Effects of various LED light wavelengths and light intensity supply strategies on synthetic high-strength wastewater purification by Chlorella vulgaris

Chemical fertilizer agricultural wastewater is a typical high-strength wastewater that has dramatically triggered numerous environmental problems in China. The Chlorella vulgaris microalgae biological wastewater treatment system used in this study can effectively decontaminate the high-strength carbon and nitrogen wastewater under an optimum light wavelength and light intensity supply strategy. The descending order of both the dry weight for C. vulgaris reproduction and wastewater nutrient removal efficiency is red > white > yellow > purple > blue > green, which indicates that red light is the optimum light wavelength. Furthermore, rather than constant light, optimal light intensity is used for the incremental light intensity strategy. The phases for the optimal light intensity supply strategy are as follows: Phase 1 from 0 to 48 h at 800 μmol m^?2 s^?1; Phase 2 from 48 to 96 h at 1,200 μmol m^?2 s^?1; and Phase 3 from 96 to 144 h at 1,600 μmol m^?2 s^?1. Additionally, the optimal cultivation time is 144 h.