The biodegradation abilities of 10 dibenzothiophene degrading microbial consortia isolated from contaminated soil were investigated. 5 highly efficient dibenzothiophene degrading bacterial strains were obtained from the consortium LKY10 by screening on LB-agar plates.The bacterial strain LKY10-5 reduced more than 90% of dibenzothiophene with 40 mg•L-1concentration, and had higher degradation efficiency than enriched bacterial consortia in 7 days of cultivation. According to species identification and phylogenetic analysis, strain LKY10-1 and LKY10-3 belonged to Actinobacteria and could be included in Rhodococcus and Cellulosimicrobium genus, LKY10-5 and LKY10-6 belonged to Proteobacteria and could be included in Pseudomonas and Devosia genus, and LKY10-13 could be included in Lysinibacillus genus and belonged to Firmicutes.
This paper present the optimum conditions for treating oily sludge with organic solvent extraction and surfactant solutions using the single factor experiment. Firstly, selecting petroleum ether (boiling range is 60-90oC) as the organic solvent, then selecting the mixture of sodium dodecyl benzene sulfonate and alkylphenol ether(OP-10) as surfactant agent to extract residual crude oil. Results obtained through experiments, the optimum parameters of petroleum ether were that ultrasonic reaction temperature was 55 oC, ultrasonic intensity was 320W, ultrasonic extraction time was 5min, liquid/solid mass rate was 7.5, then under the optimum conditions, the residual oil rate was about 6%. While the optimum parameters of surfactant mixture were that the temperature was 55 oC, ultrasonic intensity was still 320W, ultrasonic extraction time was 10min, liquid/solid mass rate was 15, under the optimum conditions, finally the residual oil rate was only about 1%.
5 highly efficient hydrocarbon-degrading mixed bacteria were obtained from the petroleum-contaminated soil samples by the traditional method of enrichment and acclimation. The KL9-1 consortium had a wide temperature tolerance range and higher hydrocarbon degrading ability. The degradation rate of thin oil and heavy oil was up to 43.27% and 20.09% respectively through 7 d at 45oC. After several times of isolation and purification, three dominant strains with the capability of hydrocarbon-degrading were obtained, and their petroleum degradation rates were all over 30%. According to its morphological and 16S rDNA sequence characteristics, KL9-1-1 and KL9-1-2 were identified as Pseudomonas sp., and the KL9-1-3 was identified as Rhodococcus sp..
A response surface methodology was applied to optimize the bioremediation condition of hydrocarbon in soil by microbial consortium KL9-1. A four-level Box-Behnken factorial design was employed to study the relationship of independent variables and dependent variable by applying pH value, inoculation amount of microbial consortium KL9-1, ratio of nitrogen and phosphorus (N/P ) and surfactant (SDBS) concentration as independent variables (factors) and crude oil removal rate as dependent variable (response). Then the statistically significant model was obtained and numerical optimization based on desirability function was carried out for pH 7.0, inoculation amount 50.0 mL, N/P 2: 1 and SDBS concentration 4.0 g, and the hydrocarbon removal rate reached as high as 52.58%. The predictive values showed good agreement with the experimental values under the optimization conditions, by standard variance <1.3%. It showed that the optimal result was reliable.
In this paper, Fenton oxidation technology was used for oxidation treatment of soil contaminated by heavy oil, and environmental conditions were investigated for improving the effect of Fenton oxidation. The results showed that under the direct sunlight, liquid to soil was 2:1, pH was 5, 10.0mL 18 mmol•L-1 Fe2+ and 10.0mL 30%H2O2 were added to 1000g soil contaminated by heavy oil which contained 8% petroleum hydrocarbons, the petroleum hydrocarbons reduced from 5.74% to 2.92%.
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