Refractory COD removal in the Chemical Industry: Technico-Economic comparison of Advanced Oxidation Processes M. Coste*, C. Batbedat*, C Feliers*, D. Olejnik*, J.Cigana *, P. Cervantes* *: Anjou-Recherche / Vivendi Water Chemin de la Digue, B.P. 76, 78603 Maisons-Laffitte, France ABSTRACT Advanced Oxidation Process (AOP) comparison was carried out on an effluent coming from cosmetic industry. Refractory COD was obtained after a complete biological treatment by membrane bioreactor (BIOSEP). Six oxidation treatments were compared for COD elimination: Fenton reagent, direct photolysis with a low pressure UV lamp, O 3 at acidic pH and pH 6.25, UV/O 3 , UV/H 2 O 2 , O 3 /H 2 O 2 , O 3 /UV/H 2 O 2 . The results obtained seem to indicate that removal of COD of this specific solution was mainly due to radical mechanism. However, even if free radical are necessary, the best results are obtained with processes involving UV irradiation. Moreover, Fenton reagent offered a maximum COD elimination of 80% whatever the peroxide concentration, presenting a fraction that may be more refractory toward free radical oxidation perhaps due to scavengers competition. Therefore, the components of the treated solution were removable by radical mechanism but a fraction needed UV photolysis to be completely oxidized. A comparison of the operating cost of these processes shows that for a COD removal of more than 80% the catalytic UV treatment of this low load industrial wastewater was the most efficient and the most cost effective. KEY WORDS Refractory COD, Industrial wastewater, Advanced oxidation processes, ozone, Fenton, UV INTRODUCTION Refractory COD is one of the most frequent and crucial problems found in industrial wastewater treatment and more specifically in the Chemical Industry. Biological processes are often unable to degrade complex compounds that can be found in such effluents, resulting in an refractory chemical organic demand (COD) fraction after treatment. Advanced oxidation processes (AOP) are one of the many possible treatments available (incineration, evapo- concentration, separation, etc..) for this refractory COD (Luck and al., 2000 – G Leboucher and al. 2000). The objective of this study is to suggest a methodology of side-by-side testing of AOP treatment in order to select the optimum treatment process. Although the methodology involved in general, this article will concentrate on the results generated from the comparison of several AOP processes on refractory COD removal of an effluent from Cosmetic Industry. An economic comparison of the different processes tested has been conducted. WEFTEC ® 2003 Copyright ©2003 Water Environment Federation. All Rights Reserved.