Geology Department, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045, United States of America.
Geology Department, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045, United States of America.
J Contam Hydrol. 2021 Mar;238:103772. doi: 10.1016/j.jconhyd.2021.103772. Epub 2021 Jan 21.
The Horizontal Reactive Media Treatment Well (HRX Well®) is a technology capable of collecting and treating groundwater passively. To monitor the internal flow rate, ensuring it remains at an acceptable level and maintains the desired capture zone size in the aquifer, Point Velocity Probes (PVPs) were adapted for the task. The modified PVP was assessed for its performance in a mock-HRX Well setting, which consisted of a laboratory sand column, similar in diameter to the HRX Well cartridges that would house the PVP in the field, with flow directed along the longitudinal axis of the probe. Experiments were conducted to assess 1) the effects of friction between the fluid and the probe surface, which could bias a velocity measurement low, and 2) the effect of gas in the porous medium, potentially generated by some reactive media, on PVP signals and measurements of velocity. It was determined that PVP length exerted no discernable effect on the quality of the PVP performance. However, the effects of gas in the porous medium were varied. Compared to velocity estimates assuming a fully saturated porous medium, the bias to velocity measurements was negative if gas was limited to locations near a PVP's injection-detection array, such as might occur by inadvertent bubble injection during the tracer pulses. The bias was positive if the gas was generated uniformly throughout the porous medium, such as might occur in a reactive porous medium like granular iron, or one featuring vigorous biological activity. A field trial of the HRX Well was subsequently undertaken with internal PVPs. The PVPs identified a missing seal that was later retrofit, and documented flow in the HRX Well at velocities in the range of 1.3 to 4.0 m/d, which compared well with expectations based on a site model that predicted velocities of 1.3 to 2.3 m/d. The results of this study demonstrate that HRX Wells perform hydraulically as designed, and that PVPs are effective devices for tracking flow rates within them in near real-time.
水平反应性介质处理井（HRX 井®）是一种能够被动采集和处理地下水的技术。为了监测内部流速，确保其保持在可接受的水平，并维持含水层中所需的捕获区尺寸，采用点速度探头（PVP）来完成这项任务。为了在模拟 HRX 井环境中评估修改后的 PVP 的性能，制作了一个实验室砂柱，其直径与 HRX 井的过滤筒相似，在现场将 PVP 安装在过滤筒内，水流沿探头的纵轴方向流动。进行了实验以评估以下两个方面：1）流体与探头表面之间的摩擦力的影响，这可能会导致流速测量值偏低；2）多孔介质中气体的影响，这些气体可能是某些反应性介质产生的，会对 PVP 信号和流速测量产生影响。结果表明，PVP 的长度对 PVP 性能的质量没有明显影响。但是，多孔介质中气体的影响是不同的。与假设完全饱和的多孔介质的流速估算值相比，如果气体仅限于靠近 PVP 的注入-检测阵列的位置，例如在示踪脉冲期间意外注入气泡时可能发生的情况，则对流速测量的偏差为负值。如果气体在整个多孔介质中均匀生成，例如在颗粒状铁等反应性多孔介质中或具有剧烈生物活性的多孔介质中可能发生的情况，则偏差为正值。随后在 HRX 井中进行了现场试验，使用内部 PVP。PVP 识别出一个缺失的密封件，后来进行了修复，并记录了 HRX 井中的流速在 1.3 至 4.0 m/d 的范围内，这与基于预测流速为 1.3 至 2.3 m/d 的站点模型的预期值非常吻合。本研究的结果表明，HRX 井的水力性能符合设计要求，并且 PVP 是实时跟踪其中流速的有效设备。
