Granular Activated Carbon Contactor

Depending on the contaminant, raw water should contact the GAC for an empty bed contact time (EBCT) typically 5-20 minutes. GAC requires periodic replacement. GAC systems are typically installed before chlorination to reduce DBP formation potential and to prevent the GAC from becoming more brittle. Raw water enters the top of the contactors and flows down through the GAC media bed. The GAC at the top of the bed reaches capacity and forms a wave front of spent GAC that progresses from top to bottom of the GAC column. Sample taps along the side of the vessel help operators predict when breakthrough will occur as they track how fast the GAC is being consumed. Operating the tanks in lead/lag configurations provides the most efficient use of the GAC media. Once the GAC in the lead contactor is fully exhausted, the media is replaced and the lag contactor becomes the new lead