Screening And Characteristics Research Of SDS Degrading Strain

Sodium dodecyl sulfate(SDS), an anionic surfactant, because of its low cost and excellent foaming characteristics, became one of the most widely used anionic detergents. It is widely used in household detergents and industrial detergents, and is a component of many industries products. In today's extensive use of detergent, sewage treatment facilities SDS usually can not handle completely. It is shown to be toxic to fishes, aquatic animals and is also inhibitory to microbes and cyanobacteria.This study based on the strain screened out from a sewage treatment plant which can use SDS as the sole carbon source for growth. Physiological and biochemical characteristics of the bacteria were observed and studied. The results of Gram stain showed that this strain is Galanz negative strains and short bacillus. Strain was identified as Pseudomonas by 16 S rDNA sequencing and alignment.Studies have shown that the optimum growth temperature of the strain was 30 ?. With the temperature range of 15 ?~ 25 ?, the strain can still grow and degrade SDS rapidly. After the strain was acclimation at 15 ?, it has the best SDS degradation rate(120.5 mg/L·h-1 SDS) and the best growth rate at 15 ?. However, it's growth and degradation rate of SDS at 25 ?~ 30 ?is lower than before. Indicates that strain after acclimation at 15 ?has been completely adapted to temperature conditions at 15 ?. The growth rate and the SDS degradation rate of the strain at 10 ?did not change significantly after acclimation. Although its growth rate and SDS degradation rate at 10 ?is much lower than at 15 ?~ 30 ?. When compared with related research reports, rate of degradation of this strain at 10 ?is still high as 42.19 mg/L·h-1 SDS, indicates that this strain in practical engineering applications in a broad prospect.The strain could grow and degrading SDS rapidly at a pH of 5 to 8.5,the optimum pH is 7.5. When at condition with pH<4.63 or pH>10, the growth and degradation of SDS is almost totally stop. According to related research reports, most SDS-degrading bacteria adapt to the condition at pH range of 7~8. Adapted pH range of strain screened in this study is broader than most SDS-degrading bacteria. It has great advantages in practical application of wastewater treatment especially the wastewater with pH <6.The optimum C/N of this strain is 100:5.22, needed much ammonia for it's growth. When the ammonia concentration is higher than 120mg/L, the growth and Degradation of SDS of strain is inhibited. Strain use ammonia to synthesis itself only. When in the solution at low concentrations of SDS, strain can not be used in ammonia. However, in the solution at low concentrations of ammonia, strain can use SDS to maintain their own activity.The optimal concentration of SDS of this strain is 2500 mg/L, it can degrade SDS rapidly when concentration of SDS is lower than 4000 mg/L. Strain is seriously inhibited when concentration of SDS is higer than 4000 mg/L, strain complete loss ability to degrade SDS when concentration of SDS is higer than 8000 mg/L. The growth and degradation of SDS of strain are required under aerobic conditions, strain can not grow and degrade SDS when dissolved oxygen is too low. This study use rotation speed of shaker to characterization of dissolved oxygen.. The results of experiments showed that the faster the rotation speed, the faster rate of biodegradation of the SDS. When the speed of rotation is 80 rpm, the biodegradation rate of SDS is only 66 mg/L·h-1. Considering the SDS degradation rate and energy consumption, we set 16 rpm rotation speed of shaker finally.Drawing growth curve at strain's optimal growth conditions, the results showed that the growth rate of the strain is very fast, in logarithmic phase growth rates is high as 0.127/h. And we found that at different inoculum, strain can quickly through the adaptation period(2~4h), enter the logarithmic growth phase and growth and metabolic SDS rapidly.After do research and explore the part physiological and chemical characteristics of the strain at laboratory, combine with actual wastewater treatment system,we want to explore the applicability of strain in actual wastewater treatment. Consider when in winter, the water temperature below 15 ? in northern at sewage treatment plant. We tried a variety of ways to enhance the rate of degradation SDS of strain at 10?. The results show: Add sodium succinate and potassium nitrate can increase the biodegradation rate of the SDS, degradation rate of SDS when cultured 24 h is 4.27% and 6.45% higher than control, respectively. However, Adding these two substances will reduce the biodegradation rate of the SDS at the beginning of cultured. Rest of measures can not increase the biodegradation rate of the SDS significantly except increasing the amount of inoculum of bacteria.In this study, SDS degrading bacteria has been screened and studied. Explore the effect of various measures on SDS degrading performance of bacteria at low temperature. This study may provide a reference and guidance in the wastewater treatment and the actual project.