New insights into algal-bacterial sludge granulation based on the tightly-bound extracellular polymeric substances regulation in response to N-Methylpyrrolidone.

Algal-bacterial granular sludge (ABGS) system is promising in wastewater treatment for its potential in energy-neutrality and carbon-neutrality. However, traditional cultivation of ABGS poses significant challenges attributable to its long start-up period and high energy consumption. Extracellular polymeric substances (EPS), which could be stimulated as a self-defense strategy in cells under toxic contaminants stress, has been considered to contribute to the ABGS granulation process. In this study, photogranulation of ABGS by EPS regulation in response to varying loading rates of N-Methylpyrrolidone (NMP) was investigated for the first time. The results indicated the formation of ABGS with a maximum average diameter of ∼3.3 mm and an exceptionally low SVI5 value of 67 ± 2 mL g-1 under an NMP loading rate of 125 mg L-1 d-1, thereby demonstrating outstanding settleability. Besides, almost complete removal of 300 mg L-1 NMP could be achieved at hydraulic retention time of 48 h, accompanied by chemical oxygen demand (COD) and total nitrogen (TN) removal efficiencies higher than 90 % and 70 %, respectively. Moreover, possible degradation pathway and metabolism mechanism in the ABGS system for enhanced removal of NMP and nitrogen were proposed. In this ABGS system, the mycelium with network structure constituted by filamentous microorganisms was a prerequisite for photogranulation, instead of necessarily leading to granulation. Stress of 100-150 mg L-1 d-1 NMP loading rate stimulated tightly-bound EPS (TB-EPS) variation, resulting in rapid photogranulation. The crucial role of TB-EPS was revealed with the involved mechanisms being clarified. This study provides a novel insight into ABGS development based on the TB-EPS regulation by NMP, which is significant for achieving the manipulation of photogranules.

Effects of nitrate reduction on the biotransformation of 1H-1,2,4-triazole: Mechanism and community evolution.

Due to the refractory of 1 H-1,2,4-triazole (TZ), conventional anaerobic biological treatment technology is usually restricted by low removal efficiency and poor system stability. In this study, TZ biodegradation and nitrate reduction was coupled to improve the removal efficiency of TZ from polluted wastewater. Batch assay was performed with pure culture strain Raoultella sp. NJUST42, which was reported to have the capability to degrade TZ in our previous study. Based on batch assay result, complete removal of TZ could be achieved in the presence of nitrate, whereas only 50% of TZ could be removed in the control system. Long-term stability experiment indicated that the relative abundance of microorganisms (Bacteroidetes_vadinHA17, Georgenia, Anaerolinea, etc) was obviously enhanced under nitrate reduction condition. During long-term period, major intermediates for TZ biodegradation such as [1,2,4]Triazolidine-3,5-diol, hydrazine dibasic carboxylic acid and carbamic acid were detected. A novel TZ biotransformation approach via hydration, TZ-ring cleavage, deamination and oxidation was speculated. PICRUSt1 and KEGG pathway analyses indicated that hydration (dch), oxidation (adhD, oah, pucG, fdhA) of TZ and nitrate reduction (Nar, napA, nrfA, nirBK, norB, nosZ) were significantly enhanced in the presence of nitrate. Moreover, the significant enrichment of TCA cycle (gab, sdh, fum, etc.) indicated that carbon and energy metabolism were facilitated with the addition of nitrate, thus improved TZ catabolism. The proposed mechanism demonstrated that TZ biodegradation coupled with nitrate reduction would be a promising approach for efficient treatment of wastewater contaminated by TZ.

Efficient utilization of photoelectron-hole at semiconductor-microbe interface for pyridine degradation with assistance of external electric field.

In this study, enhanced pyridine bio-photodegradation with assistance of electricity was achieved. Meanwhile, photoelectron-hole played a vital role in accelerating pyridine biomineralization. The significant separation of photoelectron-hole was achieved with an external electric field, which provided sufficient electron donors and acceptors for pyridine biodegradation. The enhanced electron transport system activity also revealed the full utilization of photoelectron-hole by microbes at semiconductor-microbe interface with assistance of electricity. Microbial community analysis confirmed the enrichment of functional species related to pyridine biodegradation and electron transfer. Microbial function analysis and microbial co-occurrence networks analysis indicated that upregulated functional genes and positive interactions of different species were the important reasons for enhanced pyridine bio-photodegradation with external electric field. A possible mechanism of enhanced pyridine biodegradation was proposed, i.e., more photoelectrons and holes of semiconductors were utilized by microbes to accelerate reduction and oxidation of pyridine with the assistance of electrical stimulation. The excellent performance of the photoelectrical biodegradation system showed a potential alternative for recalcitrant organic wastewater treatment.

Glycine betaine modulates extracellular polymeric substances to enhance microbial salinity tolerance.

High salinity inhibits microbial activity in the bioremediation of saline wastewater. To alleviate osmotic stress, glycine betaine (GB), an osmoprotectant, is added to enhance the secretion of extracellular polymeric substances (EPS). These EPS are pivotal in withstanding environmental stressors, yet the intricate interplay between GB supplementation and microbial responses through EPS modifications-encompassing composition, molecular architecture, and electrochemical features-remains elusive in hypersaline conditions. Here we show microbial strategies for salinity endurance by investigating the impact of GB on the dynamic alterations of EPS properties. Our findings reveal that GB supplementation at 3.5% salinity elevates the total EPS (T-EPS) content from 12.50 ± 0.05 to 24.58 ± 0.96 mg per g dry cell weight. The observed shift in zeta potential from -28.95 to -6.25 mV at 0% and 3.5% salinity, respectively, with GB treatment, indicates a reduction in electrostatic repulsion and compaction. Notably, the EPS protein secondary structure transition from ß-sheet to α-helix, with GB addition, signifies a more compact protein configuration, less susceptible to salinity fluctuations. Electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), reveal GB's role in promoting the release of exogenous electron shuttles, such as flavins and c-type cytochromes (c-Cyts). The enhancement in DPV peak areas (QDPV) with GB addition implies an increase in available extracellular electron transfer sites. This investigation advances our comprehension of microbial adaptation mechanisms to salinity through EPS modifications facilitated by GB in saline habitats.

Material and microbial perspectives on understanding the role of biochar in mitigating ammonia inhibition during anaerobic digestion.

With the increasing adoption of carbon-based strategies to enhance methanogenic processes, there is a growing concern regarding the correlation between biochar properties and its stimulating effects on anaerobic digestion (AD) under ammonia inhibition. This study delves into the relevant characteristics and potential mechanisms of biochar in the context of AD system under ammonia inhibition. The introduction of optimized biochar, distinguished by rich CO bond, abundant defect density, and high electronic capacity, resulted in a significant reduction in the lag period of anaerobic digestion system under 5.0 g/L ammonia stress, approximately by around 63 % compared to the control one. Biochar helps regulate the community structure, promotes the accumulation of acetate-consuming bacteria, in the AD system under ammonia inhibition. More examinations show that biochar promotes direct interspecies electron transfer in AD system under ammonia inhibition, as evidenced by diminished levels of bound electroactive extracellular polymeric substances, increased abundance of electroactive bacteria, and notably, the up-regulation of direct interspecies electron transfer associated genes, including the conductive pili and Cytochrome C genes, as revealed by meta-transcriptomic analysis. Additionally, gene expression related to proteins associated with ammonium detoxification were found to be up-regulated in systems supplemented with biochar. These findings provide essential evidence and insights for the selection and potential engineering of effective biochar to enhance AD performance under ammonia inhibition.

1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2 O2 via Controllable Modular Design.

The topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure-performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe-COF) with typical 4-c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge-linked atom ordinal. Finally, EO-COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2 , and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2 -to-H2 O2 activity under visible light, with a production rate of 2675 µmol g-1 h-1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2 O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure-catalysis correlation.

The humic substance analogue antraquinone-2, 6-disulfonate (AQDS) enhanced zero-valent iron based autotrophic denitrification: Performances and mechanisms.

Zero-valent iron based autotrophic denitrification (ZVI-AD) has attracted increasing attentions in nitrate removal due to saving organic carbon budget in wastewater treatment, but limited by the low reaction speed, poor electron transfer efficiency as well as the compaction/blocking by iron hydrolysis products. Humic substances (HS) were promising to regulate iron cycle and accelerate electron transfer by serving as electron mediators. In this study, HS analogue, antraquinone-2, 6-disulfonate (AQDS), was added to enhance ZVI-AD process. Results showed that the dosage of AQDS led to a NO3--N removal efficiency of 83.37 ± 3.98% within 96 h, which was 32.28 ± 1.25% higher than that in ZVI-AD system. The corrosion of ZVI and microbially nitrate reduction were both improved at the presence of AQDS. The addition of AQDS enriched the functional species, including autotrophic denitrobacteria namely Thauera and Hydrogenophaga, iron redox-related species namely Ferruginibacter and HS respiration related species namely Flavobacterium. The genes napA and napB related to electron transfer, nirK and nosZ related to the accumulation of intermediate products were also enriched by the addition of AQDS. AQDS addition boosted the electrons flowing to both abiotic and biotic nitrate reduction. Nitrate removal mechanism involved in ZVI-AQDS coupled system was proposed. This study provided an alternative strategy for improving ZVI-AD by HS.

Sulfide-modified nanozerovalent iron for rapid decontamination of Cu(â ¡) complexes in high-salinity wastewater.

Heavy metal complexes receive less attention, but they are more difficult to remove than the free heavy metals. Moreover, the high-salinity wastewaters from various industries hinder the removal of heavy metal complexes. Removal of the metal complexes is a top priority but a challenging task. Herein, a new strategy for removing Cu-EDTA from high-salinity wastewater with sulfide-modified nanozerovalent iron (S-NZVI) was proposed. The S-NZVI exhibited a considerable adsorption capacity for Cu-EDTA (∼83 mg Cu/g) at a high salt concentration (25 g/L NaCl). Similarly, the S-NZVI maintained excellent adsorption performance (∼83 mg Cu/g) in the presence of CaCl2, MgCl2, Na2SO4, and NaNO3 (25 g/L). The S-NZVI showed extremely high efficiency for Cu-EDTA removal; 50 mg/L of Cu-EDTA was almost completely removed in 1 min, and the kobs was approximately 1.5 g/(mg min). The S-NZVI showed an extensive pH working range, and within the pH range of 2-9, the Cu-EDTA was removed completely within 5 min. The excellent removal performance of the S-NZVI was due to the high reactivity and high affinity of NZVI for Cu, as well as the special substitution of Fe2+ and the interfacial reactions between S-NZVI and the copper complexes. Compared with other studies of Cu complex removal, removal with S-NZVI was a simpler process with higher efficiency. In brief, S-NZVI efficiently removed Cu complexes from harsh water environments and was reused many times. The process was simple and efficient and has broad application prospects.

Nitrification-denitrification co-metabolism in an algal-bacterial aggregates system for simultaneous pyridine and nitrogen removal.

Photosynthetic oxygenation in algal-bacterial symbiotic (ABS) system was mainly concerned to enhance contaminant biodegradation by developing an aerobic environment, while the role of nitrification-denitrification involved is often neglected. In this study, an algal-bacterial aggregates (ABA) system was developed with algae and activated sludge (PBR-1) to achieve simultaneous pyridine and nitrogen removal. In PBR-1, as high as 150 mg·L-1 pyridine could be completely removed at hydraulic residence time of 48 h. Besides, total nitrogen (TN) removal efficiency could be maintained above 80%. Nitrification-denitrification was verified as the crucial process for nitrogen removal, accounting for 79.3% of TN removal at 180 µmol·m-2·s-1. Moreover, simultaneous pyridine and nitrogen removal was enhanced through nitrification-denitrification co-metabolism in the ABA system. Integrated bioprocesses in PBR-1 including photosynthesis, pyridine biodegradation, carbon and nitrogen assimilation, and nitrification-denitrification, were revealed at metabolic and transcriptional levels. Fluorescence in situ hybridization analysis indicated that algae and aerobic species were located in the surface layer, while denitrifiers were situated in the inner layer. Microelectrode analysis confirmed the microenvironment of ABA with dissolved oxygen and pH gradients, which was beneficial for simultaneous pyridine and nitrogen removal. Mechanism of nitrification-denitrification involved in pyridine and nitrogen removal was finally elucidated under the scale of ABA.

Defense mechanism of Fe(III)-assisted anammox under salt stress: Performance and microbial community dynamics.

Anammox process has attracted attention due to its excellent nitrogen removal properties in nitrogen-rich wastewater treatment. However, there were some obstacles for the application of anammox to treat high saline wastewater due to its sensitivity to salinity. In this study, Fe(III) addition strategy was developed to assist anammox to adapt high saline surroundings, with the defense mechanism involved in Fe(III)-assisted anammox emphasized. Nitrogen removal performance of anammox was deteriorated at 3.5% salinity, with the average total nitrogen removal rate of 0.85 kg/(m3·d) observed. The continuous addition of Fe(III) could significantly assist anammox to resist high salinity through facilitating the enrichment of anammox species. Candidatus Kuenenia was the main anammox species and outcompeted Candidatus Brocadia under high saline surrounding. The relative abundance of Candidatus Kuenenia increased with increased salinity and reached 41.04% under 3.5% salinity. The synthesis of key enzymes of anammox species were improved through Fe(III) addition and then facilitated the energy metabolism of anammox bacteria under 3.5% salinity. This study provides a new thought in Fe(III)-assisted anammox enhancement technologies and deepens the insight of anammox in high saline wastewater treatment.

Mixed-Blocks-Driving Nickel-Porphyrin Covalent Organic Polymers for Photocatalytic Syngas Production from CO2 with Fine Selectivity.

CO2 photoconversion to syngas with superb selectivity is a splendid and bright option to achieve environmental improvement, energy substitution, and industrial needs. Herein, a series of Ni-porphyrin covalent organic polymers (COPs) interspersed with furan and thiophene using a mixed-blocks-engineering strategy, named as OXSY-Ni COPs (X and Y refer to the relative amounts of furan and thiophene blocks, respectively), are synthesized for photocatalytic CO2-to-syngas. Ni-coordinated porphyrin cores prefer to act as mediators of CO2-to-CO photoconversion because of the higher adsorption capacity of CO2. Ni-free porphyrins work mainly as active sites of H2 photoevolution. Furthermore, introducing different amounts of furan and thiophene modulates jointly the electronic structure of Ni-porphyrin COPs and optimizes the conduction band alignment. The above controllable variables achieve a wonderful syngas (CO/H2) ratio range from 2:1.06 to 1:1.04 for the Fischer-Tropsch process within common industrial reactions. Notably, the COP of the O1S3-Ni COPs exhibits excellent photocatalytic CO2-to-syngas activity under visible light, with a syngas yield of 8442.5 µmol g-1 h-1 (CO/H2 = 1:1.02) and an apparent quantum efficiency (AQE) of 1.92% at 450 nm. This strategy would provide a significance path to design functional and efficient organic semiconductors.

New insights into enhanced biodegradation of 4-bromphenol in a nitrate-reducing system: Process performance and mechanism.

Due to the recalcitrant nature of halogenated phenol, conventional anaerobic bioprocess is often limited by low removal efficiency and poor process stability. At the presence of electron acceptors such as nitrate, 4-bromophenol (4-BP) removal efficiency is significantly higher than that in the anaerobic control system, but the mechanism involved is still unclear. Therefore, an up-flow nitrate-reducing bioreactor (NRBR) was designed and consecutively performed for 215 days to explore the synergistic mechanism for BPs biodegradation and nitrate reduction. Complete 4-BP biodegradation could be obtained in NRBR at HRT and 4-BP loading rate of 24 h and 0.29 mol m - 3d - 1, while the TOC removal and nitrate reduction efficiencies were as high as 91.33±2.11% and 98.31±1.33%, respectively. Population evolution analyses revealed that the microorganisms involved in 4-BP debromination and biodegradation (Candidatus Peregrinibacteria, Denitratisoma, Anaerolineaceae and Ignavibacterium) as well as nitrate reduction (Denitratisoma, Anaerolineaceae, Limnobacter and Ignavibacterium) were significantly enriched in NRBR. Major intermediates during 4-BP biodegradation, including 4-bromocatechol, 4­bromo-6-oxo-hexanoic acid and succinic acid were identified, while a distinct 4-BP biodegradation pathway via hydration, aromatic-ring cleavage, hydrolysis debromination and oxidation was expounded. Metagenomic analysis indicated that oxidation (had, pht4, boh, butA), hydrolysis debromination ((S)-2-haloacid dehalogenase) and bio-mineralization (gabD, sdhA) of 4-BP were largely enhanced in NRBR. Moreover, carbon, nitrogen, energy and amino acid metabolisms were significantly facilitated with the injection of nitrate in order to provide energy and electron, thus enhanced microbial activities and enzymatic reactions in NRBR. The proposed mechanism provides new insights into our mechanistic understanding of halogenated phenol biodegradation and the development of sustainable bioremediation strategies.

Unraveling the intracellular and extracellular self-defense of Chlorella sorokiniana toward highly toxic pyridine stress.

A bottleneck of microalgae-based techniques for wastewater bioremediation is activity inhibition of microalgae by toxic pollutants. The defense strategies of Chlorella sorokinana against toxic pyridine were studied. Results indicated that pyridine caused photoinhibition and reactive oxygen species overproduction in a concentration-dependent manner. The 50% inhibitory concentration of pyridine (147 mg L-1) destroyed C/N balance, disrupted multiple metabolic pathways of C. sorokinana. In response to pyridine stress, ascorbate peroxidase and catalase activities increased to scavenge reactive oxygen species under pyridine concentrations lower than 23 mg L-1. At higher pyridine concentrations, the activation of calcium signaling pathways and phytohormones represented the predominant defense response. Extracellular polymeric substances increased 3.6-fold in 147 mg L-1 group than control, which interacted with pyridine through hydrophobic and aromatic stacking to resist pyridine entering algal cells. Unraveling the intracellular and extracellular self-defense mechanisms of microalgae against pyridine stress facilitates the development of microalgal-based technology in wastewater bioremediation.

Enhanced 4-bromophenol anaerobic biodegradation in electricity-stimulated anaerobic system: The key role of humic acid in reshaping microbial eco-interrelations and functions.

Electricity-stimulated anaerobic system (ESAS) has shown great potential for halogenated organic pollutants removal. Exogenous redox mediators can improve electron transfer efficiency to enhance pollutants removal in ESAS. In this study, humic acid (HA), a low-cost electron mediator, was added into ESAS to enhance the simultaneous reductive debromination and mineralization of 4-bromophenol (4-BP). Results showed that the highest 4-BP removal efficiency at 48 h was 95.43 % with HA dosage of 30 mg/L at - 700 mV, which was 34.67 % higher than that without HA. The addition of HA decreased the requirement for electron donors and enriched Petrimonas and Rhodococcus for humus respiratory. HA addition regulated microbial interactions, and enhanced species cooperation between Petrimonas and dehalogenation species (Thauera and Desulfovibrio), phenol degradation-related species (Rhodococcus) as well as fermentative species (Desulfobulbus). Functional genes related to 4-BP degradation (dhaA/hemE/xylC/chnB/dmpN) and electron transfer (etfB/nuoA/qor/ccoN/coxA) were increased in abundance by HA addition. The enhanced microbial functions, as well as species cooperation and facilitation, all contributed to the improved 4-BP biodegradation in HA-added ESAS. This study provided a deep insight into microbial mechanism driven by HA and offered a promising strategy for improving halogenated organic pollutants removal from wastewater.

Reaction Site Designation by Intramolecular Electric Field in Tröger's-Base-Derived Conjugated Microporous Polymer for Near-Unity Selectivity of CO2 Photoconversion.

To facilitate solar-driven overall CO2 and H2 O convsersion into fuels and O2 , a series of covalent microporous polymers derived from Tröger's base are synthesized featuring flexural backbone and unusual charge-transfer properties. The incorporation of rigid structural twist Tröger's base unit grants the polymers enhanced microporosity and CO2 adsorption/activation capacity. Density function theory calculations and photo-electrochemical analyses reveal that an electric dipole moment (from negative to positive) directed to the Tröger's base unit is formed across two obliquely opposed molecular fragments and induces an intramolecular electric field. The Tröger's base unit located at folding point becomes an electron trap to attract photogenerated electrons in the molecular network, which brings about suppression of carrier recombination and designates the reaction site in synergy with the conjugated network. In response to the discrepancy in reaction pathways across the reaction sites, the product allocation in the catalytic reaction is thereby regulated. Optimally, CMP-nTB achieves the highest photocatalytic CO production of 163.53 µmol g-1 h-1 with approximately unity selectivity, along with H2 O oxidation to O2 in the absence of any photosensitizer or co-catalyst. This work provides new insight for developing specialized artificial organic photocatalysts.

Integrated electro-Fenton system based on embedded U-tube GDE for efficient degradation of ibuprofen.

Ibuprofen (IBP) is a carcinogenic non-steroidal anti-inflammatory drug (NSAID). It is of certain hazard to aquatic animals and may cause potential harm to human health. As traditional methods cannot effectively remove such a pollutant, many advanced oxidation processes (AOPs) have been developed for its degradation. The electro-Fenton process has the advantages of strong oxidative ability, a synergistic effect of various degradation processes, and a wide application range. This study developed a high-performance gas diffusion electrode (GDE) for electrochemical hydrogen peroxide (H2O2) production. The optimum system performance was found at the current density of 10 mA cm-2, pH of 7.0, and air flow rate at 0.6 L min-1, where the accumulation of H2O2 could reach as high as 769.82 mg L-1. The computational fluid dynamics (CFD) simulation results revealed a fast mass-transfer property in this electro-Fenton system with U-tube GDEs, which resulted in a deep-level degradation (∼100%) of the pollutant (IBP) and a low-concentration degradation of 10 mg L-1 within a 120-min reaction period. The high-performance liquid chromatography-mass spectrometry (LC-MS) studies demonstrated that the hydroxyl radicals were the primary active species in the electro-Fenton system and that the degradation intermediates of IBP were mainly 1-(4-isobutylphenyl) ethanol and 2-hydroxy-2-(4-isobutyl phenyl) propanoic acid through four probable electro-Fenton degradation pathways. This report provides a facile and efficient way to construct a high-performance electro-Fenton reactor, which could be effectively used in advanced oxidation processes (AOPs) to remove emerging contaminants in wastewater and natural water.

Trichloroethylene remediation using zero-valent iron with kaolin clay, activated carbon and bacteria.

Nanoscale particles of zero-valent iron were used to form a permeable reactive barrier whose performance in dechlorinating a solution of trichloroethylene was compared with that of a barrier formed from limestone. The iron was combined with kaolin by calcination. The test liquid contained sewage sludge, and also added NH4Cl and KH2PO4. The average removal rates of trichloroethylene and phosphorus over 365 days both exceeded 94%. Chemical oxygen demand was reduced by 92% and ammonium nitrogen by 43.6%. All were significantly greater than the removals with the limestone barrier. The ceramsite barrier retained 85% of its effectiveness even after 365 days of use. Dechloromonas sp. was the main dechlorinating bacterium, but its removal ability is limited. The removal of trichloroethylene in such a barrier mainly depends on reduction by the zero-valent iron and biodegradation. The results show that the prepared ceramsite is stable and effective in removing trichloroethylene from water. It is a promising in-situ remediation material for groundwater.

Enhanced anaerobic reduction of nitrobenzene at high salinity by betaine acting as osmoprotectant and regulator of metabolism.

Anaerobic technology is extensively applied in the treatment of industrial organic wastewater, but high salinity always triggers microbial cell dehydration, causing the failure of the anaerobic process. In this work, betaine, one kind of compatible solutes which could balance the osmotic pressure of anaerobic biomass, was exogenously added for enhancing the anaerobic reduction of nitrobenzene (NB) at high salinity. Only 100 mg L-1 betaine dosing could significantly promote the removal efficiency of NB within 35 h at 9% salinity (36.92 ± 4.02% without betaine and 72.94 ± 6.57% with betaine). The relieving effects on salt stress could be observed in the promotion of more extracellular polymeric substances (EPS) secretion with betaine addition. Additionally, the oxidation-reduction potential (ORP), as well as the electron transfer system (ETS) value, was increased with betaine addition, which was reflected in the improvement of system removal efficiency and enzyme activity. Microbial community analysis demonstrated that Bacillus and Clostridiisalibacter which were positively correlated with the stability of the anaerobic process were enriched with betaine addition at high salinity. Metagenomic analysis speculated that the encoding genes for salt tolerance (kdpB/oadA/betA/opuD/epsP/epsH) and NB degradation (nfsA/wrbA/ccdA/menC) obtained higher relative abundance with betaine addition under high salt environment, which might be the key to improving salt tolerance of anaerobic biomass. The long-term assessment demonstrated that exogenous addition betaine played an important role in maintaining the stability of the anaerobic system, which would be a potential strategy to achieve a high-efficiency anaerobic process under high salinity conditions.

Self-cycled photo-Fenton-like system based on an artificial leaf with a solar-to-H2O2 conversion efficiency of 1.46.

Millions of families around the world remain vulnerable to water scarcity and have no access to drinking water. Advanced oxidation processes (AOPs) are an effective way towards water purification with qualified reactive oxygen species (ROSs) while are impeded by the high-cost and tedious process in either input of consumable reagent, production of ROSs, and the pre-treatment of supporting electrolyte. Herein, we couple solar light-assisted H2O2 production from water and photo-Fenton-like reactions into a self-cyclable system by using an artificial leaf, achieving an unassisted H2O2 production rate of 0.77 µmol/(min·cm2) under 1 Sun AM 1.5 illumination. Furthermore, a large (70 cm2) artificial leaf was used for an unassisted solar-driven bicarbonate-activated hydrogen peroxide (BAP) system with recycled catalysts for real-time wastewater purification with requirements for only water, oxygen and sunlight. This demonstration highlights the feasibility and scalability of photoelectrochemical technology for decentralized environmental governance applications from laboratory benchtops to industry.

Removal performance and mechanisms of Pb(II) and Sb(V) from water by iron-doped phosphogypsum: single and coexisting systems.

The serious environmental risks caused by Pb(II) and Sb(V) co-contamination increase the need for their efficient and simultaneous removal. In this study, the remediation feasibility by Fe-doped phosphogypsum (FPG) was elucidated for single systems with Pb or Sb pollutant and coexisting systems with both from water. As for single systems, Fe doping effectively enhanced the Pb(II) removal performance by phosphogypsum (PG) at low Pb(II) concentrations of below 100 mg/L via the combination of precipitation and complexation. The optimal removal rate of Sb(V) by FPG increased by 2.08-3.31 times as compared to that of by PG (10-120 mg/L), mainly due to the strong affinity of iron hydroxyl (≡Fe-O-H) towards Sb(V). Compared with the single systems, the coexistence greatly enhanced the Pb(II) and Sb(V) removal performance by FPG, and the interaction behavior between Pb(II) and Sb(V) on the FPG was concentration dependent. Briefly, the sorption of FPG controlled the elimination of low coexisting concentrations of Pb(II) and Sb(V), whereas the co-precipitation process between Pb(II) and Sb(V) predominated with high ions concentration. The significant synergistic effects were found during the removal of Pb(II) and Sb(V) on FPG in the coexisting system, which mainly attributed to precipitation, bridging complexation and electrostatic attraction. Considering the advantages such as facile preparation, low cost and high removal capacity, FPG is a promising material to uptake Pb(II) and/or Sb(V) from contaminated water.