Torn up over tannins
Question: I have a customer that has the worst water. It’s the color of medium tea. I have a softener with tannin (resins) in it, but the tannin only lasts about six months. Is there another solution to clearing up his water?
Steve Roberts Jr., President
Ridge Water Filter Systems Inc.
Answer: Tannins are one of those water treatment problems that aren’t easily solved. I’m enclosing a paper written on tannin removal—I hope it helps. I would like to point to several issues. It’s very important to regenerate the tannin resin frequently. Tannins are a large molecular weight organic, which generally go on to the resin easily. The problem, which you’re well aware of, is getting them back off of the resin. You shouldn’t allow the tannins to sit on the resin for a long period of time, since they’ll tend to migrate into the resin bead. Once inside the resin, they’re difficult to remove. There are a couple of cleaning procedures contained within the paper enclosed.
If you haven’t tried an acrylic type of anion resin yet, I would suggest you do. Acrylic anion resins seem to have a good ability to pick up and, more importantly, release tannins. The system should be regenerated every 2-3 days with 10 lbs. salt/cubic foot of resin.
If you’re trying to remove both hardness and tannins in the same unit and it’s failing, I suggest two separate units. You may be forming calcium carbonate precipitation during regeneration, which can occur in the resin bed, the valve and the drain line. A mild acid can be used to clean precipitation that has occurred. Two separate units, with the softening unit first followed by the tannin unit, will eliminate the precipitation problem. Some areas of the country use softening resin and tannin resin in one unit and have good success. In other areas, however, it doesn’t work well.
Last but not least, there’s no 100 percent guarantee for any media used in tannin removal. It’s not realistic.
Editor’s note: Feel free to contact us via email (firstname.lastname@example.org) if you would like a .pdf file of the paper mentioned here from Sybron Chemicals on tannins and how to deal with them.