This research carried out a comparative study of the impact of acid mine drainage from the abandoned Enugu coal mines, southeastern Nigeria. Surface water samples were collected from Onyeama, Ribadu, Okpara coal mines and Ekulu River draining the Onyeama coal mine. A total of twelve water samples were collected across the Enugu coal mines: four surface water samples from Onyeama coal mine, three samples from Ribadu coal mine, Ekulu River at confluence of Onyeama and Ribadu coal mines and three water samples from Okpara coal mine. The source of sample collection was: springs, mine ponds, streams and river. Physicochemical parameters such as temperature, pH, turbidity, total dissolved solids (TDS), electrical conductivity (EC), total hardness, Biological oxygen demand (BOD), and dissolved oxygen (DO) were measured from the water samples. Anions such as SO₄²⁺, K⁺, NO₃^-, Cl^- and F^- including major cations such as Ca²⁺, Na⁺, K⁺ and Mg²⁺ were also analysed using standard laboratory procedures such as titration and chromatography. Heavy metals (Fe, Mn and Al) were analysed using atomic absorption spectrometer (AAS). Comparison of the results with World Standards such as WHO, USEPA and SON for potable water shows that levels of pH, turbidity, F^-, Mg²⁺, and K⁺ exceeded these standards in some locations. The heavy metals concentrations were above the limits for potable water in all the mines. The average abundance of major anions was in this order: SO₄²⁺>Cl^->NO₃^->F^-. The major cationic average abundance was in the order: Mg²⁺>K⁺>Na⁺>Ca²⁺. Classification of water samples based on total hardness shows that the water ranged from soft to moderately soft. Based on BOD values, some of the water samples contain high amounts of organic wastes. There was low dissolution of oxygen in the water samples leading to moderately acidic waters. Levels of Fe, Al and Mn were above permissible limits for potable water and show a trend of Fe>Al>Mn. Results also showed that Onyeama and Okpara coal mines have more acid mine drainage conditions than other mine locations. Acid mine drainage causes high acidity, which corrodes metals in borehole installation, devegetation, and decrease in biodiversity among aquatic biota. Bioreactors can be used in remedying acid mine drainage sites.

Keywords: Acid Mine Drainage; Average Abundance; Biodiversity; Bioreactors; Haemoglobin; Potentially Harmful;