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pH of Mixed Liquor
Posted: Monday, December 31, 2012 11:10 AM
Joined: 12/31/2012
Posts: 2

We're having problems with nitrification in an enclosed HPOX aeration unit with surface aerators. The pH is probably borderline at 6.2-6.3. It is probably depressed by CO2 buildup in the headspace of the UNOX. My research indicates we would get minimal nitrification at that pH.


I'd like to know what normal pH is in mixed liquor from other types of aeration processes. Please tell me your pH and type of aeration.



Posted: Monday, December 23, 2013 9:27 AM
Joined: 5/23/2010
Posts: 7

 I have several types of aeration system none of which use pure oxygen. Our pH is between 6.5 and 7.5 at all times. I would guess the reason for your depressed pH is a lack of alkalinity or over nitrification, if there is such a thing, or a combination of the two. I would decrease the aeration rates and monitor alkalinity, ammonia and nitrate at the end of the aeration tanks.