Study On The Isolation, Screening And Identification Of N-alkane Biodegradation Strain And Its Degradation Capability

Alkanes are the major components of hydrocarbons in petrochemical waste-water, which is one of major pollutants. Biodegradation technology has been considered as an important method of petroleum pollution control due to its advantages of economic, efficient, no secondary pollution. The application of biodegradation technology is still limited due to the bacteria strains and environmental conditions. So far, the improvement of rate of degradation, the assessment of efficient and broad-spectrum, and the adaptable of strains, are still problems.For these reasons, in my study, firstly, one strain, which identified as Acinetobacter venetianus, with a high efficiency for alkanes degradation was screened from the activated sludge from wastewater structures of Fujian refinery. The optimization of environmental conditions, including temperature, pH, inoculum size, the ratio of carbon and nitrogen, the degradation capacity of bacteria were investigated, where tetradecane and mixed alkane was used as a carbon source, respectively. It was found that a 98% of tetradecane by 12 hours were degraded using the selected strain efficiency under the conditions of pH 7.0, temperature 30℃, 0.5% （V/V） inoculum size, molar ratio of carbon and nitrogen 0.4:1, and initial concentration of 50 mg/L tetradecane.Secondly, an orthogonal experiment designed was examined for the conditions affecting on the biodegradation of diesel alkanes using the initial diesel concentration of 400 mg/L, including temperature, pH, nitrogen content, salinity and trace elements. The results show that the best conditions of degradation for the strain were temperature at 30℃, pH at 7.0, a 0.1 g/L concentration of NH₄NO₃, salinity 0‰, a 0.1% （V/V） micro-nutrient concentration and inoculum volume 0.5%. In addition, the effects surfactant such as Tween80 and additional carbon sources on biodegradation of diesel alkanes were also studied under the optimal conditions, the results show that addition carbon sources and Tween80 did neither positive nor negative impacting on the strain under low concentration of 10 mg/L and 100 mg/L, respectively, and a higher concentration of Tween80 did not affecting the strain. Furthermore, dynamics studies demonstrate that four inoculum concentrations used for the biodegradation of alkanes in diesel were in agreement with the first-order kinetic equation. The research of biodegradation of alkanes in real wastewater from the petroleum industry was also carried out, and the results show that a 93% of the alkane from the sample was removed after 7 days and a 99.9%. was degraded after 9 days.Finally, to apply for the real industry, the bacteria strain immobilized on the bagasse, where bagasse was used as the support, was developed. The results show a 89% of tetradecane was degraded using a 50 mg/L tetradecane concentration after 8 hours and the strain immobilized on the bagass stable, for example, re-using this material, 96-98% of tetradecane was removed using a 50 mg/L. The optimal immobilized conditions was found as described: immobilzed time 1 day, the initial pH of 7.0, immobilized dosage of bacteria 0.5% （V/V）, immobilized bacterial dosage 0.2 g, immobilized carbon source tetradecane or diesel, immobilized carbon source concentration 100 mg/L.