BACKGROUND: The role of light intensity in microalgal cultivation supplied with CO 2 is still required to be fully investigated. This study researched the growth of Chlorella vulgaris (C. vulgaris), nutrient removal and carbon capture in the wastewater for various light intensities under the intermittent injection of CO 2 . RESULTS: The biomass for 80 mol m −2 s −1 reached maximum value within 6 days. The chlorophyll content of C. vulgaris exhibited an ascending trend when increasing the light intensity from 20 to 60 mol m −2 s −1 . Cultural pH for 80 mol m −2 s −1 showed the largest level of increase in the first 4 days, then began to decline. The light intensity of 80 mol m −2 s −1 had the quickest TN and TP reduction trend in the wastewater. The difference in consumed N versus P ratio was caused by the different specific growth rates and demands for nutrients at each growth stage of C. vulgaris. The degradation of tryptophan-like substances and the increase of other substances were likely due to the release of extracellular polymeric substance of C. vulgaris. CONCLUSION: The light intensity of 80 mol m −2 s −1 resulted in the highest biomass, the quickest TN and TP reduction trend in the wastewater. Light intensity exhibited no significant influence on removal of organic carbon, but affected the transformation of organic compounds in the wastewater under intermittent supply of 10% CO 2 .
RESULTS AND DISCUSSION
BiomassThe biomass of C. vulgaris presented an ascending trend when increasing the light intensity from 20 to 60 μmol m −2 s −1 , as described in Fig. 1(a). However, no significant differences in biomass were observed between 60 and 80 μmol m −2 s −1 . The biomass for 80 μmol m −2 s −1 reached a plateau within 6 days, being 1.04 g L −1 , whereas the plateaus (0.65, 0.95, 1.03 and 0.95 g L −1 ) were reached within 6.5 days for 20, 40, 60 μmol m −2 s −1 and gradual increase treatments. Thus, C. vulgaris attained the maximum biomass for various light intensities at 6 or 6.5 days. Higher light intensity resulted in an increase in maximum biomass concentration achievable, but when the light intensity was above a certain threshold value, the highest biomass achievable become lower. The result was in agreement with the finding J Chem Technol Biotechnol 2018; 93: [3582][3583][3584][3585][3586][3587][3588][3589]