ELECTROCOAGULATION TREATMENT OF HEAVY METALS FROM MINE IMPACTED WATER Denney Eames, P.E. & Jacob Aylesworth, EIT IWC 16-45 I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Executive Summary • Electrocoagulation (EC) introduction • History of the technology • Overview of the science of electrochemistry • Review three mine water treatment case studies for EC treated water • Underground mine dewatering • Tailings stormwater runoff • Smelter environmental cleanup water • Review the capital and operational costs associated with these treatment process I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Introduction to Electrocoagulation • First patented in 1906 by A. E. Dietrich • Original patent was used to treat bilge water from ships • Multiple attempts have been made to commercialize the technology with varying degrees of success I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Electrocoagulation Today • Electrocoagulation is used in many industries today • Stormwater treatment • Environmental remediation • Marine Pollution prevention • Automotive cleaning • Food and beverage • Mining • Oil & gas I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Electrocoagulation Process • The electrical current releases positively charged metal ions that attract a disproportionate quantity of negatively charged contaminants • Small particles agglomerate into larger particles through precipitation and absorption • Gas generated at the cathode assists in separating the lighter coagulated particles and forming a stable floc I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
OH CL - HM CL Fe 3 + - - OH - OH OH CL - - CL - - CL - HM Fe 3 OH + - Fe 3 OH - + CL HM CL - - CL CL - - OH - OH - I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Cathode H OH Anode + 2 - Fe 3 + HM OH - OH H - Fe 3 2 HM + OH - OH - H Fe 3 HM 2 + OH - Less Competition, Higher Potential Energy I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Electrocoagulation Effects Electrocoagulation I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Electrocoagulation Effects Electrocoagulation Makes Particles Larger Gravity/Floatation Separation Electrocoagulation I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Electrocoagulation Targets 1. 2. 3. Coagulation of De-emulsification Precipitation and suspended of oil and grease agglomeration of solids dissolved metals from water I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Literature Chemical Treatment “Alum, lime and/or polymers…tend to generate large volumes of sludge with high bound water content that can be slow to filter and difficult to dewater. These treatment processes also tend to increase the total dissolved solids (TDS) content of the effluent, making it unacceptable for reuse within industrial applications.”* Electrocoagulation “The characteristics of the electrocoagulated floc differ dramatically from those generated by chemical coagulation. An electrocoagulated floc tends to contain less bound water, is more shear resistant and is more readily filterable”** *Benefield, Larry D.; Judkins, Joseph F.; Weand, Barron L. (1982). Process Chemistry for Water and Wastewater Treatment. Englewood Cliffs, NJ: Prentice-Hall. P. 212. **Woytowich, David L.; Dalrymple, C.W.; Britton, M.G. (Spring 1993). “Electrocoagulation (CURE) Treatment of Ship Bilge Water for the US Coast Guard in Alaska”. Marine Technology Society Journal (Columbia, MD: Marine Technology Society, Inc.) 27(1):92 . I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Project Process Flow I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Mine Water Underground Mine Dewatering • Treated at mine surface • 30 days @ 250 gpm • Elevated cadmium, copper, arsenic, lead I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Data: Underground Mine Dewatering Standard Average Max/Min Deviation Analytical ug/L ug/L ug/L Parameter INF EFF % Reduced INF EFF INF EFF Cd 2.1 0.54 74.5% 0.54 0.44 3.7/1.4 1.7/0.14 Cu 22 1.7 92.6% 3.5 1.3 32/16 6.3/0.10 Pb 105 1.4 98.6% 15 1.1 141/60 5.4/0.55 Zn 531 70 86.9% 73 62 660/390 244/10 pH 8.1 8.1 0.0% 0.2 0.2 8.3/7.9 8.3/7.9 # of 27 27 Total Treated Volume: 2,628,600 gallons Samples I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Tailings Stormwater Runoff • Mine water storage pond • 25 days @ 250 gpm • Elevated cadmium, copper, arsenic, lead I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Data: Tailings Stormwater Runoff Standard Average Max/Min Deviation Analytical ug/L ug/L ug/L Parameter INF EFF % Reduced INF EFF INF EFF 0.44 0.20 55.5% 0.33 0.15 1.3/0.13 0.61/0.03 Cd 4.4 1.6 64.3% 1.6 0.29 9.3/2.8 2.1/1.1 Cu 27 0.48 98.2% 14 0.40 58/12 2.3/0.18 Pb 130 14 89.1% 32 6.9 242/104 37/5.6 Zn 8.0 8.0 0.0% 0.2 0.2 8.2/7.8 8.2/7.8 pH # of 23 23 Total Treated Volume: 1,930,200 gallons Samples I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Smelter Site Environmental Cleanup Water • Mine water storage pond • 12 days @ 100 gpm • Elevated cadmium, copper, arsenic, lead • pH treatment (raised to 8.6 after EC) I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Data: Smelter Environmental Cleanup Water Standard Average Max/Min Deviation Analytical ug/L ug/L ug/L Parameter INF EFF % Reduced INF EFF INF EFF Cd 2,654 12 99.5% 1,755 9.1 7,107/864 34/6 Cu 216 3.8 98.2% 211 1.0 772/34 6/3 147,959/ Pb 39,932 37 99.9% 40,594 27 105/6 3,341 22,981/ Zn 10,472 36 99.7% 5,465 17 58/15 2,212 pH 7.6 8.6 -13.1% 0.3 0.3 7.9/7.3 8.9/8.3 # of 10 10 Total Treated Volume: 375,900 gallons Samples I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Capital Costs 6,000 gpm: Water Treatment Plant Capital Cost Item Cost Engineering $425,000 Process Equipment $8,624,000 Facility, Infrastructure & Installation $2,493,000 Management, Supervision & Commissioning $357,000 Total $11,899,000 I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Operational Costs for a 6,000 gpm: EC Water Treatment Plant Operational Cost Item $/1000 gallon Annual Cost* Consumables $1.252 $3,255,200 (EC Cells, UF Membranes, Misc.) Power ($0.07/KWH) $0.272 $707,200 Operations Labor $0.162 $421,200 Total $1.686 $4,383,600 * Estimated annual cost based on treating 2.6 billion gallons per year I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Operational Costs for a 6,000 gpm: Chemical Water Treatment Plant* Operational Cost Item $/1000 gallon Annual Cost* Consumables $0.879 $2,285,400 (Chemicals, Filters, Misc.) Power ($0.07/kWh) $0.215 $559,000 Operations Labor $0.162 $421,200 Total $1.256 $3,265,600 Note: Capital cost range was estimated at $10,300,000 to $15,700,000 * Estimated annual cost based on treating 2.6 billion gallons per year I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
Conclusions • Capital cost for an EC and chemical plant were equivalent • EC advantages • Full compliance demonstrated in heavy metal reduction • Passed all aquatic toxicity testing • Reduced sludge/tailings production • EC disadvantage cell cost • 34% higher operational cost compared to chemical • The cost of the EC cell was the majority of the cost • Designing a less expensive EC cell is the key to lowering operational costs I N T E T E R N R N A T I T I O N A L W A T E R C O N F E R E N C E E 2 0 1 6 0 1 6
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