Non-invasive survey technology for estimating the distribution of oxidant solution: A pilot injection study

Abstract

In-situ chemical oxidation (ISCO) can remove pollutants efficiently. However, the most important key to successfully conducting ISCO on site is to place the oxidant in close contact with the contaminant. Therefore, monitoring tools that provide for enhanced tracking of the injectate offer considerable benefit to guide subsequent ISCO injections. In this study, we applied the MagnetoMetric Resistivity (MMR) method to survey the distribution of an injected oxidant. A pilot test was conducted on a 10 m × 10 m site, and the sodium persulfate injection involved four pulse injections from one injection well. A magnetic field survey coupled with conventional monitoring was performed before the initial injection and after each pulse injection. The results of this study showed that groundwater samples from six observation wells and seven direct-push EC loggings did not provide sufficient data to quantify the distribution and flow behavior of the injected oxidant. However, the magnetic field survey visually showed the dynamic distribution of the injected oxidant, and the flow pathways and flow behavior were assessed accordingly. Although the flow behavior of injected solution was changeable in the aquifer, but the magnetic field survey combined with the monitoring of the well samples helped to explain the abnormal changes in the electrical conductivity of the observation wells and supports the use of the magnetic field survey technology as a method of monitoring ISCO injections.

Keywords: Current density; Electrical conductivity; ISCO; MMR; Magnetic survey; Pilot test.