Abstract
During the last two decades, and particularly during the last few years, the environmental sector has shown a largely growing interest in the treatment of different types of water and wastewater by electrocoagulation (EC). The aim of this work was to review studies, conducted mainly during 2008-2011, on the wide and versatile range of feasible EC applications employed in the purification of different types of water and wastewater. The EC applications discussed here were divided into 7 following categories: tannery, textile and colored wastewater; pulp and paper industry wastewater; oily wastewater; food industry wastewater; other types of industrial wastewater; surface water as well as model water and wastewater containing heavy metals, nutrients, cyanide and other elements and ions. In addition, this paper presents an overview of the optimum process conditions (treatment times, current densities, and initial pH) and removal efficiencies (mostly high) achieved for the EC applications discussed. In the vast majority of the studies discussed in this review, the aforementioned values were found to be in the range of 5-60 min (typically less than 30 min), 10-150 A/m2 and near neutral pH, respectively. Both operating costs and electrical energy consumption values were found to vary greatly depending on the type of solution being treated, being between 0.004 -6.74 €/m3 and 0.002-58.0 kWh/m3, but in general they were rather low (typically around 0.1-1.0 €/m3 and 0.4-4.0 kWh/m3).
Highlights
Electrocoagulation (EC) is an emerging technology that combines the functions and advantages of conventional coagulation, flotation, and electrochemistry in water and wastewater treatment
An electrocoagulation system consists of an anode and a cathode made of metal plates, both submerged in the aqueous solution being treated [3]
response surface methodology (RSM) has been successfully applied by several authors to optimize the EC process, providing high levels of significance and very low percentages of experimental error in the papers discussed in this study
Summary
Electrocoagulation (EC) is an emerging technology that combines the functions and advantages of conventional coagulation, flotation, and electrochemistry in water and wastewater treatment. EC was studied extensively in the latter half of the 20th century in both the US and the Soviet Union (former USSR), but at that time it was not found to be widely feasible for water treatment This was mainly due to the high electricity and investment costs [2]. Electrocoagulation is based on dissolution of the electrode material used as an anode This so-called “sacrificial anode” produces metal ions which act as coagulant agents in the aqueous solution in situ [1]. The electrodes are usually made of aluminum, iron, or stainless steel (SS), because these metals are cheap, readily available, proven effective, and non-toxic. They have been adopted as the main electrode materials used in EC systems [6,7].
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