Oil Extraction From Oil Sludge and TPH Elimination of Solids/Water by Ozonation

About 1.1 million barrels of oil sludge are generated yearly in Indonesia by many oil and refinery industrial activities. Oil is strongly bound with solid particles in the sludge. Oilin the sludge may range from benzene, phenols to polycyclic aromatic hydrocarbons which are classified as toxic, mutagenic and carcinogenic for human and pollute the environment. Oilextraction is favorable option because of environmental and economical reasons. Oil sludge from an oil fields inSumatra, Indonesia was extracted at low temperature (40–70 °C) resulting in Total Petroleum Hydrocarbon (TPH) around 1–2%. After addition of 10,000 ppm REKLIN G04 surfactant, TPH extraction was improved to 9%. After decantation, effluent water containing ± 15,000 ppm TPH was ozonated for 60 minutes resulting in TPH reduction to ± 5 ppm. After ozonation, TPH of discharge solids was only 7–40 ppm. Fingerprint by gas chromatography showed removal of light fraction of oil after ozonation.


Introduction
Large amounts of oil sludge are generated during the cleaning of tanks, oil storage, maintenance of related facilities and processing operations prior to the sale of crude oil into the sea terminal.Disposed oil sludge normally contains toxic substances such as aromatic hydrocarbons (benzene, toluene, ethyl benzene and xylene), poly-aromatic hydrocarbons (Swoboda-Colberg, 1995).
In general, oil sludge is a complex water-in-oil (W/O) emulsion, typically including 30-50% of oil or total petroleum hydrocarbon (TPH), 30-50% of water and 10-12% of solids by mass (Ramaswamy et al., 2007).Total Petroleum Hydrocarbons (Ayotamuno et al., 2007) without adequate treatment can be a pollutant to the environment, especially on the ground.
Landfill, soil bioremediation and incineration are among common disposal methods for oil sludge.Disposal to landfill requires a lot of land that must be adequately insulated to prevent leaching of toxic compounds in the soil.Bioremediation applications with fertilizer and bacteria can lead to the accumulation of pollutants such as toxic metals.Oil sludge burning has limitations such as transportation and the release of toxic gas that evaporates into the environment.Toxic heavy metals can not be removed during the combustion process and will accumulate as solid particulates in the combustion zone (Dominguez et al., 2005).The objective of the research described in this paper is to find a more clean yet efficient method for treating oil sludge using ozonation and surfactant system.
Ozone is one of the alternative technologies that focus on achieving oxidation through chemical reactions.Ozone is very reactive and can oxidize compounds such as persistent mineral hydrocarbons.Ozone is readily generated when oxygen is exposured to electrical discharge.O atom (E o 0/H2O = 2.42 V) can be generated via dissociation of O 2 and boosts the rate of production of OH  (Bruggeman et al., 2009;Malik et al., 2001).Furthermore, O atom can directly react with contaminants and also takes part in the reactions with O 2 resulting in the formation of O 3 , E o 0/O2 = 2.07:07 V (Malik et al., 2001).Ozone as a strongly oxidizing allotropic form of oxygen reacts best when it can act as an electron transfer acceptor for the oxidation of metal ions, as an electrophile for the oxidation of phenol land other activated aromatics, and as a dipole addition reagent by addition to carbon-carbon multiple

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Effect of Ozonation on Oil Content of Water Effluent and Discharge Solids
Immidiately after 0.35 gram ozone/hour application the TPH content was reduced significantly.After 45 minute the TPH content was almost not found.Ozone attacked lighter hydrocarbon fractions easier than the heavier ones.GC fingerprints confirmed that lighter fractions (0-16 minute, or atom C1 to C12) in the left part of Figure 5 were strongly degraded.Then after 16 minute retention time (heavier hydrocarbons, C12 to C39) we could see no significant degradation.Formation of hydroxyl radicals is the vital oxidants that dominate the plasma oxidations in water application of ozone.Their reactions with organic compounds may be differentiated into three different mechanisms: abstraction of hydrogen atom; electrophilic addition to unsaturated bond and electron transfer.In the case of saturated aliphatic hydrocarbons or alcohols, hydrogen abstraction is primary for organic abatement with yielding H 2 O and an organic radical (Jiang et al., 2014).As for olefins or aromatic hydrocarbons, C-centered radical with a hydroxyl group at the a-C atom can be formed with OH radical addition to unsaturated double carbon-carbon bonds of organic compound.Besides, reduction of hydroxyl radicals to hydroxide anions by an organic substrate is of particular interest in the cases where hydrogen abstraction or electrophilic addition reactions may be disfavored by multiple halogen substitution or steric hindrance (Lukes, 2001).Ozone oxidation strength decreases with the number of branch and length of hydrocarbons.Higher intensity of ozone dose might be needed to eliminate the heavier fraction of hydrocarbons.

Environmental Compliance of Effluent Water and Discharge Sands
The main goal of oil extraction from oil sludge is to have as much as possible oil, while it is desirable to have less than 1% BSW in the extracted oil.In the other hand, due to stringent environmental regulation, effluent water from oil waste treatment must contain less than 25 mg/L Oil and Grease, and less than 200 mg/L TSS (KEP-42/MENLH/10/1996).All those expectation and regulation have been fulfilled by the method of extraction and ozonation.

Conclusion
Oil extraction of oil sludge was studied in these lab experiments.Using no surfactant, only low percentage of TPH was observed.The extracted oil increased significantly after application of heating (60 °C) and surfactant REKLIN G04.Elimination of TPH was achieved by using ozone resulting in TPH reduction to almost zero in both effluent water and discharge solids.Fingerprint by gas chromatography showed removal of light fraction of oil after ozonation. Figu