Tuas Desalination Plant opens, another milestone in Singapore’s water quest

SINGAPORE — Singapore's first desalination plant owned and operated by the Government officially opened on Thursday (June 28).

The Tuas Desalination Plant is the Republic's third and has a capacity of 30 million gallons per day (mgd).

Singapore’s water sustainability came under the spotlight earlier this week when Malaysian Prime Minister Mahathir Mohamad revived a dispute with Singapore over the terms agreed in a 1962 pact.

At the opening ceremony, Minister for the Environment and Water Resources Masagos Zulkifli reiterated that this latest milestone in Singapore's water story "did not come easy". He did not make any reference to Dr Mahathir’s latest remarks.

Mr Masagos said: "Gradually but surely, we will continue to build up the capacity of our desalination and NEWater capacities, so that by 2060, NEWater and desalination can supply a combined 85 per cent of our water needs then."

Desalination, where membranes remove salts and minerals from seawater to produce drinking water, now meets up to 30 per cent of Singapore's water demand.

Singapore currently has five desalination plants, including two still in the works. 

The Tuas Desalination Plant is the third in Singapore. Hyflux clinched contracts for the first two desalination plants, SingSpring and Tuaspring, while an upcoming fourth plant will be owned and operated by Keppel Infrastructure Holdings.  The fifth desalination plant will be built by a Tuas Power-Singapore Technologies Marine consortium.

The opening of the Tuas plant also comes after Hyflux’s financial woes came to light last month. The homegrown water treatment firm’s troubles were partly attributed to the losses it incurred on the Tuaspring project, which it has been trying in vain to sell off.  

Nevertheless, the Government had made the decision in 2015 to own and operate the Tuas Desalination Plant. 

"PUB found that there is a need for us to build that competency in water desalination treatment. And at the same time, having our own plant gives us a platform to implement new ideas, new research and development (R&D) projects," said Mr Bernard Koh, national water agency PUB's director of water supply (plants).

PUB chief executive Ng Joo Hee said the plant could serve as a "real-world testbed" for technologies that could halve the energy needed for desalination, which is currently 3.5kWh per cubic metre.

Indeed, Mr Masagos pointed out: "Desalination is an especially energy-intensive water source and if we continue with business-as-usual, Singapore's desalination energy usage in 2060 will be four times that of today."

Adding that Singapore does not wish to become energy-reliant in its quest to overcome water scarcity, Mr Masagos said PUB is exploring new technologies and the use of cleaner energy to make the desalination process more energy-efficient.

One example he cited was an experiment with electrochemical desalination technology, which has the potential the halve the current energy use in desalination through the use of reverse osmosis, that is being conducted at the plant.

And the development of such low-energy desalination technologies need to be accelerated, he added, making PUB's continual work with its R&D partners critical.

The Tuas Desalination Plant is a "strategic infrastructural asset" that will boost Singapore's desalination capacity from the current 100 mgd to 130 mgd, PUB said in its media release.

Occupying about 3.5 hectares, the plant is one of the most compact in the world and is able to meet the water demand of about 200,000 households.

Construction by HSL Constructor began in November 2015, and the plant began its testing and commissioning at the beginning of this year.

Mr Koh said equipment was stacked "to a certain extent". The plant's compactness could, however, pose challenges during maintenance work, as there is less space between the pipes and equipment, and workers would have limited space to carry out their work.

The new plant is the first that uses advanced pretreatment technology – a combination of dissolved air floatation and ultrafiltration.

Together, they reduce the deposits of impurities on reverse osmosis membranes. The membranes can last for a month before they need to be cleaned, about one to two weeks longer than with the conventional system.

SingSpring plant, which was built in 2005, has only the dissolved air floatation system, while TuaSpring, built in 2013, has only the ultrafiltration system.

In dissolved air floatation, chemicals are introduced into seawater to gather impurities into bigger particles. Fine air bubbles are then injected into the particles, which float and are removed.

During ultrafiltration, seawater passes through semi-permeable membranes that remove impurities, microorganisms and bacteria.

"From SingSpring and TuaSpring, we learned that pretreatment is very important and we combined (the two systems) as the pre-treatment," said Mr Koh.

Advanced pretreatment technology makes the plant more robust — should there be deterioration of seawater quality due to a minor oil spill or algae bloom, the dissolved air floatation system can help to reduce algae count. This helps to preserve the ultrafiltration membranes, which subsequently helps to preserve the membranes used for reverse osmosis.

The Tuas Desalination Plant cost S$217 million, an amount that includes maintenance costs for the first 24 months.

It is also the first desalination plant that will have solar panels on more than half of its roof surface. To be installed by the end of this year, the panels will cover more than 7,000 sq m and meet less than 1 per cent of the plant's needs, which is also equivalent to powering more than 300 four-room flats for a year.

Asked about the environmental impact of the plant, the PUB said an assessment was done. Seawater quality is monitored "very closely" and the brine is released into the open sea.

The fourth and fifth desalination plants in Marina East and Jurong Island are expected to be completed in 2020.