Utilization of domestic wastewater as water source of Scenedesmus obliquus PF3 for the biological removal of nitric oxide (NO)

Abstract Biological removal of NO (Bio-DeNOx) from flue gas by microalgae is a promising technology, which has attracted increasing attention. Considering water source is a limitation on practical application of the Bio-DeNOx from flue gas by microalgae, we investigated the feasibility usage of domestic wastewater as the water source. The results showed that Scenedesmus obliquus PF3 accumulated 1.75 g L−1 biomass in domestic wastewater in 8 days, and 30 mg L−1 nitrate-N should be added in domestic wastewater to fulfill the nutritional requirement of the microalgae. Ammonium nitrogen in domestic wastewater has inhibitory effects on bio-removal of NO, leading to an 8% lower NO removal efficiency than that using clean water and nutrients (BG11 medium). These inhibitory effects disappeared as ammonium was exhausted by Scenedesmus obliquus PF3 after one day. To overcome the inhibition of ammonium and achieve a high NO removal efficiency, a strategy of connecting two reactors in series was put forward. Microalgae cultures in No.1 reactor was used to remove NO from flue gas, while microalgae cultures in No.2 reactor was used to remove ammonium from domestic wastewater, which can supply sufficient water without ammonium for microalgae in No.1. The removal efficiency of NO by two series reactors reached up to 71.2 ± 2.9%, much higher than that by single reactor (43.1 ± 3.6%). Besides, About 70.9 ± 4.8% of the supplied NO was fixed into microalgae cells in two series reactors, 1.75 times as high as that in the single reactor (40.6 ± 5.1%), suggesting that this strategy by connecting two reactors in series can realize effectively recovery of NO from flue gas using domestic wastewater as water source. Thus, this study may provide an economically viable water source for the application of microalgae in the biological DeNOx of flue gases.