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topic 11849

The composition of Electroplating wastewater



Q. Hi,

I'm a researcher at the Cukurova University-Balcali/Adana/TURKEY. I'm trying to find general electroplating wastewater compositions. Especially Zn, Cu, and Pb concentrations. Thanks for your affinity.

Olcayto KESKðNKAN
Cukurova University - Adana, Turkey



A. The concentration can vary tremendously depending on the processing method, the types of parts being plated, the metal which is being plated onto the parts, the flow rate used in the rinses, whether any recovery is done on the rinses, etc. The U.S. EPA has funded many studies on this which you should be able to start finding from www.epa.gov.

But if you just want a quick number to start from for order of magnitude, my experience is that the average jobshop generates wastewater that contains from the low to middle double digits of mg/l of the primary metals it plates. In other words, a zinc plating shop will often generate a waste of 15 to 70 mg/l of zinc; higher if they've been working at water conservation. The mg/l of secondary processes seems to run in the middle single digits, like 3-7 mg/l. Metals which are not used as platings, like lead in a shop that does no lead or solder plating seem to run in the low mg/l, like 1-3 mg/l. Again, the numbers could be higher if they are trying to reduce water usage, but probably aren't lower.

Again, this is not science, it's just typical of what I personally have seen, but should be helpful for a hypothetical plating plant for a school project. Good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 18, 2009

Q. I need to know the average concentration of Cr+6 in electroplating wastewater according to your experiences, and also the pH of the very wastewater. Please send me a good e-resource.

amir mousavi rad
student - tehran, Iran


January 19, 2009

A. Hi, Amir. I really don't think there are any meaningful "averages". Some shops do a little hexavalent chromating on zinc plating, using a small amount of quite dilute Cr+6 and have no other use for it. Other shops do chromating of aluminum as a mainstay and use a lot of this rather dilute solution. Still others do hard chromium plating exclusively, using a lot of much higher concentration chromic acid on all of the parts they process. In most countries, probably including yours, there are effluent standards that dictate that this waste must be treated before discharge.

Why are you asking? Are you looking for the numbers before waste treatment, or the concentrations in the effluent? If you want to do a project for a hypothetical plant, please tell us about that hypothetical plant and what they do. If you want average numbers, to decide for example whether a treatment technology would be economically viable, it's simply not going to work. Thanks.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


May 22, 2009

A. Electroplating industries discharge different heavy metals according to the type of metal solution used in the process. The concentration of hexavalent chromium can be found in the range of 700-1500 mg/l in wastewater. Nickel concentration can reach 150-400 mg/l in wastewater.

Mohammed Wateery
- MYSORE, India


Thanks Mohammed. Your numbers are before wastewater treatment of course, and could apply to a decorative nickel-chrome plating shop. I doubt that a shop whose mainstay is zinc plating would reach numbers approaching that :-)

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



To minimize searching and offer multiple viewpoints, we've combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Water and Waste Control for the Plating Shop




O&M of Surface Finishing Wastewater Treatment Systems
Clarence Roy

(1996)

Q. Hi! My name is andy Li. I am an Environmental Engineer in Taiwan. I read your discussion on WWW. May I have some question?

1. Why most companies in the States send their concentrated to outside recycler and do not treat concentrated on site? Is that causing any problem in their treatment plant? And what is the problem? (for cyanide and Cr, Cu....)

2. What is the typical concentration of the rinse water and concentrated?

3. How the sludge be treated by you and your recycler?

Very appreciate your help. Thanks!

Andy Li
Taiwan


(1996)

A. Hello Li. I do not agree that most shops send their concentrated waste off site, but when they do ...
1). In my opinion there are three main reasons concentrated wastes are shipped off-site:
a). because the particular waste is especially difficult to treat while remaining in compliance with permits--for example, nickel cyanide wastes and electroless nickel wastes;
b). because of questions about the legality of treating them--some misguided regulatory authorities believe that the purpose of wastewater treatment systems is to treat dilute rinse waters, and shop managers are afraid of running afoul of their interpretation.
c). because the particular waste has good economic value that shouldn't be wasted, like silver and gold.

2). Concentrated wastes are usually the same strength as the plating bath, acid tank, chromate, or cleaner. Dilute wastes from rinse water can vary tremendously but, in order of magnitude, are probably diluted between 100:1 to 1000:1 compared to the original plating bath.

3). Sludges are not treated by platers, except for removing some of the water. Most recycling companies probably kiln the waste and then use it as a raw material in traditional refining processes.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



March 29, 2012

Q. I have a sample of a zinc plating wastewater which presents a high level of BOD (7.000 mg/L). What could be the origin of this organic matter? Detergents maybe? Does it make sense to you?
Thanks in advance.

Jorge Maturana
- Santiago, Chile


April 3, 2012

A. Firstly, 7. mg/l O2 is a pretty low BOD. Did you mean 700, or 7,000?

Secondly, lots of brighteners used in Zn plating are organic acids, aldehydes, etc. that will be readily metabolized by bacteria. To lower your number, you might try preoxidation with H2O2. Or, you could chlorinate; that might give rise to other problems, though.

dave wichern
Dave Wichern
Consultant - The Bronx, New York



July 14, 2016

Q. Hi sir,
I need to know how to find acid composition in electroplating wastewater.

Manish Srivastava
- New Delhi, INDIA


July 2016

thumbs up signHi Manish. You know whether you are an elementary school student, a post-doc, a regulator, author of a book on environmental engineering, chemist in a lab, wastewater treatment system operator, designer of lab instrumentation, etc. -- but we don't, so there is no way anyone can respond at shorter than book length.

Please spend more time on your own behalf in describing your situation and in composing your question than you would ask a stranger to spend on your behalf and I'm confident that you will get good answers. You're about 8 minutes in the hole :-)
Thanks for your understanding.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



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