Treatment of spent cleaning baths in E-Coat paint line.

[Matthew11]

At the facility I for at we treat all of the by products of our E-Coat line. We have been finding that when we treat our potassium hydroxide based cleaner we are still left with a yellow hue. The cleaner it self can be treated fairly easily, but once parts have been cleaned in the bath, when we treat it we can not remove the yellow hue from the remaining liquid. We believe it could possibly be a dye(in the doping oil) or iron oxide(from the parts), if anyone has also run into similar problems or has any suggestions any help would be greatly appreciated.