As containing a high concentration of petroleum hydrocarbons (PHCs) and other recalcitrant components, diesel oil sludge formed in storage tanks is recognized as a hazardous waste. The management of this sludge by disposal or treatment represents a challenge with the actual economic and environmental restrictions. A treatment process for diesel oil sludge was developed in this paper. The sludge was separated into three fractions (oil, water, and solid) where these latest are characterized, and their modes of treatment, recovery and recycling were defined. The oil fraction was treated with hot water and de-mulsifier in order to extract sodium and potassium, and their physicochemical properties were then comparable to those of the original diesel allowing its recycling. Whereas, the aqueous fraction was treated by Ferric Chloride (pH=8-9) to remove the excess of dissolved organic compounds. Their physicochemical parameters were found satisfying the permissible limits of the discharge industrial wastewater to the sea. Furthermore, catalytic thermal treatment of the solid fraction was particularly studied, and the effects of many parameters such as nature and rate of catalysts, duration and rate of heating, and temperature on the recovery of solid fraction were examined. Interesting experimental conditions were optimized as an oxygen free environment, a heating rate of 2.5 °C/min during three hours and low temperature of 300-350 °C which is the distillation range of diesel oil. A light pyrooil and a heavy one with excellent yields (60 % and 72%) were obtained respectively with copper nitrate and sodium hydroxide as catalyst, without formation of volatile hydrocarbons. Moreover, the analysis of the obtained pyro-oil showed that is composed mainly of a mixture of aliphatic hydrocarbons chains C12-16 similarly to the composition of diesel oil. Thus, it was concluded that the solid fraction was formed by the oligomerization of those chains and the optimized operation conditions are non-destructive making their conversion to their initial structure relatively easy without being decomposed. Globally, an appropriate Advanced Combined Technology composed of centrifuge process as the industrial process of separation and non- destructive thermal treatment process named soft pyrolysis, was defined as an efficient alternative method to the diesel sludge disposal. They are offering many benefits over other methods: valuable products, zero waste to be discharged of, achieving the environmental-friendly objectives with the most lowest cost.
