水体扰动对黑臭河道内源氮营养盐赋存形式的影响

Effects of turbulence on the behavior of endogenous nitrogen in malodorous river

设计了一套模拟河道底泥再悬浮装置,设定4个不同水体扰动强度的工况以及1个不扰动对照组,测量了不同水体扰动强度产生的流速以及溶解氧(DO)浓度变化情况,并据此计算出不同工况的雷诺数(Re).研究了不同扰动强度下氨氮、亚硝氮、硝氮和总氮在上覆水、浮泥层间隙水和黑泥层间隙水中的迁移转化规律.结果表明:不同曝气扰动强度引起不同溶解氧梯度分布,并导致底泥中内源氮营养盐赋存形式之间的不同转化途径,其中流速为28.8～32.0cm/s时,Re为1810～2113,DO平均值为5.08～7.50mg/L,上覆水中氨氮和总氮去除效果最好,表明曝气扰动对底泥内源氮中氨氮和总氮的转化行为影响最大.与不产生曝气扰动时相比,由于曝气复氧作用,浮泥层呈现较高的亚硝氮和硝氮浓度,这导致二者分别向上覆水和黑泥层扩散.对于扩散至黑泥层的亚硝氮和硝氮,会在缺氧或厌氧环境的黑泥层中进一步通过反硝化或厌氧氨氧化途径实现对内源氮的完全脱除.

A simulation system was designed for river sediment resuspension. Four different aeration turbulent intensity working conditions and one static control were set up. Flow velocities under different turbulent intensities and their dissolved oxygen concentrations were measured. The Reynolds number （Re） of each condition was calculated. The migration and transformation behaviors of four nitrogen forms （ammonia, nitrite, nitrate and total nitrogen in overlying water and pore water from fluid mud layer and black layer） were analyzed. The results showed that DO concentration distributed with various aeration turbulent intensities, which lead different trans- formation pathways of occurrence of endogenous nitrogen . Under the condition of 28.8 ~ 32.0 cm/s flow velocities and 1 81042 113 the Reynolds numbers, ammonia and total nitrogen in overlying water exhibited better removal efficiency, indicating that turbulent intensity played a significant role in the transformation process of endogenous ammonia and total nitrogen. Compared with static control regime, areation made the fluid mud layer have a higher nitrite and nitrate concentration, it may diffuse to overlying water and black layer. The diffusion nitrite and nitrate in black layer should adopt denitrification or anaerobic ammonium oxidation pathways to remove endogenous nitrogen under hypoxia or anaerobic condition.