NoRise pH Stabilized Activated Carbon
A patented technique to pre-treat activated carbon with a weakly adsorbed organic acid for pH sensitive applications involving treatment of potable drinking water, industrial process water, and groundwater remediation.
A common problem associated with the start-up of fresh beds of activated carbon in water treatment applications is an inadvertent pH rise. The exact intensity and duration of the pH increase is greatly dependent upon the water chemistry in any given application, but typically ranges from one to three pH points and persists for several thousand bed volumes of water. This pH change can cause substantial compliance issues for some facilities.
No definitive theory as to why this pH spike occurs has been proven. Potential causes include leaching of alkaline constituents from the carbon’s ash and ion exchange interactions with surface groups on the carbon which generate hydroxide (OH-) ions that raise the water’s pH. With these theories in mind, Evoqua Water Technologies has developed our NoRise process, a patented (US Patent Nos. 6,946,077 and 7,300,586) technique to pre-treat activated carbon with a weakly adsorbed organic acid. As a result, the pH rise is mitigated without affecting the long-term performance of the carbon. NoRise treated carbons have been rigorously tested on a myriad of influent water types, including groundwater, surface water, and process waters. In each case, the pH rise was successfully reduced with tighter pH control than standard acid washed carbons.
The NoRise process can be applied to both virgin and reactivated activated carbons in a variety of mesh sizes. For information on applying our NoRise process to our base carbons, please contact your Evoqua Water Technologies Technical Sales Representative.