JAR TESTING FOR POTASSIUM Permanganate Demand
Stock Solutions
(Strong Stock Solution)
5 grams potassium permanganate dissolved in 500 mL distilled water.
(Test Stock Solution)
1 mL strong stock solution thoroughly mixed in 100 mL distilled water.
Each 10 mL of the test stock solution added to a 1000 mL sample equals 1 ppm.
If you have a six position stirrer:
Using a graduated cylinder, measure 1000 ml . of the sample to be tested into each of the six beakers. Dose each beaker to simulate plant practices in pre-treatment, pH adjustment, coagulant, etc. Do not add carbon or chlorine. Using a graduated pipet, dose each beaker with the test stock solution in the following manner.
| Jar # | KMnO4 mL | KMnO4 ppm | Color |
| 1 | 1.0 | 0.10 | no pink |
| 2 | 1.5 | 0.15 | no pink |
| 3 | 2.0 | 0.20 | no pink |
| 4 | 2.5 | 0.25 | no pink |
| 5 | 3.0 | 0.30 | pink |
| 6 | 3.5 | 0.35 | pink |
Stir the beakers to simulate the turbulence where the KMnO4 is to be added and observe the color change.
As the iron and manganese begin to oxidize, the sample will turn varying shades of brown, indicating the presence of oxidized iron and or manganese. Samples which retain a brown or yellow color indicate that the oxidation process is incomplete and will require a higher dosage of KMnO4. The end point has been reached when a pink color is observed and remains for at least 10 minutes. In the preceding table a pink color first developed in beaker #5 which had been dosed with 3 mL/0.3 ppm. If the first jar test does not produce the correct color change, continue with increased dosages.
When applying potassium permanganate to raw water, care must be taken not to bring pink water to the filter unless you have “green sand”. Also, permanganate generally reacts more quickly at pH levels above 7.0.
A quick way to check the success of a KMnO4 application is by adding 5 mL of the test stock solution to 1000 mL finished water. If the sample turns brown there is iron or manganese remaining in the finished water. If the sample remains pink, oxidation is complete.
With proper application, potassium permanganate is an extremely useful chemical treatment. As well as being a strong oxidizer for iron and manganese, KMnO4 used as a disinfectant in pre-treatment could help control the formation of trihalomethanes by allowing chlorine to be added later in the treatment process or after filtration. Its usefulness also extends to algae control as well as many taste odor problems.