Desalination as a Source of Fresh Water Desalination 101 · Desalination as a Source of Fresh Water Desalination 101 ... and boiling point elevation are examples of ... Membrane Separation

Desalination as a Source of

Fresh Water

Desalination 101

Professor Tzahi Y. Cath

Colorado School of Mines

Department of Civil and Environmental Engineering

Advanced Water Technology Center (AQWATEC)

September 20, 2016

Presentation Overview

Source water requiring desalination

Properties of water and their impact on desalination

Desalination technologies

Water recovery and cost of desalination

Issues associated with desalination

Pre-treatment of source water

Energy demand and energy recovery

Concentrate management

Future technologies

Desalination of Impaired Water

Common water sources requiring desalination

Seawater

Brackish groundwater

Industrial water (high purity)

Domestic and industrial wastewater for advanced reuse

Surface water containing specific dissolved solids

Constituents requiring removal by desalination

Dissolved solids, simple salts/ions, heavy metals, nutrients,

hardness, organic contaminant of emerging concern, etc.

Colligative Properties of

Ionic Solutions Properties of solution that depend on the number of solute

molecules present, but not on the nature of the solute

Osmotic pressure, vapor pressure, freezing point

depression, and boiling point elevation are examples of

colligative properties

Osmotic pressure and vapor pressure are two properties of

solution that play a major role in desalination

Vapor Pressure of Water

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 20 40 60 80 100

Part

ial vap

or

pre

ssu

re o

f w

ate

r, a

tm

Temperature, °C

DI

150,000 mg/L

300,000 mg/L

500,000 mg/L

Increases with

increasing

temperature

Minimally

decreases with

increasing

concentration

Single-effect Evaporator

Multiple-effect Evaporator (MED)

Courtesy of Tom Pankratz, [email protected]

mailto:[email protected]



Multistage Flash Evaporation (MSF)





Vapour Compression Brine

Concentrator

Centrifugal

Compressor Steam

Boiling

Chamber

Heat

Exchanger

Heat

Element

Distillate

Preheated

Feedwater

Feedwater

Heat Exchanger

Feedwater





Membrane Separation

Solvent Particle or Solute

Molecule

Membrane

Feed

Membrane Separation

Solvent Particle or Solute

Molecule

Membrane

Permeate Feed

Osmotic Pressure of Solution

Osmosis

Brine Feed

Increases with increasing solute concentration

Increases with increasing temperature

Osmotic Pressure of Solution

Osmosis

DP=Dp

Brine Feed

Increases with increasing solute concentration

Increases with increasing temperature

Overcoming Osmotic Pressure

+

350 psi

membrane

Seawater

35 g/L TDS

Deionized

water


+

350 psi

membrane

Seawater

35 g/L TDS

Deionized

water

‘loose’ and ‘tight’

Domains of Filtration

GFD = LMH x 1.7

Ranges of Pressure and Flux

Process

Pressure Water Flux

PSI kPa gal/ft2/day

(GFD)

L/m2/hr

(LMH)

Nanofiltration 100 – 400 700 – 2800 15 – 30 20 – 50

Reverse Osmosis 200 – 1000 1400 – 7000 15 – 30 20 – 50

Electrochemistry

Principles of Electrodialysis



Desalination Technologies

1% 2% 3% 4% 75% 25% 50% 10% 5%

10

20

30

Sea Water RO

High Efficiency RO

Membrane • Limited Recovery • High Pressure • Simple/modular

% Total Dissolved Solids

• High recovery • Energy to boil water • Exotic metals

Crystallizer Thermal

Brine Concentrators

Sp

ecif

ic E

ner

gy, k

Wh

/m3

0

Adapted from: Oasys Water

ED/EDR

Contracted Capacity by Technology





Water Recovery in

RO/NF Systems

Overall Recovery =10048.8 gal

100 gal

æ

èç

ö

ø÷ = 48.8%

Assuming each membrane (or each stage) operates at 20%

recovery

Total permeate from all membranes (stages) = 48.8 gal

100 gal

20 gal

80 gal

16 gal

64 gal

12.8 gal

51.2 gal


+

350 psi

membrane

Seawater

35 g/L TDS

Deionized

water


+

350 psi

membrane

Seawater

35 g/L TDS

Deionized

water

Rule of thumb: 1 g/L salt ≈ 10 psi of osmotic pressure


+

350 psi

700 psi

++

membrane

Seawater

35 g/L TDS

Deionized

water

Conc. Seawater

70 g/L TDS

Deionized

water


50% water

recovery

700 psi

++

Deionized

water

Conc. Seawater

70 g/L TDS


+

350 psi

700 psi

++

membrane

Seawater

35 g/L TDS

Deionized

water

Conc. Seawater

70 g/L TDS

Deionized

water


50% water

recovery

700 psi

++

Deionized

water

Conc. Seawater

70 g/L TDS

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Recovery (%)

Rela

tive O

pera

tin

g C

ost

of

Tre

atm

en

t

Brackish Water Reverse

Osmosis (BWRO)

Rela

tive B

rin

e D

isp

osal

Co

st

Moderate

High

Water Recovery and

Associated Costs

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Recovery (%)

Rela

tive O

pera

tin

g C

ost

of

Tre

atm

en

t

Rela

tive B

rin

e D

isp

osal

Co

st

Low

High

Water Recovery and

Associated Costs

Zero Liquid Discharge (ZLD)

& Near-ZLD

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Recovery (%)

Rela

tive O

pera

tin

g C

ost

of

Tre

atm

en

t

Rela

tive B

rin

e D

isp

osal

Co

st

Emerging

Technologies

Moderate - High

Moderate

Water Recovery and

Associated Costs

Relative Desalination Costs

Process Capital Cost

$/GPD

O&M Cost

$/kgal

Water Cost

$/kgal

($/m3)

Nanofiltration 1.00 – 1.30 0.40 – 0.70 0.60 – 1.00

(0.16 – 0.26)

Brackish water

Reverse Osmosis 1.20 – 2.50 0.80 – 1.50

1.50 – 3.00

(0.40 – 0.80)

Seawater Reverse

Osmosis 3.50 – 5.00 2.00 – 4.00

2.50 – 7.00

(0.66 – 1.85)


GPD – gallon/day

kgal – 1,000 gallon




Seawater Reverse Osmosis

Desalination Plants

Adapted from: Global Water Intelligence (2010)

1.45

1.19

0.76 0.7 0.72

0.52 0.57 0.66

0.78

0.57

0.73

1.04 1.13

0.93

0.59 0.54

Bahamas Dhekelia Larnaca Taweelah Trinidad Ashkelon Tuas TampaBay

Skikda Hadera Cap Dijnet Chennai ShuweihatII

Ad Dur Tenes Soreq

Wate

r P

ric

e (

$/m

3)

Cost difference:

• Energy cost

• Concentrate management

• Project cost (engineering, permitting, etc.)

• Tax credits and other financial costs/incentives

• Size

Pre-treatment Removal of:

Suspended solids or emulsions

Microorganisms

Organic matter

Specific ions (iron, calcium, magnesium, silica, etc.)

Pre-treatment and Desalination

for Potable Reuse

Energy Recovery

Pressure Exchangers

ERI (Energy Recovery Inc.)

Pressure Exchangers

DWEER (Dual Work Exchange Energy Recovery)

Clark Pump

Desalitech CCD (Closed Circuit Desalination)

From: R. J. Aaberg, Osmotic power - A new and powerful renewable energy source, ReFocus, 4 (2003) 48-50

Osmotic Power Energy Recovery:

Pressure Retarded Osmosis

Concentrate Management

Coastal

Ocean outfall

Inland

Surface discharge (bad!)

Sewer disposal (not good!)

Deep well injection

Land application/dust control

Zero liquid discharge (ZLD) (crystallization, expensive…)

Pipeline to ocean (not common)

Future Technologies (?)

Other Desalination Technologies:

Membrane Distillation

Heated aqueous feed solution is

brought into contact with the feed side

of a hydrophobic, microporous

membrane

Colder water or gas is in contact with

the distillate side of the membrane

Vapors diffuse through the pores and

condense in the colder stream

adapted from: http://www.water-technology.net/


Humidification-Dehumidification






“water chip”

In summary…

Desalination is used for salt removal, but also for purification

of water and removal of other contaminants

Development of new membranes focuses on increasing

water flux, increasing solute rejection, and increasing

chemical resistance of membranes

Reverse osmosis is a core process to enable potable water

reuse

Desalination (especially reverse osmosis) is affordable and

provides a reliable source of potable water; and efficient

energy recovery makes it possible

Brine management is a prevailing problem, especially at

inland installations, and it drives development of high-

recovery desalination (ZLD)

Thank you

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Tzahi Cath, Ph.D.

Ben L. Fryrear Professor and AQWATEC Director

COLORADO SCHOOL OF MINES

Department of Civil and Environmental Engineering

1500 Illinois St., Golden, Colorado 80401-1887

Office: 303.273.3402

Cath URL: http://inside.mines.edu/~tcath/

AQWATEC URL: http://aqwatec.mines.edu/

ERC ReNUWIt URL: http://urbanwatererc.org/

CEE URL: http://cee.mines.edu/

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

http://inside.mines.edu/~tcath/

http://inside.mines.edu/~tcath/

http://aqwatec.mines.edu/

http://aqwatec.mines.edu/

http://urbanwatererc.org/

http://urbanwatererc.org/

http://cee.mines.edu/

http://cee.mines.edu/

Desalination as a Source of Fresh Water Desalination 101 · Desalination as a Source of Fresh Water Desalination 101 ... and boiling point elevation are examples of ... Membrane Separation

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