Photo-Fenton-assisted ozonation of p-Coumaric acid in aqueous solution

The degradation of p-Coumaric acid present in olive oil mill wastewater was investigated as a pretreatment stage to obtain more easily biodegradable molecules, with lower toxicity that facilitates subsequent anaerobic digestion. Thus, photo-Fenton-assisted ozonation has been studied and compared with ozonation at alkaline pH and conventional single ultraviolet (UV) and acid ozonation treatments. In the combined process, the overall kinetic rate constant was split into various components: direct oxidation by UV light, direct oxidation by ozone and oxidation by hydroxyl radicals. Molecular and/or radical ozone reaction was studied by conducting the reaction in the presence and absence of tert-butylalcohol at pHs 2, 7 and 9. Ozone oxidation rate increases with pH or by the addition of Fenton reagent and/or UV radiation due to generation of hydroxyl radicals, *OH. Hydrogen peroxide and ferrous ion play a double role during oxidation since at low concentrations they act as initiators of hydroxyl radicals but at high concentrations they act as radical scavengers. Finally, the additional levels of degradation by formation of hydroxyl radicals have been quantified in comparison to the conventional single processes and an equation is proposed for the reaction rate as a function of studied operating variables.     

Evaluation of different electrochemical methods on the oxidation and degradation of Reactive Blue 4 in aqueous solution

The oxidation of a reactive dye, Reactive Blue 4, RB4, (C.I. 61205), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode and reticulated vitreous carbon electrode occurs in only one step at 2.0 < pH < 12 involving a two-electron transfer to the amine group leading to the imide derivative. Dye solution was not decolorized effectively in this electrolysis process. Nevertheless, the oxidation of this dye on Ti/SnO2/SbO(x) (3% mol)/RuO2 (1% mol) electrode showed 100% of decolorization and 60% of total organic carbon removal in Na2SO4 0.2 M at pH 2.2 and potential of +2.4V. Experiments on degradation photoelectrocatalytic were also carried out for RB4 degradation in Na2SO4 0.1 M, pH 12, using a Ti/TiO2 photoanode biased at +1.0 V and UV light. After 1h of electrolysis the results indicated total color removal and 37% of mineralization.     

Aniline degradation by Electro-Fenton and peroxi-coagulation processes using a flow reactor for wastewater treatment

The degradation of 10-30 l of a 1000 ppm aniline solution in 0.050 M Na2SO4 + H2SO4 at pH 3.0 and 40 degrees C by Electro-Fenton and peroxi-coagulation processes at constant current until 20 A has been studied using a pilot flow reactor in recirculation mode with a filter-press cell containing an anode and an oxygen diffusion cathode, both of 100 cm2 area. H2O2 is produced by the two-electron reduction of O2 at the cathode, being accumulated with a current efficiency between 60% and 80% at the first stages of electrolyses performed with a Ti/Pt anode. In the presence of 1 mM Fe2+, less H2O2 is accumulated, but it is not detected using an Fe anode. The Electro-Fenton process with 1 mM Fe2+ and a Ti/Pt or DSA anode yields an insoluble violet polymer, while the soluble total organic carbon (TOC) is gradually removed, reaching 61% degradation after 2 h at 20 A. In this treatment, pollutants are preferentially oxidized by hydroxyl radicals formed in solution from reaction of Fe2+ with H2O2. The peroxi-coagulation process with an Fe anode has higher degradation power, allowing to remove more than 95% of pollutants at 20 A, since some intermediates coagulate with the Fe(OH)3 precipitate formed. Both advanced electrochemical oxidation processes (AEOPs) show moderate energy costs, which increase with increasing electrolysis time and applied current.     

Efficient removal of insecticide “imidacloprid” from water by electrochemical advanced oxidation processes

The oxidative degradation of imidacloprid (ICP) has been carried out by electrochemical advanced oxidation processes (EAOPs), anodic oxidation, and electro-Fenton, in which hydroxyl radicals are generated electrocatalytically. Carbon-felt cathode and platinum or boron-doped diamond (BDD) anodes were used in electrolysis cell. To determine optimum operating conditions, the effects of applied current and catalyst concentration were investigated. The decay of ICP during the oxidative degradation was well fitted to pseudo-first-order reaction kinetics and absolute rate constant of the oxidation of ICP by hydroxyl radicals was found to be k _abs(ICP)?=?1.23?×?10⁹ L mol^?1 s^?1. The results showed that both anodic oxidation and electro-Fenton process with BDD anode exhibited high mineralization efficiency reaching 91 and 94 % total organic carbon (TOC) removal at 2 h, respectively. For Pt-EF process, mineralization efficiency was also obtained as 71 %. The degradation products of ICP were identified and a plausible general oxidation mechanism was proposed. Some of the main reaction intermediates such as 6-chloronicotinic acid, 6-chloronicotinaldehyde, and 6-hydroxynicotinic acid were determined by GC-MS analysis. Before complete mineralization, formic, acetic, oxalic, and glyoxylic acids were identified as end-products. The initial chlorine and organic nitrogen present in ICP were found to be converted to inorganic anions Cl^?, NO₃ ^?, and NH₄ ⁺.     

Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed.     

羟基氧化铁催化臭氧氧化去除水中阿特拉津

以实验室制备的羟基氧化铁(FeOOH)为催化剂,研究了其催化臭氧氧化去除水中痕量阿特拉津的效能,并对影响催化效果因素及降解机理进行了探讨。在本实验条件下,反应8 min时催化氧化阿特拉津的去除率比单独臭氧氧化高出63.2%,而FeOOH对阿特拉津的吸附量很小,结果表明,FeOOH对臭氧氧化水中的痕量阿特拉津具有明显的催化活性。探讨了催化剂投量、pH、阿特拉津初始浓度和重碳酸盐碱度对催化氧化阿特拉津的影响。催化剂最佳投量为150 mg/L,去除率随pH和阿特拉津初始浓度的增加而升高,重碳酸盐浓度为200 mg/L时催化作用受到明显抑制。通过研究叔丁醇对催化反应的影响间接推断了催化反应的机理,叔丁醇作为羟基自由基抑制剂有效地抑制了水中羟基自由基的生成和它对阿特拉津的氧化反应,间接证明这种催化作用遵循羟基自由基的反应机理。     

Degradation of diethyl phthalate (DEP) by vacuum ultraviolet process: influencing factors,oxidation products,and toxicity assessment

The vacuum ultraviolet (VUV) process, which can directly produce hydroxyl radical from water, is considered to be a promising oxidation process in degrading contaminants of emerging concern, because of no need for extra reagents. In this study, the influencing factors and mechanism for degradation of diethyl phthalate (DEP) by the VUV process were investigated. The effects of irradiation intensity, inorganic anions, natural organic matter (NOM), and H₂O₂ dosage on the performance of VUV process were evaluated. The results showed that DEP could be more efficiently degraded by the VUV process compared with ultraviolet (UV)-254-nm irradiation. The presence of HCO₃^?, NO₃^? and NOM in the aqueous solutions inhibited the degradation of DEP to a different degree, mainly by competing hydroxyl radicals (HO^?) with DEP. Degradation rate and removal efficiency of DEP by VUV process significantly enhanced with the addition of H₂O₂, while excess H₂O₂ dosage could inhibit the DEP degradation. Moreover, based on the identified seven oxidation byproducts and their time-dependent evolution profiles, a possible pathway for DEP degradation during the VUV process was proposed. Finally, the ecotoxicity of DEP and its oxidation byproducts reduced overall according to the calculated results from Ecological Structure Activity Relationships (ECOSAR) program. The electrical energy per order (EE/O) was also assessed to analysis the energy cost of the DEP degradation in the VUV process. Our work showed the VUV process could be an alternative and environmental friendly technology for removing contaminants in water.

     

O3/H2O2法去除浮选药剂丁基黄药

采用O3/H2O2法去除水中丁基黄药,考察了H2O2/O3摩尔比、pH值、丁基黄药初始浓度、温度和自由基抑制剂对丁基黄药的去除效果的影响。结果表明,在相同O3投加量下,H2O2量越大,丁基黄药去除率越高。pH值为7～9,温度在293～303 K的范围内,O3/H2O2对丁基黄药都有很高的去除率。碳酸氢根和叔丁醇能在一定程度上降低丁基黄药的降解效率。研究还发现,在O3和H2O2投加量相同的条件下,H2O2多次投加对水中丁基黄药的处理效果明显优于一次性投加。GC/MS分析表明,O3/H2O2氧化丁基黄药氧化产物为羧酸类物质。     

O3/H2O2法去除浮选药剂丁基黄药

采用O3/H2O2法去除水中丁基黄药,考察了H2O2/O3摩尔比、pH值、丁基黄药初始浓度、温度和自由基抑制剂对丁基黄药的去除效果的影响。结果表明,在相同O3投加量下,H2O2量越大,丁基黄药去除率越高。pH值为7～9,温度在293～303 K的范围内,O3/H2O2对丁基黄药都有很高的去除率。碳酸氢根和叔丁醇能在一定程度上降低丁基黄药的降解效率。研究还发现,在O3和H2O2投加量相同的条件下,H2O2多次投加对水中丁基黄药的处理效果明显优于一次性投加。GC/MS分析表明,O3/H2O2氧化丁基黄药氧化产物为羧酸类物质。     

臭氧氧化及其他强化技术协同降解聚乙烯醇

采用O₃氧化降解水中聚乙烯醇（PVA），考察了O₃氧化的影响因素及与其他强化技术协同下的降解效果。结果表明，经12 min处理，O₃/超声波、O₃/紫外光协同作用下PVA降解率较直接O₃氧化的63.2%有显著提高，表现出了良好的协同效应。通过比较酸性条件下添加不同量Fenton试剂的作用效果可知，·OH的氧化作用是PVA降解的重要原因。     

Characteristics of electrolysis, ozonation, and their combination process on treatment of municipal wastewater.

The characteristics of municipal wastewater treatment by electrolysis, ozonation, and combination processes of electrolysis and aeration using three gaseous species (nitrogen [N2], oxygen [O2], and ozone [O3]) were discussed in this research using ruthenium oxide (RuO2)-coated titanium anodes and stainless-steel (SUS304) cathodes. Electrolysis and electrolysis with nitrogen aeration were characterized by a rapid decrease in 5-day biochemical oxygen demand (BODs) and total nitrogen and a slow decrease in chemical oxygen demand (COD). In contrast, ozonation, electrolysis with oxygen aeration, and electrolysis with ozone aeration were characterized by transformation of persistent organic matter to biodegradable matter and preservation of total nitrogen. The best energy efficiency in removing BOD5 and total nitrogen was demonstrated by electrolysis, as a result of direct anodic oxidation and indirect oxidation with free chlorine produced from the chloride ion (Cl-) at the anodes. However, electrolysis with ozone aeration was found to be superior to the other processes, in terms of its energy efficiency in removing COD and its ability to remove COD completely, as a result of hydroxyl radical (*OH) production via cathodic reduction of ozone.     

Influence of pH on persulfate oxidation of TCE at ambient temperatures

In situ chemical oxidation (ISCO) is a technology used for groundwater remediation. This laboratory study investigated the use of the oxidant sodium persulfate for the chemical oxidation of trichloroethylene (TCE) at near ambient temperatures (10, 20 and 30 degrees C) to determine the influence of pH (pH=4, 7 and 9) on the reaction rate (i.e., pseudo-first-order rate constants) over the range of temperatures utilized. TCE solutions (60 mg l(-1); 0.46 mM) were prepared in phosphate buffered RO water and a fixed persulfate/TCE molar ratio of 50/1 was employed in all tests. Half-lives of TCE degradation at 10, 20 and 30 degrees C (pH 7) were 115.5, 35.0 and 5.5h, respectively. Maximum TCE degradation occurred at pH 7. Lowering system pH resulted in a greater decrease in TCE degradation rates than increasing system pH. Radical scavenging tests used to identify predominant radical species suggested that the sulfate radical (SO(4)(.-)) predominates under acidic conditions and the hydroxyl radical (.OH) predominates under basic conditions. In a side by side comparison of TCE degradation in a groundwater vs. unbuffered RO water it was demonstrated that when the system pH is buffered to near neutral pH conditions due to the presence of natural occurring groundwater constituents that the TCE degradation rate is higher than in unbuffered RO water where the system pH dropped from 5.9 to 2.8. The results of this study suggest that in a field application of ISCO, pH should be monitored and adjusted to near neutral if necessary.     

Electrochemical oxidation of benzene on boron-doped diamond electrodes

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H₂SO₄ 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1 × 10⁻² M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10⁻⁵ M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound.     

Selective redox degradation of chlorinated aliphatic compounds by Fenton reaction in pyrite suspension

Selective redox degradation of chlorinated aliphatics by Fenton reaction in pyrite suspension was investigated in a closed system. Carbon tetrachloride (CT) was used as a representative target of perchlorinated alkanes and trichloroethylene (TCE) was used as one of highly chlorinated alkenes. Degradation of CT in Fenton reaction was significantly enhanced by pyrite used as an iron source instead of soluble Fe. Pyrite Fenton showed 93% of CT removal in 140 min, while Fenton reaction with soluble Fe(II) showed 52% and that with Fe(III) 15%. Addition of 2-propanol to the pyrite Fenton system significantly inhibited degradation of TCE (99% to 44% of TCE removal), while degradation of CT was slightly improved by the 2-propanol addition (80-91% of CT removal). The result suggests that, unlike oxidative degradation of TCE by hydroxyl radical in pyrite Fenton system, an oxidation by the hydroxyl radical is not a main degradation mechanism for the degradation of CT in pyrite Fenton system but a reductive dechlorination by superoxide can rather be the one for the CT degradation. The degradation kinetics of CT in the pyrite Fenton system was decelerated (0.13-0.03 min⁻¹), as initial suspension pH decreased from 3 to 2. The formation of superoxide during the CT degradation in the pyrite Fenton system was observed by electron spin resonance spectroscopy. The formation at initial pH 3 was greater than that at initial pH 2, which supported that superoxide was a main reductant for degradation of CT in the pyrite Fenton system.     

Evaluation of the efficiency of monopolar and bipolar BDD electrodes for electrochemical oxidation of anthraquinone textile synthetic effluent for reuse

The efficiency of the electrochemical degradation of synthetic wastewater containing an anthraquinone dye has been comparatively studied in two electrolytic cells with a synthetic boron-doped diamond (Si/BDD) as an anode. The first is an individual cell (Cell 1) with monopolar electrode BDD and the second (Cell 2) has two bipolar electrodes BDD self-polarized. The bulk electrolysis was performed at the same initial operating conditions in order to quantify the influence of the initial pH and current density on dye discoloration and global mineralization removal. The current efficiency and the consumption energy were also evaluated. When the same solutions have been comparatively treated with the two cells, a quite good mineralization is found in Cell 2. This result supposed more fraction of the applied current is used for the electrocombustion reaction on Cell 2 if compared to Cell 1 and small amount rest for the side reaction of oxygen evolution. The HPLC analyses confirmed this hypothesis and showed that the concentration trend of intermediates (sulfanilic acid, phthalate acid and salicylic acid) with electrolysis time was different on two cells. Phototoxicity tests show that the electrochemical oxidation with BDD electrodes could be useful as a pretreatment technique for reducing hazardous wastewater toxicity.     

Oxidation of TNT by photo-Fenton process

A series of photo-Fenton reactions have been performed for the degradation of 2,4,6-trinitrotoluene (TNT) in a 4.2-l reactor. The degradation reaction rate of TNT followed a pseudo-first-order behavior; and the rate constants for 2.4mW cm(-2)UV only, 2.4mW cm(-2)UV/H(2)O(2), Fenton, photo-Fenton (2.4mW cm(-2)) and photo-Fenton (4.7mW cm(-2)) were 0.002min(-1), 0.007min(-1), 0.014min(-1), 0.025min(-1) and 0.037min(-1), respectively. Increasing the intensity of UV light, and the concentrations of ferrous ions and hydrogen peroxide promoted the oxidation rate under the experimental conditions in this study. The weighting factor (f), the Fe(II)-promoted efficiency (r) and the promoted-UV light efficiency (p) were calculated to clarify their effects on the TNT oxidation. Moreover, the inhibition effect of hydroxyl radical was also observed in both Fenton and photo-Fenton oxidation when the concentration of Fe(II) were higher than 2.88mM. Solid phase micro-extraction was first applied to the separation of the organic byproducts from TNT oxidation. GC/MS was employed to identify the byproducts during the Fenton and photo-Fenton oxidation of TNT. These compounds were clarified as 1,3,5-trinitrobenzene, 1-methyl-2,4-dinitrobenzene 2,5-dinitrobenzoic acid and 1,3-dinitrobenzene. By these byproducts, the mechanisms of the methyl group oxidation, decarboxylation, aromatic ring breakage, and hydrolysis can be recognized and demonstrated. The pathway of TNT oxidation by photo-Fenton process was also proposed in this study.     

Electro-Fenton degradation of the antibiotic sulfanilamide with Pt/carbon-felt and BDD/carbon-felt cells. Kinetics,reaction intermediates,and toxicity assessment

The degradation of 230 mL of a 0.6-mM sulfanilamide solution in 0.05 M Na₂SO₄ of pH 3.0 has been studied by electro-Fenton process. The electrolytic cell contained either a Pt or boron-doped diamond (BDD) anode and a carbon-felt cathode. Under these conditions, organics are oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton’s reaction between initially added (and then electrochemically regenerated) Fe²⁺ and cathodically generated H₂O₂. From the decay of sulfanilamide concentration determined by reversed-phase liquid chromatography, an optimum Fe²⁺ concentration of 0.20 mM in both cells was found. The drug disappeared more rapidly using BDD than Pt, and, in both cases, it was more quickly removed with raising applied current. Almost total mineralization was achieved using the BDD/carbon-felt cell, whereas the alternative use of Pt anode led to a slightly lower mineralization degree. In both cells, the degradation rate was accelerated at higher current but with the concomitant fall of mineralization current efficiency due to the greater increase in rate of the parasitic reactions of hydroxyl radicals. Reversed-phase liquid chromatography allowed the identification of catechol, resorcinol, hydroquinone, p-benzoquinone, and 1,2,4-trihydroxybenzene as aromatic intermediates, whereas ion exclusion chromatography revealed the formation of malic, maleic, fumaric, acetic, oxalic, formic, and oxamic acids. NH₄ ⁺, NO₃ ^?, and SO₄ ^2? ions were released during the electro-Fenton process. A plausible reaction sequence for sulfanilamide mineralization involving all detected intermediates has been proposed. The toxicity of the solution was assessed from the Vibrio fischeri bacteria luminescence inhibition. Although it acquired its maximum value at short electrolysis time, the solution was completely detoxified at the end of the electro-Fenton treatment, regardless of the anode used.     

Enhancement of ozone oxidation and its associated processes in the presence of surfactant: degradation of atrazine

In this study, the degradation of atrazine (ATZ) by ozone (O3) oxidation and its associated processes (i.e. UV, UV/O3) in the presence and absence of surfactant was investigated and compared. A non-ionic surfactant, Brij 35, was selected. It was found that the presence of a low concentration of surfactant could improve the removal of ATZ by increasing the dissolution of ozone and the indirect generation of hydroxyl radicals. The saturated ozone level and the reaction rate constants were increased with increasing the concentration of surfactant and then decreased at higher surfactant doses at pH level of 2.5. A similar trend was observed at pH level of 7.0 in the presence of bicarbonate ion, because it is capable of deactivating the hydroxyl radicals generating at higher pH level. However, when the radical reactions become dominant in the ozonation (at pH 7.0 without bicarbonate), the saturated ozone level was higher than that with bicarbonate and the kinetic rate constants were increased first and levelled off with increasing of the dose of surfactant. Through the examining of a proposed unit performance index, the low concentration of surfactant is surely beneficial to the ozonation process. Besides, the direct photolysis and photo-assisted ozonation were compared to the ozonation. A significant enhancement on the decay rate of ATZ was resulted exclusively by adding the surfactant. An enhancement index for quantifying the improvement of the various processes was developed.     

Sonochemical degradation of a pharmaceutical waste,atenolol, in aqueous medium

Atenolol is a β-blocker drug and an identified emerging pollutant. Advanced oxidation processes (AOPs) utilise the reaction of a highly oxidising species (hydroxyl radicals, ^?OH) for the mineralisation of emerging pollutants since conventional treatment methodologies generally fail to degrade these compounds. In the present work, degradation of atenolol was carried out using ultrasound with frequencies ranging from 200 kHz to 1 MHz as a source of hydroxyl radical. The degradation was monitored by HPLC, total organic carbon (TOC) and chemical oxygen demand (COD) reduction and ion chromatography (IC). Nearly 90 % of degradation of atenolol was observed with ultrasound having 350 kHz. Both frequency and power of ultrasound affect the efficiency of degradation. Nearly 100 % degradation was obtained at a pH of 4. Presence of various additives such as sodium dodecyl sulphate, chloride, sulphate, nitrate, phosphate and bicarbonate was found to reduce the efficiency of degradation. Although nearly 100 % degradation of atenolol was observed under various experimental conditions, only about 62 % mineralisation (from TOC and COD measurements) was obtained. Nearly eight intermediate products were identified using high-resolution mass spectrometry (LC-Q-TOF). These products were understood as the results of hydroxyl radical addition to atenolol. The degradation studies were also carried out in river water which also showed a similar degradation profile. A mechanism of degradation and mineralisation is presented.     

Inactivation of Escherichia coli in the electrochemical disinfection process using a Pt anode

Recently, the electrochemical disinfection has gained a great interest as one of the alternatives to conventional chlorination due to its high effectiveness and environmental compatibility. Despite the extensive reports on electro-chlorination disinfection, few researches were reported on the systems without generating chlorine. This study mainly focused on the potential disinfecting ability of electro-generated oxidants other than chlorine with using an inert medium (chloride-free phosphate buffer solution), which was intended to exclude the formation of chlorine during the electrolysis, as the Escherichia coli as an indicator bacterium was disinfected by applying the current to a platinum anode. The electrochemical inactivation of E. coli without chlorine production was demonstrated to occur in two distinct stages. The first stage inactivation takes place rapidly at the beginning of electrolysis, which appears to be achieved by the electrosorption of negatively charged E. coli cells to the anode surface, followed by a direct electron transfer reaction. As the electrolysis continues further, the inactivation becomes slower but steady, in contrast to the first stage of inactivation. This was attributed to the action of reactive oxidants generated from water discharge, such as hydroxyl radical. Overall, this study suggests that the electrochemical disinfection could be successfully performed even without producing chlorine, recommending the potential application for disinfecting water that does not allow including any chloride ions (such as the production of ultra-pure sterilized water for semiconductor washing).