From water storage space to an in situ treatment system: Natural and enhanced purification of mine water in coal mine underground reservoirs

Coal mine underground water reservoir (CMUWR) is not only important engineering components for the large-scale, low-cost storage and regulation of mine water, but also underground reaction systems with the potential for in-situ purification. This paper mainly discusses the natural and enhanced purification of mine water in these reservoirs, focusing on the removal of suspended solids and the transformation of dissolved ions. The purification process is jointly controlled by lithology and mineral composition, hydrodynamic conditions, and the geochemical environment. However, long-term operation may cause pore blockage, reaction-site saturation, and unstable purification performance. To address these limitations, this paper evaluates the potential of artificial enhancement technologies for improving purification stability and highlights the need to develop underground-applicable technologies that promote CMUWR as integrated systems for water storage, purification, and reuse.