| More than 2.8 million people die each year from indoor air pollution,with the main pollutants being formaldehyde.The traditional method of prevention and control of indoor formaldehyde pollution have some disadvantages,such as physical adsorption efficiency of formaldehyde adsorption of low concentration is low,poor stability,easy desorption,and easy to be affected by the change of temperature and the concentration of formaldehyde;Plant on the absorption of formaldehyde purification of indoor air needs at lower concentrations of pollutants,and the role of a slower time;Ozone itself is also a kind of air pollutants,more than a certain concentration will cause harm to the human body.The safe and efficient formaldehyde degradation method is the current research trend.The purpose of this study is to reduce the efficiency of formaldehyde degradation by using microbial method to oxidize and degrade it into non-toxic and harmless inorganic materials by using microorganism as the carbon source.Several strains of formaldehyde-degrading bacteria were screened by the separation and purification of the complex bacteria,The degradation conditions of formaldehyde degrading bacteria were optimized,and the indoor formaldehyde purification device was constructed,which laid the foundation for the construction of highly tolerant and efficient formaldehyde degrading engineering bacteria and biological methods for the removal of indoor formaldehyde pollution.The research process draws conclusions as follows:(1)The degradation efficiency of formaldehyde was up to 93.68% in 24 hours with the highest initial concentration of formaldehyde at 1500 mg/L under the condition of 40 L/min high aeration condition with formaldehyde as the sole carbon source.(2)Using Illumina Miseq high-throughput sequencing technology to explore the complex bacterial enrichment process of microbial community structure changes found that,The samples from four enrichment stages were composed of 7~12 phyla with Proteobacteria and Bacteroidetes as the main part.The proportion of Proteobacteria in the four stages was 73.92%,78.38%,86.78% and 57.03% respectively.With the increase of formaldehyde concentration,the relative abundance of the samples increased,and the relative abundance of the samples was The slightest rise after the trend.The proportion of Bacteroidetes in the four stages was 25.91%,20.66%,9.46% and 11.58%,respectively.The relative abundance of the samples was opposite to Proteobacteria.The change pattern of Classes was consistent with that of Phyla,and it was proved that the microbial community structure experienced a distinct succession process during the four stages of enrichment of compound bacteria.Methylobacterium spp.and Pseudomonas spp.were the dominant genera of 11~18 species in the four stages.The proportion of Methylobacterium spp.in four samples was 34.88%,13.67%,32.63% and 16%,respectively.Pseudomonas spp.were 18.38%,32.08%,36.87% and 17.78%,respectively.With the increase of formaldehyde concentration,the relative abundance of the samples of the Methylobacterium spp.decreased,while the relative abundance of the samples of Pseudomonas spp.increased.After the formaldehyde concentration decreased,the strains of Methylobacterium spp.and Pseudomonas spp.relative abundance of the samples showed a trend of ascending and descending.(3)16 strains of formaldehyde degrading bacteria were obtained under the condition of high aeration gas,and 16 strains of formaldehyde degrading bacteria were identified as Methylobacterium spp.,Paenibacillus spp.Hyphomicrobium spp.,Ralstonia pickettii four genera,Among them,3,9,11 strains 24 hours degradation of the initial concentration of 1300 mg/L formaldehyde degradation rate as high as 90% or more.In addition,Ralstonia pickettii is a conditional pathogens may pose a threat to human health,follow-up experiments to its rounding.(4)Optimization of degradation conditions of formaldehyde degradation bacteria found that,(1)When the ratio of carbon to nitrogen is 10: 1,the formaldehyde degrading bacteria can be used to reach the stable period and the logarithmic phase.(2)Small molecular maltose as an additional carbon source,and the concentration of 1.0 g/L can also make formaldehyde degrading bacteria to reach the stable period faster and logarithmic phase,and promote the degradation of formaldehyde degradation bacteria.(3)When the nitrogen source of the medium is organic nitrogen source urea,it is easier to promote the degradation of formaldehyde degradation bacteria.(4)The content of 50~150?L trace elements on the degradation of formaldehyde degradation bacteria have a role in promoting,beyond the concentration of formaldehyde degradation bacteria degradation effect will be inhibited.In addition,formaldehyde-degrading bacteria can tolerate toluene at a concentration of 2854.5 mg/L and 5148.5 mg/L of trichloromethane.(5)The degradation rate of formaldehyde in the three mixed flora was stable at 95%~100% under the condition of 30? and 160 r/min constant temperature shaking culture.The degradation rate of formaldehyde in the culture medium was 0%~80% fluctuation.The nedeli fiber ring,quartz ball,foam filter and shell activated carbon in nine kinds of carriers have the best effect,and the degradation rate of formaldehyde can stabilize within 95%~100%.The degradation rate of formaldehyde in the mixed strains of three kinds of mixed strains was poor,and the degradation rate was fluctuating from 50%~95%.The degradation rate of formaldehyde in all the mixed bacteria and compound bacteria was stable at 97%~100%.(6)Under the optimal degradation conditions,the degradation rate of formaldehyde in the experimental group with quartz ball carrier was increased exponentially at 30? and 160 r/min,and the degradation rate of formaldehyde at the initial concentration of 1000 mg/L was complete within 84 hours.The content of formaldehyde in the initial concentration of 1700 mg/L in the range of 30~60 L/min was 92.56%.Aeration of 70~80 L/min under the conditions of 24 hours within the initial concentration of 1600 mg/L formaldehyde up to 89.14%.When the aeration rate was 60 L/min,the degradation rate of formaldehyde was more than 92.79% and the degradation efficiency was stable at the initial concentration of 600~1700 mg/L.Proving the feasibility of the device. |
PDF Full Text Request