Dosage of permanganate to oxidize manganese
You can always add a permanganate monitor and link your dosing rate to it. Just becareful some monitors have interferences such as chlorine in the case of Hach.
To help you more it would be useful to describe the treatment. Do you have other chemical? after oxydation what are you using as equipment?
We might be able to help you out, but you have to provide a few more details about your setup:
- What is the size of your plant?
- Where is it located?
- What quantity of permanganate are you using?
Sodimate is a company that specializes in water-treatment dry chemicals and powders.
After you inject the permanganate I am assuming the water goes through a filter of some kind? Is the permanganate making it through the filters or are you not adding enough and the Manganese is making it through the filters? Our setup we run a DPP (diaphram pump) that pumps the permanganate into the raw water and almost immediately it enters a greensand filter. Both the permanganate and Iron/Manganese are filtered out and the water comes out clean, at that point we add our chlorine and it goes into the holding tank or resivour. Our DPP pump is connected to our raw water pump so it only runs when the raw water pump is running. As long as you keep your concentration of permanganate the same you should have a consistent "pink" water going into your filters.
Do you use permanganate in liquid or powder form?
Is it surface or ground water?
What’s the iron count? Permanganate reacts with Fe and Mn.
The ideal would be to have air oxidation. If so, you might even be able to dispense with the permanganate entirely.
I use a permanganate preparation of 30 g/l. My average iron concentration is 0.25 mg/l and it is naturally already 90% oxidized before it gets to the well, and it is surface water. My pH at plant inlet varies on average between 7.00 and 7.50. Is air oxidation more efficient with lower concentrations of Mn? Does this type of treatment require a large contact area between air and water?
Thank you for your answers.
Take your Raw Water measurements for Fe and Mn. The dosage of Permanganate is 1:1 for Iron and 1:2 for Manganese. Figure a reaction time of 30 - 45 minutes. If you have organics ( like we do in the Southeast during the summer, then add some (0.50) to help cover that.
So typically of you have 0.65 mg/L Fe and 0.28 mg/L of Mn, you would add 0.65 + 0.56 = 1.21 mg/L of permanganate. Add a little for anything else in the water (other metals, pesticides, organics, etc.) and you will be good to go.
We have a conventional plant so I have the luxury of monitoring the color in the flocculator/basin. I go for a light purple at the top of the basin with brown coming out of the flocculator. So if the water if purple when it hits your filters you are adding too much. Hint, extra chlorine in the filters will help with that.