Naturally Occurring Elements in Groundwater Part 2 of a Series — Iron and Manganese
There are naturally occurring elements and minerals within Nebraska’s geology, and with that, it is not uncommon to find them in Nebraska’s groundwater. Calcium, magnesium, iron, manganese, fluoride, arsenic, and uranium are among the elements found in Nebraska. This month, the spotlight series continues with iron and manganese.
Iron & Manganese
Iron and manganese can be a nuisance in a private well system. They are similar metals that cause taste, appearance, and staining problems at concentrations as low as 300 micrograms per liter (μg/L) or parts per billion (ppb) to plumbing fixtures, porcelain, dishes, glassware, and laundry. The minerals can give water a metallic and/or bitter taste and can have an undesirable effect on the taste/color of food prepared with it. They may react with the tannins in coffee, tea, and some alcoholic beverages affecting both appearance and taste. They are also known for scale layer build-up and clogging issues within water pipes and plumbing fixtures, e.g. hot water heaters, pressure tanks, and water softeners. Of the two, iron is found more frequently in ground-water, though manganese is often found with iron. Iron in drinking water is not considered a health hazard. Iron and manganese bacteria are found in the soil and shallow aquifers. The bacteria are not known to present a health risk, but they do form a reddish-brown (iron) or brownish-black (manganese) slime-like residue as they feed on the iron and manganese in the water. This slime is often found in plumbing fixtures, toilet tanks, wash machines, and other water-using appliances. Another common indicator that the iron and manganese bacteria exist, is a foul odor (similar to a rotten egg smell). The odor is a byproduct of the bacteria feeding on the iron and/or manganese. If either the slime or odor are noticed, water tests should be conducted. The use of chlorine or alkaline builders (such as sodium and carbonate) to kill bacteria may intensify staining because it causes the dissolved minerals to precipitate out of solution.
At high concentrations, manganese can be a health hazard. Infant formula containing soy and rice cereal should not be made with water above 300μg/L or ppb in manganese due to the content of manganese already present in the formula or cereal. Older children and adults who drink water that is above 1,000μg/L or ppb in manganese for many years may experience adverse health effects to their nervous system. These effects may include behavioral changes, slow and/or clumsy movements, or learning problems.
As with any filtration system, one should know their water quality analysis results and research the manufacturer’s specifications of the treatment units being considered. For providing safe drinking water, point of use (POU) devices such as reverse osmosis (RO), distillation, and carbon filtration are all good options to remove dissolved manganese, and often iron. To service the whole house, a point of entry (POE) device is a better choice. Common POE devices for private water supplies include ion exchange water softener, oxidizing filters, and aeration (pressure type) followed by filtration. All of these treatment options have their advantages and limitations, thus making treatment sometimes challenging. Knowing the form and concentration of iron and manganese in your raw water, the nuisance issues, and researching the effectiveness of treatment units and frequency/cost of maintenance are all consideration factors in making a best treatment decision.
For further information about iron and manganese and the types of treatment, see Nebraska Extension’s NebGuides at https://water.unl.edu/article/drinking-water/nebguides.
This article was reviewed by Dr. Bruce Dvorak