What is Permanganate?
Permanganate (MnO4) is a strong oxidant used in water treatment to control taste, odours, biological growth, zebra mussels, and to remove colour, manganese and iron. In addition, permanganate can be used to control the formation of disinfection by-products by oxidizing the organic precursors. In industrial waste treatment, permanganate is used for odour control, toxic pollutant destruction, bio-augmentation, and grease removal.
How is Permanganate measured?
Permanganate is measured spectrophotometrically. Its concentration is directly proportional to absorbance at 525 nm due its colour (pink to violet).
Why is monitoring Permanganate important?
Although it is an effective treatment aid, residual permanganate is not desirable in the treated water. For this reason, dosing of permanganate needs to be carefully controlled and adjusted to provide just enough permanganate to achieve treatment goals but not in excess so that no residual remains in the water. Quick and reliable dose pacing of permanganate can be accomplished by monitoring its concentration in real time at a location downstream of the application point. Concentrations exceeding a pre-determined threshold at the monitoring point would indicate overdosing, and therefore dosing can be adjusted accordingly.
Where is Permanganate Measured?
Permanganate is most commonly added into water at the raw water intake. Alternatively, it can be added further downstream along the treatment train (e.g. together with coagulants at the rapid mix tank). Since sufficient contact time needs to be provided for permanganate to work effectively, monitoring its concentration after the filtration unit to detect residual amounts would be most optimal for dosage control purposes.