Costs of the electrochemical oxidation of wastewaters: A comparison with ozonation and Fenton oxidation processes Pablo Ca~ nizares, Rube ´n Paz, Cristina Sa ´ez, Manuel A. Rodrigo * Department of Chemical Engineering, Facultad de Ciencias Quı ´micas, Universidad de Castilla-La Mancha, Campus Universitario s/n, 13071 Ciudad Real, Spain Received 23 April 2007; received in revised form 2 October 2007; accepted 30 October 2007 Available online 20 February 2008 Abstract In the work described here the technical and economic feasibilities of three Advanced Oxidation Processes (AOPs) have been studied: Con- ductive-Diamond Electrochemical Oxidation (CDEO), Ozonation and Fenton oxidation. The comparison was made by assessing the three tech- nologies with synthetic wastewaters polluted with different types of organic compounds and also with actual wastes (from olive oil mills and from a fine-chemical manufacturing plant). All three technologies were able to treat the wastes, but very different results were obtained in terms of efficiency and mineralization. Only CDEO could achieve complete mineralization of the pollutants for all the wastes. However, the efficien- cies were found to depend on the concentration of pollutant (mass transfer control of the oxidation rate). Results obtained in the oxidation with ozone (at pH 12) or by Fenton’s reagent were found to depend on the nature of the pollutants, and significant concentrations of oxidation- refractory compounds were usually accumulated during the treatment. Within the discharge limits that all of the technologies can reach, the economic analysis shows that the operating cost of Fenton oxidation is lower than either CDEO or ozonation, although CD\EO can compete satisfactorily with the Fenton process in the treatment of several kinds of wastes. Likewise, the investment cost for the ozonation process seems to be higher than either CDEO or Fenton oxidation, regardless of the pollutant treated. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Cost analysis; Electrochemical oxidation; Ozonation; Fenton process 1. Introduction Many industrial processes generate flow streams that con- tain small concentrations of organic compounds. The removal of these materials is required prior to discharge or reuse of the waste flow. In appropriate circumstances, the organic com- pounds contained in these wastes can be economically recov- ered, but usually the best method to treat these streams is the destruction of the organics by different oxidation techniques, including incineration, biological oxidation, chemical oxida- tion or, in some cases, Advanced Oxidation Processes (AOPs). AOPs are defined as oxidation processes in which the hydroxyl radical is the main oxidant involved. This radical is a very powerful oxidant (E 0 : 2.80 V vs. SHE), which leads to a very effective oxidation process. Accordingly, the results reported in the literature for different AOP-based technologies (Bigda, 1996; Brillas et al., 2007; Chen et al., 2006; Diagne et al., 2007; Kavitha and Palanivelu, 2005; Ku et al., 2006a; Kusic et al., 2007a; Rivas et al., 2001; Rosenfeldt et al., 2006; Sauer et al., 2006; Sires et al., 2007) show very high ef- ficiencies, especially when compared with those obtained in conventional chemical oxidation processes. However, large amounts of oxidation-refractory compounds are usually ob- tained at the end of these processes. This behaviour is ex- plained in terms of the reactivity of hydroxyl radicals with some simple organic intermediates formed during the oxida- tion of the organics. For this reason, in order to increase the organic matter removal, several authors propose the combina- tion of these processes with other types of treatment (e.g. biological process) (Benitez et al., 1999; Contreras et al., * Corresponding author: Tel.: þ34 902 204100x3412; fax: þ34 926 295256. E-mail address: Manuel.Rodrigo@uclm.es (M.A. Rodrigo). 0301-4797/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2007.10.010 Journal of Environmental Management 90 (2009) 410e420 www.elsevier.com/locate/jenvman