Evaluating the relative adsorption and biodegradation of 2-methylisobor-neol and geosmin across granular activated carbon filter-adsorbers

This study investigated the relative contributions of adsorption vs. biodegradation towards 2-methylisoborneol (MIB) and geosmin removal in the granular activated carbon (GAC) harvested from six filter-adsorbers in three drinking water treatment plants in the Great Lakes region. Column tests using azide-treated (sterilized) and untreated GAC in parallel were used to isolate the two effects. It was identified that substantial MIB and geosmin biodegradation in the GAC was occurring in one location, and that GAC in some cases had significant adsorption capacity after as much as 9 years of operation. Four alternative biological parameters (adenosine triphosphate, esterase activity, phosphatase activity, and C-14-glucose respiration rate) were measured to quantify the biological activity of the GAC, and C-14-glucose respiration rate was identified to be a potential indicator for GAC bio-degradative capacity in terms of MIB, geosmin, and dissolved organic carbon. Several potential MIB and geosmin biodegradation products were also identified using non-targeted screening analysis. By using the new tools identified in this study, we can begin to better understand where adsorption vs. biodegradation may predominate under real-world conditions (e.g., different temperatures, influent concentrations, and empty bed contact time), leading ultimately to more cost-effective use of GAC.

Automated summary

This study investigated the contributions of adsorption and biodegradation to the removal of MIB and geosmin in GAC harvested from drinking water treatment plants in the Great Lakes region. It was found that GAC had significant adsorption and biodegradation capacity, and C-14-glucose respiration rate was identified as a potential indicator for GAC biodegradative capacity. Non-targeted screening analysis also identified potential biodegradation products. The findings of this study provide valuable insights for better understanding the use of GAC in water treatment.