Last week I wrote about the palatability of drinking water when iron (Fe) is above 4 ppm. Now let’s look at some ways to get Fe out of your water if you have a level that will interfere with water intake.
Below about 3 ppm, Fe can be removed, just like Ca and Mg, with a regular water softener, if the softener is set up for it. This can be helpful in removing the Fe which Fe-reducing bacteria thrive on. These bacteria, which form slimy, filamentous films in water pipes and troughs may also affect water intake. Either get the Fe out of the water (starve the bacteria), or be diligent in keeping water troughs clean (never a bad idea……).
Above 3 ppm, other methods have to be applied to improve water quality for dairy cows. Most will involve oxidizing the Fe and removal of the resulting complexes. Injection of a Chlorine (Cl) source will bind with the Fe and form complexes which will settle out. Either sodium hypochlorite or chlorine dioxide will work, but in either case a reaction tank is necessary after the Cl injection to allow time for the formation of the complexes and precipitation. The drinking water must then be drawn from above the layer of reddish water which will form at the bottom of the tank. Alternatively, the water can be run through a mechanical or activated carbon filter for removal of the Fe complexes.
Careful monitoring of the residual Cl levels is required! Too much, and you risk disinfecting the rumen. A swimming pool test kit will allow testing to keep residual Cl levels (at the tap) below about 0.3 ppm. This will also provide effective disinfection of the water troughs for other environmental or ion (sulfur or manganese) dependent bacteria.
Greensand filtration is another means of oxidizing Fe found in drinking water for dairy cows. This method requires routine backwashing and recharging to retain the oxidizing activity and will require additional pretreatment if Mn is present. Ozone injection is another, but more expensive, means of oxidizing Fe. Like chlorination, both of these methods will require filtration to remove the resulting Fe complexes.
Water chemistry is very complex and the design of an effective treatment system requires a complete understanding of all the constituents, pH and potential contaminants. One source of excellent information is the Penn State Water Resources website. When it comes time to consider the options for your particular water source, work with professionals who have NSF and WQA certifications.