Excessive levels of iron and manganese are very common water problems in many U.S. homes. Unlike certain health related contaminants that are typically unseen, these contaminants exhibit undesirable visual and aesthetic properties such as color, odor and poor taste. In public water systems, they can
Excessive levels of iron and manganese are very common water problems in many U.S. homes. Unlike certain health related contaminants that are typically unseen, these contaminants exhibit undesirable visual and aesthetic properties such as color, odor and poor taste. In public water systems, they can react to form products that cause significant issues such as plugging of piping, distribution lines and home plumbing networks. There are several different ways water treatment professionals can solve these issues. Here"s a look into how these problems can be solved.
Ways to treat iron and manganese
Although multiple options for iron removal are in use, most fall within one of the following three categories:
Sequestration
Cation exchange
Oxidation/filtration (e.g., specialty filtration media types).
Where iron is very low (typically 0.3-0.8 mg/L), sequestering agents, which use some form of polyphosphates to combine with the dissolved ferrous iron, can effectively keep the iron in solution by combining with the iron to form a protective coating, preventing it from forming filterable precipitants and depositing. However, it must be noted that iron is not removed, but complexes with the sequesterent. Although they can be effective, sequestering agents are not usually practical or efficacious for high flows or systems with iron concentrations over a certain threshold.
Cation exchange, using conventional softening resins, can be effective for reducing low levels of dissolved iron. In addition to calcium and magnesium, ferrous iron as Fe+2 is exchanged for sodium on the resin and regenerated with salt brine regularly depending on the hardness of the water. Most water treatment professionals would agree that softening for iron and manganese removal can be efficacious (if the elements are in the dissolved state), but for iron removal alone it is not the most practical solution for high flows or concentrations of iron and manganese exceeding 0.8 mg/L or 0.1 mg/L respectively.
This is primarily due to the degradation of the resins over time and more frequent regenerations and higher brine use. Also, regeneration effectiveness and frequency needs to be monitored closely. One other drawback is that if the constituent is oxidized prior to reaching the softener it can result in fouling, a high drop in pressure, and subsequent bleed through.
