TREATMENT OF CHLORINATED ETHENES IN GROUNDWATER WITH OZONE AND HYDROGEN-PEROXIDE

A study was conducted to enhance the performance of an advanced oxidat ion process in treating chlorinated ethenes in groundwater at IBM's gr oundwater treatment system at its Essex Junction, Vermont facility. A model describing the reaction kinetics and mass transfer of a co-curre nt ozone injection process is presented. This model, in conjunction wi th experiments, demonstrates that the treatment performance of the ozo ne treatment process at a given ozone/air concentration and ozone mass flowrate cannot be improved by varying process operating parameters s uch as number of ozone injectors utilized use of a static mixer, or va riation of groundwater flowrate through each injector This is because dissolved ozone reaches equilibrium with the injected ozone/air mixtur e 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 incre ases the overall tetrachloroethylene (PCE) treatment efficiency by a f actor 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 b y a factor of two. This enhancement of the oxidative treatment process results in a reduction in solvent mass load to a granular activated c arbon (GAC) adsorption system located downstream thus potentially redu cing the usage GAC and regeneration of spent GAG. However, residual hy drogen peroxide and/or hydroxyl free radicals from the oxidation proce ss effluent may interact adversely with certain grades of GAC; the cau ses 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 syst em operating costs can potentially be reduced significantly (up to $20 K annually). An economic analysis and system operation/cost optimizati on study are presented.