The effect of high-pressure homogenization (HPH) treatment on characteristics of dissolved organic matters (DOM) in sewage sludge was investigated. Soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), protein and polysaccharide concentration in sludge supernatant significantly increased after HPH treatment. Fourier-transform infrared (FTIR) spectra showed that the main components in the DOM for raw sludge were protein and polysaccharide, while for the treated sludge were protein, polysaccharide and lipid. The spectra of fluorescence excitation-emission matrix (EEM) for DOM showed two protein-like peaks at the excitation/emission wavelengths (Ex/Em) of 225/330-340 nm and 275/310-335 nm. A single broad shoulder representing substances with aromatic structure in range 245-270 nm was found in ultraviolet (UV) spectra of the DOM for the treated sludge. Homogenization pressure and homogenization cycle number affected the content of aromatic carbon per unit DOC. The maximum BOD5/SCOD ratio of 0.48 was achieved at 60 MPa with a single homogenization cycle. (C) 2012 Elsevier Ltd. All rights reserved.