Evaluation of granular activated carbons for removal of methylisoborneol to below odor threshold concentration in drinking water

Four granular activated carbons manufactured from different raw materials were evaluated for the removal of 2-methylisoborneol (MIB) to below odor threshold concentration using equilibrium isotherm tests. MIB adsorption isotherms were compared in the aqueous equilibrium concentration range < 10–100 ng/l. The data showed that the bituminous carbon has the highest adsorption capacity, followed by the peat, lignite, and wood carbons. This is the first time GAC isotherm data are available at such low level; such data are needed to aid selection of the appropriate carbon product to remove this musty taste-and-odor (T&O) causing compound. The precision of the analytical method used in this study was evaluated by analyzing a spiked solution at 2 ng/l MIB, and was found to be 2 ± 1 ng/l. The absence of background competition in these organic pure water isotherms was verified. In natural water, however, competition from both nanogram- to microgram-per-liter of dissolved low molecular weight hydrophobic organic compounds (< 400 daltons) and milligram-per-liter of natural organic matter (> 400 daltons) contributed to changes in isotherms and to the reduction of MIB adsorption capacity. A database of organic pure water isotherms with MIB would be of important value to water facilities requiring T&O control as it provides a reliable starting point for GAC product selection. However, field or pilot tests are still needed for the final selection owing to the varying characteristics of individual water source.