Impact of dissolved oxygen on the activity of anaerobic granular sludges

The effect of dissolved oxygen (DO) on the methanogenic activity of anaerobic granular sludges introduced into the expanded granular sludge bed (EGSB) reactor was measured in serum flasks. Results show that the specific methanogenic activity (SMA) decreases with DO increases. At 22°C, the SMA drops from 75.9 mL · (g · d)^-1, 91.1 mL · (g · d)^-1 to 47.6 mL · (g · d)^-1, 71.4 mL · (g · d)^-1, respectively as DO increases from 0.00 mg/L to 7.00 mg/L. Higher temperature can weaken this trend and significantly promote SMA. As the control levels of temperature is 28°C, 35°C, the SMA average increases by 54.0%, 114.4% compared with that of the first gas production experiment. The study confirms that the presence of dissolved oxygen in the influent of an EGSB reactor does not constitute any evidently detrimental effect on the performance of anaerobic treatment process. Anaerobic granular sludges are demonstrated high tolerance for dissolved oxygen so that in practice this factor can be neglected.