Drinking Water Treatment – Potassium Permanganate

EFFECTIVE AGAINST: Dissolved iron and manganese, and hydrogen sulfide.


Uses of potassium permanganate

Potassium permanganate is a point-of-entry treatment method that oxidizes dissolved iron, manganese, and hydrogen sulfide into solid particles that are filtered out of the water. It can also be used to control iron bacteria growth in wells.

How potassium permanganate works

Potassium permanganate is available as a dry, purplish solid. A device injects a solution of potassium permanganate into the water between the water pump and holding tank.

Potassium permanganate oxidizes iron, manganese, and hydrogen sulfide into particles. The particles are then filtered with a multimedia filter which can be either manganese-coated aluminum silicate above manganese-treated green sand or an 8-inch layer of anthracite above manganese-treated greensand. If an insufficient amount of iron, manganese, or hydrogen sulfide is oxidized prior to filtration, the manganese coating on the filter media acts as a backup oxidant to treat any remaining contaminant. If too much potassium permanganate is fed into the water prior to filtration, the excess potassium permanganate serves as a regenerant for the filter media. The water should be colorless when it leaves the filter.

When treating water to remove iron bacteria, a solution of potassium permanganate is fed into the well. A concentration of 3.8 to 7.6 grams per gallon has been found to be very effective. After the solution is added in the well, continuous agitation will help loosen and disintegrate sediment and organic material produced by the bacteria, thus enhancing treatment effectiveness. Agitation can be accomplished by turning the well on and off, which brings water up through the well casing and then lets it fall back into the well.

Maintenance of a potassium permanganate device

Potassium permanganate supplies must be periodically refilled as part of the maintenance routine. If using potassium permanganate in a well, periodic treatment to dissolve iron deposits and mineral scale may also be necessary. Such treatment requires the use of strong acids, so consult a water treatment specialist for guidance. Potassium permanganate injection devices and pumps are similar to those used in chlorination systems.

Special considerations for potassium permanaganate use

Using potassium permanganate requires careful calibration, maintenance, and monitoring. Potassium permanganate is sensitive to temperature extremes and performs best between 50 and 72 degrees Fahrenheit. Well water is approximately 55 degrees Fahrenheit.

Potassium permanganate is poisonous and irritates skin, so handle it carefully and ensure that there is no excess potassium permanganate in the treated water. The chemical gives water a slight pink tint. Water should be colorless after treatment. The concentrated chemical must be stored in its original container, away from children and animals. Protect storage containers from physical damage.

Questions to ask before you buy

Before purchasing a water treatment device, have your water tested at a state certified laboratory to determine the contaminants present. This will help you determine if potassium permanganate is an effective treatment method for your situation. See Questions to Ask Before You Buy A Water Treatment System for more information.

Adapted from: Wagenet,L., K. Mancl, and M. Sailus. (1995). Home Water Treatment. Northeast Regional Agricultural Engineering Service, Cooperative Extension. NRAES-48. Ithaca, NY.