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Abstract The energy consumed during the desalination process in a flow-electrode capacitive deionization (FCDI) is recovered by a two-chamber device, where the adsorbed electrodes are discharged with constant current. When single constant discharge current is applied, the maximum energy of 36.3 J can be obtained with 0.50 mA/cm2 discharge current density. Much more energy is recovered by applying successive discharge currents. With additional conductive agent carbon nanotubes in the suspend carbon electrodes, the ratio was further enhanced by 60%. Increased salt concentration of the electrolyte could decrease the energy consumption and improve the energy recovery. The energy recovery ratio was promoted to 9.4% when the salt concentration of the electrolyte increased to 9.60 g L−1. Highlights • Two-chamber device to recover the energy from FCDI. • Successive discharging currents benefit the energy recovery. • Additional CNT improved energy recovery ratio by 60%. • Increased salt concentration of electrode improved energy recovery performance. [ABSTRACT FROM AUTHOR]

Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6–14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm 2 . The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as <0.5 mm. The optimal configuration with 10 desalination cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications. [ABSTRACT FROM AUTHOR]

Recovery of nutrient resources from the wastewater is now an inevitable strategy to maintain the supply of both nutrient and water for our huge population. While the intensive energy consumption in conventional nutrient recovery technologies still remained as the bottleneck towards the sustainable nutrient recycle. This study proposed an enlarged microbial nutrient recovery cell (EMNRC) which was powered by the energy contained in wastewater and achieved multi-cycle nutrient recovery incorporated with in situ wastewater treatment. With the optimal recovery solution of 3 g/L NaCl and the optimal volume ratio of wastewater to recovery solution of 10:1, >89% of phosphorus and >62% of ammonium nitrogen were recovered into struvite. An extremely low water input ratio of <1% was required to obtain the recovered fertilizer and the purified water. It was proved the EMNRC system was a promising technology which could utilize the chemical energy contained in wastewater itself and energy-neutrally recover nutrient during the continuous wastewater purification process. [ABSTRACT FROM AUTHOR]