Electrocoagulation-flotation Research Articles

Optimized removal of silica during manure treatment by electrocoagulation-flotation (EC-F) in view of fouling prevention of reverse osmosis membranes

Reverse osmosis (RO) membrane fouling threatens the performance of manure treatment. In this regard, silica is considered one of the most challenging inorganic foulants. Removing silica fouling from RO membranes is difficult, ultimately leading to performance deterioration, including reduced permeability and premature membrane failure. This study examines the removal of silica during manure treatment using a novel tubular electrocoagulation-flotation (EC-F) reactor with an Al electrode. The EC-F was positioned between an ultrafiltration and a RO membrane filtration system. The operational parameters—current density, electrolysis residence time, and initial pH—were optimized for maximum silica removal efficiency and minimum operational cost. At the optimum conditions (pH of 8.2, current density of 160 A/m2 and electrolysis residence time of 23 s), 88 % of silica (initial concentration of 104 mg/L) was removed. Subsequent membrane fouling assessment revealed that EC-F pretreatment decreased the fouling potential by 28 % (from 7.11 × 1016 to 5.10 × 1016 Pa·s/m2·t), indicating efficient foulant removal. SEM-EDX analysis of the membrane confirmed the lack of scale formation when using EC-F pretreated manure as a feed stream. This study demonstrates that the use of innovative EC-F pretreatment significantly reduces the operational expenditure (1.75 €/m3) compared to prior EC-F research for silica removal from manure, thereby reducing the fouling of RO membranes.

Combined electrocoagulation/flotation technique and membrane desalination for textile wastewater reuse

A novel integrated system that combined electrocoagulation/flotation (ECF) technique with membrane desalination was used for textile wastewater treatment to reduce the environmental pollution of textile wastewater. Two scenarios were examined: the first is ECF followed by membrane desalination; the second is the application of membrane desalination for treatment of raw wastewater. Iron electrodes were used in batch-wise tests to examine the effects of electrolysis time and current intensity on percentage removals. The SiO2/PA(TFC) membrane was used to treat raw wastewater and ECF effluents. As the current intensity increased from 50 mA to 600 mA, the color elimination was improved from 94 % to 99 % and the COD elimination improved from 59.1 % to 81.5 %. The findings demonstrate the efficacy of ECF in removing color and COD, although the treated wastewater sample's TDS increased from 4200 mg/L to 19,400 mg/L (raw textile wastewater sample). The SiO2/PA(TFC) membrane displays the salt rejection and water flux reduction of the raw wastewater samples 95 %, and 22 (L/m2.h). Corresponding results for ECF treated wastewater were 94, 93, 91 % and 13, 11.5, and 10 (L/m2.h), respectively. The SiO2/PA(TFC) membrane displays the reduction of COD from 760 mg O2/L (raw) and 310 mg O2/L (ECF effluent) to zero%. Also, it proves the capabilities of SiO2/PA(TFC) membrane for the removal of TDS, COD and color. This integrated system can provide sustainable source for fresh water supply used for landscape, irrigation, industry and various purposes.

Removal of linear alkylbenzene sulfonate by electrocoagulation/flotation using a cylindrical vertical reactor

This study proposes a vertical electrocoagulation/flotation reactor model and evaluates its efficiency through hydraulic tests and the removal of linear alkylbenzene sulfonate (LAS), a common wastewater surfactant. Residence time distribution assays and computational fluid dynamics verified the fluid flow pattern. Response surface methodology (RSM) was used to assess the impact of pH, electric current, and sodium chloride concentration on LAS removal. Ecotoxicity tests using Artemia salina detected no toxic byproducts from electrocoagulation/flotation (ECF). Adsorption kinetics and isotherms were used to evaluate the removal behavior of LAS, which showed the highest efficiencies with an electric current of 1.5 A, a pH of 5.73, and a NaCl concentration of 4652.4 mg/L. The electric current and pH were the most influential variables. The ecotoxicity assay indicated no toxic byproduct generation, even at high chloride concentrations, and increased LAS biodegradability posttreatment. Adsorption kinetics followed a pseudo-first-order model at 20 mg/L and a pseudo-second-order model at 240 mg/L. The Freundlich isotherm indicated a high affinity between the LAS and aluminum hydroxide flakes, achieving nearly 90 % removal in 30 min at an energy cost of 5.25 Wh.

Treating boron-containing wastewater by electrocoagulation-flotation (ECF) process with the stepwise addition of anionic surfactants

This study presents an innovative approach for boron removal from industrial wastewater, especially from coal-fired power plants and hydraulic fracturing processes, through an advanced electrocoagulation-flotation (ECF) method. This method, enhanced by the stepwise addition of anionic surfactants, effectively reduces the sludge-volume ratio (SVR) while ensuring efficient boron removal. Anionic surfactants, due to their compatibility with the positively charged boron‑aluminum hydroxide co-precipitates, enhance coagulation and solid-liquid separation. The research highlights the correlation between the hydrophobicity of the surfactant's carbon chain and reduced sludge volume and residual turbidity. Importantly, the stepwise addition of surfactants optimizes the dosage, maintaining low residual turbidity and SVR, even in high-conductivity (30.1 mS cm−1) wastewater from actual coal-fired power plants. Further, the study shows that longer reaction times and higher surfactant doses in a mono-polar electrode reactor can significantly improve boron removal and solid-liquid separation, marking a substantial advancement in wastewater treatment technologies.Boron is a common pollutant in wastewater of coal-fired power plants and the hydraulic fracturing process. It can be effectively removed by electrocoagulation (EC). However, the boron‑aluminum hydroxide particles after EC are too tiny to settle by sedimentation, and therefore, the sludge-volume ratio (SVR) is extremely high. By adding surfactants, the solid-liquid separation mechanism of EC can be shifted from settling to flotation (known as the electrocoagulation-flotation (ECF) process), effectively reducing the SVR without affecting boron removal. Due to the positively charged nature of boron‑aluminum hydroxide co-precipitates, anionic surfactants work better than cationic surfactants as coagulants. The higher the hydrophobicity of surfactant's carbon chain, the lower the sludge volume and residual turbidity. A stepwise addition method significantly reduced the surfactant dosage without causing an increase in the residual turbidity or SVR. The efficiencies of boron removal and solid-liquid separation by ECF in actual coal-fired power plant wastewater were significantly reduced due to the extremely high conductivity (30.1 mS cm−1). A stepwise addition method was also useful when treating real wastewater. The efficiencies of boron removal and solid-liquid separation were significantly be improved by a longer reaction time and a higher SDS dose by ECF with a mono-polar electrode reactor.

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 flotation as a municipal wastewater (pre-)treatment technology: Effect of weather conditions and current density

Electrocoagulation (EC) is a promising compact alternative technology, despite its viability in municipal wastewater treatment (MWWT) is currently challenged by its energy-intensive and batch-mode operation. This study introduces an innovative continuous electrocoagulation flotation (ECF) design for MWWT. ECF shows promising pollutant removal efficiencies, with identical results using both iron (Fe) and aluminum (Al) anodes. At a current density (CD) of 120 A/m2, it achieved significant removals: 90% tCOD, 98% TP, 94% TSS, 60% BOD5, and 40% TN. Designed ECF is proposed as a pre-treatment step due to limited TN removal. The study investigated optimal ECF performance under varying weather conditions using CD ranges of 40, 80, and 120 A/m2. Both Fe and Al ECF outperformed in treating rainy weather (RW) and dry weather (DW) municipal wastewater (MWW). However, Al anode's super-faradaic behavior resulted in higher residual concentrations in effluent, (i.e., an average of 6.53–33.7 mg/L), and operational costs compared to Fe ECF. Optimized Fe ECF setting needs to be changed depending in the weather variation. Fe ECF achieved high removal rates for tCOD (94%) and TP (95%) in RW MWW at a low CD of 40 A/m2. Comparative to this, the optimum CD for treated DW MWW was between 40 and 80 A/m2, removing tCOD (71–73%) and TP (85–95%). Specifically, at these conditions, the operational expenses were respectively 0.47 ± 0.03 €/m3 (RW MWW), and 0.37 ± 0.02 €/m3 to 0.81 ± 0.04 €/m3 (DW MWW). Moreover, ECF enables resource recovery and a circular economy through anaerobic sludge digestion, with Fe ECF generating more biogas than Al.

Electrocoagulation/flotation process for removing copper from an aqueous environment

The presence of copper in aqueous environments such as drinking water has led to several environmental effects, such as flavor and odor. The increase in Cu levels in ground and surface water has been mainly attributed to anthropogenic and natural sources. Consequently, this applied-analytical study aimed to investigate copper removal from urban drinking water through batch reactor electrocoagulation/flotation (ECF) with aluminum electrodes. The copper removal efficiency was evaluated under various operating conditions of current density (0.8–2.4 mA/cm2), initial concentration (1–100 mg/L), pH (3.5–10.5), and time (10–30 min). Cu was determined using the method outlined in the standard procedures (3500-Cu B at 4571 nm). The results indicated that increasing the current density from 0.8 to 2.4 mA/cm2 and the reaction time from 10 to 30 min improved Cu+2 removal efficiency (from 95 to 100%). In addition, the results demonstrated that Cu+2 reduction is 100% with an initial concentration of 100 mg/L, a pH of 7.5, a reaction time of 30 min, and an anode current density of 2.4 mA/cm2. The Taguchi method results for copper removal efficiency show that reaction time is the most significant variable. Furthermore, Cu removal kinetics models in an ECF reactor are second-order (R2 > 0.92). The Cu removal in the ECF reactor is due to redox and adsorption. Moreover, the operational costs of Cu treatment with Al electrode pairs are estimated to range from 8857 and 9636 Rial/kg of Cu removed. Thus, it can be concluded that the ECF process is very efficient in removing Cu from aqueous environments under optimum conditions.

Harvesting of microcells from cyanobacteria-laden water by energy-efficient electro-flocculation-flotation with aluminum hydrates

Electrocoagulation-flotation (ECF) is able to effectively harvest microcells from eutrophicated drinking water reservoirs to reduce algogenic organic matter (AOM) during cyanobacteria blooming. However, ECF needs high current density (CD) and prolonged reaction time with inevitable high-energy consumption. This study aimed to investigate a novel electrocoagulation-flocculation-flotation (EFF) process, with 10 min EC reaction and 15 min flocculation followed by 10 min flotation, for Microcystis aeruginosa (MA) cell harvesting from water as well as AOM reduction with Al hydrates at various CD and pH conditions. The results have shown that significant MA cell separation and dissolved organic carbon (DOC) reduction by EFF occurred at pH 8 with 5 mA/cm2, accounting for 95 % and 56 %, respectively. At such a condition, the formation of dominant colloidal Al species (Alc) governed the EFF to promote cells and AOM destabilization by strong sweep flocculation along with weak charge neutralization by polymeric Al species (Alb). Moreover, the pronounced reduction in soluble microbial product-like (SMPL) substances could be further improved by up to 60 % with EFF. It was also found that EFF required only 2.07 × 10−2 kWh/kg in energy input and served energy saving ~63 % less than that by prolonged ECF at similar MA cell separations. It concluded that EFF was an energy-efficient technique to fast separate and harvest microcells from MA-laden water and AOM reduction with low energy input for practical application in drinking water treatment.

Impact of operating parameters of electrocoagulation-flotation on the removal of turbidity from synthetic wastewater using aluminium electrodes

This study analyzed the dominant operating parameters of electrocoagulation-flotation (ECF) that would influence the removal efficiency of turbidity from synthetic wastewater using aluminium electrodes with an inter-electrode distance of 5 mm. These parameters included current density (CD), initial pH, electrolytic conductivity, coagulant dosage, operating time, initial turbidity concentration, and stirring speed. The initial turbidity concentration and electrolytic conductivity were synthesized based on typical concentrations of various resources such as drinking water, wastewater, seawater, and oil field-produced water. A novel approach has also been proposed for the evaluation of EC performance and selection of an appropriate process for the removal of sludge based on the intake’s initial concentration. The experimental results revealed that the optimal conditions for removal of turbidity (90 %) were attained at CD = 0.0028 A/cm2, initial pH = 7.3, operating time = 5 min, and stirring speed = 500 rpm. The settling times of 5 and 15 min were also evaluated, in order to optimize the design of the settling tank. The results also revealed that ECF formed the flocs larger than 20 µm, so that after filtration with a filter paper of 20 µm, a removal efficiency of 98 % was attained.

Cationic surfactants influencing the enhancement of energy efficiency for perfluorooctanoic acid (PFOA) removal in the electrocoagulation-flotation (ECF) system

From an environmental perspective, approaching sustainability requires a fundamental conceptual shift from the wastewater treatment process toward integrated treatment systems that consider efficient and effective utilization. This study aims to investigate the effects of different surfactants on the removal of perfluorooctanoic acid (PFOA). We used cationic surfactants as both frothers and collectors in the electrocoagulation-flotation (ECF) method to improve the removal efficiency of PFOA. The results showed that, under a monopolar aluminum electrode and with an initial PFOA concentration of 0.25 mM, the ECF method with decyl-trimethyl-ammonium bromide (DTAB) was able to remove over 98% of PFOA within 10 min. Cationic surfactants with a similar linear alkyl chain shape to PFOA, but a longer chain length, are more effective at removing PFOA through the ECF process. The removal mechanism is thought to involve co-precipitation with aluminum hydroxides through Al–F bonding, co-flotation with cationic surfactants, and mixed micelle formation with cationic surfactants. The optimal conditions were tested in both synthetic and realistic wastewater matrices and produced similar results. It has the potential for real wastewater application. The energy yield (G50) of ECF with 5 mM DTAB is 497 g·kWh−1, superior to other treatments, and is an extremely energy-effective method for separating PFOA from wastewater.

Minimization of halogenated disinfection by-product precursors by Al-based electrocoagulation–flotation (ECF) toward cyanobacteria-laden water

Abstract The presence of toxic algae, such as Microcystis aeruginosa (MA), in drinking water treatment plants (DWTPs) would contribute to algal organic matter (AOM) as precursors toward disinfection by-products (DBPs). Electrocoagulation–flotation (ECF) has shown promising performance in minimizing algal cells from water and dissolved AOM. This study aimed to investigate the effect of current density (CD) and pH on alumina (Al)-based ECF for removing MA cell and DBPs precursors from cyanobacteria-laden water. The performance of Al-based ECF was evaluated at various CD and pH conditions within 20 min. In addition, the total halogenated DBPs formation of the treated suspension after ECF was quantified. At pH 8, the ECF process with 5 mA/cm2 exhibits the most significant reductions in MA cell and soluble AOM, accounting for 97 and 56%, respectively. Additionally, the precursors of trihalomethanes (THMs) and haloketones (HKs) can be effectively removed with flotation despite their significant release at EC. The tremendous reduction of humic acid-like (HAL) substances in extracellular organic matter (EOM) fraction by ECF leads to the minimized THMs formation potential. In summary, Al-based ECF at pH 8 is effective to remove cyanobacteria and minimize the precursors of regulated THMs along with an insignificant reduction in regulated haloacetic acids (HAAs) precursors.

Integrated electrocoagulation-flotation of microalgae to produce Mg-laden microalgal biochar for seeding struvite crystallization

Developing sustainable materials for recovering and recycling nutrients from wastewater is critically needed for nutrients such as phosphorus that have a diminishing supply. Struvite crystallization is emerging as a promising strategy for phosphorus recovery which can be enhanced with seeding through microalgal biochar. The main bottleneck of using microalgae is its high harvesting cost. In this study, an integrated electrocoagulation-flotation (ECF) process is used to recover and at the same time modify the algal surface with magnesium anode and inert carbon cathode. Harvesting efficiency of 98% was achieved with 40.78 mA cm−2, 0.5 cm inter-electrode distance and energy consumption of 4.03 kWh kg−1 in 15 min. The harvested microalgae were pyrolyzed to obtain a yield of 52.90% Mg-laden microalgal biochar. Simultaneously, surface impregnation of 28% magnesium was attained as confirmed by Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Phosphorus recovery and struvite yield of 93.70% and 2.66 g L−1, respectively, were obtained from dosing 1.50 g L−1 Mg-laden microalgal biochar. Comparison of physicochemical characteristics of residual supernatant after microalgal harvesting and struvite recovery showed that the combined use of both the residuals can serve as a sustainable growth medium for microalgae. The overall operating cost of the integrated process was found to be 2.48 USD kg−1 with a total energy consumption of 10.76 kWh kg−1, which was found to be lower than conventional harvesting unit processes such as centrifugation and filtration. This novel approach can help attaining a circular bioeconomy by encompassing nutrient recovery and waste management in an integrated process.

Optimization of electrocoagulation–flotation treatment with an aluminum anode to enhance Microcystis aeruginosa cell removal efficiency

Cyanobacteria adversely affect drinking water treatment and the quality of the drinking water supply. Microcystis spp. are the most abundant cyanobacteria in many surface water bodies throughout the world. Electrocoagulation–flotation (ECF) treatment has attracted considerable attention as a means of cyanobacteria removal. In this study, ECF treatment was optimized by adjusting the initial pH, electrode distance, stirring speed, and electrical conductivity (k) to maximize Microcystis aeruginosa cell removal efficiency while meeting drinking water quality standards. The treatment was performed for 200 mL M. aeruginosa suspensions (~2 × 106 cells/mL) using an aluminum anode and a graphite cathode at a constant direct current of 100 mA. An initial pH of 6, a stirring speed of 200 rpm, an electrode distance of 1 cm, and k of 500 μS/cm were selected as optimum conditions for the ECF treatment. Under these conditions, M. aeruginosa at a cell density of ~2 × 106 cells/mL was completely removed at a current density of 4.0 mA/cm2 with an average energy consumption of 1.20 ± 0.03 Wh/L. The zeta potential varied from −18.49 ± 3 mV to 1.15 ± 0.38 mV, which confirmed the complete removal of cells. Most importantly, the pH, aluminum concentration, and total dissolved solids of the treated water met the drinking water quality standards of the World Health Organization. The optimized ECF treatment was thus shown to be promising for the removal of M. aeruginosa cells.

Leachate Post-Treatment by Electrocoagulation Flotation Process(Effect of Polarity Switching, Anode to Cathode Surface Area and Rotating Electrode)

Leachate Post-Treatment by Electrocoagulation Flotation Process(Effect of Polarity Switching, Anode to Cathode Surface Area and Rotating Electrode)

Electrochemical Recovery to Overcome Direct Osmosis Concentrate-Bearing Lead: Optimization of Treatment Process via RSM-CCD

The use of electrochemistry is a promising approach for the treatment of direct osmosis concentrate that contains a high concentration of organic pollutants and has high osmotic pressure, to achieve the safe discharge of effluent. This work addresses, for the first time, this major environmental challenge using perforated aluminum electrodes mounted in an electrocoagulation–flotation cell (PA-ECF). The design of the experiments, the modeling, and the optimization of the PA-ECF conditions for the treatment of DO concentrate rich in Pb were explored using a central composite design (CCD) under response surface methodology (RSM). Therefore, the CCD-RSM was employed to optimize and study the effect of the independent variables, namely electrolysis time (5.85 min to 116.15 min) and current intensity (0.09 A to 2.91 A) on Pb removal. Optimal values of the process parameters were determined as an electrolysis time of 77.65 min and a current intensity of 0.9 A. In addition to Pb removal (97.8%), energy consumption, electrode mass-consumed material, and operating cost were estimated as 0.0025 kWh/m3, 0.217 kg Al/m3, and 0.423 USD/m3, respectively. In addition, it was found that DO concentrate obtained from metallurgical wastewater can be recovered through PA-ECF (almost 94% Pb removal). This work demonstrated that the PA-ECF technique could became a viable process applicable in the treatment of DO concentrate containing Pb-rich for reuse.

A comprehensive study on opium pharmaceutical wastewater treatment in laboratory and semi-industrial scales

The wastewater of an opium pharmaceutical industry was successfully treated using a combined process of electrocoagulation/flotation (ECF), peroxone (H2O2/O3) and adsorption filter of granular activated carbon (GAC) in a three-step operation (ECF → H2O2/O3 → GAC), in a lab and semi-industrial scales. The effect of the operating parameters such as initial pH, current density, residence time, injection dose of H2O2, the ratio of H2O2/O3 and time of adsorption process was optimized in both scales. On the lab-scale, the removal efficiency of COD, Color, TDS, TSS, electrical power consumption, electrode consumption, and operating costs have been studied. In the ECF process, the maximum removal efficiencies of COD, color, TDS and TSS were 64%, 60%, 61% and 50%, respectively. The optimum pH, ozonation time, hydrogen peroxide concentration and the ratio of H2O2/O3 in the peroxone process are 8, 45 min, 900 mg/l, 0.3 H2O2/O3, respectively. After ECF and peroxone processes, the maximum removal efficiencies of COD and color increased up to 84% and 62% and after the adsorption process, the maximum removal efficiencies of COD, Color, TDS, and TSS increased up to 99.2%, 99.0, 99.0 and 99.1%, respectively. The performance of each reactor in the semi-industrial scale was also evaluated. After the treatment operation in the ECF → H2O2/O3 → GAC semi-industrial pilot reactor, the COD removal efficiency, Color, TDS and TSS of opium wastewater reached 96%, 99%, 99% and 99%, respectively. The excellent performance, as well as the low operating cost, confirmed that this integrated system is highly applicable for the advanced treatment of opium pharmaceutical industry wastewater.

Electrocoagulation-flotation for orange II dye removal: Kinetics, costs, and process variables effects

The textile industry is considered a threat to water resources due to the high demand for water and the dye-rich wastewater production. Electrocoagulation-flotation (EF) is an attractive option for treating textile dyes, providing efficient color removal in a simple, reliable, and economical way. However, variables involved in the EF process need to be analyzed with the purpose of increasing removal efficiency and decreasing operating cost. Therefore, this study evaluated variables through statistical models, such as the electrode surface area, HCl concentration in the initial treatment, initial treatment time, and nitric acid volume added to the wastewater. Aluminum plates in the honeycomb configuration were used as anode and cathode. EF tests occurred with an electric current of 2.5 A, at 450 rpm of agitation for 280 min, treating 2 L of wastewater with 21 mg L−1 of orange II dye. The electrode surface (p-value = 0.0271) and the nitric acid volume (p-value = 0.0080) were the most significant variables on the dye removal efficiency. All variables and their interactions were significant (p-value <0.05) on the dye removal per surface area and aluminum electrode consumption. The reaction kinetics of dye removal indicated that the reaction order was 1.6, with an average reaction rate constant k = 0.006 ± 0.001 mg-0.6L0.6min-1. Therefore, the variables did not affect the removal kinetics. Daily treatment costs ranged from 4723 to 16,629 US$, demonstrating that the voltage and electrode mass consumption influence the final cost of the EF process.

A systematic diagnosis of state of the art in the use of electrocoagulation as a sustainable technology for pollutant treatment: An updated review

Electrocoagulation (EC) and electrocoagulation-flotation (ECF) are of widespread interest owing to their effectiveness for the simultaneous abatement of a broad range of pollutants in drinking and waste waters, but their capability can vary significantly depending on the operating conditions. The effect of operating conditions on the performance of EC has been the subject of much debate over the last few decades. This review aims to focus on the application of EC/ECF processes for pollutants removal under different operating conditions, emphasizing the principal issues that compose the foundation of EC/ECF. It has been found that the current density (typically 1–20 mA/cm2), type of electrode (Al or Fe), and electrolysis time are the key process parameters that influence performance. Although some key mechanisms of pollutant abatement in EC/ECF processes have been identified, recent studies have begun to reveal how the underlying removal mechanisms using the EC/ECF processes depend on the nature of pollutant. Key mechanisms of pollutant abatement include charge neutralization, reduction–oxidation, and precipitation/co-precipitation. The development of improved or innovative cell designs, as well as systematic modeling of EC reactors, are needed. Future research focused on hybrid technologies with cost-effective energy supply may lead to innovative treatment options for wastewater treatment.

Recent advances and future prospects of electrochemical processes for microalgae harvesting

Over the years, algae have found wide scope of utility in a variety of environmentally beneficial processes like biofuel production, removal of heavy metals from wastewater sources for potential bioremediation, monitoring water pollution and source of animal nutrition. However, the conventional harvesting methods pose a set-back in terms of energy, cost and operational complications due to the small size of microalgae. Of all the processes, harvesting alone corresponds to approximately 30% of the total production costs. Recent advancements in the microalgal technology have brought many efficient techniques into use for improved recovery of microalgae. This review comprehends the development, principle, influencing parameters and directions to future research of one of the state-of-the-art approaches for harvesting microalgae, electrochemical technology. Though this area was previously explored for its application in wastewater treatment, it has lately gained momentum in the field of microalgae due to its economic efficiency. This paper highlights the three prime processes used to yield microalgae namely electroflocculation, electroflotation and a combined electrocoagulation-flotation (ECF) system. Several encroachments and strategies among these techniques have also been elucidated. The review focusses on the effect of most significant process controlling parameters such as reactor and electrode design, various surface properties of microalgae, current, pH, salinity and agitation that influence harvesting. In addition, the economy and energy aspects that emphasize the welfares of this technology over others have been extensively discussed. The overall work aims to provide an insight into the electrochemical methods, their challenges and opportunities that might be beneficial for carrying out further research and scope for industrial applications.

Electrocoagulation–flotation (ECF) for microalgae harvesting – A review

Harvesting has been recognized as a major bottleneck in any microalgae-based technology, making it a relevant research topic in the field. Among applicable technologies, electrocoagulation-flotation (ECF) has been devoted a lot of attention as an effective alternative to conventional metal salts addition. This paper reports and comments the relevant available literature on ECF, aiming at retrieving and assessing the main parameters affecting process performance by identifying their optimal ranges. After introducing the basic principle of ECF, the paper presents a qualitative analysis of the main factors (electrochemical parameters, microalgae and broth characteristics) and the way they affect the process performance. Then, a quantitative assessment has been performed based on the analysis of a dataset of 190 records from 29 research papers. Metal toxicity and process costs are addressed. Finally, guidelines for future experimentations are discussed in order to support and facilitate the further development of the ECF technology.