Simultaneous Power Generation and Desalination of Microbial Desalination Cells Using Nannochloropsis salina (Marine Algae) Versus Potassium Ferricyanide as Catholytes

Power generation and desalination performance of microbial desalination cells (MDCs) were compared using two different catholytes; (1) Nannochloropsis salina, a marine algae and (2) potassium ferricyanide. Three chambered MDCs were constructed. Desalination efficiencies were 45%, 79%, and 46% when the algae was used as catholyte and 46%, 73%, and 16% when KFe(CN)6 was used as the catholyte at (35, 17.5, and 8.25g/L of NaCl) respective salt concentrations. Chemical oxygen demand removal of anolyte substrate was 85% with algae as the catholyte and 83% with KFe(CN)6 as the catholyte, after 24h of operation. MDC with the marine algae catholyte produced 384 plus or minus 5 mW/m3 during the first hour of operation while the MDC with KFe(CN)6 catholyte generated 1,532 plus or minus 14 mW/m3. Denaturing gel gradient electrophoresis of partial 16S rRNA genes showed clear differences between desalinating and nondesalinating microbial communities. Microbial community analysis reveals the shape and type of bacteria. Cyclic voltammetry showed reduction peaks for algae -250mV at a reduction current of -6mA and for potassium ferricyanide -50mV and -250mA. Results successfully demonstrated that the marine algae-assisted biocatholyte can be used for efficient desalination in MDCs, but generates low power compared to the chemical catholyte.