The Application Of The Mixed Stains And Powder Immobilization In Coal Gasification Wastewater Degradation

Coal is one of the main energy sources in China,which occupies the important status in the structure of energy production.However,a large number of industrial organic wastewater with high concentration,high pollution,toxic and difficult degradation is produced in the process of coal gasification.If the wastewater is discharged without treatment,it will cause great harm to ecological environment and human health.At present,the treatment schemes of coal gasification wastewater adopt three-level processes called"physical and chemical pretreatment,biological treatment,physical and chemical advanced treatment"in China.In this thesis,high effective bacteria immobilized by powdered materials was used to investigate the growth characteristics and the related degradation properties of coal gasification wastewater.Three kinds of strains with good capability of pollutants degradation preserved in the Lab,named X1,X2 and R1 respectively,were adopted in this study.Through investigating the growth characteristics of strains after domestication,it was found that X1 and R1 could quickly adapt to wastewater?less than 4 h?,while X2 adapted slower?about 12 h?,and the strain R1 could reach the highest concentration of 11.48g/L at 60 h;The strain X1 grew fastest.In the experiments of wastewater degradation,the COD degradation rate of the strain X2 reached 64%,while the ammonia nitrogen degradation rate of the strains X1 and R1 reached 60%,but the strain R1 was better at the beginning.The optimum mixing ratio of three strains was determined as X1:X2:R1=2:1:2,and the optimum growth conditions:30?,pH 7.0,inoculum rate of 3%,and rotating speed of 140 r/min.Studying the growth characteristics of the mixed strains showed that their biomass increased markedly compared with the single strain at the same culture conditions.The OD₆₀₀00 of the mixed strains reached 2.781 in 72 h,while the OD₆₀₀00 of strain X1 was 1.601,strain X2 was 1.539,and strain R1 was 2.030.The results of degrading coal gasification wastewater by the mixed strains showed that the COD degradation rate reached 76%,and the ammonia nitrogen degradation rate reached 72%.Two kinds of inorganic materials?Charcoal active granular and Artificial zeolite?and two kinds of organic materials?sawdust and middlings?were chosen as powder immobilized materials.The study of the performance of a single material shows that the advantages of inorganic materials was strong adsorbption in a short time,and the characteristics of organic materials was that it could provide certain nutrients for the growth of microorganisms.Through mixing four kinds of materials with different ratio,the absorption amount of mixing materials and the degradation ability of the mixed strains were evaluated to determine the optimum mixing ratio:Charcoal active granular?Zeoliteartificial?sawdust?middlings=37.50%?37.50%?12.50%?12.50%,and the best culture conditions:30?,inoculum rate 2%,and rotating speed of 160r/min.In same conditions,comparing the wastewater degradation rate of the powder immobilized mixed bacteria with free mixed bacteria,the results showed that the former had obvious advantages.The COD degradation rate of the powder immobilized mixed bacteria reached 88%,and the degradation rate of ammonia nitrogen reached 80%.Meanwhile the sludge produced by powder immobilized mixed bacteria reduced greatly,which was only 0.2797 g at 72 h,while it was 0.5230g produced by free mixed bacteria.The optimum degradation conditions were determined by orthogonal test as below:30?,pH 6.0,inoculum rate 3%,and rotating speed of 160 r/min.Under this condition,the COD degradation rate by powder immobilized mixed bacteria reached 94%,and the ammonia nitrogen degradation rate reached 88%.