回灌过程中离子强度和水流流速对胶体粒子在多孔介质中堵塞的影响

发布时间：2018-10-13 20:25

【摘要】：人工回灌过程中的堵塞问题一直是影响其推广的瓶颈,目前回灌过程中大颗粒悬浮物导致的堵塞机理研究较多,对胶体类颗粒物的堵塞机理研究相对少。采用室内砂柱实验,研究不同离子强度和不同水流流速条件下胶体在饱和多孔介质中的迁移-滞留特征。选择大肠杆菌为实验胶体,设计在不同离子强度、不同水流条件下的砂柱回灌实验;运用Hydrus-1D软件模拟,拟合穿透曲线后得到表征胶体沉积的相关参数。实验结果表明,在相同的离子强度下,流速增大会促进胶体的迁移,穿透曲线峰值增高,胶体的吸附率减小。在中等离子强度条件下(IS=30、50 mmol·L-1)流速对胶体的这种影响比在更低的离子强度(≤10 mmol·L-1)或更高的离子强度(≥300 mmol·L-1)条件下更为显著;相反地,同一流速条件下,离子强度从10 mmol·L-1升高到300 mmol·L-1时,胶体的吸附随着离子强度的增加而迅速增加。从胶体和介质相互作用势能来看,随着离子强度的增加,胶体和砂表面的相互作用增强,有利于胶体吸附在介质表面,增加介质堵塞的概率。但是,在一定的离子强度下,流速的增加产生的水动力剪切力有利于促进胶体的迁移,不利于胶体的吸附或阻塞,减少了微小颗粒堵塞的概率。模拟结果显示吸附速率系数k、最大固相沉积量Smax随着离子强度的增大而增大,随着流速的增大而减小。从整体上来看,回灌过程中胶体微粒的迁移滞留行为主要受控于离子强度,但水流因素会干扰离子强度的控制作用。在实际的人工回灌过程中,有效的预防堵塞需要将化学(降低离子强度)和水动力(增加回灌水流速)手段有效地结合起来。
[Abstract]:The blockage problem in the artificial recharge process has been the bottleneck to its popularization. At present, there are more studies on the blockage mechanism caused by the suspension of large particles in the recharge process, but less on the blocking mechanism of the colloidal particles. The migration and retention characteristics of colloids in saturated porous media with different ionic strength and flow velocity were studied by laboratory sand column experiments. Escherichia coli was selected as the experimental colloid to design the sand column recharge experiment under different ionic strength and different flow conditions, and the relevant parameters of colloid deposition were obtained by using Hydrus-1D software to simulate and fit the penetration curve. The experimental results show that under the same ionic strength, the increase of flow velocity will promote the migration of colloids, the peak value of the penetration curve will increase, and the adsorption rate of the colloid will decrease. The effect of flow rate on colloid at medium plasma intensity (IS=30,50 mmol L-1) is more significant than that at lower ion intensity (鈮，

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