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• Excellent Te(IV) bioreduction could be achieved in sulfur autotrophic reactor. • Te(IV) bioreduction process conformed to First-order kinetics. • The existence of redox substances in EPS could promote electron transfer. • Metabolic activity and key enzyme activity were favorable for Te(IV) bioreduction. • C10-HSL and C14-HSL regulated the enrichment of three microbial communities. A laboratory-scale sulfur autotrophic reactor (SAR) was first constructed for treating tellurite [Te(IV)] wastewater. The SAR had excellent Te(IV) bioreduction efficiency (90-96%) at 5-30 mg/L and conformed to the First-order kinetic model. The Te(IV) bioreduction was elaborated deeply from extracellular polymeric substances (EPS) functions, microbial metabolic activity, key enzyme activity, microbial community succession and quorum sensing. Te(IV) stimulated the increase of redox substances in EPS and the improved cell membrane permeability led to the increase of electron transport system activity. Catalase and reduced nicotinamide adenine dinucleotide (NADH) alleviated the oxidative stress caused by Te(IV) toxicity to maintain metabolic activity. The increase of sulfur dioxygenase activity (SDO) suggested that more ATP produced by sulfur oxidation might provide energy for various physiological activities. Meanwhile, nitrate reductase (NAR), nitrite reductase (NIR) and sulfide: quinone oxidoreductase (SQR) played an active role in sulfur oxidation and Te(IV) bioreduction. Combined with the above results and dynamic succession of three functional microbial communities, a synergistic mechanism was proposed to explain the excellent performance of SAR. This work provided a promising strategy for Te(IV) wastewater treatment process and Te(IV) bioreduction mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Anaerobic granular sludge under allicin stress was successfully cultivated. • Excellent allicin-containing wastewater treatment performance was achieved. • The TB-EPS and PN enhanced the formation and allicin-tolerance of AnGS. • Long-chain AHLs had a positive effect on allicin stress resistance. • Acinetobacter and Petrimonas were the dominant allicin resistant genera. In order to treat allicin-containing wastewater with antimicrobial characteristic, anaerobic granular sludge (AnGS) under allicin stress was cultivated, which completely granulated on day 143 in the up-flow anaerobic sludge bed (UASB). The mature allicin-tolerant AnGS had a granule size of 0.356–2.000 mm with an excellent settleability, and the chemical oxygen demand (COD) removal efficiency reached 93.26 %. Moreover, the tightly-bound extracellular polymeric substances (TB-EPS) and extracellular protein (PN) enchanted the formation and tolerance of AnGS under the allicin environment. Meanwhile, the short-chain N-acylhomoserine lactones (AHLs) including C4-HSL, C6-HSL and C8-HSL were utilized by quorum sensing (QS) to regulate EPS production during AnGS formation process, while the long-chain AHLs including C10-HSL, C12-HSL and C14-HSL had a positive effect towards the allicin stress. In addition, Acinetobacter and Petrimonas were observed to be the dominant allicin resistant genera, which along with the EPS producers of Comamonas and Thauera enhanced the AnGS tolerance. These results confirmed that the AHL-mediated QS regulated EPS production and the growth of functional bacteria involved in allicin-tolerant AnGS formation. This provides useful information for AnGS application in treating allicin-containing wastewater. [ABSTRACT FROM AUTHOR]

• Fe (III) promoted the Te(IV) bioreduction rate by Shewanella oneidensis MR-1. • The electron transfer efficiency was explored using electrochemical methods. • ETSA increased due to an increase in NADH (electron generation) and cytochrome c. • Fe (III) enhanced ATP level during the Te(IV) bioreduction process. • The stability of TeNRs was improved due to a surface layer of EPS. The release of highly toxic tellurite into the aquatic environment poses significant environmental risks. The acceleration mechanism and tellurium nanorods (TeNPs) characteristics with bioavailable ferric citrate (Fe(III)) were investigated in the tellurite (Te(IV)) bioreduction. Experiments showed that 5 mM Fe(III) increased the Te(IV) bioreduction rate from 0 to 12.40 mg/(L·h). Cyclic voltammetry, electrochemical impedance spectroscopy and Tafel were used to investigate electron transfer during Te(IV) bioreduction. NADH production (electron production) was significantly enhanced to 138% by Fe(III). Meanwhile Fe(III) stimulated the increase of cytochrome c , resulting in increased electron transport system activity. In addition, Fe(III) facilitated the secretion of extracellular polymeric substances (EPS) and reduced cell membrane permeability, thus reducing the toxicity of Te(IV) to cells. The increase of ATP provided energy for the metabolic process of Te(IV) bioreduction, playing an active role in cell activity. Based on the above analysis, the acceleration mechanism of Fe(III) on Te(IV) bioreduction was proposed from the aspects of electron generation, electron transfer and energy level. Zeta potential and FT-IR spectra indicated that the stability of TeNPs contributed to the covered EPS. This study provides further understanding the acceleration mechanism of Te(IV) bioreduction and promising strategy for improving the stability of TeNPs. [ABSTRACT FROM AUTHOR]

The redox-active sulfonated porphyrin meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) was novelly proposed to facilitate the mediated electron transfer (MET) of the otherwise time-consuming selenite (Se(IV)) bioreduction. TPPS (0.2 mM) increased the Se(IV) (39.5 ± 1.0 mg∙L−1) bioreduction rate by Shewanella oneidensis ·MR-1 by 4- to 5-fold. UV–vis, redox potential, cyclic voltammetry, and electrochemical impedance spectroscopy showed that the underlying mechanism was the redox-active transformation of the porphyrin ring, which led to a 25% decrease of the activation energy. Furthermore, the Michaelis-Menten fitting and the experiments on specific respiratory chain inhibitors suggested that TPPS enhanced the MET efficiencies of NADH-CoQ, FAD-CoQ, and Cyt b L -Cyt b H with stronger affinity (Km−1 TPPS = 50.0 mM−1 > Km−1 control = 0.8 mM−1) between the Se(IV) and microorganisms. Interestingly, TPPS enhanced the MET efficiencies by increasing the contents of redox-active compounds in extracellular polymeric substances. This study offers a realistic application and further mechanistic understanding of porphyrins as redox mediators for the Se(IV) bioreduction. Image 1 • Meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) facilitates Se(IV) bioreduction. • TPPS enhanced the mediated electron transfer (MET) efficiencies as redox mediator. • The MET efficiencies were explored with three electrochemical methods. • Stronger affinity enhanced the MET efficiencies of TPPS in the respiratory chain. • Optimizing the EPS contents enhanced the MET efficiencies of TPPS. [ABSTRACT FROM AUTHOR]

• NH 4 +-N, NO 3 –-N and PO 4 3−-P were simultaneously removed in a single reactor. • Fe2+ increased the autotrophic denitrification rate by 1.2-fold. • PAD and SAD aligned with Zero-order and First-order kinetics models, respectively. • Protein-like substances and nitrogen removal performance were positively correlated. • Nitrifying and autotrophic denitrifying bacteria were simultaneously enriched. A biological aerated filter (BAF) with sulfur and pyrite as fillers were structured to simultaneously remove NH 4 +-N, NO 3 –-N and PO 4 3−-P from secondary effluent. When dissolved oxygen (DO) was 1.2–1.5 mg/L, effluent concentration of NH 4 +-N, NO 3 –-N and PO 4 3−-P were below 0.65, 0.47 and 0.18 mg/L, respectively. Meanwhile, Fe2+ production via decomposing pyrite could improve autotrophic denitrification performance. Besides, sulfur and pyrite autotrophic denitrification process (PAD and SAD) aligned with the Zero-order and First-order kinetics models, respectively, indicating that the sulfur had excellent capability of providing electron. Moreover, there was a positive correlation between the nitrogen removal performance and protein-like substances in extracellular polymeric substances. Bacterial community analysis suggested the nitrifiers and autotrophic denitrifiers were simultaneously enriched. Principal component analysis indicated that the DO concentration and type of electron donors impacted bacterial community. Consequently, BAF combined with PAD and SAD processes provides an alternative method to remove nutrients. [ABSTRACT FROM AUTHOR]