Technicial Study On Microbial Desalination Cell In Salt Water Desalination

Microbial desalination cells (MDCs) is a new and sustainable technology todesalinate seawater and saltwater. The MDC was developed from the study of microbialfuel cells (MFCs). A desalination chamber, in which salt water was added. was setbetween the anode chamber and cathode chamber based on the basic model of MFC.The main purpose of this study is to achieve a high desalination efficiency through theinvestigation of the influence factors on the performance of MDC, optimization of theconfiguration and operating conditions. Meanwhile, capacitive deionization (CDI)technology was combined with MDC to accomplish a deep desalination for salt waterwithout electrical energy input.Studies of the start-up mode of MDC, electrode forms, anolyte conditions, volumeof the desalination chamber were carried out. The influencing factors that affect theperformance of the MDC were analyzed. The desalination performance of the MDCoperated under batch and continuous mode was compared. A3-chamber MDC was usedin the experiment with ferricyanide as catholyte. Tthe results showed that, under thecontinuous flow operation condition, with HRT for salt water of5d and HRT foranolyte of8.3h, the average desalination efficiency of76.2%was achieved, the averagedesalination rate was8.8mg/h, the produced voltage ranged from500to600mV and thevolume ratio of consumed anolyte to salt water was14:1. While under the batchoperation condition, the average desalination efficiency was46.6%, the averagedesalination rate was5.4mg/h, the voltage decreased from600mV to40mV within onefed batch cycle, the volume ratio of consumed anolyte to salt water was5:1. It isobvious that the performance of the MDC under the continuous operating condition wassuperior to that under the batch mode, however, more anloyte was needed. Furtherinvestigation showed that, for the desalination of the salt water with salinity lower than10g/L, the average producing water ratio would be decreased.CDI technology was employed to combine with MDC for low salinity salt watertreatment. Experiment designed for optimization of process of CDI was carried out. Theresults indicated that, by using the MDC to desalinate the salt water with high salinity,followed by CDI technology when the concentration was lower than10g/L, thecombined process was proved to be effective and economic.