Separation and Purification Technology 77 (2011) 283–293 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Treatment of potable water containing low concentration of arsenic with electrocoagulation: Different connection modes and Fe–Al electrodes Mehmet Kobya a,∗ , Feride Ulu a , Ugur Gebologlu a , Erhan Demirbas b , Mehmet S. Oncel a a Gebze Institute of Technology, Department of Environmental Engineering, Cayirova, 41400 Gebze, Turkey b Gebze Institute of Technology, Department of Chemistry, 41400 Gebze, Turkey article info Article history: Received 15 October 2010 Received in revised form 11 December 2010 Accepted 15 December 2010 Keywords: Arsenic removal Electrocoagulation Potable water Operating cost Electrode connection modes abstract In this study, effects of both Fe and Al electrode connection modes (parallel and series) and electrode materials on arsenic removal efficiency from potable water by electrocoagulation (EC) process were investigated. Experiments were carried out to remove arsenic by the EC covering wide range in operating conditions such as pH (4–9), current density (1.75–7.5 A/m 2 ) and operating time (0–15 min). The highest arsenic removal was obtained in the monopolar series (MP-S) electrode connection mode for both elec- trodes as pH 6.5 for Fe and pH 7 for Al electrodes to achieve a residual arsenic concentration of 10 g/L or less for potable water in the EC process. As the current density increased, arsenic removal efficiencies were increased with all types of electrode connection modes. However, the optimum arsenic removal at 2.5 A/m 2 was obtained with 2.5 min of operating time for Fe (94.1%) and 4 min of operating time (93.5%) for Al electrodes at MP-S mode. The electrode and energy consumption values at MP-S connection mode for Fe and Al electrodes were calculated as 0.00140 kg Fe/m 3 and 0.0025 kg Al/m 3 , and 0.0140 kWh/m 3 and 0.0254 kWh/m 3 , respectively. Therefore, the lowest operating costs were 0.0047 D /m 3 and 0.0064 D /m 3 for Fe and Al electrodes. The optimum arsenic removal from potable water by the EC process showed that Fe electrodes gave the best results at MP-S connection mode as compared to the rest in terms of operating time and operating cost. The sludge was analyzed using scanning electron microscope (SEM) imaging. The SEM image suggested that amorphous Fe/Al oxyhydroxides were present in the sludge. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Arsenic is one of the most common potentially toxic trace elements in potable water sources such as groundwater and sur- face waters. The problem of arsenic contamination in these water sources is a serious global concern in many places around the world, sometimes in relation to natural sources (geogenic origin) and in other cases in relation to anthropogenic ones [1–3]. Arsenic in potable water causes a major public health problem threaten- ing the lives of over 150 million people worldwide [2,4]. Primary potable water supplies are contaminated in Argentina, Bangladesh, Cambodia, China, Chile, Hungary, Mexico, Turkey, Vietnam, West Bengal (India), some areas of the United States, and more contam- ination continues to be discovered. Bangladesh is the hardest hit, with 35–77 million of its citizens exposed to above limit of the World Health Organization (WHO) which is 10 g/L [2,5,6]. The only way to solve this problem is to supply clean potable water free from arsenic and other toxic impurities. Therefore, effective treatment of arsenic is required to meet the maximum ∗ Corresponding author. Tel.: +90 262 6053214; fax: +90 262 6538490. E-mail address: kobya@gyte.edu.tr (M. Kobya). contamination level of arsenic in potable water as recommended by the WHO, European Commission Directive and United States Envi- ronmental Protection Agency [7–9]. As a result, these authorities recommended level of maximum arsenic concentration in potable water is 10 g/L and is adopted by the Turkish Ministry of Environ- ment and Forestry. The health effects of arsenic poisoning vary widely in sever- ity, from chronic fatigue to deadly cancers [10]. Symptoms have a latency period of 5–20 years, making early detection difficult. Chronic health effects of arsenic in potable water include devel- opment of various skin lesions such as hyperpigmentation (dark spots), hypopigmentation (white spots), and keratoses of the hands and feet. Skin cancers and internal cancers (lung, kidney, liver, and bladder) can appear due to high arsenic exposure [11,12]. The increased attention to arsenic toxicity has incited con- siderable research for developing new methods for removing arsenic from potable water. Treatment processes such as coag- ulation/filtration, modified coagulation filtration, manganese greensand filtration, modified lime softening, adsorption on activated alumina, reverse osmosis, electrodialysis reversal and oxidation/filtration ion exchange, adsorption by adsorbents such as granular ferric oxides, iron oxide coated sand have been reported for arsenic removal [13–18]. These processes take considerable 1383-5866/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2010.12.018