Landfill leachate treatment by combination of electro - fenton and sequencing batch reactor method

Landfill leachate contains a large amount of organic, inorganic and heavy metal contents. Untreated leachate is a potential source to effect of soil, surface and groundwater. The combined treatment offers an alternative technique in dealing to leachate treatment. This research is to determine the effectiveness of combined electro-Fenton and sequencing batch reactor (SBR) method on the removal of SS, colour, COD and NH3-N. The experimental involved three major parts were coagulation-flocculation, electro-Fenton and SBR method. This process could be operated independently in a batch mode and optimum conditions for each treatment were identified. In the combined process, leachate was first fed to coagulation-flocculation for pre-treatment. Then, the effluent from that process was oxidized in electro-Fenton process. The final process is the effluent of leachate was fed to a SBR method. The combined treatment was operated under the optimum conditions for all the processes. The result of coagulation-flocculation shown PAC is more effective at 2500 mg/L of optimum dosage. After coagulation-flocculation process, the removal of SS, colour, COD and NH3-N were 80%, 77%, 61% and 35% respectively. The result of electro-Fenton shown Al-Al is more effective at 200 A/m2 of optimum current density, 25 minutes of optimum reaction time, 4 of optimum pH, 800 mg/L of optimum H2O2 dosage and 1000 mg/L of optimum FeSO4•7H2O dosage. After electro-Fenton process, the removal of SS, colour, COD and NH3-N were 87%, 95%, 82% and 65% respectively. The final process of SBR effluent was approaching neutral pH at 6.90 at 2800 mg/L of optimum MLSS and 6 h of optimum reaction time. The overall performance of combined treatment on the removal of SS, colour, COD and NH3-N were 84%, 82%, 87% and 78% respectively. Thus, this combined treatment offers as an alternative technique for landfill leachate treatment on the removal of pollutants

Возможности применения электро-фэнтон процесса в очистке сточных вод

Инновационные окислительные процессы еще очень малоизученны. Одним из мощных процессов разложения большинства органических соединений, включая токсичные и не поддающихся биохимическому разложению является электро-Фентон процесс. В статье дан обзор возможности применения процесса а также предлагаются пути его развития и дальнейших исследований в области применения процесса в очистке сточных вод, пути увеличения эффективности очистки с помощью электро-Фэнтон процесса. As a novel advanced oxidation process, electro-Fenton process is powerful for degrading most organic compounds including toxic and non-biodegradable ones, and so has attracted great attention. The article rview of the application possibilities of the process and its development, further research in the field of application in wastewater treatment, ways to improve efficiency on account of of the Electro-Fenton process

Effective heterogeneous electro-Fenton process for the degradation of a malodorous compound, indole using iron loaded alginate beads as a reusable catalyst

International audienceIn this work the characterization and the performance of iron immobilized in alginate beads (Fe-ABs) as catalyst for heterogeneous electro-Fenton (EF) treatment of a malodorous compound, indole, was investigated. Experimental results demonstrated that indole was effectively removed through the electro-Fenton process; while in the considered experimental conditions, the performances of EF were only slightly improved by the addition of UVA radiation. The most efficient operating conditions were achieved at pH 3.0 in the presence of 200 mg L−1 Fe-ABs catalyst (corresponding to an average iron concentration of 64 mg L−1) with a current density of 0.53 mA cm−2. Under these conditions, 60 min were sufficient to completely degrade 20 mg L−1 of indole, whose removal was found to obey the pseudo-first order model. In terms of organic carbon removal, about 90% mineralization yield was reached in the optimal conditions for 7 h heterogeneous electro-Fenton treatment time. UPLC–MS/MS analysis was applied to identify and follow the evolution of indole oxidation products. Five stable organics intermediates were observed and four of them were identified as dioxindole, isatin, oxindole and anthranilic acid. A reaction sequence was therefore proposed for indole degradation according to the detected products. Subsequent attack of these intermediates by OH radicals led to the formation of short chain acids such as succinic, acetic, oxamic and oxalic identified by ion-exclusion chromatograph

Degradation and Mineralization of Carbamazepine Using an Electro-Fenton Reaction Catalyzed by Magnetite Nanoparticles Fixed on an Electrocatalytic Carbon Fiber Textile Cathode

Pharmaceutical wastes are considered to be important pollutants even at low concentrations. In this regard, carbamazepine has received significant attention due to its negative effect on both ecosystem and human health. However, the need for acidic conditions severely hinders the use of conventional Fenton reagent reactions for the control and elimination of carbamazepine in wastewater effluents and drinking water influents. Herein, we report of the synthesis and use of flexible bifunctional nanoelectrocatalytic textile materials, Fe_3O_4-NP@CNF, for the effective degradation and complete mineralization of carbamazepine in water. The nonwoven porous structure of the composite binder-free Fe_3O_4-NP@CNF textile is used to generate H_2O_2 on the carbon nanofiber (CNF) substrate by O_2 reduction. In addition, ·OH radical is generated on the surface of the bonded Fe_3O_4 nanoparticles (NPs) at low applied potentials (−0.345 V). The Fe_3O_4-NPs are covalently bonded to the CNF textile support with a high degree of dispersion throughout the fiber matrix. The dispersion of the nanosized catalysts results in a higher catalytic reactivity than existing electro-Fenton systems. For example, the newly synthesized Fe_3O_4-NPs system uses an Fe loading that is 2 orders of magnitude less than existing electro-Fenton systems, coupled with a current efficiency that is higher than electrolysis using a boron-doped diamond electrode. Our test results show that this process can remove carbamazepine with high pseudo-first-order rate constants (e.g., 6.85 h^(–1)) and minimal energy consumption (0.239 kW·h/g carbamazepine). This combination leads to an efficient and sustainable electro-Fenton process

Electrochemical Process for Diazinon Removal from Aqueous Media: Design of Experiments, Optimization, and DLLME-GC-FID Method for Diazinon Determination

In the present study, electrochemical process was studied via removal of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) as an insecticide/ acaricide organic case study. Influences of three operational parameters including initial ferrous ion concentration, initial hydrogen peroxide concentration, and initial diazinon concentration were measured and optimized in diazinon removal process. Response surface methodology (RSM) was used to design the experiments. The experimental data collected in a laboratory-scaled batch reactor equipped with four graphite bar electrodes as cathode and an aluminum sheet electrode as an anode. Quantitative analysis of diazinon was done with gas chromatography equipped with flame photometric detector. Disperse liquid–liquid microextraction was used prior to gas chromatography in order to extraction and preconcentration of diazinon from aqueous media to extraction phase. Acetone and chlorobenzene were used as disperser and extraction solvent, respectively. Maximum diazinon removal efficiency of 87% (0.85mg mass removal) in C0 of 2mg/L and 80% (120mg mass removal) in C0 of 300mg/L was achieved under different experimental conditions. The obtained experimental data were used for model building by RSM approach. Finally, optimization process was carried out using RSM algorithm. © 2015, King Fahd University of Petroleum & Minerals

Improvement of the activated sludge treatment by its combination with electro Fenton for the mineralization of sulfamethazine

International audienceA combined process coupling an electro-Fenton pretreatment and a biological degradation in order to mineralize sulfamethazine (SMT) was investigated. The electro-Fenton pretreatment of SMT was first examined and the intermediates products were identified for an initial SMT amount of 0.36 mM, after 1 h electrolysis at pH 3, 18 °C, 200 mA. 94.2% SMT was degraded but the level of mineralization remained low (6.5%), ensuring significant residual organic content for a subsequent biological treatment. Two possible degradation reaction pathways involving all the identified and quantified intermediates are proposed. In a second part, biological treatments with fresh activated sludge were performed to complete the mineralization of the electrolyzed solution of SMT, showing an increase of the mineralization yield with time duration of the pretreatment. For an initial SMT concentration of 0.2 mM, a ferrous ions concentration of 0.5 mM, at pH 3, 18 °C and 500 mA, the mineralization yield during the biological treatment increased as follows: 61.4, 78.8 and 93.9% for 0.5, 1 and 4 h pretreatment, confirming the relevance of the proposed combined process

Photolysis of in-situ electrogenerated hydrogen peroxide for the degradation of emerging pollutants

This study investigates the degradation of paracetamol, an emerging contaminant widely used as pain and fever reliever, by means of hydrogen peroxide either alone or in combination with UV-C photolysis. In particular, we provide a comparison between the performance of both commercial and electrogenerated H2O2 whose production has been achieved by galvanostatic electrolysis in undivided reactor with a gas diffusion cathode. The performance of the treatments has been assessed in terms of both pollutant decay and mineralization. The influence of the H2O2 to paracetamol molar ratio is discussed. The results show that the electrogenerated hydrogen peroxide, when activated by UV-C irradiation, results in faster degradation and mineralization of paracetamol. However, under the conditions adopted, complete depletion of the total organic carbon (TOC) has never been attained

Mineralization of synthetic and industrial pharmaceutical effluent containing trimethoprim by combining electro-Fenton and activated sludge treatment

International audienceA combined process coupling of an electro-Fenton and a biological degradation was investigated in order to mineralize synthetic and industrial pharmaceutical effluent containing trimethoprim, a bacteriostatic antibiotic. Electro-Fenton degradation of trimethoprim was optimized by means of a Doehlert experimental design, showing that 0.69 mM Fe2+, 466 mA and 30 min electrolysis time were optimal, leading to total trimethoprim removal, while mineralization remained limited, 12% for 30 min electrolysis times. The aromatic and aliphatic by-products were identified and a plausible degradation pathway was proposed. Biodegradability was improved, since the BOD5/COD ratio increased from 0.11 initially to 0.32 and 0.52 after 30 and 60 min electrolysis times respectively, confirmed by activated sludge culture, 47 and 59% mineralization of the byproducts from electrolysis.The relevance of the proposed combined process was then confirmed on an industrial pharmaceutical effluent. Its electrolysis under the above conditions showed an almost total removal of trimethoprim after 180 min of electrolysis, while TOC removal remained low, 14 and 16% for 180 and 300 min reaction times, respectively. Overall removal yields of the industrial effluent during the combined process were therefore 80 and 89% for 180 and 300 min of effluent pretreatment followed by 15 days activated sludge culture, respectively

Electrochemical Reduction Prior to Electro-Fenton Oxidation of Azo Dyes : Impact of the Pretreatment on Biodegradability.

International audienceThe aim of this work was to study the degradation of three azo dyes, Orange II, Methyl red and Biebrich Scarlet by electro-Fenton and the effect of the electrochemical pretreatment on the biodegradability of the solutions. The electrochemical pretreatment showed that an electrochemical reduction on the carbon felt electrode was mainly responsible for the decolorization of the azo dyes. Indeed, the electrochemical behaviour of the azo dyes highlighted their electroactivity; electrolysiswith and without ferric ions led to the same decolorization yield, namely 99 % at 15 min for Methyl red, and stable chemical oxygen demand (COD) values were recorded during decolorization. In a second step and owing to the absence of by-product electroactivity in reduction, the formation of hydroxyl radicals by the Fenton reaction led to the oxidation of by-products from the electrochemical reduction. It was illustrated by the decrease recorded for the COD values. The results also showed that the azo bond cleavage occurring during the electrochemical reduction was not sufficient to significantly reduce recalcitrance, as shown from biological oxygen demand (BOD)(5)/COD ratio examination below the limit of biodegradability (0.4). Contrarily, a positive trend was recorded for Orange II during the electro-Fenton reaction, with a BOD5/COD ratio of 0.81 after 28 h of pretreatment

Heterogeneous catalytic ozonation of 2, 4-dinitrophenol in aqueous solution by magnetic carbonaceous nanocomposite: catalytic activity and mechanism

Herein, the catalytic properties of a carbonaceous nanocomposite in the catalytic ozonation process (COP) of 2, 4-dinitrophenol (2, 4-DNP) were investigated and the results were compared with those obtained from single ozonation process (SOP). Magnetic carbonaceous nanocomposite, as a novel catalyst, was applied to optimize the condition for the removal of 2, 4-DNP in the COP, and the influential parameters such as pH, catalyst dosage, addition of radical scavengers, and durability were all evaluated. The results showed that the degradation efficiency of 2, 4-DNP and COD in the COP (98.2, 92) was higher compared to the SOP (75, 61) and the highest catalytic potential was achieved at an optimal pH of 6. The first-order modeling demonstrated that the reactions were dependent on the concentration of the catalyst, with the kinetic constants varying from 0.022 (1/min) in the SOP to 1.377 (1/min) in the COP at the catalyst dosage of 4 g/L and the optimum concentration of catalyst (2 g/L). The addition of radical scavenger noticeably diminished the removal efficiency of 2, 4-DNP in the SOP from 75 down to 54, while the corresponding values for the COP dropped from 98.2 to 93. Furthermore, a negligible reduction in the catalytic properties of the catalyst was observed (~5) after five-time reuse. The results also revealed that the applied method is effectively suitable for the removal of 2, 4-DNP contaminant from industrial wastewaters. © 2015 Balaban Desalination Publications. All rights reserved