To evaluate the possibility of utilizing polysaccharide-based biomaterial recovered from aerobic granular sludge as a coating material, the morphology, molecular weight distribution and chemical composition of the recovered biomaterial were investigated by atomic force microscopy, size exclusion chromatography and pyrolysis–GC–MS to have a better understanding of the properties of the biomaterial. The biomaterial recovered from aerobic granular sludge demonstrates chain-like structure. The molecular weight of 1/3 of the biomaterial is higher than 70 kDa. It is amphiphilic due to containing polysaccharides as a major fraction and lipids as a minor fraction. The biomaterial easily forms a film on a hydrophilic surface (e.g. paper), and functions as a water resistant barrier. Biomaterial recovery from waste aerobic granular sludge in biological wastewater treatment process provides a new resource of sustainable materials.