A novel sequence batch membrane carbonation photobioreactor developed for microalgae cultivation

In this study,a novel sequence batch membrane carbonation photobioreactor was developed for microalgae cultivation.Herein,membrane module was endowed functions as microalgae retention and CO2 carbonation.The results in the batch experiments expressed that the relatively optimal pore size of membranes was 30 nm,photosynthetically active radiation was 36 W/m^2 and the CO2 concentration was 10%(v/v).In long-term cultivation,the microalgal concentration separately accumulated up to 1179.0 mg/L and 1296.4 mg/L in two periods.The concentrations of chlorophyll a,chlorophyll b and carotenoids were increased about 23.2,14.9 and 6.3 mg/L respectively in period I;meanwhile,the accumulation was about 25.0,14.5,6.6 mg/L respectively in the periodⅡ.Furthermore,the pH was kept about 5.5-7.5 due to intermittent carbonation mode,which was suitable for the growth of microalgae.Transmembrane pressure(TMP)was only increased by 0.19 and 0.16 bar in the end of periodsⅠandⅡ,respectively.The pure flux recovered to 75%-80%of the original value by only hydraulic cleaning.Scanning electron microscope images also illustrated that carbonation through membrane module could mitigate fouling levels greatly.