:System for Decontaminating Well Water for Drinking

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 CobbDrew Galloway

Arsenic - Health and Remediation Applications,Session III Webinar

April 15, 2013

1

TDAR e s e a r c hTDAR e s e a r c hTDAR e s e a r c h

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

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

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

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

Arsenic in Groundwater Worldwide

6

International Groundwater Resources Assessment Centrehttp://www.un-igrac.org/publications/148

• Arsenic is a common, widespread contaminant

• Some areas have very high (in red) concentrations

Arsenic in Groundwater in the U.S.

7

• Areas with especially high arsenic concentrations (50 g/L) are found in almost every state

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

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

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

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

10

http://www.tdsmeter.com/what-is?id=0015

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

Sorbents

12

Arsenic removal from water/wastewater using adsorbents—A critical reviewDinesh 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.)

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

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

15

http://www.andrew.cmu.edu/course/39-801/theory/Electrical%20Double%20Layer.png

Ele

ctro

de

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

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

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

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

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

TDA Carbon Electrodes are Redox Inactive

21

• 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

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(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)

Break-In(rapid cell

improvement)

Early Testing with Flat/Stacked Plate CDI Cells

23

Typical Flat Cell Construction

24

Flow Paths in Early Flat Cell Designs

25

Serpentine Flow Cell

Parallel Flow Cell

Side-View of Stack Layers

Hybrid Flat Cell Design

26

Hybrid (Parallel/Serpentine) Flow Cell

Typical Flat Cell PerformanceHard Well Water

27

• 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

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

28

Hybrid Flat Cell

Hybrid Flat Cell: Contaminated Well Water Performance

29

Much better than low pressure RO which is typically ~10% efficient

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

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)

31

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

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

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

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

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

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

37

500 gal/day, field-portable, PV-powered, RO module built & tested by ITN

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

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

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

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

Acknowledgments

• National Institute of Environmental Health Sciences (NIEHS)

• U.S. Department of Energy (DOE)

• ITN Energy Systems

42