Competitive removal of dissolved organic carbon by adsorption and biodegradation on biological activated carbon

Improvement of biodegradability of dissolved organic carbon (DOG) by ozonation does not always induce improvement of DOG removal and extension of activated carbon service time, because most of biodegradable DOC increased by ozonation is adsorbable on activated carbon. The objective of this study is to clarify the fate of the biodegradable DOG increased by preozonation on biological activated carbon (BAC) and to evaluate effects of preozonation on BAC performance for the removal of DOC and extension of activated carbon service time. DOG breakthrough curve for BAC process obviously shifted to the right by combination with ozonation, indicating that preozonation extended BAG service time. Higher removal of DOC was noted in the ozone-BAG process than the BAG process after saturation with DOG. Ozonation increased biodegradable DOG by 2.89 mg.l(-1) (31%). Although the increased biodegradable DOC had possibilities to be removed both by adsorption and biodegradation, most of it was removed by biodegradation on BAC which resulted in longer BAG service time. Biodegradation of the increased biodegradable DOG was responsible for the higher removal of DOC after saturation with DOG in the ozone-BAG process. (C) 1997 IAWQ. Published by Elsevier Science Ltd.