Development of a Solar Powered Electrokinetic DesalinizationElectrokinetic Desalinization

System

Christopher Athmer – TerranChristopher Athmer Terran

Shane Ewert – Stealth

C d A d O CCody Anderson - OneCor

Environmental Issues for B i S illBrine Spills

• Chloride and Sodium do not breakChloride and Sodium do not break down any further… Must be removed or dilutedor diluted.

• Sodium exchanges with calcium in the soil leaving the land barrensoil leaving the land barren.

• Chloride percolates to the water table i h i i iwith precipitation.

Electrokinetic Remediation ?Electrokinetic Remediation ?

• Application of direct current (DC) electricityApplication of direct current (DC) electricity to the soil

P l i d l t d i d t f• Polarized electrodes induce movement of pore water and ions contained in the pore water even in low permeability soilswater, even in low permeability soils

• Effective in saturated and unsaturated soils

ElectrokineticsElectrokinetics• Electroosmosis – Movement of pore water

and contaminants toward the cathodeand contaminants toward the cathode

• Electromigration – Migration of ionicElectromigration Migration of ionic species toward respective electrodes (anions toward anode, cations toward cathode) by electrical attractionelectrical attraction

T t t ti l t• Transport rates proportional to voltage gradient

Principles of ElectrokineticsElectroosmosis = Water Transport from anode to cathodeElectromigration = Ion Transport to the opposite electrode

Soil ParticleSoil Particle

A d

- - - - - -

-+Soil Particle

--

++ + + ++ + +-

- ++ + WaterAnode

-- -----

Cathode

S il P ti l-

+ ++++ +++- - - -++ Velocity

Profile

Soil ParticleSoil Particle

Soil Particle

EK Desalinization Application

B i

Electromigration

Brine

+ -

Electroosmosis

Na+Cl- Salt inSolution

Rate of ion migration (electromigration) is proportional to voltage gradient and ionic mobility plus electroosmosis flow and anyAnode + Cathode -mobility plus electroosmosis flow and any bulk convectional flow.

EK Desalinization ProcessEK Desalinization Process480 Volt

AC Line Feed

Brine ToteMulti-head Peristaltic

Brine Discharge Pump

Siphon tubes

Anode buss feed

Cathode buss feed(DC)

+-

Pumps

Rectifier

Na+ Electrodes arranged

Cl-

Pore Water

in hexagonal grid

Anode(multiple)

Cathode(multiple)

Pore Water

Power Requirements for P i l EK SPractical EK Systems

• Voltage = 24 – 48 volts

• Current = 100s of ampsCurrent 100s of amps

• Constant or cyclic potentials

Robust and reliable• Robust and reliable

• Low maintenance

Ideal application for solar powerIdeal application for solar power

Solar Power Has PotentialSolar Power Has Potential

• Direct Current in cyclic mode should work well.

• No battery banks or voltage controllers• No battery banks or voltage controllers.• PV panels wired in parallel provide reliable

low voltage, high current DC power.low voltage, high current DC power.

• Received grant from NDIC to pilot a solar g f ppowered GW remediation which was installed spring 2019.

Demonstration SiteDemonstration Site

• Brine spill contaminated vernal streamBrine spill contaminated vernal stream lowlands area.

• Soil and groundwater contamination• Soil and groundwater contamination.

• Groundwater at 6-10 feet.

• Stream bisects contaminated area.

• Previous GW collection system as ytreatment.

Basic EquipmentBasic Equipment

• PV panelsPV panels

• 27 electrode/wells

M l i h d i l i• Multi-head peristaltic pumps

• Poly tubing (1/4” P.E.)

• Buss wire (350 aluminum)

• Lead wire (#10 copper PV wire)Lead wire (#10 copper PV wire)

• Data system with cellular

Electrode/Wells consist of 1” PVC well pipe with lower 5 feet

d i l d ithscreened spiral wound with dimensionally stable anode (DSA) wire.

Wells installed using Direct-Push.

Annulus backfilled with cokeAnnulus backfilled with coke breeze (Loresco SWS Cathodic backfill).

Originally set up grid to treat whole area of contaminationwhole area of contamination

Revised pilot layout to treat 3 more heavily impacted

Area for Solar gridsloped south

areas.

MW-3, MW-4 and MW-5 areas treated Original overall grid

p

treated. Original overall grid was maintained to allow orderly expansion if warranted.

Each well grouping was powered by separate mini-grids or 8 to 12 PV panelsgrids or 8 to 12 PV panels, depending on overall site electrical conductance.

S th f i l id l

GW Flow

South-facing slope was ideal for PV panel grids.Grid is 7’ side by side

5’ between red/white rows(effectively making 7x7x7 triangles)

Grid of 295W Panels -3 B dl f 8 P l3 Bundles of 8 Panels

4 more panels have since been added to the right bank for MW-3 Sector

Data acquisition and control box with cellular communications

16

Average 24 hour Voltage

Summer Solstice

14

MW-3Summer Solstice

10

12

8

Volt

s

4

6

2

4

d / / ( d )0

3/30/19 4/29/19 5/30/19 6/29/19 7/30/19 8/29/19 9/29/19 10/29/19

Operated 4/25 – 10/01 (158 days)

90

100Sunny Day

80

90MW-3 VoltageMW-3 CurrentMW-5 VoltageMW-5 Current

60

70

ps

MW 5 CurrentMW-4 VoltageMW-4 Current

40

50

Volt

s/A

mp

30

40

10

20

05:59 7:59 9:59 11:59 13:59 15:59 17:59 19:59 21:59 23:59 1:59

90

100Mostly Cloudy Day

80

90MW-3 VoltageMW-3 CurrentMW-5 VoltageMW-5 Current

60

70

ps

MW4 VoltageMW-4 Current

40

50

Volt

s/A

mp

30

40

10

20

05:59 7:59 9:59 11:59 13:59 15:59 17:59 19:59 21:59 23:59

Removed Water QualityRemoved Water Quality

• Calcium = 70.4, 98.8• Magnesium = <2.0, 26.2• Potassium = 727, 415• Sodium 11 200 7 900• Sodium = 11,200, 7,900• Chloride = 3760, 6,250• Sulfate = 960, 1870Sulfate 960, 1870• Sp. Cond. = 71.2, 39.6 mmhos/cm• pH = 13.19, 12.77

Extracted groundwater collection tanks7/16/19. Units mg/l. Roughly 500 gallons removed

Issues/LessonsIssues/Lessons

• Voltage limitation at MW-3 cellVoltage limitation at MW 3 cell– Added 4 more panels

Pump flow rates inconsistent• Pump flow rates inconsistent– Animal vandalism

l b l– Peristaltic pump tubing material

– Connections get brittle

– Will double flow next season

ConclusionsConclusions

• Simple DC power sourceSimple DC power source

• Voltage increments practical for EK systemssystems

• Lower cost, but varies seasonally

• No need for line power

• Huge potential for remote sitesg p

• Take into account seasonality issues