Metal finishing Q&As since 1989

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Reducing Total Dissolved Solids in Rinse Water

2003

What is the least costly method of reducing TDS in the final rinse water of our powder coating pretreatment system? Our water was running about 80 ppm right out of the tap and now it has jumped to 180 ppm for no apparent reason and the water company cannot give us a reason. Is it possible the water company changed chemicals or something along that line?

Thank you,

William M. Mathes
Quality Manager - Burlington, Iowa, United States

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Reverse osmosis should get you back to 80 easily with the least investment and operating cost. You do not mention the flow rate, but it is probably low enough for an off-the-shelf low pressure RO system.

Paul Morkovsky
- Shiner, Texas, USA
2004

I routinely check this site for interesting problems, as I am retired now, and need some entertainment. The company I spent 37 years with had a silver plating line we needed low dissolved solids in the make-up water. (It was not a counter rinsing line). The feedwater source was typical city water with only a moderate hardness (from a freshwater pond, not wells). We solved the problem using a combination of a deionizing filter, followed by a small distillation unit. We made water typically better than RO, but at only about 15 gallons per day. We ran it 24/7 (except for maintenance downtime of 4 hrs/week), and stored the water produced in a poly tank of 45 gallons capacity. This evened out any big periodic demands over time, of course.

Good Luck.

W. Carl Erickson
- Vernon, New York
2004

Reverse Osmosis is the reliable method to get good PPM of TDS......

V S Magesh
- Chennai, India
2004