Influence of operating parameters on phosphate removal from water by electrocoagulation using aluminum electrodes

Enhancing industrial swine slaughterhouse wastewater treatment: Optimization of electrocoagulation technique and operating mode

In this study, industrial swine slaughterhouse effluents were treated by an electrocoagulation process (EC) with aluminum and iron electrodes. Batch and semicontinuous operation were performed. EC tests were carried out in batch operating mode for 2.5 h using fixed current densities (j = 10, 20, and 30 mA cm-2) in sulfate and chloride media. At the laboratory scale, higher TOC removal efficiencies were observed using aluminum electrodes at 20 mA cm-2 without the addition of a supporting electrolyte (82.7%). However, the EC process with Fe electrodes consumed 43.6% less energy. After the best operating parameters were found at the laboratory scale, the process was tested as a semicontinuous prepilot process using a filter-press FM01-LC-type electrochemical reactor equipped with flat plate aluminum electrodes. In this stage, current densities and mean linear flow rates were assessed. The highest TOC removal efficiency of 72.7% (i.e., residual TOC concentration of 85.18 mg L-1) in the semicontinuous process was achieved by the application of j = 25 mA cm-2 and ur = 0.64 cm s-1 with an energy consumption of 19.80 kW h m-3. The residual COD and TP concentrations met the international standard limits. Moreover, complete decoloration and disinfection were accomplished. EDXRF, SEM, EDAX, XRD, and FTIR analyses indicated that pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

Ultrafine Kaolinite Removal in Recycled Water from the Overflow of Thickener Using Electroflotation: A Novel Application of Saline Water Splitting in Mineral Processing

The presence of ultrafine clay particles that are difficult to remove by conventional filtration creates many operational problems in mining processing systems. In this work, the removal of clay suspensions has been investigated using an electroflotation (EF) process with titanium electrodes. The results show that EF is a viable and novel alternative for removing ultrafine particles of kaolinite-type clay present in sedimentation tank overflows with low salt concentrations (<0.1 mol/L) in copper mining facilities based on the saline water splitting concept. Maximum suspended solid removal values of 91.4 and 83.2% in NaCl and KCl solutions, respectively, were obtained under the experimental conditions of the constant applied potential of 20 V/SHE, salinity concentration of 0.1 mol/L, and electroflotation time of 10 and 20 min in NaCl and KCl solutions, respectively. Furthermore, the visual evidence of particle aggregation by flocculation during the experiments indicates a synergy between EF and electrocoagulation (EC) that enhances the removal of ultrafine particles of kaolinite.

A novel electrocoagulation process with centrifugal electrodes for wastewater treatment: Electrochemical behavior of anode and kinetics of heavy metal removal

Anodic passivation is a key problem to impair the efficiency of in the electrocoagulation (EC) process. Process intensification of EC has attracted increasingly greater attention. In this work, a novel centrifugal electrode reactor was designed and applied in EC process to enhance the treatment of simulated heavy metal wastewater using aluminum anode. Results showed that the removal efficiency of heavy metals was significantly improved by the centrifugal electrodes, compared with the stationary electrodes. Electrochemical behavior of centrifugal electrodes was analyzed by an improved rotating disk electrode system. Anodic polarization behavior of aluminium showed a typical characteristic of dissolution in centrifugal electrodes, rather than passivation in static condition. Anode dissolution was controlled by the diffusion of Cl^- ion that was enhanced by centrifugal electrodes. Thus, anode passivation was reduced. In addition, the kinetics analysis indicated that the removal of heavy metals in EC by centrifugal electrodes conformed to Variable-Order-Kinetic (VOK) model based on the Langmuir adsorption.

Energy-efficient removal of carbamazepine in solution by electrocoagulation-electrofenton using a novel P-rGO cathode

In this study, carbamazepine (CBZ) decay in solution has been studied by coupling electrocoagulation with electro-Fenton (EC-EF) with a novel P-rGO/carbon felt (CF) cathode, aiming to accelerate the in-situ generation of •OH, instead of adding Fe²⁺ and H₂O₂. Firstly, the fabricated P-rGO and its derived cathode were characterized by XRD, SEM, AFM, XPS and electrochemical test (EIS, CV and LSV). Secondly, it was confirmed that the performance in removal efficiency and electric energy consumption (EEC) by EC-EF (k_obs=0.124 min^-1, EEC=43.98 kWh/kg CBZ) was better than EF (k_obs=0.069 min^-1, EEC=61.04 kWh/kg CBZ). Then, P-rGO/CF (k_obs=0.248 min^-1, EEC=29.47 kWh/kg CBZ, CE=61.04%) showed the best performance in EC-EF, among all studied heteroatom-doped graphene/CF. This superior performance may be associated with its largest layer spacing and richest C=C, which can promote the electron transfer rate and conductivity of the cathode. Thus, more H₂O₂ and •OH could be produced to degrade CBZ, and almost 100% CBZ was removed with k_obs being 0.337 min^-1 and the EEC was only 24.18 kWh/kg CBZ, under the optimal conditions (P-rGO loading was 6.0 mg/cm², the current density was 10.0 mA/cm², the gap between electrode was 2.0 cm). Additionally, no matter the influent is acidic, neutral or alkaline, no additional pH adjustment is required for the effluent of EC-EF. At last, an inconsecutive empirical kinetic model was firstly established to predict the effect of operating parameters on CBZ removal.

A review on electrocoagulation process for the removal of emerging contaminants: theory, fundamentals, and applications

Electrocoagulation (EC) is an excellent and promising technology in wastewater treatment, as it combines the benefits of coagulation, flotation, and electrochemistry. During the last decade, extensive researches have focused on removal of emerging contaminants by using electrocoagualtion, due to its several advantages like compactness, cost-effectiveness, efficiency, low sludge production, and eco-friendness. Emerging contaminants (ECs) are micropollutants found in trace amounts that discharging into conventional wastewater treatment (WWT) plants entering surface waters and imposing a high threat to human and aquatic life. Various studies reveal that about 90% of emerging contaminants are disposed unscientifically into water bodies, creating problems to public health and environment. The studies on removal of emerging contaminants from wastewater are by global researchers are critically reviewed. The core findings proved that still more research required into optimization of parameters, system design, and economic feasibility to explore the potential of EC combined systems. This review has introduced an innovative collection of current knowledge on electro-coagulation for the removal of emerging contaminants.

Pretreatment of Rubber Additives Processing Wastewater by Aluminum–Carbon Micro-Electrolysis Process: Process Optimization and Mechanism Analysis

The pretreatment of rubber additives processing wastewater was performed by Al/AC micro-electrolysis (ME). The single-factor experiments for the removal of COD and chroma were investigated. The Box-Behnken Design (BBD) was also applied to optimize the experimental conditions, and the fitted response surface model supplied highly significant quadratic models for the process. The COD removal efficiency reached 51.6% at an initial pH of 9.8, Al scrap dosage of 98.6 g L−1, Al/AC mass ratio of 0.26, and reaction time of 176 min, which was reasonably consistent with the predicated value of 51.9%. Moreover, we proposed a reaction mechanism of the process for the degradation of organic contaminants, and found that the removal of COD and chroma were mainly ascribed to the combination of active hydrogen [H] with strong chemical reactivity and flocculation of aluminum hydroxide. All these results showed that Al/AC ME is a promising pretreatment technique for this wastewater.

Electrocoagulation for nutrients removal in the slaughterhouse wastewater: comparison between iron and aluminum electrodes treatment

The poultry slaughterhouse wastewater has a high pollutant load, mainly organic matter, and nutrient content. The nitrogen and phosphorus discharge can cause eutrophication of the receiving water bodies. Electrocoagulation has been studied for several pollutants removal from different sources. The objective of this work was to evaluate the electrocoagulation process in the poultry slaughterhouse wastewater treatment using both iron and electrodes to remove total nitrogen and phosphorus. After the raw and polished wastewater characterisation, a 2³ Central Composite Rotatable Design was applied to evaluate the current density, initial pH, and electrocoagulation time influence on the nutrients removal and to find the optimum condition of nutrients removal. Once the optimum condition for nutrient removal was stablished, other physicochemical, microbiological, and ecotoxicological parameters, as well as the treatment cost, were investigated to determine which electrode material was the most efficient. For raw wastewater, applying the optimum treatment condition of 20 mA cm^-2 current density, initial pH 6.2, and time of 20 min, the nitrogen and phosphorus removal presented similar for both electrode materials. Besides being cheaper ($ 4.13 m^-3), iron electrode treatment presented better Chemical Oxygen Demand, oils and greases, solids, and ecotoxicity removal. For polished wastewater, the treatment with aluminum electrode was more efficient under the applied current density of 30 mA cm^-2, initial pH 8 and time of 10 min, obtaining the lowest cost $ 3.89 m^-3. In the iron electrode case, the final pH exceeds the limits established by local legislation requiring correction for release into water bodies.

Using Of Different Electrocoagulation Cell Configuration Parameters for Treating of Abu-Ghraib Dairy Products Wastewater

One of the most significant issues that people throughout the world will confront in the future years is a lack of clean and safe water. Anthropogenic activities, in particular, are polluting water systems. With rising population, urbanization, and climate change, water reuse has become a requirement in some areas of the globe, putting pressure on the development of effective water treatment methods for a range of contaminants. High biological oxygen demand (BOD), chemical oxygen demand (COD), oil-grease, and other pollutant loads define dairy sector effluent. Improved technology is required to address these issues. Electrocoagulation is a new type of therapy. It’s simple to use, ecologically friendly, and removes a wide range of contaminants from a variety of water types. The goal of this study was to see how operational factors such applied voltage, number of electrodes, distance between electrodes, electrode shape, and reaction time affected the electrocoagulation of actual dairy effluent. Aluminum and iron electrodes are used for this purpose. It was discovered that raising the applied voltage, reaction time, and decreasing the distance between electrodes improved COD, BOD, EC, TDS, color, and oil-grease removal efficiency. Moreover, switch between square, triangular electrodes and perforated cylindrical. The data show that electrocoagulation is effective at the maximum COD, BOD removal efficiency of first electrode at 20 holes of cylindrical shape is (88.03) %, (87.97) %, respectively. Second triangle shape is (100) %, (100) % respectively. Third square shape is (99.38) %, (99.42) % respectively. the maximum removal of TDS, EC efficiency of first electrode at 20 holes of cylindrical shape is (67.57) %, (62.34) %, respectively. Second triangle shape is (77.45) %, (67.68) % respectively. Third square shape is (81.96) %, (71.25) % respectively. The maximum color and oil-grease removal efficiency of first electrode at 20 holes of cylindrical shape is (100) %, (100) %, respectively. Second triangle shape is (100) %, (100) % respectively. Third square shape is (100) %, (100) % respectively. Electrocoagulation methods for the treatment of dairy wastewaters were shown to be successful in the research. Finally, the findings indicated that electrocoagulation is a technically feasible method for removing contaminants from dairy wastewaters.

Removal of inorganic pollutants using electrocoagulation technology: A review of emerging applications and mechanisms

Electrocoagulation (ECoag) technique has shown considerable potential as an effective method in separating different types of pollutants (including inorganic pollutants) from various sources of water at a lower cost, and that is environmentally friendly. The EC method's performance depends on several significant parameters, including current density, reactor geometry, pH, operation time, the gap between electrodes, and agitation speed. There are some challenges related to the ECoag technique, for example, energy consumption, and electrode passivation as well as its implementation at a larger scale. This review highlights the recent studies published about ECoag capacity to remove inorganic pollutants (including salts), the emerging reactors, and the effect of reactor geometry designs. In addition, this paper highlights the integration of the ECoag technique with other advanced technologies such as microwave and ultrasonic to achieve higher removal efficiencies. This paper also presents a critical discussion of the major and minor reactions of the electrocoagulation technique with several significant operational parameters, emerging designs of the ECoag cell, operating conditions, and techno-economic analysis. Our review concluded that optimizing the operating parameters significantly enhanced the efficiency of the ECoag technique and reduced overall operating costs. Electrodes geometry has been recommended to minimize the passivation phenomenon, promote the conductivity of the cell, and reduce energy consumption. In this review, several challenges and gaps were identified, and insights for future development were discussed. We recommend that future studies investigate the effect of other emerging parameters like perforated and ball electrodes on the ECoag technique.

FeS2/carbon felt as an efficient electro-Fenton cathode for carbamazepine degradation and detoxification: In-depth discussion of reaction contribution and empirical kinetic model

Carbamazepine (CBZ) decay by electro-Fenton (EF) oxidation using a novel FeS₂/carbon felt (CF) cathode, instead of a soluble iron salt, was studied with the aim to accelerate the reaction between H₂O₂ and ferrous ions, which helps to produce more hydroxyl radicals (^•OH) and eliminate iron sludge. First, fabricated FeS₂ and its derived cathode were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Anodes were then screened, with DSA (Ti/IrO₂-RuO₂) showing the best performance under EF oxidation regarding CBZ degradation and electrochemical characterization. Several operating parameters of this EF process, such as FeS₂ loading, current density, gap between electrodes (GBE), initial [CBZ], and electrolyte type, were also investigated. Accordingly, a nonconsecutive empirical kinetic model was established to predict changes in CBZ concentration under the given operational parameters. The contribution of different oxidation types to the EF process was calculated using kinetic analysis and quenching experiments to verify the role of the FeS₂-modified cathode. The reaction contributions of anodic oxidation (AO), H₂O₂ electrolysis (EP), and EF oxidation to CBZ removal were 12.81%, 7.41%, and 79.77%, respectively. The ^•OH exposure of EP and EF oxidation was calculated, confirming that ^•OH exposure was approximately 22.45-fold higher using FeS₂-modified CF. Finally, the 19 intermediates formed by CBZ degradation were identified by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. Accordingly, four CBZ degradation pathways were proposed. ECOSAR software was used to assess the ecotoxicity of intermediates toward fish, daphnia, and green algae, showing that this novel EF oxidation process showed good toxicity reduction performance. A prolonged EF retention time was proposed to be necessary to obtain clean and safe water, even if the targeted compound was removed at an earlier time.

Optimization of electrocoagulation process parameters for enhancing phosphate removal in a biofilm-electrocoagulation system

This study aimed to enhance the removal of phosphate in synthetic rural sewage by using a continuous electrocoagulation (EC) combined with biofilm process in an integrated system. Characteristic indexes of biofilm process effluent covering pH, dissolved oxygen (DO), suspended solids (SS), chemical oxygen demand (COD) and phosphate maintained a narrow fluctuation range and tended not readily to influence the phosphate removal of subsequent electrocoagulation. Three parameters including inter-electrode distance, current intensity and reaction time were selected to investigate the performance of enhancing phosphate removal. On the strength of single-factor tests, the Box-Behnken design (BBD) coupled with response surface methodology (RSM) was applied to investigate the individual and mutual interaction impacts of the major operating parameters and to optimize conditions. The optimum conditions were found to be inter-electrode distance of 1.8 cm, current density of 2.1 mA/cm² and EC reaction time of 34 min, and phosphate removal efficiency of 90.24% was achieved along with less than 1 mg/L in case of periodic polarity switching mode, which raised removal efficiency by 10.10% and reduced operating cost by 0.13 CNY/g PO₄^- compared to non-switching mode. The combination of biofilm processing and electrocoagulation treatment was proven to be a valid and feasible method for enhancing phosphate removal.

Industrial wastewater treatment using magnesium electrocoagulation in batch and continuous mode

In the present study, the electrocoagulation (EC) performance of a Mg-Mg system was applied for the industrial wastewater treatment, from an industrial park that covers different activities such as: food, automotive, pharmaceutical, chemistry and cosmetics, after primary clarification. The effects of major operating parameters such as pH, reaction time, and current density were investigated for chemical oxygen demand (COD), color, and turbidity removal efficiency. The batch system was found convenient, achieving 63.52% COD, 96% color, and 99.32% turbidity removal at optimized operating conditions of pH 7.12, reaction time of 75 min, and current density of 201.5 A/m². On the other hand, for continuous EC, the process removed approximately 46.58%, 95.96%, and 87.19% of the COD, color, and turbidity respectively, at 90 min of retention time, current density 440 A/m², and a rate of 20 mL/min. Additionally, concerning nutrient removal (N and P), the EC system with Mg electrodes was highly efficient; batch treatment removed 97% of total phosphorus and 67% of ammoniacal nitrogen, whereas the continuous treatment removed 98.5% of total phosphorus and 83% of ammoniacal nitrogen. The sludge characterization before and after EC treatment was made by SEM, EDS, Fluorescence spectroscopy, IR spectroscopy. Minerals such as chlorite, crossite, richterite, pyroaurite, langbeinite as weel as aliphatic and polysubstituted aromatics compounds, sulfates and phosphates inorganic ions, and organic phosphorus were reduced. The energy cost in the batch EC is US$0.05/m³. A numerical CFD model was used to estimate the velocity fields and guarantee the presence of turbulent kinetic energy within a continuous flow reactor.

Treatment of dairy industry wastewater by combined aerated electrocoagulation and phytoremediation process

As dairy industries has been emerged as one of the most rapidly developing industry in both small as well as large scale, the volume of effluent generated is also very high. In the present study, aerated electrocoagulation combined with phytoremediation treatment was conducted in dairy industry wastewater. Electrocoagulation was performed with aluminium and iron electrodes and effect of various operating parameters such as electrode combination, pH, and voltage were tested. Electrocoagulation was found effective at neutral pH and its efficiency increased with increase in applied voltage. The maximum COD removal efficiency of 86.4% was obtained in case of Al-Fe electrode combination with aeration at 120 min reaction time, initial pH 7, voltage 5 V. Significant growth of Canna indica was observed in electrocoagulation treated wastewater compared to raw dairy wastewater. COD removal of 97% was achieved when combined electrocoagulation and phytoremediation process was used. Thus, it proves to be a proficient method for the treatment of dairy industry wastewater. In addition to the above, bacterial toxicity tests were performed to investigate the toxic nature of wastewater and the results showed that both treated and untreated wastewater favoured bacterial growth.

Removal of natural organic matter from aqueous solutions using electrocoagulation pulsed current: optimization using response surface methodology

The use of the pulsed current can be an alternative to decrease the electrode polarization, as well as achieving lower energy consumption. This study investigated the electrocoagulation through pulsed current for the removal of natural organic matter from water. The experiments were carried out using Box-Behnken factorial design with the response surface methodology for the design of experiments, modeling and interpreting of the results. The electrocoagulation cell consisted of an acrylic reactor with 4 L capacity with four electrodes of aluminum, in parallel connection mode. The experimental independent variables studied were: current density (5.5 to 44.5 A m^-2), electrodes spacing (2 to 7.6 mm), stirring rate (200 to 1,000 rpm), frequency (500 to 5,000 Hz), humic acid concentration (5 to 20 mg L^-1) and NaCl (100 to 300 mg L^-1) as supporting electrolyte, evaluating the residual apparent color (RAC) and electric energy consumption (EEC). The pH of the solution increased during the experiments, reaching basic values. The response surface regression procedure was employed to fit the second-order polynomial, and the model fitted well to the obtained values, reaching R² 0.9995 (RAC) and R² 0.9989 (EEC). The lowest RAC was 11.8 Hazen units (96.2% color removal), where the EEC was 0.393 kWh m^-3.

Combined Electrocoagulation and Chemical Coagulation in Treating Brewery Wastewater

Significant over-strength discharge fees are often imposed on breweries for the disposal of high-strength effluent to sanitary sewers. In this research work, the removal performances of electrocoagulation (EC) compared with operating electrocoagulation and chemical coagulation in sequence (EC-CC) or vice-versa (CC-EC) was examined to determine the capability of treatment in reducing the strength of the wastewater. Optimal operating parameters regarding electrolysis time, initial pH, and applied power were determined in conjunction with nutrient removal performance, electrode consumption and energy usage. Combined EC-CC treatment has been demonstrated to be economically feasible for brewery wastewater applications from an energy consumption perspective due to the efficiency of nutrient removal and the reduction of sewer discharge costs. Treatment by EC-CC at 5 W for 20 min using aluminum electrodes resulted in enhanced and consistent removal efficiencies of 26%, 74%, 76%, and 85% for chemical oxygen demand (COD), reactive phosphorous (RP), total phosphorous (TP) and total suspended solids (TSS), respectively. Energy consumption was the main contributor to operating cost. By considering potential recovered over-strength discharge fees (ODF), EC-CC treatment is economically feasible and beneficial in a brewery wastewater application. The results demonstrated the effectiveness of the CC-EC process to remove phosphorous, organics and solids from brewery wastewater at lower power supply, so that the recovered ODF cost for CC-EC at 5 W-EC is 23% higher than at 10 W-EC.

Prepartion and application of novel blast furnace dust based catalytic-ceramic-filler in electrolysis assisted catalytic micro-electrolysis system for ciprofloxacin wastewater treatment

Blast furnace dust (BFD), a hazardous metallurgical waste, is generated during the iron-making process and consists plenty of Fe and C. This study is among the first to apply BFD in catalytic-ceramic-filler (CCF) preparation and degradation of ciprofloxacin (CIP). The novel BFD based Fe-Ni CCF obviously enhanced the removal of CIP (from around 42%-72% after 3 h) in comparation with troditional Fe-C ceramic-filler(CF). The Fe-Ni CCF was further applied in a coupled system of electrolysis assisted catalytic micro-electrolysis (E-CME) process for CIP wastewater treatment. Under optimal operating conditions (iron rod as anode, voltage of 10v and HRT of 3 h), nearly 97% of CIP, 90% of total organic carbon (TOC) and 99% of total phosphorus (TP) were removed by E-CME process in near-neutral solution. The degradation mechanism analysis by LC-MS revealed that polyhydroxy sub-stituted, piperazine rings cleavage and so on were the main reaction of CIP in E-CME process. Additionally, the chemical oxygen demand (COD) residue after E-CME process could be effectively eliminated by up-flow anaerobic filter (UAF), owing to the significant improvement of wastewater biodegradability by E-CME pretreatment. This study provides a new way for co-friend recycling of BFD and a highly-efficient, cost-sffective technology for CIP wastewater treatment.

Domestic wastewater treatment by real-scale electrocoagulation process

In this study, domestic wastewaters originating from a settlement with a population of 17,500 were treated by electrocoagulation process in a real-scale EC plant and the economic applicability of the process was investigated. The removal efficiencies of control parameters in the influent and effluent of the real-scale treatment plant such as suspended solids (SS), biological oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and changes of pH and conductivity parameters were monitored for 12 months. The obtained data were evaluated according to European Urban Wastewater Treatment Directive, Turkish Water Pollution Control Regulation and Turkish Urban Wastewater Treatment Regulation. According to the results obtained, the removal efficiencies of the pollutant parameters were achieved in the range of 72-83% for SS, 67-80% for COD, 69-81% for BOD, 21-47% for TN and 27-46% for TP. Considering the Turkish wastewater discharge regulations, it can be concluded that the discharge standards for SS, COD and BOD parameters were achieved while they were not achieved in certain periods for TN and TP. In addition, the energy consumption and the operating cost of this real-scale plant were determined to be 0.49-0.54 kWh/m³ and 0.24-0.28 EUR/m³, respectively.

Phosphorus removal from livestock effluents: recent technologies and new perspectives on low-cost strategies

Phosphorus is an essential element in the food production chain, even though it is a non-renewable and limited natural resource, which is going to run out soon. However, it is also a pollutant if massively introduced into soil and water ecosystems. This study focuses on the current alternative low-cost technologies for phosphorus recovery from livestock effluents. Recovering phosphorus from these wastewaters is considered a big challenge due to the high phosphorus concentration (between 478 and 1756 mg L^-1) and solids content (> 2-6% of total solids). In particular, the methods discussed in this study are (i) magnesium-based crystallization (struvite synthesis), (ii) calcium-based crystallization, (iii) electrocoagulation and (iv) biochar production, which differ among them for some advantages and disadvantages. According to the data collected, struvite crystallization achieves the highest phosphorus removal (> 95%), even when combined with the use of seawater bittern (a by-product of sea salt processing) instead of magnesium chloride pure salt as the magnesium source. Moreover, the crystallizer technology used for struvite precipitation has already been tested in wastewater treatment plants, and data reported in this review showed the feasibility of this technology for use with high total solids (> 5%) livestock manure. Furthermore, economic and energetic analyses here reported show that struvite crystallization is the most practicable among the low-cost phosphorus recovery technologies for treating livestock effluents.

Treatment of re-refining effluent from lubricating oils by combining electrocoagulation and coagulation-flocculation processes

A combination of electrocoagulation and coagulation-flocculation processes was used for re-refining effluent from lubricating oils. The efficiency of the process was evaluated based on the chemical oxygen demand (COD), color, and turbidity of the refined effluent. Electrocoagulation (EC) and coagulation-flocculation parameters, such as the initial pH (3.00, 4.41, and 9.00), and current density (4, 9, and 16 A/m²), and the use of aluminum polychloride coagulant and superfloc A300 flocculant were studied. EC performed at pH 9, with a current density of 16 A/m² and 7 V, resulted in removal efficiencies of 85.14%, 99.81%, and 99.85%, for COD, color, and turbidity, respectively. The removal efficiencies increased to 96%, 99.87%, and 99.94% for COD, color, and turbidity, respectively, by the further coagulation-flocculation treatment in the presence of 13.8 mg/L aluminum polychloride coagulant and 80 mg/L Superfloc A300 flocculant.

Are pharmaceuticals removal and membrane fouling in electromembrane bioreactor affected by current density?

Pharmaceutical active compounds (PhACs) have been detected at significant concentrations in various natural and artificial aquatic environments. In this study, electro membrane bioreactor (eMBR) technology was used to treat simulated municipal wastewater containing widely-used pharmaceuticals namely amoxicillin (AMX), diclofenac (DCF) and carbamazepine (CBZ). The effects of varying current density on the removal of PhACs (AMX, DCF and CBZ) and conventional pollutants (chemical oxygen demand (COD), dissolved organic carbon (DOC), humic substances, ammonia nitrogen (NH₄-N), nitrate nitrogen (NO₃-N) and orthophosphate (PO₄-P) species) were examined. High COD and DOC removal efficiencies (~100%) were obtained in all the experimental runs regardless of applied current density. In contrast, enhanced removal efficiencies for AMX, DCF and CBZ were achieved at high current densities. Membrane fouling rate in eMBR with respect to conventional MBR was reduced by 24, 44 and 45% at current densities of 0.3, 0.5 and 1.15 mA/cm², respectively. The mechanism for pharmaceutical removal in this study proceeded by: (1) charge neutralization between negatively-charged pharmaceutical compounds and positive electro-generated aluminium coagulants to form larger particles and (2) size exclusion by membrane filtration.

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.

Effective adsorption of trace phosphate and aluminum in realistic water by carbon nanotubes and reduced graphene oxides

In this study, carbon nanotube (CNT) and reduced graphene oxide (rGO) were studied for their potentials as novel adsorbents for trace concentrations of phosphorus and aluminum in water and wastewater. Static adsorption results demonstrated that CNT and rGO employed in this study removed up to 65.6% of total dissolved Al and 98.9% of P from a natural surface water and a secondary wastewater effluent. Hydrogen-bonding interactions between CNT/rGO and oxyanions were hypothesized to contribute to the adsorption process. Accordingly, acetaminophen (AAP), a pharmaceutical compound known to form hydrogen bonding with CNT, was spiked into the real water as a competitor for P and Al adsorption. Subsequent sorption results showed that the presence of AAP reduced Al and P adsorption by CNT and rGO by 9.3%-18.4% and 11.2%-18.2%, respectively. These results suggest that hydrogen bonding interactions with CNT/rGO influenced the adsorption of P and Al species. In addition, pH effect investigation on Al/P removal further verified the above opinion. Overall, this study provided important evidence and insights into CNT/rGO adsorption of P and Al species from water and wastewater, which expanded our understanding on the ability of carbonaceous nanomaterials for advanced water and wastewater treatment.

Simultaneous removal of Cd2+ and Zn2+ from aqueous solution using an upflow Al-electrocoagulation reactor: optimization by response surface methodology

The presence of heavy metals in the environment has increased, and cadmium (Cd) and zinc (Zn) are considered to be among the most dangerous. An upflow Al-electrocoagulation reactor was used to remove Cd²⁺ and Zn²⁺ ions from aqueous media. The system consisted of perforated aluminum circular electrodes for fluid distribution with elimination of external agitation. The effect of different parameters, i.e. current intensity, electrolysis time, concentration of Cd²⁺ and Zn²⁺ ions and electrolytic support dose were optimized by response surface methodology. The results indicated that increasing the current intensity and the electrolysis time had a positive effect on the elimination efficiency of the pollutant ions. Likewise, increasing the dose of electrolytic support and decreasing the concentration of the pollutants improved the efficiency of the system. The optimal results were: current intensity of 0.4 A, electrolysis time of 40 min, ion concentration of 44.6 mg·L^-1 and electrolytic support dose of 0.56 mg·L^-1, with the maximum elimination percentages of 96 ± 3.8% and 96 ± 2.7% for Cd²⁺ and Zn²⁺, respectively. This study showed that the electrocoagulation process in an upflow electrocoagulation reactor could be successfully applied to remove pollutants from water.

A 3DBER-S-EC process for simultaneous nitrogen and phosphorus removal from wastewater with low organic carbon content

A new process was proposed by integrating a three-dimensional biofilm electrode reactor with sulfur autotrophic denitrification and electrocoagulation within the same reactor. The results indicated that under the wastewater influent condition of NO₃^--N = 30 mg/L, COD = 45 mg/L, total phosphorus (TP) = 1.5 mg/L, hydraulic retention time (HRT) = 8 h, and I = 400 mA, the NO₃^--N and TP removal of the proposed process reached 89.8% and 83.0%, respectively. It was observed that the electrocoagulation process improved phosphorus removal, while the simultaneous existence of heterotrophic, hydrogen, sulfur and iron autotrophic denitrifying bacteria led to enhanced and stabilized nitrogen removal. The Sulfuritalea hydrogenivorans sk43H and Sulfuricella denitrificans skB26 were found as the dominant denitrifying bacteria in the electrocoagulation section and the section of biofilm electrode with sulfur filler, respectively. As compared to conventional technologies, the proposed new process can achieve simultaneous, stable and deep nitrogen and phosphorus removal from wastewater treatment plant effluent with low organic carbon content.

Comparative performance of anodic oxidation and electrocoagulation as clean processes for electrocatalytic degradation of diazo dye Acid Brown 14 in aqueous medium

In this study, a laboratory scale for the treatment of a recalcitrant and toxic synthetic wastewater containing diazo dye, acid brown 14 (AB-14) has been comparatively performed by two electro-catalytic treatment processes, namely anodic oxidation (AO) and electrocoagulation (EC) using a new batch electrochemical cell. Additionally, the influence of several operating parameters such as; current density (j), initial dye concentration (C_o), NaCl concentration (C_N), and pH on the color removal efficiency and chemical oxygen demand (COD) are evaluated. The powerful capability of the AO and EC of AB-14 which related to the mechanistic reaction pathway is shown. The poor degradation is ascribed to higher C_o and pH, while the enhancement of j and C_N is responsible for better degradation of AB-14 dye. The results indicate that the EC is more effective than AO under the same operational condition. A kinetic model is developed for evaluation of the pseudo-first-order-rate constant (k_app) as a function of various operational parameters. The results emphasize the high efficiency of AO and EC and the clean processes which are hopeful alternative for the treatment of the large volume wastewater of the textile industry.

Energy efficient electrocoagulation using a new flow column reactor to remove nitrate from drinking water - Experimental, statistical, and economic approach

In this investigation, a new bench-scale electrocoagulation reactor (FCER) has been applied for drinking water denitrification. FCER utilises the concepts of flow column to mix and aerate the water. The water being treated flows through the perforated aluminium disks electrodes, thereby efficiently mixing and aerating the water. As a result, FCER reduces the need for external stirring and aerating devices, which until now have been widely used in the electrocoagulation reactors. Therefore, FCER could be a promising cost-effective alternative to the traditional lab-scale EC reactors. A comprehensive study has been commenced to investigate the performance of the new reactor. This includes the application of FCER to remove nitrate from drinking water. Estimation of the produced amount of H₂ gas and the yieldable energy from it, an estimation of its preliminary operating cost, and a SEM (scanning electron microscope) investigation of the influence of the EC process on the morphology of the surface of electrodes. Additionally, an empirical model was developed to reproduce the nitrate removal performance of the FCER. The results obtained indicated that the FCER reduced the nitrate concentration from 100 to 15 mg/L (World Health Organization limitations for infants) after 55 min of electrolysing at initial pH of 7, GBE of 5 mm, CD of 2 mA/cm², and at operating cost of 0.455 US $/m³. Additionally, it was found that FCER emits H₂ gas enough to generate a power of 1.36 kW/m³. Statistically, the relationship between the operating parameters and nitrate removal could be modelled with R² of 0.848. The obtained SEM images showed a large number dents on anode's surface due to the production of aluminium hydroxides.

Iron removal, energy consumption and operating cost of electrocoagulation of drinking water using a new flow column reactor

The goal of this project was to remove iron from drinking water using a new electrocoagulation (EC) cell. In this research, a flow column has been employed in the designing of a new electrocoagulation reactor (FCER) to achieve the planned target. Where, the water being treated flows through the perforated disc electrodes, thereby effectively mixing and aerating the water being treated. As a result, the stirring and aerating devices that until now have been widely used in the electrocoagulation reactors are unnecessary. The obtained results indicated that FCER reduced the iron concentration from 20 to 0.3 mg/L within 20 min of electrolysis at initial pH of 6, inter-electrode distance (ID) of 5 mm, current density (CD) of 1.5 mA/cm², and minimum operating cost of 0.22 US $/m³. Additionally, it was found that FCER produces H₂ gas enough to generate energy of 10.14 kW/m³. Statistically, it was found that the relationship between iron removal and operating parameters could be modelled with R² of 0.86, and the influence of operating parameters on iron removal followed the order: C₀>t>CD>pH. Finally, the SEM (scanning electron microscopy) images showed a large number of irregularities on the surface of anode due to the generation of aluminium hydroxides.

A comprehensive review of electrocoagulation for water treatment: Potentials and challenges

Electrocoagulation is an effective electrochemical approach for the treatment of different types of contaminated water and has received considerable attention in recent years due its high efficiency in dealing with numerous stubborn pollutants. It has been successful in dealing with organic and inorganic contaminants with negligible or almost no generation of by-product wastes. During the past decade, vast amount of research has been devoted to utilizing electrocoagulation for the treatment of several types of wastewater, ranging from polluted groundwater to highly contaminated refinery wastewater. This paper offers a comprehensive review of recent literature that has been dedicated to utilizing electrocoagulation for water treatment, focusing on current successes on specific applications in water and wastewater treatment, as well as potentials for future applications. The paper examines such aspects as theory, potential applications, current challenges, recent developments as well as economical concerns associated with the technology. Most of the recent EC research has been focusing on pollutant-specific evaluation without paying attention to cell design, process modeling or industrial applications. This review attempts to highlight the main achievements in the area and outlines the major shortcomings with recommendations for promising research options that can enhance the technology and broaden its range of applications.

Application of electrochemical processes to membrane bioreactors for improving nutrient removal and fouling control

Membrane bioreactor (MBR) technology is becoming increasingly popular as wastewater treatment due to the unique advantages it offers. However, membrane fouling is being given a great deal of attention so as to improve the performance of this type of technology. Recent studies have proven that the application of electrochemical processes to MBR represents a promising technological approach for membrane fouling control. In this work, two intermittent voltage gradients of 1 and 3 V/cm were applied between two cylindrical perforated electrodes, immersed around a membrane module, at laboratory scale with the aim of investigating the treatment performance and membrane fouling formation. For comparison purposes, the reactor also operated as a conventional MBR. Mechanisms of nutrient removal were studied and membrane fouling formation evaluated in terms of transmembrane pressure variation over time and sludge relative hydrophobicity. Furthermore, the impact of electrochemical processes on transparent exopolymeric particles (TEP), proposed as a new membrane fouling precursor, was investigated in addition to conventional fouling precursors such as bound extracellular polymeric substances (bEPS) and soluble microbial products (SMP). All the results indicate that the integration of electrochemical processes into a MBR has the advantage of improving the treatment performance especially in terms of nutrient removal, with an enhancement of orthophosphate (PO₄-P) and ammonia nitrogen (NH₄-N) removal efficiencies up to 96.06 and 69.34 %, respectively. A reduction of membrane fouling was also observed with an increase of floc hydrophobicity to 71.72 %, a decrease of membrane fouling precursor concentrations, and, thus, of membrane fouling rates up to 54.33 %. The relationship found between TEP concentration and membrane fouling rate after the application of electrochemical processes confirms the applicability of this parameter as a new membrane fouling indicator.

Treatment of highly concentrated tannery wastewater using electrocoagulation: Influence of the quality of aluminium used for the electrode

This paper deals with the ability of electrocoagulation (EC) to remove simultaneously COD and chromium from a real chrome tanning wastewater in a batch stirred electro-coagulation cell provided with two aluminium-based electrodes (aluminium/copper/magnesium alloy and pure aluminium). Effects of operating time, current density and initial concentration of Cr(III) and COD have been investigated. The concentrations of pollutants have been successfully reduced to environmentally acceptable levels even if the concentrated effluent requires a long time of treatment of around 6h with a 400A/m(2) current density. The aluminium alloy was found to be more efficient than pure aluminium for removal of COD and chromium. Dilution of the waste has been tested for treatment: high abatement levels could be obtained with shorter time of treatment and lower current densities. Energy consumption of the electrocoagulation process was also discussed. The dilution by half of the concentrated waste leads to a higher abatement performance of both COD and chromium with the best energy efficiency.

Can electrocoagulation process be an appropriate technology for phosphorus removal from municipal wastewater?

This paper evaluated a novel pilot scale electrocoagulation (EC) system for improving total phosphorus (TP) removal from municipal wastewater. This EC system was operated in continuous and batch operating mode under differing conditions (e.g. flow rate, initial concentration, electrolysis time, conductivity, voltage) to evaluate correlative phosphorus and electrical energy consumption. The results demonstrated that the EC system could effectively remove phosphorus to meet current stringent discharge standards of less than 0.2mg/L within 2 to 5min. This target was achieved in all ranges of initial TP concentrations studied. It was also found that an increase in conductivity of solution, voltages, or electrolysis time, correlated with improved TP removal efficiency and reduced specific energy consumption. Based on these results, some key economic considerations, such as operating costs, cost-effectiveness, product manufacturing feasibility, facility design and retrofitting, and program implementation are also discussed. This EC process can conclusively be highly efficient in a relatively simple, easily managed, and cost-effective for wastewater treatment system.