Removal of suspended solids and turbidity from marble processing wastewaters by electrocoagulation: comparison of electrode materials and electrode connection systems

Fabrication and performance analysis of keratin based-graphene oxide nanocomposite to remove dye from tannery wastewater

In recent years, nanomaterials and composites have become increasingly significant as adsorbents in the removal of dyes and phenolic contaminants from wastewater. This study presents the development and application of a keratin-based graphene oxide nanocomposite, distinguished by its enhanced biocompatibility, cost-effectiveness, and strong affinity for organic compounds, making it highly effective in reducing dyes within tannery effluent. The nanocomposite was prepared via solution casting method, with dispersibility, chemical bonding, and morphology analyzed by UV-Vis spectroscopy, FTIR, and SEM, respectively. Furthermore, investigations of the influence of several factors, such as contact time, pH, and adsorbent dosage on the optimization of the process were conducted. An observation indicated a reduction of approximately 98.8 % in dye content within 20 min, achieved through the use of an adsorbent dosage of 1.5 g/L, with the solution pH maintained at 5. Subsequently, adsorption kinetics and isotherm modelling were analyzed. The results revealed that the adsorption process follows the pseudo-second-order kinetics and Freundlich isotherm models. Hence, the adsorption could be explained as chemisorption with a multilayer adsorption mechanism. Notably, a substantial reduction in parameters such as Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) was also achieved up to 62 % and 79 %, respectively. Therefore, the developed adsorbent could be suggested as a viable candidate for eliminating dyes from the wastewater, especially from the tannery effluent.

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.

An overview of the application of electrocoagulation for mine wastewater treatment

One of the challenges of the twenty-first century is related to the discharge and disposal of mine effluents and wastewater resulting from mine dewatering, precipitation, and surface runoff in mines, especially acidic effluents that contain a variety of toxic and heavy metals and are the main sources of surface and groundwater pollution. Various physical, chemical, and biological methods have been developed and used to treat mine effluents. All proposed methods have their own disadvantages that make their use challenging. One of the new methods used for wastewater treatment is the electrical coagulation process, which has attracted the attention of researchers in recent years due to its advantages such as simplicity, environmental friendliness, and low cost. The present review focused on the applications of electrocoagulation for mine wastewater treatment as well as metals recovery. In addition, the main mechanisms, advantages, and weaknesses of electrocoagulation were reviewed.

Development of electrocoagulation process for wastewater treatment: optimization by response surface methodology

Electrocoagulation (EC) is a process used by supply of electric current with sacrificial electrodes for the removal of pollutant from wastewater. The study was experimentally investigated taking into account various factors such as pH (3–7.5), current (0.03–0.09 A), distance between the electrodes (1–2 cm), electrolytic concentration (1–3 g/L), and electrolysis time (20–60 min) which is impact on the % removal efficiency of color, chemical oxygen demand (COD), turbidity and determination of energy consumption used for aluminum (Al) electrode used. The surface response design process based on the central composite design (CCD) has been used to optimize different operational parameters for treatment of hospital wastewater using EC process. The % color, COD and turbidity removal, and energy consumption under different conditions were predicted with the aid of a quadratic model, as were the significance and their interaction with independent variables assessed by analysis of variance (ANOVA). The optimal conditions were obtained through mathematical and statistical methods to reach maximum % color, COD, and turbidity removal with minimum energy consumption. The results showed that the maximum removal of color (92.30%), COD (95.28%), and turbidity (83.33%) were achieved at pH–7.5, current–0.09A, electrolytic concentration–3g/L, distance between electrodes–2 cm and reaction time 60 min. This means that, the process of EC can remove pollutants from various types of wastewaters and industrial effluent under the various operating parameters.

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EC effective technology used to treat wastewater generated from hospital.

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Al was used as an electrode for hospital wastewater treatment using EC process.

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EC can eliminate pollutants from wastewater under various operating parameters.

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CCD used to optimize operational parameters for treatment of hospital wastewater.

Treatment of vegetable oil wastewater by a conventional activated sludge process coupled with electrocoagulation process

The present work aims to study chemical oxygen demand (COD), oil-grease, and color removal from vegetable oil wastewater by combined electrocoagulation and activated sludge processes. For this purpose, the sample was pretreated using electrocoagulation by various optimization parameters such as electrode type (Al-Al and Fe-Fe), current density (100-400 A/m² ), pH (2-8), and electrolysis time (15-180 min). The results showed that 89.3% of COD, 100% of oil-grease, and 66.2% of color were removed by electrocoagulation under the conditions of 300-A/m² current density, pH 2, and 180-min reaction time with Al-Al electrode pairs. Then, the effluent of electrocoagulation was treated by an activated sludge process. The results depicted that the activated sludge process was also effective for vegetable oil wastewater treatment and it enhanced 98.9% COD and 79.2% color removal efficiency. The effluent of the combined process was very clear, and its quality exceeded the direct discharge standard of the water pollution control regulation. The laboratory-scale test results indicate that the combined electrocoagulation and activated sludge process is feasible for the treatment of vegetable oil wastewater. PRACTITIONER POINTS: Vegetable oil wastewater was treated by combination of electrocoagulation and activated sludge processes. The combined electrocoagulation and activated sludge processes supplied 99.9% COD, 100% oil-grease, and 93.0% color removal efficiency. The laboratory-scale test results indicate that the combined EC-SBR processes were feasible for the treatment of vegetable oil wastewater.

Electrocoagulation treatment of shale gas drilling wastewater: Performance and statistical optimization

Shale gas drilling wastewater is a challenging waste stream generated in gas industries. It is a mixture of different organic and inorganic compounds. Treatment of this complex wastewater relies on a suitable technology for the removal of small suspended particles and dissolved elements. This study employed electrocoagulation (EC) as an efficient method for shale gas drilling wastewater pretreatment. The optimum operating conditions for turbidity, TOC, and Ca²⁺ removal were determined using a response surface methodology (RSM). The chloride (Cl^-) removal and residual iron of effluent in the EC process were also tested and evaluated. Based on the analysis of variance (ANOVA), the coefficient of determination (R²) was calculated and found to be above 0.86 for all the responses. The maximum removal efficiencies were found to be around 98.3%, 78.5%, and 56.5% for turbidity, TOC, and Ca²⁺ removal under the optimum conditions, respectively. In order to treat drilling wastewater by EC process both efficiently and economically, the following operating parameters are recommended: 318 A/m² for current density, 20 min for reaction time and 4.4 for initial pH. A total operation cost of 0.80 US$/m³ was estimated under these conditions.

Solar-driven, self-sustainable electrolysis for treating eutrophic river water: Intensified nutrient removal and reshaped microbial communities

River ecosystems are the most important resource of surface freshwater, but they have frequently been contaminated by excessive nutrient input of nitrogen (N) and phosphorus (P) in particular. An efficient and economic river water treatment technology that possesses the capacity of simultaneous N and P removal is urgently required. In this study, a solar-driven, self-sustainable electrolytic treatment was conducted in situ to intensify N and P removal from eutrophic river water. Solar panel was applied to provide the electrolysis setups with energy (voltage 10 ± 0.5 V), and the current density was controlled to be 0.06 ± 0.02 mA cm^-2. Results indicated that the average removal efficiencies of total N (TN) and total P (TP) under electrolysis conditions reached 72.4 ± 11.7 and 13.8 ± 5.3 mg m^-2 d^-1, which were 3.7- and 4.7-fold higher compared to untreated conditions. Enhanced TN removal mainly reflected the abatement of nitrate N (NO₃^--N) (80.6 ± 4.1%). The formation of ferric ions through the electro-dissolution of the sacrificial iron anode improved TP removal by coprecipitation with SPS. Combined high-throughput sequencing and statistical analyses revealed that electrolysis significantly reshaped the microbial communities in both the sediment-water interface and suspended sediment (SPS), and hydrogenotrophic denitrifiers (e.g., Hydrogenophaga) were highly enriched under electrolysis conditions. These findings indicated that in situ electrolysis is a feasible and effective technology for intensified nutrient removal from river water.

Importance of Combined Electrochemical Process Sequence and Electrode Arrangements: A Lab-scale Trial of Real Reverse Osmosis Landfill Leachate Concentrate

Reverse osmosis (RO) is a widely applied technique for wastewater effluent reuse and landfill leachate treatment. The latter generates a refractory RO leachate concentrate (ROLC), for which cost-effective treatment is required. This study focuses on a two-step electrochemical method consisting of aluminum-based electrocoagulation (EC), and simultaneous electrooxidation-electrocoagulation with a titanium-based lead dioxide (Ti/ß-PbO₂) anode and aluminum cathode (EO_EC) assembly. The sequence and electrode arrangements of the combined electrochemical process were investigated to determine the organic transformation, Ti/ß-PbO₂ anode viability, and energy consumption. Series-based EC-EO_EC decreased the total chemical oxygen demand (COD) from 8750 mg L^-1 to 380 mg L^-1, a 96% removal efficiency, in 3.5 hours at 141 A m^-2. Under a low energy consumption of 28.7 kWh kg_COD^-1, the ROLC biodegradability (BOD₅/COD) significantly increased from 0.015 to 0.530, which was ascribed to aromatic removal (e.g., -C=C) and an increase in -COOH functional groups. Furthermore, the rapid removal of natural organic matter and increase in pH elevation from EC suppressed the dissolution of Pb from the Ti/ß-PbO₂ anode during the subsequent EO_EC, thereby leaving 0.061 mg L^-1 in the ROLC after treatment. The treatment cost was 3.86 USD kg_COD^-1, which was approximately 34% lower than that of previously reported electrochemical processes for ROLC treatment. These findings obtained with a real RO concentrate provide a foundation for scaling up this new electrochemical treatment approach.

Electrochemical process employing scrap metal waste as electrodes for dye removal

In the present study, efficiency of electro-coagulation-flotation (EC-F) process using waste metal scrap of Al and Fe collected from construction and demolition waste of Indian Institute of Technology Madras (IIT M) campus for the removal of double azo bond dye Acid Red 66 (AR66) was studied. The key operating parameters such as current density and electrical conductivity were optimized individually with an initial dye concentration of 50 mg/L, at pH 7. Different electrode combinations and connection modes (parallel MP-P, series (MP-S, BP-S)) were tested, at pre-optimized conditions, in order to achieve better removal of AR66 dye with minimum energy consumption. Series connection in bipolar electrode mode (BP-S) showed better COD reduction from 164 mg/L to 26.2 mg/L with complete decolourization (BDL). Hybrid electrode system of Fe-Al-Fe-Al-Fe-Al showed maximum reduction of COD from 164 mg/L to 11.3 mg/L along with 86.3% TSS reduction and complete decolourization. LC-MS analysis showed the formation of intermediates with m/z 195, m/z 210.6 and m/z 159.3 due to the destruction of AR66 dye during electrolysis. Highest current efficiency (CE φ = 107%) was observed in case of hybrid electrode system compared to Al (φ = 30.1%) and Fe (φ = 98.3%) electrode system at similar operating conditions. Compared to the same electrode material as anode and cathode, use of appropriate hybrid electrode combination can improve the removal efficiency and reduce the energy consumption (ENC). The influence of aeration on the performance of the system was also studied. Aeration significantly improved the COD removal efficiency (98.3%) along with complete decolourization (100%). The use of waste metal scrap as electrodes reduced the overall cost of the treatment process from 1.6 $/m³ to 0.06 $/m³. Using waste metal scrap as electrodes not only reduces the metal accumulation in the environment but also reduces the cost of EC-F process.

A comprehensive review on contaminants removal from pharmaceutical wastewater by electrocoagulation process

The pharmaceuticals are emergent contaminants, which can create potential threats for human health and the environment. All the pharmaceutical contaminants are becoming enormous in the environment as conventional wastewater treatment cannot be effectively implemented due to toxic and intractable action of pharmaceuticals. For this reason, the existence of pharmaceutical contaminants has brought great awareness, causing significant concern on their transformation, occurrence, risk, and fate in the environments. Electrocoagulation (EC) treatment process is effectively applied for the removal of contaminants, radionuclides, pesticides, and also harmful microorganisms. During the EC process, an electric current is employed directly, and both electrodes are dissoluted partially in the reactor under the special conditions. This electrode dissolution produces the increased concentration of cation, which is finally precipitated as hydroxides and oxides. Different anode materials usage like aluminum, stainless steel, iron, etc. are found more effective in EC operation for efficient removal of pharmaceutical contaminants. Due to the simple procedure and less costly material, EC method is extensively recognized for pharmaceutical wastewater treatment over further conventional treatment methods. The EC process has more usefulness to destabilize the pharmaceutical contaminants with the neutralization of charge and after that coagulating those contaminants to produce flocs. Thus, the review places particular emphasis on the application of EC process to remove pharmaceutical contaminants. First, the operational parameters influencing EC efficiency with the electroanalysis techniques are described. Second, in this review emerging challenges, current developments and techno-economic concerns of EC are highlighted. Finally, future recommendations and prospective on EC are envisioned.

Application of response surface methodology as a new PID tuning method in an electrocoagulation process control case

In this work the application of response surface methodology (RSM) to proportional-integral-derivative (PID) controller parameter tuning for electrocoagulation (EC) treatment of pulp and paper mill wastewater was researched. Dynamic data for two controlled variables (pH and electrical conductivity) were obtained under pseudo random binary sequence (PRBS) input signals applied to manipulated variables (acid and supporting electrolyte flow rates). Third order plus time delay model parameters were evaluated through System Identification Toolbox™ in MATLAB^®. Four level full factorial design was applied to form a design matrix for three controller tuning parameters as factors and to evaluate statistical analysis of the system in terms of integral of square error (ISE), integral of absolute error (IAE), integral of time square error (ITSE) and integral of time absolute error (ITAE) performance criteria as response. Numerical values of the responses for the runs in the design matrices were determined using closed-loop PID control system simulations designed in Simulink^®. Optimum proportional gain, integral action and derivative action values for electrical conductivity control were found to be 1,500 s, 0 s and 16.4636 s respectively. Accordingly, the same optimization scheme was followed for pH control and optimum controller parameters were found to be -8.6970 s, 0.0211 s and 50 s, respectively. Theoretically optimized controller parameters were applied to batch experimental studies. Chemical oxygen demand (COD) removal efficiency and energy consumption of pulp and paper mill wastewater treatment by EC under controlled action of pH at 5.5 and electrical conductivity at 2.72 mS/cm was found to be 85% and 3.87 kWh/m³ respectively. Results showed that multi input-multi output (MIMO) control action increased removal efficiency of COD by 15.41% and reduced energy consumption by 6.52% in comparison with treatment under uncontrolled conditions.

Emerging usage of electrocoagulation technology for oil removal from wastewater: A review

Electrocoagulation is a simple and efficient treatment method involving the electrodissolution of sacrificial anodes and formation of hydroxo-metal products as coagulants, while the simultaneous production of hydrogen at the cathode facilitates the pollutant removal by flotation. Oil is one of the most important hydrocarbon products in the modern world. It can cause environmental pollution during various stages of production, transportation, refining and use. Electrocoagulation treatment is particularly effective for destabilization of oil-in-water emulsions by neutralizing charges and bonding oil pollutants to generated flocs and hydrogen bubbles. The development of electrocoagulation technologies provided a promising alternative for oil removal from wastewater. This paper presents a review of emerging electrochemical technologies used for treating oil-containing wastewater. It includes a brief description of the oily wastewater origin and characteristics. The treatment processes developed so far for oily wastewater and the electrocoagulation mechanisms are also introduced. This paper summarizes the current applications of electrocoagulation for oil removal from wastewater. The factors that influence the electrocoagulation treatment efficiencies as well as the process optimization and modeling studies are discussed. The state-of-the-art and development trends of electrocoagulation process for oil removal are further introduced.

Purification and detoxification of petroleum refinery wastewater by electrocoagulation process

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