Application of Bimetallic Hydroxide/Graphene Composites in Wastewater Treatment.

The increasing discharge of antibiotic wastewater leads to increasing water pollution. Most of these antibiotic wastewaters are persistent, strongly carcinogenic, easy to bioaccumulate, and have other similar characteristics, seriously jeopardizing human health and the ecological environment. As a commonly used wastewater treatment technology, non-homogeneous electro-Fenton technology avoids the hazards of H2O2 storage and transportation as well as the loss of desorption and reabsorption. It also facilitates electron transfer on the electrodes and the reduction of Fe3+ on the catalysts, thereby reducing sludge production. However, the low selectivity and poor activity of electro-synthesized H2O2, along with the low concentration of its products, combined with the insufficient activity of electrically activated H2O2, results in a low ∙OH yield. To address the above problems, composites of layered bimetallic hydroxides and carbon materials were designed and prepared in this paper to enhance the performance of electro-synthesized H2O2 and non-homogeneous electro-Fenton by changing the composite mode of the materials. Three composites, NiFe layered double hydroxides (LDHs)/reduced graphene oxide (rGO), NiMn LDHs/rGO, and NiMnFe LDHs/rGO, were constructed by the electrostatic self-assembly of exfoliated LDHs with few-layer graphene. The LDHs/rGO was loaded on carbon mats to construct the electro-Fenton cathode materials, and the non-homogeneous electro-Fenton oxidative degradation of organic pollutants was realized by the in situ electrocatalytic reduction of O2 to ∙OH. Meanwhile, the effects of solution pH, applied voltage, and initial concentration on the performance of non-homogeneous electro-Fenton were investigated with ceftazidime as the target pollutant, which proved that the cathode materials have an excellent electro-Fenton degradation effect.

Efficient electrochemical oxidation of antibiotic wastewater using a graphene-loaded PbO2 membrane anode: Mechanisms and applications.

This paper aims to develop a flow-through electrochemical system with a series of graphene nanoparticles loaded PbO2 reactive electrochemical membrane electrodes (GNPs-PbO2 REMs) on porous Ti substrates with pore sizes of 100, 150, 300 and 600 µm, and apply them to treat antibiotic wastewater. Among them, the GNPs-PbO2 with Ti substrate of 150 µm (Ti-150/GNPs-PbO2) had superior electrochemical degradation performance over the REMs with other pore sizes due to its smaller crystal size, larger electrochemical active specific area, lower charge-transfer impedance and larger oxygen evolution potential. Under the relatively optimized conditions of initial pH of 5, current density of 15 mA cm-2, and membrane flux of 4.20 m3 (m2·h)-1, the Ti-150/GNPs-PbO2 REM realized 99.34% of benzylpenicillin sodium (PNG) removal with an EE/O of 6.52 kWh m-3. Its excellent performance could be explained as the increased mass transfer. Then three plausible PNG degradation pathways in the flow-through electrochemical system were proposed, and great stability and safety of Ti-150/GNPs-PbO2 REM were demonstrated. Moreover, a single-pass Ti-150/GNPs-PbO2 REM system with five-modules in series was designed, which could consistently treat real antibiotic wastewater in compliance with disposal requirements of China. Thus, this study evidenced that the flow-through electrochemical system with the Ti-150/GNPs-PbO2 REM is an efficient alternative for treating antibiotic wastewater.

Synthesis of copper/carbon nanofibers by electrostatic spinning toward persulfate activation for treatment of antibiotic wastewater.

Antibiotics in water will cause serious harm to human health and ecosystem. Carbon-based materials and transition metals activated peroxodisulfate (PDS) to produce active species, which can degrade residual antibiotics in water. In this paper, Cu/CNF (carbon nanofibers) composites were first prepared by introducing Cu into CNF using electrostatic spinning technology, which was used to activate PDS to degrade tetracycline (TC). The degradation efficiency of Cu/CNF/PDS was 36.23% higher than that of CNF/PDS. The reason is that introducing Cu can increase the number of surface functional groups and specific surface area of CNF, and then improve the catalytic performance. The functional groups and Cu species are the active sites for catalytic PDS. Moreover, the main ways to degrade TC in the Cu/CNF/PDS system are singlet oxygen (1O2) and electron transfer. Based on the above analysis, we modified CNF with transition metal salts, prepared efficient environmental functional materials, and used them for PDS activation, providing a theoretical basis and technical support for the degradation of antibiotic pollutants and creating new ideas for other research.

Novel combination of iron-carbon composite and Fenton oxidation processes for high-concentration antibiotic wastewater treatment.

The research presented herein explores the development of a novel iron-carbon composite, designed specifically for the improved treatment of high-concentration antibiotic wastewater. Employing a nitrogen-shielded thermal calcination approach, the investigation utilizes a blend of reductive iron powder, activated carbon, bentonite, copper powder, manganese dioxide, and ferric oxide to formulate an efficient iron-carbon composite. The oxygen exclusion process in iron-carbon particles results in distinctive electrochemical cells formation, markedly enhancing wastewater degradation efficiency. Iron-carbon micro-electrolysis not only boosts the biochemical degradability of concentrated antibiotic wastewater but also mitigates acute biological toxicity. In response to the increased Fe2+ levels found in micro-electrolysis wastewater, this research incorporates Fenton oxidation for advanced treatment of the micro-electrolysis byproducts. Through the synergistic application of iron-carbon micro-electrolysis and Fenton oxidation, this research accomplishes a significant decrease in the initial COD levels of high-concentration antibiotic wastewater, reducing them from 90,000 mg/L to about 30,000 mg/L, thus achieving an impressive removal efficiency of 66.9%. This integrated methodology effectively reduces the pollutant load, and the recycling of Fe2+ in the Fenton process additionally contributes to the reduction in both the volume and cost associated with solid waste treatment. This research underscores the considerable potential of the iron-carbon composite material in efficiently managing high-concentration antibiotic wastewater, thereby making a notable contribution to the field of environmental science.

A combined evaluation of the characteristics and antibiotic resistance induction potential of antibiotic wastewater during the treatment process.

Antibiotic wastewater contains a variety of pollutant stressors that can induce and promote antibiotic resistance (AR) when released into the environment. Although these substances are mostly in concentrations lower than those known to induce AR individually, it is possible that antibiotic wastewater discharge might still promote the AR transmission risk via additive or synergistic effects. However, the comprehensive effect of antibiotic wastewater on AR development has rarely been evaluated, and its treatment efficiency remains unknown. Here, samples were collected from different stages of a cephalosporin production wastewater treatment plant, and the potential AR induction effect of their chemical mixtures was explored through the exposure of the antibiotic-sensitive Escherichia coli K12 strain. Incubation with raw cephalosporin production wastewater significantly promoted mutation rates (3.6 × 103-9.3 × 103-fold) and minimum inhibition concentrations (6.0-6.7-fold) of E. coli against ampicillin and chloramphenicol. This may be attributed to the inhibition effect and oxidative stress of cephalosporin wastewater on E. coli. The AR induction effect of cephalosporin wastewater decreased after the coagulation sedimentation treatment and was completely removed after the full treatment process. A Pearson correlation analysis revealed that the reduction in the AR induction effect had a strong positive correlation with the removal of organics and biological toxicity. This indicates that the antibiotic wastewater treatment had a collaborative processing effect of conventional pollutants, toxicity, and the AR induction effect. This study illustrates the potential AR transmission risk of antibiotic wastewater and highlights the need for its adequate treatment.

Vacancy-Rich CoSx@LDH@Co-NC Catalytic Membrane for Antibiotic Degradation with Mechanistic Insights.

Improving the wettability of carbon-based catalysts and overcoming the rate-limiting step of the Mn+1/Mn+ cycle are effective strategies for activating peroxymonosulfate (PMS). In this study, the coupling of Co-NC, layered double hydroxide (LDH), and CoSx heterostructure (CoSx@LDH@Co-NC) was constructed to completely degrade ofloxacin (OFX) within 10 min via PMS activation. The reaction rate of 1.07 min-1 is about 1-2 orders of magnitude higher than other catalysts. The interfacial effect of confined Co-NC and layered double hydroxide (LDH) not only enhanced the wettability of catalysts but also increased the vacancy concentration; it facilitated easier contact with the interface reactive oxygen species (ROS). Simultaneously, reduced sulfur species (CoSx) accelerated the Co3+/Co2+ cycle, acquiring long-term catalytic activity. The catalytic mechanism revealed that the synergistic effect of hydroxyl groups and reduced sulfur species promoted the formation of 1O2, with a longer lifespan and a longer migration distance, and resisted the influence of nontarget background substances. Moreover, considering the convenience of practical application, the CoSx@LDH@Co-NC-based catalytic membrane was prepared, which had zero discharge of OFX and no decay in continuous operation for 5.0 h. The activity of the catalytic membrane was also verified in actual wastewater. Consequently, this work not only provides a novel strategy for designing excellent catalysts but also is applicable to practical organic wastewater treatment.

Three-dimensional graphene aerogel mitigated the toxic impact of chloramphenicol wastewater on microorganisms in an EGSB reactor.

Anaerobic treatment of chloramphenicol wastewater holds significant promise due to its potential for bioenergy generation. However, the high concentration of organic matter and residual toxic substances in the wastewater severely inhibit the activity of microorganisms. In this study, a three-dimensional graphene aerogel (GA), as a conductive material with high specific surface area (114.942 m2 g-1) and pore volume (0.352 cm3 g-1), was synthesized and its role in the efficiency and related mechanism for EGSB reactor to treat chloramphenicol wastewater was verified. The results indicated that synergy effects of GA for Chemical Oxygen Demand (COD) removal (increased by 8.17 %), chloramphenicol (CAP) removal (increased by 4.43 %) and methane production (increased by 70.29 %). Furthermore, GA increased the average particle size of anaerobic granular sludge (AGS) and promoted AGS to secrete more redox active substances. Microbial community analysis revealed that GA increased the relative abundance of functional bacteria and archaea, specifically Syntrophomonas, Geobacter, Methanothrix, and Methanolinea. These microbial species can participate in direct interspecific electron transfer (DIET). This research serves as a theoretical foundation for the application of GA in mitigating the toxic impact of refractory organic substances, such as antibiotics, on microorganisms during anaerobic treatment processes.

Attenuation effects of ZVI/PDS pretreatment on propagation of antibiotic resistance genes in bioreactors: Driven by antibiotic residues and sulfate assimilation.

Sulfate radical-based advanced oxidation processes (AOPs) combined biological system was a promising technology for treating antibiotic wastewater. However, how pretreatment influence antibiotic resistance genes (ARGs) propagation remains largely elusive, especially the produced by-products (antibiotic residues and sulfate) are often ignored. Herein, we investigated the effects of zero valent iron/persulfate pretreatment on ARGs in bioreactors treating sulfadiazine wastewater. Results showed absolute and relative abundance of ARGs reduced by 59.8%- 81.9% and 9.1%- 52.9% after pretreatments. The effect of 90-min pretreatment was better than that of the 30-min. The ARGs reduction was due to decreased antibiotic residues and stimulated sulfate assimilation. Reduced antibiotic residues was a major factor in ARGs attenuation, which could suppress oxidative stress, inhibit mobile genetic elements emergence and resistant strains proliferation. The presence of sulfate in influent supplemented microbial sulfur sources and facilitated the in-situ synthesis of antioxidant cysteine through sulfate assimilation, which drove ARGs attenuation by alleviating oxidative stress. This is the first detailed analysis about the regulatory mechanism of how sulfate radical-based AOPs mediate in ARGs attenuation, which is expected to provide theoretical basis for solving concerns about by-products and developing practical methods to hinder ARGs propagation.

Simultaneous removal of antibiotics and nitrogen by microbial fuel cell-constructed wetlands: Microbial response and carbon-nitrogen metabolism pathways.

Microbial fuel cell-constructed wetlands (MFC-CWs) are attracted extensive attention due to their simultaneous removal performance during the co-occurrence of various pollutants in wastewater. This study explored the performance and mechanisms on the simultaneous removal of antibiotics and nitrogen from MFC-CWs which packed with coke (MFC-CW (C)) and quartz sand (MFC-CW (Q)) substrate. Results showed that removal of sulfamethoxazole (93.60 %), COD (77.94 %), NH4+-N (79.89 %), NO3-- N (82.67 %), and TN (70.29 %) significantly enhanced by MFC-CW (C) due to the enhancement of relative abundance of membrane transport, amino acid metabolism and carbohydrate metabolism pathways. The results indicated that coke substrate can generate more electric energy in MFC-CW. Firmicutes (18.56-30.82 %), Proteobacteria (23.33-45.76 %), and Bacteroidetes (17.1-27.85 %) were dominant phyla in the MFC-CWs. MFC-CW (C) posed significant effects on the microbial diversity and structure, which motivated the functional microbes involved in the transformation of antibiotics and nitrogen and bioelectricity generation. Given the overall performance of MFC-CW, packing with cost-effective substrate to electrode region of MFC-CWs was found to be an effective strategy for simultaneously removing antibiotics and nitrogen in the wastewater treatment.

A review on three-dimensional electrochemical technology for the antibiotic wastewater treatment.

The potential genotoxicity and non-biodegradability of antibiotics in the natural water bodies threaten the survival of various living things and cause serious environmental pollution and destruction. Three-dimensional (3D) electrochemical technology is considered a powerful means for antibiotic wastewater treatment as it can degrade non-biodegradable organic substances into non-toxic or harmless substances and even completely mineralize them under the action of electric current. Therefore, antibiotic wastewater treatment using 3D electrochemical technology has now become a hot research topic. Thus, in this review, a detailed and comprehensive investigation was conducted on the antibiotic wastewater treatment using 3D electrochemical technology, including the structure of the reactor, electrode materials, the influence of operating parameters, reaction mechanism, and combination with other technologies. Many studies have shown that the materials of electrode, especially particle electrode, have a great effect on the antibiotic wastewater treatment efficiency. The influence of operating parameters such as cell voltage, solution pH, and electrolyte concentration was very significant. Combination with other technologies such as membrane and biological technologies has effectively increased antibiotic removal and mineralization efficiency. In conclusion, the 3D electrochemical technology is considered as a promising technology for the antibiotic wastewater treatment. Finally, the possible research directions of the 3D electrochemical technology for antibiotic wastewater treatment were proposed.

Enhanced degradation of oxytetracycline in aqueous solution by DBD plasma-coupled vacuum ultraviolet/ultraviolet (VUV/UVC) system.

A systematic investigation of coupling dielectric barrier discharge (DBD) plasma and different ultraviolet bands (UVA, UVB, UVC, and VUV) was constructed for antibiotic-contaminant wastewater treatment. Compared with DBD, UV, or other combined DBD/UV systems, the DBD/VUV/UVC system exhibited excellent degradation and mineralization efficiencies for oxytetracycline (OTC), achieving 93.2% removal rate (reaction rate constant 1.05 min-1) and higher decarbonization efficiency (mineralization rate 0.47 mg C min-1) within 2.5 min treatment. The radical quenching tests revealed that HO⋅, O2·-, and 1O2 were all involved in the decomposition of OTC in the DBD/VUV/UVC system, among which O2·- played a dominant role. Possible degradation pathways of OTC in the DBD/VUV/UVC process were proposed using density functional theory and detected intermediates. Four indexes were used to assess the toxicity of OTC and its degraded intermediates. The inorganic anions and HA slightly reduced the degradation efficiency of the DBD/VUV/UVC system. This research provides new ideas to broaden the application of plasma and alleviate the water environment crisis.

Algae-mediated antibiotic wastewater treatment: A critical review.

The existence of continually increasing concentrations of antibiotics in the environment is a serious potential hazard due to their toxicity and persistence. Unfortunately, conventional treatment techniques, such as those utilized in wastewater treatment plants, are not efficient for the treatment of wastewater containing antibiotic. Recently, algae-based technologies have been found to be a sustainable and promising technique for antibiotic removal. Therefore, this review aims to provide a critical summary of algae-based technologies and their important role in antibiotic wastewater treatment. Algal removal mechanisms including bioadsorption, bioaccumulation, and biodegradation are discussed in detail, with using algae-bacteria consortia for antibiotic treatment, integration of algae with other microorganisms (fungi and multiple algal species), hybrid algae-based treatment and constructed wetlands, and the factors affecting algal antibiotic degradation comprehensively described and assessed. In addition, the use of algae as a precursor for the production of biochar is highlighted, along with the modification of biochar with other materials to improve its antibiotic removal capacity and hybrid algae-based treatment with advanced oxidation processes. Furthermore, recent novel approaches for enhancing antibiotic removal, such as the use of genetic engineering to enhance the antibiotic degradation capacity of algae and the integration of algal antibiotic removal with bioelectrochemical systems are discussed. Finally, some based on the critical review, key future research perspectives are proposed. Overall, this review systematically presents the current progress in algae-mediated antibiotic removal technologies, providing some novel insights for improved alleviation of antibiotic pollution in aquatic environments.

Insights into the fate of antibiotics in constructed wetland systems: Removal performance and mechanisms.

Antibiotics have been recognized as emerging contaminants that are widely distributed and accumulated in aquatic environment, posing a risk to ecosystem at trace level. Constructed wetlands (CWs) have been regarded as a sustainable and cost-effective alternative for efficient elimination of antibiotics. This review summarizes the removal of 5 categories of widely used antibiotics in CWs, and discusses the roles of the key components in CW system, i.e., substrate, macrophytes, and microorganisms, in removing antibiotics. Overall, the vertical subsurface flow CWs have proven to perform better in terms of antibiotic removal (>78%) compared to other single CWs. The adsorption behavior of antibiotics in wetland substrates is determined by the physicochemical properties of antibiotics, substrate configuration and operating parameters. The effects of wetland plants on antibiotic removal mainly include direct (e.g., plant uptake and degradation) and indirect (e.g., rhizosphere processes) manners. The possible interactions between microorganisms and antibiotics include biosorption, bioaccumulation and biodegradation. The potential strategies for further enhancement of the antibiotic removal performance in CWs included optimizing operation parameters, innovating substrate, strengthening microbial activity, and integrating with other treatment technologies. Taken together, this review provides useful information for facilitating the development of feasible, innovative and intensive antibiotic removal technologies in CWs, as well as enhancing the economic viability and ecological sustainability.

Novel heterostructured metal doped MgFe2O4@g-C3N4 nanocomposites with superior photo-Fenton preformance for antibiotics removal: One-step synthesis and synergistic mechanism.

A novel metal doped MgFe2O4@g-C3N4 (m-MF@CN) nanocomposite was synthesized by one-pot method using saprolite laterite nickel ore and urea as raw materials. The heterostructure was verified as an effective heterogeneous Fenton-like catalyst for degrading antibiotics including tetracycline, oxytetracycline and chlortetracycline hydrochloride, and the related catalytic mechanism was elaborated in detail. Under the optimum conditions, the m-MF@CN/H2O2/vis system exhibited superior photo-Fenton property (degradation efficiency of 93.15% within 30 min, TOC removal efficiency was as high as 60.54% within 120 min) and cycle stability for tetracycline removal. The combination of MgFe2O4 and g-C3N4 enhanced the absorption of visible light, and the energy level matched heterojunction promoted the separation of photogenerated electron-holes to accelerate the redox cycle of ≡Fe3+/≡Fe2+. Free radical quenching and electron spin resonance (ESR) analysis confirmed that O2- was the main active species, h+ and OH also played a synergistic role in the degrading reactions. Notably, a possible degradation pathway of tetracycline was proposed according to the intermediates produced in the reaction process. The one-step synthesized m-MF@CN nanocomposite catalysts possessed high catalytic performance, good stability and recoverability, which not only realized the high-value utilization of ore raw materials, but also provided a potential practical way for efficient treatment of antibiotic wastewater.

Dissecting the roles of conductive materials in attenuating antibiotic resistance genes: Evolution of physiological features and bacterial community.

Supplying conductive materials (CMs) into anaerobic bioreactors is considered as a promising technology for antibiotic wastewater treatment. However, whether and how CMs influence antibiotic resistance genes (ARGs) spread remains poorly known. Here, we investigated the effects of three CMs, i.e., magnetite, activated carbon (AC), and zero valent iron (ZVI), on ARGs dissemination during treating sulfamethoxazole wastewater, by dissecting the shifts of physiological features and microbial community. With the addition of magnetite, AC, and ZVI, the SMX removal was improved from 49.05 to 71.56-92.27 %, while the absolute abundance of ARGs reducing by 26.48 %, 61.95 %, 48.45 %, respectively. The reduced mobile genetic elements and antibiotic resistant bacteria suggested the inhibition of horizontal and vertical transfer of ARGs. The physiological features, including oxidative stress response, quorum sensing, and secretion system may regulate horizontal transfer of ARGs. The addition of all CMs relieved oxidative stress compared with no CMs, but ZVI may cause additional free radicals that needs to be concerned. Further, ZVI and AC also interfered with cell communication and secretion system. This research deepens the insights about the underlying mechanisms of CMs in regulating ARGs, and is expected to propose practical ways for mitigating ARGs proliferation.

Degradation of pefloxacin by hybrid hydrodynamic cavitation with H2O2 and O3.

The degradation of toxic chemicals, antibiotics and other residues in organic wastewater has attracted much attention. Among various degradation technologies, hydrodynamic cavitation (HC) reactors have the advantage of being simple to operate. Through the combination of HC and other oxidants, the removal efficiency and energy efficiency of organic matter can be greatly improved, and the consumption of chemicals and the processing costs can be reduced. In this work, HC technology combined with oxidants was used to degrade pefloxacin (PEF), and the effect of different operating conditions on PEF degradation was investigated. The results indicated that the removal efficiency of PEF treated with HC alone was 84.9% under the optimal HC conditions of pH 3.3 and 120 min, which is much higher than that (35.5%) of pH 5.3. When co-treating the PEF solution with HC and H2O2 at 0.3 MPa and pH 5.3, the optimal molar ratio of PEF to H2O2 was 1:5, the highest PEF removal efficiency was 69.7%, and the synergy index (SI) was 4.4. When combining HC with O3, the PEF removal efficiency gradually elevated with increasing ozone addition. When the addition amount of ozone was 0.675 g/h, the removal efficiency of PEF was the highest, which was 91.5% after treatment of 20 min. The intermediate products in the reaction process were analyzed based on UV-Vis spectroscopy and LC-MS, and the mechanism and reaction pathways of PEF were proposed.

A microbubble-assisted rotary tubular titanium cathode for boosting Fenton's reagents in the electro-Fenton process.

To improve cathodic H2O2 accumulation and Fe3+ reduction synchronously in the electro-Fenton (EF) process, a microbubble-assisted rotary tubular titanium cathode (MRTTC) was designed for the first time. By utilizing this MRTTC, H2O2 accumulation improved by 4.05-fold, along with a 200% enhancement in iron reduction compared to the conventional EF process. This promotion is mainly attributed to a considerably higher oxygen mass transfer, which reduces the thickness of the adhered diffusion layer. The oxygen mass transfer coefficient (KLa) also improved from 0.0073 s-1 to 0.012 s-1 at a rotational speed of 300 rpm. In addition, the microbubble-assisted cathode further improved the KLa to 0.047 s-1. The synergistic effect between the rotating and microbubble-assisted cathodes further intensified H2O2 accumulation in MRTTC. Apart from H2O2 promotion, the iron reduction rate was elevated because the newly formed O2-• provided an additional reduction pathway for Fe3+ reduction in addition to the cathodic path. The effectiveness of MRTTC was confirmed by treating a benchmark organic pollutant, sulfamerazine (SMR), where approximately 100% SMR decay was obtained in 3 h. The results show that MRTTC is a novel and promising design in EF for antibiotic wastewater treatment.

The effect of bacterial functional characteristics on the spread of antibiotic resistance genes in Expanded Granular Sludge Bed reactor treating the antibiotic wastewater.

To explore the fate and spreading mechanism of antibiotics resistance genes (ARGs) in antibiotics wastewater system, a laboratory-scale (1.47 L) Expanded Granular Sludge Bed (EGSB) bioreactor was implemented. The operating parameters temperature (T) and hydraulic retention time (HRT) were mainly considered. This result showed the removal of ARGs and COD was asynchronous, and the recovery speed of ARGs removal was slower than that COD removal. The decreasing T was attributed to the high growth rate of ARGs host bacteria, while the shortened HRT could promote the horizontal and vertical gene transfer of ARGs in the sludge. The analysis result of potential bacterial host showed more than half of the potential host bacteria carried 2 or more ARGs and suggested an indirect mechanism of co-selection of multiple ARGs. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to investigate the functional characteristics of bacterial community. This result showed the bacterial functional genes contributed 40.41% to the abundance change of ARGs in the sludge, which was higher that of bacterial community. And the function genes of "aromatic hydrocarbon degradation", "Replication, recombination and repair proteins" and "Flagellar assembly" were mainly correlated with the transfer of ARGs in the sludge. This study further revealed the mechanism of ARGs spread in the EGSB system, which would provide new ideas for the development of ARGs reduction technology.

Fabrication of a permeable SnO2-Sb reactive anodic filter for high-efficiency electrochemical oxidation of antibiotics in wastewater.

Electrochemical oxidation (ECO) is an appealing technology for treating emerging organic pollutants in wastewater. However, the conventional flow-by ECO process is expensive with a low energy efficiency owing to the limitations of mass transport of contaminants to the limited surface area of the anode. In this study, a novel freestanding porous and permeable SnO2-Sb anode was fabricated by one-step sintering using micrometer-sized (NH4)2CO3 grains as the pore-forming agents. This permeable SnO2-Sb anode without Ti substrate functioned as a reactive anodic filter (RAF) in an ECO cell to treat wastewater containing ciprofloxacin (CIP). Forcing the wastewater through the porous RAF depth-wise improved the mass transport and vastly enlarged the electroactive surface area. Compared with the conventional flow-by configuration, the flow-through RAF exhibited a 12-fold increase in the mass transfer rate constant (60.7 × 10-6 m s-1) and a 5-fold increase in the CIP degradation rate constant (0.077 min-1). At a cell potential of 4.0 V, more than 92% of the CIP was degraded in a single-pass operation at a filtration flux of 54 L m-2 h-1 and a short retention time of 1.7 min through the RAF. The robustness and stability of the RAF were demonstrated by its remarkable CIP degradation efficacy of 99% during 200 h of operation. The mechanism of CIP degradation was examined using probe molecules and density functional theory calculations and found to be a combined effect of direct electron transfer and oxidation by generated radicals (OH and SO4-). The great potential of RAF in flow-through ECO was further validated by its effective removal (>92%) of various organic pollutants in actual municipal wastewater at a low energy consumption of 0.33 kWh m-3. The RAF-based ECO process thus provides an advanced environmental technology for the oxidation of toxic and recalcitrant organic pollutants in wastewater treatment.

Treatment of pharmaceutical wastewater by ionizing radiation: Removal of antibiotics, antimicrobial resistance genes and antimicrobial activity.

In present study, the treatment of real pharmaceutical wastewater from an erythromycin (ERY) production factory by gamma irradiation was investigated. Results showed that a variety of antimicrobial resistance genes (ARGs), involving MLSB, tet, bla, multidrug, sul, MGEs and van genes and plentiful 9 bacterial phyla were identified in the raw wastewater. In addition to ERY, sulfamethoxazole (SMX) and tetracycline (TC) were also identified with the concentration of 3 order of magnitude lower than ERY. Results showed that the abatement of ARGs and antibiotics was much higher than that of antimicrobial activity and COD. With the absorbed dose of 50 kGy, the removal percentage of ARGs, ERY, antimicrobial activity and COD was 96.5-99.8%, 90.0%, 47.8% and 10.3%, respectively. The culturable bacteria were abated fast and completely at 5.0 kGy during gamma irradiation. The genus Pseudomonas was predominant in raw wastewater (56.7%) and its relative abundance decreased after gamma irradiation, to 1.3% at 50 kGy. With addition of peroxymonosulfate (PMS, 50 mM), the antimicrobial activity disappeared completely and ERY removal reached as high as 99.2% at the lower absorbed dose of 25 kGy. Ionizing radiation-coupled technique is a potential option to treat pharmaceutical wastewater for reduction of antibiotics, ARGs and antimicrobial activity.