In situ electron generation through Fe/C supported sludge coupled with a counter-diffusion biofilm for electron-deficient wastewater treatment: Binding properties and catalytic competition mechanism of nitrate reductase.

A membrane-aerated biofilm-coupled Fe/C supported sludge system (MABR-Fe/C) was constructed to achieve in situ electron production for NO3--N reduction enhancement in different Fe/C loadings (10 g and 200 g). The anoxic environment formed in the MABR-Fe/C promoted a continual Fe2+release of Fe/C in 120 d operation (average Fe2+concentrations is 1.18 and 2.95 mg/L in MABR-Fe/C10 and MABR-Fe/C200, respectively). Metagenomics results suggested that the electrons generated from ongoing Fe2+ oxidation were transferred via the Quinone pool to EC 1.7.5.1 rather than EC 1.9.6.1 to complete the process of NO3--N reduction to NO2--N in Acidovorax, Ottowia, and Polaromonas. In the absence of organic matter, the NO3--N removal in MABR-Fe/C10 and MABR-Fe/C200 increased by 11.99 and 12.52 mg/L, respectively, compared to that in MABR. In the further NO2--N reduction, even if the minimum binding free energy (MBFE) was low, NO2--N in Acidovorax and Dechloromonas preferentially bind the Gln-residues for dissimilatory nitrate reduction (DNR) in the presence of Fe/C. Increasing Fe/C loading (MABR-Fe/C200) caused the formation of different residue binding sites, further enhancing the already dominant DNR. When DNR in MABR-Fe/C200 intensified, the TN in the effluent increased by 3.75 mg/L although the effluent NO3--N concentration was lower than that in MABR-Fe/C10. This study demonstrated a new MABR-Fe/C system for in situ electron generation to enhance biological nitrogen removal and analyzed the NO3--N reduction pathway and metabolic mechanism, thus providing new ideas for nitrogen removal in electron-deficient wastewater.

Synergistic roles of oxidation and self-aggregation in efficient ultrafiltration membrane fouling alleviation using a flow-through Sb-SnO2 anode during wastewater reclamation.

The application of ultrafiltration (UF) in wastewater reclamation alleviates the demand for limited water supplies. However, the membrane fouling caused by the effluent organic matter (EfOM) becomes a major obstacle for UF application. In this study, a pre-oxidation strategy for UF using a Sb-SnO2 (ATO) anode in flow-through mode was proposed with the hopes to improve the performance of UF during wastewater reclamation. The results indicated that this flow-through ATO (FA) anode significantly outperformed a boron-doped diamond (BDD) anode in terms of EfOM degradation and membrane fouling control. It is noteworthy that apart from oxidation, the self-aggregation behavior of foulants was also involved in the mechanisms of membrane fouling mitigation. On the one hand, FA pre-oxidation relieved the burden of membrane fouling by decomposing the macromolecular EfOM into small molecular organic matter, and even mineralizing it. The effective destruction of unsaturated EfOM by FA pre-oxidation made a remarkable contribution to fouling mitigation due to the strong correlation between the total fouling index and UV254. On the other hand, the surface morphology of membrane and interface properties of foulants revealed the self-aggregation behavior of foulants. FA pre-oxidation made the foulants aggregate spontaneously and reduced the potential of forming a dense cake layer on the membrane surface, which was conductive for water permeation. Overall, FA pre-oxidation proved to be a feasible and chemical-free option for UF pretreatment to simultaneously produce high-quality reused water and alleviate membrane fouling during wastewater reclamation.

Simulated-sunlight enhances membrane aerated biofilm reactor performance in sulfamethoxazole removal and antibiotic resistance genes reduction.

Membrane aerated biofilm reactors (MABRs) can be used to treat domestic wastewater containing sulfamethoxazole (SMX) because of their favorable performance in the treatment of refractory pollutants. However, biologics are generally subjected to antibiotics stress, which induces the production of antibiotic resistance genes (ARGs). In this study, a simulated-sunlight assisted MABR (L-MABR) was used to promote SMX removal and reduce ARGs production. The SMX removal efficiency of the l-MABR system was 9.62 % superior to that of the MABR system (83.13 %). In contrast from MABR, in the l-MABR, only 28.75 % of SMX was removed through microbial activity because functional bacteria were inactivated through radiation by simulated sunlight. In addition, photolysis (64.61 %) dominated SMX removal, and the best performing indirect photolysis process was the excited state of effluent organic matters (3EfOMs*). Through photolysis, ultraviolet (UV) and reactive oxygen species (ROS) enriched the SMX removal route, resulting in the SMX removal pathway in the l-MABR no longer being limited by enzyme catalysis. More importantly, because of the inactivation of functional bacteria, whether in the effluent or biofilm, the copy number of ARGs in the l-MABR was 1-3 orders of magnitude lower than that in the MABR. Our study demonstrates the feasibility of utilizing simulated-sunlight to enhance the antibiotic removal efficiency while reducing ARG production, thus providing a novel idea for the removal of antibiotics from wastewater.

Municipal wastewater contains antibiotic treatment using O2 transfer membrane based biofilm reactor: Interaction between regular pollutants metabolism and sulfamethoxazole degradation.

The antibiotic sulfamethoxazole (SMX) is frequently detected in wastewater treatment plant effluents and has attracted significant attention owing to its significant potential environmental effects. We present a novel O2 transfer membrane based biofilm reactor (O2TM-BR) to treat municipal wastewater to eliminate containing SMX. Furthermore, conducting metagenomics analyses, the interactions in biodegradation process between SMX and regular pollutants (NH4+-N and COD) were studied. Results suggest that O2TM-BR yields evident advantages in SMX degradation. Increasing SMX concentrations did not affect the efficiency of the system, and the effluent concentration remained consistent at approximately 17.0 µg/L. The interaction experiment showed that heterotrophic bacteria tend to consume easily degradable COD for metabolism, resulting in a delay (>36 h) in complete SMX degradation, which is 3-times longer than without COD. It is worth noting that the taxonomic and functional structure and composition in nitrogen metabolism were significantly shifted upon the SMX. NH4+-N removal remained unaffected by SMX in O2TM-BR, and the expression of K10944 and K10535 has no significant difference under the stress of SMX (P > 0.02). However, the K00376 and K02567 required in the nitrate reductase is inhibited by SMX (P < 0.01), which hinders the reduction of NO3--N and hence the accumulation of TN. This study provides a new method for SMX treatment and reveals the interaction between SMX and conventional pollutants in O2TM-BR as well as the microbial community function and assembly mechanism.

Environment-friendly and efficient electrochemical degradation of sulfamethoxazole using reduced TiO2 nanotube arrays-based Ti membrane coated with Sb-SnO2.

This study focused on the preparation, characterization, and sulfamethoxazole (SMX) removal performance of the SnO2-coated reactive electrochemical membrane (REM). This REM was fabricated by loading SnO2 on the reduced TiO2 nanotube arrays (RTNA)-based Ti membrane (TM). Regarding the dopant for SnO2, Sb was more effective in boosting the electrocatalytic activity than Bi, and the energy consumption for Sb-SnO2-coated REM (TM/RTNA/ATO) was lower than Bi-SnO2-coated REM (TM/RTNA/BTO). As for the internal layer, RTNA provided TM/RTNA/ATO with more electroactive surface areas and prolonged the service lifetime. Compared with batch mode, the SMX removal efficiency in flow-through mode was increased up to 8.4-fold. The SMX degradation performances were also affected by fluid velocity, current density, initial SMX concentration, and electrolyte concentration. The synergistic effects of •OH oxidation and direct electron transfer were responsible for the effective removal of SMX. TM/RTNA/ATO was proved to be stable and durable by multi-cycle and accelerated lifetime tests. Its extensive applicability was verified with high removal efficiencies of SMX in the surface water and wastewater effluent. These results demonstrate the promise of TM/RTNA/ATO for water treatment applications.

Dual role of boron-doped diamond (BDD) anode in effluent organic matter degradation and ultrafiltration membrane fouling mitigation.

Ultrafiltration (UF) is effective in retaining macromolecules during tertiary treatment, but the membrane fouling caused by the effluent organic matter (EfOM) limits its application. This study employed electrochemical oxidation (EO) as a pretreatment method for UF in tertiary treatment to investigate the effects of anode materials on membrane fouling alleviation and EfOM degradation. Compared with the dimensionally stable (DSA) and platinum (Pt) anodes, EO with a boron-doped diamond (BDD) anode exhibited better performances for membrane fouling mitigation due to the higher hydroxyl radical production activity of the BDD anode. It was observed that the current density and electrolysis time were closely related to membrane fouling when using a BDD anode, where increasing the current density or electrolysis time led to a significant improvement of specific flux. The BDD-based pre-oxidation efficiently removed 64% DOC, 76% UV254, and 95% fluorescence organic matter in EfOM, among which the concentrations of DOC and UV254 were positively correlated with the total fouling index (TFI). Meanwhile, 70% SMX in the secondary effluent was removed by the BDD anode. Furthermore, the BDD anode also mitigated membrane fouling by decomposing high molecular weight organic matter into smaller fractions and enhancing the electrostatic repulsion between membrane and EfOM. Therefore, the BDD-based EO process is a promising pretreatment strategy for UF to alleviate membrane fouling and improve the permeate quality.

Bacterial-algae biofilm enhance MABR adapting a wider COD/N ratios wastewater: Performance and mechanism.

Although membrane aerated biofilm reactor (MABR) is promising in nitrogen removal due to its counter-diffusion biofilms structure, it still cannot adapt a wider COD/N ratios wastewater. In this condition, expanding the MABR applicability range in different COD/N ratio wastewater is necessary. In this study, a bacterial-algae biofilm, instead of bacteria biofilm, supporting membrane aerated biofilm reactor (MABAR) was constructed, and the performance was compared to MABR. Results showed that the total nitrogen (TN) removal efficiency was promoted significantly in MABAR regardless of the COD/N ratio. Compared to MABR, effluent TN concentration in COD/N ratio of 2, 5, and 8 declined by 14.34 mg/L, 0.50 mg/L, and 12.10 mg/L, respectively. Nitrification inhibition test suggested that algae assimilation made an obvious contribution (at least 18.18 mg/L) to the NH4+-N removal in MABAR. Besides, redundancy analysis (RDA) indicates that MABAR has a negative correlation with Nitrospirae but is positively correlated with NH4+-N removal load. These results are consistent with the kinetics result that algae assimilation, instead of nitrification-denitrification, is responsible for the nitrogen removal in MABAR. Therefore, the change of nitrogen removal route further gave MABAR excellent adaptability and impact resistance to address wastewater with different COD/N ratios, which is conducive to its wide application.

Nighttime aeration mode enhanced the microalgae-bacteria symbiosis (ABS) system stability and pollutants removal efficiencies.

Utilizing external aeration to enhance the performance of microalgae-bacteria symbiosis (ABS) system has been extensively studied. However, inappropriate aeration damaged ABS system stability. A nighttime aeration mode (NA-ABS) in different aeration intensities (20, 50, 100 mL/min) was adopted to compare to continuous aeration microalgae-bacteria symbiosis (CA-ABS) mode and no-aerated mode on pollutants removal efficiencies and system stability. Results showed that NA-ABS system performed better on total organic carbon (TOC), NH4+-N, total nitrogen (TN) and PO43- removal than CA-ABS system, especially under the aeration intensity of 20 mL/min (NAI20), with the removal efficiencies of 96.59%, 99.18%, 90.30% and 89.16%, respectively. These results were because NA-ABS system prevented CO2 stripping and provided more dissolved inorganic carbon (DIC) for the microalgae growth. Furthermore, less CO2 stripping released the competition between microalgae and autotrophic bacteria for the DIC, leading to a more stable ABS system during long-term operation. This paper suggested that NA-ABS system would provide some new insights into ABS system and be helpful for further study.

Organic carbon promotes algae proliferation in membrane-aeration based bacteria-algae symbiosis system (MA-BA).

In the bacteria-algae (BA) system, the amount of oxygen produced by the algae is always insufficient for the organic carbon degradation, resulting in less inorganic carbon (IC) production. Meanwhile, the conventional extra aeration method always causes CO2 stripping and IC loss. Both two reasons limited the algae boosting. Membrane aeration (MA) has the excellent capability of organic carbon thorough degradation and gas blown-off control. In this study, MA-BA was employed to investigate the effect of organic carbon on the algae growth. Results showed that COD had a positive correlation with Chlorophyll-a (Chl-a) and algae proliferation in MA-BA system according to the redundancy analysis (RDA). The biggest Chl-a concentration (20.95 mg/cm2) occurred in R4 (COD = 400 mg/L). Stimulated algal population changed nutrient removal pathway from bacterial action to algae action. Meantime, Soared algae accumulation would selectively excite the abundance of bacteria that supported the algae growth, such as Acinetobacter, which exhibited a growing trend as the increase of influent COD, especially in the inner biofilm. This paper provided new insight into the effect of organic carbon on the algae in a novel MA-BA system, which will be helpful for future research.

Function of Thymosin Beta-4 in Ethanol-Induced Microglial Activation.

BACKGROUND/AIMS: Neuroinflammation mediated by activated microglia may play a pivotal role in a variety of central nervous system (CNS) pathologic conditions, including ethanol-induced neurotoxicity. The purpose of this study was to investigate the function of Tß4 in ethanol-induced microglia activation. METHODS: Quantitative real-time PCR was conducted to assess the expression of Tß4 and miR-339-5p. Western blot analysis was used to measure the expression of Tß4, phosphorylated p38, ERK, JNK, Akt, and NF-x03BA;B p65. The concentration of TNF-α and IL-1ß was determined using ELISA. NO concentration was measured using a nitric oxide colorimetric BioAssay Kit. Double immunofluorescence was performed to determine Tß4 expression, in order to assess microglial activation in neonatal mouse FASD model. RESULTS: Increased Tß4 expression was observed in ethanol treated microglia. Knockdown of Tß4 enhanced ethanol-induced inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) and nitric oxide (NO) in BV-2 cells was performed. Exogenous Tß4 treatment significantly inhibited expression and secretion of these inflammatory mediators. Tß4 treatment attenuated p38, ERK MAPKs, and nuclear factor-kappa B (NF-x03BA;B) pathway activation, and enhanced miR-339-5p expression induced by ethanol exposure in microglia. A neonatal mouse fetal alcohol spectrum disorders (FASD) model showed that Tß4 expression in the microglia of the hippocampus was markedly enhanced, while Tß4 treatment effectively blocked the ethanol-induced increase in inflammatory mediators, to the level expressed in vehicle-treated control animals. CONCLUSION: This study is the first to demonstrate the function of Tß4 in ethanol-induced microglia activation, thus contributing to a more robust understanding of the role of Tß4 treatment in CNS disease.

Exendin-4, a glucagon-like peptide-1 receptor agonist, inhibits Aß25-35-induced apoptosis in PC12 cells by suppressing the expression of endoplasmic reticulum stress-related proteins.

Neurodegenerative disorders are chronic and progressive disease. Exendin-4 (Ex-4) can function as a neuroprotective agent and has novel therapeutic ability for the treatment of neurodegenerative disorders. In this study, we aimed to explore the neuroprotective effect of Ex-4 on PC12 cell apoptosis induced by Aß25-35 in molecular level. The apoptosis of PC12 cells was detected by MTT assay, TUNEL staining and flow cytometry. The expression of ERS (endoplasmic reticulum stress, ERS) related proteins such as CHOP, GRP78 and Caspase-12 were determined by Western blot and cell immunocytochemistry. Results showed the apoptotic rate of PC12 cells significantly increased after Aß25-35 addition, which was remarkably reduced after Ex-4 treatment. The expression of CHOP, GRP78 and Caspase-12 were significantly upregulated, and then remarkably reduced after Ex-4 treatment, while in the presence of Exendin9-39, the effect of Ex-4 was reversed. In conclusion, endoplasmic reticulum stress might be involved in the apoptosis process of PC12 cell induced by Aß25-35 and Ex-4 might provide a potential strategy for the treatment and prevention of cell apoptosis-associated disorders.