Letter 2318

Electrocoagulation

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Is there anybody who can comment on electro-coagulation vs ion exchange for the removal of metals and cyanides in the waste streams in the plating shop?

I don't know which one is more reliable and accepted practice nowadays.

Any comment will be greatly appreciated.

Jeff Huh

I would like to see references to some published articles on electro-coagulation before I gave credence to it. I'm not saying that it doesn't work -- I don't know -- but I am saying that I personally have not yet seen evidence that it does.

Ted Mooney, P.E.  finishing.com Brick, NJ

Someone gave a paper on the electrocoagulation at either sur-fin or aesf week. AESF should be able to find the most current one.

I saw it advertised on the floor of AESF week , many years ago. My thought is, if it is so good, why haven't we heard more of it in the last 15 years? It works in the lab, but will it work at your facility with your people taking care of it??

Ion exchange is an expensive option. It does have considerable value as a polishing agent, especially if you are trying to recycle some of your rinse water. Any number of vendors will literally bury you with information about ion exchange if they think that you might buy one.

James Watts
FL

But does it work in the lab, Jim? The only electro-coagulation installation I saw had a final 'polish' through disposable resin (massive quantities thereof) . . . and I got the feeling that the whole system worked exactly as well whether the electro-coagulation device was plugged in or not.

I couldn't see the point of electrocoagulating the waste before passing it through ion-exchange.

Ted Mooney, P.E.  finishing.com Brick, NJ

What I saw was a table top demo, in a beaker. It worked quite nicely on a pure new plating solution rinse equivalent.

I had real doubts on reliability on scale up.

I did not get a satisfactory answer to my questions on real world, filthy, nasty, mixed process effluent.

I was being nice, because I had never worked with it. Personally, it would take quite a bit of pilot plant work before I would put it into a customer's facility.

I think that we are saying similar things, but in different words.

Jim

James Watts
FL

Ted and James,

Electrocoagulation was a very popular and well-developed technology in the former USSR 10 years ago. I have studied under prof. Rogov who was an authority on the matter, published books (I own one) and papers on the topic. He also lead an organization that designed and installed e/coagulation water treatment plants. What I am not sure of, is what kind of discharge concentrations they were able to achieve at the time and how those would compare to modern-day standards of this and other developed countries.

Hope this helps,

PlaterB

"PlaterB" Berl Stein NiCoForm, Inc. Rochester, NY

There seems to be a lot of confusion regarding what Electrocoagulation is.

Electrocoagulation uses DC current and consumable iron or aluminum anodes. The iron or aluminum that dissolves is the coagulant. Due to the low currents involved, it is not usually suitable for more that a trace of cyanide, or hexavalent chromium, but some oxidation and reduction does occur. If iron anodes are used in the presence of cyanide, you will form ferrocyanide complexes that cannot be destroyed by chlorination. After the electrocoagulation step, the treatment is similar to conventional treatment by flocculation and settling. It is more similar to conventional treatment than different from it. Pretreatment of cyanide wastes by chlorination before further treatment is a better idea then electrocoagulation. After that the choice to use strictly conventional means or EC is up to you.

Ion exchange is not s substitute for treatment of metals or cyanide. It can be used along with treatment for various purposes. Ion exchange does not destroy cyanides and is not used much on cyanide wastes except for precious metal recovery. It cannot treat metals to a disposable form, but is extremely useful to concentrate metals in dilute concentration so that they can be treated in a small volume more efficiently. In this regard it is used to polish the effluent from conventional treatment or as an alternate to conventional treatment.

Water treated by ion exchange to remove metals can be neutralized and discharged, while a small concentrated regeneration volume can be batch treated. In some cases a continuous treatment system ca be replaced by IX and batch treatment.

Deionization is also used to recycle water, but usually only very dilute rinses.

Ion exchange is also used extensively for precious metals recovery, including from cyanide baths and rinses. In these cases, the resin is usually not regenerated, but burned to reclaim the precious metal. This also destroys the cyanide.

Lyle Kirman
water treatment systems - Cleveland, Ohio

Dear Colleague, I would very much appreciate your comprehension, so, I have a lot of questions about a process of electrocoagulation-electrofloculation

zaina zaroual
Fac.Sc - Casa2 - MOROCCO

I am the lab manager for a company that specializes in the engineering and manufacture of equipment and reactant to treat industrial wastewater, including plating.

I, also would very much like to know if E-C works as it claims to. I have not been able to find any good documentation on what exactly is taking place in the electro -chemical process, nor how reliable it would be. Nor if discharge and TCLP are guaranteed. If anyone could send me in the right direction, I would be interested in 'scoping out the competition'.

Karen Mullin
- Auburn Hills, MI

I am interested in locating technical papers, industry applications and true industrial results of electro coagulation. Does it work? How fickle is it? Is it high maintenance? How often do the anodes need to be replaced? What material are the anodes constructed of? Please help!

Mike Davis

I'm interested in electrocoagulation. I would like to know about mechanism and method to remove and recovery metal (Cr) by electrocoagulation. If anyone to know about electrocoagulation, Please suggest to me

Virongrong Tubtimngam
Mahidol University - Bangkok, Thailand

I am also interested to know if electro-coagulation actually works. I have seen it being demonstrated in a prototype scale but does it really work in a real type situation like treating water for drinking, etc?

M Cho
Australia

We are consultants and manufacture representatives for various company's technologies in the treatment of acid mine drainage. Our primary marketing area is Pa. and West Va. as well as the TVA authority. We work with Rep. John P. Murtha here in Pa. and various governmental agencies as well as the coal companies who are treating these waters, specifically Bethlehem Mines Corp. and Barnes & Tucker Coal Co.

We represent a manufacturer of electrocoagulators that will treat AMD and the objective is to separate the metals from the sludge that results from the water being put through the electrocoagulator. We are in the process of setting up a beta site here locally and doing a demonstration of same. Lab tests have shown where we can remove 98% of the metals and there is a market for these metals which includes gold. It is estimated (through a research project funded by the Heinz Foundation) that we have in this area of Pa. 26 tons of gold in the AMD. I fell there is tremendous opportunity in this technology. The company we represent will have in 2/2000 a unit that will handle 1,000 gpm. The problem in the past with the principle of either AC or DC electrocoagulation has been that no one really did any real work above 100 gpm, and the industry saw a lot of "unethical" people doing the black box thing as well as ripping off potential investors. We are slowly changing that image and most of those companies are out of business. There are a couple still there but we know who they are. The company we represent has the financial clout to make this work and have just recently signed agreements in China for the manufacture of their equipment there.

James B. Long
- Ebensburg, Pa.

I know this is going off the tack a bit, but we are a leather manufacturer and I know I'm talking to metal finishers (I think it's called cross fertilization of ideas!) Anyway, we have been told that electrocoagulation is the ideal way to remove trivalent chrome from our effluent. Does anyone know of any tanneries that have used this method successfully? If so can I have a contact?

Thanks, Ken

Ken Hayward
Pittards - Yeovil, England

We are currently using a Kaselco 2.5 GPM electrocoagulation cell with steel electrodes to process Alodine rinse water (we use Alodine as a conversion coating prior to painting aircraft). To the best of my knowledge, this is the only such application in the AF, but there is a lot of interest now being developed. The rinse water is of variable composition, usually 100-400 ppm hexavalent chrome. It usually reduces chrome to non-detect levels in 3 passes. It works for us, but we are operating on a very small scale in batch mode.

Dennis Kirsch
U. S. Air Force - Randolph AFB TX

I have been using electrocoagulation technologies for several years in the treatment of AMD; heavy manufacturing (automotive); metal plating (Zn, Cd, Cr+6 / Cr+3, Cu, Au); and drinking water (As). I can appreciate what other commentors have said about the unethical "jack-legs" that seem to pervade this market sector.

The technology still has a way to go but is more than just a passing fancy.

Cal

Calvin Tininenko
- Longmont, Colorado USA

So what is the answer you have found ?

Jim Mothersbaugh
- Bothell, WA

I realize that this is an old string and may never be read again, but the head of the Chemistry Department at Lamar University, Beaumont, Texas, feels that this string needs one more message. Electrocoagulation works, and it will work on low or high concentrations of mixed waste from any number of sources including tanneries, dyes, plating, emulsified oils, etc. It is based on solid, scientific principles of electrochemistry and is as predictable as the waste characterization allows. There have been few technical papers prepared but that number is increasing. As water re-use interest grows, so does interest in this technology. Ion exchange is fine for relatively clean water. Dirtier water (high TDS) can be passed through EC first, increasing the effectiveness and reducing the cost of ion exchange. Unfortunately, there have been many "black boxes" and pretenders in the technology. While anyone can make it work in the laboratory, solid engineering is required to produce an industrial strength system. Electrocoagulation is now appearing from coast to coast. Those who suffer from a bad supplier experience should not rule out the technology. Lamar University is just now fielding a system jointly with the US Department of State, Mexico, and several universities in Mexico to demonstrate the technology along the US-Mexico border. Their interest is based on years of highly technical research and development and will hopefully result in the development and publication of more solid application data.

Paul Morkovsky
- Shiner, Texas, USA

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Ed. note: It has been read hundreds of times, Paul, and will be read hundreds more. Thanks.

I am looking at this technology very hard. Our company has a current EPA project that is testing one of their commercial facilities. The problem in the past is fouling of the electrodes for many different reasons and this company seems to have solved them.

Regards,

Russell Pickett
- Butler, TN

Electrocoagulation works if the process is well developed. We are currently testing two systems at a tanning plant and at a chromium plating facility. The process is well defined and results are reliable and reproducible. We are utilizing AC current EC with pulsed current.

Leonid Kelner
- Reston, VA

It looks like everyone has a common problem

I can't even count how much stuff I have kicking around in my lab and shop because of manufacture's claims on performance (luckily the stuff was never installed in the field)

First
The internet It gives people the power to look for a solution to their problems without meeting or seeing the seller These guys have something that does something really neat and is usually invented in their back yard or stolen from their students from a university But does it work???(yes in the lab)

Stay away from fancy wordy web sites with lots of big words that you would have to watch StarTrek to understand I have a University degree but ,if you can't understand me simply what did it teach me Only to talk to other university grads Look for customer support in the field and rates Is it their President that will be doing it because of his great concern??

Second
Electro-flocculation does work

But every situation is different
How he will support you with real people in the field If the seller of the goods doesn't ask for samples and a break down of what your needs or if he talks more than you (tell him it's milking time)

There are companies and people out there that know their stuff and really stand up to what they provide But there are more flim flam cons than drops in the sea

Third
Tech is good ---But Who will be running this unit three guys making $120,000 a year "no" It will be a lower employee running the equipment And it has to be simple (light switch simple) Do Not Be Blinded by Lights

Four
Costs
.002 per gal But its on a one acre lot in downtown Dallas And what about the guys making $120,000

The only reason I linked to this page was that I was researching the possibility that I could use Electro F to improve the speed our process For bilge water separation (it's very simple after the research) I have helped two companies (in the past)in the Vancouver area that use (Electro F)for waste treatment Thanks for the vent Beware It just makes you a better customer

Cheers Dave

Dave Stranks
Waste Water Treatment - Vancouver BC Canada

Good day

I have read with interest all the comments on EC going back to the 90's. I am involved in waste water treatment and have experimented with EC for a couple of years. It does work on a production basis. I never found a better way to break cutting fluid emulsions and industrial textile dyes. It is now 2006 and the men in white coats experimenting with EC have not been standing still. The problems in the past were not about "does it work" they were about cost effectiveness. We can now treat waste water for as little as 0.25 cents per 1000 gals and a energy consumption of between 3-7 watts per gallon.

EC is here to stay, you can reduce sludge in treatment water by 60% in certain cases, but the chemical guys would never agree.

Ray Long
- London

95 percent of the readers are not "chemical guys", Ray -- we are just a candid world patiently asking since 1998 for references to some articles in peer-reviewed journals. 8 years and a quarter-million messages later, we've printed references to thousands of technical articles in peer-reviewed journals on hundreds of other subjects, but we're still waiting for the "electrocoagulation guys" to give us a short list of case studies on electrocoagulation printed in reputable journals. We're not saying such citations don't exist! Just give us a few impartial case studies. Start with ONE for heaven's sake.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

I am currently a Chemical Engineering Ph.D. student at the University of Arizona. My dissertation topic is Electrocoagulation. I see a lot of talk on this thread about peer-reviewed journal articles. I'm curious, are articles on laboratory results desired or are larger, pilot-scale results what everyone is looking for? Just wondering because I have collected about 35 recent journal articles on EC right now, but most of them are lab scale studies.

Also, I was wondering in more detail how EC is being used 'in the wild' as it were. I'm having trouble finding documented sources showing active industrial usage.

Matthew Schulz
- Tucson, AZ USA

I think we'd be delighted to see any list of articles you have, Matthew. But the electrocoagulation proponents on this page are trumpeting field success, so impartial peer-reviewed articles assessing those field successes would be most interesting and convincing. Thanks.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

Not knowing what everyone is interested in, I'd feel the best place to start when looking at the reputable literature on EC are two excellent recent review articles. Here are their citations:

Mollah, M.Y.A., Morkovsky, P., Gomes, J.A.G., Kesmez, M.., Parga, J. & Cocke, D.L. 2004 Fundamentals, present and future perspectives of electrocoagulation. J. Hazard. Mater. B114:199-210.

Holt, P.K., Barton, G.W. & Mitchell, C.A. 2005 The future for electrocoagulation as a localized water treatment technology. Chemosphere 59:355-67. Chem. Eng. J. 95:205-11.

These both contain numerous citations to the extant publications available. They also do well to lay out the challenges to overcome before EC becomes a reliable, widely-accepted technology.

Matthew Schulz
- Tucson, AZ, USA

Ed. note: Thanks, Matthew.

I am a PhD student in the Department of Civil Engineering, Obafemi Awolowo University, Ile-Ife, Nigeria. My research is on Electrocoagulation for Water Treatment.My question is as follows: The concept Surface Area/Volume ratio. How is it calculated? Which surface area and which volume? Thank you.

Kamar Taiwo OLADEPO
Student - Ile-Ife, Osun State, Nigeria

I am currently researching EC at the University of Sydney, funded jointly by the Australian Research Council and a large multinational.

To answer your question Kamar, the surface area/volume ratio (specific surface area) is usually the area of the anodic surface / the volume of electrolyte in the reaction zone. Different methods are used however (e.g. total electrode area), so state the way you calculate it (if only everyone did this!).

All else equal, a higher specific surface area means a smaller reactor, higher practical flow velocities, and theoretically lower voltage requirement (though the latter is insignificant for highly conductive streams). Tradeoffs are fouling, shorting and maintenance complications.


Two other general EC papers I would add to Matthew's previous post are:

Chen, G. (2004). "Electrochemical technologies in wastewater treatment." Separation and Purification Technology 38(1): 11-41.

Jiang, J.-Q., N. Graham, et al. (2002). "Laboratory study of electro-coagulation-flotation for water treatment." Water Research 36(16): 4064-4078.

Andrew Gadd
- Sydney, NSW, Australia

Ed. note: Thank you, Andrew.

I want to post a question or inquiry of my own.

 

I want to answer this question publicly

 

This letter is within a monitored forum, very much "alive" here in 2008. If you spot any broken links or obsolete info, please advise!