The authoritative public forum
  for Metal Finishing since 1989
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Waste Water Troubles

The company manufactures solar products. The most important is the manifold that is placed in a solar collector.This manifold is made of Cu and coated with a state of the art finish that carries great optical qualities for harnessing solar heat. Which means in the solar spectrum the finish has great absorption and low emissivity. The plating line is automated and generates a small volume of waste effluent (35 gpm). Due to the engineering of the line our problems of waste treatment are a head ache. We are not generating enough waste metal in the effluent to treat it properly. As a small quantity generator I am open to suggestions on how to resolve this. Currently we are using DTC as a coagulant and we either over dose or underdose the waste stream. The metals in the stream are nickel and copper. Should we introduce Aluminum in larger amounts and if we do this are we just creating more consumption of the DTC?

Raymond Villalva
- Jacksonville, Florida

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Everything is relative, but I don't consider 35 GPM a small amount of waste water. If the dissolved metals are truly low, you probably have a good application for ion exchange, which should remove the metals to essentially zero. When the ion exchange resin is regenerated, the same metal will be in a much smaller volume so you will have the metal loading you seek.

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

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You need the right chemistry and better controls for it. While I would never support the use of DTC as it is highly toxic to your aquatic friends down in FL, there are several alternative chemistries that can work very well, even at low influent levels. They produce a smaller amount of sludge, are controllable with specific ion probes, and are economical to use as they are almost an order of magnitude stronger than DTC, meaning you use less.

I agree with Ted - 35 GPM is not a small flow. If your loading is THAT low, you should consider a small recycling system that would produce only a few hundred gallons of water per day on average and get you the high purity water that I suspect that you seek for your process. You can get better than 1 meg-ohm water from waste water with the right system design. and you get the luxury of being able to batch treat the regenerants when and how you like before you ever discharge them.

Tom Baker
wastewater treatment specialist - Warminster, Pennsylvania