Experimental Study On Remediation Of Lubricating Oil Contaminated Soil Using Aidovorax Citrullig

With the rapid development of modern industry, the lubricating oil is widely used in various fields and its consumption was increasing quickly, resulting a large number of waste lubricating oil. For this part of the waste lubricating oil, attention was focused on improving its comprehensive utilization ratio and biodegradability. However, research of the harmless treatment of lubricating oil leaked into the environment was less. Subject to some factors, such as the processing cost, technical means and recycling channel, the recovery rate of waste lubricating oil was low in our country, and most waste lubricating oil was directly discharged into the environment. So, soil is severely contaminated. Compared with the traditional physical and chemical method, bioremediation method has many advantages, which had become the most promising method.By using Acidovorax citrulli as the material basis, which was separated, purified and selected from the soil polluted by oil in laboratory, and the contaminated soil as the research object, which was collected near a lubricating oil company in Chongqing, the study of oil removal from lubricant-contaminated soil by biological method was carried out. Firstly, the properties of strain for biodegradation of lubricating oil was studied. By single factor experiments, the influences on the biodegradation of lubricating oil, such as temperature, inoculation quantity, fluid volume, and pH, were investigated. Results demonstrated that the optimum biodegradation temperature is between 30℃and 40℃,the optimum biodegradation inoculation is between 2% and 20%,the optimum biodegradation fluid volume was between 10 mL and 40 mL, the optimum biodegradation pH was 6.1 ~ 7.0. On this basis, the multi-factor orthogonal experiments were carried out. And in the optimized conditions, the largest biodegradation ability of strain was explored.Secondly, based on the above research results, the optimizer parameters of bioremediation of lubricating oil-contaminated soil were studied. The effects of soil tillage, soil moisture, bacteria liquid dosage, surfactant dosage and nitrogen source types and its C, N and P content, on the bioremediation of lubricating oil- contaminated soil were studied. And bioremediation parameters were determined by the removal rate of lubricating oil from soil.Finally, under the optimized conditions of the bioremediation, at the temperature of 37℃, 30℃ and room temperature, the long term repair of different degrees of lubricant-contaminated soil(initial oil content was 19.49%, 15.12%, 10.17%, 4.89%) were respectively studied. Results showed that under the same initial content of lubricating oil, the optimum removal rate temperature was 37℃, and the removal rate of lubricating oil is the lowest at room temperature. By contrast, it was found that repair effect of the soil added the microbial liquid was much better than the other soil samples without bacteria, illustrating that the addition of exogenous bacteria improved the removal rate of the lubricating oil in soil samples. In addition, the biodegradation kinetics of the lubricating oil in the soil sample without external bacteria was simulated by the exponential rate model.