An increasing amount of bisphenol A (BPA) is being produced and used, then discharged into sewage treatment plants and accumulated in sludge or soil, when the sludge is used as fertilizer. Accumulation of BPA in sludge or soil causes poisoning to the enzyme, which affects the biological treatment of sludge and the circulation and conversion of materials in soil. In this research, effect of BPA on sludge hydrolysis is studied from the respect of concentration and components of soluble organic matter in sludge, using three-dimensional fluorescence spectra. In order to illuminate the interaction mechanism, toxic effect of BPA on alpha-Amylase (a model of hydrolase in sludge) is investigated with multi-spectra, isothermal titration microcalorimetry and molecule docking at the molecular level. Results show that the secondary structure of alpha-Amylase and the microenvironment of amino acid residue in alpha-Amylase are changed. The molecular docking study and ITC results show that hydrophobic bond and hydrogen bond exist in the interaction between BPA and alpha-Amylase. Based on the above analysis and enzyme activity assay, sludge hydrolysis is inhibited due to the denaturation of alpha-Amylase with BPA exposure. (C) 2017 Elsevier B.V. All rights reserved.