Water desalination:

status, technology,

challenges,

and potential Noam Lior

Life Fellow ASME, Assoc. Fellow AIAA Editor-in-Chief, Advances in Water Desalination

Board of Editors Member:

Desalination, The International Journal of Desalting and Water Purification,

Desalination and Water Treatment – Science and Engineering .

The International Desalination & Water Reuse Quarterly, 1997-2003.

Chair, Scientific Committee, International Centre for Sustainable Development of Energy, Water and Environment Systems

Professor of Mechanical Engineering and Applied Mechanics

University of Pennsylvania,

Philadelphia, PA 19104, USA

lior@seas.upenn.edu

http://www.seas.upenn.edu/~lior/

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The water problem and

New Water

Rising population, standards of living and water pollution are diminishing the amounts of naturally available fresh water of good quality while the demand is increasing relentlessly

"Manufactured water" or is making a considerable contribution to the world's potable, industrial, and agricultural water supply.

The technology is improving in cost-performance

and reliability

Desalination processes remain energy intensive and are polluting, needing strong and rapid development

It is increasingly recognized that desalination must be

performed sustainably 2

Noam Lior

The major desalination methods

Distillation (2/3 of market)

multistage flash (MSF; heat)

multi-effect (ME; heat)

vapor compression (VC; mechanical power)

Membrane distillation (MD; temperature (heat), under development)

Membrane Separation (1/3 of market)

Reverse Osmosis (RO, pressure)

Electrodialysis (ED, electrical potential)

Membrane distillation (MD, temperature (heat), under development)

Forward osmosis (FO, under development)

Ion exchange (IE, adsorption, for low salinity waters;

mechanical power)

Freezing (mechanical power and cooling) 3

Noam Lior

Some Desalination Statistics

~ 15,000 large plants

Largest plant (2009?): 880,000 m3/day + 900 MW electricity, Shuaiba III, Saudi Arabia.

A large dual purpose plant (1997): 341,000 m3/day (75 MIGD) multi-stage flash (MSF) Al Taweelah B in Abu Dhabi, United Arab Emirates; dual-purpose plant, produces also 732 MWe of power.

Producing ~65 million m3/d total, globally 0.6% of total or ~3% of municipal/domestic use, abstracted water

$0.54 - 1.4 - 3/m3 (<1 for brackish water)

1,700 manufacturing companies

Global online desalination capacity

FIGURE 2-2. Global online desalination capacity.

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Noam Lior

Global online desalination capacity

Water desalination contracted and

commissioned desalted water capacity

Global Water Intelligence Report 6

o GWI DesalData 2010

Report predicts that

total contracted

capacity will reach

129.9 million m³/d by

the end of 2016.

o Capital expenditure

on desalination is

predicted to rise from

$6 billion in 2010 to

$18.3 billion by 2016.

Noam Lior

Annual new contracted and commissioned capacity

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Total worldwide installed

capacity by user type

Noam Lior

Feedwater trends

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Technology trends

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Annual new contracted seawater

desalination capacity by technology

Noam Lior

Desalination top contractors

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Top 20 EPC contractors since 2000

Top 10 desalination plant

suppliers since 2000 - now

and four years ago

EPC: Engineering, Procurement and Construction

Noam Lior

Unique challenges of water desalination

Internal: The extremely low price of the product, down to $0.5/ton

now

Corrosiveness of the saline water

Scaling (deposition of precipitates)

Organic fouling

Effect of gases

External: Environmental impact

Some health concerns (preventable) 11

Noam Lior

Desalination Plant

Security

Ingestion into the plant of contaminated saline water feed (oil spills, heavy metals, etc.) affect both product and plant

To avert consequences of poor regional management, accidents, war, and terrorism, it is vitally important to design the plant with robust safeguards against ingestion of undesirably

contaminated saline water

ensure that regional resources' management prevents such contamination

provide for adequate fresh water storage, and

provide adequate plant security.

Kuwait 1991

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Noam Lior

Dual-Purpose plants: synergetic

generation of power and desalination of water

The most economical large scale thermal water desalination systems are dual purpose plants that simultaneously produce electricity and typically MSF (Multi-Stage Flash distillation) seawater distillation.

The original dual purpose plants used a Rankine steam power plant for generating electricity, the turbine of which (having an inlet temperature 500-600 °C) was backpressure or extraction for supplying the heat to the desalination plant.

Higher efficiency and better economics were obtained in later generation systems using a topping gas turbine (inlet temperature ~1200 °C) with a bottoming back-pressure or extraction steam turbine in a combined cycle.

While the prevalent heat source for dual purpose plants is gas or oil, any heat source of sufficient temperature, such as solar, geothermal, nuclear or some type of “waste heat” can be used

RO water desalination plants are currently more efficient than thermal distillation ones, and they use electricity, not heat.

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Noam Lior

DESERTEC: An exciting

plan to solar-generate

electricity in Middle East

and North Africa (MENA)

and transmit it for use in

Europe and MENA, and

also desalt water for

MENA (originally

recommended by the Club

of Rome; from 2009 led by

DII GmbH, an association

of 12 companies,

predominantly German)

14 http://www.dlr.de/tt/trans-csp Noam Lior

ENVIRONMENTAL IMPACTS

All components of the water use cycle

should be considered

source water impacts,

the likely greenhouse and other polluting

gas emissions from the energy

requirements of the desalination process,

embodied materials emissions

potential impacts from concentrate

management approaches,

environmental health considerations in the

product water 15

Noam Lior

Practical energy demand of

desalination plants

R. Semiat, Energy Issues in Desalination Processes. Environmental Science & Technology, Vol. 42,

No. 22, 8193-8201, 2008.

Assuming ηt = 45%

tons of produced fresh waterGained Output Ratio = GOR =

ton of used heating steam

Dual purpose plants (thermal) consume (5.2 to 9.5 kWh exergy)/(m3 produced fresh water)

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Noam Lior

Price of

desalted

water Prices are site and

situation specific

depend much on

government

financing and

subsidies

Depend much on

cost of energy and

its strong

fluctuations

Proper payment for

externalities

In comparison,

municipal water

prices are between

0 and ~$4/m3,

usually < ~$1m3

SW RO SW MSF SW MED

Annualized capital

costs

0.15 0.29 0.22

Parts/maintenance 0.03 0.01 0.01

Chemicals 0.07 0.05 0.08

Labor 0.10 0.08 0.08

Membranes (life not

specified)

0.03 0.00 0.00

Thermal energy 0.00 0.27a 0.27a

Electrical energy

($0.05 k/Wh)

0.23 0.19 0.06

Total ($/m3) 0.61 0.89 0.72 a The costs of thermal energy are likely exaggerated because

offpeak electricity costs, cogeneration, or the use of waste

energy are not considered in this analysis.

SOURCE: GWI (2006a).

Comparative Total Cost Data for the Desalination

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Noam Lior

The new imperative: sustainable desalination The past goal was to produce water reliably at a low enough cost, where

the cost is unfortunately still in many cases based primarily on capital investment in the plant, operating costs for energy, materials and labor, and profit if a private company produces the water.

Desalination based on this approach has recently come under strong criticisms for being unsustainable, and for creating long-term problems which are not considered in the costing and the choice of the entire process, e.g.: Unrealistically low pricing of the energy, as done in many oil-rich countries

Unrealistically low pricing of the water, as done in many countries

Little care of the effluents, which contain highly concentrated seawater (also warm in distillation plants) that may have even far-reaching effects on oceans, various additives that are harmful to the environment and health, heavy metals, as well as the driving power plant emissions

Damage to the eco-system at the plant intake

Desalination allows the development of new regions, which may be unsustainable to begin with.

Legislation already exists in some places about restricting/penalizing such unsustainable attributes, and is likely to results in at least a real added cost (but that is insufficient because the cost is in captive markets likely to simply be passed along to the customer while the abuse continues).

There is urgent need to implement well-analyzed sustainable desalination; also an opportunity to introduce new processes and products to that end.

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Noam Lior

Conclusions, Recommendations,

and Predictions (1/2)

Desalination is vitally important for water-stressed regions that

can not import fresh water and is an important supplement

elsewhere

In reverse osmosis the energy demand has remarkably been

reduced close to the thermodynamic limits, and innovations in

distillation process are leading to lower energy demand

Important goals for desalination in general:

Water cost reduction: reduce plant, supplies and externalities costs and

increase energy efficiency

robustness improvement

developing lower cost, higher life and less polluting materials

understanding the environmental impacts of desalination and developing

approaches to minimize these impacts relative to other water supply

Developing and adopting a rigorous overall sustainable

development approach, including water conservation consideration

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Noam Lior

Conclusions, Recommendations,

and Predictions (2/2)

Membrane processes should be improved by mitigating fouling through pretreatment;

developing high-permeability, fouling-resistant, high-rejection, oxidant-resistant, longer life membranes

Distillation processes can be improved by preventing scale deposition at higher temperatures,

better energy regeneration

higher transport coefficients.

Environmental and social impacts must be understood, recognized, and significantly mitigated

R&D is extremely deficient and governments must invest since the industry has shown little interest

Desalination will continue to increase rapidly

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Noam Lior