Combination of ozonation and electrolysis process to enhance elimination of thirty structurally diverse pharmaceuticals in aqueous solution

Insight into roles of carbon anodes for removal of refractory organic contaminants in electro-peroxone system: Mechanism, performance and stability

Electro-peroxone (EP) is a novel technique for the removal of refractory organic contaminants (ROCs), while the role of anode in this system is neglected. In this work, the EP system with graphite felt anode (EP-GF) and activated carbon fiber anode (EP-ACF) was developed to enhance ibuprofen (IBP) removal. The results showed that 91.2% and 98.6% of IBP was removed within 20 min in EP-GF and EP-ACF, respectively. Hydroxy radical (O⋅H) was identified as the dominant reactive species, contributing 80.9% and 54.0% of IBP removal in EP-ACF and EP-GF systems, respectively. The roles of adsorption in EP-ACF and direct electron transfer in EP-GF cannot be ignored. Due to the differences in mechanism, EP-GF and EP-ACF systems were suitable for the removal of O⋅H-resistant ROCs (e.g., oxalic acid and pyruvic acid) and non-O⋅H-resistant ROCs (e.g., IBP and nitrobenzene), respectively. Both systems had excellent stability relying on the introduction of oxygen functional groups on the anode, and their electrolysis energy consumption was significantly lower than that of EP-Pt system. The three degradation pathways of IBP were proposed, and the toxicity of intermediates were evaluated. In general, carbon anodes have a good application prospect in the removal of ROCs in EP systems.

Electric field-enhanced heterogeneous catalytic ozonation (EHCO) process for sulfadiazine removal: The role of cathodic reduction

In this work, an electric field-enhanced heterogeneous catalytic ozonation (EHCO) was systematically investigated using a prepared FeOx/PAC catalyst. The EHCO process exhibited high sulfadiazine (SDZ) and TOC removal efficiency compared with electrocatalysis (EC) and heterogeneous catalytic ozonation (HCO) process. Almost 100% of SDZ was removed within 2 min, and the TOC removal reached approximately 85% within 60 min. Quenching experiments and EPR analysis suggested that the prominent SDZ and TOC removal performance is supported by the enhanced ·OH generation ability. Further study proved that H2O2 formed by O2 electrochemical reduction, peroxone reaction and electrochemical reduction of ozone contributed to improving ·OH generation. Furthermore, the EHCO system showed satisfactory stability and recyclability compared to conventional HCO systems, and the SDZ and TOC removal rates were maintained at ≥95% and ≥70% in 16 consecutive recycles, respectively. Meanwhile, XPS analysis and Boehm's titration for the FeOx/PAC catalyst used in HCO and EHCO process confirmed that the external electron supply could restrain the oxidation of surface functional groups of PAC and maintain a balance of the Fe(II)/Fe(III) ratio, which proved the critical role of cathode reduction in catalyst in situ regeneration during long consecutive recycles. In addition, the EHCO system could achieve more than 80% SDZ removal within 2 min in different water matrices. These results confirmed that the EHCO process has a wide application perspective for refractory organics removal in actual wastewater.

The silver lining of antibiotic resistance: Bacterial-mediated reduction of tetracycline plant stress via antibiotrophy

The reuse of water using effluents containing antibiotics from anthropogenic activities has been mainly linked to the development of antibiotic resistance. However, we report that the development of bacterial tolerance promotes plant growth. In the present study, we aimed to evaluate the efficiency of inoculation of a new antibiotic-degrading bacterium, Erwinia strain S9, in augmenting the tolerance of pea (Pisum sativum L.) plants to tetracycline (TET) (10 and 20 mg/L). Physiological parameters such as tissue elongation and biomass, as well as relative water content, were remarkably lower in plants exposed to TET than in the control. The inhibitory effects of TET were associated with reduced CO2 assimilation, stomatal conductance, transpiration, dark respiration, and light saturation point (LSP). High concentrations of TET-induced oxidative stress are attested by the overproduction of superoxide radicals (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (HO•), resulting in increased malondialdehyde content and cell death. The high activity of antioxidant enzymes such as catalase, ascorbate peroxidase, and guaiacol peroxidase validated the proposed mechanism. Under TET stress conditions, supplementation with Erwinia strain S9 was beneficial to pea plants through osmotic adjustment, increased nutrient uptake, gas exchange optimization, and increased antioxidant activities. Its presence not only ensures plant survival and growth during antibiotic stress but also degrades TET via significant antibiotrophy. This strategy is a cost-effective environmental chemical engineering tool that can be used to depollute wastewater or to improve crop resistance in rhizofiltration treatment when treated wastewater is reused for irrigation.

Multi-omic profiling of a novel activated sludge strain Sphingobacterium sp. WM1 reveals the mechanism of tetracycline biodegradation and its merits of potential application

As an emerging pollutant, the antibiotic tetracycline (TC) has been consistently detected in wastewater and activated sludge. Biodegradation represents a potentially crucial pathway to dissipate TC contamination. However, few efficient TC-degrading bacteria have been isolated and a comprehensive understanding of the molecular mechanisms underlying TC degradation is still lacking. In this study, a novel TC-degrading bacterium, designated as Sphingobacterium sp. WM1, was successfully isolated from activated sludge. Strain WM1 exhibited a remarkable performance in degrading 50 mg/L TC within 1 day under co-metabolic conditions. Genomic analysis of the strain WM1 unveiled the presence of three functional tetX genes. Unraveling the complex molecular mechanisms, transcriptome analysis highlighted the role of upregulated transmembrane transport and accelerated electron transport in facilitating TC degradation. Proteomics confirmed the up-regulation of proteins involved in cellular biosynthesis/metabolism and ribosomal processes. Crucially, the tetX gene-encoding protein showed a significant upregulation, indicating its role in TC degradation. Heterologous expression of the tetX gene resulted in TC dissipation from an initial 51.9 mg/L to 4.2 mg/L within 24 h. The degradation pathway encompassed TC hydroxylation, transforming into TP461 and subsequent metabolites, which effectively depleted TC's inhibitory activity. Notably, the tetX genes in strain WM1 showed limited potential for horizontal gene transfer. Collectively, strain WM1's potent TC degradation capacity signals a promise for enhancing TC clean-up strategies.

Antiviral drugs in wastewater are on the rise as emerging contaminants: A comprehensive review of spatiotemporal characteristics, removal technologies and environmental risks

Antiviral drugs (ATVs) are widely used to treat illnesses caused by viruses. Particularly, ATVs were consumed in such large quantities during the pandemic that high concentrations were detected in wastewater and aquatic environment. Since ATVs are not fully absorbed by the human or animal body, this results in large amounts of them being discharged into the sewage through urine or feces. Most ATVs can be degraded by microbes at wastewater treatment plants (WWTPs), while some ATVs either require deep treatment to reduce concentration and toxicity. Parent and metabolites residing in effluent posed a varying degree of risk when entering the aquatic environment, while increasing the potential of natural reservoirs for environmentally acquired antiviral drug resistance potential. There is a rising research on the behavior of ATVs in the environment has surged since the pandemic. In the context of multiple viral diseases worldwide, especially during the current COVID-19 pandemic, a comprehensive assessment of the occurrence, removal, and risk of ATVs is urgently needed. This review aims to discuss the fate of ATVs in WWTPs from various regions in the world with wastewater as the main analyzing object. The ultimate goal is to focus on ATVs with high ecological impact and regulate their use or develop advanced treatment technologies to mitigate the risk to the environment.

To promote catalytic ozonation of toluene by tuning Brönsted acid sites via introducing alkali metals into the OMS-2-SO42-/ZSM-5 catalyst

Although free hydroxyl radical (·OH) generated on OMS-2-based catalysts during the catalytic ozonation process have been shown as important reactive oxygen species (ROSs) for toluene degradation, improvement of surface ·OH formation ability remains challenging. Here, Na, K, Rb, and Cs-OMS-2-SO₄^2-/ZSM-5 catalysts were prepared, characterized and evaluated for catalytic ozonation of toluene. Both characterizations and DFT calculations showed that the appropriate alkali metal introduction made the catalyst possess with appropriate crystalline, reducibility, and acidity, which was favorable for catalytic ozonation of toluene. Characterizations also showed that alkali metal introduction resulted in water molecule adsorption on Brönsted acid sites of the catalysts, which made water molecule activation by ozone to form ·OH more easily. The introduction of K⁺ content of ∼ 5.9 wt% yielded K-OMS-2-SO₄^2-/ZSM-5 catalyst with the highest Brönsted acid sites and thus formed the most ·OH among the five prepared catalysts. As a result, the catalyst exhibited excellent toluene conversion and CO_x selectivity for catalytic ozonation of toluene at room temperature and ambient humidity. Furthermore, the catalytic activity of deactivated K-OMS-2-SO₄^2-/ZSM-5 catalyst was recovered after regeneration by a combination of water washing and heat treatment. Finally, a complete mechanism for toluene catalytic ozonation, catalyst deactivation, and regeneration was proposed.

Enrichment of tetracycline-degrading bacterial consortia: Microbial community succession and degradation characteristics and mechanism

Tetracycline (TC) is an antibiotic that is recently found as an emerging pollutant with low biodegradability. Biodegradation shows great potential for TC dissipation. In this study, two TC-degrading microbial consortia (named SL and SI) were respectively enriched from activated sludge and soil. Bacterial diversity decreased in these finally enriched consortia compared with the original microbiota. Moreover, most ARGs quantified during the acclimation process became less abundant in the finally enriched microbial consortia. Microbial compositions of the two consortia as revealed by 16 S rRNA sequencing were similar to some extent, and the dominant genera Pseudomonas, Sphingobacterium, and Achromobacter were identified as the potential TC degraders. In addition, consortia SL and SI were capable of biodegrading TC (initial 50 mg/L) by 82.92% and 86.83% within 7 days, respectively. They could retain high degradation capabilities under a wide pH range (4-10) and at moderate/high temperatures (25-40 °C). Peptone with concentrations of 4-10 g/L could serve as a desirable primary growth substrate for consortia to remove TC through co-metabolism. A total of 16 possible intermediates including a novel biodegradation product TP245 were detected during TC degradation. Peroxidase genes, tetX-like genes and the enriched genes related to aromatic compound degradation as revealed by metagenomic sequencing were likely responsible for TC biodegradation.

Changes in the catalytic activity of oxygen-doped graphitic carbon nitride for the repeated degradation of oxytetracycline

Metal-free carbonaceous catalysts have gained growing interest because of their excellence in organic pollutant degradation. However, most of them suffer from deactivation after use, and the origins have not been investigated or understood. In this study, the changes in the characteristics after multiple uses of a carbonaceous catalyst, i.e., oxygen-doped graphitic carbon nitride (O-gCN), were investigated to identify the key factors affecting its reactivity. The O-gCN was repeatedly used to remove an antibiotic (oxytetracycline, OTC) in the presence of peroxymonosulfate (PMS). OTC removal was significantly reduced as the O-gCN was repeatedly used. The reactivity of O-gCN used five times (O-gCN5) corresponded well with the decreased signals of DMPO-X, DMPO-O₂^•-, and TEMP-¹O₂ in electron paramagnetic resonance spectra. These signal changes were accompanied by a shift of the involved reactive species from ¹O₂ and OH^• for O-gCN to ¹O₂ and SO₄^•- for O-gCN5. The changes in activity and involved reactive species were attributed to the changes in the properties of O-gCN, considering the negligible OTC adsorption and slight PMS consumption. The results of X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy showed a decrease in the degree of defects, graphene-like layers, and crystallinity in graphitic structures, but an increase in the fractions of N and O, for O-gCN5. However, the OTC degradation pathways and intermediates were not significantly different for O-gCN and O-gCN5. These results provide valuable information for developing strategies for the design, practical use, and regeneration of carbonaceous catalysts.

Exploring the resourcing technology of condensate using ozonation combined with ion-exchange in ethanol fermentation

Direct reutilization of condensate can inhibit ethanol fermentation, 2-phenylethyl alcohol and furfural existed in the condensate are considered to be inhibitors. To achieve the reutilization of the condensate, the ozonation combined with ion-exchange method was used. The results showed that the elimination rates of 2-phenylethyl alcohol and furfural reached 98.0% and 100.0%, respectively after ozonation, while the concentrations of acetic acid, propionic acid, butyric acid and valeric acid increased by 14.9%, 7.7%, 35.3% and 25.5%, respectively. The fermentation results showed that the inhibition of the condensate after ozonation was alleviated but was not completely eliminated. When the effluent volume treated by the ion-exchange method reached 80 BV, the concentrations of acetic acid, propionic acid, butyric acid and valeric acid decreased by 25.8%, 8.6%, 6.5% and 34.4%, respectively. The fermentation results showed that the inhibition of the condensate was completely eliminated after ozonation combined with ion-exchange treatment.

Antiviral drugs against influenza: Treatment methods, environmental risk assessment and analytical determination

Over the past few years, antiviral drugs against influenza are considered emerging contaminants since they cause environmental toxicity even at low concentrations. They have been found in environmental matrices all around the world, showing that conventional treatment methods fail to remove them from water and wastewater. In addition, the metabolites and transformation products of these drugs can be more persistent than original in the environment. Several techniques to degrade/remove antiviral drugs against influenza have been investigated to prevent this contamination. In this study, the characteristics of antiviral drugs against influenza, their measurement by analytical methods, and their removal in both water and wastewater treatment plants (WWTPs) were presented. Different treatment methods, such as traditional procedures (biological processes, filtration, coagulation, flocculation, and sedimentation), advanced oxidation processes (AOPs), adsorption and combined methods, were assessed. Ecotoxicological effects of both the antiviral drug and its metabolites as well as the transformation products formed as a result of treatment were evaluated. In addition, future perspectives for improving the removal of antiviral drugs against influenza, their metabolites and transformation products were further discussed. The research indicated that the main tested techniques in this study were ozonation, photolysis and photocatalysis. Combined methods, particularly those that use renewable energy and waste materials, appear to be the optimum approach for the treatment of effluents containing antiviral drugs against influenza. In light of high concentrations or probable antiviral resistance, this comprehensive assessment suggests that antiviral drug monitoring is required, and some of those substances may cause toxicological effects.

Tetracycline biotransformation by a novel bacterial strain Alcaligenes sp. T17

Comprehensive knowledge on the biotransformation of tetracycline (TC) is critical for the improvement of TC removal in the bioremediation process. This work isolated a novel TC-degrading bacterial strain Alcaligenes sp. T17 and explored its degradation ability under different conditions. Temperature and pH could affect the degradation efficiency, and higher temperature as well as neutral and weakly acidic conditions were conducive to the biotransformation. Response surface methodology predicted the maximum degradation rate of TC (94.35%) under the condition of 25.15 mg/L TC, pH 7.23, and inoculation dosage 1.17% at 40 °C. According to the result of disk diffusion tests, the biodegradation products had lower antimicrobial potency than the parent compound. Five potential biodegradation products were identified, and a possible degradation pathway (degrouping, oxidation and ring-opening) was proposed. The draft genome of strain T17 was also determined. Genomic analysis indicated that strain T17 harbored multiple genes that participated in the metabolism of aromatic compounds as well as genes encoding oxygenases. These functional genes may be relevant to TC biotransformation. This study could provide new insights towards the biotransformation of TC mediated by bacteria.

Enhancement of H2O2 yield and TOC removal in electro-peroxone process by electrochemically modified graphite felt: Performance, mechanism and stability

Electro-peroxone (EP) is an emerging advanced oxidation process which combines electro-generation H₂O₂ and ozone for removing organic contaminants. In this paper, a platinum plate as anode, a method of electrochemical oxidation is adopted to modify graphite felt (GF) cathode to promote H₂O₂ yield and TOC removal from oxalic acid solution in EP process, its performance, mechanism and stability were discussed. Compared with original GF cathode, 2.6 times H₂O₂ yield can be achieved by the 5 min electrochemically modified GF (GF-5). The high electrochemical activity of the modified GF can be ascribed to introducing numerous surface oxygen-containing functional groups (OGs), which not only decreased the impedance, but also increased the amount of active site of O₂ reduction. The production of H₂O₂ with GF-5 cathode improved with the increased initial pH, cathodic potential and O₂ flow rate, while this promoting effect was not observed in GF cathode. Compared with GF cathode, TOC removal rate was improved by 21.5% with GF-5 cathode due to higher H₂O₂ yield in EP process. The primary pathway of TOC removal is electrochemically-driven peroxone process, and hydroxyl radical (·OH) is the dominant reactive species. Furthermore, GF-5 cathode had a good stability due to the protection of H₂O₂ and free electrons injected. The results indicate that the electrochemically modified GF severed as the cathode of EP processes has significant efficiency and stability in the removal of ozone-refractory organic contaminants.

Migration, Transformation and Removal of Macrolide Antibiotics in The Environment: A Review

Macrolide antibiotics (MAs), as a typical emerging pollutant, are widely detected in environmental media. When entering the environment, MAs can interfere with the growth, development and reproduction of organisms, which has attracted extensive attention. However, there are few reviews on the occurrence characteristics, migration and transformation law, ecotoxicity and related removal technologies of MAs in the environment. In this work, combined with the existing relevant research, the migration and transformation law and ecotoxicity characteristics of MAs in the environment are summarized, and the removal mechanism of MAs is clarified. Currently, most studies on MAs are based on laboratory simulation experiments, and there are few studies on the migration and transformation mechanism between multiphase states. In addition, the cost of MAs removal technology is not satisfactory. Therefore, the following suggestions are put forward for the future research direction. The migration and transformation process of MAs between multiphase states (such as soil-water-sediment) should be focused on. Apart from exploring the new treatment technology of MAs, the upgrading and coupling of existing MAs removal technologies to meet emission standards and reduce costs should also be concerned. This review provides some theoretical basis and data support for understanding the occurrence characteristics, ecotoxicity and removal mechanism of MAs.

Catalytic ozonation for degradation of sulfamethazine using NiCo2O4 as catalyst

In this study, spinel NiCo₂O₄ was prepared, characterized, and used for catalytic ozonation of SMT. The performance of NiCo₂O₄ in SMT mineralization was systematically evaluated. The results showed that NiCo₂O₄ could significantly enhance the mineralization of SMT over a wide initial pH range of 3.0-9.0. The mineralization rate of SMT increased with the increase in the dosage of NiCo₂O₄ and O₃ concentration, while the initial concentration of SMT (from 10 mg/L to 40 mg/L) had no obvious influence on the removal efficiency of TOC, indicating that the SMT mineralization was mainly affected by the mass transfer. Furthermore, according to the result of the determination of OH, NiCo₂O₄ could undoubtedly improve the generation of OH, the quenching test confirmed that OH played an important role in TOC removal in ozonation process. Moreover, the XPS spectra of as-prepared and used NiCo₂O₄ catalyst showed that Co ions might indirectly promote the catalytic ozonation process as the Lewis acid sites, while the Ni²⁺/Ni³⁺ cycle in the catalyst played a vital role in catalyzing ozone to generate free radicals and enhancing the mineralization capacity of NiCo₂O₄/O₃ system.

Occurrence, fate, and risk assessment of typical tetracycline antibiotics in the aquatic environment: A review

Tetracyclines (TCs), used as human and veterinary medicines, are the most widely used antibiotics. More than 75% of TCs are excreted in an active form and released into the environment through human and animal urine and feces, causing adverse effects on the ecological system and human health. Few articles review the environmental occurrence and behaviors of TCs, as well as their risks and toxicities. Here, we comprehensively summarized the recent advances on the following important issues: (1) Environmental occurrence of TCs. TCs are used globally and their occurrence in the aquatic environment has been documented, including surface water, groundwater, drinking water, wastewater, sediment, and sludge. (2) Environmental behaviors of TCs, particularly the fate of TCs in wastewater treatment plants (WWTPs). Most WWTPs cannot effectively remove TCs from wastewater, so alternative methods for efficient removal of TCs need to be developed. The latest degradation methods of TCs are summarized, including adsorption, photocatalytic, photochemical and electrochemical, and biological degradations. (3) Toxicities and possible risks of TCs. The toxicological data of TCs indicate that several TCs are more toxic to algae than fish and daphnia. Risk assessments based on individual compound exposure indicate that the risks arising from the current concentrations of TCs in the aquatic environment cannot be ignored.

Hybrid electrocatalytic ozonation treatment of high-salinity organic wastewater using Ni-Ce/OMC particle electrodes

Hybrid electrocatalytic ozonation is an efficient method for degrading high-salinity organic wastewater that has excellent oxidation ability and is environmentally friendly. Furthermore, the high salt content of the wastewater provides electrolyte to support the process, which avoids secondary pollution caused by the addition of electrolyte. In this work, Ni_0.2-Ce_0.2/ordered mesoporous carbon (OMC)/granular active carbon (GAC) particle electrodes with a Ni:Ce weight ratio of 1:1 were synthesized using a simple method. The electrodes were characterized by transmission electron microscopy and electron paramagnetic resonance spectroscopy, as well as other techniques. The catalytic performance was investigated using cyclic voltammetry and AC impedance. Higher reduction and oxidation peak currents were obtained with the Ni_0.2-Ce_0.2/OMC catalyst than with Ni_0.2/OMC or Ce_0.2/OMC, indicating that the bimetallic catalyst has higher activity for the reduction of O₂ to H₂O₂ and the oxidation of O₃ to ·OH. The order of the k values-which represent the mass-transfer rate-was Ni_0.2-Ce_0.2/OMC (0.157) > Ni_0.2/OMC (0.017) > Ce_0.2/OMC (0.014). The results show that cooperation between Ni, Ce, and OMC promoted the dispersion of Ni and Ce and improved the catalytic performance. Ni_0.2-Ce_0.2/OMC enhances the catalytic reduction of O₂ to H₂O₂, and, in addition, Ce is able to rapidly store and release oxygen through Ce³⁺/Ce⁴⁺ conversions and reacting with O₃ to generate ·OH, which increases the oxidation capacity of the material. Under the optimal conditions the chemical oxygen demand removal for high-salinity organic wastewater using Ni_0.2-Ce_0.2/OMC/GAC particle electrodes reached 93.7%.