Soil contamination by petroleum–hydrocarbon is an environmental concern. In this study, the effects of sewage sludge and sewage sludge biochar under corn plant on remediation of oil contaminated soil in a greenhouse study was investigated. Sewage sludge and biochar were added to the soil at 10 and 20 t/ha. The oil contamination levels were 1, 2 and 5 percent. This experiment was conducted in a completely factorial design with three replications. Corn was harvested 14 weeks after cultivation. Corn yield (roots and shoots) and plant chlorophyll content decreased significantly with increasing oil concentration. Dispersible clay content of soil decreased and soil structural stability, water repellency and bulk densityincreased with oil contamination. The treatment with only corn plant 6 to 15 percent of petroleum hydrocabons was removed. Removal of petroleum hydrocarbons from soil significantly increased the plant dry weight. Removal of petroleum hydrocarbons was mostly done in treatments containing 1% oil contamination and by increasing the oil percentage the phytoremediation efficiency decreased. By increasing the amount of sewage sludge and biochar the removal of petroleum hydrocarbons increased. The maximum petroleum hydrocarbons removal rates occurred in sewage sludge (20 tons per hectare) treatment. Sewage sludge and biochar (20 tons per hectare) eliminate the 63 and 50 percent of petroleum hydrocarbons in a 98 days period, respectively. The efficiency of treatments for the removal of petroleum hydrocarbons were as follows: Biochar 10 tons per hectare Sewage sludge 10 tons per hectare Biochar 20 tons per hectare Sewage sludge 20 tons per hectare. Based on our results, we suggest using sewage sludge and its biochar as an amendment for oil contaminated soils. Keywords: Sewage sludge, Biochar, petroleum hydrocarbons, oil pollution
