BIOREMEDIATION OF CRUDE OIL - BEARING SOIL: COMPARATIVE ANALYSIS OF THE ADDITION OF TWO ANIONIC SURFACTANTS AS FOR THE TOXICITY, AND CRUDE OIL BIODEGRADATION

The release of crude oil into the environment by oil spill is gaining attention in the world and many accidents cause soil pollution. Many techniques have been developed to cleaning up those contaminants and the biological treatments are more efficient and cheaper than chemical and physical ones. The low solubility and adsorption are two major properties of high molecular weight hydrocarbons that limit their availability to microorganisms. For this reason, the addition of surfactants enhances the solubility and removal of those contaminants, improving the oil biodegradations rates. For this purposes, this work aimed at evaluating the potentiality of the addition of two anionic surfactants, a biological and a chemical ones to improve the bioremediation rates. Some toxicity tests such as dehydrogenasic activity and seed germination with Lactuca sativa were conducted to evaluated the behavior of the addition of both surfactants into the soil, being evaluated different concentrations of the active ingredient of both surfactants (0.1 to 1.5g of active ingredient for each 100g of soil) to verify whether or not those concentrations could be poisonous to the soil. After the tests, it was verified that high concentrations of both were poisonous to the soil. Besides the toxicity tests, the oil biodegradation rates were evaluated by the addition of those different concentrations of both surfactants and the biodegradability tests were carried out in bioreactors containing 450 g of crude oil contaminated soil and a 3cm layer of support rock. The tests were carried out at room temperature; being used a humid airflow of 3L/h. The nutrients were corrected through the addition of NH4NO3 and KH2PO4, in a nutritional ratio of C:N.P=100:15:1, being the humidity adjusted in 50% of the liquid retention capacity. Those experiments were accomplished with different concentrations of each active ingredient of both surfactant that varied 0.1 up to 1.5% w/w, besides a control(without surfactant addition). The experiments were run for 45 days and the removal of oil and grease (O&G) were evaluated. After finishing the biodegradation tests, an increase about 50% in the oil biodegradation efficiency was verified when 0.4 and 0.6% w/w of biological surfactant were used. The chemical surfactant didn't improve the bioremediation rates.