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Which water treatment type for metal finishing?

 

Happy Holidays all you M-F's out there! (c'mon - metal finisher's - take it easy!) I need advice once again. We are a large anodizing job shop interested in installing either D.I., R.O., loose R.O. or nanofiltration for our rinsewaters. Does anybody have experience or knowledge of which system works the best in metal finishing operations? Thanks.

Vic Waldman
- Naugatuck, Connecticut

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I'm not a Monday to Friday'er--don't know what you mean, Vic :-)

I'm not familiar with the term 'loose R.O.' I'm afraid.

But I don't believe there is much equivalence between the other three technologies. Nanofiltration would be used after chemical precipitation to remove the solids, as an alternative to a clarifier (or direct filtration). R.O. is used for recovery, but to my knowledge does not generate a pure enough permeate for discharge. D.I. is not exactly a treatment strategy, it's more of a concentration strategy where the waste collects in the D.I. resin for later treatment.

But to compare D.I. vs. R.O. as concentration strategies, D.I. has a huge advantage in not being highly flow dependent (you can pass a relatively huge amount of dilute waste through a D.I. column at very low cost), but R.O. has the advantage of concentrating the waste without adding any more chemicals.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey