A Basic Research To The Enhancing Effects Of Surfactants On Biodegradation Of Diesel

The biodegradation of petroleum pollutants is a new technology. Due to the low cost, in-situ degradation and no pollution products, it attracts more attention. The application of biodegradation technology is limited by many factors, such as the diverse strains of petroleum-degrading bacteria and environmental conditions. So identifying the petroleum-degrading strains, enhancing its environment compatible ability and increasing the degradation efficiency play key roles in the application of biodegradation. The aerobic petroleum-degrading strains were isolated and purified. And the synergistic biodegradation results were found in diesel solution inoculated with mixed bacteria. The optimized experimental conditions have been measured. Under the excellent conditions we investigated the effect of some common surfactants on the biodegradation of diesel. The results will be useful for the application of biodegradation method. According to the growth curve, the mixed bacteria grow fast, and rapidly enter the logarithmic growth phase. After 10 hours, it's entered the balance growth phase. The bulk culture conditions for the biodegradation of diesel by mixed bacteria were investigated. The optimal culture conditions were: cultivated temperature 30℃, initial pH value 7.0 and the percentage of diesel concentration 1%. By the means of research the influence of surfactants on the growth of mixed bacteria and test the effects of surfactants to the biodegradation of diesel, we can make some conclusions that: the influence of surfactants on the growth of mixed bacteria may correlate to the concentration of surfactants. With the increased of the concentration of surfactants, the delay of logarithmic growth phase extended. In our experiment, the inhibition to the growth of mixed bacteria was anion surfactant SDBS>anion surfactant SDS>nonionic surfactant OP-10>nonionic surfactant Tween-80. In the presence of the anion surfactants, the degradation of diesel was not increased. But adding the nonionic surfactants can increase the degradation of diesel. If the concentration of Tween-80 under 160mg L^-1 and the concentration of OP-10 under 120mg L^-1, with the concentration of the nonionic surfactants increased, the degradation efficiency of diesel enhanced. The UV-visible spectrophotometer and GC date showed that the mixed bacteria in the culture medium substrate with 80mg L-1 Tween-80 can quickly adapted the culture environment. With the increased of time, the degradation efficiency of diesel was continually enhanced. A majority of diesel was degraded in initial four days, and the degradation efficiency of diesel reached 60.55% in the fourth day. In general, surfactants can enhance the biodegradability of diesel. So biodegradation technology is of great practical and scientific relevance.