Influence of sulfamethoxazole on anaerobic digestion: Methanogenesis, degradation mechanism and toxicity evolution

Mechanism of biochar in alleviating the inhibition of anaerobic digestion under ciprofloxacin press

The antibiotic ciprofloxacin (CIP), detected in various aqueous environments, has broad-spectrum antimicrobial properties that can severely affect methanogenic performance in anaerobic systems. In this study, a novel strategy to alleviate the inhibition of AD performance under CIP press with the direct addition of biochar (BC) prepared from corn stover was proposed and the corresponding alleviation mechanism was investigated. When the dosage of BC was 5 and 20 g/L, the cumulative methane production in AD could reach 317.9 and 303.0 mL/g COD, and the CIP degradation efficiencies reached 94.1 % and 96.6 %, significantly higher than those of 123.0 mL/g COD and 81.2 % in the Control system. BC avoided excessive reactive oxygen species in anaerobic systems and induced severe oxidative stress response, while protecting the cell membrane and cell wall of microorganisms. Microorganisms could consume and utilize more organic extracellular polymeric substances for their growth and metabolism. When BC was involved in AD, fewer toxic intermediates were generated during CIP biodegradation, reducing acute and chronic toxicity in anaerobic systems. Microbial diversity suggested that BC could enrich functional microorganisms involved in direct interspecies electron transfer like Methanosaeta, norank_f_Bacteroidetes_vadinHA17, JGI-0000079-D21 and Syntrophomonas, thus facilitating the methanogenic process and CIP degradation. Genetic analyses showed that BC could effectively upregulate functional genes related to the conversion of butyrate-to-acetate and acetyl-to-methane under CIP stress, while functional gene abundance associated with CIP degradation enhanced partially, about encoding translocases, oxidoreductases, lyases, and ligases. Therefore, BC can be added to AD under CIP press to address its inhibited methanogenic performance.

Enhanced activity of mixed-culture electroactive biofilms and sulfamethoxazole removal efficiency by adding N-acyl-homoserine lactones in bio-electrochemical system

The addition of exogenous quorum sensing signaling molecules significantly enhanced the degradation efficiency of antibiotics, such as chloramphenicol in bio-electrochemical systems (BESs). However, the effects and mechanisms by which AHLs addition in BES facilitated the removal of sulfamethoxazole (SMX) remained inadequately explored. This study systematically compared the electrochemical performance and SMX removal efficiency in BES under two conditions: with and without the addition of N-acyl-homoserine lactones (AHLs) signaling molecules. In comparison to the control group, the AHL-treated group exhibited an increase in maximum output voltage from 340 to 489.67 mV, alongside a notable enhancement in SMX removal efficiency over 120 h ranging from 14.65% to 15.76%. Analyses of the live and dead cells and extracellular polymeric substances (EPS) composition revealed that following AHLs addition, both the ratio of live to dead cells and protein content within EPS increased by 12.66% and 74.37%, respectively. Furthermore, microbial community structure analysis indicated that after AHLs supplementation, there was a marked increase in the abundance of electroactive microorganisms as well as antibiotic-degrading and nitrogen-removing bacteria. Notably, Klebsiella - characterised by its electroactivity along with antibiotic degradation and nitrogen removal capabilities - exhibited a relative abundance reaching 56.84% in AHL, reflecting an increase of 28.31% compared to Blank; additionally, electroactive bacteria Dysgonomonas showed a relative abundance rise of 2.49%. Collectively, these findings suggested that enhancements in SMX removal efficiency upon AHLs addition were primarily driven by improvements in electrochemical performance coupled with alterations in microbial community structure.

Aquatic plants combined with microbial fuel cells promote sulfamethoxazole and sul genes removal from aquaculture pond sediments via bioelectrochemistry

Antibiotics and antibiotic resistance genes (ARGs) in the aquaculture environment are receiving increasing public attention as emerging contaminants. In this study, aquatic plant (P) and sediment microbial fuel cells (SMFC) were used individually and in combination (P-SMFC) to simulate in situ remediation of sulfamethoxazole (SMX) and sul genes in aquaculture environments. The results showed that the average power densities of SMFC and P-SMFC were 622.18 mW m-2 and 565.99 mW m-2, respectively. The addition of 5 mg kg-1 of SMX to the sediment boosted the voltages of SMFC and P-SMFC by 36.3% and 51.5%, respectively. After 20 days of treatment, the removal efficiency of SMX from the sediment was 86.17% and 89.60% for SMFC and P-SMFC group, respectively, which were significantly higher than the control group (P < 0.05). However, removal of SMX by plants was not observed. P-SMFC group significantly reduced the biotoxicity of SMX to Staphylococcus aureus and Escherichia coli in the overlying water (P < 0.05). P and P-SMFC groups significantly reduced the abundance of ARGs intl1 and sul1 (P < 0.05). The removal rate of ARGs intl1, sul1 and sul2 from sediments by P-SMFC ranged from 94.22% to 97.08%. However, SMFC increased the abundance of sul3. SMFC and P-SMFC increased the relative abundance of some of sulfate-reducing bacteria such as Desulfatiglans, Thermodesulfovibrionia and Sva0485 in sediments. These results showed that aquatic plants promoted the removal of ARGs and SMFC promoted the removal of antibiotics, and the combination with aquatic plants and SMFC achieved a synergistic removal of both SMX and ARGs. Therefore, current study provides a promising approach for the in situ removal of antibiotics and ARGs in the aquaculture environment.

Effect, Fate and Remediation of Pharmaceuticals and Personal Care Products (PPCPs) during Anaerobic Sludge Treatment: A Review

Biomass energy recovery from sewage sludge through anaerobic treatment is vital for environmental sustainability and a circular economy. However, large amounts of pharmaceutical and personal care products (PPCPs) remain in sludge, and their interactions with microbes and enzymes would affect resource recovery. This article reviews the effects and mechanisms of PPCPs on anaerobic sludge treatment. Most PPCPs posed adverse impacts on methane production, while certain low-toxicity PPCPs could stimulate volatile fatty acids and biohydrogen accumulation. Changes in the microbial community structure and functional enzyme bioactivities were also summarized with PPCPs exposure. Notably, PPCPs such as carbamazepine could bind with the active sites of the enzyme and induce microbial stress responses. The fate of various PPCPs during anaerobic sludge treatment indicated that PPCPs featuring electron-donating groups (e.g., ·-NH2 and ·-OH), hydrophilicity, and low molecular weight were more susceptible to microbial utilization. Key biodegrading enzymes (e.g., cytochrome P450 and amidase) were crucial for PPCP degradation, although several PPCPs remain refractory to biotransformation. Therefore, remediation technologies including physical pretreatment, chemicals, bioaugmentation, and their combinations for enhancing PPCPs degradation were outlined. Among these strategies, advanced oxidation processes and combined strategies effectively removed complex and refractory PPCPs mainly by generating free radicals, providing recommendations for improving sludge detoxification.

Effects of hydrothermal pretreatment on sulfadiazine degradation during two-stage anaerobic digestion of pig manure

Antibiotics in animal manure pose significant risks to the environment and health. While anaerobic digestion (AD) is commonly used for pig manure treatment, its efficiency in antibiotic removal has been considerably limited. This study investigated the impact of hydrothermal pretreatment (HTP) on sulfadiazine (SDZ) removal in a two-stage AD system. Results indicated that the HTP process reduced SDZ concentration by 40.61%. Furthermore, the SDZ removal efficiency of the AD system coupling HTP increased from 50.90% to 65.04% compared to the untreated system. Biogas yield was also improved by 26.17% while maintaining system stability. Changes induced by HTP in the microbial communities revealed that Firmicutes, Bacteroidetes, Caldatribacteriota, and Proteobacteria emerged as the primary bacterial phyla. Following HTP, the relative abundance of Prevotella, which exhibited a strong negative correlation with SDZ concentration, increased significantly by 25-fold in the acidogenic stage. Proteiniphilum, Syntrophomonas and Sedimentibacter showed notable increases in the methanogenic stage after HTP. The N-heterocyclic metabolism carried out by Prevotella might have been the predominant SDZ degradation pathway in the acidogenic stage, while the benzene ring metabolism and hydroxylation by the Proteiniphilum emerged as the primary degradation pathways in the methanogenic stages. Furthermore, biodegradation intermediates were proven to be less toxic than SDZ itself, indicating that the HTP-enhanced two-stage AD process could be a viable way to lower the environmental risks associated with SDZ. The findings from this study provide valuable insights for removing SDZ from the environment via two-stage AD.

Deciphering the adaptation mechanism of anammox consortia under sulfamethoxazole stress: A model coupling resistance accumulation and interspecies-cooperation

Sulfamethoxazole (SMX) is frequently detected in wastewater where anammox applications are promising. While it has been demonstrated that anammox consortia can adapt to SMX stress, the underlying community adaptation strategy has not yet been fully addressed. Therefore, in this study, we initially ascertained anammox consortia's ability to co-metabolize SMX in batch tests. Then, a 200-day domestication process of anammox consortia under SMX stress was carried out with community variations and transcriptional activities monitored by metagenomic and metatranscriptomic sequencing techniques. Despite the initial drop to 41.88 %, the nitrogen removal efficiency of the anammox consortia rebounded to 84.64 % post-domestication under 5 mg/L SMX. Meanwhile, a 4.85-fold accumulation of antibiotic resistance genes (ARGs) under SMX stress was observed as compared to the control group. Interestingly, the anammox consortia may unlock the SMX-inhibited folate synthesis pathway through a novel interspecies cooperation triangle among Nitrospira (NAA), Desulfobacillus denitrificans (DSS1), and the core anammox population Candidatus Brocadia sinica (AMX1), in which the modified dihydropteroate synthase (encoded by sul1) of NAA reconnected the symbiotic cooperation between AMX1 and DSS1. Overall, this study provides a new model for the adaptation strategies of anammox consortia to SMX stress.

Unraveling the effects and mechanisms of antibiotics on aerobic simultaneous nitrogen and phosphorus removal by Acinetobacter indicus CZH-5

The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1-1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE, aarA, and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.

Deep degradation of sulfamethoxazole by the Fe-Co/γ-Al2O3-catalysed photo-Fenton system

The heterogeneous photo-Fenton system using Fe-Co/γ-Al2O3 as a catalyst was applied in the study of sulfamethoxazole(SMX) degradation. The morphology, structure, elemental composition and metal valence distribution of Fe-Co/γ-Al2O3 were found to be relatively stable before and after the reaction. The highest SMX degradation efficiency and mineralization (The ratio of organic matter being oxidized to carbon dioxide and water) were obtained under the conditions of 15% Fe-Co loading rate, 1:1 mass ratio of Fe and Co, 1 g/L catalyst dosage, 1.5 mL 30% H2O2 dosage, 18 W UV lamp power and 60 min reaction time, which were 98% and 66%, respectively. Radical quenching experiments and electronic paramagnetic resonance (EPR) characterization revealed that ·OH played an important role in the degradation and mineralization SMX in the Fe-Co/γ-Al2O3 heterogeneous photo-Fenton system. Combined with the analysis of N, S and intermediate products, there may be three degradation pathways of SMX in the heterogeneous photo-Fenton system. This work provides a technical reference for realizing the efficient degradation and mineralization of SMX in a heterogeneous photo-Fenton reaction system.

Reduced graphene oxide promotes the biodegradation of sulfamethoxazole by white-rot fungus Phanerochaete chrysosporium under cadmium stress

The biodegradation of antibiotics in aquatic environment is consistently impeded by the widespread presence of heavy metals, necessitating urgent measures to mitigate or eliminate this environmental stress. This work investigated the degradation of sulfamethoxazole (SMX) by the white-rot fungus Phanerochaete chrysosporium (WRF) under heavy metal cadmium ion (Cd2+) stress, with a focus on the protective effects of reduced graphene oxide (RGO). The pseudo-first-order rate constant and removal efficiency of 5 mg/L SMX in 48 h by WRF decrease from 0.208 h-1 and 55.6% to 0.08 h-1 and 28.6% at 16 mg/L of Cd2+, while these values recover to 0.297 h-1 and 72.8% by supplementing RGO. The results demonstrate that RGO, possessing excellent biocompatibility, effectively safeguard the mycelial structure of WRF against Cd2+ stress and provide protection against oxidative damage to WRF. Simultaneously, the production of manganese peroxidase (MnP) by WRF decreases to 38.285 U/L in the presence of 24 mg/L Cd2+, whereas it recovers to 328.51 U/L upon the supplement of RGO. RGO can induce oxidative stress in WRF, thereby stimulating the secretion of laccase (Lac) and MnP to enhance the SMX degradation. The mechanism discovered in this study provides a new strategy to mitigate heavy metal stress encountered by WRF during antibiotic degradation.

A review on co-metabolic degradation of organic micropollutants during anaerobic digestion: Linkages between functional groups and digestion stages

The emerging presence of organic micropollutants (OMPs) in water bodies produced by human activities is a source of growing concern due to their environmental and health issues. Biodegradation is a widely employed treatment method for OMPs in wastewater owing to its high efficiency and low operational cost. Compared to aerobic degradation, anaerobic degradation has numerous advantages, including energy efficiency and superior performance for certain recalcitrant compounds. Nonetheless, the low influent concentrations of OMPs in wastewater treatment plants (WWTPs) and their toxicity make it difficult to support the growth of microorganisms. Therefore, co-metabolism is a promising mechanism for OMP biodegradation in which co-substrates are added as carbon and energy sources and stimulate increased metabolic activity. Functional microorganisms and enzymes exhibit significant variations at each stage of anaerobic digestion affecting the environment for the degradation of OMPs with different structural properties, as these factors substantially influence OMPs' biodegradability and transformation pathways. However, there is a paucity of literature reviews that explicate the correlations between OMPs' chemical structure and specific metabolic conditions. This study provides a comprehensive review of the co-metabolic processes which are favored by each stage of anaerobic digestion and attempts to link various functional groups to their favorable degradation pathways. Furthermore, potential co-metabolic processes and strategies that can enhance co-digestion are also identified, providing directions for future research.

The introduction of influent sulfamethoxazole loads induces changes in the removal pathways of sulfamethoxazole in vertical flow constructed wetlands featuring hematite substrate

High frequent detection of sulfamethoxazole (SMX) in wastewater cannot be effectively removed by constructed wetlands (CWs) with a traditional river sand substrate. The role of emerging substrate of hematite in promoting SMX removal and the effect of influent SMX loads remain unclear. The removal efficiency of SMX in hematite CWs was significantly higher than that in river sand CWs by 12.7-13.8% by improving substrate adsorption capacity, plant uptake and microbial degradation. With increasing influent SMX load, the removal efficiency of SMX in hematite CWs slightly increased, and the removal pathways varied significantly. The contribution of plant uptake was relatively small (< 0.1%) under different influent SMX loads. Substrate adsorption (37.8%) primarily contributed to SMX removal in hematite CWs treated with low-influent SMX. Higher influent SMX loads decreased the contribution of substrate adsorption, and microbial degradation (67.0%) became the main removal pathway. Metagenomic analyses revealed that the rising influent load increased the abundance of SMX-degrading relative bacteria and the activity of key enzymes. Moreover, the abundance of high-risk ARGs and sulfonamide resistance genes in hematite CWs did not increase with the increasing influent load. This study elucidates the potential improvements in CWs with hematite introduction under different influent SMX loads.

Co-exposure of microplastics and sulfamethoxazole propagated antibiotic resistance genes in sediments by regulating the microbial carbon metabolism

The concerns on the carriers of microplastics (MPs) on co-existing pollutants in aquatic environments are sharply rising in recent years. However, little is known about their interactions on the colonization of microbiota, especially for the spread of pathogens and antibiotic resistance genes (ARGs). Therefore, this study aimed to investigate the influences on the propagation of ARGs in sediments by the co-exposure of different MPs and sulfamethoxazole (SMX). The results showed that the presence of MPs significantly enhanced the contents of total organic carbon, while having no effects on the removal of SMX in sediments. Exposure to SMX and MPs obviously activated the microbial carbon utilization capacities based on the BIOLOG method. The propagation of ARGs in sediments was activated by SMX, which was further promoted by the presence of polylactic acid (PLA) MPs, but significantly lowered by the co-exposed polyethylene (PE) MPs. This apparent difference may be attributed to the distinct influence on the antibiotic efflux pumps of two MPs. Moreover, the propagation of ARGs may be also dominated by microbial carbon metabolism in sediments, especially through regulating the carbon sources of carboxylic acids, carbohydrates, and amino acids. This study provides new insights into the carrier effects of MPs in sediments.

New insights into antibiotic stimulation of methane production during anaerobic digestion

Residual antibiotics in swine wastewater pose a critical challenge for stable anaerobic digestion (AD). This study offers fresh insights into the anaerobic treatment of swine wastewater. The results showed that the presence of three typical antibiotics (sulfamethoxazole (SMX), oxytetracycline (OTC) and ciprofloxacin (CIP)) in swine wastewater could promote methane production by stimulating the production and conversion of ethanol. Among them, SMX exhibited the strongest methane promotion effect, with the cumulative methane production increasing from 138.47 to 2204.19 mL/g VS. According to the microbial community structure, antibiotics could promote the growth of Corynebacterium, Lutispora and hydrogenotrophic methanogens (Methanosassiliicoccus, Methanobrevibacter, and Methanobacterium), but inhibit the enrichment of acetoclastic methanogen (Methanosaeta). The relative abundance of Methanosaeta decreased from 2.93-19.80% to 0.52-2.58% under antibiotic stress. Furthermore, there were significant differences in the influence of different antibiotic types on methanogenic pathways. Specifically, OTC and CIP promoted the acetoclastic and hydrogenotrophic pathways, respectively, to enhance methane production. However, SMX could promote both acetoclastic and hydrogenotrophic pathways.

Biodegradation of sulfadiazine by ryegrass (Lolium perenne L.) in a soil system: Analysis of detoxification mechanisms, transcriptome, and bacterial communities

The indiscriminate use of sulfadiazine has caused severe harm to the environment, and biodegradation is a viable method for the removal of sulfadiazine. However, there are few studies that consider sulfadiazine biodegradation mechanisms. To comprehensively investigate the process of sulfadiazine biodegradation by plants in a soil system, a potted system that included ryegrass and soil was constructed in this study. The removal of sulfadiazine from the system was found to be greater than 95% by determining the sulfadiazine residue. During the sulfadiazine removal process, a significant decrease in ryegrass growth and a significant increase in antioxidant enzyme activity were observed, which indicates the toxic response and detoxification mechanism of sulfadiazine on ryegrass. The ryegrass transcriptome and soil bacterial communities were further investigated. These results revealed that most of the differentially expressed genes (DEGs) were enriched in the CYP450 enzyme family and phenylpropanoid biosynthesis pathway after sulfadiazine exposure. The expression of these genes was significantly upregulated. Sulfadiazine significantly increased the abundance of Vicinamibacteraceae, RB41, Ramlibacter, and Microvirga in the soil. These key genes and bacteria play an important role in sulfadiazine biodegradation. Through network analysis of the relationship between the DEGs and soil bacteria, it was found that many soil bacteria promote the expression of plant metabolic genes. This mutual promotion enhanced the sulfadiazine biodegradation in the soil system. This study demonstrated that this pot system could substantially remove sulfadiazine and elucidated the biodegradation mechanism through changes in plants and soil bacteria.

Degradation of norfloxacin by red mud-based prussian blue activating H2O2: A strategy for treating waste with waste

The massive accumulation of red mud (RM) and the abuse of antibiotics pose a threat to environment safety and human health. In this study, we synthesized RM-based Prussian blue (RM-PB) by acid solution-coprecipitation method to activate H2O2 to degrade norfloxacin, which reached about 90% degradation efficiency at pH 5 within 60 min and maintained excellent catalytic performance over a wide pH range (3-11). Due to better dispersion and unique pore properties, RM-PB exposed more active sites, thus the RM-PB/H2O2 system produced more reactive oxygen species. As a result, the removal rate of norfloxacin by RM-PB/H2O2 system was 8.58 times and 2.62 times of that by RM/H2O2 system and PB/H2O2 system, respectively. The reactive oxygen species (ROS) produced in the degradation process included ·OH, ·O2- and 1O2, with 1O2 playing a dominant role. The formation and transformation of these ROS was accompanied by the Fe(III)/Fe(II) cycle, which was conducive for the sustained production of ROS. The RM-PB/H2O2 system maintained a higher degradation efficiency after five cycles, and the material exhibited strong stability, with a low iron leaching concentration. Further research showed the degradation process was less affected by Cl-, SO42-, NO3-, and humic acids, but was inhibited by HCO3- and HPO42-. In addition, we also proposed the possible degradation pathway of norfloxacin. This work is expected to improve the resource utilization rate of RM and achieve treating waste with waste.

Sulfamethoxazole removal from wastewater via anoxic/oxic moving bed biofilm reactor: Degradation pathways and toxicity assessment

The effects of sulfamethoxazole (SMZ), an antibiotic commonly detected in the water environment, on the performance of a single staged anoxic/oxic moving bed biofilm reactor (A/O MBBR), was investigated. The anoxic zone played a key role in the removal of SMZ with a percentage of contribution accounting for around 85% in the overall removal. Denitrifying heterotrophic microbes present in the anoxic zone showed relatively more resistance to higher SMZ loads. It was found that in extracellular polymeric substances, protein content was increased consistently with the increase in SMZ concentration. Based on the detected biotransformation products, four degradation pathways were proposed and the toxicity was evaluated. Metagenomic analysis revealed that at higher SMZ load the activity of genera, such as Proteobacteria and Actinobacteria was significantly affected. In summary, proper design and operation of staged A/O MBBR can offer a resilient and robust treatment towards SMZ removal from wastewater.

The fate of sulfamethoxazole and trimethoprim in a micro-aerated anaerobic membrane bioreactor and the occurrence of antibiotic resistance in the permeate

This study investigates the effects, conversions, and resistance induction, following the addition of 150 μg·L-1 of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in a laboratory-scale micro-aerated anaerobic membrane bioreactor (MA-AnMBR). TMP and SMX were removed at 97 and 86%, indicating that micro-aeration did not hamper their removal. These antibiotics only affected the pH and biogas composition of the process, with a significant change in pH from 7.8 to 7.5, and a decrease in biogas methane content from 84 to 78%. TMP was rapidly adsorbed onto the sludge and subsequently degraded during the long solids retention time of 27 days. SMX adsorption was minimal, but the applied hydraulic retention time of 2.6 days was sufficiently long to biodegrade SMX. The levels of three antibiotic-resistant genes (ARGs) (sul1, sul2, and dfrA1) and one mobile genetic element biomarker (intI1) were analyzed by qPCR. Additions of the antibiotics increased the relative abundances of all ARGs and intI1 in the MA-AnMBR sludge, with the sul2 gene folding 15 times after 310 days of operation. The MA-AnMBR was able to reduce the concentration of antibiotic-resistant bacteria (ARB) in the permeate by 3 log.

Facile Synthesis of gC3N4-Exfoliated BiFeO3 Nanocomposite: A Versatile and Efficient S-Scheme Photocatalyst for the Degradation of Various Textile Dyes and Antibiotics in Water

Water pollution engendered from textile dyes and antibiotics is a globally identified precarious concern that is causing dreadful risks to human health as well as aquatic lives. This predicament is escalating the quest to develop competent photocatalysts that can degrade these water pollutants under solar light irradiation. Herein, we report an efficient photocatalyst comprising a hierarchical structure by integrating the layered graphitic carbon nitride (gC3N4) with nanoflakes of exfoliated BiFeO3. The coexistence of these two semiconducting nanomaterials leads to the formation of an S-scheme heterojunction. This nanocomposite demonstrated its excellent photocatalytic activity toward the degradation of several textile dyes (Yel CL2R, Levasol Yellow-CE, Levasol Red-GN, Navy Sol-R, Terq-CL5B) and various antibiotics (such as tetracycline hydrochloride (TCH), ciprofloxacin (CPX), sulfamethoxazole (SMX), and amoxicillin (AMX)) under the simulated solar light irradiation. As this photocatalyst exhibits its versatile activity toward the degradation of several commercial dyes as well as antibiotics, this work paves the path to develop a reasonable, eco-benign, and highly efficient photocatalyst that can be used in the practical approach to remediate environmental pollution.

A novel peroxymonosulfate activation process by single-atom iron catalyst from waste biomass for efficient singlet oxygen-mediated degradation of organic pollutants

Single-atom dispersed catalysts (SACs) have gained considerable attention in organic contaminants remediation due to their superior reactivity and stability. However, the complex and costly synthesis processes limit their practical applications in environmental protection. Herein, a facile and cost-effective single-atom iron catalyst (Fe-SA/NC) anchored on nitrogen-doped porous carbon was first fabricated by using waste biomass as a carbon source. The Fe-SA/NC catalyst exhibited outstanding performance with a high turnover frequency of 1.72 min^-1 toward antibiotics degradation via peroxymonosulfate activation. ECOSAR program and algae growth experiments demonstrated that the byproducts produced during the sulfamethoxazole degradation process were not detrimental to the aquatic environment. Radical quenching and electron paramagnetic resonance experiments revealed that Fe-SA/NC remarkably promoted ¹O₂ production in PMS-assisted reaction, and thus ¹O₂ contributed as much as 78.77% to sulfamethoxazole degradation. As indicated by experiment and density functional theory (DFT) calculations, FeN₂O₂ configuration serves as the active site. DFT calculations further presented the most rational generation route of ¹O₂ as PMS→OH* →O* →¹O₂. We also designed Fe-SA/NC embedded spherical pellets for contaminants elimination at the device level. This study offers new insights into the synthesis of SACs from waste biomass and their practical application in environmental remediation.

Unveiling different antibiotic degradation mechanisms on dual reaction center catalysts with nitrogen vacancies via peroxymonosulfate activation

Metal-nitrogen-site catalysts are widely recognized as effective heterogeneous catalysts in peroxymonosulfate (PMS)-based advanced oxidation processes. However, the selective oxidation mechanism for organic pollutants is still contradictory. In this work, manganese-nitrogen active centers and tunable nitrogen vacancies were synchronously constructed on graphitic carbon nitride (LMCN) through l-cysteine-assisted thermal polymerization to reveal different antibiotic degradation mechanisms. Benefiting from the synergism of manganese-nitrogen bond and nitrogen vacancies, the LMCN catalyst exhibited excellent catalytic activity for the degradation of tetracycline (TC) and sulfamethoxazole (SMX) antibiotics with first-order kinetic rate constants of 0.136 min^-1 and 0.047 min^-1, which were higher than those of other catalysts. Electron transfer dominated TC degradation at low redox potentials, while electron transfer and high-valent manganese (Mn (V)) were responsible for SMX degradation at high redox potentials. Further experimental studies unveiled that the pivotal role of nitrogen vacancies is to promote electron transfer pathway and Mn(V) generation, while nitrogen-coordinated manganese as the primary catalytic active site determines Mn(V) generation. In addition, the antibiotic degradation pathways were proposed and the toxicity of byproducts was analyzed. This work provides an inspiring idea for the controlled generation of reactive oxygen species by targeted activation of PMS.

Insights into the efficient ozonation process focusing on 2,4-di-tert-butylphenol - A notable micropollutant of typical bamboo papermaking wastewater: Performance and mechanism

The present study applied the ozonation process to degrade 2,4-di-tert-butylphenol (2,4-DTBP), an emerging micropollutant detected in typical bamboo pulp and papermaking wastewater (BPPW). The effects of various influencing factors on the degradation performance and corresponding degradation mechanism were investigated. The results showed that ozone could degrade 2,4-DTBP rapidly with a reaction rate constant of (1.80 ± 0.05) × 10⁵ M^-1·s^-1. The removal efficiency of 2,4-DTBP (5 mg/L) could reach 100% when the ozone dosage exceed 6 mg/L in a neutral medium. The presence of coexisting chemicals in BPPW such as Cl^- and HCO₃^- promoted the removal performance of 2,4-DTBP. In contrast, NH₄⁺ and humic acid presented inhibition on 2,4-DTBP removal. The ozonation of 2,4-DTBP was dominated by the ozone molecule, and this was primarily attributed to electrophilic substitution and 1,3-dipolar cycloaddition reactions. Twenty-seven kinds of intermediate products were identified by UPLC-Q-TOF/MS. The variations in their productions were based on the changes in ozone dosage. The degradation pathways were proposed. The toxicity of 2,4-DTBP was weakened after ozonation. As for the ozonation of actual biochemical effluent of BPPW, the desirable treatment performance was obtained. This study proved the feasibility of ozonation and provided data basis for subsequent pilot study.

Simultaneous removal of sediment and water contaminants in a microbial electrochemical system with embedded active electrode by in-situ utilization of electrons

In the water environment such as lakes, there is a phenomenon that the sediment and overlying water are polluted at the same time. In this study, A microbial electrochemical system with an embedded active electrode was developed for simultaneous removal of polycyclic aromatic hydrocarbons in sediment and antibiotics in overlying water by in-situ utilization of electrons. In the closed-circuit group, the pyrene concentration in sediment decreased from 9.94 to 2.08 mg/L in 96 d, and the sulfamethoxazole concentration in water decreased from 5.12 to 1.12 mg/L in 168 h. These values were 18.71 % and 31.21 % higher, respectively, than those of the open-circuit group. The pyrene degradation pathway may be from polycyclic aromatic substances to low-cyclic aromatic hydrocarbons via successive breakdown of benzene rings. Multiple metabolites produced by reduction verified that SMX or its intermediates were reductively degraded in water. On the active electrode, the relative abundances of Acetobacterium and Piscinibacter, which were genera related to SMX degradation, was promoted, while the electricity-producing genus Pseudomonas was inhibited. ccdA, pksS, torC, and acsE genes related to extracellular electron transport may accelerate electron transport. Electrons could be transferred to SMX under the influence of proteins involved in extracellular electron transport, and SMX could be degraded reductively as an electron acceptor by microbes. Generation of electrons and in-situ utilization for simultaneous removal of solid-liquid two-phase pollutants will provide mechanistic insight into pollutant biodegradation by microbial electrochemistry and promote the development of sustainable bioremediation strategies for surface water.

Removal performance, biotransformation pathways and products of sulfamethoxazole in vertical subsurface flow constructed wetlands with different substrates

For decades, sulfamethoxazole (SMX) has been frequently detected in the aquatic environments due to its high usage and refractory to degradation. Constructed wetland (CW) is regarded as an efficient advanced wastewater technology to eliminate organic pollutants including SMX. In CW system, substrate adsorption and further biodegradation are extremely important in SMX removal; however, the removal performance of SMX by CWs with different substrates varies greatly, and the biotransformation pathways, products, and mechanisms of SMX remain unclear. To address this, we constructed a CW with conventional substrate (CS, gravel) as control (C-CW) and three CWs with emerging substrates (ES, biochar, zeolite and pyrite for B-CW, Z-CW and P-CW, respectively), and explored the performance and mechanisms of SMX removal in CWs. Results illustrated that the removal performance of SMX in CWs with ES reached 94.89-99.35%, and significantly higher than that with CS of 89.50% (p < 0.05). Biodegradation contributed >90% SMX removal in all CWs. The microbial compositions and functions differed among CWs at the middle layer (mixed layer), which shaped diverse resistance pattern and metabolism pathways of microbiomes under SMX stress: P-CW and B-CW cope with SMX stress by enhancing material and energy metabolism, whereas Z-CW does that by enhancing metabolism and exocytosis of xenobiotics. Additionally, nine transformation pathways with 15 transformation products were detected in this study. A reversible process of desamino-SMX being reconverted to SMX might exist in P-CW, which caused a lower SMX removal efficiency in P-CW. This study provided a comprehensive insight into the processes and mechanisms of SMX removal in CWs with different substrates, which would be a useful guidance for substrate selection in CWs in terms of enhanced micropollutants removal.

Biotransformation of sulfamethoxazole by a novel strain, Nitratireductor sp. GZWM139: Characterized performance, metabolic mechanism and application potential

A novel strain, Nitratireductor sp. GZWM139 capable of efficient removal of SMX was isolated from mariculture sewage, and Nitratireductor was reported to conduct the removal of antibiotics for the first time. Strain GZWM139 exhibited desirable adaptations to environmental factors with SMX removal efficiencies more than 90 % at temperatures of 28-38 °C, pH values of 4.5-8.5, salinities of 20-30 ‰, SMX levels of 1-5 mg/L and shaking speeds of 20-260 rpm. SMX removal was a cooperated process implemented by intracellular enzymes and extracellular enzymes, and was achieved through four proposed biotransformation pathways with the occurrences of demethylation, hydroxylation, nitration, formylation, oxidation, bond cleavage and ring opening. Strain GZWM139 responded to the SMX removal process by altering properties of cell membrane and motivating activities of xenobiotic-metabolizing enzymes and antioxidant system. Genomic analysis proved the existence of functional genes relevant to the SMX removal in strain GZWM139 and provided echoing genetic insights for revealing the SMX removal mechanism. Strain GZWM139 performed efficient detoxification of SMX and accomplished simultaneous removal of SMX and nitrogen in both mariculture sewage and domestic sewage. The findings are significant to the effective elimination of SMX pollution and comprehensive cognitions on metabolic mechanisms of SMX removal.

Association of long-term effects of low-level sulfamethoxazole with ovarian lipid and amino acid metabolism, sex hormone levels, and oocyte maturity in zebrafish

Sulfamethoxazole (SMZ) is an important antibiotic used to prevent and treat infections in both clinical settings and animal husbandry. High levels of SMZ may exhibit endocrine toxicity. Environmental SMZ enters the human body via food and water; however, the toxicity of environmental doses of SMZ and its effects on reproductive health are unknown. In the present study, zebrafish were exposed to low concentrations of SMZ (1000 and 5000 ng/L) from 2 h post-fertilization to 120 d post-fertilization. Consequently, the proportion of mature oocytes in adult female zebrafish ovarian tissue increased by 98.2 %, indicating that SMZ promotes ovarian maturation. Metabolomics analysis revealed significant changes in ovarian lipid and amino acid levels after SMZ treatment. An enzyme-linked immunoassay used to detect sex hormones in the ovaries showed that SMZ exposure significantly increased the levels of estradiol, a follicle-stimulating hormone, and of luteinizing hormone. Furthermore, an association analysis showed that most of the differentially expressed metabolites in the ovary were strongly correlated with the levels of sex hormones secreted by the pituitary gland. Therefore, significantly increased transcript levels of gonadotropin-releasing hormone (GnRH) and follicle-stimulating hormone detected in brain tissue suggested that SMZ may exhibit ovarian toxicity via the hypothalamus. In vitro experiments were performed to demonstrate that SMZ targets neurons in the hypothalamus. Exposure to SMZ significantly increased the GnRH content in GnRH neurons. Finally, molecular docking simulations indicated the potential interaction of SMZ with G protein-coupled receptor 54; this molecular binding can activate, synthesize, and release GnRH in neurons. In conclusion, long-term environmental exposure to SMZ may induce ovarian toxicity by affecting the hypothalamus-pituitary-gonad axis.

Sonoelectrochemical oxidation of sulfamethoxazole in simulated and actual wastewater on a piezo-polarizable FTO/BaZr x Ti(1-x)O3 electrode: reaction kinetics, mechanism and reaction pathway studies

The sonoelectrochemical (SEC) oxidation of sulfamethoxazole (SMX) in simulated and actual wastewater on FTO/BaZr_(0.1)Ti_(0.9)O₃, FTO/BaZr_(0.05)Ti_(0.95)O₃ and FTO/BaTiO₃ electrodes is hereby presented. Electrodes from piezo-polarizable BaZr_(0.1)Ti_(0.9)O₃, BaZr_(0.05)Ti_(0.95)O₃, and BaTiO₃ materials were prepared by immobilizing these materials on fluorine-doped tin dioxide (FTO) glass. Electrochemical characterization performed on the electrodes using chronoamperometry and electrochemical impedance spectroscopy techniques revealed that the FTO/BaZr_(0.1)Ti_(0.9)O₃ anode displayed the highest sonocurrent density response of 2.33 mA cm^-2 and the lowest charge transfer resistance of 57 Ω. Compared to other electrodes, these responses signaled a superior mass transfer on the FTO/BaZr_(0.1)Ti_(0.9)O₃ anode occasioned by an acoustic streaming effect. Moreover, a degradation efficiency of 86.16% (in simulated wastewater), and total organic carbon (TOC) removal efficiency of 63.16% (in simulated wastewater) and 41.47% (in actual wastewater) were obtained upon applying the FTO/BaZr_(0.1)Ti_(0.9)O₃ electrode for SEC oxidation of SMX. The piezo-polarizable impact of the FTO/BaZr_(0.1)Ti_(0.9)O₃ electrode was further established by the higher rate constant obtained for the FTO/BaZr_(0.1)Ti_(0.9)O₃ electrode as compared to the other electrodes during SEC oxidation of SMX under optimum operational conditions. The piezo-potential effect displayed by the FTO/BaZr_(0.1)Ti_(0.9)O₃ electrode can be said to have impacted the generation of reactive species, with hydroxyl radicals playing a predominant role in the degradation of SMX in the SEC system. Additionally, a positive synergistic index obtained for the electrode revealed that the piezo-polarization effect of the FTO/BaZr_(0.1)Ti_(0.9)O₃ electrode activated during sonocatalysis combined with the electrochemical oxidation process during SEC oxidation can be advantageous for the decomposition of pharmaceuticals and other organic pollutants in water.

Deciphering the internal mechanisms of ciprofloxacin affected anaerobic digestion, its degradation and detoxification mechanism

Ciprofloxacin (CIP) is widely used in livestock farms, but the internal mechanism of the effect of residual CIP in actual livestock wastewater on anaerobic digestion (AD) performance remains unknown. This study examined the dose-specific effects of CIP (0.5-2 mg/L) on livestock wastewater AD by analyzing acidogenesis and methanogenesis. 0.5 mg/L CIP promoted methane production by facilitating acidogenesis and acetogenesis. Compared with the control, the cumulative methane production increased from 331.38 to 407.44 mL/g VS at a dose of 0.5 mg/L, an increase of 22.95 %. However, as the dose of CIP increased, the cumulative methane production gradually decreased to 217.64 mL/g VS (2 mg/L). Microbial community analysis revealed that CIP had the greatest impact on methane production by influencing the activity of acidogenic bacteria. Meanwhile, acidogenesis was critical for CIP degradation. In acidogenesis, hydroxylation, amination, defluorination, decarboxylation, and piperazine ring breaking not only degraded CIP but also reduced its toxicity. Therefore, a large number of intermediates could be continuously degraded by microorganisms. However, as the dosage of CIP increased, the ability of microorganisms to degrade intermediates decreased.