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: System for Decontaminating Well Water for Drinking TDA Research, Inc. Girish Srinivas, Ph.D., M.B.A. 303-940-2321 Shawn Sapp, Ph.D.

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Presentation on theme: ": System for Decontaminating Well Water for Drinking TDA Research, Inc. Girish Srinivas, Ph.D., M.B.A. 303-940-2321 Shawn Sapp, Ph.D."— Presentation transcript:

1 : System for Decontaminating Well Water for Drinking 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 Arsenic - Health and Remediation Applications, Session III Webinar April 15,

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 ft 2 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 3

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 4

5 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 6 International Groundwater Resources Assessment Centre Arsenic is a common, widespread contaminant Some areas have very high (in red) concentrations

7 Arsenic in Groundwater in the U.S. 7 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 As 2 O 3 CDI removes all ionic species, which includes many arsenic species 8 S. Wang, C.N. Mulligan, Occurrence of arsenic contamination in Canada: 3127 sources, behavior and distribution, Sci. Total Environ. 366 (2006) 701–721.

9 9 Conventional Arsenic Removal Technologies Ion Exchange Removes ions by replacing cations with H + and anions with OH - (forming H 2 O) 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 H 2 O) Requires frequent resin bed replacement (expensive) or regeneration (time consuming) Some anions (e.g. perchlorate) require specialized resins Expensive 10

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. 11

12 Sorbents 12 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 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 14

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 /theory/Electrical%20Double%20Layer.png 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) 16

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 17

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 18

19 Testing TDA’s Carbon CDI Electrodes 19 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 20 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 21 Platinum electrode exhibits reduction- oxidation (redox) chemistry with 100 ppm lead, Pb 2+ from Pb(NO 3 ) 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 22 Cyclic voltammetry used to measure long term stability by subjecting electrodes to thousands of cycles Hard water, 394 mg/L as Ca(CO 3 ) 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 Pb 2+ 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) Break-In (rapid cell improvement)

23 Early Testing with Flat/Stacked Plate CDI Cells 23

24 Typical Flat Cell Construction 24

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

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

27 Typical Flat Cell Performance Hard Well Water 27 A real-world, sample of very hard water, 394 mg/L as Ca(CO 3 ) 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 14 th cycle

28 Contaminated Well Water Testing Hard well water contaminated with 54 ppb perchlorate (ClO 4 - ) 66 ppm nitrate (NO 3 - ) 25 ppb lead (Pb 2+ ) 83 ppb arsenic (III) (AsO 2 - ) Concentration of all contaminates reduce to levels well below EPA drinking water standards 28 Hybrid Flat Cell

29 Hybrid Flat Cell: Contaminated Well Water Performance 29 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 30

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 1 st Generation of spiral wound cell has typical removal efficiency of ~80% with simple saline feeds (500 ppm NaCl) 31

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) 32

33 Single vs. Stacked Modules As expected, stacking the two cell modules improves performance Simulates using several spiral wound modules in series 33 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 34

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 35

36 Strategic Partnerships – ITN 36 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 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 38

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 39

40 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 41

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


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