Continuous electrocoagulation of cheese whey wastewater: An application of Response Surface Methodology Umran Tezcan Un a, * , Ayse Kandemir a , Nihal Erginel b , S. Eren Ocal c a Anadolu University, Department of Environmental Engineering, Eskisehir 26555, Turkey b Anadolu University, Department of Industrial Engineering, Eskisehir 26555, Turkey c Anadolu University, Department of Chemical Engineering, Eskisehir 26555, Turkey article info Article history: Received 12 February 2014 Received in revised form 7 August 2014 Accepted 11 August 2014 Available online Keywords: Whey wastewater Response Surface Methodology Electrocoagulation Iron electrode abstract In this study, treatment of cheese whey wastewater was performed using a uniquely-designed contin- uous electrocoagulation reactor, not previously encountered in the literature. An iron horizontal rotating screw type anode was used in the continuous mode. An empirical model, in terms of effective opera- tional factors, such as current density (40, 50, 60 mA/cm 2 ), pH (3, 5, 7) and retention time (20, 40, 60 min), was developed through Response Surface Methodology. An optimal region characterized by low values of Chemical Oxygen Demand (COD) was determined. As a result of experiments, a linear effect in the removal efficiency of COD was obtained for current density and retention time, while the initial pH of the wastewater was found to have a quadratic effect in the removal efficiency of COD. The best fit nonlinear mathematical model, with a coefficient of determination value (R 2 ) of 85%, was defined. An initial COD concentration of 15.500 mg/L was reduced to 2112 mg/L with a removal efficiency of 86.4%. In conclusion, it can be said that electrocoagulation was successfully applied for the treatment of cheese whey wastewater. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Whey is the liquid remaining after the recovery of curds formed during cheese production. It contains 80e90% of the total volume of milk used in the cheese-making process. Whey can be processed and reused for animal feed or for human consumption. In small dairies which produce cheese, whey reuse is not practicable and this whey is discharged as waste along with the rest of their wastewater. The disposal of whey produced during cheese pro- duction has always been a major problem because of organic ma- terial in the dairy industry (Kandemir, 2011). Laboratory and pilot scale experiments for the treatment of dairy wastewater have been comprehensively studied under anaerobic (Banu et al., 2008; Luostarinen and Rintala, 2005; Leal et al., 2006; Schneider and Topalova, 2011) and aerobic (Carta- Escobar et al., 2005; Seesuriyachan et al., 2009; Tocchi et al., 2012) conditions. Electrocoagulation is an alternative wastewater treatment technology. In the electrocoagulation process, charac- terized by its simple equipment, easy operation and low levels of sludge, the coagulant is dissolved from the anode with a simulta- neous formation of hydroxyl ions and hydrogen gas occurring at the cathode (Tezcan Un and Aytac, 2013). The treatment of dairy wastewater by electrocoagulation is studied in the literature. S ¸ engil and Ozacar investigated the treat- ment of dairy wastewater using an iron parallel plate electrode (Sengil and Ozacar, 2006). Tchamango et al. treated synthetically prepared dairy wastewater using a parallel aluminium anode (Tchamango et al., 2010). Bensadok et al. treated artificial waste- water obtained from milk powder using two parallel plate aluminium and platinized titanium electrodes (Ti/Pt) (Bensadok et al., 2011). Kushwaha et al. also treated artificial dairy waste- water using two parallel aluminium plates (Kushwaha et al., 2011) and four parallel iron electrodes (Kushwaha et al., 2010). Tezcan Un and Ozel (2013) studied the electrocoagulation of strained (condensed) yogurt industry wastewater using a rectangular iron cathode compartment and parallel plate anodes. Although the electrocoagulation of dairy wastewater has been utilized by various researchers, only Guven et al. have studied the electrocoagulation of cheese whey wastewater in the literature (Guven et al., 2008). They prepared whey wastewater synthetically using whey powder. Six parallel plate electrodes were used as an- odes and cathodes in batch runs. The electrochemical treatment * Corresponding author. Tel.: þ90 222 321 35 50x6418; fax: þ90 222 323 95 01. E-mail address: utezcan@anadolu.edu.tr (U. Tezcan Un). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2014.08.006 0301-4797/© 2014 Elsevier Ltd. All rights reserved. Journal of Environmental Management 146 (2014) 245e250