Wastewater sludge contains most of the nutrients required for growth of microorganism. In this study, thermal and chemical (acidic and alkaline)-thermal treatments were applied to different sludge suspended solids concentrations (10-30 g/L) and the pre-treated sludge was used as raw material for lipid production by Trichosporon oleaginosus. The results showed that compared to 48 h with thermal pre-treated sludge, only 42 h was required in chemical-thermal pre-treated sludge to obtain maximum lipid content (around 39% w/w) by T. oleaginosus. The experiments using struvite formation to reduce nitrogen (ammonia nitrogen) amount and hence to increase C/N ratio showed that the formation was not an efficient way to enhance lipid accumulation as ammonia nitrogen contributes to a very small weight of total nitrogen. The biodiesel produced by pre-treated sludge in the study mainly contains C14, C16, and C18, which are also rich in currently commercial biodiesel produced from soybean seed, canola, and sunflower seed oils. It shows the new approach that wastewater sludge as a feedstock for the production of biodiesel. (C) 2014 Elsevier Ltd. All rights reserved.