Influence of light intensity on microalgal growth, nutrients removal and capture of carbon in the wastewater under intermittent supply of CO2 : Influence of light on wastewater treatment

BACKGROUND The role of light intensity in microalgal cultivation supplied with CO2 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 CO2. RESULTS The biomass for 80 mu 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 mu mol m(-2) s(-1). Cultural pH for 80 mu 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 mu 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 mu 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% CO2. (c) 2018 Society of Chemical Industry