Friday 11 January 2008 à 18:21

So much water!

Par Sophie Mouge. Correspondent aboard the Aurora Australis

The Antarctic ice cap constitutes 90% of the world’s reserves of freshwater with 30 millions km3 of continental ice. This ice cap lays on the continental base and is made of ice coming from the accumulation of precipitations.

The Antarctic ice cap which is the main freshwater reserve of our planet.

Icebergs = pieces of the Antarctic polar ice cap, seen from tens of meters away from the Aurora Australis on January 11.

Nevertheless the supply of potable water on board is a real problem.
To meet the current needs of 77 passengers, we use 45 tons of water a day. So it’s easy to understand why the bathrooms in our cabins are not equipped with tubs!

Bathroom of passengers’ cabins on the Aurora Australis.

Every time we come alongside, we can fill the 500-ton freshwater tank, which corresponds to 11 days at sea. This reserve is obviously not enough to furnish drinking water for 42 days. That is why the ship is equipped to desalinate sea water two ways:

1. Reverse osmosis unit: 60 bars of pressure is applied to sea water to force it through an osmotic membrane that retains the molecules of salts and lets the molecules of water pass through. This method can produce 30 tons of water per day with a concentration of mineral salts of 300 ppm (parts per million). This water is used after for domestic purposes (drinking water, washing dishes, showers, etc.).

Monitoring table of reverse osmosis unit.

2. Distilling plant: Pressure in a tank of sea water is lowered (to -80 kPa) to make it boil at 50°C using just the steam from a boiler. This method furnishes 10 tons of water per day with a concentration of mineral salts of 0.6 ppm. It has almost no minerals in it so that it will not damage the tubing through which it circulates. This water is used for domestic uses and supplies the boiler.

Evan, the chief engineer, operates the dials on the distilling plant: sea water is heated by the vapor from the boiler.

An enormous boiler supplies the ship with steam to heat both the inside and the outside of the ship.

Boiler fed with fuel.

So, boiling water is always available on board. Several access points are located on the decks and are used as needed to de-ice the exterior parts of the ship (notably the helicopter landing strip and the scientific equipment).

Access point for boiling water and steam on the helideck.

It is not enough to produce pure freshwater. It is also necessary to be able to dispose properly of waste water. Dirty domestic water is filtered before being dumped into the sea. Lavatory wastes are kept in a reservoir that acts like a septic tank. There they are macerated, decomposed by aerobic bacteria and assorted treatments before they, too, are dumped into the sea.

The Aurora Australis is also equipped with a stabilizer that corrects the motion of swells. It works by shifting water between two reservoirs situated on either side of the ship. For example, if the ship leans to the starboard, water is pumped from the reservoir on the right to the reservoir on the left. Thus the swell is damped much more than on a ship without a stabilizer.

Sound of the stabilizer: each sound corresponds to the movement of water from one compartment to the other. We hear it regularly but pay no attention; it has become a kind of background noise!
The image affixed to this sound track represents the rear of the ship in the evening of January 9. Pink light illuminates the trawl deck and seems to want to pervade the ship. It is a very strange moment.

Sound recorded by Margot Foster, Executive producer, 'Bush Telegraph' Radio National, Australian Broadcasting Corporation.

Demain Kel, a ship’s mechanic, proposes a visit to the engine room to anyone on the campaign who wants to go. Now, you’ve started the engine-room visit in advance!

Sunset: a treat for the eyes!!!



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