Water Pumps & Treatment News

Water Treatment: Tannin Removal

At EDS Pumps & Water Treatment Ltd., we understand how important clean drinking water is. That is why we offer a wide range of water treatments, water pumps, and services to our customers throughout the Lower Mainland. Our team of Water Treatment Specialists can help with your tannin removal needs.

Tannin removal services from EDS Pumps

What are Tannins?

Tannins are large molecular weight organic compounds. They are formed through the decomposition of plant materials. These organics are generally found in surface waters or shallow wells. There are two primary categories in which tannin fall: Humic acid and Fulvic acid. These are simplified structures of very large molecules. The structure of tannin varies from location to location, depending on the vegetation in the area. Tannins can cause a yellow to dark ‘tea’ colour in water and may impart taste and odour. Tannins are not directly regulated by a governmental agency; however, there is a secondary drinking water standard of 15 alpha units for colour. A secondary drinking water standard is not federally enforced. Tannins by themselves are not a health issue unless the water is chlorinated, then it can form a carcinogenic compound called Trihalomethanes (THM’s), On there own, tannins are aesthetically displeasing as the bathwater and toilets look dirty.

Treatment Methods of Tannin Removal

Tannins can be difficult to remove from water, as one treatment method may be effective in one area but totally ineffective 10 miles down the road. Tannin removal is dependent upon the vegetation in a given area.

Tannin removal via anion exchange resins occurs through both an ion exchange and an absorption process. Tannins have a slightly negative charge, causing them to be exchanged for chloride onto the resin. It is also believed that the anion resin can absorb organics. Salt is used to regenerate the anion resin. Generally, the resin will be brined at approximately 14 lbs per cubic foot salt (NaCl). It is extremely important to regenerate the resin frequently. Once the tannins are exchanged/absorbed onto the resin they will tend to migrate into the inner matrix of the resin bead. Once this occurs, it is very difficult to regenerate the tannins from the resin. The system should be regenerated every two to three days. Frequent regenerations will reduce the likelihood of organic fouling. Longer regeneration intervals will promote organic fouling, whether the anion resin is acrylic or styrene based.

Tannin resin is often mixed with softening resin, which reduces the amount of space required by the equipment and reduces the cost of the system. This type of design has performed satisfactorily in many areas; however, during regeneration, the salt will displace calcium from the cation resin and potentially alkalinity from the anion/tannin resin, which can promote calcium carbonate precipitation. It can be seen as a white precipitate in the resin bed and a coating on the drain line. Pressure drops through the system or a milky-white substance in the backwash water are indicators of precipitation.

Other Methods for Tannin Removal

Some of the other methods for tannin removal include:

Oxidizing Agents

Oxidizing agents like chlorine are effective at breaking down organic compounds like tannins. A simple jar test will show the concentration and retention time required to oxidize tannins. An activated carbon unit following the retention tank will remove the chlorine and may adsorb other organic compounds in the water. Some types of activated carbon alone may reduce the tannins to acceptable levels. Consult your carbon manufacturer for the appropriate type of product. As already noted, the reaction between chlorine and tannins might produce trihalomethane (THMs) which are carcinogens.

Reverse Osmosis

Reverse Osmosis is another effective method for removing tannins. Since tannins are high molecular weight organics, reverse osmosis should reject them effectively; however, tannins will tend to foul the membrane in the system. It also is very expensive to properly install a whole house reverse osmosis system to treat all of the water.

If you would like to learn more about tannin removal, or if you are interested in one of our water treatment services or products, please contact EDS Pumps & Water Treatment Ltd. at 604-534-1115 and ask to speak to one of our Water Treatment Specialists for more information and assistance.