Acid mine drainage - effect on creeks or streams in a mining community in Ghana and treatment options

摘要

Heavy metals contamination and other physico-chemical changes in underground and surface water by acid mine drainage (AMD) were determined on the impact on creeks or streams. High levels of these metals have been reported in mining areas over the years; however, investigations indicates that less monitoring has been done on water discharged as effluent for effective maintenance mechanisms to be effected. Field and laboratory studies were carried out within the mining community on Latitude S 2° 35 W and Longitude N 5° 31W to investigate the levels of heavy metals (As, Fe, Cu, Zn, Mn and Cd) and physico-chemical changes (pH, temperature, E.C, D.O, alkalinity, S042−, free CN) in both underground and surface water for seven sampling sites. Results from atomic absorption spectrometry (AAS) determination indicated an average concentrations of iron (6.185 mg/l) and manganese (2.271 mg/l) in both surface and underground waters which are higher than threshold limits for mining effluent. The physico-chemical changes were determined using standard methods. Results also indicated higher levels of electric conductivity (1435.0µs/cm) and sulphate (344.0 mg/l). Differences in pH, temperature, E.C, alkalinity, S042-, Fe, Cu, Zn and Mn levels in the seven water samples were statistically significant (p ≤ 0.05). This may be attributed to the higher release of metals, relative to H+. Result also showed significant impact of AMD on water quality in the mining area. This effect could be attributed to the release of metals as a result of oxidation of metal-bearing sulphides in the mine dumps and pits at the selected sampling sites. The study showed that addition of lime as a treatment option has not been effective. Hence new conventional methods such as Aerobic wetland, Compost or Anaerobic Wetland, Open Limestone Channels, Diversion wells, Anoxic Limestone Drains (ALD) etc. should be considered in the treatment of acidic wate--r (AMD) in the mining area.