Where the
world gathers for metal finishing
Q&As since 1989


-----

Rinsewater disposal in chem-film operation

Hello,

My name is Micheline and we have a small chem-film operation. At the present time we send our hazardous rinsewater waste out. As you all know this is a costly process.
We have looked into chemical converting the rinse but this cost was not that much better plus it comes with many headaches.
We have also looked into a closed loop system, which is probably where we are headed at this time. We will also be adding a small passivation line, that must use Nitric to meet our customers needs.
My question is - Does anyone know of an alternative that we have not thought of?

Thank-you

Micheline Forth
metal finishing shop - Savannah, Georgia, USA
2007

---

First of two simultaneous responses --

You can greatly extend the life of your flowing rinses by adding, if it is practical, low volume spray rinses that you evaporate on site.

Dave Wichern
Consultant - The Bronx, New York
2007

---

Second of two simultaneous responses -- 2007

Micheline

In a prior life, we used a DI water spray rinsing, evaporated what we collected, and returned the concentrate back to the process bath.

Check with your POPTW on the nitric acid. I would expect you could simply neutralize and discharge.

Willie Alexander
- Colorado Springs, Colorado

---

2007

Many companies have recycled the rinse water from Chem Film rinses that contain Hexavalent Chromium, with good results.

This can either minimize the volume of waste that you need to haul off site, or make it possible to use batch rather continuous treatment of the rinses.

Lyle Kirman
consultant - Cleveland Heights, Ohio

---

2007

Hi Everybody,

I would like to thank everyone who responded to my question.
However I was wondering to those who responded with suggestions of spraying the parts and letting the mist evaporate, I failed to mention that sodium Dichromate would also be in the mix.
Is this still an option?

Micheline Forth
- Georgia

---

First of two simultaneous responses --

Micheline

You don't say if the sodium dichromate is from the chem film, or possibly a passivation process. If you have two different waste streams, one for the chem film and one for the passivation, keep them separate. The same evaporation process for chem film would work for the passivation. You probably are losing more water from the passivation than the chem film due to operating temperatures.

Willie Alexander
- Colorado Springs, Colorado
2007

---

Second of two simultaneous responses --

No, that is not what I meant.

I meant, evaporate the spent spray rinse. It is important to control the volume used. The idea is to use , say, 10% of your water to remove say, 80%+ of the chemicals on the surface.

Letting this pre-rinse dry on the parts would almost certainly leave ugly marks. The parts need to be immersed in a subsequent flowing rinse while still wet.

Dave Wichern
Consultant - The Bronx, New York
2007