Seawater worth bottling ...

Excerpt from Sydney Morning Herald:

Seawater worth bottling

26 June 2007

It definitely tastes different. Not bad different or good different, just different.

Stephanie Peatling samples the water at the world's biggest desalination plant.

As the NSW Government pushes ahead with its decision to build a $1.76 billion desalination plant in Sydney, many residents are bound to be wondering what the water will taste like.

Desalinated water is a daily reality for many Israelis, via the desalination plant at Ashkelon, not far from the Gaza Strip and about 90 minutes' drive south from Tel Aviv.

The plant supplies 110 million cubic metres of water a year, or 330,000 cubic metres a day, employing reverse osmosis technology, which uses large amounts of energy to force seawater through membranes to strip the water of its salt before treating it and piping it to homes.

From the tap it tastes like it has a higher mineral content than the water Sydneysiders might be used to, but only in the way bottled waters taste different from tap water.

The plant is owned by the VID Desalination Company, a conglomerate contracted by the Israeli Government to provide drinking water for a further 20 years. Ownership of the plant will then revert to the Government.

The plant's substantial power needs are met by its natural gas plant.

On a rare tour for journalists, the operations manager, Micha Taub, explains how the plant turns salt water into fresh.

Seawater is taken from one kilometre out to sea to ensure the water is a clean as possible when it reaches the treatment plant.

The first step is to filter suspended matter such as fish, plankton and bacteria.

Even this part of the process requires intense filtration because much of the sea life that ends up at Ashkelon is as tiny as one micron, or one-1000th of a millimetre, Taub says.

Then chemicals are added and the water is filtered again to remove particles.

"But it's still very salty although much clearer, so the desalination then begins with a system of very, very fine filters," Taub says.

Using the plant's 40,000 membranes, the water is pushed through into two streams depending on its salt content. The water is desalinated again before it comes out stripped of pretty much everything.

But, Taub says, "it's not so healthy to drink water without any ions at all".

"So the last part is to reharden the water and put the minerals back. This includes calcium, carbonates, sulfates and sulfuric acid. Then you have a very high grade of drinking water, closer to mineral water."

Hence the taste.

The seawater that Ashkelon takes has 35 grams of salt in every litre, not as salty as the Saudi Arabian water supply, which has 45 grams a litre.

The brine sucked out of the seawater goes straight back into the ocean and the plant's operator says the water around the plant is constantly monitored to see the effect it is having on sea life.

But the Middle East chapter of the international environment group Friends of the Earth says the "dumping" of the brine straight back into the ocean is likely to affect sea life, although it is still too early to tell how significant it will be.

A report done by the group argued it would be cheaper and more environmentally benign to invest in upgraded sewage treatment, encouraging water saving and reducing the amount of fresh water used by agriculture.

It is also concerned about privatising water.

"Placing control of water production, supply and management into private hands is contrary to public interest as it turns this basic human resource into a commodity like any other consumption good," the report said.

Desalination was a more expensive way of securing water, it found, and had other problems such as air pollution and the amount of land needed for the plants.

But this is no deterrent to the Israeli Government, which plans to increase desalination production in the coming years from its present 15 per cent of all drinking water to 20 per cent.

See - SMH - Seawater worth bottling.