Study On Ferrous Chelate Absorption And Bioreduction For NO Removal By Sulfur-based Autotrophic Microorganism

The missions of NO caused major environmental problems such as photochemical smog,acid rain and urban haze.How to effectively remove NO is an essential topic in today’s environmental protection field.Chemical absorption-biological reduction is an environmental and friendly technology for NO removal denitrification.It has a good application prospect and a series of theoretical and technical problems which have not been solved yet.Based on this,this paper proposes a new way for NO removal in small and medium-sized industrial boilers by sulfur autotrophic microorganism.The kinetics of the reduction of Fe(II)EDTA-NO and Fe(III)EDTA was studied.The microbiological packed bed reactor was constructed to study the operating performance of single substrate and double substrate reduction reactor,and the molecular ecology in the reactor was analyzed by qPCR and high throughput sequencing technology.The conclusions of were as follows:1.The batch experiments show that nitrogen elements in are basically constant in the Fe(II)EDTA-NO reduction.The reduction process of the single substrate conforms to the Michaelis-Menten equation.When the Fe(III)EDTA is 11 mmol,the maximum Vmax is 1.87 mmol·L-1·h-1.When Fe(II)EDTA-NO is 16 mmol,the maximum Vmax is 2.11 mmol·L-1·h-1.The dual substrate reduction was described by the Michaelis-Menten equation and the substrate inhibition model,while the Vmax increased with the increasing of total iron concentration.2.The performance of the single-substrate reactor showed that when the Fe(II)EDTA-NO concentration was in the range of 1.2～16.1 mmol·L-1,the removal rate was over 90%.When the concentration of Fe(II)EDTA-NO was 5.7 mmol·L-1,the maximum reduction load was 6.6 mmol·L-1·h-1.When the total iron concentration was 8 mmol·L-1,the dual substrates reactor had the highest reduction load of 3.4 mmol·L-1·h-1.The high concentration of total iron inhibits the reduction of Fe(III)EDTA,and has less effect on Fe(II)EDTA-NO reduction.The total iron reduction rate is above 75%.The production of SO42-in both reactors is linearly related to the reduction of iron,and pH both in inlet and outlet are stable in the range of 6～8.3.The qPCR and 16S rRNA high-throughput sequencing was used to analyze the microbial structure in two reactors.In two reactors,both the archaea and the bacteria increased with the increase of the operating period.The bacteria was more abundant than that of the archaea.Both Proteobacteria and Betaproteobacteria were the dominant groups in the phylum and class level.The dominant bacteria groups of the single substrate reactor were Thiobacillus,Rhizobium and Dechloromonas,and the dominant bacteria in the dual substrate reactor were Thiobacillus,Ferritrophicum,Sulfuricmonas and Rhizobium.Among them,Rhizobium and Thiobacillus are relatively abundant,which play an important role in substrate reduction.Thiobacillus is a typical nitrifying bacterium,which decreases with the increasing of iron concentration.It is possible that high concentration iron is toxic to Thiobacillus.