Ozone: Science & Engineering, 33: 403–409 Copyright © 2011 International Ozone Association ISSN: 0191-9512 print / 1547-6545 online DOI: 10.1080/01919512.2011.604606 Oil-Refinery Wastewater Treatment Aiming Reuse by Advanced Oxidation Processes (AOPs) Combined with Biological Activated Carbon (BAC) Bianca M. Souza, 1 Ana C. Cerqueira, 2 Geraldo L. Sant’Anna Jr., 1 and Marcia Dezotti 1 1 Programa de Engenharia Química – COPPE, UFRJ, CP 68502, 21941-972, Rio de Janeiro, Brazil 2 Petrobras, CENPES, Av. Horacio Macedo, 950, 21941-915, Rio de Janeiro, Brazil The treatment of a refinery wastewater by Advanced Oxidation Processes (AOP) coupled with Biological Activated Carbon (BAC) was investigated aiming to generate water for reuse. O 3 /UV and H 2 O 2 /UV processes were employed to oxidize the organic matter and the BAC process to remove residual organic matter from the AOP effluent. AOP promoted oxidation of recalcitrant organic matter as observed by moderate drops on the treated wastewater absorbance (31–79%) and TOC values (10–18%). BAC filters showed to be effec- tive, reaching average efficiencies of 65% in a sufficiently long period of operation (84 days), while GAC filters were saturated after 28 days. Effluent TOC values in the range of 4 to 8.5 mg/L were achieved by the combined treatment (H 2 O 2 /UV + BAC), allowing water reuse. Keywords Ozone, Advanced Oxidation Processes, Activated Carbon, Biofiltration, Reuse, Oil-refinery Wastewater INTRODUCTION Due to its high potential for impacting the environment, the industrial sector has been concerned with pollution con- trol, regulation and wastewater discharge. New projects to encourage the rational use of water must consider the sus- tainability concepts and the established environmental laws (Oenning and Pawlowsky, 2007). The need to reduce water consumption is changing operation practices and treated efflu- ents become strong candidates for supplying water for some industrial applications. The oil industry produces wastewa- ters that can be considered for reuse when the requirements for high-quality water are not as stringent (Saien and Nejati, 2007). Received 4/28/2010; Accepted 5/18/2011 Address correspondence to Marcia Dezotti, Programa de Engenharia Química – COPPE, UFRJ, CP 68502, 21941-972, Rio de Janeiro, Brazil. E-mail: mdezotti@peq.coppe.ufrj.br Even in countries like Brazil, where large fresh water sources are available, there is concern regarding water avail- ability and distribution over the country (ANA, 2009). Although industry is not the main water consumer in compari- son with other economic sectors, as shown in Figure 1a, water reuse at an industrial scale can lead to economic and envi- ronmental benefits. In oil refineries there is a high demand for water used in cooling towers, steam boilers and process requirements. Figure 1b illustrates the uses of water in oil refineries, as reported by Monteiro et al. (2004). The advanced oxidation processes (AOP) are considered promising techniques for removing toxic organics and/or recalcitrant pollutants from aqueous solutions (Alsheyab and Muñoz, 2006). These processes generate hydroxyl radicals (·OH), which are highly reactive and non-selective and oxi- dize many organic compounds found in wastewaters (Glaze et al., 1987; Andreozzi et al., 1999). The resulted organic radicals react with oxygen, initiating a series of degradation reactions that can lead to harmless species, typically CO 2 and H 2 O (Amiri et al., 1997). Because conventional oxidation is not very effective for removing organic pollutants com- ing from biological processes, ozone and hydrogen peroxide associated with UV radiation can be considered as alterna- tives. Some published works have confirmed the potential of combined techniques to treat wastewaters (Stepnowski et al., 2002; Kusic et al., 2006; Li et al., 2006). Granular activated carbon (GAC) filters can be used to treat effluents from advanced oxidation processes. GAC has been widely applied for removing organic matter from wastewaters. Such filters are efficient, but must be periodically regenerated, an operation that increases process costs. An alternative treat- ment can be the degradation of the organic matter adsorbed on GAC by biofilms, a process known as biological acti- vated carbon (BAC) (Minillo et al., 2008; Simpson, 2008). The combination of adsorption and biological degradation can Oil-Refinery Wastewater Treatment September–October 2011 403