Study On The Deep Nitrogen Removal Performance Of Biological Denitrification Using Activated Ferrous Sulfide As Electron Donor

At present,hydrogen autotrophic denitrification,iron based autotrophic denitrification and sulfur autotrophic denitrification can be used for nitrate removal in water.But there are some problems such as high cost,many by-products and low safety.The autotrophic denitrification process of pyrite has been widely used to remove nitrate from water in recent years because of its low cost and high efficiency.However,the biological nitrogen removal performance of activated ferrous sulfide as electron donor has not been studied.The aim of this study was to compare and analyze the biological nitrogen removal performance of ferrous sulfide under different ball milling conditions and calcined iron sulfide as electron donor,and optimize the operating conditions of activated ferrous sulfide as electron donor for biological denitrification.In this paper,the nitrate denitrifying bacterial sludge with ferrous sulfide as electron donor was successfully acclimated using SBR reactor,and the acclimated sludge with the final nitrate removal rate of 97%was obtained in about 30 days.High throughput sequencing technology was used to analyze the microbial community structure in the denitrification sludge.The results showed that T.denitrificans and Brevundimonas denitrificans were the main microorganisms for denitrification in the denitrification system with ferrous sulfide as the electron donor.Both have denitrification capacity and can reduce nitrate.In order to investigate the biological nitrogen removal performance of ferrous sulfide as electron donor under different ball milling conditions,the acclimated sludge was used for sequencing batch experiments.The nitrate removal effect of ferrous sulfide as electron donor under different ball milling conditions was compared.The results showed that when ethanol dispersant was added and the pellet ratio was 10:After 24 h of ball milling,the nitrate removal rate of ferrous sulfide as electron donor was 67.9%at 6 h,which was nearly 30%higher than the initial water grinding of 38.8%,and the promotion effect was more obvious.Then,the removal effect of nitrate was compared when ferrous sulfide was used as electron donor at different calcination temperatures.The results showed that the removal rate of nitrate reached 99%in 6 h when ferrous sulfide was calcined at 400℃as electron donor for biological nitrogen removal.In the entire autotrophic denitrification process,nitrite accumulated in the early stage and was gradually reduced and degraded in the later stage,and the concentration of ammonia nitrogen basically did not change.The decreasing trend of nitrate was similar to that of total nitrogen,and no other products were generated,and N₂was eventually produced.To explore the effect of other physicochemical factors on autotrophic denitrification system with calcined ferrous sulfide as electron donor.The dosage of Fe S,initial nitrate concentration,particle size of Fe S,initial p H and initial reaction temperature were continuously changed,and the final nitrogen removal rate was compared.The results showed that the initial nitrate concentration was 20 mg/L,the Fe S with an average particle size of 300 nm was 400 mg/L,the initial p H of the reaction was adjusted to neutral,and the reaction temperature was kept at about 30℃.Finally,the balance of the whole biological nitrogen removal reaction could be reached within 1 hour,and the final nitrogen removal rate was 99%.Figure[26]Table[6]References[92]...