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  1. Sulphate Removal from Mining Effluents Current Developments in the Southern Hemisphere Raymond Philippe, Hatch Water, Chile Deon Nel, Hatch Water, South Africa Trevor…
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  • 1. Sulphate Removal from Mining Effluents Current Developments in the Southern Hemisphere Raymond Philippe, Hatch Water, Chile Deon Nel, Hatch Water, South Africa Trevor Clarke, Hatch Water, Australia
  • 2. Sulphate Removal from Mining Effluents Current Developments in the Southern Hemisphere <ul><li>Why Sulphate? </li></ul><ul><ul><li>Actually considered one of the most complicated contaminants in mining effluents </li></ul></ul><ul><ul><ul><li>Concentration/volume </li></ul></ul></ul><ul><ul><ul><li>“ Dynamic” Legislation </li></ul></ul></ul><ul><ul><ul><li>Technology Developments </li></ul></ul></ul><ul><ul><ul><li>Cost </li></ul></ul></ul><ul><li>Why Southern Hemisphere? </li></ul><ul><ul><li>Climate similarities </li></ul></ul><ul><ul><li>Strong Mining Countries </li></ul></ul><ul><ul><li>Regulation differences </li></ul></ul>
  • 3. International Sulphate Discharge Regulations <ul><li>Approaches </li></ul><ul><ul><li>Fixed discharge limits </li></ul></ul><ul><ul><ul><li>Directly as [SO 4 ] -2 </li></ul></ul></ul><ul><ul><ul><li>Indirectly as TDS (Total Dissolved Solids) </li></ul></ul></ul><ul><ul><ul><li>Indirectly as Electrical Conductivity </li></ul></ul></ul><ul><ul><li>Best Practices/Holistic approach </li></ul></ul><ul><ul><li>International Standards </li></ul></ul><ul><ul><li>Local Standards </li></ul></ul><ul><ul><li>Special Situations </li></ul></ul><ul><li>Most cases: Limits depend on final use of water </li></ul>
  • 4. Effluent Discharge Regulations 2400 - 500 (Class 1-3) - (Class 4) 3000 500 (Cat 4) TDS mg/l 250 (Class 1-3) - (Class 4) Resolution 357 Brazil 1000 NCADE Lib VI, 1 Ecuador 70 - 150 - Water Act 1998 South-Africa 1000 ANZECC 2000/General Water Use Stakeholders / Trigger Values Australia 300 (Cat 3) DS-002-2008-MINAM** Peru 1000-2000 250-500 250 DS90 DS46 NCh1333 Chile Conductivity mS/m [SO 4 ] -2 mg/l Legal Instrument Country
  • 5. [SO 4 ] – TDS – Conductivity <ul><li>EC (dS/m) x 670 = TDS (mg/L) > [SO 4 ] </li></ul><ul><li>Approx conversion formula (ANZECC 2000) </li></ul><ul><li>TDS = Σ [salt ions]: Examples Ca, Mg, Na, K, SO 4 , CO 3 , Cl </li></ul><ul><li>TDS and Conductivity are indirect Sulphate maximum concentration levels </li></ul><ul><li>Applied on South African and Peruvian Legislation: </li></ul><ul><ul><li>Peru: 500 mg/l TDS, if present as CaSO 4 </li></ul></ul><ul><ul><ul><li>max SO 4 discharge level = 353 mg/l </li></ul></ul></ul><ul><ul><li>South Africa: 70-150 mS/m, if present as CaSO 4 </li></ul></ul><ul><ul><ul><li>max SO 4 discharge level = 331 – 709 mg/l </li></ul></ul></ul>
  • 6. Typical mine effluent sulphate concentrations (mg/l) <ul><li>Tailings pond 2.500 </li></ul><ul><li>Acid Mine Drainage 0 – 10.000 </li></ul><ul><li>Copper Raffinate 10.000 – 20.000 </li></ul><ul><li>Smelter gas scrubber 50.000 – 200.000 </li></ul><ul><li>Seawater 5.000 </li></ul><ul><li>Desalinated Seawater (1 pass) < 5 </li></ul>
  • 7. Mining effluent types <ul><li>1. Contaminant driven </li></ul><ul><li>Contaminant bleed/Complicated Chemistry </li></ul><ul><ul><li>Saturated </li></ul></ul><ul><ul><li>Scaling </li></ul></ul><ul><ul><li>Corrosion </li></ul></ul><ul><ul><li>Production efficiency </li></ul></ul><ul><li>2. Hydraulics driven </li></ul><ul><li>(Temporary) high flowrate </li></ul><ul><li>Generally chemically not-saturated </li></ul>
  • 8. Definition of sulphate treatment from effluents <ul><li>Removal of sulphate ions from the aqueous phase, to a concentration level of sulphate compliant with discharge regulations </li></ul><ul><li>How: </li></ul><ul><li>Reduction of SO 4 to S°  </li></ul><ul><li>Precipitation of SO 4 with reagent </li></ul><ul><li>Precipitation of SO 4 as product of evaporation </li></ul><ul><li>Retention of a concentrated effluent within process inventory (to avoid effluent generation) </li></ul>
  • 9. Sulphate Treatment Technologies <ul><li>Traditional/Conventional </li></ul><ul><ul><li>Lime/limestone </li></ul></ul><ul><ul><ul><li>Industrially proven </li></ul></ul></ul><ul><ul><ul><li>Discharge compliance issues </li></ul></ul></ul><ul><li>Advanced Treatment Technologies </li></ul><ul><ul><li>Great variety of Processes </li></ul></ul><ul><ul><li>Difficult to evaluate </li></ul></ul><ul><ul><ul><li>Country/Jurisdiction dependent </li></ul></ul></ul><ul><ul><ul><li>Commercial processes </li></ul></ul></ul><ul><ul><ul><li>Various processes still under development </li></ul></ul></ul><ul><ul><li>Very little comparison studies </li></ul></ul><ul><ul><ul><li>Available public domain studies are often outdated/ not complete/applicable for specific site conditions </li></ul></ul></ul>
  • 10. Key Factors Advanced Sulphate Treatment Systems <ul><li>Effective, proven high-volume sulphate treatment systems consist of three specific unit operations: </li></ul><ul><li>Sulphate concentration step </li></ul><ul><li>Sulphate “solidification” </li></ul><ul><li>Solid/Liquid phase separation </li></ul>
  • 11. Advanced Sulphate Treatment Concept Separation Step Solidification Step Concentration Step Effluent Solids Treated effluent 2500 mg/l SO 4 <200 mg/l SO 4 5000 mg/l SO 4 2500 mg/l SO 4 CaO CaSO 4 .2H 2 O Advanced Treatment Technologies Black Box
  • 12. Concentration Technologies <ul><li>Evaporation (Solar, Mechanical) </li></ul><ul><ul><li>Location (climate/environment) </li></ul></ul><ul><li>Ion Exchange (Sulf-IX) </li></ul><ul><ul><li>In general, minimum pretreatment required </li></ul></ul><ul><ul><li>Process in combination with lime precipitation </li></ul></ul><ul><li>Membranes (Reverse Osmosis, nanofiltration) </li></ul><ul><ul><li>Proven: Industrial experience </li></ul></ul><ul><ul><li>Pretreatment (scaling, solids) </li></ul></ul>
  • 13. Solidification Technologies <ul><li>Lime precipitation </li></ul><ul><ul><li>Well known process (LDS, HDS) </li></ul></ul><ul><ul><li>Scaling issues </li></ul></ul><ul><ul><li>Alternatives with tailings/limestone (NCD) </li></ul></ul><ul><ul><li>Sludge </li></ul></ul><ul><ul><li>Effluent discharge compliance </li></ul></ul><ul><li>Barium precipitation (ABC, BaS) </li></ul><ul><ul><li>Costs/ reagent availability </li></ul></ul><ul><ul><li>Sludge </li></ul></ul><ul><ul><li>Recovery of BaS by thermal conversion treatment </li></ul></ul><ul><ul><li>Pilot test stage </li></ul></ul>
  • 14. Solidification Technologies <ul><li>Ettringite (SAVMIN, CSER) </li></ul><ul><ul><li>Precipitation of sulphate as CaO.3CaSO 4 .Al 2 O 3 .31H 2 O </li></ul></ul><ul><ul><li>Sludge handling </li></ul></ul><ul><ul><li>Al 2 O 3 availability </li></ul></ul><ul><ul><li>In piloting stage </li></ul></ul><ul><li>Biological processes (Biosure, Sulfateq) </li></ul><ul><ul><li>(Bio) Conversion of SO 4 to S° (or S-2) </li></ul></ul><ul><ul><li>Industrial scale proven </li></ul></ul><ul><ul><li>Electron/carbon source availability </li></ul></ul><ul><li>Crystallization Technologies </li></ul>
  • 15. Phase Separation Technologies <ul><li>Typical proven technologies </li></ul><ul><ul><li>Clarification/Settling </li></ul></ul><ul><ul><li>Filtering </li></ul></ul><ul><ul><li>Centrifuges </li></ul></ul><ul><ul><li>Flotation </li></ul></ul>
  • 16. Examples:Industrial Advanced Sulphate Treatment Operations Conventional (lime) treatment: 1600-2000 mg/l SO 4 <500 2008 235 NF/RO&evotransp Chile Collahuasi (Anglo/Xstrata) 2009 2005 1994 2006 2007 Year SO 4 discharge mg/l Q (m3/h) Technology Country Operation < 95 (200 μ S/cm) 290 Lime & NF & RO Aus ERA Ranger 1360 120 416 830 <30 NF/RO US Mosaic, Florida < 10 NF&RO&evap Aus Kwinana Nickel (BHP) <200 Biosure SA Ancor Works <200 RO & Lime SA eMalahleni (BHP/Anglo)
  • 17. How to select best combination of Sulphate Treatment Technologies <ul><li>Basic Design Criteria </li></ul><ul><li>Effluent characterization </li></ul><ul><li>1. Concentration Technology </li></ul><ul><li>Water discharge/reutilization criteria </li></ul><ul><li>2. Sulphate Removal Technology </li></ul><ul><li>Sludge Discharge/reutilization criteria </li></ul><ul><li>Location/Logistics/Reagents criteria </li></ul><ul><li>3. Phase Separation Technology </li></ul><ul><li>Depends on selected Sulphate Removal Technology </li></ul>
  • 18. Preselection of Concentration Technologies <ul><li>Parameters </li></ul><ul><li>Required Pretreatment </li></ul><ul><li>Possible scaling issues </li></ul><ul><li>Energy requirements </li></ul><ul><li>Space availability </li></ul><ul><li>Waste/By product handling </li></ul><ul><li>Objective: </li></ul><ul><li>Production of effluent that meets environmental discharge criteria </li></ul><ul><li>(evt. Reutilization as process water) </li></ul>
  • 19. Preselection of Sulphate Removal Technologies <ul><li>Solidification and Separation Technology are defined in conjunction: </li></ul><ul><ul><li>Sludge/Solids handling and disposal (legislation) </li></ul></ul><ul><ul><li>Logistics (reagents supply, energy) </li></ul></ul><ul><ul><li>Space availability </li></ul></ul><ul><li>Objective: </li></ul><ul><li>Removal of Sulphate from water inventory, technically feasible (waste) product management </li></ul>
  • 20. Definition of Integrated Treatment Process <ul><li>Establish integrated flow sheets/mass balances </li></ul><ul><li>Integration with existing operations </li></ul><ul><li>Closed circuit design </li></ul><ul><li>Technical - Economical comparison starting point </li></ul><ul><ul><li>Integrated Cost estimate (Investment / Operations) </li></ul></ul>Concentration Step Sulphate Removal Step Effluent Environmental discharge Solids ?? Recycle
  • 21. Conclusions <ul><li>Advanced Sulphate Treatment Technologies have been proven on industrial scale, making it possible to treat effluents to well below gypsum saturation levels, complying with strict legislation </li></ul><ul><li>Conceptual Definition: Concentration technologies (such as membranes and IX) do not remove SO 4 from the water inventory, they have to be combined with other technologies to remove sulphate </li></ul>
  • 22. Conclusions <ul><li>Optimized Advanced Sulphate Treatment of high volume effluents is a 3 - step process: </li></ul><ul><ul><li>Concentration </li></ul></ul><ul><ul><li>Sulphate solidification </li></ul></ul><ul><ul><li>Solids removal </li></ul></ul><ul><li>Every operation is unique: Selection of Optimum Treatment Combination is a multidisciplinary process that should be performed on a case-to-case basis </li></ul><ul><li>Technical-Economical Technology comparison: </li></ul><ul><li>Treatment Investment & Operation Cost can only be determined once an integral process design is established </li></ul>
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