Microbial Desalination Cell (MDC) is a developed technology for reducing salt concentration of seawater, so it could be used for people's daily needs. For increasing MDC performance, there was modification in reactor design, whereas the IEM membranes were arranged in two stacked design, yet in the end of desalination cycle there was a recirculation through anolyte-catholyte solutions to maintain pH level. The function of phosphate buffer as a buffer solution could be assisted with the recirculation of anolyte-catholyte which also maintain the pH level of solution. This research would examined the possibility of reducing the buffer phosphate volume with the recirculation process. The ratio of substrare volume and the buffer phosphate volume were: 1:1, 1:0.75, 1:0.5, and 1:0.25. The result showed that the optimum ratio of substrate volume and buffer phosphate volume in anode chamber was 1:0.5 respectively with TDR of 5.202 g/h.