This study aimed to examine the removal of nitrogen from high strength slaughterhouse wastewater at 11oC 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(SS)of 1.8 g/L,on average.The laboratory-scale IASBR reactors had a working volume of 8 Land was operated at an average organic loading rate of 0.61 g COD/(L·d).At the cycle duration of 12 hours,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(FISH)shows 12 ± 0.4%of ammonium oxidizing bacteria(AOB),and 7.2 ± 0.4%of nitrite oxidizing bacteria(NOB)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 11oC 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.