A review on efficiency and cost effectiveness of electro- and bio-electro-Fenton processes: Application to the treatment of pharmaceutical pollutants in water

•An overview of pharmaceutical removal efficiency by electro-Fenton (EF) process.•In-depth analysis and discussion of new EF reactors.•Discussion of scale-up for the EF process.•Review on treatment of pharmaceutical solutions by EF and biological treatments.•Perspective on the hybrid process Bio-EF. Nowadays, the treatment of wastewater is a worldwide concern due to the large impact on the environment and human health. Among different types of pollutant, pharmaceuticals are increasingly of emerging concern, as they are generally resistant to the conventional treatment methods and harmful to the environment. Advanced oxidation processes and especially electrochemical advanced oxidation processes (EAOPs) constitute an efficient way to eliminate this kind of pollutants. Among them, the electro-Fenton (EF) process is an environmentally friendly EAOP particularly efficient to remove persistent/toxic pollutant from the water. The main drawback of this method, however, is the relatively high cost due to the energy consumption when a complete mineralization of treated solutions is required. To reduce electrical energy consumption, the combination with a biological treatment was suggested as shown by several successful studies. This review is first addressing ways to improve the degradation efficiency and to reduce the cost of the EF process, with a focus on new types of reactors: especially geometrical modifications, change of the out streaming or the O2 supply. The continuous process is then taken into consideration in order to enable scaling-up. Secondly, the combination of the EF process with a biological treatment for efficient removal of pharmaceuticals is overviewed with focus on the cost, the treatment efficiency and the order (pre- or post-) of treatment. The efficiency of such a system is clearly demonstrated.