Water Purification - Condensation 3

[supermanboy]

I was wondering if someone could answer or direct my question:

What types of impurities (chemical, etc) are left in water if any, after condensing water on a clean surface?

 

[quark]

Ideally nothing but the conductivity of distilled water from multicolumn distillation stills can be 0.5microsiemens (max.)and bacterial load can be 1cfu/10ml max. These are the specifics for water for injection.

Clean surface and pure water are hypothetical.

Regards,

 

[JStephen]

Depends on what is in the water to begin with. Any liquid that boils at a similar temperature to water will remain in the water if distilled. You see this effect in distallation of liquor, where they increase the alcohol content by distillation, but they don't just get pure alcohol out of the process.

Generally, raw water wouldn't have liquids like that in it, and most of the crud and disolved minerals would be removed by distallation.

 

[supermanboy]

Thanks guys.

I was curious to know if anything could stay with water through the process of evaporation/boiling then condensation in its own container.

I realize that through boiling any chemicals in the water with a lower boiling point would boil first, and that if you held the temperature at 100 celcius that you would (hopefully) only be boiling water but I wasn't sure if there were any exceptions I was unaware of.

Are there special circumstances where boiling at 100 celcius and condensing the steam leaves more than just water?

 

[TheTick]

In a closed system, anything that evaporates at or below water vaporization temperature will go along for the ride. There is also a possibilty of mechanical entraintment.

U.S. Navy practice for distilling potable water is to do so at a temperature no less than 140°F (in a reduced-pressure system), as evaporation/condensation is no guarantee of bug-free H₂O.

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[quark]

TheTick is right. One fundamental rule of distillation is garbage in is garbage out. If you have chemicals in the water with boiling points less than that of water, fractional distillation is the way to go.

Vapor velocity is the key to remove suspended particulate matter. Multicolumn distillation stills use film evaporation and centrifugal seperation to remove impurities including viable and nonvialbe matter.

 

[supermanboy]

I'm still not quite sure I understand....

Lets say then that you have water from a salty swamp, with all kinds of things in it, including toxic substances for the sake of it.

If I put that mixture into a pot, and boiled it continuously then condensed the vapour I would still get filth at the other end? Even if like I said before, you maintained at temperature of 100C? I know I seem very dense, but this is directly contradictory to what I learned about differeing boiling points in school.

 

[supermanboy]

Fractional distillation was the key that I was missing, I just looked it up.

Thank you everyone for helping me with your insightful posts!

 

[bimr]

Twice distillation of municipal quality water will give you pharmaceutical grade water suitable for injection into the human body. This water must be meet the following standard:

http://www.apswater.com/page52.html

As you can see, there are traces of impurities.

Distillation of seawater will give you water suitable for drinking water. The amount of impurities is much higher.

Other than that, you have asked a general question which makes it difficult to provide further information without knowing the context in which the question is asked. If you want a more precise answer, refer to:

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[supermanboy]

Thank you for the advice. Sorry for the general post, I am inexperienced in this field and had no idea what I was getting into.

Bimr, can you suggest any books or websites to read about the fundamentals of your post? I believe that is the best place to start, and will give me the most releveant information based on what you said.

To completely specify my problem: I am experimenting with a boiler/condenser system which will use an unspecified water source to be condensed into "clean" water. Since it may use swamp water, sea water, or fresh water and I did not know what would survive the process. Since I bought all my beer in university, I hadn't even heard about fractional distillation before!

Any suggested references would be greatly appreciated!

 

[bimr]

Water Supply and Pollution Control by Viessman and Hammer is a good starting point.