Potassium permanganate has a long history of successful application in municipal drinking water treatment, providing both primary and secondary benefits. It is widely used by facilities to help meet regulatory rules and public pressures to produce quality drinking water.

Potassium permanganate is used to remove arsenic (As) in ground water treatment systems that employ filtration. Permanganate oxidizes arsenic (As3+) to As5+ that can adsorb to insoluable precipitates such as hydros manganese hydroxides or ferric hydroxide. The precipitates are then removed from the drinking water supply in the clarification and filtration processes. Permanganate can also be used for arsenic removal in surface water treatment plants that have filtration.

Factors that affect removal efficiency include water chemistry, pH, temperature, contact time, and application point. Reaction times are rapid under normal conditions of temperature and pH. However, temperatures <35°F, and pH values <5.5 require reaction times longer than two minutes. In most cases, 5 to 10 minutes of reaction time is sufficient.

It has been demonstrated that the presence or addition of iron (Fe2+) will enhance the efficiency of As removal for municipal drinking water treatment. A ratio of Fe to As of 20:1 is recommended.

1 part of soluble arsenic requires 1.26 parts of potassium permanganate.

Proper feed equipment specially designed to handle potassium permanganate is recommended and available from Carus. For proper removal of As with municipal drinking water treatment, the utility must have water filtration or coagulation/filtration to remove the arsenic containing precipitates formed during oxidation. In addition, alkalinity and hardness > 50 mg/L are recommended for proper coagulation of these precipitants.

Potassium permanganate quickly oxidizes As3+ in most cases without pH adjustment. The freshly precipitated arsenic and manganese floc will further adsorb metal ions and organic compounds while enhancing the effectiveness of the coagulation process.

• removes iron, manganese, hydrogen sulfide and other undesirable compounds,
• helps control tastes and odors of drinking water, and
• acts as a substitute oxidant to chlorine in a disinfection by-product (DBP) control program.

Lauf, G. F., Waer, M. A., Arsenic Removal Using Potassium Permanganate, AWWA WQTC, 1993

Ficek, K. J., “The Potassium Permanganate/Greensand Process for Water Treatment” Water Quality Association Conference, 1994

Permanganate is used in municipal drinking water treatment systems to aid in the control of off-flavor tastes and odors. Off-flavors are usually attributed to the presence of blue-green algae in the water supply. The oxidant has been found to be most effective in treating off-flavors described as fishy, septic, grassy, and cucumber. In many cases, permanganate will compliment activated carbon and other water treatment processes resulting in a cost-effective taste and odor control program.

To determine the Permanganate Value PVt. (where t is time), laboratory tests simulating plant conditions of time, the sequence of addition of other treatment chemicals, etc., are conducted. The procedure is described in Carus Form # 3353. This is the raw water permanganate demand in a given period of time. This value is used to calculate the feed rates needed.

Permanganate is usually fed at the intake to take advantage of the time available in the raw water transmission line and to insure that all of the oxidant is used up prior to the addition of other treatment chemicals such as alum, chlorine, activated carbon, or iron salts. Control can be visual or can be monitored using residual permanganate analytical methods given in Standard Method 4500-KMnO4.

Normal dosages to control tastes and odors will range between 0.5 and 2.5 mg/L KMnO4 depending on the degree of raw water contamination. The average dosage is ~1.0 mg/L KMnO4 .

Proper feed equipment specially designed to handle permanganate is recommended and available from Carus. The product must be put into solution before being introduced into the drinking water treatment system. Operators should be trained to monitor permanganate residuals and to exercise proper safety precautions when handling the oxidant.

Cost-effective taste and odor control programs include municipal drinking water treatment with permanganate to complement activated carbon and other control methods. In many cases, the volume of carbon is substantially reduced as a result of permanganate pre-treatment. Permanganate does not form trihalomethanes, and aids in the coagulation process.

Lauf, G. F., Waer, M. A., Arsenic Removal Using Potassium Permanganate, AWWA WQTC, 1993

Ficek, K. J., “The Potassium Permanganate/Greensand Process for Water Treatment” Water Quality Association Conference, 1994