1

Saline Ground Water Resource Development in NM:

Issues & Challenges

Bruce ThomsonCivil Engineering

Water Resources ProgramUNM

(bthomson@unm.edu)

2

Acknowledgments

• John Hawley - Hawley Geomatters • Kerry Howe - UNM• Nabil Shafike - NM Interstate Stream Commission

• Based in part on presentations at NGWA conference on Nonrenewable Ground Water Resources, Portland, OR, 2008

3

Introduction

• Demand for water by municipalities & industry leads to increased willingness to pay for water

• Improvements in treatment technologies, including desalination, lead to reduced costs

• NM water laws that may not cover saline water sources• Convergence of these 3 factors lead utilities to consider

low quality water as potential source:• Wastewater for reuse• Brackish & saline water

Time

Unit

Co

stWillingness to Pay

Treatment Cost

4

Concern

• Many developments have little consideration of sustainability• Typical projects propose extraction of small fraction of

the total resource - yet aggregate of multiple projects can be large fraction

• Short planning horizon - NM Subdivision Act gives Counties authority to establish water supply reqts. Range is 40-100 yrs.

• Five large brackish/saline water development projects under consideration at present (Tularosa Basin, Salt Basin, Bernalillo Co., Sandoval Co., Gallup).

5

Objectives of Presentation

• Saline water considerations - case study:• Size of the resource• Amount that can be recovered• Potential impact on future generations

• Consider desalination issues• Recovery• Fouling• Brine disposal• Energy

• Consider policy issues

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Saline Water Resources Case Study:Estancia Basin

7

• ~75% of ground water in NM is brackish/saline (Reynolds, 1962)

Brackish/SalineWater Sources in NM

Estancia Basin

8

Location Map

Hwy 41

9

NM Population Projections(BBER, 2007)

• Steady growth• Basin pop is small relative

to ABQ & SAF

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

2.5E+06

3.0E+06

3.5E+06

2000 2010 2020 2030 2040

YearPo

pula

tion

New MexicoMid Rio GrandeEstancia Basin

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Cost of Water in Central NM

• Pre-1907 rights sell for >$30K/AF• If consumptive use = 100 gpcd = 0.112 AF/yr-person• $3,300/person to purchase rights for new development

• Total cost of rights for new residents in Central NM ~ $1.5B by 2035

11

Uncertain Status of Brackish/Saline Water Rights

• State Engineer doesn’t have authority over water that is:• Depth > 2,500 ft• TDS > 1,000 mg/L

• State Engineer does have jurisdiction if development of deep or saline water will impact fresh water resources • Lots of work for hydrogeologists!

Mildly brackish 1,000 - 5,000 mg/l Moderately brackish 5,000 - 15,000 mg/l Heavily brackish 15,000 - 35,000 mg/l Seawater and Brine > 35,000 mg/l

12

Case StudyEstancia Basin(Estancia Basin Water Plan Update, 2008)

• 2260 mi2

• ~40 miles east of Albuquerque• Topographically closed basin

• Ground water flow to SE• Elev. 6,000 - >10,000 ft• ~38,000 residents• 97% of water used for ag• Playa lakes• Brackish water east of HW 41

(Shear zone)

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Principal Water Bearing Formations

WaterBearing Unit

SaturatedThickness (ft)

SpecificYield

Avg. SaturatedThickness (ft)

Valley Fill 50 to 325 0.125 131.6San AndresLimestone

50 to 150 0.01 117.9

GlorietaSandstone

50 to 215 0.15 125.5

YesoFormation

35 to 800 0.10 363.3

AboFormation

100 to 800 0.10 60.9

MaderaGroup

100 to 1,165 0.01 903.8

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Stratigraphy

Madera

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Annual Depletion

• Current GW depletion ~110 KAF/yr• Basin plan calls for reduction to 20

KAF/yr by 2040 in valley fill• Model predicts > 60 ft drawdown in

pumping centers Water BearingUnit

Ground Water inStorage (MAF)

DepletionRate (KAF/yr)

Valley Fill 6.58 52.1San AndresLimestone

.067 N/A

GlorietaSandstone

5.85 N/A

Yeso Formation 23.8 N/AAbo Formation 44.9 N/AMadera Group 11.1 61.2

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Summary of Brackish Water Export Proposal

• Construct wells in eastern side of basin• Extract 7200 AF/yr• Construct desalination plant & pipeline to Santa Fe (~75 miles)• Estimated project cost = $100 M ($14/KAF)

• $120 M profit at $30/KAF for water

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Limited Water Quality Information(Hawley, from Smith)

WELLS IN RANGE 8 E

ELECT. COND.

WELLS IN RANGE 10 E

ELECT. COND.

TDSCalc(mg/L)

05N.08E.15.131 380 05N.10E.13.443 4,210 2,950

05N.08E.17.323 619 06N.10E.05.300 3,010 2,110

05N.08E.24.311 416 07N10E.19.112 6,640 4,650

06N.08E.11.420 541 07N.10E.19.411 6,920 4,840

06N.08E.09.112 553 07N.10E.30.411 4,820 3,370

06N.08E.32.113 465 08N.10E.14.111 3,050 2,140

07N.08E.20.342 834 08N.10E.36.241 4,410 3,090

08N.08E.10.111 547 09N.10E.18.411 3,450 2,420

09N.08E.14.200 997 09N.10E.18.233 3,350 2,350

10N.8E.23.144 614 10N.10E.32.333 3,630 2,540

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Water Chemistry Will Present Desal Challenge

• High hardness• High SO4

2-

• Moderate SiSiavg = 19.4 mg/LSimax = 30.4 mg/L

Ca Cl+NO3

SO4AlkNa+K

Ca+MgCl+SO4

Mg

0100 0

0

00

0

100

100

100

100

10000

100 100

1000 0

100

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Recharge & Salinity(Shafike & Flannigan, 1999)

• Virtually all recharge is from mountain front on west• Salinity principally due to concentration by evaporation

• Confirms little recharge from east• No recharge studies in east

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Drawdown Is Increasing Salinity of Existing Wells

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Observations from Estancia Valley Proposal

• Very large economic incentives to develop alternative sources - “New Water”

• Estancia Basin case study offers several important observations:• Largest users are agriculture - 97%• Ground water resources are currently being depleted• Good ground water model exists, but little

understanding of salinity issues• Limited administrative authority to curtail ground water

use

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Desalination Issues

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Desalination

• Desalination• Traditional application - Removal of salts from sea

water.• Current interests - Remove all dissolved constituents

from source water (including organics)• Interest in desalination technologies for advanced

wastewater treatment for indirect (& possibly direct) potable reuse

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Seawater vs. Inland Desalination

• Much experience & familiarity with seawater desalination• Limited understanding & appreciation of differences of

inland desalination• Important differences include:

• Feed water recovery objectives• Water chemistry & fouling• Brine disposal options

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Desalination Technologies(NAS, 2007)

• Membrane technologies - RO, EDR• Phase transfer technologies - Variations of distillation

including thermal distillation, multistage flash distillation, multiple effect distillation, vapor compression

• Ion exchange

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Thermal vs Membrane Desalination(NAS, 2008)

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ParticlesSedimentAlgaeProtozoaBacteria

Small colloidsViruses

Dissolved organic matterDivalent ions (Ca2+, Mg2+)

Ionic Species (Na+, Cl-)

Water

Microfiltration

Ultrafiltration

Nanofiltration

Reverse osmosis

Incr

easi

ng p

ress

ure

Dec

reas

ing

pore

siz

e

Mem

bran

efil

tratio

nR

ever

seos

mos

isTypes of membranes in water treatment

~ 0.1 μm pores

~ 0.01 μm pores

~ 0.001 μm pores

non-porous

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Electrodialysis Reversal (EDR)

• Uses electrical potential as driving force instead of pressure

• Only removes ionic constituents• Less energy consumption than RO if TDS < 3500 mg/L• Not widely used

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Reverse Osmosis

• Use pressure to force water through semi-permeable membrane - considered diffusion of H2O molecules through membrane, not filtration

• Osmotic pressure - depends on ionic concentration & nature of ions

• π = Pressure (bar)• i = Conc. of ions (mol/L)• T = Temperature (K)• φ = Osmotic coefficient (depends on solute)

RTiφ=π

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Osmotic Pressure

• Determined by thermodynamics - not membrane characteristics

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RO Process

• Important terms• Permeate - Water that passes through membrane• Concentrate (Brine) - Solution containing retained solutes• Recovery - Fraction of feed water recovered as permeate• Rejection - Fraction of solutes not passing through

membraneP

FeedWater

Permeate

BrineRecycle

RO Modules

Module 1

Module 2

Module 3

Cartridge Filter

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RO Process

• Spiral wound membrane cartridges

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3 Major Differences Between Seawater& Inland Desalination

• Feed water recovery• Membrane fouling• Brine disposal

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Feed Water Recovery

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Feed Water Recovery

• Recovery (r) = Fraction of feed water recovered as permeate

• Concentrates dissolved salts• If rejection ~100%:• High recovery = High conc. of solutes in concentrate

⎟⎠⎞

⎜⎝⎛

−=

r11CC fc

0

5

10

15

20

25

0 20 40 60 80 100

Recovery (%)

Cco

ncen

trat

e/C

feed

• Objective of inland desalination is high recovery

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Recovery

• Consequences of high recovery• High osmotic pressure• Reduced quality of permeate - leakage through RO

membrane proportional to feed water quality• Concentrations of dissolved salts may exceed solubility

limits = fouling due to precipitation• Sea water:

• Unlimited supply hence recovery is less important. Recovery is determined by equipment limits & process economics, not value of water.

• Solutes are Na+ & Cl- - Low inorganic fouling potential

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Membrane Fouling

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Membrane Fouling

• Fouling = Accumulation of material on membrane that reduces flux through membrane.

• Four types:• Colloidal fouling• Inorganic fouling• Organic fouling• Biological fouling

• Low quality ground water may contribute to all four. • Most challenging is often inorganic fouling

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Inorganic Fouling Minerals

Precipitate log Kso

Equil. Cation Conc. (mg/L)

Equil. Anion Conc. (mg/L)

CaCO3 -8.48 60 751

CaSO4.2H2O -4.58 205. 492

SiO2 -2.71 116 - CaHPO4 -6.6 20.0 15.62

1 – Concentration of HCO3

- in units of mg CaCO3/L 2 –Other phosphate phases such as apatite (Ca5(PO4)3OH) are several orders of magnitude less soluble than CaHPO4. 3 – Ignoring ionic strength and complexation effects.

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Seawater vs. Ground Water

K+

0.9%

Na+

41.6%

Mg2+

5.1%

Ca2+

0.0

SO42-

3%

HCO3-

0.2%

Cl-

0.5

SeawaterTDS = 35,400 mg/L

Mg2+

9%K+

4% Na+

10%

SO42-

26%

HCO3-

11%

Cl-

9%

Ca2+

31%

Tularosa Basin, NMTDS = 2,860 mg/L

ABQ ground water has silica from < 20 mg/L to > 60 mg/L

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Inorganic Fouling - UNM Tap Water

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 50 100 150 200 250 300 350 400Run Time, hr

Spec

ific

Flux

, L/m

2-h-

bar

Module 1

Module 3

Module 2

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Brine Disposal

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Concentrate Disposal Options

• Seawater desalination disposal options• Return to sea

• Inland desalination disposal options (NAS, 2008)• Discharge to surface water• Evaporation ponds• Land application• Deep well injection• Landfill of solid wastes

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Municipal Concentrate Disposal Practice(Mickley, 2006)

Unreported7%

Land Disposal

2%Evaporation

Ponds2%

Injection Wells17%

Sewers31%

Surface Waters

41%

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Concentrate Disposal Considerations

• Very high TDS• Concentrated by 4x at 75% recovery

• High concentrations of toxic constituents present in feed water (As, Se, U, etc.)

• Reduced evaporation of salt saturated solutions• High TDS solutions are corrosive• Impacts on deep well injection

• Corrosion of equipment & well screens• Precipitation & cementing of subsurface formations

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Brine Disposal Case Study - Phoenix

• Study of disposal options for 20 Mgd concentrate stream• Evaporation ponds

• 10 square miles in area• Total capital cost = $410,000,000

• Pipeline to Gulf of California• 184 miles of 30- to 60-inch pipeline, additional distance

through existing canal• Would require approval from Mexico• Total capital cost = $456,000,000

(includes Tucson)

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Energy Considerations

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Energy & Environmental Considerations

• A 5 MGD facility treating 2,000 mg/L TDS water to 85% recovery:• Feed pressure will be about 250 psi.• Power requirement for the feed pumps (85% eff) will be

12,600 kWh/day.• Using Albuquerque’s electricity profile, CO2 emissions

will be 15,800 lbs CO2/day.• A 60 MGD facility treating 10,000 TDS water to 75%

recovery:• 500 psi; 340,000 kWh/day; 430,000 lbs CO2/day.

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Random Points

• Cost - Design study for 5 Mgd system in NM (TDS ~12,000 mg/L)• Capital cost =$143M• Total cost of water = $8.50/1,000 gal

• Caution• Design should be based on water demand (i.e. water

delivered to houses) not consumptive use• Can design for consumptive use if wastewater is

recycled back to RO plant for reuse

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Desalination Conclusions

• Desalination technology offers great potential for water & wastewater treatment.

• 3 important differences between seawater & inland desalination:• Recovery - Inland desalination will only recover 50 -

75% of feed water.• Fouling - Ground water has higher potential for fouling

by Ca and Si minerals than seawater• May limit recovery• Adds complexity to O&M

• Brine disposal is challenging for inland systems• Process is energy intensive

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Policy Issues

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Jurisdiction

• State Engineer doesn’t have authority over deep non-potable water• Top of formation > 2,500 ft• TDS > 1,000

• Claimant must prove that these conditions exist.• Who owns the water?

• Landowner?• Mineral rights owner?• First person to drill?• Atrisco Oil & Gas v. SunCal v. Sandoval County

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Sustainability

• Term is widely used but has many different definitions

• Brundtland Commission (1987) - “Meets needs of the present without compromising needs of future generations”

• ASCE Committee on Sustainability - “Sustainable water resources systems … contribute to objectives of society now & in the future while maintaining ecological, environmental, & hydrological integrity.”

• My perspective - Future generations will have supply to support quality of life & economy similar to that which exists today

54

Non-renewable Resources

• Extraction of non-renewable resources has been practiced forever:• Minerals• Fossil fuels

• However, is water a fundamentally different resource?• Essential for life, there is no alternative!

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Conclusions

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“New” Water

• “It’s a new source of water.” - Peter Sanchez, ABQ Journal 11/9/8

• “The implications for Sandoval County are huge” - Jack Thomas, ABQ Journal, 11/1/8

• It’s not “new” water. It’s very old water, and probably not renewable.

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Possible Roles for Saline Water Resources

• Water resource is limited but may be appropriate for drought reserve

• Mineral resources - CaSO4, etc.• Formation has value:

• Reservoir for aquifer storage & recovery (ASR)• Waste disposal

58

Saline Water Resources

• Better characterization of saline resources• Quantity• Quality• Recharge• Hydrology & hydraulics

59

Technology Needs

• Better desalination technology• Recovery• Fouling• Brine disposal• Energy requirements

60

Jurisdiction & Planning

• State Engineer must be given authority over deep saline water resources• ABQ Journal candidate profiles in May - 71%

supported authority, 18% opposed• Yet provision repeatedly fails

• Subdivision laws, ordinances and policy need to consider sustainability of water (& possibly other resources)• If saline supply is used for supply, credible plan must

be included to provide sustainable supply

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Sustainable Future or Delayed Disaster?

0.0E+00

5.0E+05

1.0E+06

1.5E+06

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2.5E+06

3.0E+06

3.5E+06

2000 2010 2020 2030 2040

Year

Popu

latio

n

New MexicoMid Rio GrandeEstancia Basin

What will we do when this water is gone?

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Acknowledgments

• John Hawley - Hawley Geomatters • Kerry Howe - UNM• Nabil Shafik - NM Interstate Stream Commission

• Based largely on presentations at NGWA conference on Nonrenewable Ground Water Resources, Portland, OR, 2008