Background: Remaining of crude oil in storage tanks usually lead to accumulation of oily sludge at the bottom of the tank which should be treated and disposed of in a suitable manner. In this research the feasibility of chemical oxidation with H2O2 and Fenton's reagent for removal of total petroleum hydrocarbons (TPH) from composted storage tank sludges was investigated.

Materials and Methods: The sludge was mixed with immature compost at various sludge to compost ratios including 1:2, 1:4, 1:6, 1:8 and 1:10 and composted for 82 days. Then, hydrogen peroxide and Fenton’s reagent were added to the composted mixture in six concentrations including 2%, 5%, 10%, 15%, 20% and 30% w w-1 for a period of 24 and 48 hr.

Results: TPH removal in composting reactors with the ratios of 1:2, 1:4, 1:6, 1:8 and 1:10 were 66.59, 73.19, 74.81, 80.20 and 79.91 percent, respectively. The mean TPH removal of 1:8 composted mixtures with 2%, 5%, 10%, 15%, 20% and 30% of oxidant concentrations were 1, 5.09, 19.37, 28.16, 34.37 and 38.05 percent, respectively. The highest removal efficiency was achieved in stepwise addition to the sludge. As well, increasing oxidation time from 24 to 48 hr had a little effect on TPH removal increase and the removal efficiencies of H2O2 and Fenton were nearly similar.

Conclusion: Chemical oxidation with hydrogen peroxide and Fenton as a post-treatment step is an acceptable process in TPH removal from bottom sludge of storage tanks.