Nutrient removal and community structure of wastewater-borne algal-bacterial consortia grown in raw wastewater with various wavelengths of light

The use of microalgae-bacteria co-culture systems is attractive for wastewater treatment. On the other hand, naturally developed wastewater-borne algal-bacterial consortia growing in real wastewater has rarely been studied and characterized. In this study, wastewater-borne algal-bacterial consortia was grown for photosynthetic oxygen production, nutrient removal, and biodiversity in real wastewater using light-emitting diodes (LEDs) with various wavelengths (blue, green, red, and white light) and intensities (250, 500, 1,000, and 2000 μmol m⁻²s⁻¹). Among the four wavelengths, green light showed the highest tolerance to photoinhibition but the energy efficiency for oxygen production was the lowest. In addition, illumination with red and white lights at 500 μmol m⁻²s⁻ onto 500 mg TSS L⁻¹ appeared to be practical and efficient. In PSBRs operation, the illumination of red and white light resulted in removal ratios of 88.3% and 79.0% for TN, 96.8% and 97.0% for TP, 92.4% and 91.9% for TSS, and an algal biomass productivity of 1.03 and 1.01 g L⁻¹ d⁻¹, respectively. The diversity of bacteria was changed by the different wavelength of light, but the dominant species of algae was not changed. These results are expected to provide valuable technical information on algae-based wastewater treatment systems.