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RE: Recovery of painting solvents from air stream



Robert,

Here are a few thoughts on the questions you pose.

1)  Does the acetic acid contribute to the BOD?

Yes.

2)  Is there a better way to approach solvent recovery from dilute air
streams?

Carbon with steam stripping is a common process especially when you can
reuse the solvent.  If the solvent has no value then carbon coupled with
thermal oxidation is common.

3)  What would be the advantages/disadvantages of using nitrogen to
re-activate the activated carbon?

Hot nitrogen stripping is practiced followed by thermal oxidation or
refrigerated condensation.  I believe one big advantage of using hot
nitrogen is that you get less degradation (i.e., acid formation).  On the
downside, it will be hard to justify the added expense since you already
have a system in place.
 
4)  What is the best treatment technology for this wastewater containing
n-butyl acetate, acetic acid, n-butanol?

Biological treatment should work.

5)  Steam stripping has been suggested, but doesn't the steam have to be
re-condensed, getting the problem of dilute organics in a wastewater
stream once again?  Can the organics be recovered from a steam stripper?

Yes, but the volume of waste to be handled would be less. Recovery of the
acidic compounds could be a problem.

6)  How about oxidation with peroxide and UV?  What is the removal
efficiency?

It depends on how the process is configured.  You could use ozone/UV to
treat the organics in the vapor phase or peroxide/UV in the liquid phase.
One configuration uses ozone/uv to break down the organics followed by a
carbon bed. Think of it as continuous regeneration of the carbon while
on-line.  Regarding exact details, its best to talk to a vendor. Since its
been many years since I've looked at the technology, I can't offer any
specific names at the present.

Hope this helps.

Mike.callahan@jacobs.com