Electrocoagulation for the treatment of textile wastewaters with Al or Fe electrodes: compared variations of COD levels, turbidity and absorbance

Innovative spiral electrode configuration for enhancement of electrocoagulation-flotation

The performance of electrocoagulation-flotation (ECF) process can profoundly be affected by the reactor design and electrode configuration. These may, in turn, influence the removal efficiency, flow hydrodynamic, floc formation, and flotation/settling characteristics. The present work aimed at developing a new spiral electrode configuration to enhance the ECF process. To do so, the impacts of parameters such as energy consumption, removal efficiency of the contaminants from industrial wastewater with a composition of turbidity, emulsified oil, and heavy metals (Si, Zn, Pb, Ni, Cu, Cr, and Cd), as well as stirring speed and foaming have been investigated. Comparison was also made between the experimental results of the new electrode configuration with the conventional rectangular cell with plate electrode configuration with the same volume and electrode surface area. The findings revealed that energy consumption of the spiral electrode configuration within the operating times of 10, 20, 30, 32, 48, and 70 min, was approximately 20% lower compared to that of the conventional ECF. Moreover, the maximum and minimum removal efficiency of 97% and 60% were obtained for turbidity and TOC for the stirring speed of 500 rpm and Reynolds number of 10,035, respectively. Finally, the formed gas bubbles tilted toward the center due to the enhanced flow hydrodynamic which resulted in substantial reduction of foam formation.

Electrocoagulation pre-treatment to simultaneously remove dissolved and colloidal substances and Ca2+ in old corrugated container wastewater

An effective electrocoagulation pre-treatment (ECP) method was proposed to simultaneously solve the problems of the micro stickies deposition and high Ca²⁺ content in old corrugated container (OCC) papermaking wastewater during the recycling process. The optimal ECP condition was investigated. The results indicated that the effect of an Al electrode on wastewater treatment was superior to that of a Fe or Mg electrode. The optimal treatment conditions of the current density, electrode distance and reaction time were 115 A m^-2, 5 cm and 60 min, respectively. After the ECP, the chemical oxygen demand (COD) and Ca²⁺ removal rates were 75.33% and 64.53%, respectively, and the turbidity and dissolved and colloidal substance (DCS) content decreased by 97.1% and 43.68%, respectively. The particle size of flocs in the liquid increased from 1.675 μm to 31.97 μm, and the floc content was 0.78 g L^-1 after ECP. The anode material and energy consumption were 0.1846 kg m^-3 and 4.56 kWh m^-3, respectively, and the cost of treatment was estimated to be 1.11 $ m^-3. The results demonstrate that ECP can effectively remove the micro stickies, COD, and Ca²⁺ in the OCC wastewater, which is conducive to reducing the cost of wastewater treatment and conform to the requirements of sustainable development.

Optimization of Electrocoagulation Conditions for the Purification of Table Olive Debittering Wastewater Using Response Surface Methodology

In the present study, the optimization of electrocoagulation (EC) conditions for the purification of olive debittering wastewater (ODW) was investigated by response surface methodology (RSM). For this purpose, a central composite design (CCD) was employed to optimize the process variables including current density (3.0–30.0 mA/cm2) and EC time (10.0–60.0 min). The results showed a significant effect of current density and EC time on the removal efficiency of total phenolic compounds (TPC) and chemical oxygen demand (COD). The best models obtained using the central composite design were quadratic polynomial for TPC (R2 = 0.993), COD (R2 = 0.982), and the inverse square root of turbidity (R2 = 0.926). Additionally, the square root of electrode consumption and energy consumption were appropriately fitted to the two-factor interaction (2FI) model (R2 = 0.977) and quadratic polynomial (R2 = 0.966) model, respectively. The predicted optimum conditions based on the highest removal efficiency for TPC were a current density of 21.1 mA cm−2 and an EC time of 58.9 min, in which the obtained model predicted 82.6% removal for TPC. This prediction was in agreement with the laboratory result (83.5%). The amount of energy consumption and the operating cost in these conditions was estimated to be 14.92 kWh and USD 6.49 m−3 per ODW, respectively.

Spectral deconvolution associated to the Gaussian fit as a tool for the optimization of photovoltaic electrocoagulation applied in the treatment of textile dyes

The objective of this study was to investigate the color removal in a binary mixture of azo dyes from the photovoltaic electrocoagulation (EC) technique, using spectral deconvolution and the Gaussian fit for qualitative and quantitative determination of the physical color parameter. Initially, a conventional energy source was used to feed the EC reactor and the experimental design was conducted according to the Rotational Central Compound Design (RCCD). The spectral deconvolution method associated to the Gaussian fit aided in the description of the composition of the sample matrix, In the first step, through the Analysis of Variance, the RCCD and the three-dimensional surface response graphs, the optimized operating conditions were identified, which corresponded to 1320 A m^-2 with an reaction time of 16.6 min, and an expected removal of 98.40% for Scarlet Red (SR) dye and 1160 A m^-2 with a run time of 15.7 min and 97.9% removal for Turquoise Blue (TB) dye. Using the photovoltaic module as the power source of the EC reactor, a maximum removal of 97 ± 0.43% for TB dye and 98% ± 0.81 for SR was obtained. The results encourage the applicability of photovoltaic module-fed EC technology as a promising alternative for the treatment of effluents containing textile dyes, as well as the use of the spectral deconvolution method associated with the Gaussian fit, for the reliability and precision of the results.

Electrocoagulation: A Promising Method to Treat and Reuse Mineral Processing Wastewater with High COD

Mineral processing wastewater contains large amounts of reagents which can lead to severe environmental problems, such as high chemical oxygen demand (COD). Inspired by the wastewater treatment in such industries as those of textiles, food, and petrochemistry, in the present work, electrocoagulation (EC) is applied for the first time to explore its feasibility in the treatment of wastewater with an initial COD of 424.29 mg/L from a Pb/Zn sulfide mineral flotation plant and its effect on water reuse. Typical parameters, such as anode materials, current density, initial pH, and additives, were characterized to evaluate the performance of the EC method. The results showed that, under optimal conditions, i.e., iron anode, pH 7.1, electrolysis time 70 min, 19.23 mA/cm2 current density, and 4.1 g/L activated carbon, the initial COD can be reduced to 72.9 mg/L, corresponding to a removal rate of 82.8%. In addition, compared with the untreated wastewater, EC-treated wastewater was found to benefit the recovery of galena and sphalerite, with galena recovery increasing from 25.01% to 36.06% and sphalerite recovery increasing from 59.99% to 65.33%. This study confirmed that EC is a promising method for the treatment and reuse of high-COD-containing wastewater in the mining industry, and it possesses great potential for wide industrial applications.

Post-treatment of paint industry effluents by filtration using Andropogon biochar (Andropogon gayanus Kunth cv. Planaltina)

This study evaluates the filtration potential of the biomass obtained from Andropogon grass (Andropogon gayanus Kunth cv. Planaltina) that was converted to biochar by pyrolysis. The biochar is used in filtration systems for the post-treatment of paint industry effluents. The biomass is characterized by elemental analysis (CHSN-O), determination of specific compounds (cellulose/hemicellulose/lignin), FTIR, and SEM. The produced biochar is characterized by SEM, TGA, and surface area analysis. The efficiency of the filters is evaluated by the following parameters: color, turbidity, removal of total solids (suspended and sedimentable), chemical oxygen demand (COD), and metals (Al, Cu, Zn, Co, Cd, and Cr(VI)). Over 99% removal of aluminum, cadmium, and hexavalent chromium is achieved. Moreover, almost 100% of COD and solids are removed, whereas turbidity and color are reduced by over 90%.

Treatment of olive processing wastewater by electrocoagulation: An effectiveness and economic assessment

In the present study, the technique of electrocoagulation (EC) followed by filtration was explored at the laboratory scale for the removal of organic compounds from olive debittering wastewater (ODW). Different parameters such as electrode type and distance as well as sample pH, current density, and electrolysis time were investigated in batch experiments with identical electrode geometries. Our results showed that highest pollutant removal efficiency and lowest operational cost were achieved using two Al electrodes at a distance of 1 cm apart with a sample pH of 4.0. Moreover, rises in the electrolysis time and current density (up to 60 min and 15 mA cm^-2, respectively) led to improvements in the removal of chemical oxygen demand (COD), total polyphenolic compounds (TPC), and turbidity. Under optimized conditions, the removal of COD, TPC and turbidity reached 78.51, 90.44 and 97.92%, respectively; the values of 1.01 g m^-3, 12.0 kWh cm^-3 and 0.12 USD m^-3 were calculated as the electrode consumption, electrical energy consumption and operating cost, respectively. Chromatography results revealed tyrosol and catechin as the main phenolic compounds present in both the initial effluent and the generated sludge.

FTIR, CHNS and XRD analyses define mechanism of glyphosate herbicide removal by electrocoagulation

In this study, the performance of glyphosate removal in an electrocoagulation batch with two electrodes formed by the same metal type, consisting of aluminum, iron, steel and copper have been compared. The aim of this study intends to remove glyphosate from an aqueous solution by an electrocoagulation process using metal electrode plates, which involves electrogeneration of metal cations as coagulant agents. The production of metal cations showed an ability to bind together to form aggregates of flocs composed of a combination of glyphosate and metal oxide. Electrocoagulation using aluminum electrodes indicated a high percentage removal of glyphosate, 94.25%; followed by iron electrodes, 88.37%; steel electrodes, 62.82%; and copper electrodes, 46.69%. The treated aqueous solution was then analyzed by Fourier Transform Infrared Spectroscopy. Percentages of Carbon, Hydrogen, Nitrogen, Sulfur remaining in the treated aqueous solution after the electrocoagulation process have been determined. The treated water and sludge were characterized and the mechanism of the overall process was concluded as an outcome. An X-Ray Diffraction analysis of dried sludge confirmed that new polymeric compounds were formed during the treatment. The sludge composed of new compounds were also verified the removals. This study revealed that an electrocoagulation process using metal electrodes is reliable and efficient.

Treatment and characterization of phosphorus from synthetic wastewater using aluminum plate electrodes in the electrocoagulation process

The main objective of this study is treatment and characterization of phosphorus from synthetic wastewater using aluminum electrodes in the electrocoagulation process. EC experimental setups were designed and different parameters were optimized. The maximum amounts of phosphorus removal efficiencies were observed at pH 7. The phosphorus removal efficiency increases from 85.16 to 97.65% as the temperature increases from 15 to 45 °C, beyond this temperature, there is small effect on removal efficiency. Pollutant removal efficiency increases with an increase in the electrolysis time. At lower initial concentrations the removal efficiencies reached to their maximum values while at the highest initial concentration, the phosphorus removal efficiency was decreased. The increase of current density improves the efficiency of phosphorus removal. Energy and aluminum consumption decreases with increasing initial concentration of phosphorus. Field Emission Scanning Electron Microscope (FESEM) image analysis demonstrated very fine structures for aluminum hydroxide/oxyhydroxides and aluminum phosphate. The existence of the different elemental composition in the sludge was proved by the help of Energy Dispersive X-ray Analysis (EDXS), indicating that the aluminum, oxygen and phosphorus were present in the product. From X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Raman analyses of the sludge product, it is concluded that the chemical speciation of the by-products can be mostly aluminum hydroxide and aluminum phosphate.

Pollutant Removal from Wastewater at Different Stages of the Tanning Process by Electrocoagulation

The removal of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and chromium content from tannery wastewater at different stages of the process was experimentally investigated using electrocoagulation (EC) with iron and aluminium electrodes. In the EC of the beamhouse wastewater (S1), the effects of initial pH and current density were analyzed and electrical energy consumption was determined. The COD and TOC in the solution were effectively removed, with an initial pH 7.0, using either metallic electrode. With a current density of 28 mA/cm2 for an electrolysis procedure of 60 minutes, the removal efficiency of COD and TOC was 72% and 57% with aluminium electrodes and 69% and 60% with iron electrodes, respectively. The minimum energy consumption for the highest COD and TOC removal was 0.37 and 0.69 kWh/m3 when employing iron or aluminium electrodes, respectively. At the optimal conditions, removal efficiencies close to 100% for turbidity and chromium content for wastewaters S1-beamhouse, S2-tanning, S3-retanning, and S4-a mixture 1 : 1 : 1 (v/v/v) were achieved. Results show that a pseudosecond-order rate equation provides a good correlation for the removal rate of the parameters. Finally, the results indicate that for tannery wastewater, the EC process does not depend noticeably on the electrode material, but that the stage of the tanning process of wastewater sample has the principal effect on treatment efficiency.

Heavy metal bioaccumulation by Miscanthus sacchariflorus and its potential for removing metals from the Dongting Lake wetlands, China

Bioaccumulation of five heavy metals (Cd, Cu, Mn, Pb, and Zn) in six plant organs (panicle, leaf, stem, root, rhizome, and bud) of the emergent and perennial plant species, Miscanthus sacchariflorus, were investigated to estimate the plant's potential for accumulating heavy metals in the wetlands of Dongting Lake. We found the highest Cd concentrations in the panicles and leaves; while the highest Cu and Mn were observed in the roots, the highest Pb in the panicles, and the highest Zn in the panicles and buds. In contrast, the lowest Cd concentrations were detected in the stem, roots, and buds; the lowest Cu concentrations in the leaves and stems; the lowest Mn concentrations in the panicles, rhizomes, and buds; the lowest Pb concentrations in the stems; and the lowest Zn concentrations in the leaves, stems, and rhizomes. Mean Cu concentration in the plant showed a positive regression coefficient with plot elevation, soil organic matter content, and soil Cu concentration, whereas it showed a negative regression coefficient with soil moisture and electrolyte leakage. Mean Mn concentration showed positive and negative regression coefficients with soil organic matter and soil moisture, respectively. Mean Pb concentration exhibited positive regression coefficient with plot elevation and soil total P concentration, and Zn concentration showed a positive regression coefficient with soil available P and total P concentrations. However, there was no significant regression coefficient between mean Cd concentration in the plant and the investigated environmental parameters. Stems and roots were the main organs involved in heavy metal accumulation from the environment. The mean quantities of heavy metals accumulated in the plant tissues were 2.2 mg Cd, 86.7 mg Cu, 290.3 mg Mn, 15.9 mg Pb, and 307 mg Zn per square meter. In the Dongting Lake wetlands, 0.7 × 10³ kg Cd, 22.9 × 10³ kg Cu, 77.5 × 10³ kg Mn, 3.1 × 10³ kg Pb, and 95.9 × 10³ kg Zn per year were accumulated by aboveground organs and removed from the lake through harvesting for paper manufacture.

A review on the sustainability of textile industries wastewater with and without treatment methodologies

The textile industry in India plays a vital role in the economic growth of the nation. The growth of the textile industry not only impacts the economy of a country but also influences the global economy and mutual exchange of technology between the countries. However, the textile industry also generates an enormous quantity of waste as waste sludge, fibers and chemically polluted waters. The chemically polluted textile wastewater degrades the quality of the soil and water when it mixes with these natural resources and its dependent habitats and environment. Owing to the existing problem of solid and liquid waste, textile industries are facing major problems in environment pollution. Therefore, researchers and the textile industries are focusing on the reduction of textile wastewater and the formulation of alternative efficient treatment techniques without hampering the environment. Hence, the present literature survey mainly concentrates on the various wastewater treatment techniques and their advantages. Moreover, the focus of the study was to describe the methods for the reduction of environmental waste and effective utilization of recycled water with zero wastewater management techniques. The alternative methods for the reduction of textile waste are also covered in this investigation. Finally, this paper also suggests utilization of solid wastes after treatment of wastewater in other sectors like construction for the preparation of low-grade tiles and or bricks by replacing the cement normally used in their manufacturing.

Modeling adsorption kinetic of crystal violet removal by electrocoagulation technique using bipolar iron electrodes

This paper studies the removal of crystal violet (CV) dye by electrocoagulation (EC) process using bipolar iron electrodes. Numerous operating parameters such as initial CV solution concentration, speed of agitation, number of electrodes, type and quantity of supporting electrolyte, temperature- and initial pH were investigated. A complete removal of 10 mg/L CV was achieved within 10 min at pH 7, 0.5 g NaCl, 1 LCV, 750 rpm, 9 sheets, 17.36 mAcm², and 25 °C. The performed energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses confirmed the adsorption of CV onto the insoluble iron hydroxide flocs. Amongst the studied adsorption isotherms models, Langmuir and Dubinin-Radushkevich were the most applicable. The kinetic of adsorption of CV onto flocs during the EC operation was studied using the pseudo-first-order, pseudo-second-order, and intraparticulate diffusion models, with results affirming that the adsorption process proceeded according to the pseudo-second-order model. The study of thermodynamic parameters (ΔG⁰, ΔH⁰, and ΔS⁰,) of the CV removal at different temperatures reflected the feasibility of the spontaneous randomness of endothermic adsorption, especially at lower temperatures. The multiple regression equation of the removal of CV by EC technique under the different studied conditions was predicted.

Treatment of paint manufacturing wastewater by coagulation/electrochemical methods: Proposals for disposal and/or reuse of treated water

This paper describes and discusses an investigation into the treatment of paint manufacturing wastewater (water-based acrylic texture) by coagulation (aluminum sulfate) coupled to electrochemical methods (BDD electrode). Two proposals are put forward, based on the results. The first proposal considers the feasibility of reusing wastewater treated by the methods separately and in combination, while the second examines the possibility of its disposal into water bodies. To this end, parameters such as toxicity, turbidity, color, organic load, dissolved aluminum, alkalinity, hardness and odor are evaluated. In addition, the proposal for water reuse is strengthened by the quality of the water-based paints produced using the wastewater treated by the two methods (combined and separate), which was evaluated based on the typical parameters for the quality control of these products. Under optimized conditions, the use of the chemical coagulation (12 mL/L of Al2(SO4)3 dosage) treatment, alone, proved the feasibility of reusing the treated wastewater in the paint manufacturing process. However, the use of the electrochemical method (i = 10 mA/cm(2) and t = 90 min) was required to render the treated wastewater suitable for discharge into water bodies.

Purification and detoxification of petroleum refinery wastewater by electrocoagulation process

The treatment of synthetic oily wastewater having the characteristics of a typical petroleum refinery wastewater (PRW) by electrocoagulation (EC) using iron and aluminum electrodes was conducted in an electrolytic reactor equipped with fluid recirculation. During the treatment, the emulsion stability was followed by the measurement of Zeta potential and particle sizes. Effects of some operating conditions such as electrodes material, current density and electrolysis time on removal efficiencies of turbidity, and chemical oxygen demand (COD) were investigated in detail. The PRW purification by the EC process was found to be the most effective using aluminum as the anode and cathode, current density of 60 A/m(2) and 30 min of electrolysis time. Under these conditions, the process efficiencies were 83.52% and 99.94%, respectively, for COD and turbidity removals which correspond to final values of 96 mg O2/L and 0.5 NTU. A moderate energy consumption (0.341 kWh) was needed to treat 1 m(3) of PRW. Besides, the ecotoxicity test proved that toxic substances presented in the PRW, and those inhibiting the germination growth of whet, were eliminated by the EC technique.

Optimization of a combined electrocoagulation-electroflotation reactor

This work studies the efficiency of an electroflotation process for the separation of the solids produced during the electrocoagulation treatment of three different types of wastewater: kaolin suspension, coloured organic solution and oil-in-water emulsion. Additionally, a combined electrocoagulation-electroflotation reactor is designed and optimized taking into account the effect of current density, residence time, pollutant concentration and the ratio floated/settled solids. To do this, an experimental design with response surface methodology (RSM) has been used. Results show that electroflotation is a good alternative to the removal of oil microdrops and dyes, but it is not recommended for the separation of solids formed during electrocoagulation of colloid suspensions due to its high density. It has been found that the use of aluminium leads to better results than the use of iron in the treatment of oil-in-water emulsions and coloured solutions. In these cases, the use of a combined electrocoagulation-electroflotation reactor is recommended and the effect of the main inputs has been studied.

Optimization of electrocoagulation (EC) process for the purification of a real industrial wastewater from toxic metals

In the present work, the efficiency evaluation of electrocoagulation (EC) in removing toxic metals from a real industrial wastewater, collected from Aspropyrgos, Athens, Greece was investigated. Manganese (Mn), copper (Cu) and zinc (Zn) at respective concentrations of 5 mg/L, 5 mg/L and 10 mg/L were present in the wastewater (pH=6), originated from the wastes produced by EBO-PYRKAL munitions industry and Hellenic Petroleum Elefsis Refineries. The effect of operational parameters such as electrode combination and distance, applied current, initial pH and initial metal concentration, was studied. The results indicated that Cu and Zn were totally removed in all experiments, while Mn exhibited equally high removal percentages (approximately 90%). Decreasing the initial pH and increasing the distance between electrodes, resulted in a negative effect on the efficiency and energy consumption of the process. On the other hand, increasing the applied current, favored metal removal but resulted in a power consumption increase. Different initial concentrations did not affect metal removal efficiency. The optimal results, regarding both cost and EC efficiency, were obtained with a combination of iron electrodes, at 2 cm distance, at initial current of 0.1 A and pH=6. After 90 min of treatment, maximum removal percentages obtained were 89% for Mn, 100% for Cu and 100% for Zn, at an energy consumption of 2.55 kWh/m(3).

Biodegradability and toxicity assessment of a real textile wastewater effluent treated by an optimized electrocoagulation process

In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 3(3) experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9 A m(-2)) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn-Wellens test (Dt), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC50) were used. According to the Dt, the DOC/LMCA ratio and LC50, an electrolysis time of 15 min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.

Effect of bipolar electrode material on the reclamation of urban wastewater by an integrated electrodisinfection/electrocoagulation process

This work presents an integrated electrodisinfection/electrocoagulation (ED-EC) process for urban wastewater reuse that employs iron bipolar electrodes. Boron doped diamond (BDD) was used as the anode and stainless steel (SS) as the cathode. A perforated iron plate was introduced between the anode and cathode to function as a bipolar electrode. This ED-EC combined cell makes it possible to conduct the simultaneous removal of microbiological content and elimination of turbidity from urban wastewater. The results show that current densities greater than or equal to 6.70 A m(-2) enable complete disinfection of the effluent and the removal of more than 90% of its initial turbidity. Hypochlorite and chloramines formed during the ED-EC process were found to be the main compounds responsible for the disinfection process. Furthermore, a cell configuration of cathode (inlet)-anode (outlet) improves the process performance by enhancing turbidity removal. Finally, the influence of the bipolar electrode material (iron or aluminium) was assessed. The results indicate that the efficiency of the electrodisinfection process depends mainly on the anodic material and is not influenced by the material of the bipolar electrode. In contrast, the removal of turbidity is more efficient when using iron as a bipolar electrode, especially at low current densities, due to the formation of a passive layer on the aluminium that hinders the dissolution of the bipolar electrode.

Treatment of wastewater by electrocoagulation: a review

The electrocoagulation (EC) process is an electrochemical means of introducing coagulants and removing suspended solids, colloidal material, and metals, as well as other dissolved solids from water and wastewaters. The EC process has been successfully employed in removing pollutants, pesticides, and radionuclides. This process also removes harmful microorganisms. More often during EC operation, direct current is applied and electrode plates are sacrificed (dissolved into solution). The dissolution causes an increased metal concentration in the solution that finally precipitates as oxide precipitates. Due to improved process design and material of construction, the EC process is being widely accepted over other physicochemical processes. Presently, this process has gained attention due to its ability to treat large volume and for its low cost. The aim of this study is to review the mechanism, affecting factors, process, and application of the electrocoagulation process.

Electrocoagulation in a packed bed reactor-complete treatment of color and cod from real textile wastewater

This paper deals with the efficiency of electrocoagulation (EC) for the abatement of COD and absorbance (i.e. color) from real textile wastewater using a packed bed electrochemical reactor in a unique design, not previously encountered in the literature for the treatment of textile wastewater by electrocoagulation. The cylindrical iron reactor was used as a cathode while the packed bed formed from wrapped iron wire netting was used as an anode. Various operating parameters, such as current density, initial pH, wastewater recirculation flow rate and continuous flow regime, were examined for intensifying the performance of the process. Also, calculation of electrical energy consumption and the characterization of sludge formed during electrocoagulation have been performed. The initial COD concentration of 1953 mg/L was reduced to 61 mg/L with a removal efficiency of 96.88%, while the color of the wastewater was almost completely removed. The experimental results, throughout the present study, have indicate that electrocoagulation of textile wastewater using a uniquely designed reactor was very effective and direct dischargeable effluent, complying with legal requirements, was obtained. The XRD analysis of the sludge produced during EC reveals that maghemite (Fe2O3) is the main by-product formed after EC.

EC treatment for reuse of tissue paper wastewater: aspects that affect energy consumption

The need for more rational use of water also calls for more efficient usage. An example is the production of tissue paper, where large amounts of water are discharged into the drain because its turbidity does not allow for recirculation. While this is a serious problem, even worse is the fact that the quality of such wastewater makes it difficult not only to recirculate but also to discharge due to environmental law restrictions. In this paper, electrocoagulation is proposed as a suitable technology to meet standards of water discharge, and even better, as a treatment option for removal of turbidity. Since energy consumption has been a drawback for EC applications, relevant aspects that contribute to increase it such as cell voltage and current density have been reviewed. For this purpose a systematic micro-electrolysis study combined with macro-electrolysis experiments have provided evidence that shows it is possible to achieve a turbidity removal of 92% with an energy consumption of 0.68 kWh/m(3). Thus, the results presented in this paper support the use of EC to obtain water of acceptable quality for reuse in the tissue paper industry.

Removal of acid green dye 50 from wastewater by anodic oxidation and electrocoagulation--a comparative study

The present work represents a comparative study for removing acid green dye 50 by anodic oxidation and electrocoagulation using a new batch self gas stirred electrochemical cell. The effect of operating parameters such as current density, initial dye concentration, NaCl concentration and pH on the efficiency of colour removal has been examined. The chemical oxygen demand (COD) reduction under suitable operating conditions was also calculated and found to be reduced by 68% and 87% in case of electrochemical oxidation and electrocoagulation methods, respectively. The results indicate that electrocoagulation is more economic than anodic oxidation, energy consumption ranged from 2.8 to 12.8 kWh/kg dye removed in case of electrocoagulation while in case of anodic oxidation it ranged from 3.31 to 16.97 kWh/kg dye removed. Although the mechanisms of electrocoagulation and anodic oxidation are different, results show that the first-order rate equation provides the best correlation for the decolourization rate of acid green 50 by the two methods.