Electrooxidation Research Articles

Electrochemical oxidation of azo dyes degradation by RuO2–IrO2–TiO2 electrode with biodegradation Aeromonas hydrophila AR1 and its degradation pathway: An integrated approach

Azo dyes are the most varied class of synthetic chemicals with non-degradable characteristics. They are complex compounds made up of many different parts. It was primarily utilized for various application procedures in the dyeing industry. Therefore, it's crucial to develop an economical and environmentally friendly approach to treating azo dyes. Our present investigation is an integrated approach to the electrooxidation (EO) process of azo dyes using RuO2–IrO2–TiO2 (anode) and titanium mesh (cathode) electrodes, followed by the biodegradation process (BD) of the treated EO dyes. Chemical oxygen demand (COD) removal efficiency as follows MB (55%) ≥ MR (45%) ≥ TB (38%) ≥ CR (37%) correspondingly. The fragment generated during the degradation process which was identified with high-resolution mass spectrometry (HRMS) and its degradation mechanism pathway was proposed as demethylation reaction and N–N and C–N/C–S cleavage reaction occurs during EO. In biodegradation studies by Aeromonas hydrophila AR1, the EO treated dyes were completely mineralized aerobically which was evident by the COD removal efficiency as MB (98%) ≥ MR (92.9%) ≥ TB (88%) ≥ CR (87%) respectively. The EO process of dyes produced intermediate components with lower molecular weights, which was effectively utilized by the Aeromonas hydrophila AR1 and resulted in higher degradation efficiency 98%. We reported the significance of the enhanced approach of electrochemical oxidation with biodegradation studies in the effective removal of the pollutants in dye industrial effluent contaminated water environment.

PMS coupled Mn(II) mediated electrochemistry processes (E-Mn(II)-PMS) on the efficient RB19 wastewater treatment: Focus on the regulation and reinforcement of Mn(III)/Mn(II)

Dye wastewater, represented by reactive blue 19 (RB19), severely threatens the aquatic ecological environment and human health, such that an efficient RB19 wastewater treatment technology should be urgently developed. Based on manganese ion-mediated electrochemistry, PMS was introduced to develop a novel electrocatalytic system (E-Mn(II)-PMS) that can efficiently remove and degrade RB19. The synergistic effect between E, Mn(II), and PMS was verified in this study through comparative experiments of a wide variety of systems. The removal efficiency of RB19 reached 95.1% in 50 min under reasonable power consumption (3.29 kWh/m3). Moreover, the effects exerted by different operating conditions (e.g., initial pH, current density, RB19 concentration, Mn(II) concentration, as well as PMS concentration) and water matrix on the degradation efficiency of RB19 were explored through single factor experiments. The active oxidation species (ROS) and their contribution rate for the degrading and removing RB19 were studied through quenching experiments, EPR experiments, TMT-15 metal capture experiments, as well as PP complexation experiments. The role played by non-free radicals took on critical significance in the oxidation removal of RB19, which comprised direct electro oxidation, Mn(III) oxidation, and 1O2 oxidation. The enhancement effect of free radicals (SO4·− and HO∙) was not sufficiently significant, with a low degree of contribution. The oxidation effect of the anode facilitated the conversion of Mn (II) to Mn (III), which was employed in PMS for expediting the production of 1O2. The reduction effect of the cathode blocked the production of Mn (IV) as a side reaction, such that the continuous circulation of manganese ions between divalent and trivalent was promoted. Meanwhile, the cathode reacted with PMS to generate a small part of SO4·− and HO∙. In addition, the reaction active site of RB19 was predicted, and a possible degradation pathway was proposed in accordance with the mass spectrometry results and the DFT calculation. As revealed by the results of the QSAR analysis and the plant culture experiments, the biological toxicity of RB19 was markedly reduced after the sample was administrated with E-Mn(II)-PMS. E-Mn(II)-PMS-mediated electrochemical technology displays several advantages (e.g., high efficiency, low consumption, recyclability, wide pH window, and strong applicability) while showing promising market development and utilization for treating dye wastewater.

Copper nanoparticle modified chain-like platinum nanocomposites for electro-oxidation of C1-, C2-, and C3- type alcohols

The design of efficient, durable and inexpensive electrocatalysts is of great importance in the development of direct alcohol fuel cells, a clean energy source. In this context, in this study, chain-like platinum-copper (PtCu) nanoparticles were synthesised by chemical reduction method to be used in alcohol oxidation studies. X-Ray diffraction analysis (XRD) of the synthesised nanoparticles showed the formation of PtCu crystal structure. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) analysis showed the formation of chain-like PtCu structures and particles with an average size of 4.04 nm. These PtCu nanocomposite structures were used in electro oxidation studies of ethanol, methanol and 2-propanol. As a result of the oxidation studies, anodic peak currents of 253.1 mA cm−2, 187.7 mA cm−2, 37.2 mA cm−2 were obtained for methanol, ethanol and 2-propanol, respectively. It was also observed that PtCu has a higher electrochemically active surface area than bare Pt and is more tolerant to CO. The results showed that the synthesised catalyst showed very high electrocatalytic activity and stability in alcohol fuel cells. With this study, important results have been given for the stability problem, which is one of the biggest problems in fuel cells.

Electrooxidation using SnO2–RuO2–IrO2|Ti and IrO2–Ta2O5|Ti anodes as tertiary treatment of oil refinery effluent

AbstractIn the present work, treatability studies were carried out with oil refinery wastewater (effluent from the secondary treatment) using electrooxidation (EO) process employing two mixed oxide anodes: SnO2–RuO2–IrO2|Ti and IrO2–Ta2O5|Ti. Both electrodes' performance were compared by their capacity to generate active chlorine in a synthetic solution and organic matter mineralization of a sample with an average phenol (C6H6O) concentration of 100 mg L−1. Before degradation experiments, surface analysis, and linear sweep voltammetry tests were performed. SnO2–RuO2–IrO2|Ti anode yielded higher active chlorine, reaching an average concentration of 340 mg L−1 at 90 min of electrolysis and 25 mA cm−2. On the other hand, IrO2–Ta2O5|Ti anode only generated an average concentration of 200 mg L−1 at 90 min and 40 mA cm−2. Regarding the degradation experiments, SnO2–RuO2–IrO2|Ti anode showed the highest dissolved organic carbon removal, ranging from 26% to 40%. In addition, through a three‐dimensional excitation–emission matrix fluorescence analysis, it was possible to elucidate the degradation of C6H6O and some possible polycyclic aromatic hydrocarbons present in the effluent. The results suggested that 65%–90% of the hydrocarbons and C6H6O present in the effluent were degraded with the SnO2–RuO2–IrO2|Ti anode applying 25 mA cm−2 within the first 30 min of electrolysis, reaching almost 99% degradation at 90 min. The EO process using SnO2–RuO2–IrO2|Ti can be an alternative for tertiary treatment of oil refinery wastewater for degradation and mineralization of the remaining organic matter of secondary effluents (biological processes) via active chlorine species.

Modelling of E. coli Inactivation from Solutions using GInaFiT via Hybrid Electrode Connected Electro-Disinfection Process

E. coli (Escherichia coli) is a bacterium found in human and animal intestines. These bacteria, which can enter the bloodstream through as anyway as the environment or food, can cause many diseases such as diarrhea, respiratory problems, and blood/urinary tract infections especially in human. Therefore, these bacteria have to be removed from drinking water sources by some inactivation methods. Conventional methods as chlorination, ozonation and UV inactivation methods are effective but the development of techniques that do not require the transportation and storage of chemicals and do not produce negative by-products and cost-effective is the basis of environmental engineering studies. In this study, the inactivation effectiveness of hybrid electrode connected electrochemical process as a new approach on E. coli was investigated. The connection system was experienced with Al/SS/SS as Anode/Cathode/Anode electrode. Simultaneously electrocoagulation (EC) and electrooxidation (EO) mechanism works together in this electrode connection system. The inactivation coefficients were determined by the GInaFiT (Geeraerd and Van Impe Inactivation Model Fitting Tool) modeling tool, which is a Microsoft Excel add-on and the model was statistically well fitted with Double-Weibull. 4D degradation of E. coli was achieved as 21 minutes at a current density of 0.3 A and an optical density (O.D.) of 0.21. It has been determined that hybrid electrode connected electro-disinfection process is an effective approach for the E.coli inactivation.

Electrochemical oxidation of perfluorooctanesulfonate (PFOS) from simulated soil leachate and landfill leachate concentrate

The near-widespread presence of poly- and perfluoroalkyl substances (PFASs) in humans has generated concerns regarding the potential negative impact of these chemicals on human health, as some PFASs are exceedingly persistent and bioaccumulative. Among the perfluorinated PFASs, which exhibit high polarity and strong carbon–fluorine bonds, perfluorooctanesulfonate (PFOS) is one of the frequently encountered species. In this study, the efficiency of electrooxidation (EO) and its application in groundwater simulation were first evaluated as a realistic approach to PFOS removal. After optimizing EO parameters including the solution pH, current density, and the effects of inlet concentration and the anode material, 83 % total organic carbon (TOC) removal was obtained. In groundwater experiments, in which the infiltration of PFOS from soil layers into groundwater was simulated, 79 % TOC removal efficiency was achieved in the more complex groundwater; moreover, an F− ion concentration of 8.78 mg/L was obtained from the decomposition of PFOS. To increase the realism of the simulation, the leachate process was repeated four times, and the EO process was applied to each sequential leachate. In addition, the process efficiency was studied in real landfill leachate wastewater to which PFOS had been added. Despite the challenging wastewater composition, 84 % TOC removal efficiency was achieved. Together, these results indicate that BDD-anodic oxidation may be a practical method to treat PFOS-contaminated groundwater and wastewater.

Assessment of the in-situ electrogenerated chloramines damaging polyamide NF membrane during secondary wastewater treatment

Nanofiltration (NF) membrane is susceptible to chlorine damage during secondary wastewater treatment, rendering it critical to investigate the structure changes in polyamide membrane in chlorine-exposed environments. In this work, chlorinated secondary wastewater was pre-treated using an electro-oxidation (EO) process, and then the potential damage to polyamide membranes during the EO-NF process was assessed by the performance of NF90 nanofiltration membrane after exposure to the EO effluent. We observed a 90% reduction in the retention of Ca2+ and Mg2+ by the NF membrane at high concentration of chloramine (i.e., 20 mg/L), which was attributed to the formation of N-chloramides due to the binding of chloramine to the lone electron pair of the polyamide. Compared with the pristine membrane directly exposed to the chloramine-containing EO effluent, the NF membrane deposited with a biofouling layer did not exhibit any changes in chemical structure and compositions, probably because the biofouling layer blocked the chlorination of polyamide. Therefore, the biofouling layer formed by the deposition and development of microorganism on the membrane surface could prolong the lifetime of the polyamide membrane during the treatment of municipal wastewater in the EO-NF system.

Performance of a pilot-scale BDD reactor by numerical analysis of reaction rate parameters and additional numbers for mass transfers

The performance of a pilot-scale boron-doped diamond (BDD) reactor through a numerical analysis of reaction rate parameters and enhanced mass transfer has been investigated. The main objective of this research is to evaluate the efficiency of the reactor in mineralizing and degrading caffeine as an emerging contaminant. Based on the kinetic mechanisms and mass transport correlations reported in the literature, two reaction rate kinetic models for caffeine degradation are proposed and analyzed. The models consider different electrolytes (NaCl and Na2SO4) and applied current densities. The kinetic fitting process utilizes the gradient-maximal electrochemical approach, together with orthogonal placement methods, fourth-order Runge-Kutta (RK4) methods, and Nelder & Mead methods for optimization of kinetic parameters and spatial discretization of the material balance. Experimental data obtained from a factorial design with four factors and two levels (24) validate the proposed kinetic models. Caffeine degradation is achieved with NaCl and Na2SO4 electrolytes at concentrations of 60 ppm and 100 ppm, respectively. The corresponding applied loads are 1.5 AhL−1 and 3 AhL−1. Na2SO4 exhibits superior performance with a total organic carbon (TOC) removal efficiency of 99.13%, while NaCl achieves 31.47% mineralization. The behavior of caffeine degradation under the operational and scale conditions demonstrates that NaCl, as a support electrolyte, enables controlled charge transfer (current density) during the degradation process. In contrast, Na2SO4 as a support electrolyte introduces a mixed control of charge and mass transfer. The pilot-scale kinetic parameters obtained in this study provide valuable insights into the support electrolyte dynamics and current density dynamics in BDD-based Electrooxidation (EO) systems, particularly in complex matrix applications. Furthermore, the observed electrical consumption supports the potential application of EO as a viable technology for industrial-scale tertiary wastewater treatment, specifically for caffeine removal.

Graphitic carbon nitride infused with PVA-Mn:ZnS modified carbon sensor for electrochemical investigation of Metoclopramide hydrochloride

The primary focus is on determining the trace amount of Metoclopramide hydrochloride (MCH) which widely used to treat gastrointestinal disorders such as gastroparesis and acid reflux. The present study involves the development of a novel carbon paste-based sensor modified with Poly vinyl alcohol capped Manganese-doped ZnS nano particles decorated g-C3N4 nanocomposite (PVA-Mn:ZnS/g-C3N4@CPE), for the detecting and investigation of MCH. Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used to measure the electrochemical performance of MCH. The limit of detection and quantification is found to be 5 nM and 16 nM respectively. Using the SWV technique in pH 7.0 phosphate buffer, the examination of urine and water spiked with MCH was monitored. When PVA-Mn:ZnS/g-C3N4 nanocomposite was used as a modifier in electrode-based sensors, results in well-resolved peaks and improved electrochemical current sensitivity. The electrode material was characterized by CV, scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy. The electro-oxidation of MCH was explored using electro-kinetic characteristics such as heterogeneous rate constant, accumulation time, entropy, enthalpy, Gibbs free energy and other parameters like scan rate and pH. A suitable mechanism was proposed for the number of protons and electrons involved in the electro oxidation of MCH.

Hybrid treatment of olive mill wastewater by iron-catalyzed percarbonate and peroxymonosulfate oxidation followed by electrooxidation

In this study, hybrid advanced oxidation processes were applied to effectively treat olive mill wastewater (OMW). In the first stage of the hybrid process, Fe2+-activated peroxymonosulfate (PMS) and percarbonate (PC) oxidation processes were applied. Optimum conditions for maximum chemical oxygen demand (COD), ultraviolet absorbance at 254 nm (UV254), and color removal were determined. Since the difference between the removal efficiencies of the two processes was negligible, the Fe2+-activated PC process was selected. Under optimum conditions (pH: 4, PC dose: 10 g/L, Fe2+ dose: 5 g/L, reaction time: 60 min) with the Fe2+-PC process, 43.3 % COD, 69.4 % UV254, and 88.6 % color removal were obtained. In the second stage, the electrooxidation (EO) process was applied to the effluent of the Fe2+-PC process. Different anode materials were evaluated in EO based on their pollutant removal efficiency, specific energy consumption, anode efficiency, and instantaneous current efficiency, and IrO2-coated Ti (Ti/IrO2) was selected. In the EO process using Ti/IrO2 anode, 1.75 A, pH 3.5, and 120 min, 59.6 % COD, 94.5 % UV254, and 100 % color removal efficiency were achieved. A total of 77.1 % COD, 98.3 % UV254, and 100 % color removal efficiencies were obtained with hybrid processes, and it was seen that hybrid advanced oxidation is an effective application in removing pollutants from OMW.

Development of gallic acid sensor based on metal oxide modified pencil graphite electrode

This study reports the fabrication of a new voltammetric sensor for the quantification of gallic acid (GA) in green tea samples. A pencil graphite electrode (PGE) modified with MnO2 (MnO2-PGE) was utilized for the electrochemical assay of GA. The developed electrode was characterized by scanning electron microscopy (SEM), Energy dispersive X-Ray analysis (EDAX), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor showed a wide linear range of 20 µM – 500 µM. Scan rate studies showed that the electro oxidation process of GA on MnO2-PGE is diffusion controlled in nature. The MnO2 modified PGE was analytically used to detect the GA content in green tea samples.

Apparent and true mineralization during combined electro‐oxidation and electro‐coagulation on stainless steel anode

AbstractPresent study is a novel attempt to experimentally verify that electrochemical treatment of organic pollutants on stainless steel (SS) anode is a combination of electro‐oxidation (EO) and electro‐coagulation (EC) with quantitative estimation of individual contributions of the two mechanisms. Target organic pollutants, metformin HCl (MET‐HCl) and lamotrigine (LAM), were electrochemically treated with SS anode for this purpose. Experiments were designed using central composite rotatable design (CCRD) to assess the effect of current density (CD) and supporting electrolyte concentration (SEC) as independent process parameters. Under all conditions, the process was experimentally verified to be a combination of EO and EC. For MET‐HCl, true mineralization (TM) as a result of EO contribution varied between 50.13% and 66.64%. EO contribution and resulting TM for LAM ranged from 37.5% to 61.83%. EC contributed 30.6%–31.84% towards MET‐HCl remediation causing the TOC to be transferred from the liquid to the sludge produced (SP). EC contribution was 23.68%–35.89% for LAM remediation. Thus, apparent mineralization (AM), the sum of EO and EC contributions, ranged from 80.63% to 97.79% for MET‐HCl and 61.18% to 96.82% for LAM.Process parameters were statistically optimized using response surface methodology (RSM) to simultaneously maximize TM and AM with minimal energy consumption and maximal current efficiency. The optimized conditions were 0.83 mA/cm2 CD and 86.66 ppm SEC for MET‐HCl. The corresponding values were 1.31 mA/cm2 CD and 79.51 ppm SEC for LAM.

Advanced Electrochemical Degradation of Organic Pollutants from Water using Sb-Doped SnO2/Ti Anode and Assisted by Granular Activated Carbon

In this paper, mesoporous electrodes consisting of Sb-doped SnO2 deposited onto Ti plates that had undergone controlled corrosion under acidic medium were synthesized via a spin-coating method and morpho-structurally characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrodes were electrochemically tested to examine their degradation/mineralization through electrooxidation (EO) of doxorubicin (DOX) as a single component and multi-component, together with capecitabine (CCB) from the cytostatic class and humic acid (HA) from the natural organic matter (NOM) class in the absence/the presence of activated carbon (AC) as a particulate electrode. The best mineralization efficiency of 67% was achieved for DOX mineralization using Sb-doped SnO2 deposited onto a Ti plate that had undergone controlled corrosion with oxalic acid during the electrooxidation process. The presence of AC within the electrolysis process generated a synergistic effect of 52.75% for total organic carbon (TOC) parameter removal, which is in accordance with and significantly better than the results reported in the literature. The aspects related to the complex mechanism of DOX degradation and mineralization are discussed. The superiority of AC assisted electrooxidation, as electrochemical filtering (EF), was proved, considering simultaneous degradation and mineralization of mixture of doxorubicin, capecitabine and humic acid.

Enhanced Purification and Disinfection of Restaurant Wastewater by Electro-coagulation Coupled with an Electro-oxidation Process: From Lab Scale to Field Scale

Several Covid-19 infection events have been reported in restaurant and food-processing factory scenarios. To block the transmission of waterborne pathogens and protect human’s safety, it is urgent to take action for the purification and disinfection of restaurant wastewater. Considering the requirement of restaurant wastewater treatment technology, such as limited spaces, low capital cost, simple to operate, and high efficiency, an integrated electro-coagulation (EC) and electro-oxidation (EO) process was put forward. The lab-scale system treatment results illustrated that the composition of restaurant wastewater underwent significant changes. The chemical oxygen demand value decreased from 1680 to 344 mg/L. Total phosphate, total nitrogen, suspended solids, petroleum, animal fat and vegetable oils, and anionic surfactants achieved a distinct decrease. Moreover, the removal of Escherichia coli and Phi6 illustrated the satisfactory disinfection performance of the EC–EO system. The acute toxicity of the EC–EO effluent was reduced compared to that of raw wastewater. Comparing the results of EC treatment with EO treatment, the EC process provided more significant contributions to the purification and disinfection of wastewater than the EO process. The oxidants generated in the EO process would ensure the residual purification and disinfection performance through the long sewer pipe. The physical–chemical parameters and disinfection performances of the field-scale EC–EO system met the requirement of “Wastewater quality standards for discharge to municipal sewers-GB/T 31962-2015”. However, a certain amount of disinfectant byproducts were formed in the effluent. Moreover, the techno-economic analysis further illustrated the feasibility of the integrated EC–EO system for the purification and disinfection of restaurant wastewater.

Treatment of vegetable oil refinery wastewater by sequential electrocoagulation-electrooxidation process

In the present study a sequential process composed of electrocoagulation (EC) followed by electrooxidation (EO) was utilized at the laboratory scale to remove the chemical oxygen demand (COD) from wastewater generated in Iraqi vegetable oil refinery plant.in the EC, impacts of operating variables such as current density (10–30 mA cm-2) and pH (4–10),and EC time (30–90 min) on the COD removal (RE%) were investigated using response surface methodology (RSM) based on Box- Behnken design(BBD). a mathematical correlation that relates the operating factors with RE% was developed and its regression coefficient was 99.02% confirming the significant of the model. Response surface plots showed that RE% increased with increasing current density and time while it decreased with increasing pH. The optimum removal with a lower cost for EC process were achieved at current density of 30mA/cm2, pH of 4, and electrolysis time of 90 min in which RE% of 69.19% was obtained with requirement of 0.513kWh/kg COD as specific energy consumption (SEC). The effluent exit from EC was treated by EO for a period of 240min at a current density of 30mA/cm2 and an initial pH value of 4 to obtain RE% of 96% at SEC of 1.554 kWh/kg COD. Combining EC with EO resulted in a total RE% of 98.72% and a total SEC of 2.067 kWh/kg COD. Based on the results of present study, the applicability of a sequential electrocoagulation-electrooxidation process for treatment vegetable oil wastewaters is feasible.

Optimisation of electrochemical oxidation process with boron doped diamond (BDD) for removing COD, colour, ammonium, and phosphate in landfill leachate

ABSTRACT This study investigated the electrooxidation (EO) of mature landfill leachate from the Brady Road Resource Management Facility, Winnipeg (Canada). EO using boron-doped diamond (BDD) electrodes were applied to treat real landfill leachate using a batch reactor. Response surface methodology (RSM) was used to determine the optimum process parameter levels. This research mainly focused on how different current densities (64, 95, and 125 mA/cm2) and operational time (30 min, 1, 1.5, 2, 2.5, and 3 hr.) influenced the optimisation of parameters such as chemical oxygen demand (COD), colour, ammonium, and phosphate removal in mature landfill leachate at varied pH. To attain a high percentage of removal for the parameters mentioned above, the optimal conditions were found to be a current density (J) of 125 mA/cm2 and a pH of 8. The optimum conditions resulted in removal percentages of 95.47%, 80.27%, 71.15%, and 47.15% for colour, NH4 +, COD, and PO4 3- respectively, with an energy consumption of 0.05 kWh/dm3. The removal is related to a mechanism of the decomposition of water molecules to hydroxyl radicals and by direct anodic oxidation where the pollutants are transformed to CO2 and H2O. The novelty of this research lies in the optimisation of BDD electrode-based treatment for the simultaneous removal of COD, ammonium, phosphate, and colour from mature leachate collected from a severely cold climatic region of Canada. The BDD electrode showed excellent removal efficiencies for the targeted contaminants with lower energy consumption, making it a feasible method for on-site landfill leachate treatment.

The challenge of non-reactive phosphorus: Mechanisms of treatment and improved recoverability using electrooxidation

Recalcitrant phosphorus (P) species, i.e., soluble non-reactive phosphorus (sNRP), are generally not effectively removed or recovered in conventional wastewater treatment processes. This was substantiated in our meta-analysis, which showed that nearly one-third of wastewater facilities’ effluent P was primarily in the non-reactive form. Transformation of sNRP to more readily removable/recoverable soluble reactive phosphorus (sRP) may offer a viable pathway to enhance P removal and recovery. Electrooxidation (EO) may offer one route for sNRP to sRP transformation. During EO, different sNRP transformation pathways may occur, influencing the extent and efficiency of sNRP transformations as a function of water quality. To explore these mechanisms, we conducted oxidant quenching tests as well as cyclic voltammetry and chronoamperometry experiments using a synthetic water matrix spiked with the sNRP compound beta-glycerol phosphate (BGP). We found that direct electron transfer was responsible for BGP transformation. To assess the applicability of EO for wastewater sNRP to sRP transformation and improved recoverability, EO was used to treat municipal wastewater centrate, followed by tests of sNRP recoverability using the P-selective LayneRT™ ion exchanger. Complete transformation of centrate sNRP to sRP was not achieved with EO, but subsequent removal of sNRP using ion exchange increased after 2 hr of EO treatment. Longer periods of EO treatment did not improve sNRP removal. Improved sNRP adsorption after EO was likely due to decreased competing organics in the centrate after EO treatment. Overall, this study showed that EO can improve sNRP removal using subsequent ion exchange and facilitate enhanced P recovery.

Fabric dyeing wastewater treatment and salt recovery using a pilot scale system consisted of graphite electrodes based on electrooxidation and nanofiltration

In this study, color removal, suspended solids removal, and salt recovery were investigated from different fabric dyeing wastewaters using a pilot scale treatment system. A pilot scale system was installed in the wastewater outlet area of five different textile companies. Experiments were planned for pollutant removal and salt recovery from wastewater. First, the wastewater was treated by electrooxidation (EO) using graphite electrodes. After a reaction time of 1 h, the wastewater was passed throughout the granular activated carbon (AC) coloumn. The pre-treated wastewater was passed through the membrane (NF) system to recover the salt in the wastewater. Finally, the recovered salt water was used for fabric dyeing. In the pilot scale treatment system (EO + AC + NF), 100% of suspended solids (SS) and an average of 99.37% of color were removed from fabric dyeing wastewaters. At the same time, a high amount of salt water was recovered and reused. Optimum conditions were determined as 4 V current, 1000 A power, wastewater's own pH values and 60 min of reaction time. The energy and operating cost for treatment of 1 m3 of wastewater were determined as 40.0 kWh/m3 and 2.2 US$/m3, respectively. In addition to the prevention of environmental pollution by the treatment of wastewater using the pilot-scale treatment system, the reuse of the recovered water will contribute to the protection of our valuable water resources. In addition, using the NF membrane process after the EO system, it will be possible to recover salt from wastewater with high salt content such as textile wastewater.

Electrochemical treatment of aquaculture wastewater effluent and optimization of the parameters using response surface methodology

The electrocoagulation (EC) and electrooxidation (EO) processes are employed widely as treatment processes for industrial, agricultural, and domestic wastewater. In the present study, EC, EO, and a combination of EC + EO were evaluated as methods of removing pollutants from shrimp aquaculture wastewater. Process parameters for electrochemical processes, including current density, pH, and operation time were studied, and response surface methodology was employed to determine the optimum condition for the treatment. The effectiveness of the combined EC + EO process was assessed by measuring the reduction of targeted pollutants, including dissolved inorganic nitrogen species, total dissolved nitrogen (TDN), phosphate, and soluble chemical oxygen demand (sCOD). Using EC + EO process, more than 87% reduction was achieved for inorganic nitrogen, TDN, and phosphate, while 76.2% reduction was achieved for sCOD. These results demonstrated that the combined EC + EO process provided better treatment performance in removing the pollutants from shrimp wastewater. The kinetic results suggested that the effects of pH, current density, and operation time were significant on the degradation process when using iron and aluminum electrodes. Comparatively, iron electrodes were effective at reducing the half-life (t1/2) of each of the pollutants in the samples. The application of the optimized process parameters on shrimp wastewater could be used for large-scale treatment in aquaculture.

Removal of pharmaceutical compounds from real urban wastewater by a continuous bio-electrochemical process at pilot scale

A coupled bio-electrochemical treatment was designed by combining a microalgae-based system with an electro-oxidation (EO) process for removing pharmaceutical compounds in real urban wastewater. First, a preliminary study was carried out at bench scale to identify the best configuration for the coupled treatment, which involved determining whether EO should be used as a pre or post-treatment of the microalgae-based system. The results showed that using EO as a post-treatment provided the best removal results for most of pharmaceuticals, with an average of 58.8% compared to 47.7% obtained with EO as a pre-treatment. Based on these results, a bio-electrochemical treatment was designed using a high rate algal pond (HRAP) followed by an EO process at pilot scale. EO process was evaluated using a Boron Doped Diamond electrode anode and cathode (BDD/BDD cell) with a current density of between 20 and 30 mA cm−2 and an electrolysis time of one hour. This coupled treatment showed removal efficiencies above 80% for hypolipidemic, analgesics and anti-inflammatory drugs. However, antiepileptic drugs showed the lowest removal rate between 36.8% and 69.1%. It is noteworthy that carbamazepine and 10,11-Dihydro-10,11-dihydroxycarbamazepine (CBZ-Diol) showed almost five times the removal rate in the coupled treatment compared to HRAP alone. Overall, the coupled bio-electrochemical treatment proved to be efficient in removing the studied pharmaceutical compounds. The HRAP pre-treatment reduced the presence of organic and inorganic load by 77.4%, allowing the EO process to remove the more recalcitrant target contaminants.