[Impact of different nitrogen concentrations on the N2O production in the denitrification process of granular sludge]

The aerobic-anoxic SBR biological wastewater treatment systems were used to examine the impact of different influent NH4(+) -N concentrations on the release of N2O and nitrogen removal in the simultaneous nitrification and denitrification of granular sludge. The results showed that when the influent NH4(+) -N concentration suddenly increased from the stable concentrations of 30 mg x L(-1) to 40 mg x L(-1), 60 mg x L(-1) and 80 mg x L(-1), the ammonia removal rate decreased from 80.04% to 61.40%, 39.65% and 31.02%, respectively, however, the ammonia nitrogen removal amount underwent little change, being about 25 mg x L(-1) in all cases; in addition, there was little influence of influent NH4(+) -N on the N2O production, under the four different influent NH4(+) -N concentrations, the N2O production in a typical cycle was 3.019 mg x m(-3), 3.489 mg x m(-3), 3.271 mg x m(-3), and 3.490 mg x m(-3), respectively, and the N2O emission rates were all around 0.0045 mg x (m3 x min)(-1). N2O was produced in both the aerobic stage and anoxic stage of the granular sludge simultaneous nitrification and denitrification system. Under different influent NH4(+) -N concentrations, the amount of NH4(+) -N removal by the granular sludge simultaneous nitrification and denitrification system was not changed, but significant decrease in nitrogen removal rate was observed with the increase in the influent NH4(+) -N concentration.