Iranian Journal of

Background & Objectives: Remaining crude oil in storage tanks lead to accumulation of oily sludge at the bottom of the tank, which should be treated and disposed of in a suitable manner. The aim of the present study was to investigate the efficiency of chemical oxidation using H₂O₂ and Fenton’s reagent in removal of Total Petroleum Hydrocarbons (TPH) from bottom sludge of crude oil storage tanks. Materials & methods: In this experimental study, hydrogen peroxide and Fenton’s reagent were added to the sludge in six concentrations including 2, 5, 10, 15, 20, and 30% (w w^-1) and TPH was measured for a period of 24 and 48 h of reaction time. The oxidants were added in a single and stepwise addition way, both to the pristine and saturated sludge. The elemental analysis of sludge and TPH measurement were carried out using ICP and TNRCC methods respectively. Results: The mean TPH removal of 2, 5, 10, 15, 20, and 30% oxidant concentrations were 1.55, 9.03, 23.85, 33.97, 41.23, and 53.03%, respectively. The highest removal efficiency was achieved in stepwise addition to the saturated sludge. Increasing oxidation time from 24 to 48 h had a little effect on increase in TPH removal. Moreover, the removal efficiency of H₂O₂ and Fenton was nearly similar. Conclusions: Mere application of chemical oxidation is not capable of complete treatment of the sludge but it is an effective process as a pre-treatment step for decreasing toxicity and increasing its biodegradability.