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This paper analyzes the advantages and drawbacks of the combination of UV irradiation with electrolysis with the aim to give insight about the feasibility of the application of this technology for the reclaiming of conventionally-treated wastewater. The oxidation of synthetic solutions containing five selected model complex pollutants has been compared, showing that UV irradiation improves the results of electrolysis for progesterone, metoprolol and caffeine and deteriorates the performance for the degradation of sulfamethoxazole and dimethyl-phthalate. Differences observed becomes lower when mineralization is compared showing that the effects of UV irradiation are diluted when a mixture of species is oxidized. Results suggest that high ThOD/TOC (Theoretical Oxygen Demand/Total Organic Carbon) ratios improve the synergistic coupling of technologies while low values lead to a clear antagonistic effect. Because during oxidation progress this ratio is decreased, the observed effect on mineralization is much lower than in the oxidation of the raw molecule. Opposite to this low effect on the oxidation of organics, the improvement in the performance of the disinfection by coupling UV to electrolysis is much clearer. In addition, UV irradiation modifies significantly the chlorine speciation and helps to prevent the formation of hazardous species such as chlorate and perchlorate during the electrochemical processes.

In this work, a novel integrated electrochemical process for urban wastewater regeneration is described. The electrochemical cell consists in a Boron Doped Diamond (BDD) or a Dimensionally Stable Anode (DSA) as anode, a Stainless Steel (SS) as cathode and a perforated aluminum plate, which behaves as bipolar electrode, between anode and cathode. Thus, in this cell, it is possible to carry out, at the same time, two different electrochemical processes: electrodisinfection (ED) and electrocoagulation (EC). The treatment of urban wastewater with different anodes and different operating conditions is studied. First of all, in order to check the process performance, experiments with synthetic wastewaters were carried out, showing that it is possible to achieve a 100% of turbidity removal by the electrodissolution of the bipolar electrode. Next, the effect of the current density and the anode material are studied during the ED-EC process of actual effluents. Results show that it is possible to remove Escherichia coli and turbidity simultaneously of an actual effluent from a WasteWater Treatment Facility (WWTF). The use of BDD anodes allows to remove the E. coli completely at an applied electric charge of 0.0077 A h dm(-3) when working with a current density of 6.65 A m(-2). On the other hand, with DSA anodes, the current density necessary to achieve the total removal of E. coli is higher (11.12 A m(-2)) than that required with BDD anodes. Finally, the influence of cell flow path and flow rate have been studied. Results show that the performance of the process strongly depends on the characteristics of the initial effluent (E. coli concentration and Cl(-)/NH(4)(+) initial ratio) and that a cell configuration cathode (inlet)-anode (outlet) and a higher flow rate enhance the removal of the turbidity from the treated effluent.

This work presents an integrated electrodisinfection/electrocoagulation (ED-EC) process for urban wastewater reuse that employs iron bipolar electrodes. Boron doped diamond (BDD) was used as the anode and stainless steel (SS) as the cathode. A perforated iron plate was introduced between the anode and cathode to function as a bipolar electrode. This ED-EC combined cell makes it possible to conduct the simultaneous removal of microbiological content and elimination of turbidity from urban wastewater. The results show that current densities greater than or equal to 6.70 A m(-2) enable complete disinfection of the effluent and the removal of more than 90% of its initial turbidity. Hypochlorite and chloramines formed during the ED-EC process were found to be the main compounds responsible for the disinfection process. Furthermore, a cell configuration of cathode (inlet)-anode (outlet) improves the process performance by enhancing turbidity removal. Finally, the influence of the bipolar electrode material (iron or aluminium) was assessed. The results indicate that the efficiency of the electrodisinfection process depends mainly on the anodic material and is not influenced by the material of the bipolar electrode. In contrast, the removal of turbidity is more efficient when using iron as a bipolar electrode, especially at low current densities, due to the formation of a passive layer on the aluminium that hinders the dissolution of the bipolar electrode.

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In this work, H2O2 is electro-generated in the cathodic compartment of a divided filterpress cell with a carbon cloth in the configuration of a gas diffusion electrode using air as oxygen source. The effect of Teflon ® content was studied and it was found that the appropriate content is within the range of 10-20%. The production was greatly enhanced after the air-brushing deposition (and subsequent annealing) of simply 0.5 mg of carbon black. Higher additions clogged the pores and resulted counterproductive in terms of H2O2 generation. At a current density of 25 mA cm -2 , the production rate was 15 mg H2O2 h -1 cm -2 with a current efficiency close to 100%. Production rate increased with current density up to more than 40 mg H2O2 h -1 cm -2 at 87.5 mA cm -2 . The good performance and ease of preparation of this electrode make it an interesting alternative to generate hydrogen peroxide for Electro-Fenton processes.

The hydrogen peroxide is a key and versatile compound that can be readily produced in one-pot electrochemical reactors via the 2 eoxygen reduction reaction. In all the electrolyzers studied up to date, the external aeration is carried out by means of a compressor. In this work, the compressor is substituted by a device based on the Venturi effect to minimize the acquisition, maintenance and operating costs associated to the aeration of the reactor. Interestingly, it was found that this aerator can super saturate in oxygen the solution thanks to the formation of air bubbles.The catalytic effect of carbon black (CB) and/or polytetrafluoroethylene (PTFE) to increase the production of H2O2 was studied, observing a synergistic effect 2 when the CB/PTFE mixture was deposited on the carbon felt cathode. Efficient hydrogen peroxide generation was obtained at 15 mA cm -2 : instantaneous production rate of around 9.2 mg H2O2 h -1 cm -2 and a corresponding current efficiency in the order of 90%. The limiting current density increased when the jet aerator was used thanks to i) the super saturation of the solution (dissolved oxygen + air bubbles) and ii) the ability of the CB/PTFE modified carbon felt to use them as oxygen source. The jet aerator is rather promising for the electrochemical generation of hydrogen peroxide.