ADVANCED OXIDATION PROCESSES AGAINST PHENOLIC-COMPOUNDS IN WASTE-WATER TREATMENT

Experimental research into the oxidative treatment of aqueous solutions and wastewaters containing phenolic compounds was undertaken. Ozone, supported by short wavelength UV-irradiation, hydrogen peroxide and titanium dioxide catalyst, was selected as an oxidant in the following combinations: O.3, O-3/H2O2, O-3/UV, O-3/TiO2, O-3/UV/H2O2 and O-3/UV/TiO2. 5-Methylresorcinol was chosen as a model compound for the experiments with synthetic phenolic solutions. The results obtained from these experiments were compared with the results of oxidative purification of wastewaters produced from the thermal treatment of oil shale in Estonia. The ''ozone - hydrogen peroxide'' combination showed a higher efficiency for the destruction of phenolic compounds compared with non-accompanied ozonation. The specific ozone consumption also was reduced 1.2-1.3 times in combination with hydrogen peroxide. Short wave UV-radiation and titanium dioxide showed no influence on the specific ozone consumption, due to the high optical density of phenolic compounds in the short UV-wavelength range. The wastewater biodegradability, described as BOD5/COD ratio, increased only slightly subsequent to ozonation. In contrast, a significant decrease in biodegradability with increasing oxidant dose was observed when an O-3/H2O2 combination was used.