Study On Screening And Nitrogen Removal Characteristics Of A Low C/N Aerobic Denitrifying Bacteria

In recent years,with the emission standard of ammonia and total nitrogen in wastewater getting stricter in our country,the difficulty of the treatment of nitrogen-containing wastewater increases sharply.How to remove nitrogen effectively and economically has become the research focus in the field of water treatment.Because of its ability to denitrification under the aerobic conditions and the advantages of less investment、low operating costs,aerobic denitrification has become the focus of research.In this paper,a highly efficient aerobic denitrification strains Y7,which can adapt to the low C/N condition,was isolated from the activated sludge of the refining wastewater.The species was determined by morphological observation,physiological and biochemical tests and 16 S r DNA sequence analysis.On this basis,the nitrification and denitrification characteristics of strain Y7 were studied,and then applying the strain Y7 to the denitrification of actual refining wastewater.The main conclusions are as follows:（1）The oil refining wastewater activated sludge was selected as the source,an aerobic denitrifying dominant strain Y7 with C/N=6 was isolated through enrichment,domestication and purification.Strain Y7 was identified as Pseudomonas sp through the study of the morphological observation,physiological properties and 16 S r DNA sequence identification.（2）Under the condition of C/N=6,the optimal conditions of nitrification for strains Y7 were: the carbon source is sodium succinate,the culture temperature is 30℃～35℃,the initial p H is 9.0,the liquid volume is 80 m L and the inoculation amount is 3%.When the initial concentration of NH₄⁺-N is 115.34mg/L,the removal rate of NH₄⁺-N could reach 90.21% in 9 h under these optimal conditions.（3）Under the condition of C/N=6,the optimal conditions of denitrification for strains Y7 were: the carbon source is sodium succinate,the culture temperature is 30℃,the initial p H is 6.0,the liquid volume is 60 and the inoculation amount is 2%.When the initial concentration of NO₃^--N is 112.68mg/L,removal rate of NO₃^--N could reach 88.03% in 9 h under these optimal conditions.（4）Under the conditions of shake flask culture,the degradation rate of ammonia nitrogen of strain Y7 was 54.77% in 48 h with the initial ammonia nitrogen concentration of 40.77 mg/L.When the concentration of the refinery wastewater was diluted 1 times,the degradation rate of ammonia nitrogen increased to 64.93% in the same time.（5）The preliminary study shows that the suitable operation conditions of actual oil refining wastewater treatment device are:the hydraulic retention time is 48 h,the aeration tank temperature is 30℃ and the initial p H is 8.0～9.0.After continuous operation for 15 days under these conditions,the effluent ammonia nitrogen is lower than 5mg/L and the total nitrogen is lower than 10mg/L,meeting the national standards for oil refinery wastewater emission.