Screening Of Characteristic Pollutant Degrading Bacteriaand Degradation Performance Of Functional Bacteria In Coal Chemical Wastewater

Coal chemical wastewater is refractory organic wastewater which the composition of pollutants includes phenols,ammonia,polycyclic aromatic hydrocarbons and so on.After biochemical treatments,there are still existed some highly toxic and refractory organic pollutants in the effluent.Enhancing biochemical degradation ability becomes the most direct and effective way to solve the problem.Phenol and phenanthrene were selected as target pollutants in this study.Two highly efficient degrading strains were screened from coal gasification wastewater;the degradation of phenanthrene by bacteria and the enhancement of humic acid and hydroxypropyl-beta-cyclodextrin(HPCD)on the degradation of pollutants were investigated.The co-metabolism of phenanthrene with phenol-degrading bacteria was investigated.Besides,the mobile bed biofilm reactor(MBBR)was used to strengthen microbial flora by simulating phenolic wastewater with different composition.The treatment effect of phenolic wastewater,the relationship between microbial community structure and degradation of phenolic pollutants were discussed.The main research contents are as follows:(1)Two phenanthrene-degrading bacteria were screened from biochemical effluent using phenanthrene as the sole carbon source and energy source.After 16 S rRNA sequence analysis,They were identified by 16 S rRNA sequence analysis and then named Rhodococcus XY916 and Chryseobacterium H202,respectively.(2)The physiological and biochemical characteristics and adhesion characteristics of Rhodococcus XY916 were investigated.The optimum growth conditions were determined and the enhancement effect of humic acid on the degradation of XY916 was discussed.The results showed that the optimum growth pH of XY916 was weak alkalinity,the tolerance range of mineralization was 0-20000 mg/L,and it could grow normally in the environment with 120 mg/L phenanthrene content.Low concentration of humic acid could enhance the hydrophobicity of XY916,increased the apparent solubility of phenanthrene and promoted the degradation of phenanthrene.The degradation rate could reach 95.3%.Nonetheless,with the increase of humic acid concentration,the adsorption of phenanthrene by humic acid could hinder the contact between XY916 and phenanthrene,thus inhibiting the degradation of phenanthrene by XY916.(3)Co-metabolism of microorganisms is an important way to remove refractory pollutants.Phenol could be used as a substrate to enhance the degradation of polycyclic aromatic hydrocarbons.In this study,phenol and phenanthrene were used as target pollutants to investigate the co-metabolism of phenol and phenanthrene by Chryseobacterium sp.H202 and the enhancement of co-metabolism by HPCD.The results showed that phenol could promote the degradation of phenanthrene by H202.The degradation pathway of phenanthrene included two metabolic pathways: salicylic acid and protocatechuic acid.In the co-metabolism process,HPCD could form an inclusion complex with phenanthrene,increased the apparent solubility of phenanthrene and reduced the biological toxicity of phenanthrene,thereby enhanced the dehydrogenase activity of degrading bacteria,and enhanced the co-metabolism of phenol and phenanthrene with H202.When the concentration of HPCD is 50 mg/L,the removal rate of phenanthrene reached 80%.(4)The effects of phenol and p-nitrophenol on bacterial community structure were studied by MBBR.When the simulated water contained only 625 mg/L phenol,the COD removal rate was 94% and the phenol was degraded completely.The dominant bacteria were Acidocella,Rhodanobacter,Acinetobacter and Burkholderia.Adding p-nitrophenol into simulated wastewater and final concentration 30 mg/L,the removal rate of COD reduced to 92% and the biodegradation rates of phenol and p-nitrophenol were 100% and90%.The dominant bacteria were transformed into acid-resistant Acidocella and Acidisoma.After regulating reactors pH to 7.3-7.5,the COD removal rate decreased but remained at about 90%.While the dominant bacteria in the control group decreased to Rhodanobacter and Burkholderia.The community structure of the experimental group changed significantly,the dominant bacteria were Burkholderia,Salinispora,Pandoraea,Chryseobacterium,Puedobacter,Comamonas,Cupriidus,Delftia,Methylobacterium and Stenotrophomonas.However,the removal rate of p-nitrophenol decreased by about 70%.It indicated that acidic environment was beneficial to the removal of p-nitrophenol.