Improvement of bioelectricity generation and microalgal productivity with concomitant wastewater treatment in flat-plate microbial carbon capture cell

Abstract

The unprecedented increase in global population has triggered the energy crisis, climate change and waste disposal issues which are necessitated the advancements in waste to energy technologies. The present study is directed towards evaluating the potential of microbial carbon capture cells (MCC) for simultaneous power generation, wastewater treatment and microalgal biomass production. Chlorella sorokiniana was used to establish the biocathode using anodic effluent as feed. The developed MCC was affected by physico-chemical parameters such as inlet pH, light intensity and photoperiod. The inoculum age of 12 h, inoculum size of 20%v/v, inlet pH 7.5, light intensity of 140 µmol m−2 s−1 and photoperiod of 12:12 (Light:dark) were asserted as most suitable conditions for achieving high performance of biocathode. The electricity generation was dependent upon the O2 availability at cathode and a drastic drop in voltage was observed under O2 limited conditions. Supplementation of anodic off-gas alone to cathode was not sufficient to sustain the growth of microalgae. However, combining internal anodic CO2 channelling with external CO2 pumping at cathode enhanced the performance of MCC. The experimental results revealed maximum open circuit voltage of 637 mV with a maximum power density of 2.32 W m−3. The maximum microalgal dry cell mass of 812 mg L−1 was achieved with an overall COD removal efficiency and energy recovery of 92–95% and 59%, respectively. These sustainability studies show that such a strategy can be applied for real time industrial flue gas treatment along with wastewater treatment in the future.