Search

• Multi-physics simulation guided the design and optimization of BES anodes. • Binary carbon anode was spatially assembled with carbon mesh skeleton and GAC. • Directional electron transfer and enhanced microbe accommodation were synergized. • Binary carbon anode improved wastewater energy conversion with cost-effectiveness. Bioelectrochemical systems (BESs) hold prospects in wastewater energy and resource recovery. Anode optimization is important for simultaneous enhancement of wastewater energy conversion and effluent quality in BESs. In this study, a multi-physics model coupling fluid flow, organic degradation and electrochemical process was constructed to guide the design and optimization of BES anodes. Based on the multi-physics simulation, spatially-assembled binary carbon anodes composed of three-dimensional carbon mesh skeleton and granular activated carbon were proposed and established. The granular activated carbon conducive to microbe accommodation played a vital role in improving effluent water quality, while the carbon mesh skeleton favoring electron collection and transfer could enhance the bioelectricity output. With an average chemical oxygen demand (COD) removal rate of 0.442 kg m−3 d−1, a maximum power density of 20.6 W m−3 was achieved in the optimized composite anode BES, which was 25% and 154% higher than carbon mesh skeleton BES and granular activated carbon BES. Electroactive bacteria were enriched in composite anodes and performed important functions related to microbial metabolism and energy production. The spatially-assembled binary carbon anode with low carbon mesh packing density was more cost-effective with a daily energy output per anode cost of 221 J d−1 RMB−1. This study not only provides a cost-efficient alternative anode to simultaneously improve organic degradation and power generation performance, but also demonstrates the potential of multi-physics simulation in offering theoretical support and prediction for BES configuration design as well as optimization. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Biomimetic membrane anode with electroactive atomically-dispersed Fe was designed. • Fe-NCM availed biofilm colonization and microbe-electrode interfacial interaction. • Fe-NCM anode intensified wastewater treatment and energy conversion in BESs. • Intracellular electron production and extracellular electron transfer were elevated. Bioelectrochemical systems (BESs) are promising for future wastewater treatment towards carbon neutrality. Hemes, as the active centers of outer-membrane c-type cytochromes, play an important role in anodic electron transfer. In this work, a biomimetic Fe–N x incorporated carbon membrane (Fe-NCM) mimicking the heme active center was proposed based on a nanocage confinement-electrospinning strategy and applied as the anode in BESs. The aligned carbon fibers with high electrical conductivity could serve as the electron "expressway" for swift electron transfer while the Fe–N x nexus served as the "gas station" and endowed the membrane anode with boosted redox activity. The Fe-NCM anode featuring great biocompatibility and electrochemical activity was conducive to microbe adhesion and biotic-abiotic interfacial interaction. The power output and chemical oxygen demand (COD) removal rate constant in the BES with this Fe-NCM anode reached 1406 ± 44 mW m−2 and 0.42 ± 0.01 h−1 under filtration operation mode, which were 156% and 191% as high as those of the pristine carbon membrane. The introduction of Fe–N x species exerted a significant influence on the anodic biofilm property, composition and function, which were of importance to bolstering wastewater energy conversion. Metagenomics unveiled that simultaneous intensification of intracellular electron production and extracellular electron transfer processes was achieved in the Fe-NCM BES. The Fe-NCM anode with electroactive Fe–N x sites facilitated the biotic-abiotic interfacial interaction in BESs and highlighted the rational design of anodes for efficient wastewater treatment and energy conversion. [ABSTRACT FROM AUTHOR]

As a viable wastewater treatment and energy recovery technology, microbial fuel cell (MFC) requires more research with regard to the simultaneous achievement of high-quality effluent and high power generation. In this study, a novel flow-through carbon-based composite anode configuration is proposed, which combines the carbon cloth of two-dimensional anode with wooden granular activated carbon of three-dimensional anode. The proposed configuration enhances the performance of power production and chemical oxygen demand degradation by promoting the mass transfer, reducing internal resistance and increasing bioburden. Microbial fuel cell with the composite anode exhibited the highest maximum power density (1300 ± 50 mW m−2) and the highest chemical oxygen demand removal rate constant (0.155 ± 0.007 h−1) compared with the microbial fuel cell using the carbon cloth anode (1136 ± 46 mW m−2 and 0.072 ± 0.008 h−1) or the wooden granular activated carbon anode (1045 ± 32 mW m−2 and 0.129 ± 0.009 h−1). Meanwhile, at a lower chemical oxygen demand concentration (about 48 mg L−1), the microbial fuel cell with the composite anode maintained a current density of 2.4 A m−2, which is 18% higher than the wooden granular activated carbon anode (2.04 A m−2) and 400% higher than the carbon cloth anode (0.48 A m−2). The cyclic voltammetry and electrochemical impedance spectroscopy tests confirmed that the composite anodes displayed better electrochemical performance. Improving the flow rate and reducing the external resistance could effectively enhance the power production and chemical oxygen demand removal performance of microbial fuel cells, while the computational fluid dynamics simulation intuitively demonstrated the positive effect of the composite anode on chemical oxygen demand degradation. These results suggest that the flow-through composite anode provides a feasible strategy to simultaneously enhance the power generation and improve the effluent quality. Image 1 • A composite anode was constructed by optimizing 2D and 3D carbon anode materials.. • Flow-through composite anode MFC had higher power generation and COD removal rate. • Flow-through composite anode MFC maintained high power generation at low COD. • Reducing external resistance and improving flow rate enhanced the MFC performance. • Flow-through composite anode MFC was proved better COD removal in CFD simulation. [ABSTRACT FROM AUTHOR]

This work achieved nitrogen recovery from the wastewater treatment by the bioelectrochemical system with the concept of biohythane generation. In this study, 3D network electrode could improve the biohythane generation to reduce energy consumption of the nitrogen recovery, achieving the highest biohythane production rate at 0.123 m3 m−3 treated wastewater to obtain energy consumption at 0.77 kWh kg−1 N under 0.8 V, significantly lower than other traditional technologies (at about 1.3 to 14 kWh kg−1 N). Further microbial analysis was processed for voltage optimization, and 0.8 V was proved as best voltage for high abundance of Geobacter over Methanosarcina. Correlation factor and heatmap analysis indicated that the suitable voltage could benefit Geobacter growth for higher energy recovery. Furthermore, genera of Bacteroides and Azospirillum were found as key species. This study proved that the biohythane generation concept could outstandingly reduce the energy consumption for higher nitrogen recovery from wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

• Carbon fiber sponge MFC generates excellent current from wastewater. • The linkage mechanism of electricity generation and COD removal is studied. • Carbon fiber sponge exhibits remarkable stability under the operation for 2 years. • Carbon fiber sponge enhances electrochemical microbial adhesion. • Carbon fiber sponge has high electrochemical activity and low internal resistance. Microbial fuel cells (MFCs), as a typical kind of microbial electrochemical technologies (METs), can achieve energy recovery and wastewater treatment. Microbial adhesion on electrodes directly affects microbe-electrode interactions, determining the performance of electricity generation and organic degradation. The anode with suitable structure and operation mode can reduce the limitation of fiber diameter-structure-interface trade-off to enhance microbe-electrode interaction. Here, we fabricated a carbon submicro fiber sponge with fiber diameter close to the size of electrogenic microorganism and operated it in filtration mode to greatly improve energy conversion. The carbon submicro fiber sponge exhibits a superior current yield of 17.4 A m−2 in the polarization curve with high electrochemical activity in MFC, which is 74% higher than that of the commonly used carbon fiber cloth anode. A higher chemical oxygen demand removal rate of 2.9 kg m−3 d−1 is obtained with this novel anode (1.3-fold that of the benchmark). The linkage mechanism of electricity generation and organic degradation is analyzed. Moreover, a long-term stability is demonstrated with excellent current production after the operation over 2 years. Our results indicate that this carbon fiber sponge has remarkable application potential in microbial electrochemical technologies for energy recovery from wastewater. [ABSTRACT FROM AUTHOR]