Waste water treatment by powder coaters is very important, not just for the environment. Water purity is measured as dissolved solids in readings of parts per million. This device actually measures the waters conductivity and PH range.
How clean is your rinse water? Clean tap water may not be as clean as we would like to believe. Problems associated with poor quality rinse waters include:
1. Limited adhesion. 
2. Accelerated corrosion of substrate.
3. Blistering.
4. Maintenance. Scale and contamination of minerals that will build up on the tank, walls, and plumbing.
The only way to be sure of water quality is to test the rinse water on a regular basis as you would your cleaning and phosphating solutions.
It is a good idea to start and maintain a log book to show trends in incoming tap water quality. If the water in your area is particularly bad a filtration device may be required to insure proper control of water purity.
Suppliers of waste water treatment systems can be found here.
