(Updated December 2013)
- Potable water is in short supply in many parts of the world. Lack of it is set to become a constraint on development in some areas.
- Nuclear energy is already being used for desalination, and has the potential for much greater use.
- Nuclear desalination is generally very cost-competitive with using fossil fuels.
It is estimated that one-fifth of the world's population does not have access to safe drinking water, and that this proportion will increase due to population growth relative to water resources. The worst-affected areas are the arid and semiarid regions of Asia and North Africa. A UNESCO report in 2002 said that the freshwater shortfall worldwide was then running at some 230 billion m3/yr and would rise to 2000 billion m3/yr by 2025. Wars over access to water, not simply energy and mineral resources, are conceivable.
Fresh water is a major priority in sustainable development. Where it cannot be obtained from streams and aquifers, desalination of seawater or mineralised groundwater is required. An IAEA study in 2006 showed that 2.3 billion people live in water-stressed areas, 1.7 billion of them having access to less than 1000 m3 of potable water per year. With population growth, these figures will increase substantially. Further demand in the longer term will come from the need to make hydrogen from water.
Water can be stored, while electricity at utility scale cannot. This suggests two synergies with base-load power generation for electrically-driven desalination: undertaking it mainly in off-peak times of the day and week, and load-shedding in unusually high peak times.
Most desalination today uses fossil fuels, and thus contributes to increased levels of greenhouse gases. Total world capacity in mid-2012 was 80 million m³/day (29,200 GL/yr) of potable water, in some 15,000 plants. A majority of these are in the Middle East and north Africa. The largest plant – the $3.8 billion Al-Jubail 2 in Saudi Arabia – has 948,000 m3/day (346 GL/yr) MED-TVC capacity, plus 2745 MWe power generation using gas turbines. The Saudi Saline Water Conversion Corporation (SWCC) takes about 62% of output to supply Riyadh. Two-thirds of the world capacity is processing seawater, and one third uses brackish artesian water. New plants with total capacity of 6 million m3/d are expected to come on line in 2013, according to the International Desalination Association.
The major technology in use and being built today is reverse osmosis (RO) driven by electric pumps which pressurise water and force it through a membrane against its osmotic pressure*. This accounted for 60% of 2011 world capacity. A thermal process, multi-stage flash (MSF) distillation process using steam, was earlier prominent and it is capable of using waste heat from power plants. It accounted for 26% of capacity in 2011. With brackish water, RO is much more cost-effective, though MSF gives purer water than RO. A minority of plants use multiple-effect distillation (MED – 8% of world capacity) or multi-effect vapour compression (MVC) or a combination of these, eg MED-TVC with thermal vapour compression. MSF-RO hybrid plants exploit the best features of each technology for different quality products.
* About 27 Bar, 2700 kPa. Therefore RO needs compression of much more than this.
Desalination is energy-intensive. Reverse Osmosis needs up to 6 kWh of electricity per cubic metre of water (depending on both process and its original salt content), though the latest RO plants such as in Perth, Western Australia, use 3.5 kWh/m3, or 4 kWh/m3 including pumping for distribution. Hence 1 MWe continuous will produce about 4000 to 6000 m3 per day from seawater. MSF and MED require heat at 70-130°C and use 25-200 kWh/m³, though a newer version of MED (MED-MVC) is reported at 10 kWh/m3 and competitive with RO. A variety of low-temperature and waste heat sources may be used, including solar energy, so the above kilowatt-hour figures are not properly comparable. For brackish water and reclamation of municipal wastewater RO requires only about 1 kWh/m3. The choice of process generally depends on the relative economic values of fresh water and particular fuels, and whether cogeneration is a possibility.
Forward osmosis (FO) may be used in conjunction with a subsequent process for desalination. The FO draws water through a membrane from a feed solution into a more concentrated draw solution, which is then desalinated without the problems of fouling, such as often encountered with simple RO. FO plants operate in Gibraltar and Oman.
Some 10% of Israel's water is desalinated, and one large RO plant provides water at 50 cents per cubic metre. It claimed to have the world’s largest seawater RO plant as of late 2013, at Soreq. Malta gets two-thirds of its potable water from RO, and this takes 4% of its electricity supply. Singapore in 2005 commissioned a large RO seawater desal plant supplying 136,000 m3/day – 10% of needs, at 49 cents US per cubic metre, and in 2013 commissioned a 318,500 m3/d RO plant on a build-own-operate basis, costing US$ 700 million, to provide water at US 36 cents/m3. Desalinated seawater will now provide 25% of Singapore's water, as one of the island state's Four National Taps, along with local catchment water, imported water, and NEWater, Singapore's own recycled wastewater.
Saudi Arabia in 2011 obtained 3.3 million m3/d from 27 government-owned (SWCC) seawater desalination plants, 70% of the country’s requirements. Twelve plants, accounting for most of production, use multi-stage flash distillation (MSF) and 7 plants use multi-effect distillation (MED), in both cases the plants are integrated with power plants (cogeneration plants), using steam from the power generation as a source of energy for desalination. Eight plants are single-purpose plants that use reverse osmosis (RO) technology and power from the grid. The UAE is heavily dependent on seawater desalination, much of it with cogeneration plants. Algeria in mid 2013 had 2.1 million m3/d capacity and another 400,000 m3/d is envisaged.
In February 2012 China's State Council announced that it aimed to have 2.2 to 2.6 million m3/day seawater desalination capacity operating by 2015.
Small and medium sized nuclear reactors are suitable for desalination, often with cogeneration of electricity using low-pressure steam from the turbine and hot seawater feed from the final cooling system. The main opportunities for nuclear plants have been identified as the 80-100,000 m³/day and 200-500,000 m³/day ranges. US Navy nuclear powered aircraft carriers reportedly desalinate 1500 m3/d each for use onboard.
A 2006 IAEA report based on country case studies showed that costs would be in the range ($US) 50 to 94 cents/m3 for RO, 60 to 96 c/m3 for MED and $1.18 to 1.48/m3 for MSF processes, with marked economies of scale. Nuclear power was very competitive at today's gas and oil prices. A French study for Tunisia compared four nuclear power options with combined cycle gas turbine and found that nuclear desalination costs were about half those of the gas plant for MED technology and about one third less for RO. With all energy sources, desalination costs with RO were lower than MED costs.
The Kwinana desalination plant near Perth, Western Australia, has been running since early 2007 and produces about 140,000 m3/day (45 GL/yr) of potable water, requiring 24 MWe of power for this, hence 576,000 kWh/day, hence 4.1 kWh/m3 overall, and about 3.7 kWh/m3 across the membranes. The plant has pre-treatment, then 12 seawater RO trains with capacity of 160,000 m3/day which feed six secondary trains producing 144,000 m3/day of water with 50 mg/L total dissolved solids. The cost is estimated at A$ 1.20/m3. Discharge flow is about 7% salt. Future WA desalination plants will have more sophisticated pre-treatment to increase efficiency. In August 2011 the state government decided to double the size of its new Southern Water Desal Plant at Binningup plant near Perth to 100 GL/yr, taking the cost to about $1.45 billion. Stage 1 of 50 GL/yr was within the A$ 955 million budget.
At the April 2010 Global Water Summit in Paris, the prospect of desalination plants being co-located with nuclear power plants was supported by leading international water experts.
Complementary wastewater treatment for irrigation
In the Middle East, a major requirement is for irrigation water for crops and landscapes. This need not be potable quality, but must be treated and with reasonably low dissolved solids.
In Oman, the 76,000 m3/day first stage of a submerged membrane bioreactor (SMBR) desalination plant was opened in 2011. Eventual plant capacity will be 220,000 m3/day. This is a low-cost wastewater treatment plant using both physical and biological processes and which produces effluent of high-enough quality for some domestic uses or reinjection into aquifers.
Desalination: nuclear experience
The feasibility of integrated nuclear desalination plants has been proven with over 150 reactor-years of experience, chiefly in Kazakhstan, India and Japan. Large-scale deployment of nuclear desalination on a commercial basis will depend primarily on economic factors. Indicative costs are US$ 70-90 cents per cubic metre, much the same as fossil-fuelled plants in the same areas.
One obvious strategy is to use power reactors which run at full capacity, but with all the electricity applied to meeting grid load when that is high and part of it to drive pumps for RO desalination when the grid demand is low.
The BN-350 fast reactor at Aktau, in Kazakhstan, successfully supplied up to 135 MWe of electric power while producing 80,000 m³/day of potable water over some 27 years, about 60% of its power being used for heat and desalination. The plant was designed as 1000 MWt but never operated at more than 750 MWt, but it established the feasibility and reliability of such cogeneration plants. (In fact, oil/gas boilers were used in conjunction with it, and total desalination capacity through ten MED units was 120,000 m³/day.)
In Japan, some ten desalination facilities linked to pressurised water reactors operating for electricity production yield some 14,000 m³/day of potable water, and over 100 reactor-years of experience have accrued. MSF was initially employed, but MED and RO have been found more efficient there. The water is used for the reactors' own cooling systems.
India has been engaged in desalination research since the 1970s. In 2002 a demonstration plant coupled to twin 170 MWe nuclear power reactors (PHWR) was set up at the Madras Atomic Power Station, Kalpakkam, in southeast India. This hybrid Nuclear Desalination Demonstration Project (NDDP) comprises a reverse osmosis (RO) unit with 1800 m3/day capacity and a multi-stage flash (MSF) plant unit of 4500 m³/day costing about 25% more, plus a recently-added barge-mounted RO unit. This is the largest nuclear desalination plant based on hybrid MSF-RO technology using low-pressure steam and seawater from a nuclear power station. They incur a 4 MWe loss in power from the plant.
In 2009 a 10,200 m3/day MVC (mechanical vapour compression) plant was set up at Kudankulam to supply fresh water for the new plant. It has four stages in each of four streams. An RO plant there supplied the plant's township initially. The full MVC plant is being commissioned in mid 2012, with quoted capacity of 7200 m3/day to supply the plant’s primary and secondary coolant and the local town. Cost is quoted at INR 0.05 per litre (USD 0.9/m3).
A low temperature (LTE) nuclear desalination plant uses waste heat from the nuclear research reactor at Trombay has operated since about 2004 to supply make-up water in the reactor.
Pakistan in 2010 commissioned a 4800 m3/day MED desalination plant, coupled to the Karachi Nuclear Power Plant (KANUPP, a 125 MWe PHWR) near Karachi. It has been operating a 454 m3/day RO plant for its own use.
China General Nuclear Power (CGN) has commissioned a 10,080 m3/day seawater desalination plant using waste heat to provide cooling water at its new Hongyanhe project at Dalian in the northeast Liaoning province.
Much relevant experience comes from nuclear plants in Russia, Eastern Europe and Canada where district heating is a by-product.
Large-scale deployment of nuclear desalination on a commercial basis will depend primarily on economic factors. The UN's International Atomic Energy Agency (IAEA) is fostering research and collaboration on the issue.
Small nuclear reactors suitable for desalination
SMART: South Korea has developed a small nuclear reactor design for cogeneration of electricity and potable water. The 330 MWt SMART reactor (an integral PWR) has a long design life and needs refuelling only every 3 years. The main concept has the SMART reactor coupled to four MED units, each with thermal-vapour compressor (MED-TVC) and producing total 40,000 m3/day, with 90 MWe.
CAREM: Argentina has designed an integral 100 MWt PWR suitable for cogeneration or desalination alone, and a prototype in being built next to Atucha. A larger version is envisaged, which may be built in Saudi Arabia.
NHR-200: China's INET has developed this, based on a 5 MW pilot plant.
Floating nuclear power plant (FNPP) from Russia, with two KLT-40S reactors derived from Russian icebreakers, or other designs for desalination. (If primarily for desalination the twin KLT-40 set-up is known as APVS-80.) ATETs-80 is a twin-reactor cogeneration unit using KLT-40 and may be floating or land-based, producing 85 MWe plus 120,000 m3/day of potable water. The small ABV-6 reactor is 38 MW thermal, and a pair mounted on a 97-metre barge is known as Volnolom floating NPP, producing 12 MWe plus 40,000 m3/day of potable water by reverse osmosis. A larger concept has two VBER-300 reactors in the central pontoon of a 170 m long barge, with ancillary equipment on two side pontoons, the whole vessel being 49,000 dwt. The plant is designed to be overhauled every 20 years and have a service life of 60 years. Another design, PAES-150, has a single VBER-300 unit on a 25,000 dwt catamaran barge.
See also: Small Nuclear Power Reactors paper.
New desalination projects
Algeria has undertaken a study on nuclear power generation and desalination using RO and MED. The 500,000 m3/d Magtaa seawater RO desal plant at Oran costing $632 million was commissioned in 2012, following the 120,000 m3/d Fouka seawater RO desal plant at Tipaza near Algiers in 2011, costing $185 million. The country is also considering MSF desalination for two new plants in addition to the 91,000 m3/d Arzew MSF plant now operating.
Australia: In Victoria, a 450,000 m3/day (150 GL/yr) RO desalination plant near Wonthaggi built by Degremont has been commissioned to supply Melbourne. It claims to use renewable energy, and is expandable to 200 GL/yr.
Adelaide's 100,000 m3/d (36 GL/yr) plant started operation in 2011, with plans to expand it to 100 GL/yr. A 200 - 280,000 m3/d desalination plant to serve the expanded Olympic Dam mine in South Australia has environmental approval but now may not proceed.
Perth has two RO seawater desal plants, a 45 GL/yr one (A$ 387 million) completed in 2006 powered by a wind farm, and a 100 GL/yr one powered by 65 MWe of dedicated renewable energy, which together provide half the city’s needs. Following extensive trials, the city plans a groundwater replenishment scheme from treated wastewater which is expected to be half the cost and use half the energy of seawater desalination. It will include a new Advanced Water Recycling Plant and provide 7 GL/yr from 2016 and 28 GL/yr eventually about 2022.
Chile: BHP Billiton and Rio Tinto plan a $3.43 billion, 216,000 m3/day (79 GL/yr) seawater desal plant with pipes and pumps for their Escondida copper mine, which is 3100 m above sea level and 150 km inland. It will require over 1000 MWe from the grid for desal alone and be commissioned in 2017.
China is looking at the feasibility of a nuclear seawater desalination plant in the Yantai area of Shandong Peninsula, producing 80-160,000 m3/day by MED process, using a 200 MWt NHR-200 reactor. A 100,000 m3/d seawater RO plant supplied by Abengoa of Spain started operating early in 2013 at Qingdao in Shandong province. Another project is for a 330,000 m3/day plant near Daya Bay.
A 50,000 m3/day Aqualyng plant was completed in October 2011 at Caofeidian in Hebei province. A second stage will double this in 2012, and possibly lead to a 1 million m3/d set up, or maybe three times this, to supply Beijing through a 230 km pipeline.
In March 2013 the National Development and Reform Commission announced new plans for seawater desalination, including for the cities of Shenzhen and Zhoushan, Luxixiang Island in Zhejiang Province, Binhai New Area in Tianjin, Bohai New Area in Hebei, and several industrial parks and companies. The cost is likely to be some CNY 21 billion ($3.35 billion). China aims to produce 2.2 million m3/day of desal water by 2015, more than three times the 2011 level. More than half of the freshwater channelled to islands and more than 15% of water delivered to coastal factories will come from the sea by 2015, according to the plan.
Egypt has undertaken a feasibility study for a cogeneration plant for electricity and potable water at El-Dabaa, on the Mediterranean coast. In 2010 plans were being formed for four 1000 MWe-class reactors to be built there and coming on line 2019-25, with significant desalination capacity.
Egypt's largest desalination plant, 24,000 m3/day RO, being built at Marsa Matrouh in the northwest is to be supplied with Pressure Exchanger (PX) energy-recovery devices by Energy Recovery Inc of California. The first of four modules is due to start in 2013.
Ghana has contracted with Abengoa to build a 60,000 m3/day seawater RO plant at Nungua. The $125 million contract overs operation and maintenance for 25 years.
In India, further plants delivering 45,000 m3 per day are envisaged, using both MSF and RO desalination technology, and building on the extensive experience outlined above. The 100,000 m3/d Nemmeli desalination plant is due for completion in December 2011, and a 200,000 m3/d plant is planned for Pattipulam nearby, both serving Chennai.
Indonesia: South Korea investigated the feasibility of building a SMART nuclear reactor with cogeneration unit employing MSF desalination technology for Madura Island, and later studies have been on larger-scale PWR cogeneration in Batan.
Iran: A 200,000 m³/day MSF desalination plant was designed for operation with the Bushehr nuclear power plant in Iran in 1977, but appears to have lapsed due to prolonged construction delays.
Iraq: Basrah has 400,000 m3/d desalination for saline river water, and a Hitachi-led consortium is building a new 199,000 m3/d RO plant there, for completion in 2016.
Israel’s 624,000 m3/d seawater RO plant at Soreq is operational from October 2013.
Jordan has a "water deficit" of about 1.4 million m3 per day and is actively looking at nuclear power to address this, as well as supplying electricity.
Kuwait has been considering cogeneration schemes up to a 1000 MWe reactor coupled to a 140,000 m3/day desalination plant. Meanwhile it has a $1.4 billion contract with Hyundai and a Veolia subsidiary to build the Az-Zour North gas-fired combined cycle 1500 MWe power plant and 486,000 m3/d MED plant. It will account for about 10% of Kuwait’s power capacity and 20% of its desal capacity from 2016.
Libya: in mid 2007 a memorandum of understanding was signed with France related to building a mid-sized nuclear plant for seawater desalination. Areva TA would supply this. Libya is also considering adapting the Tajoura research reactor for a nuclear desalination demonstration plant with a hybrid MED-RO system.
Mexico has awarded a contract for the 21,000 m3/day El Salitral plant to be in operation from the end of 2013.
Morocco has completed a pre-project study with China, at Tan-Tan on the Atlantic coast, using a 10 MWt heating reactor which produces 8000 m3/day of potable water by distillation (MED). The government has plans for building an initial nuclear power plant in 2016-17 at Sidi Boulbra, and Atomstroyexport is assisting with feasibility studies for this.
Oman commissioned a 45,460 m3/d seawater RO plant at Barka in November 2013, built under a BOO contract, expanding an existing facility. Another BOO project is Al Ghubrah, a 190,000 m3/d RO plant with commercial operation from Sept 2014. The Salalah plant was opened in May 2013 - a 69,000 m3/d seawater desal plant with 445 MWe gas-fired generation.
Qatar has been considering nuclear power and desalination for its needs which reached about 1.3 million m3/day in 2010. The Ras Abu Fontas A2 160,000 m3/d seawater desal plant has been contracted to Mitsubishi.
Russia: A new 10,000 m3/d seawater RO plant is being built offshore near Vladivostok, for commissioning over 2011-12. It is designed for severe climatic conditions.
Saudi Arabia has contracted with Doosan to build a 68,000 m3/day MED plant in its Yanbu region, the $80 million Yanbu 2 plant. It will be the world's largest MED plant and due for completion early in 2014. Doosan will also build Yanbu 3, a 550,000 m3/day MSF plant due for completion in 2016.
The largest thermal desalination plant is Saudi Arabia’s 880,000 m³/d Shoaiba 3 plant, although this will be displaced in 2014 as the largest plant in the world by the 1,025,000 m³/d Ras Al Khair (Ras Azzour) MSF project in Saudi Arabia, which uses both membrane and thermal technology, built by Doosan. Veolia has a $402 million contact to build a 178,600 m3/d ultrafiltration and RO plant for Marafiq at the $19.3 billion Sadara petrochemical complex, to come on line in mid 2015. The water will be for two cooling towers and as boiler feed water.
The first of three phases of the King Abdullah Solar water initiative is expected to be operating by the end of 2013. Phase 1 involves construction of two solar plants which will generate 10 MW of power for a 30,000 m³/d reverse-osmosis (RO) desalination plant at Al Khafji, near the Kuwait border. Phase 2 will involve construction of a 300,000 m³/d desalination plant over three years. The third phase aims to implement the solar water initiative throughout Saudi Arabia, with the eventual target of seeing all the country's desalination plants powered by solar energy by 2020. One of the main objectives of this initiative under King Abdullah City for Science & Technology (KACST) is to desalinate seawater at a cost of less than Riyal 1.5/m³ (US$ 0.40/m³) compared with the current cost of thermal desalination, which KACST says is in the range Riyal 2.0-5.5/m³ (US$ 0.53-1.47/m³), and desalination by RO, which is Riyal 2.5-5.5/m³ (US$ 0.67-1.47/m³) for a desalination plant producing 30,000 m³/d.
Singapore: The 318,500 m3/d Tuaspring RO plant was commissioned in 2013 as the second desal plant.
South Africa: Veolia is building a 1700 m3/d seawater desal plant at Lamberts Bay, Cederberg municipality, upgradable to5000 m3/d. This will be the seventh plant along the west and south Cape coasts installed by Veolia.
Spain is building 20 RO plants in the southeast to supply over 1% of the country's water. Spain has 40 years of desalination experience in the Canary Islands, where some 1.1 million m3/day is provided.
Tunisia is looking at the feasibility of a cogeneration (electricity-desalination) plant in the southeast of the country, treating slightly saline groundwater.
The UAE is planning a 68,000 m3/d plant at Ras Al Kaimah. Sembcorp is expanding the Fujairah 1 136,000 m3/d RO plant, to bring its UAE capacity to 591,000 m3/d of which 307,000 is RO and 284,000 m3/d is MSF. Also the Shuweihat S2 IPP and seawater desal plant at Al Ruwais started full operation in 2011 and provides 1510 MWe and 454,000 m3/d by MSF. The Fujairah 2 plant is hybrid SWRO-MED and produces 454,600 m3/d. The Taweelah A1 cogeneration plant produces 1430 MWe and 385,000 m3/day and Umm Al Nar produces 394,000 m3/day.
In Dubai the Jebel Ali M cogeneration plant opened in 2013 with 6x243 MWe gas turbines and 8 MSF units providing 640,000 m3/d. Earlier, Dubai invited bids for constructing a 450,000 m3/d (165 GL/yr) seawater desalination plant as part of its Hassyan independent power project, but then announced its deferral.
In the UK, a 150,000 m3/day RO plant is proposed for the lower Thames estuary, utilising brackish water.
USA-Mexico: The 375,000 m3/day Rosarito seawater plant in Baja, California, is to supply potable water on both sides of the border.
USA: San Antonio, Texas, is building a 95,000 m3/day brackish water desal plant. A 189,000 m3/d salt water desal plant is planned for Carlsbad, NM.
Most or all these have requested technical assistance from IAEA under its technical cooperation project on nuclear power and desalination. A coordinated IAEA research project initiated in 1998 reviewed reactor designs intended for coupling with desalination systems as well as advanced desalination technologies. This programme, involving more than 20 countries, is expected to enable further cost reductions of nuclear desalination.
Other CO2-free desalination
Renewable energy sources are able to be used for desalination more readily than for most electricity supply, since the product can be stored on any scale, unlike electricity. Also electricity can be borrowed from the grid and repaid when the wind is blowing or the sun shining. A 45 GL/yr RO plant at Perth, Western Australia is powered by electricity ostensibly from a wind farm. A new 100 GL/yr RO plant is powered by 65 MWe of dedicated renewable energy (10 MWe solar PV, 55 MWe wind).
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