Screening And Degradation Characteristics Of A Heterotrophic Nitrification-aerobic Denitrification Bacterium Cupriavidus Sp. S1

Since excessive nitrogen-containing wastewater discharges that causes increasingly serious water eutrophication.Therefore,the removal of nitrogen from wastewater effectively is the key to environmental governance.Biological nitrogen removal process is considered the best denitrification method because of its high efficiency,low cost and without secondary pollution.As a new technology of nitrogen removal,heterotrophic nitrification has become the research focus in the field of nitrogen removal.The source of nitrogenous wastewater is extensive,such as coking,petrochemical,steel and vanadium,tungsten,molybdenum,nickel cobalt,rare earth and other non-ferrous metals wastewater.The wastewater contains both high concentration of NH4+-N and metals ions,while metals ions are toxic to microorganisms,resulting in the reduce of the efficiency of denitrification.In this paper,a high efficient heterotrophic nitrifying-aerobicdenitrification bacterium was isolated from the coking wastewater from Jinzhong Yixing Coking Co.,Ltd.in Shanxi Province.The heterotrophic nitrification and aerobic denitrification characteristics of the strain were investigated.In addition,the degradation effect of the strain in coking wastewater was investigated,which provide the technical support for future practical engineering applications.The conclusions are as follows:1.A novel heterotrophic nitrification-aerobic denitrification bacterium was screened and was identified as Cupriavidus,named as S1 by its morphological observation,physiological and biochemical characteristics and16 S rDNA gene sequence analysis.2.The heterotrophic nitrification characteristics of strain S1 were studied,which demonstrated that the NH4+-N removal efficiency was 99.68% in 24 h with the maximum removal rate of 10.43 mg/L/h.Moreover,the levels of intermediates accumulation were all very low during the nitrification,and the degradation rate of TN was 98.69%.The aerobic denitrification characteristics of strain S1 showed that after 24 h-cultivation the degradation rates of NO3--N and NO2--N were 98.03% and 99.81% with the maximum conversions rates were 8.64 mg/L/h and 8.36 mg/L/h,respectively.The removal rates of TN were 97.4% and 96.51% respectively.The results of gas detection showed that N2 was the main heterotrophic nitrification and aerobic denitrification productwhen NH4+-N,NO3--N and NO2--N were added as the nitrogen source,which suggested the existence of heterotrophic nitrification and aerobic denitrification in strain S1.Strain S1 could grow and metabolism by using an organic nitrogen source directly.3.The experiment of simultaneous nitrification and denitrification showed that S1 was able to remove nitrogen completely in the system when（NH4）2SO4 and NaNO3 or（NH4）2SO4 and NaNO2 were added as nitrogen sources simultaneously,and S1 would utilize ammonia nitrogen preferentially.4.The optimum conditions for the NH4+-N removal of strain S1 were as follows: temperature of 28.67 oC,initial pH of 7.44,shaking speed of 133.3rpm,and carbon source was sodium pyruvate.S1 had a high capability for ammonium removal in the presence of high organic load,and it could tolerate high concentration of ammonia nitrogen and phenol.5.The effects of Cu²⁺,Zn²⁺,Ni²⁺ and Cr⁶⁺ on heterotrophic nitrogen removal of S1 were investigated.The result showed that Zn²⁺ and Ni²⁺ had no inhibitory effect on nitrogen removal in a certain concentration range,while Cu²⁺ was toxic to the strain S1 with the increase of concentration.Cr⁶⁺ showed the most toxic effect on nitrogen removal.The orders of constraint influence of metals ions differs under concentrations of 10 mg/L on heterotrophic nitrification of S1 was Cr⁶⁺ > Cu²⁺ > Ni²⁺ > Zn²⁺.Compared with the general heterotrophic nitrifying bacteria,S1 showed high tolerance to metals ions.6.The NCB（S1+Y1+W4）,a heterotrophic nitrification and aerobic denitrification functional bacteria populations,was constructed by strain combination.The NCB was adopted to treat diluted coking wastewater and it exhibited excellent heterotrophic nitrogen removal ability.By 144 h,the degradation rate of NH4+-N,phenol and COD reached 50%,40% and 50%,respectively.The NH4+-N,phenol and COD removal efficiency of NCB were increased successfully by 24.69%,60% and 10.56%,respectively,which was achieved through immobilizing by mycelial pellets.These findings demonstrate that the application of composite immobilized microorganisms in the treatment of coking wastewater has potential research value.