Treatment of chlorinated ethenes in groundwater with ozone and hydrogen peroxide

A study was conducted to enhance the performance of an advanced oxidation process in treating chlorinated ethenes in groundwater at IBM's groundwater treatment system at its Essex Junction, Vermont facility. A model describing the reaction kinetics and mass transfer of a co-current ozone injection process is presented. This model, in conjunction with experiments, demonstrates that the treatment performance of the ozone treatment process at a given ozone/air concentration and ozone mass flowrate cannot be improved by varying process operating parameters such as number of ozone injectors utilized use of a static mixer, or variation of groundwater flowrate through each injector This is because dissolved ozone reaches equilibrium with the injected ozone/air mixture within two seconds of initial contact. Also, the Venturi-type ozone injection system presently in use destroys nearly half of the injected ozone. Injection of hydrogen peroxide in conjunction with ozone increases the overall tetrachloroethylene (PCE) treatment efficiency by a factor of four (in comparison to ozone alone) at a H2O2/O-3 mass ratio of between 1 and 2. Treatment of trichloroethylene (TCE) is enhanced by a factor of two. This enhancement of the oxidative treatment process results in a reduction in solvent mass load to a granular activated carbon (GAC) adsorption system located downstream thus potentially reducing the usage GAC and regeneration of spent GAG. However, residual hydrogen peroxide and/or hydroxyl free radicals from the oxidation process effluent may interact adversely with certain grades of GAC; the causes of this interaction and methods to attenuate it (i.e., the use of more resistant graces of GAC) are discussed. Overall O-3/H2O2/GAC system operating costs can potentially be reduced significantly (up to $20K annually). An economic analysis and system operation/cost optimization study are presented.