Short Term Treatment

In the short-term you can consider point-of-use devices to remove manganese from the water or consider providing a temporary water source. We do not recommend boiling the water even though boiling would cause the manganese to oxidize and likely precipitate or settle out of the water. Water with a manganese problem may also contain elevated levels of iron, arsenic, and other trace metals. Get a comprehensive water quality analysis and consider using either a point-of-use device or an alternative potable water source, like bottled water.  If you suspect the manganese is associated with a nuisance bacterial problem, it is advisable to shock disinfect and flush the well or water distribution system.

Long Term Treatment

In the long-term the problem with manganese can usually be resolved after the cause for the condition has been documented and the chemistry and biological quality has been investigated. Common treatment systems for Manganese include phosphate treatment (sequestration approach commonly used by city water sources), an ion-exchange water softener, oxidizing filters, aeration filtration systems, and chemical oxidation using a strong oxidizer.

These treatment techniques are effective in water that has an almost neutral pH (approximately 7.0). The phosphate compound treatment is an exception and is effective in the pH range of 5.0 to 8.0. ‍

Phosphate treatment- Low levels of dissolved iron and manganese at combined concentrations up to 3 mg/l can be remedied using the phosphate compound treatment. Phosphate compounds are a family of chemicals that can surround minerals and keep them in solution. Phosphate compounds injected into the water system can stabilize and disperse dissolved manganese at this level. As a result, the iron and manganese are not available to react with oxygen and remain in solution.The phosphate compounds must be introduced into the water at a point where the manganese is still dissolved in order to maintain water clarity and prevent possible iron staining. This should be before the pressure tank and as close to the well discharge point as possible. Phosphate compound treatment is a relatively inexpensive way to treat water for low levels of iron and manganese. Since phosphate compounds do not actually remove manganese, water treated with these chemicals will retain a metallic taste. In addition, too great a concentration of phosphate compounds will make the water feel slippery.

Phosphate compounds are not stable at high temperatures. If phosphate compound-treated water is heated (for example, in a water heater or boiled water), the phosphates will break down and release iron and manganese. The released iron and manganese will then react with oxygen and precipitate.

Adding phosphate compounds is not recommended where the use of phosphate in most cleaning products is banned. Phosphate, from any source, contributes to excess nutrient content in surface water.

‍Ion-exchange water-softener - Low to moderate levels of dissolved manganese and iron, at less than 5 mg/L concentrations usually can be removed using an ion-exchange water-softener. Be sure to check the manufacturer's maximum manganese and iron removal level recommendations before you purchase a unit. Capacities for treating dissolved manganese and iron typically can range from 1 to 5 mg/L. Already oxidized manganese and iron particles or levels of dissolved manganese and iron exceeding the manufacturer's recommendations will cause a softener to become plugged.

The principle is the same as that used to remove the hardness minerals, calcium and magnesium; i.e., manganese and iron in the untreated water are exchanged with sodium or potassium on the ion-exchange-medium. Manganese and iron are flushed from the softener medium by backwashing and the manganese and iron are carried away in the wastewater. Sodium from the ion-exchange medium remains in the drinking water and could be a possible problem for those with high blood pressure.

Since manganeses and iron removal reduces the softening capacity of the unit, the softener will have to be recharged more often. The manufacturer of the softener medium is able to make recommendations concerning the appropriate material to use for a particular concentration of manganese and iron. Some manufacturers recommend adding a "bed cleaning" chemical with each backwashing to prevent clogging.

Not all water softeners are able to remove manganese and iron from water. The manufacturer's specifications should indicate whether or not the equipment is appropriate for manganese and iron removal.

Water softeners add sodium or potassium to the water, a health concern for people on sodium-restricted diets and reduce the total hardness of the water. Consider installing a separate faucet to provide unsoftened water for cooking and drinking.

‍Oxidizing filter - An oxidizing filter treatment system is an option for moderate levels of dissolved iron and manganese at combined concentrations up to 15 mg/L. The filter material is usually natural manganese greensand or manufactured zeolite coated with manganese oxide, which adsorbs dissolved iron and manganese. Synthetic zeolite requires less backwash water and softens the water as it removes iron and manganese. The system must be selected and operated based on the amount of dissolved oxygen. Dissolved oxygen content can be determined by field test kits, some water treatment companies or in a laboratory.

‍Aeration followed by filtration - High levels of dissolved iron and manganese at combined concentrations up to 25 mg/L can be oxidized to a solid form by aeration (mixing with air). For domestic water processing, the "pressure-type aerator" often is used.

In this system, air is sucked in and mixed with the passing stream of water. This air-saturated water then enters the precipitator/aerator vessel where the air separates from the water. From this point, the water flows through a filter where various filter media are used to screen out oxidized particles of iron, manganese, and some carbonate or sulfate.

The most important maintenance step involved in the operation is periodic backwashing of the filter. Manganese oxidation is slower than for iron and requires greater quantities of oxygen. Aeration is not recommended for water containing organic complexes of iron/manganese or iron/manganese bacteria that will clog the aspirator and filter.

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‍Chemical oxidation followed by filtration - High levels of dissolved or oxidized iron and manganese greater than 10 mg/L can be treated by chemical oxidation, using an oxidizing chemical such as chlorine, followed by a sand-trap filter to remove the precipitated material. Iron or manganese also can be oxidized from the dissolved to solid form by adding potassium permanganate, hydrogen peroxide, or Ozone to the untreated water. This treatment approach is particularly valuable when iron is combined with organic matter or when iron bacteria are present. I have done research using ozone and Ozone Iron and Manganese Removal is a great approach.

The oxidizing chemical is put into the water by a small feed pump that operates when the well pump operates. This may be done in the well, but typically is done just before the water enters a storage tank. A retention time of at least 20 minutes is required to allow oxidation to take place. The resulting solid particles then must be filtered. When large concentrations of iron are present, a flushing sand filter may be needed for the filtering process.

If organic-complexed or colloidal iron/manganese is present in untreated water, a longer contact time and higher concentrations of chemicals are necessary for oxidation to take place. Adding aluminum sulfate (alum) improves filtration by causing larger iron/manganese particles to form.

When chlorine is used as the oxidizing agent, excess chlorine remains in treated water. If the particle filter is made of calcite, sand, anthracite, or aluminum silicate, a minimum quantity of chlorine should be used to avoid the unpleasant taste that results from excess chlorine. An activated-carbon filter can be used to remove excess chlorine and small quantities of solid iron/manganese particles.

Any filtration material requires frequent and regular backwashing or replacement to eliminate the solid iron/manganese particles. Some units have an automatic backwash cycle to handle this task.

The ideal pH range for chlorine bleach to oxidize iron is 6.5 to 7.5. Chlorination is not the method of choice for high manganese levels since a pH greater than 9.5 is required for complete oxidation. Potassium permanganate will effectively oxidize manganese at pH values above 7.5 and is more effective than chlorine oxidation of organic iron if that is a problem.

Potassium permanganate is poisonous and a skin irritant. There must be no excess potassium permanganate in treated water and the concentrated chemical must be stored in its original container away from children and animals. Careful calibration, maintenance, and monitoring are required when potassium permanganate is used as an oxidizing agent.

Warning:  Many years ago a small housing development in Pennsylvania was required by the State to start chlorinating its community water supply system.  They complied and shortly afterward black particles started appearing in their water system.  The black particles were not manganese dioxide (MnO2) but cupric oxide (CuO).  They happened to have a copper tank and were using  that to chlorinate the water.  The chlorination oxidized the copper metal which flaked off into the water as tiny black particles of cupric oxide which then spread throughout the water distribution system.  It is a bad idea to let any strong oxidant come into contact with copper, be it a tank or pipe.  Incidentally, the residual chlorine in city water is not usually a significant problem in the copper pipes of a house although, if the water sits in the copper pipes long enough, it could develop a bit of a copper taste.