Friday, October 15, 2010


"Water, Water everywhere
And all aboard did shrink
Water, water everywhere
Nor any drop to drink"
from "The Rime of the Ancyent Marinere" (1797-98)

Today is International Blog Action Day 2010 and the theme is to write about water, not just any water but clean water around the world. For seafarers we are on the water all the time but it is sea water (NaCl+H2O) and so we need places to obtain fresh water (H2O). For thousands of years this was always the seafarers problem how to obtain and then carry clean fresh water for sea voyages particularly the long sea voyages of the world explorers. Then reverse osmosis was discovered at the University of Florida in the 1950's and basically the problem was solved. Now all that sea water could be purified into drinkable fresh water (FW).

Reverse osmosis is the method of forcing solvent from liquids using a suitable membrane. Just about all over the world drinking water purification systems include a reverse osmosis step. On board ship the sea water is pumped through the reverse osmosis system and pumped out as usable fresh water to be stored in the FW tanks. So the old problem of obtaining and using FW at sea is solved, with the system operating continuously the FW is used and replaced.

The system consists of :
  • a series of sediment filters
  • an activated carbon filter
  • a reverse osmosis filter, which is the membrane
  • a second carbon filter, to back up the membrane
  • an ultra-violet lamp for disinfecting any microbes

So there it is potable fresh water from the sea, not exactly free of course but always available. For a full explanation of 'Reverse Osmosis' and the words of "The Rime of the Ancyent Marinere" visit Wikipedia.

Good Watch.

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