Enhancement of wastewater treatment efficiency through modulation of aeration and blue light on wastewater-borne algal-bacterial consortia

Since few studies have investigated the nitrification and assimilation of nitrogens by algal-bacterial consortia, this study aimed to evaluate the effects of supplementary aeration and blue light on nitrogen removal and biomass growth of algal-bacterial consortia in real domestic wastewater. When blue light was weakly irradiated (500 μmol m⁻² s⁻¹), it was found that supplementary aeration enhanced ammonia removal from 38.5% to 96.3% and algal growth from 72.5 mg algae L⁻¹ to 345.3 mg algae L⁻¹ by providing oxygen for nitrification and inorganic carbon for photosynthesis of microalgae. It was also observed that ammonia was consumed first and then nitrate produced by nitrification was assimilated, indicating that diauxic growth of consortia on nitrogen sources occurred. Thus, it was expected that nitrogen removal could be enhanced by lowering nitrification and denitrification loads. Moreover, intense blue light was found to accumulate nitrite by selective photoinhibition of nitrite oxidizing bacteria (NOB) of which c-type cytochrome is known to be photo-bleachable at 408 nm. From these results, it was concluded that favorable conditions for growth and nitrogen removal by algal-bacterial consortia in real wastewater could be established by controlling aeration and light intensity.