Zinc Levels higher than permited

[2571]

Good afternoon,
I oversee a very small industrial wastewater process that has permitted levels to be maintained. My last two reports have shown higher than allowed Zinc levels and my attempts to correct have failed. Our system is very simple in design, we collect our water in a 7000 gallon tank maintain the pH at 10.25, transfer to a 700 gallon retention tank introduce a flocculants called Klaride. After 45 minute of retention, we then transfer small amounts to a clarifier and gently blend in a polymer to get the collagulation process started the material then falls out and the clear water flows over the weir to our discharge to be treated with sulfuric acid for a pH adjustment between 7-8.5.
We have been advised to try a Chelant Bond Breaker. This is new to me and wanted to get another opinion. I have also heard we are too high on our pH. I was told to keep it this high to keep the zinc in solution.

Thank you for your time.

2571

 

[bimr]

If your hydroxide precipitation process is not working because of the presence of chelating or complexing agents, then you probably should investigate the sulfide precipitation process.

The sulfide precipitation process will provide good effluent quality even if chelating or complexing agents are present in the water.

http://www.pfonline.com/articles/030102.html

http://p2library.nfesc.navy.mil/P2_Opportunity_Handbook/9-I-3.html

http://www.nmfrc.org/bluebook/sec624.htm

 

[GarySCWSVI]

I would also suggest that you investigate using a Chelation Resin to remove the Zinc. The look like and are similar to Ion Exchange resins that are used in Demineralizers and Water Softeners, but, remove metals by a somewhat different process. The are regenerable for reuse using acid and caustic like a Demineralizer is regenerated. Too much other detail to discuss here. Take a look at the following web site:

http://www.purolite.com/FolderID/71/PageVars/Library/Products/Index.htm

Gary Schreiber, CWS VI
The Purolite Co.

 

[tomwalz]

Just for the heck of it see if anyone has introduced anything galvanized into your stream. I know it is a long shot and not directly relevant to your question but it happened to me once.

Tom


Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

 

[FiltrationEngineer]

I know of an industrial pretreatment plant that had a similar problem. They searched for a source of zinc in the chemicals they used and couldn't find one. On a whim, the plant manager sent some tap water out for zinc testing and it came back out of limits. The city was using some kind of zinc containing chemical in their water treatment process and had the dose way off.

 

[aquaseaulutions]

Few chemicals are very effective to treat that effluent. There is few options I suggest:

AquaPerl by Atlas environmental products (819-565-9688) and obtained >98% Zn reduction with that.
Global Ionix system:

http://www.globalionix.com

Moonstone RSA:

http://www.moonstoneinc.ca

Good luck!