A Factorial Study of the Effect of Rhamnolipid and Stirring on the Electricity Production, Desalination, and Wastewater Treatment Efficiencies of a Five-Chamber Microbial Desalination Cell

This study was conducted to improve the voltage production, desalination, and COD removal efficiencies of a five-chamber Microbial Desalination Cell (MDC). To do this, rhamnolipid was added to anolytes only and catholytes stirred to determine the effects of these factors on the MDC activity. This was followed by a factorial study to investigate the effects of the interactions of rhamnolipid and stirring on the voltage production, desalination, and COD removal efficiencies of the MDC. Increasing the concentration of rhamnolipid to ۲۴۰ mg/L improved the peak voltage produced from ۱۶۴.۵۰ ± ۰.۱۱ to ۶۲۳.۷۰ ± ۱.۳۲ mV. Also, the desalination efficiency increased from ۲۰.۱۶ ± ۱.۹۷ % when no rhamnolipid was added to ۲۴.۸۹ ± ۰.۵۰ % at a rhamnolipid concentration of ۲۴۰ mg/L, and COD removal efficiency increased from ۴۸.۷۴ ± ۸.۰۶ % to ۶۴.۱۷ ± ۵.۰۰ % at a rhamnolipid concentration of ۴۰۰ mg/L. In the stirring experiments, increasing the number of stirring events increased peak voltage from ۱۶۴.۵۰ ± ۰.۱۱ to ۵۶۷.۲۷ ± ۱۸.۰۶ mV. Similarly, desalination and COD removal efficiencies increased from ۲۰.۱۶ ± ۱.۹۷ % and ۴۸.۷۴ ± ۸.۰۶ % to ۲۴.۲۶ ± ۰.۹۷ % and ۵۰.۲۳ ± ۱.۶۰ %, respectively, when the number of stirring events was more than twice a day. In the factorial study, voltage production, desalination, and COD removal efficiencies were ۶۴۷.۰۷ mV, ۲۵.۵۰ %, and ۶۸.۱۵ %, respectively. However, the effect of the interaction between rhamnolipid and stirring was found to be insignificant (p>۰.۰۵). Thus, the addition of only rhamnolipid or the stirring of catholytes only can improve the performance of the five-chamber MDC.

Keywords:

Voltage , COD , Exoelectrogens , Rhamnolipid , interaction effect