Microalgae Production Using Wastewater: Effect of Light-Emitting Diode Wavelength on Microalgal Growth

Abstract

This study investigated the use of wastewater (WW) as a culture medium for microalgae under various CO2 concentrations (i.e., 0.0375%, 1%, and 15% CO2/balanced air [Bal.air]). Total nitrogen (TN) and total phosphorous (TP) removal were experimentally measured to determine whether WW is an effective culture medium for producing microalgae and correlation with microalgal growth at the fundamental level. Using WW to produce microalgae could be a feasible alternative to biological WW treatment, due to the high efficiency of TN and TP removal (i.e., > similar to 90% at 15% CO2/Bal.air). The growth rate of microalgae was enhanced by nearly double under 15% CO2/Bal.air during the experimental period of 6 days. This study also investigated the effect of different wavelengths from light emitting diodes (LEDs) on microalgal growth. The optimum photosynthetic photon flux density for the microalgal growth with white flat-panel LEDs was similar to 135 mu mol/(m(2).s) at the stage of increasing population, indicating that light intensity >135 mu mol/(m(2).s) would expedite photosynthesis. This study also showed that blue and red LED lighting could be selectively applied to optimize the different stages of microalgal production.