Biological nutrient removal (BNR) from high strength wastewater was investigated using a newly developed integrated anaerobic fluidized bed (AF) with circulating fluidized bed bioreactor henceforth called A-CFBBR. The A-CFBBR showed 99.7% COD removal, 84% nitrogen removal, with a very low sludge yield of 0.017 g VSS/g COD while treating a synthetic wastewater containing 10,700 mg COD/L and 250 mg NH3-N/L over a period of 6 months. The system was operated at an organic loading rate (OLR) of 35 kg COD/m(AF)(3)d and nitrogen loading rate (NLR) of 1.1 kg N/m(CFBBR)(3) data hydraulic retention time (HRT) of less than 12 h in the A-CFBBR. Microbial communities analysis using DGGE confirmed the presence of both AOBs and NOBs in the riser and downer. Pseudomonas putida and Pseudomonas fluorescence were the dominant denitrifiers present in the downer. Methanogenic activity was accomplished by a microbial mixture of archaea and bacteria in the anaerobic column. (C) 2012 Elsevier Ltd. All rights reserved.