The performance and microbial community structure of a novel bio-cord carrier during treatment of a polluted river at the laboratory scale was investigated. The bio-cord exhibited good filtration performance, with 87.2% SS removal and an 84.9% reduction in turbidity in 120 min, as well as 19.4-34.4%, 55.2-74.0%, 46.2-55.9% and 13.1-18.5% reductions in the COD, NH3-N, TN and TP, respectively, under three different hydraulic retention times. The bio-cord fibers also provided suitable conditions and support media for microbial growth. Additionally, 114 cloned 16S rDNA sequences were composed of Proteobacteria (57.9%). Bacteroidetes (17.5%) and other phyla (24.6%). There were great differences in bacterial quantity and composition between the surface and inside of the bio-cord. Furthermore, nitrifying and denitrifying bacteria were detected, suggesting that simultaneous nitrification and denitrification processes were occurring. Overall, the results of this study demonstrated that the carrier could attach microorganisms for polluted river treatment. (C) 2012 Elsevier Ltd. All rights reserved.