Effects of Sea Bed Slope on Initial Dilution of Submarine Mine Tailings Disposal


NEMLİOĞLU S.

2nd International Conference on Recycling and Reuse, İstanbul, Turkey, 4 - 06 June 2014, pp.245

  • Publication Type: Conference Paper / Full Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.245

Abstract

Metal mine tailings removal is a serious environmental problem. There are three main mine tailings removal methods: Surface disposal methods (mine waste dams, etc.), mine self disposal methods (landfill paste, etc.), and disposal into aquatic ambient (submarine tailings, river or lake disposals). When waste landfill area is limited in the mining site surroundings, and if environmental conditions are positive, using mine tailings submarine disposal into the deep sea ambient could be most appropriate method. Especially, highly steep coasts and deep sea anoxic zone availability are main reasons to apply submarine tailings disposal method for metallic mine slurry removal. After metallic minerals separation from raw material, mining wastes could be injected to deep sea receiving ambient thorough an open ended submarine outfall as an open ended pipeline with singular port. A submarine tailings disposal creates a negatively buoyant plume and a density current, because of higher density of the residual part of metallic waste mixture than sea water. On the contrary of other types of negatively buoyant plume or jet discharging marine outfalls, metal mine submarine tailings disposal (STD) was not requested any dilution. However, because of momentum of the dense waste jet, and turbulent diffusion (and additionally molecular diffusion), a low amount of dilution is possible. Owing to sea bottom slope, after a free movement of dense plume, it sinks to the sea bottom in an impingement point, then moves on the sloppy sea bed as a density current. Dilution is an undesirable condition, because of high toxicity of the slurry. In this study, a scaled laboratory model was used for simulation of a metallic mine submarine tailings discharge into the Black Sea anoxic zone. Rhodamine B and sodium chloride added water was represented to the original mining waste. Tracer added injection water was discharged thorough a circular port in to a receiving water body. The receiving water was tap water and it was homogeneous and stagnant. Discharge was performed with a natural slope according to the shoreline of North Eastern Black Sea coastline of Turkey and lesser slopes. During experiments series of photos were captured both form profile and plan view. These pictures were digitally processed and jet geometrical parameters were obtained. A series of time averaged water samples were taken and dilution of waste measured. This study shows that the discharged waste jet is never exceed upper level of discharging port with highly steep bottom conditions. Tailings plume was initially diluted but it couldn’t manage to reach boundary level of the Black Sea anoxic zone. Because of continuous slope of sea ambient, waste plume kept dilution process during its transport onto lower depths.