Study On High Efficiency Biological Treatment Of Characteristic Pollutants In Coking Wastewater

Coking wastewater is a kind of industrial wastewater with high COD,high ammonia nitrogen and high phenol value.Coking wastewater which are difficult to biodegradate have large quantity,complex composition,high concentration of pollutants.Biological method is the most economical and effective method to decompose pollutants in wastewater into harmless substances by microorganisms.Compared with physical and chemical methods,it has more advantages,no secondary pollution to the environment and is easy to operate.There are many different pollutants coexist in the environment,resulting in the problem of compound pollution in the environment.Coking wastewater has typical characteristics of compound pollution.Among them,The main pollutants are nitrogen heterocycles and phenols.Therefore,pyridine and quinoline in coking wastewater are selected as the main model pollutants of nitrogen heterocycle,and phenol as typical phenolic model pollutants.Starting with the isolation and screening of high-efficiency degrading bacteria,the broad-spectrum and high-efficiency degrading bacteria were obtained,and their identification and degradation characteristics were studied.In order to further enhance the degradation effect and degrade broader-spectrum pollutants,several high-efficiency degrading bacteria were combined to obtain a high-efficiency and broad-spectrum combination.From the application point of view,the shock resistance of strains to pollutants was further strengthened by immobilization technology.The degradability provides a theoretical basis for the treatment of actual wastewater in the future.(1)Isolation and identification of degrading bacteriaIn this study,Six highly efficient degradable strains were isolated from the polluted soil of a coking plant in Beijing by enrichment culture method,which could degrade the characteristic pollutants in coking wastewater.They were identified as Rhodococcus sp.(T1),Sphingobacterium sp.(T2),Rhodococcus sp.(T7),Pseudarthrobacter sp.(T9),Flavobaterium sp.(T11)and Alcaligenes sp.(H9)by Physiological,biochemical and 16SrDNA phylogenetic.Among them,T1 had a good degradation effecton pyridine and phenol,T2 strain was for pyridine and quinoline,T7 was for pyridine,pyridine and phenol,T11 was for pyridine and phenol,T9 was for 2-hydroxypyridine,quinoline and phenol,and T9 was the only one that can degrade 2-hydroxypyridine.H9 was for 2-Picolinic acid and phenol,and H9 was the only one that can degrade 2-Picolinic acid.(2)Study on degradation characteristics of highly efficient degrading strainsAmong them,T7 strain could completely degrade pyridine,quinoline and phenol in coking wastewater time.Therefore,T7 strain was used as the research object to study the single substrate,and the relationship of double substrate and the relationship of pyridine,quinoline,and phenol.The degradation characteristics of pyridine,quinoline,and phenol by T7 strain were obtained.The results showed that when T7 strain degraded pyridine and quinoline alone,it showed good degradability.When T7 strain degraded phenol alone,it could not degrade further after 150 mg/L lacking nitrogen source.The double substrate degradation experiment showed that when pyridine and quinoline coexist,bacteria could degrade both substrates at the same time.When pyridine and quinoline was co-substrates with phenol respectively,T7 bacteria had no obvious effect on the degradation of pyridine and quinoline,Phenol could be completely degraded because of the increase of nitrogen source.Low concentration of phenol could promote the degradation of pyridine.When pyridine-phenol-quinoline coexists,they could be degraded completely without obvious delay.(3)Study on the compounding of highly effective degrading bacteriaIn order to enlarge the substrate spectrum,we used the method of constructing high-efficient bacterial flora.Six high-efficient degrading bacteria were screened and constructed high-efficient degrading bacterial flora to degradate pyridine,quinoline,2-hydroxypyridine,2-pyridinic acid and phenol.In the experiments,29 species of bacterial flora were combined.Among all the bacterial flora combinations,The number 23 was the best which average degradation rate of combination was 98.8%.It belonged to the dominant group.It was composed of three strains,T7,T9 and H9.These three strains could completely degrade five pollutants.Through orthogonal experiment,the optimum ratio of these strains were determined to be 3:1:3.(4)Immobilization of degrading bacteriaIn order to further improve the degradation effect,T7 strain was immobilized.The characteristics of immobilized bacteria in degradation of pollutants were studied.Sodium alginate was selected as the embedding agent.The optimum degradation conditions of immobilized cells were determined by orthogonal experiment.The concentration of sodium alginate was 5%,the concentration of calcium chloride was 5%,and the dosage of bacteria was 12 mL.