Electrochemical oxidation of Basic Blue 3 dye using a diamond anode: evaluation of colour,COD and toxicity removal

BACKGROUND: Textile industries generate considerable amounts of waste‐water, which may contain strong colour, suspended particles, salts, high pH and high chemical oxygen demand (COD) concentration. The disposal of these coloured wastewaters poses a major problem for the industry as well as a threat to the environment. In this study, electrochemical oxidation of Basic Blue 3 (BB3) dye was studied in a bipolar trickle tower (BTT) reactor using Raschig ring shaped boron‐doped diamond (BDD) electrodes in recirculated batch mode. The effects of current density, temperature, flow rate, sodium sulfate concentration (Na₂SO₄) as supporting electrolyte, and initial dye concentration were investigated. RESULTS: The best experimental conditions obtained were as follows: current density 0.875 mA cm^?2, temperature 30 °C, flow rate 109.5 mL min^?1, Na₂SO₄ concentration 0.01 mol L^?1. Under these conditions, 99% colour and 86.7% COD removal were achieved. Toxicity tests were also performed on BB3 solutions under the best experimental conditions. CONCLUSION: Based on these results, the BDD anode was found to be very successful for the simultaneous degradation of BB3 and removal of COD. Additional toxicity test results also showed that electrochemical treatment using a BDD Raschig ring anode in a BTT reactor is an effective way of reducing toxicity as well as removing colour and COD. Copyright © 2010 Society of Chemical Industry     

Conductive‐diamond electrochemical advanced oxidation of naproxen in aqueous solution: optimizing the process

BACKGROUND: Electrochemical advanced oxidation treatment using boron‐doped diamond (BDD) electrodes is a promising technology to treat small amounts of toxic and biorefractory pollutants in water. This process has been tested on the degradation of naproxen, a common pollutant drug present in surface waters. To optimize the process a series of experiments have been designed to study the interaction between four variables: pH (over the range 5–11); current (0–320 mA cm^?2); supporting Na₂SO₄ electrolyte concentration (0–0.375 mol L^?1); and solution flow rate (Q_v) between 3.64 and 10.8 cm³ min^?1. RESULTS: Among these variables the influence of current was the greatest, the second was the salt concentration, the third flow rate, and the fourth pH. An ANOVA test reported significance for seven of the fourteen variables involved and the degradation of naproxen was optimized using response surface methodology. CONCLUSIONS: Optimum conditions for naproxen removal (100%) were found to be pH = 10.70, Q_v = 4.10 cm³ min^?1, current density = 194 mA cm^?2 using a supporting electrolyte concentration of 0.392 mol L^?1. Copyright © 2010 Society of Chemical Industry     

Pre-Treatment of Pistachio Processing Industry Wastewaters (PPIW) by Electrocoagulation using Al Plate Electrode

The objective of the present study is to assess the efficiency of electro-coagulation treatment of pistachio processing industry wastewaters (PPIW) using an aluminum plate electrode. The effect of some of the parameters was examined on the removal of chemical oxygen demand (COD), total organic carbon (TOC), and total phenols (TP) removal efficiency. The treatment was carried out in a batch system. The influences of current density (from 1 to 6 mA cm^?2), initial pH of wastewater (from 2 to 8), constant pH of wastewater (from 3 to 7), stirring speed (from 100 to 500 rpm), and supporting electrolyte concentration (from 10 to 50 mg L^?1 NaCl) on removal efficiency were investigated to determine the best experimental conditions. The evaluation of the physico-chemical parameters during the treatment by electrocoagulation showed that the best removal efficiency was obtained under the conditions of 180 min electrolysis time, wastewater with constant pH of 6, and 6 – mA cm^?2 current density. Under such experimental conditions, COD, TOC, and TP removal efficiency were found to be 60.1%, 50.2%, and 77.3%, respectively, while energy consumption was 39.6 kW-h m^?3. The results of the study show that the electrocoagulation can be applied to PPIW pre-treatment.     

A comparison of electrochemical degradation of phenol on boron doped diamond and lead dioxide anodes

This work compares two electrode materials used to mineralize phenol contained in waste waters. Two disks covered with either boron doped diamond (BDD) or PbO₂ were used as anodes in a one compartment flow cell under the same hydrodynamic conditions. Efficiencies of galvanostatic electrolyses are compared on the basis of measurements of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD). Galvanostatic electrolyses were monitored by analysis of phenol and of its oxidation derivatives to evaluate the operating time needed for complete elimination of toxic aromatics. The experimental current efficiency is close to the theoretical value for the BDD electrode. Other parameters being equal, phenol species disappeared at the same rate using the two electrode materials but the BDD anode showed better efficiency to eliminate TOC and COD. Moreover, during the electrolysis less intermediates are formed with BDD compared to PbO₂ whatever the current density. A comparison of energy consumption is given based on the criterion of 99% removal of aromatic compounds.     

BDD anodic oxidation as tertiary wastewater treatment for the removal of emerging micro‐pollutants,pathogens and organic matter

This work reports for the first time the removal of 17α‐ethynylestradiol (EE2), a synthetic estrogen hormone, from secondary treated effluents by electrochemical oxidation. Experiments were conducted in a single compartment reactor comprising a boron‐doped diamond (BDD) anode and a zirconium cathode. EE2, in the range 100–800 µg L^?1, was spiked in the post‐chlorination effluent of a municipal treatment plant and oxidized at 0.9–2.6 mA cm^?2 current density. Complete degradation of 100 µg L^?1 EE2 was achieved in 7 min at 2.1 mA cm^?2 and inherent conditions, while the addition of 0.1 mol L^?1 NaCl achieved removal in just a few seconds. The process was then tested in the pre‐chlorination effluent at 2.1 mA cm^?2 and inherent conditions; complete E. coli killing and EE2 removal occurred in just 1.5 and 3.5 min, respectively, while overall estrogenicity (assessed by the YES assay) and residual organic matter (in terms of chemical oxygen demand (COD)) decreased by 50% and 85% after 30 min, respectively. These results clearly show the potential of BBD electrochemical oxidation to serve as an efficient tertiary wastewater treatment. Copyright © 2011 Society of Chemical Industry     

Electrochemical oxidation of Crystal Violet in the presence of hydrogen peroxide

BACKGROUND: The combination of electrochemical oxidation using a Ti/RuO₂? IrO₂ anode with hydrogen peroxide has been used for the degradation of Crystal Violet. The effect of major parameters such as initial pH, hydrogen peroxide concentration, current density, electrolyte concentration and hydroxyl radical scavenger on the decolorisation was investigated. RESULTS: The decolorisation rate increased with initial pH and hydrogen peroxide concentration, but decreased with electrolyte and radical scavenger concentration. The decolorisation rate increased with current density, but the increase became insignificant after current density exceeded 47.6 mA cm^?2. On the other hand, hydrogen peroxide decomposition rate increased with initial pH and current density, but decreased with electrolyte and radical scavenger concentration. The amount of hydrogen peroxide decomposed during 30 min reaction increased linearly with hydrogen peroxide dosage. The main intermediates were separated and identified by gas chromatography–mass spectrometry (GC–MS) technique and a plausible degradation pathway of Crystal Violet was proposed. At neutral pH, the electrochemical process in the presence of hydrogen peroxide was more efficient than that in the presence of Fenton's reagent (electro‐Fenton process). CONCLUSION: The anodic oxidation process could decolorise Crystal Violet effectively when hydrogen peroxide was present. Almost complete decolorisation was achieved after 30 min reaction under the conditions 2.43 mmol L^?1 hydrogen peroxide, 47.6 mA cm^?2 current density and pH₀ 7, while 62% COD removal efficiency was obtained when the reaction time was prolonged to 90 min. Copyright © 2010 Society of Chemical Industry     

Treatment of dairy industry wastewater by EC and EF processes using hybrid Fe?Al plate electrodes

BACKGROUND: In this study electrochemical treatment of dairy industry wastewater (DW) was investigated using a combined electrode system consisting of iron and aluminum as sacrificial electrodes. The dairy industry generates strong wastewaters characterized by high biological oxygen demand and chemical oxygen demand concentrations. Dairy industry waste effluents are concentrated in nature, and the main contributors of organic load to these effluents are carbohydrates, proteins and fats originating from the milk. Since dairy waste streams contain high concentrations of organic matter, these effluents may cause serious environmental problems. RESULTS: A pole changer device was employed to change polarization in given time intervals to generate iron and aluminum based coagulants respectively. The effects of current density, initial pH, sodium sulfate (Na₂SO₄) and H₂O₂ concentrations on the removal efficiency were investigated. The best experimental conditions obtained in electrochemical studies were as follows: current density = 15 mA cm^?2, natural pH, without supporting electrolyte addition, H₂O₂ concentration = 3 × 1000 mg L^?1. Under these conditions, 79.2% COD removal from DW was achieved. CONCLUSION: According to the results, 20 min electrolysis is enough, since insignificant variations in COD removal were observed after this time. These methods were found to be successful for the treatment of DW. Copyright © 2011 Society of Chemical Industry     

Electrochemical oxidation of 1,4‐dioxane at boron‐doped diamond electrode

BACKGROUND: The electrochemical oxidation of 1,4‐dioxane at a boron doped diamond (BDD) surface on a niobium substrate anode was studied because (i) 1,4 dioxane is a resistant contaminant in waste‐waters and ground‐waters which needs to be removed/oxidized and (ii) most of the currently applied techniques for removal/oxidation require chemicals. RESULTS: Results show that in the potential region supporting electrolyte stability 1,4‐dioxane can be oxidized directly. Adhesive products, which cause electrode fouling, are also formed during oxidation in this potential region. The BDD anode can be restored to its initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In this region, oxidation reactions leading to complete oxidation of 1,4‐dioxane, can take place due to electro‐generated hydroxyl radicals. Therefore, dioxane can only be effectively oxidized at these potentials. The effect of current density on the oxidation of 1,4‐dioxane has been investigated. The experimental results have also been compared with a theoretical chemical oxygen demand (COD)–instantaneous current efficiency (ICE) model. At a current density above 32 mA cm^?2, the oxidation process is completely controlled by mass transfer and no intermediates are formed. 92% of the COD can be removed with a total consumption of 7 Ah L^?1. CONCLUSIONS: Results show that dioxane can be effectively and completely oxidized at a BDD anode. Copyright © 2010 Society of Chemical Industry     

Veratric acid treatment by anodic oxidation with BDD anode

BACKGROUND: Veratric acid (VA, 3,4‐dimethoxy‐benzoic acid) is representative of the polyphenolic type compounds present in olive mill wastewater (OMW). Given the bactericide factor, the inhibitor character and the anti bacteriological activity of this compound, traditional biological digestion cannot be applied and therefore new technologies, such as electrochemical oxidation using a boron‐doped diamond (BDD) anode have to be considered to avoid its accumulation in the environment. RESULTS: The electrochemical oxidation of aqueous solutions containing 1 mmol L^?1 VA has been investigated using a filter‐press reactor with a BDD anode during galvanostatic electrolysis. The influence of several operating parameters, such as applied current density, temperature, flow‐rate and supporting electrolyte concentration and type has been investigated. The experimental results showed that under the experimental conditions used the oxidation of VA was under mass‐transfer control and VA was completely degraded by the reaction with hydroxyl radicals electrogenerated at the BDD surface. The chemical oxygen demand (COD) decay kinetic followed a pseudo‐first‐order reaction and the apparent rate constant increased with flow rate and temperature. Under optimal experimental conditions of flow‐rate (300 L h^?1), temperature (35 °C) and current density (10 mA cm^?2), 99.5% of COD was removed during 2 h electrolysis, with 16.4 kWh m^?3 energy consumption. CONCLUSIONS: This study suggests that anodic oxidation with a BDD electrode is an excellent method for the treatment of effluents contaminated with VA and related polyphenols. Copyright © 2011 Society of Chemical Industry     

Comparative Study of Electrocoagulation and Electrooxidation Processes for the Degradation of Ellagic Acid From Aqueous Solution

A comparative study of electrocoagulation and electrooxidation processes for the degradation of ellagic acid from aqueous solution was carried out. For the electrocoagulation process, metallic iron was used as electrodes whereas graphite and RuO₂/IrO₂/TaO₂ coated titanium electrodes were used for the electrooxidation processes. The effect of the process variables such as initial pH, concentration of the supporting electrolyte, applied current density, electrolysis time, and anode materials on COD removal were systematically examined and discussed. Maximum COD removal of 93% was obtained at optimum conditions by electrocoagultion using an iron electrode. The ellagic acid was degraded completely by electrooxidation using graphite electrodes under the optimum conditions. During electrooxidation, the chloride ion concentration was estimated and the effect of the Cl^? ion was discussed. The finding of this study shows that an increase in the applied current density, NaCl concentration, and electrolysis time enhanced the COD removal efficiency. The UV–Vis spectra analysis confirms the degradation of ellagic acid from aqueous solution.     

Treatment of Endocrine Disrupting Chemical From Aqueous Solution by Electrocoagulation

The removal of endocrine disrupting chemical (BPA; Bisphenol–A) from aqueous solution was experimentally investigated by electrocoagulation process. The effects of different combinations of aluminum (Al) and iron (Fe) electrode pair, supporting electrolyte type, supporting electrolyte concentration, initial pH and applied current density and initial BPA concentration on the Chemical Oxygen Demand (COD), and energy consumption performances were critically evaluated. The experiment results indicate that Al–Al electrode pair is the most efficient choice of the four electrode pairs. The COD removal efficiency was increased when NaCl was used as the supporting electrolyte instead of Na₂SO₄ and NaNO_3. The optimum supporting electrolyte type and its concentration, initial pH, applied current density and treatment time were found to be NaCl, 0.05 M, pH 7.0, 12 mA cm^?2 and 40 min, respectively. Energy consumption was found to decrease with increase of NaCl concentration while it increases with increasing applied current density. The initial and treated sample was characterized by UV–vis spectroscopy to confirm the treatment efficiency. The sludge formed during electrocoagulation was characterized by XRD and SEM/EDAX analysis.     

Hypochlorite production on Ru-Sn binary oxide electrode and its application in treatment of dye wastewater

Ruthenium-tin binary oxides [(Ru+Sn)O₂] were coated on titanium substrates by thermal decomposition. The surface morphologies and elemental analyses of these electrodes were examined by means of scanning electron microscopy. The electrochemical behaviours were characterized by cyclic voltammetry and linear-scan voltammetry (LSV) methods. The effects of electrolysis condition for the current efficiency (CE) of hypochlorite production on binary (Ru+Sn)O₂ electrodes and the treatment of a high salt-containing dye wastewater using this hypochlorite were also investigated. The highest CE for hypochlorite production exists on an RS3 (40 to 80 mol% Sn in coating solution) electrode. The major factors influencing CE for hypochlorite production are the electrolyte flow rate, current density, and chloride (Cl-) concentration. Major factors affecting energy yield are current density, Cl- concentration, and electrode distance. For low current density (300 mA.cm^?2), high Cl- concentration (1 mol.L^?1), and 0.45 cm electrode separation, a high specific energy is obtained. The RS3 electrode exhibits the best removal of organics and chromophor groups in the dye wastewater. On this electrode, better removal of organics and chromophor groups is obtained at 300 mA.cm^?2. The colour of black-red dye wastewater becomes light yellow when a charge of 792 A·min was passed, while the chemical oxygen demand (COD) of this wastewater is decreased from 10500 mg.L^?1 to 1250 mg.L^?1.     

Electrochemical oxidation of an acid dye by active chlorine generated using Ti/Sn<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Ir<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> electrodes

The generation of active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes, with different compositions of Ir (x = 0.01, 0.05, 0.10 and 0.30 ), was investigated by controlled current density electrolysis. Using a low concentration of chloride ions (0.05 mol L⁻¹) and a low current density (5 mA cm⁻²) it was possible to produce up to 60 mg L⁻¹ of active chlorine on a Ti/Sn_0.99Ir_0.01O₂ anode. The feasibility of the discoloration of a textile acid azo dye, acid red 29 dye (C.I. 16570), was also investigated with in situ electrogenerated active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes. The best conditions for 100% discoloration and maximum degradation (70% TOC reduction) were found to be: NaCl pH 4, 25 mA cm⁻² and 6 h of electrolysis. It is suggested that active chlorine generation and/or powerful oxidants such as chlorine radicals and hydroxyl radicals are responsible for promoting faster dye degradation. Rate constants calculated from color decay versus time reveal a zero order reaction at dye concentrations up to 1.0 × 10⁻⁴ mol L⁻¹. Effects of other electrolytes, dye concentration and applied density currents also have been investigated and are discussed.     

Batch treatment of saline wastewater by Halanaerobium lacusrosei in an anaerobic packed bed reactor

BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Halanaerobium lacusrosei . RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD₀ = 1880–9570 mg L^?1), salt concentration ([NaCl] = 30–100 g L^?1) and liquid upflow velocity (V_up = 1.0–8.5 m h^?1) on COD removal from salt (NaCl)‐containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD₀ = 1880 mg L^?1, and efficiency decreased to 43% on increasing COD₀ to 9570 mg L^?1 at 20 g L^?1 salt concentration. COD removal was in the range 50–60% for [NaCl] = 30–60 g L^?1 at COD₀ = 5200 ± .100 mg L^?1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L^?1. Increasing liquid upflow velocity from V_up = 1.0 m h^?1 to 8.5 m h^?1 provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L^?1 to 321 mg L^?1 at V_up = 8.5 m h^?1, resulting in over 92% COD removal at 30 g L^?1 salt‐containing synthetic wastewater. CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. Copyright © 2008 Society of Chemical Industry     

Arsenic removal from drinking water by electrocoagulation using iron electrodes

Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm^?2), initial arsenic concentration (50–500 μg L^?1), operating time (0–15 min), electrode surface area (266–665 cm²), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L^?1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm^?2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm² taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L^?1 for electrode surface area of 266 cm². The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.     

Electrochemical incineration of chloranilic acid using Ti/IrO2, Pb/PbO2 and Si/BDD electrodes

The electrochemical oxidation of chloranilic acid (CAA) has been studied in acidic media at Pb/PbO₂, boron-doped diamond (Si/BDD) and Ti/IrO₂ electrodes by bulk electrolysis experiments under galvanostatic control. The obtained results have clearly shown that the electrode material is an important parameter for the optimization of such processes, deciding of their mechanism and of the oxidation products. It has been observed that the oxidation of CAA generates several intermediates eventually leading to its complete mineralization. Different current efficiencies were obtained at Pb/PbO₂ and BDD, depending on the applied current density in the range from 6.3 to 50 mA cm⁻². Also the effect of the temperature on Pb/PbO₂ and BDD electrodes was studied.UV spectrometric measurements were carried out at all anodic materials, with applied current density of 25 and 50 mA cm⁻². These results showed a faster CAA elimination at the BDD electrode. Finally, a mechanism for the electrochemical oxidation of CAA has been proposed according to the results obtained with the HPLC technique.     

DSA electrochemical treatment of olive mill wastewater on Ti/RuO<Subscript>2</Subscript> anode

The electrochemical oxidation of olive mill wastewater (OMW) over a Ti/RuO₂ anode was studied by means of cyclic voltammetry and bulk electrolysis and compared with previous results over a Ti/IrO₂ anode. Experiments were conducted at 300–1,220 mg L⁻¹ initial chemical oxygen demand (COD) concentrations, 0.05–1.35 V versus SHE and 1.39–1.48 V versus SHE potential windows, 15–50 mA cm⁻² current densities, 0–20 mM NaCl, Na₂SO₄, or FeCl₃ concentrations, 80 °C temperature, and acidic conditions. Partial and total oxidation reactions occur with the overall rate being near first-order kinetics with respect to COD. Oxidation at 28 Ah L⁻¹ and 50 mA cm⁻² leads to quite high color and phenols removal (86 and 84%, respectively), elimination of ecotoxicity, and a satisfactory COD and total organic carbon reduction (52 and 38%, respectively). Similar performance can be achieved at the same charge (28 Ah L⁻¹) using lower current densities (15 mA cm⁻²) but in the presence of various salts. For example, COD removal is less than 7% at 28 Ah L⁻¹ in a salt-free sample, while addition of 20 mM NaCl results in 54% COD reduction. Decolorization of OMW using Ti/RuO₂ anode seems to be independent of the presence of salts in contrast with Ti/IrO₂ where addition of NaCl has a beneficial effect on decolorization.     

Electrochemical oxidation of 1,3,5-trimethoxybenzene in aqueous solutions at gold oxide and lead dioxide electrodes

A kinetic study of the electrochemical oxidation of 1,3,5-trimethoxybenzene (TMB) by direct electron transfer at treated gold disk was combined with results of electrolysis in order to produce total degradation into CO₂ and H₂O at Ta/PbO₂ anode. The oxidation of TMB at gold electrode was studied by cyclic voltammetry. The cyclic voltammogram shows one irreversible anodic peak (I) corresponding to the oxidation of adsorbed TMB molecules. The proposed mechanism is based on the hypothesis of two-electron oxidation of TMB molecule leading, via intermediate of a radical cation, to the formation of the 2,4,6-trimethoxyphenol (TMP) and an adsorbed polymeric film. The TMP molecule undergoes a rapid oxidation leading to the formation of 2,6-dimethoxy-p-benzoquinone (DMBQ) as a major product. Degradation of TMB was studied by galvanostatic electrolysis using Ta/PbO₂ anode. The influence of initial TMB concentration and applied current density was investigated. Measurement of total organic carbon (TOC) and analysis by HPLC were used to follow this degradation. The experimental data indicated that the removal of TMB follows a pseudo first-order kinetic. The efficiency of the electrochemical process increases at lower current density and higher TMB initial concentration while it decreases with the TOC removal progress.     

Treatment of high‐fat‐containing dairy wastewater in a sequential UASBR system: influence of recycle

BACKGROUND: Raw cheese whey originating from white cheese production results in a strong and complex wastewater excessively rich in organic matter (chemical oxygen demand, COD = 28–65 g L^?1), fatty matter (14–24.5 g L^?1) and acidity (3.9–6.1 g L^?1). It was treated in a three‐stage configuration consisting of a pre‐acidification (PA) tank and sequential upflow anaerobic sludge bed reactors (UASBRs) at 2.8–7 g COD L^?1 day^?1 organic loading rates, during which the effects of effluent recycling at low rates and promoted SRB activity were investigated. Acidification, volatile fatty acids (VFA), COD and fatty matter removal and volatile solids were monitored throughout the system during the study. RESULTS: Recycling of the effluent promoted VFA and COD removal as well as pH stability in both stages of the UASBRs and the effluent where high alkalinity levels were recovered reducing alkali requirement to 0.05 g OH g^?1 COD_applied. Higher removal rates of 71–100 and 50–92% for VFA and COD were obtained by use of recycling. Fatty matter was removed at 63–89% throughout the study. Volatile solids build‐up was significant in the inlet zones of the UASBRs. CONCLUSIONS: The system produced efficient acidification in the PA tank, balanced pH levels and an effluent high in alkalinity and BOD/COD ratio. Efficient VFA removal and solids immobilization was obtained in both stages up to the highest loading rate. Recycling improved the system performance under high fatty matter loading conditions. A major advantage of the sequential system was that the second stage UASBR compensated for reduced performance in the first stage. Copyright © 2010 Society of Chemical Industry     

Decolorisation of aqueous reactive dye Remazol Red 3B by electrocoagulation

The present study demonstrated the applicability of the electrocoagulation method for the removal of reactive dye, Remazol Red 3B, in a batch study. Iron electrode material was used as a sacrificial electrode in monopolar parallel mode in this study. The effects of the initial pH, current density, conductivity, initial concentration of dye and electrolysis time on the removal of Remazol Red 3B were investigated to determine optimum operating conditions. High decolorisation efficiency (>99%) for Remazol Red 3B dye solution was obtained with optimal value of process parameters, such as 15 mA cm^?2 of current density, 10 min of electrolysis time, pH 6 and 500 mg l^?1 dye concentration. The energy consumption, electrode consumption and operating costs under optimum operating conditions were calculated as 3.3 kW h kg dye^?1, 1.2 kg Fe kg dye^?1 and 0.6 € m^?3, respectively.