Impacts of ozonation on the adsorption and surface characteristics of powdered activated carbon

Adsorption is the process of removing substances from the liquid phase by adsorbing or accumulating them on the solid phase. This mass transfer process is used in drinking water treatment for the removal of taste- and odor- causing compounds, synthetic organic chemicals (SOCs), color forming organics, and disinfection byproduct (DBP) precursors. Powdered activated carbon (PAC) and Granular activated carbon (GAC) are the primary adsorption materials used in the adsorption process for drinking water treatment. PAC is added directly to water and can be applied at various locations within a water treatment plant, and it is usually removed by filtration or sedimentation. Ozone is used in drinking water treatment plants for disinfection, and it has been found to be effective for the oxidation of taste- and odor- causing compounds in water. Typical ozone doses are in the range of I to 5 mg/L with a minimum contact time of 10 to 15 minutes. With increasing regularity, drinking water facilities are combining ozonation and PAC treatments in a single process. This research investigates whether the effectiveness of the activated carbon is affected by adding the ozonation process and if it results in oxidation of the activated carbon, which in turn changes the surface properties. At the same time, effects of PAC on ozone concentrations are studied to see rate of ozone decay. Atrazine is the model compound considered and investigated further to determine the changes of the adsorption characteristics of PAC when reacted with ozone ---Abstract p. i