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Bypass wastewaters in excess of plant capacity require in-plant wastewater treatment strategies capable of lessening the contamination magnitude prior to their discharge into water bodies. This study introduces a novel hybrid potassium ferrate(VI)–iron electrocoagulation system for the treatment of bypass wastewater. To understand the synergistic effect of the hybrid system, the response surface methodology and the Box Behnken design were utilized based on four preselected variables (current density, potassium ferrate(VI) dosage, interelectrode distance, and time). The current density and potassium ferrate(VI) dosage and their interaction were found significant in achieving a higher soluble chemical oxygen demand (sCOD) removal and faster ferrous (Fe2+) oxidation. The addition of 0.10 mM potassium ferrate(VI) to the electrocoagulation cell operated for 45 min at a 22 mA/cm2 current density and 15 mm interelectrode distance increased the sCOD removal efficiency from 39.71% to 63.57%. Moreover, the addition of 0.1 mM potassium ferrate(VI) to the previously stated electrocoagulation cell conditions decreased the percentage of Fe2+ to the electrochemically supplied total iron (Fet) from 34.02% to 4.63%. The oxidation effect provided by the addition of potassium ferrate(VI) to the iron electrocoagulation cell increased the sCOD removal by about 10%. In addition, the pH increase that resulted from the dissociation of potassium ferrate(VI) promoted favorable conditions to quickly oxidize the Fe2+ ions generated at the iron anode to form the favorable Fe(OH)3 precipitates. The experimental results clearly demonstrated the synergetic effect of the coupled processes for the removal of sCOD from bypass wastewater. [ABSTRACT FROM AUTHOR]

The response surface method (RSM) was used to find out the best conditions for the nitrate removal by electrocoagulation (EC) process with aluminum electrodes. The independent variables were initial nitrate concentration, reaction time, initial pH, and cell voltage. A statistical analysis of variance (ANOVA) was performed for optimization of parameters obtained from the experimental data. A quadratic model was suggested as a good model for prediction of nitrate removal efficiency. The optimum conditions were obtained at pH 10, 17 V voltage, and 68 min when the initial nitrate concentration was found to be 226 mg/L. At the best conditions, the nitrate removal efficiency and energy consumption were obtained as 87.95% and 144.15 kWh/m3, respectively. In terms of nitrate removal efficiency and energy consumption, the coefficients of determinations were found to be 0.95 and 0.99, respectively. The results indicate that the initial nitrate concentration, reaction time, and cell voltage were found to be the most important parameters. The results also show good agreement between experimental data and the predicted equation. [ABSTRACT FROM AUTHOR]

Vegetable tanning effluents have very high and difficult-to-treat chemical oxygen demand (COD). The main environmental damage is due to the low biodegradability of tannins, that can create environmental problems. Tannins are recalcitrant molecules and resist microbial attack; they are toxic to a variety of microorganisms. In this work, electrocoagulation with aluminum electrodes in a batch reactor was applied to remove polyphenolic compounds of vegetable tannins from aqueous solutions. Two types of commercial tannin extracts were used: chestnut, as a representative of hydrolyzable tannins, and mimosa, as a typical condensed tannin. The effects of operating parameters on the efficiency of electrocoagulation--current density, pH, ionic strength, interelectrode distance (IEA), electrolysis time, concentration of tannin extracts, and the like--have been investigated. It has been shown that the removal efficiency of tannin polyphenols increased with the increasing applied current density and increasing ion strength. The optimum current density (J) was 47.6 A=m2 for chestnut and 71.4 A=m2 for mimosa at 1,000 mg=L. Within these values, 97.4 and 98.8% of tannin polyphenols can be removed, respectively. On the other hand, the most effective removal capacity can be achieved at normal pH (without correction) of each tannin solution in the optimum range. However, the removal efficiency of vegetable tannins from water decreases at more acidic and alkaline pH. The addition of NaCl to the solution helps increase removal efficiency and could save power consumption significantly. The optimal electrode distance is determined to be 2 cm for the electrolysis cell employed. The optimal time for achieving maximum removal of polyphenols increases with increasing tannin concentration. Nevertheless, it can be reduced by increasing the applied current. [ABSTRACT FROM AUTHOR]

Fluoride is a geogenic pollutant found in groundwater in several parts of the world. A possible treatment strategy for removing fluoride from groundwater to meet drinking water standards is the use of electrocoagulation (EC). EC has to be combined with filtration to meet drinking water standards for fluoride and turbidity. The objective of this study was to evaluate the use of iron (Fe) electrodes (mild steel) for defluoridation of groundwater using EC and filtration in continuous-flow mode. Different operating conditions were examined and included the use of baffles, varying flow rates, voltages, and different reactor configurations. The use of baffles was observed to increase removal efficiency. EC and filtration in continuous flow mode with Fe electrodes and no baffles gave a maximum removal efficiency of 36.2%. Addition of baffles improved efficiency to 42% with two baffles and 46.7% with one baffle; the difference between one versus two baffles was within analytical variability. The pH increased in all experiments indicating the need for neutralization after EC and filtration. The average energy consumed per unit volume was 4.73 Wh=L (or kWh=m3) in continuous-flow experiments. [ABSTRACT FROM AUTHOR]

This study investigated the efficiency and cost-effectiveness of electrocoagulation (EC) parameters using aluminum (Al) electrodes to remove cadmium (Cd) from synthetic and real industrial mining wastewater (MWW) discharged by the Tunisian Chemical Group (TCG), which poses serious ecological hazards. Based on individual examinations of each operation parameter, the best removal of Cd was obtained at a current density of 7.35 mAcm-2, an initial pH of 7, and a sodium chloride (NaCl) dose of 2 gL-1 corresponding to a conductivity of 5.3 mS cm-1. The effects of initial concentrations, the Faradic efficiency, the state of the Al plates, the electrical energy consumption, and the operating cost were examined in detail. These optimum conditions enabled the achievement of a largely efficient removal in a relatively short treatment time of 30 min, with a significantly low operating cost of 0.2 Tunisian national dinars (TND) m-3; a low energy consumption of 0.5 kWhm-3 yielded the total removal of Cd. In addition, an application of all the optimum EC parameters together was carried out; a total removal was achieved not only of Cd, but also of other pollutants, at the same time. The investigation of EC processes carried out in this work provides evidence for a highly cost-effective wastewater treatment method if compared to other widely used technologies such as coagulation and precipitation. [ABSTRACT FROM AUTHOR]

The peroxicoagulation (PC) process has received great consideration for the removal of various organic contaminants. The present study investigates the landfill leachate treatment mechanism of the PC process at various pH conditions. The efficiency of the PC process was compared with that of electro Fenton (EF) and electrocoagulation (EC) processes for solutions at pH ranging from 2 to 6. Fe0, Fe2+, and Fe3+ were considered as the catalysts in the EF process and the most efficient catalyst at optimal concentration was then used for further studies. At the optimal pH, 84% of the chemical oxygen demand (COD) was removed from the leachate by the PC process, out of which 67% of COD was removed by the EF process. The COD removal efficiency of the EC process increased with an increase in solution pH. The removal of contaminants by the PC process at low pH is mainly controlled by the degradation process (EF process), and at higher pH, by the electrocoagulation process. [ABSTRACT FROM AUTHOR]

The present study investigates the electrocoagulation-electroreduction (EC-ER) and ozonation process (ECRO process) for the treatment of grey wastewater (GWW) loaded with organic and inorganic matter, oil and greases (O&G), and total suspensions solids (TSS). Several factors, such as electrode materials, current density, electrolysis time, initial pH, wastewater conductivity, and ozone dosage were investigated. High treatment efficiency of GWW was recorded while applying the EC-ER technique followed by the ozonation process. The best performance forGWWtreatment by the EC-ER process was obtained using aluminum and graphite electrodes operated at current density of 0.9 A=dm2, during 90 min of electrolysis time and at pH around 10 whereas the ozonation treatment of GWW was found to be more effective at pH 8 and at 9.2 g=h of ozone dosage. Under these optimal conditions, combining the electrochemical (EC-ER) and ozonation processes enhanced the removal of organic and inorganic contaminants from GWW. The ECRO process reduced total chemical oxygen demand (CODT) by 91.31±1.09%, total organic carbon (TOC) by 84.59±1.71%, soluble chemical oxygen demand (CODs) by 90.17±0.26%, and dissolved organic carbon (DOC) by 82.11±2.19%. Besides, the removal efficiency of biological organic demand (BOD), O&G, and total phosphorous (PT) reached 92.61±0.24%, 90.40±0.31%, and 86.66±0.00%, respectively. [ABSTRACT FROM AUTHOR]

Electrocoagulation is a versatile technique used for treating various types of industrial effluent. The material of the construction and shape of the electrodes are crucial in the electrocoagulation process. The effect of the electrode shape on the performance of the electrocoagulation has been studied by performing experiments for the removal of the dye from the synthetic dye solution using punched electrodes and the results have been evaluated in terms of color removal efficiency. The effect of the number of holes, the diameter of the hole, and the configuration of the holes (square, triangular, and random pitch of the holes) on the color removal efficiency was investigated. An increase in the color removal efficiency was obtained using the punched electrode compared with the plane electrode. The effect of the current source (direct and alternating current) on the performance of the electrocoagulation was studied and no significant effect of the current source on the performance of the electrocoagulation was noticed. [ABSTRACT FROM AUTHOR]

In this study, the treatment of stabilized landfill leachate by electrocoagulation (EC) batch experiments was carried out. Commercially pure aluminum electrodes were used for conducting EC. A 67% chemical oxygen demand (COD) removal was observed when electrocoagulation was performed on landfill leachate for an electrolysis time of 30 min with a current density of 666.66 A=m². EC was compared with the classical chemical coagulation (CC) process via COD removal. The comparison results with 333.33 A=m² current densities indicated that the EC process has higher treatment performance than CC process with an alum dosage of 1.4 g=200 mL. Experiments were carried out to improve the COD removal and heavy metal removal by adding fly ash F, fly ash C, and bottom ash as supporting electrolyte. Fly ash F showed a higher COD and heavy metal removal efficiencies of 74.3 and 91.6% respectively, when compared with bottom ash and fly ash C. The results of the study reveal that electrocoagulation can be used for treatment of stabilized landfill leachate, and fly ash F, fly ash C, and bottom ash slurry can be used as a supporting electrolyte during electrocoagulation. The addition of fly ash and bottom ashes to EC increased more than 10% of the system efficiency and indicates that these waste products can be used as supporting electrolytes in EC process. [ABSTRACT FROM AUTHOR]

Electrochemical treatment of synthetic solution containing Acid Red 131 dye was studied by performing experiments in a batch mode of operation using aluminum electrode. The effect of various parameters, such as the pH of the solution, current density, interelectrode distance, agitation speed, solution conductivity, electrolysis time, retention time, and initial concentration of the dye in the solution, was investigated. The results were analyzed in terms of color removal efficiency (CRE) and the optimum values of the parameters were determined. The maximum CRE (98%) for a synthetic dye solution was obtained at the optimum conditions of current density of and a pH solution of 11 for an electrolysis time of 120 min. Electrochemical treatment of industrial effluent containing Reactive Black B, Orange 3R, and Yellow GR dyes was carried out at the optimum values of the parameters and a CRE of 93.5, 92, and 91.1% was obtained for the three dyes, respectively. Experiments were performed using aluminum sulphate as the coagulant to compare the color removal efficiencies obtained by electrocoagulation and chemical coagulation. [ABSTRACT FROM AUTHOR]

In the present study, restaurant wastewater containing high concentrations of chemical oxygen demand (COD), total suspended solids (TSS), and oil and grease (OG) was treated by the combined electrocoagulation-electroflotation (EC-EF) process on a pilot scale. A central composite design was applied to the experiment design and the response surface methodology was adopted to build the response surface models of effluent COD, TSS, and OG. The sequential quadratic programming method was utilized to optimize the operating conditions of the treatment process. The analysis of variance of the experimental data shows that the coefficients of determination of the response surface models of effluent COD, TSS, and OG were 0.98, 0.982, and 0.989, respectively. The validity of these models was tested by confirmation experiments with satisfactory results. Zero trade effluent surcharges were achieved under optimized operating conditions. In spite of the operating cost calculated with respects to energy, electrode, and chemical consumptions, up to Hong Kong Dollar water or 52% of the concession in trade effluent surcharge can be saved, revealing the cost-effectiveness of the combined EC-EF technique and its potential for full-scale implementation. [ABSTRACT FROM AUTHOR]

Experiments were performed in batch mode of operation using iron electrodes to remove chromium from effluent by electrocoagulation, and the effect of various operating parameters was investigated. The maximum hexavalent chromium removal efficiency of 100% from a synthetic solution containing hexavalent chromium was obtained for an electrolysis time of 15 min at the optimum current density of , interelectrode distance 0.5 cm, and solution pH of 4. The real electroplating industry effluent was characterized using the standard diphenylcarbazide (DPC) method. A 100% chromium removal efficiency was obtained for both trivalent and hexavalent chromium, for an electrolysis time of 45 min at 4 pH. It was found that Cr(VI) is initially reduced to Cr(III) in the acidic medium. An increase in the pH of the effluent was also noticed in the acidic medium due to the generation of hydroxyl ions. Experiments were performed for the removal of chromium using ferric chloride as the coagulant, and it was found that electrocoagulation is more efficient and relatively faster compared to chemical coagulation. [ABSTRACT FROM AUTHOR]

The present study investigates the electrocoagulation-electro-oxidation (EC-EO) process for the treatment of restaurant wastewater (RWW) loaded with organic and inorganic matter, oil, grease, and suspensions solids. The EC-EO process was evaluated in terms of its capability to simultaneously produce an oxidant and coagulant agents by using either iron or aluminum electrodes arranged in a bipolar configuration or graphite electrodes arranged in a monopolar configuration in the same electrolytic cell. Relatively high concentrations of active chlorine () and aluminum () or iron () were produced in situ. The best performance for RWW treatment was obtained by using aluminum and graphite plates alternated in the electrode pack and operated at current of 0.4 A during 90 min of treatment with pH adjusted to approximately 7.0. Under these conditions, more than 98% of oil and greases (O&G) were removed, whereas chemical oxygen demand (COD) and biological oxygen demand (BOD) removal reached 90% and 86%, respectively. Likewise, more than 88% of soluble phosphate was removed, and the process was effective in removing turbidity (98%) and suspended solids (98%). The EC-EO process operated under the best conditions involved a total cost of of treated restaurant effluent. This cost includes energy and electrode consumption, chemicals, and sludge disposal. [ABSTRACT FROM AUTHOR]

The treatment of a high-strength pharmaceutical wastewater (PW) has been carried out using two different electrochemical processes [i.e., electrocoagulation (EC) using aluminium and electrooxidation (EO) using carbon electrodes]. For EC, the main object was to study the adsorption capacity of electroflocs using the Freundlich isotherm () and the kinetics of adsorption by (Lagergren model) first-order () and second-order () kinetic models. For the EO process, the effect of current density (CD) in a range from 40 to and initial pH from 3 to 11 on the treatment efficiency was studied. Under identical operating conditions (CD ; pH 7.2), EC resulted in 24% after 25 min, whereas the EO yielded 35.6% chemical oxygen demand (COD) removal after 90 min of treatment. The kinetics of COD removal for EO was described by a two-stage, first-order kinetic model. Based on the cyclic voltammetric studies, the presence of chlorides was found to have an influence, resulting in indirect oxidation by the generation of chloride/hypochlorite oxidants. Response surface methodology (RSM) was found to be an effective optimization tool, which shows the optimum pH/CD/electrolysis time to be for achieving 30.89% COD removal by the EO process. The study has shown that electrooxidation treatment can be more effectively used as pre treatment to improve the biocompatibility of PW than as a direct biological treatment of PW. [ABSTRACT FROM AUTHOR]

Effects of groundwater cooccurring solutes such as phosphate (PO4), silicate (SiO3), bicarbonate (HCO3), calcium (Ca), and iron (Fe) on arsenic removal were investigated in this study. Investigation by two-level full-factorial designed experiments revealed that PO4 and SiO3 have negative effect on arsenic removal, whereas HCO3 has negligible positive effect. The effects of Ca and Fe present in groundwater have positive effect on arsenic removal by electrocoagulation (EC). Hypothesis testing at 5% significance level suggests that alkalinity (HCO3) is not an important parameter in arsenic removal by EC in naturally occurring pH range of water. [ABSTRACT FROM AUTHOR]

Model was developed by two-level five-factor full-factorial designed-experiment to predict arsenic removal from contaminated water by electrocoagulation. Five factors, namely arsenic concentration (As), solution volume (V); current (I), electrode area (A), and current processing time (t) were investigated. Among the factors, arsenic concentration (As) and volume (V) have negative effect, and area (A), time (t), and current (I) have positive effect on arsenic removal. Within the studied levels of the factors, variance analysis at 5% significance level indicated that electrode area is not significant in arsenic removal by electrocoagulation. The model predicted reasonably good arsenic removal (error<2%) from low (0.288 mg/L) and high (0.882 mg/L) initial arsenic concentrations in presence of naturally cooccurring solutes in the groundwater. For the range of operating variables studied, optimum removal of arsenic (98.56%) is obtained at higher arsenic concentration (1.18 mg/L), lower volume (1 L), higher current (3 A), and higher current processing time (120 s). [ABSTRACT FROM AUTHOR]

A simplistic and systematic procedure has been developed for the design and upscaling of a multichannel, continuous-flow electrocoagulation reactor of monopolar configuration for the removal of submicron particles from wastewater. Using wastewater generated from the chemical-mechanical planarization process as the target wastewater, a series of laboratory-scale studies were conducted to determine the required operating conditions for the efficient removal of the ultrafine silica particles. These operating criteria included charge loading (>=8 F/m3), current density (>=5.7 A/m2), hydraulic retention time (>=60 min), as well as the initial pH (7–10). Furthermore, a steady-state transport equation with second-order reaction kinetics was employed to describe the rate of coagulation as the rate-limiting factor. The actual kinetic constant determined from the laboratory-scale experiments was approximately 1.2×10-21 m3/s, which was three orders of magnitude smaller than that calculated based on Brownian coagulation. The model was subsequently validated with a series of experiments using a pilot-scale electrocoagulation reactor geometrically similar to the laboratory-scale reactor with nearly 20 times volumetric scaleup. [ABSTRACT FROM AUTHOR]

This study compares electrocoagulation and chemical precipitation for heavy metals removal from acidic soil saline leachate (SSL) at the laboratory pilot scale. The electrocoagulation process was evaluated via an electrolytic cell [12 cm (width)×12 cm (length)×19 cm (depth)] using mild steel electrodes (10 cm width×11 cm high), whereas chemical precipitation was evaluated using either calcium hydroxide [Ca(OH)2] or sodium hydroxide (NaOH). By comparison with chemical precipitation at a pH varying between 7 and 8, electrocoagulation was more effective in removing metals from SSL having a relatively low contamination level (124 mg Pb/L and 38 mg Zn/L). For SSL enriched with different heavy metals (each concentration of metals was initially adjusted to 100 mg/L) and treated at a pH lower than 8.5, with the exception of Cd, the residual metal concentrations at the end of the experiments were below the acceptable level recommended for effluent discharge in urban sewage works (less than 4 mg/L of each residual metal concentration was recorded) using electrocoagulation, contrary to chemical precipitation using NaOH (more than 15 mg/L of each residual metal concentration was recorded). By comparison, chemical precipitation using Ca(OH)2 was effective in reducing Cr, Cu, Ni, and Zn under the permissive level, but not for Cd and Pb. However, both chemical precipitation processes needed to be operated at higher pH values (around 10.0) to be more effective in reducing metals from SSL and, therefore, required a pH adjustment of the effluent before discharge, whereas electrochemical treatment had a practical advantage of producing an effluent having a pH close to the neutral value and suitable for stream discharge in the receiving water. On the other hand, electrocoagulation was also found to be very efficient for removing Pb from very contaminated solutions (250–2,000 mg Pb/L). At least 94% of Pb was removed regardless of the initial Pb concentration in the SSL. Electrochemical coagulation involves a total cost varying from 8.67 to 13.00 $/tds, whereas 0.84 to 16.73 $/tds is recorded using chemical precipitation. The cost included only energy consumption, chemicals consumption, and metallic sludge disposal. [ABSTRACT FROM AUTHOR]

Designing a reclaimed water system provides an economically and environmentally favorable method for disposing of wastewater. However, some critical influences on on-site reclaimed water systems, such as limited building area, often limit the effectiveness of conventional treatment methods. This work established a compact and inexpensive electrocoagulation process with a capacity of 28 m3/day to reclaim domestic greywater for human noncontact usage. The total unit cost of on-site domestic greywater reuse was U.S. $0.27/m3, which was below the local potable water rate. Moreover, the treatment facility required an area of 8 m2. Both unit cost and required area in this work are lower than those reported in the literature. The experimental results support the feasibility of the on-site reuse of greywater in high-rise buildings. [ABSTRACT FROM AUTHOR]

Presents a study which applied the combined electrocoagulation and electroflotation process to restaurant wastewater. Experimental setup; Results and discussion; Conclusions.

A method to remove oil and grease (O&G) from synthetically produced water using electrocoagulation in a batch process with a mild steel anode is proposed. Preliminary studies were conducted to explore the effects of operating parameters on chemical oxygen demand (COD) and O&G removal. Individual and interactive influences of causal variables were investigated using a response surface methodology. The experimental results indicated that electrocoagulation is very effective in pollutant removal and could successfully reduce COD and O&G to 99.7% and 96.43%, respectively, from an influent oil-in-water (O/W) emulsion concentration of 1,250±50 mg/L under optimal operating conditions. A notable observation was made on the contribution of the electrooxidative mechanism in COD and O&G removal. It was found that removal due to the oxidative mechanism was increased with increases in current density and salt composition. The methodology is very suitable for the treatment of water produced from offshore basins in particular due to the higher rate of operation and smaller amount of sludge compared with conventional biological treatment and to the presence of supporting electrolyte in situ. [ABSTRACT FROM AUTHOR]