Sludge taken from a wastewater treatment plant of the petrochemical industry was dewatered and pyrolyzed to produce liquid oil as an alternative fuel via microwave heating. Element contents of dried sludge were 45.9 +/- 3.85 wt.% carbon, 7.70 +/- 1.43 wt.% hydrogen, 4.30 +/- 0.77 wt.% nitrogen and 3.89 +/- 0.52 wt.% sulfur. Two major thermal degradation peaks of sludge were determined during the microwave pyrolysis process, one at 325-498 K (most of the water was vaporized, and the weight loss was over 85 wt.%) and the other at 548898 K for sludge constituent decomposition. Zn content was high in the dried raw material and residues. Other toxic elements such as Ni, Cr, Pb, As and Cd contents were 0.61-0.99, 0.18-0.46, 0.15-0.25, 0.018-0.034, and 0.006-0.017 mg/g, respectively. About 14-20 wt.% of oil was produced based on the dried sludge cake, and the oil major elements were C (69-72 wt.%), H (5.7-6.7 wt.%), N (1.9-2.2 wt.%), and S (0.58-0.82 wt.%). The heat values of liquid oils were 8700-9200 kcal/kg at 400-800 degrees C. (C) 2017 Elsevier B.V. All rights reserved.