Ion Exchange Treatment for Metals and Nitrate in Mine Water

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Ursula Summers
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1 Ion Exchange Treatment for Metals and Nitrate in Mine Water MSAWWA/MWEA Conference May 2006 Logan McInnis, P.E. Mark Reinsel, P.E., PhD Apex Engineering, PLLC

2 Presentation Outline 1. Background 2. Design Flows and Water Quality 3. Overview of Treatment Systems 4. Bench Testing Results 5. Design Considerations

Background Proposed underground gold mine in northeastern Washington Ore from proposed mine will be hauled 50 miles to an existing milling facility Mine life anticipated to be 8

3 Background Proposed underground gold mine in northeastern Washington Ore from proposed mine will be hauled 50 miles to an existing milling facility Mine life anticipated to be 8 years, with potential to extend mine life Treatment system expected to operate 3 years post-closure Since mine doesn t exist currently, all flows and water quality data based on modeling

4 Background Project Components 9 Buildings Potable Water & Onsite Wastewater Process Water System Major Site Grading and Roads Stormwater Collection and Treatment Electrical, Propane and Compressed Air Distribution SCADA System Mine Water Collection, Treatment and Disposal

5 Background Upper Portal Lower Portal Gold Bowl Portal Ore/Waste Stockpiles Desilt Basin Well Well Surge Pond Surge Pond Pump Station Mine Water Treatment Bldg Infiltration Gallery

6 Design Flows Design Flows Groundwater modeling developed monthly water balance throughout mine life Peak monthly flows: Years 0-4: 40 gpm (Southwest Zone) Years 5-8: 100 gpm (Gold Bowl Zone) Annual average flows Years 0-4: 3.7 gpm (Southwest Zone) Years 5-8: 30 gpm (Gold Bowl Zone)

7 Water Quality Constituent Influent (SW Zone) Influent (GB Zone) Discharge Limit Type of Limit Aluminum (Al) GW Antimony (Sb) MCL Arsenic (As) ½ MCL Copper (Cu) SW Iron (Fe) 20,000 76, SMCL Lead (Pb) SW Manganese (Mn) GW Mercury (Hg) SW Nickel (Ni) GW Selenium (Se) SW Thallium (Tl) MCL Zinc (Zn) SW Nitrate (NO3) (mg/l) GW

Treatment Systems Overview Alternatives Analysis Conducted for an AKART Analysis (All known, available and reasonable methods of prevention, control and treatment)

8 Treatment Systems Overview Alternatives Analysis Conducted for an AKART Analysis (All known, available and reasonable methods of prevention, control and treatment) Four basic alternatives were considered: Lime Precipitation Biological Treatment Ion Exchange Reverse Osmosis Ion exchange was selected for both metals and nitrate

9 What is Ion Exchange? Exchanges one ion (H+ for cationic metals resin) for an ion in dilute solution that is more readily bound Process often used in residential water softeners Typical operating cycle: 1. Service cycle 2. Backwash (water only) 3. Regeneration (salt, acid, etc.) 4. Rinsing a. Slow Rinse b. Fast Rinse

10 What is Ion Exchange? Source: Washington Dept. of Ecology

11 Bench Testing Ion Exchange Media Investigated 1. Cationic Metals IX (SIR-300) Weak acid chelating cationic resin 2. Nitrate IX (SIR-100) Strong base anionic resin 3. Arsenic-Specific IX (ASM-10-HP) Strong base anionic resin 4. Manganese greensand 5. Natural zeolites 6. Activated alumina

12 Bench Testing

13 Bench Testing

Bench Testing Summary First Round Run 2 water sources through SIR-300, ASM-10-HP and greensand to 100 BV Goal: Select 2 best media and run longerseries tests Second

14 Bench Testing Summary First Round Run 2 water sources through SIR-300, ASM-10-HP and greensand to 100 BV Goal: Select 2 best media and run longerseries tests Second Round Run 2 water sources though SIR-300 and ASM-10-HP in series to 1000 BV Set initial ph at 5 Third Round IX Similar to test but set ph at 7 Add 3 rd column for SIR-100

Bench Testing Results Ion Exchange Tests Poor results at ph 5, better results at ph 7 At ph 7, all metals removed to 1000 BV except Thallium 4th round of testing just completed using 2 natural

15 Bench Testing Results Ion Exchange Tests Poor results at ph 5, better results at ph 7 At ph 7, all metals removed to 1000 BV except Thallium 4th round of testing just completed using 2 natural zeolites for thallium removal Depending on zeolite tests, may need to run test with activated alumina Ultrafiltration Conducted by vendor with a mixture of 3 coagulants Little removal of Al, Sb, Mn, Se and Tl Won t investigate further

16 Results of 3 rd Round Test at 1200 BV Constituent Influent (ppb) Effluent (ppb) Discharge Limit (ppb) Aluminum (Al) Antimony (Sb) Arsenic (As) 9 <1 5 Copper (Cu) 22 <1 16 Iron (Fe) Lead (Pb) 6 <1 4 Manganese (Mn) 409 <2 50 Mercury (Hg) 0.8 < Nickel (Ni) 84 <5 100 Selenium (Se) Thallium (Tl) Zinc (Zn) Nitrate (NO3) (mg/l) (600 BV) 26 <

17 Treatment Scheme Oil/Grease Filter Multimedia Filter Lime Feed (ph 7) Multimedia Filter Zeolite Arsenic IX Nitrate IX Cationic Metals IX Lime/H 2 SO4 (ph 7) Discharge to Infiltration Gallery

18 Design & Operating Criteria

19 Design Considerations Multimedia Filter 2 parallel pressure filters 34 inch media depth 5 gpm/ft 2 loading rate 12 gpm/ft 2 backwash rate 3 scfm/ft 2 air scour Oil & Grease Filter Single pressure filter Organoclay media 4 gpm/ft 2 loading rate 10 gpm/ft 2 backwash rate

Design Considerations Cationic Metals Ion Exchange Vessel Single pressure vessel with SIR-300 36 inch media depth 1-2 gpm/ft 3 loading rate (EBCT = 4-7 min) 5

20 Design Considerations Cationic Metals Ion Exchange Vessel Single pressure vessel with SIR inch media depth 1-2 gpm/ft 3 loading rate (EBCT = 4-7 min) 5 gpm/ft 2 backwash rate Regenerant: Sulfuric acid followed by caustic soda Expect to regenerate every 5K-10K BV At 1000 BV, waste stream is 2% of treated volume

Design Considerations Nitrate Ion Exchange Vessel Single pressure vessel with SIR-100 36 inch media depth 1.

21 Design Considerations Nitrate Ion Exchange Vessel Single pressure vessel with SIR inch media depth 1.4 gpm/ft 3 loading rate (EBCT = 5 min) 10 gpm/ft 2 backwash rate Regenerant: Sodium chloride Initially will consume 5,000 lb/yr of salt Bench testing indicates regeneration required every 300 bed volumes at peak concentration (50 mg/l as N) Brine stream is 3% of treated volume

22 Design Considerations Arsenic Ion Exchange Vessel Single pressure vessel with ASM-10-HP 36 inch media depth 2.5 gpm/ft 3 loading rate (EBCT = 3 min) 5 gpm/ft 2 backwash rate Regenerant: Caustic soda if necessary Zeolite Vessel Single pressure vessel with natural zeolites 36 inch media depth 2.5 gpm/ft3 loading rate (EBCT = 3 min) No backwash or regenerant required

Future Work Complete bench testing with zeolites and possibly activated alumina Run Gold Bowl water and post-closure water through selected treatment

23 Future Work Complete bench testing with zeolites and possibly activated alumina Run Gold Bowl water and post-closure water through selected treatment process Optimize operating conditions to achieve discharge limits/minimize waste volume Consider biological treatment for nitrate to reduce waste volume

Removing Thallium from Industrial FGD Scrubber Water with Sorbster Adsorbent Media

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