Bioelectromics of a photosynthetic microalgae assisted microbial fuel cell for wastewater treatment and value added production
Ankesh Ahirwar, Mohd Jahir Khan, Priyanka Khandelwal, Gurpreet Singh, Harish, Vandana Vinayak, Makarand M. Ghangrekar
Abstract
Power generation and recovery of value-added products using microalgae, Haematococcus lacustris is tested in a dual chamber photosynthetic microalgae-assisted microbial fuel cell (PMA-MFCt 1 ). The microalgal cells in conical flask act as control. The performance was compared to another, test PMA-MFCt 2 . The control MFC in second test had electrode wires not connected (PMA-MFC nw ). The PMA-MFCt 1 set had microalgal catholytic media replenished unlike in PMA-MFCt 2 . A comparative PMA 0 -MFC, was used without microalgae and only water as catholyte. The results demonstrated maximum power density (PDmax) of 33.76 mW m −2 in PMA-MFCt 1 , 15.36 mW m −2 in PMA-MFCt 2 and 8.05 mW m −2 in PMA 0 -MFC. The non replenishment of catholytic media in PMA-MFCt 2 set resulted in nutrient limitations, poor photosynthesis, and disrupted redox reactions. Further lowest PDmax in PMA 0 -MFC proves that microalgae are excellent source of free nascent oxygen required for redox reaction. Taxonomic identity of microbes at the anode via 16 S rRNA showed the dominance of catalytic microbes mainly Proteobacteria. The different kinds of carotenoids from microalgae were estimated by UV-Vis and liquid chromatography-mass spectrometry (LC-MS) analysis. The microalgal growth, evaluated in terms of biomass dry weight (DW), was 118 mg L −1 , after 40 days of PMA-MFCt 1 operation, which was lesser than in control (conical flask) 123 mg L −1 . The pigments including total chlorophyll ( a + b), and total carotenoids were 699.7 µg g −1 and 224.6 µg g −1 , respectively, on day 16. Microalgal performance in PMA-MFCt 2 and its control (PMA-MFC nw ) was 10% and 32.52% inferior than in PMA-MFCt 1 and its control. The continuous replenishment of media in PMA-MFCt 1 maintained microalgal cells in continuous state of multiplication and photosynthesis resulting into higher bioelectricity generation and bioproducts than PMA-MFCt 2 , and PMA-MFC nw .