Isolation And Identification Of Xanthate Degradating Bacteria And Research On The Degradation

The waste water containing xanthate can contaminate environment severly. Recycling of this kind of waste water will affect the technical specifications and the operation of mineral flotation. Therefore, an effective treatment of xanthate has great environmental and economic significance. In this paper, biological treatment of waste water containing xanthate was studied.Bacterial strains that can degrade xanthate in the natural condition (pH=7) were isolated and identified by 16S rDNA. The growth and xanthate degradation characteristics of these strains were investigated and their optional degradation conditions were determined (pH value, temperature, inoculums amount and the concentration of substrate). Finally, the actual effect of the bacterial in treatment of wastewater polluted by xanthate was also studied. As results, six bacterial strains which can utilize xanthate as the sole carbon and energy were isolated after domestication, separation and purification,which were named as X0, X1, X2, X3, X4 and X5. Based on the observation of colony morphology, Gram staining and 16S rDNA of these strains. It was found that XO belongs to Brevundimonas diminut, X1 and X5 belong to Pseudomonas aeruqinosa, X2 and X3 belong to Methylobacterium, and X4 belongs to Pseudomonas mendocina.Then, the influence of the four factors (pH value, temperature, inoculums and concentration of substrate) on the physiological and biochemical characteristics and xanthate-degradation characteristics of the six bacterial strains were investigated. The results showed that the optimum degradation condition for X0, XI, X4 and X5 is as:pH=7.0,35℃,10%(v/v) inoculums and xanthate concentration of 2 g/L. Under this optimum condition, the logarithmic phase of four bacterial strains is within 24～72 hours, and after incubation for 72 hours the bacterial concentration can reach up to 1.36×108cells/ml,4.42×108cells/mL, 2.96×108cells/mL, and 1.52×108cells/mL respectively. The degradation percentage of xanthate reached 94.25%(X0),99.25%(X1), 94.35%(X4), and 99.25%(X5), respectively. After Incubation for 120 h, the COD removal percentage also reached 88.1%,97.55%,87.6%, and 98.93% respectively at the same time. X2 and X3 can grow with the xanthate as the sole carbon source, but the degradation extent of xanthate by these two strains was just about 60% after incubation for 144 hours..Finally, the biotreatment of plant wastewater (concentration of xanthate is 575 mg/L, initial COD is 5996 mg/L) was also investigated. It indicated that, when the pH value was 7.0, temperature was at 35℃,inoculated is 1×109 cells/mL and shaking speed was at 110 r/min, the degradation percentage of xanthate and COD removal percentage by mixed culture reached 71.4% and 51.5% respectively after incubation for 24 hours. The degradation percentage of xanthate and COD removal percentage reache 97.39% and 86.72 respectively after incubation for 144 hours.