posted by admin on Jun 8
Only 2.5% of the Earth’s water is fresh – and a third of that is frozen solid!
However, humans and animals can only drink fresh water – and you can’t water plants or crops with salt water either – so where are we supposed to get our extra water from?
Up until recently, there was only the process of either brute distillation or reverse osmosis available to take the salt out of sea water – both were very energy demanding and cost a lot of money for the ‘fresh’ water. As a result there weren’t many such plants across the globe.
So to keep getting water (rather than start to use less) most people just kept diverting rivers and making more and deeper wells to drain the planet of water to feed our rising population and demand for water.
Regardless of what we use it for – we need water, and due to our endless demands – we are now prepared to pay for it. Needless to say as a result of this – more companies are happy to extract water from even deeper or to dabble with alternative desalination processes.
There are currently 3 new alternatives for purifying sea water, and it is still to be seen which one will become the successor to reverse osmosis over time.
Forward Osmosis:
Rather than making the salt stay behind during the processing – they are encouraging the water the pass through the membrane.
Basically, the process of osmosis is where the concentration of a certain ‘thing’ needs to equal itself out and so spreads from where there is a lot to where there is little – to reach a balance.
A good example of this is milk in coffee. You add the milk to the top – but it doesn’t stay there – it spreads out until the coffee takes on a slightly lighter colour. Same with adding a dye to a jug of water. Half the jug doesn’t stay clear water – it all takes on a touch of the dye.
So, forward osmosis hopes to do just that. By having salt water (separate salt and water molecules) on one side of a membrane and a type of ‘modified’ salt on the other side – they can make the water molecules move over to the other side to balance themselves out.
The result is salt water left on one side and pure water (and modified salt) on the other. Remove the modified salt and you have drinkable water.
Modified Membranes:
The remaining 2 methods both rely on alternate membranes rather than a change in process.
By using nano-technology to hold a electrical charge, these membranes hope to repel the salt molcules allowing only the water molecule through.
Nanotubes – Using carbon technology to hold an electrical charge to hold back the salt molecules as well as funnelling the water through reduced friction tubes.
Biomimetics – Using cells which are naturally found in animal tissue to repel the salt molecules and efficiently transport the water molcules as in a living animal.
However, getting the fresh water isn’t the only problem to consider – as desalination leaves behind a huge pile of concentrated salt water with nowhere to go!
Release it back into the sea and you are raising the salinity for your future desalinations!



