Abstract Artificial groundwater recharge of aquifers by percolating water through the unsaturated zone (UZ) is a technique to enhance the water quality for drinking, irrigation, and industrial water supplies. The performance of the UZ to purify the infiltrated water is based on both the chemical and hydrodynamic properties of the porous medium. The chemical and microbially-mediated redox-reactions involving the degradation of organic substances are the key phenomena controlling the efficiency of such a process, and allow developing filtrating and reactive zones beneath an artificial recharge system. For several decades, the BRGM has been developing research and industrial projects to support the development of this technology and its implementation in various climates, soils, industrial contexts, and specific water uses. A part of the obtained results highlighting several physicochemical phenomena potentially favorable for the creation of pollutant-filtrating reactive redox zones will be presented. This study confirms the interest of the unsaturated zone for water purification processes.