Desalination Question

[Chesterton]

Why is it so difficult on a large scale? They're going to start doing it in Santa Barbara and the water guy says: "...there are a lot of challenges. This is an incredibly complicated facility, and it has many different processes that all have to get along and be working uniformly."

The USGS website says: "The 'simple' hurdle that must be overcome to turn seawater into fresh water is to remove the dissolved salt in seawater. That may seem as easy as just boiling some seawater in a pan, capturing the steam and condensing it back into water (distillation). Other methods are available but these current technological processes must be done on a large scale to be useful to large populations, and the current processes are expensive, energy-intensive, and involve large-scale facilities."

All you're doing is heating water and capturing the steam condensation? It's something even I could do on the small scale cheaply, so what makes it so difficult and expensive at larger scales?

 

[LutheranGuy123]

Literally the scale. Any idiot can boil a gallon of water to drink for the day. It costs just a few cents. But this city has to boil hundreds of millions of gallons.

 

[mnorian]

To distill the water by heating it would take way too much energy; so they use reverse osmosis desalination plants that force sea-water through membranes with micron size holes in it (one million holes per inch) at high pressure (600-1200psi) that filter out the salt.

These high-pressure pumps take a lot of power (10 times the power then a normal freshwater plant) and then they have to get rid of the waste water that is super high in salt; which can be up to 1 to 3 times the amount of fresh water the plant makes.

So desalination plants are not for the poor countries; but the ones with a lot of energy to burn like the oil producing countries of the Persian Gulf.

Link:
Desalination is an expensive energy hog, but improvements are on the way


.

 

[timewerx]

Literally the scale. Any idiot can boil a gallon of water to drink for the day. It costs just a few cents. But this city has to boil hundreds of millions of gallons.

Not to mention, fill swimming pools, leave faucet on for no reason, wash car everyday, water the lawn, play with the water hose.

Yes it's expensive because heating water requires a lot of energy. You can do it with solar heat but that would require a very large area of land to use solar heat to distill large amounts of water.