Clean 2007, 35 (4), 355 – 361 R. Saravanathamizhan et al. 355 R. Saravanathamizhan 1 N. Mohan 2 N. Balasubramanian 1 V. Ramamurthi 1 C. Ahmed Basha 3 1 Department of Chemical Engineering, A.C. College of Technology, Anna University, Chennai, India. 2 Centre for Environment & Explosive Safety, Defense Research & Development Organization, Delhi, India. 3 Department of Pollution Control, Central Electrochemical Research Institute, Karaikudi, India. Research Article Evaluation of Electro-Oxidation of Textile Effluent Using Response Surface Methods In the present investigation, treatment of textile effluent using an electrochemical technique was designed and analyzed using the Box-Behnken method. The influence of individual parameters on electro-oxidation of textile effluent has been critically examined using the response surface method (RSM), and a quadratic model for chem- ical oxygen demand (COD) reduction has been developed. It has been observed from the present analysis that the predicted values are in good agreement with experimen- tal data with a correlation coefficient of 0.945. Keywords: Box-Behnken method; COD reduction; Electrochemical oxidation; Response surface method; Received: January 14, 2007; revised: April 27, 2007; accepted: July 3, 2007 DOI: 10.1002/clen.200700005 1 Introduction Textile industries consume large amounts of water and generate considerable amounts of wastewater. The textile industry's effluents are known to be strongly colored, contain large amount of sus- pended solids (SS), have broadly fluctuating pH values, and have high chemical oxygen demand (COD). The textile effluents are treated conventionally by adsorption, biological oxidation, coagula- tion, etc. The conventional aerobic biological process, e. g., the acti- vated sludge process, cannot readily treat textile wastewater because most commercial dyes are toxic to the organisms used in the process and result in sludge bulking. Further, the dyestuff, dye- ing additives present in textile effluents, are highly complex struc- tures, which are difficult to decompose biologically. Additionally, biological and chemical methods generate a considerable quantity of sludge, which itself requires treatment. The conventional meth- ods for treating these effluents are becoming inadequate. There have been increased economic, social, legal, and environmental pressures to adopt the best technology at lower cost and to aspire to “zero discharge”. In recent years, there has been special focus on treatment of industrial wastewater using advanced oxidation tech- nologies such as catalytic wet air oxidation, and electrochemical oxidation process, etc. [1 – 3]. Among these techniques, electrochem- ical oxidation appears to be one of the most promising technologies for the treatment of wastewaters containing organic pollutants. Electrochemical technology continues to make many contribu- tions to environmental treatment, recycling, and monitoring. These include: – Treatment by electrochemically generated species, such as chlorination of swimming pools and sterilization of medical instruments using a powerful cocktail of oxidizing reagents in “super oxidized” water. – Removal of contaminants, such as metal ions and organics from industrial process streams. – Conversion of chemical to electrochemical energy using fuel cell and photovoltaic devices. Electrochemical methods have been successfully applied to the purification of several industrial wastewaters [4, 5]. Lin and Ming [6] experimented with electrochemical techniques in conjunction with chemical coagulation and ion exchange to treat effluent from the secondary wastewater treatment plant of a large-scale dyeing/ finishing unit and reported that the quality of treated wastewater is comparable with deionized water. The other major contributions to the application of electrochemical techniques for industrial efflu- ent treatment are due to Panizza et al. [7], Montilla et al. [8], and Raghu and Ahmed Basha [9], etc. In our earlier studies [10 – 12], we have reported that textile effluents can be effectively treated using an electrochemical method for effective color removal and COD reduction. The electrochemically treated textile effluent can be reused for the dyeing process. The existing literature focuses on the electrochemical treatment of industrial effluent and the influence of individual parameters on process efficiency. In electro-oxidation, the oxidation efficiency depends on several parameters and many times the combined effect plays an important role. It is attempted in the present investigation to study the electro-oxidation of Acid Blue 113 dye using the Box- Behnken method and to critically examine the effect of various parameters on COD reduction. 2 Response Surface Method In conventional experimentation, the experiments are conducted keeping all the variables constant except the parameter whose influ- ence is being studied. This type of experiment reveals the effect of the chosen parameters under set conditions, assuming that varia- bles are independent and that the effect will be the same at other values of the remaining variables. However, it does not show what Correspondence: N. Balasubramanian, Department of Chemical Engi- neering, A.C. College of Technology, Anna University, Chennai-600 025, India. E-mail: nbsbala@annauniv.edu Abbreviations: ANOVA, analysis of variance; COD, chemical oxygen de- mand; EC, energy consumption; IEC, initial effluent concentration; RSM, response surface method; SS, suspended solids i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com