Electricity generation, desalination and microalgae cultivation in a biocathode-microbial desalination cell

Recently, microalgae has received a high attention for application in bioelectrochemical systems due to its potential to be used for oxygen generation and biodiesel production. In this study performance of algal biocathode in a microbial desalination cell (MDC) was evaluated against air cathode and biocathode microbial fuel cell (MFC). Effluent of a dairy wastewater treatment plant with COD of 1000 mg l−1 was utilized as substrate in the anode and the microalgae Chlorella vulgaris was inoculated in the cathode using a synthetic culture media. Experiments were conducted using two different saline water concentrations including 15 g l−1 (MDC-1) and 35 g l−1 (MDC-2) in a desalination cell and produced power density, salt removal rate and algae growth were monitored. Maximum power density of 20.25 mW m−2 was observed in MDC-2 which was over two-times higher than that for MDC-1. This indicates the positive effect of using more concentrated saline solution on power generation due to higher conductivity and less internal resistance in the middle chamber. Moreover, salinity removal rate of 0.341 g l−1 day−1 in MDC-2 (1.5 times higher than MDC-1) as well as higher algal growth (38%) in MDC-2 proved the higher performance of the MDC when more concentrated saline solution was used. Maximum power density generated by MDC-2 was comparable to that for MFC with air cathode (19.80 mW m−2), however the MDC used in this work has the advantage of simultaneous saline removal and algae growth in a bioelectrochemical system.