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-----Wastewater turning black with high nickel numbers
Q. Hey guys, just looking for suggestions of where to look or start, we are at a loss over here with a situation that has been occurring sporadically over the last 6 or so months with our wastewater treatment plant.
We are a finishing facility with 2 wastewater treatment systems, to this side we have zinc, nickel, passivation, black oxide, cleaning and iridite line. Some of them get pre-treated before being sent to wastewater. During normal operations effluent numbers are good, then out of nowhere our nickel numbers rise and the water starts turning black from solids, the resulting effluent is a cloudy yellow. It takes a massive amount of firefighting to get the nickel numbers down and the solution at a point where we can discharge. Can anybody help? Thank you!
Asst. Director of Operations - Plainville, Ct
November 26, 2025
A. Hi Craig. From your description of your processes, can we assume you have no EN (electroless nickel)? The chelating agents in EN are often troublesome.
This doesn't sound to me like something that would result from routine treatment of waste water, so I think you need to 'walk the line' to determine what is being done because this sounds like it is resulting from a substantial dump of something, perhaps a cleaner, or a bag of chemical beyond its shelf life.
Believe or not, but I have even seen a well-meaning janitor who thought he was doing the right thing, climb the stairs to dump his buckets of ammonia, solvents, and other stuff into the treatment system.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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