| Coke wastewater is a kind of high concentration of COD,toxic and refractory industrial effluent with complex composition and low biodegradability.Phenol is recognized as the predominant compound in coke wastewater,which is known to possess toxic and mutagenic activities and harmful to human and the environment.Biological treatment is regard as economical and effective method without secondary pollutant.But it's hard to meet the need of emission due to the toxic of effluent.In this study,we screened and identified the efficient degradation bacteria,studied the optimum conditions for phenol degradation.Then applied the strains immobilized by yeast as bioaugmentations to the bioremediation of coke wastewater.In addition,the efficiency of bio-treated coke wastewater and the best conditions by immobilized stains were studied.In order to explain the internal connection between microbial system of phenol-degradation and macro-functions,the change of structure and function of microbial community have studied by Illumina high-throughput sequencing.Using the phenol as sole carbon source,8 phenol-degradation strains were screened and isolated by enrichment culture from the activated sludge sample of a chemical plant in Hubei.And 2 specific strains were screened out from them and named C1 and C2.Both of the two strains were determined as gram negative bacteria,short bacilli by electron microscopy.Based on the 16 S rDNA sequences and the phylogenetic analysis,strains C1 and C2 were designated as Pseudomonas Sp.and Acinetobacter Sp.The growth of strains C1 and C2 under different tempetature,pH and the range of substrate degradation were studied.Both C1 and C2 can use catechol,aniline,nitrobenzene,salicylic acid,catechol,p-methylphenol and 2,4-Dichlorophenol as sole carbon source to grow well,especially in low initial concentrations.Strains C1 and C2 showed better salt tolerance,and strain C2 is resistant to any antibiotics better than C1.In optimal conditions,strain C2 can completely removed the phenol in coke wastewater within 10 h.The process of phenol degradation by C2 was fitted by Monod kinetics,and found the following equations: V=204.08 x·Cs/(235.6+Cs),R2=0.9977.Compared with free bacteria,immobilization of C2 by yeast can grow well in the medium with initial phenol concentration of 1200mg/L.The optimal conditions of the immobilized C2 for degrading phenol are as follow: pH=7.0,temperature 37? and 3:2 of coke wastewater: distilled water.Under the optimal conditions,the immobilized C2 could decompose over 95% phenol of coke wastewater after 48 h.While the dose of immobilized C2 was 4%,the removal of phenol and COD could reach 98.5% and 38% within 20 h.In the meantime,the chromaticity color of coke wastewater could reduce more than 50%.Immobilized C2 obviously affected the composition of microbial community of coke wastewater,and the Alpha diversity shows the decrese tendency with richness.The microbial community had drastically changed,for instace,the richness of Actinobacteria and Bacteroidetes had decresed,the Firmicutes had increased,and the Proteobacteria gradually reduced.Further observation showed that Planococcaceae,Paenibacillaceae 1,Moraxellaceae,Pseudomonadaceae,Alcaligenaceae and Caulobacteraceae had increased while Sphingobacteriaceae,lavobacteriaceae decresed.In the 7th day of the experiment,the concentration of phenol had decresed in modified yeast group,while the richness of Sphingobacteriaceae had increased.The dominant types of microbia in coke wastewater are Firmicutes and Proteobacteria,especially in immobilized group,the change of Bacillales Incertae Sedis XII,Bacillaceae 1,Moraxellaceae and Pseudomonadaceae were positively correlated with phenol concentrations.As strain C2 of Moraxellacea,it may exists phenol-degradation bacterial genus in the other three families. |
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