ORIGINAL ARTICLE Degradation of Two Persistent Surfactants by UV-Enhanced Ozonation A. R. Tehrani-Bagha • H. Nikkar • F. M. Menger • K. Holmberg Received: 25 November 2010 / Accepted: 22 March 2011 / Published online: 7 May 2011 Ó AOCS 2011 Abstract In this study the treatment efficiency of dif- ferent ultraviolet (UV)-enhanced ozonation processes for degradation of two surfactants, sodium dodecylbenzene sulfonate [200 mg/L or 0.3 critical micelle concentration (CMC)] and a nonylphenol ethoxylate with 40 oxyethylene units (200 mg/L *0.5 CMC), were investigated in labo- ratory-scale experiments at ambient temperature. The absorbance band of the aromatic ring of the surfactants was monitored during the oxidation process. The reduction in chemical oxygen demand (COD) and total organic carbon (TOC) of the surfactant solution was evaluated. The results showed that a combination of UV irradiation and ozonation was considerably more efficient than the individual pro- cesses (at least two times more efficient in terms of COD and TOC reductions). The synergistic effect of ozonation and UV irradiation was particularly pronounced when medium-pressure UV irradiation was used. By adding alkali to the solution, the efficiency of the UV-enhanced ozonation increased with respect to COD reduction but decreased with respect to TOC reduction. This indicates partial oxidation with lower degree of mineralization of the surfactants. Keywords Oxidation  Alkylphenol ethoxylate  Sodium dodecylbenzene sulfonate  Degradation  Ozonation  UV irradiation Introduction Surfactants are used in a wide range of household and industrial applications. Their total consumption in 2003 was 8,600,000 tons, with the majority being anionic and nonionic surfactants [1]. Such extensive use leads to considerable discharge of these compounds into the environment. It is therefore necessary to minimize their environmental impact, and the biodegradability and aquatic toxicity of surfactants are matters of considerable concern today [2]. The harmful effects of anionic surfactants on the envi- ronment have been reported and critically discussed else- where. They can cause serious environmental pollution with toxic effects on living organisms. Because of their extensive use, a considerable amount of anionic surfactants is released into the environment, causing serious pollution of surface waters [3]. Discharge of alkyl phenol surfactants into sewers is often restricted. These restrictions were established because alkyl phenol polyethoxylate surfactants are biodegraded to alkyl phenols with zero, one or two oxyethylene groups, which tend to adsorb onto sewage sludge and accumulate to con- centration up to 1,000 ppm. These hydrophobic residues are much more toxic than the original surfactant, with maximum accepted concentration in the low ppb range. The discharge limit for other surfactants (in natural waters) is typically set at 2 mg/L [4, 5]. Electronic supplementary material The online version of this article (doi:10.1007/s11743-011-1271-6) contains supplementary material, which is available to authorized users. A. R. Tehrani-Bagha (&)  H. Nikkar Department of Environmental Research, Institute for Color Science and Technology, #55 Vafamanesh St., Hosein abad Sq., Pasdaran Cross, Tehran, Iran e-mail: tehrani@icrc.ac.ir F. M. Menger Chemistry Department, Emory University, Atlanta 30322, Georgia A. R. Tehrani-Bagha  K. Holmberg Department of Chemical and Biological Engineering, Chalmers University of Technology, 412 96 Go ¨teborg, Sweden 123 J Surfact Deterg (2012) 15:59–66 DOI 10.1007/s11743-011-1271-6