Removing antifreeze from water

[JP1950]

I have a wastewater recycling system. What is the most economical method of removing small amounts (~1% concentraton) of antifreeze (ethylene glycol) from my system? One person suggested using the differential in specific gravity (since antifreeze is heavier than water) to separate the liquids. I am considering using a clear 17' high tube to allow the antifreeze to settle to the bottom (similar to a tractor's "sediment bulb&quot. Will this strategy work? If so, how long will the settling take?

 

[kenvlach]

Not a chance, you could only remove sediment. The ethylene glycol is in solution.

For recycling antifreeze (at the higher concentrations normally used), the solution is first highly filtered & then partially fractionally distilled (ethylene glycol has a boiling point 196-198°C, so the excess water can be boiled off). This would take an enormous amount of energy in your case, however.

For trace amounts, a chemical or electrochemical oxidation oxidation method could be used to destroy the molecule all the way to H2O & CO2. You could consider ozone, electrocoagulation, etc., which will get rid of other impurities as well.

Probably, your most economical solution is ultrafiltration or RO.

 

[saxon]

jp, Nice idea, just one problem though, ethylene glycol is is 100 % soluble in water. Meaning it completly mixes. So you can"t separate the phases by differential specific gravities. You've got a choice, you can either separate it by distillation based on boiling points. or you can run it through an ultrafiltration system and separate it based on molecular size.

Hope this helps.
saxon

 

[KRSServices]

I'm not sure that even with ultrafiltration, you will be able to eliminate the glycol completely. What is the recycled product to be utilized for? If it contains glycol, what other trace compounds would be adverse to the final use of the product and would those compoionds interfere with the glycol elimination?

I was once involved in the wastewater recycling program in Panorama (ski hill) and participated in several planning sessions for recycling grey water to snow making or sprinkling applications. KRS Services

http://www.krs-services.com

 

[waterexpert]

You can completely separate glycol from water with reverse osmosis membranes. I think you'll find UF membranes let the glycol pass. I've seen a couple of glycol recovery plants used in the railway sector. Recycled glycol goes back into service. Works fine.