Organic Colour (Tannins) Reduction

Signs of the problem – Discoloured water from decayed vegetation or organic matter, usually from peatland, mires or bogs. The discoloration is usually worse after rainfall. The level of colour can be from a pale straw colour to deep yellow colour, similar to apple juice. Discolouration from tannins is not to be confused with iron presence in the water.

Solution. If the colour is very slight in some instances carbon filtration can be used. Carbon requires a very slow flow rate for colour reduction and can exhaust rapidly allowing the colour to pass again. The preferred approach to colour reduction is to use an organic scavenger/tannin filter. A tannin filter uses a specially selected anion resin which has an affinity to tannins, and regenerates on salt (using the chloride) to remove the colour.

ChatGPT-4 Response:

Given the description of your water quality issue, it sounds like the primary concern is the presence of tannins, which are organic compounds derived from decaying vegetation, commonly found in areas near peatlands, mires, or bogs. Tannins can give water a range of colours, from pale straw to deep yellow, resembling apple juice, especially following rainfall due to increased runoff. It’s important to differentiate this discolouration from that caused by the presence of iron, as the treatment methods differ.

To address the problem of tannin-induced discolouration in water, consider the following solution:

1. Assessment and Testing

First, it’s critical to accurately assess the water’s condition through testing. This will confirm the presence of tannins and help determine their concentration. You might also want to test for other potential contaminants to ensure a comprehensive treatment plan.

2. Filtration Systems

Anion Exchange Systems

Anion exchange units, similar to water softeners but designed specifically for tannin removal, can be highly effective. These systems work by exchanging tannins and other negatively charged ions in the water with harmless ions, usually chloride ions, effectively removing the discolouration and associated taste and odour issues.

Activated Carbon Filters

Activated carbon filters can also reduce tannins from water. These filters are particularly effective in absorbing organic compounds, including tannins, thereby improving the taste, odour, and appearance of the water. However, their effectiveness can vary based on the concentration of tannins and the specific characteristics of the water, so they are often used in conjunction with other treatment methods.

3. Maintenance and Monitoring

Regular maintenance of the chosen treatment system is crucial for sustained effectiveness. This includes monitoring the system’s performance and replacing or regenerating the treatment media as required. For anion exchange systems, this means regenerating the resin with salt, similar to how a water softener is maintained.

4. Professional Consultation

Given the complexity of water treatment and the variability of tannin concentration and composition, consulting with a water treatment professional is advisable. They can provide a tailored solution based on a thorough assessment of your water quality and specific needs.


Addressing water discolouration caused by tannins involves a combination of accurate diagnosis, selection of the appropriate filtration technology, and regular system maintenance. By following these steps, you can significantly improve the quality of your water, making it safer and more pleasant to use.