Objective The Datong mining area in Shanxi Province of China faces serious threats from goaf water hazards, while the goaf water drainage is constrained by environmental protection policies. Therefore, the reutilization of goaf water serves as an effective approach to eliminating mine water hazards, protecting water environments, and mitigating water scarcity in the mining area.

Methods This study investigated goaf water from shallow coal seams in the Datong mining area. Based on water quality assessment theories and a range of hydrogeochemical indices, including saturation index (SI), chloro-alkaline index (CAI), and sodium adsorption ratio (SAR), this study conducted a joint determination of the conventional physicochemical characteristics, hydrochemical components, and water pollution indicators of the goaf water. Accordingly, the water quality characteristics and their genetic mechanisms were analyzed, and the characteristic pollutant types under different water standards were determined. By combining practical application cases, this study proposed a technical pathway for the reutilization of goaf water in the Datong mining area.

Results and Conclusions The goaf water in the Datong mining area exhibits hydrochemical types dominated by Na-SO₄ and Ca-SO₄, consistent with those of typical mine water in the coal base of northwestern China. The goaf water shows average total dissolved solids (TDS) of 2 190 mg/L and electrical conductivity (EC) of 2 716 μS/cm, indicating high salinity and ion concentrations. The SIs, ion concentration proportions, CAI, and Gibbs diagrams reveal that the hydrochemical components of the goaf water are jointly controlled by rock weathering, as well as evaporation and concentration, with major chemical components formed primarily by the alternating cation adsorption and the dissolution and leaching effects. Based on the fundamental principle of source protection, classified treatment, and comprehensive utilization, the goaf water in the Datong mining area was classified as high-salinity, high-suspended-solid, and high-sulfate water when designated for landscape/recreational use, industrial applications, and agricultural irrigation, with exceedance indicators including TDS, \mathrmSO_4^2- , total hardness (TH), suspended solids, chemical oxygen demand (COD), and total/fecal coliform bacteria. A comprehensive technical pathway for the comprehensive reutilization of goaf water was established based on the scientific positioning of goaf water sources, water storage grading, the control and treatment of characteristic (residual) pollutants, and the assessment of the comprehensive reutilization potential. Engineering case analysis demonstrates the adaptability of mobile water treatment stations to the complex gully landform of the study area, effectively verifying the prospects for their widespread applications. The results of this study hold great strategic significance for promoting the water-saving, green development of similar water-scarce coal mines.