Effects of temperature on N2O production in the process of nitrogen removal by micro-expansion aerobic granular sludge

An SBR reactor was used to study the effect of temperature on N2O production in the process of nitrogen removal by micro-expansion aerobic granular sludge, as well as the removal efficiency of COD and ammonia nitrogen. The experiments were conducted at 21 +/- 0.5 degrees C, 26 +/- 0.5 degrees C, and 31 +/- 0.5 degrees C with low dissolved oxygen. The results showed that simultaneous nitrification and denitrification occurred in this system. The temperature had a significant influence on N2O production and N2O release rate; both increased with temperature going up. The ratios of N2O production to the influent nitrogen loading rate at 31 +/- 0.5 degrees C, 26 +/- 0.5 degrees C, and 21 +/- 0.5 degrees C were 8.07, 5.37, and 3.93%, respectively, which are higher than aerobic granular sludge. N2O release was 0.96mg/m(3) at 31 +/- 0.5 degrees C, which was 1.43 and 1.37 times the production at 21 +/- 0.5 degrees C and 26 +/- 0.5 degrees C, respectively, and dissolved N2O production was 1.46 +/- 0.05mg/m(3) at 31 +/- 0.5 degrees C, which was 2.86 and 1.60 times the production at 21 +/- 0.5 degrees C and 26 +/- 0.5 degrees C, respectively. As a result, 26 degrees C is recommended as a suitable temperature for reducing N2O emission and maintaining nitrogen removal efficiency in wastewater treatment.