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.
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 Facilities Business Model
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 Flat CDI Cell Testing
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

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

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

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. Comparison of several water purification technologies
Advantages of CDI
Comparison of several water purification technologies
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)

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
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)
Break-In
(rapid cell improvement)
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 Performance Hard 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 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