Study Of Promoting The Effect Of Denitrification Activated Sludge System By Fe(?)

The denitrification process is the key of biological denitrification in anoxic zone,and studies have shown that the denitrification rate can be improved by adding Fe(?).In this study,in regard to the phenomenon that Fe(?)promo te s denitrification in anoxic activate d sludge system,we imitate and reprod uce denitrification effect of continuous operation by adding Fe(?)in SBR reactor.We qualitatively research diversity of microbial communit y and variability of functional microorganisms in different experimental groups by High-Through p ut Sequencing.Furthermore,the related functional genes of denitrification are quantitatively studied by qPCR.Finally,we study the nitrogen metabo l i s m pathway of denitrification in the presence of Fe(?),and reveal the microb i a l mechanism of Fe(?)promoting denitrification,based on the results of highthroughput metagenomic sequencing.The comparison and simulation experiment of SBR denitrification in contro l,Fe(?)and Fe(?)group showed that,in the operation cycle,the effluent NOx-N of each reactor was lower than 0.3 mg/L,the denitrification of each reactor was complete,and the effluent NOx--N of Fe(?)and Fe(?)group was lower in comparison to control group.We summarized that the average denitrification rate of the control,Fe(?)and Fe(?)group were 15.63 mg/h·gVSS,17.63 mg/h·g V SS and 16.54 mg/h·g VSS,the denitrificat ion rate(mg/h·g VSS)of Fe(?)group increased significantly.Fe(?)and Fe(?)group can achieve better removal effec t for phosphate,and the total phosphorus level of Fe(?)and Fe(?)group were separately 0.72 mg/L and 1.11 mg/L,better than 3.53 mg/L of the control group.High-Throughput Sequencing was used to analyze the community struc t ur e and microbial composition of different experimental groups,having obvio us clustering.After the domestication of each group,betaproteobacteria was a dominant bacteria class in denitrification bacteria,and its abundance incre a s ed with acclimation time,especial ly in the Fe(?)group.Moreover,the Thaue ra denitrification bacteria dominated in dominant bacteria,and Fe(?)group was higher than other groups.In each group,the total abundance of denitrifica t i o n bacteria were about 13.2%,22.2% and 16.8%,and the Fe(?)group was highe r than that of other groups.The results of fluorescence quantitative PCR showed that the total amount of denitrification activated sludge microorganism remained unchanged at the same time,and adding Fe(?)makes denitri fication rate increase,which was the result of directed selection of microorganism.The content of narG,nirS,norB and nos Z carried by microorganism increased in Fe(?)group.The results of macro metabolic pathway showed that Fe(?)promoted the overall genes increase in nitrogen cycle.Fe(?)group,compared wit h blank and Fe(?)group,made the nirS genes,controlling rate-limit ing step of denitrifica t i o n process,significantly express,which coincided with the qPCR results.Through the three factors of denitrifying bacteria,functional gene and nitrogen metabolism pathway in the experimental group,addition of Fe(?)could promote the growth of denitrification functional bacteria represented by Thaue r a,and the increase in related denitrification genes,for example nirS,in activa t ed sludge.In addition,addition of Fe(?)affected and improved the rate-limiting step of nirS gene expression in denitrification process,consequently impro v ed denitrification efficiency.