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In the present study it is attempted to treat plating effluent using electrocoagulation. Experiments were carried out in a batch electrochemical reactor using mild steel anode and stainless steel cathode covering wide range in operating conditions. A Box–Behnken experimental design has been adopted to evaluate the individual and interactive effects...
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... In contrast, other RSM designs, such as central composite, require five levels of each numerical factor, which increases the number of experiments, prolongs the experimental part of the study, and is more expensive from an economic point of view. [32][33][34] Therefore, three numerical factors (number of cycles (A), current density (B) and flow rate (C)), and one categorical factor (ultrasound (D)) were considered as operational parameters, Table 2. These variables are independent and can be controlled with negligible error. ...
... These variables are independent and can be controlled with negligible error. [32] In addition, the high levels of the factors are coded þ1 and the low levels are coded À1 by default. These coded values are useful to determine the relative influence of each factor by comparing the factor coefficients. ...
... Thus, the outcome variable y is regressed against its predictors x 1 and x 2 , their respective quadratic terms x 12 and x 22 , and their interaction x 1 x 2 . [32][33][34] After determining the input factors, a response (output) is chosen. Since the initial and final concentrations of heavy metals (Table 1) were already below the allowable emission levels, they were not included as a response in the experimental design. ...
The increasing production of oily wastewater as a by-product of industry has become a major environmental problem. Therefore, this article investigates the removal of mineral oil from oily wastewater by a circulating flow sono-electrocoagulation. The Box-Behnken design was used to study the effects of characteristic electrocoagulation and ultrasonic parameters on mineral oil removal efficiency. A total of 34 different experimental setups were performed at a laboratory scale. A reduced cubic regression model with derived coefficients was developed to describe the mineral oil removal rate. The experimental results show that circulating flow sono-electrocoagulation with iron electrodes can effectively reduce mineral oil by 93.3% under the optimum conditions of 10.948 cycles, a current density of 107.12 A m-2 and a flow rate of 0.468 L s-1. The experimental observations agreed well with the modeled values, and the model was verified experimentally. Under the optimal conditions, the average operating cost was 0.77 EUR/m3.
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... RSM and CCD are powerful statistical techniques for modeling and optimizing the simultaneous effects of critical factors within a four-factor, five-level framework. The range of experimental variables were determined based on pretest results and the values given in the literature [51,[57][58][59]. In the current work, the modeling and optimization of critical parameters, namely initial pH ...
In this work, electrocoagulation-flotation (ECF) following sedimentation was applied as a printing and packaging wastewater treatment using four Al electrodes with a parallel monopolar configuration. A sedimentation process was applied after the ECF as a post-treatment phase to remove large pollutants. The simultaneous efficacy of the operating parameters initial color content (1,843.44-12,156.56 ADMI), initial pH (3.56-10.44), current density (6.02-22.18 mA/cm 2), and treatment time (5.62-74.38 min) on color and chemical oxygen demand (COD) removal efficien-cies were evaluated alongside processing costs. Response surface methodology (RSM) and central composite design (CCD) optimized these key parameters to achieve the highest removal efficien-cies and lowest operating costs. Based on the results analyzed by RSM-CCD, using initial color content of 5,576.38 ADMI, initial pH of 7.29, the current density of 18.49 mA/cm 2 , and treatment time of 59.76 min as optimum operational conditions can result in 97.8% and 92.1% for color and COD removal efficiencies, respectively. At these optimum conditions, operating costs (OPCs), including electrodes material and energy consumption, were 0.07 US$/(kg color removed) and 0.4 US$/(kg COD removed). The results confirm ECF-sedimentation as a promising and cost-effective tool for the treatment of printing and packaging wastewater.
This paper examines the removal of mineral oil from oily wastewater by a hybrid ultrasonic and electrochemical circulating flow process. The Box-Behnken design was used to study the effects of number of cycles, current density, flow rate and the presence of ultrasound on the efficiency of mineral oil removal and process optimization. A reduced cubic regression model with estimated coefficients was developed to describe the mineral oil removal rate. The experimental results show that this novel hybrid system can effectively reduce mineral oil by 94.3 % under the optimal conditions of 14.130 cycles, current density of 53.07 A/m² and a flow rate of 0.234 L/s. The experimental observations agreed well with the modelled values, and the model was verified experimentally. Under the optimal conditions, the electrical energy consumption was 10.04 kWh/m³ and the average operational costs were 2.04 EUR/m³.
The present research was undertaken to investigate the potential of
electrocoagulation (EC) and electrochemical oxidation (EO) techniques for
treating petroleum refinery wastewater. Different types of electrodes have
been used in both electrocoagulation and electrochemical oxidation. In
electrocoagulation, aluminium and mild steel were used as the anode. While
in the electrochemical oxidation, ruthenium oxide coated titanium (RuO2/Ti)
was used as the anode.
In electrocoagulation, the experiments were conducted in a batch
reactor. The effect of the operating parameters, such as the current density,
pH, supporting electrolyte, treatment time, and anode material, was examined.
The progress of the pollutant removal was measured through COD
measurement. The electro-coagulation mechanism was modeled using
adsorption isotherms. The sludge generated during electrocoagulation was
analyzed by scanning electron microscopy (SEM) coupled with the energy
dispersive analysis of X-rays (EDAX). The Fourier transform infrared (FTIR)
spectroscopy analysis was used for the liquid effluent analysis. The results
showed a maximum percentage COD removal of 87% can be achieved under
optimum experimental conditions. The energy consumption and anode
dissolution were 15 kWh/kg and 622 mg/dm3
respectively, within 40 min of
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treatment time. The metal hydroxide, and the gases released during the
electro-coagulation process, eliminated the pollutants in the wastewater. The
adsorptability of the pollutants in the wastewater on the surface of flocs was
modeled using the Langmuir, Tempkin, Freundlich, and Dubinin–
Radushkevich models. The Freundlich isotherm model matches satisfactorily
with the experimental observations for mild steel and aluminium anodes.
In electrochemical oxidation, the experiments were carried out in
batch, and batch recirculation systems. The study focus on evaluating
different operating parameters that affect the performance of the treatment
process to produce high quality water. In a batch electro-oxidation treatment,
the optimized conditions were the current density of 30 mA/cm2
, pH of 8,
supporting electrolyte of 2 g/L, and treatment time of 120 minutes. Under the
optimal condition, the energy consumption of 69 kWh/kg, mass transfer
coefficient of 0.006164 cm/s, and a COD removal efficiency of 92 %, were
obtained. Batch recirculation experiments were carried out in a tubular
electrochemical reactor. The performance of Tubular Electrochemical Reactor
(TER) has been investigated using Residence Time Distribution (RTD) and
Computational Fluid Dynamics (CFD) studies, which give the flow dynamic
behaviour of the electrolyte inside the reactor. The results show that an
increase in the flow rate has a considerable effect on the flow dynamics, and
brings about more turbulence, which is very helpful in increasing the mass
transfer coefficient between the electrode and the fluid flow. Also, the results
obtained show positive influence of the mesh electrode on the flow dynamics
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behavior. The presence of dead volume and short circuiting in the reactor
decreased with an increase in the flow rate. The performance of the TER was
experimentally validated by studying the mass transfer and the color removal
efficiency and the results show an improvement at higher flow rates. The
treatment of petroleum refinery wastewater using batch recirculation
experiments show about 84% of COD removal under optimum conditions.
Further the result shows that an increase in the flow rate decreases the energy
consumption, and enhances the mass transfer coefficient. The increase in the
flow rate (30 to 120 L/hr) resulted in considerable improvement of the current
efficiency, (CE), mass transfer coefficient, (km) and specific energy
consumption, (SEC).
The thesis has been divided into five chapters:
Chapter 1 gives an introduction on the petroleum industry, the
usage, recycle and reuse of water in the typical petroleum refinery, the current
regulation of discharge limits for petroleum effluents and various treatments
available to treat the petroleum effluent are discussed. Introduction
electrocoagulation and electro-oxidation processes, advantages of
electrochemical techniques in environmental protection and the purpose of
this study are presented.
Chapter 2 presents a survey of the most important and prominent
literature on the area of the research, the recent regulations for chemical
constituents and processes, various aspects to improve petroleum industry to a
viii
remarkable level and impact of petroleum refinery wastewater on the
environment are also discussed in this chapter.
Chapter 3 presents the wastewater characterization then materials,
electrochemical experimental setup, procedures, and conditions used to treat
the effluents by electrocoagulation and electrochemical oxidation.
Chapter 4 presents the results and discussion; this chapter is
focused on the electrocoagulation and electrochemical oxidation ability for
wastewater treatment. The effects of the operating conditions on the
performance of this process are presented. Adsorption isotherm models for
electrocoagulation process are proposed. The results of residence time
distribution (RTD) and computational fluid dynamics (CFD) simulation
studies are given to evaluate the performance of tubular electrochemical
reactor for effluent treatment.
Chapter 5 summarizes the experimental and theoretical
investigation and the assessment of the treatment processes were performed.
This chapter gives the conclusion made based on the analysis and further future work.
Electrocoagulation (EC) is one of the emerging technologies in water and wastewater treatment as it combines the benefits of coagulation, sedimentation, flotation and electrochemical oxidation. Extensive research efforts implementing EC technology have been executed over the last decade to treat chemical oxygen demand (COD) rich industrial wastewaters with the aim to protect pollution of freshwater streams (e.g., rivers, lakes etc.). Accordingly, the primary aim of this paper was to tender a comprehensive review of the available recent literature utilizing EC and provide recommendations for the future studies that can improve the EC technology and broaden its range of application. This review introduces, in the first part, the various technologies often adopted for industrial wastewater treatment compared to the application of EC as a treatment method of COD rich wastewater. EC process, amongst the various technologies practiced for treatment of COD rich industrial wastewater, has been viewed as the most privileged treatment technology by different research groups owing to its ability to treat abundant volumes of wastewater. In the second part, application of EC as a single and combined treatment method of COD rich wastewaters has been thoroughly reviewed. It can be concluded from this review paper that operational conditions of EC process at voltage of 10 V and reaction time of 60 min in the batch reactor can be the best for guaranteeing high COD removal efficiencies of > 90 %. This review also concludes that considerably large operation costs of the EC process appears to be the serious drawback and renders it as an unfeasible approach for handling of COD rich wastewaters. In the end, this review has attempted to highlights the potential and limitation of EC and suggests that vast research notably in the field of continuous flow EC system is essential to introduce this technology as a convincing wastewater technology.
This paper investigated the effects of parameters, like inoculum size (15, 10 and 5% of the working volume of the reactor), gas velocities (0.0027, 0.00342 and 0.0068 m/s), bed heights (0.3, 0.6 and 0.9 m), static bed heights (4.85 and 2.43 cm), sizes of solid media particles (12, 4 mm), and the height to diameter ratio (H/D: 0.25 and 0.5) onto COD reduction process for electroplating effluent (initial COD values: 1140 ppm) using Pseudomonas aeruginosa and Pseudomonas putida. The authors derived simple mathematical correlations representing the entire COD reduction process. The correlation between the inoculum volume and gas velocities was in the form of an equation Y = ax2 + bx + c, as deduced from nonlinear regressions. The correlations were validated, and percentage errors were found out to infer the effects of all parameters in the COD reduction process. The maximum COD reduction was achieved to 28.30 ppm (97.52%), in a batch mode, at 10% inoculum size, 0.0027 m/s low gas velocity and a static bed height of 2.43 cm.
