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Online 14 Aug 06
'Harvesting' nearly every drop
90% of Singapore could become water catchment areas with new technology
Tor Ching Li firstname.lastname@example.org
ASK Public Utilities Board (PUB) chairman Tan Gee Paw what's in the pipeline for Singapore's water resources and you'll probably get a flood of information.
For a start, the PUB is working on a new "two-in-one" plant that can treat both freshwater and seawater. Conceived and developed by the PUB, this variable salinity plant can potentially boost Singapore's water catchment area from two-thirds of the island's total surface area to 90 per cent.
Said Mr Tan: "With this plant, the viability of tapping marginal water catchments to produce drinkable water is enhanced and we can convert nearly the whole of Singapore into a water catchment to 'harvest' nearly every drop of rain that falls on Singapore."
And during dry spells, the plant--which has the flexibility to switch from a freshwater to seawater source, and vice versa--can produce drinking water from seawater.
An $8-million demonstration plant that can produce one million gallons of drinking water daily is under construction at Sungei Tampines and is expected to be completed by the end of the year. It will allow the PUB to test the concept and gain operational experience.
The PUB expects the variable salinity plant to produce drinking water even more cheaply than its $200-million seawater desalination plant in Tuas, which produces 30 million gallons of drinking water daily, at 78 cents per cubic metre--already half the production cost of desalinated water elsewhere.
Singapore's daily need for about 300 million gallons of water is met by four reliable sources of water, or "National Taps": Local reservoirs, water from Johor, NEWater and desalinated water.
"Today, our four National Taps are complete ... but we cannot stop there," said Mr Tan. For the past three years, the PUB has been spending $5 million annually on research and development projects--and will continue to do so.
This seed funding--together with other external funding sources such as the Ministry of Environment and Water Resources' Innovation for Environment Sustainability Fund and The Enterprise Challenge Fund--has generated about $50 million worth of R&D projects over the past two years. Among them is the variable salinity plant.
Another is the pilot testing of technology involving membrane distillation at Senoko refuse incineration plant. The test began in January and uses low-grade residual steam from the refuse incineration plant with a capacity of 1,000 tonnes per day to potentially produce five million gallons of near-distilled water per day from seawater.
"This is unlike the current conventional reverse osmosis desalination approach, which requires high pressure to push water through a reverse osmosis membrane," said Mr Tan. This technology can also be applied to exploit low-grade steam or heat from power stations and other heat-generating plants.
"The world is full of ideas waiting to be leveraged on. We cannot confine our R&D within Singapore and expect great results. Over the years, we've tracked technological developments overseas, networked with other governments, water companies and so on. Now we need to take things a step further and encourage greater collaboration with international research institutes. "I am convinced that this is the best way to gather the best ideas or technologies and the best persons for the job," said Mr Tan.
Some of the institutions the PUB works with are the Centre for Water Re search in the National University of Singapore; the Environmental Engineering Research Centre at the Nanyang Technological University; the University of California, Berkeley and Stanford University in the US; as well as the University of Western Australia's Centre for Water Research.
As a young engineer, Mr Tan was in the team that drew up Singapore's first water masterplan in 1972 that already included the possibility of reclaiming water, and witnessed PUB's first foray in 1974 to build a pilot plant to turn used water into potable water--the precursor of today's NEWater factories.
"The costs were astronomical and the membranes were unreliable, so the idea was shelved," he said. The project was revived in 1998 with the advent of the necessary technology, at which time Mr Tan was the Permanent Secretary at what was then called the Environment Ministry.
By May 2000, Singapore had its first NEWater plant in Bedok. Today, Singapore has three NEWater plants. A fourth NEWater plant is being built, which when completed will provide a total of 60 million gallons daily.
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