Treatment of diglyme containing wastewater by advanced oxidation--process design and optimisation

Diglyme (CAS No. 111-96-6), a biorefractive ether with teratogenic properties is of considerable importance as a solvent in the synthetic chemical industry. Results of lab-scale investigations into the optimal conditions for the oxidative mineralisation of 0.05 to 1 g/L of diglyme in synthetic process waters by hydrogen peroxide and ozone based advanced oxidation processes are presented. Fenton, photo-assisted Fenton and UV/H2O2 oxidation processes show acceptable TOC removals. At 50 degrees C the initial TOC removal rates varies between 0.07 and 6g TOC/L*h. The rates increase with the initial diglyme and hydrogen peroxide concentration as well as with the UV irradiation energy intensity. For example at a 1 g/l diglyme concentration a stoichiometric H2O2 addition resulted in TOC degradation of 60% to 70% after 30 minutes under the investigated conditions. Treatment with ozone/H2O2 at a pH of 8 and 25 degrees C required at least 100 minutes to achieve comparable mineralisation results. Biodegradability can be reached in far shorter times. Ozone on its own cannot be recommended for diglyme treatment. If complete mineralisation of diglyme is the objective, the UV/H2O2 oxidation process should be favoured. The ozone/H2O2 process might offer a viable alternative in cases where the oxidation step is followed by biological wastewater treatment, so that biodegradability is aimed at.