OXIDATIVE-DEGRADATION OF AOX AND COD BY DIFFERENT ADVANCED OXIDATION PROCESSES - A COMPARATIVE-STUDY WITH 2 SAMPLES OF A PHARMACEUTICAL WASTE-WATER

Using two samples of a pharmaceutical wastewater, the efficiency of th ree advanced oxidation processes (AOPs) (H2O2/UV, O-3/UV and H2O2/Fe(I I)) for the removal of adsorbable organic halogen (AOX) and chemical o xygen demand (COD) were compared on a laboratory scale. The AOX conten ts of these samples ranged from 3 to 5 mg/L. Generally the results sho wed that all three methods are suitable for the degradation of AOX and COD. UV irradiation involved a high selectivity for the degradation o f AOX compared to COD. On the other hand, processes based on hydroxyl radicals were less selective but considerably more effective in COD de gradation. This explains why the combined methods H2O2/UV and O-3/UV l ead both to a complete destruction of AOX and a large removal of COD. During ozone treatment - without UV radiation a decrease of AOX was al so observed, although to a lower degree. Using Fenton's reagent both A OX and COD could be removed almost completely. The reaction time neede d for this kind of treatment was very low compared to the other two AO Ps. O-3/UV treatment showed the largest consumption of ''activated'' o xygen (AO) during COD degradation. H2O2/Fe(II) treatment required almo st the same amount of AO as H2O2/UV. (C) 1997 IAWQ. Published by Elsev ier Science Ltd.