Nitrite accumulation and nitrous oxide emission during denitrification processes with quinoline or indole as the sole carbon source

BACKGROUNDBatch experiments were conducted to investigate nitrite accumulation and N2O emission during the denitrification processes when quinoline or indole was used as the sole carbon source. The effects of COD/NO3--N ratio and pH were studied. RESULTSWhile both significant transient nitrite accumulation and N2O emission occurred when quinoline was used as the carbon source, little denitrification intermediates were observed when indole was used as the carbon source. The optimal COD/NO3--N ratio for both complete denitrification and degradation of quinoline and indole were 6.8 and 5.1. Denitrification was inhibited under acidic conditions no matter with quinoline or indole as the carbon source. The optimal pH was 7.5 for both quinoline (or indole) degradation and denitrification. The nitrite accumulation and different carbon source further influenced N2O emission. When quinoline was used as the carbon source, N2O emission was observed at COD/NO3--N5 and pH 7.5; when indole was used as the carbon source, N2O emission was observed at COD/NO3--N3 and pH 6.5. Higher concentration of N2O was emitted at lower COD/NO3--N ratio and pH. CONCLUSIONCOD/NO3--N ratio, pH and the types of carbon source significantly influenced the accumulation of denitrification intermediates. (c) 2014 Society of Chemical Industry