Mutagenesis And Screening Of Denitrifying Bacteria In Sewage

In recent years, water pollution from industrial wastewater, domestic sewage andaquaculture wastewater, has been constantly increasing. Among them, nitrogenpollution is the most important issue of waster governance. Further enhancedenitrification microorganisms in activated sludge is the key technology of wastewatertreatment. This paper through UV mutagenesis techniques, combined with enrichmentacclimation culture, mutagenesis to single bactera or fungus water environmeng groupwicth have the ability to nitrification or denitrification, respectively, to improve thedenitrrification ability of industrial wastewater of the sludge microbial.1. Mutation and screening of nitrification strainsA strain of heterotrophic nitrification bacteria named N18was isolated fromactivated sludge of fermentation wastewater treatment by using heterotrophicnitrification medium. It was identified as Pseudomonas sp. according to the analysis ofits16S rDNAgene. It was mutagenized by UV-irradiation8s and8mutants was selectedby high concentration of (NH4)2SO4medium (15g/L). A mutant NF34with highest rateof NH+4-N removal was obtained. Studied on its function of heterotrophic nitrification,the result showed: the rate of NH+4-N removal of strain NF34was11.99%higher thanthe original strain N18. The nitrification rate of strain NF34was6.80mg/(L·h),7.43mg/(L·d) higher than the original strain N18. The denitrification rate of different initialammonia concentration100,200,500mg/L were6.14%,11.49%,10.75%higher thanthe original strain, respectively.2. Mutation and screening of denitrification strainsA strain of denitrifier bacteria named D21was isolated from activated sludge offermentation wastewater treatment by using nitrite as the substrate, through enrichment,separation and purification steps, preliminarily identified as Paracoccus. UVmutagenesis be processed by the ratio of the average diameter G of the strain to strainthe average diameter C forming blue halos on BTB panel,4mutantswere obtained, then by nitrite degradation ability of rescreening, a mutation strainDU19with good denitrification performance was obtained. The control strain andmutant strain were inoculated in sterile medium DM at an initial nitrite concentration of200mg/L, after24h culture, the rate of nitrite removal of mutant DU19reached99.91%, was49.28%higher than the original strain D21. In the denitrification process, the denitrification rate of strain DU19was6.80mg/(L·h), is about3.36mg/(L·h) higherthan the starting strain D21.3. Mutation and screening of activated sludge bacteria groupOn this basis, the activated sludge was induced by UV mutagenesis, incording todenitrification efficiency, determine the best UV irradiation time was30s,64.50mg/Lhigher than the unirradiated strains. After activated sludge bacteria three times UVmutagenesis, the amount of ammonia treatment reached536.27mg/L, increased122.45mg/L compared with the control group. The activated sludge was added into thefermentation wastewater, the removal effect of ammonia nitrogen was better than thecontrol group. After8days of culture, mutation group treatment of ammonia nitrogen isup to591.63mg/L,104.44mg/L higher than that in control group; The nitrification rateof mutation group was58.21mg/(L·d),10.42mg/(L·d) higher than the control group.Using DGGE technology to analysis changes of microbial community structure ofactivated sludge by mutagenesis. The experimental results show that, UV mutagenesisand enrichment culture changed the activated sludge microbial community structureobviously, mutagenic treatment can increase the microbial diversity index of sludgebacteria, provide a basis for denitrification ability enhance.