Electrocoagulation Flocculation Research Articles

Treatment of Textile Wastewater from Spinning Mill Using Electrocoagulation-Flocculation Process

Textile spinning mills generate wastewater containing high levels of pollutants such as suspended solids, dyes, oils, and organic compounds. This study investigates the electrocoagulation-flocculation (ECF) process as a sustainable treatment method. ECF combines electrocoagulation, where an electric current induces pollutant coagulation, and flocculation, which aggregates these pollutants for removal. Extensive lab experiments were conducted, analyzing setup, procedures, and results. The study found that ECF significantly reduced pollutants, achieving high removal efficiencies for suspended solids, COD, color, and oil/grease. Economic analysis confirmed ECF's cost- effectiveness over conventional methods. A case study demonstrated successful implementation, highlighting operational efficiency and environmental compliance. The paper concludes with recommendations for future research and industrial applications. Key Words: Electrocoagulation, Textile Wastewater, Sustainable Wastewater Treatment, Spinning Mill, Pollutant Removal

Lutein as a high-value product from anaerobic digestate using the microalgae Chlorella vulgaris: Downstream processing and application in poultry

This study examined lutein production by microalgae (Chlorella vulgaris) using anaerobic digested as the substrate, its recovery and application in poultry. The influence of different electrodes, current density, and recovery time on the recovery of C. vulgarsis biomass and lutein by electrocoagulation flocculation was evaluated. C. vulgaris biomass recovery was maximum with copper and higher with aluminium electrodes at the current density 1.5 and 2.5 mA/cm2 respectively. The maximum lutein recovery after sonication was 95.42 % for biomass concentration of 33 mg/mL and treatment time of 4.5 min. Effect of different concentration of lutein (20 to100 mg/L) and molecular weight cut-off (600 to 1000 Da) of membrane on lutein recovery was investigated. Maximum lutein obtained was 89.34 % using 800–1000 Da filter. Lutein purity obtained was 83.36, 84.84, 84.32 and 72.02 % for the applied pressures 2, 3, 4 and 5 kg/cm2 respectively. Furthermore, lutein enhancement in egg yolk was demonstrated by supplementing lutein, lutein ester and microalgae at different concentrations (75 to 450 mg/kg) in the basal diet of chicken.

Modelling and optimisation of electrocoagulation/flocculation recovery of effluent from land-based aquaculture by artificial intelligence (AI) approaches.

This study examined the modelling and optimisation of the electrocoagulation-flocculation (ECF) recovery of aquaculture effluent (AQE) using aluminium electrodes. The response surface methodology (RSM), artificial neural network (ANN), and adaptive neuro-fuzzy inference system (ANFIS) were used for the modelling, while the optimisation tools were the numerical RSM and genetic algorithm (GA). Furthermore, the kinetics of the ECF process was studied to provide insight into the mechanism governing the ECF of AQE. The experimental design was performed using the central composite design (CCD) of the RSM. The ANFIS modelling was accomplished via the Grid Partition (GP) of the data set, while the ANN used the multi-layer perceptron (MLP) based feed-forward system. Statistically, the prediction accuracy of the models followed the order: ANFIS (R2: 0.9990), ANN (R2: 0.9807), and RSM (R2: 0.9790). The process optimisation gave optimal turbidity (TD) removal efficiencies of 98.98, 97.81, and 96.01% for ANFIS-GA, ANN-GA, and RSM optimisation techniques, respectively. The ANFIS-GA gave the best optimization result at optimum conditions of pH 4, current intensity (3 A), electrolysis time (7.2min), settling time (23min), and temperature (43.8°C). In the kinetics study, the experimental data was analysed using pseudo-first-order (0.8787), pseudo-second-order (0.9395), and Elovich (R2: 0.9979) kinetic models; the Elovich model gave the best correlation with the experimental data showing that the process is governed by electrostatic interaction mechanism. This study effectively demonstrated that ECF recovery of AQE can effectively be modelled using RSM, ANN, and ANFIS and be optimised using RSM, ANN-GA, and ANFIS-GA techniques, and the order of performance is ANFIS > ANN > RSM and ANFIS-GA > ANN-GA > RSM, respectively.

Uses of electro-coagulation-flocculation (ECF) for the pre-concentration of microalgae biomass

The separation of microalgae biomass from diluted cultures found in large-scale production systems is a major challenge for microalgae-related processes. Conventional methods use centrifugation but it requires too much energy (1 kWh/m3), the combination with previous pre-concentration operations such as settling or flotation is needed to reduce this energy consumption. However, both settling and flotation of microalgae biomass require the addition of chemical coagulants/flocculants, thus contaminating the biomass. This work explores the potential use of Electro-Coagulation-Flocculation (ECF) as a method for the pre-concentration of microalgae biomass. Thus, the recovery of freshwater microalgae Scenedesmus almeriensis was studied, both in batch and continuous mode, using this technique to optimize the operating conditions. Data from batch experiments show as a minimum conductivity of 5 mS∙cm−1 is required, the electrical potential of 12 V and current density of 18 mA∙cm−2 allowing for the recovery of 90 % of the biomass, while the biomass recovery increases up to 99 % when increasing the current density to 23 mA∙cm−2. The efficiency of the process increases when increasing the biomass concentration, thus energy consumption reduces by half from 1.0 to 0.5 kWh∙Kg−1 when the biomass concentration increases from 2.8 to 5.0 g∙L−1. To optimize the performance of the system experiments were performed in continuous mode maintaining the voltage and current density at 12 V and 47 mA∙cm−2 respectively, but modifying the flow rate and biomass concentration provided to the electrocoagulation chamber. Data shows as the optimal residence time is 15 s whereas the energy consumption reduces from 3.2 to 0.58 kWh∙Kg−1 when increasing the biomass concentration from 0.75 to 4.20 g∙L−1. Results confirm the reliability of this method for the pre-concentration of microalgae biomass, it being a fast process consuming reasonable energy. Further optimization of the electrocoagulation chamber and electrical conditions will improve the efficiency of this system for further commercial processes while keeping its major advantages of non-contaminating the biomass and allowing to achieve high biomass recovery values in short times.

Electrocoagulation-flocculation of aquaculture effluent using hybrid iron and aluminium electrodes: A comparative study

This work investigated the treatment of fish pond wastewater (FPW) using electrocoagulation – flocculation (ECF) through aluminium (Al) and iron (Fe) electro-coagulants. The feasibility of using this method has been determined in terms of turbidity (TUR), biochemical demand oxygen (BOD), chemical demand oxygen (COD), and reduction of colour (COL). The study analysed the role of pH, current dosage, electrolysis time, settling time, temperature, and concentration of NaCl on the ECF process. Also, the influence of using the hybrid of Al and Fe in different configurations (Al-Al, Fe-Fe, Fe-Al, and Al-Fe) was taken into account for the ECF process. The perikinetics kinetics of the process flocculation was studied. The coefficient of regression (R2) was used to confirm the theoretical applicability of perikinetics flocculation. The forecast of the time evolution of aggregating particles or species was included. The optimum pH was 2. Al-Al electrode had a higher TUR removal (87.87%). Fe-Fe electrodes were the best for reducing COL (73.56%). Al-Al was proven to be the best electrode configuration for BOD removal (76.90%) and COD removal (86.4 %). The ECF kinetic data partially followed Von Smoluchowski's equation for the Brownian perikinetics flocculation theory. The mechanisms that accounted for the distribution of particles were sweep flocculation and charge neutralisation. The ECF was very effective for reducing FPW pollutants.

Harvesting of freshwater microalgae Scenedesmus sp. by electro–coagulation–flocculation for biofuel production: effects on spent medium recycling and lipid extraction

There is growing interest in recent times for microalgae as a sustainable energy source. However, efficient harvesting of microalgal biomass for various industrial applications is still considered a bottleneck. The present study attempts to evaluate microalgae Scenedesmus sp. harvesting using electro-coagulation-flocculation (ECF). Plackett-Burman design was exploited to explore the significant process parameters, whereas Taguchi's array design was employed for optimization. The optimal conditions were optimized as initial pH5.0, electrolysis time 15min, electrode distance 2cm, sedimentation time 60min, and current density 12mAcm-2 for complete harvesting. Under optimum conditions, the energy utilization and the operation cost of ECF process was estimated to be 2.65 kWh kg-1 and USD 0.29kg-1, respectively. Thus, ECF-based microalgae harvesting was found as a low-cost technique. In addition, neutralizing pH and supplementing macro- and micronutrients enabled the flocculated medium to maintain an approximate growth yield in algal cultivation to that of the fresh BG11 medium. ECF did not affect the amount of microalgal lipids (28.6 ± 1.2, % wt.), chlorophyll a (8.3 ± 0.3μgmL-1), and fatty acid methyl ester composition (C15:0, C16:0, C17:0, and C18:0) as well. These results strongly recommend ECF as the most appropriate and promising method for harvesting Scenedesmus sp. for biofuel production.

Treatment of oil refinery wastewater by electrocoagulation–flocculation (Case Study: Shazand Oil Refinery of Arak)

In the present study, electrocoagulation–flocculation method was used to treat the wastewater from Shazand Oil Refinery in Arak, Iran. The wastewater contained 170,000 mg/L COD and 5.3 mg/L lead (Pb). In each step of the experiment, 2 L of the refinery wastewater was poured into a pilot made up of Plexiglas, and bipolar electrode arrangement was used. Optimum values of time, pH, and voltage parameters were determined for the aluminum electrodes. Results showed that time duration of 90 m, pH of 6, and voltage of 30 V was suitable for the removal of lead and COD. It should be noted that 48% of COD was removed and lead concentration decreased from 5.3 mg/L to lower than 0.05 mg/L. In addition, the COD removal efficiencies were 56 and 64% for eight and ten aluminum electrodes, respectively. The effect of iron electrodes on the removal of COD and lead was investigated under the same optimum conditions. Comparison between iron and aluminum electrodes indicated that iron electrodes demonstrate a better efficiency by removing 66.94% of COD from wastewater. It was also found that pH played a significant role in pollutants removal due to the formation of aluminum hydroxide gelatinous polymer.

The Water-Energy Nexus: Electrocoagulation and Energy Conservation

Electrocoagulation is a multiple-purpose process re-emerging nowadays as a low-energy solution to water treatment and pollution control problems. This paper describes the development of electrocoagulation-flocculation (ECF) treatment processes of water and wastewater that could be a potential hydrogen gas source and reduce operational costs as well. ECF coupling with ultrafiltration (UF) for organics removal and flux enhancement and, with granular filtration (GF) and constructed wetland (CW) for P removal from secondary effluents are examined. Bench-scale experiments of ECF-UF and ECF-UF configurations and ECF-GF-CW pilot tests had been performed. Analysis of ECF mechanisms leads to energy conservation potential via (a) hydrogen co-generation, (b) low voltage application, (c) reduced chemicals transportation (which is also helpful in less developed cold areas where and when roads are blocked) and (d) hybridization with other low energy treatment processes such as constructed wetlands or SAT. A model developed for energy minimization is found to play a major role in process selection. It is also concluded that ECF as pretreatment for UF and MF improved filtrate quality and reduced the fouling, particularly by reducing cake influence. And, complementing CW treatment with a physicochemical process of ECF reduces soluble and particulate phosphate, and removes organic matter and nitrogen compounds.

Harvesting of microalgae Chlorella vulgaris using electro-coagulation-flocculation in the batch mode

The aim of this study was to evaluate the harvesting of microalgae Chlorella vulgaris by electro-coagulation-flocculation (ECF) using aluminum and iron electrodes, assess the mechanisms responsible for microalgae recovery, quantify the metal contamination in the effluent and biomass, analyze power requirements, and investigate the effect of ECF on lipid and pigment content in the biomass. The influence of six operating parameters (electrode material, sedimentation time, current density, stirring speed, initial pH (pHi) and inter-electrode distance) on the harvesting efficiency was tested. A specific strategy involving flotation and pH-controlled ECF experiments was developed to identify the prevailing mechanism of harvesting: adhesion on flocs was shown to be negligible; flotation contributed to a maximum of 36.6% of microalgae recovery; zeta potential highlighted that the main mechanism responsible for microalgae recovery was charge neutralization at pHi4 and 6, and sweep flocculation at pHi8. The most energy saving conditions for the harvesting of Chlorella vulgaris involved aluminum electrodes, and 60min electrolysis with a current density of 2.9mA/cm2, pHi4, stirring speed 250rpm and an inter-electrode distance of 1cm. Economic and competitive energy input (1kWh/kg microalgae) could be achieved by adding 1.5g/L NaCl. In addition, ECF did not affect significantly the amount of microalgal lipids and pigments.

Electrocoagulation flocculation as a low-cost process for pollutants removal from urban wastewater

A combined two steps electrocoagulation–flocculation was designed to remove COD, BOD5, TSS, nitrate (NO3), nitrogen (N), phosphate (P), and fecal coliform (FC) from urban wastewater. The possibility of adding a natural flocculant extracted from plant material, Spineless Prickly Pear, Opuntia ficus Indica, juice (OFIJ), by comparing it with an industrial grade flocculant as anionic polyacrylamide (APAM), in the process of electrocoagulation–flocculation (ECF) was performed. The electrocoagulation (EC) reactor was tested in two different sequences (before and after the flocculation unit). The effect of several operational parameters, such as: current density, reaction time, flocculant dose, specific amount of dissolved electrodes and initial pH, on the removal efficiency of major pollutants was determined. The application of ECF process under optimal conditions, such as: current density (200A/m2), reaction time (30min), flocculant dose (6ml/l), initial pH (7.4) and specific amount of dissolved electrodes (0.2kg/m3) allows to achieve these promised removal efficiencies: 85%COD, 84%BOD5, 94%TSS, 63%N, 73%NO3 and 99%P. Moreover, it is of interest to note that duration of 10min is sufficient to remove 99% of FC from the studied urban wastewater. These operating conditions of ECF led to reducing specific energy consumption from 6kWh/kg COD and 0.6kWh/kg P (EC process) to 5kWh/kg COD and 0.5kWh/kg P, respectively. A comparative operating cost analysis was also given and it was found that ECF performance requires 0.7$/kg of COD and 0.3$/kg of P removed vs. 0.9$/kg COD and 0.35$/kg P for EC process.

Low-energy input continuous flow rapid pre-concentration of microalgae through electro-coagulation–flocculation

This study demonstrates that Nannochloropsis sp. can be effectively pre-concentrated by separation from its growth medium (0.28–0.36g/L) using electro-coagulation–flocculation (ECF) in a continuous flow reactor with both nickel and aluminum electrodes spaced 6.35mm apart. Flow rates studied range between 0.4 and 3.9L/min. Treatment uses energy inputs between 0.08 and 6.43kWh/m3 and voltages between 4 and 20V.This paper describes a novel method that subjects flowing fluid to direct current for a very short time (between 0.8 and 7.5s), upon which algae rapidly separate, approximately 30min after ECF treatment. Fluid flow rate decreases ECF Efficiency as compared to batch tests. Maximum ECF Efficiency recorded in this study was 92% at 0.4L/min and 7V with nickel electrodes. Higher voltage inputs and lower flow rates result in higher ECF Efficiencies. However, the ratio of ECF Efficiency to energy input is the highest for the lowest voltage inputs and highest flow rates. Treatments of 3.9L/min flow rate and 6V resulted in the highest ratio of ECF Efficiency to energy input (151 and 406%/(kWh/m3) for nickel and aluminum electrodes respectively). The ECF processing leaves a large number of viable algal cells that are separated from their growth medium, 40–60% under conditions studied. Metals analysis shows the microalgae, after ECF treatment with nickel and aluminum electrodes at 8V and flow rate of 0.8L/min, sorbs a significant amount of metal, 348.6±66.7mgNi/gdry biomass and 125.2±15.2mgAl/gdry biomass.

Feasibility Study on Electro Coagulation Flocculation for Microalgae Harvesting

Although microalgae are considered as a promising feedstock for biofuels, cost-efficient harvesting of microalgae needs to be significantly improved. In this study, the use of electro coagulation as a more rapid flocculation method for harvesting a freshwater (Scenedesmus dimorphus) microalgae species was evaluated. The results showed that, electro coagulation was shown to be more efficient using an aluminum anode than using an iron anode. And optimum conditions of electro coagulation for harvesting Scenedesmus dimorphus were found. The optimum stirring speed was 100 rpm and optimum pH was 5. Furthermore, the current density which the fastest and highest recovery efficiency is achieved at , while the highest energy efficiency was achieved at . A the rapid and high recovery efficiency indicate that electro coagulation is a particularly attractive technology for harvesting microalgae.

Removal of arsenic from groundwater rich in natural organic matter (NOM) by continuous electrocoagulation/flocculation (ECF)

A novel technique of continuous ECF using bipolar Al electrode was attempted in this study to efficiently remove arsenic from groundwater rich in hydrophobic NOM (9.31±0.52mgC/L). The effects of several operational parameters such as, initial groundwater pH, evolution of temperature, conductivity and pH, electrode polarity time change on As and NOM removal efficiency were comprehensively examined by conducting 6h long experimental runs. The average residual As in treated groundwater was 4.6±0.4μg/L. NOM removal according to UV254 absorbance, DOC and SUVA was 89%, 70%, 64%, respectively. The highest As and NOM removal with the optimal residual Al below 0.2mg/L was obtained at the same groundwater pH=5.3±0.3. The change of electrode polarity at 30min successfully prevented electrode passivation and enabled highest As removal with the optimal residual Al in treated groundwater. Specific reactor electric energy and electrode consumption for operational current density of 8.86mA/cm2 was 3.03kWh/m3, 0.059kg Al/m3, respectively. Indicative reactor’s operating cost at the optimal operational conditions was estimated at 0.25€/m3.

An ultra-low energy method for rapidly pre-concentrating microalgae

This study demonstrates that Nannochloropsis sp. can be effectively separated from its growth medium (0.2-0.3g/L) using electro-coagulation-flocculation in a 100mL batch reactor with nickel electrodes and a treatment time of only 4s. Minimum energy density input for effective separation is 0.03 kWh/m(3). Both energy input and treatment time are much smaller than reported elsewhere. The process results in rapid separation of microalgae (over 90% in 120 min) with minimal damage to algal cells (>90% still alive after processing). At around 4V input, algae can be effectively separated even in very low concentrations. Pulsing is equally effective in separating microalgae as continuous direct current of same magnitude and total exposure time. Algae can separate from their growth medium even if the suspension itself is not treated, but is mixed with treated saltwater with same conductivity. The described method has significant advantages including applicability to continuous processing and water reuse.

Floc characteristics of Chlorella vulgaris: Influence of flocculation mode and presence of organic matter

Floc characteristics such as settling velocity, concentration factor and floc size were studied for five different flocculation modes for Chlorella: aluminum sulphate, electro-coagulation–flocculation, chitosan, cationic starch and pH induced flocculation. These floc characteristics were influenced by the flocculation mode, which depends on the coagulation mechanism: adsorption – charge neutralization, sweeping or bridging. Secondly, the influence of the presence of AOM was evaluated. The presence of AOM led to an increase between 1.5 and 5-fold in needed flocculant dosage for all flocculation modes. This resulted particularly in a comparable decrease of the concentration factor. The floc characteristics upon flocculation using cationic starch were least affected by the presence of AOM, while flocculation using chitosan was most affected. The impact on floc characteristics is an important parameter next to flocculation efficiency to consider in the assessment of flocculation-based harvesting of microalgae.

Influence of organic matter generated by Chlorella vulgaris on five different modes of flocculation

Microalgae excrete relatively large amounts of algal organic matter (AOM) that may interfere with flocculation. The influence of AOM on flocculation of Chlorella vulgaris was studied using five different flocculation methods: aluminum sulfate, chitosan, cationic starch, pH-induced flocculation and electro-coagulation–flocculation (ECF). The presence of AOM was found to inhibit flocculation for all flocculation methods resulting in an increase of dosage demand. For pH-induced flocculation, the dosage required to achieve 85% flocculation increased only 2-fold when AOM was present, while for chitosan, this dosage increased 9-fold. For alum, ECF and cationic starch flocculation, the dosage increased 5–6-fold. Interference by AOM is an important parameter to consider in the assessment of flocculation-based harvesting of microalgae.

Evaluation of electro‐coagulation–flocculation for harvesting marine and freshwater microalgae

Although microalgae are considered as a promising feedstock for biofuels, the energy efficiency of the production process needs to be significantly improved. Due to their small size and low concentration in the culture medium, cost-efficient harvesting of microalgae is a major challenge. In this study, the use of electro-coagulation-flocculation (ECF) as a method for harvesting a freshwater (Chlorella vulgaris) and a marine (Phaeodactylum tricornutum) microalgal species is evaluated. ECF was shown to be more efficient using an aluminum anode than using an iron anode. Furthermore, it could be concluded that the efficiency of the ECF process can be substantially improved by reducing the initial pH and by increasing the turbulence in the microalgal suspension. Although higher current densities resulted in a more rapid flocculation of the microalgal suspension, power consumption, expressed per kg of microalgae harvested, and release of aluminum were lower when a lower current density was used. The aluminum content of the harvested microalgal biomass was less than 1% while the aluminum concentration in the process water was below 2 mg L(-1). Under optimal conditions, power consumption of the ECF process was around 2 kWh kg(-1) of microalgal biomass harvested for Chlorella vulgaris and ca. 0.3 kWh kg(-1) for Phaeodactylum tricornutum. Compared to centrifugation, ECF is thus more energy efficient. Because of the lower power consumption of ECF in seawater, ECF is a particularly attractive method for harvesting marine microalgae.

Optimisation of reactive dye removal by sequential electrocoagulation–flocculation method: comparing ANN and RSM prediction

The removal of Reactive Black 5 dye in an aqueous solution by electrocoagulation (EC) as well as addition of flocculant was investigated. The effect of operational parameters, i.e. current density, treatment time, solution conductivity and polymer dosage, was investigated. Two models, namely the artificial neural network (ANN) and the response surface method (RSM), were used to model the effect of independent variables on percentage of dye removal. The findings of this work showed that current density, treatment time and dosage of polymer had the most significant effect on percentage of dye removal (p<0.001). In addition, interaction between time and current density, time and dosage of polymer, current density and dosage of polymer also significantly affected the percentage of dye removal (p=0.034, 0.003 and 0.024, respectively). It was shown that both the ANN and RSM models were able to predict well the experimental results (R(2)>0.8).

Influence of organic matter on arsenic removal by continuous flow electrocoagulation treatment of weakly mineralized waters

The aim of this study is to evaluate and understand the electrocoagulation/flocculation (ECF) process to remove arsenic from both model and natural waters with low mineral content and to compare its performances to the coagulation/flocculation (CF) process already optimized. Experiments were thus conducted with iron electrodes in the same specific treatment conditions (4 ⩽ current density (mA cm −2) ⩽ 33) to study the influence of organic matter on arsenic removal in conditions avoiding the oxidation step usually required to improve As(III) removal. The process performance was evaluated by combining quantification of arsenic residual concentrations and speciation and dissolved organic carbon residual concentrations with zeta potential and turbidity measurements. When compared to CF, ECF presented several disadvantages: (i) lower As(V) removal yield because of the ferrous iron dissolved from the anode and the subsequent negative zeta potential of the colloidal suspension, (ii) higher residual DOC concentrations because of the fractionation of high molecular weight compounds during the treatment leading to compounds less prone to coagulate and (iii) higher residual turbidities because of the charge neutralization mechanisms involved. However, during this process, As(III) was oxidized to As(V) improving considerably its removal whatever the matrix conditions. ECF thus allowed to improve As(III) removal without applying an oxidation step that could potentially lead to the formation of toxic oxidation by-products.

Electrochemical removal of pollutants from agro-industry wastewaters

Electrocoagulation was investigated for the treatment of agro-industry wastewaters, namely, meat processing, cereal products, food beverages and abattoir. Initial studies were carried out to check the performance of each of the agro-industry wastewaters (in terms of COD removal). The total cost (including, electrical power consumed, chemicals and consumption of electrodes) of the treatment varied between $ 0.95 and 4.93 m −3. Abattoir wastewater resulted in higher COD removal of 85–86%. Subsequent studies were performed in details on the selected abattoir wastewater. Bipolar mild steel electrode gave higher soluble COD removal (82%). Likewise, percent soluble COD removal as a function of pH and conductivity confirmed no need of acidification and electrolyte addition. The coupling of electrocoagulation with flocculation process resulted in effective removal of organics (82% total COD removal), inorganics (with the exception of nitrogen), pathogen destruction and solids and turbidity removal. Thus, electrocoagulation–flocculation process can be envisaged as an effective treatment process for decontamination of agro-industry wastewaters.