Removal of geosmin and 2-methylisoborneol by biological activated carbons as they age under different flow regimens

Biogenic taste and odour (T&O) events pose a series of challenges to drinking water treatment plants, increasing treatment costs and influencing consumer perception of water quality. Granular activated carbon (GAC) can be used to adsorb T&O compounds, such as geosmin and 2-methylisoborneol (2-MIB). The development of biofilms on the GAC granules convert the system into biological activated carbon (BAC), extending its lifetime; however, the evolution of biofilms in BAC systems and how it affects biofiltration performance of T&O compounds is not well understood. In this study, two sets of experiments designed to develop BACs under different conditions, such as carbon type, age, exposure to T&O and flow regimens, were conducted to investigate how the evolution of the biofilm affects the removability of geosmin and 2-MIB, and the effects of pre-exposure to T&O on removal efficiency to simulate the effects of seasonal T&O loading. The kinetics of T&O removability by BAC were statistically the same as the removability by GAC; approximately 90% removal of T&O compounds was observed and, of the total, 90% was removed within the first 72 hours as determined via the newly developed batch adsorption test. Pre-exposure to T&O had little to no effect on the BACs capacity to remove these compounds. These results indicate that adsorption still plays a major role in T&O removal even after the system has become BAC and attests to the resilience of BAC systems against intermittent periods of non-exposure to T&O. • Micropore volume had strong correlation with taste and odour adsorption. • Taste and odour removal remained high after perceived adsorption exhaustion. • Pre-exposure to taste and odour compounds had little effect on their removability. • Similar removal kinetics observed between aged and fresh granular activated carbon.