Brackish Desalination:Zero Discharge

Thomas F. Seacord, P.E.

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Topics covered includeTopics covered include

• BackgroundBackground

• Current Disposal Options

• Zero Discharge In Practice

• Case Studies

• Emerging Technologies

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Emerging Technologies

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3April 20, 2010

• 1 out of 8 people lack access to clean twater

• 3.3 million die each year from water related health problemsrelated health problems

• 83 million people are added to the world population each yeary

• Within 15 years 1.8 billion people will live in regions of severe water scarcity

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4April 20, 2010

Business as usual approaches will not meet demand for watermeet demand for water

6.5

Historical

Portion of GapPercent

5.7

Demand with no productivity

improvements

Billion AFRemaining 60%

HistoricalImprovements in

water productivity20%

4.9

4.1Increase in Supply under business-

as-usual20%

Gap 60%

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2030

as usual

2.4Today

Existing accessible, reliable supply

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SOURCE: 2030 Water Resources Group – Global Water Supply and Demand Model(A United Nations Water Working Group)

Saltwater (seawater and brackish water) is the most abundant water source on Earthmost abundant water source on Earth

0.3% Lakes and Rivers0.7% Available G d t

Fresh Water2.5%

Groundwater

69% Glaciers

29.3% Unavailable Groundwater

Total Water

Salt Water

69% Glaciers and Icecaps

Water Water

97.5%

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SOURCE: Encyclopedia of Desalination and Water Resources

The State of Texas has estimated that there is 2 7 billion acre feet of brackish groundwater2.7-billion acre-feet of brackish groundwater

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LBG-Guyton, Brackish Groundwater Manual for Regional W t Pl i G 2003

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Water Planning Groups, 2003

Desalination is the only significant solutionsolution

Unlimited supply Unlimited supply Local source Provides back-upProvides back up

and redundancy Drought proof Frees freshwater for

environmental uses

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8Image courtesy NASA, provided by Visible Earth (http://visibleearth.nasa.gov)

Global desalination capacity has i d i llincreased exponentially

20.0

15.0

17.5 ~ 14,500 Plants

10.0

12.5Global DesalinationCapacity

(Billion gal/day)7.5

5.0

( g y)

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1990

0

2.5

1995 2000 2005 2008. . . . . . . . . . . . . . . . . . . . .

2010

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1990 1995 2000 2005 2008 2010

SOURCE: Global Water Intelligence

There are 44 Desalination Plants in Texas (Capacity > 0 023 mgd)(Capacity > 0.023 mgd)

• Currently produce 116 mgdCurrently produce 116 mgd– Surface Water

• 12 plants• Capacity: 50 mgd

– Groundwater• 32 plants• 32 plants• Capacity: 66 mgd

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10Source: Texas Water Development Board Desalination Plant Database, 2010

There are several perceived barriers to implementation

Cost Power consumption

Concentrate Management

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Concentrate disposal is the “tail that wags the dog” on any desalination projecton any desalination project

• For seawater andFor seawater and brackish water desalination: – Concentrate consists of

dissolved constituents from natural waters in a more concentrated form

• Nomenclature:Concentrate

Concentrate Management

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– Concentrate– By-product– Brine

Management

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Concentrate Management Options Include

• Surface water

• Sewer• Sewer

• Deep well injection

• Land application (irrigation, dust control, etc.)

• Concentrators

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• Zero discharge technologies

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technologies

Brine management options fall into distinct categoriesg

B i Di l Beneficial Reuse Brine TreatmentBrine Disposal Beneficial Reuse Brine Treatment

Surface WaterDischarge1

Cooling Water Volume ReductionDischarge1

Sewer Disposal1 Land Application

Chemical Precipitation

Brine

Deep Well InjectionDust Control

Irrigation Concentrators

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WetlandsZero Liquid Discharge

Zero Liquid Discharge

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Evaporation Ponds Crystallizers1- Includes export pipelines/brine lines

Depending upon brine volume, several steps may be required leading to zero liquid discharge

Initial Brine Intermediate Brine Final S lidifi tiVolume Reduction Concentration Solidification

(Zero Discharge)

CrystallizersChemical Thermal

Evaporation Ponds

Precipitation

Softening followed by

Brine Concentrator

Vapor Compression

Enhanced Evaporation

using Solar Bee

followed by “Secondary RO”

Brine Concentrator

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using Solar Bee

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Brine volume minimization uses intermediate f h b itreatment to recover more water from the brine

Ch i l/ h i l1. Chemical/physical processesa. Chemical precipitation pretreatment for

dditi l d ltiadditional desalting2. Thermal treatment

H t d t l t ti fa. Heat used to accelerate evaporation of brine

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Chemical precipitation reduces the saturation of salts that would otherwise limit furtherof salts that would otherwise limit further recovery by RO

2-Stage Primary RO Secondary RO

PermeatePermeateChemical

Precipitation Process

Secondary

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Brine

Secondary RO Conc.

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Two softening processes can be used for chemical brine treatment

CONVENTIONAL SOFTENING An economic way of brine volume reduction y

proven at bench & pilot scale Low rate (1.75 gpm/sf) = large foot print Requires open tank = energy loss Requires open tank = energy loss Residuals require drying ponds or mechanical

dewatering

PELLET SOFTENING Fluidized bed using sand & lime Hi h t (35 / f) ll f t i t

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High rate (35 gpm/sf) = small footprint Can be operated in a pressure vessel = save

energy

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Residuals easily dewatered by gravity

Thermal brine minimization uses waste heat and/or electricity to evaporate concentrate

1. An example of a thermal process is a seeded-slurry, falling film vapor compression brine concentrator

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Heated Brine De-Aerated to Reduce Scaling and Corrosion

Concentrated Waste is Blown Down to Crystallizer or

Evaporation Ponds

Vapor is Heated With Compressor – Transfers Heat to Falling Brine

Causing Evaporation

Vapor Condenses as Highly Pure Distillate and Is Collected

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RO Brine Passes Through Heat

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Through Heat Exchanger Brine is Recirculated From

Sump Through Vertical Tubes

Mechanical evaporators are last resort option due to cost and energy usagecost and energy usage

• >100 ft tall• 250 gpm capacity• Up to 98% evaporation

efficiencyy• Blowdown is 175k-200k mg/L

TDS and 5-7% solids• Capital Cost = $10 million• Capital Cost = $10 million• Requires 90 to 100 kW-hr per

1,000 gallons of brine

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Deuel Vocational Institution

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at Deuel Vocational Institution

Tracy, CA

Crystallizers can be used as a final step in the ZLD process

1. Only used if evaporation ponds or other finalor other final disposal methods are not feasible

2 Produces a solid that2. Produces a solid that is dewatered and disposed of

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Crystallizers can be used as a final step in the ZLD

• 65 to 75 ft tall

ZLD process

• Flows: 2 to 50 gpm• About 80 to

120 kW-hr per 1,000 gallons of brine

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Evaporation ponds can be used for concentrate disposal• Permit

– Triple liner system and leachate collection and monitoring system

• Loading Rate– Based on net precipitation and

evaporation rate for each l ti

Evaporation Pondslocation

• Land intensive in non-desert areas

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– Can be combined with brine minimization as final disposal option

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Fences & Bird Netting

Evaporation rates can be enhancedEvaporation rates can be enhanced

• Solar BeeMi i i d i b i i– Minimizes pond size by mixing pond’s thermocline to enhance evaporation

– Enhanced evaporationp• 1.6 x during day• 1.8 x during night

– May not be applicable when using thermal concentrators due tothermal concentrators due to blowdown temperature (>200oF)

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Photos: Erik Jorgensen USBRPhotos: Erik Jorgensen USBR

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Photos: Erik Jorgensen, USBRPhotos: Erik Jorgensen, USBR

Case Study #1: Chemical Precipitation –Arlington DesalterArlington Desalter

Brine Minimization

GAC Towers(Biofilters)

Secondary RORecovery = 70%

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Filter RO SystemPellet Softener& Media Filter

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Case Study #1: Chemical Precipitation –Arlington DesalterArlington Desalter

• Location: Riverside, CA• Size: 8.5-MGD

– Primary RO: 5-MGD – Secondary RO: 1.1-MGDSecondary RO: 1.1 MGD– Brine: 0.5-MGD– Overall Recovery: 94%

• Drivers• Drivers– Reach IV-B of SARI is

hydraulically maxed out• Alternatives

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• Alternatives– New SARI Pipeline &

Conventional RO Expansion

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Case Study #1: Chemical Precipitation –Arlington DesalterArlington Desalter

• Project Costj(Brine Recovery)– Capital: $16.9-mil

O&M: $698/AF– O&M: $698/AF($2.14/kgal)

• Energy Required(Entire Treatment Plant)– 1,869 kW-hr/AF

(5.73 kW-hr/kgal)

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Case Study #2: Hybrid – Brine Concentrator/CrystallizerConcentrator/Crystallizer

RO SystemDecarbonation

Tower

Cartridge FilterCartridge FilterFinished Water Pumps

CrystallizerCrystallizerZero Liquid Discharge

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Brine Concentrator

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Case Study #2: Hybrid – Brine Concentrator/CrystallizerConcentrator/Crystallizer

• Location:Salt Lake City, Utah

• Size: 7-MGD– RO: 4,028 gpm, gp– BC: 1,007 gpm– Crystalizer: 30 gpm

• Project DriversProject Drivers– Discharge to adjacent Jordan

River was objectionable to community (selenium)

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• Alternatives– 26-mile pipeline to Great Salt

Lake

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Case Study #2: Hybrid – Brine Concentrator/Crystallizer

• Brine Concentrator / • 26-mile Pipeline to Great Crystallizer– Project Costs

• Capital: $129 8 mil

pSalt Lake– Project Cost

• Capital: $45 8 mil• Capital: $129.8-mil• O&M: $783/AF

($2.39/kgal)Energy

• Capital: $45.8-mil• O&M: $224/AF

($0.68/kgal)Energy– Energy

• 7,033 kW-hr/AF(21.5 kW-hr/kgal)

Water Cost

– Energy• 2,197 kW-hr/AF

(6.7 kW-hr/kgal)Water Cost

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– Water Cost• $1,910/AF

($5.84/kgal)

– Water Cost• $621/AF

($1.90/kgal)

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Emerging technologies may provide more iable concentrate management optionsviable concentrate management options

• Emerging technologies primarily focus on• Emerging technologies primarily focus on volume reduction:– VSEPVSEP

• TWDB, 2007 Report– Seeded precipitation (hollow fiber RO) - SPARRO

• USBR DWPR, 2008 Report

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Brackish Desalination:Zero Discharge

Thomas F. Seacord, P.E.Carollo Engineers IncCarollo Engineers, Inc.

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