Potential of a biologically activated carbon treatment to remove organic carbon from surface waters

•Biodegradable dissolved organic carbon (BDOC) matched the long term removal of BAC.•Prolonged biodegradation with saturated BAC removed much more organic carbon than BDOC.•Desorption of adsorbed organics on BAC granules controlled the lowest possible DOC.•Coagulation after biological treatment is better than biologically treating coagulated water.

This paper shows there is excellent potential to remove organic carbon by biological activated carbon (BAC). In surface waters, the reported biodegradable dissolved organic carbon (BDOC) is low (5-21%) which matches with the removal efficiency of most BAC after prolonged operation. Hence, it is thought that organic carbon removal by BAC cannot be further improved. To understand the full potential, water was incubated over a long period with granules obtained from a column of saturated BAC, i.e., exposed to the same source water over 9 months. The prolonged incubation removed between 43 and 52% of dissolved organic carbon (DOC), out of which physical adsorption accounted for 14-17%. The traditional BDOC method removed only 12-15% of DOC. Highest percentage removal was obtained for waters from the smallest reservoir with the lowest retention time. However, a significant amount of biodegradable organic matters (BOM) are still present in the reservoirs having longest storage time. Lowest possible DOC at the end of incubation was controlled by the adsorbed organic matter on BAC granules as confirmed by the aseptic desorption test with Milli-Q water. The results indicated there is a significant potential of a BAC treatment to remove organic carbon, but the traditionally experienced limitations of BAC should be overcome.

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