This type of wastewater is generated in those mines where underground mining is practiced. The source for mine water is essentially from seepage of excavated area of the mine. The mine water is collected in underground sumps with a nominal retention time. There is an opportunity for recycle of mine water in the areas of fire fighting and underground dust suppression within the mining operation.
The quantity of the mine water greatly depends on the level of ground water table and the ground conditions. The quality of the mine water varies widely from mine to mine depending upon the local conditions. The main pollutants of the mine water are dissolved minerals from the aquiferous rock strata. Typically, the suspended solids (SS) levels of this stream are extremely low (Wingrove, 1997). From the literature data (Rozkowski & Rozkowski, 1994; Singh, 1994; Sivakumar et al., 1994b) a typical range of characteristics for the mine water can be identified as follows:
•High total dissolved solids (500 - 2000 mg/L)
•High hardness (500 - 2000 mg/L as CaCO3)
•Low suspended solids (10 - 100 mg/L)
•Low BOD (< 5 mg/L)
•Low COD (10 - 100 mg/L)
•Near neutral pH (7-9.5)
•High conductivity (600 - 10,000 µs /cm)
•High apparent color (30 - 600 Units)
•Moderate concentrations of other minerals (Na, Mg, ca, CO3- , Cl- , SO42- and trace elements
such as, Al, Fe, etc..)
As seen above, the mine water contains considerable amount of dissolved minerals, which give high hardness to the water. In the case of acid mine drainage, the pH can be as low as 2 - 3. This low pH is mainly due to the oxidation of sulfides.