Optimizing the parameters of biodegradating nitrobenzene by orthogonal design

The paper aims to introduce our research on optimizing the parameters of biodegradating nitrobenzene by means of improving its orthogonal layout. As is known,biodegradation is one of the best ways to treat nitrobenzene contamination. However,since it is complicated and inconvenient to be treated,it is necessary to take the trouble to optimize the parameters of degradation,that is to say,it is necessary to isolate a number of strains of bacteria that can degrade nitrobenzene from the contaminated sludge of chemical plants. In doing so,we have inoculated eight of those strains for the experiment. At the same time,orthogonal design has been built up to determine the degradation effect of nitrobenzene at different levels of four factors,including the original concentration of nitrobenzene,pH value,heavy metal and concentration of NaCl. To avoid the complex process of pretreatment,the concentrations of nitrobenzene were detected simply and accurately by using the UV-spectrophotometer. The standard curve and the linear equation about absorbency and the nitrobenzene concentration were constructed by detecting the standard samples of nitrobenzene. We have analyzed the results of experiments by using SPSS software,which have shown that all the four factors,the original concentration of nitrobenzene,pH value,heavy metal and concentration of NaCl,have brought about very significant effect on the degradation rate of nitrobenzene. The sequential order of the respective effect from strong to week can be illustrated as:original concentration of nitrobenzenepH valueconcentration of NaClheavy metal. While the degradation rate of nitrobenzene is highest,the original bulk rate of nitrobenzene was 1 000 μL/L,value of pH was 8,the mass concentration of NaCl is 50 mg/L; the mass concentration of ZnCl2 was 50 mg/L. Therefore,it can also be concluded that the presence of some heavy metals in certain concentrations tends to promote the degradation process of nitrobenzene.