Supplementation of 5-deoxystrigol for higher pollutant removal and biogas quality improvement by different...

The treatment of biogas slurry by microalgae technology has the characteristics of low cost, environmental protection, and high efficiency. In this paper, the effects of four microalgae technologies, namely, monoculture of Scenedesmus obliquus (S. obliquus), co-culture of S. obliquus-activated sludge, co-culture of S. obliquus-Ganoderma lucidum (G. lucidum), and co-culture of S. obliquus-G. lucidum-activated sludge, on the treatment of biogas slurry were investigated. In addition, the effects of 5-deoxystrigol (5-DS) concentration and mixed light wavelengths (red-blue light intensity ratio) on nutrient removal and biogas upgrading were also investigated. The results showed that 5-DS significantly promoted the growth and photosynthetic performance of the microalgal system. The best purification performance could be achieved by co-cultivation of S. obliquus-G. lucidum-activated sludge when the 5-DS concentration was 10^-11  M, and the red-blue light intensity ratio was 5:5 (225:225 μmol m^-2  s^-1 ). The maximum average removal efficiencies for chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and carbon dioxide (CO₂ ) were 83.25 ± 7.87%, 83.62 ± 7.78%, 84.19 ± 8.25%, and 71.68 ± 6.73%, respectively. The co-culture technology of S. obliquus-G. lucidum-activated sludge had great potential and superiority in removing nutrients from biogas slurry and upgrading biogas at the same time. The results of this study will provide a reference for the simultaneous purification of wastewater and upgrading of biogas using microalgae technology. PRACTITIONER POINTS: S. obliquus-G. lucidum-activated sludge consortium showed the best removal performance. 10^-11 M 5-DS greatly promoted the purification performance. Removal efficiencies of COD, TN, and TP were more than 83%.