| Coking wastewater is a typical industrial wastewater. It contains wide range of toxic organic contaminants with high ammonia concentration. Direct discharge of coking wastewater is very harmful to the biological environment. Emissions of coking wastewater in china increases year by year, the emission standard becomes more and more strict, these two aspects is a challenge to coking wastewater treatment. Most developed and developing plants are face with continuously improving the treatment power and effect. Many new reactors and process are actively researched, however, due to the high operating expense, immature technology, unsafe operation, and causing second contamination, their applications in practice are limited. In this case, the most suitable solution of coking wastewater treatment is to study a new microbe treatment technology on the basic of an existing biological treatment process.Poly-aromatic compounds especially quinoline contribute mainly to the COD value.Quinoline and some of its derivatives were reported to be toxic, carcinogenic and mutagenic. The existence of the nitrogen atoms greatly enhanced the water-soluble of quinoline, and it can move easily in the environment. So discharging quinoline-containing wastewater does a great damage to human health and environmental quality.Based on the biological strengthening technology, we screened out the predominant quinoline-degrading bacteria from the nature. The processing effect of coking wastewater treatment by quinoline-degrading bacterium was analyzed in this paper. The influence of environmental factors, extrinsic material and the mixed bacteria on the degradation performance was investigated. The feasibility of practical application was discussed as well. And to set up an efficient engineering bacterium by the genetic engineering technology to improve the degradation effect of wastewater treatment system was introduced.Firstly, we screen the quinoline degradation bacterium. A gram negative aerobe, which can utilize quinoline as the sole carbon, nitrogen and energy source, was isolated from the activated sludge in the aeration tank of A2/O process of coking plant wastewater treatment system. According to the 16S rDNA gene sequence analysis, it was identified as Comamonas testosterone sp.Secondly, the results of biodegradation experiments showed that this strain could degrade 100 mg·L"1 of quinoline within 12 hours,350 mg·L-1 of quinoline within 24 hours, and the removal rates of quinoline can reach 96% to 98%. Concentration of quinoline in excess of 700 mg·L-1 was toxic. This strain can not survive.Thirdly, the results showed Y-01 has strong ability of quinoline degradation, it can remove quinoline almost completely in the pH 4～10, partial alkaline effect is better. The optimum temperature of strain Y-01 is 30℃. External inorganic-N source and carbon source have no effect on quinoline degradation of this strain. It indicated that the N source and C source strain Y-01 need is mainly come from quinoline.But external phenol can accelerate the biodegradation of quinoline. When this strain mixed with phenol degrading bacteria which not have the function of quinoline degrading, degradation efficiency of quinoline was raised. Put strain Y-01 into coking wastewater which contains quinoline 18.2 mg·L-1, we find Y-01 can survive in real coking wastewater, and it still has the efficient quinoline degradation ability.this strain could degrade quinoline within 5 hours, and the first 3 hours is the strain’s adaptive phase.At last, an extraction of plasmid experiment was running for making the preliminary preparation for the construction of a gene engineering bacterium. It found that this Comamonas testosterone Y-01 strain has one plasmid. The plasmid is very large, above 10000 bp. Further analysis is needed to confirm whether the plasmid contains gene segments of quinoline degradation or not and whether the plasmid is suitable for genetic engineering bacterium construction or not.。... |
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