Removing Colloidal Manganese in Surface Water

[Weizmueller]

When dissolved Mn shows up in the source water prior to drinking water treatment, oxidation is a straightforward prescription.

What about "colloidal manganese"? This feature of the river water I'm trying to treat is apparently composed of tiny particles that pass through a 0.22 micron filter, do not change with KMnO4 oxidation, and are not reduced by the normal coagulation process (with Alum and polymer) and filtration (mixed media).
Academic research says it's a coagulation challenge, and the colloids have to be destabilized. I'm working on it, but not seeing much progress.
Has anybody faced this problem? Thanks!

 

[bimr]

The most practical approach is destabilization with the addition of a pre-filter low dose of a cationic coagulant (alum). The reaction with alum may be pH dependent. Jar tests in the field with fresh water samples are recommended.

 

[ashtree]

I absolutely agree with bimr but if the water is low in turbidity it may be difficult to form sufficent floc to enmesh all the small particles.
So you could artificially introduce some turbidity in the form of something like bentonite. This is sometimes done but i am not convinced its the right approach.
Another option could be to use micro or ultrafiltration if the concentrations you are dealing with are low. You would then backwash off the trapped manganese particles.

I assume by your post that you are oxidising soluble manganese with KMNO4. Are you dosing sufficent KMNO4, operating at a suitable pH and have enough detention time to allow the reaction to run to completion.Oxidation rates slow as the concentration of manganes reduces. Likewise is there sufficent alkalinity in the water? The presence of organics also reduces the reaction rates.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"