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Impact of Mineral Fouling on Hydraulic Behavior of Permeable Reactive Barriers

机译：矿物结垢对渗透性反应障碍水力学行为的影响

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This paper describes reactive transport simulations conducted to assess the impact of mineral fouling on the hydraulic behavior of continuous-wall permeable reactive barriers (PRBs) employing granular zero-valent iron (ZVI) in carbonate-rich alluvial aquifers. The reactive transport model included a geochemical algorithm for simulating corrosion and mineral precipitation reactions that have been observed in ZVI PRBs. Results of simulations show that porosity and hydraulic conductivity of the ZVI decrease over time and that flows are redistributed throughout the PRB in response to fouling of the pore space. Under typical conditions, only subtle changes occur within the first 10 years (i.e., duration of the current field experience record with PRBs), and the most significant changes do not occur until the PRB has operated for at least 30 years. However, changes can occur sooner (or later) if the rate at which mineral-forming ions are delivered to the PRB is higher (or lower) than that expected under typical conditions (i.e., due to higher/lower flow rate or inflowing ground water that has higher/lower ionic strength). When the PRB is more permeable than the aquifer, the median Darcy flux in the PRB does not change appreciably over time because the aquifer controls the rate of flow through the PRB. However, seepage velocities in the PRB increase, and residence times decrease, due to porosity reductions caused by accumulation of minerals in the pore space. When fouling becomes extensive, bypassing and reductions in flow rate in the PRB occur.
机译：本文描述了反应输运模拟，以评估矿物结垢对富含碳酸盐冲积含水层中的颗粒零价铁（ZVI）的连续壁可渗透反应性屏障（PRB）的水力行为的影响。反应性运输模型包括一种地球化学算法，用于模拟ZVI PRB中观察到的腐蚀和矿物沉淀反应。模拟结果表明，ZVI的孔隙率和水力传导率会随着时间的推移而降低，并且随着孔隙空间的结垢，流量会在整个PRB中重新分布。在典型情况下，前10年（即PRB当前现场经验记录的持续时间）仅发生细微变化，并且直到PRB运行至少30年才会发生最重大的变化。但是，如果将成矿离子传递到PRB的速率高于（或低于）典型条件下的预期速率（例如，由于流速较高或较低或地下水流入），则更改可能会更快（或更晚）发生。具有较高/较低的离子强度）。当PRB的渗透性比含水层高时，PRB中的Darcy通量不会随时间明显变化，因为含水层控制着流过PRB的流量。但是，由于矿物在孔隙空间中的堆积而导致孔隙度降低，PRB中的渗透速度增加，停留时间减少。当结垢变得广泛时，PRB中会发生旁路并降低流速。

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