The effects of wavelength and wavelength mixing ratios on microalgae growth and nitrogen, phosphorus removal using Scenedesmus sp. for wastewater treatment

In wastewater treatment using microalgae, the effects of wavelength and wavelength mixing ratio on microalgae growth and removal of nitrogen and phosphorus were evaluated using LEDs (white light, 670 nm, 450 nm, and 525 nm). Microalgae production rates were enhanced by a maximum of 45% with 400–700 nm white light compared to that of a single wavelength. The phosphorus removal rate was as high as 90% with blue light. When red light and blue light were mixed and supplied, the microalgae production rate was about 50% higher than the rate of the culture with white light. Nitrogen and phosphorus removal rates were as high as approximately 15 mg/L/day at a wavelength mixing ratio of 7 (red light):3 (blue light) and 2.1 mg/L/day at a wavelength mixing ratio of 5 (red light):5 (blue light).