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In this study we present the cathodic Cr(VI) reduction using electrodissolution of iron anode. In batch experiments we tested four different cathodic materials; the best conditions were found when copper was used. It is observed that when more current is applied into the electrochemical cell faster reduction rates are achieved. Continuous experiments also reveal that Cr(VI) reduction could be done in a very efficient way. To confirm the experimental data, cyclic voltammetry was used and it was found that the cathodic Cr(VI) reduction is taking place., (Copyright © 2010 Elsevier B.V. All rights reserved.)

This study addresses the elimination of persistent organic compounds in industrial wastewater using a synergistic combination of electrocoagulation and electrooxidation. Electrocoagulation is a relatively quick process (30 min), which is very effective in removing colloidal and suspended particles, as seen in changes in coliforms, turbidity, and color and in the general absorbance by UV-vis spectroscopy. However, it is relatively ineffective in eliminating stable persistent organic compounds--in this work, only half of the COD was eliminated from wastewater and an oxidation peak in the cyclic voltammetry scan remained. Electrooxidation is very effective in breaking down organic compounds through oxidation as reflected in the elimination of COD, BOD(5), and oxidative peak in cyclic voltammetry, but requires so much time (21 h) that it has very limited practicality, especially when colloidal and suspended particles are present. Electrooxidative mineralization of electrocoagulated wastewater, in which most of the colloids and charged species have been removed, takes less than 2h. In the coupled technique, electrocoagulation quickly coagulates and removes the colloidal and suspended particles, as well as many charged species, then electrooxidation oxidizes the remaining organics. The coupled process eliminates COD, BOD(5), color, turbidity, and coliforms in a practical amount of time (2h)., ((c) 2009 Elsevier B.V. All rights reserved.)

The removal of pathogenic organisms from water and wastewater by electrochemical methods has gained increasing attention due to their very high efficiency, and their easy applicability in real world processes. In this regard there are several approaches utilizing different electrode materials to accomplish the pollutant removal. This minireview highlights how electrocoagulation, direct electrooxidation and indirect electrooxidation are used to remove pathogenic microorganisms from different water and wastewater sources, including industrial and municipal water and wastewater. The conditions for each treatment are describe and the material used for the electrodes are discussed. Particular attention is paid to the use of boron‐doped electrodes in such processes. This kind of electrodes have gained attention due to their excellent properties in electrochemical water treatment, including a wide electrochemical potential window in aqueous media, very low capacitance and extreme electrochemical stability. [ABSTRACT FROM AUTHOR]

Nonylphenol has been reported as an Endocrine Disruptive Chemical and aquatic organisms have shown acutely and chronically toxicity when they are exposed to this organic pollutant. Many technologies have been applied searching to degrade or remove this contaminant from wastewater; however, few proposals addresses for the technology scale up and possible real application. In this study, the results of integrating electrochemical and ozone process are presented. It is possible to propose that in acidic media electrochemical degradation is faster than ozone treatment, for example at 60 min of treatment, ozone showed a COD value of ca 30% degradation, whereas electrochemically 70% degradation was obtained. When the electrochemical process working in a continuous mode is applied (without prior O3 treatment), COD and TOC removal takes two times the period of time required when an initial ozone dose was applied. A cost comparison between the three processes reveals that the use of the sequenced treatment reduces the cost. Furthermore, when the cost of the sequenced process is compared against other process (UV/O3) the cost reduction is significant making the proposed system an attractive alternative for the treatment of persistent pollutants. Therefore, this technology proves to be highly effective, with low operational cost, simple operation and low environmental impact. Furthermore, no sludge is generated. [ABSTRACT FROM AUTHOR]

This study evaluates the effect of adding electrochemical copper(II) ions into an ozonation process for treating industrial wastewater. Combining the processes resulted in a synergy that enhanced the reduction of physicochemical parameters (COD, TOC, color, turbidity, Z-Potential, and conductivity). In only 15 minutes the integrated process reduced the COD by 83%, TOC by 78 %, color by 93%, turbidity by 77%, and conductivity by 27% at relatively low current density (12.5 mA cm−2). Thus, the combination of the electrochemical and ozonation processes noticeably improves wastewater quality, decreases the process time, and reduces the sludge production. [ABSTRACT FROM PUBLISHER]

Abstract: The effectiveness of electrochemical, ozone and integrated electrochemical–ozone processes on industrial wastewater treatment was evaluated. The effect of continuous and pulsing addition of energy was studied. In the electrochemical treatment under pulsing operation, the chemical oxygen demand COD removal was found to be 28% at 60min while pulsing ozonation led to obtain 48% COD removal after 36min. In the integrated electrochemical–ozone process with energy pulses, the COD reduction was observed to be 80% after 44min of treatment. Initial pH was 7.5 at all experiments. Finally, the sludge produced during integrated electrochemical–ozone process with energy pulses was quantified and the morphology was evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The amount of sludge produced and electrodes passivation after the integrated method was found to be lower than with the electrochemical method alone. [Copyright &y& Elsevier]

Abstract: The effectiveness of electrochemical, ozone and integrated electrochemical–ozone processes on industrial wastewater was evaluated. Electrochemical under optimal conditions of pH 7 and 40mAcm−2 of current density reduced the chemical oxygen demand (COD) by 43% and the biochemical oxygen demand (BOD5) by 42%. Ozone treatment reduced both COD and BOD5 by 60%. Integration of the two processes at pH 7 and 20mAcm−2 of current density greatly improved the reduction of COD (84%), BOD5 (79%), color (95%), turbidity (96%) and total coliforms (99%). Thus, the integrated electrochemical–ozone process noticeably improves wastewater quality. Finally, the sludge produced during integrated electrochemical–ozone process was quantified and the morphology was evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). [Copyright &y& Elsevier]

The degradation of phenol was studied under three chemical environments, ozonation (O 3 ), electro-oxidation (EO) and ozonation-electro-oxidation (O 3 -EO) coupled process. The parent compound concentration was established by UV–Vis spectrophotometry while the by-products were identified by HPLC. This allowed proposing a mechanism of phenol oxidation during the coupled process. This coupled process was found to practically mineralize all phenol (TOC removal = 99.8%) under pH 7.0 ± 0.5 and at a current density of 60 mA cm −2 , 0.05 L min −1 flowrate, ozone concentration of 5 ± 0.5 mg L −1 . Furthermore, it was found that the coupled process is practically twice faster than the EO process alone to achieve a high degree of mineralization. In this sense, it was concluded that ozone alone only partially mineralizes the phenol molecule and mainly leads to the formation of aliphatic compounds. In addition, the toxicities of phenol and its degradation products were established by using a bioassay with lettuce seeds. It was concluded that, unlike ozonation, the coupled oxidation process not only mineralizes the organic molecule but also completely eliminates the toxicity of the treated phenolic solution. [ABSTRACT FROM AUTHOR]

Abstract: This work evaluates the coupling of electrochemical oxidation and ozonation to reduce the high organic load of industrial wastewater quickly and effectively. Ozonation alone is shown to only reduce the COD of wastewater by about 45%. Electrochemical oxidation using boron-doped diamond electrodes reduces the COD by 99.9%, but requires over 2h per 0.7L batch. However, when the two processes are coupled, the COD is reduced by 99.9% along with most color and turbidity in about an hour. The coupled process practically eliminates the COD, color, and turbidity without the addition of chemical reagents or changing the pH and doesn''t generate any sludge, so it is both effective and environmentally friendly. [Copyright &y& Elsevier]

Abstract: This work assesses the disinfection for reuse of treated urban wastewaters using electrochemical-oxidation with conductive-diamond anodes, without adding any external chemical reagent. Three actual effluents of municipal wastewater treatment plants (sample collected from the secondary clarifiers) have been treated using this technology, in every case, a complete removal of Escherichia coli have been achieved. In addition, it has been found that working within the range of current densities proposed in this work (1.3–13.0Am−2), this technology does not form any hazardous by-products (neither perchlorates nor halo-compounds), even at trace level. Combined effects of chloramines and hypochlorite seem to be the main mechanisms to explain disinfection. The primary disinfectant produced in every electrolyses depends on the current density, and on the concentration of both: chlorides and non-oxidized nitrogen, present in the raw treated wastewater. Power consumption as low as 0.2kWhm−3 is enough to assure the complete disinfection of a particular treated wastewater. The lower the applied current density, the lower the energy required to get the disinfection of the treated wastewater. [Copyright &y& Elsevier]