This study is aimed to examine the removal of nitrogen from high strength slaughterhouse wastewater at 11 degreeC via partial nitrification followed by denitrification (PND), using the intermittently aerated sequencing batch reactor (IASBR) technology. The slaughterhouse wastewater contained chemical oxygen demand (COD) of 6068 mg/L, total nitrogen (TN) of 571 mg/L, total phosphorus (TP) of 51 mg/L and suspended solids of 1.8 g/L, on average. The laboratory-scale IASBR reactors had a working volume of 8 L and was operated at an average organic loading rate of 0.61 g COD/(L-d). At the cycle duration of 12 h, COD was efficiently removed under three aeration rates of 0.4, 0.6 and 0.8 L air/min. Among the three aeration rates, the optimum aeration rate was 0.6 L air/min with removals of COD, TN, and TP of 98%, 98%, and 96%, respectively. The treated wastewater met the Irish emission standards. The microbial community analysis by fluorescence in situ hybridization shows 12 +/- 0.4% of ammonium oxidizing bacteria, and 7.2 - 0.4% of nitrite oxidizing bacteria in the general bacteria (EUB) in the activated sludge at the aeration rate of 0.6 L air/min, leading to efficient partial nitrification. PND effectively removed nitrogen from slaughterhouse wastewater at 11degreeC, but PND efficiency was dependent on the aeration rate applied. PND efficiencies were up to 75.8%, 70.1% and only 25.4% at the aeration rates of 0.4, 0.6, and 0.8 L air/min.

Effects of the aeration rate on nutrient removal from synthetic domestic wastewater using an intermittently aerated sequencing batch reactor (IASBR) were studied at ambient temperature. Two aeration rates, 0.8 and 1 L air/min, were studied. At the aeration rate of 0.8 L air/min, removals of COD, NH 4 + -N, total nitrogen (TN) and PO 4 3--P were 84%, 96%, 75% and 99%, respectively. At the aeration rate of 1 L air/min, removals of COD, NH 4 + -N, TN and PO 4 3--P were 90%, 99%, 70% and 66%, respectively. The increased DO concentrations resulted in improved nitrification, but interfered with denitrification and enhanced biological phosphorus removal (EBPR).