Screening Of High Efficient Degrading Bacteria For Natural Gas Drilling Wastewater Organic Matter And Research On Its Features

In recent years, as the situation of air pollution is becoming more and more serious, natural gas are used more widely. As a clean energy, natural gas has become not only an important raw material for the modern industrial,but also necessities in people’s life, the demand for natural gas continues to rise. In this case, the number of natural gas drilling is rising, the amount of waste water caused by the drilling process is also increasing.Using the biological method to treat drilling wastewater organic compound is economic and it does not produce secondary pollution, but due to the complex composition of drilling waste water, strains which introducted require having strong ability to degradate organic compound and can adapt to the complex environment of drilling wastewater. The experiment screened three strains dominant bacterias that were able to grow in the drilling wastewater. named them for strain 1、strain 2 and strain 3. and then through domestication and enrichment culture, isolating two strains dominant bacterias from soil surrounding wastewater pool in natural gas wellhead and activated sludge, named them for strain 4 and strain 5. By 16s rDNA sequencing identification, strain 1 and strain 2 belongs to the Comamonas sp:Strain 3 belongs to Citrobacter sp; strain 4 belongs to Aeromonas sp; strain 5 belongs to the Bacillus sp.Through the comparison experiment of various strains degradating for the organic matter that in natural gas drilling wastewater, the degradation ability of Citrobacter(strain 3) was found to be the best, and the degradation rate of organic matter was the highest in 7d, which was 62.7%. Using the selected Comamonas(strain 2)、Citrobacter(strain 3)、 Aeromonas (strain 4)、Bacillus(strain 5) to conduct single strain and mixed strain experiment about degradation for drilling waste water organic matter,it was found that the Comamonas(strain 2) and Citrobacter(strain 3) mixed flora have the highest degradation rate for drilling wastewater organic matter, the degradation rate was 61.8% in fifth day, it may have a synergistic effect between the two species; while mixed flora contains Bacillus(strain 5) have the poor degradation rate for drilling wastewater organic matter, it may exist the inhibitory effect between strain 5 and other bacteria. Using optimal compound bacteria(strain 2 and strain 3 mixed flora) to degradate natrual gas drilling wastewater of organic matter, studying the effection of different factors. It was found that the best degradation conditions for flora:the temperature for 30℃、pH for 6,the rate of oscillation for 150r/min-200r/min, inoculation amount for 3%, the inoculation ratio for 4:1; when the proportion of drilling wastewater was between 30%-50%, flora’s degradation rate of drilling wastewater organic pollutants is higher. External carbon source has certain influence on flora’s degradation for natural gas drilling wastewater organic matter, low concentration of glucose can improve the flora’s organic matter degradation rate, while high concentration of glucose make the flora’s organic matter degradation rate decreased; the addition of nitrogen source has little effect on the degradation of the organic matter in natural gas drilling waste water, which may be due to the adequate nitrogen sources in the drilling wastewater. Through the study of high efficiency degradation bacteria for organic matter in natural gas drilling wastewater, can provide certain theoretical basis for the biological treatment of wastewater from natural gas drilling in practical production, and plays positive role on natural gas drilling is the environmental protection.