Activated carbon and pH Jump??

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So I decided that my tank was looking a little too cloudy and wanted to run some activated carbon to clarify the tank.

Within about 30 minutes of starting carbon filtering through a reactor, my pH jumped from 8.30 to 8.37. The setup was a pump from my sump chamber through the reactor to the return chamber and bypassing my skimmer.

As my skimmer is used to control my pH it came on using house air (high CO2) to drive down the pH. Within about 10-15 minutes of turning off the reactor, the pH went right back down to 8.30 which is my setpoint.

I'm trying to sus out why the pH jumped from running an activated carbon reactor.

The sump volume is roughly 20gal and the total volume of my system is about 105gal.

The reactor was probably moving about 120gal/hr.

Normally, I expect increased water movement to reduce my pH as my air has higher CO2.

I'll experiment a little with this and see what I can deduce.

Any insights would be appreciated...does activated carbon do anything to raise pH?
 
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shneerf

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My guess is with any reactor off you have a whole "batch" of fluid concentrated (or this case highly filtered) fluid was sitting in the reactor now suddenly dumping its entire volume into the tank. Not sure why AC would do that, I never fully understood what AC removes exactly but my guess is that it's removing some acids.
 

Randy Holmes-Farley

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If there was water stored in the reactor, the biological degradation of organics will produce CO2 and lower pH.

GAC itself usually has a quite small effect on pH, but if you do not rinse it, it may have some.
 
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If there was water stored in the reactor, the biological degradation of organics will produce CO2 and lower pH.

GAC itself usually has a quite small effect on pH, but if you do not rinse it, it may have some.

There was no water stored in the reactor...

I think I must have disturbed the pH meter or something. I could not repeat the changes...and there is nothing I could imagine that would very quickly raise and lower the pH with GAC.
 

Randy Holmes-Farley

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There was no water stored in the reactor...

I think I must have disturbed the pH meter or something. I could not repeat the changes...and there is nothing I could imagine that would very quickly raise and lower the pH with GAC.

Thanks for the update! :)
 

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