Sustainable microalgae cultivation by using anaerobic centrate and biogas from anaerobic digestion

This research was conducted to determine the effectiveness of using biogas generated from the anaerobic digestion of septic tank sludge and its anaerobic centrate on microalgal cultivation. Three types of sparging gas (biogas, air, and nitrogen gas) and two culture media (anaerobic centrate and Bold Basal Medium) were used to generate six different experimental settings. The most microalgal growth of 1074 mg VSS/L was achieved when both biogas and anaerobic centrate were used after 10 days of cultivation at 30 °C. In addition, the anaerobic centrate used had a reduction of 89% in its soluble chemical oxygen demand, a 97.3% reduction in the phosphorus concentration, and a 71.5% reduction in the nitrogen concentration. The results demonstrated tremendous benefits of biogas reuse and anaerobic centrate reclamation via microalgae cultivation.