Effect of Exogenous CO2 on Algae Growth and Wastewater Treatment under Simulated Natural LightDark Cycle using Municipal Wastewater as Feedstock（Extracts）

This study investigated the effect of exogenous CO2 on algae biomass accumulation and wastewater nutrient removal under different light intensities and a simulated natural lightdark cycle for algae strain Chlorella kessleri，using highly concentrated municipal wastewater（centrate）as feedstock.The results showed that Chlorella kessleri could easily adapt to centrate wastewater in batch reactors under simulated natural lightdark cycles with CO2 injections under all tested light intensities.Both CO2 concentration and light intensity had a significant effect on algae growth and nutrient removal from wastewater.The study confirmed that there was an optimum CO2 level for algae growth，which was 2.5% for this investigation.When the light intensity reached a certain lower limit，the effect of CO2 supplementation became minimum because the photoautotrophic efficiency was significantly reduced.It is also found that the application of continuous or fed-batch cultivation system was preferred over batch cultivation process due to the fact that the nutrients was depleted and the algae biomass concentration decreased on Day 8.