To eliminate N2O emission or utilize it for energy recovery

a laboratory-scale SBR inoculated with common activated sludge with acetate and nitrate additions decoupled

was conducted for endogenous denitrification running with anaerobic/anoxic cycles without DPAOs. During one cycle

approximately 50% of nitrate was converted to nitrite

N2O emission rate increased with nitrite accumulation

and 2.04% of removed nitrogen was emitted as nitrous oxide (N2O). Batch tests were conducted to compare the emission of N2O that was influenced by external carbon source dosage (C/N was 0

0.75 and 2.50) using nitrite as the electron acceptor before and after poly-β-hydroxybutyrate (PHB) was synthesized.The results showed that

the N2O emission was slightly decreased with the increase of total carbon source

and the N2O conversion ratio was between 0.24% and 1.61%. 15.90% of N2O conversion ratio was obtained in the absence of external organic carbon

the maximum N2O emission rate was 71.29 μg/(min·g)

and the N2O emission was 14-26 times higher than that of the other batch test results

indicating that when the PHB was the sole electron donor

the endogenous denitrification could produce more N2O using nitrite as the electron acceptor.