Evaluation of the local self-purification processes in a natural river.

探讨了天然河流冲沟的硝化能力。估算了河岸次表层细菌密度、渗流方向、渗流速度、砂砾石层孔隙度以及河水和渗水中氮的浓度。根据氮氧化细菌的指数生长模型，得到了河岸渗滤层的硝化速率。由于层级结构、孔隙度以及氨氮和亚硝酸盐氮输入的不均匀，细菌密度在空间上表现出一定的变化。在没有相当大的基质负荷的情况下，渗滤层单位体积氨氧化菌密度为0.5~1.5 mg/L，亚硝酸氧化菌密度为0.05~0.2 mg/L。安曼…的最大密度分析了渗流的物理化学条件对细菌硝化作用的影响，确定了天然河流潜流带内的硝化作用。将几种液体介质以不同的流速投加到填充河沙砾石的圆柱体中，详细地阐明了硝化能力随流速和无机氮浓度的变化规律。在间歇培养实验中，与气泡曝气产生的均匀混合条件相比，在单向、湍流较少的渗流条件下(通常在低渗流区)观察到更多的细菌生长和硝化作用。单位时间内砂砾石柱内的硝化氮受流速的影响较大。在富氮条件下，观察到较高的硝化作用，其值是用相应的细菌密度用对数生长模型估算的最大值的数倍。此外，在低浓度条件下，在渗流速度为3m/h时，几乎达到最大氧化速率，约为70%。较少

The nitrification capacity of riffles in a natural river was discussed. The bacteria density in the river bank subsurface layer was estimated together with the seepage flow direction and speed, the porosity of the sand gravel layer and the nitrogen concentrations in the river and seepage waters. On the basis of the exponential growth model for nitrogen oxidation bacteria the nitrification rate of the seepage layer on the river bank was obtained. The spatial variety of bacteria density due to the inhomogeneity of gradation structure, porosity and the input of ammonium and nitrite nitrogen was observed. Without the considerable load of substrate, the density of the ammonia oxidation bacteria per unit volume of the seepage layer was 0.5 - 1.5mg/L and that of nitrite oxidation bacteria was 0.05-0.2mg/L. The nitrification capacity in the subsurface layer of a riffle was estimated more than ten times as large as that of a pool in the same longitudinal length. The maximum density of the ammon … More ium and nitrite oxidation bacteria was 5.35mg/L and 1.46mg/L respectively in the subsurface layer adjacent to the wastewater effluent, in which approximately 20% of the inorganic nitrogen load was thoroughly oxidized.Effect of the physical and chemical conditions of the seepage flow on the bacterial nitrification were discussed in order to determine the nitrification within the hyporheric zone in a natural river. Several kinds of liquid medium were supplied into the cylindrical columns filled with the river sand gravel at different velocities, and the characteristics of the nitrifying capacity varying with both the flow velocity and the inorganic nitrogen concentration were clarified in detail. In batch incubation experiments, more bacterial growth and nitrification were observed in the unidirectional, less turbulent seepage flow condition such as usually seen in the hyporheic zone than in the well-mixed condition generated by the bubble aeration. The nitrified nitrogen within the sand gravel column in unit time was strongly affected by the flow velocity. In the rich nitrogen conditions, the high nitrification was observed which was several times as large as the maximum values estimated by the logarithmic growth model using the corresponding bacterial density. Furthermore, in low concentration conditions, where little bacterial growth was expected by the model, nearly the maximum oxidation, approximately 70% of that, was achieved under the seepage flow speed 3 meters/hour. Less