Ozone: Science and Engineering, 28: 3–8 Copyright # 2006 International Ozone Association ISSN: 0191-9512 print / 1547–6545 online DOI: 10.1080/01919510500479007 Ozonation of a Complex Industrial Effluent: Oxidation of Organic Pollutants and Removal of Toxicity A. A. Lima, 1 A. F. Montalvao, 2 M. Dezotti, 1 and G. L. Sant’Anna Jr. 1 1 Programa de Engenharia Quı ´mica/COPPE/Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil 2 Praxair White Martins, Gases Industrials, Rio de Janeiro, Brazil This work deals with the ozonation of a chemical indus- try wastewater, which contains many complex organic pol- lutants and presents high chloride content and toxicity. Batch experiments were carried out until ozone absorption reached 0.1 to 3 gO 3 /L. Ozonation promoted low to mod- erate levels of organic matter removal even when high ozone doses were applied. Organic matter removal tended to decrease when chloride content increased. Toxicity removal increased with the ozone dose up to 0.5 gO 3 /L. High or complete toxicity removal was attained after ozonation of the wastewater samples. Ozonation was also very effective in removing the polycyclic aromatic compounds found in the wastewater. Keywords Ozonation, Industrial Wastewater, Toxicity, Saline Effluents INTRODUCTION The chemical industries produce very complex efflu- ents, which may contain a large and variable number of organic compounds, high salinity and sometimes toxicity. In such cases, the wastewater treatment process requires large equalization tanks and several treatment steps in order to produce a treated effluent with the required quality to be discharged in the natural receiving waters. Ozonation may be successfully used to remove non- biodegradable or recalcitrant compounds that may impair toxicity to industrial effluents and has been applied to treat pulp and paper mill effluents (Zhou and Smith, 2000), landfill leachate (Baig et al., 1999), food industry wastewater (Beltran-Heredia et al., 2000), petro- chemical industry effluents (Lin et al., 2001), wine- distillery wastewaters (Beltran et al., 2001) and textile industry effluents (Perkowski et al., 2000). Some industrial effluents present a high chloride con- tent, which may impair the ozonation process. The effect of high chloride concentrations (above 10,000 mg/L), present in very complex chemical matrices, on the ozona- tion process, has not been deeply investigated. Chloride concentrations higher than 30,000 mg/L were shown to be deleterious to the ozonation of synthetic effluents con- taining phenol (Bessa, 2003). There is a general concern about the treatment of saline wastewaters since the pro- duction of such effluents will increase in the near future in view of the procedures adopted by the industries to reuse water and reduce water consumption. The aim of this work was to investigate the potential of the ozonation process to remove the acute toxicity of a complex industrial wastewater, presenting chloride con- centration in the range of 2,000 to 27,000 mg/L. Removal of polycyclic aromatic hydrocarbons and improvement on the effluent biodegradability were also investigated. MATERIALS AND METHODS Wastewater Bayer industry supplied the industrial effluent used in this work. This chemical and pharmaceutical industry, located at Belford Roxo (RJ, Brazil), produces many chemicals, including polyurethane and agricultural and veterinary products. Grab samples of the industrial efflu- ent were collected from the mixing vessel located down- stream the equalization tanks, during an 8-month period. These samples were transferred to the laboratory and kept under refrigeration (4 °C) until use. Ozonation Tests were carried out in a pilot ozonation column (10 cm diameter; 100 cm height) made of Plexiglas. Gas was Received 05/27/2004; Accepted 11/15/2004 Address correspondence to G. L. Sant’Anna, Programa de Engenharia Quı´mica/COPPE/Universidade Federal do Rio de Janeiro, P.O. Box 68502, CEP 21945-970 Rio de Janeiro, RJ, Brazil. E-mail: lippel@peq.coppe.ufrj.br Ozonation of a Complex Industrial Effluent February 2006 3