Potassium permanganate has a long history of successful application in 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. The reduction of trihalomethanes in water is one such use.

The Elsinore Valley Municipal Water District (E.V.M.W.D.) is located in south central California just west of Los Angles. The District covers a service area of 96 square miles, providing water and sewer services to over 86,000 persons. The average daily water demand is 37 MGD. Of that volume, 33% is well water, 37% is imported water from other districts, and the remainder is surface water. The potential for formation of trihalomethanes (THMs) was directly attributed to the surface water. Because of the potential for high THM formation, it was decided to evaluate CAIROX ® potassium permanganate as an alternative pre-oxidant to chlorine.

Full-scale evaluation of permanganate was conducted in April 2000. CAIROX ® was applied at the intake from Canyon Lake. The results of the full-scale evaluation are shown below. As seen, a significant reduction in the amount of trihalomethanes formed is realized when potassium permanganate is the pre-oxidant.

Pre-Oxidation: Potassium Permanganate vs Chlorine for THM Control

The above case study has shown that potassium permanganate is effective at:

• Replacing chlorine as a pre-oxidant
• Controlling formation of trihalomethanes in the plant and distribution system
• Improving floc settling, aided in coagulation, and reduced polymer usage
• Reducing Taste and Odor complaints (musty, fishy) from 5-10 per month to 0
• Controlling Fe/Mn episodes

Roth, J. G., Ozment, C.L., Stage 2 HAA Treatment Techniques, On-Line Trials and Costs, Presented at the Ilinois Potable Water Supply Operator Association, Sept. 2000.

Ma, J., Graham, N., Controlling the Formation of Chloroform by Permanganate Pre-oxidation-Destruction of Precursors, J Water SRT-Aqua, Vol.45, No.6, (1996).

Trihalomethanes (THMs) and Haloacetic Acids (HAA’s) are formed when chlorine reacts with the organic precursors in raw water. These precursors include humic and fulvic acids. Moving the point of chlorination from the raw water to later in the treatment and practicing effective coagulation of the precursors can result in a 40% to 70% reduction in trihalomethane levels. Current regulations limit THM concentrations in finished water to 80 µg/L and HAA concentrations in finished water to 60 µg/L.

Potassium permanganate is used in these systems as an alternate oxidant to pre-chlorination. Further reduction (5%-20%) in THM and HAA concentrations may result from permanganate addition. The primary purpose of permanganate treatment in these cases is as a substitute pre-oxidant for chlorine to oxidize organics causing tastes and odors, and to oxidize inorganic iron and manganese. Permanganate is not a substitute disinfectant for chlorine.

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

Permanganate is usually fed at the intake to allow the oxidant to react with the raw water before the addition of other treatment chemicals. A residual of 0.1 to 0.2 mg/L KMnO4 should be maintained in the water entering the treatment plant. Control can be visual or monitored using residual permanganate analytical methods given in Standard Method 4500-KMnO4.

For trihalomethanes:

Normal dosages of trihalomethane 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.

A cost-effective disinfectant by-product control program includes the application of potassium permanganate in place of raw water chlorination. Permanganate reduces formation of trihalomethanes or haloacetic acids, oxidizes taste and odor producing compounds, and aids in the coagulation process.

Zawacki, J., KMnO4 Contributes to Least Cost Treatment Solution, Water Engineering & Management, (May 1992). Form #3057

Myers, A. G., Evaluating Alternative Disinfectants For THM control in Small Systems, Jour. AWWA, , (June 1990)

Ma, J., Graham, N., Controlling the Formation of Chloroform by Permanganate Preoxidation-Destruction of Precursors, J Water SRT-Aqua, Vol.45, No.6, (1996)

Ficek K. J., Boll, J. E., Potassium Permanganate: An Alternatative to Prechlorination, Aqua, No. 7, (1980). Carus Form #240

Standard Method 4500-KMnO4 Potassium Permanganate, Standard Methods for the Examination of Water and Wastewater, 20th Edition, (1998). Carus Form CX #3353

• Taste & Odor Control
• Iron & Manganese Removal

• Industrial Wastewater Treatment
• Arsenic & Radium Removal

Carus Corporation has technical assistance available to answer questions, evaluate treatment alternatives and perform laboratory testing. Our laboratory capabilites include; Feasibility Studies, Treatability Studies and Analytical Services.

As an integral part of our technical support, Carus provides extensive on-site treatment assistance. We offer full application services, including technical expertise, supervision, testing, and feed equipment design and installation in order to accomplish a successful evaluation and/or application.

Standard feeders are designed specifically for CAIROX ® potassium permanganate. Various options and accessories are available to meet a wide range of applications. Custom-Engineered Feed Systems are complete, pre-engineered and prepackaged systems. They provide efficient, dust-free methods of storing, mixing, and feeding CAIROX ® potassium permanganate. System designs are customized to meet specific applications and customer needs.

During its more than 90-year history, Carus’ ongoing reliance on research and development, as well as its emphasis on technical support and customer service, have enabled the company to become the world leader in permanganate, manganese, oxidation, and base-metal catalyst technologies.

For further information on CAIROX ® potassium permanganate and its treatment for trihalomethanes, contact Carus Corporation at 1-800-435-6856.