AWWA JAW60923

When utility managers solicit bids for granular activated carbon (GAC) in their filters, they tend to limit it to bituminous GAC because of the perception that lignite GAC is inferior. This study, conducted at the Sweeney Water Treatment Plant in Wilmington, North Carolina was conducted to determine whether there are indeed differences between lignite and bituminous GAC. The plant treats Cape Fear River water using a series of treatment processes that include ozonation and biofiltration. For this study, the existing GAC media in two of the plant's full-scale dual-media filters was replaced; one with lignite GAC and the other with bituminous GAC. The two new filters and one control filter containing the original GAC were operated and monitored for 13 months. The first three months were used to exhaust the adsorptive capacity of the new GAC and biologically acclimate it. During the subsequent 10 months, water quality samples were collected from various points throughout the treatment plant and from the effluent of each of the three filters. The samples were analyzed for various physical, chemical, and biological constituents, and the results showed that the two types performed equally well for both filtration and biofiltration. The results of this study should encourage utility managers to include lignite GAC in bids for GAC media for use in drinking water treatment. Includes 3 references, tables, figures.