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Desalinated Water

The 4th National Tap

As Singapore is surrounded by sea, PUB has turned seawater into drinking water. And we continue to research better desalination technology to find even cheaper ways of desalting water.

Currently, we have two desalination plants with a combined capacity of 100 mgd that can meet up to 25% of Singapore’s current water demand. Three more desalination plants will be ready by 2020.

Desalinated water is expected to meet up to 30% of Singapore’s future water needs by 2060.  

SingSpring Desalination Plant

The 1st Desalination Plant

In September 2005, Singapore turned on its Fourth National Tap - Desalinated Water, with the opening of the SingSpring Desalination Plant in Tuas. A wholly owned subsidiary of Hyflux, SingSpring won a bid to construct a desalination plant under PUB’s design, build, own and operate (DBOO) model. This plant with a daily capacity of up to 30 million gallons (130,000 m3) of water supplies PUB with desalination water over a 20-year period. 

SingSpring Desalination Treatment

(Click on image for an enlarged view)

SingSpring Desalination Plant Treatment Process 

  

Tuaspring Desalination Plant

The 2nd Desalination Plant

With a daily capacity of up to 70 million gallons (or 318,500 m3 ) of water, Tuaspring Desalination Plant supplies PUB with desalinated water over a 25-year period.  

Tuaspring Desalination Treatment

(Click on image for an enlarged view)Tuas Spring Desalination Plant Treatment Process

Part 1: Intake Screening
As seawater flows into the plant, sediments like seaweed and other large debris are removed via mechanical screens. Chlorine is added to hamper marine growth in pipes and other structures in the system.

Part 2: Pre-treatment (Ultrafiltration)
The ultra-filtration membranes remove impurities, microorganisms and bacteria in water, which can foul the downstream reverse osmosis system.

Part 3: Reverse Osmosis
Reverse osmosis is a critical step in the desalination of seawater. After removal of impurities and suspended particles, water is pumped through the semi-permeable membranes at high pressure. Only water molecules can pass through the membranes at this stage.

Finally, after reverse osmosis, the water is re-mineralised and stored in PUB's service reservoir before it is distributed to homes.

PM Lee at Tuas Spring Desalination Plant Opening
Prime Minister Lee Hsien Loong officially opens Tuaspring Desalination Plant, Singapore's second and largest desalination plant From left: Permanent Secretary (MEWR) Choi Shing Kwok, PUB Chairman Tan Gee Paw, Minister for the Environment and Water Resources Vivian Balakrishnan, Prime Minister Lee Hsien Loong, 2nd Minister for the Environment and Water Resources Grace Fu, PUB Chief Executive Chew Men Leong, and Hyflux Executive Chairman and Group CEO Olivia Lum.


        

 
 
Researching for Low-energy Desalination

Singapore currently uses reverse osmosis for its desalination, which uses about 3.5kWh/m3. This process produces pure drinking water by pushing seawater through membranes to remove dissolved salts and minerals. 

Moving ahead, we are looking at exploring low-energy desalination to ensure the sustainability of Desalinated Water. PUB's goal is to halve the desalination energy used in the future.

Electro-deionisation

Electro-deionisation is a method that uses an electric field to pull dissolved salts from water. Plans are put in place to scale up the technology and demonstrate it at a 3,800 m3/day facility in Tuas.  

Biomimicry

The mimicking of biological processes by which mangrove plants and euryhaline fish extract freshwater from seawater using small amount of energy.