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pH drop across GAC filters

pH drop across GAC filters

(OP)
Has anyone experienced pH dropping across GAC filters? The filters have been installed alleviate problems with pesticide in drinking water. Since commissioning the filters, the pH has been dropping from 8.3 at the inlet to as low as pH7.2 at outlet.

One theory is development of a biological mass in the GAC being responsible for causing a larger than expected shift in treated water pH where biological growth produces CO2, which when absorbed, reduces water pH. Has anyone seen this in practice elsewhere?

RE: pH drop across GAC filters

Activated carbon is a natural material, but undergoes considerable processing. During the manufacturing process, the carbon is often washed using phosphoric, hydrochlorid, or sulfuric acid, to remove inorganic and organic residues.

Contact the supplier of the material and express your concerns.

RE: pH drop across GAC filters

Dear Mr. Tipp79

Indeed, maybe what i write doesn't written in any journal or publication. But I have the same experiece as you do.
The reason of the pH decreasing is because the activated carbon is likely absorb Calcium Carbonate. Thus the pH will goes down.

By the way The reason that stated by mr. Bimr maybe can be happening too.

To test it, why don't you conduct a simple test about the water hardness. You will see some hardness decreasing after using activated carbon. :)


www.on-water.us

RE: pH drop across GAC filters

Dear tipp79,

I completely agreed with Mr bimr.
You may be using acid washed Activated carbon.

AC is acid washed because to reduce the Ash content.
Please check AC specification.

Krunal Bhosale
http://waterengineer.co.in
All about Water and Wastewater Treatment

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