An anaerobic dynamic membrane bioreactor (AnDMBR) treating municipal wastewater with a high flux of 65 L/(m(2) h) was operated for 11 months. Organic and inorganic membrane foulants and bulk sludge characteristics were investigated using particle size distribution analyzer, three-dimensional excitation-emission matrix fluorescence spectroscopy and X-ray fluorescence analysis. The fouling layers exhibited a double-layered structure, i.e., a loosely bound outer layer and a tightly bound internal layer. Besides that, there were foulants in membrane chambers due to the imperfect interception effect of solid particles by the dynamic membranes. Compared with the bulk sludge, membrane foulants in the internal layer and in the membrane chamber were found to have more fine particles. The Dacron mesh with large pore size could not achieve a good rejection of soluble macromolecules, which led to low soluble microbial products and extracellular polymeric substances contents in the membrane fouling layers but high contents in the foulants in membrane chambers. Microorganism activity and abundance analyses showed that the membrane foulants had some different communities and lower activities compared with the bulk sludge, which was attributed to the suppressed mass transfer in the foulants. (C) 2011 Elsevier Ltd. All rights reserved.