Design of a packed-bed ozonation reactor for removal of contaminants from water

A common agent of contamination in ground water is chlorinated hydrocarbons (CHC's) originating from the spill of cleaning solvents. In this study a new treatment process which destroys the pollutant rather than merely transferring it to another phase; like air stripping or carbon absorption, is examined. This process employs wet oxidation of the contaminant using ozone as the oxidizing agent and a packed column as a reactor. The is the decomposition of CHC's into carbon dioxide, water and inorganic salts. The present work presents the results of the experiments on a pilot scale packed column reactor, together with a mathematical model to simulate the process. The removal and destruction of trichloroethylene (TCE) has been measured for a range of parameters including gas/liquid ratio, vapor-, liquid load, ozone concentration, contacting pattern and pH value. To gather the maximum information about the interacting processes in the reactor, axial liquid phase concentration profiles from sample ports along the packing have been obtained. From this information, a multiphase plug flow reactor model has been developed to predict the removal of TCE from water in a packed bed reactor for counter-current flow and cocurrent downflow. The model consists of material balances on both the gas and liquid phase TCE and ozone as a function of contact time. Comparison of the model with experimentally determined concentration profiles along the packing gives insight into packed column reactor behavior. Trials with the model are used to predict the optimal process configuration for a specific remediation application. A comparative economic evaluation shows that the use of a packed column (i.e. a plug flow reactor) instead of the conventional open bubble column reactor (i.e. a CSTR) is an economically viable process alternative in ozonation water treatment processes.