Factors influencing adsorption and biodegradation of 2-methylisoborneol by biological activated carbon for drinking water treatment

Taste and odor (T&O) issues have become a growing challenge for water utilities because they can reduce consumer confidence in drinking water even when water quality standards are met. Among T&O compounds, 2-methylisoborneol (MIB) is particularly problematic due to its extremely low odor threshold and frequent occurrence in surface waters. Biofilters using biological activated carbon (BAC) are effective in removing MIB through adsorption and biodegradation; however, the factors governing the contribution of each mechanism remain unclear. This study used the volumetric removal rate (VRR) of MIB to quantify its removal potential by BAC collected from pilot- and full-scale drinking water treatment plants in Japan. The VRR components due to adsorption and biodegradation (VRR ads and VRR bio , respectively) were separately examined. The total VRR ranged from 2.6 to 7.1 mg m −3 h −1 , and 29–96% of it was due to adsorption. VRR ads and VRR bio depended on the influent MIB concentration. Water temperature influenced VRR bio more strongly than VRR ads , highlighting that the biodegradation activity of BAC filters is more sensitive to water temperature. VRR ads was negatively correlated with the mean pore diameter of BAC and the dissolved organic carbon (DOC) concentration in the influent. In contrast, VRR bio was positively correlated with the DOC concentration in the influent and the 16S rRNA abundance of BAC. These findings indicate that DOC plays opposite roles in the MIB removal potential. Amplicon sequencing of 16S rRNA genes and reverse-transcribed 16S rRNA suggested that eight bacterial taxa, including Flavobacterium , could be associated with VRR bio .