Research article Electrochemical treatment of biologically pre-treated dairy wastewater using dimensionally stable anodes Vlasia Markou a , Maria-Christina Kontogianni a , Zacharias Frontistis a, * , Athanasia G. Tekerlekopoulou b , Alexandros Katsaounis a , Dimitris Vayenas a, c a Department of Chemical Engineering, University of Patras, Caratheodory 1, GR-26504 Patras, Greece b Department of Environmental & Natural Resources Management, University of Patras, Agrinio, Greece c Institute of Chemical Engineering Sciences, Foundation for Research and Technology, PO Box 1414, GR-26504 Patras, Greece article info Article history: Received 8 May 2017 Received in revised form 21 June 2017 Accepted 17 July 2017 Keywords: Dairy Wastewater Electrochemical Dimensionally stable anodes abstract In this work, electrochemical oxidation of aerobically pre-treated dairy wastewaters using IrO 2 -Pt coated dimensionally stable anodes was investigated. It was found that IrO 2 /Ti electrode outperforming Pt/Ti and IrO 2 -Pt/Ti at lower current densities, while Pt/Ti achieved better efficiency at higher current density. Among the different parameters which were studied, the current density was the most crucial for the efficiency of the process. A current density of 100 mA/cm 2 led to almost complete removal of 3700 mg/L COD after 360 min of treatment using IrO 2 /Ti electrode and 0.2 M of sodium chloride while complete decolorization was achieved in less than 60 min. Electrolytes also found to significantly affect the process. More specific, the use of sodium chloride instead of sodium sulfate enhanced both COD and color removal due to the formation of active chlorine species. The effect of temperature was relative low; the process was favourable at elevated temperatures while increasing COD loading resulted in a decrease of COD and color removal. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Since ancient times the consumption of dairy products consti- tutes an important part of human nutrition. In recent years, due to the intensification of the dairy industry the management of dairy effluents has become a major problem since dairy wastewaters can be a significant threat, mostly for the aquatic environment (Carvalho et al., 2013; Prazeres et al., 2012). Consequently, there is a significant need to improve the management and treatment of dairy effluents in order to reduce environmental problems and to ensure the economic viability of this essential agricultural industry. (Sarkar et al., 2006). Several research groups have studied the biological treatment of dairy wastewater, either under aerobic condition (Bumbac et al., 2015; Tatoulis et al., 2015) or anaerobic conditions (Venetsaneas et al., 2009; Demirel et al., 2005) with the simultaneous produc- tion of hydrogen and methane. However, even though biological processes may lead to a significant reduction of the organic material, usually they fail to meet the limits settled by environ- mental legislations for the disposal of effluents into the environ- ment. Therefore, the combination of biological treatment with other treatment processes such as constructed wetlands (Sultana et al., 2016) and intermittent sand filters (Healy et al., 2007) have been proposed in literature. At the same time, a considerable research on agro-industrial wastewaters treatment using physical processes like membrane technology, mainly reverse osmosis and nanofiltration (Su arez and Riera, 2015; Vourch et al., 2008; L aszl o et al., 2007) or adsorption (Kushwaha et al., 2010) has been carried out. Nevertheless, the main drawback of the physical processes is the fact that they transfer the problem from one phase to another resulting in the necessity either of the further concentrated solution treatment (Perez et al., 2010), or the regeneration of the adsorption material (Ehrenmann et al., 2011). Advanced Oxidation Processes (AOPs) is a family of technologies based on the in situ production of highly reactive radicals. Among various AOPs most studies related to dairy wastewaters have been conducted with Fenton, photo Fenton and electro Fenton like re- actions (Davarnejad and Nikseresht, 2016; Loures et al., 2014; Prazeres et al., 2013; Vlyssides et al., 2013), photocatalysis (Lamas * Corresponding author. E-mail address: zfrontistis@chemeng.upatras.gr (Z. Frontistis). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2017.07.046 0301-4797/© 2017 Elsevier Ltd. All rights reserved. Journal of Environmental Management 202 (2017) 217e224