Thus started the lament of the Ancient Mariner, â''Water, water everywhere, and not a drop to drink.â''
According the US Geological Survey, 97.2% of the worldâ''s water is saline. If we could just get that water resource so it was drinkable, all of our water shortage issues would be fixed, right?
Well, it is being done...sort of at roughly 30 billion litres per day, but at a huge expense at about $0.5 to $0.85 per cubic meter.
As a result, 60% of desalination capacity in the world is located in the Middle East where the oil-producing countries of the Gulf have access to inexpensive energy. In these countries a thermal/distillation method is typically used called multi-stage flash (MSF)â'' 70% of a MSF plantâ''s operational cost is energy.
MSF use is expected to decline in favor of less expensive methods such as Multi-effect Distillation (MED) and a hybrid approach of MED combined with membranes.
The other major method employed in most of the world outside of the Middle East, and accounting for 50% of the total market, is Reverse Osmosis (RO).
But all of these methods require huge amounts of energy and as a result are quite costly, not to mention they arenâ''t exactly environmentally friendly, discharging high salinity water as a byproduct of the desalination process.
Thatâ''s just some of the background to set the context for a White Paper recently released by the Meridian Institute that provides an excellent overview and comparison of conventional water treatment technologies with nanotechnology-based ones.
This is a thorough review of the technologies now available or in development, but I was looking for one in particular, and to my delight it was included.
It is the use of a self-assembled structure of the iron-storage protein ferritin to make nanoscale magnetic particles. It was developed by a UK-based Nanomagnetics that has now closed its doors.
The Nanomagneticsâ'' approach exploited a water purification process called Forward Osmosis.
Basically, the way this works is that if you had a bag made of a nanoporous membrane that more or less served as a filter and filled that bag with these magnetic nanoparticles and some clean â''drawâ'' water, and then put the bag into contaminated water, the dirty water would be pulled through the membrane into the bag by osmotic pressure exerted by the difference in concentration between whatâ''s outside the bag and whatâ''s inside. Then you could just pick up the nanoparticles in the bag with a magnetic field, and voila...clean water...and you could use the bag again
Compared to RO, Forward (or Direct) Osmosis offers:
â'¢ Lower energy process and efficiency
â'¢ Increased membrane lifetimes and reduced fouling
â'¢ Water recovery exceeding 85% for seawater (40-60% for Reverse Osmosis)
Just the simplicity of this proposed method always fascinated me as well as the serendipitous method it was discoveredâ''Nanomagnetics originally developed magneto-ferritin for data storage applicationsâ''always appealed to me.
But the technology has never been applied to a complete desalination system (the IP is up for sale), so it's not as if this technology is going to change the desalination plants of the world overnight.
But it is often argued against nanotechnology in water applications that they make processes more expensive, and with this technology the processes of desalination could be less expensive...at least theoretically. We'll have to see if the vagaries of capitalism watch another solution to drinkable water issues pass by the wayside or bring them into the light of day.