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GEOCHEMICAL MODULE FOR “AMDTreat”

GEOCHEMICAL MODULE FOR “AMDTreat”. Charles A. Cravotta III and David L. Parkhurst, U.S. Geological Survey Brent P. Means, Robert M. McKenzie, and Bill Arthur, U.S. Office of Surface Mining Reclamation and Enforcement. 2011 West Virginia Mine Drainage Task Force Symposium, Morgantown, WV.

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GEOCHEMICAL MODULE FOR “AMDTreat”

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  1. GEOCHEMICAL MODULE FOR “AMDTreat” Charles A. Cravotta III and David L. Parkhurst, U.S. Geological SurveyBrent P. Means, Robert M. McKenzie, and Bill Arthur, U.S. Office of Surface Mining Reclamation and Enforcement 2011 West Virginia Mine Drainage Task Force Symposium, Morgantown, WV

  2. Version 5.0 is coming soon!

  3. CONCLUSIONS • Empirical and simulated titrations indicate that: • Al and FeIII may be effectively removed at pH <6-8 by precipitation of hydroxide minerals; • FeII may be removed at pH > 8.5 as Fe(OH)2 and Mn may be removed at pH > 9.5 as Mn(OH)2; • At high pH needed to precipitate Mn(OH)2, other constituents such as Mg and Ca can precipitate, consuming caustic reagents and adding to sludge.

  4. CONCLUSIONS • If oxidized before addition of caustic chemicals: • MnO2, Fe(OH)3, and other oxidized compounds may precipitate at low pH (~6); • Chemical consumption can be decreased by avoiding precipitation of Mg and Ca compounds. • With titration simulation “add-in” to AMDTreat, costs for treatment with various chemicals and corresponding effluent quality can be estimated.

  5. Passive/Active Treatment Al3+ Fe2+ / Fe3+ Mn2+ Passive Active Alter chemistry with natural substrates & microbial activity Reactions slow Large area footprint Low maintenance Alter chemistry with aeration & reagents Reactions fast, efficient Moderate area footprint High maintenance

  6. Caustic Chemicals Common nameChemicalFormula caustic soda sodium hydroxide NaOH quick lime calcium oxide CaO hydrated lime calcium hydroxide Ca(OH)2 soda ash sodium carbonate Na2CO3 ammonia anhydrous ammonia NH3

  7. AMDTreat input screen-- Flow, net acidity, iron, aluminum, manganese, and sulfate are used for size and cost calculations.

  8. AMDTreat Chemical Cost Screen: Net Acidity or Titration to Estimate Caustic $618,917/yr

  9. AMDTreat Chemical Cost Screen: Net Acidity or Titration to Estimate Caustic $736,944/yr

  10. Metal Hydroxide Solubility vs. pH Ca MnII FeII Al Mg FeIII MnIII MnIV

  11. Neutralization of Acidity NaOH + H+ H2O + Na+ NaOH + CO2 (aq) = HCO3- + Na+ 3 NaOH + Al3+ Al(OH)3 + 3 Na+3 NaOH + Fe3+ Fe(OH)3 + 3 Na+ 2 NaOH + Fe2+ Fe(OH)2 + 2 Na+ 2 NaOH + Mn2+ Mn(OH)2 + 2 Na+ 2 NaOH + Mg2+ Mg(OH)2 + 2 Na +

  12. Acidity = Base Consumption Precipitation of Solid Hydroxide Compounds:Al3+ + 3 OH- Al(OH)3{pH >5.0} Fe3+ + 3 OH- FeIII(OH)3{pH >4.0}Fe2+ + 2 OH- FeII(OH)2{pH >8.5} Fe2+ + 2 OH- + 0.25 O2 + 0.5 H2O  FeIII(OH)3 Mn2+ + 2 OH- MnII(OH)2{pH >9.5} Mn2+ + 2 OH- + 0.5 O2 MnIVO2 + H2O

  13. Titration of “Cal Pike” 20% Caustic Soda

  14. Titration of “Cal Pike” 20% Caustic Soda SO4 Mg Ca Mn Fe Al Alk

  15. Simulated Titration of “Cal Pike”

  16. Simulated Titration of “Cal Pike” – noeq (AlOOH) (Al4(OH)10SO4) (MnO2) (MnCO3) (Mn(OH)2) (Mg(OH)2) (Ca6Al2(SO4)3(OH)12.26H2O)

  17. Simulated Titration of “Cal Pike” – noeq

  18. Simulated Titration of “Cal Pike” – pre-ox (AlOOH) (Al4(OH)10SO4) (MnO2) (MnCO3) (Mn(OH)2) (Mg(OH)2) (Ca6Al2(SO4)3(OH)12.26H2O)

  19. Simulated Titration of “Cal Pike” – pre-ox

  20. “New” AMDTreat input screen--T0: Net acidity used to compute chemical cost.For PHREEQ titration, need data forCa, Mg, Na, Cl, & TIC or alkalinity. $0.400 / 1000 gal

  21. AMDTreat Chemical Cost Screen: PHREEQ “titration amount” & effluent quality $363,387/yr

  22. “New” AMDTreat input screen--T1: PHREEQ titration w/o aeration used to compute hydrated lime cost. $0.690 / 1000 gal

  23. AMDTreat Chemical Cost Screen: PHREEQ “titration amount” & effluent quality $127,721/yr

  24. “New” AMDTreat input screen--T2: PHREEQ titration w/ aeration used to compute hydrated lime cost. $0.242 / 1000 gal

  25. MARCH 2011 STATUS OF PHREEQ-N-AMDTreat • PHREEQ titration models standardized to simulate results of empirical titrations on six AMD sources; • Recoding and coupling of PHREEQ and AMDTreat using FoxPro language completed; • Modifications of AMDTreat water-quality, chemical cost, and sludge screens using PHREEQ output and Alpha testing in progress; • Beta testing planned for spring-summer 2011.

  26. AMD Treatment Cost Estimate http://amd.osmre.gov/downloads.htm

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