Electrodialysis Metathesis (EDM) to Prevent Scaling

in Desalination of Gypsum-rich Groundwater

Thomas A. Davis, Director

Center for Inland Desalination Systems

DesalTech/ August 29, 2015

The University of Texas at El Paso

Outline

Desalination in Alamogordo, NM

Groundwater saturated with gypsum

Desal Prize at BGNDRF

Plans for Honduras

The University of Texas at El Paso

Alamogordo Water Supplies

Fresh Groundwater (local)

Surface water

Springs (local)

Bonito Lake (~60 miles northeast)

Unavailable since June 2012; Might open 2017

Brackish Groundwater (~25 miles north)

1-MGD temporary plant planned

4-6 MGD plant in future

The University of Texas at El Paso

Composition of City of Alamogordo

groundwater

Ion mg/L meq/L

Calcium 413 20.63

Magnesium 88 7.21

Potassium 4.7 0.12

Sodium 164 7.15

Bicarbonate 108 1.77

Chloride 133 3.74

Sulfate 1433 29.84

Silica 28 0.46

TDS 2500

The University of Texas at El Paso

The ZDD* process (Zero Discharge Desalination)

* T. A. Davis is a principal in ZDD Inc., licensee of the ZDD technology.

Mixed Sodium

Mixed Chloride

NaCl

Finished WaterBrackish Water

NF/RO Concentrate

2% of

original

volume

Electrodialysis

Metathesis

(EDM)

The University of Texas at El Paso

CaSO4 is problematic for ED. anode

feed solution

concentrate

diluate

cath

ode

O2

OH-

H2

H+

AEM CEM

concentrate

_ +

Cell Pair

SO42- SO4

2- SO42- SO4

2-

Ca2+ Ca2+ Ca2+ Ca2+

+ + + + _ _ _ _

The University of Texas at El Paso

Electrodialysis Metathesis (EDM)

The University of Texas at El Paso

EDM exploits solubility of Cl & Na

salts.

The University of Texas at El Paso

ZDD process with solar salt recovery

Finished Water

Brackish Water

Mg(OH)2

CaSO4

NaCl

Ca(OH)2

The University of Texas at El Paso

Recovery of NaCl improves

economics of ZDD process

Purchase of NaCl is 40% of the ZDD operating cost.

NaCl must have low levels of Ca & SO4.

NaCl in supernatant can be recovered and purified from EDM concentrate streams.

Target NaCl recovery is 90%.

Cost reduction of 25-30% possible

Evaporation ponds can be used for solar salt recovery, achieving Zero Liquid Discharge.

The University of Texas at El Paso

The Desal Prize

Sponsors: USAID, Swedish International Development

Agency, Ministry of Foreign Affairs of the Kingdom of the

Netherlands

Bureau of Reclamation was a partner

Site: BGNDRF in Alamogordo, N. M.

Purpose: Incentivize innovation in desalination for farmers in

developing nations

Outcome: UTEP team placed 2nd (MIT 1st)

Next Phase: Demonstration in Honduras

The University of Texas at El Paso

ZDD & The Desal Prize: Achieving High Recovery for Rural Farmers

The University of Texas at El Paso

UTEP Desal Prize Team

The University of Texas at El Paso

Conclusions

ZDD process removes CaSO4 as a solid byproduct.

ZDD has achieved 98% recovery compared to 75% recovery with BWRO alone.

Recovery of NaCl from CaSO4 supernatant improves the economics of ZDD.

Evaporation improves the purity and concentration of recovered NaCl.

The University of Texas at El Paso

Acknowledgement

Funding

Bureau of Reclamation

El Paso Water Utilities

The Team

Malynda Cappelle UTEP

Shane Walker UTEP

Bernie Mack Veolia

Lucy Camacho TAMU Kingsville

The University of Texas at El Paso

Thank you

Questions?