PUB to begin desalting process for Marina Reservoir in April

Timothy Ouyang, Channel NewsAsia 31 Mar 09;

SINGAPORE: Singapore's first-ever city reservoir will begin its conversion to a freshwater catchment area next month.

The Marina Barrage at the mouth of the Singapore River will prevent sea water from entering the Marina Reservoir.

From April, national water agency PUB will start a process known as desalting. Salinity in the water is expected to gradually change from brackish to freshwater conditions.

Experts said the salt content in the water will be diluted and displaced by rainwater. The desalting process is expected to be completed next year, creating Singapore's 15th reservoir.

The Marina Reservoir will meet 10 per cent of Singapore's current water needs. Water collected from areas as far as Bishan and Ang Mo Kio will flow through the Marina catchment and into the reservoir.

Yap Kheng Guan, director, 3P Network, PUB, said: "Everyone of us living in this area, working in this area, playing in this area, do have to be mindful that whatever you throw or leave behind on the streets, when the rain comes, these (items) will be washed down... This obviously mars the aesthetics of the river and eventually also the reservoir."

The reservoir is expected to help prevent flooding as water from low-lying areas in the city flows into it.

Gates at the recently built Marina Barrage will be lowered to release excess water into the sea during low tides, and during high tides, giant pumps are activated.

Each of the seven pumps is able to flush out 40 cubic metres of water per second – equivalent to draining out an entire Olympic-sized swimming pool in one minute.- CNA/so

A little less salty now
Alicia Wong, Today Online 1 Apr 09;

WATERSPORTS enthusiasts may soon find the waters calmer at the Marina Reservoir, although visitors to the barrage may get the occasional whiff of a strange smell.

These are some of the changes that can be expected as the PUB, the national water agency, begins the desalting process at the Marina Reservoir this month. The process will turn the reservoir, now a mix of freshwater and seawater, into a freshwater body that can supply water to households.

Some have already sensed the change, said Mr Yap Kheng Guan, director of PUB’s 3P (Public, Private, People sectors) Network. Dragon-boaters have said they feel less sticky because there is less salt in the water.

Singapore Dragon Boat Association president Kwek Siew Jin is looking forward to the change since a freshwater body will have no waves and currents, and hence lessens the chances of boats capsizing.

Mr Yap said while the change in salinity may result in some fish dying, most have already swum out to upstream catchment areas. Rochor Canal and Sungei Whampoa, for example, are now filled with freshwater, with freshwater fish thriving. The possible odour from dying marine species such as barnacles is “transient”, he added.

The year-long process will start once there is a heavy downpour. The rain provides freshwater, while pumps and gates that separate the reservoir from the sea, will be used to flush out the sea water. When the water level in the reservoir is higher than the sea, gates will be lowered to let the water out. When the water level in the reservoir is lower, seven huge pumps, which can drain an Olympic-sized pool in under a minute, will pump the water out. It is a gradual process that will give the ecosystem time to adjust, said Mr Yap.

Activities such as canoeing and kayaking can continue, while swimming, wakeboarding and waterskiing — activities where one’s body is submerged in water — are still not allowed on a regular basis.

Last July, the National Environment Agency said the reservoir’s water quality did not meet revised standards, because it collects rainwater from some of Singapore’s oldest developments and is transiting from being a seawater body to a freshwater one.

Mr Yap said they would test the waters again after it becomes a freshwater body.

The Marina Reservoir meets 10 per cent of Singapore’s current water needs. By 2011, two reservoirs in Punggol and Serangoon are expected to be completed and will meet an additional 10 per cent of water needs.

Dilute salt in reservoir? Look to the skies
Liaw Wy-Cin, Straits Times 1 Apr 09;

NOW that the high-tech work is done, it is time to let nature take its course.

Rainfall will be the key element in the last part of the creation of Marina Reservoir.

It will dilute the salt in the water, turning the sea water into fresh water, just like the water in the 14 other reservoirs here.

The first part of this process will take place some time this month, when the gates at the Marina Barrage will be allowed to swing both ways - allowing sea water in - for the last time.

Since the Marina Barrage opened in October last year, its gates have been allowed to swing both ways, allowing sea water to flush the reservoir and keep the water in it from becoming stagnant.

But after sea water is allowed in for the last time, the gates will swing only one way - to allow fresh water out in the event of heavy storms and prevent flooding in several parts of Singapore.

Mr Yap Kheng Guan, PUB's director for the 3P (people, public and private sectors) Network, said the water was not desalted immediately when the Marina Barrage was opened, to 'allow the water time to stabilise itself and for the marine fish to move out gradually'.

Right now, the water in the reservoir is a mixture of salt water and fresh water, with about two-thirds the salinity of sea water.

But rainfall is diluting the salt content in it.

'It's the most effective way - we have a large stock of water coming from the sky to flush it (salt water) out', said Mr Yap. 'It's a gradual process, we will wait for the system to adjust itself.'

By next year, the whole desalting process will be complete, and the water in the reservoir will be ready for processing to make it potable.

The desalting process is, however, not all about human needs.

The process also allows saltwater fish to sense the change in the water's composition and to leave the reservoir when the gates are open.

But not all the fish may make it and some may die, leading to possible odour in the reservoir, added Mr Yap.

He said there are many challenges involved in maintaining such a huge 'fish tank'.

For instance, with no more sea water flushing the reservoir, which will meet 10 per cent of Singapore's current water needs by next year, the water may become more stagnant. This could lead to algal bloom if left unchecked.

To prevent this, aeration pumps have been installed to keep water moving.

Water will also be channelled for treatment at Chestnut Avenue Waterworks, near Bukit Panjang, before being returned to the reservoir.

Meanwhile, to prevent filth from accumulating in the reservoir, cleaners will patrol it daily to scoop up litter and flotsam.

'Curtains' will also trap any silt from nearby construction sites to prevent contamination.

The Marina Barrage has been hailed as a showcase of Singapore's water technology, and is key to the country's aim of attaining self-sufficiency in a vital resource.

It recently won the 'Grand Conceptor' award, the top award of the American Council of Engineering Companies' Engineering Excellence Awards Competition 2009 for the state of Massachusetts.