Simultaneous water desalination and electricity generation in a microbial desalination cell with electrolyte recirculation for pH control

A recirculation microbial desalination cell (rMDC) was designed and operated to allow recirculation of solutions between the anode and cathode chambers. This recirculation avoided pH imbalances that could inhibit bacterial metabolism. The maximum power density was 931 ± 29 mW/m2 with a 50 mM phosphate buffer solution (PBS) and 776 ± 30 mW/m2 with 25 mM PBS. These power densities were higher than those obtained without recirculation of 698 ± 10 mW/m2 (50 mM PBS) and 508 ± 11 mW/m2 (25 mM PBS). The salt solution (20 g/L NaCl) was reduced in salinity by 34 ± 1% (50 mM) and 37 ± 2% (25 mM) with recirculation (rMDC), and by 39 ± 1% (50 mM) and 25 ± 3% (25 mM) without recirculation (MDC). These results show that electrolyte recirculation using an rMDC is an effective method to increase power and achieve efficient desalination by eliminating pH imbalances.