好氧氨氧化生物膜内氧传质特性及影响因素

Mass Transfer Performance and Influence Factors on Dissolved Oxygen Inside of Ammonium Oxidizing Biofilm

采用理论计算和实验测试相结合的方法,对流化床反应器中好氧氨氧化生物膜内溶解氧传质特性及影响因素进行了分析。建立了综合考虑反应-扩散-对流作用的一维模型,计算结果表明:溶解氧所能到达的生物膜厚度受渗流速度等因素的影响;增大渗流速度、扩散系数和进水底物浓度均可以提高膜内溶解氧浓度的最大值。建立了序批式流化床生物膜反应器,获得了高于80%的氨氮转化率,实现了好氧氨氧化生物膜的成功挂膜,获得生物膜厚度为0.1~0.3 mm,采用微电极测试了膜内溶解氧浓度。实验测试和模型计算结果表明,溶氧浓度沿生物膜厚度方向均呈现出抛物线形的不均匀下降趋势,且当扩散系数为2.2×10–4 m2/s和渗流速度为6.0 mm/s时,测试结果和计算数值具有较好的吻合度。

The mass transfer performance and influence factors on dissolved oxygen inside of ammonium oxidizing bacteria biofilm in fluid-bed bioreactor were analyzed based on the theatrical modelling and experiments.A one-dimensional model of reaction-diffusion-convection mixing was established.The results show that the seepage velocity and diffusivity have a great effect on the max depth of biofilm reached by dissolved oxygen.The higher the seepage velocity,diffusivity and feeding matrix concentration are,the higher dissolved oxygen concentration is inside of the biofilm.A sequencing batch biofilm reactor(SBR)was set up to culture aerobatic biofilm enriched by ammonia oxidation bacteria(AOB).Organic was added to accelerate the biofilm culture process in the startup phase.More than 80%of ammonia in the influent was converted to nitrite and the biofilm with a thickness of 0.1~0.3 mm was achieved.Oxygen concentration along the direction of the biofilm depth was tested by PA2000 oxygen microelectrode.The results from experiments and model calculation demonstrate that the change of dissolved oxygen concentration along the direction of biofilm depth presents a parabolic and non-uniform downward trend.When the diffusion coefficient was 2.2×10–4m2/s and the seepage velocity was 6.0 mm/s,the test results and the calculated values had a good agreement.