Treatment of persistent organic compounds by integrated advanced oxidation processes and sequential batch reactor Alex Christensen, Mirat D. Gurol, Temesgen Garoma* Department of Civil, Construction and Environmental Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, United States article info Article history: Received 13 March 2009 Received in revised form 8 April 2009 Accepted 9 April 2009 Published online - Keywords: Dichlorodiethyl ether Ozonation Fenton UV peroxide SBR Biodegradability abstract The objective of this study was to evaluate the extent of improvement in the biodegrad- ability of persistent organic compounds by pre-oxidation by using Sequential Batch Reactors (SBRs). Dichlorodiethyl ether (DCDE), a non-biodegradable compound, was used as a test chemical. Ozonation, Fenton reagent and ultra-violet light coupled with hydrogen peroxide (UV/H 2 O 2 ) were used for oxidation of DCDE at levels of 50–100%. Pre-oxidized DCDE solutions were then subjected to SBR studies using activated sludge to determine the rate and extent of biodegradation of oxidation by-products. The results indicated that the biodegradability of pre-oxidized DCDE increased drastically, reaching an average of 90% for all three oxidation methods versus zero for non-oxidized DCDE. It was concluded that the results of SBR experiments may be better indicators of biodegradability of chemically- oxidized wastewaters due to significant acclimation of microorganisms in SBRs, which cannot be observed in conventional respirometric laboratory studies. ª 2009 Elsevier Ltd. All rights reserved. 1. Introduction Biological treatment is the most common process used to treat organic-containing wastewaters. However, a large number of xenobiotic compounds can persist in the biological systems passing through the systems without any transformation (Byrns, 2001; Rieger et al., 2002). Furthermore, they may upset the biological process though toxicity to the microorganisms (Daugulis, 2001). The discharge of such compounds to municipal or industrial treatment systems that use biological systems is often restricted or prohibited. The waste is there- fore transported, and treated as ‘‘hazardous waste’’, and finally disposed through costly and potentially liable alterna- tives such as underground injection and off-site land disposal. Thus, there is need for technologies that can be used to treat persistent xenobiotic compounds at the source in order to modify their chemical characteristics to render them treatable in biological systems without any adverse effects. Advanced Oxidation Processes (AOPs) were shown before to have the capability of destruction of a variety of compounds to generally biogenic, and as a result biodegradable, interme- diate compounds, e.g., carboxylic acids, alcohols and alde- hydes (Garoma and Gurol, 2004; Klavarioti et al., 2009). On the other hand, AOPs, very much like biodegradation reactions, is essentially composed of a series of consecutive reactions, and as for any incomplete reaction, might potentially create products more toxic than the original material for the bio- logical systems. * Corresponding author. Tel.: þ1 619 594 0957; fax: þ1 619 594 8078. E-mail address: tgaroma@mail.sdsu.edu (T. Garoma). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres ARTICLE IN PRESS 0043-1354/$ – see front matter ª 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2009.04.009 water research xxx (2009) 1–12 Please cite this article in press as: Christensen, A. et al., Treatment of persistent organic compounds by integrated advanced oxidation processes and sequential batch reactor, Water Research (2009), doi:10.1016/j.watres.2009.04.009