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• The system performs best at 6 h hydraulic retention time. • It achieved 0.215 g/h salts removal at a wastewater treatment capacity of 10 L/d. • Microbial community structures are consistent with the spatial structure of cathode. • Catholyte circulation should be effective for the stratified microbial structures. In this study, two dual-anode assembled microbial desalination cells (DA-MDCs) composed of two anodes, one cathode and two membrane stacks were constructed, with a hollow fiber membrane (HFM) module coupling into the cathode to filtrate suspended solids and microbes. Enriched domestic wastewater treatment performance of the DA-MDC system under different hydraulic retention time (HRT) was investigated in detail. When HRT sequentially decreased from 10 h, 8 h, 6 h to 4 h, the conductivity in diluent effluent kept stable at first, but increased 519% at 4 h compared with 6 h. Nevertheless, the chemical oxygen demand, total nitrogen and total phosphorus in the effluent met the wastewater discharge standards in China at all HRTs. Additionally, transmembrane pressure of the HFM modules increased sharply when HRT changed from 6 h to 4 h. Therefore, HRT 6 h was selected as the optimal condition. Under such short HRT, the system realized wastewater treatment capacity of 10 L/d, surpassing all bio-cathode microbial desalination cell systems aiming to realize efficient treatment of domestic wastewater. Additionally, the salt removal rate of 0.215 g/h was more than two times compared with most similar systems. Finally, stratified microbial community structures in the cathodes of the system were found. This gave evidence on the efficient catholyte recirculation which might facilitate nitrogen removal from wastewater. [ABSTRACT FROM AUTHOR]

Conventional microbial desalination cells (MDCs) extract organic energy from wastewater for in situ desalination of saline water, but cannot treat industrial wastewater containing high strength organics that may cause blocking in the thin membrane stack. In this study, a multi-stage MDC (M-MDC) was fabricated and operated for simultaneous treatment and desalination of diluted industrial wastewater. With wastewater (COD: 8723 ± 456 mg/L, conductivity: 24,612 ± 772 μS/cm) flowing serially from anode-1 → cathode-1 → anode-2 → cathode-2, the maximum power density of the M-MDC reached 566.1 mW/m 2 , with removal efficiencies of COD, TN, NH 4 + -N, and conductivity reaching 97.8%, 90.6%, 98.4%, and 31.6% respectively with addition of 1 V external voltage. The high strength organics were significantly removed due to alternative anaerobic/oxic conditions, the nitrogen removal was enhanced by simultaneous electrical migration and biological nitrification/denitrification. Moreover, the addition of external voltage enhanced current generation (67.4 ± 3.9 mA), desalination efficiency, coulombic efficiency (14.1%), and organics removal in two anodes (47.3%), producing an effluent (COD < 500 mg/L, TN < 15 mg/L) qualified to be discharged into municipal wastewater pipe systems. These results indicated great potential of M-MDC to work as a pretreatment technology for high strength industrial wastewater. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mixed resin packed MDC removed multiple anions better than multiple cations. [•] Both molar conductivity and exchange selectivity affected migration of multiple ions. [•] Scaling was observed on the surface of CEM when desalinating multiple cations. [•] Conductivity of resin decreased when desalinating multiple cations for long time. [•] Resin packed MDC is more suitable for desalination of water with lower hardness. [Copyright &y& Elsevier]

Abstract: A novel configuration of microbial desalination cell (MDC) packed with ion-exchange resin (R-MDC) was proposed to enhance water desalination rate. Compared with classic MDC (C-MDC), an obvious increase in desalination rate (DR) was obtained by R-MDC. With relatively low concentration (10–2g/L NaCl) influents, the DR values of R-MDC were about 1.5–8 times those of C-MDC. Ion-exchange resins packed in the desalination chamber worked as conductor and thus counteracted the increase in ohmic resistance during treatment of low concentration salt water. Ohmic resistances of R-MDC stabilized at 3.0–4.7Ω. By contrast, the ohmic resistances of C-MDC ranged from 5.5 to 12.7Ω, which were 55–272% higher than those of R-MDC. Remarkable improvement in desalination rate helped improve charge efficiency for desalination in R-MDC. The results first showed the potential of R-MDC in the desalination of water with low salinity. [Copyright &y& Elsevier]