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Abstract: A new microbial desalination cell with capacitive adsorption capability (cMDC) was developed to solve the ion migration problem facing current MDC systems. Traditional MDCs remove salts by transferring ions to the anode and cathode chambers, which may prohibit wastewater beneficial reuse due to increased salinity. The cMDC uses adsorptive activated carbon cloth (ACC) as the electrodes and utilizes the formed capacitive double layers for electrochemical ion adsorption. The cMDC removed an average of 69.4% of the salt from the desalination chamber through electrode adsorption during one batch cycle, and it did not add salts to the anode or cathode chamber. It was estimated that 61–82.2mg of total dissolved solids (TDS) was adsorbed to 1g of ACC electrode. The cMDC provides a new approach for salt management, organic removal, and energy production. Further studies will be conducted to optimize reactor configuration and achieve in situ electrode regeneration. [Copyright &y& Elsevier]

Abstract: Microbial desalination cell represents a new technology for simultaneous wastewater treatment, water desalination, and energy production. This study characterized the long-term performance of MDC during wastewater treatment and identified the key factors that caused performance decline. The 8-month operation shows that MDC performance decreased over time, as indicated by a 47% decline in current density, a 46% drop in Columbic efficiency, and a 27% decrease in desalination efficiency. Advanced electrochemical, microscopy, and spectroscopy analyses all confirmed biofouling on the anion exchange membrane, which increased system resistance and reduced ionic transfer and energy conversion efficiency. Minor chemical scaling was found on the cation exchange membrane surface. Microbial communities became less diverse at the end of operation, and Proteobacteria spp. was dominant on both anode and AEM fouling layer surface. These results provide insights into the viability of long-term MDC operation on reactor performance and direct system development through membrane optimization. [Copyright &y& Elsevier]

Abstract: The low conductivity and alkalinity in municipal wastewater significantly limit power production from microbial fuel cells (MFCs). This study integrated desalination with wastewater treatment and electricity production in a microbial desalination cell (MDC) by utilizing the mutual benefits among the above functions. When using wastewater as the sole substrate, the power output from the MDC (8.01W/m3) was four times higher than a control MFC without desalination function. In addition, the MDC removed 66% of the salts and improved COD removal by 52% and Coulombic efficiency by 131%. Desalination in MDCs improved wastewater characteristics by increasing the conductivity by 2.5 times and stabilizing anolyte pH, which therefore reduced system resistance and maintained microbial activity. Microbial community analysis revealed a more diverse anode microbial structure in the MDC than in the MFC. The results demonstrated that MDC can serve as a viable option for integrated wastewater treatment, energy production, and desalination. [Copyright &y& Elsevier]

The understanding and development of functioning systems are crucial steps for microbial fuel cell (MFC) technology advancement. In this study, a compact spiral wound MFC (swMFC) was developed and hydraulic residence time distribution (RTD) tests were conducted to investigate the flow characteristics in the systems. Results show that two-chamber swMFCs have high surface area to volume ratios of 350–700 m 2 /m 3 , and by using oxygen cathode without metal-catalysts, the maximum power densities were 42 W/m 3 based on total volume and 170 W/m 3 based on effective volume. The hydraulic step-input tracer study identified 20–67% of anodic flow dead space, which presents new opportunities for system improvement. Electrochemical tools revealed very low ohmic resistance but high charge transfer and diffusion resistance due to catalyst-free oxygen reduction. The spiral wound configuration combined with RTD tool offers a holistic approach for MFC development and optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biofilm on graphite felt formed without electric field was electroactive. • Starting biocathode in the anaerobic reactor can greatly shorten the startup time. • Dominant electron transfer changed from H 2 -mediated to direct electron transfer. • Functional microorganisms changed greatly through the inoculation passage. • Microbial community changed due to the balance between H 2 production and clearance. The rapid startup of carbon dioxide reduction-methanogenic microbial electrosynthesis is crucial for its industrial application, and the development of cathode biofilm is the key to its industrialization. Based on the new discovery that biofilm formed by placing graphite felt in an anaerobic reactor was electroactive, with strong direct electron transfer and methanogenesis ability (24.52 mL/L/d), a new startup method was developed. The startup time was shortened by at least 20 days and charge transfer resistance was reduced by 4.45–10.78 times than common startup methods (inoculating cathode effluent or granular sludge into the cathode chamber). The new method enriched electroactive bacteria. Methanobacterium and Methanosaeta accounted for 62.04% and 34.96%, respectively. The common methods inoculating cathode effluent or granular sludge enriched hydrogenotrophic microorganisms (>95%) or Methanosaeta (54.10%) due to the local environments of cathode. This new rapid and easy startup method may support the scale-up of microbial electrosynthesis. [ABSTRACT FROM AUTHOR]

[Display omitted] • S0 has a good NO 2 − accumulation rate, but the NO 2 − production rate is low. • Excessive S2− reacts with NO 2 − easily, resulting in a low NO 2 − accumulation rate. • S2− is easy to be used by microorganisms and the NO 2 − production rate is fast. • The spatial distribution of microorganisms varies greatly due to different solubility. • SSADN microbial community binding varies greatly with different reduced sulfur. In this study, two short-cut sulfur autotrophic denitrification (SSADN) reactors were initiated using different reduced sulfur forms as electron donors and their effects on the start-up speed of the SSADN process, NO 2 −-N accumulation characteristics, and microbial community were investigated. Results revealed that during the same period, due to the relatively slow S0 dissolution rate, the NO 2 −-N production rate realized by microorganisms in S0-SSADN (NO 2 −-N production rate (NPR), 174 mg/(L·d)) was significantly slower than S2−-SSADN (NPR, 679 mg/(L·d)). The NO 2 −-N accumulation efficiency (NAE) was maintained > 80%, which was significantly higher than S2−-SSADN. In the SSADN system using different reduced sulfur forms, the microbial community structure and abundance considerably differed. The main sulfur-oxidizing bacteria (SOB) in S0-SSADN were Sulfurimonas (6.5%) and Thiobacillus (5.3%). The main SOB species in S2−-SSADN was Thiomonas (13.6%). Thermomonas played an important role in the two reactors as an important NO 3 −-N denitrifying bacteria species. [ABSTRACT FROM AUTHOR]