Scale-up of electrolytic and photoelectrolytic processes for water reclaiming: a preliminary study

Abstract

This work focuses on the scale-up of electrochemical and photoelectrochemical oxidation processes with diamond anodes for the removal of organic pollutants and disinfection of treated urban wastewater, two of the most important parameters for the reclaiming of wastewater. The removal of organics was studied with actual biologically treated urban wastewater intensified with 100 mg dm(-3) of caffeine, added as a trace organic pollutant. The disinfection was also studied with biologically treated urban wastewater, and Escherichia coli was used to monitor the efficiency of the process. Results obtained with a single DiaCell® 101 were compared with those obtained with a single-stack DiaCell® 1001 and with a pilot plant made up of five of these stacks. Results obtained demonstrate that scale-up is not a simple but a very complex process, in which not only the electrode and the irradiation dose are important but also mass transfer conditions. Enhanced mass transport conditions have a determining and very positive effect on the removal of organics and a negative effect on the disinfection. Likewise, ultraviolet (UV) irradiation affects in a different way in the different setups used, having a great influence on the removal of complex organics and on the speciation of oxidants produced during disinfection. This works helps to understand the key differences observed in the scale-up, and it is a first approach for future works focused on the real application of conductive diamond electrochemical oxidation.

The Role of Mediated Oxidation on the Electro-irradiated Treatment of Amoxicillin and Ampicillin Polluted Wastewater

“…Additionally, the decrease of TOC concentration seems to indicate that the depletion of any organic may occur-most likely, carboxylic or methyl As can be observed, the partial oxidation of AMX and AMP depends on the technology used. As expected [26,34,35], photolysis is not able to completely remove the antibiotics, and around 70% of AMX and AMP remains unaltered in the solutions after 8 h of treatment. Moreover, in sulphate media, the removal trends of both compounds are almost overlapping, but they differ significantly in chlorine media, in which the degradation of AMP is slower.…”

“…The formation of these species is promoted at high current density [26,34,35], but it is not always reflected by a more efficient degradation. In fact, in light of the results obtained in this study, the transformation of AMP and AMX is favored at high current densities, but not their full mineralization.…”

“…In fact, the partial oxidation of AMX and AMP is even faster in chlorine media, and after 0.25 h of electrolysis at 30 mA cm −2 , both antibiotics have completely disappeared from the reaction system. According to the literature [26,34,35], in chlorine media, the rapid chlorination of aromatic compounds occurs by the attack of electrogenerated Cl 2 /HClO/ClO -, although in many cases it is not accompanied by a rapid TOC removal.…”

Photo-assisted electrochemical advanced oxidation processes for the disinfection of aqueous solutions: A review

“…In this regard, commercial reactors such as DiaCell® cell, equipped with a BDD anode, SS cathode and a UV irradiation source, has been successfully used for the disinfection of an E. coli contaminated real secondary effluent. This study revealed an improvement of four times the inactivation rate when compared to a single electrolysis approach in which the main inactivation mechanism consisted on the indirect oxidation in the bulk solution by means of photo-activated species derived from active chlorine ( Martín de Vidales et al., 2016 ).…”

“…When electrochemical oxidation processes and UV light are not considered to be simultaneously operating at the electrode-solution interphase, and rather complementing each other’s effect in a synergistic way, indirect disinfection processes using highly electro-catalytic and non-photoactive electrodes have been shown to be effective approaches. Under this perspective, it must be noted that UV irradiation represents a highly effective disinfection method that, although costly, can be combined with other disinfection procedures such as electrochemical oxidation ( Cotillas et al., 2016a ; Haaken et al., 2013 ; Martín de Vidales et al., 2016 ; Singla et al., 2020 ). The electrodes employed in this type of processes are usually the DSA, MMO or BDD electrodes ( Panizza and Cerisola, 2005 , 2009 ).…”