Enhancing degradation of emerging organic compounds in managed aquifer recharge systems by means of chaotic advection

Abstract

Water used in Managed Aquifer Recharge (MAR) systems can contain organic micropollutants, which can contaminate the aquifer. The degradation rates of many of these compounds can be enhanced by cometabolism linked to redox processes. Previous studies have shown that the addition of Dissolved Organic Carbon (DOC) into the recharge flow enhances micropollutant degradation rates by promoting redox reactions. With the aim of improving the reactivity of the system by enhancing mixing between the recharge solution and groundwater, an Engineered Injection and Extraction protocol has been proposed and numerically optimized to generate chaotic advection around the recharge area. As a second goal of the project, a laboratory experiment to test a reducedscale version of the system has been designed. The results show that the optimal stirring protocol depends on the hydraulics and chemistry of the aquifer and the MAR system. For the specific configuration of the laboratory experiment, several stirring protocols displayed close to optimal performance according to the optimization results. Four of them were tested in a conservative transport numerical model. For all of them, results show a dramatic increase in mixing. This suggests that this kind of EIE systems have a potential to enhance micropollutant degradation in MAR systems when combined with DOC addition to the recharge solution.