Haloacetic acids (HAA) are disinfection byproducts (DBPs) in drinking water and are regulated under the Stage I Disinfectants and Disinfection Byproducts Rule (D/DBP) by the United States Environmental Protection Agency (USEPA). The current methods for DBP control are enhanced coagulation/softening processes. Granular activated carbon (GAC) adsorption is also widely used for removal of HAA precursors. Several studies revealed HAA could be removed by biologically active carbon (BAC). The purpose of this study is to explore the mechanisms of HAA removal by activated carbon adsorption and biodegradation in drinking water systems. Freundlich adsorption isotherms of HAAs were determined using the bottle-point adsorption tests. The results indicate that 1/n values decrease as the chlorine substitution increases. This suggests that the higher the number of the chlorine atom in the HAA molecule, the stronger the adsorption bonding. Bromine species had a higher adsorption capacity than chlorine species for equivalent number of halogen substituents. The effect of temperature and dissolved oxygen (DO) on the removal of HAAs by biologically active carbon (BAC) was also investigated. Extreme temperature shocks (4 and 50C) were applied to columns. Average removal efficiency for six HAAs was reduced from 97% to 48% and 73% following 4C and 50C temperature shocks, respectively. The absence of DO in the column study did not affect HAA removal efficiency, but reduced the degradation rates in the batch tests. Includes 17 references, tables, figures.
