System for Decontaminating Well Water for Drinking

1. : System for Decontaminating Well Water for Drinking Arsenic - Health and Remediation Applications, Session III Webinar April 15, 2013 TDA Research, Inc. Girish Srinivas, Ph.D., M.B.A. 303-940-2321 gsrinivas@tda.com Shawn Sapp, Ph.D. Steve Gebhard, Ph.D., P.E. Steve Dietz, Ph.D. Will Spalding Rachelle Cobb Drew Galloway

2. About TDA • Began operations in 1987 • Privately held – 8 employee partners • 88 employees • 28 Ph.D.'s in Chemistry and Engineering • $15 million in annual revenue • Facilities • Combined 50,000 ft2 in Wheat Ridge and Golden, CO • Synthetic Chemistry • Materials Processing & Testing • Process Development • Business Model • Identify opportunities with industry • Perform R&D, primarily under government contract • Secure intellectual property • Commercializes technology by licensing, joint ventures, internal business units Wheat Ridge Facility Golden Facility 2

3. Outline • Introduction/Background • Well Water Contamination & Drinking Water • Conventional Purification Technologies (IX, RO, sorbents/other) • Capacitive Deionization (CDI) • Flat CDI Cell Testing • TDA’s Activated Carbons • Electrochemical Testing & Optimization • Bench-Scale Prototypes, Testing, & Results • Spiral CDI Cell Testing • Early Results • Dual Cell Configuration • Pre-prototype Units • Commercialization and Partnerships • Competitive Advantages • Market Landscape & Strategic Partnerships

4. Executive Summary • TDA has developed a capacitive deionization (CDI) process based on • Proprietary carbon electrodes • Spiral wound capacitive deionization cells • Less expensive to manufacture • TDA has demonstrated • Arsenic removal to below drinking water standards • 83 ppb to < 5 ppb • Single pass flat cell • Currently refining the design and manufacturing method for spiral cells • Well water testing (spiked with arsenic) • Real arsenic contaminated waters • TDA partnering with ITN Energy Systems • Develop and market PV-CDI systems

5. Ground & Surface Water Contamination • Approximately 45 million people in the U.S. (~15% of the population) get their drinking water from wells, cisterns, or springs • These ground and surface waters can be contaminated by local geology or human activities • Priority inorganic contaminants include arsenic, lead, perchlorate, nitrate/nitrite, fluoride, etc. • Secondary concerns include softening hard water and desalination of briny water • Rural and remote population sites (especially foreign) • Some of the worst well-water quality • Conventional treatment may be • Unavailable • Cost-prohibitive • Impractical

6. Arsenic in Groundwater Worldwide • Arsenic is a common, widespread contaminant • Some areas have very high (in red) concentrations International Groundwater Resources Assessment Centre http://www.un-igrac.org/publications/148

7. Arsenic in Groundwater in the U.S. • Areas with especially high arsenic concentrations (50 g/L) are found in almost every state

8. Chemical Forms of Aqueous Arsenic • Many naturally occurring and anthropogenic sources of arsenic in the environment • Sulfur is present because Eh-pH diagram is for waters in contact with As rich gold ores used to make As2O3 • CDI removes all ionic species, which includes many arsenic species S. Wang, C.N. Mulligan, Occurrence of arsenic contamination in Canada: 3127 sources, behavior and distribution, Sci. Total Environ. 366 (2006) 701–721.

9. Conventional Arsenic Removal Technologies • Ion Exchange • Removes ions by replacing cations with H+ and anions with OH- (forming H2O) • Requires frequent resin bed replacement (expensive) or regeneration (time consuming) • Can increase sodium content (e.g. home water softeners where cations are replaced by Na+ and anions by Cl-) • Reverse Osmosis (RO) • Requires pumping the water to high pressures (the more TDS the higher the pressure) • Produces water at low flow rates (poor yields) • RO membrane modules are easily contaminated • Module replacement is expensive and time consuming • Sorbents/Other • Can be low cost (e.g. activated carbon) • Require disposal as hazardous waste or regenerated

10. Ion Exchange • Removes ions by replacing cations with H+ and anions with OH- (forming H2O) • Requires frequent resin bed replacement (expensive) or regeneration (time consuming) • Some anions (e.g. perchlorate) require specialized resins • Expensive http://www.tdsmeter.com/what-is?id=0015

11. Reverse Osmosis – TDS Reduction • Reverse Osmosis (RO) • Requires pumping the water to high pressures (the higher the pressure the greater the water recovery) • Requires high power even with relatively clean feeds • Produces water at low flow rates (at low feed pressure) • RO membrane modules are easily contaminated • Module replacement is expensive.

12. Sorbents Arsenic removal from water/wastewater using adsorbents—A critical review Dinesh Mohan and Charles U. Pittman Jr. Journal of Hazardous Materials 142 (2007) 1–53

13. Capacitive Deionization (CDI) • CDI for Decontaminating Drinking Water • Eliminates difficult to remove ions such as arsenic (III), perchlorate, nitrate, and other toxic inorganics • Removes both cations and anions • Removes charged particles • Units small and portable • Requires no consumables (resins, sorbents, etc.) • Can use any DC power source (batteries, solar panels, generators, etc.) • Low voltage 1.2 VDC (safe); current scales with total dissolved solids (TDS) • Low power at typically low TDS concentrations in drinking water • Can deliver potable water from many sources (wells, lakes, streams, etc.)

14. Capacitive Deionization – Ion Removal • CDI electrostatically removes dissolved cations and anions from contaminated water • TDA CDI unit • Stack (or spiral wound) high surface area carbon electrodes • Electrodes are porous and electrically conductive • Ions are removed when DC voltage is applied • V  1.2 volts to prevent electrolysis of water • Ions adsorb and are held in the electric double layers on the electrodes Deionization Cycle • Cations migrate to negative electrode • Anions migrate to positive electrode • The required current rapidly decays as ions are removed so it is inherently efficient and low-power

15. Ions are Held in the Electrical Double Layer • Ions in CDI adsorb on (are held to) the charged electrode surfaces by electrostatic forces (no chemical bonding) • IHP = Inner Helmholtz plane is where the ions are in direct contact with the electrode • OHP = Outer Helmholtz plane is where there is closest approach and the ions still carry their complement of solvating water molecules • Diffuse layer is transition to bulk solution Electrode http://www.andrew.cmu.edu/course/39-801/theory/Electrical%20Double%20Layer.png

16. Capacitive Deionization – Regeneration • Electrodes are shorted or polarity briefly reversed to force desorption • Flush in reverse direction with product water • Efficient because captured salt concentration is highest at the inlet • Use of product water during flush is minimal and resulting effluent can be sent to the drain • Can briefly reverse polarity to speed up desorption • Flush countercurrent with clean product water • Stored capacitance can be re-captured during discharge to improve efficiency (more relevant when treating brackish water)

17. Advantages of CDI • Does not require high pressures • Equipment and operational costs are reduced • Low voltages • Safe • Low power (low energy cost) • Small units can be used in remote locations and run by solar panels • Some of the energy can be recovered by utilizing stored energy (CDI is a capacitor) Comparison of several water purification technologies

18. TDA’s Carbon CDI Electrodes • TDA’s carbon electrodes • Made using proprietary method • Chemically pure • Controllable pore size distribution • Controllable surface area • Can add surface functionality

19. Testing TDA’s Carbon CDI Electrodes • Cyclic voltammetry (CV) • Used to determine carbon electrode capacity for adsorbing ions • Small static test cells • Current response as a function of a linearly ramped voltage • Shape of the CV trace gives the resistance & capacitance properties of the cell • Electrode capacitance is calculated from the current and scan rate • Varying the voltage scan rate enables kinetic measurements • Both rate and capacitance must be optimized for ideal cell performance

20. Optimum Electrode Thickness 6 mil • Cyclic voltammetry between ±1.2 V at very slow and very fast scan rates • Peak capacitance vs. scan rate plots allow for comparison between carbon materials • Plot shows the data for optimizing the thickness of our carbon electrodes • Data show that 6 mil (0.006” ~ 0.15 mm) is optimal

21. TDA Carbon Electrodes are Redox Inactive • Platinum electrode exhibits reduction-oxidation (redox) chemistry with 100 ppm lead, Pb2+ from Pb(NO3)2 • No current transients present using TDA carbon electrode indicating good chemical stability • Ions can be removed without chemical reactions occurring using TDA’s carbon CDI electrodes

22. Long Term Stability of TDA’s Carbon CDI Electrodes Break-In (rapid cell improvement) • Cyclic voltammetry used to measure long term stability by subjecting electrodes to thousands of cycles • Hard water, 394 mg/L as Ca(CO3)2 • Slow, 25 mV/s scan rate to simulate slow rate of charge and discharge during CDI • TDA carbon CDI electrodes exhibit an initial break-in period followed by gradually improving performance • Performance still slowly improving even after 6,000 cycles • Same test done with well water contaminated with 100 ppm Pb2+ which is 6,700 times EPA drinking water limit • Very small decrease in capacitance was observed (less than 0.04% drop, per 100,000 cycles, per ppb of lead) Approaching Steady-State (continued improvement)

23. Early Testing with Flat/Stacked Plate CDI Cells

24. Typical Flat Cell Construction

25. Flow Paths in Early Flat Cell Designs Serpentine Flow Cell Side-View of Stack Layers Parallel Flow Cell

26. Hybrid Flat Cell Design Hybrid (Parallel/Serpentine) Flow Cell

27. Typical Flat Cell PerformanceHard Well Water • A real-world, sample of very hard water, 394 mg/L as Ca(CO3)2 , was used to demonstrate basic CDI performance • Data show the results of a single-pass through a parallel flow, flat plate cell with water analysis before and after treatment • A standard break-in period of 6-8 cycles is typical for this type of cell, so the data are displayed for inlet the 14th cycle

28. Contaminated Well Water Testing • Hard well water contaminated with • 54 ppb perchlorate (ClO4-) • 66 ppm nitrate (NO3-) • 25 ppb lead (Pb2+) • 83 ppb arsenic (III) (AsO2-) • Concentration of all contaminates reduce to levels well below EPA drinking water standards Hybrid Flat Cell

29. Hybrid Flat Cell: Contaminated Well Water Performance Much better than low pressure RO which is typically ~10% efficient

30. TDA Spiral Wound CDI Module Technology • Flat electrodes • Satisfactory for testing the effects of • Thickness • Pore size distribution • Surface area • Too expensive to manufacture • All current CDI systems use flat electrodes • There are no spiral wound CDI modules currently in use

31. TDA Spiral Wound Design – Early Prototype • Spiral wound CDI cells have been fabricated with a factor of 4x improvement in surface/volume ratio over “plate-type” cells • 1st Generation of spiral wound cell has typical removal efficiency of ~80% with simple saline feeds (500 ppm NaCl)

32. Spiral Wound Design – Stacked Modules • Two Pyrex glass “spool piece” bodies (4”dia x 4” long) • Electrodes, spacers, current collectors, insulators rolled into a cylinder and inserted into the glass • Units are then sealed and top/bottom clamped in place • Electrical connections made to metal tabs • Can be used individually or stacked (as shown)

33. Single vs. Stacked Modules • As expected, stacking the two cell modules improves performance • Simulates using several spiral wound modules in series Carbon #1 single Carbon #2 single Carbon #2 two stacked

34. Pre-Prototype Units • Electrodes 11 inches wide (instead of 4 in) • Cells still 4 inch diameter • Both Pyrex glass and PVC housings tested • Easier to see leaks and other problems with glass unit • Designing 1 gal/hr prototype units

35. Spiral Cell Electrode Winding Machine • Previously used hand winding to roll spiral cells • Winding machine recently built in-house at TDA • Greater tension • Improves alignment at ends • Better reproducibility • Better scalability

36. Strategic Partnerships – ITN • ITN Power Systems, Inc. (ITN, Littleton, CO) develops green energy and storage technology for today’s and tomorrow’s needs. Areas of core competency include: • Energy generation & storage devices • Sensors & actuators • Separation membranes • Flexible, thin film electronic device structures • Nanotechnology • In 2005, ITN spun off Ascent Solar who manufactures cutting-edge solar technology (CIGS & thin film PV) that easily integrates into a wide range of products and applications. Areas of core competency include: • Custom turnkey PV systems • Building-integrated PV • Flexible CIGS modules Ascent Solar flexible PV panels

37. Portability & Low Power • Some domestic and many foreign population centers • Need water decontamination systems • Less likely to have a well developed power or water treatment infrastructure • Portability and low power are essential requirements • CDI modules are inherently compact; spiral wound cells reduce size by at least a factor of four and are cheaper to manufacture • No consumables, sorbents, chemicals • Power requirements are well below existing portable RO systems (ITN) • PV-battery powered systems practical • TDA has partnered with ITN to develop PV/battery powered CDI modules 500 gal/day, field-portable, PV-powered, RO module built & tested by ITN

38. ITN- Partnership • Work with ITN to build a PV unit and interface it with TDA’s prototype CDI system • PV-CDI system will be tested on • Well water spiked with contaminants • Actual arsenic contaminated waters • ITN has strategic partnerships in Asia • ITN proposes to license (non-exclusive) TDA’s spiral wound CDI cell technology worldwide

39. Competitive Advantages • TDA’s carbons are cost competitive with Kuraray & MeadWestvaco activated carbons (≤ $10/kg) • TDA electrodes long lasting, which reduces overall carbon cost per 1000 gal of water treated • TDA electrodes are chemically pure carbon (no contaminants from the carbon) • TDA electrode carbons can be optimized for improved performance • Electrode production is easily scaled up (continuous process) • TDA carbon CDI electrodes are compatible with spiral wound cell designs which dramatically decreases manufacturing costs

40. Business Environment • Drinking water market driven by: • Low cost for water treatment • Health regulations • Portability (especially military field use) • Remote applications (powered using solar cells) • Competing technologies (ion exchange and reverse osmosis) • Reverse Osmosis is power intensive (pumping water to high pressure) • Ion exchange requires expensive (and logistically inconvenient) media replacement or refill reagents • CDI is low power and has no expendables

41. Conclusions • TDA has developed a capacitive deionization process based on • Proprietary carbons • Spiral CDI cells • Less expensive to manufacture • TDA has demonstrated • Arsenic removal to below drinking water standards • 83 ppb to < 5 ppb • Single pass flat cell • Currently refining the design and manufacturing method for spiral cells • Well water testing (arsenic spiked) • Real arsenic contaminated waters • TDA partnering ITN Energy Systems • Develop and market PV-CDI systems

42. Acknowledgments • National Institute of Environmental Health Sciences (NIEHS) • U.S. Department of Energy (DOE) • ITN Energy Systems