This research was focused on differentiating the adsorption and biodegradation quantities of a biological activated carbon (BAC) column, and on evaluating the effect of empty bed contact time (EBCT) on the performance of the two mechanisms simultaneously for the removal of dissolved organic matter from water. The performance of adsorption and biodegradation on the BAC column was studied using continuous columns tests, and four typical ozonation by-products were selected as the target compounds. The results show that EBCT could influence the performance of both adsorption and biodegradation in extent. Increasing EBCTs could make the equilibrium more complete for adsorption, thereby improving the performance. The ratio of adsorption to biodegradation on the BAC column increased as EBCT increased, and this implied that adsorption was dominant in an equilibrium condition.