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Copper Mining Water Treatment"Copper mine impacted waters often have elevated concentrations of copper within the water. Usually, this copper content can be recovered and its sale can be financially beneficial to the overall cost of treating the impacted water to the necessary standards for re-use or discharge. "
Coal waste water treatment process

Copper Waste Water Treatment Processes

The impacted waters from both active and decommissioned copper mines vary greatly, depending on the age of the workings, the age of the associated soil heaps and many other factors, including the local geology and the technology that was originally used to recover the copper from the ore. Some of these waters can be strongly acidic and, in addition to their copper content, can contain high levels of dissolved sulphates and heavy metals.

Miwatek is able to design and construct copper mine water treatment plants that can recover high quality drinking or discharge water from all of these different impacted waters. These plants are able to accommodate both the quality and the quantity variations that typically occur over time and season by season.

A typical water treatment process for copper impacted water would include:
  1. Removal of suspended solids and any FOG from the copper-wastewater process feed-stream.
  2. Ultrafiltration (UF) of the product water followed by reverse osmosis (RO) treatment of the UF Permeate to concentrate the copper into the RO Concentrate (Brine). The RO Permeate, after a minor pH adjustment, is typically of discharge compliant quality.
  3. Following the RO stage, it is usually necessary to crystallize gypsum from the concentrate before it is routed to a copper recovery process.
  4. The selection of the copper recovery process is usually site specific: the ion extraction (IX) and solvent extraction (SX) methods are the most commonly used ways to recover copper from membrane brine. Where advantageous, the IX or SX strip-solutions can be sent to on-site, Miwatek-supplied, electrowin (EW) production of copper cathodes, or CuSO4 crystal production facilities. Any other valuable metals would also be removed at this stage, using a process that is appropriate for the specific metal.
  5. The copper depleted RO Brine is then pH adjusted using on-site generated sodium hydroxide and a mixed-metal hydroxides and carbonates sludge is recovered as a thickener underflow.
  6. The thickener overflow is CO2 treated to precipitate and thickener remove CaCO3.
  7. The de-calcified thickener overflow water is then UF-RO treated. The RO Permeate, after a modest pH adjustment can be added to the RO Permeate from the first-RO treatment and the total volume discharged as compliant water. Note that in this design the combined RO1 and RO2 Permeate volumes are typically equal in volume to the feed volume of water to the overall process; a Zero-Liquid-Discharge system has been described.
  8. The RO2 Brine will usually require a gypsum crystallization step prior to a lime treatment where additional gypsum is created and recovered. The solution part of the treated brine contains hydroxide ions (as caustic, NaOH) sufficient to effect the RO1 Brine pH adjustment (see item # 5).
    • Depending on the original strength of the impacted water, it is sometimes more cost-effective to route the copper-depleted RO brine directly to the caustic production stage and thereby avoid the second UF and RO stages.
Additional process steps would be added if and when they are needed. These could include:
  • Ion exchange modules to remove nitrates, etc.
  • Sludge de-watering as needed to suit the residue reuse or the local disposal arrangements.
  • Recovery of reusable salts from any excess brine.

The installed process would provide a cost-effective, practical and reliable solution and it would be designed to suit the analysis of the impacted water and the expected variability over time of both the analysis and the flow. The design would also take into account the whole life cycle cost, including the disposal options for the precipitation residues and for any brine that cannot be recycled within the process. The Miwatek process is modular, making feed water flow and quality changes easy to manage. In most cases the modules can be integrated with existing infrastructure.