Research On The Characteristics And Application Of Iron Reducing Bacteria Coupled Biological Nitrogen Removal

In this experiment,two strains with the capacity of iron reducing efficiently was isolated and purified from the water and sediments of the lake in Xi’an（China）.The molecular identification,the characteristics of iron reduction,the characteristics of biological nitrogen removal and the characteristics of nitrogen removal of the strains in the raw water reactor were also studied.The strain FC61 was Klebsiella sp.,strain CC76 was Enterobacter sp..In the four kinds of common iron source,the best source of iron for strain FC61 and CC76 was ferric citrate,the iron reduction rate were 95.09%and 88.38%.The optimal carbon sources for the four common carbon sources were glucose,and the rate of iron reduction was 95.35% and 82.20%,respectively.The removal efficiency of ammonia nitrogen of two strains increased with the increase of pH,and the ammonia nitrogen removal ability of strain FC61 was superior to that of the strain CC76.Four inoculation of 1%,5%,10% and 15%（V/V）were selected to study the optimal gradient of iron reduction,the corresponding iron reduction rate were60.26%,80.61%,83.85%,and 73.69%,in the same inoculation amount,ammonia nitrogen removal ability of strain FC61 was higher than strain CC76.And two strains of ammonia removal were increased with the increase of the amount of inoculation.Iron reducing bacteria FC61 and CC76 have similar characteristics of removal of ammonia,and ammonia nitrogen removal efficiency of strain FC61 was obviously superior to the strain CC76,separate study showed that the pathway of strain FC61 on ammonia nitrogen removal was possible partly by bacterial growth by itself,another part was by synchronous iron reduction and ammonia removal in this process of producing gas.Studying on denitrification characteristics of iron reducing bacteria showed that FC61 and CC76 could convert Fe³⁺ to Fe2+,at the same time,the reduced Fe2+ would become the electronic donor in the process of autotrophic denitrification.Thus this process would form an iron cycle.Iron reduction kinetics of denitrification bacteria showed that under different pH conditions,the maximum rate of iron reduction was a very short time.The biological nitrogen removal characteristics of immobilized iron reduction bacteria showed that the immobilized pellets had better adsorption effect on both Fe³⁺ and Fe2+,while the adsorption of Fe³⁺ was stronger than that of Fe2+.Immobilized pellet had a larger specific surface area and better physical adsorption capacity,and promoting the removal of ammonia nitrogen and nitrite nitrogen.Compared with immobilized strain FC61 and non immobilized strain FC61,the former one had a great advantage in the removal of ammonia nitrogen,and also kept a relatively low turbidity and iron ion in the solution,and the relatively low concentration by-product of nitrate nitrogen,nitrite nitrogen.The results showed that in the two states the adaptation ability of strain FC61 to remove ammonia nitrogen was not changed significantly under different temperature,pH and initial Fe³⁺ concentration.Observation of iron reducing bacteria in heterotrophic ammonia nitrogen removal in the reactor,the experimental conclusion and front research results of single strain coincide.In the research of magnetite pellets about nitrogen removal showed that adding magnetic powder was helpful to improve the removal rate of nitrate nitrogen.The average concentration of the two iron in the reactor with the addition of the magnet powder was lower than that of the reactor without the magnet powder.The overall performance and high-throughput sequencing analysis of the reactor under different influent NH4+-N and NO3--N concentrations showed that the species structure in the reactor was similar at the same concentration.The addition of magnetite powder did not have a significant effect on the results of the reactor,only by regulating the adsorption of ions on the pellets to improve the removal ability of nitrate nitrogen,at the same time,the immobilized FC61 Klebsiella had been well adapted to the requirements of the environment,which was the dominant species in the reactor.