Water Treatment Tour

Waste Treatment

To insure quality plating, thorough rinsing must occur between each operation in the plating process. The metals (copper, nickel, & chrome) collected in the rinses are soluble heavy metals. This is the form of a heavy metal that enables it to be absorbed into humans and animals creating the potential for heavy metal poisoning. It is for this reason, and justifiably so, that the EPA and State environmental agencies have heavily regulated the electroplating industry.

At Paul’s the cyanide bearing rinses are collected separately from the other rinses. The cyanide rinses are pumped into Stage 1 cyanide destruct where the pH is raised and sodium hypochlorite is introduced reducing the cyanide to cyanate. The solution is mixed and retained for a minimum of 30 minutes before flowing to Stage 2 where acid is introduced to lower the pH and more sodium hypochlorite is added to break down the cyanate into carbon dioxide & nitrogen eliminating it entirely from the water.

This water joins with the balance of the rinse water in Stage 3 where the pH is further reduced and an alum coagulant is introduced. The waste water then flows to State 4 neutralization where the pH is again raised with caustic soda causing the metals to precipitate out of solution in the form of tiny solid particles. In Stage 5 a blended poly electrolyte is added which causes the isolated small metal particles to clump together. The flow is then directed through a clarifier which by design collects the floc (metal particles) on the bottom and allows the clean water to rise to the top where it flows over the discharge and drains to a final sampling tank and then to the sewer. The floc is pumped from the bottom of the clarifier to a sludge settling tank and then through a filter press where it is compressed into a clay like substance. This sludge is then packaged as hazardous waste and sent offsite for treatment and disposal.

All of this along with the hours to operate, monitor and analyze samples to make sure compliance is met has substantially affected the cost of all plating operations and especially custom (relatively low volume) shops as Paul’s over the past 20 years. However, waste treatment has allowed us to continue to operate and to leave a clean world for ourselves and our offspring.

Click here to tour waste treatment process.

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