Removal of higher molecular weight organic compounds by the granular activated carbon adsorption unit process.

The granular activated carbon adsorption unit process in drinking water treatment typically removes purgeable organic compounds for time periods on the order of a few weeks. Experimental evidence indicates that less volatile compounds of generally higher molecular weight than the purgeable fraction, but still detectable by gas chromatography, are efficiently removed for longer periods. Field data substantiate this. Explanatory mechanisms may include stronger adsorption affinities or biodegradation. Non-gas chromatographable, higher molecular weight materials such as humic acids, as measured by Total Organic Carbon (TOC) or trihalomethane formation potential, revert to lower removal efficiencies. Biodegradation may be responsible for a continued long term removal of a fraction of these materials.