Study On The Addition Of Fe²⁺ And Nitrate-dependent Anaerobic Iron Oxidation Microorganism To Promote Denitrification Of Wastewater

The high nitrogen and phosphorus content in domestic sewage and some industrial wastewaters with the low C/N ratio have led to the unsatisfactory effect of traditional heterotrophic denitrification biological nitrogen removal.Autotrophic denitrification is a new biological denitrification idea that allows inorganic materials to be used as electron donors to convert nitrates to nitrous oxide and nitrogen.Among them,Fe~?is used as an electron donor.The discovery of autotrophic denitrifying iron bacteria is a major breakthrough in autotrophic denitrification research,which greatly reduces the cost of wastewater denitrification treatment.Based on the shortage of carbon sources in the denitrification stage in the traditional biological nitrogen removal process,this study focused on this issue.In this study,the UASB reactor was used to successfully domesticate the nitrate-type anaerobic iron oxidizing bacteria(NAIOM)sludge with Fe~?as the electron donor.The organic matter,temperature and Fe/N pair were also explored.The effect of denitrifying and denitrifying effect of NAIOM sludge showed that under the condition of adding only Fe~?to the influent,the NAIOM sludge with domestication for about 45d can achieve relatively stable denitrification.However the effect of denitrification,while the running time is too long,there will be Fe~?accumulation of precipitate in UASB,resulting in NAIOM being unable to contact with Fe~?,the reaction system The denitrification effect decreased sharply.The organic matter impact experiment showed that a small amount of organic carbon source could participate in the Fe(II)-Fe(III)cycle reaction under the microbial dominance,which indirectly increased the content of the substrate Fe~?in the wastewater and promoted the denitrification of NAIOM.Effect;Temperature also had an impact on NAIOM experiments.Results showed that the most suitable temperature for NAIOM sludge denitrification is about 30°C;a small trial test to adjust the influent Fe/N value to study Fe~?versus NAIOM.Results showed that when the Fe/N value is between 2.34 and 3.51,the NAIOM sludge nitrate removal rate fluctuates between 81%and 89%.In order to explore the feasibility of the application of NAIOM sludge in this application,the NAIOM sludge cultured in UASB for 45 days was inoculated into the ASBR reactor with ordinary heterotrophic denitrification sludge.Reactor water inflow C/N was continuously changed.Conditions and addition of Fe~?,inoculation of NAIOM sludge as a time limit for the removal of nitrate nitrogen before and after inoculation sludge and other indicators.This study also indicated that nitrate nitrogen removal rate respectively At C/N=3.42,2.28,and 1.71,it was 90.20%,85.12%,and 78.86%.After inoculation of NAIOM sludge in ASBR reactor,it was 17.80%,24.59%,and 28.70%,which is higher than that of common denitrification sludge.It is obvious that the carbon to nitrogen ratio is high,NAIOM and Fe~?have no promotion effect on denitrification and denitrification.The optimal Fe:C:N pilot test is designed for mixed sludge.Our study showed that the practical application is considered.Under the premise of economic cost,when C/N=3 and Fe~?is 15 mg/L,C/N=4,Fe~?is 10 mg/L,C/N=5,Fe~?is 2.5mg/L,the nitrate nitrogen removal rate can reach about 85%.At this time,the wastewater Fe:C:N is more realistic and reasonable state.Based on 16SrRNA gene for high-throughput sequencing analysis,the species diversity analysis of NAIOM sludge and mixed sludge samples containing NAIOM was carried out from the microbiological point of view.Results showed that the mixed sludge sample species containing NAIOM in ASBR The diversity is higher than the pure NAIOM sludge domesticated in UASB;from the classification of the population classification,the dominant bacteria at the gate level in the sludge sample are Proteobacteria proteobacteria,And it could be concluded from clustering heatmap that the overall comparison between the UASB group and the ASBR group is quite different,which is in line with the actual situation of the sludge sampling.