Characteristics And Regulation Of DNRA Bioconversion From Scrubbing Liquor Formed In Flue Gas Denitration Process

In the treatment of denitrification absorption solution,the existing physical and chemical treatment technologies have the problems of complex process,high operation cost and low removal efficiency in different degrees.The biological method has the advantages of high efficiency,low cost and no secondary pollution,and has been widely used.Denitrification converts nitrate into N₂,while DNRA converts nitrate and nitrite into NH₄⁺for recovery.When the denitrification absorption solution is treated by DNRA process,the nitrate and nitrite can be converted into ammonia for recycling and reuse,so as to achieve the purpose of harmless waste and recycling.At present,under the condition of pure culture of DNRA process study is less,in the process of DNRA transformation characteristics and influencing factors are still not clear,in order to solve this problem,this study explore DNRA ability of the mixed bacteria in the sludge,and isolated a strain which has the function of DNRA strains,investigation of denitration absorption under the condition of pure culture fluid DNRA bioconversion process characteristics and product control measures,the main contents are as follows:In the screening process of DNRA bacteria with mixed flora,NO₃^-was the only nitrogen source and NH₄⁺was produced in the medium,indicating that DNRA process was carried out in the mixed flora.The ammonium yield was similar in the shaking table and the biochemical incubator respectively,indicating that the anaerobic or micro-oxygen environment promoted the DNRA process of the strain.A strain with DNRA function was isolated from the sludge,the 16S r DNA fragment was sequenced,and the phylogenetic tree of the strain was analyzed.Combining the bacterial colony morphology,16S r DNA sequence and phylogenetic tree analysis of the strain,the bacteria was identified as Pseudomoas.The strain was transferred to guangdong provincial microbial species preservation center?GDMCC?for preservation.The GDMCC NO was 1.1547 and the strain number was ZZU seq DKF-01.The growth of strain Pseudomoas sp.DKF reached the highest concentration at 36 h,and its absorbance was 0.932.The biological transformation process characteristics and product regulation of bacterial strain under micro-oxygen conditions were investigated,and the effect of carbon source and C/N on DNRA ability of Pseudomoas sp.DKF under micro-oxygen conditions was investigated.The results showed that the p H suitable for growth of Pseudomoas sp.DKF was 9-10,and the DNRA ability of Pseudomoas sp.DKF was the strongest when sodium acetate was used as an added carbon source.When sodium acetate was used as an added carbon source,C/N was 8,the DNRA rate of the strain was the fastest and the efficiency was the highest.The effects of C/N,initial p H value,S/N(S^2-)and S/N(SO₄^2-)on the DNRA ability of Pseudomoas sp.DKF under anaerobic conditions were investigated.The results showed that the DNRA ability of Pseudomoas sp.DKF was stronger when C/N was 8 under anaerobic conditions than under microoxygen conditions.With the increase of the initial p H value,the DNRA efficiency of Pseudomoas sp.DKF increased,and the reduction rate of NO₃^-and NO₂^-was accelerated.However,the efficiency of DNRA decreased when the initial p H value was 10,indicating that the DNRA ability of Pseudomoas sp.DKF was inhibited under the condition of strong alkalinity.Under anaerobic conditions,the addition of S^2-promoted the DNRA capacity of Pseudomoas sp.DKFstrain,and the DNRA rate of NO₂^-increased with the addition of S^2-.In the environment where SO₄^2-and NO₃^-coexist,strain Pseudomoas sp.dkf first reduced NO₃^-and then reduced SO₄^2-,and the DNRA rate of NO₂^-increased with the addition of SO₄^2-.