonas and Pseudomonas occurring as dominant genera.

A method to study antibiotic emission and fate for data-scarce rural catchments

Estimations of antibiotic emission and fate and thereby ecological risk in rural catchments still lack feasible methods due to data scarcity. This study developed a new framework to evaluate the emission and fate of typical antibiotics for data-scarce catchments with uncertainty analysis. We estimated antibiotic discharge through questionnaire surveys; predicted antibiotic fate in air, water, soil, and sediment phases using a multimedia fugacity model; and analyzed the uncertainties of predicted environmental concentrations (PECs) and ecological risks of antibiotics. The developed method was tested in the Meijiang River catchment in China, and the uncertainty was systematically analyzed. Results showed that the discharge of tetracycline antibiotics (TCs) in the studied watershed was 8.56 t/a, with approximately 93% from veterinary medicine. TCs existed dominantly in the soil phase, accounting for 87.3% of total discharge. TC levels at the equilibrium states were the highest in sediment and soil, followed by water and air. The emission levels of TCs may cause slight risk to algae, daphniids, and fish in the receiving water based on the ecological risk evaluation of PECs. Despite of some uncertainties, the developed method provided an effective alternative to evaluate the ecological risks of antibiotics in catchments where sufficient monitored data are unavailable.