Water deionization with renewable energy production in microalgae - microbial desalination process

Photosynthetic microbial desalination cells (PMDCs) using microalgae biocathode (Chlorella vulgaris species) were evaluated under three different process configurations. Static (fed-batch, SPMDC), continuous flow (CFPMDC) and a photo-bioreactor MDC (PBMDC), were developed to study the impact of process operation and design on wastewater treatment, water deionization, electricity generation, nutrient removal, and biomass production capacities. The effect of TDS concentration in desalination compartment on the overall performance of SPMDC was also studied. TDS and COD removal rates and power densities have increased with increase in TDS concentrations in the desalination compartment. TDS removal rates were 21.4%, 29%, and 32.2% with corresponding COD removal of 58%, 63%, and 64% at 5 g/L, 20 g/L and 35 g/L respectively. The power densities at these TDS concentrations were 285 mW/m3, 550 mW/m3 and 675 mW/m3 respectively in SPMDCs. Although the electricity production was lower, a higher biomass growth rate of 7 mg L−1 h−1 was recorded for CFPMDC. The COD removal and nutrient removal potentials were similar in all three experimental configurations. Experimental studies show that SPMDCs are more appropriate for bioelectricity production due to biofilm formation while the continuous flow or photobioreactor PMDCs are suitable for microalgae biomass production.